Phase transitions in single macromolecules: Loop-stretch transition versus loop adsorption transition in end-grafted polymer chains

Science.gov (United States)

Zhang, Shuangshuang; Qi, Shuanhu; Klushin, Leonid I.; Skvortsov, Alexander M.; Yan, Dadong; Schmid, Friederike

2018-01-01

We use Brownian dynamics simulations and analytical theory to compare two prominent types of single molecule transitions. One is the adsorption transition of a loop (a chain with two ends bound to an attractive substrate) driven by an attraction parameter ɛ and the other is the loop-stretch transition in a chain with one end attached to a repulsive substrate, driven by an external end-force F applied to the free end. Specifically, we compare the behavior of the respective order parameters of the transitions, i.e., the mean number of surface contacts in the case of the adsorption transition and the mean position of the chain end in the case of the loop-stretch transition. Close to the transition points, both the static behavior and the dynamic behavior of chains with different length N are very well described by a scaling ansatz with the scaling parameters (ɛ - ɛ*)Nϕ (adsorption transition) and (F - F*)Nν (loop-stretch transition), respectively, where ϕ is the crossover exponent of the adsorption transition and ν is the Flory exponent. We show that both the loop-stretch and the loop adsorption transitions provide an exceptional opportunity to construct explicit analytical expressions for the crossover functions which perfectly describe all simulation results on static properties in the finite-size scaling regime. Explicit crossover functions are based on the ansatz for the analytical form of the order parameter distributions at the respective transition points. In contrast to the close similarity in equilibrium static behavior, the dynamic relaxation at the two transitions shows qualitative differences, especially in the strongly ordered regimes. This is attributed to the fact that the surface contact dynamics in a strongly adsorbed chain is governed by local processes, whereas the end height relaxation of a strongly stretched chain involves the full spectrum of Rouse modes.

Phase-locked high-order-harmonic and sub-100-as pulse generation from stretched molecules

International Nuclear Information System (INIS)

Lan Pengfei; Lu Peixiang; Cao Wei; Wang Xinlin; Yang Guang

2006-01-01

High harmonic generation from diatomic molecules in a linearly polarized intense laser field is investigated and the emission time of the harmonics is discussed with the time-frequency analysis method. It is shown that high harmonic generation from molecules at equilibrium distance is similar to that from atoms. Only the harmonics in the cutoff are synchronized, i.e., well phase-locked, whereas the other harmonics are not phase-locked. For the molecule stretched well beyond its equilibrium distance, the harmonics exhibit distinct time-frequency characteristics. The harmonic spectrum can be extended to I p +8U p , where I p and U p are the ionization and ponderomotive potential, and the harmonics with energies below I p +3.17U p are not phase-locked and the harmonics with energies beyond I p +3.17U p are well phase-locked. Thus a large range of harmonics which are well phase-locked are produced, and a train of clean attosecond (as) pulses with a single 90-as pulse in each half optical cycle can be generated with a multicycle laser pulse. Using a few-cycle laser pulse, an isolated attosecond pulse with a duration of about 95 as is obtained

Stretching

Science.gov (United States)

... after a workout. Stretching still can be a beneficial activity after you have sufficiently warmed up. The ... light aerobic activity and stretching. If you're running at a quick pace, you can slow down ...

Modified Fourier heat flux on MHD flow over stretched cylinder filled with dust, Graphene and silver nanoparticles

Directory of Open Access Journals (Sweden)

S. Mamatha Upadhya

2018-06-01

Full Text Available A Comprehensive study on laminar, magnetohydrodynamic (MHD boundary layer flow of nanofluid (water + Silver, water + Graphene embedded with conducting micrometer sized dust particles over a stretching cylinder with the incorporation of Cattaneo-Christov heat flux model is conducted. Appropriate similarity variables are employed to the flow governing equations and the resulting ordinary differential equations are solved by employing Runge-Kutta-Fehlberg method. The results for varied controlling parameters for both dusty nano fluid and dust phase are shown through graphs, table and discussed in detail. Authentication of the obtained results is provided by comparing with published results. Results indicate that Graphene + water dusty nanofluid shows better heat transfer performance compared with Silver + water dusty nanofluid. Improvement in thermal relaxation boosts temperature distribution in both fluid and dust phase. Keywords: Graphene nano particles, Silver nano particles, Stretching cylinder, Dusty fluid, Cattaneo-Christov heat flux, MHD

Stretch-dependent slow force response in isolated rabbit myocardium is Na+ dependent.

Science.gov (United States)

von Lewinski, Dirk; Stumme, Burkhard; Maier, Lars S; Luers, Claus; Bers, Donald M; Pieske, Burkert

2003-03-15

Stretch induces functional and trophic effects in mammalian myocardium via various signal transduction pathways. We tested stretch signal transduction on immediate and slow force response (SFR) in rabbit myocardium. Experiments were performed in isolated right ventricular muscles from adult rabbit hearts (37 degrees C, 1 Hz stimulation rate, bicarbonate-buffer). Muscles were rapidly stretched from 88% of optimal length (L88) to near optimal length (L98) for functional analysis. The resulting immediate and slow increases in twitch force (first phase and SFR, respectively) were assessed at reduced [Na+]o or without and with blockade of stretch activated ion channels (SACs), angiotensin-II (AT1) receptors, endothelin-A (ET(A)) receptors, Na+/H+-exchange (NHE1), reverse mode Na+/Ca2+-exchange (NCX), or Na+/K+-ATPase. The effects of stretch on sarcoplasmic reticulum Ca2+-load were characterized using rapid cooling contractures (RCCs). Intracellular pH was measured in BCECF-AM loaded muscles, and action potential duration (APD) was assessed using floating electrodes. On average, force increased to 216+/-8% of the pre-stretch value during the immediate phase, followed by a further increase to 273+/-10% during the SFR (n=81). RCCs significantly increased during SFR, whereas pH and APD did not change. Neither inhibition of SACs, AT1, or ET(A) receptors affected the stretch-dependent immediate phase nor SFR. In contrast, SFR was reduced by NHE inhibition and almost completely abolished by reduced [Na+]o or inhibition of reverse-mode NCX, whereas increased SFR was seen after raising [Na+]i by Na+/K+-ATPase inhibition. The data demonstrate the existence of a delayed, Na+- and Ca2+-dependent but pH and APD independent SFR to stretch in rabbit myocardium. This inotropic response appears to be independent of autocrine/paracrine AT1 or ET(A) receptor activation, but mediated through stretch-induced activation of NHE and reverse mode NCX.

Stretching & Flexibility: An Interactive Encyclopedia of Stretching. [CD-ROM].

Science.gov (United States)

2002

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…

Detail design of a 10.4-m stretched-membrane dish. Phase 2, Final report

Energy Technology Data Exchange (ETDEWEB)

1994-01-01

This report describes efforts conducted under Tasks 3 and 4 of the second phase of the project to develop a single-element stretched-membrane dish concept to reduce the cost of a high-performance concentrating solar collector. We completed the detailed design for such a collector suitable to drive a 25-kWe Stirling motor generator. The design includes the collectors, optical element, the drive, and support systems. The aperture of the optical element was sized to provide the required energy to the engine based on test data and analytical models of the concentrator receiver, and engine. The design of the optical element was improved based on experience gained from the design, fabrication, and testing of several prototypes.

Wealth distribution, Pareto law, and stretched exponential decay of money: Computer simulations analysis of agent-based models

Science.gov (United States)

Aydiner, Ekrem; Cherstvy, Andrey G.; Metzler, Ralf

2018-01-01

We study by Monte Carlo simulations a kinetic exchange trading model for both fixed and distributed saving propensities of the agents and rationalize the person and wealth distributions. We show that the newly introduced wealth distribution - that may be more amenable in certain situations - features a different power-law exponent, particularly for distributed saving propensities of the agents. For open agent-based systems, we analyze the person and wealth distributions and find that the presence of trap agents alters their amplitude, leaving however the scaling exponents nearly unaffected. For an open system, we show that the total wealth - for different trap agent densities and saving propensities of the agents - decreases in time according to the classical Kohlrausch-Williams-Watts stretched exponential law. Interestingly, this decay does not depend on the trap agent density, but rather on saving propensities. The system relaxation for fixed and distributed saving schemes are found to be different.

Spontaneous bending of pre-stretched bilayers.

Science.gov (United States)

DeSimone, Antonio

2018-01-01

We discuss spontaneously bent configurations of pre-stretched bilayer sheets that can be obtained by tuning the pre-stretches in the two layers. The two-dimensional nonlinear plate model we use for this purpose is an adaptation of the one recently obtained for thin sheets of nematic elastomers, by means of a rigorous dimensional reduction argument based on the theory of Gamma-convergence (Agostiniani and DeSimone in Meccanica. doi:10.1007/s11012-017-0630-4, 2017, Math Mech Solids. doi:10.1177/1081286517699991, arXiv:1509.07003, 2017). We argue that pre-stretched bilayer sheets provide us with an interesting model system to study shape programming and morphing of surfaces in other, more complex systems, where spontaneous deformations are induced by swelling due to the absorption of a liquid, phase transformations, thermal or electro-magnetic stimuli. These include bio-mimetic structures inspired by biological systems from both the plant and the animal kingdoms.

Summary of the stretching tectonics research

International Nuclear Information System (INIS)

Yu Dagan

1994-01-01

The rise of stretching tectonics is established on the basis of recent structural geology theory, the establishment of metamorphic nucleus complex structural model on one hand plays an important promoting art to the development of stretching structure, on the other hand, it needs constant supplement and perfection in practice. Metamorphic nucleus complex is the carrier of comparatively deep geological information in vertical section of the crust and has wide distribution in the era of south China. Evidently, it can be taken as the 'key' to understanding the deep and studying the basement, Strengthening the study will play the important promoting role to the deep prospecting. The study of stretching tectonics is not only limited within the range of structure and metamorphism, but combine with the studies of sedimentation, magmatism, metamorphism and mineralization, thus form a new field of tectonic geology of self-developing system

Guidelines for Stretch Flanging Advanced High Strength Steels

International Nuclear Information System (INIS)

Sriram, S.; Chintamani, J.

2005-01-01

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

Process Parameter Identification in Thin Film Flows Driven by a Stretching Surface

Directory of Open Access Journals (Sweden)

Satyananda Panda

2014-01-01

Full Text Available The flow of a thin liquid film over a heated stretching surface is considered in this study. Due to a potential nonuniform temperature distribution on the stretching sheet, a temperature gradient occurs in the fluid which produces surface tension gradient at the free surface of the thin film. As a result, the free surface deforms and these deformations are advected by the flow in the stretching direction. This work focuses on the inverse problem of reconstructing the sheet temperature distribution and the sheet stretch rate from observed free surface variations. This work builds on the analysis of Santra and Dandapat (2009 who, based on the long-wave expansion of the Navier-Stokes equations, formulate a partial differential equation which describes the evolution of the thickness of a film over a nonisothermal stretched surface. In this work, we show that after algebraic manipulation of a discrete form of the governing equations, it is possible to reconstruct either the unknown temperature field on the sheet and hence the resulting heat transfer or the stretching rate of the underlying surface. We illustrate the proposed methodology and test its applicability on a range of test problems.

Coherent time-stretch transformation for real-time capture of wideband signals.

Science.gov (United States)

Buckley, Brandon W; Madni, Asad M; Jalali, Bahram

2013-09-09

Time stretch transformation of wideband waveforms boosts the performance of analog-to-digital converters and digital signal processors by slowing down analog electrical signals before digitization. The transform is based on dispersive Fourier transformation implemented in the optical domain. A coherent receiver would be ideal for capturing the time-stretched optical signal. Coherent receivers offer improved sensitivity, allow for digital cancellation of dispersion-induced impairments and optical nonlinearities, and enable decoding of phase-modulated optical data formats. Because time-stretch uses a chirped broadband (>1 THz) optical carrier, a new coherent detection technique is required. In this paper, we introduce and demonstrate coherent time stretch transformation; a technique that combines dispersive Fourier transform with optically broadband coherent detection.

600 Volt Stretched Lens Array for Solar Electric Propulsion, Phase II

Data.gov (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...

Probabilistic model of ligaments and tendons: Quasistatic linear stretching

Science.gov (United States)

Bontempi, M.

2009-03-01

Ligaments and tendons have a significant role in the musculoskeletal system and are frequently subjected to injury. This study presents a model of collagen fibers, based on the study of a statistical distribution of fibers when they are subjected to quasistatic linear stretching. With respect to other methodologies, this model is able to describe the behavior of the bundle using less ad hoc hypotheses and is able to describe all the quasistatic stretch-load responses of the bundle, including the yield and failure regions described in the literature. It has two other important results: the first is that it is able to correlate the mechanical behavior of the bundle with its internal structure, and it suggests a methodology to deduce the fibers population distribution directly from the tensile-test data. The second is that it can follow fibers’ structure evolution during the stretching and it is possible to study the internal adaptation of fibers in physiological and pathological conditions.

Moment distributions of phase-type

DEFF Research Database (Denmark)

Bladt, Mogens; Nielsen, Bo Friis

2012-01-01

Both matrix-exponential and phase-type distributions have a number of important closure properties. Among those are the distributions of the age and residual life-time of a stationary renewal process with inter-arrivals of either type. In this talk we show that the spread, which is the sum of the...... with phase-type distributions. For the first order distribution we present an explicit formula for the related Lorenz curve and Gini index. Moment distributions of orders one, two and three have been extensively used in areas such as economy, physics, demography and civil engineering....

Moment Distributions of Phase Type

DEFF Research Database (Denmark)

Bladt, Mogens; Nielsen, Bo Friis

2011-01-01

Moment distributions of phase-type and matrix-exponential distributions are shown to remain within their respective classes. We provide a probabilistic phase-type representation for the former case and an alternative representation, with an analytically appealing form, for the latter. First order...

600 Volt Stretched Lens Array for Solar Electric Propulsion, Phase I

Data.gov (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...

Damage percolation during stretch flange forming of aluminum alloy sheet

Science.gov (United States)

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

2005-12-01

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.

Evaluation of protein adsorption onto a polyurethane nanofiber surface having different segment distributions

Energy Technology Data Exchange (ETDEWEB)

Morita, Yuko; Koizumi, Gaku [Frontier Fiber Technology and Science, Graduate School of Engineering, University of Fukui (Japan); Sakamoto, Hiroaki, E-mail: hi-saka@u-fukui.ac.jp [Tenure-Track Program for Innovative Research, University of Fukui (Japan); Suye, Shin-ichiro [Frontier Fiber Technology and Science, Graduate School of Engineering, University of Fukui (Japan)

2017-02-01

Electrospinning is well known to be an effective method for fabricating polymeric nanofibers with a diameter of several hundred nanometers. Recently, the molecular-level orientation within nanofibers has attracted particular attention. Previously, we used atomic force microscopy to visualize the phase separation between soft and hard segments of a polyurethane (PU) nanofiber surface prepared by electrospinning. The unstretched PU nanofibers exhibited irregularly distributed hard segments, whereas hard segments of stretched nanofibers prepared with a high-speed collector exhibited periodic structures along the long-axis direction. PU was originally used to inhibit protein adsorption, but because the surface segment distribution was changed in the stretched nanofiber, here, we hypothesized that the protein adsorption property on the stretched nanofiber might be affected. We investigated protein adsorption onto PU nanofibers to elucidate the effects of segment distribution on the surface properties of PU nanofibers. The amount of adsorbed protein on stretched PU nanofibers was increased compared with that of unstretched nanofibers. These results indicate that the hard segment alignment on stretched PU nanofibers mediated protein adsorption. It is therefore expected that the amount of protein adsorption can be controlled by rotation of the collector. - Highlights: • The hard segments of stretched PU nanofibers exhibit periodic structures. • The adsorbed protein on stretched PU nanofibers was increased compared with PU film. • The hard segment alignment on stretched PU nanofibers mediated protein adsorption.

The tails of rank-size distributions due to multiplicative processes: from power laws to stretched exponentials and beta-like functions

International Nuclear Information System (INIS)

Naumis, G G; Cocho, G

2007-01-01

Although power laws have been used to fit rank distributions in many different contexts, they usually fail at the tail. Here we show that many different data in rank laws, like in granular materials, codons, author impact in scientific journals, etc are very well fitted by a β-like function ({a, b} distribution). Since this distribution is indeed ubiquitous, it is reasonable to associate it with some kind of general mechanism. In particular, we have found that the macrostates of the product of discrete probability distributions imply stretched exponential-like frequency-rank functions, which qualitatively and quantitatively can be fitted with the {a,b} distribution in the limit of many random variables. We show this by transforming the problem into an algebraic one: finding the rank of successive products of a given set of numbers

Stretch-minimising stream surfaces

KAUST Repository

Barton, Michael; Kosinka, Jin; Calo, Victor M.

2015-01-01

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.

Stretch-minimising stream surfaces

KAUST Repository

Barton, Michael

2015-05-01

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.

Tibialis anterior stretch reflex in early stance is suppressed by repetitive transcranial magnetic stimulation

DEFF Research Database (Denmark)

Zuur, Abraham T; Christensen, Mark Schram; Sinkjær, Thomas

2009-01-01

Abstract A rapid plantar flexion perturbation in the early stance phase of walking elicits a large stretch reflex in tibialis anterior (TA). In this study we use repetitive Transcranial Magnetic Stimulation (rTMS) to test if this response is mediated through a transcortical pathway. TA stretch...

Stretching Safely and Effectively

Science.gov (United States)

... shown that stretching immediately before an event weakens hamstring strength. Instead of static stretching, try performing a " ... If you play soccer, for instance, stretch your hamstrings as you're more vulnerable to hamstring strains. ...

Time stretch and its applications

Science.gov (United States)

Mahjoubfar, Ata; Churkin, Dmitry V.; Barland, Stéphane; Broderick, Neil; Turitsyn, Sergei K.; Jalali, Bahram

2017-06-01

Observing non-repetitive and statistically rare signals that occur on short timescales requires fast real-time measurements that exceed the speed, precision and record length of conventional digitizers. Photonic time stretch is a data acquisition method that overcomes the speed limitations of electronic digitizers and enables continuous ultrafast single-shot spectroscopy, imaging, reflectometry, terahertz and other measurements at refresh rates reaching billions of frames per second with non-stop recording spanning trillions of consecutive frames. The technology has opened a new frontier in measurement science unveiling transient phenomena in nonlinear dynamics such as optical rogue waves and soliton molecules, and in relativistic electron bunching. It has also created a new class of instruments that have been integrated with artificial intelligence for sensing and biomedical diagnostics. We review the fundamental principles and applications of this emerging field for continuous phase and amplitude characterization at extremely high repetition rates via time-stretch spectral interferometry.

The Relation Between Stretching Typology and Stretching Duration: The Effects on Range of Motion.

Science.gov (United States)

Thomas, Ewan; Bianco, Antonino; Paoli, Antonio; Palma, Antonio

2018-04-01

Different stretching strategies and protocols are widely used to improve flexibility or maintain health, acting on the muscle tendon-unit, in order to improve the range of motion (ROM) of the joints. This review aims to evaluate the current body of literature in order to understand the relation between stretching typology and ROM, and secondly to evaluate if a relation exists between stretching volume (either as a single training session, weekly training and weekly frequency) and ROM, after long-term stretching. Twenty-three articles were considered eligible and included in the quantitative synthesis. All stretching typologies showed ROM improvements over a long-term period, however the static protocols showed significant gains (p<0.05) when compared to the ballistic or PNF protocols. Time spent stretching per week seems fundamental to elicit range of movement improvements when stretches are applied for at least or more than 5 min, whereas the time spent stretching within a single session does not seem to have significant effects for ROM gains. Weekly frequency is positively associated to ROM. Evaluated data indicates that performing stretching at least 5 days a week for at least 5 min per week using static stretching may be beneficial to promote ROM improvements. © Georg Thieme Verlag KG Stuttgart · New York.

Knotting in stretched polygons

International Nuclear Information System (INIS)

Rensburg, E J Janse van; Orlandini, E; Tesi, M C; Whittington, S G

2008-01-01

The knotting in a lattice polygon model of ring polymers is examined when a stretching force is applied to the polygon. By examining the incidence of cut-planes in the polygon, we prove a pattern theorem in the stretching regime for large applied forces. This theorem can be used to examine the incidence of entanglements such as knotting and writhing. In particular, we prove that for arbitrarily large positive, but finite, values of the stretching force, the probability that a stretched polygon is knotted approaches 1 as the length of the polygon increases. In the case of writhing, we prove that for stretched polygons of length n, and for every function f(n)=o(√n), the probability that the absolute value of the mean writhe is less than f(n) approaches 0 as n → ∞, for sufficiently large values of the applied stretching force

Maximum likelihood estimation of phase-type distributions

DEFF Research Database (Denmark)

Esparza, Luz Judith R

for both univariate and multivariate cases. Methods like the EM algorithm and Markov chain Monte Carlo are applied for this purpose. Furthermore, this thesis provides explicit formulae for computing the Fisher information matrix for discrete and continuous phase-type distributions, which is needed to find......This work is concerned with the statistical inference of phase-type distributions and the analysis of distributions with rational Laplace transform, known as matrix-exponential distributions. The thesis is focused on the estimation of the maximum likelihood parameters of phase-type distributions...... confidence regions for their estimated parameters. Finally, a new general class of distributions, called bilateral matrix-exponential distributions, is defined. These distributions have the entire real line as domain and can be used, for instance, for modelling. In addition, this class of distributions...

Bias of purine stretches in sequenced chromosomes

DEFF Research Database (Denmark)

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

2002-01-01

/pur tracts was slightly less than expected, with an average of 0.8%. One of the most surprising findings is a clear difference in the length distributions of the regions studied between prokaryotes and eukaryotes. Whereas short-range correlations can explain the length distributions in prokaryotes......, 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....

Effect of spinal manipulative therapy with stretching compared with stretching alone on full-swing performance of golf players: a randomized pilot trial☆

Science.gov (United States)

Costa, Soraya M.V.; Chibana, Yumi E.T.; Giavarotti, Leandro; Compagnoni, Débora S.; Shiono, Adriana H.; Satie, Janice; Bracher, Eduardo S.B.

2009-01-01

Abstract Objective There has been a steady growth of chiropractic treatment using spinal manipulative therapy (SMT) that aims to increase the performance of athletes in various sports. This study evaluates the effect of SMT by chiropractors on the performance of golf players. Methods Golfers of 2 golf clubs in São Paulo, Brazil, participated in this study. They were randomized to 1 of 2 groups: Group I received a stretch program, and group II received a stretch program in addition to SMT. Participants in both groups performed the same standardized stretching program. Spinal manipulative therapy to dysfunctional spinal segments was performed on group II only. All golfers performed 3 full-swing maneuvers. Ball range was considered as the average distance for the 3 shots. Treatment was performed after the initial measurement, and the same maneuvers were performed afterward. Each participant repeated these procedures for a 4-week period. Student t test, Mann-Whitney nonparametric test, and 1-way analysis of variance for repeated measures with significance level of 5% were used to analyze the study. Results Forty-three golfers completed the protocol. Twenty participants were allocated to group I and 23 to group II. Average age, handicap, and initial swing were comparable. No improvement of full-swing performance was observed during the 4 sessions on group I (stretch only). An improvement was observed at the fourth session of group II (P = .005); when comparing the posttreatment, group II had statistical significance at all phases (P = .003). Conclusions Chiropractic SMT in association with muscle stretching may be associated with an improvement of full-swing performance when compared with muscle stretching alone. PMID:19948307

Artificial intelligence in label-free microscopy biological cell classification by time stretch

CERN Document Server

Mahjoubfar, Ata; Jalali, Bahram

2017-01-01

This book introduces time-stretch quantitative phase imaging (TS-QPI), a high-throughput label-free imaging flow cytometer developed for big data acquisition and analysis in phenotypic screening. TS-QPI is able to capture quantitative optical phase and intensity images simultaneously, enabling high-content cell analysis, cancer diagnostics, personalized genomics, and drug development. The authors also demonstrate a complete machine learning pipeline that performs optical phase measurement, image processing, feature extraction, and classification, enabling high-throughput quantitative imaging that achieves record high accuracy in label -free cellular phenotypic screening and opens up a new path to data-driven diagnosis. • Demonstrates how machine learning is used in high-speed microscopy imaging to facilitate medical diagnosis; • Provides a systematic and comprehensive illustration of time stretch technology; • Enables multidisciplinary application, including industrial, biomedical, and artificial intell...

Short Durations of Static Stretching when Combined with Dynamic Stretching do not Impair Repeated Sprints and Agility.

Science.gov (United States)

Wong, Del P; Chaouachi, Anis; Lau, Patrick W C; Behm, David G

2011-01-01

This study aimed to compare the effect of different static stretching durations followed by dynamic stretching on repeated sprint ability (RSA) and change of direction (COD). Twenty-five participants performed the RSA and COD tests in a randomized order. After a 5 min aerobic warm up, participants performed one of the three static stretching protocols of 30 s, 60 s or 90 s total duration (3 stretches x 10 s, 20 s or 30 s). Three dynamic stretching exercises of 30 s duration were then performed (90 s total). Sit-and-reach flexibility tests were conducted before the aerobic warm up, after the combined static and dynamic stretching, and post- RSA/COD test. The duration of static stretching had a positive effect on flexibility with 36.3% and 85.6% greater sit-and-reach scores with the 60 s and 90 s static stretching conditions respectively than with the 30 s condition (p ≤ 0.001). However there were no significant differences in RSA and COD performance between the 3 stretching conditions. The lack of change in RSA and COD might be attributed to a counterbalancing of static and dynamic stretching effects. Furthermore, the short duration (≤ 90 s) static stretching may not have provided sufficient stimulus to elicit performance impairments. Key pointsThe duration of combined static and dynamic stretching had a positive effect on flexibility with 36.3% and 85.6% greater sit and reach scores with the 60 s and 90 s static stretching conditions respectively than with the 30 s condition (p ≤ 0.001).No significant differences in RSA and COD between the 3 stretching conditions.The lack of change in RSA and COD might be attributed to a counterbalancing of static and dynamic stretching effects.The short duration (≤ 90 s) static stretching may not have provided sufficient stimulus to elicit performance impairments.

Short Durations of Static Stretching when Combined with Dynamic Stretching do not Impair Repeated Sprints and Agility

Science.gov (United States)

Wong, Del P.; Chaouachi, Anis; Lau, Patrick W.C.; Behm, David G.

2011-01-01

This study aimed to compare the effect of different static stretching durations followed by dynamic stretching on repeated sprint ability (RSA) and change of direction (COD). Twenty-five participants performed the RSA and COD tests in a randomized order. After a 5 min aerobic warm up, participants performed one of the three static stretching protocols of 30 s, 60 s or 90 s total duration (3 stretches x 10 s, 20 s or 30 s). Three dynamic stretching exercises of 30 s duration were then performed (90 s total). Sit-and-reach flexibility tests were conducted before the aerobic warm up, after the combined static and dynamic stretching, and post- RSA/COD test. The duration of static stretching had a positive effect on flexibility with 36.3% and 85.6% greater sit-and-reach scores with the 60 s and 90 s static stretching conditions respectively than with the 30 s condition (p ≤ 0.001). However there were no significant differences in RSA and COD performance between the 3 stretching conditions. The lack of change in RSA and COD might be attributed to a counterbalancing of static and dynamic stretching effects. Furthermore, the short duration (≤ 90 s) static stretching may not have provided sufficient stimulus to elicit performance impairments. Key points The duration of combined static and dynamic stretching had a positive effect on flexibility with 36.3% and 85.6% greater sit and reach scores with the 60 s and 90 s static stretching conditions respectively than with the 30 s condition (p ≤ 0.001). No significant differences in RSA and COD between the 3 stretching conditions. The lack of change in RSA and COD might be attributed to a counterbalancing of static and dynamic stretching effects. The short duration (≤ 90 s) static stretching may not have provided sufficient stimulus to elicit performance impairments. PMID:24149890

Passive Stretch Versus Active Stretch on Intervertebral Movement in Non - Specific Neck Pain

International Nuclear Information System (INIS)

Abd El - Aziz, A.H.; Amin, D.I.; Moustafa, I.

2016-01-01

Neck pain is one of the most common and painful musculoskeletal conditions. Point prevalence ranges from 6% to 22% and up to 38% of the elderly population, while lifetime prevalence ranges from 14,2% to 71%. Up till now no randomized study showed the effect between controversy of active and passive stretch on intervertebral movement. The purpose: the current study was to investigate the effect of the passive and active stretch on intervertebral movement in non - specific neck pain. Material and methods: Forty five subjects from both sexes with age range between 18 and 30 years and assigned in three groups, group I (15) received active stretch, ultrasound and TENS. Group II (15) received passive stretch, ultrasound and TENS. Group III (15) received ultrasound and TENS. The radiological assessment was used to measure rotational and translational movement of intervertebral movement before and after treatment. Results: MANOVA test was used for radiological assessment before and after treatment there was significant increase in intervertebral movement in group I as p value =0.0001. Conclusion: active stretch had a effect in increasing the intervertebral movement compared to the passive stretch

SHORT DURATIONS OF STATIC STRETCHING WHEN COMBINED WITH DYNAMIC STRETCHING DO NOT IMPAIR REPEATED SPRINTS AND AGILITY

Directory of Open Access Journals (Sweden)

Del P. Wong

2011-06-01

Full Text Available This study aimed to compare the effect of different static stretching durations followed by dynamic stretching on repeated sprint ability (RSA and change of direction (COD. Twenty-five participants performed the RSA and COD tests in a randomized order. After a 5 min aerobic warm up, participants performed one of the three static stretching protocols of 30 s, 60 s or 90 s total duration (3 stretches x 10 s, 20 s or 30 s. Three dynamic stretching exercises of 30 s duration were then performed (90 s total. Sit-and-reach flexibility tests were conducted before the aerobic warm up, after the combined static and dynamic stretching, and post- RSA/COD test. The duration of static stretching had a positive effect on flexibility with 36.3% and 85.6% greater sit-and-reach scores with the 60 s and 90 s static stretching conditions respectively than with the 30 s condition (p < 0.001. However there were no significant differences in RSA and COD performance between the 3 stretching conditions. The lack of change in RSA and COD might be attributed to a counterbalancing of static and dynamic stretching effects. Furthermore, the short duration (< 90 s static stretching may not have provided sufficient stimulus to elicit performance impairments

Mixed quantum/classical approach to OH-stretch inelastic incoherent neutron scattering spectroscopy for ambient and supercooled liquid water and ice Ih

Energy Technology Data Exchange (ETDEWEB)

Shi, L.; Skinner, J. L. [Theoretical Chemistry Institute and Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706 (United States)

2015-07-07

OH-stretch inelastic incoherent neutron scattering (IINS) has been measured to determine the vibrational density of states (VDOS) in the OH-stretch region for liquid water, supercooled water, and ice Ih, providing complementary information to IR and Raman spectroscopies about hydrogen bonding in these phases. In this work, we extend the combined electronic-structure/molecular-dynamics (ES/MD) method, originally developed by Skinner and co-workers to simulate OH-stretch IR and Raman spectra, to the calculation of IINS spectra with small k values. The agreement between theory and experiment in the limit k → 0 is reasonable, further validating the reliability of the ES/MD method in simulating OH-stretch spectroscopy in condensed phases. The connections and differences between IINS and IR spectra are analyzed to illustrate the advantages of IINS over IR in estimating the OH-stretch VDOS.

Mixed quantum/classical approach to OH-stretch inelastic incoherent neutron scattering spectroscopy for ambient and supercooled liquid water and ice Ih

International Nuclear Information System (INIS)

Shi, L.; Skinner, J. L.

2015-01-01

OH-stretch inelastic incoherent neutron scattering (IINS) has been measured to determine the vibrational density of states (VDOS) in the OH-stretch region for liquid water, supercooled water, and ice Ih, providing complementary information to IR and Raman spectroscopies about hydrogen bonding in these phases. In this work, we extend the combined electronic-structure/molecular-dynamics (ES/MD) method, originally developed by Skinner and co-workers to simulate OH-stretch IR and Raman spectra, to the calculation of IINS spectra with small k values. The agreement between theory and experiment in the limit k → 0 is reasonable, further validating the reliability of the ES/MD method in simulating OH-stretch spectroscopy in condensed phases. The connections and differences between IINS and IR spectra are analyzed to illustrate the advantages of IINS over IR in estimating the OH-stretch VDOS

Positivity properties of phase-plane distribution functions

NARCIS (Netherlands)

Janssen, A.J.E.M.

1984-01-01

The aim of this paper is to compare the members of Cohen's class of phase-plane distributions with respect to positivity properties. It is known that certain averages (which are in a sense compatible with Heisenberg's uncertainty principle) of the Wigner distribution over the phase-plane yield

Bilinear phase-plane distribution functions and positivity

NARCIS (Netherlands)

Janssen, A.J.E.M.

1985-01-01

There is a theorem of Wigner that states that phase-plane distribution functions involving the state bilinearly and having correct marginals must take negative values for certain states. The purpose of this paper is to support the statement that these phase-plane distribution functions are for

Stretch strength of Al-Li alloy sheet

Energy Technology Data Exchange (ETDEWEB)

Sato, K.; Sawa, Y.; Yokoyama, T.; Fujimoto, S. [Science Univ. of Tokyo (Japan). Dept. of Mech. Eng.; Sakamoto, T. [Kobe Steel Works, Tokyo (Japan)

1998-07-01

Stretch test on Al-Li alloy sheet was carried out in stretch rate of 0.01 to 0.2 mm/sec. The limiting stretch depth was measured in various conditions and the following results were obtained. (1) Stretch rate does not affect the limiting stretch depth of Al-Li alloy. (2) The limiting stretch depth is increased with increase of the profile radius. (3) Strain hardening exponent(n-value) and r-value of Lankford do not affect the limiting stretch depth. (4) Rapture pattern in stretch test of Al is {alpha} type rapture and that of Al-Li alloy is straight line type rapture. (orig.) 4 refs.

Weak depth and along-strike variations in stretching from a multi-episodic finite stretching model: Evidence for uniform pure-shear extension in the opening of the South China Sea

Science.gov (United States)

Chen, Lin; Zhang, Zhongjie; Song, Haibin

2013-12-01

The South China Sea is widely believed to have been opened by seafloor spreading during the Cenozoic. The details of its lithospheric extension are still being debated, and it is unknown whether pure, simple, or conjunct shears are responsible for the opening of the South China Sea. The depth-dependent and along-strike extension derived from the single-stage finite stretching model or instantaneous stretching model is inconsistent with the observation that the South China Sea proto-margins have experienced multi-episodic extension since the Late Cretaceous. Based on the multi-episodic finite stretching model, we present the amount of lithosphere stretching at the northern continental margin of the South China Sea for different depth scales (upper crust, whole crust and lithosphere) and along several transects. The stretching factors are estimated by integrating seven deep-penetration seismic profiles, the Moho distribution derived from gravity modeling, and the tectonic subsidence data for 41 wells. The results demonstrate that the amount of stretching increases rapidly from 1.1 at the continent shelf to over 3.5 at the lower slope, but the stretching factors at the crust and lithosphere scales are consistent within error (from the uncertainty in paleobathymetry and sea-level change). Furthermore, the along-strike variation in stretching factor is within the range of 1.11-1.9 in west-east direction, accompanied by significant west-east differences in the thickness of high-velocity layers (HVLs) within the lowermost crust. This weak along-strike variation of the stretching factor is most likely produced by the preexisting contrasts in the composition and thermal structure of the lithosphere. The above observations suggest that the continental extension in the opening of the South China Sea mainly takes the form of a uniform pure shear rather than depth-dependent stretching.

Moment Distributions of Phase Type

DEFF Research Database (Denmark)

Bladt, Mogens; Nielsen, Bo Friis

In this paper we prove that the class of distributions on the positive reals with a rational Laplace transform, also known as matrix-exponential distributions, is closed under formation of moment distributions. In particular, the results are hence valid for the well known class of phase-type dist...... alternative representation in terms of sub{intensity matrices. Finally we are able to nd explicit expressions for both the Lorenz curve and the Gini index....

Atomic Stretch: Optimally bounded real-time stretching and beyond

DEFF Research Database (Denmark)

Jensen, Rasmus Ramsbøl; Nielsen, Jannik Boll

2016-01-01

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...

Cyclic mechanical stretch enhances BMP9-induced osteogenic differentiation of mesenchymal stem cells.

Science.gov (United States)

Song, Yang; Tang, Yinhong; Song, Jinlin; Lei, Mingxing; Liang, Panpan; Fu, Tiwei; Su, Xudong; Zhou, Pengfei; Yang, Li; Huang, Enyi

2018-04-01

The purpose of this study was to investigate whether mechanical stretch can enhance the bone morphogenetic protein 9 (BMP9)-induced osteogenic differentiation in MSCs. Recombinant adenoviruses were used to overexpress the BMP9 in C3H10T1/2 MSCs. Cells were seeded onto six-well BioFlex collagen I-coated plates and subjected to cyclic mechanical stretch [6% elongation at 60 cycles/minute (1 Hz)] in a Flexercell FX-4000 strain unit for up to 12 hours. Immunostaining and confocal microscope were used to detect cytoskeleton organization. Cell cycle progression was checked by flow cytometry. Alkaline phosphatase activity was measured with a Chemiluminescence Assay Kit and was quantified with a histochemical staining assay. Matrix mineralization was examined by Alizarin Red S Staining. Mechanical stretch induces cytoskeleton reorganization and inhibits cell proliferation by preventing cells entry into S phase of the cell cycle. Although mechanical stretch alone does not induce the osteogenic differentiation of C3H10T1/2 MSCs, co-stimulation with mechanical stretch and BMP9 enhances alkaline phosphatase activity. The expression of key lineage-specific regulators (e.g., osteocalcin (OCN), SRY-related HMG-box 9, and runt-related transcription factor 2) is also increased after the co-stimulation, compared to the mechanical stretch stimulation along. Furthermore, mechanical stretch augments the BMP9-mediated bone matrix mineralization of C3H10T1/2 MSCs. Our results suggest that mechanical stretch enhances BMP9-induced osteoblastic lineage specification in C3H10T1/2 MSCs.

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

DEFF Research Database (Denmark)

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

2016-01-01

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....

Modified Fourier heat flux on MHD flow over stretched cylinder filled with dust, Graphene and silver nanoparticles

Science.gov (United States)

Mamatha Upadhya, S.; Raju, C. S. K.; Saleem, S.; Alderremy, A. A.; Mahesha

2018-06-01

A Comprehensive study on laminar, magnetohydrodynamic (MHD) boundary layer flow of nanofluid (water + Silver, water + Graphene) embedded with conducting micrometer sized dust particles over a stretching cylinder with the incorporation of Cattaneo-Christov heat flux model is conducted. Appropriate similarity variables are employed to the flow governing equations and the resulting ordinary differential equations are solved by employing Runge-Kutta-Fehlberg method. The results for varied controlling parameters for both dusty nano fluid and dust phase are shown through graphs, table and discussed in detail. Authentication of the obtained results is provided by comparing with published results. Results indicate that Graphene + water dusty nanofluid shows better heat transfer performance compared with Silver + water dusty nanofluid. Improvement in thermal relaxation boosts temperature distribution in both fluid and dust phase.

Hierarchically mesoporous silica materials prepared from the uniaxially stretched polypropylene membrane and surfactant templates

International Nuclear Information System (INIS)

Wang Xiaocong; Ma Jin; Liu Jin; Zhou Chen; Zhao, Yan; Yi Shouzhi; Yang Zhenzhong

2006-01-01

Hierarchically mesoporous silica materials with a bimodal distribution were template-prepared from uniaxially stretched polypropylene membrane in the presence of a surfactant via a sol-gel process. Their regularity and morphologies were characterized by transmission electron microscopy (TEM), x-ray diffraction and Brunauer-Emmett-Teller (BET) surface area analysis. The larger channel pores formed by removing the microfibrils of uniaxially stretched polypropylene membrane have a broad pore size distribution, and their size is around 13 nm. In contrast, the smaller mesopores formed by surfactant templates have a narrow distribution; their size is about 3.9 nm. The size of the smaller pores could be tuned from 2 to 6 nm by selecting different surfactants and by changing the concentration of reactants

Analysis of a filament stretching rheometer

DEFF Research Database (Denmark)

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

1996-01-01

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....

EFFICACY OF MODIFIED PROPRIOCEPTIVE NEUROMUSCULAR FACILITATION STRETCHING WITH CRYOTHERAPY OVER MANUAL PASSIVE STRETCHING WITH CRYOTHERAPY ON HAMSTRING FLEXIBILITY

Directory of Open Access Journals (Sweden)

Shamik Bhattacharjee

2016-04-01

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.

RF phase distribution systems at the SLC

International Nuclear Information System (INIS)

Jobe, R.K.; Schwarz, H.D.

1989-04-01

Modern large linear accelerators require RF distribution systems with minimal phase drifts and errors. Through the use of existing RF coaxial waveguides, and additional installation of phase reference cables and monitoring equipment, stable RF distribution for the SLC has been achieved. This paper discusses the design and performance of SLAC systems, and some design considerations for future colliders. 6 refs., 4 figs

The effects of ramp stretches on active contractions in intact mammalian fast and slow muscle fibres.

Science.gov (United States)

Mutungi, G; Ranatunga, K W

2001-01-01

The effects of a ramp stretch (amplitude muscle fibre length (L0), speed twitch tension and twitch tension re-development were examined in intact mammalian (rat) fast and slow muscle fibre bundles. The experiments were done in vitro at 20 degrees C and at an initial sarcomere length of 2.68 microm. In both fibre types, a stretch applied during the rising phase of the twitch response (including the time of stimulation) increased the re-developed twitch tension (15-35%). A stretch applied before the stimulus had little or no effect on the twitch myogram in fast muscle fibres, but it increased the twitch tension (approximately 5%) in slow muscle fibres. A similar stretch had little or no effect on tetanic tension in either muscle fibre type. In general, the results indicate that the contractile-activation mechanism may be stretch sensitive and this is particularly pronounced in slow muscle fibres. Recorded at a high sampling rate and examined at an appropriate time scale, the transitory tension response to a stretch rose in at least two phases; an initial rapid tension rise to a break (break point tension, P1a) followed by a slower tension rise (apparent P2a) to a peak reached at the end of the stretch. Plotted against stretch velocity, P1a tension increased in direct proportion to stretch velocity (viscous-like) whereas, P2a tension (calculated as peak tension minus P1a tension) increased with stretch velocity to a plateau (visco-elastic). Examined at the peak of a twitch, P1a tension had a slope (viscosity coefficient) of 1.8 kN m(-2) per L0 s(-1) in fast fibres and 4.7 kN m(-2) per L0 s(-1) in slow muscle fibres. In the same preparations, P2a tension had a relaxation time of 8 ms in the fast muscle fibres and 25 ms in the slow muscle fibres. The amplitudes of both tension components scaled with the instantaneous twitch tension in qualitatively the same way as the instantaneous fibre stiffness. These fast/slow fibre type differences probably reflect differences in

FE-Analysis of Stretch-Blow Moulded Bottles Using an Integrative Process Simulation

Science.gov (United States)

Hopmann, C.; Michaeli, W.; Rasche, S.

2011-05-01

The two-stage stretch-blow moulding process has been established for the large scale production of high quality PET containers with excellent mechanical and optical properties. The total production costs of a bottle are significantly caused by the material costs. Due to this dominant share of the bottle material, the PET industry is interested in reducing the total production costs by an optimised material efficiency. However, a reduced material inventory means decreasing wall thicknesses and therewith a reduction of the bottle properties (e.g. mechanical properties, barrier properties). Therefore, there is often a trade-off between a minimal bottle weight and adequate properties of the bottle. In order to achieve the objectives Computer Aided Engineering (CAE) techniques can assist the designer of new stretch-blow moulded containers. Hence, tools such as the process simulation and the structural analysis have become important in the blow moulding sector. The Institute of Plastics Processing (IKV) at RWTH Aachen University, Germany, has developed an integrative three-dimensional process simulation which models the complete path of a preform through a stretch-blow moulding machine. At first, the reheating of the preform is calculated by a thermal simulation. Afterwards, the inflation of the preform to a bottle is calculated by finite element analysis (FEA). The results of this step are e.g. the local wall thickness distribution and the local biaxial stretch ratios. Not only the material distribution but also the material properties that result from the deformation history of the polymer have significant influence on the bottle properties. Therefore, a correlation between the material properties and stretch ratios is considered in an integrative simulation approach developed at IKV. The results of the process simulation (wall thickness, stretch ratios) are transferred to a further simulation program and mapped on the bottles FE mesh. This approach allows a local

An economical analysis of stretch-out for Angra 1

International Nuclear Information System (INIS)

Sakai, M.; Mascarenhas, H.A.

1990-01-01

An economical assessment of Angra 1 fuel cycle stretch-out is performed by means of NUCOST 1.0, a PWR power cost calculation code. International basic costs and an interest rate of 10%a were utilized. During the natural part of the fuel cycle an hypothetical capacity factor of 70% and in the stretch-out part a decrease in Plant's thermal efficiency have also been taken into account. The neutronic data were generated by FASER, MULTIMEDIUM, MEDIUM and PINPOW code system, simulating Angra 1 in the CAOC (constant Axial-Offset Control) operation. Assumming no proplems in the Plant's strecth-out phase, an optimum extension pont of 1 MWd/kg would be attained, what affords an US$700,000 savings by cycle when fuel and operation and maintenance costs are considered. (author) [pt

Flexibility and stretching physiology : responses and adaptations to different stretching intensities.

OpenAIRE

Freitas, Sandro Remo Martins Neves Ramos

2014-01-01

Doutoramento em Motricidade Humana, especialidade de Biomecânica Research and reported literature regarding the conceptual, methodological, and training effects of stretching with different intensities are scarce. The purposes of this thesis were to: i) explore and develop methodological conditions to achieve the second purpose (studies: 1 to 3); ii) characterize the acute and chronic effects induced by different stretching intensities on skeletal muscle and joint mechanical properti...

Conjugate Heat Transfer of Mixed Convection for Viscoelastic Fluid Past a Stretching Sheet

Directory of Open Access Journals (Sweden)

Kai-Long Hsiao

2007-01-01

Full Text Available A conjugate heat transfer problem of a second-grade viscoelastic fluid past a stretching sheet has been studied. Governing equations include heat conduction equation of a stretching sheet, continuity equation, momentum equation, and energy equation of a second-grade fluid, analyzed by a combination of a series expansion method, the similarity transformation, and a second-order accurate finite-difference method. These solutions are used to iterate with the heat conduction equation of the stretching sheet to obtain distributions of the local convective heat transfer coefficient and the stretching sheet temperature. Ranges of dimensionless parameters, the Prandtl number Pr, the elastic number E and the conduction-convection coefficient Ncc are from 0.001 to 10, 0.0001 to 0.01, and 0.5 to 2.0, respectively. A parameter G, which is used to represent the dominance of the buoyant effect, is present in governing equations. Results indicated that elastic effect in the flow could increase the local heat transfer coefficient and enhance the heat transfer of a stretching sheet. In addition, same as the results from Newtonian fluid flow and conduction analysis of a stretching sheet, a better heat transfer is obtained with a larger Ncc, G, and E.

EFFECTIVENESS OF PNF STRETCHING AND CYCLIC STRETCHING OF CALF TIGHTNESS ON COLLEGE GOING GIRLS

Directory of Open Access Journals (Sweden)

Ashlesha Sirari

2015-06-01

Full Text Available Background: Flexibility helps with injury prevention, the reduction of soreness following a workout, and a general sense of well-being. There are different stretching techniques and protocols for improvements in calf extensibility and flexibility. The purpose of the study was to investigate the effectiveness of two techniques i.e. CYCLIC and PNF stretching which improves calf flexibility. This study was done to find the effectiveness of calf Cyclic and PNF stretching technique to improve calf flexibility. Methods: 30 subjects with age group 21-22 years were randomly allocated to 2 groups equally. Group 1(n=15 were given CYCLIC and group 2(n=15 were given PNF stretching technique. Plantar flexion was used to measure the calf tightness which was done before and after the treatment. Treatment was given for 7 days and on the 7th day the calf tightness was again measured. Results: The mean difference of the CYCLIC is 4.6 and mean difference of PNF is 4.7 which indicate that CYCLIC and PNF both are effective to improve calf flexibility but PNF is more effective than CYCLIC to improve calf flexibility. Conclusion: The neurophysiological basis of PNF, stating that the excitatory efficient of the neuromuscular spindle or the inhibitory afferent of the Golgi tendon organ (GTO or both are responsible for the effects. During PNF stretch and isometric contraction of stretched agonists for extended period may cause activation of its neuromuscular spindle. The increase in tension created during the isometric contraction of the pre – lengthened agonist contracts concentrically. Both the fascia & the spindle of the agonist adjust to the nearly lengthened position. These impulses travel via causing post synaptic inhibition of the motor neuron to agonist increasing the tension from the GTO. These impulses can override the impulses coming from the neuromuscular spindles arousing the muscle to reflexly resist to the change in length, thus helping in lengthening

Lamb's plane problem in a thermo-elastic micropolar medium with stretch

Directory of Open Access Journals (Sweden)

T. K. Chadha

1987-01-01

Full Text Available A study is made of the Lamb plane problem in a thermo-elastic micropolar medium with the effect of stretch. The problem is solved for an arbitrary, normal load distribution by using the double Fourier transform. The displacement components, force stress, couple stress, vector first moment and the temperature field are determined for a half space subjected to an arbitrary normal load. Two special cases of a horizontal force and a torque which are oscillating with a frequency ω have been investigated. It is shown that results of this analysis reduce to those without stretch.

Universal Linear Motor Driven Leg Press Dynamometer and Concept of Serial Stretch Loading.

Science.gov (United States)

Hamar, Dušan

2015-08-24

Paper deals with backgrounds and principles of universal linear motor driven leg press dynamometer and concept of serial stretch loading. The device is based on two computer controlled linear motors mounted to the horizontal rails. As the motors can keep either constant resistance force in selected position or velocity in both directions, the system allows simulation of any mode of muscle contraction. In addition, it also can generate defined serial stretch stimuli in a form of repeated force peaks. This is achieved by short segments of reversed velocity (in concentric phase) or acceleration (in eccentric phase). Such stimuli, generated at the rate of 10 Hz, have proven to be a more efficient means for the improvement of rate of the force development. This capability not only affects performance in many sports, but also plays a substantial role in prevention of falls and their consequences. Universal linear motor driven and computer controlled dynamometer with its unique feature to generate serial stretch stimuli seems to be an efficient and useful tool for enhancing strength training effects on neuromuscular function not only in athletes, but as well as in senior population and rehabilitation patients.

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

LENUS (Irish Health Repository)

O'Sullivan, Kieran

2009-01-01

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

DISTRIBUTION OF TWO-PHASE FLOW IN A DISTRIBUTOR

Directory of Open Access Journals (Sweden)

AZRIDJAL AZIZ

2012-02-01

Full Text Available The flow configuration and distribution behavior of two-phase flow in a distributor made of acrylic resin have been investigated experimentally. In this study, air and water were used as two-phase flow working fluids. The distributor consists of one inlet and two outlets, which are set as upper and lower, respectively. The flow visualization at the distributor was made by using a high–speed camera. The flow rates of air and water flowing out from the upper and lower outlet branches were measured. Effects of inclination angle of the distributor were investigated. By changing the inclination angle from vertical to horizontal, uneven distributions were also observed. The distribution of two-phase flow through distributor tends even flow distribution on the vertical position and tends uneven distribution on inclined and horizontal positions. It is shown that even distribution could be achieved at high superficial velocities of both air and water.

The effect of dynamic stretching on hamstrings flexibility with respect to the spino-pelvic rhythm.

Science.gov (United States)

Hasebe, Kiyotaka; Okubo, Yu; Kaneoka, Koji; Takada, Kohei; Suzuki, Daisuke; Sairyo, Koichi

2016-01-01

To ascertain the dynamic stretch effects of flexibility of the hamstrings on lumbar spine and pelvic kinematics. Tight hamstrings are positively correlated with low back pain. However, it is unclear how flexibility of the hamstrings affects spino-pelvic rhythm. Twelve healthy men participated in the study. The straight leg raising (SLR) angle, finger floor distance (FFD), and spino-pelvic rhythm was measured before and after the 6-week stretching protocol. The forward bending task was divided into 4 phases. The paired t-test was used to determine significant differences before and after the FFD, SLR angle, lumbar motion, and pelvic motion, and spino-pelvic rhythm in each phase (phamstrings are important for preventing low back pain.

Flow past a permeable stretching/shrinking sheet in a nanofluid using two-phase model.

Directory of Open Access Journals (Sweden)

Khairy Zaimi

Full Text Available The steady two-dimensional flow and heat transfer over a stretching/shrinking sheet in a nanofluid is investigated using Buongiorno's nanofluid model. Different from the previously published papers, in the present study we consider the case when the nanofluid particle fraction on the boundary is passively rather than actively controlled, which make the model more physically realistic. The governing partial differential equations are transformed into nonlinear ordinary differential equations by a similarity transformation, before being solved numerically by a shooting method. The effects of some governing parameters on the fluid flow and heat transfer characteristics are graphically presented and discussed. Dual solutions are found to exist in a certain range of the suction and stretching/shrinking parameters. Results also indicate that both the skin friction coefficient and the local Nusselt number increase with increasing values of the suction parameter.

Speedup of minimum discontinuity phase unwrapping algorithm with a reference phase distribution

Science.gov (United States)

Liu, Yihang; Han, Yu; Li, Fengjiao; Zhang, Qican

2018-06-01

In three-dimensional (3D) shape measurement based on phase analysis, the phase analysis process usually produces a wrapped phase map ranging from - π to π with some 2 π discontinuities, and thus a phase unwrapping algorithm is necessary to recover the continuous and nature phase map from which 3D height distribution can be restored. Usually, the minimum discontinuity phase unwrapping algorithm can be used to solve many different kinds of phase unwrapping problems, but its main drawback is that it requires a large amount of computations and has low efficiency in searching for the improving loop within the phase's discontinuity area. To overcome this drawback, an improvement to speedup of the minimum discontinuity phase unwrapping algorithm by using the phase distribution on reference plane is proposed. In this improved algorithm, before the minimum discontinuity phase unwrapping algorithm is carried out to unwrap phase, an integer number K was calculated from the ratio of the wrapped phase to the nature phase on a reference plane. And then the jump counts of the unwrapped phase can be reduced by adding 2K π, so the efficiency of the minimum discontinuity phase unwrapping algorithm is significantly improved. Both simulated and experimental data results verify the feasibility of the proposed improved algorithm, and both of them clearly show that the algorithm works very well and has high efficiency.

A modified variable physical properties model, for analyzing nanofluids flow and heat transfer over nonlinearly stretching sheet

Directory of Open Access Journals (Sweden)

Pooria Akbarzadeh

2017-07-01

Full Text Available In this paper, the problem of laminar nanofluid flow which results from the nonlinear stretching of a flat sheet is investigated numerically. In this paper, a modified variable physical properties model for analyzing nanofluids flow and heat transfer is introduced. In this model, the effective viscosity, density, and thermal conductivity of the solid-liquid mixture (nanofluids which are commonly utilized in the homogenous single-phase model, are locally combined with the prevalent single-phase model. A numerical similarity solution is considered which depends on the local Prandtl number, local Brownian motion number, local Lewis number, and local thermophoresis number. The results are compared to the prevalent single-phase model. This comparison depicts that the prevalent single-phase model has a considerable deviation for predicting the behavior of nanofluids flow especially in dimensionless temperature and nanoparticle volume fraction. In addition the effect of the governing parameters such as Prandtl number, the Brownian motion number, the thermophoresis parameter, the Lewis number, and etc. on the velocity, temperature, and volume fraction distribution and the dimensionless heat and mass transfer rates are examined.

Stretches of alternating pyrimidine/purines and purines are respectively linked with pathogenicity and growth temperature in prokaryotes

DEFF Research Database (Denmark)

Ussery, David; Bohlin, J; Hardy, SP

2009-01-01

BACKGROUND: The genomic fractions of purine (RR) and alternating pyrimidine/purine (YR) stretches of 10 base pairs or more, have been linked to genomic AT content, the formation of different DNA helices, strand-biased gene distribution, DNA structure, and more. Although some of these factors are ...... phyla. RR stretches are overrepresented in all phyla except for the Actinobacteria and beta-Proteobacteria. In contrast, YR tracts are underrepresented in all phyla except for the beta-Proteobacterial group. YR-stretches are associated with phylum, pathogenicity and habitat, whilst RR...

Endovascular rescue method for undesirably stretched coil.

Science.gov (United States)

Cho, Jae Hoon

2014-10-01

Undesirable detachment or stretching of coils within the parent artery during aneurysm embolization can be related with thrombus formation, which can be caused occlusion of parent artery or embolic event(s). To escape from this situation, several rescue methods have been reported. A case with undesirably stretched coil in which another rescue method was used, is presented. When the stretched coil is still located in the coil delivery microcatheter, the stretched coil can be removed safely using a snare and a handmade monorail microcatheter. After a snare is lodged in the handmade monorail microcatheter, the snare is introduced over the coil delivery micorcatheter and located in the distal part of the stretched coil. After then, the handmade monorail microcatheter captures the stretched coil and the snare as one unit. This technique using a handmade monorail microcatheter and a snare can be a good rescue modality for the undesirably stretched coil, still remained within the coil delivery microcatheter.

Multivariate phase type distributions - Applications and parameter estimation

DEFF Research Database (Denmark)

Meisch, David

The best known univariate probability distribution is the normal distribution. It is used throughout the literature in a broad field of applications. In cases where it is not sensible to use the normal distribution alternative distributions are at hand and well understood, many of these belonging...... and statistical inference, is the multivariate normal distribution. Unfortunately only little is known about the general class of multivariate phase type distribution. Considering the results concerning parameter estimation and inference theory of univariate phase type distributions, the class of multivariate...... projects and depend on reliable cost estimates. The Successive Principle is a group analysis method primarily used for analyzing medium to large projects in relation to cost or duration. We believe that the mathematical modeling used in the Successive Principle can be improved. We suggested a novel...

Study of the solvent effects on the molecular structure and Cdbnd O stretching vibrations of flurbiprofen

Science.gov (United States)

Tekin, Nalan; Pir, Hacer; Sagdinc, Seda

2012-12-01

The effects of 15 solvents on the C=O stretching vibrational frequency of flurbiprofen (FBF) were determined to investigate solvent-solute interactions. Solvent effects on the geometry and C=O stretching vibrational frequency, ν(C=O), of FBF were studied theoretically at the DFT/B3LYP and HF level in combination with the polarizable continuum model and experimentally using attenuated total reflection infrared spectroscopy (ATR-IR). The calculated C=O stretching frequencies in the liquid phase are in agreement with experimental values. Moreover, the wavenumbers of ν(C=O) of FBF in different solvents have been obtained and correlated with the Kirkwood-Bauer-Magat equation (KBM), the solvent acceptor numbers (ANs), and the linear solvation energy relationships (LSERs). The solvent-induced stretching vibrational frequency shifts displayed a better correlation with the LSERs than with the ANs and KBM.

Graphical analysis for gel morphology II. New mathematical approach for stretched exponential function with β>1

Science.gov (United States)

Hashimoto, Chihiro; Panizza, Pascal; Rouch, Jacques; Ushiki, Hideharu

2005-10-01

A new analytical concept is applied to the kinetics of the shrinking process of poly(N-isopropylacrylamide) (PNIPA) gels. When PNIPA gels are put into hot water above the critical temperature, two-step shrinking is observed and the secondary shrinking of gels is fitted well by a stretched exponential function. The exponent β characterizing the stretched exponential is always higher than one, although there are few analytical concepts for the stretched exponential function with β>1. As a new interpretation for this function, we propose a superposition of step (Heaviside) function and a new distribution function of characteristic time is deduced.

Graphical analysis for gel morphology II. New mathematical approach for stretched exponential function with β>1

International Nuclear Information System (INIS)

Hashimoto, Chihiro; Panizza, Pascal; Rouch, Jacques; Ushiki, Hideharu

2005-01-01

A new analytical concept is applied to the kinetics of the shrinking process of poly(N-isopropylacrylamide) (PNIPA) gels. When PNIPA gels are put into hot water above the critical temperature, two-step shrinking is observed and the secondary shrinking of gels is fitted well by a stretched exponential function. The exponent β characterizing the stretched exponential is always higher than one, although there are few analytical concepts for the stretched exponential function with β>1. As a new interpretation for this function, we propose a superposition of step (Heaviside) function and a new distribution function of characteristic time is deduced

Graphical analysis for gel morphology II. New mathematical approach for stretched exponential function with {beta}>1

Energy Technology Data Exchange (ETDEWEB)

Hashimoto, Chihiro [Graduate School of Bio-Application and System Engineering (BASE), Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi Tokyo 185-0054 (Japan); Panizza, Pascal [Centre de Physique Moleculaire Optique et Hertzienne (CPMOH), Bordeaux I University, 351 Cours de la Liberation 33405 Talance (France); Rouch, Jacques [Centre de Physique Moleculaire Optique et Hertzienne (CPMOH), Bordeaux I University, 351 Cours de la Liberation 33405 Talance (France); Ushiki, Hideharu [Graduate School of Bio-Application and System Engineering (BASE), Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi Tokyo 185-0054 (Japan)

2005-10-19

A new analytical concept is applied to the kinetics of the shrinking process of poly(N-isopropylacrylamide) (PNIPA) gels. When PNIPA gels are put into hot water above the critical temperature, two-step shrinking is observed and the secondary shrinking of gels is fitted well by a stretched exponential function. The exponent {beta} characterizing the stretched exponential is always higher than one, although there are few analytical concepts for the stretched exponential function with {beta}>1. As a new interpretation for this function, we propose a superposition of step (Heaviside) function and a new distribution function of characteristic time is deduced.

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

2009-04-01

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

Phase-space distributions and orbital angular momentum

Directory of Open Access Journals (Sweden)

Pasquini B.

2014-06-01

Full Text Available We review the concept of Wigner distributions to describe the phase-space distributions of quarks in the nucleon, emphasizing the information encoded in these functions about the quark orbital angular momentum.

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

Effects of mixing methods on phase distribution in vertical bubble flow

International Nuclear Information System (INIS)

Monji, Hideaki; Matsui, Goichi; Sugiyama, Takayuki.

1992-01-01

The mechanism of the phase distribution formation in a bubble flow is one of the most important problems in the control of two-phase flow systems. The effect of mixing methods on the phase distribution was experimentally investigated by using upward nitrogen gas-water bubble flow under the condition of fixed flow rates. The experimental results show that the diameter of the gas injection hole influences the phase distribution through the bubble size. The location of the injection hole and the direction of injection do not influence the phase distribution of fully developed bubble flow. The transitive equivalent bubble size from the coring bubble flow to the sliding bubble flow corresponds to the bubble shape transition. The analytical results show that the phase distribution may be predictable if the phase profile is judged from the bubble size. (author)

Biaxial stretching of film principles and applications

CERN Document Server

Demeuse, M T

2011-01-01

Biaxial (having two axes) stretching of film is used for a range of applications and is the primary manufacturing process by which products are produced for the food packaging industry. Biaxial stretching of film: principles and applications provides an overview of the manufacturing processes and range of applications for biaxially stretched films. Part one reviews the fundamental principles of biaxial stretching. After an introductory chapter which defines terms, chapters discuss equipment design and requirements, laboratory evaluations, biaxial film structures and typical industrial processes for the biaxial orientation of films. Additional topics include post production processing of biaxially stretched films, the stress-strain behaviour of poly(ethylene terephthalate) and academic investigations of biaxially stretched films. Part two investigates the applications of biaxial films including fresh cut produce, snack packaging and product labelling. A final chapter investigates potential future trends for bi...

Effect of Strain Rate on Microscopic Deformation Behavior of High-density Polyethylene under Uniaxial Stretching

Directory of Open Access Journals (Sweden)

Kida Takumitsu

2017-01-01

Full Text Available The microscopic deformation behaviors such as the load sharing and the molecular orientation of high-density polyethylene under uniaxial stretching at various strain rates were investigated by using in-situ Raman spectroscopy. The chains within crystalline phase began to orient toward the stretching direction beyond the yielding region and the orientation behavior was not affected by the strain rate. While the stretching stress along the crystalline chains was also not affected by the strain rate, the peak shifts of the Raman bands at 1130, 1418, 1440 and 1460 cm-1, which are sensitive to the interchain interactions obviously, depended on the strain rate; the higher strain rates lead to the stronger stretching stress or negative pressure on the crystalline and amorphous chains. These effects of the strain rate on the microscopic deformation was associated with the cavitation and the void formation leading to the release of the internal pressure.

Effects of the randomly distributed magnetic field on the phase diagrams of the Ising Nanowire II: Continuous distributions

International Nuclear Information System (INIS)

Akıncı, Ümit

2012-01-01

The effect of the random magnetic field distribution on the phase diagrams and ground state magnetizations of the Ising nanowire has been investigated with effective field theory with correlations. Gaussian distribution has been chosen as a random magnetic field distribution. The variation of the phase diagrams with that distribution parameters has been obtained and some interesting results have been found such as disappearance of the reentrant behavior and first order transitions which appear in the case of discrete distributions. Also for single and double Gaussian distributions, ground state magnetizations for different distribution parameters have been determined which can be regarded as separate partially ordered phases of the system. - Highlights: ► We give the phase diagrams of the Ising nanowire under the continuous randomly distributed magnetic field. ► Ground state magnetization values obtained. ► Different partially ordered phases observed.

Stretched exponential dynamics of coupled logistic maps on a small-world network

Science.gov (United States)

Mahajan, Ashwini V.; Gade, Prashant M.

2018-02-01

We investigate the dynamic phase transition from partially or fully arrested state to spatiotemporal chaos in coupled logistic maps on a small-world network. Persistence of local variables in a coarse grained sense acts as an excellent order parameter to study this transition. We investigate the phase diagram by varying coupling strength and small-world rewiring probability p of nonlocal connections. The persistent region is a compact region bounded by two critical lines where band-merging crisis occurs. On one critical line, the persistent sites shows a nonexponential (stretched exponential) decay for all p while for another one, it shows crossover from nonexponential to exponential behavior as p → 1 . With an effectively antiferromagnetic coupling, coupling to two neighbors on either side leads to exchange frustration. Apart from exchange frustration, non-bipartite topology and nonlocal couplings in a small-world network could be a reason for anomalous relaxation. The distribution of trap times in asymptotic regime has a long tail as well. The dependence of temporal evolution of persistence on initial conditions is studied and a scaling form for persistence after waiting time is proposed. We present a simple possible model for this behavior.

Characterization of mechanical behavior of a porcine pulmonary artery strip using a randomized uniaxial stretch and stretch-rate protocol

Directory of Open Access Journals (Sweden)

Criscione John C

2008-01-01

Full Text Available Abstract Background Much of the experimental work in soft tissue mechanics has been focused on fitting approximate relations for specific tissue types from aggregate data on multiple samples of the tissue. Such relations are needed for modeling applications and have reasonable predictability – especially given the natural variance in specimens. There is, however, much theoretical and experimental work to be done in determining constitutive behaviors for particular specimens and tissues. In so doing, it may be possible to exploit the natural variation in tissue ultrastructure – so to relate ultrastructure composition to tissue behavior. Thus, this study focuses on an experimental method for determining constitutive behaviors and illustrates the method with analysis of a porcine pulmonary artery strip. The method characterizes the elastic part of the response (implicitly in terms of stretch and the inelastic part in terms of short term stretch history (i.e., stretch-rate Ht2, longer term stretch history Ht1, and time since the start of testing T. Methods A uniaxial testing protocol with a random stretch and random stretch-rate was developed. The average stress at a particular stretch was chosen as the hyperelastic stress response, and deviation from the mean at this particular stretch is chosen as the inelastic deviation. Multivariable Linear Regression Analysis (MLRA was utilized to verify if Ht2, Ht1, and T are important factors for characterizing the inelastic deviation. For acquiring Ht2 and Ht1, an integral function type of stretch history was employed with time constants chosen from the relaxation spectrum of an identical size strip from the same tissue with the same orientation. Finally, statistical models that characterize the inelasticity were developed at various, nominal values of stretch, and their predictive capability was examined. Results Inelastic deviation from hyperelasticity was high (31% for low stretch and declined

Design considerations and challenges for mechanical stretch bioreactors in tissue engineering.

Science.gov (United States)

Lei, Ying; Ferdous, Zannatul

2016-05-01

With the increase in average life expectancy and growing aging population, lack of functional grafts for replacement surgeries has become a severe problem. Engineered tissues are a promising alternative to this problem because they can mimic the physiological function of the native tissues and be cultured on demand. Cyclic stretch is important for developing many engineered tissues such as hearts, heart valves, muscles, and bones. Thus a variety of stretch bioreactors and corresponding scaffolds have been designed and tested to study the underlying mechanism of tissue formation and to optimize the mechanical conditions applied to the engineered tissues. In this review, we look at various designs of stretch bioreactors and common scaffolds and offer insights for future improvements in tissue engineering applications. First, we summarize the requirements and common configuration of stretch bioreactors. Next, we present the features of different actuating and motion transforming systems and their applications. Since most bioreactors must measure detailed distributions of loads and deformations on engineered tissues, techniques with high accuracy, precision, and frequency have been developed. We also cover the key points in designing culture chambers, nutrition exchanging systems, and regimens used for specific tissues. Since scaffolds are essential for providing biophysical microenvironments for residing cells, we discuss materials and technologies used in fabricating scaffolds to mimic anisotropic native tissues, including decellularized tissues, hydrogels, biocompatible polymers, electrospinning, and 3D bioprinting techniques. Finally, we present the potential future directions for improving stretch bioreactors and scaffolds. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:543-553, 2016. © 2016 American Institute of Chemical Engineers.

Higher-order phase transitions on financial markets

Science.gov (United States)

Kasprzak, A.; Kutner, R.; Perelló, J.; Masoliver, J.

2010-08-01

Statistical and thermodynamic properties of the anomalous multifractal structure of random interevent (or intertransaction) times were thoroughly studied by using the extended continuous-time random walk (CTRW) formalism of Montroll, Weiss, Scher, and Lax. Although this formalism is quite general (and can be applied to any interhuman communication with nontrivial priority), we consider it in the context of a financial market where heterogeneous agent activities can occur within a wide spectrum of time scales. As the main general consequence, we found (by additionally using the Saddle-Point Approximation) the scaling or power-dependent form of the partition function, Z(q'). It diverges for any negative scaling powers q' (which justifies the name anomalous) while for positive ones it shows the scaling with the general exponent τ(q'). This exponent is the nonanalytic (singular) or noninteger power of q', which is one of the pilar of higher-order phase transitions. In definition of the partition function we used the pausing-time distribution (PTD) as the central one, which takes the form of convolution (or superstatistics used, e.g. for describing turbulence as well as the financial market). Its integral kernel is given by the stretched exponential distribution (often used in disordered systems). This kernel extends both the exponential distribution assumed in the original version of the CTRW formalism (for description of the transient photocurrent measured in amorphous glassy material) as well as the Gaussian one sometimes used in this context (e.g. for diffusion of hydrogen in amorphous metals or for aging effects in glasses). Our most important finding is the third- and higher-order phase transitions, which can be roughly interpreted as transitions between the phase where high frequency trading is most visible and the phase defined by low frequency trading. The specific order of the phase transition directly depends upon the shape exponent α defining the stretched

Distribution of cesium between colloid-rock phases-establishment of experimental system and investigation of Cs distribution between colloid and rock

International Nuclear Information System (INIS)

Nakata, Kotaro

2006-01-01

Distribution and re-distribution of cesium between 3-phases (colloid, rock and water) was investigated. Analcite and bentonite colloid ware used as colloid phase and muscovite was used as rock phase. Before investigating the distribution between 3-phases, sorption and desorption behavior of Cs on analcite colloid, bentonite colloid and muscovite was investigated. It was found some fraction of Cs sorbed irreversibly on analcite colloid, while Cs sorbed reversibly on bentonite colloid. The experimental system was established for assessment of the distribution of nuclides between 3-phases by using combination of membrane filter and experimental cell. Since colloid and muscovite were separated by membrane filter, sorption of colloid on muscovite could be prevented and we could obtain distribution of Cs as ion. The distribution of Cs between 3-phases were obtained by this experimental system. Furthermore, re-distribution experiment was also carried out by using this system. After 7 days contact of colloid with Cs, distribution of sorbed Cs on colloid to liquid or muscovite phase was investigated. Comparing sorption and desorption isotherm with the distribution of Cs between 3-phases, it was found that Kd value of colloid (ratio of Cs concentration in liquid phase to amount of sorbed Cs on colloid phase) estimated in 2-phases (water and colloid) is different from that in 3-phases. Furthermore, in the case of analcite colloid, Kd value of colloid obtained in 3-phases distribution experiment was different from that obtained in re-distribution experiment. This is considered because of the irreversibility of Cs sorption on analcite colloid. Thus, it was found distribution of Cs in 3-phases was not predictable from sorption and desorption isotherm or Kd value of 2-phases (water-rock, water-colloid). (author)

Hermite-Gaussian beams with self-forming spiral phase distribution

Science.gov (United States)

Zinchik, Alexander A.; Muzychenko, Yana B.

2014-05-01

Spiral laser beams is a family of laser beams that preserve the structural stability up to scale and rotate with the propagation. Properties of spiral beams are of practical interest for laser technology, medicine and biotechnology. Researchers use a spiral beams for movement and manipulation of microparticles. Spiral beams have a complicated phase distribution in cross section. This paper describes the results of analytical and computer simulation of Hermite-Gaussian beams with self-forming spiral phase distribution. In the simulation used a laser beam consisting of the sum of the two modes HG TEMnm and TEMn1m1. The coefficients n1, n, m1, m were varied. Additional phase depending from the coefficients n, m, m1, n1 imposed on the resulting beam. As a result, formed the Hermite Gaussian beam phase distribution which takes the form of a spiral in the process of distribution. For modeling was used VirtualLab 5.0 (manufacturer LightTrans GmbH).

Fibril orientation redistribution induced by stretching of cellulose nanofibril hydrogels

International Nuclear Information System (INIS)

Josefsson, Gabriella; Gamstedt, E. Kristofer; Ahvenainen, Patrik; Mushi, Ngesa Ezekiel

2015-01-01

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

Stretched polygons in a lattice tube

Energy Technology Data Exchange (ETDEWEB)

Atapour, M [Department of Mathematics and Statistics, York University, Toronto, ON M3J 1P3 (Canada); Soteros, C E [Department of Mathematics and Statistics, University of Saskatchewan, Saskatoon, SK S7N 5E6 (Canada); Whittington, S G [Department of Chemistry, University of Toronto, Toronto, ON M5S 3H6 (Canada)], E-mail: atapour@mathstat.yorku.ca, E-mail: soteros@math.usask.ca, E-mail: swhittin@chem.utoronto.ca

2009-08-14

We examine the topological entanglements of polygons confined to a lattice tube and under the influence of an external tensile force f. The existence of the limiting free energy for these so-called stretched polygons is proved and then, using transfer matrix arguments, a pattern theorem for stretched polygons is proved. Note that the tube constraint allows us to prove a pattern theorem for any arbitrary value of f, while without the tube constraint it has so far only been proved for large values of f. The stretched polygon pattern theorem is used first to show that the average span per edge of a randomly chosen n-edge stretched polygon approaches a positive value, non-decreasing in f, as n {yields} {infinity}. We then show that the knotting probability of an n-edge stretched polygon confined to a tube goes to one exponentially as n {yields} {infinity}. Thus as n {yields} {infinity} when polygons are influenced by a force f, no matter its strength or direction, topological entanglements, as defined by knotting, occur with high probability. (fast track communication)

Stretched polygons in a lattice tube

International Nuclear Information System (INIS)

Atapour, M; Soteros, C E; Whittington, S G

2009-01-01

We examine the topological entanglements of polygons confined to a lattice tube and under the influence of an external tensile force f. The existence of the limiting free energy for these so-called stretched polygons is proved and then, using transfer matrix arguments, a pattern theorem for stretched polygons is proved. Note that the tube constraint allows us to prove a pattern theorem for any arbitrary value of f, while without the tube constraint it has so far only been proved for large values of f. The stretched polygon pattern theorem is used first to show that the average span per edge of a randomly chosen n-edge stretched polygon approaches a positive value, non-decreasing in f, as n → ∞. We then show that the knotting probability of an n-edge stretched polygon confined to a tube goes to one exponentially as n → ∞. Thus as n → ∞ when polygons are influenced by a force f, no matter its strength or direction, topological entanglements, as defined by knotting, occur with high probability. (fast track communication)

Two-dimensional distributed-phase-reference protocol for quantum key distribution

DEFF Research Database (Denmark)

Bacco, Davide; Christensen, Jesper Bjerge; Usuga Castaneda, Mario A.

2016-01-01

10 years, long-distance fiber-based DPR systems have been successfully demonstrated, although fundamental obstacles such as intrinsic channel losses limit their performance. Here, we introduce the first two-dimensional DPR-QKD protocol in which information is encoded in the time and phase of weak......Quantum key distribution (QKD) and quantum communication enable the secure exchange of information between remote parties. Currently, the distributed-phase-reference (DPR) protocols, which are based on weak coherent pulses, are among the most practical solutions for long-range QKD. During the last...... coherent pulses. The ability of extracting two bits of information per detection event, enables a higher secret key rate in specific realistic network scenarios. Moreover, despite the use of more dimensions, the proposed protocol remains simple, practical, and fully integrable....

Two-dimensional distributed-phase-reference protocol for quantum key distribution

Science.gov (United States)

Bacco, Davide; Christensen, Jesper Bjerge; Castaneda, Mario A. Usuga; Ding, Yunhong; Forchhammer, Søren; Rottwitt, Karsten; Oxenløwe, Leif Katsuo

2016-12-01

Quantum key distribution (QKD) and quantum communication enable the secure exchange of information between remote parties. Currently, the distributed-phase-reference (DPR) protocols, which are based on weak coherent pulses, are among the most practical solutions for long-range QKD. During the last 10 years, long-distance fiber-based DPR systems have been successfully demonstrated, although fundamental obstacles such as intrinsic channel losses limit their performance. Here, we introduce the first two-dimensional DPR-QKD protocol in which information is encoded in the time and phase of weak coherent pulses. The ability of extracting two bits of information per detection event, enables a higher secret key rate in specific realistic network scenarios. Moreover, despite the use of more dimensions, the proposed protocol remains simple, practical, and fully integrable.

Influence of the nematic order on the rheology and conformation of stretched comb-like liquid crystalline polymers

Science.gov (United States)

Fourmaux-Demange, V.; Brûlet, A.; Boué, F.; Davidson, P.; Keller, P.; Cotton, J. P.

2000-04-01

We have studied the rheology and the conformation of stretched comb-like liquid-crystalline polymers. Both the influence of the comb-like structure and the specific effect of the nematic interaction on the dynamics are investigated. For this purpose, two isomers of a comb-like polymetacrylate polymer, of well-defined molecular weights, were synthesized: one displays a nematic phase over a wide range of temperature, the other one has only an isotropic phase. Even with high degrees of polymerization N, between 40 and 1000, the polymer chains studied were not entangled. The stress-strain curves during the stretching and relaxation processes show differences between the isotropic and nematic comb-like polymers. They suggest that, in the nematic phase, the chain dynamics is more cooperative than for a usual linear polymer. Small-angle neutron scattering has been used in order to determine the evolution of the chain conformation after stretching, as a function of the duration of relaxation t_r. The conformation can be described with two parameters only: λ_p, the global deformation of the polymer chain, and p, the number of statistical units of locally relaxed sub-chains. For the comb-like polymer, the chain deformation is pseudo-affine: λ_p is always smaller than λ (the deformation ratio of the whole sample). In the isotropic phase, λ_p has a constant value, while p increases as t_r. This latter behavior is not that expected for non-entangled chains, in which p varies as {t_r}^{1/2} (Rouse model). In the nematic phase, λ_p decreases as a stretched exponential function of t_r, while p remains constant. The dynamics of the comb-like polymers is discussed in terms of living clusters from which junctions are produced by interactions between side chains. The nematic interaction increases the lifetime of these junctions and, strikingly, the relaxation is the same at all scales of the whole polymer chain.

A study of extracellular matrix remodeling in aortic heart valves using a novel biaxial stretch bioreactor.

Science.gov (United States)

Lei, Ying; Masjedi, Shirin; Ferdous, Zannatul

2017-11-01

In aortic valves, biaxial cyclic stretch is known to modulate cell differentiation, extracellular matrix (ECM) synthesis and organization. We designed a novel bioreactor that can apply independent and precise stretch along radial and circumferential directions in a tissue culture environment. While this bioreactor can be used for either native or engineered tissues, this study determined matrix remodeling and strain distribution of aortic cusps after culturing under biaxial stretch for 14 days. The contents of collagen and glycosaminoglycans were determined using standard biochemical assays and compared with fresh controls. Strain fields in static cusps were more uniform than those in stretched cusps, which indicated degradation of the ECM fibers. The glycosaminoglycan content was significantly elevated in the static control as compared to fresh or stretched cusps, but no difference was observed in collagen content among the groups. The strain profile of freshly isolated fibrosa vs. ventricularis and left, right, and noncoronary cusps were also determined by Digital Image Correlation technique. Distinct strain patterns were observed under stretch on fibrosa and ventricularis sides and among the three cusps. This work highlights the critical role of the anisotropic ECM structure for proper functions of native aortic valves and the beneficial effects of biaxial stretch for maintenance of the native ECM structure. Copyright © 2017 Elsevier Ltd. All rights reserved.

Assessing the stretch-blow moulding FE simulation of PET over a large process window

Science.gov (United States)

Nixon, J.; Menary, G. H.; Yan, S.

2017-10-01

Injection stretch blow moulding has been extensively researched for numerous years and is a well-established method of forming thin-walled containers. This paper is concerned with validating the finite element analysis of the stretch-blow-moulding (SBM) process in an effort to progress the development of injection stretch blow moulding of poly(ethylene terephthalate). Extensive data was obtained experimentally over a wide process window accounting for material temperature, air flow rate and stretch-rod speed while capturing cavity pressure, stretch-rod reaction force, in-mould contact timing and material thickness distribution. This data was then used to assess the accuracy of the correlating FE simulation constructed using ABAQUS/Explicit solver and an appropriate user-defined viscoelastic material subroutine. Results reveal that the simulation was able to pick up the general trends of how the pressure, reaction force and in-mould contact timings vary with the variation in preform temperature and air flow rate. Trends in material thickness were also accurately predicted over the length of the bottle relative to the process conditions. The knowledge gained from these analyses provides insight into the mechanisms of bottle formation, subsequently improving the blow moulding simulation and potentially providing a reduction in production costs.

Stretch Marks

Science.gov (United States)

... completely without the help of a dermatologist or plastic surgeon. These doctors may use one of many types of treatments — from actual surgery to techniques like microdermabrasion and laser treatment — to reduce the appearance of stretch marks. These techniques are ...

Finite element analysis of plantar fascia under stretch-the relative contribution of windlass mechanism and Achilles tendon force.

Science.gov (United States)

Cheng, Hsin-Yi Kathy; Lin, Chun-Li; Wang, Hsien-Wen; Chou, Shih-Wei

2008-01-01

Stretching plays an important role in the treatment of plantar fasciitis. Information on the internal stresses/strains of the plantar fascia under stretch is useful in enhancing knowledge on the stretch mechanisms. Although direct measurement can monitor plantar fascia changes, it is invasive and gathers only localized information. The purpose of this paper was to construct a three-dimensional finite element model of the foot to calculate the stretch effects on plantar fascia and monitor its stress/strain distributions and concentrations. A three-dimensional foot model was developed and contained 26 bones with joint cartilages, 67 ligaments and a fan-like solid plantar fascia modeling. All tissues were idealized as linear elastic, homogeneous and isotropic whilst the plantar fascia was assigned as hyperelastic to represent its nonlinearity. The plantar fascia was monitored for its biomechanical responses under various stretch combinations: three toe dorsiflexion angles (windlass effect: 15 degrees , 30 degrees and 45 degrees ) and five Achilles tendon forces (100, 200, 300, 400 and 500N). Our results indicated that the plantar fascia strain increased as the dorsiflexion angles increased, and this phenomenon was enhanced by increasing Achilles tendon force. A stress concentration was found near the medial calcaneal tubercle, and the fascia stress was higher underneath the first foot ray and gradually decreased as it moved toward the fifth ray. The current model recreated the position of the foot when stretch is placed on the plantar fascia. The results provided a general insight into the mechanical and biomechanical aspects of the influences of windlass mechanism and Achilles tendon force on plantar fascia stress and strain distribution. These findings might have practical implications onto plantar fascia stretch approaches, and provide guidelines to its surgical release.

Effects of Estrogen Fluctuation during the Menstrual Cycle on the Response to Stretch-Shortening Exercise in Females

Directory of Open Access Journals (Sweden)

Saulė Sipavičienė

2013-01-01

Full Text Available The aim of this study was to investigate whether variation in estrogen levels during the menstrual cycle influences susceptibility to exercise-induced muscle damage after stretch-shortening cycle exercise. Physically active women (n=18; age = 20.2 ± 1.7 yr participated in this research. The subjects performed one session of 100 maximal drop jumps on day 1 or 2 of the follicular phase and another identical session on day 1 or 2 of the ovulatory phase; the order of the sessions was randomized. Quadriceps femoris muscle peak torque evoked by electrical stimulation and maximal voluntary contraction, muscle pain, and CK activity were measured before and at various times up to 72 h after exercise. It was found that the high estrogen level during the ovulatory phase might be related to an earlier return to baseline muscle strength after strenuous stretch-shortening cycle exercise in that phase compared with the follicular phase. The estrogen effect appears to be highly specific to the damaged site because the differences in most EIMD markers (CK, soreness, and low-frequency fatigue between the two menstrual cycle phases were small.

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

2015-01-01

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 wa...

Structural Transitions in Supercoiled Stretched DNA

Science.gov (United States)

v, Croquette

1998-03-01

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 (for more details).

Visualization of velocity field and phase distribution in gas-liquid two-phase flow by NMR imaging

International Nuclear Information System (INIS)

Matsui, G.; Monji, H.; Obata, J.

2004-01-01

NMR imaging has been applied in the field of fluid mechanics, mainly single phase flow, to visualize the instantaneous flow velocity field. In the present study, NMR imaging was used to visualize simultaneously both the instantaneous phase structure and velocity field of gas-liquid two-phase flow. Two methods of NMR imaging were applied. One is useful to visualize both the one component of liquid velocity and the phase distribution. This method was applied to horizontal two-phase flow and a bubble rising in stagnant oil. It was successful in obtaining some pictures of velocity field and phase distribution on the cross section of the pipe. The other is used to visualize a two-dimensional velocity field. This method was applied to a bubble rising in a stagnant water. The velocity field was visualized after and before the passage of a bubble at the measuring cross section. Furthermore, the distribution of liquid velocity was obtained. (author)

A discrete electromechanical model for human cardiac tissue: effects of stretch-activated currents and stretch conditions on restitution properties and spiral wave dynamics.

Science.gov (United States)

Weise, Louis D; Panfilov, Alexander V

2013-01-01

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.

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.

Stretching and jamming of finite automata

NARCIS (Netherlands)

Beijer, de N.; Kourie, D.G.; Watson, B.W.; Cleophas, L.G.W.A.; Watson, B.W.

2004-01-01

In this paper we present two transformations on automata, called stretching and jamming. These transformations will, under certain conditions, reduce the size of the transition table, and under other conditions reduce the string processing time. Given a finite automaton, we can stretch it by

Anomalies in the coil-stretch transition of flexible polymers

Science.gov (United States)

Ghosal, Aishani; Cherayil, Binny J.

2018-03-01

The flow-induced coil-stretch transition of high molecular weight polymers has generally been held to be of first order. But evidence of significant slowing down in the rate at which the polymers relax to equilibrium in the vicinity of the transition suggests that the thermodynamic character of the transition may be less clear-cut. The above slowing down effect is actually characteristic of a second-order transition, and it points to the existence of a broad spectrum of conformational states in the transition region, analogous to the existence of fluctuations of all length scales at a critical point. In this paper, using a path integral approach based on a free-draining finitely extensible chain model, we calculate various polymer properties as a function of elongational flow as a way of exploring different statistical mechanical details of the coil-stretch transition. These properties include the molecular weight dependence of the flow-extension curve of the polymer, the distribution of its steady-state end-to-end distances, and the characteristic relaxation time τR of these distances. Among other findings, our calculations indicate that the coil-stretch transition is discontinuous in the N → ∞ limit, that the effective free energy of the chain is unimodal at all values of the flow, becoming broad and flat in the immediate vicinity of the transition, and that the ratio of τR to the Rouse relaxation time increases abruptly at the transition before eventually reaching a plateau value at large flow strengths. These aspects of the coil-stretch transition place it among a larger class of unconventional nominally first-order single chain transitions that include the adsorption transition of surface-tethered polymers and the escape transition of compressed polymers.

Distributed-phase OCDMA encoder-decoders based on fiber Bragg gratings

OpenAIRE

Zhang, Zhaowei; Tian, C.; Petropoulos, P.; Richardson, D.J.; Ibsen, M.

2007-01-01

We propose and demonstrate new optical code-division multiple-access (OCDMA) encoder-decoders having a continuous phase-distribution. With the same spatial refractive index distribution as the reconfigurable optical phase encoder-decoders, they are inherently suitable for the application in reconfigurable OCDMA systems. Furthermore, compared with conventional discrete-phase devices, they also have additional advantages of being more tolerant to input pulse width and, therefore, have the poten...

Motif distributions in phase-space networks for characterizing experimental two-phase flow patterns with chaotic features.

Science.gov (United States)

Gao, Zhong-Ke; Jin, Ning-De; Wang, Wen-Xu; Lai, Ying-Cheng

2010-07-01

The dynamics of two-phase flows have been a challenging problem in nonlinear dynamics and fluid mechanics. We propose a method to characterize and distinguish patterns from inclined water-oil flow experiments based on the concept of network motifs that have found great usage in network science and systems biology. In particular, we construct from measured time series phase-space complex networks and then calculate the distribution of a set of distinct network motifs. To gain insight, we first test the approach using time series from classical chaotic systems and find a universal feature: motif distributions from different chaotic systems are generally highly heterogeneous. Our main finding is that the distributions from experimental two-phase flows tend to be heterogeneous as well, suggesting the underlying chaotic nature of the flow patterns. Calculation of the maximal Lyapunov exponent provides further support for this. Motif distributions can thus be a feasible tool to understand the dynamics of realistic two-phase flow patterns.

Magnitude and duration of stretch modulate fibroblast remodeling.

Science.gov (United States)

Balestrini, Jenna L; Billiar, Kristen L

2009-05-01

Mechanical cues modulate fibroblast tractional forces and remodeling of extracellular matrix in healthy tissue, healing wounds, and engineered matrices. The goal of the present study is to establish dose-response relationships between stretch parameters (magnitude and duration per day) and matrix remodeling metrics (compaction, strength, extensibility, collagen content, contraction, and cellularity). Cyclic equibiaxial stretch of 2-16% was applied to fibroblast-populated fibrin gels for either 6 h or 24 h/day for 8 days. Trends in matrix remodeling metrics as a function of stretch magnitude and duration were analyzed using regression analysis. The compaction and ultimate tensile strength of the tissues increased in a dose-dependent manner with increasing stretch magnitude, yet remained unaffected by the duration in which they were cycled (6 h/day versus 24 h/day). Collagen density increased exponentially as a function of both the magnitude and duration of stretch, with samples stretched for the reduced duration per day having the highest levels of collagen accumulation. Cell number and failure tension were also dependent on both the magnitude and duration of stretch, although stretch-induced increases in these metrics were only present in the samples loaded for 6 h/day. Our results indicate that both the magnitude and the duration per day of stretch are critical parameters in modulating fibroblast remodeling of the extracellular matrix, and that these two factors regulate different aspects of this remodeling. These findings move us one step closer to fully characterizing culture conditions for tissue equivalents, developing improved wound healing treatments and understanding tissue responses to changes in mechanical environments during growth, repair, and disease states.

Single phase inverter for a three phase power generation and distribution system

Science.gov (United States)

Lindena, S. J.

1976-01-01

A breadboard design of a single-phase inverter with sinusoidal output voltage for a three-phase power generation and distribution system was developed. The three-phase system consists of three single-phase inverters, whose output voltages are connected in a delta configuration. Upon failure of one inverter the two remaining inverters will continue to deliver three-phase power. Parallel redundancy as offered by two three-phase inverters is substituted by one three-phase inverter assembly with high savings in volume, weight, components count and complexity, and a considerable increase in reliability. The following requirements must be met: (1) Each single-phase, current-fed inverter must be capable of being synchronized to a three-phase reference system such that its output voltage remains phaselocked to its respective reference voltage. (2) Each single-phase, current-fed inverter must be capable of accepting leading and lagging power factors over a range from -0.7 through 1 to +0.7.

Foam topology. Bending versus stretching dominated architectures

International Nuclear Information System (INIS)

Deshpande, V.; Ashby, M.; Fleck, N.

2000-01-01

Cellular solids can deform by either the bending or stretching of the cell walls. While most cellular solids are bending-dominated, those that are stretching-dominated are much more weight-efficient for structural applications. In this study we have investigated the topological criteria that dictate the deformation mechanism of a cellular solid by analysing the rigidity (or otherwise) of pin-jointed frameworks comprising inextensional struts. We show that the minimum node connectivity for a special class of lattice structured materials to be stretching-dominated is 6 for 2D foams and 12 for 3D foams. Similarly, sandwich plates comprising of truss cores faced with planar trusses require a minimum node connectivity of 9 to undergo stretching-dominated deformation for all loading states. (author)

Dynamics of the OH stretching mode in crystalline Ba(ClO4)2.3H2O

Science.gov (United States)

Hutzler, Daniel; Brunner, Christian; Petkov, Petko St.; Heine, Thomas; Fischer, Sighart F.; Riedle, Eberhard; Kienberger, Reinhard; Iglev, Hristo

2018-02-01

The vibrational dynamics of the OH stretching mode in Ba(ClO4)2 trihydrate are investigated by means of femtosecond infrared spectroscopy. The sample offers plane cyclic water trimers in the solid phase that feature virtually no hydrogen bond interaction between the water molecules. Selective excitation of the symmetric and asymmetric stretching leads to fast population redistribution, while simultaneous excitation yields quantum beats, which are monitored via a combination tone that dominates the overtone spectrum. The combination of steady-state and time-resolved spectroscopy with quantum chemical simulations and general theoretical considerations gives indication of various aspects of symmetry breakage. The system shows a joint population lifetime of 8 ps and a long-lived coherence between symmetric and asymmetric stretching, which decays with a time constant of 0.6 ps.

Stretched Exponential relaxation in pure Se glass

Science.gov (United States)

Dash, S.; Ravindren, S.; Boolchand, P.

A universal feature of glasses is the stretched exponential relaxation, f (t) = exp[ - t / τ ] β . The model of diffusion of excitations to randomly distributed traps in a glass by Phillips1 yields the stretched exponent β = d[d +2] where d, the effective dimensionality. We have measured the enthalpy of relaxation ΔHnr (tw) at Tg of Se glass in modulated DSC experiments as glasses age at 300K and find β = 0.43(2) for tw in the 0

A novel single-phase phase space-based voltage mode controller for distributed static compensator to improve voltage profile of distribution systems

International Nuclear Information System (INIS)

Shokri, Abdollah; Shareef, Hussain; Mohamed, Azah; Farhoodnea, Masoud; Zayandehroodi, Hadi

2014-01-01

Highlights: • A new phase space based voltage mode controller for D-STATCOM was proposed. • The proposed compensator was tested to mitigate voltage disturbances in distribution systems. • Voltage fluctuation, voltage sag and voltage swell are considered to evaluate the performance of the proposed compensator. - Abstract: Distribution static synchronous compensator (D-STATCOM) has been developed and attained a great interest to compensate the power quality disturbances of distribution systems. In this paper, a novel single-phase control scheme for D-STATCOM is proposed to improve voltage profile at the Point of Common Coupling (PCC). The proposed voltage mode (VM) controller is based on the phase space algorithm, which is able to rapidly detect and mitigate any voltage deviations from reference voltage including voltage sags and voltage swells. To investigate the efficiency and accuracy of the proposed compensator, a system is modeled using Matlab/Simulink. The simulation results approve the capability of the proposed VM controller to provide a regulated and disturbance-free voltage for the connected loads at the PCC

Optofluidic time-stretch microscopy: recent advances

Science.gov (United States)

Lei, Cheng; Nitta, Nao; Ozeki, Yasuyuki; Goda, Keisuke

2018-04-01

Flow cytometry is an indispensable method for valuable applications in numerous fields such as immunology, pathology, pharmacology, molecular biology, and marine biology. Optofluidic time-stretch microscopy is superior to conventional flow cytometry methods for its capability to acquire high-quality images of single cells at a high-throughput exceeding 10,000 cells per second. This makes it possible to extract copious information from cellular images for accurate cell detection and analysis with the assistance of machine learning. Optofluidic time-stretch microscopy has proven its effectivity in various applications, including microalga-based biofuel production, evaluation of thrombotic disorders, as well as drug screening and discovery. In this review, we discuss the principles and recent advances of optofluidic time-stretch microscopy.

Three-Phase AC Optimal Power Flow Based Distribution Locational Marginal Price: Preprint

Energy Technology Data Exchange (ETDEWEB)

Yang, Rui; Zhang, Yingchen

2017-05-17

Designing market mechanisms for electricity distribution systems has been a hot topic due to the increased presence of smart loads and distributed energy resources (DERs) in distribution systems. The distribution locational marginal pricing (DLMP) methodology is one of the real-time pricing methods to enable such market mechanisms and provide economic incentives to active market participants. Determining the DLMP is challenging due to high power losses, the voltage volatility, and the phase imbalance in distribution systems. Existing DC Optimal Power Flow (OPF) approaches are unable to model power losses and the reactive power, while single-phase AC OPF methods cannot capture the phase imbalance. To address these challenges, in this paper, a three-phase AC OPF based approach is developed to define and calculate DLMP accurately. The DLMP is modeled as the marginal cost to serve an incremental unit of demand at a specific phase at a certain bus, and is calculated using the Lagrange multipliers in the three-phase AC OPF formulation. Extensive case studies have been conducted to understand the impact of system losses and the phase imbalance on DLMPs as well as the potential benefits of flexible resources.

Stretch due to Penile Prosthesis Reservoir Migration

Directory of Open Access Journals (Sweden)

E. Baten

2016-03-01

Full Text Available A 43-year old patient presented to the emergency department with stretch, due to impossible deflation of the penile prosthesis, 4 years after successful implant. A CT-scan showed migration of the reservoir to the left rectus abdominis muscle. Refilling of the reservoir was inhibited by muscular compression, causing stretch. Removal and replacement of the reservoir was performed, after which the prosthesis was well-functioning again. Migration of the penile prosthesis reservoir is extremely rare but can cause several complications, such as stretch.

An alternative phase-space distribution to sample initial conditions for classical dynamics simulations

International Nuclear Information System (INIS)

Garcia-Vela, A.

2002-01-01

A new quantum-type phase-space distribution is proposed in order to sample initial conditions for classical trajectory simulations. The phase-space distribution is obtained as the modulus of a quantum phase-space state of the system, defined as the direct product of the coordinate and momentum representations of the quantum initial state. The distribution is tested by sampling initial conditions which reproduce the initial state of the Ar-HCl cluster prepared by ultraviolet excitation, and by simulating the photodissociation dynamics by classical trajectories. The results are compared with those of a wave packet calculation, and with a classical simulation using an initial phase-space distribution recently suggested. A better agreement is found between the classical and the quantum predictions with the present phase-space distribution, as compared with the previous one. This improvement is attributed to the fact that the phase-space distribution propagated classically in this work resembles more closely the shape of the wave packet propagated quantum mechanically

Quark imaging in the proton via quantum phase-space distributions

International Nuclear Information System (INIS)

Belitsky, A.V.; Ji Xiangdong; Yuan Feng

2004-01-01

We develop the concept of quantum phase-space (Wigner) distributions for quarks and gluons in the proton. To appreciate their physical content, we analyze the contraints from special relativity on the interpretation of elastic form factors, and examine the physics of the Feynman parton distributions in the proton's rest frame. We relate the quark Wigner functions to the transverse-momentum dependent parton distributions and generalized parton distributions, emphasizing the physical role of the skewness parameter. We show that the Wigner functions allow us to visualize quantum quarks and gluons using the language of classical phase space. We present two examples of the quark Wigner distributions and point out some model-independent features

Mechanical stretching of proteins-a theoretical survey of the Protein Data Bank

International Nuclear Information System (INIS)

Sulkowska, Joanna I; Cieplak, Marek

2007-01-01

The mechanical stretching of single proteins has been studied experimentally for about 50 proteins, yielding a variety of force patterns and peak forces. Here we perform a theoretical survey of proteins of known native structure and map out the landscape of possible dynamical behaviours under stretching at constant speed. We consider 7510 proteins comprising not more than 150 amino acids and 239 longer proteins. The model used is constructed based on the native geometry. It is solved by methods of molecular dynamics and validated by comparing the theoretical predictions to experimental results. We characterize the distribution of peak forces and investigate correlations with the system size and with the structure classification as characterized by the CATH scheme. Despite the presence of such correlations, proteins with the same CATH index may belong to different classes of dynamical behaviour. We identify proteins with the biggest forces and show that they belong to few topology classes. We determine which protein segments act as mechanical clamps and show that, in most cases, they correspond to long stretches of parallel β-strands, but other mechanisms are also possible. (topical review)

Mechanical stretching for tissue engineering: two-dimensional and three-dimensional constructs.

Science.gov (United States)

Riehl, Brandon D; Park, Jae-Hong; Kwon, Il Keun; Lim, Jung Yul

2012-08-01

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.

Immediate effects of different types of stretching exercises on badminton jump smash.

Science.gov (United States)

Jang, Hwi S; Kim, Daeho; Park, Jihong

2018-01-01

Since different types of stretching exercises may alter athletic performance, we compared the effects of three types of stretching exercises on badminton jump smash. Sixteen male collegiate badminton players performed one of three different stretching exercises in a counterbalanced order on different days. Static stretching had seven typical stretches, while dynamic stretching involved nine dynamic movements, and resistance dynamic stretching was performed with weighted vests and dumbbells. Before and after each stretching exercise, subjects performed 20 trials of jump smashes. Dependent measurements were the jump heights during jump smashes, velocities of jump-smashed shuttlecocks, and drop point of jump-smashed shuttlecocks. To test the effects of each stretching exercise, we performed mixed model ANOVAs and calculated between-time effect sizes (ES). Each stretching exercise improved the jump heights during jump smashes (type main effect: F(2,75)=1.19, P=0.31; static stretching: 22.1%, Pjump-smashed shuttlecocks (type main effect: F(2,75)=2.18, P=0.12; static stretching: 5.7%, P=0.61, ES=0.39; dynamic stretching: 3.4%, P=0.94, ES=0.28; resistance dynamic stretching: 6%, P=0.50, ES=0.66). However, there were no differences among the stretching exercises for any measurement. The drop point of jump-smashed shuttlecocks did not change (interaction: F(2,75)=0.88, P=0.42). All stretching exercises improved badminton jump smash performance, but we could not determine the best protocol. Since badminton requires high-speed movement and explosive force, we suggest performing dynamic stretching or resistance dynamic stretching.

Lattice stretching bistability and dynamic heterogeneity

DEFF Research Database (Denmark)

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

2012-01-01

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....

Comparing the effects of 3 weeks of upper-body vibration training, vibration and stretching, and stretching alone on shoulder flexibility in college-aged men.

Science.gov (United States)

Ferguson, Steven L; Kim, Eonho; Seo, Dong-Il; Bemben, Michael G

2013-12-01

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 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.

Bruxism: Is There an Indication for Muscle-Stretching Exercises?

Science.gov (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.

Tube Radial Distribution Flow Separation in a Microchannel Using an Ionic Liquid Aqueous Two-Phase System Based on Phase Separation Multi-Phase Flow.

Science.gov (United States)

Nagatani, Kosuke; Shihata, Yoshinori; Matsushita, Takahiro; Tsukagoshi, Kazuhiko

2016-01-01

Ionic liquid aqueous two-phase systems were delivered into a capillary tube to achieve tube radial distribution flow (TRDF) or annular flow in a microspace. The phase diagram, viscosity of the phases, and TRDF image of the 1-butyl-3-methylimidazolium chloride and NaOH system were examined. The TRDF was formed with inner ionic liquid-rich and outer ionic liquid-poor phases in the capillary tube. The phase configuration was explained using the viscous dissipation principle. We also examined the distribution of rhodamine B in a three-branched microchannel on a microchip with ionic liquid aqueous two-phase systems for the first time.

Distributed Strategy for Optimal Dispatch of Unbalanced Three-Phase Islanded Microgrids

DEFF Research Database (Denmark)

Vergara Barrios, Pedro Pablo; Rey-López, Juan Manuel; Shaker, Hamid Reza

2018-01-01

This paper presents a distributed strategy for the optimal dispatch of islanded microgrids, modeled as unbalanced three-phase electrical distribution systems (EDS). To set the dispatch of the distributed generation (DG) units, an optimal generation problem is stated and solved distributively based......-phase microgrid. According to the obtained results, the proposed strategy achieves a lower cost solution when compared with a centralized approach based on a static droop framework, with a considerable reduction on the communication system complexity. Additionally, it corrects the mismatch between generation...

Stretch induced endothelin-1 secretion by adult rat astrocytes involves calcium influx via stretch-activated ion channels (SACs)

International Nuclear Information System (INIS)

Ostrow, Lyle W.; Suchyna, Thomas M.; Sachs, Frederick

2011-01-01

Highlights: → Endothelin-1 expression by adult rat astrocytes correlates with cell proliferation. → Stretch-induced ET-1 is inhibited by GsMtx-4, a specific inhibitor of Ca 2+ permeant SACs. → The less specific SAC inhibitor streptomycin also inhibits ET-1 secretion. → Stretch-induced ET-1 production depends on a calcium influx. → SAC pharmacology may provide a new class of therapeutic agents for CNS pathology. -- Abstract: The expression of endothelins (ETs) and ET-receptors is often upregulated in brain pathology. ET-1, a potent vasoconstrictor, also inhibits the expression of astrocyte glutamate transporters and is mitogenic for astrocytes, glioma cells, neurons, and brain capillary endothelia. We have previously shown that mechanical stress stimulates ET-1 production by adult rat astrocytes. We now show in adult astrocytes that ET-1 production is driven by calcium influx through stretch-activated ion channels (SACs) and the ET-1 production correlates with cell proliferation. Mechanical stimulation using biaxial stretch ( 2+ threshold. This coupling of mechanical stress to the astrocyte endothelin system through SACs has treatment implications, since all pathology deforms the surrounding parenchyma.

BSDB: the Biomolecule Stretching Database

Science.gov (United States)

Cieplak, Marek; Sikora, Mateusz; Sulkowska, Joanna I.; Witkowski, Bartlomiej

2011-03-01

Despite more than a decade of experiments on single biomolecule manipulation, mechanical properties of only several scores of proteins have been measured. A characteristic scale of the force of resistance to stretching, Fmax , has been found to range between ~ 10 and 480 pN. The Biomolecule Stretching Data Base (BSDB) described here provides information about expected values of Fmax for, currently, 17 134 proteins. The values and other characteristics of the unfolding proces, including the nature of identified mechanical clamps, are available at www://info.ifpan.edu.pl/BSDB/. They have been obtained through simulations within a structure-based model which correlates satisfactorily with the available experimental data on stretching. BSDB also lists experimental data and results of the existing all-atom simulations. The database offers a Protein-Data-Bank-wide guide to mechano-stability of proteins. Its description is provided by a forthcoming Nucleic Acids Research paper. Supported by EC FUNMOL project FP7-NMP-2007-SMALL-1, and European Regional Development Fund: Innovative Economy (POIG.01.01.02-00-008/08).

Self-similar drop-size distributions produced by breakup in chaotic flows

International Nuclear Information System (INIS)

Muzzio, F.J.; Tjahjadi, M.; Ottino, J.M.; Department of Chemical Engineering, University of Massachusetts, Amherst, Massachusetts 01003; Department of Chemical Engineering, Northwestern University, Evanston, Illinois 60208)

1991-01-01

Deformation and breakup of immiscible fluids in deterministic chaotic flows is governed by self-similar distributions of stretching histories and stretching rates and produces populations of droplets of widely distributed sizes. Scaling reveals that distributions of drop sizes collapse into two self-similar families; each family exhibits a different shape, presumably due to changes in the breakup mechanism

Simulative design and process optimization of the two-stage stretch-blow molding process

Energy Technology Data Exchange (ETDEWEB)

Hopmann, Ch.; Rasche, S.; Windeck, C. [Institute of Plastics Processing at RWTH Aachen University (IKV) Pontstraße 49, 52062 Aachen (Germany)

2015-05-22

The total production costs of PET bottles are significantly affected by the costs of raw material. Approximately 70 % of the total costs are spent for the raw material. Therefore, stretch-blow molding industry intends to reduce the total production costs by an optimized material efficiency. However, there is often a trade-off between an optimized material efficiency and required product properties. Due to a multitude of complex boundary conditions, the design process of new stretch-blow molded products is still a challenging task and is often based on empirical knowledge. Application of current CAE-tools supports the design process by reducing development time and costs. This paper describes an approach to determine optimized preform geometry and corresponding process parameters iteratively. The wall thickness distribution and the local stretch ratios of the blown bottle are calculated in a three-dimensional process simulation. Thereby, the wall thickness distribution is correlated with an objective function and preform geometry as well as process parameters are varied by an optimization algorithm. Taking into account the correlation between material usage, process history and resulting product properties, integrative coupled simulation steps, e.g. structural analyses or barrier simulations, are performed. The approach is applied on a 0.5 liter PET bottle of Krones AG, Neutraubling, Germany. The investigations point out that the design process can be supported by applying this simulative optimization approach. In an optimization study the total bottle weight is reduced from 18.5 g to 15.5 g. The validation of the computed results is in progress.

Simulative design and process optimization of the two-stage stretch-blow molding process

International Nuclear Information System (INIS)

Hopmann, Ch.; Rasche, S.; Windeck, C.

2015-01-01

The total production costs of PET bottles are significantly affected by the costs of raw material. Approximately 70 % of the total costs are spent for the raw material. Therefore, stretch-blow molding industry intends to reduce the total production costs by an optimized material efficiency. However, there is often a trade-off between an optimized material efficiency and required product properties. Due to a multitude of complex boundary conditions, the design process of new stretch-blow molded products is still a challenging task and is often based on empirical knowledge. Application of current CAE-tools supports the design process by reducing development time and costs. This paper describes an approach to determine optimized preform geometry and corresponding process parameters iteratively. The wall thickness distribution and the local stretch ratios of the blown bottle are calculated in a three-dimensional process simulation. Thereby, the wall thickness distribution is correlated with an objective function and preform geometry as well as process parameters are varied by an optimization algorithm. Taking into account the correlation between material usage, process history and resulting product properties, integrative coupled simulation steps, e.g. structural analyses or barrier simulations, are performed. The approach is applied on a 0.5 liter PET bottle of Krones AG, Neutraubling, Germany. The investigations point out that the design process can be supported by applying this simulative optimization approach. In an optimization study the total bottle weight is reduced from 18.5 g to 15.5 g. The validation of the computed results is in progress

Multiplicity distributions in small phase-space domains in central nucleus-nucleus collisions

International Nuclear Information System (INIS)

Baechler, J.; Hoffmann, M.; Runge, K.; Schmoetten, E.; Bartke, J.; Gladysz, E.; Kowalski, M.; Stefanski, P.; Bialkowska, H.; Bock, R.; Brockmann, R.; Sandoval, A.; Buncic, P.; Ferenc, D.; Kadija, K.; Ljubicic, A. Jr.; Vranic, D.; Chase, S.I.; Harris, J.W.; Odyniec, G.; Pugh, H.G.; Rai, G.; Teitelbaum, L.; Tonse, S.; Derado, I.; Eckardt, V.; Gebauer, H.J.; Rauch, W.; Schmitz, N.; Seyboth, P.; Seyerlein, J.; Vesztergombi, G.; Eschke, J.; Heck, W.; Kabana, S.; Kuehmichel, A.; Lahanas, M.; Lee, Y.; Le Vine, M.; Margetis, S.; Renfordt, R.; Roehrich, D.; Rothard, H.; Schmidt, E.; Schneider, I.; Stock, R.; Stroebele, H.; Wenig, S.; Fleischmann, B.; Fuchs, M.; Gazdzicki, M.; Kosiec, J.; Skrzypczak, E.; Keidel, R.; Piper, A.; Puehlhofer, F.; Nappi, E.; Posa, F.; Paic, G.; Panagiotou, A.D.; Petridis, A.; Vassileiadis, G.; Pfenning, J.; Wosiek, B.

1992-10-01

Multiplicity distributions of negatively charged particles have been studied in restricted phase space intervals for central S + S, O + Au and S + Au collisions at 200 GeV/nucleon. It is shown that multiplicity distributions are well described by a negative binomial form irrespectively of the size and dimensionality of phase space domain. A clan structure analysis reveals interesting similarities between complex nuclear collisions and a simple partonic shower. The lognormal distribution agrees reasonably well with the multiplicity data in large domains, but fails in the case of small intervals. No universal scaling function was found to describe the shape of multiplicity distributions in phase space intervals of varying size. (orig.)

Imaging phase holdup distribution of three phase flow systems using dual source gamma ray tomography

International Nuclear Information System (INIS)

Varma, Rajneesh; Al-Dahhan, Muthanna; O'Sullivan, Joseph

2008-01-01

Full text: Multiphase reaction and process systems are used in abundance in the chemical and biochemical industry. Tomography has been successfully employed to visualize the hydrodynamics of multiphase systems. Most of the tomography methods (gamma ray, x-ray and electrical capacitance and resistance) have been successfully implemented for two phase dynamic systems. However, a significant number of chemical and biochemical systems consists of dynamic three phases. Research effort directed towards the development of tomography techniques to image such dynamic system has met with partial successes for specific systems with applicability to limited operating conditions. A dual source tomography scanner has been developed that uses the 661 keV and 1332 keV photo peaks from the 137 Cs and 60 Co for imaging three phase systems. A new approach has been developed and applied that uses the polyenergetic Alternating Minimization (A-M) algorithm, developed by O'Sullivan and Benac (2007), for imaging the holdup distribution in three phases' dynamic systems. The new approach avoids the traditional post image processing approach used to determine the holdup distribution where the attenuation images of the mixed flow obtained from gamma ray photons of two different energies are used to determine the holdup of three phases. In this approach the holdup images are directly reconstructed from the gamma ray transmission data. The dual source gamma ray tomography scanner and the algorithm were validated using a three phase phantom. Based in the validation, three phase holdup studies we carried out in slurry bubble column containing gas liquid and solid phases in a dynamic state using the dual energy gamma ray tomography. The key results of the holdup distribution studies in the slurry bubble column along with the validation of the dual source gamma ray tomography system would be presented and discussed

Phase size distribution in WC/Co hardmetal

International Nuclear Information System (INIS)

Roebuck, B.; Bennett, E.G.

1986-01-01

A high-resolution field emission scanning electron microscope was used to perform accurate quantitative metallography on a variety of WC/Co hardmetals. Particular attention was paid to obtaining the mean size and size distribution of the cobalt phase by linear analysis. Cobalt regions are frequently submicron and difficult to resolve adequately by conventional methods. The WC linear intercept distributions, and contiguity were also measured at the same time. The results were used to examine the validity of theoretic derivations of cobalt intercept size

Three-Phase Harmonic Analysis Method for Unbalanced Distribution Systems

Directory of Open Access Journals (Sweden)

Jen-Hao Teng

2014-01-01

Full Text Available Due to the unbalanced features of distribution systems, a three-phase harmonic analysis method is essential to accurately analyze the harmonic impact on distribution systems. Moreover, harmonic analysis is the basic tool for harmonic filter design and harmonic resonance mitigation; therefore, the computational performance should also be efficient. An accurate and efficient three-phase harmonic analysis method for unbalanced distribution systems is proposed in this paper. The variations of bus voltages, bus current injections and branch currents affected by harmonic current injections can be analyzed by two relationship matrices developed from the topological characteristics of distribution systems. Some useful formulas are then derived to solve the three-phase harmonic propagation problem. After the harmonic propagation for each harmonic order is calculated, the total harmonic distortion (THD for bus voltages can be calculated accordingly. The proposed method has better computational performance, since the time-consuming full admittance matrix inverse employed by the commonly-used harmonic analysis methods is not necessary in the solution procedure. In addition, the proposed method can provide novel viewpoints in calculating the branch currents and bus voltages under harmonic pollution which are vital for harmonic filter design. Test results demonstrate the effectiveness and efficiency of the proposed method.

The stretch reflex and the contributions of C David Marsden

Directory of Open Access Journals (Sweden)

Kalyan B Bhattacharyya

2017-01-01

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.

Phase pupil functions for focal-depth enhancement derived from a Wigner distribution function.

Science.gov (United States)

Zalvidea, D; Sicre, E E

1998-06-10

A method for obtaining phase-retardation functions, which give rise to an increase of the image focal depth, is proposed. To this end, the Wigner distribution function corresponding to a specific aperture that has an associated small depth of focus in image space is conveniently sheared in the phase-space domain to generate a new Wigner distribution function. From this new function a more uniform on-axis image irradiance can be accomplished. This approach is illustrated by comparison of the imaging performance of both the derived phase function and a previously reported logarithmic phase distribution.

Static stretching does not alter pre and post-landing muscle activation

Directory of Open Access Journals (Sweden)

Moss Wesley R

2011-05-01

Full Text Available Abstract Background Static stretching may result in various strength and power deficiencies. Prior research has not determined, however, if static stretching causes a change in muscle activation during a functional task requiring dynamic stability. The purpose of this study was to determine if static stretching has an effect on mean pre and postlanding muscle (vastus medialis VM, vastus lateralis VL, medial hamstring MH, and biceps femoris BF activity. Methods 26 healthy, physically active subjects were recruited, from which 13 completed a 14-day static stretching regimen for the quadriceps and hamstrings. Using the data from the force plate and EMG readings, a mean of EMG amplitude was calculated for 150 msec before and after landing. Each trial was normalized to an isometric reference position. Means were calculated for the VM, VL, MH, and BF from 5 trials in each session. Measures were collected pre, immediately following the 1st stretching session, and following 2 weeks of stretching. Results A 14-day static stretching regimen resulted in no significant differences in pre or postlanding mean EMG amplitude during a drop landing either acutely or over a 14-day period. Conclusions Static stretching, done acutely or over a 14-day period does not result in measurable differences of mean EMG amplitude during a drop landing. Static stretching may not impede dynamic stability of joints about which stretched muscles cross.

Wigner distribution, partial coherence, and phase-space optics

NARCIS (Netherlands)

Bastiaans, M.J.

2009-01-01

The Wigner distribution is presented as a perfect means to treat partially coherent optical signals and their propagation through first-order optical systems from a radiometric and phase-space optical perspective

Hydromagnetic Flow and Heat Transfer over a Porous Oscillating Stretching Surface in a Viscoelastic Fluid with Porous Medium.

Science.gov (United States)

Khan, Sami Ullah; Ali, Nasir; Abbas, Zaheer

2015-01-01

An analysis is carried out to study the heat transfer in unsteady two-dimensional boundary layer flow of a magnetohydrodynamics (MHD) second grade fluid over a porous oscillating stretching surface embedded in porous medium. The flow is induced due to infinite elastic sheet which is stretched periodically. With the help of dimensionless variables, the governing flow equations are reduced to a system of non-linear partial differential equations. This system has been solved numerically using the finite difference scheme, in which a coordinate transformation is used to transform the semi-infinite physical space to a bounded computational domain. The influence of the involved parameters on the flow, the temperature distribution, the skin-friction coefficient and the local Nusselt number is shown and discussed in detail. The study reveals that an oscillatory sheet embedded in a fluid-saturated porous medium generates oscillatory motion in the fluid. The amplitude and phase of oscillations depends on the rheology of the fluid as well as on the other parameters coming through imposed boundary conditions, inclusion of body force term and permeability of the porous medium. It is found that amplitude of flow velocity increases with increasing viscoelastic and mass suction/injection parameters. However, it decreases with increasing the strength of the applied magnetic field. Moreover, the temperature of fluid is a decreasing function of viscoelastic parameter, mass suction/injection parameter and Prandtl number.

An examination of the stretching practices of Division I and Division III college football programs in the midwestern United States.

Science.gov (United States)

Judge, Lawrence W; Craig, Bruce; Baudendistal, Steve; Bodey, Kimberly J

2009-07-01

Research supports the use of preactivity warm-up and stretching, and the purpose of this study was to determine whether college football programs follow these guidelines. Questionnaires designed to gather demographic, professional, and educational information, as well as specific pre- and postactivity practices, were distributed via e-mail to midwestern collegiate programs from NCAA Division I and III conferences. Twenty-three male coaches (12 from Division IA schools and 11 from Division III schools) participated in the study. Division I schools employed certified strength coaches (CSCS; 100%), whereas Division III schools used mainly strength coordinators (73%), with only 25% CSCS. All programs used preactivity warm-up, with the majority employing 2-5 minutes of sport-specific jogging/running drills. Pre stretching (5-10 minutes) was performed in 19 programs (91%), with 2 (9%) performing no pre stretching. Thirteen respondents used a combination of static/proprioceptive neuromuscular facilitation/ballistic and dynamic flexibility, 5 used only dynamic flexibility, and 1 used only static stretching. All 12 Division I coaches used stretching, whereas only 9 of the 11 Division III coaches did (p = 0.22). The results indicate that younger coaches did not use pre stretching (p = 0.30). The majority of the coaches indicated that they did use post stretching, with 11 of the 12 Division I coaches using stretching, whereas only 5 of the 11 Division III coaches used stretching postactivity (p = 0.027). Divisional results show that the majority of Division I coaches use static-style stretching (p = 0.049). The results of this study indicate that divisional status, age, and certification may influence how well research guidelines are followed. Further research is needed to delineate how these factors affect coaching decisions.

Simulation of the Two Stages Stretch-Blow Molding Process: Infrared Heating and Blowing Modeling

International Nuclear Information System (INIS)

Bordival, M.; Schmidt, F. M.; Le Maoult, Y.; Velay, V.

2007-01-01

In the Stretch-Blow Molding (SBM) process, the temperature distribution of the reheated perform affects drastically the blowing kinematic, the bottle thickness distribution, as well as the orientation induced by stretching. Consequently, mechanical and optical properties of the final bottle are closely related to heating conditions. In order to predict the 3D temperature distribution of a rotating preform, numerical software using control-volume method has been developed. Since PET behaves like a semi-transparent medium, the radiative flux absorption was computed using Beer Lambert law. In a second step, 2D axi-symmetric simulations of the SBM have been developed using the finite element package ABAQUS registered . Temperature profiles through the preform wall thickness and along its length were computed and applied as initial condition. Air pressure inside the preform was not considered as an input variable, but was automatically computed using a thermodynamic model. The heat transfer coefficient applied between the mold and the polymer was also measured. Finally, the G'sell law was used for modeling PET behavior. For both heating and blowing stage simulations, a good agreement has been observed with experimental measurements. This work is part of the European project ''APT P ACK'' (Advanced knowledge of Polymer deformation for Tomorrow's PACKaging)

Simulation of the Two Stages Stretch-Blow Molding Process: Infrared Heating and Blowing Modeling

Science.gov (United States)

Bordival, M.; Schmidt, F. M.; Le Maoult, Y.; Velay, V.

2007-05-01

In the Stretch-Blow Molding (SBM) process, the temperature distribution of the reheated perform affects drastically the blowing kinematic, the bottle thickness distribution, as well as the orientation induced by stretching. Consequently, mechanical and optical properties of the final bottle are closely related to heating conditions. In order to predict the 3D temperature distribution of a rotating preform, numerical software using control-volume method has been developed. Since PET behaves like a semi-transparent medium, the radiative flux absorption was computed using Beer Lambert law. In a second step, 2D axi-symmetric simulations of the SBM have been developed using the finite element package ABAQUS®. Temperature profiles through the preform wall thickness and along its length were computed and applied as initial condition. Air pressure inside the preform was not considered as an input variable, but was automatically computed using a thermodynamic model. The heat transfer coefficient applied between the mold and the polymer was also measured. Finally, the G'sell law was used for modeling PET behavior. For both heating and blowing stage simulations, a good agreement has been observed with experimental measurements. This work is part of the European project "APT_PACK" (Advanced knowledge of Polymer deformation for Tomorrow's PACKaging).

EFFECT OF DIFFERENT STRETCHING PROTOCOLS ON VERTICAL JUMP PERFORMANCE

Directory of Open Access Journals (Sweden)

Emre Serin

2018-04-01

Full Text Available This study aimed to examine the effect of different stretching exercises on vertical jump performance. A total of 14 national male athletes sporting in the elite level took part in the study. The age average of the participants was 20.25±1.03 year, the average height was 1.80±.08 m, the average body weight was 77.14±18.91 kg, average of sporting age was 9.87±3.31 year and the average number of participation in international games was 10.0±3.31. As stretching protocol: Method 1 (5 minutes of jogging and 2 minutes of active rest followed by Method 2 (static stretching for 4 different muscle groups 3 repetitions for 15 seconds of static stretching, rest for 10 seconds between groups and then consecutively, Method 3 (Dynamic stretching exercises with 3 repetitions for 15 seconds and 10 seconds rest between different muscle groups were applied in the study. The vertical jump performance before and after different stretching exercises of the participants was determined by means of the vertical jump test using the smart speed lite system. Before and after the training of all athletes, HR was recorded with a heart rate monitor (RS 800, Polar Vantage NV, Polar Electro Oy, Finland with 5 seconds intervals. Before the study, the chest band of the heartbeat monitor was placed on the chest of the athlete and the HR was recorded from the monitor. SPSS 15.0 statistical package program was used for evaluation and calculation of the data. In this study in addition to descriptive statistics (mean and standard deviation paired samples t-test was used to determine the difference between the vertical jump performance of the participants before and after different stretching exercises. As a result, this study showed that; applying the dynamic and static stretching exercises consecutively affected the vertical jump performance 4.5 cm positively (p<.05. It is suggested that different dynamic and static stretching exercises should be included in the vertical jump.

Effect of antisymmetric C–H stretching excitation on the dynamics of O({sup 1}D) + CH{sub 4} → OH + CH{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Pan, Huilin; Yang, Jiayue; Zhang, Dong; Shuai, Quan; Jiang, Bo [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023 (China); Dai, Dongxu; Wu, Guorong, E-mail: wugr@dicp.ac.cn, E-mail: xmyang@dicp.ac.cn; Yang, Xueming, E-mail: wugr@dicp.ac.cn, E-mail: xmyang@dicp.ac.cn [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023 (China); Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China)

2014-04-21

The effect of antisymmetric C–H stretching excitation of CH{sub 4} on the dynamics and reactivity of the O({sup 1}D) + CH{sub 4} → OH + CD{sub 3} reaction at the collision energy of 6.10 kcal/mol has been investigated using the crossed-beam and time-sliced velocity map imaging techniques. The antisymmetric C–H stretching mode excited CH{sub 4} molecule was prepared by direct infrared excitation. From the measured images of the CH{sub 3} products with the infrared laser on and off, the product translational energy and angular distributions were derived for both the ground and vibrationally excited reactions. Experimental results show that the vibrational energy of the antisymmetric stretching excited CH{sub 4} reagent is channeled exclusively into the vibrational energy of the OH co-products and, hence, the OH products from the excited-state reaction are about one vibrational quantum hotter than those from the ground-state reaction, and the product angular distributions are barely affected by the vibrational excitation of the CH{sub 4} reagent. The reactivity was found to be suppressed by the antisymmetric stretching excitation of CH{sub 4} for all observed CH{sub 3} vibrational states. The degree of suppression is different for different CH{sub 3} vibrational states: the suppression is about 40%–60% for the ground state and the umbrella mode excited CH{sub 3} products, while for the CH{sub 3} products with one quantum symmetric stretching mode excitation, the suppression is much less pronounced. In consequence, the vibrational state distribution of the CH{sub 3} product from the excited-state reaction is considerably different from that of the ground-state reaction.

Genomic Mapping of Human DNA provides Evidence of Difference in Stretch between AT and GC rich regions

Science.gov (United States)

Reifenberger, Jeffrey; Dorfman, Kevin; Cao, Han

Human DNA is a not a polymer consisting of a uniform distribution of all 4 nucleic acids, but rather contains regions of high AT and high GC content. When confined, these regions could have different stretch due to the extra hydrogen bond present in the GC basepair. To measure this potential difference, human genomic DNA was nicked with NtBspQI, labeled with a cy3 like fluorophore at the nick site, stained with YOYO, loaded into a device containing an array of nanochannels, and imaged. Over 473,000 individual molecules of DNA, corresponding to roughly 30x coverage of a human genome, were collected and aligned to the human reference. Based on the known AT/GC content between aligned pairs of labels, the stretch was measured for regions of similar size but different AT/GC content. We found that regions of high GC content were consistently more stretched than regions of high AT content between pairs of labels varying in size between 2.5 kbp and 500 kbp. We measured that for every 1% increase in GC content there was roughly a 0.06% increase in stretch. While this effect is small, it is important to take into account differences in stretch between AT and GC rich regions to improve the sensitivity of detection of structural variations from genomic variations. NIH Grant: R01-HG006851.

A Japanese Stretching Intervention Can Modify Lumbar Lordosis Curvature.

Science.gov (United States)

Kadono, Norio; Tsuchiya, Kazushi; Uematsu, Azusa; Kamoshita, Hiroshi; Kiryu, Kazunori; Hortobágyi, Tibor; Suzuki, Shuji

2017-08-01

Eighteen healthy male adults were assigned to either an intervention or control group. Isogai dynamic therapy (IDT) is one of Japanese stretching interventions and has been practiced for over 70 years. However, its scientific quantitative evidence remains unestablished. The objective of this study was to determine whether IDT could modify lumbar curvature in healthy young adults compared with stretching exercises used currently in clinical practice. None of previous studies have provided data that conventional stretching interventions could modify spinal curvatures. However, this study provides the first evidence that a specific form of a Japanese stretching intervention can acutely modify the spinal curvatures. We compared the effects of IDT, a Japanese stretching intervention (n=9 males), with a conventional stretching routine (n=9 males) used widely in clinics to modify pelvic tilt and lumbar lordosis (LL) angle. We measured thoracic kyphosis (TK) and LL angles 3 times during erect standing using the Spinal Mouse before and after each intervention. IDT consisted of: (1) hip joint correction, (2) pelvic tilt correction, (3) lumbar alignment correction, and (4) squat exercise stretch. The control group performed hamstring stretches while (1) standing and (2) sitting. IDT increased LL angle to 25.1 degrees (±5.9) from 21.2 degrees (±6.9) (P=0.047) without changing TK angle (pretest: 36.8 degrees [±6.9]; posttest: 36.1 degrees [±6.5]) (P=0.572). The control group showed no changes in TK (P=0.819) and LL angles (P=0.744). IDT can thus be effective for increasing LL angle, hence anterior pelvic tilt. Such modifications could ameliorate low back pain and improve mobility in old adults with an unfavorable pelvic position.

On magnetohydrodynamic flow of second grade nanofluid over a nonlinear stretching sheet

Energy Technology Data Exchange (ETDEWEB)

Hayat, Tasawar [Department of Mathematics, Quaid-I-Azam University, Islamabad 44000 (Pakistan); Nonlinear Analysis and Applied Mathematics (NAAM) Research Group, Department of Mathematics, Faculty of Science, King Abdulaziz University, P. O. Box 80203, Jeddah 21589 (Saudi Arabia); Aziz, Arsalan [Department of Mathematics, Quaid-I-Azam University, Islamabad 44000 (Pakistan); Muhammad, Taseer, E-mail: taseer_qau@yahoo.com [Department of Mathematics, Quaid-I-Azam University, Islamabad 44000 (Pakistan); Ahmad, Bashir [Nonlinear Analysis and Applied Mathematics (NAAM) Research Group, Department of Mathematics, Faculty of Science, King Abdulaziz University, P. O. Box 80203, Jeddah 21589 (Saudi Arabia)

2016-06-15

This research article addresses the magnetohydrodynamic (MHD) flow of second grade nanofluid over a nonlinear stretching sheet. Heat and mass transfer aspects are investigated through the thermophoresis and Brownian motion effects. Second grade fluid is assumed electrically conducting through a non-uniform applied magnetic field. Mathematical formulation is developed subject to small magnetic Reynolds number and boundary layer assumptions. Newly constructed condition having zero mass flux of nanoparticles at the boundary is incorporated. Transformations have been invoked for the reduction of partial differential systems into the set of nonlinear ordinary differential systems. The governing nonlinear systems have been solved for local behavior. Graphical results of different influential parameters are studied and discussed in detail. Computations for skin friction coefficient and local Nusselt number have been carried out. It is observed that the effects of thermophoresis parameter on the temperature and nanoparticles concentration distributions are qualitatively similar. The temperature and nanoparticles concentration distributions are enhanced for the larger magnetic parameter. - Highlights: • Constitutive relation for second grade fluid is employed. • Flow is caused by a nonlinear stretching surface. • Magnetic field applied is in transverse direction. • Nanofluid model consists of Brownian motion and thermophoresis. • Magnetic Reynolds number is assumed small.

On magnetohydrodynamic flow of second grade nanofluid over a nonlinear stretching sheet

International Nuclear Information System (INIS)

Hayat, Tasawar; Aziz, Arsalan; Muhammad, Taseer; Ahmad, Bashir

2016-01-01

This research article addresses the magnetohydrodynamic (MHD) flow of second grade nanofluid over a nonlinear stretching sheet. Heat and mass transfer aspects are investigated through the thermophoresis and Brownian motion effects. Second grade fluid is assumed electrically conducting through a non-uniform applied magnetic field. Mathematical formulation is developed subject to small magnetic Reynolds number and boundary layer assumptions. Newly constructed condition having zero mass flux of nanoparticles at the boundary is incorporated. Transformations have been invoked for the reduction of partial differential systems into the set of nonlinear ordinary differential systems. The governing nonlinear systems have been solved for local behavior. Graphical results of different influential parameters are studied and discussed in detail. Computations for skin friction coefficient and local Nusselt number have been carried out. It is observed that the effects of thermophoresis parameter on the temperature and nanoparticles concentration distributions are qualitatively similar. The temperature and nanoparticles concentration distributions are enhanced for the larger magnetic parameter. - Highlights: • Constitutive relation for second grade fluid is employed. • Flow is caused by a nonlinear stretching surface. • Magnetic field applied is in transverse direction. • Nanofluid model consists of Brownian motion and thermophoresis. • Magnetic Reynolds number is assumed small.

Distribution of dispersed oil phase in hydrocarbon fermentations

Energy Technology Data Exchange (ETDEWEB)

Ho, C S; Erickson, L E

1978-04-01

Recent experimental results show that the spreading coefficient frequently becomes positive when Candida lipolytica is cultivated on n-hexadecane. The effects of oil spreading at the surface of air bubbles in an airlift fermentor are examined using a mathematical model. The distribution of the oil phase with position and among the phases is determined using computer simulation. The simulation results qualitatively explain some of the experimental observations which have been previously reported.

The influence of stretching on tensile strength and solubility of poly(vinyl alcohol) fibres

NARCIS (Netherlands)

Heikens, D.; Bleijenberg, A.C.A.M.; Hoppenbrouwers, J.J.M.; Barentsen, W.M.

1971-01-01

The strength of wet-spun poly(vinyl alcohol) (pva) fibres is given as function of bath-stretching, wet-stretching and hot-stretching. In the two equations derived for strength of wet-stretching and hot-stretching the complex influence of the bath-stretching and hot-stretching is demonstrated. The

Mechanical stretching effect on the actuator performance of cellulose electroactive paper

International Nuclear Information System (INIS)

Kim, Jung-Hwan; Yun, Ki-Ju; Kim, Joo-Hyung; Kim, Jaehwan

2009-01-01

The mechanical stretching effect on the actuating performance of electroactive cellulose paper (EAPap) was studied. A lattice elongation of cellulose fibrils due to in-plane tensile stress along the stretching direction was observed by the x-ray diffraction method. The shrinkage of the fibril diameter as a function of stretching ratio was confirmed by surface and cross-sectional images. While the actuator performance in terms of bending displacement decreased as the stretching ratio increased, the resonance frequency linearly increased as the stretching ratio increased, which was compared with the theoretical frequency data found from a cantilever beam model. The actuator efficiency was evaluated from the electrical input power consumption and the mechanical output power of an EAPap actuator. It was revealed that the stretching process increased the electro-mechanical efficiency of the EAPap actuator. The mechanism of the influence of the stretching effect on the performance of an EAPap actuator is discussed

Immobilization and stretching of 5'-pyrene-terminated DNA on carbon film deposited on electron microscope grid.

Science.gov (United States)

Loukanov, Alexandre; Filipov, Chavdar; Lecheva, Marta; Emin, Saim

2015-11-01

The immobilization and stretching of randomly coiled DNA molecules on hydrophobic carbon film is a challenging microscopic technique, which possess various applications, especially for genome sequencing. In this report the pyrenyl nucleus is used as an anchor moiety to acquire higher affinity of double stranded DNA to the graphite surface. DNA and pyrene are joined through a linker composed of four aliphatic methylene groups. For the preparation of pyrene-terminated DNA a multifunctional phosphoramidite monomer compound was designed. It contains pyrenylbutoxy group as an anchor moiety for π-stacking attachment to the carbon film, 2-cyanoethyloxy, and diisopropylamino as coupling groups for conjugation to activated oligonucleotide chain or DNA molecule. This monomer derivative was suitable for incorporation into automated solid-phase DNA synthesis and was attached to the 5' terminus of the DNA chain through a phosphodiester linkage. The successful immobilization and stretching of pyrene-terminated DNA was demonstrated by conventional 100 kV transmission electron microscope. The microscopic analysis confirmed the stretched shape of the negatively charged nucleic acid pieces on the hydrophobic carbon film. © 2015 Wiley Periodicals, Inc.

ACUTE EFFECTS OF THREE DIFFERENT STRETCHING PROTOCOLS ON THE WINGATE TEST PERFORMANCE

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Bruno L. Franco

2012-03-01

Full Text Available 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 < 0.05. For PP, significant differences were observed between more comparisons, with PNF 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.

Stretching a semiflexible polymer with orientation-dependent interactions

International Nuclear Information System (INIS)

Zhen Yi; Vilgis, Thomas A

2009-01-01

The mean field variational approach is employed to study the effect of a nematic field and an external constant force field on the elasticity of a semiflexible polymer. In the stationary phase, we obtain the force–extension relationship and calculate the hairpin density of a stretched semiflexible polymer in nematic solvents. The force–extension behavior is found to be controlled by the parameters gl p and gf where g is the strength of the nematic field, l p is the bare persistence length and f is the external force. Several distinct regimes for the elastic response and the hairpin density emerge depending on the value of gl p and gf. Qualitative comparisons between our computation and other theories are presented

Eliminating electromechanical instability in dielectric elastomers by employing pre-stretch

International Nuclear Information System (INIS)

Jiang, Liang; Jerrams, Stephen; Betts, Anthony; Kennedy, David

2016-01-01

Electromechanical instability (EMI) is one of most common failure modes for dielectric elastomers (DEs). It has been reported that pre-stretching a DE sample can suppress EMI due to strain stiffening taking place for larger strains and a higher elastic modulus are achieved at high stretch ratios when a voltage is applied to the material. In this work, the influence of equi-biaxial stretch on DE secant modulus was studied using VHB 4910 and silicone rubber (SR) composites containing barium titanate (BaTiO 3 , BT) particles and also dopamine coated BT (DP-BT) particles. The investigation of equi-biaxial deformation and EMI failure for VHB 4910 was undertaken by introducing a voltage-stretch function. The results showed that EMI was suppressed by equi-biaxial pre-stretch for all the DEs fabricated and tested. The stiffening properties of the DE materials were also studied with respect to the secant modulus. Furthermore, a voltage-induced strain of above 200% was achieved for the polyacrylate film by applying a pre-stretch ratio of 2.0 without EMI occurring. However, a maximum voltage-induced strain in the polyacrylate film of 78% was obtained by the SR/20 wt% DP-BT composite for a lower applied pre-stretch ratio of 1.6 and again EMI was eliminated. (paper)

Effects of Static Stretching and Playing Soccer on Knee Laxity.

Science.gov (United States)

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

2015-11-01

This study investigated exercise-induced effects of static stretching and playing soccer on anterior tibial translation (ATT) of the knee joint. Randomized controlled trial. University biomechanics laboratory. Thirty-one athletes were randomly assigned into a stretching (26.9 ± 6.2 years, 1.77 ± 0.09 m, 67.9 ± 10.7 kg) and a control group (27.9 ± 7.4 years, 1.75 ± 0.08 m, 72.0 ± 14.9 kg). Thirty-one amateur soccer players in an additional soccer group (25.1 ± 5.6 years, 1.74 ± 0.10 m, 71.8 ± 14.8 kg). All participants had no history of knee injury requiring surgery and any previous knee ligament or cartilage injury. The stretching group performed 4 different static stretching exercises with a duration of 2 × 20 seconds interspersed with breaks of 10 seconds. The soccer group completed a 90-minute soccer-specific training program. The control group did not perform any physical activity for approximately 30 minutes. Anterior tibial translation was measured with the KT-1000 knee arthrometer at forces of 67 N, 89 N, and maximal manual force (Max) before and after the intervention. There was a significant increase in ATT after static stretching and playing soccer at all applied forces. Maximal manual testing revealed a mean increase of ATT after static stretching of 2.1 ± 1.6 mm (P soccer of 1.0 ± 1.5 mm (P = 0.001). The ATT increase after static stretching at 67 and 89 N is significantly higher than in controls. At maximum manual testing, significant differences were evident between all groups. Static stretching and playing soccer increase ATT and may consequently influence mechanical factors of the anterior cruciate ligament. The ATT increase after static stretching was greater than after playing soccer. The observed increase in ATT after static stretching and playing soccer may be associated with changes in kinesthetic perception and sensorimotor control, activation of muscles, joint stability, overall performance, and higher injury risk.

Potential pitfalls of single phasing operation in a three phase distribution network

Energy Technology Data Exchange (ETDEWEB)

Narayanan, V S

1986-07-01

Finding it difficult to cope with the increased demand for electric power, some electricity boards have resorted to single phasing techniques in distribution system. This practice is harmful to the equipment in the power system. Some of the potential dangers associated with this undesirable practice are briefly discussed.

Acute effect of different stretching methods on isometric muscle strength

Directory of Open Access Journals (Sweden)

Gabriel Vasconcellos de Lima Costa e Silva

2014-03-01

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 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.

Upper Limb Static-Stretching Protocol Decreases Maximal Concentric Jump Performance

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Paulo H. Marchetti

2014-12-01

Full Text Available The purpose of the present study was to evaluate the acute effects of an upper limb static-stretching (SS protocol on the maximal concentric jump performance. We recruited 25 young healthy, male, resistance trained individuals (stretched group, n = 15 and control group, n = 10 in this study. The randomized between group experimental protocol consisted of a three trials of maximal concentric jump task, before and after a SS of the upper limb. Vertical ground reaction forces (vGRF and surface electromyography (sEMG of both gastrocnemius lateralis (GL and vastus lateralis (VL were acquired. An extensive SS was employed consisting of ten stretches of 30 seconds, with 15 seconds of rest, and 70-90% of the point of discomfort (POD. ANOVA (2x2 (group x condition was used for shoulder joint range of motion (ROM, vGRF and sEMG. A significant interaction for passive ROM of the shoulder joint revealed significant increases between pre- and post-SS protocol (p < 0.001. A significant interaction demonstrated decreased peak force and an increased peak propulsion duration between pre- and post-stretching only for stretch group (p = 0.021, and p = 0.024, respectively. There was a significant main effect between groups (stretch and control for peak force for control group (p = 0.045. Regarding sEMG variables, there were no significant differences between groups (control versus stretched or condition (pre-stretching versus post-stretching for the peak amplitude of RMS and IEMG for both muscles (VL and GL. In conclusion, an acute extensive SS can increase the shoulder ROM, and negatively affect both the propulsion duration and peak force of the maximal concentric jump, without providing significant changes in muscle activation.

Cyclic Stretch Alters Vascular Reactivity of Mouse Aortic Segments

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Arthur Leloup

2017-10-01

Full Text Available Large, elastic arteries buffer the pressure wave originating in the left ventricle and are constantly exposed to higher amplitudes of cyclic stretch (10% than muscular arteries (2%. As a crucial factor for endothelial and smooth muscle cell function, cyclic stretch has, however, never been studied in ex vivo aortic segments of mice. To investigate the effects of cyclic stretch on vaso-reactivity of mouse aortic segments, we used the Rodent Oscillatory Tension Set-up to study Arterial Compliance (ROTSAC. The aortic segments were clamped at frequencies of 6–600 bpm between two variable preloads, thereby mimicking dilation as upon left ventricular systole and recoiling as during diastole. The preloads corresponding to different transmural pressures were chosen to correspond to a low, normal or high amplitude of cyclic stretch. At different time intervals, cyclic stretch was interrupted, the segments were afterloaded and isometric contractions by α1-adrenergic stimulation with 2 μM phenylephrine in the absence and presence of 300 μM L-NAME (eNOS inhibitor and/or 35 μM diltiazem (blocker of voltage-gated Ca2+ channels were measured. As compared with static or cyclic stretch at low amplitude (<10 mN or low frequency (0.1 Hz, cyclic stretch at physiological amplitude (>10 mN and frequency (1–10 Hz caused better ex vivo conservation of basal NO release with time after mounting. The relaxation of PE-precontracted segments by addition of ACh to stimulate NO release was unaffected by cyclic stretch. In the absence of basal NO release (hence, presence of L-NAME, physiological in comparison with aberrant cyclic stretch decreased the baseline tension, attenuated the phasic contraction by phenylephrine in the absence of extracellular Ca2+ and shifted the smaller tonic contraction more from a voltage-gated Ca2+ channel-mediated to a non-selective cation channel-mediated. Data highlight the need of sufficient mechanical activation of endothelial and

Randomly displaced phase distribution design and its advantage in page-data recording of Fourier transform holograms.

Science.gov (United States)

Emoto, Akira; Fukuda, Takashi

2013-02-20

For Fourier transform holography, an effective random phase distribution with randomly displaced phase segments is proposed for obtaining a smooth finite optical intensity distribution in the Fourier transform plane. Since unitary phase segments are randomly distributed in-plane, the blanks give various spatial frequency components to an image, and thus smooth the spectrum. Moreover, by randomly changing the phase segment size, spike generation from the unitary phase segment size in the spectrum can be reduced significantly. As a result, a smooth spectrum including sidebands can be formed at a relatively narrow extent. The proposed phase distribution sustains the primary functions of a random phase mask for holographic-data recording and reconstruction. Therefore, this distribution is expected to find applications in high-density holographic memory systems, replacing conventional random phase mask patterns.

Stretching skeletal muscle: chronic muscle lengthening through sarcomerogenesis.

Directory of Open Access Journals (Sweden)

Alexander M Zöllner

Full Text Available Skeletal muscle responds to passive overstretch through sarcomerogenesis, the creation and serial deposition of new sarcomere units. Sarcomerogenesis is critical to muscle function: It gradually re-positions the muscle back into its optimal operating regime. Animal models of immobilization, limb lengthening, and tendon transfer have provided significant insight into muscle adaptation in vivo. Yet, to date, there is no mathematical model that allows us to predict how skeletal muscle adapts to mechanical stretch in silico. Here we propose a novel mechanistic model for chronic longitudinal muscle growth in response to passive mechanical stretch. We characterize growth through a single scalar-valued internal variable, the serial sarcomere number. Sarcomerogenesis, the evolution of this variable, is driven by the elastic mechanical stretch. To analyze realistic three-dimensional muscle geometries, we embed our model into a nonlinear finite element framework. In a chronic limb lengthening study with a muscle stretch of 1.14, the model predicts an acute sarcomere lengthening from 3.09[Formula: see text]m to 3.51[Formula: see text]m, and a chronic gradual return to the initial sarcomere length within two weeks. Compared to the experiment, the acute model error was 0.00% by design of the model; the chronic model error was 2.13%, which lies within the rage of the experimental standard deviation. Our model explains, from a mechanistic point of view, why gradual multi-step muscle lengthening is less invasive than single-step lengthening. It also explains regional variations in sarcomere length, shorter close to and longer away from the muscle-tendon interface. Once calibrated with a richer data set, our model may help surgeons to prevent muscle overstretch and make informed decisions about optimal stretch increments, stretch timing, and stretch amplitudes. We anticipate our study to open new avenues in orthopedic and reconstructive surgery and enhance

Structural Studies of Three-Arm Star Block Copolymers Exposed to Extreme Stretch Suggests a Persistent Polymer Tube

Science.gov (United States)

Mortensen, Kell; Borger, Anine L.; Kirkensgaard, Jacob J. K.; Garvey, Christopher J.; Almdal, Kristoffer; Dorokhin, Andriy; Huang, Qian; Hassager, Ole

2018-05-01

We present structural small-angle neutron scattering studies of a three-armed polystyrene star polymer with short deuterated segments at the end of each arm. We show that the form factor of the three-armed star molecules in the relaxed state agrees with that of the random phase approximation of Gaussian chains. Upon exposure to large extensional flow conditions, the star polymers change conformation resulting in a highly stretched structure that mimics a fully extended three-armed tube model. All three arms are parallel to the flow, one arm being either in positive or negative stretching direction, while the two other arms are oriented parallel, right next to each other in the direction opposite to the first arm.

Filament stretching rheometer: inertia compensation revisited

DEFF Research Database (Denmark)

Szabo, Peter; McKinley, Gareth H.

2003-01-01

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...

Minimum-phase distribution of cosmic source brightness

International Nuclear Information System (INIS)

Gal'chenko, A.A.; Malov, I.F.; Mogil'nitskaya, L.F.; Frolov, V.A.

1984-01-01

Minimum-phase distributions of brightness (profiles) for cosmic radio sources 3C 144 (the wave lambda=21 cm), 3C 338 (lambda=3.5 m), and 3C 353 (labda=31.3 cm and 3.5 m) are obtained. A real possibility for the profile recovery from module fragments of its Fourier-image is shown

Hysteresis, phase transitions, and dangerous transients in electrical power distribution systems.

Science.gov (United States)

Duclut, Charlie; Backhaus, Scott; Chertkov, Michael

2013-06-01

The majority of dynamical studies in power systems focus on the high-voltage transmission grids where models consider large generators interacting with crude aggregations of individual small loads. However, new phenomena have been observed indicating that the spatial distribution of collective, nonlinear contribution of these small loads in the low-voltage distribution grid is crucial to the outcome of these dynamical transients. To elucidate the phenomenon, we study the dynamics of voltage and power flows in a spatially extended distribution feeder (circuit) connecting many asynchronous induction motors and discover that this relatively simple 1+1 (space+time) dimensional system exhibits a plethora of nontrivial spatiotemporal effects, some of which may be dangerous for power system stability. Long-range motor-motor interactions mediated by circuit voltage and electrical power flows result in coexistence and segregation of spatially extended phases defined by individual motor states, a "normal" state where the motors' mechanical (rotation) frequency is slightly smaller than the nominal frequency of the basic ac flows and a "stalled" state where the mechanical frequency is small. Transitions between the two states can be initiated by a perturbation of the voltage or base frequency at the head of the distribution feeder. Such behavior is typical of first-order phase transitions in physics, and this 1+1 dimensional model shows many other properties of a first-order phase transition with the spatial distribution of the motors' mechanical frequency playing the role of the order parameter. In particular, we observe (a) propagation of the phase-transition front with the constant speed (in very long feeders) and (b) hysteresis in transitions between the normal and stalled (or partially stalled) phases.

Numerical study of MHD nanofluid flow and heat transfer past a bidirectional exponentially stretching sheet

International Nuclear Information System (INIS)

Ahmad, Rida; Mustafa, M.; Hayat, T.; Alsaedi, A.

2016-01-01

Recent advancements in nanotechnology have led to the discovery of new generation coolants known as nanofluids. Nanofluids possess novel and unique characteristics which are fruitful in numerous cooling applications. Current work is undertaken to address the heat transfer in MHD three-dimensional flow of magnetic nanofluid (ferrofluid) over a bidirectional exponentially stretching sheet. The base fluid is considered as water which consists of magnetite–Fe 3 O 4 nanoparticles. Exponentially varying surface temperature distribution is accounted. Problem formulation is presented through the Maxwell models for effective electrical conductivity and effective thermal conductivity of nanofluid. Similarity transformations give rise to a coupled non-linear differential system which is solved numerically. Appreciable growth in the convective heat transfer coefficient is observed when nanoparticle volume fraction is augmented. Temperature exponent parameter serves to enhance the heat transfer from the surface. Moreover the skin friction coefficient is directly proportional to both magnetic field strength and nanoparticle volume fraction. - Highlights: • Nanofluid flow due to exponentially stretching sheet. • Exponentially varying surface temperature distribution is accounted. • Sparrow–Gregg type Hills (SGH) for temperature distribution exist. • Numerical values of local Nusselt number are presented. • Cooling performance of ferrofluid is superior to pure water.

Origin of stretched-exponential photoluminescence relaxation in size-separated silicon nanocrystals

Directory of Open Access Journals (Sweden)

Samuel L. Brown

2017-05-01

Full Text Available A detailed understanding of the photoluminescence (PL from silicon nanocrystals (SiNCs is convoluted by the complexity of the decay mechanism, including a stretched-exponential relaxation and the presence of both nanosecond and microsecond time scales. In this publication, we analyze the microsecond PL decay of size-resolved SiNC fractions in both full-spectrum (FS and spectrally resolved (SR configurations, where the stretching exponent and lifetime are used to deduce a probability distribution function (PDF of decay rates. For the PL decay measured at peak emission, we find a systematic shift and narrowing of the PDF in comparison to the FS measurements. In a similar fashion, we resolve the PL lifetime of the ‘blue’, ‘peak’, and ‘red’ regions of the spectrum and map PL decays of different photon energy onto their corresponding location in the PDF. A general trend is observed where higher and lower photon energies are correlated with shorter and longer lifetimes, respectively, which we relate to the PL line width and electron-phonon coupling.

No evidence hip joint angle modulates intrinsically produced stretch reflex in human hopping.

Science.gov (United States)

Gibson, W; Campbell, A; Allison, G

2013-09-01

Motor output in activities such as walking and hopping is suggested to be mediated neurally by purported stretch reflex augmentation of muscle output. Reflex EMG activity during these tasks has been frequently investigated in the soleus muscle; with alterations in reflex amplitude being associated with changes in hip joint angle/phase of the gait cycle. Previous work has focussed on reflex activity induced by an artificial perturbation or by induction of H-reflexes. As such, it is currently unknown if stretch reflex activity induced intrinsically (as part of the task) is modulated by changes in hip joint angle. This study investigated whether hip joint angle modulated reflex EMG 'burst' activity during a hopping task performed on a custom-built partially reclined sleigh. Ten subjects participated; EMG and kinematic data (VICON motor capture system) was collected for each hop cycle. Participants completed 5 sets of 30s of self-paced hopping in (1) hip neutral and (2) hip 60° flexion conditions. There was no difference in EMG 'burst' activity or in sagittal plane kinematics (knee/ankle) in the hopping task between the two conditions. The results indicate that during a functional task such as hopping, changes in hip angle do not alter the stretch reflex-like activity associated with landing. Copyright © 2013 Elsevier B.V. All rights reserved.

Three-Phase Time-Multiplexed Planar Power Transmission to Distributed Implants.

Science.gov (United States)

Lee, Byunghun; Ahn, Dukju; Ghovanloo, Maysam

2016-03-01

A platform has been presented for wireless powering of receivers (Rx's) that are arbitrarily distributed over a large area. A potential application could be powering of small Rx implants, distributed over large areas of the brain. The transmitter (Tx) consists of three overlapping layers of hexagonal planar spiral coils (hex-PSC) that are horizontally shifted to provide the strongest and most homogeneous electromagnetic flux coverage. The three-layer hex-PSC array is driven by a three-phase time-division-multiplexed power Tx that takes the advantage of the carrier phase shift, coil geometries, and Rx time constant to homogeneously power the arbitrarily distributed Rx's regardless of their misalignments. The functionality of the proposed three-phase power transmission concept has been verified in a detailed scaled-up high-frequency structure simulator Advanced Design System simulation model and measurement setup, and compared with a conventional Tx. The new Tx delivers 5.4 mW to each Rx and achieves, on average, 5.8% power transfer efficiency to the Rx at the worst case 90° angular misalignment, compared with 1.4% by the conventional Tx.

Size distribution dynamics reveal particle-phase chemistry in organic aerosol formation

Science.gov (United States)

Shiraiwa, Manabu; Yee, Lindsay D.; Schilling, Katherine A.; Loza, Christine L.; Craven, Jill S.; Zuend, Andreas; Ziemann, Paul J.; Seinfeld, John H.

2013-01-01

Organic aerosols are ubiquitous in the atmosphere and play a central role in climate, air quality, and public health. The aerosol size distribution is key in determining its optical properties and cloud condensation nucleus activity. The dominant portion of organic aerosol is formed through gas-phase oxidation of volatile organic compounds, so-called secondary organic aerosols (SOAs). Typical experimental measurements of SOA formation include total SOA mass and atomic oxygen-to-carbon ratio. These measurements, alone, are generally insufficient to reveal the extent to which condensed-phase reactions occur in conjunction with the multigeneration gas-phase photooxidation. Combining laboratory chamber experiments and kinetic gas-particle modeling for the dodecane SOA system, here we show that the presence of particle-phase chemistry is reflected in the evolution of the SOA size distribution as well as its mass concentration. Particle-phase reactions are predicted to occur mainly at the particle surface, and the reaction products contribute more than half of the SOA mass. Chamber photooxidation with a midexperiment aldehyde injection confirms that heterogeneous reaction of aldehydes with organic hydroperoxides forming peroxyhemiacetals can lead to a large increase in SOA mass. Although experiments need to be conducted with other SOA precursor hydrocarbons, current results demonstrate coupling between particle-phase chemistry and size distribution dynamics in the formation of SOAs, thereby opening up an avenue for analysis of the SOA formation process. PMID:23818634

Size distribution dynamics reveal particle-phase chemistry in organic aerosol formation.

Science.gov (United States)

Shiraiwa, Manabu; Yee, Lindsay D; Schilling, Katherine A; Loza, Christine L; Craven, Jill S; Zuend, Andreas; Ziemann, Paul J; Seinfeld, John H

2013-07-16

Organic aerosols are ubiquitous in the atmosphere and play a central role in climate, air quality, and public health. The aerosol size distribution is key in determining its optical properties and cloud condensation nucleus activity. The dominant portion of organic aerosol is formed through gas-phase oxidation of volatile organic compounds, so-called secondary organic aerosols (SOAs). Typical experimental measurements of SOA formation include total SOA mass and atomic oxygen-to-carbon ratio. These measurements, alone, are generally insufficient to reveal the extent to which condensed-phase reactions occur in conjunction with the multigeneration gas-phase photooxidation. Combining laboratory chamber experiments and kinetic gas-particle modeling for the dodecane SOA system, here we show that the presence of particle-phase chemistry is reflected in the evolution of the SOA size distribution as well as its mass concentration. Particle-phase reactions are predicted to occur mainly at the particle surface, and the reaction products contribute more than half of the SOA mass. Chamber photooxidation with a midexperiment aldehyde injection confirms that heterogeneous reaction of aldehydes with organic hydroperoxides forming peroxyhemiacetals can lead to a large increase in SOA mass. Although experiments need to be conducted with other SOA precursor hydrocarbons, current results demonstrate coupling between particle-phase chemistry and size distribution dynamics in the formation of SOAs, thereby opening up an avenue for analysis of the SOA formation process.

Stretching single fibrin fibers hampers their lysis.

Science.gov (United States)

Li, Wei; Lucioni, Tomas; Li, Rongzhong; Bonin, Keith; Cho, Samuel S; Guthold, Martin

2017-09-15

Blood clots, whose main structural component is a mesh of microscopic fibrin fibers, experience mechanical strain from blood flow, clot retraction and interactions with platelets and other cells. We developed a transparent, striated and highly stretchable substrate made from fugitive glue (a styrenic block copolymer) to investigate how mechanical strain affects lysis of single, suspended fibrin fibers. In this suspended fiber assay, lysis manifested itself by fiber elongation, thickening (disassembly), fraying and collapse. Stretching single fibrin fibers significantly hampered their lysis. This effect was seen in uncrosslinked and crosslinked fibers. Crosslinking (without stretching) also hampered single fiber lysis. Our data suggest that strain is a novel mechanosensitive factor that regulates blood clot dissolution (fibrinolysis) at the single fiber level. At the molecular level of single fibrin molecules, strain may distort, or hinder access to, plasmin cleavage sites and thereby hamper lysis. Fibrin fibers are the major structural component of a blood clot. We developed a highly stretchable substrate made from fugitive glue and a suspended fibrin fiber lysis assay to investigate the effect of stretching on single fibrin fibers lysis. The key findings from our experiments are: 1) Fibers thicken and elongate upon lysis; 2) stretching strongly reduces lysis; 3) this effect is more pronounced for uncrosslinked fibers; and 4) stretching fibers has a similar effect on reducing lysis as crosslinking fibers. At the molecular level, strain may distort plasmin cleavage sites, or restrict access to those sites. Our results suggest that strain may be a novel mechanobiological factor that regulates fibrinolysis. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Halo formation in three-dimensional bunches with various phase space distributions

Directory of Open Access Journals (Sweden)

A. V. Fedotov

1999-01-01

Full Text Available A realistic treatment of halo formation must take into account 3D beam bunches and 6D phase space distributions. We recently constructed, analytically and numerically, a new class of self-consistent 6D phase space stationary distributions, which allowed us to study the halo development mechanism without being obscured by the effect of beam redistribution. In this paper we consider nonstationary distributions and study how the halo characteristics compare with those obtained using the stationary distribution. We then discuss the effect of redistribution on the halo development mechanism. In contrast to bunches with a large aspect ratio, we find that the effect of coupling between the r and z planes is especially important as the bunch shape becomes more spherical.

Growth of non-axisymmetric disturbances of the free surface in the filament stretching rheometer: experiments and simulation

DEFF Research Database (Denmark)

Rasmussen, Henrik Koblitz; Bach, Anders; Longin, Pierre-Yves

2002-01-01

A filament stretching rheometer has been equipped with a bottom plate with a number of equally distributed perturbations of the circular rim. The temporal development of the resulting disturbance of the meniscus is followed with video recording and with simulations. At high strain rates the surface...

Characterizing the stretch-flangeability of hot rolled multiphase steels

International Nuclear Information System (INIS)

Pathak, N.; Butcher, C.; Worswick, M.; Gao, J.

2013-01-01

Hole expansion tests are commonly used to characterize the edge stretching limit of a material. Traditionally, a conical punch is used to expand a punched hole until a through-thickness crack appears. However, many automotive stretch flanging operations involve in-plane edge stretching that is best captured with a flat punch. In this paper, hole expansion tests were carried out on two different hot-rolled multiphase steels using both flat and conical punches. The fracture mechanisms for both punch types were investigated using scanning electron microscopy (SEM)

Enhanced Age Strengthening of Mg-Nd-Zn-Zr Alloy via Pre-Stretching

Directory of Open Access Journals (Sweden)

Erjun Guo

2016-08-01

Full Text Available Pre-stretching was carried out to modify the microstructure of Mg-Nd-Zn-Zr alloy to enhance its age strengthening. The results indicated that more heterogeneous nucleation sites can be provided by the high density of dislocations caused by the plastic pre-stretching deformation, as well as speeding up the growth rate of precipitates. Comparison of microstructure in non-pre-stretched specimens after artificial aging showed that pre-stretched specimens exhibited a higher number density of precipitates. The fine and coarse plate-shaped precipitates were found in the matrix. Due to an increase in the number density of precipitates, the dislocation slipping during the deformation process is effectively hindered, and the matrix is strengthened. The yield strength stabilizes at 4% pre-stretching condition, and then the evolution is stable within the error bars. The 8% pre-stretched specimens can achieve an ultimate tensile strength of 297 MPa. However, further pre-stretching strains after 8% cannot supply any increase in strength. Tensile fracture surfaces of specimens subjected to pre-stretching strain mainly exhibit a trans-granular cleavage fracture. This work indicated that a small amount of pre-stretching strain can further increase strength of alloy and also effectively enhance the formation of precipitates, which can expand the application fields of this alloy.

Duration Dependent Effect of Static Stretching on Quadriceps and Hamstring Muscle Force

Directory of Open Access Journals (Sweden)

Leyla Alizadeh Ebadi

2018-03-01

Full Text Available The aim of this study was to determine the acute effect of static stretching on hamstring and quadriceps muscles’ isokinetic strength when applied for various durations to elite athletes, to investigate the effect of different static stretching durations on isokinetic strength, and finally to determine the optimal stretching duration. Fifteen elite male athletes from two different sport branches (10 football and five basketball participated in this study. Experimental protocol was designed as 17 repetitive static stretching exercises for hamstring and quadriceps muscle groups according to the indicated experimental protocols; ((A 5 min jogging; (B 5 min jogging followed by 15 s static stretching; (C 5 min jogging followed by 30 s static stretching; (D 5 min jogging, followed by static stretching for 45 s. Immediately after each protocol, an isokinetic strength test consisting of five repetitions at 60°/s speed and 20 repetitions at 180°/s speed was recorded for the right leg by the Isomed 2000 device. Friedman variance analysis test was employed for data analysis. According to the analyzes, it was observed that 5 min jogging and 15 s stretching exercises increased the isokinetic strength, whereas 30 and 45 s stretching exercises caused a decrease.

Optical stretching as a tool to investigate the mechanical properties of lipid bilayers.

Science.gov (United States)

Solmaz, Mehmet E; Sankhagowit, Shalene; Biswas, Roshni; Mejia, Camilo A; Povinelli, Michelle L; Malmstadt, Noah

2013-10-07

Measurements of lipid bilayer bending modulus by various techniques produce widely divergent results. We attempt to resolve some of this ambiguity by measuring bending modulus in a system that can rapidly process large numbers of samples, yielding population statistics. This system is based on optical stretching of giant unilamellar vesicles (GUVs) in a microfluidic dual-beam optical trap (DBOT). The microfluidic DBOT system is used here to measure three populations of GUVs with distinct lipid compositions. We find that gel-phase membranes are significantly stiffer than liquid-phase membranes, consistent with previous reports. We also find that the addition of cholesterol does not alter the bending modulus of membranes composed of a monounsaturated phospholipid.

Optical stretching as a tool to investigate the mechanical properties of lipid bilayers†

Science.gov (United States)

Solmaz, Mehmet E.; Sankhagowit, Shalene; Biswas, Roshni; Mejia, Camilo A.; Povinelli, Michelle L.; Malmstadt, Noah

2013-01-01

Measurements of lipid bilayer bending modulus by various techniques produce widely divergent results. We attempt to resolve some of this ambiguity by measuring bending modulus in a system that can rapidly process large numbers of samples, yielding population statistics. This system is based on optical stretching of giant unilamellar vesicles (GUVs) in a microfluidic dual-beam optical trap (DBOT). The microfluidic DBOT system is used here to measure three populations of GUVs with distinct lipid compositions. We find that gel-phase membranes are significantly stiffer than liquid-phase membranes, consistent with previous reports. We also find that the addition of cholesterol does not alter the bending modulus of membranes composed of a monounsaturated phospholipid. PMID:24244843

Distributed Rocket Engine Testing Health Monitoring System, Phase II

Data.gov (United States)

National Aeronautics and Space Administration — Leveraging the Phase I achievements of the Distributed Rocket Engine Testing Health Monitoring System (DiRETHMS) including its software toolsets and system building...

The influence of foot position on stretching of the plantar fascia.

Science.gov (United States)

Flanigan, Ryan M; Nawoczenski, Deborah A; Chen, Linlin; Wu, Hulin; DiGiovanni, Benedict F

2007-07-01

A recent study found nonweightbearing stretching exercises specific to the plantar fascia to be superior to the standard program of weightbearing Achilles tendon-stretching exercises in patients with chronic plantar fasciitis. The present study used a cadaver model to demonstrate the influence of foot and ankle position on stretching of the plantar fascia. Twelve fresh-frozen lower-leg specimens were tested in 15 different configurations representing various combinations of ankle and metatarsophalangeal (MTP) joint dorsiflexion, midtarsal transverse plane abduction and adduction, and forefoot varus and valgus. Measurements were recorded by a differential variable reluctance transducer (DVRT) implanted into the medial band of the plantar fascia, and primary measurement was a percent deformation of the plantar fascia (stretch) with respect to a reference position (90 degrees ankle dorsiflexion, 0 degrees midtarsal and forefoot orientation, and 0 degrees MTP dorsiflexion). Ankle and MTP joint dorsiflexion produced a significant increase (14.91%) in stretch compared to the position of either ankle dorsiflexion alone (9.31% increase, p plantar fascia tissue-specific stretching exercises and lends support to the use of ankle and MTP joint dorsiflexion when employing stretching protocols for nonoperative treatment in patients with chronic proximal plantar fasciitis.

Numerical and experimental investigation of stretch-flange forming

International Nuclear Information System (INIS)

Cinotti, N.; Shakeri, H.R.; Worswick, M.J.; Truttmann, S.; Finn, M.J.; Jain, M.; Lloyd, D.J.

2000-01-01

Simulations of stretch flange forming operations are undertaken using explicit dynamic finite element calculations incorporating anisotropic yield criteria. Simple circular stretch flanges utilizing a single circular punch to expand the cut-out were considered. Experiments were performed using 101mm diameter tooling on AA 5754 and AA 5182 aluminum alloy sheets, with varying cut-out and gauge size. Metallurgical aspects of the formability of these aluminum alloys and damage mechanisms were studied. Both optical and Scanning Electron Microscopy (SEM) were used to study ductile fracture behaviour in these materials during the forming operation. The limit strains obtained from the circular stretch flange formability experiments are compared to forming limit diagram (FLD) data from hemispherical dome specimens. (author)

Communication: A coil-stretch transition in planar elongational flow of an entangled polymeric melt

Science.gov (United States)

Nafar Sefiddashti, Mohammad H.; Edwards, Brian J.; Khomami, Bamin

2018-04-01

Virtual experimentation of atomistic entangled polyethylene melts undergoing planar elongational flow revealed an amazingly detailed depiction of individual macromolecular dynamics and the resulting effect on bistable configurational states. A clear coil-stretch transition was evident, in much the same form as first envisioned by de Gennes for dilute solutions of high polymers, resulting in an associated hysteresis in the configurational flow profile over the range of strain rates predicted by theory. Simulations conducted at steady state revealed bimodal distribution functions, in which equilibrium configurational states were simultaneously populated by relatively coiled and stretched molecules which could transition from one conformational mode to the other over a relatively long time scale at critical values of strain rates. The implication of such behavior points to a double-well conformational free energy potential with an activation barrier between the two configurational minima.

Entangled-Pair Transmission Improvement Using Distributed Phase-Sensitive Amplification

Directory of Open Access Journals (Sweden)

Anjali Agarwal

2014-12-01

Full Text Available We demonstrate the transmission of time-bin entangled photon pairs through a distributed optical phase-sensitive amplifier (OPSA. We utilize four-wave mixing at telecom wavelengths in a 5-km dispersion-shifted fiber OPSA operating in the low-gain limit. Measurements of two-photon interference curves show no statistically significant degradation in the fringe visibility at the output of the OPSA. In addition, coincidence counting rates are higher than direct passive transmission because of constructive interference between amplitudes of input photon pairs and those generated in the OPSA. Our results suggest that application of distributed phase-sensitive amplification to transmission of entangled photon pairs could be highly beneficial towards advancing the rate and scalability of future quantum communications systems.

Tritium distribution ratios between the 30 % tributyl phosphate(TBP)-normal dodecane(nDD) organic phase and uranyl nitrate-nitric acid aqueous phase

International Nuclear Information System (INIS)

Fujine, Sachio; Uchiyama, Gunzou; Sugikawa, Susumu; Maeda, Mitsuru; Tsujino, Takeshi.

1989-10-01

Tritium distribution ratios between the organic and aqueous phases were measured for the system of 30 % tributyl phosphate(TBP)-normal dodecane(nDD)/uranyl nitrate-nitric acid water. It was confirmed that tritium is extracted by TBP into the organic phase in both chemical forms of tritiated water (HTO) and tritiated nitric acid (TNO 3 ). The value of tritium distribution ratio ranged from 0.002 to 0.005 for the conditions of 0-6 mol/L nitric acid, 0.5-800 mCi/L tritium in aqueous phase, and 0-125 g-U/L uranium in organic phase. Isotopic distribution coefficient of tritium between the organic and aqueous phases was observed to be about 0.95. (author)

Stretch activates myosin light chain kinase in arterial smooth muscle

International Nuclear Information System (INIS)

Barany, K.; Rokolya, A.; Barany, M.

1990-01-01

Stretching of porcine carotid arterial muscle increased the phosphorylation of the 20 kDa myosin light chain from 0.23 to 0.68 mol [32P]phosphate/mol light chain, whereas stretching of phorbol dibutyrate treated muscle increased the phosphorylation from 0.30 to 0.91 mol/mol. Two-dimensional gel electrophoresis followed by two-dimensional tryptic phosphopeptide mapping was used to identify the enzyme involved in the stretch-induced phosphorylation. Quantitation of the [32P]phosphate content of the peptides revealed considerable light chain phosphorylation by protein kinase C only in the phorbol dibutyrate treated arterial muscle, whereas most of the light chain phosphorylation was attributable to myosin light chain kinase. Upon stretch of either the untreated or treated muscle, the total increment in [32P]phosphate incorporation into the light chain could be accounted for by peptides characteristic for myosin light chain kinase catalyzed phosphorylation, demonstrating that the stretch-induced phosphorylation is caused by this enzyme exclusively

Convective Heat Transfer Scaling of Ignition Delay and Burning Rate with Heat Flux and Stretch Rate in the Equivalent Low Stretch Apparatus

Science.gov (United States)

Olson, Sandra

2011-01-01

To better evaluate the buoyant contributions to the convective cooling (or heating) inherent in normal-gravity material flammability test methods, we derive a convective heat transfer correlation that can be used to account for the forced convective stretch effects on the net radiant heat flux for both ignition delay time and burning rate. The Equivalent Low Stretch Apparatus (ELSA) uses an inverted cone heater to minimize buoyant effects while at the same time providing a forced stagnation flow on the sample, which ignites and burns as a ceiling fire. Ignition delay and burning rate data is correlated with incident heat flux and convective heat transfer and compared to results from other test methods and fuel geometries using similarity to determine the equivalent stretch rates and thus convective cooling (or heating) rates for those geometries. With this correlation methodology, buoyant effects inherent in normal gravity material flammability test methods can be estimated, to better apply the test results to low stretch environments relevant to spacecraft material selection.

Stretch-sensitive paresis and effort perception in hemiparesis.

Science.gov (United States)

Vinti, Maria; Bayle, Nicolas; Hutin, Emilie; Burke, David; Gracies, Jean-Michel

2015-08-01

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 hemiparesis, voluntary ability to recruit agonist motoneurones is impaired--sometimes abolished--by antagonist stretch, a phenomenon defined here as stretch-sensitive paresis. In addition, spastic co-contraction increases effort perception, an additional incentive to evaluate and treat this phenomenon.

Spectrum of OH-stretching vibrations of water in a "floating" water bridge

Science.gov (United States)

Oshurko, V. B.; Ropyanoi, A. A.; Fedorov, A. N.; Fedosov, M. V.; Shelaeva, N. A.

2012-11-01

The axial distribution (over the cross section) of the spectra of the OH-stretching band of water in a water bridge is investigated using the Raman scattering method. It is found that the axial structure of the bridge is inhomogeneous: the core at the center of the bridge contains a larger amount of water with an "icelike" structure and a presumably larger number of H+ ions, while the outer layer probably consists of water with a larger number of OH- ions.

Role of Bending Energy and Knot Chirality in Knot Distribution and Their Effective Interaction along Stretched Semiflexible Polymers

Directory of Open Access Journals (Sweden)

Saeed Najafi

2016-09-01

Full Text Available Knots appear frequently in semiflexible (biopolymers, including double-stranded DNA, and their presence can affect the polymer’s physical and functional properties. In particular, it is possible and indeed often the case that multiple knots appear on a single chain, with effects which have only come under scrutiny in the last few years. In this manuscript, we study the interaction of two knots on a stretched semiflexible polymer, expanding some recent results on the topic. Specifically, we consider an idealization of a typical optical tweezers experiment and show how the bending rigidity of the chain—And consequently its persistence length—Influences the distribution of the entanglements; possibly more importantly, we observe and report how the relative chirality of the otherwise identical knots substantially modifies their interaction. We analyze the free energy of the chain and extract the effective interactions between embedded knots, rationalizing some of their pertinent features by means of simple effective models. We believe the salient aspect of the knot–knot interactions emerging from our study will be present in a large number of semiflexible polymers under tension, with important consequences for the characterization and manipulation of these systems—Be they artificial or biologica in origin—And for their technological application.

Ca2+ influx and ATP release mediated by mechanical stretch in human lung fibroblasts

International Nuclear Information System (INIS)

Murata, Naohiko; Ito, Satoru; Furuya, Kishio; Takahara, Norihiro; Naruse, Keiji; Aso, Hiromichi; Kondo, Masashi; Sokabe, Masahiro; Hasegawa, Yoshinori

2014-01-01

Highlights: • Uniaxial stretching activates Ca 2+ signaling in human lung fibroblasts. • Stretch-induced intracellular Ca 2+ elevation is mainly via Ca 2+ influx. • Mechanical strain enhances ATP release from fibroblasts. • Stretch-induced Ca 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 2+ concentration ([Ca 2+ ] 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 2+ ] i transiently increased in a strain-dependent manner. Hypotonic stress, which causes plasma membrane stretching, also transiently increased the [Ca 2+ ] i . The stretch-induced [Ca 2+ ] i elevation was attenuated in Ca 2+ -free solution. In contrast, the increase of [Ca 2+ ] i by a 20% stretch was not inhibited by the inhibitor of stretch-activated channels GsMTx-4, Gd 3+ , ruthenium red, or cytochalasin D. Cyclic stretching induced significant ATP releases from fibroblasts. However, the stretch-induced [Ca 2+ ] i elevation was not inhibited by ATP diphosphohydrolase apyrase or a purinergic receptor antagonist suramin. Taken together, mechanical stretch induces Ca 2+ influx independently of conventional stretch-sensitive ion channels, the actin cytoskeleton, and released ATP

Investigating the role of musical genre in human perception of music stretching resistance

OpenAIRE

Chen, Jun; Wang, Chaokun

2017-01-01

To stretch a music piece to a given length is a common demand in people's daily lives, e.g., in audio-video synchronization and animation production. However, it is not always guaranteed that the stretched music piece is acceptable for general audience since music stretching suffers from people's perceptual artefacts. Over-stretching a music piece will make it uncomfortable for human psychoacoustic hearing. The research on music stretching resistance attempts to estimate the maximum stretchab...

CFD prediction of flow and phase distribution in fuel assemblies with spacers

Energy Technology Data Exchange (ETDEWEB)

Anglart, H.; Nylund, O. [ABB Atom AB, Vasteras (Switzerland); Kurul, N. [Rensselaer Polytechnic Institute, Troy, NY (United States)] [and others

1995-09-01

This paper is concerned with the modeling and computation of multi-dimensional two-phase flows in BWR fuel assemblies. The modeling principles are presented based on using a two-fluid model in which lateral interfacial effects are accounted for. This model has been used to evaluate the velocity fields of both vapor and liquid phases, as well as phase distribution, between fuel elements in geometries similar to BWR fuel bundles. Furthermore, this model has been used to predict, in a detailed mechanistic manner, the effects of spacers on flow and phase distribution between, and pressure drop along, fuel elements. The related numerical simulations have been performed using a CFD computer code, CFDS-FLOW3D.

Equibiaxial cyclic stretch stimulates fibroblasts to rapidly remodel fibrin.

Science.gov (United States)

Balestrini, Jenna Leigh; Billiar, Kristen Lawrence

2006-01-01

Understanding the effects of the mechanical environment on wound healing is critical for developing more effective treatments to reduce scar formation and contracture. The aim of this study was to investigate the effects of dynamic mechanical stretch on cell-mediated early wound remodeling independent of matrix alignment which obscures more subtle remodeling mechanisms. Cyclic equibiaxial stretch (16% stretch at 0.2 Hz) was applied to fibroblast-populated fibrin gel in vitro wound models for eight days. Compaction, density, tensile strength, and collagen content were quantified as functional measures of remodeling. Stretched samples were approximately ten times stronger, eight-fold more dense, and eight times thinner than statically cultured samples. These changes were accompanied by a 15% increase in net collagen but no significant differences in cell number or viability. When collagen crosslinking was inhibited in stretched samples, the extensibility increased and the strength decreased. The apparent weakening was due to a reduction in compaction rather than a decrease in ability of the tissue to withstand tensile forces. Interestingly, inhibiting collagen crosslinking had no measurable effects on the statically cultured samples. These results indicate that amplified cell-mediated compaction and even a slight addition in collagen content play substantial roles in mechanically induced wound strengthening. These findings increase our understanding of how mechanical forces guide the healing response in skin, and the methods employed in this study may also prove valuable tools for investigating stretch-induced remodeling of other planar connective tissues and for creating mechanically robust engineered tissues.

Effectiveness of different exercises and stretching physiotherapy on pain and movement in patellofemoral pain syndrome: a randomized controlled trial.

Science.gov (United States)

Moyano, F Revelles; Valenza, M C; Martin, L Martin; Caballero, Y Castellote; Gonzalez-Jimenez, E; Demet, G Valenza

2013-05-01

To compare the effectiveness of proprioceptive neuromuscular facilitation combined with exercise, classic stretching physiotherapy intervention, and educational intervention at improving patient function and pain in patients with patellofemoral pain syndrome. Randomized, controlled, blind trial over four months. Urban population, Spain. Patients undergoing primary care for retropatellar pain. Subjects were allocated on three different treatment options: a proprioceptive neuromuscular facilitation and aerobic exercise group, a classic stretching group, and a control treatment were applied over four months under the supervision of a physiotherapist. Knee Society Score, pain reported (Visual analogue scale) and knee range of motion. Assessments were completed at baseline and after four months. 74 patients were enrolled in the study and distributed between groups. Both the proprioceptive neuromuscular facilitation and classic stretching group showed significant changes in all variables after four months intervention (p < 0.001). The difference in mean Kujala knee score changes between groups (classic stretching group vs. proprioceptive neuromuscular facilitation group vs. control group) at four months was -24.05 (95% confidence interval (CI) -30.19, -17.90), p ≤ 0.001; vs. -39.03 (95% confidence interval (CI) -42.5, -35.5), p ≤ 0.001; vs. -0.238 (95% confidence interval (CI) -1.2, 0.726), p = 0.621, respectively. A proprioceptive neuromuscular facilitation intervention protocol combined with aerobic exercise showed a better outcome than a classic stretching protocol after four months.

Differential-phase-shift quantum key distribution using coherent light

International Nuclear Information System (INIS)

Inoue, K.; Waks, E.; Yamamoto, Y.

2003-01-01

Differential-phase-shift quantum key distribution based on two nonorthogonal states is described. A weak coherent pulse train is sent from Alice to Bob, in which the phase of each pulse is randomly modulated by {0,π}. Bob measures the differential phase by a one-bit delay circuit. The system has a simple configuration without the need for an interferometer and a bright reference pulse in Alice's site, unlike the conventional QKD system based on two nonorthogonal states, and has an advantage of improved communication efficiency. The principle of the operation is successfully demonstrated in experiments

Lewis lung carcinoma regulation of mechanical stretch-induced protein synthesis in cultured myotubes.

Science.gov (United States)

Gao, Song; Carson, James A

2016-01-01

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. Copyright © 2016 the American Physiological Society.

Comment on "Wigner phase-space distribution function for the hydrogen atom"

DEFF Research Database (Denmark)

Dahl, Jens Peder; Springborg, Michael

1999-01-01

We object to the proposal that the mapping of the three-dimensional hydrogen atom into a four-dimensional harmonic oscillator can be readily used to determine the Wigner phase-space distribution function for the hydrogen atom. [S1050-2947(99)07005-5].......We object to the proposal that the mapping of the three-dimensional hydrogen atom into a four-dimensional harmonic oscillator can be readily used to determine the Wigner phase-space distribution function for the hydrogen atom. [S1050-2947(99)07005-5]....

Effects of special composite stretching on the swing of amateur golf players.

Science.gov (United States)

Lee, Joong-Chul; Lee, Sung-Wan; Yeo, Yun-Ghi; Park, Gi Duck

2015-04-01

[Purpose] The study investigated stretching for safer a golf swing compared to present stretching methods for proper swings in order to examine the effects of stretching exercises on golf swings. [Subjects] The subjects were 20 amateur golf club members who were divided into two groups: an experimental group which performed stretching, and a control group which did not. The subjects had no bone deformity, muscle weakness, muscle soreness, or neurological problems. [Methods] A swing analyzer and a ROM measuring instrument were used as the measuring tools. The swing analyzer was a GS400-golf hit ball analyzer (Korea) and the ROM measuring instrument was a goniometer (Korea). [Results] The experimental group showed a statistically significant improvement in driving distance. After the special stretching training for golf, a statistically significant difference in hit-ball direction deviation after swings were found between the groups. The experimental group showed statistically significant decreases in hit ball direction deviation. After the special stretching training for golf, statistically significant differences in hit-ball speed were found between the groups. The experimental group showed significant increases in hit-ball speed. [Conclusion] To examine the effects of a special stretching program for golf on golf swing-related factors, 20 male amateur golf club members performed a 12-week stretching training program. After the golf stretching training, statistically significant differences were found between the groups in hit-ball driving distance, direction deviation, deflection distance, and speed.

Stretching and folding mechanism in foams

International Nuclear Information System (INIS)

Tufaile, Alberto; Pedrosa Biscaia Tufaile, Adriana

2008-01-01

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

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: tufaile@usp.br; Pedrosa Biscaia Tufaile, Adriana [Escola de Artes, Ciencias e Humanidades, Soft Matter Laboratory, Universidade de Sao Paulo, 03828-000 Sao Paulo, SP (Brazil)

2008-10-13

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.

Phase distribution measurements in narrow rectangular channels using image processing techniques

International Nuclear Information System (INIS)

Bentley, C.; Ruggles, A.

1991-01-01

Many high flux research reactor fuel assemblies are cooled by systems of parallel narrow rectangular channels. The HFIR is cooled by single phase forced convection under normal operating conditions. However, two-phase forced convection or two phase mixed convection can occur in the fueled region as a result of some hypothetical accidents. Such flow conditions would occur only at decay power levels. The system pressure would be around 0.15 MPa in such circumstances. Phase distribution of air-water flow in a narrow rectangular channel is examined using image processing techniques. Ink is added to the water and clear channel walls are used to allow high speed still photographs and video tape to be taken of the air-water flow field. Flow field images are digitized and stored in a Macintosh 2ci computer using a frame grabber board. Local grey levels are related to liquid thickness in the flow channel using a calibration fixture. Image processing shareware is used to calculate the spatially averaged liquid thickness from the image of the flow field. Time averaged spatial liquid distributions are calculated using image calculation algorithms. The spatially averaged liquid distribution is calculated from the time averaged spatial liquid distribution to formulate the combined temporally and spatially averaged fraction values. The temporally and spatially averaged liquid fractions measured using this technique compare well to those predicted from pressure gradient measurements at zero superficial liquid velocity

Fatigue Crack Growth Characteristics of Cold Stretched STS 304 Welded Joint

Energy Technology Data Exchange (ETDEWEB)

Lee, Jeong Won; Na, Seong Hyeon; Yoon, Dong Hyun; Kim, Jae Hoon [Chungnam Nat’l Univ., Daejeon (Korea, Republic of); Kim, Young Kyun; Kim, Ki Dong [Korea Gas Coporation R& D Division, Daejeon (Korea, Republic of)

2017-09-15

STS 304 steel is used as pressure vessel material, and although it exhibits excellent mechanical characteristics at a low temperature, it is heavier than other materials. To address this issue, a method using cold-stretching techniques for STS 304 can be applied. In this study, a cold-stretching part and welded joint specimen were directly obtained from a cold-stretching pressure vessel manufactured according to ASME code. Fatigue crack propagation tests were carried out at room temperature and -170℃ using the compliance method for stress ratios of 0.1 and 0.5. The results indicate that crack growth rate of the welded joint is higher than that of the cold-stretching part within the same stress intensity factor range. The outcome of this work is expected to serve as a basis for the development of a cold-stretched STS 304 pressure vessel.

Team Size and Stretching-Exercise Effects on Simulated Chest Compression Performance and Exertion

Directory of Open Access Journals (Sweden)

Jessica C. Schoen

2017-09-01

Full Text Available Introduction: Investigators conducted a prospective experimental study to evaluate the effect of team size and recovery exercises on individual providers’ compression quality and exertion. Investigators hypothesized that 1 larger teams would perform higher quality compressions with less exertion per provider when compared to smaller teams; and 2 brief stretching and breathing exercises during rest periods would sustain compressor performance and mitigate fatigue. Methods: In Phase I, a volunteer cohort of pre-clinical medical students performed four minutes of continuous compressions on a Resusci-Anne manikin to gauge the spectrum of compressor performance in the subject population. Compression rate, depth, and chest recoil were measured. In Phase II, the highest-performing Phase I subjects were placed into 2-, 3-, and/or 4-compressor teams; 2-compressor teams were assigned either to control group (no recovery exercises or intervention group (recovery exercises during rest. All Phase II teams participated in 20-minute simulations with compressor rotation every two minutes. Investigators recorded compression quality and real-time heart rate data, and calculated caloric expenditure from contact heart rate monitor measurements using validated physiologic formulas. Results: Phase I subjects delivered compressions that were 24.9% (IQR1–3: [0.5%–74.1%] correct with a median rate of 112.0 (IQR1–3: [103.5–124.9] compressions per minute and depth of 47.2 (IQR1–3: [35.7–55.2] mm. In their first rotations, all Phase II subjects delivered compressions of similar quality and correctness (p=0.09. Bivariate analyses of 2-, 3-, and 4-compressor teams’ subject compression characteristics by subsequent rotation did not identify significant differences within or across teams. On multivariate analyses, only subjects in 2-compressor teams exhibited significantly lower compression rates (control subjects; p<0.01, diminished chest release (intervention

Microstructure, mechanical properties and stretch formability of Mg-3Al-0.5Ca-0.2Gd alloy processed at various finish rolling temperatures

Science.gov (United States)

Kang, Qiang; Jiang, Haitao; Zhang, Yun

2018-04-01

Effects of various finish rolling temperatures on the microstructure, texture, mechanical properties and stretch formability of rolled and annealed Mg-3Al-0.5Ca-0.2Gd (wt%) alloy were investigated in this paper, and it was found that compared with grain size and second phase particles, the basal textures, tensile properties and stretch formability Mg-3Al-0.5Ca-0.2Gd alloy are more sensitive to the increasing finishing rolling temperature. For the rolled and annealed Mg-3Al-0.5Ca-0.2Gd alloy, their grains barely grow up and second phase particles are slightly coarsened, while their basal poles are obviously weakened and tilted with increasing finish rolling temperature. Consequently, the weakened and RD-tilted basal textures are beneficial to the gradually improved elongation and stretch formability of Mg-3Al-0.5Ca-0.2Gd alloy. It is investigated that the gradually activated non-basal slips, e. g. 〈c 〉, 〈c + a〉 dislocations due to the increasing finish rolling temperature could contribute to the weakened RD-tilted textures in rolled and annealed Mg-3Al-0.5Ca-0.2Gd alloy.

Microtomography and pore-scale modeling of two-phase Fluid Distribution

Energy Technology Data Exchange (ETDEWEB)

Silin, D.; Tomutsa, L.; Benson, S.; Patzek, T.

2010-10-19

Synchrotron-based X-ray microtomography (micro CT) at the Advanced Light Source (ALS) line 8.3.2 at the Lawrence Berkeley National Laboratory produces three-dimensional micron-scale-resolution digital images of the pore space of the reservoir rock along with the spacial distribution of the fluids. Pore-scale visualization of carbon dioxide flooding experiments performed at a reservoir pressure demonstrates that the injected gas fills some pores and pore clusters, and entirely bypasses the others. Using 3D digital images of the pore space as input data, the method of maximal inscribed spheres (MIS) predicts two-phase fluid distribution in capillary equilibrium. Verification against the tomography images shows a good agreement between the computed fluid distribution in the pores and the experimental data. The model-predicted capillary pressure curves and tomography-based porosimetry distributions compared favorably with the mercury injection data. Thus, micro CT in combination with modeling based on the MIS is a viable approach to study the pore-scale mechanisms of CO{sub 2} injection into an aquifer, as well as more general multi-phase flows.

Radiative heat transfer with hydromagnetic flow and viscous dissipation over a stretching surface in the presence of variable heat flux

Directory of Open Access Journals (Sweden)

Kumar Hitesh

2009-01-01

Full Text Available The boundary layer steady flow and heat transfer of a viscous incompressible fluid due to a stretching plate with viscous dissipation effect in the presence of a transverse magnetic field is studied. The equations of motion and heat transfer are reduced to non-linear ordinary differential equations and the exact solutions are obtained using properties of confluent hypergeometric function. It is assumed that the prescribed heat flux at the stretching porous wall varies as the square of the distance from origin. The effects of the various parameters entering into the problem on the velocity field and temperature distribution are discussed.

The effectiveness of manual stretching in the treatment of plantar heel pain: a systematic review

Directory of Open Access Journals (Sweden)

Parish Ben

2011-06-01

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

All-passive pixel super-resolution of time-stretch imaging

Science.gov (United States)

Chan, Antony C. S.; Ng, Ho-Cheung; Bogaraju, Sharat C. V.; So, Hayden K. H.; Lam, Edmund Y.; Tsia, Kevin K.

2017-03-01

Based on image encoding in a serial-temporal format, optical time-stretch imaging entails a stringent requirement of state-of-the-art fast data acquisition unit in order to preserve high image resolution at an ultrahigh frame rate — hampering the widespread utilities of such technology. Here, we propose a pixel super-resolution (pixel-SR) technique tailored for time-stretch imaging that preserves pixel resolution at a relaxed sampling rate. It harnesses the subpixel shifts between image frames inherently introduced by asynchronous digital sampling of the continuous time-stretch imaging process. Precise pixel registration is thus accomplished without any active opto-mechanical subpixel-shift control or other additional hardware. Here, we present the experimental pixel-SR image reconstruction pipeline that restores high-resolution time-stretch images of microparticles and biological cells (phytoplankton) at a relaxed sampling rate (≈2-5 GSa/s)—more than four times lower than the originally required readout rate (20 GSa/s) — is thus effective for high-throughput label-free, morphology-based cellular classification down to single-cell precision. Upon integration with the high-throughput image processing technology, this pixel-SR time-stretch imaging technique represents a cost-effective and practical solution for large scale cell-based phenotypic screening in biomedical diagnosis and machine vision for quality control in manufacturing.

Stretching the Border

DEFF Research Database (Denmark)

Horstmann, Alexander

2014-01-01

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....

An Industrial Gauge for Measuring The Phase Distribution of Galvanneal

Energy Technology Data Exchange (ETDEWEB)

Christopher BUrnett; Roland Gouel; James R. Phillips

1996-01-19

Augmentation of the internal software of a commercial x-ray fluorescence gauge is shown to enable the instrument to extend its continuous on-line real-time measurements of a galvanneal coating's total elemental content to encompass similar measurements of the relative thickness of the coating's three principal metallurgical phases. The mathematical structure of this software augmentation is derived from the theory of neural networks. The empirical basis for the numerics embedded in the software's decision logic is presented. The performance of the augmented gauge is validated by comparing the gauge-implied real-time phase distribution with the phase distribution independently measured off-line on time-tagged samples drawn from the galvanneal production line where the measurement gauge had been installed. The performance validation is shown to demonstrate good agreement between the gauge and laboratory measurements and to suggest preferred approaches to be followed in future applications of the augmented gauge.

A Novel Non-Planar Transverse Stretching Process for Micro-Porous PTFE Membranes and Resulting Characteristics

KAUST Repository

Chang, Y.-H.

2018-02-26

Polytetrafluoroethylene (PTFE) micro-porous membranes were prepared from PTFE fine powder through extruding, rolling, and uniaxial longitudinally stretching. In contrast to conventional planar transverse stretching, a novel 3D mold design of non-planar transverse stretching process was employed in this study to produce micro-porous structure. The morphology, membrane thickness, mean pore size, and porosity of the PTFE membrane were investigated. The results show that the non-planar transverse stretched membranes exhibit more uniform average pore diameter with thinner membrane thickness. Morphological changes induced by planar and non-planar transverse stretching for pore characteristics were investigated. The stretching conditions, stretching temperature and rate, affect the stretched membrane. Increasing temperature facilitated the uniformity of pore size and uniformity of membrane thickness. Moreover, increase in stretching rate resulted in finer pore size and thinner membrane.

Examining flow-flame interaction and the characteristic stretch rate in vortex-driven combustion dynamics using PIV and numerical simulation

KAUST Repository

Hong, Seunghyuck; Speth, Raymond L.; Shanbhogue, Santosh J.; Ghoniem, Ahmed F.

2013-01-01

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.

Examining flow-flame interaction and the characteristic stretch rate in vortex-driven combustion dynamics using PIV and numerical simulation

KAUST Repository

Hong, Seunghyuck

2013-08-01

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.

Theory of high-force DNA stretching and overstretching.

Science.gov (United States)

Storm, C; Nelson, P C

2003-05-01

Single-molecule experiments on single- and double-stranded DNA have sparked a renewed interest in the force versus extension of polymers. The extensible freely jointed chain (FJC) model is frequently invoked to explain the observed behavior of single-stranded DNA, but this model does not satisfactorily describe recent high-force stretching data. We instead propose a model (the discrete persistent chain) that borrows features from both the FJC and the wormlike chain, and show that it resembles the data more closely. We find that most of the high-force behavior previously attributed to stretch elasticity is really a feature of the corrected entropic elasticity; the true stretch compliance of single-stranded DNA is several times smaller than that found by previous authors. Next we elaborate our model to allow coexistence of two conformational states of DNA, each with its own stretch and bend elastic constants. Our model is computationally simple and gives an excellent fit through the entire overstretching transition of nicked, double-stranded DNA. The fit gives the first value for the bend stiffness of the overstretched state. In particular, we find the effective bend stiffness for DNA in this state to be about 12 nm k(B)T, a value quite different from either the B-form or single-stranded DNA.

Fisher information and statistical inference for phase-type distributions

DEFF Research Database (Denmark)

Bladt, Mogens; Esparza, Luz Judith R; Nielsen, Bo Friis

2011-01-01

This paper is concerned with statistical inference for both continuous and discrete phase-type distributions. We consider maximum likelihood estimation, where traditionally the expectation-maximization (EM) algorithm has been employed. Certain numerical aspects of this method are revised and we...

The Acute Effects of Upper Extremity Stretching on Throwing Velocity in Baseball Throwers

Directory of Open Access Journals (Sweden)

Michael Williams

2013-01-01

Full Text Available Purpose. To examine the effects of static and proprioceptive neuromuscular facilitation (PNF stretching of the shoulder internal rotators on throwing velocity. Subjects. 27 male throwers (mean age = 25.1 years old, SD = 2.4 with adequate knowledge of demonstrable throwing mechanics. Study Design. Randomized crossover trial with repeated measures. Methods. Subjects warmed up, threw 10 pitches at their maximum velocity, were randomly assigned to 1 of 3 stretching protocols (static, PNF, or no stretch, and then repeated their 10 pitches. Velocities were recorded after each pitch and average and peak velocities were recorded after each session. Results. Data were analyzed using a repeated measures ANOVA. No significant interaction between stretching and throwing velocity was observed. Main effects for time were not statistically significant. Main effects for the stretching groups were statistically significant. Discussion. Results suggest that stretching of the shoulder internal rotators did not significantly affect throwing velocity immediately after stretching. This may be due to the complexity of the throwing task. Conclusions. Stretching may be included in a thrower's warm-up without any effects on throwing velocity. Further research should be performed using a population with more throwing experience and skill.

Efficacy of hamstring stretching programs in schoolchildren. A systematic review

Directory of Open Access Journals (Sweden)

Carlos-Alberto BECERRA FERNANDEZ

2017-03-01

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.

Implementation of a controller for linear positioners applicable in optical fiber stretching

International Nuclear Information System (INIS)

Castrillo Piedra, Andres Rodolfo

2014-01-01

A low cost controller is implemented for linear positioners applicable in optic fiber stretching. The possibility of using a donated equipment is evaluated by the Escuela de Ingenieria Mecanica. The equipment is required by the non-linear photonic research laboratory (NLPR-LAB) for stretching of micro structured fiber. The process has required a slow and precise stretching, so the controllers must be precisely programmed to rotate the motors at different speeds. Donated equipment is evaluated to see if it is possible to use for fiber stretching [es

Post-activation depression of soleus stretch reflexes in healthy and spastic humans

DEFF Research Database (Denmark)

Grey, Michael James; Klinge, Klaus; Crone, Clarissa

2007-01-01

Reduced depression of transmitter release from Ia afferents following previous activation (post-activation depression) has been suggested to be involved in the pathophysiology of spasticity. However, the effect of this mechanism on the myotatic reflex and its possible contribution to increased...... reflex excitability in spastic participants has not been tested. To investigate these effects, we examined post-activation depression in Soleus H-reflex responses and in mechanically evoked Soleus stretch reflex responses. Stretch reflex responses were evoked with consecutive dorsiflexion perturbations...... of the soleus stretch reflex and H-reflex decreased as the interval between the stimulus/perturbation was decreased. Similarly, the stretch-evoked torque decreased. In the spastic participants, the post-activation depression of both reflexes and the stretch-evoked torque was significantly smaller than...

Modelling a reliability system governed by discrete phase-type distributions

International Nuclear Information System (INIS)

Ruiz-Castro, Juan Eloy; Perez-Ocon, Rafael; Fernandez-Villodre, Gemma

2008-01-01

We present an n-system with one online unit and the others in cold standby. There is a repairman. When the online fails it goes to repair, and instantaneously a standby unit becomes the online one. The operational and repair times follow discrete phase-type distributions. Given that any discrete distribution defined on the positive integers is a discrete phase-type distribution, the system can be considered a general one. A model with unlimited number of units is considered for approximating a system with a great number of units. We show that the process that governs the system is a quasi-birth-and-death process. For this system, performance reliability measures; the up and down periods, and the involved costs are calculated in a matrix and algorithmic form. We show that the discrete case is not a trivial case of the continuous one. The results given in this paper have been implemented computationally with Matlab

Modelling a reliability system governed by discrete phase-type distributions

Energy Technology Data Exchange (ETDEWEB)

Ruiz-Castro, Juan Eloy [Departamento de Estadistica e Investigacion Operativa, Universidad de Granada, 18071 Granada (Spain)], E-mail: jeloy@ugr.es; Perez-Ocon, Rafael [Departamento de Estadistica e Investigacion Operativa, Universidad de Granada, 18071 Granada (Spain)], E-mail: rperezo@ugr.es; Fernandez-Villodre, Gemma [Departamento de Estadistica e Investigacion Operativa, Universidad de Granada, 18071 Granada (Spain)

2008-11-15

We present an n-system with one online unit and the others in cold standby. There is a repairman. When the online fails it goes to repair, and instantaneously a standby unit becomes the online one. The operational and repair times follow discrete phase-type distributions. Given that any discrete distribution defined on the positive integers is a discrete phase-type distribution, the system can be considered a general one. A model with unlimited number of units is considered for approximating a system with a great number of units. We show that the process that governs the system is a quasi-birth-and-death process. For this system, performance reliability measures; the up and down periods, and the involved costs are calculated in a matrix and algorithmic form. We show that the discrete case is not a trivial case of the continuous one. The results given in this paper have been implemented computationally with Matlab.

An analysis of the effect of buoyancy on phase distribution phenomena

International Nuclear Information System (INIS)

Maneesh Singhal; Richard T Lahey Jr

2005-01-01

Full text of publication follows: It is well known that pronounced lateral phase distributions may occur in two-phase conduit flows. Moreover, the lateral phase distribution appears to strongly influenced by the buoyancy of the dispersed phase. This study used a state-of-the-art two-fluid model, having no arbitrary coefficients, to predict steady, fully developed phase distribution in pipe flows. In particular, bubbly up-flows and down-flows in pipes, and slurry up-flows in pipes, having positive, negative and neutral buoyant particles, were analyzed and compared against appropriate terrestrial (1 g) data. In addition, microgravity bubbly flow data were also analyzed using the same two-fluid model. It was found that this two-fluid model was able to predict these data sets, including detailed predictions of the measured phasic velocity, dispersed phase volume fraction and turbulence (i.e., turbulent kinetic energy and Reynolds stress) fields. It was also found that the numerical algorithm, which was developed and used to evaluate the two-fluid model, was extremely efficient and could be easily run on a small PC. These results clearly demonstrate that a properly formulated two-fluid model, using mechanistically-based closure laws, can predict a wide range of multidimensional multiphase flow data without the need for 'tuners' and empirical correlations. Moreover, it appears that this approach can be used to develop and/or assess other flow-regime-specific closure laws for use in computational multiphase fluid dynamic (CMFD) solvers of transient two-fluid models, which, in turn, can be used for the design and analysis of various industrially important multiphase systems and processes. (authors)

Protective role of Nrf2 against mechanical-stretch-induced apoptosis in mouse fibroblasts: a potential therapeutic target of mechanical-trauma-induced stress urinary incontinence.

Science.gov (United States)

Li, Qiannan; Li, Bingshu; Liu, Cheng; Wang, Linlin; Tang, Jianming; Hong, Li

2018-01-10

We investigated the protective effect and underlying molecular mechanism of nuclear factor-E2-related factor 2 (Nrf2) against mechanical-stretch-induced apoptosis in mouse fibroblasts. Normal cells, Nrf2 silencing cells, and Nrf2 overexpressing cells were respectively divided into two groups-nonintervention and cyclic mechanical strain (CMS)-subjected to CMS of 5333 μ (1.0 Hz for 4 h), six groups in total (control, CMS, shNfe212, shNfe212 + CMS, LV-shNfe212, and LV-shNfe212 + CMS). After treatment, cell apoptosis; cell-cycle distribution; expressions of Nrf2, Bax, Bcl-2, Cyt-C, caspase-3, caspase-9, cleaved-caspase-3, and cleaved-caspase-9; mitochondrial membrane potential (ΔΨm); reactive oxygen species (ROS); and malondialdehyde (MDA) levels were measured. Thirty virgin female C57BL/6 mice were divided into two groups: control (without intervention) and vaginal distension (VD) groups, which underwent VD for 1 h with an 8-mm dilator (0.3 ml saline). Leak-point pressure (LPP) was tested on day 7 after VD; Nrf2 expression, apoptosis, and MDA levels were then measured in urethra and anterior vaginal wall. Mechanical stretch decreased Nrf2 messenger RNA (mRNA) and protein expressions. Overexpression of Nrf2 alleviated mechanical-stretch-induced cell apoptosis; S-phase arrest of cell cycle; up-regulation of Bax, cytochrome C (Cyt-C), ROS, MDA, ratio of cleaved-caspase-3/caspase-3 and cleaved-caspase-9/caspase-9; and exacerbated the decrease of Bcl2 and ΔΨm in L929 cells. On the contrary, silencing of Nrf2 showed opposite effects. Besides, VD reduced LPP levels and Nrf2 expression and increased cell apoptosis and MDA generation in the urethra and anterior vaginal wall. Nrf2 exhibits a protective role against mechanical-stretch -induced apoptosis on mouse fibroblasts, which might indicate a potential therapeutic target of mechanical-trauma-induced stress urinary incontinence (SUI).

Simulation on Effect of Preform Diameter in Injection Stretch Blow Molding

Science.gov (United States)

Tan, Z. Q.; Rosli, Nurrina; Oktaviandri, Muchamad

2018-03-01

Polyethylene terephthalate (PET) is the most common material of resin for manufacturing plastic bottle by injection stretch blow molding due to its excellent properties. As various issues of health and environmental hazards due to the PET use have risen, PET bottle manufacture may be improved by minimizing the wall thickness to reduce the PET use. One of the critical qualifications of the manufacturing process which lead to the wall thickness distribution is the initial preform diameter. In this project, we used the ANSYS Polyflow with aim to evaluate the wall thickness distribution of PET bottle for different diameter of initial preform. As a result, only 4 mm preform diameter presented wall thickness below than 1 mm. On the other hand, at least 6 mm preform diameter can permit the wall thickness 1.3 mm i.e. at the shoulder area.

A Phase Vocoder Based on Nonstationary Gabor Frames

DEFF Research Database (Denmark)

Ottosen, Emil Solsbæk; Dörfler, Monika

2017-01-01

We propose a new algorithm for time stretching music signals based on the theory of nonstationary Gabor frames (NSGFs). The algorithm extends the techniques of the classical phase vocoder (PV) by incorporating adaptive timefrequency (TF) representations and adaptive phase locking. The adaptive TF...

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: itori@med.nagoya-u.ac.jp [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)

2014-10-10

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.

Transient filament stretching rheometer II

DEFF Research Database (Denmark)

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

1997-01-01

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...

Investing in a Large Stretch Press

Science.gov (United States)

Choate, M.; Nealson, W.; Jay, G.; Buss, W.

1986-01-01

Press for forming large aluminum parts from plates provides substantial economies. Study assessed advantages and disadvantages of investing in large stretch-forming press, and also developed procurement specification for press.

The difference of phase distributions in silicon after indentation with Berkovich and spherical indenters

International Nuclear Information System (INIS)

Zarudi, I.; Zhang, L.C.; Cheong, W.C.D.; Yu, T.X.

2005-01-01

This study analyses the microstructure of monocrystalline silicon after indentation with a Berkovich and spherical indenter. Transmission electron microscopy on cross section view samples was used to explore the detailed distributions of various phases in the subsurfaces of indented silicon. It was found that an increase of the P max would promote the growth of the crystalline R8/BC8 phase at the bottom of the deformation zone. Microcracks were always generated in the range of the P max studied. It was also found that the deformation zones formed by the Berkovich and spherical indenters have very different phase distribution characteristics. A molecular dynamics simulation and finite element analysis supported the experimental observations and suggested that the distribution of the crystalline phases in the transformation zone after indentation was highly stress-dependent

How old is this bird? The age distribution under some phase sampling schemes.

Science.gov (United States)

Hautphenne, Sophie; Massaro, Melanie; Taylor, Peter

2017-12-01

In this paper, we use a finite-state continuous-time Markov chain with one absorbing state to model an individual's lifetime. Under this model, the time of death follows a phase-type distribution, and the transient states of the Markov chain are known as phases. We then attempt to provide an answer to the simple question "What is the conditional age distribution of the individual, given its current phase"? We show that the answer depends on how we interpret the question, and in particular, on the phase observation scheme under consideration. We then apply our results to the computation of the age pyramid for the endangered Chatham Island black robin Petroica traversi during the monitoring period 2007-2014.

Optimal stretching in the reacting wake of a bluff body.

Science.gov (United States)

Wang, Jinge; Tithof, Jeffrey; Nevins, Thomas D; Colón, Rony O; Kelley, Douglas H

2017-12-01

We experimentally study spreading of the Belousov-Zhabotinsky reaction behind a bluff body in a laminar flow. Locations of reacted regions (i.e., regions with high product concentration) correlate with a moderate range of Lagrangian stretching and that range is close to the range of optimal stretching previously observed in topologically different flows [T. D. Nevins and D. H. Kelley, Phys. Rev. Lett. 117, 164502 (2016)]. The previous work found optimal stretching in a closed, vortex dominated flow, but this article uses an open flow and only a small area of appreciable vorticity. We hypothesize that optimal stretching is common in advection-reaction-diffusion systems with an excitation threshold, including excitable and bistable systems, and that the optimal range depends on reaction chemistry and not on flow shape or characteristic speed. Our results may also give insight into plankton blooms behind islands in ocean currents.

Stretching of material lines in pseudo-turbulence induced by small rising bubbles

International Nuclear Information System (INIS)

Tanaka, M; Tsujimura, Y; Kanatani, H

2011-01-01

Direct numerical simulations have been conducted for the stretching of material lines in pseudo-turbulence induced by small rising bubbles in order to understand the mixing characteristics of bubbly flows. Contaminated bubbles are considered and are treated as light solid particles. An immersed boundary method has been used for evaluating the coupling force between the bubbles and the surrounding fluid flows. Numerical results show that the total length of material lines increases exponentially in time as a result of stretching and folding due to the rising bubbles. The material lines tend to accumulate in the wake regions of the bubbles, and they are strongly stretched in the vertical direction there. It is also found that the stretching rate of material lines increases with the mean void fraction when it is normalized by the magnitude of the rate-of-strain tensor of liquid flow in pseudo-turbulence. In the case of high void fractions, material lines tend to align with the direction of maximum stretching, and are effectively stretched.

Stretching of material lines in pseudo-turbulence induced by small rising bubbles

Energy Technology Data Exchange (ETDEWEB)

Tanaka, M; Tsujimura, Y; Kanatani, H, E-mail: mtanaka@kit.ac.jp [Department of Mechanical and System Engineering, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585 (Japan)

2011-12-22

Direct numerical simulations have been conducted for the stretching of material lines in pseudo-turbulence induced by small rising bubbles in order to understand the mixing characteristics of bubbly flows. Contaminated bubbles are considered and are treated as light solid particles. An immersed boundary method has been used for evaluating the coupling force between the bubbles and the surrounding fluid flows. Numerical results show that the total length of material lines increases exponentially in time as a result of stretching and folding due to the rising bubbles. The material lines tend to accumulate in the wake regions of the bubbles, and they are strongly stretched in the vertical direction there. It is also found that the stretching rate of material lines increases with the mean void fraction when it is normalized by the magnitude of the rate-of-strain tensor of liquid flow in pseudo-turbulence. In the case of high void fractions, material lines tend to align with the direction of maximum stretching, and are effectively stretched.

New kaolinite phases expanded through intercalation with potassium acetate

International Nuclear Information System (INIS)

Frost, R.L.; Kristof, J.; Kloprogge, J.T.

1998-01-01

Full text: Changes in the hydroxyl surfaces of potassium acetate-intercalated kaolinite have been studied over the ambient to predehydroxylation temperature range using a combination of X-ray diffraction and Raman spectroscopy. Upon intercalation, the kaolinite expanded along the c-axis direction to 13.88 Angstroms. Upon heating the intercalation complex over the 50 to 300 deg C range, X-ray diffraction shows the existence of three additional intercalation phases with d-spacings of 9.09, 9.60, and 11.47 Angstroms. The amount of each phase is temperature dependent. These expansions are reversible and upon cooling the intercalation complex returned to its original spacing. The 13.88 Angstroms phase only existed in the presence of water. It is proposed that the expanded kaolinite intercalation phases result from the orientation of the acetate within the intercalation complex. The Raman spectra of the hydroxyl-stretching region (Frost and van der Gaast, 1997) of potassium acetate-intercalated kaolinite has been obtained under an atmosphere of both air and nitrogen using a thermal stage over the 25 to 300 deg C temperature range (Johansson et al., 1998). Raman spectra of the C-C, C=O stretching and O-C-O bending modes show that at least two types of acetate are present in the intercalation complex. These are assigned to two different orientations of the acetate. At 25 deg C, a new band at 3606 cm -1 attributed to the inner surface hydroxyl hydrogen bonded to the acetate ion is observed with a concomitant loss of intensity in the bands attributed to the inner surface hydroxyls (Frost and Kristof, 1997, Frost et al.,1997). Heating the intercalation complex to 50 deg C results in two hydroxyl-stretching frequencies at 3594 and 3604 cm -1 . This change in frequencies is ascribed to phase changes of the potassium acetate-intercalated kaolinite. At 100 deg C, the bands shift to 3600 and 3613 cm -1 . These shifts in frequencies are assigned to new kaolinite expanded phases. At

The relationship between collisional phase defect distribution and cascade collapse efficiency

International Nuclear Information System (INIS)

Morishita, K.; Heinisch, H.L.; Ishino, S.; Sekimura, N.

1994-01-01

Defect distributions after the collisional phase of cascade damage processes were calculated using the computer simulation code MARLOWE, which is based on the binary collision approximation. The densities of vacant sites were evaluated in defect-dense regions at the end of the collisional phase in simulated ion irradiations of several pure metals (Au, Ag, Cu, Ni, Fe, Mo and W). The vacancy density distributions were compared to the measured cascade collapse efficiencies obtained from low-dose ion irradiations of thin foils reported in the literature to identify the minimum or ''critical'' values of the vacancy densities during the collisional phase corresponding to cascade collapse. The critical densities are generally independent of the cascade energy in the same metal. The relationships between physical properties of the target elements and the critical densities are discussed within the framework of the cascade thermal spike model. ((orig.))

Ensemble distribution for immiscible two-phase flow in porous media.

Science.gov (United States)

Savani, Isha; Bedeaux, Dick; Kjelstrup, Signe; Vassvik, Morten; Sinha, Santanu; Hansen, Alex

2017-02-01

We construct an ensemble distribution to describe steady immiscible two-phase flow of two incompressible fluids in a porous medium. The system is found to be ergodic. The distribution is used to compute macroscopic flow parameters. In particular, we find an expression for the overall mobility of the system from the ensemble distribution. The entropy production at the scale of the porous medium is shown to give the expected product of the average flow and its driving force, obtained from a black-box description. We test numerically some of the central theoretical results.

EFFECTS OF DYNAMIC AND STATIC STRETCHING WITHIN GENERAL AND ACTIVITY SPECIFIC WARM-UP PROTOCOLS

Directory of Open Access Journals (Sweden)

Michael Samson

2012-06-01

Full Text Available The purpose of the study was to determine the effects of static and dynamic stretching protocols within general and activity specific warm-ups. Nine male and ten female subjects were tested under four warm-up conditions including a 1 general aerobic warm-up with static stretching, 2 general aerobic warm-up with dynamic stretching, 3 general and specific warm-up with static stretching and 4 general and specific warm-up with dynamic stretching. Following all conditions, subjects were tested for movement time (kicking movement of leg over 0.5 m distance, countermovement jump height, sit and reach flexibility and 6 repetitions of 20 metre sprints. Results indicated that when a sport specific warm-up was included, there was an 0.94% improvement (p = 0.0013 in 20 meter sprint time with both the dynamic and static stretch groups. No such difference in sprint performance between dynamic and static stretch groups existed in the absence of the sport specific warm-up. The static stretch condition increased sit and reach range of motion (ROM by 2.8% more (p = 0.0083 than the dynamic condition. These results would support the use of static stretching within an activity specific warm-up to ensure maximal ROM along with an enhancement in sprint performance

Effect of CH stretching excitation on the reaction dynamics of F + CHD{sub 3} → DF + CHD{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Yang, Jiayue; Zhang, Dong; Chen, Zhen; Jiang, Bo [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, 457 Zhongshan Road, Dalian, Liaoning 116023 (China); Blauert, Florian [Dynamics at Surfaces, Faculty of Chemistry, Georg-August-Universität Göttingen, 37077 Göttingen (Germany); Dai, Dongxu; Wu, Guorong, E-mail: wugr@dicp.ac.cn, E-mail: xmyang@dicp.ac.cn; Zhang, Donghui; Yang, Xueming, E-mail: wugr@dicp.ac.cn, E-mail: xmyang@dicp.ac.cn [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, 457 Zhongshan Road, Dalian, Liaoning 116023 (China); Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China)

2015-07-28

The vibrationally excited reaction of F + CHD{sub 3}(ν{sub 1} = 1) → DF + CHD{sub 2} at a collision energy of 9.0 kcal/mol is investigated using the crossed-beams and time-sliced velocity map imaging techniques. Detailed and quantitative information of the CH stretching excitation effects on the reactivity and dynamics of the title reaction is extracted with the help of an accurate determination of the fraction of the excited CHD{sub 3} reagent in the crossed-beam region. It is found that all vibrational states of the CHD{sub 2} products observed in the ground-state reaction, which mainly involve the excitation of the umbrella mode of the CHD{sub 2} products, are severely suppressed by the CH stretching excitation. However, there are four additional vibrational states of the CHD{sub 2} products appearing in the excited-state reaction which are not presented in the ground-state reaction. These vibrational states either have the CH stretching excitation retained or involve one quantum excitation in the CH stretching and the excitation of the umbrella mode. Including all observed vibrational states, the overall cross section of the excited-state reaction is estimated to be 66.6% of that of the ground-state one. Experimental results also show that when the energy of CH stretching excitation is released during the reaction, it is deposited almost exclusively as the rovibrational energy of the DF products, with little portion in the translational degree of freedom. For vibrational states of the CHD{sub 2} products observed in both ground- and excited-state reactions, the CH stretching excitation greatly suppresses the forward scattered products, causing a noticeable change in the product angular distributions.

Contact of a spherical probe with a stretched rubber substrate

Science.gov (United States)

Frétigny, Christian; Chateauminois, Antoine

2017-07-01

We report on a theoretical and experimental investigation of the normal contact of stretched neo-Hookean substrates with rigid spherical probes. Starting from a published formulation of surface Green's function for incremental displacements on a prestretched, neo-Hookean, substrate [J. Mech. Phys. Solids 56, 2957 (2008), 10.1016/j.jmps.2008.07.002], a model is derived for both adhesive and nonadhesive contacts. The shape of the elliptical contact area together with the contact load and the contact stiffness are predicted as a function of the in-plane stretch ratios λx and λy of the substrate. The validity of this model is assessed by contact experiments carried out using an uniaxally stretched silicone rubber. For stretch ratio below about 1.25, a good agreement is observed between theory and experiments. Above this threshold, some deviations from the theoretical predictions are induced as a result of the departure of the mechanical response of the silicone rubber from the neo-Hokeean description embedded in the model.

Periostin inhibits mechanical stretch-induced apoptosis in osteoblast-like MG-63 cells.

Science.gov (United States)

Yu, Kai-Wen; Yao, Chung-Chen; Jeng, Jiiang-Huei; Shieh, Hao-Ying; Chen, Yi-Jane

2018-04-01

Appropriate mechanical stress plays an important role in regulating the proliferation and differentiation of osteoblasts, whereas high-level mechanical stress may be harmful and compromise cell survival. Periostin, a matricellular protein, is essential in maintaining functional integrity of bone and collagen-rich connective tissue in response to mechanical stress. This study investigated whether or not high-level mechanical stretch induces cell apoptosis and the regulatory role of periostin in mechanical stretch-induced apoptosis in osteoblastic cells. Osteoblast-like MG-63 cells were seeded onto Bio-Flex I culture plates and subjected to cyclic mechanical stretching (15% elongation, 0.1 Hz) in a Flexercell tension plus system-5000. The same process was applied to cells pre-treated with exogenous human recombinant periostin before mechanical stretching. We used a chromatin condensation and membrane permeability dead cell apoptosis kit to evaluate the stretch-induced cell responses. Expression of caspase-3 and cPARP was examined by immunofluorescent stain and flow cytometry. The expression of periostin in MG-63 cells is involved in the TGF-β signaling pathway. High-level cyclic mechanical stretch induced apoptotic responses in MG-63 osteoblastic cells. The percentages of apoptotic cells and cells expressing cPARP protein increased in the groups of cells subjected to mechanical stretch, but these responses were absent in the presence of exogenous periostin. Our study revealed that high-level mechanical stretch induces apoptotic cell death, and that periostin plays a protective role against mechanical stretch-induced apoptosis in osteoblastic cells. Copyright © 2017. Published by Elsevier B.V.

Surface behaviour of the phase-space distribution for heavy nuclei

International Nuclear Information System (INIS)

Durand, M.

1987-06-01

A part of the oscillations of the phase space distribution function is shown to be a surface effect. A series expansion for this function is given, which takes partially into account this oscillatory structure

Force encoding in muscle spindles during stretch of passive muscle.

Directory of Open Access Journals (Sweden)

Kyle P Blum

2017-09-01

Full Text Available Muscle spindle proprioceptive receptors play a primary role in encoding the effects of external mechanical perturbations to the body. During externally-imposed stretches of passive, i.e. electrically-quiescent, muscles, the instantaneous firing rates (IFRs of muscle spindles are associated with characteristics of stretch such as length and velocity. However, even in passive muscle, there are history-dependent transients of muscle spindle firing that are not uniquely related to muscle length and velocity, nor reproduced by current muscle spindle models. These include acceleration-dependent initial bursts, increased dynamic response to stretch velocity if a muscle has been isometric, and rate relaxation, i.e., a decrease in tonic IFR when a muscle is held at a constant length after being stretched. We collected muscle spindle spike trains across a variety of muscle stretch kinematic conditions, including systematic changes in peak length, velocity, and acceleration. We demonstrate that muscle spindle primary afferents in passive muscle fire in direct relationship to muscle force-related variables, rather than length-related variables. Linear combinations of whole muscle-tendon force and the first time derivative of force (dF/dt predict the entire time course of transient IFRs in muscle spindle Ia afferents during stretch (i.e., lengthening of passive muscle, including the initial burst, the dynamic response to lengthening, and rate relaxation following lengthening. Similar to acceleration scaling found previously in postural responses to perturbations, initial burst amplitude scaled equally well to initial stretch acceleration or dF/dt, though later transients were only described by dF/dt. The transient increase in dF/dt at the onset of lengthening reflects muscle short-range stiffness due to cross-bridge dynamics. Our work demonstrates a critical role of muscle cross-bridge dynamics in history-dependent muscle spindle IFRs in passive muscle

Force encoding in muscle spindles during stretch of passive muscle.

Science.gov (United States)

Blum, Kyle P; Lamotte D'Incamps, Boris; Zytnicki, Daniel; Ting, Lena H

2017-09-01

Muscle spindle proprioceptive receptors play a primary role in encoding the effects of external mechanical perturbations to the body. During externally-imposed stretches of passive, i.e. electrically-quiescent, muscles, the instantaneous firing rates (IFRs) of muscle spindles are associated with characteristics of stretch such as length and velocity. However, even in passive muscle, there are history-dependent transients of muscle spindle firing that are not uniquely related to muscle length and velocity, nor reproduced by current muscle spindle models. These include acceleration-dependent initial bursts, increased dynamic response to stretch velocity if a muscle has been isometric, and rate relaxation, i.e., a decrease in tonic IFR when a muscle is held at a constant length after being stretched. We collected muscle spindle spike trains across a variety of muscle stretch kinematic conditions, including systematic changes in peak length, velocity, and acceleration. We demonstrate that muscle spindle primary afferents in passive muscle fire in direct relationship to muscle force-related variables, rather than length-related variables. Linear combinations of whole muscle-tendon force and the first time derivative of force (dF/dt) predict the entire time course of transient IFRs in muscle spindle Ia afferents during stretch (i.e., lengthening) of passive muscle, including the initial burst, the dynamic response to lengthening, and rate relaxation following lengthening. Similar to acceleration scaling found previously in postural responses to perturbations, initial burst amplitude scaled equally well to initial stretch acceleration or dF/dt, though later transients were only described by dF/dt. The transient increase in dF/dt at the onset of lengthening reflects muscle short-range stiffness due to cross-bridge dynamics. Our work demonstrates a critical role of muscle cross-bridge dynamics in history-dependent muscle spindle IFRs in passive muscle lengthening conditions

Stretch activates human myometrium via ERK, caldesmon and focal adhesion signaling.

Directory of Open Access Journals (Sweden)

Yunping Li

2009-10-01

Full Text Available An incomplete understanding of the molecular mechanisms responsible for myometrial activation from the quiescent pregnant state to the active contractile state during labor has hindered the development of effective therapies for preterm labor. Myometrial stretch has been implicated clinically in the initiation of labor and the etiology of preterm labor, but the molecular mechanisms involved in the human have not been determined. We investigated the mechanisms by which gestation-dependent stretch contributes to myometrial activation, by using human uterine samples from gynecologic hysterectomies and Cesarean sections. Here we demonstrate that the Ca requirement for activation of the contractile filaments in human myometrium increases with caldesmon protein content during gestation and that an increase in caldesmon phosphorylation can reverse this inhibitory effect during labor. By using phosphotyrosine screening and mass spectrometry of stretched human myometrial samples, we identify 3 stretch-activated focal adhesion proteins, FAK, p130Cas, and alpha actinin. FAK-Y397, which signals integrin engagement, is constitutively phosphorylated in term human myometrium whereas FAK-Y925, which signals downstream ERK activation, is phosphorylated during stretch. We have recently identified smooth muscle Archvillin (SmAV as an ERK regulator. A newly produced SmAV-specific antibody demonstrates gestation-specific increases in SmAV protein levels and stretch-specific increases in SmAV association with focal adhesion proteins. Thus, whereas increases in caldesmon levels suppress human myometrium contractility during pregnancy, stretch-dependent focal adhesion signaling, facilitated by the ERK activator SmAV, can contribute to myometrial activation. These results suggest that focal adhesion proteins may present new targets for drug discovery programs aimed at regulation of uterine contractility.

Soleus stretch reflex during cycling

DEFF Research Database (Denmark)

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

2001-01-01

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 durin...

Optical tweezers stretching of chromatin

NARCIS (Netherlands)

Pope, L.H.; Bennink, Martin L.; Greve, Jan

2003-01-01

Recently significant success has emerged from exciting research involving chromatin stretching using optical tweezers. These experiments, in which a single chromatin fibre is attached by one end to a micron-sized bead held in an optical trap and to a solid surface or second bead via the other end,

Acute effects of 15min static or contract-relax stretching modalities on plantar flexors neuromuscular properties.

Science.gov (United States)

Babault, Nicolas; Kouassi, Blah Y L; Desbrosses, Kevin

2010-03-01

The present study aimed to investigate the immediate effects of 15 min static or sub-maximal contract-relax stretching modalities on the neuromuscular properties of plantar flexor muscles. Ten male volunteers were tested before and immediately after 15 min static or contract-relax stretching programs of plantar flexor muscles (20 stretches). Static stretching consisted in 30s stretches to the point of discomfort. For the contract-relax stretching modality, subjects performed 6s sub-maximal isometric plantar flexion before 24s static stretches. Measurements included maximal voluntary isometric torque (MVT) and the corresponding electromyographic activity of soleus (SOL) and medial gastrocnemius (MG) muscles (RMS values), as well as maximal peak torque (Pt) elicited at rest by single supramaximal electrical stimulation of the tibial nerve. After 15 min stretching, significant MVT and SOL RMS decreases were obtained (-6.9+/-11.6% and -6.5+/-15.4%, respectively). No difference was obtained between stretching modalities. Pt remained unchanged after stretching. MG RMS changes were significantly different between stretching modalities (-9.4+/-18.3% and +3.5+/-11.6% after static and contract-relax stretching modalities, respectively). These findings indicated that performing 15 min static or contract-relax stretching had detrimental effects on the torque production capacity of plantar flexor muscles and should be precluded before competition. Mechanisms explaining this alteration seemed to be stretch modality dependent. Copyright 2009 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Time gated phase-correlation distributed Brillouin fibre sensor

Science.gov (United States)

Denisov, Andrey; Soto, Marcelo A.; Thévenaz, Luc

2013-05-01

A random access distributed Brillouin fibre sensor is presented, based on phase modulation using a pseudo-random bit sequence (PRBS) together with time gating. The standard phase-correlation technique is known to show a noise level increasing linearly with the number of measured points due to weak gratings generated randomly along the whole sensing fibre. Here we show how intensity modulated pump and time gated detection significantly improve the signal-tonoise ratio (SNR) of the system with no impact on the spatial resolution. A measurement with 1.1 cm spatial resolution over 3.3 km is demonstrated, representing 300'000 equivalent points. The limitations of the proposed technique are discussed through the paper.

An Experimental Study of Two-Phase Pulse Flushing Technology in Water Distribution Systems

Directory of Open Access Journals (Sweden)

Zhaozhao Tang

2017-12-01

Full Text Available The deterioration of drinking water during distribution process is caused by many factors. The microorganisms and substances peeling off from the “growth-ring” make the secondary pollution in drinking water distribution systems. To reduce the secondary pollution, two-phase pulse flushing technology is introduced to quickly remove the “growth-ring”. In this study, experiment is undertaken for investigating the efficiency of the two-phase pulse flushing and finding the best setting combination. A case study is undertaken to compare the efficiencies between the two-phase pulse and the single-phase flushing. The best setting combination of the two-phase pulse flushing is at the frequency 4 s–6 s (air inflow time is 4 s and air cut off time is 6 s and the round air inflow nozzle is set at the bottom of the pipe. Two-phase pulse flushing technology can save 95% of water and 6 h 40 min flushing time.

Stretching Diagnostics and Mixing Properties In The Stratosphere

Science.gov (United States)

Legras, B.; Shuckburgh, E.

The "finite size Lyapunov exponent" and the "effective diffusivity" are two diagnos- tics of mixing which have been recently introduced to investigate atmospheric flows. Both have been used to successfully identify the barriers to transport, for instance at the edge of the stratospheric polar vortex. Here we compare the two diagnostics in detail. The equivalent length has the advantage of arising as a mixing quantification from a rigid theoretical framework, however it has the disadvantage of being an aver- age quantity (the average around a tracer contour). The finite size Lyapunov exponent may be defined at any point in the flow, and quantifies the stretching properties expe- rienced by a fluid parcel both in its past and future evolution. In particular, the lines of maximum stretching at any time delineate the building blocks of the chaotic stirring. However the interpretation of the finite size Lyapunov exponent as a mixing time is less direct and depends on the alignment of tracer contours with the stretching lines.

Probabilistic Q-function distributions in fermionic phase-space

International Nuclear Information System (INIS)

Rosales-Zárate, Laura E C; Drummond, P D

2015-01-01

We obtain a positive probability distribution or Q-function for an arbitrary fermionic many-body system. This is different to previous Q-function proposals, which were either restricted to a subspace of the overall Hilbert space, or used Grassmann methods that do not give probabilities. The fermionic Q-function obtained here is constructed using normally ordered Gaussian operators, which include both non-interacting thermal density matrices and BCS states. We prove that the Q-function exists for any density matrix, is real and positive, and has moments that correspond to Fermi operator moments. It is defined on a finite symmetric phase-space equivalent to the space of real, antisymmetric matrices. This has the natural SO(2M) symmetry expected for Majorana fermion operators. We show that there is a physical interpretation of the Q-function: it is the relative probability for observing a given Gaussian density matrix. The distribution has a uniform probability across the space at infinite temperature, while for pure states it has a maximum value on the phase-space boundary. The advantage of probabilistic representations is that they can be used for computational sampling without a sign problem. (fast track communication)

Stretch-stimulated glucose transport in skeletal muscle is regulated by Rac1.

Science.gov (United States)

Sylow, Lykke; Møller, Lisbeth L V; Kleinert, Maximilian; Richter, Erik A; Jensen, Thomas E

2015-02-01

Rac1 regulates stretch-stimulated (i.e. mechanical stress) glucose transport in muscle. Actin depolymerization decreases stretch-induced glucose transport in skeletal muscle. Rac1 is a required part of the mechanical stress-component of the contraction-stimulus to glucose transport in skeletal muscle. An alternative to the canonical insulin signalling pathway for glucose transport is muscle contraction/exercise. Mechanical stress is an integrated part of the muscle contraction/relaxation cycle, and passive stretch stimulates muscle glucose transport. However, the signalling mechanism regulating stretch-stimulated glucose transport is not well understood. We recently reported that the actin cytoskeleton regulating GTPase, Rac1, was activated in mouse muscle in response to stretching. Rac1 is a regulator of contraction- and insulin-stimulated glucose transport, however, its role in stretch-stimulated glucose transport and signalling is unknown. We therefore investigated whether stretch-induced glucose transport in skeletal muscle required Rac1 and the actin cytoskeleton. We used muscle-specific inducible Rac1 knockout mice as well as pharmacological inhibitors of Rac1 and the actin cytoskeleton in isolated soleus and extensor digitorum longus muscles. In addition, the role of Rac1 in contraction-stimulated glucose transport during conditions without mechanical load on the muscles was evaluated in loosely hanging muscles and muscles in which cross-bridge formation was blocked by the myosin ATPase inhibitors BTS and Blebbistatin. Knockout as well as pharmacological inhibition of Rac1 reduced stretch-stimulated glucose transport by 30-50% in soleus and extensor digitorum longus muscle. The actin depolymerizing agent latrunculin B similarly decreased glucose transport in response to stretching by 40-50%. Rac1 inhibition reduced contraction-stimulated glucose transport by 30-40% in tension developing muscle but did not affect contraction-stimulated glucose transport in

Possible stretched exponential parametrization for humidity absorption in polymers.

Science.gov (United States)

Hacinliyan, A; Skarlatos, Y; Sahin, G; Atak, K; Aybar, O O

2009-04-01

Polymer thin films have irregular transient current characteristics under constant voltage. In hydrophilic and hydrophobic polymers, the irregularity is also known to depend on the humidity absorbed by the polymer sample. Different stretched exponential models are studied and it is shown that the absorption of humidity as a function of time can be adequately modelled by a class of these stretched exponential absorption models.

The acute effect of static and dynamic stretching during warm-ups on anaerobic performance in trained women

Directory of Open Access Journals (Sweden)

rouhollah haghshenas

2014-09-01

Full Text Available The purpose of this study was to investigate effects of static stretching, dynamic stretching and no stretching methods on power and speed in volleyball players. Therefore, Twenty-four volleyball players (height: 173.29 ± 7.81 m; mass: 62.12 ± 8.73 kg; age: 22.66 ± 4.02 years; experience: 3.27 ± 6.37 were tested for speed performance using the 20 meter sprint test and also for power using vertical jump test after static stretching, dynamic stretching and no stretching. The results analyzed using ANOVA showed that There was a significant increase in height jump after dynamic stretching against static stretching. But, there were no significant differences between no stretching and static stretching groups. In addition, there was a significant decrease in time 20 meter sprint after dynamic stretching against static stretching and no stretching groups. The results of this study suggest that it may be desirable for volleyball players to perform dynamic exercises before the performance of activities that require a high power output.

On the use of functional calculus for phase-type and related distributions

DEFF Research Database (Denmark)

Bladt, Mogens; Campillo Navarro, Azucena; Nielsen, Bo Friis

of matrices. Functional calculus, which is a branch of operator theory frequently associated with complex analysis, can be applied to phase-type and matrix-exponential distributions in a rather straightforward way. In this paper we provide a number of examples on how to execute the formal arguments.......The area of phase-type distributions is renowned for its ability to obtain closed form formulas or algorithmically exact solutions to many complex stochastic models. The method of functional calculus will provide an additional tool along these lines for establishing results in terms of functions...

On the use of functional calculus for phase-type and related distributions

DEFF Research Database (Denmark)

Bladt, Mogens; Navarro, Azucena Campillo; Nielsen, Bo Friis

2016-01-01

of matrices. Functional calculus, which is a branch of operator theory frequently associated with complex analysis, can be applied to phase-type and matrix-exponential distributions in a rather straightforward way. In this article we provide a number of examples of how to execute the formal arguments.......The area of phase-type distributions is renowned for its ability to obtain closed form formulas or algorithmically exact solutions to many complex stochastic models. The method of functional calculus will provide an additional tool along these lines for establishing results in terms of functions...

Velocities and joint angles during double backward stretched salto performed with stable landing and in combination with tempo salto

Directory of Open Access Journals (Sweden)

J Sadowski

2009-07-01

Full Text Available The aim of the study was to compare the values of velocity an joint angles obtained during performance of double salto backward stretched with a stable landing and its combination with salto tempo. Seven top level acrobats (track jumpers participated in study. Mean values of body height, mass and age had a value of: 170 cm ± 4.0 cm, 72.4 kg ± 3.6 kg, 20.4±1.7 years, respectively. The studies were conducted on a standard acrobatic path (type PTS 2000. Two digital video cameras (240 Hz and APAS 2000 (Ariel Dynamics Inc. were used during studies. Markers were placed in ankle, knee, hip, arm, elbow and wrist joints. All marker positions were tracked and reconstructed using the APAS system. Two sequences with the following elements were analysed: round-off - double salto backward stretched (A and round-off - double salto backward stretched - tempo salto (B. The highest differences between the key components describing performance of presented exercises exist for joint angles during launching and landing position, and resultant velocities during touchdown. In version A the athlete created prerequisites for “gliding” double salto backward stretched by means of the body segments motions, whereas in version B he executes faster motions of the body segments accentuating his actions upon backward rotation of the body. During the final phase of double salto backward stretched in combination with tempo salto the athlete performed courbette “under himself” (almost straight feet are placed in front of vertical line, pushes directly back and in 0,1 s executes stable arm swing upward-backward to tempo salto.

Models for Master-Slave Clock Distribution Networks with Third-Order Phase-Locked Loops

OpenAIRE

Piqueira, José Roberto Castilho; de Carvalho Freschi, Marcela

2007-01-01

The purpose of this work is to study the processing and transmission of clock signals in networks of geographically distributed nodes, in order to derive conditions for frequency and phase synchronization between the nodes. The focus is on the master-slave architecture, which presents a priority scheme of clock distribution. One-way master-slave (OWMS ) and two-way master-slave (TWMS) chains are studied, considering that the slave nodes are third-order phase-locked loops...

Pressure distribution over tube surfaces of tube bundle subjected to two phase cross flow

International Nuclear Information System (INIS)

Sim, Woo Gun

2013-01-01

Two phase vapor liquid flows exist in many shell and tube heat exchangers such as condensers, evaporators and nuclear steam generators. To understand the fluid dynamic forces acting on a structure subjected to a two phase flow, it is essential to obtain detailed information about the characteristics of a two phase flow. The characteristics of a two phase flow and the flow parameters were introduced, and then, an experiment was performed to evaluate the pressure loss in the tube bundles and the fluid dynamic force acting on the cylinder owing to the pressure distribution. A two phase flow was pre mixed at the entrance of the test section, and the experiments were undertaken using a normal triangular array of cylinders subjected to a two phase cross flow. The pressure loss along the flow direction in the tube bundles was measured to calculate the two phase friction multiplier, and the multiplier was compared with the analytical value. Furthermore, the circular distributions of the pressure on the cylinders were measured. Based on the distribution and the fundamental theory of two phase flow, the effects of the void fraction and mass flux per unit area on the pressure coefficient and the drag coefficient were evaluated. The drag coefficient was calculated by integrating the measured pressure coefficient and the drag coefficient were evaluated. The drag coefficient was calculated by integrating the measured pressure on the tube by a numerical method. It was found that for low mass fluxes, the measured two phase friction multipliers agree well with the analytical results, and good agreement for the effect of the void fraction on the drag coefficients, as calculated by the measured pressure distributions, is shown qualitatively, as compared to the existing experimental results

RF Phase Reference Distribution System for the TESLA Technology Based Projects

CERN Document Server

Czuba, K; Romaniuk, R S

2013-01-01

Since many decades physicists have been building particle accelerators and usually new projects became more advanced, more complicated and larger than predecessors. The importance and complexity of the phase reference distribution systems used in these accelerators have grown significantly during recent years. Amongst the most advanced of currently developed accelerators are projects based on the TESLA technology. These projects require synchronization of many RF devices with accuracy reaching femtosecond levels over kilometre distances. Design of a phase reference distribution system fulfilling such requirements is a challenging scientific task. There are many interdisciplinary problems which must be solved during the system design. Many, usually negligible issues, may became very important in such system. Furthermore, the design of a distribution system on a scale required for the TESLA technology based projects is a new challenge and there is almost no literature sufficiently covering this subject. This th...

S-phase cell distribution in the small intestine irradiated at different times of the day. 2. Recovery phase

Energy Technology Data Exchange (ETDEWEB)

Becciolini, A; Balzi, M; Cremonini, D; Fabbrica, D [Florence Univ. (Italy). Ist. di Radiologia

1983-01-01

Modifications occurring during recovery in the small intestine of animals exposed to the same radiation dose given at different times of the day were evaluated. S-phase cell distribution along the crypts and invertase activity were evaluated to ascertain the functional capacity of epithelial cells. In animals killed between 5 and 6 days after exposure, S-phase cell distribution and functional conditions tended towards normality although recovery was not complete. Labelled cells occurred also at villus junctions, demonstrating limitation in size of the differentiating compartment. This was confirmed by reduced activity of the brush border enzymes. Animals irradiated at the end of the dark period recovered more quickly and efficiently. In this group, labelled cell distribution was almost the same as in the controls starting from 120 h, and invertase activity was also closer to the controls than in any other group.

Stagnation-point flow of second grade nanofluid towards a nonlinear stretching surface with variable thickness

Directory of Open Access Journals (Sweden)

Rai Sajjad Saif

Full Text Available This paper investigates the stagnation point flow of second grade nanomaterial towards a nonlinear stretching surface subject to variable surface thickness. The process of heat transfer is examined through the melting heat and mixed convection effects. Further novel features regarding Brownian motion and thermophoresis are present. Boundary-layer approximation is employed in the problem formulation. Momentum, energy and concentration equations are converted into the non-linear ordinary differential system through the appropriate transformations. Convergent solutions for resulting problem are computed. Behaviors of various sundry variables on temperature and concentration are studied in detail. The skin friction coefficient and heat and mass transfer rates are also computed and analyzed. Our results indicate that the temperature and concentration distributions are enhanced for larger values of thermophoresis parameter. Further the present work is hoped to be useful in improving the performance of heat transfer of base fluid. Keywords: Stagnation-point flow, Second grade fluid, Nanoparticles, Melting heat process, Nonlinear stretching surface, Variable surface thickness

A Three-Phase Microgrid Restoration Model Considering Unbalanced Operation of Distributed Generation

International Nuclear Information System (INIS)

Wang, Zeyu; Wang, Jianhui; Chen, Chen

2016-01-01

Recent severe outages highlight the urgency of improving grid resiliency in the U.S. Microgrid formation schemes are proposed to restore critical loads after outages occur. Most distribution networks have unbalanced configurations that are not represented in sufficient detail by single-phase models. This study provides a microgrid formation plan that adopts a three-phase network model to represent unbalanced distribution networks. The problem formulation has a quadratic objective function with mixed-integer linear constraints. The three-phase network model enables us to examine the three-phase power outputs of distributed generators (DGs), preventing unbalanced operation that might trip DGs. Because the DG unbalanced operation constraint is non-convex, an iterative process is presented that checks whether the unbalanced operation limits for DGs are satisfied after each iteration of optimization. We also develop a relatively conservative linear approximation on the unbalanced operation constraint to handle larger networks. Compared with the iterative solution process, the conservative linear approximation is able to accelerate the solution process at the cost of sacrificing optimality to a limited extent. Simulation in the IEEE 34 node and IEEE 123 test feeders indicate that the proposed method yields more practical microgrid formations results. In addition, this paper explores the coordinated operation of DGs and energy storage (ES) installations. The unbalanced three-phase outputs of ESs combined with the relatively balanced outputs of DGs could supply unbalanced loads. In conclusion, the case study also validates the DG-ES coordination.

Dynamics and structure of stretched flames

Energy Technology Data Exchange (ETDEWEB)

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

1993-12-01

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.

Excluded Volume Effects in Gene Stretching

OpenAIRE

Lam, Pui-Man

2002-01-01

We investigate the effects excluded volume on the stretching of a single DNA in solution. We find that for small force F, the extension h is not linear in F but proportion to F^{\\chi}, with \\chi=(1-\

Stretched versus compressed exponential kinetics in α-helix folding

International Nuclear Information System (INIS)

Hamm, Peter; Helbing, Jan; Bredenbeck, Jens

2006-01-01

In a recent paper (J. Bredenbeck, J. Helbing, J.R. Kumita, G.A. Woolley, P. Hamm, α-helix formation in a photoswitchable peptide tracked from picoseconds to microseconds by time resolved IR spectroscopy, Proc. Natl. Acad. Sci USA 102 (2005) 2379), we have investigated the folding of a photo-switchable α-helix with a kinetics that could be fit by a stretched exponential function exp(-(t/τ) β ). The stretching factor β became smaller as the temperature was lowered, a result which has been interpreted in terms of activated diffusion on a rugged energy surface. In the present paper, we discuss under which conditions diffusion problems occur with stretched exponential kinetics (β 1). We show that diffusion problems do have a strong tendency to yield stretched exponential kinetics, yet, that there are conditions (strong perturbation from equilibrium, performing the experiment in the folding direction) under which compressed exponential kinetics would be expected instead. We discuss the kinetics on free energy surfaces predicted by simple initiation-propagation models (zipper models) of α-helix folding, as well as by folding funnel models. We show that our recent experiment has been performed under condition for which models with strong downhill driving force, such as the zipper model, would predict compressed, rather than stretched exponential kinetics, in disagreement with the experimental observation. We therefore propose that the free energy surface along a reaction coordinate that governs the folding kinetics must be relatively flat and has a shape similar to a 1D golf course. We discuss how this conclusion can be unified with the thermodynamically well established zipper model by introducing an additional kinetic reaction coordinate

Effect of Twisting and Stretching on Magneto Resistance and Spin Filtration in CNTs

Directory of Open Access Journals (Sweden)

Anil Kumar Singh

2017-08-01

Full Text Available Spin-dependent quantum transport properties in twisted carbon nanotube and stretched carbon nanotube are calculated using density functional theory (DFT and non-equilibrium green’s function (NEGF formulation. Twisting and stretching have no effect on spin transport in CNTs at low bias voltages. However, at high bias voltages the effects are significant. Stretching restricts any spin-up current in antiparallel configuration (APC, which results in higher magneto resistance (MR. Twisting allows spin-up current almost equivalent to the pristine CNT case, resulting in lower MR. High spin filtration is observed in PC and APC for pristine, stretched and twisted structures at all applied voltages. In APC, at low voltages spin filtration in stretched CNT is higher than in pristine and twisted ones, with pristine giving a higher spin filtration than twisted CNT.

Travelling Wave Solutions to Stretched Beam's Equation: Phase Portraits Survey

International Nuclear Information System (INIS)

Betchewe, Gambo; Victor, Kuetche Kamgang; Thomas, Bouetou Bouetou; Kofane, Timoleon Crepin

2011-01-01

In this paper, following the phase portraits analysis, we investigate the integrability of a system which physically describes the transverse oscillation of an elastic beam under end-thrust. As a result, we find that this system actually comprises two families of travelling waves: the sub- and super-sonic periodic waves of positive- and negative-definite velocities, respectively, and the localized sub-sonic loop-shaped waves of positive-definite velocity. Expressing the energy-like of this system while depicting its phase portrait dynamics, we show that these multivalued localized travelling waves appear as the boundary solutions to which the periodic travelling waves tend asymptotically. (general)

Effect of Ankle Positioning During Hamstring Stretches for Improving Straight Leg Hip Flexion Motion.

Science.gov (United States)

Laudner, Kevin G; Benjamin, Peter J; Selkow, Noelle M

2016-03-01

To compare the effects of stretching the hamstrings with the ankle in either a plantar-flexed (PF) or dorsiflexed (DF) position for improving straight leg hip flexion range of motion (ROM) over a 4-week period. Randomized, single-blinded, pretest, posttest design. Athletic training facility. Each limb of 34 asymptomatic individuals (15 males, 19 females) was randomly assigned to one of the 3 groups. Twenty-four limbs received hamstring stretches with the ankle in DF, 24 limbs received hamstring stretches with the ankle in PF, and 20 limbs received no stretch (control). Ankle position (PF, DF) during hamstring stretching. We measured pretest and posttest passive straight leg hip flexion ROM with the test ankle in a neutral position. For the intervention groups, the test limb was passively stretched with the ankle held in end range DF or PF for their respective group. Each stretch was held for 30 seconds for a total of 3 applications. Two treatment sessions were completed per week for a total of 4 weeks. The control limbs received no stretching during the 4-week period. We conducted 1-way analyses of covariance to determine significant changes in ROM between groups (P hamstrings in either PF or DF improve straight leg hip ROM compared with a control group. The results of this study should be considered by clinicians when determining the optimal stretching techniques aimed at increasing hamstring length.

Acute Effect of Different Combined Stretching Methods on Acceleration and Speed in Soccer Players

Directory of Open Access Journals (Sweden)

Amiri-Khorasani Mohammadtaghi

2016-04-01

Full Text Available The purpose of this study was to investigate the acute effect of different stretching methods, during a warm-up, on the acceleration and speed of soccer players. The acceleration performance of 20 collegiate soccer players (body height: 177.25 ± 5.31 cm; body mass: 65.10 ± 5.62 kg; age: 16.85 ± 0.87 years; BMI: 20.70 ± 5.54; experience: 8.46 ± 1.49 years was evaluated after different warm-up procedures, using 10 and 20 m tests. Subjects performed five types of a warm-up: static, dynamic, combined static + dynamic, combined dynamic + static, and no-stretching. Subjects were divided into five groups. Each group performed five different warm-up protocols in five non-consecutive days. The warm-up protocol used for each group was randomly assigned. The protocols consisted of 4 min jogging, a 1 min stretching program (except for the no-stretching protocol, and 2 min rest periods, followed by the 10 and 20 m sprint test, on the same day. The current findings showed significant differences in the 10 and 20 m tests after dynamic stretching compared with static, combined, and no-stretching protocols. There were also significant differences between the combined stretching compared with static and no-stretching protocols. We concluded that soccer players performed better with respect to acceleration and speed, after dynamic and combined stretching, as they were able to produce more force for a faster execution.

Flow of viscous fluid along an exponentially stretching curved surface

Directory of Open Access Journals (Sweden)

N.F. Okechi

Full Text Available In this paper, we present the boundary layer analysis of flow induced by rapidly stretching curved surface with exponential velocity. The governing boundary value problem is reduced into self-similar form using a new similarity transformation. The resulting equations are solved numerically using shooting and Runge-Kutta methods. The numerical results depicts that the fluid velocity as well as the skin friction coefficient increases with the surface curvature, similar trend is also observed for the pressure. The dimensionless wall shear stress defined for this problem is greater than that of a linearly stretching curved surface, but becomes comparably less for a surface stretching with a power-law velocity. In addition, the result for the plane surface is a special case of this study when the radius of curvature of the surface is sufficiently large. The numerical investigations presented in terms of the graphs are interpreted with the help of underlying physics of the fluid flow and the consequences arising from the curved geometry. Keywords: Boundary layer flow, Curved surface, Exponential stretching, Curvature

Directional Cell Migration in Response to Repeated Substratum Stretching

Science.gov (United States)

Okimura, Chika; Iwadate, Yoshiaki

2017-10-01

Crawling migration plays an essential role in a variety of biological phenomena, including development, wound healing, and immune system function. Migration properties such as anterior-posterior polarity, directionality, and velocity are regulated not only by the reception of a chemoattractant but also by sensing mechanical inputs from the external environment. In this review, we describe the mechanical response of migrating cells, particularly under repeated stretching of the elastic substratum, highlighting the fact that there appear to be two independent mechanosensing systems that generate the polarity needed for migration. Cells that have no stress fibers, such as Dictyostelium cells and neutrophil-like differentiated HL-60 cells, migrate perpendicular to the stretching direction via myosin II localization. Cells that do possess stress fibers, however, such as fish keratocytes, migrate parallel to the stretching via a stress-fiber-dependent process.

Distributions of Conductance and Shot Noise and Associated Phase Transitions

International Nuclear Information System (INIS)

Vivo, Pierpaolo; Majumdar, Satya N.; Bohigas, Oriol

2008-01-01

For a chaotic cavity with two identical leads each supporting N channels, we compute analytically, for large N, the full distribution of the conductance and the shot noise power and show that in both cases there is a central Gaussian region flanked on both sides by non-Gaussian tails. The distribution is weakly singular at the junction of Gaussian and non-Gaussian regimes, a direct consequence of two phase transitions in an associated Coulomb gas problem

Measurement of void fraction and bubble size distribution in two-phase flow system

International Nuclear Information System (INIS)

Huahun, G.

1987-01-01

The importance of study two phase flow parameter and microstructure has appeared increasingly, with the development of two-phase flow discipline. In the paper, the measurement methods of several important microstructure parameter in a two phase flow vertical channel have been studied. Using conductance probe the two phase flow pattern and the average void fraction have been measured previously by the authors. This paper concerns microstructure of the bubble size distribution and local void fraction. The authors studied the methods of measuring bubble velocity, size distribution and local void fraction using double conductance probes and a set of apparatus. Based on our experiments and Yoshihiro work, a formula of calculated local void fraction has been deduced by using the statistical characteristics of bubbles in two phase flow and the relation between calculated bubble size and voltage has been determined. Finally the authors checked by using photograph and fast valve, which is classical but reliable. The results are the same with what has been studied before

On prediction of OH stretching frequencies in intramolecularly hydrogen bonded systems

DEFF Research Database (Denmark)

Hansen, Poul Erik; Spanget-Larsen, Jens

2012-01-01

OH stretching frequencies are investigated for a series of non-tautomerizing systems with intramolecular hydrogen bonds. Effective OH stretching wavenumbers are predicted by the application of empirical correlation procedures based on the results of B3LYP/6-31G(d) theoretical calculations...

Optimization of path length stretching in Monte Carlo calculations for non-leakage problems

Energy Technology Data Exchange (ETDEWEB)

Hoogenboom, J.E. [Delft Univ. of Technology (Netherlands)

2005-07-01

Path length stretching (or exponential biasing) is a well known variance reduction technique in Monte Carlo calculations. It can especially be useful in shielding problems where particles have to penetrate a lot of material before being tallied. Several authors sought for optimization of the path length stretching parameter for detection of the leakage of neutrons from a slab. Here the adjoint function behaves as a single exponential function and can well be used to determine the stretching parameter. In this paper optimization is sought for a detector embedded in the system, which changes the adjoint function in the detector drastically. From literature it is known that the combination of path length stretching and angular biasing can result in appreciable variance reduction. However, angular biasing is not generally available in general purpose Monte Carlo codes and therefore we want to restrict ourselves to the application of pure path length stretching and finding optimum parameters for that. Nonetheless, the starting point for our research is the zero-variance scheme. In order to study the solution in detail the simplified monoenergetic two-direction model is adopted, which allows analytical solutions and can still be used in a Monte Carlo simulation. Knowing the zero-variance solution analytically, it is shown how optimum path length stretching parameters can be derived from it. It results in path length shrinking in the detector. Results for the variance in the detector response are shown in comparison with other patterns for the stretching parameter. The effect of anisotropic scattering on the path length stretching parameter is taken into account. (author)

Wigner Distribution Functions as a Tool for Studying Gas Phase Alkali Metal Plus Noble Gas Collisions

Science.gov (United States)

2014-03-27

WIGNER DISTRIBUTION FUNCTIONS AS A TOOL FOR STUDYING GAS PHASE ALKALI METAL PLUS NOBLE GAS COLLISIONS THESIS Keith A. Wyman, Second Lieutenant, USAF...the U.S. Government and is not subject to copyright protection in the United States. AFIT-ENP-14-M-39 WIGNER DISTRIBUTION FUNCTIONS AS A TOOL FOR...APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED AFIT-ENP-14-M-39 WIGNER DISTRIBUTION FUNCTIONS AS A TOOL FOR STUDYING GAS PHASE ALKALI METAL PLUS

Crustal Stretching Style and Lower Crust Flow of the South China Sea Northern Margin

Science.gov (United States)

Bai, Y.; Dong, D.; Runlin, D.

2017-12-01

There is a controversy about crustal stretching style of the South China Sea (SCS) northern margin mainly due to considerable uncertainty of stretching factor estimation, for example, as much as 40% of upper crust extension (Walsh et al., 1991) would be lost by seismic profiles due to poor resolution. To discover and understand crustal stretching style and lower crustal flow on the whole, we map the Moho and Conrad geometries based on gravity inversion constrained by deep seismic profiles, then according to the assumption of upper and lower crust initial thickness, upper and lower crust stretching factors are estimated. According to the comparison between upper and lower crust stretching factors, the SCS northern margin could be segmented into three parts, (1) sediment basins where upper crust is stretched more than lower crust, (2) COT regions where lower crust is stretched more than upper crust, (3) other regions where the two layers have similar stretching factors. Stretching factor map shows that lower crust flow happened in both of COT and sediment basin regions where upper crust decouples with lower crust due to high temperature. Pressure contrast by sediment loading in basins and erosion in sediment-source regions will lead to lower crust flow away from sediment sink to source. Decoupled and fractured upper crust is stretched further by sediment loading and the following compensation would result in relatively thick lower crust than upper crust. In COT regions with thin sediment coverage, low-viscosity lower crust is easier to thin in extensional environment, also the lower crust tends to flow away induced by magma upwelling. Therefore, continental crust on the margin is not stretching in a constant way but varies with the tectonic setting changes. This work is supported by National Natural Science Foundation of China (Grant No. 41506055, 41476042) and Fundamental Research Funds for the Central Universities China (No.17CX02003A).

Sequence-length variation of mtDNA HVS-I C-stretch in Chinese ethnic groups.

Science.gov (United States)

Chen, Feng; Dang, Yong-hui; Yan, Chun-xia; Liu, Yan-ling; Deng, Ya-jun; Fulton, David J R; Chen, Teng

2009-10-01

The purpose of this study was to investigate mitochondrial DNA (mtDNA) hypervariable segment-I (HVS-I) C-stretch variations and explore the significance of these variations in forensic and population genetics studies. The C-stretch sequence variation was studied in 919 unrelated individuals from 8 Chinese ethnic groups using both direct and clone sequencing approaches. Thirty eight C-stretch haplotypes were identified, and some novel and population specific haplotypes were also detected. The C-stretch genetic diversity (GD) values were relatively high, and probability (P) values were low. Additionally, C-stretch length heteroplasmy was observed in approximately 9% of individuals studied. There was a significant correlation (r=-0.961, Ppopulations. The results from the Fst and dA genetic distance matrix, neighbor-joining tree, and principal component map also suggest that C-stretch could be used as a reliable genetic marker in population genetics.

Mechanical stretching stimulates collagen synthesis via down-regulating SO2/AAT1 pathway

Science.gov (United States)

Liu, Jia; Yu, Wen; Liu, Yan; Chen, Selena; Huang, Yaqian; Li, Xiaohui; Liu, Cuiping; Zhang, Yanqiu; Li, Zhenzhen; Du, Jie; Tang, Chaoshu; Du, Junbao; Jin, Hongfang

2016-01-01

The aim of the study was to investigate the role of endogenous sulfur dioxide (SO2)/ aspartate aminotransferase 1 (AAT1) pathway in stretch-induced excessive collagen expression and its mechanism. The mechanical stretch downregulated SO2/AAT1 pathway and increased collagen I and III protein expression. Importantly, AAT1 overexpression blocked the increase in collagen I and III expression, transforming growth factor-β1 (TGF- β1) expression and phosphorylation of Smad2/3 induced by stretch, but AAT1 knockdown mimicked the increase in collagen I and III expression, TGF- β1 expression and phosphorylation of Smad2/3 induced by stretch. Mechanistically, SB431542, a TGF-β1/Smad2/3 inhibitor, eliminated excessive collagen I and III accumulation induced by AAT1 knockdown, stretch or stretch plus AAT1 knockdown. In a rat model of high pulmonary blood flow-induced pulmonary vascular collagen accumulation, AAT1 expression and SO2 content in lung tissues of rat were reduced in shunt rats with high pulmonary blood flow. Supplement of SO2 derivatives inhibited activation of TGF- β1/Smad2/3 pathway and alleviated the excessive collagen accumulation in lung tissues of shunt rats. The results suggested that deficiency of endogenous SO2/AAT1 pathway mediated mechanical stretch-stimulated abnormal collagen accumulation via TGF-β1/Smad2/3 pathway. PMID:26880260

Nonclassicality indicator for the real phase-space distribution functions

International Nuclear Information System (INIS)

Sadeghi, Parvin; Khademi, Siamak; Nasiri, Sadollah

2010-01-01

Benedict et al. and Kenfack et al. advocated nonclassicality indicators based on the measurement of negativity of the Wigner distribution functions. These indicators have some applications in quantum mechanics and quantum optics. In this paper we define a nonclassicality indicator in terms of the interference in phase space, which is applicable to some real distribution functions including those of Wigner. As a special case one may reproduce the previous results using our indicator for the Wigner distribution functions. This indicator is examined for cases of the Schroedinger cat state and the thermal states and the results are compared with those obtained by previous methods. It seems that the physical behavior of nonclassicality indicators originates in the uncertainty principle. This is shown by an onto correspondence between these indicators and the uncertainty principle.

DNA analysis by single molecule stretching in nanofluidic biochips

DEFF Research Database (Denmark)

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

2011-01-01

Imprint Lithography (NIL) technology combined with a conventional anodic bonding of the silicon base and Pyrex cover. Using this chip, we have performed single molecule imaging on a bench-top fluorescent microscope system. Lambda phage DNA was used as a model sample to characterize the chip. Single molecules of λ-DNA......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...... 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...

Effect of acute stretch injury on action potential and network activity of rat neocortical neurons in culture.

Science.gov (United States)

Magou, George C; Pfister, Bryan J; Berlin, Joshua R

2015-10-22

The basis for acute seizures following traumatic brain injury (TBI) remains unclear. Animal models of TBI have revealed acute hyperexcitablility in cortical neurons that could underlie seizure activity, but studying initiating events causing hyperexcitability is difficult in these models. In vitro models of stretch injury with cultured cortical neurons, a surrogate for TBI, allow facile investigation of cellular changes after injury but they have only demonstrated post-injury hypoexcitability. The goal of this study was to determine if neuronal hyperexcitability could be triggered by in vitro stretch injury. Controlled uniaxial stretch injury was delivered to a spatially delimited region of a spontaneously active network of cultured rat cortical neurons, yielding a region of stretch-injured neurons and adjacent regions of non-stretched neurons that did not directly experience stretch injury. Spontaneous electrical activity was measured in non-stretched and stretch-injured neurons, and in control neuronal networks not subjected to stretch injury. Non-stretched neurons in stretch-injured cultures displayed a three-fold increase in action potential firing rate and bursting activity 30-60 min post-injury. Stretch-injured neurons, however, displayed dramatically lower rates of action potential firing and bursting. These results demonstrate that acute hyperexcitability can be observed in non-stretched neurons located in regions adjacent to the site of stretch injury, consistent with reports that seizure activity can arise from regions surrounding the site of localized brain injury. Thus, this in vitro procedure for localized neuronal stretch injury may provide a model to study the earliest cellular changes in neuronal function associated with acute post-traumatic seizures. Copyright © 2015. Published by Elsevier B.V.

Heliostat Manufacturing for near-term markets. Phase II final report

International Nuclear Information System (INIS)

1998-01-01

This report describes a project by Science Applications International Corporation and its subcontractors Boeing/Rocketdyne and Bechtel Corp. to develop manufacturing technology for production of SAIC stretched membrane heliostats. The project consists of three phases, of which two are complete. This first phase had as its goals to identify and complete a detailed evaluation of manufacturing technology, process changes, and design enhancements to be pursued for near-term heliostat markets. In the second phase, the design of the SAIC stretched membrane heliostat was refined, manufacturing tooling for mirror facet and structural component fabrication was implemented, and four proof-of-concept/test heliostats were produced and installed in three locations. The proposed plan for Phase III calls for improvements in production tooling to enhance product quality and prepare increased production capacity. This project is part of the U.S. Department of Energy's Solar Manufacturing Technology Program (SolMaT)

The constitutive distributed parameter model of multicomponent chemical processes in gas, fluid and solid phase

International Nuclear Information System (INIS)

Niemiec, W.

1985-01-01

In the literature of distributed parameter modelling of real processes is not considered the class of multicomponent chemical processes in gas, fluid and solid phase. The aim of paper is constitutive distributed parameter physicochemical model, constructed on kinetics and phenomenal analysis of multicomponent chemical processes in gas, fluid and solid phase. The mass, energy and momentum aspects of these multicomponent chemical reactions and adequate phenomena are utilized in balance operations, by conditions of: constitutive invariance for continuous media with space and time memories, reciprocity principle for isotropic and anisotropic nonhomogeneous media with space and time memories, application of definitions of following derivative and equation of continuity, to the construction of systems of partial differential constitutive state equations, in the following derivative forms for gas, fluid and solid phase. Couched in this way all physicochemical conditions of multicomponent chemical processes in gas, fluid and solid phase are new form of constitutive distributed parameter model for automatics and its systems of equations are new form of systems of partial differential constitutive state equations in sense of phenomenal distributed parameter control

The static actuation of dielectric elastomer actuators: how does pre-stretch improve actuation?

International Nuclear Information System (INIS)

Kofod, Guggi

2008-01-01

It has previously been shown that providing dielectric elastomer actuators with a level of pre-stretch can improve properties such as breakdown strength, actuation strain and efficiency. The actuation in such actuators depends on an interplay between the highly nonlinear hyperelastic stress-strain behaviour with the electrostatic Maxwell's stress; however, the direct effects of pre-stretch on the electromechanical coupling have still not been investigated in detail. We compare several experimental results found in the literature on the hyperelastic parameters of the Ogden model for the commonly used material VHB 4910, and introduce a more detailed and thus more accurate fit to a previous uniaxial stress-strain experiment. Electrostatic actuation models for a pure shear cuboid dielectric elastomer actuator with pre-stretch are introduced, for both intensive and extensive variables. For both intensive and extensive variables the constant strain (blocked stress or force) as well as the actuation strain is presented. It is shown how in the particular case of isotropic amorphous elastomers the pre-stretch does not affect the electromechanical coupling directly, and that the enhancement in actuation strain due to pre-stretch occurs through the alteration of the geometrical dimensions of the actuator. Also, the presence of the optimum load is explained as being due to the plateau region in the force-stretch curve, and it is shown that pre-stretch is not able to affect its position. Finally, it is shown how the simplified Ogden fit leads to entirely different conclusions for actuation strain in terms of extensive variables as does the detailed fit, emphasizing the importance of employing accurate hyperelastic models for the stress-stretch behaviour of the elastomer.

Acute effect of different stretching methods on flexibility and jumping performance in competitive artistic gymnasts.

Science.gov (United States)

Dallas, G; Smirniotou, A; Tsiganos, G; Tsopani, D; Di Cagno, A; Tsolakis, Ch

2014-12-01

The purpose of this study was to investigate the acute effects of 3 different warm up methods of stretching (static, proprioceptive neuromuscular facilitation, and stretching exercises on a Vibration platform) on flexibility and legs power-jumping performance in competitive artistic gymnasts. Eighteen competitive artistic gymnasts were recruited to participate in this study. Subjects were exposed to each of 3 experimental stretching conditions: static stretching (SS), proprioceptive neuromuscular facilitation stretching (PNF), and stretching exercises on a Vibration platform (S+V). Flexibility assessed with sit and reach test (S & R) and jumping performance with squat jump (SJ) and counter movement jump (CMJ) and were measured before, immediately after and 15 min after the interventions. Significant differences were observed for flexibility after all stretching conditions for S+V (+1.1%), SS (+5.7%) and PNF (+6.8%) (P=0.000), which remained higher 15 min after interventions (S+V (1.1%), SS (5.3%) and PNF (5.5%), respectively (P=0.000). PNF stretching increased flexibility in competitive gymnasts, while S+V maintained jumping performance when both methods were used as part of a warm-up procedure.

Acute effects of static stretching on peak and end-range hamstring-to-quadriceps functional ratios

Science.gov (United States)

Sekir, Ufuk; Arabaci, Ramiz; Akova, Bedrettin

2015-01-01

AIM: To evaluate if static stretching influences peak and end-range functional hamstring-to-quadriceps (H/Q) strength ratios in elite women athletes. METHODS: Eleven healthy female athletes in an elite competitive level participated to the study. All the participants fulfilled the static stretching or non-stretching (control) intervention protocol in a randomized design on different days. Two static unassisted stretching exercises, one in standing and one in sitting position, were used to stretch both the hamstring and quadriceps muscles during these protocols. The total time for the static stretching was 6 ± 1 min. The isokinetic peak torque measurements for the hamstring and quadriceps muscles in eccentric and concentric modes and the calculations for the functional H/Q strength ratios at angular velocities of 60°/s and 180°/s were made before (pre) and after (post) the control or stretching intervention. The strength measurements and functional strength ratio calculations were based during the entire- and end-range of knee extension. RESULTS: The pre-test scores for quadriceps and hamstring peak torque and end range values were not significantly different between the groups (P > 0.05). Subsequently, although the control group did not exhibit significant changes in quadriceps and hamstring muscle strength (P > 0.05), static stretching decreased eccentric and concentric quadriceps muscle strength at both the 60°/s and 180°/s test speeds (P hamstring muscle strength at both the 60°/s and 180°/s test speeds (P 0.05). Furthermore, the functional H/Q strength ratios exhibited no significant alterations during the entire and end ranges of knee extension both in the static stretching or the control intervention (P > 0.05). CONCLUSION: According to our results, static stretching routine does not influence functional H/Q ratio. Athletes can confidently perform static stretching during their warm-up routines. PMID:26495249

The effects of static stretch duration on the flexibility of hamstring ...

African Journals Online (AJOL)

The effects of static stretch duration on the flexibility of hamstring muscles. NA Odunaiya, TK Hamzat, OF Ajayi. Abstract. The effects of duration of a static stretching protocol (Intervention) on hamstrings tightness were evaluated. Sixty purposively sampled subjects with unilateral hamstring tightness that had no history of low ...

Theory of X-ray scattering by strongly distorted aging alloys with lamellar distribution of inclusions

International Nuclear Information System (INIS)

Barabash, R.I.; Krivoglaz, M.A.; AN Ukrainskoj SSR, Kiev. Inst. Metallofiziki)

1981-01-01

The X-ray scattering by strongly distorted heterogeneous alloys containing inclusions of new phase particles is discussed. Two models describing the lamellar structure with various orientation of inclusion axes in different layers are studied. In the first model the dimensions of inclusions are small in comparison with the layer thickness and they are randomly distributed in it, in the second model lamellar inclusions stretch through the whole layer. It is shown that in both models the Debye broadened line intensity distribution consists of overlapping Lorentz curves. A case of inclusions oriented along directions [100] and layers perpendicular to axes [110] is analyzed in detail. The results obtained for this case are compared with experimental results for the Cu-Be alloy

The acute effects of stretching with vibration on dynamic flexibility in young female gymnasts.

Science.gov (United States)

Johnson, Aaron W; Warcup, Caisa N; Seeley, Matthew K; Eggett, Dennis; Feland, Jeffery B

2018-01-10

While stretching with vibration has been shown to improve static flexibility; the effect of stretching with vibration on dynamic flexibility is not well known. The purpose of this study was to examine the effectiveness of stretching with vibration on acute dynamic flexibility and jump height in novice and advanced competitive female gymnasts during a split jump. Female gymnast (n=27, age: 11.5 ± 1.7 years, Junior Olympic levels 5-10) participated in this cross-over study. Dynamic flexibility during gymnastic split jumps were video recorded and analyzed with Dartfish software. All participants completed both randomized stretching protocols with either the vibration platform turned on (VIB) (frequency of 30 Hz and 2 mm amplitude) or off (NoVIB) separated by 48 h. Participants performed 4 sets of three stretches on the vibration platform. Each stretch was held for 30 s with 5 s rest for a total of 7 min of stretch. Split jump flexibility decreased significantly from pre to post measurement in both VIB (-5.8°±5.9°) (p<0.001) and NoVIB (-2.6°±6.1°) (p=0.041) conditions (adjusted for gymnast level). This effect was greatest in lower skill level gymnasts (p=0.003), while the highest skill level gymnasts showed no significant decrease in the split jump (p=0.105). Jump height was not significantly different between conditions (p=0.892) or within groups (p=0.880). An acute session of static stretching with or without vibration immediately before performance does not alter jump height. Stretching with vibration immediately prior to gymnastics competition decreases split jump flexibility in lower level gymnasts more than upper level gymnasts.

Paradigms: How Far Does Research in Distributed Leadership "Stretch"?

Science.gov (United States)

Hartley, David

2010-01-01

Burrell and Morgan's widely-cited "Sociological Paradigms and Organizational Analysis" is applied here to research on distributed leadership in education. Nearly all of the extant research is regulatory, not radical; and the evidence which it has generated falls broadly within the paradigm of interpretivism. Few studies have generated the…

Mechanical stretch endows mesenchymal stem cells stronger angiogenic and anti-apoptotic capacities via NFκB activation

International Nuclear Information System (INIS)

Zhu, Zhuoli; Gan, Xueqi; Fan, Hongyi; Yu, Haiyang

2015-01-01

Mesenchymal stem cells (MSCs) have been broadly used for tissue regeneration and repair due to their broad differentiation potential and potent paracrine properties such as angiogenic capacity. Strategies to increase their survival rate after transplantation and the angiogenic ability are of priority for the utility of MSCs. In this study, we found that mechanical stretch (10% extension, 30 cycles/min cyclic stretch) preconditioning increase the angiogenic capacity via VEGFA induction. In addition, mechanical stretch also increases the survival rate of mesenchymal stem cells under nutrients deprivation. Consistent with the increase VEGFA expression and resistance to apoptosis, nuclear localization of NFκB activity p65 increased upon mechanical stretch. Inhibition of NFκB activity by BAY 11-708 blocks the pro-angiogenesis and anti-apoptosis function of mechanical stretch. Taken together, our findings here raise the possibility that mechanical stretch preconditioning might enhance the therapeutic efficacy of mesenchymal stem cells. - Highlights: • Mechanical stretch increases the angiogenic capacity via VEGFA induction in MSCs. • Mechanical stretch increases the survival rate of MSCs under nutrients deprivation. • Mechanical stretch manipulates MSCs via the activation of NFκB.

Mechanical stretch endows mesenchymal stem cells stronger angiogenic and anti-apoptotic capacities via NFκB activation

Energy Technology Data Exchange (ETDEWEB)

Zhu, Zhuoli; Gan, Xueqi [State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041 (China); Fan, Hongyi [State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041 (China); Department of Applied Mechanics, College of Architecture and Environment, Sichuan University, Chengdu 610065 (China); Yu, Haiyang, E-mail: yhyang6812@foxmail.com [State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041 (China)

2015-12-25

Mesenchymal stem cells (MSCs) have been broadly used for tissue regeneration and repair due to their broad differentiation potential and potent paracrine properties such as angiogenic capacity. Strategies to increase their survival rate after transplantation and the angiogenic ability are of priority for the utility of MSCs. In this study, we found that mechanical stretch (10% extension, 30 cycles/min cyclic stretch) preconditioning increase the angiogenic capacity via VEGFA induction. In addition, mechanical stretch also increases the survival rate of mesenchymal stem cells under nutrients deprivation. Consistent with the increase VEGFA expression and resistance to apoptosis, nuclear localization of NFκB activity p65 increased upon mechanical stretch. Inhibition of NFκB activity by BAY 11-708 blocks the pro-angiogenesis and anti-apoptosis function of mechanical stretch. Taken together, our findings here raise the possibility that mechanical stretch preconditioning might enhance the therapeutic efficacy of mesenchymal stem cells. - Highlights: • Mechanical stretch increases the angiogenic capacity via VEGFA induction in MSCs. • Mechanical stretch increases the survival rate of MSCs under nutrients deprivation. • Mechanical stretch manipulates MSCs via the activation of NFκB.

Numerical Analysis of AHSS Fracture in a Stretch-bending Test

Science.gov (United States)

Luo, Meng; Chen, Xiaoming; Shi, Ming F.; Shih, Hua-Chu

2010-06-01

Advanced High Strength Steels (AHSS) are increasingly used in the automotive industry due to their superior strength and substantial weight reduction advantage. However, their limited ductility gives rise to numerous manufacturing issues. One of them is the so-called `shear fracture' often observed on tight radii during stamping processes. Since traditional approaches, such as the Forming Limit Diagram (FLD), are unable to predict this type of fracture, efforts have been made to develop failure criteria that can predict shear fractures. In this paper, a recently developed Modified Mohr-Coulomb (MMC) ductile fracture criterion[1] is adopted to analyze the failure behavior of a Dual Phase (DP) steel sheet during stretch bending operations. The plasticity and ductile fracture of the present sheet are fully characterized by the Hill'48 orthotropic model and the MMC fracture model respectively. Finite Element models with three different element types (3D, shell and plane strain) were built for a Stretch Forming Simulator (SFS) test and numerical simulations with four different R/t ratios (die radius normalized by sheet thickness) were performed. It has been shown that the 3D and shell element models can accurately predict the failure location/mode, the upper die load-displacement responses as well as the wall stress and wrap angle at the onset of fracture for all R/t ratios. Furthermore, a series of parametric studies were conducted on the 3D element model, and the effects of tension level (clamping distance) and tooling friction on the failure modes/locations were investigated.

In-situ bending under tension shear fracture analysis and microstructure “earthquake” of DP780 dual phase steels

Energy Technology Data Exchange (ETDEWEB)

Zhao, Yixi, E-mail: yxzhao@sjtu.edu.cn [State Key Laboratory of Mechanical System and Vibration, Shanghai Key Laboratory of Digital Manufacture for Thin-walled Structures, Shanghai Jiao Tong University, Shanghai 200240 (China); Huang, Sheng [State Key Laboratory of Mechanical System and Vibration, Shanghai Key Laboratory of Digital Manufacture for Thin-walled Structures, Shanghai Jiao Tong University, Shanghai 200240 (China); Dan, Wenjiao; Zhang, Weigang [Innovation Center for Advanced Ship and Deep-Sea Exploration, Department of Engineering Mechanics, Shanghai Jiao Tong University, Shanghai 200240 (China); Li, Shuhui [State Key Laboratory of Mechanical System and Vibration, Shanghai Key Laboratory of Digital Manufacture for Thin-walled Structures, Shanghai Jiao Tong University, Shanghai 200240 (China)

2017-05-17

Dual phase (DP) steels consist of hard brittle martensite phase and soft ductile ferrite phase. With a novel bending under tension test system, in-situ symmetrical bending under tension experiments were carried out and photomicrographs of bending surface were recorded. The microstructure “earthquake” of DP780 dual phase steels was observed in the bending under tension process. By analyzing the in-situ images serious, the initiation, coalescence of cavities and propagation of micro-cracks until final fracture were analyzed. The micro-cracks form only in the outside surface of bending radius, and mainly appear near the phase boundary of ferrite and martensite. Micro-cracks coalesce and propagate in the direction perpendicular to the stretching direction approximately, and at the phase boundary of martensite and ferrite. Furthermore, digital image correlation technology was used in this study to analysis the strain distribution between ferrite and martensite during the bending under tension deformation and fracture.

Stretching of red blood cells at high strain rates

Science.gov (United States)

Mancuso, J. E.; Ristenpart, W. D.

2017-10-01

Most work on the mechanical behavior of red blood cells (RBCs) in flow 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 Rapid Communication, 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 both the Kelvin-Voigt and Skalak viscoelastic models capture the observed stretching dynamics, up to strain rates as high as 2000 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.

Research on three-phase unbalanced distribution network reconfiguration strategy

Science.gov (United States)

Hu, Shuang; Li, Ke-Jun; Xu, Yanshun; Liu, Zhijie; Guo, Jing; Wang, Zhuodi

2017-01-01

With the development of social economy, the loads installed in the distribution network become more and more complex which may cause the three-phase unbalance problems. This paper proposes an optimal reconfiguration approach based on mixed integer quadric programming (MIQP) method to address the three-phase unbalance problem. It aims to minimize the total network losses of the system. By using several square constraints to substitute the circular constraint, the original optimization problem is linearized and converted into a mixed-integer linear programming (MILP) model. Then this MILP problem is solved in general algebraic model system (GAMS) software using CPLEX solver. The additional losses caused by three-phase unbalanced are also considered. An IEEE 34 nodes test system is used to demonstrate the feasibility and effectiveness of the proposed method. The results show that the losses and the voltage violation mitigation in the network can be reduced significantly.

Filament stretching rheometry of polymer melts

DEFF Research Database (Denmark)

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

2005-01-01

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...

Muscle oxygenation and fascicle length during passive muscle stretching in ballet-trained subjects.

Science.gov (United States)

Otsuki, A; Fujita, E; Ikegawa, S; Kuno-Mizumura, M

2011-07-01

Muscle stretching transiently decreases muscle-blood flow corresponding to a muscle extension. It may disturb a balance between muscular oxygen demand and oxygen supply to muscles and reduce muscle oxygenation. However, muscle-stretching training may improve blood circulatory condition, resulting in the maintained muscle oxygenation during muscle stretching. The aim of this study was to investigate changes in muscle-blood volume (tHb) and tissue oxygenation index (TOI) during muscle stretching determined by using near-infrared spectroscopy (NIRS) in ballet-trained (BT) and untrained (C) subjects. 11 BT women who regularly perform muscle stretching and 11 C women participated in this study. Fascicle lengths, tHb and TOI in the tibialis anterior muscle were measured during passive plantar flexion from ankle joint angles of 120° (baseline) to 140°, 160°, the maximal comfortable position without pain (CP), and the maximal position (MP). At 160°, the % fascicle-length change from baseline was significantly lower in the BT than the C group, however, for the changes in tHb and TOI the significant interaction effect between the 2 groups was not detected. On the other hand, although the increases in the fascicle length from baseline to CP and MP were greater in BT than C, the tHb and TOI reductions were comparable between groups. We concluded that it appears that BT can extend their muscles without excessive reduction in muscle-blood volume and muscle oxygenation at relatively same but absolutely greater muscle-stretching levels than C. The attenuation in these indices during high-level muscle stretching may be associated with the repetitive muscle stretching of long-term ballet training. © Georg Thieme Verlag KG Stuttgart · New York.

Effects of Combining Running and Practical Duration Stretching on Proprioceptive Skills of National Sprinters.

Science.gov (United States)

Romero-Franco, Natalia; Párraga-Montilla, Juan Antonio; Molina-Flores, Enrique M; Jiménez-Reyes, Pedro

2018-06-01

Romero-Franco, N, Párraga-Montilla, JA, Molina-Flores, EM, and Jiménez-Reyes, P. Effects of combining running and practical duration stretching on proprioceptive skills of national sprinters. J Strength Cond Res XX(X): 000-000, 2018-Practical duration stretching after aerobic activities is a recommended component of the first part of warm-up because of its effects on performance. However, its effects on proprioceptive skills are unknown. This study aimed to analyze the effects of running and practical duration static stretching (SS) and dynamic stretching (DS) on postural balance and the joint position sense (JPS) of national sprinters. Thirty-two national sprinters were randomly classified into a SS group (n = 11), DS group (n = 11), or control group (n = 10). Static stretching performed 5 minutes of running and short-duration (20 seconds) static stretches; DS performed 5 minutes of running and short-duration dynamic (20 seconds) stretches; and the control group performed 5 minutes of running. Before and after the intervention, unipedal static postural balance and knee JPS were evaluated. Static stretching exhibited a more centralized center of pressure in the medial-lateral plane for unipedal static postural balance in right-leg support after stretching (p = 0.005, d = 1.24), whereas DS showed values further from the center after stretching for the same unipedal support compared with baseline (p = 0.042, d = 0.49), and the control group remained stable (p > 0.05). Joint position sense did not show significant differences in any group (p > 0.05). In conclusion, combining running and practical duration SS may be beneficial for right-leg postural stabilization, whereas DS may be partly and slightly deleterious. Both SS and DS combined with running and running alone have neutral effects on knee JPS. Sports professionals should consider running and practical duration SS as part of the warm-up of sprinters to partly improve unipedal static postural balance.

SANS study of deformation and relaxation of a comb-like liquid crystal polymer in the nematic phase

Science.gov (United States)

Brûlet, A.; Boué, F.; Keller, P.; Davidson, P.; Strazielle, C.; Cotton, J. P.

1994-06-01

A comb-like liquid crystal polymer is stretched and quenched after a certain time in the nematic phase. The conformation of the deformed chain is determined using small angle neutron scattering (SANS) as a function of the temperature of stretching, the stretching ratio and the duration of the relaxation. The scattering data are well fitted to junction affine and phantom network models. Some data are even well fitted by a totally affine model that we call “ pseudo affine ” because the only parameter, the stretching ratio, is found to be well below the macroscopic stretching ratio. The latter result, never encountered with amorphous polymers, is attributed to the cooperative effects of the nematic phase. We also note that the form factors of the chain in the underformed sample remain similar in the isotropic, nematic and glassy state ; they correspond to a Gaussian chain. The same samples were studied by wide angle X-ray scattering. On one hand, the orientation of the mesogenic groups is found to be parallel or perpendicular to the stretching direction depending on the stretching temperature. This result is discussed as a function of the presence of smectic fluctuations. On the other hand, longer relaxations at constant elongation ratio do not lead to a disorganization of the mesogenic group orientation whereas the polymer chains are partly relaxed.

Caspase-12 is involved in stretch-induced apoptosis mediated endoplasmic reticulum stress.

Science.gov (United States)

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

2016-04-01

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.

Influence of Welding Strength Matching Coefficient and Cold Stretching on Welding Residual Stress in Austenitic Stainless Steel

Science.gov (United States)

Lu, Yaqing; Hui, Hu; Gong, Jianguo

2018-05-01

Austenitic stainless steel is widely used in pressure vessels for the storage and transportation of liquid gases such as liquid nitrogen, liquid oxygen, and liquid hydrogen. Cryogenic pressure vessel manufacturing uses cold stretching technology, which relies heavily on welding joint performance, to construct lightweight and thin-walled vessels. Residual stress from welding is a primary factor in cases of austenitic stainless steel pressure vessel failure. In this paper, on the basis of Visual Environment 10.0 finite element simulation technology, the residual stress resulting from different welding strength matching coefficients (0.8, 1, 1.2, 1.4) for two S30408 plates welded with three-pass butt welds is calculated according to thermal elastoplastic theory. In addition, the stress field was calculated under a loading as high as 410 MPa and after the load was released. Path 1 was set to analyze stress along the welding line, and path 2 was set to analyze stress normal to the welding line. The welding strength matching coefficient strongly affected both the longitudinal residual stress (center of path 1) and the transverse residual stress (both ends of path 1) after the welding was completed. However, the coefficient had little effect on the longitudinal and transverse residual stress of path 2. Under the loading of 410 MPa, the longitudinal and transverse stress decreased and the stress distribution, with different welding strength matching coefficients, was less diverse. After the load was released, longitudinal and transverse stress distribution for both path 1 and path 2 decreased to a low level. Cold stretching could reduce the effect of residual stress to various degrees. Transverse strain along the stretching direction was also taken into consideration. The experimental results validated the reliability of the partial simulation.

Stretching After Heat But Not After Cold Decreases Contractures After Spinal Cord Injury in Rats.

Science.gov (United States)

Iwasawa, Hiroyuki; Nomura, Masato; Sakitani, Naoyoshi; Watanabe, Kosuke; Watanabe, Daichi; Moriyama, Hideki

2016-12-01

Contractures are a prevalent and potentially severe complication in patients with neurologic disorders. Although heat, cold, and stretching are commonly used for treatment of contractures and/or spasticity (the cause of many contractures), the sequential effects of these modalities remain unclear. Using an established rat model with spinal cord injury with knee flexion contracture, we sought to determine what combination of heat or cold before stretching is the most effective for treatment of contractures derived from spastic paralyses and investigated which treatment leads to the best (1) improvement in the loss of ROM; (2) restoration of deterioration in the muscular and articular factors responsible for contractures; and (3) amelioration of histopathologic features such as muscular fibrosis in biceps femoris and shortening of the joint capsule. Forty-two adolescent male Wistar rats were used. After spasticity developed at 2 weeks postinjury, each animal with spinal cord injury underwent the treatment protocol daily for 1 week. Knee extension ROM was measured with a goniometer by two examiners blinded to each other's scores. The muscular and articular factors contributing to contractures were calculated by measuring ROM before and after the myotomies. We quantitatively measured the muscular fibrosis and the synovial intima length, and observed the distribution of collagen of skeletal muscle. The results were confirmed by a blinded observer. The ROM of heat alone (34° ± 1°) and cold alone (34° ± 2°) rats were not different with the numbers available from that of rats with spinal cord injury (35° ± 2°) (p = 0.92 and 0.89, respectively). Stretching after heat (24° ± 1°) was more effective than stretching alone (27° ± 3°) at increasing ROM (p contractures. Although quantification of muscular fibrosis in the rats with spinal cord injury (11% ± 1%) was higher than that of controls (9% ± 0.4%) (p = 0.01), no difference was found between spinal cord

Influence of acute static stretching on the behavior of maximum muscle strength

Directory of Open Access Journals (Sweden)

Carmen Lúcia Borges Bastos

2014-06-01

Full Text Available The aim of this study was to compare the influence of acute static stretching on maximal muscle strength (1RM. The non-probabilistic sample consisted of 30 subjects split into two groups: static stretching (SS= 15 and without stretching group (WS= 15. Muscle strength evaluation (1RM was conducted with a Dynamometer model 32527pp400 Pound push / pull devices coupled in knee extension (KE and bench press (BP. The Wilcoxon test for intragroup comparisons and the Kruskal-Wallis test for comparisons between groups (p< 0.05 were selected. There were no significant differences (p> 0.05 between the SS and WS in exercise KE and BP. Therefore, it can be concluded that there was no reduction in the performance of 1RM performing the exercises KE and BP when preceded by static stretching.

High-pressure synchrotron x-ray diffraction and infrared microspectroscopy: applications to dense hydrous phases

CERN Document Server

Liu, Z; Yang, H; Mao Ho Kwang; Hemley, R J

2002-01-01

Synchrotron x-ray diffraction (XRD) and infrared (IR) absorption spectra of hydrous and 'anhydrous' forms of phase X were measured to 30 GPa at room temperature. Three OH stretching modes were found in the hydrous phase, and surprisingly one sharp OH mode was observed in the previously characterized anhydrous phase. All OH stretching modes soften and broaden with increasing pressure and become very weak above approx 20 GPa. XRD indicates that the crystal structure remains stable up to 30 GPa. Combining IR absorption and XRD results, the behaviour is attributed to pressure-induced distortion of the Si sub 2 O sub 7 groups and disorder of the hydrogen atoms. The bulk moduli of the hydrous and 'anhydrous' phases are in the region of 74 GPa.

From Static Stretching to Dynamic Exercises: Changing the Warm-Up Paradigm

Science.gov (United States)

Young, Shawna

2010-01-01

In the United States, pre-exercise static stretching seems to have become common practice and routine. However, research suggests that it is time for a paradigm shift--that pre-exercise static stretching be replaced with dynamic warm-up exercises. Research indicates that a dynamic warm-up elevates body temperature, decreases muscle and joint…

Combined arm stretch positioning and neuromuscular electrical stimulation during rehabilitation does not improve range of motion, shoulder pain or function in patients after stroke : a randomised trial

NARCIS (Netherlands)

de Jong, Lex D.; Dijkstra, Pieter U.; Gerritsen, Johan; Geurts, Alexander C. H.; Postema, Klaas

2013-01-01

Question Does static stretch positioning combined with simultaneous neuromuscular electrical stimulation (NMES) in the subacute phase after stroke have beneficial effects on basic arm body functions and activities? Design Multicentre randomised trial with concealed allocation, assessor blinding, and

Cross-bridge mechanism of residual force enhancement after stretching in a skeletal muscle.

Science.gov (United States)

Tamura, Youjiro

2018-01-01

A muscle model that uses a modified Langevin equation with actomyosin potentials was used to describe the residual force enhancement after active stretching. Considering that the new model uses cross-bridge theory to describe the residual force enhancement, it is different from other models that use passive stretching elements. Residual force enhancement was simulated using a half sarcomere comprising 100 myosin molecules. In this paper, impulse is defined as the integral of an excess force from the steady isometric force over the time interval for which a stretch is applied. The impulse was calculated from the force response due to fast and slow muscle stretches to demonstrate the viscoelastic property of the cross-bridges. A cross-bridge mechanism was proposed as a way to describe the residual force enhancement on the basis of the impulse results with reference to the compliance of the actin filament. It was assumed that the period of the actin potential increased by 0.5% and the amplitude of the potential decreased by 0.5% when the half sarcomere was stretched by 10%. The residual force enhancement after 21.0% sarcomere stretching was 6.9% of the maximum isometric force of the muscle; this value was due to the increase in the number of cross-bridges.

Barriers to performing stretching exercises among Korean-Chinese female migrant workers in Korea.

Science.gov (United States)

Lee, Hyeonkyeong; Wilbur, JoEllen; Chae, Duckhee; Lee, Kyongeun; Lee, Meenhye

2015-01-01

The purpose of this study was to investigate the barriers to performing stretching exercise experienced by Korean-Chinese female migrant workers during a community-based 12-week stretching exercise intervention trial. Qualitative secondary data analysis was conducted using telephone counseling interview transcripts from 27 middle-aged, Korean-Chinese migrant women workers. A semistructured interview question asking barriers to performing stretching exercise was given to women who did not adhere to recommended stretching exercise. During the 12-week home-based stretching exercise intervention trial, six telephone calls were made to participants biweekly to elicit barriers to performing stretching exercise. Directed content analysis approach was utilized using three barrier categories: intrapersonal, interpersonal, and work-related environmental factors based on the ecological model. Participants experienced an average of 2.5 barriers during the study period. Intrapersonal barriers included lack of time and lack of motivation, and interpersonal barriers included no family to provide support and also a feeling resistance from coworkers. Work-related environmental barriers included frequent job changes, long working hours, lack of rest time, and unpredictable job demands. The findings highlight that migrant workers in Korea face unique work-related difficulties which present barriers to exercise. © 2014 Wiley Periodicals, Inc.

EVOLUTION OF DARK MATTER PHASE-SPACE DENSITY DISTRIBUTIONS IN EQUAL-MASS HALO MERGERS

International Nuclear Information System (INIS)

Vass, Ileana M.; Kazanzidis, Stelios; Valluri, Monica; Kravtsov, Andrey V.

2009-01-01

We use dissipationless N-body simulations to investigate the evolution of the true coarse-grained phase-space density distribution f(x, v) in equal-mass mergers between dark matter (DM) halos. The halo models are constructed with various asymptotic power-law indices ρ ∝ r -γ ranging from steep cusps to core-like profiles and we employ the phase-space density estimator 'EnBid' developed by Sharma and Steinmetz to compute f(x, v). The adopted force resolution allows robust phase-space density profile estimates in the inner ∼1% of the virial radii of the simulated systems. We confirm that merger events result in a decrease of the coarse-grained phase-space density in accordance with expectations from Mixing Theorems for collisionless systems. We demonstrate that binary mergers between identical DM halos produce remnants that retain excellent memories of the inner slopes and overall shapes of the phase-space density distribution of their progenitors. The robustness of the phase-space density profiles holds for a range of orbital energies, and a variety of encounter configurations including sequences of several consecutive merger events, designed to mimic hierarchical merging, and collisions occurring at different cosmological epochs. If the progenitor halos are constructed with appreciably different asymptotic power-law indices, we find that the inner slope and overall shape of the phase-space density distribution of the remnant are substantially closer to that of the initial system with the steepest central density cusp. These results explicitly demonstrate that mixing is incomplete in equal-mass mergers between DM halos, as it does not erase memory of the progenitor properties. Our results also confirm the recent analytical predictions of Dehnen regarding the preservation of merging self-gravitating central density cusps.

W-phase estimation of first-order rupture distribution for megathrust earthquakes

Science.gov (United States)

Benavente, Roberto; Cummins, Phil; Dettmer, Jan

2014-05-01

Estimating the rupture pattern for large earthquakes during the first hour after the origin time can be crucial for rapid impact assessment and tsunami warning. However, the estimation of coseismic slip distribution models generally involves complex methodologies that are difficult to implement rapidly. Further, while model parameter uncertainty can be crucial for meaningful estimation, they are often ignored. In this work we develop a finite fault inversion for megathrust earthquakes which rapidly generates good first order estimates and uncertainties of spatial slip distributions. The algorithm uses W-phase waveforms and a linear automated regularization approach to invert for rupture models of some recent megathrust earthquakes. The W phase is a long period (100-1000 s) wave which arrives together with the P wave. Because it is fast, has small amplitude and a long-period character, the W phase is regularly used to estimate point source moment tensors by the NEIC and PTWC, among others, within an hour of earthquake occurrence. We use W-phase waveforms processed in a manner similar to that used for such point-source solutions. The inversion makes use of 3 component W-phase records retrieved from the Global Seismic Network. The inverse problem is formulated by a multiple time window method, resulting in a linear over-parametrized problem. The over-parametrization is addressed by Tikhonov regularization and regularization parameters are chosen according to the discrepancy principle by grid search. Noise on the data is addressed by estimating the data covariance matrix from data residuals. The matrix is obtained by starting with an a priori covariance matrix and then iteratively updating the matrix based on the residual errors of consecutive inversions. Then, a covariance matrix for the parameters is computed using a Bayesian approach. The application of this approach to recent megathrust earthquakes produces models which capture the most significant features of

Experimental validation of the Wigner distributions theory of phase-contrast imaging

International Nuclear Information System (INIS)

Donnelly, Edwin F.; Price, Ronald R.; Pickens, David R.

2005-01-01

Recently, a new theory of phase-contrast imaging has been proposed by Wu and Liu [Med. Phys. 31, 2378-2384 (2004)]. This theory, based upon Wigner distributions, provides a much stronger foundation for the evaluation of phase-contrast imaging systems than did the prior theories based upon Fresnel-Kirchhoff diffraction theory. In this paper, we compare results of measurements made in our laboratory of phase contrast for different geometries and tube voltages to the predictions of the Wu and Liu model. In our previous publications, we have used an empirical measurement (the edge enhancement index) to parametrize the degree of phase-contrast effects in an image. While the Wu and Liu model itself does not predict image contrast, it does measure the degree of phase contrast that the system can image for a given spatial frequency. We have found that our previously published experimental results relating phase-contrast effects to geometry and x-ray tube voltage are consistent with the predictions of the Wu and Liu model

Individually programmable cell stretching microwell arrays actuated by a Braille display.

Science.gov (United States)

Kamotani, Yoko; Bersano-Begey, Tommaso; Kato, Nobuhiro; Tung, Yi-Chung; Huh, Dongeun; Song, Jonathan W; Takayama, Shuichi

2008-06-01

Cell culture systems are often static and are therefore nonphysiological. In vivo, many cells are exposed to dynamic surroundings that stimulate cellular responses in a process known as mechanotransduction. To recreate this environment, stretchable cell culture substrate systems have been developed, however, these systems are limited by being macroscopic and low throughput. We have developed a device consisting of 24 miniature cell stretching chambers with flexible bottom membranes that are deformed using the computer-controlled, piezoelectrically actuated pins of a Braille display. We have also developed efficient image capture and analysis protocols to quantify morphological responses of the cells to applied strain. Human dermal microvascular endothelial cells (HDMECs) were found to show increasing degrees of alignment and elongation perpendicular to the radial strain in response to cyclic stretch at increasing frequencies of 0.2, 1, and 5 Hz, after 2, 4, and 12h. Mouse myogenic C2C12 cells were also found to align in response to the stretch, while A549 human lung adenocarcinoma epithelial cells did not respond to stretch.

To Stretch and Search for Better Ways

Science.gov (United States)

Moore, John W.

2000-06-01

There's a lot to do to get each issue of this Journal ready for publication, and there's a lot that can go awry during that process. We the editorial staff do our utmost to make certain that each issue is the best it can possibly be, but, of necessity, a lot of our effort is focused on solving problems, correcting errors, and avoiding pitfalls. It is not surprising that we sometimes lose sight of the bigger picture--all of the things that came out as well as or better than we hoped they would. Therefore it gives us great pleasure when a reader applauds (and thereby rewards) our efforts. One such communication inspired this editorial. I have appreciated the extra effort put forward by the staff to make the Journal really come alive. The high quality of the Journal serves as an incentive to chemical educators to stretch and search for better ways to inspire our students. I fervently hope that we do encourage you "to stretch and search for better ways", not only to inspire students but in everything you do. Stretching and searching for better ways is what life, science, chemistry, and teaching are all about, and it is a wonderfully stimulating and exciting way to approach anything and everything. Sometimes, though, one's ability to stretch is akin to that of a rubber band exposed too long to sunlight. Change becomes a threat or a burden instead of an opportunity. This often happens in one area but not others, as in the case of someone doing original research but whose lecture notes are yellow with age, or someone who experiments with new teaching approaches but neglects the latest chemical discoveries. Whatever its manifestation, failure to stretch and search for better ways is a great loss, both for the individual directly involved and for others. Fortunately there are many who continually stretch and search, often in conjunction with JCE. For example, some time ago the Chair of the Board of Publication, Jerry Bell, challenged Journal readers to become Journal

Brillouin suppression in a fiber optical parametric amplifier by combining temperature distribution and phase modulation

DEFF Research Database (Denmark)

Lorenzen, Michael Rodas; Noordegraaf, Danny; Nielsen, Carsten Vandel

2008-01-01

We demonstrate an increased gain in optical parametric amplier through suppression of stimulated Brillouin scattering by applying a temperature distribution along the fiber resulting in a reduction of the required phase modulation.......We demonstrate an increased gain in optical parametric amplier through suppression of stimulated Brillouin scattering by applying a temperature distribution along the fiber resulting in a reduction of the required phase modulation....

Effectiveness of Manual Therapy and Stretching for Baseball Players With Shoulder Range of Motion Deficits.

Science.gov (United States)

Bailey, Lane B; Thigpen, Charles A; Hawkins, Richard J; Beattie, Paul F; Shanley, Ellen

Baseball players displaying deficits in shoulder range of motion (ROM) are at increased risk of arm injury. Currently, there is a lack of consensus regarding the best available treatment options to restore shoulder ROM. Instrumented manual therapy with self-stretching will result in clinically significant deficit reductions when compared with self-stretching alone. Controlled laboratory study. Shoulder ROM and humeral torsion were assessed in 60 active baseball players (mean age, 19 ± 2 years) with ROM deficits (nondominant - dominant, ≥15°). Athletes were randomly assigned to receive a single treatment of instrumented manual therapy plus self-stretching (n = 30) or self-stretching only (n = 30). Deficits in internal rotation, horizontal adduction, and total arc of motion were compared between groups immediately before and after a single treatment session. Treatment effectiveness was determined by mean comparison data, and a number-needed-to-treat (NNT) analysis was used for assessing the presence of ROM risk factors. Prior to intervention, players displayed significant ( P < 0.001) dominant-sided deficits in internal rotation (-26°), total arc of motion (-18°), and horizontal adduction (-17°). After the intervention, both groups displayed significant improvements in ROM, with the instrumented manual therapy plus self-stretching group displaying greater increases in internal rotation (+5°, P = 0.010), total arc of motion (+6°, P = 0.010), and horizontal adduction (+7°, P = 0.004) compared with self-stretching alone. For horizontal adduction deficits, the added use of instrumented manual therapy with self-stretching decreased the NNT to 2.2 (95% CI, 2.1-2.4; P = 0.010). Instrumented manual therapy with self-stretching significantly reduces ROM risk factors in baseball players with motion deficits when compared with stretching alone. The added benefits of manual therapy may help to reduce ROM deficits in clinical scenarios where stretching alone is

Efficient full decay inversion of MRS data with a stretched-exponential approximation of the ? distribution

Science.gov (United States)

Behroozmand, Ahmad A.; Auken, Esben; Fiandaca, Gianluca; Christiansen, Anders Vest; Christensen, Niels B.

2012-08-01

We present a new, efficient and accurate forward modelling and inversion scheme for magnetic resonance sounding (MRS) data. MRS, also called surface-nuclear magnetic resonance (surface-NMR), is the only non-invasive geophysical technique that directly detects free water in the subsurface. Based on the physical principle of NMR, protons of the water molecules in the subsurface are excited at a specific frequency, and the superposition of signals from all protons within the excited earth volume is measured to estimate the subsurface water content and other hydrological parameters. In this paper, a new inversion scheme is presented in which the entire data set is used, and multi-exponential behaviour of the NMR signal is approximated by the simple stretched-exponential approach. Compared to the mono-exponential interpretation of the decaying NMR signal, we introduce a single extra parameter, the stretching exponent, which helps describe the porosity in terms of a single relaxation time parameter, and helps to determine correct initial amplitude and relaxation time of the signal. Moreover, compared to a multi-exponential interpretation of the MRS data, the decay behaviour is approximated with considerably fewer parameters. The forward response is calculated in an efficient numerical manner in terms of magnetic field calculation, discretization and integration schemes, which allows fast computation while maintaining accuracy. A piecewise linear transmitter loop is considered for electromagnetic modelling of conductivities in the layered half-space providing electromagnetic modelling of arbitrary loop shapes. The decaying signal is integrated over time windows, called gates, which increases the signal-to-noise ratio, particularly at late times, and the data vector is described with a minimum number of samples, that is, gates. The accuracy of the forward response is investigated by comparing a MRS forward response with responses from three other approaches outlining

[Current trends in the effects of stretching: application to physical exercise in the workplace].

Science.gov (United States)

Eguchi, Yasumasa; Ohta, Masanori; Yamato, Hiroshi

2011-09-01

A review of the Survey on the State of Employees' Health by the Ministry of Health, Labour and Welfare (2008) shows that the most commonly implemented aspect as an activity of worksite health promotion is "Health counseling", and the second is "Workplace physical exercise." Physical exercise, "Taiso", is acceptable and sustainable for workers, as it is easy to do in a group or alone. Various modes of stretching are implemented for workplace physical exercise. However, articles suggesting negative or contradictory effects of stretching have increased in recent years. Several review articles have revealed that static stretching may induce impairments of muscle power performance and no stretching will prevent or reduce muscle soreness after exercise. There are various aims of workplace physical exercise, so we have to consider the situational method when we apply stretching to occupational health.

Effectiveness of passive stretching versus hold relax technique in flexibility of hamstring muscle

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Gauri Shankar

2010-10-01

Full Text Available Aim: To compare the effectiveness of passive stretching and hold relax technique in the flexibility of hamstring muscle. Methods: A total of 80 normal healthy female subjects between age group 20-30 years referred to the department of physiotherapy, Sumandeep Vidyapeeth University, sampling method being convenient sampling. The subjects were randomly divided in two groups i.e. passive stretching group (n=40 and PNF group (n=40 and given passive stretching and proprioceptive neuromuscular facilitation technique respectively. Active knee extension range was measured before and after the intervention by goniometer. Results: t test showed a highly significant (p=0.000 increase in range of motion in PNF group. Conclusion: Proprioceptive neuromuscular facilitation technique is more effective in increasing hamstring flexibility than the passive stretching.

The distribution of Th(NO3)4, UO2(NO3)2 and HNO3 between an aqueous phase and an organic tributyl phosphate phase

International Nuclear Information System (INIS)

Nakashima, T.; Zimmer, E.

1984-05-01

The distribution of Th(NO 3 ) 4 , UO 2 (NO 3 ) 2 and HNO 3 between an aqueous phase and an organic phase, consisting of 30 Vol.% tributyl phosphate in dodecane, has been experimentally investigated. About 120 distribution data have been determined in the concentration ranges that can be seen in the THOREX process for reprocessing spent thorium bearing fuel. Based on the experimental data, two computer programs have been developed which make possible interpolations and, to some extent, extrapolations. With model 1, concentrations in the organic phase can be calculated if that in the aqueous phase are known. With model 2, concentrations in the aqueous phase can be calculated vice versa. Besides the description of the calculation models, a large body of calculated data can be found in this report. In a addition, a calculation mode is presented that makes possible the calculation of distribution data for very low thorium concentrations. (orig.) [de

Acute effect of static stretching on muscle force in older women

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André Luiz Demantova Gurjão

2010-04-01

Full Text Available The objective of this study was to investigate the acute effect of static stretching on the peak rate of force development (PRFD and maximum voluntary contraction (MVC in older women. Ten women (68.5 ± 7.0 years; 70.9 ± 8.1 kg; 159.4 ± 6.0 cm; body mass index: 28.0 ± 3.8 kg/m2 were studied. MVC and PRFD were determined by leg press exercise before and after the control or stretching condition (three sets of 30 seconds of static stretching of the quadriceps on two different days (interval of 24 hours. PRFD was determined as the steepest slope of the curve, calculated within regular windows of 20 milliseconds (∆force/∆time for the first 200 milliseconds after the onset of contraction. MVC was determined as the highest value recorded in each set. Only one condition was tested on each day and the order of application of each condition was determined randomly. The stretching intensity was evaluated by the muscle pain threshold. Four post-condition assessments (post-treatment, 10, 20, and 30 minutes were performed to monitor muscle strength. ANCOVA 2x5, followed by the Scheffé post-hoc test, showed no significant interactions between conditions vs. times (P > 0.05 for PRFD or MVC. In conclusion, acute bouts of static stretching of the quadriceps femoris do not affect the ability of rapid and maximum muscle force production in older women.

Prolonged passive static stretching-induced innervation zone shift in biceps brachii.

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Ye, Xin; Beck, Travis W; Wages, Nathan P

2015-05-01

The purpose of this study was to examine the influence of a bout of repeated and prolonged passive static stretching on the innervation zone (IZ) location of the human biceps brachii muscle. Eleven men performed 12 sets of 100-s passive stretches on their biceps brachii. Before (Pre) and immediately after (Post) the stretching intervention, isometric strength was tested during the maximal voluntary contractions (MVCs) of the forearm flexors. The subjects also performed several separate isometric forearm flexion muscle actions at 30%, 50%, and 70% of their predetermined MVCs for examining the locations of the IZ at different contraction intensities. The IZ was identified through multi-channel surface electromyographic (EMG) recordings from a linear electrode array. The stretching intervention induced an average of 10% isometric strength loss for the forearm flexors (mean±SD: Pre-MVC vs. Post-MVC=332.12±59.40 N vs. 299.53±70.51 N; p<0.001). In addition, the average IZ shift was nearly 4.5 mm in average in the proximal direction. However, this shift was not specific to the contraction intensity. We believe that the IZ shift was caused by the elongation of the entire muscle-tendon unit in the proximal direction. Therefore, caution should be taken when using surface EMG technique to examine possible changes in the EMG variables after a stretching protocol, as these variables can be contaminated by the shift of the IZ.

Intraplaque stretch in carotid atherosclerotic plaque--an effective biomechanical predictor for subsequent cerebrovascular ischemic events.

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Zhongzhao Teng

Full Text Available BACKGROUND: Stretch is a mechanical parameter, which has been proposed previously to affect the biological activities in different tissues. This study explored its utility in determining plaque vulnerability. METHODS: One hundred and six patients with mild to moderate carotid stenosis were recruited in this study (53 symptomatic and 53 asymptomatic. High resolution, multi-sequence magnetic resonance (MR imaging was performed to delineate various plaque components. Finite element method was used to predict high stretch concentration within the plaque. RESULTS: During a two-year follow-up, 11 patients in symptomatic group and 3 in asymptomatic group experienced recurrent cerebrovascular events. Plaque stretch at systole and stretch variation during one cardiac cycle was greater in symptomatic group than those in the asymptomatic. Within the symptomatic group, a similar trend was observed in patients with recurrent events compared to those without. CONCLUSION: Plaques with high stretch concentration and large stretch variation are associated with increased risk of future cerebrovascular events.

Energy management based on AM/FM/GIS for phase balancing application on distribution systems

International Nuclear Information System (INIS)

Kuo, C.-C.; Chao, Y.-T.

2010-01-01

Unbalanced feeder systems may deteriorate of power quality, and increase investment and operating costs for distribution systems. The phase swapping method recommends re-phasing circuits of laterals and transformers for making the current and voltage balanced and also reducing feeder loss and voltage drop. In this paper, an application program, based on the automated mapping/facilities management/ geographic information system (AM/FM/GIS) is developed which contains a function of automatically computing Z-bus, load flow and phase balancing of feeders with phase swapping by using easily selecting of feeder on a graphic user interface application. Therefore, the relative data need not be keyed in manually. The presented phase balancing algorithm are based on database and related data structures developed on the AM/FM/GIS and Visual Basic software, which can be integrated into the Tai-Power distribution automation system. Then, the phase balancing algorithm is designed to handle the load patterns and the load of transformers that connect specific feeders when evaluating phase swaps that will result in reduced daily circuit losses over all load points. The proposed application not only can effectively reduce the circuit loss and improves phase balancing, but also enhances power quality efficiently under easily using environment.

Biochemical analysis of force-sensitive responses using a large-scale cell stretch device.

Science.gov (United States)

Renner, Derrick J; Ewald, Makena L; Kim, Timothy; Yamada, Soichiro

2017-09-03

Physical force has emerged as a key regulator of tissue homeostasis, and plays an important role in embryogenesis, tissue regeneration, and disease progression. Currently, the details of protein interactions under elevated physical stress are largely missing, therefore, preventing the fundamental, molecular understanding of mechano-transduction. This is in part due to the difficulty isolating large quantities of cell lysates exposed to force-bearing conditions for biochemical analysis. We designed a simple, easy-to-fabricate, large-scale cell stretch device for the analysis of force-sensitive cell responses. Using proximal biotinylation (BioID) analysis or phospho-specific antibodies, we detected force-sensitive biochemical changes in cells exposed to prolonged cyclic substrate stretch. For example, using promiscuous biotin ligase BirA* tagged α-catenin, the biotinylation of myosin IIA increased with stretch, suggesting the close proximity of myosin IIA to α-catenin under a force bearing condition. Furthermore, using phospho-specific antibodies, Akt phosphorylation was reduced upon stretch while Src phosphorylation was unchanged. Interestingly, phosphorylation of GSK3β, a downstream effector of Akt pathway, was also reduced with stretch, while the phosphorylation of other Akt effectors was unchanged. These data suggest that the Akt-GSK3β pathway is force-sensitive. This simple cell stretch device enables biochemical analysis of force-sensitive responses and has potential to uncover molecules underlying mechano-transduction.

Three-Phase Unbalanced Load Flow Tool for Distribution Networks

DEFF Research Database (Denmark)

Demirok, Erhan; Kjær, Søren Bækhøj; Sera, Dezso

2012-01-01

This work develops a three-phase unbalanced load flow tool tailored for radial distribution networks based on Matlab®. The tool can be used to assess steady-state voltage variations, thermal limits of grid components and power losses in radial MV-LV networks with photovoltaic (PV) generators where...... most of the systems are single phase. New ancillary service such as static reactive power support by PV inverters can be also merged together with the load flow solution tool and thus, the impact of the various reactive power control strategies on the steady-state grid operation can be simply...... investigated. Performance of the load flow solution tool in the sense of resulting bus voltage magnitudes is compared and validated with IEEE 13-bus test feeder....

Developmental axon stretch stimulates neuron growth while maintaining normal electrical activity, intracellular calcium flux, and somatic morphology.

Science.gov (United States)

Loverde, Joseph R; Pfister, Bryan J

2015-01-01

Elongation of nerve fibers intuitively occurs throughout mammalian development, and is synchronized with expansion of the growing body. While most tissue systems enlarge through mitosis and differentiation, elongation of nerve fibers is remarkably unique. The emerging paradigm suggests that axons undergo stretch as contiguous tissues enlarge between the proximal and distal segments of spanning nerve fibers. While stretch is distinct from growth, tension is a known stimulus which regulates the growth of axons. Here, we hypothesized that the axon stretch-growth process may be a natural form of injury, whereby regenerative processes fortify elongating axons in order to prevent disconnection. Harnessing the live imaging capability of our axon stretch-growth bioreactors, we assessed neurons both during and following stretch for biomarkers associated with injury. Utilizing whole-cell patch clamp recording, we found no evidence of changes in spontaneous action potential activity or degradation of elicited action potentials during real-time axon stretch at strains of up to 18% applied over 5 min. Unlike traumatic axonal injury, functional calcium imaging of the soma revealed no shifts in free intracellular calcium during axon stretch. Finally, the cross-sectional areas of nuclei and cytoplasms were normal, with no evidence of chromatolysis following week-long stretch-growth limited to the lower of 25% strain or 3 mm total daily stretch. The neuronal growth cascade coupled to stretch was concluded to be independent of the changes in membrane potential, action potential generation, or calcium flux associated with traumatic injury. While axon stretch-growth is likely to share overlap with regenerative processes, we conclude that developmental stretch is a distinct stimulus from traumatic axon injury.

Developmental Axon Stretch Stimulates Neuron Growth While Maintaining Normal Electrical Activity, Intracellular Calcium Flux, and Somatic Morphology

Directory of Open Access Journals (Sweden)

Joseph R Loverde

2015-08-01

Full Text Available Elongation of nerve fibers intuitively occurs throughout mammalian development, and is synchronized with expansion of the growing body. While most tissue systems enlarge through mitosis and differentiation, elongation of nerve fibers is remarkably unique. The emerging paradigm suggests that axons undergo stretch as contiguous tissues enlarge between the proximal and distal segments of spanning nerve fibers. While stretch is distinct from growth, tension is a known stimulus which regulates the growth of axons. Here, we hypothesized that the axon stretch-growth process may be a natural form of injury, whereby regenerative processes fortify elongating axons in order to prevent disconnection. Harnessing the live imaging capability of our axon stretch-growth bioreactors, we assessed neurons both during and following stretch for biomarkers associated with injury. Utilizing whole-cell patch clamp recording, we found no evidence of changes in spontaneous action potential activity or degradation of elicited action potentials during real-time axon stretch at strains of up to 18 % applied over 5 minutes. Unlike traumatic axonal injury, functional calcium imaging of the soma revealed no shifts in free intracellular calcium during axon stretch. Finally, the cross-sectional areas of nuclei and cytoplasms were normal, with no evidence of chromatolysis following week-long stretch-growth limited to the lower of 25 % strain or 3 mm total daily stretch. The neuronal growth cascade coupled to stretch was concluded to be independent of the changes in membrane potential, action potential generation, or calcium flux associated with traumatic injury. While axon stretch-growth is likely to share overlap with regenerative processes, we conclude that developmental stretch is a distinct stimulus from traumatic axon injury.

Retosiban Prevents Stretch-Induced Human Myometrial Contractility and Delays Labor in Cynomolgus Monkeys.

Science.gov (United States)

Aye, Irving L M H; Moraitis, Alexandros A; Stanislaus, Dinesh; Charnock-Jones, D Stephen; Smith, Gordon C S

2018-03-01

Stretch of the myometrium promotes its contractility and is believed to contribute to the control of parturition at term and to the increased risk of preterm birth in multiple pregnancies. To determine the effects of the putative oxytocin receptor (OTR) inverse agonist retosiban on (1) the contractility of human myometrial explants and (2) labor in nonhuman primates. Human myometrial biopsies were obtained at planned term cesarean, and explants were exposed to stretch in the presence and absence of a range of drugs, including retosiban. The in vivo effects of retosiban were determined in cynomolgus monkeys. Prolonged mechanical stretch promoted myometrial extracellular signal-regulated kinase (ERK)1/2 phosphorylation. Moreover, stretch-induced stimulation of myometrial contractility was prevented by ERK1/2 inhibitors. Retosiban (10 nM) prevented stretch-induced stimulation of myometrial contractility and phosphorylation of ERK1/2. Moreover, the inhibitory effect of retosiban on stretch-induced ERK1/2 phosphorylation was prevented by coincubation with a 100-fold excess of a peptide OTR antagonist, atosiban. Compared with vehicle-treated cynomolgus monkeys, treatment with oral retosiban (100 to 150 days of gestational age) reduced the risk of spontaneous delivery (hazard ratio = 0.07, 95% confidence interval 0.01 to 0.60, P = 0.015). The OTR acts as a uterine mechanosensor, whereby stretch increases myometrial contractility through agonist-free activation of the OTR. Retosiban prevents this through inverse agonism of the OTR and, in vivo, reduced the likelihood of spontaneous labor in nonhuman primates. We hypothesize that retosiban may be an effective preventative treatment of preterm birth in high-risk multiple pregnancies, an area of unmet clinical need.

Kink and kink-like waves in pre-stretched Mooney-Rivlin viscoelastic rods

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Y. Z. Wang

2015-08-01

Full Text Available The present paper theoretically investigates kink and kink-like waves propagating in pre-stretched Mooney-Rivlin viscoelastic rods. In the constitutive modeling, the Cauchy stress tensor is assumed to consist of an elastic part and a dissipative part. The asymptotic method is adopted to simplify the nonlinear dynamic equations in the limit of finite-small amplitude and long wavelength. Using the reductive perturbation method, we further derive the well-known far-field equation (i.e. the KdV-Burgers equation, to which two kinds of explicit traveling wave solutions are presented. Examples are given to show the influences of pre-stretch and viscosity on the wave shape and wave velocity. It is shown that pre-stretch could be an effective method for modulating the two types of waves. In addition, such waves may be utilized to measure the viscosity coefficient of the material. The competition between the effects of pre-stretch and viscosity on the kink and kink-like waves is also revealed.

Phase transition in the rich-get-richer mechanism due to finite-size effects

International Nuclear Information System (INIS)

Bagrow, James P; Ben-Avraham, Daniel; Sun Jie

2008-01-01

The rich-get-richer mechanism (agents increase their 'wealth' randomly at a rate proportional to their holdings) is often invoked to explain the Pareto power-law distribution observed in many physical situations, such as the degree distribution of growing scale-free nets. We use two different analytical approaches, as well as numerical simulations, to study the case where the number of agents is fixed and finite (but large), and the rich-get-richer mechanism is invoked a fraction r of the time (the remainder of the time wealth is disbursed by a homogeneous process). At short times, we recover the Pareto law observed for an unbounded number of agents. In later times, the (moving) distribution can be scaled to reveal a phase transition with a Gaussian asymptotic form for r<1/2, and a Pareto-like tail (on the positive side) and a novel stretched exponential decay (on the negative side) for r<1/2

Cell volume and membrane stretch independently control K+ channel activity

DEFF Research Database (Denmark)

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

2009-01-01

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...... 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....... 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...

Linear response of stretch-affected premixed flames to flow oscillations

Energy Technology Data Exchange (ETDEWEB)

Wang, H.Y.; Law, C.K. [Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544 (United States); Lieuwen, T. [School of Aerospace Engineering, Georgia Institute of Technology, Atlanta, GA 30332 (United States)

2009-04-15

The linear response of 2D wedge-shaped premixed flames to harmonic velocity disturbances was studied, allowing for the influence of flame stretch manifested as variations in the local flame speed along the wrinkled flame front. Results obtained from analyzing the G-equation show that the flame response is mainly characterized by a Markstein number {sigma}{sub C}, which measures the curvature effect of the wrinkles, and a Strouhal number, St{sub f}, defined as the angular frequency of the disturbance normalized by the time taken for the disturbance to propagate the flame length. Flame stretch is found to become important when the disturbance frequency satisfies {sigma}{sub C}St{sub f}{sup 2}{proportional_to} O(1), i.e. St{sub f}{proportional_to} O({sigma}{sub C}{sup -1/2}). Specifically, for disturbance frequencies below this order, stretch effects are small and the flame responds as an unstretched one. When the disturbance frequencies are of this order, the transfer function, defined as the ratio of the normalized fluctuation of the heat release rate to that of the velocity, is contributed mostly from fluctuations of the flame surface area, which is now affected by stretch. Finally, as the disturbance frequency increases to St{sub f}{proportional_to} O({sigma}{sub C}{sup -1}), i.e. {sigma}{sub C}St{sub f}{proportional_to} O(1), the direct contribution from the stretch-affected flame speed fluctuation to the transfer function becomes comparable to that of the flame surface area. The present study phenomenologically explains the experimentally observed filtering effect in which the flame wrinkles developed at the flame base decay along the flame surface for large frequency disturbances as well as for thermal-diffusively stable and weakly unstable mixtures. (author)

The Effect of Static Stretch on Elastin Degradation in Arteries

Science.gov (United States)

Chow, Ming-Jay; Choi, Myunghwan; Yun, Seok Hyun; Zhang, Yanhang

2013-01-01

Previously we have shown that gradual changes in the structure of elastin during an elastase treatment can lead to important transition stages in the mechanical behavior of arteries [1]. However, in vivo arteries are constantly being loaded due to systolic and diastolic pressures and so understanding the effects of loading on the enzymatic degradation of elastin in arteries is important. With biaxial tensile testing, we measured the mechanical behavior of porcine thoracic aortas digested with a mild solution of purified elastase (5 U/mL) in the presence of a static stretch. Arterial mechanical properties and biochemical composition were analyzed to assess the effects of mechanical stretch on elastin degradation. As elastin is being removed, the dimensions of the artery increase by more than 20% in both the longitude and circumference directions. Elastin assays indicate a faster rate of degradation when stretch was present during the digestion. A simple exponential decay fitting confirms the time constant for digestion with stretch (0.11±0.04 h−1) is almost twice that of digestion without stretch (0.069±0.028 h−1). The transition from J-shaped to S-shaped stress vs. strain behavior in the longitudinal direction generally occurs when elastin content is reduced by about 60%. Multiphoton image analysis confirms the removal/fragmentation of elastin and also shows that the collagen fibers are closely intertwined with the elastin lamellae in the medial layer. After removal of elastin, the collagen fibers are no longer constrained and become disordered. Release of amorphous elastin during the fragmentation of the lamellae layers is observed and provides insights into the process of elastin degradation. Overall this study reveals several interesting microstructural changes in the extracellular matrix that could explain the resulting mechanical behavior of arteries with elastin degradation. PMID:24358135

Renewable Distributed Generation Models in Three-Phase Load Flow Analysis for Smart Grid

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K. M. Nor

2013-11-01

Full Text Available The paper presents renewable distributed generation  (RDG models as three-phase resource in load flow computation and analyzes their effect when they are connected in composite networks. The RDG models that have been considered comprise of photovoltaic (PV and wind turbine generation (WTG. The voltage-controlled node and complex power injection node are used in the models. These improvement models are suitable for smart grid power system analysis. The combination of IEEE transmission and distribution data used to test and analyze the algorithm in solving balanced/unbalanced active systems. The combination of IEEE transmission data and IEEE test feeder are used to test the the algorithm for balanced and unbalanced multi-phase distribution system problem. The simulation results show that by increased number and size of RDG units have improved voltage profile and reduced system losses.

Three-Phase PV CHB Inverter for a Distributed Power Generation System

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Pierluigi Guerriero

2016-10-01

Full Text Available This work deals with the design of a three-phase grid-tied photovoltaic (PV cascade H-bridge inverter for distributed power conversion. The power balancing among the phases must be properly addressed. In fact, an intra-phase power imbalance—arising from uneven irradiance and temperature conditions—generates a per-phase power imbalance. This latter can be compensated by the injection of a proper zero-sequence voltage, while the intra-phase balance is ensured by means of a hybrid modulation method which is able to guarantee the handling of unequal DC (Direct Current sources, stable circuit operation, and maximization of PV power production. The digital controller is developed and tested in Matlab/Simulink environment integrated with XSG (Xilinx System Generator, thus allowing an easy transfer on a field-programmable gate array (FPGA platform and accurately describing the behavior of a real hardware implementation. Thus, numerical results have been considered to prove the effectiveness of the proposed approach.

Mechanical stretch modulates microRNA 21 expression, participating in proliferation and apoptosis in cultured human aortic smooth muscle cells.

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Jian tao Song

Full Text Available OBJECTIVES: Stretch affects vascular smooth muscle cell proliferation and apoptosis, and several responsible genes have been proposed. We tested whether the expression of microRNA 21 (miR-21 is modulated by stretch and is involved in stretch-induced proliferation and apoptosis of human aortic smooth muscle cells (HASMCs. METHODS AND RESULTS: RT-PCR revealed that elevated stretch (16% elongation, 1 Hz increased miR-21 expression in cultured HASMCs, and moderate stretch (10% elongation, 1 Hz decreased the expression. BrdU incorporation assay and cell counting showed miR-21 involved in the proliferation of HASMCs mediated by stretch, likely by regulating the expression of p27 and phosphorylated retinoblastoma protein (p-Rb. FACS analysis revealed that the complex of miR-21 and programmed cell death protein 4 (PDCD4 participated in regulating apoptosis with stretch. Stretch increased the expression of primary miR-21 and pre-miR-21 in HASMCs. Electrophoretic mobility shift assay (EMSA demonstrated that stretch increased NF-κB and AP-1 activities in HASMCs, and blockade of AP-1 activity by c-jun siRNA significantly suppressed stretch-induced miR-21 expression. CONCLUSIONS: Cyclic stretch modulates miR-21 expression in cultured HASMCs, and miR-21 plays important roles in regulating proliferation and apoptosis mediated by stretch. Stretch upregulates miR-21 expression at least in part at the transcription level and AP-1 is essential for stretch-induced miR-21 expression.

Evaluation of Residual Stress Distribution and Relaxation on In Situ TiB2/7050 Al Composites

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Kunyang Lin

2018-04-01

Full Text Available Interior residual stresses induced by quenching may cause distortion during subsequent machining processes. Hence, various strategies have been employed to relieve the interior residual stress, such as stretching, post treatment, and other techniques. In this study, the stress distribution inside TiB2/7050 Al composite extrusions was investigated and the effects of different methods on relieving the quenching-induced stress were compared. Firstly, three TiB2/7050 Al composite extrusions were treated by stretching, stretching and heat treatment, and stretching and cold treatment processes, respectively. Then, the multiple-cut contour method was employed to assess the residual stresses in the three workpieces. Experimental results indicate that the interior stress of TiB2/7050 Al composite extrusions after stretching ranges from −89 MPa to +55 MPa, which is larger than that in 7050 aluminum alloy, which ranges from −25 Pa to +25 MPa. The heat treatment performs better than the cold treatment to reduce the post-stretching residual stress, with a reduction of 23.2–46.4% compared to 11.3–40.8%, respectively. From the stress map, it is found that the stress distribution after the heat treatment is more uniform compared with that after the cold treatment.

Parameters Controlling Dimensional Accuracy of Aluminum Extrusions Formed in Stretch Bending

International Nuclear Information System (INIS)

Baringbing, Henry Ako; Welo, Torgeir

2007-01-01

For stretch formed components used in the automotive industry, such as bumper beams, it is of primary importance to control parameters affecting dimensional accuracy. The variations in geometry and mechanical properties induced in extrusion and stretch forming lead to subsequent dimensional inaccuracy of the final product. In this work, tensile and compression samples were taken at three different positions along AA7108W extruded profiles in order to determine material parameters for a constitutive model particularly suited for strong texture materials. In addition, geometry were measured and analyzed statistically in order to study its impact on local cross sectional distortions (sagging) and springback in stretch bending of a bumper beam. These full scale experiments were combined with analytical and numerical simulations to quantify the impact of each basic parameter on product quality. It is concluded that this methodology provides a means to systematically control the product quality by focusing on reducing the acceptance limits of the main parameters controlling basic mechanisms in stretch forming. Despite the assumptions and simplifications made in order to make the analytical expressions solvable, the approach has proven its capability in establishing accurate closed-form expressions including the main influential parameters

Mediators of Yoga and Stretching for Chronic Low Back Pain

Directory of Open Access Journals (Sweden)

Karen J. Sherman

2013-01-01

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.

Longitudinal motion in high current ion beams: a self-consistent phase space distribution with an envelope equation

International Nuclear Information System (INIS)

Neuffer, D.

1979-03-01

Many applications of particle acceleration, such as heavy ion fusion, require longitudinal bunching of a high intensity particle beam to extremely high particle currents with correspondingly high space charge forces. This requires a precise analysis of longitudinal motion including stability analysis. Previous papers have treated the longitudinal space charge force as strictly linear, and have not been self-consistent; that is, they have not displayed a phase space distribution consistent with this linear force so that the transport of the phase space distribution could be followed, and departures from linearity could be analyzed. This is unlike the situation for transverse phase space where the Kapchinskij--Vladimirskij (K--V) distribution can be used as the basis of an analysis of transverse motion. In this paper a self-consistent particle distribution in longitudinal phase space is derived which is a solution of the Vlasov equation and an envelope equation for this solution is derived

Comparison between static stretching and the Pilates method on the flexibility of older women.

Science.gov (United States)

Oliveira, Laís Campos de; Oliveira, Raphael Gonçalves de; Pires-Oliveira, Deise Aparecida de Almeida

2016-10-01

Flexibility decreases with advancing age and some forms of exercise, such as static stretching and Pilates, can contribute to the improvement of this physical ability. To compare the effects of static stretching and Pilates on the flexibility of healthy older women, over the age of 60 years. Thirty-two volunteers were randomized into two groups (Static stretching or Pilates) to perform exercises for 60 min, twice a week, for three months. Evaluations to analyze the movements of the trunk (flexion and extension), hip flexion and plantar and dorsiflexion of the ankle were performed before and after the intervention, using a fleximeter. The static stretching exercises improved the trunk flexion and hip flexion movements, while the Pilates improved all evaluated movements. However, over time, the groups presented differences only for the trunk extension movement. For some body segments, Pilates may be more effective for improving flexibility in older women compared to static stretching. Copyright © 2016 Elsevier Ltd. All rights reserved.

a First-Principles Model of Fermi Resonance in the Alkyl CH Stretch Region: Application to Hydronaphthalenes, Indanes, and Cyclohexane

Science.gov (United States)

Sibert, Edwin; Kidwell, Nathanael; Zwier, Timothy S.

2014-06-01

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.

Control Method of Single-phase Inverter Based Grounding System in Distribution Networks

DEFF Research Database (Denmark)

Wang, Wen; Yan, L.; Zeng, X.

2016-01-01

of neutral-to-ground voltage is critical for the safety of distribution networks. An active grounding system based on single-phase inverter is proposed to achieve this objective. Relationship between output current of the system and neutral-to-ground voltage is derived to explain the principle of neutral......The asymmetry of the inherent distributed capacitances causes the rise of neutral-to-ground voltage in ungrounded system or high resistance grounded system. Overvoltage may occur in resonant grounded system if Petersen coil is resonant with the distributed capacitances. Thus, the restraint...

Optimizing an Intermittent Stretch Paradigm Using ERK1/2 Phosphorylation Results in Increased Collagen Synthesis in Engineered Ligaments

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Paxton, Jennifer Z.; Hagerty, Paul; Andrick, Jonathan J.

2012-01-01

Dynamic mechanical input is believed to play a critical role in the development of functional musculoskeletal tissues. To study this phenomenon, cyclic uniaxial mechanical stretch was applied to engineered ligaments using a custom-built bioreactor and the effects of different stretch frequency, amplitude, and duration were determined. Stretch acutely increased the phosphorylation of p38 (3.5±0.74-fold), S6K1 (3.9±0.19-fold), and ERK1/2 (2.45±0.32-fold). The phosphorylation of ERK1/2 was dependent on time, rather than on frequency or amplitude, within these constructs. ERK1/2 phosphorylation was similar following stretch at frequencies from 0.1 to 1 Hz and amplitudes from 2.5% to 15%, whereas phosphorylation reached maximal levels at 10 min of stretch and returned toward basal within 60 min of stretch. Following a single 10-min bout of cyclic stretch, the cells remained refractory to a second stretch for up to 6 h. Using the phosphorylation of ERK1/2 as a guide, the optimum stretch paradigm was hypothesized to be 10 min of stretch at 2.5% of resting length repeated every 6 h. Consistent with this hypothesis, 7 days of stretch using this optimized intermittent stretch program increased the collagen content of the grafts more than a continuous stretch program (CTL=3.1%±0.44%; CONT=4.8%±0.30%; and INT=5.9%±0.56%). These results suggest that short infrequent bouts of loading are optimal for improving engineered tendon and ligament physiology. PMID:21902469

High throughput web inspection system using time-stretch real-time imaging

Science.gov (United States)

Kim, Chanju

Photonic time-stretch is a novel technology that enables capturing of fast, rare and non-repetitive events. Therefore, it operates in real-time with ability to record over long period of time while having fine temporal resolution. The powerful property of photonic time-stretch has already been employed in various fields of application such as analog-to-digital conversion, spectroscopy, laser scanner and microscopy. Further expanding the scope, we fully exploit the time-stretch technology to demonstrate a high throughput web inspection system. Web inspection, namely surface inspection is a nondestructive evaluation method which is crucial for semiconductor wafer and thin film production. We successfully report a dark-field web inspection system with line scan speed of 90.9 MHz which is up to 1000 times faster than conventional inspection instruments. The manufacturing of high quality semiconductor wafer and thin film may directly benefit from this technology as it can easily locate defects with area of less than 10 microm x 10 microm where it allows maximum web flow speed of 1.8 km/s. The thesis provides an overview of our web inspection technique, followed by description of the photonic time-stretch technique which is the keystone in our system. A detailed explanation of each component is covered to provide quantitative understanding of the system. Finally, imaging results from a hard-disk sample and flexible films are presented along with performance analysis of the system. This project was the first application of time-stretch to industrial inspection, and was conducted under financial support and with close involvement by Hitachi, Ltd.

Reducing charging effects in scanning electron microscope images by Rayleigh contrast stretching method (RCS).

Science.gov (United States)

Wan Ismail, W Z; Sim, K S; Tso, C P; Ting, H Y

2011-01-01

To reduce undesirable charging effects in scanning electron microscope images, Rayleigh contrast stretching is developed and employed. First, re-scaling is performed on the input image histograms with Rayleigh algorithm. Then, contrast stretching or contrast adjustment is implemented to improve the images while reducing the contrast charging artifacts. This technique has been compared to some existing histogram equalization (HE) extension techniques: recursive sub-image HE, contrast stretching dynamic HE, multipeak HE and recursive mean separate HE. Other post processing methods, such as wavelet approach, spatial filtering, and exponential contrast stretching, are compared as well. Overall, the proposed method produces better image compensation in reducing charging artifacts. Copyright © 2011 Wiley Periodicals, Inc.

Generalised partition functions: inferences on phase space distributions

Directory of Open Access Journals (Sweden)

R. A. Treumann

2016-06-01

Full Text Available It is demonstrated that the statistical mechanical partition function can be used to construct various different forms of phase space distributions. This indicates that its structure is not restricted to the Gibbs–Boltzmann factor prescription which is based on counting statistics. With the widely used replacement of the Boltzmann factor by a generalised Lorentzian (also known as the q-deformed exponential function, where κ = 1∕|q − 1|, with κ, q ∈ R both the kappa-Bose and kappa-Fermi partition functions are obtained in quite a straightforward way, from which the conventional Bose and Fermi distributions follow for κ → ∞. For κ ≠ ∞ these are subject to the restrictions that they can be used only at temperatures far from zero. They thus, as shown earlier, have little value for quantum physics. This is reasonable, because physical κ systems imply strong correlations which are absent at zero temperature where apart from stochastics all dynamical interactions are frozen. In the classical large temperature limit one obtains physically reasonable κ distributions which depend on energy respectively momentum as well as on chemical potential. Looking for other functional dependencies, we examine Bessel functions whether they can be used for obtaining valid distributions. Again and for the same reason, no Fermi and Bose distributions exist in the low temperature limit. However, a classical Bessel–Boltzmann distribution can be constructed which is a Bessel-modified Lorentzian distribution. Whether it makes any physical sense remains an open question. This is not investigated here. The choice of Bessel functions is motivated solely by their convergence properties and not by reference to any physical demands. This result suggests that the Gibbs–Boltzmann partition function is fundamental not only to Gibbs–Boltzmann but also to a large class of generalised Lorentzian distributions as well as to the

Prolonged static stretching does not influence running economy despite changes in neuromuscular function.

Science.gov (United States)

Allison, Sarah J; Bailey, David M; Folland, Jonathan P

2008-12-01

The aim of this study was to examine the acute effects of prolonged static stretching (SS) on running economy. Ten male runners (VO2(peak) 60.1 +/- 7.3 ml x kg(-1) x min(-1)) performed 10 min of treadmill running at 70% VO2(peak) before and after SS and no stretching interventions. For the stretching intervention, each leg was stretched unilaterally for 40 s with each of eight different exercises and this was repeated three times. Respiratory gas exchange was measured throughout the running exercise with an automated gas analysis system. On a separate day, participants were tested for sit and reach range of motion, isometric strength and countermovement jump height before and after SS. The oxygen uptake, minute ventilation, energy expenditure, respiratory exchange ratio and heart rate responses to running were unaffected by the stretching intervention. This was despite a significant effect of SS on neuromuscular function (sit and reach range of motion, +2.7 +/- 0.6 cm; isometric strength, -5.6% +/- 3.4%; countermovement jump height -5.5% +/- 3.4%; all P influence running economy despite changes in neuromuscular function.

Identification of the Process of Dynamic Stretching of Threads in Warp Knitting Technology Part II: Experimental Identification of the Process of Stretching Threads, with Verification of Rheological Models

Directory of Open Access Journals (Sweden)

Prążyńska Aleksandra

2018-03-01

Full Text Available The study is a continuation of the first part of the publication, concerning the theoretical analysis of sensitivity of rheological models of dynamically stretched thread. This part presents the experimental research on the characteristics of stretching forces as a function of time, in the context of comparing the obtained results with theoretical data.

THUNDER Piezoelectric Actuators as a Method of Stretch-Tuning an Optical Fiber Grating

Science.gov (United States)

Allison, Sidney G.; Fox, Robert L.; Froggatt, Mark E.; Childers, Brooks A.

2000-01-01

A method of stretching optical fiber holds interest for measuring strain in smart structures where the physical displacement may be used to tune optical fiber lasers. A small, light weight, low power tunable fiber laser is ideal for demodulating strain in optical fiber Bragg gratings attached to smart structures such as the re-usable launch vehicle that is being developed by NASA. A method is presented for stretching optical fibers using the THUNDER piezoelectric actuators invented at NASA Langley Research Center. THUNDER actuators use a piezoelectric layer bonded to a metal backing to enable the actuators to produce displacements larger than the unbonded piezoelectric material. The shift in reflected optical wavelength resulting from stretching the fiber Bragg grating is presented. Means of adapting THUNDER actuators for stretching optical fibers is discussed, including ferrules, ferrule clamp blocks, and plastic hinges made with stereo lithography.

FUZZY BASED CONTRAST STRETCHING FOR MEDICAL IMAGE ENHANCEMENT

Directory of Open Access Journals (Sweden)

T.C. Raja Kumar

2011-07-01

Full Text Available Contrast Stretching is an important part in medical image processing applications. Contrast is the difference between two adjacent pixels. Fuzzy statistical values are analyzed and better results are produced in the spatial domain of the input image. The histogram mapping produces the resultant image with less impulsive noise and smooth nature. The probabilities of gray values are generated and the fuzzy set is determined from the position of the input image pixel. The result indicates the good performance of the proposed fuzzy based stretching. The inverse transform of the real values are mapped with the input image to generate the fuzzy statistics. This approach gives a flexible image enhancement for medical images in the presence of noises.

Soot and liquid-phase fuel distributions in a newly designed optically accessible DI diesel engine

Science.gov (United States)

Dec, J. E.; Espey, C.

1993-10-01

Two-dimensional (2-D) laser-sheet imaging has been used to examine the soot and liquid-phase fuel distributions in a newly designed, optically accessible, direct-injection diesel engine of the heavy-duty size class. The design of this engine preserves the intake port geometry and basic dimensions of a Cummins N-series production engine. It also includes several unique features to provide considerable optical access. Liquid-phase fuel and soot distribution studies were conducted at a medium speed (1,200 rpm) using a Cummins closed-nozzle fuel injector. The scattering was used to obtain planar images of the liquid-phase fuel distribution. These images show that the leading edge of the liquid-phase portion of the fuel jet reaches a maximum length of 24 mm, which is about half the combustion bowl radius for this engine. Beyond this point virtually all the fuel has vaporized. Soot distribution measurements were made at a high load condition using three imaging diagnostics: natural flame luminosity, 2-D laser-induced incandescence, and 2-D elastic scattering. This investigation showed that the soot distribution in the combusting fuel jet develops through three stages. First, just after the onset of luminous combustion, soot particles are small and nearly uniformly distributed throughout the luminous region of the fuel jet. Second, after about 2 crank angle degrees a pattern develops of a higher soot concentration of larger sized particles in the head vortex region of the jet and a lower soot concentration of smaller sized particles upstream toward the injector. Third, after fuel injection ends, both the soot concentration and soot particle size increase rapidly in the upstream portion of the fuel jet.

Pion scattering to 8- stretched states in 60Ni

International Nuclear Information System (INIS)

Clausen, B.L.

1988-03-01

Using the Energetic Pion Channel and Spectrometer at the Los Alamos Meson Physics Facility, differential cross sections for pion scattering were measured for ten previously known J/sup π/ = 8/sup /minus// stretched states in 60 Ni. A possible new pure isoscalar stretched state was also found. The data were taken near the /DELTA//sub 3,3/-resonance using 162 MeV incident pions and scattering angles of 65/degree/, 80/degree/, and 90/degree/ for π + and 65/degree/ and 80/degree/ for π/sup /minus//. The analysis of the 60 Ni data found that the use of Woods-Saxon wave functions in the theoretical calculations gave much better agreement with data than the use of the usual harmonic oscillator wave functions. The WS theory gave better predictions of: the angle at which the π/sup /minus// and π + angular distributions are maximum, the ratios of π/sup /minus// to π + cross sections for pure isovector states (which were much larger than unity), and the absolute size of the cross sections for all states (so that the normalization factor necessary to arrive at agreement of theory with data was closer to unity). The theoretical calculations used the distorted wave impulse approximation, including new methods for unbound states. The sensitivities of the calculations to input parameters were investigated. This analysis using WS wave functions was extended to five other nuclei ( 12 C, 14 C, 16 O, 28 Si, and 54 Fe) on which both pion scattering and electron scattering have been done. A significant improvement in arriving at a normalization factor close to unity was found when WS wave functions were consistently used for analyzing both pion and electron inelastic scattering data. 101 refs., 26 figs., 13 tabs

Modeling stretched solitary waves along magnetic field lines

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L. Muschietti

2002-01-01

Full Text Available A model is presented for a new type of fast solitary waves which is observed in downward current regions of the auroral zone. The three-dimensional, coherent structures are electrostatic, have a positive potential, and move along the magnetic field lines with speeds on the order of the electron drift. Their parallel potential profile is flattened and cannot fit to the Gaussian shape used in previous work. We develop a detailed BGK model which includes a flattened potential and an assumed cylindrical symmetry around a centric magnetic field line. The model envisions concentric shells of trapped electrons slowly drifting azimuthally while bouncing back and forth in the parallel direction. The electron dynamics is analysed in terms of three basic motions that occur on different time scales characterized by the cyclotron frequency We , the bounce frequency wb , and the azimuthal drift frequency wg. The ordering We >> wb >> wg is required. Self-consistent distribution functions are calculated in terms of approximate constants of motion. Constraints on the parameters characterizing the amplitude and shape of the stretched solitary wave are discussed.

Stretched flow of Oldroyd-B fluid with Cattaneo-Christov heat flux

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T. Hayat

Full Text Available The objective of present attempt is to analyse the flow and heat transfer in the flow of an Oldroyd-B fluid over a non-linear stretching sheet having variable thickness. Characteristics of heat transfer are analyzed with temperature dependent thermal conductivity and heat source/sink. Cattaneo-Christov heat flux model is considered rather than Fourier’s law of heat conduction in the present flow analysis. Thermal conductivity varies with temperature. Resulting partial differential equations through laws of conservation of mass, linear momentum and energy are converted into ordinary differential equations by suitable transformations. Convergent series solutions for the velocity and temperature distributions are developed and discussed. Keywords: Oldroyd-B fluid, Variable sheet thickness, Cattaneo-Christov heat flux model, Heat source/sink, Temperature dependent thermal conductivity

Investigating mechanically induced phase response of the tissue by using high-speed phase-resolved optical coherence tomography (Conference Presentation)

Science.gov (United States)

Ling, Yuye; Hendon, Christine P.

2017-02-01

Phase-resolved optical coherence tomography (OCT), a functional extension of OCT, provides depth-resolved phase information with extra contrast. In cardiology, changes in the mechanical properties have been associated with tissue remodeling and disease progression. Here we present the capability of profiling structural deformation of the sample in vivo by using a highly stable swept source OCT system The system, operating at 1300 nm, has an A-line acquisition rate of 200 kHz. We measured the phase noise floor to be 6.5 pm±3.2 pm by placing a cover slip in the sample arm, while blocking the reference arm. We then conducted a vibrational frequency test by measuring the phase response from a polymer membrane stimulated by a pure tone acoustic wave from 10 kHz to 80 kHz. The measured frequency response agreed with the known stimulation frequency with an error < 0.005%. We further measured the phase response of 7 fresh swine hearts obtained from Green Village Packing Company through a mechanical stretching test, within 24 hours of sacrifice. The heart tissue was cut into a 1 mm slices and fixed on two motorized stages. We acquired 100,000 consecutive M-scans, while the sample is stretched at a constant velocity of 10 um/s. The depth-resolved phase image presents linear phase response over time at each depth, but the slope varies among tissue types. Our future work includes refining our experiment protocol to quantitatively measured the elastic modulus of the tissue in vivo and building a tissue classifier based on depth-resolved phase information.

Micropatterning stretched and aligned DNA for sequence-specific nanolithography

Science.gov (United States)

Petit, Cecilia Anna Paulette

Techniques for fabricating nanostructured materials can be categorized as either "top-down" or "bottom-up". Top-down techniques use lithography and contact printing to create patterned surfaces and microfluidic channels that can corral and organize nanoscale structures, such as molecules and nanorods in contrast; bottom-up techniques use self-assembly or molecular recognition to direct the organization of materials. A central goal in nanotechnology is the integration of bottom-up and top-down assembly strategies for materials development, device design; and process integration. With this goal in mind, we have developed strategies that will allow this integration by using DNA as a template for nanofabrication; two top-down approaches allow the placement of these templates, while the bottom-up technique uses the specific sequence of bases to pattern materials along each strand of DNA. Our first top-down approach, termed combing of molecules in microchannels (COMMIC), produces microscopic patterns of stretched and aligned molecules of DNA on surfaces. This process consists of passing an air-water interface over end adsorbed molecules inside microfabricated channels. The geometry of the microchannel directs the placement of the DNA molecules, while the geometry of the airwater interface directs the local orientation and curvature of the molecules. We developed another top-down strategy for creating micropatterns of stretched and aligned DNA using surface chemistry. Because DNA stretching occurs on hydrophobic surfaces, this technique uses photolithography to pattern vinyl-terminated silanes on glass When these surface-, are immersed in DNA solution, molecules adhere preferentially to the silanized areas. This approach has also proven useful in patterning protein for cell adhesion studies. Finally, we describe the use of these stretched and aligned molecules of DNA as templates for the subsequent bottom-up construction of hetero-structures through hybridization

Distribution of activity at the solar active longitudes between 1979 - 2011 in the northern hemisphere

Science.gov (United States)

Gyenge, N.; Baranyi, T.; Ludmány, A.

The solar active longitudes were studied in the northern hemisphere in cycles 22 and 23 by using data of DPD sunspot catalogue. The active longitudes are not fixed in the Carrington system, they have a well recognizable migration path between the descending phase of cycle 21 (from about 1984) and ascending phase of cycle 23 (until about 1996), out of this interval the migration path is ambiguous. The longitudinal distribution on both sides of the path has been computed and averaged for the length of the path. The so-called flip-flop phenomenon, when the activity temporarily gets to the opposite longitude, can also be recognized. The widths of the active domains are fairly narrow in the increasing and decaying phases of cycle 22, their half widths are about 20°-30° for both the main and secondary active belts but it is more flat and stretched around the maximum with a half width of about 60°.

′Sure closure′-skin stretching system, our clinical experience

Directory of Open Access Journals (Sweden)

Subramania K

2005-01-01

Full Text Available Objective: In clinical practice of reconstructive surgery one of the problems one routinely comes across is skin and soft tissue defects, which require coverage. Coverage of such wounds requires primary/secondary closure, skin grafting or flaps. The objective of our clinical series was to assess the efficacy of sure closure skin stretching system for closure of defects which otherwise would have required major flap cover or skin grafting. Methods: Our series included five patients with different causes and types of wound defects namely: 1. Post-traumatic soft tissue defect on dorsum of hand. 2. Post fasciotomy wound on leg (anterolateral aspect. 3. Abdominal wound dehiscence following surgery for enterocutaneous fistula. 4. Leg soft tissue defect following dehiscence of fasciocutaneous flap. 5. Secondary defect following harvesting a lateral arm/forearm free flap. The device was applied to skin edges after preparing the wound under local anesthesia and the skin edges were brought together by turning the skin-stretching knob. After adequate approximation of the edges of the wound it was sutured by conventional suturing techniques. Results: All the wounds could be successfully closed using the skin stretching system in our series. The time taken for the closure ranged from 2 to 48 h. Conclusions: Sure closure skin stretching system is an effective device for closing some of the skin defects which otherwise would have required skin flaps or grafts. In all the patients wound closure could be achieved by this method and was carried out under local anesthesia. Use of this technique is simple and helps to reduce the morbidity and cost of treatment by allowing the reconstructive surgeon to avoid using major flaps or grafts.

Real-time generation of the Wigner distribution of complex functions using phase conjugation in photorefractive materials.

Science.gov (United States)

Sun, P C; Fainman, Y

1990-09-01

An optical processor for real-time generation of the Wigner distribution of complex amplitude functions is introduced. The phase conjugation of the input signal is accomplished by a highly efficient self-pumped phase conjugator based on a 45 degrees -cut barium titanate photorefractive crystal. Experimental results on the real-time generation of Wigner distribution slices for complex amplitude two-dimensional optical functions are presented and discussed.

Stretching of Active Muscle Elicits Chronic Changes in Multiple Strain Risk Factors.

Science.gov (United States)

Kay, Anthony David; Richmond, Dominic; Talbot, Chris; Mina, Minas; Baross, Anthony William; Blazevich, Anthony John

2016-07-01

The muscle stretch intensity imposed during "flexibility" training influences the magnitude of joint range of motion (ROM) adaptation. Thus, stretching while the muscle is voluntarily activated was hypothesized to provide a greater stimulus than passive stretching. The effect of a 6-wk program of stretch imposed on an isometrically contracting muscle (i.e., qualitatively similar to isokinetic eccentric training) on muscle-tendon mechanics was therefore studied in 13 healthy human volunteers. Before and after the training program, dorsiflexion ROM, passive joint moment, and maximal isometric plantarflexor moment were recorded on an isokinetic dynamometer. Simultaneous real-time motion analysis and ultrasound imaging recorded gastrocnemius medialis muscle and Achilles tendon elongation. Training was performed twice weekly and consisted of five sets of 12 maximal isokinetic eccentric contractions at 10°·s. Significant increases (P tendon stiffness) was detected (-1.5%, P > 0.05), a significant increase in tendon stiffness (31.2%, P tendon stiffness simultaneous with significant increases in tendon stiffness and decreases in passive muscle stiffness indicates that tissue-specific effects were elicited.

Pre-Stretched Low Equivalent Weight PFSA Membranes with Improved Fuel Cell Performance

DEFF Research Database (Denmark)

Zhang, Wenjing (Angela); Wycisk, Ryszard; Kish, Daniel L.

2014-01-01

for the morphological changes to be permanent. For 825 EW PFSA, stretching increased the polymer crystallinity by 22.5%, with a reduction in methanol permeability and a small increase in proton conductivity. In direct methanol fuel cell tests at 60◦C with 1.0 M methanol, the power density at 0.4 V with a DR = 4...... stretched 825 EW membrane (72 mW/cm2) was considerably greater than that obtained with a solution-cast membrane (28 mW/cm2) or with a commercial Nafion 117 membrane (55 mW/cm2). For 733 EW PFSA, stretching promoted the formation of ordered ionic domains leading to an increase in proton conductivity...

Validation of model predictions of pore-scale fluid distributions during two-phase flow

Science.gov (United States)

Bultreys, Tom; Lin, Qingyang; Gao, Ying; Raeini, Ali Q.; AlRatrout, Ahmed; Bijeljic, Branko; Blunt, Martin J.

2018-05-01

Pore-scale two-phase flow modeling is an important technology to study a rock's relative permeability behavior. To investigate if these models are predictive, the calculated pore-scale fluid distributions which determine the relative permeability need to be validated. In this work, we introduce a methodology to quantitatively compare models to experimental fluid distributions in flow experiments visualized with microcomputed tomography. First, we analyzed five repeated drainage-imbibition experiments on a single sample. In these experiments, the exact fluid distributions were not fully repeatable on a pore-by-pore basis, while the global properties of the fluid distribution were. Then two fractional flow experiments were used to validate a quasistatic pore network model. The model correctly predicted the fluid present in more than 75% of pores and throats in drainage and imbibition. To quantify what this means for the relevant global properties of the fluid distribution, we compare the main flow paths and the connectivity across the different pore sizes in the modeled and experimental fluid distributions. These essential topology characteristics matched well for drainage simulations, but not for imbibition. This suggests that the pore-filling rules in the network model we used need to be improved to make reliable predictions of imbibition. The presented analysis illustrates the potential of our methodology to systematically and robustly test two-phase flow models to aid in model development and calibration.

Development of Aluminum-Lithium 2195 Gores by the Stretch Forming Process

Science.gov (United States)

Volz, M. P.; Chen, P. S.; Gorti, S.; Salvail, P.

2014-01-01

Aluminum-Lithium alloy 2195 exhibits higher mechanical properties and lower density than aluminum alloy 2219, which is the current baseline material for Space Launch System (SLS) cryogenic tank components. Replacement of Al 2219 with Al-Li 2195 would result in substantial weight savings, as was the case when this replacement was made on the shuttle external tank. A key component of cryogenic tanks are the gores, which are welded together to make the rounded ends of the tanks. The required thicknesses of these gores depend on the specific SLS configuration and may exceed the current experience base in the manufacture of such gores by the stretch forming process. Here we describe the steps taken to enhance the formability of Al-Li 2195 by optimizing the heat treatment and stretch forming processes for gore thicknesses up to 0.75", which envelopes the maximum expected gore thicknesses for SLS tanks. An annealing treatment, developed at Marshall Space Flight Center, increased the forming range and strain hardening exponent of Al-Li 2195 plates. Using this annealing treatment, one 0.525" thick and two 0.75" thick gores were manufactured by the stretch forming process. The annealing treatment enabled the stretch forming of the largest ever cross sectional area (thickness x width) of an Al-Li 2195 plate achieved by the manufacturer. Mechanical testing of the gores showed greater than expected ultimate tensile strength, yield strength, modulus, and elongation values. The gores also exhibited acceptable fracture toughness at room and LN2 temperatures. All of the measured data indicate that the stretch formed gores have sufficient material properties to be used in flight domes.

On the issues of probability distribution of GPS carrier phase observations

Science.gov (United States)

Luo, X.; Mayer, M.; Heck, B.

2009-04-01

In common practice the observables related to Global Positioning System (GPS) are assumed to follow a Gauss-Laplace normal distribution. Actually, full knowledge of the observables' distribution is not required for parameter estimation by means of the least-squares algorithm based on the functional relation between observations and unknown parameters as well as the associated variance-covariance matrix. However, the probability distribution of GPS observations plays a key role in procedures for quality control (e.g. outlier and cycle slips detection, ambiguity resolution) and in reliability-related assessments of the estimation results. Under non-ideal observation conditions with respect to the factors impacting GPS data quality, for example multipath effects and atmospheric delays, the validity of the normal distribution postulate of GPS observations is in doubt. This paper presents a detailed analysis of the distribution properties of GPS carrier phase observations using double difference residuals. For this purpose 1-Hz observation data from the permanent SAPOS

Optical stretching on chip with acoustophoretic prefocusing

DEFF Research Database (Denmark)

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

2012-01-01

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...

Comparison electrical stimulation and passive stretching for blood glucose control type 2 diabetes mellitus patients

Science.gov (United States)

Arsianti, Rika Wahyuni; Parman, Dewy Haryanti; Lesmana, Hendy

2018-04-01

Physical exercise is one of the cornerstones for management and treatment type 2 diabetes mellitus. But not all people are able to perform physical exercise because of their physical limitation condition. The strategy for those people in this study is electrical stimulation and passive stretching. The aim of this study is to find out the effect of electrical stimulation and passive stretching to lowering blood glucose level. 20 subjects is divided into electrical stimulation and passive stretching group. The provision of electrical stimulation on lower extremities muscles for 30 minutes for electrical stimulation group (N=10). And other underwent passive stretching for 30 minutes (N=10). The result shows that blood glucose level is decrease from 192.9 ± 10.7087 mg/dL to 165.3 ± 10.527 mg/dL for electrical stimulation intervention group while for the passive stretching group the blood glucose decrease from 153 ± 12.468 mg/dL to 136.1 ± 12.346 mg/dL. Both electrical stimulation and passive stretching are effective to lowering blood glucose level and can be proposed for those people restricted to perform exercise.

Mechanical stretch induces MMP-2 release and activation in lung endothelium: role of EMMPRIN.

Science.gov (United States)

Haseneen, Nadia A; Vaday, Gayle G; Zucker, Stanley; Foda, Hussein D

2003-03-01

High-volume mechanical ventilation leads to ventilator-induced lung injury. This type of lung injury is accompanied by an increased release and activation of matrix metalloproteinases (MMPs). To investigate the mechanism leading to the increased MMP release, we systematically studied the effect of mechanical stretch on human microvascular endothelial cells isolated from the lung. We exposed cells grown on collagen 1 BioFlex plates to sinusoidal cyclic stretch at 0.5 Hz using the Flexercell system with 17-18% elongation of cells. After 4 days of cell stretching, conditioned media and cell lysate were collected and analyzed by gelatin, casein, and reverse zymograms as well as Western blotting. RT-PCR of mRNA extracted from stretched cells was performed. Our results show that 1) cyclic stretch led to increased release and activation of MMP-2 and MMP-1; 2) the activation of MMP-2 was accompanied by an increase in membrane type-1 MMP (MT1-MMP) and inhibited by a hydroxamic acid-derived inhibitor of MMPs (Prinomastat, AG3340); and 3) the MMP-2 release and activation were preceded by an increase in production of extracellular MMP inducer (EMMPRIN). These results suggest that cyclic mechanical stretch leads to MMP-2 activation through an MT1-MMP mechanism. EMMPRIN may play an important role in the release and activation of MMPs during lung injury.

Self-induced stretch syncope of adolescence: a video-EEG documentation.

Science.gov (United States)

Mazzuca, Michel; Thomas, Pierre

2007-12-01

We present the first video-EEG documentation, with ECG and EMG features, of stretch syncope of adolescence in a young, healthy 16-year-old boy. Stretch syncope of adolescence is a rarely reported, benign cause of fainting in young patients, which can be confused with epileptic seizures. In our patient, syncopes were self-induced to avoid school. Dynamic transcranial Doppler showed evidence of blood flow decrease in both posterior cerebral arteries mimicking effects of a Valsalva manoeuvre. Dynamic angiogram of the vertebral arteries was normal. Hypotheses concerning the physiopathology are discussed. [Published with video sequences].

METODE ACTIVE ISOLATED STRETCHING (AIS DAN METODE HOLD RELAX STRETCHING (HRS SAMA EFEKTIF DALAM MENINGKATKAN FLEKSIBILITAS OTOT HAMSTRING PADA MAHASISWA AKADEMI FISIOTERAPI WIDYA HUSADA SEMARANG YANG MENGALAMI HAMSTRING MUSCLE TIGHTNESS (HMTs

Directory of Open Access Journals (Sweden)

Akhmad alfajri

2015-08-01

Full Text Available Students with Hamstring Muscle Tightness (HMTs will be at risk of Anterior Crusiatum Ligament (ACL, Low Back Pain (LBP and also Plantar Faciitis. One of the efforts to reduce tightness and improve hamstring muscle flexibility is stretching. Active Isolated Stretching (AIS and Hold Relax Stretching (HRS are the methods of influential stretching to improve muscle flexibility. The goal of the research is to prove that AIS method is equally effective with the HRS method to improve hamstring muscle flexibility to the HMTs patients. The research method was true experimental with pre and post test group design. The research was conducted for 3 weeks and the samples are 23 students in range of 18-25 years old students of physical therapy in Physical Therapy Academy of Widya Husada Semarang which divided into 2 groups; AIS group (n= 12 and HRS group (n= 11. The research used Sit and Reach Test (SRT as the measurement instrument. The result of the research was the average result of AIS group used SRT before treatment was 1.75 cm, SB= 4.309 and after treatment was 10. 58 cm, SB = 8. 005 within p= 0.000 (p 0.05. Those explain that the improvement of hamstring muscle flexibility to the two groups does not show any significant difference. Conclusion from this study was active isolated stretching method and hold relax stretching method are equally effective to improving muscle flexibility of hamstring muscle tightness students of physical therapy in Physical Therapy Academy of Widya Husada Semarang.

Intrinsically stable phase-modulated polarization encoding system for quantum key distribution

Energy Technology Data Exchange (ETDEWEB)

Liu Xiaobao [Laboratory of Photonic Information Technology, School for Information and Optoelectronic Science and Engineering, South China Normal University, Guangzhou 510006 (China); Liao Changjun [Laboratory of Photonic Information Technology, School for Information and Optoelectronic Science and Engineering, South China Normal University, Guangzhou 510006 (China)], E-mail: chliao@scnu.edu.cn; Mi Jinglong; Wang Jindong; Liu Songhao [Laboratory of Photonic Information Technology, School for Information and Optoelectronic Science and Engineering, South China Normal University, Guangzhou 510006 (China)

2008-12-22

We demonstrate experimentally an intrinsically stable polarization coding and decoding system composed of optical-fiber Sagnac interferometers with integrated phase modulators for quantum key distribution. An interference visibility of 98.35% can be kept longtime during the experiment without any efforts of active compensation for coding all four desired polarization states.

Stretch sensors for human body motion

Science.gov (United States)

O'Brien, Ben; Gisby, Todd; Anderson, Iain A.

2014-03-01

Sensing motion of the human body is a difficult task. From an engineers' perspective people are soft highly mobile objects that move in and out of complex environments. As well as the technical challenge of sensing, concepts such as comfort, social intrusion, usability, and aesthetics are paramount in determining whether someone will adopt a sensing solution or not. At the same time the demands for human body motion sensing are growing fast. Athletes want feedback on posture and technique, consumers need new ways to interact with augmented reality devices, and healthcare providers wish to track recovery of a patient. Dielectric elastomer stretch sensors are ideal for bridging this gap. They are soft, flexible, and precise. They are low power, lightweight, and can be easily mounted on the body or embedded into clothing. From a commercialisation point of view stretch sensing is easier than actuation or generation - such sensors can be low voltage and integrated with conventional microelectronics. This paper takes a birds-eye view of the use of these sensors to measure human body motion. A holistic description of sensor operation and guidelines for sensor design will be presented to help technologists and developers in the space.

Twist-stretch profiles of DNA chains

Science.gov (United States)

Zoli, Marco

2017-06-01

Helical molecules change their twist number under the effect of a mechanical load. We study the twist-stretch relation for a set of short DNA molecules modeled by a mesoscopic Hamiltonian. Finite temperature path integral techniques are applied to generate a large ensemble of possible configurations for the base pairs of the sequence. The model also accounts for the bending and twisting fluctuations between adjacent base pairs along the molecules stack. Simulating a broad range of twisting conformation, we compute the helix structural parameters by averaging over the ensemble of base pairs configurations. The method selects, for any applied force, the average twist angle which minimizes the molecule’s free energy. It is found that the chains generally over-twist under an applied stretching and the over-twisting is physically associated to the contraction of the average helix diameter, i.e. to the damping of the base pair fluctuations. Instead, assuming that the maximum amplitude of the bending fluctuations may decrease against the external load, the DNA molecule first over-twists for weak applied forces and then untwists above a characteristic force value. Our results are discussed in relation to available experimental information albeit for kilo-base long molecules.

Mechanical stretch augments insulin-induced vascular smooth muscle cell proliferation by insulin-like growth factor-1 receptor

Energy Technology Data Exchange (ETDEWEB)

Liu, Gang [Department of Pharmacology, Faculty of Medicine, Kagawa University, Kagawa (Japan); Department of Anesthesiology, First Affiliated Hospital of China Medical University, Shenyang (China); Hitomi, Hirofumi, E-mail: hitomi@kms.ac.jp [Department of Pharmacology, Faculty of Medicine, Kagawa University, Kagawa (Japan); Hosomi, Naohisa [Department of Cardiorenal and Cerebrovascular Medicine, Faculty of Medicine, Kagawa University, Kagawa (Japan); Lei, Bai; Nakano, Daisuke [Department of Pharmacology, Faculty of Medicine, Kagawa University, Kagawa (Japan); Deguchi, Kazushi; Mori, Hirohito; Masaki, Tsutomu [Department of Gastroenterology and Neurology, Faculty of Medicine, Kagawa University, Kagawa (Japan); Ma, Hong [Department of Anesthesiology, First Affiliated Hospital of China Medical University, Shenyang (China); Griendling, Kathy K. [Department of Medicine, Division of Cardiology, Emory University School of Medicine, Atlanta, GA (United States); Nishiyama, Akira [Department of Pharmacology, Faculty of Medicine, Kagawa University, Kagawa (Japan)

2011-10-15

Insulin resistance and hypertension have been implicated in the pathogenesis of cardiovascular disease; however, little is known about the roles of insulin and mechanical force in vascular smooth muscle cell (VSMC) remodeling. We investigated the contribution of mechanical stretch to insulin-induced VSMC proliferation. Thymidine incorporation was stimulated by insulin in stretched VSMCs, but not in un-stretched VSMCs. Insulin increased 2-deoxy-glucose incorporation in both stretched and un-stretched VSMCs. Mechanical stretch augmented insulin-induced extracellular signal-regulated kinase (ERK) and Akt phosphorylation. Inhibitors of epidermal growth factor (EGF) receptor tyrosine kinase and Src attenuated insulin-induced ERK and Akt phosphorylation, as well as thymidine incorporation, whereas 2-deoxy-glucose incorporation was not affected by these inhibitors. Moreover, stretch augmented insulin-like growth factor (IGF)-1 receptor expression, although it did not alter the expression of insulin receptor and insulin receptor substrate-1. Insulin-induced ERK and Akt activation, and thymidine incorporation were inhibited by siRNA for the IGF-1 receptor. Mechanical stretch augments insulin-induced VSMC proliferation via upregulation of IGF-1 receptor, and downstream Src/EGF receptor-mediated ERK and Akt activation. Similar to in vitro experiment, IGF-1 receptor expression was also augmented in hypertensive rats. These results provide a basis for clarifying the molecular mechanisms of vascular remodeling in hypertensive patients with hyperinsulinemia. -- Highlights: {yields} Mechanical stretch augments insulin-induced VSMC proliferation via IGF-1 receptor. {yields} Src/EGFR-mediated ERK and Akt phosphorylation are augmented in stretched VSMCs. {yields} Similar to in vitro experiment, IGF-1 receptor is increased in hypertensive rats. {yields} Results provide possible mechanisms of vascular remodeling in hypertension with DM.

COMPARATIVE EFFECT OF STATIC AND DYNAMIC STRETCHING EXERCISE TO IMPROVE FLEXIBILITY OF HAMSTRING MUSCLES AMONG NON ATHLETES

Directory of Open Access Journals (Sweden)

Jibi Paul

2014-10-01

Full Text Available Background: Stretching exercises have been routinely used in persons with hamstring tightness and athletes to increase flexibility of muscle and to reduce joint injuries. Many studies have reported effect of static and dynamic stretching on flexibility of this muscle. Finding the best method to improve flexibility of hamstring muscle is important for athletes and individuals to reduce their injuries. Objective of the study was to find out the effect of static stretching exercise and dynamic stretching exercise on flexibility of hamstring muscle and also to compare the effect of static and dynamic stretching exercise on flexibility of hamstring muscle. Methods: This was a comparative experimental study with seventy four female healthy subjects from physiotherapy department of KPJ Healthcare University College, Malaysia. Convenient sampling method used to select the samples. The subjects were selected by inclusion criteria and randomly divided equally in to two with 37 subjects in each group. Static stretching exercise and dynamic stretching exercise were given as intervention program for four weeks respectively for experimental and control group. Pre and post data of restricted range of movement for knee extension was measured using goniometry and documented separately for both group. Result: In experimental and control group, pre-post statistical analysis found significant effect in increase of hamstring flexibility with P<0.0001, for right and left side. Comparative study between experimental and control group found that static stretching exercise have significant effect in increase of hamstring flexibility for right and left side with P<0.04. Conclusion: This study concluded that static stretching exercise is more effective to improve hamstring flexibility compared to dynamic stretching exercise.

Bending and stretching of plates

CERN Document Server

Mansfield, E H; Hemp, W S

1964-01-01

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

Phase transitions and flux distributions of SU(2) lattice gauge theory

International Nuclear Information System (INIS)

Peng, Yingcai.

1993-01-01

The strong interactions between quarks are believed to be described by Quantum Chromodynamics (QCD), which is a non-abelian SU(3) gauge theory. It is known that QCD undergoes a deconfining phase transition at very high temperatures, that is, at low temperatures QCD is in confined phase, at sufficient high temperatures it is in an unconfined phase. Also, quark confinement is believed to be due to string formation. In this dissertation the authors studied SU(2) gauge theory using numerical methods of LGT, which will provide some insights about the properties of QCD because SU(2) is similar to SU(3). They measured the flux distributions of a q bar q pair at various temperatures in different volumes. They find that in the limit of infinite volumes the flux distribution is different in the two phases. In the confined phase strong evidence is found for the string formation, however, in the unconfined phase there is no string formation. On the other hand, in the limit of zero temperature and finite volumes they find a clear signal for string formation in the large volume region, however, the string tension measured in intermediate volumes is due to finite volume effects, there is no intrinsic string formation. The color flux energies (action) of the q bar q pair are described by Michael sum rules. The original Michael sum rules deal with a static q bar q pair at zero temperature in infinite volumes. To check these sum rules with flux data at finite temperatures, they present a complete derivation for the sum rules, thus generalizing them to account for finite temperature effects. They find that the flux data are consistent with the prediction of generalized sum rules. The study elucidates the rich structures of QCD, and provides evidence for quark confinement and string formation. This supports the belief that QCD is a correct theory for strong interactions, and quark confinement can be explained by QCD

β-Phase poly(vinylidene fluoride) films encouraged more homogeneous cell distribution and more significant deposition of fibronectin towards the cell–material interface compared to α-phase poly(vinylidene fluoride) films

Energy Technology Data Exchange (ETDEWEB)

Low, Y.K.A.; Zou, X. [School of Materials Science and Engineering, Nanyang Technological University, N4.1 50 Nanyang Avenue, Singapore 639798 (Singapore); Fang, Y.M. [School of Computer Engineering, Nanyang Technological University, N4 50 Nanyang Avenue, Singapore 639798 (Singapore); Wang, J.L. [School of Materials Science and Engineering, Nanyang Technological University, N4.1 50 Nanyang Avenue, Singapore 639798 (Singapore); Lin, W.S. [School of Computer Engineering, Nanyang Technological University, N4 50 Nanyang Avenue, Singapore 639798 (Singapore); Boey, F.Y.C. [School of Materials Science and Engineering, Nanyang Technological University, N4.1 50 Nanyang Avenue, Singapore 639798 (Singapore); Ng, K.W., E-mail: kwng@ntu.edu.sg [School of Materials Science and Engineering, Nanyang Technological University, N4.1 50 Nanyang Avenue, Singapore 639798 (Singapore)

2014-01-01

The piezoelectric response from β-phase poly(vinylidene fluoride) (PVDF) can potentially be exploited for biomedical application. We hypothesized that α and β-phase PVDF exert direct but different influence on cellular behavior. α- and β-phase PVDF films were synthesized through solution casting and characterized with FT-IR, XRD, AFM and PFM to ensure successful fabrication of α and β-phase PVDF films. Cellular evaluation with L929 mouse fibroblasts over one-week was conducted with AlamarBlue® metabolic assay and PicoGreen® proliferation assay. Immunostaining of fibronectin investigated the extent and distribution of extracellular matrix deposition. Image saliency analysis quantified differences in cellular distribution on the PVDF films. Our results showed that β-phase PVDF films with the largest area expressing piezoelectric effect elicited highest cell metabolic activity at day 3 of culture. Increased fibronectin adsorption towards the cell–material interface was shown on β-phase PVDF films. Image saliency analysis showed that fibroblasts on β-phase PVDF films were more homogeneously distributed than on α-phase PVDF films. Taken collectively, the different molecular packing of α and β-phase PVDF resulted in differing physical properties of films, which in turn induced differences in cellular behaviors. Further analysis of how α and β-phase PVDF may evoke specific cellular behavior to suit particular application will be intriguing. - Highlights: • β-Phase PVDF exhibited strongest piezoelectric effects compared to α-phase PVDF. • β-Phase PVDF induced more homogeneous cell distribution than α-phase PVDF. • β-Phase PVDF encouraged more fibronectin deposition at the cell–material interface.

Modification of permeability of frog perineurium to [14C]-sucrose by stretch and hypertonicity

International Nuclear Information System (INIS)

Weerasuriya, A.; Rapoport, S.I.; Taylor, R.E.

1979-01-01

An in vitro method has been developed to determine quantitatively the permeability of the perineurium to radiotracers at room temperature. The permeability to [ 14 C]sucrose of the isolated perineurium of the sciatic nerve of the frog, Rana pipiens, was measured at rest length, when the perineurium was stretched and after the perineurium had been subjected to hypertonic treatment. Mean permeability at rest length was calculated to be 5.6 +- 0.27 (S.E.M., n=45)x10 -7 cm/sec, and both stretch and hypertonic treatment increased the permeability. A 10% stretch increased permeability reversibly, whereas a 20% stretch or immersion of the perineurium in a hypertonic bath increased permeability irreversibly. Altered permeability under these conditions might be related to changes in the ultrastructure of tight junctions in the perineurium. (Auth.)

A comparison of two stretching programs for hamstring muscles: A randomized controlled assessor-blinded study.

Science.gov (United States)

Demoulin, Christophe; Wolfs, Sébastien; Chevalier, Madeline; Granado, Caroline; Grosdent, Stéphanie; Depas, Yannick; Roussel, Nathalie; Hage, Renaud; Vanderthommen, Marc

2016-01-01

Most parameters regarding hamstring flexibility training programs have been investigated; however, the joint (i.e. hip or knee) on which the stretching should preferentially be focused needs to be further explored. This randomized controlled assessor-blinded study aimed to investigate the influence of this parameter. We randomly assigned 111 asymptomatic participants with tight hamstring muscles in three groups: a control group and two groups following a different home-based 8-week (five 10-minute sessions per week) hamstring stretching program (i.e. stretching performed by flexing the hip while keeping the knee extended [SH] or by first flexing the hip with a flexed knee and then extending the knee [SK]). Range of motion (ROM) of hip flexion and knee extension were measured before and after the stretching program by means of the straight leg raising test and the passive knee extension angle test, respectively. Eighty-nine participants completed the study. A significant increase in ROM was observed at post-test. Analyses showed significant group-by-time interactions for changes regarding all outcomes. Whereas the increase in hip flexion and knee extension ROM was higher in the stretching groups than in the CG (especially for the SH group p 0.05). In conclusion, the fact that both stretching programs resulted in similar results suggests no influence of the joint at which the stretching is focused upon, as assessed by the straight leg raising and knee extension angle tests.

Simulation of stretch forming with intermediate heat treatments of aircraft skins - A physically based modeling approach

NARCIS (Netherlands)

Kurukuri, S.; Miroux, Alexis; Wisselink, H.H.; van den Boogaard, Antonius H.

2011-01-01

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

Muscular and stato-kinetic functions rehabilitation by means of subaquatic stretching (hydrostretching

Directory of Open Access Journals (Sweden)

Zoltàn Pàsztay

2008-12-01

Full Text Available Stretching is a physical therapeutical way for maintaining the standard parameters of the body functions from a tender to anadvanced age. The most important parameter that is influenced by the different techniques of stretching, especially byhydrostretching, is flexibility. This article presents the technique and the effects of hydrostretching on human body (onmuscular balance, strength, muscular metabolism and circulation.

Stretched-to-compressed-exponential crossover observed in the electrical degradation kinetics of some spinel-metallic screen-printed structures

Science.gov (United States)

Balitska, V.; Shpotyuk, O.; Brunner, M.; Hadzaman, I.

2018-02-01

Thermally-induced (170 °C) degradation-relaxation kinetics is examined in screen-printed structures composed of spinel Cu0.1Ni0.1Co1.6Mn1.2O4 ceramics with conductive Ag or Ag-Pd layered electrodes. Structural inhomogeneities due to Ag and Ag-Pd diffusants in spinel phase environment play a decisive role in non-exponential kinetics of negative relative resistance drift. If Ag migration in spinel is inhibited by Pd addition due to Ag-Pd alloy, the kinetics attains stretched exponential behavior with ∼0.58 exponent, typical for one-stage diffusion in structurally-dispersive media. Under deep Ag penetration into spinel ceramics, as for thick films with Ag-layered electrodes, the degradation kinetics drastically changes, attaining features of two-step diffusing process governed by compressed-exponential dependence with power index of ∼1.68. Crossover from stretched- to compressed-exponential kinetics in spinel-metallic structures is mapped on free energy landscape of non-barrier multi-well system under strong perturbation from equilibrium, showing transition with a character downhill scenario resulting in faster than exponential decaying.

Experimental study on the deformation of erythrocytes under optically trapping and stretching

International Nuclear Information System (INIS)

Liu, Y.P.; Li Chuan; Lai, A.C.K.

2006-01-01

The mechanical behavior of erythrocytes is studied experimentally and numerically. In the experiment, prepared silica microbeads are attached to the surface of spherically swollen erythrocytes (red blood cells, RBCs) at room temperature (25 deg. C). The cells are then stretched by single laser beam via the microbeads. The relation of deformation and stretching force is quantitatively assessed by the image processing of digital pictures. Meanwhile, a physical model for an axisymmetric cell is introduced to study its deformation by different level of stretching force. By comparing the experimental and numerical data, stiffness of the cell membrane can be determined and the optimal values are found to agree with other studies by different techniques such as micropipette aspiration or high frequency electric field

Influence of UV and Gamma radiations on the induced birefringence of stretched poly(vinyl) alcohol foils

Science.gov (United States)

Nechifor, Cristina-Delia; Zelinschi, Carmen Beatrice; Dorohoi, Dana-Ortansa

2014-03-01

The aim of our paper is to evidence the influence of Gamma and UV radiations on the induced birefringence of poly(vinyl alcohol) stretched foils. Thin foils of PVA were prepared and dried without modifying their surfaces. The polymeric foils were irradiated from 15 min to 6 h using UV and Gamma radiations. The induced by stretching under heating birefringence of PVA films was measured at λ = 589.3 nm with a Babinet Compensator. Physico-chemical processes (photo stabilization, photo degradation, oxidation) induced by irradiation of polymer matrix influence both the stretching degree and the anisotropy of etired foils. An increase of birefringence versus the stretching ratio of the PVA foils was evidenced for all studied samples. The dependence of the birefringence on the exposure time, stretching ratio and nature of radiation was also confirmed.

Phase transitions in distributed control systems with multiplicative noise

Science.gov (United States)

Allegra, Nicolas; Bamieh, Bassam; Mitra, Partha; Sire, Clément

2018-01-01

Contemporary technological challenges often involve many degrees of freedom in a distributed or networked setting. Three aspects are notable: the variables are usually associated with the nodes of a graph with limited communication resources, hindering centralized control; the communication is subject to noise; and the number of variables can be very large. These three aspects make tools and techniques from statistical physics particularly suitable for the performance analysis of such networked systems in the limit of many variables (analogous to the thermodynamic limit in statistical physics). Perhaps not surprisingly, phase-transition like phenomena appear in these systems, where a sharp change in performance can be observed with a smooth parameter variation, with the change becoming discontinuous or singular in the limit of infinite system size. In this paper, we analyze the so called network consensus problem, prototypical of the above considerations, that has previously been analyzed mostly in the context of additive noise. We show that qualitatively new phase-transition like phenomena appear for this problem in the presence of multiplicative noise. Depending on dimensions, and on the presence or absence of a conservation law, the system performance shows a discontinuous change at a threshold value of the multiplicative noise strength. In the absence of the conservation law, and for graph spectral dimension less than two, the multiplicative noise threshold (the stability margin of the control problem) is zero. This is reminiscent of the absence of robust controllers for certain classes of centralized control problems. Although our study involves a ‘toy’ model, we believe that the qualitative features are generic, with implications for the robust stability of distributed control systems, as well as the effect of roundoff errors and communication noise on distributed algorithms.

Hyperglycemia Augments the Adipogenic Transdifferentiation Potential of Tenocytes and Is Alleviated by Cyclic Mechanical Stretch.

Science.gov (United States)

Wu, Yu-Fu; Huang, Yu-Ting; Wang, Hsing-Kuo; Yao, Chung-Chen Jane; Sun, Jui-Sheng; Chao, Yuan-Hung

2017-12-28

Diabetes mellitus is associated with damage to tendons, which may result from cellular dysfunction in response to a hyperglycemic environment. Tenocytes express diminished levels of tendon-associated genes under hyperglycemic conditions. In contrast, mechanical stretch enhances tenogenic differentiation. However, whether hyperglycemia increases the non-tenogenic differentiation potential of tenocytes and whether this can be mitigated by mechanical stretch remains elusive. We explored the in vitro effects of high glucose and mechanical stretch on rat primary tenocytes. Specifically, non-tenogenic gene expression, adipogenic potential, cell migration rate, filamentous actin expression, and the activation of signaling pathways were analyzed in tenocytes treated with high glucose, followed by the presence or absence of mechanical stretch. We analyzed tenocyte phenotype in vivo by immunohistochemistry using an STZ (streptozotocin)-induced long-term diabetic mouse model. High glucose-treated tenocytes expressed higher levels of the adipogenic transcription factors PPAR γ and C/EBPs. PPARγ was also highly expressed in diabetic tendons. In addition, increased adipogenic differentiation and decreased cell migration induced by high glucose implicated a fibroblast-to-adipocyte phenotypic change. By applying mechanical stretch to tenocytes in high-glucose conditions, adipogenic differentiation was repressed, while cell motility was enhanced, and fibroblastic morphology and gene expression profiles were strengthened. In part, these effects resulted from a stretch-induced activation of ERK (extracellular signal-regulated kinases) and a concomitant inactivation of Akt. Our results show that mechanical stretch alleviates the augmented adipogenic transdifferentiation potential of high glucose-treated tenocytes and helps maintain their fibroblastic characteristics. The alterations induced by high glucose highlight possible pathological mechanisms for diabetic tendinopathy

Tail modeling in a stretched magnetosphere 1. Methods and transformations

International Nuclear Information System (INIS)

Stern, D.P.

1987-01-01

A new method is developed for representing the magnetospheric field B as a distorted dipole field. Because delxB = 0 must be maintained,such a distortion may be viewed as a transformation of the vector potential A. The simplest form is a one-dimensional ''stretch transformation'' along the x axis, a generalization of a method introduced by Voigt. The transformation is concisely represented by the ''stretch function'' f(x), which is also a convenient tool for representing features of the substorm cycle. Onedimensional stretch transformations are extended to spherical, cylindrical, and parabolic coordinates and then to arbitrary coordinates. It is next shown that distortion transformations can be viewed as mappings of field lines from one pattern to another: Euler potentials are used in the derivation, but the final result only requires knowledge of the field and not of the potentials. General transformations in Cartesian and arbitrary coordinates are then derived,and applications to field modeling, field line motion, MHD modeling, and incompressible fluid dynamics are considered. copyrightAmerican Geophysical Union 1987

Light source distribution and scattering phase function influence light transport in diffuse multi-layered media

Science.gov (United States)

Vaudelle, Fabrice; L'Huillier, Jean-Pierre; Askoura, Mohamed Lamine

2017-06-01

Red and near-Infrared light is often used as a useful diagnostic and imaging probe for highly scattering media such as biological tissues, fruits and vegetables. Part of diffusively reflected light gives interesting information related to the tissue subsurface, whereas light recorded at further distances may probe deeper into the interrogated turbid tissues. However, modelling diffusive events occurring at short source-detector distances requires to consider both the distribution of the light sources and the scattering phase functions. In this report, a modified Monte Carlo model is used to compute light transport in curved and multi-layered tissue samples which are covered with a thin and highly diffusing tissue layer. Different light source distributions (ballistic, diffuse or Lambertian) are tested with specific scattering phase functions (modified or not modified Henyey-Greenstein, Gegenbauer and Mie) to compute the amount of backscattered and transmitted light in apple and human skin structures. Comparisons between simulation results and experiments carried out with a multispectral imaging setup confirm the soundness of the theoretical strategy and may explain the role of the skin on light transport in whole and half-cut apples. Other computational results show that a Lambertian source distribution combined with a Henyey-Greenstein phase function provides a higher photon density in the stratum corneum than in the upper dermis layer. Furthermore, it is also shown that the scattering phase function may affect the shape and the magnitude of the Bidirectional Reflectance Distribution (BRDF) exhibited at the skin surface.

Structure and properties of highly oriented polyoxymethylene produced by hot stretching

International Nuclear Information System (INIS)

Zhao Xiaowen; Ye Lin

2011-01-01

Research highlights: → Highly oriented POM was fabricated through solid hot stretching technology → Tensile strength and modulus of POM increased remarkably with draw ratio. → The crystal structure of POM changed from spherulite to mat texture by drawing. → Crystallinity and orientation factor of POM increased remarkably by drawing. → The mechanical structure model of microfibril of POM was established. - Abstract: Highly oriented self-reinforced polyoxymethylene (POM) was successfully fabricated through solid phase hot stretching technology. The tensile strength and modulus increased with draw ratio, which reached 900 MPa and 12 GPa, respectively at a high draw ratio of 900% without remarkable drop of the elongation at break. The structure and morphology of the drawn products were studied and the mechanical structure model of microfibril of POM was established. Raman spectral exhibited a low-frequency shift, which indicated two types of molecular chains with different response to the stress. During drawing, the spherulitic structure of POM was broken up and the mat texture crystals were formed. With the increase of draw ratio, the melting peak moved to high temperature and an additional shoulder peak ascribed to melting of highly chain-extended and oriented crystalline blocks was observed. X-ray diffraction showed that the crystallinity and orientation factor increased, while the grain size perpendicular to (1 0 0) crystal plane of POM decreased by drawing. The α relaxation peak corresponding to the glass transition temperature of POM (T g ) moved to high temperature with draw ratio. The section morphology of drawn POM exhibited a fibrillar structure which contributed to the significantly high tensile strength and modulus of the product.

Prediction of Ductile Failure in the Stretch-Forming of AA2024 Sheets

International Nuclear Information System (INIS)

Vallellano, C.; Guzman, C.; Garcia-Lomas, F. J.

2007-01-01

A number of ductile failure criteria are nowadays being used to predict the formability of aluminium alloy sheets. Generally speaking, integral criteria (e.g. those proposed by Cockcroft and Latham, Brozzo et al., Oyane et al Chaouadi et al., etc.) have been probed to work well when the principal strains are of opposite sign, i.e. in the left side of the Forming Limit Diagram (FLD). However, when tensile biaxial strains are present, as occurs in stretch-forming practice, their predictions are usually very poor and even non-conservatives. As an alternative, local criteria, such as the classical Tresca's and Bressan and Williams' criteria, have demonstrated a good capability to predict the failure in some automotive aluminum alloys under stretching. The present work analyses experimentally and numerically the failure in AA2024-T3 sheets subjected to biaxial stretching. A series of out-of-plane stretching tests have been simulated using ABAQUS. The experimental and the numerical FLD for different failure criteria are compared. The influence on the failure of the hydrostatic pressure and the normal stress to the fracture plane is also discussed

A Novel Stretch Sensor to Measure Venous Hemodynamics

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Syrpailyne Wankhar

2018-07-01

Full Text Available Chronic venous insufficiency is a debilitating condition causing varicose veins and venous ulcers. The pathophysiology includes reflux and venous obstruction. The diagnosis is often made by clinical examination and confirmed by Venous Doppler studies. Plethysmography helps to quantitatively examine the reflux and diagnose the burden of deep venous pathology to better understand venous hemodynamics, which is not elicited by venous duplex examination alone. However, most of these tests are qualitative, expensive, and not easily available. In this paper, we demonstrate the potential use of a novel stretch sensor in the assessment of venous hemodynamics during different maneuvers by measuring the change in calf circumference. We designed the stretch sensor by using semiconductor strain gauges pasted onto a small metal bar to form a load cell. The elastic and Velcro material attached to the load cell form a belt. It converts the change in limb circumference to a proportional tension (force of distension when placed around the calf muscle. We recorded the change in limb circumference from arrays of stretch sensors by using an in-house data acquisition system. We calculated the venous volume (VV, venous filling index (VFI, ejection fraction (EF and residual venous volume (RVV on two normal subjects and on two patients to assess venous hemodynamics. The values (VV > 60 ml, VFI 60%, RVV 2ml/s, EF 35% in patients were comparable to those reported in the literature.

Acute effect of different time periods of passive static stretching on the hamstring flexibility.

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Cini, Anelize; de Vasconcelos, Gabriela Souza; Lima, Claudia Silveira

2017-01-01

Several factors are associated with the presence of chronic low back pain; one of them is the flexibility of the hamstring muscles that influences the posture of the pelvic spine. Investigate the influence of two different time periods of passive static stretching on the flexibility of the hamstring. Forty-six physiotherapy students were divided into two groups performing stretching exercises: 30 s and 60 s duration. The collections consisted of: (1) pre-test: evaluation of the flexibility of the hip and knee, using a manual goniometer by means of the following tests: Straight Leg Raise Test (SLR), Passive Hip Flexion Test (PHFT) and Modified Knee Extension Test (MKET), (2) intervention: stretching with different runtimes, (3) post-test: reappraisal of flexibility, conducted immediately after the intervention. Significant difference was observed intra groups, group that did stretching exercises lasting 30 seconds (G30) (SLR p = 0.000. PHFT p = 0.003 and MKET p = 0.000) and group that did stretching exercises lasting 60 seconds (G60) (SLR p = 0.000. PHFT p = 0.001 and MKET p = 0.002). Comparing the groups, no significant difference was found (SLR p = 0.307; PHFT p = 0.904; MKET p = 0.132). Thus it can be inferred that 30 seconds are sufficient for increased flexibility of young women. Therefore the time-treatment sessions can be optimized. Only the acute effect of stretching was observed; further investigation of the long-term effect is required.

Current distribution in LV networks during 1-phase MV short-circuit

NARCIS (Netherlands)

Waes, van J.B.M.; Provoost, F.; Merwe, van der J.; Cobben, J.F.G.; Deursen, van A.P.J.; van Riet, M.J.M.; Laan, van der P.C.T.

2000-01-01

This paper describes the consequences of a fault in a medium voltage network on the grounding systems at the LV-side. To study the current distribution and to verify the models, we deliberately introduced one phase to ground faults in the 10 kV floating MV network. The selected site was the end of a

Hemodynamic responses during and after multiple sets of stretching exercises performed with and without the Valsalva maneuver.

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Lima, Tainah P; Farinatti, Paulo T V; Rubini, Ercole C; Silva, Elirez B; Monteiro, Walace D

2015-05-01

This study investigated the acute hemodynamic responses to multiple sets of passive stretching exercises performed with and without the Valsalva maneuver. Fifteen healthy men aged 21 to 29 years with poor flexibility performed stretching protocols comprising 10 sets of maximal passive unilateral hip flexion, sustained for 30 seconds with equal intervals between sets. Protocols without and with the Valsalva maneuver were applied in a random counterbalanced order, separated by 48-hour intervals. Hemodynamic responses were measured by photoplethysmography pre-exercise, during the stretching sets, and post-exercise. The effects of stretching sets on systolic and diastolic blood pressure were cumulative until the fourth set in protocols performed with and without the Valsalva maneuver. The heart rate and rate pressure product increased in both protocols, but no additive effect was observed due to the number of sets. Hemodynamic responses were always higher when stretching was performed with the Valsalva maneuver, causing an additional elevation in the rate pressure product. Multiple sets of unilateral hip flexion stretching significantly increased blood pressure, heart rate, and rate pressure product values. A cumulative effect of the number of sets occurred only for systolic and diastolic blood pressure, at least in the initial sets of the stretching protocols. The performance of the Valsalva maneuver intensified all hemodynamic responses, which resulted in significant increases in cardiac work during stretching exercises.

Stretched flow of Carreau nanofluid with convective boundary ...

Indian Academy of Sciences (India)

journal of. January 2016 physics pp. 3–17. Stretched flow of Carreau nanofluid with ... fluid over a flat plate subjected to convective surface condition. ... the steady laminar boundary layer flow over a permeable plate with a convective boundary.

The passive hamstring stretch test: clinical evaluation.

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Fisk, J W

1979-03-28

The passive hamstring stretch test is described. Using a modified goniometer it is shown that independent measurements taken by trained examiners approximate very closely to each other. This establishes the test as a valid objective measurement. The possible value of this test as a research tool in low back pain problems is discussed.

Alternative splicing and expression of the insulin-like growth factor (IGF-1) gene in osteoblasts under mechanical stretch

Institute of Scientific and Technical Information of China (English)

XIAN Chengyu; WANG Yuanliang; ZHANG Bingbing; TANG Liling; PAN Jun; LUO Yanfeng; JIANG Peng; LI Dajun

2006-01-01

Insulin-like growth factor 1 (IGF-1) promotes osteoblasts differentiation and bone formation,and its expression is induced by mechanical stretch,thus IGF-1 has been considered an effector molecule that links mechanical stimulation and local tissue responses. In this study, a mechanical stretching device was designed to apply physiological level static or cyclic stretching stimulation to osteoblasts.Different isoforms of IGF-1 mRNA were amplified by RT-PCR from the cells using respective primers and these amplified products were sequenced. An isoform of IGF-1 splicing product was found to be selectively produced by osteoblasts under stretching stimulation. This IGF-1 isoform had identical sequence with the mechano growth factor (MGF) which was originally identified in muscle cells. Regulations of the expression of the liver-type IGF (L.IGF-1) and MGF in osteoblasts under stretch stimulation were further studied using semi-quantitative RT-PCR.Stretch stimulation was found to promot the expression of IGF-1 (L.IGF-1 and MGF), and for both isoforms expression was more effectively stimulated by cyclic stretch than static stretch. MGF was detected only in osteoblasts subjected to mechanical stretch,suggesting MGF was a stretch sensitive growth factor.Expression of MGF peaked earlier than that of L.IGF-1, which was similar to their regulation in muscie and suggested similar roles of MGF and L.IGF-1in bone as in muscle cells. The functions of MGF and L.IGF-1 in osteoblasts shall be established by further experimental studies.

STRETCHING EXERCISES - EFFECT ON PASSIVE EXTENSIBILITY AND STIFFNESS IN SHORT HAMSTRINGS OF HEALTHY-SUBJECTS

NARCIS (Netherlands)

HALBERTSMA, JPK; GOEKEN, LNH

Passive muscle stretch tests are common practice in physical therapy and rehabilitation medicine. However, the effects of stretching exercises are not well known. With an instrumental straight-leg-raising set-up the extensibility, stiffness, and electromyographic activity of the hamstring muscles

IDENTIFICATION OF THE MASS DISTRIBUTIONS OF THE MILK FAT PHASE USING UNIVERSAL PEARSON DISTRIBUTIONS

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A. A. Khvostov

2015-01-01

Full Text Available In this paper we consider the problem of approximating the experimental values of the coefficient of attenuation of ultrasonic oscillations and the mass distribution of the fat globules in the milk and milk products. The analysis of experimental data in terms of the choice of the method of approximation was done. A approximating dependence is based on the solution of Pearson differential equations. The advantages of the proposed method for the type of approximation of the experimental data obtained. An algorithm for constructing a mathematical model describing the relaxation spectrum and mass distribution of the fat globules in the milk and milk products was implemented. As a result, a family of Pearson approximation curves of the experimental data shows the ability to qualitatively correctly describe the change in the distribution of the fat phase in the process of homogenization. It estimates the error of approximating dependence, which amounted to 18 %. It is shown that during of the process of homogenization of dairy products changes shape of the curve describing the distribution of the fat globules, in view of the fact that there is a local extremum, caused by the presence of the non-homogenized fat globules. The accuracy of the selected mathematical model is significantly reduced. At the same time, it loses its physical meaning and its parameters. To address the identified deviations in the proposed mass distribution of fat globules as a function with two modes. It is proved that the complexity of the model is not only doubles the number of its parameters, but also complicates the interpretation of measurement results in a control system, and makes it difficult to analyze the obtained parameters of approximation by decision-maker. As a result of approximation of experimental data suggested to use statistical moments of the distribution for problem decision.

Gas-Phase IR Spectroscopy of Deprotonated Amino Acids

NARCIS (Netherlands)

Oomens, J.; Steill, J. D.; Redlich, B.

2009-01-01

Gas-phase infrared multiple photon dissociation (IRMPD) spectra have been recorded for the conjugate bases of a series of amino acids (Asp, Cys, Glu, Phe, Set, Trp, Tyr). The spectra are dominated by strong symmetric and antisymmetric carboxylate stretching modes around 1300 and 1600 cm(-1),

Realizing high magnetic moments in fcc Fe nanoparticles through atomic structure stretch

International Nuclear Information System (INIS)

Baker, S H; Roy, M; Thornton, S C; Binns, C

2012-01-01

We describe the realization of a high moment state in fcc Fe nanoparticles through a controlled change in their atomic structure. Embedding Fe nanoparticles in a Cu 1-x Au x matrix causes their atomic structure to switch from bcc to fcc. Extended x-ray absorption fine structure (EXAFS) measurements show that the structure in both the matrix and the Fe nanoparticles expands as the amount of Au in the matrix is increased, with the data indicating a tetragonal stretch in the Fe nanoparticles. The samples were prepared directly from the gas phase by co-deposition, using a gas aggregation source and MBE-type sources respectively for the nanoparticle and matrix materials. The structure change in the Fe nanoparticles is accompanied by a sharp increase in atomic magnetic moment, ultimately to values of ∼2.5 ± 0.3 μ B /atom. (paper)

Breast lesion characterization using whole-lesion histogram analysis with stretched-exponential diffusion model.

Science.gov (United States)

Liu, Chunling; Wang, Kun; Li, Xiaodan; Zhang, Jine; Ding, Jie; Spuhler, Karl; Duong, Timothy; Liang, Changhong; Huang, Chuan

2018-06-01

Diffusion-weighted imaging (DWI) has been studied in breast imaging and can provide more information about diffusion, perfusion and other physiological interests than standard pulse sequences. The stretched-exponential model has previously been shown to be more reliable than conventional DWI techniques, but different diagnostic sensitivities were found from study to study. This work investigated the characteristics of whole-lesion histogram parameters derived from the stretched-exponential diffusion model for benign and malignant breast lesions, compared them with conventional apparent diffusion coefficient (ADC), and further determined which histogram metrics can be best used to differentiate malignant from benign lesions. This was a prospective study. Seventy females were included in the study. Multi-b value DWI was performed on a 1.5T scanner. Histogram parameters of whole lesions for distributed diffusion coefficient (DDC), heterogeneity index (α), and ADC were calculated by two radiologists and compared among benign lesions, ductal carcinoma in situ (DCIS), and invasive carcinoma confirmed by pathology. Nonparametric tests were performed for comparisons among invasive carcinoma, DCIS, and benign lesions. Comparisons of receiver operating characteristic (ROC) curves were performed to show the ability to discriminate malignant from benign lesions. The majority of histogram parameters (mean/min/max, skewness/kurtosis, 10-90 th percentile values) from DDC, α, and ADC were significantly different among invasive carcinoma, DCIS, and benign lesions. DDC 10% (area under curve [AUC] = 0.931), ADC 10% (AUC = 0.893), and α mean (AUC = 0.787) were found to be the best metrics in differentiating benign from malignant tumors among all histogram parameters derived from ADC and α, respectively. The combination of DDC 10% and α mean , using logistic regression, yielded the highest sensitivity (90.2%) and specificity (95.5%). DDC 10% and α mean derived from

Distribution of guppies Poecilia reticulata (Peters, 1860 and Phalloceros caudimaculatus (Hensel, 1868 along a polluted stretch of the Paraíba do Sul River, Brazil

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FG. Araújo

Full Text Available Cyprinodontiformes fishes (guppies are widely distributed in Neotropical regions and use deteriorated microhabitats in rivers where few species can occur. This study was carried out in a stretch of the Paraíba do Sul River in bracketing a large urban-industrial complex. The aim was to assess eventual effects that the industrial complex could have on distribution of two closely related fish species of guppies, Phalloceros caudimaculatus and Poecilia reticulata. The area was divided into three zones: Z1, 40 km upriver of the major urban-industrial complex of Volta Redonda; Z2, just down river of the complex; and Z3, 30 km down river of the complex. Six sites (two in each zone were sampled monthly between November 1998 and October 1999, using a standardized fishing effort with cast net throws, trays lifts and seine hauls, covering different microhabitats, that is, riffles, pools and the proximity of the river's margins. Poecilia reticulata was widely distributed, peaking at Z2, the most polluted area, while P. caudimaculatus showed the highest abundance at Z3, being almost absent in Z1. Both species occurred in high numbers throughout the year but they were scarce between April and June. Females outnumbered males for both species in most size classes and at all sites. Juveniles were more abundant than adults, with non-pregnant females outnumbering pregnant ones. Condition factor was always higher in males than females but only males P. reticulata showed significant difference among the three zones, with the highest values at Z2. The higher number of females confirms the expectation that these species can use very polluted areas and that availability of food provided by organic loads allowed their distribution all over the area. Although these two species have shown indication of spatial separation in the study area, their similar seasonal patterns of occurrence suggest that they respond in a similar way to changes in environmental conditions.

Comparison of the effects of local cryotherapy and passive cross-body stretch on extensibility in subjects with posterior shoulder tightness.

Science.gov (United States)

Park, Kyue-Nam; Kwon, Oh-Yun; Weon, Jong-Hyuck; Choung, Sung-Dae; Kim, Si-Hyun

2014-01-01

The objective was to compare the immediate effects of local cryotherapy (LC) and passive cross-body stretch on the extensibility of the posterior shoulder muscle in individuals with posterior shoulder tightness. Eighty-seven healthy subjects with a between-shoulder difference in internal rotation (IR) range of motion (ROM) greater than 10° were randomly divided into three groups: LC group, stretching group, and control group (n = 29 in each group). Subjects in the LC group received LC on infraspinatus and posterior deltoid muscles and subjects in the stretching group performed passive cross-body stretch. Stretch sensation was measured at the end range of passive IR and horizontal adduction (HA) using numerical rating scale, and the pressure pain threshold (PPT) at the infraspinatus and posterior deltoid muscles was measured using pressure algometry. Passive and active ROM of IR and HA of the glenohumeral joint were measured using an inclinometer. All measurements were performed at pre-intervention, post- intervention, and 10-min follow-up. Stretch sensation was significantly decreased and PPT was significantly increased in the LC and stretching groups at post-intervention, and these effects were maintained at 10-min follow-up, compared to the control group. Both the LC group and stretching group had a significantly greater increase in passive and active ROM of IR and HA, compared to the control group at post-intervention and 10-min follow-up. However, there were no significant differences in stretch sensation, PPT, or ROM of IR and HA between the LC group and stretching group. LC can be used to decrease the stretch sensation and increase PPT and ROM of IR and HA as much as a stretching exercise. LC could be an alternative method for increasing the restricted ROM of glenohumeral IR and HA for individuals with posterior shoulder tightness, especially for patients and sports players who have severe stretching discomfort. Key PointsLocal cryotherapy (LC) decreased the

Calcineurin /NFAT activation-dependence of leptin synthesis and vascular growth in response to mechanical stretch

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Nadia Soudani

2016-09-01

Full Text Available Background and Aims- Hypertension and obesity are important risk factors of cardiovascular disease. They are both associated with high leptin levels and have been shown to promote vascular hypertrophy, through the RhoA/ROCK and ERK1/2 phosphorylation. Calcineurin/NFAT activation also induces vascular hypertrophy by upregulating various genes. This study aimed to decipher whether a crosstalk exists between the RhoA/ROCK pathway, Ca+2/calcineurin/NFAT pathway, and ERK1/2 phosphorylation in the process of mechanical stretch-induced vascular smooth muscle cell (VSMC hypertrophy and leptin synthesis. Methods and Results- Rat portal vein (RPV organ culture was used to investigate the effect of mechanical stretch and exogenous leptin (3.1 nM on VSMC hypertrophy and leptin synthesis. Results showed that stretching the RPV significantly upregulated leptin secretion, mRNA and protein expression, which were inhibited by the calcium channel blocker nifedipine (10 μM, the selective calcineurin inhibitor FK506 (1 nM and the ERK1/2 inhibitor PD98059 (1 μM. The transcription inhibitor actinomycin D (0.1M and the translation inhibitor cycloheximide (1 mM significantly decreased stretch-induced leptin protein expression. Mechanical stretch or leptin caused an increase in wet weight changes and protein synthesis, considered as hypertrophic markers, while they were inhibited by FK506 (0.1 nM; 1 nM. In addition, stretch or exogenous leptin significantly increased calcineurin activity and MCIP1 expression whereas leptin induced NFAT nuclear translocation in VSMCs. Moreover, in response to stretch or exogenous leptin, the Rho inhibitor C3 exoenzyme (30 ng/mL, the ROCK inhibitor Y-27632 (10 μM, and the actin depolymerization agents Latrunculin B (50 nM and cytochalasin D (1 μM reduced calcineurin activation and NFAT nuclear translocation. ERK1/2 phosphorylation was inhibited by FK506 and C3. Conclusions- Mechanical stretch-induced VSMC hypertrophy and leptin

Liver fibrosis: stretched exponential model outperforms mono-exponential and bi-exponential models of diffusion-weighted MRI.

Science.gov (United States)

Seo, Nieun; Chung, Yong Eun; Park, Yung Nyun; Kim, Eunju; Hwang, Jinwoo; Kim, Myeong-Jin

2018-07-01

To compare the ability of diffusion-weighted imaging (DWI) parameters acquired from three different models for the diagnosis of hepatic fibrosis (HF). Ninety-five patients underwent DWI using nine b values at 3 T magnetic resonance. The hepatic apparent diffusion coefficient (ADC) from a mono-exponential model, the true diffusion coefficient (D t ), pseudo-diffusion coefficient (D p ) and perfusion fraction (f) from a biexponential model, and the distributed diffusion coefficient (DDC) and intravoxel heterogeneity index (α) from a stretched exponential model were compared with the pathological HF stage. For the stretched exponential model, parameters were also obtained using a dataset of six b values (DDC # , α # ). The diagnostic performances of the parameters for HF staging were evaluated with Obuchowski measures and receiver operating characteristics (ROC) analysis. The measurement variability of DWI parameters was evaluated using the coefficient of variation (CoV). Diagnostic accuracy for HF staging was highest for DDC # (Obuchowski measures, 0.770 ± 0.03), and it was significantly higher than that of ADC (0.597 ± 0.05, p bi-exponential DWI model • Acquisition of six b values is sufficient to obtain accurate DDC and α.

Deformations of a pre-stretched and lubricated finite elastic membrane driven by non-uniform external forcing

Science.gov (United States)

Boyko, Evgeniy; Gat, Amir; Bercovici, Moran

2017-11-01

We study viscous-elastic dynamics of a fluid confined between a rigid plate and a finite pre-stretched circular elastic membrane, pinned at its boundaries. The membrane is subjected to forces acting either directly on the membrane or through a pressure distribution in the fluid. Under the assumptions of strong pre-stretching and small deformations of the elastic sheet, and by applying the lubrication approximation for the flow, we derive the Green's function for the resulting linearized 4th order diffusion equation governing the deformation field in cylindrical coordinates. In addition, defining an asymptotic expansion with the ratio of the induced to prescribed tension serving as the small parameter, we reduce the coupled Reynolds and non-linear von-Karman equations to a set of three one-way coupled linear equations. The solutions to these equations provide insight onto the effects of induced tension, and enable simplified prediction of the correction for the deformation field. Funded by the European Research Council (ERC) under the European Union'sHorizon 2020 Research and Innovation Programme, Grant Agreement No. 678734 (MetamorphChip). E.B. is supported by the Adams Fellowship Program.

Optical image encryption based on phase retrieval combined with three-dimensional particle-like distribution

International Nuclear Information System (INIS)

Chen, Wen; Chen, Xudong; Sheppard, Colin J R

2012-01-01

We propose a new phase retrieval algorithm for optical image encryption in three-dimensional (3D) space. The two-dimensional (2D) plaintext is considered as a series of particles distributed in 3D space, and an iterative phase retrieval algorithm is developed to encrypt the series of particles into phase-only masks. The feasibility and effectiveness of the proposed method are demonstrated by a numerical experiment, and the advantages and security of the proposed optical cryptosystems are also analyzed and discussed. (paper)

Theta-alpha EEG phase distributions in the frontal area for dissociation of visual and auditory working memory.

Science.gov (United States)

Akiyama, Masakazu; Tero, Atsushi; Kawasaki, Masahiro; Nishiura, Yasumasa; Yamaguchi, Yoko

2017-03-07

Working memory (WM) is known to be associated with synchronization of the theta and alpha bands observed in electroencephalograms (EEGs). Although frontal-posterior global theta synchronization appears in modality-specific WM, local theta synchronization in frontal regions has been found in modality-independent WM. How frontal theta oscillations separately synchronize with task-relevant sensory brain areas remains an open question. Here, we focused on theta-alpha phase relationships in frontal areas using EEG, and then verified their functional roles with mathematical models. EEG data showed that the relationship between theta (6 Hz) and alpha (12 Hz) phases in the frontal areas was about 1:2 during both auditory and visual WM, and that the phase distributions between auditory and visual WM were different. Next, we used the differences in phase distributions to construct FitzHugh-Nagumo type mathematical models. The results replicated the modality-specific branching by orthogonally of the trigonometric functions for theta and alpha oscillations. Furthermore, mathematical and experimental results were consistent with regards to the phase relationships and amplitudes observed in frontal and sensory areas. These results indicate the important role that different phase distributions of theta and alpha oscillations have in modality-specific dissociation in the brain.

Effects of acute static, ballistic, and PNF stretching exercise on the muscle and tendon tissue properties.

Science.gov (United States)

Konrad, A; Stafilidis, S; Tilp, M

2017-10-01

The purpose of this study was to investigate the influence of a single static, ballistic, or proprioceptive neuromuscular facilitation (PNF) stretching exercise on the various muscle-tendon parameters of the lower leg and to detect possible differences in the effects between the methods. Volunteers (n = 122) were randomly divided into static, ballistic, and PNF stretching groups and a control group. Before and after the 4 × 30 s stretching intervention, we determined the maximum dorsiflexion range of motion (RoM) with the corresponding fascicle length and pennation angle of the gastrocnemius medialis. Passive resistive torque (PRT) and maximum voluntary contraction (MVC) were measured with a dynamometer. Observation of muscle-tendon junction (MTJ) displacement with ultrasound allowed us to determine the length changes in the tendon and muscle, respectively, and hence to calculate stiffness. Although RoM increased (static: +4.3%, ballistic: +4.5%, PNF: +3.5%), PRT (static: -11.4%, ballistic: -11.5%, PNF: -13,7%), muscle stiffness (static: -13.1%, ballistic: -20.3%, PNF: -20.2%), and muscle-tendon stiffness (static: -11.3%, ballistic: -10.5%, PNF: -13.7%) decreased significantly in all the stretching groups. Only in the PNF stretching group, the pennation angle in the stretched position (-4.2%) and plantar flexor MVC (-4.6%) decreased significantly. Multivariate analysis showed no clinically relevant difference between the stretching groups. The increase in RoM and the decrease in PRT and muscle-tendon stiffness could be explained by more compliant muscle tissue following a single static, ballistic, or PNF stretching exercise. © 2017 The Authors Scandinavian Journal of Medicine & Science In Sports Published by John Wiley & Sons Ltd.

On MHD nonlinear stretching flow of Powell–Eyring nanomaterial

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Tasawar Hayat

Full Text Available This communication addresses the magnetohydrodynamic (MHD flow of Powell–Eyring nanomaterial bounded by a nonlinear stretching sheet. Novel features regarding thermophoresis and Brownian motion are taken into consideration. Powell–Eyring fluid is electrically conducted subject to non-uniform applied magnetic field. Assumptions of small magnetic Reynolds number and boundary layer approximation are employed in the mathematical development. Zero nanoparticles mass flux condition at the sheet is selected. Adequate transformation yield nonlinear ordinary differential systems. The developed nonlinear systems have been computed through the homotopic approach. Effects of different pertinent parameters on velocity, temperature and concentration fields are studied and analyzed. Further numerical data of skin friction and heat transfer rate is also tabulated and interpreted. Keywords: Powell–Eyring fluid, Magnetohydrodynamics, Nanomaterial, Nonlinear stretching surface