Search results for "spring"

Dynamics of Polymer Chains Confined in Slit-Like Pores

1996

Monte Carlo simulations of an off-lattice bead spring model of polymer chains are presented, confining the chains between two repulsive parallel planes a distance D apart. Varying the chain length N from N = 16 to N = 128, we show that under good solvent conditions the chains behave like two-dimensional self-avoiding walks, their mean square gyration radius scales as (R g 2 ) N 2v with v = 3/4. The density profile across the slit is independent of N and maximal in the center of the slit. The dynamical properties of the chains are found to be in full agreement with the Rouse model with excluded volume in d = 2 dimensions, the relaxation times vary like τ N Z with z = 2v +1 = 5/2, the diffusi…

Dynamic measurement of the elastic constant of an helicoidal spring by a smartphone

2021

Abstract We describe an educational activity that can be done by using smartphones to collect data in physics experiments aimed to measure the oscillating period of a spring-mass system and the elastic constant of the helicoidal spring by the dynamic method. Results for the oscillating period and for the elastic constant of the spring agree very well with measurements obtained by different methods. We also discuss the error analysis that can be done in an introductory physics laboratory at undergraduate level.

A polymer chain trapped between two parallel repulsive walls: A Monte-Carlo test of scaling behavior

1998

An off-lattice bead-spring model of a polymer chain trapped between two parallel walls a distance D apart is studied by Monte-Carlo methods, using chain lengths N in the range $$32 \le N \le 512$$ and distances D from 4 to 32 (in units of the maximum spring extension). The scaling behavior of the coil linear dimensions parallel to the plates and of the force on the walls is studied and discussed with the help of current theoretical predictions. Also the density profiles of the monomers across the slit are obtained and it is shown that the predicted variation with the distance z from a wall, $$\rho (z) \propto {z^{1/\nu }}$$ , is obtained only when one introduces an extrapolation length λ in…

Frequency-dependent relaxation rate in superconductingYBa2Cu3O6+δ

2000

The submillimeter-wave $3 {\mathrm{cm}}^{\ensuremath{-}1}l\ensuremath{\nu}l40 {\mathrm{cm}}^{\ensuremath{-}1}$ complex conductivity of the reduced ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{6+\ensuremath{\delta}}$ film ${(T}_{C}=56.5 \mathrm{K})$ was investigated for temperatures $4 \mathrm{K}lTl300 \mathrm{K}$ and compared to the properties of the same film in the optimally doped state. The frequency dependence of the effective quasiparticle scattering rate $1/{\ensuremath{\tau}}^{*}(\ensuremath{\nu})$ was extracted from the spectra. $1/{\ensuremath{\tau}}^{*}$ is shown to be frequency independent at low frequencies and high temperatures. A gradual change to $1/{\ensuremath{\tau}}^{…

Extensible Wind Towers

2014

The diffusion of wind energy generators is restricted by their strong landscape impact. The PERIMA project is about the development of an extensible wind tower able to support a wind machine for several hundred kW at its optimal working height, up to more than 50 m. The wind tower has a telescopic structure, made by several tubes located inside each other with their axis in vertical direction. The lifting force is given by a jack-up system confined inside a shaft, drilled below the ground level. In the retracted tower configuration, at rest, tower tubes are hidden in the foundation of the telescopic structure, located below the ground surface, and the wind machine is the only emerging part …

Lidojumu plānotājs

2019

Lidojumu plānotājs ir lietojumprogrammas saskarne, kuras galvenais mērķis ir lidojumu informācijas nodrošināšana klientam, ietverot informāciju par aviosabiedrībām, lidojumu precīziem laikiem, lidojumu sākuma punktiem un galamērķiem, laikapstākļiem, kā arī potenciāli administratoram pieejamā funkcionalitāte, kas nodrošina jaunu lidojumu informācijas pievienošanu sistēmai, eksistējošu ierakstu revīziju un dzēšanu. Izstrādātais rīks nodrošina gan saņemto datu apkopošanu gan to apstrādi, kā arī tiek nodrošināta kļūdainu pieprasījumu apstrāde un atbilstošu ziņojumu sagādāšana. Pie potenciālas sistēmas realizācijas tiešsaistē, lietotāji un administratori lidojumu informācijai spētu piekļūt veico…

Analysis of reproductive toxicity and classification of glufosinate-ammonium.

2005

CONCLUSION REGARDING CLASSIFICATION OF GLUFOSINATE-AMMONIUM: Science Partners' Evaluation Group (Evaluation Group) has conducted an independent analysis of the herbicide glufosinate-ammonium (GA) relative to its potential to cause reproductive toxicity in humans. Further, the Evaluation Group has evaluated the implementation of Annex 6 of Commission Directive 2001/59/EC (28th ATP of Council Directive 67/548/EEC) and Council Directive 91/414/EEC, with respect to classification of chemicals posing potential reproductive hazards. After consideration of all information available to us relevant to the potential of glufosinate-ammonium (GA) to cause reproductive toxicity, the Science Partners Eva…

Maternal Metabolic Health Parameters During Pregnancy in Relation to Early Childhood BMI Trajectories

2018

Objective The objective of this study was to evaluate the associations between maternal metabolic parameters and early childhood BMI trajectories. Methods Two thousand two hundred fifty-one children born in Spain between 2004 and 2008 were analyzed. Five BMI z score trajectories from birth to age 4 years were identified by using latent class growth analysis. Multinomial regression assessed the associations between maternal metabolic parameters and offspring's BMI trajectories. Results Children in the reference BMI trajectory had average size at birth followed by a slower BMI gain. Maternal prepregnancy obesity was associated with trajectories of accelerated BMI gain departing from either hi…

Xéno-hormone exposure during pregnancy and lactation modify sweet preference of male but not female offspring

2008

Long-Term Effects of Delayed Fatherhood in Mice on Postnatal Development and Behavioral Traits of Offspring1

2009

This study aims to analyze, in mice, the long-term effects of delayed fatherhood on postnatal development, spontaneous motor activity, and learning capacity of offspring. Hybrid parental-generation (F 0 ) males, at the age of 12, 70, 100, and 120 wk, were individually housed with a randomly selected 12wk-old hybrid female. The resulting first-generation (F 1 ) offspring were tested for several developmental and behavioral variables. Cumulative percentage of F 1 pups that attained immediate righting in the 120-wk group was lower than that found in the 12-, 70-, and 100-wk groups. Furthermore, the postnatal day of attaining immediate righting was higher in pups from the 120-wk group when comp…