Force fluctuations in stretching a tethered polymer

The recently proposed fluctuation relation in unfolding forces [Phys. Rev. E ${\bf 84}$, $060101$(R) $(2011)$] is re-examined taking into account the explicit time dependence of the force distribution. The stretching of a tethered Rouse polymer is exactly solved and the ratio of the probabilities of positive to negative forces is shown to be an exponential in force. Extensive steered molecular dynamics simulations of unfolding of deca alanine peptide confirm the form of fluctuation relation proposed earlier, but with explicit correct time dependence of unfolding forces taken into account. From exact calculations and simulations, a linear dependence of the constant in the exponential of the fluctuation relation on average unfolding forces and inverse temperature is proposed.Comment: 5 pages, 4 figure

Aggregation of rod-like polyelectrolyte chains in the presence of monovalent counterions

Using molecular dynamics simulations, it is demonstrated that monovalent counterions can induce aggregation of similarly charged rod-like polyelectrolyte chains. The critical value of the linear charge density for aggregation is shown to be close to the critical value for the extended-collapsed transition of a single flexible polyelectrolyte chain, and decreases with increasing valency of the counterions. The effective interaction potential between two rod-like polyelectrolyte chains is measured, and is related to the angular distribution of the condensed counterions.Comment: 8 pages, 5 figure

Thermostat for non-equilibrium multiparticle collision dynamics simulations

Multiparticle collision dynamics (MPC), a particle-based mesoscale simulation technique for com- plex fluid, is widely employed in non-equilibrium simulations of soft matter systems. To maintain a defined thermodynamic state, thermalization of the fluid is often required for certain MPC variants. We investigate the influence of three thermostats on the non-equilibrium properties of a MPC fluid under shear or in Poiseuille flow. In all cases, the local velocities are scaled by a factor, which is either determined via a local simple scaling approach (LSS), a Monte Carlo-like procedure (MCS), or by the Maxwell-Boltzmann distribution of kinetic energy (MBS). We find that the various scal- ing schemes leave the flow profile unchanged and maintain the local temperature well. The fluid viscosities extracted from the various simulations are in close agreement. Moreover, the numerically determined viscosities are in remarkably good agreement with the respective theoretically predicted values. At equilibrium, the calculation of the dynamic structure factor reveals that the MBS method closely resembles an isothermal ensemble, whereas the MCS procedure exhibits signatures of an adi- abatic system at larger collision-time steps. Since the velocity distribution of the LSS approach is non-Gaussian, we recommend to apply the MBS thermostat, which has been shown to produce the correct velocity distribution even under non-equilibrium conditions.Comment: 12 pages, 5 figures in Phys. Rev. E, 201

Hydrodynamic correlations in shear flow: A Multiparticle--Collision--Dynamics simulation study

The nonequilibrium hydrodynamic correlations of a Multiparticle-Collision-Dynamics (MPC) fluid in shear flow are studied by analytical calculations and simulations. The Navier-Stokes equations for a MPC fluid are linearized about the shear flow and the hydrodynamic modes are evaluated as an expansion in the momentum vector. The shear-rate dependence and anisotropy of the transverse and longitudinal velocity correlations are analyzed. We demonstrate that hydrodynamic correlations in shear flow are anisotropic, specifically, the two transverse modes are no longer identical. In addition, our simulations reveal the directional dependence of the frequency and attenuation of the longitudinal velocity correlation function. Furthermore, the velocity autocorrelation functions of a tagged fluid particle in shear flow are determined. The simulations results for various hydrodynamic correlations agree very well with the theoretical predictions.Comment: 8 pages, 5 figure

Guidelines for inclusion of the elderly population into smartphone design

LAUREA MAGISTRALELa maggior parte dei paesi del mondo mostra un forte aumento del numero di anziani nella popolazione. I paesi sviluppati hanno una significativa popolazione che invecchia oltre i 65 anni ed è ancora in aumento. Con le tendenze attuali, la popolazione anziana sarà la maggioranza del mondo in pochi anni. Ciò significa anche il rapporto tra i consumatori. D'altra parte, il mondo sta vivendo un'espansione nell'applicazione personale di tecnologie come gli smartphone. Tuttavia, ci sono meno smartphone, che sono stati progettati per l'inclusione di consumatori anziani. Ci sono poche aziende che vendono smartphone con un tag "progettato per anziani". Quelli sono smartphone con asceti strani e strane funzionalità. Si è dimostrato che non sta rispondendo adeguatamente alle necessità e crea un sentimento negli anziani che sono vecchi e fuori dalle nuove tecnologie. Molte delle risorse di ricerca esistenti suggeriscono questa realtà. La maggior parte degli smartphone viene introdotta con nuove tecnologie, forme, design e funzionalità, rivolti alla popolazione più giovane. Questa strategia di business e design sta portando gli anziani ad essere evitati dal boom della tecnologia. In questo articolo, l'autore affronta la domanda di progettazione di smartphone che ispirerà i clienti anziani a comprare e provare. Inoltre, cerca di formulare alcune linee guida per la progettazione di smartphone, con l'inclusione di anziani nel mercato di riferimento. Poiché gli anziani si riferiscono a molte categorie di età, benessere e conoscenza, sarà difficile arrivare alle conclusioni facilmente. Questo porta a snellire lo studio solo al limite di età di 70-80 anni per non essere alle tendenze estreme di questa popolazione e considerare la parte di ponte tra solo anziani e anziani molto anziani. Attraverso la segmentazione degli smartphone disponibili sul mercato, i problemi che limitano l'uso degli smartphone da parte degli anziani e l'indagine di alcune popolazioni anziane selezionate in Italia, la ricerca ha tratto alcune conclusioni sulle linee guida di progettazione per includere gli anziani nei consumatori di smartphone.The majority of the countries in the world are showing a strong increase in the number of elderly people in the population. The developed countries have a significant ageing population above 65 years old and it is still in rise. With present trends, the elderly population will be the majority of the world in few years. That means the ratio of the consumers too. In the other hand, world is experiencing an expansion in personal application of technologies like smart phones. However, there are very less smartphones, which were designed for inclusion of elderly consumers. There are few companies, which sells smartphones with a tag “designed for elderly”. Those are smartphones with odd ascetics and strange features. It is proved to be not serving the need properly and create a feeling in elderly that they are old and out from the new technologies. Many of the existing research resources hint with this reality. Most of the smartphones are introduced with new technologies, shape, design and features, which are aimed to younger population. This business and design strategy is leading the elderly to be avoided from the technology boom. In this paper, author addresses the demand for designing smartphones that will inspire elderly customers to buy and try. In addition, tries to formulate some guidelines for designing smartphones, with the inclusion of elderly in the target market. Since the elderly refers to many age categories, wellness and knowledge, it will be difficult to arrive at conclusions easily. This leads to streamlining the study only on the age limit of 70 to 80 years for not being at extreme trends of this population and to consider the bridge part between just elderly and very old elderly. Through segmentation of available smartphones in the market, the problems that restricts elderly from using the smartphones and survey of selected elderly populations in Italy, the research is drawn into some conclusions about the design guidelines to include the elderly in to the smartphone consumers

Time correlation functions in the Lebwohl-Lasher model of liquid crystals

Time correlation functions in the Lebwohl-Lasher model of nematic liquid crystals are studied using theory and molecular dynamics simulations. In particular, the autocorrelation functions of angular momentum and nematic director fluctuations are calculated in the long-wavelength limit. The constitutive relations for the hydrodynamic currents are derived using a standard procedure based on non-negativity of the entropy production. The continuity equations are then linearized and solved to calculate the correlation functions. We find that the transverse angular momentum fluctuations are coupled to the director fluctuations, and are both propagative. The propagative nature of the fluctuations suppress the anticipated hydrodynamic long-time tails in the single-particle autocorrelation functions. The fluctuations in the isotropic phase are however diffusive, leading to $t^{-d/2}$ long-time tails in $d$ spatial dimensions. The Frank elastic constant measured using the time-correlation functions are in good agreement with previously reported results

A Non Invasive Heart Rate and Blood Pressure Remote Monitoring System

Health monitoring systems have become an important research field today. Research on health monitoring were developed for many applications such as in home care units, emergency monitoring systems etc. This paper proposes the design of a non invasive wireless heart rate and blood pressure remote monitoring system based on an embedded board and Bluetooth wireless technology. The real time biomedical signal is sensed and measured using an optical measurement circuit based on Photoplethysmography technique. Blood pressure and heart rate readings are calculated on the basis of the developed algorithm and are displayed on the LCD screen. Moreover these numerical values of heart rate, systolic and diastolic pressure can be transmitted to any bluetooth enabled computer or smart phone via Bluetooth wireless technology

Cortical Reorganisation in Complex Regional Pain Syndrome (CRPS)

Complex Regional Pain Syndrome (CRPS) is a debilitating pain condition of unknown aetiology, usually occurring post-traumatically. Early diagnosis of CRPS remains a challenge with adverse implications on rehabilitation and recovery. The main goals of my research were to help develop clinically useful bedside tests as well as objective biomarkers to improve the early diagnosis of CRPS. The first research project in this thesis, ‘Novel signs in CRPS and their diagnostic clinical utility’ was a prospective observational cohort study which defined the four novel signs (finger misperception, abnormal hand laterality, astereognosis and abnormal body scheme report) in CRPS, examined their prevalence in CRPS and other chronic pain conditions and assessed their diagnostic utility (Sensitivity, Specificity, Predictive values and Likelihood ratios) for identifying patients at risk of CRPS within a Fracture cohort. This study demonstrates that novel signs are present in the majority of CRPS patients and can be reliably detected following simple training. They are practical and have significant clinical utility in diagnosing persistent pain in a fracture group. They can be used to identify patients at high risk of developing chronic pain post-fracture thereby allowing targeted early intervention. Cortical reorganisation, defined as structural and functional changes within the cerebral cortex, is implicated in many chronic pain conditions including CRPS. The second research project in this thesis ‘Cortical reorganisation and finger misperception in CRPS- a high density electroencephalogram study’ was a prospective case control design study which investigated the EEG parameters suggestive of cortical reorganisation in CRPS patients by studying the somatosensory ERPs (Event Related Potentials) elicited on painless finger stimulation. There was no significant difference in the GFP (Global Field Power) latency in the patient group compared to healthy subjects or between affected and unaffected sides of the patient group suggesting there was no impairment of somatosensory conduction from the periphery to the somatosensory cortex. However, GFP amplitude corresponding to P300 was significantly higher in the patient affected side compared to the healthy subjects suggesting cognitive dysfunction possibly related to increased allocation of attentional resources

Ensemble Equivalence for Counterion Condensation on a Two Dimensional Charged Disc

We study the counterion condensation on a two dimensional charged disc in the limit of infinite dilution, and compare the energy-temperature relation obtained from the canonical free energy and microcanonical entropy. The microcanonical entropy is piecewise linear in energy, and is shown to be concave for all energies. As a result, even though the interactions are long-ranged, the energy-temperature relation and hence the counterion condensation transition points are identical in both the ensembles.Comment: 4 pages, 2 figure

Phase transitions of a single polyelectrolyte in a poor solvent with explicit counterions

Conformational properties of a single flexible polyelectrolyte chain in a poor solvent are studied using constant temperature molecular dynamics simulation. The effects of counterions are explicitly taken in to account. Structural properties of various phases and the transition between these phases are studied by tracking the values of asphericity, radius of gyration, fraction of condensed counterions, number of non-bonded neighbours and Coulomb interaction energies. From our simulations, we find strong evidence for a first-order phase transition from extended to collapsed phase consistent with earlier theoretical predictions. We also identify a continuous phase transition associated with the condensation of counterions and estimate the critical exponents associated with the transition. Finally, we argue that previous suggestions of existence of an independent intermediate phase between extended and collapsed phases is only a finite size effect.Comment: 7 pages, 8 figure