Methods of calculation of a friction coefficient: Application to the nanotubes

In this work we develop theoretical and numerical methods of calculation of a dynamic friction coefficient. The theoretical method is based on an adiabatic approximation which allows us to express the dynamic friction coefficient in terms of the time integral of the autocorrelation function of the force between both sliding objects. The motion of the objects and the autocorrelation function can be numerically calculated by molecular-dynamics simulations. We have successfully applied these methods to the evaluation of the dynamic friction coefficient of the relative motion of two concentric carbon nanotubes. The dynamic friction coefficient is shown to increase with the temperature.Comment: 4 pages, 6 figure

Using the nonlinear control of anaesthesia-induced hypersensitivity of EEG at burst suppression level to test the effects of radiofrequency radiation on brain function

Background In this study, investigating the effects of mobile phone radiation on test animals, eleven pigs were anaesthetised to the level where burst-suppression pattern appears in the electroencephalogram (EEG). At this level of anaesthesia both human subjects and animals show high sensitivity to external stimuli which produce EEG bursts during suppression. The burst-suppression phenomenon represents a nonlinear control system, where low-amplitude EEG abruptly switches to very high amplitude bursts. This switching can be triggered by very minor stimuli and the phenomenon has been described as hypersensitivity. To test if also radio frequency (RF) stimulation can trigger this nonlinear control, the animals were exposed to pulse modulated signal of a GSM mobile phone at 890 MHz. In the first phase of the experiment electromagnetic field (EMF) stimulation was randomly switched on and off and the relation between EEG bursts and EMF stimulation onsets and endpoints were studied. In the second phase a continuous RF stimulation at 31 W/kg was applied for 10 minutes. The ECG, the EEG, and the subcutaneous temperature were recorded. Results No correlation between the exposure and the EEG burst occurrences was observed in phase I measurements. No significant changes were observed in the EEG activity of the pigs during phase II measurements although several EEG signal analysis methods were applied. The temperature measured subcutaneously from the pigs' head increased by 1.6°C and the heart rate by 14.2 bpm on the average during the 10 min exposure periods. Conclusion The hypothesis that RF radiation would produce sensory stimulation of somatosensory, auditory or visual system or directly affect the brain so as to produce EEG bursts during suppression was not confirmed.BioMed Central Open acces

Evidence of a Sticky Boundary Layer in Nanochannels: A Neutron Spin Echo Study of n

Neutron spin echo spectra of the melts of n-hexatriacontane (C36) and poly(ethylene oxide) (PEO), 2 kg/mol, confined in circular channels with a mean diameter of 10 and 12 nm, respectively, in porous silicon, were recorded at Q values between 0.05 and 0.15 angstrom(-1). The spectra were successfully analyzed in terms of a two-state model where wall-adsorbed molecules are immobile and free molecules have a bulk-like dynamics. For C36, we find an adsorbed bilayer at 364 K and a monolayer at 435 K (in both cases, the long axis of the molecules is oriented parallel to the surface) and no adsorbed layer at 512 K. For PEO, we find an adsorbed monolayer at 413 K. The results support the existence of a sticky boundary layer inferred from capillary filling experiments

Exploring the Role of Diversity Management During Early Internationalizing Firms’ Internationalization Process

Despite their rapid internationalization, early internationalizing firms (EIFs) struggle to sustain their growth over time. Among the factors influencing their internationalization process, the diversity of human resources, and particularly its management, has yet to be studied. Building on different perspectives of diversity management, through the lens of the resource-based view, this study explores the role of diversity management during EIFs’ internationalization process. The results of a multiple-case, qualitative study of French EIFs show that prevailing perspectives on diversity management within EIFs change with the nature of diversity as a resource (strategic, ordinary, or negative), with different influences on the firms’ progress along the phases of the internationalization process. The findings highlight the importance of adopting a learning perspective on managing diversity, including specific management practices, during the transition between the entry and post-entry phases of EIFs’ internationalization process. This study thus suggests several propositions and theoretical contributions, along with managerial recommendations

Structure of a thermoset polymer near an alumina substrate as studie by dissipative particle dynamics

We performed dissipative particle dynamics (DPD) simulations to investigate the structure and cross-link formation dynamics of a thermoset polymer while interacting with a metal-oxide surface. For characterizing the polymer–surface interactions we used the surface excess, quantifying the surface selectivity of different functional groups. Mesoscopic polymer–surface interactions are determined by matching the surface excess, as computed with atomistic molecular dynamics (MD), with those for DPD, thus realizing a coupling between the mesoscopic and atomistic scales. In the structure prior to cross-linking, we observe that some functional groups prefer to be located at the interface while others are repelled. This largely determines the final cross-linked structure near the metal-oxide interface. The initial preference for cross-links to form is in the bulk region. However, at longer times toward the equilibrium structure, the trade-off between the epoxy–alumina interactions causes migration of reacted groups to the surface