1,541 research outputs found
Fractional Hereditariness of Lipid Membranes: Instabilities and Linearized Evolution
In this work lipid ordering phase changes arising in planar membrane bilayers
is investigated both accounting for elas- ticity alone and for effective
viscoelastic response of such assemblies. The mechanical response of such
membranes is studied by minimizing the Gibbs free energy which penalizes
perturbations of the changes of areal stretch and their gradients only [1]. As
material instabilities arise whenever areal stretches characterizing
homogeneous configurations lie inside the spinoidal zone of the free energy
density, bifurcations from such configurations are shown to occur as
oscillatory perturbations of the in-plane displacement. Experimental
observations [2] show a power-law in-plane viscous behavior of lipid structures
allowing for an effective viscoelastic behavior of lipid membranes [3], which
falls in the framework of Fractional Hereditariness. A suitable generalization
of the variational principle invoked for the elasticity is applied in this
case, and the corresponding Euler-Lagrange equation is found together with a
set of bound- ary and initial conditions. Separation of variables allows for
showing how Fractional Hereditariness owes bifurcated modes with a larger
number of spatial oscillations than the corresponding elastic analog. Indeed,
the available range of areal stresses for material instabilities is found to
increase with respect to the purely elastic case. Nevertheless, the time
evolution of the perturbations solving the Euler-Lagrange equation above
exhibits time-decay and the large number of spatial oscillation slowly relaxes,
thereby keeping the features of a long-tail type time-response.Comment: 21 pages, 11 figures, special issu
The Prospects of Aluminium in India
ALUMINIUM the most abundant of all the metallic elements found in the earth's crust was at one time more precious and rare than silver and gold, but in less than 100 years it has become one of the most important metals in the world. It was successfully produced commercially for the first time only a decade before the turn of century. Since then its production has rapidly increased from 12,000 tons in 1905 to over 4 million tons at present and has attained a position second only to steel. It is it young and virile industry and has surpassed lead and zinc and wrought copper
as revealed in Table I. It is observed that during the
period 1948 to 1958, aluminium's share of the four
major non-ferrous metals increased from 18 to 28 percent while copper dropped from its share of 33.4 to 28'5 percent
Galaxies into the Dark Ages
We consider the capabilities of current and future large facilities operating
at 2\,mm to 3\,mm wavelength to detect and image the [CII] 158\,m line
from galaxies into the cosmic "dark ages" ( to 20). The [CII] line
may prove to be a powerful tool in determining spectroscopic redshifts, and
galaxy dynamics, for the first galaxies. We emphasize that the nature, and even
existence, of such extreme redshift galaxies, remains at the frontier of open
questions in galaxy formation. In 40\,hr, ALMA has the sensitivity to detect
the integrated [CII] line emission from a moderate metallicity, active
star-forming galaxy [; star formation rate (SFR) =
5\,\,yr], at at a significance of 6. The
next-generation Very Large Array (ngVLA) will detect the integrated [CII] line
emission from a Milky-Way like star formation rate galaxy (, SFR = 1\,\,yr), at at a significance
of 6. Imaging simulations show that the ngVLA can determine rotation
dynamics for active star-forming galaxies at , if they exist. Based
on our very limited knowledge of the extreme redshift Universe, we calculate
the count rate in blind, volumetric surveys for [CII] emission at
to 20. The detection rates in blind surveys will be slow (of order unity per
40\,hr pointing). However, the observations are well suited to commensal
searches. We compare [CII] with the [OIII] 88m line, and other ancillary
information in high galaxies that would aid these studies.Comment: 11pages, 8 figures, Accepted for the Astrophysical Journa
Lyman Alpha Emitter Evolution in the Reionization Epoch
Combining cosmological SPH simulations with a previously developed Lyman
Alpha production/transmission model and the Early Reionization Model (ERM,
reionization ends at redshift z~7), we obtain Lyman Alpha and UV Luminosity
Functions (LFs) for Lyman Alpha Emitters (LAEs) for redshifts between 5.7 and
7.6. Matching model results to observations at z~5.7 requires escape fractions
of Lyman Alpha, f_alpha=0.3, and UV (non-ionizing) continuum photons, f_c=0.22,
corresponding to a color excess, E(B-V)=0.15. We find that (i) f_c increases
towards higher redshifts, due the decreasing mean dust content of galaxies,
(ii) the evolution of f_alpha/f_c hints at the dust content of the ISM becoming
progressively inhomogeneous/clumped with decreasing redshift. The clustering
photoionization boost is important during the initial reionization phases but
has little effect on the Lyman Alpha LF for a highly ionized IGM. Halo
(stellar) masses are in the range 10.0 < \log M_h < 11.8 (8.1 < \log M_* <
10.4) with M_h \propto M_*^{0.64}. The star formation rates are between 3-120
solar masses per year, mass-weighted mean ages are greater than 20 Myr at all
redshifts, while the mean stellar metallicity increases from Z=0.12 to 0.22
solar metallicity from z~7.6 to z~5.7; both age and metallicity positively
correlate with stellar mass. The brightest LAEs are all characterized by large
star formation rates and intermediate ages (~200 Myr), while objects in the
faint end of the Lyman Alpha LF show large age and star formation rate spreads.
With no more free parameters, the Spectral Energy Distributions of three LAE at
z~5.7 observed by Lai et al. (2007) are well reproduced by an intermediate age
(182-220 Myr) stellar population and the above E(B-V) value.Comment: 13 pages, 9 figures, accepted to MNRA
Employees Cognitive Measurement By Typing Time
Activity performed by administration staffs like typing work involves a delicate interaction between perceptual, cognitive and motoric processes. For completing this type of work requires a holistic comprehension about the job which involving coordination of speed and precision. Therefore, this research tries to study about cognitive performance measurement by employing typing time scaling. There were 60 participants involved in this research with three different backgrounds from employees, university students, and lecturers. They asked to type the provided draft then their time will be calculated by the researchers to measure how many mistakes that they have done while typing the document. This study found result that participant’s background gives a sound contribution in time record and typing error made by the participants. Three categories are found in time and typing errors by their own standard level based on time recording and typing results. However, this research needs plenty more follow ups such as more proportional selection of participants by using larger samples to have lots of variety in results. Keywords: cognitive performance, typing time, ergonomics, typing erro
Subthalamic Nucleus Deep Brain Stimulation in Parkinson's Disease: The Effect of Varying Stimulation Parameters
Subthalamic Nucleus Deep Brain Stimulation (STN DBS) is a well-established and effective treatment modality for selected patients with Parkinson's disease (PD). Since its advent, systematic exploration of the effect of stimulation parameters including the stimulation intensity, frequency, and pulse width have been carried out to establish optimal therapeutic ranges. This review examines published data on these stimulation parameters in terms of efficacy of treatment and adverse effects. Altering stimulation intensity is the mainstay of titration in DBS programming via alterations in voltage or current settings, and is characterised by a lower efficacy threshold and a higher side effect threshold which define the therapeutic window. In addition, much work has been done in exploring the effects of frequency modulation, which may help patients with gait freezing and other axial symptoms. However, there is a paucity of data on the use of ultra-short pulse width settings which are now possible with technological advances. We also discuss current evidence for the use of novel programming techniques including directional and adaptive stimulation, and highlight areas for future research
Crystal-Liquid Crystal Binary Phase Diagrams
We propose a new theoretical scheme for the binary phase diagrams of crystal-liquid crystal mixtures by a combination of a phase field model of solidification, the Flory-Huggins theory for liquid-liquid mixing and Maier-Saupe-McMillan (FH-MSM) model for nematic and smectic liquid crystal orderings. The phase field theory describes the crystal phase transition of anisotropic organic crystal and/or side chain liquid crystalline polymer crystals while the FH-MSM model explains isotropic, nematic and smectic-A phase transitions. Self-consistent calculations reveal several possible phase diagram topologies of the binary crystal-liquid crystal mixtures. The calculated phase diagrams were found to accord well to the reported experimental results. (c) 2006 American Institute of Physics
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