2,115 research outputs found
Semiflexible polymers in a random environment
We present using simple scaling arguments and one step replica symmetry
breaking a theory for the localization of semiflexible polymers in a quenched
random environment. In contrast to completely flexible polymers, localization
of semiflexible polymers depends not only on the details of the disorder but
also on the ease with which polymers can bend. The interplay of these two
effects can lead to the delocalization of a localized polymer with an increase
in either the disorder density or the stiffness. Our theory provides a general
criterion for the delocalization of polymers with varying degrees of
flexibility and allows us to propose a phase diagram for the highly folded
(localized) states of semiflexible polymers as a function of the disorder
strength and chain rigidity.Comment: 10 pages, 3 figures, Revtex
Chains in critical fluids and nanopores
The conformational behavior of a polymer in a critical binary solvent
confined in a porous medium is studied. The size of the polymer in bulk, which
is mainly governed by the correlation length of the solvent density
fluctuations, depends on the proximity to the critical point of the binary
mixture. We find that in contrast to the bulk behavior, the conformational
properties of the polymer in a porous medium depends strongly on the pore size.
The latter controls the correlation length of the solvent density fluctuations
and thus determines the polymer size.Comment: 6 page
Self-consistent variational theory for globules
A self-consistent variational theory for globules based on the uniform
expansion method is presented. This method, first introduced by Edwards and
Singh to estimate the size of a self-avoiding chain, is restricted to a good
solvent regime, where two-body repulsion leads to chain swelling. We extend the
variational method to a poor solvent regime where the balance between the
two-body attractive and the three-body repulsive interactions leads to
contraction of the chain to form a globule. By employing the Ginzburg
criterion, we recover the correct scaling for the -temperature. The
introduction of the three-body interaction term in the variational scheme
recovers the correct scaling for the two important length scales in the globule
- its overall size , and the thermal blob size . Since these two
length scales follow very different statistics - Gaussian on length scales
, and space filling on length scale - our approach extends the
validity of the uniform expansion method to non-uniform contraction rendering
it applicable to polymeric systems with attractive interactions. We present one
such application by studying the Rayleigh instability of polyelectrolyte
globules in poor solvents. At a critical fraction of charged monomers, ,
along the chain backbone, we observe a clear indication of a first-order
transition from a globular state at small , to a stretched state at large
; in the intermediate regime the bistable equilibrium between these two
states shows the existence of a pearl-necklace structure.Comment: 7 pages, 1 figur
Constrained dynamics of a polymer ring enclosing a constant area
The dynamics of a polymer ring enclosing a constant {\sl algebraic} area is
studied. The constraint of a constant area is found to couple the dynamics of
the two Cartesian components of the position vector of the polymer ring through
the Lagrange multiplier function which is time dependent. The time dependence
of the Lagrange multiplier is evaluated in a closed form both at short and long
times. At long times, the time dependence is weak, and is mainly governed by
the inverse of the first mode of the area. The presence of the constraint
changes the nature of the relaxation of the internal modes. The time
correlation of the position vectors of the ring is found to be dominated by the
first Rouse mode which does not relax even at very long times. The mean square
displacement of the radius vector is found to be diffusive, which is associated
with the rotational diffusion of the ring.Comment: 6 page
Water quality index for assessment of water quality of river ravi at Madhopur (India)
Water quality of River Ravi, a tributary of Indus River System was evaluated by Water Quality Index (WQI) technique. A water quality index provides a single number that expresses overall water quality at a certain location and time based on several water quality parameters. The objective of an index is to turn complex water quality data into information that is understandable and useable by the public. Eight most important parameters such as pH, total dissolved solids (TDS), total hardness, calcium(Ca), magnesium (Mg), total alkalinity, dissolved oxygen (DO) and electrical conductivity (EC) were taken for the calculation of WQI. The WQI values for the River Ravi ranged from 54.8 to 97.88. The values of WQI showed that the water was free of any impurities at the sampling site except for 2-3 months where its values were less than 70. Whenever there are human activities e.g., dam operations, water gets polluted to some extent, so the value of WQI decreases. It was found that the parameter which is required in least amount contributes a high statistical value to the index. It is concluded that WQI can be used as a tool in comparing the water quality of different sources. It gives the public a general idea of the possible problems with water in a particular region. The indices are among the most effective ways to communicate the information on water quality trends to the public or to the policy makers and water quality management.KEYWORDS: WQI, River Ravi, Madhopur, Indi
Scale structure, age and growth in the freshwater carp, Labeo calbasu (Pisces/Cyprinidae) from Harike wetland, India
Age structure and growth profile based on the scale studies of 468 specimens ranging from 17-62 cm total length of Labeo calbasu (Hamilton) from Harike wetland (30°13'N, 75°12'E), Punjab, India have been described, the present study showed better growth in terms of two important growth parameters namely index of species average size and population weight-growth intensity. Two distinct phases in its life history have been described that indicates the optimum exploitation of this species from this water body. Harvestable size is found to be fish of 34 cm total length. The detailed structural elaboration of scale (normal, regenerated, lateral line) has also been done using scanning electron microscopy (SEM)
Self-reported “communication technology” usage in patients attending a cardiology outpatient clinic in a remote regional hospital
Peer reviewedPublisher PD
Dissolution behaviour of aceclofenac-PVP coprecipitates
Aim: The objective of the present investigation was to study the effect of PVP on in vitro dissolution of aceclofenac from coprecipitates. Materials and Methods: Aceclofenac coprecipitates (CP) with different drug loadings were prepared and in vitro dissolution studies of pure drug, physical mixtures and coprecipitates were carried out. Results: Coprecipitates of aceclofenac with PVP showed considerable increase in the dissolution rate in comparison with physical mixture and pure drug in 0.1 N HCl, pH1.2 and phosphate buffer, pH, 7.4. Coprecipitates in 1:2 ratio showed maximum dissolution rate in comparison to other ratios. Amorphous nature of the drug in coprecipitates was confirmed by scanning electron microscopy and a decrease in enthalpy of drug melting in coprecipitates compared to the pure drug. FT- IR spectroscopy and differential scanning calorimetry studies indicated no interaction between aceclofenac and PVP in coprecipitates in solid state. Dissolution enhancement was attributed to decreased crystallinity of the drug and to the wetting, eutectic formation and solubilizing effect of the carrier from the coprecipitates of aceclofenac. Conclusion: dissolution of aceclofenac can be enhanced by the use of hydrophilic carriers like PVP
Mechanism of mesenchymal stem cells as a multitarget disease-modifying therapy for parkinson's disease.
Parkinson's disease (PD) is one of the most prevalent neurodegenerative disorders, affecting the basal nuclei, causing impairment of motor and cognitive functions. Loss of dopaminergic (DAergic) neurons or their degeneration and the aggregation of Lewy bodies is the hallmark of this disease. The medications used to treat PD relieve the symptoms and maintain quality of life, but currently, there is no cure. There is a need for the development of therapies that can cease or perhaps reverse neurodegeneration effectively. With the rapid advancements in cell replacement therapy techniques, medical professionals are trying to find a cure by which restoration of dopamine neurotransmitters can occur. Researchers have started focusing on cell-based therapies using mesenchymal stem cells (MSCs) due to their abundance in the body, the ability of proliferation, and immunomodulation. Here we review the MSC-based treatment in Parkinson's disease and the various mechanisms it repairs DAergic neurons in parkinsonian patients
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