1,729 research outputs found
A REVIEW ON MICROSPONGE DRUG DELIVERY SYSTEM
The drug delivery technology landscape has become highly competitive and rapidly evolving. More and more developments in delivery systems are being integrated to optimize the efficacy and cost-effectiveness of the therapy. Peptides, proteins and DNA-based therapeutics cannot be effectively delivered by conventional means. A Microsponges delivery system is a highly cross-linked, porous, polymeric microsphere, polymeric system consisting of porous microspheres that can entrap and release them into the skin over a long period of time. This delivery system provides extended release with reduced irritation, better tolerance, improved thermal, physical and chemical stability. The main goal of any drug delivery system is to achieve desired concentration of the drug in blood or tissue, which is therapeutically effective and non-toxic for a prolonged period In the present study various methods for preparation of microsponges drug delivery system are studied. Various advantages are also given which shows the importance of this method for the delivery of drugs over the other drug delivery system.  More and more developments in delivery systems are being integrated to optimize the efficacy and cost-effectiveness of the therapy. Microsponge technology offers entrapment of ingredients and is believed to contribute towards reduced side effects, improved stability, increased elegance, and enhanced formulation flexibility. In addition, numerous studies have confirmed that microsponge systems are non-irritating, nonmutagenic, non-allergenic, and non-toxic. Microsponges delivery technology is being used currently in cosmetics, over-the-counter (OTC) skin care, sunscreens and prescription products. One of the best feature of microsponge is it is self-sterilizing. This review is focused on method of preparation, characterization and application of microsponge. Keywords: Microsponge, Control relaease, Target release, topical formulation, oral administratio
Tuning the stacking behaviour of a 2D covalent organic framework through non-covalent interactions
Two-dimensional covalent organic frameworks (COFs) are crystalline porous materials composed of organic building blocks that are connected via covalent bonds within their layers, but through non-covalent interactions between the layers. The exact stacking sequence of the layers is of paramount importance for the optoelectronic, catalytic and sorption properties of these polymeric materials. The weak interlayer interactions lead to a variety of stacking geometries in COFs, which are both hard to characterize and poorly understood due to the low levels of crystallinity. Therefore, detailed insights into the stacking geometry in COFs is still largely elusive. In this work we show that the geometric and electronic features of the COF building blocks can be used to guide the stacking behavior of two related 2D imine COFs (TBI-COF and TTI-COF), which either adopt an averaged "eclipsed'' structure with apparent zero-offset stacking or a unidirectionally slip-stacked structure, respectively. These structural features are confirmed by XRPD and TEM measurements. Based on theoretical calculations, we were able to pinpoint the cause of the uniform slip-stacking geometry and high crystallinity of TTI-COF to the inherent self-complementarity of the building blocks and the resulting donor-acceptor-type stacking of the imine bonds in adjacent layers, which can serve as a more general design principle for the synthesis of highly crystalline COFs
One plus two-body random matrix ensembles with parity: Density of states and parity ratios
One plus two-body embedded Gaussian orthogonal ensemble of random matrices
with parity [EGOE(1+2)-] generated by a random two-body interaction
(modeled by GOE in two particle spaces) in the presence of a mean-field, for
spinless identical fermion systems, is defined, generalizing the two-body
ensemble with parity analyzed by Papenbrock and Weidenm\"{u}ller [Phys. Rev. C
{\bf 78}, 054305 (2008)], in terms of two mixing parameters and a gap between
the positive and negative parity single particle (sp)
states. Numerical calculations are used to demonstrate, using realistic values
of the mixing parameters appropriate for some nuclei, that the EGOE(1+2)-
ensemble generates Gaussian form (with corrections) for fixed parity eigenvalue
densities (i.e. state densities). The random matrix model also generates many
features in parity ratios of state densities that are similar to those
predicted by a method based on the Fermi-gas model for nuclei. We have also
obtained, by applying the formulation due to Chang et al [Ann. Phys. (N.Y.)
{\bf 66}, 137 (1971)], a simple formula for the spectral variances defined over
fixed- spaces, where is the number of fermions in the +ve
parity sp states and is the number of fermions in the -ve parity sp
states. Similarly, using the binary correlation approximation, in the dilute
limit, we have derived expressions for the lowest two shape parameters. The
smoothed densities generated by the sum of fixed- Gaussians with
lowest two shape corrections describe the numerical results in many situations.
The model also generates preponderance of +ve parity ground states for small
values of the mixing parameters and this is a feature seen in nuclear shell
model results.Comment: 38 pages, 11 figures, 3 tables, enlarged and reorganized with
additional result
Physicality and Cooperative Design
CSCW researchers have increasingly come to realize that material work setting and its population of artefacts play a crucial part in coordination of distributed or co-located work. This paper uses the notion of physicality as a basis to understand cooperative work. Using examples from an ongoing fieldwork on cooperative design practices, it provides a conceptual understanding of physicality and shows that material settings and co-worker’s working practices play an important role in understanding physicality of cooperative design
Two-Level Atom in an Optical Parametric Oscillator: Spectra of Transmitted and Fluorescent Fields in the Weak Driving Field Limit
We consider the interaction of a two-level atom inside an optical parametric
oscillator. In the weak driving field limit, we essentially have an atom-cavity
system driven by the occasional pair of correlated photons, or weakly squeezed
light. We find that we may have holes, or dips, in the spectrum of the
fluorescent and transmitted light. This occurs even in the strong-coupling
limit when we find holes in the vacuum-Rabi doublet. Also, spectra with a
sub-natural linewidth may occur. These effects disappear for larger driving
fields, unlike the spectral narrowing obtained in resonance fluorescence in a
squeezed vacuum; here it is important that the squeezing parameter tends to
zero so that the system interacts with only one correlated pair of photons at a
time. We show that a previous explanation for spectral narrowing and spectral
holes for incoherent scattering is not applicable in the present case, and
propose a new explanation. We attribute these anomalous effects to quantum
interference in the two-photon scattering of the system.Comment: 10 pages, 17 figures, submitted to Phys Rev
Random matrix ensembles with random interactions: Results for EGUE(2)-SU(4)
We introduce in this paper embedded Gaussian unitary ensemble of random
matrices, for fermions in number of single particle orbits,
generated by random two-body interactions that are SU(4) scalar, called
EGUE(2)-SU(4). Here the SU(4) algebra corresponds to Wigner's supermultiplet
SU(4) symmetry in nuclei. Formulation based on Wigner-Racah algebra of the
embedding algebra allows for
analytical treatment of this ensemble and using this analytical formulas are
derived for the covariances in energy centroids and spectral variances. It is
found that these covariances increase in magnitude as we go from EGUE(2) to
EGUE(2)-\cs to EGUE(2)-SU(4) implying that symmetries may be responsible for
chaos in finite interacting quantum systems.Comment: 11 pages, 2 figures, some formulas in Table 1 corrected, Table 1
changed to Table 1 and 2, Fig. 2 modifie
Loss of superfluidity in the Bose-Einstein condensate in an optical lattice with cubic and quintic nonlinearity
In a one-dimensional shallow optical lattice, in the presence of both cubic
and quintic nonlinearity, a superfluid density wave is identified in a
Bose-Einstein condensate. Interestingly, it ceases to exist when only one of
these interactions is operative. We predict the loss of superfluidity through a
classical dynamical phase transition, where modulational instability leads to
the loss of phase coherence. In a certain parameter domain, the competition
between lattice potential and the interactions is shown to give rise to a
stripe phase, where atoms are confined in finite domains. In a pure two-body
case, apart from the known superfluid and insulating phases, a density wave
insulating phase is found to exist, possessing two frequency modulations
commensurate with the lattice potential.Comment: 5 pages, 1 figur
Evidence for directional selection at a novel major histocompatibility class I marker in wild common frogs (Rana temporaria) exposed to a viral pathogen (Ranavirus).
(c) 2009 Teacher et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Whilst the Major Histocompatibility Complex (MHC) is well characterized in the anuran Xenopus, this region has not previously been studied in another popular model species, the common frog (Rana temporaria). Nor, to date, have there been any studies of MHC in wild amphibian host-pathogen systems. We characterise an MHC class I locus in the common frog, and present primers to amplify both the whole region, and specifically the antigen binding region. As no more than two expressed haplotypes were found in over 400 clones from 66 individuals, it is likely that there is a single class I locus in this species. This finding is consistent with the single class I locus in Xenopus, but contrasts with the multiple loci identified in axolotls, providing evidence that the diversification of MHC class I into multiple loci likely occurred after the Caudata/Anura divergence (approximately 350 million years ago) but before the Ranidae/Pipidae divergence (approximately 230 mya). We use this locus to compare wild populations of common frogs that have been infected with a viral pathogen (Ranavirus) with those that have no history of infection. We demonstrate that certain MHC supertypes are associated with infection status (even after accounting for shared ancestry), and that the diseased populations have more similar supertype frequencies (lower F(ST)) than the uninfected. These patterns were not seen in a suite of putatively neutral microsatellite loci. We interpret this pattern at the MHC locus to indicate that the disease has imposed selection for particular haplotypes, and hence that common frogs may be adapting to the presence of Ranavirus, which currently kills tens of thousands of amphibians in the UK each year
Driving the atom by atomic fluorescence: analytic results for the power and noise spectra
We study how the spectral properties of resonance fluorescence propagate
through a two-atom system. Within the weak-driving-field approximation we find
that, as we go from one atom to the next, the power spectrum exhibits both
sub-natural linewidth narrowing and large asymmetries while the spectrum of
squeezing narrows but remains otherwise unchanged. Analytical results for the
observed spectral features of the fluorescence are provided and their origin is
thoroughly discussed.Comment: 13 pages, 5 figures; to be published in Phys. Rev. A Changed title
and conten
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