Biogenic silver nanoparticles: Understanding the antimicrobial mechanism using Confocal Raman Microscopy

The antimicrobial properties of silver nanoparticles (AgNPs) have made them ubiquitous in a number of real-world industrial applications; however, the antimicrobial mode of action of biogenic AgNPs is not entirely understood. The use of Raman spectroscopy can provide molecular fingerprint information on various chemical and biochemical components in complex systems like microbial cultures, without the need for any complex sample pre-treatment. Consequently, the antimicrobial mechanism of AgNPs can be inferred through morphological and compositional changes of microbial cells that are monitored via changes in Raman band profiles. Here we show the synthesis of biogenic AgNPs using the extracellular cell-free filtrates of Penicillium expansum. The antimicrobial activity of the Penicillium expansum synthesized silver nanoparticles (hereafter PeNPs) was evaluated and the interactions between the nanoparticles and Escherichia coli were studied using Transmission Electron Microscopy (TEM) and Environmental Scanning Electron Microscopy (ESEM), showing the attachment of PeNPs to the surface of the bacteria and rupture of the bacterial cell membrane. Importantly, we show how Confocal Raman Microscopy can be used as an innovative approach to study the antimicrobial mechanisms, the results of which confirm that the PeNPs induce damage to bacterial and fungal cells, resulting in critical changes to polysaccharides, lipids, proteins and nucleic acids

Prediction of human intestinal absorption using micellar liquid chromatography with an aminopropyl stationary phase

The extent of human intestinal absorption (HIA) for a drug is considered to be an important pharmacokinetic parameter which must be determined for orally administered drugs. Traditional experimental methods relied upon animal testing and are renowned for being time consuming, expensive as well as being ethically unfavourable. As a result, developing alternative methods to evaluate a drug's pharmacokinetics is crucial. Micellar liquid chromatography (MLC) is considered to be one of these methods that can replace the use of animals in prediction of HIA. In this study, the combination of an aminopropyl column with the biosurfactant sodium deoxycholate (NaDC) bile salt were used in the experimental determination of micelle-water partition coefficients (log Pmw) for a group of compounds. Multiple linear regression (MLR) was then used for the prediction of HIA using the experimentally determined log Pmw along with other molecular descriptors leading to the construction of a model equation of R2= 85 % and a prediction power represented by R2Pred. =72 %. The use of MLC with an aminopropyl column in combination with NaDC was found to be a good method for the prediction of human intestinal absorption, providing data for a far wider range of compounds compared with previous studies

Decay of long-lived massive closed superstring states: Exact results

We find a one-parameter family of long-lived physical string states in type II superstring theory. We compute the decay rate by an exact numerical evaluation of the imaginary part of the one-loop propagator. Remarkably, the lifetime rapidly increases with the mass. We find a power-law dependence of the form $T = const. g^{-2} Mass^\alpha$, where the value of $\alpha$ depends on the parameter characterizing the state. For the most stable state in this family, one has $\alpha ~= 5$. The dominant decay channel of these massive string states is by emission of soft massless particles. The quantum states can be viewed semiclassically as closed strings which cannot break during the classical evolution.Comment: Latex, 5 figures, 35 pages (= 23 pages + appendices). Minor correction

Living with rheumatic heart disease at the intersection of biomedical and Aboriginal worldviews

Rheumatic heart disease (RHD) significantly impacts the lives of First Nations Australians. Failure to eliminate RHD is in part attributed to healthcare strategies that fail to understand the lived experience of RHD. To rectify this, a PhD study was undertaken in the Northern Territory (NT) of Australia, combining Aboriginal ways of knowing, being and doing with interviews (24 participants from clinical and community settings) and participant observation to privilege Aboriginal voices, including the interpretations and experiences of Aboriginal co-researchers (described in the adjunct article). During analysis, Aboriginal co-researchers identified three interwoven themes: maintaining good feelings; creating clear understanding (from good information); and choosing a good djalkiri (path). These affirm a worldview that prioritises relationships, positive emotions and the wellbeing of family/community. The findings demonstrate the inter-connectedness of knowledge, choice and behaviour that become increasingly complex in stressful and traumatic health, socioeconomic, political, historical and cultural contexts. Not previously heard in the RHD domain, the findings reveal fundamental differences between Aboriginal and biomedical worldviews contributing to the failure of current approaches to communicating health messages. Mitigating this, Aboriginal co-researchers provided targeted recommendations for culturally responsive health encounters, including: communicating to create positive emotions; building trust; and providing family and community data and health messages (rather than individualistic)

A measurement of parity-violating gamma-ray asymmetries in polarized cold neutron capture on 35Cl, 113Cd, and 139La

An apparatus for measuring parity-violating asymmetries in gamma-ray emission following polarized cold neutron capture was constructed as a 1/10th scale test of the design for the forthcoming n+p->d+gamma experiment at LANSCE. The elements of the polarized neutron beam, including a polarized 3He neutron spin filter and a radio frequency neutron spin rotator, are described. Using CsI(Tl) detectors and photodiode current mode readout, measurements were made of asymmetries in gamma-ray emission following neutron capture on 35Cl, 113Cd, and 139La targets. Upper limits on the parity-allowed asymmetry $s_n \cdot (k_{\gamma} \times k_n)$ were set at the level of 7 x 10^-6 for all three targets. Parity-violating asymmetries $s_n \cdot k_{\gamma}$ were observed in 35Cl, A_gamma = (-29.1 +- 6.7) x 10^-6, and 139La, A_gamma = (-15.5 +- 7.1) x 10^-6, values consistent with previous measurements.Comment: 19 pages, 4 figures, submitted to Nucl. Instr. and Meth.

Electromagnetic form factors of light vector mesons

The electromagnetic form factors G_E(q^2), G_M(q^2), and G_Q(q^2), charge radii, magnetic and quadrupole moments, and decay widths of the light vector mesons rho^+, K^{*+} and K^{*0} are calculated in a Lorentz-covariant, Dyson-Schwinger equation based model using algebraic quark propagators that incorporate confinement, asymptotic freedom, and dynamical chiral symmetry breaking, and vector meson Bethe-Salpeter amplitudes closely related to the pseudoscalar amplitudes obtained from phenomenological studies of pi and K mesons. Calculated static properties of vector mesons include the charge radii and magnetic moments: r_{rho+} = 0.61 fm, r_{K*+} = 0.54 fm, and r^2_{K*0} = -0.048 fm^2; mu_{rho+} = 2.69, mu_{K*+} = 2.37, and mu_{K*0} = -0.40. The calculated static limits of the rho-meson form factors are similar to those obtained from light-front quantum mechanical calculations, but begin to differ above q^2 = 1 GeV^2 due to the dynamical evolution of the quark propagators in our approach.Comment: 8 pages of RevTeX, 5 eps figure

Thermal history of the string universe

Thermal history of the string universe based on the Brandenberger and Vafa's scenario is examined. The analysis thereby provides a theoretical foundation of the string universe scenario. Especially the picture of the initial oscillating phase is shown to be natural from the thermodynamical point of view. A new tool is employed to evaluate the multi state density of the string gas. This analysis points out that the well-known functional form of the multi state density is not applicable for the important region $T \leq T_H$, and derives a correct form of it.Comment: 39 pages, no figures, use revtex.sty, aps.sty, aps10.sty & preprint.st

K -> pi pi and a light scalar meson

We explore the Delta-I= 1/2 rule and epsilon'/epsilon in K -> pi pi transitions using a Dyson-Schwinger equation model. Exploiting the feature that QCD penguin operators direct K^0_S transitions through 0^{++} intermediate states, we find an explanation of the enhancement of I=0 K -> pi pi transitions in the contribution of a light sigma-meson. This mechanism also affects epsilon'/epsilon.Comment: 7 pages, REVTE

Universality and Critical Phenomena in String Defect Statistics

The idea of biased symmetries to avoid or alleviate cosmological problems caused by the appearance of some topological defects is familiar in the context of domain walls, where the defect statistics lend themselves naturally to a percolation theory description, and for cosmic strings, where the proportion of infinite strings can be varied or disappear entirely depending on the bias in the symmetry. In this paper we measure the initial configurational statistics of a network of string defects after a symmetry-breaking phase transition with initial bias in the symmetry of the ground state. Using an improved algorithm, which is useful for a more general class of self-interacting walks on an infinite lattice, we extend the work in \cite{MHKS} to better statistics and a different ground state manifold, namely $\R P^2$, and explore various different discretisations. Within the statistical errors, the critical exponents of the Hagedorn transition are found to be quite possibly universal and identical to the critical exponents of three-dimensional bond or site percolation. This improves our understanding of the percolation theory description of defect statistics after a biased phase transition, as proposed in \cite{MHKS}. We also find strong evidence that the existence of infinite strings in the Vachaspati Vilenkin algorithm is generic to all (string-bearing) vacuum manifolds, all discretisations thereof, and all regular three-dimensional lattices.Comment: 62 pages, plain LaTeX, macro mathsymb.sty included, figures included. also available on http://starsky.pcss.maps.susx.ac.uk/groups/pt/preprints/96/96011.ps.g