The degradation of gel-spun poly(beta-hydroxybutyrate) fibrous matrix

Poly(β-hydroxybutyrate), (PHB), is a biologically produced, biodegradable thennoplastic with commercial potential. In this work the qualitative and quantitative investigations of the structure and degradation of a previously unstudied, novel, fibrous form of PHB, were completed. This gel-spun PHB fibrous matrix, PHB(FM), which has a similar appearance to cotton wool, possesses a relatively complex structure which combines a large volume with a low mass and has potential for use as a wound scaffolding device. As a result of the intrinsic problems presented by this novel structure, a new experimental procedure was developed to analyze the degradation of the PHB to its monomer hydroxybutyric acid, (HBA). This procedure was used in an accelerated degradation model which accurately monitored the degradation of the undegraded and degraded fractions of a fibrous matrix and the degradation of its PHB component. The in vitro degradation mechanism was also monitored using phase contrast and scanning electron microscopy, differential scanning calorimetry, fibre diameter distributions and Fourier infra-red photoacoustic spectroscopy. The accelerated degradation model was used to predict the degradation of the samples in the physiological model and this provided a clearer picture as to the samples potential biodegradation as medical implantation devices. The degradation of the matrices was characterized by an initial penetration of the degradative medium and weakening of the fibre integrity due to cleavage of the ester linkages, this then led to the physical collapse of the fibres which increased the surface area to volume ratio of the sample and facilitated its degradation. Degradation in the later stages was reduced due to the experimental kinetics, compaction and degradation resistant material, most probably the highly crystalline regions of the PHB. The in vitro degradation of the PHB(FM) was influenced by blending with various polysaccharides, copolymerizing with poly(~-hydroxyvalerate), (PHV), and changes to the manufacturing process. The degradation was also detennined to be faster than that of conventional melt processed PHB based samples. It was concluded that the material factors such as processing, sample size and shape affected the degradation of PHB based samples with the major factor of sample surface area to volume ratio being of paramount importance in determining the degradation of a sample

Rosiglitazone Metabolism in Human Liver Microsomes Using a Substrate Depletion Method

Background: Elimination of rosiglitazone in humans is via hepatic metabolism. The existing studies suggest that CYP2C8 is the major enzyme responsible, with a minor contribution from CYP2C9; however, other studies suggest the involvement of additional cytochrome P450 enzymes and metabolic pathways. Thus a full picture of rosiglitazone metabolism is unclear. Objective: This study aimed to improve the current understanding of potential drug–drug interactions and implications for therapy by evaluating the kinetics of rosiglitazone metabolism and examining the impact of specific inhibitors on its metabolism using the substrate depletion method. Methods: In vitro oxidative metabolism of rosiglitazone in human liver microsomes obtained from five donors was determined over a 0.5–500 µM substrate range including the contribution of CYP2C8, CYP2C9, CYP3A4, CYP2E1, and CYP2D6. Results: The maximum reaction velocity was 1.64 ± 0.98 nmol·mg−1·min−1. The CYP2C8 (69 ± 20%), CYP2C9 (42 ± 10%), CYP3A4 (52 ± 23%), and CEP2E1 (41 ± 13%) inhibitors all significantly inhibited rosiglitazone metabolism. Conclusion: The results suggest that other cytochrome P450 enzymes, including CYP2C9, CYP3A4, and CEP2E1, in addition to CYP28, also play an important role in the metabolism of rosiglitazone. This example demonstrates that understanding the complete metabolism of a drug is important when evaluating the potential for drug–drug interactions and will assist to improve the current therapeutic strategies.</p

Differentially Addressable Cavities within Metal-Organic Cage-Cross-Linked Polymeric Hydrogels

Here we report a new class of hydrogels formed by polymers that are cross-linked through subcomponent self-assembled metal–organic cages. Selective encapsulation of guest molecules within the cages creates two distinct internal phases within the hydrogel, which allows for contrasting release profiles of related molecules depending on their aptitude for encapsulation within the cages. The hydrogels were fabricated into microparticles via a droplet-based microfluidic approach and proved responsive to a variety of stimuli, including acid and competing amine or aldehyde subcomponents, allowing for the triggered release of cargo

On the detectability of the CMSSM light Higgs boson at the Tevatron

We examine the prospects of detecting the light Higgs h^0 of the Constrained MSSM at the Tevatron. To this end we explore the CMSSM parameter space with \mu>0, using a Markov Chain Monte Carlo technique, and apply all relevant collider and cosmological constraints including their uncertainties, as well as those of the Standard Model parameters. Taking 50 GeV < m_{1/2}, m_0 < 4 TeV, |A_0| < 7 TeV and 2 < tan(beta) < 62 as flat priors and using the formalism of Bayesian statistics we find that the 68% posterior probability region for the h^0 mass lies between 115.4 GeV and 120.4 GeV. Otherwise, h^0 is very similar to the Standard Model Higgs boson. Nevertheless, we point out some enhancements in its couplings to bottom and tau pairs, ranging from a few per cent in most of the CMSSM parameter space, up to several per cent in the favored region of tan(beta)\sim 50 and the pseudoscalar Higgs mass of m_A\lsim 1 TeV. We also find that the other Higgs bosons are typically heavier, although not necessarily much heavier. For values of the h^0 mass within the 95% probability range as determined by our analysis, a 95% CL exclusion limit can be set with about 2/fb of integrated luminosity per experiment, or else with 4/fb (12/fb) a 3 sigma evidence (5 sigma discovery) will be guaranteed. We also emphasize that the alternative statistical measure of the mean quality-of-fit favors a somewhat lower Higgs mass range; this implies even more optimistic prospects for the CMSSM light Higgs search than the more conservative Bayesian approach. In conclusion, for the above CMSSM parameter ranges, especially m_0, either some evidence will be found at the Tevatron for the light Higgs boson or, at a high confidence level, the CMSSM will be ruled out.Comment: JHEP versio

Scattering of Polarized Protons from 6,7-Li at 200 MeV

This work was supported by the National Science Foundation Grant NSF PHY 81-14339 and by Indiana Universit

Bifurcations of self-similar solutions for reversing interfaces in the slow diffusion equation with strong absorption

Bifurcations of self-similar solutions for reversing interfaces are studied in the slow diffusion equation with strong absorption. The self-similar solutions bifurcate from the time-independent solutions for standing interfaces. We show that such bifurcations occur at particular points in parameter space (characterizing the exponents in the diffusion and absorption terms) where the confluent hypergeometric functions satisfying Kummer's differential equation truncate to finite polynomials. A two-scale asymptotic method is employed to obtain the local dependencies of the self-similar reversing interfaces near the bifurcation points. The asymptotic results are shown to be in excellent agreement with numerical approximations of the self-similar solutions

The Asymptotic D- to S-State Ratio for 3-He

This work was supported by the National Science Foundation Grant NSF PHY 81-14339 and by Indiana Universit

Analyzing Powers for Deuteron-Induced Reactions Leading to Continuum Final States

This work was supported by the National Science Foundation Grant NSF PHY 78-22774 A02 & A03 and by Indiana Universit

Constraints on Supersymmetric Flavour Models from b->s gamma

We consider the effects of departures from minimal flavour violations (MFV) in the context of CMSSM-like theories. Second and third generation off-diagonal elements in the Yukawa, sfermion, and trilinear mass matrices are taken to be non-zero at the GUT scale. These are run down together with MSSM parameters to the electroweak scale. We apply constraints from fermion masses and CKM matrix elements to limit the range of the new free parameters of the model. We determine the effect of the departure from MFV on the branching ratio of b->s gamma. We find that only when the expansion parameter in the down-squark sector is relatively large there is a noticeable effect, which tends to relax the lower limit from b->s gamma on the universal gaugino mass. We also find that the expansion parameter associated with the slepton sector needs to be smaller than the corresponding parameter in the down-squark sector in order to be compliant with the bound imposed by the branching ratio of tau-> mu gamma.Comment: Comments: 43 pages, 14 figures. Version accepted for publication: typos corrected, rewritten for better understanding and references adde

Reaction Mechanism Implications of Deuteron Rainbow Scattering

This work was supported by the National Science Foundation Grant NSF PHY 78-22774 A02 & A03 and by Indiana Universit