Effect of Network Structure on Free Volume and Gas Transport Properties of Thiol-Ene and Epoxy-Amine Networks

Network parameters such as cross-link density or intermolecular interactions were used as effective parameters to control polymer chain packing or free volume and thereby control the mass transport properties of networks. A series of polyethylene glycol (PEG) based thiol-ene elastomeric networks having a broad range of molecular weight between cross-links, Mc, (inverse of cross-link density) was prepared. The specific volume of the networks was studied as a function of temperature and pressure using high pressure dilatometry, and the obtained PVT data was fit using Simha-Somcynsky equation of state (S-S eos) analysis. Fractional free volume, quantified through S-S eos analysis, changed linearly as a function of cross-link density of the networks proving that the system obeyed Fox and Loshaek model. Average free volume hole size, h\u3e, of the networks was directly probed using positron annihilation lifetime spectroscopy (PALS). h\u3e of the networks also changed linearly as a function of cross-link density. Typically, in traditional elastomers, changing cross-link density also causes simultaneous changes in chemical nature or polarity of the system, therefore those systems deviate from Fox and Loshaek model. Internal pressure Pi of the networks, calculated from PVT data, showed similar values for all networks, and the same was the case for storage permittivity values obtained from dielectric spectroscopy analysis. This proved that the chemical nature of the networks was unaffected and cross-link density was the only parameter controlling the free volume of the networks. Gas diffusivity of the networks obeyed Cohen Turnbull model, and thus the experimental gas diffusivity trends were modeled as a function of molecular weight between cross-links of the networks. The effect of intermolecular (repulsive) interactions on free volume and gas transport was studied in a series of perfluorinated thiol-ene elastomers. Perfluorinated thiol-ene elastomers were prepared via 2-step synthesis. In the first step, a four-functional thiol was converted into a three functional thiol containing a perfluorinated dangling moiety via Thio Michael addition reaction with a perfluorinated acrylate. The modified thiol monomer was then reacted with triene to obtain perfluorinated thiol-ene networks. Fluorine content was varied by changing the length of perfluorinated moiety used in Thio Michael addition and this enabled the synthesis of a series of perfluorinated networks containing perfluorinated dangling moieties of different lengths. Fast reaction kinetics of thiol-ene chemistry prevented the phase separation of perfluorinated moieties and locked-in the thermodynamically frustrated perfluorinated moieties within the thiol-ene scaffold. The repulsive interactions between highly non-polar perfluorinated moieties and polar thiol-ene backbone created huge free volume pockets in the network. For the biggest perfluorinated dangling moiety used in this study, h\u3e increased by four times in comparison to an unmodified network. The gas transport properties showed a significant improvement as a function of the length of the dangling moiety. But gas diffusivity of the networks did not obey Cohen Turnbull model. The deviation was explained by the static nature of free volume pockets around perfluorinated moieties, and percolation of free volume pockets as the sizes of free volume cavities increased. The 2-step synthetic approach was taken a step further to prepare a series of hybrid thiol-ene elastomers containing varying concentrations of polar PEG moieties and non-polar perfluorinated moieties. The effect of PEG and perfluorinated concentrations (or attractive and repulsive interactions) on chain packing was studied. PEG moieties improved CO2 gas permeability and selectivity because of the Lewis acid-base type interactions between PEG and CO2. In the final chapter, the effect of moisture sorption on free volume, oxygen, and water vapor transport was studied on five different epoxy-amine networks having Tgs in the range between -11 °C to 227 °C. Water sorption did not show any effect on h\u3e of elastomeric networks. Whereas, glassy networks showed a V-shaped trend when h\u3e was plotted as a function of relative humidity or water content. The decrease in h\u3e was due to water molecules filling free volume holes. Increasing water concentration in the networks beyond 75% relative humidity (RH) resulted in swelling of the networks and thereby h\u3e increase. Effect of water sorption on oxygen permeability of the glassy networks also showed a similar V-shaped trend, but the mechanism was more complex as water sorption affected both oxygen diffusivity and solubility. Water vapor permeability of the glassy networks was unaffected until 75% RH. Beyond 75% RH, free volume increase due to swelling resulted in water vapor permeability increase

Zero Crossing Edge Detection and Contour Tracing for Segmentation of Cervical Cell Nucleus .

To automate the process of screening of normal and abnormal cervical cells, there is a need for automatic segmentation of the nucleus of these cells. This paper presents an algorithm using the Laplacian of Gaussian operator and contour tracer to segment the nucleus from the background. The algorithm has been tested on different kinds of images of cervical cells

K_1 of products of Drinfeld modular curves and special values of L-functions

Beilinson obtained a formula relating the special value of the L-function of H^2 of a product of modular curves to the regulator of an element of a motivic cohomology group - thus providing evidence for his general conjectures on special values of L-functions. In this paper we prove a similar formula for the L-function of the product of two Drinfeld modular curves providing evidence for an analogous conjecture in the case of function fields.Comment: 34 pages, 2 figures. To appear in Compositio Mathematica. This is a completely revised and improved version of a earlier preprint with C.Consani (arXiv:math/0303130

Violence against female sex workers in Karnataka state, south India: impact on health, and reductions in violence following an intervention program.

ABSTRACT: BACKGROUND: Violence against female sex workers (FSWs) can impede HIV prevention efforts and contravenes their human rights. We developed a multi-layered violence intervention targeting policy makers, secondary stakeholders (police, lawyers, media), and primary stakeholders (FSWs), as part of wider HIV prevention programming involving >60,000 FSWs in Karnataka state. This study examined if violence against FSWs is associated with reduced condom use and increased STI/HIV risk, and if addressing violence against FSWs within a large-scale HIV prevention program can reduce levels of violence against them. METHODS: FSWs were randomly selected to participate in polling booth surveys (PBS 2006-2008; short behavioural questionnaires administered anonymously) and integrated behavioural-biological assessments (IBBAs 2005-2009; administered face-to-face). RESULTS: 3,852 FSWs participated in the IBBAs and 7,638 FSWs participated in the PBS. Overall, 11.0% of FSWs in the IBBAs and 26.4% of FSWs in the PBS reported being beaten or raped in the past year. FSWs who reported violence in the past year were significantly less likely to report condom use with clients (zero unprotected sex acts in previous month, 55.4% vs. 75.5%, adjusted odds ratio (AOR) 0.4, 95% confidence interval (CI) 0.3 to 0.5, p < 0.001); to have accessed the HIV intervention program (ever contacted by peer educator, 84.9% vs. 89.6%, AOR 0.7, 95% CI 0.4 to 1.0, p = 0.04); or to have ever visited the project sexual health clinic (59.0% vs. 68.1%, AOR 0.7, 95% CI 0.6 to 1.0, p = 0.02); and were significantly more likely to be infected with gonorrhea (5.0% vs. 2.6%, AOR 1.9, 95% CI 1.1 to 3.3, p = 0.02). By the follow-up surveys, significant reductions were seen in the proportions of FSWs reporting violence compared with baseline (IBBA 13.0% vs. 9.0%, AOR 0.7, 95% CI 0.5 to 0.9 p = 0.01; PBS 27.3% vs. 18.9%, crude OR 0.5, 95% CI 0.4 to 0.5, p < 0.001). CONCLUSIONS: This program demonstrates that a structural approach to addressing violence can be effectively delivered at scale. Addressing violence against FSWs is important for the success of HIV prevention programs, and for protecting their basic human rights

Experimental Generation of SNP Haplotype Signatures in Patients with Sickle Cell Anaemia

Sickle cell anemia is caused by a single type of mutation, a homozygous A→T substitution in the ß globin gene. Clinical severity is diverse, partially due to additional, disease-modifying genetic factors. We are studying one such modifier locus, HMIP (HBS1L-MYB intergenic polymorphism, chromosome 6q23.3). Working with a genetically admixed patient population, we have encountered the necessity to generate haplotype signatures of genetic markers to label genomic fragments with distinct genealogical origin at this locus. With the goal to generate haplotype signatures from patients experimentally, we have investigated the suitability of an existing nanofluidic assay platform to perform phase alignment with single-nucleotide polymorphism alleles.Patient DNA samples were loaded onto Fluidigm Digital Arrays and individual DNA molecules were assayed with allele-specific probes for SNP markers. Here we present data showing the utility of the nanofluidic approach, yielding haplotype data identical to those obtained with a family-based method. We then determined haplotype composition in a group of patients with sickle cell disease, including in those where a mathematical inference approach gave ambiguous or misleading results. Experimental phasing of genotypes across 3.8 kb for rs9399137, rs9402685, and rs11759553 created unequivocal haplotype signatures for each of the patients. In 68 patients, we found 8 copies of a haplotype signature ('C-C-T'), which is known to be prevalent in Europeans but to be absent in West African populations. We have confirmed the identity of our phased allele pairs by single-molecule sequencing and have demonstrated, in principle, that three-allele phasing (using three colors) is a potential extension to this method.Phased haplotypes yield more information than the individual marker genotypes. Procedures such as the one described here would therefore benefit genetic mapping and functional studies as well as diagnostic procedures where the identity or parental origin of short genetic fragments is of importance

Current Perspective of Prevention and Management of Diabetic Foot

Diabetes-related foot infections and ulcers are frequent complications of the condition. These problems are also frequent, cause significant discomfort, frequently come back, and lead to morbidity and mortality, placing a huge financial burden on the patient and society. To start and direct treatment, it is crucial to comprehend the role of important contributing factors such as diabetic neuropathy, peripheral arterial disease, and immune system dysfunction. Beginning with a comprehensive physical examination and detailed history, diabetic foot disease is managed. A thorough medical examination should pay particular attention to any indication of diabetic foot ulcers or infection, as well as the symptoms of peripheral vascular disease and diabetic neuropathy. Analgesics and antibiotics should be used for pain management and infection control respectively. A multidisciplinary strategy focusing on patient education should be incorporated into prevention measures

Investigations on microbiome of the used clinical device revealed many uncultivable newer bacterial species associated with persistent chronic infections

Introduction. Chronic persistent device-related infections (DRIs) often give culture-negative results in a microbiological investigation. In such cases, investigations on the device metagenome might have a diagnostic value. Materials and Methods. The 16SrRNA gene sequence analysis and next-generation sequencing (NGS) of clinical metagenome were performed to detect bacterial diversity on invasive medical devices possibly involved in culture-negative DRIs. Device samples were first subjected to microbiological investigation followed by metagenome analysis. Environmental DNA (e-DNA) isolated from device samples was subjected to 16SrRNA gene amplification followed by Sanger sequencing (n=14). In addition, NGS of the device metagenome was also performed (n=12). Five samples were only common in both methods. Results. Microbial growth was observed in only nine cases; among these, five cases were considered significant growth, and in the remaining four cases, growth was considered either insignificant or contaminated. Culture and sequencing analysis yielded identical results only in six cases. In culture-negative cases, Sanger sequencing of 16SrRNA gene and NGS of 16SrDNA microbiome was able to identify the presence of rarely described human pathogens, namely Streptococcus infantis, Gemella haemolysans, Meiothermus silvanus, Schlegelella aquatica, Rothia mucilaginosa, Serratia nematodiphila, and Enterobacter asburiae, along with some known common nosocomial pathogens. Bacterial species such as M. silvanus and S. nematodiphila that are never reported in human infection were also identified. Conclusions. Results of a small number of diverse samples of this pilot study might lead to a path to study a large number of device samples that may validate the diversity witnessed. The study shows that a culture free, a holistic metagenomic approach using NGS could help identify the pathogens in culture-negative chronic DRIs