The ring opening polymerization of ring strained cyclic ethers

The kinetics and mechanisms of the ring-opening polymerization of oxetane were studied using cationic and coordinated anionic catalysts. The cationic initiators used were BF30Et2!/ethanol, BF30Et2!/ethanediol and BF30Et2/propantriol. Kinetic determinations with the BF30Et2/diol system indicated that a 1: 1 BF3:0H ratio gave the maximum rate of polymerization and this ratio was employed to detenmne the overall rates of polymerization. An overall second-order dependence was obtained when the system involved ethanediol or propantriol as co-catalyst and a 3/2-order dependence with ethanol, in each case the monomer gave a first-order relationship. This suggested that two mechanisms accounted for the cationic polymerization. These mechanisms were investigated and further evidence for these was obtained from the study of the complex formation of BF30Et2 and the co-catalysts by 1H NMR. Molecular weight studies (using size-exclusion chromatography) indicated that the hydroxyl ion acted as a chain transfer reagent when the [OH] > [BF3]. A linear relationship was observed when the number average molecular weight was plotted against [oxetane] at constant [BF3:0H], and similarly a linear dependency was observed on the BF3:0H 1:1 adduct at constant oxetane concentration. Copolymerization of oxetane and THF was carried out using BF30Et2/ethanol system. The reactivity ratios were calculated as rOXT = 1.2 ± 0.30 and rTHF = 0.14 ± 0.03. These copolymers were random copolymers with no evidence of oligomer formation. The coordinated anionic catalyst, porphinato-aluminium chloride [(TPP)AICl], was used to produce a living polymerization of oxetane. An overall third-order kinetics was obtained, with a second-order with respect to the [(TPP)AICl] and a first-order with respect to the [oxetane] and a mechanism was postulated using these results. The stereochemistry of [(TPP)AlCl] catalyst was investigated using cyclohexene and cyclopentene oxide monomers, using extensive 1H NMR, 2-D COSY and decoupling NMR techniques it was concluded that [(TPP)AlCl] gave rise to stereoregular polymers

ACHIEVEMENTS IN HUMAN CAPITAL FORMATION IN SRI LANKA

Education, being one main way of human capital formation, plays a crucial role in socio-economic development. For a balanced regional development, similar to other resources, formation of human capital in all regions of a country is essential. The paper deals with how the human capital formation through formal education occurs at the regional level in Sri Lanka. The methodology, being quantitative, includes descriptive analysis and ranking of provinces through a composite index on human capital formation. The study completely depends on institutional and non-institutional secondary data sources. The results suggest that, among the provinces, the disparity in human capital formation through education is significant. The Western Province is ranked at the first place while the Eastern Province gets the last. North-Western Province and the Southern Province are also outstanding while the position of Uva and Central Provinces are not satisfactory. In addition, the study finds that there are gender-related disparities also in the formation of human capital at the regional level

Spaceborne Synthetic Aperture Radar Survey of Subsidence in Hampton Roads, Virginia (USA)

Over the past century, the Hampton Roads area of the Chesapeake Bay region has experienced one of the highest rates of relative sea level rise on the Atlantic coast of the United States. This rate of relative sea level rise results from a combination of land subsidence, which has long been known to be present in the region, and rising seas associated with global warming on long timescales and exacerbated by shifts in ocean dynamics on shorter timescales. An understanding of the current-day magnitude of each component is needed to create accurate projections of future relative sea level rise upon which to base planning efforts. The objective of this study is to estimate the land component of relative sea level rise using interferometric synthetic aperture radar (InSAR) analysis applied to ALOS-1 synthetic aperture radar data acquired during 2007–2011 to generate high-spatial resolution (20–30 m) estimates of vertical land motion. Although these results are limited by the uncertainty associated with the small set of available historical SAR data, they highlight both localized rates of high subsidence and a significant spatial variability in subsidence, emphasizing the need for further measurement, which could be done with Sentinel-1 and NASA’s upcoming NISAR mission

Women's Role in Household Food Security in Rural Sri Lanka

Food security is a major development issue which has been prioritised in domestic economic policies ofmany developing countries. Recently, there is an increasing trend of directing food security policies towardsempowering women, because, many studies have revealed that women play a significant role in reducingpoverty and food insecurity in their households. However, there is a dearth of studies that discusses thewomen's role in achieving household food security in the context of Sri Lanka, even though women areculturally assigned a huge responsibility in almost all the household tasks including household foodmanagement. Hence, this study attempted to analyze the women's role in household food security in SriLanka in the rural context. The primary data was gathered from a cross sectional sample survey inThirappane division in the Anuradhapura district, and the data was collected from 100 households whichwere selected based on simple random sampling method. To achieve the objectives, both descriptive andeconometric methods were used in the data analysis. The study found that women play a strong role inassuring household food security in all three dimensions of food security; they make a significantcontribution to farming and thereby household food availability, their contribution to income is crucial inhousehold food access especially in low income households, and their nutritional knowledge is alsoimportant inthe proper utilization of food in households. Furthermore, the study estimated a regressionmodel using ordinary least square (OLS) method and could identify that women's income, their nutritionalknowledge, and their use of indigenous food management knowledge as important determinants of householdfood security in rural households. Accordingly, the results suggested that the food security policies in thecountry should be aimed at empowering women's capacities through income and education to yield betteroutcomes.Kywords: Food security, Women’s role, Rural household

Toluene permeabilization differentially affects F- and P-type ATPase activities present in the plasma membrane of Streptococcus mutans

Streptococcus mutans membrane-bound P- and F-type ATPases are responsible for H+ extrusion from the cytoplasm thus keeping intracellular pH appropriate for cell metabolism. Toluene-permeabilized bacterial cells have long been used to study total membrane-bound ATPase activity, and to compare the properties of ATPase in situ with those in membrane-rich fractions. The aim of the present research was to determine if toluene permeabilization can significantly modify the activity of membrane-bound ATPase of both F-type and P-type. ATPase activity was assayed discontinuously by measuring phosphate release from ATP as substrate. Treatment of S. mutans membrane fractions with toluene reduced total ATPase activity by approximately 80% and did not allow differentiation between F- and P-type ATPase activities by use of the standard inhibitors vanadate (3 µM) and oligomycin (4 µg/mL). Transmission electron microscopy shows that, after S. mutans cells permeabilization with toluene, bacterial cell wall and plasma membrane are severely injured, causing cytoplasmic leakage. As a consequence, loss of cell viability and disruption of H+ extrusion were observed. These data suggest that treatment of S. mutans with toluene is an efficient method for cell disruption, but care should be taken in the interpretation of ATPase activity when toluene-permeabilized cells are used, because results may not reflect the real P- and F-type ATPase activities present in intact cell membranes. The mild conditions used for the preparation of membrane fractions may be more suitable to study specific ATPase activity in the presence of biological agents, since this method preserves ATPase selectivity for standard inhibitors.UNIUBECNPqCoordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES

Renewable energy powered membrane technology. 2. The effect of energy fluctuations on performance of a photovoltaic hybrid membrane system

This paper reports on the performance fluctuations during the operation of a batteryless hybrid ultrafiltration – nanofiltration / reverse osmosis (UF-NF/RO) membrane desalination system powered by photovoltaics treating brackish groundwater in outback Australia. The renewable energy powered membrane (RE-membrane) system is designed to supply clean drinking water to a remote community of about 50 inhabitants. The performance of the RE-membrane system over four different solar days is summarised using four different NF membranes (BW30, NF90, ESPA4, TFC-S), and examined in more detail for the BW30 membrane. On an Australian spring day, the system produced 1.1 m3 of permeate with an average conductivity of 0.28 mS.cm-1, recovering 28% of the brackish (8.29 mS.cm-1 conductivity) feedwater with an average specific energy consumption of 2.3 kWh.m-3. The RE-membrane system tolerated large fluctuations in solar irradiance (500 – 1200 W.m-2), resulting in only small increases in the permeate conductivity. When equipped with the NF90 (cloudy day) and ESPA4 (rainy day) membranes, the system was able to produce 1.36 m-3 and 0.85 m-3 of good quality permeate, respectively. The TFC-S membrane was not able to produce adequate water quality from the bore water tested. It is concluded that batteryless operation is a simple and robust way to operate such systems under conditions ranging from clear skies to medium cloud cover

Application of solar-powered desalination in a remote town in South Australia

Coober Pedy is a remote town in South Australia with abundant solar radiation and scarce and low quality water, where a reverse osmosis plant has been operating since 1967. This paper evaluates the feasibility of powering the plant with solar or photovoltaic (PV) panels whilst avoiding energy storage in batteries. Pilot tests were performed in October 2005 with a small scale PV-powered hybrid ultrafiltration-reverse osmosis (UF/RO) membrane filtration system. The performance of the system in Coober Pedy is presented over different operating conditions and two available brackish feed waters. The system has been shown to tolerate well the power variation during clear sky days due to direct use of PV panels, producing 764 L of water per solar day with average specific energy consumption of 3.2 kWh.m-3 when treating the groundwater with conductivity of 7.4 mS.cm-1. It has been concluded that a reverse osmosis plant utilising UF pre-treatment and powered by PV panels without battery storage is a promising alternative for Coober Pedy to overcome currently high energy costs for the existing RO plant

Non-equilibrium entangled steady state of two independent two-level systems

We determine and study the steady state of two independent two-level systems weakly coupled to a stationary non-equilibrium environment. Whereas this bipartite state is necessarily uncorrelated if the splitting energies of the two-level systems are different from each other, it can be entangled if they are equal. For identical two-level systems interacting with two bosonic heat baths at different temperatures, we discuss the influence of the baths temperatures and coupling parameters on their entanglement. Geometric properties, such as the baths dimensionalities and the distance between the two-level systems, are relevant. A regime is found where the steady state is a statistical mixture of the product ground state and of the entangled singlet state with respective weights 2/3 and 1/3

Search for the glueball candidates f0(1500) and fJ(1710) in gamma gamma collisions

Data taken with the ALEPH detector at LEP1 have been used to search for gamma gamma production of the glueball candidates f0(1500) and fJ(1710) via their decay to pi+pi-. No signal is observed and upper limits to the product of gamma gamma width and pi+pi- branching ratio of the f0(1500) and the fJ(1710) have been measured to be Gamma_(gamma gamma -> f0(1500)). BR(f0(1500)->pi+pi-) < 0.31 keV and Gamma_(gamma gamma -> fJ(1710)). BR(fJ(1710)->pi+pi-) < 0.55 keV at 95% confidence level.Comment: 10 pages, 3 figure