A building-up process in open-framework metal carboxylates that involves a progressive increase in dimensionality

Extensive research work has been carried out in the last few years on the synthesis and characterization of several families of open-framework materials, including aluminosilicates,[1] phosphates,[2] and carboxylates.[3] These studies have shown the occurrence of a variety of three dimensional (3D) architectures containing channels and other features.

Novel polymeric flame retardant plasticizers for poly(vinyl chloride)

Polyphosphate esters have been used as polymeric flame retardant plasticizers in poly(vinyl chloride); thermal and flammability studies were carried out to evaluate their efficiencies as fire retardants. A comparison is also made on the fire retardancy of the conventional simple phosphates with that of the polyphosphates as novel fire retardant plasticizers for PVC.

Synthesis of A1PO4, LaPO4 and KTiOPO4 by flash combustion

Fine particle AlPO4, LaPO4 and KTiOPO4 have been prepared by the flash combustion of aqueous solutions containing metal nitrate, ammonium hydrogen phosphate, ammonium nitrate or ammonium perchlorate and carbohydrazide or tetraformal trisazine. When rapidly heated at 400 °C, the solution containing the redox mixtures ignites to undergo self-propagating, gas-producing, exothermic reactions. Formation of crystalline phosphates was confirmed by powder X-ray diffraction patterns and IR spectra. The metal phosphates formed are fine and have 20�78 m2 g?1 surface area.

Soft-chemical routes to synthesis of solid oxide materials

We describe three different families of metal oxides, viz., (i) protonated layered perovskites, (ii) framework phosphates of NASICON and KTiOPO4 (KTP) structures and (iii) layered and three-dimensional oxides in the H-V-W-O system, synthesized by 'soft-chemical' routes involving respectively ion-exchange, redox deinteracalation and acid-leaching from appropriate parent oxides. Oxides of the first family, HyA2B3O10(A = La/Ca; B = Ti/Nb), exhibit variable Bronsted acidity and intercalation behaviour that depend on the interlayer structure. V2(PO4)3 prepared by oxidative deintercalation from Na3V2(PO4)3 is a new host material exhibiting reductive insertion of lithium/hydrogen, while K0.5Nb0.5 M0.5OPO4(M = Ti, V) are novel KTP-like materials exhibiting second harmonic generation of 1064 nm radiation. HxVxW1-xO3 for x = 0.125 and 0.33 possessing alpha-MoO3 and hexagonal WO3 structures, prepared by acid-leaching of LiVWO6, represent functionalized oxide materials exhibiting redox and acid-base intercalation reactivity.

Synthesis of layered MoOPO4 center dot 2H(2)O and investigation of its intercalation chemistry

We describe in this paper the synthesis and characterization of a new layered phosphate, MoOPO4 . 2H(2)O (I), and its intercalation chemistry. The phosphate I, crystallizing in a tetragonal structure (a = 6.375(7), c = 7.80(1) Angstrom, and Z = 2) similar to that of VOPO4 . 2H(2)O, has been synthesized by the reduction of MoO2(HPO4). H2O (II) using ethylene glycol in an CH3CN medium at similar to 60 degrees C. Interestingly, I could be readily oxidized back to II using Br-2 in CH3CN at room temperature. Considering the close structural relationship existing between I and II, it is likely that the reduction and oxidation of the phosphates proceed by a topotactic mechanism. I is a novel layered host intercalating a variety of organic bases such as n-alkylamines, pyridine, and aniline, mainly through an acid-base interaction. Unlike VOPO4 . 2H(2)O, I does not exhibit reductive intercalation reactivity.

New lithium-ion conductors based on the NASICON structure

Lithium-ion conduction in mixed-metal phosphates, (LiMMIII)-M-V(PO,), [M-V = Nb, Ta; M-III = Al, Cr, Fe], possessing the rhombohedral (R (3) over bar c) NASICON structure has been investigated. Among the phosphates investigated, LiTaAl(PO4)(3) exhibits the highest conductivity, sigma approximate to 1.0 x 10(-2) S cm(-1) at 350 degrees C (E-a = 0.47 eV), comparable to the conductivity of LiTi2(PO4)(3). Unlike LiTi2(PO4)(3) which contains lithium-reducible Ti-IV, LiTaAl(PO4)(3) contains stable Ta-V and Al-III oxidation states and hence deserves further attention towards tailoring new lithium-ion conductors for application as electrolytes in solid state lithium batteries.

Biphasic composite of Tricalcium phosphate reinforced with Hydroxyapatite Whiskers

Biphasic calcium phosphates have received considerable attention due to their optimum dissolution rate in the human body after implantation. These materials are composed of hydroxyapatite (HA) and resorbable tricalcium phosphate (TCP). In the present investigation, HA whiskers are reinforced into TCP to enhance the mechanical properties of this biphasic composite. Various amounts (30-50 wt%) HA whiskers are reinforced in TCP matrix. Microstructural characterization has been carried out using field-emission scanning electron microscope. Mechanical properties have been investigated by microindentation in a universal testing machine (UTM). As TCP is resorbable, it will dissolve in body fluid and there is a strong possibility for the faceted HA whiskers to interact with functional groups present in the body fluid surroundings.

Ecological Assessment of Lentic Water Bodies of Bangalore

The restoration, conservation and management of water resources require a thorough understanding of what constitutes a healthy ecosystem. Monitoring and assessment provides the basic information on the condition of our waterbodies. The present work details the study carried out at two waterbodies, namely, the Chamarajasagar reservoir and the Madiwala Lake. The waterbodies were selected on the basis of their current use and locations. Chamarajasagar reservoir serves the purpose of supplying drinking water to Bangalore city and is located on the outskirts of the city surrounded by agricultural and forest land. On the other hand, Madiwala lake is situated in the heart of Bangalore city receiving an influx of pollutants from domestic and industrial sewage. Comparative assessment of the surface water quality of both were carried out by instituting the various physico–chemical and biological parameters. The physico-chemical analyses included temperature, transparency, pH, electrical conductivity, dissolved oxygen, alkalinity, total hardness, calcium hardness, magnesium hardness, nitrates, phosphates, sodium, potassium and COD measurements of the given waterbody. The analysis was done based on the standard methods prescribed (or recommended) by (APHA) and NEERI. The biological parameter included phytoplankton analysis. The detailed investigations of the parameters, which are well within the tolerance limits in Chamarajasagar reservoir, indicate that it is fairly unpolluted, except for the pH values, which indicate greater alkalinity. This may be attributed to the natural causes and the agricultural runoff from the catchment. On the contrary, the limnology of Madiwala lake is greatly influenced by the inflow of sewage that contributes significantly to the dissolved solids of the lake water, total hardness, alkalinity and a low DO level. Although, the two study areas differ in age, physiography, chemistry and type of inflows, they still maintain a phytoplankton distribution overwhelmingly dominated by Cyanophyceae members,specifically Microcystis aeruginosa. These blue green algae apparently enter the waterbodies from soil, which are known to harbour a rich diversity of blue green flora with several species common to limnoplankton, a feature reported to be unique to the south Indian lakes.Chamarajasagar water samples revealed five classes of phytoplankton, of which Cyanophyceae (92.15 percent) that dominated other algal forms comprised of one single species of Microcystis aeruginosa. The next major class of algae was Chlorophyceae (3.752 percent) followed by Dinophyceae (3.51 percent), Bacillariophyceae (0.47 percent) and a sparsely available and unidentified class (0.12 percent).Madiwala Lake phytoplankton, in addition to Cyanophyceae (26.20 percent), revealed a high density of Chlorophyceae members (73.44 percent) dominated by Scenedesmus sp.,Pediastrum sp., and Euglena sp.,which are considered to be indicators of organic pollution. The domestic and industrial sewage, which finds its way into the lake, is a factor causing organic pollution. As compared to the other classes, Euglenophyceae and Bacillariophyceae members were the lowest in number. Thus, the analysis of various parameters indicates that Chamarajasagar reservoir is relatively unpolluted except for the high percentage of Microcystis aeruginosa, and a slightly alkaline nature of water. Madiwala lake samples revealed eutrophication and high levels of pollution, which is clarified by the physico–chemical analysis, whose values are way above the tolerance limits. Also, the phytoplankton analysis in Madiwala lake reveals the dominance of Chlorophyceae members, which indicate organic pollution (sewage being the causative factor).

Spatial Variation of Physico-Chemical and hydrological Parameters with land-use in Venkatapura Catchment,Karnataka

Social, economic and political development of a region is dependent on the health and quantity of the natural resources. Integrated approaches in the management of natural resources would ensure sustainability, which demands inventorying, mapping and monitoring of resources considering all components of an ecosystem. The monitoring of hydrological and catchment landscape of river resources have a vital role in the conservation and management of aquatic resources. This paper presents a case study Venkatapura river basin in Uttara Kannada district of Karnataka State, India based on stream hydrology and landuse analyses. The results revealed variations in dissolved oxygen and free carbon dioxide according to the flow nature of the water, and increased amount of phosphates and coliform contamination in streams closer to anthropogenic activities.

Evaluation of the Quality of Drinking Water in Kerala State, India

The quality of tap water from water supplies from 14 districts of Kerala state, India was studied. Parameters like pH, water temperature, total dissolved solids, salinity, nitrates, chloride, hardness, magnesium, calcium, sodium, potassium, fluoride, sulphate, phosphates, and coliform bacteria were enumerated. The results showed that all water samples were contaminated by coliform bacteria. About 20% of the tap water samples from Alappuzha and 15% samples from Palakkad district are above desirable limits prescribed by Bureau of Indian Standards. The contamination of the source water (due to lack of community hygiene) and insufficient treatment are the major cause for the coliform contamination in the state. Water samples from Alappuzha and Palakkad have high ionic and fluoride content which could be attributed to the geology of the region. Water supplied for drinking in rural areas are relatively free of any contamination than the water supplied in urban area by municipalities, which may be attributed higher chances of contamination in urban area due to mismanagement of solid and liquid wastes. The study highlights the need for regular bacteriological enumeration along with water quality in addition to setting up decentralised region specific improved treatment system.

Ecological and Socio Economic Assesment of Varthur Wetlnd, Bengaluru (India)

Wetlands are the most productive ecosystems, recognized globally for its vital role in sustaining a wide array of biodiversity and provide goods and services. However despite their important role in maintaining the ecology and economy, wetlands in India are endangered by inattention and lack of appreciation for their role. Increased anthropogenic activities such as intense agriculture practices, indiscriminate disposal of industrial effluents and sewage wastes have altered the physical, chemical as well as biological integrity of the ecosystem. This has resulted in the ecological degradation, which is evident from the current ecosystem valuation of Varthur wetland. Global valuation of coastal wetland ecosystem shows a total of 14,785/ha US$ annual economic value. An earlier study of relatively pristine wetland in Bangalore shows the value of Rs. 10,435/ha/day while the polluted wetland shows the value of Rs.20/ha/day. In contrast to this, Varthur, a sewage fed wetland has a value of Rs.118.9/ha/day. The pollutants and subsequent contamination of the wetland has telling effects such as disappearance of native species, dominance of invasive exotic species (such as African catfish), in addition to profuse breeding of disease vectors and pathogens. Water quality analysis revealed of high phosphates (4.22-5.76 ppm) level in addition to the enhanced BOD (119-140 ppm) and decreased DO (0-1.06 ppm). The amplified decline of ecosystem goods and services with degradation of water quality necessitates the implementation of sustainable management strategies to recover the lost wetland benefits.

Lipid composition in microalgal community under laboratory and outdoor conditions

Microalgae are the most sought after sources for biofuel production due to their capacity to utilize carbon and synthesize it into high density liquid. Current energy crisis have put microalgae under scanner for economical production of biodiesel. Modifications like physiological stress and genetic variation is done to increase the lipid yield of the microalgae. A study was conducted using a microalgal consortium for a period of 15 days to evaluate the feasibility of algal biomass from laboratory as well as outdoor culture conditions. Native algal strains were isolated from a tropical freshwater lake. Preliminary growth studies indicated the relationship between the nitrates and phosphates to the community structure through the days. The lipid profile done using Gas chromatography – Mass spectrometry, revealed the profile of the algal community. Resource competition led to isolation of algae, aided in the lipid profile of a single alga. However, further studies on the application of the mixed population are required to make this consortium approach economically viable for producing algae biofuels.

Ecological and socio-economic assessment of Varthur wetland, Bengaluru (India)

Wetlands are the most productive ecosystems, recognized globally for its vital role in sustaining a wide array of biodiversity and provide goods and services. However despite their important role in maintaining the ecology and economy, wetlands in India are endangered by inattention and lack of appreciation for their role. Increased anthropogenic activities such as intense agriculture practices, indiscriminate disposal of industrial effluents and sewage wastes have altered the physical, chemical as well as biological integrity of the ecosystem. This has resulted in the ecological degradation, which is evident from the current ecosystem valuation of Varthur wetland. Global valuation of coastal wetland ecosystem shows a total of 14,785/ha US$ annual economic value. An earlier study of relatively pristine wetland in Bangalore shows the value of Rs. 10,435/ha/day while the polluted wetland shows the value of Rs.20/ha/day. In contrast to this, Varthur, a sewage fed wetland has a value of Rs.118.9/ha/day. The pollutants and subsequent contamination of the wetland has telling effects such as disappearance of native species, dominance of invasive exotic species (such as African catfish), in addition to profuse breeding of disease vectors and pathogens. Water quality analysis revealed of high phosphates (4.22-5.76 ppm) level in addition to the enhanced BOD (119-140 ppm) and decreased DO (0-1.06 ppm). The amplified decline of ecosystem goods and services with degradation of water quality necessitates the implementation of sustainable management strategies to recover the lost wetland benefits.

Algal biofuel: bountiful lipid from Chlorococcum sp proliferating in municipal wastewater

Algae biofuel have emerged as viable renewable energy sources and are the potential alternatives to fossil-based fuels in recent times. Algae have the potential to generate significant quantities of commercially viable biofuel apart from treating wastewater. Three algal species, viz. Chlorococcum sp., Microcystis sp. and Phormidium sp. proliferating in wastewater ponds were isolated and cultured in the laboratory myxotrophically under similar wastewater conditions. Chlorococcum sp. attained a mean biomass productivity of 0.09 g. I(-1)d(-1) with the maximum `biomass density of 1.33 g I-1 and comparatively higher lipid content of 30.55% (w/w) on the ninth day of the culture experiment. Under similar conditions Microcystis sp. and Phormidium sp. attained mean biomass productivities of 0.058 and 0.063 g I-1 d(-1) with a total lipid content of 8.88% and 18.66% respectively. Biochemical composition (carbohydrates, proteins, lipids and phosphates) variations and lipid accumulation studies were performed by comparison of the ratios of carbohydrate to protein; lipid to protein (L/P) and lipid to phosphates using attenuated total reflectance-Fourier transform infrared spectroscopy which showed higher L/P ratio during the stationary phase of algal growth. Composition analysis of fatty acid methyl ester has been performed using gas chromatography and mass spectrometry. Chlorococcum sp. with higher productivity and faster growth rate has higher lipid content with about 67% of saturated fatty acid dominated by palmitate (36.3%) followed by an unsaturate as linoleate (14%) and has proved to be an economical and viable feedstock for biofuel production compared to the other wastewater-grown species.

Structures of substrate- and nucleotide-bound propionate kinase from Salmonella typhimurium: substrate specificity and phosphate-transfer mechanism

Kinases are ubiquitous enzymes that are pivotal to many biochemical processes. There are contrasting views on the phosphoryl-transfer mechanism in propionate kinase, an enzyme that reversibly transfers a phosphoryl group from propionyl phosphate to ADP in the final step of non-oxidative catabolism of L-threonine to propionate. Here, X-ray crystal structures of propionate- and nucleotide-bound Salmonella typhimurium propionate kinase are reported at 1.8-2.0 angstrom resolution. Although the mode of nucleotide binding is comparable to those of other members of the ASKHA superfamily, propionate is bound at a distinct site deeper in the hydrophobic pocket defining the active site. The propionate carboxyl is at a distance of approximate to 5 angstrom from the -phosphate of the nucleotide, supporting a direct in-line transfer mechanism. The phosphoryl-transfer reaction is likely to occur via an associative S(N)2-like transition state that involves a pentagonal bipyramidal structure with the axial positions occupied by the nucleophile of the substrate and the O atom between the - and the -phosphates, respectively. The proximity of the strictly conserved His175 and Arg236 to the carboxyl group of the propionate and the -phosphate of ATP suggests their involvement in catalysis. Moreover, ligand binding does not induce global domain movement as reported in some other members of the ASKHA superfamily. Instead, residues Arg86, Asp143 and Pro116-Leu117-His118 that define the active-site pocket move towards the substrate and expel water molecules from the active site. The role of Ala88, previously proposed to be the residue determining substrate specificity, was examined by determining the crystal structures of the propionate-bound Ala88 mutants A88V and A88G. Kinetic analysis and structural data are consistent with a significant role of Ala88 in substrate-specificity determination. The active-site pocket-defining residues Arg86, Asp143 and the Pro116-Leu117-His118 segment are also likely to contribute to substrate specificity.