Gum acacia based hydrogels and their composite for waste water treatment: A review.

The non-toxic nature of natural polysaccharides and their biodegradability makes them the first choice of researchers. Various natural polysaccharides are available nowadays, like cellulose, starch, chitosan, gum acacia, guar gum etc. Among these, gum acacia is a common natural polysaccharide presently used in research and technology. It is highly biodegradable, pH stable and shows appropriate water solubility. It is used in research to synthesize hydrogels and hydrogel nanocomposites for various applications because of its antimicrobial, anti-inflammatory and excellent absorption properties. The major fields of applications include the stabilization of metal nanoparticles in the form of nanocomposites, wound dressing materials, delivery systems of various drugs and pharmaceutical agents, bioengineering, tissue engineering, purification of water, synthesis of antibacterial and antifungal composites for agricultural improvements, and many others. Due to the increasing problem of water pollution, the major focus is on research helping to reduce this problem. Gum acacia-based hydrogel and hydrogel composites were synthesized and tested for pollutant removal efficiency from wastewater by different researchers. The research on gum acacia hydrogel and their hydrogel composite applications for water purification, as well as their synthesis processes and properties, are summarized in this review article.

Variations in the concentration, source activity, and atmospheric processing of PM2.5-associated water-soluble ionic species over Jammu, India.

Concentrations, sources, and atmospheric processing of water-soluble ionic species associated with PM2.5 collected from 2015 to 2017 were studied in Jammu, an urban location in the North-Western Himalayan Region (NWHR). Being ecologically sensitive and sparsely studied for dynamics in PM2.5 and associated WSIS, the present study is important for developing robust air pollution abatement strategies for the air-shed of NWHR. Twenty-four hourly PM2.5 samples were collected on weekly basis at a receptor site and analyzed for WSIS using ion chromatography system. On annual basis, total sum of WSIS (ΣWSIS) contributed about 28.5% of PM2.5, where the contribution of sulfate-nitrate-ammonium, a proxy for secondary inorganic aerosols (SIA), was found to be 18.7% of PM2.5. The ΣWSIS and PM2.5 concentration showed a seasonal cycle with the maximum concentration during winters and the minimum in summers. Mass fraction of ΣWSIS in PM2.5 showed an anti-phase seasonal pattern indicating more source activity during summers. Season-wise, dominant WSIS constituting PM2.5 were NO3-, SO42-, NH4+, and K+ during winters; whereas summer was marked with dominant contributions from SO42-, NH4+, Ca2+, and K+. Seasonal variability exhibited among SIA constituents underscored the crucial role of air temperature and relative humidity regime. It was observed that nss-K+ + NH4+ were sufficient to neutralize most of the acidic species arising from precursor gases (NOx and SOx). Using principal component analysis, five major sources and processes, viz. (a) biomass burning activities, (b) secondary inorganic aerosol formation, (c) input from re-suspended dust, (d) transported dust, and (e) fertilizer residue, were identified for the emissions of PM2.5-associated WSIS over Jammu. In future studies, impacts of dry and/or wet deposition of aerosol-associated WSIS on the crop productivity in the region should be studied.

Particulate bound polycyclic aromatic hydrocarbons over Dhauladhar region of the north-western Himalayas.

A systematic yearlong study was carried out in Dhauladhar region of the North-Western Himalayas to investigate dynamics in the composition and concentration of particulate bound polycyclic aromatic hydrocarbons (PAHs) and their source(s) activity. PM10 samples were collected for 24 h, once every week during January 2015-January 2016, at an urban mid-altitude site (Dharamshala) and a rural low-altitude site (Pohara). PAHs were identified and quantified using high performance liquid chromatography coupled with UV-detector. Seasonal average concentration of total PAHs followed a pattern: Summer > Winter > Autumn > Spring in the region. Seasonal average values of molecular diagnostic ratios indicated significant contribution from non-traffic (biomass burning and coal combustion) sources also during winter and spring season, whereas, traffic emissions (gasoline and diesel) were the dominant source at both the locations throughout the year in the region. The Principal Component Analysis deciphered a) emissions from gasoline driven vehicles b) diesel engine exhaust emissions c) biomass/wood burning source d) coal combustion and e) waste incineration and burning of oil/tar as major sources of PAHs in the region. Annual mean values of total Benzo(a)Pyrene Equivalent were much higher than 1 ng.m-3 over both the locations indicating higher lung cancer risk to the people living in this part of the Himalayas.

Aerosol-associated n-alkanes over Dhauladhar region of North-Western Himalaya: seasonal variations in sources and processes.

Particulate n-alkanes are major constituents of organic aerosols (OA). Being primary in origin, chemically stable and thus long-lived, n-alkanes retains source signatures and along with diagnostic parameters have extensively been used to identify source(s) of OA. Systematic, yearlong study was carried out in the Dhauladhar region of North-Western Himalaya (NWH) to investigate dynamics in the composition and concentration of aerosol-associated n-alkanes. PM10 samples were collected for 24 h, once every week, at an urban mid-altitude location (Dharamshala) and a rural low-altitude site (Pohara). Particulate bound n-alkanes were identified and quantified using thermal desorption gas chromatography mass spectrometry (TD-GCMS). Annual mean concentrations of total n-alkanes (TNA) were 211 ± 99 ng m-3 and 223 ± 83 ng m-3, while mass fractions of TNA in PM10 were 4410 ± 1759 ppm and 3622 ± 1243 ppm at Dharamshala and Pohara, respectively. At both sites, a slight dominance of odd carbon-numbered n-alkanes was noticed. The TNA concentration and associated diagnostic parameters indicated unique source profiles at rural and urban locations. Significant seasonal variations were attributed to the contrasting land-use settings and meteorological variations. Influence of petrogenic contributions at urban location and predominance of biogenic contributions at rural location were observed in spring and autumn seasons. Preliminary insights on sources of organic aerosols are presented here. The diagnostic parameters allowed apportionment of biogenic and petrogenic sources. Biogenic emissions from agricultural practices viz. harvesting and threshing were predominant in the rural settings, while tourism-led anthropogenic contributions significantly add to petrogenic contributions in urban environment of the NWH region.

Water-soluble ionic species in atmospheric aerosols over Dhauladhar region of North-Western Himalaya.

Water-soluble ionic species (WSIS) have been used as potential markers for different source(s) and underlining process(es) emitting and transforming atmospheric aerosols. PM10 aerosol sampling was performed once in a week for a complete one year, at a mid-altitude urban and a low-altitude rural location simultaneously in the Dhauladhar region of the North-Western Himalaya. Aerosol samples were analysed for major WSIS (anions: F-, Cl-, NO3-, PO43- and SO42-; cations: Na+, NH4+, K+, Ca2+ and Mg2+) using the ion chromatography system. Results showed that WSIS constitutes around 15% of PM10 aerosol load in the region. SO42- contributes the maximum (~ 50%) followed by NO3- (~ 12.5%) and NH4+ (~ 12.5%) to the total concentration of WSIS analysed. During all the seasons, average concentrations of PM10 and associated WSIS were observed to be higher over the rural location in comparison to the urban location. The total concentration of WSIS was found to be maximum during the winter season. Principal component analysis performed on the WSIS concentration dataset revealed four major sources of PM10-associated WSIS viz. re-suspension of soil or local sediments; conversion of pollutant gases (SOx, NOx and NH3) to particles, i.e., secondary inorganic aerosol formation; evaporative loss or re-suspension of inorganic (NPK) fertilizers' residues and biomass/crop-residue burning emissions in the Dhauladhar region of the North-Western Himalaya.

Wintertime carbonaceous aerosols over Dhauladhar region of North-Western Himalayas.

Carbonaceous aerosols play an important role in affecting human health, radiative forcing, hydrological cycle, and climate change. As our current understanding about the carbonaceous aerosols, the source(s) and process(es) associated with them in the ecologically sensitive North-Western Himalayas are limited; this systematic study was planned to understand inherent dynamics in the mass concentration and source contribution of carbonaceous aerosols in the Dhauladhar region. During four winter months (January 2015-April 2015), 24-h PM10 samples were collected every week simultaneously at the rural site of Pohara (32.19° N, 76.20° E; 750 m amsl) and the urban location of Dharamshala (32.20° N, 76.32° E; 1350 m amsl). These samples were analyzed by using thermal/optical carbon analyzer for different carbon forms. Organic carbon (OC) dominated over elemental carbon (EC) and was found to be 59.3 and 64.1% in total carbon (TC) at Pohara and Dharamshala, respectively. The respective mass concentrations of OC and EC were higher at Pohara (6.8 ± 2.3 and 4.8 ± 2.0 µg.m-3) in comparison to that observed in Dharamshala (5.0 ± 3.1 and 2.5 ± 0.6 µg.m-3). The OC/EC ratio at Pohara (1.51 ± 0.41) indicates the dominance of fossil fuel combustion (coal and vehicular exhaust), while at Dharamshala, an OC/EC of 2.01 ± 1.07 signified additional contribution from secondary organic carbon (SOC). Diagnostic ratios (OC/EC and char-EC/soot-EC) suggested dominance of emissions from fossil fuel combustion sources over biomass burning sources in the region. Estimated non-sea salt (nss)K+/OC and nssK+/EC ratios indicated heterogeneity within the biomass burning sources over low and high altitude locations. A strong correlation between nssK+ and SOC over a high altitude urban location further suggested possible conversion of gaseous precursors to carbonaceous particles during coniferous wood burning.

A systematic analysis of cell cycle regulators in yeast reveals that most factors act independently of cell size to control initiation of division.

Upstream events that trigger initiation of cell division, at a point called START in yeast, determine the overall rates of cell proliferation. The identity and complete sequence of those events remain unknown. Previous studies relied mainly on cell size changes to identify systematically genes required for the timely completion of START. Here, we evaluated panels of non-essential single gene deletion strains for altered DNA content by flow cytometry. This analysis revealed that most gene deletions that altered cell cycle progression did not change cell size. Our results highlight a strong requirement for ribosomal biogenesis and protein synthesis for initiation of cell division. We also identified numerous factors that have not been previously implicated in cell cycle control mechanisms. We found that CBS, which catalyzes the synthesis of cystathionine from serine and homocysteine, advances START in two ways: by promoting cell growth, which requires CBS's catalytic activity, and by a separate function, which does not require CBS's catalytic activity. CBS defects cause disease in humans, and in animals CBS has vital, non-catalytic, unknown roles. Hence, our results may be relevant for human biology. Taken together, these findings significantly expand the range of factors required for the timely initiation of cell division. The systematic identification of non-essential regulators of cell division we describe will be a valuable resource for analysis of cell cycle progression in yeast and other organisms.