Banaras Hindu University

About: Banaras Hindu University is a education organization based out in Varanasi, Uttar Pradesh, India. It is known for research contribution in the topics: Population & Catalysis. The organization has 11858 authors who have published 23917 publications receiving 464677 citations. The organization is also known as: Kashi Hindu Vishvavidyalay & Benares Hindu University.

Phycology and heavy-metal pollution

Abstract: Summary 1. All heavy metals, including those that are essential micronutrients (e.g. copper, zinc, etc.), are toxic to algae at high concentrations. 2. One characteristic feature of heavy-metal toxicity is the poisoning and inactivation of enzyme systems. Many of the physiological and biochemical processes, viz., photosynthesis, respiration, protein synthesis and chlorophyll synthesis, etc., are severely affected at high metal concentrations. 3. Some algae inhabit waters chronically polluted with heavy-metal-laden wastes from mining and smelting operations; Nodularia sp., Oscillatoria sp., Cladophora sp., Hormidium sp., Fucus sp. and Laminaria sp., etc., occur in metal-rich waters. These algal forms are probably more capable of combating the toxic levels of heavy metals and this attribute is a result of physiological and/or genetic adaptations. The sensitivity or tolerance to heavy metals varies amongst different algae. The phenomena of multiple tolerance and co-tolerance may be exhibited by some algae. 4. Heavy-metal pollution causes reduction in species diversity leading to the dominance of a few tolerant algal forms. The primary productivity also decreases after metal supplementation. 5. The uptake and accumulation of heavy metals can be active (energy-dependent), passive (energy-independent), or both. 6. Heavy metals can be safely stored as intranuclear complexes by some algae. Notwithstanding this, some changes in the cell wall can enable the algae to tolerate heavy metals by checking the entry of the metals (exclusion mechanism). 7. The metal content of algae growing in a waterbody may yield valuable information for simulating heavy metal pollution: several species of Cladophora and Fucus have been extensively used for this purpose. 8. Several factors affect and determine toxicity of heavy metals to algae. At low pH, the availability of heavy metals to algae is greatly increased, as a consequence of which pronounced toxicity is evident. Hard waters decrease metal toxicity. Some ions, e.g., calcium, magnesium and phosphorus, can alleviate toxicity of metals. 9. The presence of other metals can influence toxicity of a heavy metal through simple additive effect or by synergistic and antagonistic interactions. Similarly, other pollutants can influence heavy-metal toxicity. 10. The toxicity of heavy metals depends upon their chemical speciation. Various ionic forms of a metal characterized by different valency states, may be differentially toxic to a test alga. 11. Amino acids, organic matter, humic acids, fulvic acid, EDTA, NTA, etc. can complex with heavy metals and render them unavailable. This may eventually lead to less toxicity. 12. Heavy-metal toxicity largely depends upon algal population density: the denser the population the more numerous the cellular sites available, leading to decreased toxicity.

Carbon footprint: current methods of estimation

Abstract: Increasing greenhouse gaseous concentration in the atmosphere is perturbing the environment to cause grievous global warming and associated consequences. Following the rule that only measurable is manageable, mensuration of greenhouse gas intensiveness of different products, bodies, and processes is going on worldwide, expressed as their carbon footprints. The methodologies for carbon footprint calculations are still evolving and it is emerging as an important tool for greenhouse gas management. The concept of carbon footprinting has permeated and is being commercialized in all the areas of life and economy, but there is little coherence in definitions and calculations of carbon footprints among the studies. There are disagreements in the selection of gases, and the order of emissions to be covered in footprint calculations. Standards of greenhouse gas accounting are the common resources used in footprint calculations, although there is no mandatory provision of footprint verification. Carbon footprinting is intended to be a tool to guide the relevant emission cuts and verifications, its standardization at international level are therefore necessary. Present review describes the prevailing carbon footprinting methods and raises the related issues.

Suppressed π0 Production at Large Transverse Momentum in Central Au + Au Collisions at √sNN = 200 GeV

Abstract: Transverse momentum spectra of neutral pions in the range 1 < p_T < 10 GeV/c have been measured at mid-rapidity by the PHENIX experiment at RHIC in Au+Au collisions at sqrt(s_NN) = 200 GeV. The pi^0 multiplicity in central reactions is significantly below the yields measured at the same sqrt(s_NN) in peripheral Au+Au and p+p reactions scaled by the number of nucleon-nucleon collisions. For the most central bin, the suppression factor is ~2.5 at p_T = 2 GeV/c and increases to ~4-5 at p_T ~= 4 GeV/c. At larger p_T, the suppression remains constant within errors. The deficit is already apparent in semi-peripheral reactions and increases smoothly with centrality.

Energy loss and flow of heavy quarks in Au+Au collisions at sNN=200GeV

Abstract: The PHENIX experiment at the BNL Relativistic Heavy Ion Collider (RHIC) has measured electrons with 0.3 < p(T) < 9 GeV/c at midrapidity (y < 0.35) from heavy-flavor (charm and bottom) decays in Au + Au collisions at root s(NN) = 200 GeV. The nuclear modification factor R-AA relative to p + p collisions shows a strong suppression in central Au + Au collisions, indicating substantial energy loss of heavy quarks in the medium produced at RHIC energies. A large azimuthal anisotropy v(2) with respect to the reaction plane is observed for 0.5 < p(T) < 5 GeV/c indicating substantial heavy-flavor elliptic flow. Both R-AA and v(2) show a p(T) dependence different from those of neutral pions. A comparison to transport models which simultaneously describe R-AA(p(T)) and v(2)(p(T)) suggests that the viscosity to entropy density ratio is close to the conjectured quantum lower bound, i.e., near a perfect fluid.

Development of biodiesel: Current scenario

Abstract: Fuels are inevitable for industrial development and growth of any country. The life span of fossil fuel resources has always been terrifying. Biodiesel, a renewable source of energy seems to be an ideal solution for global energy demands including India as well. The current review is addressed to various aspects of biodiesel production. Latest literature has been critically reviewed and consulted.