The effects of surfactants on adhesion,spreading, and retention of herbicide droplet on the surface of the leaves and seeds

Droplet adhesion, spreading, and retention on leaf and seed surfaces are studied in the presence of surfactants for successful formulation of a herbicide whereby efficient coverage, less wastage, and environment protection are achieved. Cationic, anionic, and nonionic surfactants, e.g., HTAB, SDBS, and tergitol, were added to water and the static contact angle of water droplet was measured on cauliflower, cabbage, spinach leaves, French bean, wheat, and Bengal gram seeds. Droplet adhesion, spreading, and retention were analysed in terms of static contact angle and physical properties of the system. The presence of a small quantity (0.1 wt.%) of tergitol in water increased the adhesion, spreading, and retention of droplet on all leaf and seed surfaces tested. Tergitol, a nonionic surfactant, is likely to be adsorbed more than the ionic surfactants HTAB and SDBS at the water/leaf (or seed)/air interface since plant leaves and seeds are nonionic in nature. The addition of 0.1% wt. of tergitol to a common herbicide, derosal, increases the adhesion, spreading, and retention of derosal on leaf and seed surfaces, consequently, efficient coverage and minimum wastage are attained.     

Subgrid-Scale Modeling of Reacting Scalar Fluxes in Large-Eddy Simulations of Atmospheric Boundary Layers

In large-eddy simulations of atmospheric boundary layer turbulence, the lumped coefficient in the eddy-diffusion subgrid-scale (SGS) model is known to depend on scale for the case of inert scalars. This scale dependence is predominant near the surface. In this paper, a scale-dependent dynamic SGS model for the turbulent transport of reacting scalars is implemented in large-eddy simulations of a neutral boundary layer. Since the model coefficient is computed dynamically from the dynamics of the resolved scales, the simulations are free from any parameter tuning. A set of chemical cases representative of various turbulent reacting flow regimes is examined. The reactants are involved in a first-order reaction and are injected in the atmospheric boundary layer with a constant and uniform surface flux. Emphasis is placed on studying the combined effects of resolution and chemical regime on the performance of the SGS model. Simulations with the scale-dependent dynamic model yield the expected trends of the coefficients as function of resolution, position in the flow and chemical regime, leading to resolution-independent turbulent reactant fluxes.     

Mercury and selenium levels in lemon sharks (Negaprion brevirostris) in relation to a harmful red tide event

Tissue levels of mercury (Hg; total, organic) and selenium (Se) were assessed in juvenile lemon sharks (Negaprion brevirostris) from Florida nearshore waters collected during a harmful algal bloom (HAB, brevetoxin) event and compared with sharks not exposed to HABs. In all sharks studied, total Hg levels in the muscle were generally present in a molar excess over Se (which may protect against Hg toxicity) and mean muscle Hg levels (0.34  $\upmu $ g/g) exceed safe human consumption guidelines. While there was generally no difference in tissue Hg and Se levels following exposure of sharks to HABs, hepatic Hg levels were significantly lower (56% reduction) in the HAB-exposed sharks compared to controls. As Hg and HABs are globally increasing in scope and magnitude, further work is warranted to assess their interactions and biotic impacts within aquatic ecosystems, especially for a species such as the lemon shark that is classified as a near-threatened species by the International Union for the Conservation of Nature.     

Variation of cholinergic biomarkers in brain regions and blood components of captive mink

Studies are increasingly using cholinergic parameters as biomarkers of early neurotoxicity, but few have characterized this system in ecologically relevant model organisms. In the present study, key neurochemicals in the cholinergic pathway were measured and analyzed from discrete parts of brain and blood from captive mink (Mustela vison). Similar to other mammals, the regional distribution of cholinergic parameters in the brain could be ranked from highest to lowest as: basal ganglia > occipital cortex > brain stem > cerebellum (F _3,192?=?172.1, p?<?0.001). Higher variation in cholinergic parameters was found in the cerebellum (coefficient of variation = 34.9%), and the least variation was measured in the brain stem (19.7%). Variation was also assessed by calculating the difference between the lowest and highest measures among individual animals: choline acetyltransferase (1.6× fold difference), cholinesterase (2.0×), muscarinic receptor levels (2.4×), acetylcholine (3.7×), nicotinic receptor levels (3.9×), and choline transporter (5.0×). In blood samples, activity and inter-individual variation of cholinesterase was highest in whole blood and lowest in plasma and serum. By using captive mink of a common genetic source, age, gender, and rearing conditions, these data help establish normal levels, ranges, and variations of cholinergic biomarkers among brain regions, blood components, and individual animals. Such information may better enable the utility of cholinergic biomarkers in environmental assessments.     

Assessing the impacts of partial mass depletion in DNAPL source zones I. Analytical modeling of source strength functions and plume response

Analytical solutions are developed for approximating the time-dependent contaminant discharge from DNAPL source zones undergoing dissolution and other decay processes. The source functions assume a power relationship between source mass and chemical discharge and can consider partial DNAPL source remediation (depletion) at any time after the initial DNAPL release. The source functions are used as a time-dependent boundary condition in an idealized chemical transport model to develop leading order approximations of the plume response to DNAPL source removal. The results suggest that partial DNAPL remediation does not tend to have a dramatic impact on the maximum extent of the plume if very low concentration values are used to define the plume boundaries. However, the solutions show that partial DNAPL removal from the source zone is likely to lead to large reductions in plume concentrations and mass, and it reduces the longevity of the plume. When the mass discharge from the source zone is linearly related to the DNAPL mass, it is shown that partial DNAPL depletion leads to linearly proportional reductions in the plume mass and concentrations.     

Economic incentives drive the conversion of agriculture to aquaculture in the Indian Sundarbans: Livelihood and environmental implications of different aquaculture types

Expansion of aquaculture in the Sundarbans Biosphere Reserve (SBR) is irreversibly replacing agricultural land and the drivers of this change are disputed. Based on in-depth interviews with 67 aquaculture farmers, this paper characterizes major aquaculture types in the SBR, their impacts, and identifies drivers of conversion from agricultural land. Aquaculture types included traditional, improved-traditional, modified-extensive, and semi-intensive systems. Extensive capture of wild shrimp larvae is environmentally harmful but constitutes an important livelihood. Semi-intensive aquaculture of exotic shrimp (Litopenaeus vannamei) has much higher unit-area profitability than other types but involves greater financial risk. Profitability is the main driver for the transition from agriculture, but environmental factors such as lowered crop yields and cyclone impacts also contributed. Many conversions from agriculture to aquaculture are illegal according to the stakeholders. Existing legislation, if enforced, could halt the loss of agriculture, while the promotion of improved-traditional aquaculture could reduce the demand for wild seed.     

Diplomacy for science: strategies to promote international collaboration

Technology innovation is an increasingly globalized exercise with dramatic consequences for scientific and diplomatic goals alike, and requires enhanced participation and integration of scientists and science-minded diplomats within diplomatic missions to advance shared policy goals. This more general problem is addressed in the present article by focusing on recent collaborations between U.S. and German scientists, including several of the coauthors.     

Environmental radioactivity and thermoluminescence: A review

A close link exists between environmental radioactivity and thermoluminescence (TL) and this connection can be gainfully employed in (i) environmental radiation surveillance, (ii) radioactive prospecting and (iii) dating. The science of thermoluminescence dosimetry (TLD) is very well established for use in routine radiation monitoring. With the increased public awareness of health effects due to radioactivity releases from nuclear operations. TLDs have become indispensible ‘watchdogs’ in environmental surveillance; in high natural background areas such as the monazite regions, TLDs have yielded invaluable dosimetric data. Over large areas where the cosmic background can be assumed constant, the TLD-recorded radiation profiles can reflected the terrestrial gamma radioactivity distribution pattern and even seasonal variations in the radiation levels above ground may be delineated. A variety of natural materials like minerals, rocks, soils, sands, sediments, fossils, etc., as well as ancient artefacts like potteries and ceramic wares, yield TL even without any irradiation in the laboratory: the natural radioactivity in these materials, together with the radiation incident on them from the environment, causes a TL build-up during antiquity. It is possible to measure this natural TL and relate it to the natural radioactivity of the sample and hence to its age. In contrast, observations of a kind of anticorrelation between TL and a sample's radioactivity have also been made in recent times and the effect is mostly ascribable to alpha-radioactivity-induced damage effects.Typical results from recent investigations of the various aspects mentioned above are presented in this review, with particular emphasis on applications in India.     

<Emphasis Type="SmallCaps">l</Emphasis>-5-hydroxytryptophan resets the circadian locomotor activity rhythm of the nocturnal Indian pygmy field mouse, <Emphasis Type="Italic">Mus terricolor</Emphasis>

We report that l-5-hydroxytryptophan (5-HTP), a serotonin precursor, resets the overt circadian rhythm in the Indian pygmy field mouse, Mus terricolor, in a phase- and dose-dependent manner. We used wheel running to assess phase shifts in the free-running locomotor activity rhythm. Following entrainment to a 12:12 h light–dark cycle, 5-HTP (100 mg/kg in saline) was intraperitoneally administered in complete darkness at circadian time (CT)s 0, 3, 6, 9, 12, 15, 18, and 21, and the ensuing phase shifts in the locomotor activity rhythm were calculated. The results show that 5-HTP differentially shifts the phase of the rhythm, causing phase advances from CT 0 to CT 12 and phase delays from CT 12 to CT 21. Maximum advance phase shift was at CT 6 (1.18 ± 0.37 h) and maximum delay was at CT 18 (−2.36 ± 0.56 h). No extended dead zone is apparent. Vehicle (saline) at any CT did not evoke a significant phase shift. Investigations with different doses (10, 50, 100, and 200 mg/kg) of 5-HTP revealed that the phase resetting effect is dose-dependent. The shape of the phase–response curve (PRC) has a strong similarity to PRCs obtained using some serotonergic agents. There was no significant increase in wheel-running activity after 5-HTP injection, ruling out behavioral arousal-dependent shifts. This suggests that this phase resetting does not completely depend on feedback of the overt rhythmic behavior on the circadian clock. A mechanistic explanation of these shifts is currently lacking.