Electrochemical incineration of wastes

The novel technology of waste removal in space vehicles by electrochemical methods is presented to convert wastes into chemicals that can be eventually recycled. The important consideration for waste oxidation is to select a right kind of electrode (anode) material that should be stable under anodic conditions and also a poor electrocatalyst for oxygen and chlorine evolution. On the basis of long term electrolysis experiments on seven different electrodes and on the basis of total organic carbon reduced, two best electrodes were identified. The effect of redox ions on the electrolyte was studied. Though most of the experiments were done in mixtures of urine and waste, the experiments with redox couples involved 2.5 M sulfuric acid in order to avoid the precipitation of redox ions by urea. Two methods for long term electrolysis of waste were investigated: (1) the oxidation on Pt and lead dioxide electrodes using the galvanostatic methods; and (2) potentiostatic method on other electrodes. The advantage of the first method is the faster rate of oxidation. The chlorine evolution in the second method is ten times less then in the first. The accomplished research has shown that urine/feces mixtures can be oxidized to carbon dioxide and water, but current densities are low and must be improved. The perovskite and Ti4O7 coated with RuO2 are the best electrode materials found. Recent experiment with the redox agent improves the current density, however, sulphuric acid is required to keep the redox agent in solution to enhance oxidation effectively. It is desirable to reduce the use of acid and/or find substitutes

Soil Fertility under Grassland Compared to Other Land Uses in Acid Soil of Himachal Pradesh, India

In the last decades severe changes in land use occurred in tropical countries, due to increasing population and their demand for food resources. Forest land is rapidly converted into agriculture or pastureland which may cause significant changes in soil fertility. Land-use exerts significant effect on nutrient availability and may also influence secondary succession and biomass production (Lu et al., 2002). Nutrient cycling in agroforestry is in between natural forest ecosystems of the tropics and most of the agricultural systems with are ‘‘leaky’’ having higher nutrient losses. Research indicated that decline of soil organic matter may occur due to conversion of forest and grassland into agriculture (Ouattara et al., 2006). Tree growth is highly influenced by base cations (Ca, Mg, K, Na) concentration, cation exchange capacity, and concentrations of Al and Mn. Calcium and N are specifically important, as they are primary constituents of biomass and regulate cell function of many tree species. Base cations also help in alleviating the effects of Al toxicity in acid soil

Pattern formation during the evaporation of a colloidal nanoliter drop: a numerical and experimental study

An efficient way to precisely pattern particles on solid surfaces is to dispense and evaporate colloidal drops, as for bioassays. The dried deposits often exhibit complex structures exemplified by the coffee ring pattern, where most particles have accumulated at the periphery of the deposit. In this work, the formation of deposits during the drying of nanoliter colloidal drops on a flat substrate is investigated numerically and experimentally. A finite-element numerical model is developed that solves the Navier-Stokes, heat and mass transport equations in a Lagrangian framework. The diffusion of vapor in the atmosphere is solved numerically, providing an exact boundary condition for the evaporative flux at the droplet-air interface. Laplace stresses and thermal Marangoni stresses are accounted for. The particle concentration is tracked by solving a continuum advection-diffusion equation. Wetting line motion and the interaction of the free surface of the drop with the growing deposit are modeled based on criteria on wetting angles. Numerical results for evaporation times and flow field are in very good agreement with published experimental and theoretical results. We also performed transient visualization experiments of water and isopropanol drops loaded with polystyrene microsphere evaporating on respectively glass and polydimethylsiloxane substrates. Measured evaporation times, deposit shape and sizes, and flow fields are in very good agreement with the numerical results. Different flow patterns caused by the competition of Marangoni loops and radial flow are shown to determine the deposit shape to be either a ring-like pattern or a homogeneous bump

Irradiation of benzene molecules by ion-induced and light-induced intense fields

Benzene, with its sea of delocalized $\pi$-electrons in the valence orbitals, is identified as an example of a class of molecules that enable establishment of the correspondence between intense ion-induced and laser-light-induced fields in experiments that probe ionization dynamics in temporal regimes spanning the attosecond and picosecond ranges.Comment: 4 ps figure

Graphene boosts thermoelectric performance of a Zintl phase compound

The concept of nanocomposites derived by incorporating a second minor phase in bulk thermoelectric materials has established itself as an effective paradigm for optimizing high thermoelectric performance. In this work, this paradigm is for the first time extended to bulk Zintl phase Mg3Sb2 and its isoelectronically Bi-doped derivative Mg3Sb1.8Bi0.2 system. Herein, we report the synthesis, microstructural details, electronic structure and thermoelectric properties of (Mg3Sb2, Mg3Sb1.8Bi0.2)/ graphene nanosheet (GNS) nanocomposites with different mass ratios. Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) investigation reveals that Mg3Sb2 nanoparticles are homogenously anchored on the surface of GNS. We demonstrate that Mg3Sb2-based materials incorporated with a small content of graphene outperform optimally, resulting in potential p-type thermoelectric materials. The present nanocomposite additive of GNS deriving such a novel nanocomposite of (Mg3Sb2, Mg3Sb1.8Bi0.2)/GNS, enhances the electrical conductivity significantly, thereby resulting in a substantially large increase in the power factor. The enhanced electrical conductivity of these nanocomposites is attributed to the increase in the carrier concentration and high carrier mobility owing to the ultra high mobility of graphene. X-ray photoelectron spectroscopy (XPS) core level spectra confirm weak bonding between GNS and Mg3Sb2. Increase in carrier concentration is reflected in XPS valence band spectra and change in spectral weight near valence band maxima is indicative of increased electrical conductivity in the nanocomposite material. The thermal conductivity of these nanocomposites is noted to be reduced at high temperature. These favorable conditions lead to enhanced thermoelectric figure-of-merit (ZT) = 0.71 at 773 K for Mg3Sb2/GNS and a ZT = 1.35 at 773 K for Mg3Sb1.8Bi0.2/GNS nanocomposites with the mass ratio of 80 : 1 which are similar to 170% and similar to 125% higher values compared to bare Mg3Sb2 and bare Mg3Sb1.8Bi0.2 respectively. We strongly believe that the present novel strategy of fabricating such a nanocomposite of a Zintl compound by utilizing GNS as a nanocomposite additive, may provide an emerging path for improving thermoelectric properties of various Zintl phase compounds

Soil Quality Under Forest Compared to Other Land Uses

Abstract. Present research was undertaken to examine the impact of land use on soil fertility in an Alfisol, at Dharamshala district of north western Himalayan region, India. Soil samples were collected from 0-15, 15-30, 30-45 and 45 -60 cm soil depths of five land uses viz. natural forest of Pinus roxburghii, grassland, horticulture, agriculture and wasteland. Soil was examined for pH, organic carbon (OC), electrical conductivity (EC), cation exchange capacity (CEC), available nitrogen (N), phosphorus (P), exchangeable calcium (Ca), magnesium (Mg), potassium (K), aluminium (Al), microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), microbial biomass phosphorus (MBP), acid phosphatase activity (APHA) and dehydrogenase activity (DHA). Soil pH varied from 5.22 in forest and 5.72 in grassland. OC content was higher in forest (3.01%), followed by grassland (2.16%) and was least (0.36%) in deeper layers of agriculture. Highest N content was found under forest (699, 654, 623 and 597 kg/ha, at 0-15, 15-30, 30-45 and 45-60 cm depth, respectively), followed by grassland, horticulture and agriculture and least in wasteland. Maximum exchangeable Ca and Mg were found in grassland (0.801 c mol kg -1 and 0.402 c mol kg -1 , respectively). Exchangeable K and Al were higher under forest (0.231 c mol kg -1 and 1.89 c mol kg -1 , respectively) least in wasteland. Soil biological properties were highest under surface soil of forest (576 mg kg -1 , 31.24 mg kg -1 , 6.55 mg kg -1 , 29.6 mg PNP g -1 h -1 and 35.65 μg TPF 24 h -1 g -1 dry soil, respectively for MBC, MBN, MBP, APHA and DHA) and least in 45-60 cm layer, under wasteland. The forest had a higher fertility index and soil evaluation factor followed by grassland, horticulture, agriculture as compared to wasteland

Effect of varying levels of nitrogen on growth, yield, quality and profitability of transplanted fennel (Foeniculum vulgare Mill.)

Field experiments were conducted at two adjoining farmer’s field in tribal area of district Sirohi (Rajasthan) during two successive seasons from July 2012 to March 2013 and July 2013 to March 2014 to study the impact of varied levels of nitrogen (60, 90, 120 & 150 kg N ha-1) on production, quality and profitability of transplanted fennel (Foeniculum vulgare). Application of nitrogen @120 kg ha-1 recorded the highest stem girth, number of roots plant-1, root length, fresh weight of root and root: shoot ratio. The maximum value of number of umbels plant-1, umbellate umbel-1, number of seeds umbel-1, test weight, seed yield, straw yield, harvesting index was also reported in same treatment. Similarly, volatile and total oil content, soluble sugar, total carbohydrate and overall quality of seeds were also higher with application of 120 kg N ha-1, whereas, disease incidence significantly increased with application of higher dose of nitrogen (150 kg N ha-1). The maximum net return and highest benefit: cost ratio was also recorded with application of 120 kg N ha-1. However, some of the growth parameters (plant height, number of primary and secondary branches plant-1, number of leaves, fresh weight of shoot and duration of flowering, protein and nitrogen content in seed were more with 150 kg N ha-1. &nbsp

The propensity of molecules to spatially align in intense light fields

The propensity of molecules to spatially align along the polarization vector of intense, pulsed light fields is related to readily-accessible parameters (molecular polarizabilities, moment of inertia, peak intensity of the light and its pulse duration). Predictions can now be made of which molecules can be spatially aligned, and under what circumstances, upon irradiation by intense light. Accounting for both enhanced ionization and hyperpolarizability, it is shown that {\it all} molecules can be aligned, even those with the smallest static polarizability, when subjected to the shortest available laser pulses (of sufficient intensity).Comment: 8 pages, 4 figures, to be submitted to PR

Electron attachment to valence-excited CO

The possibility of electron attachment to the valence $^{3}\Pi$ state of CO is examined using an {\it ab initio} bound-state multireference configuration interaction approach. The resulting resonance has $^{4}\Sigma^{-}$ symmetry; the higher vibrational levels of this resonance state coincide with, or are nearly coincident with, levels of the parent $a^{3}\Pi$ state. Collisional relaxation to the lowest vibrational levels in hot plasma situations might yield the possibility of a long-lived CO$^-$ state.Comment: Revtex file + postscript file for one figur

High Harmonic Spectroscopy of the Cooper Minimum in Molecules

The Cooper minimum (CM) has been studied using high harmonic generation solely in atoms. Here, we present detailed experimental and theoretical studies on the CM in molecules probed by high harmonic generation using a range of near-infrared light pulses from λ = 1.3 to 1.8 µm. We demonstrate the CM to occur in CS₂ and CCl₄ at ~42 and ~40 eV, respectively, by comparing the high harmonic spectra with the known partial photoionization cross sections of different molecular orbitals, confirmed by theoretical calculations of harmonic spectra. We use CM to probe electron localization in Cl-containing molecules (CCl₄, CH₂Cl₂, and trans-C₂H₂Cl₂) and show that the position of the minimum is influenced by the molecular environment