Novel chiral dimesogenic bidentate ligands and their Cu(II) and Pd(II) metal complexes

The synthesis and characterization of cholesterol-based dimesogenic bidentate ligands and their Cu(II) and Pd(II) metallomesogens are reported in detail. To understand structure-property relationships in these materials the terminal alkoxy chains and the central metal atom have been varied. Our studies reveal that chiral dimesogenic bidentate ligands with n-butyloxy chains exhibit smectic A (SmA), twist grain boundary and chiral nematic (N*) mesophases while substitution with either n -decyloxy or 3,7-dimethyloctyloxy chains also show a ferroelectrically switchable chiral smectic C (SmC*) mesophase. The metal complexes with n-butyloxy chains show only the SmA phase whereas higher chain length derivatives exhibit N* phase irrespective of the metal atom present. The ligands are thermally stable whereas their metal complexes, especially Pd(II) systems, seem to be heat sensitive. Spontaneous polarization, response time and tilt angle measurements have been carried out in the smectic C* phase of the two ligands.     

DEVELOPMENT OF AN OPTIMAL WATER ALLOCATION DECISION TOOL FOR THE MAJOR CROPS DURING THE WATER DEFICIT PERIOD IN THE SOUTHEAST UNITED STATES

ABSTRACT. We developed a dynamic economic model to optimize irrigation water allocations during water deficit periods for three major crops grown in the humid southeastern United States. Analysis involved the use of crop simulation models to capture (a) the yield water relationship and (b) soil moisture dynamics from one week to another week. A hy‐drological model was used to find the water supply; combinations of hydrological and simulation models were used to find the optimal water allocation during each week in corn, cotton and peanuts. Results indicated that farmers should irrigate the most valuable crop first (peanuts) before applying water to other crops (corn and cotton). Results also showed that, because of restriction on total water supply, an increase in crop acreage did not increase the net revenue of the farm in a proportionate amount. Results should provide guidelines to water managers, engineers, policy makers, and farmers regarding an optimal amount of water allocation that will maximize net returns when water shortage is a serious concern.     

Taming fluorescence yield of dye insensitive to temperature by non-covalent complex with the host CB[7] for aqueous dye lasers

Quantum yield of fluorescence (QYF) of widely used Rhodamine (RhB) dye in ethanol and water was observed to decrease rapidly with increase in temperature of the dye solutions, which was correlated to enhanced torsional motion of its flexible diethylamino groups. This is harmful for its use in high-average power dye lasers, pumped by copper vapour laser (CVL) or diode-pumped solid-state green laser (DPSSGL), in which bulk temperature of the dye solution was found to increase due to the heat generated by circulation pumps and non-radiative decay processes of excited dye molecules. The QYF of RhB dye in water was found to be not sensitive to temperature in the practical operating region 16–25°C of dye laser by adopting supramolecular route to form an inclusion complex of RhB with the container molecule cucurbit[7]uril (CB[7]).     

AN ESR STUDY OF THE VISIBLE LIGHT PHOTOCHEMISTRY OF GILVOCARCIN V

Photolysis of gilvocarcin (GV) at 405 nm in argon saturated dimethylsulfoxide (DMSO) or 50% DMSO-water solutions in the presence of the sodium salt of 3,5-dibromo-2,6-dideutero-4-nitrosobenzene sulfonic acid (DBNBS-d2) generates the CH3-DBNBS-d2.spin adduct. It is postulated that this spin adduct is produced by photoreduction of DMSO by GV and the consequent formation and trapping of the generated methyl radicals. Gilvocarcin V also photoreduces oxygen and methyl viologen with quantum yields of 0.019 and 0.0012 respectively. The quantum yield for singlet oxygen formation by GV in DMSO, determined by measuring the rate of production of the nitroxyl radical produced by the reaction of 2,2,6,6-tetramethylpiperidinol with singlet oxygen, was found to be 0.15. Thus, GV photochemistry proceeds by both Type I and Type II pathways which could contribute to the reported GV phototoxicity in biological systems.     

ALTERNATIVE METHODS TO ANALYZE THE RANK ORDERED DATA: A CASE OF INVASIVE SPECIES CONTROL

ABSTRACT. Data collected regarding homeowner preferences for various Formosan Subterranean termite control methods were analyzed using ordered probit and exploded logit models. Ordered probit model for first, second and fourth preferences had similar variables significant, although the first preference model had many significant variables. The most important variable, in terms of significance, across all preferences was the perception that a respondent thinks that termite existence is a problem in their neighborhood. The results from the exploded logit model indicated that a control option with liquid treatment option and more visits by a pest control agency is a less preferred treatment option. This paper was presented at the 2004 Research Modeling Association World Conference on Natural Resource Modeling in Melbourne, Australia.     

Linearity stabilizes discrete breathers

The study of the dynamics of 1D chains with both harmonic and nonlinear interactions, as in the Fermi–Pasta–Ulam (FPU) and related problems, has played a central role in efforts to identify the broad consequences of nonlinearity in these systems. Here we study the dynamics of highly localized excitations, or discrete breathers, which are known to be initiated by the quasistatic stretching of bonds between adjacent particles. We show via dynamical simulations that acoustic waves introduced by the harmonic term stabilize the discrete breather by suppressing the breather’s tendency to delocalize and disperse. We conclude that the harmonic term, and hence acoustic waves, are essential for the existence of localized breathers in these systems.     

Nonlinear interaction of ultraintense laser pulse with relativistic thin plasma foil in the radiation pressure-dominant regime

We present a study of the effect of laser pulse temporal profile on the energy /momentum acquired by the ions as a result of the ultraintense laser pulse focussed on a thin plasma layer in the radiation pressure-dominant (RPD) regime. In the RPD regime, the plasma foil is pushed by ultraintense laser pulse when the radiation cannot propagate through the foil, while the electron and ion layers move together. The nonlinear character of laser–matter interaction is exhibited in the relativistic frequency shift, and also change in the wave amplitude as the EM wave gets reflected by the relativistically moving thin dense plasma layer. Relativistic effects in a high-energy plasma provide matching conditions that make it possible to exchange very effectively ordered kinetic energy and momentum between the EM fields and the plasma. When matter moves at relativistic velocities, the efficiency of the energy transfer from the radiation to thin plasma foil is more than 30% and in ultrarelativistic case it approaches one. The momentum /energy transfer to the ions is found to depend on the temporal profile of the laser pulse. Our numerical results show that for the same laser and plasma parameters, a Lorentzian pulse can accelerate ions upto 0.2 GeV within 10 fs which is 1.5 times larger than that a Gaussian pulse can.     

Thermal expansion behaviour and phase stability of AFe<Subscript>2</Subscript>As<Subscript>2</Subscript> (A = Ca,Sr and Eu) using powder diffraction technique

The thermal expansibilities and phase stabilities of AFe ₂As ₂ (A = Ca, Sr and Eu) have been investigated by powder diffraction techniques in the temperature range 5–600 K. We found the anisotropic thermal expansivities with temperature for all the compounds. The lattice parameter in the tetragonal phase ( A_T) of CaFe ₂As ₂ contracts with increasing temperature, whereas C_T expands. The rate of contraction in A_T is lower than the rate of expansion in C_T. Other compounds show normal thermal expansion behaviour along both a- and c-axes. In-plane expansion (i.e., along the a-axis) is found to be the smallest for EuFe ₂As ₂ and the highest for BaFe ₂As ₂. However, the rate of change of thermal expansivities along out-of-plane (i.e., along the c-axis) is higher as we go from Ba, Sr, Eu and Ca, respectively. Above 600 K, we notice the appearance /disappearance of certain reflections which suggest that tetragonal phase is not stable above this temperature for these compounds.     

GLOBAL WARMING,IMPACT ON AGRICULTURE AND ADAPTATION STRATEGY

Abstract Sensitivity of the Southeastern US agriculture sector to temperature increases will be based largely on accompanying changes in precipitation, extent of the warming, and relative impact on competing crops grown in the area. The impact of climate change in 10 Southeastern US counties was investigated under three different climate scenarios for two different reference years (2030 and 2090). Seven major crops grown in the area were selected to study the impact on crop yield, irrigation acreage, and optimal choice of crops in a representative farm in each of the southeastern states. If warming is moderate and also brings a considerable increase in precipitation—as indicated by the Hadley model—then, the effect on yields, water use, and income will be mostly benign. If warming is moderate without increased precipitation and the water for irrigation is available, then the effects on the agriculture sector are still mostly negligible. If warming is not moderate and no increased precipitation materializes, farmers could realize quite dramatic negative consequences for row crop agriculture in the Southeastern United States.