Exact treatment of some phenomenological models of layered high-Tc superconductors

Existing treatments of phenomenological models of Bi and Tl based superconductors consisting of n layers of copper oxide are unsatisfactory because they ignore the important φ⁴ terms in the free energy. An exact treatment of these models is presented, and it is shown that the condition of minimum free energy automatically excludes (n − 1) of the n critical temperatures. The critical exponent β of the order parameter is found to be independent of n and equal to as usual in the Landau theory. The specific heat discontinuity Δc at the critical temperature is calculated as a function of n. A meaningful comparison with experimental measurements of Δc at the moment is hindered by the limited availability of experimental results. Reliable determinations of Δc of a given series of layered superconductors will enable a check of the validity of theoretical results.     

Higher isoprenoids—V: Partial syntheses from cycloartenol,cyclolaudenol part 1: mangiferolic acid,ambolic acid

Conversion of cycloartenol into mangiferolic acid and of cyclolaudenol into ambolic acid is described.     

Changes in the Inner Retinal Cells after Intense and Constant Light Exposure in Sprague-Dawley Rats

Light insult causes photoreceptor death. Few studies reported that continuous exposure to light affects horizontal, Müller and ganglion cells. We aimed to see the effect of constant light exposure on bipolar and amacrine cells. Adult Sprague-Dawley rats were exposed to 300 or 3000 lux for 7 days in 12-h light: 12-h dark cycles (12L:12D). The latter group was then exposed to 24L:0D for 48 h to induce significant damage. The same animals were reverted to 300 lux and reared for 15 days in 12L:12D cycles. They were sacrificed on different days to find the degree of retinal recovery, if any, from light injury. Besides photoreceptor death, continuous light for 48 h resulted in downregulation of parvalbumin in amacrine cells and recoverin in cone bipolar cells (CBC). Rod bipolar cells (RBC) maintained an unaltered pattern of PKC-α expression. Upon reversal, there were increased expressions of parvalbumin in amacrine cells and recoverin in CBC, while RBC showed an increasing trend of PKC-α expression. The data show that damage in bipolar and amacrine cells after exposure to intense, continuous light can be ameliorated upon reversal to normal LD cycles to which the animals were initially acclimated to.     

Theoretical study of efficiency of metal cations (Mg+, Ca+, and Ag+) for effective hydrogen storage

The interaction between the metal cations and H₂ molecule has been investigated using dispersion-corrected and -uncorrected hybrid density functional and CCSD(T) methods in conjunction with the correlation consistent triple-ζ quality basis sets for the storage of the H₂ molecule. The molecular properties, potential energy surfaces, stability, binding energy and well-depth have been computed for the metal cation–dihydrogen (M⁺–H₂, M = Mg, Ca, and Ag) complexes in the gas phase. The results obtained by the dispersion-corrected hybrid density functional B2PLYP-D method agree very well with the earlier experimental and theoretical results wherever available. Different components of the interaction energy have been estimated by the symmetry adapted perturbation theory (SAPT) to get physical insight into the interaction energy. Among the three complexes, only Ag⁺–H₂ is the most stable complex and it accumulates more H₂ molecules as the interaction between the metal cation Ag⁺ and the H₂ molecule is the greatest.     

Monitoring the emission of volatile organic compounds from flowers of Jasminum sambac using solid-phase micro-extraction fibers and gas chromatography with mass spectrometry detection

Solid-phase micro-extraction (SPME) was studied as a solvent free alternative method for the extraction and characterization of volatile compounds in intact and plucked flowers of Jasminum sambac at different day time intervals using gas chromatography (GC-FID) and gas chromatography-quadrupole mass spectrometry. The analytes identified included alcohols, esters, phenolic compounds, and terpenoids. The main constituents identified in the flower aroma using different fibers were cis-3-hexenyl acetate, (E)-beta-ocimene, linalool, benzyl acetate, and (E,E)-alpha-farnesene. The benzyl acetate proportion decreased from morning to afternoon and then increased in evening collections. PDMS fiber showed a high proportion of (E,E)-alpha-farnesene in jasmine floral aroma. Among other constituents identified, cis-3-hexenyl acetate, linalool, and benzyl acetate were major aroma contributors in plucked and living flowers extracts using PDMS/DVB, Carboxen/PDMS, and DVB/Carboxen/PDMS fibers. PDMS/DVB recorded the highest emission for benzyl acetate while the (E)-beta-ocimene proportion was highest in DVB/Carboxen/PDMS when compared with the rest. The highest linalool content, with increasing proportion from morning to noon, was found using mixed coating fibers. Almost negligible volatile adsorption was recorded for the polyacrylate fiber for intact flower aroma, whereas it was most effective for benzyl acetate, followed by indole under plucked conditions. Moreover, the highest amounts extracted, evaluated from the sum of peak areas, were achieved using Carboxen/PDMS, and DVB/Carboxen/PDMS. Introduction of a rapid, and solvent free SPME method for the analysis of multicomponent volatiles can be successfully employed to monitor the extraction and characterization of flower aroma constituents.     

Novel Multiporphyrin Functionalized Single-Walled Carbon Nanotubes

Porphyrin monomers, 5,15–bis(4-(2,5,8,11-tetraoxatridecan-13-yloxy)phenyl)-10,20-bis(3-iodophenyl)porphyrin zinc (5a) and 5,10–bis(4-(2,5,8,11-tetraoxatridecan-13-yloxy)phenyl)-15,20-bis(3-iodophenyl)porphyrin zinc (5b), and their oligomers 6a and 6b were synthesized and characterized. The titration experiment of the monomers was carried out in THF by changing the solution percent of water. The optical properties (UV–vis and fluorescence spectra) of the monomers that possess slightly red-shifted optical spectra in water compared to the spectra obtained in THF are reported. The newly prepared porphyrin constructs were also mixed with SWCNTs to generate noncovalent hybrid materials.     

Biocompatible Small Molecules that Enhance Silica Solubilization Under Ambient Conditions: Chemical Profile of Such Complexes,Possible Mechanism for Enhancement,and Their Effect on the Growth and Protection from Pests in the Rice Plant (Oryza sativa L.)

Recent studies suggest that the depletion of silicon available to plants may be a major reason for the yield decline observed for rice cultivation. In the present article, a novel strategy is explored to identify small biocompatible molecules (carriers) that would enhance the solubility of sand (SiO ₂ . nH ₂ O) (here after named silica) in water under ambient conditions. All considerations, notably biocompatibility, make the 20 proteinous amino acids and their simplified analogs the first choice. Among the proteinous amino acids, notable enhancement of silica solubility was seen at 1000 μ mole.L^?1 : Blank: 1; glutamine: 3.5; histidine: 3; alanine: 2.9. Based on the assumption that the observed enhancement is related to proclivity for hydrogen bond formation with water, a large number of varied biocompatible substrates were examined. Among these, notable enhancement of silica solubilization at 1000 μ mole.L^?1 was seen as exemplified with Blank: 1; imidazole: 5; inositol: 4.5; mannitol: 3.9; 3, 4-dihydroxy phenylalanine (DOPA): 3.5. A complementary gravimetric protocol coupled with thermogravimetric analysis (TGA) enabled the estimation of an approximate empirical formula for few of the carrier–silica complexes. A possible mechanism for the interaction of the carrier at the silica–water interface is suggested. Field experiments (reported separately) with selected carriers, monitored in the stem extract by colorimetry and in the leaf by scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis showed enhanced levels of silica and were significantly beneficial for the growth and protection from predators of the rice plant.     

POM‐Catalyzed In Situ Ligand Synthesis for the Construction of Metal Complexes and Their Use in the Formation of Coordination Polymers

Six organic–inorganic hybrid materials were synthesized by the in situ oxidation of neocuproine by using MoO₃/Na₂MoO₄ as the catalyst in the presence of Cu(NO₃)₂. The crystal structures of Mo8‐Cu4‐PHEN and Mo8‐Cu2‐5(2PIC) are composed of [Mo₈O₂₆]^4? polyoxometalate (POM) units, whereas the crystal structure of Mo6‐Cu‐COPHEN is composed of a [Mo₆O₁₉]^2? POM unit; both POM units could be considered as the active form of the catalyst. Reaction of the hybrid materials with 1,3,5‐benzenetricarboxylic acid (BTC) resulted in the formation of two different coordination polymers (CPs) under different reaction conditions. These CPs, depending on their structural attributes, exhibit distinct differences in the adsorption of H₂, CO₂, and water. The use of 2‐methylpyridine instead of neocuproine does not give any oxidation products under the same reaction conditions due to the incorrect positioning of the methyl group with respect to the Cu^II center.