The effect of substituted benzene dicarboxylic acid linkers on the optical band gap energy and magnetic coupling in manganese trimer metal organic frameworks

We have systematically studied a series of eight metal-organic frameworks (MOFs) in which the secondary building unit is a manganese trimer cluster, and the linkers are differently substituted benzene dicarboxylic acids (BDC). The optical band gap energy of the compounds vary from 2.62 eV to 3.57 eV, and theoretical studies find that different functional groups result in new states in the conduction band, which lie in the gap and lower the optical band gap energy. The optical absorption between the filled Mn 3d states and the ligands is weak due to minimal overlap of the states, and the measured optical band gap energy is due to transitions on the BDC linker. The Mn atoms in the MOFs have local moments of 5 mu B, and selected MOFs are found to be antiferromagnetic, with weak coupling between the cluster units, and paramagnetic above 10 K

Role of S gene product of bacteriophage lambda in host cell lysis

Studies with the induced lysogens of λ S +R+, λS-R+, λS+R- and λS-R- phages have shown that while the S gene product is essential for the action of intracellular R gene product to release the periplasmic alkaline phosphatase in the presence of EDTA, the latter gene product can bring about this effect while acting on Escherichia coli cells from outside, in the absence of functional S gene product; chloroform, could help the intracellular R gene product in effecting bacterial lysis in the absence of S gene product. These result support the premise that the S gene product facilitates the R gene product in crossing the cytoplasmic membrane into the periplasmic space such that the latter can act on the peptidoglycan layer of the host cell thus causing both the release of alkaline phosphatase and cell lysis

Control of postharvest grape rots caused by Aspergillus niger and Botryodiplodia theobromae

Die Bekämpfung der durch Aspergillus niger und Botryodiplodia theobromae an geernteten Trauben verursachten FäulnisTrauben der Sorten Thompson Seedless, Anab-e-Shahi und Kishmish wurden nach der Ernte mit A. niger und B. theobromae - sowohl rein als auch gemischt - infiziert. Die Wirksamkeit verschiedener Nahrungskonservierungsmittel, Pflanzenöle, Wachstumsregulatoren, homoeopathischer Drogen, Antibiotika und Fungizide, vor und nach der Inokulation angewandt, wurde gepriift. Durch die Behandlung der geernteten Trauben mit Bavistin (0,1 % ) + Kaliummetabisulfit (5 % ) könnten hohe wirtschaftliche Verluste vermieden werden

Spin analog of the controlled Josephson charge current

We propose a controlled Josephson spin current across the junction of two non-centrosymmetric superconductors like CePt_3Si. The Josephson spin current arises due to direction dependent tunneling matrix element and different momentum dependent phases of the triplet components of the gap function. Its modulation with the angle \xi between the noncentrosymmetric axes of two superconductors is proportional to \sin \xi. This particular dependence on \xi may find application of the proposed set-up in making a Josephson spin switch.Comment: 4 pages, 1 figure; title is changed; article is rewritte

A fluorescence anisotropy study of tetramer-dimer equilibrium of λ repressor and its implication for function

Tetramer-dimer equilibrium of λ repressor has been studied by fluorescence anisotropy techniques. We have chosen 1-dimethylamino naphthalene-5-sulfonyl chloride (dansyl chloride)-labeled repressor to study the dissociation-association equilibrium, because of relatively long life-time of the probe (> 10 ns). Polarization of the dansyl-labeled repressor decreases with decreasing protein concentrations in the range of 20 to 0.2 μM. The decrease of anisotropy was shown to be due to reversible dissociation of the protein. Size exclusion high-performance liquid chromatography studies and polyacrylamide gel electrophoresis under native conditions (Ferguson plot) confirmed that at around 20 μM concentrations the repressor exists in predominantly tetrameric form, whereas in lower concentrations it exists in predominantly dimer form. A dissociation constant of 2.3 ± 0.9 μM was estimated in 0.1 M potassium phosphate, pH 8.0, at 25° C. A stoichiometric amount of isolated single operator shifted the tetramer-dimer equilibrium toward the dimer. Increased ionic strength had only a modest effect on the dissociation constant. The thermodynamic constants for the dissociation reaction calculated from the Van't Hoff plot was +26.6 kcal/mol for ΔH and +64.7 e.u. for ΔS. The rotational correlation times derived from isothermal Perrin plot indicated elongated dimers and tetramers

Evolution of microstructure in spray formed Al–18%Si alloy

Spray atomization and deposition process has emerged as an alternative to ingot and powder metallurgy routes. In the present investigation, we study the microstructural control during spray deposition of hypereutectic Al–Si alloy, employing different nozzle to substrate distances. Spray deposition is carried out using convergent–divergent close-coupled nozzle design at deposition distances of 200, 300, 450, and 550 mm. Microstructural characterization of oversprayed powders as well as spray formed deposits was performed. Microstructural features obtained at smaller deposition distance consist of co-existing primary Si phase and needle like eutectic Si. Dendrites of α-Al phase are observed indicating a large undercooling of the liquid pool prior to solidification. A large number of pre-solidified particles with very fine microstructure, embedded in a relatively coarse region, typically characterize those evolved at large deposition distances. However, at intermediate deposition distances, uniform and refined primary Si phases, 3–8 μm size, are observed. An undercooling effect is manifested in both the spray deposits as well as powder particles. These microstructural features have been discussed in light of a proposed model, which describes the presence of two layers (1) solidification layer and (2) interaction layer in the liquid pool