Two-Phase Flow and the Capillarity Phenomenon in Porous Solids – A Continuum Thermomechanical Approach

Two-phase flow and capillarity phenomenon in porous solids, well known in physics and engineering, are treated from a rigorous continuum thermomechanical point of view for the first time. A ternary model, consisting of a porous solid phase, a liquid phase, and a gas phase, is investigated within the framework of thermodynamics. The main result of the evaluation of the entropy principle turns out to be that the interaction forces between the solid, gas, and liquid phases are dependent on the free Helmholtz energy functions of the corresponding phases and on the gradient of the liquid density. The classical result for the driving volume force for raising a water column in a narrow tube against the force of gravity is contained in the general investigation.     

Chiral discrimination of D- and L-amino acids using iodinated tyrosines as chiral references: Effect of iodine substituent

L-Tyrosine and iodinated L-tyrosines, i.e., 3-iodo-L-tyrosine and 3,5-diiodo-L-tyrosine, are successfully used as chiral references for the chiral discrimination of aliphatic, acidic, and aromatic amino acids. Chiral discrimination is achieved by investigating the collision-induced dissociation spectra of the trimeric complex [Cu(II)(ref)(2)(A) - H](+) ion generated by electro spraying the mixture of D- or L-analyte amino acid (A), chiral reference ligand (ref) and M(II)Cl(2) (M = Ni and Cu). The relative abundances of fragment ions resulted by the competitive loss of reference and analyte amino acids are considered for measuring the degree of chiral discrimination by applying the kinetic method. The chiral discrimination ability increases as the number of iodine atom increases on the aromatic ring of the reference and the discrimination is better with Cu when compared with Ni. A large chiral discrimination is obtained for aliphatic and aromatic amino acids using iodinated L-tyrosine as the reference. Computational studies on the different stabilities of the diastereomeric complexes also support the observed differences measured by the kinetic method. The suitability of the method in the measurement of enantiomeric excess over the range of 2% to 100% ee with relative error 0.28% to 1.6% is also demonstrated.     

Identification of statistical regimes and crossovers in coherent random laser emission

We measure intensity statistics and identify statistical regimes and crossovers in random lasers based on nonresonant feedback. A single parameter extracted from an α-stable Levy fit is used to characterize the intensity distributions in all regimes. Measurements made over a range of scattering strengths, excitation energies, and sample sizes enable us to demarcate three regimes of intensity statistics and the corresponding crossovers. An initial subthreshold Gaussian regime abruptly transits into a Levy regime at the random lasing threshold, which is followed by a continuous gradual crossover toward a second Gaussian regime. We find that the prominence of the Levy regime depends upon the sample size.     

Aerosol-based coherent random laser

We demonstrate coherent random lasing from an aerosol of dye-doped microdroplets in air. The aerosol is in the form of a linear array of polydisperse, arbitrarily shaped, and randomly spaced microdroplets with average dimensions of about 30 μm. Upon optical excitation, ultranarrow lasing modes were observed in the emission along the axis of the linear array, while the transverse emission exhibited intrascatterer resonance peaks. Direct spatiospectral imaging and lasing threshold studies confirmed the origin of the lasing peaks to be from spatial modes that extended over the array of the polydisperse microdroplets.     

Saturated Elastic Porous Solids: Incompressible,Compressible and Hybrid Binary Models

Constitutive models for a general binary elastic-porous media are investigated by two complementary approaches. These models include both constituents treated as compressible/incompressible, a compressible solid phase with an incompressible fluid phase (hybrid model of first type), and an incompressible solid phase with a compressible fluid phase (hybrid model of second type). The macroscopic continuum mechanical approach uses evaluation of entropy inequality with the saturation condition always considered as a constraint. This constraint leads to an interface pressure acting in both constituents. Two constitutive equations for the interface pressure, one for each phase, are identified, thus closing the set of field equations. The micromechanical approach shows that the results of Didwania and de Boer can be easily extended to general binary porous media.     

Light-induced metastable defects in a-Se90X10 (X = Sb,In and Ag) thin films

Thin films of chalcogenide glasses in a binary system of Se₉₀X₁₀ (X = Sb, In and Ag) have been prepared by the vacuum evaporation technique. Thermally stimulated current measurements have been made to find out the trap density in these materials. To study light-induced defects in these materials, white light of intensity 1200 lux is shown on the amorphous films in vacuum for different exposure times. It is observed that the density of traps increases with exposure time, indicating the appearance of light-induced metastable defects in these materials.     

SYNERGISTIC KILLING EFFECT IN PRE-UV-IRRADIATED MICROCOCCUS RADIOPHILUS

Abstract— Both the UV- and y-radiation survival curves of Micrococcus radiophilus are distinguished by large shoulders. However, a combination radiation treatment results in an enhanced killing effect. Pre-UV treatment is found to give a synergistic kill as compared to an additive kill when the sequence of radiation treatments is reversed.     

Beta-sugar aminoxy peptides as rigid secondary structural scaffolds

Short homo-oligomers of a new building block, cis-beta(2,3)-furanoid sugar aminoxy acid, are designed, characterized, and found to exhibit rigid ribbon-like secondary structures composed of 5/7 bifurcated intramolecular hydrogen bonds.     

Remarkable Anion‐Dependent Spin‐State Switching in Diiron(III) μ‐Hydroxo Bisporphyrins: What Role Do Counterions Play?

Addition of 2,4,6‐trinitrophenol (HTNP) to an ethene‐bridged diiron(III) μ‐oxo bisporphyrin ( 1 ) in CH₂Cl₂ initially leads to the formation of diiron(III) μ‐hydroxo bisporphyrin ( 2? TNP) with a phenolate counterion that, after further addition of HTNP or dissolution in a nonpolar solvent, converts to a diiron(III) complex with axial phenoxide coordination ( 3? (TNP)₂). The progress of the reaction from μ‐oxo to μ‐hydroxo to axially ligated complex has been monitored in solution by using ¹H NMR spectroscopy because their signals appear in three different and distinct spectral regions. The X‐ray structure of 2? TNP revealed that the nearly planar TNP counterion fits perfectly within the bisporphyrin cavity to form a strong hydrogen bond with the μ‐hydroxo group, which thus stabilizes the two equivalent iron centers. In contrast, such counterions as I₅, I₃, BF₄, SbF₆, and PF₆ are found to be tightly associated with one of the porphyrin rings and, therefore, stabilize two different spin states of iron in one molecule. A spectroscopic investigation of 2? TNP has revealed the presence of two equivalent iron centers with a high‐spin state (S=5/2) in the solid state that converts to intermediate spin (S=3/2) in solution. An extensive computational study by using a range of DFT methods was performed on 2? TNP and 2 ⁺, and clearly supports the experimentally observed spin flip triggered by hydrogen‐bonding interactions. The counterion is shown to perturb the spin‐state ordering through, for example, hydrogen‐bonding interactions, switched positions between counterion and axial ligand, ion‐pair interactions, and charge polarization. The present investigation thus provides a clear rationalization of the unusual counterion‐specific spin states observed in the μ‐hydroxo bisporphyrins that have so far remained the most outstanding issue.     

Design,synthesis and biological evaluation of antimalarial activity of new derivatives of 2,4,6-<Emphasis Type="Italic">s</Emphasis>-triazine

Dihydrofolate reductase (DHFR) is an important enzyme for de novo synthesis of nucleotides in Plasmodium falciparum and it is essential for cell proliferation. DHFR is a well known antimalarial target for drugs like cycloguanil and pyrimethamine which target its inhibition for their pharmacological actions. However, the clinical efficacies of these antimalarial drugs have been compromising due to multiple mutations occurring in DHFR that lead to drug resistance. In this background, we have designed 22 s -triazine compounds using the best five parameters based 3D-QSAR model built by using genetic function approximation. In-silico designed compounds were further filtered to 6 compounds based upon their ADME properties, docking studies and predicted minimum inhibitory concentrations (MIC). Out of 6 compounds, 3 compounds were synthesized in good yield over 95% and characterized using IR, ¹HNMR, ¹³CNMR and mass spectroscopic techniques. Parasitemia inhibition assay was used to evaluate the antimalarial activity of s -triazine compounds against 3D7 strain of P. falciparum. All the three compounds (7, 13 and 18) showed 30 times higher potency than cycloguanil (standard drug). It was observed that compound 18 was the most active while the compound 13 was the least active. On the closer inspection of physicochemical properties and SAR, it was observed that the presence of electron donating groups, number of hydrogen bond formation, lipophilicity of ligands and coulson charge of nitrogen atom present in the triazine ring enhances the DHFR inhibition significantly. This study will contribute to further endeavours of more potent DHFR inhibitors.