Microbial susceptibility of condensation products of carboxy-terminated polybutadiene and glycerol

Keeping in view the prospects of biodegradable polymers, a polymer was synthesized by the condensation of carboxy-terminated polybutadiene (CTPB) of Mnsim-5000 with glycerol and tested for its microbial susceptibility. The results of end group estimations and viscosity measurements indicated a quantitative reaction between the two reactants under experimental conditions. The clear-zone method was employed in this investigation to test biodegradability. Two strains of Serratia and three strains of Staphylococcus did show a clear zone surrounding the colony. However, the microbial growth was found to diminish after 4 or 5 days.

Cytotoxicity of half sandwich ruthenium(II) complexes with strong hydrogen bond acceptor ligands and their mechanism of action

Neutral and cationic organometallic ruthenium(II) piano stool complexes of the type [(eta(6)-cymene)R-uCl(X)(Y)] (complexes R1-R8) has been synthesized and characterized. In cationic complexes, X, Y is either a eta(2) phosphorus ligand such as 1,1-bis(diphenylphosphino)methane (DPPM) and 1,2-bis(diphenylphosphino)ethane (DPPE) or partially oxidized ligands such as 1,2-bis(diphenylphosphino)methane monooxide (DPPMO) and 1,2-bis(diphenylphosphino)ethane monooxide (DPPEO) which are strong hydrogen bond acceptors. In neutral complexes. X is chloride and Y is a monodentate phosphorous donor. Complexes with DPPM and DPPMO ligands ([(eta(6)-cymene)Ru(eta(2)-DPPM)Cl]PF6 (R2), [(eta(6)-cymene)Ru(eta(2)-DPPMO)Cl]PF6 (R3), [(eta(6)-cymene)Ru(eta(1)-DPPM)Cl-2] (R5) and [(eta(6)-cymene)Ru(eta(1)-DPPMO)Cl-2] (R6) show good cytotoxicity. Growth inhibition study of several human cancer cell lines by these complexes has been carried out. Mechanistic studies for R5 and R6 show that inhibition of cancer cell growth involves both cell cycle arrest and apoptosis induction. Using an apoptosis PCR array, we identified the sets of antiapoptotic genes that were down regulated and pro-apoptotic genes that were up regulated. These complexes were also found to be potent metastasis inhibitors as they prevented cell invasion through matrigel. The complexes were shown to bind DNA in a non intercalative fashion and cause unwinding of plasmid DNA in cell-free medium by competitive ethidium bromide binding, viscosity measurements, thermal denaturation and gel mobility shift assays.

Folding a Polymer via Two-Point Interaction with an External Folding Agent: Use of H-Bonding and Charge-Transfer Interactions

A polymer containing electron-rich aromatic donors (1,5-dialkoxynaphthalene (DAN)) was coerced into a folded state by an external folding agent that contained an electron-deficient aromatic acceptor (pyromellitic diimide (PM)) unit. The donor-containing polymer was designed to carry a tertiary amine moiety in the linking segment, which served as an H-bonding site for reinforcing the interaction with the acceptor containing folding agent that also bore a carboxylic acid group. The H-bonding interaction of the carboxylic acid and the tertiary amine brings the PDI unit between two adjacent DAN units along the polymer backbone to induce charge-transfer (C-T) interactions, and this in turn causes the polymer chain to form a pleated structure. Evidence for the formation of such a pleated structure was obtained from NMR titration studies and also by monitoring the C-T band in their UV-visible spectra. By varying the length of the segment that links the PDI acceptor to the carboxylic acid group, we showed that the most effective folding agent was the one that had a single carbon spacer, as evident from the highest value of the association constant. Control experiments with propionic acid clearly demonstrated the importance of the additional C-T interactions for venerating the folded structures. Further, solution viscosity measurements in the presence of varying amounts of the folding agent revealed a gradual stiffening of the chain in the case of the PDI carrying carboxylic acid, whereas no such affect was seen in the case of simple propionic acid. These observations were supported by D FT calculations of the interactions of a dimeric model of the polymer with the various folding agents; here too the stability of the complex was seen to be highest in the case of the single carbon spacer.

Synthesis and characterization of thiocarbonohydrazone-based epoxy resins

Novel epoxy resins of various thiocarbonohydrazones have been synthesized by reacting the aldehyde or ketone derivatives of thiocarbohydrazide with excess of epichlorohydrin. The resins have been characterized by elemental analyses, epoxy equivalents, 1H-NMR and IR spectra, thermal analyses, and viscosity measurements. Curing of the resins has been carried out by mixing with thiocarbohydrazide or ethylenediamine and heating at 80°C for 48 h. A comparison of the thermal stability of the cured resin samples has been made.

Synthesis, X-ray crystal structure, DNA binding, antioxidant and cytotoxicity studies of Ni(II) and Pd(II) thiosemicarbazone complexes

New complexes, [Ni(HL)(PPh3)]Cl (1), [Pd(L)(PPh3)](2), and [Pd(L)(AsPh3)](3), were synthesized from the reactions of 4-chloro-5-methyl-salicylaldehyde thiosemicarbazone [H2L] with [NiCl2(PPh3)(2)], [PdCl2(PPh3)(2)] and [PdCl2(AsPh3)(2)]. They were characterized by IR, electronic, H-1-NMR spectral data. Further, the structures of the complexes have been determined by single crystal X-ray diffraction. While the thiosemicarbazone coordinated as binegative tridentate (ONS) in complexes 2 and 3, it is coordinated as mono negative tridentate (ONS) in 1. The interactions of the new complexes with calf thymus DNA was examined by absorption and emission spectra, and viscosity measurements. Moreover, the antioxidant properties of the new complexes have also been tested against DPPH radical in which complex 1 exhibited better activity than that of the other two complexes 2 and 3. The in vitro cytotoxicity of complexes 1-3 against A549 and HepG2 cell lines was assayed, and the new complexes exhibited higher cytotoxic activity with lower IC50 values indicating their efficiency in killing the cancer cells even at very low concentrations.

Cobalt(II), Nickel(II) and Copper(II) complexes of a tetradentate Schiff base as photosensitizers: Quantum yield of O-1(2) generation and its promising role in anti-tumor activity

In the present investigation, a Schiff base N'(1),N'(3)-bis(E)-(5-bromo-2-hydroxyphenyl)methylidene]benzene-1,3-d icarbohydrazide and its metal complexes have been synthesized and characterized. The DNA-binding studies were performed using absorption spectroscopy, emission spectra, viscosity measurements and thermal denatuaration studies. The experimental evidence indicated that, the Co(II), Ni(II) and Cu(II) complexes interact with calf thymus DNA through intercalation with an intrinsic binding constant K-b of 2.6 x 10(4) M-1, 5.7 x 10(4) M-1 and 4.5 x 10(4) M-1, respectively and they exhibited potent photo-damage abilities on pUC19 DNA, through singlet oxygen generation with quantum yields of 0.32, 0.27 and 0.30 respectively. The cytotoxic activity of the complexes resulted that they act as a potent photosensitizers for photochemical reactions. (C) 2012 Elsevier B.V. All rights reserved.

Synthesis, antimicrobial, DNA-binding and photonuclease studies of Cobalt(III) and Nickel(II) Schiff base complexes

New metal complexes of the type M(nih)(L)](PF6)(n)center dot xAH(2)O and M(nih)(2)](PF6)center dot xH(2)O (where M = Co(III) or Ni(II), L = 1,10-phenanthroline (phen)/or 2,2' bipyridine (bpy), nih = 2-hydroxy-1-naphthaldehyde isonicotinoyl hydrazone, n = 2 or 1 and x = 3 or 2) have been synthesized and characterized by elemental analysis, magnetic, IR and H-1 NMR spectral data. The electronic and magnetic moment 2.97-3.07 B.M. data infers octahedral geometry for all the complexes. The IR data reveals that Schiff base (nih) form coordination bond with the metal ion through azomethine-nitrogen, phenolic-oxygen and carbonyl-oxygen in a tridentate fashion. In addition, DNA-binding properties of these six metal complexes were investigated using absorption spectroscopy, viscosity measurements and thermal denaturation methods. The results indicated that the nickel(II) complex strongly bind with calf-thymus DNA with intrinsic DNA binding constant K-b value of 4.9 x 10(4) M-1 for (3), 4.2 x 10(4) M-1 for (4), presumably via an intercalation mechanism compared to cobalt(III) complex with K-b value of 4.6 x 10(4) M-1 (1) and 4.1 x 10(4) M-1 (2). The DNA Photoclevage experiment shows that, the complexes act as effective DNA cleavage agent. (C) 2012 Elsevier B.V. All rights reserved.

Mononuclear five-coordinate cobalt(II) complexes with N-4-coordinate pyrazole based ligand and pseudohalogens: synthesis, structures, DNA and protein binding study

A series of mononuclear five-coordinate cobalt(II) complexes, Co(dbdmp)(X)]Y, where dbdmp=N,N-diethyl-N,N-bis((3,5-dimethyl-1H-pyrazol-1-yl)methyl)ethane-1, 2-diamine, X=N-3(-)/NCO-/NCS- and Y=PF6-/BF4-/ClO4-, have been synthesized and characterized by microanalyses and spectroscopic techniques. Crystal structures of Co(N-3)(dbdmp)]PF6 (1), Co(N-3)(dbdmp)]ClO4 (3), Co(NCO)(dbdmp)]PF6 (4), Co(NCO)(dbdmp)]ClO4 (6), and Co(NCS)(dbdmp)]ClO4 (9) have been solved by single-crystal X-ray diffraction studies and showed that all the complexes have distorted trigonal bipyramidal geometry; PF6- counter anion containing complexes Co(N-3)(dbdmp)]PF6 and Co(NCO)(dbdmp)]PF6 have chiral space groups. The binding ability of synthesized complexes with CT-DNA and bovine serum albumin (BSA) has been studied by spectroscopic methods and viscosity measurements. The experimental results of absorption titration of cobalt(II) complexes with CT-DNA indicate that the complexes have ability to form adducts and they can stabilize the DNA helix. The cobalt(II) complexes exhibit good binding propensity to BSA protein.

Frequency-Dependent Viscosity of Membrane Solutions

It is shown that dilute suspensions of membranes have strongly frequency-dependent viscosities. This behaviour should be seen in a variety of measurements such as capillary flow, mechanical impedance and ultrasound damping.

Velocity and rotation measurements in acoustically levitated droplets

The velocity scale inside an acoustically levitated droplet depends on the levitator and liquid properties. Using Particle Imaging Velocimetry (PIV), detailed velocity measurements have been made in a levitated droplet of different diameters and viscosity. The maximum velocity and rotation are normalized using frequency and amplitude of acoustic levitator, and droplet viscosity. The non-dimensional data are fitted for micrometer- and millimeter-sized droplets levitated in different levitators for different viscosity fluids. It is also shown that the rotational speed of nanosilica droplets at an advanced stage of vaporization compares well with that predicted by exponentially fitted parameters. (C) 2012 Elsevier B.V. All rights reserved.

Effect of viscosity and surface tension on breakup and coalescence of bicomponent sprays

This work deals with an experimental study of the breakup characteristics of liquids with different surface tension and viscosity from a hollow cone hydraulic injector nozzle induced by pressure-swirl. The experiments were conducted at Reynolds numbers Re-p=9500-23,000. The surface tension and viscosity of the surrogate fuels were altered from 72 to 30 mN/m and 1.1 to 1.6 mN s/m(2), respectively. High speed photography and Phase Doppler Particle Anemometry were utilized to study the atomization process. Velocity and drop size measurements of the spray using PDPA in both axial and radial directions indicate a dependency on surface tension. However, these effects are dominant only at low Reynolds numbers and are negligible at high Reynolds number. Downstream of the nozzle, coalescence of droplets due to collision was also found to be significant and the diameters were compared for different liquids. For viscous fluids up to 1.6 cP, the independent effects of viscosity and injection pressure are studied. In general, the spray cone angle increases with increase in pressure. At high pressures, an increase in viscosity leads to higher drop sizes following primary and secondary breakup compared to water. This study will extend our understanding of surrogate fuel film breakup and highlight the importance of long and short wavelength instabilities. (C) 2013 Elsevier Ltd. All rights reserved

Growth and electron effective mass measurements of strained Si and Si0.94Ge0.06 on relaxed Si0.62Ge0.38 buffers grown by rapid thermal chemical vapor deposition

Abstract: We report the growth and the electron cyclotron resonance measurements of n-type Si/Si0.62Ge0.38 and Si0.94Ge0.06/Si0.62Ge0.38 modulation-doped heterostructures grown by rapid thermal chemical vapor deposition. The strained Si and Si0.94Ge0.06 channels were grown on relaxed Si0.62Ge0.38 buffer layers, which consist of 0.6 mu m uniform Si0.62Ge0.38 layers and 0.5 mu m compositionally graded relaxed SiGe layers from 0 to 38% Ge. The buffer layers were annealed at 800 degrees C for 1 h to obtain complete relaxation. A 75 Angstrom Si(SiGe) channel with a 100 Angstrom spacer and a 300 Angstrom 2 X 10(19) cm(-3) n-type supply layer was grown on the top of the buffer layers. The cross-sectional transmission electron microscope reveals that the dense dislocation network is confined to the buffer layer, and relatively few dislocations terminate on the surface. The plan-view image indicates the threading dislocation density is about 4 X 10(6) cm(-2). The far-infrared measurements of electron cyclotron resonance were performed at 4 K with the magnetic field of 4-8 T. The effective masses determined from the slope of the center frequency of the absorption peak versus applied magnetic field plot are 0.203m(0) and 0.193m(0) for the two dimensional electron gases in the Si and Si0.94Ge0.06 channels, respectively. The Si effective mass is very close to that of a two dimensional electron gas in an Si MOSFET (0.198m(0)). The electron effective mass of Si0.94Ge0.06 is reported for the first time and is about 5% lower than that of pure Si.

Rheology of particle-loaded semi-dilute polymer solutions

We present measurements of the rheology of suspensions of rigid spheres in a semi-dilute polymer solution from experiments of steady and oscillatory shear. For a given value of the shear rate gamma, addition of particles enhances the viscosity and the first normal stress difference but decreases the magnitude of the second normal stress difference. The viscosity eta exhibits a power law variation in gamma for a range of gamma that grows with phi. The first normal stress N-1 is positive and its value grows with phi; it exhibits a clear power law variation for the entire range of gamma that was studied. The second normal stress difference N-2 is negative for the pure polymer solution and much smaller in magnitude than N-1; on addition of particles, its magnitude further decreases, and it appears to change sign at large phi. The behavior of N-1 and N-2 is at odds with the findings of recent studies on particle-loaded dilute polymer solutions and polymer melts. The small-amplitude oscillatory shear experiments show the linear viscoelastic properties, G(') and G('), increasing with phi at a given value of the angular frequency omega. The dynamic viscosity of the suspension differs substantially from its steady shear viscosity, and the difference increases as gamma, omega -> 0.

Zero-bias conductance and energy gap measurements in LaNiO3-YBa2Cu3O7-x junctions

Conductance measurements of junctions between a high- superconductor and a metallic oxide have been carried out along the a-b plane to examine the tunnel-junction spectra. For these measurements, in situ films have been grown on c-axis oriented thin films using the pulsed laser deposition technique. Two distinctive energy gaps have been observed along with conductance peaks around zero bias. The analysis of zero-bias conductance and energy gap data suggests the presence of midgap states located at the centre of a finite energy gap. The results obtained are also in accordance with the d-wave nature of high- superconductors.

Vertical structure and horizontal gradients of aerosol extinction coefficients over coastal India inferred from airborne lidar measurements during the Integrated Campaign for Aerosol, Gases and Radiation Budget (ICARB) field campaign

Quantitative estimates of the vertical structure and the spatial gradients of aerosol extinction coefficients have been made from airborne lidar measurements across the coastline into offshore oceanic regions along the east and west coasts of India. The vertical structure revealed the presence of strong, elevated aerosol layers in the altitude region of similar to 2-4 km, well above the atmospheric boundary layer (ABL). Horizontal gradients also showed a vertical structure, being sharp with the e(-1) scaling distance (D-0H) as small as similar to 150 km in the well-mixed regions mostly under the influence of local source effects. Above the ABL, where local effects are subdued, the gradients were much shallower (similar to 600-800 km); nevertheless, they were steep compared to the value of similar to 1500-2500 km reported for columnar AOD during winter. The gradients of these elevated layers were steeper over the east coast of India than over the west coast. Near-simultaneous radio sonde (Vaisala, Inc., Finland) ascents made over the northern Bay of Bengal showed the presence of convectively unstable regions, first from surface to similar to 750-1000 m and the other extending from 1750 to 3000 m separated by a stable region in between. These can act as a conduit for the advection of aerosols and favor the transport of continental aerosols in the higher levels (> 2 km) into the oceans without entering the marine boundary layer below. Large spatial gradient in aerosol optical and hence radiative impacts between the coastal landmass and the adjacent oceans within a short distance of < 300 km (even at an altitude of 3 km) during summer and the premonsoon is of significance to the regional climate.