DSC studies on the curing kinetics of chitosan–alanine using glutaraldehyde as crosslinker

The curing of chitosan–alanine with glutaraldehyde as curing agent in the presence of Chlorpheniramine Maleate (CPM) is carried out with the help of differential scanning calorimeter (DSC). The effect of concentration of chitosan and percentage of crosslinker on the curing is studied at a rate of 5 °C/min. Cure kinetics are measured from 30 to 200 °C at four different heating rates (3, 5, 7 and 10 °C/min). It is observed that the crosslinking of chitosan–alanine is an exothermic process which results in a positive peak in the curves. An increase in activation energy (E _α) is observed with extent of conversion.     

Indole-based distinctive chemosensors for ‘naked-eye’ detection of CN and HSO4−, associated with hydrogen-bonded complex and their DFT study

Colorimetric detection of anions (HSO₄^? and CN^?) was achieved via analyte triggered colour changing of the dipodal and tripodal sensors in CH₃CN–H₂O (1:1). The sensors exhibited very sharp visual colour changes and fluorescence quenching–enhancing effect upon addition of the HSO₄^? and CN^?. The large downfield shift of the NH proton signals in ¹H-NMR complexation studies and quantum chemical DFT calculations proved the formation of hydrogen-bonded complexes where no proton transfer mechanism was found.     

Proximity Approach to Study the Fusion Barriers for Proton and Helium Induced Reactions

By using various proximity potentials, the fusion barrier heights and positions are calculated for proton and helium induced reactions with targets in the mass range 51≤ A ≤130 and 12≤ A ≤233, respectively. The calculated fusion barriers are parameterized by using the relations RB^Par = aX1 ＋ b and VB^Par = cX2, where X1 and X2 are A2^1/3 and Z1Z2/RB^Par, respectively. The values of the constants a, b and c are different for different versions of proximity potentials. We find that the parameterized forms derived by using Proximity 1977 yield values closer to the empirical data in proton as well as helium induced reactions and can be used further to estimate directly the barrier parameters for the fusion reactions of proton and helium with any target.     

Ionic liquid catalyzed synthesis of 7-phenyl-1,4,6,7-tetrahydro-thiazolo[5,4-d]pyrimidine-2,5-diones

A simple, green and catalyst free one pot synthesis of 7-phenyl-1,4,6,7-tetrahydro-thiazolo[5,4-d]pyrimidine-2,5-diones via a multicomponent reaction between thiazolidine-2, 4-dione (TZD), aromatic aldehyde and urea analogues is described. The ionic liquid has been used as a solvent as well as catalyst for this reaction. This reaction proceeded smoothly in good to excellent yields and offered several other advantages including short reaction time, simple experimental workup procedure and no by-products.     

A Chemodosimetric Probe Based on a Conjugated Oxidized Bis‐Indolyl System for Selective Naked‐Eye Sensing of Cyanide Ions in Water

A new bis‐indolyl‐based colorimetric probe has been synthesized. This allows a Michael‐type adduct formation for the detection of cyanide ions. The probe shows a remarkable color change from red to colorless upon addition of the cyanide ions in pure water. The cyanide ion reacts with the probe and removes the conjugation of the bis‐indolyl moiety of the probe with that of the 4‐substituted aromatic ring. This renders the probe colorless. The mechanism of the reaction of the probe with the cyanide ion was established by using ¹H and ¹³C NMR spectroscopy, mass spectrometry, and kinetic studies.     

Investigation of encapsulation of insulin biotemplate within C-methylresorcin[4]arenes

Solution structure of insulin templated C-methyl resorcin[4]arene nanocapsules has been investigated using neutron scattering. The insulin biotemplate has enhanced the limits of encapsulation and enabled formation of a larger spherical molecular host.     

Unusual room temperature CO(2) uptake in a fluoro-functionalized MOF: insight from Raman spectroscopy and theoretical studies

We herein report an unusual CO(2) adsorption behavior in a fluoro-functionalized MOF {[Zn(SiF(6))(pyz)(2)]·2MeOH}(n) (1) with a 1D channel system, which is made up of pyrazine and SiF(6)(2-) moieties. Surprisingly, desolvated 1 (1') adsorbs higher amounts of CO(2) at 298 K than at 195 K, which is in contrast to the usual trend. Combined Raman spectroscopic and theoretical studies reveal that slanted pyrazine rings in 1' with an angle of 17.2° with respect to the (200) Zn(ii)-Si plane at low temperature block the channel windows and thus reduce the uptake amount.     

Thermoanalytical studies of oxovanadium(IV)hydroxamate complexes

The thermal decomposition behavior of oxovanadium(IV)hydroxamate complexes of composition [VO(acac)(C₆H₅C(O)NHO)] (I), [VO(C₆H₅C(O)NHO)₂] (II), [VO(acac)(4-ClC₆H₄C(O)NHO)] (III), [VO(4-ClC₆H₄C(O)NHO)₂] (IV) (where acac = (CH₃COCHCOCH₃ ^–) synthesized from the reactions of VO(acac)₂ with equi- and bimolar amounts of potassium benzohydroxamate and potassium 4-chlorobenzohydroxamate in THF + MeOH solvent medium has been studied by TG and DTA techniques. TG curves indicated that complexes I, II, and IV undergo decomposition in single step to yield VO₂ as the final residue, while complex III decomposes in two steps to yield VO(acac) as the likely intermediate and VO₂ as the ultimate product of decomposition. The formation of VO₂ has been authenticated by IR and XRD studies. From the initial decomposition temperatures, the order of thermal stability for the complexes has been inferred as IV > I > III > II.     

Redox Behavior of Neptunium(V) in Tributyl Phosphate and <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-Dihexyl Octanamide Extractants Dissolved in <Emphasis Type="Italic">n</Emphasis>-Dodecane

Spectrophotometric investigations have been carried out on the disproportionation of Np(V) to form Np(IV) and Np(VI) in 1.1 mol⋅L⁻¹ solutions of tributyl phosphate (TBP) and in N,N-dihexyl octanamide (DHOA) in n-dodecane medium. The Np(V) was found to coordinate with Np(IV) in 1.1 mol⋅L⁻¹ TBP solution in n-dodecane to form a mixed valence “cation–cation” complex by bonding through an axial oxo group on Np(V). By contrast, this interaction was less prominent in the case of 1.1 mol⋅L⁻¹ DHOA solutions. The effect of 1-octanol, added as phase modifier, on the disproportionation behavior of Np(V) was also investigated. An attempt was made to calculate the disproportionation/reduction rate constants for Np(V) under the conditions of these studies. Absorbance measurements on the Np stripped from organic phases revealed the occurrence of Np(V) in the aqueous phase.     

Transient MHD stagnation flow of a non-Newtonian fluid due to impulsive motion from rest

The transient boundary layer flow and heat transfer of a viscous incompressible electrically conducting non-Newtonian power-law fluid in a stagnation region of a two-dimensional body in the presence of an applied magnetic field have been studied when the motion is induced impulsively from rest. The non-linear partial differential equations governing the flow and heat transfer have been solved by the homotopy analysis method and by an implicit finite-difference scheme. For some cases, analytical or approximate solutions have also been obtained. The special interest are the effects of the power-law index, magnetic parameter and the generalized Prandtl number on the surface shear stress and heat transfer rate. In all cases, there is a smooth transition from the transient state to steady state. The shear stress and heat transfer rate at the surface are found to be significantly influenced by the power-law index N except for large time and they show opposite behaviour for steady and unsteady flows. The magnetic field strongly affects the surface shear stress, but its effect on the surface heat transfer rate is comparatively weak except for large time. On the other hand, the generalized Prandtl number exerts strong influence on the surface heat transfer. The skin friction coefficient and the Nusselt number decrease rapidly in a small interval 0<t^*<1 and reach the steady-state values for t^*≥4.