Determination of heat transfer coefficient using transient temperature response chart

An inverse finite element computer code is developed to predict surface heat flux and surface temperature in conjunction with the measured thermocouple temperature history. Determination of convective heat-transfer coefficient and combustion gas temperature is carried out employing transient temperature response chart. Examples are illustrated which are typical of those that arise in thermal design of rocket nozzle. The results demonstrate that the method is remarkable in its ability to estimate unknown boundary conditions.     

Branched Multifunctional Polyether Polyketals: Variation of Ketal Group Structure Enables Unprecedented Control over Polymer Degradation in Solution and within Cells

Multifunctional biocompatible and biodegradable nanomaterials incorporating specific degradable linkages that respond to various stimuli and with defined degradation profiles are critical to the advancement of targeted nanomedicine. Herein we report, for the first time, a new class of multifunctional dendritic polyether polyketals containing different ketal linkages in their backbone that exhibit unprecedented control over degradation in solution and within the cells. High-molecular-weight and highly compact poly(ketal hydroxyethers) (PKHEs) were synthesized from newly designed α-epoxy-ω-hydroxyl-functionalized AB(2)-type ketal monomers carrying structurally different ketal groups (both cyclic and acyclic) with good control over polymer properties by anionic ring-opening multibranching polymerization. Polymer functionalization with multiple azide and amine groups was achieved without degradation of the ketal group. The polymer degradation was controlled primarily by the differences in the structure and torsional strain of the substituted ketal groups in the main chain, while for polymers with linear (acyclic) ketal groups, the hydrophobicity of the polymer may play an additional role. This was supported by the log?P values of the monomers and the hydrophobicity of the polymers determined by fluorescence spectroscopy using pyrene as the probe. A range of hydrolysis half-lives of the polymers at mild acidic pH values was achieved, from a few minutes to a few hundred days, directly correlating with the differences in ketal group structures. Confocal microscopy analyses demonstrated similar degradation profiles for PKHEs within live cells, as seen in solution and the delivery of fluorescent marker to the cytosol. The cell viability measured by MTS assay and blood compatibility determined by complement activation, platelet activation, and coagulation assays demonstrate that PKHEs and their degradation products are highly biocompatible. Taken together, these data demonstrate the utility this new class of biodegradable polymer as a highly promising candidate in the development of multifunctional nanomedicine.     

Ultrasonic study on binary mixture containing dimethylformamide and methanol over the entire miscibility range (0 < x < 1) at temperatures 303–323 K

The experimental density and speed of ultrasound measurements in connection with literature data have been measured for pure N,N-dimethylformamide (DMF), methanol and their binary mixtures over the whole miscibility range at different temperatures 303, 308, 313, 318 and 323 K. These parameters were used to determine the adiabatic compressibility, intermolecular free length, molar compressibility, molar sound velocity, acoustic impedance, relaxation strength and their excess values. The variation of these parameters with composition of mixture indicates the nature and extent of interaction between unlike molecules. The non-ideal behavior of the system studied was explained on the basis of the dipole-induced dipole interactions and hydrogen bonding. The complex formation through intermolecular hydrogen bonding was confirmed from the recorded FTIR spectra. Available thermal energy breaks the bonds between the associated molecules into their respective monomers on increasing the temperature.     

Numerical solution of the Navier-Stokes equations using a finite element method

A finite element algorithm for solving the Navier-Stokes equations is presented for the analysis of high-speed viscous flows. The algorithm uses triangular elements. The unsteady equations are integrated to steady state with a Runge-Kutta time-marching scheme. A postprocessing artificial dissipation term is introduced to stabilize the computations and to dampen dissipation errors. Numerical results are compared with the calculation of uniform flow on a rectangular region which encounters an embedded oblique shock. A shock/turbulent boundary layer problem is also solved and results are compared with experimental data. It is shown that the postprocessing smoothing term and boundary conditions similar to the finite difference method work well in the present numerical studies.     

Water-soluble complexes from random copolymer and oppositely charged surfactant. 2. Complexes of poly(ethylene glycol)-based cationic random copolymer and bile salts

The complexes formed between the positively charged random copolymers (RCPs) of methoxy-poly(ethylene glycol) monomethacrylate (MePEGMA) and (3-(methacryloylamino)propyl)trimethylammonium chloride (MAPTAC) with oppositely charged biosurfactants (bile salts) were studied using turbidimetric titration, steady-state fluorescence, dynamic light scattering, and electron microscopy. Studies showed that the complexes of the RCPs of MAPTAC and MePEGMA with less than 68 mol % of PEG content precipitate in water, whereas the complexes of the copolymer with 89 and 94 mol % of PEG content do not precipitate in the entire range of composition of the mixture including stoichiometric compositions when the electroneutral complexes are formed. The complexes with true hydrophobic domains, which are a prerequisite characteristic to serve as a carrier, can be obtained at much lower concentration than the critical micelle concentration of the corresponding surfactant. For a particular surfactant, hydrophobic domains are obtained at lower Z-/+ for the random copolymer with lower PEG content. The hydrodynamic radii of these complexes vary over a range of 20-35 nm. Overall results reveal that these complexes are qualitatively similar to the polyion complex micelles or block ionomer complexes obtained from the block copolymers and oppositely charged surfactants. As the surfactants used in this study are biocompatible, we hope that these soluble particles will be promising vectors in the field of drug delivery.     

Study of the potassium ion insertion of the electrodeposited electrochromic tungsten trioxide thin films

Various types of dynamic adjustable optical shutters have been proposed; they are called as “smart windows”. The electrochromic smart window utilizes the phenomenon of electrochromism. Electrochromism is the property of a material such that its color is changed by an electrochemical redox reaction. Numerous inorganic and organic electrochromic materials have been examined. During the color-bleach process, the redox reaction of the host material causes injection or ejection of both cation (or anion) and an electron (or hole). So it behaves as a mixed ion conductor and hence it has recently attracted interest in the field of solid state ionics. At present, several prototypes of electrochromic smart windows have been proposed and some of them are commercially available. The cathodic electrochromic oxides consist of n-type semiconductors such as TiO₂, V₂O₅, WO₃ and MoO₃. Among them, WO₃ has been intensively examined and used for most electrochromic devices. These materials are cathodically colored in blue. The electrochromic reaction is expressed by $$xA^ + + MO_y \left( {transparent} \right) + x e^ - \Leftrightarrow A_x MO_y \left( {blue} \right)\left( {A = H, Li, Na, K \ldots , MO_y = metal oxide} \right)$$ where the cation A⁺ and electron e^? are co-injected into the host oxide MO_y which results in the formation of the nonstiochiometric compound A_xMO_y. Here the electrodeposition method is used to deposite WO₃ films under by galvanostatic conditions. The parameters like deposition time, deposition temperature, electrolyte concentration, pH and bath temperature are optimized. The XRD results show the triclinic structure for the as-deposited film. The film shows the same structure after intercalation but the peak intensity is different. The tungsten trioxide thin films show the colour change during the intercalation and retrace the original colour. The diffusion coefficient for K⁺ ion is calculated by using the Randles-Servick equation. In this paper the electrochromic properties, the optical properties of the as deposited, ion intercalated and deintercalated WO₃ films and the diffusion coefficient values are presented.     

Attractive bridging interactions in dense polymer brushes in good solvent measured by atomic force microscopy

Using an atomic force microscope (AFM), we have investigated the interaction forces exerted by latex particles bearing densely grafted polymer brushes consisting of poly(N,N-dimethylacrylamide) (PDMA), poly(methoxyethylacrylamide) (PMEA), poly(N-isopropylacrylamide) (PNIPAM), and PMEA-b-PNIPAM in aqueous media (good solvent). The brushes were prepared by controlled surface-initiated atom transfer radical polymerization, and the hydrodynamic thicknesses were measured by dynamic light scattering. The molecular weight (Mn), grafting density (sigma), and polydispersity (PDI) of the brushes were determined by gel permeation chromatography and multiangle laser light scattering after cleaving the polymer from the latex surface by hydrolysis. Force profiles of PDMA (0.017 nm(-2) < or = sigma < or = 0.17 nm-2) and PMEA (sigma = 0.054 nm-2) brushes were purely repulsive upon compression, with forces increasing with Mn and a, as expected, due to excluded volume interactions. At a sufficiently low grafting density (sigma = 0.012 nm-2), PDMA exhibited a long-range exponentially increasing attractive force followed by repulsion upon further compression. The long-range attractive force is believed to be due to bridging between the free chain ends and the AFM tip. The PNIPAM brush exhibited a bridging force at a grafting density of 0.037 nm(-2), a value lower than the sigma needed to induce bridging in the PDMA brush. Bridging was therefore found to depend on grafting density as well as on the nature of the monomer. The grafting densities of these polymers were larger than those typically associated with bridging. Bridging interactions were used to confirm the presence of PNIPAM in a block copolymer PMEA-b-PNIPAMA brush given that the original PMEA homopolymer brush produced a purely repulsive force. The attractive force was first detected in the block copolymer brush at a separation that increased with the length of the PNIPAM block.     

Photo-fries reaction of 1-naphthyl cinnamate

The photo-Fries reaction of 1-naphthyl cinnamate afforded 2-cinnamoyl-1-naphthol. Likewise, 1-naphthylp-methyl-cinnamate gave 2-(p-methylcinnamoyl)-1-naphthol. The product chalcones were cyclised into the respective flavanones.     

Validation of a Stability Indicating LC Method for Amiodarone HCL and Related Substances

A simple, rapid and sensitive isocratic high performance liquid chromatographic (HPLC) method has been developed for the estimation of purity and quantitative determination of Amiodarone HCl active pharmaceutical ingredient (API).The method describes a quantitative estimation of five process related impurities of Amiodarone HCl with a resolution of more than or near to 3.0 between each impurity. These five known related substances are estimated by a simple, rapid and accurate reverse phase isocratic HPLC method. The method has been validated for the determination of assay and related substances in Amiodarone HCl API, using a C₈ column. The elution is carried out using a mobile phase consisting of water-methanol-acetic acid with a pH 5.8. For the quantitative determination of these relative substances, a relative response factors have been determined for all five related substances with respect to Amiodarone HCl. The precision (system precision, method precision and intermediated precision) is demonstrated for both the assay as well as related substances on six independent sample preparations. Accuracy of the method (recovery) is demonstrated for both Amiodarone and each of the five related substances. Specificity of the method is demonstrated by forced degradation study of Amiodarone HCl API under various stress conditions. The method is found to be stability indicating and useful for the analysis of assay and related substances of Amiodarone HCl API in a routine quality control laboratory and for the stability studies of drug substance.     

Facile preparation of potassium 32P-phosphonate

Simple and easy to operate experimental assemblies were for the first time designed for the successful preparation of potassium ³²P-phosphonate from ³²P-orthophosphate. Phosphate was first converted to phosphoryl chloride by reacting with phosphorus pentachloride. Then the phosphoryl chloride formed was reduced to phosphorus trichloride by heating with charcoal at 650 °C. The latter was absorbed in aqueous potassium hydroxide to obtain potassium ³²P-phosphonate at a yield of about 75%. The chemical purity of ³²P-phosphonate was assayed using ion-chromatography and the radiochemical purity was also determined.The authors thank Shri. J. K. Ghosh, Chief Executive, BRIT and Dr. N. Sivaprasad, General Manager, RPh & ILCJ, BRIT for their support and encouragement throughout this work.