Photoelastic investigation of metal-forming processes using new sapphire dies

Experimental Techniques -     

Flow boiling heat transfer on a heating element restricted by an interference sleeve

The flow boiling phenomenon over a heated tube restricted by an interference sleeve, which is a passive enhancement technique, has been analysed using a semi-empirical approach. The liquid boiled was water flowing through an annular cross-section. A model developed earlier for the case of pool boiling over porous surfaces has been adapted after modification to pool boiling with interference surfaces using equivalent geometrical parameters and a modified permeability factor. This was further extended to saturated flow boiling situation using an additive mechanism. The single phase heat transfer coefficient required for the additive mechanism is obtained from an experimental correlation developed in the present study. The suppression factors evaluated for the eight sleeve geometries used in the present investigation are expressed in terms of the single phase Reynolds number and the Martinelli parameter. Very good agreement was observed between the model predictions and experimental data validating the mechanisms postulated. Further, a purely empirical correlation based on the present experimental data has been proposed to estimate the two-phase heat transfer coefficient. While the empirical correlation shows a better fit with the experimental data, the additive model has a physical basis.     

Bending of a uniformly loaded clamped sector plate

The paper involves the expansion of the biharmonic deflection function in a series of non-orthogonal functions satisfying the condition of clamped edges. Each of these non-orthogonal functions is expanded in a series of orthogonal functions which satisfy a certain fourth order differential equation and the boundary conditions implied by the fact that the edges are clamped. This reduces the bending of a uniformly loaded clamped sector plate to the solution of a linear algebraic system of equations. Numerical results for the deflection of the central line are obtained when the semi-sector angle is 15 degrees.     

Point force in a MHB rotating fluid

We consider the steady flow of an inviscid, rotating fluid confined in a cylinder under the influence of a uniform axial magnetic field, in the presence of an isolated point force. It is found that, the wave-like terms, infinite in number, occurring on the downstream side are not persistent and decay at far distances, in contrast to the non-magnetic case. Also the presence of a uniform magnetic field induces an additional finite number of decaying modes on the upstream side and an infinite number of similar modes on the downstream side, which reduce to the geostrophic terms, in the corresponding non-magnetic case. The downstream solution reveals that discontinuities occur in the velocity gradients inside the fluid region.     

A Facile Route for the Synthesis of Novel Heterocyclic Prostaglandin F2α Analogs

A general synthetic approach has been developed for heterocyclic prostaglandins (PGF_2α type) starting from the key intermediate ( 6 ). (±) 6 was obtained from (±) ‐Corey lactone. The key intermediate (±) 6 was, in turn, converted in to several new heterocyclic prostaglandins consisting of furan and thiophene moieties in ω‐side chain in two to three steps. Horner–Wadsworth–Emmons reaction and Grignard reaction as the key reactions in these transformations.     

trans-4-Hydroxy-l-proline: a novel starting material for N-alkylpyrroles synthesis

The reaction of aldehydes with trans-4-hydroxy-l-proline was studied for the first time, resulting in the formation of N-alkylpyrroles in good to excellent yields, via decarboxylation followed by redox isomerization under neutral conditions. The neutral conditions allow access to efficient synthesis of N-alkyl pyrroles with high functional group tolerance.     

Calcium phosphate bioceramics and bioceramic composites

This paper reviews selected aspects of research work carried out in bioceramics and bioceramic composites at the Ceramics Laboratory IIT, Bombay, India. The focus here is in understanding and developing calcium hydroxyapatite (HA) bioceramics and biocomposites, including calcium hydroxyapatite-titanium (HA-Ti) and calcium hydroxyapatite-polymethylmethacrylate (HA-PMMA). Research involving apatite-wollastonite (AW) bioglass ceramics and bioceramic composites of AW with titanium as well as with polymethylmethacrylate will be presented in a future article. HA powders were precipitated from solutions with varying Ca/P ratios and calcined at a range of temperatures to investigate their structural evolution. HA-Ti composites were prepared by powder metallurgical processes using HA powders calcined at 400 °C, followed by compaction at 600 MPa and subsequent sintering at 1,000–1,200 °C. HA-PMMA composites containing up to 40 wt% PMMA were prepared by hot pressing at 150 °C and 150 MPa pressure. The phases present in the various materials were identified by X-ray diffraction (XRD) and functional groups by FTIR, while the sample morphologies were investigated by SEM. The bioactivity of the composites was evaluated by soaking them in simulated body fluid (SBF) for 7 days, to evaluate their apatite-forming ability (a key indicator of bioactivity). The results obtained are interpreted to aid in the development of “design rules” for the use of such biocomposite materials in specific biomedical application.     

Synthesis of 3,6-epoxy[1,5]dioxocines from 2-hydroxyaromatic benzaldehydes

Convenient and facile one step synthesis of medicinally relevant new 3,6-epoxy[1,5]dioxocines from 2-hydroxyaromatic benzaldehydes is described. The scope of the method was validated by examining the use of both electron rich and electron-deficient 2-hydroxyaromatic benzaldehydes.     

Total synthesis of radicamine B and 5-epi-radicamine B

Radicamine B 5 was synthesized from p-hydroxy benzaldehyde 7 stereoselectively using acid catalysed amido cyclisation with the help of neighbouring group participation (NGP). Without NGP both radicamine B 5 and its epimer 5-epi radicamine B 6 were obtained. The key steps of the synthesis are Sharpless asymmetric dihydroxylations and acid mediated amido cyclisation.     

A novel piezoelectric immunosensor for the detection of malarial Plasmodium falciparum histidine rich protein-2 antigen

A novel piezoelectric (PZ) immunosensor for the direct detection of malarial Plasmodium falciparum histidine rich protein-2 (PfHRP-2) antigen was developed. The mixed self-assembled monolayers (SAMs) of thioctic acid and 1-dodecanethiol were formed on gold surface of quartz crystal. Cyclic voltammetry, electrochemical impedance spectroscopy and surface Raman spectroscopy techniques were used to characterize the mixed SAMs. The rabbit anti-PfHRP-2 antibodies were coupled on mixed SAM modified gold surface of quartz crystal via NHS/EDC activation method. The PZ immunosensor was applied to detect PfHRP-2 in the linear range of 15-60 ng/ml with a detection limit of 12 ng/ml. It was also found that even after 14 days of storage, 50% of the activity still remained. Clinical human serum samples were tested with this method, and the results were in agreement with those obtained from commercially available ICT kit (NOW^® Malaria).