Study of interactions of various ionic species with solvents toward the design of receptors

In earlier studies, the interactions of isolated ionic species with various solvents were investigated using ab initio calculations. The ionic species investigated included cations (proton, hydronium, ammonium, and metal cations) and anions (single electron, hydroxide, and halide anions). However in the present study, we investigate the interactions of these ionic species with the solvent in the presence of other competing ionic species. We also elaborate on how the information obtained from these extensive studies have been employed in designing and synthesizing various kinds of novel ionophores and receptors.     

An estimate of the heat fluxes to the surface of blunt bodies moving at hypersonic velocity in the atmosphere

The problem of the chemically equilibrium three-dimensional boundary layer on a blunt body which is in motion in the atmosphere is considered. A solution of the system of equations of the boundary layer is found by the method of successive approximations, and simple analytic expressions are written in the first approximation for the surface friction and heat flux coefficients. Formulae are obtained in the final form for estimating the convective heat flux in the neighbourhood of the critical point of spherical blunting.     

Design and synthesis of new bidentate phosphoramidite ligands for enantioselective copper-catalyzed conjugate addition of diethylzinc to enones

Several thioaryl- and phosphino-phosphoramidite ligands have been synthesized from commercially available β-aminoalcohols. This new family of bidentate ligands are highly active in the enantioselective copper-catalyzed conjugate addition of diethylzinc to both cyclic and acyclic enones showing moderate to good enantiomeric excesses of up to 81%.     

Magnetic fluid behavior in uniform DC,AC, and rotating magnetic fields

New flows and instabilities are demonstrated for magnetic fluids and by dual analogy to dielectric fluids. If a fluid drop is contained in a thin gap between two glass plates (Hele–Shaw cell) with a simultaneously applied in-plane rotating field and a DC axial field, smooth spirals or an abrupt transformation to many small droplets can occur. A preliminary minimum magnetization and surface energy analysis is presented to model the abrupt transformation in ferrofluids. An analysis of effective DC magnetoviscosity is also presented for planar Couette flow with an applied uniform DC field transverse to a duct axis with the effective magnetoviscosity and flow spin velocity calculated as a function of field strength. Related Couette viscometer measurements of ferrofluid viscosity show zero and negative magnetoviscosity values for rotating magnetic fields.     

Large area bolometers for millimeter-wave power calibration

An accurate monolithic power meter has been developed for millimeter-wave applications. The detector is a large-area Bismuth bolometer, integrated on a fused-Quartz substrate. It simply measures the temperature change caused by the absorption of millimeter-wave radiation. The power meter is simple to fabricate, inexpensive, and can be easily calibrated using a low-frequency network. The measured responsivity for a 50 bolometer, with an area of 1×1cm, at a bias of 1V. and a video modulation of 100Hz, is 1mV/W. The noise spectrum exhibits a 1/f rolloff till 1KHz, and is limited by the Johnson noise for higher frequencies. The NEP of the detector is 3WHz^–1/2 at a video modulation of 1KHz. It is possible to decrease the current NEP by fabricating bolometers with higher responsivities. Possible application areas are absolute power calibration and localized power density measurements at millimeter and submillimeter wavelengths.     

Trace element concentration in head hair of the inhabitans of the Rawalpindi-Islamabad area

Instrumental neutron activation analysis technique has been used to determine the concentration levels of 12 trace elements in human head hair samples collected from 105 individuals living in various areas of Rawalpindi-Islamabad. The data show that the average concentrations of Mn, Co, Ag and Au are higher in the female group as compared to the male group. Four individuals were found to have elevated levels of Se due to the use of anti-dandruff shampoos, whereas two individials had elevated levels of Hg.     

An electrolytic device for preparation of hydrogen and oxygen from water for isotopic analysis

An electrolytic device for decomposition of water has been developed which readily gives hydrogen and oxygen for isotopic measurement with a mass spectrometer. A 20-mul sample can be decomposed quantitatively in 10 min with good reproducibility. The results produced are comparable with those obtained by reduction with uranium.     

Synthesis, X-ray crystal structures, and gas sorption properties of pillared square grid nets based on paddle-wheel motifs: implications for hydrogen storage in porous materials

A systematic modulation of organic ligands connecting dinuclear paddle-wheel motifs leads to a series of isomorphous metal-organic porous materials that have a three-dimensional connectivity and interconnected pores. Aromatic dicarboxylates such as 1,4-benzenedicarboxylate (1,4-bdc), tetramethylterephthalate (tmbdc), 1,4-naphthalenedicarboxylate (1,4-ndc), tetrafluoroterephthalate (tfbdc), or 2,6-naphthalenedicarboxylate (2,6-ndc) are linear linkers that form two-dimensional layers, and diamine ligands, 4-diazabicyclo[2.2.2]octane (dabco) or 4,4'-dipyridyl (bpy), coordinate at both sides of Zn(2) paddle-wheel units to bridge the layers vertically. The resulting open frameworks [Zn(2)(1,4-bdc)(2)(dabco)] (1), [Zn(2)(1,4-bdc)(tmbdc)(dabco)] (2), [Zn(2)(tmbdc)(2)(dabco)] (3), [Zn(2)(1,4-ndc)(2)(dabco)] (4), [Zn(2)(tfbdc)(2)(dabco)] (5), and [Zn(2)(tmbdc)(2)(bpy)] (8) possess varying size of pores and free apertures originating from the side groups of the 1,4-bdc derivatives. [Zn(2)(1,4-bdc)(2)(bpy)] (6) and [Zn(2)(2,6-ndc)(2)(bpy)] (7) have two- and threefold interpenetrating structures, respectively. The non-interpenetrating frameworks (1-5 and 8) possess surface areas in the range of 1450-2090 m(2)g(-1) and hydrogen sorption capacities of 1.7-2.1 wt % at 78 K and 1 atm. A detailed analysis of the sorption data in conjunction with structural similarities and differences concludes that porous materials with straight channels and large openings do not perform better than those with wavy channels and small openings in terms of hydrogen storage through physisorption.     

Controlled self-assembly of nanoporous alumina for the self-templating synthesis of polyaniline nanowires

In this report, the self-templating synthesis of polyaniline nanowires on prestructured aluminum is described, emphasizing that anodization and electropolymerization can occur at the same time by a single electrochemical process. The method is based on the principle that the anodization of predefined aluminum in H₂SO₄ leads to the formation of highly ordered porous alumina and aniline monomer can be electrochemically polymerized in the formed porous alumina by the anodic reaction. XPS analysis reveals that polyaniline nanowires prepared in this work is protonated emeraldine.