Disposition of copper(II) inβ-cyclodextrin

Distances of glucose protons in-cyclodextrin (BCD) from copper(II) in copper(II)--cyclodextrin have been determined from¹H NMR spin-lattice relaxation time (T ₁) measurements for the first time. Very lowT _1p /T _2p values indicated the dipolar mechanism to be the most dominant one in determining the paramagnetic contribution to relaxation. The distances of copper(II) from BCD glucose protons indicated copper(II) to be present almost in the centre, inside the cavity in the same plane as H-1 and H-4. An average distance of about 5.0–5.9 Å was obtained for copper(II) from the H-2, H-3, H-1, H-4 and H-6 a and b protons in BCD.     

Sodium Dithionite Reduction of 2S,5R-(-)-menthone and R-(+)-pulegone in the Presence of β-Cyclodextrin and Hydroxypropyl-β-cyclodextrin

Menthone on reduction with sodium dithionite,showed a good amount of mentholformation in the water/DMF system, withincreasing -cyclodextrin (-CD)concentration from 47.0% for 0.1 equivalent of-CD to 93.5% for 1 equivalentof -CD. Increasing hydroxypropyl--cyclodextrin(HP-CD) gave higher menthol/neomenthol (M/N) ratiosfrom 2.8 to 3.5. In the case of pulegone,increasing -CD showed an increase in the formationof menthols in thewater/DMF system from 13.3% for 0.1 equivalent of-CD to 78.1% for 1equivalent of -CD with greater proportions ofneomenthol and neoisomenthol.However, HP-CD which showed only marginalenhancement in the formationof menthol from menthone (32.1–41%), exhibiteda greater proportion of mentholformation in the case of pulegone (55.1%).However, the phase-transfer capabilityof HP-CD was not found to be significant.     

Extracting the frequencies of the pinna spectral notches in measured head related impulse responses

The head related impulse response (HRIR) characterizes the auditory cues created by scattering of sound off a person's anatomy. The experimentally measured HRIR depends on several factors such as reflections from body parts (torso, shoulder, and knees), head diffraction, and reflection/ diffraction effects due to the pinna. Structural models (Algazi et al., 2002; Brown and Duda, 1998) seek to establish direct relationships between the features in the HRIR and the anatomy. While there is evidence that particular features in the HRIR can be explained by anthropometry, the creation of such models from experimental data is hampered by the fact that the extraction of the features in the HRIR is not automatic. One of the prominent features observed in the HRIR, and one that has been shown to be important for elevation perception, are the deep spectral notches attributed to the pinna. In this paper we propose a method to robustly extract the frequencies of the pinna spectral notches from the measured HRIR, distinguishing them from other confounding features. The method also extracts the resonances described by Shaw (1997). The techniques are applied to the publicly available CIPIC HRIR database (Algazi et al., 2001c). The extracted notch frequencies are related to the physical dimensions and shape of the pinna.     

Imaging of human breast tissue using polarization sensitive optical coherence tomography

We report a study on the use of polarization sensitive optical coherence tomography (PSOCT) for discriminating malignant (invasive ductal carcinoma), benign (fibroadenoma) and normal (adipocytes) breast tissue sites. The results show that while conventional OCT, that utilizes only the intensity of light back-scattered from tissue microstructures, is able to discriminate breast tissues as normal (adipocytes) and abnormal (malignant and benign) tissues, PS-OCT helps in discriminating between malignant and benign tissue sites also. The estimated values of birefringence obtained from the PSOCT imaging show that benign breast tissue samples have significantly higher birefringence as compared to the malignant tissue samples.     

纳米贵金属插入的粘土用于催化选择性加氢反应

 The use of clay minerals in the synthesis of nanosized noble metal particles to give increased catalytic activity was investigated. Nanosized platinum and ruthenium catalysts intercalated in clay (montmorillonite/hectorite) were synthesised and their catalytic activity was evaluated for the selective hydrogenation of three different α,β-unsaturated aldehydes, namely, crotonaldehyde, cinnamaldehyde, and citral, in a gas phase microreactor. The metal nano-sol was prepared by the chemical reduction of its precursor by the micellar technique in the presence of cetyl trimethyl ammonium bromide (CTAB), and the micelle stabilized metal particles were intercalated in the clay mineral by ion exchange. TEM micrographs of the catalyst particles showed that the metal particles were in the nanometre range. The average diameters of the particles were 1–25 nm. The effects of temperature, metal loading, and hydrogen flow rate on the catalytic activity and selectivity for α,β- unsaturated alcohol were studied. The results were correlated with the structural properties of the catalysts. The products formed in each reaction over the different catalysts showed that the catalysts were very active for hydrogenation, and the selectivity for the desired product, namely, α,β-unsaturated alcohol, was good. The metal catalysts intercalated in montmorillonite showed better selectivity than that in hectorite because of its higher acidity. Increased selectivity for α,β-unsaturated alcohol was observed with increased flow rate of hydrogen.     

Muons as local probes of three-body correlations in the mixed state of type-II superconductors

The vortex glass state formed by magnetic flux lines in a type-II superconductor is shown to possess nontrivial three-body correlations. While such correlations are usually difficult to measure in glassy systems, the magnetic fields associated with the flux vortices allow us to probe these via muon-spin rotation measurements of the local field distribution. We show via numerical simulations and analytic calculations that these observations provide detailed microscopic insight into the local order of the vortex glass and more generally validate a theoretical framework for correlations in glassy systems.     

Nano-ionic thin films of gadolinia-doped ceria prepared by pulsed laser ablation

Microstructural properties of nano-ionic thin films of gadolinia-doped ceria (GDC) prepared by pulsed laser ablation from sintered targets of gadolinia (5–20 mol%) doped ceria are investigated. The ionic conductivity measurements of the sintered pellets showed a decrease in the activation energy from 1.1 to 0.65 eV for 5 and 30 mol% gadolinia-doped ceria, respectively. The microstructural properties of the GDC films as a function of substrate temperature, oxygen partial pressure, and laser energy show that the films are polycrystalline in the entire range of substrate temperature. The grain size is found to increase with increasing temperature up to 873 K. Further improved crystallinity is noticed for the films grown with oxygen partial pressure of 0.1–0.2 mbar. X-ray diffraction and transmission electron microscopy (TEM) reveal nanocrystalline grains with textured growth along <111> orientation in these films at low substrate temperature and at lower oxygen partial pressure. TEM study shows a uniform distribution of nanocrystal of 8–10 nm for energies ≤200 mJ/pulse, and nanocrystals embedded in a large crystalline matrix of doped ceria for energies in the range 400–600 mJ/pulse. Raman spectroscopy also confirms the defects in these films. The study also reveals that the substrate temperature and oxygen partial pressure could influence preferred orientation, while the laser energy could significantly influence defect concentration in these films. Invited paper presented at the Third International Conference on Ionic Devices (ICID 2006), Chennai, Tamilnadu, India, Dec. 7–9, 2006.     

Solidification of selenium melt under pressure up to 6.5 GPa

Abstract

High purity selenium samples were melted under high pressure (≤6.4 GPa) and quenched at various rates ranging from 2 K s^?1 to 500 K s^?1 and the recovered material was examined by X-ray diffraction and electron microscopy. In the entire range of pressure and cooling rate, the melt was found to solidify into a polycrystalline aggregate of the trigonal phase of selenium. The samples obtained by slow cooling of the melt at 6.4 GPa contain, in addition to crystalline phase, regions which appear to be amorphous.