Model-based processing of a holographic moiré

A state space model for the determination of dual phase distributions in a holographic moiré in the presence of nonsinusoidal waveforms, random noise, and miscalibration of the piezoelectric (PZT) devices is proposed. The extraction of these phase terms requires incorporating two PZTs into the moiré setup. A Toeplitz approximation method (TAM) is applied for phase determination, and modification to the Toeplitz covariance matrix formed from the phase-shifted moiré fringes by application of a denoising step in the state-feedback matrix is proposed. This step ensures that the phase terms can even be estimated at a signal-to-noise ratio much lower than that of the original TAM or by our previously suggested polynomial based method.     

Conformational Study of Spectrin in Presence of Submolar Concentrations of Denaturants

The presence of very low concentrations of the commonly used chemical denaturants, guanidinium chloride (GdmCl) and urea brought about conformational changes in the erythrocyte membrane skeletal protein, spectrin. Evidences in support of changes in the quaternary structure of spectrin have been put forward from quenching study of tryptophan fluorescence, by both steady state and time-resolved measurements, using acrylamide as the quencher. It revealed significant differences between the Stern–Volmer quenching constants (K_SV) and the fraction of accessible tryptophans (f_e) observed in absence and presence of GdmCl and urea concentrations below 1 M at which the association of the two subunits remains intact. The steady state anisotropy of both the spectrin tryptophans and the spectrin-bound fluorescence probe, Prodan also indicate changes in the overall flexibility of the spectrin dimer, originating from changes in the quaternary structure of spectrin. Studies on the binding of Prodan, further indicate that conformational changes also occur in spectrin near the Prodan-binding site at the terminal domain of the protein which is reflected in 3–4 fold decrease in the affinity of binding of Prodan to spectrin in the presence of GdmCl and urea compared to that observed in the absence of the denaturants. The dissociation constant (K_d) of Prodan to spectrin is 0.43 M at 25°C.     

Samarium Barbier reactions of alpha-iodomethyloxazoles and thiazoles with aliphatic aldehydes

[reaction: see text] The reductive coupling of substituted alpha-iodomethyloxazoles and thiazoles with aliphatic aldehydes under Barbier conditions provides an effective method for the direct incorporation of intact heterocyclic systems.     

Polarity Estimate of the Hydrophobic Binding Sites in Erythroid Spectrin: A Study by Pyrene Fluorescence

The apparent dielectric constant, , of the hydrophobic pyrene binding sites in erythroid spectrin and human serum albumin (HSA) were estimated using the linear relationship [Turro, N.J., Kuo, P.L., Somasundaran, P. and Wong, K. (1986). J. Phys. Chem. 90, 288–291] between the ratio of the first (373 nm) and the third (384 nm) vibronic peak intensities (l₁/l₃) and the dielectric constant of the bulk medium. Binding of the hydrophobic fluorescent probe, pyrene, to erythroid spectrin and HSA was determined from concentration dependent change in the ratio l₁/l₃ from the emission spectra. Pyrene binds to spectrin (K_app = 6.2 × 10⁶ M^–1) with a higher affinity than that of HSA (K_app = 3.7 × 10⁴ M^–1) and the binding in both cases are saturable. The for spectrin and HSA was estimated to be 7 ± 2.1 and 5.4 ± 1.6 respectively. A case study with spectrin, covalently labeled with pyrene maleimide, have been presented for aging of pyrene-labelled spectrin showing the potential of the use of vibrational peak ratios (l₁/l₃) in the study of polarity of microenvironments in the neighborhood of cysteine residues of a protein. Large changes in the pyrene spectral components indicated conformational changes in the cysteine microenvironment of the protein upon storage at 4°C.     

Hot electron diffusion in CdTe

The parallel and transverse components of diffusion constants of electrons in CdTe have been computed for fields of 30, 40, and 50 kV/cm using the Monte Carlo method. Results are presented for the velocity autocorrelation function and for the ac diffusion constants for two models of energy band structure and scattering constants, used earlier in the literature. The diffusion constants as obtained from the two models are significantly different, but none are in agreement with the available experimental results.     

The use of quinoxaline-2-carboxylic acid and its derivatives as analytical reagents

Quinoxaline-2-carboxylic acid and 3-chloro and 3-hydroxy derivatives have been studied as analytical reagents. The solubility products of the metal salts, the optimum pH range for complete precipitation and the thermal behaviours of the metal complexes have been established. Quinoxaline-2-carboxylic acid allows the gravimetric determination of Cu(II), Cd(II), Zn(II), Co(II), Ni(II) and Pd(II); with the 3-chloro and 3-hydroxy derivatives, only palladium(II) could be precipitated quantitatively.     

Borel complexity of the space of probability measures

Using a technique developed by Louveau and Saint Raymond, we find the complexity of the space of probability measures in the Borel hierarchy: if is any non-Polish Borel subspace of a Polish space, then , the space of probability Borel measures on with the weak topology, is always true , where is the least ordinal such that is .