Spectroscopic identification of S-Au interaction in cysteine capped gold nanoparticles

This study deals with the synthesis of cysteine capped gold nanoparticles with an average size of 12 nm by borohydride reduction and spectroscopic identification of SAu interaction. We have studied the interaction of thiol with gold nanoparticles in aqueous medium by employing UV-vis, Raman, NMR, and FT-IR spectroscopy. The shifting of gold plasmon resonance in the UV-vis spectra shows the stabilization of gold nanoparticles by cysteine. The disappearance of S-H stretching in both the IR and Raman spectra and the shifting of the NMR signals of the protons in close proximity to the metal center supported the existence of the S-Au interaction in cysteine capped gold nanoparticles. The TEM images shows cysteine capped gold nanoparticles as distinct and spherical entities as compared to free colloidal gold nanoparticles.     

On The Approximability Of The Traveling Salesman Problem

We show that the traveling salesman problem with triangle inequality cannot be approximated with a ratio better than when the edge lengths are allowed to be asymmetric and when the edge lengths are symmetric, unless P=NP. The best previous lower bounds were and respectively. The reduction is from H?stad’s maximum satisfiability of linear equations modulo 2, and is nonconstructive. * Supported in part by NSF ITR Grant CCR-0121555. † Supported by NSF award CCR-0307536 and a Sloan foundation fellowship.     

Functional MRI and multivariate autoregressive models

Connectivity refers to the relationships that exist between different regions of the brain. In the context of functional magnetic resonance imaging (fMRI), it implies a quantifiable relationship between hemodynamic signals from different regions. One aspect of this relationship is the existence of small timing differences in the signals in different regions. Delays of 100 ms or less may be measured with fMRI, and these may reflect important aspects of the manner in which brain circuits respond as well as the overall functional organization of the brain. The multivariate autoregressive time series model has features to recommend it for measuring these delays and is straightforward to apply to hemodynamic data. In this review, we describe the current usage of the multivariate autoregressive model for fMRI, discuss the issues that arise when it is applied to hemodynamic time series and consider several extensions. Connectivity measures like Granger causality that are based on the autoregressive model do not always reflect true neuronal connectivity; however, we conclude that careful experimental design could make this methodology quite useful in extending the information obtainable using fMRI.     

The Probability That All Eigenvalues are Real for Products of Truncated Real Orthogonal Random Matrices

The probability that all eigenvalues of a product of m independent \(N \times N\) subblocks of a Haar distributed random real orthogonal matrix of size \((L_i+N) \times (L_i+N)\), \((i=1,\dots ,m)\) are real is calculated as a multidimensional integral, and as a determinant. Both involve Meijer G-functions. Evaluation formulae of the latter, based on a recursive scheme, allow it to be proved that for any m and with each \(L_i\) even the probability is a rational number. The formulae furthermore provide for explicit computation in small order cases.     

Enhancement in nucleate pool boiling heat transfer on nano-second laser processed copper surfaces

ABSTRACT

The present paper reports the experimental investigation of pool boiling heat transfer on multiscale functionalized copper surfaces. Multiscale functionalized surfaces are fabricated by employing the nano-second laser surface process (NLSP) technique. The heat transfer coefficients (HTCs) of functionalized surfaces are estimated experimentally by using water and acetone as pool liquid. Tests are performed at atmospheric pressure, and saturated pool boiling condition with heat flux varyies between 0 and 330 kW/m². The maximum HTCs for functionalized surface and reference polished surface were found to be 41,500 W/m²K and 23,000 W/m²K, respectively, with water and 22,000 W/m²K and 14,000 W/m²K, respectively, with acetone.     

Elastic,impedance spectroscopic and dielectric properties of TiO2 doped nanocrystalline NiCuZn spinel ferrites

ABSTRACT

Nanocrystalline Ni_0.4Cu_0.3Zn_0.3Fe₂O₄ ferrites doped with TiO₂ (0–10?wt %) were prepared by the sol-gel method. Elastic properties of synthesized samples were studied with the help of ultrasonic pulse transmission method. The elastic constants initially increase with an increase in TiO₂ up to 1?wt % and then decline. LCR-Q meter was used to study the dielectric properties within 50?Hz to 5?MHz range of the frequency. The dielectric constant (?′) and dielectric loss tangents were decreased continuously with increased frequency for all the selected samples at room temperature revealing normal dielectric behavior of ferrites. Also, the AC conductivity was increased with an increase in the frequency for all the selected samples. Cole-Cole plots were obtained for all investigated samples and showed single semicircle which indicates that the electrical conduction process appears only due to grain boundaries.     

Biocatalysis for C–S bond formation: Porcine pancreatic lipase (PPL) catalysed thiolysis/hydrothiolation reactions in sole water

In this paper, a biocatalytic route is described wherein PPL, lipase from porcine pancreas, in conjunction with water on reaction with different thiophenols and styrene oxides undergo thiolysis with C-S bond formation without the use of any metal catalysts, oxidants, bases, additives or organic solvents towards formation of β-hydroxysulfides in good to excellent yields with high regioselectivity at room temperature. Furthermore, PPL also facilitates thiophenols to undergo hydrothiolation with styrenes or phenylacetylenes in sole water and thus forming linear thioethers or vinylsulfides respectively via C–S bond formation. In addition to the straightforward and atom-efficient protocol, a gram-scale synthesis of β-hydroxysulfide and recyclability for three consecutive cycles without decrease in efficiency of PPL make our biocatalytic protocol for constructing C–S bond highly valuable from both environmental and economic viewpoints than traditional chemical practices.     

Evaluation of eigenvalues of a smooth potential via Schroedinger transmission across multi-step potential

In a one-dimensional quantal solution of Schroedinger equation, the general expressions for reflection and transmission coefficients are derived for a potential constituting n number of rectangular wells and barriers. These expressions are readily used for the estimation of eigenvalues of a smooth potential which is simulated by a multi-step potential. The applicability of this method is demonstrated with success in potentials with different forms including the most versatile Ginocchio potential where the widely used numerical method like Runge-Kutta integration algorithm fails to yield the result. Accurate evaluation of eigenvalues free from numerical problem for any form of potentials, whether analytically solvable or not, is the highlight of the present multi-step approximation method in the theory of potential scattering.      

Functional analysis of repositioned anilide derivatives as anticancer compounds

Off the different types cancers 40% of the population have been observed to be affected by leukemia. Contemporary therapeutics is focusing on generation of new synthetic analogues that can exert maximum positive physiological effect with minimum dosage and negligible deleterious side effects. New generation pharmacists are focusing on such promising effects of Imatinib (a potential anti-cancer drug molecule), Dasatinib, Pelitinib and Nilotinib. The present research study focuses on novel synthesized anilides derivative against BCR-ABL kinase as potential anti-leukemic agent. Validation of the compounds by molecular docking with specific BCR-ABL kinase confirmed their activity. Toxicity prediction of these compounds helped to identify sustainability as therapeutic molecules. The IC₅₀ values were calculated (211 ug, 175 ug, 272ug for compounds A, B, C resp.) and the mode of cell death was gauged by DNA laddering assay. The cells were observed to be induced for programmed cell death. By validating and in-vivo testing of three synthesized compounds, the compound B was observed to be more stable thermodynamically with a potentially vital active site and appears to be a promising anti-leukemic factor. The present research thus lays a preliminary platform in world of pharmaceutics, where these new analogues appear to be efficient, target specific and less toxic molecules.