Kinetics and mechanism of the ruthenium(III)-catalysed oxidation of aminoalcohols by cerium(IV) in a sulphuric acid medium

Summary The kinetics of the ruthenium(III)-catalysed oxidation of primary (viz. 2-aminoethanol and 3-aminopropanol) secondary (diethanolamine) and tertiary aminoalcohols (triethanolamine) by cerium(IV) in a sulphuric acid medium have been studied spectrophotometrically. The reactions exhibit a zero-order rate-dependence with respect to the oxidant and first-order rate-dependence with respect to each of the substrate and catalyst. First order dependence of rate in sulphuric acid is found for primary aminoalcohols. A suitable mechanism, consistent with the observed kinetic data, is proposed.     

Lorentz violation in high-energy ions

The theoretical interest in small Lorentz violations has motivated experiments that investigate it by measuring deviations in the time dilation predicted by special relativity (SR) using high-energy ions. The main contribution of this article is to show that including the Doppler effect in the emission (which is of the same order as the time dilation effect) in the analysis leads to differences between experimental and theoretical predictions that indicate potential Lorentz violation.     

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.     

Confinement resonances in photoionization of Xe@C₆₀+

Experimental evidence is presented for confinement resonances associated with photoabsorption by a Xe atom in a C60 cage. The giant 4d resonance in photoionization of Xe is predicted to be redistributed into four components due to multipath interference of photoelectron waves reflected by the cage. The measurements were made in the photon energy range 60-150 eV by merging a beam of synchrotron radiation with a mass/charge selected Xe@C??+ ion beam. The phenomenon was observed in the Xe@C(58)(3+) product ion channel. [corrected]     

An extension to the ordered subcarrier selection algorithm (OSSA)

In this letter, we propose an extension to the ordered subcarrier selection algorithm (OSSA) for orthogonal frequency division multiplexing (OFDM) systems. The result is a simple algorithm for minimizing the bit error rate of the OFDM system at a fixed throughput. The proposed algorithm employs multiple modulations (non-uniform bit loading) within an OFDM symbol. However, unlike existing bit loading algorithms that have a very high computational complexity, the proposed algorithm is based only on the ordered statistics of the subcarrier gains and is consequently very simple. After ordering the subcarriers based on their gains, progressively higher order modulations are used with increasing gains. The key aspect here that greatly simplifies the algorithm is that the modulation used on a subcarrier depends only on the position of its gain in the ordered set and not on the actual values of the gains. We show an analytical approach for determining the parameters of the algorithm.     

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.