The 5T2g → 5Eg absorption in MgO: Fe2+

At helium temperatures two sharp lines at 9350 and 9510 cm^?1 have been observed for the first tune on the low-energy side of the broad double-peaked absorption corresponding to the ${}^5\text{T}{}_{\mathrm{2g}}\text{→}{}^5\text{E}{}_{\mathrm{g}}$ transition in Fe²⁺ at the octahedral site in MgO. The lower energy line has a half width of 4 cm^?1; Zeeman measurements show that it is of magnetic dipole origin. The Zeeman spectra are consistent with those expected for a pure electronic transition from the (⁵T_2g)T_2g ground state to the ⁵E_g excited state. The second line, with a halfwidth of ~ 35 cm^?1, a vibrational sideband.     

The structure of psoralidin

Psoralidin, C₂₀H₁₆O₅ the phenolic coumarin of Psoralea corylifolia Linn. has been shown to possess two hydroxyl groups, one conjugated δ-lactone, one isopentenyl group and an intramolecular ether linkage. On systematic degradation dihydropsoralidin dimethyl ether gave 2-hydroxy-4-methoxybenzaldehyde and 2,4-dimethoxy-5-(-3-methylbutyl)-benzoic acid. The synthesis of the latter compound has been described. On the basis of the degradation experiments coupled with ultra-violet and infra-red absorption data, the structure of psoralidin has been established as 6-(3-methylbut-2-enyl)-coumestrol (IV, R = H).     

Control limit policies for early detection of failure

This paper considers a class of Markov Decision problems subjects to partial observation. We develop a methodology for early detection of failure of systems that do not display symptoms of failure. We assume that the inspections used for detection are error prone and there is a fixed probability of not detecting the failure. The problem is studied as a non-stationary, finite horizon Markovian Decision Process with two states. We demonstrate that the optimal policy has a two region structure that intuition suggests. This characterization can be used to reduce the computational burden of finding the optimum inspection schedule. We also show that the form of the optimum policy remains unchanged for the unbounded horizon problem. Finally, we discuss a potential application of the model to medical diagnosis.     

High resolution gamma-ray spectroscopy of the27Al(p,γ)28Si resonance reaction

High resolution gamma-ray spectra have been measured from the²⁷Al (p,γ)²⁸Si reaction for the resonances atE _p=2·482, 2·511 and 2·735 MeV at ϑ _pγ=0°, 30°, 55° and 90° using a Ge (Li) gamma spectrometer. From the spectra and the angular distributions the properties of the resonance states have been obtained. These states are the isobaric analogues of the levels at 4·69, 4·75 and 4·93MeV levels respectively in the parent nucleus A²⁸l.     

Synthesis and intramolecular nitrile oxide cycloaddition of 3,5'-ether-linked pseudooligosaccharide derivatives: an approach to chiral macrooxacycles

3,5'-ether-linked pseudooligopentose derivatives were synthesized for the first time from readily available carbohydrate precursors. The 1,2-isopropylidene-protected ether-linked oligopentoses are potentially important as precursors of novel RNA analogues. Intramolecular cycloaddition of the nitrile oxides prepared from these derivatives led to the diastereoselective formation of chiral isoxazolines fused to 10-16-membered oxacycles. The stereochemistry of some of these isoxazolines was established by X-ray diffraction and NOESY analysis.     

Extensivity of entropy and modern form of Gibbs paradox

The extensivity property of entropy is clarified in the light of a critical examination of the entropy formula based on quantum statistics and the relevant thermodynamic requirement. The modern form of the Gibbs paradox, related to the discontinuous jump in entropy due to identity or non-identity of particles, is critically investigated. Qualitative framework of a new resolution of this paradox, which analyses the general effect of distinction mark on the Hamiltonian of a system of identical particles, is outlined.     

A modified Ashcroft pseudopotential: application to aluminium

Unified study of the different properties of metals clearly reveals the inadequacy of the empty-core Ashcroft pseudopotential even in the case of simple metals. In the present paper we propose a modification of the one-parameter Ashcroft pseudopotential by assuming the parameterr _c to be wave vector-dependent. This introduces a simple modification of the electron-ion pseudopotential in the reciprocal space. The corresponding potential in the configuration space shows that the abrupt change in the Coulomb potential atr=r _c is replaced by a continuous change spread over a small region near the core boundary. The present model has been used to make a unified study of Al and is found to be a significant improvement over the simple Ashcroft model. The agreement between the calculated and experimental values is found to be quite satisfactory.     

Bell's inequality and non-contextual dispersion-free states

With a view to exploring the possibility of wider implication of Bell's theorem, we argue that Bell's inequality is derivable as a general consequence of non-contextual hidden-variable theories. We formulate a new type of gedanken example indicating incompatibility of Bell's inequality with quantum mechanical predictions concerning simultaneous measurement of commuting observables associated with a system having no spatially separated components, where the locality condition is not at issue. Significance of this example is pointed out.     

Optimal time advancing dispersion relation preserving schemes

In this paper we examine the constrained optimization of explicit Runge–Kutta (RK) schemes coupled with central spatial discretization schemes to solve the one-dimensional convection equation. The constraints are defined with respect to the correct error propagation equation which goes beyond the traditional von Neumann analysis   developed in Sengupta et al. [T.K. Sengupta, A. Dipankar, P. Sagaut, Error dynamics: beyond von Neumann analysis, J. Comput. Phys. 226 (2007) 1211–1218]. The efficiency of these optimal schemes is demonstrated for the one-dimensional convection problem and also by solving the Navier–Stokes equations for a two-dimensional lid-driven cavity (LDC) problem. For the LDC problem, results for Re=1000$\mathit{Re}=1000$ are compared with results using spectral methods in Botella and Peyret [O. Botella, R. Peyret, Benchmark spectral results on the lid-driven cavity flow, Comput. Fluids 27 (1998) 421–433] to calibrate the method in solving the steady state problem. We also report the results of the same flow at Re=10,000$\mathit{Re}=10\text{,}000$ and compare them with some recent results to establish the correctness and accuracy of the scheme for solving unsteady flow problems. Finally, we also compare our results for a wave-packet propagation problem with another method developed for computational aeroacoustics.