Analyses of electron and proton scattering to low-excitation isoscalar states in 20Ne, 24Mg and 28Si

The excitation of low-lying isoscalar 2⁺ and 4⁺ states in ²⁰Ne, ²⁴Mg and ²⁸Si by electron and proton scattering is studied. Large basis models of nuclear structure are used to determine both the electromagnetic and hadronic transition densities. The analyses of the longitudinal form factors obtained from electron scattering show that little or no effective charges are required with these nuclear structure models. Proton inelastic scattering to these states then is analysed to test effective forces based upon the Paris and Hamada-Johnston interactions. At intermediate energies (155 MeV) density-dependent t-matrices from both potentials were used with fits to data giving a clear preference for that based upon the Paris interaction. For lower energies only the Hamada-Johnston t-matrix is available and comparison of analyses of 24 and 49 MeV data made using this (complex) t-matrix with those in which the (real) Paris G-matrix is used as the effective force show a clear preference for the t-matrix. This is particularly the case with analyses of polarization data and suggests that the use of the G-matrix as an effective force in nuclear reaction calculations is inadequate even at low energies.     

Fourier transform infrared study of two truxene-based discotic liquid crystals

We have used FTIR absorption to study the crystalline and liquid-crystalline phases of 2,3,7,8,12,13-hexa-n-tetradecanoyloxy-truxene (HATX) and 2,3,7,8,12,13-hexa(4-n-undecyloxybenzoyloxy)truxene (HBTX). Both materials show pronounced changes in the CH₂ stretching mode frequencies at their melting points. In addition, HATX shows a transition at about 20°C below the nominal melting point in which the alkyl tails gain significant disorder. Benzene stretching modes and the CH₂ deformation modes show subtle changes at the D_rd → N transition of HBTX and at the D_rd → D_hd transition of HATX.     

The effect of photoperiod and prey density on long-term survival of larvae—a data analytic approach where no parametric model is assumed and individual follow-up is not available

A data analytic approach for analysing differences in long-term survival and identifying treatment combinations which provide high survival in a factorial design set-up is presented. The methods are particularly appropriate when individual follow-up data are not available and no simple model fits the data. Upper quantiles of the survival distributions are used as the response variable and within and between-treatment differences are analysed through both a structured ANOVA model and subset-selection procedure. The methods are used to study the effects of several photoperiods and prey density treatments on the long-term survival of the larvae of gilthead seabream, Sparus aurata. The two approaches used are shown to lead to similar conclusions.     

Factorization theorems for univariate splines on regular grids

For a given univariate compactly supported distributionφ, we investigate here the spaceS(φ) spanned by its integer translates, the subspaceH(φ) of all exponentials inS(φ) and the kernelK _ϕ of the associated semi-discrete convolutionφ*. The paper addresses a variety of results including a complete structure ofH(φ) andK _ϕ and a characterization of splines of minimal support. The main result shows that eachφ can be expressed asφ = p(∇)τ * M, wherep(∇) is a finite difference operator,τ is a distribution of smaller support satisfyingH(τ) =K _τ = {0}, andM is a spline which depends onH(φ) but not onφ itself, and which in the generic case (termed here “regular”) is the exponential B-spline associated withH(φ). The approach chosen is direct and avoids entirely the Fourier analysis arguments. The fact that a distribution is examined, rather than a function, is essential for the methods employed.     

Synthesis of geiparvarin: a novel antitumor agent possessing a 3(2H)-furanone ring

The first synthesis of geiparvarin as well as assignment of configuration of the previously undefined trisubstituted olefinic bond has been achieved.     

The topological structure of 3-pseudomanifolds

A 3-pseudomanifold (briefly 3-pm) is a finite connected simplicial 3-complex in which the link of every vertex is a closed 2-manifold. Such a link issingular if it is not a sphere. It is proved that for a preassigned list Σ of closed 2-manifolds (other than spheres), there is a 3-pm in which the list of singular links is precisely Σ, iff the number of the non-orientable members in Σ with odd genus is even. Close relationship is found between 3-pms and 3-manifolds with boundary. This yields a simple proof for the 2-dimensional case of Pontrjagin-Thom’s theorem (i.e., necessary and sufficient condition for a 2-manifold to bound a 3-manifold). The concept of a 3-pm is generalized to higher dimensions.     

A remark on the polytopality of an interesting 3-sphere

We give a simple proof establishing the polytopality of the 3-sphere described in [3].     

Compactly supported tight affine spline frames in

The theory of fiberization is applied to yield compactly supported tight affine frames (wavelets) in from box splines. The wavelets obtained are smooth piecewise-polynomials on a simple mesh; furthermore, they exhibit a wealth of symmetries, and have a relatively small support. The number of ``mother wavelets', however, increases with the increase of the required smoothness.

Two bivariate constructions, of potential practical value, are highlighted. In both, the wavelets are derived from four-direction mesh box splines that are refinable with respect to the dilation matrix .

     

Radiation from a Uniformly Accelerated Charge

The emission of radiation by a uniformly accelerated charge is analyzed. According to the standard approach, a radiation is observed whenever there is a relative acceleration between the charge and the observer. Analyzing difficulties that arose in the standard approach, we propose that a radiation is created whenever a relative acceleration between the charge and its own electric field exists. The electric field induced by a charge accelerated by an external (nongravitational) force is not accelerated with the charge. Hence the electric field is curved in the instantaneous rest frame of the accelerated charge. This curvature gives rise to a stress force, and the work done to overcome the stress force is the source of the energy carried by the radiation. In this way, the energy balance paradox finds its solution.