Entropy Spectrum of Black Holes of Heterotic String Theory via Adiabatic Invariance

Using adiabatic invariance and the Bohr-Sommerfeld quantization rule we investigate the entropy spectroscopy of two black holes of heterotic string theory,the charged GMGHS and the rotating Sen solutions.It is shown that the entropy spectrum is equally spaced in both cases,identically to the spectrum obtained before for Schwarzschild,Reissner-Nordström and Kerr black holes.Since the adiabatic invariance method does not use quasinormal mode analysis,there is no need to impose the small charge or small angular momentum limits and there is no confusion on whether the real part or the imaginary part of the modes is responsible for the entropy spectrum.     

Microwave‐Assisted Solvent‐Free Synthesis of Ipsapirone

The currently applied synthetic methods of serotonin receptor ligands belonging to the group of long‐chain arylpiperazines, including ipsapirone, require the use of toxic solvents and comprise numerous synthetic steps. Moreover, the reaction yield does not exceed 60% in the majority of cases. These factors lead to an increased energy consumption and negatively impact the environment. This paper describes a more environmentally friendly method of ipsapirone synthesis that we decided to use. Ipsapirone was obtained in two different methods. The first method involved N‐alkylation of bromobutyl saccharin with 1‐(2‐pyrimidyl)piperazine dihydrochloride, while the second was a one‐pot method. Neither of these requires the use of toxic and expensive solvents. A shortened synthesis time, not exceeding 10 min due to the use of microwave radiation, is also another advantage of these methods. The yield of the final product, ipsapirone, was 85% and 67% in the first and the second method, respectively. We also attempted to obtain ipsapirone using saccharin and arylpiperazine salt (method III) as starting materials, but to no avail in the tested conditions. As described herein, the green chemistry method for ipsapirone synthesis is rapid, cost‐effective, and environment friendly.     

Network design through forests with degree- and role-constrained minimum spanning trees

Finding the degree-constrained minimum spanning tree (DCMST) of a graph is a widely studied NP-hard problem. One of its most important applications is network design. Here we deal with a new variant of the DCMST problem, which consists of finding not only the degree- but also the role-constrained minimum spanning tree (DRCMST), i.e., we add constraints to restrict the role of the nodes in the tree to root, intermediate or leaf node. Furthermore, we do not limit the number of root nodes to one, thereby, generally, building a forest of DRCMSTs. The modeling of network design problems can benefit from the possibility of generating more than one tree and determining the role of the nodes in the network. We propose a novel permutation-based representation to encode these forests. In this new representation, one permutation simultaneously encodes all the trees to be built. We simulate a wide variety of DRCMST problem instances which we optimize using different evolutionary computation algorithms encoding individuals of the population using the proposed representation. To illustrate the applicability of our approach, we formulate the trans-European transport network as a DRCMST problem. In this network design, we simultaneously optimize nine transport corridors and show that it is straightforward using the proposed representation to add constraints depending on the specific characteristics of the network.     

Effect of an α-Methyl Substituent on the Dienophile on Diels-Alder endo:exo Selectivity

A detailed computational study of the Diels-Alder reaction of cyclopentadiene with acrylonitrile, methylacrylate and their α-methylated counterparts methacrylonitrile and methyl methacrylate at the M06-2X(PCM)/TZVP level of theory has been performed. We want to understand the excellent exo-selectivities observed experimentally due the presence of this substituent. To this end, analysis of the reaction coordinate by means of activation strain model of chemical reactivity (ASM-distortion interaction model) including solvation effects and NBO second order perturbation energy have been carried out.     

Xestosaprol D and E from the Indonesian marine sponge Xestospongia sp.

Chemical investigation of an extract of the marine sponge Xestospongia yielded a suite of pentacyclic compounds, including two new xestosaprol derivatives. Xestosaprol D (1) and E (2) are regioisomers, whose structures were defined through analysis of spectroscopic data.     

On the suitability of the ILJ function to match different formulations of the electrostatic potential for water-water interactions

Energetic and structural properties of liquid water have been calculated using molecular dynamics simulations in order to investigate the effect of different formulations of the van der Waals (vdW) interaction on the behaviour of liquid water. In particular, two model potentials, the SPC/E using a Lennard Jones (LJ) function and the AMPF using an Improved Lennard Jones function (ILJ) have been considered. The flexibility of the ILJ function in the AMPF model has also been analysed, proving that its vdW component can match different parametrizations of the electrostatic component.     

Dismantling the Hyperconjugation of π-Conjugated Phosphorus Heterocycles

The development of π-extended phosphorus heterocycles has been rapidly increasing because of their unique optoelectronics properties, which are very often considered to be a consequence of special hyperconjugative interactions. However, the latter interactions have primarily been investigated within the five-membered species, phospholes, and they are often conceptually extrapolated to the rest of π-extended phosphorus heterocycles (including six-membered P-heterocycles) despite evident structural differences. Herein, we report, for the first time, a detailed investigation that sheds light on the hyperconjugative effects of a series of phosphorus heterocyclic systems by means of EDA and NBO calculations within a DFT framework. Our results lay the foundations for the future design of π-extended phosphorus heterocycles with improved optoelectronics properties.     

A 3D-analysis of cluster formation and dynamics of the X(-)-benzene (X = F, Cl, Br, I) ionic dimer solvated by Ar atoms

The specific influence of X(-) ions (X = F,Cl, Br, I) in the solvation process of halide-benzene (X(-)-Bz) ionic heterodimers by Ar atoms is investigated by means of molecular dynamic (MD) simulations. The gradual evolution from cluster rearrangement to solvation dynamics is discussed by considering ensembles of n (n = 1-15 and n = 30) Ar atoms around the X(-)-Bz stable ionic dimers. The potential energy surfaces employed are based on an atom/ion-atom and atom/ion-bond decomposition, which has been developed previously by some of the authors. The outcome of the dynamics is analyzed by employing radial distribution functions (RDF) and tridimensional (3D) probability densities.     

Singhof fillings of closed 3-manifolds

We give a complete classification of all closed, connected 3-manifolds which admit a Singhof filling with any number of solid tori. Received: 15 March 2001 / Revised version: 17 September 2001     

Size-specific interaction of alkali metal ions in the solvation of M+-benzene clusters by Ar atoms

The size-specific influence of the M+ alkali ion (M = Li, Na, K, Rb, and Cs) in the solvation process of the M+-benzene clusters by Ar atoms is investigated by means of molecular dynamic simulations. To fully understand the behavior observed in M+-bz-Ar(n) clusters, solvation is also studied in clusters containing either M+ or benzene only. The potential energy surfaces employed are based on a semiempirical bond-atom decomposition, which has been developed previously by some of the authors. The outcome of the dynamics is analyzed by employing radial distribution functions, studying the evolution of the distances between the Ar atoms and the alkali ion M+ or the benzene molecule for all M+-bz-Ar(n) clusters. For all members, in the M+-bz series, the benzene molecule (bz) is found to remain strongly bound to M+ even in the presence of solvent atoms. The radial distribution functions for the heavier clusters (K+-bz, Rb+-bz, and Cs+-bz), are found to be different than for the lighter (Na+-bz and Li+-bz) ones.