Free Energy Approach to the Formation of an Icosahedral Structure during the Freezing of Gold Nanoclusters

The freezing of metal nanoclusters such as gold, silver, and copper exhibits a novel structural evolution. The formation of the icosahedral (Ih) structure is dominant despite its energetic metastability. This important phenomenon, hitherto not understood, is studied by calculating free energies of gold nanoclusters. The structural transition barriers have been determined by using the umbrella sampling technique combined with molecular dynamics simulations. Our calculations show that the formation of Ih gold nanoclusters is attributed to the lower free energy barrier from the liquid to the Ih phases compared to the barrier from the liquid to the face-centered-cubic crystal phases

Molecular cytogenetic mapping of Cucumis sativus and C. melo using highly repetitive DNA sequences

Chromosomes often serve as one of the most important molecular aspects of studying the evolution of species. Indeed, most of the crucial mutations that led to differentiation of species during the evolution have occurred at the chromosomal level. Furthermore, the analysis of pachytene chromosomes appears to be an invaluable tool for the study of evolution due to its effectiveness in chromosome identification and precise physical gene mapping. By applying fluorescence in situ hybridization of 45S rDNA and CsCent1 probes to cucumber pachytene chromosomes, here, we demonstrate that cucumber chromosomes 1 and 2 may have evolved from fusions of ancestral karyotype with chromosome number n= 12. This conclusion is further supported by the centromeric sequence similarity between cucumber and melon, which suggests that these sequences evolved from a common ancestor. It may be after or during speciation that these sequences were specifically amplified, after which they diverged and specific sequence variants were homogenized. Additionally, a structural change on the centromeric region of cucumber chromosome 4 was revealed by fiber-FISH using the mitochondrial-related repetitive sequences, BAC-E38 and CsCent1. These showed the former sequences being integrated into the latter in multiple regions. The data presented here are useful resources for comparative genomics and cytogenetics of Cucumis and, in particular, the ongoing genome sequencing project of cucumbe

An effective thermodynamic potential from the instanton with Polyakov-loop contributions

We derive an effective thermodynamic potential (Omega_eff) at finite temperature (T>0) and zero quark-chemical potential (mu_R=0), using the singular-gauge instanton solution and Matsubara formula for N_c=3 and N_f=2 in the chiral limit. The momentum-dependent constituent-quark mass is also obtained as a function of T, employing the Harrington-Shepard caloron solution in the large-N_c limit. In addition, we take into account the imaginary quark chemical potential mu_I = A_4, translated as the traced Polayakov-loop (Phi) as an order parameter for the Z(N_c) symmsetry, characterizing the confinement (intact) and deconfinement (spontaneously broken) phases. As a result, we observe the crossover of the chiral (chi) order parameter sigma^2 and Phi. It also turns out that the critical temperature for the deconfinment phase transition, T^Z_c is lowered by about (5-10)% in comparison to the case with a constant constituent-quark mass. This behavior can be understood by considerable effects from the partial chiral restoration and nontrivial QCD vacuum on Phi. Numerical calculations show that the crossover transitions occur at (T^chi_c,T^Z_c) ~ (216,227) MeV.Comment: 15 pages, 7 figure

Calabi-Yau manifolds from pairs of non-compact Calabi-Yau manifolds

Most of Calabi-Yau manifolds that have been considered by physicists are complete intersection Calabi-Yau manifolds of toric varieties or some quotients of product types. Purpose of this paper is to introduce a different and rather new kind of construction method of Calabi-Yau manifolds by pasting two non-compact Calabi-Yau manifolds. We will also in some details explain a curious and mysterious similarity with construction of some $G_2$-manifolds (also called Joyce manifolds), which are base spaces for M-theory.Comment: 10 pages. Accepted for publication in JHE

Getting Jobs, Keeping Jobs, and Earning a Living Wage: Can Welfare Reform Work?

Most discussions of welfare and work have focused on how demographic characteristics, schooling, training, and work experience limit welfare mothers’ employment and wages, but they have largely ignored factors such as inappropriate workplace behaviors, expectations of discrimination and harassment, depression, alcoholism, and domestic violence, all of which may affect welfare mothers and make employment difficult. In this paper we review the prevalence of these individual-level barriers and argue that they, in combination with an economy which does not pay low-skill workers well, are likely to impede employment and self-sufficiency for a large proportion of welfare mothers. At the end of the review, we summarize the current state of knowledge about barriers to the employment of welfare recipients and suggest several ways in which welfare-to-work programs might address these barriers.

Area spectra of the rotating BTZ black hole from quasinormal modes

Following Bekenstein's suggestion that the horizon area of a black hole should be quantized, the discrete spectrum of the horizon area has been investigated in various ways. By considering the quasinormal mode of a black hole, we obtain the transition frequency of the black hole, analogous to the case of a hydrogen atom, in the semiclassical limit. According to Bohr's correspondence principle, this transition frequency at large quantum number is equal to classical oscillation frequency. For the corresponding classical system of periodic motion with this oscillation frequency, an action variable is identified and quantized via Bohr-Sommerfeld quantization, from which the quantized spectrum of the horizon area is obtained. This method can be applied for black holes with discrete quasinormal modes. As an example, we apply the method for the both non-rotating and rotating BTZ black holes and obtain that the spectrum of the horizon area is equally spaced and independent of the cosmological constant for both cases

CP asymmetries in penguin-induced B decays in general left-right models

We study CP asymmetries in penguin-induced b -> s\bar{s}s decays in general left-right models without imposing manifest or pseudomanifest left-right symmetry. Using the effective Hamiltonian approach, we evaluate CP asymmetries in B^\pm -> \phi K^{(\ast)\pm} decays as well as mixing induced B meson decays B -> J/\psi K_s and B -> \phi K_s decays. Based on recent measurements revealing large CP violation, we show that nonmanifest type model is more favored than manifest or pseudomanifest type.Comment: 16 pages, 12 eps figure