Observational Constraints on Silent Quartessence

We derive new constraints set by SNIa experiments (`gold' data sample of Riess et al.), X-ray galaxy cluster data (Allen et al. Chandra measurements of the X-ray gas mass fraction in 26 clusters), large scale structure (Sloan Digital Sky Survey spectrum) and cosmic microwave background (WMAP) on the quartessence Chaplygin model. We consider both adiabatic perturbations and intrinsic non-adiabatic perturbations such that the effective sound speed vanishes (Silent Chaplygin). We show that for the adiabatic case, only models with equation of state parameter $|\alpha |\lesssim 10^{-2}$ are allowed: this means that the allowed models are very close to \LambdaCDM. In the Silent case, however, the results are consistent with observations in a much broader range, -0.3<\alpha<0.7.Comment: 7 pages, 12 figures, to be submitted to JCA

Gravitational Lensing Statistics as a Probe of Dark Energy

By using the comoving distance, we derive an analytic expression for the optical depth of gravitational lensing, which depends on the redshift to the source and the cosmological model characterized by the cosmic mass density parameter $\Omega_m$, the dark energy density parameter $\Omega_x$ and its equation of state $\omega_x = p_x/\rho_x$. It is shown that, the larger the dark energy density is and the more negative its pressure is, the higher the gravitational lensing probability is. This fact can provide an independent constraint for dark energy.Comment: 9 pages, 2 figure

Phase Transition in Sexual Reproduction and Biological Evolution

Using Monte Carlo model of biological evolution we have discovered that populations can switch between two different strategies of their genomes' evolution; Darwinian purifying selection and complementing the haplotypes. The first one is exploited in the large panmictic populations while the second one in the small highly inbred populations. The choice depends on the crossover frequency. There is a power law relation between the critical value of crossover frequency and the size of panmictic population. Under the constant inbreeding this critical value of crossover does not depend on the population size and has a character of phase transition. Close to this value sympatric speciation is observed.Comment: 13 pages, 8 figure

Radiomitigative Effects of Approved Hematopoietic Drugs on Mice Exposed to Lethal Total-body Irradiation

In cases of radiological accidents, especially for victims exposed to high-dose total-body irradiation (TBI), the administration of appropriate approved hematopoietic drugs is the most rapid medical treatment for preventing severe acute radiation syndrome, which is associated with a high mortality rate. However, at present, there are few suitable pharmaceutical drugs available in Japan, aside from granulocyte colony-stimulating factor (G-CSF). Depending on the situation surrounding the accident, various drug treatment options and the development of effective drug therapies may be required. In the present study, we assessed various combinations of seven commercially available drugs-G-CSF, erythropoietin (EPO), romiplostim (RP), ancer (AN), cepharanthine (CE), leucon (LC) and leukoprol (LP)-in mice exposed to a lethal dose of 7 or 8 Gy of X-ray irradiation. Each drug was administered as a single or mixed intraperitoneal injection once or twice daily for three consecutive days. The single administration of the approved hematopoietic drugs CE, LC, or LP twice a day for 3 days significantly improved the 30-day survival rate of lethal TBI mice (p &lt; 0.05; 75%, 100%, or 100%, respectively) compared with the untreated TBI mice, accompanied by a gradual increase in the body weight. Furthermore, the combined administration of RP, EPO and G-CSF or single administration of RP alone gradually increased the body weight of mice exposed to lethal TBI, with 30-day survival rates of 75% or 100%, respectively (p &lt; 0.05). This study suggested that some new domestically approved hematopoietic drugs may have radiomitigative potential for mice exposed to lethal TBI, and the 12-h interval administration of LC or LP for 3 days to 7-Gy-TBI mice and 12-h interval administration of RP alone for 3 days to 8-Gy-TBI mice were the most suitable medications with respect to the 30-day survival rate. As long as the threat of nuclear disaster exists, diverse efforts in thefield of radiation emergency medicine, including the development of effective drug therapies, will be necessary

Inhibition of CDK activity and PCNA-dependent DNA replication by p21 is blocked by interaction with the HPV-16 E7 oncoprotein

p21 inhibits cyclin-dependent kinase (CDK) activity and proliferating cell nuclear antigen (PCNA)-dependent DNA replication by binding to CDK/cyclin complexes and to PCNA through distinct domains. The human papillomavirus (HPV)-16 E7 oncoprotein (16E7) abrogated a DNA damage-induced cell cycle arrest in vivo, despite high levels of p21. Using cell lysates and purified proteins we show that 16E7 prevented p21 both from inhibiting CDK2/cyclin E activity and PCNA-dependent DNA replication, whereas the nononcogenic HPV-6 E7 had reduced effects. Inactivation of both inhibitory functions of p21 was attained through binding between 16E7 and sequences in the carboxy-terminal end of p21 that overlap with the PCNA-binding site and the second p21 cyclin-binding motif. These data imply that the carboxyl terminus of p21 simultaneously modulates both CDK activity and PCNA-dependent DNA replication and that a single protein, 16E7, can override this modulation to disrupt normal cell cycle control

Higher spin fields and the problem of cosmological constant

The cosmological evolution of free massless vector or tensor (but not gauge) fields minimally coupled to gravity is analyzed. It is shown that there are some unstable solutions for these fields in De Sitter background. The back reaction of the energy-momentum tensor of such solutions to the original cosmological constant exactly cancels the latter and the expansion regime changes from the exponential to the power law one. In contrast to the adjustment mechanism realized by a scalar field the gravitational coupling constant in this model is time-independent and the resulting cosmology may resemble the realistic one.Comment: 15 pages, Latex twic