The Bologna submillisecond pulsar survey

Since the discovery of the original millisecond pulsar, no pulsars with a shorter spin period (P<1.56 ms) were found. However, according to the most popular equations of state, the theoretical limiting spin period of a neutron star can be much shorter. On the other hand, most of the large scale searches for millisecond pulsars carried out so far were strongly biased against the detection of ultrashort periodicities. In this paper we describe a new large scale pulsar survey with a minimum detectable period much shorter than previous searches.Comment: 4 pages, two included figures, to be published in proceedings of "Pulsar Astronomy -- 2000 and Beyond", ASP Conf. Se

Effect of matrix parameters on mesoporous matrix based quantum computation

We present a solid state implementation of quantum computation, which improves previously proposed optically driven schemes. Our proposal is based on vertical arrays of quantum dots embedded in a mesoporous material which can be fabricated with present technology. We study the feasibility of performing quantum computation with different mesoporous matrices. We analyse which matrix materials ensure that each individual stack of quantum dots can be considered isolated from the rest of the ensemble-a key requirement of our scheme. This requirement is satisfied for all matrix materials for feasible structure parameters and GaN/AlN based quantum dots. We also show that one dimensional ensembles substantially improve performances, even of CdSe/CdS based quantum dots

CMB temperature anisotropies from third order gravitational perturbations

In this paper we present a complete computation of the Cosmic Microwave Background (CMB) anisotropies up to third order from gravitational perturbations accounting for scalar, vector and tensor perturbations. We then specify our results to the large scale limit, providing the evolution of the gravitational potentials in a flat universe filled with matter and cosmological constant which characterizes the Integrated Sachs-Wolfe effect. As a byproduct in the large scale approximation we are able to give non-perturbative solutions for the photon geodesic equations. Our results are the first step to provide a complete theoretical prediction for cubic non-linearities which are particularly relevant for characterizing the level of non-Gaussianity in the CMB through the detection of the four-point angular connected correlation function (trispectrum). For this purpose we also allow for generic initial conditions due to primordial non-Gaussianity.Comment: 19 pages, LateX file; typos corrected; some corrections made and several consistency checks performed regarding Eqs.(2.18); (2.28)-(2.29) and Eqs.(3.8)-(3.24) and Eq.(4.2). Version accepted for publication in JCA

Timing the millisecond pulsars in 47 Tucanae

In the last 10 years 20 millisecond pulsars have been discovered in the globular cluster 47 Tucanae. Hitherto, only 3 of these had published timing solutions. Here we improve upon these 3 and present 12 new solutions. These measurements can be used to determine a variety of physical properties of the pulsars and of the cluster. The 15 pulsars have positions determined with typical uncertianties of only a few milliarcsec and they are all located within 1.2 arcmin of the cluster centre. We have also measured the proper motions of 5 of the pulsars, which are consistent with the proper motion of 47 Tuc based on Hipparcos data. The period derivatives measured for many of the pulsars are dominated by the dynamical effects of the cluster gravitational field, and are used to constrain the surface mass density of the cluster. All pulsars have characteristic ages T > 170 Myr and magnetic fields B < 2.4e9 Gauss, and the average T > 1 Gyr. We have measured the rate of advance of periastron for the binary pulsar J0024-7204H, implying a total system mass 1.4+-0.8 solar masses.Comment: 17 pages, 11 included figures, accepted for publication in MNRA

A Search for Pulsars in Quiescent Soft X-Ray Transients. I

We have carried out a deep search at 1.4 GHz for radio pulsed emission from six soft X-ray transient sources observed during their X-ray quiescent phase. The commonly accepted model for the formation of the millisecond radio pulsars predicts the presence of a rapidly rotating, weakly magnetized neutron star in the core of these systems. The sudden drop in accretion rate associated with the end of an X-ray outburst causes the Alfv\`en surface to move outside the light cylinder, allowing the pulsar emission process to operate. No pulsed signal was detected from the sources in our sample. We discuss several mechanisms that could hamper the detection and suggest that free-free absorption from material ejected from the system by the pulsar radiation pressure could explain our null result.Comment: accepted by Ap

Assessing physical activity in daily life, exercise, and sedentary behavior among Japanese moving to westernized environment: A cross-sectional study of Japanese migrants at an urban primary care center in Pittsburgh

Background: Noncommunicable chronic diseases (NCDs) are global public health issues. Physical activity, exercise and sedentary behavior are important lifestyle factors to determine risk of NCDs. Immigrant studies have shown higher risk of developing NCDs among immigrants. Less physical activity among Japanese immigrants to westernized environment was also documented. However, little is known about detailed physical activity, exercise and sedentary behavior among Japanese residing in westernized environment. This cross-sectional study was conducted to analyze physical activity in daily life, exercise, and sedentary behavior among Japanese in westernized environment and then to compare the results to native Japanese in Japan. Methods. Japanese adults in Pittsburgh who were registered at an urban primary care clinic were surveyed in terms of physical activity in daily life, exercise, and sedentary behavior. The results were compared to age- and gender-matched Japanese averages from the national data (Japanese National Health and Nutrition Survey, J-NHANS). Results: Of 97 identified for inclusion, all responded. Japanese in Pittsburgh did not engage physical activity in daily life as compared to J-NHANS results (p <.001 for both genders). Only 45.0% and 26.3% of Japanese men and women in Pittsburgh, respectively, reached the recommended level of exercise. The prevalence of regularly engaging moderate or vigorous level of exercise was significantly lower among Japanese in Pittsburgh than age- and gender-matched J-NHANS results. The prevalence of 2 hours or more per week of exercise at moderate or higher level among Japanese men and women in Pittsburgh were lower than J-NHANS results. Women in Pittsburgh showed significantly less sedentary time as compared to J-NHANS results, while men only showed significantly less sitting/lying time during weekend. We found no association between sedentary time (time in sitting/lying and TV/computer) and exercise time during weekday or weekend in the target population. Conclusions: Although Japanese in Pittsburgh showed lower prevalence of sedentary behavior, prevalence of regular physical activity and exercise were less than prevalence of native Japanese. © 2014 Hirooka et al.; licensee BioMed Central Ltd

Timing the Parkes Multibeam Pulsars

Measurement of accurate positions, pulse periods and period derivatives is an essential follow-up to any pulsar survey. The procedures being used to obtain timing parameters for the pulsars discovered in the Parkes multibeam pulsar survey are described. Completed solutions have been obtained so far for about 80 pulsars. They show that the survey is preferentially finding pulsars with higher than average surface dipole magnetic fields. Eight pulsars have been shown to be members of binary systems and some of the more interesting results relating to these are presented.Comment: 6 pages, 2 embedded EPS figures, to be published in proceedings of "Pulsar Astronomy - 2000 and Beyond", ASP Conf. Se