Search for serendipitous TNO occultation in X-rays

To study the population properties of small, remote objects beyond Neptune's orbit in the outer solar system, of kilometer size or smaller, serendipitous occultation search is so far the only way. For hectometer-sized Trans-Neptunian Objects (TNOs), optical shadows actually disappear because of diffraction. Observations at shorter wave lengths are needed. Here we report the effort of TNO occultation search in X-rays using RXTE/PCA data of Sco X-1 taken from June 2007 to October 2011. No definite TNO occultation events were found in the 334 ks data. We investigate the detection efficiency dependence on the TNO size to better define the sensible size range of our approach and suggest upper limits to the TNO size distribution in the size range from 30 m to 300 m. A list of X-ray sources suitable for future larger facilities to observe is proposed.Comment: Accepted to publish in MNRA

How Economic Situation Effect on Career Anchors of IT Personnel?

The paper examines how ITP (IT personnel) turnover intention is influenced by career satisfaction, and perceived job alternatives. What considerations lead an IT professional to switch jobs when they are currently satisfied; i.e. when their career anchors are satisfied

Scalar Induced Gravitational Waves from Finslerian Inflation and Pulsar Timing Arrays Observations

The recent data from NANOGrav provide strong evidence of the existence of the \acp{SGWB}. We investigate \acp{SIGW} from Finslerian inflation as a potential source of stochastic gravitational wave background. Small-scale ($\lesssim$1 Mpc) statistically anisotropic primordial scalar perturbations can be generated in Finslerian inflation. The second order \acp{SIGW} from Finslerian inflation are also anisotropic on small scales. After spatially averaging the small-scale anisotropic \acp{SIGW}, we obtain the large-scale isotropic \acp{SGWB}. We find that the parameters of small-scale anisotropic primordial power spectrum generated by Finslerian inflation affect the \acp{PTA} observations of large-scale isotropic gravitational wave background

Second order scalar perturbations induced by primordial curvature and tensor perturbations

The primordial perturbations will inevitably generate higher order perturbations. We study the second order scalar perturbations generated by the primordial curvature and tensor perturbations in the radiation-dominated era. After presenting all the possible second-order source terms, we obtain the explicit expressions of the kernel functions and the power spectra of the second order scalar perturbations. The contributions from the initial second-order perturbations are considered. We calculate the power spectra of second order scalar perturbations for different tensor-to-scalar ratio $r$

Examining the online reading behavior and performance of fifth-graders: evidence from eye-movement data

Online reading is developing at an increasingly rapid rate, but the debate concerning whether learning is more effective when using hypertexts than when using traditional linear texts is still persistent. In addition, several researchers stated that online reading comprehension always starts with a question, but little empirical evidence has been gathered to investigate this claim. This study used eye-tracking technology and retrospective think aloud technique to examine online reading behaviors of fifth-graders (N = 50). The participants were asked to read four texts on the website. The present study employed a three-way mixed design: 2 (reading ability: high vs. low) 2 (reading goals: with vs. without) 2 (text types: hypertext vs. linear text). The dependent variables were eye-movement indices and the frequencies of using online reading strategy. The results show that fifth-graders, irrespective of their reading ability, found it difficult to navigate the nonlinear structure of hypertexts when searching for and integrating information. When they read with goals, they adjusted their reading speed and the focus of their attention. Their offline reading ability also influenced their online reading performance. These results suggest that online reading skills and strategies have to be taught in order to enhance the online reading abilities of elementary-school students

Primordial black holes from second order density perturbations as probes of the small-scale primordial power spectrum

We investigate the second order energy density perturbation $\delta^{(2)}$ induced by small-scale Gaussian and local-type non-Gaussian primordial curvature perturbations. The relative abundance of primordial black hole is calculated in terms of the probability density function of total energy density perturbation $\delta_r=\delta^{(1)}+\frac{1}{2}\delta^{(2)}$. The effects of second order density perturbation greatly reduce the upper bounds of small-scale power spectra of primordial curvature perturbations by one to two orders of magnitude. For log-normal primordial power spectrum, its amplitude $A_{\zeta}$ is constrained to be about $A_{\zeta}\sim 3\times10^{-3}$. And for local-type non-Gaussianity with $f_{\mathrm{NL}}=10$, the upper bound of $A_{\zeta}$ is about $2.5\times10^{-4}$.Comment: 5 pages, 4 figure

THE DYNAMICAL ANALYSIS OF TABLE TENNIS FOREHAND AND BACKHAND DRIVES

The purpose of this study was to analyze the dynamics parameters of table tennis drives by Taiwan collegiate first class table tennis players when they were performing straight and cross court forehand and backhand drives from receiving topspin and backspin serves. Ten Vicon MX-13+ high-speed cameras (250Hz) and two Kistler force plates (1500 Hz) were used to collect the kinematics and kinetics data. The Wilcoxon matched-pairs signed-rank nonparametric statistical test was to compare the differences between forehand and backhand drives. The results showed that there were significant differences between forehand and backhand drives were in the ball initial velocity and the kinetics variables. The GRF data of the players were different between forehand and backhand drives when they performed four different paths of drive

THE UPPER LIMB EMG ACTIVITY COMPARISON OF DIFFERENT TABLE TENNIS FOREHAND DRIVES

The purpose of this study was to combine dynamics and surface EMG methods to analyze the movements of table tennis forehand drives by Taiwan elite table tennis players performing straight and cross court forehand drives from topspin and backspin serves. The kinematical data were collected by 10 Vicon MX13+ high-speed cameras and one Biovision system was used to record the EMG signal of seven muscles groups on the dominate hand. The results showed that there were significant differences among the four table tennis drives. The players exerted greater muscular activity in the wrist extensors, the biceps and the triceps for the backspin serve forehand drive than when returning the topspin serve forehand drive, not only on the straight but also on the cross court strokes

Millisecond dips in the 2007-2009 RXTE/PCA lightcurve of Sco X-1 and one possible occultation event

Serendipitous stellar occultation search is so far the only way to detect the existence of very small, very dim, remote objects in the solar system. To date, however, there are only very few reported detections for trans-Neptunian objects (TNOs) in optical bands. In the X-ray band, with the RXTE/PCA data of Sco X-1 taken from June 2007 to October 2009, we found one possible X-ray occultation event. We discuss the veracity and properties of this event, and suggest upper limits to the size distribution of TNOs at hectometer size and of Main-Belt Asteroids (MBAs) at decameter size.Comment: 8 pages, 5 figures, to appear in MNRAS (accepted on Sep. 10, 2010