The magnetospheric activity of bare strange quark stars

In Ruderman & Sutherland (RS75) model, the normal neutron stars as pulsars bear a severe problem, namely the binding energy problem that both ions (e.g., ${}_{26}^{56}$Fe) and electrons on normal neutron star surface can be pulled out freely by the unipolar generator induced electric field so that sparking on polar cap can hardly occur. {\bf This problem could be solved within the Partially Screened Gap (PSG) model in the regime of neutron stars}. However, in this paper we extensively study this problem in a bare strange quark star (BSS) model. We find that the huge potential barrier built by the electric field in the vacuum gap above polar cap could usually prevent electrons from streaming into the magnetosphere unless the electric potential of a pulsar is sufficiently lower than that at infinite interstellar medium. Other processes, such as the diffusion and thermionic emission of electrons have also been included here. Our conclusions are as follows: both positive and negative particles on a BSS's surface would be bound strongly enough to form a vacuum gap above its polar cap as long as the BSS is not charged (or not highly negative charged), and multi-accelerators could occur in a BSS's magnetosphere. Our results would be helpful to distinguish normal neutron stars and bare quark stars through pulsar's magnetospheric activities.Comment: 6 pages, 4 figures, 3 tables; accepted for publication in MNRA

Asteroseismology of Vibration Powered Neutron Stars

Chapter from the book "Astrophysics", p.287-308. Edited by Ibrahim Kucuk, ISBN 978-953-51-0473-5, InTech, March 3, 2012.Comment: http://cdn.intechopen.com/pdfs/34269/InTech-Asteroseismology_of_vibration_powered_neutron_stars.pd

Compact and high-performance vortex mode sorter for multi-dimensional multiplexed fiber communication systems

With the amplitude, time, wavelength/frequency, phase, and polarization/spin parameter dimensions of the light wave/photon almost fully utilized in both classical and quantum photonic information systems, orbital angular momentum (OAM) carried by optical vortex modes is regarded as a new modal parameter dimension for further boosting the capacity and performance of the systems. To exploit the OAM mode space for such systems, stringent performance requirements on a pair of OAM mode multiplexer and demultiplexer (also known as mode sorters) must be met. In this work, we implement a newly discovered optical spiral transformation to achieve a low-cross-Talk, wide-opticalbandwidth, polarization-insensitive, compact, and robust OAM mode sorter that realizes the desired bidirectional conversion between seven co-Axial OAM modes carried by a ring-core fiber and seven linearly displaced Gaussian-like modes in parallel single-mode fiber channels. We further apply the device to successfully demonstrate high-spectralefficiency and high-capacity data transmission in a 50-km OAM fiber communication link for the first time, in which a multi-dimensional multiplexing scheme multiplexes eight orbital-spin vortex mode channels with each mode channel simultaneously carrying 10 wavelength-division multiplexing channels, demonstrating the promising potential of both the OAM mode sorter and the multi-dimensional multiplexed OAM fiber systems enabled by the device. Our results pave the way for futureOAM-based multi-dimensional communication systems

Magic and superstition in baseball in Taiwan: an examination of the Puyama aborigines’ use of the betel nut

Much work has been published on the place of rituals in numerous areas of life with reference both to general activities and, more specifically, to sport. As yet, however, there has been no significant study of the use of magic by and on behalf of players in Taiwan where baseball can legitimately be described as the national sport. This article seeks to fill that void by focusing in particular on the practices of the island’s Puyama aboriginal people and the use of the betel nut to cast spells on opponents. The data for this study were collected during two research trips to Taidong County, where the Puyuma have traditionally used betel nuts on the baseball field for magical purposes. It is apparent from a series of personal reminiscences that the use of the betel nut spell had an influence on Puyama players and opponents alike. Its passing owes much to the increased acceptance of seemingly more rational ways of instilling confidence in athletes. The author argues, however, that the modern recourse to the sport sciences has much in common with the Puyama belief in the power of the betel nut

Vision-aided Navigation for Autonomous Aircraft Based on Unscented Kalman Filter

A vision-aided navigation system for autonomous aircraft is described in this paper. The vision navigation of the aircraft to the known scence is performed with a camera fixed on the aircraft. The location and pose of the aircraft are estimated with the corresponding control points which can be detected in the images captured. The control points are selected according their saliency and are tracked in sequential images based on Fourier-Melline transform. The simulation model of the aircraft dynamics and vision-aided navigation system based on Matlab/Simulink is built.The unscented Kalman filter is used to fuse the aircraft state information provided by the vision system and the inertial navigation system. Simulation results show that the vision-based navigation system provides satisfactory results of both accuracy and reliability.DOI: http://dx.doi.org/10.11591/telkomnika.v11i2.225

On Hoyle-Narlikar-Wheeler mechanism of vibration energy powered magneto-dipole emission of neutron stars

We revisit the well-known Hoyle-Narlikar-Wheeler proposition that neutron star emerging in the magnetic-flux-conserving process of core-collapse supernova can convert the stored energy of Alfven vibrations into power of magneto-dipole radiation. We show that the necessary requirement for the energy conversion is the decay of internal magnetic field. In this case the loss of vibration energy of the star causes its vibration period, equal to period of pulsating emission, to lengthen at a rate proportional to the rate of magnetic field decay. These prediction of the model of vibration powered neutron star are discussed in juxtaposition with data on pulsating emission of magnetars whose radiative activity is generally associated with the decay of ultra strong magnetic field.Comment: Accepted for publication in Astrophysics & Space Scienc

Normalized solutions for a Choquard equation with exponential growth in R2\mathbb{R}^{2}

In this paper, we study the existence of normalized solutions to the following nonlinear Choquard equation with exponential growth \begin{align*} \left\{ \begin{aligned} &-\Delta u+\lambda u=(I_{\alpha}\ast F(u))f(u), \quad \quad \hbox{in }\mathbb{R}^{2},\\ &\int_{\mathbb{R}^{2}}|u|^{2}dx=a^{2}, \end{aligned} \right. \end{align*} where $a>0$ is prescribed, $\lambda\in \mathbb{R}$, $\alpha\in(0,2)$, $I_{\alpha}$ denotes the Riesz potential, $\ast$ indicates the convolution operator, the function $f(t)$ has exponential growth in $\mathbb{R}^{2}$ and $F(t)=\int^{t}_{0}f(\tau)d\tau$. Using the Pohozaev manifold and variational methods, we establish the existence of normalized solutions to the above problem.Comment: arXiv admin note: text overlap with arXiv:2210.02331. text overlap with arXiv:2102.03001 by other author

A new unconventional HLA-A2-restricted epitope from HBV core protein elicits antiviral cytotoxic T lymphocytes

Cytotoxic T cells (CTLs) play a key role in the control of Hepatitis B virus (HBV) infection and viral clearance. However, most of identified CTL epitopes are derived from HBV of genotypes A and D, and few have been defined in virus of genotypes B and C which are more prevalent in Asia. As HBV core protein (HBc) is the most conservative and immunogenic component, in this study we used an overlapping 9-mer peptide pool covering HBc to screen and identify specific CTL epitopes. An unconventional HLA-A2-restricted epitope HBc141–149 was discovered and structurally characterized by crystallization analysis. The immunogenicity and anti-HBV activity were further determined in HBV and HLA-A2 transgenic mice. Finally, we show that mutations in HBc141–149 epitope are associated with viral parameters and disease progression in HBV infected patients. Our data therefore provide insights into the structure characteristics of this unconventional epitope binding to MHC-I molecules, as well as epitope specific CTL activity that orchestrate T cell response and immune evasion in HBV infected patients