Polarization of kilonova emission from a black hole-neutron star merger

A multi-messenger, black hole (BH) - neutron star (NS) merger event still remains to be detected. The tidal (dynamical) ejecta from such an event, thought to produce a kinonova, is concentrated in the equatorial plane and occupies only part of the whole azimuthal angle. In addition, recent simulations suggest that the outflow or wind from the post-merger remnant disk, presumably anisotropic, can be a major ejecta component responsible for a kilonova. For any ejecta whose photosphere shape deviates from the spherical symmetry, the electron scattering at the photosphere causes a net polarization in the kilonova light. Recent observational and theoretical polarization studies have been focused to the NS-NS merger kilonova AT2017gfo. We extend those work to the case of a BH-NS merger kilonova. We show that the degree of polarization at the first $\sim 1$ hr can be up to $\sim$ 3\% if a small amount ($10^{-4} M_{\odot}$) of free neutrons have survived in the fastest component of the dynamical ejecta, whose beta-decay causes a precursor in the kilonova light. The polarization degree can be $\sim$ 0.6\% if free neutrons survived in the fastest component of the disk wind. Future polarization detection of a kilonova will constrain the morphology and composition of the dominant ejecta component, therefore help to identify the nature of the merger.Comment: 10 pages, 5 figures. Accepted for publication in Ap

Dynamic hydration valve controlled ion permeability and stability of NaK channel

The K^+^, Na^+^, Ca^2+^ channels are essential to neural signalling, but our current knowledge at atomic level is mainly limited to that of K^+^ channels. Unlike a K^+^ channel having four equivalent K^+^-binding sites in its selectivity filter, a NaK channel conducting both Na^+^ and K^+^ ions has a vestibule in the middle part of its selectivity filter, in which ions can diffuse but not bind specifically. However, how the NaK channel conducts ions remains elusive. Here we find four water grottos connecting with the vestibule of the NaK selectivity filter. Molecular dynamics and free energy calculations show that water molecules moving in the vestibule-grotto complex hydrate and stabilize ions in the filter and serve as a valve in conveying ions through the vestibule for controllable ion permeating. During ion conducting, the water molecules are confined within the valve to guarantee structure stability. The efficient exquisite hydration valve should exist and play similar roles in the large family of cyclic nucleotide-gated channels which have similar selectivity filter sequences. The exquisite hydration valve mechanism may shed new light on the importance of water in neural signalling

Graphical model and algorithm for detecting DNA structural variation

Next-generation sequencing (NGS) has revolutionized the detection of structural variation in genome. Among NGS strategies, reading depth is widely used and paramorphism information contained inside is generally ignored. We develop an algorithm that can fully exploit both reading depth and paramorphism information. We embed mutation procedure in our system model for estimating prior likelihood of single nucleotide base. Hidden Markov model is used to connect single base into segments and belief propagation algorithm is performed for the optimal solution of the HMM model. Simulations show promising results in detecting important types of structural variation. We have applied the algorithm on the maize B73 and MO17 genome data and compared the results with those obtained from arrayCGH method based micro-array data. Inconsistency between the two sets of data is discussed

Health Care System Reform in China: Issues, Challenges and Options

This paper examines health care reform in urban and rural China. Before health care reform, Chinese health service facilities were run entirely by the state and basically they performed a social welfare function. This health care system greatly improved the population health conditions but many problems started to emerge in 1980s when the economic reform started. Since then, the government has been struggling to maintain a balance between meeting people¡¯s health care needs and develop the health care "industry". Problems and their contribution factors in organization, financing and performance of the health care reform are examined and analyzed. In terms of organization, decentralization of the decision making power in health sector and marketization of the medical establishments constitutes the main organizational changes in the health care reform. This organizational reform of health sector as an imposed institution change, encounters lots of resistance in the process of implementation. A tremendous amount of conflictions arises because of the commercialization of health sector that used to perform social welfare function. In terms of financing, share of organized financing (government and social fund) in the total health expenditure declined dramatically since the reform. In urban China, Health care insurance faced tough going on universal access. In rural China, there are lots of problems in implementing new cooperative health system partly because of its imperfect design. In terms of performance, data shows that there is growing inequity in health status between rural and urban in the past 15 years. Inefficiencies also exists in both resource allocation and service delivery. Several options are analyzed for organizational reform and health care financing. The report recommends that the aims of the future reform policy that government would adopt should be to improve the population health status instead of generating profit for institutions or industry. The social welfare function of health care system should be reinforced and at the same time managed competition in the health care market should be encouraged. In health care financing in urban area, several directions of broadening risk pooling are discussed. In rural health care financing, the designing of new cooperative health care system is analyzed. Rural financing should be more flexible in order to attract more people to join the cooperative medical system. It is recommended that Chinese government should increase funding for public health programs and subsidize health services for the disadvantaged groups.