Neutron star phase transition as the origin for the fast radio bursts and soft gamma-ray repeaters of SGR J1935+2154

Magnetars are believed as neutron stars (NSs) with strong magnetic fields. X-ray flares and fast radio bursts (FRBs) have been observed from the magnetar (soft gamma-ray repeater, SGR J1935+2154). We propose that the phase transition of the NS can power the FRBs and SGRs.Based on the equation of state provided by the MIT bag model and the mean field approximation, we solve the Tolman-Oppenheimer-Volkoff equations to get the NS structure. With spin-down of the NS, the hadronic shell gradually transfers to the quark shell.The gravitational potential energy released by one time of the phase transition can be achieved. The released energy, time interval between two successive phase transitions, and glitch are all consistent with the observations of the FRBs and the X-ray flares from SGR J1935+2154. We conclude that the phase transition of an NS is a plausible mechanism to power the SGRs as well as the repeating FRBs.Comment: 11 pages, 3 figure

Limited Genetic Connectivity Among Sargassum horneri (Phaeophyceae) Populations in the Chinese Marginal Seas Despite Their high Dispersal Capacity

Sargassum horneri is a habitat-forming species in the Northwest Pacific and an important contributor to seaweed rafts. In this study, 131 benthic samples and 156 floating samples were collected in the Yellow Sea and East China Sea (ECS) to test the effects of seaweed rafts on population structure and connectivity. Our results revealed high levels of genetic diversity in both benthic and floating samples based on concatenated mitochondrial markers (rpl5-rps3, rnl-atp9, and cob-cox2). Phylogenetic analyses consistently supported the existence of two lineages (lineages I and II), with divergence dating to c. 0.692 Mya (95% HPD: 0.255-1.841 Mya), indicating that long-term isolation may have occurred during the mid-Pleistocene (0.126-0.781 Mya). Extended Bayesian skyline plots demonstrated a constant population size over time in lineage I and slight demographic expansion in lineage II. Both lineages were found in each marginal sea (including both benthic and floating samples), but PCoA, F-ST, and AMOVA analyses consistently revealed deep genetic variation between regions. Highly structured phylogeographic pattern supports limited genetic connectivity between regions. IMA analyses demonstrated that asymmetric gene flow between benthic populations in the North Yellow Sea (NYS) and ECS was extremely low (ECS -> NYS, 2Nm = 0.6), implying that high dispersal capacity cannot be assumed to lead to widespread population connectivity, even without dispersal barriers. In addition, there were only a few shared haplotypes between benthic and floating samples, suggesting the existence of hidden donors for the floating masses in the Chinese marginal seas

An In Vivo Mouse Model of Long-Term Potentiation at Synapses between Primary Afferent C-Fibers and Spinal Dorsal Horn Neurons: Essential Role of Ephb1 Receptor

Abstract Background Long-term potentiation (LTP), a much studied cellular model of synaptic plasticity, has not been demonstrated at synapses between primary afferent C-fibers and spinal dorsal horn (DH) neurons in mice in vivo. EphrinB-EphB receptor signaling plays important roles in synaptic connection and plasticity in the nervous system, but its role in spinal synaptic plasticity remains unclear. Results This study characterizes properties of LTP at synapses of C-fibers onto neurons in the superficial DH following high-frequency stimulation (HFS) of a peripheral nerve at an intensity that activates C-fibers and examines associated activation of Ca2+/calmodulin-activated protein kinase II (p-CaMKII), extracellular signal-regulated kinase (p-ERK) and the cyclic AMP response element binding protein (p-CREB) and expression of c-Fos, and it investigates further roles for the EphB1 receptor in LTP. HFS induced LTP within 5 min and lasts for 3–8 h during the period of recording and resulted in upregulation of p-CaMKII, p-ERK and p-CREB protein levels in the spinal cord and expression of c-Fos in DH. Intrathecal pretreatment of MK-801 or EphB2-Fc prevented LTP and significantly reduced upregulation of p-CaMKII, p-ERK, p-CREB and c-Fos. Further, targeted mutation of EphB1 receptor prevented induction of LTP and associated increases in phosphorylation of CaMKII, ERK, and CREB. Conclusion This study provides an in vivo mouse model of LTP at synapses of C-fibers onto the superficial DH neurons that will be valuable for studying the DH neuron excitability and their synaptic plasticity and hyperalgesia. It further takes advantage of examining functional implications of a specific gene targeted mice and demonstrates that the EphB1 receptor is essential for development of LTP.</p

Experimental Realization of Nonadiabatic Holonomic Single-Qubit Quantum Gates with Two Dark Paths in a Trapped Ion

For circuit-based quantum computation, experimental implementation of universal set of quantum logic gates with high-fidelity and strong robustness is essential and central. Quantum gates induced by geometric phases, which depend only on global properties of the evolution paths, have built-in noise-resilience features. Here, we propose and experimentally demonstrate nonadiabatic holonomic single-qubit quantum gates on two dark paths in a trapped $^{171}\mathrm{Yb}^{+}$ ion based on four-level systems with resonant drives. We confirm the implementation with measured gate fidelity through both quantum process tomography and randomized benchmarking methods. Meanwhile, we find that nontrivial holonomic two-qubit quantum gates can also be realized within current experimental technologies. Compared with previous implementations on three-level systems, our experiment share both the advantage of fast nonadiabatic evolution and the merit of robustness against systematic errors, and thus retains the main advantage of geometric phases. Therefore, our experiment confirms a promising method for fast and robust holonomic quantum computation.Comment: 13 pages, 5 figure