Global quark polarization in non-central A+AA+A collisions

Partons produced in the early stage of non-central heavy-ion collisions can develop a longitudinal fluid shear because of unequal local number densities of participant target and projectile nucleons. Under such fluid shear, local parton pairs with non-vanishing impact parameter have finite local relative orbital angular momentum along the direction opposite to the reaction plane. Such finite relative orbital angular momentum among locally interacting quark pairs can lead to global quark polarization along the same direction due to spin-orbital coupling. Local longitudinal fluid shear is estimated within both Landau fireball and Bjorken scaling model of initial parton production. Quark polarization through quark-quark scatterings with the exchange of a thermal gluon is calculated beyond small-angle scattering approximation in a quark-gluon plasma. The polarization is shown to have a non-monotonic dependence on the local relative orbital angular momentum dictated by the interplay between electric and magnetic interaction. It peaks at a value of relative orbital angular momentum which scales with the magnetic mass of the exchanged gluons. With the estimated small longitudinal fluid shear in semi-peripheral $Au+Au$ collisions at the RHIC energy, the final quark polarization is found to be small $|P_q|<0.04$ in the weak coupling limit. Possible behavior of the quark polarization in the strong coupling limit and implications on the experimental detection of such global quark polarization at RHIC and LHC are also discussed.Comment: 28 pages,11 figure

Quantum phase transition in magnetic nanographenes on a lead superconductor

Quantum spins, referred to the spin operator preserved by full SU(2) symmetry in the absence of the magnetic anistropy, have been proposed to host exotic interactions with superconductivity4. However, spin orbit coupling and crystal field splitting normally cause a significant magnetic anisotropy for d/f-shell spins on surfaces6,9, breaking SU(2) symmetry and fabricating the spins with Ising properties10. Recently, magnetic nanographenes have been proven to host intrinsic quantum magnetism due to their negligible spin orbital coupling and crystal field splitting. Here, we fabricate three atomically precise nanographenes with the same magnetic ground state of spin S=1/2 on Pb(111) through engineering sublattice imbalance in graphene honeycomb lattice. Scanning tunneling spectroscopy reveals the coexistence of magnetic bound states and Kondo screening in such hybridized system. Through engineering the magnetic exchange strength between the unpaired spin in nanographenes and cooper pairs, quantum phase transition from the singlet to the doublet state has been observed, in consistent with quantum models of spins on superconductors. Our work demonstrates delocalized graphene magnetism host highly tunable magnetic bound states with cooper pairs, which can be further developed to study the Majorana bound states and other rich quantum physics of low-dimensional quantum spins on superconductors.Comment: 13 pages, 4figure

3-Isopropyl-2-p-tol­yloxy-5,6,7,8-tetra­hydro-1-benzothieno[2,3-d]pyrimidin-4(3H)-one

In the title compound, C20H22N2O2S, the central thieno­pyrimidine ring system is essentially planar, with a maximum displacement of 0.023 (2) Å. The attached cyclo­hexene ring is disordered over two possible conformations, with an occupancy ratio of 0.776 (12):0.224 (12). Neither inter­molecular hydrogen-bonding inter­actions nor π–π stacking inter­actions are present in the crystal structure. The mol­ecular conformation and crystal packing are stabilized by three intra­molecular C—H⋯O hydrogen bonds and two C—H⋯π inter­actions

Rapid assessment of knowledge, attitudes, practices, and risk perception related to the prevention and control of Ebola virus disease in three communities of Sierra Leone

Questionnaire on Ebola knowledge, attitudes, practices, and risk perception in three communities of Sierra Leone, 2015. (DOCX 34 kb

Salmonella paratyphi C: Genetic Divergence from Salmonella choleraesuis and Pathogenic Convergence with Salmonella typhi

BACKGROUND: Although over 1400 Salmonella serovars cause usually self-limited gastroenteritis in humans, a few, e.g., Salmonella typhi and S. paratyphi C, cause typhoid, a potentially fatal systemic infection. It is not known whether the typhoid agents have evolved from a common ancestor (by divergent processes) or acquired similar pathogenic traits independently (by convergent processes). Comparison of different typhoid agents with non-typhoidal Salmonella lineages will provide excellent models for studies on how similar pathogens might have evolved. METHODOLOGIES/PRINCIPAL FINDINGS: We sequenced a strain of S. paratyphi C, RKS4594, and compared it with previously sequenced Salmonella strains. RKS4594 contains a chromosome of 4,833,080 bp and a plasmid of 55,414 bp. We predicted 4,640 intact coding sequences (4,578 in the chromosome and 62 in the plasmid) and 152 pseudogenes (149 in the chromosome and 3 in the plasmid). RKS4594 shares as many as 4346 of the 4,640 genes with a strain of S. choleraesuis, which is primarily a swine pathogen, but only 4008 genes with another human-adapted typhoid agent, S. typhi. Comparison of 3691 genes shared by all six sequenced Salmonella strains placed S. paratyphi C and S. choleraesuis together at one end, and S. typhi at the opposite end, of the phylogenetic tree, demonstrating separate ancestries of the human-adapted typhoid agents. S. paratyphi C seemed to have suffered enormous selection pressures during its adaptation to man as suggested by the differential nucleotide substitutions and different sets of pseudogenes, between S. paratyphi C and S. choleraesuis. CONCLUSIONS: S. paratyphi C does not share a common ancestor with other human-adapted typhoid agents, supporting the convergent evolution model of the typhoid agents. S. paratyphi C has diverged from a common ancestor with S. choleraesuis by accumulating genomic novelty during adaptation to man

A new transfer matrix method to calculate the optical absorption of graphene at any position in stratified media

A new transfer matrix method is developed based on the electromagnetic boundary conditions that Maxwell's equations required. Compared with the traditional transfer matrix method, the new method can be used to calculate the optical absorption of any layer at any position in stratified media. By using this new method, we investigate the optical absorption properties of a single graphene sheet in one-dimensional photonic-crystal (1DPC) heterostructures. We demonstrate that the optical absorption of graphene can be greatly enhanced up to almost 100% by the use of the 1DPC heterostructures because of the strong photon localization in the layer of graphene

Gate-tunable nearly total absorption in graphene with resonant metal back reflector

The gate-tunable absorption of graphene layers with a resonant metal back reflector (RMBF) is theoretically investigated. We demonstrate that the absorption of graphene with RMBF can vary from nearly negligible to nearly total by tuning the external gate voltage within the terahertz (THz) spectra range. Total THz absorption is less affected by the incident angle of THz beams. This peculiar nearly total THz absorption can be attributed to the Fabry-Perot cavity effect, which enhances the absorption and reduces the reflection of graphene. The absorption spectra of the graphene-RMBF structure can also be tailored in bandwidth and center frequency by changing the thickness and dielectric constant of the spacer layer. These findings can lead to the development of tunable THz photonic devices and have potential applications in studies on the ultrafast dynamics of Dirac fermions in graphene