1,735 research outputs found
Structural and electronic properties of Al nanowires: an ab initio pseudopotential study
The stability and electronic structure of a single monatomic Al wire has been
studied using the ab initio pseudopotential method. The Al wire undergoes two
structural rearrangements under compression, i.e., zigzag configurations at
angles of and . The evolution of electronic structures of the Al
chain as a function of structural phase transition has been investigated. The
relationship between electronic structure and geometric stability is also
discussed. The 2p bands in the Al nanowire are shown to play a critical role in
its stability. The effects of density functionals (GGA and LDA) on cohesive
energy and bond length of Al nanostructures (dimmer, chains, and monolayers)
are also examined. The link between low dimensional 0D structure (dimmer) to
high dimensional 3D bulk Al is estimated. An example of optimized tip-suspended
finite atomic chain is presented to bridge the gap between hypothetical
infinite chains and experimental finite chains.Comment: 11 pages, 5 figure
Improved effective potential of Gildener-Weinberg models
The Gildener-Weinberg models are of particular interest in the context of
extensions to the Standard Model of particle physics. These extensions may
encompass a variety of theories, including double Higgs models, Grand
Unification Theories, and proposals for Dark Matter, among others. In order to
rigorously test these models experimentally, obtaining precise results is of
crucial importance. In this study, we employ the renormalization group equation
and its one-loop functions to obtain a deeper understanding of the higher-loop
effective potential. Our findings reveal that the radiatively generated mass of
the light particle in the Gildener-Weinberg approach experiences a substantial
correction. Furthermore, our results suggest that not all flat directions are
equivalent and some may be preferred by nature.Comment: 28 pages, 11 figure
Fluorophore-Doped Core-Multishell Spherical Plasmonic Nanocavities: Resonant Energy Transfer towards a Loss Compensation
Cataloged from PDF version of article.Plasmonics exhibits the potential to break the diffraction limit and bridge the gap between electronics and
photonics by routing and manipulating light at the nanoscale. However, the inherent and strong energy
dissipation present in metals, especially in the near-infrared and visible wavelength ranges, significantly
hampersthe applications in nanophotonics. Therefore, it is amajor challengetomitigatethe losses. One way
to compensate the losses is to incorporate gain media into plasmonics. Here, we experimentally show that
the incorporation of gain material into a local surface plasmonic system (Au/silica/silica dye core multishell
nanoparticles) leads to a resonant energy transfer from the gain media to the plasmon. The optimized
conditions for the largest loss compensation are reported. Both the coupling distance and the spectral
overlap arethe key factorsto determinetheresulting energy transfer. Theinterplay of these factors leadsto
a non-monotonous photoluminescence dependence as a function of the silica spacer shell thickness.
Nonradiativetransferrate is increased by morethan 3 orders of magnitude attheresonant condition, which
is key evidence of the strongest coupling occurring between the plasmon and the gain material
Changes in Local S4 Environment Provide a Voltage-sensing Mechanism for Mammalian Hyperpolarization–activated HCN Channels
The positively charged S4 transmembrane segment of voltage-gated channels is thought to function as the voltage sensor by moving charge through the membrane electric field in response to depolarization. Here we studied S4 movements in the mammalian HCN pacemaker channels. Unlike most voltage-gated channel family members that are activated by depolarization, HCN channels are activated by hyperpolarization. We determined the reactivity of the charged sulfhydryl-modifying reagent, MTSET, with substituted cysteine (Cys) residues along the HCN1 S4 segment. Using an HCN1 channel engineered to be MTS resistant except for the chosen S4 Cys substitution, we determined the reactivity of 12 S4 residues to external or internal MTSET application in either the closed or open state of the channel. Cys substitutions in the NH2-terminal half of S4 only reacted with external MTSET; the rates of reactivity were rapid, regardless of whether the channel was open or closed. In contrast, Cys substitutions in the COOH-terminal half of S4 selectively reacted with internal MTSET when the channel was open. In the open state, the boundary between externally and internally accessible residues was remarkably narrow (∼3 residues). This suggests that S4 lies in a water-filled gating canal with a very narrow barrier between the external and internal solutions, similar to depolarization-gated channels. However, the pattern of reactivity is incompatible with either classical gating models, which postulate a large translational or rotational movement of S4 within a gating canal, or with a recent model in which S4 forms a peripheral voltage-sensing paddle (with S3b) that moves within the lipid bilayer (the KvAP model). Rather, we suggest that voltage sensing is due to a rearrangement in transmembrane segments surrounding S4, leading to a collapse of an internal gating canal upon channel closure that alters the shape of the membrane field around a relatively static S4 segment
Geometric entanglement from matrix product state representations
An efficient scheme to compute the geometric entanglement per lattice site
for quantum many-body systems on a periodic finite-size chain is proposed in
the context of a tensor network algorithm based on the matrix product state
representations. It is systematically tested for three prototypical critical
quantum spin chains, which belong to the same Ising universality class. The
simulation results lend strong support to the previous claim [Q.-Q. Shi, R.
Or\'{u}s, J. O. Fj{\ae}restad, and H.-Q. Zhou, New J. Phys \textbf{12}, 025008
(2010); J.-M. St\'{e}phan, G. Misguich, and F. Alet, Phys. Rev. B \textbf{82},
180406R (2010)] that the leading finite-size correction to the geometric
entanglement per lattice site is universal, with its remarkable connection to
the celebrated Affleck-Ludwig boundary entropy corresponding to a conformally
invariant boundary condition.Comment: 4+ pages, 3 figure
Single top production associated with a neutral scalar at LHC in topcolor-assisted technicolor
The topcolor-assisted technicolor (TC2) model predicts a number of neutral
scalars like the top-pion () and the top-Higgs (). These
scalars have flavor-changing neutral-current (FCNC) top quark couplings, among
which the top-charm transition couplings may be sizable. Such FCNC couplings
induce single top productions associated with a neutral scalar at the CERN
Large Hadron Collider (LHC) through the parton processes and
. In this note we examine these productions and find their
production rates can exceed the sensitivity of the LHC in a large
part of parameter space. Since in the Standard Model and the minimal
supersymmetric model such rare productions have unobservably small production
rates at the LHC, these rare processes will serve as a good probe for the TC2
model.Comment: 7 pages, 3 fig
Scalar-Torsion Mode in a Cosmological Model of the Poincar\'{e} Gauge Theory of Gravity
We investigate the equation of state (EoS) of the scalar-torsion mode in
Poincar\'{e} gauge theory of gravity. We concentrate on two cases with the
constant curvature solution and positive kinetic energy, respectively. In the
former, we find that the torsion EoS has different values in the various stages
of the universe. In particular, it behaves like the radiation (matter) EoS of
() in the radiation (matter) dominant epoch, while in the late
time the torsion density is supportive for the accelerating universe. In the
latter, our numerical analysis shows that in general the EoS has an asymptotic
behavior in the high redshift regime, while it could cross the phantom divide
line in the low redshift regime.Comment: 12 pages, 2 figures, title changed, revised version accepted for
publication in JCA
Integromic analysis of genetic variation and gene expression identifies networks for cardiovascular disease phenotypes
Cataloged from PDF version of article.Background-Cardiovascular disease (CVD) reflects a highly coordinated complex of traits. Although genome-wide association studies have reported numerous single nucleotide polymorphisms (SNPs) to be associated with CVD, the role of most of these variants in disease processes remains unknown.
Methods and Results-We built a CVD network using 1512 SNPs associated with 21 CVD traits in genome-wide association studies (at P <= 5x10(-8)) and cross-linked different traits by virtue of their shared SNP associations. We then explored whole blood gene expression in relation to these SNPs in 5257 participants in the Framingham Heart Study. At a false discovery rate <0.05, we identified 370 cis-expression quantitative trait loci (eQTLs; SNPs associated with altered expression of nearby genes) and 44 trans-eQTLs (SNPs associated with altered expression of remote genes). The eQTL network revealed 13 CVD-related modules. Searching for association of eQTL genes with CVD risk factors (lipids, blood pressure, fasting blood glucose, and body mass index) in the same individuals, we found examples in which the expression of eQTL genes was significantly associated with these CVD phenotypes. In addition, mediation tests suggested that a subset of SNPs previously associated with CVD phenotypes in genome-wide association studies may exert their function by altering expression of eQTL genes (eg, LDLR and PCSK7), which in turn may promote interindividual variation in phenotypes.
Conclusions-Using a network approach to analyze CVD traits, we identified complex networks of SNP-phenotype and SNP-transcript connections. Integrating the CVD network with phenotypic data, we identified biological pathways that may provide insights into potential drug targets for treatment or prevention of CVD.(Circulation. 2015;131:536-549.
DOI: 10.1161/CIRCULATIONAHA.114.010696.
Entanglement and boundary critical phenomena
We investigate boundary critical phenomena from a quantum information
perspective. Bipartite entanglement in the ground state of one-dimensional
quantum systems is quantified using the Renyi entropy S_alpha, which includes
the von Neumann entropy (alpha=1) and the single-copy entanglement
(alpha=infinity) as special cases. We identify the contribution from the
boundary entropy to the Renyi entropy, and show that there is an entanglement
loss along boundary renormalization group (RG) flows. This property, which is
intimately related to the Affleck-Ludwig g-theorem, can be regarded as a
consequence of majorization relations between the spectra of the reduced
density matrix along the boundary RG flows. We also point out that the bulk
contribution to the single-copy entanglement is half of that to the von Neumann
entropy, whereas the boundary contribution is the same.Comment: 4 pages, 2 figure
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Antimicrobial Resistance in Neisseria gonorrhoeae: Proceedings of the STAR Sexually Transmitted Infection-Clinical Trial Group Programmatic Meeting.
The goal of the Sexually Transmitted Infection Clinical Trial Group's Antimicrobial Resistance (AMR) in Neisseria gonorrhoeae (NG) meeting was to assemble experts from academia, government, nonprofit and industry to discuss the current state of research, gaps and challenges in research and technology and priorities and new directions to address the continued emergence of multidrug-resistant NG infections. Topics discussed at the meeting, which will be the focus of this article, include AMR NG global surveillance initiatives, the use of whole genome sequencing and bioinformatics to understand mutations associated with AMR, mechanisms of AMR, and novel antibiotics, vaccines and other methods to treat AMR NG. Key points highlighted during the meeting include: (i) US and International surveillance programs to understand AMR in NG; (ii) the US National Strategy for combating antimicrobial-resistant bacteria; (iii) surveillance needs, challenges, and novel technologies; (iv) plasmid-mediated and chromosomally mediated mechanisms of AMR in NG; (v) novel therapeutic (eg, sialic acid analogs, factor H [FH]/Fc fusion molecule, monoclonal antibodies, topoisomerase inhibitors, fluoroketolides, LpxC inhibitors) and preventative (eg, peptide mimic) strategies to combat infection. The way forward will require renewed political will, new funding initiatives, and collaborations across academic and commercial research and public health programs
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