1,022 research outputs found
Quantum Critical Superfluid Flows and Anisotropic Domain Walls
We construct charged anisotropic AdS domain walls as solutions of a
consistent truncation of type IIB string theory. These are a one-parameter
family of solutions that flow to an AdS fixed point in the IR, exhibiting
emergent conformal invariance and quantum criticality. They represent the
zero-temperature limit of the holographic superfluids at finite superfluid
velocity constructed in arXiv:1010.5777. We show that these domain walls exist
only for velocities less than a critical value, agreeing in detail with a
conjecture made there. We also comment about the IR limits of flows with
velocities higher than this critical value, and point out an intriguing
similarity between the phase diagrams of holographic superfluid flows and those
of ordinary superconductors with imbalanced chemical potential.Comment: 11 pages, 3 figures. V2: Very minor corrections. JHEP versio
Conserved presence of G-quadruplex forming sequences in the Long Terminal Repeat Promoter of Lentiviruses
G-quadruplexes (G4s) are secondary structures of nucleic acids that epigenetically regulate cellular processes. In the human immunodeficiency lentivirus 1 (HIV-1), dynamic G4s are located in the unique viral LTR promoter. Folding of HIV-1 LTR G4s inhibits viral transcription; stabilization by G4 ligands intensifies this effect. Cellular proteins modulate viral transcription by inducing/unfolding LTR G4s. We here expanded our investigation on the presence of LTR G4s to all lentiviruses. G4s in the 5'-LTR U3 region were completely conserved in primate lentiviruses. A G4 was also present in a cattle-infecting lentivirus. All other non-primate lentiviruses displayed hints of less stable G4s. In primate lentiviruses, the possibility to fold into G4s was highly conserved among strains. LTR G4 sequences were very similar among phylogenetically related primate viruses, while they increasingly differed in viruses that diverged early from a common ancestor. A strong correlation between primate lentivirus LTR G4s and Sp1/NF\u3baB binding sites was found. All LTR G4s folded: their complexity was assessed by polymerase stop assay. Our data support a role of the lentiviruses 5'-LTR G4 region as control centre of viral transcription, where folding/unfolding of G4s and multiple recruitment of factors based on both sequence and structure may take place
Selective Constraints on Amino Acids Estimated by a Mechanistic Codon Substitution Model with Multiple Nucleotide Changes
Empirical substitution matrices represent the average tendencies of
substitutions over various protein families by sacrificing gene-level
resolution. We develop a codon-based model, in which mutational tendencies of
codon, a genetic code, and the strength of selective constraints against amino
acid replacements can be tailored to a given gene. First, selective constraints
averaged over proteins are estimated by maximizing the likelihood of each 1-PAM
matrix of empirical amino acid (JTT, WAG, and LG) and codon (KHG) substitution
matrices. Then, selective constraints specific to given proteins are
approximated as a linear function of those estimated from the empirical
substitution matrices.
Akaike information criterion (AIC) values indicate that a model allowing
multiple nucleotide changes fits the empirical substitution matrices
significantly better. Also, the ML estimates of transition-transversion bias
obtained from these empirical matrices are not so large as previously
estimated. The selective constraints are characteristic of proteins rather than
species. However, their relative strengths among amino acid pairs can be
approximated not to depend very much on protein families but amino acid pairs,
because the present model, in which selective constraints are approximated to
be a linear function of those estimated from the JTT/WAG/LG/KHG matrices, can
provide a good fit to other empirical substitution matrices including cpREV for
chloroplast proteins and mtREV for vertebrate mitochondrial proteins.
The present codon-based model with the ML estimates of selective constraints
and with adjustable mutation rates of nucleotide would be useful as a simple
substitution model in ML and Bayesian inferences of molecular phylogenetic
trees, and enables us to obtain biologically meaningful information at both
nucleotide and amino acid levels from codon and protein sequences.Comment: Table 9 in this article includes corrections for errata in the Table
9 published in 10.1371/journal.pone.0017244. Supporting information is
attached at the end of the article, and a computer-readable dataset of the ML
estimates of selective constraints is available from
10.1371/journal.pone.001724
Unbalanced Holographic Superconductors and Spintronics
We present a minimal holographic model for s-wave superconductivity with
unbalanced Fermi mixtures, in 2+1 dimensions at strong coupling. The breaking
of a U(1)_A "charge" symmetry is driven by a non-trivial profile for a charged
scalar field in a charged asymptotically AdS_4 black hole. The chemical
potential imbalance is implemented by turning on the temporal component of a
U(1)_B "spin" field under which the scalar field is uncharged. We study the
phase diagram of the model and comment on the eventual (non) occurrence of
LOFF-like inhomogeneous superconducting phases. Moreover, we study "charge" and
"spin" transport, implementing a holographic realization (and a generalization
thereof to superconducting setups) of Mott's two-current model which provides
the theoretical basis of modern spintronics. Finally we comment on possible
string or M-theory embeddings of our model and its higher dimensional
generalizations, within consistent Kaluza-Klein truncations and brane-anti
brane setups.Comment: 45 pages, 15 figures; v2: two paragraphs below eq. (3.1) slightly
modified, figure 5 (left) replaced, references added; v3: typos corrected,
comments added, figure 12 replace
Measurements of neutrino oscillation in appearance and disappearance channels by the T2K experiment with 6.6 x 10(20) protons on target
111 pages, 45 figures, submitted to Physical Review D. Minor revisions to text following referee comments111 pages, 45 figures, submitted to Physical Review D. Minor revisions to text following referee comments111 pages, 45 figures, submitted to Physical Review D. Minor revisions to text following referee commentsWe thank the J-PARC staff for superb accelerator performance and the CERN NA61/SHINE Collaboration for providing valuable particle production data. We acknowledge the support of MEXT, Japan; NSERC, NRC, and CFI, Canada; CEA and CNRS/IN2P3, France; DFG, Germany; INFN, Italy; National Science Centre (NCN), Poland; RSF, RFBR and MES, Russia; MINECO and ERDF funds, Spain; SNSF and SER, Switzerland; STFC, UK; and the U. S. Deparment of Energy, USA. We also thank CERN for the UA1/NOMAD magnet, DESY for the HERA-B magnet mover system, NII for SINET4, the WestGrid and SciNet consortia in Compute Canada, GridPP, UK, and the Emerald High Performance Computing facility in the Centre for Innovation, UK. In addition, participation of individual researchers and institutions has been further supported by funds from ERC (FP7), EU; JSPS, Japan; Royal Society, UK; and DOE Early Career program, USA
TRY plant trait database - enhanced coverage and open access
Plant traits-the morphological, anatomical, physiological, biochemical and phenological characteristics of plants-determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait-based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits-almost complete coverage for 'plant growth form'. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait-environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives
Evidence for acquisition of virulence effectors in pathogenic chytrids
Background
The decline in amphibian populations across the world is frequently linked to the infection of the chytrid fungus Batrachochytrium dendrobatidis (Bd). This is particularly perplexing because Bd was only recently discovered in 1999 and no chytrid fungus had previously been identified as a vertebrate pathogen.
Results
In this study, we show that two large families of known virulence effector genes, crinkler (CRN) proteins and serine peptidases, were acquired by Bd from oomycete pathogens and bacteria, respectively. These two families have been duplicated after their acquisition by Bd. Additional selection analyses indicate that both families evolved under strong positive selection, suggesting that they are involved in the adaptation of Bd to its hosts.
Conclusions
We propose that the acquisition of virulence effectors, in combination with habitat disruption and climate change, may have driven the Bd epidemics and the decline in amphibian populations. This finding provides a starting point for biochemical investigations of chytridiomycosis
Assessing the experience of using synthetic cannabinoids by means of interpretative phenomenological analysis
BACKGROUND: New psychoactive substances (NPS) have been increasingly consumed by people who use drugs in recent years, which pose a new challenge for treatment services. One of the largest groups of NPS is synthetic cannabinoids (SCs), which are intended as a replacement to cannabis. While there is an increasing body of research on the motivation and the effects associated with SC use, little is known about the subjective interpretation of SC use by the people who use drugs themselves. The aim of this study was to examine the experiences and personal interpretations of SC use of users who were heavily dependent on SC and are in treatment. METHODS: A qualitative research method was applied in order to explore unknown and personal aspects of SC use. Semi-structured interviews were conducted with six participants who had problematic SC use and entered treatment. The research was conducted in Hungary in 2015. We analyzed data using interpretative phenomenological analysis (IPA). RESULTS: Participants perceived SCs to be unpredictable: their initial positive experiences quickly turned negative. They also reported that SCs took over their lives both interpersonally and intrapersonally: the drug took their old friends away, and while initially it gave them new ones, in the end it not only made them asocial but the drug became their only friend, it hijacked their personalities and made them addicted. CONCLUSIONS: Participants experienced rapid development of effects and they had difficulties interpreting or integrating these experiences. The rapid alteration of effects and experiences may explain the severe psychopathological symptoms, which may be important information for harm reduction and treatment services. Since, these experiences are mostly unknown and unpredictable for people who use SCs, a forum where they could share their experiences could have a harm reducing role. For a harm reduction point of view of SCs, which are underrepresented in literature, it is important to emphasize the impossibility of knowing the quantity, purity, or even the number of different SC compounds in a particular SC product. Our study findings suggest that despite the adverse effects, including a rapid turn of experiences to negative, rapid development of addiction and withdrawal symptoms of SCs, participants continued using the drug because this drug was mostly available and cheap. Therefore, a harm reduction approach would be to make available and legal certain drugs that have less adverse effects and could cause less serious dependence and withdrawal symptoms, with controlled production and distribution (similarly to cannabis legalization in the Netherlands)
Comparative physical maps derived from BAC end sequences of tilapia (Oreochromis niloticus)
Background: The Nile tilapia is the second most important fish in aquaculture. It is an excellent laboratory model, and is closely related to the African lake cichlids famous for their rapid rates of speciation. A suite of genomic resources has been developed for this species, including genetic maps and ESTs. Here we analyze BAC endsequences to develop comparative physical maps, and estimate the number of genome rearrangements, between tilapia and other model fish species. Results: We obtained sequence from one or both ends of 106,259 tilapia BACs. BLAST analysis against the genome assemblies of stickleback, medaka and pufferfish allowed identification of homologies for approximately 25,000 BACs for each species. We calculate that rearrangement breakpoints between tilapia and these species occur about every 3 Mb across the genome. Analysis of 35,000 clones previously assembled into contigs by restriction fingerprints allowed identification of longer-range syntenies. Conclusions: Our data suggest that chromosomal evolution in recent teleosts is dominated by alternate loss of gene duplicates, and by intra-chromosomal rearrangements (~one per million years). These physical maps are a useful resource for comparative positional cloning of traits in cichlid fishes. The paired BAC end sequences from these clones will be an important resource for scaffolding forthcoming shotgun sequence assemblies of the tilapia genome. (Résumé d'auteur
Measurement of the electron neutrino charged-current interaction rate on water with the T2K ND280 pi(0) detector
10 pages, 6 figures, Submitted to PRDhttp://journals.aps.org/prd/abstract/10.1103/PhysRevD.91.112010© 2015 American Physical Society11 pages, 6 figures, as accepted to PRD11 pages, 6 figures, as accepted to PRD11 pages, 6 figures, as accepted to PR
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