15,753 research outputs found
Some comments on embedding inflation in the AdS/CFT correspondence
The anti-de Sitter space/conformal field theory correspondence (AdS/CFT) can
potentially provide a complete formulation of string theory on a landscape of
stable and metastable vacua that naturally give rise to eternal inflation. As a
model for this process, we consider bubble solutions with de Sitter interiors,
obtained by patching together dS and Schwarzschild-AdS solutions along a bubble
wall. For an interesting subclass of these solutions the bubble wall reaches
spacelike infinity in the black hole interior. Including the effects of
perturbations leads to a null singularity emanating from this point. Such
solutions are interpreted as states in a single CFT, and are shown to be
compatible with holographic entropy bounds. The construction suggests de Sitter
entropy be interpreted as the total number of degrees of freedom in effective
field theory, with a novel adaptive stepsize cutoff.Comment: 15 pages, 4 figures, revtex
Thrombotic variables and risk of idiopathic venous thromboembolism in women aged 45-64 years - Relationships to hormone replacement therapy
Hormone replacement therapy (HRT) has been shown to increase the relative risk of idiopathic venous thromboembolism (VTE) about threefold in several observational studies and one randomised controlled trial. Whether or not this relative risk is higher in women with underlying thrombophilia phenotypes, such as activated protein C (APC) resistance, is unknown. We therefore restudied the participants in a case-control study of the relationship between the use of HRT and the occurrence of idiopathic VTE in women aged 45-64 years. After protocol exclusions, 66 of the cases in the original study and 163 of the controls were studied. Twenty haematological variables relevant to risk of VTE were analysed, including thrombotic states defined from the literature. The relative risk of VTE showed significant associations with APC resistance (OR 4.06; 95% CI 1.62, 10.21); low antithrombin (3.33; 1.15, 9.65) or protein C (2.93; 1.06, 8.14); and high coagulation factor IX (2.34: 1.26, 1.35), or fibrin D-dimer (3.84; 1.99, 7.32). HRT use increased the risk of VTE in women without any of these thrombotic static; (OR 4.09; 95% CI 1.26, 13.30). A similar effect of HRT use on the relative risk of VTE was also found in women with prothrombotic states. Thus for example, the combination of HRT use and APC resistance increased the risk of VTE about 13-fold compared with women of similar age without either APC resistance or HRT use (OR 13.27; 95%, CI 4.30, 40.97). We conclude that the combination of HRT use and thrombophilias (especially if multiple) increases the relative risk of VTE substantially; hence women known to have thrombophilias (especially if multiple) should be counselled about this increased risk prior to prescription of HRT. However. HRT increases the risk of VTE about fourfold even in women without any thrombotic abnormalities: possible causes are discussed
Transcriptome sequencing, annotation and polymorphism detection in the hop bush, Dodonaea viscosa
The hop bush, Dodonaea viscosa, is a trans-oceanic species distributed oversix continents. It evolved in Australia where it is found over a wide range of habitat types and is an ecologically important species. Limited genomic resources are currently available for this species, thus our understanding of its evolutionary history and ecological adaptation is restricted. Here, we present a comprehensive transcriptome dataset for future genomic studies into this species.We performed Illumina sequencing of cDNA prepared from leaf tissue collected from seven populations of D. viscosa ssp. angustissima and spatulata distributed along an environmental gradient in South Australia. Sequenced reads were assembled to provide a transcriptome resource. Contiguous sequences (contigs) were annotated using BLAST searches against the NCBI non-redundant database and gene ontology definitions were assigned. Single nucleotide polymorphisms were detected for the establishment of a genetic marker set. A comparison between the two subspecies was also carried out.Illumina sequencing returned 268,672,818 sequence reads, which were de novoassembled into 105,125 contigs. Contigs with significant BLAST alignments (E value < 1e(-5))numbered at 44,191, with 38,311 of these having their most significant hits to sequences from land plant species. Gene Ontology terms were assigned to 28,440 contigs and KEGG analysis identified 146 pathways that the gene products from 5,070 contigs are potentially involved in. The subspecies comparison identified 8,494 fixed SNP differences across 3,979 contiguous sequences, indicating a level of genetic differentiation between them. Across all samples, 248,235 SNPs were detected.We have established a significant genomic data resource for D. viscosa,providing a comprehensive transcriptomic reference. Genetic differences among morphologically distinct subspecies were found. A wide range of putative gene regions were identified along with a large set of variable SNP markers, providing a basis for studies into the evolution and ecological adaptation of D. viscosa.Matthew J. Christmas, Ed Biffin and Andrew J. Low
Eighty years of food-web response to interannual variation in discharge recorded in river diatom frustules from an ocean sediment core.
Little is known about the importance of food-web processes as controls of river primary production due to the paucity of both long-term studies and of depositional environments which would allow retrospective fossil analysis. To investigate how freshwater algal production in the Eel River, northern California, varied over eight decades, we quantified siliceous shells (frustules) of freshwater diatoms from a well-dated undisturbed sediment core in a nearshore marine environment. Abundances of freshwater diatom frustules exported to Eel Canyon sediment from 1988 to 2001 were positively correlated with annual biomass of Cladophora surveyed over these years in upper portions of the Eel basin. Over 28 years of contemporary field research, peak algal biomass was generally higher in summers following bankfull, bed-scouring winter floods. Field surveys and experiments suggested that bed-mobilizing floods scour away overwintering grazers, releasing algae from spring and early summer grazing. During wet years, growth conditions for algae could also be enhanced by increased nutrient loading from the watershed, or by sustained summer base flows. Total annual rainfall and frustule densities in laminae over a longer 83-year record were weakly and negatively correlated, however, suggesting that positive effects of floods on annual algal production were primarily mediated by "top-down" (consumer release) rather than "bottom-up" (growth promoting) controls
Probabilistic Search for Object Segmentation and Recognition
The problem of searching for a model-based scene interpretation is analyzed
within a probabilistic framework. Object models are formulated as generative
models for range data of the scene. A new statistical criterion, the truncated
object probability, is introduced to infer an optimal sequence of object
hypotheses to be evaluated for their match to the data. The truncated
probability is partly determined by prior knowledge of the objects and partly
learned from data. Some experiments on sequence quality and object segmentation
and recognition from stereo data are presented. The article recovers classic
concepts from object recognition (grouping, geometric hashing, alignment) from
the probabilistic perspective and adds insight into the optimal ordering of
object hypotheses for evaluation. Moreover, it introduces point-relation
densities, a key component of the truncated probability, as statistical models
of local surface shape.Comment: 18 pages, 5 figure
Targeted capture to assess neutral genomic variation in the narrow-leaf hopbush across a continental biodiversity refugium
The Adelaide geosyncline, a mountainous region in central southern Australia, is purported to be an important continental refugium for Mediterranean and semi-arid Australian biota, yet few population genetic studies have been conducted to test this theory. Here, we focus on a plant species distributed widely throughout the region, the narrow-leaf hopbush, Dodonaea viscosa ssp. angustissima, and examine its genetic diversity and population structure. We used a hybrid-capture target enrichment technique to selectively sequence over 700 genes from 89 individuals across 17 sampling locations. We compared 815 single nucleotide polymorphisms among individuals and populations to investigate population genetic structure. Three distinct genetic clusters were identified; a Flinders/Gammon ranges cluster, an Eastern cluster, and a Kangaroo Island cluster. Higher genetic diversity was identified in the Flinders/Gammon Ranges cluster, indicating that this area is likely to have acted as a refugium during past climate oscillations. We discuss these findings and consider the historical range dynamics of these populations. We also provide methodological considerations for population genomics studies that aim to use novel genomic approaches (such as target capture methods) on non-model systems. The application of our findings to restoration of this species across the region are also considered.Matthew J. Christmas, Ed Biffin, Martin F. Breed & Andrew J. Low
Product recognition in store shelves as a sub-graph isomorphism problem
The arrangement of products in store shelves is carefully planned to maximize
sales and keep customers happy. However, verifying compliance of real shelves
to the ideal layout is a costly task routinely performed by the store
personnel. In this paper, we propose a computer vision pipeline to recognize
products on shelves and verify compliance to the planned layout. We deploy
local invariant features together with a novel formulation of the product
recognition problem as a sub-graph isomorphism between the items appearing in
the given image and the ideal layout. This allows for auto-localizing the given
image within the aisle or store and improving recognition dramatically.Comment: Slightly extended version of the paper accepted at ICIAP 2017. More
information @project_page -->
http://vision.disi.unibo.it/index.php?option=com_content&view=article&id=111&catid=7
On Vague Computers
Vagueness is something everyone is familiar with. In fact, most people think
that vagueness is closely related to language and exists only there. However,
vagueness is a property of the physical world. Quantum computers harness
superposition and entanglement to perform their computational tasks. Both
superposition and entanglement are vague processes. Thus quantum computers,
which process exact data without "exploiting" vagueness, are actually vague
computers
A study of blood contamination of Siqveland matrix bands
AIMS To use a sensitive forensic test to measure blood contamination of used Siqveland matrix bands following routine cleaning and sterilisation procedures in general dental practice. MATERIALS AND METHODS: Sixteen general dental practices in the West of Scotland participated. Details of instrument cleaning procedures were recorded for each practice. A total of 133 Siqveland matrix bands were recovered following cleaning and sterilisation and were examined for residual blood contamination by the Kastle-Meyer test, a well-recognised forensic technique. RESULTS: Ultrasonic baths were used for the cleaning of 62 (47%) bands and retainers and the remainder (53%) were hand scrubbed prior to autoclaving. Overall, 21% of the matrix bands and 19% of the retainers gave a positive Kastle-Meyer test, indicative of residual blood contamination, following cleaning and sterilisation. In relation to cleaning method, 34% of hand-scrubbed bands and 32% of hand-scrubbed retainers were positive for residual blood by the Kastle-Meyer test compared with 6% and 3% respectively of ultrasonically cleaned bands and retainers (P less than 0.001). CONCLUSIONS: If Siqveland matrix bands are re-processed in the assembled state, then adequate pre-sterilisation cleaning cannot be achieved reliably. Ultrasonic baths are significantly more effective than hand cleaning for these items of equipment
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