738 research outputs found
Taking regular breaks from sitting prevents reductions in brain blood flow
Supplying the brain with enough blood flow is essential to keep us alive and maintain our brain health. Reductions in brain blood flow can negatively affect the ability to think. Decreased blood flow to the brain can also lead to brain diseases, such as dementia, which is a condition that causes permanent memory loss and confusion. Scientists are beginning to think that sitting may be bad for brain blood flow. Understanding how sitting affects the brain is therefore very important. We conducted a study in which participants either sat down without any breaks for 4 h, or sat down but took a short walking break every 30 min, or took a longer walking break every 2 h. After sitting without any breaks, brain blood flow decreased. However, when participants took a walking break every 30 min that prevented the decrease in brain blood flow. These results suggest we should encourage people to take regular breaks from sitting to help maintain brain health
Geodetic Brane Gravity
Within the framework of geodetic brane gravity, the Universe is described as
a 4-dimensional extended object evolving geodetically in a higher dimensional
flat background. In this paper, by introducing a new pair of canonical fields
{lambda, P_{lambda}}, we derive the quadratic Hamiltonian for such a brane
Universe; the inclusion of matter then resembles minimal coupling. Second class
constraints enter the game, invoking the Dirac bracket formalism. The algebra
of the first class constraints is calculated, and the BRST generator of the
brane Universe turns out to be rank-1. At the quantum level, the road is open
for canonical and/or functional integral quantization. The main advantages of
geodetic brane gravity are: (i) It introduces an intrinsic, geometrically
originated, 'dark matter' component, (ii) It offers, owing to the Lorentzian
bulk time coordinate, a novel solution to the 'problem of time', and (iii) It
enables calculation of meaningful probabilities within quantum cosmology
without any auxiliary scalar field. Intriguingly, the general relativity limit
is associated with lambda being a vanishing (degenerate) eigenvalue.Comment: 23 pages, 1 figure, minor change
Stealth Branes
We discuss the brane world model of Dvali, Gabadadze and Porrati in which
branes evolve in an infinite bulk and the brane curvature term is added to the
action. If Z_2 symmetry between the two sides of the brane is not imposed, we
show that the model admits the existence of "stealth branes" which follow the
standard 4D internal evolution and have no gravitational effect on the bulk
space. Stealth branes can nucleate spontaneosly in a Minkowski bulk. This
process is described by the standard 4D quantum cosmology formalism with
tunneling boundary conditions for the brane world wave function. The notorious
ambiguity in the choice of boundary conditions is fixed in this case due to the
presence of the embedding spacetime. We also point to some problematic aspects
of models admitting stealth brane solutions.Comment: 24 pages; Final version, to appear in Phys. Rev. D. The discussion of
"embeddability obstruction" is removed (thanks to Takahiro Tanaka who
convinced us that there is no such obstruction
Cues and knowledge structures used by mental-health professionals when making risk assessments
Background: Research into mental-health risks has tended to focus on epidemiological approaches and to consider pieces of evidence in isolation. Less is known about the particular
factors and their patterns of occurrence that influence clinicians’ risk judgements in practice.
Aims: To identify the cues used by clinicians to make risk judgements and to explore how these combine within clinicians’ psychological representations of suicide, self-harm, self-neglect, and harm to others.
Method: Content analysis was applied to semi-structured interviews conducted with 46 practitioners from various mental-health disciplines, using mind maps to represent the
hierarchical relationships of data and concepts.
Results: Strong consensus between experts meant their knowledge could be integrated into a single hierarchical structure for each risk. This revealed contrasting emphases between data and concepts underpinning risks, including: reflection and forethought for suicide; motivation
for self-harm; situation and context for harm to others; and current presentation for self-neglect.
Conclusions: Analysis of experts’ risk-assessment knowledge identified influential cues and their relationships to risks. It can inform development of valid risk-screening decision support systems that combine actuarial evidence with clinical expertise
Autoimmune and autoinflammatory mechanisms in uveitis
The eye, as currently viewed, is neither immunologically ignorant nor sequestered from the systemic environment. The eye utilises distinct immunoregulatory mechanisms to preserve tissue and cellular function in the face of immune-mediated insult; clinically, inflammation following such an insult is termed uveitis. The intra-ocular inflammation in uveitis may be clinically obvious as a result of infection (e.g. toxoplasma, herpes), but in the main infection, if any, remains covert. We now recognise that healthy tissues including the retina have regulatory mechanisms imparted by control of myeloid cells through receptors (e.g. CD200R) and soluble inhibitory factors (e.g. alpha-MSH), regulation of the blood retinal barrier, and active immune surveillance. Once homoeostasis has been disrupted and inflammation ensues, the mechanisms to regulate inflammation, including T cell apoptosis, generation of Treg cells, and myeloid cell suppression in situ, are less successful. Why inflammation becomes persistent remains unknown, but extrapolating from animal models, possibilities include differential trafficking of T cells from the retina, residency of CD8(+) T cells, and alterations of myeloid cell phenotype and function. Translating lessons learned from animal models to humans has been helped by system biology approaches and informatics, which suggest that diseased animals and people share similar changes in T cell phenotypes and monocyte function to date. Together the data infer a possible cryptic infectious drive in uveitis that unlocks and drives persistent autoimmune responses, or promotes further innate immune responses. Thus there may be many mechanisms in common with those observed in autoinflammatory disorders
Refined localization of TSC1 by combined analysis of 9q34 and 16pl3 data in 14 tuberous sclerosis families
Tuberous sclerosis (TSC) is a heterogeneous trait. Since 1990, linkage studies have yielded putative TSC loci on chromosomes 9, 11, 12 and 16. Our current analysis, performed on 14 Dutch and British families, reveals only evidence for loci on chromosome 9q34 (TSC1) and chromosome 16p13 (TSC2). We have found no indication for a third locus for TSC, linked or unlinked to either of these chromosomal regions. The majority of our families shows linkage to chromosome 9. We have refined the candidate region for TSC1 to a region of approximately 5 c M between ABL and ABO
Astrobiological Complexity with Probabilistic Cellular Automata
Search for extraterrestrial life and intelligence constitutes one of the
major endeavors in science, but has yet been quantitatively modeled only rarely
and in a cursory and superficial fashion. We argue that probabilistic cellular
automata (PCA) represent the best quantitative framework for modeling
astrobiological history of the Milky Way and its Galactic Habitable Zone. The
relevant astrobiological parameters are to be modeled as the elements of the
input probability matrix for the PCA kernel. With the underlying simplicity of
the cellular automata constructs, this approach enables a quick analysis of
large and ambiguous input parameters' space. We perform a simple clustering
analysis of typical astrobiological histories and discuss the relevant boundary
conditions of practical importance for planning and guiding actual empirical
astrobiological and SETI projects. In addition to showing how the present
framework is adaptable to more complex situations and updated observational
databases from current and near-future space missions, we demonstrate how
numerical results could offer a cautious rationale for continuation of
practical SETI searches.Comment: 37 pages, 11 figures, 2 tables; added journal reference belo
Family-based association analysis to finemap bipolar linkage peak on chromosome 8q24 using 2,500 genotyped SNPs and 15,000 imputed SNPs
Zhang P, Xiang N, Chen Y, Śliwerska E, McInnis MG, Burmeister M, Zöllner S. Family-based association analysis to finemap bipolar linkage peak on chromosome 8q24 using 2,500 genotyped SNPs and 15,000 imputed SNPs. Bipolar Disord 2010: 12: 786–792. © 2010 The Authors. Journal compilation © 2010 John Wiley & Sons A/S.Multiple linkage and association studies have suggested chromosome 8q24 as a promising candidate region for bipolar disorder (BP). We performed a detailed association analysis assessing the contribution of common genetic variation in this region to the risk of BP.We analyzed 2,756 single nucleotide polymorphism (SNP) markers in the chromosome 8q24 region of 3,512 individuals from 737 families. In addition, we extended genotype imputation methods to family-based data and imputed 22,725 HapMap SNPs in the same region on 8q24. We applied a family-based method to test 15,552 high-quality genotyped or imputed SNPs for association with BP.Our association analysis identified the most significant marker (p = 4.80 × 10 −5 ), near the gene encoding potassium voltage-gated channel KQT-like protein ( KCNQ3 ). Other marginally significant markers were located near adenylate cyclase 8 ( ADCY8 ) and ST3 beta-galactoside alpha-2,3-sialyltransferase 1 ( ST3GAL1 ).We developed an approach to apply MACH imputation to family-based data, which can increase the power to detect association signals. Our association results showed suggestive evidence of association of BP with loci near KCNQ3 , ADCY8 , and ST3GAL1 . Consistent with genes identified by genome-wide association studies for BP, our results suggest the involvement of ion channelopathy in BP pathogenesis. However, common variants are insufficient to explain linkage findings in 8q24; other genetic variation should be explored.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/79302/1/j.1399-5618.2010.00883.x.pd
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