1,737 research outputs found
A systems view of risk factors for knee osteoarthritis reveals insights into the pathogenesis of the disease.
Early detection of osteoarthritis (OA) remains a critical yet unsolved multifaceted problem. To address the multifaceted nature of OA a systems model was developed to consolidate a number of observations on the biological, mechanical and structural components of OA and identify features common to the primary risk factors for OA (aging, obesity and joint trauma) that are present prior to the development of clinical OA. This analysis supports a unified view of the pathogenesis of OA such that the risk for developing OA emerges when one of the components of the disease (e.g., mechanical) becomes abnormal, and it is the interaction with the other components (e.g., biological and/or structural) that influences the ultimate convergence to cartilage breakdown and progression to clinical OA. The model, applied in a stimulus-response format, demonstrated that a mechanical stimulus at baseline can enhance the sensitivity of a biomarker to predict cartilage thinning in a 5 year follow-up in patients with knee OA. The systems approach provides new insight into the pathogenesis of the disease and offers the basis for developing multidisciplinary studies to address early detection and treatment at a stage in the disease where disease modification has the greatest potential for a successful outcome
A note on inflation and transplanckian physics
In this paper we consider the influence of transplanckian physics on the CMBR
anisotropies produced by inflation. We consider a simple toy model that allows
for analytic calculations and argue on general grounds, based on ambiguities in
the choice of vacuum, that effects are expected with a magnitude of the order
of , where is the Hubble constant during inflation and
the scale for new physics, e.g. the Planck scale.Comment: 12 pages. v2: typos corrected and references added. v3: final version
accepted for publication by PRD. Improved discussion of adiabatic vacuu
The Corley-Jacobson dispersion relation and trans-Planckian inflation
In this Letter we study the dependence of the spectrum of fluctuations in
inflationary cosmology on possible effects of trans-Planckian physics, using
the Corley/Jacobson dispersion relations as an example. We compare the methods
used in previous work [1] with the WKB approximation, give a new exact
analytical result, and study the dependence of the spectrum obtained using the
approximate method of Ref. [1] on the choice of the matching time between
different time intervals. We also comment on recent work subsequent to Ref. [1]
on the trans-Planckian problem for inflationary cosmology.Comment: 6 pages, Revtex
Ultraviolet cut off and Bosonic Dominance
We rederive the thermodynamical properties of a non interacting gas in the
presence of a minimal uncertainty in length. Apart from the phase space measure
which is modified due to a change of the Heisenberg uncertainty relations, the
presence of an ultraviolet cut-off plays a tremendous role.
The theory admits an intrinsic temperature above which the fermion
contribution to energy density, pressure and entropy is negligible.Comment: 12 pages in revtex, 2 figures. Some coefficients have been changed in
the A_2 model and two references adde
Ultraviolet cut off, black hole-radiation equilibrium and big bang
In the presence of a minimal uncertainty in length, there exists a critical
temperature above which the thermodynamics of a gas of radiation changes
drastically.
We find that the equilibrium temperature of a system composed of a
Schwarzschild black hole surrounded by radiation is unaffected by these
modifications. This is in agreement with works related to the robustness of the
Hawking evaporation. The only change the deformation introduces concerns the
critical volume at which the system ceases to be stable.
On the contrary, the evolution of the very early universe is sensitive to the
new behavior. We readdress the shortcomings of the standard big bang
model(flatness, entropy and horizon problems) in this context, assuming a
minimal coupling to general relativity. Although they are not solved, some
qualitative differences set in.Comment: 10 pages revtex, 1 figur
Classification of protein interaction sentences via gaussian processes
The increase in the availability of protein interaction studies in textual format coupled with the demand for easier access to the key results has lead to a need for text mining solutions. In the text processing pipeline, classification is a key step for extraction of small sections of relevant text. Consequently, for the task of locating protein-protein interaction sentences, we examine the use of a classifier which has rarely been applied to text, the Gaussian processes (GPs). GPs are a non-parametric probabilistic analogue to the more popular support vector machines (SVMs). We find that GPs outperform the SVM and na\"ive Bayes classifiers on binary sentence data, whilst showing equivalent performance on abstract and multiclass sentence corpora. In addition, the lack of the margin parameter, which requires costly tuning, along with the principled multiclass extensions enabled by the probabilistic framework make GPs an appealing alternative worth of further adoption
Superluminal Signals: Causal Loop Paradoxes Revisited
Recent results demonstrating superluminal group velocities and tachyonic
dispersion relations reopen the question of superluminal signals and causal
loop paradoxes. The sense in which superluminal signals are permitted is
explained in terms of pulse reshaping, and the self-consistent behavior which
prevents causal loop paradoxes is illustrated by an explicit example.Comment: 6 pages, 3 figure
Matrix Models
Matrix models and their connections to String Theory and noncommutative
geometry are discussed. Various types of matrix models are reviewed. Most of
interest are IKKT and BFSS models. They are introduced as 0+0 and 1+0
dimensional reduction of Yang--Mills model respectively. They are obtained via
the deformations of string/membrane worldsheet/worldvolume. Classical solutions
leading to noncommutative gauge models are considered.Comment: Lectures given at the Winter School on Modern Trends in
Supersymmetric Mechanics, March 2005 Frascati; 38p
Understorey plant community and light availability in conifer plantations and natural hardwood forests in Taiwan
Questions: What are the effects of replacing mixed species natural forests with Cryptomeria japonica plantations on understorey plant functional and species diversity? What is the role of the understorey light environment in determining understorey diversity and community in the two types of forest?
Location: Subtropical northeast Taiwan.
Methods: We examined light environments using hemispherical photography, and diversity and composition of understorey plants of a 35‐yr C. japonica plantation and an adjacent natural hardwood forest.
Results: Understorey plant species richness was similar in the two forests, but the communities were different; only 18 of the 91 recorded understorey plant species occurred in both forests. Relative abundance of plants among different functional groups differed between the two forests. Relative numbers of shade‐tolerant and shade‐intolerant seedling individuals were also different between the two forest types with only one shade‐intolerant seedling in the plantation compared to 23 seedlings belonging to two species in the natural forest. In the natural forest 11 species of tree seedling were found, while in the plantation only five were found, and the seedling density was only one third of that in the natural forest. Across plots in both forests, understorey plant richness and diversity were negatively correlated with direct sunlight but not indirect sunlight, possibly because direct light plays a more important role in understorey plant growth.
Conclusions: We report lower species and functional diversity and higher light availability in a natural hardwood forest than an adjacent 30‐yr C. japonica plantation, possibly due to the increased dominance of shade‐intolerant species associated with higher light availability. To maintain plant diversity, management efforts must be made to prevent localized losses of shade‐adapted understorey plants
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