10 research outputs found
Entropy-driven liquid-liquid separation in supercooled water
Twenty years ago Poole et al. (Nature 360, 324, 1992) suggested that the
anomalous properties of supercooled water may be caused by a critical point
that terminates a line of liquid-liquid separation of lower-density and
higher-density water. Here we present an explicit thermodynamic model based on
this hypothesis, which describes all available experimental data for
supercooled water with better quality and with fewer adjustable parameters than
any other model suggested so far. Liquid water at low temperatures is viewed as
an 'athermal solution' of two molecular structures with different entropies and
densities. Alternatively to popular models for water, in which the
liquid-liquid separation is driven by energy, the phase separation in the
athermal two-state water is driven by entropy upon increasing the pressure,
while the critical temperature is defined by the 'reaction' equilibrium
constant. In particular, the model predicts the location of density maxima at
the locus of a near-constant fraction (about 0.12) of the lower-density
structure.Comment: 7 pages, 6 figures. Version 2 contains an additional supplement with
tables for the mean-field equatio
Detection of high cardiovascular risk patients with ankylosing spondylitis based on the assessment of abdominal aortic calcium as compared to carotid ultrasound
ABSTRACT:
Background: This study aimed to determine whether, besides carotid ultrasound (US), a lateral lumbar spine radiography may also help identify ankylosing spondylitis (AS) patients at high risk of cardiovascular (CV) disease.
Methods: A set of 125 AS patients older than 35 years without a history of CV events, diabetes mellitus, or chronic kidney disease was recruited. Carotid US and lateral lumbar spine radiography were performed in all of them. The CV risk was calculated according to the total cholesterol systematic coronary risk evaluation (TC- CORE) algorithm.
Presence of carotid plaques was defined following the Mannheim Carotid Intima-media Thickness and Plaque Consensus. Abdominal aortic calcium (AAC) in a plain radiography was defined as calcific densities visible in an area parallel and anterior to the lumbar spine.
Results: Carotid US showed higher sensitivity than lateral lumbar spine radiography to detect high CV risk in the 54 patients with moderate TC-SCORE (61% versus 38.9%). Using carotid plaques as the gold standard test, a predictive model that included a TC-SCORE >= 5% or the presence of AAC in the lateral lumbar spine radiography in patients with both moderate and low CV risk (< 5%) according to the TC-SCORE yielded a sensitivity of 50.9% with a specificity of 95.7% to identify high/very high CV-risk AS patients. A positive correlation between AAC and carotid plaques was observed (r2 = 0.49, p < 0.001).
Conclusions: A lateral lumbar spine radiography is a useful tool to identify patients with AS at high risk of CV disease