Insights into the structure of liquid water from nuclear quantum effects on density and compressibility of ice polymorphs

Nuclear quantum effects lead to an anomalous shift of the volume of hexagonal ice; heavy ice has a larger volume than light ice. This anomaly in ice increases with temperature and persists in liquid water up to the boiling point. We study nuclear quantum effects on the density and compressibility of several ice-like structures and crystalline ice phases. By calculating the anisotropic contributions to the stain tensor, we analyze how the compressibility changes along different directions in hexagonal ice, and find that hexagonal ice is softer along the x-y plane than the z-direction. Furthermore, by performing ab initio density functional theory calculations with a van der Waals functional and with the quasiharmonic approximation, we find an anomalous isotope effect in the bulk modulus of hexagonal ice: heavy ice has a smaller bulk modulus than light ice. In agreement with the experiments, we also obtain an anomalous isotope effect for clathrate hydrate structure I. For the rest of the ice polymorphs, the isotope effect is: i) anomalous for ice IX, Ih, Ic, clathrate, and low density liquid-like amorphous ice; ii) normal at T=0 K and becomes anomalous with increasing temperature for ice IX, II, high density liquid-like amorphous ices, and ice XV; iii) normal for ice VIII up to the melting point. There is a transition from an anomalous isotope effect to a normal isotope effect for both the volume and bulk modulus, as the density (compressibility) of the structures increases (decreases). This result can explain the anomalous isotope effect in liquid water: as the compressibility decreases from melting point to the compressibility minimum temperature, the difference between the volumes of the heavy and light water rapidly decreases, but the effect stays anomalous up to the boiling temperature as the hydrogen bond network is never completely broken by fully filling all the interstitial sites.Comment: 17 pages, 15 figure

Anomalous Nuclear Quantum Effects in Ice

One striking anomaly of water ice has been largely neglected and never explained. Replacing hydrogen ($^1$H) by deuterium ($^2$H) causes ice to expand, whereas the "normal" isotope effect is volume contraction with increased mass. Furthermore, the anomaly increases with temperature $T$, even though a normal isotope shift should decrease with $T$ and vanish when $T$ is high enough to use classical nuclear motions. In this study, we show that these effects are very well described by {\it ab initio} density functional theory. Our theoretical modeling explains these anomalies, and allows us to predict and to experimentally confirm a counter effect, namely that replacement of $^{16}$O by $^{18}$O causes a normal lattice contraction.Comment: 5 pages, 3 figure

Acylation Reaction of Polystyrene with Organic Anhydrides and Investigation of the Physico-Mechanical Properties

The acylation reaction of polystyrene with organic anhydrides, such as maleic and ace-tic anhydrides were investigated in the presence of cationic catalysis (AlCl3, BF3В·O(C2H5)2, FeCl3, SnCl4, TiCl4, ZnCl2), to synthesise some polyfunctional (carbonyl-, carboxyl-, keto-, olefinic) polystyrene. The incorporation of functional groups to polystyrene were caused an increase of adhesion capability, physico-mechanical properties, elasticity and photosensitivity polyfunctional product

Methodological issues in measuring health disparities

OBJECTIVES: This report discusses six issues that affect the measurement of disparities in health between groups in a population: Selecting a reference point from which to measure disparity. Measuring disparity in absolute or in relative terms. Measuring in terms of favorable or adverse events. Measuring in pair-wise or in summary fashion. Choosing whether to weight groups according to group size. Deciding whether to consider any inherent ordering of the groups. These issues represent choices that are made when disparities are measured. METHODS: Examples are used to highlight how these choices affect specific measures of disparity. RESULTS: These choices can affect the size and direction of disparities measured at a point in time and conclusions about the size and direction of changes in disparity over time. Eleven guidelines for measuring disparities are presented. CONCLUSIONS: Choices concerning the measurement of disparity should be made deliberately, recognizing that each choice will affect the results. When results are presented, the choices on which the measurements are based should be described clearly and justified appropriately.By Kenneth Keppel, Elsie Pamuk, John Lynch, Olivia Carter-Pokras, Insun Kim, Vickie Mays, Jeffrey Pearcy, Victor Schoenbach, and Joel S. Weissma

Lymphocyte subsets and the role of Th1/Th2 balance in stressed chronic pain patients

Background: The complex regional pain syndrome (CRPS) and fibromyalgia (FM) are chronic pain syndromes occurring in highly stressed individuals. Despite the known connection between the nervous system and immune cells, information on distribution of lymphocyte subsets under stress and pain conditions is limited. Methods: We performed a comparative study in 15 patients with CRPS type I, 22 patients with FM and 37 age- and sex-matched healthy controls and investigated the influence of pain and stress on lymphocyte number, subpopulations and the Th1/Th2 cytokine ratio in T lymphocytes. Results: Lymphocyte numbers did not differ between groups. Quantitative analyses of lymphocyte subpopulations showed a significant reduction of cytotoxic CD8+ lymphocytes in both CRPS (p < 0.01) and FM (p < 0.05) patients as compared with healthy controls. Additionally, CRPS patients were characterized by a lower percentage of IL-2-producing T cell subpopulations reflecting a diminished Th1 response in contrast to no changes in the Th2 cytokine profile. Conclusions: Future studies are warranted to answer whether such immunological changes play a pathogenetic role in CRPS and FM or merely reflect the consequences of a pain-induced neurohumoral stress response, and whether they contribute to immunosuppression in stressed chronic pain patients. Copyright (c) 2008 S. Karger AG, Basel

The prevalence of giant cell arteritis and polymyalgia rheumatica in a UK primary care population

Background: To update community-based prevalence values for Polymyalgia Rheumatic (PMR) and Giant Cell Arteritis (GCA) using case record review supplemented by population survey and subsequent clinical review. Methods: Clinical data were obtained from case records of a large primary care practice in Norfolk, UK and reviewed for diagnoses of GCA and PMR. In addition postal survey was carried out to capture potentially undiagnosed cases within the practice population. Those screening positive for potential diagnoses of GCA and PMR were invited for clinical review. A cumulative prevalence estimate was subsequently calculated on those diagnosed within the GP practice and subsequently on those fulfilling the various published classification criteria sets. The date of the database lock and mail merge was March 2013. Results: Through detailed systematic review of 5,159 GP case records, 21 patients had a recorded diagnosis of GCA and 117 had PMR . No new cases were identified among 2,227 completed questionnaires returned from the population survey of a sample of 4,728. The resulting cumulative prevalence estimate in those aged ≥55 years meeting the ACR classification criteria set for GCA was 0.25% (95% CI 0.11% to 0.39%) and for five published criteria sets for PMR ranged from 0.91% to 1.53% (95% CI ranges 0.65%, 1.87%). The prevalence of both conditions was higher in women than in men and in older age groups. Conclusion: This study provides the first UK prevalence estimate of GCA and PMR in over 30 years and is the first to apply classification criteria sets