Large Decrease of Fluctuations for Supercooled Water in Hydrophobic Nanoconfinement

Using Monte Carlo simulations we study a coarse­grained model of a water layer confined in a fixed disordered matrix of hydrophobic nanoparticles at different particle concentrations c. For c = 0 we find a 1st order liquid­liquid phase transition (LLPT) ending in one critical point at low pressure P. For c > 0 our simulations are consistent with a LLPT line ending in two critical points at low and high pressure. For c = 25% at high P and low temperature T we find a dramatic decrease of compressibility, thermal expansion coefficient, and specific heat. Surprisingly, the effect is present also for c as low as 2.4%. We conclude that even a small presence of nanoscopic hydrophobes can drastically suppress thermodynamic fluctuations, making the detection of the LLPT more difficult

Large Decrease of Fluctuations for Supercooled Water in Hydrophobic Nanoconfinement

Using Monte Carlo simulations we study a coarse­grained model of a water layer confined in a fixed disordered matrix of hydrophobic nanoparticles at different particle concentrations c. For c = 0 we find a 1st order liquid­liquid phase transition (LLPT) ending in one critical point at low pressure P. For c > 0 our simulations are consistent with a LLPT line ending in two critical points at low and high pressure. For c = 25% at high P and low temperature T we find a dramatic decrease of compressibility, thermal expansion coefficient, and specific heat. Surprisingly, the effect is present also for c as low as 2.4%. We conclude that even a small presence of nanoscopic hydrophobes can drastically suppress thermodynamic fluctuations, making the detection of the LLPT more difficult

Pressure Effects in Supercooled Water: Comparison between a 2D Model of Water and Experiments for Surface Water on a Protein

Experiments in bulk water confirm the existence of two local arrangements of water molecules with different densities, but, because of inevitable freezing at low temperature $T$, can not ascertain whether the two arrangements separate in two phases. To avoid the freezing, new experiments measure the dynamics of water at low $T$ on the surface of proteins, finding a crossover from a non-Arrhenius regime at high $T$ to a regime that is approximately Arrhenius at low $T$. Motivated by these experiments, Kumar et al. [Phys. Rev. Lett. 100, 105701 (2008)] investigated, by Monte Carlo simulations and mean field calculations, the relation of the dynamic crossover with the coexistence of two liquid phases in a cell model for water and predict that: (i) the dynamic crossover is isochronic, i.e. the value of the crossover time $\tau_{\rm L}$ is approximately independent of pressure $P$; (ii) the Arrhenius activation energy $E_{\rm A}(P)$ of the low-$T$ regime decreases upon increasing $P$; (iii) the temperature $T^*(P)$ at which $\tau$ reaches a fixed macroscopic time $\tau^*\geq \tau_{\rm L}$ decreases upon increasing $P$; in particular, this is true also for the crossover temperature $T_{\rm L}(P)$ at which $\tau=\tau_{\rm L}$. Here, we compare these predictions with recent quasi elastic neutron scattering (QENS) experiments performed by X.-Q. Chu {\it et al.} on hydrated proteins at different values of $P$. We find that the experiments are consistent with these three predictions.Comment: 18 pages, 5 figures, to appear on J. Phys.: Cond. Ma

Second Trimester Amniocentesis Is Not a Risk Factor for Very Low Birth Weight and Extremely Low Birth Weight

Objectives. To assess the risk of very low birth weight (VLBW) and extremely low birth weight (ELBW) attributable to second trimester amniocentesis. Methods. Records of 4,877 consecutive amniocentesis, performed between 1997 and 2003, were analyzed. Only VLBW and ELBW in the study population (exposed) and in the control group (unexposed) were evaluated. Comparisons were made between the amniocentesis group versus nonexposed. Odds ratios (OR) and 95% confidence intervals (95% CI) were calculated for VLBW and ELBW classes. Results. In the study population, the VLBW were 35 (0.71%) and the ELBW were 20 (0.41%). In the control group, the VLBW were 220 (0.67%) and the ELBW were 112 (0.34%). The Odds ratios of the VLBW between the study and the control group did not show any statistical significant risk (OR = 1.07, 95% CI = 0.72–1.54). Also in ELBW odds ratios between study and control group were not statistically significant (OR = 1.20, 95% CI = 0.7–1.95). Conclusions. No effect of the second trimester amniocentesis was noted on VLBW and ELBW

Cluster Monte Carlo and numerical mean field analysis for the water liquid--liquid phase transition

By the Wolff's cluster Monte Carlo simulations and numerical minimization within a mean field approach, we study the low temperature phase diagram of water, adopting a cell model that reproduces the known properties of water in its fluid phases. Both methods allows us to study the water thermodynamic behavior at temperatures where other numerical approaches --both Monte Carlo and molecular dynamics-- are seriously hampered by the large increase of the correlation times. The cluster algorithm also allows us to emphasize that the liquid--liquid phase transition corresponds to the percolation transition of tetrahedrally ordered water molecules.Comment: 6 pages, 3 figure

Dynamically Slow Processes in Supercooled Water Confined Between Hydrophobic Plates

We study the dynamics of water confined between hydrophobic flat surfaces at low temperature. At different pressures, we observe different behaviors that we understand in terms of the hydrogen bonds dynamics. At high pressure, the formation of the open structure of the hydrogen bond network is inhibited and the surfaces can be rapidly dehydrated by decreasing the temperature. At lower pressure the rapid ordering of the hydrogen bonds generates heterogeneities that are responsible for strong non-exponential behavior of the correlation function, but with no strong increase of the correlation time. At very low pressures, the gradual formation of the hydrogen bond network is responsible for the large increase of the correlation time and, eventually, the dynamical arrest of the system and of the dehydration process.Comment: 14 pages, 3 figure

Renal hemodynamic response to maximal vasodilating stimulus in healthy older subjects

Renal hemodynamic response to maximal vasodilating stimulus in healthy older subjects.BackgroundIt is still unclear whether age per se is associated with preservation of renal functional reserve, that is, of the increase in glomerular filtration rate (GFR) induced by appropriate vasodilating stimulus.MethodsTo gain insights into this issue, we evaluated the renal response to a maximal vasodilating stimulus, represented by the combined infusion of mixed amino acid solution (AA) and dopamine at renal dose (D), in 10 young subjects (median age of 30 years, range of 19 to 32) and in 11 subjects of older age (median age of 67 years, range of 65 to 76). Two further age-matched groups of young (N = 15) and older (N = 11) living kidney donors underwent renal needle biopsy immediately before nephrectomy to perform semiquantitative scoring (0 to 3) of arteriosclerosis in intrarenal arteries. All of the study subjects were nonsmokers with healthy status proven by extensive diagnostic evaluation excluding any risk factor of renal dysfunction.ResultsBasal renal plasma flow (RPF) and GFR were proportionally lower in older subjects (RPF, 361 ± 29 vs. 618 ± 34mL/min/1.73m2, P < 0.001; GFR, 79 ± 4 vs. 127 ± 5.8mL/min/1.73m2, P < 0.001). After AA + D, a significant increase of RPF and GFR was observed in both groups, but the older subjects exhibited a smaller percentage increment (RPF, 25.5 ± 4.8 vs. 42.4 ± 5.8, P < 0.05; GFR, 19.6 ± 5.7 vs. + 33.8 ± 6.4, P < 0.05). Furthermore, the maximal vasodilating stimulus was not able to restore renal hemodynamics in older subjects to the level measured in young controls at baseline. Renal vascular resistances were higher (P < 0.05) in the older subjects both at baseline (0.19 ± 0.02 vs. 0.09 ± 0.004mm Hg/mL/min) and after AA + D (0.14 ± 0.01 vs. 0.06 ± 0.004). Light microscopy examination detected the presence of a greater degree of arteriosclerosis at the level of interlobular and arcuate arteries (0.89 ± 0.15 vs. 0.45 ± 0.08) and interstitial fibrosis/tubular atrophy (1.18 ± 0.13 vs. 0.53 ± 0.13) in older than in young subjects.ConclusionsTherefore, aging has adverse effects on renal function despite the absence of any risk factor for renal disease, including chronic smoking: (1) GFR and RPF are lower, and (2) the renal response to maximal vasodilating stimulus is impaired. These aging-related alterations of renal hemodynamics are possibly due to organic lesions in renal vasculature

Pathological features and survival outcomes of very young patients with early breast cancer: How much is "very young"?

Abstract We collected information on 497 consecutive breast cancer patients aged less than 35 years operated at the European Institute of Oncology. The main aim of the study is to compare biological and clinical features dividing the population by age: Patients aged p = 0.79) and overall survival ( p = 0.99) between the three age groups. This latter findings was confirmed using age as a continuous variable assuming a linear association between age and the outcomes considered, too. In conclusion, our data indicate that the group of patients with breast cancer below 35 years is essentially a homogenous group when classical clinical and immunohistochemical features were considered

Large Decrease of Fluctuations for Supercooled Water in Hydrophobic Nanoconfinement

Using Monte Carlo simulations, we study a coarse-grained model of a water layer confined in a fixed disordered matrix of hydrophobic nanoparticles at different particle concentrations c . For c = 0 , we find a first-order liquid-liquid phase transition (LLPT) ending in one critical point at low pressure P . For c > 0 , our simulations are consistent with a LLPT line ending in two critical points at low and high P . For c = 25 % , at high P and low temperature, we find a dramatic decrease of compressibility, thermal expansion coefficient, and specific heat. Surprisingly, the effect is present also for c as low as 2.4%. We conclude that even a small presence of hydrophobic nanoparticles can drastically suppress thermodynamic fluctuations, making the detection of the LLPT more difficult

Antihypertensive Treatment in the Elderly and Very Elderly: Always “the Lower, the Better?”

Arterial hypertension (HT) is age dependent and, with the prolongation of life expectancy, affects more and more elderly people. In the elderly, HT is a risk factor for organ damage and cardiovascular (CV) events. Both pharmacologic and nonpharmacologic reduction of blood pressure (BP) is associated with a corresponding decrease in systolic-diastolic or isolated systolic HT. Clinical trials have shown that BP lowering is associated with a decrease in stroke and other CV events. Therefore, BP reduction per se appears more important than a particular class of antihypertensive drugs. The benefit of antihypertensive treatment has been confirmed up to the age of 80 years, remaining unclear in the octogenarians. The benefit in lowering diastolic BP between 80 and 90 mmHg is well established, while that of lowering systolic BP below 140 mmHg requires further confirmations