Mapping at the nanometer scale the effects of sea-salt derived chlorine on cinnabar and lead white by using delayed image extraction in ToF-SIMS.

In this work, an innovative analytical approach focused on the use of advanced imaging techniques for the chemical mapping of degradation and/or restoration products is proposed. A representative cross-section showing a very complex stratigraphy from the Saint Wilgefortis Triptych (Hieronymus Bosch), exhibited in the Galleria dell'Accademia di Venezia, was investigated. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) experiments were performed using a time-of-flight detector operating in the so-called delayed extraction mode. The time delay applied during the extraction of the secondary ions permitted mass spectra to be obtained with an excellent mass resolution and chemical maps with nanometer scale spatial resolution. The painting's cross-section was also analysed at the micrometer scale by micro-Fourier transform infrared spectroscopy (micro-FTIR). The combined analytical approaches highlighted the colocalization of lead chloride, oxychloride, and hydroxychloride ions, suggesting the transformation of lead white ((PbCO3)2Pb(OH)2) into laurionite (PbClOH). Furthermore, chlorine appears evenly diffused in the cinnabar (HgS) layer, inducing the alteration of its more external part into calomel (Hg2Cl2). In fact, from the chemical maps the presence in the sample of an unaltered portion of the cinnabar layer is evident. Such degradation products were probably due to the exposure of the painting to a chloride-rich atmosphere for a long time. This led to a global blackening of the painting. To protect the painting from aggressive chemical species, siloxane compounds were probably used as a modern restorative treatment. ToF-SIMS chemical maps revealed permeation of the silicon-based consolidants within the sample's cracks and no interaction products with the other constitutive materials of the painting were found. Finally, the presence of different lead soaps was detected in correspondence with the lead white layer.

Magnetic mesoporous silica nanostructures: investigation of magnetic properties.

Magnetic mesoporous silica (MS) nanocomposites provide the possibility of generating multi-functional objects for application in different technological areas. This paper focuses on the magnetic properties of nanocomposites constituted by spinel iron oxide nanoparticles (magnetic nanoparticles (MNPs), < D > ≈ 8-9 nm) embedded in an MS matrix. The mesoporous structure of the silica matrix and the presence of the nanoparticles inside clearly emerge from transmission electron microscopy (TEM) measurements. Low temperature (5 K) field-dependent magnetization measurements reveal saturation magnetization (MS ) close to bulk value (M S bulk ∼ 90 emu g-1) for both MNPs and MNP/MS nanocomposites, indicating that the presence of silica does not affect the magnetic features of the single MNPs. Moreover, the dependence of the remanent magnetization on field (i.e. δM plots) at low temperature has shown a small but evident decrease of interaction in an MNP/MS sample with respect to MNP samples A m2 Kg-1. Finally, a partial orientation of the easy axis is observed when the MNPs are embedded in the silica matrix.

Determinants of High Parathyroid Hormone Levels in Patients With Severe Obesity and Their Relationship With the Cardiometabolic Risk Factors, Before and After a Laparoscopic Sleeve Gastrectomy Intervention.

BACKGROUND: Obesity is a risk factor for vitamin D deficiency and hyperparathyroidism. Hyperparathyroidism could exert a negative effect on glucose metabolism and vascular function. The aim of this study was to identify the determinants of hyperparathyroidism beyond vitamin D deficiency, whether hyperparathyroidism could have a negative impact on individual health and whether laparoscopic sleeve gastrectomy (LSG) negatively affects the levels of intact parathyroid hormone (iPTH) and 25(OH) vitamin D (25(OH)D). METHODS: We evaluated the levels of iPTH, 25(OH)D, and leptin, together with markers of insulin sensitivity and early cardiovascular disease, in a cohort of 160 patients with severe obesity before and after an LSG intervention. RESULTS: Ninety-seven percent of subjects had vitamin D deficiency, and 72% of them had hyperparathyroidism. After correcting for possible confounders, we found a correlation between iPTH levels and carotid intima-media thickness, as well as with the HOMA index. After the LSG, 25(OH)D levels were significantly increased, while iPTH levels were significantly reduced. The reduction of iPTH was significantly correlated with the reduction of BMI, diastolic blood pressure, and leptin, which was the independent predictor of iPTH reduction. CONCLUSIONS: Our results suggest that vitamin D deficiency is not the sole determinant of hyperparathyroidism in severe obesity because visceral fat deposition and leptin could both play a role. Obesity-related hyperparathyroidism is associated with insulin resistance and atherosclerosis, although the results from previous studies were conflicting. Finally, LSG intervention does not negatively affect vitamin D status and improves hyperparathyroidism.

Vibrational dynamics of confined supercooled water.

The quest for a possible liquid-liquid coexistence line in supercooled water below its homogeneous nucleation temperature is faced by confining water within a porous silica substrate (MCM-41). This system is investigated by synchrotron radiation infrared spectroscopy, exploring both the intramolecular and the intermolecular vibrational dynamics, in the temperature range from ambient down to ∼120 K, along several isobaric paths between 0.7 kbar and 3.0 kbar. Upon lowering the temperature, the OH-stretching band shows that the intramolecular vibrational dynamics continuously evolves from predominantly liquidlike to predominantly icelike. An abrupt change in the line shape of the intermolecular vibrational band between 220 K and 240 K, depending on the pressure, is the signature of nucleation of ice within the MCM-41 pores. These findings do not support the presence of two liquid phases and provide evidence for the coexistence of liquid water and ice in water confined in MCM-41.

Ice crystallization observed in highly supercooled confined water.

We investigate the state of water confined in the cylindrical pores of MCM-41 type mesoporous silica, with pore diameters of 2.8 nm and 4.5 nm, over the temperature range 160-290 K by combining small angle neutron scattering and wide angle diffraction. This allows us to observe simultaneously the intermolecular correlations in the local water structure (which shows up in a main water peak around Q = 1.7 Å-1), the two-dimensional hexagonal arrangement of water cylinders in the silica matrix (which gives rise to a pronounced Bragg peak around Q = 0.2 Å-1), and the so-called Porod scattering at smaller Q, which arises from larger scale interfacial scattering within the material. In the literature, the temperature evolution of the intensity of the Bragg peak has been interpreted as the signature of a density minimum in confined water at approximately 210 K. Here we show that, under the conditions of our experiment, a fraction of freezable water coexists with a layer of non-freezable water within the pore volume. The overall temperature dependence of our data in the different Q regions, as well as the comparison of the data for the two pore sizes, leads us to conclude that the observed variation in the intensity of the Bragg diffraction peak is actually caused by a liquid to ice transition in the freezable fraction of confined water.

Hydrogen Bond Length as a Key To Understanding Sweetness.

Neutron diffraction experiments have been performed to investigate and compare the structure of the hydration shell of three monosaccharides, namely, fructose, glucose, and mannose. It is found that despite their differences with respect to many thermodynamical quantities, bioprotective properties against environmental stresses, and taste, the influence of these monosaccharides on the bulk water solvent structure is virtually identical. Conversely, these sugars interact with the neighboring water molecules by forming H bonds of different length and strength. Interestingly, the sweetness of these monosaccharides, along with that of the disaccharide trehalose, is correlated with the length of these H bonds. This suggests that the small differences in stereochemistry between the different sugars determine a relevant change in polarity, which has a fundamental impact on the behavior of these molecules in vivo.

High serum levels of C-reactive protein (CRP) predict beneficial decrease of visceral fat in obese females after sleeve gastrectomy.

BACKGROUND & AIMS: Gender-related differences represent an emerging investigation field to better understand obesity heterogeneity and paradoxically associated cardiovascular (CV) risk. Here, we investigated if high-sensitivity C-reactive protein (hs-CRP) might differently affect adiposity and predict the clinical response to bariatric surgery in obese males and females. METHODS AND RESULTS: In 110 morbidly obese patients undergoing laparoscopic sleeve gastrectomy, hs-CRP as well as anthropometric assessment of adiposity, completed by electric bioimpedance and ultrasonography quantification of visceral fat area (VFA), were measured before and one year after surgery. As compared to males, obese female showed less severe overweight and prevalent subcutaneous fat deposition, but higher circulating hs-CRP. In obese females, hs-CRP was associated with VFA at baseline, independently of body mass index (BMI) and visceral adiposity index (OR 1.022 [95% CI 1.001-1.044]; p = 0.039). Based on decreases and increases in hs-CRP levels after surgery, two distinct subgroups of females were identified. Post-surgery decreases in hs-CRP was predominantly observed in patients with higher baseline levels of hs-CRP and associated with greater reduction of weight, BMI, fat and lean mass, VFA and visceral to subcutaneous fat ratio. Finally, we observed that high baseline values of hs-CRP were able to predict VFA reduction one-year after surgery, independently of BMI and visceral adiposity index (VAI) loss (OR 1.031 [95% CI 1.009-1.053]; p = 0.005). CONCLUSION: In obese females, hs-CRP levels might be a promising biomarker of visceral fat amount and dysfunction, in addition to predict the effectiveness of bariatric surgery in terms of loss of VFA one-year after surgery.

Glucose and Mannose: A Link between Hydration and Sweetness.

Glucose and mannose have a different degree of sweetness, implying different affinity to the sweet taste receptor. While the receptor structure is still undefined, there are several geometrical models for their binding mechanism. A detailed study of the hydration structure of sugars with known degree of sweetness is bound to provide information on the accuracy of such models. Our neutron diffraction study on the hydration of glucose and mannose show that both α- and ß-glucose form strong hydrogen bonds with water, and that the steric hindrance of their first hydration shell matches the receptor geometrical model. The α-anomer of mannose has a similar, well-defined first hydration shell, but with fewer and weaker hydrogen bonds compared to glucose. Conversely, the hydration shell of ß-mannose (reported as bitter) does not match the receptor geometrical model. These findings suggest a link between the hydration shell of sugars and their degree of sweetness.

Laparoscopic sleeve gastrectomy modifies cholesterol synthesis but not cholesterol absorption.

BACKGROUND AND AIMS: Each bariatric surgery procedure impacts differently on cholesterol synthesis and absorption. Although a restrictive procedure, sleeve gastrectomy resolves diabetes mellitus and, like mixed-type procedures, induces early changes in gastrointestinal hormones. To our knowledge the present study is the first to assess the effects of sleeve gastrectomy on cholesterol synthesis and absorption. METHODS AND RESULTS: 42 consecutive subjects with obesity and sleeve gastrectomy candidates were included in the study together with a control group of 20 subjects without obesity. Before sleeve gastrectomy and 10 months afterwards, all subjects underwent a clinical examination, blood tests, ultrasound visceral fat area estimation and determination of plasma lathosterol, campesterol and sitosterol concentrations. After sleeve gastrectomy, significant decreases were observed in BMI, waist circumference, visceral and subcutaneous fat, blood pressure, triglycerides, insulin and glucose levels, lathosterol and HOMA-IR. HDL-C and apolipoprotein AI levels increased significantly. No significant differences emerged in LDL-C, apolipoprotein B levels or cholesterol absorption markers. Lathosterol levels correlated significantly with BMI, visceral fat area and HOMA-IR. Differences in cholesterol intake after surgery were not significantly associated with differences in lathosterol, campesterol and sitosterol concentrations. CONCLUSIONS: Sleeve gastrectomy reduced the markers of cholesterol synthesis but did not modify cholesterol absorption. Changes in cholesterol synthesis and absorption were independent of variations in cholesterol intake, suggesting a specific sleeve gastrectomy-related effect.

Circulating Levels of the Adipokines Monocyte Chemotactic Protein-4 (MCP-4), Macrophage Inflammatory Protein-1ß (MIP-1ß), and Eotaxin-3 in Severe Obesity and Following Bariatric Surgery.

The aim of the study was to investigate the involvement of the adipokines eotaxin-3, MIP-1ß, and MCP-4 in obesity and related comorbidities and the modification of their circulating levels after bariatric surgery. Eighty severely obese subjects and 20 normal-weight controls were included in the study. Circulating levels of MCP-4, MIP-1ß, and eotaxin-3, and the main clinical, biochemical, and instrumental parameters for the evaluation of cardiovascular and metabolic profile were determined in controls and in obese subjects at baseline and 10 months after surgery. Within the obese group at baseline, eotaxin-3 levels were higher in males than females and in smokers than non-smokers and showed a positive correlation with LDL-cholesterol, apolipoprotein B, and leptin. MIP-1ß showed a positive correlation with age and leptin and a negative correlation with adiponectin and was an independent predictor of increased carotid artery intima-media thickness. MCP-4 levels were higher in obese subjects than controls and showed a positive correlation with body mass index, eotaxin-3, and MIP-1ß. Bariatric surgery induced a marked decrease in all the 3 adipokines. MCP-4 is a novel biomarker of severe obesity and could have an indirect role in favoring sub-clinical atherosclerosis in obese patients by influencing the circulating levels of eotaxin-3 and MIP-1ß, which are directly related to the main atherosclerosis markers and risk factors. The reduction of circulating levels of MCP-4, eotaxin-3, and MIP-1ß could be one of the mechanisms by which bariatric surgery contributes to the reduction of cardiovascular risk in these patients.

Hydration of Caffeine at High Temperature by Neutron Scattering and Simulation Studies.

The solvation of caffeine in water is examined with neutron diffraction experiments at 353 K. The experimental data, obtained by taking advantage of isotopic H/D substitution in water, were analyzed by empirical potential structure refinement (EPSR) in order to extract partial structure factors and site-site radial distribution functions. In parallel, molecular dynamics (MD) simulations were carried out to interpret the data and gain insight into the intermolecular interactions in the solutions and the solvation process. The results obtained with the two approaches evidence differences in the individual radial distribution functions, although both confirm the presence of caffeine stacks at this temperature. The two approaches point to different accessibility of water to the caffeine sites due to different stacking configurations.

Neutron diffraction study of aqueous Laponite suspensions at the NIMROD diffractometer.

The process of dynamical arrest, leading to formation of different arrested states such as glasses and gels, along with the closely related process of aging, is central for both basic research and technology. Here we report on a study of the time-dependent structural evolution of two aqueous Laponite clay suspensions at different weight concentrations. Neutron diffraction experiments have been performed with the near and intermediate range order diffractometer (NIMROD) that allows studies of the structure of liquids and disordered materials over a continuous length scale ranging from 1 to 300 Å, i.e., from the atomistic to the mesoscopic scales. NIMROD is presently a unique diffractometer, bridging the length scales traditionally investigated by small angle neutron scattering or small angle x-ray scattering with that accessible by traditional diffractometers for liquids. Interestingly, we have unveiled a signature of aging of both suspensions in the length scale region of NIMROD. This phenomenon, ascribed to sporadic contacts between Laponite platelets at long times, has been observed with the sample arrested as gel or as repulsive glass. Moreover, water molecules within the layers closest to Laponite platelets surface show orientational and translational order, which maps into the crystalline structure of Laponite.

Pericardial fat, insulin resistance, and left ventricular structure and function in morbid obesity.

BACKGROUND AND AIM: Morbid obesity is often accompanied by insulin resistance and increased ectopic fat surrounding the heart. We evaluated the relation of epicardial and pericardial fat with insulin resistance and left ventricular (LV) structure and function. METHODS AND RESULTS: Epicardial and pericardial fat thicknesses were determined at 2-dimensional echocardiography in 80 morbid obese subjects [age 42 ± 12 years, 31% men, body mass index (BMI) 44.4 ± 7 kg/m(2)]. LV hypertrophy (LV mass ≥51 g/m(2.7)), inappropriately high LV mass for a given cardiac workload (observed vs predicted LV mass >128%), and stress-adjusted LV mid-wall fractional shortening were determined. Pericardial and epicardial fat thicknesses had direct associations with BMI (r = 0.40 and 0.45, both p < 0.01) and waist circumference (r = 0.37 and 0.45, both p < 0.01). Pericardial (partial r = 0.35, p < 0.01), but not epicardial fat thickness (partial r = 0.05, p = n.s.), was correlated with homeostasis model assessment-insulin resistance after adjustment for BMI. Pericardial fat also had a strong negative correlation with mid-wall fractional shortening (p = 0.01) and a positive one with inappropriately high LV mass (p < 0.01), while no such relation was found for epicardial fat (both p = n.s.). Independently of age, male sex, BMI, and anti-hypertensive treatment, pericardial fat thickness had an independent positive association with inappropriately high LV mass (ß = 0.29, p = 0.02), and a negative one with stress-adjusted mid-wall fractional shortening (ß = -0.26, p = 0.04). CONCLUSIONS: Pericardial fat thickness is associated with insulin resistance, inappropriately high LV mass, and LV systolic dysfunction in obese individuals. Findings from this study confirm the existence of a connection between insulin resistance, cardiac ectopic fat deposition and cardiac dysfunction in morbid obesity.

Microscopic structure of water in a water/oil emulsion.

We have determined the microscopic structure of water within a water/oil emulsion, by combining neutron diffraction data, exploiting the isotopic H/D substitution, and a fully atomistic Monte Carlo simulation of a portion of a water droplet, containing the water/oil interface. The dependence of the data on the simulation box size and the reliability of the water-water radial distribution functions are discussed. Although water in the emulsion forms shorter and stronger hydrogen bonds compared to pure bulk water, its overall microscopic structure looks more disordered.

Aqueous solutions of divalent chlorides: ions hydration shell and water structure.

By combining neutron diffraction and Monte Carlo simulations, we have determined the microscopic structure of the hydration ions shell in aqueous solutions of MgCl(2) and CaCl(2), along with the radial distribution functions of the solvent. In particular the hydration shell of the cations, show cation specific symmetry, due to the strong and directional interaction of ions and water oxygens. The ions and their hydration shells likely form molecular moieties and bring clear signatures in the water-water radial distribution functions. Apart from these signatures, the influence of divalent salts on the microscopic structure of water is similar to that of previously investigated monovalent solutes, and it is visible as a shift of the second peak of the oxygen-oxygen radial distribution function, caused by distortion of the hydrogen bond network of water.

Proton Momentum Distribution and Diffusion Coefficient in Water: Two Sides of the Same Coin?

Water, the prototype of a liquid to ordinary people, is the most anomalous liquid to physicists, showing regions of the temperature-density (T,ρ) plane where its microscopic structure, diffusion coefficient, and density have anomalous behaviors. Structural anomalies occur over a broad bell-shaped T,ρ region. This region contains, as a matryoshka, two smaller regions, one delimiting dynamical and the other delimiting thermodynamic anomalies. Water anomalous behavior in each of these regions manifests itself as a decrease of order or an increase of the diffusion coefficient upon increasing pressure and as a decrease of density upon cooling. Here, we show that the radial momentum distribution of water protons and their mean kinetic energy have a peculiar, theoretically unpredicted anomaly in the region of dynamical anomalies. This anomaly can be rationalized as due to two distinct "families" of water protons, experiencing quite distinct local environments, leading to an enhancement of the momentum fluctuations along with an increase of kinetic energy.

Multiple relaxation processes versus the fragile-to-strong transition in confined water.

Broadband dielectric spectroscopy data on water confined in three different environments, namely at the surface of a globular protein or inside the small pores of two silica substrates, in the temperature range 140 K ≤ T ≤ 300 K, are presented and discussed in comparison with previous results from different techniques. It is found that all samples show a fast relaxation process, independently of the hydration level and confinement size. This relaxation is well known in the literature and its cross-over from Arrhenius to non-Arrhenius temperature behavior is the object of vivid debate, given its claimed relation to the existence of a second critical point of water. We find such a cross-over at a temperature of ~180 K, and assign the relaxation process to the layer of molecules adjacent and strongly interacting with the substrate surface. This is the water layer known to have the highest density and slowest translational dynamics compared to the average: its apparent cross-over may be due to the freezing of some degree of freedom and survival of very localized motions alone, to the onset of finite size effects, or to the presence of a calorimetric glass transition of the hydration shell at ~170 K. Another relaxation process is visible in water confined in the silica matrices: this is slower than the previous one and has distinct temperature behaviors, depending on the size of the confining volume and consequent ice nucleation.

Viscosity of aqueous solutions and local microscopic structure.

The effect of solutes on the structure of water has been debated intensively over the past years. Typical scenarios label different ions as water structure "makers" or "breakers": this is a quite elusive definition, which has been first introduced in the description of the effect of solutes on the viscosity of water and, although criticized, is still used in the current literature. Here, using a combination of neutron diffraction and computer modeling, we present a possible relation between the viscosity B coefficient and a local structural property of the solution. In particular, B appears in the Jones-Dole relation and its sign is traditionally used to characterize a solute as "structure maker" or "breaker". We find that B is linearly correlated to the difference between the average solute-water distance and the water-water distance in the pure liquid, in the case of monovalent electrolyte solutions.

Isotope quantum effects on the water proton mean kinetic energy.

A deep inelastic neutron scattering experiment, performed on D(2)O in the stable and metastable liquid phases, provides evidence for isotope quantum effects in the proton or deuteron single particle dynamics along the hydrogen bond. The deuteron mean kinetic energy extracted from the experimental data in the metastable supercooled phase (T = 276.15 K) exceeds the zero point energy and scales as sqrt[2] with that of protons in supercooled light water, at T = 269.15 K. The present data support the suggestion that even small changes in the short range environment of a deuteron or proton have a strong influence on its quantum behavior.

Structural study of low concentration LiCl aqueous solutions in the liquid, supercooled, and hyperquenched glassy states.

Neutron diffraction experiments on a solution of LiCl in water (R = 40) at ambient conditions and in the supercooled and hyperquenched states are reported and analyzed within the empirical potential structure refinement framework. Evidence for the modifications of the microscopic structure of the solvent in the presence of such a small amount of salt is found at all investigated thermodynamic states. On the other hand, it is evident that the structure of the hyperquenched salty sample is similar to that of pure low density amorphous water, although all the peaks of the radial distribution functions are broader in the present case. Changes upon supercooling or hyperquenching of the ion's hydration shells and contacts are of limited size and evidence for segregation phenomena at these states does not clearly show up, although the presence of water separated contacts between ion of the same sign is intriguing.