Hydrogen-bond network distortion of water in the soft confinement of Nafion membrane.

A Compton spectroscopy investigation is carried out in hydrated Nafion membranes, enabling identification of distortions in the hydrogen-bond distribution of the polymer hydrating water by means of the subtle changes reflected by the Compton profiles. Indeed, deformations of the Compton profiles are observed when varying hydration, and two different bonding kinds are associated with the water molecules: at low hydration, water surrounds the sulfonic groups, while on increasing hydration, water molecules occupy the interstitial cavities formed upon swelling of the membrane. The analysis is proposed in terms of averaged OH bond length variation. A sizable contraction of the OH distance is observed at low hydration (∼0.09 Å), while at higher hydration levels, the contraction is smaller (∼0.02 Å) and the OH bond length is closer to bulk water. An evaluation of the electron kinetic energy indicates that the spatial changes associated with the water distribution correspond to a consistent binding energy increase. Distinct temperature dependences of each water population are observed, which can be straightly related to water desorption into ice on cooling below the freezing point.

Ultrafast Plasmon Dynamics in Crystalline LiF Triggered by Intense Extreme UV Pulses.

An extreme ultraviolet pump and visible-light probe transmission experiment in crystalline LiF, carried out at the Free Electron Laser facility FERMI, revealed an oscillating time dependence of the plasmon mode excited in the high-density high-temperature electron plasma. The effect is interpreted as a fingerprint of the electron-ion interaction: the ion motion, shaped by the electron dynamic screening, induces, in turn, electron density fluctuations that cause the oscillation of the plasmon frequency at the timescale of the ion dynamics. Fitting the high resolution transmission data with an RPA model for the temperature-dependent dielectric function, which includes electron self-energy and electron-ion coupling, confirms the interpretation of the time modulation of the plasmon mode.

Polymorphism of human telomeric quadruplexes with drugs: a multi-technique biophysical study.

The human telomeric G-quadruplex structural motif of DNA has come to be known as a new and stimulating target for anticancer drug discovery. Small molecules that interact with G-quadruplex structures in a selective way have gained impressive interest in recent years as they may serve as potential therapeutic agents. Here, we show how circular dichroism, UV resonance Raman and small angle X-ray scattering spectroscopies can be effectively combined to provide insights into structural and molecular aspects of the interaction between human telomeric quadruplexes and ligands. This study focuses on the ability of berberine and palmatine to bind with human telomeric quadruplexes and provides analysis of the conformational landscape visited by the relevant complexes upon thermal unfolding. With increasing temperature, both free and bound G-quadruplexes undergo melting through a multi-state process, populating different intermediate states. Despite the structural similarity of the two ligands, valuable distinctive features characterising their interaction with the G-quadruplex emerged from our multi-technique approach.

Collective ion dynamics in liquid zinc: evidence for complex dynamics in a non-free-electron liquid metal.

A detailed inelastic neutron scattering investigation of the THz dynamics of liquid zinc is presented. The observed Q dependence clearly reveals the existence of a complex dynamics made up of two distinct excitations. The highest energy mode is the prolongation of the longitudinal acoustic density fluctuations whereas the comparison with the phonon dynamics of crystalline hcp zinc suggests a transverse acousticlike nature for the second one. This mode seems related to peculiar anisotropic interactions, possibly connected to the behavior of the crystalline phase.

Hydration-dependent dynamics of human telomeric oligonucleotides in the picosecond timescale: a neutron scattering study.

The dynamics of the human oligonucleotide AG3(T2AG3)3 has been investigated by incoherent neutron scattering in the sub-nanosecond timescale. A hydration-dependent dynamical activation of thermal fluctuations in weakly hydrated samples was found, similar to that of protein powders. The amplitudes of such thermal fluctuations were evaluated in two different exchanged wave-vector ranges, so as to single out the different contributions from intra- and inter-nucleotide dynamics. The activation energy was calculated from the temperature-dependent characteristic times of the corresponding dynamical processes. The trends of both amplitudes and activation energies support a picture where oligonucleotides possess a larger conformational flexibility than long DNA sequences. This additional flexibility, which likely results from a significant relative chain-end contribution to the average chain dynamics, could be related to the strong structural polymorphism of the investigated oligonucleotides.

Stimulus contrast, pursuit mode, and age strongly influence tracking performance on a continuous visual tracking task.

Human observers tend to naturally track moving stimuli. This tendency may be exploited towards an intuitive means of screening visual function as an impairment induced reduction in stimulus visibility will decrease tracking performance. Yet, to be able to detect subtle impairments, stimulus contrast is critical. If too high, the decrease in performance may remain undetected. Therefore, for this approach to become reliable and sensitive, we need a detailed understanding of how age, stimulus contrast, and the type of stimulus movement affect continuous tracking performance. To do so, we evaluated how well twenty younger and twenty older participants tracked a semi-randomly moving stimulus (Goldmann size III, 0.43 degrees of visual angle), presented at five contrast levels (5%-10%-20%-40%-80%). The stimulus could move smoothly only (smooth pursuit mode) or in alternation with displacements (saccadic pursuit mode). Additionally, we assessed static foveal and peripheral contrast thresholds. For all participants, tracking performance improved with increasing contrast in both pursuit modes. To reach threshold performance levels, older participants required about twice as much contrast (20% vs. 10% and 40% vs. 20% in smooth and saccadic modes respectively). Saccadic pursuit detection thresholds correlated significantly with static peripheral contrast thresholds (rho = 0.64). Smooth pursuit detection thresholds were uncorrelated with static foveal contrast thresholds (rho = 0.29). We conclude that continuous visual stimulus tracking is strongly affected by stimulus contrast, pursuit mode, and age. This provides essential insights that can be applied towards new and intuitive approaches of screening visual function.

Broadband infrared study of pressure-tunable Fano resonance and metallization transition in 2H-[Formula: see text].

High pressure is a proven effective tool for modulating inter-layer interactions in semiconducting transition metal dichalcogenides, which leads to significant band structure changes. Here, we present an extended infrared study of the pressure-induced semiconductor-to-metal transition in 2H-[Formula: see text], which reveals that the metallization process at 13-15 GPa is not associated with the indirect band-gap closure, occurring at 24 GPa. A coherent picture is drawn where n-type doping levels just below the conduction band minimum play a crucial role in the early metallization transition. Doping levels are also responsible for the asymmetric Fano line-shape of the [Formula: see text] infrared-active mode, which has been here detected and analyzed for the first time in a transition metal dichalcogenide compound. The pressure evolution of the phonon profile under pressure shows a symmetrization in the 13-15 GPa pressure range, which occurs simultaneously with the metallization and confirms the scenario proposed for the high pressure behaviour of 2H-[Formula: see text].

Debye to non-Debye scaling of the Boson peak dynamics: critical behavior and local disorder in vitreous germania.

We report on the observation of a significant softening of the Boson peak (BP) frequency of vitreous GeO(2) above the glass transition temperature. The softening reminds a critical trend, with a transition temperature intermediate between the glass transition temperature, T(g), and the melting point. The softening of the BP frequency corresponds to a transition from a region dominated by Debye scaling to a non-Debye one. Below T(g) the density of vibrational states varies according to the modification of the elastic continuum medium. Above T(g) the relevant softening of the BP modes can be explained by a broadening of the distribution of elastic constants between neighboring atoms, induced by the structural rearrangement. These findings are discussed together with recent experimental and theoretical results on the low frequency vibrations in glasses.

Periodontal therapy and biomarkers related to cardiovascular risk.

In the last 15-20 years the association between periodontitis and cardiovascular diseases has received greater attention. Clinical evidence also suggests that periodontitis is associated with a systemic host response and with a low-grade inflammatory state, as assessed by raised serum levels of CRP and endothelial dysfunction. This is a perturbation of the normal function of the endothelial cells that are responsible for a normal vascular function (dilatation, constriction). The objective of this review was to systematically appraise the available evidence on the effect of periodontal therapy on systemic biomarkers related to cardiovascular risk. An electronic search was conducted using MEDLINE via PubMed to identify published literature. The electronic search identified 836 references, of which 643 were considered irrelevant for this review. Full texts of 183 possible relevant articles were assessed, with exclusion of 174. Nine studies were included in the review. The overall effect of periodontal therapy was associated with a reduction in CRP of 0.50 mg/ml (95% CI 0.15, 0.85) (P=0.005). In conclusion, this review supports the hypothesis of an association between periodontitis and systemic inflammation. Further research is needed on the possible impact of periodontitis on cardiovascular disease events.

Structure and acoustic properties of hydrated nafion membranes.

The propagation of acoustic waves in water-hydrated Nafion membrane has been monitored using heterodyne-detected transient grating spectroscopy. At room temperature, upon increasing the water content, the speed of sound drops to a value lower than the respective velocities of sound in pure Nafion and pure water. This counterintuitive effect can be explained by a simple calculation of the sound velocity in an effective medium made of water and Nafion polymer. Upon cooling, a phase separation occurs in the sample, and the formation of ice is observed (M. Pineri et al. J. Power Sources 2007, 172, 587-596). This phase transition is characterized via a second acoustic wave observed in the signal. Sound propagation and X-ray diffraction confirm the formation of crystalline ice on the membrane surface, that reversibly melts upon heating. The amount of ice that forms in the sample is monitored as a function of temperature and represents an order parameter for the transition. This parameter follows a power law with an exponent of 0.5, indicating the critical nature of the observed process.

Disentangling time-focusing from beam divergence: A novel approach for high-flux thermal neutron spectroscopy at continuous and long-pulse sources.

We present the concept of a novel time-focusing technique for neutron spectrometers, which allows us to disentangle time-focusing from beam divergence. The core of this approach is a double rotating-crystal monochromator that can be used to extract a larger wavelength band from a white beam, thus providing a higher flux at the sample compared to standard time-of-flight instruments, yet preserving energy resolution and beam collimation. The performances of a spectrometer based on this approach are quantitatively discussed in terms of possible incident wavelengths, flux at the sample, and (Q, E)-resolution. Analytical estimates suggest flux gains of about one order of magnitude at comparable resolutions in comparison to conventional time-of-flight spectrometers. Moreover, the double monochromator configuration natively shifts the sample away from the source line-of-sight, thus significantly improving the signal-to-noise ratio. The latter, in combination with a system that does not increase the beam divergence, brings the further advantage of a cleaner access to the low-Q region, which is recognized to be of fundamental interest for magnetism and for disordered materials, from glasses to biological systems.

Real-time observation of the isothermal crystallization kinetics in a deeply supercooled liquid.

Below the melting temperature Tm, crystals are the stable phase of typical elemental or molecular systems. However, cooling down a liquid below Tm, crystallization is anything but inevitable. The liquid can be supercooled, eventually forming a glass below the glass transition temperature Tg. Despite their long lifetimes and the presence of strong barriers that produces an apparent stability, supercooled liquids and glasses remain intrinsically a metastable state and thermodynamically unstable towards the crystal. Here we investigated the isothermal crystallization kinetics of the prototypical strong glassformer GeO2 in the deep supercooled liquid at 1100 K, about half-way between Tm and Tg. The crystallization process has been observed through time-resolved neutron diffraction for about three days. Data show a continuous reorganization of the amorphous structure towards the alpha-quartz phase with the final material composed by crystalline domains plunged into a low-density, residual amorphous matrix. A quantitative analysis of the diffraction patterns allows determining the time evolution of the relative fractions of crystal and amorphous, that was interpreted through an empirical model for the crystallization kinetics. This approach provides a very good description of the experimental data and identifies a predator-prey-like mechanism between crystal and amorphous, where the density variation acts as a blocking barrier.

A high-flux upgrade for the BRISP spectrometer at ILL.

To date, the BRISP spectrometer represents the state-of-the-art for every instrument aiming to perform Brillouin neutron scattering. Exploiting accurate ray-tracing McStas simulations, we investigate an improved configuration of the BRISP primary spectrometer to provide a higher flux at the sample position, while preserving all the present capabilities of the instrument. This configuration is based on a neutron guide system and is designed to fit the instrument platform with no modifications of the secondary spectrometer. These evaluations show that this setup can achieve a flux gain factor ranging from 3 to 6, depending on the wavelength. This can expand the experimental possibilities of BRISP towards smaller samples, possibly using also complex sample environments.

Should-hand syndrome: importance of early diagnosis and treatment.

If the shoulder-hand syndrome is left without special care, it may lead to severe painful disabilities of the upper extremity. Early recognition of the clinical signs and symptoms and aggressive total care are essential for successful treatment and for the prevention of severe flexion contractures of the hand and shoulder, especially in patients whose symptoms have developed after a cerebrovascular accident. An outline is given of the treatment modalities (corticosteroids, physiotherapy and mechanical devices) used at the Institute for Rehabilitation Medicine (NYU) for obtaining maximum function of the involved upper extremity.

beta-Endorphin and cortisol abnormalities in spinal cord-injured individuals.

Plasma beta-endorphin-like immunoreactivity (BEP-ir) and cortisol levels were measured by radioimmunoassay (RIA) in nine patients who were at least 12 months status post spinal cord injury (SCI). Plasma levels were obtained at 8:00 am and 4:00 pm to determine circadian rhythm, and on the day following administration of 1 mg dexamethasone, levels were again obtained at 8:00 am and 4:00 pm. The mean morning levels of plasma BEP-ir were significantly lower than control values for this laboratory (6.2 +/- 1.2 v 12.0 +/- 2.3 pg/mL). The morning BEP-ir values were lowest in patients who were closer to the time of injury (described by a second-order polynomial regression, R = .89; P less than .01). Mean morning cortisol levels were not significantly different from controls, but showed greater variability (mean, 15.1; range, 0.7 to 22.7 micrograms/dL v control, 15.5; range, 7 to 35). Dexamethasone suppressed cortisol secretion in all patients and BEP-ir levels in six of nine patients. Failure to detect BEP-ir suppression occurred in patients whose BEP-ir levels were less than 4.5 pg/mL and close to the minimum detection limit of the assay. Depression was present in five of nine patients as measured by the Beck Depression Inventory (BDI) and in three of nine patients as measured by the Hamilton Depression Scale (HSRD). However, the depression indices did not correlate with the neuroendocrine measures.

Brillouin neutron scattering in heavy water: evidence for two-mode collective dynamics.

A high resolution (1.5 meV) inelastic neutron scattering experiment was carried out, aiming at an accurate investigation of the high frequency and low momentum dynamic response in heavy water. The experimental data confirm the existence of a dispersionless mode, besides the ordinary longitudinal collective dynamics. A simplified model, based on the interaction of two vibrational branches, is proposed to interpret the observed features of the dynamic spectra. The validity extent of this scheme is proved by applying it to room temperature neutron and x-ray data, to temperature and pressure dependent x-ray data, and to room temperature neutron data of vibrational density of states. The overall successfull results provided by this model, in conjunction with the combined analysis of the x-ray and neutron data on collective dynamics, enable a deeper insight into the complex mechanisms of the water dynamics and provide a simple phenomenological explanation for the transition from ordinary to fast sound.

Sonochemical production of a non-crystalline phase of palladium.

A non-crystalline phase of palladium was produced by cavitation technique starting from a solution of palladium acetylacetonate and toluene. The microscopic structure of the sample, a very fine powder, was investigated by X-ray diffraction and it showed the characteristic features of a disordered system. Further details about the phase of the sample were gained by studying the crystallization process induced by thermal treatments.

[Surgical risk in patients with heart valve disease in non-cardiac surgery]. / Rischio operatorio nel valvulopatico per gli interventi di chirurgia non cardiaca.

Our purpose was to retrospectively evaluate major risk of non cardiac surgery in patients with valvular heart disease. We studied retrospectively 136 patients, 44 affected by aortic, 81 by mitral and 11 by mitroaortic valve disease. NYHA class was I-II in 130 and III in 6 patients. Sixty four patients underwent orthopedic surgery, 57 patients occulistic surgery and 5 patients urological surgery. There were no hospital deaths. Fifteen patients developed major perioperative complication: 7 serious ventricular arrhythmias, 6 hypotension, 2 "hypertensive attacks". We conclude that non cardiac surgery is safe in patients with valvular heart disease.

Phenol block of the tibial nerve in the hemiplegic patient.

Selective blocks of the tibial nerve with aqueous solution of 5% phenol, after localization of the nerve by electrical stimulation, were performed in 30 patients with acquired hemiplegia for treatment of severe spasticity of the foot plantar flexors and ankle clonus. Ankle clonus disappeared in all patients and resistance to passive stretch was reduced substantially immediately after the procedure; orthotic fitting and ambulation training then were possible. Longterm followup (averaging 12.9 months) showed the gait to be improved and spasticity decreased in all patients; there were no indications for further treatment of plantar flexor spasticity. Fixed equinus deformity was prevented in all cases. The only significant complication was the development of paresthesias in eight patients (26.6%) The simplicity of the procedure, the functional results observed immediately, its longlasting effect, and the lack of serious complications, warrant its more widespread use in the treatment and prevention of deformities in the spastic foot of the hemiplegic patient. However, there should be further study about prevention of paresthesias, which occurred in a significant percentage of patients in this study.

Terahertz Dynamics in Human Cells and Their Chromatin.

The terahertz dynamics of human cells of the U937 line and their chromatin has been investigated by high-resolution inelastic X-ray scattering. To highlight its dynamical features in situ, nuclear DNA has been stained by uranyl-acetate salt. The general behavior of the collective dynamics of the whole cell is quite similar to that of bulk water, with a nearly wavevector-independent branch located at about 5 meV and a propagating mode with a linear trend corresponding to a speed of sound of 2900 ± 100 m/s. We provide the first experimental evidence for the existence of two branches also in the dispersion curves of chromatin. The high-energy mode displays an acoustic-like behavior with a sound velocity similar to unstained cells, but in this case the branch likely originates from the superposition of intramolecular DNA optic modes. A low-energy optic-like branch, distinctive of the chromatin moiety, is found at about 2.5 meV.