NMR investigation of degradation processes of ancient and modern paper at different hydration levels

The degradation process of cellulose-made materials was investigated by means of nuclear magnetic resonance （NMR） spectroscopy, with particular emphasis on the role of water and on the hydration mechanism of cellulose fibrils. To accomplish this, the structure and dynamics of water within ancient and modern samples with different aging histories were investigated. The results mainly indicated that hydrolytic and oxidative reactions provoked the formation of acidic by-products. Furthermore, degradation processes were enhanced by higher amounts of water giving a progressive consumption of the amorphous regions of the cellulose. We propose NMR experiments as a benchmark for character- ization of the degradation state of paper, as well as for investigating the effectiveness of restoration treatments.

Transcranial Direct Current Stimulation in ADHD:A Systematic Review of Efficacy,Safety,and Protocol-induced Electrical Field Modeling Results

Transcranial direct current stimulation(tDCS)is a promising method for altering cortical excitability with clinical implications.It has been increasingly used in neurodevelopmental disorders,especially attention-deficit hyperactivity disorder(ADHD),but its efficacy(based on effect size calculations),safety,and stimulation parameters have not been systematically examined.In this systematic review,we aimed to(1)explore the effectiveness of tDCS on the clinical symptoms and neuropsychological deficits of ADHD patients,(2)evaluate the safety of tDCS application,especially in children with ADHD,(3)model the electrical field intensity in the target regions based on the commonly-applied and effective versus less-effective protocols,and(4)discuss and propose advanced tDCS parameters.Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses approach,a literature search identified 14 empirical experiments investigating tDCS effects in ADHD.Partial improving effects of tDCS on cognitive deficits(response inhibition,working memory,attention,and cognitive flexibility)or clinical symptoms(e.g.,impulsivity and inattention)are reported in10 studies.No serious adverse effects are reported in 747 sessions of tDCS.The left and right dorsolateral prefrontal cortex are the regions most often targeted,and anodal tDCS the protocol most often applied.An intensity of 2 mA induced stronger electrical fields than 1 mA in adults with ADHD and was associated with significant behavioral changes.In ADHD children,however,the electrical field induced by 1 mA,which is likely larger than the electrical field induced by 1 mA in adults due to the smaller head size of children,was sufficient to result in significant behavioral change.Overall,tDCS seems to be a promising method for improving ADHD deficits.However,the clinical utility of tDCS in ADHD cannot yet be concluded and requires further systematic investigation in larger sample sizes.Cortical regions involved in ADHD pathophysiology,stimulation parameters(e.g.intensity,duration,polarity,and electrode size),and types of symptom/deficit are potential determinants of tDCS efficacy in ADHD.Developmental aspects of tDCS in childhood ADHD should be considered as well.

Water and lysozyme： Some results from the bending and stretching vibrational modes

The dynamic or glass transition in biomolecules is important to their functioning. Also essential is the transition between the protein native state and the unfolding process. To better understand these transitions, we use Fourier transform infrared spectroscopy to study the vibrational bending and stretching modes of hydrated lysozymes across a wide temperature range. We find that these transitions are triggered by the strong hydrogen bond coupling between the protein and hydration water. More precisely, we demonstrate that in both cases the water properties dominate the evolution of the system. We find that two characteristic temperatures are relevant： in the supercooled regime of confined water, the fragile-to-strong dynamic transition occurs at TL, and in the stable liquid phase, T＊ 315 ± 5 K characterizes the behavior of both isothermal compressibility KT（T, P） and the coefficient of thermal expansion ap（T, P）.

PEG-PLGA electrospun nanofibrous membranes loaded with Au@Fe2O3 nanoparticles for drug delivery applications

A PEGylated-PLGA random nanofibrous membrane loaded with gold and iron oxide nanoparticles and with silibinin was prepared by electrospinning deposition. The nanofibrous membrane can be remotely controlled and activated by a laser light or magnetic field to release biological agents on demand. The nanosystems were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, and thermogravimetric analyses. The drug loading efficiency and drug content percentages were determined by UV-vis optical absorption spectroscopy. The nanofibrous membrane irradiated by a relatively low-intensity laser or stimulated by a magnetic field showed sustained silibinin release for at least 60 h, without the burst effect. The proposed low-cost electrospinning procedure is capable of assembling, via a one-step procedure, a stimuli-responsive drug-loaded nanosystem with metallic nanoparticles to be externally activated for controlled drug delivery.

The Boson peak interpretation and evolution in confined amorphous water

We study the evolution of the Boson peak for water confined in cement paste obtained by means of Inelastic Neutron Scattering from room temperature to the deep supercooled regime.We analyze the data in terms of a universal-like model,developed for glass forming liquids in the frame of the energy landscape.In such a way it is possible to discriminate between the fragile and strong glass forming character of supercooled liquids and the dynamical crossover,fragile to strong,between them.Hence,we confirm the link between the Boson peak and the water polymorphism.In particular,the main result is represented by a crossover from a local energetic minima configuration to that characteristic of saddle points on going towards the deep supercooled regime up to the dynamical arrest.

On Some Numerical Semigroup Transforms

In this paper we introduce a particular semigroup transform A that fixes the invariants involved in Wilf's conjecture,except the embedding dimension.It also allows one to arrange the set of non-ordinary and non-irreducible numerical semigroups in a family of rooted trees.In addition,we study another transform,having similar features,that has been introduced by Bras-Amorós,and we make a comparison of them.In particular,we study the behavior of the embedding dimension under the action of such transforms,providing some consequences concerning Wilf's conjecture.

A study of the hydrogen bonds effect on the water density and the liquid-liquid transition

We study the hydrogen bonds effect on the water density as a function of temperature and pressure from the supercritical region to the metastable supercooled and amorphous phases. We identify two important thermodynamic thresholds, that is P~*■2 kbar and T~*■315 K, that separate two different water behaviors in terms of hydrogen bonding capability. For T < T~* and P < P~* the formation and stability of hydrogen bonded local structures are enhanced. The additional analyses of the proton NMR chemical shift and of the relaxation time confirm this evidence and highlight the structure breaking effects of the pressure. The investigation of both structural and dynamical quantities allow us to draw a complete picture of the water properties in terms of the temperaturepressure dependence of hydrogen bonding.

Preface to the special topic: New advances in water and water systems

Water and related systems play a central role in science and technology.Although water has unusual and anomalous behaviors,if compared with normal liquids,it is of fundamental interest in many research fields going from chemical-physics to life sciences.The first and well known example of these anomalies is the density maximum,at 277 K,intuited by Galilei[1]in 1612 and lately discovered in Florence[2].

Hydrophilic and hydrophobic competition in water-methanol solutions

We study the thermal behavior of the longitudinal spin-lattice, T1, and the transverse spin-spin, T2, relaxation times of the macroscopic magnetization in water/methanol solutions. Our aim is to investigate the reciprocal influence of hydrophobic effects on water properties and of hydrophilicity（via hydrogen bond, HB, interactions） on the solute. Using classical Nuclear Magnetic Resonance spectroscopy, we find a single characteristic correlation time τcthat reflects all local structural configurations and characterizes the thermal motion effects of the magnetic nuclei on the spin-spin interaction. We find that in the supercooled regime the correlations are stronger, with respect to ambient temperature, because the HB interactions have a lifetime long enough to sustain a stable water network. However, increasing the temperature, progressively decreases the HB interaction lifetime and destroys the water clusters with a consequent decoupling in the dynamic modes of the system. In addition, at temperatures higher than about 265 K, the hydrophobicity becomes gradually stronger and governs the physical properties of the solutions.

Connected Graphs Arising from Products of Veronese Varieties

Given a Segre squarefree Veronese configuration, following Bernd Sturmfels, we improve the study of the graphs associated to the configuration. We determine two special families of toric ideals and a finite set of moves for each of them, which still guarantee simultaneously the connection of all graphs arising from each family of moves.

The onset of the tetrabonded structure in liquid water

Water properties are dominated by the hydrogen bond interaction that gives rise in the stable liquid phase to the formation of a dynamical network.The latter drives the water thermodynamics and is at the origin of its well known anomalies.The HB structural geometry and its changes remain uncertain and still are challenging research subjects.A key question is the role and effects of the HB tetrahedral structure on the local arrangement of neighboring molecules in water.Here the hydrogen dynamics in bulk water is studied through the combined use of Neutron Compton Scattering and NMR techniques.Results are discussed in the framework of previous studies performed in a wide temperature range,in the liquid,solid,and amorphous states.For the first time this combined studies provide an experimental evidence of the onset of the water tetrahedral network at T^315 K,originally proposed in previous studies of transport coefficients and thermodynamical data;below this temperature the local order in water changes and the lifetime of local hydrogen bond network becomes long enough to gradually develop the characteristic tetrahedral network of water.

Dynamical changes in hydration water accompanying lysozyme thermal denaturation

We study the dynanfics of the first hydration shell of lysozyme to determine the role of hydra- tion water that accompanies lysozyme thermal denaturation. We use nuclear magnetic resonance spectroscopy to investigate both the translational and rotational contributions. Data on proton self-diffusion and reorentational correlation time indicate that the kinetics of the lysozyme fold- ing/unfolding process is controlled by the dynamics of the water molecules in the first hydration shell. When the hydration water dynamics change, because of the weakening of the hydrogen bond network, the three-dimensional structure of the lysozyme is lost and denaturation is triggered. Our data indicates that at temperatures above approximately 315 K, water behaves as a simple liquid and is no longer a good solvent.

The Boson peak in confined water： An experimental investigation of the liquid-liquid phase transition hypothesis

The Boson peak （BP） of deeply cooled confined water is studied by using inelastic neutron scattering （INS） in a large interval of the （P, T） phase plane. By taking into account the different behavior of such a collective vibrational mode in both strong and fragile glasses as well as in glass-forming materials, we were able to determine the Widom line that characterizes supercooled bulk water within the frame of the liquid-liquid phase transition （LLPT） hypothesis. The peak frequency and width of the BP correlated with the water polymorphism of the LLPT scenario, allowing us to distinguish the ＂low-density liquid＂ （LDL） and ＂high-density liquid＂ （HDL） phases in deeply cooled bulk water. Moreover, the BP properties afford a further confirmation of the Widom line temperature Tw as the （P, T） locus in which the local structure of water transforms from a predominately LDL form to a predominately HDL form.

Contrasting microscopic interactions determine the properties of water/methanol solutions

Herein we study the different microscopic interactions occurring in water/methanol solutions at dif- ferent methanol molar fractions, using NMR spctroscopy. Temperature was found to determine which interaction dominates. It was found that the mixing between water and methanol is non-ideal because of the presence of interactions like hydrophobicity and hydrophilicity. These results indicate that the competition between hydrophilic and hydrophobic interactions is different in different thermal regions, and that the physical properties of the solution are determined by the character of the solution itself, which in turn depends on the mole fraction of methanol and on the temperature.