The origin of titanium-rich basaltic magmatism on the Moon remains enigmatic. Ilmenite-bearing cumulates in the lunar mantle are often credited as the source, but their partial melts are not a compositional match and are too dense to enable eruption. Here we use petrological reaction experiments to show that partial melts of ilmenite-bearing cumulates react with olivine and orthopyroxene in the lunar mantle, shifting the melt composition to that of the high-Ti suite. New high-precision Mg isotope data confirm that high-Ti basalts have variable and isotopically light Mg isotope compositions that are inconsistent with equilibrium partial melting. We employ a diffusion model to demonstrate that kinetic isotope fractionation during reactive flow of partial melts derived from ilmenite-bearing cumulates can explain these anomalously light Mg isotope compositions, as well as the isotope composition of other elements such as Fe, Ca and Ti. Although this model does not fully replicate lunar melt-solid interaction, we suggest that titanium-rich magmas erupted on the surface of the Moon can be derived through partial melting of ilmenite-bearing cumulates, but melts undergo extensive modification of their elemental and isotopic composition through reactive flow in the lunar mantle. Reactive flow may therefore be the critical process that decreases melt density and allows high-Ti melts to erupt on the lunar surface.

A mild CO2-treatment of a poly(L-lactic acid) PLLA disk with tailored geometry allowed to compare cold crystallization of PLLA containing ?"-mesophase, with coldcrystallization of fully amorphous PLLA, both coexisting within a single sample. The use of PLLA disks with 0.5 mm thickness, low CO2 pressure (3.0 MPa) and short treatment time (5 min) at 25 oC, led to only partial diffusion of the gas into the polymer. CO2-induced mesophase developed in surface-near regions of the disks, where CO2 penetrated, whereas the core of the samples was not reached by the gas and remained amorphous. Cold-crystallization of CO2-treated PLLA was analyzed after full desorption of the gas, using different heating rates. Slow heating allowed to identify two cold-crystallization events: low-temperature cold-crystallization in the outer parts of the sample treated with CO2, promoted by prior formation of the ?"-mesophase, and high-temperature cold-crystallization, occurring at similar temperatures as in case of non-CO2-treated amorphous PLLA. In both cases, cold-crystallization led to formation of conformationally disordered ??-crystals, as revealed by temperature-resolved wide-angle X-ray scattering. This study confirms that formation of ??-crystals is mainly controlled by the crystallization temperature, also when crystallization is promoted by the prior presence of a mesophase.

Transport of organic solvents in polymeric matrices plays a central role in many processes of interest to the coatings industry. Previous studies have focused on individual processes taking place in the solvent-paint system. In the present study, we report results on the molecular dynamics in a solvent/paint system during the entire sequence of absorption, diffusion, swelling, and evaporation processes, obtained non-invasively, in situ, and in real time using unilateral NMR relaxometry. The associated chemical structures were investigated using HR-MAS NMR spectroscopy. Four distinct ranges of molecular motion in the solvent/paint film were identified based on proton NMR transverse relaxation time (T2) data. The fast motion of the freely moving solvent molecules was discriminated from the slower motion of the so-called bound phase of the solvent molecules physically and chemically interacting with the cross-linked polymer network. In addition, two distinct domains of the cross-linked and mobile phases of the polymerized oil were observed, allowing the study of both the dynamics of the swelling-contraction process of the polymer and of the solubilization process. Such non-invasive analyses provide significant information on transport phenomena of the solvent in the paint film, as well as on the effects of various solvents applied to oil paintings.

Applications of metamaterials in the realization of efficient devices in the terahertz band have recently been considered to achieve wave deflection, focusing, amplitude manipulation and dynamical modulation. Terahertz metamaterials offer practical advantages since their structures have typical sizes of hundreds microns and are within the reach of current three-dimensional (3D) printing technologies. Here, we propose terahertz photonic structures composed of dielectric rods layers made of acrylonitrile styrene acrylate realized by low-cost, rapid, and versatile fused deposition modeling 3D-printing. Terahertz time-domain spectroscopy is employed for the experimental study of their spectral and dynamic response. Measured spectra are interpreted by using simulations performed by an analytical exact solution of the Maxwell equations for a general incidence geometry, by a field expansion as a sum over reciprocal lattice vectors. Results show that the structures possess specific spectral forbidden bands of the incident THz radiation depending on their optical and geometrical parameters. We also find evidence of disorder in the 3D printed structure resulting in the closure of the forbidden bands at frequencies above 0.3 THz. The size disorder of the structures is quantified by studying the dynamics diffusion of THz pulses as a function of the numbers of layers of dielectric rods. Comparison with simulations of light diffusion in photonic crystals with increasing disorder allows estimating the size distributions of elements. By using a Mean Squared Displacement model, from the broadening of the pulses' widths it is also possible to estimate the diffusion coefficient of the terahertz radiation in the photonic structures.

By means of numerical simulations we study the radial-orbit instability in anisotropic self-gravitating N-body systems under the effect of noise. We find that the presence of additive or multiplicative noise has a different effect on the onset of the instability, depending on the initial value of the orbital anisotropy.

The aim of this study was to determine whether quantitative parameters obtained from intravoxel incoherent motion (IVIM) model at baseline magnetic resonance imaging (MRI) correlate with histological parameters and response to neoadjuvant chemotherapy in patients with locally advanced cervical cancer (LACC). Methods: Twenty patients with biopsy-proven cervical cancer, staged as LACC on baseline MRI and addressed for neoadjuvant chemotherapy were enrolled. At treatment completion, tumor response was assessed with a follow-up MRI evaluated using the revised response evaluation criteria in solid tumors (RECIST; version 1.1), and patients were considered good responders (GR) if they had complete response or partial remission, and poor responders/non-responders (PR/NR) if they had stable or progressive disease. MRI protocol included conventional diffusion-weighted imaging (DWI; b = 0 and 1000 s/mm) and IVIM acquisition using eight b-values (range: 0-1500 s/mm). MR-images were analyzed using a dedicated software to obtain quantitative parameters: diffusion (D), pseudo-diffusion (D*), and perfusion fraction (fp) from the IVIM model; apparent diffusion coefficient (ADC) from conventional DWI. Histologic subtype, grading, and tumor-infiltrating lymphocytes (TILs) were assessed in each LACC. Results: D showed significantly higher values in GR patients (p = 0.001) and in moderate/high TILs (p = 0.018). Fp showed significantly higher values in squamous cell tumors (p = 0.006). Conclusions: D extracted from the IVIM model could represent a promising tool to identify tumor aggressiveness and predict response to therapy.

The galvanic displacement reaction between sacrificial PbO2 layers and Fe(II) ions has been carried out in mildly acid acetate solutions. The effect of experimental variables, like morphology of the PbO2 layers, solution pH, temperature and concentration of Fe(II) ions, has been investigated by combining electrochemical methods, SEM-EDS, XRD and XPS. The reaction between PbO2 and Fe(II) ions produced secondary dual layers, consisting of an inner amorphous FeOOH film and an outer crystalline ?-FeOOH deposit, respectively. This peculiar behavior was in contrast with analogous reactions involving other transition metal ions, which yielded only continuous amorphous secondary oxide layers. PbO2/FeOOH layers were tested as anodes for the oxygen evolution reaction in basic media.

A polystyrene homopolymer with narrow molecular weight distribution (Mn = 2.3 ? 0.3 kg mol-1, ? = 1.05 ? 0.01) and end-terminated with a phosphorus containing moiety has been used to form P ?-layers embedded into a SiO2 matrix. The number of P atoms in the ?-layers has been stepwise increased from ~5 ? 1013 to ~1.6 ? 1014 atoms per cm2 by repeated doping cycles. The P ?-layers have been tested as diffusion sources at temperatures ranging from 1000 to 1200 ?C for different annealing times, up to 120 s. Variations of the diffusion coefficients with the annealing time have been observed and a clear dependence of diffusion coefficients on the P concentration has been highlighted. These results suggest the presence of two different P species diffusing through the SiO2 matrix; an initially fast diffusing P compound and a slow diffusing P atom incorporated into the oxide in a bound form. Collected data provide information about P diffusion in SiO2 that is fundamental to the development of predictive models for nanoscale doping processes based on the use of diffusion dopant sources generated by self-limiting reactions of dopant containing molecules onto deglazed or non-deglazed semiconductor substrates.

The most widely used method to measure the transport properties of dense polymeric membranes is the time lag method in a constant volume/pressure increase instrument. Although simple and quick, this method provides only relatively superficial, averaged data of the permeability, diffusivity, and solubility of gas or vapor species in the membrane. The present manuscript discusses a more sophisticated computational method to determine the transport properties on the basis of a fit of the entire permeation curve, including the transient period. The traditional tangent method and the fitting procedure were compared for the transport of six light gases (H, He, O, N, CH, and CO) and ethane and ethylene in mixed matrix membranes (MMM) based on Pebax®1657 and the metal-organic framework (MOF) Cu(S, S)-hismox·5HO. Deviations of the experimental data from the theoretical curve could be attributed to the particular MOF structure, with cavities of different sizes. The fitting procedure revealed two different effective diffusion coefficients for the same gas in the case of methane and ethylene, due to the unusual void morphology in the MOFs. The method was furthermore applied to mixed gas permeation in an innovative constant-pressure/variable-volume setup with continuous analysis of the permeate composition by an on-line mass-spectrometric residual gas analyzer. This method can provide the diffusion coefficient of individual gas species in a mixture, during mixed gas permeation experiments. Such information was previously inaccessible, and it will greatly enhance insight into the mixed gas transport in polymeric or mixed matrix membranes.

Galvanic displacement reactions between sacrificial oxide layers and metal cations, leading to the formation of secondary oxide layers, have been studied with the aim of collecting new experimental evidence on their mechanism. The study has been carried out by combining electrochemical methods, SEM-EDS and XPS depth profiling. Both porous and compact PbO2 layers have been used as sacrificial oxides and reacted, in different experiments, with: (i) a single low-valent cation, (ii) two cations in sequential exchange reactions or (iii) two cations simultaneously. The experimental results converged to show (i) a lack of correlation between the reaction driving force and the secondary oxide growth rate, (ii) the incorporation of cations from solution at the secondary oxide/electrolyte interface, (iii) the transport of Pb species through the growing secondary oxide layer and (iv) a major effect of mass transport on the growth rate.

Viruses, opinions, ideas are different contents sharing a common trait: they need carriers embedded into a social context to spread. Modeling and approximating diffusive phenomena have always played an essential role in a varied range of applications from outbreak prevention to the analysis of meme and fake news. Classical approaches to such a task assume diffusion processes unfolding in a mean-field context, every actor being able to interact with all its peers. However, during the last decade, such an assumption has been progressively superseded by the availability of data modeling the real social network of individuals, thus producing a more reliable proxy for social interactions as spreading vehicles. In this work, following such a trend, we propose alternative ways of leveraging apriori knowledge on mesoscale network topology to design community-aware diffusion models with the aim of better approximate the spreading of content over complex and clustered social tissues.

The metabolic processes related to the synthesis of the molecules needed for a new round of cell division underlie the complex behaviour of cell populations in multi-cellular systems, such as tissues and organs, whereas their deregulation can lead to pathological states, such as cancer. Even within genetically homogeneous populations, complex dynamics, such as population oscillations or the emergence of specific metabolic and/or proliferative patterns, may arise, and this aspect is highly amplified in systems characterized by extreme heterogeneity. To investigate the conditions and mechanisms that link metabolic processes to cell population dynamics, we here employ a previously introduced multi-scale model of multi-cellular system, named FBCA (Flux Balance Analysis with Cellular Automata), which couples biomass accumulation, simulated via Flux Balance Analysis of a metabolic network, with the simulation of population and spatial dynamics via Cellular Potts Models. In this work, we investigate the influence that different modes of nutrients diffusion within the system may have on the emerging behaviour of cell populations. In our model, metabolic communication among cells is allowed by letting secreted metabolites to diffuse over the lattice, in addition to diffusion of nutrients from given sources. The inclusion of the diffusion processes in the model proved its effectiveness in characterizing plausible biological scenarios.

Posterior eye segment diseases are treated through monthly intravitreal injections, that evoke serious side effects. A promising approach to reduce injection frequency consists in producing biodegradable microspheres (MPs) releasing the protein in the vitreous body for long times. Moreover, a rational design of these MPs requires a discouraged diffusion/sedimentation within the intravitreal space, which are detrimental for the vision and the control over drug release kinetics. In this work, poly(lactic-co-glycolic acid) (PLGA)-based MPs encapsulating bovine serum albumin (BSA) were coated with hyaluronic acid (HA) at two molecular weights and tested for their release, diffusion and degradation features in simulated vitreous body (SVB). Results indicate that HA corona prolongs MP degradation time and BSA release. Furthermore, HA coating increased the affinity between MPs and SVB, thereby repressing device transport compared to control PLGA MPs. Results hold promise for the possible application of HA-decorated MPs for intravitreal injection of protein drugs.

The morphological evolution of surface supported Au nanorods, induced by thermal heating, has been examined. This study is focused on the establishment of the connection of the nanorods morphology to the annealing temperature, on the elucidation of the acting microscopic mechanisms and quantitative evaluation of the involved parameters leading to the morphology evolution. In particular, after depositing the nanorods on SiO surface, thermal processes were performed to induce their morphological evolution and we pointed out our attention on: a) the study of the morphological evolution of single isolated Au nanorods, which was identified as a reshaping process towards a spherical shape. The morphological analysis led us to establish the correlation between the annealing temperature and the nanorods aspect ratio and to elucidate the basic atomic driving mechanism for the reshaping process;b) the study of the morphological evolution of closely spaced nanorods (forming a film over the substrate surface). The analysis led us to the identification of the mechanisms governing the nanorods joining and evolution in larger architectures which, then, operate a reshaping process.On the basis of the results, we set a general framework for the design of complex morphology nanostructures on surfaces with desired shape and aspect ratio.

Recent scanning tunneling microscopy experiments in NbN thin disordered superconducting films found an emergent inhomogeneity at the scale of tens of nanometers. This inhomogeneity is mirrored by an apparent dimensional crossover in the paraconductivity measured in transport above the superconducting critical temperature Tc. This behavior was interpreted in terms of an anomalous diffusion of fluctuating Cooper pairs that display a quasiconfinement (i.e., a slowing down of their diffusive dynamics) on length scales shorter than the inhomogeneity identified by tunneling experiments. Here, we assume this anomalous diffusive behavior of fluctuating Cooper pairs and calculate the effect of these fluctuations on the electron density of states above Tc. We find that the density of states is substantially suppressed up to temperatures well above Tc. This behavior, which is closely reminiscent of a pseudogap, only arises from the anomalous diffusion of fluctuating Cooper pairs in the absence of stable preformed pairs, setting the stage for an intermediate behavior between the two common paradigms in the superconducting-insulator transition, namely, the localization of Cooper pairs (the so-called bosonic scenario) and the breaking of Cooper pairs into unpaired electrons due to strong disorder (the so-called fermionic scenario).

The structural and surface quality of the material employed is one of the most critical issues as regards the large scale application of electronic devices based on hydrogenated amorphous silicon (a-Si:H), germanium (a-Ge:H) and a-SiGe:H. Atomic hydrogen migration occurs in the amorphous network. The high temperatures applied during growth of those materials, e. g. by chemical vapor deposition, or reached during device operation enhance the diffusion of H atoms, in particular of those liberated from their bonds to the host atoms as a consequence of annealing. Such enhanced diffusion favors the migration of H atoms towards nanovoids where they very likely form molecular H2 since the reaction 2MeH ? H2 +Me-Me is an exothermic one (Me indicates the host atom: Si or Ge). The accumulation on the wall of voids causes the evolution of hydrogen bubbles and then the formation of blisters. Some efforts have been made to understand the microscopic mechanisms determining the rupture of the MeH bonds and formation of H2 rich voids at the origin of the blisters in order to get rid of them. The objective of this work was to find a way to determine the threshold temperature below which surface blistering does not occur in hydrogenated a-SixGe1-x, 0 <= x <=1. This is achieved by a theoretical model that takes into account both the kinetics of the rupture of the MeH bonds and, in particular, the diffusion of the atomic H. The experimental results suggesting our theoretical approach have been obtained by Secondary Neutral Mass Spectrometry (SNMS), as regards the depth distribution of H (Fig. 1), and by surface light reflectivity measurements, as regards the assessment, as a function of temperature, of the time of the onset of blistering and its activation energy by Arrhenius plots (Fig. 2). The data supplied by the latter plots allow the validation of the theoretical model. The calculated critical temperature for blistering, in fact, is on the same order of magnitude as the experimentally observed one. The experimentally determined Vegard's law-like dependence [1] of the blistering activation energy on the Si concentration in the a-SixGe1-x alloys is interpreted by a simple formula and related 3D-like diagram. [1] M. Serényi, C. Frigeri, R. Schiller, J. Alloys Compd. 763, 471 (2018). Fig.1. SNMS depth profile of hydrogen in annealed a-Si and a-Ge layer after 40 minutes of annealing (a), and after 10 and 40 minutes in a-Si layer (b). Fig. 2. Graphical representation n of blistering onset vs. temperature in a polar coordinate system. The left-hand vertical plane belongs to the Si and the right one to the Ge Arrhenius plot.

In this work the effect of different processing routes on the kinetics of formation of Co4Sb12 phase and Yb filling in the skutterudite cage, as well as thermoelectric behaviour was evaluated. As prepared slowly cooled ingot and rapidly solidified ribbons show the presence of multiple phases, as a consequence of the complex solidification path characterized by two peritectic reactions. As solidification rate increases, grain refinement is promoted. Annealing of rapidly solidified ribbons induces a faster solubilisation of Yb due to increased grain boundary diffusivity. For this reason, rapid solidification can be considered a promising intermediate step for lowering the total processing time of skutterudites. Sintering of powders obtained from the slowly cooled ingot and rapidly solidified ribbons leads to the formation of massive samples with different densities, depending on the particle size distributions of the starting powders. The effect of Yb content on the thermoelectric properties was critically analysed, considering both data from the literature and this work.

Diffusion in waveguides with spatially modulated profiles is an important topic in modern electromagnetics and optics. Wave dynamics in the high-frequency asymptotics are governed by classical ray dynamics which can be characterised by looking at the diffusion of particles throughout the channel. We study the transport of particles (rays) in a channel with a sinusoidal profile at different values of the corrugation amplitude. We find that below a certain corrugation level the transport is ballistic, beyond this threshold, a diffusion-like behaviour emerges in the asymptotic limit of large times. In this regime particle transport slows down due to the trapping mechanism in the corrugated regions of the channel. We use the analogy with correlated random walks to discuss the observed transport regimes.

A composite system made of poly(l-lactic acid) (PLLA) and graphene nanoplatelets (GNP) was investigated by Raman and FTIR spectroscopy. Two compositions were prepared and characterized in comparison to the pristine polymer: they contained, respectively, 0.25 and 0.75 wt% of the nanofiller. The study was focused on the morphological properties of the system, and, in particular, on the level of dispersion and the homogeneity obtainable with the adopted preparation protocol. Furthermore, the possible molecular interactions taking place between the nanofiller and the polymer matrix were considered. Both the above issues were investigated by confocal Raman spectroscopy, with the aid of first-principle calculations to strengthen the spectral interpretation. Finally, the effect of the nanofiller on water diffusion was investigated by time-resolved FTIR spectroscopy, which provided accurate equilibrium and kinetic data, as well as molecular level information on the penetrant-to-substrate interactions. It was found that, for a 0.25 wt% composition, the adopted preparation protocol allowed us to achieve a dispersion at the level of single nanoplatelets, while for a 0.75 wt% composition, the GNP's aggregate into a co-continuous phase. PLLA/GNP interactions were detected by Raman spectroscopy, producing a detectable perturbation of the PLLA conformational equilibrium. Both the diffusivities and the equilibrium water uptake were found to decrease significantly by increasing the filler content.