Structural, magnetic, and magneto-optical properties of nanocrystalline face centered cubic Co70Cr30/Pt multilayers with perpendicular magnetic anisotropy

Co70Cr30 alloyed layers are combined with extremely thin Pt layers in order to produce novel face-centered-cubic multilayered films to be considered as a potential perpendicular magnetic recording medium. The films were grown on Si, glass and polyimide substrates by e-beam evaporation at a temperature slightly higher than room temperature. The multilayered structure of the films was verified by X-ray diffraction experiments. Plane-view transmission electron microscopy images have revealed the formation of very small grains in the range of 7-9 nm. Hysteresis loops as a function of temperature were recorded via the magneto-optic Kerr effect in the polar geometry configuration. The system exhibits perpendicular magnetic anisotropy, which enhances with decreasing temperature. Hysteresis loops with a squareness of 1 and a coercivity of 1.45 kOe were obtained at 10 K. Furthermore, complete magneto-optic spectra of the films are recorded, showing a strong magneto-optic enhancement in the ultraviolet region at around 4.5 eV.     

Environmental Enrichment Induces Meningeal Niche Remodeling through TrkB-Mediated Signaling

Neural precursors (NPs) present in the hippocampus can be modulated by several neurogenic stimuli, including environmental enrichment (EE) acting through BDNF-TrkB signaling. We have recently identified NPs in meninges; however, the meningeal niche response to pro-neurogenic stimuli has never been investigated. To this aim, we analyzed the effects of EE exposure on NP distribution in mouse brain meninges. Following neurogenic stimuli, although we did not detect modification of the meningeal cell number and proliferation, we observed an increased number of neural precursors in the meninges. A lineage tracing experiment suggested that EE-induced β3-Tubulin⁺ immature neuronal cells present in the meninges originated, at least in part, from GLAST⁺ radial glia cells. To investigate the molecular mechanism responsible for meningeal reaction to EE exposure, we studied the BDNF-TrkB interaction. Treatment with ANA-12, a TrkB non-competitive inhibitor, abolished the EE-induced meningeal niche changes. Overall, these data showed, for the first time, that EE exposure induced meningeal niche remodeling through TrkB-mediated signaling. Fluoxetine treatment further confirmed the meningeal niche response, suggesting it may also respond to other pharmacological neurogenic stimuli. A better understanding of the neurogenic stimuli modulation for meninges may be useful to improve the effectiveness of neurodegenerative and neuropsychiatric treatments.     

Local and Global Handovers Based on In-Band Signaling in Wireless ATM Networks

This paper presents a handover protocol for wireless ATM networks, which makes use of in-band signaling, i.e., of ATM resource management cells, to process network handovers and guarantee the in-sequence and loss-free delivery of the ATM cells containing user data. The goal of the proposed approach is to minimize the modifications of the ATM signaling standard required to overlay user mobility onto the fixed network infrastructure, and provide for a gradual upgrade of the fixed network to handle mobility. The proposed protocol handles both local handovers, in which the connection access point needs not migrate to a new ATM local exchange, and global handovers, in which the connection access point must migrate to a new local exchange. The handover scheme is devised so as to grant in-sequence delivery of cells. The performance of the network during handover is analyzed in case of connections requiring loss-free operation. The considered performance figures are the cell transmission delay introduced by the handover and the cell buffering requirements posed to the network. The behavior of the proposed protocol in presence of multiple handovers is studied via simulation, while a simple analytical method is derived for the performance evaluation of a single handover in isolation.     

Multibuffer delay line architectures for efficient contentionresolution in optical switching nodes

This paper proposes an efficient contention resolution switching architecture which can serve as the basis for all-optical switching nodes. The presented solution builds on fiber delay lines used as temporary optical storage and 2×2 space photonic switches, a solution principle also known as Quadro or switched delay lines (SDLs). The efficiency of SDLs is fundamentally linked to its storage capacity, i.e., the length of the fiber delay lines, while its cost depends on the number of 2×2 photonic switches, i.e., the number of stages in the switch. This work presents a solution that makes use of multibuffer fiber delay lines which allow multiple packets to be concurrently stored (propagated) on each line. With a novel switch control, it is shown that this solution increases the total storage capacity and significantly improves switch and network performance, without increasing the number of the 2×2 switches in the system, i.e., its cost     

Iron,Nitrogen Co-Doped Carbon Spheres as Low Cost,Scalable Electrocatalysts for the Oxygen Reduction Reaction

Atomically dispersed transition metal-nitrogen-carbon catalysts are emerging as low-cost electrocatalysts for the oxygen reduction reaction in fuel cells. However, a cost-effective and scalable synthesis strategy for these catalysts is still required, as well as a greater understanding of their mechanisms. Herein, iron, nitrogen co-doped carbon spheres (Fe@NCS) have been prepared via hydrothermal carbonization and high-temperature post carbonization. It is determined that FeN₄ is the main form of iron existing in the obtained Fe@NCS. Two different precursors containing Fe²⁺ and Fe³⁺ are compared. Both chemical and structural differences have been observed in catalysts starting from Fe²⁺ and Fe³⁺ precursors. Fe²⁺@NCS-A (starting with Fe²⁺ precursor) shows better catalytic activity for the oxygen reduction reaction. This catalyst is studied in an anion exchange membrane fuel cell. The high open-circuit voltage demonstrates the potential approach for developing high-performance, low-cost fuel cell catalysts.     

Electrophotocatalytic decolorization of an azo dye on TiO2 self-organized nanotubes in a laboratory scale reactor

It was investigated the feasibility of decolorization of an azo dye (DG 26) using a large scale nanotubular TiO₂ structured electrode in a laboratory photoelectrochemical reactor (0.8 L). Catalyst was grown by anodic oxidation directly on Ti surface and its microstructure and crystalline structure were characterized with SEM and XRD. TiO₂/Ti photoactivity under different anodic polarization values was evaluated via photoelectrochemical tests. The nanostructured TiO₂ was used in a reactor as photo-anode under UV monochromatic irradiation (254 nm) and it was subjected to bias (+ 1.5 V vs. SCE). A comparison with photolysis and photocatalysis processes was carried out under the same operating conditions to evaluate the synergistic action of photocatalysis and TiO₂/Ti electrochemical polarization.Electrophotocatalysis was proven to be more effective than photocatalysis in DG 26 decolorization. Catalyst polarization resulted in synergistic effect on process yields. The complete decolorization of a 40 mg/L solution of DG 26 was achieved in 24 h, without adding chemical reagents, and catalyst durability was demonstrated over 360 h tests. Therefore, the work done is challenging to prove that the process (irradiation + catalyst + polarization) is feasible and effectively up-grading to pilot and demonstrative scale applications after a fluid dynamics optimization of the photoreactor.     

A Double-Layer Reduced Model for Fault Flow on Slipping Domains with an Hybrid Finite Volume Scheme

In this work we are interested in single-phase flows in fractured porous media for underground processes. We focus our attention on domains where the presence of faults, with thickness several orders of magnitude smaller than other characteristic sizes, can allow one part of the domain to slide past to the other. We propose a mathematical scheme where a reduced model for the fault flows is employed yielding a problem of co-dimension one. The hybrid finite volume method is used to obtain the discretized problem, which uses two different meshes on each side of the fault. These two meshes can move with the corresponding domain, resulting in non-matching grids between the two parts of the fault. In an earlier paper a mathematical scheme was proposed where the numerical discretization considers the hybrid finite volume method. In this paper we focus on the well-posedness of the continuous problem, the convergence of the discretized problem, and we support the theoretical findings with several numerical tests.     

VPO catalyst for n-butane oxidation to maleic anhydride: A goal achieved, or a still open challenge?

This review describes recent findings in the oxidation of n-butane to maleic anhydride. The process is commercial since the 80’s, but yet the yield is far from being optimised. Therefore, it represents an emblematic example of how several scientific disciplines, from solid-state science to reactor technology, can contribute to the improvement of the process performance.     

The catalytic performance of Cs-doped V/Ti/O catalysts in the oxidation of o-xylene to phthalic anhydride: a TPR/TPO and reactivity study

Titania-supported vanadia (V/Ti/O) systems were modified by addition of cesium oxide for application as catalysts in the selective oxidation of o-xylene to phthalic anhydride (PA). Catalytic tests demonstrated that cesium is a strong promoter of the activity and selectivity to PA, but this effect is evident only under well-defined reaction conditions. Samples with a Cs content lower than 0.35 wt.% Cs₂O exhibited a considerable increase in conversion as compared with the undoped V/Ti/O system. Catalytic tests made with varying o-xylene and oxygen concentrations in the feed demonstrated that in Cs-doped V/Ti/O catalysts the rate-determining step is the re-oxidation of vanadium by molecular oxygen. Thermal-programmed reduction (TPR) and thermal-programmed re-oxidation (TPO) tests evidenced that the addition of Cs decreases the vanadium reducibility and increases the re-oxidizability of the reduced vanadium sites. The positive effect of Cs on selectivity to PA was evident only for o-xylene concentrations in feed lower than 1.5 mol%.