Formation of a Quasi‐Free‐Standing Single Layer of Graphene and Hexagonal Boron Nitride on Pt(111) by a Single Molecular Precursor

It is shown that on Pt(111) it is possible to prepare hexagonal boron nitride (h‐BN) and graphene (G) in‐plane heterojunctions from a single molecular precursor, by thermal decomposition of dimethylamine borane (DMAB). Photoemission, near‐edge X‐ray absorption spectroscopy, low energy electron microscopy, and temperature programmed desorption measurements indicate that the layer fully covers the Pt(111) surface. Evidence of in‐plane layer continuity and weak interaction with Pt substrate has been established. The findings demonstrate that dehydrogenation and pyrolitic decomposition of DMAB is an efficient and easy method for obtaining a continuous almost freestanding layer mostly made of G, h‐BN with only a low percentage (<3%) of impurities (B and N‐doped G domains or C‐doped h‐BN or boron carbonitride, BCN at the boundaries) in the same 2D sheet on a metal substrate, such as Pt(111), paving the way for the advancement of next‐generation G‐like‐based electronics and novel spintronic devices.     

On the pyrolysis of a methyl-silsesquioxane in reactive CO2 atmosphere: A TG/MS and FT-IR study

Polymer-derived SiOC-C composites are typically obtained through pyrolysis of a polysiloxane precursor in inert atmosphere. Recent studies have shown that novel SiOC microstructures and compositions can be obtained when the pyrolysis is carried out in a reactive environment, as CO₂, which leads to a selective oxidation of the Si─C bonds leaving a microstructure constituted by a nano-dispersed sp² carbon phase within an SiO₂ matrix. However, little is known about the reaction mechanisms between CO₂ and the preceramic polymer to date. In this work, we investigated the pyrolysis of a methyl-silsesquioxane in reactive (CO₂) and inert (Ar or He) atmosphere by combining TG/MS and FT-IR analysis. The results showed that CO₂ starts to react with the preceramic polymer from ≈750°C when the Si─CH₃ groups start to form Si─CH_x-Si units. The reaction breaks the Si─C bond increasing the amount of the free carbon phase and releasing water vapor, detected by MS, even at temperatures exceeding 900°C. At higher temperatures (≈950°C), CO₂ reacts with the free carbon phase leading to a weight loss and the formation of CO.     

65 nm CMOS SSB mixer for UWB synthesiser

The present work addresses the design of a 65 nm CMOS wide-band single-sideband mixer for UWB synthesiser. The circuit has been designed inductorless and with few capacitors, in order to save silicon area and, at the same time, to get a mixer independent of the adopted frequency plan and synthesiser architecture. Particular attention has been paid to reducing the spurs as much as possible. In order to address a realistic investigation, the design has accounted also for the corner cases and the possible impairments in the input signals. A comparison with the state-of-the-art of the SSB mixers shows the low power consumption of the present work.     

Affinity of nat/68Ga-Labelled Curcumin and Curcuminoid Complexes for β-Amyloid Plaques: Towards the Development of New Metal-Curcumin Based Radiotracers

Curcumin derivatives labelled with fluorine-18 or technetium-99m have recently shown their potential as diagnostic tools for Alzheimer’s disease. Nevertheless, no study by exploiting the labelling with gallium-68 has been performed so far, in spite of its suitable properties (positron emitter, generator produced radionuclide). Herein, an evaluation of the affinity for synthetic β-amyloid fibrils and for amyloid plaques of three ^nat/68Ga-labelled curcumin analogues, namely curcumin curcumin (CUR), bis-dehydroxy-curcumin (bDHC) and diacetyl-curcumin (DAC), was performed. Affinity and specificity were tested in vitro on amyloid synthetic fibrils by using gallium-68 labelled compounds. Post-mortem brain cryosections from Tg2576 mice were used for the ex vivo visualization of amyloid plaques. The affinity of ⁶⁸Ga(CUR)₂⁺, ⁶⁸Ga(DAC)₂⁺, and ⁶⁸Ga(bDHC)₂⁺ for synthetic β-amyloid fibrils was moderate and their uptake could be observed in vitro. On the other hand, amyloid plaques could not be visualized on brain sections of Tg2576 mice after injection, probably due to the low stability of the complexes in vivo and of a hampered passage through the blood–brain barrier. Like curcumin, all ^nat/68Ga-curcuminoid complexes maintain a high affinity for β-amyloid plaques. However, structural modifications are still needed to improve their applicability as radiotracers in vivo.     

Rate‐dependent self‐healing behavior of an ethylene‐co‐methacrylic acid ionomer under high‐energy impact conditions

In this work, the mechanical and the self‐healing behaviors of an ethylene‐co‐methacrylic acid ionomer were investigated in different testing conditions. The self‐healing capability was explored by ballistic impact tests at low‐velocity, midvelocity, and hypervelocity bullet speed; different experimental conditions such as sample thickness and bullet diameter were examined; in all impact tests, spherical projectiles were used. These experiments, in particular those at low and midspeed, allowed to define a critical ratio between sample thickness and bullet diameter below which full repair was not observed. After ballistic damage, the healing efficiency was evaluated by applying a pressure gradient through tested samples. Subsequently, morphology analysis of the affected areas was made observing all tested samples by scanning electron microscope. This analysis revealed different characteristic features of the damaged zones affected at different projectile speed. Stress–strain curves in uniaxial tension performed at different temperatures and strain rates revealed yield strength and postyield behavior significantly affected by these two parameters. A rise of temperature during high strain rate tests in the viscoplastic deformation region was also detected. This behavior has a strong influence on the self‐repairing mechanism exhibited by the studied material during high‐energy impact tests. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1949–1958, 2013     

Effect of Dipping and Vacuum Impregnation Pretreatments on the Quality of Frozen Apples: A Comparative Study on Organic and Conventional Fruits

The effect of dipping and vacuum impregnation (VI) pretreatments with lemon juice solution on the quality and stability of organic and conventional frozen apples was investigated. Fresh apples were characterized; organic apples showed, at equal starch and ripeness index, a lower sugar content, and higher acidity than conventional ones. The polyphenol content was slightly higher in organic apples than in conventional ones while polyphenoloxidase activity was similar. No differences in color and firmness were evidenced. Dipping affected organic and conventional apples’ color by determining an increase of lightness (ΔL^* ≈ 4) and h° (Δh° ≈ 6) parameters. VI reduced the lightness of apples (ΔL^* ≈ ?3) but the addition of lemon juice counterbalanced the lightness reduction by increasing ΔL^* from 3 to 1.5 ca. Pretreatments did not affect the firmness of organic fruits while impaired that of the conventional ones ( 26% on average), likely due to different fruit matrix porosity and cell wall composition. Freezing (?40 °C) and frozen storage (up to 300 days) dramatically reduced the firmness of organic (42%) and conventional products (58%). At equal pretreatment and storage time (that is, 15, 30, 300 days), higher firmness retention was evidenced in organic apples than in conventional ones. All through frozen storage, VI was shown to better preserve the mechanical properties of organic apples than that of conventional ones. Both freezing and frozen storage reduced the hue of frozen apple products by up to 8% due to browning reactions. Lemon juice addition increased the hue of both frozen samples and thawed samples by about 2% all through storage time.     

Flash spark plasma sintering of 3YSZ

Flash SPS (FSPS) consolidation of 3YSZ cold pressed pellets was investigated. The results show that FSPS allows ultra-rapid consolidation of 3YSZ samples in 30–90 s under an applied electric field. The DC field induces electrochemical blackening. The partial reduction process starts from the cathode (-) and propagates toward the anode (+). This phenomenon, not previously discussed in FSPS literature, induces the development of internal temperature gradients resulting in a polarity dependent grain size/densification.     

Design of microalgal biomass production in a continuous photobioreactor: An integrated experimental and modeling approach

The industrial production of microalgae in continuous photobioreactors (PBRs) was investigated using an integrated experimental-modeling approach.