Eumelanin for nature‐inspired UV‐absorption enhancement of plastics

In the human body, the black‐brown biopigment eumelanin blocks harmful ultraviolet (UV) radiation. In the plastics industry, additives are often added to polymers to increase their UV‐absorption properties. We herein report an assessment of the biopigment eumelanin as a nature‐inspired additive for plastics to enhance their UV absorption. Since eumelanin is produced by natural sources and is nontoxic, it is an interesting candidate in the field of sustainable plastic additives. In this work, the eumelanin‐containing films of commercial ethylene–vinyl acetate copolymer, a plastic used for packaging applications, were obtained by melt compounding and compression molding. The biopigment dispersion in the films was improved by means of the melanin free acid treatment. It was observed that eumelanin amounts as low as 0.8 wt% caused an increase of the UV absorption, up to one order of magnitude in the UVA range. We also evaluated the effect of eumelanin on the thermal stability and photostability of the films: the biopigment proved to be double‐edged, working both as UV‐absorption enhancer and photo‐prooxidant, as thermogravimetric analysis and infrared spectroscopy revealed. © 2019 Society of Chemical Industry     

Observation of diameter dependent carrier distribution in nanowire-based transistors

The successful implementation of nanowire (NW) based field-effect transistors (FET) critically depends on quantitative information about the carrier distribution inside such devices. Therefore, we have developed a method based on high-vacuum scanning spreading resistance microscopy (HV-SSRM) which allows two-dimensional (2D) quantitative carrier profiling of fully integrated silicon NW-based tunnel-FETs (TFETs) with 2 nm spatial resolution. The key elements of our characterization procedure are optimized NW cleaving and polishing steps, the use of in-house fabricated ultra-sharp diamond tips, measurements in high vacuum and a dedicated quantification procedure accounting for the Schottky-like tip-sample contact affected by surface states. In the case of the implanted TFET source regions we find a strong NW diameter dependence of conformality, junction abruptness and gate overlap, quantitatively in agreement with process simulations. In contrast, the arsenic doped drain regions reveal an unexpected NW diameter dependent dopant deactivation. The observed lower drain doping for smaller diameters is reflected in the device characteristics by lower TFET off-currents, as measured experimentally and confirmed by device simulations.     

Total-dose effects in double-gate-controlled NPN bipolartransistors

The sensitivity to radiation-induced degradation of new double-gate-controlled lateral NPN bipolar transistors has been investigated. The radiation hardness is improved when the device is working in the accumulation mode. The effect of positive charge and increased surface recombination velocity is analyzed by means of device simulations and experimental results     

Numerical and experimental study of the combustion of acetic acid in laminar premixed flames

Experimental mole fraction profiles of chemical species (stable, radical and intermediates) have been measured in three CH₃COOH/O₂/Ar flat premixed flames burning at low pressure (50 mbar) and with equivalence ratios equal to 0.77, 0.9 and 1.05, respectively. The experimental setup used to determine the structure of one-dimensional laminar premixed flames consists of a molecular beam mass spectrometer system (MBMS) combined with electron impact ionisation (EI). Experimental results have highlighted an important role played by ketene (CH₂CO) as an intermediate during the combustion of acetic acid. In order to simulate the experimental results, a sub-mechanism concerning the combustion of CH₃COOH and CH₂CO has been built and added to a global mechanism recently proposed. This ensures a reasonably good modelling for the structures of acetic acid flames.     

Fully-depleted SOI devices with TaSiN gate, HfO/sub 2/ gate dielectric, and elevated source/drain extensions

We report for the first time the performance of ultrathin film fully-depleted (FD) silicon-on-insulator (SOI) CMOS transistors using HfO/sub 2/ gate dielectric and TaSiN gate material. The transistors feature 100-150 /spl Aring/ silicon film thickness and selective epitaxial silicon growth in the source/drain extension regions. TaSiN-gate shows good threshold voltage control using an undoped channel, which reduces threshold voltage variation with silicon film thickness and discrete, random dopant placement. Device processing for CMOS fabrication is drastically simplified by the use of the same gate material for both n- and p-MOSFETs. Electrical characterization results illustrate the combined impact of using high-k dielectric and metal gate on the performance of ultrathin film FD SOI devices.     

Numerical and experimental study of ethanol combustion and oxidation in laminar premixed flames and in jet-stirred reactor

The main objectives of this research consist in achieving both experimental and numerical studies of the combustion and oxidation of ethanol. Experimental mole fraction profiles of chemical species (stable, radical, and intermediates) were measured in three C₂H₅OH/O₂/Ar flat premixed flames stabilized at low pressure (50 mbar) and with equivalence ratios equal to 0.75, 1, and 1.25, respectively. The experimental setup used to determine the structure of one-dimensional laminar premixed flames consists of a molecular beam mass spectrometer system (MBMS) combined with electron impact ionization (EI). The oxidation of ethanol was also experimentally studied using a fused silica jet-stirred reactor (JSR). Experiments were performed in the temperature range 890–1250 K, at 1 atm, at four equivalence ratios equal to 0.25, 0.5, 1, and 2 and with an initial fuel concentration of 2000 ppm.A kinetic study was conducted in order to simulate all experimental data measured. It enabled building a kinetic mechanism by thoroughly reviewing the available literature and by taking into account specificities of the two kinds of experiments performed. Validity of the mechanism was also checked against experimental results previously published (ethanol oxidation in a JSR at 10 atm, ignition in a shock tube, combustion in premixed, partially-premixed, and non-premixed flames). This mechanism ensures a reasonably good modelling of the combustion and oxidation of ethanol over the wide range of experimental conditions investigated.     

Traumatic rupture of the cervical trachea. Emergency diagnosis and treatment

The authors report 3 cases of traumatic rupture of the cervical trachea including one associated with total division of the oesophagus. They were impressed by the lack of precision and rapidity of the first surgical measures. They then give an account of the therapeutic gestures which are possible in a non-specialised unit.     

Experimental and modeling study of formaldehyde combustion in flames

The increased use of alcohols in internal combustion engines has driven the attention to formaldehyde emissions. Yet the experimental database on formaldehyde flames is limited. The experimental structures of two formaldehyde flames have been investigated at low pressure (30 mbar) using a molecular beam sampling coupled with a mass spectrometer. The initial compositions are for the lean flame (? = 0.22): 18% CH₂O and 82% O₂, and for the stoichiometric one (? = 1.09): 17.7% CH₂O, 16.3% O₂ and 66.0% Ar. A kinetic model, previously elaborated, has been improved by building a complete submechanism taking into account the formation and consumption of species involved in the formaldehyde combustion. The improved mechanism contains 107 chemical species and 568 reactions in order to simulate these two formaldehyde flames accurately. The reliability of this kinetic model has also been tested in ethanol and acetaldehyde flames. This allows the extension of its validity range.     

Modeling of ammonia combustion at low pressure

In the context of a hypothetic hydrogen based economy, ammonia has been suggested as a potential alternative to liquid fossil fuels for spark ignition (SI) engines. However, its use requires a detail understanding of its combustion characteristics, particularly the comprehension of the unavoidable thermal and fuel nitrogen oxides formation. This study presents the elaboration of an improved ammonia combustion mechanism validated for the flame structure prediction of ammonia, hydrogen, oxygen, argon flames investigated at several low pressures and for various conditions of equivalence ratio and of initial hydrogen content. The improved kinetic model is then reduced in order to be used in a complete SI engine numerical simulation. The comparison of the predictions of these mechanisms for the same ammonia flame structure is presented. The reduced mechanism contains 80 elementary reactions and 19 chemical species and allows a better understanding of the complete nitrogen oxides formation pathways.