Experimental and numerical study of a modified ASTM C633 adhesion test for strongly-bonded coatings

When coatings are strongly bonded to their substrates it is often difficult to measure the adhesion values. The proposed method, which is suggested naming “silver print test”, consists in covering the central part of the samples with a thin layer of silver paint, before coating. The process used for testing this new method was the Air plasma spraying (APS), and the materials used were alumina coatings on C35 steel substrates, previously pre-oxidized in CO₂. The silver painted area was composed of small grains that did not oxidize but that significantly sintered during the APS process. The silver layer reduced the surface where the coating was linked to the substrate, which allowed its debonding, using the classical adhesion test ASTM C633-13, while the direct use of this test (without silver painting) led to ruptures inside the glue used in this test. The numerical modelling, based on the finite element method with the ABAQUS software, provided results in good agreement with the experimental measurements. This concordance validated the used method and allowed accessing to the values of adherence when the experimental test ASTM C633-13 failed, because of ruptures in the glue. After standardization, the “silver print test” might be used for other kinds of deposition methods, such as PVD, CVD, PECVD.     

A Mixed Ligand Approach for the Asymmetric Hydrogenation of 2‐Substituted Pyridinium Salts

Herein we describe a new methodology for the asymmetric hydrogenation (AH) of 2‐substituted pyridinium salts. An iridium catalyst based on a mixture of a chiral monodentate phosphoramidite and an achiral phosphine was shown to hydrogenate N‐benzyl‐2‐arylpyiridinium bromides to the corresponding N‐benzyl‐2‐arylpiperidines with full conversion and good enantioselectivity. The mechanism of the reaction under optimized conditions was investigated via kinetic measurements and isotopic labeling experiments. Our study suggests that the hydrogenation starts with a 1,4‐hydride addition and that the enantiodiscriminating step involves the reduction of an iminium intermediate.

     

High throughput screening of Monophos instant ligand library leads to a ton-scale asymmetric hydrogenation process

The development of catalytic processes for pharmaceuticals intermediates is often under severe time-pressure. To cope with this constraint, high throughput experimentation (HTE) methods have been implemented for catalyst finding. In this article, we present the HTE protocols put in place at DSM in the area of enantioselective hydrogenation. They mostly rely on libraries of monodentate chiral phosphoramidites ligands. We applied our instant ligand library technology to solve a real-life case, i.e. the asymmetric hydrogenation of an α-substituted cinnamic acid derivative. This has led to a multi-ton scale process.     

Oligomerization of ethylene on platinum by a two-step reaction sequence

On Pt, substantial fractions of chemisorbed C₂h₄ can be converted to C₃₊ alkanes by subsequent hydrogenation. The absence of H₂ during chemisorption is considered as the main factor favoring C-C bonding between adsorbed species, whereas its further addition permits higher alkanes to be released.     

High-energy femtosecond pulses from an ytterbium-doped fiber laser with a new cavity design

A new architecture which is based on the chirped pulse amplification scheme is proposed to increase the pulse energy of the mode-locked fiber laser. The idea was applied to a passively mode-locked laser using an ytterbium (Yb/sup 3+/)-doped double-clad silica fiber. Mode-locking was achieved by nonlinear polarization evolution associated to frequency-shifted feedback technique for self-starting. A compressor and a stretcher, based on diffraction gratings, permitted us to manage the dispersion and to reduce the pulse power in the fiber. The laser delivered chirped pulses at 1050 nm with 11.8-nJ energy at a 9.3-MHz repetition rate (110-mW average power) which were subsequently compressed to 196-fs duration.     

Aneuploidy detection in human sperm nuclei using PRINS technique

Rapid and specific identification of chromosomes can be attained in situ using the PRimed IN Situ (PRINS) labelling technique. We have adapted this technique to mature human sperm in combination with a protocol for simultaneous decondensation and denaturation of sperm nuclei. This strategy allowed us to obtain double labelling of human spermatozoa in a < 2-hr reaction. In the present study, we report the estimates of disomy for chromosomes 3, 7, 10, 11, and 17 on 64,642 spermatozoa from 2 normal males. The incidences of disomy ranged from 0.28-0.34%. There were no significant interindividual or interchromosomal differences in disomy rates.     

Highly stable 68-fs pulse generation from a stretched-pulse Yb/sup 3+/-doped fiber laser with frequency shifted feedback

We report on the development of a passively mode-locked and highly-stable stretched pulse laser based on Yb/sup 3+/-doped silica fiber. Mode-locking is achieved by nonlinear polarization evolution coupled with the frequency-shifted feedback technique for ensuring robust self-starting. The Fabry-Perot (F-P) cavity incorporates also a diffraction grating pair to compensate for the normal dispersion of the fiber. The laser generates chirped pulses with energies of 100 pJ at a repetition rate of 23 MHz (2.3 mW average power) around 1055 nm which were subsequently compressed to near-bandwidth-limited pulses of 68 fs duration.