Dissociation of biomolecules using a ultraviolet matrix-assisted laser desorption/ionisation time-of-flight/curved field reflectron tandem mass spectrometer equipped with a differential-pumped collision cell

A commercial matrix-assisted laser desorption/ionisation time-of-flight (MALDI-ToF) instrument equipped with a curved field reflectron (CFR) was modified in order to perform collision-induced dissociation (CID) on a variety of biomolecules. The incorporation of a high-resolution ion gate together with a collision cell within the field-free region allowed tandem mass analysis (MS/MS), without the necessity to decelerate the precursor ions prior to activation. The simultaneous detection of all product ions remained possible by using the CFR. To test the MS/MS performances, ACTH (fragment 1-17), a complex high mannose carbohydrate (Man)(8)(GlcNac)(2) and a lysophosphatidylcholine lipid (18:1) were analysed on the modified instrument. Direct comparison with the low-energy product ion spectra, acquired on a MALDI quadrupole ion trap (QIT) two-stage reflectron time-of flight (ReToF) mass spectrometer, showed significant differences in the types of product ions observed. The additional ions detected were a clear indication of the high-energy fragmentation processes occurring in the collision cell.     

Surface esterification of cellulose fibers: characterization by DRIFT and contact angle measurements

The surface chemical modification of microcrystalline cellulose and cellulose fibers obtained from different sugar cane bagasse pulping processes, viz. Kraft, organosolv ethanol/water and organosolv/supercritical carbon dioxide, were studied in heterogeneous conditions using modest amounts of octadecanoyl and dodecanoyl chloride. The ensuing surfaces acquired a non-polar character, suitable for incorporating these fibers as reinforcing agents in composite materials based on polymeric matrices. The success of these chemical modifications was assessed by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, elemental analysis, scanning electron microscopy (SEM) and contact angle measurements. In particular, the dynamic and equilibrium contact angle measurements, before and after the treatments, revealed that the value of the polar component (gamma(s)p) of the surface energy had decreased very considerably following the modification.     

Fabrication and Packaging Technologies of Love-wave-based Microbalance for Fluid Analysis

Quartz crystal microbalance (QCM) based techniques have been developed for years to address various kinds of biochemical analyses in liquid media. An alternative to this approach based on guided acoustic shear waves, the socalled Love wave devices, has been proved to allow for increasing gravimetric sensitivity. However, this approach reveals more complicated to implement as the surface on which reactions are achieved is the same as the one used for electrical connection. As a consequence, a microfluidic set-up must be implemented to prevent unwanted interactions between the corresponding areas (IDTs and propagation path). The main issue when using SAW Sensors for in-liquid biochemical analyses [1-4], especially in a commercial objective, is the development of a reliable and reproducible fluidic system [5] meeting the main following requirements: i) low acoustic leakage. ii) chemically inert to biological samples. iii) reproducible fabrication at the wafer scale level.In the present work we explore the use of the SU-8 epoxy-based photoresist combined with silicon or quartz machined covers for the fabrication of this fluidic circuit. A first structure is fabricated using deep etch lithography, the cover is then glued to the remaining SU-8 structure using a thin glue layer. The packaging system prevents covering the IDTs with liquids and defines the sensing area in the region in-between the IDTs. Once the fabrication achieved, we evaluate the velocity and propagation loss using a network analyzer to measure the influence of the proposed packaging approaches on the principal wave characteristics.     

Active vibration control on a quarter-car for cancellation of road noise disturbance

In this paper, a methodology is presented for the cancellation of road noise, from the analysis of vibration transmission paths for an automotive suspension to the design of an active control system using inertial actuators on a suspension to reduce the vibrations transmitted to the chassis. First, experiments were conducted on a Chevrolet Epica LS automobile on a concrete test track to measure accelerations induced on the suspension by the road. These measurements were combined with experimental Frequency Response Functions (FRFs) measured on a quarter-car test bench to reconstruct an equivalent three dimensional force applied on the wheel hub. Second, FRFs measured on the test bench between the three-dimensional driving force and forces at each suspension/chassis linkage were used to characterize the different transmission paths of vibration energy to the chassis. Third, an experimental model of the suspension was constructed to simulate the configuration of the active control system, using the primary (disturbance) FRFs and secondary (control) FRFs also measured on the test bench. This model was used to optimize the configuration of the control actuators and to evaluate the required forces. Finally, a prototype of an active suspension was implemented and measurements were performed in order to assess the performance of the control approach. A 4.6 dB attenuation on transmitted forces was obtained in the 50–250 Hz range.     

Coulombic quantum liquids in spin-1/2 pyrochlores

We develop a nonperturbative gauge mean field theory (gMFT) method to study a general effective spin-1/2 model for magnetism in rare earth pyrochlores. gMFT is based on a novel exact slave-particle formulation, and matches both the perturbative regime near the classical spin ice limit and the semiclassical approximation far from it. We show that the full phase diagram contains two exotic phases: a quantum spin liquid and a Coulombic ferromagnet, both of which support deconfined spinon excitations and emergent quantum electrodynamics. Phenomenological properties of these phases are discussed.     

Modified Cellulose Fibers as Reinforcing Fillers for Macromolecular Matrices

Various cellulose substrates were submitted to different surface OH chemical modifications in non-swelling media and then fully characterised by FTIR, XPS, contact angle measurements and elemental analysis. The alternative procedures adopted were: (i) simple grafting with monomeric or oligomeric agents which bore one or several reactive functions, either as a single terminal moiety or as numerous moieties placed along the chain; (ii) grafting with polymerisable molecules, which involved the use of reagents of small molecular size, but bearing two functions, one able of reacting with the surface cellulose OH groups and the other used as a source of subsequent covalent linkage with the matrix; (iii) the use of planar stiff molecular configurations bearing two identical reactive functions, calling upon the working hypothesis that only one function will react with a cellulose OH group, whereas the other will be left to copolymerise with the matrix; (iv) coupling with siloxanes using the same strategy as in (ii), except for the fact that this specific approach involves molecules already commonly used in glass fibres treatment; (v) grafting with organometallics such as triethyl aluminium following the same working hypothesis as in (iii) but with a second reaction involving monomeric or polymeric alcohols or amines.     

The acid-catalyzed polycondensation of furfuryl alcohol: Old puzzles unravelled

This paper describes mechanistic studies aimed at understanding the origin of two important side events accompanying the linear polycondensation of furfuryl alcohol in acidic media. The first process concerns the formation of conjugated sequences along the polymeric chains. The use of model monomers and compounds simulating the structure of the linear polymer provided for the first time a full understanding of the reactions leading to multiple unsaturations. The main culprits for this process are the labile hydrogen atoms on the methylene moiteties bridging the furan rings. The second anomaly in these systems concerns the formation of networks following a complex branching mechanism. Again, model structures helped to pinpoint the origin of this process and to propose plausible reactions to describe it.     

Activation of N−O σ Bonds with Transition Metals: A Versatile Platform for Organic Synthesis and C−N Bonds Formation**

N−O σ bonds containing compounds are versatile substrates for organic synthesis under transition metal catalysis. Their ability to react through both polar (oxidative addition, formation of metallanitrene, nucleophilic substitution) and radical pathways (single electron transfer, homolytic bond scission) have triggered the development of various synthetic methodologies, particularly toward synthesizing nitrogen-containing compounds. In this review, we discuss the different modes of activation of N−O bonds in the presence of transition metal catalysts, emphasizing the experimental and computational mechanistic proofs in the literature to help to design new synthetic pathways toward the synthesis of C−N bonds.