Effect of temperature on high pressure cellulose compression

The effect of temperature during cellulose compression has been studied using mechanical testing, particle size analysis, density and pressure–volume–temperature (PVT) measurements, crystallinity index, scanning electron microscope photographs and water sorption isotherms. Commercial cellulose powder samples with different crystallinity levels were compacted at high pressure (177 MPa) for 10 min at two different temperatures: 25 and 160 °C. Three point bending test results for compressed samples are discussed. When pressure was applied directly to powders at room temperature, the cellulose sample with the highest level of crystallinity showed an increase in its crystallinity index of about 5 %, while this was about 22 % for the sample with the lowest level. These increases were even higher at 160 °C attaining 8 and 33 % respectively. Using density measurements, a densification phase related to this crystallinization was observed, and the PVT diagrams from different cellulose samples showed that this was associated with high temperatures. Water sorption isotherms were made on cellulose samples before and after compression. They showed a diminution of cellulose sorption capacity after compression at 160 °C, revealing the effect of temperature on high-pressure cellulose compression, reducing specific surface area. Events of this nature suggest a sintering mechanism, when temperature is associated with high pressure during cellulose compression.     

N-donor ligands based on bipyridine and ionic liquids: an efficient partnership to stabilize rhodium colloids. Focus on oxygen-containing compounds hydrogenation

Polynitrogen ligands and/in ionic liquids (ILs) are described as a pertinent tandem to efficiently stabilize rhodium nanoparticles (NPs) in the size range of 2.0 nm for catalytic applications. Several N-donor ligands based on bipyridine skeleton were used as extra protective agents in [BMI][PF(6)] and compared in the hydrogenation of functionalized aromatic compounds at 80 °C and under 40 bar H(2). The nature of the bipyridine derivative and its influence on the coordination mode on the particle surface were proposed to explain the observed different kinetic properties. The hydrogenation of various oxygen-containing arenes was investigated and original results were described in the reduction of anisole and cresols as model lignin compounds, providing a significant ratio of ketone derivatives. A first explanation based on possible reaction routes is proposed to justify the formed products.     

Targeted energy transfer with parallel nonlinear energy sinks. Part I: Design theory and numerical results

In this paper, we study a Targeted Energy Transfer (TET) problem between a p degrees-of-freedom (dof) linear master structure and several coupled parallel slave Nonlinear Energy Sink (NES) systems. In detail, each lth dof l=1,2,…,p contains n _l parallel NES; so the linear structure has (n ₁+n ₂+⋅⋅⋅+n _l +⋅⋅⋅+n _p ) NES. We are interested to study analytically the TET phenomenon during the first mode of the compound system. To this end, complexification, averaging, and multiple scales methods are used.     

Synthesis of a sialic acid alpha(2-3) galactose building block and its use in a linear synthesis of sialyl Lewis X

[reaction: see text] The ubiquity of the sialic acid alpha(2-3) galactose linkage in oligosaccharides of biological relevance necessitates a building block for the incorporation of this motif into oligosaccharides prepared by modular synthesis. The linear synthesis of the sialyl Lewis X tumor-associated antigen (1) has been accomplished in good yield using a sialic acid alpha(2-3) galactose disaccharide building block. The disaccharide building block was synthesized efficiently from readily available galactal by a high-yielding and selective sialylation reaction.     

A biomechanical inactivation principle

This paper develops the mathematical side of a theory of inactivations in human biomechanics. This theory has been validated by practical experiments, including zero-gravity experiments. The theory mostly relies on Pontryagin’s maximum principle on the one side and on transversality theory on the other side. It turns out that the periods of silence in the activation of muscles that are observed in practice during the motions of the arm can appear only if “something like the energy expenditure” is minimized. Conversely, minimization of a criterion taking into account the “energy expenditure” guaranties the presence of these periods of silence, for sufficiently short movements.     

Stark broadening of Hα and Hβ in ionized gases with space-charge field

In ionized gases created by prebreakdown discharges, the heat transfer from electrons to heavy particles is weak since it is often governed by electron-neutral collisions. Thermal ionization does not take place and the conductivity can be small enough to allow space-charge fields to appear. Under these conditions, the low frequency component of the field, which acts on the radiating hydrogen atom, is due to the vector sum of the ionic microfield and the space-charge field. Thus, a spatial anisotropy of the low frequency distribution of the field appears, which is derived in this paper and introduced in the general expressions of hydrogen-line broadening. It is shown that the emitted profile varies spatially and that the value of the space-charge field can be deduced from the difference of broadening between the light emitted perpendicular and parallel to this field. Calculations for H_α and H_β are given within the range of validity of the expressions used.     

Individual particle handling in a microfluidic system based on parallel laser trapping

We present an optical trapping system combining individually addressable multiple laser traps with fluorescence spectroscopy. An in-line set of 64 near-IR laser diodes is used to create a line of individually addressable traps inside a microfluidic chip. This system is completed by an excitation/detection line for spectrally resolved fluorescence imaging of trapped particles. Highly parallel trapping in a constant flow (up to a few millimeters per second), fast particle handling rates (up to a few particles per second), and the possibility of recording fluorescence spectra of trapped objects lead to a performing bioanalytical platform, e.g., for highly parallel analysis and sorting.     

Bi(OTf)3-catalyzed cycloisomerization of aryl-allenes

Intramolecular hydroarylation of allenes was achieved under very mild conditions using bismuth(III) triflate as the catalyst. Efficient functionalization of activated and nonactivated aromatic nuclei led to C-C bond formation through a formal Ar-H activation. A tandem bis-hydroarylation of the allene moiety was also developed giving access to various interesting polycyclic structures.