Simultaneous fabrication of superhydrophobic and superhydrophilic polyimide surfaces with low hysteresis

Polyimide is of great interest in the field of MEMS and microtechnology. It is often used for its chemical, thermal, mechanical, and optical properties. In this paper, an original study is performed on controlled variation of polyimide film wettability. A two-step microtexturing method is developed to transform hydrophilic polyimide surfaces into a superhydrophobic surface with low magnitude of hysteresis (Δθ ≈ 0° and contact angle θ ≈ 158°). This method is based on the conception of a new kind of fakir surface with triangular cross-section micropillars, the use of a two-scale roughening, and a C(4)F(8) coating. We demonstrate that the absence of hysteresis is related to a combination of two scales of structuring and the pillar shape. The technology that has been developed results in the simultaneous fabrication of adjacent superhydrophobic and superhydrophilic small areas, which allows an effect of self-positioning of water droplets when deposited on such a checkerboard-like surface.     

The discovery and validation of colorectal cancer biomarkers

Colorectal cancer is currently the third most common malignancy in the world. Patients have excellent prognosis following surgical resection if their tumour is still localized at diagnosis. By contrast, once the tumour has started to metastasize, prognosis is much poorer. Accurate early detection can therefore significantly reduce the mortality from this disease. However, current tests either lack the required sensitivity and selectivity or are costly and invasive. Improved biomarkers, or panels of biomarkers, are therefore urgently required. We have addressed current screening strategies and potential protein biomarkers that have been proposed. The role of both discovery and hypothesis-driven proteomics approaches for biomarker discovery and validation is discussed. Using such approaches we show how multiple reaction monitoring (MRM) can be successfully developed and used for quantitative multiplexed analysis of potential faecal biomarkers.     

Pickering Interfacial Catalysis for Biphasic Systems: From Emulsion Design to Green Reactions

Pickering emulsions are surfactant‐free dispersions of two immiscible fluids that are kinetically stabilized by colloidal particles. For ecological reasons, these systems have undergone a resurgence of interest to mitigate the use of synthetic surfactants and solvents. Moreover, the use of colloidal particles as stabilizers provides emulsions with original properties compared to surfactant‐stabilized emulsions, microemulsions, and micellar systems. Despite these specific advantages, the application of Pickering emulsions to catalysis has been rarely explored. This Minireview describes very recent examples of hybrid and composite amphiphilic materials for the design of interfacial catalysts in Pickering emulsions with special emphasis on their assets and challenges for industrially relevant biphasic reactions in fine chemistry, biofuel upgrading, and depollution.     

Bestimmung von Metallen in organischen Verbindungen

Ohne Zusammenfassung     

Mass spectra of liquid crystals. III—phenylpyrimidine derivatives

The 70 eV electron impact mass spectra of 34 1-phenyl-2,5-pyrimidine derivatives are presented. Based on the observed mass shifts by the various substituents, the nature of the main fragment ions is rationalized.     

On the structural changes induced by hydrogenation in polyenic schiff bases

Ab initio theoretical investigations, at the STO-3G level, of the free and protonated 1-imino-deca-2,4,6,8-tetraenes and some of the dihydroderivatives are reported. It is shown that the saturation of the CC bonds leads to drastic modifications of the ground-state potential-energy hypersurface.     

Etude des melanges d'antipodes optiques—XII: Mesure de la stabilite des racemiques vrais

The stability of true racemates is defined by the free energy change ΔG^φ of the process D-crystal + L-crystal → DL-crystal. ΔG^φ, varying in the range 0 to ?2 kcal mol^?1, is roughly proportional to the difference in melting points between racemate and antipodes, T_R^f ? T_A^f. In most of the examples studied, the formation of racemates is exothermic. The study of the variation of ΔG^φ with temperature explains the occurrence of crystalline transitions between racemate and conglomerate. Few racemates can give rise to such transitions, particularly when their enthalpies and entropies of formation, ΔH^φ and ΔS^φ, are both positive.     

The photochemical step of vision: The hydrogen bond and other associations

It is shown on the basis of quantum chemical and spectroscopic arguments that through a consideration of the hydrogen bond and other intermolecular associations affecting the Schiff-base of retinal in the ground and excited states a new assessment can be made of the conditions related to the photochemical primary step of vision.