Thin layers deposited from V2O5 gels: II. An optical absorption study

Absorption spectra of V₂O₅ layers deposited from gels of various V⁴⁺ contents C were studied from near UV down to near IR. The high absorption region due to the charge transfer transition extends above ≈ 2 eV. Whatever C the optical gap is ≈ 2.25 eV. On the low energy side an Urbach tail is observed whose slope increases with C. In the near infrared absorption is related to the V⁴⁺ ions and increases linearly with C. The absorption band due to the optically induced polaron hopping is detected. The corresponding maximum E_max suffers a red shift when C increases. The experimental E_max data are very close to the values predicted from the polaron and disorder energies as deduced from the conductivity study in an earlier paper. The slight difference between the two sets of data allowed us to estimate the transfer integral J ≈ 0.015 eV.     

Computerized MRS voxel registration and partial volume effects in single voxel H-MRS

Partial volume effects in proton magnetic resonance spectroscopy in the brain have been studied previously in terms of proper water concentration calculations, but there is a lack of disclosure in terms of voxel placement techniques that would affect the calculations. The purpose of this study is to facilitate a fully automated MRS voxel registration method which is time efficient, accurate, and can be extended to all imaging modalities. A total of thirteen healthy adults underwent single voxel 1H-MRS scans in 3.0 T MRI scanners. Transposition of a MRS voxel onto an anatomical scan is derived along with a full calculation of water concentration with a correction term to account for the partial volume effects. Five metabolites (tNAA, Glx, tCr, mI, and tCho) known to yield high reliability are studied. Pearson’s correlation analyses between tissue volume fractions and metabolite concentrations were statistically significant in parietal (tCr, Glx, and tNAA) lobe and occipital lobe (tNAA). MRS voxel overlaps quantified by dice metric over repeated visits yielded 60% ~ 70% and coefficients of variance in metabolites concentration were 4% ~ 10%. These findings reiterate an importance of considering the partial volume effects when tissue water is used as an internal concentration reference so as to avoid misinterpreting a morphometric difference as a metabolic difference.     

Micro-raman at very high pressure and variable temperature

Abstract

We have designed a mechanical coupling between a spectrometer and a cryostat which allows the use of a microoptical system placed at the entrance of the spectrometer. Micro-Raman investigations are performed with a membrane diamond anvil cell placed inside the cryostat. The capability of this setup is illustrated with results obtained on benzene at 10 K up to 33 GPa.     

Liposomal Templating,Association with Mammalian Cells,and Cytotoxicity of Poly(vinyl alcohol) Physical Hydrogel Nanoparticles

The assembly, cellular internalization, and cytotoxicity of nanoparticles based on physical hydrogels of poly(vinyl alcohol) (PVA) are reported. PVA nanoparticles are assembled using a liposomal templating technique followed by removal of the lipids using isopropanol, a process that requires the presence of a custom‐made block copolymer, poly(vinyl alcohol‐b‐vinyl pyrrolidone), to avoid aggregation of the nanoparticles. Polymer hydrogelation is induced via incubation in aqueous isopropyl alcohol solution, which results in PVA hydrogel nanoparticles (PVA HNP) with excellent colloidal stability and stability towards disintegration over at least 24 h. Pristine PVA HNP are found to be remarkably stealth‐like and exhibit negligible cellular internalization. This feature is likely inherent with the low fouling nature of PVA and makes PVA HNP attractive for targeted drug delivery with a low level of association with non‐targeted cells and tissues. Blending PVA with varied amounts of collagen results in colloidal hydrogel particles with a well pronounced tendency towards association with mammalian cells, specifically hepatocytes and endothelial cells. The association of PVA HNP elicits minimal changes in cellular proliferation, making these novel hydrogel particles convenient tools for drug delivery applications and creation of implantable artificial organelles and sensors.     

Realization of Virasoro unitarizing measures on the set of Jordan curves

Two univalent functions are equivalent, f～g, if they have the same Schwarzian derivative. The equivalence relation ～ being defined up to an homographic transformation, it gives an isomorphism between the manifold $\text{J}$ of Jordan curves and the quotient manifold $\text{S}$. It permits to obtain vector fields on $\text{S}$ and on $\text{J}$. The action of these vector fields on the Neretin polynomials is explicited. The existence of a unitarizing measure on the quotient manifold $\text{S}$ is discussed and for such a measure, orthogonality relations for the Neretin polynomials are obtained. This work is a concrete realization on the complex space $\text{C}{}^{\mathrm{\infty }}$ of the abstract quotient $\text{Diff}\text{(S}{}^1\text{)/}\text{SL}\text{(2,}\text{R}\text{)}$ considered in Airault et al., C. R. Acad. Sci. Paris, Ser. I 335 (2002) 621–626. To cite this article: H. Airault, V. Bogachev, C. R. Acad. Sci. Paris, Ser. I 336 (2003).     

Chemical characterization of gallium droplets grown by LP-MOCVD

This study is concerned with the chemical characterization of metallic gallium droplets, obtained on silicon (1 0 0) substrates with a single growth step, by the LP-MOCVD technique with TMGa like precursor. These structures are characterized by SIMS, XPS and TEM. The analyses results lead to a structure proposition for the droplets. The core is composed of metastable metallic gallium with a non-negligible carbon quantity probably coming from incomplete precursor decomposition. The outer part, composed of gallium oxide maintains the structure stability. Covering of the substrate by a thin gallium layer of gallium compounds is observed.     

An enantiopure diselenide based on a chiral bicyclic backbone—synthesis and configuration assignment

An enantiomerically pure diselenide containing two chiral bicyclic subunits was prepared from the respective halides. The stereochemical outcome of the reaction was established via NMR spectroscopy and X-ray diffraction measurements.     

Targeted Ultrasound‐Assisted Cancer‐Selective Chemical Labeling and Subsequent Cancer Imaging using Click Chemistry

Metabolic sugar labeling followed by the use of reagent‐free click chemistry is an established technique for in vitro cell targeting. However, selective metabolic labeling of the target tissues in vivo remains a challenge to overcome, which has prohibited the use of this technique for targeted in vivo applications. Herein, we report the use of targeted ultrasound pulses to induce the release of tetraacetyl N‐azidoacetylmannosamine (Ac₄ManAz) from microbubbles (MBs) and its metabolic expression in the cancer area. Ac₄ManAz‐loaded MBs showed great stability under physiological conditions, but rapidly collapsed in the presence of tumor‐localized ultrasound pulses. The released Ac₄ManAz from MBs was able to label 4T1 tumor cells with azido groups and significantly improved the tumor accumulation of dibenzocyclooctyne (DBCO)‐Cy5 by subsequent click chemistry. We demonstrated for the first time that Ac₄ManAz‐loaded MBs coupled with the use of targeted ultrasound could be a simple but powerful tool for in vivo cancer‐selective labeling and targeted cancer therapies.     

Characterization of durum wheat high molecular weight glutenin subunits Bx20 and By20 sequences by a molecular and proteomic approach

Wheat high molecular weight glutenin subunit variation is important because of its great influence on glutenin polymer structure, that is related to dough technological properties. Among the different subunits, the pair Bx20 and By20 is known to have a negative effect on quality, but the reasons are not clear: Bx20 has two cysteines, which theoretically make this subunit a chain extender of the glutenin polymer, just like the other Bx subunits, showing four cysteines, two of which should be involved in intra‐molecular disulfide bonds. By20 has never been characterized so far at molecular level. Here we report the nucleotide sequences of Bx20 and By20 genes isolated from the durum wheat cultivar ‘Lira 45’ and the validation of the corresponding deduced amino acid sequences by using MALDI‐TOF and LC‐MS/MS. Four nucleotide differences were identified in the Bx20 gene with respect to the deduced sequence present in NCBI, causing two amino acid substitutions. For the By20 subunit, nucleotide and amino acid sequences revealed a great similarity to By15, both at gene and protein levels, showing five nucleotide changes generating two amino acid differences. No evidence of post‐translational modifications has been found. Hypotheses are formulated in regard to relationships with technological quality. Copyright © 2016 John Wiley & Sons, Ltd.     

Particle motions in non-Newtonian media

Summary An experimental study of the behaviour of rigid and deformable particles suspended in pseudoplastic and elasticoviscous liquids undergoing slowCouette flow was undertaken. The velocity profiles deviated slightly from those obtained forNewtonian fluids, but the measured angular velocities of rigid spheres showed that the rotation of the field was equal to half the velocity gradient. While the measured angular velocities of rods and discs were in accord with theory applicable toNewtonian liquids, in both non-Newtonian media there was a steady drift in the orbit towards an asymptotic value corresponding to minimum energy dissipation in the flow. Furthermore, discs in elasticoviscous solutions of polyacrylamide at higher shear stresses aligned themselves in the direction of the flow and ceased to rotate.Migration of rigid particles across the planes of shear in the annul us of theCouette was also observed. In pseudoplastic liquids, the migration was towards the region of higher shear, whereas the opposite was true in elasticoviscous liquids.The deformation, orientation and burst of pseudoplastic drops inNewtonian liquids and that ofNewtonian drops in pseudoplastic fluids were similar to those previously in completelyNewtonian systems. With elasticoviscous drops, however, the deformation was smaller than given by theory.As in elasticoviscous fluids, two-body collisions of rigid uniform spheres in the pseudoplastic liquids were unsymmetrical and irreversible, thus differing from collisions inNewtonian systems where complete reversibility is observed.While some of the observed phenomena in elasticoviscous suspensions could be qualitatively interpreted, particle behaviour in the pseudoplastic liquids could not be explained in terms of the known rheological properties of the fluids.

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Zusammenfassung Es wurde experimentell das Verhalten von festen und deformierbaren Teilchen untersucht, die bei der Suspension in strukturviskosen und viskoelastischen Flüssigkeiten einer langsamenCouette-Strömung ausgesetzt sind. Die Geschwindigkeitsprofile zeigten gewisse Abweichungen von denenNewtonscher Flüssigkeiten, aber die gemessenen Winkelgeschwindigkeiten der festen Kügelchen ergaben, daß die Drehung des Feldes gleich dem halben Geschwindigkeitsgradienten war. Die gemessenen Winkelgeschwindigkeiten der Stäbchen und Scheiben stimmten mit der Theorie, die auf Newtonsche Flüssigkeiten zutrifft, überein. In beiden nicht-Newtonschen Flüssigkeiten verschob sich jedoch die Kreisbahn stetig zu einem asymptotischen Wert, der einem Minimum der Dissipationsenergie der Strömung entsprach. Scheibchen in viskoelastischen Lösungen von Polyacrylamid richteten sich bei höherer Scherspannung in Strömungsrichtung aus und zeigten keine Drehung mehr.Es wurden auch Wanderungen von festen Teilchen über die Scherebene im Spalt derCouette-Anordnung beobachtet. In strukturviskosen Flüssigkeiten erfolgte die Wanderung in Richtung der höheren Scherung, während auf elastische Flüssigkeiten das Gegenteil zutraf.Die Deformation, Orientierung und das Aufbrechen strukturviskoser Tröpfchen inNewtonschen Flüssigkeiten und das Verhalten von Newtonschen Tröpfchen in strukturviskosen Flüssigkeiten waren den früher in rein-Newtonschen Systemen beobachteten Phänomenen ähnlich. Die Deformation der viskoelastischen Tröpfchen war jedoch kleiner als die von der Theorie vorhergesagt worden war.Zweikörper-Zusammenstöße zwischen festen gleichförmigen Kügelchen in strukturviskosen Flüssigkeiten waren unsymmetritch und irreversibel. Darin unterschieden sie sich von Zusammenstößen inNewtonschen Flüssigkeiten, in denen völlige Umkehrbarkeit beobachtet worden war.Während einige der beobachteten Phänomene in viskoelastischen Suspensionen qualitativ gedeutet werden konnten, ließ sich das Teilchenverhalten in strukturviskosen Flüssigkeiten nicht anhand der bekannten Theologischen Eigenschaften der Flüssigkeiten erklären.

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This work was supported by the Defence Research Board of Canada (DRB Grant 9530-47).