The subelliptic heat kernel on the CR sphere

We study the heat kernel of the sub-Laplacian $L$ on the CR sphere $\mathbb{S }^{2n+1}$ . An explicit and geometrically meaningful formula for the heat kernel is obtained. As a by-product we recover in a simple way the Green function of the conformal sub-Laplacian $-L+n^2$ that was obtained by Geller (J Differ Geom 15:417–435, 1980), and also get an explicit formula for the sub-Riemannian distance. The key point is to work in a set of coordinates that reflects the symmetries coming from the fibration $\mathbb{S }^{2n+1} \rightarrow \mathbb{CP }^n$ .     

Absolute radiance imaging using parametric image amplification

We show that parametric image amplification can be used to achieve a 2D radiance map directly expressed in photons per spatiotemporal mode. Radiance images of incoherent signals with less than one photon per mode (typically 10(-2)) are resolved.     

Simultaneous imaging of multiple focal planes using a two-photon scanning microscope

Despite all the advances in nonlinear microscopy, all existing instruments are constrained to obtain images of one focal plane at a time. In this Letter we demonstrate a two-photon absorption fluorescence scanning microscope capable of imaging two focal planes simultaneously. This is accomplished by temporally demultiplexing the signal coming from two focal volumes at different sample depths. The scheme can be extended to three or more focal planes.     

Critical angle refractometry and sizing of bubble clouds

The principle of the critical angle refractometry and sizing technique is extended to characterize the size distribution and the mean refractive index of clouds of bubbles. For a log-normal bubble-size distribution, simulations show that the mean size, the relative width of the size distribution, and the mean refractive index of the bubbles have a particular and easily identified influence on the critical scattering patterns. Preliminary experimental results on air bubble/water flows clearly demonstrate the potential and robustness of this new technique for bubbly flow characterization.     

3-(4-Carboxybenzoyl)quinoline-2-carboxaldehyde labeling for direct analysis of amino acids in plasma is not suitable for simultaneous quantification of tryptophan,tyrosine, valine,and isoleucine by CE/fluorescence

Capillary electrophoresis coupled to LED-induced fluorescence detection is a robust and sensitive technique used for amino acids (AA) analysis in biological media, after labeling with 3-(4-carboxybenzoyl)quinoline-2-carboxaldehyde (CBQCA). We wanted to quantitate in plasma tryptophan (Trp), tyrosine (Tyr), valine (Val), and isoleucine (Ile). Among the different labeled AA-CBQCA, Trp has the lowest fluorescence yield, which makes its detection and quantification very difficult in biological samples such as plasma. We tried to improve Trp analysis by CE/LED-induced fluorescence detection to its maximal sensitivity by using large volume sample stacking as a preconcentration step in our analytical protocol. At pH 9.5, this step caused a drop in resolution during the separation of the four AAs and it was therefore necessary to work at pH 10. We have found that Tyr, Val, Ile, and Trp are detected and well separated from the other AAs, but Trp cannot be quantified in plasma samples, mainly because of the low fluorescence yield of the Trp-CBQCA derivative. The recorded LOD is 0.18 μM for Trp-CBQCA in standard solution with a resolution between Trp and Tyr of 1.2, while the LOD is 6 μM in plasma with the same resolution. Trp, Tyr, Val, and Ile are, however, efficiently quantified when using a 3 M acetic acid electrolyte and CE associated with capacitively coupled contactless conductivity detection, which also has the advantage of not requiring derivatization or large volume sample stacking. This article demonstrates, for the CE user, that quantitative analysis of these four AA in mouse plasma can be performed by CE-fluorescence after CBQCA labeling, with the exception of Trp. It can be advantageously replaced by CE/capacitively coupled contactless conductivity detection, the only efficient one for Trp, Tyr, Val, and Ile quantification. In this case, the LOD for Trp is 2 μM. The four AAs are separated with resolution with neighbors above 1.5.     

Practical stereoselective synthesis of an alpha-trifluoromethyl-alpha-alkyl epoxide via a diastereoselective trifluoromethylation reaction

A practical stereoselective synthesis is reported for an alpha-trifluoromethyl-alpha-alkyl epoxide (1), which is an important pharmaceutical intermediate. The key step involves a chiral auxiliary-controlled asymmetric trifluoromethylation reaction for the introduction of the unique trifluoromethyl-substituted tertiary alcohol stereogenic center in the target molecule. The fluoride-initiated CF3 addition to chiral keto ester 6a proceeded with a diastereoselectivity up to 86:14. The major diastereomer was readily obtained with a >99.5:0.5 dr through a simple crystallization of the crude product mixture.     

A versatile electronic hole in one-electron oxidized NiIIbis-salicylidene phenylenediamine complexes

The nickel complexes 1(+)-3(+) exhibit a delocalized radical character, the extent of which depends on the electronic properties of the phenolate para-substituent.     

Very large acceleration of the photoinduced electron transfer in a Ru(bpy)3-naphthalene bisimide dyad bridged on the naphthyl core

By linking a naphthalenebisimide (NBI) unit to [Ru(bpy)3]2+ on the naphthyl core the rate of photoinduced Ru-to-NBI electron transfer was 1000-fold increased compared to the case with a conventional linking on the nitrogen.     

Development and validation of a multi-residue method for the detection of a wide range of hormonal anabolic compounds in hair using gas chromatography-tandem mass spectrometry

The monitoring of anabolic steroid residues in hair is undoubtedly one of the most efficient strategies to demonstrate the long-term administration of these molecules in meat production animals. A multi-residue sample preparation procedure was developed and validated for 28 steroids. A 100 mg hair sample was grinded into powder and extracted at 50 degrees C with methanol. After acidic hydrolysis and extraction with ethyl acetate, phenolsteroids, such as estrogens, resorcyclic acid lactones and stilbens in one hand, are separated from androgens and progestagens in the other hand. Solid phase extractions were performed before applying a specific derivatisation for each compound sub-group. Detection and identification were achieved using gas chromatography-tandem mass spectrometry with acquisition in the selected reaction monitoring mode after electron ionisation. The method was validated according to the 2002/657/EC guideline. Decision limits (CCalpha) for main steroids were in the 0.1-10 microg kg(-1) range.     

Surface energy of talc and chlorite: Comparison between electronegativity calculation and immersion results

The surface energies of talc and chlorite is computed using a simple model, which uses the calculation of the electrostatic energy of the crystal. It is necessary to calculate the atomic charges. We have chosen to follow Henry's model of determination of partial charges using scales of electronegativity and hardness. The results are in correct agreement with a determination of the surface energy obtained from an analysis of the heat of immersion data. Both results indicate that the surface energy of talc is lower than the surface energy of chlorite, in agreement with observed behavior of wettability. The influence of Al and Fe on this phenomenon is discussed. Surface energy of this type of solids seems to depend more strongly on the geometry of the crystal than on the type of atoms pointing out of the surface; i.e., the surface energy depends more on the physics of the system than on its chemistry.