Attempted Oxidative Deamination of N-Deacetylcolchicinoids with 3,5-Di(tert-butyl)-1,2-benzoquinone: Synthesis of 2H-1,4-Benzoxazine-Type Adducts

In an attempt to use 3,5-di(tert-butyl)-1,2-benzoquinone for the oxidative deamination of N-deacetylcolchicine ( 4 ) and N-deacetylthiocolchicine (=N-deacetyl-10-demethoxy-10-(methylthio)colchicine; 5 ) to give the corresponding ketones 2 and 3 , the 2H-1,4-benzoxazine-type adducts 8 / 9 and 11 / 12 , respectively, were formed instead, showing a new and unexpected behavior of Corey's reagent. The adducts were separated and spectroscopically characterized, and a plausible scheme of formation is reported.     

Chiral Nano-Liquid Chromatography and Dispersive Liquid-Liquid Microextraction Applied to the Analysis of Antifungal Drugs in Milk

A novel chromatographic application in chiral separation by using the nano-LC technique is here reported. The chiral recognition of 12 antifungal drugs was obtained through a 75 µm I.D. fused-silica capillary, which was packed with a CSP-cellulose 3,5-dichlorophenylcarbamate (CDCPC), by means of a lab-made slurry packing procedure. The mobile phase composition and the experimental conditions were optimized in order to find the optimum chiral separation for some selected racemic mixtures of imidazole and triazole derivatives. Some important parameters, such as retention faction, enantioresolution, peak efficiency, and peak shape, were investigated as a function of the mobile phase (pH, water content, type and concentration of both the buffer and the organic modifier, and solvent dilution composition). Within one run lasting 25 min, at a flow rate of approximately 400 nL min⁻¹, eight couples of enantiomers were baseline-resolved and four of them were separated in less than 25 min. The method was then applied to milk samples, which were pretreated using a classical dispersive liquid–liquid microextraction technique preceded by protein precipitation. Finally, the DLLME-nano-LC–UV method was validated in a matrix following the main FDA guidelines for bioanalytical methods.     

Force constants of BN,SiC, AlN and GaN sheets through discrete homogenization

The force constants related to the bond stretching and angular variation of boron nitride, silicon carbide, aluminium nitride and gallium nitride nanosheets are directly evaluated from ab-initio reference solutions of the Young’s modulus and the Poisson’s ratio. To this end, the analytical expressions of the elastic constants of a generic monolayer hexagonal diatomic sheet are derived, starting from its sticks-and-springs molecular mechanics model, through proper tools of the homogenization of periodic discrete media. Numerical benchmark assessments are given.     

A numerical mapping of energy gains in a powered Swing-By maneuver

The present paper studies the effects of a powered Swing-By maneuver, considering the particular and important situations where there are energy gains for the spacecraft. The objective is to map the energy variations obtained from this maneuver as a function of the three parameters that identify the pure gravity Swing-By with a fixed mass ratio (angle of approach, periapsis distance and velocity at periapsis) and the three parameters that define the impulsive maneuver (direction, magnitude and the point where the impulse is applied). The mathematical model used here is the version of the restricted three-body problem that includes the Lemaître regularization, to increase the accuracy of the numerical integrations. It is developed and implemented by an algorithm that obtains the energy variation of the spacecraft with respect to the largest primary of the system in a maneuver where the impulse is applied inside the sphere of influence of the secondary body, during the passage of the spacecraft. The point of application of the impulse is a free parameter, as well as the direction of the impulse. The results make a complete map of the possibilities, including the maximum gains of energy, but also showing alternatives that can be used considering particularities of the mission.     

Study of luminescent defects in hafnia thin films made with different deposition techniques

Hafnia thin films for high-power optical coatings have been characterized by photoluminescence pumped by 4.66 eV photons and photothermal deflection measurements. These data are compared to the statistical laser damage behavior in order to find correlations between destructive and non-destructive characterizations. Thin films have been produced at two thicknesses and using different thin-film deposition techniques typically employed for optical coating fabrication: EBD (HfO₂ target), EBD (Hf target), RLVIP and DIBS. The photoluminescence spectra show significant differences depending on the deposition techniques and thicknesses. EBD films show significant luminescence but the luminescence of ion-assisted films could not be distinguished from the uncoated substrate. All EBD coating spectra could be described by a linear combination of four bands. Further, XRD measurements show that the 255-nm-thick films had a relatively high crystallinity: EBD films contained the monoclinic phase and the ion-assisted films contained oriented nanocrystals of orthorhombic hafnia. The presence of orthorhombic phases indicates high compressive strain quenching the photoluminescence of these samples.     

Laser-driven shock experiments on precompressed water: Implications for "icy" giant planets

Laser-driven shock compression of samples precompressed to 1 GPa produces high-pressure-temperature conditions inducing two significant changes in the optical properties of water: the onset of opacity followed by enhanced reflectivity in the initially transparent water. The onset of reflectivity at infrared wavelengths can be interpreted as a semiconductor<-->electronic conductor transition in water, and is found at pressures above approximately 130 GPa for single-shocked samples precompressed to 1 GPa. Our results indicate that conductivity in the deep interior of "icy" giant planets is greater than realized previously because of an additional contribution from electrons.     

Diastereoselective fragmentation of chiral alpha-aminophosphonic acids/metal ion aggregates

Diastereomeric clusters of general formula [MAB(2)](+) and [MA(2)B](+) (M = Li(I), Na(I), Ag(I), Ni(II)-H, or Cu(II)-H; A = (R)-(-)- and (S)-(+)-(1-aminopropyl)phosphonic acid; B = (1R)-(-)- and (1S)-(+)-(1-aminohexyl)phosphonic acid) have been readily generated in the electrospray ionization (ESI) source of a triple-quadrupole mass spectrometer and their collision-induced dissociation (CID) investigated. CID of diastereomeric complexes, e.g. [MA(S)(B(S))(2)](+) and [MA(R)(B(S))(2)](+), leads to fragmentation patterns characterized by R(homo) = [MA(S)B(S)](+)/[M(B(S))(2)](+) and R(hetero) = [MA(R)B(S)](+)/[M(B(S))(2)](+) abundance ratios, which depend upon the relative stability of the diastereomeric [MA(S)B(S)](+) and [MA(R)B(S)](+) complexes in the gas phase. The chiral resolution factor R(chiral) = R(homo)/R(hetero) is found to depend not only on the nature of the M ion but also on that of the fragmenting species, whether [MAB(2)](+) or [MA(2)B](+). The origin of this behavior is discussed.     

Thiocolchicine-podophyllotoxin conjugates: dynamic libraries based on disulfide exchange reaction

A dynamic combinatorial library of thiocolchicine-podophyllotoxin derivatives based on the disulfide bond exchange reaction is described. The influence of a biological target on the composition of the reaction mixture has been demonstrated. Use of high-resolution ESI mass spectrometry to evaluate the composition of the mixture shows promise for the design of new large libraries. The biological evaluation demonstrates that formation of a divalent compound affords a new chemical entity whose biological activity is not merely the sum of the single ligands activities, thus reflecting a different interaction with the biological target.     

Commissioning of a multi‐beamline femtoslicing facility at SOLEIL

The investigation of ultrafast dynamics, taking place on the few to sub‐picosecond time scale, is today a very active research area pursued in a variety of scientific domains. With the recent advent of X‐ray free‐electron lasers (XFELs), providing very intense X‐ray pulses of duration as short as a few femtoseconds, this research field has gained further momentum. As a consequence, the demand for access strongly exceeds the capacity of the very few XFEL facilities existing worldwide. This situation motivates the development of alternative sub‐picosecond pulsed X‐ray sources among which femtoslicing facilities at synchrotron radiation storage rings are standing out due to their tunability over an extended photon energy range and their high stability. Following the success of the femtoslicing installations at ALS, BESSY‐II, SLS and UVSOR, SOLEIL decided to implement a femtoslicing facility. Several challenges were faced, including operation at the highest electron beam energy ever, and achievement of slice separation exclusively with the natural dispersion function of the storage ring. SOLEIL's setup also enables, for the first time, delivering sub‐picosecond pulses simultaneously to several beamlines. This last feature enlarges the experimental capabilities of the facility, which covers the soft and hard X‐ray photon energy range. In this paper, the commissioning of this original femtoslicing facility is reported. Furthermore, it is shown that the slicing‐induced THz signal can be used to derive a quantitative estimate for the degree of energy exchange between the femtosecond infrared laser pulse and the circulating electron bunch.     

The female gonad of the epizoic platyhelminth Troglocaridicola sp. (Rhabdocoela, Temnocephalida, Scutariellidae): ultrastructural and cytochemical investigations

The cytoarchitecture of the female gonad of the scutariellid Troglocaridicola sp. has been investigated by means of electron microscopy and cytochemical techniques. It consists of a single germarium and two rows of vitelline follicles, both enveloped by an outer extracellular lamina (EL) and an inner cellular tunica constituted by accessory cells. Some ultrastructural features which differ from the basic pattern of all the other Rhabdocoela studied so far have been found. In the germarium the following are observed: (a) The presence in the oocytes of peripheral translucent vesicles containing glycoproteins, which differ in diameter and substructure from the peripheral egg granules observed in all the other neoophoran Platyhelminthes. These vesicles can be considered an autapomorphic feature of the taxon Troglocaridicola; (b) The presence of proteinaceous acorn-shaped granules which remain scattered in the ooplasm throughout oogenesis and can be interpreted as residual yolk. This situation is shared with some Proseriata and Tricladida; (c) The precence of accessory cell processes between growing and mature oocytes, as is typical of some Proseriata and Tricladida. In the vitellarium, the presence of polyphenolic shell globules whose substructure does not correspond either to the multigranular pattern prevailing in representatives of Eulecithophora (Prolecithophora+Rhabdocoela) or to the homogeneous pattern found in Lecithoepitheliata. They have a meandering/concentric pattern of the content similar to that described in some Proseriata and Tricladida. On the basis of the ultrastructural characteristics of the female gonad described above, the position of Troglocaridicola in the taxon Rhabdocoela is discussed.