Chromatographic analysis of salicylic compounds in different species of the genus Salix

The separation of nine phenol glycosides--salicin, salicortin, 2'-acetylsalicortin, populin, tremulacin, salidroside, triandrin, picein and helicin--by normal phase (NP), reversed phase (RP) HPLC techniques and a coupling of NP and RP monolithic silica columns was studied. Among the above nine compounds only five--salicin, populin, tremulacin, salidroside and triandrin--were resolved in an NP system with a mobile phase comprising hexane/isopropanol/methanol (87:12:1, v/v/v). Optimized separation was performed with two coupled monolithic silica columns of different polarity (bare silica and RP-18). The method was applied to verify the presence of salicylic compounds and other phenolic derivatives in the bark of six species from the genus Salix, namely S. purpurea, S. daphnoides clone 1095, S. alba clone 1100, S. triandra, S. viminalis, and S. herbacea. Gradient elution with a mobile phase composed of acetonitrile and water containing 0.05% of trifluoroacetic acid, with increasing acetonitrile concentration from 3% to 48%, was chosen as optimal. For the selective detection of the salicylic compounds, an evaporative light scattering detector was employed along with a UV detector. The differences in the composition of phenols in the different plant materials were confirmed. Additionally, it must be emphasized that for the first time the presence of 2'-acetylsalicortin was revealed in S. alba clone 1100. Furthermore, an SPE-HPLC method was developed for the rapid analysis of the salicin content, analyzed as free and total fraction, in willow barks. The determined concentrations of total salicin varied from 25.4 mg/g in S. alba clone 1100 to 96.47 mg/g in S. daphnoides clone 1095.     

Nature of ultraviolet and Gamma ray induced damage in crystalline Uracil

Abstract

A study has been made of the damage producedin situ in dry polycrystalline uracil by irradiation with high energy 60Co photons and by low energy ultraviolet (UV) photons. The techniques of electron spin resonance, thin layer chromatography, infrared spectrometry, neutron diffraction and spectrophotometry have all been utilized to investigate effects produced by the irradiations. If was found that little lattice damage and no cis-syn cyclobutane dimers are producedin situ by irradiation of dry uracil with 60Co photons. However, following dissolution of the irradiated powder in water, radiation products are detected, and several of their characteristics have been elucidated. In contrast, following irradiation by 60Co photons of uracil in an aqueous environment, massive damage was found in the dried sample. Irradiation of dry uracil with UV photons is found to cause general lattice damage, but again negligible concentrations of cis-syn dimers are producedin situ. There is evidence for the formation of a planar, dimer-like molecular configuration.     

Domino process optimized via ab initio study for an alternative access to bicyclic lactams

A totally new acid-free domino process to access highly functionalized bicyclic γ- and δ-lactams starting from commercially available and inexpensive ethoxymethylene derivatives is reported. Mechanisms elucidated by computational calculations led to new reaction conditions that boosted the yields up to 3.5 times higher.     

Identification by LC-ESI-MS of flavonoids responsible for the antioxidant properties of Mallotus species from Vietnam

Several Mallotus species (Euphorbiaceae) are used in Vietnam as edible plants or as traditional medicines for different indications, some related to the treatment of inflammatory diseases. This study investigated the antioxidant activities of 33 samples from 17 Vietnamese Mallotus species. We also evaluated potential cytotoxic activity against human cervix carcinoma HeLa and human lung fibroblast WI-38 cells. Our aim is to develop safe dietary supplements with a protective effect against various diseases caused by tissue damage and the acceleration of the aging process linked to reactive oxygen species. These tests allowed the identification of non-cytotoxic plant species exhibiting significant antiradical properties. These antioxidant properties may be explained by their polyphenol composition. The antioxidant activity of the most active Mallotus species was further analyzed with and without tannins removal. We also identified by LC-ESI-MS some flavonoids responsible for a part of this activity.     

Tactics for the asymmetric preparation of 2-azabicyclo[3.1.0]hexane and 2-azabicyclo[4.1.0]heptane scaffolds

In this contribution, two methods are presented for the removal of benzyl-type protecting groups attached to the nitrogen atom of 2-azabicyclo[3.1.0]hexane and 2-azabicyclo[4.1.0]heptane systems. The first, based on the Polonovski reaction, is suitable for [3.1.0] systems. The second relies on an elimination process, starting from derivatives of O-methyl phenylglycinol, and is more general in terms of the substrates tolerated. Secondary bicyclic cyclopropylamines, including enantiomerically pure molecules, can thus be accessed. These compounds are then ready for further functionalisation.     

Optimization of organic electrochemical transistors for sensor applications

Despite the recent interest in organic electrochemical transistors (OECTs) as chemical and biological sensors, little is known about the role that device architecture and materials parameters play in determining sensor performance. We use numerical modeling to establish design rules in two regimes of operation: We find that for operation as an ion‐to‐electron converter, the response of OECTs is maximized through the use of a gate electrode that is much larger than the channel or through the use of a nonpolarizable gate electrode. Improving the conductivity of the polymer and using a channel geometry that maximizes channel width and thickness, and minimizes channel length helps increase the response. For operation as an electrochemical sensor, the sensitivity is maximized in OECTs with gate electrodes that are smaller than their channels. The sensitivity can be improved by increasing the charge carrier mobility and the capacitance per unit area of the conducting polymer, and also its ability to be penetrated by ions from the electrolyte. A channel geometry that maximizes channel width and minimizes channel length also improves sensitivity. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010     

A finite-volume version of Aizenman–Higuchi theorem for the 2d Ising model

In the late 1970s, in two celebrated papers, Aizenman and Higuchi independently established that all infinite-volume Gibbs measures of the two-dimensional ferromagnetic nearest-neighbor Ising model at inverse temperature ${\beta\geq 0}$ are of the form ${\alpha\mu^{+}_\beta + (1-\alpha)\mu^{-}_\beta}$ , where ${\mu^{+}_\beta}$ and ${\mu^{-}_\beta}$ are the two pure phases and ${0\leq\alpha\leq 1}$ . We present here a new approach to this result, with a number of advantages: (a) We obtain an optimal finite-volume, quantitative analogue (implying the classical claim); (b) the scheme of our proof seems more natural and provides a better picture of the underlying phenomenon; (c) this new approach might be applicable to systems for which the classical method fails.     

Preparation and characterisation of silica monoliths using a triblock copolymer (F68) as porogen

Silica-based monoliths with co-continuous structure were successfully prepared through a sol–gel process in the presence of a poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (F68). The triblock copolymer was compared to the classical PEG, in the formation of silica monoliths and was demonstrated to lead to co-continuous structures in a wider composition range, presenting smaller through pores. Moreover, mesoporous structures templated at the sol–gel transition were assumed to occur at the surface of the silica skeleton while PEG exhibited no mesopore templating.     

3D tracking of foraging belugas from their clicks: Experiment from a coastal hydrophone array

A simple passive acoustic monitoring (PAM) setup was used to localize and track beluga whales underwater in three dimensions (3D) in a fjord. In June 2009, beluga clicks were recorded from a cabled hydrophone array in a regularly frequented habitat in Eastern Canada. Beluga click energy was concentrated in the 30-50 kHz frequency band. The click trains detected on several hydrophones were localized from their time difference of arrivals. Cluster analysis linked localizations into tracks based on criteria of spatial and temporal proximity. At close ranges from the array, the localized click-train series allowed three-dimensional tracking of a beluga during its dive. Clicks within a train spanned a large range of durations, inter-click intervals, source levels and bandwidths. Buzzes sometimes terminated the trains. Repeated click packets were frequent. All click characteristics are consistent with oblique observations from the beam axis, and ordered variation of the source pattern during a train, likely resulting from a scan of angles from the beam axis, was observed before click trains indicated focusing of the echolocation clicks in one direction. The click-train series is interpreted as echolocation chasing for preys during a foraging dive. Results show that a simple PAM system can be configured to passively and effectively 3D track wild belugas and small odontocetes in their regularly frequented habitat.     

Opacity calculation for target physics using the ABAKO/RAPCAL code

Radiative properties of hot dense plasmas remain a subject of current interest since they play an important role in inertial confinement fusion (ICF) research, as well as in studies on stellar physics. In particular, the understanding of ICF plasmas requires emissivities and opacities for both hydro-simulations and diagnostics. Nevertheless, the accurate calculation of these properties is still an open question and continuous efforts are being made to develop new models and numerical codes that can facilitate the evaluation of such properties. In this work the set of atomic models ABAKO/RAPCAL is presented, as well as a series of results for carbon and aluminum to show its capability for modeling the population kinetics of plasmas in both LTE and NLTE regimes. Also, the spectroscopic diagnostics of a laser-produced aluminum plasma using ABAKO/RAPCAL is discussed. Additionally, as an interesting application of these codes, fitting analytical formulas for Rosseland and Planck mean opacities for carbon plasmas are reported. These formulas are useful as input data in hydrodynamic simulation of targets where the computation task is so hard that in line computation with sophisticated opacity codes is prohibitive.