Separation of uranium and plutonium isotopes for measurement by multi collector inductively coupled plasma mass spectroscopy

Uranium (U) and plutonium (Pu) isotopes in coral soils, contaminated by nuclear weapons testing in the northern Marshall Islands, were isolated by ion-exchange chromatography and analyzed by mass spectrometry. The soil samples were spiked with ²³³U and ²⁴²Pu tracers, dissolved in minerals acids, and U and Pu isotopes isolated and purified on commercially available ion-exchange columns. The ion-exchange technique employed a TEVA^® column coupled to a UTEVA^® column. U and Pu isotope fractions were then further isolated using separate elution schemes, and the purified fractions containing U and Pu isotopes analyzed sequentially using multi-collector inductively coupled plasma mass spectrometer (MCICP-MS). High precision measurements of ²³⁴U/²³⁵U, ²³⁸U/²³⁵U, ²³⁶U/²³⁵U, and ²⁴⁰Pu/²³⁹Pu in soil samples were attained using the described methodology and instrumentation, and provide a basis for conducting more detailed assessments of the behavior and transfer of uranium and plutonium in the environment.     

Recent Advances in In Silico Target Fishing

In silico target fishing, whose aim is to identify possible protein targets for a query molecule, is an emerging approach used in drug discovery due its wide variety of applications. This strategy allows the clarification of mechanism of action and biological activities of compounds whose target is still unknown. Moreover, target fishing can be employed for the identification of off targets of drug candidates, thus recognizing and preventing their possible adverse effects. For these reasons, target fishing has increasingly become a key approach for polypharmacology, drug repurposing, and the identification of new drug targets. While experimental target fishing can be lengthy and difficult to implement, due to the plethora of interactions that may occur for a single small-molecule with different protein targets, an in silico approach can be quicker, less expensive, more efficient for specific protein structures, and thus easier to employ. Moreover, the possibility to use it in combination with docking and virtual screening studies, as well as the increasing number of web-based tools that have been recently developed, make target fishing a more appealing method for drug discovery. It is especially worth underlining the increasing implementation of machine learning in this field, both as a main target fishing approach and as a further development of already applied strategies. This review reports on the main in silico target fishing strategies, belonging to both ligand-based and receptor-based approaches, developed and applied in the last years, with a particular attention to the different web tools freely accessible by the scientific community for performing target fishing studies.     

Airborne nanoparticle exposures associated with the manual handling of nanoalumina and nanosilver in fume hoods

Manual handling of nanoparticles is a fundamental task of most nanomaterial research; such handling may expose workers to ultrafine or nanoparticles. Recent studies confirm that exposures to ultrafine or nanoparticles produce adverse inflammatory responses in rodent lungs and such particles may translocate to other areas of the body, including the brain. An important method for protecting workers handling nanoparticles from exposure to airborne nanoparticles is the laboratory fume hood. Such hoods rely on the proper face velocity for optimum performance. In addition, several other hood design and operating factors can affect worker exposure. Handling experiments were performed to measure airborne particle concentration while handling nanoparticles in three fume hoods located in different buildings under a range of operating conditions. Nanoalumina and nanosilver were selected to perform handling experiments in the fume hoods. Air samples were also collected on polycarbonate membrane filters and particles were characterized by scanning electron microscopy. Handling tasks included transferring particles from beaker to beaker by spatula and by pouring. Measurement locations were the room background, the researcher’s breathing zone and upstream and downstream from the handling location. Variable factors studied included hood design, transfer method, face velocity/sash location and material types. Airborne particle concentrations measured at breathing zone locations were analyzed to characterize exposure level. Statistics were used to test the correlation between data. The test results found that the handling of dry powders consisting of nano-sized particles inside laboratory fume hoods can result in a significant release of airborne nanoparticles from the fume hood into the laboratory environment and the researcher’s breathing zone. Many variables were found to affect the extent of particle release including hood design, hood operation (sash height, face velocity), work practices, type and quantity of the material being handled, room conditions, and the adequacy of the room exhaust.

High-frequency EPR applications of open nonradiative resonators

A new class of open single-mode cavities, the nonradiative (NR) resonators, has recently been proposed in order to overcome the limitations of standard cylindrical cavities and Fabry-Perot resonators at millimeter wavelengths. This paper presents the first applications of a NR resonator in W-band pulsed electron paramagnetic resonance spectroscopy. It consists of a cylindrical cavity having a lateral aperture that represents about 35% of its total height. Electron-spin-echo measurements performed on different samples show that the signal-to-noise ratio and the optimal pulse length obtained with the proposed device are comparable to those obtained with the closed cavity used in the commercial W-band spectrometer, at both cryogenic and room temperature. Similar results have been obtained for paramagnetic species optically activated by means of an optical fiber inserted in the aperture of the resonator. The insertion losses estimated for the probe employed with the NR resonator are higher than those of the commercial probe, hence, demonstrating that the proposed cavity holds the promise of improved resonator performance.     

Optical and structural properties of new chalcohalide glasses

New class of chalcohalide glasses has been prepared in the GeS₂–In₂S₃–CsI system with regard to their potential non-linear properties. The study of glass-forming region was undertaken to select glassy compositions, which present high non-linear (NL) optical properties with a low two-photon absorption. Thermal analyses, structural examination by Raman spectroscopy, non-linear optical measurements were investigated as a function of CsI contents. Introduction of CsI has shifted the band-gap edge towards the blue region of the absorption optical spectrum and therefore has limited the two-photon absorption. Their NL refractive index n₂ are 60 times higher than silica glasses without any NL absorption. Moreover, second harmonic signal was observed in thermally poled samples similar to silica glass. However, this second order non-linearity is not temporally stable.     

Optical efficiency of solar concentrators by a reverse optical path method

A method for the optical characterization of a solar concentrator, based on the reverse illumination by a Lambertian source and measurement of intensity of light projected on a far screen, has been developed. It is shown that the projected light intensity is simply correlated to the angle-resolved efficiency of a concentrator, conventionally obtained by a direct illumination procedure. The method has been applied by simulating simple reflective nonimaging and Fresnel lens concentrators.     

Ionic liquid structure: the conformational isomerism in 1‐butyl‐3‐methyl‐imidazolium tetrafluoroborate ([bmim][BF4])

As a probe of local structure, the vibrational properties of the 1‐butyl‐3‐methylimidazolium tetrafluoroborate [bmim][BF₄] ionic liquid were studied by infrared (IR), Raman spectroscopy, and ab initio calculations. The coexistence of at least four [bmim]⁺ conformers (GG, GA, TA, and AA) at room temperature was established through unique spectral responses. The Raman modes characteristic of the two most stable [bmim]⁺ conformers, GA and AA, according to the ab initio calculations, increase in intensity with decreasing temperature. To assess the total spectral behavior of the ionic liquid both the contributions of different [bmim]⁺ conformers and the [bmim]⁺− [BF₄]⁻ interactions to the vibrational spectra are discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

Linear and nonlinear pulse propagation in coupled resonator slow-wave optical structures

The linear and nonlinear characteristics of optical slow-wave structures made of direct coupled Fabry–Pérot and Ring Resonators are discussed. The main properties of an infinitely long slow-wave structure are derived analytically with an approach based on the Bloch theory. The spectral behaviour is periodical and closed form expressions for the bandwidth, the group velocity, the dispersion and the linear and nonlinear induced phase shift are derived. For structures of finite length the results still hold providing that proper input/output matching sections are added. In slow-wave structures most of the propagation parameters are enhanced by a factor S called the slowing ratio. In particular nonlinearities result strongly enhanced by the resonant propagation, so that slow-wave structures are likely to become a key point for all-optical processing devices. A numerical simulator has been implemented and several numerical examples of propagation are discussed. It is also shown as soliton propagation is supported by slow-wave structures, demonstrating the flexibility and potentiality of these structures in the field of the all-optical processing.