Convenient Method for Preparation of Dialkylphosphoramidopropionic Acids and Esters

Silylation at the alpha position of N-propargyl dialkylphosphoramidates enables preparation of dialkylphosphoramido propionic acids in 50–60% yield after hydroboration/oxidation. Treatment with Amberlyst 15 resin in the presence of methanol leads to a quantitative yield of the corresponding esters.     

Electric field standing wave artefacts in FTIR micro-spectroscopy of biological materials

FTIR absorption micro-spectroscopy is a widely used, powerful technique for analysing biological materials. In principle it is a straightforward linear absorption spectroscopy, but it can be affected by artefacts that complicate the interpretation of the data. In this article, artefacts produced by the electric-field standing-wave (EFSW) in micro-reflection-absorption (transflection) spectroscopy are investigated. An EFSW is present at reflective metallic surfaces due to the interference of incident and reflected light. The period of this standing wave is dependent on the wavelength of the radiation and can produce non-linear changes in absorbance with increasing sample thickness (non-Beer-Lambert like behaviour). A protein micro-structure was produced as a simple experimental model for a biological cell and used to evaluate the differences between FTIR spectra collected in transmission and transflection. By varying the thickness of the protein samples, the relationship between the absorbance and sample thickness in transflection was determined, and shown to be consistent with optical interference due to the EFSW coupled with internal reflection from the sample top surface. FTIR spectral image data from MCF 7 breast adenocarcinoma cells was then analysed to determine the severity of the EFSW artefact in data from a real sample. The results from these measurements confirmed that the EFSW artefact has a profound effect on transflection spectra, and in this case the main spectral variations were related to the sample thickness rather than any biochemical differences.     

Towards an integrated biosensor array for simultaneous and rapid multi-analysis of endocrine disrupting chemicals

In this paper we propose the construction and application of a portable multi-purpose biosensor array for the simultaneous detection of a wide range of endocrine disruptor chemicals (EDCs), based on the recognition operated by various enzymes and microorganisms. The developed biosensor combines both electrochemical and optical transduction systems, in order to increase the number of chemical species which can be monitored. Considering to the maximum residue level (MRL) of contaminants established by the European Commission, the biosensor system was able to detect most of the chemicals analysed with very high sensitivity. In particular, atrazine and diuron were detected with a limit of detection of 0.5 nM, with an RSD% less than 5%; paraoxon and chlorpyrifos were revealed with a detection of 5 μM and 4.5 μM, respectively, with an RSD% less than 6%; catechol and bisphenol A were identified with a limit of detection of 1 μM and 35 μM respectively, with an RSD% less than 5%.     

Preparation and Thermal Characterization of PTFE/PES Nanocomposites

Summary: PTFE/PES composites were prepared by precipitation of Radel A® into a PTFE latex containing nanoparticles with average diameters of 48 nm and spherical shape. Several samples were prepared by varying the relative ratio between the Radel A® and PTFE content. The combination of SEM and AFM analysis indicates that the precipitation of Radel A in the presence of PTFE leads mainly, if not exclusively, to a bimodal mixture of the two homoparticles. The fractionated crystallization behaviour of these samples is revealing of the PTFE dispersion degree within the Radel A® matrix. When the PTFE amount is lower than 2%, a perfect PTFE nanoparticle dispersion is obtained. When the amount of PTFE is comprised between 5 and 30%, larger PTFE clusters are obtained that, after melting, coalesce and crystallize at higher temperatures depending on the crystallization propensity of their individual heterogeneous nuclei. Finally, in case of samples 40%, only one crystallization exotherm is observed at 310 °C indicating the formation of very large clusters that after melting coalesce into wide domains.     

Multistep quadratic cascading in broadband optical parametric generation

We theoretically and experimentally investigate multistep parametric processes in broadband optical parametric generators (OPGs) based on periodically poled 1 mol. % MgO-doped stoichiometric LiTaO3. We demonstrate that parametric collateral processes may deplete or enhance spectral portions of the OPG output, depending on pump pulse duration.     

Infinite horizon optimal control problems with multiple thermostatic hybrid dynamics

We study an optimal control problem for a hybrid system exhibiting several internal switching variables whose discrete evolutions are governed by some delayed thermostatic laws. By the dynamic programming technique we prove that the value function is the unique viscosity solution of a system of several Hamilton-Jacobi equations, suitably coupled. The method involves a contraction principle and some suitably adapted results for exit-time problems with discontinuous exit cost.     

Eu(III) incorporation in sol-gel aluminum-yttrium matrix by non-hydrolytic route

The sol-gel method using metal alkoxide has been investigated to prepare aluminum-yttrium oxide as yttrium-aluminum garnet (YAG) matrix composite fiber. In this paper we investigate the influence of yttrium content and temperature in the synthesis of Eu(III)-doped aluminum-yttrium oxide by non-hydrolytic sol-gel route. The formation process and the local structure of the samples were discussed by means of X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and photoluminescence (PL) spectroscopy. For temperatures around 800 °C, initial crystallization was observed and the phases Y₄Al₂O₉ (YAM) and Y₃Al₅O₁₂ (YAG) appear. For samples treated at 800 and 1500 °C the emission spectra display preferentially the f-f transitions characteristic of the YAM monoclinic phase, whereas the YAG cubic appears as the favored phase at 1100 °C, in accordance with the Eu(III) centrosymmetrical local site.     

IMSPeptider: A computational peptide collision cross‐section area calculator based on a novel molecular dynamics simulation protocol

Introduction of ion mobility mass spectrometry (IMS/MS) into the proteomic workflow provides an orthogonal separation to the widely used LC‐MS platforms. IMS also provides structural information that could facilitate peptide identification. However, the lack of tools capable of predictive power in a high‐throughput fashion makes peptide global profiling quite challenging. To target this issue, a computational workflow was developed based on biophysical principles to predict the collision cross‐section area (CCS) of peptides as measured from IMS/MS experiments. Hosted on a web server, it allows the user to input a primary sequence (query) and retrieve information on peptide structure, sequence, and corresponding CCS. The current version is designed to identify peptide sequences up to 23 residues in length, in its higher charge state, based on a match of the molecule m/z and CCS. The protocol was validated against a 128‐sequences‐dataset and CCS predicted within 2.8% average error. © 2013 Wiley Periodicals, Inc.     

Axial stereo-photogrammetry for 360° measurement on tubular samples

This work presents a stereo-photogrammetry (SP) based procedure to perform whole-body measurements on tubular samples. Such a system is designed for future applications to the study of vascular wall mechanics. The use of a concave conical mirror surrounding the specimen makes it possible to capture the reflected 360° surface with a single snapshot moving neither cameras nor object. Then, according to 3-D computer vision principles, a stereo camera system retrieves control points depth information from image-pairs of the investigated surface. An axial-SP arrangement is selected since is more suitable for this specific application than the more popular lateral-stereo model.In this paper, particular emphasis is given to a formulation taking into account even small camera misalignments. A calibration process based on optimization concepts is used together with a feature-based matching algorithm to efficiently find correspondence between highly distorted images reflected by the conical mirror.Both theoretical and experimental analyses on calibrated samples demonstrated feasibility and accuracy of the proposed procedure.     

Recent advances in the synthesis of cyclodextrin derivatives under microwaves and power ultrasound

We describe improved syntheses of CD derivatives, like 6^I-monotosyl, 6^I-monoazido-6^I -monodeoxy, 6^I-monoamino-6^I-monodeoxy-βCD and 2^I-O-mono(methylamino)alkyl-βCDs, that were carried out under US or MW, to great advantage in terms of yield, purity and reaction time. In the search for more efficient procedures to prepare monosubstituted CDs, we applied MW and/or US to some fundamental preparations such as those of 6^I-amino-6^I-deoxy-βCD and a series of 2-monoaminomethyl-βCD derivatives.