Applications of deactivated GC columns for analysis of nitrogen-containing chemicals related to the chemical weapons convention

Nitrogen-containing chemicals are one of the important families of compounds relevant to the purposes of the Chemical Weapons Convention (CWC). Several applications, using various injection modes, of new deactivated columns specially designed for basic compounds are presented. These columns prove remarkably well-suited to the gas chromatographic (GC) analysis of the chemicals of interest, even to underivatized amino-alcohols, whose analysis on conventional GC columns is often difficult and hindered by poor resolution and high detection limits. Such a deactivated phase can even replace the typical GC phases used for CWC verification purposes.     

Integrated all-optical pulse restoration with coupled nonlinear microring resonators

We numerically demonstrate the feasibility of constructing an all-optical pulse restorer by using a microresonator structure with Kerr nonlinearity. We obtain a clear nonlinear power transfer curve capable of improving the signal-to-noise ratio and reducing the bit error rate for digital signals. Since we take advantage of field enhancement at resonance, this integrated reshaper could be much smaller than other gates based on nonlinear fibers or waveguides.     

In Situ Decarboxylation-Pressurized Hot Water Extraction for Selective Extraction of Cannabinoids from Cannabis sativa. Chemometric Approach

Isolation of the therapeutic cannabinoid compounds from Cannabis Sativa L. (C. Sativa) is important for the development of cannabis-based pharmaceuticals for cancer treatment, among other ailments. The main pharmacological cannabinoids are THC and CBD. However, THC also induces undesirable psychoactive effects. The decarboxylation process converts the naturally occurring acidic forms of cannabinoids, such as cannabidiolic acid (CBDA) and tetrahydrocannabinolic acid (THCA), to their more active neutral forms, known as cannabidiol (CBD) and tetrahydrocannabinol (THC). The purpose of this study was to selectively extract cannabinoids using a novel in situ decarboxylation pressurized hot water extraction (PHWE) system. The decarboxylation step was evaluated at different temperature (80–150 °C) and time (5–60 min) settings to obtain the optimal conditions for the decarboxylation-PHWE system using response surface methodology (RSM). The system was optimized to produce cannabis extracts with high CBD content, while suppressing the THC and CBN content. The identification and quantification of cannabinoid compounds were determined using UHPLC-MS/MS with external calibration. As a result, the RSM has shown good predictive capability with a p-value < 0.05, and the chosen parameters revealed to have a significant effect on the CBD, CBN and THC content. The optimal decarboxylation conditions for an extract richer in CBD than THC were set at 149.9 °C and 42 min as decarboxylation temperature and decarboxylation time, respectively. The extraction recoveries ranged between 96.56 and 103.42%, 95.22 and 99.95%, 99.62 and 99.81% for CBD, CBN and THC, respectively.     

Dynamic Cross‐Exchange in Halophosphonium Species: Direct Observation of Stereochemical Inversion in the Course of an SN2 Process

The complex fluxional interconversions between otherwise very similar phosphonium bromides and chlorides R₃PX⁺X^? (R=Alk, Ar, X=Cl or Br) were studied by NMR techniques. Their energy barriers are typically ca. 11 kcal mol^?1, but rise rapidly as bulky groups are attached to phosphorus, revealing the importance of steric factors. In contrast, electronic effects, as measured by Hammett analysis, are modest (ρ 1.46) but still clearly indicate negative charge flow towards phosphorus in the transition state. Most significantly, detailed analysis of the exchange pathways unequivocally, and for the first time in any such process, shows that nucleophilic attack of the nucleophilic anion on the tetrahedral centre results in inversion of configuration.     

Checking the odd Goldbach conjecture up to

Vinogradov's theorem states that any sufficiently large odd integer is the sum of three prime numbers. This theorem allows us to suppose the conjecture that this is true for all odd integers. In this paper, we describe the implementation of an algorithm which allowed us to check this conjecture up to .

     

Preparation and properties of starch-based colloidal microgels

Novel starch microgels were prepared by emulsion cross-linking and characterized with respect to shape, volume, and mass density. Starch microgels appear to be negatively charged ( approximately -50 mV), with a particle size varying as a function of the type of cross-linker (ca. 0.25-10 microm). Environmental scanning electron microscopy observations show a dependence of the particle swelling on the cross-linking density. Viscosimetry reveals that starch microgels behave as charged polymers, where the reduced viscosity increases with dilution (anomalous viscosity behavior) for sufficiently low kappaalpha (ca. kappaalpha <3), the ratio of the particle radius (a), and the Debye length (kappa(-1)). Analogous results are obtained for reference-charged rigid silica spheres, which approach the hard sphere limit for increasing ionic strengths. The shape of the microgels appears to play a minor role in the anomalous viscosity behavior, which is more likely dominated by electrostatic effects.     

Titanium catalysis in the Ugi reaction of alpha-amino acids with aromatic aldehydes

[reaction: see text] Ugi reaction between an (S)-alpha-amino acid, an aromatic aldehyde, and an isonitrile proceeds best under catalysis by TiCl(4) in MeOH. The sense of diastereoinduction is (S,S).     

Adsorption properties of the penicillin derivative DTPA on gold substrates.

Despite the large number of articles and patents dealing with penicillin and other beta-lactam antibiotics, there have been no reports about the self-assembly of such substances as monolayers on gold surfaces. The main reason stems from the high reactivity of the beta-lactam ring, which hinders the development of molecules possessing this entity together with a metal-anchoring function. Herein, we present the synthesis of a novel molecule, 6-[(R,S)-5-(1,2-dithiolan-3-yl)pentanoyl-amino]-penicillanic acid, which combines the beta-lactam ring and a metal-anchoring group. Using spectroscopic tools, we demonstrate the chemisorption of this compound on gold as self-assembled monolayers without any alteration of the penicillin pharmacophore and document its reactivity towards a penicillin-binding protein, BlaR-CTD. Our work is a preliminary step towards the development of new biosensors and well-ordered protein arrays, both based on the high affinity of penicillin for penicillin-binding proteins.     

One-step template-directed synthesis of multifunctionalised nanoporous silica: on the way to interactive nanomaterials

The preparation of multifunctional mesoporous silica containing a NLO chromophore in the framework (bridged azobenzene phosphonium salts) and mercaptopropyl groups able to stabilize gold(0) nanoparticles in the channel pores was achieved in one step by using the direct liquid crystal templating approach.