DFT, FT-Raman, and FT-IR investigations of 1-cyclopropylpiperazine

FT-IR and FT-Raman spectra of 1-cyclopropylpiperazine (1cppp) are experimentally examined in the range 4000-200 cm^?1. The optimized geometric parameters, conformational equilibria, normal mode frequencies and corresponding vibrational assignments of 1cppp C₇H₁₄N₂ are theoretically examined by means of B3LYP hybrid density functional theory (DFT) with the 6–31++G(d,p) basis set. Based on the potential energy distribution (PED) reliable vibrational assignments are made and the thermodynamics functions, highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO) of 1cppp are predicted. Calculations are performed for four different conformations in two point groups of 1cppp in the gas phase. A comparison between the experimental and theoretical results indicates that the B3LYP method is able to provide satisfactory results for the prediction of vibrational frequencies, structural parameters, and assignments. Furthermore, the C _s (equatorial-equatorial) point group is found as the most stable conformer of 1cppp.     

A microfluidic-based frequency-multiplexing impedance sensor (FMIS)

We present a novel technology for the simultaneous and simple impedimetric screening of multiple microfluidic channels with only one electrode pair. We have exploited the frequency dimension to distinguish between up to three channels. Each 'sub-sensor' possesses its corresponding measurement frequency where the sample-specific dielectric properties can be probed. We have shown the validity of our frequency-multiplexing impedance sensor (FMIS) by comparison with conventional 'single sensors'. Our highly sensitive FMIS was proven suitable for life science applications through usage as a cell-based toxicology platform. We are confident that our technology might find great utility in parallelized cell-based analysis systems as well as in biomedical devices where size limitations and spatially distributed probing are important parameters.     

Material transfer and polarity reversal in contact charging

In touch: the outcome of contact electrification between dielectrics depends not only on the transfer of charge but also on the transfer of material. Although only minute quantities of materials are being exchanged during contact, they can reverse the polarity of dielectrics. The reported results corroborate the mosaic model and suggest that the observations are because of the mechanical softness/hardness of the materials.     

Rewiring chemistry: algorithmic discovery and experimental validation of one-pot reactions in the network of organic chemistry

Computational algorithms are used to identify sequences of reactions that can be performed in one pot. These predictions are based on over 86?000 chemical criteria by which the putative sequences are evaluated. The "raw" algorithmic output is then validated experimentally by performing multiple two-, three-, and even four-step sequences. These sequences "rewire" synthetic pathways around popular and/or important small molecules.     

Physicochemical properties affecting lipofection potency of a new series of 1,2-dialkoylamidopropane-based cationic lipids

The in vitro transfection activity of a novel series of N,N'-diacyl-1,2-diaminopropyl-3-carbamoyl-(aminoethane) derivatives was evaluated against a mouse melanoma cell line at different +/- charge ratios, in the presence and absence of helper lipids. Only the unsaturated derivative N,N'-dioleoyl-1,2-diaminopropyl-3-carbamoyl-(aminoethane), (1,2lmp[5]) mediated significant increase in the reporter gene level which was significantly boosted in the presence of DOPE peaking at +/- charge ratio of 2. The electrostatic interactions between the cationic liposomes and plasmid DNA were investigated by gel electrophoresis, fluorescence spectroscopy, dynamic light scattering and electrophoretic mobility techniques. In agreement with the transfection results, 1,2lmp[5]/DOPE formulation was most efficient in associating with and retarding DNA migration. The improved association between the dioleoyl derivative and DNA was further confirmed by ethidium bromide displacement assay and particle size distribution analysis of the lipoplexes. Differential scanning calorimetry studies showed that 1,2lmp[5] was the only lipid that exhibited a main phase transition below 37 degrees C. Likewise, 1,2lmp[5] was the only lipid found to form all liquid expanded monolayers at 23 degrees C. In conclusion, the current findings suggest that high in vitro transfection activity is mediated by cationic lipids characterized by increased acyl chain fluidity and high interfacial elasticity.     

Mechanism of void nucleation and growth in bcc Fe: atomistic simulations at experimental time scales

Evolution of small-vacancy clusters in bcc Fe is simulated using a multiscale approach coupling an atomistic activation-relaxation method for sampling transition-state pathways with environment-dependent reaction coordinate calculations and a kinetic Monte Carlo simulation to reach time scales on the order of ~10? s. Under vacancy-supersaturated condition, di- and trivacancy clusters form and grow by coalescence (Ostwald ripening). For cluster size greater than four we find a transition temperature of 150 °C for accelerated cluster growth, as observed in positron annihilation spectroscopy experiments. Implications for the mechanism of stage-IV radiation-damage-recovery kinetics are discussed.     

The Synthesis and Acid-Catalyzed Hydrolysis of N-(4-Substitutedphenyl)-O-Benzenedisulfonimides

Abstract

The acid catalyzed hydrolyses of some cyclic disulfonimides, N-(4-substitutedphenyl)-o-benzenedisulfonimides (1a–d) have been studied in concentrated aqueous acidic solutions. Analysis of the data by the Excess Acidity Method, activation parameters, substituent, and solvent deuterium isotope effect are all indicate hydrolysis by an A-1 mechanism in the studied range.     

Morphology and thermal characterization of montmorillonite/polybenzimidazole nanocomposite

In this study, thermal and morphological properties of organically modified montmorillonite (mMMT)/poly(2,5-benzimidazole) (ABPBI) composite were investigated. The morphology and structure of mMMT/ABPBI composites were characterized by infrared, X-ray diffraction, scanning electron microscopy, and thermogravimetric analysis techniques. At low mMMT loading levels, exfoliation was the predominant mechanism of mMMT dispersion. At high mMMT loading levels, nonintercalated microcomposite morphology is partially favored in expense of the intercalated nanocomposite. Thermal degradation of nanocomposite occured in three stages. In the second stage of thermal degradation, the onset temperature of degradation for the mMMT/ABPBI nanocomposites was lower than that of ABPBI polymer. In the last stage, the improvement in thermal stability by the introduction of mMMT into the ABPBI was different from the second stage. The activation energy for degradation of ABPBI increased from 62.6 to 77.7 kJ mol^?1 after loading of 5 mass% of mMMT into ABPBI matrix under air atmosphere.