Volumetric properties, viscosity and refractive index of the protic ionic liquid, pyrrolidinium octanoate, in molecular solvents

Densities ([rho]) and viscosities ([eta]) of binary mixtures containing the Protic Ionic Liquid (PIL), pyrrolidinium octanoate with five molecular solvents: water, methanol, ethanol, n-butanol, and acetonitrile are determined at the atmospheric pressure as a function of the temperature and within the whole composition range. The refractive index of all mixtures (nD) is measured at 298.15†K. The excess molar volumes VE and deviation from additivity rules of viscosities [eta]E and refractive index [Delta][phi]n, of pyrrolidinium octanoate solutions were then deduced from the experimental results as well as apparent molar volumes V[phi]i, partial molar volumes and thermal expansion coefficients [alpha]p. The excess molar volumes VE are negative over the entire mole fraction range for mixture with water, acetonitrile, and methanol indicating strong hydrogen-bonding interaction for the entire mole fraction. In the case of longest carbon chain alcohols (such as ethanol and n-butanol)†+†pyrrolidinium octanoate solutions, the VE variation as a function of the composition describes an S shape. The deviation from additivity rules of viscosities is negative over the entire composition range for the acetonitrile, methanol, ethanol, and butanol, and becomes less negative with increasing temperature. Whereas, [eta]E of the {[Pyrr][C7CO2]†+†water} binary mixtures is positive in the whole mole fraction range and decreases with increasing temperature. the excess Gibbs free energies of activation of viscous flow ([Delta]G*E) for these systems were calculated. The deviation from additivity rules of refractive index [Delta][phi]n are positive over the whole composition range and approach a maximum of 0.25 in PIL mole fraction for all systems. The magnitude of deviation for [Delta][phi]n describes the following order: water†>†methanol†>†acetonitrile†>†ethanol. Results have been discussed in terms of molecular interactions and molecular structures in these binary mixtures.

Desorption processes and the deuterium fractionation in molecular clouds

Several processes have been suggested as ways of returning accreted grain mantles to the gas, thus preventing the total removal of molecules from the gas phase in dark quiescent clouds. We attempt to distinguish between them by considering not only the calculated gas-phase abundances, but also the ratio of the abundances of deuterated species to non-deuterated species. We find that the D/H ratio in molecules is relatively model-independent, but that desorption due to the formation of H-2 on grains gives the best overall agreement with the observations.

PROTONATED HCN IN MOLECULAR CLOUDS

Observations of protonated HCN (HCNH+) in a selection of galactic molecular clouds are reported. This species plays a key role in understanding the chemistry of the important high density tracer HCN. HCNH+ has been detected in the nearby cold dust cloud TMC-1 with an ratio relative to HCN of [HCNH+]/[HCN] between 0.015 and 0.26 (preferred value 0.03) and tentatively in DR21(OH) with a ratio of approximately 0.01. This is about 100 times higher than the ratio of protonated carbon monoxide to CO [HCO+]/[CO], but comparable to the [HCS+]/[CS] ratio. Possible explanations of these high abundance ratios are discussed in the light of model calculations.

Raman spectroscopy for the detection of AGEs/ALEs

Raman spectroscopy is a noninvasive, nondestructive tool for capturing multiplexed biochemical information across diverse molecular species including proteins, lipids, DNA, and mineralizations. Based on light scattering from molecules, cells, and tissues, it is possible to detect molecular fingerprints and discriminate between subtly different members of each biochemical class. Raman spectroscopy is ideal for detecting perturbations from the expected molecular structure such as those occurring during senescence and the modification of long-lived proteins by metabolic intermediates as we age. Here, we describe the sample preparation, data acquisition, signal processing, data analysis and interpretation involved in using Raman spectroscopy for detecting age-related protein modifications in complex biological tissues.

Bracketing: practical considerations in Husserlian phenomenological research

Nursing research leans heavily towards naturalism, with phenomenology commonly adopted. The three main schools of phenomenology used are Husserl's descriptive approach, Heidegger's interpretive hermeneutic approach and the Dutch Utrecht School of phenomenology which combines characteristics of both. Husserl's approach--the description of ordinary human experiences as perceived by each individual--involves four main steps: bracketing, intuiting, analysing and describing. Many phenomenological nurse researchers consciously decide to adopt a Heideggerian approach because of the perceived difficulties in achieving bracketing. This paper examines the concept of bracketing (epoché) and outlines some of the practical considerations when attempting to achieve it.