Collisional line shifting and broadening in the fundamental P-branch of CO in Ar between 214 and 324 K

The collisional shifts and widths of several P-branch spectral lines in the fundamental band of CO-Ar have been measured at temperatures between 214 and 324 K and pressures between 0.025 and 1 atm. The widths have been determined using a line shape model based on the solution of the transport/relaxation equation for the appropriate off-diagonal element of the density matrix. The model uses a realistic molecular potential energy surface to calculate the speed dependence of the collisional broadening, and a rigid sphere potential to calculate the translational motion. It is found that both the shifting and broadening coefficients follow a power law dependence on the temperature. Additionally, it is demonstrated that studies have tended to overestimate the accuracy of collisional widths when the line shape model used to obtain the widths involves multiple fitted line shape parameters or fails to fit the measured spectra within the experimental noise.     

Pulsed titration sensors: Part 1: A breath-by-breath CO2 sensor

A novel electrochemical sensor for the determination of CO₂ in expired breath is described. The sensor works by generating from the reduction of O₂ in dimethyl sulphoxide (DMSO) in a generating pulse. There is a rapid titration reaction between the and any CO₂ present. In the recovery pulse the amount of unreacted is determined. The larger the concentration of CO₂ the less is found in the recovery pulse. The solubilities and diffusion coefficients of O₂ and CO₂ in DMSO have been determined using rotating disc voltammetry and rotation speed step experiments. The stoichiometry, the product, and the rate constant of the titration reaction have been determined using ring—disc voltammetry and laser Raman spectroscopy. The operation and the effect of adventitious water on the sensor are described. Results are presented which show that the sensor can indeed measure the breath-by-breath rhythm of expired CO₂ from a human subject.     

ABSORPTION SPECTRA AND ACID-BASE DISSOCIATION OF THE 4-ALKYL DERIVATIVES OF 7-HYDROXYCOUMARIN IN SELF-ASSEMBLED SURFACTANT SOLUTION: COMMENTS ON THEIR USE AS ELECTROSTATIC SURFACE POTENTIAL PROBES

Abstract— The absorption spectra of the un-ionized and ionized forms of 4-heptadecyl-7-hydroxycoumarin (HHC) in aqueous self-assembled surfactant solution have been investigated. From a comparison with the absorption spectra of 7-hydroxycoumarin, 7-hydroxy-4-methylcoumarin (MHC) and HHC in neat organic solvents and organic solvent/water mixtures it is shown that the 7-hydroxycoumarin chromophore of HHC in self-assembled surfactant solution resides, on average, in an interfacial microenvironment which has a lower effective dielectric constant than that of the bulk aqueous solution. The absorption spectrum of the ionized form of HHC in aggregates of self-assembled surfactant molecules with cationic quaternary ammonium headgroups is found to be consistent with there being specific molecular interaction between the anionic chromophore and the quaternary ammonium headgroup. pH titrations performed with MHC in pure water and in four molar aqueous solutions of sodium chloride and tetra-methylammonium chloride indicate that the acid-base dissociation of HHC in charged micelles and vesicles should not be substantially influenced by any interfacial salt-effects, and that the acid-base dissociation of HHC in cationic micelles and vesicles with quaternary ammonium headgroups should not be markedly affected by the specific molecular interaction that exists. Estimates of the electrostatic surface potentials of a number of self-assembled surfactant aggregates are made by utilising the acid-base dissociation of HHC and assuming that the nonionic micelles of n -dodecyl octaoxyethylene glycol monoether (C₁₂E₈) can serve as a reference state of zero surface potential. The validity of this assumption in relation to both micelles and vesicles is discussed in detail.     

(Z)-3-p-tolylsulfinylacrylonitrile as a chiral dienophile: diels-alder reactions with furan and acyclic dienes

The behavior of (Z)-3-p-tolylsulfinylacrylonitrile (1) as a chiral dienophile has been evaluated from its reactions with furan and acyclic dienes. Electrostatic interactions of the cyano group with the sulfinyl one restrict the conformational mobility around the C-S bond, thus controlling the pi-facial selectivity, which is almost complete in all cases, the approach of the diene from the less-hindered face of the dienophile (that bearing the lone electron pair) in the predominant rotamer being the favored one. The regioselectivity is also completely controlled by the cyano group. Additionally, the reactivity of compound 1 as well as its endo-selectivity are both higher than those observed for the corresponding (Z)-3-sulfinylacrylates, thus proving the potential of sulfinylnitriles as chiral dienophiles.     

Narrow band quantitative and multivariate electroencephalogram analysis of peri-adolescent period

ABSTRACT: BACKGROUND: The peri-adolescent period is a crucial developmental moment of transition from childhood to emergent adulthood. The present report analyses the differences in Power Spectrum (PS) of the Electroencephalogram (EEG) between late childhood (24 children between 8 and 13 years old) and young adulthood (24 young adults between 18 and 23 years old). RESULTS: The narrow band analysis of the Electroencephalogram was computed in the frequency range of 0--20 Hz. The analysis of mean and variance suggested that six frequency ranges presented a different rate of maturation at these ages, namely: low delta, delta-theta, low alpha, high alpha, low beta and high beta. For most of these bands the maturation seems to occur later in anterior sites than posterior sites. Correlational analysis showed a lower pattern of correlation between different frequencies in children than in young adults, suggesting a certain asynchrony in the maturation of different rhythms. The topographical analysis revealed similar topographies of the different rhythms in children and young adults. Principal Component Analysis (PCA) demonstrated the same internal structure for the Electroencephalogram of both age groups. Principal Component Analysis allowed to separate four subcomponents in the alpha range. All these subcomponents peaked at a lower frequency in children than in young adults. CONCLUSIONS: The present approaches complement and solve some of the incertitudes when the classical brain broad rhythm analysis is applied. Children have a higher absolute power than young adults for frequency ranges between 0-20 Hz, the correlation of Power Spectrum (PS) with age and the variance age comparison showed that there are six ranges of frequencies that can distinguish the level of EEG maturation in children and adults. The establishment of maturational order of different frequencies and its possible maturational interdependence would require a complete series including all the different ages.     

Sequential Benzylic Oxidation of Naloxone 3-Methyl Ether

Naloxone 3-methyl ether was selectively oxidized by treatment with cerium ammonium nitrate in aqueous acetonitrile at ambient temperature to provide the 10-(S)-hydroxy adduct. The stereochemistry of the oxidation product was proven by single crystal X-ray structure determination. The Dess-Martin periodinane further oxidized the 10-hydroxy to the 10-keto analog. Deprotection formed 10-ketonaloxone as an analytical reference standard.     

Novel Amphiphilic Block Copolymers for the Formation of Stimuli-Responsive Non-Lamellar Lipid Nanoparticles

Non-lamellar lyotropic liquid crystalline (LLC) lipid nanoparticles contain internal multidimensional nanostructures such as the inverse bicontinuous cubic and the inverse hexagonal mesophases, which can respond to external stimuli and have the potential of controlling drug release. To date, the internal LLC mesophase responsiveness of these lipid nanoparticles is largely achieved by adding ionizable small molecules to the parent lipid such as monoolein (MO), the mixture of which is then dispersed into nanoparticle suspensions by commercially available poly(ethylene oxide)–poly(propylene oxide) block copolymers. In this study, the Reversible Addition-Fragmentation chain Transfer (RAFT) technique was used to synthesize a series of novel amphiphilic block copolymers (ABCs) containing a hydrophilic poly(ethylene glycol) (PEG) block, a hydrophobic block and one or two responsive blocks, i.e., poly(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzyl acrylate) (PTBA) and/or poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA). High throughput small angle X-ray scattering studies demonstrated that the synthesized ABCs could simultaneously stabilize a range of LLC MO nanoparticles (vesicles, cubosomes, hexosomes, inverse micelles) and provide internal particle nanostructure responsiveness to changes of hydrogen peroxide (H₂O₂) concentrations, pH and temperature. It was found that the novel functional ABCs can substitute for the commercial polymer stabilizer and the ionizable additive in the formation of next generation non-lamellar lipid nanoparticles. These novel formulations have the potential to control drug release in the tumor microenvironment with endogenous H₂O₂ and acidic pH conditions.