Small-angle neutron scattering from micelles of alkylpolyoxyethylene sulfate: Effect of chain length

Small-angle neutron scattering (SANS) data have been obtained for (i) a series of solutions of C _m H_2m+1(OCH₂–CH₂)₂SO₄Na, for m=18, 16, and 14; (ii) an approximately 0.07M solution of C₁₄H₂₉(OCH₂–CH₂)₂SO₄Na to which different amounts of NaCl were added; and (iii) a series of solutions of variable concentration of C₁₂H₂₅(OCH₂–CH₂)SO₄Na. The increase of the number of carbon atoms of the hydrocarbon chain produces a noticeable increase of the aggregation number of the micelles, while the salt tolerance decreases with increasing m. All the data can be described in terms of a monodispersed, charged, hard-spheres model interacting via a screened Coulombic potential, except the run at highest salt concentration, for which an ellipsoid model gives better results.     

Classification of gasoline data obtained by gas chromatography using a piecewise alignment algorithm combined with feature selection and principal component analysis

A fast and objective chemometric classification method is developed and applied to the analysis of gas chromatography (GC) data from five commercial gasoline samples. The gasoline samples serve as model mixtures, whereas the focus is on the development and demonstration of the classification method. The method is based on objective retention time alignment (referred to as piecewise alignment) coupled with analysis of variance (ANOVA) feature selection prior to classification by principal component analysis (PCA) using optimal parameters. The degree-of-class-separation is used as a metric to objectively optimize the alignment and feature selection parameters using a suitable training set thereby reducing user subjectivity, as well as to indicate the success of the PCA clustering and classification. The degree-of-class-separation is calculated using Euclidean distances between the PCA scores of a subset of the replicate runs from two of the five fuel types, i.e., the training set. The unaligned training set that was directly submitted to PCA had a low degree-of-class-separation (0.4), and the PCA scores plot for the raw training set combined with the raw test set failed to correctly cluster the five sample types. After submitting the training set to piecewise alignment, the degree-of-class-separation increased (1.2), but when the same alignment parameters were applied to the training set combined with the test set, the scores plot clustering still did not yield five distinct groups. Applying feature selection to the unaligned training set increased the degree-of-class-separation (4.8), but chemical variations were still obscured by retention time variation and when the same feature selection conditions were used for the training set combined with the test set, only one of the five fuels was clustered correctly. However, piecewise alignment coupled with feature selection yielded a reasonably optimal degree-of-class-separation for the training set (9.2), and when the same alignment and ANOVA parameters were applied to the training set combined with the test set, the PCA scores plot correctly classified the gasoline fingerprints into five distinct clusters.     

Products from the reaction of M3(CO)12 (M = Ru or Os) with water

Reaction of the carbonyl Ru₃(CO)₁₂ with water leads to the formation of polynuclear hydrides α-H₄Ru₄(CO)₁₂, α-H₂Ru₄(CO)₁₃; the corresponding reaction with Os₃(CO)₁₂ yields the complexes (H)(OH)Os₃(CO)₁₀, H₂Os₄(CO)₁₃, H₄Os₄(CO)₁₂, H₂Os₅(CO)₁₆, H₂Os₅(CO)₁₅, H₂Os₆(CO)₁₈ and H₂Os₇(CO)₁₉C.     

Measurements by microdialysis of free tissue concentrations of propranolol.

To determine the free concentration of a drug (propranolol) in the interstitial space in humans in vivo, seven male students were investigated by microdialysis of the periumbilical subcutaneous tissue. The microdialysis catheters were calibrated in vivo and the propranolol concentration was determined by high-performance liquid chromatography. Ten hours after intake of 80 mg of propranolol, the total plasma and free interstitial propranolol concentrations were 80 +/- 43 and 7 +/- 2 nM, respectively. After a second dose, maximum concentration was reached after 80 +/- 10 min and 98 +/- 12 min, in plasma, and the concentrations in the interstitial water were 594 +/- 138 and 27 +/- 7 nM, respectively. In a second study, microdialysis was performed on the left ventricular wall in six pigs receiving an intravenous injection of 5 mg of propranolol followed by a constant propranolol infusion for 40 min (5 mg propranolol per h). The maximum concentrations of propranolol were 97 +/- 29 and 6 +/- 2 nM in plasma and in interstitial water, respectively. The data suggest that microdialysis is a useful tool for recording the free concentrations of a drug in the interstitial space.     

Reactions of 14-hydroxy-14-azadispiro[5.1.5.2]pentadec-9-ene-7,15-dione and related compounds. II

3 When 11-diethyl- and 3, 11-di-n-propyl-14-hydroxy-14-azadispiro[5.1. 5.2]pentadec-9-ene-7, 15-dione (E-IV and n-Pr-IV) are heated with polyphosphoric acid at 55–65°, the 14-hydroxyl group cyclizes at the 11-carbon to form E-VI and n-Pr-VI, the structures of which have been established. Compounds P-IV, i-Pr-IV and t-B-IV do not cyclize under these conditions. The Beckmann rearrangement of 12-hydroxy-12-azadispiro[4.1.4.2]tridec-8-ene-6, 13-dione-6-oxime (P-I) with polyphosphoric acid at 40–50° formed only the normal product, P-II, which could not be cyclized. Compound P-IV was the only ketone of this series which would add hydrogen cyanide to form a cyanohydrin.     

THE CONTROL BY PHYTOCHROME OF NITRATE REDUCTASE IN THE CURD OF LIGHT-GROWN CAULIFLOWER

Abstract— The activity of nitrate reductase from the curd of light-grown cauliflower ( Brassica oleracea (L) var botrytis (DC) 'St. Hilary') is modulated by nitrate and by light. Using broad-band sources of equal photosynthetically active radiation but with different proportions of red and far-red light, a linear relationship between nitrate reductase activity and ψ(Estimated phytochrome photoequilibrium) was obtained. This relationship, apparent after 8 h incubation, was maintained and little altered after 48 h incubation. The linearity was apparent between ψE 0.26 and ψE 0.69; ψE 0.26 being no more effective than a dark control. Far-red reversibility confirmed the involvement of phytochrome. Brief pulses of red light were also used to establish a range of phytochrome photoequilibria within the tissue. Again a linear relationship between ψ and nitrate reductase activity was obtained with a threshold for the response at ψ 0.3. With both monochromatic and broad-band sources it was seen that neither photon fluence rate nor duration of exposure affected the final activity of the enzyme and that phytochrome was acting solely through ψ (or [Pfr] since phytochrome is stable in this tissue) to bring about these responses.     

Products of the reaction of H2Os3(CO)10 with cyclonona-1,2diene

Treatment of H₂Os₃(CO)₁₀ with cyclonona-l,2-diene produced HOs₃(CO)₉C₉H₁₃ and Os₂(CO)₆(C₉H₄)₂. Single crystal X ray analysis has shown that the latter is not isostructural with Fe₂(CO)₆(C₉H₁₄)₂.     

Vacancy contents and phase equilibria of Ti-substituted MnZn ferrite

Measurement of the divalent iron content in acid dissolved MnZn ferrites, fired in controlled atmospheres at various temperatures and quenched, allows calculation of cation vacancy contents. Addition of Ti⁴⁺ to these ferrites resulted in the introduction of vacancies at the rate of about 0 to 0.3 per Ti⁴⁺ depending on heat treatment conditions. Data are presented whereby the vacancy content with Ti⁴⁺ can be calculated based on the oxygen content of the undoped ferrite as available in the literature. Ti⁴⁺ stabilizes the hexagonal hematite-like structure and the phase boundary is presented as a function of Ti⁴⁺ and temperature. The vacancy contents at the phase boundary in Ti⁴⁺-doped ferrite as a function of temperature are in agreement with those calculated from the literature for undoped MnZn ferrites. Finally, the total oxygen content of coexisting spinel and hexagonal phases is presented.     

Adsorption of CF4 on the internal and external surfaces of opened single-walled carbon nanotubes: a vibrational spectroscopy study

Infrared spectroscopy has been used to make the first experimental discrimination between molecules bound by physisorption on the exterior surface of carbon single-walled nanotubes (SWNTs) and molecules bound in the interior. In addition, the selective displacement of the internally bound molecules has been observed as a second adsorbate is added. SWNTs were opened by oxidative treatment with O(3) at room temperature, followed by heating in a vacuum to 873 K. It was found that, at 133 K and 0.033 Torr, CF(4) adsorbs on closed SWNTs, exhibiting its nu(3) asymmetric stretching mode at 1267 cm(-1) (red shift relative to the gas phase, 15 cm(-1)). Adsorption on the nanotube exterior is accompanied by adsorption in the interior in the case of opened SWNTs. Internally bound CF(4) exhibits its nu(3) mode at 1247 cm(-1) (red shift relative to the gas phase, 35 cm(-1)). It was shown that, at 133 K, Xe preferentially displaces internally bound CF(4) species, and this counterintuitive observation was confirmed by molecular simulations. The confinement of CF(4) inside (10,10) single-walled carbon nanotubes does not result in the production of lattice modes that are observed in large 3D ensembles of CF(4).     

Ligand field transitions in PtCl2−4 calculated by the SCF Xα scattered-wave method

The SCF Xα SW method can be used to obtain uniquely all the multiplets arising from the d → d transitions in the square planar metal complex PtCl^2?₄. The agreement with the experimental absorption spectrum and the singlet transition assignments in the region ≈ 3.0–4.5 eV is excellent.