Relaxations in the transition region of crosslinked polyesters. II. The glass transition

The glass-transition region of crosslinked polymers prepared from poly(1,2-propylene phthalate fumarate) and styrene was studied using a torsion pendulum. The glass-transition temperature and the modulus in the rubbery region of these polymers were analyzed in terms of the crosslink density. The styrene concentration at which the maximum crosslink density occurs, as estimated from the viscoelastic data, is found to be in agreement with estimates made by other workers using chemical methods.     

Long range substituent-induced chemical shifts in the 13C NMR spectra of N-benzylidenebenzylamines

Carbon-13 chemical shifts for N-benzylidenebenzylamines are affected by substituents up to eleven bonds away from the substituent group. The data correlate well with Hammett constants.     

A study of SO2 adsorption on CaO (100) surfaces using X-ray photoelectron spectroscopy

The adsorption of SO₂ on CaO (100) at 300 K has been studied using X-ray photoelectron spectroscopy. Under ultrahigh-vacuum conditions, the surface was exposed to 0–500 Langmuirs of SO₂. The resulting adsorption yields a single SO surface species with an S 2p peak at 168.2 eV and an O 1s_{$\text{sol1}\text{2}$} peak at 531.7 eV. Subsequent heating of the exposed surface to 673 K indicated no desorption or changes in the binding energies of the S 2p and O 1s_{$\text{1}\text{2}$} peaks. On the basis of these data and binding-energy data for standard compounds, the adsorbed species is identified as SO₄^2?. The surface coverage due to the SO₄^2? species was also measured as a function of SO₂ exposure. From these data, the initial adsorption is found to be first-order in surface coverage, and the initial sticking probability is found to have a value of 0.4.     

Education for Operational Research. A Practitioner's Viewpoint

University education for operational research in Britain is making great and welcome strides forward, but there has been little open discussion of its aims in relation to the advance of the profession. Progress in operational research, and in its application to the really worth-while problems of industry in particular, depends primarily on strengthening the industrial operational research group in its “front line” role. We need a research study of the teaching and practice of industrial operational research, in relation to effectiveness. We need “collaborative” programmes of operational research education in which the university and the industrial operational research group each contribute, in a man's training over a period of years, in the ways in which each is most competent. We need emphasis on “breadth” as well as “depth” in operational research education, and greater attention to the mutual contributions of operational research, teaching and practice, and the teaching and development of management. An impressionist sketch of a programme which might meet these needs is put forward for discussion of principles and feasibility.     

Analysis of ochres from Clearwell Caves: the role of particle size in determining colour

Three ochre samples (A (orange-red in colour), B (red) and C (purple)) from Clearwell Caves, (Gloucestershire, UK) have been examined using an integrated analytical methodology based on the techniques of IR and diffuse reflectance UV-visible-NIR spectroscopy, X-ray diffraction, elemental analysis by ICP-AES and particle size analysis. It is shown that the chromophore in each case is haematite. The differences in colour may be accounted for by (i) different mineralogical and chemical composition in the case of the orange ochre, where higher levels of dolomite and copper are seen and (ii) an unusual particle size distribution in the case of the purple ochre. When the purple ochre was ground to give the same particle size distribution as the red ochre then the colours of the two samples became indistinguishable. An analysis has now been completed of a range of ochre samples with colours from yellow to purple from the important site of Clearwell Caves.     

Microwave spectrum of 2-chloropyridine

The microwave spectrum of 2-chloropyridine, C₅H₄NCl, has been studied in the frequency range from 26.5–40.0 GHz. The spectrum is characterized by strong parallel type transitions of a near-prolate asymmetric top. The assigned transitions have been used to evaluate the ground state rotational constants of the two chlorine isotopes. The rotational constants are (in MHz): A = 5872.52, B = 1637.83, C = 1280.48 for the ³⁵Cl isotopic species and A = 5872.16, B = 1591.76, C = 1252.17 for the ³⁷Cl isotopic species. The small inertial defect indicates the molecule is planar. In addition an excited vibrational state of C₅H₄N³⁵Cl has been observed and analyzed. The chlorine quadrupolar coupling constants were determined for the ground state and are: χ_aa = ?71.9 MHz for ³⁵Cl and χ_aa = ?54.9 MHz for ³⁷Cl. By assuming the pyridine ring structure the CCl bond length is found to be 1.72 Å.     

Low-temperature relaxations in styrene-crosslinked polyester networks. III. Influence of water concentration and chemical structure on the γ relaxation

The intensity of the water-induced γ relaxation (see ref. 1) in crosslinked polyester networks in creases rapidly at low water concentrations (0 to 0.5% by weight). At higher water concentrations (0.5 to 3.0%) the intensity of the γ relaxation approaches a constant value. The shift of the relaxation peak to lower temperatures shows a similar pattern of behavior. These results have been related to the fraction of water involved in the relaxation and the changing nature of the relaxation sites with the increase in water concentration. The important role that fumarate units play in the γ relaxation has also been confirmed; however, the chemical nature of the relaxing unit appears to be more complex than was originally considered. Two models are proposed for this behavior.