The effect of temperature on the ultraviolet spectrum of sulfur dioxide has been studied over the temperature range 20 to 1000 °C. The equilibrium constant for the reaction[Formula: see text]where (SO 2 ) is an isomeric form or an excited state of sulfur dioxide, has been obtained at several temperatures. The enthalpy change for the transition was found to be 4.1 ± 0.4 kcal mole −1 .
Abstract Since the first scientific paper on Butyl rubber was presented, numerous publications have described the properties and compounding technique of this polymer. Although Butyl has been referred to as a specialty rubber, it can also be used to replace natural rubber in many applications. Butyl was found to be a remarkable barrier to the passage of gases, including air. The polymer also deteriorated very little on aging and had excellent tear resistance. Because of these properties Butyl was first considered for inner tubes, and in this application Butyl has found its largest commercial acceptance. Automobile inner tubes were first made experimentally in September, 1940. With Butyl made in the Standard Oil pilot plant this experimental work continued until April, 1943, when the first government plant began producing Butyl commercially. From that time until the present Butyl has been used successfully to manufacture all types and sizes of inner tubes ranging from bicycle tubes of 1¼-inch cross-section to earth-mover tubes of 24-inch cross-section. Butyl tubes were first used by the United States Army for service in the European war theater in May, 1944. The following month Butyl was used in essential civilian trucks; but not until September, 1945, was sufficient Butyl available for civilian automobile tubes.
A metamaterial surface formed by three slot gratings at 60° to each other has two possible high-symmetry arrangements. One forms equilateral triangular metal patches, the other a combination of hexagons and small equilateral triangles. When spaced above a ground plane with a thin dielectric spacer both structures give strong microwave absorption at certain resonant frequencies, which is largely angle independent. The results of microwave reflectivity measurements are here presented for the two distinct sample geometries and compared with predictions from finite element method models.
Per- and polyfluoroalkyl substances (PFAS) are found in many consumer and industrial products. While some PFAS, notably perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), are developmentally toxic in mammals, the vast majority of PFAS have not been evaluated for developmental toxicity potential. A concentration-response study of 182 unique PFAS chemicals using the zebrafish medium-throughput, developmental vertebrate toxicity assay was conducted to investigate chemical structural identifiers for toxicity. Embryos were exposed to each PFAS compound (≤100 μM) beginning on the day of fertilization. At 6 days post-fertilization (dpf), two independent observers graded developmental landmarks for each larva (e.g., mortality, hatching, swim bladder inflation, edema, abnormal spine/tail, or craniofacial structure). Thirty percent of the PFAS were developmentally toxic, but there was no enrichment of any OECD structural category. PFOS was developmentally toxic (benchmark concentration [BMC] = 7.48 μM); however, other chemicals were more potent: perfluorooctanesulfonamide (PFOSA), N-methylperfluorooctane sulfonamide (N-MeFOSA), ((perfluorooctyl)ethyl)phosphonic acid, perfluoro-3,6,9-trioxatridecanoic acid, and perfluorohexane sulfonamide. The developmental toxicity profile for these more potent PFAS is largely unexplored in mammals and other species. Based on these zebrafish developmental toxicity results, additional screening may be warranted to understand the toxicity profile of these chemicals in other species.
Abstract A cone calorimeter is used to determine the fire performance of polymer composite materials containing combustible reinforcing fibres in addition to combustible matrix resins. Extended‐chain polyethylene and aramid fibre‐reinforced composites containing epoxy, vinylester and phenolic matrix resins are examined at various cone irradiances. Values for time to ignition, rate of heat release, effective heat of combustion, smoke density and evolved carbon monoxide and carbon dioxide are reported for the reinforcements, matrix resins and composites. The reinforcements have a significant effect on the fire‐hazard properties of the composite materials. For the epoxy and vinylester composites, times to ignition reflect those of the component of higher ignitability. This was not the case for the aramid‐reinforced phenolic composite, in which the resin surface layer hinders combustion of the fabric reinforcement. Resin and reinforcement contributions to the composite rate of heat release behaviour as a function of time are generally discernible.
'/%3e%3c/defs%3e%3cpath fill='%23012169' d='M0 0h10080v5040H0z'/%3e%3cpath stroke='%23fff' stroke-width='.6' d='m0 0 6 3m0-3L0 3' clip-path='url(%23b)' transform='scale(840)'/%3e%3cpath stroke='%23e4002b' stroke-width='.4' d='m0 0 6 3m0-3L0 3' clip-path='url(%23c)' transform='scale(840)'/%3e%3cpath stroke='%23fff' stroke-width='840' d='M2520 0v2520M0 1260h5040'/%3e%3cpath stroke='%23e4002b' stroke-width='504' d='M2520 0v2520M0 1260h5040'/%3e%3cg fill='%23fff'%3e%3cuse xlink:href='%23d' x='2520' y='3780'/%3e%3cuse xlink:href='%23a' x='7560' y='4200'/%3e%3cuse xlink:href='%23a' x='6300' y='2205'/%3e%3cuse xlink:href='%23a' x='7560' y='840'/%3e%3cuse xlink:href='%23a' x='8680' y='1869'/%3e%3cuse xlink:href='%23e' x='8064' y='2730'/%3e%3c/g%3e%3c/svg%3e)
'%3e%3cpath fill='%23012169' d='M0 0v30h60V0z'/%3e%3cpath stroke='%23fff' stroke-width='6' d='m0 0 60 30m0-30L0 30'/%3e%3cpath stroke='%23C8102E' stroke-width='4' d='m0 0 60 30m0-30L0 30' clip-path='url(%23b)'/%3e%3cpath stroke='%23fff' stroke-width='10' d='M30 0v30M0 15h60'/%3e%3cpath stroke='%23C8102E' stroke-width='6' d='M30 0v30M0 15h60'/%3e%3c/g%3e%3c/svg%3e)