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Specimens of pyrolytic graphite (PG) that had been previously used for kinetic oxidation studies, as well as some unoxidized specimens, were examined. The principal topographic features of oxidized PG faces included circular holes with flat bottoms and various depths. Some holes were basin-like at the top. The hole walls were striated showing layers parallel to the deposition surface. The bottom side (i.e., nearest the substrate) was more extensively oxidized than the top, and the hole diameters were an order of magnitude larger. In contrast to these essentially cylindrical pits were a few with the shape of a paraboloid of revolution. The edges had indications of circular holes also. However, a nibbled effect appeared more common. A major feature of a thick specimen was the non-uniformity of attack as a function of distance from the substrate surface. The large scatter of the earlier kinetic data is attributed to this varying reactivity.

Cumene cracking catalyzed by silica-alumina in a differential reactor was studied from 390–500 °C at cumene partial pressures from 0.06–1.00 atm. Four low aluminum concentration catalysts were made by impregnation; a fifth of much higher aluminum concentration was prepared by cogelling. The results are consistent with the rate law given by Prater and Lago; some of the rate law constants were determined. Active sites in the different impregnated catalysts are of the same type, and their number is directly proportional to aluminum concentration. There are fewer, but more active, sites in the cogelled catalyst. If the pre-exponential factor of absolute rate theory holds, then less than 0.01% of the aluminum atoms are associated with active sites in all the catalysts.

A simple derivation of the probability distribution function for the time to accumulate a preset number of counts is outlined. The result is applied to X-ray fluorescence spectrometry in order to estimate the expected precision of the various measures of quantity of an element. Examples are given to show how the results may be used as a practical guide in this field of analytical chemistry.

Two sibs, the children of healthy unrelated parents, have been evaluated because of multiple soft tissue contractures. Both were found to excrete excessive amounts of mucopolysaccharides, primarily heparitin sulfate, and chondroitin sulfate B. Neither had the bony abnormalities characteristic of the other disorders of mucopolysaccharide metabolism, but fine corneal opacities, detected only with the slit lamp, were observed in both children. Intelligence was normal. The clinical and biochemical features found in these 2 sibs were compared to the known types of mucopolysaccharidosis, and it was concluded that a new variant had been detected.

A monozygotic identical twin pair with the 45,XO Turner syndrome is reported. The twins were phenotypically identical, a surprisingly unusual occurrence among monozygotic twins with the Turner syndrome. Monozygotic twinning is apparently the most common form of twinning among reported patients with the Turner syndrome. The high incidence of mosaicism and the dissimilarity between monozygotic twins, at least one of whom had the Turner syndrome, adds support to the concept of zygotic nondisjunction at the primary cytogenetic event in the pathogenesis of most cases of the Turner syndrome.

The US Army Aviation Systems Test Activity conducted the Phase II technical evaluation of the Boeing-Vertol Model 347 winged helicopter during the period 3 through 11 April 1972. The Model 347 winged helicopter, a derivative of the CH-47 transport helicopter incorporating a variable incidence wing with normal acceleration load-sensitive flaps, was tested at the contractor's facility near Philadelphia, Pennsylvania. The evaluation was conducted to determine the improvements provided by addition of a wing system to a transport helicopter. Compliance with the provisions of military specification MIL-H-8501A was determined. Evaluations of the variable incidence wing system and the retractable landing gear system were also made. With the wing in the hover position, out-of-ground-effect hover performance of the Model 347 winged helicopter was similar to the unwinged aircraft. Both the winged and nonwinged Model 347 helicopter could hover out of ground effect using less power than could the CH-47C. Level flight performance at a heavy referred gross weight (54, 000 pounds) was improved over both the nonwinged helicopter and the production CH-47C. Addition of the wing to the Model 347 helicopter did not significantly change the generally excellent handling qualities reported for the nonwinged version of the aircraft. The strong longitudinal stability exhibited by the aircraft reduced pilot workload in maintaining trim airspeed and pitch attitude. Only minimal trim changes in all control axes were required when transitioning between climbs or descents and level flight.

The US Army Aviation Systems Test Activity conducted a limited evaluation of the performance and handling qualities of the Sikorsky S-67 Blackhawk helicopter at a high-altitude test site during the period 8 to 13 July 1972. This evaluation, which required five hours of productive flight time, was performed at Alamosa, Co, at density altitudes of 7830 to 10,790 feet. Except as specifically noted in this report, the performance and handling qualities at high altitude were essentially unchanged from those reported during the previous low-altitude testing.

Because of the possible use of pyrolytic graphite in aerospace vehicles its reaction with oxygen-containing gases is of interest, particularly with respect to chemical anisotropy. Although several authors have found different degrees of reactivity of graphite in different directions they disagree regarding the existence of a temperature coefficient. This disagreement, however, is probably due to investigators studying single crystals in some cases and pyrolytic graphite in others and in some cases different oxidizers. New data for pyrolytic graphite are presented which were obtained by oxidizing in each run several pieces of differing geometry. These together with earlier data show that the rate ratio for the two major directions is temperature dependent with an activation energy difference of about 19 kilojoules (4500 thermochemical calories) per gram atom of carbon reacted. It is shown that this difference in rates probably arises because the relative number of sites available in these directions is sufficiently different to cause a shift in which reaction step is rate-controlling. On the "faces" chemisorption is the rate controlling step followed by rapid decomposition of surface oxides. On the "edges" decomposition is the rate controlling step. This interpretation applied to the data yield 131 kJ/mol for the activation energy of chemisorption and 150 kJ/mol for decomposition (31 and 36 kcal/mol, respectively).

The heat capacity of 2 samples of NH4Cr(SO4)2 12H2O was measured from 18 to 305 K. A second-order transition was found in the region between 92 and 97 K with a heat and entropy of transition equal to 267.4 + or - 0.1 cal and 2.83 + or - 0.1 EU, respectively. The transition tended to disappear under supercooling conditions. The results are compared with the observations of Kraus and Nutting (J. Chem. Phys. 9; 133, 1941). The samples which showed transitions became opaque after a few minutes in the N or H cooling liquid, as though they were broken into an infinite number of tiny crystals by the disruption of the lattice. The production of the multicrystalline material was attributed to a volume change under hysteresis conditions.