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The objectives were to determine whether the frequency of atypical aberrant plants of Kentucky bluegrass (Poa pratensisL.) was affected by geographic origin of genotypes and by seed production environments. An increase in frequency of aberrants may adversely affect seed certification of production fields established outside the area of geographic origin of apomictic cultivars. Seed was produced in seven states for open‐pollinated progeny tests of highly apomictic and diverse clones. Progenies were grown at Beltsville, Md., and near State College, Pa. Plants of each progeny were classified as typical apomictic, aberrant, or weak. The frequency of aberrant plus weak plants (13.6%) was higher at locations (Alabama and Kentucky) with wide overall anthesis range (at least 4 weeks) and short photoperiod than the frequency (7.2%) at locations (Maryland, New Hampshire, and Vermont) with narrow anthesis range (6 to 9 days) and long photoperiod (> 14.5 hours). The frequency of aberrant and weak plants was considerably higher for four clones (13.6%) than for the remaining five (5.0%). Clones with high frequency of aberrants traced to widely diverse origin. The results indicate that the frequency of aberrant progeny of Kentucky bluegrass is not adversely affected when seed is produced outside the area of geographic origin of a cultivar. Seed produced on 40 plants scored as weak was used to ascertain whether weak plants were typical or aberrant. Only two plants produced typical progeny; the remaining 38 produced segregating apomictic or sexual progenies. Although most weak plants were aberrant and would probably not become established under competitive conditions with typical apomictic progeny, aberrant and weak plants should be rogued from space‐planted fields that are used for the production of breeder seed. Cytological examination of megasporogenesis was inconclusive in regards to the hypothesis that environments influence the initiation of aposporous nucellar cells. Examination of embryo development failed to distinguish possible effects of either genotype or environment on relative frequency of apomictic and sexual reproduction of ovules.

The purpose of this research was to ascertain the genetic control of reproductive tiller production in orchardgrass (Dactylis glomerataL.) and to determine whether sparse panicle production affects.forage yield and quality. We postulated that sparse‐flowering synthetic would retain forage quality longer than normal cultivars as reproductive tillers mature in late spring and early summer. In the greenhouse, up to 12 weeks of cool, short days were required before some orchardgrass plants would flower under long‐day conditions. The response of progeny from three crosses to floral induction treatments suggested that a complex interaction of genetic and environmental factors controls the onset and rate of reproductive tiller production. Reciprocal differences were not observed. Syn 2 generation of synthetics, that produced relatively few flowering tillers when grown in the northeastern USA, flowered and produced satisfactory seed yields at Prosser, Wash. In the field under a hay management cutting system, the most sparse‐flowering synthetic had slightly lower first harvest forage yield in June. than the check cultivars, possibly because dry matter was produced rapidly by the flowering culms of the cultivars. The absence of significant differences among entries for in vitro dry matter disappearance or lignin concentration suggests that the synthetics and cultivars were similar in forage quality. Thus, the experimental strains exhibited no apparent improvement in forage production or quality.

The location of the active site of membrane-bound activated protein C (APC) relative to the phospholipid surface was determined both in the presence and absence of its cofactor, protein S, using fluorescence resonance energy transfer (FRET). APC was chemically modified to create the FRET donor species, Fl-FPR-APC, with a fluorescein dye (Fl) covalently attached to the active site via a D-Phe-Pro-Arg (FPR) tether and located in the active site near S4. FRET was observed when Fl-FPR-APC was titrated in the presence of Ca2+ ions with phosphatidylcholine/phosphatidylserine (4:1) vesicles containing the FRET acceptor, octadecylrhodamine (OR). Assuming a random orientation of transition dipoles (kappa2 = 2/3), the average distance of closest approach between the fluorescein in the active site of the membrane-bound APC and the OR at the membrane surface is 94 A. The same calcium-dependent distance was obtained for both small and large unilamellar vesicles and for vesicles that contained phosphatidylethanolamine. The active site of membrane-bound APC is therefore located far above the phospholipid surface. Upon addition of protein S, the efficiency of Fl-FPR-APC to OR energy transfer increased due to a protein S-dependent rotational and/or translational movement of the APC protease domain relative to the surface. If this movement were solely translational, then the average height of the fluorescein in the membrane-bound APC.protein S complex would be 84 A above the surface. The extent of Fl-FPR-APC to OR energy transfer was unaltered by the addition of thrombin-inactivated protein S. The protein S effect was also specific for APC, since the addition of protein S to similarly-labeled derivatives of factor Xa, factor IXa, or factor VIIa did not alter the locations of their active sites. This direct measurement demonstrates that the binding of the protein S cofactor to its cognate enzyme elicits a relocation of the active site of APC relative to the membrane surface and thereby provides a structural explanation for the recently observed protein S-dependent change in the site of factor Va cleavage by APC.

The rat liver microsomal vitamin K-dependent carboxylase catalyzes the carboxylation of peptide-bound glutamyl residues to gamma-carboxyglutamyl (Gla) residues with the concomitant formation of vitamin K 2,3-epoxide (KO). These studies have demonstrated that the half-reaction, formation of KO, occurs in the absence of carboxylation at low glutamyl substrate concentration but that the ratio of KO/Gla approaches unity as the glutamyl substrate concentration is increased. Utilization of the carboxylase substrate Phe-Leu-[gamma-3H] Glu-Glu-Leu has demonstrated that the ratios of KO/gamma-C-H bonds cleaved and Gla/gamma-C-H bonds cleaved are equivalent at high substrate concentrations and that these ratios approach unity. At low substrate concentrations, KO formation occurs at a higher rate than gamma-H bond cleavage. These data are consistent with a mechanism involving the formation of an oxygenated intermediate from vitamin KH2 and O2 that is converted to KO during hydrogen abstraction from the gamma-position of the Glu substrate. In the absence of a Glu substrate, the intermediate is converted to KO by a mechanism not coupled to glutamyl activation.

The essential ingredient missing in existing prediction methods for the performance of multistage axial compressors is that which would account for the effect of end-wall boundary layers. It is, in fact, believed that end-wall boundary layers play a major role in compressor performance and the absence of an adequate theory represents a handicap to turbomachinery designers that might be likened to the handicap that designers of wings, for example, would face if Prandtl had not introduced the idea of a boundary layer. In this paper a new theory is developed which retains all elements of classical boundary layer theory; for example, we discuss variables such as momentum thickness and wall shear stress. However, the present theory introduces new concepts such as axial and tangential defect force thickness, a rotor exit-stator inlet “jump condition” and the importance of these concepts is demonstrated. Inherent in the derivation is an identification of the role of secondary flow and tip clearance flow. A proper means of matching the boundary layer calculations to conventional main stream calculations is suggested. Independent of empirical parametization it appears that the theory is capable of correctly modeling boundary layer blockage, losses, and end-wall stall. Near stall, the main stream-boundary layer interaction is very strong.

A centrifugal compressor stage with an unusually high inlet hub/tip ratio of 0.87 was designed for a pressure ratio of 2.0 at a corrected mass flow of 2.45 lb per sec. The geometry was selected so that the centrifugal stage could replace several of the last stages of a multistage axial compressor. The stage was tested with two diffuser schemes. One diffuser consisted of a series of drilled conical pipes, whereas the other employed multirow vaned cascades. Sea level aerodynamic tests of the compressor stage with each diffuser showed a peak total-to-total efficiency at design speed of 83.8 percent for the pipe diffuser and 82.9 percent for the vaned cascade diffuser. Additional tests were conducted with a vaneless diffuser to determine effects of impeller discharge tip clearance and inlet prewhirl on impeller performance.

Several design models of centrifugal pump impellers were tested in water to determine tip-clearance effects on noncavitating and cavitating performance. Although most of these impellers were designed without tip shrouds, three direct comparisons for shrouded versus unshrouded models are included. Within the scope of this investigation, varying degrees of tip clearance produced dissimilar trends in the hydraulic performance for the different design models tested. Fully shrouded impellers consistently yielded inferior cavitation performance as compared to unshrouded versions.

A mixed flow impeller design was tested with six, five, and four vanes in a closed water loop to study the effects of cavitation on hydraulic performance and the results were compared with the work of other investigators. Two idealized flow models for incipient cavitation were derived to illustrate limits of cavitation design. It was found that both vane blockage and solidity effects are important when designing for optimum cavitation performance. Data showing incidence and speed effects plus the tip static pressure profiles in cavitating and noncavitating flow are also presented.

The cavitation damage resistance of alloys of aluminum, columbium (niobium), tantalum, molybdenum, and stainless steel was evaluated in water using a rotating disk apparatus that simulated the cavitation vortex patterns encountered in pumps operating at high suction specific speed. The alloys in decreasing order of cavitation resistance were Ta-8W-2Hf, Cb-18W-8Hf, Ta-10W, 316SS, Mo-.5Ti, Cb-1Zr, Al-4Cu-.7Mn-.5Mg, and Al-2.5Mg-.25Cr. The damage resistance order does not follow the variation of any single property such as strain energy to failure, yield strength, or hardness, but appears to be a combination of mechanical properties and phase structure. Photomicrographs show predominant intergranular cracking for the molybdenum alloy and transgranular erosion and cracking for the remaining alloys tested. The second phase precipitate in the aluminum alloy appears to hinder the erosion of material. Investigation of small variations in the grain size of the heat-treated Cb-1Zr alloys resulted in some variation in damage resistance, with the largest grain structure exhibiting the highest resistance. Correlation curves of volume loss as a function of the peripheral velocity are presented for all materials tested. In addition, the operation of the rotating disk apparatus itself was examined in considerable detail and the effects of various design changes were evaluated.

High performance, mobile, nuclear power plants utilizing liquid metals require high temperature pumps to circulate these heat transport fluids. These pumps must have moderately high efficiency, small size, low weight, and high reliability. In order to satisfy these requirements, centrifugal pumps directly coupled to gas turbines are utilized. As part of the aircraft nuclear power plant development program, the 3000 gpm stainless steel turbopump described in this paper was designed and tested in NaK at temperatures up to 1300 F.

The circulation of the liquid-metal heat-transport fluids used in high-performance, mobile, nuclear power plants requires high-temperature pumps. These pumps must be capable of moderately high efficiency over a very long lifetime and have small size, low weight, and high reliability. As an initial phase of a lithium pump development program and to provide pumps for companion development programs, a 195-gpm pump was designed and successfully developed. Extensive testing of pump components, as well as water and liquid-metal tests of complete pump assemblies, was accomplished to meet the program objectives of high performance and high reliability for the required long operating lifetime. Several successful lithium tests of 10,000-hr duration were accomplished with the lithium development pumps and a pump used in a companion heat-exchanger development program.

Three mixed flow impellers representing a wide range of design parameters were tested in a closed water loop to obtain correlations of the high-speed photographic records of the cavitation formations with various performance parameters. It was found that cavitation existed for all impellers at much higher values of NPSH than those associated with a finite drop in the impeller head rise. The cavitation formations in the vane channels of the impellers were observed to be cyclic in nature, whereas the cavitation near the leading edge of the vanes was more stable.