Organic Rankine cycle receiver development

The selected receiver concept is a direct-heated, once-through, monotube boiler operated at supercritical pressure. The cavity is formed by a cylindrical copper shell and backwall, with stainless steel tubing brazed to the outside surface. This core is surrounded by lightweight refractory insulation, load-bearing struts, and an outer case. The aperture plate is made of copper to provide long life by conduction and reradiation of heat away from the aperture lip. The receiver thermal efficiency is estimated to be 97 percent at rated conditions (energy transferred to toluene divided by energy incident on aperture opening). Development of the core manufacturing and corrosion protection methods is complete

Effects of real-time thermal aging on graphite/polyimide composites

As part of a program to evaluate high-temperature advanced composites for use on supersonic cruise transport aircraft, two graphite/polyimide composites have been aged at elevated temperatures for times up to 5.7 years. Work on the first, HT-S/710 graphite/polyimide, was started in 1974. Evaluation of the second polyimide, Celion 6000/LARC-160, began in 1980. Baseline properties are presented, including unnotched and notched tensile data as a function of temperature, compression, flexure, shear, and constant-amplitude fatigue data at R = 0.1 and R = -1. Tensile specimens were aged in ovens where pressure and aging temperatures were controlled for various times up to and including 50,000 hours. Changes in tensile strength were determined and plotted as a function of aging time. The HT-S/710 composite aged at 450 F and 550 F if compared to the Celion 6000/LARC-160 composite aged at 350 F and 450 F. After tensile testing, many of the thermal aging specimens were examined using a scanning electron microscope. Results of these studies are presented, and changes in properties and degradation mechanisms during high-temperature aging are discussed and illustrated using metallographic techniques

Promoting Economic Mobility by Increasing Postsecondary Education

Explores policy options for expanding educational opportunities for low-income students to enhance upward economic mobility. Examines the effectiveness of student aid in promoting college completion and proposes a plan for better guidance and preparation

Plasmodial incompatibility in the myxomycetes: a review

Two myxomycete phaneroplasmodia of the same species undergo somatic fusion only if they are phenotypically identical for a complex genetic incompatibility system. This system consists of a three tiered polygenic complex with dominant and recessive alleles. Thus, plasmodia must be phenotypically identical for approximately 16 loci in order to fuse (CC and Cc are phenotypically identical, but different from cc). The first level of the system (having a minimum of seven Fus loci) controls membrane fusion, and it apparently prevents fusion unless the two plasmodia have identical membrane or slime sheath components. The second level (having a minimum of six Cz loci) produces a rapid lysis of a small mixed region, of the two plasmodia, if membrane fusion has occurred. This lysis is directional in that it targets the recessive phenotype, and it is apparently triggered by some pre-formed substances when they come into contact with a different plasmodium. The third level (having a minimum of three Let loci) comes into play if membrane fusion occurs and there is no rapid lysis of the mixed plasmodium. It produces a slow lethal reaction, which targets and degrades the nuclei of the recessive phenotype. This reaction occurs over a period of five to twenty hours and requires the synthesis of new RNA and proteins. Since, this complex system produces a minimum of 65,536 different incompatibility phenotypes, it is highly unlikely that any two phaneroplasmodia will undergo a successful fusion unless they are very closely related. Species with aphaneroplasmoida apparently have a similar system, but species with small protoplasmodia do not appear to undergo any type of plasmodial fusion

Translocation of Coumarin Across a Graft Union m Sweetclover

Despite several recent investigations of the biosynthesis of coumarin and related compounds in sweetclover, little is known of the site or sites within the plant at which coumarin is formed. Weygand and Wendt reported coumarin formation in root cultures of Melilotus officinalis (L.) Lam. when suitable precursors were supplied. Mothes and Kala concluded that scopoletin and umbelliferone, compounds closely related to coumarin, can be synthesized by root cultures of Atropa belladonna L. The experiments cited gave no indication that the roots are the preferred site of synthesis or that synthesis takes place at all in the roots of intact plants. Neither of the studies excluded the possibility of synthesis in other organs

Potential of Utilizing Scrap Processed Cheese as a Major Ration Component for Channel Catfish

Three cages (0.9 m³) were stocked with 200 channel catfish, Ictalurus punctatus Rafinesque, fingerlings (73.7 g avg.) in a 1.5 hectare pond. Two cheese rations were formulated and fed to the catfish; the first consisting of cheese, oil, and vitamin C (C + VC)and the second consisting of cheese, cottonseed meal, oil, trace minerals, and vitamins (CC + VM). A commercial trout ration (TC) was fed as a control. High mortalities occurred in the C + VC diet, thus resulting in premature removal of that cage from the study (after 86 days). A sample of 50 fish from the two remaining cages, along with harvest data from the C + VC diet, revealed a 45.6% difference in average fish weight between the C + VC and CC + VM diets, a 63.5% difference between the C + VC diet and TC ration, and 32.9% difference between the CC + VM diet and TC ration. Final harvest of CC + VM and TC cages was completed after 134 days. Comparisons revealed that a 38.3% difference in average fish weight existed between these two diets. Statistical analysis of data indicated that fish fed the CC + VM diet had a significantly lower percentage dress-out weight and a significantly higher amount of mesenteric fat. This experiment does suggest that cheese scraps, when properly balanced with other essential ingredients, may be utilized as a major component of catfish rations

Influence of Seed Size, Planting Depth, and Companion Crop on Emergence and Vigor of Seedlings in Sweetclover

Seed size has been shown to have an important influence on the emergence and early growth of seedlings of several forage legumes, but only fragmentary information on seed size effects in sweetclover (Melilotus spp.) has been published. Therefore, a 2-year study was conducted in which spring and fall seedings of small, medium, and large seeds of \u27Madrid\u27 and \u27N13\u27 sweetclover (Melilotus officinalis (L.) Lam.) were made at depths of 19, 38, and 57 mm. The spring seeding also included a comparison of a companion crop (oats) with no companion crop. Data on emergence score and plant height were collected for the spring seeding only; stand count and dry matter yield of tops and roots were measured for both spring and fall seedings. The companion crop had little effect on emergence score, but it reduced stand count and plant height, and was highly detrimental to dry matter yield. The performance of Madrid was poorer in all respects than that of N13, an experimental cultivar with relatively large seeds. As planting depth was increased, stand counts decreased, but the performance of plants that emerged from the greater depths was relatively good. The most striking results of increased seed size appeared to be improved emergence score and increased dry matter production

Rapid Detection of o-Hydroxycinnamic Acid and Beta-Glucosidase in \u3ci\u3eMelilotus alba\u3c/i\u3e

The tests utilize small samples of leaf tissue crushed on sheets of filter paper. For detection of o-hydroxycinnamic acid (o-HCA), a crude preparation containing sweetclover β-glucosidase is added to a spot of crushed tissue to insure hydrolysis of glucosidically bound o-HCA. An extract containing cis-o-HCA glucoside is added to another tissue spot to serve as the substrate for the detection of β-glucosidase activity. Finally, all spots are moistened with NaOH and are scored for fluorescence under ultraviolet light. Results of qualitative and quantitative tests on plants representing various genotypes are compared. The importance of exposing plants to sunlight before testing for o-HCA is discussed. The tests are particularly useful in genetic studies, in the development and maintenance of breeding lines, and in testing for contamination in low-o-HCA sweetclover varieties