Manipulation of avoidance behavior as a function of increased or decreased demand on repeated behavioral tests.

5 groups of 15 female undergraduates reporting fear of snakes participated in 2 behavioral avoidance tests employing a snake as the target object. 4 groups were first tested under low demand for approach and then under the same conditions or under 1 of 3 conditions of demand increase, mediated by instructions, mode of administration, or both. The 5th group was tested under high, then low demand. Ss first tested under low demand showed significantly more fear than those first tested under high demand. In addition, Ss in the demand-increase groups showed significant increases in approach at the 2nd behavior avoidance test, while Ss in the demand-decrease group showed a significant reduction in approach. Ss in the repeated-measure control group showed no significant changes. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of defects on the fatigue crack initiation process in two p/m superalloys: part i. fatigue origins

Two high strength P/M nickel-base superalloys, AF-115 and AF2-1DA, with different defect populations, were tested to determine the effect of preexisting defects on the fatigue crack initiation process. Strain controlled continuous cycle fatigue tests were performed at room and at elevated temperature; these were followed by fractographic examination to characterize both the location and character of the fatigue origins. In most cases, particularly at elevated temperature, the initiation process was associated with a large pre-existing defect, either a pore or a nonmetallic inclusion. There was also a change in the location of the crack that caused failure as the strain range varied: at high strain ranges initiation occurred at or near the specimen’s surface, while at the lower strain ranges the failure originated in the specimen’s interior. The initiation mode for both alloys at room temperature was different than at elevated temperature. At room temperature, Stage I crystallographic cracking at or near the surface dominated the process in all strain range regimes. This difference was attributed, in part, to the differences in deformation mode for nickel-base superalloys at room and elevated temperature. Formerly with Metals and Ceramics Division, Air Force Materials Laboratory, Wright-Patterson AFB, OH.     

Muscle fiber composition and blood ammonia levels after intense exercise in humans

The relationship between fiber type composition and the increase in blood ammonia was examined following a maximal O2 consumption (VO2max) test. Muscle biopsies were taken from the middle portion of the vastus lateralis for determination of fiber type percentages. Two subject groups were selected on the basis of a high (HST) or low (LST) percentage of slow-twitch fibers and compared for blood ammonia and lactate levels after exercise at work loads of approximately 85 and 110% of VO2max. An inverse relationship was found between the percentage of slow-twitch fibers and the increase in blood ammonia. Blood ammonia increased after exercise at both 85 and 110% of VO2max. However, the increase was twofold greater for the LST group following the 110% work effort. The increases in blood ammonia and lactate were positively correlated for both groups following exercise. The results suggest that the proportion of slow-twitch fibers plays an important role in determining the magnitude of the increase in blood ammonia after intense exercise.     

The power of inequality semijoins

Semijoin is a relational operator used in many relational query processing algorithms. Semijoins can be used to “reduce” the database by delimitting portions of the database that contain data relevant to a given query. For some queries, there exist sequences of semijoins that delimit the exact portions of the database needed to answer the query. Such sequences are called full reducers.

This paper considers a class of queries called natural inequality queries (NI queries), and characterizes a subclass for which full reducers exist. We also present an efficient algorithm that decides whether an NI query lies within this subclass, and constructs a full reducer for the query. The NI queries are a subset of the aggregate-free, conjunctive queries of QUEL, and permit join clauses to include <, , =, , >.     

Computers and the 16th-century Chanson a pilot project at the University of Chicago

Conclusions One cardinal principle guided our evaluation of the data provided for us by the computer: never to be deluded into believing that the computer was in any way capable of analyzing a piece of music. Rather, we used the information made available by the computer as a means of substantiating or explaining the insights into a given composition that we gained by means of a direct confrontation with the music. In this way, the data supplied by the computer proved to be very useful in explaining why a particular portion of a chanson generates a sense of tension, while another section of the same piece creates a feeling of rest. Similarly, the electronically derived information was particularly helpful in setting up stylistic profiles of the various composers whose chansons were included in our sampling. In fact, the computer output was instrumental in helping to settle more than one problem of conflicting attributions, largely on the basis of these stylistic profiles. Like any other computerized process, our program elicited from the computer no analytical operation that could not have been done without the assistance of the computer. Very little precise measurement has been done in the analysis of the music of the Renaissance, however, and for good reason: the compilation of statistical data of the type we have described takes so much time that it can be considered feasible only with mechanical assistance. The ability we gained to apply to the chanson repertory a somewhat more precise system of analytical measurement was the most encouraging aspect of the pilot project. candidate for the Ph.D. in Physics     

Correction of increased prostacyclin synthesis in Bartter's syndrome by indomethacin treatment

The role of prostacyclin and thromboxane A2 in the pathogenesis of Bartter's syndrome was investigated by measurement of the urinary excretion of 6-keto-PGF1 alpha and thromboxane B2, respectively, in five patients. The prostaglandin metabolites were extracted from urine by a reproducible method and measured by specific radioimmunoassays. The patients with Bartter's syndrome excreted about four-times as much 6-keto-PGF1 alpha as the normal controls. In contrast, there was no significant difference in the urinary excretion of thromboxane B2 between the patients and the controls. In a second part of the study, three patients were treated with indomethacin (150 mg/day for four days), an inhibitor of prostaglandin synthesis. This regimen suppressed urinary excretion of 6-keto-PGF1 alpha by 43% and that of thromboxane B2 by 46%. It is suggested that the increase in prostacyclin production is responsible for both the hyperreninemia and and the other endocrine derangements as well as the hyporesponsiveness of blood pressure to intravenous infusion of vasopressors in patients with Bartter's syndrome.     

The process of crack initiation and effective grain size for cleavage fracture in pearlitic eutectoid steel

The process of cleavage crack initiation and the character of the effective grain size which controls the fracture toughness of pearlitic eutectoid steel has been investigated using smooth tensile and precracked Charpy impact specimens. The results demonstrated that initial cracking in both specimens was largely the result of shear cracking of pearlite;i.e., localized slip bands in ferrite promoted cracking of the cementite plates, which was then followed by tearing of the adjacent ferrite laths. Such behavior initially results in a fibrous crack. In the tensile specimen, the initiation site was identified as a fibrous region which grew under the applied stress, eventually initiating an unstable cleavage crack. In precracked impact specimens, this critical crack size was much smaller due to the high state of stress near the precrack tip. Fracture mechanics analysis showed that the first one or two dimples formed by the shear cracking process can initiate a cleavage crack. Using thin foil transmission electron microscopy, a cleavage facet was found to be an orientation unit where the ferrites (and the cementites) of contiguous colonies share a common orientation. The size of this orientation unit, which is equal to the cleavage facet size, is controlled by the prior austenite grain size. The influence of austenite grain size on toughness is thus explained by the fact that the austenite grain structure can control the resultant orientation of ferrite and cementite in pearlitic structures. Y.J. PARK, formerly with Carnegie-Mellon University, Pittsburgh, PA.