Eliminating pond differences with cross-over designs     

T S Smart  J Riley  G Haylor 《Aquaculture Research》1997,28(8):621-627

Large variability between ponds in aquaculture experiments often leads to imprecise estimates of treatment effects. One solution would be to increase the number of experimental ponds but the availability of ponds is usually limited. A cross-over trial makes comparisons directly within the same pond, instead of across ponds, thus taking account of individual pond effects and potentially removing much of the variability. A cross-over trial was initiated to test the feasibility of using such designs in pond aquaculture research. When compared to a completely randomized design, the cross-over trial was more efficient for comparing the fish growth for each of the two treatments, and, on average, a considerable reduction in the standard error of the treatment estimate was achieved. Thus, under certain circumstances, the cross-over design has great potential to improve the precision of pond aquaculture experimentation.  相似文献   

Feedlot performance of Brahman x Angus versus Angus steers during cold weather     

S L Boyles  J G Riley 《Journal of animal science》1991,69(7):2677-2684

Ten Angus and 10 Brahman x Angus F1 steers were used in a 184-d trial to compare feedlot performance during cold weather (-9 to 26 degrees C). Both groups of steers were exposed to the same environment for the same amount of time. All steers were fed for the same number of days regardless of frame score to avoid frame score x environment interactions. Brahman x Angus steers were 30.7 kg heavier (P less than .05) than Angus steers at the start of the trial. Differences in age (Brahman x Angus 40 d younger) for the two breed groups did not affect final live weight or carcass weight. Brahman x Angus steers consumed .2% less feed (P less than .05) as a percentage of BW than Angus steers; however, there was no difference in overall feed efficiency. Angus steers had a higher yield grade, more fat at the 12th rib (P less than .05), and graded 90% Choice; only 10% of the Brahman x Angus were graded Choice. Brahman x Angus steers were taller at the hip (P less than .05) and longer from first rib to aitch bone (P less than .05) and from thoracic vertebrae (T12/T13) to point of hock (P less than .05). Hide thickness determined at the neck, belly, and rump was found to be similar (7.7 mm) between the two groups. Sample hair weight and diameter did not differ between groups. Fiber, fat, protein, and DM digestibility coefficients were similar between groups but Brahman x Angus feces had a higher DM content.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

Pesticide extraction efficiency of two solid phase disk types after shipping     

Riley MB  Dumas JA  Gbur EE  Massey JH  Mattice JD  Mersie W  Mueller TC  Potter T  Senseman SA  Watson E 《Journal of agricultural and food chemistry》2005,53(13):5079-5083

An interlaboratory study was conducted to compare pesticide recovery from Empore C(18) and Speedisks C(18)XF solid phase extraction disks after shipping. Four pesticides were used for the comparison of the two disk extraction materials: atrazine, diazinon, metolachlor, and tebuconazole. These pesticides were chosen to provide a range of physiochemical properties. Water samples were extracted onto the disk types and shipped to a cooperating laboratory for elution and analysis. The mean recoveries from Empore disks were atrazine, 95%; diazinon, 91%; metolachlor, 92%; and tebuconazole, 83%. The recoveries from Speedisks C(18)XF were atrazine, 89%; diazinon, 87%; metolachlor, 86%; and tebuconazole, 79%. Means for each of the pesticides using the different disk types were not statistically different (alpha = 0.05), but results were more variable when using Speedisks C(18)XF as compared to Empore disks. Reasons for the increased variability are discussed, but overall results indicate that Speedisks C(18)XF could be used as an alternative to Empore disks. Speedisks C(18)XF are enclosed in a plastic housing, so they can be used more easily in remote sampling sites without the possibility of glassware breakage, no prefiltration of samples is needed, and there are realignment problems that can be associated with the Empore disks.  相似文献   

Barriers and flow as limiting factors in the spread of an invasive crayfish (Procambarus clarkii) in southern California streams     

Jacob L. Kerby  Seth P.D. Riley  Paul Wilson 《Biological conservation》2005,126(3):402-409

Invasive crayfish are a major threat to stream ecosystems, yet research has seldom identified successful ways of preventing their spread. Thirty-two stream sections were surveyed during 2000 and 2001 in the Santa Monica Mountains of southern California to determine the distribution of the invasive crayfish Procambarus clarkii. Streams with large barriers (waterfalls, culverts) often did not have crayfish present upstream of barriers. A mark-recapture study indicated that P. clarkii moved both up and downstream between pools, but that barriers significantly reduced movement between pools. Seasonal high flow velocities likely increase passive movement downstream and reduce movement upstream. Results indicate that crayfish mainly spread downstream from a point of colonization and are restricted in their movement to adjacent upstream sections by both natural and artificial barriers. We suggest management strategies for removing invasive crayfish and reducing their spread by focusing on smaller stream segments that are bounded by a downstream barrier and by timing removal efforts to follow large flow events.  相似文献   

Overproduction and elimination of retinal axons in the fetal rhesus monkey   总被引：10，自引：0，他引：10  

P Rakic  K P Riley 《Science (New York, N.Y.)》1983,219(4591):1441-1444

Quantitative electron microscopic analysis reveals 2.85 million retinal axons in fetal rhesus monkeys--a number that is more than twice the 1.2 million present in the adult. More than 1 million supernumerary optic axons are eliminated before birth, simultaneously with the segregation of inputs from the two eyes into separate layers of the lateral geniculate nucleus. Selective elimination of optic axons may not only play a role in the segregation of binocular visual connections but, secondarily, may establish the ratio of crossed and uncrossed retinogeniculate projections.  相似文献   

THE SO-CALLED AEROSTATIC HAIRS OF CERTAIN LEPIDOPTEROUS LARVAe     

Riley WA 《Science (New York, N.Y.)》1913,37(958):715-716

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Experimental Marine Ecology     

Riley GA 《Science (New York, N.Y.)》1963,142(3600):1685-1687

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Don't call them co-eds!     

Riley DM 《Science (New York, N.Y.)》2005,308(5718):50

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Application of Chromatography to Segregation Studies of the Agent of Chicken Tumor I (Rous Sarcoma Virus)     

Riley VT 《Science (New York, N.Y.)》1948,107(2787):573-575

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Vitamin A-induced synthesis of alkaline phosphatase   总被引：1，自引：0，他引：1  

P A Riley  R I Spearman 《Science (New York, N.Y.)》1968,160(831):1006-1007

Incorporation of radioactive leucine into electrophoretically separated proteins from mouse tail epidermis indicates that synthesis of alkaline phosphatase is stimulated by vitamin A. It is suggested that some of the diverse effects of vitamin A may be the result of alkaline phosphatase induction.  相似文献