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51.
Human observers were required to discriminate the direction of motion of vertically moving, 1 c/deg luminance and colour gratings. The gratings had different contrasts and moved at temporal frequencies between 0.5 and 32 Hz. Sensitivity [the reciprocal of the contrast at which performance reached 75% correct in a temporal two-alternative forced-choice (2 AFC) discrimination task] was a band-pass function of temporal frequency for luminance gratings, and a low-pass function of temporal frequency for colour gratings. Further, when colour contrast was expressed in terms of the modulation in cone excitation produced by the stimulus, sensitivity to colour gratings was greater than sensitivity to luminance gratings at frequencies below 2 Hz. On the other hand, at temporal frequencies above 4 Hz, sensitivity to colour gratings was comparable with sensitivity to luminance gratings of double the temporal frequency. Detection sensitivity was measured for luminance and colour gratings of 1, 4 and 16 Hz. With either colour or luminance gratings, detection thresholds were very similar to those for direction-of-motion discrimination. This result confirms findings of Mullen and Boulton [(1992) Vision Research, 32, 483-488] and Cavanagh and Anstis [(1991) Vision Research, 31, 2109-2148], but is different from that reported by Lindsey and Teller [(1990) Vision Research, 30, 1751-1761] who used a smaller stimulus seen in a parafoveal region and found that motion discrimination thresholds were higher than detection threshold for colour gratings. We repeated our threshold measurements using parafoveal viewing conditions similar to those used by Lindsey and Teller (1990). We found that, although for luminance gratings detection thresholds were very close to direction-discrimination thresholds, for colour gratings, they were lower. The result is in qualitative agreement with Lindsey and Teller (1990). Our results suggest that low-level, or "first-order" motion mechanisms are not as sensitive to chromatic gratings as are colour-detection mechanisms. 相似文献
52.
Between 1945 and 1970, 101 children (86 girls and 15 boys) with systemic lupus erythematosus were evaluated at the Mayo Clinic. Only 9 children were less than 9 years old at the time of diagnosis. The most frequent presenting complaint was arthralgia; fever, fatigue, and a "butterfly" malar rash also were common. Renal involvement, found in more than 76 per cent of patients, was a prognostically poor sign. The overall survival of children with renal involvement is improved by the use of adequate steroid therapy. 相似文献
53.
Sixty feeder steers were assigned scores for frame size (small, medium or large) and muscle thickness (No. 1, No. 2 or No. 3), fed for 112 days and slaughtered. Grade data were collected for all 60 carcasses; 12 sides (four from each muscle thickness group) were fabricated into boneless, closely trimmed retail cuts and the 12 rounds from each of these sides were also physically separated into muscle, fat and bone. Marbling score and USDA quality grade varied inversely (P < 0·05) with frame size. Carcass quality grades were: 33·3% Choice; 67·7% Good and 0·0% Standard for small-framed cattle; 30·3% Choice, 42·4% Good and 27·3% Standard for medium-framed cattle and 5·5% Choice, 66·7% Good and 27·8% Standard for large-framed cattle. Analysis of variance showed significant (P < 0·05) differences among all muscle thickness groups in the longissimus muscle area and carcass weight but no difference in yield grade between the No. 1 and No. 3 muscle thickness groups; the larger mean longissimus muscle area of carcasses from steers in the No. 1 muscle thickness group was offset by their heavier carcass weight and their greater thickness of fat over the longissimus muscle. However, when analysis of covariance was used to hold fatness or fatness and frame size constant, the difference in yield grade between muscle thickness groups No. 1 and No. 3 was significant (P < 0·05). Also, carcasses from cattle assigned muscle thickness scores of No. 1, as feeders, had the highest (P < 0·05) muscle to bone ratio of the round (4·1 to 1) while carcasses from cattle assigned thickness scores of No. 3, as feeders, had the lowest (P < 0·05) muscle to bone ratio of the round (3·4 to 1). 相似文献
54.
Golden-Kreutz Deanna M.; Thornton Lisa M.; Wells-Di Gregorio Sharla; Frierson Georita M.; Jim Heather S.; Carpenter Kristen M.; Shelby Rebecca A.; Andersen Barbara L. 《Canadian Metallurgical Quarterly》2005,24(3):288
The authors investigated the relationship between stress at initial cancer diagnosis and treatment and subsequent quality of life (QoL). Women (n = 112) randomized to the assessment-only arm of a clinical trial were initially assessed after breast cancer diagnosis and surgery and then reassessed at 4 months (during adjuvant treatment) and 12 months (postadjuvant treatment). There were 3 types of stress measured: number of stressful life events (K. A. Matthews et al., 1997), cancer-related traumatic stress symptoms (M. J. Horowitz, N. Wilner, & W. Alvarez, 1979), and perceived global stress (S. Cohen, T. Kamarck, & R. Mermelstein, 1983). Using hierarchical multiple regressions, the authors found that stress predicted both psychological and physical QoL (J. E. Ware, K. K. Snow, & M. Kosinski, 2000) at the follow-ups (all ps 相似文献
55.
Here, we report a straightforward synthesis process to produce colloidal Eu3+-activated nanophosphors (NPs) for use as bioimaging probes. In this procedure, poly(ethylene glycol) serves as a high-boiling
point solvent allowing for nanoscale particle formation as well as a convenient medium for solvent exchange and subsequent
surface modification. The La(OH)3:Eu3+ NPs produced by this process were ~3.5 nm in diameter as determined by transmission electron microscopy. The NP surface was
coated with aminopropyltriethoxysilane to provide chemical functionality for attachment of biological ligands, improve chemical
stability and prevent surface quenching of luminescent centers. Photoluminescence spectroscopy of the NPs displayed emission
peaks at 597 and 615 nm (λex = 280 nm). The red emission, due to 5D0 → 7F1 and 5D0 → 7F2 transitions, was linear with concentration as observed by imaging with a conventional bioimaging system. To demonstrate the
feasibility of these NPs to serve as optical probes in biological applications, an in vitro experiment was performed with
HeLa cells. NP emission was observed in the cells by fluorescence microscopy. In addition, the NPs displayed no cytotoxicity
over the course of a 48-h MTT cell viability assay. These results suggest that La(OH)3:Eu3+ NPs possess the potential to serve as a luminescent bioimaging probe. 相似文献
56.
Shermane Benjamin Silvina Pagola Zachary Huba Everett Carpenter Tarek Abdel-Fattah 《Synthetic Metals》2011,161(11-12):996-1000
This work describes the synthesis of the green and black polymorphic forms of the tetrathiafulvalene–chloranil (TTF–CA) charge transfer salt as pure phases, by solvent-assisted mechanochemistry. Both materials were characterized using laboratory and high-resolution X-ray powder diffraction (XRPD), elemental analysis and scanning electron microscopy (SEM). The high-resolution XRPD pattern of the TTF–CA black polymorph was indexed with a triclinic lattice a = 10.756(5) Å, b = 11.057(4) Å, c = 6.614(2) Å, α = 101.36(2)°, β = 93.69(3)°, γ = 89.37(3)°, V = 769.6(5) Å3. The chemical stability of these phases upon heating was investigated using thermogravimetric analysis (TGA), elemental analysis and X-ray powder diffraction (XRPD), indicating that both polymorphs undergo chemical decomposition, and ruling out the transition to an air-stable high temperature polymorph. 相似文献
57.
Forty-five steers (9-12 months of age) of Angus (n =15), Brahman (n = 15) and Brahman × Angus (n = 15) breed-types were fed a high-energy diet and then slaughtered after 0, 112 or 224 days of feeding. At 7 days post mortem, the M. longissimus and M. biceps femoris were removed from the left side of each carcass and steaks were obtained for determination of sensory panel ratings, Warner-Bratzler shear force, sarcomere length, collagen content and collagen solubility. Tenderness ratings of steaks from the M. longissimus and M. biceps femoris from Angus were generally higher than ratings for steaks from Brahman or Brahman × Angus steers. Steaks from Brahman × Angus received higher tenderness ratings than steaks from Brahman steers in only a few comparisons. The three breed-types of cattle responded to time-on-feed differently; Brahman cattle needed to have been fed longer than Angus cattle to produce equally tender beef. With increased time-on-feed, M. longissimus tenderness increased for all breed-types, but M. biceps femoris tenderness was not related to time-on-feed. Few significant differences were observed among breed-types and among time-on-feed periods for collagen content or collagen solubility. Tenderness differences were closely correlated with the contractile state of the muscle which, in turn, was associated with weight, subcutaneous fat thickness and temperature decline of the carcass. 相似文献
58.
Incubation of bovine muscle at 37°C promoted a more drastic proteolytic change in myofibrillar proteins, as determined from sodium dodecyl sulphate polyacrylamide gels of isolated myofibrils, than incubation at 4°C. Degradation of myosin and troponin-T were the most noticeable changes at 37°C. Loss of α-actinin was observed in the 4°C incubated muscle. Ground bovine muscle incubated at pH 5·4 and 7 revealed that alterations in myosin and troponin-T were the most noticeable changes at ph 5·4 while troponin-T and α-actinin were altered at pH7. More troponin-T degradation occurred at pH 5·4 and 37°C than at pH7 and 4°C (similar to the degradation of myosin), indicating that troponin-T degradation in post-mortem muscle may be an indicator of overall myofibrillar proteolysis and not responsible for post-mortem tenderisation per se. Myosin degradation in the ground samples incubated at pH 5·4 and in whole samples incubated at 37°C was compared with the digestion of myofibrillar myosin by papain. Both pyrophosphate and Guba-Straub extracts of the 37°C and pH 5·4 treated samples confirmed that myosin degradation did occur to a much greater extent at this temperature and pH than at 4°C and pH7, and, in addition, at pH 5·4 frequent cleavage occurred near the papain sensitive site of myosin. 相似文献
59.
Consumer preferences for beef color and packaging did not affect eating satisfaction 总被引:9,自引:0,他引:9
We investigated whether consumer preferences for beef colors (red, purple, and brown) or for beef packaging systems (modified atmosphere, MAP; vacuum skin pack, VSP; or overwrap with polyvinyl chloride, PVC) influenced taste scores of beef steaks and patties. To test beef color effects, boneless beef top loin steaks (choice) and ground beef patties (20% fat) were packaged in different atmospheres to promote development of red, purple, and brown color. To test effects of package type, steaks and patties were pre-treated with carbon monoxide in MAP to promote development of red color, and some meat was repackaged using VSP or PVC overwrap. The differently colored and packaged meats were separately displayed for members of four consumer panels who evaluated appearance and indicated their likelihood to purchase similar meat. Next, the panelists tasted meat samples from what they had been told were the packaging treatments just observed. However, the meat samples actually served were from a single untreated steak or patty. Thus, any difference in taste scores should reflect expectations established during the visual evaluation. The same ballot and sample coding were used for both the visual and taste evaluations. Color and packaging influenced (P<0.001) appearance scores and likelihood to purchase. Appearance scores were rated red>purple >brown and PVC >VSP>MAP. Appearance scores and likelihood to purchase were correlated (r=0.9). However, color or packaging did not affect (P>0.5) taste scores. Thus, consumer preferences for beef color and packaging influenced likelihood to purchase, but did not bias eating satisfaction. 相似文献
60.
Optically variable windows (smart windows), which control the transmission of light into buildings and vehicles, are of interest both for the control of solar heat load and for privacy applications. Such windows are likely to utilize electrochromic technology to achieve optical control. An electrochromic device consisting of a cathodically colouring tungsten trioxide (WO3) film, an anodically colouring Prussian blue (PB) film, and a polymer electrolyte was made. The polymer electrolyte was prepared from polyvinyl alcohol doped with H3PO4 and KH2PO4 to accommodate the conduction of both H+ and K+ ions. The electrochromic WO3 and PB films functioned in a complementary way such that the device was coloured or bleached by the application of –0.5 V or +0.5 V (WO3 films vs PB film), respectively. The spectral characteristics of the coloured device confirmed the complementary colouration of WO3 and PB in the device. 相似文献