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41.
Young JF Rosenvold K Stagsted J Nielsen JH Andersen HJ 《Journal of agricultural and food chemistry》2005,53(3):745-749
The present study investigates the combined effects of feed-induced increase in polyunsaturated fatty acids (PUFA) content and/or alpha-tocopherol content in pig muscles and preslaughter stress on cell integrity. Cell integrity was determined by plasma lactate dehydrogenase (LDH) activity, and antioxidative status of muscle was measured by activities of the antioxidative enzymes catalase, superoxide dismutase, and glutathione peroxidase. Preslaughter stress increased LDH activity, reflecting loss in cell membrane integrity independent of increased content of PUFA and/or alpha-tocopherol. However, feed-induced increase of PUFA decreased the LDH activity in plasma immediately after slaughter. Catalase activity in the muscle tissue increased as a consequence of the high-PUFA diet, which may indicate an increased demand caused by introduction of oxidative labile PUFA. 相似文献
42.
Young JF Rosenvold K Stagsted J Steffensen CL Nielsen JH Andersen HJ 《Journal of agricultural and food chemistry》2003,51(23):6877-6881
Polyunsaturated fatty acids (PUFAs) and exercise-induced stress are known to increase the oxidative susceptibility of lipids in muscle tissue. In contrast, antioxidative enzymes, e.g., catalase, superoxide dismutase, and glutathione peroxidase, are known to help sustain the delicate oxidative balance in biological tissue upon the application of stressors. The present study investigates the combined effect of different diet-induced muscle PUFA contents and preslaughter stress on the activity of antioxidative muscle enzymes and the oxidative stability of cooked meat. An increased content of unsaturated fatty acids in the tissue led to a decreased activity of lactate dehydrogenase in the plasma, indicating increased cell integrity. Catalase activity in the muscle tissue increased with increasing PUFA levels. However, this upregulation in antioxidative status of the muscle could not counteract the subsequent development of accelerated lipid oxidation in cooked meat as measured in terms of thiobarbituric acid reactive substances. Moreover, preslaughter stress induced increasing oxidative changes with elevated PUFA levels in the muscle tissue. 相似文献
43.
44.
Bartels RA Paul A Green H Kapteyn HC Murnane MM Backus S Christov IP Liu Y Attwood D Jacobsen C 《Science (New York, N.Y.)》2002,297(5580):376-378
We present spatial coherence measurements of extreme ultraviolet (EUV) light generated through the process of high-harmonic up-conversion of a femtosecond laser. With a phase-matched hollow-fiber geometry, the generated beam was found to exhibit essentially full spatial coherence. The coherence of this laser-like EUV source was shown by recording Gabor holograms of small objects. This work demonstrates the capability to perform EUV holography with a tabletop experimental setup. Such an EUV source, with low divergence and high spatial coherence, can be used for experiments involving high-precision metrology, inspection of optical components for EUV lithography, and microscopy and holography with nanometer resolution. Furthermore, the short time duration of the EUV radiation (a few femtoseconds) will enable EUV microscopy and holography to be performed with ultrahigh time resolution. 相似文献
45.
McNulty I Kirz J Jacobsen C Anderson EH Howells MR Kern DP 《Science (New York, N.Y.)》1992,256(5059):1009-1012
Fourier transform x-ray holography has been used to image gold test objects with submicrometer structure, resolving features as small as 60 nanometers. The hologram-recording instrument uses coherent 3.4-nanometer radiation from the soft x-ray undulator beamline X1A at the National Synchrotron Light Source. The specimen to be imaged is placed near the first-order focal spot produced by a Fresnel zone plate; the other orders, chiefly the zeroth, illuminate the specimen. The wave scattered by the specimen interferes with the spherical reference wave from the focal spot, forming a hologram with fringes of low spatial frequency. The hologram is recorded in digital form by a charge-coupled device camera, and the specimen image is obtained by numerical reconstruction. 相似文献
46.
Kinoshita T Miura A Choi Y Kinoshita Y Cao X Jacobsen SE Fischer RL Kakutani T 《Science (New York, N.Y.)》2004,303(5657):521-523
47.
We used molecular dynamics simulations with system sizes up to 100 million atoms to simulate plastic deformation of nanocrystalline copper. By varying the grain size between 5 and 50 nanometers, we show that the flow stress and thus the strength exhibit a maximum at a grain size of 10 to 15 nanometers. This maximum is because of a shift in the microscopic deformation mechanism from dislocation-mediated plasticity in the coarse-grained material to grain boundary sliding in the nanocrystalline region. The simulations allow us to observe the mechanisms behind the grain-size dependence of the strength of polycrystalline metals. 相似文献
48.
RNA silencing genes control de novo DNA methylation 总被引:1,自引:0,他引:1
Chan SW Zilberman D Xie Z Johansen LK Carrington JC Jacobsen SE 《Science (New York, N.Y.)》2004,303(5662):1336
49.
Alsos IG Eidesen PB Ehrich D Skrede I Westergaard K Jacobsen GH Landvik JY Taberlet P Brochmann C 《Science (New York, N.Y.)》2007,316(5831):1606-1609
The ability of species to track their ecological niche after climate change is a major source of uncertainty in predicting their future distribution. By analyzing DNA fingerprinting (amplified fragment-length polymorphism) of nine plant species, we show that long-distance colonization of a remote arctic archipelago, Svalbard, has occurred repeatedly and from several source regions. Propagules are likely carried by wind and drifting sea ice. The genetic effect of restricted colonization was strongly correlated with the temperature requirements of the species, indicating that establishment limits distribution more than dispersal. Thus, it may be appropriate to assume unlimited dispersal when predicting long-term range shifts in the Arctic. 相似文献
50.
Lin JF Vankó G Jacobsen SD Iota V Struzhkin VV Prakapenka VB Kuznetsov A Yoo CS 《Science (New York, N.Y.)》2007,317(5845):1740-1743
Mineral properties in Earth's lower mantle are affected by iron electronic states, but representative pressures and temperatures have not yet been probed. Spin states of iron in lower-mantle ferropericlase have been measured up to 95 gigapascals and 2000 kelvin with x-ray emission in a laser-heated diamond cell. A gradual spin transition of iron occurs over a pressure-temperature range extending from about 1000 kilometers in depth and 1900 kelvin to 2200 kilometers and 2300 kelvin in the lower mantle. Because low-spin ferropericlase exhibits higher density and faster sound velocities relative to the high-spin ferropericlase, the observed increase in low-spin (Mg,Fe)O at mid-lower mantle conditions would manifest seismically as a lower-mantle spin transition zone characterized by a steeper-than-normal density gradient. 相似文献