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121.
DO Gough AG Kosovichev J Toomre E Anderson HM Antia S Basu B Chaboyer SM Chitre J Christensen-Dalsgaard WA Dziembowski A Eff-Darwich JR Elliott PM Giles PR Goode JA Guzik JW Harvey F Hill JW Leibacher MJPFG Monteiro O Richard T Sekii H Shibahashi M Takata MJ Thompson S Vauclair SV Vorontsov 《Science (New York, N.Y.)》1996,272(5266):1296-1300
Global Oscillation Network Group data reveal that the internal structure of the sun can be well represented by a calibrated standard model. However, immediately beneath the convection zone and at the edge of the energy-generating core, the sound-speed variation is somewhat smoother in the sun than it is in the model. This could be a consequence of chemical inhomogeneity that is too severe in the model, perhaps owing to inaccurate modeling of gravitational settling or to neglected macroscopic motion that may be present in the sun. Accurate knowledge of the sun's structure enables inferences to be made about the physics that controls the sun; for example, through the opacity, the equation of state, or wave motion. Those inferences can then be used elsewhere in astrophysics. 相似文献
122.
Bulk icosahedral-quasicrystalline aluminum-palladium-rhenium alloys of high structural quality and thermal stability are found to exhibit low-temperature electrical resistivities that are four orders of magnitude larger than those found in disordered metals and metallic glasses. Experiments suggest that these quasiperiodic alloys, which have a semimetallic electron density, are insulators at low temperature. The findings are discussed in light of theories on electron localization and band-gap formation in ordered metallic systems. 相似文献
123.
DNA identification of commercial ginseng samples 总被引:3,自引:0,他引:3
Mihalov JJ Marderosian AD Pierce JC 《Journal of agricultural and food chemistry》2000,48(8):3744-3752
An investigation was performed with the objective of developing a DNA-based protocol for the identification of commercial samples of the herbal compound ginseng. There are currently two major herbal products referred to as ginseng. They are Korean or Chinese ginseng (Panax ginseng) and American ginseng (Panax quinquefolius). The market for ginseng in the United States is estimated to be approximately $300 million annually. Current tests for ginseng species identification rely on expert botanical identification of fresh plant/root specimens or on biochemical characterization of active and marker compounds (e.g., ginsenosides). For the determination of the feasibility of ginseng identification by DNA analysis, a strategy based on the direct DNA sequence analysis of the nuclear ribosomal internal transcribed spacer region was developed. Other genetic tests included sequence analysis of the chloroplast ribulose 1,5-bisphosphate carboxylase large subunit gene and DNA fingerprinting by the rapid amplification of polymorphic DNA technique. To confirm the results, each ginseng sample was identified using high-performance liquid chromatography. All methods were successful in distinguishing American from Korean ginseng. In addition, the protocol was improved for the isolation of genomic and plastid DNA from commercial ginseng preparations by incorporating an impact homogenization step into the standard column chromatography purification procedure. 相似文献
124.
Yiannis G. Ampatzidis Matthew D. Whiting Bo Liu Patrick A. Scharf Francis J. Pierce 《Precision Agriculture》2013,14(2):162-171
Harvest costs are significant for tree fruit producers and, yet, not well studied. In this paper a prototype system for measuring harvest worker efficiency in sweet cherry (Prunus avium L.) is presented. This weighing system consists of a digital weighing platform compatible with standard commercial fruit bins and a data logger interfaced to a wireless radio. Weight data were transmitted every 5 s, filtered and stored to a laptop computer (database). System functionality and reliability were evaluated in five orchards in cooperation with three commercial growers. Preliminary tests showed that the system did not interfere with normal harvest activities and that the efficiency of pickers and picking teams varied within and across orchard blocks, (e.g. 0.75 to 2.87 kg/min), depending on their experience and skills (e.g. 1.37 kg/min for skilled workers vs. 0.64 kg/min for unskilled). Further, the mean picking rate of ‘Skeena’ without pedicels (stem-free) was 1.15 kg/min, almost 50 % greater than fruit with stems (mean = 0.75 kg/min) when picked by the same crew and orchard. 相似文献
125.
Henrique Silva Silveira Duarte Laércio Zambolim Alexandre Sandri Capucho Antonio Fernandes Nogueira Júnior André Wilson Campos Rosado Carine Rezende Cardoso Pierce Anderson Paul Eduardo Seiti Gomide Mizubuti 《European journal of plant pathology / European Foundation for Plant Pathology》2013,137(2):249-257
Standard area diagrams (SADs) to assess the severity of potato early blight (Alternaria grandis) on leaves of potato (Solanum tuberosum L.) were developed and validated. The proposed SADs include images of leaves with 10 distinct disease severities (0.1, 1, 3, 5, 10, 20, 40, 60, 80 and 100 %). The SADs were validated by 12 raters who had no previous experience in evaluating plant disease. Lin’s concordance correlation analysis of estimated vs. actual disease severity (based on image analysis) showed that precision and accuracy improved for most raters using the SADs, compared to assessments made without the SADs. The SADs improved accuracy (coefficient of bias, C b ?=?0.97 and 0.99, without and with SADs, respectively) and agreement (Lin’s concordance correlation coefficient, ρ c ?=?0.91 and 0.98 without and with SADs, respectively) of the estimates of severity. Severity estimates were more reliable when using SADs (coefficient of determination, R 2 ?=?0.80 unaided and R 2 ?=?0.95 with SADs, and the intra-class correlation ρ?=?0.86 without SADs and ρ?=?0.97 using the SADs). The SADs improved raters’ ability to accurately, precisely and reliably estimate potato early blight severity, and as such can be used to assess severity for several purposes, including breeding for resistance, fungicide screening, and pathotype characterization. 相似文献
126.
与使用无机矿物质相比,在猪饲料中添加有机矿物质可给养猪生产各个阶段的生产性能和环境带来益处。由于有机矿物质具有较好的养分利用率,因此它不仅能使猪的生产性能不受影响,而且还能使养猪生产的净收益得到提高。 相似文献
127.
PO Wennberg TF Hanisco L Jaegle DJ Jacob EJ Hintsa EJ Lanzendorf JG Anderson R Gao ER Keim SG Donnelly LAD Negro DW Fahey SA McKeen RJ Salawitch CR Webster RD May RL Herman MH Proffitt JJ Margitan EL Atlas SM Schauffler F Flocke CT McElroy TP Bui 《Science (New York, N.Y.)》1998,279(5347):49-53
The concentrations of the hydrogen radicals OH and HO2 in the middle and upper troposphere were measured simultaneously with those of NO, O3, CO, H2O, CH4, non-methane hydrocarbons, and with the ultraviolet and visible radiation field. The data allow a direct examination of the processes that produce O3 in this region of the atmosphere. Comparison of the measured concentrations of OH and HO2 with calculations based on their production from water vapor, ozone, and methane demonstrate that these sources are insufficient to explain the observed radical concentrations in the upper troposphere. The photolysis of carbonyl and peroxide compounds transported to this region from the lower troposphere may provide the source of HOx required to sustain the measured abundances of these radical species. The mechanism by which NO affects the production of O3 is also illustrated by the measurements. In the upper tropospheric air masses sampled, the production rate for ozone (determined from the measured concentrations of HO2 and NO) is calculated to be about 1 part per billion by volume each day. This production rate is faster than previously thought and implies that anthropogenic activities that add NO to the upper troposphere, such as biomass burning and aviation, will lead to production of more O3 than expected. 相似文献
128.
A tunable kondo effect in quantum dots 总被引:1,自引:0,他引:1
A tunable Kondo effect has been realized in small quantum dots. A dot can be switched from a Kondo system to a non-Kondo system as the number of electrons on the dot is changed from odd to even. The Kondo temperature can be tuned by means of a gate voltage as a single-particle energy state nears the Fermi energy. Measurements of the temperature and magnetic field dependence of a Coulomb-blockaded dot show good agreement with predictions of both equilibrium and nonequilibrium Kondo effects. 相似文献
129.
A.L. Pierce K.D. Shearer D.M. Baker W.W. Dickhoff 《Fish physiology and biochemistry》2001,25(1):83-88
We examined trends in the growth regulatory hormones growth hormone (GH) and insulin-like growth factor-I (IGF-I) from August
to December in chinook salmon. Fish on 100% (ad libitum) and 64% rations of a low fat high protein diet, and a 64% ration of commercial feed (BioOregon-grower) were sampled twice
a month. Fish were kept on simulated natural photoperiod at constant temperature. GH declined in late August and early September,
consistent with photoperiodic regulation. No effects of ration or diet composition on GH were found. IGF-I increased to a
peak on 4 October 1998 and declined thereafter. High dietary ration and the higher fat commercial diet increased IGF-I. Fish
length and IGF-I level were positively correlated. This study shows that a peak in IGF-I may occur in the fall in chinook
salmon.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
130.