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中华眼科杂志 1956年第5期 470-470页

作者： michaelson.i.c. 唐秀民

根据作者自己的經驗認为,虽然施術者怎样有意識地使环鑽垂直,仍旧是持定环鑽的手的位置,來决定环鑽進入前房第一个穿孔的子午線。这个事实是值得注意的;作者叙述有两种情况,就恰当地应用了这个事实。当移植片快要盖上虹膜前粘連的时候,...

根据作者自己的經驗認为,虽然施術者怎样有意識地使环鑽垂直,仍旧是持定环鑽的手的位置,來决定环鑽進入前房第一个穿孔的子午線。这个事实是值得注意的;作者叙述有两种情况,就恰当地应用了这个事实。当移植片快要盖上虹膜前粘連的时候,需要巧妙地运行刀口,以使粘連恰在第一个穿通处發生。这种办法使粘連較比容易切断,並且能更好地保护晶狀体。

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influence of ice on Soil Elemental characterization via Portable X-Ray Fluorescence Spectrometry

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Pedosphere 2014年第1期24卷 1-12页

作者： D.c.WEiNDORF N.BAKR Y.ZHU A.McWHiRT c.L.PiNG G.michaelson c.NELSON K.SHOOK S.NUSS Texas Tech University Department of Plant and Soil Sciences Louisiana State University Agricultural center University of Alaska Fairbanks Palmer Research Center

Field portable X-ray fluorescence （PXRF） spectrometry has become an increasingly popular technique for in-situ elemental characterization of soils. The technique is fast, portable, and accurate, requiring minimal sample preparation and no consumables. However, soil moisture 〉 20% has been known to cause fluorescence denudation and error in elemental reporting and few studies have evaluated the presence of soil moisture in solid form as ice. Gelisols （USDA Soil Taxonomy）, permafrost-affected soils, cover a large amount of the land surface in the northern and southern hemispheres. Thus, the applicability of PXRF in those areas requires further investigation. PXRF was used to scan the elemental composition （Ba, ca, cr, Fe, K, Mn, Pb, Rb, Sr, Ti, Zn, and Zr） of 13 pedons in central and northern Alaska, USA. Four types of scans were completed： 1） in-situ frozen soil, 2） re-frozen soil in the laboratory, 3） melted soil/water mixture in the laboratory, and 4） moisture-corrected soil. All were then compared to oven dry soil scans. Results showed that the majority of PXRF readings from in-situ, re-frozen, and melted samples were significantly underestimated, compared to the readings on oven dry samples, owing to the interference expected by moisture. However, when the moisture contents were divided into 〉 40% and 〈 40〈 groups, the PXRF readings under different scanning conditions performed better in the group with 〈 40% moisture contents. Most elements of the scans on the melted samples with 〈 40% moisture contents acceptably compared to those of the dry samples, with R2 values ranging from 0.446 （Mn） to 0.930 （St）. However, underestimation of the melted samples was still quite apparent. Moisture-corrected sample PXRF readings provided the best correlation to those of the dry, ground samples as indicated by higher R2 values, lower root mean square errors （RMSEs）, and slopes closer to 1 in linear regression equations. However, the in-situ （frozen） sample scans did not differ

关键词： Gelisols moisture permafrost proximal sensing regression

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in-Situ Differentiation of Acidic and Non-Acidic Tundra via Portable X-ray Fluorescence (PXRF) Spectrometry

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Pedosphere 2016年第4期26卷 549-560页

作者： Somsubhra cHAKRABORTY David c. WEiNDORF GARY J. michaelson chien Lu PiNG Ashok cHOUDHURY Tarek KANDAKJi Autumn AcREE Akriti SHARMA WANG Dandan Uttar Banga Krishi Viswavidyalaya Cooch Behar 736165 Department of Plant and Soil Science Texas Tech University Lubbock TX 79409 University of Alaska Fairbanks Palmer Research Center Palmer AK 99645 Louisiana State University Agricultural center Baton Rouge LA 70803 college of Geography and Remote Sensing Nanjing University of Information Science and Technology Nanjing 210044

Frozen soils or those with permafrost cover large areas of the earth's surface and support unique vegetative ecosystems. Plants growing in such harsh conditions have adapted to small niches, which allow them to survive. in northern Alaska, USA, both moist acidic and non-acidic tundra occur, yet determination of frozen soil p Hs currently requires thawing of the soil so that electrometric pH methods can be utilized. contrariwise, a portable X-ray fluorescence(PXRF) spectrometer was used in this study to assess elemental abundances and relate those characteristics to soil pH through predictive multiple linear regressions. Two operational modes, Soil Mode and Geochem Mode, were utilized to scan frozen soils in-situ and under laboratory conditions, respectively, after soil samples were dried and ground. Results showed that lab scanning produced optimal results with adjusted coefficient of determination(R^2) of 0.88 and 0.33 and root mean squared errors(RMSEs) of 0.87 and 0.34 between elemental data and lab-determined pH for Soil Mode and Geochem Mode, respectively. Even though the presence of ice attenuated fluoresced radiation under field conditions, adjusted R^2 and RMSEs between the datasets still provided reasonable model generalization(e.g., 0.73 and 0.49 for field Geochem Mode). Principal component analysis qualitatively separated multiple sampling sites based on elemental data provided by PXRF, reflecting differences in the chemical composition of the soils studied. Summarily, PXRF can be used for in-situ determination of soil pH in arctic environments without the need for sample modification and thawing. Furthermore, use of PXRF for determination of soil pH may provide higher sample throughput than traditional eletrometric-based methods, while generating elemental data useful for the prediction of multiple soil parameters.

关键词： frozen soil Gelisols Geochem Mode proximal sensing Soil Mode soil pH determination

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Soil Pedon carbon and Nitrogen Data for Alaska: An Analysis and Update

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Open Journal of Soil Science 2013年第2期3卷 132-142页

作者： Gary J. michaelson chien-Lu Ping Mark clark Agriculture and Forestry Experiment Station University of Alaska Fairbanks Palmer Research Center Palmer USA USDA- Natural Resources conservation Service Palmer USA

We combined c and N related pedon data from the USDA-NRcS National cooperative Soil Survey Soil characterization Database with data from the University of Alaska Fairbanks (UAF) northern soils research program, representing 58 and 30 years of field work, respectively. carbon and N data from 117 UAF pedons were added to 541 pedons from the USDA-NRcS data set for a total of 658. Missing carbon (c), nitrogen (N) and related data were added to nearly all of the USDA-NRcS Arctic region pedons from unpublished UAF data. We present relationships among soil parameters of the data set that are necessary for calculation of pedon soil organic c and N stores. These new relationships are necessary for better estimating missing soil bulk density (Db) from measured soil organic c by high-temperature combustion (SOcHTc) and for conversion of acid chromate reduction soil organic carbon (SOcAcR) to SOcHTc. For the USDA-NRcS data, missing Db data were estimated and SOcAcR corrected to SOcHTc using the new functional relationships developed. This allowed for pedon SOc and N stores to be calculated for 609 and 468 Alaska pedons respectively, the most available to-date. Additionally, functional relationships were developed for data within soil orders to estimate total SOcHTc and N stores in pedons with missing surface organic horizons where only thicknesses were known. These relationships are presented in order to fill-in missing data and to better define the existing data set for future use. Some 1904 missing Db data points and 1612 corrected SOcHTc data points were added to the total of 4240 points in the 609 pedons that constitute the updated dataset. When O-layer thickness functions developed here were used, SOc and N stores were calculated for an additional 137 and 184 pedons respectively.

关键词： Soil carbon Soil Nitrogen Arctic Soils Pedotransfer Functions Permafrost Soils

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