eCFR :: 2 CFR Part 200 Subpart D
The aggregate dollar amount of the procurement transaction is higher than the micro-purchase threshold but does not exceed the simplified acquisition threshold. If simplified acquisition procedures are used, price or rate quotations must be obtained from an adequate number of qualified sources.
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Micro-Aggregate Stability in Greenhouse Management
The combination of the macro- and micro-aggregate stability tests is a consistent way for describing the structural stability of the studied soils. View full-text. Preprint. Full-text available.
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Soil water repellency and micro-aggregate fractions in …
Micro-aggregate is the collapse of macro-aggregate, which is regarded as soil aggregates less than 250 μm fractions in size and is typically found in disturbed or cultivated soils (Udom and Anozie, 2018). The distribution of aggregate fractions can indicate the status of soil structure, and the stability of the soil aggregate is commonly ...
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Microaggregate
The organic matter associated with microaggregates (fine clay-sized aggregates < 0.02 μm diameter) has a lower C: N ratio than does silt-associated material (Tiessen and Stewart, 1983). The silt-size aggregate fraction is rich in humic materials and resistant compounds of microbial …
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Quantitative characterization of soil micro-aggregates: New
Micro-computed tomography (micro-CT), with a cross section pixel size in the micrometer 31 range, is an efficient tool to reveal the minute details of soil structure owing to its non-invasive 32 ...
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Architecture of soil microaggregates: Advanced …
The aggregate hierarchy model, prominently exposed by Jarvis et al., is widely accepted, though also critically discussed (Baveye ... (SOM; Weng et al., 2022), soil–root interaction on micro- and nanoscales (Lippold et al., 2023; Vidal et al., 2018), and soil aggregates of different sizes in two-dimensional (2–D) or three-dimensional (3 ...
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Soil aggregate mediates the impacts of land uses on …
Two possible explanations can be suggested: first, small macro-aggregates have more SOC and TN for microbial growth than micro-aggregates ; second, soil microorganisms live in aggregate pores or ...
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Macroaggregate
Mycorrhizal fungi influence the formation or stabilisation of soil at the macro aggregate (53–250 μm) and micro aggregate (< 53 μm) scales with mechanisms that Rillig and Mummey (2006) differentiate into physical (such as altered water regimes and translocation), biochemical and biological processes.
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Linkage of aggregate formation, aggregate-associated C distribution
The large macro-aggregate significantly increased while silt-and-clay particles, micro-aggregates, and small macro-aggregates decreased from day 1 to 7 (Fig. 3), suggesting that large macroaggregates are composed of smaller-sized building units. At the same time, the formation of macroaggregates was accompanied by extensive incorporation of ...
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Organic matter stabilization in soil …
Two-dimensional micro- and nano-scale observations of the C distribution in soil microaggregates have provided new insight into the mechanisms of microaggregate formation and thus stabilization of organic C.
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AASHTO Accreditation Policy and Guidance on Micro …
Sutherland Micro-Deval Fine Aggregate" are within allowed tolerance given below in 11.1.1, the mean value and range obtained with the supply of the in-house calibration aggregate shall be used thereafter. At any time a new supply of the in-house calibration aggregate is required, the calibration procedure shall be conducted. ...
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Microaggregates in soils
We propose a harmonized concept for aggregates in soils that explicitly considers the structure and build-up of microaggregates and the role of organo-mineral associations.
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Soil aggregates as massively concurrent evolutionary …
We define microbial evolution in soil aggregates as any change in the relative allele frequencies or phylotype frequencies of the microbial populations enclosed within an …
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Micro-Deval Test for Evaluating the Quality of Fine …
ness of fine aggregate. The tests studied were the attrition test and a modified version of the French micro-Deval test usually used for coarse aggregate. The micro-Deval test was found to have a significant correlation with magnesium sulfate soundness loss and water absorption of fine aggregate. Unlike the attrition
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Micro- within macro: How micro-aggregation shapes the soil …
Microaggregates are the prerequisites to the formation of complex and openwork aggregate pore space. For the studied soils, when the number of microaggregates is above …
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MICRO-DEVAL COARSE AGGREGATE TEST EVALUATION …
Based on the results of the Micro-Deval testing, it does not appear that the equipment is any more discriminating with respect to aggregate abrasive resistance than the Los Angeles abrasion testing. 17. Key Words Micro-Deval, abrasion test, aggregate test 18. Distribution Statement Available from the ODOT Research Group 19.
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Microaggregate
In preserved blood, microaggregates are formed during storage. Such microaggregates are identified as cellular (platelet conglomerates, leukocyte ghosts, and platelet ghosts with fibrin …
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The Micro–Aggregated Profit Share
aggregate markup, aggregate returns to scale, an aggregate monopsony term—and a sufficient statistic for production networks that captures double marginalization. Our first theoretical result establishes that the aggregate profit share can be con-structed from micro-level data by weighting producers' profit rates—defined as profits
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Thrombocytopenia following routine blood transfusion: micro-aggregate
11 patients with anaemia and thrombocytopenia due to bone marrow failure each received 2 sets of red-cell transfusions. They were randomised to receive 1 blood transfusion through a standard 170-micron giving set filter and another through a 40 micron micro-aggregate filter. After transfusion, the m …
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Micro-Aggregate Stability in Greenhouse Management …
micro-aggregate architecture have major effects on many soil functions, such as water storage and trans-port, cycling of carbon, nitrogen and other plant nutrients [8, 11, 17]. In micro-aggregate, specific compounds having certain chemical functional groups may be responsible for binding organic carbon to min-eral surfaces [11, 22].
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Estimating the influence of related soil properties on macro- and micro
The macro-aggregate stability was determined by wet sieving, and the micro-aggregate distribution was determined via particle size distribution analysis; however, no chemical dispersant (sodium hydroxide) was applied. Using the PLSR models, the main soil properties that affect macro-aggregate and micro-aggregate stability were estimated.
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EQUIPMENT CHECKED: MICRO DEVAL ABRASION …
CONSTRUCTION DIVISION, MATERIALS & PAVEMENTS SECTION (CST/M&P) AGGREGATE IN-HOUSE CALIBRATION PROCEDURE # 19A MICRO DEVAL ABRASION MACHINE AND APPARATUS (CST/M&P) CST/M&P 2 – 3 EFFECTIVE DATE: MAY 2014 3.2 Micro Deval Machine – Calibration Requirement 1. Read all of Section 11 in ASTM D 6928 before continuing.
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Soil Aggregate Microbial Communities: Towards …
We present a framework for understanding aggregate communities as "microbial villages" that are periodically connected through wetting events, allowing for the transfer of genetic material, metabolites, and viruses. We describe both top …
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Soil aggregates as massively concurrent evolutionary incubators
Soil aggregation is a continuous and dynamic process in which the formation and disintegration of individual micro- and macroaggregates are separated in time by periods of relative stability ...
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eCFR :: 2 CFR 200.320 -- Procurement methods.
The aggregate dollar amount of the procurement transaction is higher than the micro-purchase threshold but does not exceed the simplified acquisition threshold. If simplified acquisition procedures are used, price or rate quotations must be obtained from an adequate number of qualified sources.
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Microsurfacing | Explanation & Benefits
The aggregate mix in micro-surfacing restores surface quality and improves skid resistance helping to dramatically reduce accident rates. 9. Seals and Reduces Pavement Oxidation. Asphalt oxidation causes major changes to binder …
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Soil macroaggregate turnover and microaggregate formation…
At time 1 (t 1), macroaggregates (250–2000 μm) are formed around fresh residue which then becomes coarse intra-aggregate particulate organic matter (iPOM) (Fig. 1).The fresh residue induces the formation of macroaggregates because it is a C source for microbial activity and the production of microbial-derived binding agents (Golchin et al., 1994, Jastrow, 1996, Six …
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Micro-Deval Abrasion of Aggregates
MICRO-DEVAL ABRASION OF AGGREGATE TXDOT DESIGNATION: TEX-461-A CONSTRUCTION DIVISION 3 – 5 EFFECTIVE DATE: NOVEMBER 2016 4.3.3 Dry the material in an oven to constant weight, as defined in Section 2.1. 4.3.4 Proceed to Section 4.5. 4.4 Fine Aggregate: 4.4.1 Thoroughly wash a sufficient amount of material to prepare a test sample …
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Evolution of early hydration in mortar by using waste …
Correspondingly, the dolomite powder used as a micro-aggregate at the same water-cement ratio could improve the properties of cement – based materials and reduce the economic cost [12], [13]. Compared to the active SCMs, dolomite powder (CaMg(CO 3 ) 2 ) is an inert mineral material composed of Ca 2+, Mg 2+ and CO 2- 3 ions.
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PRODUCT DATA SHEET Sikacrete®-114 AE
FREE FLOWING MICRO-CONCRETE FOR GROUTING AND REPAIR DESCRIPTION Sikacrete®-114 AE is a one component, free-flowing, high strength, non-shrink, cement based micro-con-crete with a maximum aggregate size of 10 millimeter. Suitable for use in hot and tropical climatic conditions. USES Sikacrete®-114 AE is used for the structural repair of
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