In situ observation of synthesized nanoparticles in ultra-dilute aerosols via X-ray scattering

In-air epitaxy of nanostructures (Aerotaxy) has recently emerged as a viable route for fast, large-scale production. In this study, we use small-angle X-ray scattering to perform direct in-flight characterizations of the first step of this process, i.e., the engineered formation of Au and Pt aerosol nanoparticles by spark generation in a flow of N₂ gas. This represents a particular challenge for characterization because the particle density can be extremely low in controlled production. The particles produced are examined during production at operational pressures close to atmospheric conditions and exhibit a lognormal size distribution ranging from 5–100 nm. The Au and Pt particle production and detection are compared. We observe and characterize the nanoparticles at different stages of synthesis and extract the corresponding dominant physical properties, including the average particle diameter and sphericity, as influenced by particle sintering and the presence of aggregates. We observe highly sorted and sintered spherical Au nanoparticles at ultra-dilute concentrations (< 5 × 10⁵ particles/cm³) corresponding to a volume fraction below 3 × 10^–10, which is orders of magnitude below that of previously measured aerosols. We independently confirm an average particle radius of 25 nm via Guinier and Kratky plot analysis. Our study indicates that with high-intensity synchrotron beams and careful consideration of background removal, size and shape information can be obtained for extremely low particle concentrations with industrially relevant narrow size distributions.

     

Chloridazon-Metaboliten im Grundwasser

Grundwasser - Chloridazon ist ein Herbizidwirkstoff, der in Deutschland seit 1964 für den Einsatz in der Landwirtschaft zugelassen ist. Er wird hauptsächlich beim Anbau von Rüben,...     

Absolute Configuration of β- and α-Asymmetric Carbons within β-O-4-Structures in Hardwood Lignin

In this study, we investigated the proportion of erythro- and threo-forms of β-O-4-ether structures and their enantiomeric compositions in hardwood lignin by applying the ozonation method to birch wood meal. Optical activity was not substantially observed in either the erythronic or threonic acids obtained as the ozonation products of β-O-4-structures in birch wood meal. The proportions of the four stereoisomeric forms {(αS,βR)-erythro, (αR,βR)-threo, (αS,βS)-threo, and (αR,βS)-erythro forms} were estimated to be 37-38%, 13-14%, 12-13%, and 36-37% based on the yields of erythronic and threonic acids, and on their optical activities. The proportions suggest that the entire components of β-O-4-ether structures in birch wood lignin have R- and S-configurations at the β-carbon in approximately the same quantities {(βR)-β-O-4-structure: (βS)-β-O-4-structure = 50–52:48–50}; i.e., that the β-ether structures are essentially racemic. This estimation implies that, during lignin biosynthesis, an equal number of enantiomeric forms of β-O-4-bonded quinone methides were formed by radical coupling reactions.     

Trans-situated use of integrated information systems

Practice-based perspectives have established the situated nature of how technology is appropriated, enacted, and improvised in organisations. Empirical studies demonstrate how the same technology produces different results in different contexts of use. However, practice-based research has, to date, less to offer in terms of accounting for the relationship between instances of situated use (i.e., work practices) that are separated in space and/or time. The term trans-situated use is intended to highlight this blind spot. We focus on one type of relationship, viz., significant degrees of similarities between technologically mediated, geographically dispersed work practices. This degree of similarity is achieved through a process of commensurability consisting of (i) standardisation (addressing interdependencies between multiple instances of the ‘same’ work practice at geographically dispersed sites); and (ii) heterogeneity (addressing the entanglement of one work practice with apparently unrelated work practices and modules). Empirically, we report on a longitudinal, interpretative case study (1998–2004) of a company strategically targeting an integrated information system as a principal vehicle to establish similar services globally.     

Effect of high-pressure cooling on life of SiAlON tools in machining of Inconel 718

High-pressure cooling has proven to be very effective when machining with carbide inserts. Longer tool life and improved chip breaking are among the most commonly mentioned advantages. Nevertheless, this cooling method has been reported to reduce the life of ceramic tools in machining of heat-resistant alloys. The main reason for that is said to be the accelerated notch wear. Therefore, in this study, SiAlON ceramic inserts with improved resistance to notching were tested in machining of Inconel?718 under high-pressure cooling. The results were compared to conventional cooling. It turned out that, while notch wear was still slightly increased when high-pressure cooling was applied, it was no longer critical for the tool life. Flank wear, on the other hand, was reduced, which led to significantly longer tool life. The variation of the tool life appeared to be slightly less and chip breaking was considerably improved. This shows that, when used properly, high-pressure cooling can help to increase the productivity in machining of heat-resistant alloys with ceramic tools.