scholarly journals The connectivity of crystallite agglomerates in low-density firn at Kohnen station, Dronning Maud Land, Antarctica

2008 ◽  
Vol 49 ◽  
pp. 114-120 ◽  
Author(s):  
J. Freitag ◽  
S. Kipfstuhl ◽  
S.H. Faria
Keyword(s):  
Crystal Size ◽  
Three Dimensional ◽  
Grain Boundary Sliding ◽  
Size Distributions ◽  
Coordination Numbers ◽  
Dronning Maud Land ◽  
Mean Size ◽  
Surface Section ◽  
Boundary Sliding ◽  
The Mean

AbstractIn this study, the three-dimensional (3-D) microstructure of polar firn is investigated by means of X-ray microfocus computer tomography (mCT). Basic topological properties including the Euler and coordination numbers are derived from the reconstructed 3-D volume images. It is shown that sample volumes of about 4 cm3 are representative for polar firn in terms of their connectivity. The connectivity function defined as the change of Euler number with structure size is calculated via image-processing routines. It is used to split the ice phase at small bridges into single crystallite agglomerates. The bond-size distributions and the mean size of the agglomerates are estimated. All μCT measurements were carried out on the uppermost 9 m of a shallow firn core (B35) drilled during the 2005/06 field campaign at Kohnen station, Dronning Maud Land (DML), Antarctica. The results are compared with estimates from classical two-dimensional (2-D) surface section observations. The 3-D approach confirms the linear relationship between coordination number and density which hitherto has only been derived from 2-D observations. Layers of buried snow dunes show a stronger connectivity than layers of moderate crystal size and density. The formation of agglomerates made of crystallites is a common feature of polar firn in DML. It is proposed that the growth of agglomerates leads to reduced critical densities for the transition between the densification regime of grain boundary sliding and plastic deformation.

Batch Precipitation of Lead Iodide

1994 ◽  
Vol 59 (6) ◽  
pp. 1301-1304
Author(s):  
Jaroslav Nývlt ◽  
Stanislav Žáček
Keyword(s):  
Aqueous Solution ◽  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Crystal Size ◽  
Lead Nitrate ◽  
Lead Iodide ◽  
Constant Rate ◽  
Mean Size ◽  
The Mean

Lead iodide was precipitated by a procedure in which an aqueous solution of potassium iodide at a concentration of 0.03, 0.10 or 0.20 mol l-1 was stirred while an aqueous solution of lead nitrate at one-half concentration was added at a constant rate. The mean size of the PbI2 crystals was determined by evaluating the particle size distribution, which was measured sedimentometrically. The dependence of the mean crystal size on the duration of the experiment exhibited a minimum for any of the concentrations applied. The reason for this is discussed.

Size decrease of detonation nanodiamonds by air annealing investigated by AFM

MRS Advances ◽  
2016 ◽  
Vol 1 (16) ◽  
pp. 1067-1073 ◽  
Author(s):  
Stepan Stehlik ◽  
Daria Miliaieva ◽  
Marian Varga ◽  
Alexander Kromka ◽  
Bohuslav Rezek
Keyword(s):  
Size Distribution ◽  
Annealing Temperature ◽  
Detonation Nanodiamonds ◽  
Particle Analysis ◽  
Detonation Synthesis ◽  
Size Distributions ◽  
Force Microscopy ◽  
Atomic Force ◽  
Mean Size ◽  
The Mean

ABSTRACTNanodiamonds (NDs) represent a novel nanomaterial applicable from biomedicine to spintronics. Here we study ability of air annealing to further decrease the typical 5 nm NDs produced by detonation synthesis. We use atomic force microscopy (AFM) with sub-nm resolution to directly measure individual detonation nanodiamonds (DNDs) on a flat Si substrate. By means of particle analysis we obtain their accurate and statistically relevant size distributions. Using this approach, we characterize evolution of the size distribution as a function of time and annealing temperature: i) at constant time (25 min) with changing temperature (480, 490, 500°C) and ii) at constant temperature (490°C) with changing time (10, 25, 50 min). We show that the mean size of DNDs can be controllably reduced from 4.5 nm to 1.8 nm without noticeable particle loss and down to 1.3 nm with 36% yield. By air annealing the size distribution changes from Gaussian to lognormal with a steep edge around 1 nm, indicating instability of DNDs below 1 nm.

Experimental Characterization of Aerosol Production, Transport, Vaporization, and Atomization Systems. Part II: Factors Controlling Aerosol Size Distributions Produced

1985 ◽  
Vol 39 (6) ◽  
pp. 920-925 ◽  
Author(s):  
R. K. Skogerboe ◽  
S. J. Freeland
Keyword(s):  
Flow Rate ◽  
Gas Flow ◽  
Cross Flow ◽  
Size Distributions ◽  
Experimental Characterization ◽  
Gas Flow Rate ◽  
Mean Size ◽  
The Mean ◽  
Model Equations

The effects of nebulization conditions on the size characteristics of the aqueous aerosol produced have been investigated for a cross-flow nebulizer. It is shown that the nebulizer gas flow rate does not affect the upper limit mean sizes of the aqueous droplets transported from the nebulization chamber but that the mean size of the analyte-containing aerosol itself is affected. Model equations are presented descriptive of the effects of gas flow rate and analyte concentrations on analyte aerosol size characteristics.

scholarly journals Density and Size Distribution of the Sea Cucumber, Holothuria scabra (Jaeger, 1935), at Six Exploited Sites in Mahout Bay, Sultanate of Oman

2007 ◽  
Vol 12 ◽  
pp. 43 ◽  
Author(s):  
Khalfan M. Al-Rashdi ◽  
Michel R. Claereboudt ◽  
Saud S. Al-Busaidi
Keyword(s):  
Size Distribution ◽  
Sea Cucumber ◽  
Size Distributions ◽  
Sultanate Of Oman ◽  
Population Densities ◽  
Sea Cucumbers ◽  
Holothuria Scabra ◽  
Mean Size ◽  
Males And Females ◽  
The Mean

A rapid survey of the density and size distribution of recently exploited populations of Holothuria scabra in Mahout Bay (Ghubbat Hashish Bay) was carried out at six fishing sites. The results showed that population densities varied between 1170 and 4000 individuals ha-1 and biomass ranged between 393 and 2903 kg ha-1. The mean size of sea cucumbers and population densities were much lower in populations closer to human settlements, suggestive of overfishing. The sex ratio was estimated to be 1:1 and the size distributions of males and females did not differ significantly. The length-weight relationship for both sexes was calculated as W (g) = 0.033 Length (mm) 2.178. 

Three-dimensional blood flow analysis in a wide-necked internal carotid artery—ophthalmic artery aneurysm

2003 ◽  
Vol 99 (3) ◽  
pp. 526-533 ◽  
Author(s):  
Satoshi Tateshima ◽  
Fernando Viñuela ◽  
J. Pablo Villablanca ◽  
Yuichi Murayama ◽  
Taku Morino ◽  
...  
Keyword(s):  
Blood Flow ◽  
Secondary Flow ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Artery Aneurysm ◽  
Content Type ◽  
Mean Size ◽  
Blood Flow Analysis ◽  
The Mean ◽  
Fine Print

Object. The aim of this study was to evaluate axial and secondary flow structures in a wide-necked internal carotid artery—ophthalmic artery aneurysm, one of the most common locations for endovascular coil placement. Methods. A clear acrylic aneurysm model was manufactured from a three-dimensional computerized tomography angiogram. Intraaneurysm blood flow analysis was conducted using an acrylic aneurysm model together with laser Doppler velocimetry and particle imaging velocimetry. The maximal axial blood flow velocities in the inflow and outflow zones at the aneurysm orifice were noted at the peak systolic phase, measuring 46.8 and 24.9% of that in the parent artery, respectively. The mean size of the inflow zone during one cardiac cycle was 44.3 ± 9.8% (range 35.6–58.7%) the size of the axial section at the aneurysm orifice. In the lower and upper planes of the aneurysm dome, the mean size of inward and outward flow areas were 43.3 ± 6.7% and 43.8 ± 6.8% the size of the axial cross-sectional plane, respectively. The axial flow velocity structures were dynamically altered throughout the cardiac cycle, particularly at the aneurysm orifice. The fastest secondary flow at the opening was also noted at the peak systolic and early diastolic phases. Axial blood flow velocity was slower in the upper axial plane of the aneurysm dome than in the lower one. Conversely, the secondary flow component was faster in the upper plane. Conclusions. The side-wall aneurysm in this study did not demonstrate a simple flow pattern as was previously seen in ideally shaped experimental aneurysms in vitro and in vivo. The flow patterns of inflow and outflow zones were very difficult to predict based on the limited flow information provided on standard digital subtraction angiography, even in an aneurysm with a relatively simple dome shape.

Modelling of nanocrystalline iron nitriding process — influence of specific surface area

2011 ◽  
Vol 65 (2) ◽  
Author(s):  
Rafał Pelka ◽  
Walerian Arabczyk
Keyword(s):  
Specific Surface ◽  
Gaseous Phase ◽  
Tubular Reactor ◽  
Nitriding Process ◽  
Size Distributions ◽  
Surface Areas ◽  
Nanocrystalline Iron ◽  
Mean Size ◽  
The Mean ◽  
Nitriding Potential

AbstractSamples of iron catalysts of various specific surface areas for ammonia synthesis underwent nitriding with ammonia in a tubular reactor where continuous thermogravimetric measurement and measurements of hydrogen concentration in the gaseous phase were simultaneously performed. The nitriding process was performed under atmospheric pressure at 475°C. It was observed that, along with an increase in the mean size of iron nano-crystallites, the minimum nitriding potential (at which the iron nitriding reaction is initiated) of the gaseous phase also increased. The degree of nitriding of the catalyst samples increased with the increase in the mean size of iron crystallites. On the basis of the values of nitriding potential, nano-crystallite size distributions can be determined.

scholarly journals Shallow-ice microstructure at Dome Concordia, Antarctica

2000 ◽  
Vol 30 ◽  
pp. 8-12 ◽  
Author(s):  
Laurent Arnaud ◽  
Jérôme Weiss ◽  
Michel Gay ◽  
Paul Duval
Keyword(s):  
Crystal Size ◽  
Accumulation Rate ◽  
Ice Core ◽  
Processing Technique ◽  
Image Processing Technique ◽  
Size Distributions ◽  
Thin Sections ◽  
Crystal Size Distributions ◽  
Size Profile ◽  
The Mean

AbstractThe shallow-ice microstructure at Dome Concordia, Antarctica, has been studied between 100 m and 580 m. An original digital-image-processing technique has been specially developed to extract ice microstructure (grain boundaries) from thin sections prepared during the two first scientific EPICA field seasons (1997/98 and 1998/99). Using this, not only the mean crystal size, but also crystal-size distributions and shape anisotropy were determined. The mean crystal-size profile as well as crystal-size distributions reveal normal grain growth up to 430 m. Between 430 m and 500 m, a marked decrease of crystal size is observed and compared with a similar trend obtained in the "old" Dome C ice core formerly associated with the Holocene/Last Glacial transition (Duval and Lorius, 1980). This seems to indicate a slightly lower accumulation rate (by <10%) at Dome C. The shapes of the crystal-size distributions, though very similar, do evolve with depth and seem to be sensitive to climatic changes. An increasing flattening of crystal shape is observed with depth. This allowed estimation of the vertical strain rate in the shallow part of the ice sheet.

Effect of Synthesis Parameter on Properties of Heat-Sensitive Nanocapsules

2013 ◽  
Vol 675 ◽  
pp. 302-305
Author(s):  
Pu Ying An ◽  
Zhao Yun Yu ◽  
Hai Song Zhang ◽  
Xin Wu Ba
Keyword(s):  
Particle Size ◽  
Glass Transition ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Glass Transition Temperatures ◽  
Hyperbranched Poly ◽  
Crosslinker Content ◽  
Mean Size ◽  
The Mean ◽  
Triton X

The crosslinked poly(methylmethacrylate) (PMMA) heat-sensitive nanocapsules were prepared by emulsion polymerization, in which Triton X-100 was used as an emulsifier and unsaturated hyperbranched poly(amide-ester) (UHBP) as a crosslinker. The effects of three determinative process parameters on the particle size distributions, glass transition temperatures(Tgs) and heat sensitive color-developing properties of nanocapsules were investigated in detail. As a result, the mean size of nanocapsules became smaller and their particle size distribution became narrower with the increase in emulsifying rate. The Tg of nanocapsules was 123.8°C with the emulsifier content being 0.6%. The color-developing absorbency was the highest with the crosslinker content being 6.0 %.

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