XIV.—Mathematical Note on the Fall of Small Particles through Liquid Columns

1917 ◽  
Vol 36 (3-4) ◽  
pp. 237-239 ◽  
Author(s):  
C. G. Knott
Keyword(s):  
Deep Sea ◽  
Small Particles ◽  
Mathematical Note ◽  
Mathematical Discussion ◽  
Size Of Particles

The following note presents in a simpler form the essence of Dr Sven Odén's mathematical discussion of the fall of small particles through a column of liquid, as given in his paper (immediately preceding) “On the Size of Particles in Deep-sea Deposits.”It has the further advantage of solving the problem without taking account explicitly or implicitly of Stokes's law (or modification thereof) as to the relation connecting the time of fall with the size, form, and density of the particles considered. It is important, I think, to refrain as long as possible from making the assumptions involved in such a law of fall, and to recognise how far we may carry the investigation before introducing these assumptions.

scholarly journals Size of particles ejected from an artificial impact crater on asteroid 162173 Ryugu

2021 ◽  
Vol 647 ◽  
pp. A43
Author(s):  
K. Wada ◽  
K. Ishibashi ◽  
H. Kimura ◽  
M. Arakawa ◽  
H. Sawada ◽  
...  
Keyword(s):  
Impact Crater ◽  
Subsurface Layer ◽  
Time Lapse ◽  
Small Particles ◽  
Surface Evolution ◽  
Uppermost Layer ◽  
Solar System Bodies ◽  
Apparent Diameter ◽  
To Come ◽  
Size Of Particles

A projectile accelerated by the Hayabusa2 Small Carry-on Impactor successfully produced an artificial impact crater with a final apparent diameter of 14.5 ± 0.8 m on the surface of the near-Earth asteroid 162173 Ryugu on April 5, 2019. At the time of cratering, Deployable Camera 3 took clear time-lapse images of the ejecta curtain, an assemblage of ejected particles forming a curtain-like structure emerging from the crater. Focusing on the optical depth of the ejecta curtain and comparing it with a theoretical model, we infer the size of the ejecta particles. As a result, the typical size of the ejecta particles is estimated to be several centimeters to decimeters, although it slightly depends on the assumed size distribution. Since the ejecta particles are expected to come from a depth down to ~1 m, our result suggests that the subsurface layer of Ryugu is composed of relatively small particles compared to the uppermost layer on which we observe many meter-sized boulders. Our result also suggests a deficit of particles of less than ~1 mm in the subsurface layer. These findings will play a key role in revealing the formation and surface evolution process of Ryugu and other small Solar System bodies.

Sensitivity of SEM/EDX to Detect Small Particles on Substrates.

1997 ◽  
Vol 3 (S2) ◽  
pp. 1221-1222
Author(s):  
M.F. Thornton.
Keyword(s):  
Integrated Circuits ◽  
Semiconductor Device ◽  
Minimum Size ◽  
Analysis Tool ◽  
Small Particles ◽  
Size Of Particles ◽  
Beam Currents ◽  
Scientific Fields ◽  
Sources Of Contamination

The characterization of microscopic particles on substrates is of interest in numerous scientific fields. One example is semiconductor device defect review, where the characterization of particles or defects on a device is an essential aid in tracing sources of contamination in the production process. With the ever decreasing component separation on the integrated circuits the sensitivity of SEM/EDX to detect small particles on substrates is an important issue. The minimum size of particles causing defects in semiconductor device manufacture is predicted to decrease from 0.12µm today to 0.02µm by the year 2010. The question of interest is how long the SEM/EDX analysis tool can continue to be used to identify elements present in “killer” defect particles of ever decreasing size? This paper attempts to address this question.It has already been shown that films as thin as a monolayer can be detected with WDX provided high beam currents are available.

Antral control of canine gastric emptying of solids

1983 ◽  
Vol 245 (3) ◽  
pp. G334-G338 ◽  
Author(s):  
J. M. Becker ◽  
K. A. Kelly
Keyword(s):  
Gastric Emptying ◽  
Pore Size ◽  
Bovine Liver ◽  
Conscious Dogs ◽  
Antral Mucosa ◽  
Small Particles ◽  
Size Of Particles ◽  
A Minor

We wondered whether antral mucosal nerves sense the size of particles in gastric chyme and then activate motor mechanisms that allow only small particles to empty. Four conscious dogs with duodenal Thomas cannulas were fed 100 g of bovine liver, half of which was labeled with cyano[57Co]cobalamin. Duodenal chyme was then collected in 15-min periods for 5 h and poured through a stack of sieves of decreasing pore size, and the percentage of radioactivity recovered on each sieve was determined per hour. Five studies were carried out on each dog before and beginning 2 wk after antral mucosal neurolysis, during which the antral mucosal nerves were divided by dissecting the entire antral mucosa circumferentially free from the surrounding antral muscularis. In the control tests, nearly all liver (93%) emptied as particles less than 1.4 mm in diameter, but the percentage emptied as larger particles increased in the 3rd through 5th postprandial h. After antral mucosal neurolysis, the increase in the percentage of larger particles emptied occurred sooner and to a greater extent, but the overall rate of emptying of liver was not changed. We concluded that antral mucosal nerves have a role in regulating the size of gastric particles emptied, but a minor one.

Stereo Electron Microscopy Applied to High Resolution Freeze-Etch Replicas

1970 ◽  
Vol 28 ◽  
pp. 306-307
Author(s):  
L. Andrew Staehelin
Keyword(s):  
Electron Microscopy ◽  
Plastic Deformation ◽  
High Resolution ◽  
Smooth Surfaces ◽  
Small Particles ◽  
Membrane Surfaces ◽  
Wide Acceptance ◽  
New Information ◽  
Number Of Particles ◽  
Small Holes

Freeze-etched membranes usually appear as relatively smooth surfaces covered with numerous small particles and a few small holes (Fig. 1). In 1966 Branton (1“) suggested that these surfaces represent split inner mem¬brane faces and not true external membrane surfaces. His theory has now gained wide acceptance partly due to new information obtained from double replicas of freeze-cleaved specimens (2,3) and from freeze-etch experi¬ments with surface labeled membranes (4). While theses studies have fur¬ther substantiated the basic idea of membrane splitting and have shown clearly which membrane faces are complementary to each other, they have left the question open, why the replicated membrane faces usually exhibit con¬siderably fewer holes than particles. According to Branton's theory the number of holes should on the average equal the number of particles. The absence of these holes can be explained in either of two ways: a) it is possible that no holes are formed during the cleaving process e.g. due to plastic deformation (5); b) holes may arise during the cleaving process but remain undetected because of inadequate replication and microscope techniques.

Dynamic Scanning Electron Microscopy of Small Particles

1975 ◽  
Vol 33 ◽  
pp. 280-281
Author(s):  
W. Krakow ◽  
W. C. Nixon
Keyword(s):  
Electron Microscopy ◽  
Low Noise ◽  
Time Sequence ◽  
Field Of View ◽  
Video Tape ◽  
Small Particles ◽  
Polystyrene Spheres ◽  
Field Distributions ◽  
Dynamic Scanning ◽  
Scanning Electron

The scanning electron microscope (SEM) can be run at television scanning rates and used with a video tape recorder to observe dynamic specimen changes. With a conventional tungsten source, a low noise TV image is obtained with a field of view sufficient to cover the area of the specimen to be recorded. Contrast and resolution considerations have been elucidated and many changing specimens have been studied at TV rates.To extend the work on measuring the magnitude of charge and field distributions of small particles in the SEM, we have investigated their motion and electrostatic interaction at TV rates. Fig. 1 shows a time sequence of polystyrene spheres on a conducting grating surface inclined to the microscope axis. In (la) there are four particles present in the field of view, while in (lb) a fifth particle has moved into view.

The Shadow Widths of Very Small Particles are Formed Independently of the Metal Cap Build Up on the Particle

1981 ◽  
Vol 39 ◽  
pp. 568-569
Author(s):  
George C. Ruben
Keyword(s):  
Gold Particle ◽  
Film Surface ◽  
Small Particles ◽  
Geometric Process ◽  
Metal Free ◽  
Shadow Area

The formation of shadows behind small particles has been thought to be a geometric process (GP) where the metal cap build up on the particle creates a shadow width the same size as or larger than the particle. This GP cannot explain why gold particle shadow widths are generally larger than the gold particle and may have no appreciable metal cap build up (fig. 1). Ruben and Telford have suggested that particle shadow widths are formed by the width dependent deflection of shadow metal (SM) lateral to and infront of the particle. The trajectory of the deflected SM is determined by the incoming shadow angle (45°). Since there can be up to 1.4 times (at 45°) more SM directly striking the particle than the film surface, a ridge of metal nuclei lateral to and infront of the particle can be formed. This ridge in turn can prevent some SM from directly landing in the metal free shadow area. However, the SM that does land in the shadow area (not blocked by the particle or its ridge) does not stick and apparently surface migrates into the SM film behind the particle.

STEM Study of Surface Plasmon Excitation in Small Spherical Particles

1990 ◽  
Vol 48 (2) ◽  
pp. 42-43
Author(s):  
Daniel UGARTE
Keyword(s):  
Energy Loss ◽  
Spherical Particles ◽  
Small Particles ◽  
Bulk Materials ◽  
Low Loss ◽  
Plasmon Excitation ◽  
Surface Modes ◽  
Surface Plasmon Excitation ◽  
Analytical Electron ◽  
Analytical Electron Microscope

Small particles exhibit chemical and physical behaviors substantially different from bulk materials. This is due to the fact that boundary conditions can induce specific constraints on the observed properties. As an example, energy loss experiments carried out in an analytical electron microscope, constitute a powerful technique to investigate the excitation of collective surface modes (plasmons), which are modified in a limited size medium. In this work a STEM VG HB501 has been used to study the low energy loss spectrum (1-40 eV) of silicon spherical particles [1], and the spatial localization of the different modes has been analyzed through digitally acquired energy filtered images. This material and its oxides have been extensively studied and are very well characterized, because of their applications in microelectronics. These particles are thus ideal objects to test the validity of theories developed up to now.Typical EELS spectra in the low loss region are shown in fig. 2 and energy filtered images for the main spectral features in fig. 3.

SREM observation of the interaction between the in-situ deposited Pd small particles and MgO cleavage surface

1986 ◽  
Vol 44 ◽  
pp. 382-383
Author(s):  
H.-J. Ou
Keyword(s):  
Electron Microscopy ◽  
Small Particle ◽  
Small Particles ◽  
Cleavage Surface ◽  
Metallic Particles ◽  
Microscopy Technique ◽  
Ceramic Surfaces ◽  
Reflection Electron Microscopy ◽  
New Perspective

The understanding of the interactions between the small metallic particles and ceramic surfaces has been studied by many catalyst scientists. We had developed Scanning Reflection Electron Microscopy technique to study surface structure of MgO hulk cleaved surface and the interaction with the small particle of metals. Resolutions of 10Å has shown the periodic array of surface atomic steps on MgO. The SREM observation of the interaction between the metallic particles and the surface may provide a new perspective on such processes.

Scanning electron microscopy of composite hydroxylapatite/plaster implants for bone reconstruction

1986 ◽  
Vol 44 ◽  
pp. 326-327
Author(s):  
J. S. Hanker ◽  
B. L. Giammara
Keyword(s):  
Tooth Extraction ◽  
Alveolar Ridge ◽  
Small Particles ◽  
Alveolar Ridge Augmentation ◽  
Sintered Ceramic ◽  
Ridge Augmentation ◽  
Fibrovascular Tissue ◽  
Infrabony Defects ◽  
Edentulous Patients ◽  
Scanning Electron

Nonresorbable sintered ceramic hydroxylapatite (HA) is widely employed for filling defects in jaw bone. The small particles used for alveolar ridge augmentation in edentulous patients or for infrabony defects due to periodontal disease tend to scatter when implanted using water or saline as the vehicle. Larger blocks of this material used for filling sockets after tooth extraction don't fit well. Studies in our laboratory where we compared bovine serum albumin, collagen and plaster of Paris as binders to prevent particle scatter during implantation suggested that plaster was most useful for this purpose. In addition to preventing scatter of the particles, plaster enables the formation of implants of any size and.shape either prior to or during surgery. Studies with the PATS reaction have indicated that plaster acts as a scaffold for the incorporation of HA particles into bone in areas where the implant contacts either host bone or periosteum. The shape and integrity of the implant is maintained by the plaster component until it is replaced over a period of days by fibrovascular tissue.

Detection of viruses by electron microscopy: Increased sensitivity by direct micro-ultracentrifugation of samples

1987 ◽  
Vol 45 ◽  
pp. 908-909
Author(s):  
Alain R. Trudel ◽  
M. Trudel
Keyword(s):  
Electron Microscopy ◽  
Fold Increase ◽  
Observation Time ◽  
Clinical Samples ◽  
Maximum Speed ◽  
Viral Particles ◽  
Structural Details ◽  
Latex Spheres ◽  
Increased Sensitivity ◽  
Size Of Particles

AirfugeR (Beckman) direct ultracentrifugation of viral samples on electron microscopy grids offers a rapid way to concentrate viral particles or subunits and facilitate their detection and study. Using the A-100 fixed angle rotor (30°) with a K factor of 19 at maximum speed (95 000 rpm), samples up to 240 μl can be prepared for electron microscopy observation in a few minutes: observation time is decreased and structural details are highlighted. Using latex spheres to calculate the increase in sensitivity compared to the inverted drop procedure, we obtained a 10 to 40 fold increase in sensitivity depending on the size of particles. This technique also permits quantification of viral particles in samples if an aliquot is mixed with latex spheres of known concentration.Direct ultracentrifugation for electron microscopy can be performed on laboratory samples such as gradient or column fractions, infected cell supernatant, or on clinical samples such as urine, tears, cephalo-rachidian liquid, etc..

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