Video: Cavity formation of a towed sphere

Vacancies are introduced into the crystal phase during quenching of rapid solidified materials. Cavity formation occurs because of the coalescence of the vacancies into a cluster. However, because of the high mobility of vacancies at high temperature, most of them will diffuse back into the liquid phase, and some will be lost to defects such as dislocations. Oxygen is known to stabilize cavities by decreasing the surface energy through a chemisorption process. These stabilized cavities, furthermore, act as effective nucleation sites for precipitates to form during aging. Four different types of powders with different oxygen contents were prepared by gas atomization processing. The atomized powders were then consolidated by hot extrusion at 900 °C with an extrusion ratio 10,5:1. After consolidation, specimens were heat treated at 1000 °C for 1 hr followed by water quenching. Finally, the specimens were aged at 600 °C for about 800 hrs. TEM samples were prepared from the gripends of tensile specimens of both unaged and aged alloys.

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“Cavity” formation in superplastically deformed aluminium alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100177921 ◽

1990 ◽

Vol 48 (4) ◽

pp. 958-959

Author(s):

A. Cziráki ◽

E. Ková-csetényi ◽

T. Torma ◽

T. Turmezey

Keyword(s):

Grain Boundaries ◽

Aluminium Alloys ◽

Superplastic Deformation ◽

Volume Fraction ◽

Superplastic Forming ◽

Polished Surface ◽

Cavity Formation ◽

Stress Concentrations ◽

Electron Microscopic ◽

Commercial Aluminium

It is known that the formation of cavities during superplastic deformation can be correlated with the development of stress concentrations at irregularities along grain boundaries such as particles, ledges and triple points. In commercial aluminium alloys Al-Fe-Si particles or other coarse constituents may play an important role in cavity formation.Cavity formation during superplastic deformation was studied by optical metallography and transmission scanning electron microscopic investigations on Al-Mg-Si and Al-Mg-Mn alloys. The structure of particles was characterized by selected area diffraction and X-ray micro analysis. The volume fraction of “voids” was determined on mechanically polished surface.It was found by electron microscopy that strongly deformed regions are formed during superplastic forming at grain boundaries and around coarse particles.According to electron diffraction measurements these areas consist of small micro crystallized regions. See Fig.l.Comparing the volume fraction and morphology of cavities found by optical microscopy a good correlation was established between that of micro crystalline regions.

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Response to “Comment on ‘The Gibbs free energy of cavity formation in a diverse set of solvents’” [J. Chem. Phys. 154, 187101 (2021)]

The Journal of Chemical Physics ◽

10.1063/5.0051746 ◽

2021 ◽

Vol 154 (18) ◽

pp. 187102

Author(s):

Igor Sedov

Keyword(s):

Free Energy ◽

Gibbs Free Energy ◽

Chem Phys ◽

Cavity Formation

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Analysis of Morphokinetic Parameters of Feline Embryos Using a Time-Lapse System

Animals ◽

10.3390/ani11030748 ◽

2021 ◽

Vol 11 (3) ◽

pp. 748

Author(s):

Joanna Kochan ◽

Agnieszka Nowak ◽

Barbara Kij ◽

Sylwia Prochowska ◽

Wojciech Niżański

Keyword(s):

Embryo Development ◽

Embryo Quality ◽

Time Lapse ◽

Blastocyst Stage ◽

Cavity Formation ◽

Non Invasive ◽

Morphokinetic Parameters ◽

Morphological Defects ◽

Development In Vitro

The aim of this study was to analyze the morphokinetic parameters of feline embryos using a time lapse system. Oocytes matured in vitro were fertilized (IVF) and in vitro cultured in a time lapse-system (Primo Vision®, Gothenburg, Sweden). The first cell division of embryos occurred between 17 h post insemination (hpi) and 38 hpi, with the highest proportion of embryos (46%) cleaving between 21 and 24 hpi. The timing of the first cleavage significantly affected further embryo development, with the highest development occurring in embryos that cleaved at 21–22 hpi. Embryos that cleaved very early (17–18 hpi) developed poorly to the blastocyst stage (2%) and none of the embryos that cleaved later than 27 hpi were able to reach the blastocyst stage. Morphological defects were observed in 48% of the embryos. There were no statistically significant differences between the timing intervals of the first cleavage division and the frequency of morphological defects in embryos. Multiple (MUL) morphological defects were detected in more than half (56%) of the abnormal embryos. The most frequent single morphological defects were cytoplasmic fragmentation (FR) (8%) and blastomere asymmetry (AS) (6%). Direct cleavage (DC) from 1–3 or 3–5 blastomeres, reverse cleavage (RC) and vacuoles were rarely observed (2–3%). The timing of blastocyst cavity formation is a very good indicator of embryo quality. In our study, blastocyst cavity formation occurred between 127–167 hpi, with the highest frequency of hatching observed in blastocysts that cavitated between 142–150 hpi. Blastocysts in which cavitation began after 161 h did not hatch. In conclusion, the timing of the first and second cleavage divisions, the timing of blastocyst cavity formation and morphological anomalies can all be used as early and non-invasive indicators of cat embryo development in vitro.

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A novel concept for evaluation of biofilm adhesion strength by applying tensile force and shear force

Water Science & Technology ◽

10.2166/wst.1996.0552 ◽

1996 ◽

Vol 34 (5-6) ◽

pp. 201-211 ◽

Cited By ~ 16

Author(s):

Akiyoshi Ohashi ◽

Hideki Harada

Keyword(s):

Adhesion Strength ◽

Shear Force ◽

Growth Stage ◽

Open Channel ◽

Tensile Force ◽

Cavity Formation ◽

Channel Reactor ◽

Flat Surfaces ◽

Novel Concept ◽

Gravity Test

A novel methodology is proposed in this study to evaluate biofilm adhesion strength in two different ways: by measuring detached biomass caused by tensile force and by shear force. Tensile force was provided by centrifuging biofilm-attached plates installed on rotary tables. Shear force was provided by colliding biofilm-attached plates by gravity. Test biofilms consisting of denitrifiers were formed on the flat surfaces of square (25 cm2) plates that had been submerged in a rectangular open-channel reactor. The detachment tests revealed that, although biofilm adhesion strength was relatively high at the earlier growth stage, it drastically decreased at the later stage. The most weakened location toward biofilm depth was observed at the substratum surface, at which the adhesion strength by tensile force dropped from a several Pa to below 1 Pa as biofilms became aged. The adhesion strength by shear force was all the time more than 100 times as large as that by tensile force, even though having a similar behavior. The proportion of cavity, i.e., biofilm-absent area at the biofilm/substratum interface, increased as biofilms became mature. Cavity formation was strongly responsible for lessening the adhesion strength. It is suggested that biofilm slough-off is caused by the decline of adhesion strength by tensile force rather than by shear force.

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Use of scaled-particle theory in the assessment of the Ph4As+/Ph4B− assumption for single ions

Canadian Journal of Chemistry ◽

10.1139/v79-012 ◽

1979 ◽

Vol 57 (1) ◽

pp. 71-76 ◽

Cited By ~ 10

Author(s):

Michael H. Abraham ◽

Asadollah Nasehzadeh

Keyword(s):

Free Energy ◽

Recent Work ◽

Scaled Particle Theory ◽

Cavity Formation ◽

Energy Term ◽

Free Energies ◽

Particle Theory ◽

Novel Method ◽

Energy Of Interaction ◽

Solvent Molecules

A novel method for the assessment of the Ph4As+/Ph4B− assumption for free energies of transfer of single ions has recently been suggested by Treiner, and used by him to deduce that the assumption is not valid for transfers between water, propylene carbonate, sulpholane, dimethylsulphoxide, N-methyl-2-pyrrolidone, and perhaps also dimethylformamide. The basis of the method is the estimation of the free energy of cavity formation by scaled-particle theory, together with the hypothesis that the free energy of interaction of Ph4As+ (or Ph4B−) with solvent molecules is the same in all solvents, ΔGt0(int) = 0. It is shown in the present paper that (a) whether or not the Ph4As+/Ph4B− assumption applies to transfer to a given solvent depends on which other solvent is taken as the reference solvent in Treiner's method, (b) the calculation of the cavity free energy term by scaled-particle theory and by the theory of Sinanoglu – Reisse – Moura Ramos (SRMR) yields values so different that the method cannot be considered reliable, (c) the calculation of cavity enthalpies and entropies for Ph4As+ or Ph4B− by scaled-particle theory yields results that are chemically not reasonable, (d) the hypothesis that ΔGt0(int) = 0 conflicts with SRMR theory, and (e) the conclusions reached by Treiner are not in accord with recent work that in general supports the Ph4As+/Ph4B− assumption for solvents that are rejected by Treiner.

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