scholarly journals Development of a Freeze-Drying Stage for In-Situ µ-CT Measurements

Processes ◽  
2020 ◽  
Vol 8 (7) ◽  
pp. 869
Author(s):  
Mathias Hilmer ◽  
Sebastian Gruber ◽  
Petra Foerst
Keyword(s):  
Process Parameters ◽  
Atmospheric Pressure ◽  
Freeze Drying ◽  
Pressure Range ◽  
Neutron Imaging ◽  
Ice Crystals ◽  
Controlled Environment ◽  
Sample Holder ◽  
Ct Measurements

This paper shows the development of a freeze-drying stage for in-situ μ-CT measurements. The stage can operate in a temperature range of −40 °C up to 70 °C, and a pressure range from atmospheric pressure to 7 Pa at the sample holder. To get the best visualization of the probe, it is fundamental that the materials around the sample holder are not absorbing most of the radiation. For this reason, we built an axial symmetrical stage built out of polyetheretherketon (PEEK). A test of the stage by different freeze-drying experiments with maltodextrin and sucrose particles and solutions demonstrated its suitability to visualize the freeze-drying processes in-situ. It was possible to track the drying front during the process by radiographic and tomographic measurements, as well as to visually resolve the ice crystals and porous structure in tomographic measurements. Using different samples and process parameters, we showed that the freeze-drying stage is not only suitable for in-situ µ-CT measurements, but also allows us to use the stage for other imaging methods such as neutron imaging, and for any sample where a controlled environment is needed.

Innovative Closed-Cell Reactor Permits In Situ Heating and Gas Reactions with Atomic Resolution at Atmospheric Pressure

2012 ◽  
Vol 18 (S2) ◽  
pp. 1118-1119 ◽  
Author(s):  
L. Allard ◽  
S.H. Overbury ◽  
M.B. Katz ◽  
W.C. Bigelow ◽  
D. Nackashi ◽  
...  
Keyword(s):  
Atmospheric Pressure ◽  
Atomic Resolution ◽  
Closed Cell ◽  
Cell Reactor ◽  
In Situ Heating ◽  
Gas Reactions

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

scholarly journals Convective formation of pileus cloud near the tropopause

2006 ◽  
Vol 6 (5) ◽  
pp. 1185-1200 ◽  
Author(s):  
T. J. Garrett ◽  
J. Dean-Day ◽  
C. Liu ◽  
B. Barnett ◽  
G. Mace ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Deep Convection ◽  
Cloud Microphysics ◽  
In Situ Measurements ◽  
Ice Crystals ◽  
Total Water ◽  
Wave Analysis ◽  
Cold Temperatures ◽  
Face Experiment

Abstract. Pileus clouds form where humid, vertically stratified air is mechanically displaced ahead of rising convection. This paper describes convective formation of pileus cloud in the tropopause transition layer (TTL), and explores a possible link to the formation of long-lasting cirrus at cold temperatures. The study examines in detail in-situ measurements from off the coast of Honduras during the July 2002 CRYSTAL-FACE experiment that showed an example of TTL cirrus associated with, and penetrated by, deep convection. The TTL cirrus was enriched with total water compared to its surroundings, but was composed of extremely small ice crystals with effective radii between 2 and 4 μm. Through gravity wave analysis, and intercomparison of measured and simulated cloud microphysics, it is argued that the TTL cirrus originated neither from convectively-forced gravity wave motions nor environmental mixing alone. Rather, it is hypothesized that a combination of these two processes was involved in which, first, a pulse of convection forced pileus cloud to form from TTL air; second, the pileus layer was punctured by the convective pulse and received larger ice crystals through interfacial mixing; third, the addition of this condensate inhibited evaporation of the original pileus ice crystals where a convectively forced gravity wave entered its warm phase; fourth, through successive pulses of convection, a sheet of TTL cirrus formed. While the general incidence and longevity of pileus cloud remains unknown, in-situ measurements, and satellite-based Microwave Limb Sounder retrievals, suggest that much of the tropical TTL is sufficiently humid to be susceptible to its formation. Where these clouds form and persist, there is potential for an irreversible repartition from water vapor to ice at cold temperatures.

Sporogenesis and septum schizolysis in Dipodascus aggregates

1989 ◽  
Vol 67 (7) ◽  
pp. 2150-2153 ◽  
Author(s):  
A. Tsuneda ◽  
S. Murakami
Keyword(s):  
Electron Microscopy ◽  
Freeze Drying ◽  
The Other ◽  
Cross Wall

Asci, ascospores, and arthroconidia of Dipodascus aggregatus were examined by electron microscopy. Freeze-drying of mature asci caused rupture of the ascal walls and made it possible to observe capsulated ascospores in situ. Two types of septa occurred: (i) one having a remarkably thickened cross wall which protruded to form a circumferential ridge on the hyphae, and (ii) the other without such a bulging ridge. Schizolysis of these septa resulted in the formation of morphologically distinct arthroconidia. The scizolytic process of the ridged septa was demonstrated in detail. There was no evidence to support that the plasmadesmal canals in the septa function as disjunctive pegs in the process of arthroconidial separation.

Characterization of YBa2Cu4O8 high temperature electrical properties and thermodynamic stability

1991 ◽  
Vol 6 (10) ◽  
pp. 2054-2058 ◽  
Author(s):  
B-S. Hong ◽  
T.O. Mason
Keyword(s):  
High Temperature ◽  
Electrical Property ◽  
Electrical Properties ◽  
Seebeck Coefficient ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Pressure Range ◽  
Stability Range

Via in situ electrical property measurements (conductivity, Seebeck coefficient) over the temperature range 500–800 °C and oxygen partial pressure range 10−4-1 atm, the equilibrium transport properties and stability range of YBa2Cu4O8 were determined. YBa2Cu4O8 behaves like the intrinsically mixed-valent compound, magnetite (Fe3O4), with small variations in electrical properties with changes in oxygen partial pressure. The decomposition boundary to YBa2Cu3O6+y (or YBa2Cu3.5O7.5±z) and CuO occurs at log(po2, atm) = −1.24 × 104/T(K) + 11.01(773 ⋚ T(K) ⋚ 1073).

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