Cold Stage for X-ray diffractometer studies of lower-melting polymorphs of triglycerides

1976 ◽  
Vol 53 (5) ◽  
pp. 196-197 ◽  
Author(s):  
M. S. Gray ◽  
N. V. Lovegren ◽  
D. Mitcham
Keyword(s):  
X Ray ◽  
Lower Melting ◽  
Cold Stage

scholarly journals Coal fly ash: linking immersion freezing behavior and physicochemical particle properties

2018 ◽  
Vol 18 (19) ◽  
pp. 13903-13923 ◽  
Author(s):  
Sarah Grawe ◽  
Stefanie Augustin-Bauditz ◽  
Hans-Christian Clemen ◽  
Martin Ebert ◽  
Stine Eriksen Hammer ◽  
...  
Keyword(s):  
Fly Ash ◽  
Single Particle ◽  
Coal Fly Ash ◽  
Ice Nucleation ◽  
Freezing Behavior ◽  
Cloud Droplets ◽  
X Ray ◽  
Particle Properties ◽  
Cold Stage ◽  
Immersion Freezing

Abstract. To date, only a few studies have investigated the potential of coal fly ash particles to trigger heterogeneous ice nucleation in cloud droplets. The presented measurements aim at expanding the sparse dataset and improving process understanding of how physicochemical particle properties can influence the freezing behavior of coal fly ash particles immersed in water. Firstly, immersion freezing measurements were performed with two single particle techniques, i.e., the Leipzig Aerosol Cloud Interaction Simulator (LACIS) and the SPectrometer for Ice Nuclei (SPIN). The effect of suspension time on the efficiency of the coal fly ash particles when immersed in a cloud droplet is analyzed based on the different residence times of the two instruments and employing both dry and wet particle generation. Secondly, two cold-stage setups, one using microliter sized droplets (Leipzig Ice Nucleation Array) and one using nanoliter sized droplets (WeIzmann Supercooled Droplets Observation on Microarray setup) were applied. We found that coal fly ash particles are comparable to mineral dust in their immersion freezing behavior when being dry generated. However, a significant decrease in immersion freezing efficiency was observed during experiments with wet-generated particles in LACIS and SPIN. The efficiency of wet-generated particles is in agreement with the cold-stage measurements. In order to understand the reason behind the deactivation, a series of chemical composition, morphology, and crystallography analyses (single particle mass spectrometry, scanning electron microscopy coupled with energy dispersive X-ray microanalysis, X-ray diffraction analysis) were performed with dry- and wet-generated particles. From these investigations, we conclude that anhydrous CaSO4 and CaO – which, if investigated in pure form, show the same qualitative immersion freezing behavior as observed for dry-generated coal fly ash particles – contribute to triggering heterogeneous ice nucleation at the particle–water interface. The observed deactivation in contact with water is related to changes in the particle surface properties which are potentially caused by hydration of CaSO4 and CaO. The contribution of coal fly ash to the ambient population of ice-nucleating particles therefore depends on whether and for how long particles are immersed in cloud droplets.

Trauma causes heterogeneous compositional shifts in spinal cord

1992 ◽  
Vol 50 (2) ◽  
pp. 1594-1595
Author(s):  
Lyle G. Walsh ◽  
William B. Greene
Keyword(s):  
Spinal Cord ◽  
Electron Probe ◽  
Healthy People ◽  
Spinal Cord Trauma ◽  
Liquid Propane ◽  
X Ray ◽  
Cold Stage ◽  
Freeze Dried ◽  
Carbon Coated

Each year spinal cord trauma causes thousands of otherwise healthy people to be permanently disabled. In most cases, the axonal tracts are not mechanically severed. Instead, unknown mechanisms cause a progressive segmental necrosis. In this study, we use electron probe x-ray microanalysis, EPMA, to examine the composition of the dorsal axons and myelin 6 hours after mild and moderate trauma in order to identify the subcellular changes induced by trauma. Laminectomies were performed on anesthetized rats and sham, 6 g-cm or 20 g-cm trauma was delivered and the wound closed. Six hours after trauma the rats were again anesthetized, the dura was removed and the spinal cord was frozen in situ with a 100 psi jet of super-cooled liquid propane. Cryosections, 200 nm thick, were cut at -120°C and placed on carbon coated formvar covered folding copper grids. Samples were freeze dried and analyzed within an Hitachi H-7000 STEM on a Be tipped, GATAN, analytical cold stage with a 2-4 nA, 125 KeV beam.

X-ray microanalysis of frozen-hydrated bulk biological specimens: fundamental considerations

1978 ◽  
Vol 36 (2) ◽  
pp. 134-135
Author(s):  
W.C. Low ◽  
P.A. Burgio ◽  
L.F. Allard ◽  
S.L. BeMent ◽  
W.C. Bigelow ◽  
...  
Keyword(s):  
Biological Tissue ◽  
Ice Crystals ◽  
Tissue Fixation ◽  
Atmospheric Conditions ◽  
Bulk Specimen ◽  
X Ray ◽  
Ion Translocation ◽  
Cold Stage ◽  
Bulk Tissue ◽  
Scanning Electron

X-ray microanalysis and scanning electron microscopy used in conjunction with cold-stage techniques to examine frozen-hydrated bulk biological tissue is a promising method to determine the concentration and distribution of diffusible elements which are typically distorted by conventional techniques of biological tissue fixation. The proper application of this method, however, requires an understanding of the freezing and sublimation processes in bulk biological specimens, and the interaction of the electron beam with the bulk specimen in the frozen-hydrated state. These factors have been evaluated and are discussed below.One of the fundamental considerations in the examination of cryofixed bulk tissue is the formation of exogenous and endogenous ice crystals within the specimen or upon the surface of the specimen which can lead to tissue distortion and ion translocation. Techniques to minimize the exposure of the specimen to atmospheric conditions and to eleminate the formation of exogenous ice crystals have been developed by Burgio et al. (1978a), and Echlin and Moreton (1974).

The Microstructure of Melt-Spun Iron Neodymium Permanent Magnet Materials

1985 ◽  
Vol 43 ◽  
pp. 210-211
Author(s):  
R. C. Dickenson
Keyword(s):  
Heat Treatment ◽  
Magnetic Properties ◽  
Melt Spinning ◽  
Ion Milling ◽  
X Ray ◽  
Fine Grained ◽  
Cold Stage ◽  
Melt Spun ◽  
Fine Grained Structure ◽  
Permanent Magnet Materials

Rapidly-quenched iron rare-earth boron alloys, with appropriate heat treatment, exhibit commercially promising permanent magnetic properties. This paper will report the results of an AEM characterization undertaken to explain the origin of the magnetic properties of an iron-neodymium-boron alloy in terms of its microstructure. Ribbons of Fe76 Nd16 B8 were prepared by melt-spinning, and were subsequently annealed at 700°C for 6 minutes to promote growth of a fine-grained structure. Samples were prepared for AEM by ion-milling the ribbons on a cold stage and examined using a Philips 400T TEM/STEM equipped with an energy dispersive x-ray unit.Three different microstructures are commonly observed in these alloys, and several others have been found in isolated cases.

Specimen preparation, cryotransfer and microscope parameters for cold-stage work in SEM and application for the physical and biological sciences

1986 ◽  
Vol 44 ◽  
pp. 898-901
Author(s):  
J.A. Sargent
Keyword(s):  
Biological Sciences ◽  
Freeze Drying ◽  
Specimen Preparation ◽  
Ice Crystal ◽  
X Ray ◽  
Cold Stage ◽  
Critical Point Drying ◽  
Cryo Preservation ◽  
Precise Interpretation ◽  
Soluble Components

The availability of equipment which enables frozen-hydrated material to be viewed over prolonged periods in the SEM has greatly extended the versatility of the instrument and permitted more precise interpretation of the data obtained from it. Artifacts associated with chemical fixation are avoided and soluble components are retained which might otherwise be removed by solvents used for dehydration or critical point drying. In addition the shrinkage which frequently occurs during freeze drying is avoided. Two further advantages of cryo preservation can be invaluable: rapid cooling of motile specimens instantly arrests movement and the immobilization of diffusible compounds and ions enables X-ray microanalysis to be performed with confidence.The speed with which specimens are cooled is not critical if only surface features are to be studied. However, the examination of internal structure demands that ice crystal growth be minimised. Devices are available to maximise cooling rates using a variety of cryogens and specimen transfer to the SEM cold stage is achieved simply and effectively.

scholarly journals Application of scanning electron microscopy to x-ray analysis of frozen-hydrated sections. I. Specimen handling techniques.

1981 ◽  
Vol 88 (2) ◽  
pp. 257-267 ◽  
Author(s):  
A J Saubermann ◽  
P Echlin ◽  
P D Peters ◽  
R Beeuwkes
Keyword(s):  
Specimen Handling ◽  
X Ray ◽  
Water Fraction ◽  
Tissue Sections ◽  
Cold Stage ◽  
Mass Fractions ◽  
Wet Weight ◽  
Cellular Compartments ◽  
Scanning Electron

X-ray microanalysis of frozen-hydrated tissue sections permits direct quantitative analysis of diffusible elements in defined cellular compartments. Because the sections are hydrated, elemental concentrations can be defined as wet-weight mass fractions. Use of these techniques should also permit determination of water fraction in cellular compartments. Reliable preparative techniques provide flat, smooth, 0.5 micrometers-thick sections with little elemental and morphological disruption. The specimen support and transfer system described permits hydrated sections to be transferred to the scanning electron microscope cold stage for examination and analysis without contamination or water loss and without introduction of extraneous x-ray radiation.

scholarly journals The Location of Impurities in Antarctic Ice

1988 ◽  
Vol 11 ◽  
pp. 194-197 ◽  
Author(s):  
E.W. Wolff ◽  
R. Mulvaney ◽  
K. Oates
Keyword(s):  
Freezing Point ◽  
Ice Sheet ◽  
Chemical Substance ◽  
Triple Junctions ◽  
Sea Salts ◽  
X Ray ◽  
Cold Stage ◽  
Micro Analysis ◽  
The Antarctic ◽  
Scanning Electron

Analysis of an ice sample with an estimated age of 125 years, from the Antarctic Peninsula, using a scanning electron microscope with a cold stage and an X-ray micro-analysis facility, shows that H2SO4 occurs mainly at triple junctions. Sea salts show no such localization. The different behaviour may be due to the freezing-point behaviour of each chemical substance, and to the effect this has both in the atmosphere and during recrystallization in the ice sheet. If this finding applies generally to other parts of the Antarctic ice sheet, it has major implications for many of the physical properties of Antarctic ice. In particular, it leads to a better understanding of the d.c. electrical conductivity of such ice.

A compact, transportable, thermoelectrically cooled cold stage for reflection geometry X-ray powder diffraction

2012 ◽  
Vol 45 (3) ◽  
pp. 608-610 ◽  
Author(s):  
Ian G. Wood ◽  
N. J. Hughes ◽  
F. Browning ◽  
A. D. Fortes
Keyword(s):  
Low Temperature ◽  
Powder Diffraction ◽  
Room Temperature ◽  
The Body ◽  
Base Temperature ◽  
Thermoelectric Cooling ◽  
X Ray ◽  
Temperature Range ◽  
Cold Stage ◽  
Reflection Geometry

A cold stage for Bragg–Brentano geometry X-ray powder diffraction is described for use in the temperature range from about 250 to 300 K. The stage is constructed in such a way that it may be removed from the diffractometer and pre-cooled to its base temperature before the sample is loaded. After loading, thermoelectric cooling maintains the specimen at low temperature (ice free) whilst the body of the stage is allowed to return to room temperature prior to remounting on the diffractometer.

scholarly journals The Location of Impurities in Antarctic Ice

1988 ◽  
Vol 11 ◽  
pp. 194-197 ◽  
Author(s):  
E.W. Wolff ◽  
R. Mulvaney ◽  
K. Oates
Keyword(s):  
Freezing Point ◽  
Ice Sheet ◽  
Chemical Substance ◽  
Triple Junctions ◽  
Sea Salts ◽  
X Ray ◽  
Cold Stage ◽  
Micro Analysis ◽  
The Antarctic ◽  
Scanning Electron

Analysis of an ice sample with an estimated age of 125 years, from the Antarctic Peninsula, using a scanning electron microscope with a cold stage and an X-ray micro-analysis facility, shows that H2SO4 occurs mainly at triple junctions. Sea salts show no such localization. The different behaviour may be due to the freezing-point behaviour of each chemical substance, and to the effect this has both in the atmosphere and during recrystallization in the ice sheet. If this finding applies generally to other parts of the Antarctic ice sheet, it has major implications for many of the physical properties of Antarctic ice. In particular, it leads to a better understanding of the d.c. electrical conductivity of such ice.

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