scholarly journals High-Pressure Freezing: Current State and Future Prospects

2013 ◽  
pp. 151-171 ◽  
Author(s):  
Andres Kaech ◽  
Urs Ziegler
Keyword(s):  
High Pressure ◽  
High Pressure Freezing ◽  
Future Prospects ◽  
Current State

High-pressure freezing of cells in suspension for low-voltage scanning electron microscopy (LVSEM)

1991 ◽  
Vol 49 ◽  
pp. 64-65
Author(s):  
Marek Malecki ◽  
James Pawley ◽  
Hans Ris
Keyword(s):  
Electron Microscopy ◽  
High Pressure ◽  
Low Voltage ◽  
Culture Media ◽  
Cell Structure ◽  
Freeze Substitution ◽  
Ice Crystal ◽  
High Pressure Freezing ◽  
Cell Culture Media ◽  
Voltage Scanning

The ultrastructure of cells suspended in physiological fluids or cell culture media can only be studied if the living processes are stopped while the cells remain in suspension. Attachment of living cells to carrier surfaces to facilitate further processing for electron microscopy produces a rapid reorganization of cell structure eradicating most traces of the structures present when the cells were in suspension. The structure of cells in suspension can be immobilized by either chemical fixation or, much faster, by rapid freezing (cryo-immobilization). The fixation speed is particularly important in studies of cell surface reorganization over time. High pressure freezing provides conditions where specimens up to 500μm thick can be frozen in milliseconds without ice crystal damage. This volume is sufficient for cells to remain in suspension until frozen. However, special procedures are needed to assure that the unattached cells are not lost during subsequent processing for LVSEM or HVEM using freeze-substitution or freeze drying. We recently developed such a procedure.

Cryosectioning plant roots prepared by high-pressure freezing

1987 ◽  
Vol 45 ◽  
pp. 662-663
Author(s):  
R.E. Crang ◽  
M. Mueller ◽  
K. Zierold
Keyword(s):  
High Pressure ◽  
Cell Walls ◽  
Plant Tissues ◽  
Ice Crystal ◽  
High Pressure Freezing ◽  
Vitreous State ◽  
Radial Depth ◽  
Irregular Topography ◽  
Considerable Depth ◽  
Conventional Freezing

Obtaining frozen-hydrated sections of plant tissues for electron microscopy and microanalysis has been considered difficult, if not impossible, due primarily to the considerable depth of effective freezing in the tissues which would be required. The greatest depth of vitreous freezing is generally considered to be only 15-20 μm in animal specimens. Plant cells are often much larger in diameter and, if several cells are required to be intact, ice crystal damage can be expected to be so severe as to prevent successful cryoultramicrotomy. The very nature of cell walls, intercellular air spaces, irregular topography, and large vacuoles often make it impractical to use immersion, metal-mirror, or jet freezing techniques for botanical material.However, it has been proposed that high-pressure freezing (HPF) may offer an alternative to the more conventional freezing techniques, inasmuch as non-cryoprotected specimens may be frozen in a vitreous, or near-vitreous state, to a radial depth of at least 0.5 mm.

High-pressure freezing and freeze substitution of plant tissue

1992 ◽  
Vol 50 (1) ◽  
pp. 748-749
Author(s):  
William P. Sharp ◽  
Robert W. Roberson
Keyword(s):  
High Pressure ◽  
Cell Structure ◽  
Leaf Tissue ◽  
Freeze Substitution ◽  
Crystal Formation ◽  
Ice Crystal ◽  
High Pressure Freezing ◽  
Cell Components ◽  
Cold Metal ◽  
Brome Grass

The aim of ultrastructural investigation is to analyze cell architecture and relate a functional role(s) to cell components. It is known that aqueous chemical fixation requires seconds to minutes to penetrate and stabilize cell structure which may result in structural artifacts. The use of ultralow temperatures to fix and prepare specimens, however, leads to a much improved preservation of the cell’s living state. A critical limitation of conventional cryofixation methods (i.e., propane-jet freezing, cold-metal slamming, plunge-freezing) is that only a 10 to 40 μm thick surface layer of cells can be frozen without distorting ice crystal formation. This problem can be allayed by freezing samples under about 2100 bar of hydrostatic pressure which suppresses the formation of ice nuclei and their rate of growth. Thus, 0.6 mm thick samples with a total volume of 1 mm3 can be frozen without ice crystal damage. The purpose of this study is to describe the cellular details and identify potential artifacts in root tissue of barley (Hordeum vulgari L.) and leaf tissue of brome grass (Bromus mollis L.) fixed and prepared by high-pressure freezing (HPF) and freeze substitution (FS) techniques.

High-pressure freezing and freeze substitution of teliospores of the rust fungus Gymnosporangium clavipes

1990 ◽  
Vol 48 (3) ◽  
pp. 692-693
Author(s):  
Robert W. Roberson
Keyword(s):  
High Pressure ◽  
Room Temperature ◽  
Pathogenic Fungus ◽  
Rust Fungus ◽  
Freeze Substitution ◽  
Ice Crystals ◽  
High Pressure Freezing ◽  
Thin Walled Structures ◽  
Cytological Changes ◽  
Dextran Solution

The use of cryo-techniques for the preparation of biological specimens in electron microscopy has led to superior preservation of ultrastructural detail. Although these techniques have obvious advantages, a critical limitation is that only 10-40 μm thick cells and tissue layers can be frozen without the formation of distorting ice crystals. However, thicker samples (600 μm) may be frozen well by rapid freezing under high-pressure (2,100 bar). To date, most work using cryo-techniques on fungi have been confined to examining small, thin-walled structures. High-pressure freezing and freeze substitution are used here to analysis pre-germination stages of specialized, sexual spores (teliospores) of the plant pathogenic fungus Gymnosporangium clavipes C & P.Dormant teliospores were incubated in drops of water at room temperature (25°C) to break dormancy and stimulate germination. Spores were collected at approximately 30 min intervals after hydration so that early cytological changes associated with spore germination could be monitored. Prior to high-pressure freezing, the samples were incubated for 5-10 min in a 20% dextran solution for added cryoprotection during freezing. Forty to 50 spores were placed in specimen cups and holders and immediately frozen at high pressure using the Balzers HPM 010 apparatus.

scholarly journals Remote sensing of sun-induced chlorophyll-a fluorescence in inland and coastal waters: Current state and future prospects

2021 ◽  
Vol 262 ◽  
pp. 112482
Author(s):  
Remika S. Gupana ◽  
Daniel Odermatt ◽  
Ilaria Cesana ◽  
Claudia Giardino ◽  
Ladislav Nedbal ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Chlorophyll A ◽  
Coastal Waters ◽  
Chlorophyll A Fluorescence ◽  
Future Prospects ◽  
Current State

scholarly journals The role of adiponectin in periodontitis: Current state and future prospects

2021 ◽  
Vol 137 ◽  
pp. 111358
Author(s):  
Zhaodan Wang ◽  
Zehao Chen ◽  
Fuchun Fang ◽  
Wei Qiu
Keyword(s):  
Future Prospects ◽  
Current State

Deadlock or new opening? Current state and prospects for development of Lithuanian-Belarusian relations

2021 ◽  
Vol 19 (3) ◽  
pp. 121-141
Author(s):  
Justyna Olędzka
Keyword(s):  
International Relations ◽  
Presidential Election ◽  
Nuclear Power ◽  
Future Prospects ◽  
Bilateral Relations ◽  
Current State ◽  
The Future ◽  
Multi Level ◽  
The Moment ◽  
The Eu

The purpose of this article is to discuss the trajectory of Belarusian-Lithuanian relations with a particular focus on the period after the 2020 Belarusian presidential election, which resulted in a change in international relations in the region. This was the moment that redefined the Lithuanian-Belarusian relations, which until 2020 were satisfactory for both sides (especially in the economic aspect). However, Lithuania began to pursue a reactive policy of promoting the democratisation of Belarus and provided multi-level support to Belarusian opposition forces. The current problems in bilateral relations (e.g., the future of Belarusian Nuclear Power Plant located in Astravyets) have been put on the agenda for discussion at the EU level, while the instruments of a hybrid conflict in the form of an influx of immigrants into Lithuania, controlled by the Belarusian regime, have become a key issue for the future prospects of relations between Belarus and Lithuania.

Development and Evaluation of a Mobile Plant to Prepare Natural Gas for Use in Foam Fracturing Treatments

2017 ◽  
Author(s):  
Griffin Beck ◽  
Melissa Poerner ◽  
Kevin Hoopes ◽  
Sandeep Verma ◽  
Garud Sridhar ◽  
...  
Keyword(s):  
High Pressure ◽  
Natural Gas ◽  
Oil And Gas ◽  
Department Of Energy ◽  
Gas Processing ◽  
Current State ◽  
Fracturing Process ◽  
Mobile Plant ◽  
Processing Plants ◽  
Production Techniques

Hydraulic fracturing treatments are used to produce oil and gas reserves that would otherwise not be accessible using traditional production techniques. Fracturing treatments require a significant amount of water, which has an associated environmental impact. In recent work funded by the Department of Energy (DOE), an alternative fracturing process has been investigated that uses natural gas as the primary fracturing fluid. In the investigated method, a high-pressure foam of natural gas and water is used for fracturing, a method than could reduce water usage by as much as 80% (by volume). A significant portion of the work focused on identifying and optimizing a mobile processing facility that can be used to pressurize natural gas sourced from adjacent wells or nearby gas processing plants. This paper discusses some of the evaluated processes capable of producing a high-pressure (10,000 psia) flow of natural gas from a low-pressure source (500 psia). The processes include five refrigeration cycles producing liquefied natural gas as well as a cycle that directly compresses the gas. The identified processes are compared based on their specific energy as calculated from a thermodynamic analysis. Additionally, the processes are compared based on the estimated equipment footprint and the process safety. Details of the thermodynamic analyses used to compare the cycles are provided. This paper also discusses the current state of the art of foam fracturing methods and reviews the advantages of these techniques.

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