Prolonged Fixation Studies For Spaceflight

1973 ◽  
Vol 31 ◽  
pp. 332-333
Author(s):  
Robert Corbett ◽  
Delbert E. Philpott ◽  
Sam Black
Keyword(s):  
High Pressure ◽  
Living Systems ◽  
Prolonged Storage ◽  
Time Intervals ◽  
Early Signs ◽  
Large Numbers

Observation of subtle or early signs of change in spaceflight induced alterations on living systems require precise methods of sampling. In-flight analysis would be preferable but constraints of time, equipment, personnel and cost dictate the necessity for prolonged storage before retrieval. Because of this, various tissues have been stored in fixatives and combinations of fixatives and observed at various time intervals. High pressure and the effect of buffer alone have also been tried.Of the various tissues embedded, muscle, cartilage and liver, liver has been the most extensively studied because it contains large numbers of organelles common to all tissues (Fig. 1).

scholarly journals The accuracy of gypsum casts obtained from the disinfected extended-pour alginate impressions through prolonged storage times

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Rania A. Sharif ◽  
Khalid M. Abdelaziz ◽  
Najla M. Alshahrani ◽  
Fatimah S. Almutairi ◽  
Mohrah A. Alaseri ◽  
...  
Keyword(s):  
Dimensional Stability ◽  
Storage Time ◽  
Prolonged Storage ◽  
Time Intervals ◽  
Superior Surface ◽  
Stability Data ◽  
Surface Detail ◽  
Storage Times ◽  
One Way Anova ◽  
Chemical Disinfection

Abstract Background Manufacturers of the extended-pour alginates claimed their dimensional stability through prolonged storage. No data confirmed the ability of these materials to maintain their dimensions and the reproduced oral details following their chemical disinfection. Therefore, this study evaluated the dimensional stability and surface detail reproduction of gypsum casts obtained from disinfected extended-pour alginate impressions through different storage time intervals. Methods Two hundred and forty three hydrocolloid impressions were made from one conventional (Tropicalgin) and two extended-pour (Hydrogum 5 and Chromaprint premium) alginates. These impressions were subjected to none, spray and immersion disinfection before their storage in 100% humidity for 0, 72 and 120 h. The dimensional stability and the surface detail reproduction were indirectly evaluated under low angle illumination on the resulted gypsum casts. At α = 0.05, the parametric dimensional stability data were analyzed using One-Way ANOVA and Tukey’s comparisons, while the nonparametric detail reproduction data were analyzed using KrusKal Wallis and Mann–Whitney's tests. Results All gypsum casts exhibited a degree of expansion; however, the recorded expansion values did not differ between test categories (P > 0.05). Generally, casts obtained from spray-disinfected impressions showed lower detail accuracy (P < 0.05). Immersion-disinfected extended-pour alginates produced casts with better detail accuracy following 120 h of storage (P < 0.05). Conclusion All alginates materials offer comparable cast dimensions under different testing circumstances. Extended-pour alginates offer casts with superior surface details following their immersion disinfection and 120 h of storage. Spray-disinfection using 5.25% sodium hypochlorite affects the surface details of casts obtained from conventional and extended-pour alginates adversely.

High-Pressure Gear Pumps

1946 ◽  
Vol 155 (1) ◽  
pp. 417-452 ◽  
Author(s):  
T. E. Beacham
Keyword(s):  
High Pressure ◽  
High Pressures ◽  
Journal Bearings ◽  
Volumetric Efficiency ◽  
Solid Matter ◽  
Excessive Pressure ◽  
Low Viscosity ◽  
Large Numbers ◽  
Gear Pumps ◽  
The Relationship

Gear pumps have been used in very large numbers for the various hydraulic services of war aircraft. For the higher pressures the main problems have been in connexion with the load on the journal bearings, with wear, and with the reduction in volumetric efficiency caused by internal leakage. The journal loads are affected by the number of teeth and by the ratio of width to diameter of the gears. With high pressures it is difficult to accommodate standard ball or roller races on account of their diameter: designs are illustrated using a combination of standard races and special needle roller bearings. Small amounts of wear cause comparatively large reductions in volumetric efficiency. Major causes of wear are rubbing on the gear end faces and solid matter in suspension in the liquid and methods of dealing with these are discussed. The percentage slip due to internal leakage varies inversely as the factor (r.p.m. × viscosity). At low speeds and with low-viscosity liquids, internal leakage often limits the pressure at which the pump can be used. Multistage pumps reduce the leakage and have been used extensively for undercarriage operation. Internal leakage becomes relatively less as the size of the pump is increased and the paper gives a graph, showing the relationship between the limit of pressure at which 80 per cent volumetric efficiency is possible, the capacity and rotational speed of the pump, and the viscosity of the liquid. Aircraft pumps generally use gears with involute teeth: ports in the end covers of the casing are used to prevent excessive pressure in the liquid trapped between the teeth. Low- and high-leakage conditions call for difficult arrangements of ports, and this involves differing displacements and variations in flow velocity.

Microstructural Evolution of Mg-4Nd Alloy Processed by High-Pressure Torsion

2010 ◽  
Vol 667-669 ◽  
pp. 391-396 ◽  
Author(s):  
Jing Bai ◽  
Feng Xue ◽  
Saleh N. Alhajeri ◽  
Terence G. Langdon
Keyword(s):  
Grain Size ◽  
High Pressure ◽  
Dislocation Density ◽  
Room Temperature ◽  
High Pressure Torsion ◽  
High Angle ◽  
Sharp Rise ◽  
Large Numbers ◽  
Average Grain Size ◽  
Hardness Values

Disks of as-extruded Mg-4Nd alloy were processed by high-pressure torsion (HPT) through ¼ to 5 turns at room temperature. The first 1/4 turn of HPT induces large numbers of twins and some dislocation tangles in the center region of the disk. With increase of torsional straining, the twinning is inhibited gradually and the dislocation density increases relating to the formation of dislocation substructures and ultimately transforming to high fractions of equiaxed gains which have an average grain size of ~200 nm and high-angle boundaries. HPT significantly improves the values of microhardness of this alloy. The hardness values in both the central and edge regions show a sharp rise after HPT for 1/4 turn and exhibit nearly saturation after 1/2 turn although there is a trend of a slight increase with increasing numbers of turns. The experimental results suggest more homogeneous microstructures may be produced by larger numbers of turns in the HPT process.

Patterns Relevant to the Temporal Data-Context of an Alarm of Interest

2010 ◽  
pp. 18-39 ◽  
Author(s):  
Savo Kordic ◽  
Chiou Peng Lam ◽  
Jitian Xiao ◽  
Huaizhong Li
Keyword(s):  
Data Mining ◽  
Main Idea ◽  
High Volume ◽  
Chemical Plants ◽  
Data Mining Technique ◽  
Time Intervals ◽  
Alarm Systems ◽  
Large Numbers ◽  
Petroleum Refineries ◽  
Active Exploration

The productivity of chemical plants and petroleum refineries depends on the performance of alarm systems. Alarm history collected from distributed control systems (DCS) provides useful information about past plant alarm system performance. However, the discovery of patterns and relationships from such data can be very difficult and costly. Due to various factors such as a high volume of alarm data (especially during plant upsets), huge amounts of nuisance alarms, and very large numbers of individual alarm tags, manual identification and analysis of alarm logs is usually a labor-intensive and time-consuming task. This chapter describes a data mining approach for analyzing alarm logs in a chemical plant. The main idea of the approach is to investigate dependencies between alarms effectively by considering the temporal context and time intervals between different alarm types, and then employing a data mining technique capable of discovering patterns associated with these time intervals. A prototype has been implemented to allow an active exploration of the alarm grouping data space relevant to the tags of interest.

Line Broadening Studies on Highly Defective TiO2 Produced by High Pressure Shock Loading

1983 ◽  
Vol 27 ◽  
pp. 379-388
Author(s):  
B. Morosin ◽  
E. J. Graeber ◽  
R. A. Graham
Keyword(s):  
High Pressure ◽  
Catalytic Activity ◽  
Crystallite Size ◽  
Shock Loading ◽  
Lattice Strain ◽  
Line Broadening ◽  
X Ray Diffraction ◽  
Pressure Shock ◽  
X Ray ◽  
Large Numbers

Enhanced solid state reactivity of materials both during and after shock compression has been attributed to the introduction of large numbers of defects into the crystalline lattices and to reduction in the particle and crystallite size of powders [1]. In particular, orders of magnitude increases in the catalytic activity has been observed In shock-modified TiO2 [2]. Line broadening of x-ray diffraction profiles provides a means to determine the coherent crystallite size and the residual lattice strain resulting from defect concentrations. The present study on shock-loaded rutile is a detailed Investigation of the influence of shock loading on residual lattice strain and coherent crystallite size. Annealing of shock-modified rutile powders is also studied.

ULTRASTRUCTURAL CHANGES IN THE ADENOHYPOPHYSIS OF CASTRATED RABBITS

1966 ◽  
Vol 35 (1) ◽  
pp. 101-NP ◽  
Author(s):  
B. A. YOUNG ◽  
C. L. FOSTER ◽  
E. CAMERON
Keyword(s):  
Granule Size ◽  
Ultrastructural Changes ◽  
Pars Distalis ◽  
General Shape ◽  
Time Intervals ◽  
Early Effect ◽  
Large Numbers ◽  
Type 3 ◽  
Golgi Zone

SUMMARY The ultrastructure of the rabbit adenohypophysis is described at increasing time-intervals after castration. An early effect of castration was the appearance of large numbers of degranulated or partially degranulated cells in both the pars distalis proper and the zona tuberalis. These cells were similar in general shape and granule size to the type 3 and 3z cells of the normal rabbit adenohypophysis. Characteristically these cells show a dilatation of the cisternae of the ergastoplasm and a prominent Golgi zone. 284 days after castration the partially degranulated cells were very large and their dilated cisternae were up to 1·3 μ in diameter and more spherical in form. Since the cells most affected by castration were similar in all respects to the type 3 and 3z cells described in normal rabbits, they are considered to be the gonadotrophs.

scholarly journals Impact of High-Pressure Process on Probiotics: Viability Kinetics and Evaluation of the Quality Characteristics of Probiotic Yoghurt

Foods ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 360 ◽  
Author(s):  
Maria Tsevdou ◽  
Maria Ouli-Rousi ◽  
Christos Soukoulis ◽  
Petros Taoukis
Keyword(s):  
High Pressure ◽  
Storage Period ◽  
Bifidobacterium Bifidum ◽  
Predictive Tool ◽  
Time Intervals ◽  
Minimal Impact ◽  
Probiotic Strains ◽  
Entire Storage Period ◽  
The Impact ◽  
Kinetics Of

The impact of high-pressure (HP) processing on the viability of two probiotic microorganisms (Bifidobacterium bifidum and Lactobacillus casei) at varying pressure (100−400 MPa), temperature (20−40 °C) and pH (6.5 vs. 4.8) conditions was investigated. Appropriate mathematical models were developed to describe the kinetics of the probiotics viability loss under the implemented HP conditions, aiming to the development of a predictive tool used in the design of HP-processed yoghurt-like dairy products. The validation of these models was conducted in plain and sweet cherry-flavored probiotic dairy beverage products pressurized at 100−400M Pa at ambient temperature for 10 min. The microbiological, rheological, physicochemical and sensory characteristics of the HP-treated probiotic dairy beverages were determined in two-week time intervals and for an overall 28 days of storage. Results showed that the application of HP in the range of 200−300 MPa had minimal impact on the probiotic strains viability throughout the entire storage period. In addition, the aforementioned HP processing conditions enhanced the rheological and sensory properties without affecting post-acidification compared to the untreated product analogues.

Physicochemical Properties of Chilled Abalone as Influenced by Washing Pretreatment in Citric Acid Combined with High Pressure Processing

2014 ◽  
Vol 10 (4) ◽  
pp. 767-774
Author(s):  
Ji-Yeon Chun ◽  
Yeon-Ji Jo ◽  
Kyeong-Hun Jung ◽  
Mi-Jung Choi ◽  
Sang-Gi Min ◽  
...  
Keyword(s):  
High Pressure ◽  
Citric Acid ◽  
Physicochemical Properties ◽  
Shelf Life ◽  
Storage Period ◽  
Viable Count ◽  
High Pressure Processing ◽  
Microbial Inactivation ◽  
Prolonged Storage ◽  
Acid Pretreatment

Abstract Citric acid pretreatment (2% and 4% citric acid) and high pressure processing (200–400 MPa for 3 min) were conducted to elucidate quality characteristics and shelf life of abalone during chilled storage. Physicochemical properties, total volatile basic nitrogen (TVB-N), and total viable count (TVC) were used as indicators of quality and the shelf life of abalone. Citric acid pretreatment caused a decrease in pH and lightness, and 4% citric acid pretreatment exhibited a positive effect on TVB-N and TVC. Pressurization suppressed the formation of TVB-N and the growth of TVC in abalone. However, excessive modification in physicochemical properties of abalone resulted from processing at a pressure higher than 300 MPa. To achieve microbial inactivation without severe modification in abalone quality, citric acid pretreatment with high pressure processing offered a potential advantage in maintaining characteristics of chilled abalone during prolonged storage period.

scholarly journals Influence of the frequency of pulsating high-pressure cutting fluid jets on the resulting chip length and surface finish

2021 ◽  
Author(s):  
Antonia Splettstoesser ◽  
Daniel Schraknepper ◽  
Thomas Bergs
Keyword(s):  
High Pressure ◽  
Cutting Speed ◽  
Surface Damage ◽  
Low Pressure ◽  
Cutting Fluid ◽  
Depth Of Cut ◽  
Time Intervals ◽  
Pressure Stage ◽  
Chip Breaking ◽  
Fluid Supply

AbstractHigh-pressure cutting fluid supply is a proven technology for chip breaking when turning difficult-to-cut materials, such as Inconel 718. However, the technology is usually not suitable for the finish turning of safety-critical parts in aero engines. The acting force of the cutting fluid jet on the back of the chip causes chip breaking. The broken chips are then accelerated by the cutting fluid jet towards the workpiece surfaces where they cause damage on impact. One approach to minimize surface damage is a specific increase in the chip length. The center of gravity of the chips with an adjusted length is shifted out of the focus where the cutting fluid jet hits the chips. Hence, the already finished surface is subjected to fewer impacts of the chips. In this study, the adjustment of the chip length by pulsating high-pressure cutting fluid supply to prevent surface damage was investigated. A valve unit was used to generate two alternating cutting fluid supply pressure levels in certain time intervals. During the low-pressure stage, the force of the cutting fluid jet does not lead to chip breakage and the chip length increases until the valves switch and the high-pressure stage is released. The focus of this work was the analysis of the relationship between the duration of the low-pressure and high-pressure time intervals and the chip length. Additionally, the influence of the depth of cut, the feed, and the cutting speed on the chip length during pulsating high-pressure cutting fluid supply was investigated. Finally, a case study was carried out to evaluate the effectiveness of the pulsating high-pressure cutting fluid supply technology. Therefore, the shoulder surface of a demonstrator part was finished by face turning. Following, the cylindrical surface was finished with a continuous and pulsating high-pressure cutting fluid supply with varied supply parameters. Microscopic analyses of the surface prove that the pulsating high-pressure cutting fluid supply prevents the surface from being damaged by the impacts of chips.

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