Large Open Areas Research Articles

Coastal sea surface temperature variability along the south coast of South Africa and the relationship to regional and global climate

The southern coastline of South Africa is approximately zonal, with a wide (up to 270 km) shelf region. Intense thermoclines are known to be established by insolation on the inner shelf region during summer, upwelling is generated by easterly-component winds, and occasionally Agulhas Current water can be advected close to the coast, particularly in the east. These processes induce daily and seasonal fluctuations of coastal sea-surface temperature (SST), but their influence over longer time scales (interannual) has not yet been tested. Here time series of SST ranging from 12 to 31 years are examined for inter-relationships with local and regional winds, and the southern oscillation index (SOI). The emphasis is on the summer period, and it is found that the correlation between SST and major axis wind anomalies can be improved substantially by considering the frequency of occurrence of winds above given thresholds. Moreover, winds and SSTs are also correlated with the SOI, such that fewer easterlycomponent winds are experienced at low phases (EI Nino) with consequent increases in coastal SST, and correspondingly more easterly-component winds at high phases (La Nina) result in decreased coastal SST; however, these relationships did not hold for a measuring site within a large open bay area. Long-term trends are also established, with substantial increases in SST (0.25°C/decade) in association with greater increases in air temperature (0.36°C/ decade)

Biosphere reserves in Germany: A contribution to support sustainable development

Biosphere reserves are protected areas of representative environments internationally recognised for their value for conservation and for their ability to provide the scientific knowledge, skills and human values to support sustainable development. Biosphere reserves — as a part of the UNESCO programme “Man and the Biosphere” (MAB) — make up a world-wide network sharing research information on ecosystem conservation, management and development. They include strictly protected ‘core-areas’ — representative examples of natural or minimally disturbed ecosystems. Core areas are surrounded by ‘buffer zones’ in which research, environmental education and training and recreation can take place. Buffer zones are, in turn, surrounded by ‘transition areas’, large open areas where the aim is to ensure rational development of the natural resources of the region. At present, twelve biosphere reserves are designated in Germany, covering in all an area of 11,589 km2. The role of biosphere reserves to support sustainable development in Germany and Europe is discussed.

Treatment of wool scouring wastewater for grease removal

Most of the wool scouring wastewater treatment systems in Australia consist of open anaerobic and facultative ponds which require large open areas. Apart from being unsightly and emitting odours, the plants are usually located in environmentally sensitive areas thereby causing environmental problems. There is a great need to look at alternative treatment systems which are more efficient and more environmentally acceptable. This study set out to investigate ways of reducing the grease content of the wastewater so that the pretreated wastewater can be fed to some high rate anaerobic digester. Various combinations of additions of coagulants, flocculants as well as using sulphuric acid for pH adjustment of the wastewater were attempted for assessing the extent of grease and COD removals. The study was also conducted at temperatures of 20 to 45°C. It was found that up to 98% of grease and 79% of COD could be removed by just using sulphuric acid at a pH of between 2 and 3 and at a temperature of 20°C. This work was first done on a batch basis. The work was extended into a continuous laboratory scale mixer-settler assembly which produced comparable results to those obtained batchwise.

Combustion zone - Acoustic cavity interactions in rocket combustors

Analytical and numerical models are employed to assess the stabilizing impact of acoustic absorbers on liquid propellant rocket engine intrinsic stability. The tuning and stability behavior of cavities in which two-dimensional flow and temperature variations exist are predicted through the application of an iterative-integral, Green's function method of analysis. Results of stability calculations performed for a variety of cavity geometries and temperature gradients indicate that adding a large open area absorber to a combustion chamber significantly alters the spatial shape of the oscillation. This alteration consequently affects the driving and damping mechanisms in the chamber. Because of this interaction, the maximal stabilizing effect of a cavity with a given open area does not in general occur for a design tuned in the acoustic sense to the frequency of the oscillation, but rather for a design that is not tuned but which tends to maximize the influence of the damping mechanisms in the chamber relative to the driving mechanisms. Additionally, absorbers with large backing cavities are shown to perform better over a wider range of operating conditions than absorbers with small backing cavities. Calculations also reveal that large temperature gradients in an absorber tend to reduce its broadband effectiveness.

Performance Enhancement of Thick Film Microstripline Circuits by Metallic Thin Film Overcoat

The microwave properties of microstripline at S‐band and X‐band and ?/2 rejection filter with midband rejection at 3 GHz fabricated by thick film technology are studied. The effect of an overcoat of Ag thin film of thickness 2 µm deposited by ion plating and electroless plating on Ag and Pd‐Ag thick film circuits is reported. There is a drastic improvement in the performance of the thick film circuits after overcoating. This is attributed to the superior edge definition whereby losses are reduced. As the edge is smoother, especially at the coupling area of the filter, there is tighter coupling, thus increasing the Q of the filter. The overcoat may also reduce the large open areas of the thick film, giving a smoother upper surface finish. This type of metallic overcoat, i.e., hybrid of thick and thin film, may reduce the need for costly and time‐consuming functional trimming and expensive thick film materials.

Modeling Fire Safety in Multi-Use, Domed Stadia

Smoke control system design for domed, multi-use stadia is discussed. Two design fires were considered, one on the playing field, or the large open assembly area associated with a nonsports use of the stadium, and one under the stands, typically a fire in a concession. The open assembly area (playing field) fire included a tall fire plume which entrained a great deal of air. This resulted in diluted smoke arriving at the top of the dome, sometimes in concentrations which would pose minimal threat to occupants in the structure. Very large volume air movements were involved in venting this dilute smoke. A concession fire, under the stands on a concourse was simulated. Concourses usually loop completely around the stadium. Smoke flow laterally along the con course, if controlled, can impact ventilation requirements. The movement of patrons to the exits involved bridges across the upper concourse. Smoke density at these bridges and/or the vomitories was a major design constraint.

The Color of Light in Forests and Its Implications

Forests exhibit much variation in light environments, and this can affect communication among animals, communication between animals and plants, photosynthesis, and plant morphogenesis. Light environments are caused by, and can be predicted from, the geometry of the light paths, the weather conditions, and the time of day. The structure of forests leads to four major light habitats when the sun is not blocked by clouds: forest shade, woodland shade, small gaps, and large gaps. These are characterized by yellow—green, blue—gray, reddish, and "white" ambient light spectra, respectively. When the sun is blocked by clouds, the spectra of these four habitats converge on that of large gaps and open areas, so the single light environment during cloudy weather will be called open/cloudy. An additional light environment (early/late) is associated with low sun angles (near dawn or dusk); it is purplish. Each light environment is well defined and was found in forests of Trinidad, Panama, Costa Rica, Australia, California, and Florida. Scattered literature references suggest similar patterns elsewhere in North America, Europe, and Java. Perceived colors of animals, flowers, and fruits depend upon the interaction between ambient light color and the reflectance color of the animal or plant parts. As a result, an animal or plant may have a different appearance in each environment, i.e., a color pattern may be relatively cryptic in some light environments while relatively conspicuous in others. This has strong implications for the joint evolution of visual signals and vision, as well as microhabitat choice. Plant growth and form may also be affected by variation in the color of forest light.

Where industry meets nature. How public concern has influenced the design of Swedish industrial landscapes during the 20th century

During the 20th century in Sweden, industrial landscape design has reflected different ideals at different times. Roughly, four different periods can be distinguished, two in which the leit motif has been the encouragement of industrial objects, two in which the aim has been to hide them or tone them down. During the period 1909–1929, environmentalists usually viewed industrial exploitation as a necessity, but maintained that the industrial object should be made aesthetically pleasing. Pride in the technical achievements of the time permeated physical design and manifested itself in buildings in a nationalistic, monumental style. During the period 1930–1949, the dominating design principle was that the complexes should harmonize with their surroundings. The monumental style of the buildings was replaced by a more frugal, functional architecture and rounded land-forms, and natural vegetation was used. The aesthetic ideals from the period 1950–1964 reflected a significant change from the previous period. More emphasis was laid on the character of industry and human influence. Geometrically exact land-forms, large open areas and horticultural vegetation characterized this period. During the period 1965–1985, at the same time as the visual aspect became less important in environmental protection debates, aesthetic ideals shifted from a heavy emphasis on the industrial character to its almost complete subordination. In summary, one can say that the predominant design principles have, to a considerable extent, been characterized by adaptation to the industrial structures themselves. Industrial landscape design in Sweden has been overshadowed in recent years by the one-sided emphasis on preservation issues demonstrated by authorities as well as the ‘green movement’. If this development continues, it will result in an unfortunate polarization of untouched nature on the one hand and industrial landscape on the other. It should be a reasonable aim of landscape development to see that also positive values are given to the industrially affected landscapes.

Southern Ocean sea-ice distributions and extents

Southern Ocean sea-ice coverage undergoes a large seasonal cycle, with a nearly fivefold increase in areal ice extents from the minimum in February to the maximum in September, and significant interannual variations. Results presented here show in a variety of forms some of the variability that occurred in Southern Ocean sea-ice distributions and extents over the 1970s and 1980s. Interannual variability is examined by identifying changes in three measures: sea-ice extents, sea-ice distributions, and the length of the sea-ice season. Regarding these three: (i) Maximum ice extents varied by approximately 12%, decreasing during the mid-1970s, followed by increases over the next few years and a levelling off for much of the 1980s. (ii) The area of interannual variability in monthly average sea-ice distributions in summer far exceeds the summertime area of consistent ice coverage, in sharp contrast to the wintertime situation, when the area of consistent ice coverage is considerably larger. In winter, the ice-distribution variability is largely confined to two regions: a relatively narrow outer band (generally 2-5° of latitude) surrounding the region of consistent ice coverage, and, for the mid-1970s, the region of an occasional large open water area within the ice pack of the Weddell Sea, termed the Weddell polynya. The Weddell and other polynyas within the ice cover allow intensified heat, mass, and momentum exchanges between ocean and atmosphere, thereby affecting regional oceanic and atmospheric circulations, (iii) The length of the sea-ice season, calculated for the years 1979-1986, with satellite passive-microwave data coverage through all months of the year, showed increases over that period in the Ross Sea but decreases in the Weddell and Bellingshausen seas. In both cases it appears, through comparisons with data from 1973-1976, that the 1979-1986 changes more likely reflect a fluctuating behaviour of the ice cover than a long-term trend. The changes in the ice cover have influences not only on the ocean and the atmosphere but on aquatic plant and animal life as well.

Diffraction effects in x-ray proximity printing

The influence of diffraction on the shape and size of features printed using x-ray proximity printing with a collimated x-ray source (measured beam divergence of ∼0.2 mrad full width at half-maximum) at mask to wafer gaps of 25 μm and above is described. Three major conclusions can be drawn from the results: (1) Diffraction can distort the shape of a printed feature, and the systematic shape changes observed in resist images can be explained using simple scaling based on Fresnel diffraction; (2) The linewidth change with exposure dose is independent of feature type and size, and depends only on the square root of the mask to wafer gap; and (3) The bias of each printed feature varies when all of the feature types and sizes are printed at the same dose. Resist images of 2.0–0.25 μm contact holes printed at mask to wafer gaps ranging from 25 to 515 μm are presented. The square contact holes on the mask print diamond shaped at a Fresnel number of 2.5. Isolated lines, spaces, and line-space arrays ranging from 1.0 to 0.25 μm were printed in thin PMMA (0.1 μm thick) resist at gaps ranging from 25 to 80 μm over a series of exposure doses. A 10% increase in exposure dose results in a 16, 20, and 30 nm change in linewidth at gaps of 25, 40, 80 μm, respectively. When the 1.0–0.25 μm lines, spaces, and line-space arrays are printed with a single dose at a 40 μm gap, the bias variation among the features appears to be approximately ±20 nm. However, this bias measurement is very sensitive to the metrology technique used, and systematic errors in these absolute measurements may be a significant contributor to the observed bias variation. All the experimental results are compared to calculated aerial images. Exposures in thick PMMA (0.5 μm) show trends similar to those observed in thin resist. However, as the thickness of the resist increases, the dose at which the printed linewidth has zero bias decreases, and approaches the dose required to clear a large open area.

Study of sidewall passivation and microscopic silicon roughness phenomena in chlorine-based reactive ion etching of silicon trenches

Sidewall passivation layers produced in the formation of Si trenches by HCl/O2/BCl3 reactive ion etching have been characterized by angle-resolved x-ray photoemission measurements and secondary electron microscopy. Electron-shading effects observed at grazing electron emission angles and electrostatic charging of insulating portions have been used to differentiate photoemission contribution from (i) the trench sidewall film (moderately insulating), (ii) the oxide mask (highly insulating), and (iii) the Si trench bottom (conductive). The sidewall passivation film for this process is found to be a silicon oxide. Only minor amounts of chlorine are incorporated in this film. The thickness of the sidewall passivation layer depends on the width of the Si trench and ranges from ≂0.1 μm for narrow trenches to ≂0.7 μm for wide Si trenches for our conditions. The Si taper formed in this trench etching process is produced by the simultaneous formation of the sidewall film which protects the underlying Si from etching. It is also shown that microscopic silicon pillars (‘‘black silicon’’ or ‘‘grass’’) form by micromasking under process conditions where large areas of unmasked silicon are exposed. The microscopic Si pillars are protected by the same sidewall passivation film as the trench sidewalls. Islands of black silicon are observed only in large open silicon areas and separated from oxide masked areas by a characteristic distance which is free of silicon pillars. This roughness-free distance is of the order of the mask thickness employed. Ion scattering from the sloped mask sidewalls and sputtering of involatile micromasking material can explain this observation. Our results are consistent with a mechanism in which the processes that cause the formation of the beneficial sidewall film also initiate and control the production of undesirable silicon roughness in large unmasked Si regions.

A simple electronic volume cell sorter for clonogenicity assays.

A single-parameter electronic volume flow cell sorter that can be easily and inexpensively constructed using existing technology is described. The instrument is designed for ease and flexibility of operation, including such features as a large open area for recovering sorted cells into a variety of dishes or vessels; a remote, electrically activated fluidics system; a mechanism for heating or cooling samples during sorting; a simple arrangement for monitoring and adjusting the sorting control parameters; and an interface to a standard IBM personal computer for data acquisition, analysis, and control of the sorting windows. Several researchers in our laboratory now routinely use this sorter for plating precise numbers of cells directly into culture dishes in an aseptic manner for clonogenicity assays. The instrument can sort cells at rates of up to approximately 2,000 per second with greater than 80% sorting efficiency and no cytotoxicity. An advantage of this system is that the sorting windows can be set to exclude acellular debris and include either the entire cell volume distribution or a subset thereof. Applications of the instrument are detailed, including 1) precise cell plating for low-dose survival studies, 2) separation of cells into age compartments, and 3) rapid inoculation of single cells into multiwell dishes for cloning studies. Advantages of this technology for cell survival studies are detailed, along with some limitations to its applicability.

Moving callitrichid monkeys from cages to outside areas

AbstractTo assess the important aspects of a large area for environmental enrichment, the behavior of families of common marmosets Callithrix jacchus and cotton‐top tamarins Saguinus oedipus when in laboratory cages and when in much larger outside areas was compared. All animals avoided areas with little cover. The two tamarin families preferred an indoor cage to a large open area with little cover and consequently only showed a limited range of behavior when outside. When dense cover was provided to the marmoset family, they used this area extensively, showing a wider range of behavior than when in cages and shifting to less active behavior patterns. By feeding marmosets in a central area, it was possible to allow unlimited access to the outside while effectively containing them.

The Ecology of the Salt-Marsh Harvest Mouse (Reithrodontomys raviventris) in a Diked Salt Marsh

The salt-marsh harvest mouse (Reithrodontomys raviventris) was a fugitive species in this diked marsh. These mice were able to use more open and saltier pickleweed (Salicornia virginica) when numbers of meadow mice (Microtus californicus) were high and they moved into deeper and less salty pickleweed as the population of meadow mice declined. In this first extensive study of a diked marsh, salt-marsh harvest mice were shown to swim and run across larger open areas than they had been thought to cross previously. The salt-marsh harvest mouse (Reithrodontomys raviventris) endemic to the marshes of San Francisco Bay (Fisler, 1965), has become endangered primarily because of destruction and modification of its habitat. Approximately 80% of the historic tidal marshes have been destroyed and most of those that remain support few to no mice because of backfilling, subsidence, or vegetation changes (Shellhammer, 1982). Approximately 30% of the historic tidal marshes of San Francisco Bay remain as diked marshes. Eighty percent of the diked marshes are located in Suisun Bay, the northeasterly component of the San Francisco Bay system. The habitat is primarily managed for waterfowl use; mouse populations are small and separated by large areas of inappropriate habitat. Approximately 13 km2 of diked marshes remain in the South San Francisco Bay and constitute potential refuges for the more endangered of the two harvest mouse subspecies, R. r. raviventris, within a ring of large cities and extensive bayland development. Little, however, is known of the biology of the mouse in diked marshes subject to great changes in moisture and salinity throughout the year. Some are flooded periodically by rain waters or by bay water after breaks in outboard levees. Most surface water evaporates each summer. This study was conducted to ascertain mouse numbers, distribution, and interactions with other species during the summer when moisture is low and salinities are high; the microhabitat requirements of these mice in diked marshes; and how barriers such as sloughs and open areas affect movements of the mice.

Flow around a permeable rectangular plate standing vertically on the flat wall. (1st report The case of the permeable square plate)

The flow around a permeable square plate, normal to a stream, standing vertically against the flat wall on which the turbulent boundary layer was developing was investigated experimentally. The velocity profile of the wake, the vortex shedding from the permeable plate and the surface pressure distribution on both the plate and the fiat wall were measured for a permeable plate with various open area ratios. The profiles of wake velocity vectors and the flow visualization by both oil-film and smoke-wire techniques clarified that the circulation region behind the permeable plate was moved downstream by the bleed flow with increasing open area ratio, and that the circulation region disappeared for a large open area ratio. The vortex shedding can be found for the permeable plate with a small open area ratio. In addition, the drag coefficient shows a significant change at an open area ratio of about 0.2.

An experimental investigation of the effects of shorebird and flatfish predation on estuarine invertebrates

Shorebirds and flatfish were selectively excluded from areas of mudflat of the Ythan estuary in two separate experiments. Exclosures and control areas were monitored over several months for sediment and faunal characteristics and compared by 2-way ANOVA. There was no significant effect of the exclosures on sediment properties, due to the relatively large open area of the exclosure material used. Exclosures had little effect on invertebrate densities. The results are discussed in relation to prey mobility and the effects of predation estimated from energy demands of the predators. It is suggested that, over the study period, predators did not significantly affect the numbers of invertebrates in the mudflats. Over the winter period, Corophium within exclosures were significantly larger than those in control areas, probably due to size-selective predation by shorebirds.

Abundance and Habitat Selection of Two American Kestrel Subspecies in North-Central Florida

Abstract We censused American Kestrels (Falco sparverius) in the three vegetation communities representative of north-central Florida (pine flatwoods, sandhills, and agriculture/mixed hardwoods) along 24 16-km roadside transects. The winter kestrel population included resident F. s. paulus and migrant F. s. sparverius. Eighty-four percent of the 1,433 kestrels were sighted in winter, reflecting a significant influx of migrant F. s. sparverius, and were primarily females (65%). Significant (P < 0.05) sexual differences in winter habitat use were attributed to the large numbers of migrants. Males preferred closed habitats and smaller-sized open areas, and females preferred open habitats and larger open areas. Wintering kestrels were most abundant (P < 0.05) in the agriculture/mixed-hardwoods community (51%) and least abundant in the pine-flatwoods community (13%). Seventy-one percent of the 233 kestrels seen during summer were identified as F. s. paulus. Males and females were observed in approximately equal numbers and exhibited no differences in habitat preference. Falco s. paulus preferred the sandhill community (79%) to the agriculture/mixed hardwoods and pine flatwoods. Within the sandhill community, resident kestrels significantly increased their use of the pine/oak woodlands during summer.

Evaluation of a Tissue Cage Model for Use in Cattle

Three different types of subcutaneous tissue cages were evaluated as sources of tissue fluid in cattle. The biochemical composition of fluid sampled at various intervals after insertion was analysed and compared to corresponding serum values. It was shown that steel netting cages were quickly obliterated by ingrowing tissue and therefore unsuitable. The two types of silicone rubber tubing cages, on the other hand, were not obliterated and could be sampled repeatedly for volumes of about 2 ml tissue cage fluid (TCF) up to at least 32 weeks after insertion. Repeated sampling in a 12 h period was also possible. The levels of total protein and albumin in TCF were lower than in serum, and were shown to decline in the first 12 weeks after insertion to a level of about 35% of the serum concentration. Calcium and magnesium levels were also lower in TCF as compared to serum. The levels of chloride and potassium were slightly higher in TCF than in serum. For sodium no difference was observed and the results for inorganic phosphorous were not uniform. Repeated sampling did not alter the total protein and albumin level in TCF. It was also shown that cages with larger open areas had lower total protein content.

Seasonal Variations in Breeding Success of Common Terns: Consequences of Predation

We studied the breeding of 125 pairs of Common Terns (Sterna hirundo) in a large colony at Monomoy, Massaschusetts, in 1979. The colony was subjected to predation by one or more Great Homed Owls (Bubo virginianus). The adult terns deserted the colony for 6.5-8 hours each night throughout the season. Although the owl(s) took no adults and only about 20 chicks from our study plots, the terns suffered unusually heavy losses from other causes, including breakage and disappearance of eggs, hatching failures, attacks by ants (Lasius neoniger), chilling of newly-hatched chicks, and predation by Black-crowned NightHerons (Nycticorax nycticorax). In a 10-year study, most of these causes of egg and chick loss have been associated with nocturnal desertion and predation by Great Horned Owls. Although nocturnal desertion is effective in minimizing owl predation on adults, it leaves the eggs and chicks vulnerable to chilling and predation. In 1979, both direct and indirect effects of predation fell more heavily on terns that laid in May than on terns that laid in June. Differential predation on early nesters tends to offset other factors that presumably favor early nesting. Predation is one of the most important selective forces influencing breeding behavior in ground-nesting colonial birds, such as gulls and terns (Lack 1968). When a nocturnal predator gains access to a colony, larids usually have no effective defenses (Austin 1948, Ashmole 1963, Southern et al. 1982). However, avian predators and diurnal mammals often take only limited numbers of colonial larids (Hatch 1970, Nisbet 1975, Southern et al. 1982). Consequently, the study of differential mortality in a larid colony can throw light on the role of predation in influencing timing, synchrony, and spacing behavior (Ashmole 1963, Kruuk 1964, Patterson 1965, Tinbergen 1967, Parsons 1971, Nisbet 1975). Nisbet (1975) reported that Great Horned Owls (Bubo virginianus) preying on nesting Common Terns (Sterna hirundo) took a much higher proportion of chicks hatched earlier in the season than of chicks hatched later. We describe here a study of another Common Tern colony subjected to predation by one or more Great Homed Owls. In the case described here, direct predation by the owl(s) was less important than other causes of egg and chick losses. However, we present evidence that at least some of these other losses were indirect consequences of the owl's activity. This paper analyzes seasonal variations in both direct and indirect effects of owl predation. STUDY AREA AND METHODS We studied 125 pairs of Common Terns within a colony of about 3,300 pairs at Monomoy National Wildlife Refuge, Massachusetts (41038'N, 69058'W) in May-August 1979. This was part of a long-term study of this colony, whose results are summarized in Table 1. In 1979, we selected two study plots about 75 m apart, comprising a total area of about 570 m2. Each plot was on the edge of a large open sandy area surrounded by dense beach grass (Ammophila breviligulata). Common Terns nested earliest and most densely in a partially vegetated border strip containing scattered clumps of live and dead beach grass, seaside goldenrod (Soli ago sempervirens) and beach pea (Lathyrus japonica). Although both study plots included areas of dense grass and open sand, Common Terns occupied these habitats later and less densely than the border strips. The plots were selected to be representative of the whole colony, and the density and patterns of occupation appeared similar in other parts of the colony. We visited the study plots on most days from 22 May to 9 July, on 20, 21 and 28 July, and on 7 August 1979. P. Trull visited the colony n five other days between 10 and 25 July. N ts and eggs were marked when first seen, and eggs were weighed. When eggs were not found on the day of laying, this date was estimated from laying and hatching patterns and by flotation (Hays and LeCroy 1971); weights of fresh eggs were estimated from data on the rate of weight loss (Rahn et al. 1976). Nine banded adults, including two nesting outside the plots, were trapped to determine their ages. Chicks were banded at hatching and checked

Fast acting hydrogen valve

A valve that was developed for injecting hydrogen into the combustion chamber of a scramjet model being tested in a transient shock tunnel is described. The requirements of the project have led to the development of a valve which could have more general application in transient testing facilities. The valve is designed to open and close rapidly. It is compact, has a large opening area and closes after an adjustable opening time with a minimum value of 10 ms. It is actuated by a 3 mm solenoid valve and is suitable for use with pressures from 300-2500 kPa.