Minimum Volume Of Water Research Articles

Blue Marble, Stagnant Lid: Could Dynamic Topography Avert a Waterworld?

Abstract Topography on a wet rocky exoplanet could raise land above its sea level. Although land elevation is the product of many complex processes, the large-scale topographic features on any geodynamically active planet are the expression of the convecting mantle beneath the surface. This so-called “dynamic topography” exists regardless of a planet’s tectonic regime or volcanism; its amplitude, with a few assumptions, can be estimated via numerical simulations of convection as a function of the mantle Rayleigh number. We develop new scaling relationships for dynamic topography on stagnant lid planets using 2D convection models with temperature-dependent viscosity. These scalings are applied to 1D thermal history models to explore how dynamic topography varies with exoplanetary observables over a wide parameter space. Dynamic topography amplitudes are converted to an ocean basin capacity, the minimum water volume required to flood the entire surface. Basin capacity increases less steeply with planet mass than does the amount of water itself, assuming a water inventory that is a constant planetary mass fraction. We find that dynamically supported topography alone could be sufficient to maintain subaerial land on Earth-size stagnant lid planets with surface water inventories of up to approximately 10−4 times their mass, in the most favorable thermal states. By considering only dynamic topography, which has ∼1 km amplitudes on Earth, these results represent a lower limit to the true ocean basin capacity. Our work indicates that deterministic geophysical modeling could inform the variability of land propensity on low-mass planets.

Study of the field hydraulic conductivity of thin open-graded friction courses

Permeability of asphalt pavements is a property of interest due to its impact on durability and, potentially, safety. In the case of open-graded friction courses (OGFC), the focus with permeability is on the improved drainage capacity that reduces splash and spray, and hydroplaning potential. Multiple research efforts have developed permeameters to evaluate field permeability. However, most of these efforts consider unidirectional linear Darcy flow, which is not sufficient to describe flow through OGFC layers during testing conditions. The objective of this investigation was to examine the use of an approximate analytical solution based on 2D flow proposed by researchers at UT-Austin to study the field permeability of thin OGFC layers. Additional values for a shape factor were proposed to test relatively large areas of thin OGFC layers. Furthermore, it was found that the use of vacuum grease to prevent water flow between the base of the permeameter and the pavement surface clogged the OGFC surface voids, which notably reduced hydraulic conductivity. To overcome this issue, this study evaluated the use of a closed-cell high-density foam pad as a sealant method. Lastly, the study showed the need for a minimum volume of water to provide a smooth drop in water head during testing. This is necessary to allow for accurate measurement of the three time readings required to describe the nonlinear relationship between elevation head and flow rate during a falling-head permeability test. The lessons learned from this study were summarized in a set of guidelines for the successful development of a new permeameter. These guidelines can be used by other highway agencies interested in evaluating the field hydraulic conductivity of thin OGFC layers.

ERA5-based global assessment of irrigation requirement and validation.

While only 20% of harvested lands are actually irrigated, 40% of global agricultural production originates from irrigated areas. Therefore, assessing irrigation requirements is essential for the development of effective water-related policies for an efficient management of water resources. Moreover, global-scale analyses are becoming increasingly relevant, motivated by globalized production and international trade of food as well as by the need of common strategies to address climate change.In this study, a comprehensive model to estimate crop growth and irrigation requirements of 26 main crops at global scale is presented. The model computes a soil water balance using daily precipitation and reference evapotranspiration based on a high-resolution ERA5 reanalysis dataset from the European Copernicus Program. The irrigation requirement, defined as the minimum water volume to avoid water stress, is computed for year 2000 at the resolution of 5 arc-min (or 0.0833°) and aggregated at different spatial and temporal scales for relevant analyses.The estimated global irrigation requirements for 962 km3 is described in detail, also in relation to the spatial variability and to the monthly variation of the requirements. A focus on different areas of the world (California, Northern Italy and India) highlights the wealth of information provided by the model in different climatic conditions.National data of irrigation withdrawals have been used for an extensive comparison with model results. A crop-specific validation has also been made for the State of California, comparing model results with local data of irrigation volume and independent estimates of crop water use. In both cases, we found a good agreement between model results and real data.

Cold plasma combined with liposomal ethanolic coconut husk extract: A potential hurdle technology for shelf-life extension of Asian sea bass slices packaged under modified atmosphere

The influence of cold plasma (CP) generated using the mixed gases (oxygen, carbon dioxide argon: 10: 60:30) for 5 min in combination with ethanolic coconut husk extract (ECHE) in either free or liposomal encapsulated form (LE-ECHE) on shelf-life of refrigerated Asian sea bass slices (ASBS) packaged under modified atmosphere was studied.LE-ECHE was prepared using 60 μmol/ml lipid phase containing soybean phosphatidylcholine/cholesterol mixture (4:1, mol ratio) and 1% ECHE. ECHE or LE-ECHE were dissolved in a minimum volume of water and mixed with Asian seabass slices to obtain the final concentration of 400 ppm. Total viable mesophilic bacteria count in CP treated ASBS, particularly those enriched with ECHE or LE-ECHE (EC400-CP and LEC400-CP, respectively) were at least 1 log CFU/g lower than that of the control. Protein and lipid oxidation were lower in EC400-CP and LEC400-CP as compared to those treated with CP only. Discoloration of slices mediated by ECHE was solved by encapsulating ECHE in liposome. Therefore, CP combined with LE-ECHE, was an effective hurdle approach for shelf-life extension of ASBS for more than 18 days at 4 °C.

Associations between shrimp farming and nitrogen dynamic: A model in the Caspian Sea

Marine aquaculture has been developing over the past two decades given the demand for seafood products and the decline of wild fisheries resources. Aquaculture and environmental interactions have also been given an especial attention to investigate the impacts, to improve fish culture strategies and to prevent pollution. In this study, a predictive model with different scenarios was utilized to assess the impacts of shrimp farm effluent through nitrogen dynamic in the Gomishan Wetland, southeast of the Caspian Sea. The results showed that after 2014, total nitrogen content exceeded its standard limits. The worst scenario with the maximum capacity of the farms and the minimum water volume, represented maximum nitrogen concentration of 0.8 mg/L on the 9th day of rearing. The most ideal scenario achieved the maximum amount of shrimp production (238 tons) with no negative influences on wetland water quality, if the water depth in Gomishan Wetland remains equal to 30 cm. These models can aid managers for a better understanding about the aquaculture systems and to reach more sustainable production with the minimum risk of coastal and marine pollution.

Water acidification causes death of marine ornamental fish (Perciformes: Pomacentridae) during transport: contributing to the conservation of wild populations

Pomacentridae is a common family in the aquarium fish trade. Most species are harvested from nature. Here we evaluate the following water parameters in the pomacentrid sergeant major,Abudefdufsaxatilis(Linnaeus, 1758), to assess their stress level during a 24, 48, and 72 hours transport: dissolved oxygen (DO), total ammonia, and pH. In addition, we evaluated the following physiological parameters: plasma osmolality, muscle water content, blood glucose, and the enzyme activities of the branchial carbonic anhydrase (CA), the hepatic glutathione S-transferase (GST), catalase (CAT), and superoxide dismutase (SOD). The mortality of fish measuring >6 cm total length was 22%, while no mortality was observed for fish measuring <6 cm. The pH of the water was significantly correlated with fish mortality, especially for the initial 24 hours of transport. Hypoxia after 24–48 hours also led to fish mortality, but build up ammonia was not a problem even after 72 hours. We suggest that a minimum water volume of 125 ml/g fish is necessary for safe and cost-effective transport of the sergeant major, preferably with <6 cm in total length.

Assessment of the willingness of households to pay for clean water use in Cang Long district, Tra Vinh province

This study aimed to estimate the willingness of households to pay for domestic clean water use against its price in rural areas of Cang Long district, Tra Vinh province. This research also identified the possibility and factors affecting the willingness to pay for a given price of 6,500 VND or above per m3 of clean water. A contingent valuation method with multiple prices (bidding game) ranging from VND 5,000 to VND 9,000 per m3 of clean water was applied to interview 120 households in Cang Long district. Results showed that the mean willingness to pay was VND 6,200 for each m3 of clean water used. The income positively affected the willingness to pay against the price of 6,500 VND or above whereas the household size had a negative impact on this parameter. It is suggested that the service provider should consider to extent the minimum volume of water used up to 10 m3/month instead of 4 m3/month in accordance with the minimum price of 5,700 VND per m3 of water used.

The volume of water required to carve the martian valley networks: Improved constraints using updated methods

The martian valley networks are a key piece of evidence for the presence of liquid water on early Mars, and understanding their formation conditions can provide valuable insight into the nature of the early climate. Previous studies have used various methods to estimate the volume of water required to carve the valley networks, with results ranging from 3–5000 m Global Equivalent Layer (GEL). In comparison, other workers have found that the surface/near-surface water inventory was likely to have been ∼24 m GEL at the Noachian-Hesperian boundary. Thus, 3 m GEL may be consistent with recycling in a cold and icy Late Noachian-Early Hesperian climate, while 5000 m GEL may require continuous warm and wet conditions. In this study, we use updated methods and datasets to better constrain the necessary volume of water, finding a conservative lower limit of 640 m GEL. Based on valley network formation timescales, we find that our results do not preclude a cold and icy Late Noachian-Early Hesperian climate. Thus, this updated estimate of the minimum volume of water required to carve the valley networks is consistent with both formation in a cold and icy and warm and wet climate.

Determination of the Volume of Water for Suppressing the Thermal Decomposition of Forest Combustibles

From the results of experimental studies of the processes of suppressing the thermal decomposition of the typical forest combustibles (birch leaves, fir needles, asp twigs, and a mixture of these three materials) by water aerosol, the minimum volumes of the fire-extinguishing liquid have been determined (by varying the volume of samples of the forest combustibles from 0.00002 m3 to 0.0003 m3 and the area of their open surface from 0.0001 m2 to 0.018 m2). The dependences of the minimum volume of water on the area of the open surface of the forest combustible have been established. Approximation expressions for these dependences have been obtained. Forecast has been made of the minimum volume of water for suppressing the process of thermal decomposition of forest combustibles in areas from 1 cm2 to 1 km2, as well as of the characteristic quenching times by varying the water concentration per unit time. It has been shown that the amount of water needed for effective suppression of the process of thermal decomposition of forest combustibles is several times less than is customarily assumed.

Potenciais usos da água via regularização de vazões no Reservatório João Leite em Goiânia, GO

Reservoir operation requires a series of decisions that defines the quantity of water must be allocated over time for each one of the water demands and which volumes should be maintained in order to reach optimum predefined uses. In this context, the aim of the study is to identify potential water demands in the Joao Leite reservoir, situated in Goiânia, GO, via water balance calculations performed by the network flow model AcquaNet. The simulations show how much water is stored in the reservoir over time and whether is possible or not provide the assessment for other purposes besides both the water supply and the maintenance of the environmental flow. In order to establish target reservoir storage volumes, waiting water volumes are calculated for different return periods and it has been determined the surplus water demands for both wet and dry seasons. The results showed that the Joao Leite reservoir cannot attenuate floods, since it cannot guarantee the water demands under waiting water volumes. However, numerical results obtained considering minimum water volume as the constrained condition has shown that the reservoir can operate on 50% to 90% of total volume, in which potential water uses can be allocated besides water supply and environmental flow. Keywords: Reservoir operation, Reservoir water balance, Joao Leite Stream.

Noble gases solubility models of hydrocarbon charge mechanism in the Sleipner Vest gas field

Noble gases are chemically inert and variably soluble in crustal fluids. They are primarily introduced into hydrocarbon reservoirs through exchange with formation waters, and can be used to assess migration pathways and mechanisms, as well as reservoir storage conditions. Of particular interest is the role groundwater plays in hydrocarbon transport, which is reflected in hydrocarbon–water volume ratios. Here, we present compositional, stable isotope and noble gas isotope and abundance data from the Sleipner Vest field, in the Norwegian North Sea. Sleipner Vest gases are generated from primary cracking of kerogen and the thermal cracking of oil. Gas was emplaced into the Sleipner Vest from the south and subsequently migrated to the east, filling and spilling into the Sleipner Ost fields. Gases principally consist of hydrocarbons (83–93%), CO2 (5.4–15.3%) and N2 (0.6–0.9%), as well as trace concentrations of noble gases. Helium isotopes (3He/4He) are predominantly radiogenic and range from 0.065 to 0.116RA; reported relative to air (RA=1.4×10−6; Clarke et al., 1976; Sano et al., 1988), showing predominantly (>98%) crustal contributions, consistent with Ne (20Ne/22Ne from 9.70 to 9.91; 21Ne/22Ne from 0.0290 to 0.0344) and Ar isotopes (40Ar/36Ar from 315 to 489). Air-derived noble gas isotopes (20Ne, 36Ar, 84Kr, 132Xe) are introduced into the hydrocarbon system by direct exchange with air-saturated water (ASW). The distribution of air-derived noble gas species are controlled by phase partitioning processes; in that they preferentially partition into the gas (i.e., methane) phase, due to their low solubilities in fluids. Therefore, the extent of exchange between hydrocarbon phases and formation waters – that have previously equilibrated with the atmosphere – can be determined by investigating air-derived noble gas species. We utilize both elemental ratios to address process (i.e., open vs. closed system) and concentrations to quantify the extent of hydrocarbon–water exchange (i.e., volumetric gas–water ratios). These data are discussed within the framework of several conceptual models: (i) total gas-stripping model, which assumes all noble gases have been stripped from the water phase, thus defining the minimum volume of water to have interacted with the hydrocarbon phase; (ii) equilibrium model, which assumes equilibration between groundwater and hydrocarbon phase at reservoir P, T and salinity; and (iii) open and closed system gas-stripping models, using concentrations and elemental ratios. By applying these models to Ne–Ar data from Sleipner, we estimate volumetric gas–water ratios VgVw between 0.02 and 0.07, which are lower than standard geologic gas–water estimates of ∼0.24, estimated by combining gas-in-place estimates with groundwater porosity estimates. Sleipner Vest data can be best approximated by an open system model, which predicts more than an order of magnitude more groundwater interaction during migration than geologic estimates, indicating a dynamic aquifer system and/or a hydrous migration pathway. In an open system, the extent of gas loss can be estimated to be between 8 and 10 reservoir volumes, which have passed through the system and been lost (i.e., filled and spilled).

Development of a filtration system with high-frequency flow reversal

ABSTRACT The aim of this study was to develop a filtration system with high-frequency flow reversal and minimum requirement of water for cleaning routines. The system was developed in the period from 2011 to 2013 and consists of three screen filters and eleven solenoid valves electronically controlled by a controller that operates based on head loss measurements. The following evaluations were carried out: head loss curve as a function of flow rate; filtrating efficiency as a function of solids concentration, frequency of flow reversal and increment in head loss. The experimental design was completely randomized in a factorial scheme with three replicates and two treatment levels for each factor. The filtration efficiency was equal to 98.6% for particles larger than 50 µm. The minimum volume of water for each cleaning of the filters was 5.39 L. The head loss increment in the filtration system with flow reversal at frequencies of 11.11 and 22.22 mHz was smaller compared with the filtration system without flow reversal. The developed filtration system has potential for filtering low-quality irrigation water, but requires periodic maintenance to clean the filter element.

SWOT data assimilation for operational reservoir management on the upper Niger River Basin

The future Surface Water and Ocean Topography (SWOT) satellite mission will provide two-dimensional maps of water elevation for rivers with width greater than 100 m globally. We describe a mod-eling framework and an automatic control algorithm that prescribe optimal releases from the Selingue dam in the Upper Niger River Basin, with the objective of understanding how SWOT data might be used to the benefit of operational water management. The modeling framework was used in a twin experiment to simulate the ''true'' system state and an ensemble of corrupted model states. Virtual SWOT observations of reservoir and river levels were assimilated into the model with a repeat cycle of 21 days. The updated state was used to initialize a Model Predictive Control (MPC) algorithm that computed the optimal reservoir release that meets a minimum flow requirement 300 km downstream of the dam. The data assimilation results indicate that the model updates had a positive effect on estimates of both water level and discharge. The ''per-sistence,'' which describes the duration of the assimilation effect, was clearly improved (greater than 21 days) by integrating a smoother into the assimilation procedure. We compared performances of the MPC with SWOT data assimilation to an open-loop MPC simulation. Results show that the data assimilation resulted in substantial improvements in the performances of the Selingue dam management with a greater ability to meet environmental requirements (the number of days the target is missed falls to zero) and a minimum volume of water released from the dam.

Performance of constructed evaporation ponds for disposal of smelter waste water:: A case study at Portland Aluminum, Victoria, Australia

The construction of evaporative ponds and wetlands for the disposal of waste water high in ionic concentrations is a waste disposal strategy currently considered by many industries. However, the design, construction and management of these ponds and wetlands are not straightforward as complex chemical interactions result in both spatial and temporal changes in water quality. The effects of evaporation and drainage on the water quality in two constructed ponds, an adjacent man-made wetland and local groundwater at Portland Aluminium were investigated. The minimum volume of water entering the ponds during the study period was 0.96±0.16 ML per month. The predicted theoretical evaporative capacity of the two ponds was calculated to be 0.30±0.07 ML per month. More water enters the ponds than it is theoretically possible to evaporate under the ambient weather conditions at Portland, yet the ponds do not overflow, suggesting percolation through the pond lining. No spatial differences in solute concentrations (fluoride, sulphate, bicarbonate, carbonate, sodium, potassium, calcium, and magnesium ions) were found within the waters of either pond, although temporal differences were apparent. The results support the conclusion that the ponds are not impermeable, and that much of the waste water entering the ponds is being lost through seepage. The impacts on local groundwater chemistry of this seepage are addressed. Significant correlations exist between solute presence within and between the ponds, wetland and groundwater. Fluoride and sulphate concentrations were significantly higher in pond waters throughout the duration of the experiment. Pond sediments revealed a high degree of spatial and temporal heterogeneity in the concentration of all monitored ions resulting from the chemical heterogeneity of the material making up the pond linings. Adsorption isotherms for fluoride indicate that the adsorption capacity of the pond linings remains high for this ion. Implications for the management of waste water by this strategy are discussed.

Impaired Swallowing Reflex in Patients With Obstructive Sleep Apnea Syndrome

The swallowing reflex is well coordinated with breathing patterns in normal humans. However, patients with obstructive sleep apnea syndrome (OSAS) may have a swallowing disorder that reflects the abnormal function of nerves and muscles in the suprapharynx. To examine the relationship between the swallowing function and sleep-disordered breathing in patients with OSAS. Twenty patients with OSAS with a mean (+/-SD) age of 53.4+/-8.9 years old, and 20 age-matched control subjects with a mean age of 51.4+/-9.1 years old. OSAS was diagnosed using the recordings of overnight polysomnography. The swallowing function in the subject was tested using a swallowing provocation test. The swallowing reflex was determined according to the following criteria: latent time (LT), the time following a bolus injection of distilled water at the suprapharynx to the onset of swallowing; inspiratory suppression time (IST), the time from the termination of swallowing to the next onset of inspiration; and threshold volume, the minimum volume of water (range, 0.4 to 2 mL) that could evoke the swallowing response. Whereas the LT values in patients with OSAS were larger than the LT values in the control subjects, the IST values (which may reflect the switching mechanism from deglutition apnea to breathing) were actually shorter. In addition, a greater bolus volume was necessary to elicit swallowing in patients with OSAS than was necessary in the control subjects. Patients with OSAS are likely to exhibit an impaired swallowing reflex, probably due to the perturbed neural and muscular function of the upper airways.

Application of fungicides to foliage through overhead sprinkler irrigation - a review

Articles on chemigation with fungicides targeting foliage have been reviewed. They included 23 fungicides tested on 10 crops. Many studies compared chemigation to a check treatment, while others also included conventional methods. Chlorothalonil, followed by mancozeb, fentin hydroxide and captafol were the most studied fungicides, while peanut (Arachis hypogaea), potato (Solanum tuberosum), tomato (Lycopersicon esculentum), and dry beans (Phaseolus vulgaris) were the most studied crops. Center pivot, followed by solid set, were the irrigation systems most frequently used. The minimum volume of water applied by some center pivots (25000 litre ha -1 ) is 25 times the maximum volume of water used by conventional ground sprayers. The reduction of fungicide residue on foliage caused by the very large volume of water used by chemigation might be offset by the following factors: (1) fungicide application at the time of maximum leaf wetness when fungi are most active, (2) complete coverage of plants, (3) reducing greatly the inoculum on plant and soil surface, (4) better control of some soil pathogens, and (5) more uniform distribution of fungicides by center pivot. Furthermore, chemigation avoids mechanical damage and soil compaction. Additionally, some systemic fungicides seem to be absorbed rapidly by the leaves, by root uptake from the soil, or by both. In general, all fungicides applied through irrigation water can lessen disease severity. However, when compared to conventional methods, chemigation with fungicides can be less, equally or more effective depending on crop, pathogen, disease severity, fungicide and volume of water. For Cercosporidium personatum control on peanuts, application of protectant fungicides through irrigation water is less effective than conventional methods, but the results with some systemic fungicides mixed with non-emulsified oil and applied through a relatively low volume of water (2.5 mm) are encouraging. Important diseases of potato and tomato can be controlled nearly as well by chemigation as by conventional methods without impairing yield. The main advantage of chemigation for these crops is avoiding a large number of tractor trips through the field and reduced costs of fungicide application. Chemigation has also been shown to be a good option for control of white mold [Sclerotinia sclerotiorum] on dry beans.

Ovine Fetal Laryngeal Chemoreflex Thresholds and Respiratory Effects

In newborn infants, laryngeal contact with solutions of low chloride concentration or pH evokes swallowing, laryngeal adduction, and respiratory inhibition (laryngeal chemoreflex). To determine whether the laryngeal chemoreflex is present during fetal life and its effect on fetal respiratory activity, eight time-bred ewes (128 ± 2 days) were prepared with fetal electrocortical diaphragm and esophageal electrodes and a nasopharyngeal catheter. After a 60-minute control period, increasing volumes (0.1 to 1.0 ml/kg) of 0.15 mol/L NaCl or distilled water (0.05 to 1.0 ml/kg) and decreasing concentrations of NaCl (0.15 to 0.02 mol/L) at a fixed volume (0.3 ml/kg) were sequentially administered through the nasopharyngeal catheter (38° C). The minimum water volume that stimulated swallowing was significantly less than the minimum 0.15 mol/L NaCl volume (0.10 ± 0.02 vs. 0.70 ± 0.05 ml/kg). The maximum NaCl concentration that stimulated swallowing was 0.04 ± 0.01 mol/L. During the control period, respiratory activity averaged 14.6 ± 0.7 breaths/minute and did not change during absent swallow responses or isotonic saline-induced swallows. However, respiratory activity significantly decreased during water (4.7 ± 0.6 breaths/minute) and hypotonic saline-induced swallow responses (3.7 ± 0.7 breaths/minute). Fetal electrocortical activity did not change during absent or stimulated swallows. We conclude that laryngeal water or hypotonic saline solution may stimulate fetal swallowing and suppress fetal respiratory activity, similar to the newborn laryngeal chemoreflex. We speculate that an exaggeration of the laryngeal chemoreflex apnea response in the newborn may predispose to sudden infant death syndrome.

Ovine fetal laryngeal chemoreflex thresholds and respiratory effects

In newborn infants, laryngeal contact with solutions of low chloride concentration or pH evokes swallowing, laryngeal adduction, and respiratory inhibition (laryngeal chemoreflex). To determine whether the laryngeal chemoreflex is present during fetal life and its effect on fetal respiratory activity, eight time-bred ewes (128 ± 2 days) were prepared with fetal electrocortical diaphragm and esophageal electrodes and a nasopharyngeal catheter. After a 60-minute control period, increasing volumes (0.1 to 1.0 ml/kg) of 0.15 mol/L NaCl or distilled water (0.05 to 1.0 ml/kg) and decreasing concentrations of NaCl (0.15 to 0.02 mol/L) at a fixed volume (0.3 ml/kg) were sequentially administered through the nasopharyngeal catheter (38° C). The minimum water volume that stimulated swallowing was significantly less than the minimum 0.15 mol/L NaCl volume (0.10 ± 0.02 vs. 0.70 ± 0.05 ml/kg). The maximum NaCl concentration that stimulated swallowing was 0.04 ± 0.01 mol/L. During the control period, respiratory activity averaged 14.6 ± 0.7 breaths/minute and did not change during absent swallow responses or isotonic saline-induced swallows. However, respiratory activity significantly decreased during water (4.7 ± 0.6 breaths/minute) and hypotonic saline-induced swallow responses (3.7 ± 0.7 breaths/minute). Fetal electrocortical activity did not change during absent or stimulated swallows. We conclude that laryngeal water or hypotonic saline solution may stimulate fetal swallowing and suppress fetal respiratory activity, similar to the newborn laryngeal chemoreflex. We speculate that an exaggeration of the laryngeal chemoreflex apnea response in the newborn may predispose to sudden infant death syndrome. (Otolaryngol Head Neck Surg 1997;116:91-6.)

A new instrument for the measurement of soil moisture suction

Current methods of determining soil moisture suction are outlined and their shortcomings identified. A new instrument is then described which will overcome a number of these problems by the use of a miniature pressure transducer, and minimum volume of water between the active face of the transducer and the porous stone. The instrument uses an Entran EPX-500 stainless steel miniature pore water pressure transducer, with a working range up to 3500 kPa, shrouded by a stainless steel sheath fitted with a porous stone. The mechanics of the instrument and its evaluation against known values of suction are outlined. Reliable measurements of suction were achieved up to 1500 kPa.

The relation of catastrophic flooding of Mangala Valles, Mars, to faulting of Memnonia Fossae and Tharsis Volcanism

Detailed stratigraphic relations indicate two coeval periods of catastrophic flooding and Tharsis centered faulting (producing Memnonia Fossae) in the Mangala Valles region of Mars. Major sequences of lava flows of the Tharsis Montes Formation and local, lobate plains flows were erupted during and between these channeling and faulting episodes. First, Late Hesperian channel development overlapped in time the Tharsis‐centered faulting that trends north 75° to 90°E. Next, Late Hesperian/Early Amazonian flooding was coeval with faulting that trends north 55° to 70°E. In some reaches, resistant lava flows filled the early channels, resulting in inverted channel topography after the later flooding swept through. Both floods likely originated from the same graben, which probably was activated during each episode of faulting. Faulting broke through groundwater barriers and tapped confined aquifers in higher regions west and east of the point of discharge. The minimum volume of water required to erode Mangala Valles (about 5×1012 m3) may have been released through two floods that drained a few percent pore volume from a relatively permeable aquifer. The peak discharges of the floods may have lasted from days to weeks. The perched water discharged from the aquifer may have been produced by hydrothermal groundwater circulation induced by Tharsis magmatism, tectonic uplift centered at Tharsis Montes, and compaction of saturated crater ejecta due to loading by lava flows.