Centimeters Of Water Research Articles

Studies of the Aerodynamic Performance of a 10 kW Horizontal-Axis Windmill

The aerodynamic performance of a modern, high-tip-speed, three-bladed windmill rated at lOkW at 30 mph was studied by three methods. First, the results of field tests of the actual device with both a resistive and a battery-charging electric load are reported. Second, the predictions of a simple blade-element analysis are presented and compared with the field data. Aerodynamic blade section coefficients of an actual blade section were measured in a wind tunnel and used as input in the analysis. Third, wind tunnel test results for a 1 5th scale model are given. Reynolds number simulation from model to prototype is considered in detail. The results of all three efforts are compared, and good agreement is shown. Nomenclature C = mean chord CL -coefficient of lift CD = coefficient of drag Re — Reynolds number V —velocity c = local chord q = dynamic pressure in centimeters of water r = local radius x = tip-speed ratio (QR/ K) a = angle of attack Q = angular velocity A = scaling factor v = kinematic viscosity

Nitrate‐N Percolation through Irrigated Sandy Soil as Affected by Water Management1

AbstractFertilizer N has been considered as a source of groundwater pollution because of NO3‐N mobility in soil. This study was conducted on a Torripsammet soil (Valent fine sandy loam) during three consecutive growing seasons to determine the magnitude and differences in NO3‐N losses below corn (Zea mays L.) roots from two different, but current, farmer‐used fertilizer management practices. Three farmer‐owned and ‐operated center pivot sprinkler irrigation systems (designated A, B, and C) near Crook, Colo. were used each year. Nitrate‐N percolation losses were measured in water samples collected at 150 cm below the soil surface in vacuum extractors located in a line 91, 182, and 372 m for the pivot in each field. The A, B, and C systems were managed so that 4.8, 2.5, and 10.2% respectively, of the growing season water (irrigation plus rain) percolated to the 150‐cm depth. Three‐year average annual NO3‐N collected in the extractors was 30.4, 19.0, and 59.7 kg/ha for the A, B, and C systems, respectively. Nitrate‐N and water percolating to the 150‐cm depth were highly correlated (r = 0.95), with each centimeter of water carrying an average 10.2 kg/ha NO3‐N. Average annual total dry matter production for the systems, in the same order, was 20,763, 21,876, and 18,858 kg/ha, respectively, and was negatively related to NO,‐N percolating to the 150‐cm depth (r = −0.99), showing that production was highly related to NO3‐N loss. Total dry matter production decreased 65 kg/ha for each kg/ha of NO3‐N percolating to the 150‐cm depth. Soil NO3‐N changed very little from spring to fall in each of the systems but the soil under the A and B systems contained more than 250 kg/ha NO3‐N to a depth of 180 cm, whereas soil under the C system contained only 20 kg/ha to this depth.

Techniques for Analysis of Micturition Reflex Disturbances in Childhood

During the past two decades, improvements in technology and changes in conceptualization have contributed to greater objectivity in the assessment of micturition reflex disturbances.1,2 These changes have been applied principally to analysis of adult dysfunction and have recently been implemented in evaluation of neuromuscular dysfunction of the urinary bladder in infancy and childhood. These newer methods include gas cystometry,3 integrated sphincter electromyography (EMG),4 measurement of reflex-evoked potentials in micturition reflex pathways,5 and electroencephalography (EEG).6 Complementary urodynamic methods include uroflowmetry,7 measurement of urethral pressure profiles,8,9 and observation of pressure-flow relationships during voiding.10 These studies, when appropriately selected and individualized to the patient as a result of the history and examination, provide valuable information. They delineate the site and nature of the impairment of the nervous mechanisms used in the neural and muscular infrastructure in micturition during infancy and childhood. Finally, they provide a rational basis for selection of pharmacologic agents11 and surgical techniques12 to restore urinary continence. Gas cystometry technique Gas cystometry has replaced water cystometry in the evaluation of patients for detrusor reflex instability. The patients are catheterized, and the bladder is inflated with carbon dioxide at room temperature at a constant flow rate of up to a maximum of 200 ml/min. Intravesical pressure is recorded by an isovolumetric strain gauge and transducer amplifier calibrated in centimeters of water.4 Because of the high perfusion rate and brief test interval, additional testing for reflex instability is facilitated. These additional procedures include (1) change in posture from supine to upright, (2) determination of response to subcutaneous injection of bethanechol, and (3) sleep cystometry.

Nitrogen Movement Resulting from Surface Application of Liquid Sewage Sludge

AbstractOne of the factors limiting the rate at which sewage sludge can be applied to soil is the speed at which inorganic N is formed and the fate of that inorganic N. A greenhouse lysimeter study was initiated in order to quantify some of the sinks into which N from sludge applications might move. For 12 weeks soil columns were treated at 3‐week intervals with a surface application of 2.5 cm of liquid sewage sludge. During each 3‐day interval 2.5 cm of water was applied to: (i) soil receiving no sludge (Soil‐2.5), (ii) soil receiving sludge (Sludge‐2.5), and (iii) soil planted to Coastal bermudagrass (Cynodon dactylon L. Pers.) receiving sludge (Grass‐2.5). Five centimeters of water was added to soil + grass + sludge (Sludge‐5) during each 3‐day interval. Another treatment was used to encourage a nitrification‐denitrification cycle. This treatment (Grass‐F) was identical to Grass‐2.5 except that during each third week sufficient water was added to bring the 3‐week total to the same as that in Grass‐5. Provisions were made to collect the leachate for NO3‐N analysis and to measure NH3 volatilization from the sludge.The average loss of N as NH3 was 36% of the applied NH4‐N in the Soil‐2.5 treatment and 24% in the three grass treatments. This represented 4.9 and 3.3%, respectively, of the total N applied. The Grass‐5 treatment resulted in the maximum NO3‐N leaching loss (5.4% of the applied N). The Grass‐F treatment did not result in reduced NO3‐N leaching. Grass removed 10.3% of the applied N. From 52 to 64% of the applied N remained in the sludge crust on the soil surface.

Pressure distribution on the body surface of swimming fish.

ABSTRACT Although there are a number of papers on how fish swim (Gray, 1957; Aleev, 1969; Lighthill, 1969), we have been unable to find any measurements of the pressure on the body surface measured while a fish is swimming. A preliminary calculation using the Pitot equation indicated that the pressure against the anterior surface of the fish, expressed in centimetres of water, would be approximately equal to the square of the speed of the fish in miles per hour. A fish one foot long, swimming at six miles per hour, would have a pressure of about 36 cm H2O against the front of his head. Such pressures, if actually present, might be large enough to affect the body functions, particularly circulatory, and ultimately influence the body structure of aquatic animals. They are of the same order of magnitude as the hydrostatic pressures due to gravity acting on land animals of equal body size, and as the blood pressure in fish (Satchell, 1971). In addition, the determination of the pressure distribution on the body surface of swimming fish may be of help in explaining the mechanism of fish locomotion. Compared to pressure distribution on the body surface of dead fish, or casts, the difference may be responsible for the otherwise unexplained ability of some fish to sustain locomotion with relatively little energy expenditure (Gray, 1957; Schmidt-Nielsen, 1972). In this study we measured the pressure on the body surface of swimming bluefish, and we speculate as to the physiological implications of the pressures which were found.

Heart Activity and High-Pressure Circulation in Cirripedia

Pulsating hemolymph pressures of remarkable magnitude for invertebrates are prevalent in the Pacific gooseneck barnacle. Mean pressures of 250 centimeters of water are common with pulse pressures up to 70 centimeters of water. The pulsations are distinctly rhythmical and the pulsation rate is highly temperature-dependent. The results strongly suggest that in cirripeds hemolymph is circulated by muscular contractions of a functional heart.

Direct test of the positive pressure gradient theory of pseudopod extension and retraction in amoebae.

When one pseudopod of an amoeba is sucked into a capillary connected to a partial vacuum and subjected to a pressure reduction of 30 to 35 centimeters of water, extension of other pseudopods, exposed to atmospheric pressure, is not prevented. This result is interpreted to mean that cytoplasmic streaming cannot be the result of a positive pressure gradient generated along the length of the stream, for if it were, streaming would have reversed its direction under the applied pressure gradient of opposite sign and supposedly greater magnitude.

Changes in Subglottal Air Pressure Associated with Changes of Fundamental Frequency

Subglottal air pressure was recorded with the aid of an intratracheal catheter as three young adult males produced an upward and downward glissando. From a graphic display of both the pressure and the phonation, changes in pressure (ΔPs) and fundamental frequency (Δfo) were determined. The mean Δfo/ΔPs ratio for both phonatory activities was 7.67 semitones per centimeter of water. This is considerably larger than reported by previous investigators. Moreover, when only the range of fundamentals most often used for speech was considered an even larger ratio was found. Even though the importance of subglottal pressure to the generation of a laryngeal tone cannot be denied, the present data suggest that changes in the fundamental of that tone are probably more directly related to laryngeal adjustments such as changes in mass and length of the vocal folds.

Orientation by bulk messenger sensors in aquatic vertebrates.

All higher animals have evolved sense organs to detect minute amounts of chemicals in their environments. The stimuli they perceive affect their behavior in various ways: in locating of food, in orientation in home ranges or territories, in detection of the opposite sex, and even in the recognition of individuals of the same species. Among some fishes, the chemical sense organs are extremely well developed. The olfactory acuity of the eel (Anguilla anguilla) is such that the animal has been trained to respond to beta phenylethyl alcohol in a solution of 1.77 X 103 molecules per cubic centimeter of water (Teichmann, 1962). This, as the late Dr Teichmann so vividly stated, corresponds to a cubic centimeter of scent being dispersed in 58 times the water volume of the Lake of Constance. At this dilution, only two molecules at best would have been at one time in the nose of his small experimental eels, which had a nasal volume of only one cubic millimeter. Other fishes, however, do not appear to use their noses at all; the stickleback, for example, is anosmic. The other chemical sense, taste, is also very acute. It has been established that certain minnows have thresholds for taste several orders of magnitude lower than for humans (Glaser, 1966). Other fishes, which have many more taste sensors than these minnows, are believed to have taste thresholds that come close to olfactory ones. Sensory acuity is often reflected in the anatomy of the receptor organ. The fishes best able to smell have the olfactory epithelium thrown into the largest number of folds (e.g. the eel, FiGURE 1) and have well developed mechanisms to insure the passage of water over the receptor surfaces. Those best able to taste possess a large number of typical vertebrate taste buds (FIGURE 2) distributed all over their bodies, including the tail. In addition to large numbers of receptor cells for bulk messengers and related to the acuity of performance of smell and taste orientation, there are various adaptations that allow a fish to make comparisons of scent or taste substance concentrations in space and/or time. The hammerhead shark (FIGURE 3), for instance, bears its two nares at the extremities of its peculiarly broadened, wedge-shaped head. Directional detection of scent to the right and left of this shark is further enhanced by its sinuous swimming movements.

Growth, Yield, and Yield Components of Safflower as Affected by Irrigation Regimes

AbstractThree to nine irrigations were given in eight irrigation treatments of fall‐planted Frio safflower. Irrigations were given when 60 or 72% of the available water in the top 120 cm of soil was depleted. Five different irrigation cutoff dates were compounded on the soil moisture depletion treatments, ranging from 3 weeks before first blossoming until harvest.The yield of safflower seed increased with each increment of irrigation water to a maximum yield obtained with seven irrigations given until the last blossoms opened (3,961 kg/ha). Consumptive use for this treatment was 107 cm of water. When the last irrigation was given at the first flowering date, seed yield was reduced over 800 kg/ha. Giving the last irrigation about 10 days before blossoming reduced yields nearly one‐half. Weight per seed, oil content, and seeds per head also increased with irrigations up to seven, and the percentage of hollow seed decreased. The seven‐irrigation regime also resulted in the greatest yield per centimeter of water used by the plant. The level of moisture depletion before irrigation had no significant effect on any of the factors studied.

A SHORT CORE SAMPLER FOR SUBAQUEOUS DEPOSITS

The instrument described has been designed to obtain a core 1 m long and 5 cm diam, and to include a few centimeters of water above the sediment surface so that the position of the sediment-water interface can be determined with accuracy. The meter long core provides sufficient overlap with the longer cores to allow measurements to be continued without interruption to the present sediment surface. The ability to obtain undisturbed cores of the upper meter of sediment also has considerable value in the examination of changes in sedimentary composition resulting from relatively recent alteration in the trophic status of lakes.

The Hydraulic System of Urechis Caupo Fisher & Macginitie

ABSTRACT The hydrostatic pressures recorded in the coelom of Urechis during peristalsis, irrigation, burrowing and hind-gut ventilation have been recorded continuously. The main muscular activities except burrowing take place at pressures of a few centimetres of water and, it is suggested, are mainly carried out by the outer circular muscle layer. The high pressures involved in burrowing demand the recruitment of the whole muscle system. The hind-gut ventilation stops when internal pressure is raised, although changes in the contained volume of the body wall do not appear to provide information leading to the maintenance of a fixed volume. Instead this control is probably excercised by the hind gut. An attempt is made to calculate the energy requirements of irrigation and ventilation and it is shown that these are small compared with the respiratory rate, indicating that the movement of large volumes of water for feeding purposes is not an extravagant way of obtaining food in terms of energy expenditure.

Atrial Contribution to Stroke Volume in Dogs with Chronic Heart Block

In dogs studied without thoracotomy, under morphine-pentobarbital anesthesia and with an average heart rate of 71 beats/minute, atrial systole contributes to ventricular function to a small but significant degree. Stroke volume increased by 7 to 8% when atrial systole was timed to occur 0.1 second prior to closure of the atrioventricular valves, and decreased a similar magnitude when the contribution of atrial systole to ventricular filling was rendered ineffective by the use of an A-V delay of zero so that atrial emptying into the ventricles was prevented by the closed A-V valves. Increases or decreases in right atrial pressure of several centimeters of water induced by infusion of 6% dextran and by hemorrhage, respectively, were not associated with demonstrably significant alterations in these effects.

THE EQUIPOTENTIAL ZONE ABOVE THE WATER TABLE

The term "capillary fringe" is ambiguous due to differing definitions. Above a water table there exists a zone wherein total potentials of the soil water are equal. Laboratory experiments conducted in columns of sandy soil showed that, whilst this equipotential zone developed most rapidly over a lowered water table, less rapidly over a water table raised into moist soil, and least rapidly over a water table raised into dry soil, the final height of the zone was approximately equal in all cases. When a soil overlying an impermeable layer with no outlet was wetted from above, an equipotential zone developed prior to the development of a water table.Permeability was the factor dominating the development of the equipotential zone. Once developed, the zone exhibited high permeability, and experiments showed that water movement could occur rapidly even with extremely small total potential gradients, especially where the zone developed by desorption above a lowered water table.The height of the equipotential zone equals numerically the value of matric potential (in centimeters of water) which prevails at field capacity.The term "equipotential zone" is superior and preferable to "capillary fringe" since it describes accurately the prevailing situation and cannot be misinterpreted.

Phosphate—Ammonium—Moisture Relationships in Soils: II. Ion Concentrations in Leached Fertilizer Zones and Effects on Plants

AbstractRadioactive fertilizer pellets MCP32, MCP32 + NH4Cl, and MCP32 + KCl were placed in a Dakota sandy loam and allowed to react for 2 weeks. The pots containing the fertilizer were then leached with 0, 2, 4, and 8 cm of water. Corn (Zea mays) was grown on these pots for 2 weeks and analyzed for total and radioactive P. Results showed only trace amounts of fertilizer P taken up from all nonleached pots. Leaching the pots with 2 or more centimeter of water resulted in a significant uptake of fertilizer P. When the pots were leached with 4 cm of water, P uptake from MCP + NH4Cl pellets was nearly 3‐fold that of either MCP or MCP + KCl. Measurement of water‐soluble P and other conditions in the fertilizer zone indicated no differences between MCP + NH4Cl and MCP + KCl pellet zones. It was concluded that ammonium increased the capacity of the plant to absorb P and did not affect the availability of P in the soil.

LYMPHATIC PRESSURES IN EXTREMITIES OF DOGS.

In reviewing the literature concerning the peripheral lymphatic system, one discovers a relative lack of information with regard to its basic physiology, in terms of accurate measurements of peripheral intralymphatic pressure. In 1933, Drinker and Field 1 reported tying a glass T-tube into a lymphatic lying below the popliteal lymph node of the dog, attaching the tube to a manometer and measuring pressure in centimeters of water. The dog's foot was attached to a rotator which flexed and extended the limb at a rate of 73 times/minute. The pressures which were measured under these conditions were as follows: 41 cm of water after ten minutes and 68 cm of water after 40 minutes of exercise. They recorded no intralymphatic pressure with the animal at rest. In 1932, McMaster and Hudack 2 measured the pressure indirectly in the lymphatics of the mouse's ear as 2-4 cm of water. They rendered the

HYSTERESIS EFFECTS IN SOIL MOISTURE MOVEMENT

Hysteresis was assessed by measuring the tension and moisture content of sections of soil at different time intervals during the redistribution of moisture in uniformly packed columns of Grenville silt loam. Moisture tension was measured by a null method and moisture content was measured gravimetrically.The rate of change of tension with moisture content dψ/dθ and hence the diffusivity, in the tension range 25 to 400 centimeters of water was more than twice as great for drying as for wetting. During redistribution of moisture, when both drying and wetting were involved, different ψ, vs. θ relationships existed at different depths, and the slopes dψ/dθ and diffusivities in the profile were often lower than those for either drying or wetting alone.Further work is needed to assess the importance of hysteresis on moisture movement in practical problems. It seems possible that data on hysteresis, and a knowledge of the past history of wetting and drying, may provide estimates of moisture loss and conservation in fallowed fields.

PORE VOLUME‐SIZE DISTRIBUTION AND SWELLING OF NATURAL SOIL AGGREGATES

SummaryNon‐polar liquid (benzene and 1,1,2,2‐tetrachloroethane) content‐energy curves for soil aggregates have been obtained by using suction plate and pressure membrane apparatus (equivalent pF 0·5‐4·3). For low relative vapour pressure measurements a temperature differential was maintained between two connected chambers, one of which contained the soil aggregates and the other liquid benzene. The results are expressed as the volume of liquid retained in relation to the logarithm of the equivalent suction in centimetres of water (equivalent pF). This procedure enables a direct comparison to be made between the pF‐water content curves and the equivalent pF‐non‐polar liquid curve. When such comparisons are made for a number of clay soils it is apparent that 70 per cent. or more of the swelling takes place before pF 3 is attained on the wetting cycle. By differentiating the non‐polar liquid‐equivalent pF curves for a number of soil materials it has been possible to obtain the pore volume‐size distribution curves. All the clay materials gave broad peaks which extend between pF 2 and 4 and a small peak near pF 5. The peak which occurs just near pF 5 in clay soils is very pronounced for a loam soil. The peak in the coarse pore range occurs irrespective of origin and therefore appears characteristic of clay materials which have been through a number of wetting and drying cycles. The presence of this broad peak indicates that normal shrinkage cannot be expected for natural clay aggregates. The coarse pores which give rise to the broad peak can be regarded as structural pores which are eliminated by compression of the clay.

Combined Pressure Control and Signal Apparatus for Safer Emergency Management of Bleeding Esophagogastric Varices

Adequate tamponade for bleeding esophagogastric varices in portal hypertension poses many problems during the initial emergency care. Many methods have been described for obtaining efficient tamponade with the use of the nasogastric tubes, but few of them have been entirely satisfactory.l-lO A new apparatus for dependable and accurate control of balloon tamponade has been recently developed by the authors. The apparatus consists of two essential elements operating synchronously. This apparatus has been designed to function with any of the nasogastric tubes that have been designed by Sengstaken, Blakemore, Nachlas, Linton, and Patton.a, 6,7 A headgear unit serves to control the direct traction force on the gastric balloon (measured in grams). A cylinder reservoir unit serves to control the intraesophageal balloon pressure (measured in centimeters of water). Both units have special microswitches, which set off the standard hospital alarms should a decrease in either gastric traction force or esophageal balloon pressure occur. The tamponade controls are depicted in figures 1 to 3. The mechanisms of gastric traction with the use of the headgear unit is demonstrated in figure 1. The fulcrum (fj) is in the center of the lever arm. Thus the grams of traction force that are shown on the scale reflect the amount of pull exerted on the nasogastric tube. The scale is calibrated to 1500 gm. The direction of pull of the nasogastric tube is forward and downward to prevent any pressure necrosis of any of the nasal cartilages or epithelium at the lower portion of the nose. Sponge rubber cushions the

Effect of circulatory changes on the pulmonary compliance of normal subjects and patients with mitral stenosis.

Fulfillment by the lungs of their bellows function depends largely on their resiliency and elasticity. Unless the lungs can readily comply with the changes in the thoracic cage during inspiration and expiration, ventilation will be seriously impaired. Pulmonary compliance is expressed as the ratio of lung volume in liters to intraesophageal pressure in centimeters of water. The present study is concerned with the role of pulmonary vascular engorgement in reducing compliance in normal subjects and in patients with mitral stenosis.