Screening of polymers on selected Hawaii soils for erosion reduction and particle settling

In recent years, high‐molecular‐weight anionic polyacrylamides (PAMs) have been tested on a variety of soils, primarily in temperate climates. However, little information is available regarding the effectiveness of PAM for preventing soil loss through runoff in tropical settings. Screening tests were performed using three negatively charged PAMs and one positively charged PAM on five Hawaii soils (two Oxisols, one Vertisol, and two Aridisols) to determine erosion loss, sediment settling, and aggregate stability. A laboratory‐scale rainfall simulator was used to apply erosive rainfall at intensities from 5 to 8·5 cm h^?1 at various PAM doses applied in both dry and solution forms. Soil detachment due to splash and runoff, as well as the runoff and percolate water volumes, were measured for initial and successive storms. The impact of PAM on particle settling and aggregate stability was also evaluated for selected soil‐treatment combinations. Among the PAMs, Superfloc A‐836 was most effective, and significantly reduced runoff and splash sediment loss for the Wahiawa Oxisol and Pakini Andisol at rates varying between 10 and 50 kg ha^?1. Reduced runoff and splash sediment loss were also noted for PAM Aerotil‐D when applied in solution form to the Wahiawa Oxisol. Significant reductions in soil loss were not noted for either the Lualualei Vertisol or the Holomua Oxisol. It is believed that the high montmorillonite content of the Lualualei Vertisol and the low cation‐exchange capacity of the Holomua Oxisol diminished the effectiveness of the various PAMs tested. The polymers were also found to enhance sediment settling of all soils and helped improve their aggregate stability. This screening study shows the potential use of PAM for tropical soils for applications such as infiltration enhancement, runoff reduction, and enhanced sedimentation of detention ponds. Copyright © 2005 John Wiley & Sons, Ltd.     

A proposed search of the solar neighborhood for substellar objects

The Infrared Astronomical Satellite (IRAS) program will produce an extremely sensitive all-sky survey over the wavelength region 8 to 120 μm when the mission is flown in 1982. These data will provide a novel opportunity to detect planetary-sized objects having masses <0.08M_⊙ or near our solar system. The improved detection limit of the IRAS will greatly increase the volume of space searched for such objects as compared with previous optical and infrared studies.     

Observations of cosmic gamma-ray bursts

The occasional occurrence of brief but intense bursts of cosmic gamma-rays was disclosed through a systematic search of data acquired from the Vela satellites. Confirmation of the nature of the events and additional detail of their characteristics has subsequently been provided by 15 other groups of experimenters with instruments on 13 spacecraft. Thirty-nine such events have been identified from data spanning a period of four and a half years. The record of intensity as a function of time varies considerably for different events, with total durations ranging from 0.1 to 60s. Time-integrated flux density ranges from 10^–6 to 10^–3 erg cm^–2. Spectral measurements have been accomplished by several groups of experimenters, showing a broad maximum in the energy distribution at about 150 keV. The distribution of source directions implies either near galactic or extragalactic locations. The existing data are not sufficient to distinguish between the various models proposed to explain the phenomenon; no model is completely consistent with all observed characteristics.Work performed under the auspices of the United States Energy Research and Development Administration.Paper presented at the COSPAR Symposium on Fast Transients in X-and Gamma-Rays, held at Varna, Bulgaria, 29–31 May, 1975.     

Determination of specific yield using a water balance approach – case study of Torla Odha watershed in the Deccan Trap province, Maharastra State, India

Specific yield is an essential parameter for any groundwater management plan. Volumetric analysis in the domain of groundwater budgeting for the non-monsoon months has been undertaken for a typical watershed of the Deccan basalt province. The Torla Odha watershed covers an area of over 22 km² on a third-order tributary of the westerly flowing Bhima River. The watershed receives a normal annual rainfall of 643 mm. The entire water demand is supplied by dug wells, which penetrate a shallow aquifer. The specific yield was estimated by comparing the monthly net volume of water removed from the aquifer, with the volume of aquifer de-saturated, based on monthly water level data. The estimated specific yield ranges from 0.0019 in May to 0.0173 in November with an average value of 0.0093. A correlation of the groundwater levels with the detailed geology suggests that the higher specific yield value (0.017) corresponds to dewatering of the weathered zone within the shallow aquifer. The specific yield of the massive basalt immediately below the weathered zone varies from 0.0089 to 0.0103. The underlying vesicular basalt, which is dissected by sheet joints, has a relatively higher specific yield (0.0121). The massive basalt, which forms the base of the shallow aquifer system, has a lower specific yield from 0.0019 to 0.0022.

---

Résumé Le débit spécifique est un paramètre essentiel pour tout plan de gestion des eaux souterraines. Les analyses volumétriques, dans le cadre des bilans hydriques des eaux en dehors des mois de mousson, ont été entreprises pour un bassin-versant typique de la province basaltique du Deccan. Le bassin-versant du Torla Odha couvre une superficie de 22 km², et alimente l’affluent du troisième ordre de la rivière Bhima, qui coule vers l’Ouest. La pluviométrie annuelle atteint 643 mm. Toute la demande en eau es assurée par des puits foncés pénétrant dans l’aquifère phréatique. Le débit spécifique a été estimé en comparant le volume net mensuel d’eau captée dans l’aquifère, avec le volume de l’aquifère dé-saturé, basé sur les données des niveaux piézométriques mensuels. Le débit spécifique estimé s’étend entre 0,0019 en Mai et 0.173 en Novembre; la moyenne se situe à 0,0093. Une corrélation entre les niveaux des eaux souterraines et la géologie, suggère que les débits spécifiques les plus importants (0,017) correspondent aux zones altérées de l’aquifère phréatique. Le débit spécifique du massif basaltique, immédiatement sous la zone altérée, varie entre 0,0089 et 0,0103. Le basalte vésiculaire, situé juste en dessous et traversé par des diaclases parallèles, possède un débit spécifique sensiblement plus élevé (0,0121). Le basalte massif, qui forme la base de l’aquifère phréatique, possède un débit spécifique moins important, compris entre 0,0019 et 0,0022.

---

Resumen El rendimiento específico es un parámetro esencial para cualquier plan de manejo de aguas subterráneas. Se ha llevado a cabo el análisis volumétrico, en el entorno de balance de aguas subterráneas, para los meses sin monzón de una cuenca típica de la provincia de basaltos Deccan. La cuenca Rorla Odha cubre un área de 22 km² en un tributario de tercer orden del Río Bhima que fluye al oeste. La cuenca capta una lluvia anual normal de 643 mm. La totalidad de la demanda de agua es abastecida por pozos manuales que penetran un acuífero somero. Se estimó el rendimiento específico al comparar el volumen neto mensual de agua removido del acuífero con el volumen de agua de-saturado estimado a partir de datos de niveles de agua mensuales. Los valores estimados de rendimiento específico varían de 0.0019 en mayo a 0.0173 en noviembre con un valor promedio de 0.0093. La correlación de niveles de agua subterránea con la geología de detalle sugieren que el valor más alto (0.017) de rendimiento específico corresponden con el desaguado de la zona de intemperismo dentro del acuífero somero. El rendimiento específico del basalto masivo que se encuentra inmediatamente debajo de la zona de intemperismo varía de 0.0089 a 0.0103. El basalto vesicular subyacente, el cual está disectado por fracturas laminares, tiene un rendimiento específico relativamente más alto (0.0121). El basalto masivo, que forma la base del sistema de acuífero somero, tiene un rendimiento específico más bajo el cual varía de 0.0019 a 0.0022. Palabras clave: basalto Deccan. India. Rendimiento específico. Recarga de agua subterránea. Balance hídrico.

     

A response‐based decoupling criterion for multiply‐supported secondary systems

It is often infeasible to carry out coupled analyses of multiply‐supported secondary systems for earthquake excitations. ‘Approximate’ decoupled analyses are then resorted to, unless the response errors due to those are significantly high. This study proposes a decoupling criterion to identify such cases where these errors are likely to be larger than an acceptable level. The proposed criterion is based on the errors in the primary system response due to decoupling and has been obtained by assuming (i) the input excitation to be an ideal white noise process, (ii) cross‐modal correlation to be negligible, and (iii) the combined system to be classically damped. It uses the modal properties of the undamped combined system, and therefore, a perturbation approach has been formulated to determine the combined system properties in case of light to moderately heavy secondary systems. A numerical study has been carried out to illustrate the accuracy achieved with the proposed perturbation formulation. The proposed decoupling criterion has been validated with the help of two example primary‐secondary systems and four example excitation processes. Copyright © 2002 John Wiley & Sons, Ltd.     

Dublin days: the 2003 NAM

Mark E Bailey and Tom Ray give an overview of the National Astronomy Meeting in Dublin, where record numbers of astronomers went to talk, listen and network.     

Phosphorus retention in calcareous soils and the effect of organic matter on its mobility

A survey of the interactions between phosphorus (P) species and the components of calcareous soils shows that both surface reactions and precipitation take place, especially in the presence of calcite and limestone. The principal products of these reactions are dicalcium phosphate and octacalcium phosphate, which may interconvert after formation. The role of calcium carbonate in P retention by calcareous soils is, however, significant only at relatively high P concentrations – non-carbonate clays play a more important part at lower concentrations. In the presence of iron oxide particles, occlusion of P frequently occurs in these bodies, especially with forms of the element that are pedogenic in origin. Progressive mineralization and immobilization, often biological in nature, are generally observed when P is added as a fertilizer.     

Charged isotropic model with conformal symmetry

We investigate the behaviour of a charged isotropic model with conformal symmetry. The relationship between the gravitational potentials arising from the conformal condition is used to generate a new class of exact solutions to the Einstein-Maxwell equations. A specific form of the electric field intensity and the metric potential is required to avoid a singularity at the centre. We can find simple elementary functions for the matter variables and the potentials with realistic profiles. The causality conditions, stability conditions and energy conditions are satisfied. Masses, radii, central densities and surface redshifts are generated, and the values are consistent with the compact stars 4U 1538-52 and PSR J1614-2230.