Secondary production of antiprotons in cosmic radiation

A reliable representation to the invariant cross-section for the production of antiprotons ( ) in inclusive reactions has been obtained, which fits the data extremely well from threshold to ISR energies. Using this, the production spectrum of by cosmic ray interaction with interstellar gas is calculated and is compared with other existing calculations. The equilibrium spectrum in the Galaxy has been derived from about 100 MeV to a few hundred GeV in kinetic energy using Leaky Box Model for the propagation of cosmic rays, by taking into account all energy loss processes. It is found that /P ratio calculated here is very much smaller than the observed ratio. In view of the fact that this excess of observed /P ratio is much larger than the measured upper limits on the fraction of antimatter in the form of antinuclei, the excess /P ratio has not been attributed to the existence of antimatter. Instead, it is shown that Closed Galaxy Model for the propagation of cosmic rays predicts more antiprotons than observed. Therefore, it is suggested that if cosmic rays contain about 50% new component of local origin, the resulting Closed Galaxy Model explains well the observations. The present calculations also predict too small a flux of below a few hundred MeV to make this energy region ideally suited to look for antiprotons of primordial origin.     

Adiabatic deceleration of secondary antiprotons in the envelopes of supernova exploding in dense clouds

Within the framework of the plasma-laser star model of quasars it is proposed that the quasar 0805+046 is a helium-rich shell star. (a) The strong emission line at 4712 Å is identified with Hei 4713. (b) The discontinuity in the continuous energy distribution at 3420 is identified with the helium discontinuity at 3422. (c) In the absorption-line spectrum many lines have been identified. It is shown that the proposed model provides a consistent and satisfactory interpretation of the observed spectra.     

Free surface and saturated-unsaturated analyses of borehole infiltration tests above the water table

Constant head borehole infiltration tests are widely used for the in situ evaluation of saturated hydraulic conductivities of unsaturated soils above the water table. The formulae employed in analysing the results of such tests disregard the fact that some of the infiltrating water may flow under unsaturated conditions. Instead, these formulae are based on various approximations of the classical free surface theory which treats the flow region as if it were fully saturated and enclosed within a distinct envelope, the so-called ‘free surface’. A finite element model capable of solving free surface problems is used to examine the mathematical accuracy of the borehole infiltration formulae. The results show that in the hypothetical case where unsaturated flow does not exist, the approximate formulae are reasonably accurate within·a practical range of borehole conditions. To see what happens under conditions closer to those actually encountered in the field, the effect of unsaturated flow on borehole infiltration is investigated by means of two different numerical models: a mixed explicit-implicit finite element model, and a mixed explicit-implicit integrated finite difference model. Both of these models give nearly identical results; however, the integrated finite difference model is considerably faster than the finite element model. The relatively low computational efficiency of the finite element scheme is attributed to the large number of operations required in order to re-evaluate the conductivity (stiffness) matrix at each iteration in this highly non-linear saturated-unsaturated flow problem. The saturated-unsaturated analysis demonstrates that the classical free surface approach provides a distorted picture of the flow pattern in the soil. Contrary to what one would expect on the basis of this theory, only a finite region of the soil in the immediate vicinity of the borehole is saturated, whereas a significant percentage of the flow takes place under unsaturated conditions. As a consequence of disregarding unsaturated flow, the available formulae may underestimate the saturated hydraulic conductivity of fine grained soils by a factor of two, three, or more. Our saturated-unsaturated analysis leads to an improved design of borehole infiltration tests and a more accurate method for interpreting the results of such tests. The analysis also shows how one can predict the steady state rate of infiltration from data collected during the early transient period of the test.     

Stratigraphic and structural controls on groundwater salinity variations in the Poso Creek Oil Field,Kern County,California, USA

Hydrogeology Journal - Groundwater total dissolved solids (TDS) distribution was mapped with a three-dimensional (3D) model, and it was found that TDS variability is largely controlled by...     

Gender and the GeoWeb: divisions in the production of user-generated cartographic information

The GeoWeb presents an opportunity to expand the array of potential contributors describing the earth through digital geographic information. However, the adoption of user-generated geographic information has not been uniform, resulting in an uneven distribution of content and more nuanced digital divides. This paper uses a survey of Internet users to measure the gender divide in the contributions of cartographic information to the Internet and examine the impact of this divide within the context of OpenStreetMap and Google MapMaker. This paper argues that in both publicly available basemaps the gender divide results in men serving as the gatekeepers of local knowledge leading to gendered user-generated representations. As these digital basemaps are reproduced and utilized by almost every mobile application or web-based map, the gender divisions in the creators and content are endlessly reproduced.     

An Imminent Human Resource Crisis in Ground Water Hydrology?

Anecdotal evidence, mostly from the United States, suggests that it has become increasingly difficult to find well-trained, entry-level ground water hydrologists to fill open positions in consulting firms and regulatory agencies. The future prospects for filling positions that require training in ground water hydrology are assessed by considering three factors: the market, the numbers of qualified students entering colleges and universities, and the aging of the existing workforce. The environmental and water resources consulting industry has seen continuous albeit variable growth, and demand for environmental scientists and hydrologists is expected to increase significantly. Conversely, students' interest and their enrollment in hydrology and water resources programs have waned in recent years, and the interests of students within these departments have shifted away from ground water hydrology in some schools. This decrease in the numbers of U.S. students graduating in hydrology or emphasizing ground water hydrology is coinciding with the aging of and pending retirement of ground water scientists and engineers in the baby boomer generation. We need to both trigger the imagination of students at the elementary school level so that they later want to apply science and math and communicate the career opportunities in ground water hydrology to those high school and college graduates who have acquired the appropriate technical background. Because the success of a consulting firm, research organization, or regulatory agency is derived from the skills and judgment of the employees, human resources will be an increasingly more critical strategic issue for many years.     

Landfill Performance Assessment at a Semiarid Site: Modeling and Validation

The HELP model (Version 2.05) was applied to simulate the long-term percolation from a proposed landfill in southern New Mexico. The model predicted percolation would be about 0.0012 in/yr (10^-10 cm/s). This result compared very favorably with independent estimates of recharge at the site which used the chloride mass balance method and hydrogeologic properties. The recharge estimates at this site are also quite similar to values obtained at other sites in New Mexico and west Texas. The long-term percolation through a closed landfill at this site is very small and would be nearly 1000-fold smaller than the saturated hydraulic conductivity of a typical clay liner.     

Atmospheric Stability Effects on Wind Fields and Scalar Mixing Within and Just Above a Subalpine Forest in Sloping Terrain

Air temperature T _a , specific humidity q, CO₂ mole fraction χ _c , and three-dimensional winds were measured in mountainous terrain from five tall towers within a 1 km region encompassing a wide range of canopy densities. The measurements were sorted by a bulk Richardson number Ri _b . For stable conditions, we found vertical scalar differences developed over a “transition” region between 0.05 < Ri _b < 0.5. For strongly stable conditions (Ri _b > 1), the vertical scalar differences reached a maximum and remained fairly constant with increasing stability. The relationships q and χ _c have with Ri _b are explained by considering their sources and sinks. For winds, the strong momentum absorption in the upper canopy allows the canopy sublayer to be influenced by pressure gradient forces and terrain effects that lead to complex subcanopy flow patterns. At the dense-canopy sites, soil respiration coupled with wind-sheltering resulted in CO₂ near the ground being 5–7 μmol mol⁻¹ larger than aloft, even with strong above-canopy winds (near-neutral conditions). We found Ri _b -binning to be a useful tool for evaluating vertical scalar mixing; however, additional information (e.g., pressure gradients, detailed vegetation/topography, etc.) is needed to fully explain the subcanopy wind patterns. Implications of our results for CO₂ advection over heterogenous, complex terrain are discussed.     

Magma mixing in the subvolcanic environment: petrology of the Gerena interaction zone near Seville,Spain

The mechanisms by which felsic and mafic magmas interact and approach a uniform hybrid composition through the processes of mingling and mixing have been studied in a high-level subvolcanic setting in the Spanish Hercynian at Gerena, near Seville. The compositions involved are calc-alkaline and the situation is one of tonalite-quartz diorite synplutonic dykes injected into a granitic magma chamber. The resulting hybrids include dykes, pillows and globules of tonalite with chilled margins which are variously disrupted and homogenised with the host granite. The present investigation is based on field and petrographic observations of hybridization textures, the identification of different stages in the crystallisation history of the tonalite through mineral textures, and the characterization of mineral compositions at these various stages. Proportions of the end-member magmas involved were obtained by major-oxide mixing models and tested satisfactorily with trace elements. A mechanistic model is presented to account for these observations which involves the early quenching of the tonalite when it was emplaced into the granite magma chamber. After high temperature crystallization had occurred the two magmas attained thermal equilibrium and disruption of the tonalite in the high energy regime of this subvolcanic complex resulted in dispersion of fragments and crystals through the granite giving rise to hybrid granodiorite compositions. It is argued that such high-energy flow conditions are a necessary requirement for effective hybridization in this environment in contrast to most large-scale magma chamber settings where mixing is driven by thermal and buoyancy contrasts.     

Biotite and muscovite <Superscript>40</Superscript>Ar–<Superscript>39</Superscript>Ar geochronological constraints on the post-Svecofennian tectonothermal evolution,Forsmark site,central Sweden

In order to characterize the post-Svecofennian tectonothermal evolution of the Fennoscandian Shield, ⁴⁰Ar–³⁹Ar biotite and some ⁴⁰Ar–³⁹Ar muscovite geochronological data are reported from a total of 30 surface outcrop and 1,000 m long borehole samples at Forsmark, central Sweden. The 13 surface samples were collected across 3 branches of a major WNW to NW trending system of deformation zones, whereas the boreholes were drilled within a tectonic lens, in between two of these zones. The ⁴⁰Ar–³⁹Ar biotite ages indicate that the present erosion surface, in central Sweden, cooled below c. 300°C at 1.73–1.66 Ga, and that the rocks could have accommodated strain in a brittle manner between 1.8 and 1.7 Ga. The variation in surface ages is suggested to be due to fault along the large WNW to NW trending deformation zones, following the establishment of a sub-Cambrian peneplain. The minor variation of ages within a single crustal block may be due to disturbance along ENE to NNE trending fracture zones. Possible cooling paths, derived from ⁴⁰Ar–³⁹Ar hornblende, muscovite and biotite ages, were calculated for the time interval from 1.80 to 1.67 Ga, when the area cooled from c. 500 to 300°C. Cooling rates of 1.9–4°C/m.y. have been attained. Between 1.68 and 1.64 Ga, uplift rates of c. 22 m/m.y. were calculated from borehole ⁴⁰Ar–³⁹Ar biotite data. Tectonothermal histories, inferred from the combined cooling and uplift rates, are related to simple cooling after the Svecofennian orogeny, to crustal movement in response to far-field effects of c. 1.7 Ga orogenic activities further to the west or to a combination of these possibilities.