Water flux measurement and prediction in young cashew trees using sap flow data

Measurements of sap flow, meteorological parameters, soil water content and tension were made for 4 months in a young cashew (Anacardium occidentale L.) plantation during the 2002 rainy season in Ejura, Ghana. This experiment was part of a sustainable water management project in West Africa. The Granier system was used to measure half‐hourly whole‐tree sap flow. Weather variables were observed with an automatic weather station, whereas soil moisture and tension were measured with a Delta‐T profile probe and tensiometers respectively. Clearness index (CI), a measure of the sky condition, was significantly correlated with tree transpiration (r² = 0·73) and potential evaporation (r² = 0·86). Both diurnal and daily stomata conductance were poorly correlated with the climatic variables. Estimated daily canopy conductance g_c ranged from 4·0 to 21·2 mm s⁻¹, with a mean value of 8·0 ± 3·3 mm s⁻¹. Water flux variation was related to a range of environmental variables: soil water content, air temperature, solar radiation, relative humidity and vapour pressure deficit. Linear and non‐linear regression models, as well as a modified Priestley–Taylor formula, were fitted with transpiration, and the well‐correlated variables, using half‐hourly measurements. Measured and predicted transpiration using these regression models were in good agreement, with r² ranging from 0·71 to 0·84. The computed measure of accuracy δ indicated that a non‐linear model is better than its corresponding linear one. Furthermore, solar radiation, CI, clouds and rain were found to influence tree water flux. Copyright © 2005 John Wiley & Sons, Ltd.     

The vertical distribution of macro-insects migrating in the nocturnal boundary layer: A radar study

A special-purpose radar has been used to observe the vertical distribution of large, strong-flying insects migrating in the nocturnal boundary layer over the central-western plains region of New South Wales. During the period of take-off flight at dusk, the density of insects decreased monotonically with height, and a distribution of this type persisted for much of the night in the zone of steady temperature lapse extending from the top of the inversion layer to the flight ceiling at about 1 km. Later in the night, the insects often became concentrated in the warm air at the top of the inversion layer. The lower boundary of this concentration sometimes became sharply defined, but above the zone of maximum insect density there was usually a smooth decrease of insect numbers with altitude. When the boundary layer was disturbed by an atmospheric density current, the direction and vertical distribution of the migration was permanently changed; solitary wave disturbances, however, had only a transient effect.     

Geochemistry of tin, tungsten and molybdenum in Swedish proterozoic granitoids: Their potential use in regional mineral exploration

The primary aim of this broad regional study is to statistically determine the Li-Sn-W-Mo-bearing potential of various granitoids using geochemical criteria. Computer based, univariate and multivariate statistical methods are applied to major- and trace-element data from about 660 granitic rock samples and over 800 major element analyses, selected from the Swedish geological literature. The granitoids are subdivided following earlier geotectonic chronologic and newer geochemical-statistical principles.Most granite types occurring in known Sn-W mineralized areas, except the granites around the W deposit of Baggetorp, were identified as potentially W-Sn-bearing. That is, they show significantly high mean and variance values for W and/or Sn as well as promising values of the probability parameters for these elements, compared to corresponding statistics for a calculated Swedish average granitoid (SAG).Evidence of very high total variability of Li, Sn and W within the individual granite types suggests the need for further tests, to control the variability errors due to sampling and preparation and errors of chemical analysis. These sources of error may obscure natural elemental heterogeneity of the granite type that is of interest in geochemical prospecting.Interpretations of Sn, W and Li frequency distribution patterns, petrochemical trends and multivariate similarity tests suggest that the primary chemistry of the granitoids is overprinted by (a) postmagmatic processes of broad regional nature, which have similarly affected the individual granite types, and (b) a wide variety of secondary alterations of local character. These conclusions imply that potential Sn and W deposits may be sought within all Swedish Proterozoic granitoids and their within all Swedish Proterozoic granitoids and their immediate sorroundings, where susch processes have redistributed and concentrated these where such processes have redistributed and concentrated these elements. However, the granites which are highly differentiated, Sn-W-Li-U-Th-F-enriched, and strongly and strongly magnetic are particularly promising target areas for further, extensive rock-geochemical prospecting and other exploration surveys. rock-geochemical prospecting and other exploration surveys.     

Experimental investigations of trace element fractionation in iron meteorites,II: The influence of sulfur

We have investigated the partitioning of Ir. Ge, Ga, W, Cr, Au, P, and Ni between solid metal and metallic liquid as a function of temperature and S-concentration of the metallic liquid. Partition coefficients for siderophile elements such as Ir, W, Ga and Ge increase by factors of 10–100 as the Sconcentration of the metallic liquid increases from 0–30 wt%. Partition coefficients for other siderophile elements such as Ni, Au and P increase by only factors of 2–3. In contrast, partition coefficients for the more chalcophile element Cr decrease. These experimentally-determined partition coefficients have been used in conjunction with a fractional crystallization model to reproduce the geochemical behavior of Ni, P, Au and Ir during the magmatic evolution of groups IIAB, IIIAB, IVA and IVB iron meteorites. The mean S-concentration for each group increases in the order IVB, IVA, IIIAB, IIAB, in accord with cosmochemical prediction. However, we are unable to reproduce the geochemical behavior of Ge, Ga, W and Cr in an internally consistent way. We conclude that the magmatic histories of these iron meteorite groups are more complex than has been generally assumed.     

Syntectonic subaqueous mass flows of the Neoproterozoic Otavi Group,Namibia: where is the evidence of global glaciation?

The thick (>1 km) Neoproterozoic Otavi Group of Namibia accumulated after ca. 760 Ma along >700 km of the faulted margin of the Congo Craton. The margin shows a north to south, downbasin transition from a shallow‐water carbonate shelf (Otavi Platform) to offshore deepwater slope (Outjo Basin). Within the latter, the Abenab and Tsumeb Subgroups contain large volumes of poorly sorted breccias, conglomerates and diamictites composed principally of locally derived carbonate. Diamictite facies were reported in the 1930s as tillites left by an ice sheet (although the absence of striated clasts and other key glacial indicators was viewed as problematic). Later workers rejected a glacial origin concluding that Outjo basin facies were deposited as parts of prograding submarine wedges built by mass flows during active rifting. Recently, the Snowball Earth hypothesis has returned to the earlier glacial interpretation; arguing that these strata represent a record of extraordinary late Neoproterozoic glacial and interglacial climates when global temperatures fluctuated by up to 100°C. Facies analysis of breccias, diamictites, conglomerates and sandstone strata of the Otavi Group identifies them as genetically related, subaqueously deposited sediment gravity flows. They lack diagnostic indicators of any one specific climate in source areas. These facies were all deposited in deepwater at the foot of landslide‐prone scarp blocks where debris flows and turbidity currents moved large volumes of coarse, freshly broken carbonate debris produced by faulting. Breccias, diamictites, conglomerates and sandstones occur in composite fining‐ and thinning‐upward bundles that are directly analogous to those reported from many other faulted margins in the Phanerozoic stratigraphic record. These rocks provide no clear sedimentological signature of a glacial source or catastrophic Snowball Earth‐type temperature fluctuations. Instead, they point to a dominant tectonic control on sedimentation related to faulting along the margin of the Congo Craton.     

Some exact solutions for the flow of fluid through tubes with uniformly porous walls

Summary This paper considers an incompressible fluid flowing through a straight, circular tube whose walls are uniformly porous. The flow is steady and one dimensional. The loss of fluid through the wall is proportional to the mean static pressure in the tube. Several formulations of the wall shear stress are considered; these formulations were motivated by the results from Hamel's radial flow problem, boundary layer flows/and boundary layer suction profiles. For each of these formulations exact solutions for the mean axial velocity and the mean static pressure of the fluid are obtained. Sample results are plotted on graphs. For the constant wall shear stress problem, the theoretical solutions compare favorably with some experimental results.Notations A, B, D, E constant parameters - a, b constant parameters - Ai(z), Bi(z) Airy functions - Ai, Bi derivatives of Airy functions - k constant of proportionality betweenV andp - L length of pores - p,p mean static pressure - p ₀ static pressure outside the tube - p ₀ value ofp atx=0 - Q constant exponent - R inside radius of the tube - T wall shear stress - T ₀ shear parameter - t wall thickness - U free stream velocity - ,u mean axial velocity - u ₀ value ofu atx=0 - V,V mean seepage velocity through the wall - v ₀ mean seepage velocity - x,x axial distance along the tube - z transformed axial distance - z ₀ value ofz atx=0 - mean outflow angle through the wall - cos - density of the fluid - wall shear stress - dynamic viscosity of the fluid - over-bar dimensional terms - no bar nondimensional terms The National Center for Atmospheric Research is sponsored by the National Science Foundation     

Brief note on effects of thermal pulses on elastic moduli and Q of rock

Preliminary results of a current experimental study on relationships between elastic moduli, internal friction (Q^?1) and rock structure are compatible with lunar in situ observations which indicate that mechanisms which lower the elastic moduli of rock need not contribute significantly to the internal friction. In terrestrial rock samples which were thermally pulsed in vacuum, elastic moduli decreased andQ's increased. These results imply that the thermal pulsing induces damage such as microcracks (which lower the elastic moduli), eliminates crack surface contaminants and may destroy other possible sites of internal friction such as grain boundary mechanisms and hydrous minerals (increasingQ).     

Multiple phases of North African humidity recorded in lacustrine sediments from the Fazzan Basin, Libyan Sahara

The Fazzan Basin of south-west Libya is at present arid with less than 20 mm of rainfall per annum. However, regionally extensive limestones, lacustrine sands and coquina (fossiliferous carbonate rock) deposits show that the Fazzan Basin previously contained a large palaeolake, indicating that the climate in the past was more humid. Optically stimulated luminescence (OSL) dating techniques have been applied to key lacustrine deposits within the basin in an attempt to provide an internally consistent chronology for this humidity record. Results indicate that palaeolake sediments within the Fazzan Basin record a very long history of palaeohydrological change, ranging from present day arid conditions to humidity capable of sustaining a lake with an approximate area of 76,250 km². The existence of humid periods in mid oxygen isotope stage 5 and the early Holocene is confirmed. An older lacustrine event, tentatively correlated to oxygen isotope stage 11, is also recognized. In addition, evidence is presented for at least two humid phases beyond the age range over which the conventional OSL dating technique is applicable. This study demonstrates that OSL dating of palaeolake sediments within the Fazzan Basin offers the potential to provide a detailed record of North African humidity spanning several glacial–interglacial cycles.     

Accurate Determination of Electron Densities in Active and Quiescent Prominences: the Mid-Infrared Advantage

We have analyzed all lines in the MIR (8 to 20 micron) spectra of a quiescent and two time-frames of an active prominence. In the quiescent prominence, in addition to those lines found by Zirker (1985), we have identified a higher excitation hydrogen line and two helium recombination lines. Accounting for instrumental broadening, we can further separate out the Doppler and the Stark contributions to the line width. The former yields maximum temperatures of 6200 K, 34000 K and 12000 K and the latter electric field strengths of 7, 17, and 10 V cm^-1 for the above prominences, respectively. We show that these electric fields when divided by 2.2 are equal to the normal electric field in Holtsmark's quasi-static Stark broadening theory. Hence, we obtain electron densities of N₃=2.4(0.3), 9.1(1.2), and 5.5(0.6) in units of 10¹⁰ cm^-3 respectively. Using the same assumptions as made by Zirker, namely, (1) the strongest line (7-6) is optically thin, (2) the population of the lower level (n=6) is determined by direct radiative recombination and photo-ionization, (3) the equality of proton and electron densities, and (4) the thickness of the prominence is at least 10⁸ cm, we derive a new inequality, N_e 1.83 × 10⁸ T^0.75 e^-2195/T. Substituting our maximum temperatures into the right-hand side, we find upper bound N_e values of 9, 43, and 30 in the same units as above. These upper bound values are comfortably higher than our measurement, unlike those of Zirker's derived from the same set of assumptions. We have also observed the helium recombination spectrum which has been postulated by Tandberg-Hanssen as one of three possible ways of equilibrating the triplet/singlet ratio. Surprisingly, it is present in the quiescent as well as in the active prominence. We show that no meaningful values can be found for the turbulent velocities by combining the helium with the hydrogen line widths.