An investigation of flux-variance methods and universal functions applied to three land-use types in unstable conditions   总被引：3，自引：0，他引：3  

Jacob Padro 《Boundary-Layer Meteorology》1993,66(4):413-425

Fluxes calculated from three flux-variance methods, which depend upon three different forms of the normalized standard deviation functions (referred to as universal functions) of the surface atmospheric stability have been tested and compared with measurements for temperature and water vapour. The flux measurements were made over a fully leafed deciduous forest, a leafless deciduous forest and over a wetland region during the summer. The first method (referred to as the variance method) allows for certain constants, which are associated with the universal functions, to vary with land-use type and the scalar for which the flux is computed; the second method uses the form of the universal function developed by Tillman, which depends upon two constants; and the third method, known as the Wyngaard method, is the simplest and depends upon one constant only. Flux estimates from the variance method yield the best agreement with observations over the three hand-use types and the Wyngaard method appears to yield estimates that are quite comparable. The measurements for the univeral functions agree better with the Wyngaard function for temperature and better with the Tillman function for water vapour, although both show some scatter. The simplest formula developed by Wyngaard may be considered adequate for computing fluxes of temperature and water vapour from their variances. The main advantage of the formulae is to help define an upper limit for actual fluxes.  相似文献   

Effects of Small-Scale Vertical Variations in Well-Screen Inflow Rates and Concentrations of Organic Compounds on the Collection of Representative Ground-Water-Quality Samples   总被引：1，自引：0，他引：1  

Jacob Gibs  G. Allan Brown  Kenneth S. Turner  Cecilia L. MacLeod  James C. Jelinski  Susan A. Koehnlein 《Ground water》1993,31(2):201-208

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The proximity of sexual violence to schools: evidence from a township in South Africa     

Breetzke  Gregory D.  Fabris-Rotelli  Inger  Modiba  Jacob  Edelstein  Ian S. 《GeoJournal》2021,86(2):765-776

GeoJournal - Schools are unique places that greatly influence the daily lives of learners. Examining any factors that may be contributing to school absenteeism and dropout rates is vital as gaining...  相似文献   

Modelling of malaria incidence in Akure,Nigeria: negative binomial approach     

Makinde  Olusola Samuel  Abiodun  Gbenga Jacob  Ojo  Oluwasegun Taiwo 《GeoJournal》2021,86(3):1327-1336

The connections between malaria incidence and climate variability have been studied in recent time using some mathematical and statistical models. Many of the statistical models in literature focused on time series approach based on Box–Jenkins methodology. However, fitting time series model based on the Box–Jenkins methodology may be challenging. Most malaria incidence data are count and are over-dispersed. In this study, negative binomial models were formulated for fitting malaria incidence in Akure—one of the epidemic cities in Nigeria. In particular, negative binomial models were formulated for each of the number of outpatient individuals, number of inpatient individuals and mortality count as a function of some climate variables. It was found that an increase in minimum temperature and relative humidity at lag 1 significantly increased the chance of malaria transmission and thereby leads to an increase in the number of inpatient and outpatient individuals, as well as the total number of malaria cases. The minimum temperature, rainfall amount and relative humidity of the study area have a significant impact on the increase of number of inpatient and outpatient individuals while mortality count depends on the total number of reported malaria cases. The findings from this study is to offer in-depth understanding on climate-malaria incidence linkages in Akure, Nigeria.

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Nanoscale Chemical Imaging by Photo‐Induced Force Microscopy: Technical Aspects and Application to the Geosciences     

Laura M. Otter  Michael W. Frster  Elena Belousova  Padraic O&#x;Reilly  Derek Nowak  Sung Park  Simon Clark  Stephen F. Foley  Dorrit E. Jacob 《Geostandards and Geoanalytical Research》2021,45(1):5-27

Photo‐induced force microscopy (PiFM) is a new‐frontier technique that combines the advantages of atomic force microscopy with infrared spectroscopy and allows for the simultaneous acquisition of 3D topographic data with molecular chemical information at high spatial (~ 5 nm) and spectral (~ 1 cm^?1) resolution at the nanoscale. This non‐destructive technique is time efficient as it requires only conventional mirror‐polishing and has fast mapping rates on the order of a few minutes that allow the study of dynamic processes via time series. Here, we review the method’s historical development, working principle, data acquisition, and evaluation, and provide a comparison with traditional geochemical methods. We review PiFM studies in the areas of materials science, chemistry and biology. In addition, we provide the first applications for geochemical samples including the visualization of faint growth zonation in zircons, the identification of fluid speciation in high‐pressure experimental samples, and of nanoscale organic phases in biominerals. We demonstrate that PiFM analysis is a time‐ and cost‐efficient technique combining high‐resolution surface imaging with molecular chemical information at the nanoscale and, thus, complements and expands traditional geochemical methods.  相似文献   

Nano‐Powdered Calcium Carbonate Reference Materials: Significant Progress for Microanalysis?     

Klaus Peter Jochum  Dieter Garbe‐Schnberg  Marina Veter  Brigitte Stoll  Ulrike Weis  Michael Weber  Federico Lugli  Anna Jentzen  Ralf Schiebel  Jasper A. Wassenburg  Dorrit E. Jacob  Gerald H. Haug 《Geostandards and Geoanalytical Research》2019,43(4):595-609

Homogeneity, mass fractions of about forty trace elements and Sr isotope composition of Ca carbonate reference materials (RMs) between original and nano‐powdered pellets are compared. Our results using nanosecond and femtosecond LA‐(MC)‐ICP‐MS show that the nano‐pellets of the RMs MACS‐3NP, JCp‐1NP and JCt‐1NP are about a factor of 2–3 more homogeneous than the original samples MACS‐3, JCp‐1 and JCt‐1, and are therefore much more suitable for microanalytical purposes. With the exception of Si, the mass fractions of the synthetic RM MACS‐3 agree with its fine‐grained analogue MACS‐3NP. Very small, but significant, differences between original and nano‐pellets are observed in the RMs JCp‐1 and JCt‐1 for some trace elements with very low contents, indicating the need for re‐certification. Strontium mass fractions in the analysed RMs are high (1500–7000 mg kg^?1), and their isotope compositions determined by LA‐MC‐ICP‐MS in the original and the nano‐pellets agree within uncertainty limits.  相似文献   

Quantifying the EEJ current with ground-based ionosonde inferred vertical E × B drifts in the morning hours over Ilorin,West Africa     

Jacob O. Adeniyi  Isaac A. Adimula  Babatunde O. Adebesin  Bodo W. Reinisch  Olusola A. Oladipo  Olayinka Olawepo  Kiyohumi Yumoto 《Acta Geophysica》2014,62(3):656-678

The relationship between the ground-based inferred vertical E × B drifts, Vz, and the magnetic equatorial electrojet current during the year of solar minima was presented. Both the diurnal and seasonal Vz variations are positively directed during the daytime and negative at nighttime. The evening time pre-reversal enhancement occurs around 19:00 LT. The fairly strong linear relationship between the electrojet current strength and Vz exhibited higher correlations during the daytime (06:00–16:00 LT). The maximum morning time proxy parameter described by E = [d (ΔH _ILR)/dt]_max in the morning hours, indicating the east-west electric field in the EEJ, corresponds reasonably well with the E × B drift and, hence, can be used as a proxy parameter for representing Vz in the morning hours. The daytime EEJ magnitude seasonal changes are connected with a change in conductivity emerging from the action of turbulence and divergence of momentum flux. These waves above the dynamo region are suggested to lead to partial counter electrojet during the equinoctial months.  相似文献   

Polycyclic Aromatic Hydrocarbons in Soil – Practical Options for Remediation          下载免费PDF全文

Jacob de Boer  Marlea Wagelmans 《洁净——土壤、空气、水》2016,44(6):648-653

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40Ar/39Ar geochronology using a quadrupole mass spectrometer     

Björn Schneider  Klaudia Kuiper  Onno Postma  Jan Wijbrans 《Quaternary Geochronology》2009,4(6):508-516

Magnetic sector mass spectrometers dominate the field of ⁴⁰Ar/³⁹Ar geochronology. Recent advances in quadrupole mass spectrometer technology, especially improvements in resolution, have increased the performance of these instruments to the extent that they can be used for isotopic determinations. We describe a triple filter quadrupole mass spectrometer (Hiden HAL 3F Series Pulse Ion Counting Triple Filter QMS) linked to an automated furnace extraction and cleaning system dedicated to ⁴⁰Ar/³⁹Ar incremental heating experiments.The instrument produces peaks with broad flat tops and a width of 0.9 amu at 10 cps height and 0.84 amu at 500,000 cps height on a 1 million cps high peak (peak width at 0.01‰ and 50% peak height respectively). This allows measurement of ratios of the main Ar peaks in the 1‰ range. Measurements of 1.6 × 10^?12 mole of air reference gas over two years yields ⁴⁰Ar/³⁶Ar = 257.9 ± 1.3 (1σ, n = 34). The ability of the instrument to produce ⁴⁰Ar/³⁹Ar ages from rocks/minerals of a wide age range, reaching into the late Quaternary, are demonstrated by a series of tests and comparison with geochronological data from other studies and an in-house MAP 215-50 magnetic sector mass spectrometer. We demonstrate that high-end quadrupole systems can be used for routine ⁴⁰Ar/³⁹Ar dating purposes.  相似文献   

Simulating Seepage into Mine Shafts and Tunnels with MODFLOW     

Jacob Zaidel  Bradley Markham  David Bleiker 《Ground water》2010,48(3):390-400

In cases when an equivalent porous medium assumption is suitable for simulating groundwater flow in bedrock aquifers, estimation of seepage into underground mine workings (UMWs) can be achieved by specifying MODFLOW drain nodes at the contact between water bearing rock and dewatered mine openings. However, this approach results in significant numerical problems when applied to simulate seepage into an extensive network of UMWs, which often exist at the mine sites. Numerical simulations conducted for individual UMWs, such as a vertical shaft or a horizontal drift, showed that accurate prediction of seepage rates can be achieved by either applying grid spacing that is much finer than the diameter/width of the simulated openings (explicit modeling) or using coarser grid with cell sizes exceeding the characteristic width of shafts or drifts by a factor of 3. Theoretical insight into this phenomenon is presented, based on the so-called well-index theory. It is demonstrated that applying this theory allows to minimize numerical errors associated with MODFLOW simulation of seepage into UMWs on a relatively coarse Cartesian grid. Presented examples include simulated steady-state groundwater flow from homogeneous, heterogeneous, and/or anisotropic rock into a vertical shaft, a horizontal drift/cross-cut, a ramp, two parallel drifts, and a combined system of a vertical shaft connected to a horizontal drift.  相似文献