The implicit loss function for errors in soil information

The loss function expresses the costs to an organization that result from decisions made using erroneous information. In closely constrained circumstances, such as remediation of soil on contaminated land prior to development, it has proved possible to compute loss functions and to use these to guide rational decision making on the amount of resource to spend on sampling to collect soil information. In many circumstances it may not be possible to define loss functions prior to decision making on soil sampling. This may be the case when multiple decisions may be based on the soil information and the costs of errors are hard to predict. We propose the implicit loss function as a tool to aid decision making in these circumstances. Conditional on a logistical model which expresses costs of soil sampling as a function of effort, and statistical information from which the error of estimates can be modelled as a function of effort, the implicit loss function is the loss function which makes a particular decision on effort rational. After defining the implicit loss function we compute it for a number of arbitrary decisions on sampling effort for a hypothetical soil monitoring problem. This is based on a logistical model of sampling cost parameterized from a recent survey of soil in County Donegal, Ireland and on statistical parameters estimated with the aid of a process model for change in soil organic carbon. We show how the implicit loss function might provide a basis for reflection on a particular choice of sampling regime, specifically the simple random sample size, by comparing it with the values attributed to soil properties and functions. In a recent study rules were agreed to deal with uncertainty in soil carbon stocks for purposes of carbon trading by treating a percentile of the estimation distribution as the estimated value. We show that this is equivalent to setting a parameter of the implicit loss function, its asymmetry. We then discuss scope for further research to develop and apply the implicit loss function to help decision making by policy makers and regulators

Technical assistance in Nigeria : developing geoscience skills for tomorrow

The World Bank funded Nigerian Geochemical Mapping Technical Assistance Project was started in 2008 within the Nigerian Ministry of Mines and Steel Development, and is now nearing completion. Staff from the Nigerian Geological Survey Agency (NGSA), the Nigerian academic community, British Geological Survey, and Geological Survey of Finland, have worked alongside one another in a comprehensive program of practical training and knowledge exchange. This program has enabled researchers from a range of backgrounds and experience in Africa and Europe to exchange knowledge and develop important geoscience skills. As part of this program key skills in many areas including; GIS, statistics, QC, data management, laboratory analysis, sampling methodologies, has developed the knowledge and skills base within the Nigerian geosciences community, and has maintained momentum for Nigeria’s national geochemical mapping program. An important objective of the Project is knowledge exchange during training of Nigerian geoscientists in conducting regional geochemical surveys as part of a long term mapping program across Nigeria. Practical training in methodologies for geochemical mapping formed the basis of a major field campaign in 2009, during which over 100 personnel were trained in geochemical mapping techniques. A similar number of personnel were involved in specialist training through a series of workshops and training courses in Nigeria and the UK. Two field areas were selected for the geochemical mapping training — one in central Nigeria (the ‘Minna Cell’) and one in south-western Nigeria (the ‘South-western Cell’) — covering a combined area of 52 000 km2. Key challenges involved the procurement of field equipment and consumables, and modernisation of sample preparation laboratories and archiving facilities at the National Geosciences Research Laboratory, Kaduna. New sample preparation and analytical equipment has been purchased and the laboratory staff have received training in the use of the new equipment. In the long-term it is envisaged that the analytical facilities will be developed further, and that all samples will be prepared, analysed and archived in Nigeria. A national geochemical mapping programme involving multi-element analysis of stream sediment samples is used as a primary dataset in the exploration for new economic mineral deposits. Establishing a geochemical baseline is necessary in order to monitor the effects of anthropogenic activities e.g. contamination caused by industrial waste and mining activities, for environmental investigations and medical geology studies both in rural and in urban areas, as well as studies within the agricultural and forestry sectors

We All Know How, Don’t We? On the Role of Scrum in IT-Offshoring

Part 2: Creating Value through Software DevelopmentInternational audienceOffshoring in the IT-industry involves dual interactions between a mother company and an external supplier, often viewed with an implicit perspective from the mother company. This article review general off shoring and IT offshoring literature, focusing on the proliferation of a globally available set of routines; Scrum and Agile. Two cases are studied; a small company and short process and a large mother company with a long process. The interactions of the set ups shows that global concepts like Scrum and Agile are far from a common platform. The “well known” concepts are locally shaped and the enterprises have mixed experiences

Multi-element stream sediment geochemistry of south-western and central Nigeria

This paper presents preliminary results from geochemical baseline stream sediment surveys from two Cells (South-western Cell and Central Cell) in Nigeria completed in 2009. This work was part of the World Bank funded Nigerian Sustainable Management of Mineral Resources Project carried out by the Nigerian Geological Survey Agency in cooperation with the British Geological Survey. A total of 284 stream sediment samples were collected from the South-western Cell, with an average sampling density of 1 site every 90 km2. A total of 1288 stream sediments were collected from the Central Cell, with an average density of 1 sample every 20 km2. Geochemical analyses were by ICP-MS technique following sodium peroxide fusion-HCl-HF extractions. Au, Pt and Pt determinations were by Fire Assay-acid dissolution method. Selected findings on the distribution of trace elements, HFSE and REE in stream sediment samples are presented in relation to the geology, known mineral occurrences, as well as other factors that affect the distribution of elements in the surface environment A systematic approach to the interpretation of the elemental concentrations and distributions involved a range of statistical techniques (including correlation, cluster and factor analysis) to investigate the structure and trends within the data set, thus providing insights into the underlying geological, physical, geochemical and anthropogenic processes that are important in controlling the stream sediment geochemistry. The role of ilmenite and Fe/Mn-oxides and oxy-hydroxides in controlling trace element stream sediment geochemistry is highlighted by strong Fe/Ti-trace element associations in the multivariate statistical analyses. Rare element associations including Th-U-HREE, Zr-Hf, as well as Sn-Ta-Nb indicate resistate heavy minerals in the stream sediments derived from potentially economic deposits of minerals in the area. The spatial distribution of REE-bearing pegmatitic systems is highlighted in the high-density stream sediments geochemical dataset of the Central Cell. Rare-metal pegmatites with Sn-W-coltan mineralisation and/or economic placer deposits derived from them are recognised in the Central Cell. In the South-western Cell, element associations Li-Ni-(Cr), and Pt-Cr for stream sediments derived from crystalline geological terrains are perhaps indicative of unknown basic/ultrabasic lithologies with potential for associated mineralisation. Gold is principally found in alluvial placer deposits; As and Sb concentration data are potentially useful for pathfinder follow-up exploration for primary hydrothermal Au mineralisation in schist lithologies. A range of elements, including U and some REE, are moderately enriched in Mesozoic to Recent sedimentary (terrestrial and marine) cover sequences as a result of regional reworking of well exposed crystalline lithologies, with potential for sediment-hosted mineralisation and economic alluvium. In the South-western Cell, anomalies of Au, Ta, Nb as well as the REE (e.g. La, Ce, Nd, Sm, Pr, Nd) and U, Th and Y are associated with stream sediments derived from metasedimentary and metavolcanic lithologies and migmatitic gneisses. In the Central Cell, high anomalies of a full range of light- and heavy-REE are associated with pegmatites, genetically associated with the known Older Granites of north-central Nigeria. Compared to a range of other published regional stream sediment studies in Africa, Asia and Europe, these results from South-west and central Nigeria show comparatively high concentrations for REE, Y, U, Ta, Nb, Zr and Hf. In addition there are several anomalies for Au and Pt that need further investigation

Defect-enhanced silicon-on-insulator waveguide resonant photodetector with high sensitivity at 1.55μm

We describe the fabrication and characterization of a silicon waveguide resonant photodetector compatible with the optical-to-electrical conversion of wavelengths at, or around, 1550 nm. Sub-band responsivity is provided through the introduction of defects via inert self-implantation and subsequent annealing. The detector is located within a 20- m radius silicon microring resonator. An 18-dB resonant enhancement in absorption coefficient and 12-dB enhancement in photocurrent were measured, leading to a resonant responsivity of approximately 39 mA/W at 20-V reverse bias

Monitoring and tuning micro-ring properties using defect-enhanced silicon photodiodes at 1550 nm

We report on the application of defect-enhanced silicon waveguide photodiodes operating at 1550 nm as power monitors for use in photonic integrated circuits. In-line monitors of 250-μm length provide an efficiency of 97 mA/W by absorbing only 8% of the optical mode. The monitors were integrated onto micro-ring waveguide ports to provide measures of optical resonance characteristics and a feedback to a thermal resonance tuner. The suitability of these photodetectors for control of micro-ring resonators is demonstrated

Optical filters utilizing ion implanted Bragg gratings in SOI waveguides

The refractive index modulation associated with the implantation of oxygen or silicon into waveguides formed in silicon-on-insulator (SOI) has been investigated to determine the feasibility of producing planar, implantation induced Bragg grating optical filters. A two-dimensional coupled mode theory-based simulation suggests that relatively short grating lengths, on the order of a thousand microns, can exhibit sufficient wavelength suppression, of >10 dB, using the implantation technique. Fabricated planar implanted slab-guided SOI waveguides demonstrated an extinction of -10 dB for TE modes and -6 dB for TM modes for the case of oxygen implantation. Extinctions of -5dB and -2 dB have been demonstrated with silicon implantation

Mapping trace element deficiency by cokriging from regional geochemical soil data: a case study on cobalt for grazing sheep in Ireland

Deficiency or excess of certain trace elements in the soil causes problems for agriculture, including disorders of grazing ruminants. Geostatistics has been used to map the probability that trace element concentrations in soil exceed or fall below particular thresholds. However, deficiency or toxicity problems may depend on interactions between elements in the soil. Here we show how cokriging from a regional survey of topsoil geochemistry can be used to map the risk of deficiency, and the best management intervention, where both depend on the interaction between two elements. Our case study is on cobalt. Farmers and their advisors in Ireland use index values for the concentration of total soil cobalt and manganese to identify where grazing sheep are at risk of cobalt deficiency. We use topsoil data from a regional geochemical survey across six counties of Ireland to form local cokriging predictions of cobalt and manganese concentrations with an attendant distribution which reflects the joint uncertainty of these predictions. From this distribution we then compute conditional probabilities for different combinations of cobalt and manganese index values, and so for the corresponding inferred risk to sheep of cobalt deficiency and the appropriateness of different management interventions. We represent these results as maps, using a verbal scale for the communication of uncertain information. This scale is based on one used by the Intergovernmental Panel on Climate Change, modified in light of some recent research on its effectiveness

Charge state switching of deep levels for low-power optical modulation in silicon waveguides

We demonstrate a method for the efficient modulation of optical wavelengths around 1550 nm in silicon wave guides. The amplitude of a propagating signal is mediated via control of the charge state of indium centers, rather than using free-carriers alone as in the plasma-dispersion effect. A 1×1 switch formed of an integrated p-i-n junction in an indium-doped silicon on insulator (SOI) waveguide provides ‘normally-off’ silicon absorption of greater than 7 dB at zero bias. This loss is decreased to 2.8 dB with application of a 6 V applied reverse bias, with a power consumption of less than 1 μW