The systematic determination of accuracy and precision in geochemical exploration data

Regional geochemical data from the 1:250,000 map series of Great Britain produced by the Institute of Geological Sciences are processed using a computer system developed for the National Geochemical Data Bank. The system, which can be used for the selective or complete retrieval of data and for statistical analysis and plotting, incorporates a procedure for determining accuracy and precision. Changes in accuracy are monitored by analysis of standards and the redetermination of sub-sets of samples using an instrumental neutron activation method. Samples are assigned random numbers in the field and are re-ordered sequentially prior to preparation and analysis in order to determine systematic errors occurring within batches of samples.Sampling, sub-sampling and analytical precision are monitored using analysis of variance methods on the results obtained on duplicate samples and analyses. The system for the efficient processing of this information is described and examples of the different types of error presented.     

Seasonal characteristics of the near-surface circulation in the northern South China Sea obtained from satellite-tracked drifters

The surface circulation of northern South China Sea (hereafter SCS) for the period 1987–2005 was studied using the data of more than 500 satellite-tracked drifters and wind data from QuikSCAT. The mean flow directions in the northern SCS except the Luzon Strait (hereafter LS) during the periods October~March was southwestward, and April~September northeastward. A strong northwestward intrusion of the Kuroshio through the LS appears during the October~March period of northeasterly wind, but the intrusion became weak between April and September. When the strong intrusion occurred, the eddy kinetic energy (EKE) in the LS was 388 cm²/s² which was almost 2 times higher than that during the weak-intrusion season. The volume transport of the Kuroshio in the east of the Philippines shows an inverse relationship to that of the LS. There is a six-month phase shift between the two seasonal phenomena. The volume transport in the east of the Philippines shows its peak sis-month earlier faster than that of the LS. The strong Kuroshio intrusion is found to be also related to the seasonal variation of the wind stress curl generated by the northeasterly wind. The negative wind stress curl in the northern part of LS induces an anticyclonic flow, while the positive wind stress curl in the southern part of LS induces a cyclonic flow. The northwestward Kuroshio intrusion in the northern part of LS happened with larger negative wind stress curl, while the westward intrusion along 20.5°N in the center of the LS occurred with weaker negative wind stress curl.     

Recent increase in atmospheric deposition of mercury to California aquatic systems inferred from a 300-year geochronological assessment of lake sediments

Age-dated sediment cores from 4 remote lakes across California were analyzed for total Hg (Hg_T) concentration as a function of pre- and post-industrialization. Particle size, magnetic susceptibility and organic C and N, were measured to determine if the Hg concentration in sediment cores could be related to atmospheric deposition and/or watershed processes. Results indicate that (a) for each lake modern (1970–2004) Hg_T lake sediment concentrations have increased by an average factor of 5 times more than historic (pre-1850) Hg_T concentrations; (b) the ratio of modern to pre-industrial lake sediment Hg_T for these lakes are higher than estimated for other locations where atmospheric deposition is presumed to be the main source of Hg; (c) 2 of the 4 studied lakes demonstrated significant relationships between Hg_T concentrations and percentage organic material (r² = 0.68 and p < 0.01; r² = 0.67 and p < 0.01) whereas the other two indicated no significant relationship (r² = 0.05 and p = 0.51; r² = 0.12 and p = 0.36).     

The Effect of the Bistatic Scattering Angle on the High-Frequency Radar Cross Sections of the Ocean Surface

High-frequency (HF) bistatic Doppler cross sections of the ocean surface are examined with respect to their dependency on the bistatic angle. Previously derived results which incorporate a pulsed dipole source and two orders of scatter are considered. It is trivially seen that the first-order result has a linear dependence on the cosine of the bistatic angle. The second-order echo accounts for a double scatter of incident radiation from first-order surface waves - the so-called electromagnetic term - and a single scatter from a second-order ocean wave. The latter, generally referred to as the second-order hydrodynamic term because it originates from coupling between first-order ocean waves, predominates the Doppler continuum in most regions of interest. The analysis presented here verifies that in addition to a cosine-dependent reduction in cross section magnitude with increasing bistatic angle, both components of the second-order scatter tend to zero under the condition of near-forward scatter for bistatic HF radar operation. Of course, this imposes practical limitations on the region over which a bistatically configured HF radar system may be used to remotely sense ocean surface parameters.     

Migration of scheduled caste population in rural Bist Doab (Punjab)

Using primary data collected from 5 villages in the Bist Doab, this study analyzes migration patterns of the scheduled caste population in rural areas of this region of Punjab. During 1971-1981, the rural scheduled caste population recorded a growth rate of 28.37% as compared to the corresponding growth rate of 13.32% among the rural nonscheduled castes. The proportion of the scheduled caste population showed striking intervillage variations from 52.85% in Khark Balhra to 87.45% in Bhoyapur. It was found that the rate of in-migration of the general population was quite low; the scheduled castes were no exception. Male in-migration has been primarily due to economic reasons; female in-migration was due largely to the change of marital status. It is only in Bhoyapur that about 44% of male in-migrants came as a result of rehabilitation programs undertaken by the state government after 1947. In all the villages, the scheduled caste males have out-migrated at a far slower pace than their nonscheduled caste counterparts. Economic reasons for males and marriage for females are almost the only 2 determinants of out-migration. Scheduled caste males and females differ from each other not only in terms of their motives for migration, but also with respect to the distance of the move; compared to the short distance migration among females, males experience relatively long range migration. Scheduled caste and nonscheduled caste difference is widest in terms of gross emigration; emigration among the scheduled castes is small in volume and more recent in origin. This is directly related to their meager incomes, low literacy rates, and lack of awareness of opportunities.     

The vortex created by mass transfer between layers of a rotating fluid

Abstract

A simple way to model stratification of the ocean or atmosphere is in terms of two superposed homogeneous layers of different density. Effects of cooling of the upper layer, such as that which occurs during bottom-water formation in the ocean, can be simulated by mass transfer from the upper layer to the lower layer. A model is constructed to see What effect such a mass transfer has on the flow when the mass transfer is confined to a limited region. The main effects are (i) doming of the interface, which maintains pressure gradients in balance with the velocity field, (ii) cyclonic rotation in the upper layer due to conservation of angular momentum of particles king drawn toward the sink, yet anticyclonic vorticity for those particles outside the mass transfer region due to shrinking of vortex lines drawn up over the dome. (iii) generally anticyclonic rotation in the lower layer due to particles tending to maintain their angular momentum while being pushed outwards, but some cyclonic rotation near the centre of mass transfer, due to momentum transfer from the upper layer. Similar effects to these are seen in the Greenland Sea where bottom water formation occurs. Results of the same sort are also found in a laboratory model of the process.     

The helicoid anemometer: A long neglected but valuable anemometer

Although the helicoid anemometer has been known since 1887 (W.H. Dines) it was not until the 1940's that a rugged, accurate and reliable instrument was built (The Aerovane, by Bendix Friez). Some of the outstanding features of the helicoid anemometer are as follows: it is a primary sensor – it is not essential to calibrate in a wind tunnel; its rate of turning is linearly proportional to wind speed over a wide speed range; some versions have a very low starting speed; and some helicoids, fixed in position, measure only that component of the wind that is parallel to the axis of the helicoid.     

Microlensing in dark matter haloes

Using eight dark matter haloes extracted from fully self-consistent cosmological N -body simulations, we perform microlensing experiments. A hypothetical observer is placed at a distance of 8.5 kpc from the centre of the halo measuring optical depths, event durations and event rates towards the direction of the Large Magellanic Cloud. We simulate 1600 microlensing experiments for each halo. Assuming that the whole halo consists of massive astronomical compact halo objects (MACHOs),   f = 1.0  , and a single MACHO mass is   m _M= 1.0 M_⊙  , the simulations yield mean values of  τ= 4.7^+5.0_−2.2× 10⁻⁷  and  Γ= 1.6^+1.3_−0.6× 10⁻⁶  events star⁻¹ yr⁻¹. We find that triaxiality and substructure can have major effects on the measured values so that τ and Γ values of up to three times the mean can be found. If we fit our values of τ and Γ to the MACHO collaboration observations, we find   f = 0.23^+0.15_−0.13  and   m _M= 0.44^+0.24_−0.16  . Five out of the eight haloes under investigation produce f and m _M values mainly concentrated within these bounds.