Pulse height response of an optical particle counter to monodisperse aerosols

The pulse height response of a right angle scattering optical particle counter has been investigated using monodisperse aerosols of polystyrene latex spheres, di-octyl phthalate and methylene blue. The results confirm previous measurements for the variation of mean pulse height as a function of particle diameter and show good agreement with the relative response predicted by Mie scattering theory. Measured cumulative pulse height distributions were found to fit reasonably well to a log normal distribution with a minimum geometric standard deviation of about 1.4 for particle diameters greater than about 2 micrometers. The geometric standard deviation was found to increase significantly with decreasing particle diameter

Finite octree meshing through topologically driven geometric operators

The octree technique is developed into the finite octree, and an overview is given. Modeler requirements are given. The octree discretization is discussed along with geometric communication operators. Geometric communication operators returning topological associativity and geometric communication operators returning spatial data are also discussed and illustrated. The advantages are given of the boundary representation and of geometric communication operators. The implementation plays an important role in the integration with a variety of geometric modelers. The capabilities of closed loop processes within a complete finite element system are presented

Effect of fertility control on a population's productivity

The effect of a sterilising agent upon the productivity of vertebrate pests, such as feral horses, feral dogs, wild rabbits or fruit-eating birds, depends upon the population's social structure and mating system. We investigated the theoretical effect on productivity of three forms of dominance, two effects of sterilisation on dominance, and four modes of transmission. Seventeen of the possible 24 combinations are feasible but lead to only four possible outcomes. Three of these result in lowered productivity. The fourth, where the breeding of a dominant female suppresses breeding in the sub-ordinate females of her group, leads to a perverse outcome. Productivity increases with sterilisation unless the proportion of females sterilised exceeds (n- 2)/(n- 1) where n (> 2) is the number of females in the group. A knowledge of social structure and mating system is therefore highly desirable before population control by suppressing female fertility is attempted or even contemplated

Report B, general biological oceanographic data from the Persian Gulf and Gulf of Oman

Quantitative phytoplankton (31 samples) and zooplankton (23 samples) collections were made throughout the Persian Gulf and at several places in the Gulf of Oman in spring 1977. In addition, 34 neuston tows were made in these areas. Approximately 100 species of phytoplankton were identified. Their numerical abundance ranged from 200 to 42,000 cells per liter. Diatoms were the most diverse taxa while coccolithophores were generally the dominant species numerically. Zooplankton biomass ranged from .11 to 2.00 cc/m3 and .52 to 2.27 cc/m3 in the Persian Gulf and Gulf of Oman respectively. Significantly higher volumes were recorded from the Gulf of Oman. The numerical abundance of zooplankton varied from 79 to 5098/m3. Copepods comprised more than 50% of the zooplankton in over one-half of the collections from the Persian Gulf. Higher zooplankton volumes occurred in the Central Persian Gulf. There was no significant differences in the quantities of zooplankton between day and night. Fourteen species of pontellid copepods were identified in neuston samples from the Persian Gulf and Gulf of Oman, including 10 species that represent new records for the Persian Gulf. Information on tar balls are summarized in an Appendix to this report.Prepared with funds from the Iranian Department of the Environment

Bright source of spectrally uncorrelated polarization-entangled photons with nearly single-mode emission

We present results of a bright polarization-entangled photon source operating at 1552 nm via type-II collinear degenerate spontaneous parametric down-conversion in a periodically poled potassium titanyl phosphate crystal. We report a conservative inferred pair generation rate of 123,000 pairs/s/mW into collection modes. Minimization of spectral and spatial entanglement was achieved by group velocity matching the pump, signal and idler modes and through properly focusing the pump beam. By utilizing a pair of calcite beam displacers, we are able to overlap photons from adjacent down-conversion processes to obtain polarization-entanglement visibility of 94.7 +/- 1.1% with accidentals subtracted.Comment: 4 pages, 7 color figures. Revised manuscript includes the following changes: corrected pair generation rate from 44,000/s/mW pump to 123,000/s/mW pump; replaced Fig. 1b to enhance clarity; minor alterations to the title, abstract and introduction; grammatical correction

Fabrication of optically smooth Sn thin films

The fabrication of optically smooth thin Sn films by vacuum or electrodeposition techniques is usually challenging. Little has been published on how to address this challenge mainly because very few applications require such smooth Sn surfaces. The excitation of surface plasmon polaritons on Sn surfaces by prism-based methods represents a case that requires very smooth surfaces and has motivated this work. It is shown that the deposition rate and the substrate temperature of a vacuum evaporation method can be optimized to obtain very smooth Sn films and this is supported by direct imaging evidence from atomic force microscopy and scanning electron microscopy.Comment: 7 figure

Biomarker and isotopic trends in a Permian-Triassic sedimentary section at Kap Stosch, Greenland

We report a geochemical study of a composite sedimentary section that captures the Permian-Triassic (PT) transition at Kap Stosch, East Greenland. The samples were from the original paleontological collection of early PT researchers. The rocks, which include samples from four proximal outcrop localities, were deposited during the Late Permian and Early Triassic at the margin of the Boreal Sea with a depositional hiatus and erosional event of unknown duration. Bulk geochemical measurements for most of the samples show good correlation between S2 and TOC% which, combined with low Tmax values, indicate that the organic matter (OM) that formed contemporaneously with sediment deposition is of relatively low maturity. Significant changes through the PT transition include a pronounced switch in the δ13C of TOC from high values near -24% to lower values averaging 32%, that is matched by a significant increase in the hydrogen index (HI) of the kerogen. The Permian samples containing 13C enriched OM also have low Rock-Eval HI values and anomalous pyrograms, indicating that the kerogen is heterogeneous in terms of source and maturity, as confirmed by microscopic analysis of the kerogen concentrates.Samples from the Permian section contain an abundance of black angular fragments of woody tissue in addition to gymnosperm pollen and spinose acritarchs of the Vittatina-Association (Balme, B., 1979. Palynology of Permian-Triassic boundary beds at Kap Stosch. Meddeleleser om Gronland 200, 1-36). In contrast, black woody tissue is rare in samples from the Early Triassic section with well preserved gymnosperm and lycopod pollen and spores of the Protohaploxypinus and Taeniaesporites associations. Biomarkers indicate moderate maturity for Permian samples, with the C27 sterane 20S/(20S + 20R), C31 homohopane 22S/(22S + 22R) ratio and Ts/(Ts + Tm) values all being higher than those for Triassic sediments. The marked switch in maturity indicators across the PT transition suggests an unconformity consistent with palynological observations. The pristane/phytane values are low and the homohopane index values high, indicating that anoxic conditions prevailed throughout deposition of the sediments.Additionally, markers of photic zone euxinia (i.e. isorenieratane, crocetane and 2,3,6-aryl isoprenoids) were present in all samples and all show maximum abundance closest to the PT transition. The C33 n-alkyl cyclohexane, a potential event marker for the onset of the biotic crisis in the Late Permian, was found in samples at, and immediately following, the paleontological PT transition. Despite the distinct change in lithology across the PT transition, the redox and Chlorobi-derived biomarkers indicate that photic zone euxinic conditions prevailed throughout the deposition of the Kap Stosch sedimentary sequence