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Herbicide active ingredients, formulation type, ambient temperature, and humidity can influence volatility. A method was developed using volatility chambers to compare relative volatility of different synthetic auxin herbicide formulations in controlled environments. 2,4-D or dicamba acid vapors emanating after application were captured in air-sampling tubes at 24, 48, 72, and 96 h after herbicide application. The 2,4-D or dicamba was extracted from sample tubes and quantified using liquid chromatography and tandem mass spectrometry. Volatility from 2,4-D dimethylamine (DMA) was determined to be greater than that of 2,4-D choline in chambers where temperatures were held at 30 or 40 C and relative humidity (RH) was 20% or 50%. Air concentration of 2,4-D DMA was 0.399 µg m−3 at 40 C and 20% RH compared with 0.005 µg m−3 for 2,4-D choline at the same temperature and humidity at 24 h after application. Volatility from 2,4-D DMA and 2,4-D choline increased as temperature increased from 30 to 40 C. However, volatility from 2,4-D choline was lower than observed from 2,4-D DMA. Volatility from 2,4-D choline at 40 C increased from 0.00458 to 0.0263 µg m−3 and from 0.00341 to 0.025 µg m−3 when humidity increased from 20% to 50% at 72 and 96 h after treatment, respectively, whereas, volatility from 2,4-D DMA tended to be higher at 20% RH compared with 50% RH. Air concentration of dicamba diglycolamine was similar at all time points when measured at 40 C and 20% RH. By 96 h after treatment, there was a trend for lower air concentration of dicamba compared with earlier timings. This method using volatility chambers provided good repeatability with low variability across replications, experiments, and herbicides.
To determine the feasibility of an anthropomorphic breast polyurethane-based three-dimensional (3D) dosimeter with cavity to measure dose distributions and skin dose for a commercial strut-based applicator strut-adjusted volume implant (SAVI™) 6–1.
Materials and methods
An anthropomorphic breast 3D dosimeter was created with a cavity to accommodate the SAVI™ strut-based device. 2 Gy was prescribed to the breast dosimeter having D95 to planning target volume evaluation (PTV_EVAL) while limiting 125% of the prescribed dose to the skin. Independent dose distribution verification was performed with GAFCHROMIC® EBT2 film. The dose distribution from the 3D dosimeter was compared to the distributions from commercial brachytherapy treatment planning system (TPS) and film. Point skin doses, line profiles and dose–volume histogram (DVHs) for the skin and PTV_EVAL were compared.
The maximum difference in skin dose for TPS and the 3D dosimeter was 4% whereas 41% between the TPS and EBT2 film. The maximum dose difference for line profiles between TPS, 3D dosimeter, and film was 4·1%. DVHs of skin and PTV_EVAL for TPS and 3D dosimeter differed by a maximum of 4% at 5 mm depth and skin differed by a maximum 1·5% between TPS and 3D dosimeter. The criterion for gamma analysis comparison was 92·5% at ±5%±3 mm criterion. The TPS demonstrated at least ±5% comparability in predicting dose to the skin, PTV_EVAL and normal breast tissue.
3D anthropomorphic polyurethane dosimeter with cavity gives comparable results to the TPS dose predictions and GAFCHROMIC® EBT2 film results in the context of HDR brachytherapy.
New dating confirms that people occupied the Australian continent before the earliest time inferred from conventional radiocarbon analysis. Many of the new ages were obtained by accelerator mass spectrometry 14C dating after an acid–base–acid pretreatment with bulk combustion (ABA-BC) or after a newly developed acid–base–wet oxidation pretreatment with stepped combustion (ABOX-SC). The samples (charcoal) came from the earliest occupation levels of the Devil's Lair site in southwestern Western Australia. Initial occupation of this site was previously dated 35,000 14C yr B.P. Whereas the ABA-BC ages are indistinguishable from background beyond 42,000 14C yr B.P., the ABOX-SC ages are in stratigraphic order to ∼55,000 14C yr B.P. The ABOX-SC chronology suggests that people were in the area by 48,000 cal yr B.P. Optically stimulated luminescence (OSL), electron spin resonance (ESR) ages, U-series dating of flowstones, and 14C dating of emu eggshell carbonate are in agreement with the ABOX-SC 14C chronology. These results, based on four independent techniques, reinforce arguments for early colonization of the Australian continent.
The mineralogy and isotopic compositions of subglacially precipitated carbonate crusts (SPCCs) provide information on conditions and processes beneath former glaciers and ice sheets. Here we describe SPCCs formed on gneissic bedrock at the bed of the Laurentide Ice Sheet (LIS) during the last glacial maximum on central Baffin Island. Geochemical data indicate that the Ca in the crusts was likely derived from the subglacial chemical weathering Ca-bearing minerals in the local bedrock. C and Sr isotopic analyses reveal that the C in the calcite was derived predominantly from older plant debris. The δ18O values of the SPCCs suggest that these crusts formed in isotopic equilibrium with basal ice LIS preserved in the Barnes Ice Cap (BIC). Columnar crystal fabric and the predominance of sparite over micrite in the SPCCs are indicative of carbonate precipitation under open-system conditions. However, the mean δ18O value of the calcite crusts is ~ 10‰ higher than those of primary LIS ice preserved in the BIC, demonstrating that SPCCs record the isotopic composition of only basal ice. Palynomorph assemblages preserved within the calcite and basal BIC ice include species last endemic to the Arctic in the early Tertiary. The source of these palynomorphs remains enigmatic.
Wetland research in northern Belize provides the earliest evidence for development of agriculture in the Maya Lowlands. Pollen data confirm the introduction of maize and manioc before 3000 B.C. Dramatic deforestation, beginning ca. 2500 B.C. and intensifying in wetland environments ca. 1500-1300 B.C., marks an expansion of agriculture, which occurred in the context of a mixed foraging economy. By 1000 B.C. a rise in groundwater levels led farmers to construct drainage ditches coeval with the emergence of Maya complex society ca. 1000-400 B.C. Field manipulations often involved minor modifications of natural hummocks. Canal systems are not as extensive in northern Belize as previously reported, nor is there evidence of artificially raised planting platforms. By the Classic period, wetland fields were flooded and mostly abandoned.
We demonstrate the use of a synchrotron radiation source for in situ x-ray diffraction analysis during rapid thermal annealing (RTA) of 0.35 μm Salicide (self-aligned silicide) and 0.4 μm Polycide (silicided polysilicon) TiSi2 Complementary Metal Oxide Semiconductor (CMOS) gate structures. It is shown that the transformation from the C49 to C54 phase of TiSi2 occurs at higher temperatures in submicron gate structures than in unpatterned blanket films. In addition, the C54 that forms in submicron structures is (040) oriented, while the C54 that forms in unpatterned Salicide films is randomly oriented. Although the preferred oreintation of the initial C49 phase was different in the Salicide and Polycide gate structures, the final orientation of the C54 phase formed was the same. An incomplete conversion of C49 into C54-TiSi2 during the RTA of Polycide gate structures was observed and is attributed to the retarding effects of phosphorus on the transition.
Crystallization, precipitation, and phase transformation phenomena were observed in titanium suicide thin film samples during in situ heating experiments in a transmission electron microscope. The as-deposited TixSiy films were 110 nm in thickness with a composition of 1 Ti to 2.33 Si. Crystallization of the C49 phase was followed isothermally near the sputter deposition temperature. The movement of individual grain boundaries was recorded so that a “velocity of crystallization” could be calculated. The precipitation of excess silicon from the C49 phase was first observed in the 650°C to 750°C temperature range. The precipitates were predominantly of the incoherent type, with a smaller number existing at the grain boundaries. Ostwald ripening then occurred up to the C49 to C54 phase transformation which was accompanied by a dramatic increase in grain size. Grain boundary movement during the phase transformation was such that large precipitates, which were originally at C49-C49 boundaries, ended up within resulting C54 crystals. Many of these larger precipitates were found to exist as epitaxial “islands” at the TiSi2/Si substrate interface.
The poem Vingtième Siècle (Pleine Mer—Plein Ciel) forms the climax of the Légende des Siècles, and presents in mythical form a picture of man's ascent through science, out of a state of ignorance, slavery and hatred, into one of enlightenment, freedom and brotherly love. Hugo typifies the idyllic future by an air-ship, (Plein Ciel), the sombre past and present by the colossal steamship “Léviathan,” (Pleine Mer). The same idea, of the deliverance of man through science, had found expression in Le Satyre; but there locomotive, steamer, and airship were equally honored as factors and symbols of man's emancipation, one leading up to and merging into the other. The invention of the steamship was specifically celebrated in the lines:
Qui sait si quelque jour, grandissant d'âge en âge,
Il ne jettera pas son dragon à la nage,
Et ne franchira pas les mers, la flamme au front! (ll. 611–613)
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