A comparative analysis of the discriminating power of laser-induced breakdown spectroscopy (LIBS) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), each coupled with ...refractive index (RI) measurements, is presented for a study of 23 samples of automobile float glass. Elemental emission intensity ratios (LIBS) and elemental concentration ratios (LA-ICP-MS) and their associated confidence intervals were calculated for each float glass sample. The ratios and confidence intervals were used to determine the discrimination power of each analytical method. It was possible to discriminate 83% of the glass samples with 99% confidence based on LIBS spectra alone, and 96–99% of the samples could be discriminated based on LIBS spectra taken in conjunction with RI data at the same confidence level. LA-ICP-MS data allowed for 100% discrimination of the samples without the need for RI data. The results provide evidence to support the use of LIBS combined with RI for forensic analysis of float glass in laboratories that do not have access to LA-ICP-MS.
An equilibrium partitioning model is applied for the first time to the sequential formation of 1:1 and then 2:1 adducts between the high explosive cyclo-1,3,5-trimethylene-2,4,6-trinitramine (RDX) ...and halide anions fluoride, chloride, bromide, and iodide in electrospray ionization interface (ESI) mass spectrometry. The equilibrium partitioning model is developed and model calculations are presented to demonstrate the generic behavior of the system, which is in qualitative agreement with the observed changes in 1:1 (RDX−halide) and 2:1 (RDX−halide) responses in ESI-MS. The model is successfully applied to the experimental data with the use of octanol−water partitioning coefficients to predict interior-to-surface partitioning behavior of the complexes in droplets formed in the ESI. The data and model suggest that the significantly more hydrophobic 2:1 complexes are readily observed in ESI-MS, even though their formation constants may be several orders of magnitude less than that of the 1:1 complex. Structures for RDX−halide 1:1 and 2:1 complexes are proposed based on ion−dipole attractions and destabilizing dipole−dipole interactions.
High-quality optical resonant cavities require low optical loss, typically on the scale of parts per million. However, unintended micron-scale contaminants on the resonator mirrors that absorb the ...light circulating in the cavity can deform the surface thermoelastically and thus increase losses by scattering light out of the resonant mode. The point absorber effect is a limiting factor in some high-power cavity experiments, for example, the Advanced LIGO gravitational-wave detector. In this Letter, we present a general approach to the point absorber effect from first principles and simulate its contribution to the increased scattering. The achievable circulating power in current and future gravitational-wave detectors is calculated statistically given different point absorber configurations. Our formulation is further confirmed experimentally in comparison with the scattered power in the arm cavity of Advanced LIGO measured by in situ photodiodes. The understanding presented here provides an important tool in the global effort to design future gravitational-wave detectors that support high optical power and thus reduce quantum noise.
Interferometric gravitational wave detectors operate with high optical power in their arms in order to achieve high shot-noise limited strain sensitivity. A significant limitation to increasing the ...optical power is the phenomenon of three-mode parametric instabilities, in which the laser field in the arm cavities is scattered into higher-order optical modes by acoustic modes of the cavity mirrors. The optical modes can further drive the acoustic modes via radiation pressure, potentially producing an exponential buildup. One proposed technique to stabilize parametric instability is active damping of acoustic modes. We report here the first demonstration of damping a parametrically unstable mode using active feedback forces on the cavity mirror. A 15 538 Hz mode that grew exponentially with a time constant of 182 sec was damped using electrostatic actuation, with a resulting decay time constant of 23 sec. An average control force of 0.03 nN was required to maintain the acoustic mode at its minimum amplitude.
This in situ study used photosynthetic activity (measured as chlorophyll
a fluorescence) and photosynthetic pigment concentrations to assess the effect of copper, cadmium, lead and zinc on the ...seagrass
Zostera capricorni. Custom-made portable in situ exposure (PIE) chambers were developed so seagrasses could be dosed within the meadow.
Z. capricorni was exposed to 0.1 and 1 mg l
−1 of metal solutions for 10 h. During this time and for the subsequent four-day recovery period, the effective quantum yield of photosystem II (PS II) (
ΔF/
Fm
′) was measured. While the results were variable, copper and zinc exposed samples had a depressed
ΔF/
Fm
′ during the exposure period. Samples exposed to zinc recovered to pre-exposure levels but those exposed to copper did not. Cadmium and lead did not impact on the chlorophyll
a fluorescence and the chlorophyll pigment data supported these findings. This study presents an innovative new application of chlorophyll
a fluorescence stress assessment.
► We used energy balance to assess restoration of evaparotranspiration (ET) to a waste disposal site. ► Latent heat flux (
λE) was 60–90% of solar energy incident on the juvenile plantation. ► The
λE ...arose mostly (>80%) from the groundcover and the rest from the sparse tree canopy. ► There was no evidence of deep drainage since annual
λE was close to rainfall in the 2
years. ► Good groundcover is critical to restoring ET during the early phases of tree growth.
Revegetation to restore hydrological function to highly disturbed landscapes used for waste disposal or mining is often constrained by the initial low rates of water-use during the early phases of the developing vegetation. This problem is especially pronounced for revegetation that relies on trees due to their prolonged lead-time to achieve canopy closure. Initial low rates of water-use can however be overcome if a groundcover of quick-growing herbaceous species is planted first. To demonstrate the significance of groundcover in the early phase of revegetation, we undertook an energy balance analysis using the Bowen ratio technique for a juvenile plantation growing over a heavy groundcover of herbaceous species on a waste disposal site in 2006/2007 and 2007/2008. Latent heat flux (
λE) from the landscape (trees plus groundcover and soil) fluctuated widely between 0.5 and 22
MJ
m
−2
d
−1 and accounted for between 60% and 90% of available energy at the site; this percentage exceeded 100% during periods with significant advection. The latent heat emanating from the tree canopy (
λE
c
), derived from sapflow measurements in the trees, accounted for only between 4% and 18% of daily
λE with the balance arising from the groundcover that intercepted more than 90% of incident solar radiation. The
λE
c
was mostly smaller than the net radiation intercepted by the tree canopy (
R
nc) with the excess energy expended by the canopy as sensible heat (
H
c
), which accounted for up to 18% of bulk sensible heat from the landscape. The
λE expressed as ET was in excess (114%) of rainfall in the relatively dry first growing (September–May) season, when rainfall was only 87% of the long-term average. It was, however, smaller (80%) than rainfall during the second season, when the annual rainfall was close to the long-term average. We used these data to develop an empirical model for predicting
λE from soil–water content and the prevailing evaporative demand.
Ecophysiological studies of remnant woodlands in saline environments are scarce. We investigated seasonal fluctuations in soil water and salinity together with leaf and branch traits (area-based ...maximum assimilation (Amax), foliar nitrogen, specific leaf area (SLA) and Huber value (Hv)) and sap velocities of Eucalyptus macrorhyncha at four semi-arid sites in south-eastern Australia. Summer and winter soil salinities (10 cm depth) were 15–35 dS m−1 and 8–10 dS m−1 respectively. Gravimetric soil water content in the upper 20 cm was 2–5% in summer and 7–23% in winter, resulting in a significant inverse correlation between soil water and soil salinity. We found significant correlations between soil conditions and plant traits and function across seasons. Soil water content was significantly correlated with foliar N, SLA, Hv and maximum sap velocity while soil salinity was significantly correlated with Amax, Hv and maximum sap velocity. Correlations indicate co-variation of soil conditions and plant physiology in response to environmental conditions such as solar radiation and vapour pressure deficit (D). E. macrorhyncha tolerates the dual stresses of high salinity and low soil water during summer. While the plants appeared unhealthy, our data show that remnant vegetation can remain functional even in close proximity to saline scalds.
•Dryland salinity is a significant problem in semi-arid regions of the world.•Woodlands combat salinity by lowering groundwater, reducing surface salt.•We measured seasonal carbon assimilation, water use, soil salinity and water content.•Some plant functional measurements were correlated with some soil measurements.•Seasonal changes in meteorology drove unexpected plant-soil relationships.
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