Aerosol retrieval using ozone lidars in the ultraviolet spectral region is
challenging but necessary for correcting aerosol interference in ozone
retrieval and for studying the ozone–aerosol ...correlations. This study
describes the aerosol retrieval algorithm for a tropospheric ozone lidar,
quantifies the retrieval error budget, and intercompares the aerosol
retrieval products at 299 nm with those at 532 nm from a high spectral
resolution lidar (HSRL) and with those at 340 nm from an AErosol RObotic NETwork radiometer. After the cloud-contaminated data are filtered out, the
aerosol backscatter or extinction coefficients at 30 m and 10 min resolutions retrieved by the ozone lidar are highly correlated with the HSRL
products, with a coefficient of 0.95 suggesting that the ozone lidar can
reliably measure aerosol structures with high spatiotemporal resolution
when the signal-to-noise ratio is sufficient. The actual uncertainties of
the aerosol retrieval from the ozone lidar generally agree with our
theoretical analysis. The backscatter color ratio (backscatter-related
exponent of wavelength dependence) linking the coincident data measured by
the two instruments at 299 and 532 nm is 1.34±0.11, while the
Ångström (extinction-related) exponent is 1.49±0.16 for a
mixture of urban and fire smoke aerosols within the troposphere above
Huntsville, AL, USA.
Botrytis cinerea
is a major disease of blackcurrants causing premature flower and fruit drop in New Zealand. Because of the risk of fungicide residue from conventional methods, there is a need for ...the development of non-chemical control strategies as part of a sustainable disease control programme. Potential sources of
Botrytis cinerea
inoculum for infection of blackcurrant flowers were sampled in five blackcurrant properties in the South Island of New Zealand during dormancy and spring of 2006 and 2007. Tissues investigated were necrotic debris immediately beneath the plant, necrotic growing tips of 1-year-old canes, dead cane of previous seasons growth still attached to the base of the plant, canes damaged by harvesting or pruning, and canes damaged by currant clearwing (
Synanthedon tipuliformis
). The mean number of each tissue type within a plant varied considerably, both within a property and between different properties. Necrotic debris immediately beneath the plant and necrotic cane tips were shown to be the main sources of inoculum. Knowledge of the main sources of inoculum is an important first step towards the development of new, non-chemical control strategies, which are discussed in this context.
Neutral particle detection in high-background environments is greatly aided by the ability to easily load 6Li into liquid scintillators. In this work, we describe a readily available and inexpensive ...liquid scintillation cocktail stably loaded with a Li mass fraction up to 1%. Compositions that give thermodynamically stable microemulsions (reverse-micellar systems) were explored, using a Compton spectrum quenching technique to distinguish these from unstable emulsions. Scintillation light yield and transmittance were characterized. Pulse shape discrimination (PSD) was measured using a 252Cf source, showing that electron-like and proton-like recoil events are well-resolved even for Li loading up to 1%, providing a means of background suppression in neutron/neutrino detectors. While samples in this work were prepared with natLi (7.59% 6Li), the neutron capture peak was clearly visible in the PSD spectrum; this implies that while extremely high capture efficiency could be achieved with 6Li-enriched material, a very inexpensive neutron-sensitive detector can be prepared with natLi.
This Letter reports one of the most precise measurements to date of the antineutrino spectrum from a purely 235U-fueled reactor, made with the final dataset from the PROSPECT-I detector at the High ...Flux Isotope Reactor. By extracting information from previously unused detector segments, this analysis effectively doubles the statistics of the previous PROSPECT measurement. Further, the reconstructed energy spectrum is unfolded into antineutrino energy and compared with both the Huber-Mueller model and a spectrum from a commercial reactor burning multiple fuel isotopes. A local excess over the model is observed in the 5–7 MeV energy region. Comparison of the PROSPECT results with those from commercial reactors provides new constraints on the origin of this excess, disfavoring at 2.0 and 3.7 standard deviations the hypotheses that antineutrinos from 235U are solely responsible and noncontributors to the excess observed at commercial reactors, respectively.
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Thermally-induced martensitic phase transformations in polycrystalline CuZnAl and thin-film NiTiCu shape memory alloys were probed using photoemission electron microscopy (PEEM). Ultra-violet ...photoelectron spectroscopy shows a reversible change in the apparent work function during transformation, presumably due to the contrasting surface electronic structures of the martensite and austenite phases. In situ PEEM images provide information on the spatial distribution of these phases and the evolution of the surface microstructure during transformation. PEEM offers considerable potential for improving our understanding of martensitic transformations in shape memory alloys in real time.
A five‐year time series of lidar profiles from a site in Colorado is used to investigate the sources and scales of variability for ozone in the free troposphere. Analysis of 475 daily mean profiles ...derived from more than 25,000 individual profiles shows that ∼66% of the total variance is due to fluctuations on time scales from 1 day to 1 month, ∼30% on time scales from 1 month to 1 year, and ∼4% on time scales greater than 1 year. The analysis also identifies low‐frequency fluctuations correlated with the El Niño/Southern Oscillation (ENSO) (following a ∼6‐month lag) that may account for as much as 5% of the total variance in the data. The ENSO‐related changes can also lead to apparent ozone trends that range from −0.2 to +0.5 ppbv/yr for different 10‐year intervals between 1970 and 1990.
Signature-tagged mutagenesis (STM) provided the first widely applicable high-throughput method for detecting conditionally essential genes in bacteria by using negative selection to screen large ...pools of transposon (Tn) mutants. STM requires no prior knowledge of the bacterium's genome sequence, and has been used to study a large number of Gram-positive and Gram-negative species, greatly expanding the repertoires of known virulence factors for these organisms. Originally, hybridization of radiolabelled probes to colony or dot blots was used to detect differences in populations of tagged mutants before and after growth under a selective condition. Modifications of the tag detection method involving polymerase chain reaction (PCR) amplification and visualisation by gel electrophoresis have been developed and can be automated through the use of robotics. Genetic footprinting is another negative selection technique that uses PCR amplification to detect loss of mutants from a pool. Unlike PCR-STM, this technique allows direct amplification of Tn-flanking sequences. However, it requires the bacterium's whole genome sequence in order to design specific primers for every gene of interest. More recently, a number of techniques have been described that combine the negative-selection principle of STM and genetic footprinting with the genome-wide screening power of DNA microarrays. These techniques, although also requiring whole genome sequences, use either a form of linker-mediated or semi-random PCR to amplify and label Tn-flanking regions for hybridization to microarrays. The superior sensitivity microarray detection allows greater numbers of mutants to be screened per pool, as well as determination of the coverage/distribution of insertions in the library prior to screening, two significant advantages over STM.
We investigate the consequences of exposing an inorganic single-crystal surface to mechanical stimulation with an atomic force microscope tip in the presence of a supersaturated solution. We show ...that on the {010} cleavage surfaces of brushite (CaHPO4·2H2O) layer-by-layer growth at step edges can be induced and controlled with the tip. The growth rates are highly sensitive to the crystallographic orientation of the steps. Experimental evidence is presented that supports a mechanism involving tip-enhanced mass transport of ions to nucleation sites.
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