We report results of a search for light (≲10 GeV) particle dark matter with the XENON10 detector. The event trigger was sensitive to a single electron, with the analysis threshold of 5 electrons ...corresponding to 1.4 keV nuclear recoil energy. Considering spin-independent dark matter-nucleon scattering, we exclude cross sections σ(n)>7×10(-42) cm(2), for a dark matter particle mass m(χ)=7 GeV. We find that our data strongly constrain recent elastic dark matter interpretations of excess low-energy events observed by CoGeNT and CRESST-II, as well as the DAMA annual modulation signal.
Endoscopic retrograde cholangiography (ERC) with stenting is the procedure of choice for biliary decompression in patients with obstructive jaundice. In cases where biliary access cannot be achieved, ...interventional endoscopic ultrasound-guided cholangiography (IEUC) has become an alternative to percutaneous transhepatic cholangiography (PTC).
We report on 5 years of experience in patients who underwent IEUC after failed endoscopic retrograde cholangiopancreatography (ERCP). Endoscopic ultrasound-guided access to the targeted biliary duct was attempted with one of two approaches: transgastric-transhepatic (intrahepatic) or transenteric-transcholedochal (extrahepatic). A stent was then advanced over the wire and into the biliary tree.
A total of 49 patients underwent IEUC: 35 had biliary obstruction due to malignancy and 14 had a benign etiology. The overall success rate of IEUC was 84% (41/49), with an overall complication rate of 16%. Of the 35 patients who underwent the intrahepatic approach, 23 had a stent placed across the major papilla, one had a stent placed intraductally in the common bile duct, and three patients underwent placement of a gastrohepatic stent. Resolution of obstruction was achieved in 29 patients, with a success rate of 83%. In all, 14 patients underwent an extrahepatic approach. In 8/14 (57%), stent placement across the major papilla was achieved. A transenteric stent was placed in four patients. Biliary decompression was achieved in 12/14 cases (86%). Based on intention-to-treat analysis, the intrahepatic approach achieved success in 29 of 40 cases (73%), and the extrahepatic approach was successful in seven of nine cases (78%). There were no procedure-related deaths.
IEUC offers a feasible alternative to PTC in patients with obstructive jaundice in whom ERC has failed.
The pH of aqueous aerosols, as well as cloud and fog droplets, has an important influence on the chemistry that takes place within these unique microenvironments. Utilizing conjugate acid/base pairs ...to infer pH changes, we investigate, for the first time, changes in aerosol pH upon coalescence. In particular, we show that the pH within individual aqueous aerosols that are ∼8 μm in diameter can be titrated via droplet coalescence in an aerosol optical tweezer. Using sulfate/bisulfate and carbonate/bicarbonate as model systems, the pH of trapped aerosols is determined before and after introduction of smaller aerosols containing a strong acid. The pH change upon coalescence with the smaller, acidic aerosol is calculated using specific ion interaction theory. Furthermore, we show that the pH of an individual aerosol can be altered along a fairly wide range of pH values, paving the way for future studies requiring rigorous pH control of an aqueous aerosol.
Aerosols impact climate, human health, and the chemistry of the atmosphere, and aerosol pH plays a major role in the physicochemical properties of the aerosol. However, there remains uncertainty as ...to whether aerosols are acidic, neutral, or basic. In this research, we show that the pH of freshly emitted (nascent) sea spray aerosols is significantly lower than that of sea water (approximately four pH units, with pH being a log scale value) and that smaller aerosol particles below 1 μm in diameter have pH values that are even lower. These measurements of nascent sea spray aerosol pH, performed in a unique ocean-atmosphere facility, provide convincing data to show that acidification occurs "across the interface" within minutes, when aerosols formed from ocean surface waters become airborne. We also show there is a correlation between aerosol acidity and dissolved carbon dioxide but no correlation with marine biology within the seawater. We discuss the mechanisms and contributing factors to this acidity and its implications on atmospheric chemistry.
The XENON10 experiment at the Gran Sasso National Laboratory uses a 15 kg xenon dual phase time projection chamber to search for dark matter weakly interacting massive particles (WIMPs). The detector ...measures simultaneously the scintillation and the ionization produced by radiation in pure liquid xenon to discriminate signal from background down to 4.5 keV nuclear-recoil energy. A blind analysis of 58.6 live days of data, acquired between October 6, 2006, and February 14, 2007, and using a fiducial mass of 5.4 kg, excludes previously unexplored parameter space, setting a new 90% C.L. upper limit for the WIMP-nucleon spin-independent cross section of 8.8x10(-44) cm2 for a WIMP mass of 100 GeV/c2, and 4.5x10(-44) cm2 for a WIMP mass of 30 GeV/c2. This result further constrains predictions of supersymmetric models.
Metal hyperaccumulator plants like
Alyssum murale have a remarkable ability to hyperaccumulate Ni from soils containing mostly insoluble Ni. We have shown some rhizobacteria increase the ...phytoavailability of Ni in soils, thus enhancing Ni accumulation by
A. murale. Nine bacterial strains, originally isolated from the rhizosphere of
A. murale grown in serpentine Ni-rich soil, were examined for their ability to solubilize Ni in different soils and for their effect on Ni uptake into
Alyssum. Microbacterium oxydans AY509223;
Rhizobium galegae AY509213;
Microbacterium oxydans AY509219;
Clavibacter xyli AY509236;
Acidovorax avenae AY512827;
Microbacterium a
rabinogalactanolyticum AY509225;
M. oxydans AY509222;
M. arabinogalactanolyticum AY509226 and
M. oxydans AY509221 were added to low, moderate and high Ni-contaminated soils.
M. oxydans AY509223 significantly increased Ni extraction by 10
mM Sr(NO
3)
2 from the high and medium soils and had no effect on Ni extraction from the low Ni soils. The other eight bacterial isolates significantly increased Ni extraction from all soils. There were no significant effects of bacterial inoculation on fresh and dry weight of
A . murale shoots grown in the low and high Ni soils compared to an unamended control.
M. oxydans AY509223 significantly increased Ni uptake of
A. murale grown in the low, medium, and high soils by 36.1%, 39.3%, and 27.7%, respectively, compared with uninoculated seeds.
M. oxydans AY509223 increased foliar Ni from the same soils from 82.9, 261.3 and 2829.3
mg
kg
−1 to 129.7, 430.7, and 3914.3
mg
kg
−1, respectively, compared with uninoculated controls. These results show that bacteria are important for Ni hyperaccumulation and could potentially be developed as an inoculum for enhancing uptake during commercial phytoremediation or phytomining of Ni.
Forty-six bacterial cultures, including one culture collection strain, thirty from the rhizosphere of
Alyssum murale and fifteen from Ni-rich soil, were tested for their ability to tolerate arsenate, ...cadmium, chromium, zinc, mercury, lead, cobalt, copper, and nickel in their growth medium. The resistance patterns, expressed as minimum inhibitory concentrations, for all cultures to the nine different metal ions were surveyed by using the agar dilution method. A large number of the cultures were resistant to Ni (100%), Pb (100%), Zn (100%), Cu (98%), and Co (93%). However, 82, 71, 58 and 47% were sensitive to As, Hg, Cd and Cr(VI), respectively. All cultures had multiple metal-resistant, with heptametal resistance as the major pattern (28.8%). Five of the cultures (about of 11.2% of the total), specifically
Arthrobacter rhombi AY509239,
Clavibacter xyli AY509235,
Microbacterium arabinogalactanolyticum AY509226,
Rhizobium mongolense AY509209 and
Variovorax paradoxus AY512828 were tolerant to nine different metals. The polymerase chain reaction in combination with DNA sequence analysis was used to investigate the genetic mechanism responsible for the metal resistance in some of these gram-positive and gram-negative bacteria that were, highly resistant to Hg, Zn, Cr and Ni. The
czc,
chr,
ncc and
mer genes that are responsible for resistance to Zn, Cr, Ni and Hg, respectively, were shown to be present in these bacteria by using PCR. In the case of,
M. arabinogalactanolyticum AY509226 these genes were shown to have high homology to the
czcD,
chrB,
nccA, and
mer genes of
Ralstonia metallidurans CH34. Therefore, Hg, Zn, Cr and Ni resistance genes are widely distributed in both gram-positive and gram-negative isolates obtained from
A. murale rhizosphere and Ni-rich soils.
This paper reviews progress in phytoextraction of soil elements and illustrates the key role of hyperaccumulator plant species in useful phytoextraction technologies. Much research has focused on ...elements which are not practically phytoextracted (Pb); on addition of chelating agents which cause unacceptable contaminant leaching and are cost prohibitive; and on plant species which offer no useful phytoextraction capability (e.g., Brassica juncea Czern). Nickel phytoextraction by Alyssum hyperaccumulator species, which have been developed into a commercial phytomining technology, is discussed in more detail. Nickel is ultimately accumulated in vacuoles of leaf epidermal cells which prevents metal toxicity and provides defense against some insect predators and plant diseases. Constitutive up-regulation of trans-membrane element transporters appears to be the key process that allows these plants to achieve hyperaccumulation. Cadmium phytoextraction is needed for rice soils contaminated by mine wastes and smelter emissions with 100-fold more soil Zn than Cd. Although many plant species can accumulate high levels of Cd in the absence of Zn, when Cd/Zn > 100, only Thlaspi caerulescens from southern France has demonstrated the ability to phytoextract useful amounts of Cd. Production of element-enriched biomass with value as ore or fertilizer or improved food (Se) or feed supplement may offset costs of phytoextraction crop production. Transgenic phytoextraction plants have been achieved for Hg, but not for other elements. Although several researchers have been attempting to clone all genes required for effective hyperaccumulation of several elements, success appears years away; such demonstrations will be needed to prove we have identified all necessary processes in hyperaccumulation.
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