810 research outputs found
Effects of Chemical Feedbacks on Decadal Methane Emissions Estimates
The coupled chemistry of methane, carbon monoxide (CO), and hydroxyl radical (OH) can modulate methane's 9âyear lifetime. This is often ignored in methane flux inversions, and the impacts of neglecting interactive chemistry have not been quantified. Using a coupledâchemistry box model, we show that neglecting the effect of methane source perturbation on [OH] can lead to a 25% bias in estimating abrupt changes in methane sources after only 10 years. Further, large CO emissions, such as from biomass burning, can increase methane concentrations by extending the methane lifetime through impacts on [OH]. Finally, we quantify the biases of including (or excluding) coupled chemistry in the context of recent methane and CO trends. Decreasing CO concentrations, beginning in the 2000's, have notable impacts on methane flux inversions. Given these nonnegligible errors, decadal methane emissions inversions should incorporate chemical feedbacks for more robust methane trend analyses and source attributions
Precision Doppler Shift Measurements with a Frequency Comb Calibrated Laser Heterodyne Radiometer
We report precision atmospheric spectroscopy of using a laser
heterodyne radiometer (LHR) calibrated with an optical frequency comb. Using
the comb-calibrated LHR, we record spectra of atmospheric near 1572.33
nm with a spectral resolution of 200 MHz using sunlight as a light source. The
measured spectra exhibit frequency shifts by approximately 11 MHz over
the course of the five-hour measurement, and we show that these shifts are
caused by Doppler effects due to wind along the spectrometer line of sight. The
measured frequency shifts are in excellent agreement with an atmospheric model,
and we show that our measurements track the wind-induced Doppler shifts with a
relative frequency precision of 100 kHz (15 cm/s), equivalent to a fractional
precision of a few parts in . These results demonstrate that
frequency-comb-calibrated LHR enables precision velocimetry that can be of use
in applications ranging from climate science to astronomy.Comment: 4 pages, 3 figure
Effects of Chemical Feedbacks on Decadal Methane Emissions Estimates
The coupled chemistry of methane, carbon monoxide (CO), and hydroxyl radical (OH) can modulate methane's 9âyear lifetime. This is often ignored in methane flux inversions, and the impacts of neglecting interactive chemistry have not been quantified. Using a coupledâchemistry box model, we show that neglecting the effect of methane source perturbation on [OH] can lead to a 25% bias in estimating abrupt changes in methane sources after only 10 years. Further, large CO emissions, such as from biomass burning, can increase methane concentrations by extending the methane lifetime through impacts on [OH]. Finally, we quantify the biases of including (or excluding) coupled chemistry in the context of recent methane and CO trends. Decreasing CO concentrations, beginning in the 2000's, have notable impacts on methane flux inversions. Given these nonnegligible errors, decadal methane emissions inversions should incorporate chemical feedbacks for more robust methane trend analyses and source attributions
Effect of retained chlorine in ENCATâą 30 catalysts on the development of encapsulated Pd: insights from in situ Pd K, Lâ and Cl K-edge XAS
In situ X-ray absorption spectroscopy (XAS) and Pd K, LIII, and Cl K-edges shows that Cl can be present in significant amounts in ENCATâą 30 catalysts and that it can severely retard Pd nanoparticle (NP) development in flowing solvents. We also show that whilst polymeric encapsulation protects the Pd against solvent induced agglomeration of Pd nanoparticles the evidence suggests it does not prevent the formation PdHx through reaction with the aqeous ethanol solvent, and that, as received, ENCATâą 30 NP catalysts are not, for the most part, comprised of nanoparticulate Pd0 irrespective of the presence of Cl
Drop impact behaviour on alternately hydrophobic and hydrophilic layered bead packs
A high level of water repellency in soils has an impact on soil hydrology, plant growth and soil erosion. Studies have been performed previously on model soils; consisting of close packed layers of glass spheres (140â400 ÎŒm in diameter), to mimic the behaviour of rain water on water repellent soils. In this study measurements were performed on multi-layered bead packs, to assess the interaction of water drops impacting layers consisting of different hydrophobic and hydrophilic layers. A high speed video camera was used to record the impact behaviour of water droplets on the bead packs focussing on the spreading of the droplet and the subsequent rebound behaviour of the droplet. Observations were made from the videos of the liquid marble effect on the droplet, whereby hydrophobic particles form a coating around the droplet, and how it differed depending on the arrangement of hydrophobic and hydrophilic layers within the bead pack. The droplet release height was varied in order to establish a relationship between impact velocity and the degree to which liquid marbling occurs, with higher impact speeds leading to a greater degree of liquid marbling. Measurements were also made to find the transition speeds between the three rebound conditions; rebound, pinning and fragmentation, showing an overall decrease in pinning velocity as the bead size increased
Is this pill an antibiotic or a painkiller? Improving the identification of oral antibiotics for better use
In this Viewpoint, we discuss how the identification of oral antibiotics and their distinction from other commonly used medicines can be challenging for consumers, suppliers, and health-care professionals. There is a large variation in the names that people use to refer to antibiotics and these often relate to their physical appearance, although antibiotics come in many different physical presentations. We also reflect on how the physical appearance of medicine influences health care and public health by affecting communication between patients and health-care professionals, dispensing , medicine use, and the public understanding of health campaigns. Furthermore, we report expert and stakeholder consultations on improving the identification of oral antibiotics and discuss next steps towards a new identification system for antibiotics. We propose to use the physical appearance as a tool to support and nudge awareness about antibiotics and their responsible use
Multiplicity Structure of the Hadronic Final State in Diffractive Deep-Inelastic Scattering at HERA
The multiplicity structure of the hadronic system X produced in
deep-inelastic processes at HERA of the type ep -> eXY, where Y is a hadronic
system with mass M_Y< 1.6 GeV and where the squared momentum transfer at the pY
vertex, t, is limited to |t|<1 GeV^2, is studied as a function of the invariant
mass M_X of the system X. Results are presented on multiplicity distributions
and multiplicity moments, rapidity spectra and forward-backward correlations in
the centre-of-mass system of X. The data are compared to results in e+e-
annihilation, fixed-target lepton-nucleon collisions, hadro-produced
diffractive final states and to non-diffractive hadron-hadron collisions. The
comparison suggests a production mechanism of virtual photon dissociation which
involves a mixture of partonic states and a significant gluon content. The data
are well described by a model, based on a QCD-Regge analysis of the diffractive
structure function, which assumes a large hard gluonic component of the
colourless exchange at low Q^2. A model with soft colour interactions is also
successful.Comment: 22 pages, 4 figures, submitted to Eur. Phys. J., error in first
submission - omitted bibliograph
Single Tube, High Throughput Cloning of Inverted Repeat Constructs for Double-Stranded RNA Expression
BACKGROUND: RNA interference (RNAi) has emerged as a powerful tool for the targeted knockout of genes for functional genomics, system biology studies and drug discovery applications. To meet the requirements for high throughput screening in plants we have developed a new method for the rapid assembly of inverted repeat-containing constructs for the in vivo production of dsRNAs. METHODOLOGY/PRINCIPAL FINDINGS: The procedure that we describe is based on tagging the sense and antisense fragments with unique single-stranded (ss) tails which are then assembled in a single tube Ligase Independent Cloning (LIC) reaction. Since the assembly reaction is based on the annealing of unique complementary single stranded tails which can only assemble in one orientation, greater than ninety percent of the resultant clones contain the desired insert. CONCLUSION/SIGNIFICANCE: Our single-tube reaction provides a highly efficient method for the assembly of inverted repeat constructs for gene suppression applications. The single tube assembly is directional, highly efficient and readily adapted for high throughput applications
Differential (2+1) Jet Event Rates and Determination of alpha_s in Deep Inelastic Scattering at HERA
Events with a (2+1) jet topology in deep-inelastic scattering at HERA are
studied in the kinematic range 200 < Q^2< 10,000 GeV^2. The rate of (2+1) jet
events has been determined with the modified JADE jet algorithm as a function
of the jet resolution parameter and is compared with the predictions of Monte
Carlo models. In addition, the event rate is corrected for both hadronization
and detector effects and is compared with next-to-leading order QCD
calculations. A value of the strong coupling constant of alpha_s(M_Z^2)=
0.118+- 0.002 (stat.)^(+0.007)_(-0.008) (syst.)^(+0.007)_(-0.006) (theory) is
extracted. The systematic error includes uncertainties in the calorimeter
energy calibration, in the description of the data by current Monte Carlo
models, and in the knowledge of the parton densities. The theoretical error is
dominated by the renormalization scale ambiguity.Comment: 25 pages, 6 figures, 3 tables, submitted to Eur. Phys.
Low Q^2 Jet Production at HERA and Virtual Photon Structure
The transition between photoproduction and deep-inelastic scattering is
investigated in jet production at the HERA ep collider, using data collected by
the H1 experiment. Measurements of the differential inclusive jet
cross-sections dsigep/dEt* and dsigmep/deta*, where Et* and eta* are the
transverse energy and the pseudorapidity of the jets in the virtual
photon-proton centre of mass frame, are presented for 0 < Q2 < 49 GeV2 and 0.3
< y < 0.6. The interpretation of the results in terms of the structure of the
virtual photon is discussed. The data are best described by QCD calculations
which include a partonic structure of the virtual photon that evolves with Q2.Comment: 20 pages, 5 Figure
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