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Repeatable approaches to work with scientific uncertainty and advance climate change adaptation in US national parks
Elevated pCO2 enhances bacterioplankton removal of organic carbon.
Factors that affect the removal of organic carbon by heterotrophic bacterioplankton can impact the rate and magnitude of organic carbon loss in the ocean through the conversion of a portion of consumed organic carbon to CO2. Through enhanced rates of consumption, surface bacterioplankton communities can also reduce the amount of dissolved organic carbon (DOC) available for export from the surface ocean. The present study investigated the direct effects of elevated pCO2 on bacterioplankton removal of several forms of DOC ranging from glucose to complex phytoplankton exudate and lysate, and naturally occurring DOC. Elevated pCO2 (1000-1500 ppm) enhanced both the rate and magnitude of organic carbon removal by bacterioplankton communities compared to low (pre-industrial and ambient) pCO2 (250 -~400 ppm). The increased removal was largely due to enhanced respiration, rather than enhanced production of bacterioplankton biomass. The results suggest that elevated pCO2 can increase DOC consumption and decrease bacterioplankton growth efficiency, ultimately decreasing the amount of DOC available for vertical export and increasing the production of CO2 in the surface ocean
Monolithic Arrays of Grating-Surface-Emitting Diode Lasers and Quantum Well Modulators for Optical Communications
The electro-optic switching properties of injection-coupled coherent 2-D grating-surface-emitting laser arrays with multiple gain sections and quantum well active layers are discussed and demonstrated. Within such an array of injection-coupled grating-surface-emitting lasers, a single gain section can be operated as intra-cavity saturable loss element that can modulate the output of the entire array. Experimental results demonstrate efficient sub-nanosecond switching of high power grading-surface-emitting laser arrays by using only one gain section as an intra-cavity loss modulator
The Electromagnetic Self-Energy Contribution to M_p - M_n and the Isovector Nucleon Magnetic Polarizability
We update the determination of the isovector nucleon electromagnetic
self-energy, valid to leading order in QED. A technical oversight in the
literature concerning the elastic contribution to Cottingham's formula is
corrected and modern knowledge of the structure functions is used to precisely
determine the inelastic contribution. We find \delta M_{p-n}^\gamma =
1.30(03)(47) MeV. The largest uncertainty arises from a subtraction term
required in the dispersive analysis, which can be related to the isovector
magnetic polarizability. With plausible model assumptions, we can combine our
calculation with additional input from lattice QCD to constrain this
polarizability as: \beta_{p-n} = -0.87(85) x 10^{-4} fm^3.Comment: 5 pages, version accepted for publication in PR
Ab initio calculation of the electromagnetic and neutral-weak response functions of 4He and 12C
Precise measurement of neutrino oscillations, and hence the determination of
their masses demands a quantitative understanding of neutrino-nucleus
interactions. To this aim, two-body meson-exchange currents have to be
accounted for along within realistic models of nuclear dynamics. We summarize
our progresses towards the construction of a consistent framework, based on
quantum Monte Carlo methods and on the spectral function approach, that can be
exploited to accurately describe neutrino interactions with atomic nuclei over
the broad kinematical region covered by neutrino experiments.Comment: 8 pages, 4 figure, Proceedings of the 21st International Conference
on Few-Body Problems in Physics, Chicago, Illinois, US
Vanadium-chromium alloy system
On the basis of data obtaiined from melting point determinations, microscopic examination, and x-ray investigations, a phase I diagram is proposed for the V -Cr alloy system. The system forms a complete series of solid solutions with a minimum occurring in the solidus at 1750°C and approximately 70 w/o Cr. No intermediate phases were found in this system. Hardness and corrosion data are presented as a function of alloying composition
Relativistic electrons from sparks in the laboratory
Discharge experiments were carried out at the Eindhoven University of
Technology in 2013. The experimental setup was designed to search for electrons
produced in meter-scale sparks using a 1 MV Marx generator. Negative voltage
was applied to the high voltage (HV) electrode. Five thin (1 mm) plastic
detectors (5 each) were distributed in various configurations close
to the spark gap. Earlier studies have shown (for HV negative) that X-rays are
produced when a cloud of streamers is developed 30-60 cm from the negative
electrode. This indicates that the electrons producing the X-rays are also
accelerated at this location, that could be in the strong electric field from
counterstreamers of opposite polarity. Comparing our measurements with modeling
results, we find that 300 keV electrons produced about 30-60 cm from the
negative electrode are the most likely source of our measurements. A
statistical analysis of expected detection of photon bursts by these fiber
detectors indicates that only 20%-45% of the detected bursts could be from soft
(10 keV) photons, which further supports that the majority of detected
bursts are produced by relativistic electrons
Scaling and Duality in Semi-exclusive Processes
We discuss extending scaling and duality studies to semi-exclusive processes.
We show that semi-exclusive hard pion photoproduction should exhibit scaling
behavior in kinematic regions where the photon and pion both interact directly
with the same quark. We show that such kinematic regions exist. We also show
that the constancy with changing momentum transfer of the resonance
peak/scaling curve ratio, familiar for many resonances in deep inelastic
scattering, is also expected in the semi-exclusive case.Comment: 8 pages, 4 figures, submitted to Phys.Rev.
Quantum Monte Carlo Calculations of Nuclei
The energies of , , and ground states, the
and scattering states of , the
ground states of , , and and the and
excited states of have been accurately calculated with the Green's
function Monte Carlo method using realistic models of two- and three-nucleon
interactions. The splitting of the isospin and
isospin , multiplets is also studied. The observed
energies and radii are generally well reproduced, however, some definite
differences between theory and experiment can be identified.Comment: 12 pages, 1 figur
Masses of the 70- Baryons in Large Nc QCD
The masses of the negative parity 70-plet baryons are analyzed in large N_c
QCD to order 1/N_c and to first order in SU(3) symmetry breaking. The existing
experimental data are well reproduced and twenty new observables are predicted.
The leading order SU(6) spin-flavor symmetry breaking is small and, as it
occurs in the quark model, the subleading in 1/N_c hyperfine interaction is the
dominant source of the breaking. It is found that the Lambda(1405) and
Lambda(1520) are well described as three-quark states and spin-orbit partners.
New relations between splittings in different SU(3) multiplets are found.Comment: 11 pages; references were added and a couple of improvements to the
text were mad
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