411 research outputs found
A technique for breaking ice in the path of a ship
A technique is described for breaking ice in the path of a ship. A laser is placed on the bow of the ship with apparatus to scan the ice in the path of the ship with the laser beam. The beam cuts or shatters the ice, enabling the ship to break the ice in its path
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Impacts devalue the potential of large-scale terrestrial CO2 removal through biomass plantations
Large-scale biomass plantations (BPs) are often considered a feasible and safe climate engineering proposal for extracting carbon from the atmosphere and, thereby, reducing global mean temperatures. However, the capacity of such terrestrial carbon dioxide removal (tCDR) strategies and their larger Earth system impacts remain to be comprehensively studiedâeven more so under higher carbon emissions and progressing climate change. Here, we use a spatially explicit process-based biosphere model to systematically quantify the potentials and trade-offs of a range of BP scenarios dedicated to tCDR, representing different assumptions about which areas are convertible. Based on a moderate CO2 concentration pathway resulting in a global mean warming of 2.5 °C above preindustrial level by the end of this centuryâsimilar to the Representative Concentration Pathway (RCP) 4.5âwe assume tCDR to be implemented when a warming of 1.5 °C is reached in year 2038. Our results show that BPs can slow down the progression of increasing cumulative carbon in the atmosphere only sufficiently if emissions are reduced simultaneously like in the underlying RCP4.5 trajectory. The potential of tCDR to balance additional, unabated emissions leading towards a business-as-usual pathway alike RCP8.5 is therefore very limited. Furthermore, in the required large-scale applications, these plantations would induce significant trade-offs with food production and biodiversity and exert impacts on forest extent, biogeochemical cycles and biogeophysical properties
The limits to global-warming mitigation by terrestrial carbon removal
This is the final version of the article. Available from Wiley via the DOI in this record.Massive near-term greenhouse gas emissions reduction is a precondition for staying âwell below 2°Câ global warming as envisaged by the Paris Agreement. Furthermore, extensive terrestrial carbon dioxide removal (tCDR) through managed biomass growth and subsequent carbon capture and storage is required to avoid temperature âovershootâ in most pertinent scenarios. Here, we address two major issues: First, we calculate the extent of tCDR required to ârepairâ delayed or insufficient emissions reduction policies unable to prevent global mean temperature rise of 2.5°C or even 4.5°C above pre-industrial level. Our results show that those tCDR measures are unable to counteract âbusiness-as-usualâ emissions without eliminating virtually all natural ecosystems. Even if considerable (Representative Concentration Pathway 4.5 [RCP4.5]) emissions reductions are assumed, tCDR with 50% storage efficiency requires > 1.1 Gha of the most productive agricultural areas or the elimination of > 50% of natural forests. In addition, > 100 MtN/yr fertilizers would be needed to remove the roughly 320 GtC foreseen in these scenarios. Such interventions would severely compromise food production and/or biosphere functioning. Second, we reanalyze the requirements for achieving the 160â190 GtC tCDR that would complement strong mitigation action (RCP2.6) in order to avoid 2°C overshoot anytime. We find that a combination of high irrigation water input and/or more efficient conversion to stored carbon is necessary. In the face of severe trade-offs with society and the biosphere, we conclude that large-scale tCDR is not a viable alternative to aggressive emissions reduction. However, we argue that tCDR might serve as a valuable âsupporting actorâ for strong mitigation if sustainable schemes are established immediately.This study was funded by the German Research Foundation's priority program DFG SPP 1689 on âClimate Engineering â Risks, Challenges and Opportunities?â and specifically the CE-LAND project. T.M.L. was supported by a Royal Society Wolfson Research Merit Award
Vibrational Photoacoustic Microscopy for Depth-resolved Bond-selective Imaging of Tissues and Organisms
We realize vibrational photoacoustic microscopy (VPA) using molecular excitation of overtone vibration and acoustic detection of the resultant pressure transients. We demonstrate 3-D VPA imaging of lipid-rich atherosclerotic plaques and lipid bodies in living Drosophila larvae by exciting 2nd overtone of the CH bond stretch around 8300 cm^(â1). Depth-resolved spectral analysis and a penetration depth of several mm are available
Quantifying Capacity Loss due to Solid-Electrolyte-Interphase Layer Formation on Silicon Negative Electrodes in Lithium-ion Batteries
Charge lost per unit surface area of a silicon electrode due to the formation
of solid-electrolyte-interphase (SEI) layer during initial lithiation was
quantified, and the species that constitute this layer were identified. Coin
cells made with Si thin-film electrodes were subjected to a combination of
galvanostatic and potentiostatic lithiation and delithiation cycles to
accurately measure the capacity lost to SEI-layer formation. While the planar
geometry of amorphous thin films allows accurate calculation of surface area,
creation of additional surface by cracking was prevented by minimizing the
thickness of the Si film. The cycled electrodes were analyzed with X-ray
photoelectron spectroscopy to characterize the composition of the SEI layer.
The charge lost due to SEI formation measured from coin cell experiments was
found to be in good agreement with the first-cycle capacity loss during the
initial lithiation of a Si (100) crystal with planar geometry. The methodology
presented in this work is expected to provide a useful practical tool for
battery-material developers in estimating the expected capacity loss due to
first cycle SEI-layer formation and in choosing an appropriate particle size
distribution that balances mechanical integrity and the first cycle capacity
loss in large volume expansion electrodes for lithium-ion batteries.Comment: 15 pages, 9 figures; Journal of Power Sources, 201
Label-Free Bond-Selective Imaging by Listening to Vibrationally Excited Molecules
We report the realization of vibrational photoacoustic (VPA) microscopy using optical excitation of molecular overtone vibration and acoustic detection of the resultant pressure transients. Our approach eliminates the tissue scattering problem encountered in near-infrared spectroscopy and enables depth-resolved signal collection. The 2nd overtone of the CH bond stretch around 8300ââcm^(â1), where blood interference is minimal, is excited. We demonstrate 3D VPA imaging of lipid-rich atherosclerotic plaques by excitation from the artery lumen, and lipid storage in live Drosophila larvae, with millimeter-scale penetration depth
FAST CARS: Engineering a Laser Spectroscopic Technique for Rapid Identification of Bacterial Spores
Airborne contaminants, e.g., bacterial spores, are usually analyzed by time
consuming microscopic, chemical and biological assays. Current research into
real time laser spectroscopic detectors of such contaminants is based on e.g.
resonant Raman spectroscopy. The present approach derives from recent
experiments in which atoms and molecules are prepared by one (or more) coherent
laser(s) and probed by another set of lasers. The connection with previous
studies based on "Coherent Anti-Stokes Raman Spectroscopy" (CARS) is to be
noted. However generating and utilizing maximally coherent oscillation in
macromolecules having an enormous number of degrees of freedom is much more
challenging. This extension of the CARS technique is called FAST CARS
(Femtosecond Adaptive Spectroscopic Techniques for Coherent Anti-Stokes Raman
Spectroscopy), and the present paper proposes and analyses ways in which it
could be used to rapidly identify pre-selected molecules in real time.Comment: 43 pages, 21 figures; replacement with references added. Submitted to
the Proceedings of National Academy of Science
The origin of paramagnetic magnetization in field-cooled YBa2Cu3O7 films
Temperature dependences of the magnetic moment have been measured in
YBa_2Cu_3O_{7-\delta} thin films over a wide magnetic field range (5 <= H <=
10^4 Oe). In these films a paramagnetic signal known as the paramagnetic
Meissner effect has been observed. The experimental data in the films, which
have strong pinning and high critical current densities (J_c ~ 2 \times 10^6
A/cm^2 at 77 K), are quantitatively shown to be highly consistent with the
theoretical model proposed by Koshelev and Larkin [Phys. Rev. B 52, 13559
(1995)]. This finding indicates that the origin of the paramagnetic effect is
ultimately associated with nucleation and inhomogeneous spatial redistribution
of magnetic vortices in a sample which is cooled down in a magnetic field. It
is also shown that the distribution of vortices is extremely sensitive to the
interplay of film properties and the real experimental conditions of the
measurements.Comment: RevTex, 8 figure
Detailed investigation of the superconducting transition of niobium disks exhibiting the paramagnetic Meissner effect
The superconducting transition region in a Nb disk showing the paramagnetic
Meissner effect (PME) has been investigated in detail. From the field-cooled
magnetization behavior, two well-defined temperatures can be associated with
the appearance of the PME: T_1 (< T_c) indicates the characteristic temperature
where the paramagnetic moment first appears and a lower temperature T_p (< T_1)
defines the temperature where the positive moment no longer increases. During
the subsequent warming, the paramagnetic moment begins to decrease at T_p and
then vanishes at T_1 with the magnitude of the magnetization change between
these two temperatures being nearly the same as that during cooling. This
indicates that the nature of the PME is reversible and not associated with flux
motion. Furthermore, the appearance of this paramagnetic moment is even
observable in fields as large as 0.2 T even though the magnetization does not
remain positive to the lowest temperatures. Magnetic hysteresis loops in the
temperature range between T_1 and T_p also exhibit a distinct shape that is
different from the archetypal shape of a bulk type-II superconductor. These
behaviors are discussed in terms of the so-called 'giant vortex state'.Comment: Total 4 printed pages, 4 Figure
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