A compact Fourier-Transform-Imaging-Spectrometer (FTIS) for small satellite remote sensing missions is currently being studied under ESA contract with the objective to demonstrate its feasibility by ...breadboarding. Compared to classical hyperspectral imagers using dispersive spectrometers the major advantages of the FTIS are the very compact optics module and the tolerable higher detector temperature, thus reducing the overall mass and easing the instrument thermal design. The feasibility of this instrument concept, payload requirements to the satellite attitude stability and the data-handling concept will be discussed.
Quantum communication requires the transfer of quantum states, or quantum bits of information (qubits), from one place to another. From a fundamental perspective, this allows the distribution of ...entanglement and the demonstration of quantum non-locality over significant distances. Within the context of applications, quantum cryptography offers a provably secure way to establish a confidential key between distant partners. Photons represent the natural flying qubit carriers for quantum communication, and the presence of telecommunications optical fibres makes the wavelengths of 1,310 nm and 1,550 nm particularly suitable for distribution over long distances. However, qubits encoded into alkaline atoms that absorb and emit at wavelengths around 800 nm have been considered for the storage and processing of quantum information. Hence, future quantum information networks made of telecommunications channels and alkaline memories will require interfaces that enable qubit transfers between these useful wavelengths, while preserving quantum coherence and entanglement. Here we report a demonstration of qubit transfer between photons of wavelength 1,310 nm and 710 nm. The mechanism is a nonlinear up-conversion process, with a success probability of greater than 5 per cent. In the event of a successful qubit transfer, we observe strong two-photon interference between the 710 nm photon and a third photon at 1,550 nm, initially entangled with the 1,310 nm photon, although they never directly interacted. The corresponding fidelity is higher than 98 per cent.
•We studied DOC time series in 89 streams feeding German drinking water reservoirs.•Median DOC is best explained by the catchment topographic wetness index (TWI).•High TWI can be linked to a ...dominance of riparian wetlands in the catchment.•DOC concentration variance highest in cold and wet catchments with high TWI.•Riparian wetlands identified as dominant source zone of DOC.
Elevated concentration and high variance of dissolved organic carbon (DOC) in surface waters are a challenge for the production of drinking water. Past studies have indicated a dominant role of wetlands in DOC mobilization, but have mainly been focused on boreal and oceanic catchments. Here we analyze the observational DOC time series from 89 temperate humid catchments which drain into German drinking water reservoirs. We characterize the DOC concentration median and variability and utilize partial least squares regression in order to quantify the relation to catchment characteristics such as land use, climate, and topography. We found that the long-term median DOC concentration in the catchment is well predicted by the 90th percentile of the distribution of the topographic wetness index (0.9P TWI) over the entire catchment area. The 0.9P TWI can be directly connected to the abundance of riparian wetlands in the catchments. DOC concentration variability (represented as the ratio of the interquartile range and the median concentrations) was also found to be well predictable. Concentration variability was highest in cold and wet catchments with a high 0.9P TWI. Here we also found stronger correlations between DOC concentrations and discharge, with positive concentration-discharge patterns. Catchments with elevated DOC-concentration variance also exhibited the most severe long-term increases in concentrations. Our results thus indicate that, in temperate climates, riparian wetlands can be the dominant source zones of DOC and control the hydrological mobilization and potentially also the spatial difference in long-term concentration trends observed in surface waters. We conclude that the dominance of topography and climatic conditions in controlling spatio-temporal patterns in DOC concentrations leads to very limited management options.
There is an increasing need in many chemical sensing applications ranging from industrial process control to environmental science and medical diagnostics for fast, sensitive, and selective gas ...detection based on laser spectroscopy. The recent availability of novel pulsed and CW quantum cascade distributed feedback (QC-DFB) lasers as mid-infrared spectroscopic sources address this need. A number of spectroscopic techniques have been demonstrated worldwide by several groups. For example, the authors have employed QC-DFB lasers for the monitoring and quantification of several trace gases and isotopic species in ambient air at ppmv and ppbv levels by means of direct absorption, wavelength modulation, and cavity enhanced and cavity ringdown spectroscopy.
Dams are a globally relevant source of greenhouse gases (GHG), which impairs their function as a source of green energy. High burial rates of organic carbon (OC) in dam sediments may partly or fully ...offset the emissions. We argue that only the burial of carbon fixed in the timespan of dam operation changes the GHG balance. Here, we took sediment cores from a temperate dam. We analyzed radiocarbon age and OC molecular composition by laser desorption ionization mass spectrometry in the bulk OC and in four chemical extract fractions. The bulk samples contained modern OC, fixed after 1950. However, the extracted OC was of different ages (modern to 1900 years BP). Fractions with OC measured as old (>960 years BP) accounted for 57% of total sediment OC. Correlations of molecular composition with extract age suggest that these older fractions contained insignificant amounts of modern OC. We conclude that a substantial proportion of buried carbon did not originate from the contemporary atmosphere and cannot be offset against recent GHG emissions.
Plain Language Summary
Dams are an important source of green electricity. However, it has been known for some time that dams can release large amounts of methane, a potent greenhouse gas. This is due to the fact that dams trap suspended sediment from their tributaries, and reducing chemical conditions in sediments favor the formation of methane. Theoretically, greenhouse gas emissions can be offset by the permanent burial of carbon in sediments, if this carbon is thereby removed from the recent atmosphere. Studying a small dam in Germany, we show that at least 60% of the buried organic carbon was removed from the atmosphere by plants in the catchment, centuries before the dam was constructed. The burial of this aged carbon cannot be offset against recent emissions. This equalizes emissions and burial in the greenhouse gas balance and calls into question the potential of reservoirs to act as sinks of greenhouse gases.
Key Points
Organic carbon extract fractions from a reservoir sediment ranged in radiocarbon age from modern to 1,000 years depending on sources
Compounds with H/O ratios >2.5 correlated with old extract fractions, and compounds with ratios <2.5 correlated with modern fractions
No more than 40% of sedimentary OC can be offset with GHG emissions with reasonable certainty
Aquatic bacteria are considered to exhibit a paradoxical behaviour. They luxuriously consume phosphorus, the element often restricting the abundance of algae, which provide the organic substrates ...maintaining bacterial growth. Here, we test the hypothesis that bacteria can limit their uptake of phosphorus and increase the availability of phosphorus to algae. The physiological costs for bacteria must be compensated for by a surplus of photosynthetic exudates facilitating higher biomass production. To test the potential of such an economic behaviour, we used a new differential equation model that was parameterized by independent experiments. Model results indicate that this potential does exist. As a consequence, we conducted continuous growth chemostat experiments. Bacteria did not leave more phosphorus to, "high exudation" algae compared with algae with low release. Therefore, the hypothesis was not supported by the experiments. However, bacteria significantly increased production 1.4-1.8-fold in cultures with "high exudation" algae. This was explained by an increase in conversion of organic carbon from growth medium into bacteria biomass. Algal exudates were quantitatively negligible but could act as growth factors. The results show that biomass of algae and bacteria cannot be predicted solely by mineral nutrients and carbon as assumed by the classical theory.
Uncertainties in dissolved organic carbon load estimation in a small stream Buettner, O., Helmholtz Centre for Environmental Research, Magdeburg (Germany); Tittel, J., Helmholtz Centre for Environmental Research, Magdeburg (Germany)
Journal of Hydrology and Hydromechanics,
03/2013, Letnik:
61, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Dissolved organic carbon (DOC) transported by rivers represents an important link between carbon pools of terrestrial and oceanic ecosystems. However, it is unclear how frequent DOC must be sampled ...to obtain reasonable load estimates. Here, we used continuous records of the specific UV absorption coefficient (SAC) and discharge from a headwater stream at the Ore Mountains (Germany) to calculate load errors depending on DOC sampling frequency. SAC was used as a proxy for DOC. The results show that the load was underestimated by 13–19% with monthly, 10–13% with bi-weekly and 7–9% with weekly DOC samplings, respectively. We conclude that collecting additional data from high discharge events decrease the error significantly.
We investigate theoretically and experimentally a nondestructive interferometric measurement of the state population of an ensemble of laser-cooled and trapped atoms. This study is a step toward ...generation of (pseudo)spin squeezing of cold atoms targeted at the improvement of the cesium clock performance beyond the limit set by the quantum projection noise of atoms. We calculate the phase shift and the quantum noise of a near-resonant optical probe pulse propagating through a cloud of cold {sup 133}Cs atoms. We analyze the figure of merit for a quantum nondemolition (QND) measurement of the collective pseudospin and show that it can be expressed simply as a product of the ensemble optical density and the pulse-integrated rate of the spontaneous emission caused by the off-resonant probe light. Based on this, we propose a protocol for the sequence of operations required to generate and utilize spin squeezing for the improved atomic clock performance via a QND measurement on the probe light. In the experimental part we demonstrate that the interferometric measurement of the atomic population can reach a sensitivity of the order of {radical}(N{sub at}) in a cloud of N{sub at} cold atoms, which is an important benchmark toward the experimental realization of the theoretically analyzed protocol.
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