| 1. |
- Bengtsson, J., et al.
(författare)
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Quantum Szilard Engine with Attractively Interacting Bosons
- 2018
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Ingår i: Physical Review Letters. - 0031-9007. ; 120:10
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Tidskriftsartikel (refereegranskat)abstract
- We show that a quantum Szilard engine containing many bosons with attractive interactions enhances the conversion between information and work. Using an ab initio approach to the full quantum-mechanical many-body problem, we find that the average work output increases significantly for a larger number of bosons. The highest overshoot occurs at a finite temperature, demonstrating how thermal and quantum effects conspire to enhance the conversion between information and work. The predicted effects occur over a broad range of interaction strengths and temperatures.
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| 2. |
- Bosco, L., et al.
(författare)
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Thermoelectrically cooled THz quantum cascade laser operating up to 210 K
- 2019
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 115:1
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Tidskriftsartikel (refereegranskat)abstract
- We present a terahertz quantum cascade laser operating on a thermoelectric cooler up to a record-high temperature of 210.5 K. The active region design is based on only two quantum wells and achieves high temperature operation thanks to a systematic optimization by means of a nonequilibrium Green's function model. Laser spectra were measured with a room temperature detector, making the whole setup cryogenic free. At low temperatures (∼40 K), a maximum output power of 200 mW was measured.
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| 3. |
- Franckié, M., et al.
(författare)
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Two-well quantum cascade laser optimization by non-equilibrium Green's function modelling
- 2018
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 112:2
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Tidskriftsartikel (refereegranskat)abstract
- We present a two-quantum well THz intersubband laser operating up to 192 K. The structure has been optimized using non-equilibrium Green's function model. The result of this optimization was confirmed experimentally by growing, processing, and measuring a number of proposed designs. At high temperature (T > 200 K), the simulations indicate that lasing fails due to a combination of electron-electron scattering, thermal backfilling, and, most importantly, re-absorption coming from broadened states.
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| 4. |
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| 5. |
- Wiedemeier, Daniel B., et al.
(författare)
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Characterization, Quantification and Compound-specific Isotopic Analysis of Pyrogenic Carbon Using Benzene Polycarboxylic Acids (BPCA)
- 2016
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Ingår i: Journal of Visualized Experiments. - : MyJove Corporation. - 1940-087X. ; :111
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Tidskriftsartikel (refereegranskat)abstract
- Fire-derived, pyrogenic carbon (PyC), sometimes called black carbon (BC), is the carbonaceous solid residue of biomass and fossil fuel combustion, such as char and soot. PyC is ubiquitous in the environment due to its long persistence, and its abundance might even increase with the projected increase in global wildfire activity and the continued burning of fossil fuel. PyC is also increasingly produced from the industrial pyrolysis of organic wastes, which yields charred soil amendments (biochar). Moreover, the emergence of nanotechnology may also result in the release of PyC-like compounds to the environment. It is thus a high priority to reliably detect, characterize and quantify these charred materials in order to investigate their environmental properties and to understand their role in the carbon cycle. Here, we present the benzene polycarboxylic acid (BPCA) method, which allows the simultaneous assessment of PyC's characteristics, quantity and isotopic composition (C-13 and C-14) on a molecular level. The method is applicable to a very wide range of environmental sample materials and detects PyC over a broad range of the combustion continuum, i.e., it is sensitive to slightly charred biomass as well as high temperature chars and soot. The BPCA protocol presented here is simple to employ, highly reproducible, as well as easily extendable and modifiable to specific requirements. It thus provides a versatile tool for the investigation of PyC in various disciplines, ranging from archeology and environmental forensics to biochar and carbon cycling research.
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| 6. |
- Gierga, Merle, et al.
(författare)
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Long-stored soil carbon released by prehistoric land use : Evidence from compound-specific radiocarbon analysis on Soppensee lake sediments
- 2016
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 144, s. 123-131
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Tidskriftsartikel (refereegranskat)abstract
- Compound-specific radiocarbon (C-14) analyses allow studying the fate of individual biomarkers in ecosystems. In lakes with small catchments, terrestrial biomarkers have the potential to be used for the dating of sediments that lack the traditionally targeted terrestrial macrofossils, if the specific organic compounds are deposited soon after production. On the other hand, if the biomarkers have been stored for a significant amount of time in the soils of the catchment before transported to the lake, their age can be used to reconstruct changes in average residence time of organic material on land through time. Here we present a study based on compound-specific C-14 analysis of the sedimentary record of Lake Soppensee, Switzerland, targeting long-chain n-alkanes of exclusive terrigenous origin, and comparing them with sediment ages obtained by high-resolution macrofossil dating. Additionally, we measured C-14 ages of bulk organic matter and carbonate samples to assess the hard water effect. Prior to 3100 cal BP n-alkanes had about the same age as the sediment or they were slightly older, indicating that the vast majority of the terrestrial organic carbon transported to the lake had a short residence time on land. In the samples younger than 3100 cal BP an increasing offset is observed, indicating liberation of old buried soil organic matter that must have accumulated over the previous millennia. Our results indicate that as long as stable ecosystem conditions have prevailed, the distribution and isotopic composition of the n-alkanes can be used as environmental proxies in small catchments with limited surface runoff, confirming a few earlier studies.
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| 7. |
- Guettler, D., et al.
(författare)
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Rapid increase in cosmogenic C-14 in AD 775 measured in New Zealand kauri trees indicates short-lived increase in C-14 production spanning both hemispheres
- 2015
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Ingår i: Earth and Planetary Science Letters. - : Elsevier BV. - 1385-013X .- 0012-821X. ; 411, s. 290-297
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Tidskriftsartikel (refereegranskat)abstract
- In 2012, Miyake et al. reported a sudden and strong increase of the atmospheric radiocarbon (C-14) content in Japanese cedar trees of 1.2% between AD 774 and 775. While their findings were quickly confirmed by a German oak chronology for the Northern Hemisphere (NH), the question remained if the effect was seen in both hemispheres. Here we present the first annually resolved Southern Hemisphere (SH) C-14 record spanning the interval AD 760-787, using New Zealand kauri (Agathis australis) chronology wood. An almost identical distinct increase compared to Northern Hemisphere data was observed, suggesting a cosmic event with globally uniform impact as a potential cause for the increase. Deploying a carbon cycle box model a worldwide averaged net C-14 production of 2.2 x 10(8) C-14 atoms cm(-2) was estimated, which is 3.7 times higher than the average annual C-14 production. The immediate appearance of the event in tree rings on both hemispheres suggests a short duration event of significantly less than 1 yr.
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| 8. |
- Hoogendoorn, Martine, et al.
(författare)
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Patient Heterogeneity in Health Economic Decision Models for Chronic Obstructive Pulmonary Disease : Are Current Models Suitable to Evaluate Personalized Medicine?
- 2016
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Ingår i: Value in Health. - : Elsevier BV. - 1098-3015 .- 1524-4733. ; 19:6, s. 800-810
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: To assess how suitable current chronic obstructive pulmonary disease (COPD) cost-effectiveness models are to evaluate personalized treatment options for COPD by exploring the type of heterogeneity included in current models and by validating outcomes for subgroups of patients.METHODS: A consortium of COPD modeling groups completed three tasks. First, they reported all patient characteristics included in the model and provided the level of detail in which the input parameters were specified. Second, groups simulated disease progression, mortality, quality-adjusted life-years (QALYs), and costs for hypothetical subgroups of patients that differed in terms of sex, age, smoking status, and lung function (forced expiratory volume in 1 second [FEV1] % predicted). Finally, model outcomes for exacerbations and mortality for subgroups of patients were validated against published subgroup results of two large COPD trials.RESULTS: Nine COPD modeling groups participated. Most models included sex (seven), age (nine), smoking status (six), and FEV1% predicted (nine), mainly to specify disease progression and mortality. Trial results showed higher exacerbation rates for women (found in one model), higher mortality rates for men (two models), lower mortality for younger patients (four models), and higher exacerbation and mortality rates in patients with severe COPD (four models).CONCLUSIONS: Most currently available COPD cost-effectiveness models are able to evaluate the cost-effectiveness of personalized treatment on the basis of sex, age, smoking, and FEV1% predicted. Treatment in COPD is, however, more likely to be personalized on the basis of clinical parameters. Two models include several clinical patient characteristics and are therefore most suitable to evaluate personalized treatment, although some important clinical parameters are still missing.
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| 9. |
- Pereira, M. F., et al.
(författare)
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Theory and measurements of harmonic generation in semiconductor superlattices with applications in the 100 GHz to 1 THz range
- 2017
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Ingår i: Physical Review B. - 2469-9950. ; 96:4
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Tidskriftsartikel (refereegranskat)abstract
- This manuscript describes harmonic generation in semiconductor superlattices, starting from a nonequilibrium Green's functions input to relaxation rate-type analytical approximations for the Boltzmann equation in which imperfections in the structure lead to asymmetric current flow and scattering processes under forward and reverse bias. The resulting current-voltage curves and the predicted consequences on harmonic generation, notably the development of even harmonics, are in good agreement with experiments. Significant output for frequencies close to 1 THz (7th harmonic) at room temperature, after excitation by a 141-GHz input signal, demonstrate the potential of superlattice devices for gigahertz to terahertz applications.
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| 10. |
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| 11. |
- Sparkes, Robert B., et al.
(författare)
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Macromolecular composition of terrestrial and marine organic matter in sediments across the East Siberian Arctic Shelf
- 2016
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Ingår i: The Cryosphere. - : Copernicus GmbH. - 1994-0416 .- 1994-0424. ; 10:5, s. 2485-2500
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Tidskriftsartikel (refereegranskat)abstract
- Mobilisation of terrestrial organic carbon (terrOC) from permafrost environments in eastern Siberia has the potential to deliver significant amounts of carbon to the Arctic Ocean, via both fluvial and coastal erosion. Eroded terrOC can be degraded during offshore transport or deposited across the wide East Siberian Arctic Shelf (ESAS). Most studies of terrOC on the ESAS have concentrated on solvent-extractable organic matter, but this represents only a small proportion of the total terrOC load. In this study we have used pyrolysis-gas chromatography-mass spectrometry (py-GCMS) to study all major groups of macromolecular components of the terrOC; this is the first time that this technique has been applied to the ESAS. This has shown that there is a strong offshore trend from terrestrial phenols, aromatics and cyclopentenones to marine pyridines. There is good agreement between proportion phenols measured using py-GCMS and independent quantification of lignin phenol concentrations (r(2) = 0.67, p < 0.01, n = 24). Furfurals, thought to represent carbohydrates, show no offshore trend and are likely found in both marine and terrestrial organic matter. We have also collected new radiocarbon data for bulk OC (C-14(OC)) which, when coupled with previous measurements, allows us to produce the most comprehensive C-14(OC) map of the ESAS to date. Combining the C-14(OC) and py-GCMS data suggests that the aromatics group of compounds is likely sourced from old, aged terrOC, in contrast to the phenols group, which is likely sourced from modern woody material. We propose that an index of the relative proportions of phenols and pyridines can be used as a novel terrestrial vs. marine proxy measurement for macromolecular organic matter. Principal component analysis found that various terrestrial vs. marine proxies show different patterns across the ESAS, and it shows that multiple river-ocean transects of surface sediments transition from river-dominated to coastalerosion-dominated to marine-dominated signatures.
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