| 1. |
- Josefsson, Martin, et al.
(författare)
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A quantum-dot heat engine operating close to the thermodynamic efficiency limits
- 2018
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Ingår i: Nature Nanotechnology. - : Springer Science and Business Media LLC. - 1748-3387 .- 1748-3395. ; 13:10, s. 920-924
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Tidskriftsartikel (refereegranskat)abstract
- Cyclical heat engines are a paradigm of classical thermodynamics, but are impractical for miniaturization because they rely on moving parts. A more recent concept is particle-exchange (PE) heat engines, which uses energy filtering to control a thermally driven particle flow between two heat reservoirs1,2. As they do not require moving parts and can be realized in solid-state materials, they are suitable for low-power applications and miniaturization. It was predicted that PE engines could reach the same thermodynamically ideal efficiency limits as those accessible to cyclical engines3–6, but this prediction has not been verified experimentally. Here, we demonstrate a PE heat engine based on a quantum dot (QD) embedded into a semiconductor nanowire. We directly measure the engine’s steady-state electric power output and combine it with the calculated electronic heat flow to determine the electronic efficiency η. We find that at the maximum power conditions, η is in agreement with the Curzon–Ahlborn efficiency6–9 and that the overall maximum η is in excess of 70% of the Carnot efficiency while maintaining a finite power output. Our results demonstrate that thermoelectric power conversion can, in principle, be achieved close to the thermodynamic limits, with direct relevance for future hot-carrier photovoltaics10, on-chip coolers or energy harvesters for quantum technologies.
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| 2. |
- Josefsson, Martin, et al.
(författare)
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Double quantum-dot engine fueled by entanglement between electron spins
- 2020
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Ingår i: Physical Review B. - 2469-9950. ; 101:8
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Tidskriftsartikel (refereegranskat)abstract
- The laws of thermodynamics allow work extraction from a single heat bath provided that the entropy decrease of the bath is compensated for by another part of the system. We propose a thermodynamic quantum engine that exploits this principle and consists of two electrons on a double quantum dot (QD). The engine is fueled by providing it with singlet spin states, where the electron spins on different QDs are maximally entangled, and its operation involves only changing the tunnel coupling between the QDs. Work can be extracted since the entropy of an entangled singlet is lower than that of a thermal (mixed) state, although they look identical when measuring on a single QD. We show that the engine is an optimal thermodynamic engine in the long-time limit. In addition, we include a microscopic description of the bath and analyze the engine's finite-time performance using experimentally relevant parameters.
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| 3. |
- Josefsson, Martin, et al.
(författare)
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Optimal power and efficiency of single quantum dot heat engines : Theory and experiment
- 2019
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Ingår i: Physical Review B. - 2469-9950. ; 99:23
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Tidskriftsartikel (refereegranskat)abstract
- Quantum dots (QDs) can serve as near perfect energy filters and are therefore of significant interest for the study of thermoelectric energy conversion close to thermodynamic efficiency limits. Indeed, recent experiments in [Nat. Nano. 13, 920 (2018)1748-338710.1038/s41565-018-0200-5] realized a QD heat engine with performance near these limits and in excellent agreement with theoretical predictions. However, these experiments also highlighted a need for more theory to help guide and understand the practical optimization of QD heat engines, in particular regarding the role of tunnel couplings on the performance at maximum power and efficiency for QDs that couple seemingly weakly to electronic reservoirs. Furthermore, these experiments also highlighted the critical role of the external load when optimizing the performance of a QD heat engine in practice. To provide further insight into the operation of these engines we use the Anderson impurity model together with a Master equation approach to perform power and efficiency calculations up to co-tunneling order. This is combined with additional thermoelectric experiments on a QD embedded in a nanowire where the power is measured using two methods. We use the measurements to present an experimental procedure for efficiently finding the external load RP which should be connected to the engine to optimize power output. Our theoretical estimates of RP show good agreement with the experimental results, and we show that second order tunneling processes and nonlinear effects have little impact close to maximum power, allowing us to derive a simple analytic expression for RP. In contrast, we find that the electron contribution to the thermoelectric efficiency is significantly reduced by second order tunneling processes, even for rather weak tunnel couplings.
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| 4. |
- Josefsson, Martin
(författare)
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Studies on the enantioselective disposition of amlodipine : A challenge in bioanalysis
- 1996
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- To study the disposition of the enantiomers of the calcium channel blocker amlodipine in human plasma, an enantioselective high performance liquid chromatographic (HPLC) assay was developed. Several HPLC techniques such as chiral ion-pair forming, chiral derivatisation and direct separation on chiral columns were evaluated. A robust assay withhigh sensitivity for amlodipine's enantiomers, suitable for large scale analysis of plasma samples, was established by combining enantiomeric separation on Chiral-AGP i.e., an alfa1 acid glycoprotein material, with achiral HPLC using electrochemical detection, in a coupledcolumn system. The enantiomeric separation on the AGP material was evaluated andoptimised by performing chemometric i.e., multivariate analysis. Enantioselective pharmacokinetics, in healthy human subjects, after a single oral dose of amlodipine (Norvasc®) was shown. The pharmacologically active (S)-enantiomer was found in higher plasma concentrations than the (R)-enantiomer in all subjects, but the individual SIR ratios ranged from about 50:50 to 70:30. Comparable inter-individual differences in amlodipine concentration SIR ratio was found in patients during long-term treatment with Norvasc®. However, the changes over time, in the individual subjects, were low and were not significantly influenced if the dose was increased. A difference in systemic blood clearance of the two enantiomers is the most likely cause of the observed difference in pharmacokinetic behavior. At present, however, it cannot be discerned whether this is caused by differences in protein-binding or in intrinsic clearance of the unbound drug. Administration together with grapefruit juice was found to increase the amlodipine plasma concentrations in healthy volunteers without markedly change the plasma concentration SIR ratio. A nonstereoselective inhibition of the first-pass metabolism is proposed. Even though the effects seen were small the clinical significance of this food/drug interaction cannot be totally neglected since there are considerable differences seen between individuals.
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| 5. |
- Majidi, Danial, et al.
(författare)
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Quantum Confinement Suppressing Electronic Heat Flow below the Wiedemann–Franz Law
- 2022
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 22:2, s. 630-635
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Tidskriftsartikel (refereegranskat)abstract
- The Wiedemann–Franz law states that the charge conductance and the electronic contribution to the heat conductance are proportional. This sets stringent constraints on efficiency bounds for thermoelectric applications, which seek a large charge conduction in response to a small heat flow. We present experiments based on a quantum dot formed inside a semiconducting InAs nanowire transistor, in which the heat conduction can be tuned significantly below the Wiedemann–Franz prediction. Comparison with scattering theory shows that this is caused by quantum confinement and the resulting energy-selective transport properties of the quantum dot. Our results open up perspectives for tailoring independently the heat and electrical conduction properties in semiconductor nanostructures.
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| 6. |
- Svilans, Artis, et al.
(författare)
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Thermoelectric Characterization of the Kondo Resonance in Nanowire Quantum Dots
- 2018
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Ingår i: Physical Review Letters. - 0031-9007. ; 121:20
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Tidskriftsartikel (refereegranskat)abstract
- We experimentally verify hitherto untested theoretical predictions about the thermoelectric properties of Kondo correlated quantum dots (QDs). The specific conditions required for this study are obtained by using QDs epitaxially grown in nanowires, combined with a recently developed method for controlling and measuring temperature differences at the nanoscale. This makes it possible to obtain data of very high quality both below and above the Kondo temperature, and allows a quantitative comparison with theoretical predictions. Specifically, we verify that Kondo correlations can induce a polarity change of the thermoelectric current, which can be reversed either by increasing the temperature or by applying a magnetic field.
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| 7. |
- Wolgast, Emelie, et al.
(författare)
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Drug use in pregnant women-a pilot study of the coherence between reported use of drugs and presence of drugs in plasma
- 2018
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Ingår i: European Journal of Clinical Pharmacology. - : Springer. - 0031-6970 .- 1432-1041. ; 74:4, s. 535-539
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Tidskriftsartikel (refereegranskat)abstract
- In Sweden, information on drug use during pregnancy is obtained through an interview and recorded in a standardized medical record at every visit to the antenatal care clinic throughout the pregnancy. Antenatal, delivery, and neonatal records constitute the basis for the Swedish Medical Birth Register (MBR). The purpose of this exploratory study was to investigate the reliability of reported drug use by simultaneous screening for drug substances in the blood stream of the pregnant woman and thereby validate self-reported data in the MBR. Plasma samples from 200 women were obtained at gestational weeks 10-12 and 25 and screened for drugs by using ultra-high performance liquid chromatography with time of flight mass spectrometry (UHPLC-TOF-MS). The results from the analysis were then compared to medical records. At the first sampling occasion, the drugs found by screening had been reported by 86% of the women and on the second sampling, 85.5%. Missed reported information was clearly associated with drugs for occasional use. The most common drugs in plasma taken in early and mid-pregnancy were meclizine and paracetamol. Two types of continuously used drugs, selective serotonin reuptake inhibitors and propranolol, were used. All women using them reported it and the drug screening revealed a 100% coherence. This study shows good coherence between reported drug intake and the drugs found in plasma samples, which in turn positively validates the MBR.
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| 8. |
- Ahlin, Kjell, et al.
(författare)
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Simulation of forced response in linear and nonlinear mechanical systems using digital filters
- 2006
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Konferensbidrag (refereegranskat)abstract
- There exist many methods to calculate forced response in mechanical systems. Some methods are slow and the errors introduced are unknown. The paper presents a method that uses digital filters and modal superposition. It is shown how aliasing can be avoided as well as phase errors. The parameters describing the mechanical system are residues and poles, taken from FEA models, from lumped MCK systems, from analytic solutions or from experimental modal analysis. Modal damping may be used. The error in the calculation is derived and is shown to be only a function of the sampling frequency used. When the method is applied to linear mechanical systems in MATLAB it is very fast. The method is extended to incorporate nonlinear components. The nonlinear components could be simple, like hardening or stiffening springs, but may also contain memory, like dampers with hysteresis. The simulations are used to generate test data for development and evaluation of methods for identification of non-linear systems.
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| 9. |
- Anand, Aseem, et al.
(författare)
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Automated Bone Scan Index as a quantitative imaging biomarker in metastatic castration-resistant prostate cancer patients being treated with enzalutamide
- 2016
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Ingår i: EJNMMI Research. - : Springer. - 2191-219X. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Having performed analytical validation studies, we are now assessing the clinical utility of the upgraded automated Bone Scan Index (BSI) in metastatic castration-resistant prostate cancer (mCRPC). In the present study, we retrospectively evaluated the discriminatory strength of the automated BSI in predicting overall survival (OS) in mCRPC patients being treated with enzalutamide.METHODS: Retrospectively, we included patients who received enzalutamide as a clinically approved therapy for mCRPC and had undergone bone scan prior to starting therapy. Automated BSI, prostate-specific antigen (PSA), hemoglobin (HgB), and alkaline phosphatase (ALP) were obtained at baseline. Change in automated BSI and PSA were obtained from patients who have had bone scan at week 12 of treatment follow-up. Automated BSI was obtained using the analytically validated EXINI Bone(BSI) version 2. Kendall's tau (τ) was used to assess the correlation of BSI with other blood-based biomarkers. Concordance index (C-index) was used to evaluate the discriminating strength of automated BSI in predicting OS.RESULTS: Eighty mCRPC patients with baseline bone scans were included in the study. There was a weak correlation of automated BSI with PSA (τ = 0.30), with HgB (τ = -0.17), and with ALP (τ = 0.56). At baseline, the automated BSI was observed to be predictive of OS (C-index 0.72, standard error (SE) 0.03). Adding automated BSI to the blood-based model significantly improved the C-index from 0.67 to 0.72, p = 0.017. Treatment follow-up bone scans were available from 62 patients. Both change in BSI and percent change in PSA were predictive of OS. However, the combined predictive model of percent PSA change and change in automated BSI (C-index 0.77) was significantly higher than that of percent PSA change alone (C-index 0.73), p = 0.041.CONCLUSIONS: The upgraded and analytically validated automated BSI was found to be a strong predictor of OS in mCRPC patients. Additionally, the change in automated BSI demonstrated an additive clinical value to the change in PSA in mCRPC patients being treated with enzalutamide.
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| 10. |
- Carlsson, Andreas, et al.
(författare)
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Prediction of designer drugs: synthesis and spectroscopic analysis of synthetic cannabinoid analogues of 1H-indol-3-yl(2,2,3,3-tetramethylcyclopropyl) methanone and 1H-indol-3-yl(adamantan-1-yl)methanone
- 2016
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Ingår i: Drug Testing and Analysis. - : WILEY-BLACKWELL. - 1942-7603 .- 1942-7611. ; 8:10, s. 1015-1029
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Tidskriftsartikel (refereegranskat)abstract
- In this work, emergence patterns of synthetic cannabinoids were utilized in an attempt to predict those that may appear on the drug market in the future. Based on this information, two base structures of the synthetic cannabinoid analogues - (1H-indol-3-yl (2,2,3,3-tetramethylcyclopropyl) methanone and 1H-indol-3-yl(adamantan-1-yl)methanone) - together with three substituents butyl, 4-fluorobutyl and ethyl tetrahydropyran - were selected for synthesis. This resulted in a total of six synthetic cannabinoid analogues that to the authors knowledge have not yet appeared on the drug market. Spectroscopic data, including nuclearmagnetic resonance (NMR), mass spectrometry (MS), and Fourier transforminfrared (FTIR) spectroscopy (solid and gas phase), are presented for the synthesized analogues and some additional related cannabinoids. In this context, the suitability of the employed techniques for the identification of unknowns is discussed and the use of GC-FTIR as a secondary complementary technique to GC-MS is addressed. Examples of compounds that are difficult to differentiate by their mass spectra, but can be distinguished based upon their gas phase FTIR spectra are presented. Conversely, structural homologueswhere mass spectra aremore powerful than gas phase FTIR spectra for unambiguous assignments are also exemplified. This work further emphasizes that a combination of several techniques is the key to success in structural elucidations. Copyright (C) 2015 John Wiley amp; Sons, Ltd.
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