Quantum heat engines are expected to outperform the classical counterparts due to quantum coherences involved. Here we experimentally execute a single-ion quantum heat engine and demonstrate, for the ...first time, the dynamics and the enhanced performance of the heat engine originating from the Liouvillian exceptional points (LEPs). In addition to the topological effects related to LEPs, we focus on thermodynamic effects, which can be understood by the Landau-Zener-Stückelberg process under decoherence. We witness a positive net work from the quantum heat engine if the heat engine cycle dynamically encircles a LEP. Further investigation reveals that a larger net work is done when the system is operated closer to the LEP. We attribute the enhanced performance of the quantum heat engine to the Landau-Zener-Stückelberg process, enabled by the eigenenergy landscape in the vicinity of the LEP, and the exceptional point-induced topological transition. Therefore, our results open new possibilities toward LEP-enabled control of quantum heat engines and of thermodynamic processes in open quantum systems.
Most of the pile-supported protection structures were designed by empirical and static analyses to resist ship impact loading. Limited studies were carried out to reveal the failure modes and the ...dynamic interaction process of the pile-supported structures subjected to ship collisions. To clarify these issues, high-resolution finite element models of the ship–structure–soil interactions are developed in this paper. Several modeling issues (e.g., material model, artificial boundary and stress initialization) are discussed herein to ensure the rationality of the numerical models. Numerical simulations indicate that the platform and the connection of the protective system should be carefully designed to prevent their brittle failure besides providing the piles with enough ductility. Four interaction phases (i.e., initial contact, loading with approximate velocities, unloading and free vibration) are clearly identified for the overall flexural failure of the pile-supported structures. To efficiently predict the collision-induced responses, an analytical model with two-degree-of-freedom is proposed based on the high-resolution simulation observations. Methods of determining the equivalent mass and the force–deformation relationship involved in the analytical model are discussed in detail. The dynamic responses obtained from the analytical model are compared with the high-resolution FE results. It is found that the proposed simplified model is reasonable and efficient.
•We develop the detailed finite element models of the ship–structure–soil interactions.•Two failure modes of the protections are shown.•Four interaction phases of ship–protection collisions are identified.•The analytical model with 2-DOF is proposed to efficiently evaluate the performance of the protections.•The analytical results are in good agreement with those of the detailed finite element analyses.
Patients with severe chronic obstructive pulmonary disease (COPD) are at higher risk of developing invasive pulmonary aspergillosis (IPA). However, there are limited data for this disease. To ...evaluate risk factors and the clinical characteristics of IPA in COPD patients, we conducted a hospital-based, retrospective case-control study of 30 COPD patients with IPA and 60 COPD control patients without IPA. Patients in the case group were significantly more likely to have concurrent co-morbidities than controls. Of the IPA patients, 65.4% had worsening radiological findings vs. 11.4% in the control group (p <0.001). IPA in COPD was associated with a higher proportion of mechanical ventilation (43.3% vs. 5%; p <0.001), a longer hospital stay duration (45.8 ± 39.1 days vs. 18.4 ± 11.8 days; p <0.001), and higher mortality (43.3% vs. 11.4%; p <0.001). Systemic use of steroids in the stable phase, treatment with three or more antibiotics during hospitalization and antibiotic treatment longer than 10 days were independent risk factors associated with IPA. COPD patients with obvious dyspnoea, antibiotic-resistant lower respiratory tract infection and repeated detection of Aspergillus in sputum should be considered for the possibility of IPA.
Animal, protist and viral messenger RNAs (mRNAs) are most prominently modified at the beginning by methylation of cap‐adjacent nucleotides at the 2′‐O‐position of the ribose (cOMe) by dedicated cap ...methyltransferases (CMTrs). If the first nucleotide of an mRNA is an adenosine, PCIF1 can methylate at the N6‐position (m6A), while internally the Mettl3/14 writer complex can methylate. These modifications are introduced co‐transcriptionally to affect many aspects of gene expression including localisation to synapses and local translation. Of particular interest, transcription start sites of many genes are heterogeneous leading to sequence diversity at the beginning of mRNAs, which together with cOMe and m6Am could constitute an extensive novel layer of gene expression control. Given the role of cOMe and m6A in local gene expression at synapses and higher brain functions including learning and memory, such code could be implemented at the transcriptional level for lasting memories through local gene expression at synapses.
Variable methylation of cap‐adjacent nucleotides is abundant in animal, protist and viral messenger RNAs (mRNAs). Its combination with sequence variation from heterogenous transcription start sites can generate vast diversity in mRNAs instructing differential gene expression according to the mRNA cap code.
Friction stir processing was applied to a magnesium alloy to generate various grain sizes with the same intense basal texture. Subsequent tensile deformation along two orthogonal directions by easy ...activation or inhibition of basal slip follows the Hall–Petch relationship between yield stress and grain size in both directions. The Hall–Petch parameters are texture dependent. Easy activation of basal slip introduces lower values, while inhibition of basal slip leads to higher values. The Hall–Petch parameters are interpreted by texture and microstructural factors.
Cold rolled AZ31 magnesium alloy sheet was subjected to friction stir processing to generate four average grain sizes ranging from 0.8 to 9.6μm. The processed material exhibited a strong basal fiber ...texture with the c-axis tilted about 35–55° towards the processing direction. The grain size and texture dependence of mechanical behavior were evaluated by using tensile testing along two orthogonal directions. Remarkably high ductility of ∼65% was achieved in relatively coarse grained material that fractured without developing necking when tested in the processing direction. The ductility decreased significantly to ∼10% for ultrafine grained material as the tensile yield strength increased from ∼53MPa to ∼180MPa. Grain size had limited influence on ductility of processed material tested in transverse direction, but reduced the uniform elongation to ∼2% for ultrafine grained material which exhibited ∼320MPa yield strength. Accompanying the significant anisotropy in tensile strength in two directions, the deformation of processed AZ31 in the processing direction was mainly accommodated through basal slip and extension twinning (except for ultrafine grained material); however, the deformation of material in transverse direction was dominated by non-basal slip. Influences of grain size and texture on mechanical behavior were studied in terms of work-hardening and deformation mechanisms.
Although entanglement is considered as an essential resource for quantum information processing, whether entanglement helps for energy conversion or output in the quantum regime is still lack of ...experimental witness. Here, we report on an energy-conversion device operating as a quantum engine with the working medium acted by two entangled ions confined in a harmonic potential. The two ions are entangled by virtually coupling to one of the vibrational modes shared by the two ions, and the quantum engine couples to a quantum load, which is another shared vibrational mode. We explore the energy conversion efficiency of the quantum engine and investigate the useful energy (i.e., the maximum extractable work) stored in the quantum load by tuning the two ions in different degrees of entanglement as well as detecting the change of the phonons in the load. Our observation provides, for the first time, quantitative evidence that entanglement fuels the useful energy produced by the quantum engine, but not helpful for the energy conversion efficiency. We consider that our results may be useful to the study of quantum batteries for which one of the most indexes is the maximum extractable energy.
For a cracked solid under mixed Mode-I/II loading, the present investigation shows that six energy-based driving forces act respectively on the six subintervals around a crack tip, which controls the ...underlying fracture configurations, including complex crack branching. Using the geometrical modelling that describes multiple cracks initiation from a crack tip and a mixity parameter φn, subinterval division for crack tip boundary to maximized the energy release rate has been proposed. This is an efficient way to reveal theoretically energy-based driving forces acting on the local boundaries around a crack tip, and to show that the number of the subintervals is no greater than six. Three windows are suggested, within which the crack multiple-branching is more likely to be triggered. Compact tension shear (CTS) specimens made from general-purpose Polystyrenes (GPPS) under mixed Mode-I/II loading for a given φn are considered to investigate fracture behaviors. The typical experimental findings are consistent with some typical fracture behaviors predicted by the present modelling. The current theoretical and experimental investigations could be helpful to refresh the understanding of crack branching under quasi-static or dynamic mixed Mode-I/II loading.
Integrated high-resolution maps of carbon stocks and biodiversity that identify areas of potential co-benefits for climate change mitigation and biodiversity conservation can help facilitate the ...implementation of global climate and biodiversity commitments at local levels. However, the multi-dimensional nature of biodiversity presents a major challenge for understanding, mapping and communicating where and how biodiversity benefits coincide with climate benefits. A new integrated approach to biodiversity is therefore needed. Here, we (a) present a new high-resolution map of global above- and below-ground carbon stored in biomass and soil, (b) quantify biodiversity values using two complementary indices (BIp and BIr) representing proactive and reactive approaches to conservation, and (c) examine patterns of carbon-biodiversity overlap by identifying 'hotspots' (20% highest values for both aspects). Our indices integrate local diversity and ecosystem intactness, as well as regional ecosystem intactness across the broader area supporting a similar natural assemblage of species to the location of interest. The western Amazon Basin, Central Africa and Southeast Asia capture the last strongholds of highest local biodiversity and ecosystem intactness worldwide, while the last refuges for unique biological communities whose habitats have been greatly reduced are mostly found in the tropical Andes and central Sundaland. There is 38 and 5% overlap in carbon and biodiversity hotspots, for proactive and reactive conservation, respectively. Alarmingly, only around 12 and 21% of these proactive and reactive hotspot areas, respectively, are formally protected. This highlights that a coupled approach is urgently needed to help achieve both climate and biodiversity global targets. This would involve (1) restoring and conserving unprotected, degraded ecosystems, particularly in the Neotropics and Indomalaya, and (2) retaining the remaining strongholds of intactness. This article is part of the theme issue 'Climate change and ecosystems: threats, opportunities and solutions'.
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