Coulomb-coupled quantum-dot thermal transistors

A quantum-dot thermal transistor consisting of three Coulomb-coupled quantum dots coupled to respective electronic reservoirs by tunnel contacts is established. The heat flows through the collector and emitter can be controlled by the temperature of the base. It is found that a small change in the base heat flow can induce a large heat flow change in the collector and emitter. The huge amplification factor can be obtained by optimizing the Coulomb interaction between the collector and the emitter or by decreasing the energy-dependent tunneling rate at the base. The proposed quantum-dot thermal transistor may open up potential applications in low-temperature solid-state thermal circuits at the nanoscale.Comment: 14 pages, 6 figure

Casimir effect of an ideal Bose gas trapped in a generic power-law potential

The Casimir effect of an ideal Bose gas trapped in a generic power-law potential and confined between two slabs with Dirichlet, Neumann, and periodic boundary conditions is investigated systematically, based on the grand potential of the ideal Bose gas, the Casimir potential and force are calculated. The scaling function is obtained and discussed. The special cases of free and harmonic potentials are also discussed. It is found that when T<Tc (where Tc is the critical temperature of Bose-Einstein condensation), the Casimir force is a power-law decay function; when T>Tc, the Casimir force is an exponential decay function; and when T>>Tc, the Casimir force vanishes.Comment: 5 pages, 1 figur

Conditional statistical properties of the complex systems having long-range interactions

A new concept of the available force is proposed to investigate the performance of the complex systems having long-range interactions. Since the covariance of average velocity in double time interval and available force equals zero, it is possible to calculate the conditional probability distribution function (CPDF) within the systems. It is found that the asymmetric CPDF of the velocity between two adjacent time intervals can be derived from the symmetrical CPDF between the available force and the double time interval velocity. Two typical currency exchange databases, i.e., EUR/USD and GBP/USD, which collect the minutely opening exchange prices from 1 January 1999 to 31 December 2011, are adopted as examples. It is found that the analytical CPDF needs only six parameters for an arbitrary system. By calculating the CPDF in the currency exchange databases, it is shown that the results are well fitted by our analytical expression. The analytical CPDF can be also used to calculate the conditional expectation and the conditional variance of velocity. Interestingly, the two databases show that the conditional expectation of the velocity between two adjacent time intervals is not monotonic, while the conditional variance tends to monotonic. All of these results are well described by our theory. It is worthwhile to note that the analytical CPDF is a general expression. It is valid not only for current exchange systems but also for any complex systems having long-range interactions and/or long-duration memory.Comment: 21 pages, 4figure

Charge transport and electron-hole asymmetry in low-mobility graphene/hexagonal boron nitride heterostructures

Graphene/hexagonal boron nitride (G/$h$-BN) heterostructures offer an excellent platform for developing nanoelectronic devices and for exploring correlated states in graphene under modulation by a periodic superlattice potential. Here, we report on transport measurements of nearly $0^{\circ}$-twisted G/$h$-BN heterostructures. The heterostructures investigated are prepared by dry transfer and thermally annealing processes and are in the low mobility regime (approximately $3000~\mathrm{cm}^{2}\mathrm{V}^{-1}\mathrm{s}^{-1}$ at 1.9 K). The replica Dirac spectra and Hofstadter butterfly spectra are observed on the hole transport side, but not on the electron transport side, of the heterostructures. We associate the observed electron-hole asymmetry to the presences of a large difference between the opened gaps in the conduction and valence bands and a strong enhancement in the interband contribution to the conductivity on the electron transport side in the low-mobility G/$h$-BN heterostructures. We also show that the gaps opened at the central Dirac point and the hole-branch secondary Dirac point are large, suggesting the presence of strong graphene-substrate interaction and electron-electron interaction in our G/$h$-BN heterostructures. Our results provide additional helpful insight into the transport mechanism in G/$h$-BN heterostructures.Comment: 7 pages, 4 figure

Thermoeconomic performance optimization of an irreversible Brayton refrigeration cycle using Gd, Gd 0.95 Dy 0.05 or Gd 0.95 Er 0.05 as the working substance

Abstract(#br)An irreversible regenerative Brayton refrigerator cycle is established, in which the nonperfect regenerator, regenerative time, heat leak, and irreversible adiabatic processes are taken into account. The mathematical expressions of the refrigeration rate, coefficient of performance, and thermoeconomic function of the refrigeration cycle are derived and the thermoeconomic function is optimized. Moreover, choosing Gd, Gd 0.95 Dy 0.05 and Gd 0.95 Er 0.05 as the working substances respectively, we discussed in detail the influences of the thermoeconomic and thermodynamic parameters on the optimal thermoeconomic and thermodynamic performances. The results show that the thermoeconomic performance of the refrigeration cycle using Gd or Gd 0.95 Dy 0.05 as the working substance is better than that using Gd 0.95 Er 0.05 and the thermoeconomic performance of the refrigeration cycle using Gd 0.95 Dy 0.05 as the working substance is better than that using Gd in the situation with the lower adiabatic magnetization

Serum metabolites and hypercholesterolemia: insights from a two-sample Mendelian randomization study

BackgroundHypercholesterolemia, a critical contributor to cardiovascular disease, is not fully understood in terms of its relationship with serum metabolites and their role in disease pathogenesis.MethodsThis study leveraged GWAS data to explore the relationship between serum metabolites and hypercholesterolemia, pinpointing significant metabolites via Mendelian Randomization (MR) and KEGG pathway enrichment analysis. Data on metabolites were sourced from a European population, with analysis focusing on individuals diagnosed with hypercholesterolemia.ResultsOut of 486 metabolites analyzed, ten showed significant associations with hypercholesterolemia, categorized into those enhancing risk and those with protective effects. Specifically, 2-methoxyacetaminophen sulfate and 1-oleoylglycerol (1-monoolein) were identified as risk-enhancing, with odds ratios (OR) of 1.545 (95% CI: 1.230–1.939; P_FDR = 3E−04) and 1.462 (95% CI: 1.036–2.063; P_FDR = 0.037), respectively. On the protective side, 3-(cystein-S-yl)acetaminophen, hydroquinone sulfate, and 2-hydroxyacetaminophen sulfate demonstrated ORs of 0.793 (95% CI: 0.735–0.856; P_FDR = 6.18E−09), 0.641 (95% CI: 0.423–0.971; P_FDR = 0.042), and 0.607 (95% CI: 0.541–0.681; P_FDR = 5.39E−17), respectively. In addition, KEGG pathway enrichment analysis further revealed eight critical pathways, comprising “biosynthesis of valine, leucine, and isoleucine”, “phenylalanine metabolism”, and “pyruvate metabolism”, emphasizing their significant role in the pathogenesis of hypercholesterolemia.ConclusionThis study underscores the potential causal links between particular serum metabolites and hypercholesterolemia, offering innovative viewpoints on the metabolic basis of the disease. The identified metabolites and pathways offer promising targets for therapeutic intervention and warrant further investigation

Bleeding complications related to external ventricular drainage placement in patients with ruptured intracranial aneurysms: a single-center study

ObjectiveAcute aneurysmal rupture can be treated with endovascular therapy or surgical clipping. For patients with concurrent acute hydrocephalus, the placement of an external ventricular drainage (EVD) is required. This study aims to investigate the impact of pre-treatment EVD placement on rebleeding in ruptured aneurysms and to examine the influence of dual antiplatelet therapy and the sequencing of dual antiplatelet therapy with EVD placement on EVD-related hematomas.MethodsWe reviewed the clinical data of 83 patients with ruptured aneurysms who underwent EVD placement from a total of 606 aneurysm patients consecutively admitted between January 2018 and January 2023. The analysis focused on the impact of pre-treatment EVD placement on aneurysmal rebleeding and the effect of dual antiplatelet therapy and its sequencing with EVD placement on EVD-related hematomas.ResultsAmong the 503 patients with ruptured aneurysms, 83 required EVD placement. EVD was placed before aneurysm treatment in 63 patients and after treatment in 20 patients. The number of aneurysmal rebleeding cases in the pre-treatment EVD group and non-EVD group was 1 (1.6%) and 20 (4.8%), respectively (p = 0.406). 31 patients (37.3%) underwent stent-assisted embolization or flow diversion requiring dual antiplatelet therapy, while 52 patients (62.7%) underwent simple embolization or surgical clipping without antiplatelet therapy. EVD-related hematomas occurred in 14 patients (16.9%), with 10 cases (32.3%) in those receiving dual antiplatelet therapy and 4 cases (7.7%) in those not receiving antiplatelet therapy (p = 0.01). Among 16 patients who had EVD placed before dual antiplatelet therapy, 4 (25%) developed EVD-related hematomas. Of the 15 patients who had EVD placed after dual antiplatelet therapy, 6 (40%) developed EVD-related hematomas (p = 0.458).ConclusionIn patients with aneurysmal subarachnoid hemorrhage (aSAH) and acute hydrocephalus, the placement of EVD before aneurysm treatment does not increase the risk of rebleeding. However, dual antiplatelet therapy increases the risk of EVD-related hematoma, and the sequence of EVD placement relative to dual antiplatelet therapy does not appear to significantly affect the outcome of EVD-related hematoma