The enhancement of thermoelectric performance should be a compromise of electrical as well as thermal transports with reasonably little reduction of thermopower. In this study, the effects of ...co-doping by rare earth Pr and alkaline earth Sr on perovskite Ca0.92-xPr0.08SrxMnO3 (x = 0, 0.01, 0.02, 0.03, 0.04) bulk materials are evaluated in terms of the phase composition, microstructure, grain combination, electrical transport as well as the thermal transport properties. The results show that perovskite type phases are reserved for the doped bulk materials. The bulk Material porosity can be decreased obviously and better grain interconnection is formed by introducing co-doping. The electrical conductivity is enhanced due to increased carrier concentration and mobility. The carriers for the intrinsic CaMnO3 and the co-doped Ca0.92-xPr0.08SrxMnO3 (x = 0, 0.01, 0.02, 0.03, 0.04) bulk materials follow the adiabatic polaron transport model; the activation energy as well as the band gap are reduced. The total thermal conductivity is further reduced by co-doping of Sr comparing with the Pr single-doped bulk materials. The co-doping is effective for further confining the thermal conduction. The ZT values of the co-doped samples are increased by 12.5%, 18.7%, 25% and 18.7% comparing with the Pr single-doped materials, respectively.
The enhancement of thermoelectric performance should be a compromising of balancing electrical transport as well as the thermal transports with reasonably little reduction of thermopower. In this study, the A site co-doped CaMnO3 bulk materials are evaluated as to the phase composition, microstructure, grain combination, electrical transport as well as the thermal transport properties. The bulk material porosity is decreased obviously. The electrical conductivity is enhanced due to the increased carrier concentration and mobility. The carriers follow the adiabatic polaron transport model. The total thermal conductivity can be further reduced by co-doping. The largest ZT value of the co-doped samples is increased by 25% comparing with the Pr single-doped materials. The co-doping using rare earth element and alkaline earth element is alternatively effective for further improve thermoelectric performance of the titled CaMnO3 bulk materials. Display omitted
•The bulk material porosity is decreased obviously by introducing co-doping.•The electrical conductivity is enhanced due to the increased carrier concentration and mobility.•The carriers for the bulk materials follow the adiabatic polaron transport model.•The ZT of the co-doped materials are increased remarkably comparing with the Pr single-doped materials.
A number of large, rare copy number variants (CNVs) are deleterious for neurodevelopmental disorders, but large, rare, protective CNVs have not been reported for such phenotypes. Here we show in a ...CNV analysis of 47 005 individuals, the largest CNV analysis of schizophrenia to date, that large duplications (1.5-3.0 Mb) at 22q11.2--the reciprocal of the well-known, risk-inducing deletion of this locus--are substantially less common in schizophrenia cases than in the general population (0.014% vs 0.085%, OR=0.17, P=0.00086). 22q11.2 duplications represent the first putative protective mutation for schizophrenia.
Aim To explore the value of using flat detector (FD) equipped angiographic C-arm CT (CACT) systems in treating unresectable renal cell carcinoma (RCC) by selective renal arterial embolisation (RAE) ...followed by radiofrequency ablation (RFA) (RAE-RFA). Materials and methods A total of 28 patients who were not candidates for surgery were enrolled. The average size of tumours was 6.7±2.2 cm (range 4.1–9.6 cm). Twenty-eight tumours were treated with CACT-guided RFA, 5–7 days after CACT-guided RAE. Results CACT-guided RAE-RFA was technically successful in all patients. Tumour enhancement disappeared after a single RAE-RFA session in 20 patients, after two RAE-RFA sessions in four patients and after three RAE-RFA sessions in the other four patients. One patient died of lung metastasis and haematuria 13 months after RAE-RFA, and another patient died of pulmonary heart disease 23 months after repeat RAE-RFA. In the 26 living patients, tumours remained controlled during a mean follow-up period of 27 months and showed significant reduction in tumour size (6.7±2.2 cm to 3.9±1.7 cm, p <0.01). There were no significant changes in creatinine levels or urea nitrogen concentrations before and after the last RAE-RFA ( p >0.05). There were no serious complications during and after the procedure. Conclusion CACT-guided RAE followed by RFA appears to be a safe and effective technique for treating patients with inoperable RCC.
•A new multi-step etching process for pore fabrication was proposed.•The etching process relies on variation of etchant and track annealing.•Various new pore shapes in track etched PET membranes were ...obtained.
A method for the fabrication of different pore shapes in polyethylene terephthalate (PET)-based track etched membranes (TEMs) is reported. A multi-step etching technique involving etchant variation and track annealing was applied to fabricate different pore shapes in PET membranes. PET foils of 12-μm thickness were irradiated with Bi ions (kinetic energy 9.5MeV/u, fluence 106ions/cm2) at the Heavy Ion Research Facility (HIRFL, Lanzhou). The cross-sections of fundamental pore shapes (cylinder, cone, and double cone) were analyzed. Funnel-shaped and pencil-shaped pores were obtained using a two-step etching process. Track annealing was carried out in air at 180°C for 120min. After track annealing, the selectivity of the etching process decreased, which resulted in isotropic etching in subsequent etching steps. Rounded cylinder and rounded cone shapes were obtained by introducing a track-annealing step in the etching process. Cup and spherical funnel-shaped pores were fabricated using a three- and four-step etching process, respectively. The described multi-step etching technique provides a controllable method to fabricate new pore shapes in TEMs. Introduction of a variety of pore shapes may improve the separation properties of TEMs and enrich the series of TEM products.
Monolayer graphene and highly oriented pyrolytic graphite (HOPG) were irradiated by swift heavy ions (209Bi and 112Sn) with the fluence between 1011 and 1014ions/cm2. Both pristine and irradiated ...samples were investigated by Raman spectroscopy. It was found that D and D′ peaks appear after irradiation, which indicated the ion irradiation introduced damage both in the graphene and graphite lattice. Due to the special single atomic layer structure of graphene, the irradiation fluence threshold Φth of the D band of graphene is significantly lower (<1×1011ions/cm2) than that (2.5×1012ions/cm2) of HOPG. The larger defect density in graphene than in HOPG indicates that the monolayer graphene is much easier to be damaged than bulk graphite by swift heavy ions. Moreover, different defect types in graphene and HOPG were detected by the different values of ID/ID′. For the irradiation with the same electronic energy loss, the velocity effect was found in HOPG. However, in this experiment, the velocity effect was not observed in graphene samples irradiated by swift heavy ions.
InP crystals and GaN films were irradiated by swift heavy ions 86Kr and 209Bi with kinetic energies of 25 and 9.5MeV per nucleon and ion fluence in the range 5×1010 to 3.6×1012ions/cm2. The ...characteristic optical bands were studied by Raman spectroscopy to reveal the disorder and defects induced in the samples during the irradiation process. The crystallinity of InP and GaN was found to be deteriorated after irradiation by the swift heavy ions and resulted in the amorphous nature of the samples along the ion tracks. The amorphous tracks observed by transmission electron microscopy (TEM) images confirmed the formation of lattice defects. In typical F2(LO) mode, in case of InP, the spectra shifted towards the lower wavenumbers with a maximum shift of 7.6cm−1 induced by 1030MeV Bi ion irradiation. While in case of GaN, the typical E2(high) mode shifted towards the higher wavenumbers, with maximum shift of 5.4cm−1 induced by 760MeV Bi ion irradiation at ion fluence of 1×1012ions/cm2. The observed Raman shifts reveal the presence of lattice defects and disorder induced in the samples after irradiation by the swift heavy ions. This irradiation also generated lattice stress in the samples, which has been investigated and discussed in detail in this work.
Based on first principles calculations, the basic properties and stability of Cd
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columnar nanowires and Na-doped Cd
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nanowires are studied, along with their electronic properties under ...strain control. The results indicate that the Cd
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nanowires exhibit characteristics of direct gap semiconductors, while the doped nanowires are metallic. It is also shown that both compressive strain and tensile strain increase the band gap of semiconductor nanowires. The effect of compressive strain on the work function of metal nanowires decreases linearly with the increase in strain, and the work function increases proportional to the tensile strain. These results can be expected to have potential applications in optoelectronic devices.
Graphical abstract
High-energy cosmic-ray electrons and positrons (CREs), which lose energy quickly during their propagation, provide a probe of Galactic high-energy processes and may enable the observation of ...phenomena such as dark-matter particle annihilation or decay. The CRE spectrum has been measured directly up to approximately 2 teraelectronvolts in previous balloon- or space-borne experiments, and indirectly up to approximately 5 teraelectronvolts using ground-based Cherenkov γ-ray telescope arrays. Evidence for a spectral break in the teraelectronvolt energy range has been provided by indirect measurements, although the results were qualified by sizeable systematic uncertainties. Here we report a direct measurement of CREs in the energy range 25 gigaelectronvolts to 4.6 teraelectronvolts by the Dark Matter Particle Explorer (DAMPE) with unprecedentedly high energy resolution and low background. The largest part of the spectrum can be well fitted by a 'smoothly broken power-law' model rather than a single power-law model. The direct detection of a spectral break at about 0.9 teraelectronvolts confirms the evidence found by previous indirect measurements, clarifies the behaviour of the CRE spectrum at energies above 1 teraelectronvolt and sheds light on the physical origin of the sub-teraelectronvolt CREs.
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