The physical mechanisms responsible for the formation of a two-dimensional electron gas at the interface between insulating srTio 3 and LaAlo 3 have remained a contentious subject since its discovery in 2004. opinion is divided between an intrinsic mechanism involving the build-up of an internal electric potential due to the polar discontinuity at the interface between srTio 3 and LaAlo 3 , and extrinsic mechanisms attributed to structural imperfections. Here we show that interface conductivity is also exhibited when the LaAlo 3 layer is diluted with srTio 3 , and that the threshold thickness required to show conductivity scales inversely with the fraction of LaAlo 3 in this solid solution, and thereby also with the layer's formal polarization. These results can be best described in terms of the intrinsic polar-catastrophe model, hence providing the most compelling evidence, to date, in favour of this mechanism.

Biomaterials as bone substitutes are always considered as foreign bodies that can trigger host immune responses. Traditional designing principles have been always aimed at minimizing the immune reactions by fabricating inert biomaterials. However, clinical evidence revealed that those methods still have limitations and many of which were only feasible in the laboratory. Currently, osteoimmunology, the very pioneering concept is drawing more and more attention—it does not simply regard the immune response as an obstacle during bone healing but emphasizes the intimate relationship of the immune and skeletal system, which includes diverse cells, cytokines, and signaling pathways. Properties of biomaterials like topography, wettability, surface charge, the release of cytokines, mediators, ions and other bioactive molecules can impose effects on immune responses to interfere with the skeletal system. Based on the bone formation mechanisms, the designing methods of the biomaterials change from immune evasive to immune reprogramming. Here, we discuss the osteoimmunomodulatory effects of the new modification strategies—adjusting properties of bone biomaterials to induce a favorable osteoimmune environment. Such strategies showed potential to benefit the development of bone materials and lay a solid foundation for the future clinical application.

We investigate the two-dimensional Fermi surface of high-mobility LaAlO 3 / SrTiO 3 interfaces using Shubnikov-de Haas oscillations. Our analysis of the oscillation pattern underscores the key role played by the Rashba spin-orbit interaction brought about by the breaking of inversion symmetry, as well as the dominant contribution of the heavy d xz /d yz orbitals on electrical transport. We furthermore bring into light the complex evolution of the oscillations with the carrier density, which is tuned by the field effect.

Understanding the nature of charge carriers at the LaAlO3/SrTiO3 interface is one of the major open issues in the full comprehension of the charge confinement phenomenon in oxide heterostructures. Here, we investigate thermopower to study the electronic structure in LaAlO3/SrTiO3 at low temperature as a function of gate field. In particular, under large negative gate voltage, corresponding to the strongly depleted charge density regime, thermopower displays high negative values of the order of 104–105μVK−1, oscillating at regular intervals as a function of the gate voltage. The huge thermopower magnitude can be attributed to the phonon-drag contribution, while the oscillations map the progressive depletion and the Fermi level descent across a dense array of localized states lying at the bottom of the Ti 3d conduction band. This study provides direct evidence of a localized Anderson tail in the two-dimensional electron liquid at the LaAlO3/SrTiO3 interface.

Lithiation of the β-diketimines (2,6-C 6 H 3 R 2 )NHdC(Me)CHdC(Me)N(2,6-C 6 H 3 R 2 ) (R = Me (HL 1 ), Et (HL 2 )) by nBuLi was followed by metathesis reaction with LnCl 3 (THF) x and Y(BH 4 ) 3 (THF) 2 to afford the corresponding complexes L 1 LnCl 2 (THF) 2 (Ln = Gd (1), Nd (3), Dy (4), Er (5), Y (6)), L 2 GdCl 2 (THF) 2 (2), and L 1 Y(BH 4 ) 2 (THF) (8), respectively. Treatment of neutral HL 1 with Y(CH 2 SiMe 3 ) 3 (THF) 2 generated the bis(alkyl) complex 7, L 1 Y(CH 2 SiMe 3 ) 2 -(THF). Upon activation with [PhNHMe 2 ][B(C 6 F 5 ) 4 ] and AliBu 3 , complex 6 showed the highest cis-1,4 selectivity (99.3%, T p = 0 °C) toward the polymerization of isoprene, while complex 7 had a comparatively low cis-1,4 selectivity, and in contrast, complex 8 was completely inert. The influences of the ortho substituents of the N-aryl rings of the ligands, the types of central metals and cocatalysts, and addition sequence of the catalyst components had been thoroughly investigated. By means of X-ray diffraction and 1 H NMR spectroscopy analyses, the intermediates arising from the stoichiometric reactions among the catalyst components and the probable active species were elucidated, which facilitates further investigation of the mechanism for diene polymerization.

The role of asymptomatic infections in the transmission of COVID-19 have drawn considerable attention. Here, we performed a meta-analysis to summarize the epidemiological and radiographical characteristics of asymptomatic infections associated with COVID-19. Methods: Data on the epidemiological and radiographical characteristics of asymptomatic infections were extracted from the existing literature. Pooled proportions with 95% confidence intervals were then calculated using a random effects model. Results: A total of 104 studies involving 20,152 cases were included. The proportion of asymptomatic individuals among those with COVID-19 was 13.34% (10.86%-16.29%), among which presymptomatic and covert infections accounted for 7.64% (4.02%-14.04%) and 8.44% (5.12%-13.62%), respectively. The proportions of asymptomatic infections among infected children and healthcare workers were 32.24% (23.08%-42.13%) and 36.96% (18.51%-60.21%), respectively. The proportion of asymptomatic infections was significantly higher after 2020/02/29 than before (33.53% vs 10.19%) and in non-Asian regions than in Asia (28.76% vs 11.54%). The median viral shedding duration of asymptomatic infections was 14.14 days (11.25-17.04). A total of 47.62% (31.13%-72.87%) of asymptomatic infections showed lung abnormalities, especially ground-glass opacity (41.11% 19.7%-85.79%). Conclusions: Asymptomatic infections were more commonly found in infected children and healthcare workers and increased after 2020/02/29 and in non-Asian regions. Chest radiographical imaging could be conducive to the early identification of asymptomatic infections.

We have studied the electronic properties of the 2D electron liquid present at the LaAlO3/SrTiO3 interface in series of samples prepared at different growth temperatures. We observe that interfaces fabricated at 650 °C exhibit the highest low temperature mobility (≈10 000 cm2 V−1 s−1) and the lowest sheet carrier density (≈5×1012 cm−2). These samples show metallic behavior and Shubnikov-de Haas oscillations in their magnetoresistance. Samples grown at higher temperatures (800–900 °C) display carrier densities in the range of ≈2−5×1013 cm−2 and mobilities of ≈1000 cm2 V−1 s−1 at 4 K. Reducing their carrier density by field effect to 8×1012 cm−2 lowers their mobilities to ≈50 cm2 V−1 s−1 bringing the conductance to the weak-localization regime.

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