RESUMO
Metal-organic frameworks (MOFs) have attracted significant attention in the past two decades due to their diverse physical properties and associated functionalities. Although numerous advances have been made, the acoustic properties of MOFs have attracted very little attention. Here, we systematically investigate the acoustic velocities and impedances of 19 prototypical MOFs via first-principle calculations. Our results demonstrate that these MOFs exhibit a wider range of acoustic velocities, higher anisotropy, and lower acoustic impedances than their inorganic counterparts, which are ascribed to their structural diversity and anisotropy, as well as low densities. In addition, the piezoelectric properties, which are intimately related to the acoustic properties, were calculated for 3 MOFs via density functional perturbation theory, which reveals that MOFs can exhibit significant piezoelectricity due to the ionic contribution. Our work provides a comprehensive study of the fundamental acoustic properties of MOFs, which could stimulate further interest in this new exciting field.
RESUMO
The flexible organic amine cations on the interfaces of two-dimensional (2D) hybrid organic-inorganic perovskite nanosheets could form relaxed structures, which would lead to exotic optoelectronic properties but are hard to understand. Here, the unusual interfacial relaxation of nanosheets exfoliated from an orthorhombic 2D lead halide perovskite, [(C6H5CH2NH3)2]PbCl4, is interrogated via ultrafast second-harmonic generation (SHG) spectroscopy. The in-plane SHG intensity anisotropy of these nanosheets is found to decrease with reducing layer thickness. Combined first-principles calculations and Monte Carlo simulations reveal that the induced second-order polarization arises primarily from the (C6H5CH2NH3)+ cations; and these organic amine cations form significantly reorganized conformations with decreasing nanosheet thickness due to weakened van der Waals interactions. Because the orientations of organic components at the interface determine their electric properties and specifically the dipolar susceptibility, the resulting structure leads to striking changes in the SHG properties.
RESUMO
Objective To investigate the risk of overall and site-specific cancers in Chinese patients with type 2 diabetes mellitus (T2DM) in Minhang District of Shanghai.Methods A population-based retrospective cohort study including 51 372 T2DM patients was conducted in Minhang District,Shanghai from 2004 to 2014.All T2DM patients were enrolled from the standardized management system based on local electronic information system of Shanghai.Newly-diagnosed cancer cases were identified by record-linkage with the Shanghai Cancer Registry.Standardized incidence ratios (SIR) and 95％CI were used to estimate the risk of cancers among T2DM patients.Results Overall crude incidence rate (CIR) of cancers was 969.69 per 105 person-years in men and 834.17 per 105 person-years in women.The age-standardized rate (ASR [W]) was 206.72 per 105 person-years in men and 285.80 per 105 person-years in women.Increased risk of cancer was found in both sex,with an SIR of 0.93 (95％CI:0.88-0.98) in men and 1.07 (95％ CI:1.01-1.12) in women.Conclusions Our results indicate that patients with T2DM may have an increased risk of some cancers,and the increase may vary by sub-sites of cancers.
RESUMO
Objective To investigate the risk of overall and site-specific cancers in Chinese patients with type 2 diabetes mellitus (T2DM) in Minhang District of Shanghai.Methods A population-based retrospective cohort study including 51 372 T2DM patients was conducted in Minhang District,Shanghai from 2004 to 2014.All T2DM patients were enrolled from the standardized management system based on local electronic information system of Shanghai.Newly-diagnosed cancer cases were identified by record-linkage with the Shanghai Cancer Registry.Standardized incidence ratios (SIR) and 95％CI were used to estimate the risk of cancers among T2DM patients.Results Overall crude incidence rate (CIR) of cancers was 969.69 per 105 person-years in men and 834.17 per 105 person-years in women.The age-standardized rate (ASR [W]) was 206.72 per 105 person-years in men and 285.80 per 105 person-years in women.Increased risk of cancer was found in both sex,with an SIR of 0.93 (95％CI:0.88-0.98) in men and 1.07 (95％ CI:1.01-1.12) in women.Conclusions Our results indicate that patients with T2DM may have an increased risk of some cancers,and the increase may vary by sub-sites of cancers.
