Polymerization of ethylene oxide using yttrium isopropoxide

Well defined poly(ethylene oxide)s were prepared using yttrium isopropoxide as an initiator. End group analysis using 1H- and 13C NMR spectroscopy revealed that only polymers with isopropyl ether and hydroxyl end groups were produced. The molecular weight is controlled by the initial amount of initiator added and low polydispersity polymer (Mw/Mn ≈ 1.1) was isolated. Sequential polymerization indicated the suitability of this initiator for macromolecular engineering

On the effective plate thickness of monolayer graphene from flexural wave propagation

We utilize classical molecular dynamics to study flexural, or transverse wave propagation in monolayer graphene sheets and compare the resulting dispersion relationships to those expected from continuum thin plate theory. In doing so, we determine that regardless of the chirality for monolayer graphene, transverse waves exhibit a dispersion relationship that corresponds to the lowest order antisymmetric (A0) mode of wave propagation in a thin plate with plate thickness of h = 0.104 nm. Finally, we find that the achievable wave speeds in monolayer graphene are found to exceed those reported previously for single walled carbon nanotubes, while the frequency of wave propagation in the graphene monolayer is found to reach the terahertz range, similar to that of carbon nanotubes.open9

20 K superconductivity in heavily electron doped surface layer of FeSe bulk crystal

A superconducting transition temperature Tc as high as 100 K was recently discovered in 1 monolayer (1ML) FeSe grown on SrTiO3 (STO). The discovery immediately ignited efforts to identify the mechanism for the dramatically enhanced Tc from its bulk value of 7 K. Currently, there are two main views on the origin of the enhanced Tc; in the first view, the enhancement comes from an interfacial effect while in the other it is from excess electrons with strong correlation strength. The issue is controversial and there are evidences that support each view. Finding the origin of the Tc enhancement could be the key to achieving even higher Tc and to identifying the microscopic mechanism for the superconductivity in iron-based materials. Here, we report the observation of 20 K superconductivity in the electron doped surface layer of FeSe. The electronic state of the surface layer possesses all the key spectroscopic aspects of the 1ML FeSe on STO. Without any interface effect, the surface layer state is found to have a moderate Tc of 20 K with a smaller gap opening of 4 meV. Our results clearly show that excess electrons with strong correlation strength alone cannot induce the maximum Tc, which in turn strongly suggests need for an interfacial effect to reach the enhanced Tc found in 1ML FeSe/STO.Comment: 5 pages, 4 figure

Muon-Spin-Rotation Measurements of the Penetration Depth in the Infinite-Layer Electron-Doped Cuprate Superconductor Sr0.9La0.1CuO2

Muon spin rotation (mSR) measurements of the in-plane penetration depth lambda_ab have been performed in the electron-doped infinite layer high-Tc superconductor (HTS) Sr0.9La0.1CuO2. Absence of the magnetic rare-earth ions in this compound allowed to measure for the first time the absolute value of lambda_ab(0) in electron-doped HTS using mSR. We found lambda_ab(0)=116(2) nm. The zero-temperature depolarization rate sigma(0)?1/lambda_ab(0)^2=4.6(1) MHz is more than four times higher than expected from the Uemura line. Therefore this electron-doped HTS does not follow the Uemura relation found for hole-doped HTS.Comment: to be published in Physical Review Letter

Climate change mitigation strategies for mechanically controlled repositories: The case of The National Archives, Kew

A computer based building simulation model was developed to examine the energy load and environmental management in The National Archives Q1 repository building in Kew, UK to optimise environmental management and examine the impacts of climate change. The need to accurately simulate the hygrothermal environment inside the archive building which houses mainly paper-based records led to the choice of EnergyPlus as the modelling software. The study presents the simulation results of five environmental strategies which predict energy saving potential as high as 43% without significantly affecting the quality of the preservation environment. The effect of climate change is predicted to have little impact on the archive environment due to the filtering effect of the air conditioning system. On the other hand, an increase in total energy load by 15% and 24% is predicted under the worst case climate change scenario in 2050 and 2080, respectively, if the current environmental management practice is continued into the future. However, the identified energy saving strategies could represent possible mitigative solutions in reducing future energy load against the impact of climate change

Assessment of Climate Events in Changma Season (Korean Monsoon) for Production Trend of Sorghum-Sudangrass Hybrid (\u3ci\u3eSorghum bicolor\u3c/i\u3e L.) in the Central Inland Regions of Korea Using Time Series Analysis

This study aimed to assess the impact of climate events in the Changma (Korean Monsoon) season on the production trend of sorghum-sudangrass hybrid (SSH) in central inland regions using time series analysis. The dataset in Suwon from 1988–2013 (n = 388) was generated by merging SSH data and climate data. The accumulated temperature (SHAT, ℃), rainfall amount (SHRA, mm) and sunshine duration (SHSD, hr) from seeding to harvesting were used to assess their impact on the trend of dry matter yield (DMY, kg/ha) for SSH. Furthermore, heavy rainfall (HRF) and typhoons (TPH) were considered as climate events. As a result, the impact of climate events did not affect DMY, even though the frequency and intensity of HRF increased. Conversely, SHAT and SHRA had positive and negative effects on the trend of DMY, respectively. Therefore, the DMY trend of SSH was forecasted to increase until 2045, unlike maize, which has shown a declining trend. The forecasted DMY in 2045 was 14,926 kg/ha. It is likely that the damage by heavy rainfall and typhoons was reduced due to multiple-harvesting and a deeper extension of the root system. Therefore, in an environment that is rapidly changing due to climate change and abnormal weather, such as the Changma season, the cultivation of SSH would be advantageous as it would ensure a stable and robust yield