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The efficiency of halide perovskite solar cells has progressed rapidly through a series of major breakthroughs. Currently, a certified efficiency of 25.2% has been achieved for a solar cell using a polycrystalline thin film. This is the result of having reached 75% of the Shockley–Queisser limit for single-junction solar cells. However, for further improvements, new breakthrough technologies are required. This article reviews the impact of previous breakthrough technologies on the efficiency of halide perovskite solar cells, based on certified efficiencies. We clarify the current status of halide perovskite solar cells and introduce photon recycling as the next technological innovation for higher efficiencies. Photon recycling keeps the photon concentration inside the light-harvesting layer high, and consequently, leads to open-circuit voltages close to the theoretical value. Although photon recycling has not yet been implemented in real halide perovskite solar cells, three key technologies for implementing it are examined.
To secure the reliability of flexible electronics, the effect of multicomponent stress on the device properties during complex mechanical deformation needs to be thoroughly understood. The electrical resistances of metal interconnects are investigated by in situ monitoring at different twisting angles and with different pattern positions. As the twisting angle increased, the electrical resistance increased earlier. Furthermore, in the line pattern located far from the central axis, severe electrical degradation and fatigue damage formation were observed. Multicomponent stress evolution during twisting was analyzed by the finite-element simulation method. For easy practical application for estimating the representative twisting strain, an analytic solution of twisting deformation was formulated and compared with the simulation. Using the equivalent strain, the fatigue lifetime was fitted, and the exponents were obtained for lifetime expectation. This systematic study provides the guidelines for highly reliable flexible devices and the tools for determining the expected fatigue lifetime.
We trace Sn nanoparticles (NPs) produced from SnO2 nanotubes (NTs) during lithiation initialized by high energy e-beam irradiation. The growth dynamics of Sn NPs is visualized in liquid electrolytes by graphene liquid cell transmission electron microscopy. The observation reveals that Sn NPs grow on the surface of SnO2 NTs via coalescence and the final shape of agglomerated NPs is governed by surface energy of the Sn NPs and the interfacial energy between Sn NPs and SnO2 NTs. Our result will likely benefit more rational material design of the ideal interface for facile ion insertion.
Technologies for detecting and analyzing a single molecule help us understand and engineer numerous phenomena observed in nature. Carbon nanotubes (CNTs) are highly efficient molecular conduits due to their atomically smooth surface. Because of their small diameters, comparable to the size of a single molecule, even a single blocking molecule can obstruct CNT fluidic channels. Analyzing these pore-blocking events in CNTs therefore enables single-molecule studies. The high-aspect ratios of CNT channels, which extend the time scale of transport, allow for studying molecular transport that is too fast to record in other systems. Both theoretical studies and ensemble experimental measurements have verified the enhanced flow of various ions and molecular species in CNTs. Experimental measurements of a single-CNT fluidic channel, however, have only recently begun, demonstrating the detection of individual DNA, polymer, and alkali-metal ions. This article reviews recent advances in single-nanotube fluidic channels with a focus on experimental measurements.
The Sewol ferry disaster is one of the most tragic events in Korea’s modern history. Among the 476 people on board, which included Danwon High School students (324) and teachers (14), 304 passengers died in the disaster (295 recovered corpses and 9 missing) and 172 survived. Of the rescued survivors, 72 were attending Danwon High School, located in Ansan City, and residing in a residence nearby. Because the students were young, emotionally susceptible adolescents, both the government and the parents requested the students be grouped together at a single hospital capable of appropriate psychiatric care. Korea University Ansan Hospital was the logical choice, as the only third-tier university-grade hospital with the necessary faculty and facilities within the residential area of the families of the students. We report the experiences and the lessons learned from the processes of preparing for and managing the surviving young students as a community-based hospital. (Disaster Med Public Health Preparedness. 2017;11:389–393)
Decreased hemoglobin levels increase the risk of developing dementia among the elderly. However, the underlying mechanisms that link decreased hemoglobin levels to incident dementia still remain unclear, possibly due to the fact that few studies have reported on the relationship between low hemoglobin levels and neuroimaging markers. We, therefore, investigated the relationships between decreased hemoglobin levels, cerebral small-vessel disease (CSVD), and cortical atrophy in cognitively healthy women and men.
Cognitively normal women (n = 1,022) and men (n = 1,018) who underwent medical check-ups and magnetic resonance imaging (MRI) were enrolled at a health promotion center. We measured hemoglobin levels, white matter hyperintensities (WMH) scales, lacunes, and microbleeds. Cortical thickness was automatically measured using surface based methods. Multivariate regression analyses were performed after controlling for possible confounders.
Decreased hemoglobin levels were not associated with the presence of WMH, lacunes, or microbleeds in women and men. Among women, decreased hemoglobin levels were associated with decreased cortical thickness in the frontal (Estimates, 95% confidence interval, −0.007, (−0.013, −0.001)), temporal (−0.010, (−0.018, −0.002)), parietal (−0.009, (−0.015, −0.003)), and occipital regions (−0.011, (−0.019, −0.003)). Among men, however, no associations were observed between hemoglobin levels and cortical thickness.
Our findings suggested that decreased hemoglobin levels affected cortical atrophy, but not increased CSVD, among women, although the association is modest. Given the paucity of modifiable risk factors for age-related cognitive decline, our results have important public health implications.
The Ultra-Fast Flash Observatory (UFFO), which will be launched onboard the
Lomonosov spacecraft, contains two crucial instruments: UFFO Burst
Alert & Trigger Telescope (UBAT) for detection and localization of Gamma-Ray Bursts
(GRBs) and the fast-response Slewing Mirror Telescope (SMT) designed for the observation
of the prompt optical/UV counterparts. Here we discuss the in-space calibrations of the
UBAT detector and SMT telescope. After the launch, the observations of the standard X-ray
sources such as pulsar in Crab nebula will provide data for necessary calibrations of
UBAT. Several standard stars will be used for the photometric calibration of SMT. The
celestial X-ray sources, e.g. X-ray binaries with bright optical sources
in their close angular vicinity will serve for the cross-calibration of UBAT and SMT.
The Ultra-Fast Flash Observatory (UFFO) Pathfinder for Gamma-Ray Bursts (GRBs) consists
of two telescopes. The UFFO Burst Alert & Trigger Telescope (UBAT) handles the
detection and localization of GRBs, and the Slewing Mirror Telescope (SMT) conducts the
measurement of the UV/optical afterglow. UBAT is equipped with an X-ray detector, analog
and digital signal readout electronics that detects X-rays from GRBs and determines the
location. SMT is equipped with a stepping motor and the associated electronics to rotate
the slewing mirror targeting the GRBs identified by UBAT. First the slewing mirror points
to a GRB, then SMT obtains the optical image of the GRB using the intensified CCD and its
readout electronics. The UFFO Data Acquisition system (UDAQ) is responsible for the
overall function and operation of the observatory and the communication with the satellite
main processor. In this paper we present the design and implementation of the electronics
of UBAT and SMT as well as the architecture and implementation of UDAQ.
The UFFO (Ultra-Fast Flash Observatory) is a GRB detector on board the Lomonosov
satellite, to be launched in 2013. The GRB trigger is provided by an X-ray detector,
called UBAT (UFFO Burst Alarm & Trigger Telescope), which detects X-rays from the GRB
and then triggers to determine the direction of the GRB and then alerts the Slewing Mirror
Telescope (SMT) to turn in the direction of the GRB and record the optical photon fluxes.
This report details the calibration of the two components: the MAPMTs and the YSO crystals
and simulations of the UBAT. The results shows that this design can observe a GRB within a
field of view of ±35° and can trigger in a time scale as short as 0.2 – 1.0 s
after the appearance of a GRB X-ray spike.
The Ultra-Fast Flash Observatory (UFFO) is a space observatory for optical follow-ups of
gamma ray bursts (GRBs), aiming to explore the first 60 seconds of GRBs optical emission.
UFFO is utilized to catch early optical emissions from GRBs within few sec after trigger
using a Gimbal mirror which redirects the optical path rather than slewing entire
spacecraft. We have developed a 15 cm two-axis Gimbal mirror stage for the UFFO-Pathfinder
which is going to be on board the Lomonosov satellite which is to be launched in 2013. The
stage is designed for fast and accurate motion with given budgets of 3 kg of mass and 3
Watt of power. By employing stepping motors, the slewing mirror can rotate faster than 15
deg/sec so that objects in the UFFO coverage (60 deg × 60 deg) can be targeted in
~1 sec. The obtained targeting resolution is better 2 arcmin using a close-loop
control with high precision rotary encoder. In this presentation, we will discuss details
of design, manufacturing, space qualification tests, as well as performance tests.
Using immunostaining methodology, we traced the axonal projection of FMRFamide (Phe-Met-Arg-Phe-NH2)-like immunoreactive (LI) medial neurosecretory cells (MNCs) and lateral neurosecretory cells (LNCs) from the brain into the ventral nerve cord (VNC) and retrocerebral complex in Bombyx mori (L.) (Lepidoptera: Bombycidae). Of the seven pairs of FMRFamide-LI MNCs, one pair extended its axons from the brain pars intercerebralis into the VNC ipsilateral connective where they appeared to terminate. The axons of the remaining MNCs ran through decussation in the brain median region and contralateral nervi corporis cardiaci (NCC) I out of the brain, and eventually innervated the contralateral corpus cardiacum (CC). Axons from the single pair of FMRFamide-LI LNCs projected into the ipsilateral NCC II fused with NCC I without decussation in the brain, and finally terminated in the CC. These results suggest that transport of the FMRFamide-like neuropeptide from may be related to the modulation of functions such as gut contraction in MNCs terminating in the VNC, and regulation of production and/or secretion of specific hormones such as juvenile hormone in MNCs and LNCs terminating in the CC.
Boron-doped, single (∼54 nm) or double (∼21 + 54 nm) Si1−xGex layers were epitaxially grown on 300-mm-diameter p−-Si(100) device wafers with 20 nm technology node design features, by ultrahigh vacuum chemical vapor deposition. The Si1−xGex/Si wafers were annealed in the temperature range of 950–1050 °C for 60 s to investigate the effect of annealing on possible changes of Ge content and Si stress near the Si1−xGex/Si interface. High spectral resolution, micro-Raman spectroscopy was used as a nondestructive characterization technique with five excitation wavelengths of 363.8, 441.6, 457.9, 488.0, and 514.5 nm. Ge diffusion and generation of compressive stress at the Si1−xGex/Si interface were measured on all annealed wafers. Ge diffusion and the accumulation of compressive Si stress after annealing showed significantly different behaviors between single- and double-layer Si1−xGex/Si wafers. Raman characterization results were compared with secondary ion mass spectroscopy and high-resolution x-ray diffraction results.
To investigate the annual rate of tuberculosis (TB) infection among newly employed nurses using both tuberculin skin test (TST) and QuantiFERON-TB Gold (QFT-G; Cellestis Limited) assay.
A prospective cohort study involving newly employed nurses.
A tertiary care university hospital in South Korea.
All participants (n = 196) were tested with the TST and QFT-G assay at baseline. After 1 year, the TST and QFT-G assay were reperformed for subjects who had negative TST results at baseline and for all subjects, respectively.
The baseline TST and QFT-G assays were positive for 101 subjects (51.5%) and 28 subjects (14.3%), respectively; 22 subjects (11.2%) had positive results of both tests. Although the overall between-test agreement was 54.9% (κ = 0.151 [95% confidence interval, 0.047–0.245]), agreement improved to 78.5% (κ = 0.462 [95% confidence interval, 0.007–0.917]) for subjects who had not received bacille Calmette-Guérin vaccination. After 1 year, the TST yielded positive results for 16 (21.3%) of 75 nurses with negative baseline results, and the QFT-G assay yielded positive results for 21 (14.4%) of 146 subjects with negative baseline Results. Collectively, 5 subjects (3.0%) experienced conversion to positive results with both tests, and 32 subjects (18.9%) experienced conversion to positive results with one of the tests. Neither the employing hospital department nor exposure to patients with TB affected test conversion status.
The poor overall agreement between TST and QFT-G results may have been caused by the confounding effect of bacille Calmette-Guérin vaccination. The annual risk of TB infection among newly employed nurses was at least 3% on the basis of results of both the TST and QFT-G test. Stricter preventive strategies against TB spread should be implemented in our hospital.