Effect of High-Temperature Annealing on Ion-Implanted Silicon Solar Cells

P-type and n-type wafers were implanted with phosphorus and boron, respectively, for emitter formation and were annealed subsequently at 950∼1050∘C for 30∼90 min for activation. Boron emitters were activated at 1000∘C or higher, while phosphorus emitters were activated at 950∘C. QSSPC measurements show that the implied Voc of boron emitters increases about 15 mV and the J01 decreases by deep junction annealing even after the activation due to the reduced recombination in the emitter. However, for phosphorus emitters the implied Voc decreases from 622 mV to 560 mV and the J01 increases with deep junction annealing. This is due to the abrupt decrease in the bulk lifetime of the p-type wafer itself from 178 μs to 14 μs. PC1D simulation based on these results shows that, for p-type implanted solar cells, increasing the annealing temperature and time abruptly decreases the efficiency (Δηabs=−1.3%), while, for n-type implanted solar cells, deep junction annealing increases the efficiency and Voc, especially (Δηabs=+0.4%) for backside emitter solar cells

Cerebellar White Matter Abnormalities in Charcot–Marie–Tooth Disease: A Combined Volumetry and Diffusion Tensor Imaging Analysis

Charcot–Marie–Tooth disease (CMT) is a genetically heterogeneous hereditary peripheral neuropathy. Brain volumetry and diffusion tensor imaging (DTI) were performed in 47 controls and 47 CMT patients with PMP22 duplication (n = 10), MFN2 (n = 15), GJB1 (n = 11), or NEFL mutations (n = 11) to investigate for structural changes in the cerebellum. Volume of cerebellar white matter (WM) was significantly reduced in CMT patients with NEFL mutations. Abnormal DTI findings were observed in the superior, middle, and inferior cerebellar peduncles, predominantly in NEFL mutations and partly in GJB1 mutations. Cerebellar ataxia was more prevalent in the NEFL mutation group (72.7%) than the GJB1 mutation group (9.1%) but was not observed in other genotypic subtypes, which indicates that structural cerebellar abnormalities were associated with the presence of cerebellar ataxia. However, NEFL and GJB1 mutations did not affect cerebellar gray matter (GM), and neither cerebellar GM nor WM abnormalities were observed in the PMP22 duplication or MFN2 mutation groups. We found structural evidence of cerebellar WM abnormalities in CMT patients with NEFL and GJB1 mutations and an association between cerebellar WM involvement and cerebellar ataxia in these genetic subtypes, especially in the NEFL subgroup. Therefore, we suggest that neuroimaging, such as MRI volumetry or DTI, for CMT patients could play an important role in detecting abnormalities of cerebellar WM

Comparative analysis of environmental standards to install a rooftop temperature monitoring station

Abstract Urban climate influences economic activities and the health and safety of urban residents. Therefore, monitoring temperature in urban areas is important. However, owing to the lack of space for an appropriate observation site, an automatic weather station (AWS) was installed on a building rooftop. The rooftop installation can indicate temperature differences depending on the intensity of strong solar radiation and radiant heat of the building, and wind speed. Therefore, in this study, we aimed to provide observation standards for measuring rooftop temperature according to the optimal rooftop material and observation height. Specifically, an AWS was installed on the rooftop of the Gochang Standard Weather Station (GSWO), Jeollabuk-do Province, to observe the urban climate in South Korea and establish suitable weather standards. Different temperatures, optimum surface materials, and optimum heights for measuring the temperature at the rooftop of GSWO were investigated and compared over 1 year. The temperature recorded after installing a palm mat on the rooftop was more similar to that observed in the grassland. Furthermore, the installation height of the temperature sensor of 2.5–3.0 m for the palm mat and 3.5–4.0 m for concrete was found to be the optimal height for observing temperature at the rooftop

Association of Zolpidem With Increased Mortality in Patients With Brain Cancer: A Retrospective Cohort Study Based on the National Health Insurance Service Database

Background and Purpose Zolpidem is one of the most common hypnotics prescribed to treat insomnia worldwide. However, there are numerous reports of a positive association between zolpidem and mortality, including an association with increased cancer-specific mortality found in a Taiwanese cohort study. This study aimed to determine the association between zolpidem use and brain-cancer-specific mortality in patients with brain cancer. Methods This population-based, retrospective cohort study analyzed data in the National Health Insurance Service database. All incident cases of brain cancer at an age of =18 years at the time of brain cancer diagnosis over a 15-year period (2003-2017) were included. A multivariate Cox regression analysis after adjustment for covariables was performed to evaluate the associations of zolpidem exposure with brain-cancer-specific and all-cause mortality. Results This study identified 38,037 incident cases of brain cancer, among whom 11,823 (31.1%) patients were exposed to zolpidem. In the multivariate Cox regression model, the brain-cancer-specific mortality rate was significantly higher in patients who were prescribed zolpidem than in those with no zolpidem prescription (adjusted hazard ratio [HR]=1.14, 95% confidence interval [CI]=1.08-1.21, p<0.001). Zolpidem exposure was significantly associated with increased brain-cancer-specific mortality after adjustment in younger adults (age 1864 years; adjusted HR=1.37, 95% CI=1.27-1.49) but not in older adults (age =65 years; adjusted HR=0.94, 95% CI=0.86-1.02). Conclusions Zolpidem exposure was significantly associated with increased brain-cancerspecific mortality in patients with brain cancer aged 18-64 years. Further prospective studies are warranted to understand the mechanism underlying the effect of zolpidem on mortality in patients with brain cancer.Y

Ti3C2Tx MXene as a growth template for amorphous RuOx in carbon nanofiber-based flexible electrodes for enhanced pseudocapacitive energy storage

Abstract A noble surface engineering method was developed to create a binder-free flexible electrode comprising Ti3C2T x MXene/carbon nanofibers (MCNFs) covered by amorphous RuO x with a combined electrospinning and hydrothermal process. Utilizing the hydrophilicity of the MXene on/in the MCNFs, RuO x was easily coated on the surfaces of the MCNFs through oxygen-mediated chemical bonding between the functional groups of the MXene and Ru ions. A structural analysis revealed that the MXene acted as a growth template for RuO x and that the formed RuOx had an amorphous and disordered state in the composite electrode, which impacted the electrochemical performance. The electrochemical tests showed that these composite electrodes improved the electrochemical performance, with a two-fold increase in the gravimetric capacitance (279.4 F/g at 2 mV/s) relative to that of pristine MCNFs, a wide potential window (from 0.7 to 1 V) providing a superior energy density of 8.5 Wh/kg at a power density of 85.8 W/kg, as well as long-term cycling stability (99% after 10,000 cycles). The synergetic effect of the RuO x and MXene in the composite electrodes was attributed to an enhanced pseudocapacitive reaction. Our novel electrodes and fabrication method confirm the great potential of CNF-based composites for the development of high-performance binder-free electrodes for supercapacitors

Direct conversion of coordination compounds into Ni2P nanoparticles entrapped in 3D mesoporous graphene for an efficient hydrogen evolution reaction

This paper reports a simple preparation route to a composite of small Ni2P nanoparticles (NPs) entrapped in 3D mesoporous graphene by the thermal conversion of a coordination compound followed by phosphidation. Recently, transition metal phosphides (TMPs) have gained increasing attention owing to their promising potential as non-precious metal catalysts in the hydrogen evolution reaction (HER). In order to enhance the catalytic activity of TMPs, researchers have sought to synthesize small TMP NPs to increase the catalytically active surface area. Although surfactant-mediated syntheses can produce small TMP NPs, a cumbersome surfactant removal step is necessary to generate catalytically active clean surfaces. Interfacing TMP NPs with carbon nanomaterials is another promising approach to boost the catalytic performance by providing high electrical conductivity and durability. However, the synthesis of composites of TMP NPs and carbon demands multiple synthetic steps, including the preparation of TMP NPs, synthesis of carbon nanomaterials, and dispersion of TMP NPs onto the carbon support. The essence of our approach toward the 3D graphene encapsulating Ni2P NPs (Ni2P@mesoG) lies in the utilization of the conversion phenomenon of [Ni2(EDTA)] (EDTA = ethylenediaminetetraacetate). The thermolysis of [Ni2(EDTA)] at 600 ??C produces a composite of single-crystalline 5 nm-sized Ni NPs individually entrapped in 3D mesoG (Ni@mesoG), and the following phosphidation completely converts the Ni NPs to single-crystalline Ni2P NPs in mesoG (Ni2P@mesoG) without agglomeration. This solvent-free thermal conversion route to the Ni2P@mesoG composite is simple and scalable. Notably, graphitic shell layers in Ni2P@mesoG stabilize small Ni2P NPs possessing a large active surface area, and facilitate the electron transfer due to the intimate contact between them. Consequently, the use of Ni2P@mosoG exhibits superior electrocatalytic HER activity and durability in both strong acidic and basic media.clos

Simultaneous Observations of H2O and SiO Masers toward OH/IR Stars

Abstract We performed simultaneous observations of SiO v?=?1, 2, 29SiO v?=?0, J?=?1–0, and H2O maser lines toward 252 OH/IR stars using the individual 21 m telescopes of the Korean VLBI Network (KVN). The observations for studying SiO and H2O maser properties associated with the different evolutionary stages of OH/IR stars were carried out from 2011 November to 2012 July. Both H2O and SiO masers were detected from 50 sources with a detection rate of 20% in one epoch of observation. One-sided SiO maser emissions without H2O were detected from 108 sources and H2O maser emission was detected from 11 sources, of which the detection rates were 43% and 4%, respectively. The overall detection rate of the SiO maser was 63%, and that of the H2O maser was 24%. There were 65 new detections in the SiO maser lines, 22 new detections in the H2O maser line, and 4 new detections in the 29SiO maser line. For the H2O and/or SiO maser- detected sources, mutual relations between SiO and H2O maser properties (including peak and integrated antenna temperatures, and full widths at zero power, etc.) are investigated based on a statistical analysis. We also investigate these maser properties on an IRAS two-color diagram related to stellar evolutionary sequences. In particular, a large number of SiO v?=?2-only detected sources appear among the SiO-only detected sources compared to those of both H2O and SiO maser detected sources and also appear in the later evolutionary stages of asymptotic giant branch AGB stars in the IRAS two-color diagram. These results may be associated with the development of a hot and thick dust envelope at later stages of AGB evolution and the different excitation conditions of SiO v?=?1 and v?=?2 masers. Our observational results will be useful for statistical studies of circumstellar envelopes of OH/IR stars related to their late evolution and future very long baseline interferometry (VLBI) observations

Geosynchronous Relativistic Electron Events Associated with High-Speed Solar Wind Streams in 2006

Recurrent enhancements of relativistic electron events at geosynchronous orbit (GREEs) were observed in 2006. These GREE enhancements were associated with high-speed solar wind streams coming from the same coronal hole. For the first six months of 2006, the occurrence of GREEs has 27 day periodicity and the GREEs were enhanced with various flux levels. Several factors have been studied to be related to GREEs: (1) High speed stream, (2) Pc5 ULF wave activity, (3) Southward IMF Bz, (4) substorm occurrence, (5) Whistler mode chorus wave, and (6) Dynamic pressure. In this paper, we have examined the effectiveness about those parameters in selected periods