Jinjoo Park

Enteroendocrine cell counts correlate with visceral hypersensitivity in patients with diarrhoea‐predominant irritable bowel syndrome

Abstract  The objective of this study was to determine whether or not the number of enteroendocrine cells (ECs) in the gut is related to visceral hypersensitivity in patients with diarrhoea‐predominant irritable bowel syndrome (D‐IBS). Twenty‐five subjects with D‐IBS (mean, 43.1 years; 16 women, nine men) were recruited into our study, along with 13 healthy controls (mean, 40.7 years; nine women, four men). Maximally tolerable pressures were evaluated via barostat testing, and the levels of ECs were immunohistochemically identified and quantified via image analysis. The numbers of ECs between the D‐IBS subjects and the controls were not significantly different in the terminal ileum, ascending colon and rectum. However, the maximally tolerable pressures determined in the D‐IBS subjects were significantly lower than those of the control subjects (P < 0.01), and we detected a significant relationship between the maximally tolerable pressures and the numbers of ECs in the rectum (r = −0.37, P < 0.01). Rectal sensitivity was enhanced to a greater degree in D‐IBS patients exhibiting an elevated level of rectal ECs. This study provides some evidence to suggest that ECs play an important role in visceral hypersensitivity.

Triple-Junction Hybrid Tandem Solar Cells with Amorphous Silicon and Polymer-Fullerene Blends

Organic-inorganic hybrid tandem solar cells attract a considerable amount of attention due to their potential for realizing high efficiency photovoltaic devices at a low cost. Here, highly efficient triple-junction (TJ) hybrid tandem solar cells consisting of a double-junction (DJ) amorphous silicon (a-Si) cell and an organic photovoltaic (OPV) rear cell were developed. In order to design the TJ device in a logical manner, a simulation was carried out based on optical absorption and internal quantum efficiency. In the TJ architecture, the high-energy photons were utilized in a more efficient way than in the previously reported a-Si/OPV DJ devices, leading to a significant improvement in the overall efficiency by means of a voltage gain. The interface engineering such as tin-doped In2O3 deposition as an interlayer and its UV-ozone treatment resulted in the further improvement in the performance of the TJ solar cells. As a result, a power conversion efficiency of 7.81% was achieved with an open-circuit voltage of 2.35 V. The wavelength-resolved absorption profile provides deeper insight into the detailed optical response of the TJ hybrid solar cells.

Interface modification effect between p-type a-SiC:H and ZnO:Al in p-i-n amorphous silicon solar cells.

Aluminum-doped zinc oxide (ZnO:Al) [AZO] is a good candidate to be used as a transparent conducting oxide [TCO]. For solar cells having a hydrogenated amorphous silicon carbide [a-SiC:H] or hydrogenated amorphous silicon [a-Si:H] window layer, the use of the AZO as TCO results in a deterioration of fill factor [FF], so fluorine-doped tin oxide (Sn02:F) [FTO] is usually preferred as a TCO. In this study, interface engineering is carried out at the AZO and p-type a-SiC:H interface to obtain a better solar cell performance without loss in the FF. The abrupt potential barrier at the interface of AZO and p-type a-SiC:H is made gradual by inserting a buffer layer. A few-nanometer-thick nanocrystalline silicon buffer layer between the AZO and a-SiC:H enhances the FF from 67% to 73% and the efficiency from 7.30% to 8.18%. Further improvements in the solar cell performance are expected through optimization of cell structures and doping levels.

Impedance Spectroscopic Study of p-i-n Type a-Si Solar Cell by Doping Variation of p-Type Layer

We investigated p-i-n type amorphous silicon (a-Si) solar cell where the diborane flow rate of the p-type layer was varied and the solar cell was measured static/dynamic characteristics. The p/i interface of the thin film amorphous silicon solar cells was studied in terms of the coordination number of boron atoms in the p layer. p-type layer and p/i interface properties were obtained from the X-ray photoelectron spectroscopy (XPS) and impedance spectroscopy. One of the solar cells shows open circuit voltage (𝑉oc)=880 mV, short circuit current density (𝐽sc)=14.21 mA/cm2, fill factor (FF)=72.03%, and efficiency (𝜂)=8.8% while the p-type layer was doped with 0.1%. The impedance spectroscopic measurement showed that the diode ideality factor and built-in potential changed with change in diborane flow rate.

The Effect of Carrier Injection Stress on Boron-Doped Amorphous Silicon Suboxide Layers Investigated by X-ray Photoelectron Spectroscopy

In amorphous silicon solar cells, reducing degradation is one of the key issues in improving cell performance. The degradation of the p-layer can play an important role since it is directly related to the open circuit voltage (Voc) and fill factor (FF) in the cells. In this study, we investigated the changes in boron-doped p-type silicon suboxide (SiOx) layers after carrier injection stress. The boron doping level was varied by controlling B2H6 gas flow rate. When these layers were degraded, the dark conductivity decay decreased from 53% to less than 5%, and the increase in activation energy decreased from 11 to 0.5% depending on the B2H6 gas flow rate increase. Our improvements are explained in conjunction with the three- and four-fold coordinated boron atoms by the shift of the B 1s X-ray photoelectron spectrum. In this paper we present how to improve the stability of hydrogenated amorphous silicon (a-Si:H) thin-film solar cells.

Effects of viscosity and volume on the patterns of esophageal motility in healthy adults using high‐resolution manometry

The purpose of this study was to determine the effects of age, sex, body mass index (BMI), viscosity, and volume on esophageal motility using high-resolution manometry (HRM). Manometric studies were performed on 60 asymptomatic volunteers (27 men and 33 women, age: 19-56 years) while in a supine position. Manometric protocol included 10 water swallows (5 cc), 10 jelly swallows (5 cc), and 1 water swallow (20 cc). Evaluation of HRM parameters including length of proximal pressure trough (PPT length), distal latency (DL), contractile front velocity (CFV), distal contractile integral (DCI), and 4-second integrated relaxation pressure (IRP) was performed using MATLAB. Significant differences were noted in median IRP between water 5 cc (median 7.2 mmHg [range 5.5-9.6]), jelly 5 cc (median 6.0 mmHg [range 3.8-8.0]), and water 20 cc {(Median 4.8 mmHg [range 3.3-7.4]), P < 0.01}. DL were significantly different between water 5 cc, jelly 5 cc, and water 20 cc (P < 0.01), and in terms of PPT, proportions of small (2 cm ≤ < 5 cm) and large (5 cm≤) break for jelly 5 cc were significantly higher than those for the water 5 cc swallow (P < 0.05). Furthermore, DCI increased with age for water 5 cc, and a significant negative correlation was noticed between proportions of small break and BMI for water 5 cc. Manometric measurements vary depending on age, BMI, viscosity, and volume. These findings need to be taken into account in the interpretation of manometry results.

Front and Back TCO Research Review of a-Si/c-Si Heterojunction with Intrinsic Thin Layer (HIT) Solar Cell

In this paper, we report a technical approach regarding an amorphous silicon (a-Si)/crystalline silicon (c-Si) heterojunction solar cell to solve the previous issues, and we investigate the applications of front and back transparent conductive oxides (TCOs) on this high-efficiency solar cell. The presentation of front and rear-emitter structure solar cells is included, and we investigate the TCO-material candidates for the Si heterojunction (SHJ) solar cell according to the electrical and optical properties. A high-quality TCO film is very important because it is linked to the efficiency of the c-Si-based silicon solar cell. The intention here is the applying of a high-efficiency SHJ solar cell by fabricating the high-quality TCO materials of the investigation of this study.

Improving the efficiency of rear emitter silicon solar cell using an optimized n-type silicon oxide front surface field layer

Optical and electrical characteristics of n-type nano-crystalline-silicon oxide (n-µc-SiO:H) materials can be varied to optimize and improve the performance of a solar cell. In silicon heretojunction (SHJ) solar cells, it can be used to improve carrier selectivity and optical transmission at the front side, both of which are vitally important in device operation. For this purpose, the n-µc-SiO:H was investigated as the front surface field (FSF) layer. During film deposition, an increased CO2 flow rate from 0 to 6 sccm resulted in changes of crystalline volume fractions from 57 to 28%, optical band-gaps from 1.98 to 2.21 eV, dark conductivities from 7.29 to 1.1 × 10−5 S/cm, and activation energies from 0.019 to 0.29 eV, respectively. In device applications, a minimum optical reflection was estimated for the FSF layer that was fabricated with 4 sccm CO2 (FSF-4), and therefore obtained the highest external quantum efficiency, although short circuit current density (Jsc) was 38.83 mA/cm2 and power conversion efficiency (PCE) was 21.64%. However, the highest PCE of 22.34% with Jsc = 38.71 mA/cm2 was observed with the FSF prepared with 2 sccm CO2 (FSF-2), as the combined opto-electronic properties of FSF-2 were better than those of the FSF-4.

Development of p-type amorphous silicon oxide — Nano crystalline silicon double layer and its application in n-i-p type amorphous silicon solar cell

Single junction n-i-p type amorphous silicon solar cell was investigated with various p-type window layers. A high doped silicon oxide (P1) layer was used to extract holes from the active layer while a highly conducting micro-crystalline silicon p-type layer was used as an electrical contact layer with the transparent conducting oxide front electrode. When electrical conductivity of the second (P2) layer was raised (to 1.1 S.cm-1) the open circuit voltage and short circuit current density of the cells increased. This P2 layer was placed in between P1 and front electrode. Optical band gap of the p-type layers remain close to 2.0 eV. With an optimum fabrication condition of the p-layers, the open circuit voltage and short circuit current density of the cells were found to reach 900 mV and 11 mA/cm2 respectively.

Effect of Oxygen and Diborane Gas Ratio on P-type Amorphous Silicon Oxide films and Its Application to Amorphous Silicon Solar Cells

We reported diborane () doped wide bandgap hydrogenated amorphous silicon oxide (p-type a-SiOx:H) films prepared by using silane () hydrogen () and nitrous oxide () in a radio frequency (RF) plasma enhanced chemical vapor deposition (PECVD) system. We improved the and conductivity of p-type a-SiOx:H films with various and ratios and applied those films in regards to the a-Si thin film solar cells. For the single layer p-type a-SiOx:H films, we achieved an optical band gap energy () of 1.91 and 1.99 eV, electrical conductivity of approximately S/cm and activation energy () of 0.57 to 0.52 eV with various and ratios. We applied those films for the a-Si thin film solar cell and the current-voltage characteristics are as given as: