Hierarchical Heterogeneous NiFe Layered Double Hydroxides for Efficient Solar-Powered Water Oxidation

Highly active, stable, and low-cost oxygen evolution reaction (OER) electrocatalysts are urgently needed for the realization of large-scale industrial hydrogen production via water electrolysis. Layered double hydroxides (LDHs) stand out as one of the most promising nonprecious electrocatalysts worth pursuing. Here, a hierarchical heterogeneous Ni2+Fe3+@Ni2+Fe2+ LDH was successfully synthesized via a sequential electrodeposition technique using separate electrolytes containing iron precursors with different valence states (Fe2+, Fe3+). The underlying highly crystalline Ni2+Fe2+ LDH nanosheet array provides a large surface for the catalytically more active Ni2+Fe3+ LDH overlayer with low crystallinity. The resulting Ni2+Fe3+@Ni2+Fe2+ LDH demonstrates excellent OER activity with overpotentials of 218 and 265 mV to reach current densities of 10 and 100 mA cm-2, respectively, as well as good long-term stability for 30 h even at a high current density of 500 mA cm-2. In an overall water splitting, an electrolyzer using an electrocatalyst of Sn4P3/CoP2 as a cathode requires only a cell voltage of 1.55 V at 10 mA cm-2. Furthermore, the solar-powered overall water splitting system consisting of our electrolyzer and a perovskite/Si tandem solar cell exhibits a high solar-to-hydrogen conversion efficiency of 15.3%.

Nanoscale Characterization of Photocurrent and Photovoltage in Polycrystalline Solar Cells

We investigate the role of grain structures in nanoscale carrier dynamics of polycrystalline solar cells. By using Kelvin probe force microscopy (KPFM) and near-field scanning photocurrent microscopy (NSPM) techniques, we characterize nanoscopic photovoltage and photocurrent patterns of inorganic CdTe and organic-inorganic hybrid perovskite solar cells. For CdTe solar cells, we analyze the nanoscale electric power patterns that are created by correlating nanoscale photovoltage and photocurrent maps on the same location. Distinct relations between the sample preparation conditions and the nanoscale photovoltaic properties of microscopic CdTe grain structures are observed. The same techniques are applied for characterization of a perovskite solar cell. It is found that a moderate amount of PbI₂ near grain boundaries leads to the enhanced photogenerated carrier collections at grain boundaries. Finally, the capabilities and the limitations of the nanoscale techniques are discussed.

Interfacial modification in perovskite-based tandem solar cells

With photovoltaic performance of metal halide perovskite-based solar cells skyrocketing to approximately 26% and approaching the theoretical Shockley-Queisser limit of single junction solar cells, researchers are now exploring multi-junction tandem solar cells that use perovskite materials to achieve high efficiency next-generation photovoltaics. Various types of bottom subcells, including silicon solar cells used commercially in industry, chalcogenide thin film cells, and perovskite cells, have been combined with perovskite top subcells on the strength of facile fabrication methods based on solution processes. However, owing to the nature that photovoltages of the subcells are added up and the structure containing numerous layers, interfacial issues that cause open-circuit voltage (V_OC) deficit need to be handled carefully. In addition, morphological issues or process compatibility make it difficult to fabricate solution-processed perovskite top cells. In this paper, we summarize and review the fundamentals and strategies to overcome interfacial issues in tandem solar cells for high efficiency and stability confronting this field.

Preoperative Chemoradiotherapy With Capecitabine With or Without Temozolomide in Patients With Locally Advanced Rectal Cancer: A Prospective, Randomised Phase II Study Stratified by O6-Methylguanine DNA Methyltransferase Status: KCSG-CO17-02

AIMS

To evaluate the clinical efficacy of adding temozolomide (TMZ) to preoperative capecitabine (CAP)-based chemoradiotherapy in patients with locally advanced rectal cancer (LARC) and validate O⁶-methylguanine DNA methyltransferase (MGMT) methylation status as a predictive marker for TMZ combined regimens.

MATERIALS AND METHODS

LARC patients with clinical stage II (cT3-4N0) or III (cT_anyN+) disease were enrolled. They were stratified into unmethylated MGMT (uMGMT) and methylated MGMT (mMGMT) groups by methylation-specific polymerase chain reaction before randomisation and were then randomly assigned (1:1) to one of four treatment arms: uMGMT/CAP (arm A), uMGMT/TMZ + CAP (arm B), mMGMT/CAP (arm C) and mMGMT/TMZ + CAP (arm D). The primary end point was the pathological complete response (pCR) rate.

RESULTS

Between November 2017 and July 2020, 64 patients were randomised. Slow accrual caused early study termination. After excluding four ineligible patients, 60 were included in the full analysis set. The pCR rate was 15.0% (9/60), 0%, 14.3%, 18.8% and 26.7% for the entire cohort, arms A, B, C and D, respectively (P = 0.0498 between arms A and D). The pCR rate was 9.7% in the CAP group (arms A + C), 20.7% in the TMZ + CAP group (arms B + D), 6.9% in the uMGMT group (arms A + B) and 22.6% in the mMGMT group (arms C + D). Grade 1-2 nausea or vomiting was significantly more frequent in the TMZ + CAP treatment groups (arms B + D) than in the CAP treatment groups (arms A + C, P < 0.001) with no difference in grade 3 adverse events. There were no grade 4 or 5 adverse events.

CONCLUSION

The addition of TMZ to CAP-based chemoradiotherapy tended to improve pCR rates, particularly in those with mMGMT LARC. MGMT status may warrant further investigation as a predictive biomarker for chemotherapeutic agents and radiotherapy.

Surface-Tailored Medium Entropy Alloys as Radically Low Overpotential Oxygen Evolution Electrocatalysts

Numerous studies have explored new materials for electrocatalysts, but it is difficult to discover materials that surpass the catalytic activity of current commercially available noble metal electrocatalysts. In contrast to conventional transition metal alloys, high-entropy alloys (HEAs) have immense potential to maximize their catalytic properties because of their high stability and compositional diversity as oxygen evolution reactions (OERs). This work presents medium-entropy alloys (MEAs) as OER electrocatalysts to simultaneously satisfy the requirement of high catalytic activity and long-term stability. The surface of MEA electrocatalyst is tailored to suit the OER via anodizing and cyclic voltammetry activation methods. Optimized electrical properties and hydrophilicity of the surface enable an extremely low overpotential of 187 mV for achieving the current density of 10 mA cm^-2 alkaline media. Furthermore, a combined photovoltaic-electrochemical system with MEA electrocatalyst and a perovskite/Si tandem solar cell exhibits a solar-to-hydrogen conversion efficiency of 20.6% for an unassisted hydrogen generation system. These results present a new pathway for designing sustainable high efficiency water splitting cells.

Boosting Unassisted Alkaline Solar Water Splitting Using Silicon Photocathode with TiO2 Nanorods Decorated by Edge-Rich MoS2 Nanoplates

To construct a highly efficient photoelectrochemical tandem device with silicon photocathode operating in alkaline conditions, it is desirable to develop stable and active catalysts which enable the photocathode to reliably perform under an alkaline environment. With nanostructured passivation layer and edge-exposed transition metal disulfides, silicon photocathode provides new opportunities for achieving unbiased alkaline solar water splitting. Here, the TiO₂ nanorod arrays decorated by edge-rich MoS₂ nanoplates are elaborately synthesized and deposited on p-Si. The vertically aligned TiO₂ nanorods fully stabilize the Si surface and improve anti-reflectance. Moreover, MoS₂ nanoplates with exposed edge sites provide catalytically active regions resulting in the kinetically favored hydrogen evolution under an alkaline environment. Interfacial energy band bending between p-Si and catalyst layers facilitates the transport of photogenerated electrons under steady-state illumination. Consequently, the MoS₂ nanoplates/TiO₂ nanorods/p-Si photocathode exhibits significantly improved photoelectrochemical-hydrogen evolution reaction (PEC-HER) performance in alkaline media with a high photocurrent density of 10 mA cm^-2 at 0 V versus RHE and high stability. By integrating rationally designed photocathode with earth-abundant Fe₆₀ (NiCo)₃₀ Cr₁₀ anode and perovskite/Si tandem photovoltaic cell, an unassisted alkaline solar water splitting is accomplished with a current density of 5.4 mA cm^-2 corresponding to 6.6% solar-to-hydrogen efficiency, which is the highest among p-Si photocathodes.

Efficient, stable silicon tandem cells enabled by anion-engineered wide-bandgap perovskites

Maximizing the power conversion efficiency (PCE) of perovskite/silicon tandem solar cells that can exceed the Shockley-Queisser single-cell limit requires a high-performing, stable perovskite top cell with a wide bandgap. We developed a stable perovskite solar cell with a bandgap of ~1.7 electron volts that retained more than 80% of its initial PCE of 20.7% after 1000 hours of continuous illumination. Anion engineering of phenethylammonium-based two-dimensional (2D) additives was critical for controlling the structural and electrical properties of the 2D passivation layers based on a lead iodide framework. The high PCE of 26.7% of a monolithic two-terminal wide-bandgap perovskite/silicon tandem solar cell was made possible by the ideal combination of spectral responses of the top and bottom cells.

Water Splitting Exceeding 17% Solar-to-Hydrogen Conversion Efficiency Using Solution-Processed Ni-Based Electrocatalysts and Perovskite/Si Tandem Solar Cell

Various noble metal-free electrocatalysts have been explored to enhance the overall water splitting efficiency. Ni-based compounds have attracted substantial attention for achieving efficient oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) catalysts. Here, we show superior electrocatalysts based on NiFe alloy electroformed by a roll-to-roll process. NiFe (oxy)hydroxide synthesized by an anodization method for the OER catalyst shows an overpotential of 250 mV at 10 mA cm^-2, which is dramatically smaller than that of bare NiFe alloy with an overpotential of 380 mV at 10 mA cm^-2. Electrodeposited NiMo films for the HER catalyst also exhibit a small overpotential of 100 mV at 10 mA cm^-2 compared with that of bare NiFe alloy (550 mV at 10 mA cm^-2). A combined spectroscopic and electrochemical analysis reveals a clear relationship between the surface chemistry of NiFe (oxy)hydroxide and the water splitting properties. These outstanding fully solution-processed catalysts facilitate superb overall water splitting properties due to enlarged active surfaces and highly active catalytic properties. We combined a solution-processed monolithic perovskite/Si tandem solar cell with MAPb(I_0.85Br_0.15)₃ for the direct conversion of solar energy into hydrogen energy, leading to the high solar-to-hydrogen efficiency of 17.52%. Based on the cost-effective solution processes, our photovoltaic-electrocatalysis (PV-EC) system has advantages over latest high-performance solar water splitting systems.

Magnetic resonance tumour regression grade and pathological correlates in patients with rectal cancer

BACKGROUND

Evidence to support the specific use of magnetic resonance tumour regression grade (mrTRG) is inadequate. The aim of this study was to investigate the pathological characteristics of mrTRG after chemoradiotherapy (CRT) for rectal cancer and the implications for surgery.

METHODS

Patients undergoing long-course CRT (45-50 Gy plus a booster dose of 4-6 Gy) for mid or low rectal cancer (cT3-4 or cN+ without metastasis) between 2011 and 2015 who had post-CRT rectal MRI before surgery were included retrospectively. Three board-certified experienced radiologists assessed mrTRG. mrTRG was correlated with pathological tumour regression grade (pTRG), ypT and ypN. In a subgroup of patients with mrTRG1-2 and no tumour spread (such as nodal metastasis) on MRI, the projected rate of completion total mesorectal excision (TME) if they underwent transanal excision (TAE) and had a ypT status of ypT2 or higher was estimated, and recurrence-free survival was calculated according to the operation (TME or TAE) that patients had actually received.

RESULTS

Some 439 patients (290 men and 149 women of mean(s.d.) age 62·2(11·4) years) were analysed. The accuracy of mrTRG1 for predicting pTRG1 was 61 per cent (40 of 66), and that for ypT1 or less was 74 per cent (49 of 66). For mrTRG2, these values were 22·3 per cent (25 of 112) and 36·6 per cent (41 of 112) respectively. Patients with mrTRG1 and mrTRG2 without tumour spread were ypN+ in 3 per cent (1 of 29) and 16 per cent (8 of 50) respectively. Assuming mrTRG1 or mrTRG1-2 with no tumour spread on post-CRT MRI as the criteria for TAE, the projected completion TME rate was 26 per cent (11 of 43) and 41·0 per cent (41 of 100) respectively. For the 100 patients with mrTRG1-2 and no tumour spread, recurrence-free survival did not differ significantly between TME (79 patients) and TAE (21) (adjusted hazard ratio 1·86, 95 per cent c.i. 0·42 to 8·18).

CONCLUSION

Patients with mrTRG1 without tumour spread may be suitable for TAE.

Effect of Rubidium Incorporation on the Structural, Electrical, and Photovoltaic Properties of Methylammonium Lead Iodide-Based Perovskite Solar Cells

We report the electrical properties of rubidium-incorporated methylammonium lead iodide ((Rb_xMA_1-x)PbI₃) films and the photovoltaic performance of (Rb_xMA_1-x)PbI₃ film-based p-i-n-type perovskite solar cells (PSCs). The incorporation of a small amount of Rb⁺ (x = 0.05) increases both the open circuit voltage (V_oc) and the short circuit photocurrent density (J_sc) of the PSCs, leading to an improved power conversion efficiency (PCE). However, a high fraction of Rb⁺ incorporation (x = 0.1 and 0.2) decreases the J_sc and thus the PCE, which is attributed to the phase segregation of the single tetragonal perovskite phase to a MA-rich tetragonal perovskite phase and a RbPbI₃ orthorhombic phase at high Rb fractions. Conductive atomic force microscopic and admittance spectroscopic analyses reveal that the single-phase (Rb_0.05MA_0.95)PbI₃ film has a high electrical conductivity because of a reduced deep-level trap density. We also found that Rb substitution enhances the diode characteristics of the PSC, as evidenced by the reduced reverse saturation current (J₀). The optimized (Rb_xMA_1-x)PbI₃ PSCs exhibited a PCE of 18.8% with negligible hysteresis in the photocurrent-voltage curve. The results from this work enhance the understanding of the effect of Rb incorporation into organic-inorganic hybrid halide perovskites and enable the exploration of Rb-incorporated mixed perovskites for various applications, such as solar cells, photodetectors, and light-emitting diodes.

Highly Efficient and Uniform 1 cm2 Perovskite Solar Cells with an Electrochemically Deposited NiOx Hole-Extraction Layer

Given that the highest certified conversion efficiency of the organic-inorganic perovskite solar cell (PSC) already exceeds 22 %, which is even higher than that of the polycrystalline silicon solar cell, the significance of new scalable processes that can be utilized for preparing large-area devices and their commercialization is rapidly increasing. From this perspective, the electrodeposition method is one of the most suitable processes for preparing large-area devices because it is an already commercialized process with proven controllability and scalability. Here, a highly uniform NiO_x layer prepared by electrochemical deposition is reported as an efficient hole-extraction layer of a p-i-n-type planar PSC with a large active area of >1 cm² . It is demonstrated that the increased surface roughness of the NiO_x layer, achieved by controlling the deposition current density, facilitates the hole extraction at the interface between perovskite and NiO_x , and thus increases the fill factor and the conversion efficiency. The electrochemically deposited NiO_x layer also exhibits extremely uniform thickness and morphology, leading to highly efficient and uniform large-area PSCs. As a result, the p-i-n-type planar PSC with an area of 1.084 cm² exhibits a stable conversion efficiency of 17.0 % (19.2 % for 0.1 cm² ) without showing hysteresis effects.

300% Enhancement of Carrier Mobility in Uniaxial-Oriented Perovskite Films Formed by Topotactic-Oriented Attachment

Organic-inorganic perovskites with intriguing optical and electrical properties have attracted significant research interests due to their excellent performance in optoelectronic devices. Recent efforts on preparing uniform and large-grain polycrystalline perovskite films have led to enhanced carrier lifetime up to several microseconds. However, the mobility and trap densities of polycrystalline perovskite films are still significantly behind their single-crystal counterparts. Here, a facile topotactic-oriented attachment (TOA) process to grow highly oriented perovskite films, featuring strong uniaxial-crystallographic texture, micrometer-grain morphology, high crystallinity, low trap density (≈4 × 10¹⁴ cm^-3 ), and unprecedented 9 GHz charge-carrier mobility (71 cm² V^-1 s^-1 ), is demonstrated. TOA-perovskite-based n-i-p planar solar cells show minimal discrepancies between stabilized efficiency (19.0%) and reverse-scan efficiency (19.7%). The TOA process is also applicable for growing other state-of-the-art perovskite alloys, including triple-cation and mixed-halide perovskites.

Survival Benefit of Early Cancer Detection Through Regular Endoscopic Screening for De Novo Gastric and Colorectal Cancers in Korean Liver Transplant Recipients

BACKGROUND

De novo malignancy is not uncommon after liver transplantation (LT). Gastric cancer is one of the most common malignancies in both the Korean general population and LT recipients, and colorectal cancer prevalence is gradually increasing.

METHODS

Among 3690 adult recipients who underwent LT from January 1999 and December 2013, the screening patterns and prognosis of 26 cases of gastric cancer and 22 cases of colorectal cancer were analyzed.

RESULTS

For gastric cancer, the mean patient age was 54.6 ± 6.2 years at LT and 59.5 ± 6.7 years at cancer diagnosis, with a post-transplant interval of 60.2 ± 29.8 months. Patients were divided into regular (n = 18) and non-regular (n = 8) screening groups, with early cancer found in 14 and 0 patients; their 2-year survival rates after cancer diagnosis were 93.1% and 33.3% (P = .006), respectively. Endoscopic resection was successfully performed in 8 patients, all in the regular screening group. For colorectal cancer, the mean patient age was 53.3 ± 6.1 years at LT and 58.1 ± 6.7 years at cancer diagnosis, with a post-transplant interval of 54.3 ± 38.0 months. Patients were divided into regular (n = 19) and non-regular (n = 3) screening groups, with early cancer found in 12 and 0 patients; their 2-year survival rates after cancer diagnosis of 92.3% and 33.3% (P = .003), respectively. Endoscopic resection was successfully performed in 6 patients, all in the regular screening group.

CONCLUSIONS

LT recipients are strongly advised to undergo regular screening studies for various de novo malignancies, especially cancers common in the general population. Regular endoscopic screening contributes to the timely detection of gastric and colorectal cancers, improving post-treatment survival outcomes.

An ultra-thin, un-doped NiO hole transporting layer of highly efficient (16.4%) organic-inorganic hybrid perovskite solar cells

NiO is a wide band gap p-type oxide semiconductor and has potential for applications in solar energy conversion as a hole-transporting layer (HTL). It also has good optical transparency and high chemical stability, and the capability of aligning the band edges to the perovskite (CH3NH3PbI3) layers. Ultra-thin and un-doped NiO films with much less absorption loss were prepared by atomic layer deposition (ALD) with highly precise control over thickness without any pinholes. Thin enough (5-7.5 nm in thickness) NiO films with the thickness of few time the Debye length (LD = 1-2 nm for NiO) show enough conductivities achieved by overlapping space charge regions. The inverted planar perovskite solar cells with NiO films as HTLs exhibited the highest energy conversion efficiency of 16.40% with high open circuit voltage (1.04 V) and fill factor (0.72) with negligible current-voltage hysteresis.

Tailoring of Electron-Collecting Oxide Nanoparticulate Layer for Flexible Perovskite Solar Cells

Low-temperature-processed perovskite solar cells (PSCs), especially those fabricated on flexible substrates, exhibit device performance that is worse than that of high-temperature-processed PSCs. One of the main reasons for the inferior performance of low-temperature-processed PSCs is the loss of photogenerated electrons in the electron collection layer (ECL) or related interfaces, i.e., indium tin oxide/ECL and ECL/perovskite. Here, we report that tailoring of the energy level and electron transporting ability in oxide ECLs using Zn2SnO4 nanoparticles and quantum dots notably minimizes the loss of photogenerated electrons in the low-temperature-fabricated flexible PSC. The proposed ECL with methylammonium lead halide [MAPb(I0.9Br0.1)3] leads to fabrication of significantly improved flexible PSCs with steady-state power conversion efficiency of 16.0% under AM 1.5G illumination of 100 mW cm(-2) intensity. These results provide an effective method for fabricating high-performance, low-temperature solution-processed flexible PSCs.

Late anastomotic leakage after low anterior resection in rectal cancer patients: clinical characteristics and predisposing factors

AIM

The purpose was to examine the clinical characteristics and predisposing factors of late anastomotic leakage following low anterior resection for rectal cancer.

METHOD

We retrospectively evaluated the clinicopathological features of patients who experienced anastomotic leakage after low anterior resection for rectal cancer. Patients were divided into two groups according to the time to leakage: early leakage (within 30 days postoperatively) and late leakage (after 30 days postoperatively). Clinicopathological characteristics were compared between the two groups.

RESULTS

Anastomotic leakage occurred in 141 patients. Anastomotic leakage was diagnosed at a median of 17 (range 0-886) days postoperatively; 85 (60.3%) and 56 (39.7%) were categorized as the early and late leakage groups, respectively. Radiotherapy (hazard ratio 5.007; 95% CI 2.208-11.354; P < 0.0001) was the only significant independent predisposing factor for late leakage. Diverting stoma did not protect against late leakage. The late leakage group more frequently had the fistula type (46.4% vs. 10.6%; P < 0.001) and less frequently needed laparotomy (55.4% vs. 78.8%; P = 0.001). The rate of long-term stoma over 1 year was greater in the late leakage than the early leakage group (51.8% vs. 29.4%; P = 0.009).

CONCLUSION

Late anastomotic leakages that develop after 30 days following low anterior resection are not uncommon and may be associated with the use of radiotherapy. Late leakage should be a different entity from early leakage in terms of the type of leakage, methods of management and subsequent sequelae.

Clinical implications of mucinous components correlated with microsatellite instability in patients with colorectal cancer

AIM

Colorectal cancer (CRC) with microsatellite instability (MSI) is characterized by frequent poor differentiation or mucinous histology. The purpose of this study was to evaluate the association of MSI with clinicopathological features and the oncological outcome in patients with a mucinous component.

METHOD

CRC tissue samples were analysed for histology and MSI. Patients were grouped according to the mucinous content of the tumour, as follows: > 50%, mucinous adenocarcinoma (MA); ≤ 50%, adenocarcinoma with mucinous component (AMC); none, nonmucinous adenocarcinoma (NMA). Clinicopathological parameters and survival were compared between patient groups.

RESULTS

Of 2025 patients, 84 (4%) had MA and 124 (6%) had AMC. In addition, 202 (10%) had MSI. Patients with MA and AMC tended to have a younger age of onset, right-colon predilection, large-sized tumour and high frequency of MSI compared with those with NMA (P < 0.001). MA and AMC patients with MSI showed a trend towards right-colon predilection and infrequent lymph-node metastasis compared with those with microsatellite stability (MSS; P = 0.005-0.03). There were no survival differences between the three groups, but patients with MSI-MA demonstrated lower 4-year recurrence and better overall survival rates than those with MSS-MA (P = 0.018 and P = 0.046, respectively).

CONCLUSION

Clinicopathological features of AMC and MA were similar and closely associated with MSI status. Although the prognoses of AMC and MA were no different from that of NMA, survival of patients with an MSI-MA tumour was significantly better than for those with MSS-MA tumours.

Observation of anatase nanograins crystallizing from anodic amorphous TiO2 nanotubes

Water content in an anodic electrolyte affects the crystallization route of anodic TiO₂ nanotube arrays during annealing, which determines the crystallographic orientation of the nanotubes.

Anatase TiO2 nanorod-decoration for highly efficient photoenergy conversion

In recent studies of inorganic materials for energy applications, surface modification processes have been shown to be among the most effective methods to enhance the performance of devices. Here, we demonstrate a facile nano-decoration method which is generally applicable to anatase TiO2 nanostructures, as well as a nano-decorated hierarchical TiO2 nanostructure which improves the energy conversion efficiency of a dye-sensitized solar cell (DSSC). Using a facile sol-gel method, 0-D, 1-D, and 2-D type anatase TiO2 nanostructures were decorated with 200 nm long anatase TiO2 nanorods to create various hierarchical nanostructures. A structural analysis reveals that the branched nanorod has a highly crystalline anatase phase with anisotropic growth in the [001] longitudinal direction. When one of the hierarchical structures, a chestnut bur-like nanostructure, was employed in a dye-sensitized solar cell as a scattering layer, offering increased dye-loading properties, preserving a sufficient level of light-scattering ability and preserving superior charge transport and recombination properties as well, the energy conversion efficiency of the cell improved by 19% (from 7.16% to 9.09%) compared to a cell with a 0-D TiO2 sphere as a scattering layer. This generally applicable anatase nanorod-decorating method offers potential applications in various energy-conversion applications, especially in DSSCs, quantum-dot solar cells, photoelectrochemical water-splitting devices, photocatalysis, and lithium ion batteries.

Influence of niobium doping in hierarchically organized titania nanostructure on performance of dye-sensitized solar cells

Niobium doped hierarchically organized TiO2 nanostructures composed of 20 nm size anatase nanocrystals were synthesized using pulsed laser deposition (PLD). The Nb doping concentration could be facilely controlled by adjusting the concentration of Nb in target materials. We could investigate the influence of Nb doping in the TiO2 photoelectrode on the cell performance of dye-sensitized solar cells (DSSCs) by the exclusion of morphological effects using the prepared Nb-doped TiO2 anostructures. We found no significant change in short circuit current density (Jsc) as a function of Nb doping concentration. However, open circuit voltage (Voc) and fill factor (FF) monotonously decrease with increasing Nb concentration. Dark current characteristics of the DSSCs reveal that the decrease in Voc and FF is attributed to the decrease in shunt resistance due to the increase in conductivity TiO2 by Nb doping. However, electrochemical impedance spectra (EIS) analysis at open circuit condition under illumination showed that the resistance at the TiO2/dye/electrolyte interface increases with Nb concentration, revealing that Nb doping suppress the charge recombination at the interface. In addition, electron life time obtained using characteristic frequency in Bode plot increases from 14 msec to 56 msec with increasing Nb concentration from 0 to 1.2 at%. This implies that the improved light harvesting can be achieved by increasing diffusion length through Nb-doping in the conventional TiO2 photoelectrode.

Low-grade fibromyxoid sarcoma of the colon

Low-grade fibromyxoid sarcoma is a recently recognised soft tissue neoplasm. It is rare and has a tendency to arise from deep soft tissue of the lower extremities. An origin from the colon has not been reported in the medical literature. We report the low-grade fibromyxoid sarcoma originating from the colon in a 43-year-old male patient, treated by right hemicolectomy and nephrectomy.

Efficacy of PET/CT in the accurate evaluation of primary colorectal carcinoma

AIM

This study was performed to assess in the accurate evaluation of primary colorectal carcinoma using PET/CT.

METHODS

One hundred patients with primary colorectal carcinoma were evaluated during 2004. All patients underwent PET/CT when their preoperative serum carcinoembryonic antigen was >or=10 ng/mL or when CT showed equivocal findings. The appropriateness of PET/CT-induced changes was noted by subsequent operative findings and follow-up.

RESULTS

PET/CT more detected 15 intra-abdominal metastatic lesions than abdomino-pelvic CT scan. PET/CT showed true negative findings in 13 patients and false positive or negative findings in 10. Due to PET/CT results, management plans were altered in 27 patients; 9 had inter-modality changes, 10 received more extensive surgery, and 8 avoided unnecessary procedures.

CONCLUSIONS

PET/CT altered management plan in 24% of patients with primary colorectal carcinoma in correct direction. These findings suggest that PET/CT should be considered a part of standard work up for preoperative evaluation in a subset of patients with colorectal carcinoma.

Laparoscopic colorectal surgery using low-pressure pneumoperitoneum combined with abdominal wall lift by placement of anchoring sutures around the camera port

BACKGROUND

This study aimed to evaluate the feasibility of low-pressure pneumoperitoneum in laparoscopic colorectal surgery.

METHODS

The authors designed low-pressure (8 mmHg) laparoscopy combined with abdominal wall lift simply by placement of anchoring sutures around the camera port.

RESULTS

The operative indications were 176 colon cancers, 297 rectal cancers, and 45 benign diseases. The average blood loss was 92 ml (range, 20-1200 ml), and the mean operating time was 204 min (range, 23-525 min). Conversion to an open procedure was required in eight cases (1.5%). Two patients experienced intraoperative complications. The mean number of removed lymph nodes was 28.9 in the colon cancer cases and 23.1 in the rectal cancer cases. The mean length of resected specimen was 27.3 cm (range, 8.5-136 cm). Postoperatively, cardiopulmonary complications developed in five patients (0.9%).

CONCLUSIONS

Abdominal wall lifting by anchoring sutures around the camera port in addition to low-pressure pneumoperitoneum is a simple, safe, and effective method for laparoscopic colorectal procedure.

Metachronous colorectal cancer

OBJECTIVE

Although the diagnosis of metachronous colorectal cancer have increased, due primarily to improvements in diagnostic modalities, the potential risk factors for these tumours are not well known. We compared the characteristics of patients with metachronous and sporadic primary colorectal cancer to determine risk factors for its occurrence.

PATIENTS AND METHODS

We reviewed the records of 5447 patients with colorectal cancer, who had been treated at Asan Medical Centre between July 1989 and January 2004. A metachronous cancer was defined as a secondary colorectal cancer occurring more than 6 months after the index cancer.

RESULTS

Metachronous colorectal cancer occurred in 39 (0.7%) patients. Their average age was 53 years, somewhat younger than the average age of sporadic colorectal cancer patients (58 years). In patients with metachronous cancer, the cancer was more likely to be located in the right colon (P < 0.03), and the incidence of synchronous polyps or cancer was significantly higher (P < 0.001). The relative distributions of histological grades and clinicopathological characteristics were similar in index and metachronous cancers. Metachronous cancers were diagnosed more frequently at an early stage. The time interval between index and metachronous cancer ranged from 6 to 215 months (mean 39 months), with 13 (33.3%) patients diagnosed with metachronous cancer after 5 years.

CONCLUSION

We found that in patients aged < 50 years, existence of synchronous polyps or cancer influence on the development of metachronous colorectal cancer. Regular follow-up is necessary for early detection, even after 5 years, for these patients.

Development of a pMOSFET sensor with a Gd converter for low energy neutron dosimetry

A pMOSFET having a 10 microm thick Gadolinium (Gd) layer has been invented as a slow neutron sensor. When slow neutrons are incident to the Gd layer, conversion electrons, which generate electron-hole pairs in the SiO2 layer of the pMOSFET, are generated by a neutron capture process. The holes are easily trapped in the oxide and act as positive-charge centres in the oxide. Due to the induced charges, the threshold turn-on voltage of the pMOSFET is changed. The developed sensors were tested at a neutron beam port of the HANARO research reactor and a 60Co irradiation facility to investigate slow neutron response and gamma ray contamination, respectively. The resultant voltage change was proportional to the accumulated neutron dose and it was very sensitive to slow neutrons. Moreover, ionising radiation contamination was negligible. It can also be used in a mixed radiation field by subtracting the voltage change of a pMOSFET without Gd from that of the Gd-pMOSFET.

Biological monitoring of occupational exposure to N,N-dimethylformamide--the effects of co-exposure to toluene or dermal exposure

OBJECTIVES

The objective of this study is to assess the exposure and intake dose of N,N-dimethylformamide (DMF) and the correlation between them, according to the type of exposure for the workers in the DMF industry.

METHODS

We monitored 345 workers occupationally exposed to DMF, from 15 workshops in the synthetic fiber, fiber coating, synthetic leather and paint manufacturing industries. Ambient monitoring was carried out with personal samplers to monitor the external exposure. Biological monitoring was done to determine the internal dose by analyzing N-methylformamide (NMF) in end-shift urine. Work procedure and exposure type of each DMF workshop was carefully surveyed, to classify workers by exposure type according to work details. Workers were classified into three groups (Group A: continuous and direct exposure through inhalation and skin; Group B: intermittent and short-term exposure through inhalation and skin; Group C: continuous and indirect exposure mostly through inhalation).

RESULTS

Geometric mean of DMF concentration in air was 2.62 (GSD 5.30) ppm and that of NMF in urine was 14.50 (GSD 3.89) mg/l. In the case of continuous absorption through inhalation and dermal exposure (Group A), the value of NMF in urine corresponding to 10 ppm of DMF was 45.3 mg/l (r = 0.524, n = 178), 39.1 mg/g creatinine (r = 0.424), while it was 37.7 mg/l (r = 0.788, n = 37), 24.2 mg/g creatinine (r = 0.743) in the case of absorption mostly through inhalation (Group C). Creatinine correction reduced the correlation between two parameters.

CONCLUSION

The NMF in urine corresponding to 10 ppm DMF, of the dermal and inhalation exposure group was 39.1 mg/g creatinine (r = 0.424, n = 178), while that of the inhalation exposure-only group was 24.2 mg/g creatinine (r = 0.743, n = 37). Co-exposure with toluene reduced the NMF excretion in urine.

CD56 expression in a case of primary cutaneous CD30+ anaplastic large cell lymphoma

We describe clinicopathological features of an unusual case of CD30+/CD56+ T-cell lymphoma in a 58-year-old Korean man who presented with disseminated nodules, papules and hyperpigmented patches. Coexpression of CD30 and CD56 in T-cell lymphoma is very rare. Our patient did not respond to an intensive chemotherapy regimen, in contrast to the previously reported cases of primary cutaneous CD30+ anaplastic large cell lymphoma. Coexpression of CD56 might therefore identify a subset of CD30+ lymphomas with more aggressive features.

Increase in signal intensities on T1-weighted magnetic resonance images in asymptomatic manganese-exposed workers

OBJECTIVES

To clarify the clinical significance of increased signal intensities on T1 weighted magnetic resonance imaging (MRI) we performed a large-scale epidemiological study on asymptomatic manganese (Mn)-exposed workers with its focus on MRI.

METHODS

We randomly selected 121 male workers out of a total of 750 workers including Mn-exposed, non-exposed manual, and non-exposed clerical workers in the factories. We studied environmental and biological monitoring, neurological examination, and MRI.

RESULTS

The proportion of workers with increased signal intensities among the exposed, the non-exposed manual workers, and the non-exposed clerical workers was 46.1%, 18.8%, and 0%, respectively. Especially, 73.5% of the welders showed increased signal intensities. In no subject, were clinical signs of manganism observed. The pallidal index correlated with blood Mn concentration.

CONCLUSION

Increase in signal intensities on the T1-weighted image reflect recent exposure to Mn, but not necessarily manganism. At which increase of signal intensity, the progression of manganism from Mn exposure occurs, remains to be solved.

Two cases of linear focal elastosis (elastotic striae)

Linear focal elastosis (LFE) or elastotic striae was first described by Burket in 1989 in three elderly men. They presented with striae-like yellow palpable bands on their backs. Burket described many fine wavy bundles of elastic fibers separating the collagen in the middle to reticular dermis under microscopic examination. Until recently, there have been about 14 reported cases of LFE; elderly males are predominant. We encountered two Korean teen-aged males with linear, reddish, palpable bands and some atrophic bands across their backs. Histopathological examination revealed that elastosis was not as prominent as in previously reported cases. Our cases might represent early-evolving LFE.

Korean analytical quality assurance (KAQUA) program for biological monitoring

The Korean analytical quality assurance (KAQUA) program on biological monitoring was performed by the Industrial Health Research Institute in Korea in spring, 1995. The object of the KAQUA program is to improve the analysis capability for the biological monitoring of hazardous chemicals and to confirm the reliability of data from each laboratory. The items chosen for the first round were analyses of lead in blood (PbB) and of hippuric acid in urine (HAU). Eighty-eight laboratories in Korea participated in this program. Two levels of samples, randomly chosen among six levels for each item, were sent to the participants. The consensus value from participants and reference laboratories was determined by statistical analysis and used as a reference value. The tolerance range was +/-15% (+/-6 micrograms/dl for PbB below 40 micrograms/dl) of the reference value. The mean proficiency rate of analytical data increased dramatically in the first round compared with a pre-round that was provided as part of a training course for participants before performing the first round. The mean proficiency rate of PbB was 69% at pre-round and increased at 91% at the first round; for HAU the increase was from 58% to 88%. Not only the analytical results but also raw data were reviewed to find problems which might have arisen during the analytical process. Re-education courses provided after final evaluation of each participant by means of telephone discussion, correspondence course, and experimental practice, were helpful in achieving the purpose of the analytical quality assurance program.

Lead concentrations in blood among the general population of Korea

The purpose of this survey was to obtain information on the overall blood lead concentrations of the Korean population due to environmental exposure. Five hundred and twenty-five Korean adults from four provinces who had no previous occupational exposure to lead were chosen by random sampling to represent the general (normal) population. Blood lead determinations were performed by atomic absorption spectrometry with a graphite furnace. Interlaboratory quality control for analysis of blood lead was carried out in seven laboratories in Korea and Europe. The geometric mean were 6.36 micrograms/dl for males and 5.09 micrograms/dl for females. There was no correlation between blood lead concentration and age. The mean concentration of blood lead in smokers was higher than that in nonsmokers (P < 0.0005). The mean blood lead concentration in male nonsmokers was higher than that in female nonsmokers (P < 0.0005). Differences in mean blood lead values according to residential area were observed, and this result showed good agreement with the results of ambient monitoring.

Clinical features of Crohn's disease in Korea

Crohn's disease is a rare disease in Korea, and only 45 cases have been reported during the period of 34 years from 1952 to 1985. The male to female ratio was about 1.3 to 1 with a slight preponderance of males. The age at diagnosis ranged from 8 to 72 (mean 35.5) years, and the peak incidence occurred in the 3rd, 4th and 5th decades and declined thereafter. More than two thirds of the cases had a grossly demonstrable lesion involving the small bowel, including the terminal ileum. The proportion of patients with macroscopic disease continued to the large bowel alone was only 15%. Abdominal pain was common, presenting in 89% of the patients, while such symptoms as fever, hematochezia and diarrhea were not common. Abdominal mass was palpable in more than half the cases, which made it difficult to differentiate Crohn's disease from cancer of the colon, especially in cases with a predominant infiltration of the bowel wall and a secondary ulcer formation. That is one of the reasons why most cases in Korea have been reported by surgeons. A wide variety of complications were present, of which small bowel obstruction was the most common. Other complications were free perforation, malnutrition, fistula formation, hemorrhage and abscess formation, in decreasing order. The incidence of symptomatic perianal disease was only 11%, and this might be due to the small proportion of the disease confined to large bowel. Extraintestinal manifestations were also rare, and only three patients presented symptoms of arthritis. Other systemic features such as liver disease, skin lesion, eye complications were absent.

Spontaneous abortion after midtrimester amniocentesis

Of 371 consecutive patients who underwent midtrimester diagnostic amniocentesis, 8 subsequently aborted spontaneously (2.2%), and 1 had a stillbirth at 24 weeks of gestation (0.17%). In 3 of the 9 patients who suffered fetal loss, infection appears to have played a significant role. Whereas midtrimester diagnostic amniocentesis is widely considered to be a safe and accurate procedure, the possibility of hazard to the patient and her fetus remains and should be considered during the preliminary counseling session.

Technique of surgical sex reassignment for micropenis and allied conditions

Although the etiology of micropenis is diverse, individuals who have in common a penile length of 2 cm. or less at birth do not function well as men. For this reason, during the last 18 years, 10 individuals with this problem were selected for surgical sex reassignment. The technique of the surgical procedure is described. The immediate results are considered to be cosmetically satisfactory, and the long-term results, as judged by two individuals who have been observed for 18 plus years seem to indicate that surgical sex reassignment is a useful procedure in selected patients with this disorder.

Familial male pseudohermaphroditism with normal Leydig cell function at puberty

Four male pseudohermaphrodites from two families have been described. Although reared as females, at puberty, the timing, pattern, and degree of masculinization was similar to that of a normal male. No feminization occurred. They had normal testicular testosterone synthesis as judged by plasma testosterone, LH and FSH concentrations, as well as incubations of testicular minces with labeled precursors. Studies on cultured skin fibroblasts indicated adequate peripheral 5 alpha-reductase and normal receptor affinity and capacity for dihydrotestosterone. The histology of the testis was suggestive of a primary testicular defect. A mosaic pattern was seen: some areas contained tubules with active spermiogenesis; other areas, only Sertoli cells. These male pseudohermaphrodites appear to have a defect in fetal testicular maturation in which inadequate fetal testosterone synthesis and defective differentiation of germinal elements occurred.

A case of male pseudohermaphroditism associated with elevated LH, normal FSH and low testosterone possibly due to the secretion of an abnormal LH molecule

A 27 year old female is described who had 46,XY chromosome complement, ambiguous external genitalia with elevated LH, slightly above normal FSH and low testosterone. Her plasma testosterone level increased 15-20 fold after HCG stimulation (5000 IU X 3). then returned to prestimulation level 3 months later. This was possibly due to the secretion of an abnormal LH molecule which is immunoreactive but biologically inactive in the human.

Prenatal sex determination by observation of the X-chromatin and the Y-chromatin of exfoliated amniotic fluid cells

Using direct smears of amniotic fluid cells fixed by the flame drying technic, the validity of sex determination by X-chromatin and Y-chromatin counts has been examined. In 112 cases, the sex determination by examination of the X-chromatin was correct in 109 (97%) and was correct by the Y-chromatin technic in 111 (99%). It is concluded that prenatal sex determination by examination of the X-chromatin or the Y-chromatin from fresh amniotic fluid cells is a valuable, rapid, practical method of prenatal sex determination.

An etiologic and pathogenetic classification of male hermaphroditism

Based on defects in the central nervous system, the gonads, the end organs and the chromosomes, an etiologic and pathogenetic classification of male hermaphroditism is presented. At least 16 categories of disorders can cause male hermaphroditism--all seem to be basically genetic in origin.