Free-Standing Electrode and Fixed Surface Tiny Electrode Implemented Triboelectric Nanogenerator with High Instantaneous Current

Conventional triboelectric nanogenerators (TENGs) face challenges pertaining to low output current density at low working frequencies and high internal impedance. While strategies, such as surface modification to enhance surface charge density, permittivity regulation of materials, and circuit management, have partially mitigated these issues. However, they have also resulted in increased complexity in the fabrication process. Therefore, there is an urgent demand for a universal and simplified approach to address these challenges. To fulfill this need, this work presents a free-standing electrode and fixed surface tiny electrode implemented triboelectric nanogenerator (FFI-TENG). It is fabricated by a straightforward yet effective method: introducing a tiny electrode onto the surface of the tribo-negative material. This approach yields substantial enhancements in performance, notably a more than tenfold increase in output current density, a reduction in effective working frequencies, and a decrease in matching resistance as compared to vertical contact-separation TENGs (CS-TENGs) or single-electrode TENGs (SE-TENGs). Simultaneously, a comprehensive examination and proposition regarding the operational mechanism of FFI-TENG, highlighting its extensive applicability are also offered. Significantly, FFI-TENG excels in mechanical energy harvesting even under ultra-low working frequencies (0.1 Hz), outperforming similar contact-separation models. This innovation positions it as a practical and efficient solution for the development of low-entropy energy harvesters.

Hydrogenation of silicon-nanocrystals-embedded silicon oxide passivating contacts

We investigate the effect of hydrogen passivation of dangling bonds in silicon oxide passivating contacts with embedded silicon nanocrystals (NAnocrystalline Transport path in Ultra-thin dielectrics for REinforced passivation contact, NATURE contact). We first investigated the differences in electrical properties of the samples after hydrogen gas annealing and hydrogen plasma treatment (HPT). The results show that the NATURE contact was efficiently passivated by hydrogen after HPT owing to the introduction of hydrogen radicals into the structure. Furthermore, we examined the dependence of process parameters such as HPT temperature, duration, and H2pressure, on the electrical properties and hydrogen depth profiles. As a result, HPT at 500 °C, 15 min, and 0.5 Torr resulted in a large amount of hydrogen inside the NATURE contact and the highest implied open-circuit voltage of 724 mV. Contact resistivity and surface roughness hardly increased when HPT was performed under the optimized condition, which only improved the passivation performance without deteriorating the electron transport properties of the NATURE contact.

Fabrication of light trapping structures specialized for near-infrared light by nanoimprinting for the application to thin crystalline silicon solar cells

Vehicle-integrated photovoltaics (VIPV) are gaining attention to realize a decarbonized society in the future, and the specifications for solar cells used in VIPV are predicated on a low cost, high efficiency, and the ability to be applied to curved surfaces. One way to meet these requirements is to make the silicon substrate thinner. However, thinner substrates result in lower near-infrared light absorption and lower efficiency. To increase light absorption, light trapping structures (LTSs) can be implemented. However, conventional alkali etched pyramid textures are not specialized for near-infrared light and are insufficient to improve near-infrared light absorption. Therefore, in this study, as an alternative to alkaline etching, we employed a nanoimprinting method that can easily fabricate submicron-sized LTSs on solar cells over a large area. In addition, as a master mold fabrication method with submicron-sized patterns, silica colloidal lithography was adopted. As a result, by controlling silica coverage, diameter of silica particles (D), and etching time (t_et), the density, height, and size of LTSs could be controlled. At the silica coverage of 40%, D = 800 nm, and t_et = 5 min, the reduction of reflectance below 65% at 1100 nm and the theoretical short-circuit current gain of 1.55 mA/cm² was achieved.

Bayesian optimization of hydrogen plasma treatment in silicon quantum dot multilayer and application to solar cells

Silicon quantum dot multilayer (Si-QDML) is a promising material for a light absorber of all silicon tandem solar cells due to tunable bandgap energy in a wide range depending on the silicon quantum dot (Si-QD) size, which is possible to overcome the Shockley-Queisser limit. Since solar cell performance is degenerated by carrier recombination through dangling bonds (DBs) in Si-QDML, hydrogen termination of DBs is crucial. Hydrogen plasma treatment (HPT) is one of the methods to introduce hydrogen into Si-QDML. However, HPT has a large number of process parameters. In this study, we employed Bayesian optimization (BO) for the efficient survey of HPT process parameters. Photosensitivity (PS) was adopted as the indicator to be maximized in BO. PS (σ_p/σ_d) was calculated as the ratio of photoconductivity (σ_p) and dark conductivity (σ_d) of Si-QDML, which allowed the evaluation of important electrical characteristics in solar cells easily without fabricating process-intensive devices. 40-period layers for Si-QDML were prepared by plasma-enhanced chemical vapor deposition method and post-annealing onto quartz substrates. Ten samples were prepared by HPT under random conditions as initial data for BO. By repeating calculations and experiments, the PS was successfully improved from 22.7 to 347.2 with a small number of experiments. In addition, Si-QD solar cells were fabricated with optimized HPT process parameters; open-circuit voltage (V_OC) and fill factor (FF) values of 689 mV and 0.67, respectively, were achieved. These values are the highest for this type of device, which were achieved through an unprecedented attempt to combine HPT and BO. These results prove that BO is effective in accelerating the optimization of practical process parameters in a multidimensional parameter space, even for novel indicators such as PS.

High-frequency spin torque oscillation in orthogonal magnetization disks with strong biquadratic magnetic coupling

In this study, we numerically investigate the spin transfer torque oscillation (STO) in a magnetic orthogonal configuration by introducing a strong biquadratic magnetic coupling. The orthogonal configuration consists of top and bottom layers with in-plane and perpendicular magnetic anisotropy sandwiching a nonmagnetic spacer. The advantage of an orthogonal configuration is the high efficiency of spin transfer torque leading a high STO frequency; however, maintaining the STO in a wide range of electric current is challenging. By introducing biquadratic magnetic coupling into the orthogonal structure of FePt/spacer/Co₉₀Fe₁₀, Ni₈₀Fe₂₀ or Ni, we were able to expand the electric current region in which the stable STO is realized, resulting in a relatively high STO frequency. For example, approximately 50 GHz can be achieved in an Ni layer at a current density of 5.5 × 10⁷ A/cm². In addition, we investigated two types of initial magnetic state: out-of-plane and in-plane magnetic saturation; this leads to a vortex and an in-plane magnetic domain structure after relaxation, respectively. The transient time before the stable STO was reduced to between 0.5 and 1.8 ns by changing the initial state from out-of-plane to in-plane.

A Novel Self-Separating Silicon Nanowire Thin Film and Application in Lithium-ion Batteries

Nano silicon structures are important materials for modern electronic devices and have been widely researched with regard to photoelectricity, thermoelectricity, and lithium-ion batteries. However, since the nano silicon structures fabricated by conventional methods cannot be separated from silicon substrates, reuse of the substrate is restricted. Here, we propose a simple fabrication method to separate the nano silicon structures from the silicon substrates, which allows the reuse of the substrates. The fabrication was processed at room temperature, which allows large-area fabrication and is not restricted by the substrate thickness. Honeycomb structures of different length scales observed on both the nano silicon structure and the substrate suggest that the separation occurred due to the amplification of the silicon crystal defects. The nano silicon structures comprised porous silicon with an excellent specific surface area of 480 m2 g-1 and a mean pore diameter of 5.7 nm. Moreover, the nano silicon structures show good potential as anode materials for lithium-ion batteries wherein the measured reversible capacity was 1,966 mAh g-1 after 100 cycles. Based on the proposed method and morphological characteristics, the fabricated nano silicon structures can be considered a low-cost material with suitable applications in the energy field.

Pimitespib in patients with advanced gastrointestinal stromal tumor (CHAPTER-GIST-301): a randomized, double-blind, placebo-controlled phase 3 trial

BACKGROUND

Prognosis of advanced gastrointestinal stromal tumors (GIST) refractory to tyrosine kinase inhibitors (TKIs) is poor. This randomized, placebo-controlled, phase 3 trial evaluated the efficacy and safety of pimitespib, a novel heat shock protein 90 inhibitor, in advanced GIST refractory to standard TKIs.

PATIENTS AND METHODS

Patients with histologically confirmed GIST refractory to imatinib, sunitinib, and regorafenib were randomized 2:1 to oral pimitespib 160 mg/day or placebo for five consecutive days per week in 21-day cycles. Following disease progression by blinded central radiological review (BCRR), crossover to open-label pimitespib was permitted. The primary endpoint was progression-free survival (PFS) by BCRR in the full analysis set. Secondary endpoints included overall survival (OS) adjusted using the rank preserving structural failure time method to reduce the expected confounding impact of crossover.

RESULTS

From Oct 31, 2018 to Apr 30, 2020, 86 patients were randomized to pimitespib (n=58) or placebo (n=28). Median PFS was 2.8 months (95% CI 1.6-2.9) with pimitespib versus 1.4 months (0.9-1.8) with placebo (hazard ratio [HR] 0.51 [95% CI 0.30-0.87]; one-sided p=0.006). Pimitespib showed an improvement in crossover-adjusted OS compared with placebo (HR 0.42 [0.21-0.85], one-sided p=0.007). Seventeen (60.7%) patients receiving placebo crossed-over to pimitespib; median PFS after crossover was 2.7 (95% CI 0.7-4.1) months. The most common (≥30%) treatment-related adverse events (AEs) with pimitespib were diarrhea (74.1%) and decreased appetite (31.0%); the most common (≥10%) grade ≥3 treatment-related AE was diarrhea (13.8%). Treatment-related AEs leading to pimitespib discontinuation occurred in 3 (5.2%) patients.

CONCLUSION

Pimitespib significantly improved PFS and crossover-adjusted OS compared with placebo and had an acceptable safety profile in patients with advanced GIST refractory to standard TKIs.

Multicenter prospective trial of total gastrectomy versus proximal gastrectomy for upper third cT1 gastric cancer

BACKGROUND

The appropriate surgical procedure for patients with upper third early gastric cancer is controversial. We compared total gastrectomy (TG) with proximal gastrectomy (PG) in this patient population.

METHODS

A multicenter, non-randomized trial was conducted, with patients treated with PG or TG. We compared short- and long-term outcomes between these procedures.

RESULTS

Between 2009 and 2014, we enrolled 254 patients from 22 institutions; data from 252 were included in the analysis. These 252 patients were assigned to either the PG (n = 159) or TG (n = 93) group. Percentage of body weight loss (%BWL) at 1 year after surgery, i.e., the primary endpoint, in the PG group was significantly less than that of the TG group (- 12.8% versus - 16.9%; p = 0.0001). For short-term outcomes, operation time was significantly shorter for PG than TG (252 min versus 303 min; p < 0.0001), but there were no group-dependent differences in blood loss and postoperative complications. For long-term outcomes, incidence of reflux esophagitis in the PG group was significantly higher than that of the TG group (14.5% versus 5.4%; p = 0.02), while there were no differences in the incidence of anastomotic stenosis between the two (5.7% versus 5.4%; p = 0.92). Overall patient survival rates were similar between the two groups (3-year survival rates: 96% versus 92% in the PG and TG groups, respectively; p = 0.49).

CONCLUSIONS

Patients who underwent PG were better able to control weight loss without worsening the prognosis, relative to those in the TG group. Optimization of a reconstruction method to reduce reflux in PG patients will be important.

Effect of the Niobium-Doped Titanium Oxide Thickness and Thermal Oxide Layer for Silicon Quantum Dot Solar Cells as a Dopant-Blocking Layer

Silicon quantum dot (Si-QD) embedded in amorphous silicon oxide is used for p-i-n solar cell on quartz substrate as a photogeneration layer. To suppress diffusion of phosphorus from an n-type layer to a Si-QD photogeneration layer, niobium-doped titanium oxide (TiO_x:Nb) is adopted. Hydrofluoric acid treatment is carried out for a part of the samples to remove the thermal oxide layer in the interface of TiO_x:Nb/n-type layer. The thermal oxide acts as a photo-generated carrier-blocking layer. Solar cell properties using 10-nm-thick TiO_x:Nb without the thermal oxide are better than those with the thermal oxide, notably short circuit current density is improved up to 1.89 mA/cm². The photo-generated carrier occurs in Si-QD with quantum confinement effect. The 10-nm-thick TiO_x:Nb with the thermal oxide layer effectively blocks P; however, P-diffusion is not completely suppressed by the 10-nm-thick TiO_x:Nb without the thermal oxide. These results indicate that the total thickness of TiO_x:Nb and thermal oxide layer influence the P-blocking effect. To achieve the further improvement of Si-QD solar cell, over 10-nm-thick TiO_x:Nb is needed.

Silicon Nanowire Heterojunction Solar Cells with an Al2O3 Passivation Film Fabricated by Atomic Layer Deposition

Silicon nanowires (SiNWs) show a great potential for energy applications because of the optical confinement effect, which enables the fabrication of highly efficient and thin crystalline silicon (c-Si) solar cells. Since a 10-μm-long SiNW array can absorb sufficient solar light less than 1200 nm, the 10-μm-long SiNW was fabricated on Si wafer to eliminate the influence of the Si wafer. On the other hand, Surface passivation of the SiNWs is a crucial problem that needs to be solved to reduce surface recombination and enable the application of SiNWs to c-Si solar cells. In this study, aluminum oxide (Al₂O₃) was fabricated by atomic layer deposition for the passivation of dangling bonds. However, owing to a complete covering of the SiNWs with Al₂O₃, the carriers could not move to the external circuit. Therefore, chemical-mechanical polishing was performed to uniformly remove the oxide from the top of the SiNWs. A heterojunction solar cell with an efficiency of 1.6% was successfully fabricated using amorphous silicon (a-Si). The internal quantum efficiencies (IQE) of the SiNW and c-Si solar cells were discussed. In the wavelength region below 340 nm, the IQE of the SiNW solar cell is higher than that of the c-Si device, which results in an increase of the absorption of the SiNW cells, suggesting that SiNWs are promising for crystalline-silicon thinning.

Reflux after esophagectomy with gastric conduit reconstruction in the posterior mediastinum for esophageal cancer: original questionnaire and EORTC QLQ-C30 survey

Reflux following an esophagectomy with gastric conduit reconstruction in the posterior mediastinum is a clinically significant problem. In this study, we investigated the frequency and impact of reflux on the quality of life (QOL) among 158 patients who underwent an esophagectomy for esophageal cancer using an original questionnaire and the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Version 3.0 (EORTC QLQ-C30). Reflux frequency was assessed using the original questionnaire. The number of patients who complained of reflux every day, two or three times a week, once a week, or less than once a week was 16 (10.1%), 21 (13.3%), 26 (16.5%), and 60 (38.0%), respectively. Out of 35 patients (22.2%) reported no reflux symptoms. Patients were divided into two groups: those with reflux ≥ once/week (63 patients) and those with low frequency of symptoms (95 patients). Time elapsed following surgery was the only factor to influence reflux frequency. Reflux frequency decreased within two years of surgery; however, the frequency plateaued after more than two years. QOL was assessed using the EORTC QLQ-C30. The ≥ once/week reflux group had a significantly lower global health status score than the low-frequency reflux group (59.6 ± 24.2 vs. 70.8 ± 20.7; P = 0.007). In addition, the ≥ once/week reflux group had a significantly lower social functioning score than the low-frequency reflux group (81.6 ± 24.1 vs. 88.4 ± 19.8; P = 0.035). Regarding symptoms, the ≥ once/week reflux group had significantly higher scores for fatigue, nausea, and vomiting, dyspnea and insomnia compared to the low-frequency reflux group (fatigue: 42.4 ± 21.9 vs. 28.9 ± 18.4, P < 0.001; nausea and vomiting: 17.3 ± 17.1 vs. 4.9 ± 10.6, P < 0. 001; dyspnea: 29.2 ± 26.0 vs. 21.7 ± 26.8, P = 0.043; insomnia: 22.2 ± 31.1 vs. 10.5 ± 21.7, P = 0.015). Thus, reflux after an esophagectomy was associated with a lower QOL.

Utility of initial induction chemotherapy with 5-fluorouracil, cisplatin, and docetaxel (DCF) for T4 esophageal cancer: a propensity score-matched analysis

Although no consensus is available on the treatment of esophageal squamous cell carcinoma (ESCC) invading adjacent organs (T4), establishing effective induction treatments is crucial to altering an unresectable status and achieving curative resection. Here, we evaluated the efficacy of chemotherapy using 5-fluorouracil, cisplatin, and docetaxel (DCF) as the initial induction treatment for T4 ESCC. Fifty patients without distant metastasis who underwent initial induction chemotherapy using DCF for T4 ESCC were propensity score-matched with 50 patients who underwent radiotherapy concurrent with cisplatin and 5-fluorouracil (CRT). In the DCF group, 24 (48.0%) patients underwent surgery, achieving a 64% clinical response rate compared to 72.0% for induction CRT. CRT was also performed in another 24 (48.0%) patients in the DCF group in whom surgical resection was not indicated. The DCF group had significantly higher overall resectability than the CRT group (78.0% vs. 48.0%, P = 0.0017). The esophageal perforation rate during induction treatments was significantly lower in the DCF group than the CRT group (4.0% vs. 18.0%, P = 0.0205). Prognosis was significantly better in the DCF group than the CRT group (5-year cancer-specific survival 42.1% vs. 22.2%, P = 0.0146). Thus, induction DCF chemotherapy in patients with T4 ESCC reduced esophageal perforation and increased overall resectability, leading to better survival than CRT alone. Therefore, DCF chemotherapy may be an effective and safe option for initial induction treatment of T4 ESCC.

Tissue Engineering of the Small Intestine by Acellular Collagen Sponge Scaffold Grafting

Tissue engineering of the small intestine will prove a great benefit to patients suffering from short bowel disease. However cell seeding in tissue engineering, such as fetal cell use, is accompanied by problems of ethical issues, rejection, and short supply. To overcome these problems, we carried out an experimental study on tissue engineering of the small intestine by acellular collagen sponge scaffold grafting. We resected the 5 cm long jejunum from beagle dogs and reconstructed it by acellular collagen sponge grafting with a silicon tube stent. The graft was covered with the omentum. At 1 month after operation, the silicon stent was removed endoscopically. Animals were sacrificed 1 and 4 months after operation, and were examined microscopically. Neo-intestinal regeneration was observed and the intestinal mucosa covered the luminal side of the regenerated intestine across the anastomosis. Thus, the small intestine was regenerated by tissue engineering technology using an acellular collagen sponge scaffold.

Influence of Fabrication Processes and Annealing Treatment on the Minority Carrier Lifetime of Silicon Nanowire Films

Surface passivation and bulk carrier lifetime of silicon nanowires (SiNWs) are essential for their application in solar cell devices. The effective minority carrier lifetime of a semiconductor material is influenced by both its surface passivation and bulk carrier lifetime. We found that the effective carrier lifetime of SiNWs passivated with aluminum oxide (Al₂O₃) was significantly influenced by the fabrication process of SiNWs. We could not measure the effective lifetime of SiNWs fabricated by thermal annealing of amorphous silicon nanowires. Nevertheless, the SiNWs fabricated by metal-assisted chemical etching of polycrystalline silicon displayed an effective lifetime of 2.86 μs. Thermal annealing of SiNWs at 400 °C in a forming gas improved the effective carrier lifetime from 2.86 to 15.9 μs because of the improvement in surface passivation at the interface between the SiNWs and Al₂O₃ layers.

Comparison of short-term outcomes between 2- and 3-field lymph node dissection for esophageal cancer

Although 3-field lymph node dissection (3-FLD) is often performed for thoracic esophageal squamous cell carcinoma (ESCC), the clinical effects of cervical lymph node dissection in addition to mediastinal and abdominal dissections on postoperative complications remain unclear. A total of 367 ESCC patients who underwent curative esophagectomy for thoracic esophageal cancer in our hospital from 2010 to 2015 were included in the study: 157 patients who underwent 2-field lymph node dissection (2-FLD) and 210 patients who underwent 3-FLD. Clinicopathological parameters and postoperative complications based on the Clavien-Dindo classification were compared between the two groups. We performed propensity score matching (PSM) analyses to compare the groups with well-balanced backgrounds. In terms of patient background, clinical T (p < 0.001), N (p < 0.001), and M (p = 0.002) stage of tumor was significantly more advanced; therefore, preoperative treatment was more frequently performed in the 3-FLD group than in the 2-FLD group (91.0% vs. 79.0%, P< 0.001). However, perioperative parameters including operation time, blood loss, and the number of dissected mediastinal and abdominal lymph nodes did not differ between the groups. In terms of postoperative complications, the occurrence rate of pneumonia increased significantly in patients with 3-FLD compared to 2-FLD (grade III or higher: 10.5% vs. 3.2%, P= 0.025). Although the duration of systemic inflammatory response syndrome (SIRS) was longer in the 3-FLD group than in the 2-FLD group (median 3 days vs. 2 days, P= 0.025), other postoperative parameters (including the highest level of postoperative serum C-reactive protein, intensive care unit stay, re-operation rate, and postoperative hospital stay) were similar between the groups. After PSM, the differences in the background between the groups disappeared. PSM analysis showed that there was no significant difference in each complication between the groups. The duration of SIRS tended to be longer in the 3-FLD group than in the 2-FLD group, but the difference was not significant. The field of lymphadenectomy negatively impacted the short-term outcome in ESCC patients in terms of pneumonia and inflammatory response. However, because the results of the PSM analyses indicate that the short-term outcome was similar between the two groups, 3-FLD could be as feasible as 2-FLD in ESCC patients.

Promoting Effect of Metal Compounds on Liver, Stomach, Kidney, Pancreas, and Skin Carcinogenesis

Systemic studies have been completed in Japan to detect those chemicals in the environment that act as promoters. Well-established two-stage models for liver, stomach, kidney, pancreas, and skin carcinogenesis were employed to detect the promoting effect of Zn Cl2, Cr Cl2, Cd Cl2, Ni Cl2, and Hg Cl2. As a result, Ni Cl2 was found to act as a promoter in renal carcinogenesis.

Comparative Studies on Lipid Peroxidation in the Kidney of Rats, Mice, and Hamsters and on the Effect of Cysteine, Glutathione, and Diethyl Maleate Treatment on Mortality and Nephrotoxicity After Administration of Potassium Bromate

As an index of lipid peroxidation (LPO), levels of thiobarbituric acid (TBA)-reactive substances were examined in the kidneys of male F344 rats, BDF1, CDF1, and B6C3F1 mice, and Syrian golden hamsters after a single intravenous (IV) administration of potassium bromate (KBrO3) at various doses. In the rats, LPO levels were significantly increased in both a dose-dependent and time-dependent manner. However, when the rats were given intraperitoneal (IP) injection of cysteine, the levels of LPO were not significantly different between KBrO3-treated animals and controls. In CDF1 mice, the slight increases in LPO levels observed were much weaker and not statistically significant. On the other hand, treatment of BDF1 and B6C3F1 mice or hamsters with KBrO3 resulted in decreased values as compared to controls. The effect of treatment with cysteine, glutathione (GSH), or diethyl maleate (DEM) on mortality was tested in male F344 rats given IV injection of KBrO3 at various doses. Significant reduction and elevation in the mortality were observed in rats treated with cysteine or GSH and DEM, respectively. Significant dose-dependent and time-dependent increases were observed in the levels of serum non-protein nitrogen (NPN), blood urea nitrogen (BUN), and creatinine, and absolute and relative weight of the kidneys in male F344 rats administered KBrO3 IV. Microscopically, the appearance of numerous eosinophilic droplets in the cytoplasm of proximal tubular epithelium of KBrO3-treated rats was noteworthy. All these changes were reduced and exacerbated by treatment with cysteine or GSH and DEM, respectively. The possibility of LPO formation in the kidney by active oxygen radicals generated by KBrO3 is suggested. A possible relationship between LPO levels in the kidney and species differences in the renal toxicity and carcinogenicity of KBrO3 is implicated.

Promoting Effect of Metal Compounds on Rat Renal Tumorigenesis

Five metal compounds, zinc chloride (ZnCl2), mercury chloride (HgCl2), chromium chloride (CrCl3) hexahydrate, cadmium chloride (CdCl2) hemidihydrate, and nickel chloride (NiCl2) hexahydrate, were selected and tested for potential modifying influence on renal tumorigenesis. Six groups, each consisting of 15 male F344 rats, were given N-ethyl-N-hydroxyethylnitrosamine (EHEN) at a concentration of 500 ppm in their drinking water for the first 2 weeks as the initiation of carcinogenesis. Thereafter, the rats were treated orally for 25 weeks with ZnCl2, HgCl2, CrCl3, CdCl2, and NiCl2, respectively, at concentrations of 450, 40, 600, 100, and 600 ppm in the drinking water. The control group was given unsupplemented distilled water (DW) after EHEN initiation. Renal neoplastic lesions were classified histologically into dysplastic foci (DF) and renal cell tumors (RCT). As a result, statistically significant increases were found in the mean numbers of DF per cm2 in rats treated with the five metal compounds. On the other hand, the incidence of RCT was significantly higher only in rats treated with NiCl2. It is concluded that NiCl2 exerted a potential for promotion of renal tumorigenesis under the conditions of this study.

Lack of Promoting Effect of Sodium Chlorate and Potassium Chlorate in Two-Stage Rat Renal Carcinogenesis

Sodium chlorate (NaClO3) and potassium chlorate (KClO3), which are byproducts of water disinfection with chlorine dioxide (ClO2), were tested for potential promoting effect in two-stage rat renal carcinogenesis. Three groups of 15 male F344 rats each were given N-ethyl-N-hydroxyethylnitrosamine (EHEN) at the level of 0.05% for the first 2 weeks during the initiation phase. Thereafter, the rats were treated orally for 25 weeks with NaClO3 (1%), KClO3 (1%), or distilled water (DW). Three other groups (controls) were treated similarly, except that DW was given in the initiation phase. All animals survived for the duration of the experiment. Renal neoplastic lesions were classified histologically as dysplastic foci (DF) and renal cell tumors (RCT). The number of these lesions per unit area, in six sections from each kidney, was determined microscopically. There were no statistically significant differences in the incidences and in the mean number of DF and RCT of the kidney between compound-and DW-treated rats initiated with EHEN. It is concluded that NaClO3 and KClO3 show no promoting effect in rat renal carcinogenesis under the conditions of this study.

Development of Styrenic Copolymers for Improving Heat Resistance of Poly(methyl methacrylate)

Styrenic copolymers comprising styrene, methyl methacrylate, and maleic anhydride were developed to improve the heat-resistance property of poly(methyl methacrylate) (PMMA). The optical, thermal, and mechanical properties were examined for the blend specimens prepared by an injection-molding machine using melt-mixed samples. It was found that the copolymers, which were miscible with PMMA, increase the glass transition temperature and therefore the Vicat Softening temperature. Furthermore, the blends were completely transparent as similar to PMMA.

Inter-institutional heterogeneity in outcomes of chemotherapy for metastatic gastric cancer: correlative study in the JCOG9912 phase III trial

BACKGROUND

The standard chemotherapy regimen for gastric cancer has been established by several phase III trials. However, few studies have evaluated inter-institutional heterogeneity in randomised trials; such research may assure the generalisability of the results and also the reliability of the study group itself.

PATIENTS AND METHODS

The Japan Clinical Oncology Group (JCOG)9912 phase III trial compared irinotecan plus cisplatin and S-1 alone with fluorouracil alone for metastatic gastric cancer, and finally demonstrated the non-inferiority of S-1 alone with respect to overall survival (OS). Mixed effects models were used to evaluate outcomes of 658 patients from 22 hospitals. After adjustment for nine background factors, the heterogeneity in OS, progression-free survival (PFS), and incidences of grade 3-4 adverse events among hospitals was estimated. We also estimated the correlation between outcomes and either hospital volume or medical oncology clinical experience.

RESULTS

A large degree of heterogeneity in median OS was observed for fluorouracil alone (range, 8.3-13.3 months), while the difference in median PFS between hospitals was small (range, 2.4-3.4 months). Although some heterogeneity in the treatment effect of irinotecan plus cisplatin or S-1 alone was observed in OS and PFS, the HRs did not exceed 1.00 in any hospital for either regimen. There was minimal heterogeneity in the incidences of grade 3-4 adverse events. There was a trend towards correlation between greater medical oncology clinical experience and both better OS after fluorouracil alone and a lower HR for OS after irinotecan plus cisplatin, but it was not statistically significant.

CONCLUSIONS

Large inter-institutional heterogeneity was observed in OS, but not in PFS, after the standard regimen, but there was little heterogeneity in the treatment effects of irinotecan plus cisplatin or S-1 alone, indicating that the final results of the JCOG9912 trial can be generalised to the target population.

TRIAL REGISTRATION NUMBER

NCT00142350.

Impact of number of [(18)F]fluorodeoxyglucose-PET-positive lymph nodes on survival of patients receiving neoadjuvant chemotherapy and surgery for oesophageal cancer

BACKGROUND

[(18) F]fluorodeoxyglucose (FDG)-PET has been used to evaluate the response of primary tumours to neoadjuvant therapy for oesophageal cancer. The clinical significance of the number of PET-positive nodes before and after therapy has not been investigated previously.

METHODS

[(18) F]FDG-PET was performed before and 2-3 weeks after completion of neoadjuvant chemotherapy to identify the number of PET-positive nodes, and these numbers were assessed in relation to metabolic changes in the primary tumour.

RESULTS

Of 302 patients in total, 90 had no PET-positive nodes, 83 had one, 59 had two and 70 patients had three or more positive nodes before therapy. After treatment, the numbers were: none in 207 patients, one in 59, two in 20 and three or more in 16 patients. The number of PET-positive nodes after treatment was influenced by both the number of PET-positive nodes before therapy and the response to preoperative therapy, and correlated with the number of metastatic lymph nodes. Overall survival was longer in patients who had no PET-positive nodes after treatment than in those who had one or more. Multivariable analysis identified the numbers of PET-positive nodes before and after chemotherapy as independent prognostic factors, together with clinical response, tumour depth and lymph node involvement.

CONCLUSION

The number of PET-positive nodes after treatment correlated with survival in patients with oesophageal cancer who underwent neoadjuvant chemotherapy.

Theoretical and experimental investigation of the recombination reduction at surface and grain boundaries in Cu(In,Ga)Se2 solar cells by valence band control

We carried out theoretical calculation for Cu(In,Ga)Se2 (CIGS) solar cells with energy bandgap of 1.4 eV assuming formation of a Cu-poor layer on the surface of CIGS films. This calculation result revealed that formation of a thinner Cu-poor layer such as a few nanometers leads to improvement of the solar cells performance. This is because interfacial recombination was suppressed due to repelling holes from the interface by valence band offset (ΔEV). Next, we investigated composition distribution in the cross section of CIGS solar cells with Ga contents of 30% and 70% by transmission electron microscopy (TEM) and energy dispersive X-ray analysis (EDX). It was revealed that the Cu-poor layer was formed on the surface and at the grain boundary (GB) in the case of conversion efficiency (η) of 17.3%, although it was not formed in the case of lower η of 13.8% for a Ga content of 30%. These results indicate that formation of the Cu-poor layer contributed to improvement of cell performance by suppression of carrier recombination. Moreover, it was also confirmed that although the Cu-poor layer was observed on the surface, it was not observed at the GB in the case of CIGS solar cells with a Ga content of 70% which had η of 12.7%. It is thought that the effect of repelling holes by ΔEV is not obtained at the GB and the solar cell performance in the Ga content of 70% is lower than that in the Ga content of 30%. Thus, we suggest importance of the Cu-poor layer at the GB for high efficiency of CIGS solar cells with high Ga contents.

Ten-year follow-up results of a randomized clinical trial comparing left thoracoabdominal and abdominal transhiatal approaches to total gastrectomy for adenocarcinoma of the oesophagogastric junction or gastric cardia

Background

The optimal surgical approach for treatment of oesophagogastric junction (OGJ) cancer is controversial. A randomized clinical trial (JCOG9502) comparing transhiatal (TH) and left thoracoabdominal (LTA) approaches was stopped after the first interim analysis owing to limited efficacy for LTA resections. Complete 10‐year follow‐up data are now available.

Methods

Patients with histologically proven adenocarcinoma of the OGJ or gastric cardia with oesophageal invasion of 3 cm or less were randomized to a TH or LTA approach. Both groups underwent total gastrectomy and splenectomy with D2 nodal dissection plus para‐aortic lymphadenectomy above the left renal vein. For LTA, a thorough mediastinal lymphadenectomy below the left inferior pulmonary vein was also mandatory. The primary endpoint was overall survival.

Results

A total of 167 patients (82 TH, 85 LTA) were enrolled. The 10‐year overall survival rate was 37 (95 per cent c.i. 26 to 47) per cent for the TH approach and 24 (15 to 34) per cent for the LTA technique (P = 0·060). The hazard ratio for death was 1·42 (0·98 to 2·05) for the LTA technique. Subgroup analysis based on the Siewert classification indicated non‐significant survival advantages in favour of the TH approach.

Conclusion

LTA resections should be avoided in the treatment of adenocarcinoma of the OGJ or gastric cardia. Registration number: NCT00149266 (https://www.clinicaltrials.gov).

No survival benefit from a more extensive operation

Monitoring gastric cancer progression with circulating tumour DNA

Background:

Circulating tumour DNA (ctDNA) is an emerging candidate biomarker for malignancies and may be useful for monitoring the disease status of gastric cancer.

Methods:

We performed targeted deep sequencing of plasma cell-free DNA (cfDNA) by massively parallel sequencing in patients with tumours harbouring TP53 mutations. The quantitative values of TP53-ctDNA during the clinical course were compared with the tumour status.

Results:

Three out of ten patients with TP53 mutations in primary tumours showed detectable TP53 mutation levels in preoperative cfDNA. Although the cfDNA concentrations were not always reflective of the disease course, the ctDNA fraction correlated with the disease status.

Conclusions:

ctDNA may serve as a useful biomarker to monitor gastric cancer progression and residual disease.

Investigation of hydrogen plasma treatment for reducing defects in silicon quantum dot superlattice structure with amorphous silicon carbide matrix

We investigate the effects of hydrogen plasma treatment (HPT) on the properties of silicon quantum dot superlattice films. Hydrogen introduced in the films efficiently passivates silicon and carbon dangling bonds at a treatment temperature of approximately 400°C. The total dangling bond density decreases from 1.1 × 1019 cm-3 to 3.7 × 1017 cm-3, which is comparable to the defect density of typical hydrogenated amorphous silicon carbide films. A damaged layer is found to form on the surface by HPT; this layer can be easily removed by reactive ion etching.

Silicon quantum dot superlattice solar cell structure including silicon nanocrystals in a photogeneration layer

The solar cell structure of n-type poly-silicon/5-nm-diameter silicon nanocrystals embedded in an amorphous silicon oxycarbide matrix (30 layers)/p-type hydrogenated amorphous silicon/Al electrode was fabricated on a quartz substrate. An open-circuit voltage and a fill factor of 518 mV and 0.51 in the solar cell were obtained, respectively. The absorption edge of the solar cell was 1.49 eV, which corresponds to the optical bandgap of the silicon nanocrystal materials, suggesting that it is possible to fabricate the solar cells with silicon nanocrystal materials, whose bandgaps are wider than that of crystalline silicon.

PACS

85.35.Be; 84.60.Jt; 78.67.Bf.