RESUMEN

Lithium cobalt oxide (LCO) is a highly significant material for the positive electrodes of lithium-ion batteries. Due to the correlation between crystal morphology and electrochemical performance in the layered rock-salt structure, LCO with crystal morphology exhibiting anisotropy demonstrates superior charge-discharge characteristics. In this study, various morphologies of LCO were synthesized via hydrothermal synthesis using a plate-like precursor. Under conditions without agitation, a hexagonal plate-like LCO was synthesized, while a spherical LCO was obtained with agitation during synthesis. The particle morphology was investigated by using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Furthermore, in the performance evaluation of positive electrode materials for lithium-ion batteries, the hexagonal plate-like LCO exhibited a larger charge-discharge capacity compared to the spherical LCO.

RESUMEN

The sixth-generation communication system (6G) is the next-generation communication system and is expected to be operational in 2030. The following areas will use 6G: the frequency band employed in 6G is expected to be 100 GHz or higher, necessitating additional reduction of the dielectric constant and dielectric loss in the substrate material. In this study, we examined the effects of compounding various phases of alumina with different shapes and crystal phases on the dielectric constant and dielectric loss of cyclo-olefin polymer (COP) compounds. It was confirmed that the smaller the particle size, the higher the effect on the dielectric loss. The dielectric loss decreased from 1.6 × 10-3 of COP to 1.2 × 10-3 when the smallest filler was added at 30 wt %.

RESUMEN

It has been reported that the flexoelectric effect could be dominant in the nanoscale. The discrepancy between theory and experiments on the frequency dependence of the dielectric constant of an ordered assembly of BaTiO3 nanocubes is nearly resolved by assuming the coexistence of flexo- and ferro-electric effects. Although flexoelectric polarizations perpendicular to the applied alternating electric field contribute to the dielectric constant, those parallel to the electric field do not contribute because the magnitude of the flexoelectric polarization does not change due to the mismatch of strain at the interface of the nanocubes. On the other hand, some dielectric response is possible for the ferroelectric component of the polarization parallel to the electric field.

RESUMEN

Due to the strain gradient near each surface of a BaTiO3 nanocube in their ordered assembly, electric polarization appears due to flexoelectric effect. The magnitude of the flexoelectric polarization could be one order of magnitude larger than that of ferroelectric spontaneous polarization of BaTiO3. Thus, dielectric response of an assembly could be dominated by that of the flexoelectric polarization if there is no ferroelectric domain-wall motion. Numerical simulations of the dielectric response of a BaTiO3 nanocube in an ordered assembly are performed from kHz to MHz range based on a dynamic model of flexoelectric polarization assuming anharmonic potential. The calculated temperature dependence of the dielectric constant is consistent with the experimental data of high dielectric constant with nearly-flat temperature dependence. It is suggested that high dielectric constant with nearly-flat temperature dependence is not originated in ferroelectric nature of BaTiO3 nanocubes but originated in flexoelectric polarization in nanocubes which is also seen in non-ferroelectric materials.

RESUMEN

Highly oriented, regularly assembled nanocrystalline films have recently emerged as attractive new functional materials. In this study, we deposited a BaTiO3 (BT) nanocube dispersion on a Si substrate by electrospraying, resulting in a dense, regularly assembled BT nanocrystalline film. X-ray diffraction analysis revealed that applying a voltage between the electrospray nozzle and the Si substrate during electrospraying caused the BT nanocubes to form a regular array in the 200 plane aligned perpendicularly to the substrate. The volume fraction of BT nanocubes in the 200 plane in the assembly was estimated by the orientation distribution function analysis to be about 50%. The formation of this regularly assembled layer was determined to be linked to the interaction between the vaporized solvent and the substrate, enabled by the enhanced wettability under the electric field. Electrospray deposition has potential applications in the manufacture of nanocrystalline assembled films for nanofunctional devices.

RESUMEN

Assembly of nanocrystals into ordered two- or three-dimensional arrays is an essential technology to achieve their application in novel functional devices. Among a variety of assembly techniques, evaporation-induced self-assembly (EISA) is one of the prospective approaches because of its simplicity. Although EISA has shown its potential to form highly ordered nanocrystal arrays, the formation of uniform nanocrystal arrays over large areas remains a challenging subject. Here, we introduce a new EISA method and demonstrate the formation of large-scale highly ordered monolayers of barium titanate (BaTiO3, BT) nanocubes at the air-water interface. In our method, the addition of an extra surfactant to a water surface assists the EISA of BT nanocubes with a size of 15⁻20 nm into a highly ordered arrangement. We reveal that the compression pressure exerted by the extra surfactant on BT nanocubes during the solvent evaporation is a key factor in the self-assembly in our method. The BT nanocube monolayers transferred to substrates have sizes up to the millimeter scale and a high out-of-plane crystal orientation, containing almost no microcracks and voids.

RESUMEN

Ordered structures of barium titanate (BT) nanocubes, strontium titanate (ST) nanocubes and BT/ST nanocubes mixture were directly fabricated on Si and Pt-coated Si substrates using a capillary force assisted assembly method. The morphology of self-assembled structures was observed using field emission scanning electron microscopy (FE-SEM) and scanning probe microscopy (SPM). It was revealed that nanocubes were arranged with various degrees of ordering to develop multilayer and monolayer regions at the surface of substrates. The elemental mapping of the structure consisting of the nanocubes mixture was also investigated by transmission electron microscopy (TEM) with an energy dispersive X-ray spectroscopy (EDX). It was revealed that BT and ST nanocubes coexisted homogeneously in the structure and had possibility to be arranged in order to each other. The piezoresponse properties obtained by scanning probe microscopy (SPM) indicated that the hetero-interface between BT and ST nanocubes would introduce anomaly in piezoelectric properties.

RESUMEN

OBJECTIVE: Sonographically guided radiofrequency ablation is usually one of the most effective treatments for hepatocellular carcinoma. However, the localization of the tumor is a major limiting factor in the use of a sonographically guided procedure. In our experience, sonographic examination with artificial pleural effusion has improved the visualization of hepatocellular carcinomas under the diaphragm. We investigated the safety, benefits, and local efficacy of radiofrequency ablation with artificial pleural effusion. SUBJECTS AND METHODS: Twenty-five lesions in 23 patients were treated using radiofrequency ablation with artificial pleural effusion, for which 5% glucose solution was injected into the pleural cavity. RESULTS: Artificial pleural effusion allowed us to visualize the whole tumor on gray-scale sonography in 22 lesions that were not detectable or were poorly visible and to obtain a safer and easier puncture line in 14 lesions. In 23 (92%) of the 25 lesions, artificial pleural effusion was helpful in performing percutaneous radiofrequency ablation. Complete necrosis after radiofrequency ablation was obtained in 22 (88%) of the 25 lesions. During a mean (+/- SD) follow-up period of 10.6 +/- 6.5 months, local recurrence at the ablation site was diagnosed in only one (4.5%) of the 22 lesions. Mild cough in three patients and mild dyspnea in two patients were observed as adverse effects of artificial pleural effusion, but these effects were temporary. Oxygen saturation of the blood during artificial pleural effusion was slightly decreased. CONCLUSION: Radiofrequency ablation with artificial pleural effusion is a safe and beneficial treatment option that offers excellent local control through visualization of hepato-cellular carcinomas under the diaphragm.

Asunto(s)

Carcinoma Hepatocelular/diagnóstico por imagen , Carcinoma Hepatocelular/cirugía , Ablación por Catéter/métodos , Neoplasias Hepáticas/diagnóstico por imagen , Neoplasias Hepáticas/cirugía , Anciano , Anciano de 80 o más Años , Femenino , Humanos , Masculino , Persona de Mediana Edad , Derrame Pleural , Ultrasonografía

RESUMEN

Objectives: We investigated how radiofrequency ablation (RFA) alone or the combination with transcatheter arterial embolization (TAE-RFA) for hepatocellular carcinoma (HCC) affects the liver parenchymal function of underlying chronic liver disease to find a predictive factor for selecting appropriate candidates for RFA. Methods: In 53 HCC patients (RFA alone, 25; TAE-RFA, 28), liver laboratory tests and development of complications were monitored until 6 months after treatments. Serum albumin deteriorated within 1 month and recovered after 6 months in both groups, whereas the elevation of the Pugh score continued in RFA alone group and that of serum bilirubin continued in TAE-RFA group until 6 months. The elevation of Pugh score 6 months after RFA was significantly more frequent in patients with a high pre-treatment Pugh score (>/=8 points) than in those with a low pre-treatment Pugh score (<8 points). Complications after RFA were observed in 11 of the 53 patients: temporary complications in 5, refractory ascites in 6. Refractory ascites developed in only patients with a high pre-treatment Pugh score. Conclusion: Liver parenchymal functions in patients with a low pre-treatment Pugh score were transiently deteriorated by RFA or TAE-RFA. However, in patients with a high Pugh score, RFA or TAE-RFA induces long-term deterioration of the liver parenchymal functions and causes serious complications. Therefore, patients with a Pugh score >/=8 points would not be good candidates for RFA or TAE-RFA.

RESUMEN

The purpose of this study was to evaluate the detection rate of tumor vessels and vascularity in hepatocellular carcinoma (HCC) by contrast-enhanced coded US using Levovist, and to compare with conventional color/power Doppler US (CDUS) and dynamic CT. Ninety nodules (72 hypo/isoechoic nodules, 18 hyperechoic nodules) in 61 patients were studied. We observed tumor vessels by continuous transmission at the early vascular phase (40 s following administration of Levovist) and vascularity by intermittent transmission (intervals of 2-3 s) at the late vascular phase (40 to approximately 120 s). The detection rate of tumor vessels at the early vascular phase was 97% in hypo/isoechoic nodules and 70% in hyperechoic nodules with high density in dynamic CT being higher than that by CDUS. Tumor vascularity at the late vascular phase in hypo/isoechoic and hyperechoic nodules was hyper-enhancement in 78 and 40%, iso-enhancement in 19 and 40%, and hypo-enhancement in 3 and 0%, respectively. The detection rates of tumor vessels and vascularity in hyperechoic nodules were similar to those by CDUS. The detection rates of tumor vessels and vascularity were not affected by the tumor size in HCC tumors with high density in dynamic CT. Contrast-enhanced US with Levovist was superior to CDUS and equal to dynamic CT to assess tumor vessels in hypo/isoechoic nodules. Although it was equal to CDUS for hyperechoic nodules, this modality is useful in evaluating tumor hemodynamics.

Asunto(s)

Carcinoma Hepatocelular/irrigación sanguínea , Carcinoma Hepatocelular/diagnóstico por imagen , Neoplasias Hepáticas/irrigación sanguínea , Neoplasias Hepáticas/diagnóstico por imagen , Tomografía Computarizada por Rayos X , Adulto , Anciano , Anciano de 80 o más Años , Medios de Contraste , Femenino , Humanos , Aumento de la Imagen , Masculino , Persona de Mediana Edad , Polisacáridos , Ultrasonografía

RESUMEN

We report a case involving well-differentiated hepatocellular carcinoma (HCC) developing to HCC with sarcomatous changes after radiofrequency ablation (RFA). In a cirrhotic patient with both hepatitis B surface antigen and hepatitis C virus RNA, a well-differentiated HCC with a diameter of 2 cm was detected in segment IV of the liver. A combination of transcatheter arterial embolization and percutaneous ethanol injection (PEI) was performed and, after 8 months, PEI was performed for recurrent tumors. Fifteen months after the first treatment, a recurrent tumor measuring 3.5 cm in diameter was detected in segment IV, which was demonstrated as well-differentiated HCC by tumor biopsy, and treated by RFA. Although the treated lesion was reduced to 2.5 cm in diameter 6 months after RFA, the tumor rapidly enlarged to 6 cm in diameter 2 months later and progressed to lymph node metastasis. Aspiration biopsy showed spindle-shaped sarcomatoid cells with positive staining for both vimentin and keratin. The patient died of HCC progression 10 months after RFA. Autopsy findings showed both sarcomatoid cells and trabecular HCC cells. The sarcomatoid cells had metastasized to the lymph nodes and distant organs. This is the first case illustrating a sarcomatous HCC after RFA. Of interest, RFA may be related to the development of sarcomatous HCC.