Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 36
Filtrar
1.
Opt Express ; 32(2): 1176-1187, 2024 Jan 15.
Artículo en Inglés | MEDLINE | ID: mdl-38297675

RESUMEN

We propose a fast quality of transmission (QoT) estimation method based on cascaded artificial neural networks (ANNs) for intensity modulation-direct detection (IMDD) systems. The proposed method can calculate the bit error rate of three-span 36 km transmission within 0.7 seconds while taking account of the deterministic waveform distortion caused by the chromatic dispersion and self-phase modulation (SPM).

2.
J Clin Med ; 12(8)2023 Apr 17.
Artículo en Inglés | MEDLINE | ID: mdl-37109253

RESUMEN

INTRODUCTION: Wire-guided cannulation (WGC) during endoscopic retrograde cholangiopancreatography (ERCP) is a selective biliary cannulation technique aimed at improving the successful selective biliary cannulation rate and reducing the rate of post-ERCP pancreatitis (PEP) incidence. This study aimed to evaluate the effectiveness of angled-tip guidewires (AGW) vs. straight-tip guidewires (SGW) for biliary cannulation via WGC by a trainee. METHODS: We conducted a prospective, single-center, open-labeled, randomized, and controlled trial. Fifty-seven patients were enrolled in this study and assigned randomly to two groups (Group A to S and Group S to A). In this study, we started selective biliary cannulation via WGC with an AGW or an SGW for 7 min. If cannulation was unsuccessful, the other guidewire was used, and cannulation was continued for another 7 min (cross-over method). RESULTS: The selective biliary cannulation success rate over 14 min was significantly higher with an AGW compared with an SGW over 14 min (57.8% vs. 34.3%, p = 0.04) and for the second 7-min segment (36.4% vs. 0%, p = 0.04). No significant difference was found for adverse events such as pancreatitis between the two guidewires. CONCLUSIONS: Our results suggest that an AGW is recommended for WGC performed by a trainee.

3.
J Chem Inf Model ; 63(5): 1529-1541, 2023 03 13.
Artículo en Inglés | MEDLINE | ID: mdl-36821519

RESUMEN

We apply moving root-mean-square deviation (mRMSD), which does not require a reference structure, as a method for analyzing protein dynamics. This method can be used to calculate the root-mean-square deviation (RMSD) of structure between two specified time points and to analyze protein dynamics behavior through time series analysis. We applied this method to the Trp-cage trajectory calculated by the Anton supercomputer and found that it shows regions of stable states as well as the conventional RMSD. In addition, we extracted a characteristic structure in which the side chains of Asp1 and Arg16 form hydrogen bonds near the most stable structure of the Trp-cage. We also determined that ≥20 ns is an appropriate time interval to investigate protein dynamics using mRMSD. Applying this method to NuG2 protein, we found that mRMSD can be used to detect regions of metastable states in addition to the stable state. This method can be applied to molecular dynamics simulations of proteins whose stable structures are unknown.


Asunto(s)
Péptidos , Proteínas , Péptidos/química , Proteínas/química , Pliegue de Proteína , Simulación de Dinámica Molecular , Computadores
4.
Opt Express ; 30(26): 48030-48041, 2022 Dec 19.
Artículo en Inglés | MEDLINE | ID: mdl-36558718

RESUMEN

This paper investigates an auxiliary management and control channel (AMCC) signal extraction method using digital signal processing (DSP) blocks with 3-step moving averaging that allows a single coherent receiver to receive main signal and AMCC signal simultaneously. Receiver sensitivity characteristics versus the modulation index (MI) and average number of the proposed DSP blocks are elucidated. Based on the results, we discuss a policy for designing the parameters. Experiments apply the design policy to achieve receiver sensitivity of -41.8 dBm with both 25 Gbit/s QPSK main signal and 128 kbit/s AMCC signal; the main signal sensitivity penalty is just 0.2 dB.

5.
Chemistry ; 28(19): e202200132, 2022 Apr 01.
Artículo en Inglés | MEDLINE | ID: mdl-35174555

RESUMEN

Tri- and tetra-fluorinated [7]helicenes are photolabile and undergo a double fluorine atom transfer. Herein, we show that the transferred product further undergoes a skeletal transformation on silica gel. The transformation begins with activation of the allylic C-F bond on the silanol surface. Then, the resulting carbocation readily undergoes a regioselective nucleophilic aromatic substitution with water, depending on the position of the fluorine substituents. Hexafluoro-2-propanol also activated the allylic C-F bond and acted as a nucleophile. These findings support the generation of a highly reactive cationic electrophilic intermediate in the successive transformations involving fluorine atoms.

6.
J Clin Med ; 10(14)2021 Jul 09.
Artículo en Inglés | MEDLINE | ID: mdl-34300215

RESUMEN

A prospective study was conducted in patients with early-stage gastric cancer to determine the efficacy and safety of acupuncture stimulation as an antispasmodic compared with conventional medication during the procedure of endoscopic submucosal dissection (ESD) of the upper gastrointestinal tract. This study was a prospective single blinded quasi-randomized controlled trial. Seventy-three patients who were scheduled to undergo ESD for gastric cancer at Aizu Medical Center between 19 February 2016 and 30 June 2016 were assessed for eligibility for the study. Sixty out of 73 patients were included in the study and assigned into two intervention groups: medication group (MG) and acupuncture group (AG). Ease of the procedure was evaluated using modified NIWA classification (MNC) by endoscopist considering the frequency and amplitude of the upper gastrointestinal peristalsis. For the statistical analysis, Mann-Whitney test was used to compare the differences of MNC values (baseline and end of procedure) between two groups. The difference of MNC found in the AG (-2.00 (-3.0 to -2.0)) was significantly greater than that in the MG (-1.00 (-2.0 to -1.0), p < 0.0001, Mann-Whitney test). We consider that acupuncture to the abdomen could be an alternative antispasmodic method during upper gastrointestinal endoscopic procedure.

7.
Opt Express ; 29(11): 17499-17509, 2021 May 24.
Artículo en Inglés | MEDLINE | ID: mdl-34154291

RESUMEN

This paper introduces the concept of a symmetric 10 Gbit/s high power-budget TDM-PON based on digital coherent technology and confirms its feasibility through a bidirectional transmission experiment with a transmission distance of 40 km and power budget of more than 50 dB. Burst-mode upstream 10 Gbit/s binary-phase-shift-keying (BPSK) signals synchronized by the clock recovered from downstream 10 Gbit/s NRZ signals are detected by using an optical pre-amplifier and coherent detection based on real-time burst-mode digital signal processing (DSP) in the optical line terminal (OLT). The real-time DSP implements coefficient handover in the adaptive equalizer to allow the reception of burst-mode upstream BPSK signals with short preamble length. An experimental bit error performance evaluation of the real-time burst-mode DSP yields the receiver sensitivity of -45.1 dBm for upstream burst-mode BPSK with a preamble length of 1.3 µs. For downstream signals, the receiver sensitivity of -38.9 dBm is achieved by using a chirp-controlled transmitter with optical post-amplifier so as to avoid the signal distortion created by the chromatic dispersion of single mode fiber (SMF) when the launched power is increased.

8.
Cell ; 183(5): 1420-1435.e21, 2020 11 25.
Artículo en Inglés | MEDLINE | ID: mdl-33159857

RESUMEN

Gastroenteropancreatic (GEP) neuroendocrine neoplasm (NEN) that consists of neuroendocrine tumor and neuroendocrine carcinoma (NEC) is a lethal but under-investigated disease owing to its rarity. To fill the scarcity of clinically relevant models of GEP-NEN, we here established 25 lines of NEN organoids and performed their comprehensive molecular characterization. GEP-NEN organoids recapitulated pathohistological and functional phenotypes of the original tumors. Whole-genome sequencing revealed frequent genetic alterations in TP53 and RB1 in GEP-NECs, and characteristic chromosome-wide loss of heterozygosity in GEP-NENs. Transcriptome analysis identified molecular subtypes that are distinguished by the expression of distinct transcription factors. GEP-NEN organoids gained independence from the stem cell niche irrespective of genetic mutations. Compound knockout of TP53 and RB1, together with overexpression of key transcription factors, conferred on the normal colonic epithelium phenotypes that are compatible with GEP-NEN biology. Altogether, our study not only provides genetic understanding of GEP-NEN, but also connects its genetics and biological phenotypes.


Asunto(s)
Bancos de Muestras Biológicas , Tumores Neuroendocrinos/patología , Organoides/patología , Animales , Cromosomas Humanos/genética , Genotipo , Humanos , Péptidos y Proteínas de Señalización Intercelular/metabolismo , Neoplasias Intestinales/genética , Neoplasias Intestinales/patología , Masculino , Ratones , Modelos Genéticos , Mutación/genética , Tumores Neuroendocrinos/genética , Neoplasias Pancreáticas/genética , Neoplasias Pancreáticas/patología , Fenotipo , Neoplasias Gástricas/genética , Neoplasias Gástricas/patología , Transcriptoma/genética , Secuenciación Completa del Genoma
9.
Intern Med ; 59(3): 345-355, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-32009088

RESUMEN

Objective To prolong the health expectancy, it is important to prevent age-related diseases, such as osteoporosis and cerebrovascular disease, which are major causes of a bedridden state. Early predictable biomarkers for these diseases are urgently required in the clinical setting. Three members of the fibroblast growth factor (FGF) family - FGF19, FGF21, and FGF23 - are designated as endocrine FGFs and play crucial roles in various metabolic processes. We tried to clarify the clinical utility of endocrine FGFs as biomarkers for age-related diseases in elderly patients. Methods We examined the serum endocrine FGF levels and analyzed their association with various clinical parameters in 73 outpatients >60 years old as a single-center cross-sectional study. Results In a multivariable linear regression analysis, FGF19 was associated with ALT, a history of cardiovascular disease, and medication with active vitamin D3. FGF21 was associated with the estimated glomerular filtration rate (eGFR), triglyceride level, and hypertension. FGF23 was associated with the eGFR and the serum levels of 1,25-dihydroxy vitamin D3 and TRACP5b. In addition, a receiver operating characteristics analysis revealed that the measurement of FGF21 and FGF23 was useful for detecting chronic kidney disease (CKD) and its complications, including cardiovascular disease and metabolic bone disorder. Conclusion The measurement of FGF21 and FGF23 may be useful for evaluating CKD and its complications. Using serum endocrine FGFs as biomarkers for age-related conditions may help prevent elderly patients from entering a bedridden state.


Asunto(s)
Biomarcadores/sangre , Factores de Crecimiento de Fibroblastos/sangre , Enfermedades Metabólicas/etiología , Enfermedades Metabólicas/fisiopatología , Insuficiencia Renal Crónica/complicaciones , Insuficiencia Renal Crónica/fisiopatología , Anciano , Anciano de 80 o más Años , Estudios Transversales , Femenino , Factor-23 de Crecimiento de Fibroblastos , Humanos , Japón , Masculino , Persona de Mediana Edad
10.
Gastroenterol Res Pract ; 2019: 5810653, 2019.
Artículo en Inglés | MEDLINE | ID: mdl-31781192

RESUMEN

BACKGROUND AND OBJECTIVES: Recently, a 21G Menghini-type needle for EUS-guided fine-needle aspiration biopsy (EUS-FNAB) has been developed. The stylet of the EUS Sonopsy CY™ remains inside the needle during aspiration. Therefore, it is expected to obtain higher-quality histological core specimens without crushing the material or blood contamination. The aim of this study is to evaluate the feasibility and diagnostic accuracy of EUS-FNAB of solid pancreatic masses with this new biopsy needle. METHODS: A total of 30 patients with solid pancreatic masses who underwent EUS-FNAB with two different types of needles, EUS Sonopsy™ and ProCore™, were included in a prospective, randomized, controlled, crossover study. All the pancreatic masses were punctured with the two needles and were randomized regarding the order of the needle to be used. The primary outcome was to compare the diagnostic accuracy and the rates of tissue acquisition of the two needles. RESULTS: The tissue acquisition rate was not significantly different between the EUS Sonopsy CY™ needle and the ProCore™ needle (78.6% vs. 82.1%, P = 1.00). The histological diagnostic accuracy was also similar between the two needles (73% vs. 80%, P = .63). There was also no difference regarding the accuracy of cytology alone and the combination of both histological and cytological assessments between the EUS Sonopsy CY™ needle and the ProCore™ needle (90% vs. 87%, P = 1.00 and 90% vs. 90%, P = 1.00, respectively). CONCLUSIONS: EUS Sonopsy CY™ is a reliable device for EUS-FNAB of solid pancreatic masses.

11.
Biosci Trends ; 13(3): 216-224, 2019 Jul 22.
Artículo en Inglés | MEDLINE | ID: mdl-31168022

RESUMEN

Protein glycosylation is a diverse form of post-translational modification. Two to three consecutive O-linked N-acetylgalactosamines (Tn-antigens) are recognized by antibodies such as MLS128. MLS128 mAb inhibited cell growth and bound to a 110 kDa glycoprotein (GP) in LS180 and HT29 colon cancer cells. However, purification and identification of the 110 kDa GP was unsuccessful due to its low abundance. The present study used a highly sophisticated and sensitive mass spectrometry method to identify proteins immunoprecipitated with MLS128 and separated by two-dimensional gel electrophoresis. Three desmosome components were identified. Of these, desmocollin and desmoglein shared many similar characteristics, including molecular mass, pI, and potential Tn-antigen sites. Western blotting analyses of LS180 cell lysates revealed a common 110 kDa band recognized by MLS128 and anti-desmocollin, but not by anti-desmoglein. Immunofluorescence microscopy of LS180 cells revealed that desmocollin is membrane-bound, while desmoglein is primarily localized in the cytosol. Confocal microscopy demonstrated colocalization of the desmocollin-specific antibody with the MLS128 antibody on the cell membrane, suggesting that desmocollin may contain Tn-antigens recognized by MLS128. Treatment of LS180 cells with siRNA to knock down desmocollin expression or a desmocollin-specific antibody decreased cell viability, suggesting a critical role for this protein in cell growth and survival. N-glycosidase F digestion of the 110 kDa GP and desmocollin suggested that although both proteins contain N-glycosylation sites, they are not identical. These findings suggest that desmocollin colocalizes with the 110 kDa GP and that growth inhibition induced by the MLS128 antibody may be mediated through a mechanism that involves desmocollin.


Asunto(s)
Neoplasias del Colon/metabolismo , Desmocolinas/metabolismo , Glicoproteínas/metabolismo , Anticuerpos Monoclonales/inmunología , Antígenos de Carbohidratos Asociados a Tumores/inmunología , Antígenos de Carbohidratos Asociados a Tumores/metabolismo , Western Blotting , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Neoplasias del Colon/inmunología , Desmocolinas/inmunología , Glicoproteínas/inmunología , Células HT29 , Humanos , Microscopía Confocal , Péptido-N4-(N-acetil-beta-glucosaminil) Asparagina Amidasa/metabolismo , Espectrometría de Masas en Tándem
12.
PLoS One ; 14(2): e0212427, 2019.
Artículo en Inglés | MEDLINE | ID: mdl-30794598

RESUMEN

BACKGROUND AND AIMS: Various studies have been previously conducted on the diagnosis of lymphadenopathy as benign or malignant, but the results vary. These studies did not describe the inter-rater agreement on the EUS features of lymphadenopathy. In this study, we evaluate the inter-rater agreement on EUS features and propose EUS diagnostic norms for lymphadenopathy based on inter-rater agreement. METHOD: A total of 68 lymph nodes subjected to EUS-fine needle aspiration (FNA) were reviewed by five endoscopic experts. The EUS features evaluated lymph node size, shape, border, margin, echogenicity, homogeneity, and the hilum of the lymph node. Inter-rater agreement (multi-rater kappa statics) was performed. We established new criteria using results with a high degree of inter-rater agreement from EUS features and compared them with the former criteria. RESULT: There was a moderate agreement on shape, kappa (K) = 0.44 (95% confidence interval [CI]: 0.34-0.54), and fair agreement on echogenicity, homogeneity, border, and hilum of the lymph node, K (95% CI) = 0.33 (0.17-0.38), 0.34 (0.26-0.35), 0.22 (0.21-0.31), and 0.22 (0.11-0.26), respectively. This resulted in the establishment of new EUS diagnostic criteria using shape, long axis > 20 mm and short axis > 10 mm. New criteria were superior to old criteria (area under the curve 0.82 vs 0.52, P < 0.001). CONCLUSION: EUS diagnostic criteria for lymphadenopathy based on inter-rater agreement were more accurate than old criteria. This result will be useful for the diagnosis of lymphadenopathy.


Asunto(s)
Endosonografía/métodos , Linfadenopatía/diagnóstico por imagen , Neoplasias Abdominales/diagnóstico por imagen , Anciano , Anciano de 80 o más Años , Biopsia con Aguja Fina , Endosonografía/normas , Endosonografía/estadística & datos numéricos , Femenino , Humanos , Masculino , Neoplasias del Mediastino/diagnóstico por imagen , Persona de Mediana Edad , Variaciones Dependientes del Observador , Estudios Retrospectivos
13.
Gastroenterol Res Pract ; 2018: 7490961, 2018.
Artículo en Inglés | MEDLINE | ID: mdl-30158967

RESUMEN

OBJECTIVES: Recently, opportunities to encounter superficial nonampullary duodenal epithelial tumor (SNADET) have increased. EMR and ESD are performed to treat SNADET. However, the rate of perforation is higher than that of other gastrointestinal lesions, regardless of which method is used. Underwater EMR (UW-EMR) is immersion treatment of SNADET, which has low risk of perforation and can remove lesions safely and completely. In the present study, we retrospectively investigated patients in whom UW-EMR was performed to evaluate the feasibility and safety of UW-EMR for the treatment of SNADET. METHODS: The primary endpoint was to evaluate the feasibility of UW-EMR for the treatment of SNADET, and secondary objective was to determine the operation's safety. RESULTS: There were 14 participants, with a total of 16 lesions, who underwent UW-EMR between August 2015 and December 2017. Histological heteromorphism revealed that seven patients had low-grade adenoma, seven had high-grade adenoma, and two had adenocarcinoma. En bloc resection was performed in 14 lesions. In two patients, nodular lesions were observed in the scar and biopsy confirmed recurrences. There were no serious adverse events including bleeding or perforation. CONCLUSIONS: UW-EMR may be a safe and effective treatment method for SNADET, if its therapeutic indication is adequately considered.

14.
Clin Med Insights Case Rep ; 11: 1179547618791571, 2018.
Artículo en Inglés | MEDLINE | ID: mdl-30090022

RESUMEN

Ovarian cancer often occurs distant metastasis to the peritoneum, liver, lungs, and lymph nodes. However, there has been no reported case of direct metastasis to the duodenal major papilla. We herein reported 72-year-old woman with history of ovarian cancer surgery 11 years ago presenting with obstructive jaundice. Abdominal CT showed a small mass in the distal bile duct. Forceps biopsy from the small mass was done under endoscopic retrograde cholangiography, and histologic examination revealed adenocarcinoma. Pancreaticoduodenectomy was performed and diagnosed immunohistochemically direct metastasis to the papilla from ovarian cancer. The duodenal major papilla is known to be rich in lymph vessels, and these lymph vessels are considered the likely pathway of metastasis in this case.

15.
Org Biomol Chem ; 16(33): 5969-5972, 2018 08 22.
Artículo en Inglés | MEDLINE | ID: mdl-29947406

RESUMEN

Catalytic alkylation reactions of weakly acidic carbonyl and related pronucleophiles such as amides, esters, and sulfonamides with substituted alkenes have been reported. In the presence of a strong Brønsted base catalyst system, potassium hexamethyldisilazide and 18-crown-6 ether, the desired reactions proceeded in high yields at ambient temperature with a wide substrate scope. These are atom-economical catalytic alkylation reactions of carbonyl and related compounds.

16.
Clin Med Insights Case Rep ; 11: 1179547618775095, 2018.
Artículo en Inglés | MEDLINE | ID: mdl-29844708

RESUMEN

While some reports are available regarding metachronous gastric metastasis from renal cell carcinoma after treatment, there are few reports of primary lesion detection based on the diagnosis of a gastric metastatic lesion. The patient in this case was an 80-year-old woman who underwent upper gastrointestinal endoscopy after having developed anorexia 2 months earlier. A submucosal tumor with central umbilication was found in the gastric greater curvature. Endoscopic ultrasonography revealed a solid and hypoechoic mass with hypervascularity on color Doppler imaging that proliferated mainly within the submucosal layer. There was partial exposure of the tumor on the superficial layer. Biopsy was performed, as a neuroendocrine tumor was suspected; however, histopathological findings with immunostaining revealed gastric metastasis from clear renal cell carcinoma. Subsequently, contrast enhanced computed tomography showed right renal cell carcinoma and liver metastasis. Thus, molecularly targeted drug treatment was initiated by the Department of Urology. Our findings indicate that a primary lesion can be identified and prognosis can be assumed based on biopsy of the gastric metastatic lesion. Immunostaining of biopsy samples collected endoscopically could help achieve definite diagnosis.

17.
Phys Rev E ; 97(3-1): 033310, 2018 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-29776112

RESUMEN

An algorithm of the tensor renormalization group is proposed based on a randomized algorithm for singular value decomposition. Our algorithm is applicable to a broad range of two-dimensional classical models. In the case of a square lattice, its computational complexity and memory usage are proportional to the fifth and the third power of the bond dimension, respectively, whereas those of the conventional implementation are of the sixth and the fourth power. The oversampling parameter larger than the bond dimension is sufficient to reproduce the same result as full singular value decomposition even at the critical point of the two-dimensional Ising model.

18.
Clin Med Insights Case Rep ; 11: 1179547617749226, 2018.
Artículo en Inglés | MEDLINE | ID: mdl-29371789

RESUMEN

Gastric neuroendocrine tumors (GNETs) are rare lesions characterized by enterochromaffin-like cells of the stomach. Optimal management of GNETs has not yet been definitively determined. Endoscopic resection is approximately recommended for small GNETs associated with hypergastrinemia. However, endoscopic resection might present risk of perforation or positive vertical margin because neuroendocrine tumors occur in the deep mucosa, with some invading the submucosa. In this case, a patient with type A chronic atrophic gastritis had a small subepithelial lesion in a deep submucosal layer, and we diagnosed it as GNET using endoscopic ultrasound-guided fine-needle aspiration biopsy using a forward-viewing and curved linear-array echoendoscope. Moreover, our results show that laparoscopic and endoscopic cooperative surgery with regional lymph node dissection is a safe and feasible procedure for GNETs, especially those that cross to the muscularis propria. We suggest this approach as one therapeutic option for GNETs because it safely minimizes resection and is less invasive.

19.
Endosc Ultrasound ; 7(2): 110-118, 2018.
Artículo en Inglés | MEDLINE | ID: mdl-28685746

RESUMEN

BACKGROUND AND OBJECTIVES: The Rosemont classification (RC) was developed as a consensus-based standard for the diagnosis of chronic pancreatitis (CP) by endoscopic ultrasonography (EUS), however, it is more complicated than the conventional scoring system. We have noticed that in the early stages of CP, it is not unusual to observe pancreas with abnormal appearance coexisting with the areas of normal parenchyma. The aim of this study was to investigate the validity of a "normal" pancreas appearance and to evaluate the usefulness of modified diagnostic criteria in comparison to the traditional EUS criteria and the RC. PATIENTS AND METHODS: One hundred and seventy-seven patients who had undergone both EUS and endoscopic retrograde pancreatography (ERP) within 2 months were enrolled in the study, and patients with pancreatic cancer were excluded from the study. ERP findings were used as the gold standard for the diagnosis of CP. The EUS images obtained were classified according to both the RC and our new modified criteria. The latter includes an additional criterion to the modified traditional criteria: fine-reticular pattern (F-RP) was defined as a normal pancreatic parenchyma. We compared the accuracy between the new modified EUS criteria and the RC. RESULTS: (1) Normal or equivocal findings on ERP were obtained for 132 patients; 113 patients had F-RP on EUS. In contrast, F-RP was found in only 6 out of 45 CP cases on ERP (P < 0.0001). (2) We investigated the diagnostic capability of our new criteria for endoscopic retrograde cholangiopancreatography normal/equivocal pancreas compared to the traditional criteria. In cases where fewer than two points were defined as normal, the incidence of normal pancreas was significantly higher based on the new criteria than on the traditional criteria (P = 0.002). (3) No significant differences were found between the new criteria and the RC across all ERP grades. CONCLUSION: Our new proposed "normal-added EUS criteria" for diagnosing CP was equivalent to the RC.

20.
Inorg Chem ; 56(17): 10535-10542, 2017 Sep 05.
Artículo en Inglés | MEDLINE | ID: mdl-28812880

RESUMEN

The electronic structures of 35 A2+B4+O3 ternary cubic perovskite oxides, including their hypothetical chemical compositions, were calculated by a hybrid functional method with the expectation that peculiar electronic structures and unique carrier transport properties suitable for semiconductor applications would be hidden in high-symmetry cubic perovskite oxides. We found unique electronic structures of Si-based oxides (A = Mg, Ca, Sr, and Ba, and B = Si). In particular, the unreported cubic BaSiO3 has a very narrow band gap (4.1 eV) compared with conventional nontransition-metal silicates (e.g., ∼9 eV for SiO2 and the calculated value of 7.3 eV for orthorhombic BaSiO3) and a small electron effective mass (0.3m0, where m0 is the free electron rest mass). The narrow band gap is ascribed to the nonbonding state of Si 3s and the weakened Madelung potential. The existence of the predicted cubic perovskite structure of BaSiO3 was experimentally verified by applying a high pressure of 141 GPa. The present finding indicates that it could be possible to develop a new transparent oxide semiconductor of earth abundant silicates if the symmetry of its crystal structure is appropriately chosen. Cubic BaSiO3 is a candidate for high-performance oxide semiconductors if this phase can be stabilized at room temperature and ambient pressure.

SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA