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1.
Oral Dis ; 29(5): 2076-2085, 2023 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-35582815

RESUMEN

OBJECTIVES: To investigate the prognostic impact of preoperative Geriatric Nutritional Risk Index (GNRI) values in older adults undergoing radical surgery for oral squamous cell carcinoma (OSCC). SUBJECTS AND METHODS: This retrospective study included 61 patients ≥65 years old with OSCC (43 men, 18 women; age: 72.1 ± 5.4 years) who underwent radical surgery between 2013 and 2020. Factors influencing overall survival (OS) and disease-free survival (DFS) were examined. RESULTS: Receiver operating characteristic curve analysis indicated that the optimal GNRI value for classifying patients into low-GNRI (<93.7; OS: n = 19 [31.1%], DFS: n = 42 [68.9%]) and high-GNRI groups (≥93.7; OS, n = 19 [31.1%]; DFS, n = 42 [68.9%]) was 93.7. OS and DFS rates were significantly lower in the low-GNRI group than in the high-GNRI group. Univariate analysis indicated that alcohol use, preoperative serum C-reactive protein level, lymphatic invasion, postoperative treatment, and GNRI were significantly correlated with OS, while lymphatic invasion, postoperative treatment, and GNRI were significantly correlated with DFS. In multivariate analysis, only GNRI was significantly correlated with OS. DFS and postoperative treatment were independent predictors of DFS. CONCLUSIONS: Preoperative GNRI may be a significant prognostic factor in older adults with OSCC. GNRI assessment and nutritional intervention may improve prognosis in patients at high nutritional risk.


Asunto(s)
Carcinoma de Células Escamosas , Neoplasias de Cabeza y Cuello , Neoplasias de la Boca , Masculino , Humanos , Femenino , Anciano , Carcinoma de Células Escamosas/cirugía , Pronóstico , Estado Nutricional , Estudios Retrospectivos , Carcinoma de Células Escamosas de Cabeza y Cuello , Evaluación Nutricional , Factores de Riesgo , Neoplasias de la Boca/cirugía
2.
BMC Oral Health ; 21(1): 40, 2021 01 22.
Artículo en Inglés | MEDLINE | ID: mdl-33482792

RESUMEN

BACKGROUND: The systemic inflammatory response and nutritional status of patients with malignant tumors are related to postoperative results. We examined the usefulness of the prognostic nutritional index (PNI) as a prognostic tool in patients with oral squamous cell carcinoma who underwent radical surgery. METHODS: From 2008 to 2019, 102 patients (73 males, 29 females; age, 65.6 ± 9.8 years) who visited our hospital and underwent surgical therapy were included in this study. The endpoint was the total survival period, and the evaluation markers included the lymphocyte count and albumin level in peripheral blood obtained 4 weeks preoperatively, age, sex, alcohol consumption, smoking history, site of the tumor, pathological stage, and surgery status. The PNI was calculated using serum albumin levels and the peripheral blood lymphocyte count. The relationship between the PNI and patient characteristics were analyzed using Fisher's exact test. The Kaplan-Meier method was used to evaluate the survival rate. The survival periods were compared using the log-rank method. We evaluated the prognostic factors for overall survival (OS) and disease-free survival (DFS) in a logistic regression model. RESULTS: The tumor sites included the maxilla (n = 12), buccal mucosa (n = 11), mandible (n = 17), floor of the mouth (n = 9), and tongue (n = 53). The number of patients with stage I, II, III, and IV oral cancers was 28 (27.5%), 34 (27.5%), 26 (33.3%), and 14 (13.7%), respectively. During the observation period, 21 patients died of head and neck cancer. The optimal cut-off PNI value was 42.9, according to the receiver operating characteristic analysis. The proportion of patients with a short OS was lower in those with PNI higher than 42.9, and the 5-year OS in patients with PNI higher and lower than the cut-off value was 62.3% and 86.0%, respectively (P = 0.0105). CONCLUSIONS: The OS of patients with PNI < 42.9 was lower than that of patients with PNI ≥ 42.9. The PNI, which is a preoperative head-to-foot inflammatory marker, can help in estimating the prognosis of oral cancer.


Asunto(s)
Carcinoma de Células Escamosas , Neoplasias de la Boca , Anciano , Carcinoma de Células Escamosas/cirugía , Femenino , Humanos , Masculino , Persona de Mediana Edad , Neoplasias de la Boca/cirugía , Evaluación Nutricional , Estado Nutricional , Pronóstico , Estudios Retrospectivos , Carcinoma de Células Escamosas de Cabeza y Cuello
3.
BMC Oral Health ; 21(1): 121, 2021 03 16.
Artículo en Inglés | MEDLINE | ID: mdl-33726726

RESUMEN

BACKGROUND: A better understanding of the risk factors for postoperative nausea and vomiting (PONV) could improve patient outcomes. This study aimed to analyze the risk factors for PONV and its onset after third molar impaction surgery, and to demonstrate the importance of controlling anesthesia-related factors regardless of patient-specific factors. METHODS: We included patients who reported nausea and vomiting within 12 h of extubation. Patients with incomplete data, those who could not communicate, and those with gastrointestinal disorders were excluded. We evaluated patient-specific risk factors, and the use of volatile anesthetics and intraoperative fentanyl anesthetic-related factors. Multiple logistic regression analysis was performed taking patient background factors into account. RESULTS: In total, 182 patients who underwent disimpaction of the third molar under general anesthesia between January 2017 and December 2018 at Nagoya Ekisaikai Hospital, were included. Approximately 12.6% (n = 23) patients experienced PONV, with no significant difference in terms of sex, smoking status, age, and body mass index compared to patients without PONV. Multiple logistic regression analysis revealed no interaction between fentanyl and volatile anesthetics. The major risk factor for PONV was the use of volatile anesthetics. Patients in whom anesthesia was maintained by volatile anesthetics were 13.35 times more likely to have PONV than those in whom total intravenous anesthesia was induced (P < 0.001). CONCLUSION: Maintenance of anesthesia with volatile anesthetics is a risk factor for PONV.


Asunto(s)
Tercer Molar , Náusea y Vómito Posoperatorios , Anestesia General/efectos adversos , Estudios Transversales , Humanos , Tercer Molar/cirugía , Náusea y Vómito Posoperatorios/epidemiología , Náusea y Vómito Posoperatorios/etiología , Factores de Riesgo
4.
Opt Express ; 28(1): 607-625, 2020 Jan 06.
Artículo en Inglés | MEDLINE | ID: mdl-32118985

RESUMEN

In this work, shape-dependent mid-infrared properties of novel split ring resonator (SRR) metamaterials composed of single-walled carbon nanotube (CNT) forest are investigated. The introduction of the gap and dip shape to the closed ring geometry reduced the total reflectance by 15%, due to the generation of circular currents and LC resonances in SRRs. The increase of the SRR height reduced the total IR reflectance by 25%. Unique one-dimensional anisotropic electric and photonic properties of CNTs, combined with an artificial refractive index induced in SRR circuits, will stimulate the development of new optoelectronics applications.

5.
RSC Adv ; 13(20): 13809-13818, 2023 May 02.
Artículo en Inglés | MEDLINE | ID: mdl-37152562

RESUMEN

Long- and uniform-length, and high-density hair-like carbon nanotubes (CNTs) were produced by CNT growth on sub-micron-sized spherical catalyst supports. The nanosized catalysts (FeO x , CoO x , and NiO x ) that were supported in/on the sub-micron-sized spherical metal oxides (TiO2, ZrO2, SnO2, and CeO2) were prepared via one-step solvothermal and/or two-step impregnation methods. The nanosized catalysts supported in/on the spherical metal oxide supports were converted into CNT conjugates with the CNT-hair morphology via a chemical thermal vapor deposition technique using ethyne gas as a carbon source; the CNTs grew on the central spherical metal oxide core under the base growth process conditions. Among the many types of candidate spherical catalyst materials, the combination of FeO x as a catalyst for CNT growth and ZrO2 as a support led to the best growth of CNT-hair under the reaction conditions, which included a temperature of 730 °C, pressure of 65 Pa, a 10 sccm ethyne gas flow, and a reaction time of 10 s. The CNTs consisted of five-to-eight-layered multi-wall structures with lengths of approximately 3 µm. The CNT-hair that was obtained using the solvothermally embedded catalyst showed higher crystallinity and was dense, thick, and straight, while the corresponding CNT-hair obtained using the impregnated catalyst was slightly sparse, thin, and curly. A unique layer structure constructed using large quantities of uniform CNT-hair, including multiple CNT yarns similar to fuzzy balls or cotton candies, was assembled. The CNT-hair conjugate, specifically constructed in a layer structure with core FeO x /ZrO2 catalysts and tangled CNT yarns, had an appearance similar to frog eggs. Therefore, we successfully prepared suitable catalysts for CNT-hair production and fabricated a layer structure consisting of large numbers of CNT-hair conjugates. The unique structures are expected as a new metamaterial with intriguing physical properties, including isotropic absorption of polarized light and electromagnetic waves.

6.
Am J Hosp Palliat Care ; 40(4): 396-400, 2023 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-35579196

RESUMEN

PURPOSE: As the incidence of oral cancers is on the rise, we aimed to evaluate the usefulness of the prognostic nutritional index (PNI) as a predictor of survival in patients with terminal oral cancer. METHODS: We evaluated the association between laboratory and PNI values and survival days in 33 patients who died of oral cancer between 2004 and 2019 ,excluding 4 patients who underwent gastric banding out of 39with gastric banding. The observation period was from the date of palliative care recommendation to the date of death. RESULTS: A significant difference was observed between the PNI values recorded 3 months before death and those recorded 1 month before death (37.99 ± 6.50 vs 28.86 ± 6.01; P<.05). The median PNI value was associated with the timing of supportive care start and survival (days). CONCLUSION: This study revealed that PNI values decreased toward the end of life and correlated with survival (days), independent of patient characteristics. These findings suggest that the PNI may be useful in the prognostication of end-stage oral cancer.


Asunto(s)
Neoplasias de la Boca , Neoplasias Gástricas , Humanos , Evaluación Nutricional , Estado Nutricional , Pronóstico , Estudios Retrospectivos
7.
Nanomaterials (Basel) ; 12(21)2022 Nov 02.
Artículo en Inglés | MEDLINE | ID: mdl-36364647

RESUMEN

Population growth and the current global weather patterns have heightened the need to optimize solar energy harvesting. Solar-powered water filtration, electricity generation, and water heating have gradually multiplied as viable sources of fresh water and power generation, especially for isolated places without access to water and energy. The unique thermal and optical characteristics of carbon nanotubes (CNTs) enable their use as efficient solar absorbers with enhanced overall photothermal conversion efficiency under varying solar light intensities. Due to their exceptional optical absorption efficiency, low cost, environmental friendliness, and natural carbon availability, CNTs have attracted intense scientific interest in the production of solar thermal systems. In this review study, we evaluated CNT-based water purification, thermoelectric generation, and water heating systems under varying solar levels of illumination, ranging from domestic applications to industrial usage. The use of CNT composites or multilayered structures is also reviewed in relation to solar heat absorber applications. An aerogel containing CNTs was able to ameliorate water filtering performance at low solar intensities. CNTs with a Fresnel lens improved thermoelectric output power at high solar intensity. Solar water heating devices utilizing a nanofluid composed of CNTs proved to be the most effective. In this review, we also aimed to identify the most relevant challenges and promising opportunities in relation to CNT-based solar thermal devices.

8.
Nanomaterials (Basel) ; 12(3)2022 Jan 24.
Artículo en Inglés | MEDLINE | ID: mdl-35159710

RESUMEN

We report the formation of thermally stable catalyst nanoparticles via intermittent sputtering deposition to prevent the agglomeration of the nanoparticles during thermal chemical vapor deposition (CVD) and for the high-density growth of carbon nanotubes (CNTs). The preparation of high-areal-density and small-diameter catalyst nanoparticles on substrates for the high-density growth of CNTs is still a challenging issue because surface diffusion and Ostwald ripening of the nanoparticles induce agglomeration, which results in the low-density growth of large-diameter CNTs during high-temperature thermal CVD. Enhancing the adhesion of nanoparticles or suppressing their diffusion on the substrate to retain a small particle diameter is desirable for the preparation of thermally stable, high-areal-density, and small-diameter catalyst nanoparticles. The intermittent sputtering method was employed to deposit Ni and Fe metal nanoparticles on a substrate for the synthesis of high-areal-density CNTs for Fe nanoparticle catalyst films. The metal particles deposited via intermittent sputtering with an interval time of over 30 s maintained their areal densities and diameters during the thermal CVD process in a vacuum for CNT synthesis. An interval of over 30 s was expected to oxidize the metal particles, which resulted in thermal stability during the CVD process. The intermittent sputtering method is thus a candidate process for the preparation of thermally stable catalyst films for the growth of a high density of long CNTs, which can be combined with the present CNT production process.

9.
Nanomaterials (Basel) ; 12(3)2022 Jan 28.
Artículo en Inglés | MEDLINE | ID: mdl-35159809

RESUMEN

The investigation of the preparation of polystyrene (PS) nanosphere monolayers for the fabrication of carbon nanotube (CNT) forest fishnet metamaterial structures is studied in this paper, as a cheap alternative for top-down patterning methods. The precise control of dry etching conditions resulted in a highly controlled diameter of PS nanobeads, which were then used as a shadow mask for CNT fishnet preparation. The change of the size of the holes from 370 nm to 665 nm resulted in a gradual change of the CNT morphology from multi-walled to single-walled CNTs. The ultraviolet-visible (UV-Vis) reflectance spectra showed that the variation of the hole diameter resulted in the nonlinear light absorption in CNT fishnets that caused the change of the resonance frequency. The change of the fishnet wire width (inductance) and the hole size (capacitance) resulted in the blueshift of the broadband resonance frequency peak. The presented work has a significant potential to allow for the large-scale fabrication of CNT-based fishnet metamaterial structures for applications in energy harvesting, energy storage, solar cells, or optoelectronic devices, such as neuromorphic networks.

10.
Medicine (Baltimore) ; 101(11)2022 Mar 18.
Artículo en Inglés | MEDLINE | ID: mdl-35356942

RESUMEN

ABSTRACT: Systemic inflammatory responses and nutritional status are useful prognostic factors in gastric cancer patients. Since oral hypofunction causes undernutrition, we cross-sectionally investigated whether nutritional biomarkers were affected by the occlusal supporting zone status.In 114 gastric cancer patients, the gastric cancer stage, body mass index, albumin levels, total lymphocyte counts, cholesterol levels, C-reactive protein levels, and 4 nutritional biomarkers - the Glasgow prognostic score (GPS), neutrophil-lymphocyte ratio, prognostic nutrition index (PNI), and controlling nutritional status (CONUT) - were evaluated. Oral conditions were assessed by determining the number of remaining teeth. The occlusal supporting status was based on the Eichner classification. Patients were assigned into 3 groups per their occlusal status, and mean values were compared using the Kruskal-Wallis test. The mean age and body mass index were 72.2 ± 8.5 (50-89) years and 22.0 ± 3.6 (14.8-33.4), respectively. There were 42, 39, 23, and 10 patients in stages I, II, III, and IV, respectively. The mean number of remaining teeth was 18.1 ± 9.5. According to the Eichner classification, there were 45, 42, and 27 patients in groups A, B, and C, respectively. The GPS and neutrophil-lymphocyte ratio values and CONUT frequencies between groups A and C were significantly different (P = .033, P = .00097, P = .04, respectively; Mann-Whitney U test). PNI values were lower in group C with poor occlusal support zones than in group A with stable occlusal support zones.Occlusal supporting zone reductions were undernutrition associated. Eichner Class C patients with few occlusal supporting zones had poor GPS, PNI, and CONUT values and were undernourished.


Asunto(s)
Neoplasias Gástricas , Biomarcadores , Humanos , Evaluación Nutricional , Estado Nutricional , Pronóstico , Estudios Retrospectivos , Neoplasias Gástricas/complicaciones , Neoplasias Gástricas/diagnóstico
11.
Medicine (Baltimore) ; 100(30): e26712, 2021 Jul 30.
Artículo en Inglés | MEDLINE | ID: mdl-34397703

RESUMEN

ABSTRACT: In oral cancer surgery, the decision to perform a tracheotomy is often determined by the surgeon. In this study, we investigated the competency of clinical scoring systems in identifying patients who require tracheotomy and examined the degree of agreement between the surgeon's decision and the indications of various scoring systems. We identified 110 patients who were surgically treated for oral cancer. Of these, 67 patients (44 men and 23 women) who underwent resection and reconstruction were retrospectively analyzed. To derive the score, we evaluated the endpoint of the airway management score using clinical records and images. We divided the patients into two groups based on the Cameron and Gupta scores (tracheotomy and no-tracheotomy groups) and evaluated the degree of agreement with the surgeon's decision by calculating the κ coefficient. The κ coefficients of the Gupta and Cameron scores were 0.61 (95% confidence interval [CI]: 0.40-0.82) and 0.60 (95% CI: 0.38-0.82), respectively. The clinical evaluation of the κ coefficient indicated that the Cameron and Gupta scores agreed fairly with the surgeon's decision. In this study, the Cameron and Gupta scores fairly agreed with the decision of experienced surgeons and were confirmed as acceptable guides for making clinical judgments.


Asunto(s)
Neoplasias de la Boca/cirugía , Índice de Severidad de la Enfermedad , Traqueotomía , Adulto , Anciano , Anciano de 80 o más Años , Toma de Decisiones Clínicas , Femenino , Humanos , Masculino , Persona de Mediana Edad , Estudios Retrospectivos
12.
Medicine (Baltimore) ; 100(46): e27602, 2021 Nov 19.
Artículo en Inglés | MEDLINE | ID: mdl-34797284

RESUMEN

ABSTRACT: The incidence of accidental ingestion and aspiration of foreign body (FB) is likely to occur. Many FBs are discharged spontaneously, but many dental FBs are often sharp and may remain in the pharynx, esophagus, and stomach, causing serious complications such as hemorrhage, asphyxia, perforation of the digestive tract, mediastinal emphysema, peritonitis, and ileus. We aimed to examine which type of dental foreign bodies can be removed by endoscope.In this study, we enrolled 32 patients who were evaluated at the Emergency and Critical Center between January 2014 and December 2019 and who accidentally ingested or aspirated dental FBs. Medical records were reviewed to determine the patients' sex, age, medical history, time from accidental ingestion of a FB to consultation, cause, location, occurrence status, nature of the FB, location of retained FB, treatment, complications, and outcome.We enrolled 32 patients (14 men, 18 women), with a mean age of 74.5 ±â€Š12.8 years. Accidental ingestion at treatment was common. The most frequent site where the FB was retained was upper gastrointestinal tract (26 cases, 81.3%). In this study, endoscopic removal was indicated for dentures under the size of 43.3 mm, for dental FB (except dentures) more than 13.6 mm. In dentures, between the number of missing teeth, clasp, type, and endoscopic removal was not statistically significant.Dentures under the size of 43.3 mm was likely to be removed by endoscope. Dental FB (except dentures) more than the size of 13.6 mm was likely to be removed by endoscope. There were no indications for endoscopic removal except for size.


Asunto(s)
Endoscopía , Cuerpos Extraños/cirugía , Accidentes , Anciano , Anciano de 80 o más Años , Estudios Transversales , Operatoria Dental , Esófago , Femenino , Humanos , Japón/epidemiología , Masculino , Persona de Mediana Edad , Estudios Retrospectivos , Resultado del Tratamiento
13.
Biochem Biophys Res Commun ; 391(4): 1785-91, 2010 Jan 22.
Artículo en Inglés | MEDLINE | ID: mdl-20045673

RESUMEN

Oral cancer is one of the most common cancers worldwide, and squamous-cell carcinoma (OSCC) is the most common phenotype of oral cancer. Although patients with OSCC have poor survival rates and a high incidence of metastasis, the molecular mechanisms of OSCC development have not yet been elucidated. This study investigated whether N-myc downstream-regulated gene 2 (NDRG2) contributes to the carcinogenesis of OSCC, as NDRG2 is reported to be a candidate tumor-suppressor gene in a wide variety of cancers. The down-regulation of NDRG2 mRNA, which was dependent on promoter methylation, was seen in the majority of OSCC cases and in several cases of precancerous leukoplakia with dysplasia. Induction of NDRG2 expression in an HSC-3/OSCC cell line significantly inhibited cell proliferation and decreased colony formation ability on soft agar. The majority of OSCC cell lines showed an activation of PI3K/Akt signaling, and enforced expression of NDRG2 in HSC-3 cells decreased the level of phosphorylated Akt at Serine 473 (p-Akt). Immunohistochemical p-Akt staining was detected in 56.5% of the OSCC tumors, and 80.4% of the tumors were negative for NDRG2 staining. Moreover, positive p-Akt staining was inversely correlated with decreased NDRG2 expression in OSCC tumors with moderate to poor differentiation (p<0.005). Therefore, NDRG2 is a candidate tumor-suppressor gene for OSCC development and probably contributes to the tumorigenesis of OSCC partly via the modulation of Akt signaling.


Asunto(s)
Carcinoma de Células Escamosas/genética , Regulación Neoplásica de la Expresión Génica , Neoplasias de la Boca/genética , Proteínas Supresoras de Tumor/genética , Carcinoma de Células Escamosas/metabolismo , Línea Celular Tumoral , Metilación de ADN , Regulación hacia Abajo , Humanos , Neoplasias de la Boca/metabolismo , Regiones Promotoras Genéticas , Proteínas Proto-Oncogénicas c-akt/metabolismo
14.
Rev Sci Instrum ; 89(3): 033506, 2018 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-29604795

RESUMEN

The circuit design, assembly, and operating tests of a high-frequency and high-voltage (HV) pulsed dc generator (PDG) for capacitively coupled plasma (CCP) discharge inside a vacuum chamber are reported. For capacitive loads, it is challenging to obtain sharp rectangular pulses with fast rising and falling edges, requiring intense current for quick charging and discharging. The requirement of intense current generally limits the pulse operation frequency. In this study, we present a new type of PDG consisting of a pair of half-resonant converters and a constant current-controller circuit connected with HV solid-state power switches that can deliver almost rectangular high voltage pulses with fast rising and falling edges for CCP discharge. A prototype of the PDG is assembled to modulate from a high-voltage direct current (HVdc) input into a pulsed HVdc output, while following an input pulse signal and a set current level. The pulse rise time and fall time are less than 500 ns and 800 ns, respectively, and the minimum pulse width is 1 µs. The maximum voltage for a negative pulse is 1000 V, and the maximum repetition frequency is 500 kHz. During the pulse on time, the plasma discharge current is controlled steadily at the set value. The half-resonant converters in the PDG perform recovery of the remaining energy from the capacitive load at every termination of pulse discharge. The PDG performed with a high energy efficiency of 85% from the HVdc input to the pulsed dc output at a repetition rate of 1 kHz and with stable plasma operation in various discharge conditions. The results suggest that the developed PDG can be considered to be more efficient for plasma processing by CCP.

15.
Nanomicro Lett ; 9(4): 44, 2017.
Artículo en Inglés | MEDLINE | ID: mdl-30393739

RESUMEN

Anisotropic materials, like carbon nanotubes (CNTs), are the perfect substitutes to overcome the limitations of conventional metamaterials; however, the successful fabrication of CNT forest metamaterial structures is still very challenging. In this study, a new method utilizing a focused ion beam (FIB) with additional secondary etching is presented, which can obtain uniform and fine patterning of CNT forest nanostructures for metamaterials and ranging in sizes from hundreds of nanometers to several micrometers. The influence of the FIB processing parameters on the morphology of the catalyst surface and the growth of the CNT forest was investigated, including the removal of redeposited material, decreasing the average surface roughness (from 0.45 to 0.15 nm), and a decrease in the thickness of the Fe catalyst. The results showed that the combination of FIB patterning and secondary etching enabled the growth of highly aligned, high-density CNT forest metamaterials. The improvement in the quality of single-walled CNTs (SWNTs), defined by the very high G/D peak ratio intensity of 10.47, demonstrated successful fine patterning of CNT forest for the first time. With a FIB patterning depth of 10 nm and a secondary etching of 0.5 nm, a minimum size of 150 nm of CNT forest metamaterials was achieved. The development of the FIB secondary etching method enabled for the first time, the fabrication of SWNT forest metamaterials for the optical and infrared regime, for future applications, e.g., in superlenses, antennas, or thermal metamaterials.

16.
Micromachines (Basel) ; 8(7)2017 Jul 03.
Artículo en Inglés | MEDLINE | ID: mdl-30400402

RESUMEN

A DC micro plasma jet for local micro deposition of a:C-H film in the ambient vacuum of scanning electron microscope (SEM) chamber is proposed. Acetylene (C2H2) gas was locally fed into the chamber through an orifice shaped gas nozzle (OGN) at 6.6 sccm in flow rate by applying 80 kPa-inlet pressure with an additional direct pumping system equipped on the SEM chamber. As a cathode, a cut of n-type silicon (Si) wafer was placed right in front of the OGN at 200 µm gap distance. By applying a positive DC voltage to the OGN, C2H2 plasma was generated locally between the electrodes. During discharge, the voltage increased and the current decreased due to deposition of insulating film on the Si wafer with resulting in automatic termination of discharge at the constant source voltage. A symmetric mountain-shaped a:C-H film of 5 µm height was deposited at the center by operation for 15 s. Films were deposited with variation of gas flow rate, gap distance, voltage and current, and deposition time. The films were directly observed by SEM and analyzed by surface profiler and by Raman spectroscopy.

17.
Nanomaterials (Basel) ; 6(11)2016 Nov 07.
Artículo en Inglés | MEDLINE | ID: mdl-28335330

RESUMEN

The relationship between the physical structure of carbon nanotube (CNT) honeycomb structures and their total, diffuse, and specular reflectance is investigated for the first time. It is found that CNT honeycomb structures with average cell areas of smaller than 30 µm² show a higher total reflectance. Particularly, a thinner, highly packed CNT (buckypaper) film, along with a larger wall height and higher ratio of wall height to cell area, markedly increase the total reflectance for cell areas smaller than 30 µm², which means that a higher total area of buckypapers in CNT walls and bottom areas increases the total reflectance, including the diffuse reflectance. It is also found that the total reflection of non-absorbed light in CNT honeycomb structures consists primarily of diffuse reflectance.

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