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1.
BMJ Open ; 14(2): e080539, 2024 Feb 27.
Artículo en Inglés | MEDLINE | ID: mdl-38417952

RESUMEN

INTRODUCTION: Pulmonary vein isolation (PVI) is the cornerstone of radiofrequency (RF) ablation for atrial fibrillation (AF). However, a single ablation strategy does not always achieve the desired therapeutic effect in all patients with persistent AF, and individualised strategies are required for different clinical characteristics. METHODS AND ANALYSIS: This study aimed to determine the optimal catheter ablation strategy for persistent AF by comparing the efficacy of PVI and BCXL (BC: big circles encircling pulmonary vein isolation; XL: unfixed number of lines based on the left atrial substrate). The BCXL-AF study (clinical trial no. ChiCTR2200067081) was designed as a prospective, randomised, parallel-controlled, single-blinded clinical trial. Overall, 400 patients with persistent AF were randomised in a 1:1 ratio into PVI-only and BCXL-individualised ablation groups. Patients randomised to the individualised ablation group will be further categorised into risk strata according to their clinical condition using the actual ablation method determined by the strata. Seven postoperative visits were conducted from discharge to 24 months of age. The primary observation endpoint will be the incidence of atrial tachyarrhythmia (including AF, atrial flutter and atrial tachycardia with a duration of ≥30 s) without using antiarrhythmic drugs after a blank period of 3 months following a single ablation procedure. The BCXL-AF study will assess an optimal approach for persistent AF RF ablation and evaluate the effectiveness of individualised RF ablation strategies in reducing the recurrence rate of AF. ETHICS AND DISSEMINATION: The study protocol was reviewed, and ethical approval was obtained from the Army Medical University Human Ethics Committee (approval number: 2022-484-01). All the participants provided written informed consent. This study was conducted according to the principles of the Declaration of Helsinki and its amendments. The results of this study will be disseminated through manuscript publication and conference presentations. TRIAL REGISTRATION NUMBER: ChiCTR2200067081.


Asunto(s)
Fibrilación Atrial , Ablación por Catéter , Venas Pulmonares , Humanos , Fibrilación Atrial/etiología , Estudios Prospectivos , Atrios Cardíacos , Venas Pulmonares/cirugía , Ablación por Catéter/métodos , Resultado del Tratamiento , Recurrencia , Ensayos Clínicos Controlados Aleatorios como Asunto
2.
Oxid Med Cell Longev ; 2022: 8776566, 2022.
Artículo en Inglés | MEDLINE | ID: mdl-36275900

RESUMEN

Abdominal aortic aneurysm (AAA) refers to local abnormal expansion of the abdominal aorta and mostly occurs in elderly men. MicroRNA (miRNA) is single-stranded RNA consisting of 18-25 nucleotides. It plays a key role in posttranscriptional gene expression and in the regulation of human functions and disease development. miRNA exerts its function mainly through the binding of complementary base pairs to the 3' regulatory region of mRNA transcripts. Therefore, miRNA-related single-nucleotide polymorphisms (miRSNPs) can affect miRNA expression and processing kinetics. miRSNPs can be classified based on their location: miRSNPs within miRNA-producing genes and miRSNPs within miRNA target genes. Increasing evidence indicates that miRSNPs play an important role in the pathogenic kinetics of cardiovascular diseases. The aim of this study was to identify potential miRNAs and integrate them into a miRSNP-based disease-related pathway network, the results of which are of great significance to the interpretation of the potential mechanisms and functions of miRSNPs in the pathogenesis of diseases.


Asunto(s)
Aneurisma de la Aorta Abdominal , MicroARNs , Anciano , Humanos , Masculino , Aneurisma de la Aorta Abdominal/genética , MicroARNs/genética , MicroARNs/metabolismo , Polimorfismo de Nucleótido Simple/genética , ARN Mensajero/genética
3.
Materials (Basel) ; 15(7)2022 Mar 25.
Artículo en Inglés | MEDLINE | ID: mdl-35407752

RESUMEN

In this study, oxide dispersion-strengthened Cu alloy with a Y2O3 content of 1 wt.% was fabricated through citric acid sol-gel synthesis and spark plasma sintering (SPS). The citric acid sol-gel method provides molecular mixing for the preparation of precursor powders, which produces nanoscale and uniformly distributed Y2O3 particles in an ultrafine-grained Cu matrix. The effects of nanoscale Y2O3 particles on the microstructure, mechanical properties and thermal conductivity of the Cu-1wt.%Y2O3 alloy were investigated. The average grain size of the Cu-1wt.%Y2O3 alloy is 0.42 µm, while the average particle size of Y2O3 is 16.4 nm. The unique microstructure provides excellent mechanical properties with a tensile strength of 572 MPa and a total elongation of 6.4%. After annealing at 800 °C for 1 h, the strength of the alloy does not decrease obviously, showing excellent thermal stability. The thermal conductivity of Cu-1wt.%Y2O3 alloy is about 308 Wm-1K-1 at room temperature and it decreases with increasing temperature. The refined grain size, high strength and excellent thermal stability of Cu-1wt.%Y2O3 alloys can be ascribed to the pinning effects of nanoscale Y2O3 particles dispersed in the Cu matrix. The Cu-Y2O3 alloys with high strength and high thermal conductivity have potential applications in high thermal load components of fusion reactors.

4.
iScience ; 25(1): 103581, 2022 Jan 21.
Artículo en Inglés | MEDLINE | ID: mdl-35036861

RESUMEN

We propose CX-ToM, short for counterfactual explanations with theory-of-mind, a new explainable AI (XAI) framework for explaining decisions made by a deep convolutional neural network (CNN). In contrast to the current methods in XAI that generate explanations as a single shot response, we pose explanation as an iterative communication process, i.e., dialogue between the machine and human user. More concretely, our CX-ToM framework generates a sequence of explanations in a dialogue by mediating the differences between the minds of the machine and human user. To do this, we use Theory of Mind (ToM) which helps us in explicitly modeling the human's intention, the machine's mind as inferred by the human, as well as human's mind as inferred by the machine. Moreover, most state-of-the-art XAI frameworks provide attention (or heat map) based explanations. In our work, we show that these attention-based explanations are not sufficient for increasing human trust in the underlying CNN model. In CX-ToM, we instead use counterfactual explanations called fault-lines which we define as follows: given an input image I for which a CNN classification model M predicts class c pred , a fault-line identifies the minimal semantic-level features (e.g., stripes on zebra), referred to as explainable concepts, that need to be added to or deleted from I to alter the classification category of I by M to another specified class c alt . Extensive experiments verify our hypotheses, demonstrating that our CX-ToM significantly outperforms the state-of-the-art XAI models.

5.
J Alzheimers Dis ; 85(2): 779-789, 2022.
Artículo en Inglés | MEDLINE | ID: mdl-34864670

RESUMEN

BACKGROUND: Elevated blood pressure (BP) is a risk factor for cognitive impairment. OBJECTIVE: We aim to explore the association between the duration of hypertension in early adulthood, with cognitive function in midlife. Furthermore, we investigate whether this asssociation is altered among participants with controlled BP. METHODS: This prospective study included 2,718 adults aged 18-30 years without hypertension at baseline who participated in the Coronary Artery Risk Development in Young Adults (CARDIA) Study. Duration of hypertension was calculated based on repeat measurements of BP performed at 2, 5, 7, 10, 15, 20, and 25 years after baseline. Cognitive function was assessed at Year-25 using the Rey Auditory Verbal Learning Test (RAVLT), Digit Symbol Substitution Test (DSST), and Stroop test. RESULTS: After multivariable adjustment, a longer hypertension duration was associated with worse verbal memory (RAVLT, p trend = 0.002) but not with processing speed (DSST, p trend = 0.112) and executive function (Stroop test, p trend = 0.975). Among subgroups of participants with controlled (BP < 140/90 mmHg) and uncontrolled (SBP≥140 mmHg or DBP≥90 mmHg) BP at the time of cognitive assessment (i.e., Year-25 BP), longer duration of hypertension was associated with worse verbal memory. Similar results were observed in subgroups with controlled and uncontrolled average BP prior to cognitive assessment. CONCLUSION: Longer duration of hypertension during early adulthood is associated with worse verbal memory in midlife regardless of current or long-term BP control status. The potential risk of hypertension associated cognitive decline should not be overlooked in individuals with a long duration of hypertension, even if BP levels are controlled.


Asunto(s)
Envejecimiento/fisiología , Presión Sanguínea/fisiología , Cognición/fisiología , Disfunción Cognitiva/epidemiología , Hipertensión/epidemiología , Adulto , Función Ejecutiva , Femenino , Humanos , Estudios Longitudinales , Masculino , Memoria/fisiología , Persona de Mediana Edad , Estudios Prospectivos , Factores de Riesgo , Test de Stroop , Adulto Joven
6.
Materials (Basel) ; 14(21)2021 Nov 07.
Artículo en Inglés | MEDLINE | ID: mdl-34772230

RESUMEN

Intermetallic alloy ZrCo is a good material for storing tritium (T). However, ZrCo is prone to disproportionation reactions during the process of charging and discharging T. Alloying atoms are often added in ZrCo, occupying the Zr or Co site, in order to restrain disproportionation reactions. Meanwhile, T often decays into helium (He), and the purity of T seriously decreases once He escapes from ZrCo. Therefore, it is necessary to understand the influence of alloying atoms on the basic stability property of He. In this work, we perform systematical ab initio calculations to study the stability property of He in ZrCoH3 (ZrCo adsorbs the H isotope, forming ZrCoH3). The results suggest that the He atom will undergo displacements of 0.31 and 0.12 Å when it substitutes for Co and Zr, respectively. In contrast, the displacements are very large, at 0.67-1.09 Å, for He replacing H. Then, we introduce more than 20 alloying atoms in ZrCo to replace Co and Zr in order to examine the influence of alloying atoms on the stability of He at H sites. It is found that Ti, V, Cr, Mn, Fe, Zn, Nb, Mo, Tc, Ru, Ta, W, Re, and Os replacing Co can increase the substitution energy of H by the He closest to the alloying atom, whereas only Cr, Mn, Fe, Mo, Tc, Ru, Ta, W, Re, and Os replacing Co can increase the substitution energy of H by the He next closest to the alloying atom. The influence of the alloying atom substituting Zr site on the substitution energies is inconspicuous, and only Nb, Mo, Ru, Ta, and W increase the substitution energies of H by the He closest to the alloying atom. The increase in the substitution energy may suggest that these alloy atoms are conducive to fix the He atom in ZrCo and avoid the reduction in tritium purity.

7.
Nanomaterials (Basel) ; 11(7)2021 Jul 05.
Artículo en Inglés | MEDLINE | ID: mdl-34361140

RESUMEN

In this work, FeCr-based films with different Y2O3 contents were fabricated using radio frequency (RF) magnetron sputtering. The effects of Y2O3 content on their microstructure and mechanical properties were investigated through scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), inductive coupled plasma emission spectrometer (ICP) and a nanoindenter. It was found that the Y2O3-doped FeCr films exhibited a nanocomposite structure with nanosized Y2O3 particles uniformly distributed into a FeCr matrix. With the increase of Y2O3 content from 0 to 1.97 wt.%, the average grain size of the FeCr films decreased from 12.65 nm to 7.34 nm, demonstrating a grain refining effect of Y2O3. Furthermore, the hardness of the Y2O3-doped FeCr films showed an increasing trend with Y2O3 concentration, owing to the synergetic effect of dispersion strengthening and grain refinement strengthening. This work provides a beneficial guidance on the development and research of composite materials of nanocrystalline metal with a rare earth oxide dispersion phase.

8.
Front Med (Lausanne) ; 8: 654635, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-34109194

RESUMEN

Objective: This study aimed to systematically analyze molecular subtypes and therapeutic targets of liver cancer using integrated multi-omics analysis. Methods: DNA copy number variations (CNVs), simple nucleotide variations (SNVs), methylation, transcriptome as well as corresponding clinical information for liver carcinoma were retrieved from The Cancer Genome Atlas (TCGA). Multi-omics analysis was performed to identify molecular subtypes of liver cancer via integrating CNV, methylation as well as transcriptome data. Immune scores of two molecular subtypes were estimated using tumor immune estimation resource (TIMER) tool. Key mRNAs were screened and prognosis analysis was performed, which were validated using RT-qPCR. Furthermore, mutation spectra were analyzed in the different subtypes. Results: Two molecular subtypes (iC1 and iC2) were conducted for liver cancer. Compared with the iC2 subtype, the iC1 subtype had a worse prognosis and a higher immune score. Two key mRNAs (ANXA2 and CHAF1B) were significantly related to liver cancer patients' prognosis, which were both up-regulated in liver cancer tissues in comparison to normal tissues. Seventeen genes with p < 0.01 differed significantly for SNV loci between iC1 and iC2 subtypes. Conclusion: Our integrated multi-omics analyses provided new insights into the molecular subtypes of liver cancer, helping to identify novel mRNAs as therapeutic targets and uncover the mechanisms of liver cancer.

9.
Zhen Ci Yan Jiu ; 46(6): 480-5, 2021 Jun 25.
Artículo en Chino | MEDLINE | ID: mdl-34190451

RESUMEN

For a long time, Chinese medicine has attached great importance to "pulse diagnosis for patients before acupuncture treatment", which emphasizes the close relationship between pulse diagnosis and acupuncture. Pulse diagnosis information is closely related to acupuncture research and runs through the whole process of diagnosis and treatment. However, the lack of repeatable and quantifiable real-time detection means of pulse diagnosis information has affected the application of pulse diagnosis in acupuncture research. Photo plethysmo graphy (PPG) technology has the advantages of convenient acquisition, low price, non-invasive, easy to use and so on. Under the guidance of TCM diagnosis theory, this paper discussed the principle and characteristics of fingertip volumetric pulse wave, studied its relationship with Cunkou pulse diagnosis, developed a new fingertip blood volumetric pulse wave measuring instrument, explored the acquisition and measurement methods of volumetric pulse wave signal, and proposed the relationship between the measuring instrument and acupuncture research. It can provide basic tools and data analysis and support for acupuncture research.


Asunto(s)
Terapia por Acupuntura , Moxibustión , Frecuencia Cardíaca , Humanos , Medicina Tradicional China
10.
ACS Appl Mater Interfaces ; 13(6): 7725-7734, 2021 Feb 17.
Artículo en Inglés | MEDLINE | ID: mdl-33529524

RESUMEN

The formation mechanism of the partially crystallized ultrathin layer at the interface between GaN and SiNx grown by low-pressure chemical vapor deposition was analyzed based on the chemical components of reactants and products detected by high-resolution sputter depth profile analysis by X-ray photoelectron spectroscopy. A reasonable mass action equation for the formation of Si2N2O was proposed from the feasibility analysis of the Gibbs free energy changes of the reaction. The high-energy-activated Ga2O on the surface likely assists in the synthesis of the crystallized components. A well-defined 1ML θ-Ga2O3 transition interface was inserted into Si2N2O/GaN pure interface supercell slabs to edit the unsaturated state of the bonds. Low-density states can be achieved when the effective charges of the unsaturated atoms are adjusted to a certain interval.

11.
BMC Cardiovasc Disord ; 21(1): 57, 2021 01 28.
Artículo en Inglés | MEDLINE | ID: mdl-33509096

RESUMEN

BACKGROUND: Copper is an essential trace metal with potential interest for cardiovascular effects. Few studies have explored the association between copper and blood pressure in children and adolescents. METHOD: We conducted a cross-sectional analysis of 1242 children and adolescents aged 8-17 years who participated in the 2011 to 2016 National Health and Nutrition Examination Survey. Using 2017 American Academy of Pediatrics guidelines, elevated blood pressure (EBP) was defined as a mean systolic and/or diastolic blood pressure (BP) ≥ 90th percentile for sex, age, and height for children aged 1-12 years and systolic BP ≥ 120 mmHg or diastolic BP ≥ 80 mmHg for adolescent age 13-17 years. Mean serum copper was 114.17 µg/dL. RESULTS: After multiple adjustments, dose-response analyses revealed that EBP was associated with progressively higher serum copper concentrations in a nonlinear trend. In comparison with the lowest quartile of serum copper concentrations, the adjusted odds of EBP for the highest quartile was 5.26 (95% confidence interval, 2.76-10.03). CONCLUSION: Our results suggested that high serum copper concentrations were significantly associated with EBP in US children and adolescents.


Asunto(s)
Presión Sanguínea , Cobre/sangre , Hipertensión/sangre , Hipertensión/fisiopatología , Adolescente , Factores de Edad , Biomarcadores/sangre , Niño , Estudios Transversales , Femenino , Humanos , Hipertensión/epidemiología , Masculino , Encuestas Nutricionales , Medición de Riesgo , Factores de Riesgo , Factores de Tiempo , Estados Unidos/epidemiología
12.
RSC Adv ; 11(15): 8643-8653, 2021 Feb 23.
Artículo en Inglés | MEDLINE | ID: mdl-35423390

RESUMEN

Oxidation corrosion of steel is a universal problem in various industries and severely accelerated in nuclear reactors. First-principles calculations are performed to explore the dissolution and diffusion properties of interstitial oxygen in the body-centered-cubic iron grain boundaries Σ3〈110〉(111) and Σ5〈001〉(310). Solution energies indicate that interstitial oxygen atoms prefer to dissolve in body-centered-cubic iron, and energetically segregate to grain boundaries. Energy barriers show that oxygen atoms would segregate towards Σ3〈110〉(111) with a low energy barrier. However, they concentrate to the transition region of Σ5〈001〉(310) due to the high-energy barrier in the transition zone. When O atoms arrive at grain boundaries, they would stay there due to the larger solution energy and diffusion energy barrier in grain boundaries compared to that in the defect-free Fe bulk. These results indicate that O atoms would prefer to diffuse through the bulk, and oxidize grain boundaries. This study provides insight into oxidation phenomena in experiments and necessary parameters for future studies on the oxidation of steel under irradiation in nuclear reactors.

13.
J Hematol Oncol ; 13(1): 88, 2020 07 03.
Artículo en Inglés | MEDLINE | ID: mdl-32620135

RESUMEN

Due to acromegaly's insidious onset and slow progression, its diagnosis is usually delayed, thus causing severe complications and treatment difficulty. A convenient screening method is imperative. Based on our previous work, we herein developed a new automatic diagnosis and severity-classification model for acromegaly using facial photographs by deep learning on the data of 2148 photographs at different severity levels. Each photograph was given a score reflecting its severity (range 1~3). Our developed model achieved a prediction accuracy of 90.7% on the internal test dataset and outperformed the performance of ten junior internal medicine physicians (89.0%). The prospect of applying this model to real clinical practices is promising due to its potential health economic benefits.


Asunto(s)
Acromegalia/diagnóstico , Cefalometría/métodos , Aprendizaje Profundo , Diagnóstico por Computador/métodos , Cara/anomalías , Índice de Severidad de la Enfermedad , Adulto , Algoritmos , Conjuntos de Datos como Asunto , Autoevaluación Diagnóstica , Femenino , Humanos , Procesamiento de Imagen Asistido por Computador , Masculino , Persona de Mediana Edad , Modelos Teóricos , Fotograbar , Sensibilidad y Especificidad
14.
Materials (Basel) ; 13(1)2020 Jan 01.
Artículo en Inglés | MEDLINE | ID: mdl-31906401

RESUMEN

The strengthening energy or embrittling potency of an alloying element is a fundamental energetics of the grain boundary (GB) embrittlement that control the mechanical properties of metallic materials. A data-driven machine learning approach has recently been used to develop prediction models to uncover the physical mechanisms and design novel materials with enhanced properties. In this work, to accurately predict and uncover the key features in determining the strengthening energies, three machine learning methods were used to model and predict strengthening energies of solutes in different metallic GBs. In addition, 142 strengthening energies from previous density functional theory calculations served as our dataset to train three machine learning models: support vector machine (SVM) with linear kernel, SVM with radial basis function (RBF) kernel, and artificial neural network (ANN). Considering both the bond-breaking effect and atomic size effect, the nonlinear kernel based SVR model was found to perform the best with a correlation of r2 ~ 0.889. The size effect feature shows a significant improvement to prediction performance with respect to using bond-breaking effect only. Moreover, the mean impact value analysis was conducted to quantitatively explore the relative significance of each input feature for improving the effective prediction.

15.
J Phys Chem Lett ; 10(11): 3190-3196, 2019 Jun 06.
Artículo en Inglés | MEDLINE | ID: mdl-31144818

RESUMEN

The 2O-tαP phase is a bilayer phosphorene stacking twisted by ∼70.5° standing out from all the potential candidates predicted by our previous work. Here, by linear response theory, we directly verified that the 2O-tαP phase preserves the intrinsic features of phonon spectrum of the existing AB phase, reflecting a stable thermodynamic behavior. Then we provided three distinct fingerprints to help finding this new phase: upon comparison to the existing shifting bilayer phosphorene, the in-plane elastic constants showed a much weaker anisotropic response, providing a characteristic mechanical criterion; the calculated Raman spectrum revealed for the low frequency rang the layer-breathing mode and the out-of-plane twisted mode, L-A1 and L-A2, both of which together stabilize the twisted structure; in particular, the simulated scanning tunneling microscope image presented recognizable cross stripes, which should withstand an examination of exfoliated bilayer and few-layer black phosphorus.

16.
Artículo en Inglés | MEDLINE | ID: mdl-29994529

RESUMEN

Max-min distance analysis (MMDA) performs dimensionality reduction by maximizing the minimum pairwise distance between classes in the latent subspace under the homoscedastic assumption, which can address the class separation problem caused by the Fisher criterion, but is incapable of tackling heteroscedastic data properly. In this paper, we propose two heteroscedastic MMDA (HMMDA) methods to employ the differences of class covariances. Whitened HMMDA (WHMMDA) extends MMDA by utilizing the Chernoff distance as the separability measure between classes in the whitened space. Orthogonal HMMDA (OHMMDA) incorporates the maximization of the minimal pairwise Chernoff distance and the minimization of class compactness into a trace quotient formulation with an orthogonal constraint of the transformation, which can be solved by bisection search. Two variants of OHMMDA further encode the margin information by using only neighboring samples to construct the intra-class and inter-class scatters. Experiments on several UCI datasets and two face databases demonstrate the effectiveness of the HMMDA methods.

17.
Proc Natl Acad Sci U S A ; 114(49): 12894-12899, 2017 12 05.
Artículo en Inglés | MEDLINE | ID: mdl-29162690

RESUMEN

High-pressure single-crystal X-ray diffraction method with precise control of hydrostatic conditions, typically with helium or neon as the pressure-transmitting medium, has significantly changed our view on what happens with low-density silica phases under pressure. Coesite is a prototype material for pressure-induced amorphization. However, it was found to transform into a high-pressure octahedral (HPO) phase, or coesite-II and coesite-III. Given that the pressure is believed to be hydrostatic in two recent experiments, the different transformation pathways are striking. Based on molecular dynamic simulations with an ab initio parameterized potential, we reproduced all of the above experiments in three transformation pathways, including the one leading to an HPO phase. This octahedral phase has an oxygen hcp sublattice featuring 2 × 2 zigzag octahedral edge-sharing chains, however with some broken points (i.e., point defects). It transforms into α-PbO2 phase when it is relaxed under further compression. We show that the HPO phase forms through a continuous rearrangement of the oxygen sublattice toward hcp arrangement. The high-pressure amorphous phases can be described by an fcc and hcp sublattice mixture.

18.
IEEE Trans Image Process ; 25(6): 2610-2619, 2016 06.
Artículo en Inglés | MEDLINE | ID: mdl-27071172

RESUMEN

Canonical correlation analysis (CCA) is an effective way to find two appropriate subspaces in which Pearson's correlation coefficients are maximized between projected random vectors. Due to its well-established theoretical support and relatively efficient computation, CCA is widely used as a joint dimension reduction tool and has been successfully applied to many image processing and computer vision tasks. However, as reported, the traditional CCA suffers from overfitting in many practical cases. In this paper, we propose sufficient CCA (S-CCA) to relieve CCA's overfitting problem, which is inspired by the theory of sufficient dimension reduction. The effectiveness of S-CCA is verified both theoretically and experimentally. Experimental results also demonstrate that our S-CCA outperforms some of CCA's popular extensions during the prediction phase, especially when severe overfitting occurs.

19.
Sci Rep ; 6: 23738, 2016 Mar 29.
Artículo en Inglés | MEDLINE | ID: mdl-27020839

RESUMEN

The damage layer of a W (100) crystal irradiated with 120 eV hydrogen ions at a fluence of up to 1.5 × 10(25)/m(2) was investigated by scanning electron microscopy and conductive atomic force microscopy (CAFM). The periodic surface degeneration of the W crystal at a surface temperature of 373 K was formed at increasing hydrogen fluence. Observations by CCD camera and CAFM indicate the existence of ultrathin surface layers due to low-energy H irradiation. The W surface layer can contain a high density of nanometer-sized defects, resulting in the thermal instability of W atoms in the surface layer. Our findings suggest that the periodic surface degeneration of the W crystal can be ascribed to the lateral erosion of W surface layers falling off during the low-energy hydrogen irradiation. Our density functional theory calculations confirm the thermal instability of W atoms in the top layer, especially if H atoms are adsorbed on the surface.

20.
Nanoscale ; 4(15): 4515-21, 2012 Aug 07.
Artículo en Inglés | MEDLINE | ID: mdl-22695781

RESUMEN

In this work, we described a facile route for the fabrication of free-standing single-walled carbon nanotubes (SWCNT)-CdSe quantum dots (QDs) hybrid ultrathin films and investigated their optoelectronic conversion properties. A free-standing SWCNT film with thickness of ∼36 nm was firstly prepared via vacuum filtration. The film was then immersed into the pre-synthesized oleic acid-capped CdSe QDs (average diameter of 3.5 nm) solution, where CdSe QDs anchored spontaneously onto the surface of SWCNT film to produce SWCNT-CdSe QDs hybrid film. By using pure SWCNT films in different thicknesses as bottom and top electrodes, a flexible all-carbon electrode optoelectronic conversion device with sandwich structure of SWCNT film (thickness of ∼200 nm)/SWCNT-CdSe QDs hybrid film (thickness of ∼36 nm)/SWCNT film (thickness of ∼36 nm) was constructed to generate optoelectronic conversion under illumination of solar-simulated light. Our results demonstrated that the all-carbon electrode structure was effective for charge separation and a sensitive and stable photocurrent signal could be produced in such a device. In addition, our SWCNT-CdSe QDs hybrid film exhibited high flexibility and durability. No clear change in the resistance of the film was detected under bending in various bending angles.


Asunto(s)
Compuestos de Cadmio/química , Nanotubos de Carbono/química , Puntos Cuánticos , Compuestos de Selenio/química , Carbono/química , Electrodos , Ácido Oléico/química , Dispositivos Ópticos
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