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1.
Nanotechnology ; 2021 Dec 29.
Artigo em Inglês | MEDLINE | ID: mdl-34965523

RESUMO

Cu with nanotwin (NT) possesses great electrical, mechanical, and thermal properties and has potential for electronic applications. Various studies have reported the effect of NT orientation on Cu mechanical properties. However, its effect on Cu stress-relaxation behavior has not been clarified, particularly in nano-scale. In this study, Cu nanopillars with various orientations were examined by a picoindenter under constant strain and observed by in-situ TEM. The angles between the twin plane and the loading direction in the examined nanopillars were 0°, 60°, to 90°, and a benchmark pillar of single-crystal Cu without NT was examined. The stress drops were respectively 10%, 80%, 4%, and 50%. Owing to the interaction by NT, the dislocation behavior in nanopillars was different from that in bulk or in thin film samples. Especially, the rapid slip path of dislocations to go to the free surface of the nanopillar induced a dislocation-free zone in the 0° nanopillar, which led to work-softening. On the contrary, a high dislocation density was observed in the 90° nanopillar, which was generated by dislocation interaction and obstruction of dislocation slip by twin planes, and it led to work-hardening. The findings reveal the NT orientation in Cu nanopillars affected stress relaxation significantly.

2.
Tzu Chi Med J ; 33(3): 288-293, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34386368

RESUMO

Objective: This study aimed to evaluate whether adjuvant radiotherapy (RT) can improve the treatment outcome of patients with locally advanced gastric cancer who underwent extensive lymph node dissection (ELND). Materials and Methods: This retrospective study included patients with gastric cancer pathological stages IIA-IIIC at Taipei Tzu Chi Hospital between 2008 and 2015. Patients (a) aged >80 years, (b) with distant metastasis at diagnosis, (c) with coexisting malignancies, (d) who did not complete the prescribed RT course, and (e) who died 1 month after surgery were excluded. Among 420 patients diagnosed with gastric cancer, 98 were included. Results: The median follow-up was 24.5 months. Of 39 patients who underwent adjuvant RT, 38 also received adjuvant chemotherapy (CT). Of 59 patients who did not receive adjuvant RT, only 34 received adjuvant CT. ELND was performed in 67.3% of the patients. The 5-year overall survival (OS) rate was 40%. In the univariate analyses, adjuvant CT regimen, 5-fluorouracil + leucovorin, was associated with worst outcome, while TS-1 was associated with better survival outcome (P = 0.018). The number of involved lymph nodes was strongly related to the OS and disease-free survival (DFS) (P < 0.001). We tried using different numbers of involved lymph nodes as a cutoff point and found that adjuvant RT significantly improved both OS and DFS in patients whose involved lymph nodes were ≥4 (OS, P = 0.017; DFS, P = 0.015). In multivariate analyses, better DFS was associated with negative surgical margin (P = 0.04), earlier disease stage (P = 0.001), adjuvant radiotherapy (P = 0.045), and adjuvant CT regimen TS-1 (P = 0.001). Conclusion: Adjuvant RT could improve DFS of patients with locally advanced gastric cancer with or without ELND. When the number of involved lymph nodes is ≥4, adjuvant RT is strongly suggested.

3.
Nano Lett ; 21(8): 3355-3363, 2021 Apr 28.
Artigo em Inglês | MEDLINE | ID: mdl-33856816

RESUMO

Herein, we aim to develop a facile method for the fabrication of mechanical metamaterials from templated polymerization of thermosets including phenolic and epoxy resins using self-assembled block copolymer, polystyrene-polydimethylsiloxane with tripod network (gyroid), and tetrapod network (diamond) structures, as templates. Nanoindentation studies on the nanonetwork thermosets fabricated reveal enhanced energy dissipation from intrinsic brittle thermosets due to the deliberate structuring; the calculated energy dissipation for gyroid phenolic resins is 0.23 nJ whereas the one with diamond structure gives a value of 0.33 nJ. Consistently, the gyroid-structured epoxy gives a high energy dissipation value of 0.57 nJ, and the one with diamond structure could reach 0.78 nJ. These enhanced properties are attributed to the isotropic periodicity of the nanonetwork texture with plastic deformation, and the higher number of struts in the tetrapod diamond network in contrast to tripod gyroid, as confirmed by the finite element analysis.

4.
Small ; 17(17): e2007171, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33711202

RESUMO

Band structure by design in 2D layered semiconductors is highly desirable, with the goal to acquire the electronic properties of interest through the engineering of chemical composition, structure, defect, stacking, or doping. For atomically thin transition metal dichalcogenides, substitutional doping with more than one single type of transition metals is the task for which no feasible approach is proposed. Here, the growth of WS2 monolayer is shown codoped with multiple kinds of transition metal impurities via chemical vapor deposition controlled in a diffusion-limited mode. Multielement embedment of Cr, Fe, Nb, and Mo into the host lattice is exemplified. Abundant impurity states thus generate in the bandgap of the resultant WS2 and provide a robust switch of charging/discharging states upon sweep of an electric filed. A profound memory window exists in the transfer curves of doped WS2 field-effect transistors, forming the basis of binary states for robust nonvolatile memory. The doping technique presented in this work brings one step closer to the rational design of 2D semiconductors with desired electronic properties.

5.
J Chem Phys ; 153(18): 184902, 2020 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-33187411

RESUMO

Self-assembly of amphiphilic polymers in water is of fundamental and practical importance. Significant amounts of free unimers and associated micellar aggregates often coexist over a wide range of phase regions. The thermodynamic and kinetic properties of the microphase separation are closely related to the relative population density of unimers and micelles. Although the scattering technique has been employed to identify the structure of micellar aggregates as well as their time-evolution, the determination of the population ratio of micelles to unimers remains a challenging problem due to their difference in scattering power. Here, using small-angle neutron scattering (SANS), we present a comprehensive structural study of amphiphilic n-dodecyl-PNIPAm polymers, which shows a bimodal size distribution in water. By adjusting the deuterium/hydrogen ratio of water, the intra-micellar polymer and water distributions are obtained from the SANS spectra. The micellar size and number density are further determined, and the population densities of micelles and unimers are calculated to quantitatively address the degree of micellization at different temperatures. Our method can be used to provide an in-depth insight into the solution properties of microphase separation, which are present in many amphiphilic systems.

6.
Nanomaterials (Basel) ; 10(10)2020 Sep 26.
Artigo em Inglês | MEDLINE | ID: mdl-32993122

RESUMO

We demonstrate the fabrication of free-standing inverse opals with gradient pores via a combination of electrophoresis and electroplating techniques. Our processing scheme starts with the preparation of multilayer colloidal crystals by conducting sequential electrophoresis with polystyrene (PS) microspheres in different sizes (300, 600, and 1000 nm). The critical factors affecting the stacking of individual colloidal crystals are discussed and relevant electrophoresis parameters are identified so the larger PS microspheres are assembled successively atop of smaller ones in an orderly manner. In total, we construct multilayer colloidal crystals with vertical stacking of microspheres in 300/600, 300/1000, and 300/600/1000 nm sequences. The inverse opals with gradient pores are produced by galvanostatic plating of Ni, followed by the selective removal of colloidal template. Images from scanning electron microscopy exhibit ideal multilayer close-packed structures with well-defined boundaries among different layers. Results from porometer analysis reveal the size of bottlenecks consistent with those of interconnected pore channels from inverse opals of smallest PS microspheres. Mechanical properties determined by nanoindentation tests indicate significant improvements for multilayer inverse opals as compared to those of conventional single-layer inverse opals.

7.
J Phys Chem Lett ; 11(17): 7334-7341, 2020 Sep 03.
Artigo em Inglês | MEDLINE | ID: mdl-32813537

RESUMO

The influence of lithium chloride (LiCl) on the hydration structure of anionic micelles of sodium dodecyl sulfate (SDS) in water was studied using the contrast-variation small-angle neutron scattering (SANS) technique. In the past, extensive computational studies have shown that the distribution of invasive water plays a critical role in the self-organization of SDS molecules and the stability of the assemblies. However, in past scattering studies the degree of the hydration level was not examined explicitly. Here, a series of contrast-variation SANS data was analyzed to extract the intramicellar radial distributions of invasive water and SDS molecules from the evolving spectral lineshapes caused by the varying isotopic ratios of water. By addressing the intramicellar inhomogeneous distributions of water and SDS molecules, a detailed description of how the counterion association influences the micellization behavior of SDS molecules is provided. The extension of our method can be used to provide an in-depth insight into the micellization phenomenon, which is commonly found in many soft matter systems.

8.
Nano Lett ; 18(8): 4993-5000, 2018 08 08.
Artigo em Inglês | MEDLINE | ID: mdl-29985625

RESUMO

We observed the small-size-induced hardening and plasticity of brittle ionic MgO as a result of abnormally triggered dislocation gliding on a non-charge-balanced slip system. The indentation tests of ⟨111⟩ MgO pillars revealed an increased hardness with decreasing pillar size, and the tips of the pillars that were ≤200 nm were plastically deformed. The in situ compression tests of ⟨111⟩ MgO nanopillars in transmission electron microscopy verified aligned dislocation-mediated plasticity on the {111}⟨110⟩ and {100}⟨110⟩ systems rather than the charge-balanced {110}⟨110⟩ slip system.

9.
Sci Rep ; 7(1): 9727, 2017 08 29.
Artigo em Inglês | MEDLINE | ID: mdl-28852077

RESUMO

This study reports a mechanical stress-based technique that involves scratching or imprinting to write textured graphite conducting wires/patterns in an insulating amorphous carbon matrix for potential use as interconnects in future carbonaceous circuits. With low-energy post-annealing below the temperature that is required for the thermal graphitization of amorphous carbon, the amorphous carbon phase only in the mechanically stressed regions transforms into a well aligned crystalline graphite structure with a low electrical resistivity of 420 µΩ-cm, while the surrounding amorphous carbon matrix remains insulating. Micro-Raman spectra with obvious graphitic peaks and high-resolution transmission electron microscopic observations of clear graphitic lattice verified the localized phase transformation of amorphous carbon into textured graphite exactly in the stressed regions. The stress-induced reconstruction of carbon bonds to generate oriented graphitic nuclei is believed to assist in the pseudo-self-formation of textured graphite during low-temperature post annealing.

10.
J Natl Compr Canc Netw ; 13(12): 1510-8, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-26656520

RESUMO

BACKGROUND: Changes over time in preferences for life-sustaining treatments (LSTs) at end of life (EOL) in different patient cohorts are not well established, nor is the concept that LST preferences represent more than 2 groups (uniformly prefer/not prefer). PURPOSE: The purpose of this study was to explore heterogeneity and changes in patterns of LST preferences among 2 independent cohorts of terminally ill patients with cancer recruited a decade apart. METHODS: Preferences for cardiopulmonary resuscitation, intensive care unit care, cardiac massage, intubation with mechanical ventilation, intravenous nutritional support, nasogastric tube feeding, and dialysis were surveyed among 2,187 and 2,166 patients in 2003-2004 and 2011-2012, respectively. Patterns and changes in LST preferences were examined by multigroup latent class analysis. RESULTS: We identified 7 preference classes: uniformly preferring, uniformly rejecting, uniformly uncertain, favoring nutritional support but rejecting other treatments, favoring nutritional support but uncertain about other treatments, favoring intravenous nutritional support with mixed rejection of or uncertainty about other treatments, and preferring LSTs except intubation with mechanical ventilation. Probability of class membership decreased significantly over time for the uniformly preferring class (15.26%-8.71%); remained largely unchanged for the classes of uniformly rejecting (41.71%-40.54%) and uniformly uncertain (9.10%-10.47%), and favoring nutritional support but rejecting (20.68%-21.91%) or uncertain about (7.02%-5.47%) other treatments, and increased significantly for the other 2 classes. The LST preferences of Taiwanese terminally ill patients with cancer are not a homogeneous construct and shifted toward less-aggressive treatments over the past decade. CONCLUSIONS: Identifying LST preference patterns and tailoring interventions to the unique needs of patients in each LST preference class may lead to the provision of less-aggressive EOL care.


Assuntos
Cuidados para Prolongar a Vida , Neoplasias/epidemiologia , Neoplasias/terapia , Preferência do Paciente , Assistência Terminal , Doente Terminal , Estudos Transversais , Humanos , Cuidados para Prolongar a Vida/métodos , Cuidados para Prolongar a Vida/tendências , Taiwan/epidemiologia , Assistência Terminal/métodos , Assistência Terminal/tendências
11.
Sci Rep ; 4: 4162, 2014 Feb 24.
Artigo em Inglês | MEDLINE | ID: mdl-24561911

RESUMO

We report multi-component high-entropy materials as extraordinarily robust diffusion barriers and clarify the highly suppressed interdiffusion kinetics in the multi-component materials from structural and thermodynamic perspectives. The failures of six alloy barriers with different numbers of elements, from unitary Ti to senary TiTaCrZrAlRu, against the interdiffusion of Cu and Si were characterized, and experimental results indicated that, with more elements incorporated, the failure temperature of the barriers increased from 550 to 900°C. The activation energy of Cu diffusion through the alloy barriers was determined to increase from 110 to 163 kJ/mole. Mechanistic analyses suggest that, structurally, severe lattice distortion strains and a high packing density caused by different atom sizes, and, thermodynamically, a strengthened cohesion provide a total increase of 55 kJ/mole in the activation energy of substitutional Cu diffusion, and are believed to be the dominant factors of suppressed interdiffusion kinetics through the multi-component barrier materials.

12.
Nano Lett ; 13(11): 5247-54, 2013 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-24063581

RESUMO

In situ nanoscopic observations of healthy and osteoporotic bone nanopillars under compression were performed. The structural-mechanical property relationship at the atomic scale suggests that cortical bone performance is correlated to the feature, arrangement, movement, distortion, and fracture of hydroxyapatite nanocrystals. Healthy bone comprising tightly bound mineral nanocrystals shows high structural stability with nanoscopic lattice distortions and dislocation activities. On the other hand, osteoporotic bone exhibits brittleness owing to the movements of dispersed minerals in and intergranular fracture along a weak organic matrix.


Assuntos
Osso e Ossos/fisiopatologia , Nanotecnologia , Osteoporose/fisiopatologia , Animais , Fenômenos Biomecânicos , Camundongos , Microscopia Eletrônica de Transmissão
13.
J Mech Behav Biomed Mater ; 4(7): 1412-20, 2011 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-21783151

RESUMO

In this study, the bone structures, nanomechanical properties and fracture behaviors in different groups of female C57BL/6 mice (control, sham operated, ovariectomized, casein supplemented, and fermented milk supplemented) were examined by micro-computed tomography, scanning and transmission electron microscopy, and nanoindentation. The control and sham operated mice showed dense bone structures with high cortical bone mineral densities of 544 mg/cm(3) (average) and high hardness of 0.9-1.1 GPa; resistance to bone fracture was conferred by microcracking, crack deflections and ligament bridging attributed to aligned collagen fibers and densely packed hydroxyapatite crystals. Bone mineral density, hardness and fracture resistance in ovariectomized mice markedly dropped due to loose bone structure with randomly distributed collagens and hydroxyapatites. The acidic casein supplemented mice with blood acidosis exhibited poor mineral absorption and loose bone structure, whereas the neutralized casein or fermented milk supplemented mice were resistant to osteoporosis and had high bone mechanical properties.


Assuntos
Osso e Ossos/patologia , Osso e Ossos/fisiopatologia , Suplementos Nutricionais , Fenômenos Mecânicos , Nanotecnologia , Osteoporose/patologia , Osteoporose/fisiopatologia , Animais , Fenômenos Biomecânicos , Densidade Óssea , Osso e Ossos/diagnóstico por imagem , Osso e Ossos/metabolismo , Colágeno/química , Colágeno/metabolismo , Durapatita/química , Durapatita/metabolismo , Feminino , Fraturas Ósseas/complicações , Camundongos , Camundongos Endogâmicos C57BL , Osteoporose/complicações , Osteoporose/metabolismo , Microtomografia por Raio-X
14.
J Mech Behav Biomed Mater ; 4(4): 618-24, 2011 May.
Artigo em Inglês | MEDLINE | ID: mdl-21396611

RESUMO

In this study, the mechanical properties of bioactive coatings on Ti6Al4V substrates were investigated using instrumented nanoindentation. The aim was to observe the differences in the mechanical properties before and after immersion in collagen solution. The hydroxyapatite coatings were prepared through two processes: self-assembly in simulated body fluid and a hydrothermal method. Sintered hydroxyapatite disks were used as controls. The test samples were then incubated in a dilute collagen solution for 24 hours to produce composite coatings. The materials were investigated using XRD, SEM and nanoindentation. The results showed that the grain sizes of the hydroxyapatite coatings formed using two processes were 1 µm and 10 µm, respectively. The Young's modulus of the pure hydroxyapatite, the disk and the coatings, was 3.6 GPa. After collagen incubation treatment, the composites had a Young's modulus of 7.5 GPa. The results also showed that the strengthening phenomena of collagen were more obvious for homogeneous and small-grain hydroxyapatite coatings. These results suggest that there are similarities between these HAp/collagen composited and natural composite materials, such as teeth and bones.


Assuntos
Colágeno/química , Durapatita/química , Fenômenos Mecânicos , Ligas , Animais , Testes de Dureza , Imersão , Nanotecnologia , Soluções , Propriedades de Superfície , Temperatura , Titânio/química
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