Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 1.541
Filtrar
1.
Nat Commun ; 10(1): 3951, 2019 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-31477695

RESUMO

Ferroelastic switching in ferroelectric/multiferroic oxides plays a crucial role in determining their dielectric, piezoelectric, and magnetoelectric properties. In thin films of these materials, however, substrate clamping is generally thought to limit the electric-field- or mechanical-force-driven responses to the local scale. Here, we report mechanical-force-induced large-area, non-local, collective ferroelastic domain switching in PbTiO3 epitaxial thin films by tuning the misfit-strain to be near a phase boundary wherein c/a and a1/a2 nanodomains coexist. Phenomenological models suggest that the collective, c-a-c-a ferroelastic switching arises from the small potential barrier between the degenerate domain structures, and the large anisotropy of a and c domains, which collectively generates much larger response and large-area domain propagation. Large-area, non-local response under small stimuli, unlike traditional local response to external field, provides an opportunity of unique response to local stimuli, which has potential for use in high-sensitivity pressure sensors and switches.

2.
Phys Rev Lett ; 123(8): 087603, 2019 Aug 23.
Artigo em Inglês | MEDLINE | ID: mdl-31491229

RESUMO

Very sensitive responses to external forces are found near phase transitions. However, transition dynamics and preequilibrium phenomena are difficult to detect and control. We have observed that the equilibrium domain structure following a phase transition in ferroelectric and ferroelastic BaTiO_{3} is attained by halving of the domain periodicity multiple times. The process is reversible, with periodicity doubling as temperature is increased. This observation is reminiscent of the period-doubling cascades generally observed during bifurcation phenomena, and, thus, it conforms to the "spatial chaos" regime earlier proposed by Jensen and Bak [Phys. Scr. T 9, 64 (1985)PHSTER0281-184710.1088/0031-8949/1985/T9/009] for systems with competing spatial modulations.

3.
BMC Surg ; 19(1): 128, 2019 Sep 05.
Artigo em Inglês | MEDLINE | ID: mdl-31488117

RESUMO

BACKGROUND: The aim of the study was to develop a scoring system for the prediction of postoperative complications of open hepatectomy. METHOD: All consecutive patients receiving open hepatectomy from 2015 to 2017 were included in the study. Univariate and multivariate analyses were used to confirm the risk factors for postoperative complications. Afterwards, a novel scoring system was developed to predict the postoperative complications. RESULTS: The study included a total of 207 patients. For the test dataset, multivariate analysis indicated that diabetes, scale of surgery, serum potassium, and blood loss versus body weight were independent risk factors of the postoperative complications. The area under the curve (AUC) of the novel scoring system we proposed for prediction of postoperative complications of hepatectomy was 0.803, which is comparable with the AUCs of previous scoring systems. Furthermore, in the validation dataset, the corresponding AUC of the new scoring system was 0.717. CONCLUSION: This novel and simplified scoring system can effectively predict the postoperative complications of open hepatectomy and could help identify patients who are at high risk of postoperative complications.

5.
Artigo em Inglês | MEDLINE | ID: mdl-31508932

RESUMO

All-solid-state lithium-sulfur batteries (ASSLSBs) employing sulfide-based solid electrolytes have gained widespread attention for their high energy density and intrinsic safety. The Li10SnP2S12 is identified as one of the most rivalling candidates in sulfide electrolytes. Herein, highly Li-ion conductive Li10SnP2S12 solid-state electrolyte (SSE) is synthesized via a combination of high-energy ball milling and heat treatment process, which is more facile and efficient compared with other previously reported methods. The obtained Li10SnP2S12 SSE exhibits high ionic conductivity (3.2×10-3 S cm-1) at room temperature (RT). The effect of annealing temperature on Li-ion conductivity and activation energy (Ea) of Li10SnP2S12 are also thoroughly studied. Moreover, The ASSLSBs based on Li10SnP2S12 electrolyte are constructed and deliver a high initial capacity of 1601.7 mAh g-1 at 40 mA g-1. A favorable capacity retention upon cycling and a good rate performance are also achieved at RT. Concomitantly, the Coulombic efficiency approaches 100% during the prolonged cycling. This work tremendously accelerates the practical applications of Li10SnP2S12 SSE among the emerging high-energy ASSLSBs.

6.
Nano Lett ; 2019 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-31508969

RESUMO

Ferroelectric heterostructures, with capability of storing data at ultra-high densities, could act as the platform for next-generation memories. The development of new device paradigms has been hampered by the long-standing notion of inevitable ferroelectricity suppression under reduced dimensions. Despite recent experimental observation of stable polarized states in ferroelectric ultrathin films, the out-of-plane polarization components in these films are strongly attenuated compared to thicker films, implying a degradation of device performance in electronic miniaturization processes. Here, in a model system of BiFeO3/La0.7Sr0.3MnO3, we report observation of a dramatic out-of-plane polarization enhancement that occurs with decreasing film thickness. Our electron microscopy analysis coupled with phase-field simulations reveals a polarization-enhancement mechanism that is dominated by the accumulation of oxygen vacancies at interfacial layers. The results shed light on the interplay between polarization and defects in nanoscale ferroelectrics and suggest a route to enhance functionality in oxide devices.

7.
Artigo em Inglês | MEDLINE | ID: mdl-31518048

RESUMO

Although great effort has been made in the past several decades, challenges still remain in the design and synthesis of uranium sorbent materials with high uptake efficiency, capacity and selectivity, as well as excellent hydrolytic stability and radiation resistance. Herein, a polyoxometalate (POM)-organic framework material ( SCU-19 ) with a rare inclined polycatenation structure was successfully designed, synthesized through solvothermal method, and tested for uranium separation for the first time. Under dark condition, SCU-19 can efficiently capture uranium through ligand complexation using its exposed oxo atoms and partial chemical reduction from U(VI) to U(IV) by the low-valent Mo atoms in the POM. Additional U(VI) photocatalytic reduction mechanism can be inserted into the system under the visible light irradiation, leading to a higher uranium removal without saturation and faster sorption kinetics. SCU-19 is currently the only uranium sorbent material with three distinct sorption mechanisms, as further demonstrated by X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge structure (XANES) analysis.

8.
Artigo em Inglês | MEDLINE | ID: mdl-31443402

RESUMO

Sorption is widely used for the removal of toxic heavy metals such as hexavalent chromium (Cr(VI)) from aqueous solutions. Green sorbents prepared from biomass are attractive, because they leverage the value of waste biomass and reduce the overall cost of water treatment. In this study, we fabricated biochar (BC) adsorbent from the biomass of water hyacinth (Eichhornia crassipes), an invasive species in many river channels. Pristine BC was further modified with nanoscale zero-valent iron (nZVI) and stabilized with chitosan (C) to form C-nZVI-BC. C-nZVI-BC adsorbent showed high hexavalent chromium sorption capacity (82.2 mg/g) at pH 2 and removed 97.34% of 50 mg/L Cr(VI) from aqueous solutions. The sorption capacity of chitosan-nZVI-modified biochar decreased while increasing the solution pH value and ionic strength. The results of a sorption test indicated that multiple mechanisms accounted for Cr(VI) removal by C-nZVI-BC, including complexation, precipitation, electrostatic interactions, and reduction. Our study suggests a way of adding value to biomass waste by considering environmental treatment purposes.

9.
Int J Chron Obstruct Pulmon Dis ; 14: 1669-1680, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31440043

RESUMO

Background: The temporally dynamic changes of CD25 and Foxp3 expression in CD4+ T cells are initiated by T cell receptor (TCR) signals strength or frequency. There is a deficiency of peripheral markers for assessing COPD activity, and the current study was conducted to explore whether peripheral CD4+ T cell populations based on CD25 and Foxp3 expression could serve as an indicator for COPD inflammatory activity. Methods: The distribution and phenotypic characteristics of CD4+CD25±Foxp3± T cells from peripheral blood in different populations were determined by flow cytometry. The model for the differentiation of CD4+ T cells populations by CD25 and Foxp3 expression was explored in vitro. Results: The frequencies of peripheral CD4+CD25+Foxp3- T cells and CD4+CD25+Foxp3+ T cells were increased in AECOPD patients, whereas the frequency of CD4+CD25-Foxp3+ T cells was increased in SCOPD patients without receiving systemic treatment. Phenotypic analysis revealed that CD4+CD25+Foxp3- T cells, CD4+CD25+Foxp3+ T cells and CD4+CD25-Foxp3+ T cells had received antigenic stimulation and resembled central memory or effector memory T cells. The differentiation of CD4+ T cells populations by CD25 and Foxp3 expression was dictated by TCR signals. The paired study indicated that the frequencies of CD4+CD25+Foxp3- T cells, CD4+CD25+Foxp3+ T cells and CD4+CD25- Foxp3+ T cells were decreased while the frequency of CD4+CD25-Foxp3- T cells were increased in the same patients from AECOPD to convalescence. Conclusions: Collectively, we propose that the dynamic changes of CD4+ T cell populations by CD25 and Foxp3 expression could function as potential biomarkers for reflecting inflammatory activity in COPD.

10.
Diabetes ; 2019 Aug 22.
Artigo em Inglês | MEDLINE | ID: mdl-31439648

RESUMO

CCR2 has been proved to play an important role in diabetes. However, the role of CCR2 in diabetic cardiomyopathy has not been examined. In this study, we investigated the effects of cardiac CCR2 on diabetic cardiomyopathy. We created streptozotocin (STZ)-induced diabetic cardiomyopathy model. Expression of CCR2 were up-regulated in STZ-induced diabetic hearts. CCR2 knockout (CCR2 KO) significantly improved STZ-induced cardiac dysfunction and fibrosis. Moreover, deletion of CCR2 inhibited the STZ induced the apoptosis as well as the production of STZ-induced reactive oxygen species (ROS) in the heart. CCR2 knockout resulted in M2 polarization in heart from STZ treated-mice. Meantime, CCR2 inhibitor treatment also reversed hyperglycemia induced cardiac dysfunction in db/db mice. Our results suggested that cardiac CCR2-induced inflammation and oxidative stress are involved in the development of diabetic cardiomyopathy and CCR2 could be a novel target for therapy.

12.
Med Sci Monit ; 25: 6255-6263, 2019 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-31429423

RESUMO

BACKGROUND Acute lung injury (ALI) is one of major causes of death in newborns, making it urgent to improve therapy. Administration of low dose carbon monoxide (CO) plays a protective role in ALI but the mechanisms are not fully understood. This study was designed to test the therapeutic effect of monoxide-releasing molecule 3 (MORM3) in lipopolysaccharide (LPS) induced neonatal ALI and the possibly associated molecular mechanisms. MATERIAL AND METHODS For this study, 3- to 8-day old Newborn Sprague-Dawley rats were subjected to intraperitoneal injection of 3 mg/kg LPS to induce ALI. Then animals received intraperitoneal injection of carbon monoxide-releasing molecules 3 (CORM3) (8 mg/kg) or inactive CORM3 (iCORM3) for 7 consecutive days. Lung tissues were collected for histological examination and total cell counts and protein content in bronchoalveolar lavage fluid (BALF) were measured. Expression of Cx43 and necroptosis-related markers were detected by quantitative real-time polymerase chain reaction (qRT-PCR) and western blot. RESULTS LPS exposure induced significant lung injury indicated by histological damage, increased lung wet/dry weight ratio (W/D) and increased total cell counts and protein concentration in BALF. These changes were significantly ameliorated by administration of CORM3 but not iCORM3. LPS also increased necroptosis-related markers RIP1, RIP3, and MLKL and their elevation was blocked by CORM3. CORM3 administration ameliorated LPS induced elevation of Cx43 expression and adenoviral overexpression of Cx43 abolished lung protective effect of CORM3. CORM3 administration attenuated LPS induced activation of extracellular-signal-regulated kinase (ERK) and its protection against necroptosis was abolished by ERK inhibitor U0126. CONCLUSIONS CORM3 attenuates LPS-Induced ALI in neonatal rats and its lung protective effect might be through downregulation of Cx43 to attenuate ERK signaling and ameliorate necroptosis, suggesting CORM3 as a potential therapeutic drug for ALI in neonates.

13.
Acta Biomater ; 2019 Aug 19.
Artigo em Inglês | MEDLINE | ID: mdl-31437637

RESUMO

Human amniotic membrane (AM) offers unique advantages as a matrix to support the transplantation of limbal stem cells (LSCs) due to its inherent pro-regenerative and anti-inflammatory properties. However, the widespread use of AM in clinical treatments of ocular surface disorders is limited by its weak mechanical strength and fast degradation, and high cost associated with preserving freshly isolated AM. Here we constructed a composite membrane consisting of an electrospun bioabsorbable poly(ε-caprolactone) (PCL) nanofiber mesh to significantly improve the ultimate tensile strength, toughness, and suture retention strength by 4-10-fold in comparison with decellularized AM sheet. The composite membrane showed extended stability and conferred longer-lasting coverage on wounded cornea surface compared with dAM. The composite membrane maintained the pro-regenerative and immunomodulatory properties of dAM, promoted LSC survival, retention, and organization, improved re-epithelialization of the defect area, and reduced inflammation and neovascularization. This study demonstrates the translational potential of our composite membrane for stem cell-based treatment of ocular surface damage. STATEMENT OF SIGNIFICANCE: Human decellularized amniotic membrane (dAM) has been widely shown as a biodegradable and bioactive matrix for regenerative tissue repair. However, the weak mechanical property has limited its widespread use in the clinic. Here we constructed a composite membrane using a layer of electrospun poly(ε-caprolactone) (PCL) nanofiber mesh to reinforce the dAM sheet through covalent interfacial bonding, while retaining the unique bioactivity of dAM. In a rabbit model of limbal stem cell (LSC) deficiency induced by alkaline burn, we demonstrated the superior property of this PCL-dAM composite membrane for repairing damaged cornea through promoting LSC transplantation, improving re-epithelialization, and reducing inflammation and neovascularization. This new composite membrane offers great translational potential in supporting stem cell-based treatment of ocular surface damage.

14.
Zhongguo Yi Liao Qi Xie Za Zhi ; 43(4): 255-258, 2019 Jul 30.
Artigo em Chinês | MEDLINE | ID: mdl-31460715

RESUMO

In this paper, the classification and location of neuroblastoma in NMR images are realized by using Deep Neural Network(CNN) algorithm as the core technology. The module is integrated to realize the development of computer-aided diagnostic software. It is used to make up for the gap in the field of intelligent identification and accurate positioning of neuroblastoma in the current nuclear magnetic resonance detection technology, effectively reduce the work intensity of doctors reading films, and further promote the clinical application and technical development of nuclear magnetic resonance detection technology in the diagnosis of neuroblastoma.

15.
Environ Int ; 131: 104996, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31369980

RESUMO

Production system-related air pollution emissions are dominant components in global emission reduction targets and in realizing relevant sustainable development goals (SDGs). To better understand the air pollution emissions induced by globalized production systems through a life cycle perspective, environmental extended multiregional input-output (EE-MRIO) analysis was applied to calculate the primary product-based emissions and the final product-based emissions embodied in the global production systems. Combined with two types of linkage analysis, named the hypothetical extraction method (HEM) and the emissions pure backward linkage (EPBL), emissions were analysed at three scopes at the sector level from macro sector linkage perspectives. An illustrative analysis was presented based on the global EXIOBASE MRIO database and primary PM2.5 emissions from 1995 to 2011. The results show that from 1995 to 2011, the primary PM2.5 emissions in the global production systems increased by 35%. In 2011, China's production system generated the highest primary product-based and final product-based primary PM2.5 emissions, which accounted for 30.7% and 29.6% of the global total, respectively. The emission flows balance between primary product-based emissions and final product-based emissions revealed that most developing countries are sources of emissions and that developed countries are sinks of emissions in production systems. An approximately U-shaped relationship was found in the primary PM2.5 emissions embodied in final products, while the opposite relationship was found embodied in primary products. Meanwhile, sector-specific protocols for controlling the high indirect emissions sectors can make the supply chain cleaner. Our findings further indicated that focusing more on industries can help relevant emissions control policymaking processes.

16.
J Mol Cell Cardiol ; 135: 119-133, 2019 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-31408621

RESUMO

Angiotensin II (Ang-II)-induced fibroblast differentiation plays an important role in the development of atrial fibrosis and atrial fibrillation (AF). Here, we show that the expression of the histone methyltransferase enhancer of zeste homolog 2 (EZH2) is increased in atrial muscle and atrial fibroblasts in patients with AF, accompanied by significant atrial fibrosis and atrial fibroblast differentiation. In addition, EZH2 is induced in murine models of atrial fibrosis. Furthermore, either pharmacological GSK126 inhibition or molecular silencing of EZH2 can inhibit the differentiation of atrial fibroblasts and the ability to produce ECM induced by Ang-II. Simultaneously, inhibition of EZH2 can block the Ang-II-induced migration of atrial fibroblasts. We found that EZH2 promotes fibroblast differentiation mainly through the Smad signaling pathway and can form a transcription complex with Smad2 to bind to the promoter region of the ACTA2 gene. Finally, our in vivo experiments demonstrated that the EZH2 inhibitor GSK126 significantly inhibited Ang-II-induced atrial enlargement and fibrosis and reduced AF vulnerability. Our results demonstrate that targeting EZH2 or EZH2-regulated genes might present therapeutic potential in AF.

17.
J Am Chem Soc ; 141(35): 13822-13828, 2019 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-31407892

RESUMO

We herein develop a two-in-one molecular design strategy for facile synthesis of 2D imine based covalent organic frameworks (COFs). The integration of two different functional groups (i.e., formyl and amino groups) in one simple pyrene molecule affords a bifunctional building block: 1,6-bis(4-formylphenyl)-3,8-bis(4-aminophenyl)pyrene (BFBAPy). Highly crystalline and porous Py-COFs can be easily prepared by the self-condensation of BFBAPy in various solvents, such as CH2Cl2, CHCl3, tetrahydrofuran, methanol, ethanol, acetonitrile, and dimethylacetamide, etc. The current work, to the best of our knowledge, is a rare case of COF synthesis that exhibits excellent solvent adaptability. Highly crystalline Py-COF thin films have been facilely fabricated on various substrates and exhibit potential applications in hole transporting layers for perovskite solar cells. Furthermore, the versatility of this two-in-one strategy was also verified by two additional examples. The current work dramatically reduces the difficulty of COF synthesis, and such two-in-one strategy is anticipated to be applicable for the synthesis of other COFs constructed by different building blocks and linkages.

18.
Science ; 365(6453): 578-582, 2019 08 09.
Artigo em Inglês | MEDLINE | ID: mdl-31395780

RESUMO

Dielectric capacitors with ultrahigh power densities are fundamental energy storage components in electrical and electronic systems. However, a long-standing challenge is improving their energy densities. We report dielectrics with ultrahigh energy densities designed with polymorphic nanodomains. Guided by phase-field simulations, we conceived and synthesized lead-free BiFeO3-BaTiO3-SrTiO3 solid-solution films to realize the coexistence of rhombohedral and tetragonal nanodomains embedded in a cubic matrix. We obtained minimized hysteresis while maintaining high polarization and achieved a high energy density of 112 joules per cubic centimeter with a high energy efficiency of ~80%. This approach should be generalizable for designing high-performance dielectrics and other functional materials that benefit from nanoscale domain structure manipulation.

19.
J Neural Eng ; 2019 Jul 31.
Artigo em Inglês | MEDLINE | ID: mdl-31365911

RESUMO

OBJECTIVE: We proposed a brain-computer interface (BCI) based visual-haptic neurofeedback training (NFT) by incorporating synchronous visual scene and proprioceptive electrical stimulation feedback. The goal of this work was to improve sensorimotor cortical activations and classification performance during motor imagery (MI). In addition, their correlations and brain network patterns were also investigated respectively. APPROACH: 64-channel electroencephalographic (EEG) data were recorded in nineteen healthy subjects during MI before and after NFT. During NFT sessions, the synchronous visual-haptic feedbacks were driven by real-time lateralized relative event-related desynchronization (lrERD). MAIN RESULTS: By comparison between previous and posterior control sessions, the cortical activations measured by multi-band (i.e. alpha_1: 8-10Hz, alpha_2: 11-13Hz, beta_1: 15-20Hz and beta_2: 22-28Hz) absolute ERD powers and lrERD patterns were significantly enhanced after the NFT. The classification performance was also significantly improved, achieving a ~9% improvement and reaching ~85% in mean classification accuracy from a relatively poor performance. Additionally, there were significant correlations between lrERD patterns and classification accuracies. The partial directed coherence (PDC) based functional connectivity (FC) networks covering the sensorimotor area also showed an increase after the NFT. SIGNIFICANCE: These findings validate the feasibility of our proposed NFT to improve sensorimotor cortical activations and BCI performance during motor imagery. And it is promising to optimize conventional NFT manner and evaluate the effectiveness of motor training.

20.
Artigo em Inglês | MEDLINE | ID: mdl-31433550

RESUMO

2D covalent organic frameworks (COFs) feature open and ordered 1D column nanochannels which offer immense possibilities for incorporation of various guests for specific functions. However, the relatively low chemical stability of most COFs originated from the dynamic covalent linkages hindered their practical applications. In this work, a highly crystalline and heteroporous dibenzo[g,p]chrysene based COF (DBC-2P), was synthesized and served as host materials for ionic conduction. DBC-2P exhibits excellent stability both in strong acid and base due to the large conjugated DBC-based knot that reinforcing the interlayer interactions. Subsequent encapsulation of linear polyethylene glycol (PEG) and PEG-LiBF4 salt into the nanochannels of DBC-2P, affords a hybrid material with high ionic conductivity of 2.31 x 10-3 S cm-1. This work demonstrates an efficient post-synthetic strategy for development of new COF-polymer composites with intriguing properties.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA