Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 430
Filtrar
1.
Technol Cancer Res Treat ; 21: 15330338221099396, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35522305

RESUMO

Introduction: The purpose of this study is to investigate the effects of automatic segmentation algorithms on the performance of ultrasound (US) radiomics models in predicting the status of lymph node metastasis (LNM) for patients with early stage cervical cancer preoperatively. Methods: US images of 148 cervical cancer patients were collected and manually contoured by two senior radiologists. The four deep learning-based automatic segmentation models, namely U-net, context encoder network (CE-net), Resnet, and attention U-net were constructed to segment the tumor volumes automatically. Radiomics features were extracted and selected from manual and automatically segmented regions of interest (ROIs) to predict the LNM of these cervical cancer patients preoperatively. The reliability and reproducibility of radiomics features and the performances of prediction models were evaluated. Results: A total of 449 radiomics features were extracted from manual and automatic segmented ROIs with Pyradiomics. Features with an intraclass coefficient (ICC) > 0.9 were all 257 (57.2%) from manual and automatic segmented contours. The area under the curve (AUCs) of validation models with radiomics features extracted from manual, attention U-net, CE-net, Resnet, and U-net were 0.692, 0.755, 0.696, 0.689, and 0.710, respectively. Attention U-net showed best performance in the LNM prediction model with a lowest discrepancy between training and validation. The AUCs of models with automatic segmentation features from attention U-net, CE-net, Resnet, and U-net were 9.11%, 0.58%, -0.44%, and 2.61% higher than AUC of model with manual contoured features, respectively. Conclusion: The reliability and reproducibility of radiomics features, as well as the performance of radiomics models, were affected by manual segmentation and automatic segmentations.


Assuntos
Neoplasias do Colo do Útero , Feminino , Humanos , Linfonodos/diagnóstico por imagem , Linfonodos/patologia , Metástase Linfática/patologia , Reprodutibilidade dos Testes , Estudos Retrospectivos , Neoplasias do Colo do Útero/diagnóstico por imagem , Neoplasias do Colo do Útero/patologia , Neoplasias do Colo do Útero/cirurgia
2.
Am J Chin Med ; : 1-21, 2022 May 05.
Artigo em Inglês | MEDLINE | ID: mdl-35543160

RESUMO

Salidroside, an active ingredient in Rhodiola rosea, has potent protective activity against cerebral ischemia. However, the mechanisms underlying its pharmacological actions are poorly understood. In this study, we employed a mouse middle cerebral artery occlusion (MCAO) and cellular oxygen and glucose deprivation (OGD) models to test the hypothesis that salidroside may restore mitochondrial quality control in neurons by modulating the relevant signaling. The results indicated that salidroside mitigated almost 40% the ischemia-induced brain infarct volumes in mice and the OGD-decreased viability of neurons to ameliorate the mitochondrial functions. Furthermore, salidroside treatment alleviated the OGD- or ischemia-induced imbalance of mitochondrial fission and fusion, mitophagy and promoted mitochondrial biogenesis in neurons by attenuating the AMPK activity. Moreover, salidroside alleviated 50% the OGD-promoted mitochondrial calcium fluorescence intensity and 5% mitochondria-associated membrane (MAM) area by down-regulating GRP75 expression independent of the AMPK signaling. Finally, similar findings were achieved in primary mouse neurons. Collectively, these data indicate that salidroside effectively restores the mitochondria dynamics, facilitates mitochondrial biogenesis by attenuating the AMPK signaling, and maintains calcium homeostasis in neurons independent of the AMPK activity.

3.
Int J Mol Sci ; 23(8)2022 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-35456914

RESUMO

Manganese (Mn) is now known to have a variety of toxicities, particularly when exposed to it in the workplace. However, there are still ineffective methods for reducing Mn's hazardous effects. In this study, a new selenium polysaccharide (Se-PCS) was developed from the shell of Camellia oleifera to reduce Mn toxicity in vitro and in vivo. The results revealed that Se-PCS may boost cell survival in Hep G2 cells exposed to Mn and activate antioxidant enzyme activity, lowering ROS and cell apoptosis. Furthermore, after being treated with Se-PCS, Caenorhabditis elegans survived longer under Mn stress. daf-16, a tolerant critical gene, was turned on. Moreover, the antioxidant system was enhanced as the increase in strong antioxidant enzyme activity and high expression of the sod-3, ctl-2, and gst-1 genes. A variety of mutations were also used to confirm that Se-PCS downregulated the insulin signaling pathway. These findings showed that Se-PCS protected Hep G2 cells and C. elegans via the insulin/IGF-1 signaling pathway and that it could be developed into a promising medication to treat Mn toxicity.


Assuntos
Proteínas de Caenorhabditis elegans , Intoxicação por Manganês , Selênio , Animais , Antioxidantes/metabolismo , Antioxidantes/farmacologia , Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/metabolismo , Células Hep G2 , Humanos , Insulina/metabolismo , Manganês/metabolismo , Estresse Oxidativo , Polissacarídeos/metabolismo , Polissacarídeos/farmacologia , Selênio/metabolismo , Selênio/farmacologia
4.
BMC Nurs ; 21(1): 79, 2022 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-35387652

RESUMO

BACKGROUND: Perioperative competence is necessary to evaluate operating room nurses. The Perceived Perioperative Competence Scale-Revised (PPCS-R) is the only available tool developed specifically for the perioperative setting. However, there is a lack of research on the reliability and validity of this scale among Chinese nurses. Thus, the aim of this study is to translate, culturally adapt, and evaluate the psychometric properties of the Perioperative competence Scale-Revised (PPCS-R) among operating room nurses in China. METHODS: Instrument cultural adaptation was carried out through forward translation, back translation, expert panel evaluation and pretesting. The psychometric properties (content validation, item analysis, construct validation, and reliability coefficient) of the Chinese PPCS-R (C-PPCS-R) were examined. An online survey was completed from June to August 2020 by operating room nurses (N = 480) in five third-grade class-A hospitals in Beijing. RESULTS: The item analysis identified six items for scale reduction. Exploratory factor analysis showed the remaining 34 items loaded on six factors, which were named in accordance with the original scale. The six-factor model showed a good fit through confirmatory factor analysis. The item content validity index for the C-PPCS-R items ranged from 0.857 to 1.000, and that for the total scale was 0.875. Cronbach's alpha was showed 0.787. Together, the six factors explained 68.62% of the variance. CONCLUSIONS: The 34-item C-PPCS-R showed good validity and reliability to measure perceived competence among operating room nurses in the Chinese context. The scale can assist nurse managers to identify operating room nurses' perceived competence, and provides evaluation criteria for career planning, performance appraisal, job assignment, and continuing education.

5.
Zootaxa ; 5120(3): 449-450, 2022 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-35391155

RESUMO

Body size is perhaps the most important trait for organism biologists, as it is associated with a myriad of ecological, evolutionary, behavioral, morphological, physiological and life-history aspects (e.g., rates of molecular evolution, metabolic rates, predation, reproduction), and with extinction risk. There are, however, several measures commonly used to quantify organism body size. Within ectothermic tetrapods, the most common measures include snout-vent length (SVL, mostly in lizards), and total length (TL, in most snakes). In endotherms, however, and especially in mammals, body mass is the most common measure of size.


Assuntos
Lagartos , Répteis , Anfíbios , Animais , Tamanho Corporal , Mamíferos/anatomia & histologia , Répteis/anatomia & histologia , Serpentes
6.
ACS Nano ; 2022 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-35451839

RESUMO

The key to controlling the spread of the coronavirus disease 2019 (COVID-19) and reducing mortality is highly dependent on the safe and effective use of vaccines for the general population. Current COVID-19 vaccination practices (intramuscular injection of solution-based vaccines) are limited by heavy reliance on medical professionals, poor compliance, and laborious vaccination recording procedures, resulting in a waste of health resources and low vaccination coverage, etc. In this study, we developed a smart mushroom-inspired imprintable and lightly detachable (MILD) microneedle platform for the effective and convenient delivery of multidose COVID-19 vaccines and decentralized vaccine information storage. The mushroom-like structure allows the MILD system to be easily pressed into the skin and detached from the patch base, acting as a "tattoo" to record the vaccine counts in situ without any storage equipment, offering quick accessibility and effortless readout, saving a great deal of valuable time and energy for both patients and health professionals. After loading inactivated SARS-CoV-2 virus-based vaccines, MILD system induced a high level of antibodies against the SARS-CoV-2 receptor-binding domain (RBD) in vivo without eliciting systemic toxicity and local damage. Collectively, this smart delivery platform serves as a promising carrier to improve COVID-19 vaccination efficacy through its dual capabilities of vaccine delivery and in situ data storage, thus exhibiting great potential for helping to contain the COVID-19 pandemic or a resurgence.

7.
Front Surg ; 9: 842047, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35242806

RESUMO

BACKGROUND: The aim of this study was to analyze the clinical efficacy of different thoracoscopic procedures in patients with non-small cell lung cancer and their correlation with matrix metalloproteinase-7 mRNA (MMPs-7 mRNA) and soluble major histocompatibility complex class I molecule A (sMICA), as well as their effect on T-cell subsets. METHODS: A total of 100 patients with non-small cell lung cancer who received different thoracoscopic surgeries were divided into the Control group (three-port thoracoscopic surgery) and the study group (single-port thoracoscopic surgery). The two groups were evaluated to compare the perioperative indicators, MMPs-7 mRNA, sMICA expression levels, T-cell subsets, postoperative pain, complication rates, and prognostic outcomes at 1-year follow-up. RESULTS: The operation time, blood loss, drainage tube placement time, incision length, and hospital stay in the study group were less than those in the control group (P < 0.05). There was no significant difference in the number of lymph node dissections between the two groups (P > 0.05). After 3 days, the expression levels of MMPs-7 mRNA and sMICA in the study group were lower than those in the control group (P < 0.05); CD4 +, CD8 +, and CD4 +/CD8 + in the study group were higher than those in the control group (P < 0.05). On days 1, 3, and 5, the visual analog score (VAS) of the study group was lower than that of the control group (P < 0.05); there was no significant difference in the complication rate between the two follow-up groups (P > 0.05), in which all patients completed the follow-up. After 1 year of follow-up, there was no significant difference in the tumor-free survival rate and overall survival rate between the two groups (P > 0.05). CONCLUSION: Compared with three-port thoracoscopic surgery, single-port thoracoscopic surgery can improve perioperative expression, shorten hospital stay, reduce serum tumor micrometastasis levels, improve immune metastasis mechanisms and reduce pain, which is of great significance to patients with non-small cell lung cancer. It is an effective, convenient, and safe surgical option that deserves wide clinical reference.

8.
Neurol Sci ; 43(5): 3467-3471, 2022 May.
Artigo em Inglês | MEDLINE | ID: mdl-35257260

RESUMO

We report a case of progressive myoclonic epilepsy caused by a novel mutation in EPM2A. The female patient experienced abnormal jerky movements of the involving all four limbs and several generalized seizures, degeneration of cognition, and unsteadiness. Genetic analysis identified two rare, deleterious mutations in exon4: chr6: 145,948,751(c.G797G > A) and chr6: 145,948,761(c.T787C > T). The mutations at these two loci were from the genomes of their mother and father, respectively, which were compound heterozygous variations. This report updates the mutation sites of gene EPM2A and extends genotype-phenotype correlations in Lafora disease.


Assuntos
Doença de Lafora , Epilepsias Mioclônicas Progressivas , Feminino , Humanos , Doença de Lafora/genética , Mutação/genética , Epilepsias Mioclônicas Progressivas/genética , Proteínas Tirosina Fosfatases não Receptoras/genética , Ubiquitina-Proteína Ligases/genética
9.
Artigo em Inglês | MEDLINE | ID: mdl-35346547

RESUMO

BACKGROUND AND AIMS: In the absence of a gold standard or scientific consensus regarding the nutritional evaluation of heart failure (HF) patients, this study aimed to summarize and systematically evaluate the prognostic value of nutritional screening and assessment tools used for all-cause mortality in HF patients. METHODS AND RESULTS: Relevant studies were retrieved from major databases (PubMed, Embase, Web of Science, China National Knowledge Infrastructure (CNKI), WanFang Data, and China Biology Medicine disc (CMB)) and searched from the earliest available date until July 2021. If three or more studies used the same tool, meta-analysis using RevMan 5.3 was performed. This systematic review was registered at PROSPERO (number CRD42021275575). A total of 36 articles involving 25,141 HF patients were included for qualitative analysis and 31 studies for quantitative analysis. Meta-analysis of these studies indicated, poor nutritional status evaluated by using 5 nutritional screening tools (Prognostic Nutritional Index (PNI), Geriatric Nutritional Risk Index (GNRI), Controlling Nutritional Status Score (CONUT), Nutritional Risk Index (NRI), and Short Form Mini Nutritional Assessment (MNA-SF)) or 2 nutritional assessment tools (the Mini Nutritional Assessment (MNA) and Generated Subjective Global Assessment (SGA)) predicted all-cause mortality in HF patients. Of all tools analyzed, MNA had the maximum HR for mortality [HR = 2.62, 95%CI 1.11-6.20, P = 0.03] and MNA-SF [HR = 1.94, 95%CI 1.40-2.70, P<0.001] was the best nutritional screening tools. CONCLUSION: Poor nutritional status predicted all-cause mortality in HF patients. MNA may be the best nutritional assessment tool, and MNA-SF is most recommended for HF patient nutritional screening. The application value of MNA, especially in patients with reduced left ventricular ejection fraction (LVEF), needs to be further confirmed. The clinical application value of Mini-Nutrition Assessment Special for Heart Failure (MNA-HF) and Global Leadership Initiative on Malnutrition (GLIM) in HF patients needs to be confirmed.

10.
Sci Total Environ ; 829: 154595, 2022 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-35302013

RESUMO

Ecosystem service value (ESV) is influenced by land use and land cover (LULC), and is closely related to natural conditions and human activities. However, the interactions between human and natural systems and ESV remain unclear, especially concerning widely discussed meteorological and socioeconomic factors. In this study, three periods of LULC patterns (2000, 2010, and 2020) in the Haihe River Basin, northern China, were collected to determine the relationship between changes in LULC and ESV over time. Natural and socioeconomic data associated with ESV were obtained and the structural equation model was used to decouple interactions between these factors. Results showed that the total value of regional ecosystem services has decreased as cultivated land shrunk and artificial surfaces increased over the past two decades. The ESV was significantly decreased in the middle of the basin. The direct effects of meteorological factors and socioeconomic factors on ESV were positive (0.094) and negative (-0.203), respectively. The indirect effect of socioeconomic factors on ESV through meteorological and LULC factors was 0.149. Structural equation modeling demonstrated that under the dominance of LULC, interactions between natural and socioeconomic factors affected ESV in a complex manner. These results implied that identifying the direct and indirect effects of economic development and human activities on ESV could guide and implement effective land management policies.

11.
Front Pharmacol ; 13: 845185, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35250595

RESUMO

Alzheimer's disease (AD) is a common age-related neurodegenerative disease characterized by progressive cognitive dysfunction and behavioral impairment. The typical pathological characteristics of AD are extracellular senile plaques composed of amyloid ß (Aß) protein, intracellular neurofibrillary tangles formed by the hyperphosphorylation of the microtubule-associated protein tau, and neuron loss. In the past hundred years, although human beings have invested a lot of manpower, material and financial resources, there is no widely recognized drug for the effective prevention and clinical cure of AD in the world so far. Therefore, evaluating and exploring new drug targets for AD treatment is an important topic. At present, researchers have not stopped exploring the pathogenesis of AD, and the views on the pathogenic factors of AD are constantly changing. Multiple evidence have confirmed that chronic neuroinflammation plays a crucial role in the pathogenesis of AD. In the field of neuroinflammation, the nucleotide-binding oligomerization domain-like receptor pyrin domain-containing 3 (NLRP3) inflammasome is a key molecular link in the AD neuroinflammatory pathway. Under the stimulation of Aß oligomers and tau aggregates, it can lead to the assembly and activation of NLRP3 inflammasome in microglia and astrocytes in the brain, thereby causing caspase-1 activation and the secretion of IL-1ß and IL-18, which ultimately triggers the pathophysiological changes and cognitive decline of AD. In this review, we summarize current literatures on the activation of NLRP3 inflammasome and activation-related regulation mechanisms, and discuss its possible roles in the pathogenesis of AD. Moreover, focusing on the NLRP3 inflammasome and combining with the upstream and downstream signaling pathway-related molecules of NLRP3 inflammasome as targets, we review the pharmacologically related targets and various methods to alleviate neuroinflammation by regulating the activation of NLRP3 inflammasome, which provides new ideas for the treatment of AD.

12.
Opt Express ; 30(5): 7467-7476, 2022 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-35299508

RESUMO

In this paper, we proposed a flexible method for generating asymmetric chiro-optical fields. Different from most of the chiro-optical fields superimposed by vortex beams which are rotationally symmetric, the asymmetric chiro-optical field has a locally controllable orbital angular momentum (OAM) and polarization state. By using a helix phase plate (HPP) calculated based on coordinates transformation of the perfect vortex, the OAM controllability of a single chiro-optical field could be achieved. Then, by using the transformation matrix method, several discrete chiro-optical fields with different rotation angles and topological charges were stitched together as a multi-lobed chiro-optical field with asymmetric OAM on each side-lobe. Furthermore, we designed two HPPs that can be loaded into two spatial light modulators to modulate the polarization state of each side-lobe of the asymmetric chiro-optical field independently. The proposed asymmetric chiro-optical field breaks the characteristics of uniform OAM and polarization distribution of conventional chiro-optical fields, which may have potential applications in optical tweezers, communications, and enantiomer-selective sensing.

14.
Environ Pollut ; 299: 118911, 2022 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-35101556

RESUMO

The impact of land use type on the content of potentially toxic elements (PTEs) in the soils of the Qinghai-Tibet Plateau (QTP) and the associated ecological and human health risks has drawn great attention. Consequently, in this study, top- and subsurface soil samples were collected from areas with four different land uses (i.e., cropland, forest, grassland, and developed area) and the total contents of Cr, Cd, Cu, Pb and Zn were determined. Geostatistical analysis, self-organizing map (SOM), and positive matrix factorization (PMF), ecological risk assessment (ERA) and human health risk assessment (HRA) were applied and used to classify and identify the contamination sources and assess the potential risk. Partial least squares path modeling (PLS-PM) was applied to clarify the relationship of land use with PTE contents and risk. The PTE contents in all topsoil samples surpassed the respective background concentrations of China and corresponding subsurface concentrations. However, the ecological risk of all soil samples remained at a moderate or considerable level across the four land use types. Developed area and cropland showed a higher ecological risk than the other two land use types. Industrial discharges (32.8%), agricultural inputs (22.6%), natural sources (23.7%), and traffic emissions (20.9%) were the primary PTE sources in the tested soils, which indicate that anthropogenic activities have significantly affected soil PTE contents to a greater extent than other sources. Industrial discharge was the most prominent source of non-carcinogenic health risk, contributing 37.7% for adults and 35.2% for children of the total risk. The results of PLS-PM revealed that land use change associated with intensive human activities such as industrial activities and agricultural practices distinctly affected the PTE contents in soils of the Qinghai-Tibet Plateau.


Assuntos
Metais Pesados , Poluentes do Solo , Adulto , Criança , China , Monitoramento Ambiental , Poluição Ambiental/análise , Humanos , Metais Pesados/análise , Medição de Risco , Solo , Poluentes do Solo/análise
15.
Anal Chim Acta ; 1191: 339178, 2022 Jan 25.
Artigo em Inglês | MEDLINE | ID: mdl-35033273

RESUMO

Citric acid (CA) has been considered as a biomarker of urolithiasis due to its vital suppression role in urinary stone formation. Most analytical methods for detecting CA are complicated and require expensive equipment. Herein, a colorimetric method based on sodium dodecylsulfate (SDS) modified AgNPs was presented for convenient and portable detection of CA in urine. By detecting the absorption of the solution color, the quantitative detection of CA can be achieved. The pH value of SDS-AgNPs, concentration of Al3+ and incubation time were optimized. Under optimal conditions, the method has the detection range of 1-10 mg/L, with a limit of detection (LOD) of 0.21 mg/L. Moreover, a self-developed portable CD(Compact Disk)-spectrometer (CDs) was established for detecting CA with a LOD of 0.49 mg/L featuring high simplicity, low time cost and good portability. This method was also validated with good selectivity to CA. In addition, the artificial urine samples were also detected to verify the capability of the method and CDs. The results validated that the method integrating with the CDs can be a promising platform for citric acid detection that can be further used for early screening and prognostic monitoring of urolithiasis.


Assuntos
Nanopartículas Metálicas , Urolitíase , Biomarcadores , Ácido Cítrico , Colorimetria , Humanos , Prata , Sódio , Dodecilsulfato de Sódio , Urolitíase/diagnóstico
16.
Adv Sci (Weinh) ; 9(7): e2104561, 2022 03.
Artigo em Inglês | MEDLINE | ID: mdl-35018733

RESUMO

Developing metal-organic frameworks (MOFs) with strong near-infrared II (NIR-II, 1000-1700 nm) emission is significant for biomedical research but highly challenging. So far there are no MOFs reported for NIR-II imaging in vivo due to their poor NIR-II emission efficiency. Herein, a strategy is proposed to prepare MOFs with strong NIR-II emission, by integrating NIR dye IR-3C and Ln3+ (Ln = Yb, Nd, and Er) into a same framework. IR-3C with high photon-absorption ability harvests the excitation photons and transfers energy to Ln3+ via a resonance energy transfer pathway, significantly enhancing the NIR-II emission of Ln3+ . The as-obtained Er-BTC-IR exhibits excellent NIR-IIb (1500-1700 nm) emission efficiency in aqueous phase and good biocompatibility after surface modification, which provides advanced bioimaging performance in vivo. It is able to clearly delineate the vessels, spine, and lymph of mice, and also to differentiate the vessels with acute vascular inflammation. This strategy paves the way to the preparation of NIR-II emissive MOFs and will promote their bioapplication.


Assuntos
Elementos da Série dos Lantanídeos , Estruturas Metalorgânicas , Animais , Transferência de Energia , Camundongos , Fótons
17.
J Hazard Mater ; 427: 128117, 2022 04 05.
Artigo em Inglês | MEDLINE | ID: mdl-34974405

RESUMO

Conventional adsorbents for decontaminating arsenic exhibit low efficacy for the removal of arsenite (As(III)). This study aims to develop a robust As adsorbent from natural magnetite (M0) via a facile ball milling process, and evaluate their performance for decontaminating As(III) and As(V) in water and soil systems. The ball milling process decreased the particle size and crystallinity of M0, resulting in pronounced As removal by the ball-milled magnetite (Mm). Ball milling under air facilitated the formation of Fe-OH and Fe-COOH functional groups on Mm interface, contributing to effective elimination of As(III) and As(V) via hydrogen bonding and complexation mechanisms. Synergistic oxidation effects of hydroxyl and carboxyl groups, and reactive oxygen species (O2·-, and ·OH) on the transformation of As(III) to As(V) during the adsorption were proposed to explain the enhanced As(III) removal by Mm. A short-term soil incubation experiment indicated that the addition of Mm (10 wt%) induced a decrease in the concentration of exchangeable As by 30.25%, and facilitated the transformation of water-soluble As into residual fraction. Ball milling thus is considered as an eco-friendly (chemical-free) and inexpensive (scalable, one-stage process) method for upgrading the performance of natural magnetite towards remediating As, particularly for tackling the highly mobile As(III).


Assuntos
Arsênio , Poluentes Químicos da Água , Purificação da Água , Adsorção , Descontaminação , Óxido Ferroso-Férrico , Poluentes Químicos da Água/análise
18.
Nano Lett ; 22(2): 822-829, 2022 01 26.
Artigo em Inglês | MEDLINE | ID: mdl-35029994

RESUMO

The structural and mechanical properties of low-dimensional nanostructured metals have been attracting tremendous interest in the fast-growing fields of nanosciences and nanotechnologies. However, it still remains a challenge today to develop strong yet ductile low-dimensional metals that can support the further development of nanodevices. Here, through the polymer-assisted assembly of gold nanocrystals, we successfully fabricated the freestanding, ultrathin gold nanomaterial. Unlike conventional bulk gold or other low-dimensional gold nanostructures (i.e., nanowires and nanosheets), these gold nanosheets are composed of highly distorted gold nanocrystals that are 3-5 nm in size, which are joined together through nanosized amorphous carbon interphases. As a result, the gold nanosheets exhibit superb strength (up to 1.2 GPa), excellent ductility (>50%), and superior fracture toughness (>100 J/m2), outperforming various gold nanostructures hitherto reported.


Assuntos
Nanopartículas , Nanoestruturas , Ouro , Nanoestruturas/química , Resistência à Tração
20.
Sci Total Environ ; 821: 153440, 2022 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-35092779

RESUMO

The effects of topography, land cover type, and soil physicochemical properties on the distribution of soil organic carbon (SOC) and total nitrogen (TN) have drawn growing attention recently, but little is known about how these features-associated interactions impact SOC and TN. To elucidate how these interactions affect the preservation of carbon and nitrogen in soils, we used data-driven models (random forest regression and structural equation modeling) to identify the dominant environmental factors affecting the distribution of SOC and TN in two different soil layers (0-20 and 20-40 cm) of the Qinghai-Tibet plateau. In addition, an algorithm based on random forest ("Boruta") was chosen to identify the relevant influencing factors and partial dependence was used to depict the two most important factors. We found that rather than land cover type, environmental properties, such as soil physicochemical characteristics and altitude had the most significant effects on the distribution of SOC and TN. Our findings indicate that elevation and TN are the two most important factors influencing SOC in the surface and subsurface soil layers. Moreover, total potassium (TK) impacts TN content in the surface soil layer, but only in a specific range of concentrations, which could be attributed to anthropogenic activities such as applying nitrogen and potassium fertilizers to increase the yields of local food crop, Tibetan hulless barley. These findings provide a scientific perspective on soil nutrient preservation.


Assuntos
Carbono , Solo , Carbono/análise , China , Análise de Classes Latentes , Nitrogênio/análise , Solo/química , Tibet
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...