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1.
Small ; 20(30): e2307482, 2024 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-38412428

RESUMO

Manganese-based oxides (MnOx) suffer from sluggish charge diffusion kinetics and poor cycling stability in sodium ion storage. Herein, an interfacial electric field (IEF) in CeO2/MnOx is constructed to obtain high electronic/ionic conductivity and structural stability of MnOx. The as-designed CeO2/MnOx exhibits a remarkable capacity of 397 F g-1 and favorable cyclic stability with 92.13% capacity retention after 10,000 cycles. Soft X-ray absorption spectroscopy and partial density of states results reveal that the electrons are substantially injected into the Mn t2g orbitals driven by the formed IEF. Correspondingly, the MnO6 units in MnOx are effectively activated, endowing the CeO2/MnOx with fast charge transfer kinetics and high sodium ion storage capacity. Moreover, In situRaman verifies a remarkably increased structural stability of CeO2/MnOx, which is attributed to the enhanced Mn─O bond strength and efficiently stabilized MnO6 units. Mechanism studies show that the downshift of Mn 3d-band center dramatically increases the Mn 3d-O 2p orbitals overlap, thus inhibiting the Jahn-Teller (J-T) distortion of MnOx during sodium ion insertion/extraction. This work develops an advanced strategy to achieve both fast and sustainable sodium ion storage in metal oxides-based energy materials.

2.
Angew Chem Int Ed Engl ; 63(23): e202404834, 2024 Jun 03.
Artigo em Inglês | MEDLINE | ID: mdl-38588076

RESUMO

Transition metal oxides (TMOs) are key in electrochemical energy storage, offering cost-effectiveness and a broad potential window. However, their full potential is limited by poor understanding of their slow reaction kinetics and stability issues. This study diverges from conventional complex nano-structuring, concentrating instead on spin-related charge transfer and orbital interactions to enhance the reaction dynamics and stability of TMOs during energy storage processes. We successfully reconfigured the orbital degeneracy and spin-dependent electronic occupancy by disrupting the symmetry of magnetic cobalt (Co) sites through straightforward strain stimuli. The key to this approach lies in the unfilled Co 3d shell, which serves as a spin-dependent regulator for carrier transfer and orbital interactions within the reaction. We observed that the opening of these 'spin gates' occurs during a transition from a symmetric low-spin state to an asymmetric high-spin state, resulting in enhanced reaction kinetics and maintained structural stability. Specifically, the spin-rearranged Al-Co3O4 exhibited a specific capacitance of 1371 F g-1, which is 38 % higher than that of unaltered Co3O4. These results not only shed light on the spin effects in magnetic TMOs but also establish a new paradigm for designing electrochemical energy storage materials with improved efficiency.

3.
Angew Chem Int Ed Engl ; : e202408414, 2024 Jun 08.
Artigo em Inglês | MEDLINE | ID: mdl-38850273

RESUMO

Transition metal oxides (TMOs) are promising cathode materials for aqueous zinc ion batteries (ZIBs), however, their performance is hindered by a substantial Hubbard gap, which limits electron transfer and battery cyclability. Addressing this, we introduce a heteroatom coordination approach, using triethanolamine to induce axial N coordination on Mn centers in MnO2, yielding N-coordinated MnO2 (TEAMO). This approach leverages the change of electronegativity disparity between Mn and ligands (O and N) to disrupt spin symmetry and augment spin polarization. This enhancement leads to the closure of the Hubbard gap, primarily driven by the intensified occupancy of the Mn eg orbitals. The resultant TEAMO exhibit a significant increase in storage capacity, reaching 351 mAh g-1 at 0.1 A g-1. Our findings suggest a viable strategy for optimizing the electronic structure of TMO cathodes, enhancing the potential of ZIBs in energy storage technology.

4.
J Am Chem Soc ; 145(49): 26699-26710, 2023 Dec 13.
Artigo em Inglês | MEDLINE | ID: mdl-38039528

RESUMO

Transition-metal oxides (TMOs) often struggle with challenges related to low electronic conductivity and unsatisfactory cyclic stability toward cationic intercalation. In this work, we tackle these issues by exploring an innovative strategy: leveraging heightened π-donation to activate the t2g orbital, thereby enhancing both electron/ion conductivity and structural stability of TMOs. We engineered Ni-doped layered manganese dioxide (Ni-MnO2), which is characterized by a distinctive Ni-O-Mn bridging configuration. Remarkably, Ni-MnO2 presents an impressive capacitance of 317 F g-1 and exhibits a robust cyclic stability, maintaining 81.58% of its original capacity even after 20,000 cycles. Mechanism investigations reveal that the incorporation of Ni-O-Mn configurations stimulates a heightened π-donation effect, which is beneficial to the π-type orbital hybridization involving the O 2p and the t2g orbital of Mn, thereby accelerating charge-transfer kinetics and activating the redox capacity of the t2g orbital. Additionally, the charge redistribution from Ni to the t2g orbital of Mn effectively elevates the low-energy orbital level of Mn, thus mitigating the undesirable Jahn-Teller distortion. This results in a subsequent decrease in the electron occupancy of the π*-antibonding orbital, which promotes an overall enhancement in structural stability. Our findings pave the way for an innovative paradigm in the development of fast and stable electrode materials for intercalation energy storage by activating the low orbitals of the TM center from a molecular orbital perspective.

5.
Aging Male ; 26(1): 2261540, 2023 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-37752726

RESUMO

OBJECTIVE: This study aimed to determine whether the C-reactive protein-to-albumin ratio (CAR) can serve as a prognostic marker in patients with sepsis. METHODS: Chinese and English databases were searched to retrieve the included literature. The pooled sensitivity (SEN), specificity (SPE), positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR), and area under the curve (AUC) of the summary receiver operating characteristic (SROC) with their 95% confidence interval (CI) were calculated using the bivariate model. Moreover, the hazard ratio (HR) and 95% CI were calculated using the random effect model. RESULTS: Nine articles comprising 3224 patients with sepsis were included in the meta-analysis. The pooled SEN was 0.73 (95% CI 0.65-0.80), the pooled SPE was 0.78 (95% CI 0.69-0.84), the pooled PLR was 3.29 (95% CI 2.15-5.03), the pooled NLR was 0.35 (95% CI 0.24-0.49), and the pooled DOR was 9.50 (95% CI 4.38-20.59). The AUC under the SROC was 0.82 (95% CI 0.78-0.85) for the prognostic meta-analysis. The pooled HR was 1.10 (95% CI 1.02-1.18). CONCLUSIONS: This meta-analysis suggests that a high CAR level is associated with increased mortality and a poor prognosis.


Assuntos
Proteína C-Reativa , Sepse , Humanos , Prognóstico , Albuminas , Sepse/diagnóstico , Área Sob a Curva
6.
J Exp Bot ; 73(16): 5474-5489, 2022 09 12.
Artigo em Inglês | MEDLINE | ID: mdl-35652375

RESUMO

Wheat (Triticum aestivum) is a commercially important crop and its production is seriously threatened by the fungal pathogen Puccinia striiformis f. sp. tritici West (Pst). Resistance (R) genes are critical factors that facilitate plant immune responses. Here, we report a wheat R gene NB-ARC-LRR ortholog, TaYRG1, that is associated with distinct alternative splicing events in wheat infected by Pst. The native splice variant, TaYRG1.6, encodes internal-motif-deleted polypeptides with the same N- and C-termini as TaYRG1.1, resulting in gain of function. Transient expression of protein variants in Nicotiana benthamiana showed that the NB and ARC domains, and TaYRG1.6 (half LRR domain), stimulate robust elicitor-independent cell death based on a signal peptide, although the activity was negatively modulated by the CC and complete LRR domains. Furthermore, molecular genetic analyses indicated that TaYRG1.6 enhanced resistance to Pst in wheat. Moreover, we provide multiple lines of evidence that TaYRG1.6 interacts with a dynamin-related protein, TaDrp1. Proteome profiling suggested that the TaYRG1.6-TaDrp1-DNM complex in the membrane trafficking systems may trigger cell death by mobilizing lipid and kinase signaling in the endocytosis pathway. Our findings reveal a unique mechanism by which TaYRG1 activates cell death and enhances disease resistance by reconfiguring protein structure through alternative splicing.


Assuntos
Basidiomycota , Triticum , Processamento Alternativo , Basidiomycota/fisiologia , Resistência à Doença/genética , Dinaminas/genética , Dinaminas/metabolismo , Doenças das Plantas/microbiologia , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Puccinia , Triticum/microbiologia
7.
Int J Mol Sci ; 23(22)2022 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-36430495

RESUMO

Cyclins are involved in cell division and proliferation by activating enzymes required for the cell cycle progression. Our genome-wide analysis identified 76 cyclin genes in Brassica rapa, which were divided into nine different types (A-, B-, C-, D-, H-, L-, P-, T-, and SDS-type). Cyclin genes were unevenly scattered on all chromosomes, with a maximum of 10 on A08 and a minimum of 2 on A04. The gene structure and conserved motif analysis showed that the cyclins which belonged to the same type or subgroup have a comparable intron/exon pattern or motif. A total of 14 collinear gene pairs suggested that the B. rapa cyclin genes experienced a mass of segmental duplication. The Ka/Ks analysis revealed that the Brcyclin gene family has undergone an extensive purifying pressure. By analyzing the cis-elements in the promoters, we identified 11 cis-elements and five of them are related to the hormone response. We observed 48 potential miRNAs targeting 44 Brcyclin genes, which highlighted the involvement of miRNAs in the regulation of cyclin genes. An association analysis between the leaf size and SNPs in mutants and a transcriptome analysis of two Chinese cabbage-cabbage translocation lines also showed that the Brcyclin gene family was involved in the development of the leaves. The functional characterization of the B. rapa cyclin gene family will provide the foundation for future physiological and genetic studies in the regulation of leaf growth.


Assuntos
Brassica rapa , MicroRNAs , Brassica rapa/metabolismo , Ciclinas/genética , Ciclinas/metabolismo , Genoma de Planta , Regulação da Expressão Gênica de Plantas , Transcriptoma , Mapeamento Cromossômico , Filogenia , Perfilação da Expressão Gênica , MicroRNAs/metabolismo
8.
Theor Appl Genet ; 134(7): 1899-1924, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-33655424

RESUMO

KEY MESSAGE: The importance and potential of the multi-purpose crop sorghum in global food security have not yet been fully exploited, and the integration of the state-of-art genomics and high-throughput technologies into breeding practice is required. Sorghum, a historically vital staple food source and currently the fifth most important major cereal, is emerging as a crop with diverse end-uses as food, feed, fuel and forage and a model for functional genetics and genomics of tropical grasses. Rapid development in high-throughput experimental and data processing technologies has significantly speeded up sorghum genomic researches in the past few years. The genomes of three sorghum lines are available, thousands of genetic stocks accessible and various genetic populations, including NAM, MAGIC, and mutagenised populations released. Functional and comparative genomics have elucidated key genetic loci and genes controlling agronomical and adaptive traits. However, the knowledge gained has far away from being translated into real breeding practices. We argue that the way forward is to take a genome-based approach for tailored designing of sorghum as a multi-functional crop combining excellent agricultural traits for various end uses. In this review, we update the new concepts and innovation systems in crop breeding and summarise recent advances in sorghum genomic researches, especially the genome-wide dissection of variations in genes and alleles for agronomically important traits. Future directions and opportunities for sorghum breeding are highlighted to stimulate discussion amongst sorghum academic and industrial communities.


Assuntos
Melhoramento Vegetal , Sorghum/genética , Agricultura , Alelos , Grão Comestível/genética , Genética Populacional , Genômica , Fenótipo
10.
BMC Anesthesiol ; 20(1): 52, 2020 02 28.
Artigo em Inglês | MEDLINE | ID: mdl-32111162

RESUMO

BACKGROUND: This review and meta-analysis aims to evaluate the analgesic efficacy of continuous transversus abdominis plane (TAP) block compared with epidural analgesia (EA) in adults after abdominal surgery. METHODS: The databases PubMed, Embase and Cochrane Central Register were searched from inception to June 2019 for all available randomized controlled trials (RCTs) that evaluated the analgesic efficacy of continuous TAP block compared with EA after abdominal surgery. The weighted mean differences (WMDs) were estimates for continuous variables with a 95% confidence interval (CI) and risk ratio (RR) for dichotomous data. The pre-specified primary outcome was the dynamic pain scores 24 h postoperatively. RESULTS: Eight trials including 453 patients (TAP block:224 patients; EA: 229 patients) ultimately met the inclusion criteria and seven trials were included in the meta-analysis. Dynamic pain scores after 24 h were equivalent between TAP block and EA groups (WMD:0.44; 95% CI: 0.1 to 0.99; I2 = 91%; p = 0.11). The analysis showed a significant difference between the subgroups according to regularly administering (4 trials; WMD:-0.11; 95% CI: - 0.32 to 0.09; I2 = 0%; p = 0.28) non-steroidal anti-inflammatory drugs (NSAIDs) or not (3 trials; WMD:1.02; 95% CI: 0.09 to 1.96; I2 = 94%; p = 0.03) for adjuvant analgesics postoperatively. The measured time of the urinary catheter removal in the TAP group was significantly shorter (3 trials, WMD:-18.95, 95% CI:-25.22 to - 12.71; I2 = 0%; p < 0.01), as was time to first ambulation postoperatively (4 trials, WMD:-6.61, 95% CI: - 13.03 to - 0.19; I2 = 67%; p < 0.05). CONCLUSION: Continuous TAP block, combined with NSAIDs, can provide non-inferior dynamic analgesia efficacy compared with EA in postoperative pain management after abdominal surgery. In addition, continuous TAP block is associated with fewer postoperative side effects.


Assuntos
Abdome/cirurgia , Músculos Abdominais/inervação , Analgesia Epidural/métodos , Analgésicos/uso terapêutico , Bloqueio Nervoso/métodos , Dor Pós-Operatória/tratamento farmacológico , Ultrassonografia de Intervenção/métodos , Músculos Abdominais/diagnóstico por imagem , Humanos , Ensaios Clínicos Controlados Aleatórios como Assunto , Resultado do Tratamento
11.
Nano Lett ; 19(7): 4601-4607, 2019 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-31185572

RESUMO

Uncontrollable dendrite growth is one of the major problems that hinders the application of lithium (Li) metal anode in rechargeable Li batteries. Achieving uniform Li deposition is the key to tackle this intractable problem. Herein, we report the highly dispersed Cu2O nanoparticles (NPs) in situ anchored on partially reduced graphene oxide via a low-temperature pyrolysis process could serve as seeds for the Li metal deposition. The lithiophilic nature of Cu2O NPs reduces the overpotential of Li nucleation and relieves the electrode polarization, enabling uniform Li nucleation and smooth plating, thus effectively eliminating dendritic and dead Li. As a result, the resulted Li metal electrodes deliver a high Coulombic efficiency of 95.6% after 140 cycles at a current density of 2 mA cm-2 and a prolonged lifespan (800 h at 1 mA cm-2) for the symmetrical cell.

12.
Plant Cell Environ ; 42(1): 145-157, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-29664126

RESUMO

The plant sucrose nonfermenting kinase 1 (SnRK1) kinases play the central roles in the processes of energy balance, hormone perception, stress resistance, metabolism, growth, and development. However, the functions of these kinases are still elusive. In this study, we used GsSnRK1 of wild soybean as bait to perform library-scale screens by the means of yeast two-hybrid to identify its interacting proteins. The putative interactions were verified by yeast retransformation and ß-galactosidase assays, and the selected interactions were further confirmed in planta by bimolecular fluorescence complementation and biochemical Co-IP assays. Protein phosphorylation analyses were carried out by phos-tag assay and anti-phospho-(Ser/Thr) substrate antibodies. Finally, we obtained 24 GsSnRK1 interactors and several putative substrates that can be categorized into SnRK1 regulatory ß subunit, protein modification, biotic and abiotic stress-related, hormone perception and signalling, gene expression regulation, water and nitrogen transport, metabolism, and unknown proteins. Intriguingly, we first discovered that GsSnRK1 interacted with and phosphorylated the components of soybean nodulation and symbiotic nitrogen fixation. The interactions and potential functions of GsSnRK1 and its associated proteins were extensively discussed and analysed. This work provides plausible clues to elucidate the novel functions of SnRK1 in response to variable environmental, metabolic, and physiological requirements.


Assuntos
Glycine max/enzimologia , Proteínas de Plantas/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Imunoprecipitação , Fosforilação , Glycine max/metabolismo , Especificidade por Substrato , Técnicas do Sistema de Duplo-Híbrido
13.
Langmuir ; 35(17): 5871-5877, 2019 04 30.
Artigo em Inglês | MEDLINE | ID: mdl-30955338

RESUMO

Reverse micelles (RMs) with confined water pools have been applied in many fields. However, the water insolubility of RMs seriously limits the scope of their application, especially those needed to operate in aqueous environments. Here, we report the first successful transfer of RMs from the organic phase to water phase without disturbing their confined water pools and hydrophobic alkyl region. This transfer was achieved by virtue of a mild host-guest interaction between the hydrophobic tails of interfacial cross-linked reverse micelles (ICRMs) and the hydrophobic cavity of (2-hydroxypropyl)-ß-cyclodextrin (HP-ß-CD). Benefitting from the maintained confined water pools and the hydrophobic scaffold, the obtained water-soluble ICRMs served as multifunctional nanoplatforms for enzyme-mimicking catalysis and image-guided cancer therapy, which were impossible for normal RMs lacking water solubility or confined pool-buried water-soluble nanoparticles without a hydrophobic alkyl chain. This mild transfer approach thus surmounts the application obstacle of RMs and opens up new avenues for their application in aqueous environments.


Assuntos
Antineoplásicos/farmacologia , Portadores de Fármacos/química , Corantes Fluorescentes/química , Nanopartículas Metálicas/química , Micelas , 2-Hidroxipropil-beta-Ciclodextrina/química , Células A549 , Benzoína/química , Catálise , Portadores de Fármacos/síntese química , Liberação Controlada de Fármacos , Fluoruracila/análogos & derivados , Fluoruracila/farmacologia , Ouro/química , Humanos , Neoplasias/diagnóstico por imagem , Neoplasias/tratamento farmacológico , Oxirredução , Rodaminas/química , Água/química
14.
BMC Pregnancy Childbirth ; 19(1): 312, 2019 Aug 27.
Artigo em Inglês | MEDLINE | ID: mdl-31455322

RESUMO

BACKGROUND: This study aims to evaluate the curative effect and complications in cesarean scar pregnancy (CSP) patients treated with a transvaginal injection of absolute ethanol (AE) around the gestation sac (GS) under ultrasound guidance. METHODS: This retrospective clinical investigation analyzed 26 CSP patients treated at the Affiliated Hospital of Guilin Medical University in Guilin, Guangxi, China, between January 1, 2018 and January 30, 2019. Outcomes and complications were analyzed following treatment with AE. RESULTS: Out of the entire group, 20 patients were successfully treated with a single AE injection, while the remaining six patients required two or three repeat injections. In 21 patients, the serum beta-human chorionic gonadotropin (ß-hCG) level was reduced to > 50% 1 day after a single AE injection; in 19 patients, the serum ß-hCG level was reduced to > 80% 4 days after a single AE injection. In all patients, the average time for serum ß-hCG to reduce to normal levels (< 3.0 mIU/mL) was 36.50 ± 12.54 days. The overall cure rate of CSP by AE injection was 100%. Average length of hospitalization was 6.73 ± 3.66 days, with Patient 2 having the longest hospitalization at 17 days, and Patient 3 the shortest at 2 days. No adverse effects on hematopoietic, hepatic or renal function were observed in the short term. CONCLUSION: The study demonstrated that transvaginal injection of AE around the gestation sac under ultrasound guidance had good clinical effects, fewer complications, and merit as a novel treatment for CSP. However, larger multi-center trials are needed to confirm the safety and effectiveness of this treatment.


Assuntos
Aborto Terapêutico/métodos , Cicatriz/complicações , Etanol/administração & dosagem , Gravidez Ectópica/tratamento farmacológico , Ultrassonografia de Intervenção/métodos , Administração Intravaginal , Adulto , Cesárea/efeitos adversos , Feminino , Saco Gestacional/efeitos dos fármacos , Humanos , Gravidez , Gravidez Ectópica/etiologia , Estudos Retrospectivos , Resultado do Tratamento
15.
Am J Emerg Med ; 37(9): 1657-1664, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-30522935

RESUMO

BACKGROUND: The effects of corticosteroids on clinical outcomes of patients with sepsis remains controversial. We aimed to further determine the effectiveness of corticosteroids in reducing mortality in adult patients with severe sepsis by comparison with placebo. METHODS: Pubmed, Embase, Medline, Cochrane Central Register of Controlled Trials (CENTRAL) as well as the Information Sciences Institute (ISI) Web of Science were searched for all controlled studies that compared corticosteroids and placebo in adult patients with severe sepsis. The primary outcome was the mortality 28-day mortality and the secondary outcomes were mortality at longest follow up, occurrence, and reoccurrence of septic shock. RESULTS: A total of 19 trials involving 7035 patients were pooled in our final analyses. No significant heterogeneity was found in any of the outcome measures. Compared with placebo, corticosteroids were associated with a lower 28-day mortality (RR 0.91, 95% CI 0.85-0.98, Z = 2.57, P = 0.01) both in patients having sepsis and in those who developed septic shock (RR 0.92, 95% CI 0.85-0.99, Z = 2.19, P = 0.03), while no significant difference was found in mortality with the longest follow up in patients either having sepsis (RR 0.94, 95% CI 0.89-1.00, Z = 1.93, P = 0.05), or occurrence (RR 0.83, 95% CI 0.56-1.24, Z = 0.90, P = 0.37) or reoccurrence of septic shock (RR 1.08, 95% CI 1.00-1.16, Z = 1.89, P = 0.06). CONCLUSIONS: Corticosteroids were effective in reducing the 28-day mortality in patients with severe sepsis and in those with septic shock.


Assuntos
Corticosteroides/uso terapêutico , Sepse/tratamento farmacológico , Humanos , Sepse/mortalidade , Choque Séptico/tratamento farmacológico , Choque Séptico/mortalidade
16.
Proc Natl Acad Sci U S A ; 111(27): E2780-6, 2014 Jul 08.
Artigo em Inglês | MEDLINE | ID: mdl-24958890

RESUMO

Ferroelectricity has long been speculated to have important biological functions, although its very existence in biology has never been firmly established. Here, we present compelling evidence that elastin, the key ECM protein found in connective tissues, is ferroelectric, and we elucidate the molecular mechanism of its switching. Nanoscale piezoresponse force microscopy and macroscopic pyroelectric measurements both show that elastin retains ferroelectricity at 473 K, with polarization on the order of 1 µC/cm(2), whereas coarse-grained molecular dynamics simulations predict similar polarization with a Curie temperature of 580 K, which is higher than most synthetic molecular ferroelectrics. The polarization of elastin is found to be intrinsic in tropoelastin at the monomer level, analogous to the unit cell level polarization in classical perovskite ferroelectrics, and it switches via thermally activated cooperative rotation of dipoles. Our study sheds light onto a long-standing question on ferroelectric switching in biology and establishes ferroelectricity as an important biophysical property of proteins. This is a critical first step toward resolving its physiological significance and pathological implications.


Assuntos
Elastina/química , Eletricidade , Animais , Elastina/fisiologia , Microscopia Eletrônica de Transmissão , Simulação de Dinâmica Molecular , Suínos , Termogravimetria
17.
Angew Chem Int Ed Engl ; 53(20): 5064-8, 2014 May 12.
Artigo em Inglês | MEDLINE | ID: mdl-24692257

RESUMO

Molecular ferroelectric thin films are highly desirable for their easy and environmentally friendly processing, light weight, and mechanical flexibility. A thin film of imidazolium perchlorate processed from aqueous solution is an excellent molecular ferroelectric with high spontaneous polarization, high Curie temperature, low coercivity, and superior electromechanical coupling. These attributes make it a molecular alternative to perovskite ferroelectric films in sensing, actuation, data storage, electro-optics, and molecular/flexible electronics.

18.
Sci Rep ; 14(1): 5871, 2024 Mar 11.
Artigo em Inglês | MEDLINE | ID: mdl-38467664

RESUMO

The damage behavior of limestone rock masses containing calcite mineral filling under uniaxial compression experimental conditions is unclear, and the fracture mechanism of the rock masses needs to be further explored. In this study, uniaxial compression tests were conducted on limestone rock specimens containing veined calcite by combining acoustic emission and digital image correlation techniques. The effects of veined calcite on the generation and development of cracks on the surface of the specimens until the formation of macroscopic penetration and the strength properties of the rock mass were analyzed. The results showed that the transversely distributed veined calcite caused significant stress concentrations in the rock specimens. The longitudinally distributed veined calcite caused cracks in the specimens or influenced the expansion path of the longitudinal principal cracks. The final damage pattern of the specimens didn't differ significantly from that of conventional rock masses due to the presence of veined calcite. The presence of the veined calcite had effect on the uniaxial compressive capacity of the rock, but the load variation process of the specimen with time still conformed to the load variation pattern during the uniaxial compressive test of conventional rocks.

19.
Sci Rep ; 14(1): 13738, 2024 Jun 14.
Artigo em Inglês | MEDLINE | ID: mdl-38877085

RESUMO

Non-coplanar and discontinuously jointed rock masses are more complex than coplanar and discontinuously jointed rock masses. The mechanical properties and propagation mechanisms of non-coplanar and discontinuous joints were studied via direct shear tests with microscopic numerical simulation experiments. The numerical simulation tests were performed under different normal stresses, joint inclination angles, and shear rates. The numerical experimental results show that the microscale failure of non-coplanar and discontinuously jointed rock masses is mainly caused by tensile cracks. Additionally, when the peak shear stress is reached, the growth rate of cracks increases rapidly, and the number of cracks increases with increasing normal stress. The shear strength of non-coplanar and discontinuously jointed rock masses increases with increasing normal stress. Under the same normal stress, the variation curves of the shear strength of non-coplanar and discontinuously jointed rock masses with respect to the dip angle exhibit an "S"-shaped nonlinear pattern. Rock masses with joint inclination angles of approximately 15° and 65° have minimum and maximum shear strengths, respectively. The joint dip angle has a significant impact on the final failure mode of rock bridges in the rock mass. As the joint dip angle increases, the final failure modes of rock bridges change from "end-to-end" connection to a combination of "head-to-head" and "tail-to-tail" connections. The shear rate has a certain impact on the peak shear stress, but the impact is not significant. The spatial distribution of the tensile force chains changes as shearing progresses, and stress concentration occurs at the tips of the original joints, which is the reason for the development of long tensile cracks in the deeper parts.

20.
Food Chem ; 447: 138895, 2024 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-38492298

RESUMO

Multispectral imaging, combined with stoichiometric values, was used to construct a prediction model to measure changes in dietary fiber (DF) content in Chinese cabbage leaves across different growth periods. Based on all the spectral bands (365-970 nm) and characteristic spectral bands (430, 880, 590, 490, 690 nm), eight quantitative prediction models were established using four machine learning algorithms, namely random forest (RF), backpropagation neural network, radial basis function, and multiple linear regression. Finally, a quantitative prediction model of RF learning algorithm is constructed based on all spectral bands, which has good prediction accuracy and model robustness, prediction performance with R2 of 0.9023, root mean square error (RMSE) of 2.7182 g/100 g, residual predictive deviation (RPD) of 3.1220 > 3.0. In summary, this model efficiently detects changes in DF content across different growth periods of Chinese cabbage, which offers technical support for vegetable sorting and grading in the field.


Assuntos
Algoritmos , Brassica , Redes Neurais de Computação , Verduras , Aprendizado de Máquina
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