Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 12 de 12
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Angew Chem Int Ed Engl ; : e202409605, 2024 Jul 08.
Artigo em Inglês | MEDLINE | ID: mdl-38975961

RESUMO

Thioamides are widely used structures in pharmaceuticals and agrochemicals, as well as important synthons for the construction of sulfur-containing heterocycles. This report presents a series of visible-light-driven multicomponent reactions of amines, carbon disulfide, and olefins for the mild and versatile synthesis of linear thioamides and cyclic thiolactams. The use of inexpensive and readily available carbon disulfide as the thiocarbonyl source in a radical pathway enables the facile assembly of structurally diverse amine moieties with non-nucleophilic carbon-based reaction partners. Radical thiocarbamoylative cyclization provides a practical protocol that complements traditional approaches to thiolactams relying on deoxythionation. Mechanistic studies reveal that direct photoexcitation of in situ formed dithiocarbamate anions as well as versatile photoinduced electron transfer with diverse electron acceptors are key to the reactions.

2.
Sensors (Basel) ; 24(12)2024 Jun 09.
Artigo em Inglês | MEDLINE | ID: mdl-38931531

RESUMO

The direct-drive selective compliance assembly robot arm (SCARA) is widely used in high-end manufacturing fields, as it omits the mechanical transmission structures and has the advantages of high positioning accuracy and fast movement speed. However, due to the intensifying dynamic coupling problem of structures in the direct-drive SCARA, the permanent magnet synchronous motors (PMSMs) located at the joints will take on nonstationary loads, which causes excessive internal temperature and reduces the lifetime of PMSMs. To address these issues, the lifetime prediction of PMSMs is studied. The kinematic and dynamic models of the SCARA are established to calculate the torque curve required by the PMSM in specific typical motion tasks. Additionally, considering thermal stress as the main factor affecting lifetime, accelerated degradation tests are conducted on insulation material. Then, the reliability function of the PMSM is formulated based on the accelerated degradation model. Based on the parameters and working conditions of the PMSM, the temperature field distribution is obtained through simulation. The maximum temperature is used as the reference temperature to conduct reliability evaluation and lifetime prediction of the PMSM. The research results show that for a typical point-to-point task, the PMSM can run for 102,623 h while achieving the reliability requirement of 0.99.

3.
J Econ Entomol ; 117(1): 209-217, 2024 Feb 12.
Artigo em Inglês | MEDLINE | ID: mdl-38124401

RESUMO

Perina nuda (Lepidoptera: Lymantriidae) is a serious pest of banyan trees (Ficus spp.), which is distributed in South China, but little is known about the host preference on the different banyan tree species. To address this gap, we conducted experiments to investigate larval feeding preferences, assessing the impact of feeding experience in both choice and no-choice conditions. Fifth and sixth instars were exposed to 4 banyan species, and food intake, feeding area, and relative ingestion index were measured. Our findings reveal that Ficus concinna was the preferred host of fifth instars in choice tests, while sixth instars exhibited a preference for this host in no-choice tests. In contrast, fifth instars did not display a significant preference for any of the 4 species in no-choice tests. However, sixth instars fed on F. microcarpa, F. altissima, and F. concinna continued to exhibit a preference for the original host. These observations indicate that larval feeding preference changes with instar, and feeding experience contributes to a preference for the original host. Consequently, the feeding preference of P. nuda larvae is influenced by multiple factors, including instar and previous feeding experience. These findings enhance our understanding of P. nuda's ecological interactions and its potential impact on various banyan tree species.


Assuntos
Ficus , Lepidópteros , Mariposas , Animais , Larva , Comportamento Alimentar , Plantas , Árvores
4.
Artigo em Inglês | MEDLINE | ID: mdl-37549074

RESUMO

Fabric-based pneumatic actuators (FPAs) are extensively employed in the design of lightweight and compliant soft wearable assistive gloves. However, conventional FPAs typically exhibit limited output force, thereby restricting the applications of such gloves. This paper presents the development of a novel honeycomb pneumatic actuator (HPA) constructed using flexible thermoplastic polyurethane (TPU) coating through hot pressing or ultrasonic welding techniques. Compared to the previously utilized double-layer fabric-based pneumatic actuators (DLFPAs), the HPAs yields a remarkable 862% increase in end output force. It can produce a tip force of 13.57 N at a pressure of 150 kPa. The integration of HPAs onto a soft pneumatic glove enables the facilitation of various activities of daily living. A series of trials involving nine patients were conducted to assess the effectiveness of the soft glove. The experimental results indicate that when assisted by the glove, the patients' finger metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints achieved angles of 87.67 ± 19.27° and 64.2 ± 30.66°, respectively. Additionally, the average fingertip force reached 10.16 ± 4.24 N, the average grip force reached 26.04 ± 15.08 N, and the completion rate of daily functions for the patients increased from 39% to 76%. These outcomes demonstrate that the soft glove effectively aids in finger movements and significantly enhances the patients' daily functioning.


Assuntos
Exoesqueleto Energizado , Robótica , Humanos , Atividades Cotidianas , Desenho de Equipamento , Dedos
5.
Front Neurosci ; 17: 1219553, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37483356

RESUMO

The integration of haptic technology into affective computing has led to a new field known as affective haptics. Nonetheless, the mechanism underlying the interaction between haptics and emotions remains unclear. In this paper, we proposed a novel haptic pattern with adaptive vibration intensity and rhythm according to the volume, and applied it into the emotional experiment paradigm. To verify its superiority, the proposed haptic pattern was compared with an existing haptic pattern by combining them with conventional visual-auditory stimuli to induce emotions (joy, sadness, fear, and neutral), and the subjects' EEG signals were collected simultaneously. The features of power spectral density (PSD), differential entropy (DE), differential asymmetry (DASM), and differential caudality (DCAU) were extracted, and the support vector machine (SVM) was utilized to recognize four target emotions. The results demonstrated that haptic stimuli enhanced the activity of the lateral temporal and prefrontal areas of the emotion-related brain regions. Moreover, the classification accuracy of the existing constant haptic pattern and the proposed adaptive haptic pattern increased by 7.71 and 8.60%, respectively. These findings indicate that flexible and varied haptic patterns can enhance immersion and fully stimulate target emotions, which are of great importance for wearable haptic interfaces and emotion communication through haptics.

6.
Front Microbiol ; 14: 1123632, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37283923

RESUMO

Melatonin is a biomolecule that affects plant development and is involved in protecting plants from environmental stress. However, the mechanisms of melatonin's impact on arbuscular mycorrhizal (AM) symbiosis and cold tolerance in plants are still unclear. In this research, AM fungi inoculation and exogenous melatonin (MT) were applied to perennial ryegrass (Lolium perenne L.) seedlings alone or in combination to investigate their effect on cold tolerance. The study was conducted in two parts. The initial trial examined two variables, AM inoculation, and cold stress, to investigate the involvement of the AM fungus Rhizophagus irregularis in endogenous melatonin accumulation and the transcriptional levels of its synthesis genes in the root system of perennial ryegrass under cold stress. The subsequent trial was designed as a three-factor analysis, encompassing AM inoculation, cold stress, and melatonin application, to explore the effects of exogenous melatonin application on plant growth, AM symbiosis, antioxidant activity, and protective molecules in perennial ryegrass subjected to cold stress. The results of the study showed that compared to non-mycorrhizal (NM) plants, cold stress promoted an increase in the accumulation of melatonin in the AM-colonized counterparts. Acetylserotonin methyltransferase (ASMT) catalyzed the final enzymatic reaction in melatonin production. Melatonin accumulation was associated with the level of expression of the genes, LpASMT1 and LpASMT3. Treatment with melatonin can improve the colonization of AM fungi in plants. Simultaneous utilization of AM inoculation and melatonin treatment enhanced the growth, antioxidant activity, and phenylalanine ammonia-lyase (PAL) activity, while simultaneously reducing polyphenol oxidase (PPO) activity and altering osmotic regulation in the roots. These effects are expected to aid in the mitigation of cold stress in Lolium perenne. Overall, melatonin treatment would help Lolium perenne to improve growth by promoting AM symbiosis, improving the accumulation of protective molecules, and triggering in antioxidant activity under cold stress.

7.
Opt Express ; 31(5): 8610-8621, 2023 Feb 27.
Artigo em Inglês | MEDLINE | ID: mdl-36859972

RESUMO

We propose a novel (to our knowledge) driving scheme to suppress the stimulated Brillouin scattering (SBS) effect in master oscillator power amplification (MOPA) systems based on an external high-order phase modulation. Since seed sources with the linear chirp can uniformly broaden the SBS gain spectrum with a high SBS threshold, a chirp-like signal was designed by applying further editing and processing to the piecewise parabolic signal. Compared with the traditional piecewise parabolic signal, the chirp-like signal has similar linear chirp characteristics and can reduce the driving power and sampling rate requirements, enabling more efficient spectral spreading. The SBS threshold model is constructed theoretically based on the three-wave coupling equation. The spectrum modulated by the chirp-like signal is compared with the flat-top and Gaussian spectra in terms of the SBS threshold and the bandwidth-distribution normalized threshold, and a considerable improvement is demonstrated. Meanwhile, the experimental validation is carried out in a watt-class amplifier based on the MOPA structure. At a 3 dB bandwidth of ∼10 GHz, the SBS threshold of the seed source modulated by the chirp-like signal is improved by 35% compared to the flat-top spectrum and 18% compared to the Gaussian spectrum, respectively, and the normalized threshold is also the highest among them. Our study shows that the SBS suppression effect is not only related to the power distribution of the spectrum but also can be improved by the time domain design, which provides a new idea for analyzing and improving the SBS threshold of narrow-linewidth fiber lasers.

8.
Front Neurol ; 13: 829090, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35370905

RESUMO

Aim: This study aimed to explore the effect of enriched rehabilitation (ER) on cognitive function and serum glutamate levels in patients with stroke. Methods: Forty patients diagnosed with post-stroke cognitive impairment (PSCI), according to the inclusion criteria, and undergoing inpatient rehabilitation were enrolled in the study. Patients were randomly assigned to receive 8 weeks of ER treatment (ER group; n = 20) or conventional medical treatment (CM group; n = 20). In addition, 20 age-matched healthy subjects who were outpatients in our hospital during the same period formed the healthy control (HC) group. In- and between-group differences in cognitive function were assessed during pre-intervention and post-intervention based on the Montreal Cognitive Assessment (MoCA), the Symbol Digit Modalities Test (SDMT), and the Trail Making Test (TMT). The serum levels of glutamate, tumor necrosis factor (TNF), and malondialdehyde (MDA) levels were also detected pre-intervention and post-intervention. Results: Pre-intervention cognitive function and the levels of all the serum parameters assessed significant difference between the HC group and the PSCI group (both ER and CM groups) (p < 0.05), but not between the two groups of patients with PSCI (p > 0.05). Significant improvements were observed in cognitive function in both the ER and the CM groups post-intervention compared with pre-intervention, as evidenced by the measured improvement in MoCA, SDMT, and TMT scores. Similar improvements were seen for serum glutamate, the degree of oxidative damage, and the level of inflammation in both the treatment groups (p < 0.05). More enhancements in cognitive function, including MoCA, SDMT, TMT scores, and the serum levels of glutamate, the degree of oxidative damage, and the level of inflammation were shown in the ER group compared with the CM group post-intervention (p < 0.05). Conclusions: ER can improve cognitive function in patients with PSCI. The associated mechanism may be related to the negative regulatory effect of ER on serum glutamate, TNF, and MDA levels, which is likely to enhance synaptic plasticity and alleviate oxidative stress- and inflammation-related damage, at least to some extent.

9.
Plant Physiol ; 187(4): 2296-2310, 2021 12 04.
Artigo em Inglês | MEDLINE | ID: mdl-34601582

RESUMO

AKT2 potassium (K+) channels are members of the plant Shaker family which mediate dual-directional K+ transport with weak voltage-dependency. Here we show that OsAKT2 of rice (Oryza sativa) functions mainly as an inward rectifier with strong voltage-dependency and acutely suppressed outward activity. This is attributed to the presence of a unique K191 residue in the S4 domain. The typical bi-directional leak-like property was restored by a single K191R mutation, indicating that this functional distinction is an intrinsic characteristic of OsAKT2. Furthermore, the opposite R195K mutation of AtAKT2 changed the channel to an inward-rectifier similar to OsAKT2. OsAKT2 was modulated by OsCBL1/OsCIPK23, evoking the outward activity and diminishing the inward current. The physiological relevance in relation to the rectification diversity of OsAKT2 was addressed by functional assembly in the Arabidopsis (Arabidopsis thaliana) akt2 mutant. Overexpression (OE) of OsAKT2 complemented the K+ deficiency in the phloem sap and leaves of the mutant plants but did not significantly contribute to the transport of sugars. However, the expression of OsAKT2-K191R overcame both the shortage of phloem K+ and sucrose of the akt2 mutant, which was comparable to the effects of the OE of AtAKT2, while the expression of the inward mutation AtAKT2-R195K resembled the effects of OsAKT2. Additionally, OE of OsAKT2 ameliorated the salt tolerance of Arabidopsis.


Assuntos
Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Oryza/genética , Oryza/metabolismo , Floema/metabolismo , Canais de Potássio/metabolismo , Tolerância ao Sal/fisiologia , Produtos Agrícolas/genética , Produtos Agrícolas/metabolismo , Regulação da Expressão Gênica de Plantas , Genes de Plantas , Mutação , Floema/genética , Canais de Potássio/genética , Tolerância ao Sal/genética
10.
Zhongguo Fei Ai Za Zhi ; 23(9): 772-791, 2020 Sep 20.
Artigo em Chinês | MEDLINE | ID: mdl-32752580

RESUMO

BACKGROUND: In recent years, immune checkpoint inhibitors (ICIs) have become a hot spot in cancer because of their remarkable survival benefits on non-small cell lung cancer (NSCLC) patients. However, the immune-related adverse events (ir-AEs) induced by ICIs have been frequently reported due to its specificity and severity. This article is to summarize and evaluate ir-AEs induced by ICIs. Hopefully it can provide guidance for advanced NSCLC patients treatment options, early recognition and management of ir-AEs. METHODS: Randomized controlled trials (RCT) which involved ICIs in the treatment of advanced NSCLC were retrieved in the Cochrane Libraby, PubMed, EMBASE and other databases. The primary outcome includes the incidence, grade and organ specificity of ir-AEs. Relative risk (RR) was used as the effect size, which was expressed as 95% confidence interval (CI). The Stata 15.0 and RevMan 5.3 software are used to conduct the meta analysis. RESULTS: A total of 17 RCTs were included. The ir-AEs were generally more than those in the traditional chemotherapy group. The risk and severity of ir-AEs induced by ICIs combined group were generally higher than that of ICI monotherapy, while the incidence of severe ir-AEs induced by ICIs combination therapy was similar to that of anti-cytotoxic T-lymphocyte-asscociated antigen 4 (CTLA-4) group. CONCLUSIONS: ICIs have different toxicity profile compared with chemotherapy, and their immune-related toxicity is stronger than that of traditional chemotherapy. ICIs induced ir-AEs is organ-specific, and different ICI has specific immune-related toxicity profiles. As ICIs represent a new and distinct class of treatment for NSCLC, this article has systematically illustrated the efficacy and ir-AEs induced by ICIs, hopefully it can be useful for clinicians and patients to get a further understanding of ICIs, and facilitate early prediction, comprehensive diagnosis, and prompt management of ir-AEs by providing status reference and management suggestions, so that ICI can bring more benefit for advanced NSCLC patients.


Assuntos
Carcinoma Pulmonar de Células não Pequenas/tratamento farmacológico , Carcinoma Pulmonar de Células não Pequenas/imunologia , Inibidores de Checkpoint Imunológico/efeitos adversos , Neoplasias Pulmonares/tratamento farmacológico , Neoplasias Pulmonares/imunologia , Carcinoma Pulmonar de Células não Pequenas/patologia , Humanos , Inibidores de Checkpoint Imunológico/uso terapêutico , Neoplasias Pulmonares/patologia
11.
Sheng Wu Yi Xue Gong Cheng Xue Za Zhi ; 37(1): 129-135, 2020 Feb 25.
Artigo em Chinês | MEDLINE | ID: mdl-32096386

RESUMO

In order to stimulate the patients' active participation in the process of robot-assisted rehabilitation training of stroke patients, the rehabilitation robots should provide assistant torque to patients according to their rehabilitation needs. This paper proposed an assist-as-needed control strategy for wrist rehabilitation robots. Firstly, the ability evaluation rules were formulated and the patient's ability was evaluated according to the rules. Then the controller was designed. Based on the evaluation results, the controller can calculate the assistant torque needed by the patient to complete the rehabilitation training task and send commands to motor. Finally, the motor is controlled to output the commanded value, which assists the patient to complete the rehabilitation training task. The control strategy was implemented to the wrist function rehabilitation robot, which could achieve the training effect of assist-as-needed and could avoid the surge of assistance torque. In addition, therapists can adjust multiple parameters in the ability evaluation rules online to customize the difficulty of tasks for patients with different rehabilitation status. The method proposed in this paper does not rely on the information from force sensor, which reduces development costs and is easy to implement.


Assuntos
Robótica , Reabilitação do Acidente Vascular Cerebral/instrumentação , Punho/fisiologia , Humanos , Modalidades de Fisioterapia
12.
Zhongguo Zhong Yao Za Zhi ; 42(4): 644-648, 2017 Feb.
Artigo em Chinês | MEDLINE | ID: mdl-28959831

RESUMO

To provide guidance for quality control and variety breeding of Gastrodia elata f. glauca cultivated form in Zhaotong, nine agronomic traits of G. elata f. glauca cultivation form were measured and the traits were analyzed using multiple comparison,correlation analysis, multiple stepwise regression analysis and path analysis. The results of multiple comparison and analysis showed that the number of dot ring and the length-width ratio of tuber were no different in G. elata f. glauca cultivation form. The coefficient of variation about the single tuber fresh weigh, ring spacing and belly button diameter was about 20%. The coefficient of variation about the length of the tuber, the width of the tuber, the thickness of the tuber, the length-width ratio of tuber and the number of dot ring was near 10%. The correlation analysis results showed that the single tuber fresh weigh and the length,the width and the thickness of the tuber were extremely significant positive correlated. The results of multiple stepwise regression analysis and path analysis showed that the length, the width and the thickness of the tuber were the main factors affecting the fresh weight of single tuber,which were the best agronomic traits on high yield of G. elata f. glauca. The length of the tuber,the width of the tuber and the thickness of the tuber, which would be used as indicators of the characteristics of high yield varieties in Zhaotong. The number of dot ring and the length-width ratio of tuber, which would be selected as quality control indicators of the genuine Chinese medicinal materials in Zhaotong.


Assuntos
Gastrodia/crescimento & desenvolvimento , Tubérculos/crescimento & desenvolvimento , Plantas Medicinais/crescimento & desenvolvimento , China , Fenótipo , Melhoramento Vegetal , Controle de Qualidade
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...