Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 57
Filtrar
1.
ACS Nano ; 18(8): 6438-6444, 2024 Feb 27.
Artigo em Inglês | MEDLINE | ID: mdl-38363716

RESUMO

Lead halide perovskite nanocrystals, such as CsPbBr3, exhibit efficient photoluminescence (PL) up-conversion, also referred to as anti-Stokes photoluminescence (ASPL). This is a phenomenon where irradiating nanocrystals up to 100 meV below gap results in higher energy band edge emission. Most surprising is that ASPL efficiencies approach unity and involve single-photon interactions with multiple phonons. This is unexpected given the statistically disfavored nature of multiple-phonon absorption. Here, we report and rationalize near-unity anti-Stokes photoluminescence efficiencies in CsPbBr3 nanocrystals and attribute them to resonant multiple-phonon absorption by polarons. The theory explains paradoxically large efficiencies for intrinsically disfavored, multiple-phonon-assisted ASPL in nanocrystals. Moreover, the developed microscopic mechanism has immediate and important implications for applications of ASPL toward condensed phase optical refrigeration.

2.
Sensors (Basel) ; 24(3)2024 Feb 02.
Artigo em Inglês | MEDLINE | ID: mdl-38339686

RESUMO

Micro direct methanol fuel cells (µDMFCs) are a promising power source for microelectronic devices and systems. As the operating state and performance of a µDMFC is generally determined by both electrochemical polarization and methanol crossover, it is important to monitor the methanol concentration in µDMFCs. Here, we design and fabricate a microwave sensor and integrate it with a µDMFC for the online detection of methanol concentration in a nonintrusive way. The sensing area is set at the bottom of the anode chamber of a µDMFC which exhibits a maximum output power density of 28.8 mW cm-2 at 30 °C. With a square ring structure, the dual-mode microwave sensor shows a sensitivity of 9.5 MHz mol-1 L. Furthermore, the importance of methanol concentration monitoring is demonstrated in the long term. A relatively smooth methanol decline curve was obtained, which indicated a normal and stable operating status of the µDMFC. Derived from real-time recording data, fuel utilization was additionally calculated as 28.5%.

3.
J Laparoendosc Adv Surg Tech A ; 34(3): 207-213, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38386987

RESUMO

Objective: To introduce laparoscopic neo-pancreaticogastrostomy (neo-PG) and investigate its application potential in total laparoscopic pancreaticoduodenectomy (TLPD). Materials and Methods: We performed a single-center prospective single-arm trial to evaluate the feasibility and safety of neo-PG for its initial application in TLPD. The first 50 patients who were operated by a single surgeon and who underwent TLPD with neo-PG at our institution were recruited. The pre/intra/postoperation data were collected and analyzed. Results: Twenty-nine male patients and 21 female patients from May 2022 to March 2023 were included. The mean operation time was 272.60 ± 47.30 minutes. The median PG time was 16 (15, 23) minutes. Six patients had delayed gastric emptying (DGE), and all underwent standard LPD. None of the patients had Grade B/C postoperative pancreatic fistula (POPF) or postoperative hemorrhage, or underwent reoperation. The median length of post-LPD hospital stay was 6 (6, 8) days. None of the patients died within 90 days after surgery. Nineteen cases were pathologically classified as pancreatic lesion, 6 cases as bile duct lesion, 18 cases as duodenal lesion, and 7 cases as ampullary lesion. Conclusion: The laparoscopic neo-PG is a simple, safe, and feasible pancreatic anastomosis that can be applied in TLPD. Pylorus-preserving LPD may decrease DGE rate. Further studies involving more surgeons are warranted to prove that our new technique may terminate POPF in TLPD.


Assuntos
Laparoscopia , Neoplasias Pancreáticas , Feminino , Humanos , Masculino , Anastomose Cirúrgica/métodos , Laparoscopia/métodos , Fístula Pancreática , Neoplasias Pancreáticas/cirurgia , Neoplasias Pancreáticas/patologia , Pancreaticoduodenectomia/métodos , Complicações Pós-Operatórias/epidemiologia , Complicações Pós-Operatórias/cirurgia , Estudos Prospectivos , Estudos Retrospectivos
4.
Neural Netw ; 172: 106075, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38278092

RESUMO

The SSVEP-based paradigm serves as a prevalent approach in the realm of brain-computer interface (BCI). However, the processing of multi-channel electroencephalogram (EEG) data introduces challenges due to its non-Euclidean characteristic, necessitating methodologies that account for inter-channel topological relations. In this paper, we introduce the Dynamic Decomposition Graph Convolutional Neural Network (DDGCNN) designed for the classification of SSVEP EEG signals. Our approach incorporates layerwise dynamic graphs to address the oversmoothing issue in Graph Convolutional Networks (GCNs), employing a dense connection mechanism to mitigate the gradient vanishing problem. Furthermore, we enhance the traditional linear transformation inherent in GCNs with graph dynamic fusion, thereby elevating feature extraction and adaptive aggregation capabilities. Our experimental results demonstrate the effectiveness of proposed approach in learning and extracting features from EEG topological structure. The results shown that DDGCNN outperforms other state-of-the-art (SOTA) algorithms reported on two datasets (Dataset 1: 54 subjects, 4 targets, 2 sessions; Dataset 2: 35 subjects, 40 targets). Additionally, we showcase the implementation of DDGCNN in the context of synchronized BCI robotic fish control. This work represents a significant advancement in the field of EEG signal processing for SSVEP-based BCIs. Our proposed method processes SSVEP time domain signals directly as an end-to-end system, making it easy to deploy. The code is available at https://github.com/zshubin/DDGCNN.


Assuntos
Interfaces Cérebro-Computador , Humanos , Potenciais Evocados Visuais , Redes Neurais de Computação , Algoritmos , Eletroencefalografia/métodos , Estimulação Luminosa
5.
Transplant Cell Ther ; 30(1): 79.e1-79.e10, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-37924979

RESUMO

Graft-versus-host disease (GVHD) is a primary and often lethal complication of allogenic hematopoietic stem cell transplantation (HSCT). Prophylactic regimens for GVHD are given as standard pretransplantation therapy; however, up to 50% of these patients develop acute GVHD (aGVHD) and require additional immunosuppressive intervention. Using a mouse GVHD model, we previously showed that injecting mice with exopolysaccharide (EPS) from Bacillus subtilis prior to GVHD induction significantly increased 80-day survival after transplantation of complete allogeneic major histocompatibility complex-mismatched cells. To ask whether EPS might also inhibit GVHD in humans, we used humanized NSG-HLA-A2 mice and induced GVHD by i.v. injection of A2neg human peripheral blood mononuclear cells (PBMCs). Because we could not inject human donors with EPS, we transferred EPS-pretreated dendritic cells (DCs) to inhibit aGVHD. We derived these DCs from CD34+ human cord blood cells, treated them with EPS, and then injected them together with PBMCs into the NSG-HLA-A2 mice. We found that all mice that received untreated DCs were dead by day 35, whereas 25% of mice receiving EPS-treated DCs (EPS-DCs) survived. This DC cell therapy could be readily translatable to humans, because we can generate large numbers of human EPS-DCs and use them as an "off the shelf" treatment for patients undergoing HSCT.


Assuntos
Doença Enxerto-Hospedeiro , Antígeno HLA-A2 , Animais , Humanos , Transplante Homólogo/efeitos adversos , Leucócitos Mononucleares , Doença Enxerto-Hospedeiro/prevenção & controle , Modelos Animais de Doenças , Células Dendríticas
6.
J Leukoc Biol ; 115(2): 306-321, 2024 01 19.
Artigo em Inglês | MEDLINE | ID: mdl-37949818

RESUMO

The role of natural killer group 2D (NKG2D) in peripheral T cells as a costimulatory receptor is well established. However, its contribution to T cell thymic education and functional imprint is unknown. Here, we report significant changes in development, receptor signaling, transcriptional program, and function in T cells from mice lacking NKG2D signaling. In C57BL/6 (B6) and OT-I mice, we found that NKG2D deficiency results in Vß chain usage changes and stagnation of the double-positive stage in thymic T cell development. We found that the expression of CD5 and CD45 in thymocytes from NKG2D deficient mice were reduced, indicating a direct influence of NKG2D on the strength of T cell receptor (TCR) signaling during the developmental stage of T cells. Depicting the functional consequences of NKG2D, peripheral OT-I NKG2D-deficient cells were unresponsive to ovalbumin peptide stimulation. Paradoxically, while αCD3/CD28 agonist antibodies led to phenotypic T cell activation, their ability to produce cytokines remained severely compromised. We found that OT-I NKG2D-deficient cells activate STAT5 in response to interleukin-15 but were unable to phosphorylate ERK or S6 upon TCR engagement, underpinning a defect in TCR signaling. Finally, we showed that NKG2D is expressed in mouse and human thymic T cells at the double-negative stage, suggesting an evolutionarily conserved function during T cell development. The data presented in this study indicate that NKG2D impacts thymic T cell development at a fundamental level by reducing the TCR threshold and affecting the functional imprint of the thymic progeny. In summary, understanding the impact of NKG2D on thymic T cell development and TCR signaling contributes to our knowledge of immune system regulation, immune dysregulation, and the design of immunotherapies.


Assuntos
Subfamília K de Receptores Semelhantes a Lectina de Células NK , Timo , Animais , Camundongos , Humanos , Camundongos Endogâmicos C57BL , Timócitos , Receptores de Antígenos de Linfócitos T
7.
Tree Physiol ; 44(1)2024 02 06.
Artigo em Inglês | MEDLINE | ID: mdl-38102768

RESUMO

Leaf nutrient resorption and drought resistance are crucial for the growth and survival of plants. However, our understanding of the relationships between leaf nutrient resorption and plant drought resistance is still limited. In this study, we investigated the nitrogen and phosphorus resorption efficiencies (NRE and PRE), leaf structural traits, leaf osmotic potential at full hydration (Ψosm), xylem water potential at 50% loss of xylem-specific hydraulic conductivity (P50) and seasonal minimum water potential (Ψmin) for 18 shrub and tree species in a semiarid savanna ecosystem, in Southwest China. Our results showed that NRE and PRE exhibited trade-off against drought resistance traits (Ψosm and P50) across woody species. Moreover, this relationship was modulated by leaf structural investment. Species with low structural investment (e.g., leaf mass per area, leaf dry mass content and leaf construction cost [LCC]) tend to have high NRE and PRE, while those with high LCCs show high drought resistance, showing more negative Ψosm and P50.These results indicate that species with a lower leaf structural investment may have a greater need to recycle their nutrients, thus exhibiting higher nutrient resorption efficiencies, and vice versa. In conclusion, nutrient resorption efficiency may be a crucial adaptation strategy for coexisting plants in semiarid ecosystems, highlighting the importance of understanding the complex relationships between nutrient cycling and plant survival strategies.


Assuntos
Ecossistema , Pradaria , Resistência à Seca , Nitrogênio/análise , Fósforo/análise , Plantas , Árvores , China , Água , Folhas de Planta/química
8.
Artigo em Inglês | MEDLINE | ID: mdl-37756172

RESUMO

The classification problem for short time-window steady-state visual evoked potentials (SSVEPs) is important in practical applications because shorter time-window often means faster response speed. By combining the advantages of the local feature learning ability of convolutional neural network (CNN) and the feature importance distinguishing ability of attention mechanism, a novel network called AttentCNN is proposed to further improve the classification performance for short time-window SSVEP. Considering the frequency-domain features extracted from short time-window signals are not obvious, this network starts with the time-domain feature extraction module based on the filter bank (FB). The FB consists of four sixth-order Butterworth filters with different bandpass ranges. Then extracted multimodal features are aggregated together. The second major module is a set of residual squeeze and excitation blocks (RSEs) that has the ability to improve the quality of extracted features by learning the interdependence between features. The final major module is time-domain CNN (tCNN) that consists of four CNNs for further feature extraction and followed by a fully connected (FC) layer for output. Our designed networks are validated over two large public datasets, and necessary comparisons are given to verify the effectiveness and superiority of the proposed network. In the end, in order to demonstrate the application potential of the proposed strategy in the medical rehabilitation field, we design a novel five-finger bionic hand and connect it to our trained network to achieve the control of bionic hand by human brain signals directly. Our source codes are available on Github: https://github.com/JiannanChen/AggtCNN.git.

10.
Tree Physiol ; 43(12): 2109-2120, 2023 Dec 12.
Artigo em Inglês | MEDLINE | ID: mdl-37672225

RESUMO

Water stored in trunk sapwood is vital for the canopy to maintain its physiological function under high transpiration demands. Little is known regarding the anatomical properties that contribute to the hydraulic capacitance of tree trunks and whether trunk capacitance is correlated with the hydraulic and gas exchange traits of canopy branches. We examined sapwood capacitance, xylem anatomical characteristics of tree trunks, embolism resistance, the minimal xylem water potential of canopy branches, leaf photosynthesis and stomatal conductance in 22 species from a tropical seasonal rainforest and savanna. The results showed that the mean trunk sapwood capacitance did not differ between the two biomes. Capacitance was closely related to the fiber lumen fraction and fiber wall reinforcement and not to the axial and ray parenchyma fractions. Additionally, it was positively correlated with the theoretical hydraulic conductivity of a trunk and the specific hydraulic conductivity of branches, and showed a trade-off with branch embolism resistance. Species with a high trunk sapwood capacitance maintained less negative canopy water potentials in the dry season, but higher leaf photosynthetic rates and stomatal conductance in the wet season. This study provides a functional link among trunk sapwood capacitance, xylem anatomy, canopy hydraulics and photosynthesis in tropical trees.


Assuntos
Embolia , Árvores , Árvores/fisiologia , Xilema/fisiologia , Folhas de Planta/fisiologia , Fotossíntese/fisiologia , Água/fisiologia
11.
Opt Lett ; 48(7): 1902-1905, 2023 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-37221795

RESUMO

Image edge processing has widespread adoption in a variety of scientific and industrial scenarios. To date, implementations of image edge processing have mostly been done electronically, but there are still difficulties to achieve real-time, high-throughput, and low power consumption image edge processing. The advantages of optical analog computing include low power consumption, fast transmission speed, and high parallel processing capability, and optical analog differentiators make this process possible. However, the proposed analog differentiators can hardly meet the requirements of broadband, polarization insensitive, high contrast, and high efficiency at the same time. Moreover, they are limited to one-dimensional differentiation or work in reflection mode. To be better compatible with two-dimensional image processing or image recognition systems, two-dimensional optical differentiators that integrate the above advantages are urgently needed. In this Letter, a two-dimensional analog optical differentiator with edge detection operating in transmission mode is proposed. It can cover the visible band, is polarization uncorrelated, and has a resolution that reaches 1.7 µm. The efficiency of the metasurface is higher than 88%.

12.
Environ Sci Pollut Res Int ; 30(6): 14240-14252, 2023 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-36149563

RESUMO

Sulfidated nanoscale zerovalent iron (S-nZVI) supported on a flower spherical Mg(OH)2 with different Mg/Fe ration were successfully synthesized. The synthesized materials were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), Brunauer-Emmett-Teller (BET), and X-ray photoelectron spectroscopy (XPS). The results showed that S-nZVI particles were well dispersed on the petals of the flower spherical Mg(OH)2. The influence of factors, including the initial solution pH, Mg/Fe, S/Fe were studied. The trichloroethylene (TCE) adsorption data on Mg(OH)2 and S-nZVI @Mg(OH)2 fit well to a Langmuir isotherm model, and the maximum adsorption of S-nZVI @Mg(OH)2 was 253.55 mg/g, which was 2.6-fold of S-nZVI. Meanwhile, the S-nZVI @Mg(OH)2 composite expanded the pH selection range of S-nZVI from 2 to 11. Cycling experiments showed that removal rate was 58.3% for the 5th cycle. TCE removal was due to synergistic action of reduction coupled with adsorption. During this process, 65.43% of total remove TCE from ion chromatography data was reduced and 34.57% of total remove TCE was adsorbed finally. At the same time, adsorption favors reduction. These observations indicated that the S-nZVI @Mg(OH)2 can be considered as potential adsorbents to remove TCE for environment remediation.


Assuntos
Recuperação e Remediação Ambiental , Tricloroetileno , Poluentes Químicos da Água , Tricloroetileno/química , Ferro/química , Adsorção , Difração de Raios X , Poluentes Químicos da Água/química
13.
World J Clin Cases ; 10(20): 7130-7137, 2022 Jul 16.
Artigo em Inglês | MEDLINE | ID: mdl-36051122

RESUMO

BACKGROUND: Portal vein thrombosis (PVT) is a condition caused by hemodynamic disorders. It may be noted in the portal vein system when there is an inflammatory stimulus in the abdominal cavity. However, PVT is rarely reported after hepatectomy. At present, related guidelines and major expert opinions tend to consider vitamin K antagonists or low-molecular weight heparin (LMWH) as the standard treatment. But based on research, direct oral anticoagulants may be more effective and safe for noncirrhotic PVT and are also beneficial by reducing the recurrence rate of PVT. CASE SUMMARY: A 51-year-old woman without any history of disease felt discomfort in her right upper abdomen for 20 d, with worsening for 7 d. Contrast-enhanced computed tomography (CECT) of the upper abdomen showed right liver intrahepatic cholangiocarcinoma with multiple intrahepatic metastases but not to the left liver. Therefore, she underwent right hepatic and caudate lobectomy. One week after surgery, the patient underwent a CECT scan, due to nausea, vomiting, and abdominal distension. Thrombosis in the left branch and main trunk of the portal vein and near the confluence of the splenic vein was found. After using LMWH for 22 d, CECT showed no filling defect in the portal vein system. CONCLUSION: Although PVT after hepatectomy is rare, it needs to be prevented during the perioperative period.

14.
Artigo em Inglês | MEDLINE | ID: mdl-36091583

RESUMO

Objective: To investigate the clinical value of hepatectomy based on minimally invasive surgical images in the treatment of hepatolithiasis. Methods: The clinical data of 87 patients with hepatolithiasis who received treatment in the Department of General Surgery of our hospital from February 2020 to September 2021 were retrospectively analyzed. According to different surgical methods, the patients were divided into minimally invasive group (n = 43) and laparotomy group (n = 44). Perioperative conditions and stone clearance rate were compared. Results: The preoperative conditions of patients in the two groups were comparable, and the average operation time in the minimally invasive group was significantly longer than that in the laparotomy group (t = 18.783,P < 0.001). There was no significant difference in intraoperative bleeding, postoperative fasting time, postoperative complications, and stone clearance between the two groups (P > 0.05). Postoperative hospital stay was significantly lower in the minimally invasive group than that in the laparotomy group (t = -0.486,P < 0.001). Conclusion: Hepatectomy based on minimally invasive surgical imaging for hepatolithiasis is safe and feasible, has high clinical value, and can achieve similar short-term clinical efficacy to laparotomy and reduce the postoperative hospital stay of patients, reflecting its minimally invasive advantages, and it is worthy of clinical application.

15.
Micromachines (Basel) ; 13(5)2022 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-35630218

RESUMO

Energy harvesting technology is regarded as a feasible solution for the continuous power supply of microelectronic devices. Efforts have been made to improve the output power of all kinds of energy harvesting devices. This paper reports a 2 × 2 array piezoelectric-electromagnetic hybrid energy harvester that achieves high power output through the combination of piezoelectric and electromagnetic conversion. The harvester included four piezoelectric-electromagnetic hybrid modules, each of which consisted of a piezoelectric sheet, a permanent magnet and a wound coil. The permanent magnet, also serving as the mass block of the cantilever beam when subjected to external stimulus, contributed to a large displacement of the vibration and generated high output power. At an acceleration of 1 g and a resonance frequency of 70.4 Hz, the measured maximum output power of the hybrid energy harvester was 66.08 mW, of which the piezoelectric and electromagnetic portions were 56.96 and 9.12 mW, respectively. Furthermore, in a charging experiment, a capacitor of 23.5 mF was charged to 11.5 V within 20 s, which demonstrates a practical application of the hybrid energy harvester for microelectronic devices.

16.
Entropy (Basel) ; 24(5)2022 Apr 24.
Artigo em Inglês | MEDLINE | ID: mdl-35626481

RESUMO

The Age of Information (AoI) measures the freshness of information and is a critic performance metric for time-sensitive applications. In this paper, we consider a radio frequency energy-harvesting cognitive radio network, where the secondary user harvests energy from the primary users' transmissions and opportunistically accesses the primary users' licensed spectrum to deliver the status-update data pack. We aim to minimize the AoI subject to the energy causality and spectrum constraints by optimizing the sensing and update decisions. We formulate the AoI minimization problem as a partially observable Markov decision process and solve it via dynamic programming. Simulation results verify that our proposed policy is significantly superior to the myopic policy under different parameter settings.

17.
Tree Physiol ; 42(7): 1337-1349, 2022 07 05.
Artigo em Inglês | MEDLINE | ID: mdl-35157087

RESUMO

Evergreen and deciduous species coexist in tropical dry forests and savannas, but differ in physiological mechanisms and life-history strategies. Hydraulic conductivity and mechanical support are two major functions of the xylems of woody plant species related to plant growth and survival. In this study, we measured sapwood-specific hydraulic conductivity (Ks), leaf-specific hydraulic conductivity (KL), modulus of rupture (MOR) and elasticity (MOE), xylem anatomical traits and fiber contents in the xylems of 20 woody species with contrasting leaf phenology (evergreen vs deciduous) in a Chinese savanna. Our results showed that deciduous species had significantly higher Ks and KL but lower MOR and MOE than evergreen species. Evergreen species experienced more negative seasonal minimum water potential (Pmin) than deciduous species during the dry season. Furthermore, we found trade-offs between xylem hydraulic efficiency and mechanical strength across species and within the evergreen and deciduous groups, and these trade-offs were modulated by structural and chemical traits. Both Ks and KL were significantly related to hydraulic weighted vessel diameter (Dh) across all species and within the deciduous group. Both MOR and MOE were significantly related to wood density, neutral detergent fiber and acid detergent fiber across species and within evergreen and deciduous groups. Our findings demonstrated that Chinese evergreen and deciduous savanna species diverged in xylem hydraulic and mechanical functions, reflecting conservative and acquisitive life-history strategies for evergreen and deciduous species, respectively. This study provides new information with which to understand the hydraulic and biomechanical properties and ecological strategies of savanna species in long-term dry-hot environments.


Assuntos
Pradaria , Árvores , China , Detergentes , Folhas de Planta/fisiologia , Árvores/fisiologia , Água , Xilema
18.
Tree Physiol ; 42(4): 740-753, 2022 04 07.
Artigo em Inglês | MEDLINE | ID: mdl-35020937

RESUMO

Extreme drought events are becoming frequent globally, resulting in widespread plant mortality and forest dieback. Although savanna vegetation cover ~20% of the earth's land area, their responses to extreme drought have been less studied than that of forests. Herein, we quantified branch dieback, individual mortality and the associated physiological responses of four evergreen shrubs (Tarenna depauperate Hutch., Maytenus esquirolii (H. Lév.) C.Y. Cheng, Murraya exotica L., Jasminum nudiflorum Lindl.) in a savanna ecosystem in Southwest China to an incidence of extreme drought during 2019 and 2020. We found that 80-100% of the individuals of these species exhibited branch dieback, whereas individual mortality was only found in T. depauperate (4.5%). All species showed high resistance to stem embolism (P50, water potential at 50% loss of hydraulic conductivity ranged from -5.62 to -8.6 MPa), whereas the stem minimum water potentials reached -7.6 to ca -10.0 MPa during the drought. The low water potential caused high native embolism levels (percentage loss of hydraulic conductivity (PLC) 23-65%) in terminal branches, and the remaining stems maintained 15-35% PLC at the end of the drought. Large within-individual variations in stem vulnerability to embolism were detected, and shedding of vulnerable branches could be a mechanism for shrubs to reduce water and carbon consumption. Overall, the content of total nonstructural carbohydrates (NSC) and their components in the stem were generally comparable to or higher than those in the rainy season in three of the four species. Because the leaves were turgor-less for most time during the drought, high NSC levels during the drought could be due to recycling of NSC from dead branches or translocation from roots. Our results suggest high tolerance of savanna shrub species to extreme drought, which could be facilitated by high embolism resistance in some stems and shedding of vulnerable branches to maintain individual water and carbon balance.


Assuntos
Secas , Embolia , Carboidratos , Carbono , Ecossistema , Pradaria , Incidência , Folhas de Planta/fisiologia , Árvores/fisiologia , Água , Xilema/fisiologia
19.
Front Microbiol ; 13: 1088581, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36620038

RESUMO

Using composted soil samples, a metagenomic library consisting of 36,000 clones was constructed. Then, a novel lipase, Lip54q, which belongs to the VIII family of lipolytic enzymes, was identified from the metagenomic library by functional screening. To explore the enzymatic properties of Lip54q, lip54q was heterologous expressed in Escherichia coli with a high expression level of recombinant protein up to 720 mg/L. The recombinant enzyme showed the highest activity (28,160 U/mg) against a C10 substrate at pH 9.0 and 47°C, and was stable at temperatures ≤50°C and pH 8.0-11.0. Of particular interest, the surfactants, Tween-20, Tween-80 and Tritonx-100, exhibited strong promoting effects on Lip54q activities regardless of whether low concentrations (0.1%) or high concentrations (10%) were used. Application studies of Lip54q using six commercial detergents indicated that the enzyme had strong tolerance and immersion resistance to all six detergents. The results of oil-stain removal experiments suggested that addition of the enzyme to various commercial detergents could significantly improve the abilities of these detergents to remove oil-stains. Furthermore, the results of a molecular docking analysis of Lip54q showed that both the C10 substrate and linoleic acid molecules could form hydrogen bond interactions with the catalytic amino acids, Ser-268, Glu-168, and Asp-192, in the catalytic center of the enzyme, and the hydrogen bond distances were shorter. The electrostatic attraction between the enzyme and the substrate formed by the hydrogen bond with a shorter distance is stronger, which is conducive to the formation of a more stable complex between the enzyme and the substrate, thus increasing the activity of the enzyme to such substrate. These results 1ay a good foundation for application of this enzyme in the detergent industry in the future.

20.
Sci Total Environ ; 806(Pt 2): 150416, 2022 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-34852425

RESUMO

Climate change has great impacts on forest ecosystems, especially with the increasing frequency of heatwaves. Thermal safety margin (TSM) calculated by the difference between body temperature and thermotolerance threshold is useful to predict thermal safety of organisms. It has been widely used for animals, whereas has rarely been reported for plants. Besides, most of the previous studies used only thermotolerance to estimate thermal safety or used thermotolerance and air temperature (Ta) to calculate TSM. However, leaf temperature (Tl) is the real "body" temperature of plant leaves. Tl decoupling from Ta might induce large error in TSM. Here, we investigated TSM of photosystem II (thermotolerance of PSII - the maximum Tl) of dominant canopy plants in four forests from tropical to temperate biomes during a heatwave, and compared the TSMs calculated by Tl (TSM.Tl) and Ta (TSM.Ta) respectively. Also, thermal related leaf traits were investigated. The results showed that both TSM. Tl and TSM.Ta decreased from the cool forests to the hot forests. TSM.Tl was highly correlated with the maximum leaf temperature (Tlmax), while had an opposite trend with thermotolerance across biomes. Thus, Tlmax instead of thermotolerance can be used to evaluate TSM. The maximum Ta (Tamax), Tlmax and leaf traits explained 68% of the variance of thermotolerance in a random forest model, where Tamax and Tlmax explained 62%. TSM.Ta could not distinguish thermal safety differences between co-occurring species. The overestimation of TSM by TSM.Ta increased from the tropical to the temperate forest, and increased with Tl within biome. Therefore, it is not recommended to use TSM.Ta in cold forests. The present study enriches the dataset of photosynthetic TSMs across biomes, proposes using Tlmax to estimate TSMs of leaves, and highlights the risk of hot dry forest during heatwaves.


Assuntos
Ecossistema , Termotolerância , Animais , Mudança Climática , Fotossíntese , Folhas de Planta
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...