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Rydberg-state excitation of stretched model molecules subjected to near-infrared intense laser fields has been investigated based on a fully quantum model (QM) proposed recently and the numerical solutions of time-dependent Schrödinger equation (TDSE). Given the good agreement between QM and TDSE, it is found that, as the molecules are stretched, the electron tends to be trapped into low-lying Rydberg-states after its ionization from the core, which can be attributed to the shift of the ionization moments corresponding to maximum excitation populations. Moreover, the n-distribution is broadened for molecules with increasing internuclear distance, which results from the change of momentum distribution of emitted electrons. Analysis indicates that both of the above phenomena are closely related to the interference effect of electronic wave packets emitted from different nuclei. Our study provides a more comprehensive understanding of the molecular excitation in intense laser fields, as well as a means of possible applications to related experimental observations.
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Soil arsenic (As) pollution not only decreases plant productivity but also soil quality, in turn hampering sustainable agricultural development. Despite the negative effects of As contamination on rice yield and quality being reported widely, the responses of microbial communities and co-occurrence networks in paddy soil to As pollution have not been explored. Here, based on high-throughput sequencing technologies, we investigated bacterial abundance and diversity in paddy soils with different levels of As contamination, and constructed associated microbial co-occurrence networks. As pollution reduced soil bacterial diversity significantly (p < 0.001). In addition, bioavailable As concentrations were negatively correlated with Actinobacteria and Acidobacteria relative abundance (p < 0.05). Conversely, As pollution had a positive relationship with Chloroflexi, Betaproteobacteria, and Bacteroidetes relative abundance (p < 0.05). Firmicutes relative abundance decreased with an increase in total As concentration. The ecological clusters and key groups in bacterial co-occurrence networks exhibited distinct trends with an increase in As pollution. Notably, Acidobacteria play an important role in maintaining microbial networks in As contaminated soils. Overall, we provide empirical evidence that As contamination influences soil microbial community structure, posing a threat to soil ecosystem health and sustainable agriculture.
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Arsênio , Microbiota , Poluentes do Solo , Humanos , Arsênio/toxicidade , Solo/química , Bactérias/genética , Microbiota/genética , Acidobacteria , Atividades Humanas , Microbiologia do Solo , RNA Ribossômico 16SRESUMO
Chiral perhydroindoles are found in a number of natural products and biologically active compounds. Therefore, the development of new asymmetric methodology for rapid access to this core is of high importance. Herein, we reported a highly regio- and diastereo-selective palladium/PC-Phos-catalyzed asymmetric Heck/Tsuji-Trost reactions of readily available amino tethered 1,3-cyclohexadienes with aryl and alkenyl halides, delivering various functionalized chiral hexahydroindoles in good yields with high enantioselectivity. The application of this reaction to the concise synthesis of (-)-α-Lycorane was demonstrated. DFT computation results indicate that the difference in ΔEdis of two migration insertion transition states determines the enantioselectivity of the reaction.
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Cicloexenos , Paládio , Estrutura Molecular , CatáliseRESUMO
Background: The combined procedure of left atrial appendage closure (LAAC) and catheter ablation (CA) is a safe and feasible therapy to treat patients with atrial fibrillation (AF). However, the effect of the combined procedure on cardiac function remains unclear. This study aimed to investigate the changes in endocrine and mechanical function of the heart following the combined procedure. Methods: This retrospective study included 62 consecutive patients who underwent the combined procedure of AF ablation and WATCHMAN LAAC and 62 sex and age-matched patients who only received AF ablation. During follow-up, patients were examined for brain natriuretic peptide (BNP) levels to represent endocrine cardiac function. Mechanical cardiac function was assessed during echocardiographic examination by means of the LA ejection fraction, LA strain (Ƹ), and LA strain rate (SR). Results: (1) The BNP levels decreased acutely after the procedure, rose at day 3 postoperation, but trended downwards at 3 months postoperation in both groups. No significant difference was observed between the two groups. (2) LA ejection fraction, LA Ƹ, and SR exhibited a continuous upward trend over a 3-month follow-up in both groups. There was no significant difference in LA ejection fractions, SRe (the parameter of LA conduit function), and SRa (the parameter of LA booster pump function) between the two groups. However, the Ƹ and SRs (the parameters of LA reservoir function) improved in patients treated with CA alone. Conclusions: The combined procedure of LAAC and CA significantly improved the endocrine and mechanical function of the heart. Compared to simple CA, based on CA with LAAC intervention, it does not significantly change LA endocrine function but may lead to a decline in the LA reservoir function.
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Apêndice Atrial , Fibrilação Atrial , Ablação por Cateter , Apêndice Atrial/diagnóstico por imagem , Apêndice Atrial/cirurgia , Fibrilação Atrial/diagnóstico , Fibrilação Atrial/cirurgia , Ablação por Cateter/métodos , Humanos , Estudos Retrospectivos , Resultado do TratamentoRESUMO
Bisphenol analogues (BPs) have already attracted wide concern owing to the environmental and health risks they pose. The exposure pathways and health risk of preschool-aged children to BPs, however, are still poorly understood. In this study, we choose population survey with 184 preschool-age children from a suburb of Nanjing, eastern China, further reveal the internal and external exposures concentrations, distribution profiles, potential sources and eventually assess health risk of preschool-age children to eight kinds of BPs. The results verify that the 95th percentile (P95) concentrations of Æ©8BPs ranged from 0.27 to 41.6 ng/mL, with a median concentration of 7.83 ng/mL in the urine samples. BPA, and BPF were the predominant BPs in urine, accounting for 67.3%, and 18.0% of Æ©8BPs. The urine-based estimated daily intake (EDI) of Æ©8BPs was 187 ng/kg body weight/day. Similarly, BPA, and BPF were the main BPs in the environmental exposure sources, accounting for 80.8%, and 11.7% of the total BPs. Moreover, the total external exposure dose of Æ©8BPs via the environmental sources was 68.1 ng/kg body weight/day, including BPA (56 ng/kg body weight/day), BPF (7.68 ng/kg body weight/day) and BPB (2.62 ng/kg body weight/day). The oral intake of drinking water and food (vegetables and rice) was the main exposure pathways of BPs in preschool-age children. Furthermore, the hazard quotient (HQ) of BPs have been evaluated and the results show no occurrence of high risk. Additionally, the urine-based EDI was significantly higher than the total external exposure dose, suggesting the existence of other pathways of BP exposure to be further explored. To the best of our knowledge, this is the first study to conduct both an internal and external exposure assessment of BPs.
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The development of diversity-oriented synthesis based on fluorine-containing building blocks has been one of the hot research fields in fluorine chemistry. ß-CF3-1,3-enynes, as one type of fluorine-containing building blocks, have attracted more attention in the last few years due to their distinct reactivity. Numerous value-added trifluoromethylated or non-fluorinated compounds which have biologically relevant structural motifs, such as O-, N-, and S-heterocycles, carboncycles, fused polycycles, and multifunctionalized allenes were synthesized from these fluorine-containing building blocks. This review summarizes the most significant developments in the area of synthesis of organofluorine compounds based on ß-CF3-1,3-enynes, providing a detailed overview of the current state of the art.
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Flúor , Flúor/química , EstereoisomerismoRESUMO
BACKGROUND: A number of predictive models for aquatic toxicity are available, however, the accuracy and extent of easy to use of these in silico tools in risk assessment still need further studied. This study evaluated the performance of seven in silico tools to daphnia and fish: ECOSAR, T.E.S.T., Danish QSAR Database, VEGA, KATE, Read Across and Trent Analysis. 37 Priority Controlled Chemicals in China (PCCs) and 92 New Chemicals (NCs) were used as validation dataset. RESULTS: In the quantitative evaluation to PCCs with the criteria of 10-fold difference between experimental value and estimated value, the accuracies of VEGA is the highest among all of the models, both in prediction of daphnia and fish acute toxicity, with accuracies of 100% and 90% after considering AD, respectively. The performance of KATE, ECOSAR and T.E.S.T. is similar, with accuracies are slightly lower than VEGA. The accuracy of Danish Q.D. is the lowest among the above tools with which QSAR is the main mechanism. The performance of Read Across and Trent Analysis is lowest among all of the tested in silico tools. The predictive ability of models to NCs was lower than that of PCCs possibly because never appeared in training set of the models, and ECOSAR perform best than other in silico tools. CONCLUSION: QSAR based in silico tools had the greater prediction accuracy than category approach (Read Across and Trent Analysis) in predicting the acute toxicity of daphnia and fish. Category approach (Read Across and Trent Analysis) requires expert knowledge to be utilized effectively. ECOSAR performs well in both PCCs and NCs, and the application shoud be promoted in both risk assessment and priority activities. We suggest that distribution of multiple data and water solubility should be considered when developing in silico models. Both more intelligent in silico tools and testing are necessary to identify hazards of Chemicals.
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Daphnia , Relação Quantitativa Estrutura-Atividade , Poluentes Químicos da Água , Animais , China , Simulação por Computador , Poluentes Químicos da Água/toxicidadeRESUMO
We use a Wigner distribution-like function based on the strong field approximation theory to obtain the time-energy distributions and the ionization time distributions of electrons ionized by an XUV pulse alone and in the presence of an infrared (IR) pulse. In the case of a single XUV pulse, although the overall shape of the ionization time distribution resembles the XUV-envelope, its detail shows dependence on the emission direction of the electron and the carrier-envelope phase of the pulse, which mainly results from the low-energy interference structure. It is further found that the electron from the counter-rotating term plays an important role in the interference. In the case of the two-color pulse, both the time-energy distributions and the ionization time distributions change with varying IR field. Our analysis demonstrates that the IR field not only modifies the final electron kinetic energy but also changes the electron's emission time, which is attributed to the change of the electric field induced by the IR pulse. Moreover, the ionization time distributions of the photoelectrons emitted from atoms with higher ionization energy are also given, which show less impact of the IR field on the electron dynamics.
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BACKGROUND AND AIM: Oral anticoagulants are risk factors for post-endoscopic resection bleeding. We aimed to conduct a systematic review and meta-analysis for the risks of post-procedural bleeding (PPB) for direct oral anticoagulants (DOACs) and warfarin following endoscopic resection. METHODS: Two independent reviewers searched PubMed, Web of Science, Embase, and Cochrane Library. The Newcastle-Ottawa Scale score was used to assess the quality of the studies, the pooled odds ratio (OR) to present PPB results, and the funnel plots to assess publication bias. The Higgins I2 statistic was employed to determine the variation across studies due to heterogeneity. RESULTS: We reviewed 30 articles. PPB occurred in 586 patients on DOACs and 1782 on warfarin. The patients on DOACs had a significantly lower overall risk of PPB compared with those on warfarin (OR, 0.867, 95% confidence interval, 0.771-0.975; P = 0.017, I2 = 1.6%). Cumulative meta-analysis showed that the PPB rate of DOACs has the trend to be lower than that of warfarin with publication year and sample size. For the subgroup of endoscopic submucosal dissection, the PPB of DOACs was significantly lower than that of warfarin (OR, 0.786; 95% confidence interval, 0.633-0.976; P = 0.029, I2 = 0%). No significant difference was observed between DOACs and warfarin for anticoagulant strategies, endoscopic procedures, and lesion location. CONCLUSIONS: Compared with warfarin, DOACs have the possibility to significantly decrease the risk of PPB following endoscopic resection, especially for endoscopic submucosal dissection.
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Anticoagulantes , Ressecção Endoscópica de Mucosa , Hemorragia , Varfarina , Administração Oral , Anticoagulantes/administração & dosagem , Anticoagulantes/efeitos adversos , Ressecção Endoscópica de Mucosa/efeitos adversos , Hemorragia/induzido quimicamente , Hemorragia/epidemiologia , Humanos , Medição de Risco , Varfarina/efeitos adversosRESUMO
BACKGROUND AND AIM: The biological characterization of microbial environment in early gastric cancer (EGC), other than Helicobacter pylori, is limited. This study aimed to explore the microbial microenvironment in chronic gastritis (CG), fundic gland polyps (FGPs), low-grade intraepithelial neoplasia (LGIN), and EGC. METHODS: 16S-rRNA gene sequencing and bioinformatic analysis were performed on 63 individuals with 252 mucosal biopsies or endoscopic submucosal dissection margin samples from endoscopy. RESULTS: The microbiota in gastric LGIN functions analogously to EGC in terms of functional prediction. Neoplastic lesions showed a significant difference to CG or FGPs in beta diversity of the microbiota. Bacteria genera including Paracoccus, Blautia, Barnesiella, Lactobacillus, Thauera, Collinsella were significantly enriched in gastric neoplastic mucosa (LGIN and EGC) compared with non-neoplastic tissues (CG and FGPs). While Pseudomonas and Kingella were depleted in neoplastic tissues. FGPs showed a distinctive microbial network system that negatively interacted with Helicobacter. CONCLUSIONS: In terms of the mucosal microbial microenvironment, gastric LGIN and EGC showed no significant difference as early neoplastic lesions. We observed a coordinated microbial microenvironment that correlated negatively with Helicobacter.
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Carcinoma in Situ , Mucosa Gástrica , Gastrite/microbiologia , Microbioma Gastrointestinal , Pólipos/microbiologia , Neoplasias Gástricas , Infecções Bacterianas/genética , Infecções Bacterianas/microbiologia , Biópsia , Carcinoma in Situ/microbiologia , Carcinoma in Situ/patologia , Doença Crônica , Endoscopia Gastrointestinal , Fundo Gástrico/microbiologia , Fundo Gástrico/patologia , Mucosa Gástrica/microbiologia , Mucosa Gástrica/patologia , Gastrite/patologia , Microbioma Gastrointestinal/genética , Infecções por Helicobacter/genética , Helicobacter pylori/genética , Humanos , Pólipos/patologia , RNA Ribossômico 16S/genética , Análise de Sequência de RNA , Gastropatias/microbiologia , Gastropatias/patologia , Neoplasias Gástricas/microbiologia , Neoplasias Gástricas/patologia , Microambiente TumoralRESUMO
We have performed a comparison study of the Rydberg-state excitation of model molecules (1πg and 1πu states) in different laser fields by the approaches of time-dependent Schrödinger equation and a fully quantum-mechanical model, and both simulations show good accordance. It is found that the peak structure of the Rydberg-state population vs laser intensity becomes pronounced for longer laser pulses due to the stronger interference effect between the subwave packets released in different optical cycles, and the locations of the intensity-dependent peaks closely satisfy the multi-photon resonant transition condition. In addition, it is demonstrated that the populations of the Rydberg states possessing the identical parity oscillate in an inverse manner with increasing laser intensity for different initial states (1πg and 1πu), and the aforementioned distinct phenomenon is attributed to the additional phase introduced by the symmetry of 1πg state with respect to that of 1πu state.
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BACKGROUND AND AIM: Endoscopic submucosal dissection (ESD) has a high en bloc resection rate and is widely performed for large colorectal lesions. However, colorectal ESD is associated with a high frequency of adverse events (AEs), and the efficacy of prophylactic endoscopic closure after ESD for preventing AEs is still controversial. This meta-analysis was conducted to assess the efficacy of closure on AEs following colorectal ESD. METHODS: We searched PubMed, Embase, and the Cochrane Library for eligible studies. The chi-square-based Q statistics and the I2 test were used to test for heterogeneity. Pooling was conducted using a fixed or random effects model. RESULTS: We identified eight eligible studies that compared the effects of closure vs non-closure with respect to delayed bleeding, delayed perforation, and post-ESD coagulation syndrome. Compared with non-closure (5.2%), closure was associated with a lower incidence (0.9%) of delayed bleeding (pooled odd ratios [ORs]:0.19, 95% CI: 0.08-0.49) following ESD. The pooled ORs showed no significant differences in incidence of delayed perforation (pooled OR: 0.22; 95% CI: 0.05-1.03) or post-ESD coagulation syndrome (pooled OR:0.75; 95% CI: 0.26-2.18) between the closure and non-closure groups. CONCLUSION: Prophylactic endoscopic closure may reduce the incidence of delayed bleeding following ESD of colorectal lesions. Future studies are needed to further illuminate risk factors and stratify high risk subjects for a cost-effective preventive strategy.
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Neoplasias Colorretais/cirurgia , Ressecção Endoscópica de Mucosa/efeitos adversos , Ressecção Endoscópica de Mucosa/métodos , Endoscopia Gastrointestinal/métodos , Mucosa Intestinal/cirurgia , Hemorragia Pós-Operatória/etiologia , Hemorragia Pós-Operatória/prevenção & controle , Técnicas de Fechamento de Ferimentos , Adulto , Idoso , Idoso de 80 Anos ou mais , Transtornos da Coagulação Sanguínea/etiologia , Transtornos da Coagulação Sanguínea/prevenção & controle , Feminino , Humanos , Incidência , Perfuração Intestinal/etiologia , Perfuração Intestinal/prevenção & controle , Masculino , Pessoa de Meia-Idade , Fatores de Tempo , Resultado do TratamentoRESUMO
Neutral atoms have been observed to survive intense laser pulses in high Rydberg states with surprisingly large probability. Only with this Rydberg-state excitation (RSE) included is the picture of intense-laser-atom interaction complete. Various mechanisms have been proposed to explain the underlying physics. However, neither one can explain all the features observed in experiments and in time-dependent Schrödinger equation (TDSE) simulations. Here we propose a fully quantum-mechanical model based on the strong-field approximation (SFA). It well reproduces the intensity dependence of RSE obtained by the TDSE, which exhibits a series of modulated peaks. They are due to recapture of the liberated electron and the fact that the pertinent probability strongly depends on the position and the parity of the Rydberg state. We also present measurements of RSE in xenon at 800 nm, which display the peak structure consistent with the calculations.
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The TDP-43 is originally a nuclear protein but translocates to the cytoplasm in the pathological condition. TDP-43, as an RNA-binding protein, consists of two RNA Recognition Motifs (RRM1 and RRM2). RRMs are known to involve both protein-nucleotide and protein-protein interactions and mediate the formation of stress granules. Thus, they assist the entire TDP-43 protein with participating in neurodegenerative and cancer diseases. Consequently, they are potential therapeutic targets. Protein-observed and ligand-observed nuclear magnetic resonance (NMR) spectroscopy were used to uncover the small molecule inhibitors against the tandem RRM of TDP-43. We identified three hits weakly binding the tandem RRMs using the ligand-observed NMR fragment-based screening. The binding topology of these hits is then depicted by chemical shift perturbations (CSP) of the 15N-labeled tandem RRM and RRM2, respectively, and modeled by the CSP-guided High Ambiguity Driven biomolecular DOCKing (HADDOCK). These hits mainly bind to the RRM2 domain, which suggests the druggability of the RRM2 domain of TDP-43. These hits also facilitate further studies regarding the hit-to-lead evolution against the TDP-43 RRM domain.
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Proteínas de Ligação a DNA/antagonistas & inibidores , Simulação de Acoplamento Molecular , Bibliotecas de Moléculas Pequenas/farmacologia , Sítios de Ligação , Proteínas de Ligação a DNA/química , Proteínas de Ligação a DNA/metabolismo , Humanos , Ligantes , Espectroscopia de Ressonância Magnética , Ligação Proteica , Bibliotecas de Moléculas Pequenas/químicaRESUMO
We introduce an ab initio approach and the modified strong-field approximation to investigate the alignment-dependent ionization of H2+(1πu) exposed to different few-cycle laser fields. The ab initio calculations are performed by the B-splines one-center method and the Crank-Nicolson method in spherical coordinates. It is shown that the peak ionization probabilities appear around alignment angles 50° and 40° at the laser intensities 3×1013 W/cm2 and 5×1013 W/cm2, respectively, and the above distinct features come from the resonant excitation of the molecular ion, which is confirmed by calculation including and excluding the state 2σg in the basis expansion. Furthermore, the results obtained by including the state 2σg in the ab initio simulations can be qualitatively reproduced by the modified molecular length gauge strong-field approximation (SFA) taking account of the 1πu and 2σg states simultaneously. Analysis indicates that a part of electron is directly emitted from the 1πu orbital and another portion of electron is released from 2σg orbital and other excited state after the single-photon resonant transition between 1πu and 2σg orbitals.
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Sporolactobacillus inulinus is a superior D-lactic acid-producing bacterium and proposed species for industrial production. The major pathway for D-lactic acid biosynthesis, glycolysis, is mainly regulated via the two irreversible steps catalyzed by the allosteric enzymes, phosphofructokinase (PFK) and pyruvate kinase. The activity level of PFK was significantly consistent with the cell growth and D-lactic acid production, indicating its vital role in control and regulation of glycolysis. In this study, the ATP-dependent PFK from S. inulinus was expressed in Escherichia coli and purified to homogeneity. The PFK was allosterically activated by both GDP and ADP and inhibited by phosphoenolpyruvate; the addition of activators could partly relieve the inhibition by phosphoenolpyruvate. Furthermore, monovalent cations could enhance the activity, and Na+ was the most efficient one. Considering this kind activation, NaOH was investigated as the neutralizer instead of the traditional neutralizer CaCO3. In the early growth stage, the significant accelerated glucose consumption was achieved in the NaOH case probably for the enhanced activity of Na+-activated PFK. Using NaOH as the neutralizer at pH 6.5, the fermentation time was greatly shortened about 22 h; simultaneously, the glucose consumption rate and the D-lactic acid productivity were increased by 34 and 17%, respectively. This probably contributed to the increased pH and Na+-promoted activity of PFK. Thus, fermentations by S. inulinus using the NaOH neutralizer provide a green and highly efficient D-lactic acid production with easy subsequent purification.
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Bacillales/enzimologia , Ativadores de Enzimas/metabolismo , Ácido Láctico/metabolismo , Fosfofrutoquinases/metabolismo , Hidróxido de Sódio/metabolismo , Difosfato de Adenosina/metabolismo , Bacillales/genética , Cátions/metabolismo , Clonagem Molecular , Inibidores Enzimáticos/metabolismo , Escherichia coli/genética , Escherichia coli/metabolismo , Expressão Gênica , Guanosina Difosfato/metabolismo , Fosfoenolpiruvato/metabolismo , Fosfofrutoquinases/genética , Fosfofrutoquinases/isolamento & purificação , Proteínas Recombinantes/genética , Proteínas Recombinantes/isolamento & purificação , Proteínas Recombinantes/metabolismoRESUMO
Object tracking is a crucial research subfield in computer vision and it has wide applications in navigation, robotics and military applications and so on. In this paper, the real-time visualization of 3D point clouds data based on the VLP-16 3D Light Detection and Ranging (LiDAR) sensor is achieved, and on the basis of preprocessing, fast ground segmentation, Euclidean clustering segmentation for outliers, View Feature Histogram (VFH) feature extraction, establishing object models and searching matching a moving spherical target, the Kalman filter and adaptive particle filter are used to estimate in real-time the position of a moving spherical target. The experimental results show that the Kalman filter has the advantages of high efficiency while adaptive particle filter has the advantages of high robustness and high precision when tested and validated on three kinds of scenes under the condition of target partial occlusion and interference, different moving speed and different trajectories. The research can be applied in the natural environment of fruit identification and tracking, robot navigation and control and other fields.
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In this study, a high-sensitivity and low-hysteresis porous metal-insulator-metal-type capacitive humidity sensor is investigated using a functional polymer mixed with TiO2 microparticles. The humidity sensor consists of an optimally designed porous top electrode, a functional polymer humidity sensitive layer, a bottom electrode, and a glass substrate. The porous top electrode is designed to increase the contact area between the sensing layer and water vapor, leading to high sensitivity and quick response time. The functional polymer mixed with TiO2 microparticles shows excellent hysteresis under a wide humidity-sensing range with good longterm stability. The results show that as the relative humidity ranges from 10% RH to 90% RH, the proposed humidity sensor achieves a high sensitivity of 0.85 pF/% RH and a fast response time of less than 35 s. Furthermore, the sensor shows an ultra-low hysteresis of 0.95% RH at 60% RH, a good temperature dependence, and a stable capacitance value with a maximum of 0.17% RH drift during 120 h of continuous test.
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This study focuses on the underground shallow gas detection project in the Lingkun Island area of the northern entrance tunnel of the Wenzhou City Light Rail S2 line. Based on geological exploration data of shallow gas, we chose the technique of controlled-release gas with static pressure as the experimental foundation, integrating various technologies such as multi-functional in-situ probing, electrical methods, and seismic waves, comprehensively researching shallow gas detection technology in the Lingkun Island area. We conducted field probing experiments to accurately obtain the physical and mechanical properties of gas-rich soil layers and further studied the possibility of determining gas-rich locations. By applying parallel electrical methods, we can accurately identify and distinguish areas of anomalous resistivity in shallow geological structures. Based on abnormal changes in acoustic impedance in strata, we used seismic wave methods, including seismic CT and seismic wave scattering technology, to accurately reveal the presence and depth of shallow gas, providing reliable basis for accurate determination of shallow gas. Finally, we summarized a comprehensive plan for underground shallow gas detection technology, covering on-site data collection, data processing, and image interpretation of results, which will provide valuable references for future shallow gas exploration in relevant areas.
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The rhizosphere is generally depleted in nutrients, but as a hotspot of microbial activity it fosters crop P uptake. We hypothesized that P contents of water extractable nanoparticles (<0.1 µm) and small sized colloids (<0.45 µm) differ between non-rhizosphere and rhizosphere soil. To test this hypothesis, rhizosphere and non-rhizosphere soils (Luvisol and Cambisol) were sampled at harvest period of winter wheat near Selhausen (Germany). Microaggregate and colloidal fractions in the size range of 53-250 µm, 20-53 µm, 0.45-20 µm, and <0.45 µm were separated by wet-sieving and centrifugation. Subsequently, the colloids <0.45 µm were further isolated in 0.66-20 nm, 20-100 nm and 100-450 nm fractions using asymmetric flow field flow fractionation (AF4) and directly analyzed by online coupled organic carbon detector (OCD) and inductively coupled plasma mass spectrometry (ICP-MS) for element composition. No significant differences (p > 0.05) were measured between rhizosphere and non-rhizosphere soil P contents of microaggregate fractions. The rhizosphere soil, however, showed â¼26 % depletion of average P content in the 0.66-20 nm fraction, which went along with an enrichment of P content of the 100-450 nm fraction by a factor of two. Apparently, P uptake by plants results in a redistribution of P in the rhizosphere, with small nanoparticles providing available P to plants while excess residual P is bound to fine colloids.