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1.
Neural Netw ; 178: 106466, 2024 Jun 22.
Artigo em Inglês | MEDLINE | ID: mdl-38968778

RESUMO

The brain is targeted for processing temporal sequence information. It remains largely unclear how the brain learns to store and retrieve sequence memories. Here, we study how recurrent networks of binary neurons learn sequence attractors to store predefined pattern sequences and retrieve them robustly. We show that to store arbitrary pattern sequences, it is necessary for the network to include hidden neurons even though their role in displaying sequence memories is indirect. We develop a local learning algorithm to learn sequence attractors in the networks with hidden neurons. The algorithm is proven to converge and lead to sequence attractors. We demonstrate that the network model can store and retrieve sequences robustly on synthetic and real-world datasets. We hope that this study provides new insights in understanding sequence memory and temporal information processing in the brain.

2.
Huan Jing Ke Xue ; 45(7): 3911-3918, 2024 Jul 08.
Artigo em Chinês | MEDLINE | ID: mdl-39022939

RESUMO

Microplastics (MPs) are ubiquitous in the marine environment and have become an emerging pollutant that is attracting great attention. To reveal the pollution characteristics of MPs in surface seawater of coastal waters in Guangdong Province, nine bays (estuaries) were selected from Jiangmen to Shantou. The distribution and compositional characteristics of MPs were investigated through field sampling, oxidation digestion, and visual and compositional identification, and their potential sources were analyzed. The ecological risks were assessed by combining the pollution load index and the polymer risk index. The results showed that MPs were detected in all 30 surface seawater samples from the coastal waters of Guangdong Province, with an abundance range of 70-920 n·m-3 and an average abundance of (295.3 ±175.3) n·m-3. The highest MPs abundance was found in the Pearl River estuary, and the lowest abundance was found in Shenquan bay. The distribution patterns were mainly influenced by human activities and ocean currents. The dominant polymer types included polypropylene (31.2%), phenol resin (16.0%), polyethylene terephthalate (15.3%), and polyethylene (10.9%). The main shape, color, and size categories of MPs were fiber (57.5%), transparent (72.0%), and 0.5-1 mm (32.8%), respectively. The possible sources of MPs mainly included aquaculture, fishing, navigation, tourism, municipal sewage discharge, and ocean current transportation. The model assessment results showed that the pollution load risk of MPs was relatively low, but the polymer risk was at a medium-high level. This study provides a data basis for the action plan of plastic pollution control in Guangdong Province and supports the prevention and control of marine MPs pollution.

3.
Commun Biol ; 7(1): 800, 2024 Jul 02.
Artigo em Inglês | MEDLINE | ID: mdl-38956367

RESUMO

Gastric cancer (GC) is the 5th most prevalent cancer and the 4th primary cancer-associated mortality globally. As the first identified m6A demethylase for removing RNA methylation modification, fat mass and obesity-associated protein (FTO) plays instrumental roles in cancer development. Therefore, we study the biological functions and oncogenic mechanisms of FTO in GC tumorigenesis and progression. In our study, FTO expression is obviously upregulated in GC tissues and cells. The upregulation of FTO is associated with advanced nerve invasion, tumor size, and LNM, as well as the poor prognosis in GC patients, and promoted GC cell viability, colony formation, migration and invasion. Mechanistically, FTO targeted specificity protein 1 and Aurora Kinase B, resulting in the phosphorylation of ataxia telangiectasia mutated and P38 and dephosphorylation of P53. In conclusion, the m6A demethylase FTO promotes GC tumorigenesis and progression by regulating the SP1-AURKB-ATM pathway, which may highlight the potential of FTO as a diagnostic biomarker for GC patients' therapy response and prognosis.


Assuntos
Dioxigenase FTO Dependente de alfa-Cetoglutarato , Proteínas Mutadas de Ataxia Telangiectasia , Aurora Quinase B , Fator de Transcrição Sp1 , Neoplasias Gástricas , Humanos , Dioxigenase FTO Dependente de alfa-Cetoglutarato/metabolismo , Dioxigenase FTO Dependente de alfa-Cetoglutarato/genética , Neoplasias Gástricas/genética , Neoplasias Gástricas/patologia , Neoplasias Gástricas/metabolismo , Linhagem Celular Tumoral , Proteínas Mutadas de Ataxia Telangiectasia/metabolismo , Proteínas Mutadas de Ataxia Telangiectasia/genética , Fator de Transcrição Sp1/metabolismo , Fator de Transcrição Sp1/genética , Aurora Quinase B/metabolismo , Aurora Quinase B/genética , Masculino , Feminino , Regulação Neoplásica da Expressão Gênica , Progressão da Doença , Pessoa de Meia-Idade , Transdução de Sinais , Prognóstico , Camundongos , Animais
4.
Eur J Radiol ; 178: 111622, 2024 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-39018648

RESUMO

PURPOSE: To investigate the value of microstructural characteristics derived from time-dependent diffusion MRI in distinguishing high-grade serous ovarian cancer (HGSOC) from serous borderline ovarian tumor (SBOT) and the associations of immunohistochemical markers with microstructural features. METHODS: Totally 34 HGSOC and 12 SBOT cases who received preoperative pelvic MRI were retrospectively included in this study. Two radiologists delineated the tumors to obtain the regions of interest (ROIs). Time-dependent diffusion MRI signals were fitted by the IMPULSED (imaging microstructural parameters using limited spectrally edited diffusion) model, to extract microstructural parameters, including fraction of the intracellular component (fin), cell diameter (d), cellularity and extracellular diffusivity (Dex). Apparent diffusion coefficient (ADC) values were obtained from standard diffusion-weighted imaging (DWI). The parameters of HGSOCs and SBOTs were compared, and the diagnostic performance was evaluated. The associations of microstructural indexes with immunopathological parameters were assessed, including Ki-67, P53, Pax-8, ER and PR. RESULTS: In this study, fin, cellularity, Dex and ADC had good diagnostic performance levels in differentiating HGSOC from SBOT, with AUCs of 0.936, 0.909, 0.902 and 0.914, respectively. There were no significant differences in diagnostic performance among these parameters. Spearman analysis revealed in the HGSOC group, cellularity had a significant positive correlation with P53 expression (P = 0.028, r = 0.389) and Dex had a significant positive correlation with Pax-8 expression (P = 0.018, r = 0.415). ICC showed excellent agreement for all parameters. CONCLUSION: Time-dependent diffusion MRI had value in evaluating the microstructures of HGSOC and SBOT and could discriminate between these tumors.

5.
Front Optoelectron ; 17(1): 23, 2024 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-39014042

RESUMO

This study presents a high-accuracy, all-fiber mode division multiplexing (MDM) reconstructive spectrometer (RS). The MDM was achieved by utilizing a custom-designed 3 × 1 mode-selective photonics lantern to launch distinct spatial modes into the multimode fiber (MMF). This facilitated the information transmission by increasing light scattering processes, thereby encoding the optical spectra more comprehensively into speckle patterns. Spectral resolution of 2 pm and the recovery of 2000 spectral channels were accomplished. Compared to methods employing single-mode excitation and two-mode excitation, the three-mode excitation method reduced the recovered error by 88% and 50% respectively. A resolution enhancement approach based on alternating mode modulation was proposed, reaching the MMF limit for the 3 dB bandwidth of the spectral correlation function. The proof-of-concept study can be further extended to encompass diverse programmable mode excitations. It is not only succinct and highly efficient but also well-suited for a variety of high-accuracy, high-resolution spectral measurement scenarios.

6.
Front Endocrinol (Lausanne) ; 15: 1414481, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38978628

RESUMO

Objective: To determine whether endometrial thickness (EMT) differs between i) clomiphene citrate (CC) and gonadotropin (Gn) utilizing patients as their own controls, and ii) patients who conceived with CC and those who did not. Furthermore, to investigate the association between late-follicular EMT and pregnancy outcomes, in CC and Gn cycles. Methods: Retrospective study. Three sets of analyses were conducted separately for the purpose of this study. In analysis 1, we included all cycles from women who initially underwent CC/IUI (CC1, n=1252), followed by Gn/IUI (Gn1, n=1307), to compare EMT differences between CC/IUI and Gn/IUI, utilizing women as their own controls. In analysis 2, we included all CC/IUI cycles (CC2, n=686) from women who eventually conceived with CC during the same study period, to evaluate EMT differences between patients who conceived with CC (CC2) and those who did not (CC1). In analysis 3, pregnancy outcomes among different EMT quartiles were evaluated in CC/IUI and Gn/IUI cycles, separately, to investigate the potential association between EMT and pregnancy outcomes. Results: In analysis 1, when CC1 was compared to Gn1 cycles, EMT was noted to be significantly thinner [Median (IQR): 6.8 (5.5-8.0) vs. 8.3 (7.0-10.0) mm, p<0.001]. Within-patient, CC1 compared to Gn1 EMT was on average 1.7mm thinner. Generalized linear mixed models, adjusted for confounders, revealed similar results (coefficient: 1.69, 95% CI: 1.52-1.85, CC1 as ref.). In analysis 2, CC1 was compared to CC2 EMT, the former being thinner both before [Median (IQR): 6.8 (5.5-8.0) vs. 7.2 (6.0-8.9) mm, p<0.001] and after adjustment (coefficient: 0.59, 95%CI: 0.34-0.85, CC1 as ref.). In analysis 3, clinical pregnancy rates (CPRs) and ongoing pregnancy rates (OPRs) improved as EMT quartiles increased (Q1 to Q4) among CC cycles (p<0.001, p<0.001, respectively), while no such trend was observed among Gn cycles (p=0.94, p=0.68, respectively). Generalized estimating equations models, adjusted for confounders, suggested that EMT was positively associated with CPR and OPR in CC cycles, but not in Gn cycles. Conclusions: Within-patient, CC generally resulted in thinner EMT compared to Gn. Thinner endometrium was associated with decreased OPR in CC cycles, while no such association was detected in Gn cycles.


Assuntos
Clomifeno , Endométrio , Fármacos para a Fertilidade Feminina , Gonadotropinas , Inseminação Artificial , Humanos , Feminino , Clomifeno/uso terapêutico , Clomifeno/administração & dosagem , Endométrio/efeitos dos fármacos , Endométrio/patologia , Gravidez , Adulto , Estudos Retrospectivos , Fármacos para a Fertilidade Feminina/uso terapêutico , Fármacos para a Fertilidade Feminina/administração & dosagem , Resultado da Gravidez , Indução da Ovulação/métodos , Taxa de Gravidez , Infertilidade Feminina/terapia , Infertilidade Feminina/tratamento farmacológico
7.
Expert Rev Anti Infect Ther ; : 1-12, 2024 Jul 09.
Artigo em Inglês | MEDLINE | ID: mdl-38975666

RESUMO

BACKGROUND: The potential of ursodeoxycholic acid (UDCA) in inhibiting angiotensin-converting enzyme 2 was demonstrated. However, conflicting evidence emerged regarding the association between UDCA and COVID-19 outcomes, prompting the need for a comprehensive investigation. RESEARCH DESIGN AND METHODS: Patients diagnosed with COVID-19 infection were retrospectively analyzed and divided into two groups: the UDCA-treated group and the control group. Kaplan-Meier recovery analysis and Cox proportional hazards models were used to evaluate the recovery time and hazard ratios. Additionally, study-level pooled analyses for multiple clinical outcomes were performed. RESULTS: In the 115-patient cohort, UDCA treatment was significantly associated with a reduced recovery time. The subgroup analysis suggests that the 300 mg subgroup had a significant (adjusted hazard ratio: 1.63 [95% CI, 1.01 to 2.60]) benefit with a shorter duration of fever. The results of pooled analyses also show that UDCA treatment can significantly reduce the incidence of severe/critical diseases in COVID-19 (adjusted odds ratio: 0.68 [95% CI, 0.50 to 0.94]). CONCLUSIONS: UDCA treatment notably improves the recovery time following an Omicron strain infection without observed safety concerns. These promising results advocate for UDCA as a viable treatment for COVID-19, paving the way for further large-scale and prospective research to explore the full potential of UDCA.

8.
bioRxiv ; 2024 Jun 22.
Artigo em Inglês | MEDLINE | ID: mdl-38948734

RESUMO

Comprehensive molecular and cellular phenotyping of human islets can enable deep mechanistic insights for diabetes research. We established the Human Islet Data Analysis and Sharing (HI-DAS) consortium to advance goals in accessibility, usability, and integration of data from human islets isolated from donors with and without diabetes at the Alberta Diabetes Institute (ADI) IsletCore. Here we introduce HumanIslets.com, an open resource for the research community. This platform, which presently includes data on 547 human islet donors, allows users to access linked datasets describing molecular profiles, islet function and donor phenotypes, and to perform various statistical and functional analyses at the donor, islet and single-cell levels. As an example of the analytic capacity of this resource we show a dissociation between cell culture effects on transcript and protein expression, and an approach to correct for exocrine contamination found in hand-picked islets. Finally, we provide an example workflow and visualization that highlights links between type 2 diabetes status, SERCA3b Ca2+-ATPase levels at the transcript and protein level, insulin secretion and islet cell phenotypes. HumanIslets.com provides a growing and adaptable set of resources and tools to support the metabolism and diabetes research community.

10.
Artigo em Inglês | MEDLINE | ID: mdl-39013587

RESUMO

BACKGROUND AND AIM: Helicobacter pylori infection is linked to various gastrointestinal conditions, such as chronic active gastritis, peptic ulcers, and gastric cancer. Traditional treatment options encounter difficulties due to antibiotic resistance and adverse effects. Therefore, the aim of this study was to explore the effectiveness of a new treatment plan that combines vonoprazan (VPZ), amoxicillin, and bismuth for the eradication of H. pylori. METHODS: A total of 600 patients infected with H. pylori were recruited for this multicenter randomized controlled trial. Patients treated for H. pylori elimination were randomly assigned at a 1:1 ratio to receive 14 days of vonoprazan-based triple therapy (vonoprazan + amoxicillin + bismuth, group A) or standard quadruple therapy (esomeprazole + clarithromycin + amoxicillin + bismuth, group B). Compliance and adverse effects were tracked through daily medication and side effect records. All patients underwent a 13C/14C-urea breath test 4 weeks after treatment completion. RESULTS: Intention-to-treat (ITT) and per-protocol (PP) analyses revealed no substantial differences in H. pylori eradication rates between groups A and B (ITT: 83.7% vs 83.2%; PP: 90.9% vs 89.7%). However, significant differences were observed in the assessment of side effects (13.7% vs 28.6%, P < 0.001). Specifically, group A had significantly fewer "bitter mouths" than group B did (3.7% vs 16.2%, P < 0.001). CONCLUSION: Triple therapy comprising vonoprazan (20 mg), amoxicillin (750 mg), and bismuth potassium citrate (220 mg) achieved a PP eradication rate ≥90%, paralleling standard quadruple therapy, and had fewer adverse events and lower costs (¥306.8 vs ¥645.8) for treatment-naive patients.

11.
J Agric Food Chem ; 72(28): 16018-16031, 2024 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-38960914

RESUMO

Flow-injection spin-trapping electron paramagnetic resonance (FI-EPR) methods that involve the use of 5,5-dimethyl-pyrroline-N-oxide (DMPO) as a spin-trapping reagent have been developed for the kinetic study of the O2•- radical scavenging reactions occurring in the presence of various plant-derived and synthetic phenolic antioxidants (Aox), such as flavonoid, pyrogallol, catechol, hydroquinone, resorcinol, and phenol derivatives in aqueous media (pH 7.4 at 25 °C). The systematically estimated second-order rate constants (ks) of these phenolic compounds span a wide range (from 4.5 × 10 to 1.0 × 106 M-1 s-1). The semilogarithm plots presenting the relationship between ks values and oxidation peak potential (Ep) values of phenolic Aox are divided into three groups (A1, A2, and B). The ks-Ep plots of phenolic Aox bearing two or three OH moieties, such as pyrogallol, catechol, and hydroquinone derivatives, belonged to Groups A1 and A2. These molecules are potent O2•- radical scavengers with ks values above 3.8 × 104 (M-1 s-1). The ks-Ep plots of all phenol and resorcinol derivatives, and a few catechol and hydroquinone derivatives containing carboxyl groups adjacent to the OH groups, were categorized into the group poor scavengers (ks < 1.6 × 103 M-1 s-1). The ks values of each group correlated negatively with Ep values, supporting the hypothesis that the O2•- radical scavenging reaction proceeds via one-electron and two-proton processes. The processes were accompanied by the production of hydrogen peroxide at pH 7.4. Furthermore, the correlation between the plots of ks and the OH proton dissociation constant (pKa•) of the intermediate aroxyl radicals (ks-pKa• plots) revealed that the second proton transfer process could potentially be the rate-determining step of the O2•- radical scavenging reaction of phenolic compounds. The ks-Ep plots provide practical information to predict the O2•- radical scavenging activity of plant-derived phenolic compounds based on those molecular structures.


Assuntos
Sequestradores de Radicais Livres , Oxirredução , Fenóis , Superóxidos , Espectroscopia de Ressonância de Spin Eletrônica , Cinética , Fenóis/química , Sequestradores de Radicais Livres/química , Superóxidos/química , Detecção de Spin
12.
Artigo em Inglês | MEDLINE | ID: mdl-39004817

RESUMO

The large-scale application of aqueous Al-air batteries is highly restricted by the performance of Al anodes. The severe self-corrosion and hydrogen evolution of the Al anode in a concentrated alkaline electrolyte are the main reason. Here, aimed at relieving side reactions and enhancing the utilization of metal Al, we propose a hybrid electrolyte additive of 2-mercaptobenzothiazole (MBT) and ZnO to form a protective film at the anode/electrolyte interface and to decrease the hydrogen evolution active site. The strong absorption capability of MBT on the metal surface, along with the reduced Zn-containing layer, enables a compact protective film with high hydrogen evolution potential on the Al surface. With this benefit, the hydrogen evolution reaction (HER) inhibition efficiency is up to 83.58%, endowing a superior Al-air battery with an energy density of 2376.71 Wh kgAl-1 under a current density of 25 mA cm-2. The conception of constructing a hybrid protective film on the metal surface not only favors the development of metal-air batteries but also facilitates metal corrosion protection.

13.
Adv Mater ; : e2405433, 2024 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-39007283

RESUMO

Collective excitations including plasmons, magnons, and layer-breathing vibration modes emerge at an ultralow frequency (<1 THz) and are crucial for understanding van der Waals materials. Strain at the nanoscale can drastically change the property of van der Waals materials and create localized states like quantum emitters. However, it remains unclear how nanoscale strain changes collective excitations. Herein, ultralow-frequency tip-enhanced Raman spectroscopy (TERS) with sub-10 nm resolution under ambient conditions is developed to explore the localized collective excitation on monolayer semiconductors with nanoscale strains. A new vibrational mode is discovered at around 12 cm-1 (0.36 THz) on monolayer MoSe2 nanobubbles and it is identified as the radial breathing mode (RBM) of the curved monolayer. The correlation is determined between the RBM frequency and the strain by simultaneously performing deterministic nanoindentation and TERS measurement on monolayer MoSe2. The generality of the RBM in nanoscale curved monolayer WSe2 and bilayer MoSe2 is demonstrated. Using the RBM frequency, the strain of the monolayer MoSe2 on the nanoscale can be mapped. Such an ultralow-frequency vibration from curved van der Waals materials provides a new approach to study nanoscale strains and points to more localized collective excitations to be discovered at the nanoscale.

14.
J Clin Nurs ; 2024 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-39021041

RESUMO

AIM: To evaluate the effectiveness and safety of nutritional interventions (i.e. nutritional support, dietary patterns and dietary supplements) on cognitive function in cancer survivors. DESIGN: Systematic review. METHODS: A systematic and comprehensive search of PubMed, Web of Science, the Cochrane Library, Embase, and CINAHL was conducted from the inception until March 10, 2023. The last search was conducted on December 10, 2023. REPORTING METHOD: PRISMA. RESULTS: A total of 59 randomized controlled trials were included for analysis. Nutritional support, dietary patterns and dietary supplements improved cognitive function in cancer survivors with no apparent safety concerns. The anti-inflammatory diet, the fasting-mimicking diet and the web-based diet significantly improved cognitive function. Whereas the ketogenic diet or dietary advice to consume more soluble dietary fibres and less insoluble dietary fibres and lactose could not. There was evidence from dietary supplements to support the beneficial effects of polyunsaturated fatty acid supplements, traditional herbal medicines and other supplements. CONCLUSIONS: Nutritional interventions have great promise for improving cognitive function in adult cancer survivors. Further validation of the nutritional interventions supported in this study in other survivors and exploration of more effective nutritional interventions are needed. IMPLICATIONS FOR THE PROFESSION AND/OR PATIENT CARE: This work can support the construction of nutritional support interventions and dietary guidance programs to prevent cancer-related cognitive decline. IMPACT: This work filled a gap in preventive strategies for cancer-related cognitive decline from a nutritional perspective. Nutritional support, dietary patterns, and dietary supplements can prevent cancer-related cognitive decline without serious safety concerns. This work highlighted nutritional interventions that have the potential to improve cognitive function in cancer survivors, benefiting the further construction of evidence-based nutritional intervention programs. PROTOCOL REGISTRATION: PROSPERO. PATIENT OR PUBLIC CONTRIBUTION: No patient or public contribution.

15.
Mater Today Bio ; 26: 101101, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38883419

RESUMO

Messenger ribonucleic acid (mRNA) has emerged as a promising molecular preventive and therapeutic approach that opens new avenues for healthcare. Although the use of delivery systems, especially lipid nanoparticles (LNPs), greatly improves the efficiency and stability of mRNA, mRNA tends to accumulate in the liver and hardly penetrates physiological barriers to reach the target site after intravenous injection. Hence, the rational design of targeting strategies aimed at directing mRNA to specific tissues and cells remains an enormous challenge in mRNA therapy. High-throughput screening (HTS) is a cutting-edge targeted technique capable of synthesizing chemical compound libraries for the large-scale experiments to validate the efficiency of mRNA delivery system. In this review, we firstly provide an overview of conventional low-throughput targeting strategies. Then the latest advancements in HTS techniques for mRNA targeted delivery, encompassing optimizing structures of large-scale delivery vehicles and developing large-scale surface ligands, as well as the applications of HTS techniques in extrahepatic systemic diseases are comprehensively summarized. Moreover, we illustrate the selection of administration routes for targeted mRNA delivery. Finally, challenges in the field and potential solutions to tackle them are proposed, offering insights for future development toward mRNA targeted therapy.

16.
Huan Jing Ke Xue ; 45(6): 3756-3764, 2024 Jun 08.
Artigo em Chinês | MEDLINE | ID: mdl-38897795

RESUMO

To investigate the concentration characteristics and sources of metal elements in PM2.5 during winter heavy pollution in the southern Sichuan urban agglomeration (Zigong, Luzhou, Neijiang, and Yibin), the metal elements in PM2.5 were measured using membrane sampling methods from December 30, 2018 to January 14, 2019, and the enrichment factor method (EF) and positive matrix factorization(PMF) were applied to investigate the sources of metal elements. The metal element observation data of Zigong in the same period of 2015 were also used to investigate the changes in metal element pollution and enrichment in Zigong in the middle and end of the implementation of China's Air Pollution Prevention and Control Action Plan. The main findings were as follows:① The concentrations and percentages of metal elements in particulate matter in different cities did not differ significantly. The elements with higher concentrations in the four cities showed similarities, with Al, Sb, and Fe at the top. From the comparison of different observation periods in Zigong, the concentrations of all elements except Tl changed. ② The results of the enrichment factor calculation showed that the enrichment of the elements Cr (Zigong and Yibin), Ni, Cu, As, Se, Ag, Cd, Sb, Tl, and Pb in the urban agglomeration was high. The comparison of the enrichment levels of elements in Zigong for different observation periods showed that the enrichment levels of all elements, except Cu, tended to decrease in the winter observation period of 2018. ③ The results of PMF source analysis showed that the metal elements in each city mainly originated from dust sources, coal-fired sources, industrial sources, and traffic sources, whereas there was a mixed contribution among the sources. The contribution of the main sources differed among cities, in which Zigong was dominated by traffic dust sources and mixed sources, Luzhou was dominated by industrial sources, Neijiang had a similar contribution from different sources, and Yibin was dominated by traffic sources.

17.
Sci Total Environ ; 945: 174093, 2024 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-38906307

RESUMO

Black carbon (BC) and brown carbon (BrC) over the high-altitude Tibetan Plateau (TP) can significantly influence regional and global climate change as well as glacial melting. However, obtaining plateau-scale in situ observations is challenging due to its high altitude. By integrating reanalysis data with on-site measurements, the spatial distribution of BC and BrC can be accurately estimated using the random forest algorithm (RF). In our study, the on-site observations of BC and BrC were successively conducted at four sites from 2018 to 2021. Ground-level BC and BrC concentrations were then obtained at a spatial resolution of 0.25° × 0.25° for three periods (including Periods-1980, 2000, and 2020) using RF and multi-source data. The highest annual concentrations of BC (1363.9 ± 338.7 ng/m3) and BrC (372.1 ± 96.2 ng/m3) were observed during Period-2000. BC contributed a dominant proportion of carbonaceous aerosol, with concentrations 3-4 times higher than those of BrC across the three periods. The ratios of BrC to BC decreased from Period-1980 to Period-2020, indicating the increasing importance of BC over the TP. Spatial distributions of plateau-scale BC and BrC concentrations showed heightened levels in the southeastern TP, particularly during Period-2000. These findings significantly enhance our understanding of the spatio-temporal distribution of light-absorbing carbonaceous aerosol over the TP.

18.
Chem Commun (Camb) ; 60(57): 7374-7377, 2024 Jul 11.
Artigo em Inglês | MEDLINE | ID: mdl-38922126

RESUMO

Detailed photophysical processes of two AuCu14 clusters with different substituents (-F or -C(CH3)3) of the thiol ligand were studied in this work. The electronic effect of the substituents led to structural shrinkage, thus enhancing the luminous intensity. The internal conversion (IC) and intersystem crossing (ISC) rates in the AuCu14-C(CH3)3 crystal were slower compared with the AuCu14-F crystal, which was caused by the steric effect.

19.
Org Lett ; 26(27): 5770-5775, 2024 Jul 12.
Artigo em Inglês | MEDLINE | ID: mdl-38940694

RESUMO

In this paper, we described a palladium/norbornene-catalyzed ortho-C-H phosphormethylation of aryl iodides using XCH2P(O)RR', offering a reliable method for the modular synthesis of polysubstituted α-phosphorylated arenes. Alkenylation, hydrogenation, cyanation, methylation, and arylation were all viable termination steps compatible with the reaction. This method demonstrates excellent functional group tolerance and can be extended to the late-stage modification of bioactive molecules. Furthermore, the synthetic transformations of the products demonstrate the practical utility of this reaction.

20.
Heliyon ; 10(11): e31665, 2024 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-38845874

RESUMO

In this paper, foam concrete is modified using graphite and carbon fiber as absorbents. The mechanical properties are analyzed in conjunction with hydration products, pore size distribution based on XCT test. Additionally, the resistivity, complex permittivity and complex permeability are tested. The results demonstrate that carbon fiber enhances the proportion of pores with diameters less than 200 µm in foam concrete, thereby significantly enhancing its flexural strength. Furthermore, incorporating graphite helps offset the initial retardation of sulfoaluminate cement hydration induced by carbon fibers, leading to an increase in the average pore size and a reduction in compressive strength. The incorporation of carbon fibers at a concentration of 0.6 wt% achieves the percolation threshold, akin to scenarios with singular fiber incorporation. Exceeding 2 wt% graphite content results in negligible influence on the conductivity. The synergistic integration of graphite and carbon fibers significantly improves the electromagnetic wave absorption performance of the composite. At a thickness of 6 mm, the material exhibits an effective bandwidth where the reflection loss is less than -10 dB, extending up to 2.5 GHz, which constitutes 52.08 % of the tested frequency spectrum.

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