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1.
Antibiotics (Basel) ; 10(4)2021 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-33800674

RESUMO

Food safety has attracted attention worldwide, and how to detect various kinds of hazardous substances in an efficient way has always been a focus. Metal-Organic Frameworks (MOFs) are a class of hybrid porous materials formed by organic ligand and metal ions. Nanoscale MOFs (NMOFs) exhibit great potential in serving as fluorescence sensors for food safety due to their superior properties including high accuracy, great stability, fast response, etc. In this review, we focus on the recent development of NMOFs sensing for food safety. Several typical methods of NMOFs synthesis are presented. NMOFs-based fluorescence sensors for contaminants and adulterants, such as antibiotics, food additives, ions and mycotoxin etc. are summarized, and the sensing mechanisms are also presented. We explore these challenges in detail and provide suggestions about how they may be surmounted. This review could help the exploration of NMOFs sensors in food related work.

2.
J Immunol ; 206(8): 1752-1764, 2021 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-33811103

RESUMO

Macrophages play an important role in the pathogenesis of systemic lupus erythematosus-associated diffuse alveolar hemorrhage (DAH). The immunomodulation of macrophage responses might be a potential approach for the prevention and treatment of DAH. Erythropoietin (EPO) could regulate macrophage bioactivities by binding to the EPO receptor expressing on macrophages. This study assessed the effects of EPO on DAH protection using an immune-mediated DAH murine model with macrophages as the major contributor. A DAH murine model was established in female C57BL/6 mice by an i.p. injection of pristane. We found that EPO administration alleviates DAH by reducing pulmonary macrophages recruitment and promoting phenotype switch toward M2 macrophages in vivo. EPO drove macrophages to the anti-inflammatory phenotype in the primary murine bone marrow-derived macrophages and macrophages cell line RAW 264.7 with LPS, IFN-γ, and IL-4 in vitro. Moreover, EPO treatment increases the expression of EPOR and decreases the expression of miR-494-3p, resulting in increased phosphorylation of JAK2 and STAT3. In conclusion, EPO can be a potential therapeutic agent in DAH by reducing cell apoptosis and regulating macrophage polarization through the EPOR/JAK2/STAT3 axis. Further studies are also needed to validate the direct target of miR-494-3p in regulating JAK2/STAT3 signaling transduction.

3.
Mater Sci Eng C Mater Biol Appl ; 123: 112014, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33812633

RESUMO

Nano-graphene oxide (nGO), an effective drug nanocarrier, is used for simultaneous photothermal therapy (PTT) and near-infrared fluorescence imaging. Dacarbazine (DTIC) is used in the treatment of melanoma with limited clinical efficacy. PTT shows promise in the treatment of skin cancer. Herein, chitosan oligosaccharide (COS)-grafted nGO was further modified with CD47 antibody, and loaded DTIC was prepared using a versatile nanoplatform (nGO-COS-CD47/DTIC) for the treatment of melanoma as a synergistic targeted chemo-photothermal therapy. The in vitro results demonstrated that nGO-COS-CD47/DTIC nanocarriers have excellent biocompatibility, photothermal conversion efficiency, high targeting efficiency, fast drug release under NIR irradiation, and tumor cell killing efficiency. Notably, nGO-COS-CD47/DTIC plus NIR irradiation significantly promoted early cell apoptosis through the mitochondrial apoptosis pathway and exhibited a significant joint function of antitumor efficacy. The demonstrated nGO-COS-CD47/DTIC can provide a highly efficient malignant melanoma therapy using this multifunctional intelligent nanoplatform.

4.
Crit Rev Biotechnol ; : 1-25, 2021 Apr 04.
Artigo em Inglês | MEDLINE | ID: mdl-33818232

RESUMO

This is the first comprehensive overview of laccase-triggered anabolism from fundamental theory to biotechnology applications. Laccase is a typical biological oxidordeuctase that induces the one-electronic transfer of diverse substrates for engendering four phenoxy radicals with concomitant reduction of O2 into 2H2O. In vivo, laccase can participate in anabolic processes to create multifarious functional biopolymers such as fungal pigments, plant lignins, and insect cuticles, using mono/polyphenols and their derivatives as enzymatic substrates, and is thus conducive to biological tissue morphogenesis and global carbon storage. Exhilaratingly, fungal laccase has high redox potential (E° = 500-800 mV) and thermodynamic efficiency, making it a remarkable candidate for utilization as a versatile catalyst in the green and circular economy. This review elaborates the anabolic mechanisms of laccase in initiating the polymerization of natural phenolic compounds and their derivatives in vivo via radical-based self/cross-coupling. Information is also presented on laccase immobilization engineering that expands the practical application ranges of laccase in biotechnology by improving the enzymatic catalytic activity, stability, and reuse rate. Particularly, advances in biotechnology applications in vitro through fungal laccase-triggered macromolecular biosynthesis may provide a key research direction beneficial to the rational design of green chemistry.

5.
Polymers (Basel) ; 13(6)2021 Mar 23.
Artigo em Inglês | MEDLINE | ID: mdl-33806844

RESUMO

The heat generated by a high-power device will seriously affect the operating efficiency and service life of electronic devices, which greatly limits the development of the microelectronic industry. Carbon fiber (CF) materials with excellent thermal conductivity have been favored by scientific researchers. In this paper, CF/carbon felt (CF/C felt) was fabricated by CF and phenolic resin using the "airflow network method", "needle-punching method" and "graphitization process method". Then, the CF/C/Epoxy composites (CF/C/EP) were prepared by the CF/C felt and epoxy resin using the "liquid phase impregnation method" and "compression molding method". The results show that the CF/C felt has a 3D network structure, which is very conducive to improving the thermal conductivity of the CF/C/EP composite. The thermal conductivity of the CF/C/EP composite reaches 3.39 W/mK with 31.2 wt% CF/C, which is about 17 times of that of pure epoxy.

6.
Eur J Med Chem ; 217: 113326, 2021 Mar 12.
Artigo em Inglês | MEDLINE | ID: mdl-33756127

RESUMO

Defective in cullin neddylation 1(DCN1) is a co-E3 ligase that is important for cullin neddylation. Dysregulation of DCN1 highly correlates with the development of various cancers. Herein, from the initial high-throughput screening, a novel hit compound 5a containing a phenyltriazole thiol core (IC50 value of 0.95 µM for DCN1-UBC12 interaction) was discovered. Further structure-based optimization leads to the development of SK-464 (IC50 value of 26 nM). We found that SK-464 not only directly bound to DCN1 in vitro, but also engaged cellular DCN1, suppressed the neddylation of cullin3, and hindered the migration and invasion of two DCN1-overexpressed squamous carcinoma cell lines (KYSE70 and H2170). These findings indicate that SK-464 may be a novel lead compound targeting DCN1-UBC12 interaction.

7.
Org Lett ; 2021 Mar 29.
Artigo em Inglês | MEDLINE | ID: mdl-33780256

RESUMO

A general and metal-free visible-light-induced decarboxylative arylation procedure at room temperature was described for the construction of acylated heterocyclic derivatives, such as benzimidazo/indolo[2,1-a]isoquinolin-6(5H)-ones, aroylazaspiro[4.5]trienones, thioflavones, and so on. This practical arylation procedure was conducted by using 2,4,5,6-tetra(9H-carbazol-9-yl)isophthalonitrile (4CzIPN) as a photocatalyst under mild conditions, which avoided the use of an additional base, traditional heating, and metal reagents.

8.
Environ Microbiol ; 2021 Mar 22.
Artigo em Inglês | MEDLINE | ID: mdl-33754450

RESUMO

Novosphingobium sp. ES2-1 is an efficient 17ß-estradiol (E2)-degrading bacterium, which can convert E2 to estrone (E1), then to 4-hydroxyestrone (4-OH-E1) for subsequent oxidative cracking. In this study, the molecular bases for this process were elucidated. Two novel monooxygenase systems EstP and EstO were shown to catalyse the oxygenation of E1 and 4-OH-E1, respectively. EstP was a three-component cytochrome P450 monooxygenase system consisting of EstP1 (P450 monooxygenase), EstP2 (ferredoxin) and EstP3 (ferredoxin reductase). Ultraperformance liquid chromatography-high resolution mass spectrometry (UPLC-HRMS) analysis revealed that EstP catalysed the 4-hydroxylation of E1 to produce 4-OH-E1. The resultant 4-OH-E1 was further oxidized by a two-component monooxygenase system EstO consisting of EstO1 (flavin-dependent monooxygenases) and EstO2 (flavin reductase). UPLC-HRMS combined with 1 H-nuclear magnetic resonance analysis demonstrated that EstO catalysed the breakage of C9-C10 to yield a ring B-cleavage product. In addition, the oxygenase component genes estP1 and estO1 exhibited contrary inductive behaviours when exposed to different steroids, suggesting that EstP1-mediated 4-hydroxylation was E2-specific, whereas EstO1-mediated monooxygenation might be involved in the degradation of testosterone, androstenedione, progesterone and pregnenolone. This also implied that the mechanisms of the catabolism of different steroids by the same microorganism might be partially interlinked.

9.
Medicine (Baltimore) ; 100(13): e24567, 2021 Apr 02.
Artigo em Inglês | MEDLINE | ID: mdl-33787572

RESUMO

RATIONALE: Acute promyelocytic leukemia (APL) with myelofibrosis (MF) is rare, and only 14 cases have been reported in the literature to date. PATIENT CONCERNS: A 42-year-old woman was admitted to the hospital with easy bruising and excessive bleeding. With the remission of the primary disease during treatment, the degree of fibrosis did not decrease, but worsened progressively. DIAGNOSIS: The woman was diagnosed with acute promyelocytic leukemia with secondary myelofibrosis. INTERVENTIONS: All-trans retinoic acid (ATRA) was discontinued after 6 months of complete remission of APL. Arsenic trioxide (ATO) was discontinued because of supraventricular tachycardia 9 months after complete remission of APL. OUTCOMES: After withdrawal of ATRA for 2 months, the degree of fibrosis was significantly alleviated, and after withdrawal of ATRA for 8 months and ATO for 5 months, bone marrow biopsy showed no reticular fiber deposition. LESSONS: In this case report and review of an additional 14 cases of APL with MF, we highlighted the importance of the degree of MF to be evaluated by bone marrow biopsy at the time of bone marrow aspiration when APL is suspected. If MF is present, the type of MF should be determined in a timely manner, and appropriate intervention measures should be taken accordingly.

10.
Radiother Oncol ; 2021 Mar 19.
Artigo em Inglês | MEDLINE | ID: mdl-33753157

RESUMO

PURPOSE/OBJECTIVE(S): With reports of CNS toxicity in patients treated with proton therapy at doses lower than would be expected based on photon data, it has been proposed that heavy monitor unit (MU) weighting of pencil beam scanning (PBS) proton therapy spots may potentially increase the risk of toxicity. We evaluated the impact of maximum MU weighting per spot (maxMU/spot) restrictions on PBS plan quality, prior to implementing clinic-wide maxMU/spot restrictions. MATERIALS/METHODS: PBS plans of 11 patients, of which 3 plans included boosts, for a total of 14 PBS sample cases were included. Per sample case, a single dosimetrist created 4 test plans, gradually reducing the maxMU/spot in the plan. Test Plan 1, unrestricted in maxMU/spot, was the reference for all restricted plan comparisons (comparison sets 2 vs. 1; 3 vs. 1; and 4 vs. 1). The impact of MU/spot restrictions on plan quality metrics were analyzed with Wilcoxon signed rank test analyses. Treatment delivery time was modeled for a representative case. RESULTS: A total of 14 PBS sample cases, 7 (50%) single-field optimized, 7 (50%) multi-field optimized, 9 (64%) delivering >3500cGy, 9 (64%) with 3 beams, and 7 (50%) without a range shifter were included. There were no differences in plan quality metrics of target coverage (V95% and V100% prescription), conformality and gradient indices, hot spot volume (V105% prescription), and dose to normal brain (V10%/30%/50%/70%/90%/100% prescription) with reductions of allowable maxMU/spot across all comparison sets (p>0.05). Max MU/spot restrictions did not increase treatment delivery time when analyzed for a representative case. CONCLUSION: MaxMU/spot restrictions within the thresholds evaluated in this study did not degrade overall plan quality metrics. Future studies should evaluate spot weighting with linear energy transfer/relative biologic effectiveness-informed planning to determine if spot weighting manipulation impacts clinical outcomes and mitigates toxicity.

11.
Polymers (Basel) ; 13(5)2021 Feb 24.
Artigo em Inglês | MEDLINE | ID: mdl-33668296

RESUMO

Because the aerogel has ultra-low density and good impact resistance, the aerogel material, epoxy-hardener system, and expandable polystyrene beads (EPS) were used to prepare the lightweight aerogel reinforced hollow epoxy macro-spheres (AR-HEMS). The multi-phase epoxy syntactic foam (ESF) was manufactured with the epoxy-hardener system, HGMS (EP-hardener-HGMS), and AR-HEMS by "the compression modeling method." In this experiment, in order to enhance the strength of the ESF, some different kinds of the carbon fiber (CF) were added into the EP-hardener-HGMS system (CFR-EP). The influence of the volume stacking fraction, inner diameter, and layer of the AR-HEMS and the content and type of the CF in the EP-HGMS (CFR-EP) system on the compressive strength of the ESF were studied. Weighing the two factors of the density and compressive strength, the ESF reinforced by 1.5 wt% CF with 90% AR-HEMS has the better performance. This kind of the ESF has 0.428 g/cm3 nd 20.76 Mpa, which could be applied in 2076 m deep sea.

12.
Artigo em Inglês | MEDLINE | ID: mdl-33662174

RESUMO

OBJECTIVE: Underrepresented racial and ethnic minorities are disproportionately affected by systemic lupus erythematosus (SLE). Racial and ethnic minorities also have more severe SLE manifestations that require use of immunosuppressive medications, and often have lower rates of medication adherence. We aimed to explore barriers of adherence to SLE immunosuppressive medications among minority SLE patients. METHODS: We conducted a qualitative descriptive study using in-depth interviews with a purposeful sample of 1) racial minority SLE patients taking oral immunosuppressants (methotrexate, azathioprine, or mycophenolate), and 2) lupus clinic providers and staff. Interviews were audio-recorded, transcribed, and analyzed using applied thematic analysis. We grouped themes using the Capability, Opportunity, Motivation, Behavior conceptual model. RESULTS: We interviewed 12 SLE patients (4 adherent, 8 non-adherent) and 12 providers and staff. We identified Capability barriers to include external factors related to acquiring medications, specifically cost, pharmacy, and clinic related issues; Opportunity barriers to include external barriers to taking medications, specifically logistic and medication related issues; and Motivation factors to include intrinsic barriers, encompassing patients' knowledge, beliefs, attitudes, and physical and mental health. The most frequently described barriers were cost, side effects, busyness/forgetting, and lack of understanding, although barriers differed by patient and adherence level, with logistic and intrinsic barriers described predominantly by non-adherent patients and side effects described predominantly by adherent patients. CONCLUSION: Our findings suggest that interventions may be most impactful if they are designed to facilitate logistics of taking medications and increase patients' motivation while allowing for personalization to address the individual differences in adherence barriers.

13.
JCI Insight ; 2021 Mar 11.
Artigo em Inglês | MEDLINE | ID: mdl-33705361

RESUMO

Compromised regenerative capacity of lung epithelial cells can lead to cellular senescence, which may precipitate fibrosis. While increased markers of senescence have been reported in idiopathic pulmonary fibrosis (IPF), the origin and identity of these senescent cells remain unclear, and tools to characterize context-specific cellular senescence in human lung are lacking. We observed that the senescent marker p16 is predominantly localized to bronchiolized epithelial structures in scarred regions of IPF and systemic sclerosis associated interstitial lung disease ILD (SSc-ILD) lung tissue, overlapping with the basal epithelial markers Keratin 5 and Keratin 17. Using in vitro models, we derived transcriptional signatures of senescence programming specific to different types of lung epithelial cells, and interrogated these signatures in a single-cell RNA-seq data set derived from control, IPF, and SSc-ILD lung tissue. We identified a population of basal epithelial cells defined by, and enriched for, markers of cellular senescence, and identified candidate markers specific to senescent basal epithelial cells in ILD that can enable future functional studies. Notably, gene expression of these cells significantly overlaps with terminally differentiating cells in stratified epithelia, where it is driven by p53 activation as part of the senescence program.

14.
Artigo em Inglês | MEDLINE | ID: mdl-33656835

RESUMO

INTRODUCTION: The objective of this study is to evaluate the efficacy and midterm prognosis of transcatheter device closure of atrial septal defects (ASDs) in sexagenary patients in China. METHODS: Forty-six sexagenary patients who underwent transcatheter device closure of ASDs in our hospital were included in this study. The patients' preoperative and postoperative clinical symptoms, echocardiographic results, and quality of life were investigated and analyzed. RESULTS: Of the 46 sexagenary patients who participated in the study, 40 completed the study. After ASD closure, the clinical symptoms of the patients significantly improved, and the number of patients with dyspnea and palpitations significantly decreased after the operation. According to the echocardiographic results, few patients had a tiny residual shunt after closure, but the shunt disappeared completely at the three-month follow-up. The size of the right ventricular cavity was significantly smaller postoperatively compared with preoperatively. Regarding the patients' quality of life, their feedback in all dimensions of the 36-Item Short-Form Health Survey (or SF-36) was significantly improved at the three-month follow-up, and it remained improved at the one-year follow-up. CONCLUSION: The clinical outcomes and subjective quality of life of sexagenary patients with ASDs improved significantly after transcatheter device closure of ASDs. Therefore, we believe that for sexagenary patients with ASDs, transcatheter device closure is a favorable treatment.

15.
Biochem Genet ; 2021 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-33786672

RESUMO

The involvement of aberrantly expressed genes in the pathogenesis and progression of various human malignancies has been widely reported, including clear cell renal cell carcinoma (ccRCC). This study aimed to identify potential crucial genes in ccRCC and further investigate the role of these genes in ccRCC prognosis. Three gene expression profiles (GSE3, GSE6344 and GSE53000) were downloaded from GEO database. GEO2R was performed to identify the differentially expressed genes (DEGs) between ccRCC and normal samples. GO analysis and KEGG pathway enrichment analysis were applied for the function analysis. The DEGs were mapped into the PPI network, then the hub genes were identified and verified using the ONCOMINE database. Kaplan-Meier plotter was used to evaluate of the prognostic value of the identified hub genes. A total of 113 DEGs were identified from the three gene expression profiles, including 64 up-regulated genes and 69 down-regulated genes. DEGs were observed to be enriched in biological processes related to the progress and pathogenesis of human cancers. According to PPI network, 5 hub genes were collected, including TYROBP, C1QB, ITGB2, CD53 and FCER1G. Among them, CD53 was newly identified, and Kaplan-Meier survival curves suggested that high expression of CD53 was significantly associated with poor survival in ccRCC patients (log-rank P < 0.01). The present results may provide new insight into the understanding of molecular mechanisms and the clinical prognosis of ccRCC.

16.
Cell Prolif ; 54(3): e12998, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33522652

RESUMO

Growth differentiation factor 5 (GDF-5) is essential for cartilage development and homeostasis. The expression and function of GDF-5 are highly associated with the pathogenesis of osteoarthritis (OA). OA, characterized by progressive degeneration of joint, particularly in cartilage, causes severe social burden. However, there is no effective approach to reverse the progression of this disease. Over the past decades, extensive studies have demonstrated the protective effects of GDF-5 against cartilage degeneration and defects. Here, we summarize the current literature describing the role of GDF-5 in development of cartilage and joints, and the association between the GDF-5 gene polymorphisms and OA susceptibility. We also shed light on the protective effects of GDF-5 against OA in terms of direct GDF-5 supplementation and modulation of the GDF-5-related signalling. Finally, we discuss the current limitations in the application of GDF-5 for the clinical treatment of OA. This review provides a comprehensive insight into the role of GDF-5 in cartilage and emphasizes GDF-5 as a potential therapeutic candidate in OA.


Assuntos
Condrócitos/metabolismo , Fator 5 de Diferenciação de Crescimento/metabolismo , Osteoartrite/tratamento farmacológico , Osteoartrite/metabolismo , Animais , Doenças das Cartilagens/tratamento farmacológico , Cartilagem Articular/efeitos dos fármacos , Cartilagem Articular/metabolismo , Diferenciação Celular/fisiologia , Fator 5 de Diferenciação de Crescimento/genética , Fator 5 de Diferenciação de Crescimento/farmacologia , Humanos
17.
Anal Chem ; 93(6): 3196-3201, 2021 02 16.
Artigo em Inglês | MEDLINE | ID: mdl-33528996

RESUMO

Isolation and analysis of circulating rare cells is a promising approach for early detection of cancer and other diseases and for prenatal diagnosis. Isolation of rare cells is usually difficult due to their heterogeneity as well as their low abundance in peripheral blood. We previously reported a two-stage ensemble-decision aliquot ranking platform (S-eDAR) for isolating circulating tumor cells from whole blood with high throughput, high recovery rate (>90%), and good purity (>70%), allowing detection of low surface antigen-expressing cancer cells linked to metastasis. However, due to the scarcity of these cells, large sample volumes and large quantities of antibodies were required to isolate sufficient cells for downstream analysis. Here, we drastically increased the number of nucleated cells analyzed by first concentrating peripheral blood mononuclear cells (PBMCs) from whole blood by density gradient centrifugation. The S-eDAR platform was capable of isolating rare cells from concentrated PBMCs (108/mL, equivalent to processing ∼20 mL of whole blood in the 1 mL sample volume used by our instrument) at a high recovery rate (>85%). We then applied the S-eDAR platform for isolating rare fetal nucleated red blood cells (fNRBCs) from concentrated PBMCs spiked with umbilical cord blood cells and confirmed fNRBC recovery by immunostaining and fluorescence in situ hybridization, demonstrating the potential of the S-eDAR system for isolating rare fetal cells from maternal PBMCs to improve noninvasive prenatal diagnosis.

18.
BMC Anesthesiol ; 21(1): 33, 2021 Feb 02.
Artigo em Inglês | MEDLINE | ID: mdl-33530942

RESUMO

BACKGROUND: The blood saving efficacy of TXA in cardiac surgery has been proved in several studies, but TXA dosing regimens were varied in those studies. Therefore, we performed this study to investigate if there is a dose dependent in-vivo effect of TXA on fibrinolysis parameters by measurement of fibrinolysis markers in adults undergoing cardiac surgery with CPB. METHODS: A double-blind, randomized, controlled prospective trial was conducted from February 11, 2017 to May 05, 2017. Thirty patients undergoing cardiac valve surgery were identified and randomly divided into a placebo group, low-dose group and high-dose group by 1: 1: 1. Fibrinolysis parameters were measured by plasma levels of D-Dimers, plasminogen activator inhibitor-1 (PAI-1), thrombin activatable fibrinolysis inhibitor (TAFI), plasmin-antiplasmin complex (PAP), tissue plasminogen activator (tPA) and thrombomodulin (TM). Those proteins were measured at five different sample times: preoperatively before the TXA injection (T1), 5 min after the TXA bolus (T2), 5 min after the initiation of CPB (T3), 5 min before the end of CPB (T4) and 5 min after the protamine administration (T5). A Thrombelastography (TEG) and standard coagulation test were also performed. RESULTS: Compared with the control group, the level of the D-Dimers decreased in the low-dose and high-dose groups when the patients arrived at the ICU and on the first postoperative morning. Over time, the concentrations of PAI-1, TAFI, and TM, but not PAP and tPA, showed significant differences between the three groups (P <  0.05). Compared with the placebo group, the plasma concentrations of PAI-1 and TAFI decreased significantly at the T3 and T4 (P <  0.05); TAFI concentrations also decreased at the T5 in low-dose group (P < 0.05). Compared with the low-dose group, the concentration of TM increased significantly at the T4 in high-dose group. CONCLUSIONS: The in-vivo effect of low dose TXA is equivalent to high dose TXA on fibrinolysis parameters in adults with a low bleeding risk undergoing valvular cardiac surgery with cardiopulmonary bypass, and a low dose TXA regimen might be equivalent to high dose TXA for those patients. TRIAL REGISTRATION: ChiCTR-IPR-17010303 , Principal investigator: Zhen-feng ZHOU, Date of registration: January 1, 2017.

19.
Phys Rev Lett ; 126(3): 037201, 2021 Jan 22.
Artigo em Inglês | MEDLINE | ID: mdl-33543946

RESUMO

Sr_{2}CuTeO_{6} is a square-lattice Néel antiferromagnet with superexchange between first-neighbor S=1/2 Cu spins mediated by plaquette centered Te ions. Substituting Te by W, the affected impurity plaquettes have predominantly second-neighbor interactions, thus causing local magnetic frustration. Here we report a study of Sr_{2}CuTe_{1-x}W_{x}O_{6} using neutron diffraction and µSR techniques, showing that the Néel order vanishes already at x=0.025±0.005. We explain this extreme order suppression using a two-dimensional Heisenberg spin model, demonstrating that a W-type impurity induces a deformation of the order parameter that decays with distance as 1/r^{2} at temperature T=0. The associated logarithmic singularity leads to loss of order for any x>0. Order for small x>0 and T>0 is induced by weak interplane couplings. In the nonmagnetic phase of Sr_{2}CuTe_{1-x}W_{x}O_{6}, the µSR relaxation rate exhibits quantum critical scaling with a large dynamic exponent, z≈3, consistent with a random-singlet state.

20.
J Hazard Mater ; 412: 125197, 2021 Jan 27.
Artigo em Inglês | MEDLINE | ID: mdl-33540263

RESUMO

Naturally-occurring phenolic acids (PAs) act as humic precursors that participate in the conversion behaviors and coupling pathways of steroidal estrogens (SEs) during laccase-triggered humification processes (L-THPs). Herein, the influences and mechanisms of PAs on Trametes versicolor laccase-evoked 17ß-estradiol (E2) conversion kinetics and humification routes were explored. Fungal laccase was fleet in converting > 99% of E2, and the calculated pseudo-first-order velocity constant and half-time values were respectively 0.039 min-1 and 17.906 min. PAs containing an O-dihydroxy moiety such as gallic acid and caffeic acid evidently hampered E2 humification owning to the yielded highly reactive O-quinones reversed E2 radicals by hydrogen transfer mechanism, implying that the inhibition effect was enormously dependent upon the number and position of the phenolic -OH present in humic precursors. Oligomers and polymers with carbon-carbon/oxygen links were tentatively found as E2 main humified species resulting from laccase-evoked successive oxidative-coupling. Note that PAs participating in the humification also encountered oxydehydrogenation, self-polymerization, and cross-binding to E2. Interestingly, the -COOH and -OCH3 groups of PAs could be deprived in radical-caused self/co-polymerization. The generation of humified products not only circumvented the environmental risks of parent compounds but accelerated global carbon sequestration. To our knowledge, this is the first in-depth revelation of the humification pathways and related mechanisms of SEs with humic precursors in aquatic ecosystems by L-THPs.

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