Search

Bone marrow-derived mesenchymal stem cells (BMSCs) exhibit multi-lineage differentiation potential and robust proliferative capacity. The late stage of differentiation signifies the functional maturation and characterization of specific cell lineages, which is crucial for studying lineage-specific differentiation mechanisms. However, the molecular processes governing late-stage BMSC differentiation remain poorly understood. This study aimed to elucidate the key biological processes involved in late-stage BMSC differentiation. Publicly available transcriptomic data from human BMSCs were analyzed after approximately 14 days of osteogenic, adipogenic, and chondrogenic differentiation. Thirty-one differentially expressed genes (DEGs) associated with differentiation were identified. Pathway enrichment analysis indicated that the DEGs were involved in extracellular matrix (ECM)-receptor interactions, focal adhesion, and glycolipid biosynthesis, a ganglion series process. Subsequently, the target genes were validated using publicly available single-cell RNA-seq data from mouse BMSCs. Lamc1 exhibited predominant distribution in adipocytes and osteoblasts, primarily during the G2/M phase. Tln2 and Hexb were expressed in chondroblasts, osteoblasts, and adipocytes, while St3gal5 was abundantly distributed in stem cells. Cell communication analysis identified two receptors that interact with LAMCI. q-PCR results confirmed the upregulation of Lamc1, Tln2, Hexb, and St3gal5 during osteogenic differentiation and their downregulation during adipogenic differentiation. Knockdown of Lamc1 inhibited adipogenic and osteogenic differentiation. In conclusion, this study identified four genes, Lamc1, Tln2, Hexb, and St3gal5, that may play important roles in the late-stage differentiation of BMSCs. It elucidated their interactions and the pathways they influence, providing a foundation for further research on BMSC differentiation. [ABSTRACT FROM AUTHOR]

Developing efficient artificial proteases still remains a great challenge due to the high stability of peptide bonds. Nanozymes have attracted great attention for their high stability, low cost and inherent physicochemical properties, providing new opportunities to break through natural enzyme inherent limitations, but the intrinsic mimic proteases properties of nanomaterials were seldom explored. Herein, we describe for the first time that SBA-3 supported Cu2O (Cu2O/SBA-3) exhibited excellent protease-like activity to hydrolysis of bovine serum albumin (BSA) and casein under neutral conditions, which is even superior to natural proteases (trypsin) and most of the other protease mimics under identical conditions. It exhibited surprisingly high catalytic activity and possessed good stability. As the first example of protease mimics consist of metallic compounds and mesoporous materials, Cu2O/SBA-3 has many advantages, such as easy preparation and separation, high activity and stability, mild reaction conditions, which makes this catalytic system have multiple of potential applications in biological systems. [ABSTRACT FROM AUTHOR]

Compressed leachate is a contaminated liquid containing various organic and inorganic pollutants produced in municipal refuse transfer stations, which pollute soil and groundwater, posing serious risks to the environment and human health. The Environmental Technology Co., Ltd. (Shenzhen, Guangdong Province, South China) treated compressed leachate obtained from a refuse transfer station. The chemical oxygen demand (COD) (641.2 mg/L) of treated compressed leachate did not meet the wastewater quality standards in China for discharge into municipal sewers (COD ≤ 500 mg/L) and the company's design discharge requirements (COD ≤ 400 mg/L). Therefore, their further in-depth treatment is necessary. To this end, waste tobacco leaves were used as the biotemplate herein, and Fe/La-co-doped TiO2 (xFe,yLa)-TTiO2(g) was synthesized using a solvothermal-assisted biotemplating method. The photocatalytic depth treatment of compressed leachate was performed under simulated solar light using the prepared catalysts. After (3Fe,3La)-TTiO2(g) treatment, the COD of the leachate decreased from 641.2 to 280.1 mg/L, and the COD removal rate was 1.2, 1.1, and 1.6 times higher than that of pure Fe-doped, La-doped and non-biological template TiO2, respectively. Characterization confirmed that the biological template endowed the catalyst with a unique morphology and high specific surface area. Its rich activity sites are conducive to enhancing the adsorption capacity of pollutants and providing an ideal place for photocatalytic reactions. Co-doping with iron and lanthanum ions altered the band structure of TiO2 and promoted the interconversion of Fe3+/Fe2+ and La3+/La2+ during photocatalysis. First-principles density functional theory simulations demonstrated that co-doping Fe and La in TiO2 created impurity levels that facilitated the transfer of photogenerated electrons. This study provides a new purification pathway for the depth treatment of compressed leachate. [ABSTRACT FROM AUTHOR]

The elimination of antimony pollution has attracted increasing concerns because of its high toxicity to human health and the natural environment. In this work, biomimetic δ-MnO2 was synthesized by using waste tobacco stem-silks as biotemplate (Bio-δ-MnO2) and used in the capture of Sb(III)from aqueous solution. The tobacco stem-silks not only provided unique wrinkled morphologies but also contained carbon element self-doped into the resulting samples. The maximum Sb(III) adsorption capacity reached 763.4 mg∙g −1, which is 2.06 times higher than δ-MnO2 without template (370.0 mg∙g −1), 4.53 times than tobacco stem-silks carbon (168.5 mg∙g −1), and 10.39 times than commercial MnO2 (73.5 mg∙g −1), respectively. The isotherm and kinetic studies indicated that the adsorption behavior was consistent with the Langmuir isotherm model and the pseudo-second-order kinetic equation. As far as we are aware, the adsorption capacity of Bio-δ-MnO2 is much higher than that of most Sb(III) adsorbents. FT-IR, XPS, SEM, XRD, and Zeta potential analyses showed that the main mechanism for the adsorption of Sb(III) by Bio-δ-MnO2 includes electrostatic attraction, surface complexation, and redox. Overall, this study provides a new sustainable way to convert agricultural wastes to more valuable products such as biomimetic adsorbent for Sb(III) removal in addition to conventional activated carbon and biochar. [ABSTRACT FROM AUTHOR]

Hemerocallis citrina Borani is a commonly consumed food in Asia and possesses many biologically active ingredients. In this study, a protein named Hemerocallis citrina Borani protein (HcBP) was purified using ammonium sulfate fractionation and anion exchange chromatography. Protease assays revealed that HcBP has peroxidase activity. Meanwhile, the UV absorption spectrum showed that HcBP contains heme. Notably, HcBP showed significant inhibitory effects on human hepatoma cancer cell proliferation. Mechanism investigations indicated that HcBP treatment resulted in overproduction of reactive oxygen species (ROS) and induced mitochondria-dependent apoptosis in human hepatoma cancer cells. Furthermore, we found HcBP not only downregulated pyruvate kinase M2 (PKM2) activity but also decreased the expression and nuclear levels of PKM2. The inhibition of PKM2 led to the downregulation of GLUT1, LDHA and PDK, and thus caused the suppression of glycolysis. In summary, our results suggested that HcBP has potential anti-hepatocellular carcinoma activity. [ABSTRACT FROM AUTHOR]

Due to the low melt index of polylactic acid (PLA) polymer, it is difficult to melt-blown processing. Here, a new modified method to obtain a high melt index of PLA polymer and melt-blown nonwoven cloth was studied. PLA polymers are modified by the thermally degraded method of stannous octoate (Sn(Oct)2) and polyethylene glycol (PEG) to obtain a high melt index (1054 g/10 min) in comparison with a low melt index (23 g/10 min) of original unmodified PLA polymer. The fiber of modified PLA polymer melt-blown cloth is obviously thinner, having sub-micron fibers, the smallest fiber is about 200 nm. From our test, modified PLA polymer melt-blown cloth has good oil absorption, oil–water separation, and potential air filtration property. In terms of degradation, the modified PLA polymer melt-blown cloth showed excellent degradation performance in basic aqueous solutions at 55 °C at pH 12, reaching a degradation rate of around 95% at 60 h. [ABSTRACT FROM AUTHOR]

Magnetic tunnel junctions (MTJs) with conventional bulk ferromagnets separated by a nonmagnetic insulating layer are key building blocks in spintronics for magnetic sensors and memory. A radically different approach of using atomically-thin van der Waals (vdW) materials in MTJs is expected to boost their figure of merit, the tunneling magnetoresistance (TMR), while relaxing the lattice-matching requirements from the epitaxial growth and supporting high-quality integration of dissimilar materials with atomically-sharp interfaces. We report TMR up to 192% at 10 K in all-vdW Fe3GeTe2/GaSe/Fe3GeTe2 MTJs. Remarkably, instead of the usual insulating spacer, this large TMR is realized with a vdW semiconductor GaSe. Integration of semiconductors into the MTJs offers energy-band-tunability, bias dependence, magnetic proximity effects, and spin-dependent optical-selection rules. We demonstrate that not only the magnitude of the TMR is tuned by the semiconductor thickness but also the TMR sign can be reversed by varying the bias voltages, enabling modulation of highly spin-polarized carriers in vdW semiconductors. Van der Waals materials are composed of layers held weakly by van der Waals forces. This feature allows different materials to be combined into heterostructures, with fewer restrictions on growth and lattice matching. Here, Zhu et al make use of this feature to create a van der Waals magnetic tunnel junction with a semiconducting spacer, allowing for improved tunability and reduced device thickness. [ABSTRACT FROM AUTHOR]

The excessive application of herbicides on farmlands can substantially reduce labor costs and increase crop yields, but can also have undesirable effects on terrestrial ecosystems. To evaluate the ecological toxicity of herbicides, metolachlor and fomesafen, two typical herbicides that are extensively used worldwide were chosen as target pollutants, and the endogeic earthworm Pheretima guillelmi, which is widely distributed in China, was selected as the test organism. A laboratory-scale microcosmic experiment was set, and energy resources, enzymes, and the composition and connections of intestinal microorganisms in earthworms were determined. Both herbicides depleted the energy resources of the earthworms, especially glycogen contents; increased the levels of antioxidant enzymes; and inhibited acetylcholinesterase. Moreover, the richness and diversity of the intestinal bacterial community of the earthworms were suppressed. Additionally, the bacterial composition at the genus level changed greatly and the connections between dominant bacteria increased dramatically. Most interactions among the bacterial genera belonging to the same and different phyla showed mutualism and competition, respectively. Importantly, metolachlor with higher toxicity had a transitory effect on these indicators in earthworms, whereas fomesafen, with lower toxicity but stronger bioaccumulation potential, exerted a sustaining impact on earthworms. Collectively, these results indicate that the toxic effects of herbicides on terrestrial organisms should be comprehensively considered in combination with biological toxicity, persistence, bioaccumulation potential, and other factors. [ABSTRACT FROM AUTHOR]

Cucurbitaceous fruits and vegetables are important crops. Viral and bacterial diseases cause substantial economic losses to cucurbit crops globally. For rapid detection of these pathogens and improved disease control, a one-step multiplex reverse-transcription polymerase chain reaction (mRT-PCR) system was created. This method allowed for the concurrent detection of Tobacco mosaic virus (TMV), Zucchini yellow mosaic virus (ZYMV), Watermelon mosaic virus (WMV), Cucumber green mottle mosaic virus (CGMMV), Cucumber mosaic virus (CMV), and Acidovorax citrulli. Five pairs of specific primers were created according to the conserved regions around the coat protein (CP) genes of each virus, and one pair was based on the A. citrulli internal transcribed spacer (ITS). To limit false negatives, one pair of primers, created based on the Transcriptional elongation factor 1-α (EF1-α) from the major cucurbitaceous crop species, was put into the mRT-PCR reaction system. Primer concentrations, annealing temperature, extension time, and amplification cycles were optimized. Anticipated fragments of 152 bp (TMV), 205 bp (ZYMV), 318 bp (WMV), 419 bp (CGMMV), 529 bp (CMV), 662 bp (A. citrulli), and 821 bp (EF1-α) were amplified by the multiplex RT-PCR system, and their origin was established via DNA sequencing. This method was successfully used to examine field-collected seed samples of cucurbitaceous crops from China. The results demonstrated that the one-step mRT-PCR technique is a quick, efficient, and sensitive assay for the concurrent detection of six pathogens of cucurbits. It provides a method for monitoring and preventing these diseases. [ABSTRACT FROM AUTHOR]

This article, published in Digestive Diseases & Sciences, describes a case study of a 60-year-old woman who presented with upper abdominal distention caused by a large cystic mass near the pancreatic tail. The patient refused surgery, so natural orifice transluminal endoscopic surgery (NOTES) was performed instead. The cystic lesion was dissected and drained, and the mass was completely removed. The patient recovered well, and the histological report confirmed that the cyst lining was consistent with an epithelial cyst. The authors of the article provided the manuscript, pictures, and video, while one author performed the procedure and provided technical support. The study was funded by the Zhongyuan talent program and the key R&D program of Henan Province. The authors declared no conflict of interest, and informed consent was obtained from the patient for the publication of their information and imaging. [Extracted from the article]

Interest Flooding Attack (IFA) is one of the main security threats for the Named Data Networking (NDN). Most of its existing countermeasures enable intermediate routers near the attackers to independently detect the attack and consider the typical attack scenario in which attackers directly send malicious Interests at a constant and relatively high rate after the attack starts. Moreover, they may also throttle legitimate Interests when enforcing the existing defense measures at intermediate routers as it is still difficult for them to distinguish the Interests issued by attackers from those issued by legitimate consumers. Instead, this work aims at a more sophisticated attack scenario in which attackers start the attack at a relatively lower rate but gradually speed up to keep the Pending Interest Tables (PITs) of the victims increasing to finally deplete the PIT resources for legitimate consumers. It is relatively difficult for intermediate routers to independently and timely detect such a sophisticated IFA. To solve this problem, we propose a mechanism to detect and mitigate the sophisticated IFA from the network-wide view, dubbed as DMNWV. In DMNWV, a central controller monitors the network and makes a comprehensive and prompt decision on whether there is an ongoing IFA based on the overall state of the whole network collected from the abnormity information reports sent by the first-hop routers of attackers. Attack sources can be directly located after an IFA is determined, and then the routers directly connected to attackers (i.e., access routers) can take targeted measures based on the located attackers to prevent malicious Interest from entering the network without throttling legitimate Interests. We conduct an experimental study to evaluate the performance of DMNWV, explore the parameter settings of the attack detection algorithm at access routers, and measure the communication overhead of the central controller. The experimental results validate that DMNWV can timely detect and mitigate the sophisticated IFA without throttling requests from legitimate consumers with significantly low communication overhead of the central controller, which will not bring about too much burden to the network. [ABSTRACT FROM AUTHOR]

Background and Aim: Esophageal stricture is a major complication of large areas endoscopic submucosal dissection (ESD). Until now, the critical mechanism of esophageal stricture remains unclear. We examined the role of mucosal loss versus submucosal damage in esophageal stricture formation after mucosal resection using a porcine model.Materials and Methods: Twelve swine were randomly divided into two groups, each of 6. In each group, two 5-cm-long submucosal tunnels were made to involve 1/3rd of the widths of the anterior and posterior esophageal circumference. The entire mucosal roofs of both tunnels were resected in group A. In group B, the tunnel roof mucosa was incised longitudinally along the length of the tunnel, but without excision of any mucosa. Stricture formation was evaluated by endoscopy after 1, 2, and 4 weeks, respectively. Anatomical and histological examinations were performed after euthanasia.Results: Healing observed on endoscopy in both groups after 1 week. Group A (mucosa resected) developed mild-to-severe esophageal stricture, dysphagia, and weight loss. In contrast, no esophageal stricture was evident in group B (mucosa incisions without resection) after 2 and 4 weeks, respectively. Macroscopic examination showed severe esophageal stricture and shortening of esophagus in only group A. Inflammation and fibrous hyperplasia of the submucosal layer was observed on histological examination in both groups.Conclusion: The extent of loss of esophageal mucosa appears to be a critical factor for esophageal stricture. Inflammation followed by fibrosis may contribute to alteration in compliance of the esophagus but is not the main mechanism of postresection stricture. [ABSTRACT FROM AUTHOR]

The anaerobic oxidation of ammonium (anammox) process plays a critical role in the loss of nitrogen (N) in paddy soils, yet the response of anammox to different fertilization is not well documented. In this study, three different fertilized (control, CK; soil treated with inorganic fertilizers, NPK; soil treated with inorganic fertilizer and involving the incorporation of straw, NPKS) paddy soils were selected to investigate the activity, functional gene abundance, diversity, and composition of anammox bacterial community using isotope-tracing technique, quantitative PCR assays, and Illumina sequencing. The anammox rate in the NPKS treatment was 2.4 nmol N g−1 soil h−1, significantly higher than that in CK and NPK treatments (1.7 and 1.8 nmol N g−1 soil h−1, respectively). Potential anammox contributed 6.2-7.8% to total N loss with the remainder being due to denitrification. Significant differences in the number of hydrazine synthase β-subunit (hzsB) gene were observed in three treatments with the highest value being observed in the NPK treatment. The anammox rate of per functional gene in the NPKS treatment (11.4 fmol day−1) was higher than that in CK and NPK treatments (8.3 and 7.0 fmol day−1, respectively). Three genera of anammox bacteria were identified: Candidatus Brocadia, Candidatus Anammoxoglobus, and Candidatus Scalindua, with Candidatus Brocadia being the dominant. Anammox bacteria diversity was significantly lower in the NPK than in CK and NPKS treatments as shown by Shannon, Simpson, Chao 1, and ACE indices (p < 0.05). The results showed that activity, abundance, and composition of anammox bacterial community depended on the type of fertilization. [ABSTRACT FROM AUTHOR]

The lowest-energy structures and low-lying isomers of double impurity atoms, Ga and Mn, doped Li ( n = 1-12) clusters have been systematically investigated using density functional theory. The trimetallic clusters show larger relative binding energies compared with the bare Li partners, indicating doping with Ga and Mn atoms could enhance the stabilities of Li clusters. The HOMO-LUMO gaps, the vertical ionization potentials and the vertical electron affinities have also been analyzed and compared with the pure lithium clusters. The magnetism calculations demonstrate that the magnetic moments of GaMnLi clusters show a tunable magnetic properties with the increasing number of Li atoms. [ABSTRACT FROM AUTHOR]

Bisphenol A (BPA) is widely used in consumer products such as plastic bottles and food containers. It has become a ubiquitous environmental contaminant and poses a serious risk to human health. A rapid, sensitive, and high-throughput method for detecting BPA is therefore desirable. Herein, a donor/acceptor nanoparticle pair-based singlet oxygen channeling chemiluminescence homogenous immunoassay is developed for the determination of BPA. The donor nanoparticles were modified with phthalocyanine as a photosensitizer and were then coated with streptavidin. The acceptor nanoparticles were doped with thioxene derivatives and Eu(III) as a chemiluminescence emitter and then coated with anti-BPA antibody. Under light irradiation, oxygen near the donor surface transforms to singlet oxygen (O), which migrates to the acceptor and reacts with it, generating luminescence. Because O has a very short lifetime, luminescence is generated only when the donor and acceptor are in close proximity. This occurs when they are brought together by the antigen/antibody and streptavidin/biotin reaction. Based on this singlet oxygen channeling mechanism, a competitive homogenous chemiluminescence immunoassay for BPA was developed on 384 microplates. The assay exhibited linear detection over the range 10-1000 ng/mL and a limit of detection of 2.9 ng/mL. The intra- and inter-assay precisions were both below 5.1 %. The average recoveries of three spiked samples in tap and river water samples were in the range 95.5-121.0 %, in agreement with values obtained using high-performance liquid chromatography. The homogeneous assay is rapid, low cost, sensitive, and allows high-throughput, so is well suited for screening large numbers of environmental samples. [ABSTRACT FROM AUTHOR]

Reaumuria trigyna is a highly xeric small shrub and is a rare wild plant in Mediterranean areas. The flavonoid biosynthesis pathway in R. trigyna is strongly activated under salt stress, and many genes related to this pathway showed significant differences in transcript abundance under salt stress in a previous transcriptomic profiling analysis. The F3H gene, which encodes flavanone-3-hydroxylase, is an essential gene in the flavonoid biosynthetic pathway. The transcript levels of two F3H genes, RtF3H1 and RtF3H2, were increased in R. trigyna not only under salt stress but also under drought and cold stresses, and by abscisic acid. We measured the transcript levels of the two genes in different organs. There were high transcript levels of RtF3H1 in stems, and high transcript levels of RtF3H2 in roots and stems. The full-length cDNAs for RtF3H1 (Accession No. AB850638) and RtF3H2 (Accession No. AB850639) were cloned and were found to encode 353- and 358-amino-acid proteins, respectively. Escherichia coli overexpressing RtF3H1 or RtF3H2 showed better growth than that of a control E. coli line under various stress treatments. The survival rate of the recombinant E. coli strain expressing RtF3H2 was higher than that of the strain expressing RtF3H1 under salt and drought stresses. [ABSTRACT FROM AUTHOR]

Asparaginyl endopeptidase (AEP) is an endo/lysosomal cysteine endopeptidase with a preference for an asparagine residue at the P1 site and plays an important role in the maturation of toll-like receptors 3/7/9. AEP is known to undergo autoproteolytic maturation at acidic pH for catalytic activation. Here, we describe crystal structures of the AEP proenzyme and the mature forms of AEP. Structural comparisons between AEP and caspases revealed similarities in the composition of key residues and in the catalytic mechanism. Mutagenesis studies identified N44, R46, H150, E189, C191, S217/S218 and D233 as residues that are essential for the cleavage of the peptide substrate. During maturation, autoproteolytic cleavage of AEP's cap domain opens up access to the active site on the core domain. Unexpectedly, an intermediate autoproteolytic maturation stage was discovered at approximately pH 4.5 in which the partially activated AEP could be reversed back to its proenzyme form. This unique feature was confirmed by the crystal structure of AEPpH4.5 (AEP was matured at pH 4.5 and crystallized at pH 8.5), in which the broken peptide bonds were religated and the structure was transformed back to its proenzyme form. Additionally, the AEP inhibitor cystatin C could be digested by the fully activated AEP, but could not be digested by activated cathepsins. Thus, we demonstrate for the first time that cystatins may regulate the activity of AEP through substrate competition for the active site. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to the article "Structural basis for termination of AIM2-mediated signaling by p202" by Heng Ru and colleagues in a 2013 issue of the periodical, which discusses the role of absent in melanoma 2 (AIM2) as a sensor in the innate immune system.

A new oral delivery system, polybutylcyanoacrylate nanoparticles (PBCNs), was introduced to improve the oral bioavailability of curcumin (CUR), a poorly soluble drug. The formulation was optimized by orthogonal design and the optimal PBCNs loading CUR exhibited a spherical shape under transmission electron microscopy with a range of 40-400 nm. Physicochemical state of CUR in PBCN was investigated by X-ray diffraction and the possible structure changes occurring in CUR after conjugating with polybutylcyanoacrylate were studied with FTIR. The results indicated that CUR in PBCN was in a non-crystalline state and CUR was encapsulated in PBCN without chemical reaction. The oral pharmacokinetic study was conducted in rats and the relative bioavailability of CUR encapsulated PBCNs to the crude CUR was more than 800%. The in situ absorption experiment in rat intestine indicated the absorption was first order with passive diffusion mechanism. The absorption results in various segments of intestine showed that the main absorption sites were ileum and colon. It can be concluded that PBCNs as an oral carrier can significantly improve the oral absorption of a poorly soluble drug. [ABSTRACT FROM AUTHOR]

A micro-plate magnetic chemiluminescence immunoassay was developed for rapid and high throughput detection of carcinoembryonic antigens (CEA) in human sera. This method was based on a sandwich immunoreaction of fluorescein isothiocyanate (FITC)-labeled anti-CEA antibodies, CEA antigens, and horseradish peroxidase (HRP)-conjugated anti-CEA antibodies in micro-plate. The immunomagnetic particles coated with anti-FITC antibodies were used as the solid phase for the immunoassay. The separation procedure was carried out by a magnetic plate adaptor and the luminol-hydrogen peroxide (H2O2)-HRP system was employed for the chemiluminescence detection. The proposed method combined the advantages of the micro-plate reactor and magnetic particle separation technology with the linear range of 5–250 ng·mL−1. The detection limit of CEA was 0.61 ng·mL−1. The coefficient of the variation was less than 7% and 13% for intra-assay and inter-assay precision, respectively. Compared with the commercial micro-plate chemiluminescent kit, the proposed method showed a good correlation. [ABSTRACT FROM AUTHOR]

Ten highly potent estrogens including estrone (E1), 17β-estradiol (E2), estriol (E3), 4-hydroxyestrone (4-OHE1), 2-hydroxyestradiol (2-OHE2), 16α-hydroxyestrone (16α-OHE1), 2-methoxyestrone (2-MeO-E1), 2-methoxyestradiol (2-MeO-E2), diethylstilbestrol (DES), 17α-ethynylestradiol (EE2) were identified and quantified by solid-phase extraction followed by liquid chromatography–mass spectrometry. An improved two-step SPE process was employed in this work. C18 cartridge was used for both enrichment of all target estrogens and retention of some nonpolar impurities, and then a polar florisil cartridge was subsequently used to separate the interested estrogens from the polar impurities. After this pretreatment for water samples, the results showed clean chromatograms without interference from matrix effects. Besides, this method was accurate (recovery percentages between 70.4 and 106.8% for river water and 73.4 and 101.3% for raw sewage, except 4-OHE1 and 2-OHE2), and precise (RSD varying between 1.3 and 17.8% for river water and 3.4 and 16.7% for raw sewage). In the optimized condition, this method was used to verify the presence of the target analytes in the Qinghe River and influent of sewage treatment plant in the northwest of Beijing, China. Some estrogens were detected in the river water and sewage water samples at a relatively high concentration. The developed method proved to be effective for analyzing estrogen compounds in complex matrices. Moreover, the achieved results demonstrated that a great concern should be addressed to the potential risk of the presence of estrogens in the aquatic environment. [ABSTRACT FROM AUTHOR]

A nonaqueous capillary electrophoresis (NACE) method, 30 mM ammonium acetate in methanol as background electrolyte (BGE), was developed for separation of the organomercury species without complexing reagents. The effects of different solutes and solvents in BGE were studied. Three species of organomercury, methylmercury, ethylmercury and phenylmercury, were separated well and all the number of theoretical plates were over 106. The present NACE method was also coupled with sample stacking and electrokinetic injection techniques to enhance the detection sensitivity. Under the optimum conditions, the limit of detection ( S/ N = 3) is 18 ng mL−1 and the linear relation range from 40 to 750 ng mL−1 were obtained for methylmercury. [ABSTRACT FROM AUTHOR]

A critical challenge for the integration of optoelectronics is that photodetectors have relatively poor sensitivities at the nanometer scale. Generally, a large electrodes spacing in photodetectors is required to absorb sufficient light to maintain high photoresponsivity and reduce the dark current. However, this will limit the optoelectronic integration density. Through spatially resolved photocurrent investigation, we find that the photocurrent in metal-semiconductor-metal (MSM) photodetectors based on layered GaSe is mainly generated from the region close to the metal-GaSe interface with higher electrical potential. The photoresponsivity monotonically increases with shrinking the spacing distance before the direct tunneling happens, which was significantly enhanced up to 5,000 AW−1 for the bottom Ti/Au contacted device. It is more than 1,700-fold improvement over the previously reported results. The response time of the Ti/Au contacted devices is about 10-20 ms and reduced down to 270 μs for the devices with single layer graphene as metallic electrodes. A theoretical model has been developed to well explain the photoresponsivity for these two types of device configurations. Our findings realize reducing the size and improving the performance of 2D semiconductor based MSM photodetectors simultaneously, which could pave the way for future high density integration of optoelectronics with high performances. [ABSTRACT FROM AUTHOR]

When compared with Si-based devices, Gallium Nitride High Electron Mobility Transistors (GaN HEMTs) possess the advantages of lower junction-to-case thermal resistance, smaller on-state resistance, faster switching velocity, and higher switching frequency. These advantages make them a promising power semiconductor device. However, with the enhancement of switching frequencies, the influence of parasitic parameters on switching ringing and the losses of GaN HEMTs are increasingly severe. Thus, it is necessary to predict the loss distribution by establishing an accurate loss model of the switching process. On the premise of considering parasitic inductance, nonlinear junction capacitance, and reverse transfer characteristics, this article proposes a precise switching loss model of GaN HEMTs to predict the loss distribution in the switching process. In addition, it verifies results based on the double pulse test (DPT) circuit, which validates the accuracy of the proposed model. Ultimately, based on the above-mentioned loss model, this article discussed the influence of parasitic capacitance and inductance on the output capacitance loss (Eqoss), the reverse conduction loss (ESD), the opening V–I overlap loss (Eopen), the closing V–I overlap loss (Eclose), and the total loss (Etotal). Then, this article produces an optimizing method to enhance the conversion efficiency of GaN HEMTs in accordance with laboratory findings. [ABSTRACT FROM AUTHOR]