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1.
Sci Total Environ ; 708: 135227, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-31812419

RESUMO

To better understand the risk assessment of Lead (Pb) in contaminated soils, 78 soil samples were collected from different locations in China and Pb bioaccessibility was assessed using the PBET (The Physiologically Based Extraction Test) method combined with SHIME (The Simulator of the Human Intestinal Microbial Ecosystem), and Pb bioaccessibility data from the PBET method on 88 soil samples that found in the literature were also used for the assessment. For all the soils, the mean Pb bioaccessibility was as follows: the gastric phase (31.25%) > colon phase (17.78%) > small intestinal phase (10.13%). The values of Pb bioaccessibility in most soils were lower than 60%, which is the typical default assumption for Pb (RBA, relatively bioavailability) by the US EPA. Mean Pb bioaccessibility (41.10% and 14.00% for gastric and small intestinal phases, respectively) in the present study was slightly higher than the values from the literature (24.80% and 8.68% for gastric and small intestinal phases, respectively) in the gastrointestinal tract. Mean Pb bioaccessibility was lower in acidic soil during the small intestinal phase, while the values for the alkaline soil were higher in the small intestinal and colon phases. In the gastric and small intestinal phases, mean Pb bioaccessibility in farming soils was slightly lower than it was in mining soils. However, the mean Pb bioaccessibility from farming soils was increased compared with mining soils in the colon phase given the action of human gut microbiota. Soil pH and type are important factors for predicting soil Pb bioaccessibility and health risk.

2.
J Dairy Sci ; 103(1): 220-227, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31704015

RESUMO

This study was conducted to analyze the effect of milk types on the attributes of the glutinous rice wine-fermented yogurt-like product named Kouwan Lao (KWL). Four types of raw milks were used in this study, including high temperature, long time (HTLT: H milk), HTLT milk supplemented with 3% skim milk powder (S milk), pasteurized milk (P milk), and ultra-high temperature milk (U milk). Microbiological compositions of the fermented glutinous rice and KWL at different stages were analyzed using PCR-denaturing gradient gel electrophoresis and gene sequencing based on 16S rRNA and 26S rRNA. The physicochemical properties of KWL samples were determined, and textural properties of those were analyzed using a texture analyzer (Jiawei Innovation and Technology Co. Ltd., Zhejiang Province, China). The microstructure of KWL samples was observed using scanning electron microscopy. The results showed that the milk types had significant influences on the bacterial composition of KWL. In the curdling process, the predominant bacteria of H, S, P, and U KWL samples were Lactobacillus brevis, Janthinobacterium sp., Lactobacillus casei, and Streptococcus agalactiae, respectively. In the ripening process, the main strains in H KWL were Enterococcus faecium and Pediococcus pentosaceus. Lactobacillus casei and Lactobacillus paracasei were the dominant bacteria of U KWL. Lactobacillus casei was the main strain of P KWL, and no bacteria were detected in S KWL. Saccharomyces cerevisiae was the dominant fungus of KWL, and no significant effect of milk types on fungal composition of KWL was found. The results of physicochemical properties showed that significant differences in protein contents were found in the KWL samples, and P KWL had the highest protein content. The fat content of U KWL was significantly higher than that of samples from the other 3 groups. The U KWL and P KWL showed lower moisture than that of the other 2 KWL samples. In addition, no significant difference in pH value was found in all samples. The results of texture analysis and microstructure showed that compared with other 3 types of KWL samples, the related mass parameters of U KWL were more advantageous and improved significantly with the increase of the heat treatment temperature of raw milk and the addition of skim milk powder. Our findings revealed the effects of milk types on microbial composition, physicochemical properties, textural properties, and microstructure of KWL, and provided a basic theory for the optimization and industrial production of KWL.

3.
J Hazard Mater ; 381: 120975, 2020 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-31445471

RESUMO

Organic matter (OM) was proved to have a high affinity for arsenic (As) in the presence of ferric iron (Fe(III)), the formed ternary complex OM-Fe(III)-As(V) were frequently studied before; however, the mobilization and transformation of As from OM-Fe(III)-As(V) in the presence of As(V)-reducing bacteria remains unclear. Two different strains (Desulfitobacterium sp. DJ-3, Exiguobacterium sp. DJ-4) were incubated with OM-Fe(III)-As(V) to assess the biotransformation of As and Fe. Results showed that Desulfitobacterium sp. DJ-3 could substantially stimulate the reduction and release of OM-Fe complexed As(V) and resulted in notable As(III) release (30 mg/L). The linear combination fitting result of k3-weighted As K-edge EXAFS spectra showed that 56% of OM-Fe-As(V) was transformed to OM-Fe-As(III) after 144 h. Besides, strain DJ-3 could also reduce OM complexed Fe(III), which lead to the decomposition of ternary complex and the release of 11.8 mg/g Fe(II), this microbial Fe(III) reduction process has resulted in 11% more As liberation from OM-Fe(III)-As(V) than without bacteria. In contrast, Exiguobacterium sp. DJ-4 could only reduce free As(V) but cannot stimulate As release from the complex. Our study provides the first evidence for microbial As reduction and release from ternary complex OM-Fe(III)-As(V), which could be of great importance in As geochemical circulation.

4.
Appl Opt ; 58(1): 94-101, 2019 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-30645517

RESUMO

The transmission properties of one-dimensional photonic crystals (PCs) containing a metamaterial (MM) defect layer are investigated using the transfer matrix method. The MM is composed of alternating layers of a dielectric material and a Dirac semimetal (DS) material. Numerical results show that the defective PCs possess a tunable defect mode, which is significantly dependent on the Fermi level of the DS as well as the structural parameters of the MM defect layer. The defect mode properties under different incident angles for TE and TM polarizations are also studied. Such defective structures have potential applications in tunable filters and sensors in terahertz regions.

5.
Food Chem ; 277: 347-352, 2019 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-30502156

RESUMO

There is limited research concentrating on the effects of gut microbiota on the bioaccessibility and speciation of chromium (Cr) in vegetables. In this study, the physiologically based extraction test (PBET) and the unified BARGE method (UBM), were combined with the simulator of human intestinal microbial ecosystems (SHIME) to determine the bioaccessibility and speciation of Cr from vegetables. The results showed that the Cr bioaccessibility was the highest in the gastric phase. The Cr bioaccessibility from the water spinach was the highest, and was 1.6-3.4 and 1.1-1.8 times that of leaf lettuce and celery, respectively. The Cr bioaccessibilities of the UBM method were slightly greater than those of the PBET method. Additionally, the gut microbiota increased the Cr bioaccessibility and reduced more toxic Cr(VI) to less toxic Cr(III) from vegetables. Therefore, our study reveals the possible health risks of consuming Cr-contaminated vegetables based on the bioaccessibility and speciation of Cr.


Assuntos
Cromo/farmacocinética , Microbioma Gastrointestinal , Verduras/química , Adulto , Apium/química , Fezes/microbiologia , Contaminação de Alimentos/análise , Humanos , Intestinos/efeitos dos fármacos , Intestinos/microbiologia , Alface/química , Masculino , Modelos Teóricos , Spinacia oleracea/química , Verduras/classificação
6.
Nanoscale Res Lett ; 13(1): 404, 2018 Dec 12.
Artigo em Inglês | MEDLINE | ID: mdl-30542773

RESUMO

Searching for new stable free-standing atomically thin two-dimensional (2D) materials is of great interest in the fundamental and practical aspects of contemporary material sciences. Recently, the synthesis of layered SiAs single crystals has been realized, which indicates that their few layer structure can be mechanically exfoliated. Performing a first-principles density functional theory calculations, we proposed two dynamically and thermodynamically stable semiconducting SiAs and SiAs2 monolayers. Band structure calculation reveals that both of them exhibit indirect band gaps and an indirect to direct band even to metal transition are found by application of strain. Moreover, we find that SiAs and SiAs2 monolayers possess much higher carrier mobility than MoS2 and display anisotropic transportation like the black phosphorene, rendering them potential application in optoelectronics. Our works pave a new route at nanoscale for novel functionalities of optical devices.

7.
Materials (Basel) ; 11(10)2018 Oct 11.
Artigo em Inglês | MEDLINE | ID: mdl-30314320

RESUMO

On the basis of density functional theory (DFT) calculations, we propose a stable two-dimensional (2D) monolayer phosphorus carbide (PC) with a GaSe-like structure, which has intriguing electronic and optical properties. Our calculated results show that this 2D monolayer structure is more stable than the other allotropes predicted by Tománek et al. [Nano Lett., 2016, 16, 3247⁻3252]. More importantly, this structure exhibits superb optical absorption, which can be mainly attributed to its direct band gap of 2.65 eV. The band edge alignments indicate that the 2D PC monolayer structure can be a promising candidate for photocatalytic water splitting. Furthermore, we found that strain is an effective method used to tune the electronic structures varying from direct to indirect band-gap semiconductor or even to metal. In addition, the introduction of one carbon vacancy in such a 2D PC structure can induce a magnetic moment of 1.22 µB. Our findings add a new member to the 2D material family and provide a promising candidate for optoelectronic devices in the future.

8.
Nanoscale Res Lett ; 13(1): 300, 2018 Sep 26.
Artigo em Inglês | MEDLINE | ID: mdl-30259233

RESUMO

Recently, GaTe and C2N monolayers have been successfully synthesized and show fascinating electronic and optical properties. Such hybrid of GaTe with C2N may induce new novel physical properties. In this work, we perform ab initio simulations on the structural, electronic, and optical properties of the GaTe/C2N van der Waals (vdW) heterostructure. Our calculations show that the GaTe/C2N vdW heterostructure is an indirect-gap semiconductor with type-II band alignment, facilitating an effective separation of photogenerated carriers. Intriguingly, it also presents enhanced visible-UV light absorption compared to its components and can be tailored to be a good photocatalyst for water splitting at certain pH by applying vertical strains. Further, we explore specifically the adsorption and decomposition of water molecules on the surface of C2N layer in the heterostructure and the subsequent formation of hydrogen, which reveals the mechanism of photocatalytic hydrogen production on the 2D GaTe/C2N heterostructure. Moreover, it is found that in-plane biaxial strains can induce indirect-direct-indirect, semiconductor-metal, and type II to type I or type III transitions. These interesting results make the GaTe/C2N vdW heterostructure a promising candidate for applications in next generation of multifunctional optoelectronic devices.

9.
Huan Jing Ke Xue ; 39(10): 4778-4782, 2018 Oct 08.
Artigo em Chinês | MEDLINE | ID: mdl-30229627

RESUMO

The interaction between soil arsenic and soil microorganisms has been identified as one of the important parts of the morphological transformation of soil arsenic. In order to investigate the interaction between Humic Acid complexing As(Ⅲ)[HA-As(Ⅲ)] and As(Ⅲ)-oxidizing bacteria (HN-2), the changes in arsenic speciation in the liquid phase and the solid phase, with different pH, were studied. The results indicated there was better As(Ⅲ) oxidation efficiency in the pH 7 reaction system. A part of As(Ⅲ) would be discharged from the HA-As(Ⅲ) solid phase during hours 0-10 in the reaction system, with or without HN-2, and meanwhile it was found that HN-2 oxidized As(Ⅲ) to As(Ⅴ) rapidly, while As(Ⅲ) was oxidized into As(Ⅴ) by HA gradually. As(Ⅲ) complexing HA can be transformed into free-As(Ⅲ), and then oxidized into free-As(Ⅴ) by HN-2 over hours 10-24 of the reaction. The system achieved the equilibrium state after 48 h. The results of the X-ray absorption near edge structure (XANES) further confirmed the conclusions above.


Assuntos
Arsênico/análise , Bactérias/metabolismo , Substâncias Húmicas/análise , Oxirredução , Espectroscopia por Absorção de Raios X
10.
Exp Dermatol ; 27(11): 1254-1260, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-30144329

RESUMO

Forkhead box-O1 (FoxO1) is a key nutrient- and growth factor-dependent regulator of metabolism, but its functional role in human primary keratinocytes (HPKs) is less known. To investigate the role of FoxO1 in HPKs and effect of insulin-like growth factor 1 (IGF-1) and isotretinoin on FoxO1 expression, HPKs were treated with 1.2 mmol/L calcium chloride, 1-20 ng/mL IGF-1 and 0.1-10 µmol/L isotretinoin. Recombinant adenovirus expressing FoxO1 or FKHR shRNA lentivirus transfection was introduced to upregulate or silence FoxO1 expression. Epidermal FoxO1 immunostaining was lower in acne lesion than in normal skin. FoxO1 overexpression induced involucrin expression, G2/M arrest and apoptosis but suppressed proliferation, while FoxO1 silencing decreased involucrin expression but increased proliferation, S phase and viable cells in HPKs. IGF-1 downregulated FoxO1 and involucrin but upregulated p-Akt expression in HPKs, which was blocked by pretreatment with LY294002. Isotretinoin enhanced FoxO1, p53 and p21 but inhibited p-FoxO1 and involucrin expression in HPKs. These results demonstrate that FoxO1 promotes differentiation and apoptosis in HPKs. IGF-1 may reduce keratinocyte differentiation through PI3K/Akt/FoxO1 pathway, while isotretinoin can reinforce FoxO1 expression. FoxO1 may be involved in acne pathogenesis and could serve as a potential therapeutic target.


Assuntos
Apoptose/genética , Pontos de Checagem do Ciclo Celular/genética , Diferenciação Celular/genética , Proteína Forkhead Box O1/genética , Queratinócitos/fisiologia , Acne Vulgar/metabolismo , Diferenciação Celular/efeitos dos fármacos , Proliferação de Células/genética , Sobrevivência Celular/genética , Células Cultivadas , Cromonas/farmacologia , Fármacos Dermatológicos/farmacologia , Inibidores Enzimáticos/farmacologia , Proteína Forkhead Box O1/metabolismo , Expressão Gênica/efeitos dos fármacos , Inativação Gênica , Humanos , Fator de Crescimento Insulin-Like I/farmacologia , Isotretinoína/farmacologia , Morfolinas/farmacologia , Fosforilação , Cultura Primária de Células , Precursores de Proteínas/genética , Precursores de Proteínas/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , Transdução de Sinais/efeitos dos fármacos , Transfecção , Proteína Supressora de Tumor p53/metabolismo , Regulação para Cima
11.
Sci Total Environ ; 644: 815-821, 2018 Dec 10.
Artigo em Inglês | MEDLINE | ID: mdl-29990930

RESUMO

Arsenic (As) is a highly toxic contaminant in food and soil. In this study, we investigated the effects of four nutritional states (including a fed state with vitamin C, a fed state with protein powder, a fed state with glucose and a fasted state) on the variability of soil As bioaccessibility and biotransformation using the physiologically based extraction test (PBET) combined with a simulator of the human intestinal microbial ecosystem model (SHIME). The results indicated that the vitamin C and protein powder increased As bioaccessibility in gastric digests. In the colon phase, As bioaccessibility was observably enhanced by protein powder, and it varied under the vitamin C and glucose conditions. Additionally, the order of As methylation percentages in the four nutritional states was protein powder > vitamin C > fasted state > glucose (except S2); As bioaccessibility increased 1.3-13.7% and 15.8-35.4% in treatments of the vitamin C and protein powder, respectively. Meanwhile, large amounts of monomethylarsonic acid (MMAV) were observed in the colon digest in the protein powder condition. In contrast, As methylation was significantly decreased with the addition of glucose, with a decline of 25.9-45.5%. Additionally, glucose enhanced the reduction of As(V). Therefore, nutritional status is a crucial parameter for the prediction of bioaccessibility and speciation of As when assessing health risks from As following oral exposure.


Assuntos
Arsênico/análise , Ecossistema , Microbiota , Poluentes do Solo/análise , Exposição Ambiental/análise , Exposição Ambiental/estatística & dados numéricos , Humanos , Estado Nutricional , Solo/química
12.
Nanoscale ; 10(29): 13969-13975, 2018 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-30009303

RESUMO

First-principles calculations within density functional theory reveal the preferred structures of red phosphorus in the two-dimensional (2D) limit to be porous with intriguing structural, electronic, and chemical properties. These few-atomic-layer structures are stabilized as novel 2D clathrates with tunable pore sizes and varying semiconducting band gaps, labelled as V-Hex, P-Monoclinic, P-Hex, and V-Tetr in descending energetic stabilities. The cohesive energies of the 2D clathrates are all substantially higher than that of white phosphorus. More strikingly, the V-Hex structure is energetically as stable as black phosphorene, but possesses distinctly superior chemical stability when exposed to O2 due to the presence of a much higher activation barrier against chemisorption. We also exploit the salient properties of these 2D clathrates for their important application potentials, including serving as effective elemental photocatalysts for visible-light-driven water splitting, and as a new class of sieves for molecular separation and DNA sequencing.

13.
Biomed Res Int ; 2018: 7174561, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29850553

RESUMO

Sebocyte differentiation is a continuous process, but its potential molecular mechanism remains unclear. We aimed to establish a novel sebocyte differentiation model using human primary sebocytes and to identify the expression profiles of differentiation-associated proteins. Primary human sebocytes were cultured on Sebomed medium supplemented with 2% serum for 7 days. Flow cytometry showed that S phase cells were decreased time-dependently, while G1 and subG1 (apoptosis) phase cells increased under serum starvation. Transmission electron microscopy and Oil Red O staining revealed a gradual increase of intracellular lipid accumulation. Expression of proliferation marker was diminished, while expression of differentiation, apoptosis, and lipogenic markers elevated gradually during 7-day culture. iTRAQ analysis identified 3582 expressed proteins in this differentiation model. Compared with day 0, number of differentially expressed proteins was 132, 54, 321, and 96 at days 1, 3, 5, and 7, respectively. Two overexpressed proteins (S100 calcium binding protein P and ferredoxin reductase) and 2 downexpressed proteins (adenosine deaminase and keratin 10) were further confirmed by Western blot and immunohistochemistry.


Assuntos
Diferenciação Celular , Células Epiteliais/citologia , Modelos Biológicos , Proteoma/metabolismo , Proteômica/métodos , Sebo/citologia , Acne Vulgar/patologia , Apoptose , Biomarcadores/metabolismo , Proliferação de Células , Células Cultivadas , Humanos , Lipogênese , Reprodutibilidade dos Testes , Pele/patologia
14.
Inorg Chem ; 57(9): 5083-5088, 2018 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-29697976

RESUMO

Bulk tellurium (Te) is composed of one-dimensional (1D) helical chains which have been considered to be coupled by van der Waals (vdW) interactions. However, on the basis of first-principles density functional theory calculations, we here propose a different bonding nature between neighboring chains: i.e., helical chains made of normal covalent bonds are connected together by coordinate covalent bonds. It is revealed that the lone pairs of electrons of Te atoms participate in forming coordinate covalent bonds between neighboring chains, where each Te atom behaves as both an electron donor to neighboring chains and an electron acceptor from neighboring chains. This ligand-metal-like bonding nature in bulk Te results in the same order of bulk moduli along the directions parallel and perpendicular to the chains, contrasting with the large anisotropy of bulk moduli in vdW crystals. We further find that the electron effective masses parallel and perpendicular to the chains are almost the same as each other, consistent with the observed nearly isotropic electrical resistivity. It is thus demonstrated that the normal/coordinate covalent bonds parallel/perpendicular to the chains in bulk Te lead to a minor anisotropy in structural and transport properties.

15.
Food Funct ; 8(12): 4592-4600, 2017 Dec 13.
Artigo em Inglês | MEDLINE | ID: mdl-29236119

RESUMO

The influence of the human gut microbiota on the bioaccessibility and bioavailability of trace elements in vegetables has barely been studied. An in vitro digestion model combining the physiologically based extraction test (PBET) and the Simulator of Human Intestinal Microbial Ecosystem (SHIME) was applied. Results showed that the gut microbiota increased the bioaccessibility of iron (Fe) in ten test vegetables by 1.3-1.8 times, but reduced the bioaccessibility of manganese (Mn), copper (Cu), and zinc (Zn) in vegetables in the colon phase by 3.7% to 89.6%, 24.8% to 100.0%, and 59.9% to 100.0%, respectively. Using the Caco-2 cell model to simulate the human absorption process, the bioavailable contents and the bioavailability of the trace elements were further determined. Swamp cabbage was the best source of Fe and Cu; spinach and lettuce provided the highest amounts of bioavailable Mn and Zn, respectively. Referring to the daily reference intakes of trace elements, the obtained data provide a scientific basis for both reasonable ingestion of vegetables in diets and diversification of diets.


Assuntos
Cobre/metabolismo , Microbioma Gastrointestinal , Mucosa Intestinal/metabolismo , Intestinos/microbiologia , Ferro/metabolismo , Manganês/metabolismo , Verduras/metabolismo , Zinco/metabolismo , Disponibilidade Biológica , Células CACO-2 , China , Cobre/análise , Digestão , Humanos , Ferro/análise , Manganês/análise , Modelos Biológicos , Oligoelementos/análise , Oligoelementos/metabolismo , Verduras/química , Zinco/análise
16.
Sci Rep ; 7(1): 17578, 2017 12 14.
Artigo em Inglês | MEDLINE | ID: mdl-29242507

RESUMO

The in vitro bioaccessibility of trace metals associated with oral ingestion of market vegetables (lettuce, pak choi, cole, and leaf lettuce) of Beijing, China was studied. The physiologically based extraction test (PBET) combined with the Simulator of Human Intestinal Microbial Ecosystem (SHIME) was applied to simulate stomach, small intestine, and colon of human. In the gastro-intestinal phases, the bioaccessibility of Cu, Fe, Mn, and Zn varied within 5.7-75.5%, 17.3-50.4%, 13.3-49.1%, and 19.9-63.7%, respectively. There was no significant difference in the metal bioaccessibility between the gastric and small intestinal phases, except for higher Cu bioaccessibility in the small intestine. Besides, the bioaccessibility of the four trace metals in the colon phase was first ever reported. A significant decline in Cu bioaccessibility (1.8-63.7%) and slight increases in the bioaccessibility of Fe (16.7-56.4%), Mn (21.2-71.6%), and Zn (15.7-69.7%) were revealed, which could mainly be attributed to the effect of colon microbiota. In addition, the estimated daily intakes (EDIs) of Cu, Fe, Mn, and Zn were worked out to be 0.7, 8.8, 2.7, and 4.5 µg kg-1 body weight d-1, based on which the potential influences of these trace metals in vegetables on the health of the local consumers was demonstrated.


Assuntos
Colo/metabolismo , Microbioma Gastrointestinal , Poluentes do Solo/isolamento & purificação , Poluentes do Solo/metabolismo , Oligoelementos/isolamento & purificação , Oligoelementos/metabolismo , Verduras/metabolismo , Disponibilidade Biológica , Biomimética , Colo/microbiologia , Cobre/isolamento & purificação , Cobre/metabolismo , Humanos , Ferro/isolamento & purificação , Ferro/metabolismo , Manganês/isolamento & purificação , Manganês/metabolismo , Solo/química , Zinco/isolamento & purificação , Zinco/metabolismo
17.
Phys Chem Chem Phys ; 19(41): 28354-28359, 2017 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-29034945

RESUMO

Manipulating magnetism of low-dimensional materials is of great importance for their practical applications. Here, using first-principles calculations, we report a systematic investigation of the magnetic properties of C-doped H saturated zigzag phosphorene nanoribbons (H-ZPNRs), which are rather different from those of 2D periodic systems due to the quantum size effect. First of all, we observed a greatly enhanced magnetic moment locating mainly on the C atom and also slightly on its surrounding P atoms. Our results also indicated a strong dependence of the magnetic moment of the C atom on its location, which decays from the edge to the center site of the nanoribbons with an odd-even oscillating behavior originating from Friedel oscillation in low-dimensional materials. As for the C atom on a specific location, its magnetic moment decreases gradually with increasing width of H-ZPNRs, degenerating to the 2D case. What is more, we found that both the magnitude and the oscillating behavior of the magnetic moment on the C atom can be tuned by the edge saturation atoms. In addition, the case of two C atoms co-doping H-ZPNRs was also studied, showing non-magnetic (NM), ferromagnetic (FM) and antiferromagnetic (AFM) states depending on the locations of the two C atoms. Our findings suggest a plausible route for manipulating magnetism of the sp element doped H-ZPNRs, which are expected to have potential applications in spintronics.

18.
Phys Rev Lett ; 119(10): 106101, 2017 Sep 08.
Artigo em Inglês | MEDLINE | ID: mdl-28949181

RESUMO

Contemporary science is witnessing a rapid expansion of the two-dimensional (2D) materials family, each member possessing intriguing emergent properties of fundamental and practical importance. Using the particle-swarm optimization method in combination with first-principles density functional theory calculations, here we predict a new category of 2D monolayers named tellurene, composed of the metalloid element Te, with stable 1T-MoS_{2}-like (α-Te), and metastable tetragonal (ß-Te) and 2H-MoS_{2}-like (γ-Te) structures. The underlying formation mechanism is inherently rooted in the multivalent nature of Te, with the central-layer Te behaving more metal-like (e.g., Mo), and the two outer layers more semiconductorlike (e.g., S). We also show that the α-Te phase can be spontaneously obtained from the magic thicknesses divisible by three layers truncated along the [001] direction of the trigonal structure of bulk Te, and both the α- and ß-Te phases possess electron and hole mobilities much higher than MoS_{2}. Furthermore, we present preliminary but convincing experimental evidence for the layering behavior of Te on HOPG substrates, and predict the importance of multivalency in the layering behavior of Se. These findings effectively extend the realm of 2D materials to group-VI elements.

19.
Chemosphere ; 184: 460-466, 2017 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-28618278

RESUMO

Arsenic (As) metabolism by human gut microbiota has been evidenced with in vitro experiments from contaminated soils. In this study, the variability in the metabolic potency toward As-contaminated soils and gut microbial diversity were investigated between healthy individuals (Adult versus Child). Arsenic bioaccessibility in the colon phase increased by 1.4-6.8 and 1.2-8.7 folds for adult and child, respectively. We found a high degree of As methylation for the colon digests of the adult (mean 2 µg methylarsenicals/hr/g biomass), 3-folds higher than that of the child. Besides, arsenite [As(III)] concentration (1.5-391.3 µg/L) for the child was 2-18 times for the adult. 16S rRNA gene sequencing revealed that human gut microbiota from 20 various genera potentially had resistance genes to reduce and methylate As under conservative statistics. Our results indicated that As metabolism by gut microbiota from adult and child was significantly different. The adult gut microbiota had a great ability of As methylation; the child gut microbiota exhibited high As(III) level, which could encounter high health risk. The identity and activity of arsenic-metabolizing bacteria isolated from human gut and its homologous role in As metabolism need be further explored. This study provides a better understanding of health risk assessment to adults and children upon soil As exposures.


Assuntos
Arsênico/metabolismo , Microbioma Gastrointestinal , Poluentes do Solo/análise , Adulto , Fatores Etários , Arsênico/análise , Arsenitos , Bactérias/metabolismo , Criança , Colo/metabolismo , Colo/microbiologia , Humanos , Metilação , RNA Ribossômico 16S/genética , Poluentes do Solo/metabolismo
20.
Chemosphere ; 168: 358-364, 2017 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-27810535

RESUMO

Arsenic (As) speciation is essential in assessing health risks from As-contaminated soil. Release of soil-bound arsenic, As transformation by human gut microbiota, and the subsequent intestinal absorption of soil As metabolites were evaluated. A colon microbial community in a dynamic human gut model and the intestinal epithelial cell line Caco-2 were cultured. Arsenic speciation analysis and absorption of different As species were undertaken. In this study, soil As release (3.7-581.2 mg kg-1) was observed in the colon. Arsenic in the colon digests was transformed more quickly than that in the soil solid phase. X-ray absorption near-edge spectroscopy (XANES) analysis showed that 44.2-97.6% of arsenite [As(III)] generated due to arsenate [As(V)] reduction was in the soil solid phase after the colon phase. We observed a high degree of cellular absorption of soil As metabolites, exhibiting that the intestinal absorption of monomethylarsonic acid and As(III) (33.6% and 30.2% resp.) was slightly higher than that of dimethylarsinic acid and As(V) (25.1% and 21.7% resp.). Our findings demonstrate that human gut microbiota can directly release soil-bound arsenic, particularly As-bearing amorphous Fe/Al-oxides. Determining As transformation and intestinal absorption simultaneously will result in an accurate risk assessment of human health with soil As exposures.


Assuntos
Arsênico/análise , Microbioma Gastrointestinal/efeitos dos fármacos , Intestinos/efeitos dos fármacos , Poluentes do Solo/análise , Arseniatos/análise , Arsenicais/análise , Arsenitos/análise , Células CACO-2 , Ácido Cacodílico/análise , Colo/efeitos dos fármacos , Colo/metabolismo , Humanos , Absorção Intestinal , Mucosa Intestinal/metabolismo , Espectroscopia por Absorção de Raios X
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