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1.
Environ Sci Technol ; 58(19): 8182-8193, 2024 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-38691136

RESUMO

As an alternative plasticizer to conventional phthalates, di(2-ethylhexyl) terephthalate (DEHTP) has attracted considerable concerns, given its widespread detection in the environment and humans. However, the potential toxicity, especially liver toxicity, posed by DEHTP remains unclear. In this study, based on the 2017-2018 National Health and Nutrition Examination Survey, two metabolites of DEHTP, i.e., mono(2-ethyl-5-hydroxyhexyl) terephthalate (MEHHTP) and mono(2-ethyl-5-carboxypentyl) terephthalate (MECPTP), were found to be present in the urine samples of nearly all representative U.S. adults. Moreover, a positive linear correlation was observed between the concentrations of the two metabolites and the risk of nonalcoholic fatty liver disease (NAFLD) in the population. Results of weighted quantile sum and Bayesian kernel machine regression indicated that MEHHTP contributed a greater weight to the risk of NAFLD in comparison with 12 conventional phthalate metabolites. In vitro experiments with hepatocyte HepG2 revealed that MEHHTP exposure could increase lipogenic gene programs, thereby promoting a dose-dependent hepatic lipid accumulation. Activation of liver X receptor α may be an important regulator of MEHHTP-induced hepatic lipid disorders. These findings provide new insights into the liver lipid metabolism toxicity potential of DEHTP exposure in the population.


Assuntos
Hepatopatia Gordurosa não Alcoólica , Ácidos Ftálicos , Hepatopatia Gordurosa não Alcoólica/epidemiologia , Hepatopatia Gordurosa não Alcoólica/metabolismo , Humanos , Ácidos Ftálicos/toxicidade , Ácidos Ftálicos/metabolismo , Masculino , Adulto , Feminino
2.
Curr Mol Med ; 2024 Jan 04.
Artigo em Inglês | MEDLINE | ID: mdl-38289639

RESUMO

Obesity dramatically increases the risk of type 2 diabetes, fatty liver, hypertension, cardiovascular disease, and cancer, causing both declines in quality of life and life expectancy, which is a serious worldwide epidemic. At present, more and more patients with obesity are choosing drug therapy. However, given the high failure rate, high cost, and long design and testing process for discovering and developing new anti-obesity drugs, drug repurposing could be an innovative method and opportunity to broaden and improve pharmacological tools in this context. Because different diseases share molecular pathways and targets in the cells, anti-obesity drugs discovered in other fields are a viable option for treating obesity. Recently, some drugs initially developed for other diseases, such as treating diabetes, tumors, depression, alcoholism, erectile dysfunction, and Parkinson's disease, have been found to exert potential anti-obesity effects, which provides another treatment prospect. In this review, we will discuss the potential benefits and barriers associated with these drugs being used as obesity medications by focusing on their mechanisms of action when treating obesity. This could be a viable strategy for treating obesity as a significant advance in human health.

3.
PeerJ Comput Sci ; 9: e1447, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37409076

RESUMO

High dimension and complexity of network high-dimensional data lead to poor feature selection effect network high-dimensional data. To effectively solve this problem, feature selection algorithms for high-dimensional network data based on supervised discriminant projection (SDP) have been designed. The sparse representation problem of high-dimensional network data is transformed into an Lp norm optimization problem, and the sparse subspace clustering method is used to cluster high-dimensional network data. Dimensionless processing is carried out for the clustering processing results. Based on the linear projection matrix and the best transformation matrix, the dimensionless processing results are reduced by combining the SDP. The sparse constraint method is used to achieve feature selection of high-dimensional data in the network, and the relevant feature selection results are obtained. The experimental findings demonstrate that the suggested algorithm can effectively cluster seven different types of data and converges when the number of iterations approaches 24. The F1 value, recall, and precision are all kept at high levels. High-dimensional network data feature selection accuracy on average is 96.9%, and feature selection time on average is 65.1 milliseconds. The selection effect for network high-dimensional data features is good.

4.
Materials (Basel) ; 16(9)2023 Apr 26.
Artigo em Inglês | MEDLINE | ID: mdl-37176265

RESUMO

The present work describes the potential application of environmentally friendly sodium carboxymethylcellulose/gelatin (CMC/Gel) semi-interpenetrating hydrogels prepared by citric acid as a nontoxic cross-linking agent to adsorb dyes. The prepared hydrogels were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA/DTG), and swelling study. The adsorption performance of CMC/Gel2 (C/G2) hydrogel on methylene blue (MB) was investigated. The results showed the better adsorption conditions: adsorption time of 300 min, initial MB concentration of 500 mg/L, adsorbent dosage of 1.2 g/L, solution pH of 7, and temperature of 30 °C. The adsorption kinetics fit the pseudo-second order kinetics model, and the adsorption isotherm fit the Langmuir isotherm model. The maximum adsorption capacity reached 943.40 mg/g. The adsorption process is a spontaneous exothermic process. After three adsorption-desorption cycles, the removal rate of MB by hydrogel still reached 85%, with good reusability. Consequently, the hydrogel can be used as an environmentally friendly, stable, and efficient adsorbent for dyes in wastewater treatment.

5.
Front Endocrinol (Lausanne) ; 14: 1094458, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-36936164

RESUMO

Hyperglycemia, which can be caused by either an insulin deficit and/or insulin resistance, is the main symptom of Type 2 diabetes, a significant endocrine metabolic illness. Conventional medications, including insulin and oral antidiabetic medicines, can alleviate the signs of diabetes but cannot restore insulin release in a physiologically normal amount. The liver detects and reacts to shifts in the nutritional condition that occur under a wide variety of metabolic situations, making it an essential organ for maintaining energy homeostasis. It also performs a crucial function in glucolipid metabolism through the secretion of hepatokines. Emerging research shows that feeding induces hepatokines release, which regulates glucose and lipid metabolism. Notably, these feeding-induced hepatokines act on multiple organs to regulate glucolipotoxicity and thus influence the development of T2DM. In this review, we focus on describing how feeding-induced cross-talk between hepatokines, including Adropin, Manf, Leap2 and Pcsk9, and metabolic organs (e.g.brain, heart, pancreas, and adipose tissue) affects metabolic disorders, thus revealing a novel approach for both controlling and managing of Type 2 diabetes as a promising medication.


Assuntos
Diabetes Mellitus Tipo 2 , Humanos , Diabetes Mellitus Tipo 2/tratamento farmacológico , Diabetes Mellitus Tipo 2/metabolismo , Insulina/metabolismo , Fígado/metabolismo
7.
Emerg Med Int ; 2022: 3837995, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36247705

RESUMO

Background: With the accelerated pace of life in modern society, changes in work style, and the popularity of computers, the prevalence of cervical spondylosis (CSR) is increasing, and the age of onset is advancing. Once suffering from this disease, it is often difficult to cure and recurring, with complex clinical symptoms, causing a serious impact on human health. Objective: To evaluate the efficacy of manipulation and cervical traction in the treatment of radical cervical spondylosis. Methods: The PubMed, CNKI, and Wanfang databases were searched for literature. The literature related to this study was included according to selective criteria and inhibitory elimination criteria, and valuable information was selected for statistical analysis, resulting in a total of 11 randomized controlled trials with 994 subjects. Results: The short-term efficacy of manual treatment for CSR was superior to that of cervical traction alone (P < 0.05); subgroup analysis showed that the short-term efficacy of pulling or rotational manipulation was superior to that of cervical traction (P < 0.05). The mean difference between symptoms and manipulation VAS scores was higher before and after treatment when compared with cervical traction for CSR (P < 0.05); the subgroup analysis showed that VAS scores, upper extremity anesthesia scores, and survivorship scores were lower for pulling or rotating manipulation than for cervical traction (P < 0.05). Conclusion: The advantages of manual therapy in terms of short-term efficacy, VAS pain scores, neck pain, upper extremity anesthesia, and survivorship improvement provide a theoretical basis for its clinical impact.

8.
Ying Yong Sheng Tai Xue Bao ; 33(6): 1669-1678, 2022 Jun.
Artigo em Chinês | MEDLINE | ID: mdl-35729146

RESUMO

In order to solve the problem that soil soluble phosphorus content in most cultivated land in China is insufficient and the plant growth is inhibited, a phosphate solubilizing microorganism (PB) was screened and identified, and its phosphate solubilizing performance was optimized. The results showed that the PB strain was belonged to Burkholderia stabilis. It had the ability of nitrogen fixation and indole-3-acetic acid (IAA) secretion, as well as a certain inhibitory effect on Escherichia coli. It could maintain high activity and phosphorus solubilizing ability at pH 8.0-10.0, indicating good alkali resistance. The results of phosphorus dissolving performance optimization showed that the phosphate solubilizing capacity of strain PB reached the best at 30℃, pH 7.0, 180 r·min-1, using glucose as carbon source, ammonium sulfate as nitrogen source, tricalcium phosphate as phosphorus source and adding 50 µmol·L-1 lysine. The amount of dissolved phosphorus was 569.33 mg·L-1, which was 1.9 times of that before optimization. The strain mainly secreted citric acid, malonic acid, and glucuronic acid during metabolism. After adding lysine, the type of organic acids secreted by the strain did not change, but the content increased significantly. Results from pot experiments showed that the application of PB bacterial fertilizer could significantly improve the growth and physiological indicators of garlic seedlings, and that the promotion effect was more obvious after adding lysine. Compared with the control, the height of seedling was increased by 18.6%, seedling diameter was increased by 16.7%, aboveground fresh and dry weight were increased by 22.1% and 15.7%, and belowground fresh and dry weight were increased by 22.0% and 28.7%, respectively in PB with lysine treatment. Soil available phosphorus content was 2.1 and 2.3 times of the control in PB and PB+lysine treatments, indicating that PB could improve soil available phosphate content. Adding lysine could strengthen such function.


Assuntos
Burkholderia , Fosfatos , Burkholderia/metabolismo , Lisina , Fosfatos/metabolismo , Fósforo , Plântula/metabolismo , Solo/química , Microbiologia do Solo
9.
Chin Med ; 16(1): 88, 2021 Sep 16.
Artigo em Inglês | MEDLINE | ID: mdl-34530875

RESUMO

BACKGROUND: Amending from ancient classic, Ziyin Tongluo Formula (ZYTLF) has been prescribed to treat postmenopausal osteoporosis (PMOP) for decades with good curative effect. However, the possible mechanisms of it are still unknown. METHODS: Ovariectomized rat model was established to validate the therapeutic effect of ZYTLF on PMOP by Micro-CT bone analysis and pathological observation. Subsequently, active ingredients of ZYTLF and corresponding putative targets were identified by online databases. Overlapping genes were first obtained from mining genes associated with PMOP and then overlapped them with the putative targets. Key genes were selected from the multiple constructed and analyzed networks. GO and KEGG pathway enrichment analysis were performed by importing the key genes to the DAVID database. Moreover, validation of the binding association between key targets and their corresponding active compounds were accomplished by AutoDock Tools and other software. Lastly, Enzyme linked immunosorbent assay (Elisa) detection and Western blot analysis were utilized to further explore the possible mechanism of ZYTLF on PMOP. RESULTS: With 129 target genes interacting with PMOP, 92 active compounds of ZYTLF corresponded to 243 targets, and 50 key genes were chosen. Network analysis revealed the top 10 active ingredients, such as quercetin and kaempferol and the top 50 key genes, such as ERα, p38 MAPK, p-AKT and TGF-ß1. Enrichment analysis uncovered multiple signaling pathways, including estrogen signaling pathway, TNF signaling pathway, PI3K-Akt signaling pathway and MAPK signaling pathway. Furthermore, our finding of the foremost active compounds was tightly bound to the core proteins, which were verified by molecular docking analysis. Through experimental studies, we confirmed that the prescription of ZYTLF could ameliorate the OVX-induced bone loss, suppress the osteoclast activity and boost osteoblast ability through experimental studies. CONCLUSION: The potential mechanisms and therapeutic effects of ZYTLF against PMOP may be ascribed to inhibition of osteoclast activity, boost of osteoblast activity and enhancement of the expression of ERα.

10.
World J Microbiol Biotechnol ; 36(2): 27, 2020 Jan 29.
Artigo em Inglês | MEDLINE | ID: mdl-31997003

RESUMO

A phosphate solubilizing bacterium ZB was isolated from the rhizosphere soil of Araucaria, which falls into the species Pantoea agglomerans. Optimization for phosphate solubilization by strain ZB was performed. At optimum culture conditions, the isolate showed great ability of solubilizing different insoluble inorganic phosphate sources viz. Ca3(PO4)2 (TCP), Hydroxyapatite (HP), CaHPO4, AlPO4, FePO4 along with rock phosphates (RPs). Inoculation with planktonic cells was found to enhance dissolved phosphorous as compared to that achieved by symplasma inoculation. Besides inoculation with different status of cells, pre-incubation could also exert a great effect on phosphate solubilization ability of P. agglomerans. When isolate ZB was cultured with glucose as carbon sources, phosphorous was more efficiently dissolved from HP and RP without pre-incubation in comparison to that obtained with pre-cultivation. Pre-cultivation, however, was more suitable for P solubilization than no pre-cultivation when bacteria were grown with xylose. A positive correlation was detected between the production of organic acids and phosphate solubilization. P. agglomerans ZB possessed many plant growth promotion traits such as N2 fixation and production of indole 3-acetic acid, phytase, alkaline phosphatase. Pot experiment showed inoculation with single isolate ZB or biofertilizer prepared from semi-solid fermentation of isolate ZB with spent mushroom substrate (SMS) compost could enhance plant growth with respect to number of leaves, plant leave area, stem diameter, root length, root dry mass, shoot dry mass and biomass when compared to the abiotic control, revealing strain ZB could be a promising environmental-friendly biofertilizer to apply for agricultural field.


Assuntos
Araucaria/microbiologia , Pantoea/isolamento & purificação , Fosfatos/química , Carbono/química , Fermentação , Glucose/química , Fixação de Nitrogênio , Pantoea/metabolismo , Rizosfera , Microbiologia do Solo , Solubilidade
11.
Eur J Neurosci ; 50(2): 1972-1980, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-30762917

RESUMO

Sympathetic hyperactivity occurs in a subgroup of patients after traumatic brain injury (TBI). The rostral ventrolateral medulla (RVLM) is a key region for the activity of sympathetic nervous system. Oxidative stress in the RVLM is proved to be responsible for the increased level of sympathetic activity in animal models of hypertension and heart failure. In this study, we investigated whether oxidative stress in the RVLM contributed to the development of sympathetic hyperactivity after TBI in rats. Model of diffuse axonal injury was induced using Sprague-Dawley rats, and level of mean arterial pressure (MAP) and plasma Norepinephrine (NE) was measured to evaluate the sympathetic activity. For the assessment of oxidative stress, expression of reactive oxygen species (ROS), malondialdehyde (MDA), and superoxide dismutase (SOD) in the RVLM was determined. Microinjection of Tempol into the RVLM was performed to determine the effect of oxidative stress on sympathetic hyperactivity. According to the results, TBI led to elevated MAP and plasma NE in rats. It also induced a significantly increased level of ROS, MDA production and decreased level of SOD in the RVLM. The sympathetic activity, ROS, and MDA in the RVLM decreased significantly after microinjection of Tempol. Therefore, the present results suggested that oxidative stress in the RVLM was involved in the development of sympathetic hyperactivity following TBI.


Assuntos
Lesões Encefálicas Difusas , Hipercinese , Bulbo , Estresse Oxidativo , Agitação Psicomotora , Sistema Nervoso Simpático , Animais , Lesões Encefálicas Difusas/metabolismo , Lesões Encefálicas Difusas/fisiopatologia , Modelos Animais de Doenças , Hipercinese/metabolismo , Hipercinese/fisiopatologia , Masculino , Bulbo/metabolismo , Bulbo/fisiopatologia , Estresse Oxidativo/fisiologia , Agitação Psicomotora/metabolismo , Agitação Psicomotora/fisiopatologia , Ratos , Ratos Sprague-Dawley , Sistema Nervoso Simpático/metabolismo , Sistema Nervoso Simpático/fisiopatologia
12.
Opt Lett ; 43(24): 6089-6092, 2018 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-30548012

RESUMO

Optical excitations of monolayer bismuthene present very rich and unique absorption spectra. The optical energy gap corresponding to the threshold frequency is not equal to an indirect energy gap, and it becomes zero under the critical electric field. The frequency, number, intensity, and form of the absorption structures are dramatically changed when an external electric field is applied. The prominent peaks and the observable shoulders, respectively, arise from the constant-energy loop and the band-edge states of parabolic dispersions. These directly reflect the unusual electronic properties, being very different from those in monolayer graphene. The novel optical properties of bismuthine that are easily manipulated by electric fields may find a lot of various applications in optoelectronics, either combined with or complementary to those graphene-based systems.

13.
Biomed Res Int ; 2018: 6069756, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29713644

RESUMO

BACKGROUND: Existing evidence suggests the potential therapy of transplanting olfactory ensheathing cells (OEC) either alone or in combination with neurotrophic factors or other cell types in optic nerve injury (ONI). However, clinical use of autologous OEC in the acute stages of ONI is not possible. On the other hand, acute application of heterologous transplantation may bring the issue of immune rejection. The olfactory mucosa (OM) with OEC in the lamina propria layer is located in the upper region of the nasal cavity and is easy to dissect under nasal endoscopy, which makes it a candidate as autograft material in acute stages of ONI. To investigate the potential of the OM on the protection of injured neurons and on the promotion of axonal regeneration, we developed a transplantation of syngenic OM in rats with ONI model. METHODS: After the right optic nerve was crushed in Lewis rats, pieces of syngenic whole-layer OM were transplanted into the lesion. Rats undergoing phosphate buffered saline (PBS) injection were used as negative controls (NC). The authors evaluated the regeneration of retinal ganglion cells (RGCs) and axons for 3, 7, 14, and 28 days after transplantation. Obtained retinas and optic nerves were analyzed histologically. RESULTS: Transplantations of OM significantly promoted the survival of retinal ganglion cells (RGCs) and axonal growth of RGCs compared with PBS alone. Moreover, OM group was associated with higher expression of GAP-43 in comparison with the PBS group. In addition to the potential effects on RGCs, transplantations of OM significantly decreased the expression of GFAP in the retinas, suggesting inhibiting astrocyte activation. CONCLUSIONS: Transplantation of whole-layer OM in rats contributes to the neuronal survival and axon regeneration after ONI.


Assuntos
Endoscopia , Mucosa Olfatória/transplante , Traumatismos do Nervo Óptico/cirurgia , Células Ganglionares da Retina/metabolismo , Animais , Autoenxertos , Sobrevivência Celular , Masculino , Mucosa Olfatória/metabolismo , Mucosa Olfatória/patologia , Traumatismos do Nervo Óptico/metabolismo , Traumatismos do Nervo Óptico/patologia , Ratos , Ratos Endogâmicos Lew , Células Ganglionares da Retina/patologia
14.
Nanoscale Res Lett ; 13(1): 43, 2018 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-29417237

RESUMO

The abounding possibilities of discovering novel materials has driven enhanced research effort in the field of materials physics. Only recently, the quantum anomalous hall effect (QAHE) was realized in magnetic topological insulators (TIs) albeit existing at extremely low temperatures. Here, we predict that MPn (M =Ti, Zr, and Hf; Pn =Sb and Bi) honeycombs are capable of possessing QAH insulating phases based on first-principles electronic structure calculations. We found that HfBi, HfSb, TiBi, and TiSb honeycomb systems possess QAHE with the largest band gap of 15 meV under the effect of tensile strain. In low-buckled HfBi honeycomb, we demonstrated the change of Chern number with increasing lattice constant. The band crossings occurred at low symmetry points. We also found that by varying the buckling distance we can induce a phase transition such that the band crossing between two Hf d-orbitals occurs along high-symmetry point K2. Moreover, edge states are demonstrated in buckled HfBi zigzag nanoribbons. This study contributes additional novel materials to the current pool of predicted QAH insulators which have promising applications in spintronics.

15.
Sci Rep ; 7(1): 10694, 2017 09 06.
Artigo em Inglês | MEDLINE | ID: mdl-28878305

RESUMO

Current opinions about the effect of intensive blood pressure (BP) reduction for acute intracerebral hemorrhage (ICH) are inconsistent. We performed a meta-analysis to evaluate the efficacy and safety of intensive BP reduction for acute ICH by analyzing data from several recent randomized controlled trials (RCTs). There were six eligible studies that met the inclusion criteria, for a total of 4,385 acute ICH patients in this meta-analysis. After analyzing these data, we found differences between intensive and standard BP lowering treatment groups in total mortality rates, unfavorable outcomes, hematoma expansion, neurologic deterioration, and severe hypotension were not significant. Moreover, compared with the standard treatment, the rate of renal adverse event in intensive treatment group was significantly higher. The intensive treatment approach was recommended in the following situations: (1) longer prehospital duration; (2) lower National Institute of Health stroke scale (NIHSS) score; (3) no hypertension history.


Assuntos
Anti-Hipertensivos/uso terapêutico , Pressão Sanguínea/efeitos dos fármacos , Hemorragia Cerebral/tratamento farmacológico , Hemorragia Cerebral/fisiopatologia , Fatores Etários , Anti-Hipertensivos/farmacologia , Hemorragia Cerebral/etiologia , Hemorragia Cerebral/mortalidade , Progressão da Doença , Humanos , Hipertensão/complicações , Razão de Chances , Ensaios Clínicos Controlados Aleatórios como Assunto , Resultado do Tratamento
16.
Sci Rep ; 7(1): 1849, 2017 05 12.
Artigo em Inglês | MEDLINE | ID: mdl-28500317

RESUMO

The absorption spectra of monolayer tinene in perpendicular electric fields are studied by the tight-binding model. There are three kinds of special structures, namely shoulders, logarithmical symmetric peaks and asymmetric peaks in the square-root form, corresponding to the optical excitations of the extreme points, saddle points and constant-energy loops. With the increasing field strength, two splitting shoulder structures, which are dominated by the parabolic bands of 5p z orbitals, come to exist because of the spin-split energy bands. The frequency of threshold shoulder declines to zero and then linearly grows. The third shoulder at 0.75~0.85 eV mainly comes from (5p x , 5p y ) orbitals. The former and the latter orbitals, respectively, create the saddle-point symmetric peaks near the M point, while they hybridize with one another to generate the loop-related asymmetric peaks. Tinene quite differs from graphene, silicene, and germanene. The special relationship among the multi-orbital chemical bondings, spin-orbital couplings and Coulomb potentials accounts for the feature-rich optical properties.

17.
Food Chem Toxicol ; 50(12): 4285-91, 2012 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-22982472

RESUMO

Xiamen is a representative coastal city in China. Shellfish is widely consumed by local people. A broad spectrum of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) were measured in representative shellfish from Xiamen. Despite being banned many years ago, these chemicals were still detected at varying levels. The total PCB levels ranged from 0.48 to 3.28 ng/g wet wt. for the shellfish surveyed. The tetra-, penta- and hexa-PCB congeners were found to be predominant. The estimated WHO-TEQ PCB intakes through shellfish consumption ranged from 0.063 to 0.102 pg/kg body wt. for Xiamen adults and children, which were significantly lower than tolerable weekly intake. Among OCPs, DDTs were predominant, followed by aldrin-like chemicals and endosulfans. The increase in aldrin-like chemicals and endosulfans, and the decrease in DDTs were observed in this study when compared to historical data in Xiamen. HCHs, chlordanes, HCB, heptachlors and mirex were detected with low concentrations in the shellfish. The estimated intakes of OCPs were several orders lower than tolerable daily intakes. However, the high carcinogenic risk of aldrin and dieldrin were found in the measured shellfish species. p,p'-DDD, p'p-DDT, α-HCH and ß-HCH in certain species should also be concerned for their potential carcinogenic risks.


Assuntos
DDT/análise , Hexaclorobenzeno/análise , Hexaclorocicloexano/análise , Resíduos de Praguicidas/análise , Bifenilos Policlorados/análise , Frutos do Mar/análise , Adulto , Aldrina/análise , Animais , Carcinógenos/toxicidade , Criança , China , Clordano/análise , Dieldrin/análise , Dieta , Monitoramento Ambiental/métodos , Feminino , Contaminação de Alimentos/análise , Humanos , Masculino , Praguicidas/análise , Medição de Risco , Fatores de Risco , Alimentos Marinhos/análise , Poluentes Químicos da Água/análise
18.
J Nanosci Nanotechnol ; 12(3): 2557-66, 2012 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-22755090

RESUMO

Magneto-electronic properties of AA-stacked graphene superlattice (simple hexagonal graphite) are studied by the tight-binding model with an exact diagonalization method. The Landau subbands (LSs) with strong energy dispersions exist along k(z) and each subband possesses two band-edge states. Density of states reflects main features of the LSs, such as asymmetric prominent peak structures and the semimetallic behavior. Under the AA-stacked configuration, the LS wave functions are characterized by two sublattices, a and b. The quantum number (n(c,v)) of each LS, which corresponds to the number of zero points in the dominating carrier distributions, is determined by a certain sublattice and independent of k(z). For each LS, the difference between the number of zero point of the a and b sublattices is fixed and equals one. Furthermore, a reliable approximate solution of the low-lying LS energy is obtained. Through observing this solution, the dependence of the LS energy on the field strength and quantum number, k(z)-dependent energy spacing between two LSs, and the values of atomic hopping integrals are reasonably determined. A comparison of the AA-stacked graphene superlattice and monolayer graphene demonstrates that they possess some similar magneto-electronic properties.

19.
J Nanosci Nanotechnol ; 11(6): 4938-47, 2011 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-21770126

RESUMO

The low-lying Landau level (LL) properties of ABC-stacked trilayer graphene are investigated by the tight-binding (TB) model. The LL spectra exhibit an asymmetric structure around the Fermi level and three finely split LLs close to the Fermi level. The LL wave functions are described by six magnetic TB Bloch functions associated with six sublattices. These Bloch functions possess oscillation modes and localization features. An effective quantum number, which is used to define a LL, is defined by the oscillation mode of the Bloch function with the largest amplitude. The LL energies in the low-field and high-field regions exhibit different features since the trigonal warping effect strongly dominates the LL properties in the low-field region. Furthermore, the LLs do not present a simple relation between the magnetic field strength (effective quantum number) and the LL energy. A detailed comparison of the calculation with all atomic interactions taken into account and that ignoring some interlayer interactions is offered. The dissimilarities between these two calculations demonstrate that interlayer interactions strongly affect the main features of LLs and should not be ignored. The dissimilarities could be further examined by experimental measurements.

20.
J Nanosci Nanotechnol ; 10(1): 643-9, 2010 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-20352905

RESUMO

The tight-binding model and the modified gradient approximation are, respectively, used to calculate the electronic states and optical properties of finite double-walled carbon nanotubes (DWCNTs). The optical absorption spectra allow us to decompose the total DWCNT spectral function into the contributions from the inner and outer walls. Intertube interactions can cause drastic changes in the symmetry of the electronic states, the Fermi level, the energy spacing, and the state degeneracy. Such effects are directly reflected in the joint density of states and optical absorption spectra. Thus, the first absorption peaks of the energy degeneracy (nondegeneracy) of two finite single-walled carbon nanotubes would be separated into three or four peaks in the shorter DWCNTs. For finite armchair DWCNTs, the number of the first group peaks decreases as the length increases. These results demonstrate a competition between the tube length, the intertube interactions, and the geometric structures. For finite zigzag DWCNTs however, the number of the first group peaks remains constant as the length increases. This phenomenon can be attributed to the states exclusively localized at the outermost zigzag positions. The energies of the peaks make a red-shift as the tube length increases. For sufficiently long DWCNTs absorption peak energies are almost independent of length.

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