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1.
Sci Total Environ ; 671: 883-896, 2019 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-30947059

RESUMO

To scientifically understand the emissions and chemistry of volatile organic compounds (VOCs) in a typical petrochemical industrialized and dust-rich region of Northwest China, VOCs were measured at a receptor site in the Lanzhou Valley using a high-resolution online proton transfer reaction-mass spectrometer (PTR-MS). The ranking of VOC mixing ratios was methanol (32.72 ±â€¯8.94 ppb) > acetaldehyde (5.05 ±â€¯2.4 ppb) > acetic acid (3.42 ±â€¯1.71 ppb). Lanzhou has higher oxygenated VOCs (OVOCs) mixing ratios (methanol and acetaldehyde) and lower aromatics levels (benzene, toluene and C8-aromatics) compared with other cities. The positive matrix factorization (PMF) model showed eight sources of VOCs as follows: (1) mixed industrial process-1 (13.5%), (2) secondary formation (13.2%), (3) mixed industrial process-2 (11.8%), (4) residential biofuel use and waste disposal (13.80%), (5) solvent usage (10.1%), (6) vehicular exhaust (11.8%), (7) biogenic (13.8%) and (8) biomass burning (12.0%). Both the PSCF and the CWT results of mixed industrial process-1 were mainly from the northeast of Lanzhou and the biomass burning was from the southeast; the other four sources (without secondary formation and biogenic) were mainly from the west and northwest of Lanzhou, which were associated with the dust area of the Gobi Desert. A trajectory sector analysis revealed that the local emissions contributed 64.9-71.1% to the VOCs. OVOCs accounted for 43% of the ozone production potential (OFP), and residential biofuel use and waste disposal (25.1%), mixed industrial process-2 (15.3%) and solvent usage (13.4%) appeared to be the dominant sources contributors to O3 production. The rank of main secondary organic aerosols (SOA) precursors under low-NOx conditions is xylene > toluene > benzene > naphthalene > styrene > C10-aromatics > isoprene, while under high-NOx conditions, it is toluene > naphthalene > xylene > C10-aromatics > styrene > benzene > isoprene. Solvent usage and vehicular exhaust appeared to be the dominant contributors to SOA formation.

2.
Sci Total Environ ; 650(Pt 2): 2545-2558, 2019 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-30293007

RESUMO

To investigate the pollution characteristics and potential sources in a dusty season, an online analyzer was used to measure trace gases and major water-soluble ions in PM10 from April 1st to May 29th, 2011 in Lanzhou. The average concentrations of HONO, HNO3, HCl, SO2 and NH3 were 0.93, 1.16, 0.48, 9.29 and 5.54 µg/m3, respectively, and 2.8, 2.76, 8.28 and 2.48 µg/m3 for Cl-, NO3-, SO42- and NH4+. In the non-dust period, diurnal variations of SO42-, NO3- and their gaseous precursors showed similar change trend. NH4+ showed unimodal pattern whereas NH3 illustrated a bimodal pattern. HCl and Cl- showed an opposite diurnal pattern. In the dust event, temporal profiles of HCl and Cl-, SO2 and SO42- all presented similar change trend, and SO42- and Cl- preceded dust ions (Ca2+ and Mg2+) 13 h. The ratios of NO3- to SO42- were 0.65 in the non-dust period and 0.31 in the dust event. In the dust event, the sulfur oxidation ratio (SOR) was a factor of 1.33 greater than that in the non-dust period, and [SO42-]/[SO2] was 2.31 times of that in the non-dust period. The source apportionment using Probabilistic Matrix Factorization (PMF) suggested that fugitive dust (58.09%), secondary aerosols (33.98%), and biomass burning (7.93%) were the major sources in the non-dust period whereas dust (67.01%), salt lake (29.68%), biomass burning (0.8%), and motor vehicle (2.51%) were the primary sources in the dust event. Concentration weighted trajectory (CWT) model indicated that NO3-, Cl- and K+ could be regarded as local source species, the potential sources of Na+, Mg2+ and Ca2+ concentrated in the two large areas with the one covered in the junction areas of Xinjiang, Qinghai and Gansu and another one covered the places around in Lanzhou, the potential sources of SO42- were mainly localized in the areas adjacent to Lanzhou.

3.
ACS Appl Mater Interfaces ; 9(14): 12743-12749, 2017 Apr 12.
Artigo em Inglês | MEDLINE | ID: mdl-28322049

RESUMO

The carbon nanotube (CNT) has been proved to be a promising material in infrared detection, due to its many advantages of high mobility, strong infrared light absorption, and carrier collection efficiency. However, the absorption restriction from the single layer limits its effective utilization of incident light. In this paper, we introduce a plasmonic electrode structure in a CNT thin-film photodetector based on random deposited high-purity semiconducting CNTs, which can collect photoinduced carriers effectively and enhance light absorption at the same time. The largest enhancement of photocurrents can be achieved at 1650 nm wavelength with suitable plasmonic structure size. Especially, we further discuss the influence of plasmonic structures on the performance of devices. We demonstrate that the best performance improvement of the carbon nanotube detector with plasmonic structure can be enhanced by 13.7 times for photocurrent mode and 5.62 times for photovoltage mode compared to those devices without structure at 1650 nm resonant wavelength. At last, the plasmonic structures are applied on tandem photodetectors with nine virtual contacts, and both the photocurrent and photovoltage are increased. The application of plasmonic electrodes can improve detector performance and retain compact device structures, which shows great potential for optimizing infrared detectors based on nanomaterials.

4.
ACS Nano ; 10(10): 9595-9601, 2016 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-27632420

RESUMO

Conversion efficiency (CE) is the most important figure of merit for photodetectors. For carbon nanotubes (CNT) based photodetectors, the CE is mainly determined by excitons dissociation and transport of free carriers toward contacts. While phonon-assisted exciton dissociation mechanism is effective in split-gate CNT p-n diodes, the CE is typically low in these devices, approximately 1-5%. Here, we evaluate the performance of a barrier-free bipolar diode (BFBD), which is basically a semiconducting CNT asymmetrically contacted by perfect n-type ohmic contact (Sc) and p-type ohmic contact (Pd) at the two ends of the diode. We show that the CE in short channel BFBD devices (e.g., 60 nm) is over 60%, and it reduces rapidly with increasing channel length. We find that the electric-field-assisted mechanism dominates the dissociation rate of excitons in BFBD devices at zero bias and thus the photocurrent generation process. By performing a time-resolved and spatial-resolved Monte Carlo simulation, we find that there exists an effective electron (hole)-rich region near the n-type (p-type) electrode in the asymmetrically contacted BFBD device, where the electric-field strength is larger than 17 V/µm and exciton dissociation is extremely fast (<0.1 ps), leading to very high CE in the BFBD devices.

5.
ACS Nano ; 10(7): 6737-43, 2016 07 26.
Artigo em Inglês | MEDLINE | ID: mdl-27322134

RESUMO

A nano self-gating diode (SGD) based on nanoscale semiconducting material is proposed, simulated, and realized on semiconducting carbon nanotubes (CNTs) through a doping-free fabrication process. The relationships between the performance and material/structural parameters of the SGD are explored through numerical simulation and verified by experiment results. Based on these results, performance optimization strategy is outlined, and high performance CNT SGDs are fabricated and demonstrated to surpass other published CNT diodes. In particular the CNT SGD exhibits high rectifier factor of up to 1.4 × 10(6) while retains large on-state current. Benefiting from high yield and stability, CNT SGDs are used for constructing logic and analog integrated circuits. Two kinds of basic digital gates (AND and OR) have been realized on chip through using CNT SGDs and on-chip Ti wire resistances, and a full wave rectifier circuit has been demonstrated through using two CNT SGDs. Although demonstrated here using CNT SGDs, this device structure may in principle be implemented using other semiconducting nanomaterials, to provide ideas and building blocks for electronic applications based on nanoscale materials.

6.
Chin J Nat Med ; 11(2): 171-6, 2013 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-23787185

RESUMO

AIM: To discover new bioactive constituents from Kaempferia galanga L. (Zingiberaceae). METHODS: The extract of K. galanga was divided into the chloroform and water-soluble portions. The latter fraction was successively subjected to column chromatography over a D101 macroporous adsorption resin, MCI, Sephadex LH-20, and preparative HPLC to obtain two compounds. RESULTS: Two novel sulfonated diarylheptanoid epimers, namely kaempsulfonic acids A (1) and B (2), were isolated from the rhizomes of K. galanga. Their structures were established by analysis of spectroscopic data. The absolute configurations of 1 and 2 were determined by the comparison of experimental electronic circular dichroism (ECD) spectroscopy and the computational calculation method, combined with Mo2(OAc)4 induced circular dichroism (ICD). CONCLUSION: The isolates 1 and 2 are new compounds and their absolute configurations were determined for the first time.


Assuntos
Diarileptanoides/química , Extratos Vegetais/química , Zingiberaceae/química , Cromatografia Líquida de Alta Pressão , Diarileptanoides/isolamento & purificação , Isomerismo , Extratos Vegetais/isolamento & purificação , Rizoma/química
7.
PLoS One ; 8(6): e64601, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23805178

RESUMO

Lexical gap in cQA search, resulted by the variability of languages, has been recognized as an important and widespread phenomenon. To address the problem, this paper presents a question reformulation scheme to enhance the question retrieval model by fully exploring the intelligence of paraphrase in phrase-level. It compensates for the existing paraphrasing research in a suitable granularity, which either falls into fine-grained lexical-level or coarse-grained sentence-level. Given a question in natural language, our scheme first detects the involved key-phrases by jointly integrating the corpus-dependent knowledge and question-aware cues. Next, it automatically extracts the paraphrases for each identified key-phrase utilizing multiple online translation engines, and then selects the most relevant reformulations from a large group of question rewrites, which is formed by full permutation and combination of the generated paraphrases. Extensive evaluations on a real world data set demonstrate that our model is able to characterize the complex questions and achieves promising performance as compared to the state-of-the-art methods.


Assuntos
Mineração de Dados/métodos , Linguagem , Humanos , Software
8.
PLoS One ; 8(9)2013.
Artigo em Inglês | MEDLINE | ID: mdl-29220835

RESUMO

[This corrects the article DOI: 10.1371/journal.pone.0064601.].

9.
Zhongguo Dang Dai Er Ke Za Zhi ; 13(4): 285-7, 2011 Apr.
Artigo em Chinês | MEDLINE | ID: mdl-21507295

RESUMO

OBJECTIVE: To study the effects of TNF-α on ICAM-1 and LFA-1 expression in peripheral blood mononuclear cells (PBMC) of children with febrile seizures (FS). METHODS: Sixteen children with FS and 16 age- and gender-matched healthy children were enrolled. The samples of PBMC from FS children were randomized into two groups with or without TNF-α treatment (TNF-α concentration 1.0 ng/mL). PBMC were purified and cultured with a conventional method in vitro. The expression of ICAM-1 and LFA-1 in PBMC was determined by flow cytometry (FCM). RESULTS: ICAM-1ï¼»(20±9)% vs (14±7)%)ï¼½and LFA-1ï¼»(43±16)% vs (30±16)%ï¼½expression in PBMC in the untreated FS group was significantly higher than that in the normal control group (P<0.05). Compared with the untreated FS group, the treatment with TNF-α remarkably increased the ICAM-1 expressionï¼»(27±11)%ï¼½(P<0.05). PBMC LFA-1 expressionï¼»(52±21)%ï¼½in the TNF-α-treated group was higher than that in the untreated FS group, although there were no statistical differences between the two groups. CONCLUSIONS: TNF-α treatment may increase LFA-1 and ICAM-1 expression in PBMC of children with FS.


Assuntos
Molécula 1 de Adesão Intercelular/sangue , Leucócitos Mononucleares/química , Antígeno-1 Associado à Função Linfocitária/sangue , Convulsões Febris/imunologia , Fator de Necrose Tumoral alfa/farmacologia , Criança , Pré-Escolar , Feminino , Humanos , Lactente , Leucócitos Mononucleares/efeitos dos fármacos , Masculino
11.
Zhonghua Yi Xue Za Zhi ; 90(39): 2763-6, 2010 Oct 26.
Artigo em Chinês | MEDLINE | ID: mdl-21162913

RESUMO

OBJECTIVE: To investigate the cutaneous adverse reactions to antiepileptic drugs (AEDs), clinical characteristic and the association with HLA-B*1502. METHODS: A retrospective analysis of four cases of antiepileptic drug hypersensitive syndrome (AHS) were performed on the basis of clinical data, cutaneous adverse reactions to carbamazepine (CBZ) (n = 2) including Stevens-Johnson syndrome (SJS) (n = 1) and hypersensitivity syndrome (HSS) (n = 1); phenobarbital-induced HSS (n = 1) and oxcarbazepine (OXC)-induced HSS (n = 1). All patients received the examinations of polymerase chain reaction (PCR) with sequence specific primers to analyze HLA-B*1502. Two healthy subjects had no history of using antiepileptic drugs as the control. RESULTS: All patients had manifestations of fever, eruption, mucosal involvement and visceral injury. Two cases were diagnosed as Stevens-Johnson syndrome associated with apparent bullae formation. Genotype positive for HLA-B*1502 was association with 2 patients with CBZ/OXC-induced SJS while the other 1 case of CBZ and 1 case of phenobarbital-induced HSS were genotype non-HLA-B*1502. CONCLUSION: AHS usually occurs within 1 to 2 weeks after initiation of AEDs therapy. The typical presentations are fever, eruption and internal organ involvements, etc. The epileptic patients with CBZ/OXC-induced SJS are related with HLA-B*1502 genotype. But it is not found in HSS patients.


Assuntos
Anticonvulsivantes/efeitos adversos , Hipersensibilidade a Drogas/genética , Epilepsia/genética , Antígenos HLA-B/genética , Anticonvulsivantes/farmacologia , Anticonvulsivantes/uso terapêutico , Criança , Pré-Escolar , Epilepsia/tratamento farmacológico , Epilepsia/imunologia , Feminino , Humanos , Lactente , Masculino , Estudos Retrospectivos
12.
Appl Opt ; 46(31): 7780-91, 2007 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-17973024

RESUMO

Fukunaga-Koontz transform (FKT), stemming from principal component analysis (PCA), is used in many pattern recognition and image-processing fields. It cannot capture the higher-order statistical property of natural images, so its detection performance is not satisfying. PCA has been extended into kernel PCA in order to capture the higher-order statistics. However, thus far there have been no researchers who have definitely proposed kernel FKT (KFKT) and researched its detection performance. For accurately detecting potential small targets from infrared images, we first extend FKT into KFKT to capture the higher-order statistical properties of images. Then a framework based on Kalman prediction and KFKT, which can automatically detect and track small targets, is developed. Results of experiments show that KFKT outperforms FKT and the proposed framework is competent to automatically detect and track infrared point targets.

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