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1.
PLoS One ; 14(10): e0223650, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31622370

RESUMO

Public transit, especially urban rail systems, plays a vital role in shaping commuting patterns. Compared with census data and survey data, large-scale and real-time big data can track the impacts of urban policy implementations at finer spatial and temporal scales. Therefore, this study proposed a multi-level analytical framework using transit smartcard data to examine urban commuting dynamics in response to rail transit upgrades. The study area was Shenzhen, one of the most highly urbanized and densely populated cities in China, which provides the opportunity to examine the effects of rail transit upgrades on commuting patterns in a rapidly developing urban context. Changes in commuting patterns were examined at three levels: city, region, and individual. At the city level, we considered the average commuting time, commuting speed, and commuting distance across the whole city. At the region level, we analyzed changes in the job accessibility of residential zones. Finally, this study evaluated the potential effects of rail transit upgrades on the jobs-housing relationship at the individual level. Difference-in-difference models were used for causal inference between rail transit upgrades and commuting patterns. In the very short term, the opening of new rail transit lines resulted in no significant changes in overall commuting patterns across the whole city; however, two effects of rail transit upgrades on commuting patterns were identified. First, rail transit upgrades enhanced regional connectivity between residential zones and employment centers, thus improving job accessibility. Second, rail transit improvement increased the commuting distances of individuals and contributed to the separation of workplaces and residences. This study provides meaningful insights into the effects of rail transit upgrades on commuting patterns.

2.
Small ; 15(48): e1901545, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31087782

RESUMO

Development of high-performance and low-cost nonprecious metal electrocatalysts is critical for eco-friendly hydrogen production through electrolysis. Herein, a novel nanoflower-like electrocatalyst comprising few-layer nitrogen-doped graphene-encapsulated nickel-copper alloy directly on a porous nitrogen-doped graphic carbon framework (denoted as Nix Cuy @ NG-NC) is successfully synthesized using a facile and scalable method through calcinating the carbon, copper, and nickel hydroxy carbonate composite under inert atmosphere. The introduction of Cu can effectively modulate the morphologies and hydrogen evolution reaction (HER) performance. Moreover, the calcination temperature is an important factor to tune the thickness of graphene layers of the Nix Cuy @ NG-NC composites and the associated electrocatalytic performance. Due to the collective effects including unique porous flowered architecture and the synergetic effect between the bimetallic alloy core and graphene shell, the Ni3 Cu1 @ NG-NC electrocatalyst obtained under optimized conditions exhibits highly efficient and ultrastable activity toward HER in harsh environments, i.e., a low overpotential of 122 mV to achieve a current density of 10 mA cm-2 with a low Tafel slope of 84.2 mV dec-1 in alkaline media, and a low overpotential of 95 mV to achieve a current density of 10 mA cm-2 with a low Tafel slope of 77.1 mV dec-1 in acidic electrolyte.

3.
Nanoscale ; 9(38): 14612-14619, 2017 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-28936500

RESUMO

NaAlH4 has been widely regarded as a potential hydrogen storage material due to its favorable thermodynamics and high energy density. The high activation energy barrier and high dehydrogenation temperature, however, significantly hinder its practical application. In this paper, CeO2 hollow nanotubes (HNTs) prepared by a simple electrospinning technique are adopted as functional scaffolds to support NaAlH4 nanoparticles (NPs) towards advanced hydrogen storage performance. The nanoconfined NaAlH4 inside CeO2 HNTs, synthesized via the infiltration of molten NaAlH4 into the CeO2 HNTs under high hydrogen pressure, exhibited significantly improved dehydrogenation properties compared with both bulk and ball-milled CeO2 HNTs-catalyzed NaAlH4. The onset dehydrogenation temperature of the NaAlH4@CeO2 composite was reduced to below 100 °C, with only one main dehydrogenation peak appearing at 130 °C, which is 120 °C and 50 °C lower than for its bulk counterpart and for the ball-milled CeO2 HNTs-catalyzed NaAlH4, respectively. Moreover, ∼5.09 wt% hydrogen could be released within 30 min at 180 °C, while only 1.6 wt% hydrogen was desorbed from the ball-milled NaAlH4 under the same conditions. This significant improvement is mainly attributed to the synergistic effects contributed by the CeO2 HNTs, which could act as not only a structural scaffold to fabricate and confine the NaAlH4 NPs, but also as an effective catalyst to enhance the hydrogen storage performance of NaAlH4.

4.
Small ; 13(44)2017 11.
Artigo em Inglês | MEDLINE | ID: mdl-28722318

RESUMO

Fe2 O3 is regarded as a promising anode material for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) due to its high specific capacity. The large volume change during discharge and charge processes, however, induces significant cracking of the Fe2 O3 anodes, leading to rapid fading of the capacity. Herein, a novel peapod-like nanostructured material, consisting of Fe2 O3 nanoparticles homogeneously encapsulated in the hollow interior of N-doped porous carbon nanofibers, as a high-performance anode material is reported. The distinctive structure not only provides enough voids to accommodate the volume expansion of the pea-like Fe2 O3 nanoparticles but also offers a continuous conducting framework for electron transport and accessible nanoporous channels for fast diffusion and transport of Li/Na-ions. As a consequence, this peapod-like structure exhibits a stable discharge capacity of 1434 mAh g-1 (at 100 mA g-1 ) and 806 mAh g-1 (at 200 mA g-1 ) over 100 cycles as anode materials for LIBs and SIBs, respectively. More importantly, a stable capacity of 958 mAh g-1 after 1000 cycles and 396 mAh g-1 after 1500 cycles can be achieved for LIBs and SIBs, respectively, at a large current density of 2000 mA g-1 . This study provides a promising strategy for developing long-cycle-life LIBs and SIBs.

5.
Int J Health Geogr ; 13: 42, 2014 Oct 22.
Artigo em Inglês | MEDLINE | ID: mdl-25336302

RESUMO

BACKGROUND: In a conventional P-median model, demanding points are likely assigned to the closest supplying facilities, but this method exhibits evident limitations in real cases. METHODS: This paper proposed a modified P-median model in which exact and approximate strategies are used. The first strategy aims to enumerate all of the possible combinations of P facilities, and the second strategy adopts simulated annealing to allocate resources considering capacity constraint and spatial compactness constraint. These strategies allow us to choose optimal locations by applying visual analytics, which is rarely employed in location allocation planning. RESULTS: This model is applied to a case study in Henan Province, China, where three optimal healthcare centers are selected from candidate cities. First, the weighting factor in spatial compactness constraint is visually evaluated to obtain a plausible spatial pattern. Second, three optimal healthcare centers, namely, Zhengzhou, Xinxiang, and Nanyang, are identified in a hybrid transportation network by performing visual analytics. Third, alternative healthcare centers are obtained in a road network and compared with the above solution to understand the impacts of transportation network types. CONCLUSIONS: The optimal healthcare centers are visually detected by employing an improved P-median model, which considers both geographic accessibility and service quality. The optimal solutions are obtained in two transportation networks, which suggest high-speed railways and highways play a significant role respectively.


Assuntos
Assistência à Saúde/métodos , Modelos Teóricos , Centros de Atenção Terciária , Transportes/métodos , China/epidemiologia , Assistência à Saúde/estatística & dados numéricos , Acesso aos Serviços de Saúde/estatística & dados numéricos , Humanos , Centros de Atenção Terciária/estatística & dados numéricos , Transportes/estatística & dados numéricos
6.
J Clin Microbiol ; 47(10): 3178-84, 2009 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-19641057

RESUMO

Pathogen detection is critical to the process of generating and testing powdered infant formula (PIF). An obstacle associated with PIF microbial surveillance is that most current procedures are time-consuming and labor-intensive. We have developed a rapid, DNA microarray-based detection technique to identify 10 different pathogenic bacteria associated with PIF contamination based on the 16S-23S rRNA gene internal transcribed spacer (ITS) sequences and wzy (O antigen polymerase) gene. Using this procedure, Enterobacter sakazakii, Salmonella enterica, Klebsiella pneumoniae, Klebsiella oxytoca, Serratia marcescens, Acinetobacter baumannii, Bacillus cereus, Listeria monocytogenes, Staphylococcus aureus, and Escherichia coli O157 were identified. One hundred eighty-five strains were used to validate the microarray assay (including 134 target pathogen strains and 51 closely related bacteria). Twenty-seven probes reproducibly detected multiple pathogens with high specificity and sensitivity (0.100 ng genomic DNA or 10(4) CFU/ml). Twenty-one real PIF samples were tested by the microarray with 100% accuracy. The data presented reveal that the designed oligonucleotide microarray is a promising method for basic microbiology, clinical diagnosis, food safety, and epidemiological surveillance.


Assuntos
Técnicas Bacteriológicas/métodos , Microbiologia de Alimentos , Bactérias Gram-Negativas/isolamento & purificação , Bactérias Gram-Positivas/isolamento & purificação , Fórmulas Infantis , Análise em Microsséries/métodos , Cronobacter sakazakii/genética , Cronobacter sakazakii/isolamento & purificação , DNA Bacteriano/genética , DNA Espaçador Ribossômico/genética , Bactérias Gram-Negativas/genética , Bactérias Gram-Positivas/genética , Humanos , Dados de Sequência Molecular , Análise de Sequência com Séries de Oligonucleotídeos , Sondas de Oligonucleotídeos/genética , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Análise de Sequência de DNA
7.
J Med Microbiol ; 58(Pt 1): 69-81, 2009 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-19074655

RESUMO

Shigella is the cause of shigellosis or bacillary dysentery, the occurrence of which is estimated to be 165 million cases per year worldwide, resulting in 1.1 million deaths. Rapid and reliable assays for detecting and identifying Shigella in food, environmental and clinical samples are therefore necessary. Shigella species are traditionally identified by their O antigens. This study developed a DNA microarray targeting O-serotype-specific genes to detect all 34 distinct O-antigen forms of Shigella, including Shigella boydii types 1-18, Shigella dysenteriae types 1-13, Shigella flexneri types 1-5 and 6, and Shigella sonnei. A total of 282 strains were used to test the specificity of the microarray, including 186 Shigella and Escherichia coli representative strains, 86 Shigella clinical isolates and ten strains of other bacterial species that are commonly isolated from food or clinical stool specimens. The oligonucleotide probes were printed on the microarray in concentrations from 1 to 100 muM, and 10 muM proved to be the optimal probe concentration. The detection sensitivity for each serotype was 50 ng genomic DNA or 1 c.f.u. in 25 g milk powder sample following a 6 h enrichment in broth. The microarray is specific, sensitive and reproducible, and, to our knowledge, is the first report of a microarray for serotyping all O-antigen forms of Shigella.


Assuntos
Antígenos O/genética , Análise de Sequência com Séries de Oligonucleotídeos/métodos , Shigella/genética , Shigella/isolamento & purificação , DNA Bacteriano/classificação , DNA Bacteriano/genética , Escherichia coli/classificação , Escherichia coli/isolamento & purificação , Sondas de Oligonucleotídeos , Reação em Cadeia da Polimerase , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Sorotipagem , Shigella/classificação
8.
J Clin Microbiol ; 46(11): 3555-63, 2008 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-18753345

RESUMO

The 16S-23S rRNA gene internal transcribed spacer (ITS) regions of Klebsiella spp., including Klebsiella pneumoniae subsp. pneumoniae, Klebsiella pneumoniae subsp. ozaenae, Klebsiella pneumoniae subsp. rhinoscleromatis, Klebsiella oxytoca, Klebsiella planticola, Klebsiella terrigena, and Klebsiella ornithinolytica, were characterized, and the feasibility of using ITS sequences to discriminate Klebsiella species and subspecies was explored. A total of 336 ITS sequences from 21 representative strains and 11 clinical isolates of Klebsiella were sequenced and analyzed. Three distinct ITS types-ITS(none) (without tRNA genes), ITS(glu) [with a tRNA(Glu (UUC)) gene], and ITS(ile+ala) [with tRNA(Ile (GAU)) and tRNA(Ala (UGC)) genes]-were detected in all species except for K. pneumoniae subsp. rhinoscleromatis, which has only ITS(glu) and ITS(ile+ala). The presence of ITS(none) in Enterobacteriaceae had never been reported before. Both the length and the sequence of each ITS type are highly conserved within the species, with identity levels from 0.961 to 1.000 for ITS(none), from 0.967 to 1.000 for ITS(glu), and from 0.968 to 1.000 for ITS(ile+ala). Interspecies sequence identities range from 0.775 to 0.989 for ITS(none), from 0.798 to 0.997 for ITS(glu), and from 0.712 to 0.985 for ITS(ile+ala). Regions with significant interspecies variations but low intraspecies polymorphisms were identified; these may be targeted in the design of probes for the identification of Klebsiella to the species level. Phylogenetic analysis based on ITS regions reveals the relationships among Klebsiella species similarly to that based on 16S rRNA genes.


Assuntos
DNA Bacteriano/genética , DNA Espaçador Ribossômico/genética , Klebsiella/classificação , Klebsiella/genética , Sequência Conservada , DNA Bacteriano/química , DNA Espaçador Ribossômico/química , Genes Bacterianos , Humanos , Klebsiella/isolamento & purificação , Infecções por Klebsiella/microbiologia , Dados de Sequência Molecular , Filogenia , Polimorfismo Genético , RNA de Transferência/genética , Análise de Sequência de DNA , Homologia de Sequência do Ácido Nucleico
9.
Int J Food Microbiol ; 125(3): 230-5, 2008 Jul 31.
Artigo em Inglês | MEDLINE | ID: mdl-18579248

RESUMO

A PCR detection based on 16S-23S rDNA internal transcribed spacer (ITS) of Klebsiella pneumoniae was developed in the present study. Nineteen different ITS sequences were amplified from 6 strains of K. pneumoniae by universal primers. By sequencing and alignment of these sequences to the other homologous in GenBank, species-specific primers of K. pneumoniae, Pf/Pr1 and Pf/Pr2, were designed for amplification of the ITS sequence from the operon containing tDNA(Ala) and tDNA(Ile). Ten type strains and 21 isolates of K. pneumoniae were positive to the PCR detection, and all of the non-K. pneumoniae reference strains (79 strains) were negative. The enrichment was performed in this procedure with a modified growth media to enrich K. pneumoniae from 1.5 CFU/100 g infant formula to about 10(5) CFU/ml in 900 ml of the media. Combination of the enrichment, with the PCR assay can detect 1.5 CFU/100 g infant formula of K. pneumoniae within 48 h. Furthermore, K. pneumoniae strains KPE050803 and KPE 050830 were identified by this method in 63 infant formula samples.


Assuntos
DNA Bacteriano/genética , DNA Intergênico/genética , Contaminação de Alimentos/análise , Alimentos Infantis/microbiologia , Klebsiella pneumoniae/isolamento & purificação , Reação em Cadeia da Polimerase/métodos , Sequência de Bases , DNA Espaçador Ribossômico , Microbiologia de Alimentos , Amplificação de Genes , Humanos , Lactente , Fórmulas Infantis , Recém-Nascido , Klebsiella pneumoniae/classificação , Klebsiella pneumoniae/genética , Dados de Sequência Molecular , RNA Ribossômico 16S/genética , RNA Ribossômico 23S/genética , Ribotipagem , Análise de Sequência , Especificidade da Espécie
10.
J Microbiol Methods ; 65(1): 21-31, 2006 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-16081174

RESUMO

Enterobacter sakazakii is an emerging pathogen that causes meningitis, bacteremia, sepsis, and necrotizing enterocolitis in neonates and children. Powdered milk-based infant formulas have been associated with the E. sakazakii-related outbreaks in premature or other immunocompromised infants. In this study, we developed two real time PCR assays using TaqMan and SYBR Green to identify the pathogen after selective enrichment in mLST and BHI. The accuracy of two detections was tested by 35 strains of E. sakazakii and 88 non-E. sakazakii bacterial strains. The results showed that all of these E. sakazakii strains were positive reaction to the detections and all of the non-E. sakazakii strains were negative. The newly developed assays enable us to detect 1.1 CFU/100 g infant formula. And both of the assays can be accomplished within 2 business days. Compared to the traditional detection, the real time PCR procedures are quicker and simpler. In this study, we also developed a new method to design the primers, which can support multiple real time PCR with one pair of primers in SYBR Green detection. The detection methods are more sensitive and effective based on Two-Tm-Value of PCR.


Assuntos
Cronobacter sakazakii/genética , Microbiologia de Alimentos , Fórmulas Infantis , Leite/microbiologia , Reação em Cadeia da Polimerase/métodos , Animais , Sequência de Bases , Bovinos , DNA Bacteriano/química , DNA Bacteriano/genética , DNA Espaçador Ribossômico/química , DNA Espaçador Ribossômico/genética , Dados de Sequência Molecular , Compostos Orgânicos/química , RNA Ribossômico 16S/química , RNA Ribossômico 16S/genética , RNA Ribossômico 23S/química , RNA Ribossômico 23S/genética , Sensibilidade e Especificidade , Análise de Sequência de DNA , Taq Polimerase/química
11.
Mol Cell Probes ; 20(1): 11-7, 2006 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-16226871

RESUMO

Enterobacter sakazakii has been implicated in a several form of neonatal meningitis with a high mortality rate. In the present study, the species-specific PCR and oligonucleotide array assays were developed to detect the 16S-23S rDNA internal transcribed spacer (ITS) of E. sakazakii. Two pairs of specific PCR primers and 10 oligonucleotide probes were designed by sequencing the ITS of six strains of E. sakazakii and BLAST of GenBank. The specificity and efficiency of the PCR and oligonucleotide array methods were tested against a panel of numerous strains from 88 different bacterial strains. All of the E. sakazakii strains generated positive signal, and no cross-reaction was observed with non-E. sakazakii strains in the PCR and oligonucleotide array detections based on ITS sequences. Sensitivity of the detections is 1.3 CFU/100 g infant formula with the selective enrichment. Both of the PCR and oligonucleotide array procedures take only 48 h including the enrichment culture, whereas the conventional methods required at least 5 days. This study demonstrated that both of the pathogenic detections are time-saved and reliable.


Assuntos
Cronobacter sakazakii/genética , Contaminação de Alimentos , Microbiologia de Alimentos , Fórmulas Infantis , Análise de Sequência com Séries de Oligonucleotídeos/métodos , Reação em Cadeia da Polimerase/métodos , Humanos , Lactente , Sensibilidade e Especificidade
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