Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 15 de 15
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
BMC Oral Health ; 22(1): 179, 2022 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-35568838

RESUMO

BACKGROUNDS: To compare the irrigation efficiency with different needle working length and different root canal curvature based on a real unshaped root canal using computational fluid dynamics (CFD) method. METHODS: Images of the root canal of the maxillary first molar after being prepared to .04/15 were scanned using micro-CT, and then imported into the software for three-dimensional reconstruction. A palatal root canal with a curvature of 23.4° was selected as the experiment canal. The needle working length of the 30-G flat needle was 4.75 mm, 5 mm, 5.25 mm and 5.5 mm short of apical foramen respectively, the flow pattern, irrigation velocity, shear stress were compared. The modified curved canals with a curvature of 0°, 5°, 10°, 20° and 30°were reconstructed via software. The flat needle was replaced at the optical inserted depth, and key parameters of irrigation efficiency were analyzed. RESULTS: Decreased needle working length had a positive impact on irrigation efficiency. With the optimal needle working length, the replacement of the apical irrigation fluid, the effective velocity, and wall shear stress were significantly improved in more severely curved root canals. With the same needle working depth and analogous canal curvature, irrigation efficiency is higher in real canal than that of modified canal. CONCLUSIONS: Short needle working depth, large curvature and the anomalous inner wall of canals help to improve irrigation efficiency.

2.
Plant Biotechnol J ; 20(3): 437-453, 2022 03.
Artigo em Inglês | MEDLINE | ID: mdl-34655511

RESUMO

Starch accounts for over 80% of the total dry weight in cereal endosperm and determines the kernel texture and nutritional quality. Amyloplasts, terminally differentiated plastids, are responsible for starch biosynthesis and storage. We screened a series of rice mutants with floury endosperm to clarify the mechanism underlying amyloplast development and starch synthesis. We identified the floury endosperm19 (flo19) mutant which shows opaque of the interior endosperm. Abnormal compound starch grains (SGs) were present in the endosperm cells of the mutant. Molecular cloning revealed that the FLO19 allele encodes a plastid-localized pyruvate dehydrogenase complex E1 component subunit α1 (ptPDC-E1-α1) that is expressed in all rice tissues. In vivo enzyme assays demonstrated that the flo19 mutant showed decreased activity of the plastidic pyruvate dehydrogenase complex. In addition, the amounts of monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG) were much lower in the developing flo19 mutant endosperm, suggesting that FLO19 participates in fatty acid supply for galactolipid biosynthesis in amyloplasts. FLO19 overexpression significantly increased seed size and weight, but did not affect other important agronomic traits, such as panicle length, tiller number and seed setting rate. An analysis of single nucleotide polymorphism data from a panel of rice accessions identified that the pFLO19L haplotype was positively associated with grain length, implying a potential application in rice breeding. In summary, our study demonstrates that FLO19 is involved in galactolipid biosynthesis which is essential for amyloplast development and starch biosynthesis in rice.


Assuntos
Oryza , Grão Comestível , Endosperma/metabolismo , Galactolipídeos , Regulação da Expressão Gênica de Plantas , Mutação/genética , Melhoramento Vegetal , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Plastídeos/metabolismo , Complexo Piruvato Desidrogenase , Amido/metabolismo
3.
Ann Work Expo Health ; 66(4): 520-536, 2022 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-34365499

RESUMO

STOFFENMANAGER® and the Advanced REACH Tool (ART) are recommended tools by the European Chemical Agency for regulatory chemical safety assessment. The models are widely used and accepted within the scientific community. STOFFENMANAGER® alone has more than 37 000 users globally and more than 310 000 risk assessment have been carried out by 2020. Regardless of their widespread use, this is the first study evaluating the theoretical backgrounds of each model. STOFFENMANAGER® and ART are based on a modified multiplicative model where an exposure base level (mg m-3) is replaced with a dimensionless intrinsic emission score and the exposure modifying factors are replaced with multipliers that are mainly based on subjective categories that are selected by using exposure taxonomy. The intrinsic emission is a unit of concentration to the substance emission potential that represents the concentration generated in a standardized task without local ventilation. Further information or scientific justification for this selection is not provided. The multipliers have mainly discrete values given in natural logarithm steps (…, 0.3, 1, 3, …) that are allocated by expert judgements. The multipliers scientific reasoning or link to physical quantities is not reported. The models calculate a subjective exposure score, which is then translated to an exposure level (mg m-3) by using a calibration factor. The calibration factor is assigned by comparing the measured personal exposure levels with the exposure score that is calculated for the respective exposure scenarios. A mixed effect regression model was used to calculate correlation factors for four exposure group [e.g. dusts, vapors, mists (low-volatiles), and solid object/abrasion] by using ~1000 measurements for STOFFENMANAGER® and 3000 measurements for ART. The measurement data for calibration are collected from different exposure groups. For example, for dusts the calibration data were pooled from exposure measurements sampled from pharmacies, bakeries, construction industry, and so on, which violates the empirical model basic principles. The calibration databases are not publicly available and thus their quality or subjective selections cannot be evaluated. STOFFENMANAGER® and ART can be classified as subjective categorization tools providing qualitative values as their outputs. By definition, STOFFENMANAGER® and ART cannot be classified as mechanistic models or empirical models. This modeling algorithm does not reflect the physical concept originally presented for the STOFFENMANAGER® and ART. A literature review showed that the models have been validated only at the 'operational analysis' level that describes the model usability. This review revealed that the accuracy of STOFFENMANAGER® is in the range of 100 000 and for ART 100. Calibration and validation studies have shown that typical log-transformed predicted exposure concentration and measured exposure levels often exhibit weak Pearson's correlations (r is <0.6) for both STOFFENMANAGER® and ART. Based on these limitations and performance departure from regulatory criteria for risk assessment models, it is recommended that STOFFENMANAGER® and ART regulatory acceptance for chemical safety decision making should be explicitly qualified as to their current deficiencies.


Assuntos
Exposição Ocupacional , Algoritmos , Monitoramento Ambiental , Humanos , Exposição Ocupacional/análise , Medição de Risco , Ventilação
4.
Plant Physiol ; 187(4): 2174-2191, 2021 12 04.
Artigo em Inglês | MEDLINE | ID: mdl-33871646

RESUMO

Protein storage vacuoles (PSVs) are unique organelles that accumulate storage proteins in plant seeds. Although morphological evidence points to the existence of multiple PSV-trafficking pathways for storage protein targeting, the molecular mechanisms that regulate these processes remain mostly unknown. Here, we report the functional characterization of the rice (Oryza sativa) glutelin precursor accumulation7 (gpa7) mutant, which over-accumulates 57-kDa glutelin precursors in dry seeds. Cytological and immunocytochemistry studies revealed that the gpa7 mutant exhibits abnormal accumulation of storage prevacuolar compartment-like structures, accompanied by the partial mistargeting of glutelins to the extracellular space. The gpa7 mutant was altered in the CCZ1 locus, which encodes the rice homolog of Arabidopsis (Arabidopsis thaliana) CALCIUM CAFFEINE ZINC SENSITIVITY1a (CCZ1a) and CCZ1b. Biochemical evidence showed that rice CCZ1 interacts with MONENSIN SENSITIVITY1 (MON1) and that these proteins function together as the Rat brain 5 (Rab5) effector and the Rab7 guanine nucleotide exchange factor (GEF). Notably, loss of CCZ1 function promoted the endosomal localization of vacuolar protein sorting-associated protein 9 (VPS9), which is the GEF for Rab5 in plants. Together, our results indicate that the MON1-CCZ1 complex is involved in post-Golgi trafficking of rice storage protein through a Rab5- and Rab7-dependent pathway.


Assuntos
Glutens/genética , Glutens/metabolismo , Oryza/genética , Oryza/metabolismo , Sementes/metabolismo , Proteínas de Transporte Vesicular/metabolismo , Proteínas rab de Ligação ao GTP/metabolismo , China , Produtos Agrícolas/genética , Produtos Agrícolas/metabolismo , Regulação da Expressão Gênica de Plantas , Genes de Plantas , Variação Genética , Genótipo , Mutação , Sementes/genética , Proteínas de Transporte Vesicular/genética , Proteínas rab de Ligação ao GTP/genética
5.
J Integr Plant Biol ; 63(5): 834-847, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33283410

RESUMO

Pentatricopeptide repeat (PPR) proteins, composing one of the largest protein families in plants, are involved in RNA binding and regulation of organelle RNA metabolism at the post-transcriptional level. Although several PPR proteins have been implicated in endosperm development in rice (Oryza sativa), the molecular functions of many PPRs remain obscure. Here, we identified a rice endosperm mutant named floury endosperm 18 (flo18) with pleiotropic defects in both reproductive and vegetative development. Map-based cloning and complementation tests showed that FLO18 encodes a mitochondrion-targeted P-type PPR protein with 15 PPR motifs. Mitochondrial function was disrupted in the flo18 mutant, as evidenced by decreased assembly of Complex I in the mitochondrial electron transport chain and altered mitochondrial morphology. Loss of FLO18 function resulted in defective 5'-end processing of mitochondrial nad5 transcripts encoding subunit 5 of nicotinamide adenine dinucleotide hydrogenase. These results suggested that FLO18 is involved in 5'-end processing of nad5 messenger RNA and plays an important role in mitochondrial function and endosperm development.


Assuntos
Endosperma/metabolismo , Oryza/metabolismo , Proteínas de Plantas/metabolismo , Complexo I de Transporte de Elétrons/genética , Complexo I de Transporte de Elétrons/metabolismo , Regulação da Expressão Gênica de Plantas , Mitocôndrias/metabolismo , Proteínas Mitocondriais/genética , Proteínas Mitocondriais/metabolismo , Oryza/genética , Proteínas de Plantas/genética , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , RNA Mitocondrial/genética , RNA Mitocondrial/metabolismo
6.
Psychiatry Res ; 291: 113190, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32563745

RESUMO

The coronavirus disease 2019 (COVID-19) pandemic has caused enormous psychological impact worldwide. We conducted a systematic review and meta-analysis on the psychological and mental impact of COVID-19 among healthcare workers, the general population, and patients with higher COVID-19 risk published between 1 Nov 2019 to 25 May 2020. We conducted literature research using Embase, PubMed, Google scholar and WHO COVID-19 databases. Among the initial search of 9207 studies, 62 studies with 162,639 participants from 17 countries were included in the review. The pooled prevalence of anxiety and depression was 33% (95% confidence interval: 28%-38%) and 28% (23%-32%), respectively. The prevalence of anxiety and depression was the highest among patients with pre-existing conditions and COVID-19 infection (56% [39%-73%] and 55% [48%-62%]), and it was similar between healthcare workers and the general public. Studies from China, Italy, Turkey, Spain and Iran reported higher-than-pooled prevalence among healthcare workers and the general public. Common risk factors included being women, being nurses, having lower socioeconomic status, having high risks of contracting COVID-19, and social isolation. Protective factors included having sufficient medical resources, up-to-date and accurate information, and taking precautionary measures. In conclusion, psychological interventions targeting high-risk populations with heavy psychological distress are in urgent need.


Assuntos
Ansiedade/epidemiologia , Betacoronavirus , Infecções por Coronavirus/psicologia , Depressão/epidemiologia , Pessoal de Saúde/psicologia , Pneumonia Viral/psicologia , Ansiedade/psicologia , COVID-19 , China/epidemiologia , Depressão/psicologia , Humanos , Pandemias , Prevalência , SARS-CoV-2
7.
Environ Sci Pollut Res Int ; 27(18): 22414-22422, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32314292

RESUMO

The Sinkiang Uygur Autonomous Region is located in western China and the centre of the Asian-European continent, which frequently suffers from sandstorm disasters and haze weathers. A 1-year measurement campaign in two selected points in Shihezi and Urumqi of Sinkiang was conducted to characterise the effects of particle matters and factors on particle extinction under different weather conditions. Results showed that the average concentration of PM1-2.5 was 19.83, 9.230, 28.93 and 122.4 µg/m3 in Shihezi and 67.25, 16.80, 59.19 and 324.0 µg/m3 in Urumqi for spring, summer, autumn and winter, respectively. PM5-10 concentrations can reach up to 500.0 and 160.0 µg/m3 during polluted weather conditions in Shihezi and Urumqi, respectively. PM5-10 also accounted for the largest fraction in Shihezi and Urumqi for all types of weather, reaching up to 40.0% under dusty weather conditions. PM1-2.5 significantly increased during winter possibly due to the increased demand for heating compared with non-heating periods. PM0.5-1 is possibly produced from motor vehicle exhaust. Particle size is concluded to be the dominant factor for particle extinction capability under fine weather based on calculations of aerosol optical properties. The refractive index for a particle with a diameter of 100 µm (3.10-3.11i) is substantially larger than that with a diameter of 0.5000 µm (1.600-0.07000i), but the extinction capability of the latter is 1.30 times that of the former. Comparatively, when the mass concentration of coarse particles is over 17.0 times that of the fine particles, and then mass concentration becomes the dominant factor. Therefore, visibility is negatively correlated to particle mass variations during dust storms and hazy days but not for fine days.


Assuntos
Poluentes Atmosféricos/análise , Material Particulado/análise , Aerossóis/análise , China , Monitoramento Ambiental , Tamanho da Partícula , Estações do Ano , Tempo (Meteorologia)
8.
Plant Mol Biol ; 100(6): 635-645, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31147815

RESUMO

KEY MESSAGE: Rice WSL6 is involved in chloroplast ribosome biogenesis and is essential for early chloroplast development. Construction of the genetic translation system is a prerequisite for chloroplast development in plants. However, the molecular mechanism underlying this process is largely unknown. Here, we isolated a white stripe leaf6 (wsl6) mutant in rice. The mutant seedlings displayed white-striped leaves that were more severe under low-temperature conditions. Transmission electron microscopy analysis showed that the wsl6 mutant was defective in early chloroplast development. Map-based cloning revealed that WSL6 encodes an Era-type guanosine-5'-triphosphate (GTP)-binding protein located in chloroplasts. Immunoblotting and quantitative real-time polymerase chain reaction (qRT-PCR) analyses demonstrated an absence of 70S ribosomes in wsl6 chloroplasts. Further research showed that WSL6 binds to the 16S ribosomal RNA (rRNA) subunit of chloroplast ribosome 30S. In summary, these results show that WSL6 is essential for chloroplast ribosome biogenesis during early chloroplast development in rice.


Assuntos
Cloroplastos/fisiologia , Proteínas de Ligação ao GTP/metabolismo , Oryza/genética , Proteínas de Plantas/genética , Clonagem Molecular , Proteínas de Ligação ao GTP/fisiologia , Regulação da Expressão Gênica de Plantas , Teste de Complementação Genética , Microscopia Eletrônica de Transmissão , Mutação , Oryza/fisiologia , Fenótipo , Pigmentação , Proteínas de Plantas/fisiologia , Biossíntese de Proteínas , RNA Ribossômico 16S/genética , Temperatura
9.
J Environ Sci (China) ; 72: 98-106, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30244755

RESUMO

Cooking fume produced by oil and food at a high temperature releases large amount of fine particulate matter (PM) which have a potential hazard to human health. This chamber study investigated particle emission characteristics originated from using four types of oil (soybean oil, olive oil, peanut oil and lard) and different kinds of food materials (meat and vegetable). The corresponding emission factors (EFs) of number, mass, surface area and volume for particles were discussed. Temporal variation of size-fractionated particle concentration showed that olive oil produced the highest number PM concentration for the entire cooking process. Multiple path particle dosimetry (MPPD) model was performed to predict deposition in the human respiratory tract. Results showed that the pulmonary airway deposition fraction was the largest. It was also found that particles produced from olive oil led to the highest deposition. We strongly recommend minimizing the moisture content of ingredients before cooking and giving priority to the use of peanut oil instead of olive oil to reduce human exposure to PM.


Assuntos
Poluição do Ar em Ambientes Fechados/estatística & dados numéricos , Culinária/métodos , Monitoramento Ambiental , Exposição por Inalação/estatística & dados numéricos , Material Particulado/análise , Poluição do Ar em Ambientes Fechados/análise , China , Culinária/estatística & dados numéricos , Humanos
10.
Sci Total Environ ; 630: 1283-1291, 2018 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-29554749

RESUMO

Nanoscale TiO2 (nTiO2) is manufactured in high volumes and is of potential concern in occupational health. Here, we measured workers exposure levels while ceramic honeycombs were dip coated with liquid photoactive nanoparticle suspension and dried with an air blade. The measured nTiO2 concentration levels were used to assess process specific emission rates using a convolution theorem and to calculate inhalation dose rates of deposited nTiO2 particles. Dip coating did not result in detectable release of particles but air blade drying released fine-sized TiO2 and nTiO2 particles. nTiO2 was found in pure nTiO2 agglomerates and as individual particles deposited onto background particles. Total particle emission rates were 420×109min-1, 1.33×109µm2min-1, and 3.5mgmin-1 respirable mass. During a continued repeated process, the average exposure level was 2.5×104cm-3, 30.3µm2cm-3, <116µgm-3 for particulate matter. The TiO2 average exposure level was 4.2µgm-3, which is well below the maximum recommended exposure limit of 300µgm-3 for nTiO2 proposed by the US National Institute for Occupational Safety and Health. During an 8-hour exposure, the observed concentrations would result in a lung deposited surface area of 4.3×10-3cm2g-1 of lung tissue and 13µg of TiO2 to the trachea-bronchi, and alveolar regions. The dose levels were well below the one hundredth of the no observed effect level (NOEL1/100) of 0.11cm2g-1 for granular biodurable particles and a daily no significant risk dose level of 44µgday-1. These emission rates can be used in a mass flow model to predict the impact of process emissions on personal and environmental exposure levels.


Assuntos
Filtros de Ar , Poluentes Ocupacionais do Ar/análise , Exposição por Inalação/prevenção & controle , Exposição Ocupacional/prevenção & controle , Cerâmica , Monitoramento Ambiental , Humanos , Nanopartículas , Tamanho da Partícula , Material Particulado , Titânio
11.
Chemosphere ; 191: 962-970, 2018 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-29145141

RESUMO

Mosquito-repellent incense is one of the most popular products used for dispelling mosquitos during summer in China. It releases large amounts of particulate and gaseous pollutants which constitute a potential hazard to human health. We conducted chamber experiment to characterize major pollutants from three types of mosquito-repellent incenses, further assessed the size-fractionated deposition in human respiratory system, and evaluated the indoor removing efficiency by fresh air. Results showed that the released pollutant concentrations were greater than permissible levels in regulations in GB3095-2012, as well as suggested by the World Health Organization (WHO). Formaldehyde accounted for 10-20% of the total amount of pollutants. Fine particles dominated in the total particulate concentrations. Geometric standard deviation (GSD) of particle number size distributions was in the range of 1.45-1.93. Count median diameter (CMD) ranged from 100 to 500 nm. Emission rates, burning rates and emission factors of both particulate and gaseous pollutants were compared and discussed. The deposition fractions in pulmonary airway from the disc solid types reached up to 52.7% of the total deposition, and the largest deposition appeared on juvenile group. Computational Fluid Dynamics (CFD) modellings indicated air-conditioner on and windows closed was the worst case. The highest concentration was 180-200 times over the standard limit.


Assuntos
Poluentes Atmosféricos/análise , Repelentes de Insetos/análise , Poluição do Ar em Ambientes Fechados/análise , Animais , China , Culicidae , Formaldeído/análise , Humanos , Repelentes de Insetos/toxicidade , Tamanho da Partícula , Material Particulado/análise , Medição de Risco
12.
Chemosphere ; 190: 9-16, 2018 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-28972921

RESUMO

Urban public parks provide a recreational environment for residents, hence more and more citizens would spend time in parks, especially elderly and kids. Therefore, it is important to evaluate the quality of ecological environment inside parks. Therefore, this study conducted the first measurements in ten public parks of Shanghai to investigate heavy metals in air, soil and leaf, growth parameters of leaf, and ambient PM2.5 and black carbon (BC) concentrations. Results showed Al and Mg appeared the highest in air. Cr, Cu, Mn and Zn were dominating in soil. Ca and Mg were much greater in leaves. It was concluded geographical locations were major reasons to explain the level of heavy metals, which mainly came from vehicle emissions. A small portion was attributing to chemical industries nearby. PM2.5 concentrations ranged from 0.01 mg/m3 to 0.10 mg/m3, which met up level I and level II of air quality standard in China. BC concentrations ranged from 1000 ng/m3 to 6000 ng/m3. Via comparing the correlation between photosynthesis and PM2.5, as well as chlorophyll content and PM2.5, it was concluded that chlorophyll can be regarded as an indicator for assessing air quality, but not photosynthesis. Unexpectedly, a positive correlation was observed between the stomatal conductance and PM2.5 as well as BC, which might be attributed to plants resisting the ambient stress. The results of this study can be used for assessments of air quality and health exposure inside parks, and also could provide urban policy maker with scientific evidences for urban park planning.


Assuntos
Poluição do Ar , Monitoramento Ambiental/métodos , Metais Pesados/análise , Parques Recreativos , Poluentes Atmosféricos/análise , China , Clorofila/análise , Humanos , Material Particulado/análise , Folhas de Planta/química , Poluentes do Solo/análise , Inquéritos e Questionários , Emissões de Veículos/análise
13.
Sci Total Environ ; 621: 1300-1309, 2018 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-29054635

RESUMO

Cooking emission is one of sources for ambient volatile organic compounds (VOCs), which is deleterious to air quality, climate and human health. These emissions are especially of great interest in large cities of East and Southeast Asia. We conducted a case study in which VOC emissions from kitchen extraction stacks have been sampled in total 57 times in the Megacity Shanghai. To obtain representative data, we sampled VOC emissions from kitchens, including restaurants of seven common cuisine types, canteens, and family kitchens. VOC species profiles and their chemical reactivities have been determined. The results showed that 51.26%±23.87% of alkane and 24.33±11.69% of oxygenated VOCs (O-VOCs) dominate the VOC cooking emissions. Yet, the VOCs with the largest ozone formation potential (OFP) and secondary organic aerosol potential (SOAP) were from the alkene and aromatic categories, accounting for 6.8-97.0% and 73.8-98.0%, respectively. Barbequing has the most potential of harming people's heath due to its significant higher emissions of acetaldehyde, hexanal, and acrolein. Methodologies for calculating VOC emission factors (EF) for restaurants that take into account VOCs emitted per person (EFperson), per kitchen stove (EFkitchen stove) and per hour (EFhour) are developed and discussed. Methodologies for deriving VOC emission inventories (S) from restaurants are further defined and discussed based on two categories: cuisine types (Stype) and restaurant scales (Sscale). The range of Stype and Sscale are 4124.33-7818.04t/year and 1355.11-2402.21t/year, respectively. We also found that Stype and Sscale for 100,000 people are 17.07-32.36t/year and 5.61-9.95t/year, respectively. Based on Environmental Kuznets Curve, the annual total amount of VOCs emissions from catering industry in different provinces in China was estimated, which was 5680.53t/year, 6122.43t/year, and 66,244.59t/year for Shangdong and Guangdong provinces and whole China, respectively. Large and medium-scaled restaurants should be paid more attention with respect to regulation of VOCs.


Assuntos
Poluentes Atmosféricos/análise , Culinária , Monitoramento Ambiental , Compostos Orgânicos Voláteis/análise , China , Cidades , Humanos , Ozônio
14.
Int J Environ Res Public Health ; 11(5): 5382-402, 2014 May 16.
Artigo em Inglês | MEDLINE | ID: mdl-24840353

RESUMO

This study considers fundamental methods in occupational risk assessment of exposure to airborne engineered nanomaterials. We discuss characterization of particle emissions, exposure assessment, hazard assessment with in vitro studies, and risk range characterization using calculated inhaled doses and dose-response translated to humans from in vitro studies. Here, the methods were utilized to assess workers' risk range of inhalation exposure to nanodiamonds (NDs) during handling and sieving of ND powder. NDs were agglomerated to over 500 nm particles, and mean exposure levels of different work tasks varied from 0.24 to 4.96 µg·m(-3) (0.08 to 0.74 cm(-3)). In vitro-experiments suggested that ND exposure may cause a risk for activation of inflammatory cascade. However, risk range characterization based on in vitro dose-response was not performed because accurate assessment of delivered (settled) dose on the cells was not possible. Comparison of ND exposure with common pollutants revealed that ND exposure was below 5 µg·m(-3), which is one of the proposed exposure limits for diesel particulate matter, and the workers' calculated dose of NDs during the measurement day was 74 ng which corresponded to 0.02% of the modeled daily (24 h) dose of submicrometer urban air particles.


Assuntos
Poluentes Ocupacionais do Ar/análise , Monitoramento Ambiental , Exposição por Inalação , Nanodiamantes/análise , Exposição Ocupacional , Poluentes Ocupacionais do Ar/toxicidade , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Citocinas/metabolismo , Humanos , Nanodiamantes/toxicidade , Medição de Risco
15.
J Colloid Interface Sci ; 336(1): 142-9, 2009 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-19394954

RESUMO

The newly proposed Taylor-expansion moment method (TEMOM) is extended to solve agglomerate coagulation in the free-molecule regime and in the continuum regime, respectively. The moment equations with respect to fractal dimension are derived based on 3rd Taylor-series expansion technique. The validation of this method is done by comparing its result with the published data at each limited size regime. By comparing with analytical method, sectional method (SM) and quadrature method of moments (QMOMs), this new approach is shown to produce the most efficiency without losing much accuracy. At each limited size regime, the effect of fractal dimension on the decay of particle number and particle size growth is mainly investigated, and especially in the continuum regime the relation of mean diameters of size distributions with different fractal dimensions is first proposed. The agglomerate size distribution is found to be sensitive to the fractal dimension and the initial geometric mean deviation before the self-preserving size distribution is achieved in the continuum regime.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...