Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 19 de 19
Filtrar
1.
Int J Geriatr Psychiatry ; 38(10): e6010, 2023 10.
Artigo em Inglês | MEDLINE | ID: mdl-37794769

RESUMO

OBJECTIVES: The proportion of older people with dementia in China is gradually increasing with the increase in the aging population over recent years. Hypertension and diabetes are common non-communicable diseases among rural populations in China. However, it remains unclear whether these conditions affect the occurrence and development of cognitive impairment as there is limited research on cognitive status and its risk factors among residents of rural areas. METHODS: A multi-stage stratified cluster random sampling method was used to select 5400 participants from rural permanent residents. A self-designed structured questionnaire was used to investigate demographic data of the participants. Cognitive function was assessed using the Montreal Cognitive Function Assessment Scale (MoCA). The results were analyzed using chi-square test, ANOVA and multiple linear regression analysis. RESULTS: A total of 5028 participants returned the survey, giving a response rate of 93.1%. Higher education (odds ratio (OR) = 3.2, 95% confidence interval (CI) 2.87-3.54, p < 0.001), higher income (OR = 1.61, 95% CI 1.16-2.07, p < 0.001), and dietary control (OR = 0.66, 95%CI 0.34-0.98, p < 0.001) were protective factors. A visual representation of the relationship between annual income and MoCA score showed an inverted U-curve, the group with an annual income of 6000-7999 RMB had a maximum OR of 1.93 (95%CI 0.12-2.74, p < 0.001). While difficulty in maintaining sleep were risk factors for cognitive impairment (OR = -2.28, 95% CI-4.18-0.39, p = 0.018). CONCLUSIONS: Participants with middle incomes had better cognitive status than those with the highest incomes. Higher education, proper diet control and good sleep are beneficial to the cognitive status of residents in rural areas.


Assuntos
Diabetes Mellitus , Hipertensão , Humanos , Idoso , Estudos Transversais , População Rural , Fatores de Risco , Hipertensão/epidemiologia , Cognição , China/epidemiologia
2.
Sensors (Basel) ; 18(11)2018 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-30445741

RESUMO

With the development in the exploitation of maritime resources, the structural health monitoring (SHM) of offshore structures becomes necessary. This study focuses on addressing the practical issues of application of fiber Bragg grating (FBG) sensors for the SHM of offshore structures, in particular an FPSO (floating, production, storage, and offloading unit) vessel. Due to the harsh marine environment and tough working conditions, the FBG sensors must have sufficient protection and good repeatability for long-term monitoring. Thorough research has been conducted to identify the most suitable, commercially available protection packaging for FBG sensors for offshore applications. Further, the performance of the selected FBG sensor packaging is tested under conditions of strong sunlight, heavy rain, and salty water in order to emulate the marine environment. Moreover, the installation method of the packaged FBG sensors is equally important, as it ensures the repeatability and durability of the sensors for their long-term performance. It is shown that the packaged FBG sensors can be installed using resin-based epoxy to maintain the repeatability of the sensor over the long-term. Further, the packaged FBG sensors are installed and tested on a simple FPSO model. The experimental results under full load and ballast draft conditions show that the proposed FBG sensors are competent for the SHM of offshore structures.

3.
Breed Sci ; 66(3): 391-5, 2016 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-27436949

RESUMO

Amomum tsaoko is a flexistylous ginger. Flexistyly is a unique floral mechanism promoting outcrossing, which is known only in some species of Zingiberaceae till date. This is a pioneer report on flexistyly in A. tsaoko from the aspect of fructification percentage to clarify its influence on reproduction. We observed in 2007 and 2008 that the fructification percentage of the anaflexistyled and the cataflexistyled inflorescence were 14.89 ± 10.35% and 11.31 ± 7.91% respectively, with significant difference (d.f. = 141.920, t = 2.518, P = 0.013 < 0.05). The greatly significant difference between 2007 and 2008 were present in both the flower number (d.f. = 93, t = -2.819, P = 0.006 < 0.01) and the fructification percentage (d.f. = 93, t = -2.894, P = 0.005 < 0.01) of the cataflexistylous inflorescence. Although the two morphs were similar in morphological characteristics, there was some gender differentiation between them, showing a possibility that the anaflexistylous morph might function more as females and the cataflexistylous morph more as males. Reproduction of the cataflexistylous morph was significantly sensitive to change of environmental factors, in contrast to the anaflexistylous morph, thus the yield varied between the abundant year (2008) and the off year (2007).

4.
Zhong Yao Cai ; 37(3): 388-92, 2014 Mar.
Artigo em Zh | MEDLINE | ID: mdl-25174100

RESUMO

OBJECTIVE: To lay the foundation for quality evaluation of medicinal materials of Amomum tsao-ko and its selection of fine varieties, the variation of percentage of volatile oil in the seeds among populations and individuals and its influencing factors were studied. METHODS: Extracted volatile oil from the seeds according to the Chinese Pharmacopoeia, studied quantitative characters of fruit, and analyzed the data according to SPSS 13.0. RESULTS: The percentage of volatile oil in seeds was greatly significantly different among the 7 populations (P = 0.000 < 0.001), and among different individuals (P = 0.000 < 0.001). A significantly positive correlation was detected between the percentage of volatile oil in seeds and length of fruit (P = 0.024 < 0.05), and significantly negative correlation occurred between the percentage and other quantitative characters or factors, viz. thousand seeds weight (P = 0.031 < 0.05), flower number per inflorescence (P = 0.028 < 0.05), weight of seeds masses per fruit (P = 0.038 < 0.05), altitude (P = 0.014 < 0.05), and latitude (P = 0.000 < 0.001). The regression equation (Y = 1.031 - 1.744 X2 - 1.119 X3 + 2.207 X1) was the optimal regression model of percentage of volatile oil in seeds (X1, X2 and X3 were respectively represented as the length and length-width ratio of fruit,and the weight of seeds masses). CONCLUSION: Environmental factors influence greatly significantly on the percentage of volatile oil in seeds. The production and accumulation of volatile oil would decrease with altitude and latitude increasing. The longer fruit has the higher percentage volatile oil.


Assuntos
Altitude , Amomum/química , Óleos Voláteis/análise , Sementes/química , Amomum/fisiologia , Clima , Ecossistema , Frutas/química , Frutas/fisiologia , Modelos Logísticos , Sementes/fisiologia
5.
Front Public Health ; 12: 1447290, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-39386954

RESUMO

Background: Exposure to occupational metallic mixtures has a potential impact on olfactory function. However, research evidence is limited on the potential impact of exposure to metallic mixtures and olfactory dysfunction. Furthermore, the coal dust generated contains multiple various metals during coal mining, and no study yet has focus on the olfactory dysfunction of coal miners. Objectives: In this study, we evaluate the association between urinary metallic mixtures and olfactory function in coal miners, while also exploring the potential applicability of plasma olfactory marker protein (OMP) as a biomarker for assessing olfaction. Methods: From July to October 2023, coal workers from seven different coal mining enterprises were recruited for the survey when they come for the employee health checkup. Ultimately, 376 participants were met the inclusion criteria and, respectively, determined with the concentrations of urine (16 metals) and plasma (OMP). Meanwhile, applying UPSIT to access their olfactory function. Binary logistic regression and restricted cubic spline (RCS) model were used to estimate the association of individual metals with olfactory function. Bayesian kernel machine regression (BKMR) and Quantile g-computation (QG-C) regression were employed to assess the overall association between metal mixtures and olfactory function and identify the major contributing elements. Results: In a single-metal model, two metals in urine were found to be significantly associated with olfactory function. RCS analysis further revealed that the association between Iron (Fe) and olfactory function was linear, while Lead (Pb) exhibited a non-linear. The BKMR model demonstrated a significant positive association between metal mixture concentration and olfactory function. Combined QG-C regression analysis suggested that metals Cr, Fe, Se, Sb, and Pb could impact the performance of the olfactory test (UPSIT), with Pb being identified as the most influential contributor. The correlation between plasma OMP protein levels and urinary metal concentrations was weak. Conclusion: Multiple metals are associated with olfactory function in the coal miners. A significant positive association was observed between metal mixture concentrations and olfactory function, with Pb being the most important contributor. In this study, plasma OMP has not been demonstrated to serve as a biomarker for olfactory function.


Assuntos
Minas de Carvão , Exposição Ocupacional , Humanos , Masculino , Exposição Ocupacional/efeitos adversos , Exposição Ocupacional/análise , Adulto , Pessoa de Meia-Idade , Biomarcadores/urina , Biomarcadores/sangue , Metais/urina , Metais/sangue , Transtornos do Olfato , Mineradores/estatística & dados numéricos , Feminino , China
6.
Micromachines (Basel) ; 13(11)2022 Nov 09.
Artigo em Inglês | MEDLINE | ID: mdl-36363957

RESUMO

In recent years, vortex-induced vibration (VIV) has been widely employed to collect small-scale wind energy as a renewable energy source for microelectronics and wireless sensors. In this paper, a two-degree-of-freedom (2DOF) VIV-based piezoelectric energy harvester (VIVPEH) was designed, and its aerodynamic characteristics were thoroughly investigated. First, based on the traditional model theory and combined with the knowledge of vibration dynamics, the governing equations of the 2DOF VIVPEH were established. The dynamic responses, including the displacement and voltage output, were numerically simulated. Compared with the traditional 1DOF VIVPEH, the 2DOF VIVPEH proposed in this paper produced two lock-in regions for broadband wind energy harvesting. Furthermore, it was unveiled that the first- and second-order resonances were induced in the first and lock-in regions, respectively. Subsequently, a parametric study was conducted to investigate the influences of the circuit and mechanical parameters on the energy harvesting performance of the 2DOF VIVPEH. It was found that when the 2DOF VIVPEH was induced to vibrate in different lock-in regions, its optimal resistance became different. Moreover, by varying the masses and stiffnesses of the primary and secondary DOFs, we could adjust the lock-in regions in terms of their bandwidths, locations, and amplitudes, which provides a possibility for further customization and optimization.

7.
Sensors (Basel) ; 10(12): 11644-61, 2010.
Artigo em Inglês | MEDLINE | ID: mdl-22163548

RESUMO

The electromechanical (EM) impedance technique using piezoelectric lead zirconate titanate (PZT) transducers for structural health monitoring (SHM) has attracted considerable attention in various engineering fields. In the conventional EM impedance technique, the EM admittance of a PZT transducer is used as a damage indicator. Statistical analysis methods such as root mean square deviation (RMSD) have been employed to associate the damage level with the changes in the EM admittance signatures, but it is difficult to determine the location of damage using such methods. This paper proposes a new approach by dividing the large frequency (30-400 kHz) range into sub-frequency intervals and calculating their respective RMSD values. The RMSD of the sub-frequency intervals (RMSD-S) will be used to study the severity and location of damage. An experiment is carried out on a real size concrete structure subjected to artificial damage. It is observed that damage close to the PZT changes the high frequency range RMSD-S significantly, while the damage far away from the PZT changes the RMSD-S in the low frequency range significantly. The relationship between the frequency range and the PZT sensing region is also presented. Finally, a damage identification scheme is proposed to estimate the location and severity of damage in concrete structures.


Assuntos
Materiais de Construção , Análise de Falha de Equipamento/instrumentação , Chumbo/química , Titânio/química , Transdutores , Zircônio/química , Fenômenos Biomecânicos/fisiologia , Indústria da Construção/instrumentação , Indústria da Construção/métodos , Impedância Elétrica , Engenharia/instrumentação , Engenharia/métodos , Desenho de Equipamento , Análise de Falha de Equipamento/métodos , Humanos , Modelos Teóricos
8.
Sensors (Basel) ; 10(5): 5193-208, 2010.
Artigo em Inglês | MEDLINE | ID: mdl-22399929

RESUMO

During the construction of a concrete structure, strength monitoring is important to ensure the safety of both personnel and the structure. Furthermore, to increase the efficiency of in situ casting or precast of concrete, determining the optimal time of demolding is important for concrete suppliers. Surface bonded lead zirconate titanate (PZT) transducers have been used for damage detection and parameter identification for various engineering structures over the last two decades. In this work, a reusable PZT transducer setup for monitoring initial hydration of concrete and structural health is developed, where a piece of PZT is bonded to an enclosure with two bolts tightened inside the holes drilled in the enclosure. An impedance analyzer is used to acquire the admittance signatures of the PZT. Root mean square deviation (RMSD) is employed to associate the change in concrete strength with changes in the PZT admittance signatures. The results show that the reusable setup is able to effectively monitor the initial hydration of concrete and the structural health. It can also be detached from the concrete for future re-use.

9.
Zhong Yao Cai ; 33(4): 507-10, 2010 Apr.
Artigo em Zh | MEDLINE | ID: mdl-20845775

RESUMO

OBJECTIVE: To study the anatomical structure of endangered alpine medical plant Neopicrorhiza scrophulariiflora and the high altitude adaptability. METHODS: The leaf epidermis character as well as section structure of leaf, aerial stem and rhizome were observed by light microscopical technique. RESULTS: The leaf surface of Neopicrorhiza scrophulariiflora was covered with two kinds of glandular hair, and the stommata was anomocytic type. Moreover, the leaf was isolateral and differed from most of alpine plant. The aerial stem had well-developed mechanical tissue. The rhizome was distributed by well-developed cork layers and collenchyma. Large numbers of aerenchymas distributed widely in leaf, aerial stem and rhizome. CONCLUSION: There existed characteristic traits in Neopicrorhiza scrophulariiflora that adapted the alpine environment, however, there still had some particular character different from other alpine plant. Thus, the adaptive style of alpine plant to high altitude environment was diversity.


Assuntos
Aclimatação/fisiologia , Altitude , Folhas de Planta/anatomia & histologia , Plantas Medicinais/anatomia & histologia , Scrophulariaceae/anatomia & histologia , Adaptação Fisiológica , Conservação dos Recursos Naturais , Ecossistema , Folhas de Planta/ultraestrutura , Caules de Planta/anatomia & histologia , Caules de Planta/ultraestrutura , Plantas Medicinais/crescimento & desenvolvimento , Rizoma/anatomia & histologia , Rizoma/ultraestrutura , Scrophulariaceae/crescimento & desenvolvimento , Scrophulariaceae/ultraestrutura
10.
Zhong Yao Cai ; 33(7): 1034-8, 2010 Jul.
Artigo em Zh | MEDLINE | ID: mdl-21137356

RESUMO

OBJECTIVE: To study the difference of the quantitative multistate character of infructescence of Amomum tsao-ko from five populations, and the correlations between the quantitative multistate character and altitude, longitude and latitude. METHODS: By observing and analyzing the quantitative multistate character of infructescence of Amomum tsao-ko from five populations. RESULTS: There is highly significant difference among the number of flowerlets each inflorescence from five populations. The higher the altitude, the less the number of flowerlets each inflorescence; and the higher the longitude is, the more the number of flowerlets each inflorescence. The temperature and the humidity of the circumstance affects the number of flowerlets each inflorescence. Lower temperature, higher diurnal variation of temperature, and higher diurnal variation of relative humidity causes less number of flowerlets each inflorescence. There is significantly negative correlation between the number of flowerlets each inflorescence and the maturing rate of infructescence. The difference of the maturing rate of infructescence from five populations don't approach significant level. The difference of the maturing rate of infructescence approaches significant level by multiple comparisons between Magnan population and Baoshan population, Gongshan population and Xichou population. There is not significant correlation between the maturing rate of infructescence and the altitude, the longitude and the latitude. CONCLUSION: The factors of the circumstance affects the number of flowerlets each inflorescence. The climate by the change of the altitude affects the number of flowerlets each inflorescence highly significantly. Selecting the fine genetic resources of Amomum tsao-ko for high yielding, the number of flowerlets of inflorescence is not better character. Maybe the difference of the maturing rate of inflorescence is mainly caused by different genetic resources. Analyzing the difference of genetic regenetic resources of Amomum tsao-ko.


Assuntos
Amomum/fisiologia , Frutas/fisiologia , Inflorescência/fisiologia , Altitude , Amomum/crescimento & desenvolvimento , Clima , Ecossistema , Frutas/crescimento & desenvolvimento , Umidade , Inflorescência/crescimento & desenvolvimento
11.
Zhong Yao Cai ; 32(8): 1184-7, 2009 Aug.
Artigo em Zh | MEDLINE | ID: mdl-19960937

RESUMO

OBJECTIVE: To explore the regulation of the growth of fruit of Amomum tsaoko and the factors influencing the weight of fruit. METHODS: To compare and analyze the quantitative multistate character of fruit and seed of Amomum tsaoko. RESULTS: The quantitative multistate character of fruit and seed of Amomum tsaoko in populations and between populations were abundant. There was positive relativity between the rate of fertilization of ovule and the rate of fructify and this indicated the different heredity character among plants. The weight of fruit was mainly decided by the weight of seed regiment, The more the seed quantity, the larger the weight of seed regiment, and the larger the weight of fruit, then the higher the yield. The variety of the weight of fruit and the quantity of seed presented peak form along with the proper order of fruit growth in inflorescence but had no relativity. CONCLUSION: The abundant quantitative multistate character of fruit and seed of Amomum tsaoko provide the abundant materials for selecting good varieties. For high yield we should not only choose plants with high rate of fructify and high rate of fertilization of ovule the, but also pay attention to the influence of pollination to yield.


Assuntos
Amomum/fisiologia , Frutas/fisiologia , Plantas Medicinais/fisiologia , Sementes/fisiologia , Amomum/crescimento & desenvolvimento , Flores/crescimento & desenvolvimento , Flores/fisiologia , Frutas/crescimento & desenvolvimento , Filogenia , Sementes/crescimento & desenvolvimento
12.
Mitochondrial DNA B Resour ; 4(2): 3795-3796, 2019 Oct 26.
Artigo em Inglês | MEDLINE | ID: mdl-33366195

RESUMO

Amomum tsao-ko and Amomum paratsaoko are well known medicinal and edible plants with a strong fragrance and flavour in China. Here, we have sequenced the two complete chloroplast genomes of Amomum tsao-ko and Amomum paratsaoko, which are 163,612 bp and 163,487 bp in length, respectively, and exhibited LSC and SSC regions separated by a pair of inverted repeat regions. The cp genome of A. tsao-ko has 120 annotated genes, including 82 protein-coding genes, while A. paratsaoko has 121 annotated genes, including 83 protein-coding genes. Both cp genomes contained 30 tRNA genes and 8 rRNA genes. Phylogenetic analysis using a total chloroplast genome DNA sequence of 28 species revealed a close relationship between A. tsao-ko and A. paratsaoko with 100% bootstrap value.

13.
Sensors (Basel) ; 8(11): 6846-6859, 2008 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-27873903

RESUMO

Piezoelectric ceramic Lead Zirconate Titanate (PZT) transducers, working on the principle of electromechanical impedance (EMI), are increasingly applied for structural health monitoring (SHM) in aerospace, civil and mechanical engineering. The PZT transducers are usually surface bonded to or embedded in a structure and subjected to actuation so as to interrogate the structure at the desired frequency range. The interrogation results in the electromechanical admittance (inverse of EMI) signatures which can be used to estimate the structural health or integrity according to the changes of the signatures. In the existing EMI method, the monitored structure is only excited by the PZT transducers for the interrogating of EMI signature, while the vibration of the structure caused by the external excitations other than the PZT actuation is not considered. However, many structures work under vibrations in practice. To monitor such structures, issues related to the effects of vibration on the EMI signature need to be addressed because these effects may lead to misinterpretation of the structural health. This paper develops an EMI model for beam structures, which takes into account the effect of beam vibration caused by the external excitations. An experimental study is carried out to verify the theoretical model. A lab size specimen with different external excitations is tested and the effect of vibration on EMI signature is discussed.

14.
Sensors (Basel) ; 8(1): 327-346, 2008 01 21.
Artigo em Inglês | MEDLINE | ID: mdl-27879711

RESUMO

Piezoelectric ceramic Lead Zirconate Titanate (PZT) based electro-mechanicalimpedance (EMI) technique for structural health monitoring (SHM) has been successfullyapplied to various engineering systems. However, fundamental research work on thesensitivity of the PZT impedance sensors for damage detection is still in need. In thetraditional EMI method, the PZT electro-mechanical (EM) admittance (inverse of theimpedance) is used as damage indicator, which is difficult to specify the effect of damage onstructural properties. This paper uses the structural mechanical impedance (SMI) extractedfrom the PZT EM admittance signature as the damage indicator. A comparison study on thesensitivity of the EM admittance and the structural mechanical impedance to the damages ina concrete structure is conducted. Results show that the SMI is more sensitive to the damagethan the EM admittance thus a better indicator for damage detection. Furthermore, this paperproposes a dynamic system consisting of a number of single-degree-of-freedom elementswith mass, spring and damper components to model the SMI. A genetic algorithm isemployed to search for the optimal value of the unknown parameters in the dynamic system.An experiment is carried out on a two-storey concrete frame subjected to base vibrations thatsimulate earthquake. A number of PZT sensors are regularly arrayed and bonded to the framestructure to acquire PZT EM admittance signatures. The relationship between the damageindex and the distance of the PZT sensor from the damage is studied. Consequently, thesensitivity of the PZT sensors is discussed and their sensing region in concrete is derived.

15.
Sensors (Basel) ; 8(1): 271-289, 2008 01 21.
Artigo em Inglês | MEDLINE | ID: mdl-27879708

RESUMO

Reliable structural health monitoring (SHM) including nondestructiveevaluation (NDE) is essential for safe operation of infrastructure systems. Effectivemonitoring of the rock components of civil infrastructures such as tunnels and cavernsremains challenging. The feasibility of employing smart optical fibre sensor (OFS) andpiezoelectric impedance sensor made up of lead zirconate titanate (PZT) forcomprehensive health monitoring of rocks, covering load history monitoring/retrieval aswell as damage assessment is presented in this paper. The rock specimens are subjected tocyclic loading and their conditions are continuously monitored using OFS and PZTsensors. OFS based multiplexed fibre Bragg grating (FBG) sensors are surface bonded onthe rock specimens. Their strain sensing performance is compared with the conventionalelectric strain gauges (ESGs). In addition, PZT patches are also bonded on the specimensto study the damage pattern during different loading cycles. Unlike the FBGs or ESGs,PZT patches are used as bi-functional sensors and actuators, enabling them to be efficientdetectors of incipient damages using the principle of electromechanical impedance. Theexperimental study demonstrated superior performance of these smart FBG and PZTimpedance sensors. This work is expected to be useful for SHM based NDE application ofrock structures such as caverns and tunnels.

16.
Micromachines (Basel) ; 9(12)2018 Dec 17.
Artigo em Inglês | MEDLINE | ID: mdl-30562985

RESUMO

This paper presents an upright piezoelectric energy harvester (UPEH) with cylinder extension along its longitudinal direction. The UPEH can generate energy from low-speed wind by bending deformation produced by vortex-induced vibrations (VIVs). The UPEH has the advantages of less working space and ease of setting up an array over conventional vortex-induced vibration harvesters. The nonlinear distributed modeling method is established based on Euler⁻Bernoulli beam theory and aerodynamic vortex-induced force of the cylinder is obtained by the van der Pol wake oscillator theory. The fluid⁻solid⁻electricity governing coupled equations are derived using Lagrange's equation and solved through Galerkin discretization. The effect of cylinder gravity on the dynamic characteristics of the UPEH is also considered using the energy method. The influences of substrate dimension, piezoelectric dimension, the mass of cylinder extension, and electrical load resistance on the output performance of harvester are studied using the theoretical model. Experiments were carried out and the results were in good agreement with the numerical results. The results showed that a UPEH configuration achieves the maximum power of 635.04 µW at optimum resistance of 250 kΩ when tested at a wind speed of 4.20 m/s. The theoretical results show that the UPEH can get better energy harvesting output performance with a lighter tip mass of cylinder, and thicker and shorter substrate in its synchronization working region. This work will provide the theoretical guidance for studying the array of multiple upright energy harvesters.

17.
Zhong Yao Cai ; 29(2): 110-1, 2006 Feb.
Artigo em Zh | MEDLINE | ID: mdl-16617774

RESUMO

The comparison between the growth of eight populations from Psammosilene tunicoides at Yunnan Province was made by the tissue culture. The initial results showed out two populations from Yunshanping (Lijiang) and Xiaomoyu (Kunming) was dominant than orthers. It would be regard as one of fine germplasm resources for the culture of Psammosilence tunicoides.


Assuntos
Caryophyllaceae/crescimento & desenvolvimento , Plantas Medicinais/crescimento & desenvolvimento , Caryophyllaceae/anatomia & histologia , Caryophyllaceae/classificação , Meios de Cultura , Caules de Planta/crescimento & desenvolvimento , Técnicas de Cultura de Tecidos/métodos
18.
J Air Waste Manag Assoc ; 55(4): 411-4, 2005 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-15887883

RESUMO

Clay that contains kaolinite has been used extensively as a raw material for manufacturing of bricks and china at 900-1100 degrees C. This study used clay to stabilize the contaminant chromium(VI) [Cr(VI)] through a heating process at 500-1100 degrees C. X-ray absorption spectroscopic results indicated that the 500-900 degrees C heating process transformed hazardous Cr(VI) to nontoxic Cr(III); Cr2O3 was the species detected as most abundant. The 1100 degrees C heating process caused the formation of Cr2SiO5, which was not detected in the samples heated at 500-900 degrees C. Fourier transformed extended X-ray absorption fine structure spectra were fitted by use of WinXAS software. Phase shifts and backscatter(ing) amplitudes for specific atom pairs, based on the crystallographic data for CrO3 and Cr2O3, were theoretically calculated with the FEFF software. The processed XAS data show that the first shell coordination numbers were similar to each other as the temperature was increased from 500 to 900 degrees C and 1100 degrees C, implying that their Cr(III) crystallite size was relatively similar. The interatomic distance between the target center element and the first shell for the 500-1100 degrees C samples was 1.98 A. The Debye-Waller factor for the 1100 degrees C sample was increased compared with the 500 and 900 degrees C samples and probably indicates the formation of Cr2SiO5.


Assuntos
Silicatos de Alumínio , Carcinógenos Ambientais/química , Cromo/química , Adsorção , Argila , Poluição Ambiental/prevenção & controle , Solubilidade , Temperatura
19.
J Air Waste Manag Assoc ; 55(10): 1451-5, 2005 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-16295269

RESUMO

Scanning electron microscopy, X-ray diffractometry, X-ray absorption spectroscopy, and other means are used to investigate the effect of thermal treatment temperature, 105-1100 degrees C, on the immobilization of nickel (Ni) by the inorganic oxides of latosol. Ni is more firmly immobilized by the latosol with increasing temperature. Spectral analyses indicate that a shoulder toward the edge-jump appears in the spectra of X-ray absorption near-edge structure for the samples heated at 900 and 1100 degrees C. Moreover, the intensity of the main peak at the edge increases with higher temperature; this information indicates the distortion of the divalent nickel [Ni(II)] environment in the samples heated at 900 and 1100 degrees C. Nevertheless, the distortion is absent from the samples heated at 105 and 500 degrees C. The fact of the distortion of the Ni(II) environment suggests the occurrence of a chemical reaction between the Ni compound and the inorganic matrices of the latosol soil during the heating process at 900 and 1100 degrees C. In addition, the extended X-ray absorption fine structure results correspond well to the X-ray absorption near-edge structure results; the former are supportive of the occurrence of a distorted Ni(II) environment in the samples heated at 900 and 1100 degrees C. The wet-chemistry results show that the samples heated at 900-1100 degrees C leach less Ni than the 105-500 degrees C samples do. The change of the Ni environment is related to the observation that less Ni is leached from the samples heated at 900-1100 degrees C. Furthermore, the pore closing phenomenon is observed only in the 1100 degrees C sample; this phenomenon corresponds with the fact that the 1100 degrees C sample leaches less Ni than the 900 degrees C sample does.


Assuntos
Níquel/química , Óxidos/química , Microscopia Eletrônica de Varredura , Taiwan , Temperatura , Difração de Raios X
SELEÇÃO DE REFERÊNCIAS
Detalhe da pesquisa