Mass and isotopic concentrations of water-insoluble refractory carbon in total suspended particulates at Mt. Waliguan Observatory (China)

Mass concentration and isotopic values δ¹³C and ¹⁴C are presented for the water-insoluble refractory carbon (WIRC) component of total suspended particulates (TSP), collected weekly during 2003, as well as from October 2005 to May 2006 at the WMO-GAW Mt. Waliguan (WLG) site. The overall average WIRC mass concentration was (1183 ± 120) ng/m³ (n = 79), while seasonal averages were 2081 ± 1707 (spring), 454 ± 205 (summer), 650 ± 411 (autumn), and 1019 ± 703 (winter) ng/m³. Seasonal variations in WIRC mass concentrations were consistent with black carbon measurements from an aethalometer, although WIRC concentrations were typically higher, especially in winter and spring. The δ¹³C PDB value (−25.3 ± 0.8)‰ determined for WIRC suggests that its sources are C₃ biomass or fossil fuel combustion. No seasonal change in δ¹³C PDB was evident. The average percent Modern Carbon (pMC) for ¹⁴C in WIRC for winter and spring was (67.2 ± 7.7)% (n = 29). Lower pMC values were associated with air masses transported from the area east of WLG, while higher pMC values were associated with air masses from the Tibetan Plateau, southwest of WLG. Elevated pMC values with abnormally high mass concentrations of TSP and WIRC were measured during a dust storm event.     

Influence of topography on ground deformation at Mt. Vesuvius (Italy) by finite element modelling

Ground deformations are observed in connection with volcanic activity, and therefore, geodetic monitoring can provide significant indication of changes of equilibrium conditions. The aim of this paper is to study the deformation of Mount Vesuvius (Italy) caused by overpressure sources at various depths, using a commercial (Ansys) 3D finite element code, in the framework of linear elastic isotropic material behavior. Both homogenous and heterogeneous media with carbonate basement were analyzed to understand the influence of topography on the ground deformations. The topography of the Somma-Vesuvius was taken into account, using a digital terrain model, and the carbonate basement was schematically modelled by assuming two horizontal layers with different Young moduli. The presence of a strong deviation from axially symmetric pattern of the displacement field, and of small subsidence areas, was found. These characteristics are completely unknown from the simple Mogi model and by simplified topography model, as verified by ad hoc simulations. These preliminary results, showing areas of the volcanic edifice experiencing high deformation, can improve the determination of the sources of deformations, i.e. the most relevant problem in the volcano monitoring. Moreover, the knowledge of the deformation pattern, including the topography effects, can provide significant indications to optimize the location of sensors and the characteristics needed to design an efficient and reliable geodetic monitoring network able to detect shallow intrusion events.     

Effect of CNT length and CNT-matrix interphase in carbon nanotube (CNT) reinforced composites

The load transfer mechanisms and effective moduli of single-walled nanotube (SWNT) reinforced composites are studied using a continuum model. A “critical” fiber length is defined for full load transfer by numerically evaluating the strain-energy-changes for different fiber lengths. The effective longitudinal Young’s modulus and bulk modulus of the composite are derived. The effect of the interphase is also discussed. The results indicate the fiber length is critical both to the load transfer efficiency and effective moduli of the composite. The SWNT-matrix interphase plays an important role in load transfer efficiency but affects the effective moduli only slightly.     

Dispersion of multi-walled carbon nanotubes in poly（p-phenylene） thin films and their electrical characteristics

Dispersion of multi-walled carbon nanotubes in poly（p-phenylene） composite exposed to toluene was experimentally investigated. 3 mg of multi-walled carbon nanotubes with nominal size of 20 nm was compounded with 30 mg of poly（p-phenylene） with the presence of terpineol as binding initiator. To investigate an optimal condition for homogenizing all constituents, ultrasonication with an output power of 750W was employed with compounding time of 3, 10, 20 and 30 min. With FTIR analyses, it could be confirmed that homogeneous composite of multi-walled carbon nanotubes and poly（p-phenylene） could be prepared. SEM analyses were also conducted to examine the dispersion of multi-walled carbon nanotubes in the polymer matrix. Then intrinsic electrical resistance of the composites after being exposed to toluene was also investigated. It was found that the composite film prepared with ultrasonication for 20 min could provide sufficiently sensitive response with respect to varied concentration of toluene.     

玄武岩鳞片和氟化石墨增强织物复合材料在高速摩擦磨损工况中的应用

将改性玄武岩颗粒和氟化石墨构成的二元复合填料引入PTFE/Nomex混纺织物,制备了适用于高速工况的织物复合材料. 机械性能方面,二元填料的引入同时增加了复合材料的拉伸强度和断裂伸长率. 热学性能研究则证实,二元填料提高了复合材料的热稳定性能. 对摩擦对偶的扫描电镜(SEM)观察说明,改性玄武岩颗粒既能单独应用快速在摩擦对偶表面形成转移膜,又能与氟化石墨复配起到研磨作用,协助氟化石墨的部分原位剥离,极大增强复合材料的抗磨性能. 在高速摩擦磨损试验中,当载荷为10 MPa,线速度为0.98 m/s时,仅添加改性玄武岩颗粒的复合材料磨损率较未改性复合材料降低了32%. 当载荷为50 MPa,线速度为1.18 m/s时,二元填料改性的复合材料磨损率较未改性复合材料降低了53%.      

Chemical composition and source apportionment of the ambient PM_(2.5)in Hangzhou,China

To identify and apportion the sources of the ambient PM_(2.5) in the urban area of Hangzhou,China,PM_(2.5)samples were collected at three sites in the city from April 2004 to March 2005.Water-soluble ions,metal elements,and total carbon(TC) in PM_(2.5) samples were analyzed.The results indicated that the 24-h mean concentrations of PM_(2.5) ranged from 17.1 to 267.0 μg/m~3,with an annual average value of 108.2 μg/m~3.Moreover,the seasonal mean values for PM_(2.5) in spring,summer,autumn,and winter were 116,73.1,114.2,and 136.0 μg/m~3.respectively.According to the Chinese ambient quality standard,at least 70% of the monitoring data exceeded the limit value.The total contribution of water-soluble ions,including F~-,Cl~-,NO_3~-,SO_4~(2-).NH_4~+,K~+,and Na~+.to PM_(2.5) mass varied from 32.3% to 36.7%.SO_4~(2-),NO_3~-,and NH_4~+were the main constituents of the ions,with contributions to PM_(2.5) varying from 14.1% to 14.7%,6.0%to 7.8%,and 6.4% to 7.7%,respectively.In addition,the annual mean mass fraction of TC in PM_(2.5) was27.8%.The annual average total contribution of the group of elements of Zn,Pb,Cu,Mn,Cr,Ni,Se,Mo.Cd,Sb,and Ag to the aerosol was in the range of 1.7-2.0%.Furthermore,positive matrix factorization was applied to analyze the PM_(2.5) data collected from the central area,and five factors were identified.The factor contributions to PM_(2.5) mass were 12.8%,31.9%,10.1%,17.2%,and 27.9%,respectively.Iron/steel manufacturing and secondary aerosol were the main sources for the fine particles.These findings may have significance for controlling the atmospheric contamination in the city.     

Processes of hydrate formation and dissolution behind a shock wave in a liquid containing gas bubbles (mixture of nitrogen and carbon dioxide)

The processes of dissolution and hydrate formation behind a moderate-amplitude shock wave in water containing gas bubbles (mixture of nitrogen and carbon dioxide) are studied in experiments with different initial static pressures in the medium and concentrations of carbon dioxide in bubbles. An increase in static pressure in the gas-liquid medium is demonstrated to enhance the influence of the non-reacting gas (nitrogen) on the processes of dissolution and hydrate formation. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 50, No. 2, pp. 178–187, March–April, 2009.     

Chemical characteristics and source apportionment of PM_(10) during a brown haze episode in Harbin, China

This study investigates the correlation between PM 10 and meteorological factors such as wind speed, atmospheric visibility, dew point, relative humidity, and ambient temperature during a brown haze episode. In order to identify the potential sources of PM 10 during brown haze episode, respirable particulate matter (PM 10 ) was collected during both non-haze days and haze days and further analyzed for metallic elements, ionic species, and carbonaceous contents. Among them, ionic species contributed 45-64% t...     

Comments to the paper “An application of a damage constitutive model to concrete at high temperature and prediction of spalling” by Rosen Tenchev and Phil Purnell [Int. J. Solids Struct. 42 (26) (2005) 6550–6565]

The assumption that pressures of water and gas in concrete at high temperature are equal one to another and its theoretical consequences are discussed. The results of hygro-thermal simulations performed by Tenchev and Purnell are analysed and compared to the Authors’ results based on the assumption about local thermodynamic equilibrium.     

Assessment of heavy metal pollution characteristics and human health risk of exposure to ambient PM_(2.5) in Tianjin,China

To examine the features of heavy metal pollution of PM_(2.5)(particulate matter less than 2.5 μm) in Tianjin,China,as well as the exposure risk of PM_(2.5) to human health,we analyzed ambient PM_(2.5) samples collected from a campus of Nankai University in June,August,and October 2012.The concentrations of PM_(2.5) and heavy metals(Ni,Cu,Pb,Zn,Cr,Cd,Hg,As and Mn) in PM2.5 were analyzed by gravimetric analysis and inductively coupled plasma-mass spectrometry,respectively.The results show that the heavy metals contained in PM_(2.5) were,in descending order,Cu,Zn,Pb,Mn,Cr,Ni,Cd,As,and Hg.The proportion of Cd exceeded the secondary level of National Ambient Air Quality Standard of China(GB 3095-2012) by 1.3times,while others were within the limit.Enrichment factor analysis indicated that Cu,Zn,Cd,Pb,and Hg are mainly from anthropogenic sources.Principal component analysis indicated that the main sources of the heavy metals are vehicle exhaust,chemical waste,and coal-burning activities.The nine heavy metals which may cause health issues by exposure through the human respiratory system and should be further examined are Cr,Cd,As,Ni,Cu,Pb,Mn,Zn,and Hg,in the order of decreasing risk levels.With reference to the U.S.EPA standard the risk levels of all nine metals were below the acceptable level(10~(-6)/year).     

Short-term psychological impact of predictive testing for Machado-Joseph disease: depression and anxiety levels in individuals at risk from the Azores (Portugal)

OBJECTIVE: The short-term impact of the pre-symptomatic genetic test (PT) for Machado-Joseph disease (MJD) in the Azores (Portuguese Islands) was assessed in 46 individuals at risk who completed the PT Program. METHODS: Scores for depression and anxiety were used as indicators of the subjects' emotional status immediately before the PT and 1 year after disclosure of the results. RESULTS: Global levels of participation in the Azorean PT Program for MJD were high (20.7%), particularly in Flores Island (35.8%). For the total sample, mean scores of depression and anxiety before and after the PT presented without clinical significance. No differences were found for depression and anxiety scores before and after the PT. Furthermore, when grouped by test results (carriers/non-carriers), there were no differences between pre- and post-test levels. CONCLUSIONS: Results indicate that the test result did not cause a decrease in the psychological well-being of the individuals tested. The high number of participants performing the PT in the small and isolated community of Flores Island, where MJD represents a source of stigma, was interpreted as an indication that in this particular population the PT offers the individuals at risk the possibility of liberating from a stigma, and, hence, from exclusion.     

A Commentary on the Paper Titled “Relative Permeability Analysis of Tube Bundle Models”, by J. T. Bartley and D. W. Ruth,Transport in Porous Media 36(2): 161–187 (1999)

Transport in Porous Media -