Organic carbon (OC) and elemental carbon (EC) in fine particles (PM
2.5) at two background sites, Kosan and Kangwha in Korea were measured during intensive field studies between 1994 and 1999. Fine ...particles were collected on pre-fired quartz filters in a low-volume sampler and analyzed using the selective thermal oxidation method with MnO
2 catalyst. The OC and EC concentrations at Kosan located at western tip of Cheju Island in southern Korea are lower than those at Kangwha located at western coastal area in mid-Korean peninsula. Still, the OC concentrations at Kosan are generally higher than those at other background areas in Japan and USA. The EC concentrations at Kosan are lower than or comparable to those at other background areas. The total carbon (TC, sum of OC and EC) to EC ratio values at both sites were higher than those at other background areas in Japan and USA. At Kosan, the OC and EC concentrations when air parcels were from southern China were higher than those when air parcels were coming from northern China. However, at Kangwha, the differences were statistically not clear since most air parcels were from northern China. Except when air parcels were from the North Pacific during summer, the OC and EC concentrations are well correlated indicating that both OC and EC share the same emission/transport characteristics. From the gaseous hydrocarbon data and the OC and EC relationship, it was found that during summer local biogenic emissions of OC might be significant at Kosan.
This paper studies the prevention of premature failures of LED backlights used in mobile devices that are subject to different use conditions. This is a vitally important topic for consumer mobile ...device manufacturers as the life expectancy of two identical devices from the same production line may vary substantially under different operating environments and use conditions. These differences are not addressed by traditional reliability assessment methods documented in many electronics handbooks. The paper outlines the use of a prognostics approach and condition-based monitoring for optimizing the reliability in the LED backlight display unit of mobile devices.
To provide a secure traversal service, firewalls need more than static packet filtering and application-level proxies. SOCKS (Secure sOCKets) is an application-independent transport-level proxy that ...offers user-level authentification and data encryption. An extended SOCKS UDP (user datagram protocol) binding model with appropriate socket calls is proposed to provide complete support for UDP-based multimedia streaming applications.
The Pearl River Delta (PRD) region, located in the southern part of Guangdong Province in China, is one of the most rapidly developing regions in the world. The evolution of local and regional ...sea-breeze circulation (SBC) is believed to be responsible for forming meteorological conditions for high air-pollution episodes in the PRD. To understand better the impacts of urbanization and its associated urban heat island (UHI) on the local- and regional-scale atmospheric circulations over PRD, a number of high-resolution numerical experiments, with different approaches to treat the land surface and urban processes, have been conducted using the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5). The results show that an accurate urban land-use dataset and a proper urban land-use parameterization are critical for the mesoscale model to capture the major features of the observed UHI effect and land–sea-breeze circulations in the PRD. Stronger UHI in the PRD increases the differential temperature gradient between urbanized areas and nearby ocean surface and hence enhances the mesoscale SBC. The SBC front consequently penetrates farther inland to overcome the prevailing easterly flow in the western part of inland Hong Kong. Additional sensitivity studies indicate that further industrial development and urbanization will strengthen the daytime SBC as well as increase the air temperature in the lowest 2 km of the atmosphere.
Retinal ischemia/reperfusion injury is a common feature of various retinal diseases such as glaucoma and diabetic retinopathy. Lutein, a potent anti-oxidant, is used to improve visual function in ...patients with age-related macular degeneration (AMD). Lutein attenuates apoptosis, oxidative stress and inflammation in animal models of acute retinal ischemia/hypoxia. Here, we further show that lutein improved Mueller cell viability and enhanced cell survival upon hypoxia-induced cell death through regulation of intrinsic apoptotic pathway. Moreover, autophagy was activated upon treatment of cobalt (II) chloride, indicating that hypoxic injury not only triggered apoptosis but also autophagy in our in vitro model. Most importantly, we report for the first time that lutein treatment suppressed autophagosome formation after hypoxic insult and lutein administration could inhibit autophagic event after activation of autophagy by a pharmacological approach (rapamycin). Taken together, lutein may have a beneficial role in enhancing glial cell survival after hypoxic injury through regulating both apoptosis and autophagy.
A general series solution to the problem of interacting circular inclusions in plane thermoelasticity is provided in this paper. Based upon the complex variable theory and the use of Laurent series ...expansion, the general expression of the stress functions is derived explicitly for the circular inclusion problem under remote uniform heat flow. By applying the use of the superposition, the problem dealing with any number of arbitrarily located inclusions can be then reduced to a set of linear algebraic equations which are solved with the aid of a perturbation technique. For illustrating the use of the present approach, an approximate closed form solution of the stress functions is derived explicitly for the problem containing two arbitrarily located inclusions. Numerical results of the interfacial stresses around a rigid circular inclusion or hoop stress along a circular hole due to the presence of an elastic inclusion are provided to demonstrate the dependence of the solution upon the pertinent parameters.
In this study, the trend of PM2.5 concentrations and its adverse health effects in China from 2001 to 2017 are estimated utilizing 1-km high-resolution annual satellite-retrieved PM2.5 data. PM2.5 ...concentrations for most of the provinces/cities remained stable from 2001 to 2012; however, following the issue of the Air Pollution Prevention and Control Action Plan (APPCAP) by the central government of China, a dramatic decrease in PM2.5 concentrations from 2013 to 2017 occurred. Premature mortality caused by PM2.5 dropped from 1,078,800 in 2014 to 962,900 in 2017. The PM2.5 caused 17-year average mortality ranges from 3800 in Hainan Province to 124,800 in Henan Province. The health cost benefits gained by the reduction of PM2.5 pollution amounted to US $193,800 in 2017 (compared to the costs due to PM2.5 concentrations in 2013), amounting to 1.58% of the total national GDP. The impacts of urbanization on PM2.5 concentration and mortality are analyzed. The PM2.5 concentration and its induced mortality density in dense urban areas are much higher than those in rural areas. The aggravation of PM2.5 associated premature mortality in urban areas is mainly due to the larger amount of emissions and to urban migration, and 6500 deaths in 2014 could have been avoided were the population ratios in dense-urban/normal-urban/rural areas to be reversed to the ones in 2001. It is recommended that people with respiratory-related diseases live in rural areas, where the pollutant concentration is relatively low.
Display omitted
•PM2.5 concentrations have shown a sharply decreasing trend during the period from 2013 to 2017 in China.•The premature mortality associated with PM2.5 concentrations dropped from 1,078,800 in 2014 to 962,900 in 2017.•The health cost avoided in 2017 as a result of the reduction of PM2.5 concentrations amounted to 1.58% of the national GDP.•The mortality density in dense urban areas is much higher than that in rural area.•The urban migration can increase the premature mortality caused by PM2.5 indirectly.
Eight sediment cores from Sai Kung Bay area were sampled and analysed for Cd, Cr, Cu, Fe, Ni, Pb, Zn, Ca, and organic matters. The cores were dated from an overall consideration of the
210Pb and ...maximum
137Cs activities, and historical records of previous land use, past heavy typhoon and rainstorm activities. Contamination by Cd, Cr, Cu, Pb, and Zn was found at coastal cores with a mean Enrichment Factor of 5.0, 1.0, 1.7, 1.4, and 1.3, respectively. The overall mass sedimentation rates were found varying from 0.111 – 0.454 g/cm
2·y and recent average anthropogenic fluxes in μg/cm
2·y for coastal/offshore cores were estimated as
0.52
0.028
(Cd)
,
2.0
0.26
(Cr)
,
7.6
0.92
(Zn)
,
2.8
1.4
(Cu)
, and
2.9
2.3
(Pb)
, respectively. The major problem is Cd and Cr, in particular at coastal cores. The heavy metal input to the Sai Kung Bay areas was found to change considerably over the past 50 y starting from a low background level, via an intermediate period with cottage industries discharging Cr and Cd, to recent years with rapid urbanization and heavy boating activities emitting Cu, Pb, and Zn in addition to Cr and Cd. A rapid increase in heavy metal contents and a significant decrease in biological activities were found at the recently deposited coastal sediments, indicating a problem requiring urgent remedial action to stop further deterioration of the coastal environment of the beautiful resort area at Sai Kung Bay.
Nitrate (NO3−) is often among the leading components of urban particulate matter (PM) during PM pollution episodes. However, the factors controlling its prevalence remain inadequately understood. In ...this work, we analyzed concurrent hourly monitoring data of NO3− in PM2.5 at a pair of urban and suburban locations (28 km apart) in Hong Kong for a period of two months. The concentration gradient in PM2.5 NO3− was 3.0 ± 2.9 (urban) vs. 1.3 ± 0.9 μg m−3 (suburban) while that for its precursors nitrogen oxides (NOx) was 38.1 vs 4.1 ppb. NO3− accounted for 45 % of the difference in PM2.5 between the sites. Both sites were characterized to have more available NH3 than HNO3. Urban nitrate episodes, defined as periods of urban-suburban NO3− difference exceeding 2 μg m−3, constituted 21 % of the total measurement hours, with an hourly NO3− average gradient of 4.2 and a peak value of 23.6 μg m−3. Our comparative analysis, together with 3-D air quality model simulations, indicates that the high NOx levels largely explain the excessive NO3− concentrations in our urban site, with the gas phase HNO3 formation reaction contributing significantly during the daytime and the N2O5 hydrolysis pathway playing a prominent role during nighttime. This study presents a first quantitative analysis that unambiguously shows local formation of NO3− in urban environments as a driver for urban episodic PM2.5 pollution, suggesting effective benefits of lowering urban NOx.
Display omitted
•PM2.5 NO3− formation concurrently probed at urban and suburban sites in Hong Kong.•91 % (urban) and 76 % (suburban) of the measurement periods were ammonium-rich.•Consistently higher NO3− at the urban site was attributed to local NOx oxidation.•Local NO3− formation contributed significantly to elevated PM2.5 at the urban site.
PDF
