Abstract. Continuous measurements of atmospheric organic and elemental carbon (OC and EC) were taken during the high-pollution fall and winter seasons at Xi'an, Shaanxi Province, China from September 2003 through February 2004. Battery-powered mini-volume samplers collected PM 2.5 samples daily and PM 10 samples every third day. Samples were also obtained from the plumes of residential coal combustion, motor-vehicle exhaust, and biomass burning sources. These samples were analyzed for OC/EC by thermal/optical reflectance (TOR) following the Interagency Monitoring of Protected Visual Environments (IM-PROVE) protocol. OC and EC levels at Xi'an are higher than most urban cities in Asia. Average PM 2.5 OC concentrations in fall and winter were 34.1±18.0 µg m −3 and 61.9±33.2 µg m −3 , respectively; while EC concentrations were 11.3±6.9 µg m −3 and 12.3±5.3 µg m −3 , respectively. Most of the OC and EC were in the PM 2.5 fraction. OC was strongly correlated (R>0.95) with EC in the autumn and moderately correlated (R=0.81) with EC during winter. Carbonaceous aerosol (OC×1.6+EC) accounted for 48.8%±10.1% of the PM 2.5 mass during fall and 45.9±7.5% during winter. The average OC/EC ratio was 3.3 in fall and 5.1 in winter, with individual OC/EC ratios nearly always exceeding 2.0. The higher wintertime OC/EC corresponded to increased residential coal combustion for heating. Total carbon (TC) was associated with source contributions using absolute principal component analysis (APCA) with eight thermally-derived carbon fractions. During fall, 73% of TC was attributed to gasoline engine exhaust, 23% to diesel exhaust, and 4% to biomass burning. During winter, 44% of TC was attributed to gasoline engine exhaust, 44% to coal Correspondence to: J. J. Cao (cao@loess.llqg.ac.cn) burning, 9% to biomass burning, and 3% to diesel engine exhaust.

The alternative charge arrangement on the {010} facet of BiOCl facilitates benzyl oxidation and selectivity for benzoic acid ring-opening reactions, subsequently resulting in remarkably enhanced photocatalytic efficiency.

Daily mass concentrations of PM 1.0 (particles less than 1.0 µm in diameter), PM 2.5 (particles less than 2.5 µm in diameter), organic carbon (OC), and elemental carbon (EC) were measured from January through May 2004 at a heavily trafficked sampling site in Hong Kong (PU). The average concentrations for PM 1.0 and PM 2.5 were 35.9 ± 12.4 µg cm −3 and 52.3 ± 18.3 µg cm −3 . Carbonaceous aerosols were the dominant species in fine particles, accounting for ∼45.7% of PM 1.0 and ∼44.4% of PM 2.5 . During the study period, seven fine-particle episodes occurred, due to the influence of longrange transport of air masses from mainland China. PM 1.0 and PM 2.5 responded in similar ways; i.e., with elevated mass and OC concentrations in those episode days. During the sampling period, PM 1.0 OC and EC generally behaved similarly to the carbonaceous aerosols in PM 2.5 , regardless of seasonal variations and influence by regional pollutions. The low and relatively constant OC/EC ratios in PM 1.0 and PM 2.5 indicated that vehicular emissions were major sources of carbonaceous aerosols. PM 1.0 and PM 2.5 had the same dominant sources of vehicular emissions in winter, while in spring PM 2.5 was more influenced by PM 1−2.5 (particles 1-2.5 µm in diameter) that did not form from vehicle exhausts. Therefore, PM 1.0 was a better indicator for vehicular emissions at the Roadside Station.

Facet-dependent photocatalytic NO conversion pathways on Bi2O2CO3 nanoflakes are revealed to be predetermined by adsorption activation patterns.

A fully integrated dual-band (868/915 MHz and 2.4 GHz) low-noise amplifier is designed using 0.18 mm RFCMOS technology for ZigBee development. In both bands, achieved gains are better than 15 dB and the resulting noise figures are better than 2.0 dB. The input and the output reflections are measured to be better than 210 dB in both bands. By tuning varactors in input and output LC tanks, frequency drifts due to unexpected parasitics and process variations are easily compensated. The amplifier works at 1.2 V supply voltage with 10 mA current dissipation.Introduction: The development of IEEE 802.15.4 ZigBee, operating in the 868/915 MHz (low band) and 2.4 GHz (high band) ISM bands, has been studied extensively recently as a result of its wide range of applications. One of the mostly adopted early approaches to achieve dual-band for other applications was to implement two receiver chains and use a switch to select one of the frequencies [1]. Such an approach generally degrades the noise figure (NF) because of the insertion loss of the switch. The second approach is to select one set of tuning networks by using a switch [2]. The drawbacks are the signal loss due to the switches in the signal path as well as the area hungry topology for the two sets of tuning networks. A third approach is to tune the input and the output to different frequencies by using complex multiband filters. However multiband filters are difficult to implement on chip [3].The present development is based on a multiband theory [4] to cater for dual-band characteristics. In the present ZigBee investigation, the receiver receives two signal bands simultaneously without using switches, hence resulting in lower loss. Our former work on 0.35 mm simulation [5] for RFCMOS showed that the dual-band topology shown in Fig. 1 is feasible and the analysis in [5] is used in the present work and hence is not repeated here. In the present 0.18 mm RFCMOS development, a frequency calibration method is also developed and realised by using varactors to compensate the frequency drifts due to the random parasitics and process variation.