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81.
Numerous backcountry and wilderness use studies have been conducted over the last decade, but nearly all of them have concentrated on peak season and summer use. This study investigates use patterns and user characteristics of winter campers, and implications for the management of winter backcountry overnight use. Use pattern data were collected from 580 backcountry use permits for both winter and summer campers of Great Smoky Mountains National Park (GSMNP). A two-page questionnaire was also mailed to 300 of the winter users to survey their characteristics, past backpacking experience, and reasons for winter camping. Backcountry permit data indicate that use patterns differ significantly between winter and summer campers, with winter campers taking shorter, weekend, destination-type trips. Winter campers engage in backcountry camping nearly twice as often during winter as other seasons of the year, both in and outside GSMNP. They are also experienced hikers that tend to avoid camping in Great Smoky Mountains National Park during the summer because of heavy visitor use. This suggests that winter backcountry campers are different enough from peak season campers that management of these two user groups may require different styles.  相似文献   
82.
The flow pathways of water in the soils of the Gnangara Mound are highly irregular and depend upon the moisture content, the repellency and preferential wettability potential of the soils. The occurrence of preferential flow is more evident in dry soils. As the soil wets during the rainy season, the water repellence and differential wettability decreases, the fingering and the preferential flow paths disappear. Most of the agricultural sites in the Spearwood Sands which showed more irregular flow than the Bassendean Sands are under continuous irrigation during cultivation season. As the repellency problems are chemically treated, it is therefore expected that the flow will be more uniform all the year round. Landuse is mainly responsible for variation in recharge rates; however, the hydraulic properties control aquifer response and water level pattern to a greater degree. Water levels in the mid 1970s were in a semi steady state. Since that time, a combination of increasing water use by pine plantations, heavy pumping from private boreholes in market gardens and private homes and intensive pumping from the Gnangara Mound for the metropolitan water supply have caused water levels to continually decline in the Superficial aquifer. Nitrate and phosphate concentrations in the regional Superficial aquifer are generally very low. None of the tested pesticides (atrazine, diazinon, dimethoate, endosulfan, fenamiphos, iprodione, malathion and chlorpyrifos) were detected in the groundwater samples collected from the monitoring bores.  相似文献   
83.
Summary The performance of a cellular phone commercial helical antenna at 900~MHz band, both in free space and in the presence of a human head phantom was studied. Numerical simulation of the phone model for the latter case has been performed giving 3D radiation diagrams. The effect of the phantom head on radiation diagrams is presented. The relative amount of the EM power absorbed in the head was obtained for several distances of the phone. Measurements were carried out in a RF anechoic chamber using standard horn antennas and a calibrated measuring system. Absolute radiation patterns of the antenna gain were obtained in the three principal planes. Significant reduction of the absorbed power could be achieved just by moving the phone 1 cm away from the head.  相似文献   
84.
焦化厂土壤中多环芳烃分布特征及淋洗粒级分割点确定   总被引:5,自引:1,他引:5  
土壤粒径分布和污染物在不同粒级土壤中的分布特征是污染土壤淋洗可处理性的重要依据,淋洗粒级分割点则是淋洗工艺的重要参数.根据土壤异位淋洗的技术要求,在焦化厂污染场地进行了采样,测定了土样的粒径分布曲线及不同粒级土壤中美国EPA优控的16种多环芳烃(PAHs)的初始浓度,并采用Tween 80和Triton X-100溶液对不同粒级污染土样进行了振荡清洗实验.结果表明,16种PAHs在6个粒级中的总浓度在6.27~40.18 mg/kg范围,呈双峰分布模式,单个PAH污染物的最高浓度大多出现在250~500 μm的颗粒中, 50~75 μm的颗粒中污染物浓度最低;PAHs去除率与其初始浓度及土壤特性有关,初始浓度越低,去除率越高,粗颗粒中由于有机碳含量较高,PAHs去除效率反而低于细颗粒.根据清洗效果并从废物减量化角度出发,确定以50 μm作为土壤淋洗的粒级分割点,这样减容率可以达到82.95%.  相似文献   
85.
Objectives: The objective of this study was to examine the frequency of psychoactive drugs and alcohol in drivers under suspicion of driving under the influence of drugs and alcohol in 2015 and 2016 in the eastern part of Denmark. The trends in the number of traffic cases sent for drug analysis since 2000 and alcohol analysis since 2011 are also discussed.

Methods: Blood samples from drivers suspected of being under the influence of alcohol and/or medication and/or illicit drugs in 2015 and 2016 were investigated as requested by the police. The blood samples were screened for alcohol and/or tetrahydrocannabinol (THC) alone, for other drugs (covering all drugs, except THC, listed in the Danish list of narcotic drugs), or for THC and other drugs. Age and gender were also recorded. The number of drug traffic cases since 2000 and the number of alcohol cases since 2011 were extracted from our Laboratory Information Management System (LIMS).

Results: In total, 11,493 traffic cases were investigated. Alcohol and/or drugs exceeded the legal limit in 9,657 (84%) cases. Men constituted 95% of the drivers investigated for drugs and 88% of the alcohol cases. The drivers investigated for drugs consisted primarily of young men, whereas drivers investigated for alcohol were older.

The frequency was higher for positive alcohol cases above the legal limit (87%) than for drug cases (76%) above the fixed concentration limit. THC (67–69%) was the most frequently detected drug above the legal limit, followed by cocaine (27–28.5%), amphetamine (17%), and clonazepam (6–7%) in both years. Morphine (5.4%), included among the 5 most frequent drugs in 2015, was replaced by methadone (4.6%) in 2016. Few new psychoactive drugs (NPS) were detected.

The number of traffic cases sent for drug analysis has increased more than 30-fold since 2000–2006, and the number of traffic cases submitted in 2016 for drug analysis was higher than the number for alcohol analysis; the latter has decreased since 2011.

Conclusion: Overall, alcohol was the most frequent compound detected above the legal limit in both years, followed by the well-known illicit drugs THC, cocaine, and amphetamine. NPS were seldom seen. One consequence of the increased focus on drugs in traffic has been an immense increase in drug traffic cases sent for analysis since 2006 in the eastern part of Denmark. Although this survey revealed only minimal changes compared to earlier investigations, surveys like this are invaluable for monitoring abuse patterns and trends in drugged and drunken driving.  相似文献   

86.
Perfluorooctane sulfonate (PFOS) is a globally distributed persistent organic pollutant that has been found to bioaccumulate and biomagnify in aquatic food webs. Although principally in its linear isomeric configuration, 21–35% of the PFOS manufactured via electrochemical fluorination is produced as a branched structural isomer. PFOS isomer patterns were investigated in multiple tissues of polar bears (Ursus maritimus) from East Greenland. The liver (n = 9), blood (n = 19), brain (n = 16), muscle (n = 5), and adipose (n = 5) were analyzed for linear PFOS (n-PFOS), as well as multiple mono- and di-trifluoromethyl-substituted branched isomers. n-PFOS accounted for 93.0 ± 0.5% of Σ-PFOS isomer concentrations in the liver, whereas the proportion was significantly lower (p < 0.05) in the blood (85.4 ± 0.5%). Branched isomers were quantifiable in the liver and blood, but not in the brain, muscle, or adipose. In both the liver and blood, 6-perfluoromethylheptane sulfonate (P6MHpS) was the dominant branched isomer (2.61 ± 0.10%, and 3.26 ± 0.13% of Σ-PFOS concentrations, respectively). No di-trifluoromethyl-substituted isomers were detectable in any of the tissues analyzed. These tissue-specific isomer patterns suggest isomer-specific pharmacokinetics, perhaps due to differences in protein affinities, and thus differences in protein interactions, as well transport, absorption, and/or metabolism in the body.  相似文献   
87.
Analyses of commercially available wines suggested non-Brettanomyces sources of 4-ethylphenol and 4-ethylguaiacol. Grapes, enological additions, exposure to plastics, and oak-barrel aging were potential inputs considered. Investigations of whole grape bunch samples from two major red wine Vitis vinifera cultivars (L. cv. Cabernet Franc and Pinot Noir), a commercial mannoprotein additive, and three commercial enological tannin additions indicated they are not likely significant sources of these compounds. Studies on 15 commercial oak barrelled red wines from six Vitis vinifera cultivars (L. cv. Cabernet Franc, Cabernet Sauvignon, Dunkelfelder, Merlot, Pinot Meunier, and Pinot Noir), and a review of volatile phenol extraction from toasted oak wood, suggested that oak-aging may produce concentrations of up to 50 μg L?1 4-ethylphenol and 4-ethylguaiacol. Thus, following potential Brettanomyces-sourced aroma impacts in wine using 4-ethylphenol and/or 4-ethylguaiacol concentrations as proxies should only be considered reliable at analyte levels > 100 μg L?1. A review of worldwide 4-ethylphenol and 4-ethylguaiacol concentrations in wine, consumption patterns, and available toxicological data also suggested that levels of 4-ethylphenol being observed in wines worldwide do not warrant concerns about acute or long-term effects. While little is known about the toxicology of 4-ethylguaiacol, it is unlikely that elevated concentrations will pose any health-related concerns.  相似文献   
88.
以木糖为碳源采用间歇培养方式,对木糖厌氧发酵产酸进行研究。考察木糖浓度和初始pH值对木糖厌氧产酸的影响。结果表明,随着木糖浓度的增加,总产酸量得到提高,但木糖利用率却呈现下降的趋势。当木糖浓度为5 g/L时,其利用率为100%,15 g/L时利用率为73.9%,此时挥发性脂肪酸(VFAs)为9.22 g/L。木糖的分批投加可有效促进产酸,尤其是促进乙酸浓度的提高。pH为5.0和6.0左右时,VFAs主要成分为乙酸和丁酸;而pH为7.0~9.0时,乙酸含量明显增高,在pH值为8.0的条件下乙酸含量占总VFAs的80.1%。在pH=8.0时经过8 d左右的发酵,VFAs浓度可达9.34 g/L。  相似文献   
89.
结合大连的开发区时间,从集聚和引力扩散、制度创新、跨国公司主导下的产业链式成长、对母城的有机疏散、产业空间优化与重组、行政区划调整等6个方面探讨了开发区城市化效应的作用机制.在此基础上,总结了开发区城市化的3种空间模式,即大型综合经济功能区的飞地型模式、大型高新技术园区的郊区化模式、中小园区组群发展的嵌入与填充模式,提出了优化开发区城市化效应的对策建议.  相似文献   
90.
中国低碳城市发展模式与行动策略   总被引:2,自引:0,他引:2  
建设低碳城市是促进节能减排和经济社会持续发展的重要战略举措,成为未来城市发展的重要导向和路径选择.从低碳城市发展重要性和紧迫性入手,在立足基本国情的基础上设计了低碳城市发展愿景.结合城市化快速推进预期和经济社会发展需求,分阶段提出了低碳城市发展目标.从总体模式、指导理念、基本思路、主要领域等对我国低碳城市发展模式进行了构想.在此基础上,提出我国低碳城市发展的实施步骤和行动策略.研究认为,我国低碳城市发展模式应选择“C”模式,以低碳发展为主导方向,以节能减排为发展方式,以低碳生产和低碳生活为主要方法.按照控源、减碳、增汇的基本思路,依靠理念创新、技术创新和制度创新,在低碳产业、低碳能源、低碳技术以及低碳生活等领域,通过构建低碳城市规划理论框架、建立低碳城市评价标准和体系、加快相关政策规章与制度建设、开展城市碳交易试点以及加强监督指导等措施,立足国情、统筹兼顾,分步骤、分阶段有序推进低碳城市发展.  相似文献   
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