互联网对网民身心健康的影响

21世纪互联网已经成为人们生活中重要的组成部分,改变了人们的行为和生活习惯,影响着人们的身体健康和心理健康。身体健康方面主要包括网络使用对网民眼睛、睡眠和特殊人群的影响,也包括了网络信息和社交媒介对身体健康的影响;心理健康方面主要包括网络对心理健康、抑郁和孤独感的影响。未来,有必要对互联网、心理健康和生理健康三者之间的关系,移动互联网对身心健康的影响以及开展本土化和健康上网进行研究,只有正确看待和使用互联网才能愉悦健康。     

降水量与积温对玉米气象产量影响的综合分析

气象条件的改变对农作物的产量和品质产生严重的影响,研究好玉米产量和气象因素之间的关系就显得十分重要了。本次研究过程中采用了文献分析法、回归分析法和通径分析法,综合对本溪地区玉米气象产量与本溪地区积温之间的关系,通过对研究结果进行分析,玉米的气象产量和玉米生育期内降水量的多少呈现明显的正相关的现象,而在对玉米的气象产量与玉米生育期内降水量和积温进行线性分析发现,可以使用特定线性方程对本溪地区的玉米气象产量和玉米剩余期内的降雨量和积温之间的关系进行分析和描述,对方程中的各个变量进行偏回归方程分析和通径分析都显示出,在本溪地区降雨量的多少对玉米气象产量的影响明显大于积温对玉米气象产量的影响。对辽宁本溪地区的降雨量来说,其对该地区玉米气象产量起着明显的促进作用,而积温呈现出负面作用的现象。     

浅谈加强会计基础工作

会计基础工作是对会计核算和会计管理的基础性工作的统称．包括对会计核算依据的基本要求，对会计资料的基本要求对会计电算化的基本要求、对会计机构和会计人员的配备及管理的要求．对会计档案管理要求、对会计监督的基本程序和要求．以及单位内部会计管理制度等。     

库哈斯建筑理念的现代启思

通过对库哈斯部分作品和著作的阅读,扼要介绍了库哈斯对当今城市发展和建设的新理念和实践。阐明了他的新现代主义倾向,对批评建筑和对中国“大跃进”的态度,介绍了库哈斯部分作品及其评价和影响。     

结构损伤识别中的小波变换法研究

对小波变换在结构损伤识别中使用归结为，对结构服役状态的监测和对结构损伤的定位和评估两类，并选取典型的使用实例进行介绍和评论，最后对小波理论在该领域的应用前景进行了展望。     

南非作家库切作品中的人性主题

南非小说家库切是2003年诺贝尔文学奖得主。对人性的探讨和追问是库切小说的重要主题之一。库切在其小说中对人性的探讨并非一般意义上对人性善恶本质的讨论,而是对新南非制度下种种扭曲和变异的人性的探求、声讨和追问,实质上是对南非殖民主义和种族隔离制度的痛斥和批驳。     

地下水对市政建设的影响

在工程建设中,由于地下水的特殊性和其化学成分,对钢筋混泥土具有很大的侵蚀性,对工程建筑有极大的作用和影响。地下水的浮力对结构设计和施工也着有不容忽视的影响。结构施工中需处理好地下水对工程建设的影响。     

秦岭林区森林抚育间伐对林地土壤养分的影响探究

本文主要对秦岭中段南坡林区具有植被优势的锐齿栎、红桦、油松和华山松来进行研究，结合室外调查和室内实验两种方式，对抚育间伐对林地土壤养分的影响进行研究，对不同树种林地土壤养分的差异进行比较。主要对间伐强度对土壤养分的作用效果和机制进行研究，期望更好地使森林经营过程中抚育间伐强度可以得到科学有效的设定。本文的研究将理论基础和实践应用相结合，既可以用来对林地土壤肥力和林业技术措施效果进行评价，也能为森林生态功能的维持和可持续发展提供科学的依据，并提出笔者的思考和建议，仅供参考。     

2008投资还是主旋律——王春鸣的经济预言

作为四川知名企业家,王春鸣不仅对企业管理有着自己丰富的实战经验和独特见解,对宏观经济也具有敏锐的眼光和认识。在此,摘录几段他对2008宏观经济的一些看法和认识。     

居住室内颗粒物沉积研究

室内颗粒物是影响室内空气品质的主要因素之一,可能给人体健康或对设备和物品带来危害,因而对室内颗粒物的穿透、沉积特性的研究就非常重要。讨论自然通风条件下,送风速度和颗粒物直径对颗粒物沉积率和穿透率影响,为改善室内环境提供参考和借鉴,对室内空气品质的影响和评价方面提供指导。文章通过对马鞍山这一地区的空气特性研究,用数值模拟方法分析在自然通风条件下,风速、粒径对室内颗粒物的穿透和沉积的影响。对于颗粒直径大于10um的粒子,送风速度对穿透率的影响显著;对于直径大的粒子并且送风速度小其沉降率最大,送风速度以及粒径对PM10的颗粒物影响最大。     

Total arsenic, lead, cadmium, copper, and zinc in some salt rivers in the northern Andes of Antofagasta, Chile

Lake Velenje is located in one of the most polluted regions in Slovenia, the Salek Valley. The major source of pollution in the valley is the coal-fired thermal power plant in Sostanj (STPP, capacity 775 MW). It has five separate units. All units have electrostatic precipitators for fly ash removal. Unit 4 also has installed a wet flue gas desulfurisation system (FGD system). Total mercury (THg) concentrations were measured in lignite, slag and ash samples from the STPP. In flue gas, different mercury species (THg, MeHg, Hg2+, Hg0) were determined separately for unit 4 and unit 5 which use different flue gas cleaning technology. Mercury and methyl mercury (MeHg) concentrations were also measured in lake water at different depths, in inflow water, outflow water, rain, snow and lake sediments in order to establish the influence of the power plant on the lake. Most mercury emitted from the power plant is in the elemental form. The ratio between oxidised and elemental Hg depends on the flue gas cleaning technology. Mass balance calculations have been performed for the STPP. The results show that the major sources of mercury in Lake Velenje are wet deposition and lake inflows. Total and MeHg concentrations in the water column are very low and can be compared to other non-contaminated freshwater lakes in the world.     

Pollution of montane soil with Cu, Zn, As, Sb, Pb, and nitrate in Kanto, Japan

Soil cores and rainwater were sampled under canopies of Cryptomeria japonica in four montane areas along an atmospheric depositional gradient in Kanto, Japan. Soil cores (30 cm in depth) were divided into 2-cm or 4-cm segments for analysis. Vertical distributions of elemental enrichment ratios in soils were calculated as follows: (X/Al)_i/(X/Al)_BG (where the numerator and denominator are concentration ratios of element-X and Al in the i- and bottom segments of soil cores, respectively). The upper 14-cm soil layer showed higher levels of Cu, Zn, As, Sb, and Pb than the lower (14-30 cm) soil layer. In the four areas, the average enrichment ratios in the upper 6-cm soil layer were as follows: Pb (4.93) ≥ Sb (4.06) ≥ As (3.04) > Zn (1.71) ≥ Cu (1.56). Exogenous elements (kg/ha) accumulated in the upper 14-cm soil layer were as follows: Zn (26.0) > Pb (12.4) > Cu (4.48) ≥ As (3.43) ≥ Sb (0.49). These rank orders were consistent with those of elements in anthropogenic aerosols and polluted (roadside) air, respectively, indicating that air pollutants probably caused enrichment of these elements in the soil surface layer. Approximately half of the total concentrations of As, Sb, and Pb in the upper 14-cm soil layer were derived from exogenous (anthropogenic) sources. Sb showed the highest enrichment factor in anthropogenic aerosols, and shows similar deposition behavior to NO₃⁻, which is a typical acidic air pollutant. There was a strong correlation between Sb and NO₃⁻ concentrations in rainfall (e.g., in the throughfall under C. japonica: [NO₃⁻] = 21.1 [dissolved Sb], r = 0.938, p < 0.0001, n = 182). Using this correlation, total (cumulative) inputs of NO₃⁻ were estimated from the accumulated amounts of exogenous Sb in soils, i.e., 16.7 t/ha at Mt. Kinsyo (most polluted), 8.6 t/ha at Mt. Tsukuba (moderately polluted), and 5.8 t/ha at the Taga mountain system (least polluted). There are no visible ecological effects of these accumulated elements in the Kanto region at present. However, the concentrations of some elements are within a harmful range, according to the Ecological Soil Screening Levels determined by the U.S. Environmental Protection Agency.     

Determination of Co,Cu, Fe,Hg, Mn,Sb, Se and Zn in milk samples

Concentrations of Co, Cu, Fe, Hg, Mn, Sb, Se and Zn in IAEA milk (dry) standard A-11 were re-evaluated with the help of instrumental and radiochemical neutron activation analysis (NAA). The results show reasonably good agreement for Co (5.1 ± 0.55 ng/g) and Zn (34 ± 2.5 μg/g), in relation to the recommended values. For Cu (374 ± 15 ng/g), Fe (2.4 ± 0.34 μg/g) and Mn (250 ± 20 ng/g); the results obtained are lower than the reported values.Cu, Mn, and Zn were cross-checked by atomic absorption spectrophotometry (AAS). The results, Cu = 331 ± 27 ng/g, Mn = 302 ± 62 ng/g, and Zn = 35 ± 1 μg/g, fall within the range of mean values obtained by NAA.For Hg and Se, using instrumental NAA, only upper limits could be indicated; because of the low levels of concentrations of Hg and Se on one hand, and high content of P (9100 μg/g) in A-11 milk standard on the other, NAA coupled with radiochemistry is to be preferred for these two elements.In pooled human milk, in addition to Cu and Mn (radiochemical) and Co, Fe, Sb and Zn (instrumental), Hg and Se could also be determined non-destructively because of the favourable Hg/P and Se/P ratios in this matrix.     

Levels of antimony,arsenic, cadmium,copper, lead,mercury, selenium,silver, tin and zinc in bone tissue of industrially exposed workers

The contents of the elements antimony, arsenic, cadmium, copper, lead, mercury, selenium, silver, tin and zinc in bone tissue from autopsy specimens of the femur of workers who had been exposed to a large number of metals in a smeltery and refinery in Northern Sweden as well as of a control group have been quantitatively assayed.The analytical techniques used were atomic absorption spectrophotometry, neutron activation analysis and particle induced X-ray emission analysis (PIXE) in a proton microprobe. Increased levels of lead in the bone tissue of exposed workers compared to a non-exposed control group were observed. The median level of lead in the group of exposed workers exceeded the corresponding value of the control group about 5 times.Using the proton microprobe in the PIXE-mode, concentration profiles of copper, lead and zinc were examined within the Haversian system of the bone samples.     

Distribution, speciation, and transport of mercury in stream-sediment, stream-water, and fish collected near abandoned mercury mines in southwestern Alaska, USA

Concentrations of total Hg, Hg (II), and methylmercury were measured in stream-sediment, stream-water, and fish collected downstream from abandoned mercury mines in southwestern Alaska to evaluate environmental effects to surrounding ecosystems. These mines are found in a broad belt covering several tens of thousands of square kilometers, primarily in the Kuskokwim River basin. Mercury ore is dominantly cinnabar (HgS), but elemental mercury (Hg degrees) is present in ore at one mine and near retorts and in streams at several mine sites. Approximately 1400 t of mercury have been produced from the region, which is approximately 99% of all mercury produced from Alaska. These mines are not presently operating because of low prices and low demand for mercury. Stream-sediment samples collected downstream from the mines contain as much as 5500 microg/g Hg. Such high Hg concentrations are related to the abundance of cinnabar, which is highly resistant to physical and chemical weathering, and is visible in streams below mine sites. Although total Hg concentrations in the stream-sediment samples collected near mines are high, Hg speciation data indicate that concentrations of Hg (II) are generally less than 5%, and methylmercury concentrations are less than 1% of the total Hg. Stream waters below the mines are neutral to slightly alkaline (pH 6.8-8.4), which is a result of the insolubility of cinnabar and the lack of acid-generating minerals such as pyrite in the deposits. Unfiltered stream-water samples collected below the mines generally contain 500-2500 ng/l Hg; whereas, corresponding stream-water samples filtered through a 0.45-microm membrane contain less than 50 ng/l Hg. These stream-water results indicate that most of the Hg transported downstream from the mines is as finely-suspended material rather than dissolved Hg. Mercury speciation data show that concentrations of Hg (II) and methylmercury in stream-water samples are typically less than 22 ng/l, and generally less than 5% of the total Hg. Muscle samples of fish collected downstream from mines contain as much as 620 ng/g Hg (wet wt.), of which 90-100% is methylmercury. Although these Hg concentrations are several times higher than that in fish collected from regional baseline sites, the concentration of Hg in fish is below the 1000 ng/g action level for edible fish established by the US Food and Drug Administration (FDA). Salmon contain less than 100 ng/g Hg, which are among the lowest Hg contents observed for fish in the study, and well below the FDA action level.     

ICP-AES法测定海水中钾、钠、钙、镁、锂、锶、锰

研究了采用等离子体发射光谱法(ICP-AES)测定海水中钾、钠、钙、镁、锂、锶、锰7种元素的方法。此方法标准曲线线性关系好,相对标准偏差3.35%,相对误差5.5%,加标回收率达90%～104.3%,有较高的测定精密度和准确度,干扰小,值得推广应用。     

Biomonitorization of cadmium, chromium, manganese, nickel and lead in whole blood, urine, axillary hair and saliva in an occupationally exposed population

Heavy metal contamination from occupational origin is a cause for concern because of its potential accumulation in the environment and in living organisms leading to long term toxic effects. This study was aimed to assess Cd, Cr, Mn, Ni and Pb levels in whole blood, urine, axillary hair and saliva from 178 individuals with occupational exposure to heavy metals. Levels of metal compounds were determined by atomic absorption spectrometry. We collected information on occupation, lifestyle habits and food intake by questionnaire. Multiple linear regression analyses for metal ion concentration in whole blood, urine, axillary hair and saliva were adjusted for age, gender, smoking and alcohol consumption, lifetime workplace exposure, residence area and food habits. Overall, blood and urine median concentrations found for the five metals analyzed do not exceed biological exposure indexes, so that they are very similar to a non-occupationally exposed population. Toxicokinetic differences may account for the lack of correlations found for metal levels in hair and saliva with those in blood or urine. For those heavy metals showing higher median levels in blood with respect to hair (Cd, Mn and Pb) indicating lesser hair incorporation from blood, the lifetime working experience was inversely correlated with their hair levels. The longer the lifetime working experience in industrial environments, the higher the Mn and Ni concentration in saliva. Axillary hair and saliva may be used as additional and/or alternative samples to blood or urine for biomonitoring hair Mn, and saliva Ni in subjects with occupational exposure.     

Spaces of resilience,ingenuity, and entrepreneurship in informal work in Ghana

Despite playing an important role in the economies of low-income countries, there is a perception that informal markets are haphazard and disorganized. Using in-depth interviews conducted in Accra, Ghana, this study examines the strategic choices that market women pursue to gain access to and thrive in informal working spaces and ensure long-term survival. The findings reveal that entry into the informal working spaces is contingent on women’s ability to forge and nourish ties with acquaintances, kinsmen and middlemen. Further, the study found that in contrast to the notion of unregulated competition typically associated with street vending, market relations among women traders in informal market spaces are marked by alliances between rival sellers that transcended religious, ethnic, linguistic, and generational divides. As well, a strict code of conduct governs market behaviour, underpinned by an ethos of cooperation and mutual assistance among rival sellers. Furthermore, market women in Accra articulate the rationale behind informal entrepreneurship in ways that align with local and national development agenda. In so doing, the market women lend legitimacy to their trade, demand accountability from local authorities, and oppose repressive practices by the state. We highlight the implications of our findings for city planning and development.     

Occurrence of sulfonylurea, sulfonamide, imidazolinone, and other herbicides in rivers, reservoirs and ground water in the Midwestern United States, 1998

Sulfonylurea (SU), sulfonamide (SA), and imidazolinone (IMI) herbicides are relatively new classes of chemical compounds that function by inhibiting the action of a plant enzyme, stopping plant growth, and eventually killing the plant. These compounds generally have low mammalian toxicity, but plants demonstrate a wide range in sensitivity to SUs, SAs, and IMIs with over a 10,000-fold difference in observed toxicity levels for some compounds. SUs, SAs, and IMIs are applied either pre- or post-emergence to crops commonly at 1/50th or less of the rate of other herbicides. Little is known about their occurrence, fate, or transport in surface water or ground water in the USA. To obtain information on the occurrence of SU, SA, and IMI herbicides in the Midwestern United States, 212 water samples were collected from 75 surface-water and 25 ground-water sites in 1998. These samples were analyzed for 16 SU, SA and IMI herbicides by USGS Methods Research and Development Program staff using high-performance liquid chromatography/mass spectrometry. Samples were also analyzed for 47 pesticides or pesticide degradation products. At least one of the 16 SUs, SAs or IMIs was detected above the method reporting limit (MRL) of 0.01 microg/l in 83% of 130 stream samples. Imazethapyr was detected most frequently (71% of samples) followed by flumetsulam (63% of samples) and nicosulfuron (52% of samples). The sum of SU, SA and IMI concentrations exceeded 0.5 microg/l in less than 10% of stream samples. Acetochlor, alachlor, atrazine, cyanazine and metolachlor were all detected in 90% or more of 129 stream samples. The sum of the concentration of these five herbicides exceeded 50 microg/l in approximately 10% of stream samples. At least one SU, SA, or IMI herbicide was detected above the MRL in 24% of 25 ground-water samples and 86% of seven reservoir samples.     

Burdens of PBBs, PBDEs, and PCBs in tissues of the cancer patients in the e-waste disassembly sites in Zhejiang, China

This study was conducted to explore the burdens of PBBs, PBDEs, and PCBs among cancer patients living in the e-waste disassembly sites. The contents of 23 PBB congeners, 12 PBDE congeners, and 27 PCB congeners in kidney, liver, and lung samples were measured by GC-MS. The results showed that low-brominated PBBs and PBB153 were the predominant congeners. PBDE47 were the most predominant PBDE congeners. PBDE209 were detected in > 70% of the samples, with geometric means ranging from 64.2 to 113.9 ng g^− 1 lipid. Among the three subfamilies of PHAHs, PCB concentrations were the highest. The detected levels of PHAHs were in the same order of magnitude in the three tissues, which indicated that any of the three tissues could be the suitable indicator for assessing body burdens of PHAHs. PBB contents (181-192 ng g^− 1 lipid) were obviously higher than those reported in the general USA population (3-8 ng g^− 1 lipid). PBDE levels (174.1-182.3 ng g^− 1 lipid) were comparable to those reported in the USA population, but significantly higher than those of the European population. PCBs levels were comparable to those of the European population. The high cancer incidence in the disassembly sites may be related to higher burdens of PBBs, PBDEs, and PCBs in tissues.