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1.
Rossella Lorenzi 《海外英语》2003,(7)
Bacteria found in a 2.000-year-old piece of cheese couldbe the final evidence that this food was a continuoussource of infectious disease(传染病)in the ancientRoman World.According to a study published in a recent issue of theJournal of Infection,a tiny piece of cheese containing diseasebacteria was carbonized in the volcanic eruption that one nightin late August,79 A.D.covered Pompeii(庞培)and thenearby towns of Herculaneum(赫库兰尼姆)and Stabiae withnine tO 20 feet ofhot ash and pumice(浮石).About 250 people fled to the beach,trying in vain toescape the molten lava(熔岩)and boiling mud pouring downMount VesuviUS.They died from extreme thermal shock(热冲击),wrapped in a 750-degree Fahrenheit cloud.The intenseheat and rapid cooling of the mud has left their bones in aremarkable state of preservation,allowing in-depth medicalStUdies. 相似文献
2.
Multi-year monitoring of paddy rice planting area in Northeast China using MODIS time series data 总被引：1，自引：0，他引：1
Jing-jing SHI Jing-feng HUANG Feng ZHANG 《Journal of Zhejiang University. Science. B》2013,14(10):934-946
The objective of this study was to investigate the tempo-spatial distribution of paddy rice in Northeast China using moderate resolution imaging spectroradiometer(MODIS) data.We developed an algorithm for detection and estimation of the transplanting and flooding periods of paddy rice with a combination of enhanced vegetation index(EVI) and land surface water index with a central wavelength at 2130 nm(LSWI2130).In two intensive sites in Northeast China,fine resolution satellite imagery was used to validate the performance of the algorithm at pixel and 3×3 pixel window levels,respectively.The commission and omission errors in both of the intensive sites were approximately less than 20%.Based on the algorithm,annual distribution of paddy rice in Northeast China from 2001 to 2009 was mapped and analyzed.The results demonstrated that the MODIS-derived area was highly correlated with published agricultural statistical data with a coefficient of determination(R2) value of 0.847.It also revealed a sharp decline in 2003,especially in the Sanjiang Plain located in the northeast of Heilongjiang Province,due to the oversupply and price decline of rice in 2002.These results suggest that the approaches are available for accurate and reliable monitoring of rice cultivated areas and variation on a large scale. 相似文献
3.
RAHIMI N SADEGHI M. H. MAHJOOB M.J. 《浙江大学学报(A卷英文版)》2007,8(9):1443-1451
In this paper,a geometric approach to fault detection and isolation (FDI) is applied to a Multiple-Input Multi-ple-Output (MIMO) model of a frame and the FDI results are compared to the ones obtained in the Single-Input Single-Output (SISO),Multiple-Input Single-Output (MISO),and Single-Input Multiple-Output (SIMO) cases. A proper distance function based on parameters obtained from parametric system identification method is used in the geometric approach. ARX (Auto Regressive with eXogenous input) and VARX (Vector ARX) models with 12 parameters are used in all of the above-mentioned models. The obtained results reveal that by increasing the number of inputs,the classification errors reduce,even in the case of applying only one of the inputs in the computations. Furthermore,increasing the number of measured outputs in the FDI scheme results in decreasing classification errors. Also,it is shown that by using probabilistic space in the distance function,fault diagnosis scheme has better performance in comparison with the deterministic one. 相似文献
4.
Interaction Between DEHP and Particulate in a Eutrophic Lake 总被引：2，自引：0，他引：2
Characteristics of interaction between di-2-ethylhexyl phthalate(DEHP) and particulate in a eutrophic lake were studied in this paper. DEHP concentrations ranged from 89.9 to 247 μg/L with an average value of 146 μg/L in subsurface water (SSW) samples, and from 82.0 to 390 μg/L with an average value of 211 μg/L in water surface microlayer (SM) samples. The results indicate that there was only a weak correlation between the DEHP concentrations and suspended particulate material(SPM) concentrations in both SSW and SM,while the significant correlation between DEHP concentrations and chlorophyll a concentrations was found,which suggestes that DEHP was principally bound to phytoplankton in the eutrophic lake. Correlation between DEHP concentrations and total phosphor (TP) concentrations was also found in this investigation. Enrichment factors (EF) of DEHP in SM were in the range of 0.85 to 2.12 with an average value of 1.35..DEHP EFs were significantly related to the enrichment of chlorophyll a in SM. The results suggest that the enrichment of DEHP in SM of this eutrophic lake was mainly due to DEHP accumulation in phytoplankton and was controlled by distribution of phytoplankton between SM and SSW. 相似文献
5.
Type-dependent differential expression of neuropeptide Y in chicken hypothalamus （Gallus domesticus）
Chen GQ Hu XF Sugahara K Chen JS Song XM Zheng HC Jiang YQ Huang X Jiang JF Zhou WD 《Journal of Zhejiang University. Science. B》2007,8(11):839-844
Neuropeptide Y (NPY) is one of the most important orexigenic agents in central regulation of feeding behavior, body weight and energy homeostasis in domestic chickens. To examine differences in the hypothalamic NPY between layer-type and meat-type of chickens, which are two divergent kinds of the domestic chickens in feeding behavior and body weight, we detected mRNA levels of NPY in hypothalamic infundibular nucleus (IN), paraventricular nucleus (PVN) and lateral hypothalamic area (LHA) of these two types of chickens using one-step real time RT-PCR. The meat-type chicken had more food daily (about 1.7 folds) and greater body weights (about 1.5 folds) and brain weights than the layer-type chicken at the age of 14 d. In the meat-type of chicken, NPY mRNA levels of the IN and PVN were significantly greater than those of the LHA, and were not significantly different between the IN and PVN. However, in the layer-type of chicken, NPY mRNA levels were significantly greater in the IN than those in the LHA and PVN, and were not significantly different between the PVN and LHA. In all these hypothalamic regions, the layer-type of chicken had significantly higher NPY mRNA levels than the meat-type chicken did. These results suggest the expression of NPY in the hypothalamus has a type-dependent pattern in domestic chickens. 相似文献
6.
Norman,the hero of the movie,is the son of apriest.He was born in a middle—class fami-ly.He and his families live in a town,not farfrom a clear stream and a waterfall.His father is apious(虔诚的),who takes belief to the hearts andsouls.Norman is good at learning,and going to be-come a professor in the University of Chicago.Theonly libertine(浪子)of the family is his little broth-er,Paul,who is a journalist in a newspaper inMontana.Though the two brothers and their fa-ther are quite different persons,they like fishing 相似文献
7.
Response surface methodology(RSM) was employed to optimize the control parameters of TiO_2/graphene with exposed {001} facets during synthesis, and its enhanced photocatalytic activities were evaluated in the photodegradation of toluene. Experimental results were in good agreement with the predicted results obtained using RSM with a correlation coefficient(R~2) of 0.9345. When 22.06 mg of graphite oxide(GO) and 2.09 mL of hydrofluoric acid(HF) were added and a hydrothermal time of 28 h was used, a maximum efficiency in the degradation of toluene was achieved. X-ray diffraction(XRD), transmission electron microscopy(TEM), and scanning electron microscopy(SEM) were employed to characterize the obtained hybrid photocatalyst. The electron transferred between Ti and C retarded the combination of electron–hole pairs and hastened the transferring of electrons, which enhanced the photocatalytic activity. 相似文献
8.
Lipid peroxide (LPO) plays pivotal roles in the process and development of many diseases. In this work, we studied the inhibitory effect of probimane (Pro), a Chinese anticancer agent, on erythrocyte LPO and the interaction of Pro with sialic acids (sia). Malondialdehyde (MDA) of erythrocytes activated by hydrogen peroxide was measured. Pro was found to inhibit the product of LPO induced by hydrogen peroxide in a non-enzyme system of both rabbit and human erythrocytes in the absence of doxorubicin. Sia were 相似文献
9.
Present English learning and teaching in colleges especially in Art Academy is far from satisfactory.English,as one of the most important international languages,plays a more and more important role in the international communication.In this paper,the author tries to apply TBLT(Task-based Language Teaching) to oral English teaching.The experiment chose 102 freshmen of two classes in College of Broadcasting and Hosting in CUCN(Communication University of China,Nanjing) as subjects,lasting 16 weeks all together.In the experimental class,the participants are taught with the new method with the aid of TBLT,while in the controlled class,the traditional approach was utilized.By means of data analysis and daily observation of teaching experiment,with the help of the software SPSS and MATLAB,the comparison of both class and of the EC before and after the experiment has verified that the new method with the aid of TBLT has a more positive effect in improving students’oral proficiency,es pecially for students who had a poor performance in speaking before. 相似文献
10.
Guo-dong SHAN Guo-qiang XU You-ming LI 《Journal of Zhejiang University. Science. B》2013,14(9):844-848
The objective of this study was to investigate the endosonographic appearance of gastric linitis plastica(GLP) and to study the usefulness of endoscopic ultrasonography(EUS) for the T and N staging of GLP.EUS examinations of 55 patients with histologically proven GLP were retrospectively studied.In all patients,EUS showed that lesions involved at least one-third of the circumference of the stomach.Based on the findings of the EUS,the 55 patients were divided into two groups.There were 32(58.2%) patients in the first group.EUS of this group showed that the five sonographic layers had disappeared and had been replaced by a hypoechogenic thickening of the gastric wall.There were 23(41.8%) patients in the second group.EUS of this group showed that the first three sonographic layers were blurred and thickened,and the fourth layer was significantly thickened.The full thickness of the gastric wall was significantly thicker in first than in the second group of patients(P<0.01).The incidence of perigastric lesions was significantly higher in the first than in the second group of patients(P<0.01).Results for the 15 patients following preoperative EUS were compared postoperatively with histopathologic findings for T and N staging.The overall diagnostic accuracy of the T stage was 73.3% and of the N stage was 60.0%.In eight patients,we used EUS to assess a therapeutic response.No response was observed in five patients and a partial response in three.EUS images of GLP are characteristic.EUS is helpful in diagnosing GLP and for assessing the T and N stages. 相似文献
11.
INTRODUCTION Regulation, handling and bioremediation of hazardous materials require an assessment of the risk to some living species other than human being, or assessment of hazard to the entire ecosystem. As- sessment endpoints are values of the ecosystem that are to be protected and are identified early in the analysis. Such endpoints may include life cycle stages of a species and reproductive or growth patterns. Ecosystem risk assessment is at its dawn with this area of environment sci… 相似文献
12.
Assessing potential dietary toxicity of heavy metals in selected vegetables and food crops 总被引：3，自引：0，他引：3
Heavy metals, such as cadmium, copper, lead, chromium and mercury, are important environmental pollutants, particularly in areas with high anthropogenic pressure. Their presence in the atmosphere, soil and water, even in traces can cause serious problems to all organisms, and heavy metal bioaccumulation in the food chain especially can be highly dangerous to human health. Heavy metals enter the human body mainly through two routes namely： inhalation and ingestion, ingestion being the main route of exposure to these elements in human population. Heavy metals intake by human populations through food chain has been reported in many countries. Soil threshold for heavy metal toxicity is an important factor affecting soil environmental capacity of heavy metal and determines heavy metal cumulative loading limits. For soil-plant system, heavy metal toxicity threshold is the highest permissible content in the soil （total or bioavailable concentration） that does not pose any phytotoxic effects or heavy metals in the edible parts of the crops does not exceed food hygiene standards. Factors affecting the thresholds of dietary toxicity of heavy metal in soil-crop system include： soil type which includes soil pH, organic matter content, clay mineral and other soil chemical and biochemical properties; and crop species or cultivars regulated by genetic basis for heavy metal transport and accumulation in plants. In addition, the interactions of soil-plant root-microbes play important roles in regulating heavy metal movement from soil to the edible parts of crops. Agronomic practices such as fertilizer and water managements as well as crop rotation system can affect bioavailability and crop accumulation of heavy metals, thus influencing the thresholds for assessing dietary toxicity of heavy metals in the food chain. This paper reviews the phytotoxic effects and bioaccumulation of heavy metals in vegetables and food crops and assesses soil heavy metal thresholds for potential dietary toxicity. 相似文献
13.
该文采用湿法消解法（硝酸-高氯酸）预处理待测实验室废水,火焰原子吸收法测定废水中重金属离子（铅、铬、镉、铁、铜、锌、镍、锰）的含量;并通过配制模拟废液实验、精密度检测实验、加标回收试验三种方法验证本次研究的可行性和准确性．结果表明,火焰原子吸收法测定重金属离子含量的准确度、灵敏度较高,相对标准偏差低于5％,回收率92．3％-104．0％,方法简便、灵敏、准确,适用于实验室废水中重金属离子的测定． 相似文献
14.
15.
2006年4至6月,对淮南地区克氏原螯虾(Procambarus clakii)的重金属含量进行了测定.研究结果表明:淮南地区克氏原螯虾肌肉中有一定程度的重金属积累,Cu、和Pb的检出率为100%,Cd的检出率为87.6%.Cu检测出含量的平均值为1.88mg/kg;Cd检测出含量的平均值为0.16mg/kg;Pb检测出含量的平均值为0.67mg/kg.同种生物对不同的重金属含有不同的蓄积能力. 相似文献
16.
着重介绍综合利用海滨的巨大风能和地场对电镀污泥酸解液进行自然浓缩、结晶提取浸出液中的铜、镍、铬、锌等金属及其化合物的工艺方法,进而阐述利用天然海边晒场资源浓缩结晶回收电镀污泥中的有价金属,既节能,又环保,可实现循环生产。 相似文献
17.
重金属的排放造成了严重的环境问题。而消除重金属污染成为世界性的难题．有关研究结果表明。虽然重金属污染对植物有毒害作用，但是某些特殊植物具有从污染环境中吸收、转移以及积累重金属的潜能。从而修复土壤和水体等环境中的重金属污染．植物修复技术的出现虽然有很好的应用前景，但仍存在一些问题。 相似文献
18.
姜叶琴 《湖州师范学院学报》2005,27(2):59-61
大蒜在铜、铬、铅、钡四种金属离子溶液中分别培养的实验证明：实验重金属均对大蒜根生长有抑制作用,且随着各重金属离子溶液浓度的增加和处理时间的延长,大蒜根生长的速度变慢或停止.同浓度的不同重金属离子溶液对大蒜根生长的抑制作用,从强到弱依次为：Cu^2＋〉 Cr^3＋〉 Pb^2＋溶液.非重金属Ba^2＋对大蒜根生长无明显影响. 相似文献
19.
ZHANG Ming-kui ZHENG Shun-an 《浙江大学学报(A卷英文版)》2007,8(11):1808-1815
Soils can often be contaminated simultaneously by more than one heavy metal. The sorption-desorption behavior of a metal in a soil will be affected by the presence of other metals. Therefore, selective retention and competitive adsorption of the soils to heavy metals can affect their availability and movement through the soils. In this study, the simultaneous competitive adsorption of four heavy metals (Cd, Cu, Hg, and Pb) on ten agricultural soils collected from the Changjiang and Zhujiang deltas, China was assessed. The results showed that the competition affected the behavior of heavy metal cations in such a way that the soils adsorbed less Cd and Hg, and more Pb and Cu with increasing total metal concentrations, regardless of the molar concen- tration applied. As the applied concentrations increased, Pb and Cu adsorption increased, while Cd and Hg adsorption decreased. The adsorption sequence most found was Pb>Cu>Hg>Cd. The maximum adsorption capacity for the heavy metal cations was calculated, and affected markedly by soil properties. The results suggest that Hg and Cd have higher mobility associated to the lower adsorption and that Pb and Cu present the opposite behavior. Significant correlations were found between the maximum adsorption capacity of the metals and pH value and exchangeable acid, suggesting that soil pH and exchangeable acid were key factors controlling the solubility and mobility of the metals in the agricultural soils. 相似文献
20.
Daqing Wetland was contaminated by heavy metals for holding lots of industrial and domestic waste water. Due to their high stability and non-degradation, heavy metals are possible to gather in human body through the food chain and then threaten health. Water samples were collected from Longfeng Wetland and lake marshes in the vicinity of Daqing City. The contents of heavy metals （Cd, Pb, Cr, Cu, Zn, Ni） were determined, and the contamination degrees were evaluated simultaneously. The results indicate that heavy metals of Zn, Ni, Cd, Cr and Pd have contaminated the Longfeng Wetland severely. In addition the concentrations of Cr and Cd in some lakes around oil wells are excessively high, and have overrun the grade V based on the threshold values of surface water given by the National Environmental Protection Agency of China. Some measures have to be taken to tackle heavy metal contamination of Longfeng Wetland and lake marshes in Daqing City. 相似文献