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1.
The results of studies carried out using a computer programme simulating the coagulation of suspensions containing spherical sol particles and spherical coagulant particles are reported.The influence of the degree of dispersion of the system on the coagulation reaction kinetics was investigated. The obtained results of kinetic studies were tested in the light of classical Müller–Smoluchowski equations. The influence of the physical properties of the coagulant,such as size, density and mass, on the coagulation rate was tested. It was found that within the range described in this paper, the rate of the simulated coagulation process fulfils both the kinetic equation of a first-order reaction, and the kinetic equation of a second-order reaction.Within the tested range, a significant influence of the mass and size of the coagulant on the coagulation rate was ascertained. The kinetic Müller–Smoluchowski dependence is fulfilled in a broader range of the degree of dispersion, when the coagulant particle mass and the sol particle mass are equal. When the particle mass increases with an increase in the particle radius, the coagulation rate increases faster that it would result from the Müller's dependence.  相似文献   

2.
Agustinia ligabuei is an Early Cretaceous sauropod dinosaur from the northwest of Patagonia that is currently the topic of debate with respect to its phylogenetic position and atypical dermal armor. The presence of four morphotypes of laminar and transversely elongated putative osteoderms was used to consider Agustinia as an armored sauropod. Regarding the different hypotheses about the identity of the bony structures of Agustinia (e.g., osteoderms, cervical or dorsal ribs, hypertrophied elements), a comparative histological analysis has been carried out. Histological evidence is presented herein and reveals that none of the morphotypes of Agustinia shows a primary bone tissue formed by structural fiber bundles as in other sauropod dinosaur osteoderms. Furthermore, on the basis of their gross morphology and microstructure, the bony structures originally classified as types 1 + 4 and 3 are more comparable respectively with dorsal and cervical ribs than any other kind of dermal or bony element. Due to poor preservation, the nature of the type 2 cannot be assessed but is here tentatively assigned to a pelvic girdle element. Although a phylogenetic reassessment of Agustinia is not the purpose of this paper, our paleohistological analyses have broader implications: by not supporting the dermal armor hypothesis for Agustinia, its inclusion in Lithostrotia is not justified in the absence of other diagnostic features.  相似文献   

3.
DevelopmentoftheprocedureforthestabilizationofrainwatersamplesYuanZhongxin;Chung-ShinYuan(DepartmentofChemicalEngineeringNati...  相似文献   

4.
The lower troposphere is an excellent receptacle, which integrates anthropogenic greenhouse gases emissions over large areas. Therefore, atmospheric concentration observations over populated regions would provide the ultimate proof if sustained emissions changes have occurred. The most important anthropogenic greenhouse gas, carbon dioxide (CO(2)), also shows large natural concentration variations, which need to be disentangled from anthropogenic signals to assess changes in associated emissions. This is in principle possible for the fossil fuel CO(2) component (FFCO(2)) by high-precision radiocarbon ((14)C) analyses because FFCO(2) is free of radiocarbon. Long-term observations of (14)CO(2) conducted at two sites in south-western Germany do not yet reveal any significant trends in the regional fossil fuel CO(2) component. We rather observe strong inter-annual variations, which are largely imprinted by changes of atmospheric transport as supported by dedicated transport model simulations of fossil fuel CO(2). In this paper, we show that, depending on the remoteness of the site, changes of about 7-26% in fossil fuel emissions in respective catchment areas could be detected with confidence by high-precision atmospheric (14)CO(2) measurements when comparing 5-year averages if these inter-annual variations were taken into account. This perspective constitutes the urgently needed tool for validation of fossil fuel CO(2) emissions changes in the framework of the Kyoto protocol and successive climate initiatives.  相似文献   

5.
In the obligate mutualism between figs (Ficus) and their specific pollinators (Chalcidoidea, Agaonidae), each species of fig wasp typically reproduces in figs of a single host species. Host specificity is maintained largely because pollinators are attracted to tree-specific volatiles released from their host figs, but whether the wasps can reproduce if they enter figs of non-host species is unclear. We investigated the reproductive success of Ceratosolen emarginatus (associated with Ficus auriculata) and Ceratosolen sp. (associated with F. hainanensis) in atypical hosts by experimentally introducing foundresses into host and non-host figs. F. auriculata figs entered by Ceratosolen sp. were more likely to abort than if entered by C. emarginatus, but abortion of F. hainanensis figs was not affected by pollinator species. Single C. emarginatus foundresses produced more but smaller offspring in F. hainanensis than in their normal host. Conversely Ceratosolen sp. produced fewer but larger offspring in F. auriculata than in their normal host, probably as a result of having longer to develop. Mean style length differences, relative to the lengths of the wasps’ ovipositors, may have dictated the number of offspring produced, with oviposition made easier by the shorter styles in F. hainanensis figs. Our results imply that, in addition to morphological constraints and tree-specific volatiles, reduced reproductive success in atypical hosts can be another factor maintaining host specificity, but for other species only behavioural changes are required for host switching to occur.  相似文献   

6.
On the study of ecosystem health:state of the art   总被引:2,自引:0,他引:2  
IntroductionDuringlastdecades,theterm“ecosystemhealth”isusedwithincreasingfrequencyintheliterature.Thegrowinginterestsinthestu...  相似文献   

7.
A three-dimensional, iron-cemented structure found in the anterior thoracic cavity of articulated Thescelosaurus skeletal remains was hypothesized to be the fossilized remains of the animal’s four-chambered heart. This was important because the finding could be interpreted to support a hypothesis that non-avian dinosaurs were endothermic. Mammals and birds, the only extant organisms with four-chambered hearts and single aortae, are endotherms. The hypothesis that this Thescelosaurus has a preserved heart was controversial, and therefore, we reexamined it using higher-resolution computed tomography, paleohistological examination, X-ray diffraction analysis, X-ray photoelectron spectroscopy, and scanning electron microscopy. This suite of analyses allows for detailed morphological and chemical examination beyond what was provided in the original work. Neither the more detailed examination of the gross morphology and orientation of the thoracic “heart” nor the microstructural studies supported the hypothesis that the structure was a heart. The more advanced computed tomography showed the same three areas of low density as the earlier studies with no evidence of additional low-density areas as might be expected from examinations of an ex situ ostrich heart. Microstructural examination of a fragment taken from the “heart” was consistent with cemented sand grains, and no chemical signal consistent with a biological origin was detected. However, small patches of cell-like microstructures were preserved in the sandstone matrix of the thoracic structure. A possible biological origin for these microstructures is the focus of ongoing investigation.  相似文献   

8.
Males of the genus Parastizopus (Coleoptera: Tenebrionidae) exhibit a special pheromone-emitting behaviour. They do a headstand, expose the aedeagus and remain in this posture for a few seconds. The pheromone emitted by P. transgariepinus was collected by solid-phase micro-extraction (100 microm polydimethylsiloxane fibre) and identified as 1-tridecene by gas chromatography/mass spectrometry. Presumably, this compound originates from the aedeagal gland, a special feature in Parastizopus, as 1-tridecene is the main compound in the gland reservoirs (23.6+/-3.8%), accompanied by various less volatile fatty acid esters (25.2+/-2.0%) and hydrocarbons (51.2+/-5.7%). 1-Tridecene is also part of the pygidial defensive secretion of both sexes, together with other 1-alkenes, monoterpene hydrocarbons and 1,4-benzoquinones, but as none of these other compounds was detected during calling, the pygidial gland could be ruled out as pheromone source. Extracts of the aedeagal gland reservoirs and the pygidial defensive secretion contained comparable amounts of 1-tridecene, 1.24+/-0.41 and 1.88+/-0.54 microg/male, respectively. Chemo-orientation experiments using a servosphere showed that 1 microg of 1-tridecene was attractive to females but not to males.  相似文献   

9.
The Environmental technology (ET) sector delivers environmentally preferably products. Little is known about whether companies in the ET sector set environmental objectives relating to their own production processes. This paper presents results from an online survey on environmental work in enterprises listed by the Swedish Environmental Technology Council (Swentec). The survey found that depending on the specific subsector, only between 21% and 45% of companies provide information about their environmental work on their website. This paper proposes environmental aspects of production and products as bases for corporate greening and for defining ‘green’ and ‘green-green’ business and identifies three main motivations for the companies within ET sector to operate as ‘green-green’ businesses: ‘competitive advantage’, ‘environmental responsibility’ and ‘environmental leadership’.  相似文献   

10.
11.
Yanornis martini is an Early Cretaceous basal ornithurine bird. Its fish-eating diet was previously recognized from a discrete mass of disarticulated fish remains discovered in its abdominal region. A new complete and articulated specimen of Yanornis martini preserves abundant in-situ gastroliths such as have been associated with a herbivorous diet. We suggest that the occurrence of gastroliths in this specimen, fish remains in a second, and the lack of gastroliths in three others, is consistent with diet-switching in Yanornis martini. Incompatibility of the preserved data with explanations of the grit as an artifact of preservation or result of accidental ingestion is discussed. This discovery indicates the earliest presence of intermittent diet change (and associated gizzard plasticity) observed in extant birds seasonally and in response to changes in available food sources.  相似文献   

12.
A new mass estimate for the dodo (Raphus cucullatus), based on the lengths of the femur, tibiotarsus and tarsometatarsus, is attempted. The obtained mean mass is 10.2 kg, which is less than previous estimates based on other methods, which ranged from 10.6 to 21.1 kg, and much lower than the 50 lbs reported by a seventeenth-century eyewitness. The new estimated mass, which is similar to that of a large wild turkey, seems more realistic than previous ones and supports the hypothesis that contemporary illustrations of extremely fat dodos were either exaggerations, or based on overfed specimens. Pictures of “fat” dodos may also have been based on individuals exhibiting a display behaviour with puffed out feathers.  相似文献   

13.

Objective

To explore the views and practices of maternal-fetal medicine specialists on offering fetoscopic endoluminal tracheal occlusion (FETO) for left- and right-sided congenital diaphragmatic hernia (LCDH, RCDH) in the post Tracheal Occlusion To Accelerate Lung growth (TOTAL)-trial era.

Method

Cross-sectional knowledge, attitude and practice survey was conducted among 105 attendees of the 19th World Congress of Fetal Medicine.

Results

On average, respondents were knowledgeable about CDH, involved in research, and provided antenatal treatment options. Four out of five (82%) agreed that neonatal survival in LCDH can be reliably predicted in the prenatal period. Few respondents considered the exact risks and benefits of FETO for severe LCDH as being unclear (16%), yet half were uncertain about this for moderate LCDH (57%) and severe RCDH (45%). Most respondents offer FETO for severe LCDH (97%) and RCDH (79%), but only 59% offer it for moderate LCDH. However, half of respondents (58%) stated that not offering FETO for moderate LCDH would be a psychological burden for parents.

Conclusion

Respondents consider the risk-benefit ratio of FETO for severe LCDH clear and consistently offer FETO, but not for moderate LDCH and severe RCDH. However, not offering the option of FETO to parents was considered a psychological burden.  相似文献   

14.
Based on the significant enhancement of fluorescence intensity of carbaryl in inclusion complex, a spetrofluorimetric method with high sensitivity was developed for the determination of carbaryl in aqueous solution. Under the optimum conditions, the complex had excitation and emission maxima at 278 nm and 332 nm, respectively. The linear range of the method was 7.0 ng/ml-1500 ng/ml with a detection limit of 1.2 ng/ml. The proposed method was successfully used to determine quantitatively of carbaryl in cottonseeds.  相似文献   

15.
Central to the mission of America's environmental schools is the development of professional environmental managers. The majority of our graduate students at Yale are enrolled in our master of environmental management program. But what exactly is environmental management? When I am asked this question, I reply that environmental management is the new business of bringing our human enterprise into harmony with the natural world of which we are a part. And I add: it's the most important thing in the world.  相似文献   

16.
17.
Based on the significant enhancement of fluorescence intensity of carbaryl in inclusion complex, a spetrofluorimetdc method with high sensitivity was developed for the determination of carbaryl in aqueous solution. Under the optimum conditions, the complex had excitation and emission maxima at 278 nm and 332 nm, respectively. The linear range of the method was 7.0 ng/ml-1500 ng/ml with a detection limit of 1.2 ng/ml. The proposed method was successfully used to determine quantitativelv of carbarvl in cottonseeds.  相似文献   

18.
IntroductionNowweallconcernourselveswiththecontemporaryproblemsofoverpopulation,resourceexploitation,environmentalpollutionand...  相似文献   

19.
New finds of bones of the Egyptian Mongoose (Herpestes ichneumon), one from Portugal and one from Spain, were directly 14C dated to the first century AD. While the Portuguese specimen was found without connection to the Chalcolithic occupation of the Pedra Furada cave where it was recovered, the Spanish find, collected in the city of Mérida, comes from a ritual pit that also contained three human and 40 dog burials. The finds reported here show that the Egyptian mongoose, contrary to the traditional and predominant view, did not first arrive in the Iberian Peninsula during the Muslim occupation of Iberia. Instead, our findings are consistent with the hypothesis that the species was first introduced by the Romans, or at least sometime during the Roman occupation of Hispania. Therefore, radiocarbon dating of new archaeological finds of bones of the Egyptian Mongoose (Herpestes ichneumon) in the Iberian Peninsula push back the confirmed presence of the species in the region by approximately eight centuries, as the previously oldest dated record is from the ninth century. With these new dates, there are now a total of four 14C dated specimens of Egyptian mongooses from the Iberian Peninsula, and all of these dates fall within the last 2000 years. This offers support for the hypothesis that the presence of the species in Iberia is due to historical introductions and is at odds with a scenario of natural sweepstake dispersal across the Straits of Gibraltar in the Late Pleistocene (126,000–11,700 years ago), recently proposed based on genetic data.  相似文献   

20.
With the development of rural pollution, its characteristic and institutional factor should be studied for pollution control through economics and sociology. Based on the data gathered from investigations by several government sectors, rural environmental pollution can be divided into two types by its sources: internal source type and external source type. The internal source type is the main component of rural pollution at present, which can be further divided into three types. Research shows that the contributing institutional factors of rural pollution issues and the effectiveness of environmental management system over rural pollution can be summarized as distinctiveness. In essence, the rural pollution issue results from the dualism of rural and urban areas’ inadaptability to rural modernization. In detail, the contributing factors can be summed up on three institutional levels. There are obvious loopholes in rural environmental management system which, in the meantime, is incapable and inadaptable to rural pollution control. There exist similar questions in the related public service system, which are intensified by inappropriate reform which brought about incompatible incentive in the recent years. However, in the eleventh five-year plan period, there are advantageous trends in the three institutional levels. Main data sources in this paper: ➀ the surveys on TVEs (township and village enterprises) conducted by Township Enterprise Bureau of Ministry of Agriculture of China in 1997 and 2002; ➁ the partial survey on rural environmental conditions by EPA (environmental protection administration) of Zhejiang Province in 2002; ➂ the survey on the pollution of IPLFs (livestock and poultry farms) in 23 provinces, municipalities, and directly administered cities by the State Environmental Protection Administration of China in 2002; ➃ the research report on Mechanism of Investment and Financing for Environmental Protection by China Council for International Environment and Development Cooperation in 2003; ➄ the third investigation on national hygiene service in 2003; ➅ the regular monitoring of safe quality of agricultural products by the Ministry of Agriculture of China in 2005; ➆ the investigation arranged by the Ministry of Health which finished in 2007 and showed the total situation of rural environmental health and drinking water security of the whole country.  相似文献   

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