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1.
《Die Naturwissenschaften》1989,76(3):140
Naturwissenschaften Aktuell
Beilslein-Datenbank bietet öffentlich an 相似文献2.
Sidney W. Fox 《Die Naturwissenschaften》1980,67(12):576-581
Recent astrophysical studies suggest a high degree of order in the inanimate universe, stemming from cosmic beginnings. This state is consistent with the nonrandomness observed experimentally in the thermal polymers of amino acids that figure as an early inanimate stage in organic evolution. The various stages in inanimate matter, protocells, and evolved cells and the degree of order that they represent comport with the second law of thermodynamics on a cosmic scale. 相似文献
3.
An ultrasound examination at 17 weeks gestation on a woman with a family history of spina bifida suggested that the fetus had a closed encephalocele. Amniotic fluid alphafetoprotein, rapidly adhering cells and acetylcholinesterase gel electrophoresis were normal. The pregnancy was terminated and the fetus was found to have a large cystic hygroma. It is suggested that in counselling parents of an infant or fetus with a cystic hygroma and with a normal chromosome constitution, ultrasound examination in future pregnancies is advisable, because of the possibility of autosomal recessive inheritance. 相似文献
4.
实现经济、社会和环境可持续发展,是社会发展的必然趋势.该文分析三明市建设生态市的紧迫性、必要性与可行性,并提出对策,为三明市建设生态市提供参考。 相似文献
5.
《Atmospheric Environment. Part A. General Topics》1990,24(8):2263-2266
A prototype design for a cloud and mist collector is presented. The collector is a relatively simple and inexpensive design and excludes precipitation, making it suitable for long term collection of chemical data related to occult deposition. Chemical data obtained from weekly samples taken during an 18 month period using the occult collector and an adjacent bulk collector are presented. 相似文献
6.
Christopher D. Pull William O. H. Hughes Mark J. F. Brown 《Die Naturwissenschaften》2013,100(12):1125-1136
Pathogens exert a strong selection pressure on organisms to evolve effective immune defences. In addition to individual immunity, social organisms can act cooperatively to produce collective defences. In many ant species, queens have the option to found a colony alone or in groups with other, often unrelated, conspecifics. These associations are transient, usually lasting only as long as each queen benefits from the presence of others. In fact, once the first workers emerge, queens fight to the death for dominance. One potential advantage of co-founding may be that queens benefit from collective disease defences, such as mutual grooming, that act against common soil pathogens. We test this hypothesis by exposing single and co-founding queens to a fungal parasite, in order to assess whether queens in co-founding associations have improved survival. Surprisingly, co-foundresses exposed to the entomopathogenic fungus Metarhizium did not engage in cooperative disease defences, and consequently, we find no direct benefit of multiple queens on survival. However, an indirect benefit was observed, with parasite-exposed queens producing more brood when they co-founded, than when they were alone. We suggest this is due to a trade-off between reproduction and immunity. Additionally, we report an extraordinary ability of the queens to tolerate an infection for long periods after parasite exposure. Our study suggests that there are no social immunity benefits for co-founding ant queens, but that in parasite-rich environments, the presence of additional queens may nevertheless improve the chances of colony founding success. 相似文献
7.
Introduction Theenrichmentofnutrientsinwaterbodiesisoneofthecrucialfactorsaffectingwaterquality(Romanski,1997).Ithasbeenreportedthatdischargingwastewaterwithhighlevelsofphosphorus(P)andnitrogen(N)canresultineutrophicationofreceivingwaters,particularlylake… 相似文献
8.
L. I. Van Der Ham T. E. Cohen-Overbeek H. D. Y Paz Geuze Chr. Vermeij-Keers MD PhD 《黑龙江环境通报》1995,15(12):1189-1192
The prenatal detection of scaphocephaly, an isolated form of craniosynostosis, is presented. The diagnosis was made at 34 weeks of gestation in a woman with polyhydramnios. The ultrasound appearance and postnatal follow-up are presented. 相似文献
9.
Herein, we report evidence of an envenomation apparatus (EA) in two different species of extinct “giant” shrews, Beremendia and an indeterminate soricine (Mammalia, Eulipotyphla, Soricidae), documented by very well preserved fossil specimens recovered
from two Early Pleistocene cave deposits of the Sierra de Atapuerca in Burgos, Spain. The two soricine taxa from Atapuerca
have evolved specialized teeth as EAs, which differ from those of recently reported mammals of the Paleocene age, being more
similar to the ones described in the modern Solenodon. This discovery reveals the first instance of shrews possessing what appears to be an EA, an evolutionary adaptation that,
in these species, was probably related to an increase in body mass and hunting of a larger-sized prey. The Atapuerca specimens
would have a highly specialized EA, one of the very few reported for an extinct or living mammal of any time. In addition
to the presence of a gutter-like groove along the medial side of the crown of the lower incisors, these two species also present
stout jaws and a modified mandibular symphysis with a conspicuous cavity, which in life would likely contain large amounts
of connective tissue. The strong mandible architecture of these large shrews would be, in this way, reinforced by a more immovable
symphysis, increasing the bite force exerted over a potential prey. This adaptation, together with the grooved incisors, would
ensure a rapid and efficient transmission of the poisonous saliva to paralyze relatively large-sized prey. 相似文献
10.
Host selection and infection strategies of parasitoids often correlate with high parental investment and low numbers of progeny.
In this study, we investigate how additional internal mechanisms might shape brood size and fitness of the offspring. Emblemasoma auditrix is a parasitoid fly in which about 38 larvae hatch simultaneously in utero. After host location, a single larva is deposited
into the host, where it rapidly develops and pupates after about 5 days. The search for hosts can take several weeks, and
during that time, the larvae arrest their development and remain in the first larval instar. Nevertheless, the larvae increase
in weight within the uterus, and this growth correlates to a decrease in the number of larvae, although no larvae are deposited.
Thus, our data indicate a first case of prenatal cannibalism in an invertebrate with larvae feeding on each other within the
uterus of the adult. 相似文献
11.
The electronics industry is generally recognized as a leader in clean production practices. Industrial ecology, however, encourages a systemic approach to sectoral behavior, which means that not just production, but also the role of electronics products and services in supporting an information culture should be considered as part of a comprehensive analysis. The eventual goal should be the production of social practices and systems that provide the desired functionality and quality of life in an environmentally acceptable manner. A conceptual framework for such an analysis of information infrastructure is presented, although the analyses and data required for a full understanding remain limited and preliminary in many ways. 相似文献
12.
Lavenda BH 《Die Naturwissenschaften》2005,92(11):523-531
The property that power means are monotonically increasing functions of their order is shown to be the basis of the second laws not only for processes involving heat conduction, but also for processes involving deformations. This generalizes earlier work involving only pure heat conduction and underlines the incomparability of the internal energy and adiabatic potentials when expressed as powers of the adiabatic variable. In an L-potential equilibration, the final state will be one of maximum entropy, whereas in an entropy equilibration, the final state will be one of minimum L. Unlike classical equilibrium thermodynamic phase space, which lacks an intrinsic metric structure insofar as distances and other geometrical concepts do not have an intrinsic thermodynamic significance in such spaces, a metric space can be constructed for the power means: the distance between means of different order is related to the Carnot efficiency. In the ideal classical gas limit, the average change in the entropy is shown to be proportional to the difference between the Shannon and Rényi entropies for nonextensive systems that are multifractal in nature. The L potential, like the internal energy, is a Schur convex function of the empirical temperature, which satisfies Jensen's inequality, and serves as a measure of the tendency to uniformity in processes involving pure thermal conduction. 相似文献
13.
An insect parasitoid carrying an ochratoxin producing fungus 总被引:2,自引:0,他引:2
The insect parasitoid Prorops nasuta has been introduced from Africa to many coffee-producing countries in an attempt to control the coffee berry borer. In this
paper, we report on the sequencing of the ITS LSU-rDNA and beta-tubulin loci used to identify a fungus isolated from the cuticle
of a P. nasuta that emerged from coffee berries infected with the coffee berry borer. The sequences were compared with deposits in GenBank
and the fungus was identified as Aspergillus westerdijkiae. The fungus tested positive for ochratoxin A production, with varying levels depending on the media in which it was grown.
These results raise the possibility that an insect parasitoid might be disseminating an ochratoxin-producing fungus in coffee
plantations. 相似文献
14.
The effect of nonuniform alternating fields on neutral or charged particles is named dielectrophoresis in contrast to the action of a uniform steady field on charged particles, named electrophoresis. Dielectrophoresis exhibits e.g. collection of the cells at the electrodes, pearl chain formation everywhere in the experimental chamber, cord formation with ramification, orientation of asymmetric cells, rotation and membrane fusion. In the presented experiments frequencies between 100 Hz and 5 MHz and voltages up to 70 V between electrodes of a few millimeter distance were applied to yeast cells. Dielectrophoresis may offer an interesting biophysical and microbiologic tool for collecting cells and discriminating between living and dead ones, for investigation of influence of drugs on the status of cells, for experiments on membrane or cell fusion and for the study of surface charges in different cells. Its biologic application has just begun. 相似文献
15.
1992~1993年在富营养湖泊五里湖中开展了常绿型人工水生植被组建实验,在面积为2000m2的半封闭式围隔实验区中,选用耐寒植物伊乐藻和喜温植物菱及风眼莲,组建成了常绿型人工水生植被。这种常绿型人工水生植被不仅使实验区内常年保持较好的水质,而且对外来污染冲击有很强的缓冲能力。它可用于水源保护、局部性水质控制、污水净化生态工程、小型富营养水体的生态恢复等。如能解决耐寒型沉水植物伊乐藻与喜温型沉水植物种类间的衔接过渡,这种常绿型人工水生植被技术还可望用于富营养水体中天然水生植被的恢复。 相似文献
16.
17.
《Atmospheric Environment. Part A. General Topics》1992,26(9):1643-1649
Sensitivity analysis is a necessary component in the evaluation of computer models utilized in support of performance assessment activities. Understanding the behavior of predictive models with respect to input data is important for (1) verifying the validity of a model, (2) determining parameters for which it is important to have accurate values, and (3) understanding the behavior of the system being modeled. This paper describes an automated procedure for performing a comprehensive sensitivity analysis using computer calculus. The procedure employs an automated system called GRESS that utilizes a precompiler to enhance a FORTRAN computer code by adding derivative-taking capabilities. From a single run of an enhanced model, GRESS calculates and reports normalized sensitivities of selected results with respect to all input data. GRESS computes a normalized sensitivity by multiplying a derivative by its associated input enhanced model, GRESS calculates and reports normalized sensitivities of selected results with respect to all parameter value and dividing by the associated output value. The automated GRESS procedure is applied to the code AIRDOS-EPA, which estimates radiation doses caused by atmospheric dispersion of radionuclides around nuclear facilities. The sensitivity calculations for a sample problem show good agreement with those obtained by perturbation analysis. Results demonstrate that an automated procedure can be used cheaply and efficiently to perform a comprehensive sensitivity analysis of existing computer models. A methodology for developing enhanced versions of assessment models that include the capability to report routinely sensitivities for important parameters is discussed. Both GRESS and AIRDOS-EPA are available from the Radiation Shielding Information Center at Oak Ridge National Laboratory, P.O. Box 2008. 相似文献
18.
生态企业的构架与考核指标的探讨 总被引:3,自引:0,他引:3
从论述生态企业的构架———经营思想、理念、生产方式、环境管理、环境建设入手 ,对生态企业创建的考核指标进行了探讨 ,提出了五个方面共 2 5项指标的考核体系 ,为生态企业的创建及验收提供了依据。 相似文献
19.
How do birds recognize their own eggs? Do they have a stored template for their own egg characteristics, or do they use another mechanism? Intraspecific brood parasitism is considered to be an additional reproductive tactic where females can increase their own reproductive success. Because of the costs involved in rearing young that are not their own, it will pay females to detect and reject the eggs of a parasite, although it is not known how they do this. Here, we show experimentally that moorhens will cease laying in a nest when their first egg is replaced with another hen’s egg but not when it is replaced with their own egg taken from an earlier clutch. This provides good evidence that birds have an internal representation of their own eggs and use this in decisions about whether to reject foreign eggs. 相似文献
20.
厌氧/一体化工艺处理生活污水运行特性研究 总被引:4,自引:2,他引:2
为了提高污水处理装置的效能,采用新型厌氧/一体化工艺处理生活污水,研究系统的启动和运行特性,并对系统中COD和总氮的去除效果作了初步考察。试验结果表明:当系统中进水C/N为7~15,缺氧区溶解氧保持在0.1~0.4mg/L时TN的去除率保持在60%以上,其值偏高或偏低都会影响硝化和反硝化的作用;通过在系统中设置导流墙和导流板,改善了缺氧区和混合区水力条件,有效避免了缺氧区内侧液能量较低造成的污泥沉积问题,并通过调节缺氧与好氧区的流入量,提高反硝化作用。在试验稳定运行期间,COD和TN的去除率分别为90%和80%以上,出水水质达到或优于污水综合排放标准。 相似文献