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1.
Iberian gypsophile plant communities are considered a priority for conservation by the European Community because of their highly specialized flora in gypsum outcrops in arid and semiarid regions. Despite the ecological importance of these ecosystems, the edaphic factors that constrain plant communities on gypsiferous soils remain unclear. It has been proposed that both the chemical and physical restrictive conditions of gypsum soils determine gypsophily in plants. Here we hypothesize that the rigors of the gypsum soil environment depends on topography, decreasing from flat areas on hilltops to south-oriented slopes and finally to slopes oriented to the north. We also hypothesized that the relaxation of the rigors of the gypsum soil environment with topography affects both to individual plant and community characteristics of gypsophile vegetation: we expect a reduction of gypsophyte abundance, an increase of diversity and the amelioration of facilitative interactions of plant species. We analysed the physical and chemical properties of gypsum soils that have been proposed that determine the rigors of the gypsum soil environment (i.e.: unbalanced ion concentrations and superficial soil crust). The predicted rigor gradient along topographical locations was confirmed and was mainly caused by superficial soil crust. The decreasing rigor gradient was accompanied by a fall in the abundance of gypsophytes. However, when gypsophytes were considered separately, several patterns were observed, indicating distinct tolerance to relaxation of rigor of the gypsum soil conditions and different competition abilities between gypsophytes. Plant species were more clumped, and gypsophile communities presented higher diversity, evenness and richness values where rigor of gypsum soil conditions were maximum (flat hilltop positions). Relaxation of rigor (north-oriented slopes) was characterized by loss of facilitative interaction between species and the dominance of the gypsovag Rosmarinus officinalis L., although richness was still very high, which can be attributed to the coexistence of gypsophytes and gypsovags. We conclude that the rigor of gypsum soil environment gradient with topography is mainly determined by superficial soil crust, and it is a crucial determinant of gypsophile plant communities.  相似文献   

2.
Over four years five previously healthy young adults developed necrobacillosis , a severe septicaemic illness caused by Fusobacterium necrophorum. The infections were characterised by sore throat followed by rigors and the formation of metastatic abscesses and all caused considerable diagnostic confusion.  相似文献   

3.
Winter darkness may be experienced differently according to cultures. In the far North as well as in Canada, because of the age-old battle against climatic hardship, people had to get used to winter’s rigors by initiating feasts and festivals to make up for the lack of light — e.g. St Lucia’s Day, etc. In Ancient China, the way of life took into account each season’s characteristics and made the best of it. Contrary to the western world, winter is not regarded as a negative experience.  相似文献   

4.
One hundred and fifty cases of typhoid in infants and young children are reported. In children over 5 years of age the features resembled those in adults, but in those under this age they were often nonspecific including fever, convulsions, diarrhoea, and vomiting. Attention is drawn to the importance of a blood culture in anaemic afebrile children who develop rigors and high fever after blood transfusions.  相似文献   

5.
常绿阔叶树种的耐低温特性及其生态学评价   总被引:11,自引:1,他引:10  
谢晓金  郝日明  张纪林 《生态学报》2004,24(11):2671-2378
选取在南京地区已露地引种的 2 4种常绿阔叶树种 ,其自然分布北界止于亚热带不同的纬度 ,运用生理生态方法 ,测定它们在模拟低温处理下的电导率 ,并结合寒冷指数和引种后其适应性表现 ,分析这些树种的耐低温能力。结果表明 ,以某一树种自然分布北界气象资料为依据的寒冷指数与其自然植被的水温条件关系更为密切 ,寒冷指数有时不能反映树种本身耐低温能力的高低。如乐东拟单性木兰 ,其自然分布于亚热带南部 2 6°N,引种到南京耐低温表现明显好于自然分布于亚热带北部的香樟。而采用低温循环仪自动降温程序模拟冰冻处理来测定离体叶片的相对电导率 ,计算出各常绿阔叶树种叶片的半致死温度 ,能定量地反映这些树种本身的耐低温能力高低。在测试中如借助已知耐低温能力的树种作对照 ,其数据结果可作为常绿园林阔叶树种能否向更高纬度引种的重要参考依据。在上述研究基础上选出 6种 ,以其离体叶片为试材 ,测定其可溶性糖和游离脯氨酸含量 ,结果显示 ,随处理温度的降低 ,可溶性糖和游离脯氨酸的含量呈增加趋势 ,然而只有在适宜的处理下才呈现规律性变化 ,这些研究结果可作为树种耐低温能力的定性补充证据。对常绿阔叶树种的耐低温能力评价及预测有重要的参考价值  相似文献   

6.
Athletes with complete separation of the acromioclavicular joint were uniformly restored to full athletic competence by an operation consisting of direct repair of the involved ligamentous structures with temporary fixation by a metallic lag screw approximating the clavicle to the coracoid. The metallic fixation was left in place an average of eight weeks and the screw was then removed under local anesthesia. A number of professional and collegiate football players returned to the rigors of football with no discomfort or disability.  相似文献   

7.
Athletes with complete separation of the acromioclavicular joint were uniformly restored to full athletic competence by an operation consisting of direct repair of the involved ligamentous structures with temporary fixation by a metallic lag screw approximating the clavicle to the coracoid. The metallic fixation was left in place an average of eight weeks and the screw was then removed under local anesthesia. A number of professional and collegiate football players returned to the rigors of football with no discomfort or disability.  相似文献   

8.
There is a need for simple, inexpensive methods to maintain algal clones of constant genotype over long periods of time. Pandorina zygospores survive many environmental rigors which destroy the vegetative cells. The zygospores are the preferable from for storage of the alga and remain viable for at least 15 yr. storage procedures and germination techniques are described for zygospores of 2 species. These are compared with reports in the literature concerning other algal genera. General procedures for storage and maintenance of both vegetative cells and spores are proposed.  相似文献   

9.
The historical debate of the 1960s between group and individual selection hinged on how the slow breeding of seabirds could be explained. While this debate was settled by the ascendance of individual selection, championed by David Lack, explanations for slow breeding in seabirds remain to be tested. We examined the slowest breeding of these birds, the albatrosses and petrels (order Procellariiformes), using analyses that statistically controlled for variations in body size and phylogeny. Incubation and fledging periods appeared strongly correlated, but this turned out to be largely explained by phylogeny. Nonetheless, developmental and reproductive rates were associated with the distance to the foraging range, as predicted under the hypothesis of ecological constraints on breeding pairs, and these results were independent of body size and phylogeny. Slower breeding in these seabirds appeared associated with the rigors of farther pelagic feeding, as Lack originally hypothesized.  相似文献   

10.
Several years of research on seven different plants (five terrestrial and two aquatic species) suggest that the beneficial effects of atmospheric CO2 enrichment may be divided into three distinct growth response phases. First is a well-watered optimum-growth-rate phase where a 300 parts per million increase in the CO2 content of the air generally increases plant productivity by approximately 30%. Next comes a nonlethal water-stressed phase where the same increase in atmospheric CO2 is more than half again as effective in increasing plant productivity. Finally, there is a water-stressed phase normally indicative of impending death, where atmospheric CO2 enrichment may actually prevent plants from succumbing to the rigors of the environment and enable them to maintain essential life processes, as life ebbs from corresponding ambient-treatment plants.  相似文献   

11.
A review of the published analytical methodology for the tricyclic antiviral (TAV) drugs is presented. While amantadine and rimantadine are the only two approved drugs for the prophylaxis and treatment of the influenza A virus, amantadine has also been approved for the treatment of Parkinson’s disease. In addition, a few structurally related compounds are finding important clinical applications in other central nervous system-related disorders. To effectively evaluate the pharmacokinetics, biotransformations, stability, and other critical parameters that are necessary for pre-clinical and clinical studies, analytical methodology that conforms to the rigors of regulatory requirements must be developed and made available. This review discusses the analytical methods used in the determination of amantadine, rimantadine, tromantadine and memantine and the pre-clinical and clinical application of these techniques.  相似文献   

12.
13.
P.H. Lysaker  M.A. Erickson 《PSN》2010,8(4):187-196
Empirical study of long-term outcomes for persons with schizophrenia suggests that recovery is often possible. This literature also emphasizes that recovery may involve different kinds of experiences for different people with the same psychiatric condition. For some, recovery may mean symptom remission while for others it may be reflected by the achievement of psychosocial milestones. For yet others, however, to recover can involve subjective changes in how those persons experience themselves as meaningful agents in the world. For some, to recover could be to reclaim a full sense of self, a sense of self that permits to engage in relationship with others and the rigors of daily life. In this chapter, we review the potential of individual psychotherapy to address the more subjective aspects of recovery related to sense of self. We first review literature on the effectiveness of psychotherapy for persons with schizophrenia. We then discuss literature on the larger issue of how decrement in personal narrative metacognition may underpin some of the disturbance in sense of self observed in schizophrenia. Finally, we focus on how psychotherapy could be conceptualized and adapted to help enrich self-experience by addressing narrative and metacognition. Directions for future research are discussed.  相似文献   

14.
15.
Lactobacillus sakei is a psychotrophic lactic acid bacterium found naturally on fresh meat and fish. This microorganism is widely used in the manufacture of fermented meats and has biotechnological potential in biopreservation and food safety. We have explored the 1,884,661-base-pair (bp) circular chromosome of strain 23K encoding 1,883 predicted genes. Genome sequencing revealed a specialized metabolic repertoire, including purine nucleoside scavenging that may contribute to an ability to successfully compete on raw meat products. Many genes appear responsible for robustness during the rigors of food processing--particularly resilience against changing redox and oxygen levels. Genes potentially responsible for biofilm formation and cellular aggregation that may assist the organism to colonize meat surfaces were also identified. This genome project is an initial step for investigating new biotechnological approaches to meat and fish processing and for exploring fundamental aspects of bacterial adaptation to these specific environments.  相似文献   

16.
SYNOPSIS. Living corals are routinely collected and shippedto destinations thousands of miles from their point of origin.The fact that corals can survive the rigors of collecting, transport,and acclimation to totally artificial environments was consideredimpossible not long ago, but hobbyists and some researchershave persevered and have developed aquarium systems and techniquescapable of maintaining corals in apparently healthy conditionfor many years. In particular, new lighting equipment, advancesin the control of water chemistry, and new technology for simulatingwater movement have all contributed to the ability to keep coralsalive indefinitely in captivity. Despite the completely artificialconditions of most aquariums, coral extension rates and calcificationrates in some aquarium systems are close to those reported fornatural reefs, although anomalies have been observed such asdecreased skeletal density and unusual changes in colony morphology.Nonetheless, aquariums present real opportunities to culturecorals for a variety of bioassay, medicinal, and conservationpurposes. As model reef communities ("microcosms"), these systemsallow us to test hypotheses concerning the effects of rapidlychanging environmental conditions.  相似文献   

17.
Srinivas V  Shapiro IM 《Autophagy》2006,2(3):215-216
Bone growth takes place through the activities of chondrocytes embedded in the epiphyseal growth plate. Stress conditions in the plate can promote the autophagic response through the modulation of genes controlling metabolite utilization. mTOR plays a critical role in autophagy serving as the sensor that integrates metabolic and growth factor signals. Ongoing studies indicate that terminal chondrocytes exhibit autophagic characteristics. Morphologically, the arrested cells contain double membrane vacuoles; there is a loss of membrane structure, limited staining and organelle destruction. Since the life history of the growth plate chondrocyte is very short, even minor disturbances in the metabolic state can result in gross impairment of growth. We contend that the induction of the autophagic response, permits the terminally differentiated cells to survive the brief rigors of the harsh local microenvironment. Whether chondrocytes can recover from this state, and possibly participate in osteogenesis, is not known at this time.  相似文献   

18.
Nearly half a century ago, H.T. Odum envisioned a sustainable approach to systems design where human intervention would be supplementary to nature. He referred to this concept as ecological engineering and suggested that practitioners should receive an education beyond the rigors of engineering. To understand natural processes needed to design, develop, and restore natural systems successfully, Odum suggested ecological engineers should have an expanded knowledge of environmental systems and ecology. Furthermore, he recommended broadening educational exposure to social science and liberal arts. The field of ecological engineering has blossomed in the years since Odum expressed his vision, but universities have not adopted his suggested curriculum, and undergraduate engineering students have generally seen a reduction in social science and liberal arts courses. This paper compares Odum's vision with the surveyed visions of an international group of ecological engineers, who assessed the value and characteristics of an ecological engineering undergraduate education. The respondents’ perspectives vary with their location, education, and profession; however, most participants in this survey share Odum's vision, and are dissatisfied with existing curricula. Participants outside of the United States were more confident that something approaching Odum's vision for a program in ecological engineering could be delivered at the undergraduate level.  相似文献   

19.
A population-enrichment adaptive design allows a prospective use for study population selection. It has the flexibility allowing pre-specified modifications to an ongoing trial to mitigate the potential risk associated with the assumptions made at design stage. In this way, the trial can potentially encompass a broader target patient population, and move forward only with the subpopulations that appear to be benefiting from the treatment. Our work is motivated by a Phase III event-driven vaccine efficacy trial. Two target patient subpopulations were enrolled with the assumption that vaccine efficacy can be demonstrated based on the combined population. It is recognized due to the nature of patients’ underlying conditions, one subpopulation might respond to the treatment better than the other. To maximize the probability of demonstrating vaccine efficacy in at least one patient population while taking advantage of combining two subpopulations in one single trial, an adaptive design strategy with potential population enrichment is developed. Specifically, if the observed vaccine efficacy at interim for one subpopulation is not promising to warrant carrying forward, the population may be enriched with the other subpopulation with better performance. Simulations were conducted to evaluate the operational characteristics from a selection of interim analysis plans. This population-enrichment design provides a more efficient way as compared to the conventional approaches when targeting multiple subpopulations. If executed and planned with caution, this strategy can provide a greater chance of success of the trial and help maintain scientific and regulatory rigors.  相似文献   

20.
The ability to heal wounds is vital to all organisms. In mammalian tissues, alterations in intermediate filament (IF) gene expression represent an early reaction of cells surviving injury. We investigated the role of keratin IFs during the epithelialization of skin wounds using a keratin 6alpha and 6beta (K6alpha/K6beta)-null mouse model. In skin explant culture, null keratinocytes exhibit an enhanced epithelialization potential due to increased migration. The extent of the phenotype is strain dependent, and is accompanied by alterations in keratin IF and F-actin organization. However, in wounded skin in vivo, null keratinocytes rupture as they attempt to migrate under the blood clot. Fragility of the K6alpha/K6beta-null epidermis is confirmed when applying trauma to chemically treated skin. We propose that the alterations in IF gene expression after tissue injury foster a compromise between the need to display the cellular pliability necessary for timely migration and the requirement for resilience sufficient to withstand the rigors of a wound site.  相似文献   

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