共查询到20条相似文献,搜索用时 0 毫秒
1.
2.
L. V. Nedorezov 《Biophysics》2016,61(1):149-154
The Lotka–Volterra model of predator–prey dynamics was used for approximation of the wellknown empirical time series on the lynx–hare system in Canada that was collected by the Hudson Bay Company in 1845–1935. The model was assumed to demonstrate satisfactory data approximation if the sets of deviations of the model and empirical data for both time series satisfied a number of statistical criteria (for the selected significance level). The frequency distributions of deviations between the theoretical (model) trajectories and empirical datasets were tested for symmetry (with respect to the Y-axis; the Kolmogorov–Smirnov and Lehmann–Rosenblatt tests) and the presence or absence of serial correlation (the Swed–Eisenhart and “jumps up–jumps down” tests). The numerical calculations show that the set of points of the space of model parameters, when the deviations satisfy the statistical criteria, is not empty and, consequently, the model is suitable for describing empirical data. 相似文献
3.
S. Parma 《Hydrobiologia》1982,95(1):1-9
This paper marks the silver jubilee in 1982 of the Limnological Institute, The Netherlands. It describes the history, present research programme and organisation of the Institute, as well as its cooperative studies with other institutes and its training facilities.Some remarks about its future plans of work are made. 相似文献
4.
The liver stands in a unique position between the gastrointestinal tract and systemic venous system. Its constant exposure to food antigens, bacterial products and potential pathogens through the mesenteric circulation, requires the liver to maintain tolerogenic capabilities while preserving the means to mount effective immune responses. The liver has the unique ability amongst solid organs, to activate na?ve CD8+ T lymphocytes in an antigen-specific manner. However, this activation can be inefficient and lead to apoptosis. This phenomenon is believed to be involved in both, the development of oral tolerance and the induction of tolerance in liver allografts. The liver is the target of both autoimmune diseases and of chronic viral infections and its unique tolerogenic environment has frequently been suggested as a factor in the development of these diseases. A better grasp of the liver's unique immunological processes would lead to a better understanding of immune tolerance mechanisms and their role in the development of autoimmune diseases and chronic viral infections. 相似文献
5.
6.
Tulley Long 《Journal of the history of biology》2009,42(4):765-809
In 1948, a dynamic junior member of the Johns Hopkins Biology Department, William McElroy, became the first director of the McCollum–Pratt Institute for the Investigation of Micronutrient Elements. The Institute was founded at the university to further studies into the practicalities of animal nutrition. Ultimately, however, the Institute reflected McElroy’s vision that all biological problems, including nutrition, could be best investigated through basic biochemical and enzyme studies. The Institute quickly became a hub of biochemical research over the following decade, producing foundational work on metabolism and a respected series of symposia. In this paper, I argue that McElroy’s biochemical vantage on biology also permeated the traditionally morphological and embryological Biology Department at Hopkins. Largely due to the activity of McElroy and the Institute, the faculty, course offerings, and research underwent a radical reorientation toward biochemistry and molecular biology in the 1950s, even while maintaining a commitment to developmental biology. While the history of postwar biology is often told as the ascendancy of the “new” biology over “traditional” biology, the case of McElroy and the McCollum–Pratt Institute affords an opportunity for historical examination of biochemical and molecular science as a lens through which all branches of biology at an institution were reconceived and unified. 相似文献
7.
8.
This article is a testimonial written by the first author regarding the research work performed with Drosophila between 1943 and 1959, at the Departamento de Biologia Geral of the Universidade de São Paulo (USP), which permitted the building of a nucleus of excellence. This research work, focused on the systematics and population genetics of the Neotropical species, began during the first of Dobzhansky’s six visits to USP. Special attention was given to the multinational megaprojects conducted during his longer stays, from August 1948 to July 1949 and from June 1955 to July 1956. The role played by the Rockefeller Foundation is duly remembered, and so is the undeniable contribution brought by Dobzhansky, to the establishment of several laboratories dedicated to research in the field of natural population genetics and to the qualification of human resources. On the other hand, important “backstage” episodes are retrieved which were omitted in the official history and occurred from the planning to the execution of the project, carried out on the Angra dos Reis islands. Special attention was given to the relationship problems which resulted from Dobzhansky’s, the leader’s, difficult personality and contributed to the failure of the second and last multinational project. 相似文献
9.
The industrialization of microalgae-based biofuel production has been hampered by low biomass productivity of conventional open ponds. In this research, a hybrid cultivation system that combined an open pond and photobioreactor (PBR), with broth circulating between both, was introduced. The hybrid system was tested under indoor and outdoor conditions using the oleaginous microalgal species Scenedesmus dimorphus. When the PBR(s) in the hybrid system reinforced the light supply to the carbon-replete open pond the biomass reached 1.34 g l–1, 116% higher than in the non-hybrid system. Subsequent studies showed that higher circulation speed and low volume ratio of PBR vs. open pond would further improve the hybrid effects. When applied outdoors at pilot scale, the biomass productivity of the hybrid system increased 46.3–74.3% compared with the open pond and in September was 12.5% higher than that of PBRs. These results indicate that hybrid cultivation might be a cost-effective way to improve the light usage efficiency of current open pond systems. 相似文献
10.
Use of affinity chromatography for the quantitative study of acceptor–ligand interactions: the lactose synthetase system (Short Communication) 总被引:1,自引:0,他引:1
下载免费PDF全文

From the effects of N-acetyl-d-glucosamine and d-glucose on the elution of the A protein of human lactose synthetase from a column of Sepharose-alpha-lactalbumin, values of 200m(-1) and 0.57m(-1) are deduced for the association constants describing the interaction between the enzyme and the respective monosaccharides. 相似文献
11.
12.
《Biochimica et Biophysica Acta (BBA) - Enzymology》1972,258(2):531-540
- 1.1.|The action pattern of an exo-β-(1 → 3)-d-glucanase (β-1,3-glucan glucanohydrolase, EC 3.2.1.39) from Basidiomycete sp. QM 806 was investigated from the point of view of whether it acts by single-chain or multi-chain mechanism.
- 2.2.|Labeled substrate was prepared by reduction of insoluble laminarin with NaB3H4. The kinetics of its hydrolysis with the enzyme were monitored by following loss of polysaccharide, production of oligosaccharide and appearance of glucose. The specific determination of glucose and paper chromatographic separation followed by radioactivity measurements were used as the main analytical methods.
- 3.3.|The rate of loss of polysaccharide was found to be approximately the same as the rate of glucose appearance. The principal products (excluding glucose) were tetra- and trisaccharide (depending on enzyme concentration). Only a small amount of products with molecular weight in the range between polysaccharide and tetrasaccharide was formed during the whole period of hydrolysis.
- 4.4.|A similar picture was observed when the enzymic hydrolysis of unlabeled soluble laminarin was monitored by chromatography of the products on Biogel P-2.
- 5.5.|The data obtained prove that the enzymic hydrolysis is a single-chain process and that the normal end-products of this process are tetrasaccharide or trisaccharide. Some speculations are made as to the mechanism of the process.
13.
《基因组蛋白质组与生物信息学报(英文版)》2004,(2)
Year Event and Theoretical Implication/Extension1901 Hugo de Vries adopts the term MUTATION to describe sudden, spontaneous, drastic alterations in the hereditary material of Oenothera. Thomas Harrison Montgomery studies sper- matogenesis in various species of Hemiptera and ?nds that maternal chromosomes only pair with paternal chromosomes during meiosis. Clarence Ervin McClung postulates that the so- called accessory chromosome (now known as the “X” chromosome) is male determining.… 相似文献
14.
15.
Nutrient and carbon budgets of the western part of the Dutch Wadden Sea are based on the concept formulated by Postma (1954): import of organic compounds from the North Sea, mineralization in the estuary ans subsequently an export of dissolved inorganic nutrients to the North Sea. In this paper the phosphorus budget of the westernmost part of the Wadden Sea (Marsdiep basin) during the period 1950–1985 is considered to evaluate this concept and to investigate whether eutrophication processes have changed these P-budgets during the last decades. Most attention is paid to the importance of the exchange of P-components between the tidal basin and the open sea. The budgets are based on a general mass balance equation in which the main entries are the loadings via the freshwater sources, the net sediment-water exchange, the exchange with the North Sea, the input from the adjacent Vlie basin, and a transformation term representing the interchange between dissolved and particulate phosphorus. Averaged over the entire period 55% of the phosphate input (SRP) to the basin is delivered by the fresh water sources, and 45% by the Vlie basin. For non-SRP components these numbers are 50% and 40% respectively, while only 10% comes from the North Sea. The import from the North Sea, as calculated by our model thus seems less important than previously documented. There is a clear effect of the eutrophication during the last decades. In the first 20 years of the period investigated there was a moderate increase in the TP input to the basin, partly caused by an increasing input of non-SRP (TP minus soluble reactive phosphorus) from the North Sea. In 1970/71 almost 30% of the non-SRP loading originated from the North Sea. From approximately 1975 onwards this import of non-SRP turns into an export, while the TP-loading from the other sources inclined, until a maximum was reached in 1981. Recently a decrease in the TP-inputs has been observed. It is concluded that the recent output of phosphorus from the Marsdiep basin may have a considerable impact on the adjacent area of the North Sea.Publication no. 2 of the project Applied Scientific Research Neth Inst. for Sea Res. (BEWON). 相似文献
16.
Paleontological Journal - The Tournaisian–Viséan boundary of the Lower Carboniferous was established in carbonate facies deposits of the “Kipchak” section (Southern Urals).... 相似文献
17.
N. V. Belova N. G. Emel’yanova A. P. Makeeva I. N. Ryabov 《Journal of Ichthyology》2006,46(9):779-787
The state of the reproductive system of Tinca tinca—descendants of individuals that were exposed to radiation as a result of the catastrophe at the Chernobyl Nuclear Power Plant in 1986 was studied. Material was collected in the postemergency period in radionuclide-polluted water bodies: in the Ukraine, in Kiev Reservoir, the Teterev River, and Lake Glubokoe (1999–2005) and in Belarus, in Lake Svyatoe (1998–1999). It is demonstrated that the total number and the extent of disturbances in the gonads of T. tinca are positively related to the levels of pollution in water bodies: in the cleanest water body, the Teterev River, the proportion of fish with gonads without considerable deviations was about 93%; in Kiev Reservoir, 79%, and in Lake Svyatoe, only 18%. Among the “postemergency” generations of T. tinca, the maximum number of disturbances in sexual cells and gonads was recorded in F3–4, which is evidently caused by a phenomenon of the “prolonged mutagenesis”. A relatively high species resistance of the reproductive system of T. tinca to the radiation impact, in comparison with other cyprinids, was recorded. 相似文献
18.
Kruff Niclas Lax Christian Liebscher Volkmar Walcher Sebastian 《Journal of mathematical biology》2019,78(1-2):413-439
Journal of Mathematical Biology - The Rosenzweig–MacArthur system is a particular case of the Gause model, which is widely used to describe predator–prey systems. In the classical... 相似文献
19.
《Peptides》2013
The heptadecapeptide nociceptin/orphanin FQ (N/OFQ) is the endogenous ligand for the N/OFQ peptide (NOP) receptor. It is cleaved from a larger precursor identified as prepronociceptin (ppN/OFQ). NOP is a member of the seven transmembrane-spanning G-protein coupled receptor (GPCR) family. ppN/OFQ and NOP receptors are widely distributed in different human tissues. Asthma is a complex heterogeneous disease characterized by variable airflow obstruction, bronchial hyper-responsiveness and chronic airway inflammation. Limited therapeutic effectiveness of currently available asthma therapies warrants identification of new drug compounds. Evidence from animal studies suggests that N/OFQ modulates airway contraction and inflammation. Interestingly up regulation of the N/OFQ–NOP system reduces airway hyper-responsiveness. In contrast, inflammatory cells central to the inflammatory response in asthma may be both sources of N/OFQ and respond to NOP activation. Hence paradoxical dysregulation of the N/OFQ–NOP system may potentially play an important role in regulating airway inflammation and airway tone. To date there is no data on N/OFQ–NOP expression in the human airways. Therefore, the potential role of N/OFQ–NOP system in asthma is unknown. This review focuses on its physiological effects within airways and potential value as a novel asthma therapy. 相似文献