首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
Rupert Barneby had 263 publications (two of which were published with two volumes each) during his career (including 56 book reviews), and additionally published new taxa and combinations in 16 publications by B. A. Krukoff, S. L. Welsh, and A. Lourteig. In total, these publications amount to 7676 pages. Each entry was examined, was dated as accurately as possible, and was annotated with any new nomenclauture presented in the publication. Barneby published 4 new subtribes within the legumes, 9 new genera of legumes (one based on a new combination) and 6 new genera of Menispermaceae, 621 new species (including 6 new nothospecies), 16 new subspecies, 355 new varieties, and 1 new form. Additionally, he published 238 new infrageneric taxa (subgenera, sections, or subsections). he made numerous new combinations (including nomina nova) at the infrageneric level (169), the species level (582), the subspecific level (27), and the varietal level (533), as well as a single combination at the form level.  相似文献   

2.
A higher category is the result of a population's breaking-throuh into a new adaptive zone (attaining a new grade), and the subsequent adaptive radiation tiere. The taxonomic level of the new group is determined by the amount (quantitative and ualitative) of radiation that occurs; and tgis amount in turn is determined by the number of open sub-zones in the new zone and by the genetic plasticity of the new population. The more the new adaptive zone differs from the old one, the less likely a new population can survive in it. Should such survival occur, however, adaptations of the new population to the new zone will appear quickly. The new population will rapidly become quite different from the old one, minimizing the likelihood of finding intermediate forms, i. e., “missing links.” In addition, the intermediate population – the early entrants into the new zone – will be less well adapted to it than their descendents, and will become extinct. The combination of rapid extinction and an ephemeral transitional population explains the apparent gaps between higher-category taxa. These ideas do not help in solving such dilemmas of taxonomists as equivalence of taxa in different groups, and the taxonomic level at which to place a given group of species. But a higher taxonomic category itself is the result of a very real biological phenomenon, and that fact must influence systematicists.  相似文献   

3.
Flowers and leaves of Disynaphia multicrenulata from Argentina afforded a large number of known germacradienolides and heliangolides, a new germacradienolide, a known melampolide, a new parthenolide derivative, one known and seven new cronquistiolides, a new 4Z-melampolide, three known and five new eudesmanolides, a new elemadienolide, a known grazielolide, an isoguaiagrazielolide, two diepoxygermacran-8,12-olides, three common kauranoic acids, pinoresinol, jaceosidin and the sesquiterpene oplopanone. Structures were elucidated by high-field 1H NMR spectrometry. The relationship to the known chemistry of other members of the Disynaphiinae is discussed.  相似文献   

4.
The hypothesis of a qualitative new field permits the prediction of a new fundamental constant. With this constant a relation between c and h can be found. The new constant permits not only a system of physics but also a new transition from physics into biology.  相似文献   

5.
R Rothstein  R Wu 《Gene》1981,15(2-3):167-176
The construction of two new derivatives of the bacteriophage cloning vector M13mp2 is described. One derivative, mWJ22, contains a new HindIII site while the other, mWJ43, contains a new BamHI site. These new sites were both introduced at the EcoRI site at amino acid five of the 145 amino acid-long fragment of Escherichia coli beta-galactosidase within the phage. The new restriction sites do not disrupt the blue color detection system of M13mp2; therefore insertion of cloned fragments results in colorless plaques on indicator plates for the new derivatives.  相似文献   

6.
Protein farnesyltransferase (FTase) has recently appeared as a new target of parasitic diseases, a field poor in drugs in development. With the aim of creating new bisubstrate inhibitors of FTase, new farnesyl pyrophosphate analogues have been studied. Farnesyl analogues with a malonic acid function exhibited the best inhibitory activity on FTase. This group was introduced into our imidazole-containing model leading to new compounds with submicromolar activities. Kinetic experiments have been realized to determine their binding mode to the enzyme.  相似文献   

7.
Metagenome sequencing presents an exciting new tool for assessing microbial diversity in complex, natural communities that cannot be cultured in the laboratory. Using metagenomics as a starting point, Bryant et al. (2007) have discovered a new thermophilic phototroph from a poorly characterized bacterial phylum with no previously known photosynthetic members, extending the range of photosynthesis into a new branch on the tree of life. This new organism, Candidatus Chloracidobacterium thermophilum, encompasses a mélange of traits distinct from known phototrophs.  相似文献   

8.
This paper represents new discoveries of the genus Hippophae L, including two new sections: i. e. Sect. I. Hippophae and Sect. II. Gyantsenses Lian, a new rank species H. gyantsensis (Rousi) Lian, as well as a new record of H. rhamnoides L. subsp. turkestanica Rousi in Gansu. Besides, a key to the sections and species is provided and an account of the new classification scheme on the genus is given.  相似文献   

9.
生物育种新技术作物的安全管理   总被引:2,自引:0,他引:2  
生物育种新技术(new breeding techniques,NBTs)是指基于分子生物学工具进行作物分子育种的一类新技术,可以短期内使作物产生新的有利性状,促进作物新品种的开发,如基因编辑技术、RNA干扰(RNA interference,RNAi)技术、同源转基因技术等。这些新技术目前正在全球农业育种中广泛应用,并且已有部分作物新品种获准商业化生产。然而,针对生物育种新技术产生的作物新品种的安全性和安全管理政策,全球尚未达成统一共识,对其安全监管的思考也不尽相同,限制了这些作物新品种的研发和商业化应用进程。综述了现阶段全球主要发达国家对于生物育种新技术作物的安全性和监管方面实施的管理政策和法规,以期对我国生物育种新技术作物的安全性管理政策的制定提供一定的借鉴。  相似文献   

10.
The present paper is devoted to the evolutionary role of genetic modules shuffing. The mechanisms capable to produce new molecular functions and significant complications of ontogenesis are reviewed. Two-step model of macroevolution is proposed. This model comprises: (1) Arising of a new combination of genetic modules. This step does not result in formation of a new taxon but makes necessary ground for that process. (2) Precise structure completing of the new combination of modules and corresponding genome optimization by use of various mechanisms including point mutations. This step concerns many genes and finally leads to formation of a new taxon. It is shown that arising of new combinations of genetic modules might work out as molecular basis for progressive evolution, while alternative structural completing of the same combination might result in adaptive radiation.  相似文献   

11.
A new form of structural lipoprotein of outer membrane of Escherichia coli.   总被引:1,自引:0,他引:1  
Among the membrane proteins synthesized in toluene-treated cells of Escherichia coli were two distinct membrane proteins of different molecular weights, which were cross-reactive with antiserum against a structural lipoprotein of the outer membrane. One was thought to be the known membrane lipoprotein since it migrated to the same position as that of the lipoprotein (Mr = 7,200) in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. However, the other protein migrated slower than the lipoprotein. No protein corresponding to the slower-migrating species was detected in the membrane proteins synthesized in vivo. The apparent molecular weight of the protein at the new peak was estimated to be between 10,000 and 15,000. Both the new protein and the lipoprotein were found to be synthesized from stable mRNA(s) in the toluene-treated cells. The synthesis of the new protein as well as the lipoprotein was sensitive to chloramphenicol, indicating that both proteins were synthesized on ribosomes. Peptides mapping of the new protein revealed the same COOH-terminal sequence as in the lipoprotein. This indicates that the new protein has an extra sequence at the NH2-terminal end. This hypothesis is supported by the finding that the NH2 terminus of the new lipoprotein is methionine, while that of the lipoprotein is a substituted cysteine. From double label experiments with each of 17 different amino acids and arginine, the amino acid composition of the extra region was deduced. The new protein was found to contain at least 18 to 19 extra amino acid residues over the lipoprotein, if it is assumed that the new protein has no extra arginine residues. It was found that 4 out of the 5 amino acids which were deficient in the lipoprotein (phenylalanine, tryptophan, proline, and histidine) were also deficient in the new protein, but the fifth one, glycine, was present in the new protein. From these results, it seems possible that this new form of the lipoprotine is a precursor of the lipoprotein (prolipoprotein) in the process of biosynthesis and assembly of the lipoprotein in the outer membrane.  相似文献   

12.
A review is presented of the history and recent trends in the exploration and development of food plants in southern Africa. The opportunities for developing new crops and new products for local and international markets are discussed. More than 120 species with potential as new food and beverage products (including functional foods, herbal teas and new flavours) are listed and a subjective rating of the commercial potential is provided for each of them. Some noteworthy examples are discussed and illustrated, including several indigenous fruits and vegetables that are as yet poorly known. There is a growing awareness of the importance of indigenous plants in new product development and numerous new products are already being developed. Basic research in botany (to guide genotype selection), horticulture (to develop new crops), food science (to focus on nutritional analyses) and marketing (to understand and develop new marketing approaches) is mentioned as important priorities.  相似文献   

13.
Within a historical perspective, different experimental approaches are reviewed that have used new tools and new concepts to gain an insight into the functional significance of the architecture of dendritic arborizations of nerve cells. A single type of neurons, the motoneurons, were taken as a case study to show how different fields, such as histology, morphology, electrophysiology, and neuronal modeling, have developed in parallel and accumulated a wealth of new data, and how consideration of these new informations led to new working hypotheses. Matching geometrical and electrical parameters of dendrites is critically analyzed as a basis for understanding of the dendritic functions.  相似文献   

14.
In April 1964, seven physicians met to discuss the formation of a new medical society for clinicians interested in the management of patients with cancer. Chemical warfare research during World War II had led to the advent of chemotherapeutic agents, a new, systemic approach toward cancer treatment. While skeptics questioned the benefits of chemotherapy, some internists viewed these drugs as promising new tools. Founders of the American Society of Clinical Oncology built their organization upon the importance, despite potential dangers, of utilizing chemotherapy as an essential component of cancer treatment, and positioned themselves as best qualified to manage the care of patients with cancer. The establishment of a new professional organization helped to anchor medical oncology as a distinct field during a time of increasing medical specialization in the United States. This essay examines the Society's early history within a broader context of the development of new chemical agents and cooperative groups, the formation of a new subspecialty, and increasing federal involvement in health care policy and funding, and describes the struggle of medical oncologists to solidify their authority over clinical cancer research and patient care.  相似文献   

15.
On prediction of genetic values in marker-assisted selection.   总被引:13,自引:0,他引:13  
C Lange  J C Whittaker 《Genetics》2001,159(3):1375-1381
We suggest a new approximation for the prediction of genetic values in marker-assisted selection. The new approximation is compared to the standard approach. It is shown that the new approach will often provide substantially better prediction of genetic values; furthermore the new approximation avoids some of the known statistical problems of the standard approach. The advantages of the new approach are illustrated by a simulation study in which the new approximation outperforms both the standard approach and phenotypic selection.  相似文献   

16.
Summary A new modified Square Root model and two new modified Schoolfield models were evaluated for their ability to predict the growth rate ofYersinia enterocolitica as a function of temperature. The new Square Root model fits the data better than both the original Square Root model and the Zwietering Square Root model. Both new Schoolfield models, a six-and a four-parameter equation, fit the data better than the original Schoolfield model. The new four-parameter Schoolfield model was developed by removing the term describing low temperature inactivation from the new six-parameter Schoolfield model. Inclusion of the two extra parameters in the new six-parameter Schoolfield model (F=318) did not significantly improve the fit compared to the new fourparameter Schoolfield model (F=488).  相似文献   

17.
When the axis of castor-bean which has been fixed in a horizontalposition for some time is rotated around its longitudinal axisand is then fixed in a new horizontal position, the zone ofmucilaginous layers which was being formed (in a symmetricalcrescent shape with its thickest portion situated at the topmostpart of the xylem on the upper side), ceases further formation,and a new, less symmetrical, zone begins to form in the areawhich extends from the new upper side to the new lower one inthe direction opposite to that of rotation. The greater theangle of rotation, the further the area where the new zone ofmucilaginous layers is laid down extends; in the case wherethe horizontal axis is turned upside-down, the new zone of mucilaginouslayers is formed symmetrically in the xylem on the new upperside. Moreover, if the axis once horizontally fixed is turnedto a vertical position, the formation of mucilaginous layersstops on the old upper side and starts on the old lower one.However, formation on the lower side is soon discontinued. As a possible physiological factor for producing these results,the effect of the accommodation of protoplasm to the precedinghorizontal fixation upon the formative and metabolic responsesto the stimulation of gravitational forces is discussed.  相似文献   

18.
Starting up a brand new lab is difficult enough. But when a hurricane soon forces you thousands of miles from your new research home, a whole new layer of complications arises, as Rebecca Worthylake recently found.  相似文献   

19.
Three-dimensional reconstruction methods were applied to electron micrographs of Streptococcus faecium to study the initiation of cell wall growth sites during a nutritional shift experiment. Upon lowering the mass doubling time from 76 to 33 min by the addition of excess glutamate, the formation of new cell wall growth sites accelerated above the old steady-state rate at about the same time (10 to 15 min) as did mass, RNA, protein, cell numbers, and autolytic capacity but considerably before DNA (30 min) and peptidoglycan (20 min) synthesis did. During the shift, the average range of cell volumes over which new wall growth sites were introduced did not change significantly. However, upon the shift there was an increase in the frequency of cells having new sites, which was due to the faster-growing cells initiating more new sites in peripheral locations before division. After a transition period, the number of new sites per milliliter of culture increased at a rate that paralleled that of the culture mass. These findings support a model in which new sites are introduced when cells grow to a relatively constant, growth rate-independent size, while the rate at which sites form and grow increases with the growth rate. In this model, chromosome synthesis does not regulate the formation of new sites of cell wall growth, but existing sites cannot be completed until rounds of chromosome synthesis are completed.  相似文献   

20.
The potential for second-hand markets to reduce demand for new goods is investigated. Using a variant of an economic model originally developed by Anderson and Ginsburgh, the physical implications for material use are explored. The second-hand market grows if transaction costs decrease or if product lifetime increases. In this model, growth of the secondhand market reduces demand for new goods if there are waste used goods that can be brought into the market. But if there is not a ready supply of waste used goods, growth of the second-hand market can increase demand for new goods, thereby increasing material consumption. Moreover, even when second-hand sales reduce demand for new goods, it is typically not on a one-for-one basis. The extent to which the purchase of used goods replaces the purchase of new goods is shown to be an explicit function of the relative value provided by used versus new goods.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号