共查询到20条相似文献,搜索用时 0 毫秒
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Ling GN 《Physiological chemistry and physics and medical NMR》2003,35(2):91-130
Over the centuries, a vast amount of evidence has been gathering that layers of water sometimes measuring tens of thousands of water molecules thick exhibit altered properties in consequence of exposure to some solid surfaces. Yet, a clear cut theory based on the laws of physics that would predict this kind of long range dynamic ordering of water molecules has been long missing. It is thus with great joy that I announce that a new theory has been developed, which offers theoretical confirmation of the phenomena of long-range dynamic structuring of water by appropriate solid surfaces and which gives clear cut quantitative answers to some key questions about the phenomenon. Thus, for example, under an ideal condition, an idealized checkerboard of alternatingly positively-, and negatively-charged sites of the correct size and distribution could polarize and orient deep layers of water molecules ad infinitum. Based on the quantitative data thus obtained and a relevant simple statistical mechanical law, the new theory predicts that a thin layer of water held between two juxtaposed ideal or near-ideal NP surfaces will not freeze at any (attainable) temperature. On the other hand, water polarized and oriented by an ideal or near-ideal NP-NP system may also not evaporate at temperature hundreds of degrees higher than the normal boiling temperature of water. Both predictions have been confirmed (retroactively) by experimental observations made in the past, accidentally or by design. In a following paper, I will demonstrate that the conclusion reached from the study of the two-dimensional NP surface can be smoothly passed on to the living cells. In the living cell, only one-dimensional linear chains of fully extended protein chains exist. Nonetheless, by proper orientation and distribution, they can achieve similar though less intense water polarization-orientation--as experimentally demonstrated worldwide during the 40 years past. 相似文献
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Harald H. Rossi 《Radiation and environmental biophysics》1977,14(4):275-283
As a result of recent radiobiological research it has become evident that the RBE of neurons can at low absorbed doses reach values that are substantially higher than the values of the quality factor (Q) currently adopted for radiation protection. There is theoretical and observational evidence that such high RBE values are the rule rather than the exception and that they apply to at least one radiation effect on humans. New values as well as different formulations are proposed for the factor that is employed in radiation protection to weight absorbed doses for their biological effectiveness. 相似文献
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The endoplasmic reticulum (ER) is a contiguous network of interconnected membrane sheets and tubules. The ER is differentiated into distinct domains, including the peripheral ER and nuclear envelope. Inhibition of two ER proteins, Rtn4a and DP1/NogoA, was previously shown to inhibit the formation of ER tubules in vitro. We show that the formation of ER tubules in vitro also requires a Rab family GTPase. Characterization of the 29 Caenorhabditis elegans Rab GTPases reveals that depletion of RAB-5 phenocopies the defects in peripheral ER structure that result from depletion of RET-1 and YOP-1, the C. elegans homologues of Rtn4a and DP1/NogoA. Perturbation of endocytosis by other means did not affect ER structure; the role of RAB-5 in ER morphology is thus independent of its well-studied requirement for endocytosis. RAB-5 and YOP-1/RET-1 also control the kinetics of nuclear envelope disassembly, which suggests an important role for the morphology of the peripheral ER in this process. 相似文献
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A new catalytic mechanism is proposed for the hydration of CO2 by the zinc metalloenzyme carbonic anhydrase. This mechanism identifies the group controlling catalytic activity as an active site histidine, in which the protonated imidazole ring coordinates to zinc, losing a proton. Geometric constraints on the histidine unit make the metal-ligand bond a strained and, therefore, labile one. In the hydration reaction, the metal-bound neutral histidine moiety serves as a proton acceptor for the transient ionization of metal-bound water. Zinc-bound hydroxide attacks the carbon of the substrate to generate metal-bound bicarbonate, and the system regenerates itself by losing the elements of carbonic acid. 相似文献
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H. J. Phaff 《Antonie van Leeuwenhoek》1956,22(1):113-116
Summary An amended diagnosis has been given for the genusPichia Hansen to allow inclusion of species characterized by a lack of pellicle formation, by the absence or a strongly reduced
pseudomycelium or by a combination of both properties. The following species fit the amended diagnosis ofPichia: P haplophila Shifrine et Phaff,P. carsonii Phaff et Knapp,P. quercibus Phaff et Knapp andP. xylosa Phaff, Miller et Shifrine. Furthermore, it has been proposed to transferSaccharomyces pastori Guilliermond,Saccharomyces pini Holst andDebaryomyces vini Zimmermann to the amended genusPichia, where they fit well rather than occupying and exceptional position in their present genera. 相似文献
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Modifications to a standard biological water quality assessment method, used in Belgium since 1979, were studied.As a result, we recommend the following:- samples should be processed live- samples should not be washed through a series of sieves- systematic units represented by only one individual should be included in the calculation of the biotic index.Using this modification, the biotic index can be calculated more rapidly and shows a higher correlation with a chemical water quality assessment index. 相似文献
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《IRBM》2008,29(6):340-349
Falls affect, each year, tens of million of elderly people throughout the world. It can have immediate lethal consequences but also causes many disabling fractures and dramatic psychological consequences which reduce the independence of the person. Falls in the elderly is thus a major public health problem. The “early” detection of fall consequently raises the interest of searchers, as most of elderly fallers cannot return to a standing position on their own following a fall. It is also an interesting scientific problem because it is an ill-defined process. The goals of this study were to classify various approaches used to detect the fall and to point out the difficulty to compare the results of these studies, as there is currently no common evaluation benchmark. 相似文献
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The pantropical Cucurbitaceae is one of the most important families ofvascular plants. The family includes 118 genera and 825 species, and Mexicois one of its most important centers of diversity, with 34 genera and 141species and subspecific taxa, including 13 cultivated ones. Five genera and 70taxa are endemic to the country. Some Mexican and Latin American wild speciesare close relatives of important crops, and others are employed as food ormedicine. Accordingly, in countries like Mexico the conservation of members ofthis family should be a priority. In this paper a list of members ofCucurbitaceae occurring in Mexico and their distribution patterns at state levelare discussed. Using cluster strategies, the states were classified according totheir floristic similarities. Hotspots of total diversity and endemismsat state level are identified, in order to discuss their role in futureconservation strategies. Iterative methods applied by conservation biology todetermine the best places for conservation are used to identify hierarchicallythe most important states that merit to be considered in this goal. Resultsindicate that implementing conservation strategies in half of the states wouldallow the protection of all the diversity found in the country, especially theendemisms. The combination of the results provided by the different methods isalso discussed as a possibly more efficient way to propose conservationstrategies for important species of the family. 相似文献
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C C Entwistle 《BMJ (Clinical research ed.)》1987,294(6569):444-445
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Richard Doll 《BMJ (Clinical research ed.)》1987,294(6566):244-245
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A proposal for universal formulas for estimating leaf water status of herbaceous and woody plants based on spectral reflectance properties 总被引:3,自引:0,他引:3
Yu Gui-Rui Miwa Takuji Nakayama Keiichi Matsuoka Nobuhiro Kon Hisashi 《Plant and Soil》2000,227(1-2):47-58
The present study deals with the relationships between water status parameters of plant leaves and reflectances (Rλ) at characteristic wavelengths, between 522 and 2450 nm, as well as reflectance ratios, Rλ/R1430, Rλ/R1650, Rλ/R1850, Rλ/R1920, and Rλ/R1950, based on the air-drying experimental results of soybean (Glycine max Merr.), maize (Zea mays L.), tuliptree (Liriodendron tulipifera L.) and viburnum (Viburnum awabuki K. Koch.) plants. The water status parameters include leaf water content per unit leaf area (LWC), specific leaf water content (SWC), leaf moisture percentage of fresh weight (LMP), relative leaf water content (RWC) and relative leaf moisture percentage on fresh weight basis (RMP). Effective spectral reflectances and reflectance ratios for estimating the LWC, SWC, LMP, RWC and RMP were identified. With these spectral indices, approaches to estimating LWC, RWC and RMP were discussed. Eventually, an attempt on universal formulas was made for estimating the leaf moisture conditions of both herbaceous and woody plants as mentioned above. Moreover, applicability of these formulas was checked with the field experimental results of soybean and maize grown under water and nutrient stresses. This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
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PHAFF HJ 《Antonie van Leeuwenhoek》1956,22(2):113-116
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