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Leigh EG 《Proceedings of the National Academy of Sciences of the United States of America》1983,80(10):2985-2989
In a system of N populations of n reproductive individuals apiece, in which each population has constant variance v2 and lasts L generations, group selection on a quantitative character has a reasonable chance of overriding selection within populations if (and only if) the populations never exchange migrants, each population is founded by colonists from a single parent population, and the number of populations exceeds the effective number of reproductive individuals per population. If each population derives from a single parent population, then the exchange of a single successful migrant per population per L generations can triple the strength of group selection required to overcome a given selection within populations. If populations exchange no migrants, then the derivation of one in every N populations from two equally represented parents (while the others all derive from a single parent) doubles the strength of group selection required to prevail. Group selection is accordingly likely to be effective only in certain categories of parasites. 相似文献
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In this paper we report on a project that aimed to evaluate the potential of the Internet to reduce social isolation amongst
the elderly, and thereby, improve psychosocial functioning. Twenty residents of a retirement village volunteered to be given
access to, and training in, the use of computers and the Internet. After 3 months, they exhibited little change in measures
of self-esteem, positive affect, personal well-being, optimism and social connectedness. However, they reported that they
found the use of the Internet to be of great benefit. Over the 12 months of the study 12 participants discontinued their involvement
for a variety of reasons. After 12 months, the eight participants who remained in the study again reported a range of positive
outcomes however, quantitative survey data did not confirm these findings of a generally-positive experience. This discrepancy
between the qualitative (interview) data and the quantitative (survey) data suggests that impact of the Internet on the wellbeing
of the elderly may be more complex than suggested, and broader than was assessed psychometrically. We make specific recommendations
about the introduction of computers to elderly with care both in how participants are selected and how their well being is
monitored subsequently.
相似文献
David MellorEmail: |
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Slovak (SR) and Czech (CR) Republics reach up the highest recorded incidence rates of colorectal cancer. In analysis of the development and changes in colorectal cancer incidence in the above-mentioned countries, it was reported the most considerable incidence increase of the disease in males in the SR, then in males in the CR, subsequently in females in the SR and the slowest incidence rate was reported in females in the CR. Colorectal cancer mortality increased most rapidly in males in the SR, then in males in the CR, slower increase was reported in females in the SR and in females in the CR the mortality was in the long term stabilized. In both countries and both sexes clinical stage II is noted most frequently, also the decrease of the disease number in the clinical stage I and in undefined stage, and a slight decrease in other clinical stages. The trends in risk factors of colorectal cancer in the SR and CR would support the hypotheses of the later culmination of incidence and on the higher levels than in other developed countries. The purpose of this study is to analyse the character and changes in development of incidence, mortality and clinical stages of colorectal cancer (1980-2005) and to assess the influence of selected risk factors on the highest disease incidence in above-mentioned two Central European countries. 相似文献
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After the genome—the phenome? 总被引:2,自引:0,他引:2
Scriver CR 《Journal of inherited metabolic disease》2004,27(3):305-317
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Rheumatoid arthritis (RA) represents a chronic joint inflammation that leads to destructive lesions of joint cartilage and periarticular bone. Increased understanding of the molecular and cellular mechanisms of RA and recent advantages in molecular technology have resulted in new antirheumatic drugs such as tumor necrosis factor-alpha blockers, inhibitors of interleukin-1, and novel disease-modifying antirheumatic drugs such as leflunomide. This review summarizes the important effects of the novel antirheumatic drugs and their potential impact on the work of orthopedic surgeons. The ability of these agents not only to improve the clinical signs and symptoms of RA but also to prevent progressive joint damage promises support to the work of orthopedic surgeons and to the interdisciplinary treatment of RA patients. The challenge, however, will be to conduct studies that show the concrete way in which the single drugs may best relieve the burden of the orthopedic surgeon. 相似文献
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Segal IE 《Proceedings of the National Academy of Sciences of the United States of America》1991,88(3):994-998
The apparently new hadron-like particle ("cygnet") indicated by cosmic ray observations on certain neutron stars is predicted to be a spin 1/2 fermion of magnetic moment and charge 0 and lifetime infinity. This derives from the natural identification of the cygnet with the one hitherto unobserved fundamental fermion of chronometric particle theory, the x or "exon", which plays the role of a quintessential baryon. The "partons" are represented by the other fundamental fermions, consisting of e, nue, and numu; e.g., n = x + e+ + e-, p = x + e+ + nue. With further empirical assignments, chronometric theory has a potential for explaining diverse phenomena, such as mixing in the neutral kaon complex and the nature of the higher electrons. Its fundamental fermion and boson fields transform indecomposably under its symmetry group, the conformal group G. Theoretical elementary particles transforming irreducibly under G derive as successive quotients in a maximal chain of invariant subspaces. Mass fixing by Mach's principle breaks the symmetry down to microscopically observed covariance with respect to the Poincare group P0. The resulting representation is normally irreducible, but splits in the case of the K0 into two P0-irreducible components that are mixed by the excess of the chronometric over the relativistic energy ("gravity"), which provides a "superweak" force that may be explanatory of CP violation. 相似文献
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常乐 《World journal of gastroenterology : WJG》2014,(24):40-42
小熊维尼最近参加了一个英语俱乐部(English Club),学到了不少知识。听,他正在和小伙伴们展示自己学到的新本领呢!:嗨,小伙伴们!你们听说过"the"吗?:这有什么稀奇!"the"是冠词的一种,叫定冠词!:我也听说过定冠词"the",我还能说一些短语呢!the Greens(格林一家),the Great Wall(长城),the policeman(警察) 相似文献
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Drug targeting to the liver with lactosylated albumins: does the glycoprotein target the drug or is the drug targeting the glycoprotein? 总被引:1,自引:0,他引:1
P van der Sluijs H P Bootsma B Postema F Moolenaar D K Meijer 《Hepatology (Baltimore, Md.)》1986,6(4):723-728
The isolated perfused rat liver preparation was employed to study hepatic disposition of the model drug-carrier conjugate fluorescein-lactosylated albumin (F-LnHSA) with special reference to the influence of the organic anion fluorescein on liver cell specificity of the endocytosed neoglycoprotein. Hepatic clearance of fluoresceinated neoglycoproteins was significantly faster than clearance of radioiodinated neoglycoproteins. Perfusate clearance of F-L7HSA and F-L25HSA could not completely be inhibited by a dose of 10 mg asialoorosomucoid that saturates the hepatocyte receptor-mediated endocytic process. From these data, we inferred an additional hepatic uptake mechanism, competing with the Ashwell-receptor-mediated internalization of galactose-terminated glycoproteins. Clearance experiments with fluoresceinated 125I-human serum albumin in the presence of the polyanionic probe dextran sulfate revealed a nearly complete (approximately 90%) inhibition of hepatic uptake, while also a pronounced effect was obtained with colloidal carbon. These data point to nonparenchymal cell uptake of fluoresceinated protein via interaction with scavenger receptors. In wash-out studies, it was shown that about 25% of ligand sequestrated by sinusoidal liver cells escaped degradation and recycled to the perfusion medium. Our results show that care should be taken in the use of neoglycoproteins as drug carriers to hepatocytes, since a load of only 2 to 3 moles fluorescein per mole neoglycoprotein considerably affects intrahepatic distribution. The relative contribution of nonparenchymal cell uptake by coupling of acidic drugs to the neoglycoproteins is very probably inversely related to the number of exposing galactose groups per molecule neoglycoprotein. This phenomenon of "inversed targeting" could therapeutically both be useful or detrimental, dependent on the spectrum of cell types that should be reached by the drug. 相似文献
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Akihiro Cho Shinichi Okazumi Harufumi Makino Fumihiko Miura Kiyohiko Shuto Ryouyu Mochiduki Takayuki Tohma Hidehiro Kudo Katsuhiko Matsubara Hisashi Gunji Hiroshi Yamamoto Munemasa Ryu Takenori Ochiai 《Journal of hepato-biliary-pancreatic sciences》2004,11(6):390-396
Background/Purpose
Although the anterior segment of the liver has been divided into segments 8 and 5, we have, during surgical or interventional procedures, occasionally encountered patients in whom the right anterior portal vein does not bifurcate into the superior and inferior branches. Thus, the in vivo anatomy of the right liver was reevaluated to clarify the segmental anatomy.Methods
We evaluated the hepatic venous and portal ramification patterns, using three-dimensional images reconstructed from computed tomography. In addition, liver volumetry was performed.Results
All branches arising from the anterior trunk were divided into two groups: the right ventral portal branches (RVP) and the right dorsal portal branches (RDP), and the anterior fissure vein crossed between the RVP and RDP. The ventral and dorsal regions of the anterior segment were approximately equal from a volumetric point of view.Conclusions
The anterior segment seems to be divided into the ventral and dorsal segments by the anterior fissure, and we propose a reclassification of the right liver that divides the right liver into three segments. Dissection of the parenchyma along the anterior fissure makes the third door of the liver open, resulting in the exposing of all Glissonian pedicles of the right liver. The introduction of our segmental anatomy and surgical procedure will allow more systematic and limited liver resections. 相似文献20.
Lowry PJ 《Journal of molecular endocrinology》2003,31(3):341-347
The endocrine placenta has a dilemma; it shares the foetal circulation and yet it needs to secrete active peptide hormones into the maternal circulation to control her metabolism to meet the demands of the growing foetus. Simultaneously, it needs to allow the endocrine systems of the foetus to develop independently. This Article will describe how peptide hormones are processed from inactive intermediates and will propose a hypothesis of how the placenta has revised this process to protect the foetus from the potentially damaging affects of these products. 相似文献