These chromosomal and genetic alterations as well as aneuploidic sets of chromosomes are widely believed until nowadays to underlie the neoplastic transformation of normal cells into morphologically overt cancer cells although a recent re-evaluation of this aspect has revealed that aneuploidy can under certain conditions have also the opposite effect of tumor suppression [6]. Notwithstanding these significant leaps in our knowledge on cancer, this disease remained largely undefeated by the end of the 1990s [7] and has stayed so in its metastatic form until even today, despite recent drug achievements such as herceptin and imatinib that each target the product of an altered oncogene. The reason why a genuine therapeutic breakthrough remains as yet unachieved [8] could likely be that our strategies to tackle cancer are still incompletely integrating the many pieces of the puzzle that we have already accumulated and the various concepts already advanced on the basis of this knowledge.
fluid concepts and creative analogies epub format
Traditionally, members of a learning community reside in the same location[22]. However, as groups migrate and become less homogenous, configurations of 'group identity' based on geographic location become less appropriate. Nowadays communities are linked less by location and more by common interests and goals. Many new learning communities have developed as technology makes global communication increasingly easier and faster. E-mail discussion lists and online information management systems (e.g., the Blackboard [24]) have become popular communication tools for synchronized and asynchronized dialogues. Hence, virtual learning communities are more fluid than traditional communities[25].
Because CoP is an evolving concept, it may be premature to set concrete boundaries to differentiate CoPs from other types of group structure. Nonetheless, the CoP concept can be used to provide some guidance for the development of groups, teams, and networks. Our analysis of the germinal literature highlighted several key characteristics of the CoP concepts, such as the support for formal and informal interaction between novices and experts, the emphasis on learning and sharing knowledge, and the investment to foster the sense of belonging among members. Hence, research in CoP may be more productive if we endeavor to develop and refine interventions that optimise these characteristics. Examples of promising interventions may include using a facilitator to promote network/group activities and enhance interaction among members[47], using information technology to facilitate communication of individuals in distributed networks/groups[52], or providing organizational infrastructures that promote the uptake of new knowledge in health care settings[55]. Furthermore, we believe that the functions of these network/groups may be optimized by improving the understanding of the process of negotiating boundaries of emerging CoPs, and the roles and responsibilities of CoP members.
Unlike ribose, the purine coding elements of RNA can be synthesized in the same abiotic reactions that yield amino acids [22, 23, 26, 37]. Amino acids may be synthesized in putative prebiotic chemistries like Strecker type reactions (synthesis of amino acids from cyanide and aldehyde in the presence of ammonia) in hydrothermal environments at fairly low temperatures (150C) [38]. Amino acids can also be released by hydrolysis of HCN oligomers that form by the self-condensation of hydrogen cyanide in aqueous solution [23]. Such reactions do not require alkaline conditions. Purines are formed from HCN via two routes. One route is via the HCN oligomers that also forms amino acids; the second one is via the HCN tetramer diaminomaleonitrile (DAMN) [22, 23]. HCN may be formed in a variety of ways but normally occur in trace amounts. In order to participate in abiotic organic reactions they must first be concentrated. One possibility is concentration to a reservoir of iron cyanide at relatively low pH from which free HCN can be released upon local elevation of the pH [11]. This would avoid the 'Miller paradox', which refers to the side reaction of stable cyanohydrin formation from free HCN and ubiquitous formaldehyde. Russell and coworkers have presented a model involving alkaline hydrothermal mounds as flow reactors in which strongly polar compounds such as the cyanide ion is retained by fresh FeS/Fe3S4 membranes [2]. According to their model, the fluctuations in pH at the interface between hydrothermal fluid and seawater would determine adsorption and desorption of the cyanide. In natural environments, the occurrence of ferrocyanides in hydrothermal systems has so far been reported from the Kurile Islands and the Kamchatka Peninsula [39, 40].
Recent work by Bach and coworkers suggests that serpentinization goes through a sequence of reactions that start with low fluid flux serpentinization of olivine to serpentine and ferroan brucite [58]. Later-stage serpentinization invokes formation of magnetite and brucite by the breakdown of the ferroan brucite [58]. This means that phosphate (orthophosphate and pyrophosphate) and borate that is scavenged by the brucite will be in close contact with the authigenic magnetite while it is being formed as a microcrystalline compound with a large surface area and, presumably, is most potent for the abiotic formation of organic compounds.
The Ocean Drilling Program (ODP) Leg 201 was devoted to the controls on microbial communities in deeply buried sediments and was carried out in 2002. Results from ODP Leg 201 reveal that fresh seawater is channelled upwards into deep-sea sediments from the rocks underneath [59, 60]. This happens still 40 Ma or more after formation of the basement and is illustrated by the concentration profiles of dissolved nitrate in sediment porewater from ODP Sites 1225 and 1231 (Fig. 2). Similar profiles have been obtained for dissolved sulfate. Such fluid flow must, therefore, be considered a global process that occurs over a wide range of temperatures. The fact that seawater circulates through ocean basement millions of years after its formation shows that hydrothermal processes at moderate temperatures can be quite extended in time. This, together with the recent discoveries of mechanism of serpentinization and abiotic organic synthesis, adds a dimension of universatility to possible scenarios for the prebiotic formation of the first genetic material.
A feature matrix which addresses a wide range of system properties, from abstract concepts like query language expressiveness down to practicalities such as data formats and ingestion tool support. This aids future comparative tests as a large matrix is available against which further systems can be readily compared. Array system designers get a feature list, including relevant standards, along which they can craft their own tool.
It is highly believed that all spiral galaxies have black holes in their centers, the black holes are very small objects with extremely high density and gravitational force, the matter is swirling into the black holes, nothing within the horizon range can come out of the black holes. So far, we know little about the black holes and it is full of mysteries. However, Hawking proposed that radiation (Hawking radiation) is predicted by black holes due to quantum effects near the event horizon 17, such radiation reduces the mass and rotation energy of black holes, therefore, the black holes will shrink and ultimately vanish if they do not gain mass through other means. Pan proposed that the rotation of the galaxies can be treated as ideal fluid system and followed by both fluid mechanism and gravitational mechanism 18, the gravitational force serves as fluid viscosity and binding force; it is further concluded in that paper that the combination of the fluid mechanics and gravitational mechanics is the only mechanism to restore the galaxies into flat disc shapes with flat rotation curves after galaxy collision or merging. By adapting this ideal fluid concept and evaluating various other aspects, the following rotating double-side sprinkle emission model is proposed for the spiral arm formation of galaxies:
The equation (41) tells us some useful information about the evolution of the galaxy. The current value of ρ is 0.55, the spiral arm pattern should look like Figure 5a, a spiral-plus-ring pattern if ρ was constant through its history to the past; but its ρ gradually increased with the backward time, i.e., the ρ (which reflects the IM emission velocity with assumption that the rotation velocity remains stable) has been gradually decreasing from past to now, the decrease rate depends on the square of the time with very small coefficient 6.8 * 10-7. The inner ring could be formed by hydrogens converted from a portion of the IM which has very slow emission velocity or by other mechanism. The most arms near the edge are broken into pieces like spurs due to many reasons which may include but not limited to: 1. The galaxy is not a perfect ideal fluid system; 2. Local chaos and disturbance in matter distribution and motion velocity; 3. IM spreads and diffuses to the galactic fluid system. The IM band gradually loses its coherence on its moving path under the effect of those reasons; the edge arms will gradually fade and disappear in the future when they move out the visible range. Those reasons may also cause the formation of spurs, branches and feathers of the spiral arms in the galaxies like famous pinwheel galaxy M101. This topic was studied in detail by Chakrabarti et al. 19. 2ff7e9595c
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