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  • 1
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Rhizobium meliloti FixL and FixJ are members of a symbiotically essential two-component system that regulates nitrogen-fixation genes in response to environmental oxygen concentrations. FixL is a membrane protein that is thought to relay information about oxygen availability to FixJ via a phosphotransfer mechanism. FixJ increases expression of the nifA and fixK genes by activating transcription of the nifA and fixK promoters (p-nifA and p-fixK, respectively). In this study, we examined the relationship between the in vivo activity of FixJ as a transcriptional regulator and its ability to be phosphorylated in vitro by the sensor FixL. FixJ mutants were isolated that showed decreased activity on p-nifA in Escherichia coli. Most of the FixJ mutant proteins also showed decreased activity on the fixK promoter. These mutants were analysed in R. meliloti for activity on p-nifA during vegetative growth, where similarities and differences were observed when compared with their phenotypes in E. coli. Three mutants showing significantly less activity in R. meliloti were examined for symbiotic activity in planta and were found to be ineffective. When these three mutant FixJ proteins were examined in vitro for their ability to be phosphorylated by FixL, two mutants were found to have a significantly decreased ability to accept phosphate from FixL. These findings are discussed in relation to signal transduction in the FixLJ system.
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  • 2
    Electronic Resource
    Electronic Resource
    Bradford : Emerald
    Industrial robot 25 (1998), S. 20-26 
    ISSN: 0143-991X
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Discusses process automation in bakery manufacturing. States that although automation has occurred in the preparation and process areas, packaging has remained a manual operation. Presents a flexible automated packaging system which can cope with the demanding variables encountered when dealing with bakery products.
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  • 3
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The retinoblastoma (Rb) gene was the first tumour suppressor identified. Inactivation of Rb in mice results in unscheduled cell proliferation, apoptosis and widespread developmental defects, leading to embryonic death by day 14.5 (refs 2–4). However, the actual cause of the ...
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  • 4
    Electronic Resource
    Electronic Resource
    Bingley : Emerald
    Journal of management history 4 (1998), S. 350-362 
    ISSN: 1355-252X
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Economics
    Notes: The practitioners of postmodern organization theory have had to respond to the charge that postmodernism has a declivity toward skepticism. Their response to organizational skepticisim is to decenter dominant theories, paradigms and organizational forms, rather than to negate them. Decentering supplements discourse by augmenting its repertoire; the opposite of skepticism, which diminishes its object. The main ways in which postmodern organization theories try to overcome the specific sceptical position of paradigm incommensurability (the reduction of discourse about organizations and organizational discourse to a solipsism of private language games) are described and assessed in terms of three positions: John Hassard's "multiple paradigm" approach on the level of methodology, Stewart Clegg's "embedded rationalities" on the level of empirical conceptualization, and Kenneth Gergen's "heteroglossia" on the level of discursive practice. Hassard and Clegg are engaged in the mapping function of postmodern organization theory, whereas Gergen is engaged in deconstraining organizations.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Communications in mathematical physics 106 (1986), S. 569-580 
    ISSN: 1432-0916
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Abstract We consider the initial value problem for the Zakharov equations $$\begin{gathered} \left( Z \right)\frac{1}{{\lambda ^2 }}n_{tt} - \Delta (n + \left| {\rm E} \right|^2 ) = 0n(x,0) = n_0 (x) \hfill \\ n_t (x,0) = n_1 (x) \hfill \\ iE_t + \Delta E - nE = 0E(x,0) = E_0 (x) \hfill \\ \end{gathered} $$ (x∈ℝ k ,k=2, 3,t ≧0) which model the propagation of Langmuir waves in plasmas. For suitable initial data solutions are shown to exist for a time interval independent of λ, a parameter proportional to the ion acoustic speed. For such data, solutions of (Z) converge as λ → ∞ to a solution of the cubic nonlinear Schrödinger equation (CSE)iE t +ΔE+|E|2 E=0. We consider both weak and strong solutions. For the case of strong solutions the results are analogous to previous results on the incompressible limit of compressible fluids.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Communications in mathematical physics 87 (1983), S. 567-576 
    ISSN: 1432-0916
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Abstract A sharp sufficient condition for global existence is obtained for the nonlinear Schrödinger equation $$\begin{array}{*{20}c} {(NLS)} & {2i\phi _t + \Delta \phi + \left| \phi \right|^{2\sigma } \phi = 0,} & {x \in \mathbb{R}^N } & {t \in \mathbb{R}^ + } \\ \end{array} $$ in the case σ=2/N. This condition is in terms of an exact stationary solution (nonlinear ground state) of (NLS). It is derived by solving a variational problem to obtain the “best constant” for classical interpolation estimates of Nirenberg and Gagliardo.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Communications in mathematical physics 164 (1994), S. 305-349 
    ISSN: 1432-0916
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Abstract We show that the family of solitary waves (1-solitons) of the Korteweg-de Vries equation $$\partial _t u + u\partial _x u + \partial _x^3 u = 0 ,$$ is asymptotically stable. Our methods also apply for the solitary waves of a class of generalized Korteweg-de Vries equations, $$\partial _t u + \partial _x f(u) + \partial _x^3 u = 0 .$$ In particular, we study the case wheref(u)=u p+1/(p+1),p=1, 2, 3 (and 3〈p〈4, foru〉0, withf∈C 4). The same asymptotic stability result for KdV is also proved for the casep=2 (the modified Korteweg-de Vries equation). We also prove asymptotic stability for the family of solitary waves for all but a finite number of values ofp between 3 and 4. (The solitary waves are known to undergo a transition from stability to instability as the parameterp increases beyond the critical valuep=4.) The solution is decomposed into a modulating solitary wave, with time-varying speedc(t) and phase γ(t) (bound state part), and an infinite dimensional perturbation (radiating part). The perturbation is shown to decay exponentially in time, in a local sense relative to a frame moving with the solitary wave. Asp→4−, the local decay or radiation rate decreases due to the presence of aresonance pole associated with the linearized evolution equation for solitary wave perturbations.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 296 (1999), S. 33-43 
    ISSN: 1432-0878
    Keywords: Key words FGF-FGF receptors ; Limb initiation ; Progress zone activity ; Hand and foot anomalies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Fibroblast growth factor (FGF) receptors constitute a family of four membrane-spanning tyrosine kinases (FGFR1–4) which serve as high-affinity receptors for 17 growth factors (FGF1–17). To study functions of FGF/ FGFR signals in development, mice that carry mutations in each receptor have been created by gene targeting. Analysis of these mutant mice revealed essential functions of FGF receptors in multiple biological processes, including mesoderm induction and patterning, cell growth and migration, organ formation and bone growth. In this review we discuss recent work with FGF receptors to illustrate mechanisms, through which the FGF/FGFR signals specify vertebrate limb initiation, outgrowth and patterning.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Wetlands ecology and management 4 (1997), S. 111-127 
    ISSN: 1572-9834
    Keywords: restoration ; wetlands ; success criteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We are using a 20+ year photographic history of relatively undisturbed and formerly diked sites to predict the restoration trajectories and equilibrium size of a 4,050 ha salt marsh on Delaware Bay, New Jersey (USA). The project was initiated to offset the loss of finfishes from once-through cooling at a local power plant. We used a simple food chain model to estimate the required restoration size. This model assumed that annual macrophyte detritus production and benthic algal production resulted in production of finfishes, including certain species of local interest. Because the marsh surface and intertidal drainage system are used by many finfishes and are the focal points for exchange of detrital materials, the restoration planning focused on both vegetational and hydrogeomorphological parameters. Recolonization bySpartina spp. and other desirable taxa will be promoted by returning a natural hydroperiod and drainage configuration to two types of degraded salt marsh: diked salt hay (Spartina patens) farms and brackish marsh dominated byPhragmites australis. The criteria for success of the project address two questions: What is the “bound of expectation” for restoration success, and how long will it take to get there? Measurements to be made are macrophyte production, vegetation composition, benthic algal production, and drainage features including stream order, drainage density, channel length, bifurcation ratios and sinuosity. A method for combining these individual parameters into a single success index is also presented. Finally, we developed adaptive management thresholds and corrective measures to guide the restoration process.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Environmental biology of fishes 31 (1991), S. 87-94 
    ISSN: 1573-5133
    Keywords: Young-of-the-year ; Microincrement ; Early life history
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Synopsis Scale circuli of juvenile weakfish,Cynoscion regalis, were counted to determine if deposition was daily. Scale circuli counts were precise with little variation between counts (99% of the two counts from an individual scale were identical, N = 3580). Tetracycline marked juveniles (N = 71) had mean scale circuli deposition rates that were daily up to 24 d after marked. Data from several sources suggest that daily deposition of weakfish scale circuli occurred over a relatively narrow size range, approximately 14.3 to 111.9 mm standard length, however it is during this time that juvenile weakfish occupy estuarine nursery areas, where growth, mortality, and survival may alter subsequent year class strength. The estimated upper size limit at which scale circuli were no longer daily occurred over a wide range (82–142 mm standard length), and additional research is required to further clarify the limits of size and age of daily circuli deposition.
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