Dominant Node Research Articles

THE EMERGENCE OF CENTRALITY IN A TRANSITION ECONOMY: COMPARING LAND MARKET DYNAMICS MEASURED UNDER MONOCENTRIC AND SEMIPARAMETRIC MODELS*

ABSTRACT This paper focuses on the emergence of Krakow's historic core as the city's economic center after Poland's economic reforms of 1989—reforms that introduced market forces into land markets. Using a semiparametric approach to identify pricing centers, an evolving and polycentric price surface is revealed. While the traditional city center emerges as the dominant node, the evolution of the price surface is far more complex than that found using alternative approaches. Accordingly, it yields superior explanatory power compared to simpler monocentric models and should caution against their use in metropolitan areas in transition or those that are polycentric.

On the mechanisms underlying diastolic voltage oscillations in the sinoatrial node

Aim The study of the mechanisms underlying the oscillatory afterpotential (V os) and prepotential (ThV os). Background It has been recently shown that V os and ThV os play an obligatory role in the dominant sinoatrial node (SAN) discharge. Methods Guinea pig isolated SAN was studied in vitro by means of a microelectrode technique. Results High [K +] o and premature stimuli unmask V os superimposed on early diastolic depolarization and ThV os within a less negative voltage range (“oscillatory zone”). Subthreshold stimuli elicit ThV os in the oscillatory zone, but not at more negative values. Drive and caffeine shift the oscillatory zone in a negative direction. Low caffeine concentrations increase the size of V os and of ThV os, rate, and force. High caffeine concentrations suppress V os but increase the size of ThV os and shift them to more negative values until they eventually miss the threshold. In quiescent SAN in high caffeine, a fast drive enhances ThV os size, thereby initiating a transient spontaneous rhythm (“overdrive excitation”). Adrenergic agonists potentiate caffeine-induced overdrive excitation through an increase in ThV os. In high caffeine, the first twitch after quiescence is not larger, twitch relaxation is slower, V os is abolished, and the prolonged nonoscillatory afterdepolarization V ex is induced, consistent with an impairment of Ca 2+ handling by the sarcoplasmic reticulum. The effects of caffeine in Tyrode's solution are accounted for by the caffeine-induced changes in the oscillatory potentials. Tetrodotoxin decreases force and size of both V os and ThV os. Conclusions The mechanism underlying V os is related to a diastolic release of Ca 2+ from a Ca 2+-overloaded sarcoplasmic reticulum, whereas that of ThV os appears to be related to ionic currents in the resting potential range that can initiate and sustain spontaneous discharge.

Identification of Sialoadhesin as a Dominant Lymph Node Counter-receptor for Mouse Macrophage Galactose-type C-type Lectin 1

In the sensitization phase of contact hypersensitivity in mice, dermal macrophages (MOs) expressing MO galactose-type C-type lectin1 (MGL1) are known to migrate from the dermis to lymph nodes (LNs) where they accumulate in the subcapsular sinus, interfollicular regions, and areas surrounding high endothelial venules. We hypothesize that the interactions between MGL1 and its ligands determine the localizations of MGL1-positive cells within the LNs. In the present study, our major aim was to isolate MGL1 counter-receptor(s) from lysates of LNs using affinity chromatography with immobilized recombinant MGL1. Fractions bound and eluted with EDTA were analyzed by SDS-PAGE and matrix-assisted laser desorption ionization time-of-flight mass spectrometry. One of the predominant components was sialoadhesin (Sn, Siglec-1). Sn from lysates of LNs was immobilized on microtiter plates precoated with anti-Sn monoclonal antibody, and binding of recombinant MGL1 and adhesion of cells expressing MGL1 were tested. The binding of recombinant MGL1 to Sn was shown to be dependent on Ca2+ and N-glycans on Sn. MGL1-transfected Chinese hamster ovary cells adhered to the Sn-coated plates, whereas mock transfectants did not. Immunohistochemical localization of anti-Sn monoclonal antibody in LN coincided with the subcapsular sinus area to which recombinant MGL1 was bound. Furthermore, the distribution of MGL1+ cells after sensitization with FITC was demonstrated to overlap with that of Sn within the subcapsular sinus of draining LNs. These results suggest that Sn acts as an endogenous counter-receptor for MGL1.

Knowledge Networks as Channels and Conduits: The Effects of Spillovers in the Boston Biotechnology Community

We contend that two important, nonrelational, features of formal interorganizational networks—geographic propinquity and organizational form—fundamentally alter the flow of information through a network. Within regional economies, contractual linkages among physically proximate organizations represent relatively transparent channels for information transfer because they are embedded in an ecology rich in informal and labor market transmission mechanisms. Similarly, we argue that the spillovers that result from proprietary alliances are a function of the institutional commitments and practices of members of the network. When the dominant nodes in an innovation network are committed to open regimes of information disclosure, the entire structure is characterized by less tightly monitored ties. The relative accessibility of knowledge transferred through contractual linkages to organizations determines whether innovation benefits accrue broadly to membership in a coherent network component or narrowly to centrality. We draw on novel network visualization methods and conditional fixed effects negative binomial regressions to test these arguments for human therapeutic biotechnology firms located in the Boston metropolitan area.

The architecture of the climate network

We consider climate as a network of many dynamical systems and apply ideas from graph theory to a global data set to study its collective behavior. We find that the network has properties of ‘small-world’ networks (Nature 393 (1999) 440). A detailed investigation of the coupling architecture of this network reveals that the overall dynamics emerge from the interaction of two interweaved subnetworks. One subnetwork operates in the tropics and the other at higher latitudes with the equatorial one acting as an agent that establishes links between the two hemispheres. Both subsystems are ‘small-world’ networks, but there are distinct differences between the two subsystems. The tropical one is an almost fully connected network, whereas the mid-latitude one is more like a scale-free network characterized by dominant super nodes, and multifractal properties. This unique architecture may lead to new insights not only about the dynamics of the climate system but of other spatially extended complex systems with a large number of degrees of freedom.

Growth and structure of the World Wide Web: Towards realistic modeling

We simulate evolution of the World Wide Web from the dynamic rules incorporating growth, bias attachment, and rewiring. We show that the emergent double-hierarchical structure with distinct distributions of out- and in-links is comparable with the observed empirical data when the control parameter (average graph flexibility β) is kept in the range β = 3-4. We then explore the Web graph by simulating (a) Web crawling to determine size and depth of connected components, and (b) a random walker that discovers the structure of connected subgraphs with dominant attractor and promoter nodes. A random walker that adapts its move strategy to mimic local node linking preferences is shown to have a short access time to important nodes on the Web graph.

Critical Theory, Information Society and Surveillance Technologies

This article offers an account of information and communication technologies (ICTs) that draws upon the tradition of critical theory, arguing that an application of the latter to the former can be categorized as a theory of 'cyber criticalism'. Its aim is not to provide an exhaustive theoretical analysis or any kind of literature review, but to suggest that such a theorization is possible because cyber criticalism (1) offers an account of social power and (2) suggests how and why alternatives to existing social practices and institutions can be formed. The first section relates the debate about information society to that concerning globalization and argues that two main theories square off against each other in the race to explain that society: one which, in Castells's terminology, emphasizes the power of flows and the other which emphasizes the flows of power. If the former is inadequate in crucial respects then the way is clear for critical theorists to explore the latter. Cyber criticalism is then sketched in outline and the article proceeds to identify information systems, the flows of power, as potential sites of resistance. The final section focuses upon biometrics and argues that the way forward for cyber critical theorists lies in exploiting the cultural insecurities of informatic capitalism. Ultimately, then, cyber criticalism is critical theory updated for the information age. Unlike those such as Castells it identifies flows of power and the intensification of those flows around the dominant nodes of the informational net. It insists that information systems constitute potential sites of resistance. Nevertheless, acts of resistance are still relatively marginal and fragmented events due to they way in which social problems are pathologized and criminalized.

The dominant sentinel node in breast cancer: A new technique

The dominant sentinel node in breast cancer: A new technique

Prognostic significance of lymph node reactivity in the control of pathologic negative node squamous cell carcinomas of the oral cavity

Identification of high-risk patients and defining prognostic factors may be useful in the treatment of head and neck cancer. The role of the lymph node reactivity is still obscure. The value of the node reactivity pattern as a predictor of tumor control in oral cavity cancer was analyzed. Retrospective analysis of patients with oral cavity squamous cell carcinoma (OCSCC), submitted to tumor resection and neck dissection, with pathologic negative lymph nodes (pN0). Dominant node reactivity pattern was defined as lymphocytic predominance (LP), germinal centers (GC), normal (NL), sinus hystiocytosis (SH), and lymphocytic depletion (LD). Clinical and pathological characteristics of patients free of disease (DF) were compared with those of patients with control failure (CF), which included local, regional, and distant recurrences. Of the 26 patients with pN0 OCSCC, prevalence of SH was found in 10 cases, GC in 13, and LD, NL and PL in 1 case each. Comparing CF and DF groups, there was no significant statistical difference regarding: age, gender, performance status index, weight loss, smoking and drinking habits, complementary treatment, average follow-up, tumor grade or thickness, margins, or tumor inflammatory and desmoplastic reaction. Although there was a higher proportion of perineural invasion and larger tumors in the CF group, the difference was not statistically significant either. Germinal centers or LP were noted in only 27% of the CF group and in 73% of the DF group. Collectively, NL, SH, or LD patterns were observed in 73% of CF. This incidence was statistically different from 27% of the DF group (P <0.05). Lymph node reactivity pattern seems to be a prognostic index in pN0 OCSCC patients. Prospective analysis is advised to confirm these results. Prophylactic neck dissection as a staging procedure could select high-risk patients even when no metastasis is found.

Urban revitalization in the Netherlands: Current trends versus actual policies

Abstract The paper focuses at the discrepancy between actual urban policies and current spatial socio‐economic developments. Three discrepancies are discussed: homogeneous concepts versus developments directed at heterogeneity; economic seduction policies versus comprehensive developments; and small‐scale policies versus higher level developments. Basic to the current spatial trends is the evolution of a large‐scale urban network. This results in a less hierarchical urban structure and a heterogenization of economic centres and living areas which occurs both within and between urban places. Because of this, the steering possibilities of hierarchic organized urban policies are hampered. In contrast to these developments, urban policy in the Netherlands has a hierarchical nature and focuses heavily on the traditional dominant urban nodes. The present phase of policy, ‘urban management’, illustrates this. An adaption of the spatial framework of policy is needed. The paper also shows that present policies haue a too narrow economic perspective which leads to an underestimation of present and future problems related to the labour and housing market. A plea is made for an explicit dynamic approach to urban revitalization in which the normative and instrumental function is stressed. Moreover, the suggested distinction between efficiency and equity is rejected The article is based on a survey of current trends and future research needs under the authority of the Advisory Council for the Programming of Future Directions in Spatial Research in the Netherlands.

Soviet Air-Passenger Transportation Network

Soviet air-passenger transportation system reflects the physical, political, and economic conditions under which it operates. Air service from Moscow, the dominant node, differs from service patterns in the United States. Distance, population, and complementarity all explain variations in levels of service in the Soviet Union. HE growth of air-passenger transportation in the Soviet Union has been phenomenal since 1945. Between 1950 and 1987, the number of passengers carried annually within the country increased almost eightyfold, and the volume of passenger-kilometers grew by a factor of more than 170. In 1987, Soviet aircraft carried 119 million passengers, of whom 115 million were on domestic flights. By comparison, airline passengers in the United States numbered 418 million, of whom 393 million were on domestic flights (Narodnoye khozyaystvo SSSR 1988, 308, 336; Statistical abstract 1988). In the United States and many other countries, passengers are carried by numerous independent airlines. In the Soviet Union there is only one passenger airline, the government-owned Aeroflot, although a few small operators such as the air arm of the Northern Sea Route supplement its services. As a result, Aeroflot is the world's largest single airline (MacDonald 1975). Air transportation is crucial to a large and relatively roadless country such as the Soviet Union. However, very little recent information exists on the spatial structure of its air-passenger system. The purpose of this article is to further understanding of that system by describing the geographical circumstances under which air transportation evolved, by analyzing air service from the four Moscow airports, and by comparing selected aspects of Soviet air-passenger transportation with those in the United States.

The origins of the sinus node pacemaker complex in man: Demonstration of dominant and subsidiary foci

To test the hypothesis that the human sinus node is capable of demonstrating multiple sites of impulse generation, we assessed spontaneous shifts in the sinus node pacemaker complex, and shifts after overdrive atrial pacing, premature atrial stimulation and carotid sinus massage. A total of 24 patients aged 59 +/- 15 years (mean +/- SD) in whom stable sinus node electrograms were obtained were selected for the study. Ten of the 24 patients had sick sinus syndrome, whereas 14 had no sinus node dysfunction. All 24 patients had atrial pacing at cycle lengths of 1,000 to 300 ms; 9 patients had premature atrial stimulation and 12 had carotid sinus massage. Shifts in the sinus node pacemaker complex occurred spontaneously in 4 (17%) of the 24 patients; after atrial pacing at cycle lengths of 800 to 300 ms (mean 387 +/- 92) in 15 (63%) of 24 patients; after premature atrial stimulation at one or more coupling intervals in 5 (56%) of 9 patients and during carotid sinus massage in 9 (75%) of 12 patients. Shifts in the sinus node pacemaker complex lasted one to six beats and returned to the original site within two to seven beats. Spontaneous shifts in the sinus node pacemaker complex occurred in 3 of 14 patients without sick sinus syndrome and were induced in 6 (60%) of 10 patients with sick sinus syndrome and 11 (79%) of 14 patients without sick sinus syndrome. Shifts in sinus node pacemaker complex were characterized by loss of primary negativity, change in P wave morphology, significant (p less than 0.001) prolongation of sinoatrial interval and sinus cycle length.