Measuring "small-world" connectivity in international trade: a shift-share and ANOVA approach

Improvements in telecommunications and transportation appear to be bringing the world closer making physical location less of a factor in determining interaction between nations. The formation of regional and global trading pacts and arrangements seem to be further contribution to this interaction. Some would argue that what is evolving, as a result of these developments, is a 'small world' network. This type of network has a high degree of cliquishness, or local connectivity, and a relatively short average minimum path, or strong overall network connectivity. 'Small-world networks' is a new concept that is receiving a lot of attention. Introduced by Watts and Strogatz (1998), a 'small-world network' is based on 'six degrees of separation' or the notion that everyone in the world is related to everyone else through at most six acquaintances. 'Six degrees of separation' arises from the existence of cliques and a few popular individuals who provide connections between these cliques. The huge appeal of 'small-world networks' lies in the impact they are said to have on dynamical systems. According to Watts and Strogatz(1998), for example, models of dynamical systems with small-world coupling display enhanced signal propagation speed, computational power, and synchronizability. Furthermore, contagious diseases tend to spread more freely in 'small-world networks'. These findings have profound implications for many manmade and natural systems. In a trading network, 'small-world' topology might contribute to the regional and global economic spillover effects. This paper introduces a method, based on shift-share analysis and one-way analysis of variance (ANOVA), which can be used to measure the extent of 'small-world' connectivity is evolving in a network. The shift-share model is basically a rule of thumb/empirical method and is used in identifying the "small world" activity. ANOVA is used as a theoretical explanation of the shift-share results and an alternate way to measure "small world". The model is applied to two distinct time periods, the first from 1996 to 1998 and the second from 1989 to 1992. The first time period is representative of the trading network topology that was present in the 1980's, in particular a lot of local trading arrangements (cliques) and very few multilateral alliances and agreements between nations of different cliques, while the latter time period reflects stronger local trading arrangements (cliques) and the introduction of multilateral and bilateral agreements between nations of different cliques. Results are summarized using a geographic information system.

Spatial-Structural Relations among Technology Industrial Clusters: A Comparative Analysis of Metropolitan Regions in the U.S

Technical industrial clusters are defined and analyzed for a sample of U.S. metropolitan regions. Economic structure, spatial proximity and shape of the clusters are examined across the metropolitan regions through various economic and spatial measures and statistics. The data for this research are used to test the hypothesis that close spatial proximity results in stronger economic functional interdependence. This hypothesis is examined and the implications of the test are explored.

Uniform Micro-Patterning of an Arbitrary Surface

According to the literature, creating specific micro-level patterns on some surfaces can significantly reduce friction. To this effect, a method is presented to create a regular pattern of micro-level indentations on any irregular surface. Creating a uniform pattern on a regular surface is possible using commercial CAD software, where regular surface is the surface obtained by extrusion or revolution of a 2D sketch along any curve. But, it is complicated and often incorrect for irregular surfaces. The thesis presents the approach followed to create parameterized regular patterns on arbitrary surfaces. Three different algorithms are presented, each achieving a progressively increased quality solution. The last and best method provides a set of points with their corresponding normals to the surface to enable the creation of the patterning feature. The algorithm reads an STL file, a format neutral output of any CAD software and implements the method on the approximated surface. Each facet surface upon which the pattern has to be created is sliced by planes at specific distances from each other. The intersections of the facets and the planes are calculated and chains are formed from the intersections in each plane. Points are interpolated at the required pitch in different chains formed at the intersection of a single plane and the facets. This procedure is repeated for each plane. Thus, a pattern of points of specified pitch distance that can be as low as microns can be generated. Given specifications of a machine, this method generates the X, Y, and Z translations and the axis rotation angles needed to generate a g-code specific to a micro-milling machine. This code can be used directly for any metal removing process that has to create micro-level indentations on an arbitrary surface. If instead, the features are protrusions on some irregular surface, then the resultant points obtained with the developed approach can be used to apply the pattern at each of the identified locations

Scale-Free Phenomena in Communication Networks: A Cross-Atlantic Comparison

?Small-world networks? have a high degree of local clustering or cliqueness, like a regular lattice and a relatively short average minimum path, like a completely random network. The huge appeal of ?small-world networks? lies in the impact they are said to have on dynamical systems. In a transportation network, ?small-world? topology could improve the flow of people or goods through the network, which has important implications for the design of such networks. Preliminary research has shown that ?small-world network? phenomenon can arise in traffic networks possessing ?small-world? network topology (i.e., in a network that has a structure somewhere in between a regular lattice and random graph) and that, at least under certain circumstances, traffic appears to flow more efficiently through a network with such topology (Schintler and Kulkarni, 2000). This paper will explore this further through simulation under varying assumptions regarding the size of the network (i.e., in terms of number of nodes and edges), the level of traffic in the network, the uniformity of nodes and edges and the information levels of travelers in the network. The simulations will be done using the random rewiring process introduced by Watts and Strogatz (1998), where each time the network is rewired, the distribution of traffic and congestion through the network, and the ?small-world? network parameters, shortest average minimum path and clustering coefficient, will be examined. Traffic flow will be estimated using a gravity model framework and a route choice optimization program. The simulations will also be used to reveal whether or not there are certain nodes or links that suffer at the expense of the entire network becoming more efficient. In addition, the possibility of a self-organised criticality (SOC) structure will be examined. The concept, introduced by Bak et al.,(1987), gained a great deal of attention in past decades for its capability to explore the significant and structural transformation of a dynamic system. SOC sets out how prominent exogenous forces together with strong localized interactions at the micro level lead a system to a critical state at the macro-level. A further step in our analysis is the investigation of whether a power-law distribution, characteristic of the SOC state, evolves in the traffic network. While ?small-world? network topology may be shown to improve the efficiency of traffic flow through a network, it should be recognized that ?small-world? networks are sparse by nature. The shut down or major disruption of any link in such a network, particularly one with heavy congestion, could provoke significant disorder. This paper will also explore the effect that disruptions of this nature have on networks designed with a high degree of local clustering and a short average minimum path. The fact that a ?small-world? network is sparse also raises other issues for the transportation planner. If ?small-world? topology is in fact a desirable property for transportation networks, how do we transform existing networks to produce these results? Unlike other networks, such as those for telecommunications or socialization, a transportation network cannot be rewired to achieve a more efficient network structure. This issue will also be addressed in the paper. REFERENCES Bak, P., C. Tang, and K. Wiesenfeld (1987), ?Self-Organised Criticality?, Physical Review Letters, Vol. 59 (4), pp. 381-384. Watts, D.J. and S.H. Strogatz (1998). ?Collective Dynamics of ?Small-World? Networks? Nature, Vol 393, 4, pp. 440-442. Schintler, L.A. and R. Kulkarni (2000). ?The Emergence of Small-World Phenonmenon in Urban Transportation Networks? in Reggiani, A. (ed.), Spatial Economic Science: New Frontiers in Theory and Methodology, Springer-Verlag, Berlin-NewYork, pp. 419-434.

Development and characterization of amoxicillin loaded floating microballoons for the treatment of Helicobacter pylori induced gastric ulcer

AbstractThe current communication reports in vitro characterization of the optimized hollow floating microballoons of amoxicillin on the basis of micromeritic properties and in vitro minimum inhibitory concentration (MIC). Amoxicillin loaded hollow microballoons were prepared by emulsion solvent diffusion method. The morphological characterization was done on the basis of scanning electron microscopy (SEM). Fourier Transformed Infrared Spectroscopy (FTIR) was used to investigate drug–polymer interactions. The correlation between the in vitro buoyancy of microballoons and their physical properties, e.g. density and porosity were elucidated. The results of FTIR spectroscopy revealed the absence of any drug–polymer interactions. The porosity values of more than 69% and diameter to thickness ratio greater than 2.90, proved a high cavity volume within the microballoons in all size ranges. The spherical shape of microballoons with hollow internal cavity was confirmed from SEM photomicrographs. The in vitro MIC results showed a sustained drug effect from the microballoons. In conclusion, it can be said that the developed microballoons can be used for the effective treatment of Helicobacter pylori induced gastric ulcer

A New Method for Assessing the Resiliency of Large, Complex Networks

Designing resilient and reliable networks is a principle concern of planners and private firms. Traffic congestion whether recurring or as the result of some aperiodic event is extremely costly. This paper describes an alternative process and a model for analyzing the resiliency of networks that address some of the shortcomings of more traditional approaches – e.g., the four-step modeling process used in transportation planning. It should be noted that the authors do not view this as a replacement to current approaches but rather as a complementary tool designed to augment analysis capabilities. The process that is described in this paper for analyzing the resiliency of a network involves at least three steps: 1. assessment or identification of important nodes and links according to different criteria 2. verification of critical nodes and links based on failure simulations and 3. consequence. Raster analysis, graph-theory principles and GIS are used to develop a model for carrying out each of these steps. The methods are demonstrated using two, large interdependent networks for a metropolitan area in the United States.

DEVELOPMENT AND EVALUATION OF CHRONOMODULATED DELIVERY SYSTEM OF METOCLOPRAMIDE HYDROCHLORIDE

Objective: Metoclopramide hydrochloride (meto) is indicated in the treatment of diabetic gastro paresis. It is also used in the treatment of pregnancy-induced morning sickness. Present work involved the development of a chrono-modulated delivery system of meto, intended to be taken at bedtime which would elicit the therapeutic response early in the morning when needed the most to prevent the symptoms of diabetic gastro paresis and morning sickness. Methods: Immediate release tablets of meto were prepared and optimized for disintegration time and in vitro drug release. Subsequently, these tablets were compression coated using various ratios of glyceryl dibehenate and diluents. The resulting tablets were evaluated for disintegration time and in vitro drug release. Optimized formulation was subjected to accelerated stability studies for 3 mo. Results: The optimized immediate release tablets exhibited disintegration time of 2-3 min and more than 90% drug release within 30 min. These tablets when compression coated with the optimized ratio of glyceryl dibehenate and di-calcium phosphate could delay the disintegration time to 251 min. In vitro release study of the tablets showed the lag phase of 4 h after which there was a complete drug release within 1 h. Accelerated stability studies indicated good physical and chemical stability of the formulation. Conclusion: Chrono-modulated formulation of meto could delay the release of the drug by four h. This lag in the release is expected to modulate the time of therapeutic response of meto early in the morning at 6-7 h interval after the administration of dosage form at bedtime