Livestock products in the Third World: past trends and projections to 1990 and 2000

Meat industry and trade Developing countries Statistics., Dairy products industry Developing countries Statistics., Meat industry and trade Developing countries Forecasting Statistical methods., Dairy products industry Developing countries Forecasting Statistical methods.,

Corporate Stability and Economic Growth

Greater instability in a country's list of top corporations is associated with faster economic growth. This faster growth is primarily due to faster growth in total factor productivity in industrialized countries, and faster capital accumulation in developing countries. These findings are consistent with the view that economic growth is more closely tied to the rise of new large firms than to the prosperity of established large firms. Although a stable list of leading corporations is highly correlated with government size, it is unrelated to other possible policy goals, such as (successful) income equalization and avoiding economic crises, it is related to other political factors. However, the list of top firms is more stable in countries with fewer rights for creditors in bankruptcy and with bank-based rather than stock market-based financial systems. These findings appear to oppugn arguments of the form “What’s good for General Motors is good for America”. We propose that political rent-seeking by large established firms underlies increased corporate stabilityCorporate Stability and Economic Growth

Corporate Stability and Economic Growth

Greater instability in a country's list of top corporations is associated with faster economic growth. This faster growth is primarily due to faster growth in total factor productivity in industrialized countries, and faster capital accumulation in developing countries. These findings are consistent with the view that economic growth is more closely tied to the rise of new large firms than to the prosperity of established large firms. Although a stable list of leading corporations is highly correlated with government size, it is unrelated to other possible policy goals, such as (successful) income equalization and avoiding economic crises, it is related to other political factors. However, the list of top firms is more stable in countries with fewer rights for creditors in bankruptcy and with bank-based rather than stock market-based financial systems. These findings appear to oppugn arguments of the form “What’s good for General Motors is good for America”. We propose that political rent-seeking by large established firms underlies increased corporate stability.

Experimental Study of Two-Phase Air–Water Flow in Large-Diameter Vertical Pipes

Recently, due to an increase in production demand in nuclear and oil and gas industries, the requirement to migrate toward larger pipe sizes for future developments has become essential. However, it is interesting to note that almost all the research on two-phase gas–liquid flow in vertical pipe upflow is based on small-diameter pipes (D_100 mm), and the experimental work on the two-phase gas–liquid flow in large-diameter (D>100 mm) vertical pipes is scarce. Under the above circumstances, the application of modelling tools=correlations based on small-diameter pipes in predicting flow behaviour (flow pattern, void fraction, and pressure gradient) poses severe challenges in terms of accuracy. The results presented in this article are motivated by the need to introduce the research work done to the industries where the data pertaining to large-diameter vertical pipes are scarce and there is a lack of understanding of two-phase gas-liquid flow behaviour in large-diameter (D>100 mm) vertical pipes. The unique aspect of the results presented here is that the experimental data have been generated for a 254-mm inner diameter vertical pipe that forms an excellent basis for the assessment of modelling tools=correlations. This article (i) presents the results of a systematic investigation of the flow patterns in large-diameter vertical pipes and identifies the transition between subsequent flow patterns, (ii) compares it directly with the existing large- (150 mm) and small-diameter data (28mm and 32 mm) in the same air–water superficial velocity range, (iii) exemplifies that the existing available empirical correlations=models=codes are significantly in error when applied to large-diameter vertical pipes for predictions, and last (iv) assesses the predictive capability of a well-known commercial multiphase flow simulator

Hydrodynamic Flow Behaviour in Large Diameter Vertical Riser: Experimental and Simulation Studies

An experimental campaign has been performed to investigate the hydrodynamic behaviour in 12m high and 254mm nominal diameter horizontal flowline-vertical riser setup using air-water as working fluid. The data generated from near riser base and flowline pressure variations were used to characterize the stable and unstable flows encountered during the experiments. A model to study the dynamic behaviour of the large diameter horizontal flowline-vertical riser system is developed using OLGA software (v5.1). Experimental results were compared with simulated model. The major objective of undertaking this work is to investigate the performance of the well-known code for flows encountered in large diameter horizontal flowline-vertical riser. Additionally based on the results, also identify the areas of the improvement in the simulator

Performance Assessment of Void Fraction Correlations in Large Diameter Vertical Pipe Up Flow

Recently, due the to increase in the production demand in many industries such as Nuclear, Oil & Gas and process industries, the requirement to migrate toward larger pipe sizes has become essential. However it is interesting to note that almost all of the earlier two phase flow research is based on small diameter pipes (D≤100mm) and experimental work on predicting the two phase flow behaviour in large diameter (D>100mm) pipes is rare. Thus, the application of methodologies/correlations/equations for predicting flow pattern, void fraction, and pressure gradient based on small diameter poses severe challenges in terms of accuracy. Specifically, the prediction of void fraction in two phase flows, as it plays a fundamental role in characterizing the distribution of the phases within the system. With large number of the void fraction correlations available in the different fields of multiphase flows, the choice for the selection of any void fraction correlation existing in the literature is bewildering. This paper presents an assessment of the predictive capabilities of forty (40) void fraction correlations belonging to different multiphase flow industries. The assessment is performed by comparing the independent experimental data obtained from a 254mm diameter and a 12.2m high vertical pipe upflow loop using air-water as working fluid. The final assessment indicated that most of the void fraction correlations are flow regime dependent as none of the correlations successfully predicted all the four regimes (bubbly, agitated bubbly, unstable slug and churn turbulent) encountered in large diameter vertical upflow experiments

Effect of upstream conditions on the two phase flow in the large diameter vertical pipe

Two phase flow in large diameter vertical pipes is of considerable importance to various fields of multiphase flows. Recently, due to increase in demand in various energy sectors considerable attention has been paid in understanding the flow behavior in large diameter vertical pipes. This paper reports the experimental results of flow pattern identification in relatively large diameter (254mm) vertical pipe. The present work also investigates the effect of upstream conditions on the flow patterns occurring in the vertical test section. The observed flow patterns are classified as bubbly, agitated bubbly, unstable slug and churn/froth flow. Absence of hydrodynamic slugging i.e. non occurrence of Taylor bubble in the riser is also reported. It is found that agitated bubbly and churn/froth type of flows dominates in the vertical large diameter pipe under the condition where conventional small diameter pipe indicates slug flow. Experimental results demonstrate the sensitivity of the flow patterns occurring in the vertical section with the upstream conditions in the flowline. The statistical analysis performed on the data along with visual observations, suggests that liquid slugs formed in flowline dissipate as they travelled up the riser, due to the high velocity distorted bubble clusters

Hysteresis in the cell response to time-dependent substrate stiffness

Mechanical cues like the rigidity of the substrate are main determinants for the decision making of adherent cells. Here we use a mechano-chemical model to predict the cellular response to varying substrate stiffness. The model equations combine the mechanics of contractile actin filament bundles with a model for the Rho-signaling pathway triggered by forces at cell-matrix contacts. A bifurcation analysis of cellular contractility as a function of substrate stiffness reveals a bistable response, thus defining a lower threshold of stiffness, below which cells are not able to build up contractile forces, and an upper threshold of stiffness, above which cells are always in a strongly contracted state. Using the full dynamical model, we predict that rate-dependent hysteresis will occur in the cellular traction forces when cells are exposed to substrates of time-dependent stiffness.Comment: Revtex, 4 PDF figure

Selectivity and Metaplasticity in a Unified Calcium-Dependent Model

A unified, biophysically motivated Calcium-Dependent Learning model has been shown to account for various rate-based and spike time-dependent paradigms for inducing synaptic plasticity. Here, we investigate the properties of this model for a multi-synapse neuron that receives inputs with different spike-train statistics. In addition, we present a physiological form of metaplasticity, an activity-driven regulation mechanism, that is essential for the robustness of the model. A neuron thus implemented develops stable and selective receptive fields, given various input statistic