Flowing active liquids in a pipe: Hysteretic response of polar flocks to external fields

We investigate the response of colloidal flocks to external fields. We first show that individual colloidal rollers align with external flows as would a classical spin with magnetic fields. Assembling polar active liquids from colloidal rollers, we experimentally demonstrate their hysteretic response: confined colloidal flocks can proceed against external flows. We theoretically explain this collective robustness, using an active hydrodynamic description, and show how orientational elasticity and confinement protect the direction of collective motion. Finally, we exploit the intrinsic bistability of confined active flows to devise self-sustained microfluidic oscillators.Comment: 12 pages, 7 figure; accepted for publication in Physical Review

REMITTANCES: THE NEW DEVELOPMENT MANTRA?

Remittances have emerged as an important source of external development finance for developing countries in recent years. This paper examines the causes and implications of remittance flows. It first highlights the severe limitations in remittance data, in sharp contrast to other sources of external finance. It then examines the key trends in remittance flows, and their importance relative to other sources of external finance. The paper subsequently analyses the many complex economic and political effects of remittances. It highlights the fact that remittances are the most stable source of external finance and play a critical social insurance role in many countries afflicted by economic and political crises. While remittances are generally pro-poor, their effects are greatest on transient poverty. However, the long-term effects on structural poverty are less clear, principally because the consequences of remittances on long-term economic development are not well understood. The paper then concludes with some policy options. It suggests a role for an international organization to intermediate these flows to lower transaction costs and increase transparency, which would both enhance these flows and maximize their benefits

Statics and dynamics of fluids in nanotubes

The purpose of this article is to study the statics and dynamics of nanotubes by using the methods of continuum mechanics. The nanotube can be filled with only a liquid or a vapour phase according to the physicochemical characteristics of the wall and to the disjoining pressure associated with the liquid and vapour mother bulks of the fluid, regardless of the nature of the external mother bulk. In dynamics, flows through nanotubes can be much more important than classical Poiseuille flows. When the external mother bulk is of vapour, the flow can be a million times larger than the classical flows when slippage on wall does not exist.Comment: 20 page

Determinants of Portfolio Flows into CIS Countries

This paper employs a standard Tobin-Markowitz framework to analyse the determinants of capital flows into the CIS countries. Using data from 1996-2006, we find that the Russian financial crisis of 1998 has had a profound impact on capital flows into the CIS (both directly and indirectly). Firstly, it introduced a structural shift in the investors' behaviour by shifting the focus from the external factors to the internal ones, e.g. domestic interest and GDP growth rates. Secondly, it also drastically changed the impact of a number of explanatory variables on capital flows into the CIS. Political risk was found to be the second most important determinant of capital flows into the CIS. Additionally, we report some strong evidence of co-movement between portfolio flows into the CIS and CEEC, coupled with strong complementarity between global stock market activity and portfolio inflows into the CIS. Interestingly, external factors tend to be of a higher significance than internal factors for the largest members (Russia, Ukraine and Kazakhstan) of the CIS; whereas domestic variables tend to have a greater impact on the capital flows into the smaller CIS countries.portfolio investment, CIS, the Russian crisis, emerging markets

Computation of high Reynolds number internal/external flows

A general, user oriented computer program, called VNAF2, developed to calculate high Reynolds number internal/external flows is described. The program solves the two dimensional, time dependent Navier-Stokes equations. Turbulence is modeled with either a mixing length, a one transport equation, or a two transport equation model. Interior grid points are computed using the explicit MacCormack scheme with special procedures to speed up the calculation in the fine grid. All boundary conditions are calculated using a reference plane characteristic scheme with the viscous terms treated as source terms. Several internal, external, and internal/external flow calculations are presented

Capital flows to South Asian and ASEAN countries : trends, determinants, and policy implications

The authors compare the experiences of selected Asian countries in attracting different forms of external financing and examine how that financing has contributed to growth. They carry out the analysis for two subgroups - South Asian and ASEAN countries - with distinctly different dominant forms of capital flows. After reviewing recent trends in financial flows to individual countries, they perform a statistical analysis of the effects of foreign capital flows on the macroeconomic performance of developing countries in the region. They find that foreign direct investment has been a more significant positive factor than other types of resource flows in shaping the economic growth of ASEAN countries. Substantial increases in ODA flows are unlikely, and so is the resumption of significant bank lending, so policy makers in South Asia should pursue policies and nondistortionary incentive systems conducive to the infusion of foreign direct investment flows. The main findings are consistent with the Bank's emphasis on an increasingly important role for the private sector - and direct investment flows - in development. A focus on foreign direct investment is appropriate, given current constraints on external financing, particularly through traditional bank credits.Economic Theory&Research,Banks&Banking Reform,International Terrorism&Counterterrorism,Environmental Economics&Policies,Financial Intermediation

Progress and challenges in modeling turbulent aerodynamic flows

Progress in modeling external aerodynamic flows achieved by using computations and experiments designed to guide turbulence modeling is presented. The computational procedures emphasize utilization of the Reynolds-averaged Navier-Stokes equations and various statistical modeling approaches. Developments for including the influence of compressibility are provided; they point up some of the complexities involved in modeling high-speed flows. Examples of complementary studies that provide the status, limitations, and future challenges of modeling for transonic, supersonic, and hypersonic flows are given

Managing external knowledge flows: The moderating role of absorptive capacity.

In this paper, we argue that those firms with higher levels of absorptive capacity can manage external knowledge flows more efficiently, and stimulate innovative outcomes. We test this contention with a sample of 2265 Spanish firms, drawn from the Community Innovation Surveys (CIS) for 2000 and 2002, produced by the Spanish National Statistics Institute (INE). We find that absorptive capacity is indeed an important source of competitive advantage, especially in sectors characterized by turbulent knowledge and strong intellectual property rights protection. The implications for management practice and policy are also discussed.Absorptive capacity; Innovation; External knowledge flows;

Verification of the proteus two-dimensional Navier-Stokes code for flat plate and pipe flows

The Proteus Navier-Stokes Code is evaluated for 2-D/axisymmetric, viscous, incompressible, internal, and external flows. The particular cases to be discussed are laminar and turbulent flows over a flat plate, laminar and turbulent developing pipe flows, and turbulent pipe flow with swirl. Results are compared with exact solutions, empirical correlations, and experimental data. A detailed description of the code set-up, including boundary conditions, initial conditions, grid size, and grid packing is given for each case