High-Dimensional Menger-Type Curvatures - Part I: Geometric Multipoles and Multiscale Inequalities

We define a discrete Menger-type curvature of d+2 points in a real separable Hilbert space H by an appropriate scaling of the squared volume of the corresponding (d+1)-simplex. We then form a continuous curvature of an Ahlfors d-regular measure on H by integrating the discrete curvature according to the product measure. The aim of this work, continued in a subsequent paper, is to estimate multiscale least squares approximations of such measures by the Menger-type curvature. More formally, we show that the continuous d-dimensional Menger-type curvature is comparable to the ``Jones-type flatness''. The latter quantity adds up scaled errors of approximations of a measure by d-planes at different scales and locations, and is commonly used to characterize uniform rectifiability. We thus obtain a characterization of uniform rectifiability by using the Menger-type curvature. In the current paper (part I) we control the continuous Menger-type curvature of an Ahlfors d-regular measure by its Jones-type flatness.Comment: 47 pages, 13 figures. Minor revisions and the inclusion of figure

RURAL LIVELIHOODS IN ARMENIA

In this paper the structure of the rural economy in Armenia is explored from a household perspective. The paper draws on the livelihoods framework, recognizing the different capitals and activities that support rural households' livelihood strategies. Ownership of capitals and access to activities are examined in relation to the incidence of poverty on the basis of data from a recent large-scale survey of rural households in Armenia. Different measures for the outcome of livelihood strategies in terms of well-being are observed, which are consistently linked to income levels across poor and other households. Income-poor households are found to be less well-endowed especially with financial and social capital. They derive smaller income shares from economic activities, and more from dissaving and social payments. The findings are relevant to policies aimed at alleviating rural poverty.Community/Rural/Urban Development, Labor and Human Capital,

Farm debt in transition countries: Lessons for Tajikistan

Farms in Tajikistan currently face a severe debt crisis that has been caused by a combination of two factors typical of such situations in many countries: (a) the inability of the farms to make a profit under current conditions and (b) continued lending by the banks to cotton producers regardless of reduced payment capacity and lack of credit-worthiness. The paper traces the accumulation of farm debt in Tajikistan to pervasive government intervention in both financing and production decisions, which has led to soft budget constraints and moral hazard behavior. The purpose of the paper is to inform the debate around the issue of cotton farm debt in Tajikistan by studying the experience of other countries that had to contend with farm debt overhangs in the 1980s and the 1990s. Five CIS transition countries (Belarus, Kazakhstan, Moldova, Russia, and Ukraine) and one market economy (Israel) are studied using time series of aggregate financial reports of the farm sectors. The comparative analysis shows that the farm debt issue is not strictly a transition economy phenomenon. The problem can occur in market economies (e.g., Israel) if the state pursues policies directed toward the expansion of farm production without heed to creditworthiness of the farms and if the farm structure is incompatible with profitability and efficiency criteria. The basic reasons that led to debt accumulation in CIS and in Israel remain valid to this day, and the policy solutions implemented in these countries are relevant for Tajikistan.Farm debt, transition economies, Tajikistan, CIS, Israel, farm restructuring, agricultural reforms, Agricultural Finance, Institutional and Behavioral Economics, Q140, P210, P320, G300,

Sources of Agricultural Productivity Growth in Central Asia

The paper examines agricultural production and productivity growth in two Central Asian countries – Tajikistan and Uzbekistan. Both countries are characterized by a significant shift of resources from the traditional Soviet model of collective agriculture to more market-compliant individual and family farming. In both countries, the beginning of the policy-driven switch to family farming around 1997 coincided with the beginning of recovery in agriculture, namely resumption of agricultural growth after a phase of transition decline since 1991. In addition to growth in total agricultural production, we also observe significant increases in productivity of both land and labor since 1997. These observations suggest that productivity growth may be attributable to the changes in farming structure in Central Asia. To check this conjecture we assess the sources of growth by applying the standard Solow growth accounting methodology. Using time series of country statistics for farms of different organizational forms, we decompose the growth in output into growth in the resource base (extensive growth) and growth in productivity (intensive growth). Solow growth accounting clearly shows that, first, much of the growth at the country level is attributable to increases in productivity rather than increases in resources and, second, the increases in productivity in family farms (especially household plots) outstrip the increases in productivity in former collective and state farms. These findings confirm that the recovery of agricultural production in Central Asia has been driven largely by productivity increases, and it is the individual farms that are the main source of agricultural productivity increases.agricultural productivity, agricultural growth, family farms, corporate farms, comparative performance, agrarian reforms, transition countries, Central Asia, Tajikistan, Uzbekistan, Agricultural and Food Policy, Institutional and Behavioral Economics, Land Economics/Use, Productivity Analysis, P27, P31, P32, Q15, R14,

Productivity and Efficiency of Corporate and Individual Farms in Ukraine

The paper presents a comparative analysis of the productivity of corporate and individual farms in Ukraine based primarily on cross-section data from a farm survey conducted by FAO in 2005. We calculate partial land and labor productivity, total factor productivity, and technical efficiency scores (using Stochastic Frontier Analysis) for farms of different organizational forms. Our results demonstrate with considerable confidence that, contrary to established convictions among the Ukrainian decision makers, the large corporate farms are not more productive than the smaller family farms. This finding is not restricted to Ukraine, as a similar result has been obtained by in Moldova, Russia, and the U.S. Policies encouraging a shift from large corporate farms to smaller individual farms, rather than the reverse, can be expected to produce beneficial results for Ukrainian agriculture and the economy in general. The government of Ukraine should abandon its inherited preference for large-scale corporate farms and concentrate on policies to improve the operating conditions for small individual farms. At the very least, the government should ensure a level playing field for farms of all sizes and organizational forms, and desist from biasing its policies in favor of large farms.family farms, corporate farms, comparative performance, technical efficiency, total factor productivity, agrarian reforms, transition countries, Farm Management, Productivity Analysis, D24, J24, P27, P31, P32, Q12, Q15, R14,

Promoting Economic Mobility by Increasing Postsecondary Education

Explores policy options for expanding educational opportunities for low-income students to enhance upward economic mobility. Examines the effectiveness of student aid in promoting college completion and proposes a plan for better guidance and preparation

Equivariant differential characters and symplectic reduction

We describe equivariant differential characters (classifying equivariant circle bundles with connections), their prequantization, and reduction

Teacher Responses to Anxiety in Children Questionnaire (TRAC): psychometric properties and relationship with teaching staff characteristics

This study describes the development and evaluation of a new measure, the Teacher Responses to Anxiety in Children (TRAC) questionnaire in 74 primary school teachers. TRAC presents 9 hypothetical scenarios in which a child displays generalized anxiety/worry, social anxiety or separation anxiety symptoms. Teachers rate each scenario on six subscales that reflect different ways of responding to child anxiety. Overall, TRAC showed good internal reliability, with factor analytic results suggesting that it assesses three factors: Autonomy-Promoting, Anxiety-Promoting and Reward responses. Male teachers were significantly more likely than female teachers to use Anxiety-Promoting responses. More experienced teachers reported significantly more reinforcement of anxious avoidance than less experienced teachers, and teaching assistants reported significantly fewer overprotective responses. Teaching staff reported significantly more Autonomy-Promoting responses in social anxiety or generalised anxiety/worry scenarios compared to separation anxiety scenarios. Findings are discussed in terms of their implications for teacher training in the management of child anxiety

Analysis of Dynamic Task Allocation in Multi-Robot Systems

Dynamic task allocation is an essential requirement for multi-robot systems operating in unknown dynamic environments. It allows robots to change their behavior in response to environmental changes or actions of other robots in order to improve overall system performance. Emergent coordination algorithms for task allocation that use only local sensing and no direct communication between robots are attractive because they are robust and scalable. However, a lack of formal analysis tools makes emergent coordination algorithms difficult to design. In this paper we present a mathematical model of a general dynamic task allocation mechanism. Robots using this mechanism have to choose between two types of task, and the goal is to achieve a desired task division in the absence of explicit communication and global knowledge. Robots estimate the state of the environment from repeated local observations and decide which task to choose based on these observations. We model the robots and observations as stochastic processes and study the dynamics of the collective behavior. Specifically, we analyze the effect that the number of observations and the choice of the decision function have on the performance of the system. The mathematical models are validated in a multi-robot multi-foraging scenario. The model's predictions agree very closely with experimental results from sensor-based simulations.Comment: Preprint version of the paper published in International Journal of Robotics, March 2006, Volume 25, pp. 225-24