Descriptive Complexity of #P Functions

AbstractWe give a logic-based framework for defining counting problems and show that it exactly captures the problems in Valiant′s counting class #P. We study the expressive power of the framework under natural syntactic restrictions and show that some of the subclasses obtained in this way contain problems in #P with interesting computational properties. In particular, using syntactic conditions, we isolate a class of polynomial time computable #P problems and, also, a class in which every problem is approximable by a polynomial time randomized algorithm. These results set the foundation for further study of the descriptive complexity of the class #P. In contrast, we show, under reasonable complexity theoretic assumptions, that it is an undecidable problem to tell if a counting problem expressed in our framework is polynomial time computable or if it is approximable by a randomized polynomial time algorithm. Finally, we discuss some open problems which arise naturally from this work

Abstract and Generic Rigidity in the Plane

AbstractWe consider the concept of abstract two-dimensional rigidity and provide necessary and sufficient conditions for a matroid to be an abstract rigidity matroid of a complete graph. This characterization is a natural extension of the characterization of graphic matroids due to Graver or Sachs. We also give an example of an abstract rigidity matroid which is not infinitesimal

Requirements of leaf wetness and temperature for infection of groundnut by rust

Experiments are described to quantify the effects of temp. and duration of leaf wetness on infection of groundnut by Puccinia arachidis. After inoculation, a min. period of leaf wetness, m, was necessary for infection. When leaf wetness duration was >m, lesion density increased with increasing wetness duration to an asymptote, Dmax. The principal effects of temp. were on m and Dmax. The value of m decreased linearly from 6 h, as temp. increased from 15 to 25°C and increased slightly at temp. >25°. Dmax increased with temp. from zero at 8° to a max. at 22°, and decreased to zero again at c. 30°. The experimental results were used to produce a set of curves relating an infection index to leaf wetness duration at different temp. The implications for infection of groundnut crops are discussed in relation to the climate at Patancheru in southern India

On monotone undirected contact networks computing T^n_<n-1>

リサーチレポート（北陸先端科学技術大学院大学情報科学研究科）本文は図書館に配架されています。 / This material is stored in the JAIST library

Not Available

Not AvailableIn a study that was carried out by Central Research Institute for Dryland Agriculture, Hyderabad a novel institutional arrangements was tried for both leveraging better project administration and eliciting higher community participation. Salaha samithis that were formed to liaise between project staff and the poor people of the project area came out as useful arrangement that could go beyond achieving project goals. This case study shares experiences in which institutional innovation evolved as a result of consultations between the project staff and the stakeholders facilitated the process of best natural resource management practices for improved livelihoodsNot Availabl