Category equivalences involving graded modules over path algebras of quivers

Let kQ be the path algebra of a quiver Q with its standard grading. We show that the category of graded kQ-modules modulo those that are the sum of their finite dimensional submodules, QGr(kQ), is equivalent to several other categories: the graded modules over a suitable Leavitt path algebra, the modules over a certain direct limit of finite dimensional multi-matrix algebras, QGr(kQ') where Q' is the quiver whose incidence matrix is the n^{th} power of that for Q, and others. A relation with a suitable Cuntz-Krieger algebra is established. All short exact sequences in the full subcategory of finitely presented objects in QGr(kQ), split so that subcategory can be given the structure of a triangulated category with suspension functor the Serre degree twist (-1); it is shown that this triangulated category is equivalent to the "singularity category" for the radical square zero algebra kQ/kQ_{\ge 2}.Comment: Several changes made as a result of the referee's report. Added Lemma 3.5 and Prop. 3.6 showing that O is a generato

Power and Practice in Academic Library Materials Selection Paradigms

This article examines the theoretical and practical implications of three methods of materials acquisitions in an academic library. First, it evaluates how traditional collection development, electronic patron driven acquisitions (PDA) and other older forms of PDA affect materials storage, preservation, purchase speed and usage. Then this paper employs Foucault’s theories about power to discuss the ramifications of these acquisitions methods for librarians and three major user groups: faculty, graduate students and undergraduates. The article concludes that each method presents different practical and theoretical advantages and disadvantages

DVCS with CLAS

Generalized parton distributions provide a unifying framework for the interpretation of exclusive reactions at high $Q^2$. The most promising reaction for the investigation of these distributions is the hard production of photons using Deeply Virtual Compton Scattering (DVCS). This reaction can be accessed experimentally by determining the production asymmetry using polarized electrons on a proton target. Pioneering experiments with CLAS and HERMES have produced the first measurements of this asymmetry. We will review the current experimental program to study DVCS at Jefferson Lab. Recent high statistics data taken with CLAS at 5.75 GeV allows us to determine this asymmetry at low -$t$ in the valence region ($x_{B}$=0.1-0.5) up to a $Q^2$ of 4 GeV$^2/c^2$.Comment: 5 pages, 3 figures, Conference on the Intersections of Particle and Nuclear Physics, New York City, May 19-24, 200

Circuit switches latching relay in response to signals of different polarity

A circuit using one power supply and two storage capacitors, which may be separately discharged in opposite directions through a relay in response to change in polarity of a signal, is described