Data structures for retrieval on integer grids

A family of data structures is presented for retrieval of the sum of values of points within a half-plane or polygon, given that the points are on integer coordinates in the plane. Fredman has shown that the problem has a lower bound of Ω(N^2/3) for intermixed updates and retrievals. Willard has shown an upper bound of O(N^2log6^4) for the case where the points are not restricted to integer coordinates.We have developed families of related data structures for retrievals of half-planes or polygons. One of the data structures permits intermixed updates and half-plane retrievals in O(N^2/3log N) time, where N is the size of the grid.We use a technique we call "Rotation" to permit a better match of a portion of the data structure to the particular problem. Rotations appear to be an effective method for trading-off storage redundancy against retrieval time for certain classes of problems

The For-Profit Postsecondary School Sector: Nimble Critters or Agile Predators?

Private for-profit institutions have been the fastest growing part of the U.S. higher education sector. For-profit enrollment increased from 0.2 percent to 9.1 percent of total enrollment in degree-granting schools from 1970 to 2009, and for-profit institutions account for the majority of enrollments in non-degree granting postsecondary schools. We describe the schools, students, and programs in the for-profit higher education sector, its phenomenal recent growth, and its relationship to the federal and state governments. Using the 2004 to 2009 Beginning Postsecondary Students (BPS) longitudinal survey we assess outcomes of a recent cohort of first-time undergraduates who attended for-profits relative to comparable students who attended community colleges or other public or private non-profit institutions. We find that relative to these other institutions, for-profits educate a larger fraction of minority, disadvantaged, and older students, and they have greater success at retaining students in their first year and getting them to complete short programs at the certificate and associate degree levels. But we also find that for-profit students end up with higher unemployment and “idleness” rates and lower earnings six years after entering programs than do comparable students from other schools, and that they have far greater student debt burdens and default rates on their student loans.

Rapidly reconfigurable optically induced photonic crystals in hot rubidium vapor

Through periodic index modulation, we create two different types of photonic structures in a heated rubidium vapor for controlled reflection, transmission and diffraction of light. The modulation is achieved through the use of the AC Stark effect resulting from a standing-wave control field. The periodic intensity structures create translationally invariant index profiles analogous to photonic crystals in spectral regions of steep dispersion. Experimental results are consistent with modeling.Comment: 6 pages, 6 figure

Do we need to rethink guidance on repeated interviews?

Within the legal system, children are frequently interviewed about their experiences more than once, with different information elicited in different interviews. The presumed positive and negative effects of multiple interviewing have generated debate and controversy within the legal system and among researchers. Some commentators emphasise that repeated interviews foster inaccurate recall and are inherently suggestive, whereas others emphasise the benefits of allowing witnesses more than one opportunity to recall information. In this article we briefly review the literature on repeated interviewing before presenting a series of cases highlighting what happens when children are interviewed more than once for various reasons. We conclude that, when interviewers follow internationally recognised best-practice guidelines emphasising open-questions and free memory recall, alleged victims of abuse should be interviewed more than once to ensure that more complete accounts are obtained. Implications for current legal guidelines concerning repeated interviewing are discussed

Compositional Idioms

In this paper we argue that there is a large class of expressions, typified by ‘plastic flower’, ‘stuffed animal’ and ‘kosher bacon’, that have a unique semantics combining compositional, idiomatic and decompositional interpretation. These expressions are compositional because their constituents contribute their meanings to the meanings of the wholes; they are idiomatic because their interpretation involves assigning dictionary entries to non-terminal elements in their syntactic structure; and they are decompositional because their meanings have proper parts that are not the meanings of any of their syntactic constituents. We argue that extensionalist semantics, on which the meaning of an expression is a function from domains to extensions in those domains, cannot provide an adequate account of the semantics of these expressions, and that supplementation with a theory of pragmatic interpretation does not improve the situation. We show how our account explains the intensionality and the productivity of these expressions