The American Community Survey

Analytical data report #15 is the latest in a series of bulletins designed to complement our traditional data releases. The American Community Survey (ACS) is a continuous household survey conducted by the United States Census Bureau that will replace the long-form of the traditional decennial Census. ADR #15 provides background information on the ACS and the benefits and challenges associated with its use. The report also reviews some of the estimates currently available for the region's nine counties and six largest municipalities and, based on this data, discusses demographic changes in the Delaware Valley between 2000 and 2006

Computer performance analysis - Measurement objectives and tools

Objectives and measurements in computer performance analysi

Generalized Derivations with Commutativity and Anti-commutativity Conditions

Let R be a prime ring with 1, with char(R) &#8800; 2; and let F : R &#8594; R be a generalized derivation. We determine when one of the following holds for all x,y &#8712; R: (i) [F(x); F(y)] = 0; (ii) F(x)&#927;F(y) = 0; (iii) F(x) &#927; F(y) = x &#927; y .</p

E-Learning in Postsecondary Education

Over the past decade postsecondary education has been moving increasingly from the class room to online. During the fall 2010 term 31 percent of U.S. college students took at least one online course. The primary reasons for the growth of e-learning in the nation\u27s colleges and universities include the desire of those institutions to generate new revenue streams, improve access, and offer students greater scheduling flexibility. Yet the growth of e-learning has been accompanied by a continuing debate about its effectiveness and by the recognition that a number of barriers impede its widespread adoption in higher education

Amplitude control of quantum interference

Usually, the oscillations of interference effects are controlled by relative phases. We show that varying the amplitudes of quantum waves, for instance by changing the reflectivity of beam splitters, can also lead to quantum oscillations and even to Bell violations of local realism. We first study theoretically a generalization of the Hong-Ou-Mandel experiment to arbitrary source numbers and beam splitter transmittivity. We then consider a Bell type experiment with two independent sources, and find strong violations of local realism for arbitrarily large source number $N$; for small $N$, one operator measures essentially the relative phase of the sources and the other their intensities. Since, experimentally, one can measure the parity of the number of atoms in an optical lattice more easily than the number itself, we assume that the detectors measure parity.Comment: 4 pages; 4 figure

The Relativistically Spinning Charged Sphere

When the equatorial spin velocity, $v$, of a charged conducting sphere approaches $c$, the Lorentz force causes a remarkable rearrangement of the total charge $q$. Charge of that sign is confined to a narrow equatorial belt at latitudes $b \leqslant \sqrt{3} (1 - v^2/c^2)^{{1/2}}$ while charge of the opposite sign occupies most of the sphere's surface. The change in field structure is shown to be a growing contribution of the `magic' electromagnetic field of the charged Kerr-Newman black hole with Newton's G set to zero. The total charge within the narrow equatorial belt grows as $(1-v^2/c^2)^{-{1/4}}$ and tends to infinity as $v$ approaches $c$. The electromagnetic field, Poynting vector, field angular momentum and field energy are calculated for these configurations. Gyromagnetic ratio, g-factor and electromagnetic mass are illustrated in terms of a 19th Century electron model. Classical models with no spin had the small classical electron radius $e^2/mc^2\sim$ a hundredth of the Compton wavelength, but models with spin take that larger size but are so relativistically concentrated to the equator that most of their mass is electromagnetic. The method of images at inverse points of the sphere is shown to extend to charges at points with imaginary co-ordinates.Comment: 15 pages, 1figur

Threshold bounds for noisy bipartite states

For a nonseparable bipartite quantum state violating the Clauser-Horne-Shimony-Holt (CHSH) inequality, we evaluate amounts of noise breaking the quantum character of its statistical correlations under any generalized quantum measurements of Alice and Bob. Expressed in terms of the reduced states, these new threshold bounds can be easily calculated for any concrete bipartite state. A noisy bipartite state, satisfying the extended CHSH inequality and the perfect correlation form of the original Bell inequality for any quantum observables, neither necessarily admits a local hidden variable model nor exhibits the perfect correlation of outcomes whenever the same quantum observable is measured on both "sides".Comment: 9 pages; v.2: minor editing corrections; to appear in J. Phys. A: Math. Ge