Method to determine vented electrochemical cell quality

Cell mass is measured periodically or monitored continuously by balances and clocks to determine water loss and rate of mass loss during trickle charge period

The Event Horizon of M87

The 6 billion solar mass supermassive black hole at the center of the giant elliptical galaxy M87 powers a relativistic jet. Observations at millimeter wavelengths with the Event Horizon Telescope have localized the emission from the base of this jet to angular scales comparable to the putative black hole horizon. The jet might be powered directly by an accretion disk or by electromagnetic extraction of the rotational energy of the black hole. However, even the latter mechanism requires a confining thick accretion disk to maintain the required magnetic flux near the black hole. Therefore, regardless of the jet mechanism, the observed jet power in M87 implies a certain minimum mass accretion rate. If the central compact object in M87 were not a black hole but had a surface, this accretion would result in considerable thermal near-infrared and optical emission from the surface. Current flux limits on the nucleus of M87 strongly constrain any such surface emission. This rules out the presence of a surface and thereby provides indirect evidence for an event horizon.Comment: 9 pages, 2 figures, submitted to Ap

Relativistic model of hidden bottom tetraquarks

The relativistic model of the ground state and excited heavy tetraquarks with hidden bottom is formulated within the diquark-antidiquark picture. The diquark structure is taken into account by calculating the diquark-gluon vertex in terms of the diquark wave functions. Predictions for the masses of bottom counterparts to the charm tetraquark candidates are given.Comment: 6 page

Law and Economic Exploitation in an Anti-Classification Age

Does our legal system permit the economic exploitation of extreme vulnerability? Focusing on predatory housing loans—a thriving business at the dawn of the twenty-first century—this Article argues that the answer in most cases is yes. Under an individualistic neoliberal paradigm, borrowers are held liable for their contracts, even if they were targeted with predatory practices. Further, borrowers’ attempts to resort to antidiscrimination law, and frame their exploitation as “reverse redlining,” have offered no real answer. An important yet undertheorized explanation for this problem is the impact of the Supreme Court’s anti-classification jurisprudence on lower courts. In an anti-classification age, even outside of the constitutional arena, courts are reluctant to accept race-based arguments. As a result, colorblind analysis of predatory lending permits economic exploitation to thrive. This Article proposes a unique solution to this deadlock: embedding the analysis of individual borrowers in the context of their neighborhood, a move that neither denies nor relies on their race. Drawing on a variety of disciplines, including psychology, sociology, and public health, this Article explains how residing in distressed neighborhoods—the most embattled neighborhoods of our country—creates conditions especially fertile for exploitation. Based on this interdisciplinary analysis, this Article suggests an alternative legal framework which would circumvent the anti-classification problem. The new framework is tailored around the idea of individual dignity, which includes the right to freedom from economic exploitation. To protect such right it is suggested to utilize contract law and particularly the doctrine of unconscionability—which is highly apposite for a contextual analysis of predatory agreements. More broadly this Article argues that one of the important lessons to be learned from the tragic subprime crisis is how urgent it is to find an appropriate legal response to market exploitation of vulnerable individuals. Notably, the contractual framework suggested in this Article for predatory housing loans is useful for handling other exploitative loans, such as pay-day loans and auto-title loans. Further, the proposed framework is valuable beyond the contexts of lending and distressed neighborhoods, to address other forms of economic exploitation perpetuated by contract. Given persistent weakness in our economy, establishing an anti-exploitation norm in the market seems more important than eve

van der Waals interactions of the benzene dimer: towards treatment of polycyclic aromatic hydrocarbon dimers

Although density functional theory (DFT) in principle includes even long-range interactions, standard implementations employ local or semi-local approximations of the interaction energy and fail at describing the van der Waals interactions. We show how to modify a recent density functional that includes van der Waals interactions in planar systems [Phys. Rev. Lett. 91, 126402 (2003)] to also give an approximate interaction description of planar molecules. As a test case we use this modified functional to calculate the binding distance and energy for benzene dimers, with the perspective of treating also larger, flat molecules, such as the polycyclic aromatic hydrocarbons (PAH).Comment: 7 pages, 2 figures (3 figure files) submitted to Materials Science and Engineering

Competition Among Public Schools: A Reply to Rothstein (2004)

Rothstein has produced two comments, Rothstein (2003) and Rothstein (2004), on Hoxby "Does Competition Among Public Schools Benefit Students and Taxpayers," American Economic Review, 2000. In this paper, I discuss every claim of any importance in the comments. I show that every claim is wrong. I also discuss a number of Rothstein's innuendos--that is, claims that are made by implication rather than with the support of explicit arguments or evidence. I show that, when held up against the evidence, each innuendo proves to be false. One of the major points of Rothstein (2003) is that lagged school districts are a valid instrumental variable for today's school districts. This is not credible. Another major claim of Rothstein (2003) is that it is better to use highly non-representative achievement data based on students' self-selecting into test-taking than to use nationally representative achievement data. This claim is wrong for multiple reasons. The most important claim of Rothstein (2004) is that the results of Hoxby (2000) are not robust to including private school students in the sample. This is incorrect. While Rothstein appears merely to be adding private school students to the data, he actually substitutes error-prone data for error-free data on all students, generating substantial attenuation bias. He attributes the change in estimates to the addition of the private school students, but I show that the change in estimates is actually due to his using erroneous data for public school students. Another important claim in Rothstein (2004) that the results in Hoxby (2000) are not robust to associating streams with the metropolitan areas through which they flow rather than the metropolitan areas where they have their source. This is false: the results are virtually unchanged when the association is shifted from source to flow. Since 93.5 percent of streams flow only in the metropolitan area where they have their source, it would be surprising if the results did change much. The comments Rothstein (2003) and Rothstein (2004) are without merit. All of the data and code used in Hoxby (2000) are available to other researchers. An easy-to-use CD provides not only extracts and estimation code, but all of the raw data and the code for constructing the dataset.

Cylindrical and spherical shells with cracks

Numerical analysis of meridional crack in cylindrical and spherical shells subjected to internal pressur