On the Minimum/Stopping Distance of Array Low-Density Parity-Check Codes

In this work, we study the minimum/stopping distance of array low-density parity-check (LDPC) codes. An array LDPC code is a quasi-cyclic LDPC code specified by two integers q and m, where q is an odd prime and m <= q. In the literature, the minimum/stopping distance of these codes (denoted by d(q,m) and h(q,m), respectively) has been thoroughly studied for m <= 5. Both exact results, for small values of q and m, and general (i.e., independent of q) bounds have been established. For m=6, the best known minimum distance upper bound, derived by Mittelholzer (IEEE Int. Symp. Inf. Theory, Jun./Jul. 2002), is d(q,6) <= 32. In this work, we derive an improved upper bound of d(q,6) <= 20 and a new upper bound d(q,7) <= 24 by using the concept of a template support matrix of a codeword/stopping set. The bounds are tight with high probability in the sense that we have not been able to find codewords of strictly lower weight for several values of q using a minimum distance probabilistic algorithm. Finally, we provide new specific minimum/stopping distance results for m <= 7 and low-to-moderate values of q <= 79.Comment: To appear in IEEE Trans. Inf. Theory. The material in this paper was presented in part at the 2014 IEEE International Symposium on Information Theory, Honolulu, HI, June/July 201

The growth of paracoccus halodenitrificans in a defined medium

A synthetic medium, consisting of inorganic salts and any of a number of carbon sources, supported the aerobic growth of Paracoccus halodenitrificans when supplemented with thiamine. The same medium plus a nitrogenous oxide supported anaerobic growth when additionally supplemented with methionine. The observation that vitamin B12 or betaine replaced methionine suggested that P. halodenitrificans had a defect in the cobalamin dependent pathway for methionine biosynthesis, as well as the inability to synthesize betaine when growing anaerobically

The Determinants of Lateness: Evidence from British Workers

Using a sample of male and female workers from the 1992 Employment in Britain survey we estimate a generalised grouped zero-inflated Poisson regression model of employeesÕ self-reported lateness. Reflecting theoretical predictions from both psychology and economics, lateness is modelled as a function of incentives, the monitoring of and sanctions for lateness within the workplace, job satisfaction and attitudes to work. Various aspects of workplace incentive and disciplinary policies turn out to affect lateness, however, once these are controlled for, an important role for job satisfaction remains.

Velocity weakening and possibility of aftershocks in nanofriction experiments

We study the frictional behavior of small contacts as those realized in the atomic force microscope and other experimental setups, in the framework of generalized Prandtl-Tomlinson models. Particular attention is paid to mechanisms that generate velocity weakening, namely a decreasing average friction force with the relative sliding velocity.The mechanisms studied model the possibility of viscous relaxation, or aging effects in the contact. It is found that, in addition to producing velocity weakening, these mechanisms can also produce aftershocks at sufficiently low sliding velocities. This provides a remarkable analogy at the microscale, of friction properties at the macroscale, where aftershocks and velocity weakening are two fundamental features of seismic phenomena.Comment: 8 pages, 7 figure

The Village of River Ranch: A Post Occupancy Evaluation of a Traditional Neighborhood Development in Lafayette, Louisiana

The proponents of New Urbanism claim the neighborhoods they design, called Traditional Neighborhood Developments (TNDs), promote community, sense of place, physical health, and environmental sustainability. Critics assert that community is stressed at the expense of individuality, that design unity has become rigid uniformity, and that the neighborhoods are orchestrated and do not reflect real life. This thesis, a post occupancy evaluation (POE), examines how one TND works for its residents and whether it accomplishes the goals of the architect/planner. An additional, essential purpose of this POE is to serve the feed-forward role of informing future neighborhood planning projects. The Village of River Ranch in Lafayette, Louisiana is the site of my research. Utilization of multiple research methods (survey, interviews, naturalistic observations) offered opportunities for triangulation and the ability to produce a more comprehensive analysis