Effect of rotational disruption on the size-frequency distribution of the Main Belt asteroid population

The size distribution of small asteroids in the Main Belt is assumed to be determined by an equilibrium between the creation of new bodies out of the impact debris of larger asteroids and the destruction of small asteroids by collisions with smaller projectiles. However, for a diameter less than 6 km we find that YORP-induced rotational disruption significantly contributes to the erosion even exceeding the effects of collisional fragmentation. Including this additional grinding mechanism in a collision evolution model for the asteroid belt, we generate size-frequency distributions from either an accretional (Weidenschilling, 2011) or an "Asteroids were born big" (Morbidelli, 2009) initial size-frequency distribution that are consistent with observations reported in Gladman et al. (2009). Rotational disruption is a new mechanism that must be included in all future collisional evolution models of asteroids.Comment: 5 pages, 3 figures, accepted in MNRAS letter

When is S=A/4?

Black hole entropy and its relation to the horizon area are considered. More precisely, the conditions and specifications that are expected to be required for the assignment of entropy, and the consequences that these expectations have when applied to a black hole are explored. In particular, the following questions are addressed: When do we expect to assign an entropy?; when are entropy and area proportional? and, what is the nature of the horizon? It is concluded that our present understanding of black hole entropy is somewhat incomplete, and some of the relevant issues that should be addressed in pursuing these questions are pointed out.Comment: 14 pages, no figures. Revtex file. Manuscript edited and discussion expanded. References added, conclusions unchanged. Version to be published in MPL

Belfast Without Sight: Exploring Geographies of Blindness

In this paper (he transformed spaces of visually impaired and blind people is explored through a detailed analysis of interview transcripts with twenty seven visually impaired people living in or around Belfast. Data were collected using a structured open-ended interview and were analysed within NUD-IST, a qualitative data analysis package. Analysis revealed that visually impaired people become spatially confused (e.g. lost or disorientated) for two primary reasons. "Self-produced" confusion is spatial confusion caused by the misperception/miscognition of a route (e.g. miscounting intersections). "Situational" confusion is spatial confusion caused by a permanent or temporary localised occurrences such as road works, vehicles parked on pavements, and street furniture. Both types of spatial confusion were found to induce feelings of fear and anxiety, leading to a loss of selfconfidence, embarrassment and frustration, which in turn led to less independent travel and exploration, and constrained patterns of spatial behaviour. Respondents detailed a number of strategies for coping with spatial confusion. In addition, they assessed methods to make Belfast more navigable including environmental modifications and orientation and mobility aid

Belfast Without Sight: Exploring Geographies of Blindness

In this paper (he transformed spaces of visually impaired and blind people is explored through a detailed analysis of interview transcripts with twenty seven visually impaired people living in or around Belfast. Data were collected using a structured open-ended interview and were analysed within NUD-IST, a qualitative data analysis package. Analysis revealed that visually impaired people become spatially confused (e.g. lost or disorientated) for two primary reasons. "Self-produced" confusion is spatial confusion caused by the misperception/miscognition of a route (e.g. miscounting intersections). "Situational" confusion is spatial confusion caused by a permanent or temporary localised occurrences such as road works, vehicles parked on pavements, and street furniture. Both types of spatial confusion were found to induce feelings of fear and anxiety, leading to a loss of selfconfidence, embarrassment and frustration, which in turn led to less independent travel and exploration, and constrained patterns of spatial behaviour. Respondents detailed a number of strategies for coping with spatial confusion. In addition, they assessed methods to make Belfast more navigable including environmental modifications and orientation and mobility aid

The Effect of Spatial Tasks on Visually Impaired Peoples' Wayfinding Abilities

Thirty-eight people with visual impairments learned a 483-meter novel route through a university campus in four groups: verbalization, modeling, pointing, and control. The performance of all four groups improved with greater experience of the route, but the modeling group improved more than did the control group

The Domination Number of Grids

In this paper, we conclude the calculation of the domination number of all $n\times m$ grid graphs. Indeed, we prove Chang's conjecture saying that for every $16\le n\le m$, $\gamma(G_{n,m})=\lfloor\frac{(n+2)(m+2)}{5}\rfloor -4$.Comment: 12 pages, 4 figure

The prevalence and distribution of the amyloidogenic transthyretin (TTR) V122I allele in Africa

Transthyretin (TTR) pV142I (rs76992529-A) is one of the 113 variants in the human TTR gene associated with systemic amyloidosis. It results from a G to A transition at a CG dinucleotide in the codon for amino acid 122 of the mature protein (TTR V122I). The allele frequency is 0.0173 in African Americans

A First-Quantized Formalism for Cosmological Particle Production

We show that the amount of particle production in an arbitrary cosmological background can be determined using only the late-time positive-frequency modes. We don't refer to modes at early times, so there is no need for a Bogolubov transformation. We also show that particle production can be extracted from the Feynman propagator in an auxiliary spacetime. This provides a first-quantized formalism for computing particle production which, unlike conventional Bogolubov transformations, may be amenable to a string-theoretic generalization.Comment: 18 pages, LaTeX; v2: significantly revised for clarity; conclusions unchange