Agricultural Tariff Rate Quotas: Impacts on Market Access

We study the impacts of the implementation of agricultural tariff rate quotas on market access. A doble-censored Tobit model is specified to examine factors that affect the performance of tariff rate quotas. The results show that both in-quota tariff rates and administrative methods restrict market access and lower quota fill rate. The effect of over-quota tariff, however, is insignificant during the study period.International Relations/Trade,

Recursive n-gram hashing is pairwise independent, at best

Many applications use sequences of n consecutive symbols (n-grams). Hashing these n-grams can be a performance bottleneck. For more speed, recursive hash families compute hash values by updating previous values. We prove that recursive hash families cannot be more than pairwise independent. While hashing by irreducible polynomials is pairwise independent, our implementations either run in time O(n) or use an exponential amount of memory. As a more scalable alternative, we make hashing by cyclic polynomials pairwise independent by ignoring n-1 bits. Experimentally, we show that hashing by cyclic polynomials is is twice as fast as hashing by irreducible polynomials. We also show that randomized Karp-Rabin hash families are not pairwise independent.Comment: See software at https://github.com/lemire/rollinghashcp

Observable Properties of Orbits in Exact Bumpy Spacetimes

We explore the properties of test-particle orbits in "bumpy" spacetimes - stationary, reflection-symmetric, asymptotically flat solutions of Einstein equations that have a non-Kerr (anomalous) higher-order multipole-moment structure but can be tuned arbitrarily close to the Kerr metric. Future detectors should observe gravitational waves generated during inspirals of compact objects into supermassive central bodies. If the central body deviates from the Kerr metric, this will manifest itself in the emitted waves. Here, we explore some of the features of orbits in non-Kerr spacetimes that might lead to observable signatures. As a basis for this analysis, we use a family of exact solutions proposed by Manko & Novikov which deviate from the Kerr metric in the quadrupole and higher moments, but we also compare our results to other work in the literature. We examine isolating integrals of the orbits and find that the majority of geodesic orbits have an approximate fourth constant of the motion (in addition to the energy, angular momentum and rest mass) and the resulting orbits are tri-periodic to high precision. We also find that this fourth integral can be lost for certain orbits in some oblately deformed Manko-Novikov spacetimes. However, compact objects will probably not end up on these chaotic orbits in nature. We compute the location of the innermost stable circular orbit (ISCO) and find that the behavior of orbtis near the ISCO can be qualitatively different depending on whether the ISCO is determined by the onset of an instability in the radial or vertical direction. Finally, we compute periapsis and orbital-plane precessions for nearly circular and nearly equatorial orbits in both the strong and weak field, and discuss weak-field precessions for eccentric equatorial orbits.Comment: 42 pages, 20 figures, accepted by Phys. Rev. D, v2 has minor changes to make it consistent with published versio

Fast Locality-Sensitive Hashing Frameworks for Approximate Near Neighbor Search

The Indyk-Motwani Locality-Sensitive Hashing (LSH) framework (STOC 1998) is a general technique for constructing a data structure to answer approximate near neighbor queries by using a distribution $\mathcal{H}$ over locality-sensitive hash functions that partition space. For a collection of $n$ points, after preprocessing, the query time is dominated by $O(n^{\rho} \log n)$ evaluations of hash functions from $\mathcal{H}$ and $O(n^{\rho})$ hash table lookups and distance computations where $\rho \in (0,1)$ is determined by the locality-sensitivity properties of $\mathcal{H}$. It follows from a recent result by Dahlgaard et al. (FOCS 2017) that the number of locality-sensitive hash functions can be reduced to $O(\log^2 n)$, leaving the query time to be dominated by $O(n^{\rho})$ distance computations and $O(n^{\rho} \log n)$ additional word-RAM operations. We state this result as a general framework and provide a simpler analysis showing that the number of lookups and distance computations closely match the Indyk-Motwani framework, making it a viable replacement in practice. Using ideas from another locality-sensitive hashing framework by Andoni and Indyk (SODA 2006) we are able to reduce the number of additional word-RAM operations to $O(n^\rho)$.Comment: 15 pages, 3 figure

Fitness Technology and Exercise Engagement: How Technology Affordances Facilitate Fitness Goal Attainment

To realize desired health returns, fitness technology providers, users, and corporate wellness program managers need to understand how individuals’ different uses of fitness technologies influence their fitness experience and fitness goal achievements. Thus, this study draws on the theory of affordances and the concept of engagement to develop and empirically test a model of fitness technology use as goal-directed behavior. Doing so highlights the relationship between trying to use fitness technologies and trying to perform fitness activities with fitness goal attainment. Our results show that while actualized self-appraisal affordance amplifies users’ cognitive exercise engagement, cognitive exercise engagement does not significantly influence fitness goal attainment. Furthermore, actualized self-appraisal and social appraisal affordances enhance users’ emotional exercise engagement, positively influencing fitness goal attainment. Thus, facilitating the actualization of self-appraisal and social appraisal affordances that increase individuals’ emotional exercise engagement is essential to the effective use of fitness technologies

Distorted, non-spherical transiting planets: impact on the transit depth and on the radius determination

We quantify the systematic impact of the non-spherical shape of transiting planets and brown dwarfs, due to tidal forces and rotation, on the observed transit depth. Such a departure from sphericity leads to a bias in the derivation of the transit radius from the light curve and affects the comparison with planet structure and evolution models which assume spherical symmetry. As the tidally deformed planet projects its smallest cross section area during the transit, the measured effective radius is smaller than the one of the unperturbed spherical planet. This effect can be corrected by calculating the theoretical shape of the observed planet. We derive simple analytical expressions for the ellipsoidal shape of a fluid object (star or planet) accounting for both tidal and rotational deformations and calibratre it with fully numerical evolution models in the 0.3Mjup-75Mjup mass range. Our calculations yield a 20% effect on the transit depth, i.e. a 10% decrease of the measured radius, for the extreme case of a 1Mjup planet orbiting a Sun-like star at 0.01AU. For the closest planets detected so far (< 0.05 AU), the effect on the radius is of the order of 1 to 10%, by no means a negligible effect, enhancing the puzzling problem of the anomalously large bloated planets. These corrections must thus be taken into account for a correct determination of the radius from the transit light curve. Our analytical expressions can be easily used to calculate these corrections, due to the non-spherical shape of the planet, on the observed transit depth and thus to derive the planet's real equilibrium radius. They can also be used to model ellipsoidal variations of the stellar flux now detected in the CoRoT and Kepler light curves. We also derive directly usable analytical expressions for the moment of inertia, oblateness and Love number (k_2) of a fluid planet as a function of its mass.Comment: 19 pages, 6 figures, 5 tables. Published in A&A. Correction of minor errors in Appendix B. An electronic version of the grids of planetary models is available at http://perso.ens-lyon.fr/jeremy.leconte/JLSite/JLsite/Exoplanets_Simulations.htm

The C-value enigma and timing of the Cambrian explosion

The Cambrian explosion is a grand challenge to science today and involves multidisciplinary study. This event is generally believed as a result of genetic innovations, environmental factors and ecological interactions, even though there are many conflicts on nature and timing of metazoan origins. The crux of the matter is that an entire roadmap of the evolution is missing to discern the biological complexity transition and to evaluate the critical role of the Cambrian explosion in the overall evolutionary context. Here we calculate the time of the Cambrian explosion by an innovative and accurate "C-value clock"; our result (560 million years ago) quite fits the fossil records. We clarify that the intrinsic reason of genome evolution determined the Cambrian explosion. A general formula for evaluating genome size of different species has been found, by which major questions of the C-value enigma can be solved and the genome size evolution can be illustrated. The Cambrian explosion is essentially a major transition of biological complexity, which corresponds to a turning point in genome size evolution. The observed maximum prokaryotic complexity is just a relic of the Cambrian explosion and it is supervised by the maximum information storage capability in the observed universe. Our results open a new prospect of studying metazoan origins and molecular evolution.Comment: 46 pages, 10 figure

A Review on Consumer Health Information Technology Research in IS

While there is a rapid growth in the application of consumer health information technology (CHIT), its growth as an area of interest in IS research is still relatively slow. While there is great potential for research in this area, knowledge barriers to conducting CHIT research do exist. These include a lack of a clear definition of CHIT and lack of knowledge on the current state of CHIT research in IS. To overcome these barriers, we offer a definition of CHIT and then use that definition, together with the IT artifact perspective, to conduct a thematic analysis of CHIT research in the IS domain. We find that CHIT research spans all five IT views but to different degrees: nominal, proxy, and tool views are the most widely used perspectives. Based on our analysis, we suggest future research directions to enrich understanding of CHIT

Electromagnetic Energy for a Charged Kerr Black Hole in a Uniform Magnetic Field

With the Komar mass formula we calculate the electromagnetic energy for a charged Kerr black hole in a uniform magnetic field. We find that the total electromagnetic energy takes the minimum when the Kerr black hole possesses a non-zero net charge $Q = 2\xi B_0 J_H$ where $B_0$ is the strength of the magnetic field, $J_H$ is the angular momentum of the black hole, $\xi$ is a dimensionless parameter determined by the spin of the black hole.Comment: 9 pages, 1 figur