Refined Young inequalities with Specht's ratio

In this paper, we show that the $\nu$-weighted arithmetic mean is greater than the product of the $\nu$-weighted geometric mean and Specht's ratio. As a corollary, we also show that the $\nu$-weighted geometric mean is greater than the product of the $\nu$-weighted harmonic mean and Specht's ratio. These results give the improvements for the classical Young inequalities, since Specht's ratio is generally greater than 1. In addition, we give an operator inequality for positive operators, applying our refined Young inequality.Comment: A small mistake of calculation in page 4 was corrected. References were updated. 7 page

The prospects for African urban economies

Cities generally function as sources of economic development and human progress. One of the puzzles about Africa's urbanization is that it has not been accompanied by greater economic dynamism. The paper considers the distinctive development trajectory of African urban economies. It considers the applicability of the argument that cities are drivers of economic growth, and the idea that cities develop more complex, higher-value functions over time. It examines the recent revival of African economies, and asks whether the fashionable idea of enhanced international integration through cross-border collaboration might facilitate greater urban prosperity

Abundance, Diversity and Distribution of Benthic Macro-Invertebrates in the Flat Bayou Drainage Area, Jefferson County, Arkansas

The main ditch of Flat Bayou Drainage in north central Jefferson County carries water southward into Plum Bayou which then shortly empties into the Arkansas River. Flat Bayou proper flows northward into Wabbaseka Bayou which in turn flows into the Arkansas River in northeastern Lincoln County. Two sites on the main ditch were sampled for physico-chemical parameters and benthic macroin vertebrates on 9 September, 7 October and 11 November 1978. No visible detrimental effects were attributed to physico-chemical characteristics. Thirty-one below-family taxa and 19 families were found in abundance from zero at one site and date to 3580 per m² at one site and date. Corbicula was by far the most numerous taxon whereas several taxa (e.g. Placobdella, Piscicolarla, Lampsilis, Uniomerus, Campeloma, Berosus and Palpomyia) were represented by a per m² density of 8.6 on one date at one site. Dominance indices were generally greater, and distribution values indicated stronger clumping at Site 1 whereas diversity values were generally greater at Site 2. These indicated the substrate at Site 2 was more suitable for community development

Free surface effect on dune morphology and evolution

Our aim in this paper is to illustrate the importance of free water surface effects and sediment transport mode in the morphological evolution of sand dunes to upper stage plane beds. We have analyzed a large number of bed form data, 414 experiments from flumes and field, showing significantly different evolution of dune height and length in shallow (high Froude numbers) and in deep flows (low Froude numbers). In shallow flows, dune heights are observed to grow only in bed load dominant transport regime and start to decay for Suspension numbers greater than 1. Dunes in this case are not observed for Suspension number greater than 2.5. For low Froude numbers, dune heights continue to grow from bed load to suspended load dominant transport regime. Dunes in this case are not observed for Suspension number greater than 5. Furthermore, dunes in shallow flows reach significantly greater heights compared to dune heights in deep flows and dune lengths are generally larger in shallow flows

Energy and environmental burdens of organic and non-organic agriculture and horticulture

Production of 10 major commodities in England and Wales was studied using Life Cycle Analysis (LCA). Organic and non-organic (contemporary conventional) systems were compared. Organic production was generally less energy consuming, except for poultry meat, eggs and tomatoes. Environmental burdens, such as global warming potential or eutrophication were often greater per unit of production from organic than non-organic systems

Alternate Heegaard genus bounds distance

Suppose M is a compact orientable irreducible 3-manifold with Heegaard splitting surfaces P and Q. Then either Q is isotopic to a possibly stabilized copy of P or the Hempel distance of the splitting P is no greater than twice the genus of Q. More generally, if P and Q are bicompressible but weakly incompressible connected closed separating surfaces in M then either a) P and Q can be well-separated or b) P and Q are isotopic or c) the Hempel distance of P is no greater than twice the genus of Q.Comment: This is the version published by Geometry & Topology on 4 May 2006 (V4: typesetting correction

Cumulative Risk and a Call for Action in Environmental Justice Communities

Health disparities, social inequalities, and environmental injustice cumulatively affect individual and community vulnerability and overall health; yet health researchers, social scientists and environmental scientists generally study them separately. Cumulative risk assessment in poor, racially segregated, economically isolated and medically underserved communities needs to account for their multiple layers of vulnerability, including greater susceptibility, greater exposure, less preparedness to cope, and less ability to recover in the face of exposure. Recommendations for evidence-based action in environmental justice communities include: reducing pollution in communities of highest burden; building on community resources; redressing inequality when doing community-based research; and creating a screening framework to identify communities of greatest risk

Do Investors Value Insider Trading Laws? International Evidence

The article presents a simple agency model of the relationship between corporate valuation and insider trading laws. The article then investigates the model’s three testable hypotheses using firm-level data from a cross-section of developed countries. I find that more stringent insider trading laws and enforcement are associated with greater corporate valuation among the sample firms in common countries, while they are generally irrelevant to corporate valuation for the sample firms in civil law countries. This puzzling dichotomy is robust to various alternative specifications and to controlling for a wide range of potentially omitted variables. The result for the firms in common law countries is consistent with the claim that insider trading laws can help to reduce corporate agency costs. I also find that insider trading laws and cash flow ownership appear to be complementary means to reduce agency costs, contrary to my hypothesis that they are substitute mechanisms for controlling agency costs; however, this result is generally statistically insignificant. Finally, I confirm prior findings of an “incentive effect” of greater cash flow ownership by controlling shareholders.http://deepblue.lib.umich.edu/bitstream/2027.42/57217/1/wp837 .pd

A comparison of head and manual control for a position-control pursuit tracking task

Head control was compared with manual control in a pursuit tracking task involving proportional controlled-element dynamics. An integrated control/display system was used to explore tracking effectiveness in horizontal and vertical axes tracked singly and concurrently. Compared with manual tracking, head tracking resulted in a 50 percent greater rms error score, lower pilot gain, greater high-frequency phase lag and greater low-frequency remnant. These differences were statistically significant, but differences between horizontal- and vertical-axis tracking and between 1- and 2-axis tracking were generally small and not highly significant. Manual tracking results were matched with the optimal control model using pilot-related parameters typical of those found in previous manual control studies. Head tracking performance was predicted with good accuracy using the manual tracking model plus a model for head/neck response dynamics obtained from the literature

The dependence of precipitation and its footprint on atmospheric temperature in idealized extratropical cyclones

Flood hazard is a function of the magnitude and spatial pattern of precipitation accumulation. The sensitivity of precipitation to atmospheric temperature is investigated for idealized extratropical cyclones, enabling us to examine the footprint of extreme precipitation (surface area where accumulated precipitation exceeds high thresholds) and the accumulation in different-sized catchment areas. The mean precipitation increases with temperature, with the mean increase at 5.40%/∘C. The 99.9th percentile of accumulated precipitation increases at 12.7%/∘C for 1 h and 9.38%/∘C for 24 h, both greater than Clausius-Clapeyron scaling. The footprint of extreme precipitation grows considerably with temperature, with the relative increase generally greater for longer durations. The sensitivity of the footprint of extreme precipitation is generally super Clausius-Clapeyron. The surface area of all precipitation shrinks with increasing temperature. Greater relative changes in the number of catchment areas exceeding extreme total precipitation are found when the domain is divided into larger rather than smaller catchment areas. This indicates that fluvial flooding may increase faster than pluvial flooding from extratropical cyclones in a warming world. When the catchment areas are ranked in order of total precipitation, the 99.9th percentile is found to increase slightly above Clausius-Clapeyron expectations for all of the catchment sizes, from 9 km2 to 22,500 km2. This is surprising for larger catchment areas given the change in mean precipitation. We propose that this is due to spatially concentrated changes in extreme precipitation in the occluded fron