On the arithmetic of a family of twisted constant elliptic curves

Let $\mathbb{F}_r$ be a finite field of characteristic $p>3$. For any power $q$ of $p$, consider the elliptic curve $E=E_{q,r}$ defined by $y^2=x^3 + t^q -t$ over $K=\mathbb{F}_r(t)$. We describe several arithmetic invariants of $E$ such as the rank of its Mordell--Weil group $E(K)$, the size of its N\'eron--Tate regulator $\text{Reg}(E)$, and the order of its Tate--Shafarevich group $III(E)$ (which we prove is finite). These invariants have radically different behaviors depending on the congruence class of $p$ modulo 6. For instance $III(E)$ either has trivial $p$-part or is a $p$-group. On the other hand, we show that the product $|III(E)|\text{Reg}(E)$ has size comparable to $r^{q/6}$ as $q\to\infty$, regardless of $p\pmod{6}$. Our approach relies on the BSD conjecture, an explicit expression for the $L$-function of $E$, and a geometric analysis of the N\'eron model of $E$.Comment: 38 pages. v2: minor changes following referee repor

Black-White Appreciation of Owner Occupied Homes in Upper Income Suburban Integrated Communities: The Cases of Maplewood and Montclair, New Jersey

The purpose of this paper is to examine black-white differences in housing appreciation in northern New Jersey, with particular emphasis on the communities of Montclair and Maplewood in the 1970 to 2000 period. We find that home appreciation at the block group level in these communities was inversely related to changes in the black population. The effect of changes in the proportion of the population that was black on home appreciation was similar to the effects of changes in black population at the census tract level in the northern New Jersey region as a whole. These high income communities with award winning school districts and well maintained housing stocks were not immune from the effects of race on home appreciation.Black-white house appreciation

Agriculture, Roads, and Economic Development in Uganda

A large fraction of Uganda's population continues to earn a living from quasi-subsistence agriculture. This paper uses a static general equilibrium model to explore the relationships between high transportation costs, low productivity, and the size of the quasi-subsistence sector. We parameterize the model to replicate some key features of the Ugandan data, and we then perform a series of quantitative experiments. Our results suggest that the population in quasi-subsistence agriculture is highly sensitive both to agricultural productivity levels and to transportation costs. The model also suggests positive complementarities between improvements in agricultural productivity and transportation.

A MATHEMATICAL MODEL FOR DEVELOPING ETHNO-BIOLOGICALLY DIVERSE TROPICAL FORESTS

This paper presents a dynamic optimal control model describing the benefits and costs associated with the development of tropical forests rich in plant and animal species and folk knowledge. The model is a framework to assess how various market and institutional incentives might influence both deforestation and the collection of "ethno-biological information."Resource /Energy Economics and Policy,

Prediction techniques for jet-induced effects in hover on STOVL aircraft

Prediction techniques for jet induced lift effects during hover are available, relatively easy to use, and produce adequate results for preliminary design work. Although deficiencies of the current method were found, it is still currently the best way to estimate jet induced lift effects short of using computational fluid dynamics. Its use is summarized. The new summarized method, represents the first step toward the use of surface pressure data in an empirical method, as opposed to just balance data in the current method, for calculating jet induced effects. Although the new method is currently limited to flat plate configurations having two circular jets of equal thrust, it has the potential of more accurately predicting jet induced effects including a means for estimating the pitching moment in hover. As this method was developed from a very limited amount of data, broader applications of the method require the inclusion of new data on additional configurations. However, within this small data base, the new method does a better job in predicting jet induced effects in hover than the current method

Stability and reactivity of dimethylethoxysilane

The chemistry of the compound dimethylethoxysilane (DMES) is discussed especially as it relates to waterproofing silica surfaces. Some of the desirable properties of this compound are that it readily reacts with silica in the vapor phase, it is a low boiling point liquid (54 C), and the by-product of its reaction with silica is the rather inert substances ethanol. It is currently used by NASA to re-waterproof the HRSI shuttle tiles before relaunching the vehicle. Very little information is available on this particular compound in the literature or even on related silane compounds that have both a hydride group and an alkoxy group. Since the close proximity of two groups often drastically affects the chemical behavior of each group, chemical reactions were carried out in the laboratory with DMES to verify the expected behavior of these two functional groups located on DMES. Some of the reactions tested would be potentially useful for quantitative or qualitative measurements on DMES. To study the reactions of DMES with silica surfaces, cabosil was used as a silica substrate because of its high surface area and the ease of detection by infrared spectroscopy as well as other techniques

The Role of Agriculture in Development

A longstanding question in economics is why some countries are so much richer than others. Today, for example, income per capita in the worldÂ’s richest countries is roughly thirty-five times greater than it is in the worldÂ’s poorest countries. Recent work (e.g., Robert E. Lucas 2001, and Rachel Ngai 1999) argues that the proximate cause of this disparity is that todayÂ’s poor countries began the process of industrialization much later and that this process is slow. In this paper we argue that a model of structural transformation provides a useful theory of both why industrialization occurs at different dates, and why it proceeds slowly. A key implication of this model is that growth in agricultural productivity is central to development, a message that also appears prominently in the traditional development literature. (See, e.g., Peter Timmer (1986)).

Experimental evaluation of blockage ratio and plenum evacuation system flow effects on pressure distribution for bodies of revolution in 0.1 scale model test section of NASA Lewis Research Center's proposed altitude wind tunnel

An experimental investigation was conducted in the slotted test section of the 0.1-scale model of the proposed Altitude Wind Tunnel to evaluate wall interference effects at tunnel Mach numbers from 0.70 to 0.95 on bodies of revolution with blockage rates of 0.43, 3, 6, and 12 percent. The amount of flow that had to be removed from the plenum chamber (which surrounded the slotted test section) by the plenum evacuation system (PES) to eliminate wall interference effects was determined. The effectiveness of tunnel reentry flaps in removing flow from the plenum chamber was examined. The 0.43-percent blockage model was the only one free of wall interference effects with no PES flow. Surface pressures on the forward part of the other models were greater than interference-free results and were not influenced by PES flow. Interference-free results were achieved on the aft part of the 3- and 6-percent blockage models with the proper amount of PES flow. The required PES flow was substantially reduced by opening the reentry flaps