Environmentally Adjusted Agricultural Productivity in the Great Plains

This study adjusts 1960-1996 agricultural productivity gains in a panel of Great Plains states to account for the discharge of pesticide and nitrogen effluents into the environment. The agricultural-environmental technology is approximated with translog distance functions that allow us to contrast traditional versus environmentally adjusted productivity gains. Findings indicate technical change has been increasingly biased toward environmentally friendly production. While the environmental adjustment reduced overall productivity gains during the sample period, in recent years adjusted productivity outpaced the traditional measure, reflecting the pro-environment bias in technical change.agricultural productivity, distance function, environmental externalities, nitrogen, pesticides, technical change bias, Environmental Economics and Policy, Productivity Analysis,

Impact of AFM-induced nano-pits in a-Si:H films on silicon crystal growth

Conductive tips in atomic force microscopy (AFM) can be used to localize field-enhanced metal-induced solid-phase crystallization (FE-MISPC) of amorphous silicon (a-Si:H) at room temperature down to nanoscale dimensions. In this article, the authors show that such local modifications can be used to selectively induce further localized growth of silicon nanocrystals. First, a-Si:H films by plasma-enhanced chemical vapor deposition on nickel/glass substrates are prepared. After the FE-MISPC process, yielding both conductive and non-conductive nano-pits in the films, the second silicon layer at the boundary condition of amorphous and microcrystalline growth is deposited. Comparing AFM morphology and current-sensing AFM data on the first and second layers, it is observed that the second deposition changes the morphology and increases the local conductivity of FE-MISPC-induced pits by up to an order of magnitude irrespective of their prior conductivity. This is attributed to the silicon nanocrystals (<100 nm) that tend to nucleate and grow inside the pits. This is also supported by micro-Raman spectroscopy

Guided assembly of nanoparticles on electrostatically charged nanocrystalline diamond thin films

We apply atomic force microscope for local electrostatic charging of oxygen-terminated nanocrystalline diamond (NCD) thin films deposited on silicon, to induce electrostatically driven self-assembly of colloidal alumina nanoparticles into micro-patterns. Considering possible capacitive, sp2 phase and spatial uniformity factors to charging, we employ films with sub-100 nm thickness and about 60% relative sp2 phase content, probe the spatial material uniformity by Raman and electron microscopy, and repeat experiments at various positions. We demonstrate that electrostatic potential contrast on the NCD films varies between 0.1 and 1.2 V and that the contrast of more than ±1 V (as detected by Kelvin force microscopy) is able to induce self-assembly of the nanoparticles via coulombic and polarization forces. This opens prospects for applications of diamond and its unique set of properties in self-assembly of nano-devices and nano-systems

The Quantum Refrigerator: The quest for absolute zero

The scaling of the optimal cooling power of a reciprocating quantum refrigerator is sought as a function of the cold bath temperature as $T_c \to 0$. The working medium consists of noninteracting particles in a harmonic potential. Two closed-form solutions of the refrigeration cycle are analyzed, and compared to a numerical optimization scheme, focusing on cooling toward zero temperature. The optimal cycle is characterized by linear relations between the heat extracted from the cold bath, the energy level spacing of the working medium and the temperature. The scaling of the optimal cooling rate is found to be proportional to $T_c^{3/2}$ giving a dynamical interpretation to the third law of thermodynamics

Academic Success and the Transfer of Community College Credits in the Principles of Economics

A growing number of today’s college students attend local 2-year community colleges. Many of these students will ultimately transfer to major universities in pursuit of the traditional Bachelors degree. The question of whether such transfer credits adequately prepare students for future academic endeavors is important for educators interested in preparing successful students and maintaining the quality of their institution. In this paper, we examine whether students who transfer credits earned for the traditional Principles of Economics course sequence achieve the same levels of academic success, measured in terms of GPA, as students taking the sequence at a major state university. The model indicates that community college transfer students perform poorly relative to native students in terms of cumulative GPA. This result is driven by a self-selection process whereby the more academically challenged students are those who choose to transfer credit from 2-year schools. The results of our model are used to develop a grade equivalency measure between the university and 2-year schools. Using this measure we are able to reject the hypothesis that grades are equivalent between 2- and 4-year institutions. Finally, we find that grades in the Principles of Economics sequence are strong predictors of overall academic success

The smallest refrigerators can reach maximal efficiency

We investigate whether size imposes a fundamental constraint on the efficiency of small thermal machines. We analyse in detail a model of a small self-contained refrigerator consisting of three qubits. We show analytically that this system can reach the Carnot efficiency, thus demonstrating that there exists no complementarity between size and efficiency.Comment: 9 pages, 1 figure. v2: published versio

Spaceborne Fiber Optic Data Bus (SFODB)

Spaceborne Fiber Optic Data Bus (SFODB) is an IEEE 1393 compliant, gigabit per second, fiber optic network specifically designed to support the real-time, on-board data handling requirements of remote sensing spacecraft. The network is fault tolerant highly reliable, and capable of withstanding the rigors of launch and the harsh space environment. SFODB achieves this operational and environmental performance while maintaining the small size, light weight, and low power necessary for spaceborne applications. On December 9, 1998, SFODB was successfully demonstrated at NASA's Goddard Space Flight Center (GSFC)

Irreversible Performance of a Quantum Harmonic Heat Engine

The unavoidable irreversible losses of power in a heat engine are found to be of quantum origin. Following thermodynamic tradition a model quantum heat engine operating by the Otto cycle is analyzed. The working medium of the model is composed of an ensemble of harmonic oscillators. A link is established between the quantum observables and thermodynamical variables based on the concept of canonical invariance. These quantum variables are sufficient to determine the state of the system and with it all thermodynamical variables. Conditions for optimal work, power and entropy production show that maximum power is a compromise between the quasistatic limit of adiabatic following on the compression and expansion branches and a sudden limit of very short time allocation to these branches. At high temperatures and quasistatic operating conditions the efficiency at maximum power coincides with the endoreversible result. The optimal compression ratio varies from the square root of the temperature ratio in the quasistatic limit where their reversibility is dominated by heat conductance to the temperature ratio to the power of 1/4 in the sudden limit when the irreversibility is dominated by friction. When the engine deviates from adiabatic conditions the performance is subject to friction. The origin of this friction can be traced to the noncommutability of the kinetic and potential energy of the working medium.Comment: 25 pages, 7 figures. Revision added explicit heat-transfer expression and extended the discussion on the quantum origin of frictio

Academic Success and the Transfer of Community College Credits in the Principles of Economics

A growing number of today’s college students attend local 2-year community colleges. Many of these students will ultimately transfer to major universities in pursuit of the traditional Bachelors degree. The question of whether such transfer credits adequately prepare students for future academic endeavors is important for educators interested in preparing successful students and maintaining the quality of their institution. In this paper, we examine whether students who transfer credits earned for the traditional Principles of Economics course sequence achieve the same levels of academic success, measured in terms of GPA, as students taking the sequence at a major state university. The model indicates that community college transfer students perform poorly relative to native students in terms of cumulative GPA. This result is driven by a self-selection process whereby the more academically challenged students are those who choose to transfer credit from 2-year schools. The results of our model are used to develop a grade equivalency measure between the university and 2-year schools. Using this measure we are able to reject the hypothesis that grades are equivalent between 2- and 4-year institutions. Finally, we find that grades in the Principles of Economics sequence are strong predictors of overall academic success

Synthesis, structure, and opto-electronic properties of organic-based nanoscale heterojunctions

Enormous research effort has been put into optimizing organic-based opto-electronic systems for efficient generation of free charge carriers. This optimization is mainly due to typically high dissociation energy (0.1-1 eV) and short diffusion length (10 nm) of excitons in organic materials. Inherently, interplay of microscopic structural, chemical, and opto-electronic properties plays crucial role. We show that employing and combining advanced scanning probe techniques can provide us significant insight into the correlation of these properties. By adjusting parameters of contact- and tapping-mode atomic force microscopy (AFM), we perform morphologic and mechanical characterizations (nanoshaving) of organic layers, measure their electrical conductivity by current-sensing AFM, and deduce work functions and surface photovoltage (SPV) effects by Kelvin force microscopy using high spatial resolution. These data are further correlated with local material composition detected using micro-Raman spectroscopy and with other electronic transport data. We demonstrate benefits of this multi-dimensional characterizations on (i) bulk heterojunction of fully organic composite films, indicating differences in blend quality and component segregation leading to local shunts of photovoltaic cell, and (ii) thin-film heterojunction of polypyrrole (PPy) electropolymerized on hydrogen-terminated diamond, indicating covalent bonding and transfer of charge carriers from PPy to diamond