Chemical sensor

A sensor for detecting a chemical substance includes an insertion element having a structure which enables insertion of the chemical substance with a resulting change in the bulk electrical characteristics of the insertion element under conditions sufficient to permit effective insertion; the change in the bulk electrical characteristics of the insertion element is detected as an indication of the presence of the chemical substance

Discrimination Without Taste - How Discrimination can Spillover and Persist

We introduce coordination failures driven by beliefs regarding the presence of taste discriminators as a channel of discrimination in activities requiring the input of more than one individual for production to occur. We show discrimination can persist forever under perfectly observable ability, when taste for discrimination has died out, and under absence of discriminatory social norms. Empirically, we analyze the market for self-employment in the US, a market requiring input from multiple sources. Consistent with the theoretical prediction, we find beliefs about discrimination to be a significant negative correlate of self-employment rates of blacks in the US

Hydrogen production by photoelectrolytic decomposition of H2O using solar energy

Photoelectrochemical systems for the efficient decomposition of water are discussed. Semiconducting d band oxides which would yield the combination of stability, low electron affinity, and moderate band gap essential for an efficient photoanode are sought. The materials PdO and Fe-xRhxO3 appear most likely. Oxygen evolution yields may also be improved by mediation of high energy oxidizing agents, such as CO3(-). Examination of several p type semiconductors as photocathodes revealed remarkable stability for p-GaAs, and also indicated p-CdTe as a stable H2 photoelectrode. Several potentially economical schemes for photoelectrochemical decomposition of water were examined, including photoelectrochemical diodes and two stage, four photon processes

Photoelectrochemical fabrication of spectroscopic diffraction gratings

Photoelectrochemical etching was demonstrated as a means of fabricating a variety of periodic structures in semiconductors. The semiconductor is used as an electrode in an electrochemical cell, and is in contact with a liquid electrolyte. When the crystal is held at a positive voltage and illuminated, etching occurs in only the illuminated regions to a depth proportional to the illumination intensity and exposure time. In Phase 1, it was determined that diffraction gratings could be produced in gallium arsenide crystals by this method, using either a scanned focused laser beam or by uniform illumination of a ruling mask defined in metal or photoresist on the crystal surface. The latter approach was determined to produce V-grooves if the mask is oriented along certain crystallographic directions. These V-grooves were produced with an exceedingly smooth crystal morphology due to the highly controllable nature of the process and the mild electrolytes involved. The results form the basis for photoelectrochemical fabrication of deep, low pitch Eschelle gratings for use in high orders in NASA spectrographic instrumentation such as the Space Telescope Imaging Spectrograph

Electrochemical Detection of Multiple Bioprocess Analytes

An apparatus that includes highly miniaturized thin-film electrochemical sensor array has been demonstrated as a prototype of instruments for simultaneous detection of multiple substances of interest (analytes) and measurement of acidity or alkalinity in bioprocess streams. Measurements of pH and of concentrations of nutrients and wastes in cell-culture media, made by use of these instruments, are to be used as feedback for optimizing the growth of cells or the production of desired substances by the cultured cells. The apparatus is designed to utilize samples of minimal volume so as to minimize any perturbation of monitored processes. The apparatus can function in a potentiometric mode (for measuring pH), an amperometric mode (detecting analytes via oxidation/reduction reactions), or both. The sensor array is planar and includes multiple thin-film microelectrodes covered with hydrous iridium oxide. The oxide layer on each electrode serves as both a protective and electrochemical transducing layer. In its transducing role, the oxide provides electrical conductivity for amperometric measurement or pH response for potentiometric measurement. The oxide on an electrode can also serve as a matrix for one or more enzymes that render the electrode sensitive to a specific analyte. In addition to transducing electrodes, the array includes electrodes for potential control. The array can be fabricated by techniques familiar to the microelectronics industry. The sensor array is housed in a thin-film liquid-flow cell that has a total volume of about 100 mL. The flow cell is connected to a computer-controlled subsystem that periodically draws samples from the bioprocess stream to be monitored. Before entering the cell, each 100-mL sample is subjected to tangential-flow filtration to remove particles. In the present version of the apparatus, the electrodes are operated under control by a potentiostat and are used to simultaneously measure the pH and the concentration of glucose. It is anticipated that development of procedures for trapping more enzymes into hydrous iridium oxide (and possibly into other electroactive metal oxides) and of means for imparting long-term stability to the transducer layers should make it possible to monitor concentrations of products of many enzyme reactions for example, such key bioprocess analytes as amino acids, vitamins, lactose, and acetate

The Imperium of the Colonial Tongue? Evidence on Language Policy Preferences in Zambia

Sub-Saharan Africa stands out as a part of the world that primarily uses, as its official languages, former colonial languages that are neither spoken at home nor in the community. In this paper, we elicit preferences for colonial versus local languages and analyze the role of perceived costs and returns to different languages. In order to do so, we elicit beliefs about the effects of hypothetical changes to Zambia’s language policy on schooling outcomes, income, and social cohesion. Our results show overwhelming support for the use of the colonial language to act as official. Looking at the determinants, we find that fears of being disadvantaged by the installation of another group’s language, high perceived costs of learning in another group’s language, and lack of association between retaining the elite language and socioeconomic inequality as crucial factors in affecting preferences over language policies

How do transfers and universal basic income impact the labor market and inequality?

This paper studies the impact of existing and universal transfer programs on vacancy creation, wages, and welfare using a search-and-matching model with heterogeneous agents and on-the-job human capital accumulation. We calibrate the general equilibrium model to match key moments concerning unemployment, wage and wealth distributions, as well as the distribution of EITC and transfers. In addition, unemployment insurance benefits are related to pre-unemployment earnings and subject to exhaustion, after which agents can only rely on transfers and savings. First, we show that existing transfers hamper economic activity but provide sizeable welfare gains. Next, we show that a universal basic income of nearly $12,500 to each household per year, which replaces all existing transfer programs and unemployment benefits, can lead to small aggregate welfare gains. These welfare gains mostly accrue to less skilled individuals despite their sizable fall in wages, and the overall rise in skill premia and wage inequality. Albeit the extra burden of higher taxes to finance UBI, we show that the increased action in hiring is a key channel though which outcomes for low education groups improve with the reform. However, if we keep the UI benefits in place, the positive effects on job creation vanish and UBI does not improve upon the current system

Knockouts, Robustness and Cell Cycles

The response to a knockout of a node is a characteristic feature of a networked dynamical system. Knockout resilience in the dynamics of the remaining nodes is a sign of robustness. Here we study the effect of knockouts for binary state sequences and their implementations in terms of Boolean threshold networks. Beside random sequences with biologically plausible constraints, we analyze the cell cycle sequence of the species Saccharomyces cerevisiae and the Boolean networks implementing it. Comparing with an appropriate null model we do not find evidence that the yeast wildtype network is optimized for high knockout resilience. Our notion of knockout resilience weakly correlates with the size of the basin of attraction, which has also been considered a measure of robustness.Comment: 11 pages, 3 figures, 3 table

Photoelectrochemical fabrication of spectroscopic diffraction gratings, phase 2

This program was directed toward the production of Echelle diffraction gratings by a light-driven, electrochemical etching technique (photoelectrochemical etching). Etching is carried out in single crystal materials, and the differential rate of etching of the different crystallographic planes used to define the groove profiles. Etching of V-groove profiles was first discovered by us during the first phase of this project, which was initially conceived as a general exploration of photoelectrochemical etching techniques for grating fabrication. This highly controllable V-groove etching process was considered to be of high significance for producing low pitch Echelles, and provided the basis for a more extensive Phase 2 investigation

The Economics of State and Local Public Pensions

This paper provides an overview of an economics-based perspective on the financial aspects of state and local public pensions in the U.S. Drawing on the research commissioned for an NBER research program on this topic, we discuss the large degree to which public pension liabilities exceed the assets set aside to fund them. We summarize issues related to the optimality of pre-funding, portfolio allocation, the discounting of liabilities, as well as how plans operate in practice. We also lay out an agenda for future research related to financial aspects of public pensions, retiree health plans for public employees, as well as issues related to plan design and labor market outcomes.