Formaldehyde sensor using non-dispersive UV spectroscopy at 340nm

Formaldehyde is a volatile organic compound that exists as a gas at room temperature. It is hazardous to human health causing irritation of the eyes, nose and throat, headaches, limited pulmonary function and is a potential human carcinogen. Sources include incomplete combustion, numerous modern building materials and vehicle fumes. Here we describe a simple method for detecting formaldehyde using low resolution non-dispersive UV absorption spectroscopy for the first time. A two channel system has been developed, making use of a strong absorption peak at 339nm and a neighbouring region of negligible absorption at 336nm as a reference. Using a modulated UV LED as a light source and narrowband filters to select the desired spectral bands, a simple detection system was constructed that was specifically targeted at formaldehyde. A minimum detectable absorbance of 4.5 × 10-5 AU was estimated (as ΔI/I0), corresponding to a limit of detection of approximately 6.6 ppm for a 195mm gas cell, with a response time of 20s. However, thermally-induced drift in the LED spectral output caused this to deteriorate over longer time periods to around 30 ppm or 2 × 10-4 A

Noise analysis for CCD-based ultraviolet and visible spectrophotometry

Full-text not yet available due to publisher embargo.We present the results of a detailed analysis of the noise behavior of two CCD spectrometers in common use, an AvaSpec-3648 CCD UV spectrometer and an Ocean Optics S2000 Vis spectrometer. Light sources used include a deuterium UV/Vis lamp and UV and visible LEDs. Common noise phenomena include source fluctuation noise, photoresponse nonuniformity, dark current noise, fixed pattern noise, and read noise. These were identified and characterized by varying light source, spectrometer settings, or temperature. A number of noise-limiting techniques are proposed, demonstrating a best-case spectroscopic noise equivalent absorbance of 3.5×10−4  AU for the AvaSpec-3648 and 5.6×10−4  AU for the Ocean Optics S2000 over a 30 s integration period. These techniques can be used on other CCD spectrometers to optimize performance

A measurement strategy for non-dispersive ultra-violet detection of formaldehyde in indoor air: Spectral analysis and interferent gases

We have conducted an extensive review of published spectra in order to identify a region with potential for detection of formaldehyde in indoor air. 85 chemicals and chemical groups common to the indoor environment were identified, 32 of which had absorption spectra in the UV-vis region. Of these, 11 were found to overlap with the formaldehyde UV region. It was found that the region between 320 to 360 nm is relatively free from interference from indoor gases, with NO being the only major interferent. A method is proposed for a low resolution (3 nm) spectroscopic detection method, specifically targeted at formaldehyde absorption features at 327 nm with a reference at 334 nm. 32 ppb of NO was found to have a cross-sensitivity with equivalent magnitude to 100 ppb of formaldehyde. A second reference at 348 nm would reduce this cross-sensitivity.This work was funded by the Engineering and Physics Science Research Council (EPSRC) under grants GR/T18424, EP/P504880 and EP/H02252X. Enquiries for access to the data referred to in this article should be directed to [email protected]

Does State Growth Management Change the Pattern of Urban Growth? Evidence From Florida.

This paper evaluates growth management in Florida by using a land use based regional adjustment model to project adjustments toward equilibrium densities of population and employment at the county level. The analysis utilizes a unique data set that contains detailed information on initial outcomes of the 1992 plan review in the State of Florida. These plan review outcomes are interacted with adjustment variables to test the hypothesis that Growth Management-specific policies have affected equilibrium adjustments in the following time period. The analysis is motivated by three specific research questions: Has Florida’s (1985) Growth Management Act increased changes in density during any of the three year time periods? Does plan compliance affect the growth trajectories of approved counties? And, finally, does the inclusion of optional plan elements further affect these growth trajectories? The findings suggest that compliance with state growth management mandates in Florida may push the adjustment process toward higher population densities in the1992-1997 time period. Additionally, the inclusion of an optional educational plan element may also push adjustments toward higher density. The results indicate that growth management efforts to address the technical planning process, as well as human capital needs, can increase the desirability, and thus the density, of sprawling counties in the Atlantic Southeast. Finally, because population and employment growth are jointly determined in the Atlantic Southeast, the long-term sustainability of economic development in Florida may depend on policies that preserve its desirability as a place to live. This paper elaborates upon work by Carruthers, McLaughlin, and Boarnet (2006) that shows Florida’s growth trajectory during the early 1990’s was significantly different than the Atlantic Southeast region.

ECONOMIC FORCES INFLUENCING VALUE-ADDED FOOD INDUSTRIES: IMPLICATIONS FOR SOUTHERN AGRICULTURE

Agribusiness,

A Smoothed-Distribution Form of Nadaraya-Watson Estimation

Given observation-pairs (xi ,yi ), i = 1,...,n , taken to be independent observations of the random pair (X ,Y), we sometimes want to form a nonparametric estimate of m(x) = E(Y/ X = x). Let YE have the empirical distribution of the yi , and let (XS ,YS ) have the kernel-smoothed distribution of the (xi ,yi ). Then the standard estimator, the Nadaraya-Watson form mNW(x) can be interpreted as E(YE?XS = x). The smoothed-distribution estimator ms (x)=E(YS/XS = x) is a more general form than  mNW (x) and often has better properties. Similar considerations apply to estimating Var(Y/X = x), and to local polynomial estimation. The discussion generalizes to vector (xi ,yi ).nonparametric regression, Nadaraya-Watson, kernel density, conditional expectation estimator, conditional variance estimator, local polynomial estimator

Evaluating international economic policy with the Federal Reserve's global model

FRB/Global is a large-scale macroeconomic model developed and maintained by the Board's staff. This article provides a historical perspective on the development of the model, gives an overview of its structure, and highlights its dynamic properties with three simulation experiments: a reduction in U.S. government purchases; a depreciation of the U.S. dollar; and an increase in the price of oil exported by OPEC. The article illustrates other uses of FRB/Global by examining the spillover effects of fiscal and monetary policy under alternative European monetary policy regimes.Econometric models ; Economic policy

Conflation of short identity-by-descent segments bias their inferred length distribution

Identity-by-descent (IBD) is a fundamental concept in genetics with many applications. In a common definition, two haplotypes are said to contain an IBD segment if they share a segment that is inherited from a recent shared common ancestor without intervening recombination. Long IBD segments (> 1cM) can be efficiently detected by a number of algorithms using high-density SNP array data from a population sample. However, these approaches detect IBD based on contiguous segments of identity-by-state, and such segments may exist due to the conflation of smaller, nearby IBD segments. We quantified this effect using coalescent simulations, finding that nearly 40% of inferred segments 1-2cM long are results of conflations of two or more shorter segments, under demographic scenarios typical for modern humans. This biases the inferred IBD segment length distribution, and so can affect downstream inferences. We observed this conflation effect universally across different IBD detection programs and human demographic histories, and found inference of segments longer than 2cM to be much more reliable (less than 5% conflation rate). As an example of how this can negatively affect downstream analyses, we present and analyze a novel estimator of the de novo mutation rate using IBD segments, and demonstrate that the biased length distribution of the IBD segments due to conflation can lead to inflated estimates if the conflation is not modeled. Understanding the conflation effect in detail will make its correction in future methods more tractable

Hepatitis C Diagnoses in an American Indian Primary Care Population

BACKGROUND: Despite large disparities in the burden of chronic liver disease, data on hepatitis C virus (HCV) infection among American Indians (AIs) are lacking. We reviewed hepatitis C diagnoses in 35,712 AI/AN primary care patients. MAIN FINDINGS: At least one HCV-associated ICD-9 code was recorded in 251 (1%) patients between October 1, 2001 and September 30, 2003. An HCV enzyme-linked immunoassay (HCVEIA) was sent in 209 (83.0%); 206/209 (99%) were positive. Confirmatory testing was performed in 144/206 (70%) HCV-EIA positive patients; HCV infection was confirmed in 144 (100%). In the 90/144 (63%) charts with risk factor documentation, injection drug use was the most common risk factor (61/90, 68%). Deficiencies were present in hepatitis B and HIV testing, and hepatitis A and B vaccination. PRINCIPAL CONCLUSIONS: Improvements in laboratory workup of HCV and co-infections, risk factor ascertainment and documentation, and adult vaccination are needed to address HCV effectively in this population