Showing papers by "University of Colorado Boulder published in 2003"

Variation in trophic shift for stable isotope ratios of carbon, nitrogen, and sulfur

Abstract: Use of stable isotope ratios to trace pathways of organic matter among consumers requires knowledge of the isotopic shift between diet and consumer. Variation in trophic shift among consumers can be substantial. For data from the published literature and supplementary original data (excluding fluid-feeding consumers), the mean isotopic shift for C was + 0.5 + 0.13%o rather than 0.0%o, as commonly assumed. The shift for C was higher for consumers analyzed as muscle (+ 1.3 + 0.30%o) than for consumers analyzed whole (+ 0.3 +0.14%o). Among consumers analyzed whole, the trophic shift for C was lower for consumers acidified prior to analysis (-0.2 + 0.21%o) than for unacidified samples ( +0.5 + 0.17%o). For N, trophic shift was lower for consumers raised on invertebrate diets (+ 1.4 + 0.21%o) than for consumers raised on other high-protein diets (+3.3 +0.26%o) and was intermediate for consumers raised on plant and algal diets (+2.2 +0.30%o). The trophic shift for S differed between high-protein (+ 2.0 + 0.65%o) and low-protein diets (-0.5 + 0.56%o). Thus, methods of analysis and dietary differences can affect trophic shift for consumers; the utility of stable isotope methods can be improved if this information is incorporated into studies of trophic relationships. Although few studies of stable isotope ratios have considered variation in the trophic shift, such variation is important because small errors in estimates of trophic shift can result in large errors in estimates of the contribution of sources to consumers or in estimates of trophic position.

Anonymous Usage of Location-Based Services Through Spatial and Temporal Cloaking

Abstract: Advances in sensing and tracking technology enable location-based applications but they also create significant privacy risks. Anonymity can provide a high degree of privacy, save service users from dealing with service providers’ privacy policies, and reduce the service providers’ requirements for safeguarding private information. However, guaranteeing anonymous usage of location-based services requires that the precise location information transmitted by a user cannot be easily used to re-identify the subject. This paper presents a middleware architecture and algorithms that can be used by a centralized location broker service. The adaptive algorithms adjust the resolution of location information along spatial or temporal dimensions to meet specified anonymity constraints based on the entities who may be using location services within a given area. Using a model based on automotive traffic counts and cartographic material, we estimate the realistically expected spatial resolution for different anonymity constraints. The median resolution generated by our algorithms is 125 meters. Thus, anonymous location-based requests for urban areas would have the same accuracy currently needed for E-911 services; this would provide sufficient resolution for wayfinding, automated bus routing services and similar location-dependent services.

Bond Dissociation Energies of Organic Molecules

Abstract: In this Account we have compiled a list of reliable bond energies that are based on a set of critically evaluated experiments. A brief description of the three most important experimental techniques for measuring bond energies is provided. We demonstrate how these experimental data can be applied to yield the heats of formation of organic radicals and the bond enthalpies of more than 100 representative organic molecules.

Successful weight loss maintenance

Abstract: ▪ Abstract Obesity is now recognized as a serious chronic disease, but there is pessimism about how successful treatment can be. A general perception is that almost no one succeeds in long-term maintenance of weight loss. To define long-term weight loss success, we need an accepted definition. We propose defining successful long-term weight loss maintenance as intentionally losing at least 10% of initial body weight and keeping it off for at least 1 year. According to this definition, the picture is much more optimistic, with perhaps greater than 20% of overweight/obese persons able to achieve success. We found that in the National Weight Control Registry, successful long-term weight loss maintainers (average weight loss of 30 kg for an average of 5.5 years) share common behavioral strategies, including eating a diet low in fat, frequent self-monitoring of body weight and food intake, and high levels of regular physical activity. Weight loss maintenance may get easier over time. Once these successful main...

Physical Stability of Proteins in Aqueous Solution: Mechanism and Driving Forces in Nonnative Protein Aggregation

Abstract: Irreversible protein aggregation is problematic in the biotechnology industry, where aggregation is encountered throughout the lifetime of a therapeutic protein, including during refolding, purification, sterilization, shipping, and storage processes. The purpose of the current review is to provide a fundamental understanding of the mechanisms by which proteins aggregate and by which varying solution conditions, such as temperature, pH, salt type, salt concentration, cosolutes, preservatives, and surfactants, affect this process.

Two-dimensional femtosecond spectroscopy

Abstract: The simplest two-dimensional (2D) spectra show how excitation with one (variable) frequency affects the spectrum at all other frequencies, thus revealing the molecular connections between transitions. Femtosecond 2D Fourier transform (2D FT) spectra are more flexible and share some of the remarkable properties of their conceptual parent, 2D FT nuclear magnetic resonance. When 2D FT spectra are experimentally separated into real absorptive and imaginary refractive parts, the time resolution and frequency resolution can both reach the uncertainty limit set for each resonance by the sample itself. Coherent four-level contributions to the signal provide new molecular phase information, such as relative signs of transition dipoles. The nonlinear response can be picked apart by selecting a single coherence pathway (e.g., specifying the relative signs of energy level difference frequencies during different time intervals as in the photon echo). Because molecules are frozen on the femtosecond timescale, femtosecond 2D FT experiments can separate a distribution of instantaneous molecular environments and intramolecular geometries as inhomogeneous broadening. This review provides an introduction to two-dimensional Fourier transform experiments exploiting second- and third-order vibrational and electronic nonlinearities.

Unpacking "privacy" for a networked world

Abstract: Although privacy is broadly recognized as a dominant concern for the development of novel interactive technologies, our ability to reason analytically about privacy in real settings is limited. A lack of conceptual interpretive frameworks makes it difficult to unpack interrelated privacy issues in settings where information technology is also present. Building on theory developed by social psychologist Irwin Altman, we outline a model of privacy as a dynamic, dialectic process. We discuss three tensions that govern interpersonal privacy management in everyday life, and use these to explore select technology case studies drawn from the research literature. These suggest new ways for thinking about privacy in socio-technical environments as a practical matter.

Nutrition and Physical Activity During and After Cancer Treatment: An American Cancer Society Guide for Informed Choices

Abstract: Cancer survivors are often highly motivated to seek information about food choices, physical activity, dietary supplement use, and complementary nutritional therapies to improve their treatment outcomes, quality of life, and survival. To address these concerns, the American Cancer Society (ACS) convened a group of experts in nutrition, physical activity, and cancer to evaluate the scientific evidence and best clinical practices related to optimal nutrition and physical activity after the diagnosis of cancer. This report summarizes their findings and is intended to present health care providers with the best possible information on which to help cancer survivors and their families make informed choices related to nutrition and physical activity. The report discusses nutrition and physical activity issues during the phases of cancer treatment and recovery, living after recovery from treatment, and living with advanced cancer; selected nutritional and physical activity issues such as body weight, food choices, and complementary and alternative nutritional options; and selected issues related to breast, colorectal, lung, prostate, head and neck, and upper gastrointestinal cancers. In addition, handouts containing commonly asked questions and answers and a resource list are provided for survivors and families. Tables that grade the scientific evidence for benefit versus harm related to nutrition and physical activity for breast, colorectal, lung, and prostate cancers are also included for this growing body of knowledge to provide guidance for informed decision making and to identify areas for future research.

To Do or to Have? That Is the Question

Abstract: We live in a world of unprecedented abundance. Although few of us can live up to the advertising slogan that invites us to “have it all,” a growing swath of the population in developed countries has more discretionary income than ever before. We devote a considerable portion of our resources to the pursuit of “the good life”— one of contentment, pleasure, and happiness. For many of us, deciding how to invest our resources to maximize happiness is a challenge: We wonder whether we are as happy as we might be, given the resources at our disposal. We wonder whether more money, more leisure, or more stuff would make us happier. These queries may not apply to everyone, of course; individuals with severely limited resources may (rightfully) worry more about satisfying basic needs such as food, shelter, and clothing (Maslow, 1943). But for the fortunate majority in developed countries who enjoy a substantial measure of discretionary income, one can ask whether there is a simple, empirically grounded strategy to guide the allocation of resources in the pursuit of happiness. The thesis examined in this article is that happiness is advanced more by allocating discretionary income toward the acquisition of life experiences than toward the acquisition of material possessions. “The good life,” in other words, may be better lived by doing things than by having things.

Learning from Business Failure: Propositions of Grief Recovery for the Self-Employed

Abstract: In this paper I use the psychological literature on grief to explore the emotion of business failure, suggesting that the loss of a business from failure can cause the self-employed to feel grief—a negative emotional response interfering with the ability to learn from the events surrounding that loss. I discuss how a dual process of grief recovery maximizes the learning from business failure.

Brain-derived neurotrophic factor regulates energy balance downstream of melanocortin-4 receptor

Abstract: The melanocortin-4 receptor (MC4R) is critically involved in regulating energy balance, and obesity has been observed in mice with mutations in the gene for brain-derived neurotrophic factor (BDNF). Here we report that BDNF is expressed at high levels in the ventromedial hypothalamus (VMH) where its expression is regulated by nutritional state and by MC4R signaling. In addition, similar to MC4R mutants, mouse mutants that expresses the BDNF receptor TrkB at a quarter of the normal amount showed hyperphagia and excessive weight gain on higher-fat diets. Furthermore, BDNF infusion into the brain suppressed the hyperphagia and excessive weight gain observed on higher-fat diets in mice with deficient MC4R signaling. These results show that MC4R signaling controls BDNF expression in the VMH and support the hypothesis that BDNF is an important effector through which MC4R signaling controls energy balance.

ENSO-Forced Variability of the Pacific Decadal Oscillation

Abstract: Variability of the Pacific decadal oscillation (PDO), on both interannual and decadal timescales, is well modeled as the sum of direct forcing by El Nino-Southern Oscillation (ENSO), the ''reemergence'' of North Pacific sea surface temperature anomalies in subsequent winters, and white noise atmospheric forcing. This simple model may be taken as a null hypothesis for the PDO, and may also be relevant for other climate integrators that have been previously related to the PDO.

Spinal Glia and Proinflammatory Cytokines Mediate Mirror-Image Neuropathic Pain in Rats

Abstract: Mirror-image allodynia is a mysterious phenomenon that occurs in association with many clinical pain syndromes. Allodynia refers to pain in response to light touch/pressure stimuli, which normally are perceived as innocuous. Mirror-image allodynia arises from the healthy body region contralateral to the actual site of trauma/inflammation. Virtually nothing is known about the mechanisms underlying such pain. A recently developed animal model of inflammatory neuropathy reliably produces mirror-image allodynia, thus allowing this pain phenomenon to be analyzed. In this sciatic inflammatory neuropathy (SIN) model, decreased response threshold to tactile stimuli (mechanical allodynia) develops in rats after microinjection of immune activators around one healthy sciatic nerve at mid-thigh level. Low level immune activation produces unilateral allodynia ipsilateral to the site of sciatic inflammation; more intense immune activation produces bilateral (ipsilateral + mirror image) allodynia. The present studies demonstrate that both ipsilateral and mirror-image SIN-induced allodynias are (1) reversed by intrathecal (peri-spinal) delivery of fluorocitrate, a glial metabolic inhibitor; (2) prevented and reversed by intrathecal CNI-1493, an inhibitor of p38 mitogen-activated kinases implicated in proinflammatory cytokine production and signaling; and (3) prevented or reversed by intrathecal proinflammatory cytokine antagonists specific for interleukin-1, tumor necrosis factor, or interleukin-6. Reversal of ipsilateral and mirror-image allodynias was rapid and complete even when SIN was maintained constantly for 2 weeks before proinflammatory cytokine antagonist administration. These results provide the first evidence that ipsilateral and mirror-image inflammatory neuropathy pain are created both acutely and chronically through glial and proinflammatory cytokine actions.

Ecological Effects of Nitrogen Deposition in the Western United States

Abstract: In the western United States vast acreages of land are exposed to low levels of atmospheric nitrogen (N) deposition, with interspersed hotspots of elevated N deposition downwind of large, expanding metropolitan centers or large agricultural operations. Biological response studies in western North America demonstrate that some aquatic and terrestrial plant and microbial communities are significantly altered by N deposition. Greater plant productivity is counterbalanced by biotic community changes and deleterious effects on sensitive organisms (lichens and phytoplankton) that respond to low inputs of N (3 to 8 kilograms N per hectare per year). Streamwater nitrate concentrations are elevated in high-elevation catchments in Colorado and are unusually high in southern California and in some chaparral catchments in the southwestern Sierra Nevada. Chronic N deposition in the West is implicated in increased fire frequency in some areas and habitat alteration for threatened species. Between hotspots, N deposition is too low to cause noticeable effects or has not been studied.

High-frequency digital PWM controller IC for DC-DC converters

Abstract: This paper describes a complete digital PWM controller IC for high-frequency switching converters. Novel architecture and configurations of the key building blocks are A/D converter, compensator, and digital pulse-width modulator, are introduced to meet the requirements of tight output voltage regulation, high-speed dynamic response, and programmability without external passive components. The implementation techniques are experimentally verified on a prototype chip that takes less than 1 mm/sup 2/ of silicon area in a standard 0.5 /spl mu/ digital complementary metal oxide semiconductor (CMOS) process and operates at the switching frequency of 1 MHz.

GLIA: A novel drug discovery target for clinical pain

Abstract: In many clinical pain syndromes, painful sensations are greatly amplified so that normally innocuous sensations, such as light touch or warmth, are perceived as pain. Presently available drugs are ineffective in controlling such pain in most patients and abolish the pain in only few. Why do they fail? These drugs were developed to target neurons that transmit nociceptive ('pain') information. However, glia have recently been recognized as powerful modulators of nociception, and could hold the key to the control of clinical pain and present a new target for drug discovery. This review examines the evidence for glial regulation of nociception and pharmacological approaches that might successfully control glially driven clinical pain syndromes.

Predictive digital current programmed control

Abstract: This paper explores predictive digital current programmed control for valley, peak or average current. The control laws are derived for the three basic converters: buck, boost, and buck-boost. It is found that for each variable of interest (valley, peak or average current) there is a choice of the appropriate pulse-width modulation method to achieve predictive digital current control without oscillation problems. The proposed digital control techniques can be used in a range of power conversion applications, including rectifiers with power factor correction (PFC). Very low current distortion meeting strict avionics requirements (400-800 Hz line frequency) is experimentally demonstrated on a digitally controlled boost PFC employing predictive average current programmed control.

High resolution foreground cleaned CMB map from WMAP

Abstract: We perform an independent foreground analysis of the Wilkinson Microwave Anisotropy Probe (WMAP) maps to produce a cleaned cosmic microwave background (CMB) map (available online) useful for cross-correlation with, e.g., galaxy and x-ray maps. We use a variant of the Tegmark-Efstathiou technique that assumes that the CMB has a blackbody spectrum, but is otherwise completely blind, making no assumptions about the CMB power spectrum, the foregrounds, WMAP detector noise or external templates. Compared with the foreground-cleaned internal linear combination map produced by the WMAP team, our map has the advantage of containing less non-CMB power (from foregrounds and detector noise) outside the Galactic plane. The difference is most important on the angular scale of the first acoustic peak and below, since our cleaned map is at the highest ${(12.6}^{\ensuremath{'}})$ rather than lowest ${(49.2}^{\ensuremath{'}})$ WMAP resolution. We also produce a Wiener filtered CMB map, representing our best guess as to what the CMB sky actually looks like, as well as CMB-free maps at the five WMAP frequencies useful for foreground studies. We argue that our CMB map is clean enough that the lowest multipoles can be measured without any galaxy cut, and obtain a quadrupole value that is slightly less low than that from the cut-sky WMAP team analysis. This can be understood from a map of the CMB quadrupole, which shows much of its power falling within the Galaxy cut region, seemingly coincidentally. Intriguingly, both the quadrupole and the octopole are seen to have power suppressed along a particular spatial axis, which lines up between the two, roughly towards $(l,b)\ensuremath{\sim}(\ensuremath{-}110\ifmmode^\circ\else\textdegree\fi{},60\ifmmode^\circ\else\textdegree\fi{})$ in Virgo.

Artificial neural networks for RF and microwave design - from theory to practice

Abstract: Neural-network computational modules have recently gained recognition as an unconventional and useful tool for RF and microwave modeling and design. Neural networks can be trained to learn the behavior of passive/active components/circuits. A trained neural network can be used for high-level design, providing fast and accurate answers to the task it has learned. Neural networks are attractive alternatives to conventional methods such as numerical modeling methods, which could be computationally expensive, or analytical methods which could be difficult to obtain for new devices, or empirical modeling solutions whose range and accuracy may be limited. This tutorial describes fundamental concepts in this emerging area aimed at teaching RF/microwave engineers what neural networks are, why they are useful, when they can be used, and how to use them. Neural-network structures and their training methods are described from the RF/microwave designer's perspective. Electromagnetics-based training for passive component models and physics-based training for active device models are illustrated. Circuit design and yield optimization using passive/active neural models are also presented. A multimedia slide presentation along with narrative audio clips is included in the electronic version of this paper. A hyperlink to the NeuroModeler demonstration software is provided to allow readers practice neural-network-based design concepts.

Averaged transition conditions for electromagnetic fields at a metafilm

Abstract: This paper derives generalized sheet transition conditions (GSTCs) for the average electromagnetic fields across a surface distribution of electrically small scatterers characterized by electric and magnetic polarization densities. We call such an arrangement of scatterers a metafilm-the two-dimensional (2-D) equivalent of a metamaterial. The derivation is based on a replacement of the discrete distribution of scatterers by a continuous one, resulting in a continuous distribution of electric and magnetic polarization densities in the surface. This is done in a manner analogous to the Clausius-Mossotti-Lorenz-Lorentz procedure for determining the dielectric constant of a volume distribution of small scatterers. The result contains as special cases many particular ones found throughout the literature. The GSTCs are expected to have wide application to the design and analysis of antennas, reflectors, and other devices where controllable scatterers are used to form a "smart" surface.

Seasonal dynamics of previously unknown fungal lineages in tundra soils.

Abstract: The finding that microbial communities are active under snow has changed the estimated global rates of biogeochemical processes beneath seasonal snow packs. We used microbiological and molecular techniques to elucidate the phylogenetic composition of undersnow microbial communities in Colorado, the United States. Here, we show that tundra soil microbial biomass reaches its annual peak under snow, and that fungi account for most of the biomass. Phylogenetic analysis of tundra soil fungi revealed a high diversity of fungi and three novel clades that constitute major new groups of fungi (divergent at the subphylum or class level). An abundance of previously unknown fungi that are active beneath the snow substantially broadens our understanding of both the diversity and biogeochemical functioning of fungi in cold environments.

Conformal Coating on Ultrahigh-Aspect-Ratio Nanopores of Anodic Alumina by Atomic Layer Deposition

Abstract: Anodic alumina (AA) membranes are composed of highly uniform, nanometer-scale pores arranged in a hexagonal close-packed array. Depositing conformal films inside the nanopores is extremely difficult because the nanopores have an ultrahigh aspect ratio of L/d ≈ 103. Atomic layer deposition (ALD) is a thin film growth technique that can deposit highly uniform films on high-aspect-ratio substrates with monolayer thickness control. In this study, AA membranes were coated with Al2O3 and ZnO ALD films and subsequently analyzed using cross-sectional scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). SEM analysis of individual nanopores revealed that the AA membranes with nanopore diameters of d = 65 nm and lengths of L = 50 μm could be coated conformally by Al2O3 ALD using sufficient reactant exposure times. Zn concentration profiles measured by EPMA following ZnO ALD showed the progressive infiltration of the ZnO ALD into the nanopores with increasing exposure times for aspect ratios as...

Quantitative sampling using an Aerodyne aerosol mass spectrometer 1. Techniques of data interpretation and error analysis

Abstract: Received 22 March 2002; revised 2 July 2002; accepted 5 August 2002; published 4 February 2003. [1] The aerosol mass spectrometer (AMS), manufactured by Aerodyne Research, Inc., has been shown to be capable of delivering quantitative information on the chemical composition and size of volatile and semivolatile fine airborne particulate matter with high time resolution. Analytical and software tools for interpreting the data from this instrument and generating meaningful, quantitative results have been developed and are presented here with a brief description of the instrument. These include the conversion of detected ion rates from the quadrupole mass spectrometer during the mass spectrum (MS) mode of operation to atmospheric mass concentrations of chemical species (in m gm � 3 ) by applying calibration data. It is also necessary to correct for variations in the electron multiplier performance, and a method involving the measurement of the instrument’s response to gas phase signals is also presented. The techniques for applying particle velocity calibration data and transforming signals from time of flight (TOF) mode to chemical mass distributions in terms of aerodynamic diameter (dM/dlog(Da) distributions) are also presented. It is also possible to quantify the uncertainties in both MS and TOF data by evaluating the ion counting statistics and variability of the background signal, respectively. This paper is accompanied by part 2 of this series, in which these methods are used to process and analyze AMS results on ambient aerosol from two U.K. cities at different times of the year. INDEX TERMS: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 0394 Atmospheric Composition and Structure: Instruments and techniques; 0399 Atmospheric Composition and Structure: General or miscellaneous; KEYWORDS: aerosols, chemical composition, mass spectrometry, analysis techniques

Race and gender on the brain: electrocortical measures of attention to the race and gender of multiply categorizable individuals.

Abstract: The degree to which perceivers automatically attend to and encode social category information was investigated. Event-related brain potentials were used to assess attentional and working-memory processes on-line as participants were presented with pictures of Black and White males and females. The authors found that attention was preferentially directed to Black targets very early in processing (by about 100 ms after stimulus onset) in both experiments. Attention to gender also emerged early but occurred about 50 ms later than attention to race. Later working-memory processes were sensitive to more complex relations between the group memberships of a target individual and the surrounding social context. These working-memory processes were sensitive to both the explicit categorization task participants were performing as well as more implicit, task-irrelevant categorization dimensions. Results are consistent with models suggesting that information about certain category dimensions is encoded relatively automatically.

A randomized study of family-focused psychoeducation and pharmacotherapy in the outpatient management of bipolar disorder.

Abstract: Background Bipolar patients are at risk for relapses of their illness even when undergoing optimal pharmacotherapy. This study was performed to determine whether combining family-focused therapy (FFT) with pharmacotherapy during a postepisode interval enhances patients' mood stability during maintenance treatment. Methods In a randomized controlled trial, 101 bipolar patients were assigned to FFT and pharmacotherapy or a less intensive crisis management (CM) intervention and pharmacotherapy. Outcome assessments were conducted every 3 to 6 months for 2 years. Participants (mean +/- SD age, 35.6 +/- 10.2 years) were referred from inpatient or outpatient clinics after onset of a manic, mixed, or depressed episode. FFT consisted of 21 sessions of psychoeducation, communication training, and problem-solving skills training. Crisis management consisted of 2 sessions of family education plus crisis intervention sessions as needed. Both protocols lasted 9 months. Patients received pharmacotherapy for 2 study years. Main outcome measures included time to relapse, depressive and manic symptoms, and medication adherence. Results Rates of study completion did not differ across the FFT (22/31, 71%) and CM groups (43/70, 61%). Patients undergoing FFT had fewer relapses (11/31, 35%) and longer survival intervals (mean +/- SD, 73.5 +/- 28.8 weeks) than patients undergoing CM (38/70, 54%; mean +/- SD, 53.2 +/- 39.6 weeks; hazard ratio, 0.38; 95% confidence interval, 0.20-0.75; P =.003; intent to treat). Patients undergoing FFT showed greater reductions in mood disorder symptoms and better medication adherence during the 2 years than patients undergoing CM. Conclusion Combining family psychoeducation with pharmacotherapy enhances the postepisode symptomatic adjustment and drug adherence of bipolar patients.

Highly Ionized High-Velocity Gas in the Vicinity of the Galaxy

Abstract: We report the results of a FUSE study of high-velocity O VI absorption along complete sight lines through the Galactic halo in directions toward 100 extragalactic objects and two halo stars. The high-velocity O VI traces a variety of phenomena, including tidal interactions with the Magellanic Clouds, accretion of gas, outflowing material from the Galactic disk, warm/hot gas interactions in a highly extended Galactic corona, and intergalactic gas in the Local Group. We identify 84 high-velocity O VI features at ≥3 σ confidence at velocities of -500 106 K), low-density (n 10-4-10-5 cm-3) Galactic corona or Local Group medium. The existence of a hot, highly extended Galactic corona or Local Group medium and the prevalence of high-velocity O VI are consistent with predictions of current galaxy formation scenarios. Distinguishing between the various phenomena producing high-velocity O VI in and near the Galaxy will require continuing studies of the distances, kinematics, elemental abundances, and physical states of the different types of high-velocity O VI found in this study. Descriptions of galaxy evolution will need to account for the highly ionized gas, and future X-ray studies of hot gas in the Local Group will need to consider carefully the relationship of the X-ray absorption/emission to the complex high-velocity absorption observed in O VI.

The impact of urban spatial structure on travel demand in the United States

Abstract: We examine the effects of urban form and public transit supply on the commute mode choices and annual vehicle miles traveled (VMTs) of households living in 114 urban areas in 1990. The probability of driving to work is lower the higher are population centrality and rail miles supplied and the lower is road density. Population centrality, jobs-housing balance, city shape, and road density have a significant effect on annual household VMTs. Although individual elasticities are small absolute values (≤0.10), moving sample households from a city with the characteristics of Atlanta to a city with the characteristics of Boston reduces annual VMTs by 25%.