100 research outputs found
MONEY ILLUSION, GORMAN AND LAU
Any demand equation satisfying Lau’s (1982) Fundamental Theorem of Exact Aggregation and 0° homogeneity in prices and income will have a Gorman (1981) functional form for each income term. This property does not depend on symmetry or adding up. The implications of this result are illustrated by an extensive example.Demand, exact aggregation, functional form, homogeneity
Theoretical Evaluation of Anisotropic Reflectance Correction Approaches for Addressing Multi-Scale Topographic Effects on the Radiation-Transfer Cascade in Mountain Environments
Research involving anisotropic-reflectance correction (ARC) of multispectral imagery to account for topographic effects has been ongoing for approximately 40 years. A large body of research has focused on evaluating empirical ARC methods, resulting in inconsistent results. Consequently, our research objective was to evaluate commonly used ARC methods using first-order radiation-transfer modeling to simulate ASTER multispectral imagery over Nanga Parbat, Himalaya. Specifically, we accounted for orbital dynamics, atmospheric absorption and scattering, direct- and diffuse-skylight irradiance, land cover structure, and surface biophysical variations to evaluate their effectiveness in reducing multi-scale topographic effects. Our results clearly reveal that the empirical methods we evaluated could not reasonably account for multi-scale topographic effects at Nanga Parbat. The magnitude of reflectance and the correlation structure of biophysical properties were not preserved in the topographically-corrected multispectral imagery. The CCOR and SCS+C methods were able to remove topographic effects, given the Lambertian assumption, although atmospheric correction was required, and we did not account for other primary and secondary topographic effects that are thought to significantly influence spectral variation in imagery acquired over mountains. Evaluation of structural-similarity index images revealed spatially variable results that are wavelength dependent. Collectively, our simulation and evaluation procedures strongly suggest that empirical ARC methods have significant limitations for addressing anisotropic reflectance caused by multi-scale topographic effects. Results indicate that atmospheric correction is essential, and most methods failed to adequately produce the appropriate magnitude and spatial variation of surface reflectance in corrected imagery. Results were also wavelength dependent, as topographic effects influence radiation-transfer components differently in different regions of the electromagnetic spectrum. Our results explain inconsistencies described in the literature, and indicate that numerical modeling efforts are required to better account for multi-scale topographic effects in various radiation-transfer components.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
Dose-Response of Aerobic Exercise on Cognition: A Community-Based, Pilot Randomized Controlled Trial
Epidemiological studies suggest a dose-response relationship exists between physical activity and cognitive outcomes. However, no direct data from randomized trials exists to support these indirect observations. The purpose of this study was to explore the possible relationship of aerobic exercise dose on cognition. Underactive or sedentary participants without cognitive impairment were randomized to one of four groups: no-change control, 75, 150, and 225 minutes per week of moderate-intensity semi-supervised aerobic exercise for 26-weeks in a community setting. Cognitive outcomes were latent residual scores derived from a battery of 16 cognitive tests: Verbal Memory, Visuospatial Processing, Simple Attention, Set Maintenance and Shifting, and Reasoning. Other outcome measures were cardiorespiratory fitness (peak oxygen consumption) and measures of function functional health. In intent-to-treat (ITT) analyses (n = 101), cardiorespiratory fitness increased and perceived disability decreased in a dose-dependent manner across the 4 groups. No other exercise-related effects were observed in ITT analyses. Analyses restricted to individuals who exercised per-protocol (n = 77) demonstrated that Simple Attention improved equivalently across all exercise groups compared to controls and a dose-response relationship was present for Visuospatial Processing. A clear dose-response relationship exists between exercise and cardiorespiratory fitness. Cognitive benefits were apparent at low doses with possible increased benefits in visuospatial function at higher doses but only in those who adhered to the exercise protocol. An individual’s cardiorespiratory fitness response was a better predictor of cognitive gains than exercise dose (i.e., duration) and thus maximizing an individual’s cardiorespiratory fitness may be an important therapeutic target for achieving cognitive benefits
Theory of Thermodynamic Stresses in Colloidal Dispersions at the Glass Transition
We discuss the nonlinear rheology of dense colloidal dispersions at the glass
transition. A first principles approach starting with interacting Brownian
particles in given arbitrary homogeneous (incompressible) flow neglecting
hydrodynamic interactions is sketched. It e.g. explains steady state flow
curves for finite shear rates measured in dense suspensions of thermosensitive
core-shell particles consisting of a polystyrene core and a crosslinked
poly(N-isopropylacrylamide)(PNIPAM) shell. The exponents of simple and
generalized Herschel Bulkley laws are computed for hard spheres.Comment: 3 pages, 1 figure; contribution to The XVth International Congress on
Rheology, August 3-8, 2008, Monterey, California; submitted to J. Rheo
Sex differences in physiological progression of idiopathic pulmonary fibrosis
In idiopathic pulmonary fibrosis, incidence is higher in males, and females may have
better survival. The aim of the present study was to determine whether the rate of increase in
desaturation during serial 6-min walk testing would be greater, and survival worse, for males
versus females.
Serial changes in the percentage of maximum desaturation area (DA) over 1 yr were estimated
using mixed models in 215 patients. DA was defined as the total area above the curve created
using desaturation percentage values observed during each minute of the 6-min walk test.
Multivariate Cox regression assessed survival differences.
Adjusting for baseline DA, 6-min walk distance, change in 6-min walk distance over time and
smoking history, the percentage of maximum DA increased by an average of 2.83 and 1.37% per
month for males and females, respectively. Females demonstrated better survival overall, which
was more pronounced in patients who did not desaturate below 88% on ambulation at baseline
and after additionally adjusting for 6-month relative changes in DA and forced vital capacity.
These data suggest that differences in disease progression contribute to, but do not completely
explain, better survival of females with idiopathic pulmonary fibrosis.This work was supported by National
Institutes of Health grants
5P50HL56402, U10HL080371,
2K24HL04212, K12RR024987 and
K23HL68713, and the Alberta
Heritage Medical Foundation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/91966/1/2008 ERJ - Sex Differences in Physiologic Progression of Idiopathic Pulmonary Fibrosis.pd
Clinical Predictors of a Diagnosis of Idiopathic Pulmonary Fibrosis
Rationale: Idiopathic pulmonary fibrosis (IPF) and other idiopathic
interstitial pneumonias (IIPs) have similar clinical and radiographic
features, but their histopathology, response to therapy, and natural
history differ. A surgical lung biopsy is often required to distinguish
between these entities.
Objectives: We sought to determine if clinical variables could predict
a histopathologic diagnosis of IPF in patients without honeycomb
change on high-resolution computed tomography (HRCT).
Methods: Data from 97 patients with biopsy-proven IPF and 38
patients with other IIPs were examined. Logistic regression models
were built to identify the clinical variables that predict histopathologic
diagnosis of IPF.
Measurements and Main Results: Increasing age and average total
HRCT interstitial score on HRCT scan of the chest may predict
a biopsy confirmation of IPF. Sex, pulmonary function, presence
of desaturation, or distance walked during a 6-minute walk test
did not help discriminate pulmonary fibrosis from other IIPs.
Conclusions: Clinical data may be used to predict a diagnosis of IPF
over other IIPs. Validation of these data with a prospective study is
needed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/91953/1/2010 AJRCCM Clinical Predictors of a Diagnosis of Idiopathic Pulmonary Fibrosis.pd
The University of California San Francisco, Brain Metastases Stereotactic Radiosurgery (UCSF-BMSR) MRI Dataset
The University of California San Francisco Brain Metastases Stereotactic
Radiosurgery (UCSF-BMSR) dataset is a public, clinical, multimodal brain MRI
dataset consisting of 560 brain MRIs from 412 patients with expert annotations
of 5136 brain metastases. Data consists of registered and skull stripped T1
post-contrast, T1 pre-contrast, FLAIR and subtraction (T1 pre-contrast - T1
post-contrast) images and voxelwise segmentations of enhancing brain metastases
in NifTI format. The dataset also includes patient demographics, surgical
status and primary cancer types. The UCSF-BSMR has been made publicly available
in the hopes that researchers will use these data to push the boundaries of AI
applications for brain metastases.Comment: 15 pages, 2 tables, 2 figure
Idiopathic interstitial pneumonia: Do community and academic physicians agree on diagnosis?
Rationale: Treatment and prognoses of diffuse parenchymal lung
diseases (DPLDs) varies by diagnosis. Obtaining a uniform diagnosis
among observers is difficult.
Objectives: Evaluate diagnostic agreement between academic and
community-based physicians for patients with DPLDs, and determine
if an interactive approach between clinicians, radiologists,
and pathologists improved diagnostic agreement in community
and academic centers.
Methods: Retrospective review of 39 patients with DPLD. A total of
19 participants reviewed cases at 2 community locations and 1
academic location. Information from the history, physical examination,
pulmonary function testing, high-resolution computed tomography,
and surgical lung biopsy was collected. Data were presented
in the same sequential fashion to three groups of physicians on
separate days.
Measurements and Main Results: Each observer’s diagnosis was coded
into one of eight categories. A statistic allowing formultiple raters
was used to assess agreement in diagnosis. Interactions between
clinicians, radiologists, and pathologists improved interobserver
agreement at both community and academic sites; however, final
agreement was better within academic centers (Kappa= 0.55–0.71) than
within community centers (Kappa=0.32–0.44). Clinically significant
disagreement was present between academic and communitybased
physicians (Kappa=0.11–0.56). Community physicians were more
likely to assign a final diagnosis of idiopathic pulmonary fibrosis
compared with academic physicians.
Conclusions: Significant disagreement exists in the diagnosis of
DPLD between physicians based in communities compared with
those in academic centers. Wherever possible, patients should be
referred to centers with expertise in diffuse parenchymal lung disorders
to help clarify the diagnosis and provide suggestions regarding
treatment options.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/91941/1/2007 AJRCCM Idiopathic interstitial pneumonia - Do community and academic physicians agree on diagnosis.pd
- …