208 research outputs found
ModelizaciĂłn de datos longitudinales con estructuras de covarianza no estacionarias: modelos de coeficientes aleatorios frente a modelos alternativos
Un tema que ha suscitado el interĂ©s de los investigadores en datos longitudinales durante las dos Ășltimas dĂ©cadas, ha sido el desarrollo y uso de modelos paramĂ©tricos explĂcitos para la estructura de covarianza de los datos. Sin embargo, el anĂĄlisis de estructuras de covarianza no estacionarias en el contexto de datos longitudinales no se ha realizado de forma detallada principalmente debido a que las distintas aplicaciones no hacĂan necesario su uso. Muchos son los modelos propuestos recientemente, pero la mayorĂa son estacionarios de segundo orden. Algunos de Ă©stos, sin embargo, no son estacionarios y suficientemente flexibles, de tal forma que es posible modelizar varianzas no constantes y/o correlaciones que no sean sĂłlo funciĂłn del tiempo que separa a dos observaciones dadas. Estudiaremos algunas de estas propuestas y las compararemos con los modelos de coeficientes aleatorios, evaluando sus ventajas y desventajas e indicando cuĂĄndo su uso no es apropiado o Ăștil. Presentaremos dos ejemplos para ilustrar el ajuste de estos modelos y los compararemos entre sĂ, mostrando de esta forma cĂłmo pueden modelizarse datos longitudinales de forma efectiva y simple. En estos ejemplos, los distintos modelos alternativos, especialmente los modelos antedependientes, fueron superiores a los modelos de coeficientes aleatorios
Modeling the probability distribution of positional errors incurred by residential address geocoding
BACKGROUND: The assignment of a point-level geocode to subjects' residences is an important data assimilation component of many geographic public health studies. Often, these assignments are made by a method known as automated geocoding, which attempts to match each subject's address to an address-ranged street segment georeferenced within a streetline database and then interpolate the position of the address along that segment. Unfortunately, this process results in positional errors. Our study sought to model the probability distribution of positional errors associated with automated geocoding and E911 geocoding. RESULTS: Positional errors were determined for 1423 rural addresses in Carroll County, Iowa as the vector difference between each 100%-matched automated geocode and its true location as determined by orthophoto and parcel information. Errors were also determined for 1449 60%-matched geocodes and 2354 E911 geocodes. Huge (> 15 km) outliers occurred among the 60%-matched geocoding errors; outliers occurred for the other two types of geocoding errors also but were much smaller. E911 geocoding was more accurate (median error length = 44 m) than 100%-matched automated geocoding (median error length = 168 m). The empirical distributions of positional errors associated with 100%-matched automated geocoding and E911 geocoding exhibited a distinctive Greek-cross shape and had many other interesting features that were not capable of being fitted adequately by a single bivariate normal or t distribution. However, mixtures of t distributions with two or three components fit the errors very well. CONCLUSION: Mixtures of bivariate t distributions with few components appear to be flexible enough to fit many positional error datasets associated with geocoding, yet parsimonious enough to be feasible for nascent applications of measurement-error methodology to spatial epidemiology
Effects Of Length, Complexity, And Grammatical Correctness On Stuttering In Spanish-Speaking Preschool Children
Purpose: To explore the effects of utterance length, syntactic complexity, and grammatical correctness on stuttering in the spontaneous speech of young, monolingual Spanish-speaking children. Method: Spontaneous speech samples of 11 monolingual Spanish-speaking children who stuttered, ages 35 to 70 months, were examined. Mean number of syllables, total number of clauses, utterance complexity (i.e., containing no clauses, simple clauses, or subordinate and/or conjoined clauses), and grammatical correctness (i.e., the presence or absence of morphological and syntactical errors) in stuttered and fluent utterances were compared. Results: Findings revealed that stuttered utterances in Spanish tended to be longer and more often grammatically incorrect, and contain more clauses, including more subordinate and/or conjoined clauses. However, when controlling for the interrelatedness of syllable number and clause number and complexity, only utterance length and grammatical incorrectness were significant predictors of stuttering in the spontaneous speech of these Spanish-speaking children. Use of complex utterances did not appear to contribute to the prediction of stuttering when controlling for utterance length. Conclusions: Results from the present study were consistent with many earlier reports of English-speaking children. Both length and grammatical factors appear to affect stuttering in Spanish-speaking children. Grammatical errors, however, served as the greatest predictor of stuttering.Communication Sciences and Disorder
ACE2-Mediated Reduction of Oxidative Stress in the Central Nervous System Is Associated with Improvement of Autonomic Function
Oxidative stress in the central nervous system mediates the increase in sympathetic tone that precedes the development of hypertension. We hypothesized that by transforming Angiotensin-II (AngII) into Ang-(1â7), ACE2 might reduce AngII-mediated oxidative stress in the brain and prevent autonomic dysfunction. To test this hypothesis, a relationship between ACE2 and oxidative stress was first confirmed in a mouse neuroblastoma cell line (Neuro2A cells) treated with AngII and infected with Ad-hACE2. ACE2 overexpression resulted in a reduction of reactive oxygen species (ROS) formation. In vivo, ACE2 knockout (ACE2â/y) mice and non-transgenic (NT) littermates were infused with AngII (10 days) and infected with Ad-hACE2 in the paraventricular nucleus (PVN). Baseline blood pressure (BP), AngII and brain ROS levels were not different between young mice (12 weeks). However, cardiac sympathetic tone, brain NADPH oxidase and SOD activities were significantly increased in ACE2â/y. Post infusion, plasma and brain AngII levels were also significantly higher in ACE2â/y, although BP was similarly increased in both genotypes. ROS formation in the PVN and RVLM was significantly higher in ACE2â/y mice following AngII infusion. Similar phenotypes, i.e. increased oxidative stress, exacerbated dysautonomia and hypertension, were also observed on baseline in mature ACE2â/y mice (48 weeks). ACE2 gene therapy to the PVN reduced AngII-mediated increase in NADPH oxidase activity and normalized cardiac dysautonomia in ACE2â/y mice. Altogether, these data indicate that ACE2 gene deletion promotes age-dependent oxidative stress, autonomic dysfunction and hypertension, while PVN-targeted ACE2 gene therapy decreases ROS formation via NADPH oxidase inhibition and improves autonomic function. Accordingly, ACE2 could represent a new target for the treatment of hypertension-associated dysautonomia and oxidative stress
Long-Baseline Neutrino Facility (LBNF) and Deep Underground Neutrino Experiment (DUNE) Conceptual Design Report Volume 2: The Physics Program for DUNE at LBNF
The Physics Program for the Deep Underground Neutrino Experiment (DUNE) at
the Fermilab Long-Baseline Neutrino Facility (LBNF) is described
Aboveground Biomass Accumulation in a Tropical Wet Forest in Nicaragua Following a Catastrophic Hurricane Disturbance 1
Among their effects on forest structure and carbon dynamics, hurricanes frequently create large-scale canopy gaps that promote secondary growth. To measure the accumulation of aboveground biomass (AGBM) in a hurricane damaged forest, we established permanent plots 4 mo after the landfall of Hurricane Joan on the Atlantic coast of Nicaragua in October 1988. We quantified AGBM accumulation in these plots by correlating diameter measurements to AGBM values using a published allometric regression equation for tropical wet forests. In the first measurement year following the storm, AGBM in hurricane-affected plots was quite variable, ranging from 26 to 153 Mg/ha, with a mean of 78 (±15) Mg/ha. AGBM was substantially lower than in two control plots several kilometers outside the hurricane's path (331 ±15 Mg/ha). Biomass accumulation was slow (5.36 ± 0.74 Mg/ha/yr), relative to previous studies of forest regeneration following another hurricane (Hugo) and agricultural activity. We suggest that large-scale, homogenous canopy damage caused by Hurricane Joan impeded the dispersal and establishment of pioneer trees and led to a secondary forest dominated by late successional species that resprouted and survived the disturbance. With the relatively slow rate of biomass accumulation, any tightening in disturbance interval could reduce the maximum capacity of the living biomass to store carbon.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73646/1/j.1744-7429.2005.00077.x.pd
Fortnightly changes in water transport direction across the mouth of a narrow estuary
This research investigates the dynamics of the axial
tidal flow and residual circulation at the lower Guadiana
Estuary, south Portugal, a narrow mesotidal estuary with low
freshwater inputs. Current data were collected near the deepest
part of the channel for 21 months and across the channel
during two (spring and neap) tidal cycles. Results indicate
that at the deep channel, depth-averaged currents are stronger
and longer during the ebb at spring and during the flood at
neap, resulting in opposite water transport directions at a
fortnightly time scale. The net water transport across the entire
channel is up-estuary at spring and down-estuary at neap, i.e.,
opposite to the one at the deep channel. At spring tide, when
the estuary is considered to be well mixed, the observed
pattern of circulation (outflow in the deep channel, inflow
over the shoals) results from the combination of the Stokes
transport and compensating return flow, which varies laterally
with the bathymetry. At neap tide (in particular for those of
lowest amplitude each month), inflows at the deep channel are
consistently associated with the development of gravitational
circulation. Comparisons with previous studies suggest that
the baroclinic pressure gradient (rather than internal tidal
asymmetries) is the main driver of the residual water transport.
Our observations also indicate that the flushing out of the
water accumulated up-estuary (at spring) may also produce
strong unidirectional barotropic outflow across the entire
channel around neap tide.info:eu-repo/semantics/publishedVersio
NADPH oxidases in cardiovascular disease: insights from in vivo models and clinical studies
NADPH oxidase family enzymes (or NOXs) are the major sources of reactive oxygen species (ROS) that are implicated in the pathophysiology of many cardiovascular diseases. These enzymes appear to be especially important in the modulation of redox-sensitive signalling pathways that underlie key cellular functions such as growth, differentiation, migration and proliferation. Seven distinct members of the family have been identified of which four (namely NOX1, 2, 4 and 5) may have cardiovascular functions. In this article, we review our current understanding of the roles of NOX enzymes in several common cardiovascular disease states, with a focus on data from genetic studies and clinical data where available
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