The human sympathetic nervous system: its relevance in hypertension and heart failure

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A Lagrangian perspective of the tropopause and the ventilation of the lowermost stratosphere

Back trajectories driven by large-scale analyzed wind fields are used to investigate troposphere to stratosphere transport (TST) in the Northern Hemisphere tropopause region, as well as the surface sources for such transport, defined in terms of the locations where each trajectory last left the atmospheric boundary layer ( log pressure height z* < 1 km). The proportion chi(BL) of those trajectories arriving in the tropopause region that have visited the boundary layer within the previous fixed time period ( typically 30 days) is determined as a function of each trajectory's final equivalent latitude and potential temperature. For a range of potential temperature surfaces ( similar to 300-380 K), chi(BL) is shown to have a sharp gradient in the extratropics indicative of a partial permeable barrier to transport that can be identified as a "Lagrangian tropopause.'' Variations in chi(BL) with equivalent latitude and potential temperature and on seasonal timescales are shown to provide a novel measure for the relative location and permeability of the tropopause barrier. Details such as the presence of a "ventilated layer'' in the northern summer extratropical lower stratosphere ( similar to 370-410 K) are clearly apparent. Directly below this layer ( 340-370 K) the tropopause barrier to transport is shown to be relatively strong, whereas below 340 K it is again more permeable. A distinction can therefore be made between "extratropical'' TST that primarily ventilates the lowermost stratosphere below 340 K and "tropical'' TST that occurs into the 370-410 K ventilated layer. The boundary layer source regions for extratropical TST are shown to correspond to those regions previously identified as sources for deep frontal uplift in the warm conveyor belt circulations of extratropical cyclones, although elevated regions such as the Himalayan plateau are also seen to be important. Tropical TST has different source regions associated with regions of active deep convection such as the western tropical Pacific and, in the northern summer, the Indian subcontinent. The source regions are, in general, found to be geographically localized, leading to the conclusion that subject to the limitations of the methodology, trace gas emissions in specific regions are substantially more likely to be transported to the lowermost stratosphere than elsewhere. The implications for the assessment of ozone depletion by very short lived halogenated species are mentioned

Transport and Mixing of Chemical Air Masses in Idealized Baroclinic Life Cycles

The transport, mixing, and three-dimensional evolution of chemically distinct air masses within growing baroclinic waves are studied in idealized, high-resolution, life cycle experiments using suitably initialized passive tracers, contrasting the two well-known life cycle paradigms, distinguished by predominantly anticyclonic (LC1) or cyclonic (LC2) flow at upper levels. Stratosphere-troposphere exchange differs significantly between the two life cycles. Specifically, transport from the stratosphere into the troposphere is significantly larger for LC2 (typically by 50%), due to the presence of large and deep cyclonic vortices that create a wider surf zone than for LC1. In contrast, the transport of tropospheric air into the stratosphere is nearly identical between the two life cycles. The mass of boundary layer air uplifted into the free troposphere is similar for both life cycles, but much more is directly injected into the stratosphere in the case of LC1 (fourfold, approximately). However, the total mixing of boundary layer with stratospheric air is larger for LC2, owing to the presence of the deep cyclonic vortices that entrain and mix both boundary layer air from the surface and stratospheric air from the upper levels. For LC1, boundary layer and stratospheric air are brought together by smaller cyclonic structures that develop on the poleward side of the jet in the lower part of the middleworld, resulting in correspondingly weaker mixing. As both the El Niño-Southern Oscillation and the North Atlantic Oscillation are correlated with the relative frequency of life cycle behaviors, corresponding changes in chemical transport and mixing are to be expected

Technical Note: Adjoint formulation of the TOMCAT atmospheric transport scheme in the Eulerian backtracking framework (RETRO-TOM)

A new methodology for the formulation of an adjoint to the transport component of the chemistry transport model TOMCAT is described and implemented in a new model, RETRO-TOM. The Eulerian backtracking method is used, allowing the forward advection scheme (Prather's second-order moments) to be efficiently exploited in the backward adjoint calculations. Prather's scheme is shown to be time symmetric, suggesting the possibility of high accuracy. To attain this accuracy, however, it is necessary to make a careful treatment of the "density inconsistency" problem inherent to offline transport models. The results are verified using a series of test experiments. These demonstrate the high accuracy of RETRO-TOM when compared with direct forward sensitivity calculations, at least for problems in which flux limiters in the advection scheme are not required. RETRO-TOM therefore combines the flexibility and stability of a "finite difference of adjoint" formulation with the accuracy of an "adjoint of finite difference" formulation

Birds of the Indigirka River Delta, Russia: Historical and Biogeographic Comparisons

We documented the breeding status and relative abundance of all avian species on the coastal portion of the Indigirka River Delta during spring and summer 1993-95. Data on avifaunal composition were then compared to data from adjacent areas from Eastern Siberia to the Chukotka Peninsula to evaluate how species composition changes longitudinally within the arctic and typical tundra zones of northern Russia. We recorded 63 species on the Indigirka River Delta, 37 (58.7%) of which were confirmed breeders during at least one of the three years. Five new species were recorded breeding (Arenaria interpres, Calidris acuminata, Limnodromus scolopaceus, Stercorarius parasiticus, and Asio flammeus), and 13 previously unrecorded species were observed during this study. We also identified several species of rare or threatened status in Russia and North America, including Branta bernicla, Somateria fischeri, Polysticta stelleri, and Rhodostethia rosea. We used parsimony and distance matrix methods to compare the breeding species richness on the Indigirka River Delta to that of six other Russian Arctic areas. Biogeographic comparisons revealed the presence of two clades in the Russian Arctic: the Lena River Delta east to Chaun Delta and the Chukotka Peninsula.Durant le printemps et l'été de 1993-95, on a documenté le statut de reproducteurs ainsi que l'abondance relative de toutes les espèces aviaires dans la partie littorale du delta de l'Indigirka. On a ensuite comparé les données sur la composition aviaire à des données provenant de régions contiguës allant de la Sibérie orientale à la péninsule Tchoukotka, en vue d'évaluer la façon dont la composition des espèces évolue longitudinalement à l'intérieur des zones arctiques et des zones typiques de la toundra de la Russie septentrionale. On a enregistré 63 espèces dans le delta de l'Indigirka, dont 37 (58,7 p. cent) étaient des reproducteurs durant au moins une des trois années. On a enregistré cinq nouvelles espèces reproductrices (Arenaria interpres, Calidris acuminata, Limnodromus scolopaceus, Stercocarius parasiticus et Asio flammeus), et, au cours de l'étude, on a observé 13 espèces qui n'avaient jamais été relevées auparavant. On a aussi identifié plusieurs espèces classées rares ou menacées en Russie et en Amérique du Nord, y compris Branta bernicla, Somateria fischeri, Polysticta stelleri et Rhodostethia rosea. On a employé les méthodes de parcimonie et de matrices de distance pour comparer la diversité des espèces reproductrices présentes dans le delta de l'Indigirka avec six autres régions arctiques de Russie. Les comparaisons biogéographiques ont révélé la présence de deux clades dans l'Arctique russe: le delta de la Lena à l'est jusqu'au delta du fleuve Chaun, et la péninsule Tchoukotka

Positionally dependent ^(15)N fraction factors in the UV photolysis of N_2O determined by high resolution FTIR spectroscopy

Positionally dependent fractionation factors for the photolysis of isotopomers of N_2O in natural abundance have been determined by high resolution FTIR spectroscopy at three photolysis wavelengths. Fractionation factors show clear 15N position and photolysis wavelength dependence and are in qualitative agreement with theoretical models but are twice as large. The fractionation factors increase with photolysis wavelength from 193 to 211 nm, with the fractionation factors at 207.6 nm for ^(14)N^(15)N^916)O, ^(15)N^(14)N^(16)O and ^(14)N^(14)N^(18)O equal to −66.5±5‰,−27.1±6‰ and −49±10‰, respectively

The Antarctic Stratospheric Sudden Warming of 2002: A Self-Tuned Resonance?

The extraordinary Antarctic stratospheric warming event of 2002 was characterized by a remarkable vertical structure, with the vortex observed to divide at upper levels in the stratosphere but not at lower levels: such ‘partially’ split vortex events are relatively rare. A simple, yet fully three-dimensional, model is constructed to investigate the dynamics of this unique event. Planetary waves are excited on the model vortex edge by a lower boundary forcing characterized by two parameters: an amplitude hF and a frequency ωF, measured relative to a stationary frame. For realistic forcing amplitudes, a partial vortex split resembling that observed during the 2002 event is found only within a specific, narrow band of forcing frequencies. Exploiting the relative simplicity of our model, these frequencies are shown to be those causing a ‘self-tuning’ resonant excitation of the gravest linear mode, during which nonlinear feedback causes an initially off-resonant forcing to approach resonance

A quantitative analysis of grid-related systematic errors in oxidising capacity and ozone production rates in chemistry transport models

Limited resolution in chemistry transport models (CTMs) is necessarily associated with systematic errors in the calculated chemistry, due to the artificial mixing of species on the scale of the model grid (grid-averaging). Here, the errors in calculated hydroxyl radical (OH) concentrations and ozone production rates 3 are investigated quantitatively using both direct observations and model results. Photochemical steady-state models of radical chemistry are exploited in each case to examine the effect on both OH and 3 of averaging relatively long-lived precursor species, such as O3, NOx, CO, H2O, etc. over different spatial scales. Changes in modelled 3 are estimated, independently of other model errors, by calculating the systematic effect of spatial averaging on the ozone production efficiency 1, defined as the ratio of ozone molecules produced per NOx molecule destroyed. Firstly, an investigation of in-flight measurements suggests that, at least in the northern midlatitude upper-troposphere/lower stratosphere, averaging precursor species on the scale of a T42 grid (2.75° x 2.75°) leads to a 15-20% increase in OH concentrations and a 5-10% increase in 1. Secondly, results from CTM model experiments are compared at different horizontal resolutions. Low resolution experiments are found to have significantly higher [OH] and 3 compared with high resolution experiments. The extent to which these differences may be explained by the systematic error in the model chemistry associated with grid size is estimated by degrading the high resolution data onto a low resolution grid and then recalculating 1 and [OH]. The change in calculated 1 is found to be significant and can account for much of the difference in 3 between the high and low resolution experiments. The calculated change in [OH] is less than the difference in [OH] found between the experiments, although the shortfall is likely to be due to the indirect effect of the change in modelled NOx, which is not accounted for in the calculation. It is argued that systematic errors caused by limited resolution need to be considered when evaluating the relative impacts of different pollutant sources on tropospheric ozone

Computer vision tools for the non-invasive assessment of autism-related behavioral markers

The early detection of developmental disorders is key to child outcome, allowing interventions to be initiated that promote development and improve prognosis. Research on autism spectrum disorder (ASD) suggests behavioral markers can be observed late in the first year of life. Many of these studies involved extensive frame-by-frame video observation and analysis of a child's natural behavior. Although non-intrusive, these methods are extremely time-intensive and require a high level of observer training; thus, they are impractical for clinical and large population research purposes. Diagnostic measures for ASD are available for infants but are only accurate when used by specialists experienced in early diagnosis. This work is a first milestone in a long-term multidisciplinary project that aims at helping clinicians and general practitioners accomplish this early detection/measurement task automatically. We focus on providing computer vision tools to measure and identify ASD behavioral markers based on components of the Autism Observation Scale for Infants (AOSI). In particular, we develop algorithms to measure three critical AOSI activities that assess visual attention. We augment these AOSI activities with an additional test that analyzes asymmetrical patterns in unsupported gait. The first set of algorithms involves assessing head motion by tracking facial features, while the gait analysis relies on joint foreground segmentation and 2D body pose estimation in video. We show results that provide insightful knowledge to augment the clinician's behavioral observations obtained from real in-clinic assessments

MRI scans significantly change target coverage decisions in radical radiotherapy for prostate cancer

INTRODUCTION: Conventional clinical staging for prostate cancer has many limitations. This study evaluates the impact of adding MRI scans to conventional clinical staging for guiding decisions about radiotherapy target coverage. METHODS: This was a retrospective review of 115 patients who were treated between February 2002 and September 2005 with radical radiotherapy for prostate cancer. All patients had MRI scans approximately 2 weeks before the initiation of radiotherapy. The T stage was assessed by both conventional clinical methods (cT-staging) as well as by MRI (mT-staging). The radiotherapy target volumes were determined first based on cT-staging and then taking the additional mT staging into account. The number of times extracapsular extension or seminal vesicle invasion was incorporated into target volumes was quantified based on both cT-staging and the additional mT-staging. RESULTS: Extracapsular extension was incorporated into target volumes significantly more often with the addition of mT-staging (46 patients (40%) ) compared with cT-staging alone (37 patients (32%) ) (P = 0.002). Seminal vesicle invasion was incorporated into target volumes significantly more often with the addition of mT-staging (21 patients (18%) ) compared with cT-staging alone (three patients (3%) ) (P < 0.001). A total of 23 patients (20%) had changes to their target coverage based on the mT-staging. CONCLUSIONS: MRI scans can significantly change decisions about target coverage in radical radiotherapy for prostate cancer.Joe H. Chang, Daryl Lim Joon, Brandon T. Nguyen, Chee-Yan Hiew, Stephen Esler, David Angus, Michael Chao, Morikatsu Wada, George Quong, and Vincent Kho