This paper investigates the effect of fine‐scale spatial variability in carbon fluxes upon regional carbon flux inversion estimates in North America using simulated data from 1 May through 31 August ...2004 and a hypothetical sparse network of eight towers in North America. A suite of random smooth regional carbon flux patterns are created and then obscured with random fine‐scale spatial flux “noise” to mimic the effect of fine‐scale heterogeneity in carbon fluxes found in nature. Five hundred and forty grid‐scale atmospheric inversions are run using the synthetic data. We find that, regardless of the particular fine spatial scale carbon fluxes used (noise), the inversions can improve a priori carbon flux estimates significantly by capturing the large‐scale regional flux patterns. We also find significant improvement in the root‐mean‐square error of the model are possible across a wide range of spatial decorrelation length scales. Errors associated with the inversion decrease as estimates are sought for larger and larger areas. Results show dramatic differences between postaggregated fine‐scale inversion results and preaggregated coarse‐scale inversion results confirming recent warnings about the “preaggregation” of inversion regions.
We present a detailed investigation of the gross 12C and 13C exchanges between the atmosphere and biosphere and their influence on the δ13C variations in the atmosphere. The photosynthetic ...discrimination Δ against 13C is derived from a biophysical model coupled to a general circulation model Sellers et al., 1996a, where stomatal conductance and carbon assimilation are determined simultaneously with the ambient climate. The δ13C of the respired carbon is calculated by a biogeochemical model Potter et al., 1993; Randerson et al., 1996 as the sum of the contributions from compartments with varying ages. The global flux‐weighted mean photosynthetic discrimination is 12–16‰, which is lower than previous estimates. Factors that lower the discrimination are reduced stomatal conductance and C4 photosynthesis. The decreasing atmospheric δ13C causes an isotopic disequilibrium between the outgoing and incoming fluxes; the disequilibrium is ∼0.33‰ for 1988. The disequilibrium is higher than previous estimates because it accounts for the lifetime of trees and for the ages rather than turnover times of the biospheric pools. The atmospheric δ13C signature resulting from the biospheric fluxes is investigated using a three‐dimensional atmospheric tracer model. The isotopic disequilibrium alone produces a hemispheric difference of ∼0.02‰ in atmospheric δ13C, comparable to the signal from a hypothetical carbon sink of 0.5 Gt C yr−1 into the midlatitude northern hemisphere biosphere. However, the rectifier effect, due to the seasonal covariation of CO2 fluxes and height of the atmospheric boundary layer, yields a background δ13C gradient of the opposite sign. These effects nearly cancel thus favoring a stronger net biospheric uptake than without the background CO2 gradient. Our analysis of the globally averaged carbon budget for the decade of the 1980s indicates that the biospheric uptake of fossil fuel CO2 is likely to be greater than the oceanic uptake; the relative proportions of the sinks cannot be uniquely determined using 12C and 13C alone. The land‐ocean sink partitioning requires, in addition, information about the land use source, isotopic disequilibrium associated with gross oceanic exchanges, as well as the fractions of C3 and C4 vegetation involved in the biospheric uptake.
The purpose of this study was to compare the reliability of triplane fracture classification, displacement measurement, and treatment planning with the use of radiographs with and without computed ...tomography.
One pediatric radiologist, one musculoskeletal radiologist, and three fellowship-trained pediatric orthopaedic surgeons rated a spectrum of twenty-five triplane fractures with use of radiographs alone and then with computed tomography scans on two separate occasions (two to four weeks apart). Raters classified the fracture pattern with use of the Rapariz classification system, measured the maximum intra-articular displacement, and drew the fracture on four outlines of the distal part of the tibia: one lateral view, one anteroposterior view, one axial view above the tibial physis, and one axial view below the physis. Reliability was assessed with kappa values and intraclass correlation coefficients.
The Rapariz triplane fracture classification had poor inter-rater reliability (a kappa of 0.17) and intra-rater reliability (a kappa of 0.31) with radiographs alone but moderate inter-rater reliability (a kappa of 0.41) and intra-rater reliability (a kappa of 0.54) with the addition of computed tomography. After reviewing computed tomography, raters changed the fracture pattern in 46% of ratings, the displacement from ≤2 mm to >2 mm in 39% of ratings, the treatment from nonoperative to operative in 27% of ratings, and either the orientation or number of screws in 41% of ratings.
Computed tomography had a definite impact on the fracture classification, displacement, and treatment plan, supporting its use as an adjunct to radiographs for the treatment of pediatric triplane fractures.
This paper overviews the short‐term (biophysical) and long‐term (out to around 100 year timescales; biogeochemical and biogeographical) influences of the land surface on weather and climate. From our ...review of the literature, the evidence is convincing that terrestrial ecosystem dynamics on these timescales significantly influence atmospheric processes. In studies of past and possible future climate change, terrestrial ecosystem dynamics are as important as changes in atmospheric dynamics and composition, ocean circulation, ice sheet extent, and orbit perturbations.
A forward atmospheric transport modeling experiment has been coordinated by the TransCom group to investigate synoptic and diurnal variations in CO2. Model simulations were run for biospheric, ...fossil, and air‐sea exchange of CO2 and for SF6 and radon for 2000–2003. Twenty‐five models or model variants participated in the comparison. Hourly concentration time series were submitted for 280 sites along with vertical profiles, fluxes, and meteorological variables at 100 sites. The submitted results have been analyzed for diurnal variations and are compared with observed CO2 in 2002. Mean summer diurnal cycles vary widely in amplitude across models. The choice of sampling location and model level account for part of the spread suggesting that representation errors in these types of models are potentially large. Despite the model spread, most models simulate the relative variation in diurnal amplitude between sites reasonably well. The modeled diurnal amplitude only shows a weak relationship with vertical resolution across models; differences in near‐surface transport simulation appear to play a major role. Examples are also presented where there is evidence that the models show useful skill in simulating seasonal and synoptic changes in diurnal amplitude.
Ecosystem CO2 exchange and atmosphere boundary layer (ABL) mixing are correlated diurnally and seasonally as they are both driven by solar insulation. Tracer transport models predict that these ...covariance signals produce a meridional gradient of annual mean CO2 concentration in the marine boundary layer that is half as strong as the signal produced by fossil fuel emissions. This rectifier effect is simulated by most global tracer transport models. However, observations to constrain the strength of these covariance signals in nature are lacking. We investigate the covariance between ecosystem carbon dioxide exchange and ABL dynamics by comparing one widely cited transport model with observations in the middle of the North American continent. We measured CO2 flux and mixing ratio using an eddy‐covariance system from a 447‐m tower in northern Wisconsin, mixed layer depths using a 915‐MHz boundary layer profiling radar near the tower, and vertical CO2 profiles from aircraft in the vicinity of the tower. We find (1) that simulated and observed net daily CO2 fluxes are similar; (2) the simulated maximum ABL depths were too shallow throughout year; (3) the simulated seasonal variability of the CO2 mixing ratio in the lowest layer of the free troposphere is 3 ppm smaller than that inferred from a mixed layer jump model and boundary layer observations; and (4) the simulated diurnal and seasonal covariance between CO2 flux and mixing ratio are weaker than the observed covariance. The comparison between model and observations is limited by the questionable representativeness of a single observing site and a bias towards fair weather observing conditions.
Pseudomonas aeruginosa secretes numerous factors that alter host cell function and may contribute to disease pathogenesis. Among recognized virulence factors is the redox-active phenazine pyocyanin. ...We have recently demonstrated that the precursor for pyocyanin, phenazine-1-carboxylic acid (PCA), increases oxidant formation and alters gene expression in human airway epithelial cells. We report in this work that PCA and pyocyanin increase expression of ICAM-1 both in vivo and in vitro. Moreover, phenazines enhanced cytokine-dependent increases in IL-8 and ICAM-1. Antioxidant intervention studies indicated both similarities and differences between PCA and pyocyanin. The thiol antioxidant N-acetyl cysteine, extracellular catalase, and inducible NO synthase inhibitors inhibited ICAM-1 and IL-8 increases in response to both phenazines. However, pyocyanin was significantly more sensitive to N-acetylcysteine inhibition. Interestingly, hydroxyl radical scavengers inhibited the response to pyocyanin, but not to PCA. These studies suggest that P. aeruginosa phenazines coordinately up-regulate chemokines (IL-8) and adhesion molecules (ICAM-1) by mechanisms that are, at least in part, oxidant dependent. However, results indicate that the mechanisms by which PCA and pyocyanin exert their effects are not identical, and not all antioxidant interventions are equally effective in inhibiting phenazine-mediated proinflammatory effects.
Variations of atmospheric CO2 at regional scales are becoming increasingly important in understanding regional carbon budgets, yet the processes that drive them remain relatively unexplored. A ...simulation was conducted to test a coupled biosphere‐atmospheric model (SiB2‐RAMS), by comparing with measurements made at the WLEF‐TV tower in Wisconsin, and to investigate some of the mechanisms leading to CO2 variability, both on local and regional scales. The simulation was run for a 5‐day period from 26 to 30 July 1997. Multiple nested grids were employed, which enabled mesoscale features to be simulated and which resolved small‐scale features in the vicinity of the WLEF tower. In many respects the model was successful at simulating observed meteorological variables and CO2 fluxes and concentrations. The two most significant deficiencies were that excessive nighttime cooling occurred on two of the nights and that late afternoon uptake of CO2 was larger than observed. Results of the simulation suggest that in addition to biological processes causing variations in CO2 concentrations at the WLEF site other factors, such as small nearby lakes, turbulence induced by vertical wind shear, boundary layer thermals, and clouds, also had significant impacts. These factors add to the difficulty of interpreting CO2 measurements. Regional‐scale patterns of CO2 variability caused by meteorological processes were also identified. Katabatic winds had a significant effect by causing respired CO2 to pool in valleys and along the shores of the Great Lakes during the night. Furthermore, a large diurnal cycle of CO2 concentration occurred over the lakes, which appeared to be mainly due to the combined action of katabatic winds, ambient winds, and the lake breeze circulation. These results suggest that meteorological processes associated with the complex terrain in this region leads to substantial CO2 advection. Therefore meteorological as well as biological processes are likely to be important causes of regional‐scale CO2 variability in the Great Lakes region. A sensitivity test conducted to examine the differences between using a turbulent kinetic energy based subgrid‐scale scheme versus a deformation‐type subgrid‐scale scheme showed advantages and disadvantages to both approaches. Our results suggest that continuous records of CO2 variability measured over heterogeneous continental regions must be interpreted with caution because of the impact of mesoscale circulations on the concentration time series.
Amphotericin B has been the standard therapy for invasive aspergillosis since its introduction in 1957. It is only moderately effective. Many susceptibility tests have been used but little variation ...has been noted between strains. We have studied three strains of Aspergillus fumigatusand one of Aspergillus terreusin a neutropenic mouse model of invasive aspergillosis and attempted to correlate the variable efficacy in vivowith MICs generated by over 30 different susceptibility test formats. One strain of A. fumigatus(AF65) and the strain of A. terreus(AT49) were 'resistant' and the remaining two strains of A. fumigatus(AF210 and AF294) were 'susceptible' in vivo. Only AT49 had elevated MICs of amphotericin (MIC 2 mg/L) by 41 of 54 in vitrotesting systems. With each test format, including Etest, there was no distinction between MICs obtained for AF65, AF210 and AF294 (MICs 0.125-64 mg/L depending on the test). Thus despite extensive efforts we have been unable to correlate susceptible test results with in vivooutcome in A. fumigatusbut we have with A. terreus, with some test formats. This suggests that, at present, amphotericin B susceptibility testing of A. fumigatus is of limited clinical value and further work needs to be done to find testing systems that can identify the 'resistance' documented in vivo.
The desmosome is a highly organized plasma membrane domain that couples intermediate filaments to the plasma membrane at regions of cell-cell adhesion. Desmosomes contain two classes of cadherins, ...desmogleins, and desmocollins, that bind to the cytoplasmic protein plakoglobin. Desmoplakin is a desmosomal component that plays a critical role in linking intermediate filament networks to the desmosomal plaque, and the amino-terminal domain of desmoplakin targets desmoplakin to the desmosome. However, the desmosomal protein(s) that bind the amino-terminal domain of desmoplakin have not been identified. To determine if the desmosomal cadherins and plakoglobin interact with the amino-terminal domain of desmoplakin, these proteins were co-expressed in L-cell fibroblasts, cells that do not normally express desmosomal components. When expressed in L-cells, the desmosomal cadherins and plakoglobin exhibited a diffuse distribution. However, in the presence of an amino-terminal desmoplakin polypeptide (DP-NTP), the desmosomal cadherins and plakoglobin were observed in punctate clusters that also contained DP-NTP. In addition, plakoglobin and DP-NTP were recruited to cell-cell interfaces in L-cells co-expressing a chimeric cadherin with the E-cadherin extracellular domain and the desmoglein-1 cytoplasmic domain, and these cells formed structures that were ultrastructurally similar to the outer plaque of the desmosome. In transient expression experiments in COS cells, the recruitment of DP-NTP to cell borders by the chimera required co-expression of plakoglobin. Plakoglobin and DP-NTP co-immunoprecipitated when extracted from L-cells, and yeast two hybrid analysis indicated that DP-NTP binds directly to plakoglobin but not Dsg1. These results identify a role for desmoplakin in organizing the desmosomal cadherin-plakoglobin complex and provide new insights into the hierarchy of protein interactions that occur in the desmosomal plaque.
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