Error estimate and control in the MSFV method for multiphase flow in porous media

n this paper the iterative MSFV method is extended to include the sequential implicit simulation of time dependent problems involving the solution of a system of pressure-saturation equations. To control numerical errors in simulation results, an error estimate, based on the residual of the MSFV approximate pressure field, is introduced. In the initial time steps in simulation iterations are employed until a specified accuracy in pressure is achieved. This initial solution is then used to improve the localization assumption at later time steps. Additional iterations in pressure solution are employed only when the pressure residual becomes larger than a specified threshold value. Efficiency of the strategy and the error control criteria are numerically investigated. This paper also shows that it is possible to derive an a-priori estimate and control based on the allowed pressure-equation residual to guarantee the desired accuracy in saturation calculation.

Perfusion ct based thrombolysis in acute ischaemic stroke

Background Despite use in clinical practice and trials of thrombolysis, a non-contrast CT is not sensitive for identifying penumbral tissue in acute stroke. This study evaluated how it compares with physiological imaging using CT perfusion.Methods 40 imaging datasets with non-contrast CT (NCCT) and perfusion CT (CTP) were retrospectively identified. 2 sets of observers (n¼6) and a neuroradiologist made a blind evaluation of the images. Inter-observer agreement was calculated for identifying ischaemic change on NCCT, and abnormalities on cerebral blood flow, time to peak and cerebral blood volume maps. A prospective cohort of 73 patients with anterior circulation cortical strokes were thrombolysed based on qualitative assessment of penumbral tissue on CTP within 3 h of stroke onset. Functional outcome was assessed at 3 months.Results Inter-rater agreement was moderate (k¼0.54) for early ischaemic change on NCCT. Perfusion maps improved this to substantial for deficit in cerebral blood volume (k¼0.67) and almost perfect for time to peak and cerebral blood flow (both k¼0.87). In the prospective arm, 58.9% of patients with cortical strokes were thrombolysed. There was no significant difference in attainment of complete recovery (p¼0.184) between the thrombolysed and nonthrombolysed group.Conclusions We demonstrate how perfusion CT aids clinical decision- making in acute stroke. Good functional outcomes from thrombolysis can be safely achieved using this physiologically informed approach.

Performance of an ICU ventilator and two turbin-based ventilators dedicated to non invasive ventilation (NIV) in simulated high inspiratory effort and rate: a NIV-bench-study.

INTRODUCTION. The role of turbine-based NIV ventilators (TBV) versus ICU ventilators with NIV mode activated (ICUV) to deliver NIV in case of severe respiratory failure remains debated. OBJECTIVES. To compare the response time and pressurization capacity of TBV and ICUV during simulated NIV with normal and increased respiratory demand, in condition of normal and obstructive respiratory mechanics. METHODS. In a two-chamber lung model, a ventilator simulated normal (P0.1 = 2 mbar, respiratory rate RR = 15/min) or increased (P0.1 = 6 mbar, RR = 25/min) respiratory demand. NIV was simulated by connecting the lung model (compliance 100 ml/mbar; resistance 5 or 20 l/mbar) to a dummy head equipped with a naso-buccal mask. Connections allowed intentional leaks (29 ± 5 % of insufflated volume). Ventilators to test: Servo-i (Maquet), V60 and Vision (Philips Respironics) were connected via a standard circuit to the mask. Applied pressure support levels (PSL) were 7 mbar for normal and 14 mbar for increased demand. Airway pressure and flow were measured in the ventilator circuit and in the simulated airway. Ventilator performance was assessed by determining trigger delay (Td, ms), pressure time product at 300 ms (PTP300, mbar s) and inspiratory tidal volume (VT, ml) and compared by three-way ANOVA for the effect of inspiratory effort, resistance and the ventilator. Differences between ventilators for each condition were tested by oneway ANOVA and contrast (JMP 8.0.1, p\0.05). RESULTS. Inspiratory demand and resistance had a significant effect throughout all comparisons. Ventilator data figure in Table 1 (normal demand) and 2 (increased demand): (a) different from Servo-i, (b) different from V60.CONCLUSION. In this NIV bench study, with leaks, trigger delay was shorter for TBV with normal respiratory demand. By contrast, it was shorter for ICUV when respiratory demand was high. ICUV afforded better pressurization (PTP 300) with increased demand and PSL, particularly with increased resistance. TBV provided a higher inspiratory VT (i.e., downstream from the leaks) with normal demand, and a significantly (although minimally) lower VT with increased demand and PSL.

Fluid flow regulates stromal cell organization and CCL21 expression in a tissue-engineered lymph node microenvironment.

In the paracortex of the lymph node (LN), T zone fibroblastic reticular cells (TRCs) orchestrate an immune response by guiding lymphocyte migration both physically, by creating three-dimensional (3D) cell networks, and chemically, by secreting the chemokines CCL19 and CCL21 that direct interactions between CCR7-expressing cells, including mature dendritic cells and naive T cells. TRCs also enwrap matrix-based conduits that transport fluid from the subcapsular sinus to high endothelial venules, and fluid flow through the draining LN rapidly increases upon tissue injury or inflammation. To determine whether fluid flow affects TRC organization or function within a 3D network, we regenerated the 3D LN T zone stromal network by culturing murine TRC clones within a macroporous polyurethane scaffold containing type I collagen and Matrigel and applying slow interstitial flow (1-23 microm/min). We show that the 3D environment and slow interstitial flow are important regulators of TRC morphology, organization, and CCL21 secretion. Without flow, CCL21 expression could not be detected. Furthermore, when flow through the LN was blocked in mice in vivo, CCL21 gene expression was down-regulated within 2 h. These results highlight the importance of lymph flow as a homeostatic regulator of constitutive TRC activity and introduce the concept that increased lymph flow may act as an early inflammatory cue to enhance CCL21 expression by TRCs, thereby ensuring efficient immune cell trafficking, lymph sampling, and immune response induction.

Debris flow hazard modelling on medium scale: Valtellina di Tirano, Italy

Debris flow hazard modelling at medium (regional) scale has been subject of various studies in recent years. In this study, hazard zonation was carried out, incorporating information about debris flow initiation probability (spatial and temporal), and the delimitation of the potential runout areas. Debris flow hazard zonation was carried out in the area of the Consortium of Mountain Municipalities of Valtellina di Tirano (Central Alps, Italy). The complexity of the phenomenon, the scale of the study, the variability of local conditioning factors, and the lacking data limited the use of process-based models for the runout zone delimitation. Firstly, a map of hazard initiation probabilities was prepared for the study area, based on the available susceptibility zoning information, and the analysis of two sets of aerial photographs for the temporal probability estimation. Afterwards, the hazard initiation map was used as one of the inputs for an empirical GIS-based model (Flow-R), developed at the University of Lausanne (Switzerland). An estimation of the debris flow magnitude was neglected as the main aim of the analysis was to prepare a debris flow hazard map at medium scale. A digital elevation model, with a 10 m resolution, was used together with landuse, geology and debris flow hazard initiation maps as inputs of the Flow-R model to restrict potential areas within each hazard initiation probability class to locations where debris flows are most likely to initiate. Afterwards, runout areas were calculated using multiple flow direction and energy based algorithms. Maximum probable runout zones were calibrated using documented past events and aerial photographs. Finally, two debris flow hazard maps were prepared. The first simply delimits five hazard zones, while the second incorporates the information about debris flow spreading direction probabilities, showing areas more likely to be affected by future debris flows. Limitations of the modelling arise mainly from the models applied and analysis scale, which are neglecting local controlling factors of debris flow hazard. The presented approach of debris flow hazard analysis, associating automatic detection of the source areas and a simple assessment of the debris flow spreading, provided results for consequent hazard and risk studies. However, for the validation and transferability of the parameters and results to other study areas, more testing is needed.

Flow-R, a model for susceptibility mapping of debris flows and other gravitational hazards at a regional scale: some case studies

Every year, debris flows cause huge damage in mountainous areas. Due to population pressure in hazardous zones, the socio-economic impact is much higher than in the past. Therefore, the development of indicative susceptibility hazard maps is of primary importance, particularly in developing countries. However, the complexity of the phenomenon and the variability of local controlling factors limit the use of processbased models for a first assessment. A debris flow model has been developed for regional susceptibility assessments using digital elevation model (DEM) with a GIS-based approach.. The automatic identification of source areas and the estimation of debris flow spreading, based on GIS tools, provide a substantial basis for a preliminary susceptibility assessment at a regional scale. One of the main advantages of this model is its workability. In fact, everything is open to the user, from the data choice to the selection of the algorithms and their parameters. The Flow-R model was tested in three different contexts: two in Switzerland and one in Pakistan, for indicative susceptibility hazard mapping. It was shown that the quality of the DEM is the most important parameter to obtain reliable results for propagation, but also to identify the potential debris flows sources.

Risk-based modelling of diffuse land use impacts from rural landscapes upon salmonid fry abundance

Research has demonstrated that landscape or watershed scale processes can influence instream aquatic ecosystems, in terms of the impacts of delivery of fine sediment, solutes and organic matter. Testing such impacts upon populations of organisms (i.e. at the catchment scale) has not proven straightforward and differences have emerged in the conclusions reached. This is: (1) partly because different studies have focused upon different scales of enquiry; but also (2) because the emphasis upon upstream land cover has rarely addressed the extent to which such land covers are hydrologically connected, and hence able to deliver diffuse pollution, to the drainage network However, there is a third issue. In order to develop suitable hydrological models, we need to conceptualise the process cascade. To do this, we need to know what matters to the organism being impacted by the hydrological system, such that we can identify which processes need to be modelled. Acquiring such knowledge is not easy, especially for organisms like fish that might occupy very different locations in the river over relatively short periods of time. However, and inevitably, hydrological modellers have started by building up piecemeal the aspects of the problem that we think matter to fish. Herein, we report two developments: (a) for the case of sediment associated diffuse pollution from agriculture, a risk-based modelling framework, SCIMAP, has been developed, which is distinct because it has an explicit focus upon hydrological connectivity; and (b) we use spatially distributed ecological data to infer the processes and the associated process parameters that matter to salmonid fry. We apply the model to spatially distributed salmon and fry data from the River Eden, Cumbria, England. The analysis shows, quite surprisingly, that arable land covers are relatively unimportant as drivers of fry abundance. What matters most is intensive pasture, a land cover that could be associated with a number of stressors on salmonid fry (e.g. pesticides, fine sediment) and which allows us to identify a series of risky field locations, where this land cover is readily connected to the river system by overland flow. (C) 2010 Elsevier B.V. All rights reserved.

Using flow cytometry for in situ monitoring of antimicrobial compound production in the biocontrol bacterium Pseudomonas fluorescens CHA0.

Pseudomonas fluorescens strain CHA0 is able to protect plants against a variety of pathogens, notably by producing the two antimicrobial compounds 2,4-diacetylphloroglucinol (DAPG) and pyoluteorin (PLT). The regulation of the expression of these compounds is affected by many biotic factors, such as fungal pathogens, rhizosphere bacteria as well as plant species. Therefore, the influence of some plant phenolic compounds on the expression of DAPG and PLT biosynthetic genes has been tested using GFP-based reporter, monitored by standard fluometry and flow cytometry. In situ experiments were also performed with cucumber plants. We found that several plant metabolites such as IAA and umbelliferone are able to modify significantly the expression of DAPG and PLT. The use of flow cytometry with autofluorescents proteins seems to be a promising method to study rhizobacteria-plant interactions.

Artificial neural network study of whole-cell bacterial bioreporter response determined using fluorescence flow cytometry.

Genetically engineered bioreporters are an excellent complement to traditional methods of chemical analysis. The application of fluorescence flow cytometry to detection of bioreporter response enables rapid and efficient characterization of bacterial bioreporter population response on a single-cell basis. In the present study, intrapopulation response variability was used to obtain higher analytical sensitivity and precision. We have analyzed flow cytometric data for an arsenic-sensitive bacterial bioreporter using an artificial neural network-based adaptive clustering approach (a single-layer perceptron model). Results for this approach are far superior to other methods that we have applied to this fluorescent bioreporter (e.g., the arsenic detection limit is 0.01 microM, substantially lower than for other detection methods/algorithms). The approach is highly efficient computationally and can be implemented on a real-time basis, thus having potential for future development of high-throughput screening applications.

Coronary vasomotor control in obesity and morbid obesity: contrasting flow responses with endocannabinoids, leptin, and inflammation.

OBJECTIVES: This study sought to investigate abnormalities in coronary circulatory function in 2 different disease entities of obese (OB) and morbidly obese (MOB) individuals and to evaluate whether these would differ in severity with different profiles of endocannabinoids, leptin, and C-reactive protein (CRP) plasma levels. BACKGROUND: There is increasing evidence that altered plasma levels of endocannabinoids, leptin, and CRP may affect coronary circulatory function in OB and MOB. METHODS: Myocardial blood flow (MBF) responses to cold pressor test from rest and during pharmacologically induced hyperemia were measured with N-13 ammonia positron emission tomography/computed tomography. Study participants (n = 111) were divided into 4 groups based on their body mass index (BMI) (kg/m(2)): 1) control group (BMI: 20 to 24.9, n = 30); 2) overweight group (BMI: 25 to 29.9, n = 31), 3) OB group (BMI: 30 to 39.9, n = 25); and 4) MOB group (BMI ≥40, n = 25). RESULTS: The cold pressor test-induced change in endothelium-related MBF response (ΔMBF) progressively declined in overweight and OB groups when compared with the control group [median: 0.19 (interquartile range [IQR] 0.08, 0.27) and 0.11 (0.03, 0.17) vs. 0.27 (0.23, 0.38) ml/g/min; p ≤ 0.01, respectively], whereas it did not differ significantly between OB and MOB groups [median: 0.11 (IQR: 0.03, 0.17) and 0.09 (-0.01, 0.19) ml/g/min; p = 0.93]. Compared with control subjects, hyperemic MBF subjects comparably declined in the overweight, OB, and MOB groups [median: 2.40 (IQR 1.92, 2.63) vs. 1.94 (1.65, 2.30), 2.05 (1.67, 2.38), and 2.14 (1.78, 2.76) ml/g/min; p ≤ 0.05, respectively]. In OB individuals, ΔMBF was inversely correlated with increase in endocannabinoid anandamide (r = -0.45, p = 0.044), but not with leptin (r = -0.02, p = 0.946) or with CRP (r = -0.33, p = 0.168). Conversely, there was a significant and positive correlation among ΔMBF and elevated leptin (r = 0.43, p = 0.031) and CRP (r = 0.55, p = 0.006), respectively, in MOB individuals that was not observed for endocannabinoid anandamide (r = 0.07, p = 0.740). CONCLUSIONS: Contrasting associations of altered coronary endothelial function with increases in endocannabinoid anandamide, leptin, and CRP plasma levels identify and characterize OB and MOB as different disease entities affecting coronary circulatory function.

Methods for the ex vivo characterization of human CD8+ T subsets based on gene expression and replicative history analysis.

The generation of an antigen-specific T-lymphocyte response is a complex multi-step process. Upon T-cell receptor-mediated recognition of antigen presented by activated dendritic cells, naive T-lymphocytes enter a program of proliferation and differentiation, during the course of which they acquire effector functions and may ultimately become memory T-cells. A major goal of modern immunology is to precisely identify and characterize effector and memory T-cell subpopulations that may be most efficient in disease protection. Sensitive methods are required to address these questions in exceedingly low numbers of antigen-specific lymphocytes recovered from clinical samples, and not manipulated in vitro. We have developed new techniques to dissect immune responses against viral or tumor antigens. These allow the isolation of various subsets of antigen-specific T-cells (with major histocompatibility complex [MHC]-peptide multimers and five-color FACS sorting) and the monitoring of gene expression in individual cells (by five-cell reverse transcription-polymerase chain reaction [RT-PCR]). We can also follow their proliferative life history by flow-fluorescence in situ hybridization (FISH) analysis of average telomere length. Recently, using these tools, we have identified subpopulations of CD8+ T-lymphocytes with distinct proliferative history and partial effector-like properties. Our data suggest that these subsets descend from recently activated T-cells and are committed to become differentiated effector T-lymphocytes.

Genetic clusters and sex-biased gene flow in a unicolonial Formica ant.

BACKGROUND: Animal societies are diverse, ranging from small family-based groups to extraordinarily large social networks in which many unrelated individuals interact. At the extreme of this continuum, some ant species form unicolonial populations in which workers and queens can move among multiple interconnected nests without eliciting aggression. Although unicoloniality has been mostly studied in invasive ants, it also occurs in some native non-invasive species. Unicoloniality is commonly associated with very high queen number, which may result in levels of relatedness among nestmates being so low as to raise the question of the maintenance of altruism by kin selection in such systems. However, the actual relatedness among cooperating individuals critically depends on effective dispersal and the ensuing pattern of genetic structuring. In order to better understand the evolution of unicoloniality in native non-invasive ants, we investigated the fine-scale population genetic structure and gene flow in three unicolonial populations of the wood ant F. paralugubris. RESULTS: The analysis of geo-referenced microsatellite genotypes and mitochondrial haplotypes revealed the presence of cryptic clusters of genetically-differentiated nests in the three populations of F. paralugubris. Because of this spatial genetic heterogeneity, members of the same clusters were moderately but significantly related. The comparison of nuclear (microsatellite) and mitochondrial differentiation indicated that effective gene flow was male-biased in all populations. CONCLUSION: The three unicolonial populations exhibited male-biased and mostly local gene flow. The high number of queens per nest, exchanges among neighbouring nests and restricted long-distance gene flow resulted in large clusters of genetically similar nests. The positive relatedness among clustermates suggests that kin selection may still contribute to the maintenance of altruism in unicolonial populations if competition occurs among clusters.

The Effect of Valsartan versus Non-RAAS Treatment on Autoregulation of Cerebral Blood Flow.

Background: Cerebral autoregulation (CA) is a protective mechanism which maintains the steadiness of the cerebral blood flow (CBF) through a broad range of systemic blood pressure (BP). Acute hypertension has been shown to reduce the cerebrovascular adaptation to BP variations. However, it is still unknown whether CA is impaired in chronic hypertension. This study evaluated whether a strict control of BP affects the CA in patients with chronic hypertension, and compared a valsartan-based regimen to a regimen not inhibiting the renin-angiotensin-aldosterone system (non-RAAS). Methods: Eighty untreated patients with isolated systolic hypertension were randomized to valsartan 320 mg or to a non-RAAS regimen during 6 months. The medication was upgraded to obtain BP <140/90 mm Hg. Continuous recordings of arterial BP and CBF velocity (transcranial Doppler) were performed during periods of 5 minutes, at rest, and at different levels of alveolar CO(2) pressure provided by respiratory maneuvers. The dominant frequency of CBF oscillations was determined for each patient. Dynamic CA was measured as the mean phase shift between BP and CBF by cross-spectral analysis in the medium frequency and in the dominant CBF frequency. Results: Mean ambulatory 24-hour BP fell from 144/87 to 127/79 mm Hg in the valsartan group and from 144/87 to 134/81 mm Hg in the non-RAAS group (p = 0.13). Both groups had a similar reduction in the central BP and in the carotido-femoral pulse wave velocity. The average phase shift between BP fluctuations and CBF response at rest was normal at randomization (1.82 ± 0.08 s), which is considered a preserved autoregulation and increased to 1.91 ± 0.12 s at the end of study (p = 0.45). The comparison of both treatments showed no significant difference (-0.01 ± 0.17 s vs. 0.16 ± 0.16 s, p = 0.45) for valsartan versus non-RAAS groups. The plasmatic level of glycosylated hemoglobin decreased in the valsartan arm compared to the non-RAAS arm (-0.23 ± 0.06 vs. -0.08 ± 0.07%, p = 0.07). Conclusions: In elderly hypertensive men with isolated chronic systolic hypertension, CA seems efficient at baseline and is not significantly affected by 6 months of BP-lowering treatment. This suggests that the preventive effects of BP medication against stroke are not mediated through a restoration of the CA.

Incremental Prognostic Value of Myocardial Blood Flow Quantification with Rb-82 Cardiac PET in Patients With Known or Suspected CAD

Rb-82cardiac PET has been used to non-invasively assess myocardial blood flow (MBF)and myocardial flow reserve (MFR). The impact of MBF and MFR for predictingmajor adverse cardiovascular events (MACE) has not been investigated in aprospective study, which was our aim. MATERIAL AND METHODS: In total, 280patients (65±10y, 36% women) with known or suspected CAD were prospectivelyenrolled. They all underwent both a rest and adenosine stress Rb-82 cardiacPET/CT. Dynamic acquisitions were processed with the FlowQuant 2.1.3 softwareand analyzed semi-quantitatively (SSS, SDS) and quantitatively (MBF, MFR) andreported using the 17-segment AHA model. Patients were stratified based on SDS,stress MBF and MFR and allocated into tertiles. For each group, annualizedevent rates were computed by dividing the number of annualized MACE (cardiacdeath, myocardial infarction, revascularisation or hospitalisation forcardiac-related event) by the sum of individual follow-up periods in years.Outcome were analysed for each group using Kaplan-Meier event-free survivalcurves and compared using the log-rank test. Multivariate analysis wasperformed in a stepwise fashion using Cox proportional hazards regressionmodels (p<0.05 for model inclusion). RESULTS: In a median follow-up of 256days (range 168-440d), 44 MACE were observed. Ischemia (SDS≥2) was observed in95 patients who had higher annualized MACE rate as compared to those without(55% vs. 9.8%, p<0.0001). The group with the lowest MFR tertile (MFR<1.76)had higher MACE rate than the two highest tertiles (51% vs. 9% and 14%,p<0.0001). Similarly, the group with the lowest stress MBF tertile(MBF<1.78mL/min/g) had the highest annualized MACE rate (41% vs. 26% and 6%,p=0.0002). On multivariate analysis, the addition of MFR or stress MBF to SDSsignificantly increased the global χ2 (from 56 to 60, p=0.04; and from56 to 63, p=0.01). The best prognostic power was obtained in a model combiningSDS (p<0.001) and stress MBF (p=0.01). Interestingly, the integration ofstress MBF enhanced risk stratification even in absence of ischemia.CONCLUSIONS: Quantification of MBF or MFR in Rb-82 cardiac PET/CT providesindependent and incremental prognostic information over semi-quantitativeassessment with SDS and is of value for risk stratification.

MHC class II/ESO tetramer-based generation of in vitro primed anti-tumor T-helper lines for adoptive cell therapy of cancer.

Generation of tumor-antigen specific CD4(+) T-helper (T(H)) lines through in vitro priming is of interest for adoptive cell therapy of cancer, but the development of this approach has been limited by the lack of appropriate tools to identify and isolate low frequency tumor antigen-specific CD4(+) T cells. Here, we have used recently developed MHC class II/peptide tetramers incorporating an immunodominant peptide from NY-ESO-1 (ESO), a tumor antigen frequently expressed in different human solid and hematologic cancers, to implement an in vitro priming platform allowing the generation of ESO-specific T(H) lines. We isolated phenotypically defined CD4(+) T-cell subpopulations from circulating lymphocytes of DR52b(+) healthy donors by flow cytometry cell sorting and stimulated them in vitro with peptide ESO(119-143), autologous APC and IL-2. We assessed the frequency of ESO-specific cells in the cultures by staining with DR52b/ESO(119-143) tetramers (ESO-tetramers) and TCR repertoire of ESO-tetramer(+) cells by co-staining with TCR variable β chain (BV) specific antibodies. We isolated ESO-tetramer(+) cells by flow cytometry cell sorting and expanded them with PHA, APC and IL-2 to generate ESO-specific T(H) lines. We characterized the lines for antigen recognition, by stimulation with ESO peptide or recombinant protein, cytokine production, by intracellular staining using specific antibodies, and alloreactivity, by stimulation with allo-APC. Using this approach, we could consistently generate ESO-tetramer(+) T(H) lines from conventional CD4(+)CD25(-) naïve and central memory populations, but not from effector memory populations or CD4(+)CD25(+) Treg. In vitro primed T(H) lines recognized ESO with affinities comparable to ESO-tetramer(+) cells from patients immunized with an ESO vaccine and used a similar TCR repertoire. In this study, using MHC class II/ESO tetramers, we have implemented an in vitro priming platform allowing the generation of ESO-monospecific polyclonal T(H) lines from non-immune individuals. This is an approach that is of potential interest for adoptive cell therapy of patients bearing ESO-expressing cancers.