Oxygen Transfer Function Research Articles

Кровозамінники з газотранспортною функцією: надії і реалії

Робота присвячена сучасному стану проблеми створення та клінічного використання кровозамінників із газотранспортною функцією. Описано технологічні напрямки розробок кровозамінників із газотранспортною функцією. Здійснено аналіз проведених досліджень кровозамінників на основі модифікованого гемоглобіну, перфторвуглеців, а також використання молекулярних, клітинних і нанотехнологій. Надано досвід широкого клінічного застосування кровозамінника з газотранспортною функцією на основі перфторвуглеців. Продемонстровані потенційні переваги використання кровозамінників із газотранспортною функцією порівняно з алогенною кров’ю.

DIVERSITY AND ABUNDANCE TRENDS OF BENTHIC FORAMINIFERA FROM THE SOUTHERN PART OF THE IRAKLION BASIN, CENTRAL CRETE

Benthic foraminiferai fossil assemblages of the Roufas Section, southern Iraklion Basin, central Crete, were analyzed for the first time. Taxonomic and quantitative analyses were made in order to obtain paleoenvironmental (physical as well biological) information. A data set has been subjected to R- and Q-mode cluster analyses in order to demonstrate the linkage between taxa distribution and paleoenvironmental gradients. Our results suggest that oxygenation and trophic conditions of the near-surface sediments are the most important factors that control the community structure of the benthic foraminiferai fauna. The application of the oxygen transfer function - based on the use of benthic foraminiferai taxa from oxyphilic habitats - to the benthic faunas of the Roufas Section, allows the reconstruction of the oxygen contents of the bottom waters. Apart from the middle part of the section, no severe disturbances are recorded, pointing to the fact that we are dealing with an overall rather well ventilated water column during most of the part of the sequence.

T1 relaxation time constants, influence of oxygen, and the oxygen transfer function of the human lung at 1.5 T—A meta-analysis

PurposeTo pool and summarize published data from magnetic resonance longitudinal relaxation measurements of the human lung at 1.5T to provide a reliable basis of T1 relaxation time constants of healthy lung tissue both under respiration of room air and of pure oxygen. In particular, the oxygen-induced shortening of T1 was evaluated. Materials and methodsThe PubMed database was comprehensively searched up to June 2016 for original publications in English containing quantitative T1 data (at least mean values and standard deviations) of the lung parenchyma of healthy subjects (minimum subject number: 3) at 1.5T. From all included publications, T1 values of the lung of healthy subjects were extracted (inhaling room air and, if available, inhaling pure oxygen). Weighted mean values and standard deviations of all extracted data and the oxygen transfer function (OTF) were calculated. Results22 publications were included with a total number of 188 examined healthy subjects. 103 of these subjects (from 13 studies) were examined while breathing pure oxygen and room air; 85 subjects were examined only under room-air conditions. The weighted mean value (weighted sample standard deviation) of the room-air T1 values over all 22 studies was 1196ms (152ms). Based on studies with room-air and oxygen results, the mean T1 value at room-air conditions was 1172ms (161ms); breathing pure oxygen, the mean T1 value was reduced to 1054ms (138 ms). This corresponds to a mean T1 reduction by 118ms (35ms) or 10.0 % (2.3 %) and to a mean OTF value of 1.22 (0.32)×10−3s−1/(%O2). ConclusionThis meta-analysis with data from 188 subjects indicates that the average T1 relaxation time constant of healthy lung tissue at 1.5T is distributed around 1200ms with a standard deviation of about 150 ms; breathing pure oxygen reduces this value significantly by 10 % to about 1050 ms.

DFT analysis of the electronic structure of Fe(IV) species active in nitrene transfer catalysis: influence of the coordination sphere.

Nitrene transfer reactions to various hydrocarbon molecules can be efficiently catalyzed by Fe complexes through a mechanism reminiscent of the oxygen transfer function of oxygenase enzymes. Such enzymes exhibit a high-valent iron oxo Fe(IV) = O as the active species, and it has also been proposed that an analogous species, i.e., Fe(IV) = NR (NR being the nitrene group) is responsible for the nitrene transfer activity. We describe here the influence of the Fe(IV) coordination sphere on some key parameters for nitrene transfer efficacy, such as the spin state of the Fe(IV) cation, the electronic affinity, and the bond dissociation energy of the NHR moiety. We explore here the electronic properties of Fe(IV) = NTs (NTs = tolylsulfonylimido group) mononuclear complexes with ligands involving phenolate and nitrogen donor groups, as catalytic properties with such ligands have been found to be quite promising. Six tetradentate ligands were studied, which derive from three different scaffolds: 2-methylenepyridine-N,N-bis(2-methylene-4,6-dichlorophenol) and 2-methylenepyridine-N,N-bis(2-methylene-4,6-dimethylphenol), N,N-dimethyl-N',N'-bis(2-methylene-4,6-dichlorophenol) ethylenediamine, and N,N-dimethyl-N',N'- bis(2-methylene-4,6-dimethylphenol) ethylenediamine, N,N'-bis(2-methylene-4,6-dichlorophenol)-N,N'-dimethyl-1,2-diaminoethane and N,N'-bis(2-methylene-4,6-dimethylphenol)-N,N'-dimethyl-1,2-diaminoethane. Thanks to thorough DFT computations, we present some rationalization of the electronic properties of the resulting Fe(IV) = NTs complexes in relation to their coordination sphere and compare them to other Fe(IV) nitrene active species. We show in particular the important role of the anionic character and strong π-donation of the phenolate groups.

Chronic Lung Allograft Dysfunction: Oxygen-enhanced T1-Mapping MR Imaging of the Lung.

To evaluate oxygen-enhanced T1-mapping magnetic resonance (MR) imaging of the lungs for detection of chronic lung allograft dysfunction (CLAD) in patients who have undergone double lung transplantation. The local ethics committee approved this study. Seventy-six recipients of double lung allografts who underwent MR imaging of the lungs during an outpatient visit between 2011 and 2013 were included in this study after they provided written informed consent. Patients were classified as having CLAD on the basis of spirometric results and were divided into three groups: no CLAD (bronchiolitis obliterans syndrome level 0 [BOS 0]), early CLAD (BOS 0p), and late-stage CLAD (BOS 1-3). Coronal T1 maps of the lungs were acquired with the patient breathing room air and 100% oxygen by using an inversion-recovery snapshot fast low-angle shot sequence at 1.5 T. The median and interquartile range of T1 values at room air and at 100% oxygen and the oxygen transfer function were calculated. Statistical analysis was performed with analysis of variance and the Tukey honestly significant difference test or the Kruskal-Wallis test and the Mann-Whitney U test (α = 0.05). Bonferroni correction was applied for multiple comparisons. The oxygen transfer function was significantly lower in patients in the BOS 0p (P = .025) and BOS 1-3 groups (P = .003) than it was in the patients with BOS 0. Absolute T1 values (room air, P = .66; 100% oxygen, P = .67) did not differ significantly among the groups. The heterogeneity of T1 values, measured by using the interquartile range, showed a strong trend toward higher values in patients with BOS (room air, P = .06; 100% oxygen, P = .08). Oxygen transfer function may serve as an early marker for detection of CLAD.

Noninvasive quantification of airway inflammation following segmental allergen challenge with functional MR imaging: a proof of concept study.

To evaluate oxygen-enhanced T1-mapping magnetic resonance (MR) imaging as a noninvasive method for visualization and quantification of regional inflammation after segmental allergen challenge in asthmatic patients compared with control subjects. After institutional review board approval, nine asthmatic and four healthy individuals gave written informed consent. MR imaging (1.5 T) was performed by using an inversion-recovery snapshot fast low-angle shot sequence before (0 hours) and 6 hours and 24 hours after segmental allergen challenge by using either normal- or low-dose allergen or saline. The volume of lung tissue with increased relaxation times was determined by using a threshold-based method. As a biomarker for oxygen transfer from the lungs into the blood, the oxygen transfer function ( OTF oxygen transfer function ) was calculated. After the third MR imaging examination, eosinophils in bronchoalveolar lavage fluid were counted. Differences between times and segments were analyzed with nonparametric Wilcoxon matched-pairs test and Spearman correlation. In lung segments treated with the standard dose of allergen, the OTF oxygen transfer function was decreased at 6 hours in asthmatic patients, compared with saline-treated segments (P = .0078). In asthmatic patients at 24 hours, the volume over threshold was significantly increased in normal allergen dose-treated segments compared with saline-treated segments (P = .004). In corresponding lung segments, the volume over threshold at 24 hours in the asthmatic group showed a positive correlation (r = 0.65, P = .0001) and the OTF oxygen transfer function at 6 hours showed an inverse correlation (r = -0.67, P = .0001) with the percentage of eosinophils in the bronchoalveolar lavage fluid. OTF oxygen transfer function and volume over threshold are noninvasive MR imaging-derived parameters to visualize and quantify the regional allergic reaction after segmental endobronchial allergen challenge.

Clinical use of oxygen‐enhanced T1 mapping MRI of the lung: Reproducibility and impact of closed versus loose fit oxygen delivery system

To evaluate the reproducibility of oxygen-enhanced magnetic resonance imaging (MRI), and the influence of different gas delivery methods, in a clinical environment. Twelve healthy volunteers were examined on two visits with an inversion recovery snapshot fast low angle shot sequence on a 1.5 T system. Coronal slices were obtained breathing room air as well as 100% oxygen with a flow rate of 15 L/min. For oxygen delivery a standard nontight face mask and a full closed air-cushion face mask were used. T1 relaxation times and the oxygen transfer function (OTF) were calculated. The mean T1 values did not change significantly between the two visits (P > 0.05). The T1 values breathing 100% oxygen obtained using the full closed mask were significantly lower (1093 ± 38 msec; P < 0.05) compared to the standard mask (1157 ± 52 msec). Accordingly, the OTF was significantly higher for the full closed mask (P < 0.05). The OTF changed significantly on the second visit using the standard mask (P < 0.05). The full closed mask showed lower interindividual variation for both the T1 values (3.5% vs. 4.5%) as well as the OTF (12.4% vs. 22.0%) and no difference of the OTF on the second visit (P > 0.05). Oxygen-enhanced T1 mapping MRI produces reproducible data when using a full closed face mask.

Inferring Reference Conditions of Hypolimnetic Oxygen for Deteriorated Lake Mallusjärvi in the Cultural Landscape of Mallusjoki, Southern Finland Using Fossil Midge Assemblages

Lake Mallusjarvi in the cultural landscape of Mallusjoki, southern Finland, suffers from algal blooms during summers and oxygen depletions during winters due to increased nutrient input resulting from extensive agricultural activities in the catchment. In this study, a sediment profile from the lake was studied using fossil midge (Diptera: Nematocera) analysis and a hypolimnetic oxygen transfer function was applied to establish baseline conditions of hypolimnetic oxygen. In addition, physical properties of the sediment were determined. The inferred late winter hypolimnetic oxygen content was elevated in the beginning of the sediment sequence, but decreased dramatically at ca. 200 cal BP, as the inferred values indicated frequently anoxic condition coinciding with increased agricultural use in the catchment. The results indicated that dramatic changes have occurred in the taxon composition. The high-oxygen Stempellina–Ablabesmyia monilis-type community first changed to moderate-oxygen Procladius–Stempellinella community, and finally to low-oxygen Microchironomus tener–Chironomus plumosus-type community, following the eutrophication process. These changes in macrobenthic faunal assemblages reproduced considerably higher inferred hypolimnetic oxygen reference condition values for hypolimnetic oxygen, compared to the present status.

Chronic endurance exercise induces quadriceps nitrosative stress in patients with severe COPD

Background:Although exercise training has beneficial effects on skeletal muscle bioenergetics and exercise performance in patients with severe chronic obstructive pulmonary disease (COPD), it may also be associated with increased quadriceps...

Quantitative and O2 Enhanced MRI of the Pathologic Lung: Findings in Emphysema, Fibrosis, and Cystic Fibrosis

Purpose: beyond the pure morphological visual representation, MR imaging offers the possibility to quantify parameters in the healthy, as well as, in pathologic lung parenchyma. Gas exchange is the primary function of the lung and the transport of oxygen plays a key role in pulmonary physiology and pathophysiology. The purpose of this review is to present a short overview of the relaxation mechanisms of the lung and the current technical concepts of T1 mapping and methods of oxygen enhanced MR imaging. Material and Methods: molecular oxygen has weak paramagnetic properties so that an increase in oxygen concentration results in shortening of the T1 relaxation time and thus to an increase of the signal intensity in T1 weighted images. A possible way to gain deeper insights into the relaxation mechanisms of the lung is the calculation of parameter Maps. T1 Maps based on a snapshot FLASH sequence obtained during the inhalation of various oxygen concentrations provide data for the creation of the so-called oxygen transfer function (OTF), assigning a measurement for local oxygen transfer. T1 weighted single shot TSE sequences also permit expression of the signal changing effects associated with the inhalation of pure oxygen. Results: the average of the mean T1 values over the entire lung in inspiration amounts to 1199 +/− 117 milliseconds, the average of the mean T1 values in expiration was 1333 +/− 167 milliseconds. T1 Maps of patients with emphysema and lung fibrosis show fundamentally different behavior patterns. Oxygen enhanced MRT is able to demonstrate reduced diffusion capacity and diminished oxygen transport in patients with emphysema and cystic fibrosis. Discussion: results published in literature indicate that T1 mapping and oxygen enhanced MR imaging are promising new methods in functional imaging of the lung and when evaluated in conjunction with the pure morphological images can provide additional valuable information.

Assessment of human pulmonary function using oxygen-enhanced T(1) imaging in patients with cystic fibrosis.

Indirect qualitative MRI of pulmonary function is feasible using the paramagnetic effects of oxygen physically dissolved in blood. In this study, a more quantitative oxygen-enhanced pulmonary function test based on the slope of a plot of R(1) vs. oxygen concentration-the oxygen transfer function (OTF)-was developed and tested in a pool of five healthy volunteers and five patients with cystic fibrosis (CF). The lung T(1) relaxation rate, R(1), under normoxic conditions (room air, 21% O(2)), and the response to various hyperoxic conditions (40%-100% O(2)) were studied. Lung T(1) in healthy volunteers showed a relatively homogeneous distribution while they breathed room air, and a homogeneous decrease under hyperoxic conditions. Lung T(1) in CF patients showed an inhomogeneous distribution while they breathed room air, and the observed lung T(1) decrease under hyperoxia depended on the actual state of the diseased lung tissue. In the selected group of CF patients, areas with reduced OTF also showed reduced perfusion, as confirmed by qualitative contrast-enhanced MR pulmonary perfusion imaging. The results demonstrate that this completely noninvasive oxygen-enhanced pulmonary function test has potential for clinical applications in the serial diagnosis of lung diseases such as CF. .

Software sensor for on-line estimation of the microbial activity in activated sludge systems

Abstract This paper considers the design of a software sensor (or soft-sensor) for the on-line estimation of the biological activities of a colony of aerobic micro-organisms acting on activated sludge processes, where the carbonaceous waste degradation and nitrification processes are taken into account. These bioactivities are intimately related to the dissolved oxygen concentration. Two factors that affect the dynamics of the dissolved oxygen are the respiration rate or the oxygen uptake rate (OUR) and the oxygen transfer function (K la). These items are challenging topics for the application of recursive identification due the nonlinear characteristic of the oxygen transfer function, and to the time-varying feature of the respiration rate. In this work, OUR and the oxygen transfer function are estimated through a software sensor, which is based on a modified version of the discrete extended Kalman filter. Numerical simulations are carried out in a predenitrifying activated sludge process benchmark and the obtained results demonstrate the applicability and efficiency of the proposed methodology, which should provide a valuable tool to supervise and control activated sludge processes.

Nonlinear state and parameter estimation in batch biological wastewater treatment

Wastewater treatment is an active research area from both the technological and the control points of view. Various types of supervisory and low-level control approaches can be applied in this field. However, the inaccessibility of sensors which should provide the data needed for control is one of the major obstacles in current development. Estimation is therefore a prerequisite for performing those control tasks that rely on important process variables which cannot be measured directly. In this paper an estimation algorithm for simultaneous state and parameter estimation of a nonlinear process is derived for a batch biological wastewater treatment process. The aim is to estimate two important process variables related to dissolved oxygen dynamics during the aerobic phase of a batch cycle: the oxygen transfer function and biomass respiration rate. The main contributions of the work presented are providing on-line information about these variables for improved process control and diagnosis, and the applica...

Nonlinear state and parameter estimation in batch biological wastewater treatment

Wastewater treatment is an active research area from both the technological and the control points of view. Various types of supervisory and low-level control approaches can be applied in this field. However, the inaccessibility of sensors which should provide the data needed for control is one of the major obstacles in current development. Estimation is therefore a prerequisite for performing those control tasks that rely on important process variables which cannot be measured directly. In this paper an estimation algorithm for simultaneous state and parameter estimation of a nonlinear process is derived for a batch biological wastewater treatment process. The aim is to estimate two important process variables related to dissolved oxygen dynamics during the aerobic phase of a batch cycle: the oxygen transfer function and biomass respiration rate. The main contributions of the work presented are providing on-line information about these variables for improved process control and diagnosis, and the application of the chosen nonlinear estimation algorithms for simultaneous state and parameter estimation in process control.

Nonlinear and set-point control of the dissolved oxygen concentration in an activated sludge process

Control of the dissolved oxygen concentration (DO) in an activated sludge process is of considerable importance because of economy and process efficiency. A strategy for designing a nonlinear DO controller was developed. The basic idea was to take the nonlinear oxygen transfer function into account in the controller design. Simulations illustrated that a nonlinear DO controller outperforms a standard PI controller. This was also confirmed in a pilot-scale plant experiment. A supervision (set-point) controller for the DO is also outlined. Initial simulations showed promising results where the aeration system is used more efficiently and the effluent ammonia concentration could be maintained low.

Estimation of the respiration rate and oxygen transfer function utilizing a slow do sensor

In this paper a software sensor for estimating the respiration rate and the nonlinear oxygen transfer functionKLa is presented. The respiration rate and the oxygen transfer function were estimated from measurements of the dissolved oxygen concentration (DO) and airflow rate by a Kalman filter. In particular, a filtering procedure was applied for the case when the DO sensor dynamic cannot be neglected. In the estimation scheme the time varying respiration rate was modelled by a filtered random walk model, and the nonlinearKLa function was modelled with an exponential model. A numerical study illustrated the advantage of the method. Also, real data were applied to the software sensor with promising results.

Estimation of the respiration rate and oxygen transfer function utilizing a slow do sensor

In this paper a software sensor for estimating the respiration rate and the nonlinear oxygen transfer function {itK{inL}a} is presented. The respiration rate and the oxygen transfer function were estimated from measurements of the dissolved oxygen concentration (DO) and airflow rate by a Kalman filter. In particular, a filtering procedure was applied for the case when the DO sensor dynamic cannot be neglected. In the estimation scheme the time varying respiration rate was modelled by a filtered random walk model, and the nonlinear {itK{inL}a} function was modelled with an exponential model. A numerical study illustrated the advantage of the method. Also, real data were applied to the software sensor with promising results

Nonlinear and set-point control of the dissolved oxygen concentration in an activated sludge process

Control of the dissolved oxygen concentration (DO) in an activated sludge process is of considerable importance because of economy and process efficiency. A strategy for designing a nonlinear DO controller was developed. The basic idea was to take the nonlinear oxygen transfer function into account in the controller design. Simulations illustrated that a nonlinear DO controller outperforms a standard PI controller. This was also confirmed in a pilot-scale plant experiment. A supervision (set-point) controller for the DO is also outlined. Initial simulations showed promising results where the aeration system is used more efficiently and the effluent ammonia concentration could be maintained low.

Late glacial-Holocene paleoclimatic and paleoceanographic evolution of the Aegean Sea: micropaleontological and stable isotopic evidence

Late glacial to Holocene paleoclimatic and paleoceanographic changes are examined using records of calcareous and organic-walled marine microfossils, pollen and terrestrial spores and oxygen isotope data in cores from the Aegean Sea basins. Planktic foraminiferal, coccolith and dinoflagellate data show that the late glacial-Holocene transition in the region was associated with a large warming of surface water. Mediterranean-based paleotransfer functions for planktic foraminifera show a 5 °–10 °C increase in surface water temperature from ~14,000 to ~9600 yr B.P. Estimates of surface water oxygen isotopic composition (δ18Ow) derived from planktic foraminiferal oxygen isotopic and transfer function data indicate that this warming was associated with a 2.0 to 2.5‰ reduction in δ18Ow. Transfer function results indicate corresponding 1.0 to 1.5‰ salinity reductions for this tim (ca. 6400–9600 yr B.P.) throughout the Aegean Sea. Pollen, dinoflagellate and isotopic data show that the early Holocene excess fresh water originated from rapid melting of the northern European and Siberian ice sheets, supplied primarily from the Black Sea by the opening of Bosphorus and Dardanelles Channels, during the post glacial sea-level rise, and supplemented by major rivers entering the Aegean Sea. Continuous outflow of fresh water into the Aegean Sea provided a low salinity surface lid, preventing the ventilation of the deep water. Benthic foraminifera shows a major turn-over that indicates low dissolved oxygen; however, bottom waters were not anoxic. Sapropel level S1 resulted from a combination of stagnant deep water in isolated depressions, increased terrigenous organic matter and periods of high primary productivity, as indicated by pollen and dinocysts, respectively. The surface water temperature and salinity reached present-day values at ~6400 yr B.P., with little subsequent change despite the major deforestation onshore.