Biomedical subjects

B Tartakovsky

Publications and source records attributed to B Tartakovsky.

At least 19 recordsLinked to original sources

PubMed2006

Fluorescence-based monitoring of tracer and substrate distribution in an UASB reactor.

In this work, rhodamine-related fluorescence was measured on-line at four reactor heights in order to study hydrodynamics within an upflow anaerobic sludge bed reactor. A linear dependence of the dispersion coefficient (D) on the upflow velocity was observed, while the influence of the organic loading rate (OLR) was insignificant. Furthermore, the Bodenstein number of the reactor loaded with granulated sludge was found to be position-dependent with the largest values measured at the bottom of the sludge bed. This trend was not observed in the reactor without sludge. Chemical oxygen demand (COD) and volatile fatty acid (VFA) concentrations were measured at the same reactor heights as in rhodamine tests using conventional off-line analytical methods and on-line multiwavelength fluorometry. Significant spatial COD and VFA gradients were observed at organic loading rates above 6g COD l(R)(-1)d(-1) and linear upflow velocities below 0.8m h(-1).

Bioreactors↗

PubMed2006

On-line estimation of kinetic parameters in anaerobic digestion using observer-based estimators and multiwavelength fluorometry.

Observer-based estimators (OBE) were used for estimation of state variables and kinetic parameters in an anaerobic digestion (AD) process. A simplified first-order model with time-varying kinetic parameters was used to design an OBE for kinetic parameter estimation. This approach was validated on a laboratory-scale anaerobic reactor equipped with a multiwavelength fluorometer for on-line measurements of COD and VFA concentrations in the reactor effluent. The proposed estimators provide continuous adjustment of kinetic parameters and can be used for predictions of state variables between samples acquisition and during sensor failure.

Bacteria, Anaerobic↗

PubMed2006

ADM1 application for tuning and performance analysis of a multi-model observer-based estimator.

Anaerobic digestion model no.1 (ADM1) was used for tuning and performance analysis of the multi-model observer based estimator (mmOBE). The mmOBE was based on the variable structure model (VSM) of the anaerobic digestion model, which consists of several local submodels, each of which describes a typical process state. Depending on the hydraulic retention time, ADM1 simulated the methanogenic, organic overload, and acidogenic states of the process. These simulations allowed for optimising tunable parameters of the mmOBE. Owing to relatively slow process dynamics, a data acquisition interval as large as one day was sufficient to obtain acceptable accuracy. The simulations of mmOBE performance showed excellent rate of mmOBE convergence to ADM1 outputs. Moreover, mmOBE successfully estimated key kinetic parameters, such as maximal transformation rates of CODs, VFAs, and methane. These estimations can be used in the development of the advanced knowledge-based process system, which uses both available measurements and estimations of key kinetic parameters for extended diagnosis of failures and process trend analysis.

Anaerobiosis↗

PubMed2005

Multi-wavelength fluorometry for anaerobic digestion process monitoring.

Applicability of multi-wavelength fluorometry for anaerobic digestion process monitoring was investigated in a 3.5 L upflow anaerobic sludge bed (UASB) lab-scale reactor. Both off-line and on-line monitoring of key process parameters was tested. Off-line emission spectra were measured at an angle of 90 degrees to the excitation beam using a cuvette. On-line measurements were carried out using a fiber optic probe in the external recirculation line of the digester. Fluorescence spectra were correlated to available analytical measurements to obtain partial least square regression models. An independent set of measurements was used to validate the regression models. Model estimations showed reasonable agreement with analytical measurements with multiple determination coefficients (R2) between 0.6 and 0.95. Results showed that offline fluorescence measurements can be used for fast estimation of anaerobic digestor effluent quality. At the same time, the on-line implementation of multi-wavelength fluorescence measurements can be used for realtime process monitoring and, potentially, for on-line process control.

Bacteria, Anaerobic↗

PubMed2004

Comparison of different carbon sources for ground water denitrification.

This study presents a comparison of denitrification rates and denitrification stoichiometry when using different sources of carbon. Denitrification tests were carried out in test bottles containing water and soil samples acquired at a nitrate-contaminated site and supplemented with either sucrose, acetate or ethanol. The tests demonstrated nitrate removal in all carbon source supplemented bottles. The rate of denitrification and the required amount of a carbon source, however, depended on the choice of substrate. Ethanol and acetate were found to provide the highest denitrification rate, that of 1.4 - 1.6 mg-N l(-1) d(-1). Sucrose-supplemented bottles demonstrated a significantly slower denitrification rate, that of 0.6 - 0.9 mg-N l(-1) d(-1). In addition to slow denitrification rates, sucrose-supported denitrification required more carbon source.

Acetates↗

PubMed2003

Trichloroethylene degradation in a coupled anaerobic/aerobic reactor oxygenated using hydrogen peroxide.

In this work, trichloroethylene (TCE) degradation under combined anaerobic-aerobic conditions was studied in an ethanol-fed biofilm reactor oxygenated using hydrogen peroxide. The reactor was inoculated with a biomass originating from an anaerobic digestor. Granulated peat was added to the reactor as a substratum for biofilm development. Extensive characterization of reactor populations using activity tests and PCR analysis revealed the development of a mutualistic consortium, particularly methanotrophic and methanogenic microorganisms. This consortium was shown to degrade TCE by a combination of reductive and oxidative pathways. A near complete degradation of TCE at a load of 18 mg L(R)(-1) day(-1) was evidenced by a stoichiometric release of inorganic chloride.

Bacteria, Aerobic↗

PubMed2002

A microcosm test for potential mineralization of chlorinated compounds under coupled aerobic/anaerobic conditions.

In this study, the feasibility of using a mineralization test under coupled aerobic/anaerobic conditions was demonstrated. The coupling of anaerobic methanogenic and aerobic methanotrophic conditions in a microcosm required the presence of both a carbon source for anaerobic metabolism and oxygen for aerobic metabolism. These requirements were fulfilled by using a slow hydrolyzing organic matter along with intermittent addition of oxygen to the bottle headspace. Perchloroethylene (PCE) mineralization tests confirmed the effectiveness of the proposed methodology as well as PCE mineralization under coupled conditions.

Bacteria, Aerobic↗

PubMed2002

Microstructure of anaerobic granules bioaugmented with Desulfitobacterium frappieri PCP-1.

Oligonucleotide probes were used to study the structure of anaerobic granular biofilm originating from a pentachlorophenol-fed upflow anaerobic sludge bed reactor augmented with Desulfitobacterium frappieri PCP-1. Fluorescence in situ hybridization demonstrated successful colonization of anaerobic granules by strain PCP-1. Scattered microcolonies of strain PCP-1 were detected on the biofilm surface after 3 weeks of reactor operation, and a dense outer layer of strain PCP-1 was observed after 9 weeks. Hybridization with probes specific for Eubacteria and Archaea probes showed that Eubacteria predominantly colonized the outer layer, while Archaea were observed in the granule interior. Mathematical simulations showed a distribution similar to that observed experimentally when using a specific growth rate of 2.2 day(-1) and a low bacterial diffusion of 10(-7) dm(2) day(-1). Also, the simulations showed that strain PCP-1 proliferation in the outer biofilm layer provided excellent protection of the biofilm from pentachlorophenol toxicity.

Anaerobiosis↗

PubMed2002

Strategies for augmenting the pentachlorophenol degradation potential of UASB anaerobic granules.

Anaerobic degradation of pentachlorophenol (PCP) is an example of a process that may benefit from enrichment or bioaugmentation. In one approach, enrichment acceleration was attempted by applying an on-line control-based selective stress strategy to a native anaerobic upflow sludge bed (UASB) system; this strategy linked PCP loading rate to methane production. As a result, the reactor biomass potential for PCP complete dechlorination reached a rate of 4 mg g(-1) volatile suspended solid (VSS) day(-1) within a period of 120 days. In another approach, a pure culture, Desulfitobacterium frappieri PCP-1, a strictly anaerobic Gram-positive bacterium, was used to augment the granular biomass of the UASB reactor. This also resulted in a specific degradation rate of 4 mg PCPg(-1) VSS day(-1); however, this potential was attained within 56 days. Fluorescent in situ hybridization (FISH) showed that the PCP-1 strain was able to rapidly attach to the granule and densely colonize the outer biofilm layer.

Bacteria, Anaerobic↗

PubMed2001

Enhanced selection of an anaerobic pentachlorophenol-degrading consortium.

A rapid enrichment approach based on a pentachlorophenol (PCP) feeding strategy which linked the PCP loading rate to methane production was applied to an upflow anaerobic sludge bed reactor inoculated with anaerobic sludge. Due to this strategy, over a 140-day experimental period the PCP volumetric load increased from 2 to 65 mg L(R)(-1) day(-1) with a near zero effluent concentration of PCP. Dechlorination dynamics featured sequential appearance of 3,4,5-chlorophenol, 3,5-chloro- phenol, and 3-chlorophenol in the reactor effluent. Profiling of the reactor population by denaturing gradient gel electrophoresis (DGGE) revealed a correlation between the appearance of dechlorination intermediates and bands on the DGGE profile. Nucleotide sequencing of newly detected 16S rDNA fragments suggested the proliferation of Clostridium and Syntrophobacter/Syntrophomonas spp. in the reactor during PCP degradation. Published by John Wiley & Sons, Inc.

Anaerobiosis↗

PubMed2001

Degradation of aroclor 1242 in a single-stage coupled anaerobic/aerobic bioreactor.

Degradation of Aroclor 1242 was studied in granular biofilm reactors with limited aeration. An aerobic biphenyl degrader, Rhodococcus sp. M5, was used to supplement a natural bacterial population present in a "bioaugmented" reactor, while the "non-bioaugmented" reactor only contained natural granular sludge. The bioaugmentation, however appeared to have no effect on the reactor performance. Aroclor measurements showed its disappearance in both reactors with only 16-19% of Aroclor recovered from the reactor biomass and effluent. Simultaneously, a chlorine balance indicated that dechlorination occurred at a specific rate of 1.43 mg PCB (g volatile suspended solids)(-1) d(-1), which was comparable to the observed rate of Aroclor disappearance. Intermediates detected in both reactors were biphenyl, benzoic acid, and mono-hydroxybiphenyls. This suggests that a near-complete mineralization of Aroclor can be achieved in a single-stage anaerobic/aerobic system due to a combination of reductive and oxidative degradation mechanisms.

Aroclors↗

PubMed1999

Increased intracellular accumulation of macrophage inflammatory protein 1beta and its decreased secretion correlate with advanced HIV disease.

Considering that the chemokine macrophage inflammatory protein 1beta (MIP1beta) may serve as a competitive inhibitor for HIV entry, the objective of this study was to compare intracellular and extracellular levels of MIP1beta, in untreated HIV-infected individuals. HIV patients and healthy controls were tested by two-color flow cytometry for intracellular MIP1beta, in freshly explanted CD4 and CD8 lymphocytes, and in monocytes. Sera and plasma collected on the same day were tested, respectively, by enzyme-linked immunosorbent assay (ELISA) for MIP1beta concentration and for number of HIV-RNA copies, using nucleic acid sequence-based amplification procedure (NASBA) methodology. Results demonstrate that a high intracellular level of MIP1beta appears to be linked to a deterioration in the immune status of HIV patients (i.e., low CD4 counts) and to a high viral load. Moreover, an inverse relationship exists between the intracellular and the "secreted" form of MIP1beta, thus leading to the hypothesis that the regulation of cellular accumulation and secretion of MIP1beta and of other chemokines may be disrupted during AIDS development.

Case-Control Studies↗

PubMed1999

Biodegradation of pentachlorophenol in a continuous anaerobic reactor augmented with Desulfitobacterium frappieri PCP-1.

In this work, a strain of anaerobic pentachlorophenol (PCP) degrader, Desulfitobacterium frappieri PCP-1, was used to augment a mixed bacterial community of an anaerobic upflow sludge bed reactor degrading PCP. To estimate the efficiency of augmentation, the population of PCP-1 in the reactor was enumerated by a competitive PCR technique. The PCP-1 strain appeared to compete well with other microorganisms of the mixed bacterial community, with its population increasing from 10(6) to 10(10) cells/g of volatile suspended solids within a period of 70 days. Proliferation of strain PCP-1 allowed for a substantial increase of the volumetric PCP load from 5 to 80 mg/liter of reaction volume/day. A PCP removal efficiency of 99% and a dechlorination efficiency of not less than 90.5% were observed throughout the experiment, with 3-Cl-phenol and phenol being observable dechlorination intermediates.

Bacteria, Anaerobic↗

PubMed1998

Increased intracellular macrophage inflammatory protein-1beta correlates with advanced HIV disease.

The objective of this study was to correlate between macrophage inflammatory protein-1beta (MIP1beta) and viral loads in untreated, HIV-infected individuals. For that purpose, HIV-positive patients were tested for number of copies of HIV-RNA in plasma and for intracellular MIP1beta in freshly explanted CD8 and CD4 lymphocytes and monocytes. Results demonstrate that the levels of MIP1beta in the various cell populations were significantly higher in the HIV group than in age-matched healthy individuals. Moreover, patients with low CD4 cell counts (<500/microl) and relatively high viral loads exhibited much higher levels of intracellular MIP1beta than patients with lower viral loads and CD4 counts >500/microl. We conclude therefore that although MIP1beta is induced in the various cell populations as a result of HIV infection in vivo, a high intracellular level of MIP1beta appears to be linked to a deterioration in the immune status of the patients.

CD4 Lymphocyte Count↗

PubMed1997

Tumour necrosis factor alpha binding to human and mouse trophoblast.

Tumour necrosis factor alpha (TNF-alpha) is a cytokine with pleiotropic effects, modulating cell growth, differentiation, and synthesis of various substances. Recent demonstration of TNF-alpha mRNA and protein in the uteroplacental unit suggests that this cytokine may be involved in the development of the embryo. To determine whether the embryo itself binds TNF-alpha, mouse blastocyst outgrowths and human first trimester villous trophoblast were analysed for TNF-alpha binding. Our experiments revealed that binding of TNF-alpha could be specifically detected on the trophectoderm of the outgrowing mouse embryos. They also show a complete disappearance of the colony-stimulating factor 1 (CSF-1) receptor that occurs shortly after the binding of TNF-alpha by the trophectoderm. In human first trimester villous trophoblast, TNF-alpha binding was found to be predominantly detectable on the syncytiotrophoblast and to a lesser extent on the cytotrophoblastic cells. Binding was not observed on adjacent embryonic or maternal cells. Our results further support the idea that TNF-alpha as well as other cytokines may modulate early embryonic development and implantation.

Animals↗

PubMed1997

[Abnormal endometrial reactivity to colony stimulating factor 1 and leukemia inhibitory factor dependent female infertility].

Maternal LIF is essential for embryo implantation in mice and it may also be the case in humans. We recently reported that endometrial LIF secretion from infertile women presenting repeated failures of embryonic implantation or unexplained sterility was significantly lower than the secretion of explants from fertile women. We now report on the modulation of the endometrial LIF secretion according to the obstetrical status. CSF-1 has little effect or increases LIF secretion from fertile women whereas it inhibits secretion from infertile women with repeated failures of embryonic implantation.

Adult↗

PubMed1996

Anticardiolipin, but not the 16/6 Id anti-DNA antibody induces pregnancy failure.

The primary antiphospholipid syndrome or the antiphospholipid syndrome in systemic lupus erythematosus patients (defined as secondary antiphospholipid syndrome) are characterized by the presence of thrombosis, thrombocytopenia and recurrent fetal loss in association with anticardiolipin antibodies. To determine the causal role of these antibodies in the pathogenesis of pregnancy failure we studied the effects of immunization with monoclonal anti-DNA antibody (designated 16/6 Id; no cardiolipin reactivity) and anticardiolipin monoclonal antibody (designated 2C4C2; binds DNA as well) on the outcome of allogeneic pregnancies in BALB/c mice. Mating of BALB/c females 4 weeks after active immunization with the 16/6 Id, anti-DNA monoclonal antibody resulted in normal pregnancy outcome, similar to control mouse groups. In contrast to that, immunization with the 2C4C2 anticardiolipin antibodies resulted in severe gestational failure with low pregnancy rate, low numbers of fetuses and high rates of resorptions. The fertility index of those mice was extremely low as compared to the 16/6 Id-immunized mice or the control groups. Furthermore, a correlation was shown between the presence of anticardiolipin antibody levels in the sera of the mice at the time of gestation and the pregnancy fate. The 2C4C2-immunized mice which produced high levels of anticardiolipin antibodies demonstrated severe pregnancy failure, whereas normal gestations were observed in the 16/6 Id primed or the control mouse groups that did not produce measurable amounts of the latter antibodies. Thus, our studies demonstrate that anticardiolipin but not the 16/6 Id anti-DNA antibodies can induce severe gestational impairment.

Abortion, Spontaneous↗

PubMed1996

Defective maternal-fetal interaction in a murine autoimmune model.

Anti-cardiolipin antibodies (ACA) are associated with recurrent fetal loss, but their role in this pathological condition is unknown. We recently developed an experimental mouse model of the anti-phospholipid syndrome, in which immunization of female mice with a monoclonal anti-cardiolipin antibody resulted in substantial failure of pregnancy. We observed that pre-implantation embryos derived from ACA-injected mothers exhibited morphological abnormalities and failed to implant in vitro. In the present study, we designed embryo transfer experiments to determine whether defective embryonic development originated as a maternal defect, an embryonic defect or both. Embryos (3.5 day old), taken from ACA- and control-immunized mothers were transferred into either an ACA- or a control-treated uterine environment (day 2.5 pseudopregnant females). On day 14 of gestation the incidence of pregnancy, the average number of fetuses per female and fetal resorptions were assessed. The ACA-treated uterine environment was found to be non-supportive for the development and implantation of normal embryos. Moreover, embryos derived from ACA-immunized mothers, even after their removal from the ACA-environment and transfer to a normal uterus, remained deficient. These results demonstrate that both the maternal and the embryonic compartments were defective, as a result of previous exposure to the ACA.

Animals↗