935 resultados para Ability to take risks
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Quantifying the spatial configuration of hydraulic conductivity (K) in heterogeneous geological environments is essential for accurate predictions of contaminant transport, but is difficult because of the inherent limitations in resolution and coverage associated with traditional hydrological measurements. To address this issue, we consider crosshole and surface-based electrical resistivity geophysical measurements, collected in time during a saline tracer experiment. We use a Bayesian Markov-chain-Monte-Carlo (McMC) methodology to jointly invert the dynamic resistivity data, together with borehole tracer concentration data, to generate multiple posterior realizations of K that are consistent with all available information. We do this within a coupled inversion framework, whereby the geophysical and hydrological forward models are linked through an uncertain relationship between electrical resistivity and concentration. To minimize computational expense, a facies-based subsurface parameterization is developed. The Bayesian-McMC methodology allows us to explore the potential benefits of including the geophysical data into the inverse problem by examining their effect on our ability to identify fast flowpaths in the subsurface, and their impact on hydrological prediction uncertainty. Using a complex, geostatistically generated, two-dimensional numerical example representative of a fluvial environment, we demonstrate that flow model calibration is improved and prediction error is decreased when the electrical resistivity data are included. The worth of the geophysical data is found to be greatest for long spatial correlation lengths of subsurface heterogeneity with respect to wellbore separation, where flow and transport are largely controlled by highly connected flowpaths.
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[spa] Este texto recoge las contribuciones al I Seminario internacional REUNI+D. Creando redes, estableciendo sinergias: la contribución de la investigación a la educación, que tuvo lugar en Barcelona el 11 de octubre de 2013. La organización del seminario partió de la necesidad de contribuir a la difusión, el intercambio y la discusión de las aportaciones y resultados de la investigación educativa y sus implicaciones para la mejora de la educación. Sus finalidades fueron: (a) Ofrecer una visión de conjunto de los ámbitos y temas de investigación abordados en los últimos años por los miembros de REUNI+D y los grupos que participaron en el evento; y (b) Debatir la capacidad de los investigadores para intervenir en las decisiones sobre políticas de investigación y reivindicar su papel como interlocutores a la hora de establecerlas.
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During John Lake's visit to Barcelona to take part in a seminar organized by the Facultat de Biblioteconomia i Documentació (Department of Library and Information Science) at the University of Barcelona (UB)1 EPI sought an interview to further explore some of the themes addressed in the seminar, drawing on his extensive experience in the world of public libraries.
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Most butterfly monitoring protocols rely on counts along transects (Pollard walks) to generate species abundance indices and track population trends. It is still too often ignored that a population count results from two processes: the biological process (true abundance) and the statistical process (our ability to properly quantify abundance). Because individual detectability tends to vary in space (e.g., among sites) and time (e.g., among years), it remains unclear whether index counts truly reflect population sizes and trends. This study compares capture-mark-recapture (absolute abundance) and count-index (relative abundance) monitoring methods in three species (Maculinea nausithous and Iolana iolas: Lycaenidae; Minois dryas: Satyridae) in contrasted habitat types. We demonstrate that intraspecific variability in individual detectability under standard monitoring conditions is probably the rule rather than the exception, which questions the reliability of count-based indices to estimate and compare specific population abundance. Our results suggest that the accuracy of count-based methods depends heavily on the ecology and behavior of the target species, as well as on the type of habitat in which surveys take place. Monitoring programs designed to assess the abundance and trends in butterfly populations should incorporate a measure of detectability. We discuss the relative advantages and inconveniences of current monitoring methods and analytical approaches with respect to the characteristics of the species under scrutiny and resources availability.
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OBJECTIVES: To test the validity of a simple, rapid, field-adapted, portable hand-held impedancemeter (HHI) for the estimation of lean body mass (LBM) and percentage body fat (%BF) in African women, and to develop specific predictive equations. DESIGN: Cross-sectional observational study. SETTINGS: Dakar, the capital city of Senegal, West Africa. SUBJECTS: A total sample of 146 women volunteered. Their mean age was of 31.0 y (s.d. 9.1), weight 60.9 kg (s.d. 13.1) and BMI 22.6 kg/m(2) (s.d. 4.5). METHODS: Body composition values estimated by HHI were compared to those measured by whole body densitometry performed by air displacement plethysmography (ADP). The specific density of LBM in black subjects was taken into account for the calculation of %BF from body density. RESULTS: : Estimations from HHI showed a large bias (mean difference) of 5.6 kg LBM (P<10(-4)) and -8.8 %BF (P<10(-4)) and errors (s.d. of the bias) of 2.6 kg LBM and 3.7 %BF. In order to correct for the bias, specific predictive equations were developed. With the HHI result as a single predictor, error values were of 1.9 kg LBM and 3.7 %BF in the prediction group (n=100), and of 2.2 kg LBM and 3.6 %BF in the cross-validation group (n=46). Addition of anthropometrical predictors was not necessary. CONCLUSIONS: The HHI analyser significantly overestimated LBM and underestimated %BF in African women. After correction for the bias, the body compartments could easily be estimated in African women by using the HHI result in an appropriate prediction equation with a good precision. It remains to be seen whether a combination of arm and leg impedancemetry in order to take into account lower limbs would further improve the prediction of body composition in Africans.
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The Iowa Department of Transportation, like many other state transportation agencies, is experiencing growing congestion and traffic delays in work zones on rural interstate highways. The congestion results in unproductive and wasteful delays for both motorists and commercial vehicles. It also results in hazardous conditions where vehicle stopped in queues on rural interstate highways are being approached by vehicles upstream at very high speeds. The delays also result in driver frustration, making some drivers willing to take unsafe risks in an effort to bypass delays. To reduce the safety hazards and unproductive delays of congested rural interstate work zones, the Iowa Department of Transportation would like to improve its traffic management strategies at these locations. Applying better management practices requires knowledge of the traffic flow properties and driver behavior in and around work zones, and knowledge of possible management strategies. The project reported here and in a companion report documents research which seeks to better understand traffic flow behavior at rural interstate highway work zones and to estimate the traffic carrying capacity of work zone lane closures. In addition, this document also reports on technology available to better manage traffic in and around work zones.
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Résumé Les tumeurs sont diverses et hétérogènes, mais toutes partagent la capacité de proliférer sans contrôle. Une prolifération dérégulée de cellules couplée à une insensibilité à une réponse apoptotique constitue une condition minimale pour que l'évolution d'une tumeur se produise. Un des traitements les plus utilisés pour traité le cancer à l'heure actuelle sont les chimiothérapies, qui sont fréquemment des composés chimiques qui induisent des dommages dans l'ADN. Les agents anticancéreux sont efficaces seulement quand les cellules tumorales sont plus aisément tuées que le tissu normal environnant. L'efficacité de ces agents est en partie déterminée par leur capacité à induire l'apoptose. Nous avons récemment démontré que la protéine RasGAP est un substrat non conventionnel des caspases parce elle peut induire à la fois des signaux anti et pro-apoptotiques, selon l'ampleur de son clivage par les caspases. A un faible niveau d'activité des caspases, RasGAP est clivé, générant deux fragments (le fragment N et le fragment C). Le fragment N semble être un inhibiteur général de l'apoptose en aval de l'activation des caspases. À des niveaux plus élevés d'activité des caspases, la capacité du fragment N de contrecarrer l'apoptose est supprimée quand il est clivé à nouveau par les caspases. Ce dernier clivage produit deux nouveaux fragments, N 1 et N2, qui contrairement au fragment N sensibilisent efficacement des cellules cancéreuses envers des agents chimiothérapeutiques. Dans cette étude nous avons prouvé qu'un peptide, appelé par la suite TAT-RasGAP317-326, qui est dérivé du fragment N2 de RasGAP et est rendu perméable aux cellules, sensibilise spécifiquement des cellules cancéreuses à trois génotoxines différentes utilisées couramment dans des traitements anticancéreux, et cela dans des modèles in vitro et in vivo. Il est important de noté que ce peptide semble ne pas avoir d'effet sur des cellules non cancéreuses. Nous avons également commencé à caractériser les mécanismes moléculaires expliquant les fonctions de sensibilisation de TAT-RasGAP317-326. Nous avons démontré que le facteur de transcription p53 et une protéine sous son activité transcriptionelle, nommée Puma, sont indispensables pour l'activité de TAT-RasGAP317-326. Nous avons également prouvé que TAT-RasGAP317-326 exige la présence d'une protéine appelée G3BP1, une protéine se liant a RasGAP, pour potentialisé les effets d'agents anticancéreux. Les données obtenues dans cette étude montrent qu'il pourrait être possible d'augmenter l'efficacité des chimiothérapies à l'aide d'un composé capable d'augmenter la sensibilité des tumeurs aux génotoxines et ainsi pourrait permettre de traiter de manière plus efficace des patients sous traitement chimiothérapeutiques. Summary Tumors are diverse and heterogeneous, but all share the ability to proliferate without control. Deregulated cell proliferation coupled with suppressed apoptotic sensitivity constitutes a minimal requirement upon which tumor evolution occurs. One of the most commonly used treatments is chemotherapy, which frequently uses chemical compounds that induce DNA damages. Anticancer agents are effective only when tumors cells are more readily killed than the surrounding normal tissue. The efficacy of these agents is partly determined by their ability to induce apoptosis. We have recently demonstrated that the protein RasGAP is an unconventional caspase substrate because it can induce both anti- and pro-apoptotic signals, depending on the extent of its cleavage by caspases. At low levels of caspase activity, RasGAP is cleaved, generating an N-terminal fragment (fragment N) and a C-terminal fragment (fragment C). Fragment N appears to be a general Mocker of apoptosis downstream of caspase activation. At higher levels of caspase activity, the ability of fragment N to counteract apoptosis is suppressed when it is further cleaved. This latter cleavage event generates two fragments, N1 and N2, which in contrast to fragment N potently sensitizes cancer cells toward DNA-damaging agents induced apoptosis. In the present study we show that a cell permeable peptide derived from the N2 fragment of RasGAP, thereafter called TAT-RasGAP317-326, specifically sensitizes cancer cells to three different genotoxins commonly used in chemotherapy in vitro and in vivo models. Importantly this peptide seems not to have any effect on non cancer cells. We have also started to characterize the molecular mechanisms underlying the sensitizing functions of TAT-RasGAP317-326. We have demonstrated that the p53 transcription factor and a protein under its transcriptional activity, called Puma, are required for the activity of TATRasGAP317-326. We have also showed that TAT-RasGAP317-326 requires the presence of a protein called G3BP1, which have been shown to interact with RasGAP, to increase the effect of the DNA-damaging drug cisplatin. The data obtained in this study showed that it is possible to increase the efficacy of current used chemotherapies with a compound able to increase the efficacy of genotoxins which could be beneficial for patients subjected to chemotherapy.
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In eukaryotic cells, transgene expression levels may be limited by an unfavourable chromatin structure at the integration site. Epigenetic regulators are DNA sequences which may protect transgenes from such position effect. We evaluated different epigenetic regulators for their ability to protect transgene expression at telomeres, which are commonly associated to low or inconsistent expression because of their repressive chromatin environment. Although to variable extents, matrix attachment regions (MARs), ubiquitous chromatin opening element (UCOE) and the chicken cHS4 insulator acted as barrier elements, protecting a telomeric-distal transgene from silencing. MARs also increased the probability of silent gene reactivation in time-course experiments. Additionally, all MARs improved the level of expression in non-silenced cells, unlike other elements. MARs were associated to histone marks usually linked to actively expressed genes, especially acetylation of histone H3 and H4, suggesting that they may prevent the spread of silencing chromatin by imposing acetylation marks on nearby nucleosomes. Alternatively, an UCOE was found to act by preventing deposition of repressive chromatin marks. We conclude that epigenetic DNA elements used to enhance and stabilize transgene expression all have specific epigenetic signature that might be at the basis of their mode of action.
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The JXTA-Overlay project is an effort to use JXTA technologyto provide a generic set of functionalities that can be used by developers to deploy P2P applications. Since its design mainly focuses on issues such as scalability or overall performance, it does not take security into account. However, as P2P applications have evolved to fulfill more complex scenarios, security has become a very important aspect to take into account when evaluating a P2P framework. This work proposes a security extension specifically suited to JXTA-Overlay¿s idiosyncrasies, providing an acceptable solution to some of its current shortcomings.
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In recent years, considerable research has focused on the biological effect of endocrine-disrupting chemicals. Bisphenol A (BPA) has been implicated as an endocrine-disrupting chemical (EDC) due to its ability to mimic the action of endogenous estrogenic hormones. The aim of this study was to assess the effect of perinatal exposure to BPA on cerebral structural development and metabolism after birth. BPA (1mg/l) was administered in the drinking water of pregnant dams from day 6 of gestation until pup weaning. At postnatal day 20, in vivo metabolite concentrations in the rat pup hippocampus were measured using high field proton magnetic resonance spectroscopy. Further, brain was assessed histologically for growth, gross morphology, glial and neuronal development and extent of myelination. Localized proton magnetic resonance spectroscopy ((1)H MRS) showed in the BPA-exposed rat a significant increase in glutamate concentration in the hippocampus as well as in the Glu/Asp ratio. Interestingly these two metabolites are metabolically linked together in the malate-aspartate metabolic shuttle. Quantitative histological analysis revealed that the density of NeuN-positive neurons in the hippocampus was decreased in the BPA-treated offspring when compared to controls. Conversely, the density of GFAP-positive astrocytes in the cingulum was increased in BPA-treated offspring. In conclusion, exposure to low-dose BPA during gestation and lactation leads to significant changes in the Glu/Asp ratio in the hippocampus, which may reflect impaired mitochondrial function and also result in neuronal and glial developmental alterations.
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RésuméLa coexistence de nombreuses espèces différentes a de tout temps intrigué les biologistes. La diversité et la composition des communautés sont influencées par les perturbations et l'hétérogénéité des conditions environnementales. Bien que dans la nature la distribution spatiale des conditions environnementales soit généralement autocorrélée, cet aspect est rarement pris en compte dans les modèles étudiant la coexistence des espèces. Dans ce travail, nous avons donc abordé, à l'aide de simulations numériques, la coexistence des espèces ainsi que leurs caractéristiques au sein d'un environnement autocorrélé.Afin de prendre en compte cet élément spatial, nous avons développé un modèle de métacommunauté (un ensemble de communautés reliées par la dispersion des espèces) spatialement explicite. Dans ce modèle, les espèces sont en compétition les unes avec les autres pour s'établir dans un nombre de places limité, dans un environnement hétérogène. Les espèces sont caractérisées par six traits: optimum de niche, largeur de niche, capacité de dispersion, compétitivité, investissement dans la reproduction et taux de survie. Nous nous sommes particulièrement intéressés à l'influence de l'autocorrélation spatiale et des perturbations sur la diversité des espèces et sur les traits favorisés dans la métacommunauté. Nous avons montré que l'autocorrélation spatiale peut avoir des effets antagonistes sur la diversité, en fonction du taux de perturbations considéré. L'influence de l'autocorrélation spatiale sur la capacité de dispersion moyenne dans la métacommunauté dépend également des taux de perturbations et survie. Nos résultats ont aussi révélé que de nombreuses espèces avec différents degrés de spécialisation (i.e. différentes largeurs de niche) peuvent coexister. Toutefois, les espèces spécialistes sont favorisées en absence de perturbations et quand la dispersion est illimitée. A l'opposé, un taux élevé de perturbations sélectionne des espèces plus généralistes, associées avec une faible compétitivité.L'autocorrélation spatiale de l'environnement, en interaction avec l'intensité des perturbations, influence donc de manière considérable la coexistence ainsi que les caractéristiques des espèces. Ces caractéristiques sont à leur tour souvent impliquées dans d'importants processus, comme le fonctionnement des écosystèmes, la capacité des espèces à réagir aux invasions, à la fragmentation de l'habitat ou aux changements climatiques. Ce travail a permis une meilleure compréhension des mécanismes responsables de la coexistence et des caractéristiques des espèces, ce qui est crucial afin de prédire le devenir des communautés naturelles dans un environnement changeant.AbstractUnderstanding how so many different species can coexist in nature is a fundamental and long-standing question in ecology. Community diversity and composition are known to be influenced by heterogeneity in environmental conditions and disturbance. Though in nature the spatial distribution of environmental conditions is frequently autocorrelated, this aspect is seldom considered in models investigating species coexistence. In this work, we thus addressed several questions pertaining to species coexistence and composition in spatially autocorrelated environments, with a numerical simulations approach.To take into account this spatial aspect, we developed a spatially explicit model of metacommunity (a set of communities linked by dispersal of species). In this model, species are trophically equivalent, and compete for space in a heterogeneous environment. Species are characterized by six life-history traits: niche optimum, niche breadth, dispersal, competitiveness, reproductive investment and survival rate. We were particularly interested in the influence of environmental spatial autocorrelation and disturbance on species diversity and on the traits of the species favoured in the metacommunity. We showed that spatial autocorrelation can have antagonistic effects on diversity depending on disturbance rate. Similarly, spatial autocorrelation interacted with disturbance rate and survival rate to shape the mean dispersal ability observed in the metacommunity. Our results also revealed that many species with various degrees of specialization (i.e. different niche breadths) can coexist together. However specialist species were favoured in the absence of disturbance, and when dispersal was unlimited. In contrast, high disturbance rate selected for more generalist species, associated with low competitive ability.The spatial structure of the environment, together with disturbance and species traits, thus strongly impacts species diversity and, more importantly, species composition. Species composition is known to affect several important metacommunity properties such as ecosystem functioning, resistance and reaction to invasion, to habitat fragmentation and to climate changes. This work allowed a better understanding of the mechanisms responsible for species composition, which is of crucial importance to predict the fate of natural metacommunities in changing environments
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This work describes a simulation tool being developed at UPC to predict the microwave nonlinear behavior of planar superconducting structures with very few restrictions on the geometry of the planar layout. The software is intended to be applicable to most structures used in planar HTS circuits, including line, patch, and quasi-lumped microstrip resonators. The tool combines Method of Moments (MoM) algorithms for general electromagnetic simulation with Harmonic Balance algorithms to take into account the nonlinearities in the HTS material. The Method of Moments code is based on discretization of the Electric Field Integral Equation in Rao, Wilton and Glisson Basis Functions. The multilayer dyadic Green's function is used with Sommerfeld integral formulation. The Harmonic Balance algorithm has been adapted to this application where the nonlinearity is distributed and where compatibility with the MoM algorithm is required. Tests of the algorithm in TM010 disk resonators agree with closed-form equations for both the fundamental and third-order intermodulation currents. Simulations of hairpin resonators show good qualitative agreement with previously published results, but it is found that a finer meshing would be necessary to get correct quantitative results. Possible improvements are suggested.
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A variety of cellular proteins has the ability to recognize DNA lesions induced by the anti-cancer drug cisplatin, with diverse consequences on their repair and on the therapeutic effectiveness of this drug. We report a novel gene involved in the cell response to cisplatin in vertebrates. The RDM1 gene (for RAD52 Motif 1) was identified while searching databases for sequences showing similarities to RAD52, a protein involved in homologous recombination and DNA double-strand break repair. Ablation of RDM1 in the chicken B cell line DT40 led to a more than 3-fold increase in sensitivity to cisplatin. However, RDM1-/- cells were not hypersensitive to DNA damages caused by ionizing radiation, UV irradiation, or the alkylating agent methylmethane sulfonate. The RDM1 protein displays a nucleic acid binding domain of the RNA recognition motif (RRM) type. By using gel-shift assays and electron microscopy, we show that purified, recombinant chicken RDM1 protein interacts with single-stranded DNA as well as double-stranded DNA, on which it assembles filament-like structures. Notably, RDM1 recognizes DNA distortions induced by cisplatin-DNA adducts in vitro. Finally, human RDM1 transcripts are abundant in the testis, suggesting a possible role during spermatogenesis.
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A firm that wishes to launch a new product to the market is faced with a difficult task of deciding what the best moment for the launch is. Timing may also be critical when a firm plans to adopt new processes or intends to head for new markets. The critical question the firm needs to tackle is whether it will try to reach the so-called first-mover advantage by acting earlier than its rivals. The first-mover position may reward the entrant with various opportunities to gain competitive advantage over later movers. However, there are also great risks involved in the early market entry, and sometimes the very first entrant fails even before the followers enter the market. The follower, on the other hand, may be able to free-ride on the earlier entrants' investments and gain from the languished uncertainties that characterize the new markets. According to the current understanding the occurrence of entry order advantages depends not only on the mechanism and attributes in the firm's environment that provide the initial opportunities but also on the firm's ability to capitalize on these advantage opportunities. This study contributes to this discussion by analyzing the linkages between the asset base of the firm, characteristics of the operating environment and the firm's entry timing orientation. To shed light on the relationship between the entry timing strategy and competitive advantage, this study utilizes the concept of entry timing orientation. The rationale for choosing this type of approach arises from the inability of previously employed research tools to reach the underlying factors that result in entry timing advantage. The work consists of an introductory theoretical discussion on entry timing advantages and of four research publication. The empirical findings support the understanding that entry timing advantage is related to the characteristics of the firm's operating environment but may also be related to firm-specific factors. This in turn suggests that some of the traditional ways of detecting and measuring first-mover advantage - which to some extent ignore these dimensions - may be outdated.
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Laktoosi eli maitosokeri on tärkein ainesosa useimpien nisäkkäiden tuottamassa maidossa. Sitä erotetaan herasta, juustosta ja maidosta. Laktoosia käytetään elintarvike- ja lääketeollisuuden raaka-aineena monissaeri tuotteissa. Lääketeollisuudessa laktoosia käytetään esimerkiksi tablettien täyteaineena. Hapettamalla laktoosia voidaan valmistaa laktobionihappoa, 2-keto-laktobionihappoa ja laktuloosia. Laktobionihappoa käytetään biohajoavien pintojen ja kosmetiikkatuotteiden valmistuksessa, sekä sisäelinten säilöntäliuoksissa, joissa laktobionihappo estää happiradikaalien aiheuttamien kudosvaurioiden syntymistä. Tässä työssä laktoosia hapetettiin laktobionihapoksi sekoittimella varustetussa laboratoriomittakaavaisessa panosreaktorissa käyttäenkatalyyttinä palladiumia aktiivihiilellä. Muutamissa kokeissa katalyytin promoottorina käytettiin vismuttia, joka hidastaa katalyytin deaktivoitumista. Työn tarkoituksena oli saada lisää tietoa laktoosin hapettamisen kinetiikasta. Laktoosin hapettumisessa laktobionihapoksi havaittiin selektiivisyyteen vaikuttavan muunmuassa reaktiolämpötila, paine, pH ja käytetyn katalyytin määrä. Katalyyttiä kierrättämällä eri kokeiden välillä saatiin paremmat konversiot, selektiivisyydet ja saannot. Parhaat koetulokset saatiin hapetettaessa synteettisellä ilmalla 60 oC lämpötilassa ja 1 bar paineessa. Tehdyissä kokeissa pH:n säätö tehtiin manuaalisesti, joten pH ei pysynyt koko ajan haluttuna. Laktoosin konversio oli parhaimmillaan 95 %. Laktobionihapon suhteellinen selektiivisyys oli 100% ja suhteellinen saanto 100 %. Kinetiikan matemaattinen mallinnus tehtiin Modest-ohjelmalla käyttäen kokeista saatuja mittaustuloksia.Ohjelman avulla estimoitiin parametreja ja saatiin matemaattinen malli reaktorille. Tässä työssä tehtiin kineettinen mallinnus myös ravistelureaktorissa tehdyille laktoosin hapetuskokeille, missä pH pysyi koko ajan haluttuna 'in-situ' titrauksen avulla. Työn yhteydessä selvitettiin myös mahdollisuutta käyttää monoliittikatalyyttejä laktoosin hapetusreaktiossa.