An overview of state-of-the-art image restoration in electron microscopy.

In Life Science research, electron microscopy (EM) is an essential tool for morphological analysis at the subcellular level as it allows for visualization at nanometer resolution. However, electron micrographs contain image degradations such as noise and blur caused by electromagnetic interference, electron counting errors, magnetic lens imperfections, electron diffraction, etc. These imperfections in raw image quality are inevitable and hamper subsequent image analysis and visualization. In an effort to mitigate these artefacts, many electron microscopy image restoration algorithms have been proposed in the last years. Most of these methods rely on generic assumptions on the image or degradations and are therefore outperformed by advanced methods that are based on more accurate models. Ideally, a method will accurately model the specific degradations that fit the physical acquisition settings. In this overview paper, we discuss different electron microscopy image degradation solutions and demonstrate that dedicated artefact regularisation results in higher quality restoration and is applicable through recently developed probabilistic methods.

Membrane bioreactor (MBR) sludge inoculation in a hybrid process scheme concept to assist overloaded conventional activated sludge (CAS) process operations.

This study analyzes the effect of inoculating membrane bioreactor (MBR) sludge in a parallel-operated overloaded conventional activated sludge (CAS) system. Modelling studies that showed the beneficial effect of this inoculation were confirmed though full scale tests. Total nitrogen (TN) removal in the CAS increased and higher nitrate formation rates were achieved. During MBR sludge inoculation, the TN removal in the CAS was proven to be dependent on MBR sludge loading. Special attention was given to the effect of inoculation on sludge quality. The MBR flocs, grown without selection pressure, were clearly distinct from the more compact flocs in the CAS system and also contained more filamentous bacteria. After inoculation the MBR flocs did not evolve into good-settling compact flocs, resulting in a decreasing sludge quality. During high flow conditions the effluent CAS contained more suspended solids. Sludge volume index, however, did not increase. Laboratory tests were held to determine the threshold volume of MBR sludge to be seeded into the CAS reactor. Above 16-30%, supernatant turbidity and scum formation increased markedly.

Parametric instability of an integrated micromechanical oscillator by means of active optomechanical feedback.

Mass sensing and time keeping applications require high frequency integrated micromechanical oscillators. To overcome the increasing mechanical stiffness of these structures sensitive optical vibration detection and efficient actuation is required. Therefore we have implemented an active feedback system, where the feedback signal is provided by the optical gradient force that is present between nanophotonic waveguides on a silicon-on-insulator chip. We found that access to the parametric instability regime can be easily controlled by tuning the wavelength.

Cost optimisation and minimisation of the environmental impact through life cycle analysis of the waste water treatment plant of Bree (Belgium).

An ASM2da model of the full-scale waste water plant of Bree (Belgium) has been made. It showed very good correlation with reference operational data. This basic model has been extended to include an accurate calculation of environmental footprint and operational costs (energy consumption, dosing of chemicals and sludge treatment). Two optimisation strategies were compared: lowest cost meeting the effluent consent versus lowest environmental footprint. Six optimisation scenarios have been studied, namely (i) implementation of an online control system based on ammonium and nitrate sensors, (ii) implementation of a control on MLSS concentration, (iii) evaluation of internal recirculation flow, (iv) oxygen set point, (v) installation of mixing in the aeration tank, and (vi) evaluation of nitrate setpoint for post denitrification. Both an environmental impact or Life Cycle Assessment (LCA) based approach for optimisation are able to significantly lower the cost and environmental footprint. However, the LCA approach has some advantages over cost minimisation of an existing full-scale plant. LCA tends to chose control settings that are more logic: it results in a safer operation of the plant with less risks regarding the consents. It results in a better effluent at a slightly increased cost.

Intracranial pressure changes in patients with head trauma during haemodialysis.

Intracranial hypertension and acute renal failure are frequent complications in polytraumatized patients with head trauma. This paper deals with the evolution of intracranial pressure during haemodialysis in two cases of traumatic coma. Significant changes in intracranial pressure were noted. Increase of intracranial pressure during haemodialysis was 7.6 mmHg for the first patient and 4.6 mmHg for the second patient. Prophylactic measures are discussed.

A quantitative description of the growth of Saccharomyces cerevisiae CBS 426 on a mixed substrate of glucose and ethanol.

Saccharomyces cerevisiae CBS 426 was grown aerobically in continuous culture with a mixture of glucose and ethanol as the carbon source. The flows of biomass, glucose, ethanol, oxygen, and carbon dioxide were measured. A model for growth with two substrates was derived. Application of this model to the above-mentioned system yielded values for YATP and P/O. The joint confidence regions for these parameters were calculated. The relevance to industrial production of bakers' yeast is discussed.

Immunohistochemical analysis of E-cadherin expression in human colorectal tumours.

The homotypic homophilic cell-cell adhesion molecule E-cadherin is crucial in the organization and maintenance of most epithelia. The expression of E-cadherin was studied immunohistochemically in various human colorectal tumours. Therefore we stained 1 tubular adenoma with low grade dysplasia, 18 adenocarcinomas with different histologic degrees of differentiation and invasion, and 1 metastasis using a modified peroxidase-anti-peroxidase technique. In the adenoma as well as in all well differentiated adenocarcinomas we found E-cadherin immunopositivity at the cell membrane of almost all cancer cells. The immunopositivity of E-cadherin was clearly weaker and sometimes even absent in isolated neoplastic cells and glands of less differentiated adenocarcinomas. The moderately differentiated adenocarcinomas showed an intermediate staining pattern. These findings are in line with experimental evidence that downregulation of E-cadherin favours invasion, eventually leading to metastasis.

Patellar tendinitis (jumper's knee).

A jumper's knee is an overload lesion of patellar or quadriceps tendon near its insertion at the lower or upper pole of the patella. If conservative treatment fails, an operation can be performed in Phase 3 where disabling symptoms, are present. The necrotic tissue in the patellar tendon is excised. The early results of this surgery are encouraging.

Biological formation of volatile phosphorus compounds.

Phosphine and phosphides are reported to occur at numerous environmental sites such as fresh and marine sediments, landfills, faecal matter, biogas digesters and soils. The concentrations are several log units lower than the time-weighted average exposure standard, i.e. in the order of ng per m3 of gas or ng per kg material. Research about the biological formation of highly reduced gaseous phosphorus compounds dates back more than a hundred years. The early reports had to deal with a lot of scepticism. Thanks to new analytical tools (gas chromatography) it has become clear, during the last decade, that phosphine is a global constituent of the atmosphere. Pure strains of micro-organisms cultivated under highly anaerobic conditions were shown to produce phosphine. Thermodynamic considerations indicate that it is very improbable that the reduction of phosphate to phosphine is endergonic. Therefore the generation of phosphine cannot be compared with sulphidogenesis and methanogenesis. There seems to be a link between the existence of highly reactive gaseous phosphorus compounds and increased levels of metal corrosion. The reactive compounds could be formed by micro-organisms or they are liberated from phosphorus-containing impurities in the iron by the action of bacterial metabolites. The biochemical pathways responsible for the production of gaseous phosphorus compounds have not been characterised yet.

Radiographic measurement from the lateromedial projection of the equine foot with navicular disease.

Radiographic measurements from the lateromedial projection of the equine foot were compared in three groups of horses. Group 1 consisted of 143 normal horses, group 2 were 60 horses with clinical navicular disease and group 3 were 161 horses with clinical and radiographic navicular disease. Several measurements tended to be larger in group 3 than group 1. An enlargement of the navicular bone was observed in proximodistal and dorsopalmar directions. Partial enlargement of the pedal bone was observed in groups 2 and 3. Few differences were observed between age classes. All horses aged four years and over had an increased length of the hoof in the dorosopalmar direction and a decrease of the cranial angle of the hoof. Enlargement of the navicular bone fits well into the concept of osteoarthrosis. The pedal bone was partly engaged. These findings may be an expression of a regional acceleratory phenomenon.

Occurrence and origin of phosphine in landfill gas.

A landfill (Hooge Maey, Flanders, Belgium) was subjected to an in-depth study in order to explain the origin of phosphine detected in high amounts in landfill gas during a previous study. The spatial and temporal variability of the phosphine concentration in landfill gas was assessed. Twenty four wells were monitored and differences in phosphine concentration up to one log unit were observed (3.2-32.4 microg/m3). The phosphine concentration in each well was constant in time over a period of 4 months. No correlation was found between the phosphine concentration and methane, carbon dioxide, hydrogen sulphide, ethene or ethane concentration. In a series of laboratory tests, it was shown that phosphine was emitted during batch fermentation tests inoculated with landfill leachate when Fe0 or Al0 specimens were added. Conditions favouring corrosion of iron gave rise to higher emissions of phosphine. The phosphine concentration in the headspace of a batch test rose to 1.43 mg/m3 after 27 days of incubation. Weight loss of corroding steel coupons correlated with phosphine emission. Calculations showed that all phosphine emitted from the 0.005 km3 landfill (160 g/year) could be attributed to corrosion of metals. No evidence of de novo synthesis could be established

Comments on "In search of a thermodynamic description of biomass yields for the chemotrophic growth of microorganisms".

In a recent publication, Heijnen and van Dijken (Biotechnol. Bioeng. 39: 833-858, 1992) reviewed the state of the art regarding the use of macroscopic methods in the correlation of biomass yields in growing microorganisms. In their article, reference is made to this author's work of some 10 years ago.Heijnen and van Dijken introduce the Gibbs' energy dissipation as a concept with favorable characteristics compared with various other approaches, including thermodynamic efficiency, as introduced by this author.In this communication, it will be shown that the "dissipation" and the "thermodynamic efficiency" description are completely equivalent and that there can be no preference for one of these in terms of rigor or characteristics.

The inhibition of the maximum specific growth and fermentation rate of Zymomonas mobilis by ethanol.

The inhibition of the maximum specific growth and fermentation rate of Zymomonas mobilis by ethanol was studied in turbidostat cultures at constant and stepwise changed ethanol concentrations. Up to 50 g/L ethanol, the inhibition kinetics can be approximated by a linear relationship between the specific growth rate and the ethanol concentration. Above this level, deviations from this linearity are observed. The specific fermentation rates were less inhibited by ethanol than was the specific growth rate. The maximum ethanol concentration achieved was 72 g/L.The response time for the adaptation of a turbidostat culture to step changes in the ethanol concentration was markedly dependent on the concentration level, the response time being large at high ethanol concentrations.

Fermentation kinetics of Zymomonas mobilis near zero growth rate.

The fermentation kinetics Zymomonas mobilis were studied near zero growth rate in fed-batch cultures and continuous cultures with complete cell recycle. The results show the ethanol enhances that specific substrate conversion rate under these conditions. The maximum achievable ethanol concentration in continuous cultures with cell recycle (66 g/L) was significantly lower than in fed-batch cultures (100 g/L). The results indicate that growth-rate-independent metabolism is not instantaneous and can lag behind steadily increasing ethanol concentrations in fed-batch fermentations. A model is proposed to account for this slow adaptation.

Penicillin production: biotechnology at its best.

A brief description is given of the history of penicillin production in the Netherlands. The development of today's penicillin production technology is analysed in terms of changes in the quality and intensity of the production process. Technological as well as genetical developments are shown to be of influence on the quality and the intensity of the production process. The analysis is illustrated by a brief description of the productivity improvement of the penicillin fermentation as it occurred at Gist-brocades during the past 20 years.

Application of balancing methods in modeling the penicillin fermentation.

This paper shows the application of elementary balancing methods in combination with simple kinetic equations in the formulation of an unstructured model for the fed-batch process for the production of penicillin. The rate of substrate uptake is modeled with a Monod-type relationship. The specific penicillin production rate is assumed to be a function of growth rate. Hydrolysis of penicillin to penicilloic acid is assumed to be first order in penicillin. In simulations with the present model it is shown that the model, although assuming a strict relationship between specific growth rate and penicillin productivity, allows for the commonly observed lag phase in the penicillin concentration curve and the apparent separation between growth and production phase (idiophase-trophophase concept). Furthermore it is shown that the feed rate profile during fermentation is of vital importance in the realization of a high production rate throughout the duration of the fermentation. It is emphasized that the method of modeling presented may also prove rewarding for an analysis of fermentation processes other than the penicillin fermentation.

Theory and applications of unstructured growth models: Kinetic and energetic aspects.

Microbial kinetics and energetics are discussed in connection with the formulation of unstructured growth models. The development of microbial energetics and the use of macroscopic methods in the study of microbial growth are briefly evaluated. The general approach to the modelling of microbial growth has been critically discussed and a strategy for the formulation of unstructured models is presented. A simple unstructured model based on Monod kinetics and the linear relation for substrate consumption is evaluated with reference to extensive experimental and simulation data obtained in batch, fed-batch, and continuous cultivation modes. Choice for a kinetic expression is discussed and has been shown not to be critical in most situations. It is shown that during growth in batch mode, the behavior of the system is rigidly fixed by the kinetic parameter: the maximum specific growth rate. The energetic parameters have minimal influence. In continuous cultivation the behavior is fixed by the energetic parameters: the maximum yield and the coefficient of maintenance. Implications of these observations have also been discussed. The linear relation for substrate consumption is tested with continuous culture data. It is shown that significant deviations at low growth rates cannot be fully accounted by the loss of viability. The situations where unstructured models will be adequate or not for system description, are evaluated and checked experimentally. Influence of an environmental factor, the temperature, on the unstructured model parameters is also quantitatively described. It is concluded that the art of unstructured model building has already reached its maturity and that now much effort should be channelled into the development and verification of structured models.

The growth of Saccharomyces cerevisiae CBS 426 on mixtures of glucose and succinic acid: A model.

Saccharomyces cerevisiae CBS 426 was grown in continuous culture in a defined medium with a mixture of glucose and succinic acid as the carbon source. Growth on succinic acid was possible after long adaptation periods. The flows of glucose, succinic acid, oxygen, carbon dioxide, and biomass to and from the system were measured. It proved necessary to expand our previous model to accommodate the active transport of succinic acid by the cell. The values found for the efficiency of the oxidative phosphorylation (P/O) and the amount of ATP needed for production of biomass from monomers gave the same values as found for substrate mixtures taken up passively.