Flow-Based Network Management: A Report from the IRTF NMRG Workshop

This is the report on the Workshop on Flow-Based Network Management, held within the 37th IRTF NMRG meeting, during IETF 93, on 24th July 2015, in Prague, Czech Republic. Following the tradition of the IRTF NMRG, the workshop focused on technologies, developments, and challenges of using flow-level traffic measurements for network management.     

In vitro studies and preliminary in vivo evaluation of silicified concentrated collagen hydrogels

Hybrid and nanocomposite silica-collagen materials derived from concentrated collagen hydrogels were evaluated in vitro and in vivo to establish their potentialities for biological dressings. Silicification significantly improved the mechanical and thermal stability of the collagen network within the hybrid systems. Nanocomposites were found to favor the metabolic activity of immobilized human dermal fibroblasts while decreasing the hydrogel contraction. Cell adhesion experiments suggested that in vitro cell behavior was dictated by mechanical properties and surface structure of the scaffold. First-to-date in vivo implantation of bulk hydrogels in subcutaneous sites of rats was performed over the vascular inflammatory period. These materials were colonized and vascularized without inducing strong inflammatory response. These data raise reasonable hope for the future application of silica-collagen biomaterials as biological dressings.     

Job mobility, residential mobility and commuting: A theoretical analysis using search theory

The decision to move job and the decision to move residence are closely related dynamic discrete choices, as both moves involve a change of commuting distance. This suggests that labour and residential mobility are mutually dependent and should be simultaneously analysed, based on a theory which incorporates these dynamic decisions explicitly. In the present paper, we base our analysis on search theory and choose the point of departure that individuals maximise utility by moving through different labour market and housing market states, while taking into consideration that moving from one state to another is costly. Based on these assumptions, a search model is constructed and the optimality conditions are derived.  One of main conclusions based on the search model is that the effect of factors which cause housing market imperfections (viz. the residential moving costs and the residence arrival rate) have ambiguous effects on he job acceptance and job search behaviour of employed individuals. For some interesting cases however, the effect of the residential moving costs on the job acceptance behaviour can be derived. In contrast, the effect of housing market imperfections on the labour market behaviour of nonemployed persons is determined. We find for example that housing policies which discourage nonemployed persons to move residence (e.g. housing subsidies) also decrease the probability of becoming employed and may therefore unintentionally increase the number of nonemployed persons. Received: December 1997/Accepted: March 1999     

Encephalocytozoon intestinalis-specific monoclonal antibodies for laboratory diagnosis of microsporidiosis

Two monoclonal antibodies which can be used for the unambiguous identification by fluorescence microscopy of Encephalitozoon intestinalis spores in clinical specimens are described. Monoclonal antibody Si91 is specific for the extruded polar filament, and Si13 recognizes the surfaces of E. intestinalis spores. No cross-reaction with spores of Encephalitozoon hellem was observed. Immunogold electron microscopy confirmed the specific reactivities of both antibodies. Combined in an indirect immunofluorescence assay, these antibodies are used to identify spores in feces. Although there was some cross-reaction with fecal bacteria and fungi, the typical morphology of the extruded polar filaments enabled proper identification of the E. intestinalis spores. Parasites could also be demonstrated to be present in urine, nasal swabs, lung brush biopsy specimens, and bronchoalveolar lavage fluid from a patient with disseminated infection with E. intestinalis. The use of these monoclonal antibodies facilitates the detection and species determination of E. intestinalis in clinical specimens.     

Employment effects of changes in transportation infrastructure: methodological aspects of the gravity model

Assessing the employment effects of changes in transport infrastructure, such as the construction of the Channel Tunnel or high-speed rail connections, is not an easy task. The gravity model is sometimes used to analyse changes in the potentials of the regions concerned. One sttep further would be the translation of changes in potentials into changes in employment per region. This paper will be devoted to analysing some properties and limitation of such a translation process. Special attention is paid to an operational model developed by Evers et al. (1987) for this purpose. It is shown that this model is almost consistent with the theory of locational behaviou of firms.     

Estimation of Alonso's Theory of Movements by Means of Instrumental Variables

Alonso's Theory of Movements is a widely applicable Spatial Interaction Model, describing an equilibrium of inflows and outflows. Based on a survey of estimation attempts in the past, we conclude that econometric estimation of the so-called systemic parameters is somewhat problematic. In this paper we describe a new estimation method, using instrumental variables which are derived from the model. The distance deterrence parameter and the unobserved balancing factors can be estimated first, with known methods. The remaining parameters can be estimated in an iterative regression procedure, using instruments for the balancing factors. These instruments are derived as the predicted values of the balancing factors, based on the last obtained parameter estimates.     

A system for accurate on-line measurement of total gas consumption or production rates in microbioreactors

A system has been developed, based on pressure controlled gas pumping, for accurate measurement of total gas consumption or production rates in the nmol/min range, applicable for on-line monitoring of bioconversions in microbioreactors. The system was validated by carrying out a bioconversion with known stoichiometric relation between gas consumption and substrate conversion, that is, the enzymatic oxidation of glucose to gluconic acid. The reaction was carried out in a stirred microreactor with a working volume of 100 μL, whereby the oxygen consumption was monitored on-line. Subsequently the system was applied to determine the oxygen transfer capacity of the microbioreactor. The dissolved oxygen concentration was measured with an optical dissolved oxygen sensor, which was integrated near the bottom of the reactor. Different stirrer sizes and geometries were investigated for their effect on the mass transfer of oxygen. A maximal k_La of 156±10 h⁻¹, allowing a maximal O₂-transfer rate up to 50 mmol O₂/L/h, was reached which is sufficient to grow cells aerobically in (fed-)batch mode at relatively high biomass concentrations.     

Evaluation of experimental techniques to validate numerical computations of the hydraulics inside a UV bench-scale reactor

Computational fluid dynamics (CFD) is widely used to predict the hydraulics in environmental systems, but the validity of these predictions continues to receive attention. The hydraulics of a UV bench-scale reactor was evaluated by numerical and experimental techniques. Different experimental techniques were used to examine the hydraulics: salt injection to measure the residence time distribution, dye injection to visualize the mixing patterns, and LDA to measure the local velocity profiles. The combination of these measurements techniques provides information in unprecedented detail of the hydraulics inside UV systems. A CFD model with a standard k?ε turbulence model was used for comparison with the experimental results. The main flow patterns were predicted well. The largest differences were found at regions in the reactor where recirculation occurred, for example in the wake region of a lamp. Also, the CFD model predicted a larger mixing over the flow cross-section, resulting in a narrower residence time distribution.     

Selection of anionic exchange resins for removal of natural organic matter (NOM) fractions

Early elimination of natural organic matter (NOM) by ion exchange (IEX) in water treatment is expected to improve subsequent water treatment processes and the final drinking water quality. Nine anionic exchange resins were investigated to remove NOM and specific NOM fractions determined by liquid chromatography in combination with organic carbon detection (LC-OCD) and fluorescence excitation-emission matrices (EEM). Breakthrough of NOM was predicted by model calculations using Freundlich isotherms and IEX rate experiments. The time to breakthrough varied from 4 to 38 days. Removal of specific NOM fractions proved to vary considerably for the different types of IEX resins, ranging from 1% to almost 60%. The removal of NOM fractions, specifically humic substances, increased with an increase in water content of the investigated IEX resins and with a decrease in resin size. The best-performing IEX resins consisted of the smallest resins and/or those with the highest water content. The worst-performing IEX resins reflected the highest exchanging capacities and the lowest water contents.