Digital speckle photography: visualization of mesoflow through clustered fiber networks

Digital speckle photography (DSP) is used for velocity field measurements inside a fiber network. The width of the channels in which the flow is measured is typically less than 1 mm. Therefore a microscope is used to image the fiber network. When we sample 30 images/s and separate the moving parts of the images from the stationary parts, the velocity field can be deduced with DSP.     

A proposal for the catalytic mechanism in phospholipase C based on interaction energy and distance geometry calculations

The non-specific phospholipase C from Bacillus cereus preferentiallyhydrolyses phosphatidylcholine but is also active against phosphatidylserine,phosphatidylethanolaniine and at a much lower level, sphingomyelin.A minimal substrate model containing all required structuraland configurational elements of a high affinity substrate wasdocked into the active site. The enzyme–substrate attachmentpoints were from molecular interaction energy calculations usingthe program GRID and from a previous phosphate inhibitor complexstructure. Available conformational space for the substratewas sampled by distance geometry calculations using the programDGEOM. This investigation clearly identifies the attacking nucleophile,a catalytically favourable orientation of the phosphate groupin its tetra-, as well as its penta-, coordinated state anda crucial stabilizing environment for the alkoxide intermediate.Based on this information a complete catalytic cycle is proposed.     

Substituted Mo–V(Ti)–Te(Ce)-oxide M2 Catalysts for Propene Ammoxidation

One of the most effective propane to acrylonitrile ammoxidation catalyst is comprised of the two phases M1 (orthorhombic) Mo_7.5V_1.5NbTeO₂₉ and M2 (pseudo-hexagonal) Mo₄V₂Te₂O₂₀. Under reaction conditions, the two phases work in symbiosis with each other where M1 is the paraffin activating component and M2 is the olefin activating component. Since the catalytic improvement of either phase should result in an enhancement of the overall acrylonitrile yield, controlled substitution of certain elements in either or both phases might result in the desired improvement. Our current study concentrates on the partial substitutions of V with Ti and Te with Ce in the M2 phase. Ti substitution results in a considerable propene activity improvement, whereas the selectivity to acrylonitrile is unaffected. Substitution with Ce, on the contrary, substantially improves the selectivity to acrylonitrile. Also, a minor improvement of the activity is notable. The acrylonitrile selectivity improvement is a result of better NH₃ utilization and comes at the expense of reduced acrolein make. XRD reveals that all of the substituted compositions retain the M2 structure and essentially are monophasic. XANES recordings show for the bulk that the Mo is 6+, the V is 4+, or 4+ and 5+ when Ce is present, the Ti is 4+, the Ce is 3+, and the Te 4+ with some 6+ also present. According to the ESR data, in the M2 with Ce (7Te/3Ce) only 21% of the V is 4+, the remainder being 5+, which tentatively can be explained by the existence of some cation vacancies in the hexagonal channels. HRTEM imaging reveals little if any differences between the materials, all have the typical pseudo-hexagonal habit of the M2 phase and expose a 1–2 nm thick surface layer without any apparent long-range ordering. XPS data show that all catalysts, including the base, are highly enriched at the surface with Te at the expense of other metals. The 7Te/3Ce composition exhibits also substantial Ce surface enrichment. Moreover, the valences of the cations at the surface differ from the bulk in that for all fresh catalysts V is 5+ and Te is 6+ on the surface. Characterization by XPS of catalysts used in propene ammoxidation, reveals reduction of Te and, except when Ce is present, also Mo. Therefore, it might be inferred that the surfaces of the catalysts studied here are comprised essentially of one or a few monolayers of TeMoO or TeCeMoO on an interacting M2 crystalline base.     

The Dissolution of Cationic Potato Amylopectin

The dissolution of a cationic potato amylopectin was studied at low dissolution temperatures 50°–97°C. The dissolution was followed by two methods: (1) iodine binding and (2) the flocculation efficiency with nanosized silica particles. The first method gives us information whether the iodine can penetrate the amylopectin structure or not. The second method gives us qualitative information about the size of the amylopectin molecules. At low dissolution temperatures it was found that the molecular weight of the amylopectin (or aggregate size) was larger than those obtained at higher dissolution temperatures. It was also found that the cationic potato starch only containing amylopectin was easier to dissolve than the cationic starch containing both amylose and amylopectin.     

Building energy parameter investigations based on multivariate analysis

System identification can be used for evaluations of how measured energy use is influenced by the operation, design and equipment of buildings and their users. However, it can be difficult to access appropriate data for modelling purposes due to a small number of buildings, parameters not distributed normally, lumped information, etc. In this work, data of a subset of 112 comparable multifamily buildings located in the Stockholm area were derived from a larger Swedish building energy consumption survey. In that database, the accessible data are monthly consumption data together with a large number of building-specific classification parameters, e.g. building code, age of control system, type of owner, maintenance organization, area to let, etc.A multivariate PLS method (partial least squares to latent structures) was used to model different energy performance measures, such as the use of energy for heating, electricity used to operate the building technical system, the building total heat loss coefficient and the use of domestic cold water. The PLS model was investigated for both the total annual use and the annual use normalized to the available floor area. For most measures of performance, only qualitative estimates of the impact of different classification parameters could be drawn due to the goodness value of the model. However, for some of the investigated parameters, quantitative estimates could also be drawn. The obtained results are, in most cases, in good agreement with what might be expected.To enable benchmarking of different energy use measures, the area to let is commonly used as a normalizer by real estate managers in Sweden. In this study, we find strong indications that the area to let is not suitable for this purpose.     

Is it time to use activity-based urban transport models? A discussion of planning needs and modelling possibilities

For some decades now, transport researchers have put considerable efforts into developing what is called activity-based approaches for modelling urban travel demand. The basic idea is that travel demand is derived from people’s desires to take part in different activities. In particular, the interrelationships among different activities with respect to temporal and spatial constraints are in focus. It means that such models treat the activities and the travelling of the households with respect to where and when the activities can be carried out and how they may be scheduled, given characteristics of the households and potential opportunities, the transport networks and various institutional constraints. We discuss what demands we see on future travel demand models, with a focus on urban analysis. This discussion is somewhat biased towards what role activity-based models could play in meeting these demands. We then review in some detail three prominent and distinctly different representatives of operational activity-based models to give an indication of what new modelling possibilities they offer. Theoretical appeal, empirical validity, usefulness for planning, need for data and easiness of implementation are discussed. In the final section we draw some conclusions about the prospects of these models and of their descendants.     

Screening of nucleation conditions using levitated drops for protein crystallization

The growth of suitable protein crystals is an essential step in the structure determination of a protein by X-ray crystallography. At present, crystals are mostly grown using trial-and-error procedures, and protocols that rapidly screen for the crystal nucleation step are rare. Presented here is an approach to minimize the consumption of precious protein material while searching for the nucleation conditions. Acoustically levitated drops of known protein concentration (0.25-1.5-microL volumes) are injected with crystallizing agents using piezoelectric flow-through dispensers (ejecting 50-100-pL droplets at 1-9000 droplets/s). A restricted number of crystallizing agents representing three classes are used: poly(ethylene glycol), salts, and the viscous alcohol 2-methyl 2,4-pentanediol. From a digitized picture of the levitated drop volume, calculations are performed giving the concentrations of all components in the drop at any time during a "precipitation experiment". Supersaturation is the prerequisite for crystal nucleation, and protein precipitation indicates high supersaturation. A light source illuminates the levitated drop, and protein precipitation is monitored using right-angle light scattering. On the basis of these intensity measurements and the volume determination, precipitation diagrams for each crystallizing agent are constructed that give the protein/crystallizing agent concentration boundaries between the minimum and the maximum detectable protein precipitation. Guided by the concentration values obtained from such plots, when approaching the supersaturation region, separate crystallization drops are mixed and allowed to equilibrate under paraffin oil. At conditions in which microcrystals can be observed, the nucleation tendency of the macromolecule is confirmed. Optimization of crystallization conditions can then follow. Proteins tested include alcohol dehydrogenase and D-serine dehydratase. Alcohol dehydrogenase, known to crystallize easily, was used to evaluate whether the ultrasonic field inhibits nucleation. Details are given for the screening procedure of D-serine dehydratase, an enzyme earlier found to be difficult to crystallize reproducibly. The time and material-saving qualities of this method are emphasized, since a range of conditions can quickly be screened using small amounts of protein to roughly determine solubility characteristics of a protein before crystallization trials are initiated.     

Quantitative analysis of film coating in a fluidized bed process by in-line NIR spectrometry and multivariate batch calibration

A method is described which enables real-time analysis of film coating on pharmaceutical pellets during an industrial manufacturing process. Measurements were conducted on the solid particulate material by near-infrared (NIR) spectrometry utilizing a diffuse reflectance fiber-optic probe positioned inside a fluidized bed process vessel. Time series of NIR spectra from 11 batches generated a three-way data matrix that was unfolded and modeled by partial least squares (PLS) in a multivariate batch calibration. The process conditions were deliberately varied according to an experimental design. This yielded good predictability of the coating thickness with a best model fit, R2 = 0.97, for one PLS-projection, and a root-mean-square error of calibration = 2.2 microm (range tested 0-50 microm). The regression vector was shown to be highly influenced by responses that are both direct (aliphatic C-H stretch overtones) and indirect (aromatic C-H stretch overtones), from film component and core material, respectively. The impact of different data pre-treatment methods on the normalization of the regression vector is reported. Justification of the process calibration approach is emphasized by good correlation between values predicted from NIR data and reference image analysis data on dissected pellets and a theoretical nonlinear coating thickness growth model. General aspects of in-line NIR on solids and multivariate batch calibration are discussed.     

Melt spinning of conducting polymeric composites containing carbonaceous fillers

Fibers produced by melt spinning of conductive polymer composites are attractive for several applications; the main drawback is however reduced processability at high filler concentrations. Carbon nanotubes (CNTs) are considered suitable fillers for conductive polymer composites, replacing conductive grades of carbon black (CB). In this study, the fiber‐forming properties of conductive polymer composites based on a conductive grade of CB and two masterbatches with CNT in a polyethylene matrix were investigated. The CB was also used in a polypropylene matrix for comparison. The rheological properties of the filler‐containing melts in shear and their extensional behavior were evaluated. A piston‐driven device was used to extrude the molten materials through a capillary; different capillary geometries were tested. Fibers were produced at various draw ratios, and their conductivity was determined. To assess the ultimate extensibility, a modified Rheotens method was used. The results showed that a conductive CB grade can have a lower percolation threshold and higher conductivity than a material with CNT. Conductivity decreased with increasing melt draw ratio for both types of fillers. The spinnability of the materials decreased with increasing concentration of filler material and correlations were found between spinnability and melt elasticity. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011