Plasma assisted nitrogen oxide production from air: Using pulsed powered gliding arc reactor for a containerized plant

The production of NO_x from air and air + O₂ is investigated in a pulsed powered milli‐scale gliding arc (GA) reactor, aiming at a containerized process for fertilizer production. Influence of feed mixture, flow rate, temperature, and Ar and O₂ content are investigated at varying specific energy input. The findings are correlated with high‐speed imaging of the GA dynamics. An O₂ content of 40–48% was optimum, with an enhancement of 11% in NO_x production. Addition of Ar and preheating of the feed resulted in lower NO_x production. Lower flow rates produced higher NO_x concentrations due to longer residence time in the GA. The volume covered by GA depends strongly on the gas flow rate, emphasizing that the gas flow rate has a major impact on the GA dynamics and the reaction kinetics. For 0.5 L/min, 1.4 vol % of NO_x concentration was realized, which is promising for a containerized process plant to produce fertilizer in remote locations. © 2017 American Institute of Chemical Engineers AIChE J, 64: 526–537, 2018     

Quantitative Structural Analysis of Fat Crystal Networks by Means of Raman Confocal Imaging

The techniques that are currently available to assess fat crystal networks are compromised with respect to invasive sample preparation and ability to quantify compositional and structural features. Raman confocal hyperspectral imaging coupled to analysis with multivariate curve resolution can address these bottlenecks, as it provides label‐free, noninvasive chemical information in three dimensions (3D). We demonstrate the ability to acquire compositional maps of dispersions of micronized fat crystals (MFC) in oil, which contain local concentrations of liquid oil and solid fat with submicron spatial resolution and with acquisition times in the order of 10 min. From the compositional maps, we can derive quantitative information on the size and porosity of fat crystal flocs, as well as the solid fat content of the embedding continuous phase. Furthermore, the fractal dimension of the fat crystal network could be determined from the compositional maps via the box‐counting method and via the porosities of the crystal flocs. This makes it feasible to assess the validity of the weak‐link network theory under industrial relevant conditions. The confocal imaging mode allows for straightforward acquisition of 3D compositional cubes by recording a stack of two‐dimensional (2D) images. The box‐counting fractal dimension analysis performed on 2D maps can be extended to 3D cubes, which allows for straightforward verification that MFC networks are self‐similar rather than self‐affine.     

Hip arthroplasty by matching cups

A total hip surface arthroplasty consisting of matching cups and uncemented prosthetic components is a noteworthy operation. The femoral cup obtains cylindrical support from the femoral head which is reamed in the shape of a cylinder. The acetabular cup is metallic with a polyethylene liner. It is mobile over the bone but its position is constrained by contact with the femoral cup and therefore "self-centering." On the femoral side, the cup must be placed strictly in the axis of the femoral neck. The main consideration in femoral head surface replacement is the vitality of the underlying bone. Necrosis was observed in the earliest clinical trials but there have been no cases of necrosis in the past 3 1/2 years. This is attributed to a more limited surgical approach in which only the anterior part of the gluteus medius is divided and all the posterior elements of the hip are preserved. The acetabulum is sufficiently reamed to receive the cup, which protrudes beyond the external margins of the acetabulum in all positions. Errors have been committed while perfecting the prosthetic material, but the results as determined by a 6 1/2 year follow-up on purely metallic cups are encouraging. Metal-polyethylene cups presently under investigation have almost a 2 year follow-up. The reaction of the acetabulum to an uncemented cup is not yet known. However, the existence of 2 sliding surfaces and the fact that the acetabular cup moves only during the extremes of hip movement, is reason to assume that if the acetabulum is not reamed to expose cancellous bone, the risks of protrusion are minimal or delayed. Total surface arthroplasty by concentric cups has been performed in 335 hips to date. The operation is especially recommended when osteotomy is no longer possible and disabling coxarthrosis is present in relatively young patients.     

Influence of size and polarity of residue 31 in porcine pancreatic phospholipase A2 on catalytic properties

Residue 31 of porcine pancreatic phospholipase A₂ (PLA₂) islocated at the entrance to the active site. To study the roleof residue 31 in PLA₂, six mutant enzymes were produced by site-directedmutagenesis, replacing Leu by either Trp, Arg, Ala, Thr, Seror Gly. Direct binding studies indicated a three to six timesgreater affinity of the Trp31 PLA₂ for both monomeric and micellarsubstrate analogs, relative to the wild-type enzyme. The otherfive mutants possess an unchanged affinity for monomers of theproduct analog n-decylphosphocholine and for micelles of thediacyl substrate analog rac-l,2-dioctanoylamino-dideoxy-glycero-3-phosphocholine.The affinities for micelles of the monoacyl product analog n-hexadecylphosphocholinewere decreased 9–20 times for these five mutants. Kineticstudies with monomeric substrates showed that the mutants haveV_max values which range between 15 and 70% relative to the wild-typeenzyme. The V_max values for micelles of the zwitterionic substratel,2-dioctanoyl-sn-glycero-3-phosphocholine were lowered 3–50times. The K_m values for the monomeric substrate and the k_mvalues for the micellar substrate were hardly affected in thecase of five of the six mutants, but were considerably decreasedwhen Trp was present at position 31. The results of these investigationspoint to a versatile role for the residue at position 31: involvementin the binding and orientating of monomeric substrate (analogs),involvement in the binding of the enzyme to micellar substrateanalogs and possibly involvement in shielding the active sitefrom excess water.     

Laboratory-scale coal reactivity testing for entrained gasification

A relatively simple and rapid micro-gasification test has been developed for measuring gasification reactivities of carbonaceous materials under conditions which are more or less representative of an entrained gasification process, such as the Shell coal gasification process. Coal particles of < 100 μm are heated within a few seconds to a predetermined temperature level of 1000–2000 °C, which is subsequently maintained. Gasification is carried out with either CO₂ or H₂O. It is shown that gasification reactivity increases with decreasing coal rank. The CO₂ and H₂O gasification reactions of lignite, bituminous coal and fluid petroleum coke are probably controlled by diffusion at temperatures 1300–1400 °C. Below these temperatures, the CO₂ gasification reaction has an activation energy of about 100 kJ mol^?1 for lignite and 220–230 kJ mol^?1 for bituminous coals and fluid petroleum coke. The activation energies for H₂O gasification are about 100 kJ mol^?1 for lignite, 290–360 kJ mol^?1 for bituminous coals and about 200 kJ mol^?1 for fluid petroleum coke. Relative ranking of feedstocks with the micro-gasification test is in general agreement with 6 t/d plant results.     

UV‐Induced Cross‐Linking of Poly(ethylene oxide) in Aqueous Solution

Summary: Hydrogels of high‐molecular‐weight poly(ethylene oxide) (PEO) have been obtained in situ by applying a very simple procedure that involves UV cross‐linking of PEO in aqueous solution. The efficiency of the photoactivated cross‐linking of thin layers of PEO in aqueous solution in the presence of (4‐benzoylbenzyl) trimethylammonium chloride as a photoinitiator has been determined at room temperature and in a frozen state (?25 °C). It was found that the efficiency varies with the concentration of PEO solution, the molecular weight of PEO, and especially with the temperature. When the UV cross‐linking was performed in the frozen state, porous hydrogels with very high yield of gel fraction (above 90%) and high cross‐linking density were obtained. After drying the hydrogels, films of 50–150 μm thickness were prepared. The films swell extremely fast in water and act as asymmetric membranes.

SEM of a dried PEO hydrogel obtained by UV cross‐linking of an aqueous solution at room temperature.     

A unified approach to the recognition of complex actions from sequences of zone-crossings

We present a method for the recognition of complex actions. Our method combines automatic learning of simple actions and manual definition of complex actions in a single grammar. Contrary to the general trend in complex action recognition that consists in dividing recognition into two stages, our method performs recognition of simple and complex actions in a unified way. This is performed by encoding simple action HMMs within the stochastic grammar that models complex actions. This unified approach enables a more effective influence of the higher activity layers into the recognition of simple actions which leads to a substantial improvement in the classification of complex actions. We consider the recognition of complex actions based on person transits between areas in the scene. As input, our method receives crossings of tracks along a set of zones which are derived using unsupervised learning of the movement patterns of the objects in the scene. We evaluate our method on a large dataset showing normal, suspicious and threat behaviour on a parking lot. Experiments show an improvement of ~ 30% in the recognition of both high-level scenarios and their composing simple actions with respect to a two-stage approach. Experiments with synthetic noise simulating the most common tracking failures show that our method only experiences a limited decrease in performance when moderate amounts of noise are added.     

Purification and preliminary characterization of a frog-derived proteinaceous chemoattractant eliciting prey attack by checkered garter snakes (Thamnophis marcianus)

A potent proteinaceous chemoattractant, eliciting prey attack by checkered garter snakes (Thamnophis marcianus) was isolated from aqueous washes of the common frogRana temporaria and purified by preparative continuous-elution electrophoresis. The biological activity of the frog crude extract or of the purified chemoattractive protein, measured by a snake bioassay, was unaffected by freezing, lyophilization, or dialysis but was lost after proteolytic digestion. The purified chemoattractant is glycosylated, has an apparent molecular mass of 24 kDa, estimated by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS-PAGE), and a pI of 4.8. It gave one spot in two-dimensional electrophoresis. The bioassay showed that this protein is highly attractive to snakes. The lowest concentration yielding positive responses in the snake bioassay was approximately 25 µg/ml. These results suggest that a water-soluble Mr 24 kDa glycoprotein molecule produced by the common frog may be a vomeronasal stimulus used by checkered garter snakes for prey recognition.     

Larvicidal Effect of a Cell-Wall Fraction Isolated from Alder Decaying Leaves

Decaying alder leaves in water from Alpine Aedes breeding sites, particularly their toxicity to larval Culicidae, were investigated and characterized with comparative toxicological and chemical methods. Bioassays that used third-instar Aedes aegypti as a reference species indicated that the larvicidal effect of crude leaf litter varied with decaying age of the litter, while no toxicity was detected from leaching water of the mosquito breeding sites. Ten-month-old leaf litter was the most toxic. Comparison of the different soluble and insoluble fractions obtained after sequential extraction of decomposed litter allowed us to localize the toxicity factor to an insoluble cell-wall fraction. The toxicity seems to be linked to phenolic activity. It is higher than that found for tannic acid solutions used as a reference to mimic the larvicidal effects of the molecules naturally occurring in decaying litter. The pattern of establishing the larvicidal effect of alder leaf litter in water of Alpine Aedes breeding sites is discussed.     

Introduction of disulfide bonds into Bacillus subtilis neutral protease

The effects of engineered disulfide bonds on autodigestion andthermostability of Bacillus subtilis neutral protease (NP-sub)were studied using site-directed mutagenesis. After modellingstudies two locations that might be capable of forming disulfidebonds, both near previously determined autodigestion sites inNP-sub, were selected for the introduction of cysteines. Analysisof mutant enzymes showed that disulfide bonds were indeed formedin vivo, and that the mutant enzymes were fully active. Theintroduced disulfides did not alter the autodigestion patternof the NP-sub. All mutant NP-subs exhibited decreased thermostability,which, by using reducing agents, was shown to be caused by theintroduction of the cysteines and not by the formation of thedisulfides. Mutants containing one cysteine exhibited intermoleculardisulfide formation at elevated temperatures, which, however,was shown not to be the cause of the decreased thermostability.Combining the present data with literature data, it would seemthat the introduction of disulfide bridges is unsuitable forthe stabilization of proteases. Possible explanations for thisphenomenon are discussed.