Modeling the diffusion-adsorption kinetics of 1-methylcyclopropene (1-MCP) in apple fruit and non-target materials in storage rooms

The purpose of this research was to model the kinetics of adsorption of 1-methylcyclopropene (1-MCP) in apple fruit and non-target solid materials found in apple storage rooms. The process was described by Fick’s second law of diffusion of the gas through the pores of the material coupled with adsorption kinetics of the gas on the material’s binding sites. A finite element formulation of the model, describing the diffusion and adsorption mechanisms separately, was first developed. The values of the relevant parameters were estimated based on headspace measurements of the decrease of 1-MCP in jars containing the different materials. The headspace concentration of 1-MCP was measured using gas chromatography. Apple fruit (Golden Delicious and Jonagold) and the following bin construction materials were investigated: high density polyethylene (HDPE), oak, poplar wood and card lining. The range in the magnitude of the diffusion coefficient, adsorption coefficient, and concentration of active sites in the various solids was 10,000-, 8-, and 30-fold, respectively.     

Asymmetric synthesis and conformational analysis by NMR spectroscopy and MD of Aba- and α-MeAba-containing dermorphin analogues

Dermorphin analogues, containing a (S)‐ and (R)‐4‐amino‐1,2,4,5‐tetrahydro‐2‐benzazepin‐3‐one scaffold (Aba) and the α‐methylated analogues as conformationally constrained phenylalanines, were prepared. Asymmetric phase‐transfer catalysis was unable to provide the (S)‐α‐Me‐o‐cyanophenylalanine precursor for (S)‐α‐MeAba in acceptable enantiomeric purity. However, by using a Schöllkopf chiral auxiliary, this intermediate was obtained in 88 % ee. [(S)‐Aba 3‐Gly 4]dermorphin retained μ‐opioid affinity but displayed an increased δ‐affinity. The corresponding R epimer was considerably less potent. In contrast, the [(R)‐α‐MeAba 3‐Gly 4]dermorphin isomer was more potent than its S epimer. Tar‐MD simulations of both non‐methylated [Aba 3‐Gly 4]dermorphin analogues showed a degree of folding at the C‐terminal residues toward the N terminus of the peptide, without however, adopting a stabilized β‐turn conformation. The α‐methylated analogues, on the other hand, exhibited a type I/I′ β‐turn conformation over the α‐MeAba 3 and Gly 4 residues, which was stabilized by a hydrogen bond involving Tyr 5‐H_N and D ‐Ala 2‐CO.     

Stability of rare‐earth‐doped spherical yttria‐stabilized zirconia synthesized by ultrasonic spray pyrolysis

Phase stability is one of the crucial requirements for any material that can be used at elevated temperature applications such as thermal barrier coating (TBC). The most traditional TBC material, partially stabilized zirconia, limits the operating temperature due to its phase transformation. Conversely, the low thermal conductivity of fully stabilized zirconia (YSZ) may enable effective reduction in the surface temperature on the coated component, while avoiding deleterious phase transitions, although still being subjected to sintering and grain growth. It has been reported that addition of rare‐earths as dopants to YSZ can significantly increase resistance to grain growth at high temperature. Keeping this under consideration, this work investigates the role of rare‐earths (lanthanum and gadolinium) in increasing thermal stability of YSZ microspheres, the building blocks for high‐temperature photonics for reflective TBC. The spheres were produced by ultrasonic spray pyrolysis, and the doping led to significant improvement of stability by significant inhibition of grain growth. While the individual dopants showed significant growth and sintering inhibition up to 900°C, co‐doping with 4% (in mol) of each (Gd and La) led to coarsening resistance up to 1000°C for 3 hours, when particles retained reasonable spherical features with nanometric crystallite sizes.     

Tuberculosis reinfection rate as a proportion of total infection rate correlates with the logarithm of the incidence rate: a mathematical model

In a significant number of instances, an episode of tuberculosis can be attributed to a reinfection event. Because reinfection is more likely in high incidence regions than in regions of low incidence, more tuberculosis (TB) cases due to reinfection could be expected in high-incidence regions than in low-incidence regions. Empirical data from regions with various incidence rates appear to confirm the conjecture that, in fact, the incidence rate due to reinfection only, as a proportion of all cases, correlates with the logarithm of the incidence rate, rather than with the incidence rate itself. A theoretical model that supports this conjecture is presented. A Markov model was used to obtain a relationship between incidence and reinfection rates. It was assumed in this model that the rate of reinfection is a multiple, ρ (the reinfection factor), of the rate of first-time infection, λ. The results obtained show a relationship between the proportion of cases due to reinfection and the rate of incidence that is approximately logarithmic for a range of values of the incidence rate typical of those observed in communities across the globe. A value of ρ is determined such that the relationship between the proportion of cases due to reinfection and the logarithm of the incidence rate closely correlates with empirical data. From a purely theoretical investigation, it is shown that a simple relationship can be expected between the logarithm of the incidence rates and the proportions of cases due to reinfection after a prior episode of TB. This relationship is sustained by a rate of reinfection that is higher than the rate of first-time infection and this latter consideration underscores the great importance of monitoring recovered TB cases for repeat disease episodes, especially in regions where TB incidence is high. Awareness of this may assist in attempts to control the epidemic.     

Creative connections: user, designer, context, and tools

The design symposium ‘creative connections discusses the designers’ tools in the conceptual phase. Over the past few decades, many considerations, which hitherto occured before or after conceptualizing have become an integrated part of concept development. Examples are studies of users and contexts, and expressive new materials. Also, design tools are becoming increasingly, almost exclusively, computer-based. But current computer tools lack fluency, directness, and bodily involvement of the traditional paper tools, properties which are essential in the creative activities of conceptualizing, The symposium, and its four attached bazaar papers, deal with new tools that are being developed, and old tools that are evolving, to help designers at coping with this complexity of factors. This paper is part of the 3AD design colloquium creative connections.     

EFFECT OF MICROBIAL ADSORPTION AT THE GAS/LIQUID INTERFACE ON OXYGEN ENHANCEMENT FACTORS

The adsorption of micro-organisms at the gas/liquid interface causes both an increase in the oxygen respiration rate and a decrease in the oxygen diffusion coefficient near the interface. An increase in the oxygen consumption rate increases the oxygen mass transfer rate into the bacterial broth but a decreased oxygen diffusion coefficient reduces the mass transfer rate. These two factors must be taken into account when enhancement factors are calculated.     

On-Line Harmonic Analysis as a Diagnostic Design and Control Tool for Power Systems Feeding Arc Furnaces, Thyristor-Controlled Mill Drives, and Power Factor Correction Equipment

Microprocessor-based signal processing equipment for frequencies up to 20 kHz have become compact and fast enough to allow direct on-line real-time analysis on power systems to determine behavior. A case study is presented for a small steelworks operating a 25-MVA open arc furnace, installing 6.5 MVA of thyristor control equipment and further power factor correcting equipment and harmonic filters on a system with ill-defined parameters, low short- circuit capacity, and already containing power factor correcting capacitors tuned at the third harmonic. Discrete spectrum analysis equipment, microprocessor-based and coupled via IEEE-bus to a microcomputer system, was used to do on-line analysis at various points in the system. The high-speed system enabled sophisticated signal processing to yield even and uneven harmonics, stochastic components, system parameters and resonances and mutual interference. It is shown how this is used to rectify problems in the system, adapt equipment, and design power factor and filter equipment.     

Aversive schedules with independent probabilities of reinforcement for responding and not responding by rhesus monkeys: I. With signal.

Applied 2 independent probabilities of electric shock presentation to 12 naive male rhesus monkeys (Macaca mulatta) as the independent variables defining schedules of aversive control: (a) the probability that a fixed signal period would end with a shock if a specified response were made and (b) the probability that the fixed signal period would end with shock if a specified response were not made. Systematic changes in the probability values generated several familiar schedules of aversive control, as well as several intermittent procedures. Response rate tended to rise during the signal period when the probability values were set so that not responding was more likely to produce a shock than responding; response rate tended to fall during the signal period when the probabilities were set so that responding was more likely to produce shock than not responding. Response patterning in time was also evident during the interval between signals when no consequences were programmed. These characteristics of response patterning reflected the changes in the 2 independent probability variables in ways that simple measures of response rate and shock rate alone did not. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)