A preliminary study of ester oxidation on an aluminum surface using chemiluminescence

The oxidation characteristics of a pure ester (trimethyolpropane triheptanoate) were studied by using a chemiluminescence technique. Tests were run in a thin-film micro-oxidation apparatus with an aluminum alloy catalyst. Conditions included a pure oxygen atmosphere and a temperature range of 176 to 206 C. Results indicated that oxidation of the ester (containing 10 to the minus 3 power M diphenylanthracene as an intensifier) was accompanied by emission of light. The maximum intensity of light emission (I sub max) was a function of the amount of ester, the concentration of intensifier, and the test temperature. The induction period or the time to reach one-half of maximum intensity (t sub 1/2) was an inverse function of test temperature. Decreases in light emission at the later stages of a test were caused by depletion of the intensifier

Inclusion of chemical effect in a fully coupled THM finite element code

Bentonite-rich clays can be used as a buffer / backfill material in deep geological repositories for nuclear waste. The prediction of the long-term performance of a buffer / backfill in such a complex environment, where the temperature, humidity and chemistry of water change, requires a fully thermo-hydro-mechanical-chemical (THMC) coupled numerical code. This paper presents a simple extension of a THM coupled finite element code to include chemical effects. After deriving the governing salt mass balance equation and discussing its implementation into the code, the paper verifies the extended framework against an analytical solution for 1D salt transport. In addition, the article presents a validation example in which the code replicates experimental data. The numerical results obtained from the extended THMC coupled finite element code encourage further investigation of the chemical effects on the mechanical and thermal behaviour of the material, which would serve the ultimate goal of achieving a safer design of the nuclear waste storage facility.Postprint (published version

Soliton ratchets in homogeneous nonlinear Klein-Gordon systems

We study in detail the ratchet-like dynamics of topological solitons in homogeneous nonlinear Klein-Gordon systems driven by a bi-harmonic force. By using a collective coordinate approach with two degrees of freedom, namely the center of the soliton, $X(t)$, and its width, $l(t)$, we show, first, that energy is inhomogeneously pumped into the system, generating as result a directed motion; and, second, that the breaking of the time shift symmetry gives rise to a resonance mechanism that takes place whenever the width $l(t)$ oscillates with at least one frequency of the external ac force. In addition, we show that for the appearance of soliton ratchets, it is also necesary to break the time-reversal symmetry. We analyze in detail the effects of dissipation in the system, calculating the average velocity of the soliton as a function of the ac force and the damping. We find current reversal phenomena depending on the parameter choice and discuss the important role played by the phases of the ac force. Our analytical calculations are confirmed by numerical simulations of the full partial differential equations of the sine-Gordon and $\phi^4$ systems, which are seen to exhibit the same qualitative behavior. Our results are in agreement with recent experimental work on dissipation induced symmetry breaking.Comment: Minor corrections, several references added, accepted for publication in Chao

Change in soy and nutrition knowledge and perceptions of smallholder South African farmers after attending a single one day soy nutrition training workshop: A pilot study

The main aim of this pilot study was to assess smallholder soy farmers’ knowledge and perceptions of soy immediately before and after participating in a one-day soy nutrition training workshop. A pre-post study design was used among a convenience sample of 78soy smallholder farmers from KwaZulu-Natal, South Africa (SA). A total of 78 men and five women participated in the training, but  because only five women attended, gender comparison analysis was not carried out. A soy nutrition training workshop, including soy cooking demonstrations, tasting, recipe development, that is based on the Social Cognitive Theory, was implemented for eight  consecutive hours with one break of 30 minutes. Pre- and post-quantitative data measuring,soy knowledge and perceptions werecollected using a modified version of a survey, tested for face and content validity and reliability, and used previously in other research study projects by the same authors among low-resource communities in SA. The data from the pre and post questionnaires indicated that only 41% of the soy smallholder farmers used soy in the household and mainly in meat dishes. The rest of the harvested soy was either sold or used for animal feed. The mean±standard deviation (SD) score of taste preference changed significantly (p=0.002) from 4.60±0.84 before, to 4.93±0.13 after the training (p=0.002) and the majority of the participants perceived it was easy to prepare soy foods; 82.1% and 88.5% before and after the training, respectively (p=0.013). Participants’ soy knowledge improved significantly (p<0.001) from a mean± (SD) score of 26.33±4.06 before to 32.00±9.46 after the intervention, indicating a significant improvement of 5.67±9.11 [13.83%] in the total score. The results from this study indicate that there is a need for nutrition education programs for smallholder farmers. Thus, improvement in both soy knowledge and preference should result in more soy being consumed first for household nutritional needs before giving it to either animals or sell it on the market. Since smallholder farmers’ nutrition education can impact both food insecurity and nutritional status improvement in one setting, more interventions of this kind are needed to further advance the frontier of this niche area of research. Key words: nutrition education, smallholder famers, soy training, South Africa emerging farmers, Knowledge perceptio

Internal mode mechanism for collective energy transport in extended systems

We study directed energy transport in homogeneous nonlinear extended systems in the presence of homogeneous ac forces and dissipation. We show that the mechanism responsible for unidirectional motion of topological excitations is the coupling of their internal and translation degrees of freedom. Our results lead to a selection rule for the existence of such motion based on resonances that explains earlier symmetry analysis of this phenomenon. The direction of motion is found to depend both on the initial and the relative phases of the two harmonic drivings, even in the presence of noise.Comment: Final version, to appear in Physical Review Letter