On the dynamics of bubbles in boiling water

We investigate the dynamics of many interacting bubbles in boiling water by using a laser scattering experiment. Specifically, we analyze the temporal variations of a laser intensity signal which passed through a sample of boiling water. Our empirical results indicate that the return interval distribution of the laser signal does not follow an exponential distribution; contrariwise, a heavy-tailed distribution has been found. Additionally, we compare the experimental results with those obtained from a minimalist phenomenological model, finding a good agreement.Comment: Accepted for publication in Chaos, Solitons & Fractal

Agricultural Production and Technical Change Around the World, 1961-2010

This paper extends the induced innovation research of Hayami and Ruttan by including 129 more countries, extending the time frame to 50 years and explaining the production process for those countries using a Cobb-Douglas function. From this data, the paper illustrates trade-offs between five inputs in agricultural production in empirical isoquants, and measures the progress of agricultural productivity by the magnitude of the shift in isoquants toward the origin. We can further test the implications of technical change on the productivity of the inputs: labor, land, fertilizer, and capital. We illustrate the response of input demands to rising agricultural wages and estimate scale and substitution effects using the fundamental law of derived demand. Lastly, we explore possible explanations for variation in agricultural productivity increases across countries by examining the relationship between countries’ trade protection policies and democracy level and unit labor costs

The influence of the copper content in grape must on alcoholic fermentation kinetics and wine quality. A survey on the performance of 50 commercial Active Dry Yeasts

The effects of copper on the viability and fermentative activity of 50 active dry yeasts purchased on the northern Italian market were studied, and revealed that Copper excess may cause massive death of yeast cells, leading to a significant delay in the start and progress of alcoholic fermentation. A two-log units reduction in cell viability was observed when copper content of musts was around 20 mg∙L-1. Despite this, the difference noted in the kinetics after 20 days' fermentation was lower than that observed 48 hours after in the grape must. An excess of copper in must affected also the composition of the produced wines. The increase in acetic acid and in the sulphur dioxide concentration, observed in wines made using grape must with a high copper concentration, raises serious doubts both regarding the possibility of obtaining good wines from these raw materials and in relation to the progress of subsequent steps of winemaking, such as malolactic fermentation. While it is an important tool in preventing vine diseases, copper must be used very carefully to avoid serious troubles during wine fermentation, even if some yeasts seem more suited to ferment musts containing up to 20-30 mg∙L-1 copper.

Relationship between molecular connectivity and carcinogenic activity: a confirmation with a new software program based on graph theory.

For a database of 826 chemicals tested for carcinogenicity, we fragmented the structural formula of the chemicals into all possible contiguous-atom fragments with size between two and eight (nonhydrogen) atoms. The fragmentation was obtained using a new software program based on graph theory. We used 80% of the chemicals as a training set and 20% as a test set. The two sets were obtained by random sorting. From the training sets, an average (8 computer runs with independently sorted chemicals) of 315 different fragments were significantly (p < 0.125) associated with carcinogenicity or lack thereof. Even using this relatively low level of statistical significance, 23% of the molecules of the test sets lacked significant fragments. For 77% of the molecules of the test sets, we used the presence of significant fragments to predict carcinogenicity. The average level of accuracy of the predictions in the test sets was 67.5%. Chemicals containing only positive fragments were predicted with an accuracy of 78.7%. The level of accuracy was around 60% for chemicals characterized by contradictory fragments or only negative fragments. In a parallel manner, we performed eight paired runs in which carcinogenicity was attributed randomly to the molecules of the training sets. The fragments generated by these pseudo-training sets were devoid of any predictivity in the corresponding test sets. Using an independent software program, we confirmed (for the complex biological endpoint of carcinogenicity) the validity of a structure-activity relationship approach of the type proposed by Klopman and Rosenkranz with their CASE program

On the equivalence of the self-dual and Maxwell-Chern-Simons models coupled to Fermions

We study the exact equivalence between the self-dual model minimally coupled with a Dirac field and the Maxwell-Chern-Simons model with non-minimal magnetic coupling to fermions. We show that the fermion sectors of the models are equivalent only if a Thirring like interaction is included. Using functional methods we verify that, up to renormalizations, the equivalence persists at the quantum level.Comment: 8 pages, revte

Effects of milk storage temperature at the farm on the characteristics of Parmigiano Reggiano cheese: chemical composition and proteolysis.

Parmigiano Reggiano is a Protected Designation of Origin (PDO) cheese whose official production protocol provides that milk cannot be stored at less than 18 °C at the farm. The possibility of refrigerating milk at the farm is highly debated, since it should allow for the limiting of bacterial growth, thus improving the quality of the cheese. The present research aimed to study the influence of storing the milk at 9 °C on the chemical composition and proteolysis during the ripening of Parmigiano Reggiano cheese. The experimentation considered six cheese-making trials, in which both evening and morning milks were subdivided into two parts that were maintained at 9 and 20 °C. After Parmigiano Reggiano cheese-making, one of the twin wheels obtained was analyzed after 21 months of ripening. From each cheese, two different samples were taken, one from the inner zone, and the other from the outer zone. The results of the chemical analyses evidenced that milk storage at 9 °C significantly (p ≤ 0.05) influenced fat, crude protein, soluble nitrogen and peptone nitrogen contents. Nevertheless, the differences observed with respect to the cheese obtained with milk stored under standard condition were very small and should be considered within the “normal variations” of Parmigiano Reggiano chemical characteristics