PROTECTIVE EFFECT OF LYSOSTAPHIN FROM STAPHYLOCOCCUS SIMULANS AGAINST GROWTH OF STAPHYLOCOCCUS AUREUS IN MILK AND SOME OTHER FOOD PRODUCTS

The effect of lysostaphin from Staphylococcus simulans expressed in Escherichia coli TOP10 strain on Staphylococcus aureus used for inoculation of milk, ground pork and mayonnaise salad was investigated. The populations of this pathogen in ultrahigh‐temperature milk preserved at 4C by lysostaphin added up to concentrations of 1.5 or 3.0 µg/mL were reduced by 0.73 and 0.92 log(cfu/mL) in control samples without enzyme addition. The protective influence of lysostaphin was diminished in case of milk storage (20C) prolonged up to 24 h. Furthermore, a final reduction level by 0.92 log(cfu/mL) was achieved after 24 h of pork storage. The smaller and more dependent on enzyme concentration inactivation of S. aureus was observed in the case of the mayonnaise salad, and it led to the conclusion that some food components or proteolytic enzymes originating from other bacteria caused lysostaphin inactivation.     

EFFECT OF POLYDIMETHYL SILOXANE ON RAPESEED OIL TRANSFORMATION DURING DEEP FRYING

During deep fat frying a series of undesirable transformations occur. These include oxidation, polymerization, and hydrolysis. Use of additives to reduce the access of air to the frying oil may be one of the preventive methods. Such additives reduce the amount of foam formed. In this work, polydimethyl siloxane (PDMS) at 3 ppm was added to the frying rapeseed oil for frying potato fritters. It was found that oxidation was significantly limited as it reduced peroxide, anisidine, E^1%_lcm values and oxidized triacylglycerol (TAG) contents. Polymerization was also limited as a reduction in the contents of TAG polymer and dimer occurred. Addition of PDMS also reduced degradation of polyenoic acids of the frying oil. Oil without PDMS was less resistant to these transformations.     

Using decision trees for the minimization of multiple-valued functions

This paper presents a simple procedure for the approximate minimization of multiple-valued functions using multiple-valued decision trees. The proposed procedure is compared with a near-absolute procedure, using for the test four-valued functions of four variables. The results show a great advantage for our procedure with respect to the CPU time needed.     

Visualizations for Mathematics Courses Based on a Computer Algebra System

This paper discusses the introduction of a computer-algebra system to perform visualizations in mathematics education.With theIllustrated Mathematicsproject, we provide a comprehensive collection of graphics and animations for various topics in mathematics, which can directly be used for teaching. Because the programs (written inMathematica) we used for the creation of this collection are included, it is easy to design new examples by modifying parameters in existing examples. Therefore,Illustrated Mathematicscan be used as a first step of the introduction of a computer-algebra system in mathematics education.In the second part, we report on the development of a workbench and learning environment, with which the students can discover the mathematical concepts by themselves. For that, the given examples have to be didactically enriched and processed. By creating their own visualizations of increasing complexity, the students improve their knowledge about the underlying computer-algebra system.     

LOW‐INCOME HOMEOWNERSHIP: DOES IT NECESSARILY MEAN SACRIFICING NEIGHBORHOOD QUALITY TO BUY A HOME?

ABSTRACT: Questions have been raised about the wisdom of low‐income homeownership policies for many reasons. One potential reason to be skeptical: low‐income homebuyers perhaps may be constrained to purchase homes in disadvantaged neighborhoods. This is a potential problem because home purchases in such neighborhoods: (1) may limit appreciation; (2) may reduce quality of life for adults; and (3) may militate against reputed advantages of homeownership for children. Our study examines the neighborhood conditions of a group of 126 low‐income homebuyers who purchased their first home with assistance from the Home Ownership Program (HOP) operated by the Denver Housing Authority. Our approach is distinguished by its use of a comprehensive set of objective and subjective indicators measuring the neighborhood quality of pre‐move and post‐move neighborhoods. Do low‐income homebuyers sacrifice neighborhood quality to buy their homes? Our results suggest that the answer to this question is more complex than it might at first appear. On the one hand, HOP homebuyers purchased in a wide variety of city and suburban neighborhoods. Nonetheless, a variety of neighborhood quality indicators suggest that these neighborhoods, on average, were indeed inferior to those of Denver homeowners overall and to those in the same ethnic group. However, our analyses also revealed that their post‐move neighborhoods were superior to the ones they lived in prior to homeownership. Moreover, very few HOP destination neighborhoods evinced severe physical, environmental, infrastructural, or socioeconomic problems, as measured by a wide variety of objective indicators or by the homebuyers' own perceptions. Indeed, only 10% of HOP homebuyers perceived that their new neighborhoods were worse than their prior ones, and only 8% held pessimistic expectations about their new neighborhoods' quality of life. Finally, we found that Black homebuyers fared less well than their Latino counterparts, on average, in both objective and subjective measures.     

Electronic implementation of the discrete Walsh transform with a variable number of data

We present an electronic system that calculates the discrete Walsh transform of a function of which any number of samples has been previously taken. In previous publications, one finds systems designed for a fixed number of samples, normally a power of two. This restriction is too great bearing in mind that no physical function is really periodical, especially in the field of biophysics, where -many important applications of this type of device are found. This makes it impossible to obtain a preset number of samples and makes the selection of sampling frequency difficult.     

Wind-fetch dependence of Seasat scatterometer measurements

Abstract

This work is focused on the effects of large-scale wind-generated gravity waves on scatterometer wind-measurement accuracy. We present theoretical and experimental evidence of the important role played by the degree of wind-wave coupling in surface geometry and therefore in microwave signatures. Seasat scatterometer wind-measurement errors are analysed, and an error bias is found to be related to the degree of wind-wave development. Attention is focused on a dynamic measure of wind-wave development that characterizes the rate of energy transfer from the mean wind to the energy-carrying portion of the wave spectrum. An explanation of the bias is suggested based on the consideration of an additional component of surface scattering caused by electromagnetic-wave diffraction at the crests of individual, sufficiently steep wavelets.