CONSTRAINED NON-LINEAR PROGRAMMING: A MINIMUM CROSS-ENTROPY ALGORITHM

The paper presents an information-theoretic algorithm for solving constrained non-linear programming problems based upon the principle of minimum cross-entropy and surrogate mathematical programming. It is an alternative to the earlier work by Templeman and Li [4-6] based on the maximum entropy principle and so far as the rate of convergence of the solution is concerned it is an improvement upon it, The merit of the present technique is illustrated with two numerical examples.     

Emergence of recombinant strains of Helicobacter pylori during human infection

Genetic recombination can be important evolutionarily in speeding the adaptation of organisms to new environments and in purging deleterious mutations. Here, we describe polymerase chain reaction (PCR), hybridization and DNA sequence-based evidence of six such exchanges between two strains of Helicobacter pylori during natural mixed infection of a patient in Lithuania. One parent strain contained the 37 kb long, virulence-associated cag pathogenicity island (PAI), and the other strain lacked this PAI. Most H. pylori from the patient had descended from the cag+ parent, but had become cag- during infection. This had resulted from transfer of DNA containing the 'empty site' allele from the cag- strain and homologous recombination, not from excision of the cag PAI without DNA transfer. Other cases of recombination involved genes for an outer membrane protein (omp5 and omp29; also called HP0227 and HP1342) and a putative phosphoenolpyruvate synthase (ppsA; HP0121). Replacement of a short patch of DNA sequence (36-124 bp) was also seen. As the chance of forming any given recombinant is small, the abundance of recombinants in this patient suggests selection for particular recombinant genotypes during years of chronic infection. We suggest that genetic exchange among unrelated H. pylori strains, as documented here, is important because of the diversity of this gastric pathogen and its human hosts. Certain H. pylori recombinants may grow better in a given host than either parent. The vigour of growth, in turn, could impact on the severity of disease that infection can elicit.     

EVOLUTION OF THE AROMATIC FRACTION IN RED PEPPER FOR PAPRIKA DURING LA VERA REGION TRADITIONAL DRYING PROCESS

Paprika from the region of La Vera (Cáceres) is prepared using a particular process of mild, slow drying in traditional drying barns heated by oakwood fires. This makes it possible for the fruit to maintain its natural components at the same time as contributing certain organoleptic characteristics that are highly appreciated by consumers. We analyzed the changes in the aromatic fraction that occur over the course of this traditional drying technology, using dynamic head space as the isolation method and gas chromatography–mass spectrometry as the identification system. We identified 96 compounds, 55 of which presented significant differences (P < 0.05) between different days of the drying process. Some 40% of the aromatic potential of the end product corresponded to volatile compounds that appeared during the drying process, originating from the wood smoke or as the result of typical reactions of the dehydrated products.     

Improving the energy spread and brightness of thermal-field (Schottky) emitters with PHAST—PHoto Assisted Schottky Tip

Using a relatively simple model of photoemission we derive an expression for the reduced on axis brightness of a thermal-photofield emitter. We then show that it is theoretically possible to reduce the energy spread of a Schottky (thermal field) emitter whilst increasing the reduced brightness. This can be achieved by the illumination of the tip with a high intensity laser light. We call the source PHAST—PHoto Assisted Schottky Tip. We find that due to the strong E-fields applied PHAST may operate at photon energies below the (Schottky reduced) work function. Thus removing the need for UV lasers, we will show that it is in fact preferable to work in the red, or in the green. The necessary laser intensities probably limit the application to pulsed operation.     

PHYSICOCHEMICAL PROPERTIES OF EUROPEAN BAKERY MARGARINES WITH AND WITHOUT TRANS FATTY ACIDS

Physicochemical properties of commercially available European bakery margarines (cream margarines, cake margarines [CM] and puff pastry margarines [PPM]) containing and devoid of trans fatty acids (TFAs) were investigated. Studied physical properties were the solid fat content (SFC), dropping points (DPs), polymorphism, texture (hardness), plasticity and the melting profile by differential scanning calorimetry. Experimental results confirm that physical properties of the margarines corresponded with their application area. For example, SFC and DPs of PPM were higher than cream margarines and CM; they were also harder at 15C. Moreover, all the investigated physical properties were affected by the suppression of TFA in bakery margarines .

PRACTICAL APPLICATIONS

This study has shown that margarines present different physical properties with respect to their purposed application but also highlight changes that appear due to the absence of trans-fatty acids in the formulations. These changes can really affect the bakery abilities and will, finally, influence the quality of the bakery products.     

EFFECT OF pH AND TEMPERATURE ON JUMBO SQUID PROTEINS

Evaluation of the effect of pH (2 to 13) and temperature (0 to 50C) on functional properties of jumbo squid proteins was performed, followed by a 2  ×  3 factorial design for producing squid protein hydrolysates bearing useful functional properties. In particular, the effects of pH (8, 9 and 10) and temperature (30, 35, 40C) were evaluated. Alcalase and papain were tested on each treatment. The protein recovery, whippability and emulsifying capacity of the hydrolysates were evaluated. Almost 80% of the proteins were recovered in water-soluble form after hydrolysis with papain at pH 10 at the three temperatures. The highest values of whippability (245  ±  17.7%), foam stability (100%), emulsion-forming capacity (27  ±  0.97%) and stability (99.99  ±  8.8%) occurred with papain-produced hydrolysates. When squid protein was treated at 50C and pH 8, the highest whippability value (390.0  ±  0.1%) and foam stability (100%) were obtained when no enzyme was added.

PRACTICAL APPLICATIONS

This paper assesses how process variables, particularly temperature and pH, affect the functional properties of squid proteins. Making use of such process variables will produce more useful and efficient processes, as the application of a hydrolysis system. The processing of jumbo squid protein to obtain proteins bearing adequate functional properties would be an inexpensive way to provide added value to this marine resource and the production of a high-quality protein ingredient. These results hold promise for jumbo squid proteins as useful food ingredient because of their functional properties.     

Production of Structure Components with Selective Properties by means of Action Media based Cold Forming

Minimising a metallic component's weight can be achieved by either using lightweight alloys or by improving the component's properties. In both cases, the material formability affects the utilisability for mass production processes. Most of the high‐strength materials show a material‐restricted formability and are difficult to forge. The formability of a material is described by its maximum forming limit. Large plastic strains can lead to mechanical damage within the material. A promising approach of handling low ductile, high‐strength alloys in a forming process is deformation under superimposed hydrostatic pressure by active media. In the present study, the influence of superimposed hydrostatic pressure on the flow stress is analysed as well as the forming ability for different sample geometries at different hydrostatic pressure and temperature levels. The experimental results show that the superimposed pressure has no influence on the plastic deformation, nor does a pressure dependent near‐surface material hardening occur. Nevertheless, the formability is improved with increasing hydrostatic pressure. The relative gain at room temperature and increase in the superimposed pressure from 0 bar to 600 bar for tested materials was at least 140 % and max. 220 %. Therefore, a cold forming process under superimposed pressure is developed to produce structure components with selective properties. For example, the gain in formability will be used to enlarge local plastic strains to higher limits resulting in higher local strain hardening and hardness. This offers new design possibilities with selectively adjusted local structure or structure component properties, especially adapted to their technical application. Additionally, by applying damage models, finite‐element analysis is used in order to predict damage occurring in the cold forming process under superimposed hydrostatic pressure for various sample geometries.