Quantitative Determination of Ascorbic Acid in Potatoes and Potato Products by High Performance Liquid Chromatography

A simple, rapid and accurate method for the quantitative determination of ascorbic acid in potatoes and potato products has been developed. The system is based on the reverse-phase, ion-pairing concept of high-performance liquid chromatography. Sample preparation is minimal and involves a one-step extraction followed by filtration and/or centrifugation. Recoveries were near the 100% level. As low as 0.02 mcg ascorbic acid could be determined.     

THYROTROPIC FEEDBACK CONTROL: EVIDENCE FOR AN ADDITIONAL ULTRASHORT FEEDBACK LOOP FROM FRACTAL ANALYSIS

More than 70 years after the discovery of the pituitary–thyroid feedback control mechanism, a classical endocrine regulation system, most of its parameters have been identified. However, the regulation of its central component in the pituitary gland, probably responsible for pulsatile release of thyrotropin (TSH), remains obscure. In order to infer its structure from the system's behavior, four different pituitary models were created and compared regarding their fractal properties. Based on the simplest model showing noncompetitive inhibition of TSH release by thyroid hormones—a physiologically plausible correlation—one alternative model added stochastic stimulation by central signals and another added an additional intrapituitary feedback loop, whereas the fourth model combined both effects. This latter model combining noncompetitive inhibition with the two additional effects showed the same fractal dimensions as in vivo time series, whereas the simpler models yielded significantly lower time-series complexity. These results suggest that both stochastic stimulation and ultrashort loop feedback are involved in the generation of TSH pulses in the human pituitary.     

DIET-MEDIATED INTER-COLONIAL AGGRESSION IN THE FORMOSAN SUBTERRANEAN TERMITE <Emphasis Type="Italic">Coptotermes formosanus</Emphasis>

In most social insects, intercolonial and interspecific aggression are expressions of territoriality. In termites, cuticular hydrocarbons (CHCs) have been extensively studied for their role in nestmate recognition and aggressive discrimination of nonnest-mates. More recently, molecular genetic techniques have made it possible to determine relatedness between colonies and to investigate the influence of genetics on aggression. In the Formosan subterranean termite, Coptotermes formosanus, however, the role of CHCs and genetic relatedness in inter-colony aggression has been ambiguous, suggesting the involvement of additional factors in nest-mate recognition. In this study we assess the range of aggression in this termite species and characterize the influence of genetic relatedness, CHC profiles and diet on aggression levels. We collected four colonies of C. formosanus, feeding either on bald cypress or birch, from three locations in Louisiana. Inter-colony aggression ranged from low to high. Differences in CHC profiles, as well as genetic distances between colonies determined by using microsatellite DNA markers, showed no significant correlation with aggression. However, termite diet (host tree) played a significant role in determining the level of aggression. Thus, two distantly related colonies, each feeding on different diets, showed high aggression that significantly diminished if they were fed on the same wood in the laboratory (spruce). Using headspace solid phase microextraction, we found three compounds from workers fed on birch that were absent in workers fed on spruce. Such diet-derived chemicals may be involved in the complex determination of nest-mate recognition in C. formosanus.     

OPTIMAL ROBUST DESIGN OF NOVEL MATERIALS: PROBLEMS OF STABILITY AND VIBRATIONS

A numerical method for the optimal design of thin anisotropic laminates is presented, layer thicknesses and lamination angles being the design variables. An optimal solution is pursued with respect to frequency domain objectives, e.g. fundamental frequency and Euler critical load. A special feature of the method is the semi-analytical second order design sensitivity that is computed with the aid of a Rayleigh-Ritz analysis approach. A modified sequential quadratic programming scheme is then introduced, where standard quasi-Newton approximations are avoided by an exact calculation of the Hessian matrix. Furthermore, the robustness of the method with respect to scatter in material properties such as mass density and elastic moduli is assessed. A stochastic extension of the Rayleigh-Ritz approach is developed on this purpose that allows the location of those regions in the design space that are most sensitive to physical parameter randomness. This allows the use of a modified objective function that penalizes sensitive solution.     

SENSORY QUALITY OF GALA APPLES AS INFLUENCED BY CONTROLLED AND REGULAR ATMOSPHERE STORAGE

The sensory quality of Gala apples stored for up to 4 months in delayed controlled atmosphere (CA), regular atmosphere (RA), and a combination of sequential CA and RA storage (CR) was evaluated. Sensory analysis included difference and acceptance testing. Firmness, soluble solids and titratable acidity contents, and volatile flavor profiles were measured analytically. Acceptability decreased with storage time. Apples stored in RA were more acceptable than apples stored in CA or CR; the differences between storage treatment were not significant after 4 months of storage. Firmness decreased with storage time, but was not affected by storage treatment. Soluble solids and titratable acidity contents were not affected by storage treatment or time. Storage treatment, storage time, and lot had a significant effect on the volatile flavor profiles. CA storage and extended storage contributed to decreases in the content of volatile flavor compounds.     

Leaf blade anatomy and ultrastructure of six <i>Simira</i> species (Rubiaceae) from the Atlantic Rain Forest,Brazil

Simira is a predominantly woody Neotropical genus comprising 41 taxa, 16 of which occur in Brazil and eight of them in the southeastern region of Brazil. Leaf blades of Simira eliezeriana Peixoto, S. glaziovii (K. Schum.) Steyerm., S. grazielae Peixoto, S. pikia (K. Schum.) Steyerm., S. rubra (Mart.) Steyerm., S. sampaioana (Standl.) Steyerm. were collected in the southeastern region of Brazil and fixed according to usual methods for light and electron microscopy. The leaf blades show typical characteristics of the Rubiaceae family as dorsiventral mesophyll and paracytic stomata. The presence of two bundle sheaths that extend to the upper epidermal layer, prismatic crystal and crystal-sand, alkaloids in the mesophyll and the organization micromorphological of the outer periclinal wall are considered characteristics representative for the genus. This study also demonstrates some leaf blade characteristics that can be used to Simira species identification (leaf surface, domatia types, epicuticular wax types and patterns of epidermis anticlinal cell walls).     

An Environment for Modeling and Design of Geographic Applications

This paper presents UAPÉ—a computational environment for modeling and designing environmental geographic applications. UAPÉ is aimed at end-users who are experts in their application domain, but who do not have adequate background in software engineering or database design, and thus are unable to take full advantage of available GIS tools. Its goal is to reduce the impedance between the end-users view of the world and its implementation in Geographic Information Systems. The environment has been designed and implemented so that it can be considered as an auxiliary layer to be coupled to a GIS. The major features of this layer are: it has an open architecture, being independent of a specific GIS, so that it can be coupled to different systems; it allows the user to deal only with the conceptual view of the geographic reality, abstracting the implementation details; it supports a geographic application design methodology, fully integrated with a high-level semantic data model, so there is no impedance mismatch between application design and data modeling.