In-situ measurement of magnetic nanoparticle quantity in a microfluidic device

Microsystem Technologies - In this article we demonstrate a method for the accurate in situ determination of the quantity of the entrapped magnetic nanoparticles in the reaction chamber of a...     

Two-dimensional combustion conditions in flow

Chernogolovka. Translated from Fizika Goreniya i Vzryva, Vol. 26, No. 4, pp. 45–50, July–August, 1990.     

Phenotypic heterogeneity of the progeny of Streptomyces griseus conidia

In order to understand the complex ontogenetical processes, the development of Streptomyces (S.) griseus was applied as a model. The developmental cycle of S. griseus starts and ends as a conidium. In between, coenocytic mycelium develops which, if studied by cytomorphological or biochemical methods, exhibits conspicious heterogeneity. The hyphae develop into young, transient and old vegetative hyphae and different stages of reproductive forms. In developmentally blocked mutants these sequences of events appear mixed in all possible associations. It seems as if the program of development could be divided into several subprograms. The quantitative evaluation of the results show that the individual morphological markers exhibit certain independence from each other realized with a given probability. The conidia of S. griseus are also heterogeneous concerning all morphological and physiological traits examined so far (shape, size, light refraction, staining and shape of nucleoids with Feulgen, methyl green--pyronine, intensity and form of polysaccharide distribution, heat resistance, etc.). Kinetics of the survival curves of two S. griseus strains--a well-sporulating and its developmentally blocked mutant /24/--are different from each other, one has many more heat resistant conidia than the other but the kinetics of the survival curves of the two S. griseus strains indicate that spore populations of both react differently to heat treatment and heat resistance can be modeled by assuming the presence of two independent subpopulations of spores with different heat sensitivity. The emergence of two distinct subpopulations with (possibly) the same genetic make-up is designated: phenotypic segregation. Heat resistance is first of all species specific (genetically determined) but the epigenetic segregation seems to be characteristic of the developmental process. This process can in certain mutants be affected by environmental conditions and more importantly by the so-called autoregulators (A-factor and factor C). Factor C and A-factor are needed to normal development, if their quantity or the time of addition to the culture was not optimal, the quantity of spores decreased.     

Present and future use of semiochemicals in pest management of bark beetles

Attractive compounds affecting the mass aggregation of bark beetle populations on host trees suitable for colonization usually consist of two obligatory components that act synergistically and species-specifically. Semiochemicals inhibiting response act on their own and seem less specific. From nearly 100 species investigated so far, mass aggregation can be simulated with commercial synthetics in about nine species of economic importance. Aspects leading to the application of attractants in monitoring and mass trapping pest populations affecting European spruce forests result from intensive coordinated research at the university, industry, and forestry level. Technology transfer was facilitated by, and adapted to, the infrastructure of European forestry; traps economically replace the trap tree methods conventionally used for centuries. Expected applications in the near future are refined monitoring methods to measure population levels and predict damages. Also, mass trapping should remain a worthwhile tool in preventing beetle damage in forests under management intensive enough to remove excessive breeding material. In the long run, response-inhibiting semiochemicals resulting in the dispersal of pest populations (Ablenkstoffe) may gain wider application. The spruce engraverIps typographus L. and its associatePityogenes chalcographus L. are used as examples to describe the feasibility of developing and applying inhibitors as new tools in the management of bark beetle pests: Applying a slow-release verbenone formulation (verbenone strip) wrapped around the trunk of spruce trees at breast height appears to protect spruces from destructive attack byIps typographus, while small polyethylene ampullae containing terpinene-4-ol counteract aggregation of P. chalcographus. Inhibitors appear applicable in both strategies, damage prevention as well as damage restriction, and consequently may accommodate also pest control in less intensively managed forests. Future application of semiochemicals in the management of bark beetle pests will rest with the availability of effective means and methods and their acceptance by the forestry interest. This acceptance is presently somewhat hampered by misconceptions about mass trapping, and by (1) missing links in the knowledge of the beetles dispersal and aggregation behavior, (2) the chemosynthesis of chiral pheromone components at the industrial level, and (3) legal barriers.Suported by a grant of the deutsche Forschngsgemeinschaft.     

Potential of teff (Eragrostis tef) flour as an ingredient in gluten-free cakes: chemical,technological and sensory quality

This article aimed to evaluate the chemical, technological and sensory characteristics of gluten-free cakes made with teff (Eragrostis tef). Four cakes were evaluated: T1, 100% teff flour; T2, 75% teff flour, 12.5% rice flour, 12.5% cassava starch; T3, 50% teff flour, 25% rice flour, 25% cassava starch and T4, 25% teff flour, 37.5% rice flour, 37.5% cassava starch. Higher percentages of teff increased total ash. For apparent and specific volumes, T4 was the one with the highest mean. In sensory analysis, the attributes of appearance, colour and odour did not have significant difference among treatments. T1 received the lowest overall average for flavour (5.03). Regarding the purchase intention, the cakes did not show significant difference between T3 and T2 (3.25 and 3.08). T2, T3 and T4 obtained acceptance index higher than 70%. The use of teff flour in cakes can be promising in gluten free diet.     

Evaluation of the psychrotrophic specific signatures for cspA gene and 16S rDNA on the phenotype of Bacillus cereus sensu strictu

This study characterised the psychrotrophic genotypes and phenotypes behaviour of 63 strains of Bacillus cereus sensu stricto isolated from dairy products. The presence of the cspA gene signature and the 16S rDNA mesophilic and/or psychrotrophic specific signatures was evaluated. Among the strains, 25 (39.7%) had the cspA gene signature, 38 (60.3%) had both mesophilic and psychrotrophic 16S rDNA signatures, 24 (38.1%) had only mesophilic and one exhibited only psychrotrophic. No strain grew at 7 °C. The results indicate that the presence of psychrotrophic signatures for cspA gene or the 16S rDNA did not ensure a psychrotrophic behaviour on a B. cereus phenotype.     

Flavonoids in Meliponinae honeys from Venezuela related to their botanical, geographical and entomological origin to assess their putative anticataract activity

 Honey was collected from 24 stinglessbee nests in Venezuela. The flavonoid compounds in the phenolic extracts were analysed and related to the botanical, geographical and entomological origin of the honey. Honeys produced in savannas were richer in flavonoids compared with honeys from the forests. It was found that phenolic extracts of honey of the same geographical origin had similar flavonoid profiles, whereas the same could not be said of honeys of the same entomological origin, although the botanical origin of the samples was variable. It is proposed that analysis of stinglessbee honey eyedrops in terms of their flavonoid content can be used as a basis of authenticating and controlling for their geographical origin. Received: 28 July 1997