Biodegradation of Polyvinyl Alcohol-Based Binary Composites

The behavior of binary composites (BC) containing polyvinyl alcohol (PVA‑1799) and various amounts of microcellulose (MC) in water and biochemical media (soil, compost, water-silt mixture) is studied. The results of the experiment emphasize the complex nature of the biodegradation of the studied composites under natural conditions. Introduction of microcellulose into the polymer matrix of PVA about 60 vol.% is accompanied by the formation of a porous structure that promotes the penetration of water and components of biochemical media into the volume of the material. At the same time, the uniform distribution of the MC fibers creates the effect of a reinforcing filler and allows you to maintain strength even with prolonged soaking of the BC. The achievement of «zero» strength at exposure in water is observed after 2 days, 14 days, 2 months. for BC with a content of MC 0, 80–60, 40–10 vol.%, respectively. After 6 months of incubation in the soil environment, the index of destruction of composites was 0.89, 0.87, 0.95, 0.96 with a degree of filling with microcellulose of 10, 20,40, 80 vol.%, respectively, while there was a lack of fragmentation of the samples. A method of computer colorometry in the dynamics of biodegradation of polysaccharide-filled thermoplastics is proposed to assess the degree of penetration of components of biochemical media into the volume of the material

Semut sebagai vektor mekanik bakteri di dalam gedung Balai Litbang P2B2 Tanah Bumbu, Kalimantan Selatan: studi pendahuluan

Ants are now now noticeable as a mechanical vector of pathogenic bacteria, some of which have been resistant to certain antibiotics. Its wide presence allows ants to easily transmit disease agents. This study aims to determine the type of ants in Balai Litbang P2B2 Tanah Bumbu and possible role as a vector mechanical bacteria. This research was conducted at Balai Litbang P2B2 Tanah Bumbu from August to September 2017, the sample was obtained from 15 rooms by using the sugar solution feed placed in the microtube, then the ant was identified by referring to Key to Identifying Common Household Ants and Pictorial Key to the Common Urban Ants of North Carolina, followed by identification of bacteria on selective and biochemical media referring to Bergey's Manual of Systematic Bacteriology Volume 2. Out of a total of 16 samples, five types of ants are known: Tapinoma melanochephalum, Paratrechina longicornis, Tetramorium caespitum, and Anoplolepis gracilipes , and Solenopsis spp. Bacteria are found in all types of ants. The bacteria identified were Bacillus alvei, Bacillus badius, Bacillus insulitus, Serratia liquefaciens, Enterobacter aglomerans, and Klebsiella ozonae, and Enterobacter spp. The ants found in Balai P2B2 Tanah Bumbu are potentially bacterial mechanical vectors.

Influence of thermodynamic database on the modelisation of americium(III) speciation in a simulated biological medium

SummaryAn intercomparison exercise was led in order to study the impact of thermodynamic database (TDB) on the speciation of americium(III) in biochemical media.A first exercice was led, considering only the americium(III) species in solution. Even with different data sets, all the exercises are in relatively good agreement, concluding to successive complexation of the radioelement by phosphate (pH range from 0 to 3), citrate (pH range from 3 to 8) and hydroxo-carbonate (pH range from 8 to 14). Nevertheless, the speciation of americium differs for each pH range from one work to an other.These results are still observed when the speciation calculation includes the formation of solids. Nevertheless, some workers did not integrate in their data set the formation constant of Am(POThis work is a representative example of the impact of the thermodynamic data used in speciation exercises. Some exercices, using uncompleted TDB had wrong results and led to the conclusion of the necessity in the use of expertised and extended TDB.

Rapid immunochemical identification of enterococci with use of a centrifugal analyzer after a brief antigen-extraction step.

The precipitin reaction between antigens from enterococci and group-specific antisera was monitored turbidimetrically with a centrifugal analyzer. Linear standard curves (absorbance vs antigen concentration) were developed for studying optimal conditions for enzymic extraction of the antigen by use of an enzyme-containing filtrate from Streptomyces albus. This extraction was optimized by adding to the filtrate 1 mg of lysozyme per milliliter and incubating the bacteria for 40 min at 52 degrees C. The assay was adjusted so that detection of enterococci was indicated by positive absorbance changes near 0.1 A. When the concentration of bacteria from which the antigen was extracted was within a standardized range, non-enterococci produced no positive absorbance changes. Reproducibility of standard antigen and antisera solutions was excellent during three months. The procedure provides an objective, well-controlled means for identifying clinically important enterococci from pure cultures in about 1 h. In contrast, current methods involving biochemical media require as long as 48 h.