Short communication: Comparison of the fecal bacterial communities in diarrheic and nondiarrheic dairy calves from multiple farms in southeastern Pennsylvania

Diarrhea is a major cause of illness and death in preweaned calves and causes significant economic losses to producers. A better understanding of the fecal microbiota in diarrheic and nondiarrheic calves could lead to improved treatment and prevention strategies. The purpose of this study was to compare the fecal microbiota of diarrheic and nondiarrheic calves to improve our understanding of what constitutes a healthy fecal microbiota in preweaned calves. At each of 7 farms, fecal samples were obtained from 1 to 3 diarrheic Holstein dairy calves (2 to 17 d old at sampling time) and age-matched (within 5 d) nondiarrheic controls for a total of 20 samples. Calves were fed either acidified bulk milk, pasteurized or unpasteurized waste milk, or milk replacer depending on farm. Fecal samples were extracted for genomic DNA, PCR-amplified for the V1–V2 region of the 16S rRNA bacterial gene, sequenced on the Illumina MiSeq (Illumina Inc., San Diego, CA) platform, and analyzed using QIIME2. Firmicutes and Bacteroidetes were the most abundant phyla in both groups; Fusobacteria was numerically more abundant in the diarrheic group, whereas Proteobacteria and Actinobacteria were numerically more abundant in the nondiarrheic group. At the genus level, Bacteroides was the most abundant genus in both groups and was numerically more abundant in the nondiarrheic group. Results from the mixed-effects regression model showed that Faecalibacterium and Butyricimonas were more abundant in the nondiarrheic calves, whereas Clostridium and Peptostreptococcus were more abundant in the diarrheic calves. Our results indicate that commensal bacteria acquired in the neonatal period may have been replaced with potential pathogens in diarrheic calves, which may have contributed to the incidence of diarrhea either directly or indirectly.     

Phase behavior and mechanism of formation of protofiber morphology of solution spun poly(acrylonitrile) copolymers in DMF‐water system

Phase diagrams of a series of copolymers of acrylonitrile (AN) and acrylic acid (AAc) were constructed using linearized cloud point correlation. The miscibility region in the phase diagram was found to increase with the increase in AAc content of the copolymers. For various compositions, χ₁₃ (polymer–water interaction parameter) values were estimated by sorption experiment. As the hydrophilic nature of the polymer increased with the increase in the content of acrylic acid, the χ₁₃ interaction parameter was found to decrease from poly(acrylonitrile) homopolymer to its copolymer with 50 mol % acrylic acid (AA50B). The polymer–solvent interaction parameters (χ₂₃) and composition at the critical points for all the polymers were determined by fitting the theoretical bimodal curves to the experimental cloud point curves using Kenji Kamide equations. The polymer composition at the critical point was found to increase by 400% with increasing AAc content. The polymers were solution spun in DMF‐water coagulation bath at 30°C and their protofiber structures were investigated under scanning electron microscopy. The observed morphological differences in protofibers were explained on the changes brought about in the phase separation behavior of the polymer–solvent–nonsolvent systems. The copolymers with higher acrylic acid content could be solution spun into void free homogeneous fibers even at conditions that produced void‐filled inhomogeneous fibers in poly(acrylonitrile) and its copolymers with lower AAc content. The experiments demonstrate the important role of thermodynamics in deciding the protofiber morphology during coagulation process. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Role of additives in influencing heating and melting of polymers during thermoforming

The heating stage in thermoforming of amorphous and semi-crystalline polymers was analyzed for constant heat flux conditions using an energy balance model; candidate polymers were high impact polystyrene and isotactic polypropylene. Using an analytical solution, temperature differences as large as 100°C were predicted to arise between the surface and the interior of the sheet being thermoformed for conditions chosen in this work, and these can limit the heat flux being used. A Matlab program was used to compute temperature and crystallinity profiles for crystal melting. Melting took almost as much time as required to heat the surface of the film to the crystal melting point. High thermal conductivity additives, such as calcium carbonate and graphene, can provide temperature uniformity, and the additive uniformity can be verified using thermogravimetric analysis. The ability of these additives to provide temperature uniformity and to reduce energy consumption and heating time is determined in a quantitative manner. Both additives improve heat transfer, and, at the same added volume fraction, graphene is more effective. However, calcium carbonate has a lower cost. The role of density, specific heat, thermal conductivity, and amount of the polymers and additives in influencing temperature and crystallinity profiles was explored, and methods of carrying out thermoforming in an energy efficient manner are proposed.