Assessing the effect of a single dose florfenicol treatment in feedlot cattle on the antimicrobial resistance patterns in faecal Escherichia coli

The objective of this clinical trial was to examine the effect of a single dose of florfenicol on antimicrobial resistance patterns in faecal E. coli of feedlot steers. Steers (n = 370), were purchased from two sources and housed in outdoor concrete floored pens. Two cattle from each pen (n = 42 pens, 84 cattle) were randomly selected for faecal sampling at study day 1, 14, 28, and 42. One sampled animal from each of 21 pens was randomly selected to receive a single 39.6 mg/kg dose of florfenicol subcutaneously at study day 11. Ten lactose positive colonies were isolated from faecal swabs and tested for antimicrobial resistance to 11 antimicrobials using the disk diffusion method. Zones of inhibition were grouped using cluster analysis and clusters were ordered by increasing multiple resistance. A cumulative logistic regression model using generalized estimating equations was used to assess factors associated with increasing levels of multiple resistance. Immediately post-treatment, all isolates obtained from treated cattle belonged to multiple resistant clusters containing chloramphenicol resistance. Though less pronounced in later sampling, resistance to chloramphenicol and other antimicrobials persisted. Antimicrobial treatment, sampling time and animal source, as well as interactions between these variables, were important predictors of the odds of E. coli belonging to a more resistant cluster. A very clear but transitory shift to increasingly multiple resistant faecal E. coli in response to florfenicol treatment was observed. There was no indication of horizontal transfer of resistant E. coli between steers. Level of resistance was influenced by complex interaction of animal source and previous managemen

Nanofiller-tuned microporous polymer molecular sieves for energy and environmental processes

10.1039/c5ta09060aJournal of Materials Chemistry A41270-27

Vitrification and plastic flow in transient elastomer networks

We investigate how the crossover temperature of the elastic-plastic transition, the ‘vitrification point’ Tv, changes under load for isotropic vitrimers and exchangeable liquid crystal elastomers (xLCEs), using the thermoplastic SIS triblock polymer as a reference. In all these cases, the elastic network cross-links are transient: physical micro-phase separation in SIS and covalent transesterification bonds in vitrimers. From the analysis of SIS we define Tv as the point when entropic rubber-elasticity contraction due to heating under load turns into the irreversible plastic extension due to cross-links breaking and reforming. In xLCEs, the response to mechanical stress is heavily influenced by the smectic liquid-crystalline order, which makes the material much stiffer than normal rubbery networks, and also leads to the shape-memory effect across the smectic-isotropic transition point. The vitrification in the isotropic phase of xLCE, and in isotropic vitrimers, was found to be independent of stress, which can be attributed to the thermal activity of the catalyst determining Tv and it not being mechanically coupled to the elastic network. Beyond Tv, with increasing stress the plastic extension rapidly increases with temperature, as cross-link dynamics becomes more apparent.This work was funded by the EPSRC (EP/J017639), the Ernest Oppenheimer Trust in Cambridge, and by China Scholarship Council.This is the final version of the article. It first appeared from Elsevier via http://dx.doi.org/10.1016/j.polymer.2016.04.06

Oscillations and damping in the fractional Maxwell materials

This paper examines the oscillatory behavior of complex viscoelastic systems with power law like relaxation behavior. Specifically, we use the fractional Maxwell model, consisting of a spring and fractional dashpot in series, which produces a power-law creep behavior and a relaxation law following the Mittag-Leffler function. The fractional dashpot is characterized by a parameter $\textit{β }$, continuously moving from the pure viscous behavior when $\textit{β }$= 1 to the purely elastic response when $\textit{β }$ = 0. In this work, we study the general response function and focus on the oscillatory behavior of a fractional Maxwell system in four regimes: Stress impulse, strain impulse, step stress, and driven oscillations. The solutions are presented in a format analogous to the classical oscillator, showing how the fractional nature of relaxation changes the long-time equilibrium behavior and the short-time transient solutions. We specifically test the critical damping conditions in the fractional regime, since these have a particular relevance in biomechanics.This research was supported by the EPSRC Critical Mass Grant for Cambridge Theoretical Condensed Matter (EP/J017639)

Hydrolyzed Feather Meal as a Protein Supplement for Steer Calves Fed Corn Silage

Hydrolyzed feather meal (HFM) was evaluated for soybean meal replacement value in corn silage diets fed t o steer calves. One hundred ninety-two steers (692 lb) were fed corn silage diets formulated to contain 11.5% crude protein. Hydrolyzed feather meal was substituted for soybean meal at levels providing 0, 25, 50 or 75% of the supplemental protein. Overall performance for the 98-day feeding trial was as follows: 2.10 lb average daily gain; 17.91 lb/day dry matter (DM) intake and 8.58 DM/gain. Protein supplements had no effect on performance, indicating that cost per unit protein is the primary consideration when formulating supplements containing HFM for growing calves fed high quality corn silage

Evaluation of an Acid Hydrolyzed Wood By-Product as an Energy and Protein Source in Rumiant Diets

An acid hydrolyzed wood pulp (AHWP) product that had been buffered with NH4OH was evaluated as a potential feedstuff for ruminant diets. The finely ground low dry matter (33%) material was evaluated for acceptability, digestibility and protein feeding value. In vitro fermentation indicated that fermentable dry matter was extremely low, 35.1%. Diets were not readily consumed by cattle if they contained \u3e 60% AHWP. In vivo dry matter digestibility (DMD) coefficients where AHWP replaced corn as 0, 15, 30 or 45% of the diet were 76.5, 69.3, 65.6 and 78.5%, respectively. A similar response was noted for crude protein and acid detergent fiber disappearance and indicated that negative associative effects due to forage: concentrate ratios may have existed. Nitrogen balance data indicated that the 16% crude protein AHWP contributed no useful dietary nitrogen

A signature of dynamic biogeography: enclaves indicate past species replacement

Understanding how species have replaced each other in the past is important to predicting future species turnover. While past species replacement is difficult to detect after the fact, the process may be inferred from present-day distribution patterns. Species with abutting ranges sometimes show a characteristic distribution pattern, where a section of one species range is enveloped by that of the other. Such an enclave could indicate past species replacement: when a species is partly supplanted by a competitor, but a population endures locally while the invading species moves around and past it, an enclave forms. If the two species hybridize and backcross, the receding species is predicted to leave genetic traces within the expanding one under a scenario of species replacement. By screening dozens of genes in hybridizing crested newts, we uncover genetic remnants of the ancestral species, now inhabiting an enclave, in the range of the surrounding invading species. This independent genetic evidence supports the past distribution dynamics we predicted from the enclave. We suggest that enclaves provide a valuable tool in understanding historical species replacement, which is important because a major conservation concern arising from anthropogenic climate change is increased species replacement in the future

Low-Voltage Continuous Electrospinning Patterning

Electrospinning is a versatile technique for the construction of microfibrous and nanofibrous structures with considerable potential in applications ranging from textile manufacturing to tissue engineering scaffolds. In the simplest form, electrospinning uses a high voltage of tens of thousands volts to draw out ultrafine polymer fibers over a large distance. However, the high voltage limits the flexible combination of material selection, deposition substrate, and control of patterns. Prior studies show that by performing electrospinning with a well-defined "near-field" condition, the operation voltage can be decreased to the kilovolt range, and further enable more precise patterning of fibril structures on a planar surface. In this work, by using solution dependent "initiators", we demonstrate a further lowering of voltage with an ultralow voltage continuous electrospinning patterning (LEP) technique, which reduces the applied voltage threshold to as low as 50 V, simultaneously permitting direct fiber patterning. The versatility of LEP is shown using a wide range of combination of polymer and solvent systems for thermoplastics and biopolymers. Novel functionalities are also incorporated when a low voltage mode is used in place of a high voltage mode, such as direct printing of living bacteria; the construction of suspended single fibers and membrane networks. The LEP technique reported here should open up new avenues in the patterning of bioelements and free-form nano- to microscale fibrous structures.Studentship and scholarship funding supports from the China Scholarship Council scholarship, EPSRC doctoral training partnership, Schlumberger Foundation, WD Armstrong Trus

A complex pattern of post‐divergence expansion, contraction, introgression and asynchronous responses to Pleistocene climate changes in two Dipelta sister species from western China

The well-known vicariance and dispersal models dominate in understanding the allopatric pattern for related species and presume the simultaneous occurrence of speciation and biogeographic events. However, the formation of allopatry may postdate the species divergence. We examined this hypothesis using DNA sequence data from 3 chloroplast fragments and 5 nuclear loci of Dipelta floribunda and D. yunnanensis, two shrub species with the circum Sichuan Basin distribution, combining the climatic niche modeling approach. The best-fit model supported by the approximate Bayesian computation (ABC) analysis indicated that, D. floribunda and D. yunnanensis diverged during the mid-Pleistocene period, consistent with the largest glacial period in the Qinghai-Tibet Plateau (QTP). The historically inter-specific gene flow was identified but seemed to have ceased after the last interglacial period (LIG), when the range of D. floribunda moved northward from the south of the Sichuan Basin. Further, populations of D. floribunda had expanded obviously in the north of the Sichuan Basin after the last glacial maximum (LGM). Relatively, the range of D. yunnanensis expanded before the LGM, reduced during the post-LGM especially in the north of the Sichuan Basin, reflecting the asynchronous responses of related species to the contemporary climate changes. Our results suggested that complex topography should be considered in understanding the distributional patterns even for closely related species and their demographic responses