Small-Scale Food Animal Production and Antimicrobial Resistance: Mountain, Molehill, or Something in-between?

SummarySmall-scale food animal production is widely practiced around the globe, yet it is often overlooked in terms of the environmental health risks. Evidence suggests that small-scale food animal producers often employ the use of antimicrobials to improve the survival and growth of their animals, and that this practice leads to the development of antimicrobial resistance (AMR) that can potentially spread to humans. The nature of human-animal interactions in small-scale food animal production systems, generally practiced in and around the home, likely augments spillover events of AMR into the community on a scale that is currently unrecognized and deserves greater attention. https://doi.org/10.1289/EHP2116

Ionization fronts in negative corona discharges

In this paper we use a hydrodynamic minimal streamer model to study negative corona discharge. By reformulating the model in terms of a quantity called shielding factor, we deduce laws for the evolution in time of both the radius and the intensity of ionization fronts. We also compute the evolution of the front thickness under the conditions for which it diffuses due to the geometry of the problem and show its self-similar character.Comment: 4 pages, 4 figure

EFFETTO DELLA SOLLECITAZIONE MECCANICA A FLESSIONE SUL COMPORTAMENTO A CORROSIONE DI LEGHE DI Al STRUTTURALI

The present work reports on the effect of constant bending load on the electrochemical behavior of structural aluminum alloys AA 2024-T3 (Al-Cu-Mg) and AA 7075-T6 (Al-Zn-Mg-Cu). The single cycle anodic polarization curves in 0.6 M NaCl (pH 6.5) were carried out using four-point bent beam specimens (4PBB). Lower propensity to localized corrosion has been indicated for compressive stresses. The effect of tensile stresses on the electrochemical response is more complex and depends on the alloy nature

Detection of Zoonotic Enteropathogens in Children and Domestic Animals in a Semirural Community in Ecuador.

UNLABELLED: Animals are important reservoirs of zoonotic enteropathogens, and transmission to humans occurs more frequently in low- and middle-income countries (LMICs), where small-scale livestock production is common. In this study, we investigated the presence of zoonotic enteropathogens in stool samples from 64 asymptomatic children and 203 domestic animals of 62 households in a semirural community in Ecuador between June and August 2014. Multilocus sequence typing (MLST) was used to assess zoonotic transmission of Campylobacter jejuni and atypical enteropathogenic Escherichia coli (aEPEC), which were the most prevalent bacterial pathogens in children and domestic animals (30.7% and 10.5%, respectively). Four sequence types (STs) of C. jejuni and four STs of aEPEC were identical between children and domestic animals. The apparent sources of human infection were chickens, dogs, guinea pigs, and rabbits for C. jejuni and pigs, dogs, and chickens for aEPEC. Other pathogens detected in children and domestic animals were Giardia lamblia (13.1%), Cryptosporidium parvum (1.1%), and Shiga toxin-producing E. coli (STEC) (2.6%). Salmonella enterica was detected in 5 dogs and Yersinia enterocolitica was identified in 1 pig. Even though we identified 7 enteric pathogens in children, we encountered evidence of active transmission between domestic animals and humans only for C. jejuni and aEPEC. We also found evidence that C. jejuni strains from chickens were more likely to be transmitted to humans than those coming from other domestic animals. Our findings demonstrate the complex nature of enteropathogen transmission between domestic animals and humans and stress the need for further studies. IMPORTANCE: We found evidence that Campylobacter jejuni, Giardia, and aEPEC organisms were the most common zoonotic enteropathogens in children and domestic animals in a region close to Quito, the capital of Ecuador. Genetic analysis of the isolates suggests transmission of some genotypes of C. jejuni and aEPEC from domestic animals to humans in this region. We also found that the genotypes associated with C. jejuni from chickens were present more often in children than were those from other domestic animals. The potential environmental factors associated with transmission of these pathogens to humans then are discussed

Energy dissipation in a nonlinearly damped Duffing oscillator

International audienceIn this paper, we study the effect of including a nonlinear damping term proportional to the power of the velocity in the dynamics of a double-well Duffing oscillator. In particular, we focus our attention in understanding how the energy dissipates over a cycle and along the time, by the use of different tools of analysis. Analytical and numerical results for different damping terms are shown, and the presence of a discontinuity and an inversion of behavior depending on the initial energy are discussed. An averaged power loss in a period is defined, showing similar characteristics as the energy dissipation over a cycle, although no discontinuity is present. The discontinuity gap which appears for the energy dissipation at a certain value of the initial energy decreases as the power of the damping term increases and an associated scaling law is found

Investigation of electrochemically-induced repassivation of Al 7075-T6 and Al 2024-T3 as a function of applied stress and galvanic corrosion

The repassivation behavior of Al alloys 7075-T6 and 2024-T3 was investigated by means of pitting scan (PS) technique (Fig. 1) (Trueba, Trasatti, 2015). The effect of mechanical load and galvanic coupling was estimated by considering principally the electrochemical characteristics of the reverse curve, namely the pit transition potential (Eptp), the associated current density (iptp) and the steepness. The load levels explored were mostly below the elastic limit, using four point bent-beam (4PBB) stress-corrosion test specimens (ASTM G39-99). CRES 304 or Ti6Al4V alloy were physically joined with Al sheet for simulating stress-induced galvanic corrosion. Different experimental variables (e.g. irev, [Cl-], pH, scan rate, etc.) were also considered. The study was complemented with corrosion morphology analysis. Please click Additional Files below to see the full abstract

Determinants of Childhood Zoonotic Enteric Infections in a Semirural Community of Quito, Ecuador.

Domestic animals in the household environment have the potential to affect a child's carriage of zoonotic enteric pathogens and risk of diarrhea. This study examines the risk factors associated with pediatric diarrhea and carriage of zoonotic enteric pathogens among children living in communities where smallholder livestock production is prevalent. We conducted an observational study of children younger than 5 years that included the analysis of child (n = 306) and animal (n = 480) fecal samples for Campylobacter spp., atypical enteropathogenic Escherichia coli, Shiga toxin-producing E. coli, Salmonella spp., Yersinia spp., Cryptosporidium parvum, and Giardia lamblia. Among these seven pathogens, Giardia was the most commonly identified pathogen among children and animals in the same household, most of which was found in child-dog pairs. Campylobacter spp. was also relatively common within households, particularly among child-chicken and child-guinea pig pairs. We used multivariable Poisson regression models to assess risk factors associated with a child being positive for at least one zoonotic enteric pathogen or having diarrhea during the last week. Children who interacted with domestic animals-a behavior reported by nearly three-quarters of households owning animals-were at an increased risk of colonization with at least one zoonotic enteric pathogen (prevalence ratio [PR] = 1.56, 95% CI: 1.00-2.42). The risk of diarrhea in the last seven days was elevated but not statistically significant (PR = 2.27, CI: 0.91, 5.67). Interventions that aim to reduce pediatric exposures to enteric pathogens will likely need to be incorporated with approaches that remove animal fecal contamination from the domestic environment and encourage behavior change aimed at reducing children's contact with animal feces through diverse exposure pathways

Power laws and self-similar behavior in negative ionization fronts

We study anode-directed ionization fronts in curved geometries. When the magnetic effects can be neglected, an electric shielding factor determines the behavior of the electric field and the charged particle densities. From a minimal streamer model, a Burgers type equation which governs the dynamics of the electric shielding factor is obtained. A Lagrangian formulation is then derived to analyze the ionization fronts. Power laws for the velocity and the amplitude of streamer fronts are observed numerically and calculated analytically by using the shielding factor formulation. The phenomenon of geometrical diffusion is explained and clarified, and a universal self-similar asymptotic behavior is derived.Comment: 25 pages, 9 figure

Investigation of SCC of high strength aluminum alloys by means of slow strain rate test and cyclic anodic polarization in combination

The stress corrosion cracking (SCC) behavior of high strength 7075-T6 and 2024-T3 Al alloys in NaCl solutions is investigated by means of slow strain rate test (SSRT) and cyclic anodic polarization in combination. Smooth, dog-bone shaped flat tension test specimens, having gage section areas of 40 mm2 and 32 mm2, respectively, and 90 mm of gage length, were machined in the longitudinal (rolling) direction from the commercial wrought sheets (Aviometal Spa). The tensile test was performed at a constant strain rate (ἐ = 10-7, 10-6 or 10-5 s-1) from a pre-load of about 5 kN until fracture. The electrochemical system consisted in non-connected two Plexiglas cylindrical cells that were fixed at the middle of the opposite surfaces of the tensile specimen (working electrode, surface area at each side of 2 cm2). The variation of the open circuit potential (OCP) during straining was measured with respect to saturated calomel reference electrode (SCE) by connecting the two electrode system to a Gamry potentiostat. Contemporarily, the opposite surface was electrochemically perturbed by imposing consecutive cyclic anodic polarizations with open circuit potential measurements in between (OCP/polarization sequences), using an Ir-coated Ti auxiliary electrode, another SCE and a second Gamry potentiostat. At least two combined experiments for each test condition were carried out for repeatability check. Experiments with no OCP/polarization sequence during straining, and vice versa, were performed for reference purposes. The stress-strain curves of Al 7075-T6 (Fig. 1a) show that the ultimate strength and failure strain decrease in aggressive environment as the strain rate is lowered, regardless the electrochemical perturbation, being in agreement with reported data [1]. More interestingly, quasi-periodic stress relaxation/recovery events above the elastic region in correspondence with the dissolution/repassivation cycle were detected for ἐ ≤ 10-6 s-1 and 0.1667 mV/s of potential scan rate (n). The resolved negative spikes in the stress time derivative curve and the related polarization curves (as log | I | - t) for ἐ = 10-7 s-1, 0.6 M NaCl and n = 0.1667 mV/s are reported in Figure 1b. The spike pattern along the time axe was dependent on ἐ and NaCl concentration. The results from ongoing combined experiments with Al 2024-T3 for verification of the above findings will be presented altogether with empirical data analysis for a quantitative insight into the environmentally assisted failure mechanisms. Please click Additional Files below to see the full abstract