Cascading effects of composts and cover crops on soil chemistry, bacterial communities and the survival of foodborne pathogens.

AIMS: Recent foodborne disease outbreaks have caused farmers to re-evaluate their practices. In particular, concern that soil amendments could introduce foodborne pathogens onto farms and promote their survival in soils has led farmers to reduce or eliminate the application of animal-based composts. However, organic amendments (such as composts and cover crops) could bolster food safety by increasing soil microbial diversity and activity, which can act as competitors or antagonists and reduce pathogen survival. METHODS AND RESULTS: Leveraging a study of a 27-year experiment comparing organic and conventional soil management, we evaluate the impacts of composted poultry litter and cover crops on soil chemistry, bacterial communities and survival of Salmonella enterica and Listeria monocytogenes. We found that bacterial community composition strongly affected pathogen survival in soils. Specifically, organic soils managed with cover crops and composts hosted more macronutrients and bacterial communities that were better able to suppress Salmonella and Listeria. For example, after incubating soils for 10 days at 20°C, soils without composts retained fourfold to fivefold more Salmonella compared to compost-amended soils. However, treatment effects dissipated as bacterial communities converged over the growing season. CONCLUSIONS: Our results suggest that composts and cover crops may be used to build healthy soils without increasing foodborne pathogen survival. SIGNIFICANCE AND IMPACT OF THE STUDY: Our work suggests that animal-based composts do not promote pathogen survival and may even promote bacterial communities that suppress pathogens. Critically, proper composting techniques are known to reduce pathogen populations in biological soil amendments of animal origin, which can reduce the risks of introducing pathogens to farm fields in soil amendments. Thus, animal-based composts and cover crops may be a safe alternative to conventional fertilizers, both because of the known benefits of composts for soil health and because it may be possible to apply amendments in such a way that food-safety risks are mitigated rather than exacerbated.

Charge Puddles in Graphene near the Dirac Point.

The charge carrier density in graphene on a dielectric substrate such as SiO_{2} displays inhomogeneities, the so-called charge puddles. Because of the linear dispersion relation in monolayer graphene, the puddles are predicted to grow near charge neutrality, a markedly distinct property from conventional two-dimensional electron gases. By performing scanning tunneling microscopy and spectroscopy on a mesoscopic graphene device, we directly observe the puddles' growth, both in spatial extent and in amplitude, as the Fermi level approaches the Dirac point. Self-consistent screening theory provides a unified description of both the macroscopic transport properties and the microscopically observed charge disorder.

Niobium-based superconducting nano-device fabrication using all-metal suspended masks.

We report a novel method for the fabrication of superconducting nano-devices based on niobium. The well-known difficulties of lithographic patterning of high-quality niobium are overcome by replacing the usual organic resist mask by a metallic one. The quality of the fabrication procedure is demonstrated by the realization and characterization of long and narrow superconducting lines and niobium-gold-niobium proximity SQUIDs.

Determining the density content of symmetry energy and neutron skin: an empirical approach.

The density dependence of nuclear symmetry energy remains poorly constrained. Starting from precise empirical values of the nuclear volume and surface symmetry energy coefficients and the nuclear saturation density, we show how in the ambit of microscopic calculations with different energy density functionals, the value of the symmetry energy slope parameter L along with that for neutron skin can be put in tighter bounds. The value of L is found to be L=64±5 MeV. For 208Pb, the neutron skin thickness comes out to be 0.188±0.014 fm. Knowing L, the method can be applied to predict neutron skin thicknesses of other nuclei.

Exploring the art of medical photography - an otolaryngologist's perspective.

BACKGROUND: Modern day otolaryngology has expanded beyond the ear, nose and throat to include head and neck surgery and aesthetic facial procedures. Photographic documentation is important within this expanded horizon. The spectrum of clinical photography includes photomicrographs, endoscopic photographs, peri-operative photography and medical social photography. METHOD: This article aimed to review the standard guidelines essential to obtain, store and disseminate photographs and looked at setting up a small clinic with minimal gadgets to suit clinical photography requirements. Elaboration of basic photography techniques in otolaryngology was reviewed, with examples of photographs taken in a clinic by a clinician. Advances and innovation in clinical photography, in the form of smartphone photography, artificial intelligence, device editing and newer hardware and software in otorhinolaryngology was reviewed. CONCLUSION: Having a professional photographer to aid a clinician is a luxury. Simple knowledge and regular practice of basic photography guidelines by a clinician is imperative.

Electron removal from H2O by hydrogen-like projectile impact.

The four-body distorted-wave approximation (DW-4B) is used to investigate the electron removal from water molecules by the impact of hydrogen-like projectiles. The incident energy is considered in a range of 20 to 2000 keV/amu. Our goal is to establish the relative importance of the intermediate ionization continua of the active electron and the electron-electron correlations. The calculations are based on the independent electron model. The description of initial ground state molecular orbitals of water are described by a complete-neglect-of-differential-overlap method based on the linear combination of atomic orbitals. Numerical results for the total cross sections are compared with other results and found to be in good agreement with the available experimental findings. Differentiation between the reactions of single-electron ionization and single-electron capture in electron removal process as a function of impact energies is also analyzed. Finally, the dependence of cross sections regarding electron removal on different descriptions of molecular orbitals as well as the simplest additivity rule are discussed.

Cyclization and unsaturation rather than isomerisation of side chains govern the selective antibacterial activity of cationic-amphiphilic polymers.

Membrane-active agents represent a promising alternative to overcome antibiotic resistance. Here, we report cationic-amphiphilic polymers with variations in the side chain architecture such as cyclization, isomerization and unsaturation that resulted in potent antibacterial activity and low mammalian cell toxicity with a membrane-active mode of action.

Isosteric substitution in cationic-amphiphilic polymers reveals an important role for hydrogen bonding in bacterial membrane interactions.

Biomimetic antibacterial polymers, the functional mimics of antimicrobial peptides (AMPs), targeting the bacterial cell membrane have been developed to combat the problem of antibiotic resistance. Amphiphilicity, a balance of cationic charge and hydrophobicity, in these polymers has been shown to be pivotal for their selective interactions with anionic lipid membranes of bacteria instead of zwitterionic mammalian (human erythrocyte) membranes. However, it is unclear if and to what extent hydrogen bonding in amphiphilic antibacterial polymers contributes to this membrane binding specificity. To address this, we employ isosteric substitution of ester with amide moieties that differ in their potency for hydrogen bonding in the side chains of N-alkyl maleimide based amphiphilic polymers. Our studies reveal that amide polymer (AC3P) is a potent antibacterial agent with high membrane-disrupting properties compared to its ester counterpart (EC3P). To understand these differences we performed bio-physical experiments and molecular dynamics (MD) simulations which showed strong interactions of AC3P including hydrogen bonding with lipid head groups of bacterial model lipid bilayers, that are absent in EC3P, make them selective for bacterial membranes. Mechanistic investigations of these polymers in bacteria revealed specific membrane disruptive activity leading to the delocalization of cell division related proteins. This unprecedented and unique concept provides an understanding of bacterial membrane interactions highlighting the role of hydrogen bonding. Thus, these findings will have significant implications in efficient design of potent membrane-active agents.