Hydrogen in α\alpha-iron: stress and diffusion

First-principles density-functional theory has been used to investigate equilibrium geometries, total energies, and diffusion barriers for H as an interstitial impurity absorbed in $\alpha$-Fe. Internal strains/stresses upon hydrogen absorption are a crucial factor to understand preferred absorption sites and diffusion. For high concentrations, H absorbs near the octahedral site favoring a large tetragonal distortion of the BCC lattice. For low concentration, H absorbs near the tetrahedral site minimizing the elastic energy stored on nearby cells. Diffusion paths depend on the concentration regime too; hydrogen diffuses about ten times faster in the distorted BCT lattice. External stresses of several GPa modify barriers by $\approx$ 10%, and diffusion rates by $\approx$ 30%

Ab-initio molecular dynamics simulation of hydrogen diffusion in α\alpha-iron

First-principles atomistic molecular dynamics simulation in the micro-canonical and canonical ensembles has been used to study the diffusion of interstitial hydrogen in $\alpha$-iron. Hydrogen to Iron ratios between $\theta=1/16 and 1/2 have been considered by locating interstitial hydrogen atoms at random positions in a$2 \times 2 \times 2$ supercell. We find that the average optimum absorption site and the barrier for diffusion depend on the concentration of interestitials. Iron Debye temperature decreases monotonically for increasing concentration of interstitial hydrogen, proving that iron-iron interatomic potential is significantly weakened in the presence of a large number of diffusing hydrogen atoms

Proximal hyperspectral sensing and data analysis approaches for field-based plant phenomics

Field-based plant phenomics requires robust crop sensing platforms and data analysis tools to successfully identify cultivars that exhibit phenotypes with high agronomic and economic importance. Such efforts will lead to genetic improvements that maintain high crop yield with concomitant tolerance to environmental stresses. The objectives of this study were to investigate proximal hyperspectral sensing with a field spectroradiometer and to compare data analysis approaches for estimating four cotton phenotypes: leaf water content (Cw), specific leaf mass (Cm), leaf chlorophyll a+b content (Cab), and leaf area index (LAI). Field studies tested 25 Pima cotton cultivars grown under well-watered and water-limited conditions in central Arizona from 2010 to 2012. Several vegetation indices, including the normalized difference vegetation index (NDVI), the normalized difference water index (NDWI), and the physiological (or photochemical) reflectance index (PRI) were compared with partial least squares regression (PLSR) approaches to estimate the four phenotypes. Additionally, inversion of the PROSAIL plant canopy reflectance model was investigated to estimate phenotypes based on 3.68 billion PROSAIL simulations on a supercomputer. Phenotypic estimates from each approach were compared with field measurements, and hierarchical linear mixed modeling was used to identify differences in the estimates among the cultivars and water levels. The PLSR approach performed best and estimated Cw,Cm,Cab, and LAI with root mean squared errors (RMSEs) between measured and modeled values of 6.8%, 10.9%, 13.1%, and 18.5%, respectively. Using linear regression with the vegetation indices, no index estimated Cw,Cm,Cab, and LAI with RMSEs better than 9.6%, 16.9%, 14.2%, and 28.8%, respectively. PROSAIL model inversion could estimate Cab and LAI with RMSEs of about 16% and 29%, depending on the objective function. However, the RMSEs for Cw and Cm from PROSAIL model inversion were greater than 30%. Compared to PLSR, advantages to the physically-based PROSAIL model include its ability to simulate the canopy's bidirectional reflectance distribution function (BRDF) and to estimate phenotypes from canopy spectral reflectance without a training data set. All proximal hyperspectral approaches were able to identify differences in phenotypic estimates among the cultivars and irrigation regimes tested during the field studies. Improvements to these proximal hyperspectral sensing approaches could be realized with a high-throughput phenotyping platform able to rapidly collect canopy spectral reflectance data from multiple view angles

Assessment of conjunctival, episcleral and scleral thickness in healthy individuals using anterior segment optical coherence tomography

Purpose: To determine the thickness of the conjunctiva, episclera and sclera in healthy individuals using anterior segment optical coherence tomography (AS-OCT).Methods: We prospectively included 107 healthy individuals of different age groups (18-39 years, 40-54 years, 55-69 years and >= 70 years). For each eye, AS-OCT scans of four quadrants (temporal, nasal, superior and inferior) were acquired. The thickness of the conjunctiva, episclera and sclera was measured for each scan. In addition, the axial length of both eyes was measured, and general characteristics, including smoking, allergies and contact lens use, were collected.Results: The mean conjunctival thickness was significantly different between the nasal and superior quadrants (87 +/- 30 mu m vs. 77 +/- 16 mu m; p < 0.001), as well as the superior and inferior quadrants (77 +/- 16 mu m vs. 86 +/- 19 mu m; p = 0.001). The mean episcleral thickness was larger in the superior (174 +/- 54 mu m) and inferior (141 +/- 43 mu m) quadrants, compared to the nasal (83 +/- 38 mu m) and temporal quadrants (90 +/- 44 mu m). The mean scleral thickness of the inferior quadrant was the largest (596 +/- 64 mu m), followed by the nasal (567 +/- 76 mu m), temporal (516 +/- 67 mu m) and superior (467 +/- 52 mu m) quadrants (all p < 0.001). The averaged scleral thickness increased 0.96 mu m per age year (0.41-1.47 mu m, p < 0.001).Conclusions: This study provides an assessment of the thickness of scleral and adjacent superficial layers in healthy individuals determined on AS-OCT, which could enable future research into the use of AS-OCT in diseases affecting the anterior eye wall

Assessment of conjunctival, episcleral and scleral thickness in healthy individuals using anterior segment optical coherence tomography

Purpose: To determine the thickness of the conjunctiva, episclera and sclera in healthy individuals using anterior segment optical coherence tomography (AS-OCT).Methods: We prospectively included 107 healthy individuals of different age groups (18-39 years, 40-54 years, 55-69 years and >= 70 years). For each eye, AS-OCT scans of four quadrants (temporal, nasal, superior and inferior) were acquired. The thickness of the conjunctiva, episclera and sclera was measured for each scan. In addition, the axial length of both eyes was measured, and general characteristics, including smoking, allergies and contact lens use, were collected.Results: The mean conjunctival thickness was significantly different between the nasal and superior quadrants (87 +/- 30 mu m vs. 77 +/- 16 mu m; p < 0.001), as well as the superior and inferior quadrants (77 +/- 16 mu m vs. 86 +/- 19 mu m; p = 0.001). The mean episcleral thickness was larger in the superior (174 +/- 54 mu m) and inferior (141 +/- 43 mu m) quadrants, compared to the nasal (83 +/- 38 mu m) and temporal quadrants (90 +/- 44 mu m). The mean scleral thickness of the inferior quadrant was the largest (596 +/- 64 mu m), followed by the nasal (567 +/- 76 mu m), temporal (516 +/- 67 mu m) and superior (467 +/- 52 mu m) quadrants (all p < 0.001). The averaged scleral thickness increased 0.96 mu m per age year (0.41-1.47 mu m, p < 0.001).Conclusions: This study provides an assessment of the thickness of scleral and adjacent superficial layers in healthy individuals determined on AS-OCT, which could enable future research into the use of AS-OCT in diseases affecting the anterior eye wall

Bacillus subtilis polynucleotide phosphorylase 3′-to-5′ DNase activity is involved in DNA repair

In the presence of Mn2+, an activity in a preparation of purified Bacillus subtilis RecN degrades single-stranded (ss) DNA with a 3′ → 5′ polarity. This activity is not associated with RecN itself, because RecN purified from cells lacking polynucleotide phosphorylase (PNPase) does not show the exonuclease activity. We show here that, in the presence of Mn2+ and low-level inorganic phosphate (Pi), PNPase degrades ssDNA. The limited end-processing of DNA is regulated by ATP and is inactive in the presence of Mg2+ or high-level Pi. In contrast, the RNase activity of PNPase requires Mg2+ and Pi, suggesting that PNPase degradation of RNA and ssDNA occur by mutually exclusive mechanisms. A null pnpA mutation (ΔpnpA) is not epistatic with ΔrecA, but is epistatic with ΔrecN and Δku, which by themselves are non-epistatic. The addA5, ΔrecO, ΔrecQ (ΔrecJ), ΔrecU and ΔrecG mutations (representative of different epistatic groups), in the context of ΔpnpA, demonstrate gain- or loss-of-function by inactivation of repair-by-recombination, depending on acute or chronic exposure to the damaging agent and the nature of the DNA lesion. Our data suggest that PNPase is involved in various nucleic acid metabolic pathways, and its limited ssDNA exonuclease activity plays an important role in RecA-dependent and RecA-independent repair pathways

Acute Putrescine Supplementation with Schwann Cell Implantation Improves Sensory and Serotonergic Axon Growth and Functional Recovery in Spinal Cord Injured Rats

Schwann cell (SC) transplantation exhibits significant potential for spinal cord injury (SCI) repair and its use as a therapeutic modality has now progressed to clinical trials for subacute and chronic human SCI. Although SC implants provide a receptive environment for axonal regrowth and support functional recovery in a number of experimental SCI models, axonal regeneration is largely limited to local systems and the behavioral improvements are modest without additional combinatory approaches. In the current study we investigated whether the concurrent delivery of the polyamine putrescine, started either 30 min or 1 week after SCI, could enhance the efficacy of SCs when implanted subacutely (1 week after injury) into the contused rat spinal cord. Polyamines are ubiquitous organic cations that play an important role in the regulation of the cell cycle, cell division, cytoskeletal organization, and cell differentiation. We show that the combination of putrescine with SCs provides a significant increase in implant size, an enhancement in axonal (sensory and serotonergic) sparing and/or growth, and improved open field locomotion after SCI, as compared to SC implantation alone. These findings demonstrate that polyamine supplementation can augment the effectiveness of SCs when used as a therapeutic approach for subacute SCI repair

Silver nanoparticles-composing alginate/gelatine hydrogel improves wound healing in vivo

Polymer hydrogels have been suggested as dressing materials for the treatment of cutaneous wounds and tissue revitalization. In this work, we report the development of a hydrogel composed of natural polymers (sodium alginate and gelatin) and silver nanoparticles (AgNPs) with recognized antimicrobial activity for healing cutaneous lesions. For the development of the hydrogel, different ratios of sodium alginate and gelatin have been tested, while different concentrations of AgNO3 precursor (1.0, 2.0, and 4.0 mM) were assayed for the production of AgNPs. The obtained AgNPs exhibited a characteristic peak between 430450 nm in the ultraviolet-visible (UVVis) spectrum suggesting a spheroidal form, which was confirmed by Transmission Electron Microscopy (TEM). Fourier Transform Infra-red (FTIR) analysis suggested the formation of strong intermolecular interactions as hydrogen bonds and electrostatic attractions between polymers, showing bands at 2920, 2852, 1500, and 1640 cm1. Significant bactericidal activity was observed for the hydrogel, with a Minimum Inhibitory Concentration (MIC) of 0.50 µg/mL against Pseudomonas aeruginosa and 53.0 µg/mL against Staphylococcus aureus. AgNPs were shown to be non-cytotoxic against fibroblast cells. The in vivo studies in female Wister rats confirmed the capacity of the AgNP-loaded hydrogels to reduce the wound size compared to uncoated injuries promoting histological changes in the healing tissue over the time course of wound healing, as in earlier development and maturation of granulation tissue. The developed hydrogel with AgNPs has healing potential for clinical applications.This research received funding from the Coordenação Aperfeiçoamento de Pessoal de Nivel Superior (CAPES), Fundação de Amparo à Pesquisa do Estado de Sergipe (FAPITEC), Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, #443238/2014-6, #470388/2014-5), and from the Portuguese Science and Technology Foundation (FCT) projects M-ERA-NET/0004/2015 (PAIRED) and UIDB/04469/2020 (strategic fund).info:eu-repo/semantics/publishedVersio