Radiation damage to lyophilized mineral solutions during electron probe analysis: quantitative study of chlorine loss as a function of beam current-density and sample mass-thickness

The quantitative effects of beam current-density and sample mass-thickness on the loss of chlorine which occurs from lyophilized solutes of micro-droplets of mineral salt solutions irradiated in an electron probe analyser were studied. Results are reported for chlorine loss from lyophilized deposits with mass-thickness varying between 5 and 50 mg mm^?2 for NaCl salts and 5 and 80 mg mm^?2 for KCl salts. Electron accelerating voltage was kept constant at 15 kV. The range of beam current-density (I/S, current/sample surface area) was from 0.1 to 1.5 A mm^?2. Samples were irradiated for 1200 s. The results show that under some conditions there is a period of stable chlorine signal before chlorine loss occurs. This is observed between 0.1 and 1 A mm^?2, for a period which can last several hundred seconds depending on beam current-density and sample mass-thickness. For each value of I/S, however, no stable chlorine signal can be observed for samples whose mass-thickness exceeds a value negatively correlated with I/S. The curves of decrease of characteristic chlorine X-ray signal (expressed as per cent of count rate in the initial counting interval) versus irradiation time can be fitted by the sum of two exponentials with half lives T₁ and T₂. In NaCl, T₁ and T₂ values are highly correlated with I/S but not with mass-thickness. In KCl, T₁ is correlated only with mass-thickness and T₂ only with I/S. Mixing plasma with mineral solutions prevents chlorine loss.     

Analysis of microstructure and microhardness of Zr-2.5Nb processed by High-Pressure Torsion (HPT)

Nanostructured materials have been widely studied due to the improvement of their mechanical properties comparing to those of coarse grain materials. The present work intended to analyze the microstructure and microhardness of Zr-2.5Nb processed by high-pressure torsion (HPT), one of the severe plastic deformation techniques. The deformations were carried out at room temperature using a pressure of 5?GPa and 5 anvil turns. Vickers indentation was used to evaluate the microhardness of the samples. Transmission electron microscopy and X-ray diffraction were used to analyze the microstructure. The results showed a significant refinement from the initial microstructure achieving nanometric grain size around 50?nm and phase transformation α?→?ω?+?β_I induced by shear. The Vickers microhardness values of the material submitted to HPT technique were significantly higher than those of non-deformed material. Also, HPT procedure resulted in a huge grain refinement of the material and in phase transformation.     

Analysis of self-overlap reveals trade-offs in plankton swimming trajectories

Movement is a fundamental behaviour of organisms that not only brings about beneficial encounters with resources and mates, but also at the same time exposes the organism to dangerous encounters with predators. The movement patterns adopted by organisms should reflect a balance between these contrasting processes. This trade-off can be hypothesized as being evident in the behaviour of plankton, which inhabit a dilute three-dimensional environment with few refuges or orienting landmarks. We present an analysis of the swimming path geometries based on a volumetric Monte Carlo sampling approach, which is particularly adept at revealing such trade-offs by measuring the self-overlap of the trajectories. Application of this method to experimentally measured trajectories reveals that swimming patterns in copepods are shaped to efficiently explore volumes at small scales, while achieving a large overlap at larger scales. Regularities in the observed trajectories make the transition between these two regimes always sharper than in randomized trajectories or as predicted by random walk theory. Thus, real trajectories present a stronger separation between exploration for food and exposure to predators. The specific scale and features of this transition depend on species, gender and local environmental conditions, pointing at adaptation to state and stage-dependent evolutionary trade-offs.     

A New Approach to Quantify Na-Fluorescein (Uranine) in Acid Mine Waters

Sodium fluorescein (uranine) is one of the most popular fluorescent dyes for tracer experiments due to its chemical properties, low detection limits and low costs. As a limiting factor, it is generally assumed that Na-fluorescein cannot be properly detected under acid conditions because of weak fluorescence intensities at the standard excitation wavelength (490 nm). This laboratory study introduces a method to quantify Na-fluorescein in low pH waters without having to raise pH to alkaline conditions, which spares the time- and cost-intensive filtration of hydroxide precipitates prior to analysis. It was applied for recovery tests in water samples from five mining sites in Germany. These were buffered to pH 1.5 where Na-fluorescein shows a second fluorescence intensity maximum at an excitation wavelength of 438 nm. The method had satisfying recovery rates although, as expected, a higher detection limit compared to standard wavelength and pH. High Fe contents in the waters are a limiting factor—the impact of increasing Fe concentrations at a constant dye spike was evaluated and yielded a distinct negative trend between Fe and detected Na-fluorescein, probably due to Fe-fluorescein complexation. However, good recovery can be expected in mine waters with up to ≈100 mg L⁻¹ Fe. The method of standard addition offers a potential calculative solution for higher Fe concentrations, resulting in significantly better Na-fluorescein recovery rates, compared to direct measurements. The method introduced here represents a promising approach for improving Na-fluorescein applicability in acid environments.     

Sensory Neuron-Specific Deletion of Tropomyosin Receptor Kinase A (TrkA) in Mice Abolishes Osteoarthritis (OA) Pain via NGF/TrkA Intervention of Peripheral Sensitization

Tropomyosin receptor kinase A (TrkA/NTRK1) is a high-affinity receptor for nerve growth factor (NGF), a potent pain mediator. NGF/TrkA signaling elevates synovial sensory neuronal distributions in the joints and causes osteoarthritis (OA) pain. We investigated the mechanisms of pain transmission as to whether peripheral sensory neurons are linked to the cellular plasticity in the dorsal root ganglia (DRG) and are critical for OA hyperalgesia. Sensory neuron-specific deletion of TrkA was achieved by tamoxifen injection in 4-week-old TrkA^fl/fl;Na_V1.8^CreERT2 (Ntrk1 ^fl/fl;Scn10a^CreERT2) mice. OA was induced by partial medial meniscectomy (PMM) in 12-week-old mice, and OA-pain-related behavior was analyzed for 12 weeks followed by comprehensive histopathological examinations. OA-associated joint pain was markedly improved without cartilage protection in sensory-neuron-specific conditional TrkA knock-out (cKO) mice. Alleviated hyperalgesia was associated with suppression of the NGF/TrkA pathway and reduced angiogenesis in fibroblast-like synovial cells. Elevated pain transmitters in the DRG of OA-induced mice were significantly diminished in sensory-neuron-specific TrkA cKO and global TrkA cKO mice. Spinal glial activity and brain-derived neurotropic factor (BDNF) were significantly increased in OA-induced mice but were substantially eliminated by sensory-neuron-specific deletion. Our results suggest that augmentation of NGF/TrkA signaling in the joint synovium and the peripheral sensory neurons facilitate pro-nociception and centralized pain sensitization.     

Performance analysis of an integrated tangential microfilter‐fermenter

A specially designed bioreactor including an axial microfilter for cell retention was evaluated for continuous‐flow operation with selected liquid media as controls and in aerobic cultivations of Saccharomyces yeasts. In the initial tests, performance characteristics such as filtration rates and cell accumulation were assessed as a function of filter rotational speed, operating pressure, cultivation time and microfilter type (i.e. membrane or porous metal). The bioreactor did not perform satisfactorily when viscous extracellular polymer was present in the liquid. In the continuous‐flow culture enabling cell retention, Saccharomyces cerevisiae yeast cell concentrations were enhanced by as much as 16‐fold over ordinary batch growth. Concomitant filtration rates were stable over operating times of up to 130 h and hence were independent of the cell concentration. The maximum steady‐state flux was enhanced at rotational speeds up to 400‐700 rpm ranging from 22 to 42 L m^?2 h^?1. Higher rotation rates offered no further improvements. The maximum stabilized flux was independent of operating pressure. Pressure increases caused momentary flux improvements, which rapidly declined and eventually restabilized. Copyright © 2006 Society of Chemical Industry     

Hermansky-Pudlak syndrome: a case report and discussion

Hermansky-Pudlak syndrome is a rare, inherited, autosomal recessive disease. Diagnosis is based on a triad of signs: oculocutaneous albinism, a hemorrhagic tendency due to a platelet disorder, and an accumulation of lipopigments in different organs, particularly the medullary macrophages. We describe a child with the characteristic findings of this syndrome, which often goes unrecognized because of the discrete nature of the cutaneous and hemorrhagic manifestations. This diagnosis is important because of the risk not only of hemorrhage but also of granulomatous colitis and long-term pulmonary fibrosis.