Iron (Fe) limits or co-limits primary productivity and nitrogen fixation in large regions of the world's oceans, and the supply of Fe from hydrothermal vents to the deep ocean is now known to be ...extensive. However, the mechanisms that control the amount of hydrothermal Fe that is stabilized in the deep ocean, and thus dictate the impact of hydrothermal Fe sources on surface ocean biogeochemistry, are unclear. To learn more, we have examined the dispersion of total dissolvable Fe (TDFe), dissolved Fe (dFe) and soluble Fe (sFe) in the buoyant and non-buoyant hydrothermal plume above the Beebe vent field, Caribbean Sea. We have also characterized plume particles using electron microscopy and synchrotron based spectromicroscopy.
We show that the majority of dFe in the Beebe hydrothermal plume was present as colloidal Fe (cFe = dFe − sFe). During ascent of the buoyant plume, a significant fraction of particulate Fe (pFe = TDFe − dFe) was lost to settling and exchange with colloids. Conversely, the opposite was observed in the non-buoyant plume, where pFe concentrations increased during non-buoyant plume dilution, cFe concentrations decreased apparently due to colloid aggregation. Elemental mapping of carbon, oxygen and iron in plume particles reveals their close association and indicates that exchanges of Fe between colloids and particles must include transformations of organic carbon and Fe oxyhydroxide minerals. Notably, sFe is largely conserved during plume dilution, and this is likely to be due to stabilization by organic ligands, in contrast to the more dynamic exchanges between pFe and cFe.
This study highlights that the size of the sFe stabilizing ligand pool, and the rate of iron-rich colloid aggregation will control the amount and physico-chemical composition of dFe supplied to the ocean interior from hydrothermal systems. Both the ligand pool, and the rate of cFe aggregation in hydrothermal plumes remain uncertain and determining these are important intermediate goals to more accurately assess the impact of hydrothermalism on the ocean's carbon cycle.
This article is part of a special issue entitled: “Cycles of trace elements and isotopes in the ocean – GEOTRACES and beyond” - edited by Tim M. Conway, Tristan Horner, Yves Plancherel, and Aridane G. González.
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•Soluble iron behaves quasi-conservatively in the hydrothermal plume as iron rich plume waters mix with low iron seawater.•Particulate iron is formed by the aggregation of colloidal iron as the hydrothermal plume disperses into the deep ocean.•Colloid aggregation is an important control on the amount of dissolved iron added to the ocean by hydrothermal vents.•Co-location of iron and carbon in particles implies that organic carbon mediates iron exchange between different species.
► First time comprehensive treatise of the Pt-O-interaction in the electrode system Pt/YSZ. ► Detailed view on interface reactions of well defined interfaces between Pt/YSZ. ► Highly porous thin film ...model electrodes for studying non stationary effects. ► In situ monitoring of the chemical state of Pt at the TPB during polarization by SPEM.
The existence and role of platinum oxide in the solid state electrode system Pt(O
2)/yttria-stabilized zirconia is discussed. Covering and porous model-type Pt film electrodes on YSZ single crystals are investigated by cyclic voltammetry, electrochemical impedance spectroscopy, and in situ scanning photoelectron microscopy. The formation of Pt oxide and its amount strongly depend on the experimental conditions, such as temperature, oxygen partial pressure, and oxygen flux towards the electrode during anodic polarization. Electrode activation and deactivation processes can be explained by formation and decomposition of Pt oxide, which is reducing or inhibiting the oxygen exchange rate.
A Dynamic High Pressure (DHP) system has been developed, tested and implemented in the scanning photoelectron microscope (SPEM) operated at ESCAmicroscopy beamline at Elettra synchrotron. The system ...consists of a compact gas injection set up that allows experiments with local pressure near the sample several orders of magnitude higher that the allowable pressure for X-ray photoelectron spectroscopy setups. The DHP setup controls the amount of gas injected toward the sample by fine tuning the time and spatial profiles using a pulsed valve and a nozzle, respectively. The DHP functionality and effectiveness has been demonstrated by in operando oxidation experiments of Ru and Si. The obtained results confirmed that using the DHP the gas exposure onto the sample is equivalent to a static pressure between 10 super(-3) and 10 super(-2) mbar, about 3 orders of magnitude higher than the maximum gas pressure for the XPS machines under operation.
An enzymatic synthesis route to peptide‐capped gold nanoparticles has been developed. Gold nanoparticles were synthesized using α‐NADPH‐dependent sulfite reductase and phytochelatin in vitro. The ...gold ions were reduced in the presence of the enzyme sulfite reductase, leading to the formation of a stable gold hydrosol of dimensions 7–20 nm and were stabilized by the capping peptide. The nanoparticles were characterized by X‐ray diffraction, transmission electron microscopy, X‐ray photoelectron spectroscopy and UV–visible optical absorption. These studies will help in designing a rational enzymatic strategy for the synthesis of nanomaterials of different chemical compositions, shapes and sizes as well as their separation.
Argyria is a benign skin disease characterized by blue to slate‐grey discoloration that is caused by deposition of silver granules in the skin and/or mucus membranes as a result of long‐term ...ingestion of ionized silver solutions or exposure to airborne silver particles. The skin discoloration can be generalized or localized and is exacerbated by sunlight. The skin discoloration is usually permanent, and until recently, there has been no effective treatment for argyria. Over the past 6 years, a number of case reports and one case series have described cases of argyria that were successfully treated with a 1064 nm Q‐switched (QS) neodymium‐doped yttrium aluminium garnet (Nd:YAG) laser; however, a review of these studies has never been reported in the dermatologic literature. To review the use of the 1064 nm QS Nd:YAG laser for the treatment of argyria. A search of the National Library of Medicine's PubMed Database and the SCOPUS Database was performed to find articles that detailed the treatment of argyria with 1064 nm QS Nd:YAG laser. Six articles were selected for inclusion in this review. Each article was reviewed and summarized in a table. A 1064 nm QS Nd:YAG laser offers a novel and effective treatment for argyria. A systematic review of the dermatologic literature revealed a limited number of case reports and case series using this treatment. However, the results gleaned by the authors from the literature review provide important information to the clinician. For patients with argyria, a single pass of the 1064 nm QS Nd:YAG laser offers immediate, effective and sustained pigment clearing without any long‐term adverse effects.
In this paper, a new method for optimum coordination of overcurrent relays is proposed. The proposed method is based on only constraints. Minimization is inherently included by setting the time dials ...to minimum and increasing their values gradually. Configuration changes of the network are taken into account. The method does not need any initial solution. It can consider both linear and nonlinear relay characteristics models. The optimal settings of overcurrent relays for 8-Bus and England Norweb networks are obtained and comparison between the new method and existing methods is made.
Synthesis of silver nanoparticles using alpha-NADPH-dependent nitrate reductase and phytochelatin in vitro has been demonstrated for the first time. The silver ions were reduced in the presence of ...nitrate reductase, leading to the formation of a stable silver hydrosol 10-25 nm diam. and stabilized by the capping peptide. The nanoparticles were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy and UV-Vis absorption. These studies will help in designing a rational enzymatic strategy for the synthesis of nanomaterials of different chemical composition, shapes and sizes as well as their separation.
Vitiligo is a disorder of pigmentation affecting about 1% of the global population. It is a psychologically devastating disease with suboptimal treatment options. Narrowband ultraviolet B (NB‐UVB) ...phototherapy has become a first‐line choice for treating generalized disease. In recent years, topical calcineurin inhibitors, vitamin D analogues, antioxidant agents and other therapies have been combined with NB‐UVB to improve its efficacy. This article will address what is known about the mechanisms of action of these treatments and how they may complement NB‐UVB on a cellular level, as well as offer a comprehensive, evidence‐based review of clinical outcomes with combination therapies.
Benign familial chronic pemphigus, or Hailey–Hailey disease (HHD), is a recurrent bullous dermatitis that tends to have a chronic course with frequent relapses. Long‐term treatment options include ...surgery with skin grafting or dermabrasion. Both are highly invasive and carry significant risks and complications. More recently, ‘laser‐abrasion’ has been described as a less invasive option with a better side‐effect profile. In this article, we systematically review the safety and efficacy of carbon dioxide laser therapy as a long‐term treatment option for HHD, as well as provide a review of other lasers that have been reported with this goal. A total of 23 patients who had been treated with a carbon dioxide laser were identified. After treatment, 10 patients (43%) had had no recurrence, 10 (43%) had greater than 50% improvement, 2 (8%) had less than 50% improvement and 1 (4%) patient had no improvement at all (follow‐up period ranged from 4 to 144 months). Laser parameter variability was wide and adverse effects were minimal, including dyspigmentation and scarring. Reviewed evidence indicates this therapy offers a safe, effective treatment alternative for HHD with minimal risk of side‐effects. Larger, well‐designed studies are necessary to determine the optimal treatment parameters.
Cold-load pickup as a result of a major contribution of thermostatically controlled loads in the distribution networks causes unpredictable outages in the system. Most of the studies carried out thus ...far have been devoted to find the nature of the cold-load pickup and have attempted to model its behavior in distribution systems. However, less effort has been made toward estimating the occurrence rate of the cold-load pickup in distribution systems. The occurrence of this phenomenon is a stochastic process, which depends on several factors. Hence, it seems necessary to develop a methodology which enables the estimation of the occurrence rate of the cold-load pickup in distribution systems. The purpose of this paper is to provide this methodology based on a model that estimates the cold-load pickup peak magnitude relating to the outage time. The operation of the protective devices is evaluated within the cold-load pickup situations, and the resulting outages are investigated in the network. The IEEE 34-bus system and a real test system are used as case studies to show the methodology results and to present the cold-load contribution in the network outages based on the simulation of the real measured load data.
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