Field dependent transition to the non-linear regime in magnetic hyperthermia experiments: Comparison between maghemite, copper, zinc, nickel and cobalt ferrite nanoparticles of similar sizes

Further advances in magnetic hyperthermia might be limited by biological constraints, such as using sufficiently low frequencies and low field amplitudes to inhibit harmful eddy currents inside the patient's body. These incite the need to optimize the heating efficiency of the nanoparticles, referred to as the specific absorption rate (SAR). Among the several properties currently under research, one of particular importance is the transition from the linear to the non-linear regime that takes place as the field amplitude is increased, an aspect where the magnetic anisotropy is expected to play a fundamental role. In this paper we investigate the heating properties of cobalt ferrite and maghemite nanoparticles under the influence of a 500 kHz sinusoidal magnetic field with varying amplitude, up to 134 Oe. The particles were characterized by TEM, XRD, FMR and VSM, from which most relevant morphological, structural and magnetic properties were inferred. Both materials have similar size distributions and saturation magnetization, but strikingly different magnetic anisotropies. From magnetic hyperthermia experiments we found that, while at low fields maghemite is the best nanomaterial for hyperthermia applications, above a critical field, close to the transition from the linear to the non-linear regime, cobalt ferrite becomes more efficient. The results were also analyzed with respect to the energy conversion efficiency and compared with dynamic hysteresis simulations. Additional analysis with nickel, zinc and copper-ferrite nanoparticles of similar sizes confirmed the importance of the magnetic anisotropy and the damping factor. Further, the analysis of the characterization parameters suggested core-shell nanostructures, probably due to a surface passivation process during the nanoparticle synthesis. Finally, we discussed the effect of particle-particle interactions and its consequences, in particular regarding discrepancies between estimated parameters and expected theoretical predictions. Copyright 2012 Author(s). This article is distributed under a Creative Commons Attribution 3.0 Unported License. [http://dx.doi. org/10.1063/1.4739533]

Runoff Water Quality and Pollutant Mass Loads From Extensive Green Roofs

Green roof mitigation of volume and peak flow-rate of stormwater runoff has been studied extensively. However, due to the common practice of green roof fertilization, there is the potential for introduction of nutrients into local bodies of water. Therefore, this study compares green roof runoff quality with the water quality of precipitation and runoff from a bare shingle roof. The runoff from a demonstration-scale extensive green roof was analyzed during the summer of 2011 for its effect on runoff volume and analyzed during eleven storm events in the fall and winter for concentrations of copper, cadmium, zinc, lead, nitrogen species, total nitrogen, total organic carbon, sulfate, orthophosphate, and other monovalent and divalent ions. The green roof reduced the overall volume of runoff and served as a sink for NO3 - and NH4 +. However, the green roof was also a source for the pollutants PO4 3-, SO4 2-, TOC, cations, and total nitrogen. Metals such as zinc and lead showed trends of higher mass loads in the bare roof runoff than in precipitation and green roof runoff, although results were not statistically significant. The green roof also showed trends, although also not statistically significant, of retaining cadmium and copper. With the green roof serving as a source of phosphorous species and a sink for nitrogen species, and appearing to a retain metals and total volume, the life cycle impact analysis shows minimum impacts from the green roof, when compared with precipitation and bare roof runoff, in all but fresh water eutrophication. Therefore, the best environments to install a green roof may be in coastal environments.

Computational and Biochemical Approaches to Molecular Epidemiology

Mining activity in Butte, Montana has taken place, or continues to take place, within the urban residence of Butte itself. This has led to urban areas with high concentrations of toxic metals such as arsenic, lead, copper, zinc, mercury and cadmium. Advances in protein study and gene sequencing has opened the possibility of finding molecular biomarkers whose presence, absence or morphological changes could indicate disease processes in populations exposed to environmental toxins. While in principle, biomarkers can be any chemicals or metabolites, as well as proteins and genes that are indicative of exposure to xenobiotics, this study seeks to identify changes in cellular pathways that suggest chronic (or acute) exposure to low-levels of metals associated with historical mining activities on the Butte Hill that could cause oxidative stress or other stress to the cell.

Hydrogen Overvoltage of Cadmium Bismuth and Antimony Bismuth Alloys

A method to measure hydrogen overvoltage was devel­oped and checked with metals of known overvoltage. Alloys of bismuth and antimony and of bismuth and cad­mium were prepared and their overvoltages determined.

Heavy Metals in Crop Plants: Transport and Redistribution Processes on the Whole Plant Level

Copper, zinc, manganese, iron, nickel and molybdenum are essential micronutrients for plants. However, when present in excess they may damage the plant or decrease the quality of harvested plant products. Some other heavy metals such as cadmium, lead or mercury are not needed by plants and represent pollutants. The uptake into the roots, the loading into the xylem, the acropetal transport to the shoot with the transpiration stream and the further redistribution in the phloem are crucial for the distribution in aerial plant parts. This review is focused on long-distance transport of heavy metals via xylem and phloem and on interactions between the two transport systems. Phloem transport is the basis for the redistribution within the shoot and for the accumulation in fruits and seeds. Solutes may be transferred from the xylem to the phloem (e.g., in the small bundles in stems of cereals, in minor leaf veins). Nickel is highly phloem-mobile and directed to expanding plant parts. Zinc and to a lesser degree also cadmium are also mobile in the phloem and accumulate in meristems (root tips, shoot apex, axillary buds). Iron and manganese are characterized by poor phloem mobility and are retained in older leaves.

(Table 2) Concentrations of dissolved Zn, Cd, Pb, and Cu in waters of the Baltic Sea

A method of determination of low concentrations of zinc, cadmium, lead, and copper dissolved in seawater and interstitial water with use of inversion voltammetry with AC solution conditions is described. The optimum conditions for measurements with accumulation on a mercury-film electrode with a silver substrate are presented. Detection limit is 0.2 ?g/l for zinc and 0.05 ?g/l for cadmium, lead, and copper. Large number of determinations can be carried out during expeditions at natural pH of seawater containing these four metals.

Composition of bottom sediments and their exchange with seawater in the Amur and Zolotoy Rog bays, Sea of Japan

Transition of Zn, Cu, Cd, and Pb into solution is studied for experimental suspensions of coastal marine sediments with different degrees of pollution from the Amur Bay (Sea of Japan) over 30-70 days. Concentrations of dissolved metals were measured by a voltammetry method. Transition of Zn and Cd into solution was shown to be linearly dependent on initial pollution of sediments with these metals. Cadmium mobilization is due to gradual degradation of organic matter from sediments. Under degradation processes Zn quickly goes into solution during sedimentation and from silts, while in case of polluted sediments it is slowly mobilized during oxidation of sulfides. Behavior of Cu is complex because of binding of mobilized metal by dissolved organic compounds. Transition of lead into solution is negligible. Calculation of potential transition of metals from sediments into water on the basis of experimental data and its comparison with downward sedimentary flux showed that in the studied area secondary pollution of water by aerobic degradation of sediments is possible only for Cd.

Cd/Ca ratios and element analyses of ODP Hole 115-709C

During three to four d18O cycles (determined on Globigerinoides ruber), more positive d18O (= higher global ice volume) values correlated with higher Globorotalia menardii percentages, total numbers of benthic foraminifers, number of benthic foraminifer species, and the percent of total foraminifers composed of benthic foraminifers. During the same intervals, barite and insoluble residues also generally recorded higher values; however, there was no clear evidence of systematic variation in cadmium/calcium ratios (in benthic foraminifers). Maximum percentages of Globigerinoides sacculifer and Globigerinoides ruber correlate with more negative d18O (= lower global ice volume) values, although they sometimes appear to lead the d18O changes by < =4,000 yr. The increase in percentage of the tropical "divergence" planktonic foraminifer species G. menardii and the reduction of the "nondivergence" tropical species G. ruber and G. sacculifer at times of inferred ice growth is attributed to periodic intensification of divergence associated with the Equatorial Counter Current. Barite and insoluble residue sedi- mentation at the site also generally show a relative increase at those times.

CO2 and vitamin B12 interactions determine bioactive trace metal requirements of a subarctic Pacific diatom

Phytoplankton growth can be limited by numerous inorganic nutrients and organic growth factors. Using the subarctic diatom Attheya sp. in culture studies, we examined how the availability of vitamin B(12) and carbon dioxide partial pressure (pCO(2)) influences growth rate, primary productivity, cellular iron (Fe), cobalt (Co), zinc (Zn) and cadmium (Cd) quotas, and the net use efficiencies (NUEs) of these bioactive trace metals (mol C fixed per mol cellular trace metal per day). Under B(12)-replete conditions, cells grown at high pCO(2) had lower Fe, Zn and Cd quotas, and used those trace metals more efficiently in comparison with cells grown at low pCO(2). At high pCO(2), B(12)-limited cells had ~50% lower specific growth and carbon fixation rates, and used Fe ~15-fold less efficiently, and Zn and Cd ~3-fold less efficiently, in comparison with B(12)-replete cells. The observed higher Fe, Zn and Cd NUE under high pCO(2)/B(12)-replete conditions are consistent with predicted downregulation of carbon-concentrating mechanisms. Co quotas of B(12)-replete cells were 5- to 14-fold higher in comparison with B(12)-limited cells, suggesting that >80% of cellular Co of B(12)-limited cells was likely from B(12). Our results demonstrate that CO(2) and vitamin B(12) interactively influence growth, carbon fixation, trace metal requirements and trace metal NUE of this diatom. This suggests the need to consider complex feedback interactions between multiple environmental factors for this biogeochemically critical group of phytoplankton in the last glacial maximum as well as the current and future changing ocean.

Synthetic strategy of porous ZnO and CdS nanostructures doped ferroelectric liquid crystal and its optical behavior

A simple and scalable chemical approach has been proposed for the generation of 1-dimensional nanostructures of two most important inorganic materials such as zinc oxide and cadmium sulfide. By controlling the growth habit of the nanostructures with manipulated reaction conditions, the diameter and uniformity of the nanowires/nanorods were tailored. We studied extensively optical behavior and structural growth of CdS NWs and ZnO NRs doped ferroelectric liquid crystal Felix-017/100. Due to doping band gap has been changed and several blue shifts occurred in photoluminescence spectra because of nanoconfinement effect and mobility of charges.

Ultrastructural localization of zinc transporter-3 (ZnT-3) to synaptic vesicle membranes within mossy fiber boutons in the hippocampus of mouse and monkey

Zinc transporter-3 (ZnT-3), a member of a growing family of mammalian zinc transporters, is expressed in regions of the brain that are rich in histochemically reactive zinc (as revealed by the Timm’s stain), including entorhinal cortex, amygdala, and hippocampus. ZnT-3 protein is most abundant in the zinc-enriched mossy fibers that project from the dentate granule cells to hilar and CA3 pyramidal neurons. We show here by electron microscopy that ZnT-3 decorates the membranes of all clear, small, round synaptic vesicles (SVs) in the mossy fiber boutons of both mouse and monkey. Furthermore, up to 60–80% of these SVs contain Timm’s-stainable zinc. The coincidence of ZnT-3 on the membranes of SVs that accumulate zinc, and its homology with known zinc transporters, suggest that ZnT-3 is responsible for the transport of zinc into SVs, and hence for the ability of these neurons to release zinc upon excitation.

A straightforward wet-chemical route to the nanocomposites of general layered clays and metal sulfides

The nanocomposites of general layered clays and metal sulfides could be produced from reactions of the layered clay aqueous suspensions and water-soluble metal-thiourea complexes. The clay could be saponite, montmorillonite, hectorite and laponite, while the metal sulfide could be cobalt sulfide, nickel sulfide, zinc sulfide, cadmium sulfide, and lead sulfide. In the nanocomposites, the clay could be incorporated with the metal sulfide pillars and metal sulfide nanoparticles. (c) 2006 Elsevier B.V. All rights reserved.