Μm For CO Research Articles

Dual-responsive solvatochromic sensor for simultaneous detection and mechanism of Cr(III) and Co(II) cations by a new N2O4-donor tetrabenzodiaza-crown ether Macrocyclic ligand anchored to dipyridine moieties

The present study describes the chemosensing capability of an N2O4-donor tetrabenzodiaza-crown ether macrocyclic ligand derivatized by two pyridine side arms to afford the flexible macrocyclic ligand, 5,20-bis(pyridin-4-ylmethyl)-5,6,12,13,19,20,26,27octahydrotetrabenzo [e,i,o,s][1,4,11,14]tetraoxa[7,18]diazacycloicosine (PMHBOA). A selective colorimetric behavior of PMHBOA for the prompt detection of Cr(ΙΙΙ) and Co(ΙΙ) can be observed with naked eyes. The 1H, 13C{H} NMR, and infrared spectroscopy disclosed the ligand binding capability for selective metal ions, ascribed to a 1:1 complex formation with Cr(III) and Co(II) cations in isopropanol. The limit of detection (LOD) values were calculated as 580 and 850 nM for Cr(ΙΙΙ) and Co(ΙΙ), respectively, accompanied with suitable LOQs as 1.95 µM for Cr(III) and 2.85 µM for Co(II), respectively. The reusability was confirmed in the presence of ethylenediaminetetraacetic acid (EDTA). Moreover, a TLC-based fabricated paper strip successfully applied PMHBOA as a chemosensor for synchronous visible detection of Cr(III) and Co(II) in their alcoholic solution. Meanwhile, the observed color change along with the turn-off fluorescent of PMHBOA guaranteed a felicitous choice of candidate for Cr(III) in the presence of other library metal ions in isopropanol:H2O (9/1 v/v) solution. A fast separation test on the filter paper, impregnated with PMHBOA, was also employed to separate Cr(III) and Co(II) cations from aqueous solutions by recording UV–vis spectra. The 1H NMR spectroscopy supported the macrocycle ring and side arms as the parallel coordination site of PMHBOA with Cr(III) and Co(II).

Tunable dual optical frequency comb at 2 μm for CO2 sensing.

In this article, we demonstrate a dual frequency comb (DFC) based on the gain-switching of mutually injection-locked semiconductor lasers in the 2 μm wavelength region with a tunable free spectral range (FSR) between 500 MHz and 3 GHz. Through the down-conversion process enabled by DFCs, the beating spectra of the optical frequency combs were captured in a 15 MHz electrical bandwidth with high resolution and millisecond acquisition times. A first experimental demonstration of sensing CO2 with this architecture is also presented.

Toxicity and Metabolomic Impact of Cobalt, Chromium, and Nickel Exposure on HepaRG Hepatocytes.

Cobalt, chromium, and nickel are used in orthopedic prostheses. They can be released, accumulate in many organs, and be toxic. The aim of this study is to evaluate the cytotoxicity of these metals on human hepatocytes and to improve our knowledge of their cellular toxicity mechanisms by metabolomic analysis. HepaRG cells were incubated for 48 h with increasing concentrations of metals to determine their IC50. Then, a nontargeted metabolomic study using liquid chromatography-high-resolution mass spectrometry (LC-HRMS) was done at IC50 and at a lower concentration (100 nM), near to those found in the blood and liver of patients with prostheses. IC50 were defined at 940, 2, and 1380 μM for Co, Cr, and Ni, respectively. In vitro, Cr appears to be much more toxic than Co and Ni. Metabolomic analysis revealed the disruption of metabolic pathways from the low concentration of 100 nM, in particular tryptophan metabolism and lipid metabolism illustrated by an increase in phenylacetylglycine, a marker of phospholipidosis, for all three metals. They also appear to be responsible for oxidative stress. Dysregulation of these pathways impacts hepatocyte metabolism and may result in hepatotoxicity. Further investigations on accessible biological matrices should be conducted to correlate our in vitro results with the clinical data of prostheses-bearing patients.

Towards High-Power Densely Step-Tunable Mid-Infrared Fiber Source From 4.27 to 4.43 µm in CO_2-Filled Anti-Resonant Hollow-Core Silica Fibers

Towards High-Power Densely Step-Tunable Mid-Infrared Fiber Source From 4.27 to 4.43 µm in CO_2-Filled Anti-Resonant Hollow-Core Silica Fibers

Determination of lethal dose (LD50) of chromium (Cr), cobalt (Co) and nickel (Ni) in HepaRG cells. Comparison to concentrations found in liver from autopsied prosthesis-bearing patients

Many publications have highlighted the release of metal particles used in the composition of metal-metal prostheses, such as Cr, Co and Ni. They are stored in the liver and can accumulate there. Few data are available on their toxicity in this tissue when present. The cytotoxicity of these 3 heavy metals was investigated in cultures of human hepatocytes cell lines, in order to determine LD50s and to compare to the concentrations found in the liver from 10 autopsied prosthesis-bearing patients. HepaRG is a human hepatoma cell line commonly used as a model for toxicity studies. Cells were cultured in William's E medium with glutamine supplemented with 10% fetal bovine serum, human insulin, hydrocortisone hemisuccinate and penicillin/streptomycin. Differentiation was induced by adding 2% DMSO to nutrient medium. After 14 days, the cells were placed in a 24-well plate in a concentration of 500,000 cells/well. Solutions with ten increasing concentrations of NiCl 2 or CoCl 2 or Na 2 Cr 2 O 7 were incubated with cells for 48 hours at 37 °C. These concentrations were established based on literature data for other hepatocyte models [1] , [2] . Cell viability was evaluated by LDH release (Pierce LDH Cytotoxicity Assay Kit, ThermoFisher) and MTT assay (Vybrant ® MTT cell proliferation assay kit). Concentration response profiles were realized with GraphPad Prism 2.0. Measurements of the heavy metals in liver from autopsied patients were carried out using ICP-HRMS (Element XR, ThermoFisher) after mineralization by microwave (Ultrawave ® , ThermoFisher) [3] . Expected LD50 according to literature data were around 25, 500 and 1000 μM for Cr, Co and Ni, respectively. For Cr, testing concentrations were 0.5, 5, 10, 50, 100, 500, 1000, 5000, 10,000, 50,000 μM. For Co and Ni, they were 10, 50, 100, 250, 500, 1000, 2500, 5000, 10,000, 50,000 μM. The first cytotoxicity assay performed was the LDH release. It measures quantitatively the LDH released in the medium when cells are damaged. But William's E medium is pink and had altered the reading of absorbance. So, results could not be exploited. The MTT assay is carried out on the cell pellet and thus, makes it possible to overcome the culture medium. The dose/response curves for each metal could be realized. Experimental LD50s are 2 μM for Cr, 940 μM for Co, 1380 μM for Ni. The average Cr, Co, Ni concentrations found in the livers of the 10 dead patients carrying prostheses were 0.05, 0.03 and 0.035 μM, respectively. As expected, concentrations found in the liver of autopsied patients are much lower than the experimental LD50. The LD50s were determined for Cr, Co and Ni in HepaRG cells, much higher than concentrations found in the liver from 10 autopsied prosthesis-bearing patients. However, the impact of these elements on hepatocyte metabolism can be reasonably considered at low concentrations. Consequently, further researches using metabolomics approach will be performed.

Growth evaluation and anatomical root structure of Campomanesia pubescens (Mart. ex DC.) O. Berg (Myrtaceae) under different concentrations of aluminum

Soil acidity is one of the main factors limiting agricultural production due to high aluminum (Al(3+)) saturation in soil. Campomanesia pubescens (Mart. ex DC.) O. Berg, popularly known as “gabiroba”, is a species of Myrtaceae family and typical of Brazilian Cerrado. The aim of this study was to evaluate the root growth and anatomical structure of C. pubescens roots, subjected to different concentrations of Al(3+), grown in a simple and complete solution as culture form. This experiment was performed with seedlings cultivated hydroponically using a simple and complete solution. The simple nutrient solution was carried out using 0.1 mM of Ca (CaCl(2).2H(2)O) and five concentrations of Al in the form of Al(2)(SO(4))3.18H(2)O, while the complete nutrient solution of low ionic strength was conducted using 0.5 mM of N (NH(4)NO(3)), 0.2 mM of Ca (CaCl(2).H(2)O), 0.2 mM of Mg (MgSO(4).7H(2)O), 0.5 mM of K (K(2)SO(4)), 0.1 mM of P (NaH(2)PO(4).2H(2)O), 10 μM of Fe (FeNa) EDTA, 0.4 μM of Mn (MnSO(4).H(2)O), 0.16 μM of Zn (ZnSO(4)), 0.04 μM of Cu (CuSO(4)), 0.5 μM of Mo (MoO(3)), and 0.04 μM of Co (CoSO(4).7H(2)O).The experiment was a factorial design (2×5) with two nutrient solutions (single and complete) and five aluminum concentrations (0, 150, 300, 600 and 1200 μmol L-1). It was observed that both in simple and complete nutrient solution the rate of root elongation and root growth decreased with increasing Al(3+) concentration. At the concentration of 300 μmol L-1, were observed cellular disorganization and rupture of the epidermis. The presence of aluminum inside the vascular cells may indicate some mechanism of transport to other parts of the plant. It was concluded that Campomanesia pubescens showed sensitivity towards high Al(3+) concentrations, indicating that the establishment of these plants can be compromised in acidic soils with toxic concentrations of Al(3+).

Molecular docking, PASS analysis, bioactivity score prediction, synthesis, characterization and biological activity evaluationof a functionalized 2-butanone thiosemicarbazone ligand and its complexes.

2-Butanone thiosemicarbazone ligand was prepared by condensation reaction between thiosemicarbazide and butanone. The ligand was characterized by 1H NMR, 13C NMR, FT-IR, mass spectrometry and UV spectroscopic studies. Docking studies were performed to study inhibitory action against topoisomerase II (Topo II) and ribonucleoside diphosphate reductase (RR) enzymes. Inhibition constants (Ki ) of the ligand were 437.87 and 327.4μM for the two enzymes, respectively. The ligand was tested for its potential anticancer activity against two cancer cell lines MDA-MB-231 and A549 using MTT assay and was found to exhibit good activity at higher doses with an IC50=80μM against human breast cancer cell line MDA-MB-231. On the other hand, no significant activity was obtained against the lung carcinoma cell line A549. Antibacterial activity of the ligand was tested against Staphylococcus aureus and E. coli using the disc diffusion method. Ligand did not exhibit any significant antibacterial activity. Four complexes of Co(III), Fe(II), Cu(II), and Zn(II) were prepared with the ligand and characterized by various spectroscopic studies. Low molar conductance values were obtained for all complexes displaying non-electrolyte nature except in Co(III) complex. As expected, complexation with metal ions significantly increased the cytotoxicity of the ligand against the tested cell lines viz. IC50 values of <20μM for Co, Fe, and Zn complexes and approx. 80μM against MDA cells versus IC50 value of <20μM for Co and Cu complexes and that of 30 and 50μM for Fe and Zn complexes, respectively, against A549 cells. The Cu complex was found to be active against E. coli and S. aureus with MIC values in the range of 6-10mg/mL. Other than Cu, only Co complex was found to possess antibacterial activity with MIC values of 5-10mg/mL when tested against S. aureus. Bioactivity score and Prediction of Activity Spectra for Substances (PASS) analysis also depicted the drug-like nature of ligand and complexes.

Carbon Monoxide May Regulate BK slo1 Channel Activity by Partially Disrupting Heme Coordination

The putative gasotransmitter CO is reported to activate large-conductance K+ channels (BK); however, the mechanism remains controversial. We recently found evidence that M691, within the RCK1-RCK2 linker of the BK C-terminus, coordinates heme together with the distal, conserved heme regulatory motif (HRM), acting as a second axial ligand to the heme Fe atom. A similar binding configuration is observed in cytochrome c (CytC). Based on this and other lines of evidence, we have proposed that BK channels possess a CytC-like domain (BKCytCD). In CytC, CO associates with heme by cleaving the Met80 S-Fe2+ bond; in this work, we are testing the hypothesis that BK channels bind CO by a similar mechanism. We expressed and purified the intracellular C-terminal portion of the human BK channel (gating ring, GR). We first strengthened the evidence for the participation of M691 in heme coordination by detecting an absorption peak at 690nm, characteristic of the Met-Fe2+ bond, which was eliminated by either mutation M691A or HRM disruption (C615S/H616R). We then probed for CO-induced GR conformational rearrangements using the 8-anilino-1-naphthalenesulfonic acid (ANS) fluorescent label in the presence of heme: the wild-type GR/heme complex exhibited strong ANS fluorescence reduction in response to CO, reporting structural transitions likely underlying CO regulation of BK conductance. The GR-M691A/heme complex was unresponsive up to 1.2 μM of CO. However, in the presence of CO-releasing CORM-2 ([RuCO3CI2]2), the GR-M691A/heme complex exhibited β/α absorption bands (540, 570nm) characteristic of CO binding. We propose that CO regulates BK conductance by inducing conformational rearrangements in its GR ligand-sensing domain. Specifically, CO substitutes M691 as the second heme axial ligand; cleavage of the M691-heme bond partially unfolds the BKCytCD, generating the optically-tracked conformational changes. This action may relieve heme-induced inhibition of BK opening.

Mie scattering from submicron-sized CO_2 clusters formed in a supersonic expansion of a gas mixture

A detailed mathematical model is presented for a submicron-sized cluster formation in a binary gas mixture flowing through a three-staged conical nozzle. By measuring the angular distribution of light scattered from the clusters, the size of CO(2) clusters, produced in a supersonic expansion of the mixture gas of CO(2)(30%)/H(2)(70%) or CO(2)(10%)/He(90%), has been evaluated using the Mie scattering method. The mean sizes of CO(2) clusters are estimated to be 0.28 ± 0.03 μm for CO(2)/H(2) and 0.26 ± 0.04 μm for CO(2)/He, respectively. In addition, total gas density profiles in radial direction of the gas jet, measuring the phase shift of the light passing through the target by utilizing an interferometer, are found to be agreed with the numerical modeling within a factor of two. The dryness (= monomer/(monomer + cluster) ratio) in the targets is found to support the numerical modeling. The apparatus developed to evaluate the cluster-gas targets proved that our mathematical model of cluster formation is reliable enough for the binary gas mixture.

Development of laser absorption techniques for real-time, in-situ dual-species monitoring (NO/NH3, CO/O2) in combustion exhaust

Simultaneous dual-species monitoring offers potential for control of large-scale practical combustion systems. The development and demonstration of two dual-species sensors for characterizing NOx abatement (NO/NH3) and combustor performance (CO/O2) are described for potential application in boiler exhaust at coal-fired electric utilities. Tunable laser absorption sensors for simultaneous in-situ detection of these paired species were developed using fundamental-band vibrational transitions in the mid-infrared near 5.2μm for NO, combination-band transitions near 2.25μm for NH3, overtone-band transitions near 2.3μm for CO, and electronic transitions in the b-X system near 760nm for O2. Scanned-wavelength, 1f-normalized wavelength modulation spectroscopy with second harmonic detection (WMS-2f) was employed for real-time data processing. Spatial- and time-demultiplexing strategies were used to combine and separate the laser signals. The sensors were tested for simultaneous, continuous monitoring in laboratory combustion exhaust from a premixed ethylene-air flame at atmospheric pressure and varied equivalence ratios with exhaust temperature of ∼620K. A retro-reflected 3.58m beam-path was used to mimic a single-ended installation in a boiler exhaust duct. NH3 mixtures were metered into the flame at different rates to test the response of the NO/NH3 sensor, and the CO/CO2 ratio was adjusted by fuel/air equivalence ratio. Trends in the measured concentration ratio of NO to NH3 were found to agree qualitatively with theoretical expectation, and the CO and O2 measurements were confirmed by analysis of sampled gases. The laser absorption exhibited the fast time response needed for control sensors. These fast-response, simultaneous dual-species sensors for NO/NH3 and CO/O2 show excellent promise for control and optimization of NOx abatement and furnace efficiency in practical combustion systems.

High-Affinity Ni 2+ Binding Selectively Promotes Binding of Helicobacter pylori NikR to Its Target Urease Promoter

NikR is a prokaryotic transcription factor that regulates the expression of Ni 2 + enzymes and other proteins involved in Ni 2 + trafficking. In the human pathogen Helicobacter pylori, NikR controls transcription of the Ni 2 + enzyme urease, which allows survival of the bacterium in the acidic gastric niche. The in vitro affinity of NikR from H. pylori ( HpNikR) for different metal ions and the metal-ion-dependent capability of HpNikR to bind P ureA , the promoter of the urease operon, were the object of this study. Electrophoretic mobility shift and DNase I footprinting assays indicated that Ni 2+ is necessary and sufficient to promote HpNikR binding to P ureA , while the effect of other metal ions in identical conditions is significantly lower (Zn 2+ and Co 2+) or absent (Ca 2+ and Mg 2+). Isothermal titration calorimetry (ITC) demonstrated the absence of specific Ca 2+ and Mg 2+ binding to the protein. ITC also established the binding of Zn 2+ and Co 2+ to two sets of high-affinity sites on HpNikR, differing in stoichiometry ( n 1 = 2, n 2 = 4) and dissociation constant ( K d 1 = 6 nM, K d2 = 90 nM for Zn 2+; K d 1 = 0.3 μM, K d 2 = 2.7 μM for Co 2+). Additional low-affinity binding sites were observed for Zn 2+ ( n = 8, K d = 1.6 μM). Mobility shift assays and ITC proved that binding of stoichiometric Ni 2+ (but not Zn 2+ or Co 2+) to the high-affinity sites (but not to the low-affinity sites) selectively activates HpNikR to bind its target operator with 1:1 stoichiometry and K d = 56 nM. A protein conformational rearrangement is selectively induced by Ni 2+ and not by Zn 2+, as indicated by fluorescence spectroscopy and microcalorimetry. Accordingly, competition experiments showed that stoichiometric Ni 2+ outperforms Zn 2+, as well as Co 2+, in functionally activating HpNikR toward high affinity binding to P ureA . A general scheme for the nickel-selective HpNikR–DNA interaction is proposed.

Shock-tube and modeling study of ethyl methyl ether pyrolysis and oxidation

Pyrolysis and oxidation of ethyl methyl ether (EME) were studied behind reflected shock waves in the temperature range 900–1750 K at total pressures between 0.9 and 3.1 atm. The study was carried out using following methods, (1) time-resolved IR-laser absorption at 3.39 μm for EME decay and CH-compound formation rates, (2) time-resolved UV absorption at 216 nm for mainly CH 3 radical formation rate, (3) time-resolved UV absorption at 306.7 nm for OH radical formation rate, (4) time-resolved IR emission at 4.24 μm for CO 2 formation rate and (5) a single-pulse technique for product yields. The pyrolysis and oxidation of EME were modeled using a reaction mechanism including the sub-mechanisms for methane, acetylene, ethylene, ethane, formaldehyde, acetaldehyde and ketene oxidation. The reaction mechanism used in this study could reproduce almost all of experimental results. The sub-mechanisms of methane, ethylene, ethane, formaldehyde, and acetaldehyde were found to play an important role in EME oxidation.

Surface and elemental alterations of dental alloys induced by electro discharge machining (EDM)

Objectives To evaluate the surface and elemental alterations induced by electro discharge machining (EDM) on the surface of dental cast alloys used for the fabrication of implant retained meso- and super-structures. Methods A completed cast model of an arch that received dental implants was used for the preparation of six wax patterns which were divided into three groups (Au, Co and Ti). The wax patterns of the Au and Co groups were invested with conventional phosphate-bonded silica-based investment material and the Ti group with magnesia-based investment material. The investment rings of the Au and Co groups were cast with an Au–Ag alloy (Stabilor G) and a Co–Cr base alloy (Okta C), respectively, while the investment rings of group Ti were cast with cp Ti (Biotan). One casting of each group was subjected to electro discharge machining (EDM); the other was conventionally ground and polished. The surface morphology and the elemental compositions of conventionally and EDM-finished surfaces were studied by SEM/X-ray EDS analysis. Six spectra were collected from each surface employing the area scan mode and the mean value of each element between conventionally and EDM-finished surfaces was statistically analyzed by t-test ( a = 0.05). Then the specimens of each group were cut perpendicular to their longitudinal axis and after metallographic grinding and polishing the cross-sections studied under the SEM. Results The EDM surfaces showed a significant increase in C due to the decomposition of the dielectric fluid during spark erosion. Moreover, a significant Cu uptake was noted on these surfaces from the decomposition of the Cu electrodes used for EDM. Cross-sectional analysis showed that all alloys developed a superficial zone (recast layer) varying from 2 μm for Au–Ag to 10 μm for Co–Cr alloy. Significance The elemental composition of dental alloy surfaces is significantly altered after EDM treatment.

Novel integrated paired emitter-detector diode (PEDD) as a miniaturized photometric detector in HPLC

A novel low power, low cost, highly sensitive, miniaturized light emitting diode (LED) based flow detector has been used as optical detector for the detection of sample components in high performance liquid chromatography (HPLC). This colorimetric detector employs two LEDs, one operating in normal mode as a light source and the other is reverse biased to work as a light detector. Instead of measuring the photocurrent directly, a simple timer circuit is used to measure the time taken for the photocurrent generated by the emitter LED (lambda(max) 500 nm) to discharge the detector LED (lambda(max) 621 nm) from 5 V (logic 1) to 1.7 V (logic 0) to give digital output directly without using an A/D converter. Employing a post-column reagent method, a Nucleosil 100-7 column (functionalized with iminodiacetic acid (IDA) groups) was used to separate a mixture of transition metal complexes, manganese(II) and cobalt(II) in 4-(2-pyridylazo)-resorcinol (PAR). All optical measurements were taken by using both the in-built HPLC variable wavelength detector and the proposed paired-emitter-detector-diode (PEDD) optical detector configured in-line for data comparison. The concentration range investigated using the PEDD was found to give a linear response to the Mn(II) and Co(II) PAR complexes. The effects of flow rate and emitter LED light source intensity were investigated. Under optimised conditions the PEDD detector offered a linear range of 0.9-100 microM and LOD of 0.09 microM for Mn-PAR complex. A linear range of 0.2-100 microM and LOD of 0.09 microM for Co-PAR complex was achieved.

The Catalytic Role of Glutamate 151 in the Leucine Aminopeptidase from Aeromonas proteolytica

Glutamate 151 has been proposed to act as the general acid/base during the peptide hydrolysis reaction catalyzed by the co-catalytic metallohydrolase from Aeromonas proteolytica (AAP). However, to date, no direct evidence has been reported for the role of Glu-151 during catalytic turnover by AAP. In order to elucidate the catalytic role of Glu-151, altered AAP enzymes have been prepared in which Glu-151 has been substituted with a glutamine, an alanine, and an aspartate. The Michaelis constant (K(m)) does not change upon substitution to aspartate or glutamine, but the rate of the reaction changes drastically in the following order: glutamate (100% activity), aspartate (0.05%), glutamine (0.004%), and alanine (0%). Examination of the pH dependence of the kinetic constants k(cat) and K(m) revealed a change in the pK(a) of a group that ionizes at pH 4.8 in recombinant leucine aminopeptidase (rAAP) to 4.2 for E151D-AAP. The remaining pK(a) values at 5.2, 7.5, and 9.9 do not change. Proton inventory studies indicate that one proton is transferred in the rate-limiting step of the reaction at pH 10.50 for both rAAP and E151D-AAP, but at pH 6.50 two protons and general solvation effects are responsible for the observed effects in the reaction catalyzed by rAAP and E151D-AAP, respectively. Based on these data, Glu-151 is intrinsically involved in the peptide hydrolysis reaction catalyzed by AAP and can be assigned the role of a general acid and base.

A microbial biosensor to predict bioavailable nickel in soil and its transfer to plants

Ralstonia eutropha strain AE2515 was constructed and optimised to serve as a whole-cell biosensor for the detection of bioavailable concentrations of Ni 2+ and Co 2+ in soil samples. Strain AE2515 is a Ralstonia eutropha CH34 derivative containing pMOL1550, in which the cnrYXH regulatory genes are transcriptionally fused to the bioluminescent luxCDABE reporter system. Strain AE2515 was standardised for its specific responses to Co 2+ and Ni 2+. The detection limits for AE2515 were 0.1 μM Ni 2+ and 9 μM Co 2+, respectively. The signal to noise (S/N) bioluminescence response and the metal cation concentration could be linearly correlated: for Ni 2+ this was applicable within the range 0.1–60 μM, and between 9 and 400 μM for Co 2+. The AE2515 biosensor strain was found to be highly selective for nickel and cobalt: no induction was observed with Zn(II), Cd(II), Mn(II), Cu(III) and Cr(VI). In mixed metal solutions, the bioluminescent response always corresponded to the nickel concentrations. Only in the presence of high concentrations of Co 2+ (2 mM), the sensitivity to nickel was reduced due to metal toxicity. AE2515 was used to quantify the metal bioavailability in various nickel-enriched soils, which had been treated with additives for in situ metal immobilisation. The data obtained with strain AE2515 confirmed that the bioavailability of nickel was greatly reduced following the treatment of the soils with the additives beringite and steel shots. Furthermore, the data were found to correlate linearly with those on the biological accumulation of Ni 2+ in specific parts of important agricultural crops, such as maize and potato. Therefore, the test can be used to assess the potential transfer of nickel to organisms of higher trophic levels, in this case maize and potato plants grown on nickel-enriched soils, and the potential risk of transfer of these elements to the food chain.

New and simple method for fabricating polymer-coated silver hollow fibers with large mechanical strength

A new method is proposed for fabricating polymer-coated silver hollow glass fibers to avoid the flexibility deterioration after the curing process. Transmission properties of fibers made by the two procedures with and without curing process are compared. Little difference was observed in the transmission properties at the wavelength 2.94 μm of Er:YAG laser light and 10.6 μm of CO 2 laser light. The polymer layer is shown to be stable after 2-h, 5-W, continuous wave CO 2 laser light transmission.

Structure of Langmuir-Blodgett Films of Tetra-t-butyl Phthalocyanine.

Formation of the Langmuir monolayer, and structure of the Langmuir-Blodgett (LB) films of Tetra-t-butyl metallophthalocyanines (MTBP) were investigated by the surface pressure-area isotherm and X-ray diffraction (XRD) method, respectively. We obtained a well-defined monolayer on the subphase at concentrations of 5 .EM for the CuTBP and 2.5μM for Co, Zn, and VOTBP solutions. CuTBP yields a well-defined monolayer, due to formation of twodimensional aggregates on the surface where the limiting area of the monolayer is much greater than the intrinsic side area of MTBP. Since intensity of the XRD was so small, the LB layers with one to three layers may not be welloriented. An annealing procedure refined molecular organization of LB films significantly.

Effects of bar length on switching field of nanoscale nickel and cobalt bars fabricated using lithography

The switching behavior of isolated nanoscale nickel and cobalt bars, which were fabricated using electron-beam lithography, was studied as a function of bar length. The bars have a 35 nm thickness, a 100 nm width, and a length varying from 200 nm to 5 μm. Magnetic force microscopy showed that except for the Ni bars with a length equal to or less than 250 nm, all other as-fabricated bars were single domain. Unlike the bar width dependence, the switching field of the single-domain bars was found to first increase with the bar length, then decrease after reaching a peak. The peak switching field and the corresponding bar length are 640 Oe and 1 μm for Ni and 1250 Oe and 2 μm for Co, respectively. The nonmonotonic length dependence suggests that the magnetization switching may be quasicoherent in the short bars and incoherent in the long bars, and that the exchange coupling is much stronger in Co bars than in Ni bars. Furthermore, the switching field of 1-μm-long Co bars was found to increase monotonically as the bar width decreases, reaching 3000 Oe at a 30 nm width.

Nonmonotonic length dependence of switching field of nanolithographically defined single-domain nickel and cobalt bars (abstract)

Previously, the switching field of nanolithographically defined single-domain permalloy and nickel bars was found to increase monotonically as the bar aspect ratio increases or as the bar width decreases. In this work, we will show, for the first time, that when the bar width is fixed, the switching field of nanolithographically defined single-domain nickel and cobalt bars changes nonmonotonically with the bar length (hence the aspect ratio). The isolated Ni and Co bars were fabricated using electron-beam lithography and a lift-off process, and have a thickness of 35 nm, a fixed width of 100 nm, and a length varying from 200 nm to 5 μm. The magnetic force microscopy (MFM) showed that all the as-fabricated bars, except for the Ni bars with a length less than 500 nm, are single domain. The switching field of the single-domain bars was found to increase with the bar length first, then decrease after reaching a peak. The peak switching field and corresponding bar length are 640 Oe and 1 μm for Ni, and 1250 Oe and 2 μm for Co. This behavior, which clearly deviates from Stoner-Wohlfarth model, suggests that two different mechanisms should be responsible for the magnetization reversal process in different bar lengths. When the bar length is small, the exchange energy can be much larger than the magnetostatic energy to keep the bar switching quasicoherently and the switching field increases with the bar length. However, when the bar length is large, the exchange energy cannot overweigh the magnetostatic energy for quasi-coherent switching and therefore the lowest switching energy state would be incoherent switching which involves multidomain (or vortex) reversal leading to an decrease of switching field. The detailed analysis will be presented in the paper.