Hyperfine interaction studies with (181)Ta and (111)Cd probes in the compound Ti(2)Ag

By using the time-differential perturbed angular correlation technique, the electric field gradients (EFG) at (181)Hf/(181)Ta and (111)In/(111)Cd probe sites in the MoSi(2)-type compound Ti(2)Ag have been measured as a function of temperature in the range from 24 to 1073 K. Ab initio EFG calculations have been performed within the framework of density functional theory using the full-potential augmented plane wave + local orbitals method as implemented in the WIEN2k package. These calculations allowed assignments of the probe lattice sites. For Ta, a single well-defined EFG with very weak temperature dependence was established and attributed to the [4(e)4mm] Ti site. For (111)Cd probes, two of the three measured EFGs are well defined and correlated with substitutional lattice sites, i.e. both the [4(e)4mm] Ti site and the [2(a)4/mmm] Ag site.

Enzyme immobilization on Ag nanoparticles/polyaniline nanocomposites

We show a simple strategy to obtain all efficient enzymatic broelectrochemical device, in which urease was immobilized oil electroactive nanostructured membranes (ENMs) made with polyaniline and silver nanoparticles (AgNP) stabilized in polyvinyl alcohol (PAni/PVA-AgNP). Fabrication of the modified electrodes comprised the chemical deposition of polyaniline followed by drop-coating of PVA-AgNP and urease, resulting in a final ITO/PAni/PVA-AgNP/urease electrode Configuration. For comparison. the electrochemical performance of ITO/PAni/urease electrodes (without Ag nanoparticles) was also studied. The performance of the modified electrodes toward Urea hydrolysis was investigated via amperometric measurements, revealing a fast increase in cathodic current with a well-defined peak upon addition of urea to the electrolytic solution. The cathodic currents for the ITO/PAni/PVA-AgNP urease electrodes were significantly higher than for the ITO/PAni/urease electrodes. The friendly environment provided by the ITO/PAni/PVA-AgNP electrode to the immobilized enzyme promoted efficient catalytic conversion of urea into ammonium and bicarbonate tons. Using the Michaelis-Menten kinetics equation, a K(M)(aPP) of 2.7 mmol L(-1) was obtained. indicating that the electrode architecture employed may be advantageous for fabrication of enzymatic devices with improved biocatalytic properties. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.

Pt(II) and Ag(I) complexes with acesulfame: Crystal structure and a study of their antitumoral, antimicrobial and antiviral activities

Two new complexes of platinum(II) and silver(I) with acesulfame were synthesized. Acesulfame is in the anionic form acesulfamate (ace). The structures of both complexes were determined by X-ray crystallography. For K(2)[PtCl(2)(ace)(2)] the platinum atom is coordinated to two Cl(-) and two N-acesulfamate atoms forming a trans-square planar geometry. Each K(+) ion interacts with two oxygen atoms of the S(=O)(2) group of each acesulfamate. For the polymeric complex [Ag(ace)](n) the water molecule bridges between two crystallographic equivalent Agl atoms which are related each other by a twofold symmetry axis. Two Agl atoms, related to each other by a symmetry centre, make bond contact with two equivalent oxygen atoms. These bonds give rise to infinite chains along the unit cell diagonal in the ac plane. The in vitro cytotoxic analyses for the platinum complex using HeLa (human cervix cancer) cells show its low activity when compared to the vehicle-treated cells. The Ag(I) complex submitted to in vitro antimycobacterial tests, using the Microplate Alamar Blue (MABA) method, showed a good activity against Mycobacterium tuberculosis, responsible for tuberculosis, with a minimal inhibitory concentration (MIC) value of 11.6 mu M. The Ag(I) complex also presented a promising activity against Gram negative (Escherichia colt and Pseudomonas aeruginosa) and Gram positive (Enterococcus faecalis) microorganisms. The complex K(2)[PtCl(2)(ace)(2)] was also evaluated for antiviral properties against dengue virus type 2 (New Guinea C strain) in Vero cells and showed a good inhibition of dengue virus type 2 (New Guinea G strain) replication at 200 mu M, when compared to vehicle-treated cells. (C) 2010 Elsevier Inc. All rights reserved.

Recovery of DNA for the detection and genotyping of human papillomavirus from clinical cervical specimens stored for up to 2 years in a universal collection medium with denaturing reagent

The recovery and stability of DNA for the detection and genotyping of HPV in UCM-containing specimens, after exposure to denaturing reagents and stored for up to 2 years were evaluated. Samples were collected from 60 women who had cervical cytology specimens harboring cervical intraepithelial neoplasia (CIN) 2 or 3. All samples were stored in UCM and had been frozen at -20 degrees C following the addition of the denaturing reagent (sodium hydroxide) and the removal of the aliquot required for Hybrid Capture 2 testing for the identification of HPV DNA. The samples had been stored for 6, 12 and 24 months (20 samples for each storage time). HPV DNA extraction was performed according to a protocol designed specifically and the presence and quality of DNA was confirmed by human P-globin detection using the consensus primers G73 and G74. HPV DNA was amplified using the consensus primers PGMY09 and PGMY11, and reverse line-blot hybridization was used to detect type-specific amplicons for 37 HPV types. The DNA extracted from the denatured specimen was recovered in 57/60 (95%) of the samples. HPV DNA was detected in 56/57 (98%) of the recovered samples. Twenty-six of the 56 samples recovered (48%) were genotyped successfully. (c) 2007 Elsevier B.V. All rights reserved.

Group 11 (Cu, Ag, Au) promotion of 15%Co/Al(2)O(3) Fischer-Tropsch synthesis catalysts

Co/Al(2)O(3) Fischer-Tropsch synthesis catalysts promoted with different quantities of Group 11 metals (Cu, Ag, Au) were characterized and tested. The presence of relatively small quantities of such metals enhanced Co reducibility and, in the cases of Ag and Au, improved the surface Co metal active site densities. EXAFS experiments with the most loaded catalyst samples show that only Co-Co and Me-Me (Me = Cu, Ag and Au) coordination could be observed. This suggests that the greater fraction of the metals form different phases. However, the reduction promoting effect of the Group 11 metal is severely hampered once the catalyst receives a mild passivation treatment following primary reduction. An explanation in terms of promoter segregation during primary reduction is proposed. At lower promoter levels (0.83%Ag and 1.51%Au) and higher Ag levels (2.76%), significant gains in Co active site densities were achieved resulting in improved CO conversion levels relative to the unpromoted catalyst. Moreover, slight decreases in light product (e.g., CH(4)) selectivity and slight increases in C(5)+ selectivity were achieved. At high Au loading (5.05%), however, too much Au was loaded which, although significantly increasing the fraction of Co reduced, blocked Co surface sites and resulted in decreased Co conversion rates. While Cu facilitated Co reduction, the increased fraction of reduced Co did not translate to improved active site densities. It appears that a fraction of Cu tended to cover the rim of Co clusters, resulting in decreases in CO conversion rates and detrimental increases in light product selectivity. (C) 2009 Elsevier B.V. All rights reserved.

Square wave adsorptive cathodic stripping voltarnmetry automated by sequential injection analysis - Potentialities and limitations exemplified by the determination of methyl parathion in water samples

This paper describes the development and evaluation of a sequential injection method to automate the determination of methyl parathion by square wave adsorptive cathodic stripping voltammetry exploiting the concept of monosegmented flow analysis to perform in-line sample conditioning and standard addition. Accumulation and stripping steps are made in the sample medium conditioned with 40 mmol L-1 Britton-Robinson buffer (pH 10) in 0.25 mol L-1 NaNO3. The homogenized mixture is injected at a flow rate of 10 mu Ls(-1) toward the flow cell, which is adapted to the capillary of a hanging drop mercury electrode. After a suitable deposition time, the flow is stopped and the potential is scanned from -0.3 to -1.0 V versus Ag/AgCl at frequency of 250 Hz and pulse height of 25 mV The linear dynamic range is observed for methyl parathion concentrations between 0.010 and 0.50 mgL(-1), with detection and quantification limits of 2 and 7 mu gL(-1), respectively. The sampling throughput is 25 h(-1) if the in line standard addition and sample conditioning protocols are followed, but this frequency can be increased up to 61 h(-1) if the sample is conditioned off-line and quantified using an external calibration curve. The method was applied for determination of methyl parathion in spiked water samples and the accuracy was evaluated either by comparison to high performance liquid chromatography with UV detection, or by the recovery percentages. Although no evidences of statistically significant differences were observed between the expected and obtained concentrations, because of the susceptibility of the method to interference by other pesticides (e.g., parathion, dichlorvos) and natural organic matter (e.g., fulvic and humic acids), isolation of the analyte may be required when more complex sample matrices are encountered. (C) 2007 Elsevier B.V. All rights reserved.

Adsorption of 4-aminopyridine on Co and Ag electrodes probed by SERS

The adsorption of 4-aminopyridine (4-AP) on Co and Ag electrodes in acid or alkaline solutions of KCl and KI electrolyte salts were monitored by the Surface-enhanced Raman Spectroscopy (SERS) technique. The SERS intensity for the Ag electrode was in 2 orders of magnitude higher than for the Co electrode, due to the enhancement of the Raman cross-section on Ag by the surface-plasmon excitation. In acidic chloride medium (pH 4), the SERS results for Ag electrodes indicate that the protonated form of 4-AP (4-APH(+)) adsorbs in the potential range of -0.1 to -0.6 V (Ag broken vertical bar AgCl broken vertical bar KCl sat) through hydrogen-bonding between 4-APH(+) and Cl(-) adsorbed on the electrode surface: at more negative potentials the neutral form 4-AP is the predominant adsorbed species. For Co electrode in the same medium, only bands due to neutral 4-AP were observed in the spectra at -0.8 and -0.9 V. For more negative potentials bands assigned to both 4-AP and 4-AP surface complex are observed, with the lasts being enhanced, as the potentials are turned more negative. In alkaline chloride medium (pH 13), for less negative potentials the bands assigned to free 4-AP were observed in the spectra of both Ag and Co surfaces. For more negative potentials, only bands assigned to the 4-AP surface complex were observed. For 0.1 mol L(-1) KI acidic or alkaline solutions, bands assigned to 4-AP and 4-APH(+) were observed in a wider potential range than in chloride solutions. An adsorption scheme of 4-AP on Ag and Co is proposed for acidic and alkaline solutions. (C) 2010 Elsevier B.V. All rights reserved.

A New Indirect Electrochemical Method for Determination of Ozone in Water Using Multiwalled Carbon Nanotubes

A new electrochemical methodology has been developed for the detection of ozone using multiwalled carbon nanotubes (MWCNT). The method presented here is based on the reaction of ozone with indigo blue dye producing anthranilic acid (ATN). The electrochemical profile of ATN on an electrode of glassy carbon (GC) modified with MWCNT showed an oxidation peak potential at 750 mV vs. Ag/AgCl. An analytical method was developed using differential pulse voltammetry (DPV) to determine ATN in a range of 50-400 nmol L(-1), with a detection limit of 9.7 nmol L(-1). Ozonated water samples were successfully analyzed by GC/MWCNT electrode and the recovery procedure yielded values between of 96.5 and 102.3%.

Pendimethalin determination in natural water, baby food and river sediment samples using electroanalytical methods

This work describes the electroanalytical determination of pendimethalin herbicide levels in natural waters, river sediment and baby food samples, based on the electro-reduction of herbicide on the hanging mercury drop electrode using square wave voltammetry (SWV). A number of experimental and voltammetric conditions were evaluated and the best responses were achieved in Britton-Robinson buffer solutions at pH 8.0, using a frequency of 500 s(-1). a scan increment of 10 mV and a square wave amplitude of 50 mV. Under these conditions, the pendimethalin is reduced in an irreversible process, with two reduction peaks at -0.60 V and -0.71 V. using a Ag/AgCl reference system. Analytical curves were constructed and the detection limit values were calculated to be 7.79 mu g L(-1) and 4.88 mu g L(-1), for peak 1 and peak 2, respectively. The precision and accuracy were determinate as a function of experimental repeatability and reproducibility, which showed standard relative deviation values that were lower than 2% for both voltammetric peaks. The applicability of the proposed methodology was evaluated in natural water, river sediments and baby food samples. The calculated recovery efficiencies demonstrate that the proposed methodology is suitable for determining any contamination by pendimethalin in these samples. Additionally, adsorption isotherms were used to evaluate information about the behavior of pendimethalin in river sediment samples. (C) 2010 Elsevier B.V. All rights reserved.

Anodic stripping voltammetric determination of copper(II) using a functionalized carbon nanotubes paste electrode modified with crosslinked chitosan

The development and application of a functionalized carbon nanotubes paste electrode (CNPE) modified with crosslinked chitosan for determination of Cu(II) in industrial wastewater, natural water and human urine samples by linear scan anodic stripping voltammetry (LSASV) are described. Different electrodes were constructed using chitosan and chitosan crosslinked with glutaraldehyde (CTS-GA) and epichlorohydrin (CTS-ECH). The best voltammetric response for Cu(II) was obtained with a paste composition of 65% (m/m) of functionalized carbon nanotubes, 15% (m/m) of CTS-ECH, and 20% (m/m) of mineral oil using a solution of 0.05 mol L(-1) KNO(3) with pH adjusted to 2.25 with HNO(3), an accumulation potential of 0.3V vs. Ag/AgCl (3.0 mol L(-1) KCl) for 300 s and a scan rate of 100 mV s(-1). Under these optimal experimental conditions, the voltammetric response was linearly dependent on the Cu(II) concentration in the range from 7.90 x 10(-8) to 1.60 x 10(-5) mol L(-1) with a detection limit of 1.00 x 10(-8) mol L(-1). The samples analyses were evaluated using the proposed sensor and a good recovery of Cu(II) was obtained with results in the range from 98.0% to 104%. The analysis of industrial wastewater, natural water and human urine samples obtained using the proposed CNPE modified with CTS-ECH electrode and those obtained using a comparative method are in agreement at the 95% confidence level. (C) 2009 Elsevier B. V. All rights reserved.

Development and Application of a Highly Selective Biomimetic Sensor for Detection of Captopril, an Important Ally in Hypertension Control

A biomimetic sensor is proposed as a promising new analytical method for determination of captopril in different classes of samples. The sensor was prepared by modifying a carbon paste electrode with iron (II) phthalocyanine bis(pyridine) [FePe(dipy)] complex. Amperometric measurements in a batch analytical mode were first carried out in order to optimize the sensor response. An applied potential lower than 0.2 V vs Ag vertical bar AgCl in 0.1 mol L(-1) of TRIS buffer at pH 8.0 provided the best response, with a linear range of 2.5 x 10(-5) to 1.7 x 10(-4) mol L(-1). A detailed investigation of the selectivity of the sensor, employing seventeen other drugs, was also performed. Recovery studies were carried out using biological and environment samples in order to evaluate the sensor`s potential for use with these sample classes. Finally, the performance of the biomimetic sensor was optimized in a flow injection (FIA) system using a wall jet electrochemical cell. Under optimized flow conditions, a broad linear response range, from 5.0 x 10(-4) to 2.5 x 10(-2) mol L(-1), was obtained for captopril, with a sensitivity of 210 +/- 1 mu A L mol(-1).

RECOVERY OF p-TBC FROM A BUTADIENE WASHING STREAM IN A PILOT PLANT

Results obtained in a pilot-scale unit designed for COD removal and p-TBC (p-tert-butylcatechol) recovery from a butadiene washing stream (pH 14, 200,000 mg COD L(-1), highly toxic) at a petrochemical industry are presented. By adding H(3)PO(4), phase separation is achieved and p-TBC is successfully recovered (88 g L(-1) of washing stream). Information (time for phase separation and organic phase characterization) was gathered for designing a future industrial unit. The estimated heat generation rate was 990 kJ min(-1) and 15 min were enough to promote phase separation for a liquid column of approximately 1.15 m.

Calucaltion of waste heat from hot rolled steel coils at SSAB and its recovery

Hot rolling process is heat input process. The heat energy in hot rolled steel coils can be utilized. At SSAB Strip Product Borlänge when the hot rolled steel coils came out of the hot rolling mill they are at the temperature range of 500°C to 800°C. Heat energy contained by the one hot rolled steel coil is about 1981Kwh whereas the total heat energy for the year 2008 is 230 GWh/year.The potential of heat is too much but the heat dissipation rate is too slow. Different factors on which heat dissipation rate depends are discussed.Three suggestions are proposed to collect the waste heat from hot rolled steel coils.The 2nd proposal in which water basin is suggested would help not only to collect the waste heat but to decrease in the cooling time.

Energy efficient and economic renovation of residential buildings with low-temperature heating and air heat recovery

With the building sector accounting for around 40% of the total energy consumption in the EU, energy efficiency in buildings is and continues to be an important issue. Great progress has been made in reducing the energy consumption in new buildings, but the large stock of existing buildings with poor energy performance is probably an even more crucial area of focus. This thesis deals with energy efficiency measures that can be suitable for renovation of existing houses, particularly low-temperature heating systems and ventilation systems with heat recovery. The energy performance, environmental impact and costs are evaluated for a range of system combinations, for small and large houses with various heating demands and for different climates in Europe. The results were derived through simulation with energy calculation tools. Low-temperature heating and air heat recovery were both found to be promising with regard to increasing energy efficiency in European houses. These solutions proved particularly effective in Northern Europe as low-temperature heating and air heat recovery have a greater impact in cold climates and on houses with high heating demands. The performance of heat pumps, both with outdoor air and exhaust air, was seen to improve with low-temperature heating. The choice between an exhaust air heat pump and a ventilation system with heat recovery is likely to depend on case specific conditions, but both choices are more cost-effective and have a lower environmental impact than systems without heat recovery. The advantage of the heat pump is that it can be used all year round, given that it produces DHW. Economic and environmental aspects of energy efficiency measures do not always harmonize. On the one hand, lower costs can sometimes mean larger environmental impact; on the other hand there can be divergence between different environmental aspects. This makes it difficult to define financial subsidies to promote energy efficiency measures.