Stable isotope analysis reveals lower-order river dissolved inorganic carbon pools are highly dynamic

River systems draining peaty catchments are considered a source of atmospheric CO2,thus understanding the behavior of the dissolved inorganic carbon pool (DIC) is valuable. The carbon isotopic composition, delta13C(DIC), and concentration, [DIC], of fluvial samples collected diurnally, over 14 months, reveal the DIC pools to be dynamic in range (-22 to -4.9% per hundred, 0.012 to 0.468 mmol L(-1) C), responding predictably to environmental influences such as changing hydrologic conditions or increased levels of primary production. delta(18)O of dissolved oxygen (DO) corroborates the delta(13)C(DIC) interpretation. A nested catchment sampling matrix reveals that similar processes affect the DIC pool and thus delta(13)C(DIC) across catchment sizes. Not so with [DIC]: at high flow, the DIC export converges across catchment size, but at low flow catchments diverge in their DIC load. Contextualizing delta(13)C with discharge reveals that organic soil-waters and groundwaters comprise end-member sources, which in varying proportions constitute the fluvial DIC pool. Discharge and pH describe well [DIC] and delta(13)C(DIC), allowing carbon to be apportioned to each end-member from continuous profiles, demonstrated here for the hydrological year 2003-2004. This approach is powerful for assessing whether the dynamic response exhibited here is ubiquitous in other fluvial systems at the terrestrial-aquatic interface or in larger catchments.     

Fabrication of nanoporous TiO2 by electrochemical anodization

The formation of self-organized porous titania is achieved by electrochemical anodization under a potentiostatic regime. Anodic titanium oxide (ATO) was fabricated by a three-step self-organized anodization of the Ti foil in an ethylene glycol electrolyte containing 0.38 wt% of NH₄F and 1.79 wt% of H₂O. Anodizing was carried out at the constant cell potential ranging from 30 to 70 V at the temperature of 20 °C. It was found that nanoporous TiO₂ arrays can be obtain only after a short duration of the third step (10 min). The influence of anodizing potential on the structural parameters of porous anodic titania including pore diameter, interpore distance, wall thickness, porosity and pore density was extensively studied. The linear dependencies between interpore distance, pore diameter and wall thickness upon the anodizing potential were found. The regularity of pore arrangement was monitored qualitatively by fast Fourier transforms (FFTs) of top-view FE-SEM images. It was found that the best arrangement of nanopores is observed at 40 V. This finding was confirmed by the analysis of pore circularity. The highest circularity of pores was observed once again at 40 V.     

Dynamic experimental simulation of hydrogen oriented underground gasification of lignite

The main goal of the study presented in the paper was to experimentally demonstrate the feasibility of lignite gasification to hydrogen-rich gas under the underground conditions simulated in the ex situ reactor. The in situ gasification conditions were simulated both in respect to the coal seam and the surrounding stratum. In the 54-h experiment the process of lignite gasification with oxygen and steam as gasifying medium was tested. The experiment was initially divided into three stages: the ignition stage, the oxygen stage and the steam stage.The gas produced in the steam gasification stage was characterized by the calorific value of 7.8 MJ/m³ and average hydrogen content of 46.3 vol.%. Unfortunately a rapid decrease in the temperature levels and in the amount of produced gas proved that the tested lignite of 53 vol.% moisture content was not suitable for steam gasification. A great amount of thermal energy was consumed for water evaporation which led to a considerable heat loss. An addition of stoichiometric amount of water in the system by adding steam caused the seam to extinguish. Thus only oxygen could be used as the gasifying medium in the gasification of the tested lignite. The average calorific value of gas produced in the stable operation during oxygen gasification stage equaled 5.2 MJ/m³ with the average gas production rate of 16.0 m³/h and the average hydrogen content in the produced gas of 26.4 vol.%.     

Properties of welded joints made of Weldox 1100 steel

This study evaluated both the joint strength of copper wire on a copper substrate with tin plating and the joint reliability of copper wire bonding after heat treatment. The suitable tin thickness and bonding conditions, which are stage temperature, wire bonding power and bonding time, were chosen by the peel test after copper wire bonding. Tin thickness of 10 m showed a high bonding rate under the conditions of stage temperature 373 K, bonding power 500–700 mW and bonding time 30 50 ms. Before heat treatment, the peel strength of the copper wire on the copper substrate with tin plating conditions was weaker than that of gold wire on a gold substrate. After heat treatment for more than 70 h at 298 K, the peel strength of the copper wire became higher than that of the gold wire and twice as high as the initial bonding strength. The tin layer remained between the copper wire and copper substrate before heat treatment. When the samples were held at 298 K, tin reacted with copper and turned into a Cu–Sn intermetallic compound. Upon completion of this reaction at 298 K for over 70 h, the soft tin layer between the copper wire and copper substrate disappeared. Therefore, the peel strength of copper wire after heat treatment increased. These results were observed by scanning electron microscope images of the interface between the copper wire and copper substrate before and after heat treatment.     

Antioxidant vs. Prooxidant Properties of the Flavonoid,Kaempferol, in the Presence of Cu(II) Ions: A ROS-Scavenging Activity,Fenton Reaction and DNA Damage Study

Kaempferol is a flavonoid that occurs in tea and in many vegetables and fruits, including broccoli, cabbage, beans, grapes, apples, and strawberries. The efficacy of Kaempferol has been demonstrated in the treatment of breast, esophageal, cervical, ovarian, and liver cancers and leukemia, which very likely arises from its prooxidant properties and the activation of pro-apoptotic pathways. Indeed, this matter has already been the focus of a number of published studies and reviews. The aim of the present study was to elucidate the antioxidant vs. prooxidant properties of flavonoids in the presence of the redox-active metal, copper (II) ion, by means of the Fenton reaction. The specific motivation of this work is that, since an increased level of Cu(II) ions is known to be associated with many disease states such as neurological conditions (Alzheimer’s disease) and cancer, any interaction between these ions and flavonoids might affect the outcome of therapeutic uses of the latter. The structure of the Cu-kaempferol complex in DMSO was investigated by means of low temperature EPR spectroscopy, which confirmed the existence of at least two distinct coordination environments around the copper (II) ion. UV vis-spectra of kaempferol and its Cu(II) complex in DMSO revealed an interaction between the 5-OH (A ring) group and the 4-CO (C ring) group of kaempferol with Cu(II) ions. An ABTS assay confirmed that kaempferol acted as an effective radical scavenger, and that this effect was further enhanced in the form of the Cu(II)-kaempferol complex. Quantitative EPR spin trapping experiments, using DMPO as the spin trap, confirmed suppression of the formation of a mixture of hydroxyl, superoxide, and methyl radicals, in a Fenton reaction system, upon coordination of kaempferol to the redox-active Cu(II) ions, by 80% with respect to the free Cu(II) ions. A viscometric study revealed a better DNA-intercalating ability of the Cu-kaempferol complex than for free kaempferol, essential for conferring anticancer activity of these substances. The results of the viscometric measurements were compared with those from a DNA damage study of Cu-kaempferol complexes in a Fenton reaction system, using gel electrophoresis. At low concentrations of kaempferol (Cu–kaempferol ratios of 1:1 and 1:2), a very weak protective effect on DNA was noted, whereas when kaempferol was present in excess, a significant DNA-protective effect was found. This can be explained if the weakly intercalated kaempferol molecules present at the surface of DNA provide protection against attack by ROS that originate from the Fenton reaction involving intercalated Cu(II)-kaempferol complexes. Following the application of ROS scavengers, L-histidine, DMSO, and SOD, gel electrophoresis confirmed the formation of singlet oxygen, hydroxyl radicals, and superoxide radical anions, respectively. We propose that the prooxidant properties of Cu-kaempferol complexes may provide anticancer activity of these substances. When present in excess, kaempferol displays antioxidant properties under Cu-Fenton conditions. This suggests that kaempferol might prove a suitable candidate for the prevention or treatment of oxidative stress related medical conditions that involve a disturbed metabolism of redox metals such as copper, for example, Menkes disease, and neurological disorders, including Alzheimer’s disease. For the potential use of kaempferol in clinical practice, it will be necessary to optimize the dose size and critical age of the patient so that this flavonoid may be beneficial as a preventive drug against cancer and neurological disorders.     

Electrospun ultrathin nylon fibers for protective applications

Electrospun nylon 6 fiber mats were deposited on woven 50/50 nylon/cotton fabric with the motive of making them into protective material against submicron‐level aerosol chemical and biological threats. Polymer solution concentration, electrospinning voltage, and deposition areal densities were varied to establish the relationships of processing‐structure‐filtration efficiency of electrospun fiber mats. A high barrier efficiency of greater than 99.5% was achieved on electrospun fiber mats without sacrificing air permeability and pressure drop. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

A Solvent‐Free Dispersion Method for the Preparation of PET/MWCNT Composites

A simple, easily accessible solvent‐free method for the dispersion of MWCNTs into PET is proposed, based on the preparation of a microparticulate polymer/nanotube masterbatch via cryogenic impact‐milling and its subsequent melt blending with the bulk polymer. Thermal and mechanical properties of nanocomposites prepared using this method were evaluated as a function of nanotube concentration. Thermal stability was improved, and superior crystallization behavior of PET in the nanocomposites was observed. Significant improvements of around 25% in tensile strength and tensile modulus of the nanocomposites was achieved using this strategy, with only 0.25 wt.‐% MWCNT, compared to previous literature data where 1 wt.‐% MWCNT was employed.

     

The Effect of Liquid Crystalline Structures on Antiseizure Properties of Aqueous Solutions of Ethoxylated Alcohols

Aqueous solutions of ethoxylated alcohols which form lyotropic liquid crystals at high concentrations (40–80%) were selected as model lubricating substances. Microscopic studies under polarized light and viscosity measurements were carried out in order to confirm the presence of liquid crystalline structures in the case of alcohol solutions with ethoxylation degrees of 3, 5, 7 and 10. Microscopic images and viscosity coefficient values characteristic of various mesophases were obtained. As expected, the viscosity of LLCs decreases considerably with an increase in shearing rate which is characteristic of liquid crystals being non-Newtonian liquids. Antiseizure properties were determined by means of a four-ball machine (T-02 Tester) and characterized by scuffing load (P_t), seizure load (P_oz) and limiting pressure of seizure (p_oz). Alcohol ethoxylates forming mesophases in aqueous solutions have the strongest effect on the P_t values which are several times higher than those measured in the presence of water. Ethoxylates with higher degrees of ethoxylation exhibit higher values of scuffing load. Those changes have been interpreted as a result of higher cloud points at which those compounds lose their amphiphilic properties. In general, the presence of mesophases in the bulk phase and particularly in the surface phase may lead to the formation of a lubricant film which separates the frictionally cooperating elements of a friction pair. The antiseizure efficiency of alcohol solutions is highest up to the load value which does not exceed the scuffing load value.     

Kinetic and spectral aspects in chemiluminescence system Eu(III)/HCO3/H2O2

Chemiluminescence (CL) of the systems containing Eu₂⁺ or HCO₃⁻ ions and hydrogen peroxide was studied. The kinetic curves and CL emission spectra of the systems were discussed. The emission spectrum of the system containing carbonates revealed two emission maxima: the first directly after initiation of the reaction by hydrogen peroxide and the second in several seconds after the first. On the basis of the characteristic bands in the CL spectrum the emitters in the system Eu₂⁺/HCO₃⁻/H₂O₂ were identified as: excited Eu³⁺ ions and excited products of carbonate decomposition. The emission bands for λ=600 and 420 nm appeared in a time distance of a few ten seconds.