Speciation of Iron in Soils and the Relation with Its Concentration in Fruits

An attempt was made to identify the iron species that is most responsible for plant-available Fe. Iron concentrations in fruit samples were determined by using flame atomic absorption spectrometry (FAAS). The soil samples related to these fruits were also analyzed for Fe by using various digestion and extraction reagents. The relation between the fruit-Fe and soil-extractable-Fe concentrations was examined to explain the Fe uptake of fruit from soil. The probable chemical forms of Fe in the soil were evaluated for the speciation of Fe.     

Determination of molybdenum in biological samples by flame atomic spectrometry after preconcentration on activated carbon

Abstract  

Molybdenum is well known for its toxic effects, although it is also essential for N₂-fixing cyanobacteria and several enzymes. This study proposes a simple and accurate procedure for separation, preconcentration, and determination of trace amounts of molybdenum in biological samples by flame atomic absorption spectrometry. It is based on complexation of Mo by cupferron and sorption onto activated carbon. Effects of parameters such as pH, stirring time, and amounts of activated carbon and cupferron on recovery were examined. The results demonstrated that Mo at pH range of 2.5–3.5 was quantitatively sorbed onto activated carbon as its cupferron complex. The optimum stirring time was found to be 30 min. The relative standard deviation was found to be 12% for 200 cm³ 50 ng/cm³ Mo using 10 replicate preconcentration procedures. The limits of detection and quantification were found to be 1.0 and 3 ng/cm³, respectively, by preconcentration of 200 cm³ initial sample to 2 cm³ final volume. As a result, an enrichment factor of 100-fold was achieved. The proposed preconcentration procedure was applied to determine Mo in biological samples such as vegetables, milk, and animal liver. The molybdenum concentrations were found (as μg/dm³ or μg/kg) in the range of 70–5,500 for plants, 3–124 for milk and milk powder, and 960 for liver samples.     

A new rational approximation technique based on transformational high dimensional model representation

In this work, a new rational approximation scheme, based on the recently developed Transformational High Dimensional Model Representation (THDMR) approximation method is developed. As an initial step to the construction of a rational approximation for multivariate functions via THDMR, this paper focuses on the general theoretical background of the method and gives explicit formulae for the computation of such approximants. The performance of the technique is shown by several examples both in univariate and bivariate cases.     

Screening the oxidative potential of several mono- and di-halogenated biphenyls and biphenyl ethers in rat hepatocytes

The present study was designed to investigate the potential of reactive oxygen species (ROS) generating and subsequent ROS-mediated lipid peroxidation (LPO) inducing effect of several mono- and di-halogenated biphenyls and biphenyl ethers in rat hepatocytes in vitro. For this aim, 4-chloro- and 4-bromo biphenyl (4-CB and 4-BB), 4-OH, 4'-BB, 4-bromo diphenylether (4-BDE), 4,4'-dichlorobiphenyl (4,4'-DCB), 4,4'-dibromobiphenyl (4,4'-DBB), and 3,4-dichlorobiphenyl (3,4-DCB) were incubated with freshly isolated rat hepatocytes. Their oxidative potential was evaluated by detecting the intracellular ROS formation by oxidant-sensing fluorescent probes (2',7'-dichlorofluorescein diacetate and C(11)-BODIPY(581/591)) using a multiplate reader and determining the levels of eight LPO products (formaldehyde, malondialdehyde, propanal, butanal, pentanal, hexanal, octanal, and nonanal) by a gas chromatography-electron capture detection. 4-BDE was found to be active both in cytoplasm and in the cell membrane in terms of inducing the formation of ROS. Another important finding was the increase in ROS-inducing potential of 4-BB when the same concentration of the hydroxylated derivative, 4-OH,4'-BB, was incubated with hepatocytes. 4-BDE was also found to be the most effective among all tested compounds in inducing LPO where 4-OH, 4'-BB was again more potent than its unmetabolized form, 4-BB. Lactate dehydrogenase leakage analyses indicated that all tested compounds are cytotoxic; 4-BDE caused the highest LDH leakage compared to other mono-halogenated biphenyls tested. Our results suggest that ROS formation by chlorinated biphenyls and mono-hydroxylated bromobiphenyls, and concomitant induction of LPO might be involved in the cytotoxic effects of these industrial pollutants. Similar effects of mono-BDE are also reported, which is a novel observation.     

Health network mergers and hospital re-planning

This paper presents an integer programming formulation for the hospital re-planning problem which arises after hospital network mergers. The model finds the best re-allocation of resources among hospitals, the assignment of patients to hospitals and the service portfolio to minimize the system costs subject to quality and capacity constraints. An application in the Turkish hospital networks case is illustrated to show the implications of consolidation of health insurance funds on resource allocations and flow of patients in the system.     

Cubic regularization in symmetric rank-1 quasi-Newton methods

Quasi-Newton methods based on the symmetric rank-one (SR1) update have been known to be fast and provide better approximations of the true Hessian than popular rank-two approaches, but these properties are guaranteed under certain conditions which frequently do not hold. Additionally, SR1 is plagued by the lack of guarantee of positive definiteness for the Hessian estimate. In this paper, we propose cubic regularization as a remedy to relax the conditions on the proofs of convergence for both speed and accuracy and to provide a positive definite approximation at each step. We show that the n-step convergence property for strictly convex quadratic programs is retained by the proposed approach. Extensive numerical results on unconstrained problems from the CUTEr test set are provided to demonstrate the computational efficiency and robustness of the approach.     

Radiation‐grafted solid polymer electrolyte membrane: thermal and mechanical properties of sulfonated fluorinated ethylene propylene copolymer (FEP)‐graft‐acrylic acid membranes

Acrylic acid was grafted onto fluorinated ethylene propylene copolymer (FEP) using a simultaneous radiation technique and the resulting membranes were subsequently sulfonated. Thermal and mechanical properties of these membranes were investigated and were found to be strongly influenced by the degree of grafting. Thermogravimetric analysis (TGA) of these membranes showed that these membranes undergo multistep degradation unlike virgin FEP which degrades in a single step. Glass transition temperature and degree of crystallinity were determined by differential scanning calorimetry (DSC). Glass transition temperature increased while crystallinity decreased with increase in degree of grafting. Tensile strength and elongation at break were found to decrease on grafting and further on sulfonation. Copyright © 2004 John Wiley & Sons, Ltd.     

Oil recovery performances of surfactant solutions by capillary imbibition

Critical parameters playing a role in oil recovery by capillary imbibition of surfactant solutions were studied. Experiments conducted on sandstone and carbonate samples using different oil and surfactant types were evaluated for surfactant selection. In this evaluation interfacial tension (IFT), surfactant type, solubility characteristics of surfactants, rock type, initial water (pre-wet rock), and surfactant concentration were considered. In addition to these, a new technique was adopted to facilitate the surfactant screening process. This technique is based on assigning inorganic and organic property values and plotting organic conception diagrams (OCD) for surfactants. OCD defines the property of a compound in terms of physical chemistry in such a way that the property that depends much on the van der Waals force is called "organic" and the one that depends much on electric affinity is called "inorganic." Correlations between the capillary imbibition recovery performance and the properties of surfactant and oil (organic value (OV), inorganic value (IV), and IFT of surfactant solutions, oil viscosity, and surfactant type) were obtained. These correlations are expected to be useful in selecting the proper surfactant for improved oil recovery as well as identifying the effects of surfactant properties on the capillary imbibition performance.     

p-Hertz excitation spectroscopy of an optical antenna, optical transmitter-receiver mechanism

o-Xylene sensitized biacetyl fluorescence and phosphorescence have been investigated and photosensitized fluorescence and phosphorescence lifetimes of biacetyl in the vapor phase have been determined. Attempts to detect the triplet of biacetyl by its absorption spectrum were unsuccessful, primarily due to, it is believed, the low extinction coefficients of the triplet, and the low triplet concentrations produced by the optical pumping device at room temperature.     

Photoredox mediated CN cross coupling of sulfoximines with aryl iodides

A new photoredox-catalyzed CN coupling reaction of sulfoximines with aryl halides has been developed for a general N-arylation of sulfoximines. The reactions proceed in the presence of visible light with high levels of chemoselectivity and a wide range of functionality is tolerated. There is a rapidly increasing interest in sulfoximines as pharmacophores in drug discovery and this new method offers potential in terms of high functional group tolerance and late-stage functionalization of compounds.