Olefin epoxidation with metal-based nanocatalysts

Alkene epoxidations are an important class of reactions carried out in industry; however, current methods are plagued by problems, including high cost, difficulty in recovering catalysts, and generation of large quantities of acidic and chlorinated waste. In recent years, nanocatalysts have been considered as robust, heterogeneous alternatives to homogeneous catalysts. This work evaluates silver- and base metal-containing nanocatalysts as olefin epoxidation catalysts, highlighting the industrial applicability and green aspects of these catalytic systems. The nanocatalysts discussed are mostly supported or composite materials that showed (generally) good activity and selectivity for various/multiple olefin epoxidation reactions.     

Current Immunoassay Methods for the Rapid Detection of Aflatoxin in Milk and Dairy Products

The presence of mycotoxins in foodstuff causes serious health problems to consumers and economically affects the food industry. Among the mycotoxins, aflatoxins are very toxic and highly carcinogenic contaminants which affect the safety of many foods, and therefore endanger human health. Aflatoxin M₁ (AFM₁) found in milk results from the biotransformation of aflatoxin B₁. Many efforts have been made to control the source of AFM₁ from farmers to dairy product companies. However, AFM₁ escapes ordinary methods of food treatment such as cooking, sterilization, and freezing, hence it appears in milk and dairy products. The presence of high levels of AFM₁ constitutes an alarming threat as milk and dairy products contain essential nutrients for human health, especially for infants and children. For this reason, there is a pressing need for developing a fast and reliable screening method for detecting trace aflatoxins in food. Several analytical methods based on high‐performance liquid chromatography (HPLC) and mass spectroscopy have been used for aflatoxin detection; however, they are expensive, time‐consuming, and require many skills. Recently, immunoassay methods, including enzyme‐linked immunosorbent assay (ELISA), immunosensors, and lateral flow immunoassay (LFIA), have been preferred for food analysis because of their improved qualities such as high sensitivity, simplicity, and capability of onsite monitoring. This paper reviews the new developments and applications of immunoassays for the rapid detection of AFM₁ in milk.     

Right-handers and Americans favor turning to the right

We tested a finding by E. S. Robinson (1933) that people have a bias to turn right upon entering a building. We hypothesized that this bias is attributable to learning derived from traffic rules that specify driving on the right side of the road and that it also could be related to handedness. We tested participants in both the United States and England in a simple "T-maze" task in order to compare their directional preference. Handedness was the best predictor of participants' directional preference. However, U.S. participants also were statistically more likely to turn right than were English participants. The preference to turn right was not found to be significantly related to eye dominance or reading direction of the primary written language of the participant, although in the case of reading direction, the sample size of right-to-left readers was too small to be conclusive. The findings support that walking direction preference is an additive function of both learned driving patterns and genetic handedness. These findings have practical implications for the design of public spaces such as schools, businesses, and urban centers.     

Glucose Biosensor Based on a Glassy Carbon Electrode Modified with Multi-Walled Carbon Nanotubes-Chitosan for the Determination of Beef Freshness

In this study, the glucose biosensor was developed for the determination of the beef meat freshness based on a glassy carbon electrode (GCE) modified with multi-walled carbon nanotubes (MWCNTs) and chitosan (Chi). Glucose oxidase (GOx) was immobilized onto the MWCNTs-Chi/GCE surface by cross-linking the enzyme through glutaraldehyde with bovine serum albumin (BSA). Glutaraldehyde solution (0.25%, w/w) was also added to prevent enzyme release. The properties of the developed biosensor were characterized with cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) using [Fe (CN)₆]^3?/4?as the supporting electrolyte. The influence of various parameters was investigated, and 0.1 mol L^?1 PBS with pH = 6.4 was chosen as the optimal supporting electrolyte for this experiment. The linear relationship between the current and the concentration of glucose was obtained from 0.2 to 1.2 mmol L^?1, with a detection limit of 0.05 mM at a signal-to-noise ratio of 3 and displayed good linearity (R ² = 0.9902), while the biosensor showed a rapid response to glucose. In addition, the developed glucose biosensor was applied in the determination of glucose in beef as an indicator of beef freshness compared to the total volatile basic nitrogen (TVB-N) method. The glucose level was decreased with increasing beef storage time.     

A simulation of the temperature distribution in the SPIRAL target

We developed a model and a computer program to calculate the temperature distribution in the target which will be used in the SPIRAL project a GANIL. The results of the numerical simulation are compared with measurements performed with several types of targets.     

Non-contact,nondestructive hydrogen and microstructural assessment of steel welds

Nondestructive low-frequency impedance has been developed to determine hydrogen content in operating pipeline steel and weldments through a structural coating. A low frequency impedance measurement is similar to a resistivity measurement with a depth function due to the sensor coil reactance. Resistivity introduces variability in impedance measurements because resistivity is a function of the conductivity of the material, the depth of the measurement, and the alloy content. The conductivity, based on the free electron model, is a function of the electronic effective mass, the electron concentration, and the dominating scattering mechanisms, which is altered by such factors as inclusions, microstructure, temperature, and strain. Each of these variables must be separated out to obtain a hydrogen content measurement in operating pipelines (with a structural coating) using low frequency impedance. Techniques used to separate out the variables associated with operating pipeline steels are presented. The use of real-time low frequency impedance measurements to monitor hydrogen content as it diffuses out of a steel weldment is presented and discussed.     

Direct evidence of sequestration in sediments affecting the bioavailability of hydrophobic organic chemicals to benthic deposit-feeders

In contrast to equilibrium partitioning model (EqP) calculations, biota to sediment accumulation factors (BSAF) of hydrophobic organic compounds for deposit-feeders are highly variable. Recent literature suggests that this variability can be attributed to differences in sequestration or the presence of slowly desorbing fractions in the sediment. In the present study, we investigated whether the observed relationship between bioavailability and sequestration is causal. We determined BSAF values and sequestration status, measured as the distribution over rapidly and slowly desorbing fractions, of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) in a manipulated sediment as well as in the original, unmanipulated sediment The manipulation, 48 h suspending with Tenax, resulted in reduction of the rapidly desorbing fraction, while other factors such as contact time and sediment properties remained constant. Contrary to expectations based on EqP, BSAF values did not remain constant but were reduced by a factor of 2-27, proportional to the reduction in rapidly desorbing fractions. The results provide direct evidence of a causal relationship between sequestration and bioavailability to deposit-feeders. Furthermore, the present study demonstrates the need to modify traditional use of the equilibrium partitioning model to account for variation in the sequestration status of HOC in sediments.     

Measured pore-water concentrations make equilibrium partitioning work--a data analysis

There is an increasing body of evidence that the bioaccumulation of sediment-associated hydrophobic organic compounds (HOCs) is strongly influenced by sequestration. At present, it is not known how equilibrium partitioning theory (EqP), the most commonly employed approach for describing sediment bioaccumulation can be applied to sediments with sequestered contaminants. In this paper, we present freely dissolved pore-water concentrations of HOCs. These data were employed to interpret sediment bioaccumulation and sequestration data in order to arrive at a process based evaluation of EqP. The data analysis suggests that sediment bioaccumulation of compounds up to log K(ow) 7.5 in Tubificidae can be described as bioconcentration from pore-water. In addition, the pore-water concentrations of HOCs (4.5 < log K(ow) < 7.5) are established by equilibrium partitioning between the rapidly desorbing HOCs fraction in the sediment and the pore-water. Taken together, these findings indicate that EqP is a conceptually correct representation of sediment bioaccumulation, provided that sequestration is accounted for. This implies that the risk assessment of sediment-associated HOCs can be significantly simplified: With a method at hand for measuring freely dissolved pore-water concentrations of HOCs, it appears that HOCs' body residues in sediment dwelling organisms can be estimated on the basis of concentrations in pore-water and bioconcentration factors.