Nitrate intake from drinking water on Tenerife island (Spain)

Although meat and vegetable products contain higher concentrations of nitrate, drinking water is the fastest and most direct form of nitrate consumption by the population. It becomes contaminated with nitrates when sea water infiltrates fresh water aquifers and when rain and irrigation water wash through soils that have been excessively treated with nitrated fertilizers. Nitrates are of great toxicological interest as they are involved in the origin of nitrites and nitrosamines and the development of metahaemoglobinaemia in infants. The objective of this study was to determine the quantities of NO(3)(-) in the water supply of each of the Island's municipalities and in the leading brands of bottled waters consumed by the population of Tenerife. This parameter is necessary for the determination of Acceptable Daily Intake (A.D.I.) of nitrates from drinking water. With one unremarkable exception, the nitrate levels found in the water analyzed were optimum for human consumption and amply complied with current European Legislation.     

Functional Chromatography Reveals Three Natural Products that Target the Same Protein with Distinct Mechanisms of Action

Access to lead compounds with defined molecular targets continues to be a barrier to the translation of natural product resources. As a solution, we developed a system that uses discrete, recombinant proteins as the vehicles for natural product isolation. Here, we describe the use of this functional chromatographic method to identify natural products that bind to the AAA+ chaperone, p97, a promising cancer target. Application of this method to a panel of fungal and plant extracts identified rheoemodin, 1‐hydroxydehydroherbarin, and phomapyrrolidone A as distinct p97 modulators. Excitingly, each of these molecules displayed a unique mechanism of p97 modulation. This discovery provides strong support for the application of functional chromatography to the discovery of protein modulators that would likely escape traditional high‐throughput or phenotypic screening platforms.     

Synthesis of new silicas with high stable and large mesopores and macropores for biocatalysis applications

Monomodal or bimodal porous silicas with large mesopores, constituted by particles or having a monolithic (block type) morphology, respectively, are synthesized using sodium silicate as siliceous species source, cetyltrimethylammonium bromide (CTAB) as pore template and ethyl acetate (EtAc) as pH modifier. The monomodal porosity is represented by 20–30 nm pores and the bimodal one by these pores and also macropores. These characteristics are modulated in function of the CTAB and EtAc concentrations as well as the pH and hydrothermal treatment. The role of these reagents upon the porosity is rationalized. The presence of high CTAB concentration and a rather low pH decreasing rate (function of EtAc concentration and hydrothermal treatment) are essential for having the already known bimodal mesoporous silicas (BMS). On the contrary a rather high pH decreasing rate promotes the formation of the new bimodal mesoporous–macroporous silicas (BMMS) synthesized in this work, where the EtAc also plays the role of emulsion forming agent. The hydrolytic stability of the synthesized silica under aqueous conditions, at different pH values, makes these silicas good candidates for application in different areas of catalysis, especially in the enzymatic one.     

Study of electrical properties of CIGS thin films prepared by multistage processes

In this work, the dispersion mechanisms affecting the electric transport in CuIn_1−xGa_xSe₂ (CIGS) thin films grown by a chemical reaction of the precursor species, which are evaporated sequentially in two and three-stage processes are analyzed. It was found, through conductivity and Hall coefficient measurements carried out as functions of temperature, that the electrical conductivity of the CuIn_1−xGa_xSe₂ films is affected by the transport of free carriers in extended states of the conduction band as well as for variable range hopping transport mechanisms, each one predominating in a different temperature range.     

Lower bounds on the rotation distance of binary trees

The rotation distanced(S,T) between two binary trees S, T of n vertices is the minimum number of rotations to transform S into T. While it is known that d(S,T)?2n−6, a well-known conjecture states that there are trees for which this bound is sharp for any value of n?11. We are unable to prove the conjecture, but we give here some simple criteria for lower bound evaluation, leading for example to individuate some “regular” tree structures for which d(S,T)=3n/2−O(1), or d(S,T)=5n/3−O(1).     

Effect of substitution of Sn for Bi on structural and electrical transport properties of SnS thin films

In this work, results are reported concerning the effect of the Bi concentration on the structural and electrical transport properties of SnS thin films, grown through a chemical reaction of the metallic precursors with elemental sulfur (sulfurization) in a two-stage process. XRD measurements revealed that the samples deposited by sulfurization of Sn or Bi grow in the SnS and Bi₂S₃ phases, respectively, whereas those obtained by sulfurization of a Sn:Bi alloy grow with a mixture of several phases. Special emphasis was placed on studying through σ versus T measurements, the effect of the Bi concentration on the transport properties of SnS:Bi films. To identify the dominant transport mechanisms, the σ versus T curves were analyzed in two different temperature ranges. It was also found that in the range of temperatures greater than 300 K, the conductivity is predominantly affected by transport of free carriers in extended states of the conduction band, whereas in the range of temperatures below 250 K, the conductivity is dominated by the VRH (variable range hopping) transport mechanism.     

Optical absorption and selective thermal emission in directionally solidified Al2O3-Er3Al5O12 and Al2O3-Er3Al5O12-ZrO2 eutectics

Al₂O₃-Er₃Al₅O₁₂ and Al₂O₃-Er₃Al₅O₁₂-ZrO₂ eutectic ceramic rods were directionally solidified using the laser floating zone technique at several growth rates. Binary eutectic microstructure consisted in a three-dimensional interpenetrated network of the eutectic phases whereas the ternary eutectic showed a geometrical microstructure at low growth rates and a nanofibrillar pattern at high rates. The microstructure size was strongly dependent on the growth rate, decreasing when the processing rate increased. The optical absorption was measured in the samples at room temperature and Judd–Ofelt analysis was used to model the optical absorption of the Er³⁺ ions. Thermal emission of the eutectic rods was studied at temperatures up to 1600 °C. An intense narrow emission band at 1.55 μm matching with the sensitive region of the GaSb photoconverter was obtained. The intensity of the selective emission band is larger for the binary eutectic than for the ternary compound and increases as the microstructural size decreases.     

Measuring the Impact of an Individual Course on Students' Success

Background At the University of Michigan, qualified first‐year students who place out of the first‐semester calculus course may enroll in either the regular second‐semester calculus course or Applied Honors Calculus II. Students who enroll in Applied Honors Calculus II show higher academic performance than students enrolling in the Regular Calculus II. Purpose (Hypothesis ) The study addressed the question: does enrollment in Applied Honors Calculus II have a positive causal impact on subsequent academic performance for engineering students at the University of Michigan? Design /Method We acquired seven years of institutional data for engineering students who entered the University of Michigan from 1996 through 2003 and who qualified to enroll in Applied Honors Calculus II. Using regression analyses, we tested a causal model of impact of Applied Honors Calculus II on four measures of subsequent academic performance: grade in Physics II and average grade in all subsequent physics, mathematics, and engineering courses. Results After controlling for students' personal characteristics and prior academic achievement, the impact of Applied Honors Calculus II on students' academic performance was not statistically significant. In particular Advanced Placement scores accounted for the higher performance observed in Applied Honors Calculus II students. Conclusions We recommend including Advanced Placement scores in models that predict academic performance. Future research should also include measures of socioeconomic status (SES) and explore interactions between SES and academic background. Finally, in evaluations of specific curricula, the treatment effect—measured as treatment group mean minus control group mean, after controlling for covariates—is unlikely to be large if the control group receives high quality instruction.     

Biomass briquetting and its perspectives in Brazil

A study of the status of biomass briquetting and its perspectives in Brazil was conducted including determination of the availability and characteristics of the agro-residues for briquetting. Wood residues, rice husk and coffee husk were characterized and identified as the more promising agro-residues for briquetting in the short-term in Brazil. A survey was carried out in order to determine the number of briquetting factories in Brazil, and also to determine: used briquetting technologies, briquettes production, briquettes sale prices, the status of biomass briquetting market and its future perspectives.