Multilayer film preparation of poly(4-vinylphenol) from aqueous media

The use of weak polyelectrolytes in multilayer polymer systems provides a means of altering the physico-chemical properties of these thin films. This paper examines the limits of the polyanions by incorporating the extremely weak polyelectrolyte, poly(4-vinylphenol) (PVPh), into a multilayer system with poly(allylamine hydrochloride) (PAH) from a dilute aqueous media. Film growth was monitored using absorption spectroscopy and revealed a clear linear trend in film thickness. The surface morphology, thickness, and swelling of the multilayer films systems were examined using atomic force microscopy (AFM). Film thickness greatly depended upon the pH of the polymer precursor solutions; 50-layer systems created at pH 12.5 and 11.0 were 8.2 and 246.6 nm thick, respectively, a difference of over 2900%. This is the first report on the incorporation of PVPh into a multilayer system from an aqueous media.     

Multi-criteria Decision Analysis (MCDA) for Integrated Water Resources Management (IWRM) in the Lake Poopo Basin, Bolivia

Integrated Water Resources Management (IWRM) is a relatively new approach in Bolivia. However, it is now generally accepted that this approach needs to be established in order to find sustainable solutions for development and is actively promoted by the Water Ministry, especially in environmentally fragile regions, such as the Lake Poopo basin. The Lake Poopo basin is one of the poorest regions in the Bolivian Altiplano. It is confronted with severe water scarcity during the dry season, leading to low water quality, a high water-poverty index and low values of the watershed sustainability index. Furthermore, salinization and environmental degradation of soil and water are forcing people to migrate to urban areas. These are some of the factors underlying an ever-increasing complexity in integrated water resources management in the region. This paper proposes and develops a Multi-criteria Decision Analysis (MCDA) in the Lake Poopo basin, based on economic, social and environmental criteria in an uncertain decision environment in order to support stakeholders in managing their water resources. Saaty’s analytical hierarchy process (AHP) theory is applied here to solve the MCDA and to identify the alternatives using the highest expected utility value. The paper identifies the best solutions for existing conflicts, while promoting interaction with stakeholders and instruments in order to reach a sustainable strategy for water resources management in this water-scarce region.     

A field survey of metal binding to metallothionein and other cytosolic ligands in liver of eels using an on-line isotope dilution method in combination with size exclusion (SE) high pressure liquid chromatography (HPLC) coupled to Inductively Coupled Plasma time-of-flight Mass Spectrometry (ICP-TOFMS)

The effect of metal exposure on the accumulation and cytosolic speciation of metals in livers of wild populations of European eel with special emphasis on metallothioneins (MT) was studied. Four sampling sites in Flanders showing different degrees of heavy metal contamination were selected for this purpose. An on-line isotope dilution method in combination with size exclusion (SE) high pressure liquid chromatography (HPLC) coupled to Inductively Coupled Plasma time-of-flight Mass Spectrometry (ICP-TOFMS) was used to study the cytosolic speciation of the metals. The distribution of the metals Cd, Cu, Ni, Pb and Zn among cytosolic fractions displayed strong differences. The cytosolic concentration of Cd, Ni and Pb increased proportionally with the total liver levels. However, the cytosolic concentrations of Cu and Zn only increased above a certain liver tissue threshold level. Cd, Cu and Zn, but not Pb and Ni, were largely associated with the MT pool in correspondence with the environmental exposure and liver tissue concentrations. Most of the Pb and Ni and a considerable fraction of Cu and Zn, but not Cd, were associated to High Molecular Weight (HMW) fractions. The relative importance of the Cu and Zn in the HMW fraction decreased with increasing contamination levels while the MT pool became progressively more important. The close relationship between the cytosolic metal load and the total MT levels or the metals bound on the MT pool indicates that the metals, rather than other stress factors, are the major factor determining MT induction.     

Pulsed Nd:YAG laser cutting of NiTi shape memory alloys—Influence of process parameters

Shape memory alloys (SMAs), in particular Nitinol (NiTi), are of increasing interest in research and industry due to their outstanding properties, e.g. the shape memory effect (SME) and high biocompatibility. Obviously, it is necessary to machine these elements from NiTi sheet materials using suitable processing methods that provide high precision and retain the shape memory effect. Pulsed Nd:YAG laser cutting of 1 mm thick NiTi shape memory alloys for medical applications (SMA-implants) has been investigated. Due to the local energy input only small heat-affected zones (HAZ) occur and the shape memory properties remain. The influence of key parameters like pulse energy, pulse width, and spot overlap on the cut geometry, roughness and HAZ is shown.     

Analyzing course configurations for teaching object-oriented modeling and design

This paper presents and analyzes an object-oriented analysis and design course that has been given in three different configurations for students who are already familiar with object-oriented programming. The results show that the course configurations have not had a major impact on the students' performances.     

Prediction of tablet velocity in pan coaters for scale-up

The purpose of this study was to investigate the influence of scale-up on the tablet velocity and surface time of tablets (oblong and biconvex) in the spray zone of different perforated pan coaters. A Bohle Film Coater (BFC) 5 and 10 for the laboratory scale, a BFC 40 for the pilot scale and a BFC 200 for the production scale were used. The pan speeds were scaled-up using the same peripheral speeds. The tablet velocities for 5 peripheral speeds were determined using video imaging of blue tracer tablets. An increasing pan size resulted in a higher tablet velocity and lower surface time in the spray zone for same peripheral speeds. A mathematical model in the literature was proved to predict the tablet velocities in scale-up in the BFCs. The tablet velocities in the pilot or production scale can be predicted based on the measured tablet velocities in the laboratory scale. Furthermore, depending on the pan size, the increase in tablet velocity (R_V-value) can be predicted for the scale-up process using BFCs. The R_V-values were validated for three pan sizes, different pan speeds and three different tablet types. The R_V-value can be used as a correction factor to calculate the scaled-up spray rate based on the same spray rate per spray width ratios.     

Laser-induced breakdown spectroscopy analysis of solids using a long-pulse (150 ns) Q-switched Nd:YAG laser

Laser-induced breakdown spectroscopy (LIBS) measurements are typically carried out using pulses (<20 ns, >50 mJ) from a flashlamp-pumped electro-optically Q-switched Nd:YAG laser (EO-laser) or excimer laser. Here we report LIBS analyses of solids using an acousto-optically Q-switched Nd:YAG laser (AO-laser) producing 150 ns pulses of lower energy (10 mJ) at repetition rates up to 6 kHz. The high repetition rate allows increased spatial or depth sampling over a given time period compared to the EO-laser. Results of AO-laser based LIBS analysis of (1) steels, (2) soils, and (3) surface stains and dusts are described. Detection limits for Cr, Cu, Mn, Ni, and Si in steel ranged from 0.11 to 0.24% using a commercial polychromator-based detection system with limits 4--30 times lower achieved using a laboratory-based detection system. The minimum detectable masses of Ba, Cr, Mn, and Sr on a metal surface were estimated with 1.2 pg/shot achieved for Sr. Detection limits for Ba and Sr in soil were 296 and 52 ppm, respectively. The temperatures, spectra, and emission decay curves from plasmas generated by the AO- and EO-lasers are compared and some characteristics of particles ablated by the AO-laser are described.     

High accumulation of perfluorooctane sulfonate (PFOS) in marine tucuxi dolphins (Sotalia guianensis) from the Brazilian coast

Perfluorooctane sulfonate (PFOS) and other perfluoroalkyl compounds (PFCs) were measured in liver samples from 29 marine tucuxi dolphins from Rio de Janeiro state (RJ), Brazil. PFC measurement combined liquid chromatography and mass spectrometry, using a CapLC system connected to a Quadrupole-LIT mass spectrometer. PFOS was the only PFC detected and it was so in all samples. PFOS concentrations (ng x g(-1) dw) of dolphins (n=23) from the highly contaminated Guanabara Bay (in RJ) varied between 43 and 2431 as well as between 76 and 427 from areas of RJ other than the quoted bay (n=6). Concentrations of three fetuses and one neonate varied between 664 and 1590. Fetus/mother ratios were calculated in two situations (2.75 and 2.62). It seems that mother-to-calf transference plays important role for relationships between PFOS and age. When a one-year-old male calf presenting 2431 ng x g(-1) dw was excluded from the test, significant correlations were observed between PFOS concentrations and both age and total length. Despite the placental transference, PFOS concentrations were not significantly lower in females than in males. PFOS levels in marine tucuxi dolphins from Guanabara Bay are among the highest detected to date in cetaceans, and this may represent a threat to the small population concerned.     

Exploration of GH94 Sequence Space for Enzyme Discovery Reveals a Novel Glucosylgalactose Phosphorylase Specificity

The substantial increase in DNA sequencing efforts has led to a rapid expansion of available sequences in glycoside hydrolase families. The ever-increasing sequence space presents considerable opportunities for the search for enzymes with novel functionalities. In this work, the sequence-function space of glycoside hydrolase family 94 (GH94) was explored in detail, using a combined approach of phylogenetic analysis and sequence similarity networks. The identification and experimental screening of unknown clusters led to the discovery of an enzyme from the soil bacterium Paenibacillus polymyxa that acts as a 4-O-β-d -glucosyl-d -galactose phosphorylase (GGalP), a specificity that has not been reported to date. Detailed characterization of GGalP revealed that its kinetic parameters were consistent with those of other known phosphorylases. Furthermore, the enzyme could be used for production of the rare disaccharides 4-O-β-d -glucosyl-d -galactose and 4-O-β-d -glucosyl-l -arabinose. Our current work highlights the power of rational sequence space exploration in the search for novel enzyme specificities, as well as the potential of phosphorylases for rare disaccharide synthesis.