Naphthalene oxidation over vanadium-modified Pt catalysts supported on γ-Al2O3

Alumina-supported platinum catalysts modified by vanadium were synthesised and tested for the complete oxidation of naphthalene. The catalysts were characterised by BET, pulsed CO chemisorption, powder X-ray diffraction, laser Raman spectroscopy and temperature-programmed reduction. Whilst BET and CO chemisorption results showed that the addition of vanadium modified both the textural properties of the support and the distribution of Pt, XRD and TPR data suggested the presence of V₂O₅ on catalysts with higher V loadings. TPR data showed that the concentration of V₂O₅ and possibly some other vanadium species increased as the V loading increased. Only 0.5%V was found to promote the activity of the 0.5%Pt/γ-Al₂O₃ catalyst. The activity enhancement has been related to the presence of a more easily reducible vanadium species coupled with the enhanced number of surface Pt sites. On the other hand, the reduced activity demonstrated by catalysts with higher vanadium content (1 – 12%) has been attributed to the presence of crystalline V₂O₅.     

Flexible lock-in detection system based on synchronized computer plug-in boards applied in sensitive gas spectroscopy

We present a flexible and compact, digital, lock-in detection system and its use in high-resolution tunable diode laser spectroscopy. The system involves coherent sampling, and is based on the synchronization of two data acquisition cards running on a single standard computer. A software-controlled arbitrary waveform generator is used for laser modulation, and a four-channel analog/digital board records detector signals. Gas spectroscopy is performed in the wavelength modulation regime. The coherently detected signal is averaged a selected number of times before it is stored or analyzed by software-based, lock-in techniques. Multiple harmonics of the modulation signal (1f, 2f, 3f, 4f, etc.) are available in each single data set. The sensitivity is of the order of 10(-5), being limited by interference fringes in the measurement setup. The capabilities of the system are demonstrated by measurements of molecular oxygen in ambient air, as well as dispersed gas in scattering materials, such as plants and human tissue.     

Equilibrium approaches to natural water systems—6. Acid-base properties of a concentrated bog-water and its complexation reactions with aluminium(III)

A filtered bog-water, concentrated by means of a freezing technique, has been studied with respect to acid-base properties and aluminium(III) complexation reactions. Sampling was performed during autumn and winter periods with a resulting acidity or alkalinity due to oxic (autumn) or anoxic (winter) conditions. The measurements were performed as potentiometric titrations in constant ionic media (0.02, 0.1 and 0.6 M NaCl) with the use of a glass electrode. The samples show buffer ranges at 3 pH 5 and pH 7.5. The first is ascribed to the presence of carboxylate groups and is characterized by fast equilibria. The second is due to phenolic OH⁻ groups and precipitation reactions with resulting sluggish equilibria. For one sampling period comprehensive measurements were undertaken to study the possible polyelectrolytic character of the organic acids. Due to the small increase in apparent carboxylate pKa-values with the degree of dissociation at low (0.02 M) as well as at high (0.6 M) ionic strength, the possible polyelectrolytic feature of the acids was neglected. Instead, a good fit to data was obtained by introducing a di-protic acid (H₂L) as a model compound. Furthermore the medium dependence of the two acidity constants could satisfactorily be fitted to the expression:

Full-size image (1K)

, where K is the constant at infinite dilution, a and b parameters of which b has been adjusted to present data. The following K values were obtained: pK₁ = 3.65 and pK₂ = 4.30. The complexation with Al(III) could be described by the formation of AlL⁺, AlL₂⁻ and the ternary species AlLH₋₁. The stability constants (log k₁ = 4.4 (winter), 4.2 (autumn); log k₂ = 4.2, 4.7; pKa (AlL⁺) = 4.2, 4.2) show no significant trend with sampling period but indicate a stability of the complexes greater than for phtalic acid but lower than for oxalic acid. Finally, the theoretical solubility of the clay mineral kaolinite in the presence of bog-water was computer modelled. The calculations show up on a 10-fold increase with respect to soluble aluminium at pH = 5.     

Building a new supply chain position: an exploratory study of companies in the timber housing industry

Innovation is an important source of growth for many companies. It is also challenging, as it may require that the companies build a new position in the supply chain. The literature is devoid of analysis of different ways to build such positions in the construction industry. The purpose here is to explore the challenges involved in implementing innovations that require companies to establish new positions in a construction supply chain. Three in‐depth case studies in the Swedish timber housing industry illustrate different challenges that arise with the different modes of repositioning of organic growth, collaboration and acquisition, and with moving either backward or forward in the supply chain. Organic growth is a slow process that prevents companies from taking a first‐mover advantage. Acquisitions can involve difficulties with exploiting acquired competences. Collaboration brings the risks of diversity of interests and transient solutions. Furthermore, and as shown in the cases studied, challenges are associated with pre‐existing competencies and relationships, with technology‐oriented companies facing customer‐related difficulties and market‐oriented companies mainly facing ones involving technological solutions. The construction industry’s idiosyncrasies amplify these challenges, as its fragmentation makes it difficult to connect with external companies at new positions. Stronger ties with business partners are likely to enable construction companies to exploit more easily innovations that require repositioning in the supply chain.     

Application of DEM to evaluate and compare process parameters for a particle failure under different loading conditions

The paper presents an application of Discrete Element Modelling (DEM) in understanding the micro-process parameters of a particle failure under different loading conditions. A composite particle has been modelled using many primary particles to represent a quasi-homogeneous particle. Some of the examples of quasi-homogeneous particles are constituents of tablets, pellets, granules and concrete. These particles can behave differently under identical loading conditions even though they consist of same primary particles and proportions. This is a typical behaviour of such particles which is governed by the imperfections present in the particles. A DEM has been used to model the composite particle consisting of bi-modal distribution (smaller particles—matrices and larger particles—aggregates) of primary particles. The particle has been loaded under single plate compression, double plate compression and normal impact on different types of target. The single plate compression and normal impact experiments have also been performed. Process parameters like, fracture pattern, particle size distribution, liberation degree and new surface generation have been evaluated and compared. The results are applicable in understanding the particle failure under different processing operations like, transportation, handling and comminution. The results are also useful in selecting the better loading method for liberating aggregates from cheaper matrices for recycling.     

Hierarchical classifier: Based on neural networks searching tree with iterative traversal and stop criterion

The paper offers an algorithm that extends the binary tree search algorithm so that it can deal with distorted input vectors. Perceptrons are the tree nodes. The algorithm features an iterative solution search and stopping criterion.     

The Effects of Cryogenic Storage on Human Dental Pulp Stem Cells

Dental pulp stem cells (DPSCs) are a type of easily accessible adult mesenchymal stem cell. Due to their ease of access, DPSCs show great promise in regenerative medicine. However, the tooth extractions from which DPSCs can be obtained are usually performed at a period of life when donors would have no therapeutic need of them. For this reason, it is imperative that successful stem cell storage techniques are employed so that these cells remain viable for future use. Any such techniques must result in high post-thaw stem cell recovery without compromising stemness, proliferation, or multipotency. Uncontrolled-rate freezing is not a technically or financially demanding technique compared to expensive and laborious controlled-rate freezing techniques. This study was aimed at observing the effect of uncontrolled-rate freezing on DPSCs stored for 6 and 12 months. Dimethyl sulfoxide at a concentration of 10% was used as a cryoprotective agent. Various features such as shape, proliferation capacity, phenotype, and multipotency were studied after DPSC thawing. The DPSCs did not compromise their stemness, viability, proliferation, or differentiating capabilities, even after one year of cryopreservation at −80 °C. After thawing, they retained their stemness markers and low-level expression of hematopoietic markers. We observed a size reduction in recovery DPSCs after one year of storage. This observation indicates that DPSCs can be successfully used in potential clinical applications, even after a year of uncontrolled cryopreservation.