Technology as small group face-to-face Collaborative Scaffolding

There is a wealth of evidence that collaboration between learners can enhance the outcomes for all concerned. This supports the theorization of learning as a socio-cultural practice, framed by Vygotsky and developed by other researchers such as Rogoff, Lave and Wenger. However, there is also evidence that working collaboratively may not be a spontaneous response to working in a group, and that teaching learners how to collaborate, and in particular how to work together to negotiate meaning, is a necessary part of the process of learning collaboratively which can enhance outcomes further. A question for the computer supported collaborative learning community then arises as to whether learning to collaborate can be scaffolded through the use of digital tools, and what such tools might look like. This paper reports on the design of a digital system that aims to support the practice of face-to-face collaboration on open-ended tasks. Findings from trials of the system in classrooms in the UK and Chile show that the model is welcomed both by teachers and pupils, and met its objectives of ensuring greater interaction between class members who did not normally work together, and involvement of all individuals in discussion based activities.     

Use of Poultry Byproduct for Production of Keratinolytic Enzymes

The production of keratinolytic enzymes by Chryseobacterium sp. isolated from the poultry industry was tested on different growth substrates: casein, peptone, yeast extract, gelatin, soybean meal, fish meal, feather meal, raw feathers, and cheese whey. Raw feather, an important byproduct from the poultry industry, was the selected growth substrate to test the effect of three variables (temperature, initial pH, and feather concentration) on keratinase production by response surface methodology. A 2³ central composite design was performed with the central point chosen as: temperature 30 °C, initial pH 8.0, and feather concentration 20 g l⁻¹. Statistical analysis of results showed that, in the range studied, temperature had a strong effect on keratinase production. The interaction between temperature and feather concentration and between temperature and initial pH had a significant effect on enzyme production. Response surface data showed maximum keratinase production at 23 °C, initial pH 9.0, and 30 g l⁻¹ of raw feathers. Under these conditions, the model predicted a keratinase activity of 1,559 U ml⁻¹.     

A novel potentiometric sensor for l-ascorbic acid based on molecularly imprinted polypyrrole

A polymeric membrane-based ion-selective electrode (ISE) for the determination of l-ascorbic acid (l-AA) was developed. The sensor was fabricated by modifying glassy carbon electrodes with molecularly imprinted polypyrrole (PPy) synthesized by electropolymerization of the monomer in the presence of ascorbate. A comparison between the non-imprinted modified electrode (PPy-NIP) and the molecularly imprinted polymer (PPy-MIP) is reported. The molecularly imprinted polymer improves the performances of the sensor, especially if the PPy film has been submitted to an oxidation treatment. The PPy-MIPox electrode shows near-Nernstian response (approx. −57 mV/decade) to the ascorbate over the concentration range between 5 × 10⁻⁶ M and 2 × 10⁻³ M and it can be used for more than 3 weeks without any considerable change in the measured response. The potentiometric sensor has been successfully applied to the determination of ascorbate in food and pharmaceutical samples (recoveries of about 100%).     

Electrochemical synthesis and characterization of poly[3-(ω-bromoalkyl)thiophene]s

A novel series of functionalized polythiophenes incorporating 3-(ω-bromoalkyl) pendants are synthesized by electrochemical polymerization. The effect of the solvent on the electrosynthesis is investigated. The polymeric films are characterized using cyclic voltammetry, FT-IR, AFM and SEM microscopy. The poly[3-(6-bromohexyl)thiophene] film cast on GC or ITO electrode surface is compared with a sample obtained by a chemical method.     

6th San Luis Conference on Surfaces,Interfaces and Catalysis

Topics in Catalysis -     

Kinetic and thermodynamic study of thermal inactivation of the antimicrobial peptide P34 in milk

The knowledge on thermal inactivation of biopreservatives in a food matrix is essential to allow their proper utilisation in food industry, enabling the reduction of heating times and optimisation of heating temperatures. In this work, thermal inactivation of the antimicrobial peptide P34 in skimmed and fat milk was kinetically investigated within the temperature range of 90–120 °C. The inactivation kinetic follows a first-order reaction with k-values between 0.071 and 0.007 min⁻¹ in skimmed milk, and 0.1346 and 0.0119 min⁻¹ in fat milk. At high temperatures, peptide P34 was less resistant in fat milk, with a significant decrease in residual activity as compared with skimmed milk. At temperatures below 110 °C, the fat globules seem to have protective effect to the peptide P34. Results suggest that peptide P34 is heat stable in milk with activation energy of 90 kJ mol⁻¹ in skimmed milk and 136 kJ mol⁻¹ in fat milk.     

Influence of ligand structure and water interactions on the physical properties of β-cyclodextrins complexes

The water sorption and physical properties of freeze-dried β-cyclodextrin (BCD) and 2-hydroxypropyl-β-cyclodextrin (HBCD) were studied. The stability of the inclusion complexes of these cyclodextrins with different hydrophobic ingredients, such as myristic acid and α-terpineol, was investigated as a function of the storage time and water content of the systems. Besides increasing its solubility, BCD ring modification with hydroxypropyl groups conferred amorficity to the dehydrated matrices, and modified the sorption properties and their ability to form hydrates.     

Transcriptional Analysis of C-Repeat Binding Factors in Fruit of Citrus Species with Differential Sensitivity to Chilling Injury during Postharvest Storage

Citrus fruit are sensitive to chilling injury (CI) during cold storage, a peel disorder that causes economic losses. C-repeat binding factors (CBFs) are related to cold acclimation and tolerance in different plants. To explore the role of Citrus CBFs in fruit response to cold, an in silico study was performed, revealing three genes (CBF1, CBF2, and CBF3) whose expression in CI sensitive and tolerant cultivars was followed. Major changes occurred at the early stages of cold exposure (1–5 d). Interestingly, CBF1 was the most stimulated gene in the peel of CI-tolerant cultivars (Lisbon lemon, Star Ruby grapefruit, and Navelina orange), remaining unaltered in sensitive cultivars (Meyer lemon, Marsh grapefruit, and Salustiana orange). Results suggest a positive association of CBF1 expression with cold tolerance in Citrus cultivars (except for mandarins), whereas the expression of CBF2 or CBF3 genes did not reveal a clear relationship with the susceptibility to CI. Light avoidance during fruit growth reduced postharvest CI in most sensitive cultivars, associated with a rapid and transient enhance in the expression of the three CBFs. Results suggest that CBFs-dependent pathways mediate at least part of the cold tolerance responses in sensitive Citrus, indicating that CBF1 participates in the natural tolerance to CI.