A content analysis method to measure critical thinking in face-to-face and computer supported group learning

This paper gives a detailed account of the content analysis method developed at Queen's University Belfast to measure critical thinking during group learning, as used in our controlled comparisons between learning in face-to-face and computer conference seminars. From Garrison's 5 stages of critical thinking, and Henri's cognitive skills needed in CMC, we have developed two research instruments: a student questionnaire and this content analysis method. The content analysis relies on identifying, within transcripts, examples of indicators of obviously critical and obviously uncritical thinking, from which several critical thinking ratios can be calculated.

Characterisation of the Interaction of Lactate Dehydrogenase With Tween-20 Using Isothermal Titration Calorimetry, Interfacial Rheometry and Surface Tension Measurements

In this study the nature of the interaction between Tween-20 and lactate dehydrogenase (LDH) was investigated using isothermal titration calorimetry (ITC). In addition the effects of the protein and surfactant on the interfacial properties were followed with interfacial rheology and surface tension measurements in order to understand the mechanism by which the surfactant prevents protein adsorption to the air– water interface. Comparisons were made with Tween-40 and Tween-80 in order to further investigate the mechanism. ITC measurements indicated a weak, probably hydrophobic, interaction between Tween-20 and LDH. Prevention of LDH adsorption to the air–water interface by the Tween surfactants was correlated with surface energy rather than surfactant CMC. While surface pressure appears to be the main driving force for the displacement of LDH from the air–water interface by Tween-20 a solubilisation mechanism may exist for other protein molecules. More generally the results of this study highlight the value of the use of ITC and interfacial measurements in characterising the surface behaviour of mixed surfactant and protein systems.

New catanionic surfactants based on 1-alkyl-3-methylimidazolium alkylsulfonates, [C(n)H(2n+1)mim][CmH2m+1SO3]: mesomorphism and aggregation

Anionic and cationic alkyl-chain effects on the self-aggregation of both neat and aqueous solutions of 1-alkyl-3-methylimidazolium alkylsulfonate salts ([C(n)H(2n+ 1)mim][CmH2m+1SO3]; n = 8, 10 or 12; m = 1 and n = 4 or 8; m = 4 or 8) have been investigated. Some of these salts constitute a novel family of pure catanionic surfactants in aqueous solution. Examples of this class of materials are rare; they are distinct from both mixed cationic-anionic surfactants (obtained by mixing two salts) and gemini surfactants (with two or more amphiphilic groups bound by a covalent linker). Fluorescence spectroscopy and interfacial tension measurements have been used to determine critical micelle concentrations (CMCs), surface activity, and to compare the effects of the alkyl-substitution patterns in both the cation and anion on the surfactant properties of these salts. With relatively small methylsulfonate anions (n = 8, 10 and 12, m = 1), the salts behave as conventional single chain cationic surfactants, showing a decrease of the CMC upon increase of the alkyl chain length (n) in the cation. When the amphiphilic character is present in both the cation and anion (n = 4 and 8, m = 4 and 8), novel catanionic surfactants with CMC values lower than those of the corresponding cationic analogues, and which exhibited an unanticipated enhanced reduction of surface tension, were obtained. In addition, the thermotropic phase behaviour of [C(8)H(18)mim][C8H18SO3] (n = m = 8) was investigated using variable temperature X-ray scattering, polarising optical microscopy and differential scanning calorimetry; formation of a smectic liquid crystalline phase with a broad temperature range was observed.

In vitro testing of Advanced JAX (TM) Bone Void Filler System: species differences in the response of bone marrow stromal cells to beta tri-calcium phosphate and carboxymethylcellulose gel

The Advanced JAX (TM) Bone Void Filler System (AJBVFS) is a novel bone graft material manufactured by Smith and Nephew Orthopaedics Ltd. and comprises beta tri-calcium phosphate granules with carboxymethylcellulose (CMC) gel as a handling agent. This study investigated the potential, in vitro, of the AJBVFS to function as a delivery system for cell therapy to enhance healing of bone defects. The attachment of rabbit bone marrow stromal cells (rbBMSCs), human BMSCs (hBMSCs) and human bone-derived cells (hBDCs) to JAX (TM) granules and the effect of CMC gel on cell proliferation and differentiation were investigated. There were slight species differences in the number and morphology of cells attached on the JAX (TM) granules with less rbBMSC attachment than human. All cells tolerated the presence of CMC gel and a reduction in cell number was only seen after longer exposure to higher gel concentrations. Low concentrations of CMC gel enhanced proliferation, alkaline phosphatase (ALP) expression and ALP activity in human cells but had no effect on rbBMSC. This study suggests that AJBVFS is an appropriate scaffold for the delivery of osteogenic cells and the addition of CMC gel as a handling agent promotes osteogenic proliferation and differentiation and is therefore likely to encourage bone healing.

On the self-aggregation and fluorescence quenching aptitude of surfactant ionic liquids

The aggregation behavior in aqueous solution of a number of ionic liquids was investigated at ambient conditions by using three techniques: fluorescence, interfacial tension, and H-1 NMR spectroscopy. For the first time, the fluorescence quenching effect has been used for the determination of critical micelle concentrations. This study focuses on the following ionic liquids: [C(n)mpy]Cl (1-alkyl-3-methylpyridinium chlorides) with different linear alkyl chain lengths (n = 4, 10, 12, 14, 16, or 18), [C(12)mpip]Br (1-dodecyl-1-methylpiperidinium bromide), [C(12)mpy]Br (1-dodecyl-3-methylpyridinium bromide), and [C(12)mpyrr]Br (1-dodecyl-1-methylpyrrolidinium bromide). Both the influence of the alkyl side-chain length and the type of ring in the cation (head) on the CMC were investigated. A comparison of the self-aggregation behavior of ionic liquids based on 1-alkyl-3-methylpyridinium and 1-alkyl-3-methylpyridinium cations is provided. It was observed that 1-alkyl-3-methylpyridinium ionic liquids could be used as quenchers for some fluorescence probes (fluorophores). As a consequence, a simple and convenient method to probe early evidence of aggregate formation was established.

Aggregation behavior in water of new imidazolium and pyrrolidinium alkycarboxylates protic ionic liquids

A novel class of anionic surfactants was prepared through the neutralization of pyrrolidine or imidazole by alkylcarboxylic acids. The compounds, namely the pyrrolidinium alkylcarboxylates ([Pyrr][CnH2n+1COO]) and imidazolium alkylcarboxylates ([Im][CnH2n+1COO]), were obtained as ionic liquids at room temperature. Their aggregation behavior has been examined as a function of the alkyl chain length (from n = 5 to 8) by surface tensiometry and conductivity. Decreases in the critical micelle concentration (cmc) were obtained, for both studied PIL families, when increasing the anionic alkyl chain length (n). Surprisingly, a large effect of the alkyl chain length was observed on the minimum surface area per surfactant molecule (Amin) and, hence the maximum surface excess concentration (Gmax) when the counterion was the pyrrolidinium cation. This unusual comportment has been interpreted in term of a balance between van der Waals and coulombic interactions. Conductimetric measurements permit determination of the degree of ionization of the micelle (a) and the molar conductivity (?M) of these surfactants as a function of n. The molar conductivities at infinite dilution in water (?8) of the [Pyrr]+ and [Im]+ cations have been then determined by using the classical Kohlraush equation. Observed change in the physicochemical, surface, and micellar properties of these new protonic ionic liquid surfactants can be linked to the nature of the cation. By comparison with classical anionic surfactants having inorganic counterions, pyrrolidinium alkylcarboxylates and imidazolium alkylcarboxylates exhibit a higher ability to aggregate in aqueous solution, demonstrating their potential applicability as surfactant.

Textural, viscoelastic and mucoadhesive properties of pharmaceutical gels composed of cellulose polymers

This study examined the mechanical/textural, viscoeiastic and mucoadhesive properties of a range of aqueous gels composed of either hydroxyethylcellulose (HEC) or sodium carboxymethylcellulose (Na CMC). The mechanical/textural properties of each formulation were determined using texture profile analysis. The viscoelastic properties of each formulation were examined over a defined frequency range (0.01-1.0 Hz) using oscillatory rheometry in conjunction with stainless steel parallel plate geometry. The mucoadhesive properties of the gels were evaluated by measuring the tensile force required to overcome the gel/mucin adhesive interaction. Both gel hardness and compressibility, properties that affect the ease of product removal from a container and spreadability, increased as a function of increasing polymer concentrations. This is attributed to the effects of HEC and Na CMC on gel viscosity. Gel adhesiveness, a property related to bioadhesion, also increased as a function of polymer concentration and is attributed to the reported adhesive nature of these polymers. Increasing frequency of oscillation increased the storage and loss moduli yet decreased bath the dynamic viscosity of each gel type and also the loss tangent of HEC (but not Na CMC) gels. Therefore, following exposure to the range of oscillatory stresses that may be expected in vivo, HEC gels will be more susceptible than Na CMC gels to alterations in these rheological properties. Consequently, it would be expected that the clinical performance of HEC gels will be modified to a greater extent than Na CMC gels. In general, HEC gels exhibited a greater elastic nature than Na CMC gels over the frequency range employed for oscillation The storage and loss moduli and dynamic viscosity of both gel types increased, yet the loss tangent of both gel types decreased as a function of increasing polymer concentration. Gel mucoadhesive strength was dependent on both the time of contact of the formulation with mucin and also on polymer concentration. In conclusion, this study has characterised a number of gels containing either HEC or Na CMC in terms of their mechanical/textural, viscoelastic and mucoadhesive properties. Due to its relevance to the clinical performance, it is suggested that the information derived from these methods may be usefully combined to provide a more rational basis for the selection of polymers and their formulation as topical drug delivery systems. (C) 1997 Elsevier Science B.V.