Co-melt fluidised bed granulation of pharmaceutical powders: Improvements in drug bioavailability

This study investigates the use of co-melt fluidised bed granulation for the agglomeration of model pharmaceutical powders, namely, lactose mono-hydrate, PEG 10000, poly-vinyl pyrolidone and ibuprofen as a model drug. Granulation within the co-melt system was found to follow a nucleationâ??steady growthâ??coating regime profile. Using high molecular weight PEG binder, the granulation mechanism and thus the extent of granulation was found to be significantly influenced by binder viscosity. The compression properties of the granulate within the hot fluidised bed were correlated using a novel high temperature experimental procedure. It was found that the fracture stress and fractural modulus of the materials under hot processing conditions were orders of magnitude lower than those measured under ambient conditions. A range of particle velocities within the granulator were considered based on theoretical models. After an initial period of nucleation, the Stokes deformation number analysis indicated that only velocities within the high shear region of the fluidised bed were sufficient to promote significant granule deformation and therefore, coalescence. The data also indicated that larger granules de-fluidised preventing agglomeration by coalescence. Furthermore, experimental data indicated that dissipation of the viscous molten binder to the surface was the most important factor in the latter stages of the granulation process. From a pharmaceutical perspective the inclusion of the model drug, ibuprofen, combined with PVP in the co-melt process proved to be highly significant. It was found that using DSC analysis on the formulations that the decrease in the heat of fusion associated with the melting of ibuprofen within the FHMG systems may be attributed to interaction between PVP and ibuprofen through inter-molecular hydrogen bonding. This interaction decreases the crystallinity of ibuprofen and facilitates solubilisation and bioavailability within the solid matrix.

Real time monitoring of the polymerisation of PMMA bone cement using Raman spectroscopy

In this investigation Raman spectroscopy was shown to be a method that could be used to monitor the polymerisation of PMMA bone cement. Presently there is no objective method that orthopaedic surgeons can use to quantify the curing process of cement during surgery. Raman spectroscopy is a non-invasive, non-destructive technique that could offer such an option. Two commercially available bone cements (Palacos® R and SmartSet® HV) and different storage conditions (4 and 22°C) were used to validate the technique. Raman spectroscopy was found to be repeatable across all conditions with the completion of the polymerisation process particularly easy to establish. All tests were benchmarked against current temperature monitoring methods outlined in ISO and ASTM standards. There was found to be close agreement with the standard methods and the Raman spectroscopy used in this study.

Raman spectroscopic studies of the cure of dicyclopentadiene (DCPD)

The cure of polydicyclopentadiene conducted by ring-opening metathesis polymerisation in the presence of a Grubbs catalyst was studied using non-invasive Raman spectroscopy. The spectra of the monomer precursor and polymerised product were fully characterised and all stages of polymerisation monitored. Because of the monomer's high reactivity, the cure process is adaptable to reaction injection moulding and reactive rotational moulding. The viscosity of the dicyclopentadiene undergoes a rapid change at the beginning of the polymerisation process and it is critical that the induction time of the viscosity increase is determined and controlled for successful manufacturing. The results from this work show non-invasive Raman spectroscopic monitoring to be an effective method for monitoring the degree of cure, paving the way for possible implementation of the technique as a method of real-time analysis for control and optimisation during reactive processing. Agreement is shown between Raman measurements and ultrasonic time of flight data acquired during the initial induction period of the curing process. (c) 2004 Elsevier B.V. All rights reserved.

Development of Disulfiram-Loaded Vaginal Rings for the Localised Treatment of Cervical Cancer

Cervical cancer is the third most prevalent cancer in women and disproportionately affects those in low resource settings due to limited programs for screening and prevention. In the developed world treatment for the disease in the non-metastasised state usually takes the form of surgical intervention and/or radiotherapy. In the developing world such techniques are less widely available. This paper describes the development of an intravaginal ring for the localised delivery of a chemotherapeutic drug to the cervix that has the potential to reduce the need for surgical intervention and will also provide a novel anti-cancer therapy for women in low resource settings. Disulfiram has demonstrated antineoplastic action against prostate, breast and lung cancer. Both PEVA and silicone elastomer were investigated for suitability as materials in the manufacture of DSF eluting intravaginal rings. DSF inhibited the curing process of the silicone elastomer, therefore PEVA was chosen as the material to manufacture the DSF-loaded vaginal rings. The vaginal rings had an excellent content uniformity while the DSF remained stable throughout the manufacturing process. Furthermore, the rings provided diffusion controlled release of DSF at levels well in excess of the IC50 value for the HeLa cervical cancer cell line.

Laboratizing the border: The production, translation and anticipation of security technologies

This paper critically interrogates how borders are produced by scientists, engineers and security experts in advance of the actual deployment of technical devices they develop. This paper explores the prior stages of translation and decision-making as a socio-technical device is conceived and developed. Drawing on in-depth interviews, observations and ethnographic research of the EU-funded Handhold project (consisting of nine teams in five countries), it explores how assumptions about the way security technologies will and should perform at the border shape the way that scientists, engineers, and security experts develop a portable, integrated device to detect CBRNE threats at borders. In disaggregating the moments of sovereign decision making across multiple sites and times, this paper questions the supposed linearity of how science comes out of and feeds back into the world of border security. An interrogation of competing assumptions and understandings of security threats and needs, of competing logics of innovation and pragmatism, of the demands of differentiated temporalities in detection and interrogation, and of the presumed capacities, behaviours, and needs of phantasmic competitors and end-users reveals a complex, circulating and co-constitutive process of device development that laboratises the border itself. We trace how sovereign decisions are enacted as assemblages in the antecedent register of device development itself through the everyday decisions of researchers in the laboratory, and the material components of the Handhold device itself.

Process simulation of co-firing torrefied biomass in a 220 MWe coal-fired power plant

Torrefaction based co-firing in a pulverized coal boiler has been proposed for large percentage of biomass co-firing. A 220 MWe pulverized coal-power plant is simulated using Aspen Plus for full understanding the impacts of an additional torrefaction unit on the efficiency of the whole power plant, the studied process includes biomass drying, biomass torrefaction, mill systems, biomass/coal devolatilization and combustion, heat exchanges and power generation. Palm kernel shells (PKS) were torrefied at same residence time but 4 different temperatures, to prepare 4 torrefied biomasses with different degrees of torrefaction. During biomass torrefaction processes, the mass loss properties and released gaseous components have been studied. In addition, process simulations at varying torrefaction degrees and biomass co-firing ratios have been carried out to understand the properties of CO₂ emission and electricity efficiency in the studied torrefaction based co-firing power plant. According to the experimental results, the mole fractions of CO ₂ and CO account for 69-91% and 4-27% in torrefied gases. The predicted results also showed that the electrical efficiency reduced when increasing either torrefaction temperature or substitution ratio of biomass. A deep torrefaction may not be recommended, because the power saved from biomass grinding is less than the heat consumed by the extra torrefaction process, depending on the heat sources. 

Consulting pupils in Assessment for Learning classrooms: the twists and turns of working with students as co-researchers

This is an invited paper to a special issue on pupil voice focusing on methodological issues arising from the ESRC/TLRP project on consulting pupils about assessment practices in their classrooms. The issue of consulting pupils about assessment has rarely been researched before but what this article illustrates are some of the difficulties, tensions and positive outcomes of engaging with students as researchers within a nationally funded (and therefore externally driven), university-based project. This study adds considerably to the body of knowledge in this area by engaging students in the process as researchers in different capacities within the project. Issues discussed include the use of student advisory groups, ethical negotiation, students undertaking videotaped classroom observations and their subsequent role in co-interpreting video excerpts and visual images. The paper has attracted considerable interest already through the ESRC pupil seminar series forum and also from a prior paper presentation to the European Educational Research Association in September 2006 in Switzerland to the Childrens' Rights SIG becasue of researchers' current interests in embedding democratic principles and practices within research with children and young people.

Insight into the key aspects of the regeneration process in the NOx storage reduction (NSR) reaction probed using fast transient kinetics coupled with isotopically labelled (NO)-N-15 over Pt and Rh-containing Ba/Al2O3 catalysts

For the first time, the coupling of fast transient kinetic switching and the use of an isotopically labelled reactant (15NO) has allowed detailed analysis of the evolution of all the products and reactants involved in the regeneration of a NOx storage reduction (NSR) material. Using realistic regeneration times (ca. 1 s) for Pt, Rh and Pt/Rh-containing Ba/Al2O3 catalysts we have revealed an unexpected double peak in the evolution of nitrogen. The first peak occurred immediately on switching from lean to rich conditions, while the second peak started at the point at which the gases switched from rich to lean. The first evolution of nitrogen occurs as a result of the fast reaction between H2 and/or CO and NO on reduced Rh and/or Pt sites. The second N2 peak which occurs upon removal of the rich phase can be explained by reaction of stored ammonia with stored NOx, gas phase NOx or O2. The ammonia can be formed either by hydrolysis of isocyanates or by direct reaction of NO and H2.

The study highlights the importance of the relative rates of regeneration and storage in determining the overall performance of the catalysts. The performance of the monometallic 1.1%Rh/Ba/Al2O3 catalyst at 250 and 350 °C was found to be dependent on the rate of NOx storage, since the rate of regeneration was sufficient to remove the NOx stored in the lean phase. In contrast, for the monometallic 1.6%Pt/Ba/Al2O3 catalyst at 250 °C, the rate of regeneration was the determining factor with the result that the amount of NOx stored on the catalyst deteriorated from cycle to cycle until the amount of NOx stored in the lean phase matched the NOx reduced in the rich phase. On the basis of the ratio of exposed metal surface atoms to total Ba content, the monometallic 1.6%Pt/Ba/Al2O3 catalyst outperformed the Rh-containing catalysts at 250 and 350 °C even when CO was used as a reductant.

CO multipulse TAP studies of 2% Pt/CeO2 catalyst: Influence of catalyst pretreatment and temperature on the number of active sites observed

CO multipulse temporal analysis of products (TAP) experiments were used to characterize a ceria-supported platinum catalyst after various oxidative and reductive pretreatments using O-2, H2O, CO2, and H-2. Based on the amount of CO consumed, using the final CO-saturated catalyst composition as the common state point, the oxidatively pretreated catalyst could be described using a general scale. From a kinetic analysis of the CO multipulse responses, two kinetic regimes corresponding to two types of active sites could be identified. As the temperature was raised, the number of the most active sites did not change while the amount of the less active site increased. Comparison of the number of active sites determined from the TAP data reported herein with that determined by a previous steady-state isotope transient kinetic analysis experiment showed excellent agreement. This correlation indicates that the (very fast response) TAP experiments can provide information regarding the number and type of active sites that are relevant to a catalyst under real reaction conditions. (c) 2007 Elsevier Inc. All rights reserved.

CHx hydrogenation on Co(0001): A density functional theory study

Hydrogenation is an important process in the Fischer-Tropsch synthesis. In this work, all the elementary steps of the hydrogenation from C to CH4 are studied on both flat and stepped Co(0001) using density functional theory (DFT). We found that (i) CH3 hydrogenation (CH3+H-->CH4) is the most difficult one among all the elementary reactions on both surfaces, possessing barriers of around 1.0 eV; (ii) the other elementary reactions have the barriers below 0.9 eV on the flat and stepped surfaces; (iii) CH2 is the least stable species among all the CHx(x=1-3) species on both surfaces; and (iv) surface restructuring may have little effect on the CHx(x=0-3) hydrogenation. The barriers of each elementary step on both flat and stepped surfaces are similar and energy profiles are also similar. The reason as to why CHx hydrogenation is not structure-sensitive is also discussed. (C) 2005 American Institute of Physics.

The catalytic role of water in CO oxidation

Water, one of the most popular species in our planet, can play a catalytic role in many reactions, including reactions in heterogeneous catalysis. In a recent experimental work, Bergeld, Kasemo, and Chakarov demonstrated that water is able to promote CO oxidation under low temperatures (similar to200 K). In this study, we choose CO oxidation on Pt(111) in the presence of water as a model system to address the catalytic role of water for surface reactions in general using density functional theory. Many elementary steps possibly involved in the CO oxidation on Pt(111) at low temperatures have been investigated. We find the following. First, in the presence of water, the CO oxidation barrier is reduced to 0.33 eV (without water the barrier is 0.80 eV). This barrier reduction is mainly due to the H-bonding between the H in the H2O and the O at the transition state (TS), which stabilizes the TS. Second, CO can readily react with OH with a barrier of 0.44 eV, while COOH dissociation to produce CO2 is not easy (the barrier is 1.02 eV). Third, in the H2O+OH mixed phase, CO can be easily converted into CO2. It occurs through two steps: CO reacts with OH, forming COOH; and COOH transfers the H to a nearby H2O and, at the same time, an H in the H2O transfers to a OH, leading to CO2 formation. The reaction barrier of this process is 0.60 eV under CO coverage of 1/6 ML and 0.33 eV under CO coverage of 1/3 ML. The mechanism of CO oxidation at low temperatures is discussed. On the basis of our calculations, we propose that the water promotion effect can in general be divided into two classes: (i) By H-bonding between the H of H2O and an electron negative species such as the O in the reaction of CO+O+H2O-->CO2+H2O, H2O can stabilize the TS of the reaction and hence reduce the barrier. (ii) H2O first dissociates into H and OH and then OH or H participates directly in the reaction to induce new reaction mechanism with more favorable routes, in which OH or H can act as an intermediate. (C) 2003 American Institute of Physics.