Synthesis and characterization of K2Ca5(SO4)6· H2O, the equivalent of görgeyite, a rare evaporite mineral

Görgeyite, K2Ca5(SO4)6··H2O, is a very rare monoclinic double salt found in evaporites related to the slightly more common mineral syngenite. At 1 atmosphere with increasing external temperature from 25 to 150 °C, the following succession of minerals was formed: first gypsum and K2O, followed at 100 °C by görgeyite. Changes in concentration at 150 °C due to evaporation resulted in the formation of syngenite and finally arcanite. Under hydrothermal conditions, the succession is syngenite at 50 °C, followed by görgyeite at 100 and 150 °C. Increasing the synthesis time at 100 °C and 1 atmosphere showed that initially gypsum was formed, later being replaced by görgeyite. Finally görgeyite was replaced by syngenite, indicating that görgeyite is a metastable phase under these conditions. Under hydrothermal conditions, syngenite plus a small amount of gypsum was formed, after two days being replaced by görgeyite. No further changes were observed with increasing time. Pure görgeyite showed elongated crystals approximately 500 to 1000 µ m in length. The infrared and Raman spectra are mainly showing the vibrational modes of the sulfate groups and the crystal water (structural water). Water is characterized by OH-stretching modes at 3526 and 3577 cm–1 , OH-bending modes at 1615 and 1647 cm–1 , and an OH-libration mode at 876 cm–1 . The sulfate 1 mode is weak in the infrared but showed strong bands at 1005 and 1013 cm–1 in the Raman spectrum. The 2 mode also showed strong bands in the Raman spectrum at 433, 440, 457, and 480 cm–1 . The 3 mode is characterized by a complex set of bands in both infrared and Raman spectra around 1150 cm–1 , whereas 4 is found at 650 cm–1.

Development of a colorimetric assay for heparanase activity suitable for kinetic analysis and inhibitor screening

The role that heparanase plays during metastasis and angiogenesis in tumors makes it an attractive target for cancer therapeutics. Despite this enzyme’s significance, most of the assays developed to measure its activity are complex. Moreover, they usually rely on labeling variable preparations of the natural substrate heparan sulfate, making comparisons across studies precarious. To overcome these problems, we have developed a convenient assay based on the cleavage of the synthetic heparin oligosaccharide fondaparinux. The assay measures the appearance of the disaccharide product of heparanase-catalyzed fondaparinux cleavage colorimetrically using the tetrazolium salt WST-1. Because this assay has a homogeneous substrate with a single point of cleavage, the kinetics of the enzyme can be reliably characterized, giving a Km of 46 μM and a kcat of 3.5 s−1 with fondaparinux as substrate. The inhibition of heparanase by the published inhibitor, PI-88, was also studied, and a Ki of 7.9 nM was determined. The simplicity and robustness of this method, should, not only greatly assist routine assay of heparanase activity but also could be adapted for high-throughput screening of compound libraries, with the data generated being directly comparable across studies.

Raman spectroscopic study of the uranyl mineral pseudojohannite Cu6.5[(UO2)4O4(SO4)2]2(OH)5.25H2O

Raman spectra of pseudojohannite were studied and related to the structure of the mineral. Observed bands were assigned to the stretching and bending vibrations of (UO2)2+ and (SO4)2- units and of water molecules. The published formula of pseudojohannite is Cu6.5(UO2)8\[O8](OH)5\[(SO4)4].25H2O; however Raman spectroscopy does not detect any hydroxyl units. Raman bands at 805 and 810 cm-1 are assigned to (UO2)2+ stretching modes. The Raman bands at 1017 and 1100 cm-1 are assigned to the (SO4)2- symmetric and antisymmetric stretching vibrations. The three Raman bands at 423, 465 and 496 cm-1 are assigned to the (SO4)2- ν2 bending modes. The bands at 210 and 279 cm-1 are assigned to the doubly degenerate ν2 bending vibration of the (UO2)2+ units. U-O bond lengths in uranyl and O-H…O hydrogen bond lengths were calculated from the Raman and infrared spectra.

Zinc supplementation at conventional doses does not improve the disturbance of taste perception in hemodialysis patients

Objective: To determine the effect of zinc supplementation on taste perception in a group of hemodialysis patients. Design and Setting: Double-blind randomized placebo-controlled study in a teaching hospital dialysis unit. Patients: Fifteen stable hemodialysis patients randomized to placebo (6 male, 2 female; median age, 67; range, 30 to 72 years) or treatment (5 male, 2 female; median age, 60; range, 31 to 76 years). Intervention: Treatment group received zinc sulfate 220 mg per day for 6 weeks, and the placebo group received an apparently identical dummy pill. Main Outcome Measures: Taste scores by visual analogue scales, normalized protein catabolic rate and plasma, whole blood and red cell zinc levels. Results: At baseline, sweet and salt tastes were identified correctly by both groups. Sour was often confused with salt. Sour solutions of different concentrations were not distinguishable. Taste scores were not different after 6 weeks for either group. There was no significant increment in zinc levels or normalized protein catabolic rate for either group. Conclusion: We found a disturbance of taste perception in hemodialysis patients, particularly for the sour modality, which was not corrected by this regimen of zinc supplementation. These results cast doubts on the conclusions of earlier studies that indicated an improvement in taste after zinc supplementation.

Developing a hybrid expert system program to aid in the design of plastic injection molding process

Experts in injection molding often refer to previous solutions to find a mold design similar to the current mold and use previous successful molding process parameters with intuitive adjustment and modification as a start for the new molding application. This approach saves a substantial amount of time and cost in experimental based corrective actions which are required in order to reach optimum molding conditions. A Case-Based Reasoning (CBR) System can perform the same task by retrieving a similar case which is applied to the new case from the case library and uses the modification rules to adapt a solution to the new case. Therefore, a CBR System can simulate human e~pertise in injection molding process design. This research is aimed at developing an interactive Hybrid Expert System to reduce expert dependency needed on the production floor. The Hybrid Expert System (HES) is comprised of CBR, flow analysis, post-processor and trouble shooting systems. The HES can provide the first set of operating parameters in order to achieve moldability condition and producing moldings free of stress cracks and warpage. In this work C++ programming language is used to implement the expert system. The Case-Based Reasoning sub-system is constructed to derive the optimum magnitude of process parameters in the cavity. Toward this end the Flow Analysis sub-system is employed to calculate the pressure drop and temperature difference in the feed system to determine the required magnitude of parameters at the nozzle. The Post-Processor is implemented to convert the molding parameters to machine setting parameters. The parameters designed by HES are implemented using the injection molding machine. In the presence of any molding defect, a trouble shooting subsystem can determine which combination of process parameters must be changed iii during the process to deal with possible variations. Constraints in relation to the application of this HES are as follows. - flow length (L) constraint: 40 mm < L < I 00 mm, - flow thickness (Th) constraint: -flow type: - material types: I mm < Th < 4 mm, unidirectional flow, High Impact Polystyrene (HIPS) and Acrylic. In order to test the HES, experiments were conducted and satisfactory results were obtained.

Modulation of dermal microvascular endithelial cell responses to growth factors and haemostatic factors in the presence of vitronectin

In order to effect permanent closure in burns patients suffering from full thickness wounds, replacing their skin via split thickness autografting, is essential. Dermal substitutes in conjunction with widely meshed split thickness autografts (+/- cultured keratinocytes) reduce scarring at the donor and recipient sites of burns patients by reducing demand for autologous skin (both surface area and thickness), without compromising dermal delivery at the wound face. Tissue engineered products such as Integra consist of a dermal template which is rapidly remodelled to form a neodermis, at which time the temporary silicone outer layer is removed and replaced with autologous split thickness skin. Whilst provision of a thick tissue engineered dermis at full thickness burn sites reduces scarring, it is hampered by delays in vascularisation which results in clinical failure. The ultimate success of any skin graft product is dependent upon a number of basic factors including adherence, haemostasis and in the case of viable tissue grafts, success is ultimately dependent upon restoration of a normal blood supply, and hence this study. Ultimately, the goal of this research is to improve the therapeutic properties of tissue replacements, through impregnation with growth factors aimed at stimulating migration and proliferation of microvascular endothelial cells into the donor tissue post grafting. For the purpose of my masters, the aim was to evaluate the responsiveness of a dermal microvascular endothelial cell line to growth factors and haemostatic factors, in the presence of the glycoprotein vitronectin. Vitronectin formed the backbone for my hypothesis and research due to its association with both epithelial and, more specifically, endothelial migration and proliferation. Early work using a platform technology referred to as VitroGro (Tissue Therapies Ltd), which is comprised of vitronectin bound BP5/IGF-1, aided keratinocyte proliferation. I hypothesised that this result would translate to another epithelium - endothelium. VitroGro had no effect on endothelial proliferation or migration. Vitronectin increases the presence of Fibroblast Growth Factor (FGF) and Vascular Endothelial Growth Factor (VEGF) receptors, enhancing cell responsiveness to their respective ligands. So, although Human Microvascular Endothelial Cell line 1 (HMEC-1) VEGF receptor expression is generally low, it was hypothesised that exposure to vitronectin would up-regulate this receptor. HMEC-1 migration, but not proliferation, was enhanced by vitronectin bound VEGF, as well as vitronectin bound Epidermal Growth Factor (EGF), both of which could be used to stimulate microvascular endothelial cell migration for the purpose of transplantation. In addition to vitronectin's synergy with various growth factors, it has also been shown to play a role in haemostasis. Vitronectin binds thrombin-antithrombin III (TAT) to form a trimeric complex that takes on many of the attributes of vitronectin, such as heparin affinity, which results in its adherence to endothelium via heparan sulfate proteoglycans (HSP), followed by unaltered transcytosis through the endothelium, and ultimately its removal from the circulation. This has been documented as a mechanism designed to remove thrombin from the circulation. Equally, it could be argued that it is a mechanism for delivering vitronectin to the matrix. My results show that matrix-bound vitronectin dramatically alters the effect that conformationally altered antithrombin three (cATIII) has on proliferation of microvascular endothelial cells. cATIII stimulates HMEC-1 proliferation in the presence of matrix-bound vitronectin, as opposed to inhibiting proliferation in its absence. Binding vitronectin to tissues and organs prior to transplant, in the presence of cATIII, will have a profound effect on microvascular infiltration of the graft, by preventing occlusion of existing vessels whilst stimulating migration and proliferation of endothelium within the tissue.

Rationalizing the SER spectra of bacteria

The SER spectra of riboflavin and FAD are identical and are resonance enhanced at 514 or 532 nm. Signals from FAD/ riboflavin dominated SER spectra whenever these compounds were present with proteins or bacteria. SER spectra of very different bacteria such as Pseudomonas. aeruginosa, Bacillu. subtilis and Geobacillus. stearothermophilus were dominated by signals from FAD, even when these bacteria were added to a preformed colloid. The SERS signal of FAD is greatly reduced at 785 nm, and SER spectra of bacteria excited at 785 nm are quite different than those collected at 514 or 532 nm. This supports the assignment of the peaks in the 514 nm SER spectra of bacteria to FAD rather to amino acids or N-acetylglucosamine. The SER spectra of certain mixes of adenine and FAD showed similar changes to those of bacteria when the excitation was changed from 514/532 nm to 785 nm. The ratio of colloid: bacteria was of critical important for obtaining good SER spectra, and the addition of sodium sulfate was also beneficial. Removal of EPS from bacteria before analysis facilitated interaction with the silver surface, and may be a useful step to include in identification protocols.

Highly efficient, stoichiometric radical exchange reactions using isoindoline profluorescent nitroxides

Exchange reactions between the isoindoline profluorescent nitroxide 1,1,3,3-tetramethyldibenzo[e,g]isoindolin-2-yloxyl (TMDBIO) and a TEMPO capped polystyrene were carried out. High conversions to the desired products were achieved using only stoichiometric ratios of nitroxide relative to polymer. The scope of this study was expanded by exploiting a di-nitroxide 9,10-bis(5-[1,1,3,3-tetramethylisoindolin-2-yloxy])anthracene (BTMIOA) as a connector between two polymer chains forming PS–nitroxide–PS systems.

A poly(D,L-lactide) resin for the preparation of tissue engineering scaffolds by stereolithography

Porous polylactide constructs were prepared by stereolithography, for the first time without the use of reactive diluents. Star-shaped poly(D,L-lactide) oligomers with 2, 3 and 6 arms were synthesised, end-functionalised with methacryloyl chloride and photocrosslinked in the presence of ethyl lactate as a non-reactive diluent. The molecular weights of the arms of the macromers were 0.2, 0.6, 1.1 and 5 kg/mol, allowing variation of the crosslink density of the resulting networks. Networks prepared from macromers of which the molecular weight per arm was 0.6 kg/mol or higher had good mechanical properties, similar to linear high molecular weight poly(D,L-lactide). A resin based on a 2-armed poly(D,L-lactide) macromer with a molecular weight of 0.6 kg/mol per arm (75 wt%), ethyl lactate (19 wt%), photo-initiator (6 wt%), inhibitor and dye was prepared. Using this resin, films and computer-designed porous constructs were accurately fabricated by stereolithography. Pre-osteoblasts showed good adherence to these photocrosslinked networks. The proliferation rate on these materials was comparable to that on high molecular weight poly(D,L-lactide) and tissue culture polystyrene.

Bubble rise velocity and trajectory in xanthan gum crystal suspension

An experimental set-up was used to visually observe the characteristics of bubbles as they moved up a column holding xanthan gum crystal suspensions. The bubble rise characteristics in xanthan gum solutions with crystal suspension are presented in this paper. The suspensions were made by using different concentrations of xanthan gum solutions with 0.23 mm mean diameter polystyrene crystal particles. The influence of the dimensionless quantities; namely the Reynolds number, Re, the Weber number, We, and the drag co-efficient, cd, are identified for the determination of the bubble rise velocity. The effect of these dimensionless groups together with the Eötvös number, Eo, the Froude number, Fr, and the bubble deformation parameter, D, on the bubble rise velocity and bubble trajectory are analysed. The experimental results show that the average bubble velocity increases with the increase in bubble volume for xanthan gum crystal suspensions. At high We, Eo and Re, bubbles are spherical-capped and their velocities are found to be very high. At low We and Eo, the surface tension force is significant compared to the inertia force. The viscous forces were shown to have no substantial effect on the bubble rise velocity for 45 < Re < 299. The results show that the drag co-efficient decreases with the increase in bubble velocity and Re. The trajectory analysis showed that small bubbles followed a zigzag motion while larger bubbles followed a spiral motion. The smaller bubbles experienced less horizontal motion in crystal suspended xanthan gum solutions while larger bubbles exhibited a greater degree of spiral motion than those seen in the previous studies on the bubble rise in xanthan gum solutions without crystal.

PLGA-based microparticles for the sustained release of BMP-2

The development of growth factor delivery strategies to circumvent the burst release phenomenon prevalent in most current systems has driven research towards encapsulating molecules in resorbable polymer matrices. For these polymer release techniques to be efficacious in a clinical setting, several key points need to be addressed. This present study has investigated the encapsulation of the growth factor, BMP-2 within PLGA/PLGA-PEG-PLGA microparticles. Morphology, size distribution, encapsulation efficiency and release kinetics were investigated and we have demonstrated a sustained release of bioactive BMP-2. Furthermore, biocompatibility of the PLGA microparticles was established and released BMP-2 was shown to promote the differentiation of MC3T3-E1 cells towards the osteogenic lineage to a greater extent than osteogenic supplements (as early as day 10 in culture), as determined using alkaline phosphatase and alizarin red assays. This study showcases a potential BMP-2 delivery system which may now be translated into more complex delivery systems, such as 3D, mechanically robust scaffolds for bone tissue regeneration applications.

The synthesis and spectroscopic characterisation of hydrotalcite formed from aluminate solutions

Raman spectroscopy has been used to characterise nine hydrotalcites prepared from aluminate and magnesium solutions (magnesium chloride and seawater). The aluminate hydrotalcites are proposed to have the following formula Mg6Al2(OH)16(CO32-).xH2O, Mg6Al2(OH)16(CO32-,SO42-).xH2O, and Mg6Al2(OH)16(SO42-).xH2O. The synthesis of these hydrotalcites using seawater results in the intercalation of sulfate anions into the hydrotalcite interlayer. The spectra have been used to assess the molecular assembly of the cations and anions in the hydrotalcite structures. The spectra have been conveniently subdivided into spectral features based upon the carbonate anion, the hydroxyl units and water units. This investigation has shown the ideal conditions to form hydrotalcite from aluminate solutions is at pH 14 using magnesium chloride. Changes in synthesis conditions resulted in the formation of impurity products aragonite, thenardite, and gypsum.

Drag coefficient in a crystal suspension

A single air bubble rising in xanthan gum crystal suspension has been studied experimentally. The suspension was made by different concentrations of xanthan gum solutions with 0.23 mm polystyrene crystal particles. Drag co-efficient data and a new correlation of drag coefficient is presented for spherical and nonspherical bubbles in non-Newtonian crystal suspension. The correlation is developed in terms of the Reynolds number, Re and the bubble shape factor, � (the ratio between the surface equivalent sphere diameter to the volume equivalent sphere diameter). The experimental drag coefficient was found to be consistent with this new predicted correlation and published data over the ranges, 0.1

A Raman spectroscopic study of copiapites Fe2+Fe3+(SO4)6(OH)2 · 20H2O: environmental implications

Raman spectroscopy has been used to study selected mineral samples of the copiapite group. Copiapite (Fe2+Fe3+(SO4)6(OH)2 · 20H2O) is a secondary mineral formed through the oxidn. of pyrite. Minerals of the copiapite group have the general formula AFe4(SO4)6(OH)2 · 20H2O, where A has a + 2 charge and can be either magnesium, iron, copper, calcium and/or zinc. The formula can also be B2/3Fe4(SO4)6(OH)2 · 20H2O, where B has a + 3 charge and may be either aluminum or iron. For each mineral, two Raman bands are obsd. at around 992 and 1029 cm-1, assigned to the (SO4)2-ν1 sym. stretching mode. The observation of two bands provides evidence for the existence of two non-equiv. sulfate anions in the mineral structure. Three Raman bands at 1112, 1142 and 1161 cm-1 are obsd. in the Raman spectrum of copiapites, indicating a redn. of symmetry of the sulfate anion in the copiapite structure. This redn. in symmetry is supported by multiple bands in the ν2 and ν4(SO4)2- spectral regions.

The effect of synthesis temperature on the formation of hydrotalcites in Bayer liquor : a vibrational spectroscopic analysis

The seawater neutralisation process is currently used in the Alumina industry to reduce the pH and dissolved metal concentrations in bauxite refinery residues, through the precipitation of Mg, Al, and Ca hydroxide and carbonate minerals. This neutralisation method is very similar to the co-precipitation method used to synthesise hydrotalcite (Mg6Al2(OH)16CO3•4H2O). This study looks at the effect of temperature on the type of precipitates that form from the seawater neutralisation process of Bayer liquor. The Bayer precipitates have been characterised by a variety of techniques, including X-ray diffraction, Raman spectroscopy and infrared spectroscopy. The mineralogical composition of Bayer precipitates largely includes hydrotalcite, hydromagnesite, and calcium carbonate species. XRD determined that Bayer hydrotalcites that are synthesised at 55 °C have a larger interlayer distance, indicating more anions are removed from Bayer liquor. Vibrational spectroscopic techniques have identified an increase in hydrogen bond strength for precipitates formed at 55 °C, suggesting the formation of a more stable Bayer hydrotalcite. Raman spectroscopy identified the intercalation of sulfate and carbonate anions into Bayer hydrotalcites using these synthesis conditions.