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HAP
Terms modified by HAP Selected AbstractsSpectroscopic investigation of the function of aqueous 2-hydroxyethylmethacrylate/glutaraldehyde solution as a dentin desensitizerEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 4 2006Chuangye Qin Fourier-transform (FT)-Raman and -infrared (IR) spectroscopy were employed to investigate the function of the aqueous 2-hydroxyethylmethacrylate/glutaraldehyde solution (Gluma) as a desensitizer. 2-Hydroxyethylmethacrylate (HEMA), glutaraldehyde (GA), and the mixture of HEMA/GA (i.e. Gluma) were used to interact with dentin, collagen, hydroxyapatite (HAP), and bovine serum albumin (BSA) individually. All the interactions were monitored by an FT-Raman spectrometer. FT-IR spectroscopy was also used in this study. The results show that HEMA could be absorbed by dentin and collagen; GA could cross-link collagen and BSA; and when BSA was added to Gluma, polymerization of HEMA occurred. The results suggest that Gluma acts as a desensitizer whereby, first, GA reacts with part of the serum albumin in dentinal fluid, which induces a precipitation of serum albumin, then, second, a reaction of GA with serum albumin induces polymerization of HEMA. The function of Gluma as a desensitizer to block dentinal tubules occurs via these two reactions. [source] Microstructural Engineering of Hydroxyapatite Membranes to Enhance Proton ConductivityADVANCED FUNCTIONAL MATERIALS, Issue 24 2009Dongxia Liu Abstract A new approach to enhancing proton conductivity of ceramics is demonstrated by aligning proton conductive pathways and eliminating resistive grain boundaries. Hydroxyapatite (HAP) membranes are synthesized by multistage crystallization onto palladium. The synthesis involves three steps: electrochemical deposition of HAP seeds, secondary hydrothermal crystallization onto the seed layer to promote c -axis growth normal to the substrate, and tertiary hydrothermal crystallization to promote a- axis growth to fill the gaps between the aligned crystals. The c -axis alignment with crystal domains spanning the membrane thickness significantly enhances proton conduction since protons are primarily transported along the c -axes of HAP crystals. The novel HAP membranes display proton conductivity almost four orders of magnitude higher than traditional sintered HAP ceramics. The HAP membranes on palladium hydrogen membrane substrates hold promise for use in intermediate-temperature fuel cells, chemical sensors, and other devices. The synthesis approach presented may also be applied to other ion-conducting membrane materials to enhance transport properties. [source] A Combined Cluster and Interaction Model: The Hierarchical Assignment ProblemGEOGRAPHICAL ANALYSIS, Issue 3 2005Mark W. Horner This article presents a new spatial modeling approach that deals with interactions between individual geographic entities. The developed model represents a generalization of the transportation problem and the classical assignment problem and is termed the hierarchical assignment problem (HAP). The HAP optimizes the spatial flow pattern between individual origin and destination locations, given that some grouping, or aggregation of individual origins and destinations is permitted to occur. The level of aggregation is user specified, and the aggregation step is endogenous to the model itself. This allows for the direct accounting of aggregation costs in pursuit of optimal problem solutions. The HAP is formulated and solved with several sample data sets using commercial optimization software. Trials illustrate how HAP solutions respond to changes in levels of aggregation, as well as reveal the diverse network designs and allocation schemes obtainable with the HAP. Connections between the HAP and the literature on the p-median problem, cluster analysis, and hub-and-spoke networks are discussed and suggestions for future research are made. [source] Bioactivity of novel carboxymethyl chitosan scaffold incorporating MTA in a tooth modelINTERNATIONAL ENDODONTIC JOURNAL, Issue 10 2010R. Budiraharjo Budiraharjo R, Neoh KG, Kang ET, Kishen A. Bioactivity of novel carboxymethyl chitosan scaffold incorporating MTA in a tooth model. International Endodontic Journal, 43, 930,939, 2010. Abstract Aim, To characterise the bioactivity of a novel carboxymethyl chitosan (CMCS) scaffold with and without incorporating mineral trioxide aggregate (MTA) in a tooth model. Methodology, Cross-linked CMCS scaffold (CaC) and MTA-coated CaC (CaMT) scaffold were prepared by freeze-drying. The bioactivity of the scaffolds was tested in vitro in four different mineralisation solutions (bulk system) and ex vivo in simulated body fluid (SBF) in the tooth model. After mineralisation, the mineral deposits on the scaffolds were analysed using scanning electron microscopy, energy dispersive X-ray, and inductively coupled plasma mass spectroscopy. All data were statistically analysed using the two-sample t -test (P < 0.05). Results, Hydroxyapatite (HAP) deposition was observed on CaC and CaMT scaffolds after 1 week of mineralisation in the tooth model and in the bulk system. The deposition was significantly higher (P < 0.05) on CaMT scaffold than that on CaC scaffold. The amount of HAP formed in the tooth model was significantly lower (P < 0.05) than that in the bulk solution. Conclusions, The CMCS scaffolds are bioactive and capable of biomineralisation by forming HAP within a tooth model ex vivo. The bioactivity of the CMCS scaffold can be enhanced by incorporating MTA. [source] Reaction characteristics of a tooth-bleaching agent containing H2O2 and NaF: in vitro study of crystal structure change in treated hydroxyapatite and chemical states of incorporated fluorineINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 5 2005Y. Tanizawa This in vitro study was performed to elucidate the reaction mechanism of sodium fluoride (NaF), which is added to tooth-bleaching agents to lessen the adverse effect of hydrogen peroxide (H2O2) on teeth. Both hydroxyapatite (HAP) and dihydrated dicalcium phosphate (DCPD), model substances for dental hard tissues, dissolved easily in a simple H2O2 solution. In the H2O2/NaF solutions, however, fluorine compounds that could not be identified by X-ray diffraction (XRD) due to the smallness of the products were formed on the surface of the HAP. X-ray photoelectron spectroscopy (XPS) studies demonstrated that fluoridated hydroxyapatite (FHAP) was formed on HAP, and that calcium fluoride (CaF2) formation was accelerated by increasing the concentrations of fluorine and H2O2 along with the partial dissolution of HAP. In H2O2/NaF solution, DCPD also transformed easily to FHAP and CaF2, which are favorable to the remineralization process on the tooth surface. Thus, the mechanism of NaF was elucidated, and its use together with H2O2 for tooth bleaching was proved to be effective. Methodologically, the XPS two-dimensional plot made it possible for the first time to directly estimate the ratio of FHAP and CaF2 in the reaction products, in contrast to the conventional wet-analytical method, which is simply based on the difference in solubility of the two components. [source] Reaction characteristics of a tooth-bleaching agent containing H2O2 and NaF: in vitro study of crystal structure change in treated hydroxyapatite and chemical states of incorporated fluorineINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 4 2005Y. Tanizawa This in vitro study was performed to elucidate the reaction mechanism of sodium fluoride (NaF), which is added to tooth-bleaching agents to lessen the adverse effect of hydrogen peroxide (H2O2) on teeth. Both hydroxyapatite (HAP) and dihydrated dicalcium phosphate (DCPD), model substances for dental hard tissues, dissolved easily in a simple H2O2 solution. In the H2O2/NaF solutions, however, fluorine compounds that could not be identified by X-ray diffraction (XRD) due to the smallness of the products were formed on the surface of the HAP. X-ray photoelectron spectroscopy (XPS) studies demonstrated that fluoridated hydroxyapatite (FHAP) was formed on HAP, and that calcium fluoride (CaF2) formation was accelerated by increasing the concentrations of fluorine and H2O2 along with the partial dissolution of HAP. In H2O2/NaF solution, DCPD also transformed easily to FHAP and CaF2, which are favorable to the remineralization process on the tooth surface. Thus, the mechanism of NaF was elucidated, and its use together with H2O2 for tooth bleaching was proved to be effective. Methodologically, the XPS two-dimensional plot made it possible for the first time to directly estimate the ratio of FHAP and CaF2 in the reaction products, in contrast to the conventional wet-analytical method, which is simply based on the difference in solubility of the two components. [source] Rietveld structure and in vitro analysis on the influence of magnesium in biphasic (hydroxyapatite and ,-tricalcium phosphate) mixturesJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2009S. Kannan Abstract The structure of two different Mg-substituted biphasic (HAP and ,-TCP) mixtures along with the biphasic mixtures without substituted Mg2+ was investigated using Rietveld refinement technique. The substituted Mg2+ was found in the ,-TCP phase and its influence on the composition has led to an increase in HAP content of Mg-containing biphasic mixtures when compared with the HAP content detected in pure biphasic mixtures. The refined structural parameters of Ca10(PO4)6(OH)2 and ,-Ca3(PO4)2 confirmed that all the investigated compositions have crystallized in the corresponding hexagonal (space group P63/m) and rhombohedral (space group R3c) structures. The substitution of lower sized magnesium was found preferentially incorporated at the sixfold-coordinated Ca (5) site of ,-TCP, which is due to the strong Ca (5)·O interaction among all the five different Ca sites of ,-Ca3(PO4)2. The in vitro tests using primary culture of osteoblasts showed that all the tested samples are biocompatible and promising materials for in vivo studies. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009 [source] Influence of cosolvents and in situ forming hydroxyapatite on the mechanical characteristics of collagen filmsJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2002Hsiu-O Ho Abstract Collagen was processed into films in mixtures containing various ratios of water, propylene glycol, and ethanol. An experimental mixture design was applied to characterize the effects of individual solvents and their interactions on the mechanical properties of collagen films. Scanning electron microscopy (SEM) was used to examine the surface properties of collagen films. The ultimate tensile strength (UTS) and related characteristics of collagen films were also evaluated with dynamic mechanical analysis. The effect of in situ forming hydroxyapatite (HAP) within collagen films at a concentration of 10 mM on the physical characteristics of these films was evaluated by the same methods. With X-ray and SEM examinations, it was confirmed that HAP was formed inside the collagen film. However, the UTS of collagen films without HAP was 4,5 times higher than that with HAP. This was probably due to the discontinuity of the film structure caused by HAP in the collagen films. The results of a statistical analysis of the experimental design revealed the influence of the solvent mixtures on the mechanical properties of the collagen films with and without HAP, showing similar responses for the UTS and modulus of elasticity. Both parameters showed a maximal response in the solvent range containing a lower percentage of ethanol with the desired percentage of propylene glycol to plasticize the collagen films. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 62: 22,29, 2002 [source] Pharmacologic Dissociation Between Impulsivity and Alcohol Drinking in High Alcohol Preferring MiceALCOHOLISM, Issue 8 2010Brandon G. Oberlin Background:, Impulsivity is genetically correlated with, and precedes, addictive behaviors and alcoholism. If impulsivity or attention is causally related to addiction, certain pharmacological manipulations of impulsivity and/or attention may affect alcohol drinking, and vice versa. The current studies were designed to explore the relationship among impulsivity, drinking, and vigilance in selectively bred High Alcohol Preferring (HAP) mice, a line that has previously demonstrated both high impulsivity and high alcohol consumption. Amphetamine, naltrexone, and memantine were tested in a delay discounting (DD) task for their effects on impulsivity and vigilance. The same drugs and doses were also assessed for effects on alcohol drinking in a 2-bottle choice test. Methods:, HAP mice were subjected to a modified version of adjusting amount DD using 0.5-second and 10-second delays to detect decreases and increases, respectively, in impulsive responding. In 2 experiments, mice were given amphetamine (0.4, 0.8, or 1.2 mg/kg), naltrexone (3 and 10 mg/kg), and memantine (1 and 5 mg/kg) before DD testing. Another pair of studies used scheduled access, 2-bottle choice drinking to assess effects of amphetamine (0.4, 1.2, or 3.0 mg/kg), naltrexone (3 and 10 mg/kg), and memantine (1 and 5 mg/kg) on alcohol consumption. Results:, Amphetamine dose-dependently reduced impulsivity and vigilance decrement in DD, but similar doses left alcohol drinking unaffected. Naltrexone and memantine decreased alcohol intake at doses that did not affect water drinking but had no effects on impulsivity or vigilance decrement in the DD task. Conclusions:, Contrary to our hypothesis, none of the drugs tested here, while effective on either alcohol drinking or impulsivity, decreased both behaviors. These findings suggest that the genetic association between drinking and impulsivity observed in this population is mediated by mechanisms other than those targeted by the drugs tested in these studies. [source] High-Alcohol Preferring Mice Are More Impulsive Than Low-Alcohol Preferring Mice as Measured in the Delay Discounting TaskALCOHOLISM, Issue 7 2009B. G. Oberlin Background:, Repeated studies have shown that high impulsivity, when defined as the tendency to choose small immediate rewards over larger delayed rewards, is more prevalent in drug addicts and alcoholics when compared with nonaddicts. Assessing whether impulsivity precedes and potentially causes addiction disorders is difficult in humans because they all share a history of drug use. In this study, we address this question by testing alcohol-naïve mice from lines showing heritable differences in alcohol intake. Methods:, Replicated selected lines of outbred high-alcohol preferring (HAP) mice were compared to a low-alcohol preferring (LAP) line as well as the low-drinking progenitor line (HS/Ibg) on an adjusting amount delay discounting (DD) task. The DD task employs 2 levers to present subjects with a choice between a small, immediate and a large, delayed saccharin reward. By adjusting the quantity of the immediate reward up and down based on choice behavior, the task allows an estimate of how the subjective value of the delayed reinforcer decreases as delays increase. Latency to respond was also measured for each trial. Results:, Both HAP2 and HAP1 lines of mice were more impulsive than the LAP2 and HS/Ibg lines, respectively. Hyperbolic curve-fitting confirmed steeper discounting in the high-alcohol drinking lines. In addition, the high-alcohol drinking lines demonstrated greater within-session increases in reaction times relative to the low-alcohol drinking lines. No other differences (consumption of saccharin, total trials completed) consistently mapped onto genetic differences in alcohol drinking. Conclusions:, Alcohol-naïve outbred mice selected for high-alcohol drinking were more impulsive with saccharin reinforcers than low-alcohol drinkers. These data are consistent with results seen using inbred strain descendents of high-alcohol drinking and low-alcohol drinking rat lines, and suggest that impulsivity is a heritable difference that precedes alcoholism. [source] Hydroxyapatite Coating on Thermally Oxidized Titanium SubstratesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2001Minkmas Vatanatham Titanium substrates were oxidized in oxygen or air at temperatures of 600°,800°C, then immersed in solutions of 2.0mM, 20.7mM CaCl2 and 1.2mM,12.4mM KH2PO4 for aging periods of 0.5,10 d. The titanium surface was successfully coated with hydroxyapatite (HAP) when the substrates were oxidized in oxygen gas at 610°C for 1 h and then aged in a solution of 2.00mM Ca2+ and 1.20mM PO43,. The Ca/P ratio of the surface coating increased toward its stoichiometric HAP value (return 10/6) as the aging time increased; the Ca/P ratio attained a value of 1.66 after 10 d. [source] Plasmepsins as potential targets for new antimalarial therapyMEDICINAL RESEARCH REVIEWS, Issue 5 2006Karolina Ersmark Abstract Malaria is one of the major diseases in the world. Due to the rapid spread of parasite resistance to available antimalarial drugs there is an urgent need for new antimalarials with novel mechanisms of action. Several promising targets for drug intervention have been revealed in recent years. This review addresses the parasitic aspartic proteases termed plasmepsins (Plms) that are involved in the hemoglobin catabolism that occurs during the erythrocytic stage of the malarial parasite life cycle. Four Plasmodium species are responsible for human malaria; P. vivax, P. ovale, P. malariae, and P. falciparum. This review focuses on inhibitors of the haemoglobin-degrading plasmepsins of the most lethal species, P. falciparum; Plm I, Plm II, Plm IV, and histo-aspartic protease (HAP). Previously, Plm II has attracted the most attention. With the identification and characterization of new plasmepsins and the results from recent plasmepsin knockout studies, it now seems clear that in order to achieve high-antiparasitic activities in P. falciparum -infected erythrocytes it is necessary to inhibit several of the haemoglobin-degrading plasmepsins. Herein we summarize the structure,activity relationships of the Plm I, II, IV, and HAP inhibitors. These inhibitors represent all classes which, to the best of our knowledge, have been disclosed in journal articles to date. The 3D structures of inhibitor/plasmepsin II complexes available in the protein data bank are briefly discussed and compared. © 2006 Wiley Periodicals, Inc. Med Res Rev, 26, No. 5, 626,666, 2006 [source] Photophysical Properties of Terbium Molecular-based Hybrids Assembled with Novel Ureasil LinkagesPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2007Bing Yan Three silica-based organic,inorganic hybrid systems composed of hydroxyl aromatic derivatives (2-acetylphenol [HAP], 2-hydroxy-3-methylbenzoic acid [HMBA], 3-hydroxy-meta-phthalic acid [HMPHTH] complexes) were prepared via a sol,gel process. The active hydroxyl groups of the three ligands grafted by 3-(triethoxysilyl)-propyl isocyanate (TESPIC) through hydrogen transfer addition reaction were used as multi-functional bridge components, which can coordinate to Tb3+ with carbonyl groups, strongly absorb ultraviolet light and effectively transfer energy to Tb3+ through their triplet excited state, as well as undergo polymerization or crosslinking reactions with tetraethoxysilane (TEOS), for anchoring terbium ions to silica backbone. NMR, FT-IR, UV,vis absorption, luminescence spectroscopy was used to investigate the obtained hybrid material. UV excitation in the organic component resulted in strong green emission from Tb3+ ions due to an efficient ligand-to-metal energy transfer mechanism. [source] Prefertilization barriers to interspecific hybridization involving Gossypium hirsutum and four diploid wild speciesPLANT BREEDING, Issue 3 2008S. Ganesh Ram Abstract Interspecific hybridization among species of cotton has lead to improvement in productivity, earliness, fibre quality and resistance to pests and diseases. However, wide crosses is often limited by the operation of either pre- or/and post-fertilization barriers. An investigation on pollen tube behaviour of four wild species in the pistils of Gossypium hirsutum was taken up. Pollen germination was normal in crosses involving Gossypium triphyllum and Gossypium armourianum and markedly inhibited in the crosses involving Gossypium davidsonii and Gossypium thurberi. Pollen tubes reached the pistils and fertilization was accomplished within 8 h after pollination (HAP) in control cross. Even though delay in pollen tube was a common phenomenon in all the four crosses successful fertilization was observed in crosses involving G. triphyllum and G. armourianum, as they reached the ovary at 24 HAP. In crosses with G. davidsonii and G. thurberi, pollen tubes failed to reach the ovary even at 24 HAP indicating the presence of strong stylar and ovarian incompatibility. Measures to overcome such barriers to interspecific hybridization in the incompatible crosses are discussed. [source] Healthy aging demonstration project: Nurse coaching for behavior change in older adults,RESEARCH IN NURSING & HEALTH, Issue 3 2005Jill A. Bennett Abstract The Healthy Aging Project (HAP) tested nurse coaching as a method to support healthy behavior change in older adults. The sample included 111 individuals randomized to a nurse coaching group or usual-care control group. Participants in the intervention group chose the health behaviors they wanted to change and received coaching by nurses in a single in-person session followed by telephone calls or email contact for 6 months. Nurses were trained in motivational interviewing (MI). The intervention group had significantly less illness intrusiveness and health distress than the control group at 6 months, although it is not known whether these health outcomes resulted from behavior changes. This clinical demonstration project showed that nurse-delivered MI, primarily using the telephone and email, is a feasible method to discuss behavioral change with older adults. However, future clinical trials will be needed to evaluate the efficacy of nurse-delivered MI on actual behavioral changes in older adults. © 2005 Wiley Periodicals, Inc. Res Nurs Health 28: 187,197, 2005 [source] Revision of the severity rating and classification of hospital-acquired pneumonia in the Japanese Respiratory Society guidelinesRESPIROLOGY, Issue 6 2008Masafumi SEKI Background and objective: Based on the results of a multicentre collaborative survey of hospital-acquired pneumonia (HAP) conducted in Japan, the severity rating and classification of pneumonia in the Japanese Respiratory Society guidelines for management of HAP were examined. Methods: Parameters for the severity classification were selected from the factors associated with prognosis in the HAP survey and in other previous reports. Depending on the presence of the parameters listed below, patients with HAP were stratified into those with high, moderate or low-risk. The high-risk group was defined as patients with three or more of the following risk factors: ,malignant tumour or immunocompromised status', ,impaired consciousness', ,requiring fraction of inspired oxygen (FiO2) >35% to maintain SaO2 >90%', ,man aged 70 years or older, or woman aged 75 years or older' and ,oliguria or dehydration.' The moderate-risk group was defined as patients with any of the secondary risk factors as follows: ,CRP , 200 mg/L' and ,extent of infiltration on CXR covers at least 2/3 of one lung'. The low-risk group was defined as all other patients. Results: Application of this classification scheme to the patients enrolled in the HAP survey revealed a mortality rate of 40.8% (98/240) in the high-risk group, which was significantly higher than the mortality rates in the moderate and low-risk groups: 24.9% (69/277) and 12.1% (101/834), respectively. Conclusion: These results indicate that it is possible to classify patients using these parameters as prognostic indicators. [source] Polycyclic aromatic hydrocarbons (PAHs) adsorption on solid surfaces applied to waste lubricant oils recovery processTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2010José Lima Assunção Filho Abstract Lubricant oils undergo degradation increasing polycyclic aromatic hydrocarbons (PAHs) concentration. In this work, PAHs adsorption onto activated carbon, powder silica, and powder chitosan surfaces was estimated, with their concentrations in organic solvents (ethanol, 2-propanol, 1-butanol, and terc -butanol) monitored by UV-visible absorption. Equilibrium concentration was attained after 72,h and the isotherms presented characteristic of multilayer formation. The greater surface density was determined for the chitosan, but the system containing activated carbon and 1-butanol presented better efficiency for PAHs removal. Results indicated that the adsorption evaluated in this work can be a potential stage in the waste lubricant oils global recovery process. Les huiles de lubrification subissent une dégradation augmentant la concentration d'hydrocarbures aromatiques polycycliques (HAP). Dans ce travail, on a estimé l'adsorption de HAPs sur du carbone activé, de la silice en poudre et des surfaces de chitosane en poudre, leurs concentrations dans des solvants organiques (éthanol, 2-propanol, 1-butanol et terc -butanol) étant suivies par absorption UV et dans le domaine visible. Une concentration d'équilibre a été atteinte après 72,h et les isothermes présentaient des caractéristiques de formation de couches multiples. La densité de surface la plus importante a été déterminée pour le chitosane mais le système contenant du carbone activé et du 1-butanol présentait une meilleure efficience en matière de retrait des HAPs. Les résultats indiquaient que l'adsorption évaluée dans ce travail pourrait constituer une étape potentielle du processus global de récupération des résidus d'huiles de lubrification. [source] Helikite aerial photography , a versatile means of unmanned, radio controlled, low-altitude aerial archaeologyARCHAEOLOGICAL PROSPECTION, Issue 2 2009Geert J. J. Verhoeven Abstract During the past 100 years, various devices have been developed and applied in order to acquire archaeologically useful aerial imagery from low altitudes (e.g. balloons, kites, poles). This paper introduces Helikite aerial photography (HAP), a new form of close range aerial photography suitable for site or defined area photography, based on a camera suspended from a Helikite: a combination of both a helium balloon and kite wings. By largely overcoming the drawbacks of conventional kite- and balloon-based photography, HAP allows for a very versatile, remotely controlled approach to low-altitude aerial photography (LAAP). In addition to a detailed outline of the whole HAP system, its working procedure and possible improvements, some of the resulting imagery is shown to demonstrate the usefulness of HAP for several archaeological applications. Copyright © 2009 John Wiley & Sons, Ltd. [source] An in,vitro Assay to Measure Targeted Drug Delivery to Bone MineralCHEMMEDCHEM, Issue 5 2010Wolfgang Jahnke Dr. Abstract Targeted delivery of drugs to their site of action is a promising strategy to decrease adverse effects and enhance efficacy, but successful applications of this strategy have been scarce. Human bone is a tissue with unique properties due to its high hydroxyapatite mineral content. However, with the exception of bisphosphonates, bone mineral has not been targeted in a successful clinical application of drugs that act on bone, such as anti-resorptive or bone anabolic agents. Herein we present an NMR-based in,vitro assay to measure binding affinities of small molecules to hydroxyapatite (HAP) or bone powder. Binding was shown to be specific and competitive, and the assay can be carried out in a direct binding format or in competition mode. A selection of clinically relevant bisphosphonates was ranked by their binding affinity for HAP. The binding affinity decreases in the order: pamidronate > alendronate > zoledronate > risedronate > ibandronate. The differences in binding affinities span a factor of 2.1 between pamidronate and ibandronate, consistent with previous studies. The rank order is very similar with bone powder, although the binding capacity of bone powder is smaller and binding kinetics are slower. A zoledronate derivative that lacks the central hydroxy group binds to HAP with 2.3-fold weaker affinity than zoledronate itself. Any small molecule can be analyzed for its binding to HAP or bone powder, and the binding of common bone-staining agents such as alizarin and its derivatives was confirmed in the new assay. This assay supports a strategy for targeted delivery of drugs to bone by attaching a bone-affinity tag to the active drug substance. [source] High Sensibility of Quantum Dots to Metal Ions Inspired by Hydroxyapatite MicrobeadsCHINESE JOURNAL OF CHEMISTRY, Issue 6 2010Xiang Wang Abstract An approach for the sensitive and selective determination of Ag+, Cu2+ and Hg2+ ions was developed based on the fluorescence quenching of mercaptopropionic acid (MPA) capped CdTe quantum dots in the existence of hydroxyapatite (HAP) nanoribbon spherulites. Among various metal ions investigated, it was found that the fluorescence of CdTe QDs was only sensitive to Ag+, Cu2+ and Hg2+ ions. The addition of HAP into the CdTe system could bring forward a sensitivity improvement of about 1 to 2 orders of magnitude in the detection of Ag+ and Cu2+ compared with the plain CdTe system without the existence of HAP; while there was no sensitization effect for Hg2+. Under optimal conditions, the detection limits for Ag+, Cu2+ and Hg2+ were 20, 56 and 3.0 nmol·L,1, respectively, and the linear ranges were 0.02,50, 0.056,54 and 0.003,2.4 µmol·L,1, respectively. Mechanisms of both QDs fluorescence quenching by metal ions and the sensitization effect by HAP were also discussed. [source] Photocatalytic oxidation of methanol using silica-titania composites in a packed-bed reactorENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 4 2006Jennifer M. Stokke Abstract The processing of forest products into pulp, paper, paperboard, and other wood products results in the generation of volatile organic compounds (VOCs) and hazardous air pollutants (HAPs). This work focused on the development of a photocatalytic packed-bed reactor for the oxidation of methanol, which is the primary constituent in high volume low concentration gases emitted from pulp and paper mills. Bench-scale studies using an annular reactor packed with silica-titania composite (STC) pellets were conducted to maximize methanol removal and minimize the formation of byproducts, such as formaldehyde. Parameters such as STC pore size (ca. 40, 120, and 260 Å) and UV wavelength (UVA and UVC) were varied. In the dark, the STC pellets removed methanol via adsorption and had a finite adsorption capacity dependent on the surface area of the composite. When irradiated with UV light, the STC pellets adsorbed and oxidized methanol simultaneously. At the bench-scale, 40 Å STC pellets irradiated with UVC light achieved the greatest methanol removal (ca. 90%) with minimal byproduct formation (i.e., effluent formaldehyde concentration was <1 ppmv). Based on these results, a 40 acfm pilot reactor was fabricated and achieved methanol removal rates up to 66% ± 7% with <1 ppmv formaldehyde production at steady state. © 2006 American Institute of Chemical Engineers Environ Prog, 2006 [source] Polycyclic aromatic hydrocarbons (PAHs) adsorption on solid surfaces applied to waste lubricant oils recovery processTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2010José Lima Assunção Filho Abstract Lubricant oils undergo degradation increasing polycyclic aromatic hydrocarbons (PAHs) concentration. In this work, PAHs adsorption onto activated carbon, powder silica, and powder chitosan surfaces was estimated, with their concentrations in organic solvents (ethanol, 2-propanol, 1-butanol, and terc -butanol) monitored by UV-visible absorption. Equilibrium concentration was attained after 72,h and the isotherms presented characteristic of multilayer formation. The greater surface density was determined for the chitosan, but the system containing activated carbon and 1-butanol presented better efficiency for PAHs removal. Results indicated that the adsorption evaluated in this work can be a potential stage in the waste lubricant oils global recovery process. Les huiles de lubrification subissent une dégradation augmentant la concentration d'hydrocarbures aromatiques polycycliques (HAP). Dans ce travail, on a estimé l'adsorption de HAPs sur du carbone activé, de la silice en poudre et des surfaces de chitosane en poudre, leurs concentrations dans des solvants organiques (éthanol, 2-propanol, 1-butanol et terc -butanol) étant suivies par absorption UV et dans le domaine visible. Une concentration d'équilibre a été atteinte après 72,h et les isothermes présentaient des caractéristiques de formation de couches multiples. La densité de surface la plus importante a été déterminée pour le chitosane mais le système contenant du carbone activé et du 1-butanol présentait une meilleure efficience en matière de retrait des HAPs. Les résultats indiquaient que l'adsorption évaluée dans ce travail pourrait constituer une étape potentielle du processus global de récupération des résidus d'huiles de lubrification. [source] Hazardous air pollutants emission from coal and oil-fired power plantsASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2010Deepak Pudasainee Abstract Hazardous air pollutants (HAPs) emission characteristics from coal (anthracite, bituminous) and oil-fired power plants were studied in order to control pollutants by formulating US maximum achievable control technology (MACT)-like regulation in Korea. Sampling and analysis were carried out according to either Korean standard test method or US EPA method. Relatively lower levels of NOx and SOx were emitted from plants burning bituminous than the anthracite coal. Less dust was emitted from oil-fired power plants. Mercury, lead, and chromium were dominant in coal-fired power plants, following which, nickel and chromium were emitted from oil-fired power plants. The major volatile organic compounds (VOCs) emitted from coal-fired plants were 1,2-dichloroethane, benzene, carbon tetrachloride, chloroform, trichloro-ethylene. The emission of mercury and other heavy metals in flue gas was attributed to fuel types, operating conditions, residence time in the control devices and air pollution control devices configuration. After emission tests in the field and on analysis of the continuous emission monitoring data collected from facilities under operation and consideration of other various factors, management guidelines will be suggested with special reference to US MACT-like regulation. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Polymer Matrix Nanocomposites from Biodegradable Thermoplastic Elastomers,ADVANCED ENGINEERING MATERIALS, Issue 5 2009Miroslawa El Fray Soft and elastomeric poly(ester,ether,ester) multiblock terpolymers were synthesized in presence of 0.5 wt % hydroxyapatite (HAp) nanoparticles to form nanocomposites. The addition of sintered HAp particles enhanced cell proliferation and diminished the number of dead and apoptotic cells. Implantation tests indicated that the observed hard tissue changes led to intense bone remodeling (see picture) [source] Preparation of Nano Carbonate-Substituted Hydroxyapatite from an Amorphous PrecursorINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 5 2008Yanbao Li Carbonated amorphous calcium phosphate (CACP) precursors were precipitated by the wet chemical method at 5°C in the presence of poly(ethylene glycol) and carbonates. The nano carbonate-substituted hydroxyapatite (HAp) was obtained after heat treat CACP precursors at a low temperature (800°C) for 3 h. The calcium phosphates were investigated by X-ray diffraction, Fourier transform infrared spectroscopy, inductively coupled plasma, thermal gravimetric and differential thermal analysis, transmission electron microscopy, and scanning electron microscopy. The results show that calcium phosphate particles with a Ca/P molar ratio of 1.73 are AB-type carbonate-substituted HAp with about 50 nm in diameter. [source] Synthesis and Characterization of Hydroxyapatite/Poly(Vinyl Alcohol Phosphate) Nanocomposite BiomaterialsINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 1 2008Nabakumar Pramanik A hydroxyapatite (HAp)/poly(vinyl alcohol phosphate) (PVAP) nanocomposite has been prepared by a chemical method by varying the HAp content by 10,60% (w/w). The bonding between HAp and PVAP has been investigated through Fourier transform infrared absorption spectra, X-ray diffraction, and thermogravimetric analyses. Transmission electron microscopy study shows a homogeneous dispersion of nanoparticles in the polymer matrix. Scanning electron microscopy study shows enhancement of the surface roughness of the composite with an increase in the nanoparticle content. The mechanical properties of the composites improve significantly with an increase in the HAp content. The HAp/PVAP nanocomposite prepared may have bone,implant applications. [source] Crystal structure of cobalt-substituted calcium hydroxyapatite nanopowders prepared by hydrothermal processingJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2 2010Ljiljana Veselinovi A series of cobalt-exchanged hydroxyapatite (CoHAp) powders with different Ca/Co ratios and nominal unit-cell contents Ca10,xCox(PO4)6(OH)2, x = 0, 0.5, 1.0, 1.5 and 2.0, were synthesized by hydrothermal treatment of a precipitate at 473,K for 8,h. Based on ICP (inductively coupled plasma) emission spectroscopy analysis, it was established that the maximum amount of cobalt incorporation saturated at ,12,at.% under these conditions. The effects of cobalt content on the CoHAp powders were investigated using ICP emission spectroscopy, particle size analysis, transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) analyses as well as X-ray powder diffraction (XRPD) including Rietveld analysis. According to XRPD, all the materials are single-phase HAp and CoHAp of low crystallinity. Rietveld analysis shows that Co enrichment causes the c cell parameter to decrease at a faster rate than the a cell parameter. A microstructural analysis showed anisotropic X-ray line broadening due to crystallite size reduction. In CoHAp there is significant crystal elongation in [001], and the average size decreases with increasing cobalt content. The crystallite morphology transforms from rod-like for the pure HAp to lamellae at the highest degree of Co substitution. The results of Rietveld refinement (symmetry, size and morphology of the crystallites) were confirmed by TEM and HRTEM analysis. [source] Theoretical Defect Energetics in Calcium Phosphate BioceramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2010Katsuyuki Matsunaga Vacancies, impurities, and foreign ions dissolving in calcium phosphate bioceramics play an important role in the biological properties of the materials. However, little is known about the thermodynamic stability of the defects. In this regard, point defects in hydroxyapatite (HAp) and octacalcium phosphate (OCP) were calculated in a first-principles manner, and the chemical-potential dependence of the defect formation energies was revealed. In particular, because calcium phosphates are usually subjected to an aqueous solution, a methodology to evaluate ionic chemical potentials under chemical equilibrium of the solid,aqueous solution was introduced. In the present article, recent results based on such a methodology (the solution pH dependence of Ca/P molar ratio of HAp and the ion-exchange ability with foreign cations in HAp and OCP) were reviewed. [source] Deposition of Carbonated Hydroxyapatite (CO3HAp) on Poly(Methylmethacrylate) Surfaces by Decomposition of Calcium,EDTA ChelateJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2008Yusuf Yusufoglu Inspired from the nature, the development of organic,inorganic composites between polymers and hydroxyapatite (HAp) has been investigated extensively. In this study, bone-like apatite (carbonated hydroxyapatite, CO3HAp) was precipitated on poly(methylmethacrylate) (PMMA) films by the oxidative decomposition of Ca,EDTA (calcium,ethylenediamine tetraacetate) chelates. Corona-treated PMMA films were soaked in a Ca,EDTA,PO4,H2O2 solution and aged at 63°C and pH,9 for times ranging from 1 to 24 h. Apatite formed on PMMA films was characterized by X-ray diffraction, Fourier transform infrared (FTIR), Scanning electron microscope, energy-dipersive X-ray spectroscopy, and carbon analysis. The apatite was found to be CO3HAp with Ca/P atomic ratio ranging between 1.3 and 1.9. Elemental analyses indicated that the carbonate content of the apatite phase was around 6.5 wt% after 24 h of aging time. Lattice parameters were estimated using a Rietveld profile-analysis and found to be a=0.9438 nm and c=0.6901 nm. Furthermore, FTIR spectra indicated that the apatite deposited on PMMA was B-type CO3HAp, in which carbonate ions occupy the phosphate sites. In the first 3 h of aging, isolated rod-like HAp particles were observed. With time, the needle-like crystallites radiate from a nucleus to form double-spherulite shape particles. The crystallites grew into a continuous layer with a thickness of ,15 ,m after 24-h aging. The adhesive strength between the PMMA substrate and the apatite layer was determined to be around 1.7 MPa. [source] Effect of pH on the Carbonate Incorporation into the Hydroxyapatite Prepared by an Oxidative Decomposition of Calcium,EDTA ChelateJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2008Yusuf Yusufoglu In this study, the carbonate incorporation into the hydroxyapatite (HAp) lattice under various pH conditions was investigated. Crystalline-sodium and carbonate-containing calcium HAp (NaCO3HAp) powders were prepared using an oxidative decomposition of calcium,EDTA chelates in a sodium phosphate solution with hydrogen peroxide. The powders obtained were characterized by X-ray diffraction, infrared spectroscopy, thermal gravimetric analysis, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and elemental analysis. Depending on pH, spherical particles approximately 3.5 ,m in diameter or hexagonal prismatic particles measuring 3,9 ,m in length were obtained. Various characterization techniques showed that the precipitates were a single-phase NaCO3HAp. The carbonate content and the lattice parameters of the HAp were a function of solution pH. Maximum carbonate incorporated into the HAp lattice was at pH=10, corresponding to lattice parameters of a=0.93880 nm and c=0.69070 nm. Furthermore, spectroscopic analyses indicate that the as-prepared samples are B-type carbonated HAp, in which carbonate ions occupy the phosphate sites. After heat treatment at 965°C, most of the carbonate is removed from the HAp lattice. [source] | |||||||||||||||||||||||||||||||||||||