Capping Solution Research Articles

Comparative Efficacy of Experimental Solutions in Occluding Dentin Tubules: Calcium Phosphate Based and Oxalate-Based Solutions

To investigate the efficacy in occluding dentin tubules of a modified calcium phosphate based solution supplemented with fluoride and zinc ions (CaP), dentine discs were separately treated with CaP and certain common desensitizing agents including potassium oxalate solution (OX), modified oxalate solutions supplemented with calcium ions (OX/Ca) or phosphate ions (OX/P) for 8 minutes, followed by occluding abilities evaluation with scanning electron microscopy (SEM). CaP showed the highest per cent of sealed dentin tubules and penetrated the most deeply into the tubules, whereas the oxalate modified and unmodified groups showed predominantly open or partially occluded tubules. OX/Ca and OX/P were more efficient in occluding dentin tubules compared with OX. Furthermore, the occluded material obtained with the experimental CaP solutions was more stable (less susceptible to acid dissolution) compared with those from experimental oxalate solutions. Thus CaP could be a new desensitizing agent in dentin hypersensitivity.

Analytical prediction of radiation from a multi-element variable-directivity spherical loudspeaker array and construction and measurement of a prototype

An analysis of radiation from a spherical surface with twelve radiating spherical caps oriented in a dodecahedral arrangement is performed. The approach generalizes the classical single cap solution by utilizing spherical trigonometry transformations to create many spherical caps in different orientations. The calculations include far-field directivity, surface impedances, and net radiated power for a variety of cap motions within the spherical array. Simulations show how well the discrete caps can produce monopole, dipole, and higher mode directivity patterns. Relative motions of the caps are calculated that best simulate these individual radiation modes. The frequency ranges for accurate reproduction of these radiation modes using discrete caps are quantified, and the role of large cap sizes to extend the range is shown. At higher frequencies, the phase interference between discrete cap radiators cause the intended radiation patterns to break down in complicated ways. A prototype 12-element spherical speaker enclosure has been constructed, with the help of a 3-D printer, and tested in an anechoic chamber. The configuration of typical cone loudspeakers creates constraints on the practical design of spherical speakers, limiting the radiating area fraction. Driver design changes to allow more compact spherical speakers with extended frequency range are suggested.

Repair of dentin defects from DSPP knockout mice by PILP mineralization.

Dentinogenesis imperfecta type II (DGI-II) lacks intrafibrillar mineral with severe compromise of dentin mechanical properties. A Dspp knockout (Dspp-/-) mouse, with a phenotype similar to that of human DGI-II, was used to determine if poly-L-aspartic acid [poly(ASP)] in the "polymer-induced liquid-precursor" (PILP) system can restore its mechanical properties. Dentin from six-week old Dspp-/- and wild-type mice was treated with CaP solution containing poly(ASP) for up to 14 days. Elastic modulus and hardness before and after treatment were correlated with mineralization from Micro x-ray computed tomography (Micro-XCT). Transmission electron microscopy (TEM)/Selected area electron diffraction (SAED) were used to compare matrix mineralization and crystallography. Mechanical properties of the Dspp-/- dentin were significantly less than wild-type dentin and recovered significantly (P < 0.05) after PILP-treatment, reaching values comparable to wild-type dentin. Micro-XCT showed mineral recovery similar to wild-type dentin after PILP-treatment. TEM/SAED showed repair of patchy mineralization and complete mineralization of defective dentin. This approach may lead to new strategies for hard tissue repair.

Accuracy of laser-ablation (LA)-MC-ICPMS Sr isotope analysis of (bio)apatite – a problem reassessed

Accurate in situ Sr isotope analysis of (bio)apatite via ‘robust-plasma’ laser-ablation MC-ICPMS with negligible 40Ca31P16O and reliable 87Rb interference correction.

Fabrication of porous carbonate apatite based on setting reaction of carbonate apatite granules

Event Abstract Back to Event Fabrication of porous carbonate apatite based on setting reaction of carbonate apatite granules Kunio Ishikawa1, Kanji Tsuru1 and Song Chen1 1 Kyushu University, Department of Biomaterials, Faculty of Dental Science, Japan Introduction: Carbonate apatite (CO3Ap) was found to up-regulate differentiation of the osteoblastic cells and resorbed by the osteoclasts[1],[2]. Thus, CO3Ap demonstrated much higher osteoconductivity than hydroxyapatite (HAp) and replaced to bone. Replacement to bone is expected to be accelerated by the introduction of interconnected porous structure. In this study, therefore, interconnected porous CO3Ap was fabricated based on setting reaction of CO3Ap granules, and tissue response to the interconnected porous CO3Ap was evaluated histologically. Materials and Method: CO3Ap granules with 100-200 µm in diameter were exposed to acidic calcium phosphate solution (acidic Ca−P: Ca(HPO4)2·H2O − H3PO4) in the presence and absence of the loading. Then, porous body was further immersed in NaHCO3 solution. Composition was analyzed with XRD and the structure was evaluated by micro-CT and SEM. Mechanical strength was evaluated using a universal testing machine. For histological evaluation, porous CO3Ap was placed in the bone defect made at tibiae of rabbit for 4 and 12 wks, and observed after Villanueva Goldner staining. Result and Discussion: When CO3Ap granules were exposed to acidic Ca-P solution, CO2 bubble was formed and no setting reaction was observed even though surface of the CO3Ap was coated with dicalcium phosphate dihydrate [DCPD: CaHPO4·2H2O]. In contrast, interconnected porous body was fabricated when CO3Ap was exposed to acidic Ca-P solution under loading. DCPD crystals formed on the surface of CO3Ap granules bridged the CO3Ap granules one another. These difference indicated that contact of CO3Ap granules one another is the key for the bridging of CO3Ap granules with the DCPD crystals. The DCPD formed on the surface of CO3Ap granules was converted to CO3Ap when immersed in NaHCO3 solution. The pore was interconnected pore and the porosity was 42%. And the compressive strength was approximately 2MPa. When implanted in the rabbit tibiae, bone penetration inside the porous structure was confirmed within 4 wks whereas no bone penetration was observed in the case of dense CO3Ap as shown in Fig. 1. After 12 wks, larger amount of bone was found inside the porous CO3Ap, and CO3Ap was replaced to the bone. In contrast, replacement to bone was limited in the case of dense CO3Ap. Conclusion: Interconnected porous CO3Ap was fabricated based on the setting reaction of CO3Ap granules with acidic Ca-P solution. Interconnected porous CO3Ap elicited the bone tissue penetration interior to the CO3Ap body and accelerated its replacement to bone. Japan Agency for Medical Research and Development.

Preparation and characterization of dopamine-induced biomimetic hydroxyapatite coatings on the AZ31 magnesium alloy

Mg alloys have great potential in biodegradable orthopedic implant applications owing to their rapid degradation in physiological environments and mechanical properties similar to those of bone. However, the extremely high corrosion rate of magnesium alloys has also restricted their medical applications. In this work, a hydroxyapatite (HA) coating was prepared by polydopamine (PDA) induced biomimetic mineralization in a CaP solution to improve the in vitro corrosion resistance and biocompatibility of the AZ31 Mg alloy. The evolution of the phase structure, chemical composition, and surface morphology of the modified AZ31 Mg alloy substrate was evaluated by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and Fourier transform infrared spectroscopy. Potentiodynamic polarization and hydrogen evolution tests demonstrated that the corrosion resistance of the modified AZ31 Mg alloy significantly increased compared with that of the pristine sample. Cytotoxicity testing and cell morphology analysis showed that the as-modified alloy did not induce toxic effects, and promoted the proliferation of L-929 cells. The results suggest that the dopamine-induced biomimetic apatite coating approach is of significant value in the development of biodegradable Mg alloy implants.

Carbon nanotube-gelatin-hydroxyapatite nanohybrids with multilayer core–shell structure for mimicking natural bone

We attempted to mimic collagen fibrils bearing apatite crystals in natural bone, using gelatin, carboxylic acid functionalized carbon nanotubes (f-CNTs), and hydroxyapatite (HA). Gelatin molecules were covalently grafted on the surface of f-CNTs by the formation of amide linkages. HA crystals were then assembled onto the gelatin-grafted f-CNTs in a highly concentrated CaP solution, resulting a multilayered core–shell structure, consisting of a f-CNT core and gelatin-HA shells (as a fibrous multilayered f-CNT/Gel/HA nanohybrid), and in a similar formation to the collagen fibers of natural bone. The tensile strength, elastic modulus, and elongation rate of the new hybrid material were significantly improved compared to both pure (f-CNT free) gelatin and a mixture of f-CNT and gelatin, by 4.6–8.8, 9–10, and 28–42 times, respectively. Cell viability studies of the f-CNT/Gel/HA nanohybrid also suggest a higher degree of biocompatibility compared to pure gelatin.

GW24-e1356 The histocompatibility of angiotensin converting enzyme does not promote its function on inhibitory to negative ventricular remodelling

ObjectivesRenin-angiontensin-aldosterone system (RAAS) is widely evidenced its point on inhibiting ventricular remodelling post myocardial infarction. The increasing expression of angiotensin and angiotensin-converting enzyme (ACE) post infarction and the effectiveness of...

The need for speed and stability in data center power capping

Data centers can lower costs significantly by provisioning expensive electrical equipment (such as UPS, diesel generators, and cooling capacity) for the actual peak power consumption rather than server nameplate power ratings. However, it is possible that this under-provisioned power level is exceeded due to software behaviors on rare occasions and could cause the entire data center infrastructure to breach the safety limits. A mechanism to cap servers to stay within the provisioned budget is needed, and processor frequency scaling based power capping methods are readily available for this purpose. We show that existing methods, when applied across a large number of servers, are not fast enough to operate correctly under rapid power dynamics observed in data centers. We also show that existing methods when applied to an open system (where demand is independent of service rate) can cause cascading failures in the software service hosted, causing the service performance to fall uncontrollably even when power capping is applied for only a small reduction in power consumption. We discuss the causes for both these short-comings and point out techniques that can yield a safe, fast, and stable power capping solution. Our techniques use admission control to limit power consumption and ensure stability, resulting in orders of magnitude improvement in performance. We also discuss why admission control cannot replace existing power capping methods but must be combined with them.

Coprecipitation of DNA and Calcium Phosphate Using an Infusion Fluid Mixture

A surface-mediated gene transfer system using DNA-calcium phosphate (CaP) composite layers (D-CaP layers) would be useful in tissue engineeing. In previous studies, D-CaP layers were fabricated in supersaturated CaP solutions prepared using chemical reagents. In this study, a so-called RKM solution prepared using clinically approved infusion fluids was employed as a supersaturated CaP solution. A D-CaP layer consisting of submicron spherical particles was successfully fabricated on a polystyrene substrate by immersing the substrate in the RKM solution for 24 h. When the immersion period was prolonged from 24 to 72 h, amount of CaP and DNA on the substrate increased. However, the gene transfer capability of the D-CaP layer for the CHO-K1 cells was kept unchanged irrespective of the immersion period. In the RKM solution process, immersion period of 24 h was found to be long enough for gene transfer application of the D-CaP layer. More importantly, the D-CaP layer fabricated by the RKM solution process exhibited a significantly higher gene transfer capability than our previous D-CaP layer fabricated in the conventional CaP solution with the same DNA concentration. The RKM solution process for the fabrication of D-CaP layers was found to be advantageous to the previous process in terms of not only safety but the layers gene transfer capability.

Avascular Necrosis of the Humeral Head: Hemi-Cap, Cap, or Stemmed Solution?

Avascular necrosis of the humeral head, as in other joints, can have a spectrum of severity. The degree of humeral head involvement should dictate the degree of prosthetic replacement required to restore congruity and function. In some very early phases of disease, observation or core decompression and supportive bone grafting may be considered. This article will focus on management of later problems where articular subsidence, degeneration, and arthrosis have dictated the need for varying degrees of prosthetic replacement. With a focal area of necrosis and collapse, but maintenance of peripheral articular congruity and subchondral support, a central core articular humeral replacement can be performed using a focal surface replacement or hemi-cap implant. For more global surface degeneration with maintenance of a relatively healthy surrounding subchondral bone support, total resurfacing of the articular surface can provide a seamless means of restoring congruity without burning the bridges of complete humeral head excision. When advanced, collapse occurs, and there is not enough supportive bone to provide foundation for a resurfacing implant, a stemmed implant should be considered. When biarticular disease ensues, following humeral head collapse and erosion of the glenoid, more formal total shoulder arthroplasty resurfacing is needed. The approach that will be presented here uses a straightforward minimalist conservative approach to the replacement of only the diseased articular surface with preservation of as much bony architecture as possible. This approach provides the surgeon with a process to restore articular congruity while at the same time preserving all viable bony architecture. In young patients, this is important when considering the long-term prospect of the need for future revision surgery.

Microwave‐Assisted Aqueous Synthesis of Small‐Sized, Highly Luminescent CdSeS/ZnS Core/Shell Quantum Dots for Live Cell Imaging

AbstractThis study develops a reliable aqueous‐phase method for the synthesis of CdSeS/ZnS core/shell QDs employing microwave irradiation technique. Firstly, CdSeS core QDs were produced by heating a precursor solution containing Cd2+, 3‐mercaptopropionic acid (MPA) and Na2SeSO3 at 130 °C for 30 min. After purification through centrifugation, the CdSeS core QDs were successfully capped with a ZnS shell through heating a capping solution containing Zn2+, S2– and MPA at 100 °C for 1 h. Both the core/shell QDs and core QDs were characterised by X‐ray powder diffraction, transmission electron microscopy and X‐ray photoelectron spectroscopy, and the epitaxial growth of a ZnS shell on the surface of CdSeS QDs was confirmed. The prepared CdSeS/ZnS core/shell QDs showed significantly enhanced luminescence and photostability than that of CdSeS core QDs. Finally, the CdSeS/ZnS core/shell QDs were applied to image live Hela cells. The pilot experiments showed that the cells were successfully stained and exhibited bright green fluorescence. The small size QDs were localised predominantly in the nuclear compartment of Hela cells with negligible cytotoxicity, even at a concentration of 300 μg mL−1 after 24 h incubation. Our results suggest that the new core/shell QDs could be highly biocompatible and have wide applications in biolabelling and imaging.

Thermal Processing of Calcium Phosphate Coatings on Zirconia Ceramics

A two-step, biomimetic approach was applied for the rapid deposition of octacalcium phosphate (OCP) coatings on zirconia ceramics (Y-TZP). In the first step, sintered zirconia discs were immersed into a supersaturated Ca-P solution with pH=7.4 (CPS1). In the second step, the substrates were transferred from the CPS1 to another Ca-P solution with a lower pH (CPS2). After 6 hours of immersion in the CPS2, a thick coating consisting of large OCP crystals was obtained. Afterwards, the coated substrates were subjected to a thermal treatment in order to improve the attachment of the coating to the substrate.

Analysis for Axial Vibration and Internal Forces of Totally and Partially Embedded Pile Groups with Flexible Caps

In this paper, a simplified analytical method is developed for the axial harmonic response of totally and partially embedded pile groups in homogeneous and layered soil deposits. Based on BDWF model, finite element sub-structure method is used to setup the dynamic model of cap-pile groups which can precisely simulate kinetic interaction and inertial interaction. A comprehensive parameter study focuses on the influence of caps’ elastic modulus and mass density on pile groups’ dynamic response, and then points out the limition of rigid cap in practical design. An approximate solution is finally presented for the internal forces distributed on pile heads due to pile-to-pile interaction. The solution of above approach was compared with that of traditional simplified model (rigid and massless cap solution) in simulating an in-site experiment and dynamics response of partially embedded pile groups for offshore wind farm.

Conical singularities regularized in warped six-dimensional flux compactification and their induced brane cosmology

We discuss the regularization of codimension-2 singularities in warped six-dimensional Einstein-Maxwell axisymmetric models by replacing them by codimension-1 branes of a ring form, situated around the axis of symmetry. Further we consider the case of one capped regularized conical brane of codimension one and study the cosmological evolution which is induced on it as it moves in between the known static bulk and cap solutions. We present the resulting brane Friedmann equation which gives a dominant five-dimensional ρ2 energy density term at high energies and a term linear to the energy density at low energies with, however, negative coefficient in the small four-brane radius limit (i.e., with negative effective Newton's constant).

Induced cosmology on a regularized brane in six-dimensional flux compactification

We consider a six-dimensional Einstein–Maxwell system compactified in an axisymmetric two-dimensional space with one capped regularized conical brane of codimension one. We study the cosmological evolution which is induced on the regularized brane as it moves in between known static bulk and cap solutions. Looking at the resulting Friedmann equation, we see that the brane cosmology at high energies is dominated by a five-dimensional ρ 2 energy density term. At low energies, we obtain a Friedmann equation with a term linear to the energy density with, however, negative coefficient in the small four-brane radius limit (i.e., with negative effective Newton's constant). We discuss ways out of this problem.

Distinct Uptake Mechanisms but Similar Intracellular Processing of Two Different Toll-like Receptor Ligand-Peptide Conjugates in Dendritic Cells

Covalent conjugation of Toll-like receptor ligands (TLR-L) to synthetic antigenic peptides strongly improves antigen presentation in vitro and T lymphocyte priming in vivo. These molecularly well defined TLR-L-peptide conjugates, constitute an attractive vaccination modality, sharing the peptide antigen and a defined adjuvant in one single molecule. We have analyzed the intracellular trafficking and processing of two TLR-L conjugates in dendritic cells (DCs). Long synthetic peptides containing an ovalbumin cytotoxic T-cell epitope were chemically conjugated to two different TLR-Ls the TLR2 ligand, Pam(3)CysSK(4) (Pam) or the TLR9 ligand CpG. Rapid and enhanced uptake of both types of TLR-L-conjugated peptide occurred in DCs. Moreover, TLR-L conjugation greatly enhanced antigen presentation, a process that was dependent on endosomal acidification, proteasomal cleavage, and TAP translocation. The uptake of the CpG approximately conjugate was independent of endosomally-expressed TLR9 as reported previously. Unexpectedly, we found that Pam approximately conjugated peptides were likewise internalized independently of the expression of cell surface-expressed TLR2. Further characterization of the uptake mechanisms revealed that TLR2-L employed a different uptake route than TLR9-L. Inhibition of clathrin- or caveolin-dependent endocytosis greatly reduced uptake and antigen presentation of the Pam-conjugate. In contrast, internalization and antigen presentation of CpG approximately conjugates was independent of clathrin-coated pits but partly dependent on caveolae formation. Importantly, in contrast to the TLR-independent uptake of the conjugates, TLR expression and downstream TLR signaling was required for dendritic cell maturation and for priming of naïve CD8(+) T-cells. Together, our data show that targeting to two distinct TLRs requires distinct uptake mechanism but follows similar trafficking and intracellular processing pathways leading to optimal antigen presentation and T-cell priming.

In vitro culture of mesenchymal cells onto nanocrystalline hydroxyapatite‐coated Ti13Nb13Zr alloy

In this study we coated a new biocompatible, nanostructured titanium alloy, Ti13Nb13Zr, with a thin layer of hydroxyapatite nanocrystals and we investigated the response of human bone-marrow-derived mesenchymal cells. The coating was realized using a slightly supersaturated CaP solution, which provokes a fast deposition of nanocrystalline hydroxyapatite. A thin layer of deposition is appreciable on the etched Ti13Nb13Zr substrates after just 1.5 h soaking in the CaP solution, and it reaches a thickness of 1-2 mum after 3 h soaking. The coating seems thinner than that deposited on Ti6Al4V, which was examined for comparison, likely because of the different roughness profiles of the two etched alloys, and it is constituted of elongated HA nanocrystals, with a mean length of about 100 nm. Mesenchymal stem cells were seeded onto coated and uncoated Ti alloys and cultured for up to 35 days. Cell morphology, proliferation and differentiation were evaluated. The cells display good adhesion and proliferation on the uncoated substrates, whereas the presence of hydroxyapatite coating slightly reduces cell proliferation and induces differentiation of MSCs towards a phenotypic osteoblastic lineage, in agreement with the increase of the expression of osteopontin, osteonectin and collagen type I, evaluated by means of rt-PCR. Type I collagen expression is higher in Ti13Nb13Zr MSC culture compared to Ti6Al4V, standing for a more efficient extracellular matrix deposition.

Osteoinduction using by Human BMP-2-physio-functional Bioactive Ceramics

Pur p ose: T o assess the properties and the osteogenic potency of the calcium phosphate-recom - binant human morphogenetic protein-2 (C aP- rhBMP- 2 composite) on glass-ceramics. Mat e r ia ls and Met h ods: Bioactive glass-ceramics,as a scaffold, and a calcium phosphate (C aP) solution (pH 7.4) were prepared. R ecombinant human bone morphogenetic protein-2 (rhBMP- 2) was purified from C HO- K1 cells by transfecting the cells with BMP- 2 cD NA. T he glass-ceramics were soaked for 3 days at room temperature in saline, a CaP only solution, and a CaP solution containing rhBMP- 2. S canning electron microscopy (S EM) , Fourier transform infrared reflection spectroscopy (F T-IR ), thin film X -ray diffraction (T F-X RD) and immunofluorescent staining (IF) of the anti-human BM P -2 to composite-coated scaffold were performed to verify the characterization of the scaffold surface. In addition, R T-P CR of osteogenic marker gene and S EM photography were performed after adhering the mouse preosteoblast M C3T3- E 1 cells in order to assess the osteoinductivity. Resul ts : CaP-rhBMP-2 composite was coated on the surface of glass-ceramics, as confirmed by S EM, FT-IR , TF-X RD spectrum, and IF . The C aP- rhBMP- 2 composite on the glass-ceramic showed a globular shape covered with fine spikes while the C aP on the glass-ceramic showed a fine spike structure on the flat glass surface. The expression of collagen type I and alkaline phosphatase mRNAs had increased 4 hours after cell seeding. In addition, the level of osteocalcin mRNA ex- pression had increased significantly by 3 days in the CaP-rhBMP-2 composite compared with the control and C aP group. The S EM photographs showed more active filopodia formation in the C aP- rhBMP- 2 composite than the other groups. T here was extensive newly synthesized extracellular matrix around the osteoblasts and C aP- rhBMP- 2 composite nodule.

Substrate Profiling of Cysteine Proteases Using a Combinatorial Peptide Library Identifies Functionally Unique Specificities

The substrate specificities of papain-like cysteine proteases (clan CA, family C1) papain, bromelain, and human cathepsins L, V, K, S, F, B, and five proteases of parasitic origin were studied using a completely diversified positional scanning synthetic combinatorial library. A bifunctional coumarin fluorophore was used that facilitated synthesis of the library and individual peptide substrates. The library has a total of 160,000 tetrapeptide substrate sequences completely randomizing each of the P1, P2, P3, and P4 positions with 20 amino acids. A microtiter plate assay format permitted a rapid determination of the specificity profile of each enzyme. Individual peptide substrates were then synthesized and tested for a quantitative determination of the specificity of the human cathepsins. Despite the conserved three-dimensional structure and similar substrate specificity of the enzymes studied, distinct amino acid preferences that differentiate each enzyme were identified. The specificities of cathepsins K and S partially match the cleavage site sequences in their physiological substrates. Capitalizing on its unique preference for proline and glycine at the P2 and P3 positions, respectively, selective substrates and a substrate-based inhibitor were developed for cathepsin K. A cluster analysis of the proteases based on the complete specificity profile provided a functional characterization distinct from standard sequence analysis. This approach provides useful information for developing selective chemical probes to study protease-related pathologies and physiologies.