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Sample records for microtopography accelerated osseointegration

  1. Single-stage osseointegrated reconstruction and rehabilitation of lower limb amputees: the Osseointegration Group of Australia Accelerated Protocol-2 (OGAAP-2) for a prospective cohort study

    PubMed Central

    Al Muderis, Munjed; Lu, William; Tetsworth, Kevin; Bosley, Belinda; Li, Jiao Jiao

    2017-01-01

    Introduction Lower limb amputations have detrimental influences on the quality of life, function and body image of the affected patients. Following amputation, prolonged rehabilitation is required for patients to be fitted with traditional socket prostheses, and many patients experience symptomatic socket–residuum interface problems which lead to reduced prosthetic use and quality of life. Osseointegration has recently emerged as a novel approach for the reconstruction of amputated limbs, which overcomes many of the socket-related problems by directly attaching the prosthesis to the skeletal residuum. To date, the vast majority of osseointegration procedures worldwide have been performed in 2 stages, which require at least 4 months and up to 18 months for the completion of reconstruction and rehabilitation from the time of the initial surgery. The current prospective cohort study evaluates the safety and efficacy of a single-stage osseointegration procedure performed under the Osseointegration Group of Australia Accelerated Protocol-2 (OGAAP-2), which dramatically reduces the time of recovery to ∼3–6 weeks. Methods and analysis The inclusion criteria for osseointegrated reconstruction under the OGAAP-2 procedure are age over 18 years, unilateral transfemoral amputation and experiencing problems or difficulties in using socket prostheses. All patients receive osseointegrated implants which are press-fitted into the residual bone. Functional and quality-of-life outcome measures are recorded preoperatively and at defined postoperative follow-up intervals up to 2 years. Postoperative adverse events are also recorded. The preoperative and postoperative values are compared for each outcome measure, and the benefits and harms of the single-stage OGAAP-2 procedure will be compared with the results obtained using a previously employed 2-stage procedure. Ethics and dissemination This study has received ethics approval from the University of Notre Dame, Sydney

  2. PDGF-B gene therapy accelerates bone engineering and oral implant osseointegration.

    PubMed

    Chang, P-C; Seol, Y-J; Cirelli, J A; Pellegrini, G; Jin, Q; Franco, L M; Goldstein, S A; Chandler, L A; Sosnowski, B; Giannobile, W V

    2010-01-01

    Platelet-derived growth factor-BB (PDGF-BB) stimulates repair of healing-impaired chronic wounds such as diabetic ulcers and periodontal lesions. However, limitations in predictability of tissue regeneration occur due, in part, to transient growth factor bioavailability in vivo. Here, we report that gene delivery of PDGF-B stimulates repair of oral implant extraction socket defects. Alveolar ridge defects were created in rats and were treated at the time of titanium implant installation with a collagen matrix containing an adenoviral (Ad) vector encoding PDGF-B (5.5 x 10(8) or 5.5 x 10(9) pfu ml(-1)), Ad encoding luciferase (Ad-Luc; 5.5 x 10(9) pfu ml(-1); control) or recombinant human PDGF-BB protein (rhPDGF-BB, 0.3 mg ml(-1)). Bone repair and osseointegration were measured through backscattered scanning electron microscopy, histomorphometry, micro-computed tomography and biomechanical assessments. Furthermore, a panel of local and systemic safety assessments was performed. Results indicated that bone repair was accelerated by Ad-PDGF-B and rhPDGF-BB delivery compared with Ad-Luc, with the high dose of Ad-PDGF-B more effective than the low dose. No significant dissemination of the vector construct or alteration of systemic parameters was noted. In summary, gene delivery of Ad-PDGF-B shows regenerative and safety capabilities for bone tissue engineering and osseointegration in alveolar bone defects comparable with rhPDGF-BB protein delivery in vivo.

  3. Osseointegrated implant prosthodontics.

    PubMed

    Rogoff, G S

    1992-06-01

    This review covers recent literature on prosthodontic aspects of osseointegrated implants. Long-term prognosis, diagnosis and treatment planning, and clinical impression techniques and fabrication technology are discussed.

  4. Osseointegrated finger prostheses.

    PubMed

    Doppen, P; Solomons, M; Kritzinger, S

    2009-02-01

    Amputation of a digit can lead to functional and psychological problems and patients can benefit from digital prostheses. Unfortunately, standard prostheses are often unstable, particularly when fitted over short amputation stumps. Prosthesis fixation by osseointegration is widely used in oral and extraoral applications and may help avoid the problem of instability. This paper reports the results of four patients with five finger amputations who were treated with osseointegrated implants to attach finger prostheses. One implant failed to osseointegrate and the procedure was abandoned. Three patients were successfully treated to completion of three finger prostheses and are extremely satisfied with their outcomes, both cosmetically and functionally, with osseoperception reported by all three patients.

  5. Microtopography of manganese crusts

    NASA Astrophysics Data System (ADS)

    Morgan, Charles L.

    Quantitative examination of the seafloor surface roughness will be necessary for any design of equipment intended for use in collecting surface deposits such as cobalt-rich manganese crusts or nodules. Furthermore, it is an essential prerequisite to the confident interpretation of returns from high frequency side-scan and other acoustic systems. The objectives of the project were to develop the capability at the University of Hawaii of generating high resolution (less than 1 cm horizontal and vertical) topographic models of the seafloor from 35 mm stereo photographs; to produce such models from existing photographs of cobalt-rich manganese crust deposits; and to optimize the configuration of the existing Hawaii Undersea Research Laboratory (HURL) camera system for stereo photograph collection and correlation of acoustic data with the photographic ground-truth. These tasks were accomplished and have also led to the development of a follow-on project (MMTC/OBD Project 1512) dedicated to the simultaneous acquisition of both optical and side-scan acoustic data for future accurate determination of seabed microtopography.

  6. System of optical noncontact microtopography.

    PubMed

    Costa, M F; Almeida, J B

    1993-09-01

    In this paper we describe a method of noncontact optical microtopography based on discrete triangulation. We show that a light beam with an oblique incidence on a surface can be used to assess the distance of the latter to a reference plane if the bright spot produced on the surface is imaged onto an array of detectors that tracks its lateral displacement. The light beam is swept over the surface so that large areas can be scanned. The authors have used their system with success for the topographic inspection of several surfaces, e.g., thin copper and silver films, polyethylene rough films and molds, graphite, machined metallic parts, and fabrics.

  7. Microtopography of the skin and scar formation.

    PubMed

    Tring, F C

    1976-11-01

    The surface microtopography of normal human skin varies from one anatomical region to another. The patterns at different sites are considered to reflect different orientations of dermal fibers. A simple technique is described that enables such orientations to be accurately delineated. Various scars resulting from lacerations, surgical incisions, and steroid-induced striae were examined in the manner described.

  8. Evaluation of Functional Dynamics during Osseointegration and Regeneration Associated with Oral Implants: A Review

    PubMed Central

    Chang, Po-Chun; Lang, Niklaus P.; Giannobile, William V.

    2009-01-01

    Objectives The aim of this paper is to review current investigations on functional assessments of osseointegration and assess correlations to the peri-implant structure. Material and methods The literature was electronically searched for studies of promoting dental implant osseointegration, functional assessments of implant stability, and finite element (FE) analyses in the field of implant dentistry, and any references regarding biological events during osseointegration were also cited as background information. Results Osseointegration involves a cascade of protein and cell apposition, vascular invasion, de novo bone formation and maturation to achieve the primary and secondary dental implant stability. This process may be accelerated by alteration of the implant surface roughness, developing a biomimetric interface, or local delivery of growth-promoting factors. The current available preclinical and clinical biomechanical assessments demonstrated a variety of correlations to the peri-implant structural parameters, and functionally integrated peri-implant structure through FE optimization can offer strong correlation to the interfacial biomechanics. Conclusions The progression of osseointegration may be accelerated by alteration of the implant interface as well as growth factor applications, and functional integration of peri-implant structure may be feasible to predict the implant function during osseointegration. More research in this field is still needed. PMID:20070743

  9. Vertisols with Gilgai Microtopography: Classification and Parameters of Microtopography and Morphological Types of Soils (a Review)

    NASA Astrophysics Data System (ADS)

    Khitrov, N. B.

    2016-02-01

    Data on clayey swelling soils with gilgai microtopography are systematized. Classifications of gilgai microtopography representing regularly alternating microhighs and microlows are discussed, and its geometric parameters under different landscape conditions are considered. Gilgai microtopography is developed within flat or slightly inclined elements of the mesorelief composed of swelling clays of different geneses. These materials are characterized by the high swelling-shrinking capacity upon wetting-drying cycles owing to the predominance of clay minerals of smectitic group. These processes are especially pronounced under conditions of the impeded surface drainage and contrasting of the wet seasons with strong soil moistening by atmospheric precipitation or surface water and the seasons with deep soil drying under the impact of physical evaporation and transpiration. The areas with gilgai microtopography have complex soil cover patterns composed of Vertisols and vertic soils. Their formation is related to lateral movements of solid material in the soil profiles and along the curved soil surface. The morphological types of soil complexes in such area are systematized.

  10. Mechanisms regulating osteoblast response to surface microtopography and vitamin D

    NASA Astrophysics Data System (ADS)

    Bell, Bryan Frederick, Jr.

    A comprehensive understanding of the interactions between orthopaedic and dental implant surfaces with the surrounding host tissue is essential in the design of advanced biomaterials that better promote bone growth and osseointegration of implants. Dental implants with roughened surfaces and high surface energy are well known to promote osteoblast differentiation in vitro and promote increased bone-to-implant contact in vivo. In addition, increased surface roughness increases osteoblasts response to the vitamin D metabolite 1alpha,25(OH)2D3. However, the exact mechanisms mediating cell response to surface properties and 1alpha,25(OH)2D3 are still being elucidated. The central aim of the thesis is to investigate whether integrin signaling in response to rough surface microtopography enhances osteoblast differentiation and responsiveness to 1alpha,25(OH)2D3. The hypothesis is that the integrin alpha5beta1 plays a role in osteoblast response to surface microtopography and that 1alpha,25(OH) 2D3 acts through VDR-independent pathways involving caveolae to synergistically enhance osteoblast response to surface roughness and 1alpha,25(OH) 2D3. To test this hypothesis the objectives of the studies performed in this thesis were: (1) to determine if alpha5beta 1 signaling is required for osteoblast response to surface microstructure; (2) to determine if increased responsiveness to 1alpha,25(OH)2D 3 requires the vitamin D receptor, (3) to determine if rough titanium surfaces functionalized with the peptides targeting integrins (RGD) and transmembrane proteoglycans (KRSR) will enhance both osteoblast proliferation and differentiation, and (4) to determine whether caveolae, which are associated with integrin and 1alpha,25(OH)2D3 signaling, are required for enhance osteogenic response to surface microstructure and 1alpha,25(OH)2D 3. The results demonstrate that integrins, VDR, and caveolae play important roles in mediating osteoblast response to surface properties and 1alpha,25

  11. Effects of capillarity and microtopography on wetland specific yield

    USGS Publications Warehouse

    Sumner, D.M.

    2007-01-01

    Hydrologic models aid in describing water flows and levels in wetlands. Frequently, these models use a specific yield conceptualization to relate water flows to water level changes. Traditionally, a simple conceptualization of specific yield is used, composed of two constant values for above- and below-surface water levels and neglecting the effects of soil capillarity and land surface microtopography. The effects of capiltarity and microtopography on specific yield were evaluated at three wetland sites in the Florida Everglades. The effect of capillarity on specific yield was incorporated based on the fillable pore space within a soil moisture profile at hydrostatic equilibrium with the water table. The effect of microtopography was based on areal averaging of topographically varying values of specific yield. The results indicate that a more physically-based conceptualization of specific yield incorporating capillary and microtopographic considerations can be substantially different from the traditional two-part conceptualization, and from simpler conceptualizations incorporating only capillarity or only microtopography. For the sites considered, traditional estimates of specific yield could under- or overestimate the more physically based estimates by a factor of two or more. The results suggest that consideration of both capillarity and microtopography is important to the formulation of specific yield in physically based hydrologic models of wetlands. ?? 2007, The Society of Wetland Scientists.

  12. Evaluation of structure from motion for soil microtopography measurement

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Recent developments in low cost structure from motion (SFM) technologies offer new opportunities for geoscientists to acquire high resolution soil microtopography data at a fraction of the cost of conventional techniques. However, these new methodologies often lack easily accessible error metrics an...

  13. SOIL MICROTOPOGRAPHY ON GRAZING GRADIENTS IN CHIHUAHUAN DESERT GRASSLANDS

    EPA Science Inventory

    We tested the hypothesis that one of the significant impacts of livestock in the creation of
    piospheres centered on water points is the loss of soil microtopography. The size, height, and spatial distribution of micromounds and surrounding depressions were measured by a modi...

  14. Engineering the microstructure of electrospun fibrous scaffolds by microtopography.

    PubMed

    Cheng, Qian; Lee, Benjamin L-P; Komvopoulos, Kyriakos; Li, Song

    2013-05-13

    Controlling the structure and organization of electrospun fibers is desirable for fabricating scaffolds and materials with defined microstructures. However, the effects of microtopography on the deposition and, in turn, the organization of the electrospun fibers are not well understood. In this study, conductive polydimethylsiloxane (PDMS) templates with different micropatterns were fabricated by combining photolithography, silicon wet etching, and PDMS molding techniques. The fiber organization was varied by fine-tuning the microtopography of the electrospinning collector. Fiber conformity and alignment were influenced by the depth and the slope of microtopography features, resulting in scaffolds comprising either an array of microdomains with different porosity and fiber alignment or an array of microwells. Microtopography affected the fiber organization for hundreds of micrometers below the scaffold surface, resulting in scaffolds with distinct surface properties on each side. In addition, the fiber diameter was also affected by the fiber conformity. The effects of the fiber arrangement in the scaffolds on the morphology, migration, and infiltration of cells were examined by in vitro and in vivo experiments. Cell morphology and organization were guided by the fibers in the microdomains, and cell migration was enhanced by the aligned fibers and the three-dimensional scaffold structure. Cell infiltration was correlated with the microdomain porosity. Microscale control of the fiber organization and the porosity at the surface and through the thickness of the fibrous scaffolds, as demonstrated by the results of this study, provides a powerful means of engineering the three-dimensional structure of electrospun fibrous scaffolds for cell and tissue engineering.

  15. Surface microtopography regulates osteointegration: the role of implant surface microtopography in osteointegration.

    PubMed

    Schwartz, Zvi; Nasazky, Erez; Boyan, Barbara D

    2005-07-01

    Increased surface roughness of dental implants enhances the process of osseointegration. It increases bone conduction and increases BIC in all types of bone, resulting in elevated removal torque values. Surface roughness elevated the CSR of implants implanted in adverse conditions as augmented ridges and sinuses and areas of poor bone, such as the posterior maxilla, and in some cases abolished the deleterious effect of smoking. A growing number of clinical studies suggest that early and immediate loading of rough-surfaced implants may lead to predictable osseointegration. However, it is important to note that these studies provide short-term results based on radiographic observation and clinical mobility only. Before we adopt new surgical and prosthetic guidelines, longer and broader studies are needed. Most recent research has examined the effect of surface roughness on bone healing around implants in vivo and the influence of surface roughness on osteoblasts in vitro. In a study just published, it was found that changing the surface chemistry by submerging an implant in an isotonic sodium chloride solution following acid etching to avoid contamination with molecules from the atmosphere significantly increased osteoblast differentiation in vitro and BIC in vivo. This finding may lead us to a new era in dental implants.

  16. Nanostructured tantala as a template for enhanced osseointegration

    NASA Astrophysics Data System (ADS)

    Ruckh, Timothy; Porter, Joshua R.; Allam, Nageh K.; Feng, Xinjian; Grimes, Craig A.; Popat, Ketul C.

    2009-01-01

    The goal of current dental and orthopedic biomaterials research is to design implants that induce controlled and guided tissue growth, and rapid healing. In addition to acceleration of normal wound healing phenomena, these implants should result in the formation of a characteristic interfacial layer with adequate biomechanical properties. To achieve these goals, however, a better understanding of events at the bone-material interface is needed, as well as the development of new materials and approaches that promote osseointegration. Here we present novel nanostructured nanoarrays from tantala that can promote cell adhesion and differentiation. Our results suggest that tantala nanotube arrays enhance osteoblast cell adhesion, proliferation and differentiation. The routes of fabrication of tantala nanotube arrays are flexible and cost-effective, enabling realization of desired platform topologies on existing non-planar orthopedic implants.

  17. Modeling of surface microtopography and its impacts on hydrologic processes

    NASA Astrophysics Data System (ADS)

    Habtezion, Noah Lebassi

    Understanding the impacts of surface microtopography on hydrologic processes is critical. The objectives of this thesis research are: (1) to evaluate the effects of DEM resolution on microtopographic characteristics, hydrologic connectivity, and modeling of hydrologic processes; and (2) to assess the influences of multiple rainfall events on surface and subsurface hydrologic processes with the use of a puddle-to-puddle (P2P) modeling system. The change in DEM resolution has a significant effect on how surface microtopography is depicted, which in turn alters the hydrologic response of a topographic surface. The smoothing of reduced DEM resolution tends to enhance hydrologic connectivity, reduce the depression storage and infiltration, and increase surface runoff. Temporal rainfall distribution results in spatio-temporal variations in soil water dynamics, depression storage, infiltration, hydrologic connectivity, and surface runoff. The reduction in ponding time and infiltration, and the enhancement of hydrologic connectivity further caused earlier and greater surface runoff generation.

  18. STUDY OF NON-UNIFORMITY COEFFICIENT CONSIDERING MICROTOPOGRAPHY FOR SEISMIC DESIGN OF WATER PIPELINE

    NASA Astrophysics Data System (ADS)

    Shichiroumaru, Kazutaka; Miyajima, Masakatsu

    This study is focusing on a non-uniformity coefficient of ground in the earthquake-resistant of a water pipeline. A lot of earthquake damage occurs at high non-uniformity ground. Therefore it is necessary to consider non-uniformity at the earthquake-resistant of the underground pipeline. By using a microtopography classification, non-uniformity coefficient in the boundary in the microtopography is studied. As a result, earthquake damage rate of underground pipeline at the boundary of the microtopography tends to be high. Therefore, the non-uniformity at the boundary can be obtained from a kind of microtopography and the boundary condition.

  19. Evaluation of skin microtopography as a measure of ultraviolet exposure.

    PubMed

    Seddon, J M; Egan, K M; Zhang, Y; Gelles, E J; Glynn, R J; Tucker, C A; Gragoudas, E S

    1992-05-01

    A pilot study was conducted to investigate the use of skin microtopography as a semiquantitative noninvasive method for estimating cumulative sun exposure in epidemiologic studies of eye disease. The subjects received a kit through the mail containing materials needed to make a replica of the skin texture of a sun-exposed area of the hand. Each subject previously had undergone a skin biopsy around the same site to evaluate elastotic degeneration, and all were interviewed about past sun exposures. A gradable skin impression was obtained from 96 of 115 (83%) participants after two mailings. The impressions were graded according to the degree of skin texture alteration using standard photographs; interobserver reliability was 0.73 using a weighted kappa statistic. The impression score was correlated most strongly with age (r = 0.53). Independent predictors of higher impression scores (more skin texture changes) were older age, cigar or pipe smoking, less education, lighter iris color, lighter skin color, male gender, and tendency to sunburn. After adjustment for age and the other predictor variables, the biopsy score was not correlated with the impression grade (r = 0.18, P = 0.13). Behaviors indexing sun exposure were not correlated with microtopography. These results suggest that skin microtopography as done in this study reflects aging from intrinsic parameters more than from actinic damage.

  20. Engineered antifouling microtopographies: surface pattern effects on cell distribution.

    PubMed

    Decker, Joseph T; Sheats, Julian T; Brennan, Anthony B

    2014-12-23

    Microtopography has been observed to lead to altered attachment behavior for marine fouling organisms; however, quantification of this phenomenon is lacking in the scientific literature. Here, we present quantitative measurement of the disruption of normal attachment behavior of the fouling algae Ulva linza by antifouling microtopographies. The distribution of the diatom Navicula incerta was shown to be unaffected by the presence of topography. The radial distribution function was calculated for both individual zoospores and cells as well as aggregates of zoospores from attachment data for a variety topographic configurations and at a number of different attachment densities. Additionally, the screening distance and maximum values were mapped according to the location of zoospore aggregates within a single unit cell. We found that engineered topographies decreased the distance between spore aggregates compared to that for a smooth control surface; however, the distributions for individual spores were unchanged. We also found that the local attachment site geometry affected the screening distance for aggregates of zoospores, with certain geometries decreasing screening distance and others having no measurable effect. The distribution mapping techniques developed and explored in this article have yielded important insight into the design parameters for antifouling microtopographies that can be implemented in the next generation of antifouling surfaces.

  1. Engineered microtopographies and surface chemistries direct cell attachment and function

    NASA Astrophysics Data System (ADS)

    Magin, Chelsea Marie

    Harrison, in 1914, first recognized that cells respond to physicochemical cues such as substratum topography when he observed that fibroblasts elongated while cultured on spider silk. Recently, techniques developed in the micro-electronics industry have been used to create molds for producing microscaled topographies with various shapes and spatial arrangements. Although these patterning techniques are well-established, very little is known about the mechanisms underlying cell sensing and response to microtopographies. In this work cellular micro-environments with varying surface topographies and chemistries were evaluated with marine organisms and mammalian cells to investigate cellular sensing and response. Biofouling---the accumulation of micro-organisms, plants, and animals on submerged surfaces---is an environmental and economic concern. Engineered topographies, replicated in polydimethylsiloxane elastomer (PDMSe) and functionalized poly(ethylene glycol)-dimethacrylate (PEGDMA) hydrogels, were evaluated for inhibition of marine fouling organism attachment. Microtopographies replicated in PDMSe inhibited attachment of the marine bacterium, Cobetia marina up to 99% versus smooth. The average normalized attachment densities of cells of C. marina and zoospores of the green algae Ulva on PDMSe topographies scaled inversely with the Engineered Roughness Index (ERIII), a representation of surface energy. Attachment densities of Ulva from four assays and C. marina from two growth phases to PDMSe surfaces scaled inversely with one equation: ERI II multiplied by the Reynolds number of the organism (Re) (R 2 = 0.77). The same microtopographies created in PDMSe reduced the initial attachment density and attachment strength of cells of the diatoms Navicula incerta and Seminavis robusta compared to smooth PDMSe. The average normalized attachment density of Navicula after exposure to shear stress (48 Pa) was correlated with the contact area between the diatom and a

  2. Posıtıve effect of platelet rich fibrin on osseointegration

    PubMed Central

    Bayram, Burak; Kantarcı, Alpdoğan; Gülsever, Serap; Alaaddinoğlu, Emine-Elif

    2016-01-01

    Background Leukocyte-platelet rich fibrin (L-PRF) is a second generation platelet concentrate clinically used to accelerate tissue healing and bone regeneration. Achieving reduced implant osseointegration time could provide immediate or early loading of implants. The aim of this study was to evaluate the L-PRF-induced osseointegration and bone-implant contact (BIC) in an experimental animal model. Material and Methods Twelve 4-month-old New Zealand white rabbits were used. Following general anesthesia, 3-5 mL of blood was obtained from the central artery in rabbit ear and L-PRF was prepared. Two implant cavities (5 mm long and 3 mm in diameter) were created in each tibia with a total of four cavities in each animal. Two of these cavities were selected and covered with PRF (test group). The remaining L-PRF was used to soak the implants placed into the L-PRF covered sockets. Other cavities were left as controls. In total, 48 implants were placed. Animals were sacrificed after two, three, or four weeks. Histological samples were obtained and peri-implant tissues were histomorphometrically evaluated for bone-to-implant contact and new bone formation. Results Histomorphometric analyses of the defects revealed that the L-PRF was detectable up to the second week. Application of L-PRF increased the rate and amount of new bone formation in the experimental group compared to the control group. Bone-to-implant contact was enhanced when the surface was pre-wetted with L-PRF (p<0.01). Conclusions The results of this study demonstrated that L-PRF application may increases amount and rate of new bone formation during the early healing period and provides a faster osseointegration around implants. Key words:Dental implants, platelet rich fibrin, osseointegration, bone regeneration, matrix for growth factors. PMID:27475686

  3. The genesis of vertisols with gilgai microtopography: A review

    NASA Astrophysics Data System (ADS)

    Khitrov, N. B.

    2016-05-01

    Different hypotheses about the genesis of gilgai microtopography and corresponding soil complexes with clayey swelling soils are considered in this review. Their diversity is stipulated by specificities of the objects themselves and by the history of studies of the composition, properties, regimes, and landscape conditions of the areas with Vertisols in different countries. Most of the hypotheses about the genesis of Vertisols with the gilgai microtopography suggest that strong swelling-shrinking processes take place in these soils in the course of moistening-drying cycles; the origin of shear stress in the soils, its spatial patterns, and the particular ways of translocation of the soil material are discussed. At the early stage of Vertisol studies, a hypothesis about the leading role of the process of "self-swallowing" of the soils as a result of filling of open cracks with the material from the upper soil horizons was popular. However, numerous facts suggest that the intensity of this process is relatively low, so that it cannot play the major role in the gilgai formation and cyclic changes in the thickness and properties of the soil horizons in Vertisols. Another important mechanism is the uneven moistening and drying of the whole soil volume resulting in the irregular distribution of inner tensions in the soil with the development of shear stress and plastic deformation of the soil mass. The hypotheses suggested in the recent decades are based on the models of soil mechanics. A number of hypotheses consider possible alternation and duration of evolutionary stages of the development of Vertisols with the gilgai microtopography.

  4. Microtopography enhances nitrogen cycling and removal in created mitigation wetlands

    USGS Publications Warehouse

    Wolf, K.L.; Ahn, C.; Noe, G.B.

    2011-01-01

    Natural wetlands often have a heterogeneous soil surface topography, or microtopography (MT), that creates microsites of variable hydrology, vegetation, and soil biogeochemistry. Created mitigation wetlands are designed to mimic natural wetlands in structure and function, and recent mitigation projects have incorporated MT as one way to attain this goal. Microtopography may influence nitrogen (N) cycling in wetlands by providing adjacent areas of aerobic and anaerobic conditions and by increasing carbon storage, which together facilitate N cycling and removal. This study investigated three created wetlands in the Virginia Piedmont that incorporated disking-induced MT during construction. One site had paired disked and undisked plots, allowing an evaluation of the effects of this design feature on N flux rates. Microtopography was measured using conventional survey equipment along a 1-m circular transect and was described using two indices: tortuosity (T), describing soil surface roughness and relief, and limiting elevation difference (LD), describing soil surface relief. Ammonification, nitrification, and net N mineralization were determined with in situ incubation of modified ion-exchange resin cores and denitrification potential was determined using denitrification enzyme assay (DEA). Results demonstrated that disked plots had significantly greater LD than undisked plots one year after construction. Autogenic sources of MT (e.g. tussock-forming vegetation) in concert with variable hydrology and sedimentation maintained and in some cases enhanced MT in study wetlands. Tortuosity and LD values remained the same in one wetland when compared over a two-year period, suggesting a dynamic equilibrium of MT-forming and -eroding processes at play. Microtopography values also increased when comparing the original induced MT of a one-year old wetland with MT of older created wetlands (five and eight years old) with disking-induced MT, indicating that MT can increase by

  5. Simulating effects of microtopography on wetland specific yield and hydroperiod

    USGS Publications Warehouse

    Summer, David M.; Wang, Xixi

    2011-01-01

    Specific yield and hydroperiod have proven to be useful parameters in hydrologic analysis of wetlands. Specific yield is a critical parameter to quantitatively relate hydrologic fluxes (e.g., rainfall, evapotranspiration, and runoff) and water level changes. Hydroperiod measures the temporal variability and frequency of land-surface inundation. Conventionally, hydrologic analyses used these concepts without considering the effects of land surface microtopography and assumed a smoothly-varying land surface. However, these microtopographic effects could result in small-scale variations in land surface inundation and water depth above or below the land surface, which in turn affect ecologic and hydrologic processes of wetlands. The objective of this chapter is to develop a physically-based approach for estimating specific yield and hydroperiod that enables the consideration of microtopographic features of wetlands, and to illustrate the approach at sites in the Florida Everglades. The results indicate that the physically-based approach can better capture the variations of specific yield with water level, in particular when the water level falls between the minimum and maximum land surface elevations. The suggested approach for hydroperiod computation predicted that the wetlands might be completely dry or completely wet much less frequently than suggested by the conventional approach neglecting microtopography. One reasonable generalization may be that the hydroperiod approaches presented in this chapter can be a more accurate prediction tool for water resources management to meet the specific hydroperiod threshold as required by a species of plant or animal of interest.

  6. Longevity of treethrow microtopography: implications for mass wasting

    USGS Publications Warehouse

    Schaetzl, R.J.; Follmer, L.R.

    1990-01-01

    This study examines and compares methods of dating pit/mound microtopography formed by tree uprooting, and provides 14C evidence for the longevity of these landforms. Microtopography can often by dated by reference to known meteorological phenomena, or within certain age constraints, by dendrochronologic means. We used 14C analysis of buried wood and charcoal in treethrow mounds in Michigan and Wisconsin, U.S.A. to arrive at estimates of the geochronometric ages of treethrow mounds. Results indicate that mounds in these areas often persist for more than 1000 years, which are two to five times longer than published estimates by less reliable methods. The longevity of treethrow mounds in these regions is ascribed to (l) sandy, porous soils which minimize runoff, (2) a continuous mat of forest litter and vegetation cover, (3) surface concentrations of gravel which may act as an "armor", (4) large initial size of the features, and (5) soil freezing. Implications are that rates of mass movement due to uprooting may be substantially less than studies from other regions suggest. ?? 1990.

  7. Properties and regimes of vertisols with gilgai microtopography (a review)

    NASA Astrophysics Data System (ADS)

    Khitrov, N. B.

    2016-03-01

    Data on the morphology and spatial distribution of slickensides and cracks, particle-size distribution, the organic carbon content, the content and forms of carbonate concentrations, and physical and physicochemical properties of Vertisols with the gilgai microtopography are systematized. Relatively scarce information on the functioning regimes of gilgai soil complexes (their temperature and moisture conditions, redox potential, vertical and horizontal deformations, and soil density changes) is discussed. Common properties of gilgai soils are the clayey texture of their profiles and the high portion of smectitic minerals specifying the high shrink-swell capacity of the soil material. The most important specificity of soils with the gilgai microtopography is a significant horizontal differentiation of the soil profiles with alternation of bowl-shaped morphostructures with a thick dark layer without carbonates in microlows and diapiric morphostructures composed of the rising material of the lower layers with diverse carbonate concentrations on microhighs. Data on the spatial distribution of soil properties within the gilgai microcatenas can be applied in the studies of the genesis and evolution stages of the gilgai soil complexes.

  8. Longevity of treethrow microtopography: implications for mass wasting

    NASA Astrophysics Data System (ADS)

    Schaetzl, Randall J.; Follmer, Leon R.

    1990-06-01

    This study examines and compares methods of dating pit/mound microtopography formed by tree uprooting, and provides 14C evidence for the longevity of these landforms. Microtopography can often by dated by reference to known meteorological phenomena, or within certain age constraints, by dendrochronologic means. We used 14C analysis of buried wood and charcoal in treethrow mounds in Michigan and Wisconsin, U.S.A. to arrive at estimates of the geochronometric ages of treethrow mounds. Results indicate that mounds in these areas often persist for more than 1000 years, which are two to five times longer than published estimates by less reliable methods. The longevity of treethrow mounds in these regions is ascribed to (l) sandy, porous soils which minimize runoff, (2) a continuous mat of forest litter and vegetation cover, (3) surface concentrations of gravel which may act as an "armor", (4) large initial size of the features, and (5) soil freezing. Implications are that rates of mass movement due to uprooting may be substantially less than studies from other regions suggest.

  9. The influence of controlled surface nanotopography on the early biological events of osseointegration.

    PubMed

    Karazisis, Dimitrios; Petronis, Sarunas; Agheli, Hossein; Emanuelsson, Lena; Norlindh, Birgitta; Johansson, Anna; Rasmusson, Lars; Thomsen, Peter; Omar, Omar

    2017-02-21

    The early cell and tissue interactions with nanopatterned titanium implants are insufficiently described in vivo. A limitation has been to transfer a pre-determined, well-controlled nanotopography to 3D titanium implants, without affecting other surface parameters, including surface microtopography and chemistry. This in vivo study aimed to investigate the early cellular and molecular events at the bone interface with screw-shaped titanium implants superimposed with controlled nanotopography. Polished and machined titanium implants were firstly patterned with 75-nm semispherical protrusions. Polished and machined implants without nano-patterns were designated as controls. Thereafter, all nanopatterned and control implants were sputter-coated with a 30nm titanium layer to unify the surface chemistry. The implants were inserted in rat tibiae and samples were harvested after 12h, 1d and 3d. In one group, the implants were unscrewed and the implant-adherent cells were analyzed using quantitative polymerase chain reaction. In another group, implants with surrounding bone were harvested en bloc for histology and immunohistochemistry. The results showed that nanotopography downregulated the expression of monocyte chemoattractant protein-1 (MCP-1), at 1d, and triggered the expression of osteocalcin (OC) at 3d. This was in parallel with a relatively lower number of recruited CD68-positive macrophages in the tissue surrounding the nanopatterned implants. Moreover, a higher proportion of newly formed osteoid and woven bone was found at the nanopatterned implants at 3d. It is concluded that nanotopography, per se, attenuates the inflammatory process and enhances the osteogenic response during the early phase of osseointegration. This nanotopography-induced effect appeared to be independent of the underlying microscale topography.

  10. Bone and metal: an orthopaedic perspective on osseointegration of metals.

    PubMed

    Goriainov, Vitali; Cook, Richard; M Latham, Jeremy; G Dunlop, Douglas; Oreffo, Richard O C

    2014-10-01

    The area of implant osseointegration is of major importance, given the predicted significant rise in the number of orthopaedic procedures and an increasingly ageing population. Osseointegration is a complex process involving a number of distinct mechanisms affected by the implant bulk properties and surface characteristics. Our understanding and ability to modify these mechanisms through alterations in implant design is continuously expanding. The following review considers the main aspects of material and surface alterations in metal implants, and the extent of their subsequent influence on osseointegration. Clinically, osseointegration results in asymptomatic stable durable fixation of orthopaedic implants. The complexity of achieving this outcome through incorporation and balance of contributory factors is highlighted through a clinical case report.

  11. Where bone meets implant: the characterization of nano-osseointegration

    NASA Astrophysics Data System (ADS)

    Grandfield, Kathryn; Gustafsson, Stefan; Palmquist, Anders

    2013-05-01

    The recent application of electron tomography to the study of biomaterial interfaces with bone has brought about an awareness of nano-osseointegration and, to a further extent, demanded increasingly advanced characterization methodologies. In this study, nanoscale osseointegration has been studied via laser-modified titanium implants. The micro- and nano-structured implants were placed in the proximal tibia of New Zealand white rabbits for six months. High-resolution transmission electron microscopy (HRTEM), analytical microscopy, including energy dispersive X-ray spectroscopy (EDXS) and energy-filtered TEM (EFTEM), as well as electron tomography studies were used to investigate the degree of nano-osseointegration in two- and three-dimensions. HRTEM indicated the laser-modified surface encouraged the formation of crystalline hydroxyapatite in the immediate vicinity of the implant. Analytical studies suggested the presence of a functionally graded interface at the implant surface, characterized by the gradual intermixing of bone with oxide layer. Yet, the most compelling of techniques, which enabled straightforward visualization of nano-osseointegration, proved to be segmentation of electron tomographic reconstructions, where thresholding techniques identified bone penetrating into the nanoscale roughened surface features of laser-modified titanium. Combining high-resolution, analytical and three-dimensional electron microscopy techniques has proven to encourage identification and understanding of nano-osseointegration.The recent application of electron tomography to the study of biomaterial interfaces with bone has brought about an awareness of nano-osseointegration and, to a further extent, demanded increasingly advanced characterization methodologies. In this study, nanoscale osseointegration has been studied via laser-modified titanium implants. The micro- and nano-structured implants were placed in the proximal tibia of New Zealand white rabbits for six months

  12. Adhesion and migration of cells responding to microtopography.

    PubMed

    Estévez, Maruxa; Martínez, Elena; Yarwood, Stephen J; Dalby, Matthew J; Samitier, Josep

    2015-05-01

    It is known that cells respond strongly to microtopography. However, cellular mechanisms of response are unclear. Here, we study wild-type fibroblasts responding to 25 µm(2) posts and compare their response to that of FAK(-/-) fibroblasts and fibroblasts with PMA treatment to stimulate protein kinase C (PKC) and the small g-protein Rac. FAK knockout cells modulated adhesion number and size in a similar way to cells on topography; that is, they used more, smaller adhesions, but migration was almost completely stalled demonstrating the importance of FAK signaling in contact guidance and adhesion turnover. Little similarity, however, was observed to PKC stimulated cells and cells on the topography. Interestingly, with PKC stimulation the cell nuclei became highly deformable bringing focus on these surfaces to the study of metastasis. Surfaces that aid the study of cellular migration are important in developing understanding of mechanisms of wound healing and repair in aligned tissues such as ligament and tendon.

  13. Unusual Microtopography on an Apollo 12 Soil Grain

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, K. L.; Keprta, N. T.; Clemett, S. J.; Berger, E. L.; Rahman, Z.; McKay, D. S.; Gibson, E. K.; Wentworth, S. J.

    2014-01-01

    We have observed the presence of a previously undescribed microtopography in several regions on the surface of a lunar grain from Apollo regolith sample 12070,29. This microtopography consists of flattened triangular prisms, henceforth referred to as denticles, set in an orderly arrangement. We propose three possible processes to describe the presence of these structures: (1) radiation; (2) aqueous activity; or (3) impact. Radiation—the surface of the Earth’s moon is subject to energetic ion and photon irradiation which can produce a multitude of morphological effects on grain surfaces including erosion/sputtering, vesicle formation, and amorphization of crystalline phases. Under certain conditions surface erosion can result in the formation of well-ordered nanostructures including mounds, dots, wave-shaped, rippled or corrugated features typically <10s nm in size and organized into pattered arrays. However larger pyramid-shaped features up to approx. 300 nm at the base, similar in shape to lunar denticles, were produced on Cu substrates ex-posed to ion beam sputtering.. Aqueous alteration—recent reports of purported water on the Moon imply the possibility of brief, limited exposure of surface materials to aqueous fluids. Aqueous corrosion of silicates can result in the formation of crystallographically controlled denticulated features, up to 10s of micron at the base, arranged in a patterned formation. Impact—the surface of the moon is impacted by meteorites, particularly by micron-size particles, resulting in the formation of a variety of crater types. While it is difficult to envision a scenario in which a patterned array could be formed by impact, fracturing along planes of crystallographic structural weakness due to external stress could explain these features.

  14. Fire and Microtopography in Peatlands: Feedbacks and Carbon Dynamics

    NASA Astrophysics Data System (ADS)

    Benscoter, B.; Turetsky, M. R.

    2011-12-01

    Fire is the dominant natural disturbance in peatland ecosystems. Over the past decade, peat fires have emerged as an important issue for global climate change, human health, and economic loss, largely due to the extreme peat fire events in Indonesia and Russia that severely impacted metropolitan areas and social infrastructure. However, the impact and importance of fire in peatland ecosystems are more far-reaching. Combustion of vegetation and soil organic matter releases an average of 2.2 kg C m-2 to the atmosphere, primarily as CO2, as well as a number of potentially harmful emissions such as fine particulate matter and mercury. Additionally, while peatlands are generally considered to be net sinks of atmospheric carbon, the removal of living vegetation by combustion halts primary production following fire resulting in a net loss of ecosystem carbon to the atmosphere for several years. The recovery of carbon sink function is linked to plant community succession and development, which can vary based on combustion severity and the resulting post-fire microhabitat conditions. Microtopography has a strong influence on fire behavior and combustion severity during peatland wildfires. In boreal continental peatlands, combustion severity is typically greatest in low-lying hollows while raised hummocks are often lightly burned or unburned. The cross-scale influence of microtopography on landscape fire behavior is due to differences in plant community composition between microforms. The physiological and ecohydrological differences among plant communities result in spatial patterns in fuel availability and condition, influencing the spread, severity, and type of combustion over local to landscape scales. In addition to heterogeneous combustion loss of soil carbon, this differential fire behavior creates variability in post-fire microhabitat conditions, resulting in differences in post-fire vegetation succession and carbon exchange trajectories. These immediate and legacy

  15. [Oromandibular reconstruction with free peroneal flap and osseointegrated implants].

    PubMed

    Navarro Cuéllar, C; Cuesta Gil, M; Plasencia Delgado, J; Guerra Martínez, B; Acero Sanz, J; López de Atalaya, F J; Ochandiano Caicoya, S; Navarro Vila, C

    2003-01-01

    Free fibula flaps have proved to be one of the most versatile for oromandibular reconstruction due to the available length of bone and the possibility of incorporating a long skin paddle to cover intraoral soft tissues. The use of a osseointegrated dental implants is an important technique for the oral rehabilitation of these patients. Osseointegrated implants provide the most rigid prosthetic stabilization available to withstand masticatory forces. These implants can be placed immediately or in second time procedure. In our case, implantation in the fibula free flap is done after 6-9 months because of the large amount of osteosynthesis material required for the fixation of the flap. Four or six months later, when osseointegration has taken place, the implants are loaded with a dental rehabilitation. We analize 10 cases of mandibular reconstruction with fibula free flap and their aesthetic and functional rehabilitation with osseointegrated implants with a 2 year follow up. Forty-six dental implants were placed developing all of them but one a correct osseointegration. All these patients recovered masticatory function and underwent a considerable improvement in labial competence, salivary continence, speech articulation and facial harmony.

  16. Advances in surfaces and osseointegration in implantology. Biomimetic surfaces

    PubMed Central

    Albertini, Matteo; Fernandez-Yague, Marc; Lázaro, Pedro; Herrero-Climent, Mariano; Bullon, Pedro; Gil, Francisco-Javier

    2015-01-01

    The present work is a revision of the processes occurring in osseointegration of titanium dental implants according to different types of surfaces -namely, polished surfaces, rough surfaces obtained from subtraction methods, as well as the new hydroxyapatite biomimetic surfaces obtained from thermochemical processes. Hydroxyapatite’s high plasma-projection temperatures have proven to prevent the formation of crystalline apatite on the titanium dental implant, but lead to the formation of amorphous calcium phosphate (i.e., with no crystal structure) instead. This layer produce some osseointegration yet the calcium phosphate layer will eventually dissolve and leave a gap between the bone and the dental implant, thus leading to osseointegration failure due to bacterial colonization. A new surface -recently obtained by thermochemical processes- produces, by crystallization, a layer of apatite with the same mineral content as human bone that is chemically bonded to the titanium surface. Osseointegration speed was tested by means of minipigs, showing bone formation after 3 to 4 weeks, with the security that a dental implant can be loaded. This surface can be an excellent candidate for immediate or early loading procedures. Key words:Dental implants, implants surfaces, osseointegration, biomimetics surfaces. PMID:25662555

  17. Osseointegration and guided bone regeneration in ectodermal dysplasia patients.

    PubMed

    Garagiola, Umberto; Umberto, Garagiola; Maiorana, Carlo; Ghiglione, Valentino; Marzo, Giuseppe; Santoro, Franco; Szabò, Gyorgy

    2007-11-01

    Dental and surgical implant treatment for patients affected by ectodermal dysplasia syndrome can be very complicated. The guided bone regeneration (GBR) membrane technique together with bone grafting is used to facilitate the placement of osseointegrated implants in a prosthetically guided position. Two groups with the same bony anatomical features were assessed. The first consisted of 13 ectodermal dysplasia patients in whom 66 implants with bone grafts and membranes were inserted. In the second control group, 120 implants with GBR were placed in 20 patients. The implants were assessed at the second stage of surgery, and at a follow-up after 1, 2, and 3 years of functional loading. There was no statistically significant difference in the osseointegration rate between the two groups. Despite the anatomical defects associated with the decreased occlusal vertical dimension and the reduced edentulous alveolar ridges, both in height and width, osseointegrated implants together with GBR and bone grafts can be used successfully in patients with ectodermal dysplasia syndrome.

  18. Resonance Frequency Analysis for Osseointegration in Four Surgical Conditions of Dental Implants

    DTIC Science & Technology

    2001-10-25

    Abstract-The establishment of osseointegration following dental implant placement is a major contributing factor to the clinical success and long...period. Our results showed that there was an increase in resonance frequency related to stiffness increment during osseointegration. Keywords – dental ...implant, osseointegration, resonance frequency, stability I. INTRODUCTION Dental implants are being used increasingly to provide support and retention

  19. Three dimensional spatial separation of cells in response to microtopography.

    PubMed

    Leclerc, Alexandre; Tremblay, Dominique; Hadjiantoniou, Sebastian; Bukoreshtliev, Nickolay V; Rogowski, Jacob L; Godin, Michel; Pelling, Andrew E

    2013-11-01

    Cellular organization, migration and proliferation in three-dimensions play a critical role in numerous physiological and pathological processes. Nano- and micro-fabrication approaches have demonstrated that nano- and micro-scale topographies of the cellular microenvironment directly impact organization, migration and proliferation. In this study, we investigated these dynamics of two cell types (NIH3T3 fibroblast and MDCK epithelial cells) in response to microscale grooves whose dimensions exceed typical cell sizes. Our results demonstrate that fibroblasts display a clear preference for proliferating along groove ridges whereas epithelial cells preferentially proliferate in the grooves. Importantly, these cell-type dependent behaviours were also maintained when in co-culture. We show that it is possible to spatially separate a mixed suspension of two cell types by allowing them to migrate and proliferate on a substrate with engineered microtopographies. This ability may have important implications for investigating the mechanisms that facilitate cellular topographic sensing. Moreover, our results may provide insights towards the controlled development of complex three-dimensional multi-cellular constructs.

  20. AFM analysis of bleaching effects on dental enamel microtopography

    NASA Astrophysics Data System (ADS)

    Pedreira de Freitas, Ana Carolina; Espejo, Luciana Cardoso; Botta, Sergio Brossi; Teixeira, Fernanda de Sa; Luz, Maria Aparecida A. Cerqueira; Garone-Netto, Narciso; Matos, Adriana Bona; Salvadori, Maria Cecilia Barbosa da Silveira

    2010-02-01

    The purpose of this in vitro study was to test a new methodology to evaluate the effects of 35% hydrogen peroxide agent on the microtopography of sound enamel using an atomic force microscope (AFM). The buccal sound surfaces of three extracted human lower incisors were used, without polishing the surfaces to maintain them with natural morphology. These unpolished surfaces were subjected to bleaching procedure with 35% hydrogen peroxide that consisted of 4 applications of the bleaching agent on enamel surfaces for 10 min each application. Surface images were obtained in a 15 μm × 15 μm area using an AFM. The roughness (Ra and RMS) and the power spectral density (PSD) were obtained before and after the bleaching treatment. As results we could inquire that the PSD analyses were very suitable to identifying the morphological changes on the surfaces, while the Ra and RMS parameters were insufficient to represent the morphological alterations promoted by bleaching procedure on enamel. The morphological wavelength in the range of visible light spectrum (380-750 nm) was analyzed, showing a considerable increase of the PSD with the bleaching treatment.

  1. Microtopography of hillslopes and initiation of channels by horton overland flow

    NASA Astrophysics Data System (ADS)

    Dunne, Thomas; Whipple, Kelin X.; Aubry, Brian F.

    On long hillsides one can examine systematic downslope changes in the ground surface as Horton overland flow gathers into depressions and eventually incises the surface to form channels. Microtopography plays an important role in this process. We have sampled the microtopography of two long hillslopes in a savanna region of southern Kenya, and defined the spectral characteristics of its roughness at various distances from the drainage divide. The microtopography is fractal with a dimension that decreases systematically downslope, and the overall roughness varies between and along hillslopes in response to: (i) the weathering characteristics of the underlying bedrock; (ii) the type and density of patchy vegetation, and (iii) the tendency for wash to incise the surface with increasing intensity as runoff discharge increases downslope. The downslope decrease in fractal dimension reflects the progressive development of low-frequency roughness, here referred to as "swaley" microtopography, which the wash develops even far upslope of the channel head. The statistical analysis of surface roughness motivates a discussion of the role of microtopography in the interaction between wash and diffusive sediment transport processes that ultimately determines the critical distance from the divide at which channels begin.

  2. Incorporating Information on (micro)Topography when Modelling Soil Erosion at the Watershed Scale

    NASA Astrophysics Data System (ADS)

    Cerdan, O.

    2015-12-01

    In the context of shallow flows, the spatial distribution of the flow is highly influenced by the micro-topography. For instance, local oriented depressions may exist in which the flow depth and velocity may exceed the threshold for soil erosion initiation. If a mean uniform flow shear stress is used to characterize the area, it would be smaller and therefore may not initiate erosion. However, management of water and sediment fluxes requires analysis and modeling at the watershed scale in order to integrate the relations between upstream and downstream areas. At this scale, high resolution information on the microtopography is usually not always available and would anyway require too extensive computation resources to be explicitly integrated in modelling attempt. Moreover, in agricultural context, this information is likely to change during the year depending on the agricultural practices. In this context, the objective of this study is to propose a parameterisation of the influence of microtopography on erosion into the framework of the shallow water equation. For each cell, the proportion of wetted area is used as a microtopography indicator. For the case of erosion, the system is coupled to the sediment transport equations. In such context, an additional equation describing the micro-topography evolution caused by erosion is introduced. Different case study will be presented to investigate the potential of the approach.

  3. Osseointegration and osseoconductivity of hydroxyapatite of different microporosities.

    PubMed

    Rosa, A L; Beloti, M M; Oliveira, P T; Van Noort, R

    2002-11-01

    The aim of this study was to determine the relationship between changes in microporosity and the osseointegration and the osseoconductivity of hydroxyapatite (HAp). HAp cylinders were manufactured by a combination of uniaxial powder pressing and different sintering conditions, with different percentages of microporosity: HAp-I with 3.96+/-0.75% microporosity, HAp-II with 15.66+/-1.60% microporosity, and HAp-III with 29.72+/-0.69% microporosity. These HAp cylinders were surgically implanted in rabbit femurs. After 8 and 12 weeks, the femurs were removed, fixed, sectioned, ground, and stained by Stevenel's blue/Van Gieson for light microscopy and histomorphometry. Some ground sections were routinely processed for SEM. The osseointegration and the osseoconductivity were determined by means of image analysis and the data were submitted to ANOVA. In all cases the cortical bone was repaired and the HAp facing the medullary canal was lined with endosteum, which in some areas exhibited thin bone tissue formation. SEM observations showed no differences in the morphology of tissue-HAp interfaces for the three different porosities of HAp. There were no statistical differences between the groups related to either osseointegration or osseoconductivity. These results suggest that neither osseointegration nor osseoconductivity of HAp are influenced by changes in HAp microporosity.

  4. Osseointegrated prostheses for rehabilitation following amputation : The pioneering Swedish model.

    PubMed

    Li, Yan; Brånemark, Rickard

    2017-04-01

    The direct attachment of osseointegrated (OI) prostheses to the skeleton avoids the inherent problems of socket suspension. It also provides physiological weight bearing, improved range of motion in the proximal joint, as well as osseoperceptive sensory feedback, enabling better control of the artificial limbs by amputees. The present article briefly reviews the pioneering efforts on extremity osseointegration surgeries in Sweden and the development of the OPRA (Osseointegrated Prostheses for the Rehabilitation of Amputees) program. The standard implant design of the OPRA system and surgical techniques are described as well as the special rehabilitation protocols based on surgical sites. The results of long-term follow-up for transradial, transhumeral, and thumb amputee operations are briefly reported including the prospective study of transfemoral amputees according to OPRA protocol. The importance of refinement on implant designs and surgical techniques based on the biomechanical analysis and early clinical trials is emphasized. Future aspects on osseointegration surgery are briefly described, including novel treatment options using implanted electrodes.

  5. RADIOGRAPHIC ASSESSMENT OF EXTREMITY OSSEOINTEGRATION FOR THE AMPUTEE.

    PubMed

    Al Muderis, Munjed; Bosley, Belinda A; Florschutz, Anthony V; Lunseth, Paul A; Klenow, Tyler D; Highsmith, M Jason; Kahle, Jason T

    2016-09-01

    Osseointegration (OI) is a bone-anchoring procedure that allows the direct skeletal attachment of a prosthesis through the use of an implant. Transcutaneous OI implants are similar to subcutaneous intramedullary joint implants with some exceptions. Particularly, OI implants are inserted at the distal aspect of the femur, while intramedullary implants are inserted at the proximal aspect of the femur. In this report, an additional adaptation of the radiographic zonal analysis used for intramedullary implants, known as Gruen zones, is introduced to include OI implants of extremity prosthetics. Radiographic zonal analyses and interpretations are proposed. Gruen zones are used for intramedullary implants, which are generally inserted from the proximal aspect of the bone. OI extremity implants are inserted from the distal end of the bone. Therefore, the zonal analysis is inverted. A radiographic zonal analysis has been introduced by the Osseointegration Group of Australia (OGA). This analysis is needed specifically for the clinical evaluation of extremity OI, as significant changes to the bone and OI implant have been reported and need to be clinically described. A classification technique is necessary for establishing treatment guidelines for the extremity osseointegrated implant. The OGA Zonal analysis addresses this need by adapting a common reference standard to osseointegration of the extremity amputee.

  6. RADIOGRAPHIC ASSESSMENT OF EXTREMITY OSSEOINTEGRATION FOR THE AMPUTEE

    PubMed Central

    Al Muderis, Munjed; Bosley, Belinda A.; Florschutz, Anthony V.; Lunseth, Paul A.; Klenow, Tyler D.; Highsmith, M. Jason; Kahle, Jason T.

    2016-01-01

    Osseointegration (OI) is a bone-anchoring procedure that allows the direct skeletal attachment of a prosthesis through the use of an implant. Transcutaneous OI implants are similar to subcutaneous intramedullary joint implants with some exceptions. Particularly, OI implants are inserted at the distal aspect of the femur, while intramedullary implants are inserted at the proximal aspect of the femur. In this report, an additional adaptation of the radiographic zonal analysis used for intramedullary implants, known as Gruen zones, is introduced to include OI implants of extremity prosthetics. Radiographic zonal analyses and interpretations are proposed. Gruen zones are used for intramedullary implants, which are generally inserted from the proximal aspect of the bone. OI extremity implants are inserted from the distal end of the bone. Therefore, the zonal analysis is inverted. A radiographic zonal analysis has been introduced by the Osseointegration Group of Australia (OGA). This analysis is needed specifically for the clinical evaluation of extremity OI, as significant changes to the bone and OI implant have been reported and need to be clinically described. A classification technique is necessary for establishing treatment guidelines for the extremity osseointegrated implant. The OGA Zonal analysis addresses this need by adapting a common reference standard to osseointegration of the extremity amputee. PMID:28066531

  7. Predicting the roughness length of turbulent flows over landscapes with multi-scale microtopography

    NASA Astrophysics Data System (ADS)

    Pelletier, J. D.; Field, J. P.

    2015-10-01

    The fully rough form of the law of the wall is commonly used to quantify velocity profiles and associated bed shear stresses in fluvial, aeolian, and coastal environments. A key parameter in this law is the roughness length, z0. Here we propose a predictive formula for z0 that uses the amplitude and slope of each wavelength of microtopography within a discrete-Fourier-transform-based approach. Computational fluid dynamics (CFD) modeling is used to quantify the effective z0 value of sinusoidal microtopography as a function of the amplitude and slope. The effective z0 value of landscapes with multi-scale roughness is then given by the sum of contributions from each Fourier mode of the microtopography. Predictions of the equation are tested against z0 values measured in ~105 wind velocity profiles from southwestern US playa surfaces. Our equation is capable of predicting z0 values to 50 % accuracy, on average, across a four order-of-magnitude range.

  8. Plasma electrolytic oxidation of titanium and improvement in osseointegration.

    PubMed

    Chung, Chi-Jen; Su, Rein-Teng; Chu, Hou-Jen; Chen, Hsien-Te; Tsou, Hsi-Kai; He, Ju-Liang

    2013-08-01

    Reducing the osseointegration time for biomedical titanium implants in surgical patients is an important goal. However, a huge controversy exists over the effectiveness of osseointegration of the surface layer by plasma electrolytic oxidation (PEO), which is a widely favored surface modification for titanium-based implants. In this study, various surface coatings, including anatase-TiO2 (A-TiO2 ), rutile-TiO2 (R-TiO2 ), hydroxyapatite (HAp), strontium-containing hydroxyapatite (Sr-HAp), and dual-phase HAp-TiO2 were synthesized on titanium implants by PEO. A comparative study of osseointegration performance (both in vitro and in vivo) and bone/implant adhesion strength conducted using push-out thrust tests were demonstrated. The in vitro experimental test results agree strongly with the in vivo test results: the dual-phase HAp-TiO2 coating exhibits the superior cell adhesion and differentiation condition among all of the coatings in the in vitro tests and therefore has the highest push-out bonding strength of 5.37 MPa after 12 wk of implantation in the in vivo test. The HAp-containing coatings benefit from its bioactivity and therefore perform the others in terms of long-term osteocyte growth (from the in vitro results) and the extent of osseointegration (from the in vivo results). The dual-phase HAp-TiO2 coating provides the advantages of both the bioactive HAp and structural enhancement by the TiO2 , effectively promoting osseointegration.

  9. Small is beautiful: why microtopography should be included in bog hydrology

    NASA Astrophysics Data System (ADS)

    Appels, Willemijn; van der Ploeg, Martine; Oosterwoud, Marieke; Cirkel, Gijsbert; van der Zee, Sjoerd; Witte, Jan-Philip

    2014-05-01

    Microtopography can have a large effect on flow processes at the soil surface and the composition of soil water. In peat areas, microtopography is shaped by differences in species, the growth rate and transpiration of the vegetation, and the amount of water flowing from higher areas. Microtopography is often represented by a roughness parameter in hillslope hydrological models. In areas without a strong topographical gradient however, microtopography may be underestimated when accumulated in a single parameter, especially in the presence of shallow groundwater systems. In this study, we review the intricate relationships between microtopography, surface runoff, and ecohydrology in systems featuring shallow water tables. In an analogy to surface runoff, the hydrology of a raised bog can be described as a combination of open water flow on a saturated medium, instead of the traditional acrotelm-catotelm concept that only acknowledges the saturated medium. We explored water flow through the microtopography of a raised bog with a simple conceptual model that accounts explicitly for microtopographic features and the changing flow directions these may cause. With this approach we were able to investigate the activation of fast flow paths on different areas of the bog as a function of their wetness level and bog-specific morphological features, such as hummocks and hollows. Our type of approach could be used to improve the understanding of the spatial and temporal variability of rainfall-runoff responses on raised bogs. In addition, similar approaches could be used to investigate how various runoff regimes affect the mixing of water with different chemical signatures, another driver of variations of the occurrence of plant species.

  10. Osseointegrated fixture placement with simultaneous tooth extraction.

    PubMed

    Schabes, G A; Sacks, H G; Kaufman, P S

    1992-03-01

    Three cases are presented that illustrate the potential for accelerating the healing phase with fixture-based treatment. Depending on the clinical circumstances, techniques may include radical alveolectomy, the use of fresh extraction sockets, and fixture placement in inter-radicular bone.

  11. Aspects of goethite surface microtopography, structure, chemistry, and reactivity

    SciTech Connect

    Rakovan, J.; Becker, U.; Hochella, M.F. Jr.

    1999-05-01

    Goethite (010), (110), and (111) growth faces and (010) cleavage surfaces of large, natural single crystals, as well as a high surface area synthetic sample were characterized using various surface sensitive microscopies and spectroscopies. Differential interference contrast and atomic force microscopy characterization of the natural single crystal faces showed microtopography indicative of growth, dissolution, and cleavage. Low energy electron diffraction patterns of the goethite (010) surface exhibit sharp, intense diffraction spots, indicating long-range order on this important surface. Ultra-high vacuum scanning tunneling microscopy was performed on (010) cleavage faces, although the tunneling properties of the surface were very heterogeneous. Atomic resolution was not obtained; however, microtopographic images are identical to those collected with AFM. XPS spectra from the (010) faces of two natural samples as well as the synthetic powder all have peak maxima for Fe(2p{sub 3/2}) at 711.5 {+-} 0.1 eV. The O(1s) line originating from the goethite can be fit with two peaks with a chemical shift of 1.3 eV. The peak at higher binding energy represents the protonated oxygen in the structure, and the peak at lower binding energy represents the proton-free oxygen in the structure. Ab initio and semi-empirical models of the (010) surface suggest that cleavage occurs through the hydroxide plane at 1/4 b in the structure. This is contrary to cleavage through the oxide plane at 1/2 b, which has been assumed in several previous studies.

  12. Microtopography and flow modulate the direction of endothelial cell migration.

    PubMed

    Uttayarat, P; Chen, M; Li, M; Allen, F D; Composto, R J; Lelkes, P I

    2008-02-01

    The migration of vascular endothelial cells under flow can be modulated by the addition of chemical or mechanical stimuli. The aim of this study was to investigate how topographic cues derived from a substrate containing three-dimensional microtopography interact with fluid shear stress in directing endothelial cell migration. Subconfluent bovine aortic endothelial cells were seeded on fibronectin-coated poly(dimethylsiloxane) substrates patterned with a combinatorial array of parallel and orthogonal microgrooves ranging from 2 to 5 microm in width at a constant depth of 1 microm. During a 4-h time-lapse observation in the absence of flow, the majority of the prealigned cells migrated parallel to the grooves with the distribution of their focal adhesions (FAs) depending on the groove width. No change in this migratory pattern was observed after the cells were exposed to moderate shear stress (13.5 dyn/cm(2)), irrespective of groove direction with respect to flow. After 4-h exposure to high shear stress (58 dyn/cm(2)) parallel to the grooves, the cells continued to migrate in the direction of both grooves and flow. By contrast, when microgrooves were oriented perpendicular to flow, most cells migrated orthogonal to the grooves and downstream with flow. Despite the change in the migration direction of the cells under high shear stress, most FAs and actin microfilaments maintained their original alignment parallel to the grooves, suggesting that topographic cues were more effective than those derived from shear stress in guiding the orientation of cytoskeletal and adhesion proteins during the initial exposure to flow.

  13. How sedge meadow soils, microtopography, and vegetation respond to sedimentation

    USGS Publications Warehouse

    Werner, K.J.; Zedler, Joy B.

    2002-01-01

    The expansion of urban and agricultural activities in watersheds of the Midwestern USA facilitates the conversion of species-rich sedge meadows to stands of Phalaris arundinacea and Typha spp. We document the role of sediment accumulation in this process based on field surveys of three sedge meadows dominated by Carex stricta, their adjacent Phalaris or Typha stands, and transitions from Carex to these invasive species. The complex microtopography of Carex tussocks facilitates the occurrence of other native species. Tussock surface area and species richness were positively correlated in two marshes (r2 = 0.57 and 0.41); on average, a 33-cm-tall tussock supported 7.6 species. Phalaris also grew in tussock form in wetter areas but did not support native species. We found an average of 10.5 Carex tussocks per 10-m transect, but only 3.5 Phalaris tussocks. Microtopographic relief, determined with a high-precision GPS, measured 11% greater in Carex meadows than Phalaris stands. Inflowing sediments reduced microtopographic variation and surface area for native species. We calculated a loss of one species per 1000 cm2 of lost tussock surface area, and loss of 1.2 species for every 10-cm addition of sediment over the sedge meadow surface. Alluvium overlying the sedge meadow soil had a smaller proportion of organic matter content and higher dry bulk density than the buried histic materials. We conclude that sedimentation contributes to the loss of native species in remnant wetlands. ?? 2002, The Society of Wetland Scientists.

  14. Laser-Modified Surface Enhances Osseointegration and Biomechanical Anchorage of Commercially Pure Titanium Implants for Bone-Anchored Hearing Systems

    PubMed Central

    Omar, Omar; Simonsson, Hanna; Palmquist, Anders; Thomsen, Peter

    2016-01-01

    Osseointegrated implants inserted in the temporal bone are a vital component of bone-anchored hearing systems (BAHS). Despite low implant failure levels, early loading protocols and simplified procedures necessitate the application of implants which promote bone formation, bone bonding and biomechanical stability. Here, screw-shaped, commercially pure titanium implants were selectively laser ablated within the thread valley using an Nd:YAG laser to produce a microtopography with a superimposed nanotexture and a thickened surface oxide layer. State-of-the-art machined implants served as controls. After eight weeks’ implantation in rabbit tibiae, resonance frequency analysis (RFA) values increased from insertion to retrieval for both implant types, while removal torque (RTQ) measurements showed 153% higher biomechanical anchorage of the laser-modified implants. Comparably high bone area (BA) and bone-implant contact (BIC) were recorded for both implant types but with distinctly different failure patterns following biomechanical testing. Fracture lines appeared within the bone ~30–50 μm from the laser-modified surface, while separation occurred at the bone-implant interface for the machined surface. Strong correlations were found between RTQ and BIC and between RFA at retrieval and BA. In the endosteal threads, where all the bone had formed de novo, the extracellular matrix composition, the mineralised bone area and osteocyte densities were comparable for the two types of implant. Using resin cast etching, osteocyte canaliculi were observed directly approaching the laser-modified implant surface. Transmission electron microscopy showed canaliculi in close proximity to the laser-modified surface, in addition to a highly ordered arrangement of collagen fibrils aligned parallel to the implant surface contour. It is concluded that the physico-chemical surface properties of laser-modified surfaces (thicker oxide, micro- and nanoscale texture) promote bone bonding

  15. EFFECTS OF INTENSE, SHORT-DURATION GRAZING ON MICROTOPOGRAPHY IN A CHIHUAHUAN DESERT GRASSLAND

    EPA Science Inventory

    We measured the effects of short-term intense grazing by domestic cattle on the microtopography of a black-grama grass (Bouteloua eriopoda) dominated desert grassland. Plots were grazed during winter or summer for 24-36 hours by 20-40 yearlings in 1995 and 1996. Soil microtopogra...

  16. Relevance of mytilid shell microtopographies for fouling defence--a global comparison.

    PubMed

    Bers, A V; Díaz, E R; da Gama, B A P; Vieira-Silva, F; Dobretsov, S; Valdivia, N; Thiel, M; Scardino, A J; McQuaid, C D; Sudgen, H E; Thomason, J C; Wahl, M

    2010-04-01

    Prevention of epibiosis is of vital importance for most aquatic organisms, which can have consequences for their ability to invade new areas. Surface microtopography of the shell periostracum has been shown to have antifouling properties for mytilid mussels, and the topography shows regional differences. This article examines whether an optimal shell design exists and evaluates the degree to which shell microstructure is matched with the properties of the local fouling community. Biomimics of four mytilid species from different regional provenances were exposed at eight different sites in both northern and southern hemispheres. Tendencies of the microtopography to both inhibit and facilitate fouling were detected after 3 and 6 weeks of immersion. However, on a global scale, all microtopographies failed to prevent fouling in a consistent manner when exposed to various fouling communities and when decoupled from other shell properties. It is therefore suggested that the recently discovered chemical anti-microfouling properties of the periostracum complement the anti-macrofouling defence offered by shell microtopography.

  17. EFFECTS OF INTENSE, SHORT DURATION GRAZING ON MICROTOPOGRAPHY IN A CHIHUAHUAN DESERT GRASSLAND

    EPA Science Inventory

    Microtopography describes variations in soil surface elevation (nim or cm) for a scale of a few meters of horizontal distance, Small-scale (few centimeters) changes in vegetation communities synchronized with the elevation differences were observed in drained marsh (Zedler & Zedl...

  18. MICROTOPOGRAPHY AND GRAZING IN DESERT RANGE LAND: A LESSON IN STATISTICS VERSUS REALITY IN THE FIELD

    EPA Science Inventory

    This presentation summarizes two experiments on the effects of grazing on soil microtopography in a Chihuahuan Desert rangeland. In the first experiment, we measured the effect of three consecutive years of short duration <48 hours per year) intense grazing (20--40 yearling cows ...

  19. An evaluation of impression techniques for osseointegrated implants.

    PubMed

    Spector, M R; Donovan, T E; Nicholls, J I

    1990-04-01

    A passive fit between osseointegrated implants and the prosthesis they will support has been advocated. An experimental model was developed to test the accuracy of three impression techniques and the components used to make the transfer records. Statistically, no significant difference was found between the three methods tested. From this initial study, it appears that further work is needed to isolate techniques that will predictably provide accurate registration of the position of endosseous implants.

  20. The effect of osteoprotegerin on implant osseointegration in ovariectomized rats

    PubMed Central

    Liu, Yiming; Hu, Jing; Liu, Biao; Jiang, Xiliang

    2017-01-01

    Introduction Osteoprotegerin (OPG), the endogenous inhibitor of RANKL, prevents or reverses bone loss in a variety of preclinical models of bone disease. Preclinical studies indicate that osteoporosis significantly impairs implant fixation. This study aims to investigate the role of OPG in implant osseointegration in ovariectomized rats. Material and methods Twelve weeks after bilateral ovariectomy, each rat accepted two titanium screws in the proximal tibiae. All animals were then randomly divided into two groups: the control (10 rats) and OPG group (10 rats). Subcutaneous injection of OPG (10 mg/kg) or vehicle was performed three times a week. Eight weeks later, tibiae with screws were harvested for micro-computed tomography (μCT), histological and biomechanical analysis. Results Compared to control, OPG increased the percent bone volume by 124%, the percent osseointegration by 167%, the mean trabecular number by 111%, the mean trabecular thickness by 92% (p < 0.01), the mean connective density by 95% (p < 0.05); and decreased the mean trabecular separation by 64% in μCT analysis (p < 0.05). Osteoprotegerin also increased bone area density by 160% and bone-to-implant contact by 234% in histomorphometric evaluation (p < 0.01), and increased the maximal push-out force by 228% in biomechanical test (p < 0.01). Conclusions Systemic administration of OPG improved implant osseointegration and fixation in ovariectomized rats, resulting from the increased peri-implant bone mass and improved trabecular microarchitecture. PMID:28261305

  1. Bone dynamics of osseointegration, ankylosis, and tooth movement.

    PubMed

    Roberts, W E

    1999-01-01

    Masticatory function challenges the strength and adaptive capability of supporting bone. When osseous tissue is loaded, it accumulates fatigue damage which must be repaired by bone modeling and remodeling. The three principal masticatory abutments (normal teeth, ankylosed teeth and osseointegrated implants) are a dynamic physiologic continuum relative to bone biomechanics. Implants are rigidly integrated units that can only be moved by fracturing the interface. Normal teeth and some ankylosed teeth can be moved using implants for orthodontic and orthopedic anchorage. Because orthodontic translation generates new bone and attached gingiva, it is a form of tissue engineering. Modern interdisciplinary practice requires a thorough knowledge of the principles of bone physiology and biomechanics.

  2. Multiscale design of surface morphological gradient for osseointegration.

    PubMed

    Chen, Junning; Rungsiyakull, Chaiy; Li, Wei; Chen, Yuhang; Swain, Michael; Li, Qing

    2013-04-01

    Rapid and stable osseointegration signifies a major concern in design of implantable prostheses, which stimulates continuous development of new implant materials and structures. This study aims to develop a graded configuration of a bead/particle coated porous surface for implants by exploring how its micromechanical features determine osseointegration through multiscale modeling and remodeling techniques. A typical dental implantation setting was exemplified for investigation by using the remodeling parameters determined from a systematic review of bone-implant-contact (BIC) ratio published in literature. The global responses of a macroscale model were obtained through 48 month remodeling simulation, which forms the basis for the 27 microscopic models created with different particle gradients ranging from 30 to 70μm. The osseointegration responses are evaluated in terms of the BIC ratio and the averaged 10% peak Tresca shear stress (PTS). Within the sampling designs considered, the configuration with 50-30-30μm particle sizes provides the best outcome, counting 20% more BIC ratio and 0.17MPa less PTS compared with the worst case scenario, also outperforming the best uniform morphology of 70μm particles. Furthermore, the response surface method (RSM) was utilized to formulate the bone remodeling responses in terms of gradient parameters across three layers. Gradient 30.0-30.0-32.1 is found an optimal gradient for BIC ratio, and 70-45.4-40.8 the best for the minimum PTS. The multiobjective optimization was finally performed to simultaneously maximize BIC ratio and minimize PTS for achieving the best possible overall outcome. Due to strong competition between these two design objectives, a Pareto front is generated. To make a proper trade-off, the minimum distance selection criterion is considered and the gradient of 37.1-70.0-67.7 appears an optimal solution. This study provides a novel surface configuration and design methodology for individual patient that

  3. Prosthesis auricular with osseointegrated implants and quality of life.

    PubMed

    dos Santos, Daniela Micheline; Goiato, Marcelo Coelho; Pesqueira, Aldiéres Alves; Bannwart, Lisiane Cristina; Rezende, Maria Cristina Rosifini Alves; Magro-Filho, Osvaldo; Moreno, Amália

    2010-01-01

    Implants in craniofacial reconstructions improve prostheses retention and stability, comfort, and safety for the patient. According to biomechanical principles, the treatment success regarding osseointegration maintenance depends on an adequate surgery technique associated to a retention system that provides favorable tension distribution to implants. Implants in the mastoid area are a very important aid for retention of auricular prostheses. Color stability of resin and silicone is an important factor for longevity of auricular prostheses, and the high degree of satisfaction of patients with head and neck defects receiving epithesial reconstruction in the maxillofacial region is demonstrated.

  4. [AFM study on microtopography of NOM and newly formed hydrous manganese dioxide adsorbed on mica].

    PubMed

    Guo, Jin; Ma, Jun; Shi, Xue-hua

    2006-05-01

    With the methods of mica adsorbing, the microtopography of the newly formed hydrous manganese dioxide was perfectly captured. The tapping mode AFM study results revealed that the newly formed hydrous manganese dioxide possesses a perforated sheet (with a thickness of 0-1.75 nm) as well as some spheric particle structures compared with the hydrous manganese dioxide with 2 h aging time, which demonstrated that the newly formed hydrous manganese dioxide have a large surface area and adsorption capacity. When 1 mmol/L newly formed hydrous manganese dioxide was added, the microtopography of NOM molecules shifted from loosely dispersed pancake shape (with adsorption height of 5-8.5 nm) to densely dispersed and uniform spheric structure. NOM was prone to adsorb on the surface of the newly formed hydrous manganese dioxide, which provided a valid proof for the coagulation-aid mechanism of permanganate preoxidation.

  5. A new modeling approach for simulating microtopography-dominated, discontinuous overland flow on infiltrating surfaces

    NASA Astrophysics Data System (ADS)

    Yang, Jun; Chu, Xuefeng

    2015-04-01

    Realistic modeling of discontinuous overland flow on irregular topographic surfaces has been proven to be a challenge. This study is aimed to develop a new modeling framework to simulate the discontinuous puddle-to-puddle (P2P) overland flow dynamics for infiltrating surfaces with various microtopographic characteristics. In the P2P model, puddles were integrated in a well-delineated, cascaded drainage system to facilitate explicit simulation of their dynamic behaviors and interactions. Overland flow and infiltration were respectively simulated by using the diffusion wave model and a modified Green-Ampt model for the DEM-derived flow drainage network that consisted of a series of puddle-based units (PBUs). The P2P model was tested by using a series of data from laboratory overland flow experiments for various microtopography, soil, and rainfall conditions. The modeling results indicated that the hierarchical relationships and microtopographic properties of puddles significantly affected their connectivity, filling-spilling dynamics, and the associated threshold flow. Surface microtopography and rainfall characteristics also exhibited strong influences on the spatio-temporal distributions of infiltration rates, runoff fluxes, and unsaturated flow. The model tests demonstrated its applicability in simulating microtopography-dominated overland flow on infiltrating surfaces.

  6. Predicting the roughness length of turbulent flows over landscapes with multi-scale microtopography

    NASA Astrophysics Data System (ADS)

    Pelletier, Jon D.; Field, Jason P.

    2016-05-01

    The fully rough form of the law of the wall is commonly used to quantify velocity profiles and associated bed shear stresses in fluvial, aeolian, and coastal environments. A key parameter in this law is the roughness length, z0. Here we propose a predictive formula for z0 that uses the amplitude and slope of each wavelength of microtopography within a discrete-Fourier-transform-based approach. Computational fluid dynamics (CFD) modeling is used to quantify the effective z0 value of sinusoidal microtopography as a function of the amplitude and slope. The effective z0 value of landscapes with multi-scale roughness is then given by the sum of contributions from each Fourier mode of the microtopography. Predictions of the equation are tested against z0 values measured in ˜ 105 wind-velocity profiles from southwestern US playa surfaces. Our equation is capable of predicting z0 values to 50 % accuracy, on average, across a 4 order of magnitude range. We also use our results to provide an alternative formula that, while somewhat less accurate than the one obtained from a full multi-scale analysis, has an advantage of being simpler and easier to apply.

  7. Asymmetric Nano/Microtopography Biases Cytoskeletal Dynamics and Promotes Unidirectional Cell Guidance

    NASA Astrophysics Data System (ADS)

    Sun, Xiaoyu; Driscoll, Meghan; Guven, Can; Das, Satarupa; Parent, Carole; Fourkas, John; Losert, Wolfgang

    Many biological and physiological processes depend upon directed migration of cells, which is typically mediated by chemical or physical gradients or by signal relay. Here we show that cells can be guided in a single preferred direction based solely on local asymmetries in nano/microtopography on subcellular scales. These asymmetries can be repeated, and thereby provide directional guidance, over arbitrarily large areas. The direction and strength of the guidance is sensitive to the details of the nano/microtopography, suggesting that this phenomenon plays a context-dependent role in vivo. We demonstrate that asymmetric nano/microtopography guides the direction of internal actin polymerization waves (esotaxis), and that cells move in the same direction as these waves (microthigmotaxis). This phenomenon is observed both for the pseudopod-dominated migration of the amoeboid Dictyostelium discoideum and for the lamellipod-driven migration of human neutrophils. The conservation of this mechanism across cell types and the asymmetric shape of many natural scaffolds suggests that actin-wave-based guidance is important in biology and physiology.

  8. Effects of TiO2 nanotubes with different diameters on gene expression and osseointegration of implants in minipigs.

    PubMed

    Wang, Na; Li, Hongyi; Lü, Wulong; Li, Jinghui; Wang, Jinshu; Zhang, Zhenting; Liu, Yiran

    2011-10-01

    Titanium dioxide (TiO(2)) nanotubes can accelerate the adhesion and differentiation of osteoblasts, yet little is known how this nano-modified implant surface affects osseointegration at molecular level in vivo. The aim of this study was to investigate the effects of TiO(2) nanotubes with different diameters (30 nm, 70 nm and 100 nm) on biological attachment mechanism of implants to bone in vivo by studying the gene expression and bone formation around the implants. The histological features and fluorochrome labeling changes of bone around implants on the non-decalcified sections (at 3, 5 and 8 weeks after implantation) were investigated by using traditional light- and fluorescent microscopy, and the gene expression of alkaline phosphatase (ALP), osterix (Osx), collagen-I (Col-I) and tartrate-resistant acid phosphatase (TRAP) was examined by using real-time PCR at 1, 2, 3, 4 and 5 weeks after implantation. Comparing with machined titanium implants, a significant increase in bone-implant contact (BIC) and gene expression levels was found in the bone attached to implants with TiO(2) nanotubes, especially with 70 nm diameter nanotubes. At the same time, the sequential fluorescent labeling images illustrated dynamic bone deposition. In conclusion, TiO(2) nanotubes can modulate bone formation events at the bone-implant interface as to reach favorable molecular response and osseointegration; in addition, the diameters of nanotubes can be precisely controlled in order to obtain better bone formation.

  9. Titanium alloys (AoN) and their involvement in osseointegration

    PubMed Central

    Danza, Matteo; Zollino, Ilaria; Candotto, Valentina; Cura, Francesca; Carinci, Francesco

    2012-01-01

    Background: Osseointegration is essential for a long-term successful and inflammation-free dental implant. Such a result depends on osteoblastic cells growth and differentiation at the tissue-implant interface. The aim of this study was to compare two different AoN titanium layers (GR4 and GR5) to investigate which one had a greater osteoconductive power using human osteoblasts (HOb) culture at two different time-points. Materials and Methods: The expression levels of some bone-related (ALPL, COL1A1, COL3A1, SPP1, RUNX2, and SPARC) were analyzed using real time reverse transcription-polymerase chain reaction (real time RT-PCR). Results: Real-time RT-PCR data showed that after 3 days of treatment with TiA4GR, the genes up-regulated were COL3A1, ALPL, SPP1, and RUNX2. Moreover, no difference in gene expression was noticed 4 days later. On the other hand, the genes that overexpressed after 3 days of treatment with AoN5GR were ALPL, SPP1, and RUNX2. In both cases, the expression of COL1A1 and SPARC was negatively regulated. Conclusion: Our data showed that both titanium surfaces led to osteoblasts recruitment, maturation, and differentiation, thus promoting osseointegration at the tissue-implant interface. PMID:23814585

  10. Electrical Implications of Corrosion for Osseointegration of Titanium Implants

    PubMed Central

    Gittens, R.A.; Olivares-Navarrete, R.; Tannenbaum, R.; Boyan, B.D.; Schwartz, Z.

    2011-01-01

    The success rate of titanium implants for dental and orthopedic applications depends on the ability of surrounding bone tissue to integrate with the surface of the device, and it remains far from ideal in patients with bone compromised by physiological factors. The electrical properties and electrical stimulation of bone have been shown to control its growth and healing and can enhance osseointegration. Bone cells are also sensitive to the chemical products generated during corrosion events, but less is known about how the electrical signals associated with corrosion might affect osseointegration. The metallic nature of the materials used for implant applications and the corrosive environments found in the human body, in combination with the continuous and cyclic loads to which these implants are exposed, may lead to corrosion and its corresponding electrochemical products. The abnormal electrical currents produced during corrosion can convert any metallic implant into an electrode, and the negative impact on the surrounding tissue due to these extreme signals could be an additional cause of poor performance and rejection of implants. Here, we review basic aspects of the electrical properties and electrical stimulation of bone, as well as fundamental concepts of aqueous corrosion and its electrical and clinical implications. PMID:21555775

  11. Impact of Dental Implant Surface Modifications on Osseointegration

    PubMed Central

    Smeets, Ralf; Stadlinger, Bernd; Schwarz, Frank; Beck-Broichsitter, Benedicta; Jung, Ole; Precht, Clarissa; Kloss, Frank; Gröbe, Alexander; Heiland, Max

    2016-01-01

    Objective. The aim of this paper is to review different surface modifications of dental implants and their effect on osseointegration. Common marketed as well as experimental surface modifications are discussed. Discussion. The major challenge for contemporary dental implantologists is to provide oral rehabilitation to patients with healthy bone conditions asking for rapid loading protocols or to patients with quantitatively or qualitatively compromised bone. These charging conditions require advances in implant surface design. The elucidation of bone healing physiology has driven investigators to engineer implant surfaces that closely mimic natural bone characteristics. This paper provides a comprehensive overview of surface modifications that beneficially alter the topography, hydrophilicity, and outer coating of dental implants in order to enhance osseointegration in healthy as well as in compromised bone. In the first part, this paper discusses dental implants that have been successfully used for a number of years focusing on sandblasting, acid-etching, and hydrophilic surface textures. Hereafter, new techniques like Discrete Crystalline Deposition, laser ablation, and surface coatings with proteins, drugs, or growth factors are presented. Conclusion. Major advancements have been made in developing novel surfaces of dental implants. These innovations set the stage for rehabilitating patients with high success and predictable survival rates even in challenging conditions. PMID:27478833

  12. Osteoporotic rat models for evaluation of osseointegration of bone implants.

    PubMed

    Alghamdi, Hamdan S; van den Beucken, Jeroen J J P; Jansen, John A

    2014-06-01

    Osseointegration of dental and orthopedic bone implants is the important process that leads to mechanical fixation of implants and warrants implant functionality. In view of increasing numbers of osteoporotic patients, bone implant surface optimization strategies with instructive and drug-loading ability have been heavily explored. However, few animal models are available to study the effect of novel implant surface modifications in osteoporotic conditions. Since laboratory rats comply with a number of practical advantages, including the reliability of several methods for rapid induction of osteoporotic conditions, the present work aimed to define the use of the femoral condyle in osteoporotic female and male rats as a suitable implantation model to study osseointegration of bone implants. The method describes the procedures for induction (by hypogonadism) and assessment (by in vivo micro-computed tomography [CT]) of osteoporotic conditions in both female and male rats. The implantation site architecture (femoral condyle bone properties and dimensions) was comparatively evaluated for female and male rats, and the implant installation procedures are described. Finally, the possible analytical techniques to evaluate bone responses via mechanical tests, ex vivo micro-CT, and histological methods are provided.

  13. Osseointegration of alumina bioceramic granules: A comparative experimental study

    NASA Astrophysics Data System (ADS)

    Rerikh, V. V.; Avetisyan, A. R.; Zaydman, A. M.; Anikin, K. A.; Bataev, V. A.; Nikulina, A. A.; Sadovoy, M. A.; Aronov, A. M.; Semantsova, E. S.

    2016-08-01

    To perform a comparative analysis of osseointegration of bioceramic alumina-based granules, hydroxyapatite-based granules, and deproteinized bone granules. The experiment was conducted on 52 adult male Kyoto-Wistar rats weighing 350 to 520 g. The animals were divided into five matched groups that differed only in the type of an implanted material. The granules were implanted in the lumbar vertebral bodies and in the distal right femur of each laboratory animal. Two months after surgery, the animals were euthanized, followed by tissue sampling for morphological studies. An examination of specimens from the groups with implanted alumina granules revealed the newly formed trabecular bone with remodeling signs. The bone tissue filled the intragranular space, tightly adhering to the granule surface. There was no connective tissue capsule on the border between bone tissue and alumina granules. Cylindrical bioceramic alumina-based granules with an open internal channel have a higher strength surpassing than that of analogs and the osseointegration ability close to that of hydroxyapatite and deproteinized bone granules.

  14. Assessment of Atmospheric Pressure Plasma Treatment for Implant Osseointegration

    PubMed Central

    Danna, Natalie R.; Beutel, Bryan G.; Tovar, Nick; Witek, Lukasz; Marin, Charles; Granato, Rodrigo; Suzuki, Marcelo; Coelho, Paulo G.

    2015-01-01

    This study assessed the osseointegrative effects of atmospheric pressure plasma (APP) surface treatment for implants in a canine model. Control surfaces were untreated textured titanium (Ti) and calcium phosphate (CaP). Experimental surfaces were their 80-second air-based APP-treated counterparts. Physicochemical characterization was performed to assess topography, surface energy, and chemical composition. One implant from each control and experimental group (four in total) was placed in one radius of each of the seven male beagles for three weeks, and one implant from each group was placed in the contralateral radius for six weeks. After sacrifice, bone-to-implant contact (BIC) and bone area fraction occupancy (BAFO) were assessed. X-ray photoelectron spectroscopy showed decreased surface levels of carbon and increased Ti and oxygen, and calcium and oxygen, posttreatment for Ti and CaP surfaces, respectively. There was a significant (P < 0.001) increase in BIC for APP-treated textured Ti surfaces at six weeks but not at three weeks or for CaP surfaces. There were no significant (P = 0.57) differences for BAFO between treated and untreated surfaces for either material at either time point. This suggests that air-based APP surface treatment may improve osseointegration of textured Ti surfaces but not CaP surfaces. Studies optimizing APP parameters and applications are warranted. PMID:26090443

  15. Novel Zirconia Surface Treatments for Enhanced Osseointegration: Laboratory Characterization

    PubMed Central

    Ewais, Ola H.; Al Abbassy, Fayza; Ghoneim, Mona M.; Aboushelib, Moustafa N.

    2014-01-01

    Purpose. The aim of this study was to evaluate three novel surface treatments intended to improve osseointegration of zirconia implants: selective infiltration etching treatment (SIE), fusion sputtering (FS), and low pressure particle abrasion (LPPA). The effects of surface treatments on roughness, topography, hardness, and porosity of implants were also assessed. Materials and Methods. 45 zirconia discs (19 mm in diameter × 3 mm in thickness) received 3 different surface treatments: selective infiltration etching, low pressure particle abrasion with 30 µm alumina, and fusion sputtering while nontreated surface served as control. Surface roughness was evaluated quantitatively using profilometery, porosity was evaluated using mercury prosimetry, and Vickers microhardness was used to assess surface hardness. Surface topography was analyzed using scanning and atomic force microscopy (α = 0.05). Results. There were significant differences between all groups regarding surface roughness (F = 1678, P < 0.001), porosity (F = 3278, P < 0.001), and hardness (F = 1106.158, P < 0.001). Scanning and atomic force microscopy revealed a nanoporous surface characteristic of SIE, and FS resulted in the creation of surface microbeads, while LPPA resulted in limited abrasion of the surface. Conclusion. Within the limitations of the study, changes in surface characteristics and topography of zirconia implants have been observed after different surface treatment approaches. Thus possibilities for enhanced osseointegration could be additionally offered. PMID:25349610

  16. Relative significance of microtopography and vegetation as controls on surface water flow on a low-gradient floodplain

    USGS Publications Warehouse

    Choi, Jungyill; Harvey, Judson W.

    2014-01-01

    Surface water flow controls water velocities, water depths, and residence times, and influences sediment and nutrient transport and other ecological processes in shallow aquatic systems. Flow through wetlands is substantially influenced by drag on vegetation stems but is also affected by microtopography. Our goal was to use microtopography data directly in a widely used wetland model while retaining the advantages of the model’s one-dimensional structure. The base simulation with no explicit treatment of microtopography only performed well for a period of high water when vegetation dominated flow resistance. Extended simulations using microtopography can improve the fit to low-water conditions substantially. The best fit simulation had a flow conductance parameter that decreased in value by 70 % during dry season such that mcrotopographic features blocked 40 % of the cross sectional width for flow. Modeled surface water became ponded and flow ceased when 85 % of the cross sectional width became blocked by microtopographic features. We conclude that vegetation drag dominates wetland flow resistance at higher water levels and microtopography dominates at low water levels with the threshold delineated by the top of microtopographic features. Our results support the practicality of predicting flow on floodplains using relatively easily measured physical and biological variables.

  17. Advanced glycation endproducts and rat dental implant osseointegration.

    PubMed

    Quintero, David G; Winger, Julia N; Khashaba, Rania; Borke, James L

    2010-01-01

    Advanced glycation endproducts (AGEs) are a diverse group of molecular adducts formed in environments high in reducing sugars that accumulate with aging and in diabetes. This study tests the hypothesis that AGEs inhibit the stabile osseointegration of dental implants through tissue interactions that interfere with bone turnover and compromise the biomechanical properties at the bone-implant interface. Maxillary first molars were extracted from 32 rats and allowed to heal for 4 weeks. Titanium implants (1 mm x 3 mm) were placed in the healed sockets of 2 groups of 16 rats consisting of 8 rats injected 3 times/wk for 1 month with AGE (prepared from glucose and lysine) and 8 rats injected with vehicle as a control. AGE injections continued for an additional 14 or 28 days before sacrifice. X-ray images, blood, and tissues were collected to examine bone/implant contact ratio, serum pyridinoline ([PYD] a collagen breakdown marker), osteocalcin ([OSC] a bone formation marker), and for immunohistochemistry with antibodies to AGE and the bone turnover-marker protein matrix metalloproteinase1. Compared with the AGE-treated groups, the controls showed significantly higher bone/implant contact at both 14- and 28-day time points. PYD (P < .05) and OSC (trend) levels from controls showed decreases at 28 days when compared with AGE-treated groups. Immunohistochemistry with AGE-specific and bone turnover marker antibodies showed stronger staining associated with the implant/tissue interface in AGE-treated rats. Our studies indicate an association between AGE and inhibition of bone turnover, suggesting that the formation of AGE in high glycemic conditions, such as diabetes, may contribute to a slower rate of osseointegration that negatively affects implant stability.

  18. Effects of alveolar ridge preservation on delayed implant osseointegration

    PubMed Central

    Shao, Shan; Li, Bin; Xue, Hui-Min; Huang, Hai-Yun; Liu, Gang-Li

    2015-01-01

    To evaluate the effects of alveolar ridge preservation with Bio-Oss bone substitute (Geistlich Pharma) on delayed implant osseointegration. The 3rd and 4th left and right mandibular premolars were extracted from four adult healthy male and female dogs. For the experimental group, we randomly selected two extraction sockets in each dog to be filled with Bio-Oss bone substitute (Geistlich Pharma). The two remaining extraction sockets remained untreated and served as the control group. Three months after Bio-Oss placement, dental implants were inserted into the alveolar bone of the experimental group and the control group. The osteogenic activity of the bone around the implants was assessed by evaluating the histological morphology and by estimating histomorphometric parameters at 3 and 6 months after delayed implantation. At 3 months, Goldner’s trichrome staining analysis showed that the bone-implant contact rate and mineralised bone area around the implant were significantly higher in the experimental group (75.98% ± 8.97% and 69.52% ± 9.63%, respectively) than in the control group (56.13% ± 8.18% and 52.82% ± 7.25%, respectively; P < 0.05). However, at 6 months, the two groups showed no significant difference. Fluorescence microscopy analysis revealed that the average mineralisation apposition rate of the bone tissue around the dental implant in the experimental group at 3 and 6 months was 6.80 ± 0.43 μm and 8.38 ± 0.84 μm, respectively, which was significantly higher than the rate in the control group (P < 0.05). These data indicated that alveolar ridge preservation by using Bio-Oss placement can promote osseointegration of delayed implantation. This may be a promising option for clinical use. PMID:26379871

  19. Osseointegrated Finger Prostheses Using a Tripod Titanium Mini-Plate

    PubMed Central

    Ciudad, Pedro; Doscher, Matthew; Lo Torto, Federico; Liebling, Ralph; Galan, Ricardo

    2017-01-01

    Background Digital amputation is a common upper extremity injury and can cause significant impairment in hand function, as well as psychosocial stigma. Currently, the gold standard for the reconstruction of such injuries involves autologous reconstruction. However, when this or other autologous options are not available, prosthetic reconstruction can provide a functionally and aesthetically viable alternative. This study describes a novel technique, known as a tripod titanium mini-plate, for osseointegrated digit prostheses, and reviews the outcomes in a set of consecutive patients. Methods A retrospective review of patients who underwent 2-stage prosthetic reconstruction of digit amputations was performed. Demographic information, occupation, mechanism of injury, number of amputated fingers, and level of amputation were reviewed. Functional and aesthetic outcomes were assessed using the quick disabilities of the arm, shoulder, and hand (Q-DASH) scale and a visual analog scale (VAS) score, respectively. In addition, complications during the postoperative period were recorded. Results Seven patients were included in this study. Their average age was 29 years. Five patients had single-digit amputations and 2 patients had multiple-digit amputations. Functional and aesthetic outcomes were assessed using the Q-DASH score (average, 10.4) and VAS score (average, 9.1), respectively. One episode of mild cellulitis was seen at 24 months of follow-up. However, it was treated successfully with oral antibiotics. No other complications were reported. Conclusions When autologous reconstruction is not suitable for digit reconstruction, prosthetic osseointegrated reconstruction can provide good aesthetic and functional results. However, larger series with longer-term follow-up are required in order to rule out the possibility of other complications. PMID:28352604

  20. Engineered antifouling microtopographies: kinetic analysis of the attachment of zoospores of the green alga Ulva to silicone elastomers.

    PubMed

    Cooper, Scott P; Finlay, John A; Cone, Gemma; Callow, Maureen E; Callow, James A; Brennan, Anthony B

    2011-09-01

    Microtopography has been demonstrated as an effective deterrent to biofouling. The majority of published studies are fixed-time assays that raise questions regarding the kinetics of the attachment process. This study investigated the time-dependent attachment density of zoospores of Ulva, in a laboratory assay, on a micropatterned and smooth silicone elastomer. The attachment density of zoospores was reduced on average 70-80% by the microtopography relative to smooth surfaces over a 4 h exposure. Mapping the zoospore locations on the topography revealed that they settled preferentially in specific, recessed areas of the pattern. The kinetic data fit, with high correlation (r(2) > 0.9), models commonly used to describe the adhesion of bacteria to surfaces. The grouping of spores on the microtopography indicated that the pattern inhibited the ability of attached spores to recruit neighbors. This study demonstrates that the antifouling mechanism of topographies may involve disruption of the cooperative effects exhibited by fouling organisms such as Ulva.

  1. Microdeflectometry--a novel tool to acquire three-dimensional microtopography with nanometer height resolution.

    PubMed

    Häusler, Gerd; Richter, Claus; Leitz, Karl-Heinz; Knauer, Markus C

    2008-02-15

    We introduce "microdeflectometry," a novel technique for measuring the microtopography of specular surfaces. The primary data are the local slope of the surface under test. Measuring the slope instead of the height implies high information efficiency and extreme sensitivity to local shape irregularities. The lateral resolution can be better than 1 microm, whereas the resulting height resolution is in the range of 1nm. Microdeflectometry can be supplemented by methods to expand the depth of field, with the potential to provide quantitative 3D imaging with scanning-electron-microscope-like features.

  2. Characterization of microtopography and its influence on vegetation patterns in created wetlands

    USGS Publications Warehouse

    Moser, K.; Ahn, C.; Noe, G.

    2007-01-01

    Created wetlands are increasingly used to mitigate wetland loss. Thus, identifying wetland creation methods that enhance ecosystem development might increase the likelihood of mitigation success. Noting that the microtopographic variation found in natural wetland settings may not commonly be found in created wetlands, this study explores relationships between induced microtopography, hydrology, and plant species richness/ diversity in non-tidal freshwater wetlands, comparing results from two created wetland complexes with those from a mature reference wetland complex in northern Virginia. Elevation, steel rod oxidation depth, and species cover were measured along replicate multiscale (0.5 m-, 1 m-, 2 m-, and 4 m-diameter) tangentially conjoined circular transects in each wetland. Microtopography was surveyed using a total station and results used to derive three roughness indices: tortuosity, limiting slope, and limiting elevation difference. Steel rod oxidation depth was used to estimate water table depth, with data collected four times during the growing season for each study site. Plant species cover was estimated visually in 0.2 m2 plots surveyed at peak growth and used to assess species richness, diversity, and wetland prevalence index. Differences in each attribute were examined among disked and non-disked created wetlands and compared to a natural wetland as a reference. Disked and non-disked created wetlands differed in microtopography, both in terms of limiting elevation difference and tortuosity. However, both were within the range of microtopography encompassed by natural wetlands. Disked wetlands supported higher plant diversity and species richness than either natural or non-disked wetlands, as well as greater within-site species assemblage variability than non-disked wetlands. Irrespective of creation method, plant diversity in created wetlands was correlated with tortuosity and limiting elevation difference, similar to correlations observed for

  3. Spatial heterogeneity of microtopography and its influence on the flow convergence of slopes under different rainfall patterns

    NASA Astrophysics Data System (ADS)

    Luo, Jian; Zheng, Zicheng; Li, Tingxuan; He, Shuqin

    2017-02-01

    This study aimed to reveal the spatial heterogeneity of the microtopography and its influence on flow convergence on sloping farmland of purple soil area in China. Methods involving artificial rainfall, pin meter and photographic measurements were adopted to generate DEM (digital elevation model). Geographic statistics and multifractal theory were used for quantitative and hydrological analyses of microtopography based on ArcGIS. Two artificial tillage practices (ridge tillage and conservation tillage) were used to simulate different types of microtopography. Ridge tillage (RT) was designed according to local agricultural customs in China, with conservation tillage (CK) used for comparison purposes. A total of 12 rainfall simulation experiments were conducted in two 1 m by 2 m boxes under increased rainfall series (1.0, 1.5, and 2.0 mm min-1) and decreased rainfall series (2.0, 1.5, and 1.0 mm min-1) on a typical slope gradient of 15°. Artificial tillage was the major contributing factor to the spatial heterogeneity of microtopography on sloping farmland of the purple soil area. Spatiotemporal variability of microtopography was expressed using semivariogram and multifractal spectrum, and spatial heterogeneity of drainage networks was expressed using general fractal dimension ΔD based on multifractal theory. In general, the drainage networks was mostly effected by microrelief. The drainage density of ridge tillage was smaller than that of the conservation tillage under different rainfall patterns, and the drainage density decreased remarkably with the increasing microrelief. Moreover, the ΔD values of ridge tillage ranged from 0.1817 to 0.5677. By contrast, the ΔD values of the conservation tillage ranged from 0.9662 to 1.3013, and thus the lower spatial heterogeneity of drainage networks in ridge tillage compared to conservation tillage. In this study, we established a novel method for analysis of the spatial heterogeneity of microtopography and demonstrated

  4. Long-term neurite orientation on astrocyte monolayers aligned by microtopography.

    PubMed

    Sørensen, Annette; Alekseeva, Tijna; Katechia, Kashyap; Robertson, Mary; Riehle, Mathis O; Barnett, Susan C

    2007-12-01

    After spinal cord injury neuronal connections are not easily re-established. Success has been hampered by the lack of orientation of neurites inside scar tissue and a lack of neurites crossing out of the site of injury. Oriented scaffolds in biodegradable polymers could be an excellent way to support both the orientation of neurites within the injury site as well as aiding their crossing out of the lesion. To establish the validity of using grooved micro-topography in polycaprolactone in combination with glia we have studied the long-term (3 weeks) orientation of neuronal cells on monolayers of astrocytes on the top of grooved topographies of various dimensions. We find that neurites are significantly aligned by groove/ridge type topographies which are "buried" under a monolayer of astrocytes for up to 3 weeks. This alignment is significantly lower than that of neurites growing directly on the topography, but these neurons do not survive on the poly-l-lysine coated polymer for more than a week. The alignment of neurites on the astrocyte layer to the underlying topography decreases over time, and with groove width. Topographies with 12.5 or 25 microm lateral dimension appear optimal for the long-term alignment and can support myelination. We have shown for the first time that micro-topography can act through an overlaid astrocyte layer and results in aligned neurites in long-term culture and that these can be myelinated by endogenous oligodendrocytes.

  5. Surface roughness variations in time - modelling the effects of precipitation on microtopography

    NASA Astrophysics Data System (ADS)

    Schwanghart, W.; Kuhn, N. J.; Anderson, K.

    2009-04-01

    Microtopography strongly affects velocities and patterns of overland flow, water retention and mineralization of soil organic matter. Bare surfaces experience a restructuring of the small-scale relief during rainfall events due to rainsplash, crusting, sealing and rill initiation. Such restructuring in turn affects hydrologic processes at larger scales. Considering these processes in rainfall-runoff models is challenging due to the different scales involved. (Semi-)variograms provide valuable parameters about the spatial organization of microrelief, which can be used as measure of surface roughness at different scales. Our work focuses on the changes of the variogram parameters during rainfall events and how topographic variations can be parameterized based on these changes. We applied rainfall experiments on bare soil surfaces and surveyed relief evolution at fixed timesteps using a laser scanner. We also used the grid representation of the initial surface conditions to simulate relief evolution with a diffusion equation. Our study shows that the variogram parameters significantly change during a rainfall event. This variability can be reproduced by analyzing variogram parameters of surfaces simulated by the diffusion equation. With the development of distinct flow pathways a significant reorganization of microtopography occurs. These surface patterns can be parameterized by anisotropic variogram models. Anisotropy in variogram models offers another parameter for surface roughness characterization in hydrologic models and may have the potential to serve as parameter describing surface conditions relevant for runoff concentration. Therefor anisotropy could provide a measure to bridge the gap between micro-scale processes and catchment scale hydrology.

  6. Osseointegrative Properties of Electrospun Hydroxyapatite-Containing Nanofibrous Chitosan Scaffolds

    PubMed Central

    Frohbergh, Michael E.; Katsman, Anya; Mondrinos, Mark J.; Stabler, Collin T.; Hankenson, Kurt D.; Oristaglio, Jeffrey T.

    2015-01-01

    Our long-term goal is to develop smart biomaterials that can facilitate regeneration of critical-size craniofacial lesions. In this study, we tested the hypothesis that biomimetic scaffolds electrospun from chitosan (CTS) will promote tissue repair and regeneration in a critical size calvarial defect. To test this hypothesis, we first compared in vitro ability of electrospun CTS scaffolds crosslinked with genipin (CTS-GP) to those of mineralized CTS-GP scaffolds containing hydroxyapatite (CTS-HA-GP), by assessing proliferation/metabolic activity and alkaline phosphatase (ALP) levels of murine mesenchymal stem cells (mMSCs). The cells' metabolic activity exhibited a biphasic behavior, indicative of initial proliferation followed by subsequent differentiation for all scaffolds. ALP activity of mMSCs, a surrogate measure of osteogenic differentiation, increased over time in culture. After 3 weeks in maintenance medium, ALP activity of mMSCs seeded onto CTS-HA-GP scaffolds was approximately two times higher than that of cells cultured on CTS-GP scaffolds. The mineralized CTS-HA-GP scaffolds were also osseointegrative in vivo, as inferred from the enhanced bone regeneration in a murine model of critical size calvarial defects. Tissue regeneration was evaluated over a 3 month period by microCT and histology (Hematoxylin and Eosin and Masson's Trichrome). Treatment of the lesions with CTS-HA-GP scaffolds induced a 38% increase in the area of de novo generated mineralized tissue area after 3 months, whereas CTS-GP scaffolds only led to a 10% increase. Preseeding with mMSCs significantly enhanced the regenerative capacity of CTS-GP scaffolds (by ∼3-fold), to 35% increase in mineralized tissue area after 3 months. CTS-HA-GP scaffolds preseeded with mMSCs yielded 45% new mineralized tissue formation in the defects. We conclude that the presence of HA in the CTS-GP scaffolds significantly enhances their osseointegrative capacity and that mineralized chitosan-based scaffolds

  7. Osseointegration properties of titanium dental implants modified with a nanostructured coating based on ordered porous silica and bioactive glass nanoparticles

    NASA Astrophysics Data System (ADS)

    Covarrubias, Cristian; Mattmann, Matías; Von Marttens, Alfredo; Caviedes, Pablo; Arriagada, Cristián; Valenzuela, Francisco; Rodríguez, Juan Pablo; Corral, Camila

    2016-02-01

    The fabrication of a nanoporous silica coating loaded with bioactive glass nanoparticles (nBG/NSC) on titanium dental implant surface and its in vitro and in vivo evaluation is presented. The coating was produced by a combined sol-gel and evaporation induced self-assembly process. In vitro bioactivity was assessed in simulated body fluid (SBF) and investigating the osteogenic differentiation of human bone marrow mesenchymal stem cells (hBMSCs). A rat tibial model was employed to analyze the bone response to nBG/NSC-modified titanium implant surface in vivo. The nBG/NSC coating was confirmed at nano level to be constituted by a highly ordered nanoporous silica structure. The coating nanotopography in conjunction with the bioactivity of the BG particles accelerate the in vitro apatite formation and promote the osteogenic differentiation of hBMSCs in absence of osteogenic supplements. These properties accelerate the formation of bone tissue in the periphery of the implant after 3 weeks of implantation. Backscattered scanning electron microscopy images revealed the presence of gaps and soft tissue in the unmodified implant after 6 weeks, whereas the nBG/NSC-modified implant showed mature bone in intimate contact with the implant surface. The nBG/NSC coating appears promising for accelerating the osseointegration of dental implants.

  8. Impact of Lanice conchilega on seafloor microtopography off the island of Sylt (German Bight, SE North Sea)

    NASA Astrophysics Data System (ADS)

    Schönke, M.; Feldens, P.; Wilken, D.; Papenmeier, S.; Heinrich, C.; von Deimling, J. Schneider; Held, P.; Krastel, S.

    2016-12-01

    This study presents a new in situ method to explore the impact of macrofauna on seafloor microtopography and corresponding microroughness based on underwater laser line scanning. The local microtopography was determined with mm-level accuracy at three stations colonised by the tubeworm Lanice conchilega offshore of the island of Sylt in the German Bight (south-eastern North Sea), covering approximately 0.5 m2 each. Ground truthing was done using underwater video data. Two stations were populated by tubeworm colonies of different population densities, and one station had a hydrodynamically rippled seafloor. Tubeworms caused an increased skewness of the microtopography height distribution and an increased root mean square roughness at short spatial wavelengths compared with hydrodynamic bedforms. Spectral analysis of the 2D Fourier transformed microtopography showed that the roughness magnitude increased at spatial wavelengths between 0.020 and 0.003 m independently of the tubeworm density. This effect was not detected by commonly used 1D roughness profiles but required consideration of the complete spectrum. Overall, the results reveal that new indicator variables for benthic organisms may be developed based on microtopographic data. An example demonstrates the use of local slope and skewness to detect tubeworms in the measured digital elevation model.

  9. Patient satisfaction after insertion of an osseointegrated implant bridge.

    PubMed

    Hoogstraten, J; Lamers, L M

    1987-09-01

    The general and specific satisfaction of patients treated with a jawbone-anchored bridge was compared with their pretreatment satisfaction with dentures (condition 1, n = 31). Patients who asked for information on the osseointegration method but did not apply for treatment (condition 2, n = 32), and a group of patients that did not ask for information (condition 3, n = 10) were also questioned on their satisfaction with dentures. The results indicated that condition 1 subjects were both socially and physically substantially more satisfied with their bridge than with their earlier dentures. On all satisfaction measures condition 3 subjects indicated more satisfaction with dentures than either condition 1 or condition 2 subjects. There were no significant differences between the three groups on several personality characteristics (neuroticism, test-taking attitudes, internal/external control). Condition 3 subjects were less extrovert (socially oriented) than the other subjects. Condition 1 subjects made several suggestions towards improvement of the pre- and post-operation phase, concerning the amount of pain involved and the cleaning of the bridge, etc.

  10. Enhancement of biomechanical behavior on osseointegration of implant with SLAffinity.

    PubMed

    Chu, Kuo-Tien; Cheng, Han-Yi; Pan, Yung-Ning; Chen, Shyuan-Yow; Ou, Keng-Liang

    2013-04-01

    The purpose of this study was to investigate stresses resulting from different thicknesses of hydroxyapatite- and titanium dioxide (TiO(2))-treated layers at the interface between temporomandibular joint (TMJ) implants and bones using three-dimensional finite element models. For ensuring osseointegration of implant treatment, one must examine the stresses of interface between implant and bone tissue. Treated layers on TMJ implants are a very important factor in clinical application. Several studies have investigated finite element models for TMJs, but few have examined a model for TMJ implants with treated layers. In this study, TMJ models were reconstructed using computer tomography data, and the effects of treated layer thickness on the stress field during jaw movement were investigated; this index has not yet been reported with respect to TMJ implant. The maximum stresses in the bone occurred at the position of the first screw. Data analysis indicated a greater decrease in this stress in the case of using TMJ implants with TiO(2)-treated layers, and the stresses decreased with increasing layer thicknesses. Results confirmed that the treated layers improve biomechanical properties of the TMJ implants and release abnormal stress concentration in them. The results of our study offer the potential clinical benefit of inducing superior biomechanical behavior in TMJ implants.

  11. Vibrotactile evaluation: osseointegrated versus socket-suspended transfemoral prostheses.

    PubMed

    Häggström, Eva; Hagberg, Kerstin; Rydevik, Björn; Brånemark, Rickard

    2013-01-01

    This study investigated detection thresholds of vibrometric stimuli in patients with transfemoral amputation supplied with osseointegrated (OI) and socket-suspended prostheses. It included 17 patients tested preoperatively with socket-suspended prostheses and after 2 yr with OI prostheses and a control group (n = 17) using socket-suspended prostheses, evaluated once. Assessments on the prosthetic and intact feet were conducted at six frequencies (8, 16, 32, 64, 125, and 250 Hz). Furthermore, measurements were conducted to investigate how vibrometric signals are transmitted through a test prosthesis. The results showed that the OI group had improved ability to detect vibrations through the prosthesis at 125 Hz (p = 0.01) at follow-up compared with the preoperative measurement. Compared with the control group, the OI group at follow-up had better ability to detect high frequency vibrations through the prosthesis (125 Hz, p = 0.02; 250 Hz, p = 0.03). The vibrometric signal transmitted through the test prosthesis was reduced at 8, 125, and 250 Hz but was amplified at 16, 32, and 64 Hz. Differences between the OI and the control groups were found in the highest frequencies in which the test prosthesis showed reduction of the vibrometric signal. The study provides insight into the mechanisms of vibration transmission between the exterior and bone-anchored as well as socket-suspended amputation prostheses.

  12. Machine oil inhibits the osseointegration of orthopaedic implants by impairing osteoblast attachment and spreading.

    PubMed

    Bonsignore, Lindsay A; Goldberg, Victor M; Greenfield, Edward M

    2015-07-01

    The most important factor contributing to short-term and long-term success of cementless total joint arthroplasties is osseointegration. Osseointegration leads to a direct structural and functional connection between living bone and the surface of an implant. Surface contaminants may remain on orthopaedic implants after sterilization procedures and impair osseointegration. For example, specific lots of hip replacement Sulzer Inter-OP(TM) acetabular shells that were associated with impaired osseointegration and early failure rates were found to be contaminated with both bacterial debris and machine oil residues. However, the effect of machine oil on implant integration is unknown. Therefore, the goal of this study was to determine if machine oil inhibits the osseointegration of orthopaedic implants. To test this hypothesis in vivo we used our murine model of osseointegration where titanium alloy implants are implanted into a unicortical pilot hole in the mid-diaphysis of the femur. We found that machine oil inhibited bone-to-implant contact and biomechanical pullout measures. Machine oil on titanium alloy discs inhibited early stages of MC3T3-E1 osteogenesis in vitro such as attachment and spreading. Inhibition of osteoblast attachment and spreading occurred in both areas with and without detectable oil. Osteoblast growth was in turn inhibited on discs with machine oil due to both a decrease in proliferation and an increase in cell death. Later stages of osteogenic differentiation and mineralization on titanium alloy discs were also inhibited. Thus, machine oil can inhibit osseointegration through cell autonomous effects on osteoblast cells. These results support routine testing by manufacturers of machine oil residues on orthopaedic implants.

  13. Investigating the Lack of Pit/Mound Microtopography in Subalpine Forests of the Canadian Rockies

    NASA Astrophysics Data System (ADS)

    Martin, Y.; Johnson, E.; Chaikina, O.

    2012-04-01

    This investigation is a followup to our earlier study analyzing tree throw and associated sediment transport in Hawk Creek Watershed, Canadian Rockies (Gallaway et al., 2009). The motivation for the present study is that landscapes in subalpine forests in the Canadian Rockies do not show the pronounced pit/mound microtopography found in some other forests, such as some deciduous forests of eastern North America or coniferous forests in western British Columbia, Canada. Given the impact that pit/mound topography can have on both soils and hydrology, it was decided to investigate why some forests demonstrate notable pit/mound microtopography while other forests do not. First, we analyze field data from our study drainage basin in the Canadian Rockies to define the sizes of pit/mound features in these forests and how slope gradient influences pit/mound dimensions. Next, we test a series of possible formulae to simulate degradation for different sizes of pit/mound features in profile form for slopes ranging from 10 to 30 degrees. For slopes of zero or near-zero gradient, our field results show that the majority of sediment from the root plate is returned to the pit and does not form a distinct pit/mound feature; this finding is in agreement with other studies in the published literature. Our model results show that the magnitude of a pit/mound feature and the choice of formula to simulate pit/mound degradation play key roles in determining pit/mound longevity. Finally, we connect our earlier numerical model of tree population dynamics in the Canadian Rockies to a numerical model of pit/mound degradation to explore how these elements combine to influence landscape microtopography over time. At any time, the density and size of pit-mound features on the landscape is a function of pit/mound formation rates (not necessarily constant) and the rate of pit/mound degradation (Schaetzl and Follmer, 1990). Our tree population dynamics model is driven by wildfire disturbance

  14. Establishing Multiscale Models for Simulating Whole Limb Estimates of Electric Fields for Osseointegrated Implants

    PubMed Central

    Isaacson, Brad M.; Stinstra, Jeroen G.; Bloebaum, Roy D.; Pasquina, COL Paul F.; MacLeod, Rob S.

    2011-01-01

    Although the survival rates of warfighters in recent conflicts are among the highest in military history, those who have sustained proximal limb amputations, may pose additional rehabilitation concerns. In some of these cases, traditional prosthetic limbs may not provide adequate function for returning to an active lifestyle. Osseointegration has emerged as a potential prosthetic alternative for those with limited residual limb length. Using this technology, direct skeletal attachment occurs between a transcutaneous osseointegrated implant (TOI) and the host bone, thereby eliminating the need for a socket. While reports from the first 100 patients with a TOI have been promising, some rehabilitation regimens require 12–18 months of restricted weight bearing to prevent overloading at the bone implant-interface. Electrically induced osseointegration has been proposed as an option for expediting periprosthetic fixation and preliminary studies have demonstrated the feasibility of adapting the TOI into a functional cathode. To assure safe and effective electrical fields that are conducive for osseoinduction and osseointegration, we have developed multiscale modeling approaches to simulate the expected electric metrics at the bone-implant interface. We have used computed tomography scans and volume segmentation tools to create anatomically accurate models that clearly distinguish tissue parameters and serve as the basis for finite element analysis. This translational computational biological process has supported biomedical electrode design, implant placement, and experiments to date have demonstrated the clinical feasibility of electrically induced osseointegration. PMID:21712151

  15. Osseointegrated total knee replacement connected to a lower limb prosthesis: 4 cases

    PubMed Central

    Khemka, Aditya; Frossard, Laurent; Lord, Sarah J; Bosley, Belinda; Al Muderis, Munjed

    2015-01-01

    Background and purpose — Osseointegrated implants are an alternative for prosthetic attachment in individuals with amputation who are unable to wear a socket. However, the load transmitted through the osseointegrated fixation to the residual tibia and knee joint can be unbearable for those with transtibial amputation and knee arthritis. We report on the feasibility of combining total knee replacement (TKR) with an osseointegrated implant for prosthetic attachment. Patients and methods — We retrospectively reviewed all 4 cases (aged 38–77 years) of transtibial amputations managed with osseointegration and TKR in 2012–2014. The below-the-knee prosthesis was connected to the tibial base plate of a TKR, enabling the tibial residuum and knee joint to act as weight-sharing structures. A 2-stage procedure involved connecting a standard hinged TKR to custom-made implants and creation of a skin-implant interface. Clinical outcomes were assessed at baseline and after 1–3 years of follow-up using standard measures of health-related quality of life, ambulation, and activity level including the questionnaire for transfemoral amputees (Q-TFA) and the 6-minute walk test. Results — There were no major complications, and there was 1 case of superficial infection. All patients showed improved clinical outcomes, with a Q-TFA improvement range of 29–52 and a 6-minute walk test improvement range of 37–84 meters. Interpretation — It is possible to combine TKR with osseointegrated implants. PMID:26145721

  16. Evaluation of Surface Microtopography Engineered by Direct Laser Interference for Bacterial Anti-Biofouling.

    PubMed

    Valle, Jaione; Burgui, Saioa; Langheinrich, Denise; Gil, Carmen; Solano, Cristina; Toledo-Arana, Alejandro; Helbig, Ralf; Lasagni, Andrés; Lasa, Iñigo

    2015-08-01

    Modification of the biomaterial surface topography is a promising strategy to prevent bacterial adhesion and biofilm formation. In this study, we use direct laser interference patterning (DLIP) to modify polystyrene surface topography at sub-micrometer scale. The results revealed that three-dimensional micrometer structures have a profound impact on bacterial adhesion. Thus, line- and pillar-like patterns enhanced S. aureus adhesion, whereas complex lamella microtopography reduced S. aureus adhesion in static and continuous flow culture conditions. Interestingly, lamella-like textured surfaces retained the capacity to inhibit S. aureus adhesion both when the surface is coated with human serum proteins and when the material is implanted subcutaneously in a foreign-body associated infection model.

  17. [Myxomatous remnants in the human middle ear. Histologic studies of their regression and microtopography].

    PubMed

    Rauchfuss, A

    1985-08-01

    Remnants of embryonic mesenchyma in the human middle ear are visible until the end of the first year of life. They occur in the lateral part of the epitympanon as well as in the region of the cochlear fenestra. However, as a result of an incomplete pneumatisation of the middle ear, they undergo regressive changes via differentiation to precollageneous tissue to form, finally, the tunica propria of the mucoperiosteal layer of the middle ear. Microtopography of these remnants is due to genetic factors but also depends on the function of the Eustachian tube. Alterations of the impedance of the tympanic membrane and the ossicular chain are possible because of the location of these remnants. The importance of obstructions of the Eustachian tube for the persistence of the remnants is discussed, as well as the part that they play in the pathogenesis of cholesteatoma of the middle ear.

  18. The joint effect of surface microtopography and near-surface structure on microcontact conditions

    SciTech Connect

    McCool, J.I.

    1990-11-01

    This is the Final Technical Report of the project The Joint Effect of Surface Microtopography and Near Surface Structure on Microcontact Conditions The purpose of this project was to extend, apply, and evaluate the usefuleness of, microcontact models for assessing the tribological performance of machine elements in rolling/sliding contact. Because of their projected importance to the field of energy conservation, emphasis was placed on application to ceramic and coated specimens. The project was multi-institutional as well as multi-disciplinary with technical contributions in testing and the evaluation of specimens by the Argonne National Laboratory (G. Fenske), Oak Ridge National Laboratory (P. Blau), and the University of Michigan (K. Ludema and Layo Ajayi). To accomplish the Project aims it was necessary to extend the state-of-the-art of microcontact modelling. 59 refs., 46 figs., 35 tabs.

  19. The Topographic Mapping Flash Lidar for micro-topography of river systems

    NASA Astrophysics Data System (ADS)

    Donley, B.; Ramond, T.; Weimer, C. S.; Ruppert, L.; Delker, T.; Applegate, J.

    2010-12-01

    The Topographic Mapping Flash Lidar (TMFL) instrument built by Ball Aerospace is a pushbroom lidar operating at 1064nm that provides the ability to map the topographic structure of river beds and surrounding terrain. The receiver is a pixilated array, allowing small-scale resolution of micro-topography that is critical to understanding river dynamics and the biodiversity of the area. The instrument uses no mechanical scanning, which is a key feature allowing the design to be applicable to space flight like the NASA Decadal Survey mission LIST. The TMFL instrument has been flown on a Twin Otter aircraft. This poster will exhibit examples of river topography over dry and wet riverbeds. Examples are given of imaging a river even when partially obscured under trees in an area of high canopy density.

  20. Microtopography for Ductile Fracture Process Characterization - Part 2: Application for CTOA Analysis

    SciTech Connect

    Lloyd, Wilson Randolph; F. A. McClintock

    2003-02-01

    The crack tip opening angle (CTOA) is seeing increased use to characterize fracture in so-called "low constraint" geometries, such as thin sheet aerospace structures and thin-walled pipes. With this increase in application comes a need to more fully understand and measure actual CTOA behavior. CTOA is a measure of the material response during ductile fracture, a "crack tip response function". In some range of crack extension following growth initiation, a constant value of CTOA is often assumed. However, many questions concerning the use of CTOA as a material response-characterizing parameter remain. For example, when is CTOA truly constant? What three-dimensional effects may be involved (even in thin sheet material)? What are the effects of crack tunneling on general CTOA behavior? How do laboratory specimen measurements of CTOA compare to actual structural behavior? Measurements of CTOA on the outer surface of test specimens reveal little about threedimensional effects in the specimen interior, and the actual measurements themselves are frequently difficult. The Idaho National Engineering and Environmental Laboratory (INEEL) use their microtopography system to collect data from the actual fracture surfaces following a test. Analyses of these data provide full three-dimensional CTOA distributions, at any amount of crack extension. The analysis is accomplished using only a single specimen and is performed entirely after the completion of a test. The resultant CTOA distributions allow development of full and effective understanding of CTOA behaviors. This paper presents underlying principles, various sources of measurement error and their corrections, and experimental and analytical verification of CTOA analysis with the microtopography method.

  1. The influence of microtopography on soil nutrients in created mitigation wetlands

    USGS Publications Warehouse

    Moser, K.F.; Ahn, C.; Noe, G.B.

    2009-01-01

    This study explores the relationship between microtopography and soil nutrients (and trace elements), comparing results for created and reference wetlands in Virginia, and examining the effects of disking during wetland creation. Replicate multiscale tangentially conjoined circular transects were used to quantify microtopography both in terms of elevation and by two microtopographic indices. Corresponding soil samples were analyzed for moisture content, total C and N, KCl-extractable NH4-N and NO3-N, and Mehlich-3 extractable P, Ca, Mg, K, Al, Fe, and Mn. Means and variances of soil nutrient/element concentrations were compared between created and natural wetlands and between disked and nondisked created wetlands. Natural sites had higher and more variable soil moisture, higher extractable P and Fe, lower Mn than created wetlands, and comparatively high variability in nutrient concentrations. Disked sites had higher soil moisture, NH4-N, Fe, and Mn than did nondisked sites. Consistently low variances (Levene test for inequality) suggested that nondisked sites had minimal nutrient heterogeneity. Across sites, low P availability was inferred by the molar ratio (Mehlich-3 [P/(Al + Fe)] < 0.06); strong intercorrelations among total C, total N, and extractable Fe, Al, and P suggested that humic-metal-P complexes may be important for P retention and availability. Correlations between nutrient/element concentrations and microtopographic indices suggested increased Mn and decreased K and Al availability with increased surface roughness. Disking appears to enhance water and nutrient retention, as well as nutrient heterogeneity otherwise absent from created wetlands, thus potentially promoting ecosystem development. ?? 2008 Society for Ecological Restoration International.

  2. Osseointegration of a hydroxyapatite-coated multilayered mesh stem.

    PubMed

    Kusakabe, Hiroshi; Sakamaki, Toyonori; Nihei, Kotaro; Oyama, Yasuo; Yanagimoto, Shigeru; Ichimiya, Masaru; Kimura, Jun; Toyama, Yoshiaki

    2004-07-01

    -coated multilayered mesh surface. The difference between the break sites was significant at 12 months (p<0.05). The HA-coated multilayered mesh stem provided faster, stronger, and more durable osseointegration than the conventional bead stem.

  3. Systematic variation of microtopography, surface chemistry and elastic modulus and the state dependent effect on endothelial cell alignment.

    PubMed

    Feinberg, Adam W; Wilkerson, Wade R; Seegert, Charles A; Gibson, Amy L; Hoipkemeier-Wilson, Leslie; Brennan, Anthony B

    2008-08-01

    We examined how variations in elastic modulus, surface chemistry and the height and spacing of micro-ridges interact and effect endothelial cell (EC) alignment. Specifically, we employed independent control of the surface properties in order to elucidate the relative importance of each factor. Polydimethylsiloxane elastomer (PDMSe) was fabricated with 1.5 or 5 microm tall, 5 microm spaced and 5, 10, or 20 microm wide ridge microtopographies. Elastic modulus was varied from 0.3, 1.0, 1.4, and 2.3 MPa by controlling oligomeric additives and crosslink density. Surface chemistry was left untreated, argon plasma treated, coated with fibronectin (Fn) or patterned with Fn tracks on flat PDMSe or the tops of micro-ridges. Primary porcine vascular ECs were cultured on the PDMSe substrates and nuclear form factor (NFF) was used to determine cell orientation relative to surface microtopography. Experimental results showed that microtopographical variation strongly altered EC alignment on Fn coated surfaces, but not on plasma treated surfaces. Interestingly, similar alignment was achieved with different orientation cues, either micropatterned chemistry (2D) or microtopography (3D). In total, the effect of varying one of the experimental parameters depended strongly on the state of the others, highlighting the need for multi-factor analysis of surface properties for applications where cells and tissue will contact synthetic materials.

  4. A comparative study on three methods of soil quality evaluation of microtopography in the semi-arid Loess Plateau, China.

    PubMed

    Bo, Yaojun; Zhu, Qingke; Bao, Yaoxian; Zhao, Weijun; Zhao, Yanming; Zhang, Hongzhi

    2015-01-01

    Three soil property test data of microtopography in the semi-arid Loess Plateau were used to compare the following three soil quality evaluation methods: correlation coefficient method, factor analysis method and Nemoro index method. The results of these methods were analyzed and compared to determine the most suitable method for comprehensive evaluation of soil quality. While correlation coefficient method and factor analysis method produced similar results, Nemoro index method showed several differences from the othertwo methods and exhibited higher sensitivity in its assessment results. The soil quality index (SQI) parameters of three methods showed consistent scales and variation trends among the various microtopographies, and there was a highly significant linear positive correlation between the SQI parameters of any two given methods. This result suggested that the three methods were all reliable and could be employed for comprehensive assessment of soil quality of microtopography in the study region. However, the Nemoro index method involves relatively uncomplicated mathematics and is very easy to absorb, and thus should be preferentially employed when three grading standards can be identified. The factor analysis method is the next most preferable, followed by correlation coefficient method.

  5. Implant design and its effects on osseointegration over time within cortical and trabecular bone.

    PubMed

    Beutel, Bryan G; Danna, Natalie R; Granato, Rodrigo; Bonfante, Estevam A; Marin, Charles; Tovar, Nick; Suzuki, Marcelo; Coelho, Paulo G

    2016-08-01

    Healing chambers present at the interface between implant and bone have become a target for improving osseointegration. The objective of the present study was to compare osseointegration of several implant healing chamber configurations at early time points and regions of interest within bone using an in vivo animal femur model. Six implants, each with a different healing chamber configuration, were surgically implanted into each femur of six skeletally mature beagle dogs (n = 12 implants per dog, total n = 72). The implants were harvested at 3 and 5 weeks post-implantation, non-decalcified processed to slides, and underwent histomorphometry with measurement of bone-to-implant contact (BIC) and bone area fraction occupied (BAFO) within healing chambers at both cortical and trabecular bone sites. Microscopy demonstrated predominantly woven bone at 3 weeks and initial replacement of woven bone by lamellar bone by 5 weeks. BIC and BAFO were both significantly increased by 5 weeks (p < 0.001), and significantly higher in cortical than trabecular bone (p < 0.001). The trapezoidal healing chamber design demonstrated a higher BIC than other configurations. Overall, a strong temporal and region-specific dependence of implant osseointegration in femurs was noted. Moreover, the findings suggest that a trapezoidal healing chamber configuration may facilitate the best osseointegration. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1091-1097, 2016.

  6. Proton Pump Inhibitors and the Risk of Osseointegrated Dental Implant Failure: A Cohort Study.

    PubMed

    Wu, Xixi; Al-Abedalla, Khadijeh; Abi-Nader, Samer; Daniel, Nach G; Nicolau, Belinda; Tamimi, Faleh

    2017-04-01

    Proton pump inhibitors (PPIs) have a negative impact on bone accrual. Because osseointegration is influenced by bone metabolism, this study investigates the association between PPIs and the risk of osseointegrated implant failure. This retrospective cohort study included a total of 1,773 osseointegrated dental implants in 799 patients (133 implants in 58 PPIs users and 1,640 in 741 non-users) who were treated at the East Coast Oral Surgery Clinic in Moncton, Canada, from January 2007 to September 2015. Kaplan-Meier estimator was used to describe the hazard function of dental implant failure by PPIs usage. Multilevel mixed effects parametric survival analyses were used to test the association between PPIs exposure and risk of implant failure adjusting for potential confounders. The failure rates were 6.8% for people using PPIs compared to 3.2% for non-users. Subjects using PPIs had a higher risk of dental implant failure (HR = 2.73; 95% CI = 1.10-6.78) compared to those who did not use the drugs. The findings suggest that treatment with PPIs may be associated with an increased risk of osseointegrated dental implant failure.

  7. Osseointegration of zirconia implants: an SEM observation of the bone-implant interface

    PubMed Central

    Depprich, Rita; Zipprich, Holger; Ommerborn, Michelle; Mahn, Eduardo; Lammers, Lydia; Handschel, Jörg; Naujoks, Christian; Wiesmann, Hans-Peter; Kübler, Norbert R; Meyer, Ulrich

    2008-01-01

    Background The successful use of zirconia ceramics in orthopedic surgery led to a demand for dental zirconium-based implant systems. Because of its excellent biomechanical characteristics, biocompatibility, and bright tooth-like color, zirconia (zirconium dioxide, ZrO2) has the potential to become a substitute for titanium as dental implant material. The present study aimed at investigating the osseointegration of zirconia implants with modified ablative surface at an ultrastructural level. Methods A total of 24 zirconia implants with modified ablative surfaces and 24 titanium implants all of similar shape and surface structure were inserted into the tibia of 12 Göttinger minipigs. Block biopsies were harvested 1 week, 4 weeks or 12 weeks (four animals each) after surgery. Scanning electron microscopy (SEM) analysis was performed at the bone implant interface. Results Remarkable bone attachment was already seen after 1 week which increased further to intimate bone contact after 4 weeks, observed on both zirconia and titanium implant surfaces. After 12 weeks, osseointegration without interposition of an interfacial layer was detected. At the ultrastructural level, there was no obvious difference between the osseointegration of zirconia implants with modified ablative surfaces and titanium implants with a similar surface topography. Conclusion The results of this study indicate similar osseointegration of zirconia and titanium implants at the ultrastructural level. PMID:18990214

  8. Berberine in Combination with Insulin Has Additive Effects on Titanium Implants Osseointegration in Diabetes Mellitus Rats.

    PubMed

    Lu, Li; Zhijian, Huang; Lei, Li; Wenchuan, Chen; Zhimin, Zhu

    2015-01-01

    This study evaluated the effects of berberine in combination with insulin on early osseointegration of implants in diabetic rats. Fifty male Sprague-Dawley rats were randomly divided into 5 groups: healthy rats were used as control (HC), and streptozotocin-induced diabetic rats were treated with insulin, berberine, berberine + insulin (IB), or no treatment. Each rat received one machined-surface cp-Ti implant into the right tibia and was given insulin injection and/or gavage feeding with berberine daily for 8 weeks until being sacrificed. Serum levels of alkaline phosphatase (ALP) and bone gamma-carboxyglutamic acid-containing protein (BGP) were analyzed in each group. Peri-implant mineral apposition was marked by fluorochrome double-labeling and osseointegration was histomorphologically examined. The ALP and BGP levels decreased in diabetic rats but were successfully corrected by insulin and berberine combined treatment. Moreover, untreated diabetic rats had less labeled mineral apposition and impaired osseointegration. In contrast, Groups I, B, and IB were observed with increased peri-implant bone formation. The combination treatment of insulin and berberine was more effective than each administrated as a monotherapy. These results suggest that berberine combined with insulin could promote osseointegration in diabetic rats, thereby highlighting its potential application to patients, though further studies are needed.

  9. Berberine in Combination with Insulin Has Additive Effects on Titanium Implants Osseointegration in Diabetes Mellitus Rats

    PubMed Central

    Lu, Li; Zhijian, Huang; Lei, Li; Wenchuan, Chen; Zhimin, Zhu

    2015-01-01

    This study evaluated the effects of berberine in combination with insulin on early osseointegration of implants in diabetic rats. Fifty male Sprague-Dawley rats were randomly divided into 5 groups: healthy rats were used as control (HC), and streptozotocin-induced diabetic rats were treated with insulin, berberine, berberine + insulin (IB), or no treatment. Each rat received one machined-surface cp-Ti implant into the right tibia and was given insulin injection and/or gavage feeding with berberine daily for 8 weeks until being sacrificed. Serum levels of alkaline phosphatase (ALP) and bone gamma-carboxyglutamic acid-containing protein (BGP) were analyzed in each group. Peri-implant mineral apposition was marked by fluorochrome double-labeling and osseointegration was histomorphologically examined. The ALP and BGP levels decreased in diabetic rats but were successfully corrected by insulin and berberine combined treatment. Moreover, untreated diabetic rats had less labeled mineral apposition and impaired osseointegration. In contrast, Groups I, B, and IB were observed with increased peri-implant bone formation. The combination treatment of insulin and berberine was more effective than each administrated as a monotherapy. These results suggest that berberine combined with insulin could promote osseointegration in diabetic rats, thereby highlighting its potential application to patients, though further studies are needed. PMID:26783411

  10. A strontium-incorporated nanoporous titanium implant surface for rapid osseointegration.

    PubMed

    Zhang, Wenjie; Cao, Huiliang; Zhang, Xiaochen; Li, Guanglong; Chang, Qing; Zhao, Jun; Qiao, Yuqin; Ding, Xun; Yang, Guangzheng; Liu, Xuanyong; Jiang, Xinquan

    2016-03-07

    Rapid osseointegration of dental implants will shorten the period of treatment and enhance the comfort of patients. Due to the vital role of angiogenesis played during bone development and regeneration, it might be feasible to promote rapid osseointegration by modifying the implant surface to gain a combined angiogenesis/osteogenesis inducing capacity. In this study, a novel coating (MAO-Sr) with strontium-incorporated nanoporous structures on titanium implants was generated via a new micro-arc oxidation, in an attempt to induce angiogenesis and osteogenesis to enhance rapid osseointegration. In vitro, the nanoporous structure significantly enhanced the initial adhesion of canine BMSCs. More importantly, sustained release of strontium ions also displayed a stronger effect on the BMSCs in facilitating their osteogenic differentiation and promoting the angiogenic growth factor secretion to recruit endothelial cells and promote blood vessel formation. Advanced mechanism analyses indicated that MAPK/Erk and PI3K/Akt signaling pathways were involved in these effects of the MAO-Sr coating. Finally, in the canine dental implantation study, the MAO-Sr coating induced faster bone formation within the initial six weeks and the osseointegration effect was comparable to that of the commercially available ITI implants. These results suggest that the MAO-Sr coating has the potential for future use in dental implants.

  11. Osteoblast-mediated mineral deposition in culture is dependent on surface microtopography.

    PubMed

    Boyan, B D; Bonewald, L F; Paschalis, E P; Lohmann, C H; Rosser, J; Cochran, D L; Dean, D D; Schwartz, Z; Boskey, A L

    2002-12-01

    Osteoblast phenotypic expression in monolayer culture depends on surface microtopography. Here we tested the hypothesis that mineralized bone nodule formation in response to osteotropic agents such as bone morphogenetic protein-2 (BMP-2) and dexamethasone is also influenced by surface microtopography. Fetal rat calvarial (FRC) cells were cultured on Ti implant materials (PT [pretreated], Ra = 0.6 microm; SLA [course grit blasted and acid etched], Ra = 4.0 microm; TPS [Ti plasma sprayed], Ra = 5.2 microm) in the presence of either BMP-2 (20 ng/ml) or 10(-8) M dexamethasone (Dex). At 14 days post-confluence, a homogenous layer of cells covered the surfaces, and stacks of cells that appeared to be nodules emerging from the culture surface were present in some areas on all three Ti surfaces. Cell proliferation decreased while alkaline phosphatase specific activity (ALPase) and nodule number generally increased with increasing surface roughness in both control and treated cultures. There was no difference in cell number between the control and Dex-treated cultures for a particular surface, but BMP-2 significantly reduced cell number compared with control or Dex-treated cultures. Treatment with Dex or BMP-2 further increased ALPase on all surfaces except for PT cultures with Dex. Dex had no effect on nodule area in cultures grown on PT or SLA disks, yet increased nodule number by more than 100% in cultures on PT disks. Though the effect of BMP-2 on nodule number was the same as Dex, BMP-2 increased nodule area on all surfaces except TPS, where area was decreased. Ca and P content of the cell layers in control cultures did not vary with surface roughness. However, cultures treated with Dex had increased Ca content on all surfaces, but the greatest increase was seen on SLA and TPS. BMP-2 increased Ca content in cultures on all surfaces, with the greatest increase on the PT surface. BMP-2 treatment increased P content on all surfaces, whereas Dex only increased P on rough

  12. Intermittent Parathyroid Hormone Enhances Cancellous Osseointegration of a Novel Murine Tibial Implant

    PubMed Central

    Yang, Xu; Ricciardi, Benjamin F.; Dvorzhinskiy, Aleksey; Brial, Caroline; Lane, Zachary; Bhimani, Samrath; Burket, Jayme C.; Hu, Bin; Sarkisian, Alexander M.; Ross, F. Patrick; van der Meulen, Marjolein C.H.; Bostrom, Mathias P.G.

    2015-01-01

    Background: Long-term fixation of uncemented joint implants requires early mechanical stability and implant osseointegration. To date, osseointegration has been unreliable and remains a major challenge in cementless total knee arthroplasty. We developed a murine model in which an intra-articular proximal tibial titanium implant with a roughened stem can be loaded through the knee joint. Using this model, we tested the hypothesis that intermittent injection of parathyroid hormone (iPTH) would increase proximal tibial cancellous osseointegration. Methods: Ten-week-old female C57BL/6 mice received a subcutaneous injection of PTH (40 μg/kg/day) or a vehicle (n = 45 per treatment group) five days per week for six weeks, at which time the baseline group was killed (n = 6 per treatment group) and an implant was inserted into the proximal part of the tibiae of the remaining mice. Injections were continued until the animals were killed at one week (n = 7 per treatment group), two weeks (n = 14 per treatment group), or four weeks (n = 17 per treatment group) after implantation. Outcomes included peri-implant bone morphology as analyzed with micro-computed tomography (microCT), osseointegration percentage and bone area fraction as shown with backscattered electron microscopy, cellular composition as demonstrated by immunohistochemical analysis, and pullout strength as measured with mechanical testing. Results: Preimplantation iPTH increased the epiphyseal bone volume fraction by 31.6%. When the data at post-implantation weeks 1, 2, and 4 were averaged for the iPTH-treated mice, the bone volume fraction was 74.5% higher in the peri-implant region and 168% higher distal to the implant compared with the bone volume fractions in the same regions in the vehicle-treated mice. Additionally, the trabecular number was 84.8% greater in the peri-implant region and 74.3% greater distal to the implant. Metaphyseal osseointegration and bone area fraction were 28.1% and 70.1% higher

  13. Osseointegration and biocompatibility of different metal implants - a comparative experimental investigation in sheep

    PubMed Central

    2012-01-01

    Background In the present study, 4 different metallic implant materials, either partly coated or polished, were tested for their osseointegration and biocompatibility in a pelvic implantation model in sheep. Methods Materials to be evaluated were: Cobalt-Chrome (CC), Cobalt-Chrome/Titanium coating (CCTC), Cobalt-Chrome/Zirconium/Titanium coating (CCZTC), Pure Titanium Standard (PTST), Steel, TAN Standard (TANST) and TAN new finish (TANNEW). Surgery was performed on 7 sheep, with 18 implants per sheep, for a total of 63 implants. After 8 weeks, the specimens were harvested and evaluated macroscopically, radiologically, biomechanically (removal torque), histomorphometrically and histologically. Results Cobalt-Chrome screws showed significantly (p = 0.031) lower removal torque values than pure titanium screws and also a tendency towards lower values compared to the other materials, except for steel. Steel screws showed no significant differences, in comparison to cobalt-chrome and TANST, however also a trend towards lower torque values than the remaining materials. The results of the fluorescence sections agreed with those of the biomechanical test. Histomorphometrically, there were no significant differences of bone area between the groups. The BIC (bone-to-implant-contact), used for the assessment of the osseointegration, was significantly lower for cobalt-chrome, compared to steel (p = 0.001). Steel again showed a lower ratio (p = 0.0001) compared to the other materials. Conclusion This study demonstrated that cobalt-chrome and steel show less osseointegration than the other metals and metal-alloys. However, osseointegration of cobalt-chrome was improved by zirconium and/or titanium based coatings (CCTC, TANST, TAN, TANNEW) being similar as pure titanium in their osseointegrative behavior. PMID:22400715

  14. Importance of the Roughness and Residual Stresses of Dental Implants on Fatigue and Osseointegration Behavior. In Vivo Study in Rabbits.

    PubMed

    Velasco, Eugenio; Monsalve-Guil, Loreto; Jimenez, Alvaro; Ortiz, Iván; Moreno-Muñoz, Jesús; Nuñez-Marquez, Enrique; Pegueroles, Marta; Pérez, Román A; Gil, Francisco Javier

    2016-12-01

    This study focuses on the fatigue behavior and bone-implant attachment for the more usual surfaces of the different CP-titanium dental implants. The implants studied were: as-received (CTR), acid etching (AE), spark-anodization (SA), and with a grit-blasted surface (GB). Residual stresses were determined by means of X-ray diffraction. The fatigue tests were carried out at 37°C on 160 dental implants, and the stress-failure (S-N) curve was determined. The fatigue tests showed that the grit-blasting process improved fatigue life. This is a consequence of the layer of compressive residual stresses that the treatment generates in titanium surfaces. Further, our aim was to assess and compare the short- and midterm bone regenerative potential and mechanical retention of the implants in bone of New Zealand rabbits. The mechanical retention after 4 and 10 weeks of implantation was evaluated with histometric and pull-out tests, respectively, as a measure of the osseointegration of the implants. The results demonstrated that the GB treatment produced microrough that accelerated bone tissue regeneration and increased mechanical retention in the bone bed at short periods of implantation in comparison with all other implants tested. The GB surface produced an improvement in mechanical long-time behavior and improved bone growth. These types of treated implants can have great potential in clinical applications, as evidenced by the outcomes of the current study.

  15. Microtopography for Ductile Fracture Process Characterization - Part 1: Theory and Methodology

    SciTech Connect

    Lloyd, Wilson Randolph

    2003-02-01

    The mechanics of ductile fracture is receiving increased focus as the importance of integrity of structures constructed from ductile materials is increasing. The non-linear, irreversible mechanical response of ductile materials makes generalized models of ductile cracking very difficult to develop. Therefore, research and testing of ductile fracture have taken a path leading to deformation-based parameters such as crack tip opening displacement (CTOD) and crack tip opening angle (CTOA). Constrained by conventional test techniques and instrumentation, physical values (e.g. crack mouth opening displacement, CMOD, and CTOA angles) are measured on the test specimen exterior and a single through-thickness "average" interior value is inferred. Because of three-dimensional issues such as crack curvature, constraint variation, and material inhomogeneity, inference of average parameter values may introduce errors. The microtopography methodology described here measures and maps three-dimensional fracture surfaces. The analyses of these data provide direct extraction of the parameters of interest at any location within the specimen interior, and at any desired increment of crack opening or extension. A single test specimen can provide all necessary information for the analysis of a particular material and geometry combination.

  16. The effect of surface microtopography of poly(dimethylsiloxane) on protein adsorption, platelet and cell adhesion.

    PubMed

    Chen, Hong; Song, Wei; Zhou, Feng; Wu, Zhongkui; Huang, He; Zhang, Junhu; Lin, Quan; Yang, Bai

    2009-07-01

    Chemical homogeneous poly(dimethylsiloxane) (PDMS) surface with dot-like protrusion pattern was used to investigate the individual effect of surface microtopography on protein adsorption and subsequent biological responses. Fibrinogen (Fg) and fibronectin (Fn) were chosen as model proteins due to their effect on platelet and cell adhesion, respectively. Fg labeled with (125)I and fluorescein isothiocyanate (FITC) was used to study its adsorption on flat and patterned surfaces. Patterned surface has a 46% increase in the adsorption of Fg when compared with flat surface. However, the surface area of the patterned surface was only 8% larger than that of the flat surface. Therefore, the increase in the surface area was not the only factor responsible for the increase in protein adsorption. Clear fluorescent pattern was visualized on patterned surface, indicating that adsorbed Fg regularly distributed and adsorbed most on the flanks and valleys of the protrusions. Such distribution and local enrichment of Fg presumably caused the specific location of platelets adhered from platelet-rich plasma (PRP) and flowing whole blood (FWB) on patterned surface. Furthermore, the different combination of surface topography and pre-adsorbed Fn could influence the adhesion of L929 cells. The flat surface with pre-adsorbed Fn was the optimum substrate while the virgin patterned surface was the poor substrate in terms of L929 cells spread.

  17. Analysis of surface microtopography of biodegradable polymer matrices using confocal reflection microscopy.

    PubMed

    Semler, E J; Tjia, J S; Moghe, P V

    1997-01-01

    Currently, synthetic degradable polymers are frequently employed as culture substrates prior to cell transplantation and as implantable scaffolds for cellular infiltration during soft and hard tissue repair. The surface microstructure of matrices based on such polymers may be important in controlling cellular anchorage, spreading, and growth on the external surface, as well as infiltration into the voids of porous polymer scaffolds. While the chemistry, bulk structure, and mechanical properties of such polymers have been extensively studied, the surface microstructure has not yet been systematically examined, particularly following polymer degradation. In this study, we present the first account of the use of confocal laser-scanning reflection microscopy (CLSM) to visualize and quantitate the microtopography of the surface of porous matrices of poly(lactic acid)/poly(glycolic acid) (PLAGA) copolymers following polymer degradation. Utilizing this technique, we report that the surface morphology of PLAGA matrices changes significantly upon degradation, with increased local clustering of textured regions. Our quantitative analysis suggests that polymer degradation results in a lower spatially-averaged surface roughness, with significant cyclical variations observed at later time points. The computed surface correlation function was observed to increase upon degradation, confirming the results from our morphological studies. Finally, we demonstrate the efficacy of CLSM to concomitantly image both the polymer surface and locally attached cells, in real time.

  18. Combined effects of microtopography and cyclic strain on vascular smooth muscle cell orientation.

    PubMed

    Houtchens, Graham R; Foster, Michael D; Desai, Tejal A; Morgan, Elise F; Wong, Joyce Y

    2008-01-01

    Cellular alignment studies have shown that cell orientation has a large effect on the expression and behavior of cells. Cyclic strain and substrate microtopography have each been shown to regulate cellular alignment. This study examined the combined effects of these two stimuli on the alignment of bovine vascular smooth muscle cells (VSMCs). Cells were cultured on substrates with microgrooves of varying widths oriented either parallel or perpendicular to the direction of an applied cyclic tensile strain. We found that microgrooves oriented parallel to the direction of the applied strain limited the orientation response of VSMCs to the mechanical stimulus, while grooves perpendicular to the applied strain enhanced cellular alignment. Further, the extent to which parallel grooves limited cell alignment was found to be dependent on the groove width. It was found that for both a small (15microm) and a large (70microm) groove width, cells were better able to reorient in response to the applied strain than for an intermediate groove width (40microm). This study indicates that microtopographical cues modulate the orientation response of VSMCs to cyclic strain. The results suggest that there is a range of microgroove dimensions that is most effective at maintaining the orientation of the cells in the presence of an opposing stimulus induced by cyclic strain.

  19. Surface microtopography modulates sealing zone development in osteoclasts cultured on bone.

    PubMed

    Shemesh, Michal; Addadi, Lia; Geiger, Benjamin

    2017-02-01

    Bone homeostasis is continuously regulated by the coordinated action of bone-resorbing osteoclasts and bone-forming osteoblasts. Imbalance between these two cell populations leads to pathological bone diseases such as osteoporosis and osteopetrosis. Osteoclast functionality relies on the formation of sealing zone (SZ) rings that define the resorption lacuna. It is commonly assumed that the structure and dynamic properties of the SZ depend on the physical and chemical properties of the substrate. Considering the unique complex structure of native bone, elucidation of the relevant parameters affecting SZ formation and stability is challenging. In this study, we examined in detail the dynamic response of the SZ to the microtopography of devitalized bone surfaces, taken from the same area in cattle femur. We show that there is a significant enrichment in large and stable SZs (diameter larger than 14 µm; lifespan of hours) in cells cultured on rough bone surfaces, compared with small and fast turning over SZ rings (diameter below 7 µm; lifespan approx. 7 min) formed on smooth bone surfaces. Based on these results, we propose that the surface roughness of the physiologically relevant substrate of osteoclasts, namely bone, affects primarily the local stability of growing SZs.

  20. Micro-topographies promote late chondrogenic differentiation markers in the ATDC5 cell line.

    PubMed

    Bach, Le Q; Vasilevich, Aliaksei; Vermeulen, Steven; Hulshof, Frits; Stamatialis, Dimitrios; van Blitterswijk, Clemens; de Boer, Jan

    2017-02-03

    Chemical and mechanical cues are well-established influencers of the in vitro chondrogenic differentiation of ATDC5 cells. Here, we investigate the role of topographical cues in this differentiation process. Previously using a library of surface micro-topographies, we found some distinct patterns that induced alkaline phosphatase (ALP) production in human mesenchymal stromal cells. ALP is also a marker for hypertrophy, the end stage of chondrogenic differentiation. Thus, we hypothesized that these patterns could influence chondrogenic differentiation of ATDC5 cells. We randomly selected seven topographies among the ALP influencing hits. Cells grown on these surfaces displayed varying nuclear shape and actin filament structure. When stimulated with Insulin-Transferrin-Selenium (ITS) medium, nodule formation occurred and in some cases showed alignment to the topographical patterns. Gene expression analysis of cells growing on topographical surfaces in the presence of ITS medium revealed a down-regulation of early markers and up-regulation of late markers of chondrogenic differentiation compared to cells grown on a flat surface. In conclusion, we demonstrated that surface topography in addition with other cues can promote hypertrophic differentiation suitable for bone tissue engineering.

  1. Impact of engineered surface microtopography on biofilm formation of Staphylococcus aureus.

    PubMed

    Chung, Kenneth K; Schumacher, James F; Sampson, Edith M; Burne, Robert A; Antonelli, Patrick J; Brennan, Anthony B

    2007-06-01

    The surface of an indwelling medical device can be colonized by human pathogens that can form biofilms and cause infections. In most cases, these biofilms are resistant to antimicrobial therapy and eventually necessitate removal or replacement of the device. An engineered surface microtopography based on the skin of sharks, Sharklet AF, has been designed on a poly(dimethyl siloxane) elastomer (PDMSe) to disrupt the formation of bacterial biofilms without the use of bactericidal agents. The Sharklet AF PDMSe was tested against smooth PDMSe for biofilm formation of Staphylococcus aureus over the course of 21 days. The smooth surface exhibited early-stage biofilm colonies at 7 days and mature biofilms at 14 days, while the topographical surface did not show evidence of early biofilm colonization until day 21. At 14 days, the mean value of percent area coverage of S. aureus on the smooth surface was 54% compared to 7% for the Sharklet AF surface (p<0.01). These results suggest that surface modification of indwelling medical devices and exposed sterile surfaces with the Sharklet AF engineered topography may be an effective solution in disrupting biofilm formation of S. aureus.

  2. Long-term outcomes of osseointegrated digital prostheses for proximal amputations.

    PubMed

    Sierakowski, A; Watts, C; Thomas, K; Elliot, D

    2011-02-01

    This paper presents outcomes after 13, 4, and 3½ years in three digital amputees treated with osseointegrated prostheses. One had prosthetic replacement of the index and middle fingers at the PIP level. The second had four fingers replaced at the PIP level, but only three prostheses were retained. The third had a thumb replacement at the MCP level. All patients scored their reconstructed hand highly in terms of appearance and frequency of use. The first and third patients rated the function of the reconstructed hand as similar to the normal hand, and this was confirmed by the Jebsen Test, but the second patient had poor function. All patients could detect pressure and vibration through their prostheses, although grip and pinch strengths were weaker in all three. All three also experienced some pain in the implanted fingers. This study identifies osseointegration as a stable long-term reconstructive option.

  3. A strontium-incorporated nanoporous titanium implant surface for rapid osseointegration

    NASA Astrophysics Data System (ADS)

    Zhang, Wenjie; Cao, Huiliang; Zhang, Xiaochen; Li, Guanglong; Chang, Qing; Zhao, Jun; Qiao, Yuqin; Ding, Xun; Yang, Guangzheng; Liu, Xuanyong; Jiang, Xinquan

    2016-02-01

    Rapid osseointegration of dental implants will shorten the period of treatment and enhance the comfort of patients. Due to the vital role of angiogenesis played during bone development and regeneration, it might be feasible to promote rapid osseointegration by modifying the implant surface to gain a combined angiogenesis/osteogenesis inducing capacity. In this study, a novel coating (MAO-Sr) with strontium-incorporated nanoporous structures on titanium implants was generated via a new micro-arc oxidation, in an attempt to induce angiogenesis and osteogenesis to enhance rapid osseointegration. In vitro, the nanoporous structure significantly enhanced the initial adhesion of canine BMSCs. More importantly, sustained release of strontium ions also displayed a stronger effect on the BMSCs in facilitating their osteogenic differentiation and promoting the angiogenic growth factor secretion to recruit endothelial cells and promote blood vessel formation. Advanced mechanism analyses indicated that MAPK/Erk and PI3K/Akt signaling pathways were involved in these effects of the MAO-Sr coating. Finally, in the canine dental implantation study, the MAO-Sr coating induced faster bone formation within the initial six weeks and the osseointegration effect was comparable to that of the commercially available ITI implants. These results suggest that the MAO-Sr coating has the potential for future use in dental implants.Rapid osseointegration of dental implants will shorten the period of treatment and enhance the comfort of patients. Due to the vital role of angiogenesis played during bone development and regeneration, it might be feasible to promote rapid osseointegration by modifying the implant surface to gain a combined angiogenesis/osteogenesis inducing capacity. In this study, a novel coating (MAO-Sr) with strontium-incorporated nanoporous structures on titanium implants was generated via a new micro-arc oxidation, in an attempt to induce angiogenesis and osteogenesis to

  4. Biomaterial strategies for engineering implants for enhanced osseointegration and bone repair

    PubMed Central

    Agarwal, Rachit; García, Andrés J.

    2015-01-01

    Bone tissue has a remarkable ability to regenerate and heal itself. However, large bone defects and complex fractures still present a significant challenge to the medical community. Current treatments center on metal implants for structural and mechanical support and auto- or allo-grafts to substitute long bone defects. Metal implants are associated with several complications such as implant loosening and infections. Bone grafts suffer from donor site morbidity, reduced bioactivity, and risk of pathogen transmission. Surgical implants can be modified to provide vital biological cues, growth factors and cells in order to improve osseointegration and repair of bone defects. Here we review strategies and technologies to engineer metal surfaces to promote osseointegration with the host tissue. We also discuss strategies for modifying implants for cell adhesion and bone growth via integrin signaling and growth factor and cytokine delivery for bone defect repair. PMID:25861724

  5. Biomaterial strategies for engineering implants for enhanced osseointegration and bone repair.

    PubMed

    Agarwal, Rachit; García, Andrés J

    2015-11-01

    Bone tissue has a remarkable ability to regenerate and heal itself. However, large bone defects and complex fractures still present a significant challenge to the medical community. Current treatments center on metal implants for structural and mechanical support and auto- or allo-grafts to substitute long bone defects. Metal implants are associated with several complications such as implant loosening and infections. Bone grafts suffer from donor site morbidity, reduced bioactivity, and risk of pathogen transmission. Surgical implants can be modified to provide vital biological cues, growth factors and cells in order to improve osseointegration and repair of bone defects. Here we review strategies and technologies to engineer metal surfaces to promote osseointegration with the host tissue. We also discuss strategies for modifying implants for cell adhesion and bone growth via integrin signaling and growth factor and cytokine delivery for bone defect repair.

  6. Biosorption of thorium on the external shell surface of bivalve mollusks: the role of shell surface microtopography.

    PubMed

    Zuykov, Michael; Pelletier, Emilien; Saint-Louis, Richard; Checa, Antonio; Demers, Serge

    2012-02-01

    External shell surface (ESS) of bivalve mollusks is known to adsorb various metals dissolved in ambient water in high concentration. It is hypothesized here that the surface microtopography of the thin organic coating layer, periostracum, or calcareous shell (if periostracum was destroyed) plays a major role in the adsorption of actinides on ESS. Thorium (natural alpha-emitter) was used in short-term biosorption experiment with shell fragments of five bivalve mollusks. After a 72 h exposure to Th (~6 kBq L(-1)), thorium concentration was measured on ESS using laser ablation inductively coupled plasma mass spectrometry; the distribution and density of alpha tracks were subsequently visualized by α-track autoradiography. A trend in reduced Th concentrations on the ESS was observed depending upon the species tested: (group 1 ~4000 μg g(-1)) Chlamys islandica (M.), Mercenaria mercenaria (L.), Dreissena polymorpha (P.)>(group 2 ~1200 μg g(-1)) Crassostrea virginica (G.)≫(group 3 ~150 μg g(-1)) Mytilus edulis L. The microtopography of ESS was characterized by scanning electron microscopy revealing the high porosity of the calcareous surface of C. islandica and M. mercenaria, lamellate surface of periostracum in D. polymorpha, uneven but a weakly porous surface of periostracum of C. virginica, and a nearly smooth surface of the periostracum of M. edulis. This work has demonstrated, for the first time, the presence of a strong correlation between concentration of adsorbed Th and ESS microtopography, and the role of the periostracum in this process is discussed.

  7. Engineered PlyCB as a Novel Implant Coating for Osseointegration

    DTIC Science & Technology

    2012-03-01

    The lack of osseointegration is the primary cause of implant failure or shortened lifespan under physiological loads. Coatings such as hydroxyapatite ...the mineral component of bone, are often used to promote integration of bone with implant. However, hydroxyapatite coatings do not contain any...protein, was found to have a particularly high affinity for hydroxyapatite (Nelson, 2006). Based on the crystal structure, we plan to introduce mutants

  8. Osseointegration of nanohydroxyapatite- or nano-calcium silicate-incorporated polyetheretherketone bioactive composites in vivo.

    PubMed

    Ma, Rui; Yu, Zhifeng; Tang, Songchao; Pan, Yongkang; Wei, Jie; Tang, Tingting

    Polyetheretherketone (PEEK) exhibits appropriate biomechanical strength as well as good biocompatibility and stable chemical properties but lacks bioactivity and cannot achieve highly efficient osseointegration after implantation. Incorporating bioceramics into the PEEK matrix is a feasible approach for improving its bioactivity. In this study, nanohydroxyapatite (n-HA) and nano-calcium silicate (n-CS) were separately incorporated into PEEK to prepare n-HA/PEEK and n-CS/PEEK biocomposites, respectively, using a compounding and injection-molding technique, and the in vitro degradation characteristics were evaluated. Discs with a diameter of 8 mm were inserted in 8 mm full-thickness cranial defects in rabbits for 4 and 8 weeks, and implantation of pure PEEK was used as the control. Three-dimensional microcomputed tomography, histological analysis, fluorescence microscopy of new bone formation, and scanning electron microscopy were used to evaluate the osseointegration performance at the bone/implant interface. The results of the in vitro degradation study demonstrated that degradation of n-CS on the surface of n-CS/PEEK could release Ca and Si ions and form a porous structure. In vivo tests revealed that both n-CS/PEEK and n-HA/PEEK promoted osseointegration at the bone/implant interface compared to PEEK, and n-CS/PEEK exhibited higher bone contact ratio and more new bone formation compared with those of n-HA/PEEK, implying that n-CS/PEEK possessed a stronger ability to promote osseointegration. These two PEEK biocomposites are promising materials for the preparation of orthopedic or craniofacial implants.

  9. Titanium Implant Osseointegration Problems with Alternate Solutions Using Epoxy/Carbon-Fiber-Reinforced Composite

    PubMed Central

    Petersen, Richard C.

    2014-01-01

    The aim of the article is to present recent developments in material research with bisphenyl-polymer/carbon-fiber-reinforced composite that have produced highly influential results toward improving upon current titanium bone implant clinical osseointegration success. Titanium is now the standard intra-oral tooth root/bone implant material with biocompatible interface relationships that confer potential osseointegration. Titanium produces a TiO2 oxide surface layer reactively that can provide chemical bonding through various electron interactions as a possible explanation for biocompatibility. Nevertheless, titanium alloy implants produce corrosion particles and fail by mechanisms generally related to surface interaction on bone to promote an inflammation with fibrous aseptic loosening or infection that can require implant removal. Further, lowered oxygen concentrations from poor vasculature at a foreign metal surface interface promote a build-up of host-cell-related electrons as free radicals and proton acid that can encourage infection and inflammation to greatly influence implant failure. To provide improved osseointegration many different coating processes and alternate polymer matrix composite (PMC) solutions have been considered that supply new designing potential to possibly overcome problems with titanium bone implants. Now for important consideration, PMCs have decisive biofunctional fabrication possibilities while maintaining mechanical properties from addition of high-strengthening varied fiber-reinforcement and complex fillers/additives to include hydroxyapatite or antimicrobial incorporation through thermoset polymers that cure at low temperatures. Topics/issues reviewed in this manuscript include titanium corrosion, implant infection, coatings and the new epoxy/carbon-fiber implant results discussing osseointegration with biocompatibility related to nonpolar molecular attractions with secondary bonding, carbon fiber in vivo properties, electrical

  10. Titanium Implant Osseointegration Problems with Alternate Solutions Using Epoxy/Carbon-Fiber-Reinforced Composite.

    PubMed

    Petersen, Richard C

    2014-12-01

    The aim of the article is to present recent developments in material research with bisphenyl-polymer/carbon-fiber-reinforced composite that have produced highly influential results toward improving upon current titanium bone implant clinical osseointegration success. Titanium is now the standard intra-oral tooth root/bone implant material with biocompatible interface relationships that confer potential osseointegration. Titanium produces a TiO2 oxide surface layer reactively that can provide chemical bonding through various electron interactions as a possible explanation for biocompatibility. Nevertheless, titanium alloy implants produce corrosion particles and fail by mechanisms generally related to surface interaction on bone to promote an inflammation with fibrous aseptic loosening or infection that can require implant removal. Further, lowered oxygen concentrations from poor vasculature at a foreign metal surface interface promote a build-up of host-cell-related electrons as free radicals and proton acid that can encourage infection and inflammation to greatly influence implant failure. To provide improved osseointegration many different coating processes and alternate polymer matrix composite (PMC) solutions have been considered that supply new designing potential to possibly overcome problems with titanium bone implants. Now for important consideration, PMCs have decisive biofunctional fabrication possibilities while maintaining mechanical properties from addition of high-strengthening varied fiber-reinforcement and complex fillers/additives to include hydroxyapatite or antimicrobial incorporation through thermoset polymers that cure at low temperatures. Topics/issues reviewed in this manuscript include titanium corrosion, implant infection, coatings and the new epoxy/carbon-fiber implant results discussing osseointegration with biocompatibility related to nonpolar molecular attractions with secondary bonding, carbon fiber in vivo properties, electrical

  11. Osseointegration of nanohydroxyapatite- or nano-calcium silicate-incorporated polyetheretherketone bioactive composites in vivo

    PubMed Central

    Ma, Rui; Yu, Zhifeng; Tang, Songchao; Pan, Yongkang; Wei, Jie; Tang, Tingting

    2016-01-01

    Polyetheretherketone (PEEK) exhibits appropriate biomechanical strength as well as good biocompatibility and stable chemical properties but lacks bioactivity and cannot achieve highly efficient osseointegration after implantation. Incorporating bioceramics into the PEEK matrix is a feasible approach for improving its bioactivity. In this study, nanohydroxyapatite (n-HA) and nano-calcium silicate (n-CS) were separately incorporated into PEEK to prepare n-HA/PEEK and n-CS/PEEK biocomposites, respectively, using a compounding and injection-molding technique, and the in vitro degradation characteristics were evaluated. Discs with a diameter of 8 mm were inserted in 8 mm full-thickness cranial defects in rabbits for 4 and 8 weeks, and implantation of pure PEEK was used as the control. Three-dimensional microcomputed tomography, histological analysis, fluorescence microscopy of new bone formation, and scanning electron microscopy were used to evaluate the osseointegration performance at the bone/implant interface. The results of the in vitro degradation study demonstrated that degradation of n-CS on the surface of n-CS/PEEK could release Ca and Si ions and form a porous structure. In vivo tests revealed that both n-CS/PEEK and n-HA/PEEK promoted osseointegration at the bone/implant interface compared to PEEK, and n-CS/PEEK exhibited higher bone contact ratio and more new bone formation compared with those of n-HA/PEEK, implying that n-CS/PEEK possessed a stronger ability to promote osseointegration. These two PEEK biocomposites are promising materials for the preparation of orthopedic or craniofacial implants. PMID:27881916

  12. [Osseointegrated endosseous implants, University of Liège concepts. Various clinical applications].

    PubMed

    Lahmouzi, J; Simain, F; Legrand, R

    1998-04-01

    Based on fundamental experimental studies performed by the research teams of Professor Bränemark (Göteborg, Sweden), the use of dental implants has become a scientifically accepted treatment concept in Dentistry to replace lost or missing teeth in fully and partially edentulous patients. The use of dental implants was initiated by the discovery that dental implants made of titanium can be anchored in the jawbone with direct bone contact (osseointegration).

  13. Representing northern peatland microtopography and hydrology within the Community Land Model

    SciTech Connect

    Shi, X.; Thornton, P. E.; Ricciuto, D. M.; Hanson, P. J.; Mao, J.; Sebestyen, S. D.; Griffiths, N. A.; Bisht, G.

    2015-02-20

    Predictive understanding of northern peatland hydrology is a necessary precursor to understanding the fate of massive carbon stores in these systems under the influence of present and future climate change. Current models have begun to address microtopographic controls on peatland hydrology, but none have included a prognostic calculation of peatland water table depth for a vegetated wetland, independent of prescribed regional water tables. We introduce here a new configuration of the Community Land Model (CLM) which includes a fully prognostic water table calculation for a vegetated peatland. Our structural and process changes to CLM focus on modifications needed to represent the hydrologic cycle of bogs environment with perched water tables, as well as distinct hydrologic dynamics and vegetation communities of the raised hummock and sunken hollow microtopography characteristic of peatland bogs. The modified model was parameterized and independently evaluated against observations from an ombrotrophic raised-dome bog in northern Minnesota (S1-Bog), the site for the Spruce and Peatland Responses Under Climatic and Environmental Change experiment (SPRUCE). Simulated water table levels compared well with site-level observations. The new model predicts significant hydrologic changes in response to planned warming at the SPRUCE site. At present, standing water is commonly observed in bog hollows after large rainfall events during the growing season, but simulations suggest a sharp decrease in water table levels due to increased evapotranspiration under the most extreme warming level, nearly eliminating the occurrence of standing water in the growing season. Simulated soil energy balance was strongly influenced by reduced winter snowpack under warming simulations, with the warming influence on soil temperature partly offset by the loss of insulating snowpack in early and late winter. The new model provides improved predictive capacity for seasonal hydrological dynamics

  14. Influence of steel implant surface microtopography on soft and hard tissue integration.

    PubMed

    Hayes, J S; Klöppel, H; Wieling, R; Sprecher, C M; Richards, R G

    2017-03-21

    After implantation of an internal fracture fixation device, blood contacts the surface, followed by protein adsorption, resulting in either soft-tissue adhesion or matrix adhesion and mineralization. Without protein adsorption and cell adhesion under the presence of micro-motion, fibrous capsule formation can occur, often surrounding a liquid filled void at the implant-tissue interface. Clinically, fibrous capsule formation is more prevalent with electropolished stainless steel (EPSS) plates than with current commercially pure titanium (cpTi) plates. We hypothesize that this is due to lack of micro-discontinuities on the standard EPSS plates. To test our hypothesis, four EPSS experimental surfaces with varying microtopographies were produced and characterized for morphology using the scanning electron microscope, quantitative roughness analysis using laser profilometry and chemical analysis using X-ray photoelectron spectroscopy. Clinically used EPSS (smooth) and cpTi (microrough) were included as controls. Six plates of each type were randomly implanted, one on both the left and right intact tibia of 18 white New Zealand rabbits for 12 weeks, to allow for a surface interface study. The results demonstrate that the micro-discontinuities on the upper surface of internal steel fixation plates reduced the presence of liquid filled voids within soft-tissue capsules. The micro-discontinuities on the plate under-surface increased bony integration without the presence of fibrous tissue interface. These results support the hypothesis that the fibrous capsule and the liquid filled void formation occurs mainly due to lack of micro-discontinuities on the polished smooth steel plates and that bony integration is increased to surfaces with higher amounts of micro-discontinuities. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2017.

  15. Fine morphological characteristics and microtopography of the free nerve endings of the human digital skin.

    PubMed

    Cauna, N

    1980-12-01

    Blocks of osmium-fixed human digital skin, representing a total area of 5 sq mm, were cut serially parallel to the skin surface starting with the epidermis for electron microscopical studies. At intervals, single 1-mu sections were taken and used for recording the microtopography of the receptor organs at various levels. Graphic reconstructions of 28 nerve endings were made. It was found that the digital skin accommodated up to 80 dermal papillae and three to four sweat duct orifices per square millimeter. Each papilla contained one to three fenestrated capillary loops. More than 60% of all papillae contained free nerve endings, sometimes up to five in a single papilla. As a result, up to 100 free nerve endings were counted per square millimeter. Intraepidermal endings were also present, one to five per square millimeter. No endings of any kind were found within the boundary zones between the papillary ridges and in the immediate vicinity of the sweat ducts. The origin of a free ending was marked by the perikaryon of a modified Schwann cell, which constituted the terminal cell of the Schwann sheath. The perikaryon was situated at the base of the dermal papilla, while its distal process provided the cytoplasmic sheath to the axon terminals and their branches. Sometimes two endings merged into a single receptor organ. The terminal Schwann cell frequently served as a rallying point of endings. Three morphological kinds of free endings were observed: open endings, beaded endings, and plain endings. The intraepidermal endings were the derivatives of the plain endings. The free endings in the digital skin had essentially vertical distribution. Each ending covered a minute surface area of skin in a punctate pattern. This is in contrast to the mode of distribution of the free (penicillate) endings of the human hairy skin. Each penicillus covers a large horizontal skin area and overlaps that of their neighbors.

  16. Characteristics of soil moisture in relation to microtopography in the Loess region of Northern Shaanxi, China.

    PubMed

    Bo, Yaojun; Zhu, Qingke; Zhao, Weijun

    2014-07-01

    Soil moisture is the primary factor limiting plant growth and vegetation rehabilitation in the loess region of northern Shaanxi, China. This 5-year (2008-2012) study investigated methods of selecting appropriate microsites for vegetation restoration based on efficient use of soil moisture; 5-year data were compared with 56 years of precipitation data using standardized precipitation index. In addition, the effects of microtopography on the spatiotemporal variations of soil moisture were analyzed at the Wuqi Ecological Station of Beijing Forestry University. Results showed that average annual precipitation during last 5 years fell by 12.4% during the growing season compared with 1957-2012 data and soil moisture content at depth of 0-160 cm under went dramatic changes and became relatively low in July and August. Soil moisture content varied in different microtopographical units as follows: gullies > gently-sloped terraces > collapsed soils > undisturbed slopes (control) > furrows > escarpments. The vertical distribution of soil moisture content in different microtopographical units showed dramatic changes at depth of 0-40 cm. Soil moisture content of gently-sloped terraces, gullies, collapsed areas, furrows, and undisturbed slopes was highest at depth of 80-160 cm with a level of instability at depth of 40-80 cm. For gently-sloped terraces and gullies, soil moisture content followed the order of 40-80 cm > 0-40 cm; for collapsed areas, furrows, and undisturbed slopes, soil moisture content follows the order of 0-40 cm > 40-80 cm. For escarpments, soil moisture content varied with depth in a different pattern: 0-40 cm > 80-160 cm > 40-80 cm. This study is of theoretical significance and will help guide the sustainable development of ecological restoration and vegetation rehabilitation in the Loess region.

  17. Substrate microtopography can enhance cell adhesive and migratory responsiveness to matrix ligand density.

    PubMed

    Ranucci, C S; Moghe, P V

    2001-02-01

    The regulation of cell motility by ligand density on substrates with variable microtopography is not well understood. In this report, we studied the adhesion and motility behavior of HepG2 cells on microtextured poly(glycolic-co-lactic)acid (PGLA) copolymer substrates, whose surface bioactivity was differentially modified through the adsorption of 0-5.5 ng/cm(2) collagen. Microtextured PGLA substrates were fabricated as thin films with a uniform surface distribution of micropores of median size of 3.1 +/- 1.5 microm and three-dimensional root mean squared roughness of 0.253 microm. Even in the absence of collagen, cells on microtextured substrates responded to substrate topography by exhibiting a 200% increase in adhesion strength compared with untextured controls and ventral localization of the intracellular adhesion protein vinculin. Further enhancement in adhesion strength (420% over untextured, untreated substrates) was demonstrated with bioactivated, microtextured surfaces, indicating that cell adhesion responses to topography and surface ligand density were cooperative. Our motility studies of cells on untextured substrates adsorbed with different levels of collagen demonstrated that a classical biphasic relationship between the cell population averaged migration rate, mu, and the collagen ligand density was preserved. However, comparison of cell motility responses between untextured and microtextured substrates indicates that the motility versus ligand density curve shifted, such that equivalent levels of cell motility were achieved at lower ligand density on microtextured surfaces. Furthermore, the maximum mu values achieved on the microtextured substrates exceeded those on untextured substrates by twofold. Taken together, we show that the magnitude of subcellular scale microtexture of a polymer substrate can sensitize the cell motility responsiveness to substrate ligand concentration; we suggest that the underlying mechanisms involve alteration in the

  18. Inhibition of fibroblast proliferation in cardiac myocyte cultures by surface microtopography.

    PubMed

    Boateng, Samuel Y; Hartman, Thomas J; Ahluwalia, Neil; Vidula, Himabindu; Desai, Tejal A; Russell, Brenda

    2003-07-01

    Cardiac myocyte cultures usually require pharmacological intervention to prevent overproliferation of contaminating nonmyocytes. Our aim is to prevent excessive fibroblast cell proliferation without the use of cytostatins. We have produced a silicone surface with 10-microm vertical projections that we term "pegs," to which over 80% of rat neonatal cardiac fibroblasts attach within 48 h after plating. There was a 50% decrease in cell proliferation by 5 days of culture compared with flat membranes (P < 0.001) and a concomitant 60% decrease (P < 0.01) in cyclin D1 protein levels, suggesting a G1/S1 cell cycle arrest due to microtopography. Inhibition of Rho kinase with 5 or 20 microM Y-27632 reduced attachment of fibroblasts to the pegs by over 50% (P < 0.001), suggesting that this signaling pathway plays an important role in the process. Using mobile and immobile 10-microm polystyrene spheres, we show that reactive forces are important for inhibiting fibroblast cell proliferation, because mobile spheres failed to reduce cell proliferation. In primary myocyte cultures, pegs also inhibit fibroblast proliferation in the absence of cytostatins. The ratio of aminopropeptide of collagen protein from fibroblasts to myosin from myocytes was significantly reduced in cultures from pegged surfaces (P < 0.01), suggesting an increase in the proportion of myocytes on the pegged surfaces. Connexin43 protein expression was also increased, suggesting improved myocyte-myocyte interaction in the presence of pegs. We conclude that this microtextured culture system is useful for preventing proliferation of fibroblasts in myocyte cultures and may ultimately be useful for tissue engineering applications in vivo.

  19. Comparison of self-reported lifetime sun exposure with two methods of cutaneous microtopography.

    PubMed

    Weiler, Lynn; Knight, Julia A; Vieth, Reinhold; Barnett, Heidi; Wong, Ansely

    2007-01-15

    There is currently no "gold standard" for measuring lifetime sun exposure. Exploration of alternatives to self-reports is important for examining illnesses related to ultraviolet light exposure. Using skin replicas obtained from 184 controls in a breast cancer case-control study (Toronto, Ontario, Canada, 2004-2005), the authors compared self-reported indicators of lifetime sun exposure with two measures of cutaneous microtopography, the Beagley-Gibson system and skin line counts. With the Beagley-Gibson system, significantly increased odds ratios were found for age (odds ratio (OR) = 1.10, 95% confidence interval (CI): 1.05, 1.16), spending 7 days outside per week during the summer (OR = 3.33, 95% CI: 1.48, 7.50), and lifetime number of sunlamp sessions. Significantly decreased odds ratios were found for having darker skin, ever giving birth, and ever using sunlamps. With the skin line count approach, significant positive associations were found for age (OR = 2.31, 95% CI: 1.23, 4.35), age squared, duration of working in outdoor jobs (OR = 0.88, 95% CI: 0.79, 0.98), and average number of outdoor activities per week at ages 20-29 years (OR = 1.05, 95% CI: 1.00, 1.10). While the Beagley-Gibson method was associated with more variables than the skin line count method, both methods require further refinement before graded skin replicas can be recommended as a substitute for self-report measures.

  20. Representing northern peatland microtopography and hydrology within the Community Land Model

    NASA Astrophysics Data System (ADS)

    Shi, X.; Thornton, P. E.; Ricciuto, D. M.; Hanson, P. J.; Mao, J.; Sebestyen, S. D.; Griffiths, N. A.; Bisht, G.

    2015-11-01

    Predictive understanding of northern peatland hydrology is a necessary precursor to understanding the fate of massive carbon stores in these systems under the influence of present and future climate change. Current models have begun to address microtopographic controls on peatland hydrology, but none have included a prognostic calculation of peatland water table depth for a vegetated wetland, independent of prescribed regional water tables. We introduce here a new configuration of the Community Land Model (CLM) which includes a fully prognostic water table calculation for a vegetated peatland. Our structural and process changes to CLM focus on modifications needed to represent the hydrologic cycle of bogs environment with perched water tables, as well as distinct hydrologic dynamics and vegetation communities of the raised hummock and sunken hollow microtopography characteristic of peatland bogs. The modified model was parameterized and independently evaluated against observations from an ombrotrophic raised-dome bog in northern Minnesota (S1-Bog), the site for the Spruce and Peatland Responses Under Climatic and Environmental Change experiment (SPRUCE). Simulated water table levels compared well with site-level observations. The new model predicts hydrologic changes in response to planned warming at the SPRUCE site. At present, standing water is commonly observed in bog hollows after large rainfall events during the growing season, but simulations suggest a sharp decrease in water table levels due to increased evapotranspiration under the most extreme warming level, nearly eliminating the occurrence of standing water in the growing season. Simulated soil energy balance was strongly influenced by reduced winter snowpack under warming simulations, with the warming influence on soil temperature partly offset by the loss of insulating snowpack in early and late winter. The new model provides improved predictive capacity for seasonal hydrological dynamics in northern

  1. Representing northern peatland microtopography and hydrology within the Community Land Model

    SciTech Connect

    Shi, Xiaoying; Thornton, Peter E.; Ricciuto, Daniel M.; Hanson, Paul J.; Mao, Jiafu; Sebestyen, Stephen D.; Griffiths, Natalie A.; Bisht, Gautam

    2015-11-12

    Predictive understanding of northern peatland hydrology is a necessary precursor to understanding the fate of massive carbon stores in these systems under the influence of present and future climate change. Current models have begun to address microtopographic controls on peatland hydrology, but none have included a prognostic calculation of peatland water table depth for a vegetated wetland, independent of prescribed regional water tables. We introduce here a new configuration of the Community Land Model (CLM) which includes a fully prognostic water table calculation for a vegetated peatland. Our structural and process changes to CLM focus on modifications needed to represent the hydrologic cycle of bogs environment with perched water tables, as well as distinct hydrologic dynamics and vegetation communities of the raised hummock and sunken hollow microtopography characteristic of peatland bogs. The modified model was parameterized and independently evaluated against observations from an ombrotrophic raised-dome bog in northern Minnesota (S1-Bog), the site for the Spruce and Peatland Responses Under Climatic and Environmental Change experiment (SPRUCE). Simulated water table levels compared well with site-level observations. The new model predicts hydrologic changes in response to planned warming at the SPRUCE site. At present, standing water is commonly observed in bog hollows after large rainfall events during the growing season, but simulations suggest a sharp decrease in water table levels due to increased evapotranspiration under the most extreme warming level, nearly eliminating the occurrence of standing water in the growing season. Simulated soil energy balance was strongly influenced by reduced winter snowpack under warming simulations, with the warming influence on soil temperature partly offset by the loss of insulating snowpack in early and late winter. Furthermore, the new model provides improved predictive capacity for seasonal hydrological dynamics

  2. Representing northern peatland microtopography and hydrology within the Community Land Model

    DOE PAGES

    Shi, X.; Thornton, P. E.; Ricciuto, D. M.; ...

    2015-02-20

    Predictive understanding of northern peatland hydrology is a necessary precursor to understanding the fate of massive carbon stores in these systems under the influence of present and future climate change. Current models have begun to address microtopographic controls on peatland hydrology, but none have included a prognostic calculation of peatland water table depth for a vegetated wetland, independent of prescribed regional water tables. We introduce here a new configuration of the Community Land Model (CLM) which includes a fully prognostic water table calculation for a vegetated peatland. Our structural and process changes to CLM focus on modifications needed to representmore » the hydrologic cycle of bogs environment with perched water tables, as well as distinct hydrologic dynamics and vegetation communities of the raised hummock and sunken hollow microtopography characteristic of peatland bogs. The modified model was parameterized and independently evaluated against observations from an ombrotrophic raised-dome bog in northern Minnesota (S1-Bog), the site for the Spruce and Peatland Responses Under Climatic and Environmental Change experiment (SPRUCE). Simulated water table levels compared well with site-level observations. The new model predicts significant hydrologic changes in response to planned warming at the SPRUCE site. At present, standing water is commonly observed in bog hollows after large rainfall events during the growing season, but simulations suggest a sharp decrease in water table levels due to increased evapotranspiration under the most extreme warming level, nearly eliminating the occurrence of standing water in the growing season. Simulated soil energy balance was strongly influenced by reduced winter snowpack under warming simulations, with the warming influence on soil temperature partly offset by the loss of insulating snowpack in early and late winter. The new model provides improved predictive capacity for seasonal hydrological

  3. Representing northern peatland microtopography and hydrology within the Community Land Model

    DOE PAGES

    Shi, Xiaoying; Thornton, Peter E.; Ricciuto, Daniel M.; ...

    2015-11-12

    Predictive understanding of northern peatland hydrology is a necessary precursor to understanding the fate of massive carbon stores in these systems under the influence of present and future climate change. Current models have begun to address microtopographic controls on peatland hydrology, but none have included a prognostic calculation of peatland water table depth for a vegetated wetland, independent of prescribed regional water tables. We introduce here a new configuration of the Community Land Model (CLM) which includes a fully prognostic water table calculation for a vegetated peatland. Our structural and process changes to CLM focus on modifications needed to representmore » the hydrologic cycle of bogs environment with perched water tables, as well as distinct hydrologic dynamics and vegetation communities of the raised hummock and sunken hollow microtopography characteristic of peatland bogs. The modified model was parameterized and independently evaluated against observations from an ombrotrophic raised-dome bog in northern Minnesota (S1-Bog), the site for the Spruce and Peatland Responses Under Climatic and Environmental Change experiment (SPRUCE). Simulated water table levels compared well with site-level observations. The new model predicts hydrologic changes in response to planned warming at the SPRUCE site. At present, standing water is commonly observed in bog hollows after large rainfall events during the growing season, but simulations suggest a sharp decrease in water table levels due to increased evapotranspiration under the most extreme warming level, nearly eliminating the occurrence of standing water in the growing season. Simulated soil energy balance was strongly influenced by reduced winter snowpack under warming simulations, with the warming influence on soil temperature partly offset by the loss of insulating snowpack in early and late winter. Furthermore, the new model provides improved predictive capacity for seasonal hydrological

  4. FGF23 neutralization improves bone quality and osseointegration of titanium implants in chronic kidney disease mice.

    PubMed

    Sun, Ningyuan; Guo, Yuchen; Liu, Weiqing; Densmore, Michael; Shalhoub, Victoria; Erben, Reinhold G; Ye, Ling; Lanske, Beate; Yuan, Quan

    2015-02-10

    Chronic kidney disease (CKD) is a worldwide health problem. Serum levels of FGF23, a phosphaturic hormone, increase at the earliest stages of CKD, and have been found to be independently associated with the mortality and morbidity of CKD patients. The purpose of this study was to evaluate whether FGF23 neutralization was able to improve bone quality and osseointegration of titanium implants. Uremia was induced by 5/6 nephrectomy in adult female mice. Postsurgery, the mice were injected with vehicle or FGF23 neutralizing antibody (5 mg/kg body weight) 3 times a week. Experimental titanium implants were inserted in the distal end of the femurs. FGF23 neutralization significantly increased serum phosphate, 1,25(OH)2D and BUN, and decreased serum PTH and FGF23, relative to vehicle-treated CKD mice. Histomorphometric analysis of the tibiae indicated that FGF23 neutralization normalized the osteoidosis observed in vehicle-treated CKD mice. Although bone-implant contact ratio remained unchanged by anti-FGF23 antibody treatment, the strength of osseointegration, as evidenced by a biomechanical push-in test, was significantly improved by FGF23 neutralization. Our findings revealed that FGF23 neutralization effectively improves bone quality and osseointegration of titanium implants in CKD mice, suggesting FGF23 as a key factor of CKD related bone diseases.

  5. Surface thermal oxidation on titanium implants to enhance osteogenic activity and in vivo osseointegration

    PubMed Central

    Wang, Guifang; Li, Jinhua; Lv, Kaige; Zhang, Wenjie; Ding, Xun; Yang, Guangzheng; Liu, Xuanyong; Jiang, Xinquan

    2016-01-01

    Thermal oxidation, which serves as a low-cost, effective and relatively simple/facile method, was used to modify a micro-structured titanium surface in ambient atmosphere at 450 °C for different time periods to improve in vitro and in vivo bioactivity. The surface morphology, crystallinity of the surface layers, chemical composition and chemical states were evaluated by field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Cell behaviours including cell adhesion, attachment, proliferation, and osteogenic differentiation were observed in vitro study. The ability of the titanium surface to promote osseointegration was evaluated in an in vivo animal model. Surface thermal oxidation on titanium implants maintained the microstructure and, thus, both slightly changed the nanoscale structure of titanium and enhanced the crystallinity of the titanium surface layer. Cells cultured on the three oxidized titanium surfaces grew well and exhibited better osteogenic activity than did the control samples. The in vivo bone-implant contact also showed enhanced osseointegration after several hours of oxidization. This heat-treated titanium enhanced the osteogenic differentiation activity of rBMMSCs and improved osseointegration in vivo, suggesting that surface thermal oxidation could potentially be used in clinical applications to improve bone-implant integration. PMID:27546196

  6. Implant osseointegration and the role of microroughness and nanostructures: lessons for spine implants.

    PubMed

    Gittens, Rolando A; Olivares-Navarrete, Rene; Schwartz, Zvi; Boyan, Barbara D

    2014-08-01

    The use of spinal implants for spine fusion has been steadily increasing to avoid the risks of complications and donor site morbidity involved when using autologous bone. A variety of fusion cages are clinically available, with different shapes and chemical compositions. However, detailed information about their surface properties and the effects of such properties on osteogenesis is lacking in the literature. Here we evaluate the role of surface properties for spinal implant applications, covering some of the key biological processes that occur around an implant and focusing on the role of surface properties, specifically the surface structure, on osseointegration, drawing examples from other implantology fields when required. Our findings revealed that surface properties such as microroughness and nanostructures can directly affect early cell behavior and long-term osseointegration. Microroughness has been well established in the literature to have a beneficial effect on osseointegration of implants. In the case of the role of nanostructures, the number of reports is increasing and most studies reveal a positive effect from the nanostructures alone and a synergistic effect when combined with microrough surfaces. Long-term clinical results are nevertheless necessary to establish the full implications of surface nanomodifications.

  7. In vivo osseointegration of Ti implants with a strontium-containing nanotubular coating

    PubMed Central

    Dang, Yonggang; Zhang, Li; Song, Wen; Chang, Bei; Han, Tianxiao; Zhang, Yumei; Zhao, Lingzhou

    2016-01-01

    Novel biomedical titanium (Ti) implants with high osteogenic ability for fast and good osseointegration under normal as well as osteoporotic conditions are urgently needed. Expanding on our previous in vitro results, we hypothesized that nanotubular, strontium-loaded (NT-Sr) structures on Ti implants would have favorable osteogenic effects and evaluated the in vivo osseointegration of these implants in rats. The structures with nanotubes of different diameters were fabricated by electrochemical anodization at 10 and 40 V, and the amounts of Sr loaded were adjusted by using two hydrothermal treatment times of 1 and 3 hours. Qualitative microcomputed tomography in two and three dimensions showed that the NT-Sr formed with an anodization voltage of 10 V and hydrothermal treatment time of 3 hours best supported bone growth in vivo. Histomorphometric examination of osseointegration also showed that more newly formed bone was found at its surface. The bone–implant contact percentage was highest (92.48%±0.76%) at 12 weeks. In conclusion, the NT-Sr formed with an anodization voltage of 10 V and hydrothermal treatment time of 3 hours showed excellent osteogenic properties, making it an attractive option for Ti surface modification with considerable clinical potential. PMID:27042055

  8. Plasma Surface Functionalized Polyetheretherketone for Enhanced Osseo-Integration at Bone-Implant Interface.

    PubMed

    Zhao, Ying; Wong, Hoi Man; Lui, So Ching; Chong, Eva Y W; Wu, Guosong; Zhao, Xiaoli; Wang, Chong; Pan, Haobo; Cheung, Kenneth M C; Wu, Shuilin; Chu, Paul K; Yeung, Kelvin W K

    2016-02-17

    This study aims at improving osseo-integration at the bone-implant interface of polyetheretherketone (PEEK) by water (H2O) and ammonia (NH3) plasma immersion ion implantation (PIII). The pertinent surface characteristics including surface energy, roughness, morphology, and chemical composition are investigated systematically and the in vitro biological performance is evaluated by cell adhesion and proliferation, alkaline phosphatase (ALP) activity, real-time RT-PCR evaluation, and mineralization tests. In vivo osseo-integration is examined via implanting samples into the distal femur of the rats. The hydrophilicity, surface roughness, cell adhesion, and proliferation, ALP activity, and osteogenic differentiation after H2O PIII or NH3 PIII are improved significantly. Furthermore, substantially enhanced osseo-integration is achieved in vivo. Nonline-of-sight plasma surface functionalization, which is particularly suitable for biomedical implants with an irregular geometry, does not alter the bulk compressive yield strength and elastic modulus of the materials. Consequently, the favorable bulk attributes of PEEK are preserved while the surface biological properties are enhanced thus boding well for wider orthopedic application of the biopolymer.

  9. Evaluating the osseointegration of nanostructured titanium implants in animal models: Current experimental methods and perspectives (Review).

    PubMed

    Babuska, Vaclav; Moztarzadeh, Omid; Kubikova, Tereza; Moztarzadeh, Amin; Hrusak, Daniel; Tonar, Zbynek

    2016-09-15

    The aim of this paper is to review the experimental methods currently being used to evaluate the osseointegration of nanostructured titanium implants using animal models. The material modifications are linked to the biocompatibility of various types of oral implants, such as laser-treated, acid-etched, plasma-coated, and sand-blasted surface modifications. The types of implants are reviewed according to their implantation site (endoosseous, subperiosteal, and transosseous implants). The animal species and target bones used in experimental implantology are carefully compared in terms of the ratio of compact to spongy bone. The surgical technique in animal experiments is briefly described, and all phases of the histological evaluation of osseointegration are described in detail, including harvesting tissue samples, processing undemineralized ground sections, and qualitative and quantitative histological assessment of the bone-implant interface. The results of histological staining methods used in implantology are illustrated and compared. A standardized and reproducible technique for stereological quantification of bone-implant contact is proposed and demonstrated. In conclusion, histological evaluation of the experimental osseointegration of dental implants requires careful selection of the experimental animals, bones, and implantation sites. It is also advisable to use larger animal models and older animals with a slower growth rate rather than small or growing experimental animals. Bones with a similar ratio of compact to spongy bone, such as the human maxilla and mandible, are preferred. A number of practical recommendations for the experimental procedures, harvesting of samples, tissue processing, and quantitative histological evaluations are provided.

  10. Surface thermal oxidation on titanium implants to enhance osteogenic activity and in vivo osseointegration

    NASA Astrophysics Data System (ADS)

    Wang, Guifang; Li, Jinhua; Lv, Kaige; Zhang, Wenjie; Ding, Xun; Yang, Guangzheng; Liu, Xuanyong; Jiang, Xinquan

    2016-08-01

    Thermal oxidation, which serves as a low-cost, effective and relatively simple/facile method, was used to modify a micro-structured titanium surface in ambient atmosphere at 450 °C for different time periods to improve in vitro and in vivo bioactivity. The surface morphology, crystallinity of the surface layers, chemical composition and chemical states were evaluated by field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Cell behaviours including cell adhesion, attachment, proliferation, and osteogenic differentiation were observed in vitro study. The ability of the titanium surface to promote osseointegration was evaluated in an in vivo animal model. Surface thermal oxidation on titanium implants maintained the microstructure and, thus, both slightly changed the nanoscale structure of titanium and enhanced the crystallinity of the titanium surface layer. Cells cultured on the three oxidized titanium surfaces grew well and exhibited better osteogenic activity than did the control samples. The in vivo bone-implant contact also showed enhanced osseointegration after several hours of oxidization. This heat-treated titanium enhanced the osteogenic differentiation activity of rBMMSCs and improved osseointegration in vivo, suggesting that surface thermal oxidation could potentially be used in clinical applications to improve bone-implant integration.

  11. Improvements in hip- and pelvic motion for patients with osseointegrated trans-femoral prostheses.

    PubMed

    Tranberg, R; Zügner, R; Kärrholm, J

    2011-02-01

    This study describes the changes in hip and pelvic kinematics in 19 trans-femoral amputees, who were treated with an osseointegrated trans-femoral prosthesis. Patients were studied with 3-dimensional gait analysis, walking with socket prosthesis within two days before the osseointergration procedure. The post-operative gait analysis was carried out at the 2 year follow-up visit. Fifty-seven; age-, side- and gender-matched healthy subjects served as controls. Post-operative data showed that patients who had an osseointegrated transfemoral prosthesis increased their hip extension by 7.3° (p=0.007), changing from -2.6° (range -13.4° to 10.7°) to -9.9° (range -29.4° to 5°). Moreover, the pre-operative anterior pelvic tilt was reduced by 4.0° (p=0.016), changing from 21.7° (range 11.9-34.8°) to 17.7° (range 5.5-25.7°). Values for hip extension and pelvic tilt changed toward those of controls. These results confirm that patients treated with osseointegrated trans-femoral prosthesis encounter significant changes of their kinematic pattern in terms of hip extension and anterior pelvic tilt. Even though the changes were moderate they may, in the long-term have a positive influence on low-back biomechanics and could contribute to reducing the risk of further problems with low back pain.

  12. Negative effects of alcohol intake and estrogen deficiency combination on osseointegration in a rat model.

    PubMed

    de Deco, Camila Porto; da Silva Marchini, Adriana Mathias Pereira; Bárbara, Mary Anne Moreira; de Vasconcellos, Luana Marotta Reis; da Rocha, Rosilene Fernandes; Marchini, Leonardo

    2011-12-01

    Alcohol intake and estrogen deficiency can both affect bone physiology and have shown to have an adverse effect on dental implant therapy. However, the combination of both factors on osseointegration is unknown. The aim of this study was to evaluate osseointegration in rats fed with alcohol and presenting induced estrogen deficiency. Ninety-six female rats were divided according to diet and hormonal condition into 6 groups as follows: group Sh-W: sham (simulated ovariectomy) control, food and water ad libitum; group Sh-Et: sham, food and 20% ethanol solution ad libitum; group Sh-Su: sham, food and sucrose solution controlled to ensure an isocaloric diet in relation to Sh-Et; group Ov-W: ovariectomy, food and water ad libitum; group Ov-Et: ovariectomy, food and 20% ethanol solution ad libitum; and group Ov-Su: ovariectomy, food and sucrose solution controlled to ensure an isocaloric diet as Ov-Et. The groups were subdivided according to time of euthanasia: 30 and 45 days after placement of implants. Implant surgery was performed 1 month after ovariectomy or sham. After euthanasia, the femurs were removed and evaluated by histomorphometry. Groups Ov-Et and Ov-Su showed the lowest percentage of bone-to-implant contact. The combination of alcohol intake and estrogen deficiency, and the combination of estrogen deficiency and reduced ingestion of food can negatively affect osseointegration in rats.

  13. In vivo osseointegration of Ti implants with a strontium-containing nanotubular coating.

    PubMed

    Dang, Yonggang; Zhang, Li; Song, Wen; Chang, Bei; Han, Tianxiao; Zhang, Yumei; Zhao, Lingzhou

    2016-01-01

    Novel biomedical titanium (Ti) implants with high osteogenic ability for fast and good osseointegration under normal as well as osteoporotic conditions are urgently needed. Expanding on our previous in vitro results, we hypothesized that nanotubular, strontium-loaded (NT-Sr) structures on Ti implants would have favorable osteogenic effects and evaluated the in vivo osseointegration of these implants in rats. The structures with nanotubes of different diameters were fabricated by electrochemical anodization at 10 and 40 V, and the amounts of Sr loaded were adjusted by using two hydrothermal treatment times of 1 and 3 hours. Qualitative microcomputed tomography in two and three dimensions showed that the NT-Sr formed with an anodization voltage of 10 V and hydrothermal treatment time of 3 hours best supported bone growth in vivo. Histomorphometric examination of osseointegration also showed that more newly formed bone was found at its surface. The bone-implant contact percentage was highest (92.48%±0.76%) at 12 weeks. In conclusion, the NT-Sr formed with an anodization voltage of 10 V and hydrothermal treatment time of 3 hours showed excellent osteogenic properties, making it an attractive option for Ti surface modification with considerable clinical potential.

  14. A comparative study of zirconium and titanium implants in rat: osseointegration and bone material quality.

    PubMed

    Hoerth, Rebecca M; Katunar, María R; Gomez Sanchez, Andrea; Orellano, Juan C; Ceré, Silvia M; Wagermaier, Wolfgang; Ballarre, Josefina

    2014-02-01

    Permanent metal implants are widely used in human medical treatments and orthopedics, for example as hip joint replacements. They are commonly made of titanium alloys and beyond the optimization of this established material, it is also essential to explore alternative implant materials in view of improved osseointegration. The aim of our study was to characterize the implant performance of zirconium in comparison to titanium implants. Zirconium implants have been characterized in a previous study concerning material properties and surface characteristics in vitro, such as oxide layer thickness and surface roughness. In the present study, we compare bone material quality around zirconium and titanium implants in terms of osseointegration and therefore characterized bone material properties in a rat model using a multi-method approach. We used light and electron microscopy, micro Raman spectroscopy, micro X-ray fluorescence and X-ray scattering techniques to investigate the osseointegration in terms of compositional and structural properties of the newly formed bone. Regarding the mineralization level, the mineral composition, and the alignment and order of the mineral particles, our results show that the maturity of the newly formed bone after 8 weeks of implantation is already very high. In conclusion, the bone material quality obtained for zirconium implants is at least as good as for titanium. It seems that the zirconium implants can be a good candidate for using as permanent metal prosthesis for orthopedic treatments.

  15. Numerical investigations on the osseointegration of uncemented endoprostheses based on bio-active interface theory

    NASA Astrophysics Data System (ADS)

    Lutz, André; Nackenhorst, Udo

    2012-09-01

    In order to simulate the osseointegration of bone implants, a bio-active interface theory is necessary. The thin bone-implant interface layer is described by the Drucker-Prager plasticity model. The formulation of bone mineral density depends on the local mechanical environment. For the simulation of the osseointegration of bone implants a bio-active interface theory is suggested. A thin bone-implant interface layer is described by a Drucker-Prager plasticity model. An evolution rule for the bone mineral density is formulated in dependency of the local mechanical environment. The time dependent ingrowth is modeled by a hardening rule which modifies the Drucker-Prager yield-surface cone in the principle stress state in dependency of the local bone mineral density. The osseointegration process is limited by the violation of a so called micromotion threshold. This relative motion in the implant-bone interface is computed by dynamic loads of daily motion activity. For parameter studies on detailed 3D models model reduction techniques are introduced. The applicability is demonstrated on a hip-joint prosthesis which is in clinical usage.

  16. Fractal analysis of surface micro-topography for a rolled anisotropic thick sheet of aluminium alloy AA2024-T351

    NASA Astrophysics Data System (ADS)

    Pirva, E.; Tudor, A.; Gavrus, A.

    2016-08-01

    Fractal geometry has gained attention in recent years and represents a problem of high interest for the characterization of surface topography. In this study it was analyzed the surface micro-topography for a rolled thick sheet anisotropic metallic material of type 2000 series aluminium alloy (AA2024-T351). In order to analyze and to characterize the corresponding anisotropic surfaces, profile of particular samples were recorded with a specialized apparatus Mitutoyo SJ-301 (Japan). The random nature of the roughness height is described through statistical analysis. The irregularity of the surface profile has been measured using a lot of conventional surface roughness parameters such as: arithmetic average, mean square root, maximum height of the profile, etc. Fractal analysis provides a useful way to characterize the observed spatial complexity of surface micro-topography. For this study it was used the structural function method to calculate two specific fractal parameters: D (fractal dimension) and L (topothesy). The fractal dimension of all samples it's been be calculated by plotting curves on log-log axes.

  17. The extracellular matrix microtopography drives critical changes in cellular motility and Rho A activity in colon cancer cells.

    PubMed

    Rapier, Rebecca; Huq, Jameela; Vishnubhotla, Ramana; Bulic, Marinka; Perrault, Cecile M; Metlushko, Vitali; Cho, Michael; Tay, Roger Tran Son; Glover, Sarah C

    2010-07-28

    We have shown that the microtopography (mT) underlying colon cancer changes as a tumor de-differentiates. We distinguish the well-differentiated mT based on the increasing number of "pits" and poorly differentiated mT on the basis of increasing number of "posts." We investigated Rho A as a mechanosensing protein using mT features derived from those observed in the ECM of colon cancer. We evaluated Rho A activity in less-tumorogenic (Caco-2 E) and more tumorigenic (SW620) colon cancer cell-lines on microfabricated pits and posts at 2.5 mum diameter and 200 nm depth/height. In Caco-2 E cells, we observed a decrease in Rho A activity as well as in the ratio of G/F actin on surfaces with either pits or posts but despite this low activity, knockdown of Rho A led to a significant decrease in confined motility suggesting that while Rho A activity is reduced on these surfaces it still plays an important role in controlling cellular response to barriers. In SW620 cells, we observed that Rho A activity was greatest in cells plated on a post microtopography which led to increased cell motility, and an increase in actin cytoskeletal turnover.

  18. Proliferation of mouse embryonic stem cell progeny and the spontaneous contractile activity of cardiomyocytes are affected by microtopography.

    PubMed

    Biehl, Jesse K; Yamanaka, Satoshi; Desai, Tejal A; Boheler, Kenneth R; Russell, Brenda

    2009-08-01

    The niche in which stem cells reside and differentiate is a complex physicochemical microenvironment that regulates cell function. The role played by three-dimensional physical contours was studied on cell progeny derived from mouse embryonic stem cells using microtopographies created on PDMS (poly-dimethyl-siloxane) membranes. While markers of differentiation were not affected, the proliferation of heterogeneous mouse embryonic stem cell-derived progeny was attenuated by 15 microm-, but not 5 microm-high microprojections. This reduction was reversed by Rho kinase and myosin light chain kinase inhibition, which diminishes the tension generating ability of stress fibers. Purified cardiomyocytes derived from embryonic stem cells also showed significant blunting of proliferation and increased beating rates compared with cells grown on flat substrates. Thus, proliferation of stem cell-derived progeny appears to be regulated by microtopography through tension-generation of contractility in the third-dimension. These results emphasize the importance of topographic cues in the modulation of stem cell progeny behavior.

  19. Weight-bearing-induced changes in the microtopography and structural stiffness of human skin in vivo following immobility periods.

    PubMed

    Dobos, Gabor; Gefen, Amit; Blume-Peytavi, Ulrike; Kottner, Jan

    2015-01-01

    Pressure ulcers (PUs) are injuries to the skin and underlying tissues, caused by sustained deformations and occur frequently in aged patients. Skin microtopography and stiffness affect the interaction of skin with contact surfaces contributing to PU development. We simulated immobility in 20 healthy females (mean age 69.9 years). Skin microtopography and stiffness were measured at the PU predilection sites before and after loading. Skin roughness decreased at the heels by 18.1% after 90 minutes (p = 0.022), but remained unchanged at the sacrum and the upper back. Structural elasticity and elastic deformations increased at all skin areas; changes over time were significant at the sacrum (p = 0.005) and the heel, (p = 0.002). The residual skin deformation increased at all skin areas after loading significantly at the sacrum (32.0%, p = 0.013) and upper back (20.6%, p = 0.007). The structural "biological" elasticity of the skin decreased significantly at the upper back after loading, but remained unchanged at the heels. All skin changes recovered after unloading. Results indicate that prolonged loading causes structural skin changes in humans in vivo in PU predilection sites. The pathogenesis of PUs is different at the heels, the sacral and upper back skin.

  20. Enhancing the settlement and attachment strength of pediveligers of Mytilus galloprovincialis by changing surface wettability and microtopography.

    PubMed

    Carl, C; Poole, A J; Sexton, B A; Glenn, F L; Vucko, M J; Williams, M R; Whalan, S; de Nys, R

    2012-01-01

    Surface wettability and microtopography can either enhance or deter larval settlement of many sessile marine organisms. This study quantifies the effect of these surface properties on the settlement of pediveligers of Mytilus galloprovincialis, using polymers spanning a range of wettability and microtextured polydimethylsiloxane (PDMS). Furthermore, the adhesion strength of settled pediveligers on microtextured PDMS surfaces was quantified using a flow chamber. Settlement was enhanced at the hydrophilic end of the wettability spectrum, where mean settlement on nylon reached 33.5 ± 13.1%. In contrast, mean settlement on the most hydrophobic polymer (PDMS) was 4.2 ± 3.2%. Microtopography had a much stronger effect compared to wettability, where 400 μm textured PDMS enhanced settlement above 90%. Settlement preferences were also positively correlated to adhesion strength at flow rates of 4 knots, with all initially settled pediveligers on smooth PDMS detaching, while 79.9 ± 5.7% of pediveligers remained on the 400 μm texture.

  1. Cyclic strain dominates over microtopography in regulating cytoskeletal and focal adhesion remodeling of human mesenchymal stem cells.

    PubMed

    Doroudian, Golnar; Curtis, Matthew W; Gang, Anjulie; Russell, Brenda

    2013-01-18

    Human bone marrow-derived mesenchymal stem cell (hMSCs) function depends on chemical factors and also on the physical cues of the microenvironmental niche. Here, this physical microenvironment is recapitulated with controlled modes of mechanical strain applied to substrata containing three-dimensional features in order to analyze the effects on cell morphology, focal adhesion distribution, and gene expression. Ten percentage of strain at 1 Hz is delivered for 48 h to hMSCs cultured on flat surfaces, or on substrata with 15 μm-high microtopographic posts spaced 75 μm apart. Adding strain to microtopography produced stable semicircular focal adhesions, and actin spanning from post to post. Strain dominated over microtopography for expression of genes for the cytoskeleton (caldesmon-1 and calponin 3), cell adhesion (integrin-α2, vinculin, and paxillin), and extracellular matrix remodeling (MMP13) (p<0.05). Overall, attention to external mechanical stimuli is necessary for optimizing the stem cell niche for regenerative medicine.

  2. Assessing the performance of structure-from-motion photogrammetry and terrestrial lidar 1 at reconstructing soil surface microtopography of naturally vegetated plots

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil microtopography or soil roughness is a property of critical importance in many earth surface processes but is often difficult to measure. Advances in computer vision technologies have made image-based 3D depiction of the soil surface or Structure-from-Motion (SfM) available to many scientists ...

  3. Current-controlled, abyssal microtopography and sedimentation in Mozambique Basin, southwest Indian Ocean

    USGS Publications Warehouse

    Kolla, V.; Eittreim, S.; Sullivan, L.; Kostecki, J.A.; Burckle, L.H.

    1980-01-01

    The Antarctic Bottom Water (AABW) activity and the variations in the abundance and grain size of the terrigenous sediments, derived from Africa and Madagascar land masses, are reflected in different types of microtopography in the Mozambique Basin. In southerly areas, where the sediment supply is much less, the bottom-current activity has resulted in the presence of manganese nodules, a thin veneer of sediments, and the absence of sediment waves. Farther north, along the marginal areas of the basin where the fine-grained sediments from the Africa-Madagascar source have been supplied in abundance, wavy bedforms have been generated by AABW. Wavy bedforms do not exist even in the northerly areas if coarse-grained, turbidite sediments are present on the sea floor. The continuation of acoustic reflectors from the zone of turbidites in the central areas of the basin into the zone of sediment waves along the margins, and the lithology and structures in sediment cores from these zones suggest that the turbidity-current-fed, fine-grained sediments were deposited as wavy bedforms by AABW flow. Thus, sediment waves formed readily during Pleistocene times. The enrichment of quartz and displaced Antarctic diatoms, and the relatively low kaolinite/chlorite ratios in the sediments, the north-pointing current lineations on the sea floor, the lack of any perceptible sedimentary fill in the troughs of waves, and the dense nepheloid layer in the westerly areas of the Mozambique Basin, attest to the current-controlled sedimentation and generation of wavy bedforms during Holocene time also. The formation of sediment waves in the Mozambique Basin can be modeled after a fluvial antidune mechanism. This model envisages that internal waves, focussed on a benthic boundary layer cap, have been locked in phase with sediment waves in the presence of an 8-10 cm/sec current in the Mozambique Basin. A density contrast of 2??10-6 g/cm3 appears to exist at the tops of benthic boundary layers in the

  4. Biofunctionalization strategies on tantalum-based materials for osseointegrative applications.

    PubMed

    Mas-Moruno, Carlos; Garrido, Beatriz; Rodriguez, Daniel; Ruperez, Elisa; Gil, F Javier

    2015-02-01

    The use of tantalum as biomaterial for orthopedic applications is gaining considerable attention in the clinical practice because it presents an excellent chemical stability, body fluid resistance, biocompatibility, and it is more osteoconductive than titanium or cobalt-chromium alloys. Nonetheless, metallic biomaterials are commonly bioinert and may not provide fast and long-lasting interactions with surrounding tissues. The use of short cell adhesive peptides derived from the extracellular matrix has shown to improve cell adhesion and accelerate the implant's biointegration in vivo. However, this strategy has been rarely applied to tantalum materials. In this work, we have studied two immobilization strategies (physical adsorption and covalent binding via silanization) to functionalize tantalum surfaces with a cell adhesive RGD peptide. Surfaces were used untreated or activated with either HNO3 or UV/ozone treatments. The process of biofunctionalization was characterized by means of physicochemical and biological methods. Physisorption of the RGD peptide on control and HNO3-treated tantalum surfaces significantly enhanced the attachment and spreading of osteoblast-like cells; however, no effect on cell adhesion was observed in ozone-treated samples. This effect was attributed to the inefficient binding of the peptide on these highly hydrophilic surfaces, as evidenced by contact angle measurements and X-ray photoelectron spectroscopy. In contrast, activation of tantalum with UV/ozone proved to be the most efficient method to support silanization and subsequent peptide attachment, displaying the highest values of cell adhesion. This study demonstrates that both physical adsorption and silanization are feasible methods to immobilize peptides onto tantalum-based materials, providing them with superior bioactivity.

  5. Selective serotonin reuptake inhibitors and the risk of osseointegrated implant failure: a cohort study.

    PubMed

    Wu, X; Al-Abedalla, K; Rastikerdar, E; Abi Nader, S; Daniel, N G; Nicolau, B; Tamimi, F

    2014-11-01

    Selective serotonin reuptake inhibitors (SSRIs), the most widely used drugs for the treatment of depression, have been reported to reduce bone formation and increase the risk of bone fracture. Since osseointegration is influenced by bone metabolism, this study aimed to investigate the association between SSRIs and the risk of failures in osseointegrated implants. This retrospective cohort study was conducted on patients treated with dental implants from January 2007 to January 2013. A total of 916 dental implants in 490 patients (94 implants on 51 patients using SSRIs) were used to estimate the risk of failure associated with the use of SSRIs. Data analysis involved Cox proportional hazards, generalized estimating equation models, multilevel mixed effects parametric survival analysis, and Kaplan-Meier analysis. After 3 to 67 mo of follow-up, 38 dental implants failed and 784 succeeded in the nonusers group, while 10 failed and 84 succeeded in the SSRI-users group. The main limitation of this retrospective study was that drug compliance dose and treatment period could not be acquired from the files of the patients. The primary outcome was that compared with nonusers of SSRIs, SSRI usage was associated with an increased risk of dental implants failure (hazard ratio, 6.28; 95% confidence interval, 1.25-31.61; p = .03). The failure rates were 4.6% for SSRI nonusers and 10.6% for SSRI users. The secondary outcomes were that small implant diameters (≤4 mm; p = .02) and smoking habits (p = .01) also seemed to be associated with higher risk of implant failure. Our findings indicate that treatment with SSRIs is associated with an increased failure risk of osseointegrated implants, which might suggest a careful surgical treatment planning for SSRI users.

  6. Selective Serotonin Reuptake Inhibitors and the Risk of Osseointegrated Implant Failure

    PubMed Central

    Wu, X.; Al-Abedalla, K.; Rastikerdar, E.; Abi Nader, S.; Daniel, N.G.; Nicolau, B.; Tamimi, F.

    2014-01-01

    Selective serotonin reuptake inhibitors (SSRIs), the most widely used drugs for the treatment of depression, have been reported to reduce bone formation and increase the risk of bone fracture. Since osseointegration is influenced by bone metabolism, this study aimed to investigate the association between SSRIs and the risk of failures in osseointegrated implants. This retrospective cohort study was conducted on patients treated with dental implants from January 2007 to January 2013. A total of 916 dental implants in 490 patients (94 implants on 51 patients using SSRIs) were used to estimate the risk of failure associated with the use of SSRIs. Data analysis involved Cox proportional hazards, generalized estimating equation models, multilevel mixed effects parametric survival analysis, and Kaplan-Meier analysis. After 3 to 67 mo of follow-up, 38 dental implants failed and 784 succeeded in the nonusers group, while 10 failed and 84 succeeded in the SSRI-users group. The main limitation of this retrospective study was that drug compliance dose and treatment period could not be acquired from the files of the patients. The primary outcome was that compared with nonusers of SSRIs, SSRI usage was associated with an increased risk of dental implants failure (hazard ratio, 6.28; 95% confidence interval, 1.25-31.61; p = .03). The failure rates were 4.6% for SSRI nonusers and 10.6% for SSRI users. The secondary outcomes were that small implant diameters (≤4 mm; p = .02) and smoking habits (p = .01) also seemed to be associated with higher risk of implant failure. Our findings indicate that treatment with SSRIs is associated with an increased failure risk of osseointegrated implants, which might suggest a careful surgical treatment planning for SSRI users. PMID:25186831

  7. Experimental study on the osseointegration of foam TiC/Ti composites.

    PubMed

    Jingyu, Wang; Lin, Wu; Yong, Gao; Jinsong, Zhang; Cuicui, Zhang

    2013-08-01

    Macroporous ceramics have demonstrated osteoconductive properties because of their biocompatibility and 3D macroporous structure, and these materials have recently been widely studied as bone replacement materials. The foam TiC/Ti composites discussed in this study have good mechanical properties, balancing out metallic toughness and ceramic strength. Furthermore, because of the high porosity and pore connectivity of these TiC/Ti composites, they have the potential to be a new bone replacement material. The purpose of this study was to evaluate the osseointegration of foam TiC/Ti composites, preliminarily discuss the TiC/Ti ossification mechanism, and to obtain reliable data on the use of foam TiC/Ti composites as bone replacement materials. The foam TiC/Ti composites were sited in 40 Japanese white rabbits for 4, 8, 12 and 24 weeks. The foam TiC/Ti composites were compared to foam SiC. M-CT (micro-computed tomography) analysis, histological analysis, SEM (scanning electron microscopy) observation and EDS (energy-dispersive x-ray spectrometer) analysis were conducted to estimate the osseointegration of the materials. The histological observations and quantitative analysis exhibited significantly more ossification area (volume), trabeculae maturity, and calcium and phosphorus content in the foam TiC/Ti composites compared to the foam SiC (p < 0.05). The results from this study suggest that the foam TiC/Ti composites possess good osseointegration capacity and have the potential to be a new bone replacement material.

  8. Enhanced Osseointegration of Hierarchical Micro/Nanotopographic Titanium Fabricated by Microarc Oxidation and Electrochemical Treatment.

    PubMed

    Li, Guanglong; Cao, Huiliang; Zhang, Wenjie; Ding, Xun; Yang, Guangzheng; Qiao, Yuqin; Liu, Xuanyong; Jiang, Xinquan

    2016-02-17

    Rapid osseointegration is recognized as a critical factor in determining the success rate of orthopedic and dental implants. Microarc oxidation (MAO) fabricated titanium oxide coatings with a porous topography have been proven to be a potent approach to enhance osteogenic capacity. Now we report two kinds of new hierarchical coatings with similar micromorphologies but different nanotopographies (i.e., MAO and MAO-AK coatings), and both coatings significantly promote cell attachment and osteogenic differentiation through mediating the integrin β1 signaling pathway. In this study, titanium with a unique hierarchical micro/nanomorphology surface was fabricated by a novel duplex coating process, that is, the first a titanium oxide layer was coated by MAO, and then the coating was electrochemically reduced in alkaline solution (MAO-AK). A series of in vitro stem cell differentiation and in vivo osseointegration experiments were carried out to evaluate the osteogenic capacity of the resulting coatings. In vitro, the initial adhesion of the canine bone marrow stem cells (BMSCs) seeded on the MAO and MAO-AK coatings was significantly enhanced, and cell proliferation was promoted. In addition, the expression levels of osteogenesis-related genes, osteorix, alkaline phosphates (ALP), osteopontin, and osteocalcin, in the canine BMSCs, were all up-regulated after incubation on these coatings, especially on the MAO-AK coating. Also, the in vitro ALP activity and mineralization capacity of canine BMSC cultured on the MAO-AK group was better than that on the MAO group. Furthermore, 6 weeks after insertion of the titanium implants into canine femurs, both the bone formation speed and the bone-implant contact ratio of the MAO-AK group were significantly higher than those of the MAO group. All these results suggest that this duplex coating process is promising for engineering titanium surfaces to promote osseointegration for dental and orthopedic applications.

  9. Linear Accelerators

    NASA Astrophysics Data System (ADS)

    Sidorin, Anatoly

    2010-01-01

    In linear accelerators the particles are accelerated by either electrostatic fields or oscillating Radio Frequency (RF) fields. Accordingly the linear accelerators are divided in three large groups: electrostatic, induction and RF accelerators. Overview of the different types of accelerators is given. Stability of longitudinal and transverse motion in the RF linear accelerators is briefly discussed. The methods of beam focusing in linacs are described.

  10. Engineered antifouling microtopographies - effect of feature size, geometry, and roughness on settlement of zoospores of the green alga Ulva.

    PubMed

    Schumacher, James F; Carman, Michelle L; Estes, Thomas G; Feinberg, Adam W; Wilson, Leslie H; Callow, Maureen E; Callow, James A; Finlay, John A; Brennan, Anthony B

    2007-01-01

    The effect of feature size, geometry, and roughness on the settlement of zoospores of the ship fouling alga Ulva was evaluated using engineered microtopographies in polydimethylsiloxane elastomer. The topographies studied were designed at a feature spacing of 2 microm and all significantly reduced spore settlement compared to a smooth surface. An indirect correlation between spore settlement and a newly described engineered roughness index (ERI) was identified. ERI is a dimensionless ratio based on Wenzel's roughness factor, depressed surface fraction, and the degree of freedom of spore movement. Uniform surfaces of either 2 mum diameter circular pillars (ERI=5.0) or 2 microm wide ridges (ERI=6.1) reduced settlement by 36% and 31%, respectively. A novel multi-feature topography consisting of 2 mum diameter circular pillars and 10 microm equilateral triangles (ERI=8.7) reduced spore settlement by 58%. The largest reduction in spore settlement, 77%, was obtained with the Sharklet AF topography (ERI=9.5).

  11. Numerical analysis of ponding and surface runoff in flat areas due to microtopography

    NASA Astrophysics Data System (ADS)

    Appels, W. M.; Bogaart, P. W.; van der Zee, S. E. A. T. M.

    2009-04-01

    When the storage capacity of a soil has been depleted or the precipitation intensity of a rainstorm exceeds the infiltration capacity of a soil, water accumulates at the soil surface. The excess water fills small depressions, that may connect and eventually form a fast overland flow route to surrounding surface waters. We hypothesize that even in relatively flat areas such as the Netherlands, surface runoff forms a significant factor on the local water balance during a rainfall event. In particular if solute fluxes towards surface water are of concern (as in the EU Water Framework Directive), the relatively fast runoff pathway may be of major importance for surface water quality. Classic studies on depression storage and surface runoff focus on a small spatial scale (1-2 m2) with a microtopography in order of magnitude of centimeters. State-of-the-art modelling of surface runoff focuses on solving physical flow equations for this type of plots. When upscaling to field or basin studies depression storage and connectivity are often parameterized as a roughness parameter since solving the flow equations on a complex topography is computationally too intensive. When flow equations are solved in a model, the basins are monotonuously descending. When studying depression storage, pool formation, connectivity, and surface runoff on a field scale in flat areas, we have to account for complex topography (in orders of magnitude of decimeters) and hydrological processes in the subsoil. Since these demands cannot be met with current hydrological models, we developed a routine that explicitly deals with the filling, merging, and connecting of depressions in a field. The routine has a successive steady-state setup: in every timestep the excess water in each cell is routed to its ultimate sink, either in the field or in the surrounding surface water, under the assumption of instantaneous water transfer. When the capacity of a depression is exceeded, water is routed to a

  12. Microtopography and antifouling properties of the shell surface of the bivalve molluscs Mytilus galloprovincialis and Pinctada imbricata.

    PubMed

    Scardino, Andrew; De Nys, Rocky; Ison, Odette; O'Connor, Wayne; Steinberg, Peter

    2003-04-01

    Biofouling rapidly covers most submerged surfaces in the marine environment. However, some marine organisms remain clean despite strong fouling pressure. Potential physical inhibitors of fouling were investigated by comparing the thickness, cover, and microtopographic structure of the periostracum of two bivalve molluscs, the blue mussel, Mytilus galloprovincialis, and the pearl oyster, Pinctada imbricata. The cover and thickness of the periostracum were measured on four size classes of each species using histological and microscopic techniques. The periostracum of M. galloprovincialis was significantly thicker than that of P. imbricata and did not differ significantly between size classes. In contrast, the periostracum of P. imbricata decreased significantly with increasing size in both thickness and cover. The microtopography of the shell surface of both species was measured using atomic force microscopy (AFM) and scanning electron microscopy (SEM), which revealed a homogeneous ridged surface for M. galloprovincialis with a uniform distance of 1-2 microns between ridges with a mean depth of 1.5 microns. P. imbricata had a heterogeneous surface structure without a repeating structural pattern. To compare the potential antifouling properties of the shell surface the four size classes of both species were tested in fourteen-week field exposure trials. M. galloprovincialis was rarely fouled over the trial period with less than 10% of M. galloprovincialis shell across all size classes being fouled. In contrast, P. imbricata had significantly higher levels of fouling. Both the proportion of P. imbricata shells fouled and the density of fouling organisms were positively correlated with the age of the shell and the amount of intact periostracum. The relationship between the shell surface microtopography and the intensity of fouling is discussed.

  13. Osseointegration of Titanium Implants in Onlay of Cerament™, a New Ceramic Bone Substitute

    PubMed Central

    Truedsson, Anna; Wang, Jian-Sheng; Lindberg, Pia; Warfvinge, Gunnar

    2016-01-01

    The purpose was to investigate whether a new biphasic and injectable ceramic bone substitute Cerament™ that rapidly remodels to bone, may contribute to the retention of titanium implant screws during the healing period, and to analyze the pattern of bone formation around titanium implants.Titanium screws were implanted in rat tibiae and embedded with or without Cerament™ on the cortical surface. Torsional resistance was measured after 1 day, and after 6 and 12 weeks. Implant areas without bone substitute were analyzed histologically for comparison. The torsional resistance increased over time as the screws were osseointegrated. There was no difference in resistance between screws embedded in the bone substitute and control screws. The bone apposition was more pronounced on the proximal side of the screw than on the distal side. Cerament™ is capable of conducting bone growth from a cortical bone surface. The newly formed bone in this application does not significantly add to the osseointegrative strength of the implant screw, as measured by torque resistance, during the first 12 weeks. PMID:26751485

  14. Clodronate combined with a surfactant (Tween 20) does not improve osseointegration: a rabbit immunohistomorphometric study.

    PubMed

    Berardi, D; Raffaelli, L; Perfetti, G; Paolantonio, M; Trisi, P

    2009-01-01

    Biphosphonates are compounds that inhibit bone reabsorption mediated by osteoclasts or the progression of periodontal disease independent on the host response to pathogenic bacteria that colonize the tooth surface. The use of biphosphonates in oral implantology is still in the experimental stage. The aim of this study is to evaluate the efficacy of a non-aminobiphosphonate combined with a surfactant to increase the ability of the drug to link to the implant and bone surfaces in the development of osseointegration in rabbits. Smooth titanium implants were devised to be used on rabbit femurs. A topical administration of clodronate combined with the surfactant (Tween 20) at different concentrations was made on the implant surface and in the implant site to increase the bone and implant adhesiveness. Placebo was given to the control group. New Zealand rabbits were used and sacrificed by CO2 after 8 weeks from the implantations. A histologic and histomorphometric analysis was carried out. Results did not show significant difference between the tests and the placebo groups. Our data are different from other similar studies obtaining statistically significant differences. These differences could depend on the efficacy of the drug used and on the procedure of application of the drug on the implant. This study demonstrates poor efficacy of clodronate applied topically to the implant and implant site during surgery to increase the percentage of osseointegration in the implant. Further studies using different fixation techniques of the drug may be necessary to confirm the present data.

  15. Histological and three-dimensional evaluation of osseointegration to nanostructured calcium phosphate-coated implants.

    PubMed

    Jimbo, Ryo; Coelho, Paulo G; Vandeweghe, Stefan; Schwartz-Filho, Humberto Osvaldo; Hayashi, Mariko; Ono, Daisuke; Andersson, Martin; Wennerberg, Ann

    2011-12-01

    Nanostructures on implant surfaces have been shown to enhance osseointegration; however, commonly used evaluation techniques are probably not sufficiently sensitive to fully determine the effects of this process. This study aimed to observe the osseointegration properties of nanostructured calcium phosphate (CaP)-coated implants, by using a combination of three-dimensional imaging and conventional histology. Titanium implants were coated with stable CaP nanoparticles using an immersion technique followed by heat treatment. Uncoated implants were used as the control. After topographical and chemical characterizations, implants were inserted into the rabbit femur. After 2 and 4weeks, the samples were retrieved for micro-computed tomography and histomorphometric evaluation. Scanning electron microscopy evaluation indicated that the implant surface was modified at the nanoscale by CaP to obtain surface textured with rod-shaped structures. Relative to the control, the bone-to-implant contact for the CaP-coated implant was significantly higher at 4weeks after the implant surgery. Further, corresponding 3-D images showed active bone formation surrounding the implant. 3-D quantification and 2-D histology demonstrated statistical correlation; moreover, 3-D quantification indicated a statistical decrease in bone density in the non-coated control implant group between 2 and 4weeks after the surgery. The application of 3-D evaluation further clarified the temporal characteristics and biological reaction of implants in bone.

  16. Cell adhesion and in vivo osseointegration of sandblasted/acid etched/anodized dental implants.

    PubMed

    Kim, Mu-Hyon; Park, Kyeongsoon; Choi, Kyung-Hee; Kim, Soo-Hong; Kim, Se Eun; Jeong, Chang-Mo; Huh, Jung-Bo

    2015-05-06

    The authors describe a new type of titanium (Ti) implant as a Modi-anodized (ANO) Ti implant, the surface of which was treated by sandblasting, acid etching (SLA), and anodized techniques. The aim of the present study was to evaluate the adhesion of MG-63 cells to Modi-ANO surface treated Ti in vitro and to investigate its osseointegration characteristics in vivo. Four different types of Ti implants were examined, that is, machined Ti (control), SLA, anodized, and Modi-ANO Ti. In the cell adhesion study, Modi-ANO Ti showed higher initial MG-63 cell adhesion and induced greater filopodia growth than other groups. In vivo study in a beagle model revealed the bone-to-implant contact (BIC) of Modi-ANO Ti (74.20%±10.89%) was much greater than those of machined (33.58%±8.63%), SLA (58.47%±12.89), or ANO Ti (59.62%±18.30%). In conclusion, this study demonstrates that Modi-ANO Ti implants produced by sandblasting, acid etching, and anodizing improve cell adhesion and bone ongrowth as compared with machined, SLA, or ANO Ti implants. These findings suggest that the application of Modi-ANO surface treatment could improve the osseointegration of dental implant.

  17. Biological Strategies for Improved Osseointegration and Osteoinduction of Porous Metal Orthopedic Implants

    PubMed Central

    Riester, Scott M.; Bonin, Carolina A.; Kremers, Hilal Maradit; Dudakovic, Amel; Kakar, Sanjeev; Cohen, Robert C.; Westendorf, Jennifer J.

    2015-01-01

    The biological interface between an orthopedic implant and the surrounding host tissue may have a dramatic effect upon clinical outcome. Desired effects include bony ingrowth (osseointegration), stimulation of osteogenesis (osteoinduction), increased vascularization, and improved mechanical stability. Implant loosening, fibrous encapsulation, corrosion, infection, and inflammation, as well as physical mismatch may have deleterious clinical effects. This is particularly true of implants used in the reconstruction of load-bearing synovial joints such as the knee, hip, and the shoulder. The surfaces of orthopedic implants have evolved from solid-smooth to roughened-coarse and most recently, to porous in an effort to create a three-dimensional architecture for bone apposition and osseointegration. Total joint surgeries are increasingly performed in younger individuals with a longer life expectancy, and therefore, the postimplantation lifespan of devices must increase commensurately. This review discusses advancements in biomaterials science and cell-based therapies that may further improve orthopedic success rates. We focus on material and biological properties of orthopedic implants fabricated from porous metal and highlight some relevant developments in stem-cell research. We posit that the ideal primary and revision orthopedic load-bearing metal implants are highly porous and may be chemically modified to induce stem cell growth and osteogenic differentiation, while minimizing inflammation and infection. We conclude that integration of new biological, chemical, and mechanical methods is likely to yield more effective strategies to control and modify the implant–bone interface and thereby improve long-term clinical outcomes. PMID:25348836

  18. Improved osseointegration of long-term stored SLA implant by hydrothermal sterilization.

    PubMed

    Shi, Xingling; Xu, Lingli; Violin, Kalan Bastos; Lu, Sheng

    2016-01-01

    The sandblasted, large-grit and acid-etched (SLA) surface is easy to be contaminated during storage and its surface chemical state is usually changed by different sterilization methods. This causes an undesirable increase in surface hydrophobicity and results in osseointegration degradation. To overcome this problem, a low temperature hydrothermal (HT) sterilization method was proposed in this study. Briefly, 4 weeks-stored pure titanium SLA specimens were sterilized using a sealed glass bottle with pure water in an autoclave set at 121 °C for 20 min. Results showed that, stored SLA specimens were superhydrophobic before and after conventional autoclaving, whereas, HT sterilization decontaminated and endowed stored SLA surface with superhydrophilicity. Osteoblast spreading was greatly enhanced, ALP expression was upgraded and bone nodule formation was obviously promoted on HT sterilized specimens compared with autoclaved ones. More bone formation around HT sterilized specimens was observed and HT sterilization increased bonding strength of implant to bone by 95% and 127% after 2 and 4 weeks of healing, respectively. The simple, feasible HT sterilization restored osseointegration of SLA implant while diminishing recontamination as much as possible. Therefore, it is proposed as a standard sterilization method for implant practitioners and researches.

  19. MicroCT Analysis of Micro-Nano Titanium Implant Surface on the Osseointegration.

    PubMed

    Ban, Jaesam; Kang, Seongsoo; Kim, Jihyun; Lee, Kwangmin; Hyunpil, Lim; Vang, Mongsook; Yang, Hongso; Oh, Gyejeong; Kim, Hyunseung; Hwang, Gabwoon; Jung, Yongho; Lee, Kyungku; Park, Sangwon; Yunl, Kwidug

    2015-01-01

    This study was to investigate the effects of micro-nano titanium implant surface on the osseointegration. A total of 36 screw-shaped implants were used. The implant surfaces were classified into 3 groups (n = 12): machined surface (M group), nanosurface which is nanotube formation on the machined surface (MA group) and nano-micro surface which is nanotube formation on the RBM surface (RA group). Anodic oxidation was performed at a 20 V for 10 min with 1 M H3PO4 and 1.5 wt% HF solutions. The implants were installed on the humerus on 6 beagles. After 4 and 12 weeks, the morphometric analysis with micro CT (skyscan 1172, SKYSCAN, Antwerpen, Belgium) was done. The data were statistically analyzed with two-way ANOVA. Bone mineral density and bone volume were significantly increased depending on time. RA group showed the highest bone mineral density and bone volume at 4 weeks and 12 weeks significantly. It indicated that nano-micro titanium implant surface showed faster and more mature osseointegration.

  20. Evaluating the bending response of two osseointegrated transfemoral implant systems using 3D digital image correlation.

    PubMed

    Thompson, Melanie L; Backman, David; Branemark, Rickard; Mechefske, Chris K

    2011-05-01

    Osseointegrated transfemoral implants have been introduced as a prosthetic solution for above knee amputees. They have shown great promise, providing an alternative for individuals who could not be accommodated by conventional, socket-based prostheses; however, the occurrence of device failures is of concern. In an effort to improve the strength and longevity of the device, a new design has been proposed. This study investigates the mechanical behavior of the new taper-based assembly in comparison to the current hex-based connection for osseointegrated transfemoral implant systems. This was done to better understand the behavior of components under loading, in order to optimize the assembly specifications and improve the useful life of the system. Digital image correlation was used to measure surface strains on two assemblies during static loading in bending. This provided a means to measure deformation over the entire sample and identify critical locations as the assembly was subjected to a series of loading conditions. It provided a means to determine the effects of tightening specifications and connection geometry on the material response and mechanical behavior of the assemblies. Both osseoinegrated assemblies exhibited improved strength and mechanical performance when tightened to a level beyond the current specified tightening torque of 12 N m. This was shown by decreased strain concentration values and improved distribution of tensile strain. Increased tightening torque provides an improved connection between components regardless of design, leading to increased torque retention, decreased peak tensile strain values, and a more gradual, primarily compressive distribution of strains throughout the assembly.

  1. [Transcutaneous osseointegrated prosthesis (TOP) after limb amputation : Status quo and perspectives].

    PubMed

    Willy, Christian; Krettek, Christian

    2017-04-10

    The majority of transfemoral and transtibial amputees can be functionally fitted with conventional suspension sockets; however, due to socket problems using conventional stump care, 60% of the patients have limited function and even in younger patients approximately one sixth are unable to wear the prosthesis daily. After the introduction of transcutaneous osseointegrated prostheses (TOP) the inherent problems of socket-stump care can be avoided for these patients. Against this background this article reviews the recent clinical development of TOP in Sweden, Germany, the Netherlands, Australia and USA currently in nine centers. Unanimously, all groups show that TOP enables physiological weight bearing, improved range of motion in the proximal joint, as well as osseoperceptive sensory feedback and better control of the artificial limb. Likewise, there is agreement that as a rule that there is a clinically less relevant superficial contamination of the stoma. Furthermore, TOP is nowadays also used for transhumeral amputees and after thumb amputation and the development of the indications for this technique are increasing. Future aspects include novel treatment options using implanted intramedullary electrodes allowing permanent and unlimited bidirectional communication with the human body (osseointegrated human-machine gateway). This could possibly realize an innovative form of prosthesis control as well as the combination of TOP and targeted muscle reinnervation (TMR) surgery to create more advanced prosthesis systems for upper and lower extremity amputees.

  2. Effects of Osseointegration by Bone Morphogenetic Protein-2 on Titanium Implants In Vitro and In Vivo

    PubMed Central

    Teng, Fu-Yuan; Chen, Wen-Cheng; Wang, Yin-Lai; Hung, Chun-Cheng; Tseng, Chun-Chieh

    2016-01-01

    This study designed a biomimetic implant for reducing healing time and achieving early osseointegration to create an active surface. Bone morphogenetic protein-2 (BMP-2) is a strong regulator protein in osteogenic pathways. Due to hardly maintaining BMP-2 biological function and specificity, BMP-2 efficient delivery on implant surfaces is the main challenge for the clinic application. In this study, a novel method for synthesizing functionalized silane film for superior modification with BMP-2 on titanium surfaces is proposed. Three groups were compared with and without BMP-2 on modified titanium surfaces in vitro and in vivo: mechanical grinding; electrochemical modification through potentiostatic anodization (ECH); and sandblasting, alkali heating, and etching (SMART). Cell tests indicated that the ECH and SMART groups with BMP-2 markedly promoted D1 cell activity and differentiation compared with the groups without BMP-2. Moreover, the SMART group with a BMP-2 surface markedly promoted early alkaline phosphatase expression in the D1 cells compared with the other surface groups. Compared with these groups in vivo, SMART silaning with BMP-2 showed superior bone quality and created contact areas between implant and surrounding bones. The SMART group with BMP-2 could promote cell mineralization in vitro and osseointegration in vivo, indicating potential clinical use. PMID:26977141

  3. Effects of Calcium Phosphate Nanocrystals on Osseointegration of Titanium Implant in Irradiated Bone

    PubMed Central

    Li, Jun Yuan; Pow, Edmond Ho Nang; Kwong, Dora Lai Wan; Cheung, Lim Kwong

    2015-01-01

    Radiotherapy may compromise the integration of implant and cause implant loss. Implant surface modifications have the possibility of promoting cell attachment, cell growth, and bone formation which ultimately enhance the osseointegration process. The present study aimed to investigate the effects of calcium phosphate nanocrystals on implant osseointegration in irradiated bone. Sixteen rabbits were randomly assigned into control and nano-CaP groups, receiving implants with dual acid-etched surface or dual acid-etched surface discretely deposited of nanoscale calcium-phosphate crystals, respectively. The left leg of all the rabbits received 15 Gy radiation, followed by implants placement one week after. Four animals in each group were sacrificed after 4 and 12 weeks, respectively. Implant stability quotient (ISQ), ratio of bone volume to total volume (BV/TV), bone growth rate, and bone-to-implant contact (BIC) were evaluated. The nano-CaP group showed significantly higher ISQ (week 12, P = 0.031) and bone growth rate (week 6, P = 0.021; week 9, P = 0.001) than that in control group. No significant differences in BV/TV and BIC were found between two groups. Titanium implant surface modified with CaP nanocrystals provides a potential alternative to improve bone healing around implant in irradiated bone. PMID:25685809

  4. Polyetheretherketone/nano-fluorohydroxyapatite composite with antimicrobial activity and osseointegration properties.

    PubMed

    Wang, Lixin; He, Shu; Wu, Xiaomian; Liang, Shanshan; Mu, Zhonglin; Wei, Jie; Deng, Feng; Deng, Yi; Wei, Shicheng

    2014-08-01

    Lack of antibacterial activity and binding ability to natural bone tissue has significantly limited polyetheretherketone (PEEK) for many challenging dental implant applications. Here, we have developed a polyetheretherketone/nano-fluorohydroxyapatite (PEEK/nano-FHA) biocomposite with enhanced antibacterial activity and osseointegration through blending method. Smooth and rough surfaces of PEEK/nano-FHA biocomposites were also prepared. Our results showed that in vitro initial cell adhesion and proliferation on the nano-FHA reinforced PEEK composite were improved. In addition, higher alkaline phosphatase activity and cell mineralization were also detected in cells cultured on PEEK/nano-FHA biocomposites, especially for rough PEEK/nano-FHA surfaces. More importantly, the as-prepared PEEK/nano-FHA biocomposite could effectively prevent the proliferation and biofilm formation of bacterial. For in vivo test, the newly formed bone volume of PEEK/nano-FHA group was higher than that of bare PEEK group based on 3D microcomputed tomography and 2D histomorphometric analysis. These reports demonstrate that the developed PEEK/nano-FHA biocomposite has increased biocompatibility and antibacterial activity in vitro, and promoted osseointegration in vivo, which suggests that it holds potential to be applied as dental implant material in dental tissue engineering applications.

  5. Can Accelerators Accelerate Learning?

    NASA Astrophysics Data System (ADS)

    Santos, A. C. F.; Fonseca, P.; Coelho, L. F. S.

    2009-03-01

    The 'Young Talented' education program developed by the Brazilian State Funding Agency (FAPERJ) [1] makes it possible for high-schools students from public high schools to perform activities in scientific laboratories. In the Atomic and Molecular Physics Laboratory at Federal University of Rio de Janeiro (UFRJ), the students are confronted with modern research tools like the 1.7 MV ion accelerator. Being a user-friendly machine, the accelerator is easily manageable by the students, who can perform simple hands-on activities, stimulating interest in physics, and getting the students close to modern laboratory techniques.

  6. PARTICLE ACCELERATOR

    DOEpatents

    Teng, L.C.

    1960-01-19

    ABS>A combination of two accelerators, a cyclotron and a ring-shaped accelerator which has a portion disposed tangentially to the cyclotron, is described. Means are provided to transfer particles from the cyclotron to the ring accelerator including a magnetic deflector within the cyclotron, a magnetic shield between the ring accelerator and the cyclotron, and a magnetic inflector within the ring accelerator.

  7. Installing multifunctionality on titanium with RGD-decorated polyurethane-polyurea roxithromycin loaded nanoparticles: toward new osseointegrative therapies.

    PubMed

    Rocas, Pau; Hoyos-Nogués, Mireia; Rocas, Josep; Manero, José M; Gil, Javier; Albericio, Fernando; Mas-Moruno, Carlos

    2015-09-16

    A novel class of polyurethane-polyurea nanoparticles (PUUa NPs) to install multifunctionality on biomaterials is presented. Biofunctionalization of titanium with roxithromycin loaded RGD-decorated PUUa NPs results in an outstanding improvement of osteoblast adhesion and strong suppression of bacterial attachment. This strategy represents a powerful approach to enhance the osseointegration of implant materials.

  8. The effect of osteotomy dimension on osseointegration to resorbable media-treated implants: a study in the sheep.

    PubMed

    Galli, Silvia; Jimbo, Ryo; Tovar, Nick; Yoo, Daniel Y; Anchieta, Rodolfo B; Yamaguchi, Satoshi; Coelho, Paulo G

    2015-03-01

    The drilling technique and the surface characteristics are known to influence the healing times of oral implants. The influence of osteotomy dimension on osseointegration of microroughned implant surfaces treated with resorbable blasting media was tested in an in vivo model. Ninety-six implants (ø4.5 mm, 8 mm in length) with resorbable blasting media-treated surfaces were placed in the ileum of six sheep. The final osteotomy diameters were 4.6 mm (reamer), 4.1 mm (loose), 3.7 mm (medium), and 3.2 mm (tight). After three and six weeks of healing, the implants were biomechanically tested and histologically evaluated. Statistical analysis was performed using Page L trend test for ordered and paired sample and linear regression, with significance level at p < 0.05. An overall increase in all dependent variables was observed with the reduction of osteotomy diameter. In addition, all osseointegration scores increased over time. At three weeks, the retention was significantly higher for smaller osteotomies. The histological sections depicted intimate contact of bone with all the implant surfaces and osteoblast lines were visible in all sections. The resorbable blasting media microroughed surfaces achieved successful osseointegration for all the instrumentation procedures tested, with higher osseointegration scores for the high insertion torque group.

  9. Reconstruction of alveolar bone defect with autogenous bone particles and osseointegrated implants: Histologic analysis and 10 years monitoring

    PubMed Central

    de Carvalho, Paulo Sérgio Perri; de Carvalho, Mariliza Comar Astolphi; Ponzoni, Daniela

    2015-01-01

    Maintaining the volume of the alveolar process after extraction can be achieved by immediate implant placement and guided bone regeneration, with or without the use of biomaterials. The authors present a case report with a 10 years follow-up, rehabilitation using osseointegrated implants in the extraction area and maintenance of the volume of the alveolar process with autogenous cortical bone shavings. PMID:26389054

  10. Genome Wide assessment of Early Osseointegration in Implant-Adherent Cells

    NASA Astrophysics Data System (ADS)

    Thalji, Ghadeer N.

    Objectives: To determine the molecular processes involved in osseointegration. Materials and methods: A structured literature review concerning in vitro and in vivo molecular assessment of osseointegration was performed. A rat and a human model were then used to identify the early molecular processes involved in osseointegration associated with a micro roughened and nanosurface superimposed featured implants. In the rat model, 32 titanium implants with surface topographies exhibiting a micro roughened (AT-II) and nanosurface superimposed featured implants (AT-I) were placed in the tibiae of 8 rats and subsequently harvested at 2 and 4 days after placement. Whereas in the human model, four titanium mini-implants with either a moderately roughened surface (TiOblast) or super-imposed nanoscale topography (Osseospeed) were placed in edentulous sites of eleven systemically healthy subjects and subsequently removed after 3 and 7 days. Total RNA was isolated from cells adherent to retrieved implants. A whole genome microarray using the Affymetrix 1.1 ST Array platform was used to describe the gene expression profiles that were differentially regulated by the implant surfaces. Results: The literature review provided evidence that particular topographic cues can be specifically integrated among the many extracellular signals received by the cell in its signal transduction network. In the rat model, functionally relevant categories related to ossification, skeletal system development, osteoblast differentiation, bone development and biomineral tissue development were upregulated and more prominent at AT-I compared to AT-II. In the human model, there were no significant differences when comparing the two-implant surfaces at each time point. However, the microarray identified several genes that were differentially regulated at day 7 vs. day 3 for both implant surfaces. Functionally relevant categories related to the extracellular matrix, collagen fibril organization and

  11. Influence of diamond wheel grinding process on surface micro-topography and properties of SiO2/SiO2 composite

    NASA Astrophysics Data System (ADS)

    Cao, Xiaoyan; Lin, Bin; Wang, Yan; Wang, Shaolei

    2014-02-01

    According to anisotropic and inhomogeneous structure of fiber-reinforced ceramic matrix composites (FRCMC), it is difficult to control the surface quality with the traditional method used in metal material. The present paper studies the influence of diamond wheel grinding process on surface micro-topography and properties of SiO2/SiO2 composite. The research is based on some new discovery that the material enhanced fiber orientations play a key role in micro-topography of FRCMC grinding surface. Through a series of experiments, we investigate the relationship between grinding process and the quality of composites surface. We also analyze characteristics of the material surface topography height, wave distribution and surface support properties in details. This paper employs the orthogonal design to optimize grinding process parameters and also successfully models a critical condition to modify the surface characteristics. The results show that speed of grinding wheel has the greatest influence on height and surface support properties, the next is grain mesh size and depth of cut. The grain mesh size is the key factor for surface micro-topography modification. Compared to the surface with woven texture, the modified surface has better symmetrical characteristic. The research obtained will be an important technical support on improving the processing quality of FRCMC.

  12. Osseointegration of multiphase anodic spark deposition treated porous titanium implants in an ovine model.

    PubMed

    Bertollo, Nicky; Sandrini, Enrico; Dalla Pria, Paolo; Walsh, William R

    2015-03-01

    Modification of titanium oxide by multiphase anodic spark deposition (ASD) has the potential to increase bioactivity and hasten osseointegration and biological fixation in uncemented arthroplasty. This study assessed the in vivo performance of control (Ti), plasma-sprayed HA-coated (TiHA) and ASD (Biospark) treated (TiAn) porous titanium implants with a solid core using a standard uncemented implant fixation sheep model. Cortical interfacial shear-strength and bone ingrowth in cortical and cancellous sites were quantified following 12 weeks in situ. Ultimate shear-strength for the Ti, TiHA and TiAn coatings was 33±9.5, 35.4±8.4 and 33.8±7.8 MPa, respectively, which was limited by coating delamination. ASD treatment was associated with significantly higher mean bone ingrowth at both sites. These results support the osteoconductive potential of the BioSpark treatment of porous titanium.

  13. Demographical, odontological, and psychological variables in individuals referred for osseointegrated dental implants.

    PubMed

    Hogenius, S; Berggren, U; Blomberg, S; Jemt, T; Ohman, S C

    1992-08-01

    Edentulism and/or the wearing of a removable denture always requires adaptation, not only on a functional, but also on an emotional, level. Four hundred and seventy-three patients referred for treatment with osseointegrated implants due to problems with removable prostheses entered the study and 315 (66.6%) completed it. The average age was close to 60 yr, and the majority of patients were women. The average time of edentulousness was 14.3 yr. Twelve percent experienced profound negative effects from wearing dentures, this to an extent that it led to overt psychological and social effects. Subjective ratings revealed that functional and/or intra-personal effects were of higher significance than social consequences. The group was found to be more depressed than average as well as having an external health locus of control orientation.

  14. Reconstruction of a complex midfacial defect with the folded fibular free flap and osseointegrated implants.

    PubMed

    Anthony, J P; Foster, R D; Sharma, A B; Kearns, G J; Hoffman, W Y; Pogrel, M A

    1996-08-01

    Refinements in microsurgical techniques, plate fixation, and osseointegration have changed the conceptual approach to midface reconstruction. Free tissue transfer has emerged as the ideal method of reconstructing complex midfacial defects. Single-stage bony restoration of the palate and orbital rim using the folded fibular osteocutaneous free flap is described. The fibular free flap is our first choice for reconstructing complex midfacial defects. The thin, soft, pliable tissue is ideal for intraoral and palatal reconstructions. The bone can be tailored precisely to fit any desired shape, and forms a sturdy support for both orbital and dental prostheses. With a single flap, rapid and reliable restoration of midfacial appearance, orbital support, and palatal function can be achieved.

  15. Single-stage osseointegrated implants for nasal prosthodontic rehabilitation: A clinical report.

    PubMed

    de Carvalho, Bruna M D F; Freitas-Pontes, Karina M; de Negreiros, Wagner A; Verde, Marcus A R L

    2015-08-01

    Malignant tumors in the nasal region may be treated by means of invasive surgical procedures, with large facial losses. Nasal prostheses, retained by osseointegrated facial implants, instead of plastic surgery, will, in most patients, offer good biomechanical and cosmetic results. This clinical report describes the prosthetic rehabilitation of a patient with nasal cancer who had the entire nasal vestibule removed in a single-stage surgical procedure in order to shorten the rehabilitation time. The nasal prosthesis was built on a 3-magnet bar and was made of platinum silicone with intrinsic pigmentation, thereby restoring the patient's appearance and self-esteem. The authors concluded that single-stage implants may reduce the rehabilitation time to as little as 1 month, and the correct use of materials and techniques may significantly improve the nasal prosthesis.

  16. Bioactivity and Osseointegration of PEEK Are Inferior to Those of Titanium: A Systematic Review.

    PubMed

    Najeeb, Shariq; Bds, Zohaib Khurshid; Bds, Sana Zohaib; Bds, Muhammad Sohail Zafar

    2016-12-01

    Polyetheretherketone (PEEK) has been suggested as an alternative to replace titanium as a dental implant material. However, PEEK's bioactivity and osseointegration are debatable. This review has systematically analyzed studies that have compared PEEK (or PEEK-based) implants with titanium implants so that its feasibility as a possible replacement for titanium can be determined. The focused question was: "Are the bioactivity and osseointegration of PEEK implants comparable to or better than titanium implants?" Using the key words "dental implant," "implant," "polyetheretherketone," "PEEK," and "titanium" in various combinations, the following databases were searched electronically: PubMED/MEDLINE, Embase, Google Scholar, ISI Web of Knowledge, and Cochrane Database. 5 in vitro and 4 animal studies were included in the review. In 4 out of 5 in vitro studies, titanium exhibited more cellular proliferation, angiogenesis, osteoblast maturation, and osteogenesis compared to PEEK; one in vitro study observed comparable outcomes regardless of the implant material. In all animal studies, uncoated and coated titanium exhibited a more osteogenic behavior than did uncoated PEEK, while comparable bone-implant contact was observed in HA-coated PEEK and coated titanium implants. Unmodified PEEK is less osseoconductive and bioactive than titanium. Furthermore, the majority of studies had multiple sources of bias; hence, in its unmodified form, PEEK is unsuitable to be used as dental implant. Significantly more research and long-term trials must focus on improving the bioactivity of PEEK before it can be used as dental implant. More comparative animal and clinical studies are warranted to ascertain the potential of PEEK as a viable alternative to titanium.

  17. Clinical Outcomes of Osseointegrated Prosthetic Auricular Reconstruction in Patients With a Compromised Ipsilateral Temporoparietal Fascial Flap.

    PubMed

    Zuo, Kevin J; Wilkes, Gordon H

    2016-01-01

    Patients with major ear deformities and associated compromise of the superficial temporal artery are poor candidates for autogenous ear reconstruction because of a tenuous ipsilateral temporoparietal fascial flap (TPFF). Osseointegrated prosthetic auricular reconstruction (OPAR) is an alternative to contralateral free TPFF microsurgical and autogenous reconstruction, but data on clinical outcomes are limited. The records of patients with ear loss or major deformity and a compromised ipsilateral TPFF who underwent OPAR from 1989 to 2013 were reviewed. Satisfaction was assessed using a questionnaire based on a 5 point Likert scale. Thirty-two patients (8 women, 24 men) with mean age 43.0 years (range, 10-70 years) underwent OPAR. The ipsilateral TPFF was compromised due to major trauma (13 patients), cancer extirpation (9), burn injury (4), previous harvest (4), arteriovenous malformation (1), or infection (1). All but 2 patients had an associated craniofacial defect, such as soft tissue deformity (87.5%), hearing loss (46.9%), or bony deformity (31.3%). The overall implant success rate was 88.6% at mean follow-up time of 7.6 years post-OPAR. Prosthesis wear averaged 12.2 hours/day and 6.6 days/week (80.5 hours/week). All 5 patients who experienced implant failures had received prior head and neck irradiation. With their prosthesis, 76.2% (16 patients) stated that their self-consciousness and self-esteem were "better" or "much better," whereas 85.7% (18 patients) stated that their self-image was "better" or "much better." All patients declared that they would undergo the treatment again. Osseointegrated prosthetic auricular reconstruction is a reliable option in this challenging population with high patient satisfaction. Patients with prior radiotherapy may have a higher chance of implant failure and would benefit from extended annual follow-up.

  18. Influence of pores created by laser superfinishing on osseointegration of titanium alloy implants.

    PubMed

    Stangl, R; Pries, A; Loos, B; Müller, M; Erben, R G

    2004-06-01

    The aim of this study was to assess the osseointegration of copper vapor laser-superfinished titanium alloy (Ti6Al4V) implants with pore sizes of 25, 50, and 200 microm in a rabbit intramedullary model. Control implants were prepared by corundum blasting. Each animal received all four different implants in both femora and humeri. Using static and dynamic histomorphometry, the bone-implant interface and the peri-implant bone tissue were examined 3, 6, and 12 weeks postimplantation. Among the laser-superfinished implants, total bone-implant contact was smallest for the 25-microm pores, and was similar for 50- and 200-microm pore sizes at all time points. However, all laser-superfinished surfaces were inferior to corundum-blasted (CB) control implants in terms of bone-implant contact. Within the 12-week study period, remodeling of woven bone initially formed within pores occurred only in the implants with 200-microm pores. Implants with 25-microm pores showed the highest amount of peri-implant bone volume at all time points, indicating that the amount of peri-implant bone was not correlated with the quality of the bone-implant interface. At 3 and 6 weeks postsurgery, we did not find any differences in mineral apposition rates or bone formation rates between the various implant surfaces. However, the peri-implant bone formation rate at the end of the trial was 70 and 62% higher in implants with 50- and 200-microm pores compared with CB implants, respectively. We conclude that, although laser-superfinished implants were not superior to CB control implants in terms of osseointegration, our study has provided further insights into the mechanisms of bone remodeling within pores of various sizes, and may form a basis for future experiments to design optimal implant surfaces with the help of modern laser technology.

  19. Osseointegration improvement by plasma electrolytic oxidation of modified titanium alloys surfaces.

    PubMed

    Echeverry-Rendón, Mónica; Galvis, Oscar; Quintero Giraldo, David; Pavón, Juan; López-Lacomba, José Luis; Jiménez-Piqué, Emilio; Anglada, Marc; Robledo, Sara M; Castaño, Juan G; Echeverría, Félix

    2015-02-01

    Titanium (Ti) is a material frequently used in orthopedic applications, due to its good mechanical properties and high corrosion resistance. However, formation of a non-adherent fibrous tissue between material and bone drastically could affect the osseointegration process and, therefore, the mechanical stability of the implant. Modifications of topography and configuration of the tissue/material interface is one of the mechanisms to improve that process by manipulating parameters such as morphology and roughness. There are different techniques that can be used to modify the titanium surface; plasma electrolytic oxidation (PEO) is one of those alternatives, which consists of obtaining porous anodic coatings by controlling parameters such as voltage, current, anodizing solution and time of the reaction. From all of the above factors, and based on previous studies that demonstrated that bone cells sense substrates features to grow new tissue, in this work commercially pure Ti (c.p Ti) and Ti6Al4V alloy samples were modified at their surface by PEO in different anodizing solutions composed of H2SO4 and H3PO4 mixtures. Treated surfaces were characterized and used as platforms to grow osteoblasts; subsequently, cell behavior parameters like adhesion, proliferation and differentiation were also studied. Although the results showed no significant differences in proliferation, differentiation and cell biological activity, overall results showed an important influence of topography of the modified surfaces compared with polished untreated surfaces. Finally, this study offers an alternative protocol to modify surfaces of Ti and their alloys in a controlled and reproducible way in which biocompatibility of the material is not compromised and osseointegration would be improved.

  20. Osseointegration of Dental Implants in a Patient with Hajdu-cheney Syndrome

    PubMed Central

    Dokou, Panagiota; Karoussis, Ioannis K.; Papavasiliou, George; Kamposiora, Phophi; Vrahopoulos, Theophilos P.; Vrotsos, John A.

    2016-01-01

    Background: Hajdu-Cheney Syndrome (HCS) is a rare hereditary bone metabolism disorder characterized by acro-osteolysis, short stature, craniofacial changes, periodontitis and premature tooth loss. Extensive search of the current literature revealed no reports of implant placement in patients with HCS. Case Report: A 22-year old woman with osteoporosis, generalized advanced chronic periodontitis and premature tooth loss was referred to the Postgraduate Clinic of Periodontology, University of Athens-Greece. The patient was diagnosed in 2001 with HCS. The patient received non-surgical periodontal treatment and several teeth were extracted due to extensive alveolar bone loss. After careful consideration of the possible implications deriving from the patient’s condition and having taken her young age into account, initially, a dental implant was placed in the upper right first premolar region. Specific protocols such as longer healing periods were implemented, so five years after placement and successful osseointegration of this implant, four additional dental implants were placed in the posterior regions of the maxilla and the mandible. Prosthetic rehabilitation followed 6 months after implant placement. Upon completion of periodontal treatment, the patient was enrolled in a periodontal maintenance program. Results: Clinical and radiographic examination of the patient during the periodontal maintenance program after implant placement revealed no abnormalities in the implant region. Conclusion: Patients with HCS suffer from periodontitis, bone destruction and premature tooth loss. This case indicates the successful osseointegration of dental implants in patients with HCS. However, further research is required in order to determine the predictability of dental implant placement in those patients. PMID:27857819

  1. A three-dimensional finite element analysis of the osseointegration progression in the human mandible

    NASA Astrophysics Data System (ADS)

    Esmail, Enas; Hassan, Noha; Kadah, Yasser

    2010-02-01

    In this study, three-dimensional (3D) finite element analysis was used to model the effect of the peri-implant bone geometry and thickness on the biomechanical behavior of a dental implant/supporting bone system. The 3D finite element model of the jaw bone, cancellous and cortical, was developed based on computerized tomography (CT) scan technology while the dental implant model was created based on a commercially available implant design. Two models, cylindrical and threaded, representing the peri-implant bone region were simulated. In addition, various thicknesses (0.1 mm, 0.3 mm, 0.5 mm) of the peri-implant bone region were modeled to account for the misalingnment during the drilling process. Different biomechanical properties of the peri-implant bone region were used to simulate the progression of the osseointegration process with time. Four stages of osseointegration were modeled to mimic different phases of tissue healing of the peri- implant region starting with soft connective tissue and ending with complete bone maturation. For the realistic threaded model of the peri-implant bone region, the maximum von Mises stress and displacement in the dental implant and jaw bone were higher than those computed for the simple cylindrical peri-implant bone region model. The average von Mises stress and displacement in the dental implant and the jaw bone decreased as the oseeointegration progressed with time for all thicknesses of the peri-implant bone region. On the other hand, the maximum absolute vertical displacement of the dental implant increased as the drilled thickness of the peri-implant bone region increased.

  2. Bone cutting capacity and osseointegration of surface-treated orthodontic mini-implants

    PubMed Central

    Kim, Ho-Young

    2016-01-01

    Objective The objective of the study was to evaluate the practicality and the validity of different surface treatments of self-drilling orthodontic mini-implants (OMIs) by comparing bone cutting capacity and osseointegration. Methods Self-drilling OMIs were surface-treated in three ways: Acid etched (Etched), resorbable blasting media (RBM), partially resorbabla balsting media (Hybrid). We compared the bone cutting capacity by measuring insertion depths into artificial bone (polyurethane foam). To compare osseointegration, OMIs were placed in the tibia of 25 rabbits and the removal torque value was measured at 1, 2, 4, and 8 weeks after placement. The specimens were analyzed by optical microscopy, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). Results The bone cutting capacity of the etched and hybrid group was lower than the machined (control) group, and was most inhibited in the RBM group (p < 0.05). At 4 weeks, the removal torque in the machined group was significantly decreased (p < 0.05), but was increased in the etched group (p < 0.05). In the hybrid group, the removal torque significantly increased at 2 weeks, and was the highest among all measured values at 8 weeks (p < 0.05). The infiltration of bone-like tissue surface was evaluated by SEM, and calcium and phosphorus were detected via EDS only in the hybrid group. Conclusions Partial RBM surface treatment (hybrid type in this study) produced the most stable self-drilling OMIs, without a corresponding reduction in bone cutting capacity. PMID:27896213

  3. Immobilized nerve growth factor and microtopography have distinct effects on polarization versus axon elongation in hippocampal cells in culture.

    PubMed

    Gomez, Natalia; Lu, Yi; Chen, Shaochen; Schmidt, Christine E

    2007-01-01

    Cell interfacing with biomaterial surfaces dictates important aspects of cell behavior. In particular, axon extension in neurons is effectively influenced by surface properties, both for the initial formation of an axon as well as for the maintenance of axon growth. Here, we investigated how neurons behaved on poly(dimethyl siloxane) (PDMS) surfaces decorated with biochemical and physical cues presented individually or in combination. In particular, nerve growth factor (NGF) was covalently tethered to PDMS to create a bioactive surface, and microtopography was introduced to the material in the form of microchannels. Embryonic hippocampal neurons were used to investigate the impact of these surface cues on polarization (i.e., axon initiation or axogenesis) and overall axon length. We found that topography had a more pronounced effect on polarization (68% increase over controls) compared to immobilized NGF (0.1 ng/mm(2)) (27% increase). However, the effect of NGF was negligible when both types of stimuli were simultaneously presented on the biomaterial surface. In addition to axon formation, chemical and physical cues are also involved in axon growth following the initiation process. Interestingly, for the same studies described above, the effects of microchannels and NGF were opposite from the effects on polarization; the most evident effect was for the immobilized growth factor (10% increase in axon length with respect to controls) whereas there was no effect in general for the microtopography. More importantly, when the two surface stimuli were presented in combination, a synergistic increase in axon length was detected (25% increase with respect to controls), which could be a result of faster polarization triggered by topography plus enhanced growth from NGF. Additionally, axon orientation was also analyzed and we found the well-known tendency of perpendicular or parallel axonal alignment to be dependent on the width and depth of the channels. This investigation

  4. Analysis of the microtopography of the skin by silicone replicas after repeated exposure to actinic radiation at high altitudes.

    PubMed

    Mazzarello, V; Cametti, M; Leone, G; Iacovelli, P; Ena, P; Leigheb, G

    2001-05-01

    We investigated the superficial microtopography of the normal skin of 11 volunteers (not exposed to sunlight during the last 4 months), before and after sun exposure for 5 days at high altitudes of 2900-4559 m. The experiments were carried out on Mount Rosa in Italy, and cutaneous replicas using silicone resin were taken every day after 7 h of sun exposure. Casts were taken from the forehead, glabella, dorsum nasi, radial side (protected with a cream SPF 9.72) and ulnar side of the back of the hands, the only areas not protected. A total of 422 replicas were metallized with gold-palladium and observed under Zeiss 940A scanning electron microscope. The images were elaborated and analysed on computer with appropriate software supplying geometrical features of cutaneous surface using parameters proposed by Takahashi (1994). A Student's test for paired series was used to analyse the differences before and after 1-5 days of exposure giving uniform and significant data compared with controls. Using cutaneous replicas we demonstrated that repeated exposure of skin to sunlight in a short time elicits temporary defence mechanisms with increased obstruction of cutaneous pores, deepening of primary cutaneous furrows and shallowing of part of the secondary furrows; the two latter alterations are the consequence of reactive oedema.

  5. The effect of substrate microtopography on focal adhesion maturation and actin organization via the RhoA/ROCK pathway.

    PubMed

    Seo, Chang Ho; Furukawa, Katsuko; Montagne, Kevin; Jeong, Heonuk; Ushida, Takashi

    2011-12-01

    Recently, a growing number of reports have reported that micro- or nanoscale topography enhances cellular functions such as cell adhesion and stem cell differentiation, but the mechanisms responsible for this topography-mediated cell behavior are not fully understood. In this study, we examine the underlying processes and mechanisms behind specific topography-mediated cellular functions. Formation of focal adhesions (FA) was studied by culturing cells on different kinds of topographies, including a flat surface and surfaces with a micropatterned topography (2 μm lattice pattern with 3 μm intervals). We found that the formation and maturation of focal adhesions were highly dependent on the topography of the substrate although the shape, morphology and spreading of cells on the different substrates were not significantly affected. Focal adhesion maturation and actin polymerization were also promoted in cells cultured on the micropatterned substrate. These differences in cell adhesion led us to focus on the Rho GTPases, RhoA and downstream pathways since a number of reports have demonstrated that RhoA-activated cells have highly enhanced focal adhesions and actin activation such as polymerization. By inhibiting the Rho-associated kinase (ROCK) and downstream myosin II, we found that the FA formation, actin organization, and FAK phosphorylation were dramatically decreased. The topographical dependency of FA formation was also highly decreased. These results show that the FA formation and actin cytoskeleton organization of cells on the microtopography is regulated by the RhoA/ROCK pathway.

  6. Simulation of Runoff Hydrograph on Soil Surfaces with Different Microtopography Using a Travel Time Method at the Plot Scale.

    PubMed

    Zhao, Longshan; Wu, Faqi

    2015-01-01

    In this study, a simple travel time-based runoff model was proposed to simulate a runoff hydrograph on soil surfaces with different microtopographies. Three main parameters, i.e., rainfall intensity (I), mean flow velocity (vm) and ponding time of depression (tp), were inputted into this model. The soil surface was divided into numerous grid cells, and the flow length of each grid cell (li) was then calculated from a digital elevation model (DEM). The flow velocity in each grid cell (vi) was derived from the upstream flow accumulation area using vm. The total flow travel time through each grid cell to the surface outlet was the sum of the sum of flow travel times along the flow path (i.e., the sum of li/vi) and tp. The runoff rate at the slope outlet for each respective travel time was estimated by finding the sum of the rain rate from all contributing cells for all time intervals. The results show positive agreement between the measured and predicted runoff hydrographs.

  7. Conversion of traditional osseointegrated bone-anchored hearing aids to the Baha(®) attract in four pediatric patients.

    PubMed

    Cedars, Elizabeth; Chan, Dylan; Lao, Anga; Hardies, Lauren; Meyer, Anna; Rosbe, Kristina

    2016-12-01

    Bone-anchored hearing aids are external devices attached to the skull via a titanium implant, and can be used for multiple types of hearing loss. Traditionally, osseointegrated implants have been coupled to the external processor with a percutaneous abutment, but more recently, a fully implanted, transcutaneous magnet-based system has become available. Skin reactions from the percutaneous portion are a common complication that can prevent use of the device during critical windows of language development and learning in children. We describe our experience replacing the Baha(®) abutment system with the Baha(®) Attract in four pediatric patients. Specific operative considerations for incision placement, and magnet and implant coverage are discussed. All patients maintained osseointegration, had excellent long-term wound healing without post-operative infection, and were able to wear their devices more consistently.

  8. Osseointegration of dental implants and osteonecrosis of the jaw in patients treated with bisphosphonate therapy: A systematic review.

    PubMed

    Chadha, Gurpreet K; Ahmadieh, Azadeh; Kumar, Satish K S; Sedghizadeh, Parish P

    2012-04-16

    Abstract Bisphosphonate (BP) drugs are a commonly prescribed group of medications used in the treatment of metabolic and oncologic bone pathoses. The aim of this study was to conduct a systematic review in order to evaluate whether patients on BP therapy are appropriate candidates for dental implants as compared to patients not taking BP with respect to successful implant osseointegration and the risk of developing bisphosphonate-related osteonecrosis of the jaw (BRONJ). Based on the current literature, a history of oral or intravenous BP use is not an absolute contraindication for dental implant placement, and dental implants can osseointegrate successfully in this patient population. Importantly, the studies currently available on this topic are of moderate to weak strength of evidence with inherent bias and limitations and hence results must be interpreted in this context. Well-controlled studies with higher strength of evidence and larger population sizes are required to more accurately address this topic in the future.

  9. Osseointegration of dental implants and osteonecrosis of the jaw in patients treated with bisphosphonate therapy: a systematic review.

    PubMed

    Chadha, Gurpreet K; Ahmadieh, Azadeh; Kumar, Satish; Sedghizadeh, Parish P

    2013-08-01

    Bisphosphonate (BP) drugs are a commonly prescribed group of medications used in the treatment of metabolic and oncologic bone disorders. The aim of this study was to conduct a systematic review in order to evaluate whether patients on BP therapy are appropriate candidates for dental implants as compared to patients not taking BP drugs with respect to successful implant osseointegration and the risk of developing bisphosphonate-related osteonecrosis of the jaw. Based on the current literature, a history of oral or intravenous BP use is not an absolute contraindication for dental implant placement, and dental implants can osseointegrate successfully in this patient population. Importantly, the studies currently available on this topic are of moderate to weak strength of evidence with inherent bias and limitations, and hence results must be interpreted in this context. Well-controlled studies with higher strength of evidence and larger population sizes are required to address this topic more accurately in the future.

  10. Future accelerators (?)

    SciTech Connect

    John Womersley

    2003-08-21

    I describe the future accelerator facilities that are currently foreseen for electroweak scale physics, neutrino physics, and nuclear structure. I will explore the physics justification for these machines, and suggest how the case for future accelerators can be made.

  11. A novel osseointegrated percutaneous prosthetic system for the treatment of patients with transfemoral amputation: A prospective study of 51 patients.

    PubMed

    Brånemark, R; Berlin, O; Hagberg, K; Bergh, P; Gunterberg, B; Rydevik, B

    2014-01-01

    Patients with transfemoral amputation (TFA) often experience problems related to the use of socket-suspended prostheses. The clinical development of osseointegrated percutaneous prostheses for patients with a TFA started in 1990, based on the long-term successful results of osseointegrated dental implants. Between 1999 and 2007, 51 patients with 55 TFAs were consecutively enrolled in a prospective, single-centre non-randomised study and followed for two years. The indication for amputation was trauma in 33 patients (65%) and tumour in 12 (24%). A two-stage surgical procedure was used to introduce a percutaneous implant to which an external amputation prosthesis was attached. The assessment of outcome included the use of two self-report questionnaires, the Questionnaire for Persons with a Transfemoral Amputation (Q-TFA) and the Short-Form (SF)-36. The cumulative survival at two years' follow-up was 92%. The Q-TFA showed improved prosthetic use, mobility, global situation and fewer problems (all p < 0.001). The physical function SF-36 scores were also improved (p < 0.001). Superficial infection was the most frequent complication, occurring 41 times in 28 patients (rate of infection 54.9%). Most were treated effectively with oral antibiotics. The implant was removed in four patients because of loosening (three aseptic, one infection). Osseointegrated percutaneous implants constitute a novel form of treatment for patients with TFA. The high cumulative survival rate at two years (92%) combined with enhanced prosthetic use and mobility, fewer problems and improved quality of life, supports the 'revolutionary change' that patients with TFA have reported following treatment with osseointegrated percutaneous prostheses.

  12. A Reductionist Approach to Extract Robust Molecular Markers from Microarray Data Series -Isolating Markers to Track Osseointegration.

    PubMed

    Barik, Anwesha; Banerjee, Satarupa; Dhara, Santanu; Chakravorty, Nishant

    2017-03-10

    Complexities in the full genome expression studies hinder the extraction of tracker genes to analyze the course of biological events. In this study, we demonstrate the applications of supervised machine learning methods to reduce the irrelevance in microarray data series and thereby extract robust molecular markers to track biological processes. The methodology has been illustrated by analyzing whole genome expression studies on bone-implant integration (ossointegration). Being a biological process, osseointegration is known to leave a trail of genetic footprint during the course. In spite of existence of enormous amount of raw data in public repositories, researchers still do not have access to a panel of genes that can definitively track osseointegrtion. The results from our study revealed panels comprising of matrix metalloproteinases and collagen genes were able to track osseointegration on implant surfaces (MMP9 and COL1A2 on micro-textured; MMP12 and COL6A3 on superimposed nano-textured surfaces) 100% classification accuracy, specificity and sensitivity. Further, our analysis showed the importance of the progression of the duration in establishment of the mechanical connection at bone-implant surface. The findings from this study are expected to be useful to researchers investigating osseointegration of novel implant materials especially at the early stage. The methodology demonstrated can be easily adapted by scientists in different fields to analyze large databases for other biological processes.

  13. Effects of a micro/nano rough strontium-loaded surface on osseointegration.

    PubMed

    Li, Yongfeng; Qi, Yaping; Gao, Qi; Niu, Qiang; Shen, Mingming; Fu, Qian; Hu, Kaijin; Kong, Liang

    2015-01-01

    We developed a hierarchical hybrid micro/nanorough strontium-loaded Ti (MNT-Sr) surface fabricated through hydrofluoric acid etching followed by magnetron sputtering and evaluated the effects of this surface on osseointegration. Samples with a smooth Ti (ST) surface, micro Ti (MT) surface treated with hydrofluoric acid etching, and strontium-loaded nano Ti (NT-Sr) surface treated with SrTiO3 target deposited via magnetron sputtering technique were investigated in parallel for comparison. The results showed that MNT-Sr surfaces were prepared successfully and with high interface bonding strength. Moreover, slow Sr release could be detected when the MNT-Sr and NT-Sr samples were immersed in phosphate-buffered saline. In in vitro experiments, the MNT-Sr surface significantly improved the proliferation and differentiation of osteoblasts compared with the other three groups. Twelve weeks after the four different surface implants were inserted into the distal femurs of 40 rats, the bone-implant contact in the ST, MT, NT-Sr, and MNT-Sr groups were 39.70%±6.00%, 57.60%±7.79%, 46.10%±5.51%, and 70.38%±8.61%, respectively. In terms of the mineral apposition ratio, the MNT-Sr group increased by 129%, 58%, and 25% compared with the values of the ST, MT, and NT-Sr groups, respectively. Moreover, the maximal pullout force in the MNT-Sr group was 1.12-, 0.31-, and 0.69-fold higher than the values of the ST, MT, and NT-Sr groups, respectively. These results suggested that the MNT-Sr surface has a synergistic effect of hierarchical micro/nano-topography and strontium for enhanced osseointegration, and it may be a promising option for clinical use. Compared with the MT surface, the NT-Sr surface significantly improved the differentiation of osteoblasts in vitro. In the in vivo animal experiment, the MT surface significantly enhanced the bone-implant contact and maximal pullout force than the NT-Sr surface.

  14. New cosurface capacitive stimulators for the development of active osseointegrative implantable devices

    NASA Astrophysics Data System (ADS)

    Soares Dos Santos, Marco P.; Marote, Ana; Santos, T.; Torrão, João; Ramos, A.; Simões, José A. O.; da Cruz E Silva, Odete A. B.; Furlani, Edward P.; Vieira, Sandra I.; Ferreira, Jorge A. F.

    2016-07-01

    Non-drug strategies based on biophysical stimulation have been emphasized for the treatment and prevention of musculoskeletal conditions. However, to date, an effective stimulation system for intracorporeal therapies has not been proposed. This is particularly true for active intramedullary implants that aim to optimize osseointegration. The increasing demand for these implants, particularly for hip and knee replacements, has driven the design of innovative stimulation systems that are effective in bone-implant integration. In this paper, a new cosurface-based capacitive system concept is proposed for the design of implantable devices that deliver controllable and personalized electric field stimuli to target tissues. A prototype architecture of this system was constructed for in vitro tests, and its ability to deliver controllable stimuli was numerically analyzed. Successful results were obtained for osteoblastic proliferation and differentiation in the in vitro tests. This work provides, for the first time, a design of a stimulation system that can be embedded in active implantable devices for controllable bone-implant integration and regeneration. The proposed cosurface design holds potential for the implementation of novel and innovative personalized stimulatory therapies based on the delivery of electric fields to bone cells.

  15. Comparative study on the osseointegration of implants in dog mandibles according to the implant surface treatment

    PubMed Central

    2016-01-01

    Objectives This study compared the impact of implant surface treatment on the stability and osseointegration of implants in dog mandibles. Materials and Methods Six adult dogs received a total of 48 implants that were prepared using four different surface treatments; resorbable blast media (RBM), hydroxyapatite (HA), hydrothermal-treated HA, and sand blasting and acid etching (SLA). Implants were installed, and dogs were separated into 2- and 4-week groups. Implant stability was evaluated via Periotest M, Osstell Mentor, and removal torque analyzers. A histomorphometric analysis was also performed. Results The stability evaluation showed that all groups generally had satisfactory values. The histomorphometric evaluation via a light microscope revealed that the HA surface implant group had the highest ratio of new bone formation on the entire fixture. The hydrothermal-treated HA surface implant group showed a high ratio of bone-to-implant contact in the upper half of the implant area. Conclusion The hydrothermal-treated HA implant improved the bone-to-implant contact ratio on the upper fixture, which increased the implant stability. PMID:28053904

  16. The effect of controlled microrobotized blasting on implant surface texturing and early osseointegration.

    PubMed

    Gil, Luiz F; Marin, Charles; Teixeira, Hellen; Marão, Heloisa F; Tovar, Nick; Khan, Rehan; Bonfante, Estevam A; Janal, Malvin; Coelho, Paulo G

    2016-02-01

    Surface topography modifications have become a key strategy for hastening the host-to-implant response to implantable materials. The present study evaluated the effect of three different carefully controlled surface texture patterns achieved through microrobotized blasting (controlled to high, medium and low roughness) relative to a larger scale blasting procedure (control) in early osseointegration in a canine model. Four commercially pure grade 2 titanium alloy implants (one of each surface) were bilaterally placed in the radii of six beagle dogs and allowed end points of 1 and 6 weeks in vivo. Following sacrifice, implants in bone were non-decalcified processed for bone morphologic and histometric (bone-to-implant contact; bone area fraction occupancy) evaluation. Surface topography was characterized by scanning electron microscopy and optical interferometry. Results showed initial osteogenic tissue interaction at one week and new bone in intimate contact with all implant surfaces at 6 weeks. At 1 and 6 weeks in vivo, higher bone-to-implant and bone area fraction occupancy were observed for the high texture pattern microrobotized blasted surface relative to others.

  17. Progressive plateau root form dental implant osseointegration: A human retrieval study.

    PubMed

    Gil, Luiz F; Suzuki, Marcelo; Janal, Malvin N; Tovar, Nick; Marin, Charles; Granato, Rodrigo; Bonfante, Estevam A; Jimbo, Ryo; Gil, Jose N; Coelho, Paulo G

    2015-08-01

    Although preclinical and sparse human histology retrieval studies have shown that the interface between implant and bone is constantly remodeling, no human retrieval database has been developed to determine the effect of functional loading time and other clinical/implant design variables on osseointegration. The present study tested the hypothesis that bone-to-implant contact (BIC) and bone area fraction occupancy (BAFO) increase over functional loading time around dental implants. Due to prosthetic retreatment reasons, 93 human implant retrievals from the same manufacturer (Bicon LLC, Boston, MA, USA) were obtained over a period of approximately 15 years. The retrieved implants were under functional loading from 120 days to ∼18 years and were histomorphologic/metrically evaluated. BIC/BAFO were assessed as a function of multiple independent variables: implant surface type, diameter, length, jaw (maxilla/mandible), region (anterior/posterior), and time of functional loading. The results showed that both BIC and BAFO increased over time independently of implant design/clinical variables, supporting the postulated hypothesis.

  18. The promotion of osseointegration of titanium surfaces by coating with silk protein sericin.

    PubMed

    Nayak, Sunita; Dey, Tuli; Naskar, Deboki; Kundu, Subhas C

    2013-04-01

    A promising strategy to influence the osseointegration process around orthopaedic titanium implants is the immobilization of bioactive molecules. This recruits appropriate interaction between the surface and the tissue by directing cells adhesion, proliferation, differentiation and active matrix remodelling. In this study, we aimed to investigate the functionalization of metallic implant titanium with silk protein sericin. Titanium surface was immobilized with non-mulberry Antheraea mylitta sericin using glutaraldehyde as crosslinker. To analyse combinatorial effects the sericin immobilized titanium was further conjugated with integrin binding peptide sequence Arg-Gly-Asp (RGD) using ethyl (dimethylaminopropyl) carbodiimide and N-hydroxysulfosuccinimide as coupling agents. The surface of sericin immobilized titanium was characterized biophysically. Osteoblast-like cells were cultured on sericin and sericin/RGD functionalized titanium and found to be more viable than those on pristine titanium. The enhanced adhesion, proliferation, and differentiation of osteoblast cells were observed. RT-PCR analysis showed that mRNA expressions of bone sialoprotein, osteocalcin and alkaline phosphatase were upregulated in osteoblast cells cultured on sericin and sericin/RGD immobilized titanium substrates. Additionally, no significant amount of pro-inflammatory cytokines TNF-α, IL-1β and nitric oxide production were recorded when macrophages cells and osteoblast-macrophages co culture cells were grown on sericin immobilized titanium. The findings demonstrate that the sericin immobilized titanium surfaces are potentially useful bioactive coated materials for titanium-based medical implants.

  19. Inhibition of cathepsin K promotes osseointegration of titanium implants in ovariectomised rats

    PubMed Central

    Yi, Chun; Hao, Ke-Yi; Ma, Ting; Lin, Ye; Ge, Xi-Yuan; Zhang, Yu

    2017-01-01

    The bone mineral deficiency in osteoporosis poses a threat to the long-term outcomes of endosseous implants. The inhibitors of cathepsin K (CatK) significantly affect bone turnover, bone mineral density (BMD) and bone strength in the patients with osteoporosis. Therefore, we hypothesised that the application of a CatK inhibitor (CatKI) could increase the osseointegration of endosseous implants under osteoporotic conditions. Odanacatib (ODN), a highly selective CatKI, was chosen as the experimental drug. Sixteen rats were randomised into 4 groups: sham, ovariectomy (OVX) with vehicle, OVX with low-dose ODN (5 mg/kg) and OVX with high-dose ODN (30 mg/kg). Titanium implants were placed into the distal metaphysis of bilateral femurs of each OVX rat. After 8 weeks of gavaging, CatKI treatment increased the removal torque, BMD and bone-to-implant contact (BIC). Moreover, high-dose CatKI exerted a better influence than low-dose CatKI. Furthermore, CatKI treatment not only robustly suppressed CatK gene (CTSK) expression, but also moderately reduced expression of the osteoblast-related genes Runx2, Collagen-1, BSP, Osterix, OPN, SPP1 and ALP. Thus, CatKI could affect the osteoblast-related genes, although the balance of bone turnover was achieved mainly by CatK inhibition. In conclusion, CatKI prevented bone loss and aided endosseous implantation in osteoporotic conditions. PMID:28304382

  20. Engineered Protein Coatings to Improve the Osseointegration of Dental and Orthopaedic Implants

    PubMed Central

    Raphel, Jordan; Karlsson, Johan; Galli, Silvia; Wennerberg, Ann; Lindsay, Christopher; Haugh, Matthew; Pajarinen, Jukka; Goodman, Stuart B.; Jimbo, Ryo; Andersson, Martin; Heilshorn, Sarah C.

    2016-01-01

    Here we present the design of an engineered, elastin-like protein (ELP) that is chemically modified to enable stable coatings on the surfaces of titanium-based dental and orthopaedic implants by novel photocrosslinking and solution processing steps. The ELP includes an extended RGD sequence to confer bio-signaling and an elastin-like sequence for mechanical stability. ELP thin films were fabricated on cp-Ti and Ti6Al4V surfaces using scalable spin and dip coating processes with photoactive covalent crosslinking through a carbene insertion mechanism. The coatings withstood procedures mimicking dental screw and hip replacement stem implantations, a key metric for clinical translation. They promoted rapid adhesion of MG63 osteoblast-like cells, with over 80% adhesion after 24 hours, compared to 38% adhesion on uncoated Ti6Al4V. MG63 cells produced significantly more mineralization on ELP coatings compared to uncoated Ti6Al4V. Human bone marrow mesenchymal stem cells (hMSCs) had an earlier increase in alkaline phosphatase activity, indicating more rapid osteogenic differentiation and mineral deposition on adhesive ELP coatings. Rat tibia and femur in vivo studies demonstrated that cell-adhesive ELP-coated implants increased bone-implant contact area and interfacial strength after one week. These results suggest that ELP coatings withstand surgical implantation and promote rapid osseointegration, enabling earlier implant loading and potentially preventing micromotion that leads to aseptic loosening and premature implant failure. PMID:26790146

  1. Simple Coating with Fibronectin Fragment Enhances Stainless Steel Screw Osseointegration in Healthy and Osteoporotic Rats

    PubMed Central

    Agarwal, Rachit; González-García, Cristina; Torstrick, Brennan; Guldberg, Robert E.; Salmerón-Sánchez, Manuel; García, Andrés J.

    2015-01-01

    Metal implants are widely used to provide structural support and stability in current surgical treatments for bone fractures, spinal fusions, and joint arthroplasties as well as craniofacial and dental applications. Early implant-bone mechanical fixation is an important requirement for the successful performance of such implants. However, adequate osseointegration has been difficult to achieve especially in challenging disease states like osteoporosis due to reduced bone mass and strength. Here, we present a simple coating strategy based on passive adsorption of FN7-10, a recombinant fragment of human fibronectin encompassing the major cell adhesive, integrin-binding site, onto 316-grade stainless steel (SS). FN7-10 coating on SS surfaces promoted α5β1 integrin-dependent adhesion and osteogenic differentiation of human mesenchymal stem cells. FN7-10-coated SS screws increased bone-implant mechanical fixation compared to uncoated screws by 30% and 45% at 1 and 3 months, respectively, in healthy rats. Importantly, FN7-10 coating significantly enhanced bone-screw fixation by 57% and 32% at 1 and 3 months, respectively, and bone-implant ingrowth by 30% at 3 months compared to uncoated screws in osteoporotic rats. These coatings are easy to apply intra-operatively, even to implants with complex geometries and structures, facilitating the potential for rapid translation to clinical settings. PMID:26100343

  2. Osseointegration of three-dimensional designed titanium implants manufactured by selective laser melting.

    PubMed

    Shaoki, Algabri; Xu, Jia-Yun; Sun, Haipeng; Chen, Xian-Shuai; Ouyang, Jianglin; Zhuang, Xiu-Mei; Deng, Fei-Long

    2016-10-27

    The selective laser melting (SLM) technique is a recent additive manufacturing (AM) technique. Several studies have reported success in the SLM-based production of biocompatible orthopaedic implants and three-dimensional bone defect constructs. In this study, we evaluated the surface properties and biocompatibility of an SLM titanium implant in vitro and compared them with those of a machined (MA) titanium control surface. In addition, we evaluated the osseointegration capability of the SLM implants in vivo and compared it with those of MA and Nobel-speedy (Nobel-S) implants. SLM microtopographical surface analysis revealed porous and high roughness with varied geometry compared with a smooth surface in MA Ti samples but with similar favourable wettability. Osteoblast proliferation and alkaline phosphatase activity were significantly enhanced on the SLM surface. Histological analysis of the bone-implant contact ratio revealed no significant difference among SLM, MA, and Nobel-S implants. Micro-CT assessment indicated that there was no significant difference in bone volume fraction around the implant among SLM implants and other types of surface modification implants. The removal torque value measurement of SLM implants was significantly lower that of than Nobel-S implants P < 0.001 and higher than that of MA implants. The study demonstrates the capability of SLM implants to integrate with living bone. The SLM technique holds promise as a new dental implant manufacturing technique.

  3. Antimicrobial surface coatings for a permanent percutaneous passage in the concept of osseointegrated extremity prosthesis.

    PubMed

    Calliess, Tilman; Sluszniak, Magda; Winkel, Andreas; Pfaffenroth, Cornelia; Dempwolf, Wibke; Heuer, Wieland; Menzel, Henning; Windhagen, Henning; Stiesch, Meike

    2012-12-01

    The clinical implementation of percutaneous implants is still limited owing to infections at the side of the stoma. In our concept, this issue is addressed by designing copolymer surface coatings possessing biocompatibility and antimicrobial activity to improve the maintenance of a physiological skin seal at the skin-implant interface. Different copolymers with surface-active phosphonate and antimicrobial cationic groups were designed. Thus, coated titanium samples were cultured with bacterial strains or fibroblasts, respectively. Antimicrobial impact was evaluated by imaging the reduction of bacterial adherence. Biocompatibility was displayed by fibroblast proliferation and morphology. A variety of copolymers of 4-vinylpyridine with vinylbenzylphosphonate or dimethyl(2-methacryloyloxy-ethyl) phosphonate were prepared by free radical polymerization. The optimized polymer coating (copolymer D) showed a reduction of adherent bacteria up to 95%, with only a slight reduction in the adherence of human fibroblasts compared with blank titanium controls. In this study, we demonstrate in vitro that polymer surface coatings can be simultaneously antimicrobial and biocompatible. We consider this to be a promising technology for the realization of a permanent aseptic percutaneous passage as needed for the advancement of osseointegrated limb prosthesis.

  4. Simple coating with fibronectin fragment enhances stainless steel screw osseointegration in healthy and osteoporotic rats.

    PubMed

    Agarwal, Rachit; González-García, Cristina; Torstrick, Brennan; Guldberg, Robert E; Salmerón-Sánchez, Manuel; García, Andrés J

    2015-09-01

    Metal implants are widely used to provide structural support and stability in current surgical treatments for bone fractures, spinal fusions, and joint arthroplasties as well as craniofacial and dental applications. Early implant-bone mechanical fixation is an important requirement for the successful performance of such implants. However, adequate osseointegration has been difficult to achieve especially in challenging disease states like osteoporosis due to reduced bone mass and strength. Here, we present a simple coating strategy based on passive adsorption of FN7-10, a recombinant fragment of human fibronectin encompassing the major cell adhesive, integrin-binding site, onto 316-grade stainless steel (SS). FN7-10 coating on SS surfaces promoted α5β1 integrin-dependent adhesion and osteogenic differentiation of human mesenchymal stem cells. FN7-10-coated SS screws increased bone-implant mechanical fixation compared to uncoated screws by 30% and 45% at 1 and 3 months, respectively, in healthy rats. Importantly, FN7-10 coating significantly enhanced bone-screw fixation by 57% and 32% at 1 and 3 months, respectively, and bone-implant ingrowth by 30% at 3 months compared to uncoated screws in osteoporotic rats. These coatings are easy to apply intra-operatively, even to implants with complex geometries and structures, facilitating the potential for rapid translation to clinical settings.

  5. Shape-memory alloy overload protection device for osseointegrated transfemoral implant prosthetic limb attachment system

    NASA Astrophysics Data System (ADS)

    Xu, Wei; Shao, Fei; Hughes, Steven

    2002-11-01

    The osseointegrated trans-femoral implant system provides a direct anchoring technique to attach prosthetic limb. This technique was first introduced PI Brenmark in Sweden. The UK had the first clinical trial in 1997 and currently has 6 active limb wearers. The success of this procedure has the potential for improved gait function and mobility, increased employability and significant long-term improvements in the quality of life for above knee amputees. However, the significant load involved in the trans-femoral implant system has caused permanent deformation and/or fractures of the implant abutment in several occasions. To protect the implant system, the implant abutment in particularly, an overloading protection device was introduced. The device uses mechanical mechanism to release torsion overload on the abutment. However, the bending overload protection remains unsolved. To solve the problem, a new overload protection device was developed. This device uses SMA component for bending overload protection. In this paper, the results of non-linear finite element modelling of the SMA and steel (AISI 1040) components were presented. Experiments were also carried out using steel components to assess the design which is based on the non-linear property of the materials.

  6. Engineered protein coatings to improve the osseointegration of dental and orthopaedic implants.

    PubMed

    Raphel, Jordan; Karlsson, Johan; Galli, Silvia; Wennerberg, Ann; Lindsay, Christopher; Haugh, Matthew G; Pajarinen, Jukka; Goodman, Stuart B; Jimbo, Ryo; Andersson, Martin; Heilshorn, Sarah C

    2016-03-01

    Here we present the design of an engineered, elastin-like protein (ELP) that is chemically modified to enable stable coatings on the surfaces of titanium-based dental and orthopaedic implants by novel photocrosslinking and solution processing steps. The ELP includes an extended RGD sequence to confer bio-signaling and an elastin-like sequence for mechanical stability. ELP thin films were fabricated on cp-Ti and Ti6Al4V surfaces using scalable spin and dip coating processes with photoactive covalent crosslinking through a carbene insertion mechanism. The coatings withstood procedures mimicking dental screw and hip replacement stem implantations, a key metric for clinical translation. They promoted rapid adhesion of MG63 osteoblast-like cells, with over 80% adhesion after 24 h, compared to 38% adhesion on uncoated Ti6Al4V. MG63 cells produced significantly more mineralization on ELP coatings compared to uncoated Ti6Al4V. Human bone marrow mesenchymal stem cells (hMSCs) had an earlier increase in alkaline phosphatase activity, indicating more rapid osteogenic differentiation and mineral deposition on adhesive ELP coatings. Rat tibia and femur in vivo studies demonstrated that cell-adhesive ELP-coated implants increased bone-implant contact area and interfacial strength after one week. These results suggest that ELP coatings withstand surgical implantation and promote rapid osseointegration, enabling earlier implant loading and potentially preventing micromotion that leads to aseptic loosening and premature implant failure.

  7. Tantalum implanted entangled porous titanium promotes surface osseointegration and bone ingrowth

    PubMed Central

    Wang, Qi; Qiao, Yuqin; Cheng, Mengqi; Jiang, Guofeng; He, Guo; Chen, Yunsu; Zhang, Xianlong; Liu, Xuanyong

    2016-01-01

    Porous Ti is considered to be an ideal graft material in orthopaedic and dental surgeries due to its similar spatial structures and mechanical properties to cancellous bone. In this work, to overcome the bioinertia of Ti, Ta-implanted entangled porous titanium (EPT) was constructed by plasma immersion ion implantation & deposition (PIII&D) method. Ca-implanted and unimplanted EPTs were investigated as control groups. Although no difference was found in surface topography and mechanical performances, both Ca- and Ta-implanted groups had better effects in promoting MG-63 cell viability, proliferation, differentiation, and mineralization than those of unimplanted group. The expression of osteogenic-related markers examined by qRT-PCR and western blotting was upregulated in Ca- and Ta-implanted groups. Moreover, Ta-implanted EPT group could reach a higher level of these effects than that of Ca-implanted group. Enhanced osseointegration of both Ca- and Ta-implanted EPT implants was demonstrated through in vivo experiments, including micro-CT evaluation, push-out test, sequential fluorescent labeling and histological observation. However, the Ta-implanted group possessed more stable and continuous osteogenic activity. Our results suggest that Ta-implanted EPT can be developed as one of the highly efficient graft material for bone reconstruction situations. PMID:27185196

  8. A computational model for stress reduction at the skin-implant interface of osseointegrated prostheses.

    PubMed

    Yerneni, Srinivasu; Dhaher, Yasin; Kuiken, Todd A

    2012-04-01

    Osseointegrated implants (OI)s for transfemoral prosthetic attachment offer amputees an alternative to the traditional socket attachment. Potential benefits include a natural transfer of loads directly to the skeleton via the percutaneous abutment, relief of pain and discomfort of residual limb soft tissues by eliminating sockets, increased sensory feedback, and improved function. Despite the benefits, the skin-implant interface remains a critical limitation, as it is highly prone to bacterial infection. One approach to improve clinical outcomes is to minimize stress concentrations at the skin-implant interface due to shear loading, reducing soft tissue breakdown and subsequent risk of infection. We hypothesized that broadening the bone base at the distal end of the femur would provide added surface area for skin adhesion and reduce stresses at the skin-implant interface. We tested this hypothesis using finite element models of an OI in a residual limb. Results showed a dramatic decrease in stress reduction, with up to ~90% decrease in stresses at the skin-implant interface as cortical bone thickness increased from 2 to 8 mm. The findings in this study suggests that surgical techniques could stabilize the skin-implant interface, thus enhancing a skin-to-bone seal around the percutaneous device and minimizing infection.

  9. New cosurface capacitive stimulators for the development of active osseointegrative implantable devices

    PubMed Central

    Soares dos Santos, Marco P.; Marote, Ana; Santos, T.; Torrão, João; Ramos, A.; Simões, José A. O.; da Cruz e Silva, Odete A. B.; Furlani, Edward P.; Vieira, Sandra I.; Ferreira, Jorge A. F.

    2016-01-01

    Non-drug strategies based on biophysical stimulation have been emphasized for the treatment and prevention of musculoskeletal conditions. However, to date, an effective stimulation system for intracorporeal therapies has not been proposed. This is particularly true for active intramedullary implants that aim to optimize osseointegration. The increasing demand for these implants, particularly for hip and knee replacements, has driven the design of innovative stimulation systems that are effective in bone-implant integration. In this paper, a new cosurface-based capacitive system concept is proposed for the design of implantable devices that deliver controllable and personalized electric field stimuli to target tissues. A prototype architecture of this system was constructed for in vitro tests, and its ability to deliver controllable stimuli was numerically analyzed. Successful results were obtained for osteoblastic proliferation and differentiation in the in vitro tests. This work provides, for the first time, a design of a stimulation system that can be embedded in active implantable devices for controllable bone-implant integration and regeneration. The proposed cosurface design holds potential for the implementation of novel and innovative personalized stimulatory therapies based on the delivery of electric fields to bone cells. PMID:27456818

  10. Tantalum implanted entangled porous titanium promotes surface osseointegration and bone ingrowth

    NASA Astrophysics Data System (ADS)

    Wang, Qi; Qiao, Yuqin; Cheng, Mengqi; Jiang, Guofeng; He, Guo; Chen, Yunsu; Zhang, Xianlong; Liu, Xuanyong

    2016-05-01

    Porous Ti is considered to be an ideal graft material in orthopaedic and dental surgeries due to its similar spatial structures and mechanical properties to cancellous bone. In this work, to overcome the bioinertia of Ti, Ta-implanted entangled porous titanium (EPT) was constructed by plasma immersion ion implantation & deposition (PIII&D) method. Ca-implanted and unimplanted EPTs were investigated as control groups. Although no difference was found in surface topography and mechanical performances, both Ca- and Ta-implanted groups had better effects in promoting MG-63 cell viability, proliferation, differentiation, and mineralization than those of unimplanted group. The expression of osteogenic-related markers examined by qRT-PCR and western blotting was upregulated in Ca- and Ta-implanted groups. Moreover, Ta-implanted EPT group could reach a higher level of these effects than that of Ca-implanted group. Enhanced osseointegration of both Ca- and Ta-implanted EPT implants was demonstrated through in vivo experiments, including micro-CT evaluation, push-out test, sequential fluorescent labeling and histological observation. However, the Ta-implanted group possessed more stable and continuous osteogenic activity. Our results suggest that Ta-implanted EPT can be developed as one of the highly efficient graft material for bone reconstruction situations.

  11. The impact of a modified cutting flute implant design on osseointegration.

    PubMed

    Jimbo, R; Tovar, N; Marin, C; Teixeira, H S; Anchieta, R B; Silveira, L M; Janal, M N; Shibli, J A; Coelho, P G

    2014-07-01

    Information concerning the effects of the implant cutting flute design on initial stability and its influence on osseointegration in vivo is limited. This study evaluated the early effects of implants with a specific cutting flute design placed in the sheep mandible. Forty-eight dental implants with two different macro-geometries (24 with a specific cutting flute design - Blossom group; 24 with a self-tapping design - DT group) were inserted into the mandibular bodies of six sheep; the maximum insertion torque was recorded. Samples were retrieved and processed for histomorphometric analysis after 3 and 6 weeks. The mean insertion torque was lower for Blossom implants (P<0.001). No differences in histomorphometric results were observed between the groups. At 3 weeks, P=0.58 for bone-to-implant contact (BIC) and P=0.52 for bone area fraction occupied (BAFO); at 6 weeks, P=0.55 for BIC and P=0.45 for BAFO. While no histomorphometric differences were observed, ground sections showed different healing patterns between the implants, with better peri-implant bone organization around those with the specific cutting flute design (Blossom group). Implants with the modified cutting flute design had a significantly reduced insertion torque compared to the DT implants with a traditional cutting thread, and resulted in a different healing pattern.

  12. Tantalum implanted entangled porous titanium promotes surface osseointegration and bone ingrowth.

    PubMed

    Wang, Qi; Qiao, Yuqin; Cheng, Mengqi; Jiang, Guofeng; He, Guo; Chen, Yunsu; Zhang, Xianlong; Liu, Xuanyong

    2016-05-17

    Porous Ti is considered to be an ideal graft material in orthopaedic and dental surgeries due to its similar spatial structures and mechanical properties to cancellous bone. In this work, to overcome the bioinertia of Ti, Ta-implanted entangled porous titanium (EPT) was constructed by plasma immersion ion implantation &deposition (PIII&D) method. Ca-implanted and unimplanted EPTs were investigated as control groups. Although no difference was found in surface topography and mechanical performances, both Ca- and Ta-implanted groups had better effects in promoting MG-63 cell viability, proliferation, differentiation, and mineralization than those of unimplanted group. The expression of osteogenic-related markers examined by qRT-PCR and western blotting was upregulated in Ca- and Ta-implanted groups. Moreover, Ta-implanted EPT group could reach a higher level of these effects than that of Ca-implanted group. Enhanced osseointegration of both Ca- and Ta-implanted EPT implants was demonstrated through in vivo experiments, including micro-CT evaluation, push-out test, sequential fluorescent labeling and histological observation. However, the Ta-implanted group possessed more stable and continuous osteogenic activity. Our results suggest that Ta-implanted EPT can be developed as one of the highly efficient graft material for bone reconstruction situations.

  13. Osseointegration into a Novel Titanium Foam Implant in the Distal Femur of a Rabbit

    PubMed Central

    Willie, Bettina M.; Yang, Xu; Kelly, Natalie H.; Merkow, Justin; Gagne, Shawn; Ware, Robin; Wright, Timothy M.; Bostrom, Mathias P.G.

    2010-01-01

    A novel porous titanium foam implant has recently been developed to enhance biological fixation of orthopaedic implants to bone. The aim of this study was to examine the mechanical and histological characteristics of bone apposition into two different pore sizes of this titanium foam (565 and 464 micron mean void intercept length) and to compare these characteristics to those obtained with a fully porous conventionally sintered titanium bead implant. Cylindrical implants were studied in a rabbit distal femoral intramedullary osseointegration model at time zero and at 3, 6, and 12 weeks. The amount of bone ingrowth, amount of periprosthetic bone, and mineral apposition rate of periprosthetic bone measured did not differ among the three implant designs at 3, 6, or 12 weeks. By 12 weeks, the interface stiffness and maximum load of the beaded implant was significantly greater than either foam implant. No significant difference was found in the interface stiffness or maximum load between the two foam implant designs at 3, 6, or 12 weeks. The lower compressive modulus of the foam compared to the more dense sintered beaded implants likely contributed to the difference in failure mode. However, the foam implants have a similar compressive modulus to other clinically successful coatings, suggesting they are nonetheless clinically adequate. Additional studies are required to confirm this in weight-bearing models. Histological data suggest that these novel titanium foam implants are a promising alternative to current porous coatings and should be further investigated for clinical application in cementless joint replacement. PMID:20024964

  14. Effect of microtopography and species composition on small-scale variability of CO2 fluxes in a subalpine grassland

    NASA Astrophysics Data System (ADS)

    Galvagno, Marta; Filippa, Gianluca; Cremonese, Edoardo; Morra di Cella, Umberto; Isabellon, Michel

    2015-04-01

    Grassland ecosystems cover around 30% of the Earth's land surface and consequently play an important role in the terrestrial carbon balance. Climate and land use changes have a significant effect on the sink/source strength of grasslands, especially in mountain regions. For these reasons the carbon cycle of high-altitude grasslands has recently received higher attention, however little is know on the within-ecosystem variability in CO2 fluxes. In fact, alpine and subalpine grasslands are often characterized by complex topography which generates differences in snowmelt dynamics at site level and related different microhabitats. The deriving patchy distribution of vegetation leads to the coexistence of different plant functional traits and developmental strategies within the same ecosystem. In this study we evaluated the effect of microtopography and associated vegetation types on the CO2 flux components of an unamanaged subalpine grassland located at 2160 m asl, by means of automated clear and opaque chambers. In order to disentangle the contribution of different growth forms to the whole ecosystem carbon sequestration we compare chambers with eddy covariance CO2 flux data. Results show that: i) different growth forms are associated with concave o convex shapes of the terrain and, in detail, grass species dominate in convex areas while forbs are especially found in concave ones ii) two distinct CO2 flux trajectories associated to these shapes can be distinguished in this ecosystem: graminoids show a later beginning of the carbon uptake period but higher CO2 net uptake (NEE), while forbs develop just after snowmelt but show lower NEE. The observed small-scale patterns of carbon sequestration may reflect the distinct vegetation type responses to snowmelt and different adaptations to resource use efficiency (light, temperature, nutrients) specific of their own microhabitat. Further investigations will be carried on to better evaluate the role of microhabitat

  15. Microtopography of titanium suppresses osteoblastic differentiation but enhances chondroblastic differentiation of rat femoral periosteum-derived cells.

    PubMed

    Kubo, Katsutoshi; Att, Wael; Yamada, Masahiro; Ohmi, Kuzuhiro; Tsukimura, Naoki; Suzuki, Takeo; Maeda, Hatsuhiko; Ogawa, Takahiro

    2008-11-01

    Despite the clinical fact that endosseous titanium implants directly contacts periosteum, the behavior and response of the periosteum-derived cells to surface topography of titanium have rarely been studied. This study examines the effect of titanium surface microtopography on osteoblastic and possibly-modulated chondroblastic phenotypes of femoral periosteum-derived cells. Rat femoral periosteum-derived cells were cultured on either relatively smooth, machined titanium surface or acid-etched, micro-roughened titanium surface. The osteoblastic gene expressions, including collagen I, osteopontin and osteocalcin, were downregulated on the acid-etched surface, compared with the machined surface. Alkaline phosphatase and mineralization activities on the acid-etched surface were approximately 20% of those on the machined surface. Instead, chondroblastic specific genes, including collagen II and IX, and sox 9, were exclusively expressed or highly upregulated on the acid-etched surface. Alcian blue stain revealed an extensive deposition of glycosaminoglycan on the acid-etched surface. The cultured matrix on the acid-etched surface lacked the submicron globular structures that were extensively seen on the machined surface, and contained a remarkably increased percentage of sulfur relative to calcium compared with the culture on the machined surface. These results indicated that titanium microroughness suppresses the osteoblastic phenotype and induces or at least considerably enhances the chondroblastic phenotype of the periosteal cells, suggesting the unique role of titanium surface topography in regulating the periosteal cell differentiation. The suppressive effect of titanium microroughness on the periosteal cells toward the osteoblastic linage was contrasted to the known promotive effect on the bone marrow-derived osteoblasts.

  16. Microtopography of the surface of adult Schistosoma japonicum-like (Malaysian) as observed by scanning electron microscopy.

    PubMed

    Sobhon, P; Upatham, E S; Koonchornboon, T; Saitongdee, P; Khunborivan, V; Yuan, H C; Vongpayabal, P; Ow-Yang, C K; Greer, G J

    1983-12-01

    The surface of adult Schistosoma japonicum-like (Malaysian) was studied by scanning electron microscopy. The basic pattern of surface microtopography is similar to other strains of S. japonicum as previously reported. However, among male member there are some unique differences in the types, number and distribution of surface papillae and morphology of ridges. Three kinds of papillae were observed: (1) the large fungiform papillae (3.5-4 micron in diameter, most without cilia) are more numerous than in other strains of S. japonicum, they concentrate on the lateral aspect of the anterior and middle parts close to the edge of the gynecophoral canal, and on the dorso-lateral aspect of the posterior part towards the tail tip; (2) the small hemispherical papillae (1.5-2 micron in diameter, all bearing cilia) are especially numerous in the suckers, the gynecophoral canal and parts of the tegument around the suckers and close to the tail tip; on the rest of the surface they are evenly distributed; (3) the cratered papillae (3-4 micron in diameter, about half having cilia) are more numerous than on other strains, they concentrate on the lateral aspect of the middle part and on the edges of the gynecophoral canal. The surface ridges (about 0.2-0.3 micron in width) are tall, highly branching and perforated; they are most developed in the middle part. Spines were observed only in the suckers and the gynecophoral canals. In contrast to the male, the female has numerous spines on all parts of the surface except the most anterior, where a large number of long cilia were observed. All three kinds of papillae were present; fungiform papillae are more numerous than in females of other strains; they concentrate on the latero-dorsal aspect of middle and posterior parts, and around the excretory pore. Ridges are much less developed than in the male and are prominent only in the middle part.

  17. Can common adhesion molecules and microtopography affect cellular elasticity? A combined atomic force microscopy and optical study.

    PubMed

    McPhee, Gordon; Dalby, Matthew J; Riehle, Mathis; Yin, Huabing

    2010-10-01

    The phenomenon that cells respond to chemical and topographic cues in their surroundings has been widely examined and exploited in many fields ranging from basic life science research to biomedical therapeutics. Adhesion promoting molecules such as poly-L-lysine (PLL) and fibronectin (Fn) are commonly used for in vitro cell assays to promote cell spreading/proliferation on tissue culture plastic and to enhance the biocompatibility of biomedical devices. Likewise, engineered topography is often used to guide cell growth and differentiation. Little is known about how these cues affect the biomechanical properties of cells and subsequent cell function. In this study we have applied atomic force microscopy (AFM) to investigate these biomechanical properties. In the first stage of the study we formulated a rigorous approach to quantify cellular elasticity using AFM. Operational factors, including indentation depth and speed, and mathematical models for data fitting have been systematically evaluated. We then quantified how PLL, Fn and microtopography affected cellular elasticity and the organization of the cytoskeleton. Cellular elasticity after 1 day in culture was greater on a Fn-coated surface as compared to PLL or glass. These statistically significant differences disappeared after two more days in culture. In contrast, the significantly higher elasticity associated with cells grown on micrometric grooves remained for at least 3 days. This work sheds light on the apparently simple but debatable questions: "Are engineered chemical cues eventually masked by a cell's own matrix proteins and so only exert short-term influence? Does engineered topography as well as engineered chemistry affect cell elasticity?"

  18. Surface Properties and Osteoblastic Cytocompatibility of Two Blasted and Acid-Etched Titanium Implant Systems with Distinct Microtopography

    PubMed Central

    Mesquita, Pedro; Gomes, Pedro de Sousa; Sampaio, Paula; Juodzbalys, Gintaras; Afonso, Américo

    2012-01-01

    ABSTRACT Objectives The aim of this study is to compare two commercially available screw-type sandblasted and acid-etched (SLA) Ti implant systems from Eckermann Laboratorium S.L., with similar geometry and distinct microtopography, regarding surface properties and osteoblastic cytocompatibility. Material and Methods Implant I (referred as a conventional SLA system) and Implant II (a system patented as Eckcyte®) were characterized for macro and microtopograpphy, surface roughness and chemical composition. For the cytocompatibility studies, human bone marrow osteoblastic cells were seeded over the implants' surface, and the cell response was assessed for cell adhesion and proliferation, alkaline phosphatase (ALP) activity and matrix mineralization. Results Implant I presented a rough surface with irregularly shaped and sized cavities among flatter-appearing areas, whereas Implant II exhibited a homogeneous rough microporous surface. Compared to Implant I, Implant II presented higher Ra values (0.8 [SD 0.008] μm and 1.21 [SD 0.15] μm, respectively, P < 0.05) and also increased values of Rz, Rt and Rsm, a more negative value of Rsk, and similar RKu values. XPS showed the expected presence of Ti, O, C and N; Al, Si, F, P and Ca were detected in low concentrations. Implant II exhibited significantly lower Al levels. Both implants supported the adhesion, proliferation and differentiation of osteoblastic cells. Implant II showed a thicker fibrilar cell layer and an earlier onset and more abundant matrix mineralization. Conclusions The homogeneous rough and microporous surface of Implant II is most probably a main contributor for its improved cell response. PMID:24422006

  19. Effects of near-bed turbulence and micro-topography on macroinvertebrate movements across contrasting gravel-bed surfaces (Invited)

    NASA Astrophysics Data System (ADS)

    Buffin-Belanger, T. K.; Rice, S. P.; Reid, I.; Lancaster, J.

    2009-12-01

    Fluvial habitats can be described from a series of physical variables but to adequately address the habitat quality it becomes necessary to develop an understanding that combines the physical variables with the behaviour of the inhabitating organisms. The hypothesis of flow refugia provide a rational that can explain the persistence of macroinvertebrate communities in gravel-bed rivers when spates occur. The movement behaviour of macroinvertebrates is a key element to the flow refugia hypothesis, but little is known about how local near-bed turbulence and bed microtopography may affect macroinvertebrate movements. We reproduced natural gravel-bed substrates with contrasting gravel bed textures in a large flume where we were able to document the movement behaviour of the cased caddisfly Potamophylax latipennis for a specific discharge. The crawling paths and drift events of animals were analysed from video recordings. Characteristics of movements differ from one substrate to another. The crawling speed is higher for the small grain-size substrates but the mean travel distance remains approximately the same between substrates. For each substrate, the animals tended to follow consistent paths across the surface. The number of drift events and mean distance drifted is higher for the small grain-size substrate. ADV measurements close to the boundary allow detailed characterisation of near-bed hydraulic variables, including : skewness coefficients, TKE, UV correlation coefficients and integral time scales from autocorrelation analysis. For these variables, the vertical patterns of turbulence parameters are similar between the substrates but the amplitude of the average values and standard errors vary significantly. The spatial distribution of this variability is considered in relation to the crawling paths. It appears that the animals tend to crawl within areas of the substrate where low flow velocities and low turbulent kinetic energies are found, while sites that

  20. A comparative study of zinc, magnesium, strontium-incorporated hydroxyapatite-coated titanium implants for osseointegration of osteopenic rats.

    PubMed

    Tao, Zhou-Shan; Zhou, Wan-Shu; He, Xing-Wen; Liu, Wei; Bai, Bing-Li; Zhou, Qiang; Huang, Zheng-Liang; Tu, Kai-kai; Li, Hang; Sun, Tao; Lv, Yang-Xun; Cui, Wei; Yang, Lei

    2016-05-01

    Surface modification techniques have been applied to generate titanium implant surfaces that promote osseointegration for the implants in cementless arthroplasty. However, its effect is not sufficient for osteoporotic bone. Zinc (Zn), magnesium (Mg), and strontium (Sr) present a beneficial effect on bone growth, and positively affect bone regeneration. The aim of this study was to confirm the different effects of the fixation strength of Zn, Mg, Sr-substituted hydroxyapatite-coated (Zn-HA-coated, Mg-HA-coated, Sr-HA-coated) titanium implants via electrochemical deposition in the osteoporotic condition. Female Sprague-Dawley rats were used for this study. Twelve weeks after bilateral ovariectomy, all animals were randomly divided into four groups: group HA; group Zn-HA; group Mg-HA and group Sr-HA. Afterwards, all rats from groups HA, Zn-HA, Mg-HA and Sr-HA received implants with hydroxyapatite containing 0%, 10% Zn ions, 10% Mg ions, and 10% Sr ions. Implants were inserted bilaterally in all animals until death at 12 weeks. The bilateral femurs of rats were harvested for evaluation. All treatment groups increased new bone formation around the surface of titanium rods and push-out force; group Sr-HA showed the strongest effects on new bone formation and biomechanical strength. Additionally, there are significant differences in bone formation and push-out force was observed between groups Zn-HA and Mg-HA. This finding suggests that Zn, Mg, Sr-substituted hydroxyapatite coatings can improve implant osseointegration, and the 10% Sr coating exhibited the best properties for implant osseointegration among the tested coatings in osteoporosis rats.

  1. Micro-topography and reactivity of implant surfaces: an in vitro study in simulated body fluid (SBF).

    PubMed

    Gandolfi, M G; Taddei, P; Siboni, F; Perrotti, V; Iezzi, G; Piattelli, A; Prati, C

    2015-02-01

    The creation of micro-textured dental implant surfaces possessing a stimulating activity represents a challenge in implant dentistry; particularly, the formation of a thin, biologically active, calcium-phosphate layer on their surface could help to strengthen the bond to the surrounding bone. The aim of the present study was to characterize in terms of macrostructure, micro-topography and reactivity in simulated body fluid (SBF), the surface of titanium (Ti) implants blasted with TiO2 particles, acid etched with hydrofluoric acid, and activated with Ca and Mg-containing nanoparticles. Sandblasted and acid-etched implants were analyzed by ESEM-EDX (environmental scanning electron microscope with energy dispersive X-ray system) to study the micromorphology of the surface and to perform elemental X-ray microanalysis (microchemical analyses) and element mapping. ESEM-EDX analyses were performed at time 0 and after a 28-day soaking period in SBF Hank's balanced salt solution (HBSS) following ISO 23317 (implants for surgery—in vitro evaluation for apatite-forming ability of implant materials). Microchemical analyses (weight % and atomic %) and element mapping were carried out to evaluate the relative element content, element distribution, and calcium/phosphorus (Ca/P) atomic ratio. Raman spectroscopy was used to assess the possible presence of impurities due to manufacturing and to investigate the phases formed upon HBSS soaking. Micro-morphological analyses showed a micro-textured, highly rough surface with microgrooves. Microchemical analyses showed compositional differences among the apical, middle, and distal thirds. The micro-Raman analyses of the as-received implant showed the presence of amorphous Ti oxide and traces of anatase, calcite, and a carbonaceous material derived from the decomposition of an organic component of lipidic nature (presumably used as lubricant). A uniform layer of Ca-poor calcium phosphates (CaPs) (Ca/P ratio <1.47) was observed after

  2. LINEAR ACCELERATOR

    DOEpatents

    Colgate, S.A.

    1958-05-27

    An improvement is presented in linear accelerators for charged particles with respect to the stable focusing of the particle beam. The improvement consists of providing a radial electric field transverse to the accelerating electric fields and angularly introducing the beam of particles in the field. The results of the foregoing is to achieve a beam which spirals about the axis of the acceleration path. The combination of the electric fields and angular motion of the particles cooperate to provide a stable and focused particle beam.

  3. Acceleration switch

    DOEpatents

    Abbin, Jr., Joseph P.; Devaney, Howard F.; Hake, Lewis W.

    1982-08-17

    The disclosure relates to an improved integrating acceleration switch of the type having a mass suspended within a fluid filled chamber, with the motion of the mass initially opposed by a spring and subsequently not so opposed.

  4. Acceleration switch

    DOEpatents

    Abbin, J.P. Jr.; Devaney, H.F.; Hake, L.W.

    1979-08-29

    The disclosure relates to an improved integrating acceleration switch of the type having a mass suspended within a fluid filled chamber, with the motion of the mass initially opposed by a spring and subsequently not so opposed.

  5. ION ACCELERATOR

    DOEpatents

    Bell, J.S.

    1959-09-15

    An arrangement for the drift tubes in a linear accelerator is described whereby each drift tube acts to shield the particles from the influence of the accelerating field and focuses the particles passing through the tube. In one embodiment the drift tube is splii longitudinally into quadrants supported along the axis of the accelerator by webs from a yoke, the quadrants. webs, and yoke being of magnetic material. A magnetic focusing action is produced by energizing a winding on each web to set up a magnetic field between adjacent quadrants. In the other embodiment the quadrants are electrically insulated from each other and have opposite polarity voltages on adjacent quadrants to provide an electric focusing fleld for the particles, with the quadrants spaced sufficienily close enough to shield the particles within the tube from the accelerating electric field.

  6. LINEAR ACCELERATOR

    DOEpatents

    Christofilos, N.C.; Polk, I.J.

    1959-02-17

    Improvements in linear particle accelerators are described. A drift tube system for a linear ion accelerator reduces gap capacity between adjacent drift tube ends. This is accomplished by reducing the ratio of the diameter of the drift tube to the diameter of the resonant cavity. Concentration of magnetic field intensity at the longitudinal midpoint of the external sunface of each drift tube is reduced by increasing the external drift tube diameter at the longitudinal center region.

  7. In Vivo Osseointegration Performance of Titanium Dioxide Coating Modified Polyetheretherketone Using Arc Ion Plating for Spinal Implant Application

    PubMed Central

    Tsou, Hsi-Kai; Chi, Meng-Hui; Hung, Yi-Wen; Chung, Chi-Jen; He, Ju-Liang

    2015-01-01

    Polyetheretherketone (PEEK), which has biomechanical performance similar to that of human cancellous bone, is used widely as a spinal implant material. However, its bioinertness and hydrophobic surface properties result in poor osseointegration. This study applies a novel modification method, arc ion plating (AIP), that produces a highly osteoblast compatible titanium dioxide (TiO2) coatings on a PEEK substrate. This PEEK with TiO2 coating (TiO2/PEEK) was implanted into the femurs of New Zealand white male rabbits to evaluate its in vivo performance by the push-out test and histological observation. Analytical results show that AIP can prepare TiO2 coatings on bullet-shaped PEEK substrates as implant materials. After prolonged implantation in rabbits, no signs of inflammation existed. Newly regenerated bone formed more prominently with the TiO2/PEEK implant by histological observation. The shear strength of the bone/implant interface increases as implantation period increases. Most importantly, bone bonding performance of the TiO2/PEEK implant was superior to that of bare PEEK. The rutile-TiO2 coatings achieved better osseointegration than the anatase-TiO2 coatings. Therefore, AIP-TiO2 can serve as a novel surface modification method on PEEK for spinal interbody fusion cages. PMID:26504800

  8. The role of nanostructures and hydrophilicity in osseointegration: In-vitro protein-adsorption and blood-interaction studies.

    PubMed

    Kopf, Brigitte S; Ruch, Sylvie; Berner, Simon; Spencer, Nicholas D; Maniura-Weber, Katharina

    2015-08-01

    Protein adsorption and blood coagulation play important roles in the early stages of osseointegration and are strongly influenced by surface properties. We present a systematic investigation of the influence of different surface properties on the adsorption of the blood proteins fibrinogen and fibronectin and the degree of early blood coagulation. Experiments on custom-made and commercially available, microroughened hydrophobic titanium (Ti) surfaces (Ti SLA-Hphob ), hydrophilic (Hphil ) microroughened Ti surfaces with nanostructures (Ti SLActive-Hphil NS), and on bimetallic Ti zirconium alloy (TiZr, Roxolid®) samples were performed, to study the biological response in relation to the surface wettability and the presence of nanostructures (NS). Protein adsorption on the different substrates showed a highly significant effect of surface NS. Hydrophilicity alone did not significantly enhance protein adsorption. Overall, the combination of NS and hydrophilicity led to the highest adsorption levels; independent of whether Ti or TiZr were used. Hydrophilicity induced a strong effect on blood coagulation, whereas the effect of NS alone was weak. The combination of both surface characteristics led to early and most pronounced blood-coagulation. Therefore, nanostructured, hydrophilic Ti and TiZr surfaces may perform better in terms of osseointegration due to continuous protein adsorption and the formation of a layer of blood components on the implant surface.

  9. Effects on the torsional vibration behavior in the investigation of dental implant osseointegration using resonance frequency analysis: a numerical approach.

    PubMed

    Zhai, Min; Li, Bing; Li, Dehua

    2017-02-07

    Resonance frequency analysis (RFA) methods are widely used to assess implant stability, particularly the Osstell(®) device. The potential effects associated with this method have been discussed in the literature. Torsional RFA (T-RFA), mentioned in our previous study, could represent a new measurement method. The purpose of this study was to simulate T-shaped and Osstell(®) transducer-implant-bone system models; compare their vibration modes and corresponding resonance frequencies; and investigate the effects of their parameters, such as the effective implant length (EIL), bone quality, and osseointegration level, on the torsional resonance frequency (TRF) and bending resonance frequency (BRF) using three-dimensional finite element analysis. Following the finite element model validation, the TRFs and BRFs for three different EILs and four types of bone quality were obtained, and the change rates during 25 degrees of osseointegration were observed. The analysis showed that an increase in the EIL and a decrease in bone quality have less effect on the declination rate of TRFs than on that of BRFs. TRFs are highly sensitive to the stiffness of the implant-bone interface during the healing period. It was concluded that T-RFA has better sensitivity and specificity.

  10. Osseointegration aspects of placed implant in bone reconstruction with newly developed block-type interconnected porous calcium hydroxyapatite

    PubMed Central

    DOI, Kazuya; KUBO, Takayasu; MAKIHARA, Yusuke; OUE, Hiroshi; MORITA, Koji; OKI, Yoshifumi; KAJIHARA, Shiho; TSUGA, Kazuhiro

    2016-01-01

    ABSTRACT Artificial bone has been employed to reconstruct bone defects. However, only few reports on implant placement after block bone grafting exist. Objectives The purpose of this study was to evaluate the osseointegration of dental implant in bone reconstructions with interconnected porous calcium hydroxyapatite (IP-CHA). Material and Methods The IP-CHA cylinders (D; 4.3 mm, H; 10.0 mm) were placed into bone sockets in each side of the femurs of four male dogs. The IP-CHA on the right side was a 24-week sample. Twelve weeks after placement, a titanium implant was placed into a socket that was prepared in half of the placed IP-CHA cylinder on the right side. On the left side, another IP-CHA cylinder was placed as a 12-week sample. After another 12 weeks, the samples were harvested, and the bone regeneration and bone-implant contact (BIC) ratios were measured. Results New bone formation area was superior in the 24-week IP-CHA compared with the 12-week IP-CHA. BIC was not significantly different between IP-CHA and the parent sites. Osseointegration was detected around the implant in IP-CHA-reconstructed bone. Conclusion Our preliminary results suggest that IP-CHA may be a suitable bone graft material for reconstructing bones that require implant placement. PMID:27556202

  11. Femtosecond laser treatment of 316L improves its surface nanoroughness and carbon content and promotes osseointegration: An in vitro evaluation.

    PubMed

    Kenar, Halime; Akman, Erhan; Kacar, Elif; Demir, Arif; Park, Haiwoong; Abdul-Khaliq, Hashim; Aktas, Cenk; Karaoz, Erdal

    2013-08-01

    Cell-material surface interaction plays a critical role in osseointegration of prosthetic implants used in orthopedic surgeries and dentistry. Different technical approaches exist to improve surface properties of such implants either by coating or by modification of their topography. Femtosecond laser treatment was used in this study to generate microspotted lines separated by 75, 125, or 175μm wide nanostructured interlines on stainless steel (316L) plates. The hydrophobicity and carbon content of the metallic surface were improved simultaneously through this method. In vitro testing of the laser treated plates revealed a significant improvement in adhesion of human endothelial cells and human bone marrow mesenchymal stem cells (hBM MSCs), the cells involved in microvessel and bone formation, respectively, and a significant decrease in fibroblast adhesion, which is implicated in osteolysis and aseptic loosening of prostheses. The hBM MSCs showed an increased bone formation rate on the laser treated plates under osteogenic conditions; the highest mineral deposition was obtained on the surface with 125μm interline distance (292±18mg/cm(2) vs. 228±43mg/cm(2) on untreated surface). Further in vivo testing of these laser treated surfaces in the native prosthetic implant niche would give a real insight into their effectiveness in improving osseointegration and their potential use in clinical applications.

  12. Surface modifications to enhance the wear resistance and the osseo-integration properties of biomedical Ti-alloy

    NASA Astrophysics Data System (ADS)

    Kami, Pavani

    The current study focuses on improving the wear resistance of femoral head component and enhancing the osseo-integration properties of femoral stem component of a hip implant made of a new generation low modulus alloy, Ti-35Nb-7Zr-5Ta or TNZT. Different techniques that were adopted to improve the wear resistance of low-modulus TNZT alloy included; (a) fabrication of graded TNZT-xB (x= 0, 1, 2 wt%) samples using LENS, (b) oxidation, and (c) LASER nitriding of TNZT. TNZT-1B and TNZT-O samples have shown improved wear resistance when tested against UHMWPE ball in SBF medium. A new class of bio-ceramic coatings based on calcium phosphate (CaP), was applied on the TNZT sample surface and was further laser processed with the objective of enhancing their osseointegration properties. With optimized LASER parameters, TNZT-CaP samples have shown improved corrosion resistance, surface wettability and cellular response when compared to the base TNZT sample.

  13. Histomorphometric and biomechanical analyses of osseointegration of four different orthodontic mini implant surfaces

    NASA Astrophysics Data System (ADS)

    Yadav, Sumit

    Objective: To evaluate the osseointegration potential of four different surfaces of mini-implants. We hypothesized that mini-implants surface roughness alters the intrinsic biomechanical properties of the bone integrated to titanium. Materials and Methods: Mini implants and circular discs were made from alloy Ti6Al4V grade 5. On the basis of surface treatment study was divided into 4 groups: Group 1: Machined: no surface treatment, Group 2: Acid etched: with hydrochloric acid, Group 3: Grit Blasted with alumina and Group 4: Grit blasted +Acid etched. Surface roughness parameters (mean surface roughness: Ra and Quadratic Average roughness: Rq) of the four discs from each group were measured by the optical profilometer. Contact angle measurement of 3 discs from each group was done with a Goniometer. Contact angle of liquids with different hydrophobicity and hydrophilicity were measured. 128 mini implants, differing in surface treatment, were placed into the tibias and femurs of 8 adult male New Zealand white rabbits. Biomechanical properties (Removal torque and hardness) measurements and histomorphometric observations were measured. Results: Ra and Rq of groups were: Machined (1.17+/-0.11, 2.59+/-0.09) Acid etched (1.82+/-0.04, 3.17+/-0.13), Grit blasted (4.83+/-0.23, 7.04+/-0.08), Grit blasted + Acid etched (3.64+/-0.03, 4.95+/-0.04) respectively. Group 4 had significantly (p=0.000) lower Ra and Rq than Group 3. The interaction between the groups and liquid was significant. Group 4 had significantly lower contact angle measurements (40.4°, 26.9°), both for blood and NaCl when compared to other three groups (p≤0.01). Group 4 had significantly higher torque than Group 3 (Tibia: 13.67>9.07N-cm; Femur: 18.21>14.12N-cm), Group 4 (Tibia: 13.67>9.78N-cm; Femur: 18.21>12.87N-cm), and machined (Tibia: 13.67>4.08N-cm; Femur: 18.21>6.49N-cm). SEM analysis reveals significantly more bone implant gap in machined implant surfaces than treated implant surfaces. Bone to implant

  14. Stiffness and ultimate load of osseointegrated prosthesis fixations in the upper and lower extremity

    PubMed Central

    2013-01-01

    Background Techniques for the skeletal attachment of amputation-prostheses have been developed over recent decades. This type of attachment has only been performed on a small number of patients. It poses various potential advantages compared to conventional treatment with a socket, but is also associated with an increased risk of bone or implant-bone interface fracture in the case of a fall. We therefore investigated the bending stiffness and ultimate bending moment of such devices implanted in human and synthetic bones. Methods Eight human specimens and 16 synthetic models of the proximal femora were implanted with lower extremity prostheses and eight human specimens and six synthetic humeri were implanted with upper extremity prostheses. They were dissected according to typical amputation levels and underwent loading in a material testing machine in a four-point bending setup. Bending stiffness, ultimate bending moment and fracture modes were determined in a load to failure experiment. Additionally, axial pull-out was performed on eight synthetic specimens of the lower extremity. Results Maximum bending moment of the synthetic femora was 160.6±27.5 Nm, the flexural rigidity of the synthetic femora was 189.0±22.6 Nm2. Maximum bending moment of the human femora was 100.4±38.5 Nm, and the flexural rigidity was 137.8±29.4 Nm2. The maximum bending moment of the six synthetic humeri was 104.9±19.0 Nm, and the flexural rigidity was 63.7±3.6 Nm2. For the human humeri the maximum bending moment was 36.7±11.0 Nm, and the flexural rigidity at was 43.7±10.5 Nm2. The maximum pull-out force for the eight synthetic femora was 3571±919 N. Conclusion Significant differences were found between human and synthetic specimens of the lower and upper extremity regarding maximum bending moment, bending displacement and flexural rigidity. The results of this study are relevant with respect to previous finding regarding the load at the interfaces of osseointegrated prosthesis

  15. Measurement of surface microtopography

    NASA Technical Reports Server (NTRS)

    Wall, S. D.; Farr, T. G.; Muller, J.-P.; Lewis, P.; Leberl, F. W.

    1991-01-01

    Acquisition of ground truth data for use in microwave interaction modeling requires measurement of surface roughness sampled at intervals comparable to a fraction of the microwave wavelength and extensive enough to adequately represent the statistics of a surface unit. Sub-centimetric measurement accuracy is thus required over large areas, and existing techniques are usually inadequate. A technique is discussed for acquiring the necessary photogrammetric data using twin film cameras mounted on a helicopter. In an attempt to eliminate tedious data reduction, an automated technique was applied to the helicopter photographs, and results were compared to those produced by conventional stereogrammetry. Derived root-mean-square (RMS) roughness for the same stereo-pair was 7.5 cm for the automated technique versus 6.5 cm for the manual method. The principal source of error is probably due to vegetation in the scene, which affects the automated technique but is ignored by a human operator.

  16. Exploring LiDAR data for mapping the micro-topography and tidal hydro-dynamics of mangrove systems: An example from southeast Queensland, Australia

    NASA Astrophysics Data System (ADS)

    Knight, Jon M.; Dale, Pat E. R.; Spencer, John; Griffin, Lachlan

    2009-12-01

    The aim was to explore the use of Light Detection and Ranging (LiDAR) data to map the micro-topography of an intertidal wetland in southeast Queensland Australia. The driver for this was the need to identify and map the habitats of the immature stages of an aedine disease vector mosquito ( Aedes vigilax (Skuse)). We derived a high resolution digital elevation model (DEM) data set at a vertical resolution of 0.05 m from LiDAR data. The relative accuracy of the DEM across the site was tested by comparing water depth predictions derived from the DEM against in-situ water depth readings from pressure sensors over a 10-day tidal cycle, which included high spring tides. We found that the field observations of micro-topographic units important for mosquito management matched those delineated from the DEM. The micro-topography included a low berm or central ridge that was more or less continuous across the site, a shallow back basin and fringing mangroves. The fringing mangroves had unimpeded connection to the tidal source, however the central ridge blocked tidal water from the back basin for all but the highest tides. Eggshell survey indicated that the back basin was the area suitable for immature mosquitoes. We conclude that LiDAR data has application for understanding and mapping the structure of mangrove wetlands. We have also demonstrated (in a small area) that LiDAR is useful for modelling the effect of sea level changes on the coastal fringe. LiDAR may be the only method to inform research on changes to land use and ecosystems caused by sea level change.

  17. Acceleration Studies

    NASA Technical Reports Server (NTRS)

    Rogers, Melissa J. B.

    1993-01-01

    Work to support the NASA MSFC Acceleration Characterization and Analysis Project (ACAP) was performed. Four tasks (analysis development, analysis research, analysis documentation, and acceleration analysis) were addressed by parallel projects. Work concentrated on preparation for and implementation of near real-time SAMS data analysis during the USMP-1 mission. User support documents and case specific software documentation and tutorials were developed. Information and results were presented to microgravity users. ACAP computer facilities need to be fully implemented and networked, data resources must be cataloged and accessible, future microgravity missions must be coordinated, and continued Orbiter characterization is necessary.

  18. Effect of low-level mechanical vibration on osteogenesis and osseointegration of porous titanium implants in the repair of long bone defects

    NASA Astrophysics Data System (ADS)

    Jing, Da; Tong, Shichao; Zhai, Mingming; Li, Xiaokang; Cai, Jing; Wu, Yan; Shen, Guanghao; Zhang, Xuhui; Xu, Qiaoling; Guo, Zheng; Luo, Erping

    2015-11-01

    Emerging evidence substantiates the potential of porous titanium alloy (pTi) as an ideal bone-graft substitute because of its excellent biocompatibility and structural properties. However, it remains a major clinical concern for promoting high-efficiency and high-quality osseointegration of pTi, which is beneficial for securing long-term implant stability. Accumulating evidence demonstrates the capacity of low-amplitude whole-body vibration (WBV) in preventing osteopenia, whereas the effects and mechanisms of WBV on osteogenesis and osseointegration of pTi remain unclear. Our present study shows that WBV enhanced cellular attachment and proliferation, and induced well-organized cytoskeleton of primary osteoblasts in pTi. WBV upregulated osteogenesis-associated gene and protein expression in primary osteoblasts, including OCN, Runx2, Wnt3a, Lrp6 and β-catenin. In vivo findings demonstrate that 6-week and 12-week WBV stimulated osseointegration, bone ingrowth and bone formation rate of pTi in rabbit femoral bone defects via μCT, histological and histomorphometric analyses. WBV induced higher ALP, OCN, Runx2, BMP2, Wnt3a, Lrp6 and β-catenin, and lower Sost and RANKL/OPG gene expression in rabbit femora. Our findings demonstrate that WBV promotes osteogenesis and osseointegration of pTi via its anabolic effect and potential anti-catabolic activity, and imply the promising potential of WBV for enhancing the repair efficiency and quality of pTi in osseous defects.

  19. Effect of low-level mechanical vibration on osteogenesis and osseointegration of porous titanium implants in the repair of long bone defects

    PubMed Central

    Jing, Da; Tong, Shichao; Zhai, Mingming; Li, Xiaokang; Cai, Jing; Wu, Yan; Shen, Guanghao; Zhang, Xuhui; Xu, Qiaoling; Guo, Zheng; Luo, Erping

    2015-01-01

    Emerging evidence substantiates the potential of porous titanium alloy (pTi) as an ideal bone-graft substitute because of its excellent biocompatibility and structural properties. However, it remains a major clinical concern for promoting high-efficiency and high-quality osseointegration of pTi, which is beneficial for securing long-term implant stability. Accumulating evidence demonstrates the capacity of low-amplitude whole-body vibration (WBV) in preventing osteopenia, whereas the effects and mechanisms of WBV on osteogenesis and osseointegration of pTi remain unclear. Our present study shows that WBV enhanced cellular attachment and proliferation, and induced well-organized cytoskeleton of primary osteoblasts in pTi. WBV upregulated osteogenesis-associated gene and protein expression in primary osteoblasts, including OCN, Runx2, Wnt3a, Lrp6 and β-catenin. In vivo findings demonstrate that 6-week and 12-week WBV stimulated osseointegration, bone ingrowth and bone formation rate of pTi in rabbit femoral bone defects via μCT, histological and histomorphometric analyses. WBV induced higher ALP, OCN, Runx2, BMP2, Wnt3a, Lrp6 and β-catenin, and lower Sost and RANKL/OPG gene expression in rabbit femora. Our findings demonstrate that WBV promotes osteogenesis and osseointegration of pTi via its anabolic effect and potential anti-catabolic activity, and imply the promising potential of WBV for enhancing the repair efficiency and quality of pTi in osseous defects. PMID:26601709

  20. Particle acceleration

    NASA Technical Reports Server (NTRS)

    Vlahos, L.; Machado, M. E.; Ramaty, R.; Murphy, R. J.; Alissandrakis, C.; Bai, T.; Batchelor, D.; Benz, A. O.; Chupp, E.; Ellison, D.

    1986-01-01

    Data is compiled from Solar Maximum Mission and Hinothori satellites, particle detectors in several satellites, ground based instruments, and balloon flights in order to answer fundamental questions relating to: (1) the requirements for the coronal magnetic field structure in the vicinity of the energization source; (2) the height (above the photosphere) of the energization source; (3) the time of energization; (4) transistion between coronal heating and flares; (5) evidence for purely thermal, purely nonthermal and hybrid type flares; (6) the time characteristics of the energization source; (7) whether every flare accelerates protons; (8) the location of the interaction site of the ions and relativistic electrons; (9) the energy spectra for ions and relativistic electrons; (10) the relationship between particles at the Sun and interplanetary space; (11) evidence for more than one acceleration mechanism; (12) whether there is single mechanism that will accelerate particles to all energies and also heat the plasma; and (13) how fast the existing mechanisms accelerate electrons up to several MeV and ions to 1 GeV.

  1. Plasma accelerator

    DOEpatents

    Wang, Zhehui; Barnes, Cris W.

    2002-01-01

    There has been invented an apparatus for acceleration of a plasma having coaxially positioned, constant diameter, cylindrical electrodes which are modified to converge (for a positive polarity inner electrode and a negatively charged outer electrode) at the plasma output end of the annulus between the electrodes to achieve improved particle flux per unit of power.

  2. Accelerated Achievement

    ERIC Educational Resources Information Center

    Ford, William J.

    2010-01-01

    This article focuses on the accelerated associate degree program at Ivy Tech Community College (Indiana) in which low-income students will receive an associate degree in one year. The three-year pilot program is funded by a $2.3 million grant from the Lumina Foundation for Education in Indianapolis and a $270,000 grant from the Indiana Commission…

  3. ACCELERATION INTEGRATOR

    DOEpatents

    Pope, K.E.

    1958-01-01

    This patent relates to an improved acceleration integrator and more particularly to apparatus of this nature which is gyrostabilized. The device may be used to sense the attainment by an airborne vehicle of a predetermined velocitv or distance along a given vector path. In its broad aspects, the acceleration integrator utilizes a magnetized element rotatable driven by a synchronous motor and having a cylin drical flux gap and a restrained eddy- current drag cap deposed to move into the gap. The angular velocity imparted to the rotatable cap shaft is transmitted in a positive manner to the magnetized element through a servo feedback loop. The resultant angular velocity of tae cap is proportional to the acceleration of the housing in this manner and means may be used to measure the velocity and operate switches at a pre-set magnitude. To make the above-described dcvice sensitive to acceleration in only one direction the magnetized element forms the spinning inertia element of a free gyroscope, and the outer housing functions as a gimbal of a gyroscope.

  4. Synergistic effects of surface chemistry and topologic structure from modified microarc oxidation coatings on Ti implants for improving osseointegration.

    PubMed

    Zhou, Rui; Wei, Daqing; Cao, Jianyun; Feng, Wei; Cheng, Su; Du, Qing; Li, Baoqiang; Wang, Yaming; Jia, Dechang; Zhou, Yu

    2015-04-29

    Microarc oxidation (MAO) coating containing Ca, P, Si, and Na elements on a titanium (Ti) implant has been steam-hydrothermally treated and further mediated by post-heat treatment to overcome the compromised bone-implant integration. The bone regeneration, bone-implant contact, and biomechanical push-out force of the modified Ti implants are discussed thoroughly in this work. The best in vivo performances for the steam-hydrothermally treated one is attributed to the synergistic effects of surface chemistry and topologic structure. Through post-heat treatment, we can decouple the effects of surface chemistry and the nanoscale topologic structure easily. Attributed to the excellent in vivo performance of the surface-modified Ti implant, the steam-hydrothermal treatment could be a promising strategy to improve the osseointegration of the MAO coating covered Ti implant.

  5. Orthodontic Microimplants Assisted Intrusion of Supra-erupted Maxillary Molar Enabling Osseointegrated Implant Supported Mandibular Prosthesis: Case Reports.

    PubMed

    Rai, Deepak; Bhasin, Saranjeet Singh; Rai, Sheetal

    2014-12-01

    Loss of mandibular molars, when not replaced in time, are usually associated with overeruption of maxillary molars. To provide prosthetic replacement for missing lower posteriors, over erupted maxillary teeth have been intruded in past with great difficulty in adults with conventional orthodontics, along with associated problems of root resorption. Currently orthodontic microimplants provide stable intraoral anchorage, allow predictable maxillary molar intrusion enabling reestablishment of functional posterior occlusion with mandibular implant supported prosthesis, thereby reducing need for prosthetic crown reduction in maxillary arch. The added advantage of microimplant is it enables use of sectional appliance in area of concern instead of full arch bracketed appliance which an adult may not accept. The case reports demonstrates, overerupted maxillary molars were intruded using orthodontic microimplants to enable prosthetic rehabilitation of mandibular dentition by osseointegrated implant supported prosthesis. The second case report also demonstrates use of CBCT scan in planning and execution.

  6. Particle Accelerators in China

    NASA Astrophysics Data System (ADS)

    Zhang, Chuang; Fang, Shouxian

    As the special machines that can accelerate charged particle beams to high energy by using electromagnetic fields, particle accelerators have been widely applied in scientific research and various areas of society. The development of particle accelerators in China started in the early 1950s. After a brief review of the history of accelerators, this article describes in the following sections: particle colliders, heavy-ion accelerators, high-intensity proton accelerators, accelerator-based light sources, pulsed power accelerators, small scale accelerators, accelerators for applications, accelerator technology development and advanced accelerator concepts. The prospects of particle accelerators in China are also presented.

  7. Compact accelerator

    DOEpatents

    Caporaso, George J.; Sampayan, Stephen E.; Kirbie, Hugh C.

    2007-02-06

    A compact linear accelerator having at least one strip-shaped Blumlein module which guides a propagating wavefront between first and second ends and controls the output pulse at the second end. Each Blumlein module has first, second, and third planar conductor strips, with a first dielectric strip between the first and second conductor strips, and a second dielectric strip between the second and third conductor strips. Additionally, the compact linear accelerator includes a high voltage power supply connected to charge the second conductor strip to a high potential, and a switch for switching the high potential in the second conductor strip to at least one of the first and third conductor strips so as to initiate a propagating reverse polarity wavefront(s) in the corresponding dielectric strip(s).

  8. Gastrodin inhibits osteoclastogenesis via down-regulating the NFATc1 signaling pathway and stimulates osseointegration in vitro.

    PubMed

    Zhou, Feng; Shen, Yi; Liu, Bo; Chen, Xia; Wan, Lu; Peng, Dan

    2017-03-18

    Bone is a rigid yet dynamic organ, and this dynamism is mediated by the delicate balance between osteoclastic bone resorption and osteoblastic bone formation. However, excessive activation of osteoclasts is responsible for many bone diseases such as osteoporosis, Paget disease, and tumor bone metastasis. Agents that could inhibit osteoclast formation or function are regarded as promising alternatives to treat osteoclast-related diseases. Recently, traditional Chinese medicine has attracted attention because of its multiple activities in bone metabolism. Among them, gastrodin has been reported as an anti-osteoporosis agent that reduces reactive oxygen species. However, the direct action of gastrodin on osteoclast differentiation and bone resorption, and its underlying molecular mechanism, remain unknown. In this study, we investigated the effects of gastrodin on receptor activator NF-κB ligand (RANKL)-activated osteoclasts formation and bone resorption. Our results showed that gastrodin retarded RANKL-induced osteoclast differentiation efficiently by downregulating transcriptional and translational expression of nuclear factor of activated T cells cl (NFATc1), a major factor in RANKL-mediated osteoclastogenesis. Meanwhile, gastrodin prevented osteoclast maturation and migration by inhibiting the gene expression of dendrocyte expressed seven transmembrane protein (DC-STAMP), an osteoclastic-specific gene that controls cells fusion and movement. And gastrodin prevented RANKL-induced osteoclastic bone erosion in vitro. In addition, gastrodin also stimulated bone mesenchymal stem cell (BMSC) spreading and osseointegration in titanium plate. In summary, gastrodin could prevent osteoclasts formation and bone resorption via blockage of NFATc1 activity, and stimulate osseointegration in vitro. Gastrodin could be developed as a potent phytochemical candidate to treat osteolytic diseases.

  9. The role of well-defined nanotopography of titanium implants on osseointegration: cellular and molecular events in vivo

    PubMed Central

    Karazisis, Dimitrios; Ballo, Ahmed M; Petronis, Sarunas; Agheli, Hossein; Emanuelsson, Lena; Thomsen, Peter; Omar, Omar

    2016-01-01

    Purpose Mechanisms governing the cellular interactions with well-defined nanotopography are not well described in vivo. This is partly due to the difficulty in isolating a particular effect of nanotopography from other surface properties. This study employed colloidal lithography for nanofabrication on titanium implants in combination with an in vivo sampling procedure and different analytical techniques. The aim was to elucidate the effect of well-defined nanotopography on the molecular, cellular, and structural events of osseointegration. Materials and methods Titanium implants were nanopatterned (Nano) with semispherical protrusions using colloidal lithography. Implants, with and without nanotopography, were implanted in rat tibia and retrieved after 3, 6, and 28 days. Retrieved implants were evaluated using quantitative polymerase chain reaction, histology, immunohistochemistry, and energy dispersive X-ray spectroscopy (EDS). Results Surface characterization showed that the nanotopography was well defined in terms of shape (semispherical), size (79±6 nm), and distribution (31±2 particles/µm2). EDS showed similar levels of titanium, oxygen, and carbon for test and control implants, confirming similar chemistry. The molecular analysis of the retrieved implants revealed that the expression levels of the inflammatory cytokine, TNF-α, and the osteoclastic marker, CatK, were reduced in cells adherent to the Nano implants. This was consistent with the observation of less CD163-positive macrophages in the tissue surrounding the Nano implant. Furthermore, periostin immunostaining was frequently detected around the Nano implant, indicating higher osteogenic activity. This was supported by the EDS analysis of the retrieved implants showing higher content of calcium and phosphate on the Nano implants. Conclusion The results show that Nano implants elicit less periimplant macrophage infiltration and downregulate the early expression of inflammatory (TNF-α) and

  10. Low-level laser therapy affects osseointegration in titanium implants: resonance frequency, removal torque, and histomorphometric analysis in rabbits

    PubMed Central

    2016-01-01

    Objectives The purpose of this study was to investigate the effects of low-level laser therapy (LLLT) with a diode gallium-aluminum-arsenide (Ga-Al-As) low-level laser device on the healing and attachment of titanium implants in bone. Materials and Methods Thirteen New Zealand white male rabbits weighing 3.0±0.5 kg were used for this study. Dental titanium implants (3.75 mm in diameter and 8.5 mm in length, US II RBM plus fixture; Osstem, Seoul, Korea) were implanted into both femurs of each rabbit. The rabbits were randomly divided into a LLLT group and a control group. The LLLT was initiated immediately after surgery and then repeated daily for 7 consecutive days in the LLLT group. Six weeks and 12 weeks after implantation, we evaluated and compared the osseointegration of the LLLT group and control group, using histomorphometric analysis, removal torque testing, and resonance frequency analysis (RFA). The results were statistically significant when the level of probability was 0.05 or less based on a non-parametric Mann-Whitney U-test. Results The implant survival rate was about 96%. Histologically and histomorphometrically, we observed that the titanium implants were more strongly attached in LLLT group than in control group. However, there was no significant difference between the LLLT group and control group in removal torque or RFA. Conclusion Histologically, LLLT might promote cell-level osseointegration of titanium implants, but there was no statistically significant effects. PMID:26904488

  11. Effect of a local, one time, low-dose injection of zoledronic acid on titanium implant osseointegration in ovariectomized rats

    PubMed Central

    Ying, Gao; Bo, Lian; Yanjun, Jiao; Lina, Wu

    2016-01-01

    Introduction Local application of bisphosphonates has been proven to be safer than systemic administration to promote implant fixation. The objective of this study was to introduce such a simple, convenient and efficient method to enhance titanium (Ti) implant osseointegration in ovariectomized (OVX) rats. Material and methods Twenty female Sprague-Dawley rats sequentially underwent bilateral ovariectomy and tibia implantation, and injection of 30 µg/implant zoledronic acid (ZOL) at the site of implantation was performed. At the end of the study, the tibiae, mandibles, femurs and vertebrae were harvested for dual energy X-ray absorptiometry, histology and micro-computed tomography examination. Results Ovariectomized rats showed poor bone density, bone mass and trabecular microstructure. OVX + ZOL rats were characterized by significantly improved peri-implant bone area (1.72-fold), bone contact (2.30-fold), bone mineral density (1.57-fold) and bone mineral content (1.67-fold), as well as moderately increased bone volume to total volume ratio (1.34-fold), percentage osteointegration (1.54-fold), connectivity density (1.45-fold), and trabecular number (1.43-fold), but decreased trabecular separation (57.69%) when compared with the control levels (p < 0.05). No histological signs of jaw osteonecrosis were observed in the rats treated with ZOL, and there was no significant difference between the OVX group and OVX + ZOL group in the bone mass of the mandible, femur and 5th lumbar vertebra (p > 0.05). In addition, the overproduction of osteoporosis-induced advanced glycation end-products (AGEs) was completely prevented by local treatment with 30 µg/implant ZOL. Conclusions A local, one time, low-dose injection of ZOL at the site of implantation is able to promote the osseointegration of Ti implants following postmenopausal osteoporosis, and this action may be partly mediated by inhibition of the osteoporosis-induced AGE overproduction in the bone marrow. PMID:27695483

  12. Laser acceleration

    NASA Astrophysics Data System (ADS)

    Tajima, T.; Nakajima, K.; Mourou, G.

    2017-02-01

    The fundamental idea of Laser Wakefield Acceleration (LWFA) is reviewed. An ultrafast intense laser pulse drives coherent wakefield with a relativistic amplitude robustly supported by the plasma. While the large amplitude of wakefields involves collective resonant oscillations of the eigenmode of the entire plasma electrons, the wake phase velocity ˜ c and ultrafastness of the laser pulse introduce the wake stability and rigidity. A large number of worldwide experiments show a rapid progress of this concept realization toward both the high-energy accelerator prospect and broad applications. The strong interest in this has been spurring and stimulating novel laser technologies, including the Chirped Pulse Amplification, the Thin Film Compression, the Coherent Amplification Network, and the Relativistic Mirror Compression. These in turn have created a conglomerate of novel science and technology with LWFA to form a new genre of high field science with many parameters of merit in this field increasing exponentially lately. This science has triggered a number of worldwide research centers and initiatives. Associated physics of ion acceleration, X-ray generation, and astrophysical processes of ultrahigh energy cosmic rays are reviewed. Applications such as X-ray free electron laser, cancer therapy, and radioisotope production etc. are considered. A new avenue of LWFA using nanomaterials is also emerging.

  13. BICEP's acceleration

    SciTech Connect

    Contaldi, Carlo R.

    2014-10-01

    The recent Bicep2 [1] detection of, what is claimed to be primordial B-modes, opens up the possibility of constraining not only the energy scale of inflation but also the detailed acceleration history that occurred during inflation. In turn this can be used to determine the shape of the inflaton potential V(φ) for the first time — if a single, scalar inflaton is assumed to be driving the acceleration. We carry out a Monte Carlo exploration of inflationary trajectories given the current data. Using this method we obtain a posterior distribution of possible acceleration profiles ε(N) as a function of e-fold N and derived posterior distributions of the primordial power spectrum P(k) and potential V(φ). We find that the Bicep2 result, in combination with Planck measurements of total intensity Cosmic Microwave Background (CMB) anisotropies, induces a significant feature in the scalar primordial spectrum at scales k∼ 10{sup -3} Mpc {sup -1}. This is in agreement with a previous detection of a suppression in the scalar power [2].

  14. Advanced concepts for acceleration

    SciTech Connect

    Keefe, D.

    1986-07-01

    Selected examples of advanced accelerator concepts are reviewed. Such plasma accelerators as plasma beat wave accelerator, plasma wake field accelerator, and plasma grating accelerator are discussed particularly as examples of concepts for accelerating relativistic electrons or positrons. Also covered are the pulsed electron-beam, pulsed laser accelerator, inverse Cherenkov accelerator, inverse free-electron laser, switched radial-line accelerators, and two-beam accelerator. Advanced concepts for ion acceleration discussed include the electron ring accelerator, excitation of waves on intense electron beams, and two-wave combinations. (LEW)

  15. Accelerators and the Accelerator Community

    SciTech Connect

    Malamud, Ernest; Sessler, Andrew

    2008-06-01

    In this paper, standing back--looking from afar--and adopting a historical perspective, the field of accelerator science is examined. How it grew, what are the forces that made it what it is, where it is now, and what it is likely to be in the future are the subjects explored. Clearly, a great deal of personal opinion is invoked in this process.

  16. Impact accelerations

    NASA Technical Reports Server (NTRS)

    Vongierke, H. E.; Brinkley, J. W.

    1975-01-01

    The degree to which impact acceleration is an important factor in space flight environments depends primarily upon the technology of capsule landing deceleration and the weight permissible for the associated hardware: parachutes or deceleration rockets, inflatable air bags, or other impact attenuation systems. The problem most specific to space medicine is the potential change of impact tolerance due to reduced bone mass and muscle strength caused by prolonged weightlessness and physical inactivity. Impact hazards, tolerance limits, and human impact tolerance related to space missions are described.

  17. Composite coating of 58S bioglass and hydroxyapatite on a poly (ethylene terepthalate) artificial ligament graft for the graft osseointegration in a bone tunnel

    NASA Astrophysics Data System (ADS)

    Li, Hong; Wu, Yang; Ge, Yunsheng; Jiang, Jia; Gao, Kai; Zhang, Pengyun; Wu, Lingxiang; Chen, Shiyi

    2011-09-01

    The purpose of this study was to determine the effect of the combination of hydroxyapatite (HA) and bioglass (BG) on polyethylene terephthalate (PET) artificial ligament graft osseointegration within the bone tunnel. The results of in vitro culturing of MC3T3-E1 mouse osteoblastic cells proved that this HA/BG composite coating can promote the cell compatibility of grafts. A rabbit extraarticular tendon-to-bone healing model was used to evaluate the effect of this composite coating on PET artificial ligaments in vivo. The final results demonstrated that HA/BG coating improved new bone formation at the graft-bone interface and increased the load-to-failure property of graft in bone tunnel compared to the control group at early time. The study has shown that HA/BG composite coating on the PET artificial ligament surface has a positive effect in the induction of artificial ligament osseointegration within the bone tunnel.

  18. Fabrication of an rhBMP-2 loaded porous β-TCP microsphere-hyaluronic acid-based powder gel composite and evaluation of implant osseointegration.

    PubMed

    Lee, Jae Hyup; Kim, Jungju; Baek, Hae-Ri; Lee, Kyung Mee; Seo, Jun-Hyuk; Lee, Hyun-Kyung; Lee, A-Young; Zheng, Guang Bin; Chang, Bong-Soon; Lee, Choon-Ki

    2014-09-01

    Methods to improve osseointegration that include implantation of rhBMP-2 with various kinds of carriers are currently of considerable interest. The present study was conducted to evaluate if the rhBMP-2 loaded β-TCP microsphere-hyaluronic acid-based powder-like hydrogel composite (powder gel) can act as an effective rhBMP-2 carrier for implantation in host bone with a bone defect or poor bone quality. The release pattern for rhBMP-2 was then evaluated against an rhBMP-2-loaded collagen sponge as a control group. Dental implants were also inserted into the tibias of three groups of rabbits: an rhBMP-2 (200 µg) loaded powder gel composite implanted group, an implant only group, and a powder gel implanted group. Micro-CT and histology of the implanted areas were carried out four weeks later. The rhBMP-2 powder gel released less rhBMP-2 than the collagen sponge, but it continued a slow release for more than 7 days. The rhBMP-2 powder gel composite improved osseointegration of the dental implant by increasing the amount of new bone formation in the implant pitch and it improved the bone quality and bone quantity of new bone. The histology results indicated that the rhBMP-2 powder gel composite improved the osseointegration in the cortical bone as well as the marrow space along the fixture. The bone-to-implant contact ratio of the rhBMP-2 (200 µg) loaded powder gel composite implanted group was significantly higher than those of the implant only group and the powder gel implanted group. The powder gel appeared to be a good carrier and could release rhBMP-2 slowly to promote the formation of new bone following implantation in a bone defect, thereby improving implant osseointegration.

  19. Accelerator system and method of accelerating particles

    NASA Technical Reports Server (NTRS)

    Wirz, Richard E. (Inventor)

    2010-01-01

    An accelerator system and method that utilize dust as the primary mass flux for generating thrust are provided. The accelerator system can include an accelerator capable of operating in a self-neutralizing mode and having a discharge chamber and at least one ionizer capable of charging dust particles. The system can also include a dust particle feeder that is capable of introducing the dust particles into the accelerator. By applying a pulsed positive and negative charge voltage to the accelerator, the charged dust particles can be accelerated thereby generating thrust and neutralizing the accelerator system.

  20. Pulsed electromagnetic fields promote osteogenesis and osseointegration of porous titanium implants in bone defect repair through a Wnt/β-catenin signaling-associated mechanism

    PubMed Central

    Jing, Da; Zhai, Mingming; Tong, Shichao; Xu, Fei; Cai, Jing; Shen, Guanghao; Wu, Yan; Li, Xiaokang; Xie, Kangning; Liu, Juan; Xu, Qiaoling; Luo, Erping

    2016-01-01

    Treatment of osseous defects remains a formidable clinical challenge. Porous titanium alloys (pTi) have been emerging as ideal endosseous implants due to the excellent biocompatibility and structural properties, whereas inadequate osseointegration poses risks for unreliable long-term implant stability. Substantial evidence indicates that pulsed electromagnetic fields (PEMF), as a safe noninvasive method, inhibit osteopenia/osteoporosis experimentally and clinically. We herein investigated the efficiency and potential mechanisms of PEMF on osteogenesis and osseointegration of pTi in vitro and in vivo. We demonstrate that PEMF enhanced cellular attachment and proliferation, and induced well-organized cytoskeleton for in vitro osteoblasts seeded in pTi. PEMF promoted gene expressions in Runx2, OSX, COL-1 and Wnt/β-catenin signaling. PEMF-stimulated group exhibited higher Runx2, Wnt1, Lrp6 and β-catenin protein expressions. In vivo results via μCT and histomorphometry show that 6-week and 12-week PEMF promoted osteogenesis, bone ingrowth and bone formation rate of pTi in rabbit femoral bone defect. PEMF promoted femoral gene expressions of Runx2, BMP2, OCN and Wnt/β-catenin signaling. Together, we demonstrate that PEMF improve osteogenesis and osseointegration of pTi by promoting skeletal anabolic activities through a Wnt/β-catenin signaling-associated mechanism. PEMF might become a promising biophysical modality for enhancing the repair efficiency and quality of pTi in bone defect. PMID:27555216

  1. The effect of APH treatment on surface bonding and osseointegration of Ti-6Al-7Nb implants: an in vitro and in vivo study.

    PubMed

    Nguyen, Thuy-Duong Thi; Moon, So-Hee; Oh, Tae-Ju; Park, Il-Song; Lee, Min-Ho; Bae, Tae-Sung

    2015-04-01

    This study investigated the effects of anodization-cyclic precalcification-heat (APH) treatment on the bonding ability of Ca-P coating to the parent metal and osseointegration of Ti-6Al-7Nb implants. Eighteen Ti-6Al-7Nb discs, 9 untreated and 9 APH-treated, were cultured with osteoblast cells in vitro, and the cellular differentiation ability was assayed at 1, 2, and 3 weeks. For in vivo testing, 28 Ti-6Al-7Nb implants (14 implants of each group) were inserted to rat tibias, and after each 4 and 6 weeks of implantation, bone bonding, and osseointegration were evaluated through removal torque and histological analysis. Osteoblast-culturing showed twice as much of the alkaline phosphatase activity on the treated surface at 3 weeks than on the untreated surface (p < 0.05). The treated implants exhibited higher removal torque values than the untreated ones (15.5 vs. 1.8 Ncm at 4 weeks and 19.7 vs. 2.6 Ncm at 6 weeks, p < 0.05). Moreover, the excellent bonding quality of coats was confirmed by the existence of cohesive fractures on the surface of removed APH implants (field emission scanning electron microscopy and histological observation). Within the limits of this study, it can be concluded that the APH treatment significantly enhanced osseointegration of the Ti-6Al-7Nb implant, with the stable bonding between the coating and the implant surface.

  2. Semaphorin 3A-modified adipose-derived stem cell sheet may improve osseointegration in a type 2 diabetes mellitus rat model.

    PubMed

    Fang, Kaixiu; Song, Wen; Wang, Lifeng; Xu, Xiaoru; Tan, Naiwen; Zhang, Sijia; Wei, Hongbo; Song, Yingliang

    2016-09-01

    Although titanium (Ti) implants are considered to be an optimal choice for the replacement of missing teeth, it remains difficult to obtain sufficient osseointegration in patients with type 2 diabetes mellitus (T2DM). The present study aimed to investigate whether adipose-derived stem cells (ASCs) may be used to improve Ti implant osseointegration in T2DM conditions with the addition of semaphorin 3A (Sema3A), a recently identified osteoprotective protein. Cell morphology was observed using a scanning electron microscope. Cell proliferation was determined using Cell Counting Kit‑8. Osteogenic differentiation was confirmed by the staining of alkaline phosphatase, collagen secretion and calcium deposition. An in vivo evaluation was performed in the T2DM rat model, which was induced by a high‑fat diet and a low‑dose streptozotocin intraperitoneal injection. A Sema3A‑modified ASC sheet was wrapped around the Ti implant, which was subsequently inserted into the tibia. The rats were then exposed to Sema3A stimulation. The morphology and proliferation ability of ASCs remained unchanged; however, their osteogenic differentiation ability was increased. Micro‑computed tomography scanning and histological observations confirmed that formation of new bone was improved with the use of the Sema3A-modified ASCs sheet. The present study indicated that the Sema3A‑modified ASCs sheet may be used to improve osseointegration under T2DM conditions.

  3. Semaphorin 3A-modified adipose-derived stem cell sheet may improve osseointegration in a type 2 diabetes mellitus rat model

    PubMed Central

    Fang, Kaixiu; Song, Wen; Wang, Lifeng; Xu, Xiaoru; Tan, Naiwen; Zhang, Sijia; Wei, Hongbo; Song, Yingliang

    2016-01-01

    Although titanium (Ti) implants are considered to be an optimal choice for the replacement of missing teeth, it remains difficult to obtain sufficient osseointegration in patients with type 2 diabetes mellitus (T2DM). The present study aimed to investigate whether adipose-derived stem cells (ASCs) may be used to improve Ti implant osseointegration in T2DM conditions with the addition of semaphorin 3A (Sema3A), a recently identified osteoprotective protein. Cell morphology was observed using a scanning electron microscope. Cell proliferation was determined using Cell Counting Kit-8. Osteogenic differentiation was confirmed by the staining of alkaline phosphatase, collagen secretion and calcium deposition. An in vivo evaluation was performed in the T2DM rat model, which was induced by a high-fat diet and a low-dose streptozotocin intraperitoneal injection. A Sema3A-modified ASC sheet was wrapped around the Ti implant, which was subsequently inserted into the tibia. The rats were then exposed to Sema3A stimulation. The morphology and proliferation ability of ASCs remained unchanged; however, their osteogenic differentiation ability was increased. Micro-computed tomography scanning and histological observations confirmed that formation of new bone was improved with the use of the Sema3A-modified ASCs sheet. The present study indicated that the Sema3A-modified ASCs sheet may be used to improve osseointegration under T2DM conditions. PMID:27484405

  4. Developing a quantitative measurement system for assessing heterotopic ossification and monitoring the bioelectric metrics from electrically induced osseointegration in the residual limb of service members.

    PubMed

    Isaacson, Brad M; Stinstra, Jeroen G; MacLeod, Rob S; Pasquina, Paul F; Bloebaum, Roy D

    2010-09-01

    Poor prosthetic fit is often the result of heterotopic ossification (HO), a frequent problem following blast injuries for returning service members. Osseointegration technology offers an advantage for individuals with significant HO and poor socket tolerance by using direct skeletal attachment of a prosthesis to the distal residual limb, but remains limited due to prolonged post-operative rehabilitation regimens. Therefore, electrical stimulation has been proposed as a catalyst for expediting skeletal attachment and the bioelectric effects of HO were evaluated using finite element analysis in 11 servicemen with transfemoral amputations. Retrospective computed tomography (CT) scans provided accurate reconstructions, and volume conductor models demonstrated the variability in residual limb anatomy and necessity for patient-specific modeling to characterize electrical field variance if patients were to undergo a theoretical osseointegration of a prosthesis. In this investigation, the volume of HO was statistically significant when selecting the optimal potential difference for enhanced skeletal fixation, since higher HO volumes required increased voltages at the periprosthetic bone (p = 0.024, r = 0.670). Results from Spearman's rho correlations also indicated that the age of the subject and volume of HO were statistically significant and inversely proportional, in which younger service members had a higher frequency of HO (p = 0.041, r = -0.622). This study demonstrates that the volume of HO and age may affect the voltage threshold necessary to improve current osseointegration procedures.

  5. A new adaptive method to filter terrestrial laser scanner point clouds using morphological filters and spectral information to conserve surface micro-topography

    NASA Astrophysics Data System (ADS)

    Rodríguez-Caballero, E.; Afana, A.; Chamizo, S.; Solé-Benet, A.; Canton, Y.

    2016-07-01

    Terrestrial laser scanning (TLS), widely known as light detection and ranging (LiDAR) technology, is increasingly used to provide highly detailed digital terrain models (DTM) with millimetric precision and accuracy. In order to generate a DTM, TLS data has to be filtered from undesired spurious objects, such as vegetation, artificial structures, etc., Early filtering techniques, successfully applied to airborne laser scanning (ALS), fail when applied to TLS data, as they heavily smooth the terrain surface and do not retain their real morphology. In this article, we present a new methodology for filtering TLS data based on the geometric and radiometric properties of the scanned surfaces. This methodology was built on previous morphological filters that select the minimum point height within a sliding window as the real surface. However, contrary to those methods, which use a fixed window size, the new methodology operates under different spatial scales represented by different window sizes, and can be adapted to different types and sizes of plants. This methodology has been applied to two study areas of differing vegetation type and density. The accuracy of the final DTMs was improved by ∼30% under dense canopy plants and over ∼40% on the open spaces between plants, where other methodologies drastically underestimated the real surface heights. This resulted in more accurate representation of the soil surface and microtopography than up-to-date techniques, eventually having strong implications in hydrological and geomorphological studies.

  6. Acceleration modules in linear induction accelerators

    NASA Astrophysics Data System (ADS)

    Wang, Shao-Heng; Deng, Jian-Jun

    2014-05-01

    The Linear Induction Accelerator (LIA) is a unique type of accelerator that is capable of accelerating kilo-Ampere charged particle current to tens of MeV energy. The present development of LIA in MHz bursting mode and the successful application into a synchrotron have broadened LIA's usage scope. Although the transformer model is widely used to explain the acceleration mechanism of LIAs, it is not appropriate to consider the induction electric field as the field which accelerates charged particles for many modern LIAs. We have examined the transition of the magnetic cores' functions during the LIA acceleration modules' evolution, distinguished transformer type and transmission line type LIA acceleration modules, and re-considered several related issues based on transmission line type LIA acceleration module. This clarified understanding should help in the further development and design of LIA acceleration modules.

  7. Muscle activity during stance phase of walking: comparison of males with transfemoral amputation with osseointegrated fixations to nondisabled male volunteers.

    PubMed

    Pantall, Annette; Ewins, David

    2013-01-01

    A recent development in prosthetics is the osseointegrated fixation (OF), with improvements in comfort, fatigue, hip movement, and ease of prosthetic attachment reported. However, little information is available regarding muscle function. This study reports on selected gait parameters of the residual limb during the stance phase of level overground walking, focusing on muscle activity. Five males with transfemoral amputation (TFA) with OFs were recruited. Ground reaction force (GRF), lower-limb kinematics, and surface electromyography (sEMG) from residual-limb muscles were recorded. sEMG data were also collected from a group of 10 nondisabled male subjects. Interstance variability of gait parameters was assessed by coefficient of multiple correlations. Repeatability of GRF and hip kinematics was high, whereas repeatability of the sEMG was low for four of the five individuals with TFA. Interstance variability of the sEMG for gluteus medius (GMED) was significantly greater in the group with TFA. The main difference in sEMG between the groups was the phase, with GMED and adductor magnus displaying greater differences than their counterparts in the nondisabled group. Results demonstrate that muscles in the residual limb retain aspects of their previous functional pattern.

  8. The Evaluation of Daily Life Activities after Application of an Osseointegrated Prosthesis Fixation in a Bilateral Transfemoral Amputee

    PubMed Central

    Schalk, Stephanie A.F.; Jonkergouw, Niels; van der Meer, Fred; Swaan, Willem M.; Aschoff, Horst-H.; van der Wurff, Peter

    2015-01-01

    Abstract Individuals with a transfemoral amputation (TFA) may experience limitations in daily life due to reduced mobility and prosthesis-related problems. An osseointegrated prosthesis fixation (OPF) procedure in amputees might contribute to a solution for patients with short stumps or socket-related problems. To date, no study has specifically described the application of an OPF procedure in individuals with a TFA. This study evaluated the level of daily life activities of a 21-year old service member with a bilateral TFA and cerebral trauma. Due to a short stump length and coordination problems, an OPF procedure was deemed the most suitable option. The result of this procedure and the rehabilitation program showed an increased mobility and satisfaction as obtained by the assessment of life habits questionnaire (LIFE-H) and lower extremity functional scale. The participant was able to walk short distances and the Genium knee provided a stance position. Stair ambulation is impossible because of inadequate muscle capacity. In this specific case we conclude that the quality of life improved through the use of an OPF. However, OPF might not be the appropriate device for every individual with TFA, due to varying bone compositions, co-morbidities, and limited clinical experience and unknown long-term effects. PMID:26356693

  9. Load on osseointegrated fixation of a transfemoral amputee during a fall: Determination of the time and duration of descent.

    PubMed

    Frossard, Laurent Alain

    2010-12-01

    Mitigation of fall-related injuries for populations of transfemoral amputees fitted with a socket or an osseointegrated fixation is challenging. Wearing a protective device fitted within the prosthesis might be a possible solution, provided that issues with automated fall detection and time of deployment of the protective mechanism are solved. The first objective of this study was to give some examples of the times and durations of descent during a real forward fall of a transfemoral amputee that occurred inadvertently while attending a gait measurement session to assess the load applied on the residuum. The second objective was to present five semi-automated methods of detection of the time of descent using the load data. The load was measured directly at 200 Hz using a six-channel transducer. The average time and duration of descent were 242 ± 42 ms (145-310 ms) and 619 ± 42 ms (550-715 ms), respectively. This study demonstrated that the transition between walking and falling was characterized by times of descent that occurred sequentially. The sensitivity and specificity of an automated algorithm might be improved by combining several methods of detection based on the deviation of the loads measured from their own trends and from a template previously established.

  10. Peri-implant evaluation of osseointegrated implants subjected to orthodontic forces: results after three years of functional loading

    PubMed Central

    Marins, Bruna de Rezende; Pramiu, Suy Ellen; Busato, Mauro Carlos Agner; Marchi, Luiz Carlos; Togashi, Adriane Yaeko

    2016-01-01

    ABSTRACT Objective: The objective of this study was to clinically and radiographically assess the peri-implant conditions of implants used as orthodontic anchorage. Methods: Two groups were studied: 1) a test group in which osseointegrated implants were used as orthodontic anchorage, with the application of 200-cN force; and 2) a control group in which implants were not subjected to orthodontic force, but supported a screw-retained prosthesis. Clinical evaluations were performed three, six and nine months after prosthesis installation and 1- and 3-year follow-up examinations. Intraoral periapical radiographs were obtained 30 days after surgical implant placement, at the time of prosthesis installation, and one, two and three years thereafter. The results were compared by Kruskal-Wallis test. Results: There was no statistically significant difference in clinical probing depth (p = 0.1078) or mesial and distal crestal bone resorption (p = 0.1832) during the study period. After three years of follow-up, the mean probing depth was 2.21 mm for the control group and 2.39 mm for the test group. The implants of the control group showed a mean distance between the bone crest and implant shoulder of 2.39 mm, whereas the implants used as orthodontic anchorage showed a mean distance of 2.58 mm at the distal site. Conclusion: Results suggest that the use of stable intraoral orthodontic anchorage did not compromise the health of peri-implant tissues or the longevity of the implant. PMID:27275618

  11. Osseointegration of Prostheses on the Stapes Footplate: Evaluation of the Biomechanical Feasibility by Using a Finite Element Model

    PubMed Central

    Berner, Matthias; Bornitz, Matthias; Beleites, Thomas; Ney, Michael; Zahnert, Thomas

    2007-01-01

    Restoration of hearing is one of the main issues of tympanoplasty. Depending on the extent of destruction, the ossicular chain is partially or totally replaced by prostheses. In the unfavorable event of complete ossicular chain destruction with only the stapes footplate remaining in the oval niche, implanting of a columella prosthesis represents the gold standard. Besides ventilation problems, the main causes of unsatisfactory hearing results are dislocation of the prosthesis and poor coupling to the footplate. Therefore, stable fixation of prostheses is desirable but has not been realized to date. In line with our experimental intention to realize a bony prosthesis fixation on the footplate, we designed a finite element model for the simulation of the interacting forces once an osseointegration was achieved. These preliminary results predict the mechanical feasibility of this endeavor and the necessary general preconditions, which have to be carefully considered. A specially designed titanium prosthesis anchor needs a minimal bony fixation of 104 μm accretion height on the footplate to withstand all emerging forces. Therefore, providing a sort of artificial stapedial suprastructure in the form of a firm, preferably bony, integration of a prosthesis anchor on the footplate seems to be realistic and worthwhile from a mechanical and medical point of view. PMID:17828428

  12. Progress on plasma accelerators

    SciTech Connect

    Chen, P.

    1986-05-01

    Several plasma accelerator concepts are reviewed, with emphasis on the Plasma Beat Wave Accelerator (PBWA) and the Plasma Wake Field Accelerator (PWFA). Various accelerator physics issues regarding these schemes are discussed, and numerical examples on laboratory scale experiments are given. The efficiency of plasma accelerators is then revealed with suggestions on improvements. Sources that cause emittance growth are discussed briefly.

  13. Clinical evaluation of 262 osseointegrated implants placed in sites grafted with calcium phosphosilicate putty: a retrospective study.

    PubMed

    Babbush, Charles A; Kanawati, Ali

    2015-02-01

    Along with the widespread use of dental implants, regenerative procedures have become an indispensable tool for implant surgeons in managing residual ridges and the surrounding bone. Putty bone grafts have significantly superior handling characteristics in comparison to particulates. These include ease of placement, enhanced particle containment, and a viscous consistency that has allowed for unique delivery systems to be developed. The aim of this study was to report the clinical efficacy of calcium phosphosilicate (CPS) putty in a wide variety of indications related to implant reconstruction and to report the survival rate of implants placed in these grafted sites. The CPS putty was used as the graft material of choice. Treatments were categorized into following groups: extraction graft, extraction with immediate implant placement, all-on-four concept, peri-implantitis treatment, bone augmentation before implant placement, implant replacement graft, and grafting around implant placed in resorbed ridges. Included in the analysis were 65 patients (36 men, 29 women) with a mean age of 63 ± 12 years. In total, 262 implants were placed. Four implants were diagnosed with peri-implantitis and were treated as described in category 4, for a total of 266 grafted sites. Two implants from the extraction graft category and 3 implants from the all-on-four group were lost and replaced with successfully osseointegrated implants during a mean study follow-up period of 12.24 ± 2.32 months. The implant success rate at 1 year was 98.1% (257/262). Based on results of this large-scale, retrospective study we conclude that (1) the use of putty bone grafts can simplify bone-grafting procedures and reduce intraoperative time in various grafting indications, (2) this study verified the efficacy of a CPS putty bone graft biomaterial in a large array of implant-related surgical indications, and (3) implants placed in sites grafted with CPS putty yield very high survival rates.

  14. Effects of hydrofluoric acid and anodised micro and micro/nano surface implants on early osseointegration in rats.

    PubMed

    Li, Yongfeng; Gao, Yuan; Shao, Bo; Xiao, Jianrui; Hu, Kaijin; Kong, Liang

    2012-12-01

    Our aim was to evaluate the effects of hydrofluoric acid and anodised micro and micro/nano surface implants on bony ingrowth in the earliest stage of implantation in rats. Sixty cylindrical screwed titanium alloy implants with machined, micro, and hierarchical hybrid micro/nano surfaces (n=20 in each group) were inserted into the distal femurs of 30 female Sprague-Dawley rats. In vivo microcomputed tomography (micro CT) was used to assess microarchitectural changes in the bone around the implants 2 weeks after implantation. All the animals were then killed and the femurs with implants harvested for histological analysis and pull-out testing. Micro CT analysis showed that the trabecular thickness and the bone:volume ratio (bone volume:total volume) (BV:TV) increased significantly in the micro/nano group compared with the other two groups, while the trabecular separation decreased significantly in the micro/nano group compared with the machined group. The mean (SD) bone-implant contacts (%) were 38.94 (9.48), 41.67 (8.71), and 51.49 (12.49) in the machined, micro, and micro/nano groups, respectively. The maximum pull-out forces (N) were 64.95 (6.11), 71.45 (7.15), and 81.90 (13.1), respectively. Both bone-implant contacts and maximum pull-out forces were significantly higher in the micro/nano group, but there was no significant difference between the micro group and the machined group. These data indicate that the hierarchical hybrid micro/nano surface of the implant can promote osseointegration in the earliest stage of implantation, and may be a promising option for further clinical use.

  15. Impact of implant diameter and length on stress distribution in osseointegrated implants: A 3D FEA study

    PubMed Central

    Eazhil, R.; Swaminathan, Siva Vadivel; Gunaseelan, Madhan; Kannan, G. Vijay; Alagesan, Chandrapandian

    2016-01-01

    Aims and Objectives: Dimension of dental implant is an important parameter which has a considerable impact on the biomechanical load transfer characters and its prognosis. Excessive stress in the bone–implant interface may result in the failure of the implant. The aim of this study was to evaluate the impact of implant diameter and length on neighboring tissues around the implant. The results of the study will help in developing a scientific methodology to select appropriate implant diameter and length. Materials and Methods: In this study, tapered implants of different diameter and length were numerically analyzed using bone–implant models developed from computed tomography generated images of mandible with osseointegrated implants. The impact of various diameters on stress distribution was examined using implants with a length of 13 mm and diameters of 3.5 mm, 4.3 mm and 5.0 mm. Implants with a diameter of 4.3 mm and lengths of 10 mm, 13 mm, 16 mm was developed to examine the impact of various implant length. All materials were assumed to be linearly elastic and isotropic. Masticatory load was applied in a natural direction, oblique to the occlusal plane. The Statistical Package for the Social Sciences software package was used for statistical analysis. Results: Maximum von Mises stresses were located around the implant neck. It was demonstrated that there was statistically significant decrease in von Mises stress as the implant diameter increased. Conclusion: Within the limitations of this study there was statistically significant decrease in von Mises stress as the implant diameter increased. PMID:28032053

  16. Cytocompatibility and early osseointegration of nanoTiO2-modified Ti-24 Nb-4 Zr-7.9 Sn surfaces.

    PubMed

    Liu, X H; Wu, L; Ai, H J; Han, Y; Hu, Y

    2015-03-01

    This study aimed to evaluate the cytocompatibility and early osseointegration of Ti-24 Nb-4 Zr-7.9 Sn (Ti-2448) surfaces that were modified with a nanoscale TiO2 coating. The coating was fabricated using a hydrothermal synthesis method to generate nanoTiO2/Ti-2448. The surface characteristics of the samples were evaluated using scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD). The cytotoxicity of the fabricated nanoTiO2/Ti-2448 was determined using MTT assays. The proliferation and alkaline phosphatase (ALP) activity of MC3T3-E1 osteoblasts cultured on nanoTiO2/Ti-2448 were compared with those cultured on Ti-2448. Disk-shaped implants were placed in Wistar rats. The histological sections were stained with haematoxylin and eosin (HE), and the histocompatibility was analysed at 4 and 12weeks post-implantation. Cylindrical implants were embedded in Japanese white rabbits, and the histological sections were stained with HE and anti-TGF-β1 to evaluate the histocompatibility and early osseointegration at 4, 12 and 26weeks post-implantation. NanoTiO2/Ti-2448 exhibited a rougher surface than did Ti-2448. NanoTiO2/Ti-2448 was determined to be non-cytotoxic. More osteoblasts and higher ALP activity were observed for nanoTiO2/Ti-2448 than Ti-2448 (p<0.05). Few inflammatory cells were detected around nanoTiO2/Ti-2448, and the expression of TGF-β1 on nanoTiO2/Ti-2448 peaked at earlier time than that on Ti-2448. The results indicate that the cytocompatibility and early osseointegration were enhanced by the nanoTiO2 coating.

  17. Effect of surface roughness on osteogenesis in vitro and osseointegration in vivo of carbon fiber-reinforced polyetheretherketone–nanohydroxyapatite composite

    PubMed Central

    Deng, Yi; Liu, Xiaochen; Xu, Anxiu; Wang, Lixin; Luo, Zuyuan; Zheng, Yunfei; Deng, Feng; Wei, Jie; Tang, Zhihui; Wei, Shicheng

    2015-01-01

    As United States Food and Drug Administration-approved implantable material, carbon fiber-reinforced polyetheretherketone (CFRPEEK) possesses an adjustable elastic modulus similar to cortical bone and is a prime candidate to replace surgical metallic implants. The bioinertness and inferior osteogenic properties of CFRPEEK, however, limit its clinical application as orthopedic/dental implants. In this study, CFRPEEK–nanohydroxyapatite ternary composites (PEEK/n-HA/CF) with variable surface roughness have been successfully fabricated. The effect of surface roughness on their in vitro cellular responses of osteoblast-like MG-63 cells (attachment, proliferation, apoptosis, and differentiation) and in vivo osseointegration is evaluated. The results show that the hydrophilicity and the amount of Ca ions on the surface are significantly improved as the surface roughness of composite increases. In cell culture tests, the results reveal that the cell proliferation rate and the extent of osteogenic differentiation of cells are a function of the size of surface roughness. The composite with moderate surface roughness significantly increases cell attachment/proliferation and promotes the production of alkaline phosphatase (ALP) activity and calcium nodule formation compared with the other groups. More importantly, the PEEK/n-HA/CF implant with appropriate surface roughness exhibits remarkably enhanced bioactivity and osseointegration in vivo in the animal experiment. These findings will provide critical guidance for the design of CFRPEEK-based implants with optimal roughness to regulate cellular behaviors, and to enhance biocompability and osseointegration. Meanwhile, the PEEK/n-HA/CF ternary composite with optimal surface roughness might hold great potential as bioactive biomaterial for bone grafting and tissue engineering applications. PMID:25733834

  18. Future accelerator technology

    SciTech Connect

    Sessler, A.M.

    1986-05-01

    A general discussion is presented of the acceleration of particles. Upon this foundation is built a categorization scheme into which all accelerators can be placed. Special attention is devoted to accelerators which employ a wake-field mechanism and a restricting theorem is examined. It is shown how the theorem may be circumvented. Comments are made on various acceleration schemes.

  19. ACCELERATION AND THE GIFTED.

    ERIC Educational Resources Information Center

    GIBSON, ARTHUR R.; STEPHANS, THOMAS M.

    ACCELERATION OF PUPILS AND SUBJECTS IS CONSIDERED A MEANS OF EDUCATING THE ACADEMICALLY GIFTED STUDENT. FIVE INTRODUCTORY ARTICLES PROVIDE A FRAMEWORK FOR THINKING ABOUT ACCELERATION. FIVE PROJECT REPORTS OF ACCELERATED PROGRAMS IN OHIO ARE INCLUDED. ACCELERATION IS NOW BEING REGARDED MORE FAVORABLY THAN FORMERLY, BECAUSE METHODS HAVE BEEN…

  20. Laser driven ion accelerator

    DOEpatents

    Tajima, Toshiki

    2005-06-14

    A system and method of accelerating ions in an accelerator to optimize the energy produced by a light source. Several parameters may be controlled in constructing a target used in the accelerator system to adjust performance of the accelerator system. These parameters include the material, thickness, geometry and surface of the target.

  1. Laser driven ion accelerator

    DOEpatents

    Tajima, Toshiki

    2006-04-18

    A system and method of accelerating ions in an accelerator to optimize the energy produced by a light source. Several parameters may be controlled in constructing a target used in the accelerator system to adjust performance of the accelerator system. These parameters include the material, thickness, geometry and surface of the target.

  2. The distribution of organic material and its contribution to the micro-topography of particles from wettable and water repellent soils

    NASA Astrophysics Data System (ADS)

    Bryant, Rob; Cheng, Shuying; Doerr, Stefan H.; Wright, Chris J.; Bayer, Julia V.; Williams, Rhodri P.

    2010-05-01

    repellency of a soil is the result of not only of particle surface chemistry and soil pore space geometry, but also of the micro-topography generated by organic material adsorbed on particle surfaces.

  3. Early osseointegration of implants with cortex-like TiO2 coatings formed by micro-arc oxidation: A histomorphometric study in rabbits.

    PubMed

    Zhou, Hong-Zhi; Li, Ya-da; Liu, Lin; Chen, Xiao-Dong; Wang, Wei-Qiang; Ma, Guo-Wu; Su, Yu-Cheng; Qi, Min; Shi, Bin

    2017-02-01

    In our previous studies, a novel cortex-like TiO2 coating was prepared on Ti surface through micro-arc oxidation (MAO) by using sodium tetraborate as electrolyte, and the effects of the coating on cell attachment were testified. This study aimed to investigate the effects of this cortex-like MAO coating on osseointegration. A sand-blasting and acid-etching (SLA) coating that has been widely used in clinical practice served as control. Topographical and chemical characterizations were conducted by scanning electron microscopy, energy dispersive X-ray spectrometer, X-ray diffraction, contact angle meter, and step profiler. Results showed that the cortex-like coating had microslots and nanopores and it was superhydrophilic, whereas the SLA surface was hydrophobic. The roughness of MAO was similar to that of SLA. The MAO and SLA implants were implanted into the femoral condyles of New Zealand rabbits to evaluate their in-vivo performance through micro-CT, histological analysis, and fluorescent labeling at the bone-implant interface four weeks after surgery. The micro-CT showed that the bone volume ratio and mean trabecular thickness were similar between MAO and SLA groups four weeks after implantation. Histological analysis and fluorescent labeling showed no significant differences in the bone-implant contact between the MAO and SLA surfaces. It was suggested that with micro/nanostructure and superhydrophilicity, the cortex-like MAO coating causes excellent osseointegration, holding a promise of an application to implant modification.

  4. Effects of rhBMP-2 on Sandblasted and Acid Etched Titanium Implant Surfaces on Bone Regeneration and Osseointegration: Spilt-Mouth Designed Pilot Study

    PubMed Central

    Kim, Nam-Ho; Lee, So-Hyoun; Ryu, Jae-Jun; Choi, Kyung-Hee; Huh, Jung-Bo

    2015-01-01

    This study was conducted to evaluate effects of rhBMP-2 applied at different concentrations to sandblasted and acid etched (SLA) implants on osseointegration and bone regeneration in a bone defect of beagle dogs as pilot study using split-mouth design. Methods. For experimental groups, SLA implants were coated with different concentrations of rhBMP-2 (0.1, 0.5, and 1 mg/mL). After assessment of surface characteristics and rhBMP-2 releasing profile, the experimental groups and untreated control groups (n = 6 in each group, two animals in each group) were placed in split-mouth designed animal models with buccal open defect. At 8 weeks after implant placement, implant stability quotients (ISQ) values were recorded and vertical bone height (VBH, mm), bone-to-implant contact ratio (BIC, %), and bone volume (BV, %) in the upper 3 mm defect areas were measured. Results. The ISQ values were highest in the 1.0 group. Mean values of VBH (mm), BIC (%), and BV (%) were greater in the 0.5 mg/mL and 1.0 mg/mL groups than those in 0.1 and control groups in buccal defect areas. Conclusion. In the open defect area surrounding the SLA implant, coating with 0.5 and 1.0 mg/mL concentrations of rhBMP-2 was more effective, compared with untreated group, in promoting bone regeneration and osseointegration. PMID:26504807

  5. Multi-body simulation of various falling scenarios for determining resulting loads at the prosthesis interface of transfemoral amputees with osseointegrated fixation.

    PubMed

    Welke, Bastian; Schwarze, Michael; Hurschler, Christof; Calliess, Tilman; Seehaus, Frank

    2013-07-01

    Conventionally, transfemoral amputees are treated with a shaft prosthesis fitted over the residual limb. To improve the quality of life of such patients, in particular those with complications relating to conventional attachment (e.g., skin irritation, stump ulcers, and poor motor-control with short stumps), osseointegrated prosthesis fixation implants have been developed and implanted in a limited population of patients. To assess possible damage to the implant/prosthesis during falling scenarios, the loads in high-risk situations were estimated using a multi-body simulation of motion. Five falling scenarios were identified and performed by healthy volunteer wearing safety equipment. Kinematic data and ground reaction forces were captured as input for the inverse-dynamics-based simulations, from which the forces and moments at a typical implant-prosthesis interface location were computed. The estimated peak loads in all five scenarios were of a magnitude that could lead to bone fracture. The largest peak force observed was 3274 ± 519 N, with an associated resultant moment of 176 ± 55 Nm on the prosthesis-implant interface. A typical femur is prone to fracture under this load, thus illustrating the need for a safety-release element in osseointegrated prosthesis fixation.

  6. Osseointegration of dental implants in 3D-printed synthetic onlay grafts customized according to bone metabolic activity in recipient site.

    PubMed

    Tamimi, Faleh; Torres, Jesus; Al-Abedalla, Khadijeh; Lopez-Cabarcos, Enrique; Alkhraisat, Mohammad H; Bassett, David C; Gbureck, Uwe; Barralet, Jake E

    2014-07-01

    Onlay grafts made of monolithic microporous monetite bioresorbable bioceramics have the capacity to conduct bone augmentation. However, there is heterogeneity in the graft behaviour in vivo that seems to correlate with the host anatomy. In this study, we sought to investigate the metabolic activity of the regenerated bone in monolithic monetite onlays by using positron emission tomography-computed tomography (PET-CT) in rats. This information was used to optimize the design of monetite onlays with different macroporous architecture that were then fabricated using a 3D-printing technique. In vivo, bone augmentation was attempted with these customized onlays in rabbits. PET-CT findings demonstrated that bone metabolism in the calvarial bone showed higher activity in the inferior and lateral areas of the onlays. Histological observations revealed higher bone volume (up to 47%), less heterogeneity and more implant osseointegration (up to 38%) in the augmented bone with the customized monetite onlays. Our results demonstrated for the first time that it is possible to achieve osseointegration of dental implants in bone augmented with 3D-printed synthetic onlays. It was also observed that designing the macropore geometry according to the bone metabolic activity was a key parameter in increasing the volume of bone augmented within monetite onlays.

  7. Accelerating Particles with Plasma

    ScienceCinema

    Litos, Michael; Hogan, Mark

    2016-07-12

    Researchers at SLAC explain how they use plasma wakefields to accelerate bunches of electrons to very high energies over only a short distance. Their experiments offer a possible path for the future of particle accelerators.

  8. Peak acceleration limiter

    NASA Technical Reports Server (NTRS)

    Chapman, C. P.

    1972-01-01

    Device is described that limits accelerations by shutting off shaker table power very rapidly in acceleration tests. Absolute value of accelerometer signal is used to trigger electronic switch which terminates test and sounds alarm.

  9. Linear Accelerator (LINAC)

    MedlinePlus

    ... equipment? How is safety ensured? What is this equipment used for? A linear accelerator (LINAC) is the ... Therapy (SBRT) . top of page How does the equipment work? The linear accelerator uses microwave technology (similar ...

  10. Accelerating Particles with Plasma

    SciTech Connect

    Litos, Michael; Hogan, Mark

    2014-11-05

    Researchers at SLAC explain how they use plasma wakefields to accelerate bunches of electrons to very high energies over only a short distance. Their experiments offer a possible path for the future of particle accelerators.

  11. Improved plasma accelerator

    NASA Technical Reports Server (NTRS)

    Cheng, D. Y.

    1971-01-01

    Converging, coaxial accelerator electrode configuration operates in vacuum as plasma gun. Plasma forms by periodic injections of high pressure gas that is ionized by electrical discharges. Deflagration mode of discharge provides acceleration, and converging contours of plasma gun provide focusing.

  12. Accelerator Technology Division

    NASA Astrophysics Data System (ADS)

    1992-04-01

    In fiscal year (FY) 1991, the Accelerator Technology (AT) division continued fulfilling its mission to pursue accelerator science and technology and to develop new accelerator concepts for application to research, defense, energy, industry, and other areas of national interest. This report discusses the following programs: The Ground Test Accelerator Program; APLE Free-Electron Laser Program; Accelerator Transmutation of Waste; JAERI, OMEGA Project, and Intense Neutron Source for Materials Testing; Advanced Free-Electron Laser Initiative; Superconducting Super Collider; The High-Power Microwave Program; (Phi) Factory Collaboration; Neutral Particle Beam Power System Highlights; Accelerator Physics and Special Projects; Magnetic Optics and Beam Diagnostics; Accelerator Design and Engineering; Radio-Frequency Technology; Free-Electron Laser Technology; Accelerator Controls and Automation; Very High-Power Microwave Sources and Effects; and GTA Installation, Commissioning, and Operations.

  13. Accelerators, Colliders, and Snakes

    NASA Astrophysics Data System (ADS)

    Courant, Ernest D.

    2003-12-01

    The author traces his involvement in the evolution of particle accelerators over the past 50 years. He participated in building the first billion-volt accelerator, the Brookhaven Cosmotron, which led to the introduction of the "strong-focusing" method that has in turn led to the very large accelerators and colliders of the present day. The problems of acceleration of spin-polarized protons are also addressed, with discussions of depolarizing resonances and "Siberian snakes" as a technique for mitigating these resonances.

  14. Acceleration: It's Elementary

    ERIC Educational Resources Information Center

    Willis, Mariam

    2012-01-01

    Acceleration is one tool for providing high-ability students the opportunity to learn something new every day. Some people talk about acceleration as taking a student out of step. In actuality, what one is doing is putting a student in step with the right curriculum. Whole-grade acceleration, also called grade-skipping, usually happens between…

  15. Angular Acceleration without Torque?

    ERIC Educational Resources Information Center

    Kaufman, Richard D.

    2012-01-01

    Hardly. Just as Robert Johns qualitatively describes angular acceleration by an internal force in his article "Acceleration Without Force?" here we will extend the discussion to consider angular acceleration by an internal torque. As we will see, this internal torque is due to an internal force acting at a distance from an instantaneous center.

  16. Accelerated test design

    NASA Technical Reports Server (NTRS)

    Mcdermott, P. P.

    1980-01-01

    The design of an accelerated life test program for electric batteries is discussed. A number of observations and suggestions on the procedures and objectives for conducting an accelerated life test program are presented. Equations based on nonlinear regression analysis for predicting the accelerated life test parameters are discussed.

  17. Peri-implant osseointegration after low-level laser therapy: micro-computed tomography and resonance frequency analysis in an animal model.

    PubMed

    Mayer, Luciano; Gomes, Fernando Vacilotto; de Oliveira, Marília Gerhardt; de Moraes, João Feliz Duarte; Carlsson, Lennart

    2016-12-01

    The purpose of the present study is to evaluate the effects of low-level laser therapy on the osseointegration process by comparing resonance frequency analysis measurements performed at implant placement and after 30 days and micro-computed tomography images in irradiated vs nonirradiated rabbits. Fourteen male New Zealand rabbits were randomly divided into two groups of seven animals each, one control group (nonirradiated animals) and one experimental group that received low-level laser therapy (Thera Lase®, aluminum-gallium-arsenide laser diode, 10 J per spot, two spots per session, seven sessions, 830 nm, 50 mW, CW, Ø 0.0028 cm(2)). The mandibular left incisor was surgically extracted in all animals, and one osseointegrated implant was placed immediately afterward (3.25ø × 11.5 mm; NanoTite, BIOMET 3i). Resonance frequency analysis was performed with the Osstell® device at implant placement and at 30 days (immediately before euthanasia). Micro-computed tomography analyses were then conducted using a high-resolution scanner (SkyScan 1172 X-ray Micro-CT) to evaluate the amount of newly formed bone around the implants. Irradiated animals showed significantly higher implant stability quotients at 30 days (64.286 ± 1.596; 95 % confidence interval (CI) 60.808-67.764) than controls (56.357 ± 1.596; 95 %CI 52.879-59.835) (P = .000). The percentage of newly formed bone around the implants was also significantly higher in irradiated animals (75.523 ± 8.510; 95 %CI 61.893-89.155) than in controls (55.012 ± 19.840; 95 %CI 41.380-68.643) (P = .027). Laser therapy, based on the irradiation protocol used in this study, was able to provide greater implant stability and increase the volume of peri-implant newly formed bone, indicating that laser irradiation effected an improvement in the osseointegration process.

  18. Fiber Accelerating Structures

    SciTech Connect

    Hammond, Andrew P.; /Reed Coll. /SLAC

    2010-08-25

    One of the options for future particle accelerators are photonic band gap (PBG) fiber accelerators. PBG fibers are specially designed optical fibers that use lasers to excite an electric field that is used to accelerate electrons. To improve PBG accelerators, the basic parameters of the fiber were tested to maximize defect size and acceleration. Using the program CUDOS, several accelerating modes were found that maximized these parameters for several wavelengths. The design of multiple defects, similar to having closely bound fibers, was studied to find possible coupling or the change of modes. The amount of coupling was found to be dependent on distance separated. For certain distances accelerating coupled modes were found and examined. In addition, several non-periodic fiber structures were examined using CUDOS. The non-periodic fibers produced several interesting results and promised more modes given time to study them in more detail.

  19. High brightness electron accelerator

    DOEpatents

    Sheffield, Richard L.; Carlsten, Bruce E.; Young, Lloyd M.

    1994-01-01

    A compact high brightness linear accelerator is provided for use, e.g., in a free electron laser. The accelerator has a first plurality of acclerating cavities having end walls with four coupling slots for accelerating electrons to high velocities in the absence of quadrupole fields. A second plurality of cavities receives the high velocity electrons for further acceleration, where each of the second cavities has end walls with two coupling slots for acceleration in the absence of dipole fields. The accelerator also includes a first cavity with an extended length to provide for phase matching the electron beam along the accelerating cavities. A solenoid is provided about the photocathode that emits the electons, where the solenoid is configured to provide a substantially uniform magnetic field over the photocathode surface to minimize emittance of the electons as the electrons enter the first cavity.

  20. Acceleration in astrophysics

    SciTech Connect

    Colgate, S.A.

    1993-12-31

    The origin of cosmic rays and applicable laboratory experiments are discussed. Some of the problems of shock acceleration for the production of cosmic rays are discussed in the context of astrophysical conditions. These are: The presumed unique explanation of the power law spectrum is shown instead to be a universal property of all lossy accelerators; the extraordinary isotropy of cosmic rays and the limited diffusion distances implied by supernova induced shock acceleration requires a more frequent and space-filling source than supernovae; the near perfect adiabaticity of strong hydromagnetic turbulence necessary for reflecting the accelerated particles each doubling in energy roughly 10{sup 5} to {sup 6} scatterings with negligible energy loss seems most unlikely; the evidence for acceleration due to quasi-parallel heliosphere shocks is weak. There is small evidence for the expected strong hydromagnetic turbulence, and instead, only a small number of particles accelerate after only a few shock traversals; the acceleration of electrons in the same collisionless shock that accelerates ions is difficult to reconcile with the theoretical picture of strong hydromagnetic turbulence that reflects the ions. The hydromagnetic turbulence will appear adiabatic to the electrons at their much higher Larmor frequency and so the electrons should not be scattered incoherently as they must be for acceleration. Therefore the electrons must be accelerated by a different mechanism. This is unsatisfactory, because wherever electrons are accelerated these sites, observed in radio emission, may accelerate ions more favorably. The acceleration is coherent provided the reconnection is coherent, in which case the total flux, as for example of collimated radio sources, predicts single charge accelerated energies much greater than observed.

  1. Modelling effects of tree population dynamics, tree throw and pit-mound formation/diffusion on microtopography over time in different forest settings

    NASA Astrophysics Data System (ADS)

    Martin, Y. E.; Johnson, E. A.; Gallaway, J.; Chaikina, O.

    2011-12-01

    Herein we conduct a followup investigation to an earlier research project in which we developed a numerical model of tree population dynamics, tree throw, and sediment transport associated with the formation of pit-mound features for Hawk Creek watershed, Canadian Rockies (Gallaway et al., 2009). We extend this earlier work by exploring the most appropriate transport relations to simulate the diffusion over time of newly-formed pit-pound features due to tree throw. We combine our earlier model with a landscape development model that can incorporate these diffusive transport relations. Using these combined models, changes in hillslope microtopography over time associated with the formation of pit-mound features and their decay will be investigated. The following ideas have motivated this particular study: (i) Rates of pit-mound degradation remain a source of almost complete speculation, as there is almost no long-term information on process rates. Therefore, we will attempt to tackle the issue of pit-mound degradation in a methodical way that can guide future field studies; (ii) The degree of visible pit-mound topography at any point in time on the landscape is a joint function of the rate of formation of new pit-mound features due to tree death/topple and their magnitude vs. the rate of decay of pit-mound features. An example of one interesting observation that arises is the following: it appears that pit-mound topography is often more pronounced in some eastern North American forests vs. field sites along the eastern slopes of the Canadian Rockies. Why is this the case? Our investigation begins by considering whether pit-mound decay might occur by linear or nonlinear diffusion. What differences might arise depending on which diffusive approach is adopted? What is the magnitude of transport rates associated with these possible forms of transport relations? We explore linear and nonlinear diffusion at varying rates and for different sizes of pit-mound pairs using a

  2. An introduction to acceleration mechanisms

    SciTech Connect

    Palmer, R.B.

    1987-05-01

    This paper discusses the acceleration of charged particles by electromagnetic fields, i.e., by fields that are produced by the motion of other charged particles driven by some power source. The mechanisms that are discussed include: Ponderamotive Forces, Acceleration, Plasma Beat Wave Acceleration, Inverse Free Electron Laser Acceleration, Inverse Cerenkov Acceleration, Gravity Acceleration, 2D Linac Acceleration and Conventional Iris Loaded Linac Structure Acceleration. (LSP)

  3. Schooling in Times of Acceleration

    ERIC Educational Resources Information Center

    Buddeberg, Magdalena; Hornberg, Sabine

    2017-01-01

    Modern societies are characterised by forms of acceleration, which influence social processes. Sociologist Hartmut Rosa has systematised temporal structures by focusing on three categories of social acceleration: technical acceleration, acceleration of social change, and acceleration of the pace of life. All three processes of acceleration are…

  4. Uniformly accelerated black holes

    NASA Astrophysics Data System (ADS)

    Letelier, Patricio S.; Oliveira, Samuel R.

    2001-09-01

    The static and stationary C metric are examined in a generic framework and their interpretations studied in some detail, especially those with two event horizons, one for the black hole and another for the acceleration. We find that (i) the spacetime of an accelerated static black hole is plagued by either conical singularities or a lack of smoothness and compactness of the black hole horizon, (ii) by using standard black hole thermodynamics we show that accelerated black holes have a higher Hawking temperature than Unruh temperature of the accelerated frame, and (iii) the usual upper bound on the product of the mass and acceleration parameters (<1/27) is just a coordinate artifact. The main results are extended to accelerated rotating black holes with no significant changes.

  5. The Dielectric Wall Accelerator

    SciTech Connect

    Caporaso, George J.; Chen, Yu-Jiuan; Sampayan, Stephen E.

    2009-01-01

    The Dielectric Wall Accelerator (DWA), a class of induction accelerators, employs a novel insulating beam tube to impress a longitudinal electric field on a bunch of charged particles. The surface flashover characteristics of this tube may permit the attainment of accelerating gradients on the order of 100 MV/m for accelerating pulses on the order of a nanosecond in duration. A virtual traveling wave of excitation along the tube is produced at any desired speed by controlling the timing of pulse generating modules that supply a tangential electric field to the tube wall. Because of the ability to control the speed of this virtual wave, the accelerator is capable of handling any charge to mass ratio particle; hence it can be used for electrons, protons and any ion. The accelerator architectures, key technologies and development challenges will be described.

  6. Optically pulsed electron accelerator

    DOEpatents

    Fraser, J.S.; Sheffield, R.L.

    1985-05-20

    An optically pulsed electron accelerator can be used as an injector for a free electron laser and comprises a pulsed light source, such as a laser, for providing discrete incident light pulses. A photoemissive electron source emits electron bursts having the same duration as the incident light pulses when impinged upon by same. The photoemissive electron source is located on an inside wall of a radiofrequency-powered accelerator cell which accelerates the electron burst emitted by the photoemissive electron source.

  7. Optically pulsed electron accelerator

    DOEpatents

    Fraser, John S.; Sheffield, Richard L.

    1987-01-01

    An optically pulsed electron accelerator can be used as an injector for a free electron laser and comprises a pulsed light source, such as a laser, for providing discrete incident light pulses. A photoemissive electron source emits electron bursts having the same duration as the incident light pulses when impinged upon by same. The photoemissive electron source is located on an inside wall of a radio frequency powered accelerator cell which accelerates the electron burst emitted by the photoemissive electron source.

  8. ACCELERATION RESPONSIVE SWITCH

    DOEpatents

    Chabrek, A.F.; Maxwell, R.L.

    1963-07-01

    An acceleration-responsive device with dual channel capabilities whereby a first circuit is actuated upon attainment of a predetermined maximum acceleration level and when the acceleration drops to a predetermined minimum acceleriltion level another circuit is actuated is described. A fluid-damped sensing mass slidably mounted in a relatively frictionless manner on a shaft through the intermediation of a ball bushing and biased by an adjustable compression spring provides inertially operated means for actuating the circuits. (AEC)

  9. The foxhole accelerating structure

    SciTech Connect

    Fernow, R.C.; Claus, J.

    1992-07-17

    This report examines some properties of a new type of open accelerating structure. It consists of a series of rectangular cavities, which we call foxholes, joined by a beam channel. The power for accelerating the particles comes from an external radiation source and enters the cavities through their open upper surfaces. Analytic and computer calculations are presented showing that the foxhole is a suitable structure for accelerating relativistic electrons.

  10. Particle acceleration in flares

    NASA Technical Reports Server (NTRS)

    Benz, Arnold O.; Kosugi, Takeo; Aschwanden, Markus J.; Benka, Steve G.; Chupp, Edward L.; Enome, Shinzo; Garcia, Howard; Holman, Gordon D.; Kurt, Victoria G.; Sakao, Taro

    1994-01-01

    Particle acceleration is intrinsic to the primary energy release in the impulsive phase of solar flares, and we cannot understand flares without understanding acceleration. New observations in soft and hard X-rays, gamma-rays and coherent radio emissions are presented, suggesting flare fragmentation in time and space. X-ray and radio measurements exhibit at least five different time scales in flares. In addition, some new observations of delayed acceleration signatures are also presented. The theory of acceleration by parallel electric fields is used to model the spectral shape and evolution of hard X-rays. The possibility of the appearance of double layers is further investigated.

  11. Charged particle accelerator grating

    DOEpatents

    Palmer, Robert B.

    1986-01-01

    A readily disposable and replaceable accelerator grating for a relativistic particle accelerator. The grating is formed for a plurality of liquid droplets that are directed in precisely positioned jet streams to periodically dispose rows of droplets along the borders of a predetermined particle beam path. A plurality of lasers are used to direct laser beams into the droplets, at predetermined angles, thereby to excite the droplets to support electromagnetic accelerating resonances on their surfaces. Those resonances operate to accelerate and focus particles moving along the beam path. As the droplets are distorted or destroyed by the incoming radiation, they are replaced at a predetermined frequency by other droplets supplied through the jet streams.

  12. Charged particle accelerator grating

    DOEpatents

    Palmer, Robert B.

    1986-09-02

    A readily disposable and replaceable accelerator grating for a relativistic particle accelerator. The grating is formed for a plurality of liquid droplets that are directed in precisely positioned jet streams to periodically dispose rows of droplets along the borders of a predetermined particle beam path. A plurality of lasers are used to direct laser beams into the droplets, at predetermined angles, thereby to excite the droplets to support electromagnetic accelerating resonances on their surfaces. Those resonances operate to accelerate and focus particles moving along the beam path. As the droplets are distorted or destroyed by the incoming radiation, they are replaced at a predetermined frequency by other droplets supplied through the jet streams.

  13. Accelerator-based BNCT.

    PubMed

    Kreiner, A J; Baldo, M; Bergueiro, J R; Cartelli, D; Castell, W; Thatar Vento, V; Gomez Asoia, J; Mercuri, D; Padulo, J; Suarez Sandin, J C; Erhardt, J; Kesque, J M; Valda, A A; Debray, M E; Somacal, H R; Igarzabal, M; Minsky, D M; Herrera, M S; Capoulat, M E; Gonzalez, S J; del Grosso, M F; Gagetti, L; Suarez Anzorena, M; Gun, M; Carranza, O

    2014-06-01

    The activity in accelerator development for accelerator-based BNCT (AB-BNCT) both worldwide and in Argentina is described. Projects in Russia, UK, Italy, Japan, Israel, and Argentina to develop AB-BNCT around different types of accelerators are briefly presented. In particular, the present status and recent progress of the Argentine project will be reviewed. The topics will cover: intense ion sources, accelerator tubes, transport of intense beams, beam diagnostics, the (9)Be(d,n) reaction as a possible neutron source, Beam Shaping Assemblies (BSA), a treatment room, and treatment planning in realistic cases.

  14. High Gradient Accelerator Research

    SciTech Connect

    Temkin, Richard

    2016-07-12

    The goal of the MIT program of research on high gradient acceleration is the development of advanced acceleration concepts that lead to a practical and affordable next generation linear collider at the TeV energy level. Other applications, which are more near-term, include accelerators for materials processing; medicine; defense; mining; security; and inspection. The specific goals of the MIT program are: • Pioneering theoretical research on advanced structures for high gradient acceleration, including photonic structures and metamaterial structures; evaluation of the wakefields in these advanced structures • Experimental research to demonstrate the properties of advanced structures both in low-power microwave cold test and high-power, high-gradient test at megawatt power levels • Experimental research on microwave breakdown at high gradient including studies of breakdown phenomena induced by RF electric fields and RF magnetic fields; development of new diagnostics of the breakdown process • Theoretical research on the physics and engineering features of RF vacuum breakdown • Maintaining and improving the Haimson / MIT 17 GHz accelerator, the highest frequency operational accelerator in the world, a unique facility for accelerator research • Providing the Haimson / MIT 17 GHz accelerator facility as a facility for outside users • Active participation in the US DOE program of High Gradient Collaboration, including joint work with SLAC and with Los Alamos National Laboratory; participation of MIT students in research at the national laboratories • Training the next generation of Ph. D. students in the field of accelerator physics.

  15. FFAGS for rapid acceleration

    SciTech Connect

    Carol J. Johnstone and Shane Koscielniak

    2002-09-30

    When large transverse and longitudinal emittances are to be transported through a circular machine, extremely rapid acceleration holds the advantage that the beam becomes immune to nonlinear resonances because there is insufficient time for amplitudes to build up. Uncooled muon beams exhibit large emittances and require fast acceleration to avoid decay losses and would benefit from this style of acceleration. The approach here employs a fixed-field alternating gradient or FFAG magnet structure and a fixed frequency acceleration system. Acceptance is enhanced by the use only of linear lattice elements, and fixed-frequency rf enables the use of cavities with large shunt resistance and quality factor.

  16. Acceleration of polarized protons in circular accelerators

    SciTech Connect

    Courant, E.D.; Ruth, R.D.

    1980-09-12

    The theory of depolarization in circular accelerators is presented. The spin equation is first expressed in terms of the particle orbit and then converted to the equivalent spinor equation. The spinor equation is then solved for three different situations: (1) a beam on a flat top near a resonance, (2) uniform acceleration through an isolated resonance, and (3) a model of a fast resonance jump. Finally, the depolarization coefficient, epsilon, is calculated in terms of properties of the particle orbit and the results are applied to a calculation of depolarization in the AGS.

  17. Scaling FFAG accelerator for muon acceleration

    SciTech Connect

    Lagrange, JB.; Planche, T.; Mori, Y.

    2011-10-06

    Recent developments in scaling fixed field alternating gradient (FFAG) accelerators have opened new ways for lattice design, with straight sections, and insertions like dispersion suppressors. Such principles and matching issues are detailed in this paper. An application of these new concepts is presented to overcome problems in the PRISM project.

  18. Scaling FFAG accelerator for muon acceleration

    NASA Astrophysics Data System (ADS)

    Lagrange, JB.; Planche, T.; Mori, Y.

    2011-10-01

    Recent developments in scaling fixed field alternating gradient (FFAG) accelerators have opened new ways for lattice design, with straight sections, and insertions like dispersion suppressors. Such principles and matching issues are detailed in this paper. An application of these new concepts is presented to overcome problems in the PRISM project.

  19. Angular velocities, angular accelerations, and coriolis accelerations

    NASA Technical Reports Server (NTRS)

    Graybiel, A.

    1975-01-01

    Weightlessness, rotating environment, and mathematical analysis of Coriolis acceleration is described for man's biological effective force environments. Effects on the vestibular system are summarized, including the end organs, functional neurology, and input-output relations. Ground-based studies in preparation for space missions are examined, including functional tests, provocative tests, adaptive capacity tests, simulation studies, and antimotion sickness.

  20. Induction linear accelerators

    NASA Astrophysics Data System (ADS)

    Birx, Daniel

    1992-03-01

    Among the family of particle accelerators, the Induction Linear Accelerator is the best suited for the acceleration of high current electron beams. Because the electromagnetic radiation used to accelerate the electron beam is not stored in the cavities but is supplied by transmission lines during the beam pulse it is possible to utilize very low Q (typically<10) structures and very large beam pipes. This combination increases the beam breakup limited maximum currents to of order kiloamperes. The micropulse lengths of these machines are measured in 10's of nanoseconds and duty factors as high as 10-4 have been achieved. Until recently the major problem with these machines has been associated with the pulse power drive. Beam currents of kiloamperes and accelerating potentials of megavolts require peak power drives of gigawatts since no energy is stored in the structure. The marriage of liner accelerator technology and nonlinear magnetic compressors has produced some unique capabilities. It now appears possible to produce electron beams with average currents measured in amperes, peak currents in kiloamperes and gradients exceeding 1 MeV/meter, with power efficiencies approaching 50%. The nonlinear magnetic compression technology has replaced the spark gap drivers used on earlier accelerators with state-of-the-art all-solid-state SCR commutated compression chains. The reliability of these machines is now approaching 1010 shot MTBF. In the following paper we will briefly review the historical development of induction linear accelerators and then discuss the design considerations.

  1. Accelerator Science: Why RF?

    SciTech Connect

    Lincoln, Don

    2016-12-21

    Particle accelerators can fire beams of subatomic particles at near the speed of light. The accelerating force is generated using radio frequency technology and a whole lot of interesting features. In this video, Fermilab’s Dr. Don Lincoln explains how it all works.

  2. Particle Acceleration in Jets

    NASA Technical Reports Server (NTRS)

    Nishikawa, Ken-Ichi

    2005-01-01

    Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., active galactic nuclei (AGNs), gamma ray burst (GRBs), and Galactic microquasar systems usually have power-law emission spectra. Fermi acceleration is the mechanism usually assumed for the acceleration of particles in astrophysical environments.

  3. Accelerators Beyond The Tevatron?

    SciTech Connect

    Lach, Joseph; /Fermilab

    2010-07-01

    Following the successful operation of the Fermilab superconducting accelerator three new higher energy accelerators were planned. They were the UNK in the Soviet Union, the LHC in Europe, and the SSC in the United States. All were expected to start producing physics about 1995. They did not. Why?

  4. Accelerators (3/5)

    ScienceCinema

    None

    2016-07-12

    1a) Introduction and motivation 1b) History and accelerator types 2) Transverse beam dynamics 3a) Longitudinal beam dynamics 3b) Figure of merit of a synchrotron/collider 3c) Beam control 4) Main limiting factors 5) Technical challenges Prerequisite knowledge: Previous knowledge of accelerators is not required.

  5. Diagnostics for induction accelerators

    SciTech Connect

    Fessenden, T.J.

    1996-04-01

    The induction accelerator was conceived by N. C. Christofilos and first realized as the Astron accelerator that operated at LLNL from the early 1960`s to the end of 1975. This accelerator generated electron beams at energies near 6 MeV with typical currents of 600 Amperes in 400 ns pulses. The Advanced Test Accelerator (ATA) built at Livermore`s Site 300 produced 10,000 Ampere beams with pulse widths of 70 ns at energies approaching 50 MeV. Several other electron and ion induction accelerators have been fabricated at LLNL and LBNL. This paper reviews the principal diagnostics developed through efforts by scientists at both laboratories for measuring the current, position, energy, and emittance of beams generated by these high current, short pulse accelerators. Many of these diagnostics are closely related to those developed for other accelerators. However, the very fast and intense current pulses often require special diagnostic techniques and considerations. The physics and design of the more unique diagnostics developed for electron induction accelerators are presented and discussed in detail.

  6. Accelerators (4/5)

    ScienceCinema

    None

    2016-07-12

    1a) Introduction and motivation 1b) History and accelerator types 2) Transverse beam dynamics 3a) Longitudinal beam dynamics 3b) Figure of merit of a synchrotron/collider 3c) Beam control 4) Main limiting factors 5) Technical challenges Prerequisite knowledge: Previous knowledge of accelerators is not required.

  7. Measuring Model Rocket Acceleration.

    ERIC Educational Resources Information Center

    Jenkins, Randy A.

    1993-01-01

    Presents an experiment that measures the acceleration and velocity of a model rocket. Lift-off information is transmitted to a computer that creates a graph of the velocity. Discusses the analysis of the computer-generated data and differences between calculated and experimental velocity and acceleration of several rocket types. (MDH)

  8. Microscale acceleration history discriminators

    DOEpatents

    Polosky, Marc A.; Plummer, David W.

    2002-01-01

    A new class of micromechanical acceleration history discriminators is claimed. These discriminators allow the precise differentiation of a wide range of acceleration-time histories, thereby allowing adaptive events to be triggered in response to the severity (or lack thereof) of an external environment. Such devices have applications in airbag activation, and other safety and surety applications.

  9. Accelerators (5/5)

    ScienceCinema

    None

    2016-07-12

    1a) Introduction and motivation 1b) History and accelerator types 2) Transverse beam dynamics 3a) Longitudinal beam dynamics 3b) Figure of merit of a synchrotron/collider 3c) Beam control 4) Main limiting factors 5) Technical challenges Prerequisite knowledge: Previous knowledge of accelerators is not required.

  10. Accelerators Beyond The Tevatron?

    SciTech Connect

    Lach, Joseph

    2010-07-29

    Following the successful operation of the Fermilab superconducting accelerator three new higher energy accelerators were planned. They were the UNK in the Soviet Union, the LHC in Europe, and the SSC in the United States. All were expected to start producing physics about 1995. They did not. Why?.

  11. Accelerators, Beams And Physical Review Special Topics - Accelerators And Beams

    SciTech Connect

    Siemann, R.H.; /SLAC

    2011-10-24

    Accelerator science and technology have evolved as accelerators became larger and important to a broad range of science. Physical Review Special Topics - Accelerators and Beams was established to serve the accelerator community as a timely, widely circulated, international journal covering the full breadth of accelerators and beams. The history of the journal and the innovations associated with it are reviewed.

  12. Large electrostatic accelerators

    SciTech Connect

    Jones, C.M.

    1984-01-01

    The increasing importance of energetic heavy ion beams in the study of atomic physics, nuclear physics, and materials science has partially or wholly motivated the construction of a new generation of large electrostatic accelerators designed to operate at terminal potentials of 20 MV or above. In this paper, the author briefly discusses the status of these new accelerators and also discusses several recent technological advances which may be expected to further improve their performance. The paper is divided into four parts: (1) a discussion of the motivation for the construction of large electrostatic accelerators, (2) a description and discussion of several large electrostatic accelerators which have been recently completed or are under construction, (3) a description of several recent innovations which may be expected to improve the performance of large electrostatic accelerators in the future, and (4) a description of an innovative new large electrostatic accelerator whose construction is scheduled to begin next year. Due to time and space constraints, discussion is restricted to consideration of only tandem accelerators.

  13. Vacuum Beat Wave Accelerator

    NASA Astrophysics Data System (ADS)

    Moore, C. I.; Hafizi, B.; Ting, A.; Burris, H. R.; Sprangle, P.; Esarey, E.; Ganguly, A.; Hirshfield, J. L.

    1997-11-01

    The Vacuum Beat Wave Accelerator (VBWA) is a particle acceleration scheme which uses the non-linear ponderomotive beating of two different frequency laser beams to accelerate electrons. A proof-of-principle experiment to demonstrate the VBWA is underway at the Naval Research Laboratory (NRL). This experiment will use the beating of a 1054 nm and 527 nm laser pulse from the NRL T-cubed laser to generate the beat wave and a 4.5 MeV RF electron gun as the electron source. Simulation results and the experimental design will be presented. The suitability of using axicon or higher order Gaussian laser beams will also be discussed.

  14. Ion beam accelerator system

    NASA Technical Reports Server (NTRS)

    Aston, Graeme (Inventor)

    1984-01-01

    A system is described that combines geometrical and electrostatic focusing to provide high ion extraction efficiency and good focusing of an accelerated ion beam. The apparatus includes a pair of curved extraction grids (16, 18) with multiple pairs of aligned holes positioned to direct a group of beamlets (20) along converging paths. The extraction grids are closely spaced and maintained at a moderate potential to efficiently extract beamlets of ions and allow them to combine into a single beam (14). An accelerator electrode device (22) downstream from the extraction grids, is at a much lower potential than the grids to accelerate the combined beam.

  15. Ion beam accelerator system

    NASA Technical Reports Server (NTRS)

    Aston, G. (Inventor)

    1981-01-01

    A system is described that combines geometrical and electrostatic focusing to provide high ion extraction efficiency and good focusing of an accelerated ion beam. The apparatus includes a pair of curved extraction grids with multiple pairs of aligned holes positioned to direct a group of beamlets along converging paths. The extraction grids are closely spaced and maintained at a moderate potential to efficiently extract beamlets of ions and allow them to combine into a single beam. An accelerator electrode device downstream from the extraction grids is at a much lower potential than the grids to accelerate the combined beam. The application of the system to ion implantation is mentioned.

  16. Stability, Survival, and Tolerability of an Auditory Osseointegrated Implant for Bone Conduction Hearing: Long-Term Follow-Up of a Randomized Controlled Trial

    PubMed Central

    den Besten, Christine A.; Stalfors, Joacim; Wigren, Stina; Blechert, Johan Ivarsson; Flynn, Mark; Eeg-Olofsson, Måns; Aggarwal, Rohini; Green, Kevin; Nelissen, Rik C.; Mylanus, Emmanuel A. M.; Hol, Myrthe K. S.

    2016-01-01

    Objective: To compare implant stability, survival, and soft tissue reactions for a novel (test) and previous generation (control) percutaneous auditory osseointegrated implant for bone conduction hearing at long-term follow-up of 5 years. Study Design: Single follow-up visit of a previously completed multicenter, randomized, controlled trial. Patients: Fifty-seven of the 77 participants of a completed randomized controlled trial on a new auditory osseointegrated implant underwent a single follow-up visit 5 years after implantation, which comprised implant stability measurements and collection of Holgers scores. Additionally, implant survival was recorded for all 77 patients from the original trial. Results: The test implant showed significantly higher implant stability quotient (ISQ) values compared with the control implant throughout the 5-year follow-up. Mean area under the curve of ISQ high from baseline to 5 years was 71.6 (standard deviation [SD] ±2.0) and 66.7 (SD ±3.4) for the test and control implant, respectively (p < 0.0001). For both implants, the mean ISQ value recorded at 5 years was higher compared with implantation (test group +2.03 [SD ±2.55, within group p < 0.0001] and control group +2.25 [SD ±4.95, within group p = 0.12]). No difference was noticed in increase from baseline between groups (p = 0.64). Furthermore, evaluation of soft tissue reactions continued to show superiority of the test implant. At the 5-year follow-up visit, one patient (2.5%) presented with a Holgers grade 2 in the test group, compared with four patients (23.5%) in the control group (p = 0.048); no patient presented with more severe soft tissue reactions. Excluding explantations, the survival rate was 95.8% for the test group and 95.0% for the control group. The corresponding rates including explantations were 93.9 and 90.0%. Conclusion: The test implant showed superiority in terms of higher mean ISQ values and less adverse soft tissue reactions, both

  17. CLASHING BEAM PARTICLE ACCELERATOR

    DOEpatents

    Burleigh, R.J.

    1961-04-11

    A charged-particle accelerator of the proton synchrotron class having means for simultaneously accelerating two separate contra-rotating particle beams within a single annular magnet structure is reported. The magnet provides two concentric circular field regions of opposite magnetic polarity with one field region being of slightly less diameter than the other. The accelerator includes a deflector means straddling the two particle orbits and acting to collide the two particle beams after each has been accelerated to a desired energy. The deflector has the further property of returning particles which do not undergo collision to the regular orbits whereby the particles recirculate with the possibility of colliding upon subsequent passages through the deflector.

  18. Vibration control in accelerators

    SciTech Connect

    Montag, C.

    2011-01-01

    In the vast majority of accelerator applications, ground vibration amplitudes are well below tolerable magnet jitter amplitudes. In these cases, it is necessary and sufficient to design a rigid magnet support structure that does not amplify ground vibration. Since accelerator beam lines are typically installed at an elevation of 1-2m above ground level, special care has to be taken in order to avoid designing a support structure that acts like an inverted pendulum with a low resonance frequency, resulting in untolerable lateral vibration amplitudes of the accelerator components when excited by either ambient ground motion or vibration sources within the accelerator itself, such as cooling water pumps or helium flow in superconducting magnets. In cases where ground motion amplitudes already exceed the required jiter tolerances, for instance in future linear colliders, passive vibration damping or active stabilization may be considered.

  19. Dielectric assist accelerating structure

    NASA Astrophysics Data System (ADS)

    Satoh, D.; Yoshida, M.; Hayashizaki, N.

    2016-01-01

    A higher-order TM02 n mode accelerating structure is proposed based on a novel concept of dielectric loaded rf cavities. This accelerating structure consists of ultralow-loss dielectric cylinders and disks with irises which are periodically arranged in a metallic enclosure. Unlike conventional dielectric loaded accelerating structures, most of the rf power is stored in the vacuum space near the beam axis, leading to a significant reduction of the wall loss, much lower than that of conventional normal-conducting linac structures. This allows us to realize an extremely high quality factor and a very high shunt impedance at room temperature. A simulation of a 5 cell prototype design with an existing alumina ceramic indicates an unloaded quality factor of the accelerating mode over 120 000 and a shunt impedance exceeding 650 M Ω /m at room temperature.

  20. Wake field acceleration experiments

    SciTech Connect

    Simpson, J.D.

    1988-01-01

    Where and how will wake field acceleration devices find use for other than, possibly, accelerators for high energy physics. I don't know that this can be responsibly answered at this time. What I can do is describe some recent results from an ongoing experimental program at Argonne which support the idea that wake field techniques and devices are potentially important for future accelerators. Perhaps this will spawn expanded interest and even new ideas for the use of this new technology. The Argonne program, and in particular the Advanced Accelerator Test Facility (AATF), has been reported in several fairly recent papers and reports. But because this is a substantially new audience for the subject, I will include a brief review of the program and the facility before describing experiments. 10 refs., 7 figs.

  1. Accelerator on a Chip

    SciTech Connect

    England, Joel

    2014-06-30

    SLAC's Joel England explains how the same fabrication techniques used for silicon computer microchips allowed their team to create the new laser-driven particle accelerator chips. (SLAC Multimedia Communications)

  2. Charged particle accelerator grating

    DOEpatents

    Palmer, R.B.

    1985-09-09

    A readily disposable and replaceable accelerator grating for a relativistic particle accelerator is described. The grating is formed for a plurality of liquid droplets that are directed in precisely positioned jet streams to periodically dispose rows of droplets along the borders of a predetermined particle beam path. A plurality of lasers are used to direct laser beams onto the droplets, at predetermined angles, thereby to excite the droplets to support electromagnetic accelerating resonances on their surfaces. Those resonances operate to accelerate and focus particles moving along the beam path. As the droplets are distorted or destroyed by the incoming radiation, they are replaced at a predetermined frequency by other droplets supplied through the jet streams.

  3. HEAVY ION LINEAR ACCELERATOR

    DOEpatents

    Van Atta, C.M.; Beringer, R.; Smith, L.

    1959-01-01

    A linear accelerator of heavy ions is described. The basic contributions of the invention consist of a method and apparatus for obtaining high energy particles of an element with an increased charge-to-mass ratio. The method comprises the steps of ionizing the atoms of an element, accelerating the resultant ions to an energy substantially equal to one Mev per nucleon, stripping orbital electrons from the accelerated ions by passing the ions through a curtain of elemental vapor disposed transversely of the path of the ions to provide a second charge-to-mass ratio, and finally accelerating the resultant stripped ions to a final energy of at least ten Mev per nucleon.

  4. Principles of Induction Accelerators

    NASA Astrophysics Data System (ADS)

    Briggs*, Richard J.

    The basic concepts involved in induction accelerators are introduced in this chapter. The objective is to provide a foundation for the more detailed coverage of key technology elements and specific applications in the following chapters. A wide variety of induction accelerators are discussed in the following chapters, from the high current linear electron accelerator configurations that have been the main focus of the original developments, to circular configurations like the ion synchrotrons that are the subject of more recent research. The main focus in the present chapter is on the induction module containing the magnetic core that plays the role of a transformer in coupling the pulsed power from the modulator to the charged particle beam. This is the essential common element in all these induction accelerators, and an understanding of the basic processes involved in its operation is the main objective of this chapter. (See [1] for a useful and complementary presentation of the basic principles in induction linacs.)

  5. Accelerator on a Chip

    ScienceCinema

    England, Joel

    2016-07-12

    SLAC's Joel England explains how the same fabrication techniques used for silicon computer microchips allowed their team to create the new laser-driven particle accelerator chips. (SLAC Multimedia Communications)

  6. DIELECTRIC WALL ACCELERATOR TECHNOLOGY

    SciTech Connect

    Sampayan, S; Caporaso, G; Chen, Y; Harris, J; Hawkins, S; Holmes, C; Nelson, S; Poole, B; Rhodes, M; Sanders, D; Sullivan, J; Wang, L; Watson, J

    2007-10-18

    The dielectric wall accelerator (DWA) is a compact pulsed power device where the pulse forming lines, switching, and vacuum wall are integrated into a single compact geometry. For this effort, we initiated a extensive compact pulsed power development program and have pursued the study of switching (gas, oil, laser induced surface flashover and photoconductive), dielectrics (ceramics and nanoparticle composites), pulse forming line topologies (asymmetric and symmetric Blumleins and zero integral pulse forming lines), and multilayered vacuum insulator (HGI) technology. Finally, we fabricated an accelerator cell for test on ETAII (a 5.5 MeV, 2 kA, 70 ns pulsewidth electron beam accelerator). We review our past results and report on the progress of accelerator cell testing.

  7. Amps particle accelerator definition study

    NASA Technical Reports Server (NTRS)

    Sellen, J. M., Jr.

    1975-01-01

    The Particle Accelerator System of the AMPS (Atmospheric, Magnetospheric, and Plasmas in Space) payload is a series of charged particle accelerators to be flown with the Space Transportation System Shuttle on Spacelab missions. In the configuration presented, the total particle accelerator system consists of an energetic electron beam, an energetic ion accelerator, and both low voltage and high voltage plasma acceleration devices. The Orbiter is illustrated with such a particle accelerator system.

  8. Designing reliability into accelerators

    NASA Astrophysics Data System (ADS)

    Hutton, A.

    1992-07-01

    Future accelerators will have to provide a high degree of reliability. Quality must be designed in right from the beginning and must remain a central theme throughout the project. The problem is similar to the problems facing US industry today, and examples of the successful application of quality engineering will be given. Different aspects of an accelerator project will be addressed: Concept, Design, Motivation, Management Techniques, and Fault Diagnosis. The importance of creating and maintaining a coherent team will be stressed.

  9. Microgravity Acceleration Measurement System

    NASA Technical Reports Server (NTRS)

    Foster, William

    2009-01-01

    Microgravity Acceleration Measurement System (MAMS) is an ongoing study of the small forces (vibrations and accelerations) on the ISS that result from the operation of hardware, crew activities, as well as dockings and maneuvering. Results will be used to generalize the types of vibrations affecting vibration-sensitive experiments. Investigators seek to better understand the vibration environment on the space station to enable future research.

  10. CEBAF Accelerator Achievements

    NASA Astrophysics Data System (ADS)

    Chao, Y. C.; Drury, M.; Hovater, C.; Hutton, A.; Krafft, G. A.; Poelker, M.; Reece, C.; Tiefenback, M.

    2011-05-01

    In the past decade, nuclear physics users of Jefferson Lab's Continuous Electron Beam Accelerator Facility (CEBAF) have benefited from accelerator physics advances and machine improvements. As of early 2011, CEBAF operates routinely at 6 GeV, with a 12 GeV upgrade underway. This article reports highlights of CEBAF's scientific and technological evolution in the areas of cryomodule refurbishment, RF control, polarized source development, beam transport for parity experiments, magnets and hysteresis handling, beam breakup, and helium refrigerator operational optimization.

  11. Breakthrough: Fermilab Accelerator Technology

    ScienceCinema

    None

    2016-07-12

    There are more than 30,000 particle accelerators in operation around the world. At Fermilab, scientists are collaborating with other laboratories and industry to optimize the manufacturing processes for a new type of powerful accelerator that uses superconducting niobium cavities. Experimenting with unique polishing materials, a Fermilab team has now developed an efficient and environmentally friendly way of creating cavities that can propel particles with more than 30 million volts per meter.

  12. Rolamite acceleration sensor

    DOEpatents

    Abbin, Joseph P.; Briner, Clifton F.; Martin, Samuel B.

    1993-01-01

    A rolamite acceleration sensor which has a failsafe feature including a housing, a pair of rollers, a tension band wrapped in an S shaped fashion around the rollers, wherein the band has a force-generation cut out and a failsafe cut out or weak portion. The failsafe cut out or weak portion breaks when the sensor is subjected to an excessive acceleration so that the sensor fails in an open circuit (non-conducting) state permanently.

  13. Rolamite acceleration sensor

    DOEpatents

    Abbin, J.P.; Briner, C.F.; Martin, S.B.

    1993-12-21

    A rolamite acceleration sensor is described which has a failsafe feature including a housing, a pair of rollers, a tension band wrapped in an S shaped fashion around the rollers, wherein the band has a force-generation cut out and a failsafe cut out or weak portion. The failsafe cut out or weak portion breaks when the sensor is subjected to an excessive acceleration so that the sensor fails in an open circuit (non-conducting) state permanently. 6 figures.

  14. Collective field accelerator

    DOEpatents

    Luce, John S.

    1978-01-01

    A collective field accelerator which operates with a vacuum diode and utilizes a grooved cathode and a dielectric anode that operates with a relativistic electron beam with a .nu./.gamma. of .about. 1, and a plurality of dielectric lenses having an axial magnetic field thereabout to focus the collectively accelerated electrons and ions which are ejected from the anode. The anode and lenses operate as unoptimized r-f cavities which modulate and focus the beam.

  15. Accelerators for America's Future

    NASA Astrophysics Data System (ADS)

    Bai, Mei

    2016-03-01

    Particle accelerator, a powerful tool to energize beams of charged particles to a desired speed and energy, has been the working horse for investigating the fundamental structure of matter and fundermental laws of nature. Most known examples are the 2-mile long Stanford Linear Accelerator at SLAC, the high energy proton and anti-proton collider Tevatron at FermiLab, and Large Hadron Collider that is currently under operation at CERN. During the less than a century development of accelerator science and technology that led to a dazzling list of discoveries, particle accelerators have also found various applications beyond particle and nuclear physics research, and become an indispensible part of the economy. Today, one can find a particle accelerator at almost every corner of our lives, ranging from the x-ray machine at the airport security to radiation diagnostic and therapy in hospitals. This presentation will give a brief introduction of the applications of this powerful tool in fundermental research as well as in industry. Challenges in accelerator science and technology will also be briefly presented

  16. Biomedical accelerator mass spectrometry

    NASA Astrophysics Data System (ADS)

    Freeman, Stewart P. H. T.; Vogel, John S.

    1995-05-01

    Ultrasensitive SIMS with accelerator based spectrometers has recently begun to be applied to biomedical problems. Certain very long-lived radioisotopes of very low natural abundances can be used to trace metabolism at environmental dose levels ( [greater-or-equal, slanted] z mol in mg samples). 14C in particular can be employed to label a myriad of compounds. Competing technologies typically require super environmental doses that can perturb the system under investigation, followed by uncertain extrapolation to the low dose regime. 41Ca and 26Al are also used as elemental tracers. Given the sensitivity of the accelerator method, care must be taken to avoid contamination of the mass spectrometer and the apparatus employed in prior sample handling including chemical separation. This infant field comprises the efforts of a dozen accelerator laboratories. The Center for Accelerator Mass Spectrometry has been particularly active. In addition to collaborating with groups further afield, we are researching the kinematics and binding of genotoxins in-house, and we support innovative uses of our capability in the disciplines of chemistry, pharmacology, nutrition and physiology within the University of California. The field can be expected to grow further given the numerous potential applications and the efforts of several groups and companies to integrate more the accelerator technology into biomedical research programs; the development of miniaturized accelerator systems and ion sources capable of interfacing to conventional HPLC and GMC, etc. apparatus for complementary chemical analysis is anticipated for biomedical laboratories.

  17. A new method to routinely achieve passive fit of ceramometal prostheses over Brånemark osseointegrated implants: a two-year report.

    PubMed

    Aparicio, C

    1994-10-01

    To maintain osseointegration, it is essential that the prosthesis fit with total passivity because the absence of a periodontal ligament makes the implant unable to adapt its position to a nonpassive framework. The traditional system of building a metal framework by melting over mechanized pieces--called gold cylinders in the Brånemark system--has been modified so these pieces are joined to the metal framework by means of physicochemical bonding. This bond is achieved by treating the metallic surfaces with a Silicoater system and a composite resin cement that sets in the mouth using an improved cementing protocol. In this paper, the clinical viability of this new philosophy, shown over 2 years, is presented. A total of 64 prostheses (39 maxillary and 25 mandibular) supported by 214 abutments, with an average observation period of 9 months, were evaluated. The results show that it is possible to routinely obtain a ceramometal prosthesis with a totally passive circular fitting while maintaining the possibility of retrieval, thus making postceramic soldering unnecessary.

  18. The Evaluation of Daily Life Activities after Application of an Osseointegrated Prosthesis Fixation in a Bilateral Transfemoral Amputee: A Case Study.

    PubMed

    Schalk, Stephanie A F; Jonkergouw, Niels; van der Meer, Fred; Swaan, Willem M; Aschoff, Horst-H; van der Wurff, Peter

    2015-09-01

    Individuals with a transfemoral amputation (TFA) may experience limitations in daily life due to reduced mobility and prosthesis-related problems. An osseointegrated prosthesis fixation (OPF) procedure in amputees might contribute to a solution for patients with short stumps or socket-related problems. To date, no study has specifically described the application of an OPF procedure in individuals with a TFA. This study evaluated the level of daily life activities of a 21-year old service member with a bilateral TFA and cerebral trauma. Due to a short stump length and coordination problems, an OPF procedure was deemed the most suitable option.The result of this procedure and the rehabilitation program showed an increased mobility and satisfaction as obtained by the assessment of life habits questionnaire (LIFE-H) and lower extremity functional scale. The participant was able to walk short distances and the Genium knee provided a stance position. Stair ambulation is impossible because of inadequate muscle capacity.In this specific case we conclude that the quality of life improved through the use of an OPF. However, OPF might not be the appropriate device for every individual with TFA, due to varying bone compositions, co-morbidities, and limited clinical experience and unknown long-term effects.

  19. Laser Ion Acceleration Control

    NASA Astrophysics Data System (ADS)

    Kawata, Shigeo; Nagashima, T.; Izumiyama, T.; Sato, D.; Takano, M.; Barada, D.; Ma, Y. Y.; Gu, Y. J.; Kong, Q.; Wang, P. X.; Wang, W. M.

    2013-10-01

    An intense femtosecond pulsed laser is employed to accelerate ions. The issues in the laser ion accelerator include the energy efficiency from the laser to the ions, the ion beam collimation, the ion energy spectrum control, the ion beam bunching, the ion particle energy control, etc. In the study particle computer simulations were performed to solve the issues, and each component was designed to control the ion beam quality. When an intense laser illuminates a target, electrons in the target are accelerated and leave from the target; temporarily a strong electric field is formed between the high-energy electrons and the target ions, and the target ions are accelerated. The energy efficiency from the laser to ions was improved by using a solid target with a fine sub-wavelength structure or by a near critical density gas plasma. The ion beam collimation was realized by holes behind the solid target. The control of the ion energy spectrum and the ion particle energy, and the ion beam bunching were successfully realized by a multi-stage laser-target interaction. The present study proposed a novel concept for a future compact laser ion accelerator, based on each component study required to control the ion beam quality and parameters. Partly supported by JSPS, MEXT, CORE, Japan/US Cooperation program, ASHULA and ILE/Osaka University.

  20. Dielectric laser accelerators

    NASA Astrophysics Data System (ADS)

    England, R. Joel; Noble, Robert J.; Bane, Karl; Dowell, David H.; Ng, Cho-Kuen; Spencer, James E.; Tantawi, Sami; Wu, Ziran; Byer, Robert L.; Peralta, Edgar; Soong, Ken; Chang, Chia-Ming; Montazeri, Behnam; Wolf, Stephen J.; Cowan, Benjamin; Dawson, Jay; Gai, Wei; Hommelhoff, Peter; Huang, Yen-Chieh; Jing, Chunguang; McGuinness, Christopher; Palmer, Robert B.; Naranjo, Brian; Rosenzweig, James; Travish, Gil; Mizrahi, Amit; Schachter, Levi; Sears, Christopher; Werner, Gregory R.; Yoder, Rodney B.

    2014-10-01

    The use of infrared lasers to power optical-scale lithographically fabricated particle accelerators is a developing area of research that has garnered increasing interest in recent years. The physics and technology of this approach is reviewed, which is referred to as dielectric laser acceleration (DLA). In the DLA scheme operating at typical laser pulse lengths of 0.1 to 1 ps, the laser damage fluences for robust dielectric materials correspond to peak surface electric fields in the GV /m regime. The corresponding accelerating field enhancement represents a potential reduction in active length of the accelerator between 1 and 2 orders of magnitude. Power sources for DLA-based accelerators (lasers) are less costly than microwave sources (klystrons) for equivalent average power levels due to wider availability and private sector investment. Because of the high laser-to-particle coupling efficiency, required pulse energies are consistent with tabletop microJoule class lasers. Combined with the very high (MHz) repetition rates these lasers can provide, the DLA approach appears promising for a variety of applications, including future high-energy physics colliders, compact light sources, and portable medical scanners and radiative therapy machines.

  1. Electrostatic Plasma Accelerator (EPA)

    NASA Technical Reports Server (NTRS)

    Brophy, John R.; Aston, Graeme

    1989-01-01

    The Electrostatic Plasma Accelerator (EPA) is a thruster concept which promises specific impulse levels between low power arcjets and those of the ion engine while retaining the relative simplicity of the arcjet. The EPA thruster produces thrust through the electrostatic acceleration of a moderately dense plasma. No accelerating electrodes are used and the specific impulse is a direct function of the applied discharge voltage and the propellant atomic mass. The goal of the present program is to demonstrate feasibility of the EPA thruster concept through experimental and theoretical investigations of the EPA acceleration mechanism and discharge chamber performance. Experimental investigations will include operating the test bed ion (TBI) engine as an EPA thruster and parametrically varying the thruster geometry and operating conditions to quantify the electrostatic plasma acceleration effect. The theoretical investigations will include the development of a discharge chamber model which describes the relationships between the engine size, plasma properties, and overall performance. For the EPA thruster to be a viable propulsion concept, overall thruster efficiencies approaching 30% with specific impulses approaching 1000 s must be achieved.

  2. Advanced accelerator theory development

    SciTech Connect

    Sampayan, S.E.; Houck, T.L.; Poole, B.; Tishchenko, N.; Vitello, P.A.; Wang, I.

    1998-02-09

    A new accelerator technology, the dielectric wall accelerator (DWA), is potentially an ultra compact accelerator/pulsed power driver. This new accelerator relies on three new components: the ultra-high gradient insulator, the asymmetric Blumlein and low jitter switches. In this report, we focused our attention on the first two components of the DWA system the insulators and the asymmetric Blumlein. First, we sought to develop the necessary design tools to model and scale the behavior of the high gradient insulator. To perform this task we concentrated on modeling the discharge processes (i.e., initiation and creation of the surface discharge). In addition, because these high gradient structures exhibit favorable microwave properties in certain accelerator configurations, we performed experiments and calculations to determine the relevant electromagnetic properties. Second, we performed circuit modeling to understand energy coupling to dynamic loads by the asymmetric Blumlein. Further, we have experimentally observed a non-linear coupling effect in certain asymmetric Blumlein configurations. That is, as these structures are stacked into a complete module, the output voltage does not sum linearly and a lower than expected output voltage results. Although we solved this effect experimentally, we performed calculations to understand this effect more fully to allow better optimization of this DWA pulse-forming line system.

  3. Adipose-Derived Stem Cells as a Tool for Dental Implant Osseointegration: an Experimental Study in the Dog

    PubMed Central

    Bressan, Eriberto; Botticelli, Daniele; Sivolella, Stefano; Bengazi, Franco; Guazzo, Riccardo; Sbricoli, Luca; Ricci, Sara; Ferroni, Letizia; Gardin, Chiara; Velez, Joaquin Urbizo; Zavan, Barbara

    2015-01-01

    The biological interaction between the jaw bones and dental implant is fundamental for the long-term success of dental implant placement. Nevertheless, the insufficient bone volume remains a major clinical problem, especially in case of immediate dental implant. Using a canine model, the present study proves the regenerative potential of adipose- derived stem cells (ADSCs) to repair peri-implant bone defects occurring in immediate dental implant placement. In six labradors, all mandibular premolars and the first molars were extracted bilaterally and three months later dental implants were installed with a marginal gap. The marginal defects were filled with hydroxyapatite (HA)-based scaffolds previously seeded with ADSCs. After one month of healing, specimens were prepared for histological and histomorphometric evaluations. Histological analyses of ground sections show that ADSCs significantly increase bone regeneration. Several new vessels, osteoblasts and new bone matrix were detected. By contrast, no inflammatory cells have been revealed. ADSCs could be used to accelerate bone healing in peri- implant defects in case of immediate dental implant placement. PMID:27014644

  4. Plasma-based accelerator structures

    SciTech Connect

    Schroeder, Carl B.

    1999-12-01

    Plasma-based accelerators have the ability to sustain extremely large accelerating gradients, with possible high-energy physics applications. This dissertation further develops the theory of plasma-based accelerators by addressing three topics: the performance of a hollow plasma channel as an accelerating structure, the generation of ultrashort electron bunches, and the propagation of laser pulses is underdense plasmas.

  5. Perturbations for transient acceleration

    SciTech Connect

    Vargas, Cristofher Zuñiga; Zimdahl, Winfried; Hipólito-Ricaldi, Wiliam S. E-mail: hipolito@ceunes.ufes.br

    2012-04-01

    According to the standard ΛCDM model, the accelerated expansion of the Universe will go on forever. Motivated by recent observational results, we explore the possibility of a finite phase of acceleration which asymptotically approaches another period of decelerated expansion. Extending an earlier study on a corresponding homogeneous and isotropic dynamics, in which interactions between dark matter and dark energy are crucial, the present paper also investigates the dynamics of the matter perturbations both on the Newtonian and General Relativistic (GR) levels and quantifies the potential relevance of perturbations of the dark-energy component. In the background, the model is tested against the Supernova type Ia (SNIa) data of the Constitution set and on the perturbative level against growth rate data, among them those of the WiggleZ survey, and the data of the 2dFGRS project. Our results indicate that a transient phase of accelerated expansion is not excluded by current observations.

  6. Uniform acceleration in general relativity

    NASA Astrophysics Data System (ADS)

    Friedman, Yaakov; Scarr, Tzvi

    2015-10-01

    We extend de la Fuente and Romero's (Gen Relativ Gravit 47:33, 2015) defining equation for uniform acceleration in a general curved spacetime from linear acceleration to the full Lorentz covariant uniform acceleration. In a flat spacetime background, we have explicit solutions. We use generalized Fermi-Walker transport to parallel transport the Frenet basis along the trajectory. In flat spacetime, we obtain velocity and acceleration transformations from a uniformly accelerated system to an inertial system. We obtain the time dilation between accelerated clocks. We apply our acceleration transformations to the motion of a charged particle in a constant electromagnetic field and recover the Lorentz-Abraham-Dirac equation.

  7. Microelectromechanical acceleration-sensing apparatus

    DOEpatents

    Lee, Robb M.; Shul, Randy J.; Polosky, Marc A.; Hoke, Darren A.; Vernon, George E.

    2006-12-12

    An acceleration-sensing apparatus is disclosed which includes a moveable shuttle (i.e. a suspended mass) and a latch for capturing and holding the shuttle when an acceleration event is sensed above a predetermined threshold level. The acceleration-sensing apparatus provides a switch closure upon sensing the acceleration event and remains latched in place thereafter. Examples of the acceleration-sensing apparatus are provided which are responsive to an acceleration component in a single direction (i.e. a single-sided device) or to two oppositely-directed acceleration components (i.e. a dual-sided device). A two-stage acceleration-sensing apparatus is also disclosed which can sense two acceleration events separated in time. The acceleration-sensing apparatus of the present invention has applications, for example, in an automotive airbag deployment system.

  8. Diffusive Shock Acceleration

    NASA Astrophysics Data System (ADS)

    Baring, Matthew

    2003-04-01

    The process of diffusive acceleration of charged particles in shocked plasmas is widely invoked in astrophysics to account for the ubiquitous presence of signatures of non-thermal relativistic electrons and ions in the universe. This statistical energization mechanism, manifested in turbulent media, was first posited by Enrico Fermi in 1949 to explain the observed cosmic ray population, which exhibits an almost power-law distribution in rigidity. The absence of a momentum scale is a key characteristic of diffusive shock acceleration, and astrophysical systems generally only impose scales at the injection (low energy) and loss (high energy) ends of the particle spectrum. The existence of structure in the cosmic ray spectrum (the "knee") at around 3000 TeV has promoted contentions that there are at least two origins for cosmic rays, a galactic one supplying those up to the knee, and perhaps an extragalactic one that can explain even the ultra-high energy cosmic rays (UHECRs) seen at 1-300 EeV. Accounting for the UHECRs with familiar astrophysical sites of acceleration has historically proven difficult due to the need to assume high magnetic fields in order to reduce the shortest diffusive acceleration timescale, the ion gyroperiod, to meaningful values. Yet active galaxies and gamma-ray bursts remain strong and interesting candidate sources for UHECRs, turning the theoretical focus to relativistic shocks. This review summarizes properties of diffusive shock acceleration that are salient to the issue of UHECR generation. These include spectral indices, anisotropies, acceleration efficencies and timescales, as functions of the shock speed and mean field orientation, and also the degree of field turbulence. Astrophysical sites for UHECR production are also critiqued.

  9. 'Light Sail' Acceleration Reexamined

    SciTech Connect

    Macchi, Andrea; Veghini, Silvia; Pegoraro, Francesco

    2009-08-21

    The dynamics of the acceleration of ultrathin foil targets by the radiation pressure of superintense, circularly polarized laser pulses is investigated by analytical modeling and particle-in-cell simulations. By addressing self-induced transparency and charge separation effects, it is shown that for 'optimal' values of the foil thickness only a thin layer at the rear side is accelerated by radiation pressure. The simple 'light sail' model gives a good estimate of the energy per nucleon, but overestimates the conversion efficiency of laser energy into monoenergetic ions.

  10. HIGH GRADIENT INDUCTION ACCELERATOR

    SciTech Connect

    Caporaso, G J; Sampayan, S; Chen, Y; Blackfield, D; Harris, J; Hawkins, S; Holmes, C; Krogh, M; Nelson, S; Nunnally, W; Paul, A; Poole, B; Rhodes, M; Sanders, D; Selenes, K; Sullivan, J; Wang, L; Watson, J

    2007-06-21

    A new type of compact induction accelerator is under development at the Lawrence Livermore National Laboratory that promises to increase the average accelerating gradient by at least an order of magnitude over that of existing induction machines. The machine is based on the use of high gradient vacuum insulators, advanced dielectric materials and switches and is stimulated by the desire for compact flash x-ray radiography sources. Research describing an extreme variant of this technology aimed at proton therapy for cancer will be described. Progress in applying this technology to several applications will be reviewed.

  11. "Light sail" acceleration reexamined.

    PubMed

    Macchi, Andrea; Veghini, Silvia; Pegoraro, Francesco

    2009-08-21

    The dynamics of the acceleration of ultrathin foil targets by the radiation pressure of superintense, circularly polarized laser pulses is investigated by analytical modeling and particle-in-cell simulations. By addressing self-induced transparency and charge separation effects, it is shown that for "optimal" values of the foil thickness only a thin layer at the rear side is accelerated by radiation pressure. The simple "light sail" model gives a good estimate of the energy per nucleon, but overestimates the conversion efficiency of laser energy into monoenergetic ions.

  12. High intensity hadron accelerators

    SciTech Connect

    Teng, L.C.

    1989-05-01

    This rapporteur report consists mainly of two parts. Part I is an abridged review of the status of all High Intensity Hadron Accelerator projects in the world in semi-tabulated form for quick reference and comparison. Part II is a brief discussion of the salient features of the different technologies involved. The discussion is based mainly on my personal experiences and opinions, tempered, I hope, by the discussions I participated in in the various parallel sessions of the workshop. In addition, appended at the end is my evaluation and expression of the merits of high intensity hadron accelerators as research facilities for nuclear and particle physics.

  13. Metal plasma immersion ion implantation and deposition (MePIIID) on screw-shaped titanium implant: The effects of ion source, ion dose and acceleration voltage on surface chemistry and morphology.

    PubMed

    Kang, Byung-Soo; Sul, Young-Taeg; Jeong, Yongsoo; Byon, Eungsun; Kim, Jong-Kuk; Cho, Suyeon; Oh, Se-Jung; Albrektsson, Tomas

    2011-07-01

    The present study investigated the effect of metal plasma immersion ion implantation and deposition (MePIIID) process parameters, i.e., plasma sources of magnesium and calcium, ion dose, and acceleration voltage on the surface chemistry and morphology of screw-type titanium implants that have been most widely used for osseointegrated implants. It is found that irrespective of plasma ion source, surface topography and roughness showed no differences at the nanometer level; that atom concentrations increased with ion dose but decreased with acceleration voltage. Data obtained from X-ray photoelectron spectroscopy and auger electron spectroscopy suggested that MePIIID process produces 'intermixed' layer of cathodic arc deposition and plasma immersion ion implantation. The MePIIID process may create desired bioactive surface chemistry of dental and orthopaedic implants by tailoring ion and plasma sources and thus enable investigations of the effect of the surface chemistry on bone response.

  14. Radioisotope Dating with Accelerators.

    ERIC Educational Resources Information Center

    Muller, Richard A.

    1979-01-01

    Explains a new method of detecting radioactive isotopes by counting their accelerated ions rather than the atoms that decay during the counting period. This method increases the sensitivity by several orders of magnitude, and allows one to find the ages of much older and smaller samples. (GA)

  15. Accelerated Management Development

    ERIC Educational Resources Information Center

    Munn, Kenn

    1974-01-01

    Western Electric's accelerated management development program for hand picked college graduate students consists of a high risk training project in which the management candidate accomplishes his task or is terminated. The success of such projects puts candidates in third level management in seven years or half the normal time. (DS)

  16. FPGA Verification Accelerator (FVAX)

    NASA Technical Reports Server (NTRS)

    Oh, Jane; Burke, Gary

    2008-01-01

    Is Verification Acceleration Possible? - Increasing the visibility of the internal nodes of the FPGA results in much faster debug time - Forcing internal signals directly allows a problem condition to be setup very quickly center dot Is this all? - No, this is part of a comprehensive effort to improve the JPL FPGA design and V&V process.

  17. Combined generating-accelerating buncher for compact linear accelerators

    NASA Astrophysics Data System (ADS)

    Savin, E. A.; Matsievskiy, S. V.; Sobenin, N. P.; Sokolov, I. D.; Zavadtsev, A. A.

    2016-09-01

    Described in the previous article [1] method of the power extraction from the modulated electron beam has been applied to the compact standing wave electron linear accelerator feeding system, which doesnt require any connection waveguides between the power source and the accelerator itself [2]. Generating and accelerating bunches meet in the hybrid accelerating cell operating at TM020 mode, thus the accelerating module is placed on the axis of the generating module, which consists from the pulsed high voltage electron sources and electrons dumps. This combination makes the accelerator very compact in size which is very valuable for the modern applications such as portable inspection sources. Simulations and geometry cold tests are presented.

  18. Neurodegeneration in accelerated aging.

    PubMed

    Scheibye-Knudsen, Moren

    2016-11-01

    The growing proportion of elderly people represents an increasing economic burden, not least because of age-associated diseases that pose a significant cost to the health service. Finding possible interventions to age-associated disorders therefore have wide ranging implications. A number of genetically defined accelerated aging diseases have been characterized that can aid in our understanding of aging. Interestingly, all these diseases are associated with defects in the maintenance of our genome. A subset of these disorders, Cockayne syndrome, Xeroderma pigmentosum group A and ataxia-telangiectasia, show neurological involvement reminiscent of what is seen in primary human mitochondrial diseases. Mitochondria are the power plants of the cells converting energy stored in oxygen, sugar, fat, and protein into ATP, the energetic currency of our body. Emerging evidence has linked this organelle to aging and finding mitochondrial dysfunction in accelerated aging disorders thereby strengthens the mitochondrial theory of aging. This theory states that an accumulation of damage to the mitochondria may underlie the process of aging. Indeed, it appears that some accelerated aging disorders that show neurodegeneration also have mitochondrial dysfunction. The mitochondrial alterations may be secondary to defects in nuclear DNA repair. Indeed, nuclear DNA damage may lead to increased energy consumption, alterations in mitochondrial ATP production and defects in mitochondrial recycling, a term called mitophagy. These changes may be caused by activation of poly-ADP-ribose-polymerase 1 (PARP1), an enzyme that responds to DNA damage. Upon activation PARP1 utilizes key metabolites that attenuate pathways that are normally protective for the cell. Notably, pharmacological inhibition of PARP1 or reconstitution of the metabolites rescues the changes caused by PARP1 hyperactivation and in many cases reverse the phenotypes associated with accelerated aging. This implies that modulation

  19. Menopause accelerates biological aging

    PubMed Central

    Levine, Morgan E.; Lu, Ake T.; Chen, Brian H.; Hernandez, Dena G.; Singleton, Andrew B.; Ferrucci, Luigi; Bandinelli, Stefania; Salfati, Elias; Manson, JoAnn E.; Quach, Austin; Kusters, Cynthia D. J.; Kuh, Diana; Wong, Andrew; Teschendorff, Andrew E.; Widschwendter, Martin; Ritz, Beate R.; Absher, Devin; Assimes, Themistocles L.; Horvath, Steve

    2016-01-01

    Although epigenetic processes have been linked to aging and disease in other systems, it is not yet known whether they relate to reproductive aging. Recently, we developed a highly accurate epigenetic biomarker of age (known as the “epigenetic clock”), which is based on DNA methylation levels. Here we carry out an epigenetic clock analysis of blood, saliva, and buccal epithelium using data from four large studies: the Women's Health Initiative (n = 1,864); Invecchiare nel Chianti (n = 200); Parkinson's disease, Environment, and Genes (n = 256); and the United Kingdom Medical Research Council National Survey of Health and Development (n = 790). We find that increased epigenetic age acceleration in blood is significantly associated with earlier menopause (P = 0.00091), bilateral oophorectomy (P = 0.0018), and a longer time since menopause (P = 0.017). Conversely, epigenetic age acceleration in buccal epithelium and saliva do not relate to age at menopause; however, a higher epigenetic age in saliva is exhibited in women who undergo bilateral oophorectomy (P = 0.0079), while a lower epigenetic age in buccal epithelium was found for women who underwent menopausal hormone therapy (P = 0.00078). Using genetic data, we find evidence of coheritability between age at menopause and epigenetic age acceleration in blood. Using Mendelian randomization analysis, we find that two SNPs that are highly associated with age at menopause exhibit a significant association with epigenetic age acceleration. Overall, our Mendelian randomization approach and other lines of evidence suggest that menopause accelerates epigenetic aging of blood, but mechanistic studies will be needed to dissect cause-and-effect relationships further. PMID:27457926

  20. Stacked insulator induction accelerator gaps

    SciTech Connect

    Houck, T.I.; Westenskow, G.A.; Kim, J.S.; Eylon, S.; Henestroza, E.; Yu, S.S.; Vanecek, D.

    1997-05-01

    Stacked insulators, with alternating layers of insulating material and conducting film, have been shown to support high surface electrical field stresses. We have investigated the application of the stacked insulator technology to the design of induction accelerator modules for the Relativistic-Klystron Two-Beam Accelerator program. The rf properties of the accelerating gaps using stacked insulators, particularly the impedance at frequencies above the beam pipe cutoff frequency, are investigated. Low impedance is critical for Relativistic-Klystron Two-Beam Accelerator applications where a high current, bunched beam is trsnsported through many accelerating gaps. An induction accelerator module designs using a stacked insulator is presented.

  1. Mass spectrometry with accelerators.

    PubMed

    Litherland, A E; Zhao, X-L; Kieser, W E

    2011-01-01

    As one in a series of articles on Canadian contributions to mass spectrometry, this review begins with an outline of the history of accelerator mass spectrometry (AMS), noting roles played by researchers at three Canadian AMS laboratories. After a description of the unique features of AMS, three examples, (14)C, (10)Be, and (129)I are given to illustrate the methods. The capabilities of mass spectrometry have been extended by the addition of atomic isobar selection, molecular isobar attenuation, further ion acceleration, followed by ion detection and ion identification at essentially zero dark current or ion flux. This has been accomplished by exploiting the techniques and accelerators of atomic and nuclear physics. In 1939, the first principles of AMS were established using a cyclotron. In 1977 the selection of isobars in the ion source was established when it was shown that the (14)N(-) ion was very unstable, or extremely difficult to create, making a tandem electrostatic accelerator highly suitable for assisting the mass spectrometric measurement of the rare long-lived radioactive isotope (14)C in the environment. This observation, together with the large attenuation of the molecular isobars (13)CH(-) and (12)CH 2(-) during tandem acceleration and the observed very low background contamination from the ion source, was found to facilitate the mass spectrometry of (14)C to at least a level of (14)C/C ~ 6 × 10(-16), the equivalent of a radiocarbon age of 60,000 years. Tandem Accelerator Mass Spectrometry, or AMS, has now made possible the accurate radiocarbon dating of milligram-sized carbon samples by ion counting as well as dating and tracing with many other long-lived radioactive isotopes such as (10)Be, (26)Al, (36)Cl, and (129)I. The difficulty of obtaining large anion currents with low electron affinities and the difficulties of isobar separation, especially for the heavier mass ions, has prompted the use of molecular anions and the search for alternative

  2. Review of ion accelerators

    SciTech Connect

    Alonso, J.

    1990-06-01

    The field of ion acceleration to higher energies has grown rapidly in the last years. Many new facilities as well as substantial upgrades of existing facilities have extended the mass and energy range of available beams. Perhaps more significant for the long-term development of the field has been the expansion in the applications of these beams, and the building of facilities dedicated to areas outside of nuclear physics. This review will cover many of these new developments. Emphasis will be placed on accelerators with final energies above 50 MeV/amu. Facilities such as superconducting cyclotrons and storage rings are adequately covered in other review papers, and so will not be covered here.

  3. Accelerator research studies

    SciTech Connect

    Not Available

    1992-01-01

    The Accelerator Research Studies program at the University of Maryland, sponsored by the Department of Energy under grant number DE-FG05-91ER40642, is currently in the first year of a three-year funding cycle. The program consists of the following three tasks: TASK A, Study of Transport and Longitudinal Compression of Intense, High-Brightness Beams, TASK B, Study of Collective Ion Acceleration by Intense Electron Beams and Pseudospark Produced High Brightness Electron Beams; TASK C, Study of a Gyroklystron High-power Microwave Source for Linear Colliders. In this report we document the progress that has been made during the past year for each of the three tasks.

  4. Commissioning the GTA accelerator

    SciTech Connect

    Sander, O.R.; Atkins, W.H.; Bolme, G.O.; Bowling, S.; Brown, S.; Cole, R.; Gilpatrick, J.D.; Garnett, R.; Guy, F.W.; Ingalls, W.B.; Johnson, K.F.; Kerstiens, D.; Little, C.; Lohsen, R.A.; Lloyd, S.; Lysenko, W.P.; Mottershead, C.T.; Neuschaefer, G.; Power, J.; Rusthoi, D.P.; Sandoval, D.P. Stevens, R.R. Jr.; Vaughn, G.; Wadlinger, E.A.; Yuan, V.; Connolly, R.; Weiss, R.; Saadatmand, K.

    1992-09-01

    The Ground Test Accelerator (GTA) is supported by the Strategic Defense command as part of their Neutral Particle Beam (NPB) program. Neutral particles have the advantage that in space they are unaffected by the earth`s magnetic field and travel in straight lines unless they enter the earth`s atmosphere and become charged by stripping. Heavy particles are difficult to stop and can probe the interior of space vehicles; hence, NPB can function as a discriminator between warheads and decoys. We are using GTA to resolve the physics and engineering issues related to accelerating, focusing, and steering a high-brightness, high-current H{sup -} beam and then neutralizing it. Our immediate goal is to produce a 24-MeV, 50mA device with a 2% duty factor.

  5. Commissioning the GTA accelerator

    SciTech Connect

    Sander, O.R.; Atkins, W.H.; Bolme, G.O.; Bowling, S.; Brown, S.; Cole, R.; Gilpatrick, J.D.; Garnett, R.; Guy, F.W.; Ingalls, W.B.; Johnson, K.F.; Kerstiens, D.; Little, C.; Lohsen, R.A.; Lloyd, S.; Lysenko, W.P.; Mottershead, C.T.; Neuschaefer, G.; Power, J.; Rusthoi, D.P.; Sandoval, D.P. Stevens, R.R. Jr.; Vaughn, G.; Wadlinger, E.A.; Yuan, V. ); Connolly, R.; Weiss, R. (Gr

    1992-01-01

    The Ground Test Accelerator (GTA) is supported by the Strategic Defense command as part of their Neutral Particle Beam (NPB) program. Neutral particles have the advantage that in space they are unaffected by the earth's magnetic field and travel in straight lines unless they enter the earth's atmosphere and become charged by stripping. Heavy particles are difficult to stop and can probe the interior of space vehicles; hence, NPB can function as a discriminator between warheads and decoys. We are using GTA to resolve the physics and engineering issues related to accelerating, focusing, and steering a high-brightness, high-current H{sup -} beam and then neutralizing it. Our immediate goal is to produce a 24-MeV, 50mA device with a 2% duty factor.

  6. Auroral ion acceleration

    NASA Astrophysics Data System (ADS)

    Shalimov, S. L.

    From the altitude of 500 km to 15 R sub E everywhere conic like distributions of H+, O+, He+ ions are moving upwards from the ionosphere along the geomagnetic field lines in the auroral zone. The distributed ions suggest the existence of ion transverse acceleration mechanisms (ITAM) acting below the observation point. The more plausible mechanisms are connected with the resonance of the type wave particle between ions and the observed EIC and LH waves and are also due to the existence of the local transverse electric fields in the ionoshere and the magnetosphere. The known ion transverse acceleration mechanisms were complemented by new results. The conical distributions of ionospheric ions at different altitudes in the auroral zone are pointed out.

  7. Review of accelerator instrumentation

    SciTech Connect

    Pellegrin, J.L.

    1980-05-01

    Some of the problems associated with the monitoring of accelerator beams, particularly storage rings' beams, are reviewed along with their most common solutions. The various electrode structures used for the measurement of beam current, beam position, and the detection of the bunches' transverse oscillations, yield pulses with sub-nanosecond widths. The electronics for the processing of these short pulses involves wide band techniques and circuits usually not readily available from industry or the integrated circuit market: passive or active, successive integrations, linear gating, sample-and-hold circuits with nanosecond acquisition time, etc. This report also presents the work performed recently for monitoring the ultrashort beams of colliding linear accelerators or single-pass colliders. To minimize the beam emittance, the beam position must be measured with a high resolution, and digitized on a pulse-to-pulse basis. Experimental results obtained with the Stanford two-mile Linac single bunches are included.

  8. Hardware Accelerated Simulated Radiography

    SciTech Connect

    Laney, D; Callahan, S; Max, N; Silva, C; Langer, S; Frank, R

    2005-04-12

    We present the application of hardware accelerated volume rendering algorithms to the simulation of radiographs as an aid to scientists designing experiments, validating simulation codes, and understanding experimental data. The techniques presented take advantage of 32 bit floating point texture capabilities to obtain validated solutions to the radiative transport equation for X-rays. An unsorted hexahedron projection algorithm is presented for curvilinear hexahedra that produces simulated radiographs in the absorption-only regime. A sorted tetrahedral projection algorithm is presented that simulates radiographs of emissive materials. We apply the tetrahedral projection algorithm to the simulation of experimental diagnostics for inertial confinement fusion experiments on a laser at the University of Rochester. We show that the hardware accelerated solution is faster than the current technique used by scientists.

  9. Adaptive control for accelerators

    DOEpatents

    Eaton, Lawrie E.; Jachim, Stephen P.; Natter, Eckard F.

    1991-01-01

    An adaptive feedforward control loop is provided to stabilize accelerator beam loading of the radio frequency field in an accelerator cavity during successive pulses of the beam into the cavity. A digital signal processor enables an adaptive algorithm to generate a feedforward error correcting signal functionally determined by the feedback error obtained by a beam pulse loading the cavity after the previous correcting signal was applied to the cavity. Each cavity feedforward correcting signal is successively stored in the digital processor and modified by the feedback error resulting from its application to generate the next feedforward error correcting signal. A feedforward error correcting signal is generated by the digital processor in advance of the beam pulse to enable a composite correcting signal and the beam pulse to arrive concurrently at the cavity.

  10. Pulsed electromagnetic gas acceleration

    NASA Technical Reports Server (NTRS)

    Jahn, R. G.; Vonjaskowsky, W. F.; Clark, K. E.

    1971-01-01

    Experimental data were combined with one-dimensional conservation relations to yield information on the energy deposition ratio in a parallel-plate accelerator, where the downstream flow was confined to a constant area channel. Approximately 70% of the total input power was detected in the exhaust flow, of which only about 20% appeared as directed kinetic energy, thus implying that a downstream expansion to convert chamber enthalpy into kinetic energy must be an important aspect of conventional high power MPD arcs. Spectroscopic experiments on a quasi-steady MPD argon accelerator verified the presence of A(III) and the absence of A(I), and indicated an azimuthal structure in the jet related to the mass injection locations. Measurements of pressure in the arc chamber and impact pressure in the exhaust jet using a piezocrystal backed by a Plexiglas rod were in good agreement with the electromagnetic thrust model.

  11. Pulsed Drift Tube Accelerator

    SciTech Connect

    Faltens, A.

    2004-10-25

    The pulsed drift-tube accelerator (DTA) concept was revived by Joe Kwan and John Staples and is being considered for the HEDP/WDM application. It could be used to reach the full energy or as an intermediate accelerator between the diode and a high gradient accelerator such as multi-beam r.f. In the earliest LBNL HIF proposals and conceptual drivers it was used as an extended injector to reach energies where an induction linac with magnetic quadrupoles is the best choice. For HEDP, because of the very short pulse duration, the DTA could provide an acceleration rate of about 1MV/m. This note is divided into two parts: the first, a design based on existing experience; the second, an optimistic extrapolation. The first accelerates 16 parallel K{sup +} beams at a constant line charge density of 0.25{micro} C/m per beam to 10 MeV; the second uses a stripper and charge selector at around 4MeV followed by further acceleration to reach 40 MeV. Both benefit from more compact sources than the present 2MV injector source, although that beam is the basis of the first design and is a viable option. A pulsed drift-tube accelerator was the first major HIF experiment at LBNL. It was designed to produce a 2{micro}s rectangular 1 Ampere C{sub s}{sup +} beam at 2MeV. It ran comfortably at 1.6MeV for several years, then at lower voltages and currents for other experiments, and remnants of that experiment are in use in present experiments, still running 25 years later. The 1A current, completely equivalent to 1.8A K{sup +}, was chosen to be intermediate between the beamlets appropriate for a multi-beam accelerator, and a single beam of, say, 10A, at injection energies. The original driver scenarios using one large beam on each side of the reactor rapidly fell out of favor because of the very high transverse and longitudinal fields from the beam space charge, circa 1MV/cm and 250 kV/cm respectively, near the chamber and because of aberrations in focusing a large diameter beam down to a 1

  12. SUPERDIFFUSIVE SHOCK ACCELERATION

    SciTech Connect

    Perri, S.; Zimbardo, G.

    2012-05-10

    The theory of diffusive shock acceleration is extended to the case of superdiffusive transport, i.e., when the mean square deviation grows proportionally to t{sup {alpha}}, with {alpha} > 1. Superdiffusion can be described by a statistical process called Levy random walk, in which the propagator is not a Gaussian but it exhibits power-law tails. By using the propagator appropriate for Levy random walk, it is found that the indices of energy spectra of particles are harder than those obtained where a normal diffusion is envisaged, with the spectral index decreasing with the increase of {alpha}. A new scaling for the acceleration time is also found, allowing substantially shorter times than in the case of normal diffusion. Within this framework we can explain a number of observations of flat spectra in various astrophysical and heliospheric contexts, for instance, for the Crab Nebula and the termination shock of the solar wind.

  13. Accelerators for Cancer Therapy

    DOE R&D Accomplishments Database

    Lennox, Arlene J.

    2000-05-30

    The vast majority of radiation treatments for cancerous tumors are given using electron linacs that provide both electrons and photons at several energies. Design and construction of these linacs are based on mature technology that is rapidly becoming more and more standardized and sophisticated. The use of hadrons such as neutrons, protons, alphas, or carbon, oxygen and neon ions is relatively new. Accelerators for hadron therapy are far from standardized, but the use of hadron therapy as an alternative to conventional radiation has led to significant improvements and refinements in conventional treatment techniques. This paper presents the rationale for radiation therapy, describes the accelerators used in conventional and hadron therapy, and outlines the issues that must still be resolved in the emerging field of hadron therapy.

  14. Accelerated plate tectonics.

    PubMed

    Anderson, D L

    1975-03-21

    The concept of a stressed elastic lithospheric plate riding on a viscous asthenosphere is used to calculate the recurrence interval of great earthquakes at convergent plate boundaries, the separation of decoupling and lithospheric earthquakes, and the migration pattern of large earthquakes along an arc. It is proposed that plate motions accelerate after great decoupling earthquakes and that most of the observed plate motions occur during short periods of time, separated by periods of relative quiescence.

  15. Linear induction accelerator

    DOEpatents

    Buttram, M.T.; Ginn, J.W.

    1988-06-21

    A linear induction accelerator includes a plurality of adder cavities arranged in a series and provided in a structure which is evacuated so that a vacuum inductance is provided between each adder cavity and the structure. An energy storage system for the adder cavities includes a pulsed current source and a respective plurality of bipolar converting networks connected thereto. The bipolar high-voltage, high-repetition-rate square pulse train sets and resets the cavities. 4 figs.

  16. Compact pulsed accelerator

    SciTech Connect

    Rhee, M.J.; Schneider, R.F.

    1983-01-01

    The formation of fast pulses from a current charged transmission line and opening switch is described. By employing a plasma focus as an opening switch and diode in the prototype device, a proton beam of peak energy 250 keV is produced. The time integrated energy spectrum of the beam is constructed from a Thomson spectrograph. Applications of this device as an inexpensive and portable charged particle accelerator are discussed. 7 refs., 5 figs., 1 tab.

  17. ION ACCELERATION SYSTEM

    DOEpatents

    Luce, J.S.; Martin, J.A.

    1960-02-23

    Well focused, intense ion beams are obtained by providing a multi- apertured source grid in front of an ion source chamber and an accelerating multi- apertured grid closely spaced from and in alignment with the source grid. The longest dimensions of the elongated apertures in the grids are normal to the direction of the magnetic field used with the device. Large ion currents may be withdrawn from the source, since they do not pass through any small focal region between the grids.

  18. Frontiers of accelerator instrumentation

    SciTech Connect

    Ross, M.

    1992-08-01

    New technology has permitted significant performance improvements of established instrumentation techniques including beam position and profile monitoring. Fundamentally new profile monitor strategies are required for the next generation of accelerators, especially linear colliders (LC). Beams in these machines may be three orders of magnitude smaller than typical beams in present colliders. In this paper we review both the present performance levels achieved by conventional systems and present some new ideas for future colliders.

  19. Accelerator simulation using computers

    SciTech Connect

    Lee, M.; Zambre, Y.; Corbett, W.

    1992-01-01

    Every accelerator or storage ring system consists of a charged particle beam propagating through a beam line. Although a number of computer programs exits that simulate the propagation of a beam in a given beam line, only a few provide the capabilities for designing, commissioning and operating the beam line. This paper shows how a multi-track'' simulation and analysis code can be used for these applications.

  20. Accelerator simulation using computers

    SciTech Connect

    Lee, M.; Zambre, Y.; Corbett, W.

    1992-01-01

    Every accelerator or storage ring system consists of a charged particle beam propagating through a beam line. Although a number of computer programs exits that simulate the propagation of a beam in a given beam line, only a few provide the capabilities for designing, commissioning and operating the beam line. This paper shows how a ``multi-track`` simulation and analysis code can be used for these applications.

  1. Accelerated Profile HMM Searches.

    PubMed

    Eddy, Sean R

    2011-10-01

    Profile hidden Markov models (profile HMMs) and probabilistic inference methods have made important contributions to the theory of sequence database homology search. However, practical use of profile HMM methods has been hindered by the computational expense of existing software implementations. Here I describe an acceleration heuristic for profile HMMs, the "multiple segment Viterbi" (MSV) algorithm. The MSV algorithm computes an optimal sum of multiple ungapped local alignment segments using a striped vector-parallel approach previously described for fast Smith/Waterman alignment. MSV scores follow the same statistical distribution as gapped optimal local alignment scores, allowing rapid evaluation of significance of an MSV score and thus facilitating its use as a heuristic filter. I also describe a 20-fold acceleration of the standard profile HMM Forward/Backward algorithms using a method I call "sparse rescaling". These methods are assembled in a pipeline in which high-scoring MSV hits are passed on for reanalysis with the full HMM Forward/Backward algorithm. This accelerated pipeline is implemented in the freely available HMMER3 software package. Performance benchmarks show that the use of the heuristic MSV filter sacrifices negligible sensitivity compared to unaccelerated profile HMM searches. HMMER3 is substantially more sensitive and 100- to 1000-fold faster than HMMER2. HMMER3 is now about as fast as BLAST for protein searches.

  2. Acceleration during magnetic reconnection

    SciTech Connect

    Beresnyak, Andrey; Li, Hui

    2015-07-16

    The presentation begins with colorful depictions of solar x-ray flares and references to pulsar phenomena. Plasma reconnection is complex, could be x-point dominated or turbulent, field lines could break due to either resistivity or non-ideal effects, such as electron pressure anisotropy. Electron acceleration is sometimes observed, and sometimes not. One way to study this complex problem is to have many examples of the process (reconnection) and compare them; the other way is to simplify and come to something robust. Ideal MHD (E=0) turbulence driven by magnetic energy is assumed, and the first-order acceleration is sought. It is found that dissipation in big (length >100 ion skin depths) current sheets is universal and independent on microscopic resistivity and the mean imposed field; particles are regularly accelerated while experiencing curvature drift in flows driven by magnetic tension. One example of such flow is spontaneous reconnection. This explains hot electrons with a power-law tail in solar flares, as well as ultrashort time variability in some astrophysical sources.

  3. Accelerator mass spectrometry.

    PubMed

    Hellborg, Ragnar; Skog, Göran

    2008-01-01

    In this overview the technique of accelerator mass spectrometry (AMS) and its use are described. AMS is a highly sensitive method of counting atoms. It is used to detect very low concentrations of natural isotopic abundances (typically in the range between 10(-12) and 10(-16)) of both radionuclides and stable nuclides. The main advantages of AMS compared to conventional radiometric methods are the use of smaller samples (mg and even sub-mg size) and shorter measuring times (less than 1 hr). The equipment used for AMS is almost exclusively based on the electrostatic tandem accelerator, although some of the newest systems are based on a slightly different principle. Dedicated accelerators as well as older "nuclear physics machines" can be found in the 80 or so AMS laboratories in existence today. The most widely used isotope studied with AMS is 14C. Besides radiocarbon dating this isotope is used in climate studies, biomedicine applications and many other fields. More than 100,000 14C samples are measured per year. Other isotopes studied include 10Be, 26Al, 36Cl, 41Ca, 59Ni, 129I, U, and Pu. Although these measurements are important, the number of samples of these other isotopes measured each year is estimated to be less than 10% of the number of 14C samples.

  4. Electrostatic Plasma Accelerator (EPA)

    NASA Technical Reports Server (NTRS)

    Brophy, John R.; Aston, Graeme

    1995-01-01

    The application of electric propulsion to communications satellites, however, has been limited to the use of hydrazine thrusters with electric heaters for thrust and specific impulse augmentation. These electrothermal thrusters operate at specific impulse levels of approximately 300 s with heater powers of about 500 W. Low power arcjets (1-3 kW) are currently being investigated as a way to increase specific impulse levels to approximately 500 s. Ion propulsion systems can easily produce specific impulses of 3000 s or greater, but have yet to be applied to communications satellites. The reasons most often given for not using ion propulsion systems are their high level of overall complexity, low thrust with long burn times, and the difficulty of integrating the propulsion system into existing commercial spacecraft busses. The Electrostatic Plasma Accelerator (EPA) is a thruster concept which promises specific impulse levels between low power arcjets and those of the ion engine while retaining the relative simplicity of the arcjet. The EPA thruster produces thrust through the electrostatic acceleration of a moderately dense plasma. No accelerating electrodes are used and the specific impulse is a direct function of the applied discharge voltage and the propellant atomic mass.

  5. Berkeley Proton Linear Accelerator

    DOE R&D Accomplishments Database

    Alvarez, L. W.; Bradner, H.; Franck, J.; Gordon, H.; Gow, J. D.; Marshall, L. C.; Oppenheimer, F. F.; Panofsky, W. K. H.; Richman, C.; Woodyard, J. R.

    1953-10-13

    A linear accelerator, which increases the energy of protons from a 4 Mev Van de Graaff injector, to a final energy of 31.5 Mev, has been constructed. The accelerator consists of a cavity 40 feet long and 39 inches in diameter, excited at resonance in a longitudinal electric mode with a radio-frequency power of about 2.2 x 10{sup 6} watts peak at 202.5 mc. Acceleration is made possible by the introduction of 46 axial "drift tubes" into the cavity, which is designed such that the particles traverse the distance between the centers of successive tubes in one cycle of the r.f. power. The protons are longitudinally stable as in the synchrotron, and are stabilized transversely by the action of converging fields produced by focusing grids. The electrical cavity is constructed like an inverted airplane fuselage and is supported in a vacuum tank. Power is supplied by 9 high powered oscillators fed from a pulse generator of the artificial transmission line type.

  6. ACCELERATION INTEGRATING MEANS

    DOEpatents

    Wilkes, D.F.

    1961-08-29

    An acceleration responsive device is described. A housing has at one end normally open electrical contacts and contains a piston system with a first part of non-magnetic material having metering orifices in the side walls for forming an air bearing between it and the walls of the housing; this first piston part is normally held against the other end of the housing from the noted contacts by a second piston or reset part. The reset part is of partly magnetic material, is separable from the flrst piston part, and is positioned within the housing intermediate the contacts and the first piston part. A magnet carried by the housing imposes a retaining force upon the reset part, along with a helical compression spring that is between the reset part and the end with the contacts. When a predetermined acceleration level is attained, the reset part overcomes the bias or retaining force provided by the magnet and the spring'' snaps'' into a depression in the housing adjacent the contacts. The first piston part is then free to move toward the contacts with its movement responsive tc acceleration forces and the metering orifices. (AEC)

  7. French nuclear physics accelerator opens

    NASA Astrophysics Data System (ADS)

    Dumé, Belle

    2016-12-01

    A new €140m particle accelerator for nuclear physics located at the French Large Heavy Ion National Accelerator (GANIL) in Caen was inaugurated last month in a ceremony attended by French president François Hollande.

  8. Plasma accelerator experiments in Yugoslavia

    NASA Astrophysics Data System (ADS)

    Purić, J.; Astashynski, V. M.; Kuraica, M. M.; Dojčinovié, I. P.

    2002-12-01

    An overview is given of the results obtained in the Plasma Accelerator Experiments in Belgrade, using quasi-stationary high current plasma accelerators constructed within the framework of the Yugoslavia-Belarus Joint Project. So far, the following plasma accelerators have been realized: Magnetoplasma Compressor type (MPC); MPC Yu type; one stage Erosive Plasma Dynamic System (EPDS) and, in final stage of construction two stage Quasi-Stationary High Current Plasma Accelerator (QHPA).

  9. Science and Technology of Accelerators

    NASA Astrophysics Data System (ADS)

    Valerio Lizarraga, Cristhian; Castilla Loaeza, Alejandro; Guillermo Cantón, Gerardo; Duarte, Carlos; Chavez Valenzuela, Daniel; Hernández Chahín, Karim; Cuna, Humberto Maury; Medina Medrano, Luis; Reyes Herrera, Juan; Sosa Güitrón, Salvador; Valdivia García, Alan; Rendón, Bruce Yee

    2016-10-01

    The Mexican Particle Accelerator Community (CMAP) was created in 2015 and currently its members participate in different experiments around the world. Using their expertise, they are working in the development of the particle accelerators area in Mexico. This paper provides a summary of the research done by its members and presents the preliminary design of an electron linear particle accelerator (eLINAC). This proposal will be the first accelerator designed and created in Mexico.

  10. Accelerator Science: Proton vs. Electron

    ScienceCinema

    Lincoln, Don

    2016-10-19

    Particle accelerators are one of the most powerful ways to study the fundamental laws that govern the universe. However, there are many design considerations that go into selecting and building a particular accelerator. In this video, Fermilab’s Dr. Don Lincoln explains the pros and cons of building an accelerator that collides pairs of protons to one that collides electrons.

  11. Accelerator Science: Circular vs. Linear

    ScienceCinema

    Lincoln, Don

    2016-12-14

    Particle accelerator are scientific instruments that allow scientists to collide particles together at incredible energies to study the secrets of the universe. However, there are many manners in which particle accelerators can be constructed. In this video, Fermilab’s Dr. Don Lincoln explains the pros and cons of circular and linear accelerators.

  12. Accelerator Science: Circular vs. Linear

    SciTech Connect

    Lincoln, Don

    2016-11-10

    Particle accelerator are scientific instruments that allow scientists to collide particles together at incredible energies to study the secrets of the universe. However, there are many manners in which particle accelerators can be constructed. In this video, Fermilab’s Dr. Don Lincoln explains the pros and cons of circular and linear accelerators.

  13. Accelerator Science: Proton vs. Electron

    SciTech Connect

    Lincoln, Don

    2016-10-11

    Particle accelerators are one of the most powerful ways to study the fundamental laws that govern the universe. However, there are many design considerations that go into selecting and building a particular accelerator. In this video, Fermilab’s Dr. Don Lincoln explains the pros and cons of building an accelerator that collides pairs of protons to one that collides electrons.

  14. APT accelerator. Topical report

    SciTech Connect

    Lawrence, G.; Rusthoi, D.

    1995-03-01

    The Accelerator Production of Tritium (APT) project, sponsored by Department of Energy Defense Programs (DOE/DP), involves the preconceptual design of an accelerator system to produce tritium for the nation`s stockpile of nuclear weapons. Tritium is an isotope of hydrogen used in nuclear weapons, and must be replenished because of radioactive decay (its half-life is approximately 12 years). Because the annual production requirements for tritium has greatly decreased since the end of the Cold War, an alternative approach to reactors for tritium production, based on a linear accelerator, is now being seriously considered. The annual tritium requirement at the time this study was undertaken (1992-1993) was 3/8 that of the 1988 goal, usually stated as 3/8-Goal. Continued reduction in the number of weapons in the stockpile has led to a revised (lower) production requirement today (March, 1995). The production requirement needed to maintain the reduced stockpile, as stated in the recent Nuclear Posture Review (summer 1994) is approximately 3/16-Goal, half the previous level. The Nuclear Posture Review also requires that the production plant be designed to accomodate a production increase (surge) to 3/8-Goal capability within five years, to allow recovery from a possible extended outage of the tritium plant. A multi-laboratory team, collaborating with several industrial partners, has developed a preconceptual APT design for the 3/8-Goal, operating at 75% capacity. The team has presented APT as a promising alternative to the reactor concepts proposed for Complex-21. Given the requirements of a reduced weapons stockpile, APT offers both significant safety, environmental, and production-fexibility advantages in comparison with reactor systems, and the prospect of successful development in time to meet the US defense requirements of the 21st Century.

  15. VLHC accelerator physics

    SciTech Connect

    Michael Blaskiewicz et al.

    2001-11-01

    A six-month design study for a future high energy hadron collider was initiated by the Fermilab director in October 2000. The request was to study a staged approach where a large circumference tunnel is built that initially would house a low field ({approx}2 T) collider with center-of-mass energy greater than 30 TeV and a peak (initial) luminosity of 10{sup 34} cm{sup -2}s{sup -1}. The tunnel was to be scoped, however, to support a future upgrade to a center-of-mass energy greater than 150 TeV with a peak luminosity of 2 x 10{sup 34} cm{sup -2} sec{sup -1} using high field ({approx} 10 T) superconducting magnet technology. In a collaboration with Brookhaven National Laboratory and Lawrence Berkeley National Laboratory, a report of the Design Study was produced by Fermilab in June 2001. 1 The Design Study focused on a Stage 1, 20 x 20 TeV collider using a 2-in-1 transmission line magnet and leads to a Stage 2, 87.5 x 87.5 TeV collider using 10 T Nb{sub 3}Sn magnet technology. The article that follows is a compilation of accelerator physics designs and computational results which contributed to the Design Study. Many of the parameters found in this report evolved during the study, and thus slight differences between this text and the Design Study report can be found. The present text, however, presents the major accelerator physics issues of the Very Large Hadron Collider as examined by the Design Study collaboration and provides a basis for discussion and further studies of VLHC accelerator parameters and design philosophies.

  16. Recent Advances in Plasma Acceleration

    SciTech Connect

    Hogan, Mark

    2007-03-19

    The costs and the time scales of colliders intended to reach the energy frontier are such that it is important to explore new methods of accelerating particles to high energies. Plasma-based accelerators are particularly attractive because they are capable of producing accelerating fields that are orders of magnitude larger than those used in conventional colliders. In these accelerators a drive beam, either laser or particle, produces a plasma wave (wakefield) that accelerates charged particles. The ultimate utility of plasma accelerators will depend on sustaining ultra-high accelerating fields over a substantial length to achieve a significant energy gain. More than 42 GeV energy gain was achieved in an 85 cm long plasma wakefield accelerator driven by a 42 GeV electron drive beam in the Final Focus Test Beam (FFTB) Facility at SLAC. Most of the beam electrons lose energy to the plasma wave, but some electrons in the back of the same beam pulse are accelerated with a field of {approx}52 GV/m. This effectively doubles their energy, producing the energy gain of the 3 km long SLAC accelerator in less than a meter for a small fraction of the electrons in the injected bunch. Prospects for a drive-witness bunch configuration and high-gradient positron acceleration experiments planned for the SABER facility will be discussed.

  17. Accelerating Gallstone Dissolution

    PubMed Central

    Tao, J. C.; Cussler, E. L.; Evans, D. F.

    1974-01-01

    The dissolution rates of cholesterol in model bile salt solutions are controlled by diffusion in slowly flowing bile and by interfacial kinetics in rapidly flowing bile. At low flow, dissolution varies with the square root of bile flow and can be predicted, a priori, from existing correlations of mass transfer. At high bile flow, dissolution is independent of bile flow and is probably dominated by the rate of micelle adsorption. These results show that cholesterol gallstone dissolution, a potential nonsurgical therapy for cholelithiasis, can be accelerated little in slow bile, but more significantly in rapidly flowing bile. PMID:4530271

  18. Accelerating Commercial Remote Sensing

    NASA Technical Reports Server (NTRS)

    1995-01-01

    Through the Visiting Investigator Program (VIP) at Stennis Space Center, Community Coffee was able to use satellites to forecast coffee crops in Guatemala. Using satellite imagery, the company can produce detailed maps that separate coffee cropland from wild vegetation and show information on the health of specific crops. The data can control coffee prices and eventually may be used to optimize application of fertilizers, pesticides and irrigation. This would result in maximal crop yields, minimal pollution and lower production costs. VIP is a mechanism involving NASA funding designed to accelerate the growth of commercial remote sensing by promoting general awareness and basic training in the technology.

  19. Accelerated Innovation Pilot

    NASA Technical Reports Server (NTRS)

    Davis, Jeffrey

    2012-01-01

    Opportunities: I. Engage NASA team (examples) a) Research and technology calls . provide suggestions to AES, HRP, OCT. b) Use NASA@Work to solicit other ideas; (possibly before R+D calls). II. Stimulate collaboration (examples) a) NHHPC. b) Wharton Mack Center for Technological Innovation (Feb 2013). c) International ] DLR ] :envihab (July 2013). d) Accelerated research models . NSF, Myelin Repair Foundation. III. Engage public Prizes (open platform: InnoCentive, yet2.com, NTL; Rice Business Plan, etc.) IV. Use same methods to engage STEM.

  20. The Accelerating Universe

    NASA Astrophysics Data System (ADS)

    Schmidt, Brian P.

    2012-05-01

    In 1998 two teams traced back the expansion of the universe over billions of years and discovered that it was accelerating, a startling discovery that suggests that more than 70% of the cosmos is contained in a previously unknown form of matter, called Dark Energy. The 2011 Nobel Laureate for Physics, Brian Schmidt, leader of the High-Redshift Supernova Search Team, will describe this discovery and explain how astronomers have used observations to trace our universe's history back more than 13 billion years, leading them to ponder the ultimate fate of the cosmos.

  1. Acceleration in Linear and Circular Motion

    ERIC Educational Resources Information Center

    Kellington, S. H.; Docherty, W.

    1975-01-01

    Describes the construction of a simple accelerometer and explains its use in demonstrating acceleration, deceleration, constant speed, measurement of acceleration, acceleration and the inclined plane and angular and radial acceleration. (GS)

  2. Ion Accelerator With Negatively Biased Decelerator Grid

    NASA Technical Reports Server (NTRS)

    Brophy, John R.

    1994-01-01

    Three-grid ion accelerator in which accelerator grid is biased at negative potential and decelerator grid downstream of accelerator grid biased at smaller negative potential. This grid and bias arrangement reduces frequency of impacts, upon accelerator grid, of charge-exchange ions produced downstream in collisions between accelerated ions and atoms and molecules of background gas. Sputter erosion of accelerator grid reduced.

  3. Advanced Accelerators for Medical Applications

    NASA Astrophysics Data System (ADS)

    Uesaka, Mitsuru; Koyama, Kazuyoshi

    We review advanced accelerators for medical applications with respect to the following key technologies: (i) higher RF electron linear accelerator (hereafter “linac”); (ii) optimization of alignment for the proton linac, cyclotron and synchrotron; (iii) superconducting magnet; (iv) laser technology. Advanced accelerators for medical applications are categorized into two groups. The first group consists of compact medical linacs with high RF, cyclotrons and synchrotrons downsized by optimization of alignment and superconducting magnets. The second group comprises laser-based acceleration systems aimed of medical applications in the future. Laser plasma electron/ion accelerating systems for cancer therapy and laser dielectric accelerating systems for radiation biology are mentioned. Since the second group has important potential for a compact system, the current status of the established energy and intensity and of the required stability are given.

  4. Accelerator simulation of astrophysical processes

    NASA Technical Reports Server (NTRS)

    Tombrello, T. A.

    1983-01-01

    Phenomena that involve accelerated ions in stellar processes that can be simulated with laboratory accelerators are described. Stellar evolutionary phases, such as the CNO cycle, have been partially explored with accelerators, up to the consumption of He by alpha particle radiative capture reactions. Further experimentation is indicated on reactions featuring N-13(p,gamma)O-14, O-15(alpha, gamma)Ne-19, and O-14(alpha,p)F-17. Accelerated beams interacting with thin foils produce reaction products that permit a determination of possible elemental abundances in stellar objects. Additionally, isotopic ratios observed in chondrites can be duplicated with accelerator beam interactions and thus constraints can be set on the conditions producing the meteorites. Data from isotopic fractionation from sputtering, i.e., blasting surface atoms from a material using a low energy ion beam, leads to possible models for processes occurring in supernova explosions. Finally, molecules can be synthesized with accelerators and compared with spectroscopic observations of stellar winds.

  5. Laser acceleration and its future

    PubMed Central

    Tajima, Toshiki

    2010-01-01

    Laser acceleration is based on the concept to marshal collective fields that may be induced by laser. In order to exceed the material breakdown field by a large factor, we employ the broken-down matter of plasma. While the generated wakefields resemble with the fields in conventional accelerators in their structure (at least qualitatively), it is their extreme accelerating fields that distinguish the laser wakefield from others, amounting to tiny emittance and compact accelerator. The current research largely falls on how to master the control of acceleration process in spatial and temporal scales several orders of magnitude smaller than the conventional method. The efforts over the last several years have come to a fruition of generating good beam properties with GeV energies on a table top, leading to many applications, such as ultrafast radiolysis, intraoperative radiation therapy, injection to X-ray free electron laser, and a candidate for future high energy accelerators. PMID:20228616

  6. Accelerating Spectrum Sharing Technologies

    SciTech Connect

    Juan D. Deaton; Lynda L. Brighton; Rangam Subramanian; Hussein Moradi; Jose Loera

    2013-09-01

    Spectrum sharing potentially holds the promise of solving the emerging spectrum crisis. However, technology innovators face the conundrum of developing spectrum sharing technologies without the ability to experiment and test with real incumbent systems. Interference with operational incumbents can prevent critical services, and the cost of deploying and operating an incumbent system can be prohibitive. Thus, the lack of incumbent systems and frequency authorization for technology incubation and demonstration has stymied spectrum sharing research. To this end, industry, academia, and regulators all require a test facility for validating hypotheses and demonstrating functionality without affecting operational incumbent systems. This article proposes a four-phase program supported by our spectrum accountability architecture. We propose that our comprehensive experimentation and testing approach for technology incubation and demonstration will accelerate the development of spectrum sharing technologies.

  7. Accelerated Decay of Radioisotopes

    DTIC Science & Technology

    2013-01-01

    00-01 -2013 Technical June20 l l-June 2012 4 . TITLE AND SUBTITLE Sa. CONTRACT NUMBER DTRA MIPR 11-2362M Accelerated Decay of Radioisotopes Sb...268 x E +2 4.788 026 x E -2 6.894 757 4.535 924 x E -1 4.214 011 x E -2 1.601 846 x E +1 1.000 000 x E -2 2.579 760 x E - 4 1.000 000 x E -8...c a y o f R a d i o i s o t o p e s " P r o p o s a l # B R C A L L 0 7 - N - 2 - 0 0 4 7 I l l u s t r a t i o n o f \\ P F R P a s p o

  8. Understanding projectile acceleration.

    PubMed

    Hecht, H; Bertamini, M

    2000-04-01

    Throwing and catching balls or other objects is a generally highly practiced skill; however, conceptual as well as perceptual understanding of the mechanics that underlie this skill is surprisingly poor. In 5 experiments, we investigated conceptual and perceptual understanding of simple ballistic motion. Paper-and-pencil tests revealed that up to half of all participants mistakenly believed that a ball would continue to accelerate after it left the thrower's hand. Observers also showed a remarkable tolerance for anomalous trajectory shapes. Perceptual judgments based on graphics animations replicated these erroneous beliefs for shallow release angles. Observers' tolerance for anomalies tended to decrease with their distance from the actor. The findings are at odds with claims of the naive physics literature that liken intuitive understanding to Aristotelian or medieval physics theories. Instead, observers seem to project their intentions to the ball itself (externalization) or even feel that they have power over the ball when it is still close.

  9. Pulsed Plasma Accelerator Modeling

    NASA Technical Reports Server (NTRS)

    Goodman, M.; Kazeminezhad, F.; Owens, T.

    2009-01-01

    This report presents the main results of the modeling task of the PPA project. The objective of this task is to make major progress towards developing a new computational tool with new capabilities for simulating cylindrically symmetric 2.5 dimensional (2.5 D) PPA's. This tool may be used for designing, optimizing, and understanding the operation of PPA s and other pulsed power devices. The foundation for this task is the 2-D, cylindrically symmetric, magnetohydrodynamic (MHD) code PCAPPS (Princeton Code for Advanced Plasma Propulsion Simulation). PCAPPS was originally developed by Sankaran (2001, 2005) to model Lithium Lorentz Force Accelerators (LLFA's), which are electrode based devices, and are typically operated in continuous magnetic field to the model, and implementing a first principles, self-consistent algorithm to couple the plasma and power circuit that drives the plasma dynamics.

  10. Pulsed electromagnetic acceleration

    NASA Technical Reports Server (NTRS)

    Jahn, R. G.; Vonjaskowsky, W. F.; Clark, K. E.

    1973-01-01

    Direct measurements of the power deposited in the anode of a multimegawatt MPD accelerator using thermocouples attached to a thin shell anode reveal a dramatic decrease in the fractional anode power from 50% at 200 KW input power to less than 10% at 20 MW power. The corresponding local power flux peak at a value of 10,000 W/sq cm at the lip of the anode exhaust orifice, a distribution traced to a corresponding peak in the local current density at the anode. A comparison of voltage-current characteristics and spectral photographs of the MPD discharge using quartz, boron nitride and plexiglas insulators with various mass injection configurations led to the identification of different voltage modes and regions of ablation free operation. The technique of piezoelectric impact pressure measurement in the MPD exhaust flow was refined to account for the effects due to probe yaw angle.

  11. Linac-accelerator-radiosurgery.

    PubMed

    Sturm, V; Schlegel, W; Pastyr, O; Treuer, H; Voges, J; Müller, R P; Lorenz, W J

    1993-01-01

    A survey is given of the actual possibilities and limitations of the use of linear accelerators (Linac radiosurgery systems) for intra = cranial radiosurgery. Depending on the collimator size, spherical fields from 5-54 mm in diameter can be irradiated with dose gradients from 10% (large fields) to 20% (small fields) per millimeter distance between surface and treatment volume. This is comparable to the possibilities of Gamma-Knife and Proton-irradiation. Optimal mechanical adjustment of gantry and linac table are necessary for the required stability of the isocenter. Mechanical inaccuracy should be smaller than 0.8 mm. Advanced computerized 3D-treatment planning systems are indispensable prerequisites for accurate treatment and use of the flexibility of the linac system. Future developments are outlined.

  12. Network acceleration techniques

    NASA Technical Reports Server (NTRS)

    Crowley, Patricia (Inventor); Awrach, James Michael (Inventor); Maccabe, Arthur Barney (Inventor)

    2012-01-01

    Splintered offloading techniques with receive batch processing are described for network acceleration. Such techniques offload specific functionality to a NIC while maintaining the bulk of the protocol processing in the host operating system ("OS"). The resulting protocol implementation allows the application to bypass the protocol processing of the received data. Such can be accomplished this by moving data from the NIC directly to the application through direct memory access ("DMA") and batch processing the receive headers in the host OS when the host OS is interrupted to perform other work. Batch processing receive headers allows the data path to be separated from the control path. Unlike operating system bypass, however, the operating system still fully manages the network resource and has relevant feedback about traffic and flows. Embodiments of the present disclosure can therefore address the challenges of networks with extreme bandwidth delay products (BWDP).

  13. Paraelectric gas flow accelerator

    NASA Technical Reports Server (NTRS)

    Sherman, Daniel M. (Inventor); Wilkinson, Stephen P. (Inventor); Roth, J. Reece (Inventor)

    2001-01-01

    A substrate is configured with first and second sets of electrodes, where the second set of electrodes is positioned asymmetrically between the first set of electrodes. When a RF voltage is applied to the electrodes sufficient to generate a discharge plasma (e.g., a one-atmosphere uniform glow discharge plasma) in the gas adjacent to the substrate, the asymmetry in the electrode configuration results in force being applied to the active species in the plasma and in turn to the neutral background gas. Depending on the relative orientation of the electrodes to the gas, the present invention can be used to accelerate or decelerate the gas. The present invention has many potential applications, including increasing or decreasing aerodynamic drag or turbulence, and controlling the flow of active and/or neutral species for such uses as flow separation, altering heat flow, plasma cleaning, sterilization, deposition, etching, or alteration in wettability, printability, and/or adhesion.

  14. Lectures in accelerator theory

    SciTech Connect

    Month, M

    1980-01-01

    Lecture I deals with the behavior of particles in the nonlinear field arising from the electromagnetic interaction of colliding beams. The case treated, that of counter-rotating proton beams crossing each other at a non-zero angle, has the simple feature that the force between the beam is one dimensional. In lecture II, an analysis of the development of traveling waves on particle beams is presented. The situation studied is that of a uniform beam current in a circular accelerator and the excitation for the coherent motion is induced by the resistivity of the vacuum chamber wall. Finally, in lecture III, a description of the current accumulation process used at the proton storage rings at CERN (The ISR) is given. Particle pulses of rather low average current are injected and stored along the length and width of the vacuum chamber. The efficiency is very high and large currents (over 40 amperes) have been achieved.

  15. HIGH ENERGY PARTICLE ACCELERATOR

    DOEpatents

    Courant, E.D.; Livingston, M.S.; Snyder, H.S.

    1959-04-14

    An improved apparatus is presented for focusing charged particles in an accelerator. In essence, the invention includes means for establishing a magnetic field in discrete sectors along the path of moving charged particles, the magnetic field varying in each sector in accordance with the relation. B = B/ sub 0/ STAln (r-r/sub 0/)/r/sub 0/!, where B/sub 0/ is the value of the magnetic field at the equilibrium orbit of radius r/sub 0/ of the path of the particles, B equals the magnetic field at the radius r of the chamber and n equals the magnetic field gradient index, the polarity of n being abruptly reversed a plurality of times as the particles travel along their arcuate path. With this arrangement, the particles are alternately converged towards the axis of their equillbrium orbit and diverged therefrom in successive sectors with a resultant focusing effect.

  16. Cast dielectric composite linear accelerator

    DOEpatents

    Sanders, David M.; Sampayan, Stephen; Slenes, Kirk; Stoller, H. M.

    2009-11-10

    A linear accelerator having cast dielectric composite layers integrally formed with conductor electrodes in a solventless fabrication process, with the cast dielectric composite preferably having a nanoparticle filler in an organic polymer such as a thermosetting resin. By incorporating this cast dielectric composite the dielectric constant of critical insulating layers of the transmission lines of the accelerator are increased while simultaneously maintaining high dielectric strengths for the accelerator.

  17. NIIEFA accelerators for applied purposes

    NASA Astrophysics Data System (ADS)

    Vorogushin, M. F.; Strokach, A. P.; Filatov, O. G.

    2016-12-01

    Since the foundation of the institute, we have designed and delivered more than three hundred different accelerators to Russia and abroad: cyclotrons, linear accelerators, and neutron generators. The technical characteristics of our equipment makes it competitive on the international market. Here we present the application, main parameters, and status of accelerators manufactured by NIIEFA, as well as prospects for the development of electrophysical systems for applied purposes.

  18. Collective accelerator for electron colliders

    SciTech Connect

    Briggs, R.J.

    1985-05-13

    A recent concept for collective acceleration and focusing of a high energy electron bunch is discussed, in the context of its possible applicability to large linear colliders in the TeV range. The scheme can be considered to be a member of the general class of two-beam accelerators, where a high current, low voltage beam produces the acceleration fields for a trailing high energy bunch.

  19. Basic concepts in plasma accelerators.

    PubMed

    Bingham, Robert

    2006-03-15

    In this article, we present the underlying physics and the present status of high gradient and high-energy plasma accelerators. With the development of compact short pulse high-brightness lasers and electron and positron beams, new areas of studies for laser/particle beam-matter interactions is opening up. A number of methods are being pursued vigorously to achieve ultra-high-acceleration gradients. These include the plasma beat wave accelerator (PBWA) mechanism which uses conventional long pulse ( approximately 100 ps) modest intensity lasers (I approximately 10(14)-10(16) W cm(-2)), the laser wakefield accelerator (LWFA) which uses the new breed of compact high-brightness lasers (<1 ps) and intensities >10(18) W cm(-2), self-modulated laser wakefield accelerator (SMLWFA) concept which combines elements of stimulated Raman forward scattering (SRFS) and electron acceleration by nonlinear plasma waves excited by relativistic electron and positron bunches the plasma wakefield accelerator. In the ultra-high intensity regime, laser/particle beam-plasma interactions are highly nonlinear and relativistic, leading to new phenomenon such as the plasma wakefield excitation for particle acceleration, relativistic self-focusing and guiding of laser beams, high-harmonic generation, acceleration of electrons, positrons, protons and photons. Fields greater than 1 GV cm(-1) have been generated with monoenergetic particle beams accelerated to about 100 MeV in millimetre distances recorded. Plasma wakefields driven by both electron and positron beams at the Stanford linear accelerator centre (SLAC) facility have accelerated the tail of the beams.

  20. Compact accelerator for medical therapy

    DOEpatents

    Caporaso, George J.; Chen, Yu-Jiuan; Hawkins, Steven A.; Sampayan, Stephen E.; Paul, Arthur C.

    2010-05-04

    A compact accelerator system having an integrated particle generator-linear accelerator with a compact, small-scale construction capable of producing an energetic (.about.70-250 MeV) proton beam or other nuclei and transporting the beam direction to a medical therapy patient without the need for bending magnets or other hardware often required for remote beam transport. The integrated particle generator-accelerator is actuable as a unitary body on a support structure to enable scanning of a particle beam by direction actuation of the particle generator-accelerator.

  1. Accelerator based epithermal neutron source

    NASA Astrophysics Data System (ADS)

    Taskaev, S. Yu.

    2015-11-01

    We review the current status of the development of accelerator sources of epithermal neutrons for boron neutron capture therapy (BNCT), a promising method of malignant tumor treatment. Particular attention is given to the source of epithermal neutrons on the basis of a new type of charged particle accelerator: tandem accelerator with vacuum insulation and lithium neutron-producing target. It is also shown that the accelerator with specialized targets makes it possible to generate fast and monoenergetic neutrons, resonance and monoenergetic gamma-rays, alpha-particles, and positrons.

  2. High field gradient particle accelerator

    DOEpatents

    Nation, John A.; Greenwald, Shlomo

    1989-01-01

    A high electric field gradient electron accelerator utilizing short duration, microwave radiation, and capable of operating at high field gradients for high energy physics applications or at reduced electric field gradients for high average current intermediate energy accelerator applications. Particles are accelerated in a smooth bore, periodic undulating waveguide, wherein the period is so selected that the particles slip an integral number of cycles of the r.f. wave every period of the structure. This phase step of the particles produces substantially continuous acceleration in a traveling wave without transverse magnetic or other guide means for the particle.

  3. High field gradient particle accelerator

    DOEpatents

    Nation, J.A.; Greenwald, S.

    1989-05-30

    A high electric field gradient electron accelerator utilizing short duration, microwave radiation, and capable of operating at high field gradients for high energy physics applications or at reduced electric field gradients for high average current intermediate energy accelerator applications is disclosed. Particles are accelerated in a smooth bore, periodic undulating waveguide, wherein the period is so selected that the particles slip an integral number of cycles of the r.f. wave every period of the structure. This phase step of the particles produces substantially continuous acceleration in a traveling wave without transverse magnetic or other guide means for the particle. 10 figs.

  4. Accelerators for research and applications

    SciTech Connect

    Alonso, J.R.

    1990-06-01

    The newest particle accelerators are almost always built for extending the frontiers of research, at the cutting edge of science and technology. Once these machines are operating and these technologies mature, new applications are always found, many of which touch our lives in profound ways. The evolution of accelerator technologies will be discussed, with descriptions of accelerator types and characteristics. The wide range of applications of accelerators will be discussed, in fields such as nuclear science, medicine, astrophysics and space-sciences, power generation, airport security, materials processing and microcircuit fabrication. 13 figs.

  5. ADS Based on Linear Accelerators

    NASA Astrophysics Data System (ADS)

    Pan, Weimin; Dai, Jianping

    An accelerator-driven system (ADS), which combines a particle accelerator with a subcritical core, is commonly regarded as a promising device for the transmutation of nuclear waste, as well as a potential scheme for thorium-based energy production. So far the predominant choice of the accelerator for ADS is a superconducting linear accelerator (linac). This article gives a brief overview of ADS based on linacs, including the motivation, principle, challenges and research activities around the world. The status and future plan of the Chinease ADS (C-ADS) project will be highlighted and discussed in depth as an example.

  6. SHORT ACCELERATION TIMES FROM SUPERDIFFUSIVE SHOCK ACCELERATION IN THE HELIOSPHERE

    SciTech Connect

    Perri, S.; Zimbardo, G.

    2015-12-10

    The analysis of time profiles of particles accelerated at interplanetary shocks allows particle transport properties to be inferred. The frequently observed power-law decay upstream, indeed, implies a superdiffusive particle transport when the level of magnetic field variance does not change as the time interval from the shock front increases. In this context, a superdiffusive shock acceleration (SSA) theory has been developed, allowing us to make predictions of the acceleration times. In this work we estimate for a number of interplanetary shocks, including the solar wind termination shock, the acceleration times for energetic protons in the framework of SSA and we compare the results with the acceleration times predicted by standard diffusive shock acceleration. The acceleration times due to SSA are found to be much shorter than in the classical model, and also shorter than the interplanetary shock lifetimes. This decrease of the acceleration times is due to the scale-free nature of the particle displacements in the framework of superdiffusion. Indeed, very long displacements are possible, increasing the probability for particles far from the front of the shock to return, and short displacements have a high probability of occurrence, increasing the chances for particles close to the front to cross the shock many times.

  7. Thomas Edison Accelerated Elementary School.

    ERIC Educational Resources Information Center

    Levin, Henry M.; Chasin, Gene

    This paper describes early outcomes of a Sacramento, California, elementary school that participated in the Accelerated Schools Project. The school, which serves many minority and poor students, began training for the project in 1992. Accelerated Schools were designed to advance the learning rate of students through a gifted and talented approach,…

  8. Natural Acceleration: Supporting Creative Trajectories

    ERIC Educational Resources Information Center

    Cohen, LeoNora M.

    2011-01-01

    "Natural acceleration" happens through an internal fire that burns to learn and may transcend school boundaries. Based on their passionate interests and connections with a domain, children who hunger for domain understandings outside school curricula require different types of acceleration, motivated by these interests. The lifeworks,…

  9. COMPASS Accelerator Design Technical Overview

    SciTech Connect

    Nanni, Emilio; Dolgashev, Valery; Tantawi, Sami; Neilson, Jeff

    2016-03-14

    This report is a survey of technical options for generating a MeV-class accelerator for space based science applications. The survey was performed focusing on the primary technical requirements of the accelerator in the context of a satellite environment with its unique challenges of limited electrical power (PE), thermal isolation, dimensions, payload requirement and electrical isolation.

  10. Switching mechanism senses angular acceleration

    NASA Technical Reports Server (NTRS)

    1966-01-01

    Switching mechanism actuates an electrical circuit when a predetermined angular acceleration and displacement are reached. A rotor in the mechanism overcomes the restraint of a magnetic detent when the case in which the detent is mounted reaches the predetermined angular acceleration.

  11. General purpose programmable accelerator board

    DOEpatents

    Robertson, Perry J.; Witzke, Edward L.

    2001-01-01

    A general purpose accelerator board and acceleration method comprising use of: one or more programmable logic devices; a plurality of memory blocks; bus interface for communicating data between the memory blocks and devices external to the board; and dynamic programming capabilities for providing logic to the programmable logic device to be executed on data in the memory blocks.

  12. EXOTIC MAGNETS FOR ACCELERATORS.

    SciTech Connect

    WANDERER, P.

    2005-09-18

    Over the last few years, several novel magnet designs have been introduced to meet the requirements of new, high performance accelerators and beam lines. For example, the FAIR project at GSI requires superconducting magnets ramped at high rates ({approx} 4 T/s) in order to achieve the design intensity. Magnets for the RIA and FAIR projects and for the next generation of LHC interaction regions will need to withstand high doses of radiation. Helical magnets are required to maintain and control the polarization of high energy protons at RHIC. In other cases, novel magnets have been designed in response to limited budgets and space. For example, it is planned to use combined function superconducting magnets for the 50 GeV proton transport line at J-PARC to satisfy both budget and performance requirements. Novel coil winding methods have been developed for short, large aperture magnets such as those used in the insertion region upgrade at BEPC. This paper will highlight the novel features of these exotic magnets.

  13. Energy Innovation Acceleration Program

    SciTech Connect

    Wolfson, Johanna

    2015-06-15

    The Energy Innovation Acceleration Program (IAP) – also called U-Launch – has had a significant impact on early stage clean energy companies in the Northeast and on the clean energy economy in the Northeast, not only during program execution (2010-2014), but continuing into the future. Key results include: Leverage ratio of 105:1; $105M in follow-on funding (upon $1M investment by EERE); At least 19 commercial products launched; At least 17 new industry partnerships formed; At least $6.5M in revenue generated; >140 jobs created; 60% of assisted companies received follow-on funding within 1 year of program completion; In addition to the direct measurable program results summarized above, two primary lessons emerged from our work executing Energy IAP:; Validation and demonstration awards have an outsized, ‘tipping-point’ effect for startups looking to secure investments and strategic partnerships. An ecosystem approach is valuable, but an approach that evaluates the needs of individual companies and then draws from diverse ecosystem resources to fill them, is most valuable of all.

  14. Pulsars and Acceleration Sites

    NASA Technical Reports Server (NTRS)

    Harding, Alice

    2008-01-01

    Rotation-powered pulsars are excellent laboratories for the studying particle acceleration as well as fundamental physics of strong gravity, strong magnetic fields and relativity. But even forty years after their discovery, we still do not understand their pulsed emission at any wavelength. I will review both the basic physics of pulsars as well as the latest developments in understanding their high-energy emission. Special and general relativistic effects play important roles in pulsar emission, from inertial frame-dragging near the stellar surface to aberration, time-of-flight and retardation of the magnetic field near the light cylinder. Understanding how these effects determine what we observe at different wavelengths is critical to unraveling the emission physics. Fortunately the Gamma-Ray Large Area Space Telescope (GLAST), with launch in May 2008 will detect many new gamma-ray pulsars and test the predictions of these models with unprecedented sensitivity and energy resolution for gamma-rays in the range of 30 MeV to 300 GeV.

  15. RFQ accelerator tuning system

    DOEpatents

    Bolie, Victor W.

    1990-01-01

    A cooling system is provided for maintaining a preselected operating temperature in a device, which may be an RFQ accelerator, having a variable heat removal requirement, by circulating a cooling fluid through a cooling system remote from the device. Internal sensors in the device enable an estimated error signal to be generated from parameters which are indicative of the heat removal requirement from the device. Sensors are provided at predetermined locations in the cooling system for outputting operational temperature signals. Analog and digital computers define a control signal functionally related to the temperature signals and the estimated error signal, where the control signal is defined effective to return the device to the preselected operating temperature in a stable manner. The cooling system includes a first heat sink responsive to a first portion of the control signal to remove heat from a major portion of the circulating fluid. A second heat sink is responsive to a second portion of the control signal to remove heat from a minor portion of the circulating fluid. The cooled major and minor portions of the circulating fluid are mixed in response to a mixing portion of the control signal, which is effective to proportion the major and minor portions of the circulating fluid to establish a mixed fluid temperature which is effective to define the preselected operating temperature for the remote device. In an RFQ environment the stable temperature control enables the resonant frequency of the device to be maintained at substantially a predetermined value during transient operations.

  16. RFQ accelerator tuning system

    DOEpatents

    Bolie, V.W.

    1990-07-03

    A cooling system is provided for maintaining a preselected operating temperature in a device, which may be an RFQ accelerator, having a variable heat removal requirement, by circulating a cooling fluid through a cooling system remote from the device. Internal sensors in the device enable an estimated error signal to be generated from parameters which are indicative of the heat removal requirement from the device. Sensors are provided at predetermined locations in the cooling system for outputting operational temperature signals. Analog and digital computers define a control signal functionally related to the temperature signals and the estimated error signal, where the control signal is defined effective to return the device to the preselected operating temperature in a stable manner. The cooling system includes a first heat sink responsive to a first portion of the control signal to remove heat from a major portion of the circulating fluid. A second heat sink is responsive to a second portion of the control signal to remove heat from a minor portion of the circulating fluid. The cooled major and minor portions of the circulating fluid are mixed in response to a mixing portion of the control signal, which is effective to proportion the major and minor portions of the circulating fluid to establish a mixed fluid temperature which is effective to define the preselected operating temperature for the remote device. In an RFQ environment the stable temperature control enables the resonant frequency of the device to be maintained at substantially a predetermined value during transient operations. 3 figs.

  17. Is Global Warming Accelerating?

    NASA Astrophysics Data System (ADS)

    Shukla, J.; Delsole, T. M.; Tippett, M. K.

    2009-12-01

    A global pattern that fluctuates naturally on decadal time scales is identified in climate simulations and observations. This newly discovered component, called the Global Multidecadal Oscillation (GMO), is related to the Atlantic Meridional Oscillation and shown to account for a substantial fraction of decadal fluctuations in the observed global average sea surface temperature. IPCC-class climate models generally underestimate the variance of the GMO, and hence underestimate the decadal fluctuations due to this component of natural variability. Decomposing observed sea surface temperature into a component due to anthropogenic and natural radiative forcing plus the GMO, reveals that most multidecadal fluctuations in the observed global average sea surface temperature can be accounted for by these two components alone. The fact that the GMO varies naturally on multidecadal time scales implies that it can be predicted with some skill on decadal time scales, which provides a scientific rationale for decadal predictions. Furthermore, the GMO is shown to account for about half of the warming in the last 25 years and hence a substantial fraction of the recent acceleration in the rate of increase in global average sea surface temperature. Nevertheless, in terms of the global average “well-observed” sea surface temperature, the GMO can account for only about 0.1° C in transient, decadal-scale fluctuations, not the century-long 1° C warming that has been observed during the twentieth century.

  18. Accelerated Adaptive Integration Method

    PubMed Central

    2015-01-01

    Conformational changes that occur upon ligand binding may be too slow to observe on the time scales routinely accessible using molecular dynamics simulations. The adaptive integration method (AIM) leverages the notion that when a ligand is either fully coupled or decoupled, according to λ, barrier heights may change, making some conformational transitions more accessible at certain λ values. AIM adaptively changes the value of λ in a single simulation so that conformations sampled at one value of λ seed the conformational space sampled at another λ value. Adapting the value of λ throughout a simulation, however, does not resolve issues in sampling when barriers remain high regardless of the λ value. In this work, we introduce a new method, called Accelerated AIM (AcclAIM), in which the potential energy function is flattened at intermediate values of λ, promoting the exploration of conformational space as the ligand is decoupled from its receptor. We show, with both a simple model system (Bromocyclohexane) and the more complex biomolecule Thrombin, that AcclAIM is a promising approach to overcome high barriers in the calculation of free energies, without the need for any statistical reweighting or additional processors. PMID:24780083

  19. Accelerated shallow water modeling

    NASA Astrophysics Data System (ADS)

    Gandham, Rajesh; Medina, David; Warburton, Timothy

    2015-04-01

    ln this talk we will describe our ongoing developments in accelerated numerical methods for modeling tsunamis, and oceanic fluid flows using two dimensional shallow water model and/or three dimensional incompressible Navier Stokes model discretized with high order discontinuous Galerkin methods. High order discontinuous Galerkin methods can be computationally demanding, requiring extensive computational time to simulate real time events on traditional CPU architectures. However, recent advances in computing architectures and hardware aware algorithms make it possible to reduce simulation time and provide accurate predictions in a timely manner. Hence we tailor these algorithms to take advantage of single instruction multiple data (SIMD) architecture that is seen in modern many core compute devices such as GPUs. We will discuss our unified and extensive many-core programming library OCCA that alleviates the need to completely re-design the solvers to keep up with constantly evolving parallel programming models and hardware architectures. We will present performance results for the flow simulations demonstrating performance leveraging multiple different multi-threading APIs on GPU and CPU targets.

  20. Compact plasma accelerator

    NASA Technical Reports Server (NTRS)

    Foster, John E. (Inventor)

    2004-01-01

    A compact plasma accelerator having components including a cathode electron source, an anodic ionizing gas source, and a magnetic field that is cusped. The components are held by an electrically insulating body having a central axis, a top axial end, and a bottom axial end. The cusped magnetic field is formed by a cylindrical magnet having an axis of rotation that is the same as the axis of rotation of the insulating body, and magnetized with opposite poles at its two axial ends; and an annular magnet coaxially surrounding the cylindrical magnet, magnetized with opposite poles at its two axial ends such that a top axial end has a magnetic polarity that is opposite to the magnetic polarity of a top axial end of the cylindrical magnet. The ionizing gas source is a tubular plenum that has been curved into a substantially annular shape, positioned above the top axial end of the annular magnet such that the plenum is centered in a ring-shaped cusp of the magnetic field generated by the magnets. The plenum has one or more capillary-like orifices spaced around its top such that an ionizing gas supplied through the plenum is sprayed through the one or more orifices. The plenum is electrically conductive and is positively charged relative to the cathode electron source such that the plenum functions as the anode; and the cathode is positioned above and radially outward relative to the plenum.

  1. Hot Spot Cosmic Accelerators

    NASA Astrophysics Data System (ADS)

    2002-11-01

    length of more than 3 million light-years, or no less than one-and-a-half times the distance from the Milky Way to the Andromeda galaxy, this structure is indeed gigantic. The region where the jets collide with the intergalactic medium are known as " hot spots ". Superposing the intensity contours of the radio emission from the southern "hot spot" on a near-infrared J-band (wavelength 1.25 µm) VLT ISAAC image ("b") shows three distinct emitting areas; they are even better visible on the I-band (0.9 µm) FORS1 image ("c"). This emission is obviously associated with the shock front visible on the radio image. This is one of the first times it has been possible to obtain an optical/near-IR image of synchrotron emission from such an intergalactic shock and, thanks to the sensitivity and image sharpness of the VLT, the most detailed view of its kind so far . The central area (with the strongest emission) is where the plasma jet from the galaxy centre hits the intergalactic medium. The light from the two other "knots", some 10 - 15,000 light-years away from the central "hot spot", is also interpreted as synchrotron emission. However, in view of the large distance, the astronomers are convinced that it must be caused by electrons accelerated in secondary processes at those sites . The new images thus confirm that electrons are being continuously accelerated in these "knots" - hence called "cosmic accelerators" - far from the galaxy and the main jets, and in nearly empty space. The exact physical circumstances of this effect are not well known and will be the subject of further investigations. The present VLT-images of the "hot spots" near 3C 445 may not have the same public appeal as some of those beautiful images that have been produced by the same instruments during the past years. But they are not less valuable - their unusual importance is of a different kind, as they now herald the advent of fundamentally new insights into the mysteries of this class of remote and active

  2. Touch Accelerates Visual Awareness

    PubMed Central

    Lo Verde, Luca; Alais, David

    2017-01-01

    To efficiently interact with the external environment, our nervous system combines information arising from different sensory modalities. Recent evidence suggests that cross-modal interactions can be automatic and even unconscious, reflecting the ecological relevance of cross-modal processing. Here, we use continuous flash suppression (CFS) to directly investigate whether haptic signals can interact with visual signals outside of visual awareness. We measured suppression durations of visual gratings rendered invisible by CFS either during visual stimulation alone or during visuo-haptic stimulation. We found that active exploration of a haptic grating congruent in orientation with the suppressed visual grating reduced suppression durations both compared with visual-only stimulation and to incongruent visuo-haptic stimulation. We also found that the facilitatory effect of touch on visual suppression disappeared when the visual and haptic gratings were mismatched in either spatial frequency or orientation. Together, these results demonstrate that congruent touch can accelerate the rise to consciousness of a suppressed visual stimulus and that this unconscious cross-modal interaction depends on visuo-haptic congruency. Furthermore, since CFS suppression is thought to occur early in visual cortical processing, our data reinforce the evidence suggesting that visuo-haptic interactions can occur at the earliest stages of cortical processing. PMID:28210486

  3. Electron cyclotron harmonic wave acceleration

    NASA Technical Reports Server (NTRS)

    Karimabadi, H.; Menyuk, C. R.; Sprangle, P.; Vlahos, L.

    1987-01-01

    A nonlinear analysis of particle acceleration in a finite bandwidth, obliquely propagating electromagnetic cyclotron wave is presented. It has been suggested by Sprangle and Vlahos in 1983 that the narrow bandwidth cyclotron radiation emitted by the unstable electron distribution inside a flaring solar loop can accelerate electrons outside the loop by the interaction of a monochromatic wave propagating along the ambient magnetic field with the ambient electrons. It is shown here that electrons gyrating and streaming along a uniform, static magnetic field can be accelerated by interacting with the fundamental or second harmonic of a monochromatic, obliquely propagating cyclotron wave. It is also shown that the acceleration is virtually unchanged when a wave with finite bandwidth is considered. This acceleration mechanism can explain the observed high-energy electrons in type III bursts.

  4. Shear Acceleration in Expanding Flows

    NASA Astrophysics Data System (ADS)

    Rieger, F. M.; Duffy, P.

    2016-12-01

    Shear flows are naturally expected to occur in astrophysical environments and potential sites of continuous non-thermal Fermi-type particle acceleration. Here we investigate the efficiency of expanding relativistic outflows to facilitate the acceleration of energetic charged particles to higher energies. To this end, the gradual shear acceleration coefficient is derived based on an analytical treatment. The results are applied to the context of the relativistic jets from active galactic nuclei. The inferred acceleration timescale is investigated for a variety of conical flow profiles (i.e., power law, Gaussian, Fermi-Dirac) and compared to the relevant radiative and non-radiative loss timescales. The results exemplify that relativistic shear flows are capable of boosting cosmic-rays to extreme energies. Efficient electron acceleration, on the other hand, requires weak magnetic fields and may thus be accompanied by a delayed onset of particle energization and affect the overall jet appearance (e.g., core, ridge line, and limb-brightening).

  5. The ISAC post-accelerator

    NASA Astrophysics Data System (ADS)

    Laxdal, R. E.; Marchetto, M.

    2014-01-01

    The acceleration chain of the ISAC facility boosts the energy of both radioactive and stable light and heavy ions for beam delivery to both a medium energy area in ISAC-I and a high energy area in ISAC-II. The post-accelerator comprises a 35.4 MHz RFQ to accelerate beams of A/q ≤ 30 from 2 keV/u to 150 keV/u and a post stripper, 106.1 MHz variable energy drift tube linac (DTL) to accelerate ions of A/q ≤ 6 to a final energy between 0.15 MeV/u to 1.5 MeV/u. A 40 MV superconducting linac further accelerates beam from 1.5 MeV/u to energies above the Coulomb barrier. All linacs operate cw to preserve beam intensity.

  6. Critical Issues in Plasma Accelerator

    NASA Astrophysics Data System (ADS)

    Uesaka, M.; Hosokai, T.

    2004-10-01

    Updated achievements and critical issues in plasma accelerators are summarized. As to laser plasma accelerators, we cover the results of plasma cathodes by U.Michigan, LBNL, LOA and U.Tokyo. Although many new results of accelerated electrons have been reported, the electrons do not yet form a bunch with narrow energy spread. Several injection schemes and measurements to verify ultrashort bunch (tens fs) with narrow energy spread, low emittance and many charges are planned. E-162 experiments by UCLA / USC / SLAC and a newly proposed experiment on density transition trapping are introduced for electron beam driven plasma accelerators. Their main purpose is realization of GeV plasma accelerator, but application to pump-and-probe analysis for investigation of ultrafast quantum phenomena is also promising.

  7. EDITORIAL: Laser and plasma accelerators Laser and plasma accelerators

    NASA Astrophysics Data System (ADS)

    Bingham, Robert

    2009-02-01

    This special issue on laser and plasma accelerators illustrates the rapid advancement and diverse applications of laser and plasma accelerators. Plasma is an attractive medium for particle acceleration because of the high electric field it can sustain, with studies of acceleration processes remaining one of the most important areas of research in both laboratory and astrophysical plasmas. The rapid advance in laser and accelerator technology has led to the development of terawatt and petawatt laser systems with ultra-high intensities and short sub-picosecond pulses, which are used to generate wakefields in plasma. Recent successes include the demonstration by several groups in 2004 of quasi-monoenergetic electron beams by wakefields in the bubble regime with the GeV energy barrier being reached in 2006, and the energy doubling of the SLAC high-energy electron beam from 42 to 85 GeV. The electron beams generated by the laser plasma driven wakefields have good spatial quality with energies ranging from MeV to GeV. A unique feature is that they are ultra-short bunches with simulations showing that they can be as short as a few femtoseconds with low-energy spread, making these beams ideal for a variety of applications ranging from novel high-brightness radiation sources for medicine, material science and ultrafast time-resolved radiobiology or chemistry. Laser driven ion acceleration experiments have also made significant advances over the last few years with applications in laser fusion, nuclear physics and medicine. Attention is focused on the possibility of producing quasi-mono-energetic ions with energies ranging from hundreds of MeV to GeV per nucleon. New acceleration mechanisms are being studied, including ion acceleration from ultra-thin foils and direct laser acceleration. The application of wakefields or beat waves in other areas of science such as astrophysics and particle physics is beginning to take off, such as the study of cosmic accelerators considered

  8. Electron beam accelerator with magnetic pulse compression and accelerator switching

    DOEpatents

    Birx, D.L.; Reginato, L.L.

    1984-03-22

    An electron beam accelerator is described comprising an electron beam generator-injector to produce a focused beam of greater than or equal to .1 MeV energy electrons; a plurality of substantially identical, aligned accelerator modules to sequentially receive and increase the kinetic energies of the beam electron by about .1-1 MeV per module. Each accelerator module includes a pulse-forming network that delivers a voltage pulse to the module of substantially .1-1 MeV maximum energy over a time duration of less than or equal to 1 ..mu..sec.

  9. Electron beam accelerator with magnetic pulse compression and accelerator switching

    DOEpatents

    Birx, Daniel L.; Reginato, Louis L.

    1987-01-01

    An electron beam accelerator comprising an electron beam generator-injector to produce a focused beam of .gtoreq.0.1 MeV energy electrons; a plurality of substantially identical, aligned accelerator modules to sequentially receive and increase the kinetic energies of the beam electrons by about 0.1-1 MeV per module. Each accelerator module includes a pulse-forming network that delivers a voltage pulse to the module of substantially 0.1-1 MeV maximum energy over a time duration of .ltoreq.1 .mu.sec.

  10. Electron beam accelerator with magnetic pulse compression and accelerator switching

    DOEpatents

    Birx, Daniel L.; Reginato, Louis L.

    1988-01-01

    An electron beam accelerator comprising an electron beam generator-injector to produce a focused beam of .gtoreq.0.1 MeV energy electrons; a plurality of substantially identical, aligned accelerator modules to sequentially receive and increase the kinetic energies of the beam electrons by about 0.1-1 MeV per module. Each accelerator module includes a pulse-forming network that delivers a voltage pulse to the module of substantially .gtoreq.0.1-1 MeV maximum energy over a time duration of .ltoreq.1 .mu.sec.

  11. Effects of bone marrow-derived mesenchymal stem cells and platelet-rich plasma on bone regeneration for osseointegration of dental implants: preliminary study in canine three-wall intrabony defects.

    PubMed

    Yun, Jeong-Ho; Han, Sang-Hyun; Choi, Seong-Ho; Lee, Myung-Hyun; Lee, Sang-Jin; Song, Sun U; Oh, Namsik

    2014-07-01

    Tissue engineering has been applied to overcome the obstacles encountered with bone regeneration for the placement of dental implants. The purpose of this study was to determine the bone formation ability of human bone marrow-derived mesenchymal stem cells (BMMSCs) and platelet-rich plasma (PRP) when applied separately or together to the intrabony defect around dental implants with a porous hydroxyapatite (HA) scaffold. Standardized three-wall intrabony defects (4 × 4 × 4 mm) were created at the mesial of each dental implant site in four mongrel dogs. Defects were then grafted with the following materials: HA + BMMSCs (HS group), HA + PRP (HP group), HA + BMMSCs + PRP (HSP group), and HA scaffold alone (HA group). The level of bone formation (bone density) and osseointegration (bone-to-implant contact [BIC]) in bone defects around the implants were evaluated by histological and histometric analysis at 6 and 12 weeks after the placement of implants. HA, HS, HP, and HSP groups generally showed an increase in bone density and BIC between 6 and 12 weeks, except BIC in the HS group. Although no statistically significant differences were found among HA, HS, HP, and HSP groups (p > 0.05), the highest level of bone density and BIC were observed in the HSP group after the 12-week healing period. Furthermore, the level of bone maturation was higher in the HSP group than in the other groups as determined histologically. The findings of this preliminary study suggest that BMMSCs and PRP combined with HA scaffold may provide additional therapeutic effects on bone regeneration and improve osseointegration in bone defects around dental implants.

  12. Accelerated cleanup risk reduction

    SciTech Connect

    Knapp, R.B.; Aines, R.M.; Blake, R.G.; Copeland, A.B.; Newmark, R.L.; Tompson, A.F.B.

    1998-02-01

    There is no proven technology for remediating contaminant plume source regions in a heterogeneous subsurface. This project is an interdisciplinary effort to develop the requisite new technologies so that will be rapidly accepted by the remediation community. Our technology focus is hydrous pyrolysis/oxidation (HPO) which is a novel in situ thermal technique. We have expanded this core technology to leverage the action of steam injection and place an in situ microbial filter downstream to intercept and destroy the accelerated movement of contaminated groundwater. Most contaminant plume source regions, including the chlorinated solvent plume at LLNL, are in subsurface media characterized by a wide range in hydraulic conductivity. At LLNL, the main conduits for contaminant transport are buried stream channels composed of gravels and sands; these have a hydraulic conductivity in the range of 10{sup -1} to 10{sup -2} cm/s. Clay and silt units with a hydraulic conductivity of 10{sup -1} to 10{sup -6} cm/s bound these buried channels; these are barriers to groundwater movement and contain the highest contaminant concentrations in the source region. New remediation technologies are required because the current ones preferentially access the high conductivity units. HPO is an innovative process for the in situ destruction of contaminants in the entire subsurface. It operates by the injection of steam. We have demonstrated in laboratory experiments that many contaminants rapidly oxidize to harmless compounds at temperatures easily achieved by injecting steam, provided sufficient dissolved oxygen is present. One important challenge in a heterogeneous source region is getting heat, contaminants, and an oxidizing agent in the same place at the same time. We have used the NUFT computer program to simulate the cyclic injection of steam into a contaminated aquifer for design of a field demonstration. We used an 8 hour, steam/oxygen injection cycle followed by a 56 hour relaxation

  13. Operation of the accelerator

    SciTech Connect

    Pardo, R.C.; Batzka, B.; Billquist, P.J.

    1995-08-01

    Fiscal Year 1994 was the first year of seven-day operation since ATLAS became a national user facility in 1985. ATLAS made the most of the opportunity this year by providing 5200 hours of beam on-target to the research program. A record number of 60 experiments were completed and the {open_quotes}facility reliability{close_quotes} remained near the 90% level. Seven-day operation was made possible with the addition to the staff of two operator positions providing single-operator coverage during the weekend period. The normally scheduled coverage was augmented by an on-call list of system experts who respond to emergencies with phone-in advice and return to the Laboratory when necessary. This staffing approach continues but we rearranged our staffing patterns so that we now have one cryogenics engineer working a shift pattern which includes 8-hour daily coverage during the weekend. ATLAS provided a beam mix to users consisting of 26 different isotopic species, 23% of which were for A>100 in FY 1994. Approximately 60% of the beam time was provided by the Positive Ion Injector, slightly less than the usage rate of FY 1993. Experiments using uranium or lead beams accounted for 16.4% of the total beam time. The ECR ion source and high-voltage platform functioned well throughout the year. A new technique for solid material production in the source was developed which uses a sputtering process wherein the sample of material placed near the plasma chamber wall is biased negatively. Plasma ions are accelerated into the sample and material is sputtered from the surface into the plasma. This technique is now used routinely for many elements. Runs of calcium, germanium, nickel, lead, tellurium, and uranium were carried out with this technique.

  14. A Fundamental Theorem on Particle Acceleration

    SciTech Connect

    Xie, Ming

    2003-05-01

    A fundamental theorem on particle acceleration is derived from the reciprocity principle of electromagnetism and a rigorous proof of the theorem is presented. The theorem establishes a relation between acceleration and radiation, which is particularly useful for insightful understanding of and practical calculation about the first order acceleration in which energy gain of the accelerated particle is linearly proportional to the accelerating field.

  15. Enhancement of chronic acceleration tolerance by selection

    NASA Technical Reports Server (NTRS)

    Smith, A. H.

    1982-01-01

    A review is presented of experiments concerning the physiological consequences of chronic acceleration and of studies of selection for acceleration tolerance over many generations. It is shown that acceleration selection is effective in improving chronic acceleration tolerance. However, it is determined that the variable selection procedure employed in developing this acceleration-tolerant line limits the confidence in the quantitative evaluation of the procedure.

  16. Proton Acceleration at Oblique Shocks

    NASA Astrophysics Data System (ADS)

    Galinsky, V. L.; Shevchenko, V. I.

    2011-06-01

    Acceleration at the shock waves propagating oblique to the magnetic field is studied using a recently developed theoretical/numerical model. The model assumes that resonant hydromagnetic wave-particle interaction is the most important physical mechanism relevant to motion and acceleration of particles as well as to excitation and damping of waves. The treatment of plasma and waves is self-consistent and time dependent. The model uses conservation laws and resonance conditions to find where waves will be generated or damped, and hence particles will be pitch-angle-scattered. The total distribution is included in the model and neither introduction of separate population of seed particles nor some ad hoc escape rate of accelerated particles is needed. Results of the study show agreement with diffusive shock acceleration models in the prediction of power spectra for accelerated particles in the upstream region. However, they also reveal the presence of spectral break in the high-energy part of the spectra. The role of the second-order Fermi-like acceleration at the initial stage of the acceleration is discussed. The test case used in the paper is based on ISEE-3 data collected for the shock of 1978 November 12.

  17. PROTON ACCELERATION AT OBLIQUE SHOCKS

    SciTech Connect

    Galinsky, V. L.; Shevchenko, V. I.

    2011-06-20

    Acceleration at the shock waves propagating oblique to the magnetic field is studied using a recently developed theoretical/numerical model. The model assumes that resonant hydromagnetic wave-particle interaction is the most important physical mechanism relevant to motion and acceleration of particles as well as to excitation and damping of waves. The treatment of plasma and waves is self-consistent and time dependent. The model uses conservation laws and resonance conditions to find where waves will be generated or damped, and hence particles will be pitch-angle-scattered. The total distribution is included in the model and neither introduction of separate population of seed particles nor some ad hoc escape rate of accelerated particles is needed. Results of the study show agreement with diffusive shock acceleration models in the prediction of power spectra for accelerated particles in the upstream region. However, they also reveal the presence of spectral break in the high-energy part of the spectra. The role of the second-order Fermi-like acceleration at the initial stage of the acceleration is discussed. The test case used in the paper is based on ISEE-3 data collected for the shock of 1978 November 12.

  18. Universe acceleration and nonlinear electrodynamics

    NASA Astrophysics Data System (ADS)

    Kruglov, S. I.

    2015-12-01

    A new model of nonlinear electrodynamics with a dimensional parameter β coupled to gravity is considered. We show that an accelerated expansion of the universe takes place if the nonlinear electromagnetic field is the source of the gravitational field. A pure magnetic universe is investigated, and the magnetic field drives the universe to accelerate. In this model, after the big bang, the universe undergoes inflation and the accelerated expansion and then decelerates approaching Minkowski spacetime asymptotically. We demonstrate the causality of the model and a classical stability at the deceleration phase.

  19. Accelerating Around an Unbanked Curve

    DTIC Science & Technology

    2006-02-01

    FEB 2006 2. REPORT TYPE 3. DATES COVERED 00-00-2006 to 00-00-2006 4. TITLE AND SUBTITLE Accelerating Around an Unbanked Curve 5a. CONTRACT...December 2004 issue of TPT presented a problem concerning how a car should acceler-ate around an unbanked curve of constant radius r starting from rest...Accelerating Around an Unbanked Curve Carl E. Mungan, U.S. Naval Academy, Annapolis, MD 100 THE PHYSICS TEACHER ◆ Vol. 44, February 2006 The shapes

  20. Imaging using accelerated heavy ions

    SciTech Connect

    Chu, W.T.

    1982-05-01

    Several methods for imaging using accelerated heavy ion beams are being investigated at Lawrence Berkeley Laboratory. Using the HILAC (Heavy-Ion Linear Accelerator) as an injector, the Bevalac can accelerate fully stripped atomic nuclei from carbon (Z = 6) to krypton (Z = 34), and partly stripped ions up to uranium (Z = 92). Radiographic studies to date have been conducted with helium (from 184-inch cyclotron), carbon, oxygen, and neon beams. Useful ranges in tissue of 40 cm or more are available. To investigate the potential of heavy-ion projection radiography and computed tomography (CT), several methods and instrumentation have been studied.