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Sample records for implantation range distributions

  1. Calculation of recoil implantation profiles using known range statistics

    NASA Technical Reports Server (NTRS)

    Fung, C. D.; Avila, R. E.

    1985-01-01

    A method has been developed to calculate the depth distribution of recoil atoms that result from ion implantation onto a substrate covered with a thin surface layer. The calculation includes first order recoils considering projected range straggles, and lateral straggles of recoils but neglecting lateral straggles of projectiles. Projectile range distributions at intermediate energies in the surface layer are deduced from look-up tables of known range statistics. A great saving of computing time and human effort is thus attained in comparison with existing procedures. The method is used to calculate recoil profiles of oxygen from implantation of arsenic through SiO2 and of nitrogen from implantation of phosphorus through Si3N4 films on silicon. The calculated recoil profiles are in good agreement with results obtained by other investigators using the Boltzmann transport equation and they also compare very well with available experimental results in the literature. The deviation between calculated and experimental results is discussed in relation to lateral straggles. From this discussion, a range of surface layer thickness for which the method applies is recommended.

  2. Long-range effect of ion implantation of Raex and Hardox steels

    NASA Astrophysics Data System (ADS)

    Budzyński, P.; Kamiński, M.; Droździel, A.; Wiertel, M.

    2016-09-01

    Ion implantation involves introduction of ionized atoms of any element (nitrogen) to metals thanks to the high kinetic energy that they acquired in the electric field. The distribution of nitrogen ions implanted at E = 65 keV energy and D = 1.1017 N+ /cm2 fluence in the steel sample and vacancies produced by them was calculated using the SRIM program. This result was confirmed by RBS measurements. The initial maximum range of the implanted nitrogen ions is ∼⃒0.17 μm. This value is relatively small compared to the influence of nitriding on the thickness surface layer of modified steel piston rings. Measurements of the friction coefficient during the pin-on-disc tribological test were performed under dry friction conditions. The friction coefficient of the implanted sample increased to values characteristic of an unimplanted sample after ca. 1500 measurement cycles. The depth of wear trace is ca. 2.4 μm. This implies that the thickness of the layer modified by the implantation process is ∼⃒2.4 μm and exceeds the initial range of the implanted ions by an order of magnitude. This effect, referred to as a long-range implantation effect, is caused by migration of vacancies and nitrogen atoms into the sample. This phenomenon makes ion implantation a legitimate process of modification of the surface layer in order to enhance the tribological properties of critical components of internal combustion engines such as steel piston rings.

  3. Distribution of solar wind implanted noble gases in lunar samples

    NASA Technical Reports Server (NTRS)

    Kiko, J.; Kirsten, T.

    1986-01-01

    The distribution of solar wind implanted noble gases in lunar samples depends on implantation energy, fluence, diffusion, radiation damage and erosion. It is known that at least the lighter rare gases are fractionated after implantation, but the redistribution processes, which mainly drive the losses, are not well understood. Some information about this one can get by looking at the concentration profiles of solar wind implanted He-4 measured by the Gas Ion Probe in single lunar grains. The observed profiles were divided in three groups. These groups are illustrated and briefly discussed.

  4. The roles of different scale ranges of surface implant topography on the stability of the bone/implant interface.

    PubMed

    Davies, John E; Ajami, Elnaz; Moineddin, Rahim; Mendes, Vanessa C

    2013-05-01

    We sought to deconvolute the effects of sub-micron topography and microtopography on the phenomena of bone bonding and interfacial stability of endosseous implants. To address this experimentally, we implanted custom-made titanium alloy implants of varying surface topographical complexity in rat femora, for 6, 9 or 12 days. The five surfaces were polished, machined, dual acid etched, and two forms of grit blasted and acid etched; each surface type was further modified with the deposition of nanocrystals of calcium phosphate to make a total of 10 materials groups (n = 10 for each time point; total 300 implants). At sacrifice, we subjected the bone-implant interface to a mechanical disruption test. We found that even the smoothest surfaces, when modified with sub-micron scale crystals, could be bone-bonding. However, as locomotor loading through bone to the implant increased with time of healing, such interfaces failed while others, with sub-micron features superimposed on surfaces of increasing microtopographical complexity remained intact under loading. We demonstrate here that higher order, micron or coarse-micron, topography is a requirement for longer-term interfacial stability. We show that each of these topographical scale-ranges represents a scale-range seen in natural bone tissue. Thus, what emerges from an analysis of our findings is a new means by which biologically-relevant criteria can be employed to assess the importance of implant surface topography at different scale-ranges. PMID:23415644

  5. Photoelastic analysis of stress distribution with different implant systems.

    PubMed

    Pellizzer, Eduardo Piza; Carli, Rafael Imai; Falcón-Antenucci, Rosse Mary; Verri, Fellippo Ramos; Goiato, Marcelo Coelho; Villa, Luiz Marcelo Ribeiro

    2014-04-01

    The aim of this study was to evaluate stress distribution with different implant systems through photoelasticity. Five models were fabricated with photoelastic resin PL-2. Each model was composed of a block of photoelastic resin (10 × 40 × 45 mm) with an implant and a healing abutment: model 1, internal hexagon implant (4.0 × 10 mm; Conect AR, Conexão, São Paulo, Brazil); model 2, Morse taper/internal octagon implant (4.1 × 10 mm; Standard, Straumann ITI, Andover, Mass); model 3, Morse taper implant (4.0 × 10 mm; AR Morse, Conexão); model 4, locking taper implant (4.0 × 11 mm; Bicon, Boston, Mass); model 5, external hexagon implant (4.0 × 10 mm; Master Screw, Conexão). Axial and oblique load (45°) of 150 N were applied by a universal testing machine (EMIC-DL 3000), and a circular polariscope was used to visualize the stress. The results were photographed and analyzed qualitatively using Adobe Photoshop software. For the axial load, the greatest stress concentration was exhibited in the cervical and apical thirds. However, the highest number of isochromatic fringes was observed in the implant apex and in the cervical adjacent to the load direction in all models for the oblique load. Model 2 (Morse taper, internal octagon, Straumann ITI) presented the lowest stress concentration, while model 5 (external hexagon, Master Screw, Conexão) exhibited the greatest stress. It was concluded that Morse taper implants presented a more favorable stress distribution among the test groups. The external hexagon implant showed the highest stress concentration. Oblique load generated the highest stress in all models analyzed.

  6. Photoelastic Analysis of Fixed Partial Prosthesis Crown Height and Implant Length on Distribution of Stress in Two Dental Implant Systems

    PubMed Central

    Figueirêdo, Evandro Portela; Sigua-Rodriguez, Eder Alberto; Pimentel, Marcele Jardim; Nóbilo, Mauro Antônio de Arruda; de Albergaria-Barbosa, José Ricardo

    2014-01-01

    The aim of this study was to evaluate by photoelastic analysis stress distribution on short and long implants of two dental implant systems with 2-unit implant-supported fixed partial prostheses of 8 mm and 13 mm heights. Sixteen photoelastic models were divided into 4 groups: I: long implant (5 × 11 mm) (Neodent), II: long implant (5 × 11 mm) (Bicon), III: short implant (5 × 6 mm) (Neodent), and IV: short implants (5 × 6 mm) (Bicon). The models were positioned in a circular polariscope associated with a cell load and static axial (0.5 Kgf) and nonaxial load (15°, 0.5 Kgf) were applied to each group for both prosthetic crown heights. Three-way ANOVA was used to compare the factors implant length, crown height, and implant system (α = 0.05). The results showed that implant length was a statistically significant factor for both axial and nonaxial loading. The 13 mm prosthetic crown did not result in statistically significant differences in stress distribution between the implant systems and implant lengths studied, regardless of load type (P > 0.05). It can be concluded that short implants showed higher stress levels than long implants. Implant system and length was not relevant factors when prosthetic crown height were increased. PMID:25374603

  7. The effects of hydroxyapatite coatings on stress distribution near the dental implant bone interface

    NASA Astrophysics Data System (ADS)

    Jiang, W.; Wang, W. D.; Shi, X. H.; Chen, H. Z.; Zou, W.; Guo, Z.; Luo, J. M.; Gu, Z. W.; Zhang, X. D.

    2008-11-01

    The effects of different thickness of hydroxyapatite (HA) coatings on bone stress distribution near the dental implant-bone interface are very important factors for the HA-coated dental implant design and clinical application. By means of finite element analysis (FEA), the bone stress distributions near the dental implant coated with different thicknesses from 0 to 200 μm were calculated and analyzed under the 200 N chewing load. In all cases, the maximal von Mises stresses in the bone are at the positions near the neck of dental implant on the lingual side, and decrease with the increase of the HA coatings thickness. The HA coatings weaken the stress concentration and improve the biomechanical property in the bone, however, in HA coatings thickness range of 60-120 μm, the distinctions of that benefit are not obvious. In addition, considering the technical reason of HA coatings, we conclude that thickness of HA coatings range from 60 to 120 μm would be the better choice for clinical application.

  8. Effect of cantilever length on stress distribution around implants in mandibular overdentures supported by two and three implants

    PubMed Central

    Ebadian, Behnaz; Mosharraf, Ramin; Khodaeian, Niloufar

    2016-01-01

    Objective: There is no definitive study comparing stress distribution around two versus three implants in implant-retained overdentures with different cantilever length. The purpose of this finite element study was to evaluate stress pattern around the implants of the 2 or 3 implant- supported mandibular overdenture with different cantilevered length. Materials and Methods: The models used in this study were 2 and 3 implant-supported overdenture with bar and clip attachment system on an edentulous mandibular arch. Each model was modified according to cantilever length (0 mm, 7 mm, and 13 mm); thus, 6 models were obtained. The vertical load of 15 and 30 pounds were applied unilaterally to the first molar and 15 pounds to the first premolar, and the stress in bone was analyzed. Results: With increasing cantilever length, no similar stress pattern changes were observed in different areas, but in most instances, an increase in cantilever length did not increase the stress around the implant adjacent to cantilever. Conclusions: Within the limitations of this study, it can be concluded that increasing of cantilever length in mandibular overdentures retained by 2–3 implants did not cause distinct increasing in stress, especially around the implant adjacent to cantilever, it may be helpful to use cantilever in cases of mandibular overdenture supported by splinted implants with insufficient retention and stability. Based on the findings of this study, optimal cantilever length in mandibular overdenture cannot be determined. PMID:27403049

  9. Adaptive dynamic range optimization (ADRO): a digital amplification strategy for hearing aids and cochlear implants.

    PubMed

    Blamey, Peter J

    2005-01-01

    Adaptive dynamic range optimization (ADRO) is an amplification strategy that uses digital signal processing techniques to improve the audibility, comfort, and intelligibility of sounds for people who use cochlear implants and/or hearing aids. The strategy uses statistical analysis to select the most information-rich section of the input dynamic range in multiple-frequency channels. Fuzzy logic rules control the gain in each frequency channel so that the selected section of the dynamic range is presented at an audible and comfortable level. The ADRO processing thus adaptively optimizes the dynamic range of the signal in multiple-frequency channels. Clinical studies show that ADRO can be fitted easily to all degrees of hearing loss for hearing aids and cochlear implants in a direct and intuitive manner, taking the preferences of the listener into account. The result is high acceptance by new and experienced hearing aid users and strong preferences for ADRO compared with alternative amplification strategies. The ADRO processing is particularly well suited to bimodal and hybrid stimulation which combine electric and acoustic stimulation in opposite ears or in the same ear, respectively.

  10. Adaptive Dynamic Range Optimization (ADRO): A Digital Amplification Strategy for Hearing Aids and Cochlear Implants

    PubMed Central

    Blamey, Peter J.

    2005-01-01

    Adaptive dynamic range optimization (ADRO) is an amplification strategy that uses digital signal processing techniques to improve the audibility, comfort, and intelligibility of sounds for people who use cochlear implants and/or hearing aids. The strategy uses statistical analysis to select the most information-rich section of the input dynamic range in multiple-frequency channels. Fuzzy logic rules control the gain in each frequency channel so that the selected section of the dynamic range is presented at an audible and comfortable level. The ADRO processing thus adaptively optimizes the dynamic range of the signal in multiple-frequency channels. Clinical studies show that ADRO can be fitted easily to all degrees of hearing loss for hearing aids and cochlear implants in a direct and intuitive manner, taking the preferences of the listener into account. The result is high acceptance by new and experienced hearing aid users and strong preferences for ADRO compared with alternative amplification strategies. The ADRO processing is particularly well suited to bimodal and hybrid stimulation which combine electric and acoustic stimulation in opposite ears or in the same ear, respectively. PMID:16012705

  11. Effects of an implant on temperature distribution in tissue during ultrasound diathermy.

    PubMed

    Sun, Ming-Kuan; Shieh, Jay; Chen, Chuin-Shan; Chiang, Hongsen; Huang, Chang-Wei; Chen, Wen-Shiang

    2016-09-01

    The effects of an implant on temperature distribution in a tissue-mimicking hydrogel phantom during the application of therapeutic ultrasound were investigated. In vitro experiments were conducted to compare the influences of plastic and metal implants on ultrasound diathermy and to calibrate parameters in finite element simulation models. The temperature histories and characteristics of the opaque (denatured) areas in the hydrogel phantoms predicted by the numerical simulations show good correlation with those observed in the in vitro experiments. This study provides an insight into the temperature profile in the vicinity of an implant by therapeutic ultrasound heating typically used for physiotherapy. A parametric study was conducted through numerical simulations to investigate the effects of several factors, such as implant material type, ultrasound operation frequency, implant thickness and tissue thickness on the temperature distribution in the hydrogel phantom. The results indicate that the implant material type and implant thickness are the main parameters influencing the temperature distribution. In addition, once the implant material and ultrasound operation frequency are chosen, an optimal implant thickness can be obtained so as to avoid overheating injuries in tissue. PMID:27150744

  12. Swift and heavy ion implanted chalcogenide laser glass waveguides and their different refractive index distributions

    SciTech Connect

    Qiu Feng; Narusawa, Tadashi; Zheng Jie

    2011-02-10

    Planar waveguides have been fabricated in Nd- or Ho-doped gallium lanthanum sulfide laser glasses by 60 MeV Ar or 20 MeV N ion implantation. The refractive index profiles were reconstructed based on the results of prism coupling. The Ar implanted waveguides exhibit an approximate steplike distribution, while the N implanted ones show a ''well + barrier'' type. This difference can be attributed to the much lower dose of Ar ions. After annealing, the N implanted waveguides can support two modes at 1539 nm and have low propagation loss, which makes them candidates for novel waveguide lasers.

  13. Stress Distribution on Short Implants at Maxillary Posterior Alveolar Bone Model With Different Bone-to-Implant Contact Ratio: Finite Element Analysis.

    PubMed

    Yazicioglu, Duygu; Bayram, Burak; Oguz, Yener; Cinar, Duygu; Uckan, Sina

    2016-02-01

    The aim of this study was to evaluate the stress distribution of the short dental implants and bone-to-implant contact ratios in the posterior maxilla using 3-dimensional (3D) finite element models. Two different 3D maxillary posterior bone segments were modeled. Group 1 was composed of a bone segment consisting of cortical bone and type IV cancellous bone with 100% bone-to-implant contact. Group 2 was composed of a bone segment consisting of cortical bone and type IV cancellous bone including spherical bone design and homogenous tubular hollow spaced structures with 30% spherical porosities and 70% bone-to-implant contact ratio. Four-millimeter-diameter and 5-mm-height dental implants were assumed to be osseointegrated and placed at the center of the segments. Lateral occlusal bite force (300 N) was applied at a 25° inclination to the implants long axis. The maximum von Mises stresses in cortical and cancellous bones and implant-abutment complex were calculated. The von Mises stress values on the implants and the cancellous bone around the implants of the 70% bone-to-implant contact group were almost 3 times higher compared with the values of the 100% bone-to-implant contact group. For clinical reality, use of the 70% model for finite element analysis simulation of the posterior maxilla region better represents real alveolar bone and the increased stress and strain distributions evaluated on the cortical and cancellous bone around the dental implants.

  14. Stress Distribution in Implant Retained Finger Prosthesis: A Finite Element Study

    PubMed Central

    Amornvit, Pokpong; Rokaya, Dinesh; Keawcharoen, Konrawee; Thongpulsawasdi, Nimit

    2013-01-01

    Background: Finger amputation may result from congenital cause, trauma, infection and tumours. The finger amputation may be rehabilitated with dental implant-retained finger prosthesis. The success of implant-retained finger prosthesis is determined by the implant loading. The type of the force is a determining factor in implant loading. Objective: To evaluate stress distributions in finger bone when the loading force is applied along the long axis of the implant using finite element analysis. Method: The finite element models were created. The finger bone model containing cortical bone and cancellous bone was constructed by using radiograph. Astra Tech Osseo Speed bone level implant of 4.5 mm diameter and 14 mm length was selected. The force was applied to the top of the abutment along the long axis of the implant. Results: Finite element analysis indicated that the maximum stress was located at the head of abutment screw. The minimum stress was located in the apical third of the implant fixture. The weakest point was calculated by safety factor which is located in the spongy bone at apical third of the fixtures. Finally, 4.9 times yield stress of spongy bone was needed for the deformation of the spongy bone. Conclusion: Finite element study showed that when the force was applied along the long axis of the implant, the maximum stress was located around the neck of the implant and the cortex bone received more stress than cancellous bone. So, to achieve long term success, the designers of implant systems must confront biomaterial and biomechanical problems including in vivo forces on implants, load transmission to the interface and interfacial tissue response. PMID:24551656

  15. Three Dimensional Finite Element Analysis to Detect Stress Distribution in Spiral Implants and Surrounding Bone

    PubMed Central

    Danza, Matteo; Palmieri, Annalisa; Farinella, Francesca; Brunelli, Giorgio; Carinci, Francesco; Girardi, Ambra; Spinelli, Giuseppe

    2009-01-01

    Background: The aim of research was to study spiral family implant by finite element analysis (FEA) inserted in different bone qualities connected with abutments of different angulations. Methods: The biomechanical behaviour of 4.2 × 13 mm dental implants, connecting screw, straight and 15° and 25° angulated abutments subjected to static loads, in contact with high and poor bone qualities was evaluated by FEA. Results: The lowest stress value was found in the system composed by implants and straight abut-ments loaded with a vertical force, while the highest stress value was found in implants with 15° angulated abutment loaded with an angulated force. In addition, we found the lower the bone quality, the higher the distribution of the stress within the bone. Conclusion: Spiral family implants can be used successfully in low bone quality but applying a straight force is recommended. PMID:21528032

  16. Genetic similarity, breeding distribution range and sexual selection.

    PubMed

    Møller, A P; Garamszegi, L Z; Spottiswoode, C N

    2008-01-01

    Large populations with extensive breeding distributions may sustain greater genetic variability, thus producing a positive relationship between genetic variation and population size. Levels of genetic variability may also be affected by sexual selection, which could either reduce levels because a small fraction of males contribute to the following generation, or augment them by generating genetic variability through elevated rates of mutations. We investigated to what extent genetic variability, as estimated from band sharing coefficients for minisatellite markers, could be predicted by breeding distribution range, population size and intensity of sexual selection (as reflected by degree of polygyny and extra-pair paternity). Across a sample of 62 species of birds in the Western Palearctic, we found extensive interspecific variation in band sharing coefficients. High band sharing coefficients (implying low local genetic variability among individuals) were associated with restricted breeding distributions, a conclusion confirmed by analysis of statistically independent linear contrasts. Independently, species with large population sizes had small band sharing coefficients. Furthermore, bird species with a high richness of subspecies for their breeding distribution range had higher band sharing coefficients. Finally, bird species with high levels of polygyny and extra-pair paternity had small band sharing coefficients. These results suggest that breeding distribution range, population size and intensity of sexual selection are important predictors of levels of genetic variability in extant populations.

  17. Spatial distribution of RF-induced E-fields and implant heating in MRI.

    PubMed

    Nordbeck, Peter; Fidler, Florian; Weiss, Ingo; Warmuth, Marcus; Friedrich, Michael T; Ehses, Philipp; Geistert, Wolfgang; Ritter, Oliver; Jakob, Peter M; Ladd, Mark E; Quick, Harald H; Bauer, Wolfgang R

    2008-08-01

    The purpose of this study was to assess the distribution of RF-induced E-fields inside a gel-filled phantom of the human head and torso and compare the results with the RF-induced temperature rise at the tip of a straight conductive implant, specifically examining the dependence of the temperature rise on the position of the implant inside the gel. MRI experiments were performed in two different 1.5T MR systems of the same manufacturer. E-field distribution inside the liquid was assessed using a custom measurement system. The temperature rise at the implant tip was measured in various implant positions and orientations using fluoroptic thermometry. The results show that local E-field strength in the direction of the implant is a critical factor in RF-related tissue heating. The actual E-field distribution, which is dependent on phantom/body properties and the MR-system employed, must be considered when assessing the effects of RF power deposition in implant safety investigations.

  18. Species data: National inventory of range maps and distribution models

    USGS Publications Warehouse

    Gergely, Kevin J.; McKerrow, Alexa

    2013-01-01

    The Gap Analysis Program (GAP) produces data and tools that help meet critical national challenges such as biodiversity conservation, renewable energy development, climate change adaptation, and infrastructure investment. The GAP species data includes vertebrate range maps and distribution models for the continental United States, as well as Alaska, Hawaii, Puerto Rico, and U.S. Virgin Islands. The vertebrate species include amphibians, birds, mammals, and reptiles. Furthermore, data used to create the distribution models (for example, percent canopy cover, elevation, and so forth) also are available.

  19. Temperature distribution in tissues from a regular array of hot source implants: an analytical approximation.

    PubMed

    Haider, S A; Cetas, T C; Roemer, R B

    1993-05-01

    An approximate analytical model based upon the bioheat transfer equation is derived and used to calculate temperatures within a perfused region implanted regularly with dielectrically coated hot source implants; for example, hot water tubes, electrically heated rods, or inductively heated ferromagnetic implants. The effect of a regular array of mutually parallel heat sources of cylindrical shape is approximated by idealizing one of the boundary conditions. The solution, as could be expected, is in terms of modified Bessel functions. In calculating the temperature of each thermoregulating source in the array, the steady state power balance is enforced. The important feature of the model is that the finite size of implant diameter and its dielectric coating can be incorporated. The effect of thickness and thermal conductivity of the coating on the source and tissue temperatures along with various other interesting features are deduced from this model. The analytically calculated implant and tissue temperatures are compared with those of a numerical 3-D finite difference model. The analytical model also is used to define a range of parameters such that minimal therapeutic temperatures will be achieved in the implanted volume without exceeding prescribed maximum temperatures. This approach leads to a simple means of selecting implant spacing and regulation temperatures of hot source methods prospectively.

  20. Numerical estimation of heat distribution from the implantable battery system of an undulation pump LVAD.

    PubMed

    Okamoto, Eiji; Makino, Tsutomu; Nakamura, Masatoshi; Tanaka, Shuji; Chinzei, Tsuneo; Abe, Yusuke; Isoyama, Takashi; Saito, Itsuro; Mochizuki, Shu-ichi; Imachi, Kou; Inoue, Yusuke; Mitamura, Yoshinori

    2006-01-01

    We have been developing an implantable battery system using three series-connected lithium ion batteries having an energy capacity of 1,800 mAh to drive an undulation pump left ventricular assist device. However, the lithium ion battery undergoes an exothermic reaction during the discharge phase, and the temperature rise of the lithium ion battery is a critical issue for implantation usage. Heat generation in the lithium ion battery depends on the intensity of the discharge current, and we obtained a relationship between the heat flow from the lithium ion battery q(c)(I) and the intensity of the discharge current I as q(c)(I) = 0.63 x I (W) in in vitro experiments. The temperature distribution of the implantable battery system was estimated by means of three-dimentional finite-element method (FEM) heat transfer analysis using the heat flow function q(c)(I), and we also measured the temperature rise of the implantable battery system in in vitro experiments to conduct verification of the estimation. The maximum temperatures of the lithium ion battery and the implantable battery case were measured as 52.2 degrees C and 41.1 degrees C, respectively. The estimated result of temperature distribution of the implantable battery system agreed well with the measured results using thermography. In conclusion, FEM heat transfer analysis is promising as a tool to estimate the temperature of the implantable lithium ion battery system under any pump current without the need for animal experiments, and it is a convenient tool for optimization of heat transfer characteristics of the implantable battery system.

  1. Effect of coating thickness and its material on the stress distribution for dental implants.

    PubMed

    Hedia, H S

    2007-01-01

    Dental implants have been increasingly used to recover the masticatory function of lost teeth. It has been well known that the success of a dental implant is heavily dependent on initial stability and long-term osseointegration due to optimal stress distribution in the surrounding bones by the concept implant surface coating. Hydroxyapatite (HAP), as a coating material, has been widely used in dentistry due to its biocompatibility. Some investigations show a benefit of coating dental implants with HAP, and others concluded that HAP coating reduces the long-term implant survival. Therefore, the aim of this investigation is to design a new functionally graded dental implant coating, as well as studying the effect of coating thickness on the maximum von Mises stresses in bone adjacent to the coating layer. The gradation of the elastic modulus is changed along the longitudinal direction. Stress analysis using a finite element method showed that using a coating thickness of 150 microm, functionally graded from titanium at the apex to the collagen at the root, will successfully reduce the maximum von Mises stress in bone by 19% and 17% compared to collagen and HAP coating respectively.

  2. Stress distribution in implant-supported prostheses using different connection systems and cantilever lengths: digital photoelasticity.

    PubMed

    Goiato, Marcelo Coelho; Shibayama, Ricardo; Gennari Filho, Humberto; de Medeiros, Rodrigo Antonio; Pesqueira, Aldiéris Alves; dos Santos, Daniela Micheline; de Araújo, Cleudmar Amaral

    2016-01-01

    Photoelastic analysis was used to evaluate the biomechanical behaviour of implant-supported, double-screwed crowns with different connection systems and cantilever lengths. Three models were made in PL-2 photoelastic resin and divided into six groups, on the basis of the implant connection system (external hexagon [EH] or Morse taper [MT]), type of abutment (Mini Pilar [Neodent, Curitiba, Paraná, Brazil] or "UCLA") and number of crowns in the cantilever (one or two). The implant-prosthesis unit was placed in a circular polariscope. Occlusal surfaces of the crowns were subjected to 100-N loads in the axial and oblique (45°) directions in a universal testing machine (EMIC). Generated stresses were recorded and analysed qualitatively in a graphics program (Adobe Photoshop). Under axial loading, all of the groups had similar numbers of fringes, which were increased when the crowns were subjected to oblique loading. The highest number of fringes was found during oblique loading in the EH + Mini Pilar group. In conclusion, although the type of implant connection system did not have a direct influence on the stress distribution for axial loading, the cantilever length did have a direct influence on stress distribution. Models with two crowns in the cantilever showed more stress, with a greater concentration of force on the cervical part of the implant.

  3. Exploring the Full Range of Properties of Quasar Spectral Distributions

    NASA Technical Reports Server (NTRS)

    Wilkes, B.

    1998-01-01

    The aim of this work is to support our ISO, far-infrared (IR) observing program of quasars and active galaxies. We have obtained, as far as possible, complete spectral energy distributions (radio-X-ray) of the ISO sample in order to fully delineate the continuum shapes and to allow detailed modelling of that continuum. This includes: ground-based optical, near-IR and mm data, the spectral ranges closest to the ISO data, within 1-2 years of the ISO observations themselves. ISO was launched in Nov 1995 and is currently observing routinely. It has an estimated lifetime is 2 years. All near-IR and optical imaging and spectroscopy are now in hand and in the process of being reduced, mm data collection and proposal writing continues.

  4. Annealing behaviour of c-SiO 2 implanted layer distributed with high density Ag nanoparticles

    NASA Astrophysics Data System (ADS)

    Liu, Zhengxin; Wang, Honghong

    1997-01-01

    High volume density Ag nanoparticles embedded in c-SiO 2 matrix have been prepared by Ag ion implantation at an energy of 200 keV and a current density of about 20 μA/cm 2 to a nominal dose of 6.7 × 10 16ions/cm 2 at RT. Bright-field transmission electron microscopy (TEM) image indicates that Ag nanoparticles show two groups of sizes: the larger diameter is about 25 nm and the smaller is less than 10 nm. RBS spectra show that the distribution of implanted Ag atoms is bimodal which is associated with the two groups of nanoparticles above. Thermal stability of the implanted layer which consists of Ag nanoparticles, dissolved Ag atoms and c-SiO 2 matrix has been investigated by RBS, TEM and Raman spectroscopy. RBS spectra prove that little migration of Ag atoms is found and Ag nanoparticles are considerably stable at 300°C annealing. Though the obvious change in the distribution of Ag is observed at 400°C annealing in RBS spectra, TEM image identifies that both the larger and the smaller Ag nanoparticles still exist at relatively stable state. Following 750°C annealing, Ag atoms drastically move, and furthermore, the bimodal character of the distribution disappears. On the other hand, the amorphized SiO 2 implanted layer recrystal after 300°C, 400°C annealing.

  5. Influence of bone parameters on peri-implant bone strain distribution in the posterior mandible

    PubMed Central

    Yamamoto, Kazuhiko; Kawakami, Masayoshi; Horita, Satoshi; Murakami, Kazuhiro; Kirita, Tadaaki

    2015-01-01

    Objectives: The success rate of dental implants depends on the type of bone at the implant site. The purpose of the present study was to investigate the effects of the bone parameters at the implant-placement site on peri-implant bone strain distributions. Study Design: The morphologies and bone densities of seventy-five potential implant sites in the posterior mandible were measured using computed tomography (CT). Based on the CT data, we defined bone parameters (low and high in terms of cancellous-bone density and crestal-cortical bone density, and thin and thick in terms of crestal-cortical bone thickness), and we constructed finite-element models simulating the various bone types. A buccolingual oblique load of 200 N was applied to the top of the abutment. The von Mises equivalent (EQV) strains in the crestal-cortical bone and in the cancellous bone around the implant were calculated. Results: Cancellous-bone density greatly affected the maximum EQV strain regardless of the density and thickness of the crestal cortical-bone. The maximum EQV strains in the crestal cortical-bone and the cancellous bone in the low-density cancellous-bone models (of 150 Hounsfield units (HU) were 1.56 to 2.62-fold and 3.49 to 5.31-fold higher than those in the high-density cancellous-bone models (of 850 HU), respectively. The crestal cortical-bone density affected the maximum EQV strains in the crestal cortical-bone and in the cancellous bone in the low-density cancellous-bone models. The crestal cortical-bone thickness affected the maximum EQV strains in the cancellous bone and in the crestal cortical-bone in the low-density cancellous-bone models. Conclusions: Our results confirm the importance of bone types for the peri-implant bone strain distribution. Cancellous-bone density may be a critical factor for peri-implant bone strain. Key words:Dental implant, bone density, finite-element analysis. PMID:25129251

  6. The effects of bone density and crestal cortical bone thickness on micromotion and peri-implant bone strain distribution in an immediately loaded implant: a nonlinear finite element analysis

    PubMed Central

    2016-01-01

    Purpose This study investigated the effects of bone density and crestal cortical bone thickness at the implant-placement site on micromotion (relative displacement between the implant and bone) and the peri-implant bone strain distribution under immediate-loading conditions. Methods A three-dimensional finite element model of the posterior mandible with an implant was constructed. Various bone parameters were simulated, including low or high cancellous bone density, low or high crestal cortical bone density, and crestal cortical bone thicknesses ranging from 0.5 to 2.5 mm. Delayed- and immediate-loading conditions were simulated. A buccolingual oblique load of 200 N was applied to the top of the abutment. Results The maximum extent of micromotion was approximately 100 μm in the low-density cancellous bone models, whereas it was under 30 μm in the high-density cancellous bone models. Crestal cortical bone thickness significantly affected the maximum micromotion in the low-density cancellous bone models. The minimum principal strain in the peri-implant cortical bone was affected by the density of the crestal cortical bone and cancellous bone to the same degree for both delayed and immediate loading. In the low-density cancellous bone models under immediate loading, the minimum principal strain in the peri-implant cortical bone decreased with an increase in crestal cortical bone thickness. Conclusions Cancellous bone density may be a critical factor for avoiding excessive micromotion in immediately loaded implants. Crestal cortical bone thickness significantly affected the maximum extent of micromotion and peri-implant bone strain in simulations of low-density cancellous bone under immediate loading. PMID:27382504

  7. Influence of Implant Position on Stress Distribution in Implant-Assisted Distal Extension Removable Partial Dentures: A 3D Finite Element Analysis

    PubMed Central

    Memari, Yeganeh; Geramy, Allahyar; Fayaz, Amir; Rezvani Habib Abadi, Shirin; Mansouri, Yasaman

    2014-01-01

    Objective: Distal extension removable partial denture is a prosthesis with lack of distal dental support with a 13-fold difference in resiliency between the mucosa and the periodontal ligament, resulting in leverage during compression forces. It may be potentially destructive to the abutments and the surrounding tissues. The aim of this study was to assess the effect of implant location on stress distribution, in distal extension implant assisted removable partial dentures. Materials and Methods: Three-dimensional models of a bilateral distal extension partially edentulous mandible containing anterior teeth and first premolar in both sides of the arch, a partial removable denture and an implant (4×10mm) were designed. With the aid of the finite element program ANSYS 8.0, the models were meshed and strictly vertical forces of 10 N were applied to each cusp tip. Displacement and von Mises Maps were plotted for visualization of results. Results: When an implant was placed in the second premolar region, the highest stress on implant, abutment tooth and cancellous bone was shown. The lowest stress was shown on implant and bone in the 1st molar area. Conclusion: Implants located in the first molar area showed the least distribution of stresses in the analyzed models. PMID:25628678

  8. Distribution and Morphology of Calcium-Binding Proteins Immunoreactive Neurons following Chronic Tungsten Multielectrode Implants

    PubMed Central

    Freire, Marco Aurelio M.; Faber, Jean; Lemos, Nelson Alessandretti M.; Santos, Jose Ronaldo; Cavalcanti, Pedro França; Lima, Ramon Hypolito; Morya, Edgard

    2015-01-01

    The development of therapeutic approaches to improve the life quality of people suffering from different types of body paralysis is a current major medical challenge. Brain-machine interface (BMI) can potentially help reestablishing lost sensory and motor functions, allowing patients to use their own brain activity to restore sensorimotor control of paralyzed body parts. Chronic implants of multielectrodes, employed to record neural activity directly from the brain parenchyma, constitute the fundamental component of a BMI. However, before this technique may be effectively available to human clinical trials, it is essential to characterize its long-term impact on the nervous tissue in animal models. In the present study we evaluated how chronic implanted tungsten microelectrode arrays impact the distribution and morphology of interneurons reactive to calcium-binding proteins calbindin (CB), calretinin (CR) and parvalbumin (PV) across the rat’s motor cortex. Our results revealed that chronic microelectrode arrays were well tolerated by the nervous tissue, with recordings remaining viable for up to 6 months after implantation. Furthermore, neither the morphology nor the distribution of inhibitory neurons were broadly impacted. Moreover, restricted microglial activation was observed on the implanted sites. On the whole, our results confirm and expand the notion that tungsten multielectrodes can be deemed as a feasible candidate to future human BMI studies. PMID:26098896

  9. Coefficient of variation calculated from the range for skewed distributions.

    PubMed

    Rhiel, G Steven

    2006-02-01

    In this research a coefficient of variation (CVS(high.low)) is developed that is calculated from the highest and lowest values in a set of data for samples from skewed distributions. A correction factor is determined such that CVS(high-low) is a dose estimate of the population coefficient of variation when sampling from three skewed chi-squared distributions and three skewed empirical distributions. The empirical distributions are from "real-world" data sets in psychology and education.

  10. Comparison of observed and calculated implanted ion distributions outside comet Halley's bow shock

    SciTech Connect

    Gombosi, T.I. ); Neugebauer, M. ); Johnstone, A.D.; Coates, A.J.; Huddleston, D.E. )

    1991-06-01

    This paper compares calculated and measured energy spectra of implanted H{sup +} and O{sup +} ions on the assumption that the pickup geometry is quasi-parallel and about 1% of the waves generated by the cometray pickup process propagate backward (toward the comet). The model provides a good description of the implaneted O{sup +} and H{sup +} energy distribution near the pickup energies. The thickness of the implanted ion velocity distribution shells was nearly constant between 2.50 {times} 10{sup 6} km and 1.20 {times} 10{sup 6} km (just outside the shock) along the inbound Giotto trajectory. The explanation is that the velocity diffusion coefficient and characteristic diffusion time vary approximately as 1/r and r, respectively, and therefore their product (which determines the velocity shell thickness) remains nearly constant.

  11. Short-range ordering of ion-implanted nitrogen atoms in SiC-graphene

    SciTech Connect

    Willke, P.; Druga, T.; Wenderoth, M.; Amani, J. A.; Weikert, S.; Hofsäss, H.; Thakur, S.; Maiti, K.

    2014-09-15

    We perform a structural analysis of nitrogen-doped graphene on SiC(0001) prepared by ultra low-energy ion bombardment. Using scanning tunneling microscopy, we show that nitrogen atoms are incorporated almost exclusively as graphitic substitution in the graphene honeycomb lattice. With an irradiation energy of 25 eV and a fluence of approximately 5 × 10{sup 14 }cm{sup −2}, we achieve a nitrogen content of around 1%. By quantitatively comparing the position of the N-atoms in the topography measurements with simulated random distributions, we find statistically significant short-range correlations. Consequently, we are able to show that the dopants arrange preferably at lattice sites given by the 6 × 6-reconstruction of the underlying substrate. This selective incorporation is most likely triggered by adsorbate layers present during the ion bombardment. This study identifies low-energy ion irradiation as a promising method for controlled doping in epitaxial graphene.

  12. Effects of different abutment connection designs on the stress distribution around five different implants: a 3-dimensional finite element analysis.

    PubMed

    Balik, Ali; Karatas, Meltem Ozdemir; Keskin, Haluk

    2012-09-01

    The stability of the bone-implant interface is required for the long-term favorable clinical outcome of implant-supported prosthetic rehabilitation. The implant failures that occur after the functional loading are mainly related to biomechanical factors. Micro movements and vibrations due to occlusal forces can lead to mechanical complications such as loosening of the screw and fractures of the abutment or implants. The aim of this study was to investigate the strain distributions in the connection areas of different implant-abutment connection systems under similar loading conditions. Five different implant-abutment connection designs from 5 different manufacturers were evaluated in this study. The investigation was performed with software using the finite element method. The geometrical modeling of the implant systems was done with CATIA virtual design software. The MSC NASTRAN solver and PATRAN postprocessing program were used to perform the linear static solution. According to the analysis, the implant-abutment connection system with external hexagonal connection showed the highest strain values, and the internal hexagonal implant-abutment connection system showed the lowest strain values. Conical + internal hexagonal and screw-in implant abutment connection interface is more successful than other systems in cases with increased vertical dimension, particularly in the posterior region.

  13. Evaluation of design parameters of dental implant shape, diameter and length on stress distribution: a finite element analysis.

    PubMed

    Mohammed Ibrahim, M; Thulasingam, C; Nasser, K S G A; Balaji, V; Rajakumar, M; Rupkumar, P

    2011-09-01

    The aim was to evaluate the design parameters of dental implants shape, diameter and length on stress distribution by finite element analysis (FEA).The objectives of the study was to compare the influence of stress distribution in the implants of screw-vent tapered and parallel design by varying the implant diameter with a standard implant length. Six dental implant models have been simulated three-dimensionally. The influence of diameter and length on stress distribution was evaluated by Group I: for screw-vent tapered design (Zimmer Dental Implant Carlsbad, CA, USA) (1) Dental implant model with diameter 3.7 mm and length 13 mm. (2) Dental implant model with diameter 4.1 mm and length 13 mm. (3) Dental implant model with diameter 4.7 mm and length 13 mm. Group II: for parallel design (Zimmer Dental Implant Carlsbad, CA, USA) (4) Dental implant model with diameter 3.7 mm and length 13 mm. (5) Dental implant model with diameter 4.1 mm and length 13 mm. (6) Dental implant model with diameter 4.7 mm and length 13 mm. The 3-D model of the implant was created in the pro-e wildfire 4.0 software by giving various commands. This model was imported to the ANSYS software through IGES (initial graphic exchange specification) file for further analysis. All six models were loaded with a force of 17.1, 114.6 and 23.4 N in a lingual, an axial and disto-mesial direction respectively, simulating average masticatory force in a natural oblique direction, to analyze the stress distribution on these implants. The increase in implant diameter in Group I and Group II from 3.7 to 4.1 mm and from 4.1 to 4.7 mm with constant 13 mm length for screw-vent tapered and parallel design implant resulted in a reduction in maximum value of Von Mises stress in the bone surrounding the implant was statistically significant at 5% level done by student "t" test. The overall maximum value of Von Mises stress was decreased in parallel design implant diameter of 4.7 mm with constant

  14. Can megavoltage computed tomography reduce proton range uncertainties in treatment plans for patients with large metal implants?

    NASA Astrophysics Data System (ADS)

    Newhauser, Wayne D.; Giebeler, Annelise; Langen, Katja M.; Mirkovic, Dragan; Mohan, Radhe

    2008-05-01

    Treatment planning calculations for proton therapy require an accurate knowledge of radiological path length, or range, to the distal edge of the target volume. In most cases, the range may be calculated with sufficient accuracy using kilovoltage (kV) computed tomography (CT) images. However, metal implants such as hip prostheses can cause severe streak artifacts that lead to large uncertainties in proton range. The purposes of this study were to quantify streak-related range errors and to determine if they could be avoided by using artifact-free megavoltage (MV) CT images in treatment planning. Proton treatment plans were prepared for a rigid, heterogeneous phantom and for a prostate cancer patient with a metal hip prosthesis using corrected and uncorrected kVCT images alone, uncorrected MVCT images and a combination of registered MVCT and kVCT images (the hybrid approach). Streak-induced range errors of 5-12 mm were present in the uncorrected kVCT-based patient plan. Correcting the streaks by manually assigning estimated true Hounsfield units improved the range accuracy. In a rigid heterogeneous phantom, the implant-related range uncertainty was estimated at <3 mm for both the corrected kVCT-based plan and the uncorrected MVCT-based plan. The hybrid planning approach yielded the best overall result. In this approach, the kVCT images provided good delineation of soft tissues due to high-contrast resolution, and the streak-free MVCT images provided smaller range uncertainties because they did not require artifact correction.

  15. Biomechanical influence of crown-to-implant ratio on stress distribution over internal hexagon short implant: 3-D finite element analysis with statistical test.

    PubMed

    Ramos Verri, Fellippo; Santiago Junior, Joel Ferreira; de Faria Almeida, Daniel Augusto; de Oliveira, Guilherme Bérgamo Brandão; de Souza Batista, Victor Eduardo; Marques Honório, Heitor; Noritomi, Pedro Yoshito; Pellizzer, Eduardo Piza

    2015-01-01

    The study of short implants is relevant to the biomechanics of dental implants, and research on crown increase has implications for the daily clinic. The aim of this study was to analyze the biomechanical interactions of a singular implant-supported prosthesis of different crown heights under vertical and oblique force, using the 3-D finite element method. Six 3-D models were designed with Invesalius 3.0, Rhinoceros 3D 4.0, and Solidworks 2010 software. Each model was constructed with a mandibular segment of bone block, including an implant supporting a screwed metal-ceramic crown. The crown height was set at 10, 12.5, and 15 mm. The applied force was 200 N (axial) and 100 N (oblique). We performed an ANOVA statistical test and Tukey tests; p<0.05 was considered statistically significant. The increase of crown height did not influence the stress distribution on screw prosthetic (p>0.05) under axial load. However, crown heights of 12.5 and 15 mm caused statistically significant damage to the stress distribution of screws and to the cortical bone (p<0.001) under oblique load. High crown to implant (C/I) ratio harmed microstrain distribution on bone tissue under axial and oblique loads (p<0.001). Crown increase was a possible deleterious factor to the screws and to the different regions of bone tissue.

  16. A 1-channel 3-band wide dynamic range compression chip for vibration transducer of implantable hearing aids.

    PubMed

    Kim, Dongwook; Seong, Kiwoong; Kim, Myoungnam; Cho, Jinho; Lee, Jyunghyun

    2014-01-01

    In this paper, a digital audio processing chip which uses a wide dynamic range compression (WDRC) algorithm is designed and implemented for implantable hearing aids system. The designed chip operates at a single voltage of 3.3V and drives a 16 bit parallel input and output at 32 kHz sample. The designed chip has 1-channel 3-band WDRC composed of a FIR filter bank, a level detector, and a compression part. To verify the performance of the designed chip, we measured the frequency separations of bands and compression gain control to reflect the hearing threshold level. PMID:24211991

  17. A 1-channel 3-band wide dynamic range compression chip for vibration transducer of implantable hearing aids.

    PubMed

    Kim, Dongwook; Seong, Kiwoong; Kim, Myoungnam; Cho, Jinho; Lee, Jyunghyun

    2014-01-01

    In this paper, a digital audio processing chip which uses a wide dynamic range compression (WDRC) algorithm is designed and implemented for implantable hearing aids system. The designed chip operates at a single voltage of 3.3V and drives a 16 bit parallel input and output at 32 kHz sample. The designed chip has 1-channel 3-band WDRC composed of a FIR filter bank, a level detector, and a compression part. To verify the performance of the designed chip, we measured the frequency separations of bands and compression gain control to reflect the hearing threshold level.

  18. Gas swelling and deuterium distribution in beryllium implanted with deuterium ions

    SciTech Connect

    Chernikov, V.N.; Alimov, V.Kh.; Zakharov, A.P.

    1995-09-01

    An extensive TEM study of the microstructure of Be TIP-30 irradiated with 3 and 10 keV D ions up to fluences, {Phi}, in the range from 3 x 10{sup 20} to 8 x 10{sup 21} D/m{sup 2} at temperatures T{sub irr} = 300 K, 500 K and 700 K has been carried out. Depth distributions of deuterium in the form of separate D atoms and D{sub 2} molecules have been investigated by means of SIMS and RGA methods, correspondingly. D ion irradiation is accompanied by blistering and gives rise to different kind of destructions depending mainly on the irradiation temperature. Irradiation with D ions at 300 K leads to the formation of tiny highly pressurized D{sub 2} bubbles reminiscent of He bubbles in Be. Under 3 keV D ion irradiation D{sub 2} bubbles ({bar r}{sub b} {approx} 0.7 nm) appear at a fluence as low as 3x10{sup 20} D/m{sup 2}. Irradiation at 500 K results in the development, along with relatively small facetted bubbles, of larger oblate gas-filled cavities accumulating most of injected D atoms and providing for much higher gas swelling values as compared to irradiation at 300 K. The increase of D and/or T{sub irr}, to 700 K causes the further coarsening of large cavities which are transformed into sub-surface labyrinth structures. D and He ion implantation leads to the enhanced growth of porous microcrystalline layers of c.p.h.-BeO oxide with a microstructure which differs considerably from that of oxide layers on electropolished surfaces of Be. Based on the analysis of experimental data questions of deuterium reemission, thermal desorption and trapping in Be have been discussed in detail.

  19. The scaling of geographic ranges: implications for species distribution models

    USGS Publications Warehouse

    Yackulic, Charles B.; Ginsberg, Joshua R.

    2016-01-01

    There is a need for timely science to inform policy and management decisions; however, we must also strive to provide predictions that best reflect our understanding of ecological systems. Species distributions evolve through time and reflect responses to environmental conditions that are mediated through individual and population processes. Species distribution models that reflect this understanding, and explicitly model dynamics, are likely to give more accurate predictions.

  20. Photon beam dose distributions for patients with implanted temporary tissue expanders

    NASA Astrophysics Data System (ADS)

    Asena, A.; Kairn, T.; Crowe, S. B.; Trapp, J. V.

    2015-01-01

    This study examines the effects of temporary tissue expanders (TTEs) on the dose distributions of photon beams in breast cancer radiotherapy treatments. EBT2 radiochromic film and ion chamber measurements were taken to quantify the attenuation and backscatter effects of the inhomogeneity. Results illustrate that the internal magnetic port present in a tissue expander causes a dose reduction of approximately 25% in photon tangent fields immediately downstream of the implant. It was also shown that the silicone elastomer shell of the tissue expander reduced the dose to the target volume by as much as 8%. This work demonstrates the importance for an accurately modelled high-density implant in the treatment planning system for post-mastectomy breast cancer patients.

  1. Distribution of ACTFL Ratings by TOEFL Score Ranges.

    ERIC Educational Resources Information Center

    Boldt, R. F.; And Others

    The purpose of this study was to align verbal descriptions of test takers' language performance with distributions of the numerical scores they received on the three sections (Listening Comprehension, Structure and Written Expression, and Reading Comprehension and Vocabulary) of the Test of English as a Foreign Language (TOEFL). The descriptors of…

  2. Measurement of strain distribution in cortical bone around miniscrew implants used for orthodontic anchorage using digital speckle pattern interferometry

    NASA Astrophysics Data System (ADS)

    Kumar, Manoj; Agarwal, Rupali; Bhutani, Ravi; Shakher, Chandra

    2016-05-01

    An application of digital speckle pattern interferometry (DSPI) for the measurement of deformations and strain-field distributions developed in cortical bone around orthodontic miniscrew implants inserted into the human maxilla is presented. The purpose of this study is to measure and compare the strain distribution in cortical bone/miniscrew interface of human maxilla around miniscrew implants of different diameters, different implant lengths, and implants of different commercially available companies. The technique is also used to measure tilt/rotation of canine caused due to the application of retraction springs. The proposed technique has high sensitivity and enables the observation of deformation/strain distribution. In DSPI, two specklegrams are recorded corresponding to pre- and postloading of the retraction spring. The DSPI fringe pattern is observed by subtracting these two specklegrams. Optical phase was extracted using Riesz transform and the monogenic signal from a single DSPI fringe pattern. The obtained phase is used to calculate the parameters of interest such as displacement/deformation and strain/stress. The experiment was conducted on a dry human skull fulfilling the criteria of intact dental arches and all teeth present. Eight different miniscrew implants were loaded with an insertion angulation of 45 deg in the inter-radicular region of the maxillary second premolar and molar region. The loading of miniscrew implants was done with force level (150 gf) by nickel-titanium closed-coil springs (9 mm). The obtained results from DSPI reveal that implant diameter and implant length affect the displacement and strain distribution in cortical bone layer surrounding the miniscrew implant.

  3. Measurement of strain distribution in cortical bone around miniscrew implants used for orthodontic anchorage using digital speckle pattern interferometry

    NASA Astrophysics Data System (ADS)

    Kumar, Manoj; Agarwal, Rupali; Bhutani, Ravi; Shakher, Chandra

    2016-05-01

    An application of digital speckle pattern interferometry (DSPI) for the measurement of deformations and strain-field distributions developed in cortical bone around orthodontic miniscrew implants inserted into the human maxilla is presented. The purpose of this study is to measure and compare the strain distribution in cortical bone/miniscrew interface of human maxilla around miniscrew implants of different diameters, different implant lengths, and implants of different commercially available companies. The technique is also used to measure tilt/rotation of canine caused due to the application of retraction springs. The proposed technique has high sensitivity and enables the observation of deformation/strain distribution. In DSPI, two specklegrams are recorded corresponding to pre- and postloading of the retraction spring. The DSPI fringe pattern is observed by subtracting these two specklegrams. Optical phase was extracted using Riesz transform and the monogenic signal from a single DSPI fringe pattern. The obtained phase is used to calculate the parameters of interest such as displacement/deformation and strain/stress. The experiment was conducted on a dry human skull fulfilling the criteria of intact dental arches and all teeth present. Eight different miniscrew implants were loaded with an insertion angulation of 45 deg in the inter-radicular region of the maxillary second premolar and molar region. The loading of miniscrew implants was done with force level (150 gf) by nickel-titanium closed-coil springs (9 mm). The obtained results from DSPI reveal that implant diameter and implant length affect the displacement and strain distribution in cortical bone layer surrounding the miniscrew implant.

  4. Effect of attachment type on load distribution to implant abutments and the residual ridge in mandibular implant-supported overdentures

    PubMed Central

    Matsudate, Yoshiki; Abue, Masaru; Hong, Guang; Sasaki, Keiichi

    2015-01-01

    This study aimed to investigate the effect of attachment type on the load transmitted to implants and the residual ridge in a mandibular two-implant-supported overdenture in a model study. Ball attachments, locator attachments, and round-bar attachments were selected and examined. Static and dynamic vertical loads of 100 N were applied in the right first molar region. The load on the implants was measured by piezoelectric three-dimensional force transducers, and the load on the residual ridge beneath the denture base was measured using a tactile sheet sensor. The load on the implants with ball attachments was significantly higher than that with the other two attachments. The load on the residual ridge with round-bar attachments was significantly higher than that with the other two attachments. Our findings indicate that the three-dimensional load on implants and the residual ridge beneath the denture base is significantly associated with the type of attachment used in implant-supported overdentures. PMID:25798201

  5. Effect of attachment type on load distribution to implant abutments and the residual ridge in mandibular implant-supported overdentures.

    PubMed

    Yoda, Nobuhiro; Matsudate, Yoshiki; Abue, Masaru; Hong, Guang; Sasaki, Keiichi

    2015-01-01

    This study aimed to investigate the effect of attachment type on the load transmitted to implants and the residual ridge in a mandibular two-implant-supported overdenture in a model study. Ball attachments, locator attachments, and round-bar attachments were selected and examined. Static and dynamic vertical loads of 100 N were applied in the right first molar region. The load on the implants was measured by piezoelectric three-dimensional force transducers, and the load on the residual ridge beneath the denture base was measured using a tactile sheet sensor. The load on the implants with ball attachments was significantly higher than that with the other two attachments. The load on the residual ridge with round-bar attachments was significantly higher than that with the other two attachments. Our findings indicate that the three-dimensional load on implants and the residual ridge beneath the denture base is significantly associated with the type of attachment used in implant-supported overdentures.

  6. N-pulse logic peak detection for laser radar range measurement of distributed range targets

    NASA Astrophysics Data System (ADS)

    Fluckiger, David U.

    1988-08-01

    In this report N-pulse detection logic is discussed in the context of high angular resolution laser radar range processing. In the event that a resolved target is obscured by one or more unresolved scatterers such as wires, tree branches, camouflage netting, antennas, and the like, one sees multiple returns in the range I.F. due to the multiple scatterers in the line-of-sight path to the target. A laser radar that peak detects the N largest pulses in the range I.F. utilizes N-pulse peak detection logic. This report contains a discussion of the utility of N-pulse logic and also samples of data of N-pulse returns from trees and wires. A limit is found for the average resolvable distance between two scatterers based on Gaussian pulse shapes but not taking into account noise and target fluctuations (speckle).

  7. Exploring the Full Range of Properties of Quasar Spectral Distribution

    NASA Technical Reports Server (NTRS)

    Wilkes, B.

    1999-01-01

    The aim of this work is to obtain multi-wavelength supporting data for the sample of quasars and active galaxies observed in the far-infrared (IR) by ISO as part of our Key Project on quasars and active galaxies. This dataset then provides complete spectral energy distributions (radio-X-ray) of the ISO sample in order to fully delineate the continuum shapes and to allow detailed modeling of that continuum. The report is made up of a short project summary, and a bibliography of published papers, proceedings and presentations.

  8. Depth distribution of deuterium atoms and molecules in beryllium implanted with D ions

    NASA Astrophysics Data System (ADS)

    Alimov, V. Kh.; Chernikov, V. N.; Zakharov, A. P.

    1997-02-01

    In-depth concentration profiles of deuterium atoms and molecules in beryllium implanted with 9 keV D ions to fluences, Φ, in the range from 6 × 10 19 to 9 × 10 22D/ m2 at temperatures, Tirr, of 300 and 700 K have been determined using SIMS and RGA (residual gas analysis) measurements in the course of surface sputtering. The microstructure of implanted specimens was studied by TEM. Implanted deuterium is retained in Be matrix in the form of both D atoms and D 2 molecules. The total amount of gas captured within the sub-surface layer of ˜ 700 nm in thickness as a result of implantation at 300 and 700 K reaches 4 × 10 21 and 1 × 10 21D/ m2, correspondingly. The ratio of deuterium quantities retained in the form of atoms and molecules, QD: QD2, varies from 1:3 for Tirr = 300 K to 1:4 for Tirr = 700 K. At Tirr = 300 K the concentration of D 2 molecules at the depth of the ion mean range reaches its maximum of 4 × 10 27molecules/ m3 at Φ ≈ 2 × 10 21D/ m2. The molecules are present in tiny bubbles which show a tendency toward interconnection at higher fluences. At Tirr = 700 K, along with relatively small facetted bubbles (near the very surface), large oblate gas-filled cavities and channels forming extended labyrinths appear and they accumulate most of the injected gas. The maximum D 2 concentration in the latter case is of 1 × 10 27molecules/ m3. The high concentration of D atoms in the ion stopping zone after implantation at Tirr = 300 and 700 K (about 2 × 10 27and 1 × 10 27atoms/ m3, respectively) is attributed to deuterium (i) trapped in radiation vacancies, (ii) adsorbed on the walls of bubbles and channels and (iii) bonded to/by BeO formed on the surface and present in the form of metallurgical inclusions in the bulk.

  9. Daptomycin and tigecycline have broader effective dose ranges than vancomycin as prophylaxis against a Staphylococcus aureus surgical implant infection in mice.

    PubMed

    Niska, Jared A; Shahbazian, Jonathan H; Ramos, Romela Irene; Pribaz, Jonathan R; Billi, Fabrizio; Francis, Kevin P; Miller, Lloyd S

    2012-05-01

    Vancomycin is widely used for intravenous prophylaxis against surgical implant infections. However, it is unclear whether alternative antibiotics used to treat methicillin-resistant Staphylococcus aureus (MRSA) infections are effective as prophylactic agents. The aim of this study was to compare the efficacies of vancomycin, daptomycin, and tigecycline as prophylactic therapy against a methicillin-sensitive S. aureus (MSSA) or MRSA surgical implant infection in mice. MSSA or MRSA was inoculated into the knee joints of mice in the presence of a surgically placed medical-grade metallic implant. The efficacies of low- versus high-dose vancomycin (10 versus 110 mg/kg), daptomycin (1 versus 10 mg/kg), and tigecycline (1 versus 10 mg/kg) intravenous prophylaxis were compared using in vivo bioluminescence imaging, ex vivo bacterial counts, and biofilm formation. High-dose vancomycin, daptomycin, and tigecycline resulted in similar reductions in bacterial burden and biofilm formation. In contrast, low-dose daptomycin and tigecycline were more effective than low-dose vancomycin against the implant infection. In this mouse model of surgical implant MSSA or MRSA infection, daptomycin and tigecycline prophylaxis were effective over a broader dosage range than vancomycin. Future studies in humans will be required to determine whether these broader effective dose ranges for daptomycin and tigecycline in mice translate to improved efficacy in preventing surgical implant infections in clinical practice.

  10. Three dimensional finite element analysis of stress distribution around implant with straight and angled abutments in different bone qualities.

    PubMed

    Arun Kumar, G; Mahesh, B; George, Dadu

    2013-12-01

    The aim of the study was to compare the stress distribution around implant in different bone qualities of D1, D2, D3, and D4 with straight and angled abutments using three dimensional finite element analysis. A three dimensional finite element model of the premaxilla region, and two solid 4.3 × 10 mm implant, one with a straight abutment and the other with an angled abutment was done. Four distinctly different bone qualities of D1, D2, D3, and D4 were made. A static load of 178 N was applied at the centre of incisal edge along the long axis of each abutment. The maximum equivalent von Misses stress values around the implants were recorded. The distribution of stresses changed considerably with abutment angulation. As angulation increased from 0° to 15° the concentration of Von Misses stresses shifted to the cortical layer of bone on the facial side of the fixture. Although Von Misses stress increased in straight abutment as the bone quality changed from D1 to D4, it was more noticeable under the loading side of the angulated abutments. The high stresses induced through angled abutments at the cervical zone of the implant due to forces and moments could be a dominant factor that may aggravate the peri-implant bone loss or changes the existing peri-implantitis direction.

  11. Stress Distribution in Single Dental Implant System: Three-Dimensional Finite Element Analysis Based on an In Vitro Experimental Model.

    PubMed

    Rezende, Carlos Eduardo Edwards; Chase-Diaz, Melody; Costa, Max Doria; Albarracin, Max Laurent; Paschoeto, Gabriela; Sousa, Edson Antonio Capello; Rubo, José Henrique; Borges, Ana Flávia Sanches

    2015-10-01

    This study aimed to analyze the stress distribution in single implant system and to evaluate the compatibility of an in vitro model with finite element (FE) model. The in vitro model consisted of Brånemark implant; multiunit set abutment of 5 mm height; metal-ceramic screw-retained crown, and polyurethane simulating the bone. Deformations were recorded in the peri-implant region in the mesial and distal aspects, after an axial 300 N load application at the center of the occlusal aspect of the crown, using strain gauges. This in vitro model was scanned with micro CT to design a three-dimensional FE model and the strains in the peri-implant bone region were registered to check the compatibility between both models. The FE model was used to evaluate stress distribution in different parts of the system. The values obtained from the in vitro model (20-587 με) and the finite element analysis (81-588 με) showed agreement among them. The highest stresses because of axial and oblique load, respectively were 5.83 and 40 MPa for the cortical bone, 55 and 1200 MPa for the implant, and 80 and 470 MPa for the abutment screw. The FE method proved to be effective for evaluating the deformation around single implant. Oblique loads lead to higher stress concentrations. PMID:26192032

  12. A CMOS frontend chip for implantable neural recording with wide voltage supply range

    NASA Astrophysics Data System (ADS)

    Jialin, Liu; Xu, Zhang; Xiaohui, Hu; Yatao, Guo; Peng, Li; Ming, Liu; Bin, Li; Hongda, Chen

    2015-10-01

    A design for a CMOS frontend integrated circuit (chip) for neural signal acquisition working at wide voltage supply range is presented in this paper. The chip consists of a preamplifier, a serial instrumental amplifier (IA) and a cyclic analog-to-digital converter (CADC). The capacitive-coupled and capacitive-feedback topology combined with MOS-bipolar pseudo-resistor element is adopted in the preamplifier to create a -3 dB upper cut-off frequency less than 1 Hz without using a ponderous discrete device. A dual-amplifier instrumental amplifier is used to provide a low output impedance interface for ADC as well as to boost the gain. The preamplifier and the serial instrumental amplifier together provide a midband gain of 45.8 dB and have an input-referred noise of 6.7 μVrms integrated from 1 Hz to 5 kHz. The ADC digitizes the amplified signal at 12-bits precision with a highest sampling rate of 130 kS/s. The measured effective number of bits (ENOB) of the ADC is 8.7 bits. The entire circuit draws 165 to 216 μA current from the supply voltage varied from 1.34 to 3.3 V. The prototype chip is fabricated in the 0.18-μm CMOS process and occupies an area of 1.23 mm2 (including pads). In-vitro recording was successfully carried out by the proposed frontend chip. Project supported by the National Natural Science Foundation of China (Nos. 61474107, 61372060, 61335010, 61275200, 61178051) and the Key Program of the Chinese Academy of Sciences (No. KJZD-EW-L11-01).

  13. Dosimetric distribution of the surroundings of different dental crowns and implants during LINAC photon irradiation

    NASA Astrophysics Data System (ADS)

    Chang, Kwo-Ping; Lin, Wei-Ting; Shiau, An-Cheng; Chie, Yu-Huang

    2014-11-01

    In radiotherapy of the head and neck, metal dentures or implants will increase the risk of complications such as mucositis and osteoradionecrosis. The aim of this study is to explore the back scatter effect of commercially available dental metal alloys on the mucosa and bone under 6 MV LINAC irradiation. The Monte Carlo method has been employed to calculate the dose distribution in the heterogeneous media of the designed oral phantom based on the oral cavity geometry. Backscatter dose increases up to a maximum of 53%, and is primarily dependent on the physical density and electron density of the metal crown alloy. Ceramic metal crowns have been quantified to increase backscatter dose up to 10% on mucosa. Ceramic serves as an inherent shield of mucosa. The backscatter dose will be greater for a small field size if the tumor is located at a deeper region. Titanium implants will increase the backscatter dose by 13% to bone but will not affect the mucosa. QC-20 (polystyrene resin) is recommended as a shield material (3 mm) to eliminate the backscatter dose on mucosa due to the high density metals.

  14. FEM and Von Mises analyses of different dental implant shapes for masticatory loading distribution.

    PubMed

    Cicciù, M; Bramanti, E; Cecchetti, F; Scappaticci, L; Guglielmino, E; Risitano, G

    2014-01-01

    The rehabilitation of edentulous patients is today a challenge for the clinicians. The healthy of the hard and soft issue may be considered a fundamental element for having long-term results. The dental implant progresses about the predictable and safe results made this technique chosen from a large group of practitioners. However some problems related intra-operative and postoperative conditions may create discomfort on the patients and consequently to the clinician. The unfavourable results are often related to the bone tissue quality but sometime the dental implant shape and the prosthesis framework may undergo to technical difficulties. The purpose of this work is, through the use of appropriate FEM models, to analyse the effect of all these parameters in the construction of a prosthesis type "Toronto", evaluating all the surgical and prosthetic components in order to direct the choices made by the surgeon and to optimize the distribution of loads reducing the patient's discomfort and having a long term clinical success. PMID:25694795

  15. FEM and Von Mises analyses of different dental implant shapes for masticatory loading distribution

    PubMed Central

    CICCIÙ, M.; BRAMANTI, E.; CECCHETTI, F.; SCAPPATICCI, L.; GUGLIELMINO, E.; RISITANO, G.

    2014-01-01

    SUMMARY The rehabilitation of edentulous patients is today a challenge for the clinicians. The healthy of the hard and soft issue may be considered a fundamental element for having long-term results. The dental implant progresses about the predictable and safe results made this technique chosen from a large group of practitioners. However some problems related intra-operative and postoperative conditions may create discomfort on the patients and consequently to the clinician. The unfavourable results are often related to the bone tissue quality but sometime the dental implant shape and the prosthesis framework may undergo to technical difficulties. The purpose of this work is, through the use of appropriate FEM models, to analyse the effect of all these parameters in the construction of a prosthesis type “Toronto”, evaluating all the surgical and prosthetic components in order to direct the choices made by the surgeon and to optimize the distribution of loads reducing the patient’s discomfort and having a long term clinical success. PMID:25694795

  16. Three-dimensional finite element analysis of stress distribution on different bony ridges with different lengths of morse taper implants and prosthesis dimensions.

    PubMed

    Toniollo, Marcelo Bighetti; Macedo, Ana Paula; Rodrigues, Renata Cristina Silveira; Ribeiro, Ricardo Faria; de Mattos, Maria da Gloria Chiarello

    2012-11-01

    This finite element analysis (FEA) compared stress distribution on different bony ridges rehabilitated with different lengths of morse taper implants, varying dimensions of metal-ceramic crowns to maintain the occlusal alignment. Three-dimensional FE models were designed representing a posterior left side segment of the mandible: group control, 3 implants of 11 mm length; group 1, implants of 13 mm, 11 mm and 5 mm length; group 2, 1 implant of 11 mm and 2 implants of 5 mm length; and group 3, 3 implants of 5 mm length. The abutments heights were 3.5 mm for 13- and 11-mm implants (regular), and 0.8 mm for 5-mm implants (short). Evaluation was performed on Ansys software, oblique loads of 365N for molars and 200N for premolars. There was 50% higher stress on cortical bone for the short implants than regular implants. There was 80% higher stress on trabecular bone for the short implants than regular implants. There was higher stress concentration on the bone region of the short implants neck. However, these implants were capable of dissipating the stress to the bones, given the applied loads, but achieving near the threshold between elastic and plastic deformation to the trabecular bone. Distal implants and/or with biggest occlusal table generated greatest stress regions on the surrounding bone. It was concluded that patients requiring short implants associated with increased proportions implant prostheses need careful evaluation and occlusal adjustment, as a possible overload in these short implants, and even in regular ones, can generate stress beyond the physiological threshold of the surrounding bone, compromising the whole system.

  17. In vitro analysis of resistance to cyclic load and preload distribution of two implant/abutment screwed connections.

    PubMed

    Murmura, Giovanna; Di Iorio, Donato; Cicchetti, Angelo Raffaele; Sinjari, Bruna; Caputi, Sergio

    2013-06-01

    The aim of the present research is an in vitro evaluation of the preload distribution in screw-retained implant systems under cyclic load. Two implant systems with internal connection were tested: fifteen 4.5 × 10 mm implants with internal hexagon and fifteen 4.5 × 10 mm implants with internal octagon. Samples underwent cyclic load that was between 20 N and 200 N for 1 × 10(6) cycles. After mechanical tests, samples were sectioned along the long axis and analyzed under a scanning electron microscope. Five 4.5 × 10 mm implants with internal hexagon and five 4.5 × 10 mm implants with internal octagon were collected for photoelastic analysis. Each fixture was mounted in a wax-made parallelepiped measuring 20 mm × 20 mm × 10 mm. A mold was made for each wax parallelepiped/fixture assembly using a silicone-based impression material, and an epoxy resin was poured in each mold. After setting of the resin, 25° angled titanium abutments were screwed onto each replica; afterwards, assemblies underwent photoelastic analysis. After cyclic load, screw threads and heads were still in contact with internal fixture threads and abutment holes, respectively, suggesting that preload has not been lost during load. During load, SSO and Xsigñ implants behave in a different way. SSO samples revealed the presence of fringes radiating from the base of the abutment. Xsigñ implants showed the presence of fringes radiating from the threads of the retention screw. From the present in vitro research, it is possible to state that screw-retained abutment based on an internal octagonal connection is less likely to come loose after cyclic load.

  18. An Evaluation of the Stress Distribution in Screw Retained Implants of Different Crown Implant Ratios in Different Bone Densities Under Various Loads-A FEM Study

    PubMed Central

    Vootla, Naveen Reddy; Kumar, VHC; Surapaneni, Hemchand; Balusu, Srilatha; Kalyanam, Swetha

    2016-01-01

    Introduction Studies on stress distribution around screw retained implants in different bone densities are limited. In clinical situations crowns of different heights are placed on the implants and the effect of varying crown implant ratio on the bone is not understood properly. Aim To evaluate and compare the stress distribution in different screw retained implants for different crown–implant ratios in different bone densities under various occlusal loads using three dimensional finite element analyses. Materials and Methods In this invitro study the stress distribution was evaluated and compared between two different crown heights (7.5mm, 10mm) retained on implants by using different screw materials (commercially pure titanium, titanium alloy) in two different densities of bone D2, D3 under various load (100N, 200N) applications by using finite element analysis. Results For crown height of 7.5mm, in D2 bone density when vertical load of 200N was applied, the maximum stress concentration was 1780N/cm2, for oblique load of 100N it was 2936N/cm2 respectively and in D3 bone density when vertical load of 200N was applied, the maximum stress concentration was 1820N/cm2, for oblique load of 100N it was 3477N/cm2 respectively. When the crown height is increased to 10mm, the maximum stress concentration in D2 bone was 1875N/cm2 for vertical load, 4015N/cm2 for oblique load and in D3 bone the maximum stress concentration was 2123N/cm2 for vertical load and 4236N/ cm2 for oblique load. In case of titanium screws for crown height of 7.5 mm, when vertical load was applied, stress concentration was 1603 N/cm2 where as for titanium alloy screw it was 1820N/cm2. In case of 10mm crown height stress concentration was 1904N/cm2 for titanium screw and 2123N/cm2 for titanium alloy screw. In case of oblique loading for 7.5mm crown height stress concentration was 3155N/cm2 for titanium screw 3477N/cm2 for titanium alloy screw. For 10mm crown height stress concentration was 4236N/cm2

  19. The effect of thread design on stress distribution in a solid screw implant: a 3D finite element analysis.

    PubMed

    Eraslan, Oğuz; Inan, Ozgür

    2010-08-01

    The biomechanical behavior of implant thread plays an important role on stresses at implant-bone interface. Information about the effect of different thread profiles upon the bone stresses is limited. The purpose of this study was to evaluate the effects of different implant thread designs on stress distribution characteristics at supporting structures. In this study, three-dimensional (3D) finite element (FE) stress-analysis method was used. Four types of 3D mathematical models simulating four different thread-form configurations for a solid screw implant was prepared with supporting bone structure. V-thread (1), buttress (2), reverse buttress (3), and square thread designs were simulated. A 100-N static axial occlusal load was applied to occlusal surface of abutment to calculate the stress distributions. Solidworks/Cosmosworks structural analysis programs were used for FE modeling/analysis. The analysis of the von Mises stress values revealed that maximum stress concentrations were located at loading areas of implant abutments and cervical cortical bone regions for all models. Stress concentration at cortical bone (18.3 MPa) was higher than spongious bone (13.3 MPa), and concentration of first thread (18 MPa) was higher than other threads (13.3 MPa). It was seen that, while the von Mises stress distribution patterns at different implant thread models were similar, the concentration of compressive stresses were different. The present study showed that the use of different thread form designs did not affect the von Mises concentration at supporting bone structure. However, the compressive stress concentrations differ by various thread profiles.

  20. Finite element analysis on stress distribution of maxillary implant-retained overdentures depending on the Bar attachment design and palatal coverage

    PubMed Central

    2016-01-01

    PURPOSE The purpose of this study was to determine the effect of anchorage systems and palatal coverage of denture base on load transfer in maxillary implant-retained overdenture. MATERIALS AND METHODS Maxillary implant-retained overdentures with 4 implants placed in the anterior region of edentulous maxilla were converted into a 3-D numerical model, and stress distribution patterns in implant supporting bone in the case of unilateral vertical loading on maxillary right first molar were compared with each other depending on various types of anchorage system and palatal coverage extent of denture base using three-dimensional finite element analysis. RESULTS In all experimental models, the highest stress was concentrated on the most distal implant and implant supporting bone on loaded side. The stress at the most distal implant-supporting bone was concentrated on the cortical bone. In all anchorage system without palatal coverage of denture base, higher stresses were concentrated on the most distal implant and implant supporting bone on loaded side. CONCLUSION It could be suggested that when making maxillary implant retained overdenture, using Hader bar instead of milled bar and full palatal coverage rather than partial palatal coverage are more beneficial in distributing the stress that is applied on implant supporting bone. PMID:27141251

  1. A proof for Rhiel's range estimator of the coefficient of variation for skewed distributions.

    PubMed

    Rhiel, G Steven

    2007-02-01

    In this research study is proof that the coefficient of variation (CV(high-low)) calculated from the highest and lowest values in a set of data is applicable to specific skewed distributions with varying means and standard deviations. Earlier Rhiel provided values for d(n), the standardized mean range, and a(n), an adjustment for bias in the range estimator of micro. These values are used in estimating the coefficient of variation from the range for skewed distributions. The d(n) and an values were specified for specific skewed distributions with a fixed mean and standard deviation. In this proof it is shown that the d(n) and an values are applicable for the specific skewed distributions when the mean and standard deviation can take on differing values. This will give the researcher confidence in using this statistic for skewed distributions regardless of the mean and standard deviation.

  2. Species-range size distributions: products of speciation, extinction and transformation

    PubMed Central

    Gaston, K. J.

    1998-01-01

    One basic summary of the spatial pattern of biodiversity across the surface of the Earth is provided by a species-range size distribution, the frequency distribution of the numbers of species exhibiting geographic ranges of different sizes. Although widely considered to be approximately lognormal, increasingly it appears that across a variety of groups of organisms this distribution systematically departs from such a form. Whatever its detailed shape, however, the distribution must arise as a product of three processes, speciation, extinction and transformation (the temporal dynamics of the range sizes of species during their life times). Considering the role potentially played by each of these processes necessitates drawing on information from a diverse array of research fields, and highlights the possible role of geographic range size as a common currency uniting them.

  3. The effect of implant splinting on the load distribution in bone bed around implant-supported fixed prosthesis with different framework materials: A finite element study.

    PubMed

    Hasan, I; Bourauel, C; Keilig, L; Stark, H; Lückerath, W

    2015-05-01

    Analysing the influence of implant splinting and its relation to different framework materials is a complex issue. The stiffness of framework materials and the overload of the implant system directly affect the final transferred load of the bone around implants. A finite element model of a long-span cementable implant-supported fixed prosthesis was created. Three materials were analysed for the framework: Titanium, gold alloy, and zirconia. The connection screws were first preloaded with 200 N. Two loading conditions were studied: The implant at the molar region was first loaded without splinting to the framework, and in the second condition, the implant was splinted to the framework. A total force of 500 N and 1000 N in 30° from the long axis of the framework were applied in buccal or distal direction on the implant system. The stresses and strains within the framework materials, implant system, and bone bed around the supporting implants were analysed. Loading the implant distally was associated with high stresses within the implant system in comparison to buccal loading. By splinting the implant, the stress in the implant system was reduced from 5393 MPa to 2942 MPa. Buccal loading of the implant was more critical than the distal loading. In the splinted condition of the implant, the stresses in the cortical bone were reduced from 570 MPa to 275 MPa.

  4. Red cell distribution width in anemic patients undergoing transcatheter aortic valve implantation

    PubMed Central

    Hellhammer, Katharina; Zeus, Tobias; Verde, Pablo E; Veulemanns, Verena; Kahlstadt, Lisa; Wolff, Georg; Erkens, Ralf; Westenfeld, Ralf; Navarese, Eliano P; Merx, Marc W; Rassaf, Tienush; Kelm, Malte

    2016-01-01

    AIM: To determine the impact of red blood cell distribution width on outcome in anemic patients undergoing transcatheter aortic valve implantation (TAVI). METHODS: In a retrospective single center cohort study we determined the impact of baseline red cell distribution width (RDW) and anemia on outcome in 376 patients with aortic stenosis undergoing TAVI. All patients were discussed in the institutional heart team and declined for surgical aortic valve replacement due to high operative risk. Collected data included patient characteristics, imaging findings, periprocedural in hospital data, laboratory results and follow up data. Blood samples for hematology and biochemistry analysis were taken from every patient before and at fixed intervals up to 72 h after TAVI including blood count and creatinine. Descriptive statistics were used for patient’s characteristics. Kaplan-Meier survival curves were used for time to event outcomes. A recursive partitioning regression and classification was used to investigate the association between potential risk factors and outcome variables. RESULTS: Mean age in our study population was 81 ± 6.1 years. Anemia was prevalent in 63.6% (n = 239) of our patients. Age and creatinine were identified as risk factors for anemia. In our study population, anemia per se did influence 30-d mortality but did not predict longterm mortality. In contrast, a RDW > 14% showed to be highly predictable for a reduced short- and longterm survival in patients with aortic valve disease after TAVI procedure. CONCLUSION: Age and kidney function determine the degree of anemia. The anisocytosis of red blood cells in anemic patients supplements prognostic information in addition to that derived from the WHO-based definition of anemia. PMID:26981217

  5. Optimal use of resources structures home ranges and spatial distribution of black bears

    USGS Publications Warehouse

    Mitchell, M.S.; Powell, R.A.

    2007-01-01

    Research has shown that territories of animals are economical. Home ranges should be similarly efficient with respect to spatially distributed resources and this should structure their distribution on a landscape, although neither has been demonstrated empirically. To test these hypotheses, we used home range models that optimize resource use according to resource-maximizing and area-minimizing strategies to evaluate the home ranges of female black bears, Ursus americanus, living in the southern Appalachian Mountains. We tested general predictions of our models using 104 home ranges of adult female bears studied in the Pisgah Bear Sanctuary, North Carolina, U.S.A., from 1981 to 2001. We also used our models to estimate home ranges for each real home range under a variety of strategies and constraints and compared similarity of simulated to real home ranges. We found that home ranges of female bears were efficient with respect to the spatial distribution of resources and were best explained by an area-minimizing strategy with moderate resource thresholds and low levels of resource depression. Although resource depression probably influenced the spatial distribution of home ranges on the landscape, levels of resource depression were too low to quantify accurately. Home ranges of lactating females had higher resource thresholds and were more susceptible to resource depression than those of breeding females. We conclude that home ranges of animals, like territories, are economical with respect to resources, and that resource depression may be the mechanism behind ideal free or ideal preemptive distributions on complex, heterogeneous landscapes. ?? 2007 The Association for the Study of Animal Behaviour.

  6. Comparative study on stress distribution around internal tapered connection implants according to fit of cement- and screw-retained prostheses

    PubMed Central

    Lee, Mi-Young; Heo, Seong-Joo; Park, Eun-Jin

    2013-01-01

    PURPOSE The aim of this study was to compare the passivity of implant superstructures by assessing the strain development around the internal tapered connection implants with strain gauges. MATERIALS AND METHODS A polyurethane resin block in which two implants were embedded served as a measurement model. Two groups of implant restorations utilized cement-retained design and internal surface of the first group was adjusted until premature contact between the restoration and the abutment completely disappeared. In the second group, only nodules detectable to the naked eye were removed. The third group employed screw-retained design and specimens were generated by computer-aided design/computer-aided manufacturing system (n=10). Four strain gauges were fixed on the measurement model mesially and distally to the implants. The strains developed in each strain gauge were recorded during fixation of specimens. To compare the difference among groups, repeated measures 2-factor analysis was performed at a level of significance of α=.05. RESULTS The absolute strain values were measured to analyze the magnitude of strain. The mean absolute strain value ranged from 29.53 to 412.94 µm/m at the different strain gauge locations. According to the result of overall comparison, the cement-retained prosthesis groups exhibited significant difference. No significant difference was detected between milled screw-retained prostheses group and cement-retained prosthesis groups. CONCLUSION Within the limitations of the study, it was concluded that the cement-retained designs do not always exhibit lower levels of stress than screw-retained designs. The internal adjustment of a cement-retained implant restoration is essential to achieve passive fit. PMID:24049573

  7. Evaluation of stress distributions in peri-implant and periodontal bone tissues in 3- and 5-unit tooth and implant-supported fixed zirconia restorations by finite elements analysis

    PubMed Central

    Guven, Sedat; Beydemir, Koksal; Dundar, Serkan; Eratilla, Veysel

    2015-01-01

    Objective: In this study, it is aimed to compare the distribution of stress on periodontal and peri-implant bone tissues in 3- and 5-unit-dental and implant-supported zirconia restorations using finite element analysis. Materials and Methods: Stress distribution formed in periodontal and peri-implant bone tissues as a result of chewing forces was analyzed in dental and implant-supported three-dimensional (3D) finite element models of zirconia restoration with 5-unit placed on the numbers of 43, 44, 45, 46, and 47 and with 3-unit placed on the number of 45, 46, and 47. Four different loading conditions were used. 200 N force was applied in 30° from the buccal inclination of number 43, 45, and 47 restorations separately and totally 850 N force was applied in 30° from the buccal inclination of whole restoration. The study was performed through static nonlinear analysis with the 3D finite element analysis method. Results: Stress accumulation in bone tissues in the tooth-supported model was found less than in implant-supported models. Stress accumulation was observed in the cervical portion of the implant in implant-supported models, and stress accumulation was observed surrounding bone of roots in tooth-supported models. The highest stress values were occurred in 5 unit implant-supported model in all loadings. Conclusion: In posterior restorations increased in the number of supported teeth and implant can reduce the destructive forces on periodontal and peri-implant bone tissues and may allow longer period retention of the restorations in the mouth. PMID:26430359

  8. Bryophyte diversity and range size distribution along two altitudinal gradients: Continent vs. island

    NASA Astrophysics Data System (ADS)

    Ah-Peng, Claudine; Wilding, Nicholas; Kluge, Juergen; Descamps-Julien, Blandine; Bardat, Jacques; Chuah-Petiot, Min; Strasberg, Dominique; Hedderson, Terry A. J.

    2012-07-01

    We compare patterns of bryophyte diversity and variation in species altitudinal ranges between a continental and an island altitudinal gradient. We use our ecological data set along the highest summit (Piton des Neiges, 3069 m) of Réunion Island (Mascarene archipelago) and compare it to available published data of another high volcanic massif in Colombia (Nevado del Ruiz, 5321 m). The distribution of narrow-ranged and large-ranged species was investigated. We tested the effect of geometric constraints on species distribution along the two gradients by comparing empirical to predicted data using the Mid-Domain Null Programme (McCain, 2004). Species richness was comparable between the island and continental gradient for epiphytic bryophytes, 265 and 295 species respectively. The comparison between the two tropical high mountains demonstrates important differences in the distribution of range sizes with altitude and a dominance of species with small range sizes on the Réunion gradient. For the island gradient, mean altitudinal range increases with altitude whilst concurrently species richness decreases revealing a Rapoport effect in altitudinal distribution of bryophyte communities. Geometric constraints did not explain much of the species richness pattern for the island. Conversely, for the continental gradient, dominated by large-ranged species, geometric constraints could not be ruled out as a primary structuring feature for the species richness pattern. This study also highlights that the island's cloud forest hosts not only high species richness but also high number of rare species, which is of prime interest for conservation planners.

  9. Stable distribution and long-range correlation of Brent crude oil market

    NASA Astrophysics Data System (ADS)

    Yuan, Ying; Zhuang, Xin-tian; Jin, Xiu; Huang, Wei-qiang

    2014-11-01

    An empirical study of stable distribution and long-range correlation in Brent crude oil market was presented. First, it is found that the empirical distribution of Brent crude oil returns can be fitted well by a stable distribution, which is significantly different from a normal distribution. Second, the detrended fluctuation analysis for the Brent crude oil returns shows that there are long-range correlation in returns. It implies that there are patterns or trends in returns that persist over time. Third, the detrended fluctuation analysis for the Brent crude oil returns shows that after the financial crisis 2008, the Brent crude oil market becomes more persistence. It implies that the financial crisis 2008 could increase the frequency and strength of the interdependence and correlations between the financial time series. All of these findings may be used to improve the current fractal theories.

  10. Stress distribution patterns of implant supported overdentures-analog versus finite element analysis: A comparative in-vitro study

    PubMed Central

    Satpathy, Soumyadev; Babu, C. L. Satish; Shetty, Shilpa; Raj, Bharat

    2015-01-01

    Aims and Objectives: The aim of this study was to asses & compare the load transfer characteristics of Ball/O-ring and Bar/Clip attachment systems in implant supported overdentures using analog and finite element analysis models. Methodology: For the analog part of the study, castable bar was used for the bar and clip attachment and a metallic housing with a rubber O-ring component was used for the ball/O-ring attachment. The stress on the implant surface was measured using the strain-gauge technique. For the finite element analysis, the model were fabricated and load applications were done in a similar manner as in analog study. Results: The difference between both the attachment systems was found to be statistically significant (P<0.001). Conclusion: Ball/O-ring attachment system transmitted lesser amount of stresses to the implants on the non-loading side, as compared to the Bar-Clip attachment system. When overall stress distribution is compared, the Bar-Clip attachment seems to perform better than the Ball/O-ring attachment, because the force was distributed better. PMID:26929521

  11. Process-based modeling of species' distributions: what limits temperate tree species' range boundaries?

    PubMed

    Morin, Xavier; Augspurger, Carol; Chuine, Isabelle

    2007-09-01

    Niche-based models are widely used to understand what environmental factors determine species' distributions, but they do not provide a clear framework to study the processes involved in defining species' ranges. Here we used a process-based model to identify these processes and to assess the potential distribution of 17 North American boreal/temperate tree species. Using input of only climate and soil properties, the model reproduced the 17 species' distributions accurately. Our results allowed us to identify the climatic factors as well as the biological processes involved in limiting species' ranges. The model showed that climatic constraints limit species' distributions mainly through their impact on phenological processes, and secondarily through their impact on drought and frost mortality. The northern limit of species' ranges appears to be caused mainly by the inability to undergo full fruit ripening and/or flowering, while the southern limit is caused by the inability to flower or by frost injury to flowers. These findings about the ecological processes shaping tree species' distribution represent a crucial step toward obtaining a more complete picture of the potential impact of climate on species' ranges. PMID:17918406

  12. a Vomr-Tree Based Parallel Range Query Method on Distributed Spatial Database

    NASA Astrophysics Data System (ADS)

    Fu, Z.; Liu, S.

    2012-07-01

    Spatial index impacts upon the efficiency of spatial query seriously in distributed spatial database. In this paper, we introduce a parallel spatial range query algorithm, based on VoMR-tree index, which incorporates Voronoi diagrams into MR-tree, benefiting from the nearest neighbors. We first augments MR-tree to store the nearest neighbors and constructs the VoMR-tree index by Voronoi diagram. We then propose a novel range query algorithm based on VoMR-tree index. In processing a range query, we discuss the data partition method so that we can improve the efficiency by parallelization in distributed database. Just then a verification strategy is promoted. We show the superiority of the proposed method by extensive experiments using data sets of various sizes. The experimental results reveal that the proposed method improves the performance of range query processing up to three times in comparison with the widely-used R-tree variants.

  13. Microfocus study of metal distribution and speciation in tissue extracted from revised metal on metal hip implants

    NASA Astrophysics Data System (ADS)

    Hart, Alister J.; Sandison, Ann; Quinn, Paul; Sampson, Barry; Atkinson, Kirk D.; Skinner, John A.; Goode, Angela; Powell, Jonathan J.; Mosselmans, J. Frederick W.

    2009-11-01

    Unexplained tissue inflammation in metal-on-metal hip replacements is suspected to be caused by implant-derived nanoparticles. The aim of this study was to investigate the nature of the metal particles in tissue surrounding metal-on-metal (MOM) hips that has been extracted during revision. Mapping of tissue surrounding the failed MOM hips was performed using microfocus X-ray Fluorescence (XRF). This revealed mainly Cr which was localized to the cellular regions. There was co-localisation of Co, were present, to areas of high Cr abundance. XANES of the tissue and appropriate standards revealed that the most common species were Cr(III) and Co(II). EXAFS analysis of the tissue and various metal standards revealed that the most abundant implant-related species was Cr(III) phosphate. Different tissue preparation methods, including frozen sectioning, were examined but were found not to affect the distribution or speciation of the metals in the tissue.

  14. Climate controls the distribution of a widespread invasive species: Implications for future range expansion

    USGS Publications Warehouse

    McDowell, W.G.; Benson, A.J.; Byers, J.E.

    2014-01-01

    1. Two dominant drivers of species distributions are climate and habitat, both of which are changing rapidly. Understanding the relative importance of variables that can control distributions is critical, especially for invasive species that may spread rapidly and have strong effects on ecosystems. 2. Here, we examine the relative importance of climate and habitat variables in controlling the distribution of the widespread invasive freshwater clam Corbicula fluminea, and we model its future distribution under a suite of climate scenarios using logistic regression and maximum entropy modelling (MaxEnt). 3. Logistic regression identified climate variables as more important than habitat variables in controlling Corbicula distribution. MaxEnt modelling predicted Corbicula's range expansion westward and northward to occupy half of the contiguous United States. By 2080, Corbicula's potential range will expand 25–32%, with more than half of the continental United States being climatically suitable. 4. Our combination of multiple approaches has revealed the importance of climate over habitat in controlling Corbicula's distribution and validates the climate-only MaxEnt model, which can readily examine the consequences of future climate projections. 5. Given the strong influence of climate variables on Corbicula's distribution, as well as Corbicula's ability to disperse quickly and over long distances, Corbicula is poised to expand into New England and the northern Midwest of the United States. Thus, the direct effects of climate change will probably be compounded by the addition of Corbicula and its own influences on ecosystem function.

  15. The Comparison of Stress Distribution with Different Implant Numbers and Inclination Angles In All-on-four and Conventional Methods in Maxilla: A Finite Element Analysis

    PubMed Central

    Saleh Saber, Fariba; Ghasemi, Shima; Koodaryan, Rodabeh; Babaloo, Amirreza; Abolfazli, Nader

    2015-01-01

    Background and aims. All-on-four technique involves the use of tilted implants to allow for shorter cantilevers. This finite element analysis aimed at investigating the amount and distribution of stress in maxillary bone surrounding the implants with all-on-four vs. frequently used method with six implants technique using different numbers and inclination angles. Materials and methods. A 3D edentulous maxillary model was created and implants were virtually placed anterior to the maxillary sinus and splinted with a superstructure. In total, five models were designed. In the first to the fourth models, four implants were placed with distal implants inclined 0, 15, 30, and 45 degrees, respectively. In the fifth model, six vertical implants were placed. 100 N loading was placed in the left most distal region of the superstructure. Maximum von Mises stress values were evaluated in cancellous and cortical bone. Results. The maximum stress values recorded in cancellous and cortical bone were 7.15 MPa and 51.69 MPa, respectively (model I). The reduction in stress values in models II to V 6%, 18%, 54%, and 24% in cancellous bone and 12%, 36%,62%, and 62% in cortical bone, respectively. Conclusion. Increasing the inclination in posterior implants resulted in reduction of cantilever length and maximum stress decline in both cancellous and cortical bone. The effect of cantilever length seems to be a dominant factor which can diminish stress even with less number of implants. PMID:26889362

  16. Pushing the limit: experimental evidence of climate effects on plant range distributions.

    PubMed

    Pfeifer-Meister, Laurel; Bridgham, Scott D; Little, Chelsea J; Reynolds, Lorien L; Goklany, Maya E; Johnson, Bart R

    2013-10-01

    Whether species will be extirpated in their current geographic ranges due to rapidly changing climate, and if so, whether they can avoid extinction by shifting their distributions are pressing questions for biodiversity conservation. However, forecasts of climate change impacts on species' geographic distributions rarely incorporate a demographic understanding of species' responses to climate. Because many biotic and abiotic factors at multiple scales control species' range limits, experimentation is essential to establish underlying mechanisms. We used a manipulative climate change experiment embedded within a natural climate gradient to examine demographic responses of 12 prairie species with northern range limits within the Pacific Northwest, USA. During the first year, warming decreased recruitment of species even at the coolest edge of their current ranges, but this effect disappeared when they were moved poleward beyond their current ranges. This response was largely driven by differences in germination rates. Other vital rates responded in unique and sometimes opposing ways (survivorship vs. fitness) to species' current ranges and climate change, and were mediated by indirect effects of climate on competition and nutrient availability. Our results demonstrate the importance of using regional-scale climate manipulations and the need for longer-term experiments on the demographic responses that control species' distributions.

  17. Heading for new shores: projecting marine distribution ranges of selected larger foraminifera.

    PubMed

    Weinmann, Anna E; Rödder, Dennis; Lötters, Stefan; Langer, Martin R

    2013-01-01

    The distribution of modern symbiont-bearing larger foraminifera is confined to tropical and subtropical shallow water marine habitats and a narrow range of environmental variables (e.g. temperature). Most of today's taxa are restricted to tropical and subtropical regions (between 30°N and 30°S) and their minimum temperature limits are governed by the 14 to 20°C isotherms. However, during times of extensive global warming (e.g., the Eocene and Miocene), larger foraminifera have been found as far north as 50°N (North America and Central Europe) as well as towards 47°S in New Zealand. During the last century, sea surface temperatures have been rising significantly. This trend is expected to continue and climate change scenarios for 2050 suggest a further increase by 1 to 3°C. We applied Species Distribution Models to assess potential distribution range changes of three taxa of larger foraminifera under current and future climate. The studied foraminifera include Archaias angulatus, Calcarina spp., and Amphistegina spp., and represent taxa with regional, superregional and global distribution patterns. Under present environmental conditions, Amphistegina spp. shows the largest potential distribution, apparently due to its temperature tolerance. Both Archaias angulatus and Calcarina spp. display potential distributions that cover currently uninhabited regions. Under climate conditions expected for the year 2050, all taxa should display latitudinal range expansions between 1 to 2.5 degrees both north- and southward. The modeled range projections suggest that some larger foraminifera may colonize biogeographic regions that so far seemed unsuitable. Archaias angulatus and Calcarina spp. also show an increase in habitat suitability within their native occurrence ranges, suggesting that their tolerance for maximum temperatures has yet not been fully exploited and that they benefit from ocean warming. Our findings suggest an increased role of larger foraminifera as

  18. Heading for New Shores: Projecting Marine Distribution Ranges of Selected Larger Foraminifera

    PubMed Central

    Weinmann, Anna E.; Rödder, Dennis; Lötters, Stefan; Langer, Martin R.

    2013-01-01

    The distribution of modern symbiont-bearing larger foraminifera is confined to tropical and subtropical shallow water marine habitats and a narrow range of environmental variables (e.g. temperature). Most of today's taxa are restricted to tropical and subtropical regions (between 30°N and 30°S) and their minimum temperature limits are governed by the 14 to 20°C isotherms. However, during times of extensive global warming (e.g., the Eocene and Miocene), larger foraminifera have been found as far north as 50°N (North America and Central Europe) as well as towards 47°S in New Zealand. During the last century, sea surface temperatures have been rising significantly. This trend is expected to continue and climate change scenarios for 2050 suggest a further increase by 1 to 3°C. We applied Species Distribution Models to assess potential distribution range changes of three taxa of larger foraminifera under current and future climate. The studied foraminifera include Archaias angulatus, Calcarina spp., and Amphistegina spp., and represent taxa with regional, superregional and global distribution patterns. Under present environmental conditions, Amphistegina spp. shows the largest potential distribution, apparently due to its temperature tolerance. Both Archaias angulatus and Calcarina spp. display potential distributions that cover currently uninhabited regions. Under climate conditions expected for the year 2050, all taxa should display latitudinal range expansions between 1 to 2.5 degrees both north- and southward. The modeled range projections suggest that some larger foraminifera may colonize biogeographic regions that so far seemed unsuitable. Archaias angulatus and Calcarina spp. also show an increase in habitat suitability within their native occurrence ranges, suggesting that their tolerance for maximum temperatures has yet not been fully exploited and that they benefit from ocean warming. Our findings suggest an increased role of larger foraminifera as

  19. A three-dimensional finite element analysis of a passive and friction fit implant abutment interface and the influence of occlusal table dimension on the stress distribution pattern on the implant and surrounding bone

    PubMed Central

    Sarfaraz, Hasan; Paulose, Anoopa; Shenoy, K. Kamalakanth; Hussain, Akhter

    2015-01-01

    Aims: The aim of the study was to evaluate the stress distribution pattern in the implant and the surrounding bone for a passive and a friction fit implant abutment interface and to analyze the influence of occlusal table dimension on the stress generated. Materials and Methods: CAD models of two different types of implant abutment connections, the passive fit or the slip-fit represented by the Nobel Replace Tri-lobe connection and the friction fit or active fit represented by the Nobel active conical connection were made. The stress distribution pattern was studied at different occlusal dimension. Six models were constructed in PRO-ENGINEER 05 of the two implant abutment connection for three different occlusal dimensions each. The implant and abutment complex was placed in cortical and cancellous bone modeled using a computed tomography scan. This complex was subjected to a force of 100 N in the axial and oblique direction. The amount of stress and the pattern of stress generated were recorded on a color scale using ANSYS 13 software. Results: The results showed that overall maximum Von Misses stress on the bone is significantly less for friction fit than the passive fit in any loading conditions stresses on the implant were significantly higher for the friction fit than the passive fit. The narrow occlusal table models generated the least amount of stress on the implant abutment interface. Conclusion: It can thus be concluded that the conical connection distributes more stress to the implant body and dissipates less stress to the surrounding bone. A narrow occlusal table considerably reduces the occlusal overload. PMID:26929518

  20. Compressive mechanical compatibility of anisotropic porous Ti6Al4V alloys in the range of physiological strain rate for cortical bone implant applications.

    PubMed

    Li, Fuping; Li, Jinshan; Kou, Hongchao; Huang, Tingting; Zhou, Lian

    2015-09-01

    Porous titanium and its alloys are believed to be promising materials for bone implant applications, since they can reduce the "stress shielding" effect by tailoring porosity and improve fixation of implant through bone ingrowth. In the present work, porous Ti6Al4V alloys for biomedical application were fabricated by diffusion bonding of alloy meshes. Compressive mechanical behavior and compatibility in the range of physiological strain rate were studied under quasi-static and dynamic conditions. The results show that porous Ti6Al4V alloys possess anisotropic structure with elongated pores in the out-of-plane direction. For porous Ti6Al4V alloys with 60-70 % porosity, more than 40 % pores are in the range of 200-500 μm which is the optimum pore size suited for bone ingrowth. Quasi-static Young's modulus and yield stress of porous Ti6Al4V alloys with 30-70 % relative density are in the range of 6-40 GPa and 100-500 MPa, respectively. Quasi-static compressive properties can be quantitatively tailored by porosity to match those of cortical bone. Strain rate sensitivity of porous Ti6Al4V alloys is related to porosity. Porous Ti6Al4V alloys with porosity higher than 50 % show enhanced strain rate sensitivity, which is originated from that of base materials and micro-inertia effect. Porous Ti6Al4V alloys with 60-70 % porosity show superior compressive mechanical compatibility in the range of physiological strain rate for cortical bone implant applications.

  1. Thermal sensitivity of cold climate lizards and the importance of distributional ranges.

    PubMed

    Bonino, Marcelo F; Moreno Azócar, Débora L; Schulte, James A; Abdala, Cristian S; Cruz, Félix B

    2015-08-01

    One of the fundamental goals in macroecology is to understand the relationship among species' geographic ranges, ecophysiology, and climate; however, the mechanisms underlying the distributional geographic patterns observed remain unknown for most organisms. In the case of ectotherms this is particularly important because the knowledge of these interactions may provide a robust framework for predicting the potential consequences of climate change in these organisms. Here we studied the relationship of thermal sensitivity and thermal tolerance in Patagonian lizards and their geographic ranges, proposing that species with wider distributions have broader plasticity and thermal tolerance. We predicted that lizard thermal physiology is related to the thermal characteristics of the environment. We also explored the presence of trade-offs of some thermal traits and evaluated the potential effects of a predicted scenario of climate change for these species. We examined sixteen species of Liolaemini lizards from Patagonia representing species with different geographic range sizes. We obtained thermal tolerance data and performance curves for each species in laboratory trials. We found evidence supporting the idea that higher physiological plasticity allows species to achieve broader distribution ranges compared to species with restricted distributions. We also found a trade-off between broad levels of plasticity and higher optimum temperatures of performance. Finally, results from contrasting performance curves against the highest environmental temperatures that lizards may face in a future scenario (year 2080) suggest that the activity of species occurring at high latitudes may be unaffected by predicted climatic changes.

  2. Frequency-Range Distribution of Boulders Around Cone Crater: Relevance to Landing Site Hazard Avoidance

    NASA Technical Reports Server (NTRS)

    Clegg-Watkins, R. N.; Jolliff, B. L.; Lawrence, S. J.

    2016-01-01

    Boulders represent a landing hazard that must be addressed in the planning of future landings on the Moon. A boulder under a landing leg can contribute to deck tilt and boulders can damage spacecraft during landing. Using orbital data to characterize boulder populations at locations where landers have safely touched down (Apollo, Luna, Surveyor, and Chang'e-3 sites) is important for determining landing hazard criteria for future missions. Additionally, assessing the distribution of boulders can address broader science issues, e.g., how far craters distribute boulders and how this distribution varies as a function of crater size and age. The availability of new Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC) images [1] enables the use of boulder size- and range frequency distributions for a variety of purposes [2-6]. Boulders degrade over time and primarily occur around young or fresh craters that are large enough to excavate bedrock. Here we use NAC images to analyze boulder distributions around Cone crater (340 m diameter) at the Apollo 14 site. Cone crater (CC) was selected because it is the largest crater where astronaut surface photography is available for a radial traverse to the rim. Cone crater is young (approximately 29 Ma [7]) relative to the time required to break down boulders [3,8], giving us a data point for boulder range-frequency distributions (BRFDs) as a function of crater age.

  3. Predicting species richness and distribution ranges of centipedes at the northern edge of Europe

    NASA Astrophysics Data System (ADS)

    Georgopoulou, Elisavet; Djursvoll, Per; Simaiakis, Stylianos M.

    2016-07-01

    In recent decades, interest in understanding species distributions and exploring processes that shape species diversity has increased, leading to the development of advanced methods for the exploitation of occurrence data for analytical and ecological purposes. Here, with the use of georeferenced centipede data, we explore the importance and contribution of bioclimatic variables and land cover, and predict distribution ranges and potential hotspots in Norway. We used a maximum entropy analysis (Maxent) to model species' distributions, aiming at exploring centres of distribution, latitudinal spans and northern range boundaries of centipedes in Norway. The performance of all Maxent models was better than random with average test area under the curve (AUC) values above 0.893 and True Skill Statistic (TSS) values above 0.593. Our results showed a highly significant latitudinal gradient of increased species richness in southern grid-cells. Mean temperatures of warmest and coldest quarters explained much of the potential distribution of species. Predictive modelling analyses revealed that south-eastern Norway and the Atlantic coast in the west (inclusive of the major fjord system of Sognefjord), are local biodiversity hotspots with regard to high predictive species co-occurrence. We conclude that our predicted northward shifts of centipedes' distributions in Norway are likely a result of post-glacial recolonization patterns, species' ecological requirements and dispersal abilities.

  4. Magnesium from bioresorbable implants: Distribution and impact on the nano- and mineral structure of bone.

    PubMed

    Grünewald, T A; Rennhofer, H; Hesse, B; Burghammer, M; Stanzl-Tschegg, S E; Cotte, M; Löffler, J F; Weinberg, A M; Lichtenegger, H C

    2016-01-01

    Biocompatibility is a key issue in the development of new implant materials. In this context, a novel class of biodegrading Mg implants exhibits promising properties with regard to inflammatory response and mechanical properties. The interaction between Mg degradation products and the nanoscale structure and mineralization of bone, however, is not yet sufficiently understood. Investigations by synchrotron microbeam x-ray fluorescence (μXRF), small angle x-ray scattering (μSAXS) and x-ray diffraction (μXRD) have shown the impact of degradation speed on the sites of Mg accumulation in the bone, which are around blood vessels, lacunae and the bone marrow. Only at the highest degradation rates was Mg found at the implant-bone interface. The Mg inclusion into the bone matrix appeared to be non-permanent as the Mg-level decreased after completed implant degradation. μSAXS and μXRD showed that Mg influences the hydroxyl apatite (HAP) crystallite structure, because markedly shorter and thinner HAP crystallites were found in zones of high Mg concentration. These zones also exhibited a contraction of the HAP lattice and lower crystalline order.

  5. A finite element study on stress distribution of two different attachment designs under implant supported overdenture

    PubMed Central

    El-Anwar, Mohamed I.; Yousief, Salah A.; Soliman, Tarek A.; Saleh, Mahmoud M.; Omar, Wael S.

    2015-01-01

    Objective This study aimed to evaluate stress patterns generated within implant-supported mandibular overdentures retained by two different attachment types: ball and socket and locator attachments. Materials and methods Commercial CAD/CAM and finite element analysis software packages were utilized to construct two 3D finite element models for the two attachment types. Unilateral masticatory compressive loads of 50, 100, and 150 N were applied vertically to the overdentures, parallel to the longitudinal axes of the implants. Loads were directed toward the central fossa in the molar region of each overdenture, that linear static analysis was carried out to find the generated stresses and deformation on each part of the studied model. Results According to FEA results the ball attachment neck is highly stressed in comparison to the locator one. On the other hand mucosa and cortical bone received less stresses under ball and socket attachment. Conclusions Locator and ball and socket attachments induce equivalent stresses on bone surrounding implants. Locator attachment performance was superior to that of the ball and socket attachment in the implants, nylon caps, and overdenture. Locator attachments are highly recommended and can increase the interval between successive maintenance sessions. PMID:26644755

  6. Depth distribution of deuterium atoms and molecules in beryllium oxide implanted with deuterium ions

    NASA Astrophysics Data System (ADS)

    Alimov, V. Kh; Chernikov, V. N.

    1999-08-01

    In-depth concentration profiles of deuterium (D) in beryllium oxide (BeO) films implanted with 3 keV D ions at 300 and 700 K have been determined using SIMS and RGA (residual gas analysis) measurements in the course of surface sputtering. The microstructure of implanted specimens was studied by TEM. Implanted D is found to be retained in the BeO matrix in the form of D atoms and D 2 molecules. At 300 and 700 K, the maximum concentration of deuterium in both states reaches values of 0.2 and 0.07 D/BeO, respectively. Irradiation with D ions at 300 and 700 K leads to the formation of tiny D 2 bubbles of 0.6-0.7 nm radius and of high volume density ≈(4-5) × 10 24 m -3. These bubbles together with the intercrystalline gaps are responsible for the accumulation of D 2 molecules. At both irradiation temperatures, D 2 concentration reaches in the ion stopping zone its maximum of 0.01 molecules/BeO. At 300 and 700 K, the major part of deuterium implanted in BeO films is present in the form of D atoms, probably chemically bound to O atoms. Maximum D atom concentration is 0.18 D atoms/BeO for 300 K and 0.05 D atoms/BeO for 700 K.

  7. Historical range, current distribution, and conservation status of the Swift Fox, Vulpes velox, in North America

    USGS Publications Warehouse

    Sovada, Marsha A.; Woodward, Robert O.; Igl, Lawrence D.

    2009-01-01

    The Swift Fox (Vulpes velox) was once common in the shortgrass and mixed-grass prairies of the Great Plains of North America. The species' abundance declined and its distribution retracted following European settlement of the plains. By the late 1800s, the species had been largely extirpated from the northern portion of its historical range, and its populations were acutely depleted elsewhere. Swift Fox populations have naturally recovered somewhat since the 1950s, but overall abundance and distribution remain below historical levels. In a 1995 assessment of the species' status under the US Endangered Species Act, the US Fish and Wildlife Service concluded that a designation of threatened or endangered was warranted, but the species was "precluded from listing by higher listing priorities." A major revelation of the 1995 assessment was the recognition that information useful for determining population status was limited. Fundamental information was missing, including an accurate estimate of the species' distribution before European settlement and an estimate of the species' current distribution and trends. The objectives of this paper are to fill those gaps in knowledge. Historical records were compiled and, in combination with knowledge of the habitat requirements of the species, the historical range of the Swift Fox is estimated to be approximately 1.5 million km2. Using data collected between 2001 and 2006, the species' current distribution is estimated to be about 44% of its historical range in the United States and 3% in Canada. Under current land use, approximately 39% of the species' historical range contains grassland habitats with very good potential for Swift Fox occupation and another 10% supports grasslands with characteristics that are less preferred (e.g., a sparse shrub component or taller stature) but still suitable. Additionally, land use on at least 25% of the historical range supports dryland farming, which can be suitable for Swift Fox

  8. Historical range, current distribution, and conservation status of the Swift Fox, Vulpes velox, in North America

    USGS Publications Warehouse

    Sovada, M.A.; Woodward, R.O.; Igl, L.D.

    2009-01-01

    The Swift Fox (Vulpes velox) was once common in the shortgrass and mixed-grass prairies of the Great Plains of NorthAmerica. The species' abundance declined and its distribution retracted following European settlement of the plains. By the late 1800s, the species had been largely extirpated from the northern portion of its historical range, and its populations were acutely depleted elsewhere. Swift Fox populations have naturally recovered somewhat since the 1950s, but overall abundance and distribution remain below historical levels. In a 1995 assessment of the species' status under the US Endangered Species Act, the US Fish and Wildlife Service concluded that a designation of threatened or endangered was warranted, but the species was "precluded from listing by higher listing priorities." A major revelation of the 1995 assessment was the recognition that information useful for determining population status was limited. Fundamental information was missing, including an accurate estimate of the species' distribution before European settlement and an estimate of the species' current distribution and trends. The objectives of this paper are to fill those gaps in knowledge. Historical records were compiled and, in combination with knowledge of the habitat requirements of the species, the historical range of the Swift Fox is estimated to be approximately 1.5 million km2. Using data collected between 2001 and 2006, the species' current distribution is estimated to be about 44% of its historical range in the United States and 3% in Canada. Under current land use, approximately 39% of the species' historical range contains grassland habitats with very good potential for Swift Fox occupation and another 10% supports grasslands with characteristics that are less preferred (e.g., a sparse shrub component or taller stature) but still suitable. Additionally, land use on at least 25% of the historical range supports dryland farming, which can be suitable for Swift Fox occupation

  9. Implication of high dynamic range and wide color gamut content distribution

    NASA Astrophysics Data System (ADS)

    Lu, Taoran; Pu, Fangjun; Yin, Peng; Chen, Tao; Husak, Walt

    2015-09-01

    High Dynamic Range (HDR) and Wider Color Gamut (WCG) content represents a greater range of luminance levels and a more complete reproduction of colors found in real-world scenes. The current video distribution environments deliver Standard Dynamic Range (SDR) signal. Therefore, there might be some significant implication on today's end-to-end ecosystem from content creation to distribution and finally to consumption. For SDR content, the common practice is to apply compression on Y'CbCr 4:2:0 using gamma transfer function and non-constant luminance 4:2:0 chroma subsampling. For HDR and WCG content, it is desirable to examine if such signal format still works well for compression, and it is interesting to know if the overall system performance can be further improved by exploring different signal formats and processing workflows. In this paper, we will provide some of our insight into those problems.

  10. Leopard (Panthera pardus) status, distribution, and the research efforts across its range

    PubMed Central

    Gerngross, Peter; Lemeris Jr., Joseph R.; Schoonover, Rebecca F.; Anco, Corey; Breitenmoser-Würsten, Christine; Durant, Sarah M.; Farhadinia, Mohammad S.; Henschel, Philipp; Kamler, Jan F.; Laguardia, Alice; Rostro-García, Susana; Stein, Andrew B.; Dollar, Luke

    2016-01-01

    The leopard’s (Panthera pardus) broad geographic range, remarkable adaptability, and secretive nature have contributed to a misconception that this species might not be severely threatened across its range. We find that not only are several subspecies and regional populations critically endangered but also the overall range loss is greater than the average for terrestrial large carnivores. To assess the leopard’s status, we compile 6,000 records at 2,500 locations from over 1,300 sources on its historic (post 1750) and current distribution. We map the species across Africa and Asia, delineating areas where the species is confirmed present, is possibly present, is possibly extinct or is almost certainly extinct. The leopard now occupies 25–37% of its historic range, but this obscures important differences between subspecies. Of the nine recognized subspecies, three (P. p. pardus, fusca, and saxicolor) account for 97% of the leopard’s extant range while another three (P. p. orientalis, nimr, and japonensis) have each lost as much as 98% of their historic range. Isolation, small patch sizes, and few remaining patches further threaten the six subspecies that each have less than 100,000 km2 of extant range. Approximately 17% of extant leopard range is protected, although some endangered subspecies have far less. We found that while leopard research was increasing, research effort was primarily on the subspecies with the most remaining range whereas subspecies that are most in need of urgent attention were neglected. PMID:27168983

  11. Leopard (Panthera pardus) status, distribution, and the research efforts across its range.

    PubMed

    Jacobson, Andrew P; Gerngross, Peter; Lemeris, Joseph R; Schoonover, Rebecca F; Anco, Corey; Breitenmoser-Würsten, Christine; Durant, Sarah M; Farhadinia, Mohammad S; Henschel, Philipp; Kamler, Jan F; Laguardia, Alice; Rostro-García, Susana; Stein, Andrew B; Dollar, Luke

    2016-01-01

    The leopard's (Panthera pardus) broad geographic range, remarkable adaptability, and secretive nature have contributed to a misconception that this species might not be severely threatened across its range. We find that not only are several subspecies and regional populations critically endangered but also the overall range loss is greater than the average for terrestrial large carnivores. To assess the leopard's status, we compile 6,000 records at 2,500 locations from over 1,300 sources on its historic (post 1750) and current distribution. We map the species across Africa and Asia, delineating areas where the species is confirmed present, is possibly present, is possibly extinct or is almost certainly extinct. The leopard now occupies 25-37% of its historic range, but this obscures important differences between subspecies. Of the nine recognized subspecies, three (P. p. pardus, fusca, and saxicolor) account for 97% of the leopard's extant range while another three (P. p. orientalis, nimr, and japonensis) have each lost as much as 98% of their historic range. Isolation, small patch sizes, and few remaining patches further threaten the six subspecies that each have less than 100,000 km(2) of extant range. Approximately 17% of extant leopard range is protected, although some endangered subspecies have far less. We found that while leopard research was increasing, research effort was primarily on the subspecies with the most remaining range whereas subspecies that are most in need of urgent attention were neglected.

  12. Leopard (Panthera pardus) status, distribution, and the research efforts across its range.

    PubMed

    Jacobson, Andrew P; Gerngross, Peter; Lemeris, Joseph R; Schoonover, Rebecca F; Anco, Corey; Breitenmoser-Würsten, Christine; Durant, Sarah M; Farhadinia, Mohammad S; Henschel, Philipp; Kamler, Jan F; Laguardia, Alice; Rostro-García, Susana; Stein, Andrew B; Dollar, Luke

    2016-01-01

    The leopard's (Panthera pardus) broad geographic range, remarkable adaptability, and secretive nature have contributed to a misconception that this species might not be severely threatened across its range. We find that not only are several subspecies and regional populations critically endangered but also the overall range loss is greater than the average for terrestrial large carnivores. To assess the leopard's status, we compile 6,000 records at 2,500 locations from over 1,300 sources on its historic (post 1750) and current distribution. We map the species across Africa and Asia, delineating areas where the species is confirmed present, is possibly present, is possibly extinct or is almost certainly extinct. The leopard now occupies 25-37% of its historic range, but this obscures important differences between subspecies. Of the nine recognized subspecies, three (P. p. pardus, fusca, and saxicolor) account for 97% of the leopard's extant range while another three (P. p. orientalis, nimr, and japonensis) have each lost as much as 98% of their historic range. Isolation, small patch sizes, and few remaining patches further threaten the six subspecies that each have less than 100,000 km(2) of extant range. Approximately 17% of extant leopard range is protected, although some endangered subspecies have far less. We found that while leopard research was increasing, research effort was primarily on the subspecies with the most remaining range whereas subspecies that are most in need of urgent attention were neglected. PMID:27168983

  13. Dynamic changes in leptin distribution in the progression from ovum to blastocyst of the pre-implantation mouse embryo.

    PubMed

    Schulz, Laura C; Roberts, R Michael

    2011-06-01

    The hormone leptin, which is primarily produced by adipose tissue, is a critical permissive factor for multiple reproductive events in the mouse, including implantation. In the CD1 strain, maternally derived leptin from the oocyte becomes differentially distributed among the blastomeres of pre-implantation embryos to create a polarized pattern, a feature consistent with a model of development in which blastomeres are biased toward a particular fate as early as the two-cell stage. In this study, we have confirmed that embryonic leptin is of maternal origin and re-examined leptin distribution in two distinct strains in which embryos were derived after either normal ovulation or superovulation. A polarized pattern of leptin distribution was found in the majority of both CD1 and CF1 embryos (79.1 and 76.9% respectively) collected following superovulation but was reduced, particularly in CF1 embryos (29.8%; P<0.0001), after natural ovulation. The difference in leptin asymmetries in the CF1 strain arose between ovulation and the first cleavage division and was not affected by removal of the zona pellucida. The presence or absence of leptin polarization was not linked to differences in the ability of embryos to normally develop to blastocyst. In the early blastocyst, leptin was confined subcortically to trophectoderm, but on blastocoel expansion, it was lost from the cells. Throughout development, leptin co-localized with LRP2, a multi-ligand transport protein, and its patterning resembled that noted for the maternal-effect proteins OOEP, NLRP5, and PADI6, suggesting that it is a component of the subcortical maternal complex with as yet unknown significance in pre-implantation development.

  14. DISTRIBUTION AND RANGE OF RADIONUCLIDE SORPTION COEFFICIENTS IN A SAVANNAH RIVER SITE SUBSURFACE: STOCHASTIC MODELING CONSIDERATIONS

    SciTech Connect

    Kaplan, D.; et. al

    2010-01-11

    The uncertainty associated with the sorption coefficient, or K{sub d} value, is one of the key uncertainties in estimating risk associated with burying low-level nuclear waste in the subsurface. The objective of this study was to measure >648 K{sub d} values and provide a measure of the range and distribution (normal or log-normal) of radionuclide K{sub d} values appropriate for the E-Area disposal site, within the Savannah River Site, near Aiken South Carolina. The 95% confidence level for the mean K{sub d} was twice the mean in the Aquifer Zone (18-30.5 m depth), equal to the mean for the Upper Vadose Zone (3.3-10 m depth), and half the mean for the Lower Vadose Zone (3.10-18 m depth). The distribution of K{sub d} values was log normal in the Upper Vadose Zone and Aquifer Zone, and normal in the Lower Vadose Zone. To our knowledge, this is the first report of natural radionuclide Kd variability in the literature. Using ranges and distribution coefficients that are specific to the hydrostratigraphic unit improved model accuracy and reduced model uncertainty. Unfortunately, extension of these conclusions to other sites is likely not appropriate given that each site has its own sources of hydrogeological variability. However, this study provides one of the first examples of the development stochastic ranges and distributions of K{sub d} values for a hydrological unit for stochastic modeling.

  15. The potential effects of climate change on amphibian distribution, range fragmentation and turnover in China.

    PubMed

    Duan, Ren-Yan; Kong, Xiao-Quan; Huang, Min-Yi; Varela, Sara; Ji, Xiang

    2016-01-01

    Many studies predict that climate change will cause species movement and turnover, but few have considered the effect of climate change on range fragmentation for current species and/or populations. We used MaxEnt to predict suitable habitat, fragmentation and turnover for 134 amphibian species in China under 40 future climate change scenarios spanning four pathways (RCP2.6, RCP4.5, RCP6 and RCP8.5) and two time periods (the 2050s and 2070s). Our results show that climate change may cause a major shift in spatial patterns of amphibian diversity. Amphibians in China would lose 20% of their original ranges on average; the distribution outside current ranges would increase by 15%. Suitable habitats for over 90% of species will be located in the north of their current range, for over 95% of species in higher altitudes (from currently 137-4,124 m to 286-4,396 m in the 2050s or 314-4,448 m in the 2070s), and for over 75% of species in the west of their current range. Also, our results predict two different general responses to the climate change: some species contract their ranges while moving westwards, southwards and to higher altitudes, while others expand their ranges. Finally, our analyses indicate that range dynamics and fragmentation are related, which means that the effects of climate change on Chinese amphibians might be two-folded.

  16. The potential effects of climate change on amphibian distribution, range fragmentation and turnover in China

    PubMed Central

    Huang, Min-Yi; Varela, Sara

    2016-01-01

    Many studies predict that climate change will cause species movement and turnover, but few have considered the effect of climate change on range fragmentation for current species and/or populations. We used MaxEnt to predict suitable habitat, fragmentation and turnover for 134 amphibian species in China under 40 future climate change scenarios spanning four pathways (RCP2.6, RCP4.5, RCP6 and RCP8.5) and two time periods (the 2050s and 2070s). Our results show that climate change may cause a major shift in spatial patterns of amphibian diversity. Amphibians in China would lose 20% of their original ranges on average; the distribution outside current ranges would increase by 15%. Suitable habitats for over 90% of species will be located in the north of their current range, for over 95% of species in higher altitudes (from currently 137–4,124 m to 286–4,396 m in the 2050s or 314–4,448 m in the 2070s), and for over 75% of species in the west of their current range. Also, our results predict two different general responses to the climate change: some species contract their ranges while moving westwards, southwards and to higher altitudes, while others expand their ranges. Finally, our analyses indicate that range dynamics and fragmentation are related, which means that the effects of climate change on Chinese amphibians might be two-folded. PMID:27547522

  17. The potential effects of climate change on amphibian distribution, range fragmentation and turnover in China.

    PubMed

    Duan, Ren-Yan; Kong, Xiao-Quan; Huang, Min-Yi; Varela, Sara; Ji, Xiang

    2016-01-01

    Many studies predict that climate change will cause species movement and turnover, but few have considered the effect of climate change on range fragmentation for current species and/or populations. We used MaxEnt to predict suitable habitat, fragmentation and turnover for 134 amphibian species in China under 40 future climate change scenarios spanning four pathways (RCP2.6, RCP4.5, RCP6 and RCP8.5) and two time periods (the 2050s and 2070s). Our results show that climate change may cause a major shift in spatial patterns of amphibian diversity. Amphibians in China would lose 20% of their original ranges on average; the distribution outside current ranges would increase by 15%. Suitable habitats for over 90% of species will be located in the north of their current range, for over 95% of species in higher altitudes (from currently 137-4,124 m to 286-4,396 m in the 2050s or 314-4,448 m in the 2070s), and for over 75% of species in the west of their current range. Also, our results predict two different general responses to the climate change: some species contract their ranges while moving westwards, southwards and to higher altitudes, while others expand their ranges. Finally, our analyses indicate that range dynamics and fragmentation are related, which means that the effects of climate change on Chinese amphibians might be two-folded. PMID:27547522

  18. Correction for Rhiel's theory for the range estimator of the coefficient of variation for skewed distributions.

    PubMed

    Rhiel, G Steven

    2010-02-01

    In 2007, Rhiel presented a technique to estimate the coefficient of variation from the range when sampling from skewed distributions. To provide an unbiased estimate, a correction factor (a(n)) for the mean was included. Numerical correction factors for a number of skewed distributions were provided. In a follow-up paper, he provided a proof he claimed showed the correction factor was independent of the mean and standard deviation, making the factors useful as these parameters vary; however, that proof did not establish independence. Herein is a proof which establishes the independence.

  19. Methods to estimate distribution and range extent of grizzly bears in the Greater Yellowstone Ecosystem

    USGS Publications Warehouse

    Haroldson, Mark A.; Schwartz, Charles C.; , Daniel D. Bjornlie; , Daniel J. Thompson; , Kerry A. Gunther; , Steven L. Cain; , Daniel B. Tyers; Frey, Kevin L.; Aber, Bryan C.

    2014-01-01

    The distribution of the Greater Yellowstone Ecosystem grizzly bear (Ursus arctos) population has expanded into areas unoccupied since the early 20th century. Up-to-date information on the area and extent of this distribution is crucial for federal, state, and tribal wildlife and land managers to make informed decisions regarding grizzly bear management. The most recent estimate of grizzly bear distribution (2004) utilized fixed-kernel density estimators to describe distribution. This method was complex and computationally time consuming and excluded observations of unmarked bears. Our objective was to develop a technique to estimate grizzly bear distribution that would allow for the use of all verified grizzly bear location data, as well as provide the simplicity to be updated more frequently. We placed all verified grizzly bear locations from all sources from 1990 to 2004 and 1990 to 2010 onto a 3-km × 3-km grid and used zonal analysis and ordinary kriging to develop a predicted surface of grizzly bear distribution. We compared the area and extent of the 2004 kriging surface with the previous 2004 effort and evaluated changes in grizzly bear distribution from 2004 to 2010. The 2004 kriging surface was 2.4% smaller than the previous fixed-kernel estimate, but more closely represented the data. Grizzly bear distribution increased 38.3% from 2004 to 2010, with most expansion in the northern and southern regions of the range. This technique can be used to provide a current estimate of grizzly bear distribution for management and conservation applications.

  20. Past and ongoing shifts in Joshua tree distribution support future modeled range contraction

    USGS Publications Warehouse

    Cole, Kenneth L.; Ironside, Kirsten; Eischeid, Jon K.; Garfin, Gregg; Duffy, Phil; Toney, Chris

    2011-01-01

    The future distribution of the Joshua tree (Yucca brevifolia) is projected by combining a geostatistical analysis of 20th-century climates over its current range, future modeled climates, and paleoecological data showing its response to a past similar climate change. As climate rapidly warmed ;11 700 years ago, the range of Joshua tree contracted, leaving only the populations near what had been its northernmost limit. Its ability to spread northward into new suitable habitats after this time may have been inhibited by the somewhat earlier extinction of megafaunal dispersers, especially the Shasta ground sloth. We applied a model of climate suitability for Joshua tree, developed from its 20th-century range and climates, to future climates modeled through a set of six individual general circulation models (GCM) and one suite of 22 models for the late 21st century. All distribution data, observed climate data, and future GCM results were scaled to spatial grids of ;1 km and ;4 km in order to facilitate application within this topographically complex region. All of the models project the future elimination of Joshua tree throughout most of the southern portions of its current range. Although estimates of future monthly precipitation differ between the models, these changes are outweighed by large increases in temperature common to all the models. Only a few populations within the current range are predicted to be sustainable. Several models project significant potential future expansion into new areas beyond the current range, but the species' Historical and current rates of dispersal would seem to prevent natural expansion into these new areas. Several areas are predicted to be potential sites for relocation/ assisted migration. This project demonstrates how information from paleoecology and modern ecology can be integrated in order to understand ongoing processes and future distributions.

  1. Strain Distribution in a Kennedy Class I Implant Assisted Removable Partial Denture under Various Loading Conditions

    PubMed Central

    Shahmiri, Reza; Aarts, John M.; Bennani, Vincent; Swain, Michael V.

    2013-01-01

    Purpose. This in vitro study investigates how unilateral and bilateral occlusal loads are transferred to an implant assisted removable partial denture (IARPD). Materials and Methods. A duplicate model of a Kennedy class I edentulous mandibular arch was made and then a conventional removable partial denture (RPD) fabricated. Two Straumann implants were placed in the second molar region, and the prosthesis was modified to accommodate implant retained ball attachments. Strain gages were incorporated into the fitting surface of both the framework and acrylic to measure microstrain (μStrain). The IARPD was loaded to 120Ns unilaterally and bilaterally in three different loading positions. Statistical analysis was carried out using SPSS version 18.0 (SPSS, Inc., Chicago, IL, USA) with an alpha level of 0.05 to compare the maximum μStrain values of the different loading conditions. Results. During unilateral and bilateral loading the maximum μStrain was predominantly observed in a buccal direction. As the load was moved anteriorly the μStrain increased in the mesial area. Unilateral loading resulted in a twisting of the structure and generated a strain mismatch between the metal and acrylic surfaces. Conclusions. Unilateral loading created lateral and vertical displacement of the IARPD. The curvature of the dental arch resulted in a twisting action which intensified as the unilateral load was moved anteriorly. PMID:23737788

  2. Off to new shores: Modeling the potential distribution and future range expansion of larger foraminifera

    NASA Astrophysics Data System (ADS)

    Weinmann, A. E.; Rödder, D.; Lötters, S.; Langer, M. R.

    2012-04-01

    The distribution of larger foraminifera is strongly controlled by environmental variables, especially temperature. Most of today's taxa of larger foraminifera are restricted to tropical and subtropical regions (between 30° N and 30° S) and their minimum temperature limits are governed by the 14 to 20° C isotherms. However, during times of extensive global warming (e.g. the Eocene and Miocene), larger foraminifera have been found as far North as 50° N (North America and Central Europe) as well as towards 40° S in New Zealand. It has been stated that larger foraminifera are more tolerant of rising sea surface temperatures than reef-building corals. As such they may play a more prominent role as future reef framework and carbonate producers in a steadily warming ocean. During the last century, sea surface temperatures have been rising significantly due to higher CO2 concentrations in the atmosphere. This trend is expected to continue and climate change scenarios for 2100 suggest a further increase by 1 to 6° C (IPCC Synthesis Report, 2007). We applied Species Distribution Models (SDMs) on several taxa of larger foraminifera in order to evaluate their potential distribution under current climate conditions and to predict range expansions within the next 40 years. The studied taxa include Archaias angulatus, which is regionally distributed within the Caribbean region, Calcarina spp., which occurs in the Indo-Pacific area and the true circumglobal taxon Amphistegina spp. Under present climate, Amphistegina spp. shows the widest distribution range due to its greater temperature tolerance. Both Archaias angulatus and Calcarina spp. display potential distributions that cover currently uninhabitet regions, suggesting that weak dispersal abilities are major reasons for their limited distributions. Under future climate, Archaias angulatus and Calcarina spp. show an increase in habitat suitability within their native occurrence ranges, suggesting that their tolerance for

  3. Comparative stress distribution of implant-retained mandibular ball-supported and bar-supported overlay dentures: a finite element analysis.

    PubMed

    Vafaei, Fariborz; Khoshhal, Masoumeh; Bayat-Movahed, Saeed; Ahangary, Ahmad Hassan; Firooz, Farnaz; Izady, Alireza; Rakhshan, Vahid

    2011-08-01

    Implant-retained mandibular ball-supported and bar-supported overlay dentures are the two most common treatment options for the edentulous mandible. The superior option in terms of strain distribution should be determined. The three-dimensional model of mandible (based on computerized tomography scan) and its overlying implant-retained bar-supported and ball-supported overlay dentures were simulated using SolidWorks, NURBS, and ANSYS Workbench. Loads A (60 N) and B (60 N) were exerted, respectively, in protrusive and laterotrusive motions, on second molar mesial, first molar mesial, and first premolar. The strain distribution patterns were assessed on (1) implant tissue, (2) first implant-bone, and (3) second implant-bone interfaces. Protrusive: Strain was mostly detected in the apical of the fixtures and least in the cervical when bar design was used. On the nonworking side, however, strain was higher in the cervical and lower in the apical compared with the working side implant. Laterotrusive: The strain values were closely similar in the two designs. It seems that both designs are acceptable in terms of stress distribution, although a superior pattern is associated with the application of bar design in protrusive motion.

  4. Fabrication of an inexpensive, implantable cooling device for reversible brain deactivation in animals ranging from rodents to primates

    PubMed Central

    Cooke, Dylan F.; Goldring, Adam B.; Yamayoshi, Itsukyo; Tsourkas, Phillippos; Recanzone, Gregg H.; Tiriac, Alex; Pan, Tingrui; Simon, Scott I.

    2012-01-01

    We have developed a compact and lightweight microfluidic cooling device to reversibly deactivate one or more areas of the neocortex to examine its functional macrocircuitry as well as behavioral and cortical plasticity. The device, which we term the “cooling chip,” consists of thin silicone tubing (through which chilled ethanol is circulated) embedded in mechanically compliant polydimethylsiloxane (PDMS). PDMS is tailored to compact device dimensions (as small as 21 mm3) that precisely accommodate the geometry of the targeted cortical area. The biocompatible design makes it suitable for both acute preparations and chronic implantation for long-term behavioral studies. The cooling chip accommodates an in-cortex microthermocouple measuring local cortical temperature. A microelectrode may be used to record simultaneous neural responses at the same location. Cortex temperature is controlled by computer regulation of the coolant flow, which can achieve a localized cortical temperature drop from 37 to 20°C in less than 3 min and maintain target temperature to within ±0.3°C indefinitely. Here we describe cooling chip fabrication and performance in mediating cessation of neural signaling in acute preparations of rodents, ferrets, and primates. PMID:22402651

  5. Fabrication of an inexpensive, implantable cooling device for reversible brain deactivation in animals ranging from rodents to primates.

    PubMed

    Cooke, Dylan F; Goldring, Adam B; Yamayoshi, Itsukyo; Tsourkas, Phillippos; Recanzone, Gregg H; Tiriac, Alex; Pan, Tingrui; Simon, Scott I; Krubitzer, Leah

    2012-06-01

    We have developed a compact and lightweight microfluidic cooling device to reversibly deactivate one or more areas of the neocortex to examine its functional macrocircuitry as well as behavioral and cortical plasticity. The device, which we term the "cooling chip," consists of thin silicone tubing (through which chilled ethanol is circulated) embedded in mechanically compliant polydimethylsiloxane (PDMS). PDMS is tailored to compact device dimensions (as small as 21 mm(3)) that precisely accommodate the geometry of the targeted cortical area. The biocompatible design makes it suitable for both acute preparations and chronic implantation for long-term behavioral studies. The cooling chip accommodates an in-cortex microthermocouple measuring local cortical temperature. A microelectrode may be used to record simultaneous neural responses at the same location. Cortex temperature is controlled by computer regulation of the coolant flow, which can achieve a localized cortical temperature drop from 37 to 20°C in less than 3 min and maintain target temperature to within ±0.3°C indefinitely. Here we describe cooling chip fabrication and performance in mediating cessation of neural signaling in acute preparations of rodents, ferrets, and primates. PMID:22402651

  6. Impact of the end of range damage from low energy Ge preamorphizing implants on the thermal stability of shallow boron profiles

    SciTech Connect

    Camillo-Castillo, R.A.; Law, M.E.; Jones, K.S.

    2004-11-01

    A fundamental understanding of the effect of scaling amorphous layers on the thermal stability of active concentrations is required for the formation of ultrashallow junctions. A study on the influence of boron on the evolution of the end of range defects for samples containing shallow amorphous layers formed by low energy germanium implants is conducted. Czochralski grown (100) silicon wafers are preamorphized with 1x10{sup 15} cm{sup -2}, 10 keV Ge{sup +} and subsequently implanted with 1x10{sup 15} cm{sup -2}, 1 keV B{sup +} such that high boron levels are attained in the end of range region. A sequence of anneals are performed at 750 deg. C, under nitrogen ambient for times ranging from 1 s to 6 h and the end of range defect evolution is imaged via plan-view transmission electron microscopy (TEM). Defect analyses are conducted utilizing quantitative TEM which indicates substantial differences in the defect evolution for samples with boron in the end of range. The extended defects observed are very unstable and undergo a fast dissolution. In contrast, stable defects are observed in the experimental control in which the evolution follows an Ostwald ripening behavior. Secondary ion mass spectroscopy analyses confirm the ephemeral nature of the defects observed and also demonstrates drastic reductions in interstitial supersaturation. In addition, uphill-type diffusion is observed to occur for a short time frame, which emphasizes a transient interstitial supersaturation. Correlation of this data with sheet resistance and active dose measurements conducted on a Hall measurement system strongly indicates the formation of boron interstitial clusters. The high boron concentrations and supersaturation levels attained at the anneal temperature enables the cluster formation. An estimate of the boron concentrations trapped in the clusters is determined from the active dose obtained from the Hall measurements and indicates concentrations much higher than those available in

  7. Effect of cantilever length and alloy framework on the stress distribution in peri-implant area of cantilevered implant-supported fixed partial dentures.

    PubMed

    Suedam, Valdey; Moretti Neto, Rafael Tobias; Sousa, Edson Antonio Capello; Rubo, José Henrique

    2016-04-01

    Because many mechanical variables are present in the oral cavity, the proper load transfer between the prosthesis and the bone is important for treatment planning and for the longevity of the implant-supported fixed partial denture. Objectives To verify the stress generated on the peri-implant area of cantilevered implant-supported fixed partial dentures and the potential effects of such variable. Material and Methods A U-shaped polyurethane model simulating the mandibular bone containing two implants (Ø 3.75 mm) was used. Six groups were formed according to the alloy's framework (CoCr or PdAg) and the point of load application (5 mm, 10 mm and 15 mm of cantilever arm). A 300 N load was applied in pre-determined reference points. The tension generated on the mesial, lingual, distal and buccal sides of the peri-implant regions was assessed using strain gauges. Results Two-way ANOVA and Tukey statistical tests were applied showing significant differences (p<0.05) between the groups. Pearson correlation test (p<0.05) was applied showing positive correlations between the increase of the cantilever arm and the deformation of the peri-implant area. Conclusions This report demonstrated the CoCr alloy shows larger compression values compared to the PdAg alloy for the same distances of cantilever. The point of load application influences the deformation on the peri-implant area, increasing in accordance with the increase of the lever arm. PMID:27119758

  8. Sipha maydis: distribution and host range of a new aphid pest of winter cereals in Argentina.

    PubMed

    Corrales, C E; Castro, A M; Ricci, M; Dixon, A F G

    2007-12-01

    Sipha maydis (Passerini) is a new aphid pest of cereals and cultivated and wild grasses in Argentina. This species was recently introduced into America, and nothing is known of its distribution or host range in South America. A better understanding of its biology is likely to facilitate control. This article records 1) the distribution and 2) the host range of S. maydis in Argentina. Over the period 2004-2006 samples were collected from 32 populations at several localities in Argentina. The number of S. maydis, accompanying aphid species, and the host from which they were collected were recorded. The distribution of S. maydis ranged from 32 degrees 52' to 42 degrees 03' S, and from 57 degrees 41' to 71 degrees 24' W, bounded by isothermals 18 and 10 degrees C and isohyets 200-400 and <1,200 mm. No S. maydis were found in the subtropical region, even in winter. In the field, the different populations showed very different host preferences. S. maydis was found mainly on cultivated barley and wheat and on wild Bromus spp. and Sorghum halepense (L.) Pers. No aphids were found on maize, Zea mays L. Most of the damage to winter cereal crops occurred at the seedling stage in early autumn and of adult plants when infestations occurred in late spring. In the 4 yr after the first record of S. maydis in Argentina, it colonized a huge area similar to that colonized by Diuraphis noxia (Mordvilko) in 10 yr. The wide range of regions, hosts and climatic conditions this species is adapted to is likely to make the control of this pest very difficult.

  9. Distribution of a climate-sensitive species at an interior range margin

    USGS Publications Warehouse

    Ray, Chris; Beever, Erik; Rodhouse, Thomas J.

    2016-01-01

    Advances in understanding the factors that limit a species’ range, particularly in the context of climate change, have come disproportionately through investigations at range edges or margins. The margins of a species’ range might often correspond with anomalous microclimates that confer habitat suitability where the species would otherwise fail to persist. We addressed this hypothesis using data from an interior, climatic range margin of the American pika (Ochotona princeps), an indicator of relatively cool, mesic climates in rocky habitats of western North America. Pikas in Lava Beds National Monument, northeastern California, USA, occur at elevations much lower than predicted by latitude and longitude. We hypothesized that pika occurrence within Lava Beds would be associated primarily with features such as “ice caves” in which sub-surface ice persists outside the winter months. We used data loggers to monitor sub-surface temperatures at cave entrances and at non-cave sites, confirming that temperatures were cooler and more stable at cave entrances. We surveyed habitat characteristics and evidence of pika occupancy across a random sample of cave and non-cave sites over a 2-yr period. Pika detection probability was high (~0.97), and the combined occupancy of cave and non-cave sites varied across the 2 yr from 27% to 69%. Contrary to our hypothesis, occupancy was not higher at cave sites. Vegetation metrics were the best predictors of site use by pikas, followed by an edge effect and elevation. The importance of vegetation as a predictor of pika distribution at this interior range margin is congruent with recent studies from other portions of the species’ range. However, we caution that vegetation composition depends on microclimate, which might be the proximal driver of pika distribution. The microclimates available in non-cave crevices accessible to small animals have not been characterized adequately for lava landscapes. We advocate innovation in the

  10. Spatial concentration distribution model for short-range continuous gas leakage of small amount

    NASA Astrophysics Data System (ADS)

    Wang, Meirong; Wang, Lingxue; Li, Jiakun; Long, Yunting; Gao, Yue

    2012-06-01

    Passive infrared gas imaging systems have been utilized in the equipment leak detection and repair in chemical manufacturers and petroleum refineries. The detection performance mainly relates to the sensitivity of infrared detector, optical depth of gas, atmospheric transmission, wind speed, and so on. Based on our knowledge, the spatial concentration distribution of continuously leaking gas plays an important part in leak detection. Several computational model of gas diffusion were proposed by researchers, such as Gaussian model, BM model, Sutton model and FEM3 model. But these models focus on calculating a large scale gas concentration distribution for a great amount of gas leaks above over 100- meter height, and not applicable to assess detection limit of a gas imaging system in short range. In this paper, a wind tunnel experiment is designed. Under different leaking rate and wind speed, concentration in different spatial positions is measured by portable gas detectors. Through analyzing the experimental data, the two parameters σy(x) and σz (x) that determine the plume dispersion in Gaussian model are adjusted to produce the best curve fit to the gas concentration data. Then a concentration distribution model for small mount gas leakage in short range is established. Various gases, ethylene and methane are used to testify this model.

  11. Effect of soil type on distribution and bioaccessibility of metal contaminants in shooting range soils.

    PubMed

    Sanderson, Peter; Naidu, Ravi; Bolan, Nanthi; Bowman, Mark; McLure, Stuart

    2012-11-01

    Shooting ranges from Department of Defence sites around Australia were investigated for extent of metal contamination. Shooting range soils contained concentrations ranging from 399 to 10,403 mg/kg Pb, 6.57 to 252 mg/kg Sb, 28.7 to 1250 mg/kg Cu, 5.63 to 153 mg/kg Zn, 1.35 to 8.8 mg/kg Ni and 3.08 to 15.8 mg/kg As. Metal(loid)s were primarily concentrated in the stop butt and the surface soil (0-10 cm). The distribution of contamination reflected firing activity, soil properties, climate and management practices. Climatic variations among sites in Australia are significant, with a temperate climate in the south and tropical climate with high rainfall in the north. Up to 8% of total Pb resided in soil fines (<0.075 mm), due to the fragmentation of bullets on impact. Distribution and bioaccessibility varied between each site. Acidic Townsville soil had the highest proportion of water extractable Pb at 10%, compared to the alkaline Murray Bridge with only 2% Pb water extractable. Soil properties such as CEC, pH and dissolved organic carbon influence mobility. This is reflected in the subsoil concentrations of Pb in Townsville and Darwin which are up to 30 and 46% of surface concentration in the subsoil respectively. Similarly bioaccessibility is influenced by soil properties and ranges from 46% in Townsville to 70% in Perth. Acidic pH promotes dissolution of secondary minerals and the downward movement of Pb in the profile. The secondary Pb minerals formed as a result of weathering in these soils were cerussite, hydrocerussite, pyromorphite, galena and anglesite. Copper oxide was also reported on fragments from bullet jackets. These results have implications for range management. PMID:23026152

  12. A regional density distribution based wide dynamic range algorithm for infrared camera systems

    NASA Astrophysics Data System (ADS)

    Park, Gyuhee; Kim, Yongsung; Joung, Shichang; Shin, Sanghoon

    2014-10-01

    Forward Looking InfraRed (FLIR) imaging system has been widely used for both military and civilian purposes. Military applications include target acquisition and tracking, night vision system. Civilian applications include thermal efficiency analysis, short-ranged wireless communication, weather forecasting and other various applications. The dynamic range of FLIR imaging system is larger than one of commercial display. Generally, auto gain controlling and contrast enhancement algorithm are applied to FLIR imaging system. In IR imaging system, histogram equalization and plateau equalization is generally used for contrast enhancement. However, they have no solution about the excessive enhancing when luminance histogram has been distributed in specific narrow region. In this paper, we proposed a Regional Density Distribution based Wide Dynamic Range algorithm for Infrared Camera Systems. Depending on the way of implementation, the result of WDR is quite different. Our approach is single frame type WDR algorithm for enhancing the contrast of both dark and white detail without loss of bins of histogram with real-time processing. The significant change in luminance caused by conventional contrast enhancement methods may introduce luminance saturation and failure in object tracking. Proposed method guarantees both the effective enhancing in contrast and successive object tracking. Moreover, since proposed method does not using multiple images on WDR, computation complexity might be significantly reduced in software / hardware implementation. The experimental results show that proposed method has better performance compared with conventional Contrast enhancement methods.

  13. Size distribution of radon decay products in the range 0.1-10 nm.

    PubMed

    Zhukovsky, Michael; Rogozina, Marina; Suponkina, Anna

    2014-07-01

    Information about the size distribution of radioactive aerosols in nanometre range is essential for the purposes of air contamination monitoring, dose assessment to respiratory tract and planning of protective measures. The diffusion battery, which allows capturing particles in the size range of 0.1-10 nm, has developed. Interpreting data obtained from diffusion battery is very complex. The method of expectation maximisation by Maher and Laird was chosen for indirect inversion data. The experiments were performed in the box with equivalent equilibrium concentration of radon in the range of 7000-10,000 Bq m(-3). The three modes of size distribution of radon decay products aerosols were obtained: activity median thermodynamic diameter (AMTD) 0.3, 1.5 and 5 nm. These modes can be identified as: AMTD 0.3 nm--atoms of radon progeny (218Po in general); AMTD 1.5 nm--clusters of radon progeny atoms and non-radioactive atoms in the atmosphere; AMTD 5 nm--particles formed by coagulation of previous mode clusters with existing aerosol particles or nucleation of condensation nuclei containing atoms of radon progeny.

  14. The influence of patient positioning uncertainties in proton radiotherapy on proton range and dose distributions

    SciTech Connect

    Liebl, Jakob; Paganetti, Harald; Zhu, Mingyao; Winey, Brian A.

    2014-09-15

    Purpose: Proton radiotherapy allows radiation treatment delivery with high dose gradients. The nature of such dose distributions increases the influence of patient positioning uncertainties on their fidelity when compared to photon radiotherapy. The present work quantitatively analyzes the influence of setup uncertainties on proton range and dose distributions. Methods: Thirty-eight clinical passive scattering treatment fields for small lesions in the head were studied. Dose distributions for shifted and rotated patient positions were Monte Carlo-simulated. Proton range uncertainties at the 50%- and 90%-dose falloff position were calculated considering 18 arbitrary combinations of maximal patient position shifts and rotations for two patient positioning methods. Normal tissue complication probabilities (NTCPs), equivalent uniform doses (EUDs), and tumor control probabilities (TCPs) were studied for organs at risk (OARs) and target volumes of eight patients. Results: The authors identified a median 1σ proton range uncertainty at the 50%-dose falloff of 2.8 mm for anatomy-based patient positioning and 1.6 mm for fiducial-based patient positioning as well as 7.2 and 5.8 mm for the 90%-dose falloff position, respectively. These range uncertainties were correlated to heterogeneity indices (HIs) calculated for each treatment field (38% < R{sup 2} < 50%). A NTCP increase of more than 10% (absolute) was observed for less than 2.9% (anatomy-based positioning) and 1.2% (fiducial-based positioning) of the studied OARs and patient shifts. For target volumes TCP decreases by more than 10% (absolute) occurred in less than 2.2% of the considered treatment scenarios for anatomy-based patient positioning and were nonexistent for fiducial-based patient positioning. EUD changes for target volumes were up to 35% (anatomy-based positioning) and 16% (fiducial-based positioning). Conclusions: The influence of patient positioning uncertainties on proton range in therapy of small lesions

  15. Stress and strain analysis of the bone-implant interface: a comparison of fiber-reinforced composite and titanium implants utilizing 3-dimensional finite element study.

    PubMed

    Shinya, Akikazu; Ballo, Ahmed M; Lassila, Lippo V J; Shinya, Akiyoshi; Närhi, Timo O; Vallittu, Pekka K

    2011-03-01

    This study analyzed stress and strain mediated by 2 different implant materials, titanium (Ti) and experimental fiber-reinforced composite (FRC), on the implant and on the bone tissue surrounding the implant. Three-dimensional finite element models constructed from a mandibular bone and an implant were subjected to a load of 50 N in vertical and horizontal directions. Postprocessing files allowed the calculation of stress and strain within the implant materials and stresses at the bone-to-implant interface (stress path). Maximum stress concentrations were located around the implant on the rim of the cortical bone in both implant materials; Ti and overall stresses decreased toward the Ti implant apex. In the FRC implant, a stress value of 0.6 to 2.0 MPa was detected not only on the screw threads but also on the implant surface between the threads. Clear differences were observed in the strain distribution between the materials. Based on the results, the vertical load stress range of the FRC implant was close to the stress level for optimal bone growth. Furthermore, the stress at the bone around the FRC implant was more evenly distributed than that with Ti implant.

  16. Range dynamics, rather than convergent selection, explain the mosaic distribution of red-winged blackbird phenotypes.

    PubMed

    Dufort, Matthew J; Keith Barker, F

    2013-12-01

    Geographic distributions of genetic and phenotypic characters can illuminate historical evolutionary processes. In particular, mosaic distributions of phenotypically similar populations can arise from parallel evolution or from irregular patterns of dispersal and colonization by divergent forms. Two phenotypically divergent forms of the red-winged blackbird (Agelaius phoeniceus) show a mosaic phenotypic distribution, with a "bicolored" form occurring disjunctly in California and Mexico. We analyzed the relationships among these bicolored populations and neighboring typical populations, using ∼600 bp of mitochondrial DNA sequence data and 10 nuclear short tandem repeat loci. We find that bicolored populations, although separated by ∼3000 km, are genetically more similar to one other than they are to typical populations separated by ∼400 km. We also find evidence of ongoing gene flow among populations, including some evidence of asymmetric gene flow. We conclude that the current distribution of bicolored forms represents incomplete speciation, where recent asymmetric hybridization with typical A. phoeniceus is dividing the range of a formerly widespread bicolored form. This hypothesis predicts that bicolored forms may suffer extinction by hybridization. Future work will use fine-scaled geographical sampling and nuclear sequence data to test for hybrid origins of currently typical populations and to more precisely quantify the directionality of gene flow.

  17. Range dynamics, rather than convergent selection, explain the mosaic distribution of red-winged blackbird phenotypes

    PubMed Central

    Dufort, Matthew J; Keith Barker, F

    2013-01-01

    Geographic distributions of genetic and phenotypic characters can illuminate historical evolutionary processes. In particular, mosaic distributions of phenotypically similar populations can arise from parallel evolution or from irregular patterns of dispersal and colonization by divergent forms. Two phenotypically divergent forms of the red-winged blackbird (Agelaius phoeniceus) show a mosaic phenotypic distribution, with a “bicolored” form occurring disjunctly in California and Mexico. We analyzed the relationships among these bicolored populations and neighboring typical populations, using ∼600 bp of mitochondrial DNA sequence data and 10 nuclear short tandem repeat loci. We find that bicolored populations, although separated by ∼3000 km, are genetically more similar to one other than they are to typical populations separated by ∼400 km. We also find evidence of ongoing gene flow among populations, including some evidence of asymmetric gene flow. We conclude that the current distribution of bicolored forms represents incomplete speciation, where recent asymmetric hybridization with typical A. phoeniceus is dividing the range of a formerly widespread bicolored form. This hypothesis predicts that bicolored forms may suffer extinction by hybridization. Future work will use fine-scaled geographical sampling and nuclear sequence data to test for hybrid origins of currently typical populations and to more precisely quantify the directionality of gene flow. PMID:24455125

  18. Shallow landsliding, root reinforcement, and the spatial distribution of trees in the Oregon Coast Range

    USGS Publications Warehouse

    Roering, J.J.; Schmidt, K.M.; Stock, J.D.; Dietrich, W.E.; Montgomery, D.R.

    2003-01-01

    The influence of root reinforcement on shallow landsliding has been well established through mechanistic and empirical studies, yet few studies have examined how local vegetative patterns influence slope stability. Because root networks spread outward from trees, the species, size, and spacing of trees should influence the spatial distribution of root strength. We documented the distribution and characteristics of trees adjacent to 32 shallow landslides that occurred during 1996 in the Oregon Coast Range. Although broadly classified as a conifer-dominated forest, we observed sparse coniferous and abundant hardwood trees near landslide scars in an industrial forest (Mapleton) that experienced widespread burning in the 19th century. In industrial forests that were burned, selectively harvested, and not replanted (Elliott State Forest), swordfern was ubiquitous near landslides, and we observed similar numbers of live conifer and hardwood trees proximal to landslide scarps. We demonstrate that root strength quantified in landslide scarps and soil pits correlates with a geometry-based index of root network contribution derived from mapping the size, species, condition, and spacing of local trees, indicating that root strength can be predicted by mapping the distribution and characteristics of trees on potentially unstable slopes. In our study sites, landslides tend to occur in areas of reduced root strength, suggesting that to make site-specific predictions of landslide occurrence slope stability analyses must account for the diversity and distribution of vegetation in potentially unstable terrain.

  19. Influence of finish line in the distribution of stress trough an all ceramic implant-supported crown.

    PubMed Central

    SANNINO, G.; GLORIA, F.; OTTRIA, L.; BARLATTANI, A.

    2010-01-01

    SUMMARY Porpose. The aim of this study was to evaluate, by finite element analysis (FEA), the influence of finish line on stress distribution and resistance to the loads of a ZrO2 crown and porcelain in implant-supported. Material and methods. The object of this analysis consisted of a fxture, an abutment, a passing screw, a layer of cement, a framework crown, a feldspatic porcelain veneering. The abutment’s marginal design was used in 3 different types of preparation: feather edge, slight chamfer and 50°, each of them was of 1 mm depth over the entire circumference. The ZrO2Y-TZP coping was 0.6 mm thick. Two material matching for the abutment and the framework was used for the simulations: ZrO2 framework and ZrO2 abutment, ZrO2 framework and T abutment. A 600 N axial force distributed over the entire surface of the crown was applied. The numerical simulations with finite elements were used to verify the different distribution of equivalent von Mises stress for three different geometries of abutment and framework. Results Slight chamfer on the matching ZrO2 - ZrO2 is the geometry with minimum equivalent stress of von Mises. Even for T abutment and ZrO2 framework slight chamfer is the best configuration to minimize the localized stress. Geometry that has the highest average stress is one with abutment at 50°, we see a downward trend for all three configurations using only zirconium for both components. Conclusions Finite element analysis. performed for the manifacturing of implant-supported crown, gives exact geometric guide lines about the choice of chamfer preparation, while the analysis of other marginal geometries suggests a possible improved behavior of the mating between ZrO2 abutment and ZrO2 coping. for three different geometries of the abutment and the coping. PMID:23285359

  20. Effect of attachment types and number of implants supporting mandibular overdentures on stress distribution: a computed tomography-based 3D finite element analysis.

    PubMed

    Arat Bilhan, Selda; Baykasoglu, Cengiz; Bilhan, Hakan; Kutay, Omer; Mugan, Ata

    2015-01-01

    The objective of this study was to calculate stresses in bone tissue surrounding uncoupled and splinted implants that are induced by a bite force applied to the mandible and to determine whether the number of mandibular overdenture supporting implants in mandibular bone influence the stress distribution. A human adult edentulous mandible retrieved from a formalin fixed cadaver was used to define the geometry of finite element (FE) model and the FE model was verified with experimental measurements. Following the FE model validation, three different biting situations were simulated for the 2-, 3- and 4-implant retentive anchor as well as bar attachment overdentures under vertical loading of 100 N. As a result of the analyses, it was concluded that an increment in implant number and the splinted attachment type tended to cause lower stresses and the use of two single attachments seems to be a safe and sufficient solution for the treatment of mandibular edentulism with overdentures.

  1. Energy Analysis of Aluminosilicate Zeolites with Comprehensive Ranges of Framework Topologies, Chemical Compositions, and Aluminum Distributions.

    PubMed

    Muraoka, Koki; Chaikittisilp, Watcharop; Okubo, Tatsuya

    2016-05-18

    The contents and locations of Al in the zeolite frameworks are one of the key factors determining the physicochemical properties of zeolites. Systematic evaluation of the characteristics of zeolites with a wide variety of framework topologies, a wide range of Si/Al ratios, and various locations of Al is of great significance, but very challenging due to the limitation of the realizable ranges of Al contents in zeolites as well as the limited information on the Al locations obtained from the current analytical techniques. Here, we report the systematic analysis of the energetics of aluminosilicate zeolites with 209 existing framework topologies at different Si/Al ratios using molecular mechanics. More than 43 000 initial structures were generated to give comprehensive views of the energetics of zeolites. The results coincide well with the structural knowledge obtained experimentally. It was revealed that the relation between the relative framework energies versus the Al contents varies in accordance with the topologies, suggesting that the relative stability of zeolites depends not only on the topologies, but also on the substituting contents of Al. For particular topologies with the same Al contents, in addition, comparisons between random and specific distributions of Al showed that zeolite with Al at a particular T site is energetically more stable than those with random distributions, suggesting the inherent influences of the Al locations. The contents and locations of Al in zeolites likely have a certain preference that may reflect the range of chemical compositions, the Al distributions, and consequently the physicochemical properties of realizable aluminosilicate zeolites. PMID:27097121

  2. Comparison of different designs of implant-retained overdentures and fixed full-arch implant-supported prosthesis on stress distribution in edentulous mandible--a computed tomography-based three-dimensional finite element analysis.

    PubMed

    Barão, V A R; Delben, J A; Lima, J; Cabral, T; Assunção, W G

    2013-04-26

    A finite element analysis was used to compare the effect of different designs of implant-retained overdentures and fixed full-arch implant-supported prosthesis on stress distribution in edentulous mandible. Four models of an human mandible were constructed. In the OR (O'ring) group, the mandible was restored with an overdenture retained by four unsplinted implants with O'ring attachment; in the BC (bar-clip) -C and BC groups, the mandibles were restored with overdentures retained by four splinted implants with bar-clip anchor associated or not with two distally placed cantilevers, respectively; in the FD (fixed denture) group, the mandible was restored with a fixed full-arch four-implant-supported prosthesis. Models were supported by the masticatory muscles and temporomandibular joints. A 100-N oblique load was applied on the left first molar. Von Mises (σvM), maximum (σmax) and minimum (σmin) principal stresses (in MPa) analyses were obtained. BC-C group exhibited the highest stress values (σvM=398.8, σmax=580.5 and σmin=-455.2) while FD group showed the lowest one (σvM=128.9, σmax=185.9 and σmin=-172.1). Within overdenture groups, the use of unsplinted implants reduced the stress level in the implant/prosthetic components (59.4% for σvM, 66.2% for σmax and 57.7% for σmin versus BC-C group) and supporting tissues (maximum stress reduction of 72% and 79.5% for σmax, and 15.7% and 85.7% for σmin on the cortical and trabecular bones, respectively). Cortical bone exhibited greater stress concentration than the trabecular bone for all groups. The use of fixed implant dentures and removable dentures retained by unsplinted implants to rehabilitate edentulous mandible reduced the stresses in the periimplant bone tissue, mucosa and implant/prosthetic components. PMID:23518207

  3. Estimated solar wind-implanted helium-3 distribution on the Moon

    USGS Publications Warehouse

    Johnson, J. R.; Swindle, T.D.; Lucey, P.G.

    1999-01-01

    Among the solar wind-implanted volatiles present in the lunar regolith, 3 He is possibly the most valuable resource because of its potential as a fusion fuel. The abundance of 3 He in the lunar regolith at a given location depends on surface maturity, the amount of solar wind fluence, and titanium content, because ilmenite (FeTiO3) retains helium much better than other major lunar minerals. Surface maturity and TiO2 maps from Clementine multispectral data sets are combined here with a solar wind fluence model to produce a 3He abundance map of the Moon. Comparison of the predicted 3He values to landing site observations shows good correlation. The highest 3He abundances occur in the farside maria (due to greater solar wind fluence received) and in higher TiO2 nearside mare regions.

  4. Effect of cantilever length and alloy framework on the stress distribution in peri-implant area of cantilevered implant-supported fixed partial dentures

    PubMed Central

    SUEDAM, Valdey; MORETTI, Rafael Tobias; SOUSA, Edson Antonio Capello; RUBO, José Henrique

    2016-01-01

    ABSTRACT Because many mechanical variables are present in the oral cavity, the proper load transfer between the prosthesis and the bone is important for treatment planning and for the longevity of the implant-supported fixed partial denture. Objectives To verify the stress generated on the peri-implant area of cantilevered implant-supported fixed partial dentures and the potential effects of such variable. Material and Methods A U-shaped polyurethane model simulating the mandibular bone containing two implants (Ø 3.75 mm) was used. Six groups were formed according to the alloy’s framework (CoCr or PdAg) and the point of load application (5 mm, 10 mm and 15 mm of cantilever arm). A 300 N load was applied in pre-determined reference points. The tension generated on the mesial, lingual, distal and buccal sides of the peri-implant regions was assessed using strain gauges. Results Two-way ANOVA and Tukey statistical tests were applied showing significant differences (p<0.05) between the groups. Pearson correlation test (p<0.05) was applied showing positive correlations between the increase of the cantilever arm and the deformation of the peri-implant area. Conclusions This report demonstrated the CoCr alloy shows larger compression values compared to the PdAg alloy for the same distances of cantilever. The point of load application influences the deformation on the peri-implant area, increasing in accordance with the increase of the lever arm. PMID:27119758

  5. Factors Affecting Date of Implantation, Parturition, and Den Entry Estimated from Activity and Body Temperature in Free-Ranging Brown Bears

    PubMed Central

    Friebe, Andrea; Evans, Alina L.; Arnemo, Jon M.; Blanc, Stéphane; Brunberg, Sven; Fleissner, Günther; Swenson, Jon E.; Zedrosser, Andreas

    2014-01-01

    Knowledge of factors influencing the timing of reproduction is important for animal conservation and management. Brown bears (Ursus arctos) are able to vary the birth date of their cubs in response to their fat stores, but little information is available about the timing of implantation and parturition in free-ranging brown bears. Body temperature and activity of pregnant brown bears is higher during the gestation period than during the rest of hibernation and drops at parturition. We compared mean daily body temperature and activity levels of pregnant and nonpregnant females during preimplantation, gestation, and lactation. Additionally we tested whether age, litter size, primiparity, environmental conditions, and the start of hibernation influence the timing of parturition. The mean date of implantation was 1 December (SD = 12), the mean date of parturition was 26 January (SD = 12), and the mean duration of the gestation period was 56 days (SD = 2). The body temperature of pregnant females was higher during the gestation and lactation periods than that of nonpregnant bears. The body temperature of pregnant females decreased during the gestation period. Activity recordings were also used to determine the date of parturition. The parturition dates calculated with activity and body temperature data did not differ significantly and were the same in 50% of the females. Older females started hibernation earlier. The start of hibernation was earlier during years with favorable environmental conditions. Dates of parturition were later during years with good environmental conditions which was unexpected. We suggest that free-ranging pregnant brown bears in areas with high levels of human activities at the beginning of the denning period, as in our study area, might prioritize investing energy in early denning than in early parturition during years with favorable environmental conditions, as a strategy to prevent disturbances caused by human. PMID:24988486

  6. Factors affecting date of implantation, parturition, and den entry estimated from activity and body temperature in free-ranging brown bears.

    PubMed

    Friebe, Andrea; Evans, Alina L; Arnemo, Jon M; Blanc, Stéphane; Brunberg, Sven; Fleissner, Günther; Swenson, Jon E; Zedrosser, Andreas

    2014-01-01

    Knowledge of factors influencing the timing of reproduction is important for animal conservation and management. Brown bears (Ursus arctos) are able to vary the birth date of their cubs in response to their fat stores, but little information is available about the timing of implantation and parturition in free-ranging brown bears. Body temperature and activity of pregnant brown bears is higher during the gestation period than during the rest of hibernation and drops at parturition. We compared mean daily body temperature and activity levels of pregnant and nonpregnant females during preimplantation, gestation, and lactation. Additionally we tested whether age, litter size, primiparity, environmental conditions, and the start of hibernation influence the timing of parturition. The mean date of implantation was 1 December (SD = 12), the mean date of parturition was 26 January (SD = 12), and the mean duration of the gestation period was 56 days (SD = 2). The body temperature of pregnant females was higher during the gestation and lactation periods than that of nonpregnant bears. The body temperature of pregnant females decreased during the gestation period. Activity recordings were also used to determine the date of parturition. The parturition dates calculated with activity and body temperature data did not differ significantly and were the same in 50% of the females. Older females started hibernation earlier. The start of hibernation was earlier during years with favorable environmental conditions. Dates of parturition were later during years with good environmental conditions which was unexpected. We suggest that free-ranging pregnant brown bears in areas with high levels of human activities at the beginning of the denning period, as in our study area, might prioritize investing energy in early denning than in early parturition during years with favorable environmental conditions, as a strategy to prevent disturbances caused by human.

  7. Transaction-neutral implanted data collection interface as EMR driver: a model for emerging distributed medical technologies.

    PubMed

    Lorence, Daniel; Sivaramakrishnan, Anusha; Richards, Michael

    2010-08-01

    Electronic Medical Record (EMR) and Electronic Health Record (EHR) adoption continues to lag across the US. Cost, inconsistent formats, and concerns about control of patient information are among the most common reasons for non-adoption in physician practice settings. The emergence of wearable and implanted mobile technologies, employed in distributed environments, promises a fundamentally different information infrastructure, which could serve to minimize existing adoption resistance. Proposed here is one technology model for overcoming adoption inconsistency and high organization-specific implementation costs, using seamless, patient controlled data collection. While the conceptual applications employed in this technology set are provided by way of illustration, they may also serve as a transformative model for emerging EMR/EHR requirements. PMID:20703915

  8. Bone stability around dental implants: Treatment related factors.

    PubMed

    Heinemann, Friedhelm; Hasan, Istabrak; Bourauel, Christoph; Biffar, Reiner; Mundt, Torsten

    2015-05-01

    The bone bed around dental implants is influenced by implant and augmentation materials, as well as the insertion technique used. The primary influencing factors include the dental implant design, augmentation technique, treatment protocol, and surgical procedure. In addition to these treatment-related factors, in the literature, local and systemic factors have been found to be related to the bone stability around implants. Bone is a dynamic organ that optimises itself depending on the loading condition above it. Bone achieves this optimisation through the remodelling process. Several studies have confirmed the importance of the implant design and direction of the applied force on the implant system. Equally dispersed strains and stresses in the physiological range should be achieved to ensure the success of an implant treatment. If a patient wishes to accelerate the treatment time, different protocols can be chosen. However, each one must consider the amount and quality of the available local bone. Immediate implantation is only successful if the primary stability of the implant can be provided from residual bone in the socket after tooth extraction. Immediate loading demands high primary stability and, sometimes, the distribution of mastication forces by splinting or even by inserting additional implants to ensure their success. Augmentation materials with various properties have been developed in recent years. In particular, resorption time and stableness affect the usefulness in different situations. Hence, treatment protocols can optimise the time for simultaneous implant placements or optimise the follow-up time for implant placement.

  9. The effects of cluster carbon implantation at low temperature on damage recovery after annealing

    NASA Astrophysics Data System (ADS)

    Onoda, Hiroshi; Nakashima, Yoshiki; Hamamoto, Nariaki; Nagayama, Tsutomu; Koga, Yuji; Umisedo, Sei; Kawamura, Yasunori; Hashimoto, Masahiro

    2012-11-01

    Amorphous Si layer formation with cluster carbon ion implantations at low substrate temperature and its effects on damage recovery and diffusion suppression have been discussed. Cluster carbon molecule species (C3Hx˜C7Hx), implantation temperature (RT ˜ -60°C), implantation dose and energy were used as parameters. Amorphous Si formation by cluster carbon implantation is more effective compared with monomer carbon implantation. Low temperature cluster carbon implantations increase amorphous Si thickness far beyond monomer carbon implantation even at very low temperature. Amorphous-crystal interface smoothness was characterized by Rutherford Backscattering Spectroscopy, and is improved by lower temperature implantations. The smoothness improvement affects the residual damage, End of Range Defects, after annealing. Thicker amorphous Si over 100 nm depth can be formed with light Cn+ molecule implantations. That makes it possible to suppress wide distributed phosphorus diffusion.

  10. On the Vertical Distribution of Aerosols and Long-Range Transport Inferred from Calipso Satellite Observations

    NASA Astrophysics Data System (ADS)

    Trepte, Charles; Winker, David; Kittaka, Chieko

    Knowledge on the long-range transport and evolution of aerosols originating from natural and anthropogenic sources is important for understanding their impact on the composition of the atmosphere and the climate system. Over the past several decades a wealth of information on aerosol distributions has been obtained from ground-based instrument networks, dedicated field experiments, and passive remote sensing satellite instruments that has helped to establish the primary aerosol transport pathways over the globe. In many instances, these pathways are broadly reproduced geographically in different chemical-transport models. The models, however, have difficulties at times with accurately projecting the vertical distribution of aerosols, which can lead to significant discrepancies in the lifetimes of the modeled aerosols. This issue is compounded at high latitudes where observations are especially sparse. New measurements from the CALIPSO satellite mission can provide additional insight on the vertical distribution of aerosols over the globe. The mission is a joint effort between the United States (NASA) and France (CNES) and was launched on April 28, 2008 into the A-train satellite constellation. CALIPSO's primary instrument is a two-wavelength polarization-sensitive lidar operating at 532 and 1064 nm with a repetition rate of 20.16 Hz. Lidar observations in the lower troposphere (¡ 8 km) have a vertical resolution of 30 m for the 532 nm channel and 60 m for the 1064 channel. The instrument has been operational since early June 2006. The CALIPSO data set reveals a rich distribution of aerosols in clear and cloudy scenes for both day and night conditions. Information on aerosol type is also available based on their wavelength dependence and polarization characteristics. From these data, a climatology on the vertical and geographic distribution and optical characteristics of aerosols (and clouds) is being developed that can aid diagnostic studies of aerosol transport

  11. Efficacy of adding a supporting implant in stress distribution of long-span fixed partial dentures: a 3D finite element analysis.

    PubMed

    Shurbaji Mozayek, Rami; Allaf, Mirza; B Abuharb, Mohammad

    2016-01-01

    Background. Long span is seen in many clinical situations. Treatmentplanning options of these cases are difficult and may require FPD, RPD or ISP. Each option has its own disadvantages, including mechanical problems, patient comfort and cost. This article will evaluate the stress distribution of a different treatment option, which consists of adding a single sup-porting implant to the FPD by using 3D finite element analysis. Methods. Three models, each consisting of 5 units, were created as follows: 1. Tooth Pontic Pontic Pontic Tooth; 2. Tooth Pontic Implant Pontic Tooth; 3. Tooth Pontic Pontic Implant Tooth. An axial force was applied to the prostheses by using 3D finite element method and stresses were evaluated. Results. The maximum stress was found in the prostheses in all the models; the highest stress values in all the shared components of the models were almost similar. Stress in implants was lower in the second model than the third one. Conclusion. Adding a supporting implant in long-span FPD has no advantages while it has the disadvantages of complicating treatment and the complications that may occur to the implant and surrounding bone. PMID:27429723

  12. Efficacy of adding a supporting implant in stress distribution of long-span fixed partial dentures: a 3D finite element analysis

    PubMed Central

    Shurbaji Mozayek, Rami; Allaf, Mirza; B. Abuharb, Mohammad

    2016-01-01

    Background. Long span is seen in many clinical situations. Treatmentplanning options of these cases are difficult and may require FPD, RPD or ISP. Each option has its own disadvantages, including mechanical problems, patient comfort and cost. This article will evaluate the stress distribution of a different treatment option, which consists of adding a single sup-porting implant to the FPD by using 3D finite element analysis. Methods. Three models, each consisting of 5 units, were created as follows: 1. Tooth Pontic Pontic Pontic Tooth; 2. Tooth Pontic Implant Pontic Tooth; 3. Tooth Pontic Pontic Implant Tooth. An axial force was applied to the prostheses by using 3D finite element method and stresses were evaluated. Results. The maximum stress was found in the prostheses in all the models; the highest stress values in all the shared components of the models were almost similar. Stress in implants was lower in the second model than the third one. Conclusion. Adding a supporting implant in long-span FPD has no advantages while it has the disadvantages of complicating treatment and the complications that may occur to the implant and surrounding bone. PMID:27429723

  13. Fish geographic distribution range shifts as recorded in the eastern Mediterranean during the last 5 Ma

    NASA Astrophysics Data System (ADS)

    Agiadi, Konstantina; Karakitsios, Vasileios

    2013-04-01

    Marine fish species geographic distribution is known to reflect the individuals' response to changes in oceanic circulation, temperature, salinity, local geography, other species presence and/or abundance, food availability and other biotic and abiotic factors1. New and published records on the eastern Mediterranean fish, from the end of the Messinian salinity crisis to the present, are here examined, in correlation with palaeoenvironmental data, in order to draw conclusions regarding the abiotic parameters most affecting the fish distribution during the last 5 Ma in this area. This investigation shows that the environmental variables do not affect the fish fauna in a uniform way. Rather, three faunal components may be separated, each occupying a different depth range in the water column. Pelagic fish dwell for the most part on the uppermost 200 m, and their distribution seems to be affected mainly by climatic variability. Mesopelagic fish occupy mostly intermediate depths and their distribution is regulated by the prevailing water circulation patterns. Benthic and benthopelagic fish, which live close or in contact with the sea bottom, are mostly affected by the nature and depth of the substratum. Furthermore, examples from the Ionian2,3 and the Aegean Sea indicate that, during the last 5 Ma, large-scale range shifts, similar to those occurring today, frequently took place in this area. This observation significantly alters previously views on the stability of fish assemblages and the processes occurring today. Acknowledgments. This research has been co-financed by the European Union (European Social Fund - ESF) and Greek national funds through the Operational Program "Education and Lifelong Learning" of the National Strategic Reference Framework (NSRF) - Research Funding Program: Heracleitus II. Investing in knowledge society through the European Social Fund. References 1 Wooton RJ. 1998. Ecology of teleost fishes,Fish and Fisheries Series,24.Kluwers.392p. 2

  14. Matrilineal distribution of louse egg-handling techniques during grooming in free-ranging Japanese macaques.

    PubMed

    Tanaka, I

    1995-10-01

    Grooming behavior of which the primary function appears to be the removal of lice on other (Tanaka and Takefushi [1993] Anthropological Science 101:187-193) was studied in Japanese maceques at Jigokudani Monkey Park, Japan, June 1990-July 1993. Several louse egg-handling techniques used during grooming were identified (with differences in efficiency) in a free-ranging group. In the low-ranking maternal lineages, the distribution of these techniques is quite homogeneous, suggesting social transmission with goal emulation (one form of social learning) based on maternal kin. However, there is considerable variation in the high-ranking matriline. The social system of dominance--the tendency of subordinates to groom more often than to be groomed--may result in oblique transmission of more effective techniques from low-ranking monkeys to some offspring of high-ranking females.

  15. A finite element analysis of stress distribution in the bone, around the implant supporting a mandibular overdenture with ball/o ring and magnetic attachment.

    PubMed

    John, Jins; Rangarajan, V; Savadi, Ravindra C; Satheesh Kumar, K S; Satheesh Kumar, Preeti

    2012-03-01

    Today implant dentistry has made great inroads into the treatment modalities that are available in treating an edentulous patient. Popularity of a two implant retained overdenture has created a necessity to examine the various attachment systems being used and the stresses that are transmitted to the alveolar bone. Hence a Three dimensional Finite Element Analysis was done to analyze the stress distribution in the mandibular bone with implant-supported overdenture having Ball/O-ring and Magnet attachments of different diameters. A segment of the anterior region of the mandible was modeled with implant and the overdenture. Four different models were generated having Ball/O-Ring and Magnet Attachments. Forces of 10 N, 35 N and 70 N were applied from the horizontal, vertical and oblique directions respectively and the stress distribution studied. It was concluded that the greatest stress concentrations were seen at the crest of the cortical bone and could be reduced by using smaller sized attachments for implant supported-overdenture. PMID:23450217

  16. Ion implanted dielectric elastomer circuits

    NASA Astrophysics Data System (ADS)

    O'Brien, Benjamin M.; Rosset, Samuel; Anderson, Iain A.; Shea, Herbert R.

    2013-06-01

    Starfish and octopuses control their infinite degree-of-freedom arms with panache—capabilities typical of nature where the distribution of reflex-like intelligence throughout soft muscular networks greatly outperforms anything hard, heavy, and man-made. Dielectric elastomer actuators show great promise for soft artificial muscle networks. One way to make them smart is with piezo-resistive Dielectric Elastomer Switches (DES) that can be combined with artificial muscles to create arbitrary digital logic circuits. Unfortunately there are currently no reliable materials or fabrication process. Thus devices typically fail within a few thousand cycles. As a first step in the search for better materials we present a preliminary exploration of piezo-resistors made with filtered cathodic vacuum arc metal ion implantation. DES were formed on polydimethylsiloxane silicone membranes out of ion implanted gold nano-clusters. We propose that there are four distinct regimes (high dose, above percolation, on percolation, low dose) in which gold ion implanted piezo-resistors can operate and present experimental results on implanted piezo-resistors switching high voltages as well as a simple artificial muscle inverter. While gold ion implanted DES are limited by high hysteresis and low sensitivity, they already show promise for a range of applications including hysteretic oscillators and soft generators. With improvements to implanter process control the promise of artificial muscle circuitry for soft smart actuator networks could become a reality.

  17. Plasticity in dendroclimatic response across the distribution range of Aleppo pine (Pinus halepensis).

    PubMed

    de Luis, Martin; Čufar, Katarina; Di Filippo, Alfredo; Novak, Klemen; Papadopoulos, Andreas; Piovesan, Gianluca; Rathgeber, Cyrille B K; Raventós, José; Saz, Miguel Angel; Smith, Kevin T

    2013-01-01

    We investigated the variability of the climate-growth relationship of Aleppo pine across its distribution range in the Mediterranean Basin. We constructed a network of tree-ring index chronologies from 63 sites across the region. Correlation function analysis identified the relationships of tree-ring index to climate factors for each site. We also estimated the dominant climatic gradients of the region using principal component analysis of monthly, seasonal, and annual mean temperature and total precipitation from 1,068 climatic gridpoints. Variation in ring width index was primarily related to precipitation and secondarily to temperature. However, we found that the dendroclimatic relationship depended on the position of the site along the climatic gradient. In the southern part of the distribution range, where temperature was generally higher and precipitation lower than the regional average, reduced growth was also associated with warm and dry conditions. In the northern part, where the average temperature was lower and the precipitation more abundant than the regional average, reduced growth was associated with cool conditions. Thus, our study highlights the substantial plasticity of Aleppo pine in response to different climatic conditions. These results do not resolve the source of response variability as being due to either genetic variation in provenance, to phenotypic plasticity, or a combination of factors. However, as current growth responses to inter-annual climate variability vary spatially across existing climate gradients, future climate-growth relationships will also likely be determined by differential adaptation and/or acclimation responses to spatial climatic variation. The contribution of local adaptation and/or phenotypic plasticity across populations to the persistence of species under global warming could be decisive for prediction of climate change impacts across populations. In this sense, a more complex forest dynamics modeling approach that

  18. Plasticity in Dendroclimatic Response across the Distribution Range of Aleppo Pine (Pinus halepensis)

    PubMed Central

    de Luis, Martin; Čufar, Katarina; Di Filippo, Alfredo; Novak, Klemen; Papadopoulos, Andreas; Piovesan, Gianluca; Rathgeber, Cyrille B. K.; Raventós, José; Saz, Miguel Angel; Smith, Kevin T.

    2013-01-01

    We investigated the variability of the climate-growth relationship of Aleppo pine across its distribution range in the Mediterranean Basin. We constructed a network of tree-ring index chronologies from 63 sites across the region. Correlation function analysis identified the relationships of tree-ring index to climate factors for each site. We also estimated the dominant climatic gradients of the region using principal component analysis of monthly, seasonal, and annual mean temperature and total precipitation from 1,068 climatic gridpoints. Variation in ring width index was primarily related to precipitation and secondarily to temperature. However, we found that the dendroclimatic relationship depended on the position of the site along the climatic gradient. In the southern part of the distribution range, where temperature was generally higher and precipitation lower than the regional average, reduced growth was also associated with warm and dry conditions. In the northern part, where the average temperature was lower and the precipitation more abundant than the regional average, reduced growth was associated with cool conditions. Thus, our study highlights the substantial plasticity of Aleppo pine in response to different climatic conditions. These results do not resolve the source of response variability as being due to either genetic variation in provenance, to phenotypic plasticity, or a combination of factors. However, as current growth responses to inter-annual climate variability vary spatially across existing climate gradients, future climate-growth relationships will also likely be determined by differential adaptation and/or acclimation responses to spatial climatic variation. The contribution of local adaptation and/or phenotypic plasticity across populations to the persistence of species under global warming could be decisive for prediction of climate change impacts across populations. In this sense, a more complex forest dynamics modeling approach that

  19. On Road Study of Colorado Front Range Greenhouse Gases Distribution and Sources

    NASA Astrophysics Data System (ADS)

    Petron, G.; Hirsch, A.; Trainer, M. K.; Karion, A.; Kofler, J.; Sweeney, C.; Andrews, A.; Kolodzey, W.; Miller, B. R.; Miller, L.; Montzka, S. A.; Kitzis, D. R.; Patrick, L.; Frost, G. J.; Ryerson, T. B.; Robers, J. M.; Tans, P.

    2008-12-01

    The Global Monitoring Division and Chemical Sciences Division of the NOAA Earth System Research Laboratory have teamed up over the summer 2008 to experiment with a new measurement strategy to characterize greenhouse gases distribution and sources in the Colorado Front Range. Combining expertise in greenhouse gases measurements and in local to regional scales air quality study intensive campaigns, we have built the 'Hybrid Lab'. A continuous CO2 and CH4 cavity ring down spectroscopic analyzer (Picarro, Inc.), a CO gas-filter correlation instrument (Thermo Environmental, Inc.) and a continuous UV absorption ozone monitor (2B Technologies, Inc., model 202SC) have been installed securely onboard a 2006 Toyota Prius Hybrid vehicle with an inlet bringing in outside air from a few meters above the ground. To better characterize point and distributed sources, air samples were taken with a Portable Flask Package (PFP) for later multiple species analysis in the lab. A GPS unit hooked up to the ozone analyzer and another one installed on the PFP kept track of our location allowing us to map measured concentrations on the driving route using Google Earth. The Hybrid Lab went out for several drives in the vicinity of the NOAA Boulder Atmospheric Observatory (BAO) tall tower located in Erie, CO and covering areas from Boulder, Denver, Longmont, Fort Collins and Greeley. Enhancements in CO2, CO and destruction of ozone mainly reflect emissions from traffic. Methane enhancements however are clearly correlated with nearby point sources (landfill, feedlot, natural gas compressor ...) or with larger scale air masses advected from the NE Colorado, where oil and gas drilling operations are widespread. The multiple species analysis (hydrocarbons, CFCs, HFCs) of the air samples collected along the way bring insightful information about the methane sources at play. We will present results of the analysis and interpretation of the Hybrid Lab Front Range Study and conclude with perspectives

  20. Prevalence, host range, and spatial distribution of black band disease in the Maldivian Archipelago.

    PubMed

    Montano, Simone; Strona, Giovanni; Seveso, Davide; Galli, Paolo

    2013-07-01

    Little research has been conducted on diseases affecting reef-building corals in the central Indian Ocean. During 2010 and 2011, we performed a quantitative assessment of black band disease (BBD) in the central Republic of Maldives. Distribution, host range, and prevalence of BBD were investigated at 6 coral islands (Magoodhoo, Adanga, Ihuru, Vabbinfaru, Thudufushi, and Athuruga) belonging to 3 different atolls. BBD was found to be widespread among the atolls. All the islands showed a prevalence lower than 0.5%. Magoodhoo Island showed the highest mean disease prevalence. In the whole surveyed area, shallow sites showed higher overall mean BBD prevalence than deep ones. BBD was recorded from 6 scleractinian families (Acroporidae, Faviidae, Poritidae, Siderastreidae, Agariciidae, Fungiidae) and 13 scleractinian genera. Two of them, Gardineroseris and Sandalolitha, constitute new records for the disease. The siderastreid Psammocora (BBD prevalence: 5.33 ± 1.41%, mean ± SE) was the most affected genus, followed by Goniopora (2.7 ± 1.3%). BBD prevalence was positively correlated to the respective host density in both genera. Favites and Acropora were the less affected genera (both <0.1%). Although we observed an extremely low overall disease prevalence in the surveyed area (<1%), the large number of different scleractinian genera affected and the widespread distribution of BBD indicate a need for further investigation. PMID:23836771

  1. Prevalence, host range, and spatial distribution of black band disease in the Maldivian Archipelago.

    PubMed

    Montano, Simone; Strona, Giovanni; Seveso, Davide; Galli, Paolo

    2013-07-01

    Little research has been conducted on diseases affecting reef-building corals in the central Indian Ocean. During 2010 and 2011, we performed a quantitative assessment of black band disease (BBD) in the central Republic of Maldives. Distribution, host range, and prevalence of BBD were investigated at 6 coral islands (Magoodhoo, Adanga, Ihuru, Vabbinfaru, Thudufushi, and Athuruga) belonging to 3 different atolls. BBD was found to be widespread among the atolls. All the islands showed a prevalence lower than 0.5%. Magoodhoo Island showed the highest mean disease prevalence. In the whole surveyed area, shallow sites showed higher overall mean BBD prevalence than deep ones. BBD was recorded from 6 scleractinian families (Acroporidae, Faviidae, Poritidae, Siderastreidae, Agariciidae, Fungiidae) and 13 scleractinian genera. Two of them, Gardineroseris and Sandalolitha, constitute new records for the disease. The siderastreid Psammocora (BBD prevalence: 5.33 ± 1.41%, mean ± SE) was the most affected genus, followed by Goniopora (2.7 ± 1.3%). BBD prevalence was positively correlated to the respective host density in both genera. Favites and Acropora were the less affected genera (both <0.1%). Although we observed an extremely low overall disease prevalence in the surveyed area (<1%), the large number of different scleractinian genera affected and the widespread distribution of BBD indicate a need for further investigation.

  2. Drift-insensitive distributed calibration of probe microscope scanner in nanometer range: Virtual mode

    NASA Astrophysics Data System (ADS)

    Lapshin, Rostislav V.

    2016-08-01

    A method of distributed calibration of a probe microscope scanner is suggested. The main idea consists in a search for a net of local calibration coefficients (LCCs) in the process of automatic measurement of a standard surface, whereby each point of the movement space of the scanner can be characterized by a unique set of scale factors. Feature-oriented scanning (FOS) methodology is used as a basis for implementation of the distributed calibration permitting to exclude in situ the negative influence of thermal drift, creep and hysteresis on the obtained results. Possessing the calibration database enables correcting in one procedure all the spatial systematic distortions caused by nonlinearity, nonorthogonality and spurious crosstalk couplings of the microscope scanner piezomanipulators. To provide high precision of spatial measurements in nanometer range, the calibration is carried out using natural standards - constants of crystal lattice. One of the useful modes of the developed calibration method is a virtual mode. In the virtual mode, instead of measurement of a real surface of the standard, the calibration program makes a surface image "measurement" of the standard, which was obtained earlier using conventional raster scanning. The application of the virtual mode permits simulation of the calibration process and detail analysis of raster distortions occurring in both conventional and counter surface scanning. Moreover, the mode allows to estimate the thermal drift and the creep velocities acting while surface scanning. Virtual calibration makes possible automatic characterization of a surface by the method of scanning probe microscopy (SPM).

  3. Drift-insensitive distributed calibration of probe microscope scanner in nanometer range: Approach description

    NASA Astrophysics Data System (ADS)

    Lapshin, Rostislav V.

    2015-12-01

    The method of distributed calibration of a probe microscope scanner consists in a search for a net of local calibration coefficients (LCCs) in the process of automatic measurement of a standard surface, whereby each point of the movement space of the scanner can be defined by a unique set of scale factors. Feature-oriented scanning (FOS) methodology is used to implement the distributed calibration, which permits to exclude in situ the negative influence of thermal drift, creep and hysteresis on the obtained results. The sensitivity of LCCs to errors in determination of position coordinates of surface features forming the local calibration structure (LCS) is eliminated by performing multiple repeated measurements followed by building regression surfaces. There are no principle restrictions on the number of repeated LCS measurements. Possessing the calibration database enables correcting in one procedure all the spatial distortions caused by nonlinearity, nonorthogonality and spurious crosstalk couplings of the microscope scanner piezomanipulators. To provide high precision of spatial measurements in nanometer range, the calibration is carried out using natural standards - constants of crystal lattice. The method may be used with any scanning probe instrument.

  4. On measuring depth-dose distribution of range-modulated proton therapy fields

    SciTech Connect

    Lu, H.-M.

    2006-07-15

    Depth-dose profile measurements are frequently performed for the characterization of spread-out Bragg peak treatment fields in proton therapy. The measured distribution often contains a significant amount of noise with a persistent pattern. As a result, substantial smoothing has to be applied which can alter a measurement. We explored the origin of the observed noise by closely examining the sampling process in the scanning algorithm. We will show that the time characteristics of the signal in the range-modulated proton therapy beams differ significantly from those in the photon beams, and as a result the measurement error is very sensitive to the sampling duration. The observed noise results mainly from inappropriate choices for this value, rather than from the dose distribution itself. Increasing the value arbitrarily may actually increase the noise magnitude. We will demonstrate that with an optimal value for the sampling duration and its accurate control, the noise magnitude can be reduced significantly, without increasing the measurement time.

  5. Global inventory, long-range transport and environmental distribution of dicofol.

    PubMed

    Li, Li; Liu, Jianguo; Hu, Jianxin

    2015-01-01

    The uncertainties on whether dicofol can be identified as a persistent organic pollutant (POP) in terms of its long-range transport (LRT) potential and global distribution, are always a controversial topic during international regulation deliberations. The lack of monitoring data in remote background regions necessitates a model-based evaluation approach for assessing the global distribution of dicofol. However, few model simulations are available at present, as there is no inventory available for global historical usage of dicofol that has sufficiently high spatial and temporal resolution. To describe the current status of global emission, we first developed an inventory of global dicofol usage for the period of 2000-2012 at 1° × 1° latitude/longitude resolution. We then assessed the LRT potential of dicofol by calculating its Arctic Contamination Potential using the Globo-POP model. In addition, we simulated the global mass distribution and the fate of dicofol in the environment using the BETR-Global model at 15° × 15° latitude/longitude resolution. Our estimated inventory established that over the period of 13 years, a total of 28.2 kilo tonnes (kt) of dicofol was applied and released into the environment. East and Southeast Asia, the Mediterranean Coast, and Northern and Central America were identified as hotspots of usage and release. Dicofol exhibited a higher Arctic Contamination Potential than several confirmed Arctic contaminants, and a larger current volume of consumption than most existing POPs. The results of our BETR-Global simulation suggest that (i) dicofol can indeed be transported northward, most likely driven by both atmospheric and oceanic advections from source regions at midlatitudes, and (ii) dicofol will be enriched in remote background regions. Continuous use of dicofol in source regions will result in exposure both locally and in remote regions, and the examination of the potential for adverse effects is therefore of paramount

  6. High-speed Imaging of Global Surface Temperature Distributions on Hypersonic Ballistic-Range Projectiles

    NASA Technical Reports Server (NTRS)

    Wilder, Michael C.; Reda, Daniel C.

    2004-01-01

    The NASA-Ames ballistic range provides a unique capability for aerothermodynamic testing of configurations in hypersonic, real-gas, free-flight environments. The facility can closely simulate conditions at any point along practically any trajectory of interest experienced by a spacecraft entering an atmosphere. Sub-scale models of blunt atmospheric entry vehicles are accelerated by a two-stage light-gas gun to speeds as high as 20 times the speed of sound to fly ballistic trajectories through an 24 m long vacuum-rated test section. The test-section pressure (effective altitude), the launch velocity of the model (flight Mach number), and the test-section working gas (planetary atmosphere) are independently variable. The model travels at hypersonic speeds through a quiescent test gas, creating a strong bow-shock wave and real-gas effects that closely match conditions achieved during actual atmospheric entry. The challenge with ballistic range experiments is to obtain quantitative surface measurements from a model traveling at hypersonic speeds. The models are relatively small (less than 3.8 cm in diameter), which limits the spatial resolution possible with surface mounted sensors. Furthermore, since the model is in flight, surface-mounted sensors require some form of on-board telemetry, which must survive the massive acceleration loads experienced during launch (up to 500,000 gravities). Finally, the model and any on-board instrumentation will be destroyed at the terminal wall of the range. For these reasons, optical measurement techniques are the most practical means of acquiring data. High-speed thermal imaging has been employed in the Ames ballistic range to measure global surface temperature distributions and to visualize the onset of transition to turbulent-flow on the forward regions of hypersonic blunt bodies. Both visible wavelength and infrared high-speed cameras are in use. The visible wavelength cameras are intensified CCD imagers capable of integration

  7. A three-dimensional finite element study on the stress distribution pattern of two prosthetic abutments for external hexagon implants

    PubMed Central

    Moreira, Wagner; Hermann, Caio; Pereira, Jucélio Tomás; Balbinoti, Jean Anacleto; Tiossi, Rodrigo

    2013-01-01

    Objective: The purpose of this study was to evaluate the mechanical behavior of two different straight prosthetic abutments (one- and two-piece) for external hex butt-joint connection implants using three-dimensional finite element analysis (3D-FEA). Materials and Methods: Two 3D-FEA models were designed, one for the two-piece prosthetic abutment (2 mm in height, two-piece mini-conical abutment, Neodent) and another one for the one-piece abutment (2 mm in height, Slim Fit one-piece mini-conical abutment, Neodent), with their corresponding screws and implants (Titamax Ti, 3.75 diameter by 13 mm in length, Neodent). The model simulated the single restoration of a lower premolar using data from a computerized tomography of a mandible. The preload (20 N) after torque application for installation of the abutment and an occlusal loading were simulated. The occlusal load was simulated using average physiological bite force and direction (114.6 N in the axial direction, 17.1 N in the lingual direction and 23.4 N toward the mesial at an angle of 75° to the occlusal plan). Results: The regions with the highest von Mises stress results were at the bottom of the initial two threads of both prosthetic abutments that were tested. The one-piece prosthetic abutment presented a more homogeneous behavior of stress distribution when compared with the two-piece abutment. Conclusions: Under the simulated chewing loads, the von Mises stresses for both tested prosthetic-abutments were within the tensile strength values of the materials analyzed which thus supports the clinical use of both prosthetic abutments. PMID:24932125

  8. RANGE AND DISTRIBUTION OF TECHNETIUM KD VALUES IN THE SRS SUBSURFACE ENVIRONMENT

    SciTech Connect

    Kaplan, D

    2008-10-28

    Performance assessments (PAs) are risk calculations used to estimate the amount of low-level radioactive waste that can be disposed at DOE sites. Distribution coefficients (K{sub d} values) are input parameters used in PA calculations to provide a measure of radionuclide sorption to sediment; the greater the K{sub d} value, the greater the sorption and the slower the estimated movement of the radionuclide through sediment. Understanding and quantifying K{sub d} value variability is important for estimating the uncertainty of PA calculations. Without this information, it is necessary to make overly conservative estimates about the possible limits of K{sub d} values, which in turn may increase disposal costs. Finally, technetium is commonly found to be amongst the radionuclides posing potential risk at waste disposal locations because it is believed to be highly mobile in its anionic form (pertechnetate, TcO{sub 4}{sup -}), it exists in relatively high concentrations in SRS waste, and it has a long half-life (213,000 years). The objectives of this laboratory study were to determine under SRS environmental conditions: (1) whether and to what extent TcO{sub 4}{sup -} sorbs to sediments, (2) the range of Tc K{sub d} values, (3) the distribution (normal or log-normal) of Tc K{sub d} values, and (4) how strongly Tc sorbs to SRS sediments through desorption experiments. Objective 3, to identify the Tc K{sub d} distribution is important because it provides a statistical description that influences stochastic modeling of estimated risk. The approach taken was to collect 26 sediments from a non-radioactive containing sediment core collected from E-Area, measure Tc K{sub d} values and then perform statistical analysis to describe the measured Tc K{sub d} values. The mean K{sub d} value was 3.4 {+-} 0.5 mL/g and ranged from -2.9 to 11.2 mL/g. The data did not have a Normal distribution (as defined by the Shapiro-Wilk's Statistic) and had a 95-percentile range of 2.4 to 4.4 m

  9. High-density dental implants and radiotherapy planning: evaluation of effects on dose distribution using pencil beam convolution algorithm and Monte Carlo method.

    PubMed

    Çatli, Serap

    2015-09-08

    High atomic number and density of dental implants leads to major problems at providing an accurate dose distribution in radiotherapy and contouring tumors and organs caused by the artifact in head and neck tumors. The limits and deficiencies of the algorithms using in the treatment planning systems can lead to large errors in dose calculation, and this may adversely affect the patient's treatment. In the present study, four commercial dental implants were used: pure titanium, titanium alloy (Ti-6Al-4V), amalgam, and crown. The effects of dental implants on dose distribution are determined with two methods: pencil beam convolution (PBC) algorithm and Monte Carlo code for 6 MV photon beam. The central axis depth doses were calculated on the phantom for a source-skin distance (SSD) of 100 cm and a 10 × 10 cm2 field using both of algorithms. The results of Monte Carlo method and Eclipse TPS were compared to each other and to those previously reported. In the present study, dose increases in tissue at a distance of 2 mm in front of the dental implants were seen due to the backscatter of electrons for dental implants at 6 MV using the Monte Carlo method. The Eclipse treatment planning system (TPS) couldn't precisely account for the backscatter radiation caused by the dental prostheses. TPS underestimated the back scatter dose and overestimated the dose after the dental implants. The large errors found for TPS in this study are due to the limits and deficiencies of the algorithms. The accuracy of the PBC algorithm of Eclipse TPS was evaluated in comparison to Monte Carlo calculations in consideration of the recommendations of the American Association of Physicists in Medicine Radiation Therapy Committee Task Group 65. From the comparisons of the TPS and Monte Carlo calculations, it is verified that the Monte Carlo simulation is a good approach to derive the dose distribution in heterogeneous media.

  10. Long-range atmospheric transport and the distribution of polycyclic aromatic hydrocarbons in Changbai Mountain.

    PubMed

    Zhao, Xiangai; Kim, Seung-Kyu; Zhu, Weihong; Kannan, Narayanan; Li, Donghao

    2015-01-01

    The Changbai (also known as "Baekdu") Mountain, on the border between China and North Korea, is the highest mountain (2750 m) in northeastern China. Recently, this mountain region has experienced a dramatic increase in air pollution, not only because of increasing volumes of tourism-derived traffic but also because of the long-range transport of polluted westerly winds passing through major industrial and urban cities in the eastern region of China. To assess the relative importance of the two sources of pollution, 16 polycyclic aromatic hydrocarbons (PAHs) as model substances were determined in the mountain soil. A total of 32 soil samples were collected from different sides of the mountain at different latitudes between July and August of 2009. The ∑PAH concentrations were within the range 38.5-190.1 ng g(-1) on the northern side, 117.7-443.6 ng g(-1) on the southern side, and 75.3-437.3 ng g(-1) on the western side. A progressive increase in the level of ∑PAHs with latitude was observed on the southern and western sides that face the westerly wind with abundant precipitation. However, a similar concentration gradient was not observed on the northern side that receives less rain and is on the leeward direction of the wind. The high-molecular-weight PAH compounds were predominant in the soils on the southern and western sides, while low-molecular-weight PAHs dominated the northern side soils. These findings show that the distribution of PAHs in the mountain soil is strongly influenced by the atmospheric long-range transport and cold trapping.

  11. Long-range atmospheric transport and the distribution of polycyclic aromatic hydrocarbons in Changbai Mountain.

    PubMed

    Zhao, Xiangai; Kim, Seung-Kyu; Zhu, Weihong; Kannan, Narayanan; Li, Donghao

    2015-01-01

    The Changbai (also known as "Baekdu") Mountain, on the border between China and North Korea, is the highest mountain (2750 m) in northeastern China. Recently, this mountain region has experienced a dramatic increase in air pollution, not only because of increasing volumes of tourism-derived traffic but also because of the long-range transport of polluted westerly winds passing through major industrial and urban cities in the eastern region of China. To assess the relative importance of the two sources of pollution, 16 polycyclic aromatic hydrocarbons (PAHs) as model substances were determined in the mountain soil. A total of 32 soil samples were collected from different sides of the mountain at different latitudes between July and August of 2009. The ∑PAH concentrations were within the range 38.5-190.1 ng g(-1) on the northern side, 117.7-443.6 ng g(-1) on the southern side, and 75.3-437.3 ng g(-1) on the western side. A progressive increase in the level of ∑PAHs with latitude was observed on the southern and western sides that face the westerly wind with abundant precipitation. However, a similar concentration gradient was not observed on the northern side that receives less rain and is on the leeward direction of the wind. The high-molecular-weight PAH compounds were predominant in the soils on the southern and western sides, while low-molecular-weight PAHs dominated the northern side soils. These findings show that the distribution of PAHs in the mountain soil is strongly influenced by the atmospheric long-range transport and cold trapping. PMID:25036943

  12. LoCoH: Nonparameteric Kernel Methods for Constructing Home Ranges and Utilization Distributions

    PubMed Central

    Getz, Wayne M.; Fortmann-Roe, Scott; Wilmers, Christopher C.

    2007-01-01

    Parametric kernel methods currently dominate the literature regarding the construction of animal home ranges (HRs) and utilization distributions (UDs). These methods frequently fail to capture the kinds of hard boundaries common to many natural systems. Recently a local convex hull (LoCoH) nonparametric kernel method, which generalizes the minimum convex polygon (MCP) method, was shown to be more appropriate than parametric kernel methods for constructing HRs and UDs, because of its ability to identify hard boundaries (e.g., rivers, cliff edges) and convergence to the true distribution as sample size increases. Here we extend the LoCoH in two ways: “fixed sphere-of-influence,” or r-LoCoH (kernels constructed from all points within a fixed radius r of each reference point), and an “adaptive sphere-of-influence,” or a-LoCoH (kernels constructed from all points within a radius a such that the distances of all points within the radius to the reference point sum to a value less than or equal to a), and compare them to the original “fixed-number-of-points,” or k-LoCoH (all kernels constructed from k-1 nearest neighbors of root points). We also compare these nonparametric LoCoH to parametric kernel methods using manufactured data and data collected from GPS collars on African buffalo in the Kruger National Park, South Africa. Our results demonstrate that LoCoH methods are superior to parametric kernel methods in estimating areas used by animals, excluding unused areas (holes) and, generally, in constructing UDs and HRs arising from the movement of animals influenced by hard boundaries and irregular structures (e.g., rocky outcrops). We also demonstrate that a-LoCoH is generally superior to k- and r-LoCoH (with software for all three methods available at http://locoh.cnr.berkeley.edu). PMID:17299587

  13. LoCoH: Non-parameteric kernel methods for constructing home ranges and utilization distributions

    USGS Publications Warehouse

    Getz, Wayne M.; Fortmann-Roe, Scott; Cross, Paul C.; Lyons, Andrew J.; Ryan, Sadie J.; Wilmers, Christopher C.

    2007-01-01

    Parametric kernel methods currently dominate the literature regarding the construction of animal home ranges (HRs) and utilization distributions (UDs). These methods frequently fail to capture the kinds of hard boundaries common to many natural systems. Recently a local convex hull (LoCoH) nonparametric kernel method, which generalizes the minimum convex polygon (MCP) method, was shown to be more appropriate than parametric kernel methods for constructing HRs and UDs, because of its ability to identify hard boundaries (e.g., rivers, cliff edges) and convergence to the true distribution as sample size increases. Here we extend the LoCoH in two ways: ‘‘fixed sphere-of-influence,’’ or r -LoCoH (kernels constructed from all points within a fixed radius r of each reference point), and an ‘‘adaptive sphere-of-influence,’’ or a -LoCoH (kernels constructed from all points within a radius a such that the distances of all points within the radius to the reference point sum to a value less than or equal to a ), and compare them to the original ‘‘fixed-number-of-points,’’ or k -LoCoH (all kernels constructed from k -1 nearest neighbors of root points). We also compare these nonparametric LoCoH to parametric kernel methods using manufactured data and data collected from GPS collars on African buffalo in the Kruger National Park, South Africa. Our results demonstrate that LoCoH methods are superior to parametric kernel methods in estimating areas used by animals, excluding unused areas (holes) and, generally, in constructing UDs and HRs arising from the movement of animals influenced by hard boundaries and irregular structures (e.g., rocky outcrops). We also demonstrate that a -LoCoH is generally superior to k - and r -LoCoH (with software for all three methods available at http://locoh.cnr.berkeley.edu).

  14. LoCoH: nonparameteric kernel methods for constructing home ranges and utilization distributions.

    PubMed

    Getz, Wayne M; Fortmann-Roe, Scott; Cross, Paul C; Lyons, Andrew J; Ryan, Sadie J; Wilmers, Christopher C

    2007-02-14

    Parametric kernel methods currently dominate the literature regarding the construction of animal home ranges (HRs) and utilization distributions (UDs). These methods frequently fail to capture the kinds of hard boundaries common to many natural systems. Recently a local convex hull (LoCoH) nonparametric kernel method, which generalizes the minimum convex polygon (MCP) method, was shown to be more appropriate than parametric kernel methods for constructing HRs and UDs, because of its ability to identify hard boundaries (e.g., rivers, cliff edges) and convergence to the true distribution as sample size increases. Here we extend the LoCoH in two ways: "fixed sphere-of-influence," or r-LoCoH (kernels constructed from all points within a fixed radius r of each reference point), and an "adaptive sphere-of-influence," or a-LoCoH (kernels constructed from all points within a radius a such that the distances of all points within the radius to the reference point sum to a value less than or equal to a), and compare them to the original "fixed-number-of-points," or k-LoCoH (all kernels constructed from k-1 nearest neighbors of root points). We also compare these nonparametric LoCoH to parametric kernel methods using manufactured data and data collected from GPS collars on African buffalo in the Kruger National Park, South Africa. Our results demonstrate that LoCoH methods are superior to parametric kernel methods in estimating areas used by animals, excluding unused areas (holes) and, generally, in constructing UDs and HRs arising from the movement of animals influenced by hard boundaries and irregular structures (e.g., rocky outcrops). We also demonstrate that a-LoCoH is generally superior to k- and r-LoCoH (with software for all three methods available at http://locoh.cnr.berkeley.edu).

  15. Host range, host ecology, and distribution of more than 11800 fish parasite species

    USGS Publications Warehouse

    Strona, Giovanni; Palomares, Maria Lourdes D.; Bailly, Nicholas; Galli, Paolo; Lafferty, Kevin D.

    2013-01-01

    Our data set includes 38 008 fish parasite records (for Acanthocephala, Cestoda, Monogenea, Nematoda, Trematoda) compiled from the scientific literature, Internet databases, and museum collections paired to the corresponding host ecological, biogeographical, and phylogenetic traits (maximum length, growth rate, life span, age at maturity, trophic level, habitat preference, geographical range size, taxonomy). The data focus on host features, because specific parasite traits are not consistently available across records. For this reason, the data set is intended as a flexible resource able to extend the principles of ecological niche modeling to the host–parasite system, providing researchers with the data to model parasite niches based on their distribution in host species and the associated host features. In this sense, the database offers a framework for testing general ecological, biogeographical, and phylogenetic hypotheses based on the identification of hosts as parasite habitat. Potential applications of the data set are, for example, the investigation of species–area relationships or the taxonomic distribution of host-specificity. The provided host–parasite list is that currently used by Fish Parasite Ecology Software Tool (FishPEST, http://purl.oclc.org/fishpest), which is a website that allows researchers to model several aspects of the relationships between fish parasites and their hosts. The database is intended for researchers who wish to have more freedom to analyze the database than currently possible with FishPEST. However, for readers who have not seen FishPEST, we recommend using this as a starting point for interacting with the database.

  16. A statistical approach to modelling permafrost distribution in the European Alps or similar mountain ranges

    NASA Astrophysics Data System (ADS)

    Boeckli, L.; Brenning, A.; Gruber, S.; Noetzli, J.

    2012-01-01

    and PISR. The linear regression achieves a root mean square error (RMSE) of 1.6 °C. The final model combines the two sub-models and accounts for the different scales used for model calibration. The modelling approach provides a theoretical basis for estimating mountain permafrost distribution over larger mountain ranges and can be expanded to more surface types and sub-models than considered, here. The analyses performed with the Alpine data set further provide quantitative insight into larger-area patterns as well as the model coefficients for a later spatial application. The transfer into a map-based product, however, requires further steps such as the definition of offset terms that usually contain a degree of subjectivity.

  17. Contrasting Influences of Geographic Range and Distribution of Populations on Patterns of Genetic Diversity in Two Sympatric Pilbara Acacias

    PubMed Central

    Levy, E.; Byrne, M.; Coates, D. J.; Macdonald, B. M.; McArthur, S.; van Leeuwen, S.

    2016-01-01

    The influence of geographic range on species persistence has long been of interest and there is a need for a better understanding of the genetic consequences for species with restricted distributions, particularly with the increasing rate of global species extinctions. However, the genetic effects of restricted range are often confounded by the impacts of population distribution. We compared chloroplast and nuclear genetic diversity and differentiation in two acacias, the restricted, patchily distributed Acacia atkinsiana and the widespread, semi-continuously distributed A. ancistrocarpa. Lower intra-population diversity and higher differentiation between populations were seen in A. atkinsiana compared to its widespread congener, A. ancistrocarpa. There was little evidence of geographical influences on population genetic structure in A. ancistrocarpa whereas A. atkinsiana exhibited nuclear genetic structure with isolation by distance, differentiation of near-coastal populations from those in the ranges, and differentiation of peripheral populations from those in the centre of the distribution. These results are consistent with expectations of the effect of geographic range and population distribution on genetic diversity, but indicate that distribution of populations rather than geographic range has influenced the observed genetic structure. The contrasting patterns observed here demonstrate that conservation approaches for species management and ecological restoration need to consider the distribution of populations in geographically restricted species. PMID:27768703

  18. Temperature Prediction Model for Bone Drilling Based on Density Distribution and In Vivo Experiments for Minimally Invasive Robotic Cochlear Implantation.

    PubMed

    Feldmann, Arne; Anso, Juan; Bell, Brett; Williamson, Tom; Gavaghan, Kate; Gerber, Nicolas; Rohrbach, Helene; Weber, Stefan; Zysset, Philippe

    2016-05-01

    Surgical robots have been proposed ex vivo to drill precise holes in the temporal bone for minimally invasive cochlear implantation. The main risk of the procedure is damage of the facial nerve due to mechanical interaction or due to temperature elevation during the drilling process. To evaluate the thermal risk of the drilling process, a simplified model is proposed which aims to enable an assessment of risk posed to the facial nerve for a given set of constant process parameters for different mastoid bone densities. The model uses the bone density distribution along the drilling trajectory in the mastoid bone to calculate a time dependent heat production function at the tip of the drill bit. Using a time dependent moving point source Green's function, the heat equation can be solved at a certain point in space so that the resulting temperatures can be calculated over time. The model was calibrated and initially verified with in vivo temperature data. The data was collected in minimally invasive robotic drilling of 12 holes in four different sheep. The sheep were anesthetized and the temperature elevations were measured with a thermocouple which was inserted in a previously drilled hole next to the planned drilling trajectory. Bone density distributions were extracted from pre-operative CT data by averaging Hounsfield values over the drill bit diameter. Post-operative [Formula: see text]CT data was used to verify the drilling accuracy of the trajectories. The comparison of measured and calculated temperatures shows a very good match for both heating and cooling phases. The average prediction error of the maximum temperature was less than 0.7 °C and the average root mean square error was approximately 0.5 °C. To analyze potential thermal damage, the model was used to calculate temperature profiles and cumulative equivalent minutes at 43 °C at a minimal distance to the facial nerve. For the selected drilling parameters, temperature elevation profiles and

  19. Temperature Prediction Model for Bone Drilling Based on Density Distribution and In Vivo Experiments for Minimally Invasive Robotic Cochlear Implantation.

    PubMed

    Feldmann, Arne; Anso, Juan; Bell, Brett; Williamson, Tom; Gavaghan, Kate; Gerber, Nicolas; Rohrbach, Helene; Weber, Stefan; Zysset, Philippe

    2016-05-01

    Surgical robots have been proposed ex vivo to drill precise holes in the temporal bone for minimally invasive cochlear implantation. The main risk of the procedure is damage of the facial nerve due to mechanical interaction or due to temperature elevation during the drilling process. To evaluate the thermal risk of the drilling process, a simplified model is proposed which aims to enable an assessment of risk posed to the facial nerve for a given set of constant process parameters for different mastoid bone densities. The model uses the bone density distribution along the drilling trajectory in the mastoid bone to calculate a time dependent heat production function at the tip of the drill bit. Using a time dependent moving point source Green's function, the heat equation can be solved at a certain point in space so that the resulting temperatures can be calculated over time. The model was calibrated and initially verified with in vivo temperature data. The data was collected in minimally invasive robotic drilling of 12 holes in four different sheep. The sheep were anesthetized and the temperature elevations were measured with a thermocouple which was inserted in a previously drilled hole next to the planned drilling trajectory. Bone density distributions were extracted from pre-operative CT data by averaging Hounsfield values over the drill bit diameter. Post-operative [Formula: see text]CT data was used to verify the drilling accuracy of the trajectories. The comparison of measured and calculated temperatures shows a very good match for both heating and cooling phases. The average prediction error of the maximum temperature was less than 0.7 °C and the average root mean square error was approximately 0.5 °C. To analyze potential thermal damage, the model was used to calculate temperature profiles and cumulative equivalent minutes at 43 °C at a minimal distance to the facial nerve. For the selected drilling parameters, temperature elevation profiles and

  20. Uncertainty analysis of hydrological ensemble forecasts in a distributed model utilising short-range rainfall prediction

    NASA Astrophysics Data System (ADS)

    Xuan, Y.; Cluckie, I. D.; Wang, Y.

    2009-03-01

    Advances in mesoscale numerical weather predication make it possible to provide rainfall forecasts along with many other data fields at increasingly higher spatial resolutions. It is currently possible to incorporate high-resolution NWPs directly into flood forecasting systems in order to obtain an extended lead time. It is recognised, however, that direct application of rainfall outputs from the NWP model can contribute considerable uncertainty to the final river flow forecasts as the uncertainties inherent in the NWP are propagated into hydrological domains and can also be magnified by the scaling process. As the ensemble weather forecast has become operationally available, it is of particular interest to the hydrologist to investigate both the potential and implication of ensemble rainfall inputs to the hydrological modelling systems in terms of uncertainty propagation. In this paper, we employ a distributed hydrological model to analyse the performance of the ensemble flow forecasts based on the ensemble rainfall inputs from a short-range high-resolution mesoscale weather model. The results show that: (1) The hydrological model driven by QPF can produce forecasts comparable with those from a raingauge-driven one; (2) The ensemble hydrological forecast is able to disseminate abundant information with regard to the nature of the weather system and the confidence of the forecast itself; and (3) the uncertainties as well as systematic biases are sometimes significant and, as such, extra effort needs to be made to improve the quality of such a system.

  1. Uncertainty analysis of hydrological ensemble forecasts in a distributed model utilising short-range rainfall prediction

    NASA Astrophysics Data System (ADS)

    Cluckie, I. D.; Xuan, Y.; Wang, Y.

    2006-10-01

    Advances in meso-scale numerical weather predication make it possible to provide rainfall forecasts along with many other data fields at increasingly higher spatial resolutions. It is currently possible to incorporate high-resolution NWPs directly into flood forecasting systems in order to obtain an extended lead time. It is recognised, however, that direct application of rainfall outputs from the NWP model can contribute considerable uncertainty to the final river flow forecasts as the uncertainties inherent in the NWP are propagated into hydrological domains and can also be magnified by the scaling process. As the ensemble weather forecast has become operationally available, it is of particular interest to the hydrologist to investigate both the potential and implication of ensemble rainfall inputs to the hydrological modelling systems in terms of uncertainty propagation. In this paper, we employ a distributed hydrological model to analyse the performance of the ensemble flow forecasts based on the ensemble rainfall inputs from a short-range high-resolution mesoscale weather model. The results show that: (1) The hydrological model driven by QPF can produce forecasts comparable with those from a raingauge-driven one; (2) The ensemble hydrological forecast is able to disseminate abundant information with regard to the nature of the weather system and the confidence of the forecast itself; and (3) the uncertainties as well as systematic biases are sometimes significant and, as such, extra effort needs to be made to improve the quality of such a system.

  2. Distribution of lead in biotic and abiotic media associated with a military shooting range

    SciTech Connect

    Petroff, D.M.; Mahoney, L.A.; Pintenich, J.L.

    1995-12-31

    A comprehensive investigation was conducted at a military shooting range to characterize the distribution and potential toxicity of lead from shot deposited at the site over many years. Site biota (vegetation and small mammals), soils, surface water, and groundwater were collected and analyzed for total lead concentrations. Acute terrestrial and acute and chronic aquatic toxicity tests were performed on site soils and water samples, respectively. Results of the investigation indicated that surface water was not impacted by lead. Lead was detected in groundwater in concentrations up to 159 {micro}g/L, and was shown to cause chronic toxicity effects in test organisms. Site soils had lead concentrations up to 31,000 mg/kg, and lead was found above background in the deepest soil samples collected (12 to 24 inches). Toxicity was noted in the majority of soil samples analyzed. Lead was also detected in site vegetation (foliar portions) at levels above background, and in small mammals, but at fairly low concentrations (up to 4 mg/kg). As a relative indicator of the degree of transfer of lead between the site media evaluated, a series of concentration ratios were calculated. As a result, the ranking of the transfer of lead between site media appeared to be (in descending order): (1) surficial soil to roots; (2) surficial soil to subsurface soil; (3) vegetation (foliar) to mammals; (4) roots to vegetation (foliar); (5) surficial soil to vegetation (foliar); (6) surficial soil to mammals; and (7) subsurface soil to groundwater.

  3. Quantifying the spatial distribution of rapid exhumation from glacial detritus, St. Elias Range (Alaska)

    NASA Astrophysics Data System (ADS)

    Grabowski, D.; Enkelmann, E.; Ehlers, T. A.

    2012-04-01

    We present a provenance analysis, zircon (U-Th)/He thermochronometer cooling ages, and petrologic characterization of exhumation processes active under the Malaspina Glacier, St. Elias Range, Alaska. The collision of the Yakutat Terrane with North America formed the St. Elias Range in southeast Alaska. This region is subject to active faulting, high seismicity, and intense glacial erosion. Recent thermochronology studies document rapid rock exhumation at the Yakutat corner where strike-slip deformation transitions to convergence. Published detrital zircon fission track ages from sand samples of the Seward - Malaspina Glacier yielded a young age population of 2 Ma, suggesting a region of rapid exhumation somewhere in the glacier drainage basin. However, the glaciers cover the area and prevent direct observation and sampling, thereby inhibiting detailed bedrock exhumation studies of the Yakutat corner region. We investigate the lithologies of the bedrock at the Yakutat corner to quantify patterns of rock exhumation using clasts collected from the toe of the Malaspina Glacier. Seven different locations 50 km around the glacier were sampled and lithologies characterized by point counting in the field. In total, 1998 clasts were analyzed. We identified six main lithological groups that are assignable to specific geological units. Most of the detritus is gneiss and granulite (26%), micashist and phyllite (26%), and granite (11%) and are typical lithologies of the Chugach Terrane located at the southern margin of the North American plate. Mafic rocks of amphibolite, gabbro, and basalts (21%), and metapelite, sandstone, quartzite and breccia (14%) were also present and are typical for the colliding Yakutat Terrane. Two percent of the clasts are tightly foliated and mylonitic. These clasts are inferred to originate from the Contact Fault, an old suture zone that has been reactivated during Yakutat Terrane collision. Individual clasts from each sample locality and from all

  4. Population variation and natural selection on leaf traits in cork oak throughout its distribution range

    NASA Astrophysics Data System (ADS)

    Ramírez-Valiente, José Alberto; Valladares, Fernando; Sánchez-Gómez, David; Delgado, Antonio; Aranda, Ismael

    2014-07-01

    A central issue in evolutionary biology is the exploration of functional trait variation among populations and the extent to which this variation has adaptive value. It was recently proposed that specific leaf area (SLA), leaf nitrogen concentration per mass (Nmass) and water use efficiency in cork oak play an important role in adaptation to water availability in the environment. In order to investigate this hypothesis, we explored, first, whether there was population-level variation in cork oak (Quercus suber) for these functional traits throughout its distribution range; if this were the case, it would be consistent with the hypothesis that different rainfall patterns have led to ecotypic differentiation in this species. Second, we studied whether the population-level variation matched short-term selection on these traits under different water availability conditions using two fitness components: survival and growth. We found high population-level differentiation in SLA and Nmass, with populations from dry places exhibiting the lowest values for SLA and Nmass. Likewise, reduced SLA had fitness benefits in terms of growth for plants under dry conditions. However, contrary to our expectations, we did not find any pattern of association between functional traits and survival in nine-year-old saplings despite considerable drought during one year of the study period. These results together with findings from the literature suggest that early stages of development are the most critical period for this species. Most importantly, these findings suggest that cork oak saplings have a considerable potential to cope with dry conditions. This capacity to withstand aridity has important implications for conservation of cork oak woodlands under the ongoing climate change.

  5. Food resources, distribution and seasonal variations in ranging in lion-tailed macaques, Macaca silenus in the Western Ghats, India.

    PubMed

    Erinjery, Joseph J; Kavana, T S; Singh, Mewa

    2015-01-01

    The distribution and availability of food was examined to see how it influenced ranging patterns and sleeping site selection in a group of lion-tailed macaques. The home range and core area were 130.48 ha (95% kernel) and 26.68 ha (50% kernel) respectively. The lion-tailed macaques had a longer day range, had a greater number of sleeping sites and used more core areas in the summer as compared to the monsoon and the post-monsoon seasons. The ranging patterns and sleeping site use were influenced by the major food resources used in a particular season. The ranging was mainly influenced by Artocarpus heterophyllus in monsoon, Cullenia exarillata and Toona ciliata in post- monsoon, and Artocarpus heterophyllus and Ficus amplissima in summer. The distribution of these four plant species is, therefore, critical to ranging, and thus to conservation of the lion-tailed macaque. PMID:25217980

  6. Food resources, distribution and seasonal variations in ranging in lion-tailed macaques, Macaca silenus in the Western Ghats, India.

    PubMed

    Erinjery, Joseph J; Kavana, T S; Singh, Mewa

    2015-01-01

    The distribution and availability of food was examined to see how it influenced ranging patterns and sleeping site selection in a group of lion-tailed macaques. The home range and core area were 130.48 ha (95% kernel) and 26.68 ha (50% kernel) respectively. The lion-tailed macaques had a longer day range, had a greater number of sleeping sites and used more core areas in the summer as compared to the monsoon and the post-monsoon seasons. The ranging patterns and sleeping site use were influenced by the major food resources used in a particular season. The ranging was mainly influenced by Artocarpus heterophyllus in monsoon, Cullenia exarillata and Toona ciliata in post- monsoon, and Artocarpus heterophyllus and Ficus amplissima in summer. The distribution of these four plant species is, therefore, critical to ranging, and thus to conservation of the lion-tailed macaque.

  7. Comparison of the Effect of Three Abutment-implant Connections on Stress Distribution at the Internal Surface of Dental Implants: A Finite Element Analysis

    PubMed Central

    Raoofi, Saeed; Khademi, Maryam; Amid, Reza; Kadkhodazadeh, Mahdi; Movahhedi, Mohammad Reza

    2013-01-01

    Background and aims. The aim of this study was to determine the stress patterns within an implant and the effect of different types of connections on load transfer. Materials and methods. Three different types of implant-abutment connections were selected for this study. Sample A: 1.5-mm deep internal hex corresponding to a lead-in bevel; sample B: a tri-channel internal connection; and sample C: in-ternal Morse taper with 110 degrees of tapering and 6 anti-rotational grooves. Four types of loading conditions were simu-lated in a finite element model, with the maximum von Mises stress set as output variables. Results. The maximum stress concentration at the inner surface of the fixtures was higher than the stress value in bone in all of the samples. Stress values in sample B were the lowest amongst all of the models. Any alterations in the amount and direction of the 100-N axial load resulted in an increase in fixture surfaces stress. Overall, the highest amount of stress (112 MPa) was detected in sample C at the inner surface of the fixture under a non-axial load of 300 N. Conclusion. Stress concentration decreased when the internal surface area increased. Creating three or six stops in the internal surface of the fixtures resulted in a decrease in stress. PMID:24082983

  8. Distributional changes and range predictions of downy brome (Bromus tectorum) in Rocky Mountain National Park

    USGS Publications Warehouse

    Bromberg, J.E.; Kumar, S.; Brown, C.S.; Stohlgren, T.J.

    2011-01-01

    Downy brome (Bromus tectorum L.), an invasive winter annual grass, may be increasing in extent and abundance at high elevations in the western United States. This would pose a great threat to high-elevation plant communities and resources. However, data to track this species in high-elevation environments are limited. To address changes in the distribution and abundance of downy brome and the factors most associated with its occurrence, we used field sampling and statistical methods, and niche modeling. In 2007, we resampled plots from two vegetation surveys in Rocky Mountain National Park for presence and cover of downy brome. One survey was established in 1993 and had been resampled in 1999. The other survey was established in 1996 and had not been resampled until our study. Although not all comparisons between years demonstrated significant changes in downy brome abundance, its mean cover increased nearly fivefold from 1993 (0.7%) to 2007 (3.6%) in one of the two vegetation surveys (P = 0.06). Although the average cover of downy brome within the second survey appeared to be increasing from 1996 to 2007, this slight change from 0.5% to 1.2% was not statistically significant (P = 0.24). Downy brome was present in 50% more plots in 1999 than in 1993 (P = 0.02) in the first survey. In the second survey, downy brome was present in 30% more plots in 2007 than in 1996 (P = 0.08). Maxent, a species-environmental matching model, was generally able to predict occurrences of downy brome, as new locations were in the ranges predicted by earlier generated models. The model found that distance to roads, elevation, and vegetation community influenced the predictions most. The strong response of downy brome to interannual environmental variability makes detecting change challenging, especially with small sample sizes. However, our results suggest that the area in which downy brome occurs is likely increasing in Rocky Mountain National Park through increased frequency and cover

  9. Mapping the strain distribution on the proximal femur with titanium and flexible-stemmed implants using digital image correlation.

    PubMed

    Tayton, E; Evans, S; O'Doherty, D

    2010-08-01

    We implanted titanium and carbon fibre-reinforced plastic (CFRP) femoral prostheses of the same dimensions into five prosthetic femora. An abductor jig was attached and a 1 kN load applied. This was repeated with five control femora. Digital image correlation was used to give a detailed two-dimensional strain map of the medial cortex of the proximal femur. Both implants caused stress shielding around the calcar. Distally, the titanium implant showed stress shielding, whereas the CFRP prosthesis did not produce a strain pattern which was statistically different from the controls. There was a reduction in strain beyond the tip of both the implants. This investigation indicates that use of the CFRP stem should avoid stress shielding in total hip replacement.

  10. Cochlear Implants.

    ERIC Educational Resources Information Center

    Clark, Catherine; Scott, Larry

    This brochure explains what a cochlear implant is, lists the types of individuals with deafness who may be helped by a cochlear implant, describes the process of evaluating people for cochlear implants, discusses the surgical process for implanting the aid, traces the path of sound through the cochlear implant to the brain, notes the costs of…

  11. Small range and distinct distribution in a satellite breeding colony of the critically endangered Waved Albatross

    EPA Science Inventory

    To determine the proximate consequences of the limited breeding distribution of the critically endangered Waved Albatross (Phoebastria irrorata), we present continuous breeding season GPS tracks highlighting differences in behaviour, destinations, and distances travelled between ...

  12. Experimental determination of particle range and dose distribution in thick targets through fragmentation reactions of stable heavy ions.

    PubMed

    Inaniwa, Taku; Kohno, Toshiyuki; Tomitani, Takehiro; Urakabe, Eriko; Sato, Shinji; Kanazawa, Mitsutaka; Kanai, Tatsuaki

    2006-09-01

    In radiation therapy with highly energetic heavy ions, the conformal irradiation of a tumour can be achieved by using their advantageous features such as the good dose localization and the high relative biological effectiveness around their mean range. For effective utilization of such properties, it is necessary to evaluate the range of incident ions and the deposited dose distribution in a patient's body. Several methods have been proposed to derive such physical quantities; one of them uses positron emitters generated through projectile fragmentation reactions of incident ions with target nuclei. We have proposed the application of the maximum likelihood estimation (MLE) method to a detected annihilation gamma-ray distribution for determination of the range of incident ions in a target and we have demonstrated the effectiveness of the method with computer simulations. In this paper, a water, a polyethylene and a polymethyl methacrylate target were each irradiated with stable (12)C, (14)N, (16)O and (20)Ne beams. Except for a few combinations of incident beams and targets, the MLE method could determine the range of incident ions R(MLE) with a difference between R(MLE) and the experimental range of less than 2.0 mm under the circumstance that the measurement of annihilation gamma rays was started just after the irradiation of 61.4 s and lasted for 500 s. In the process of evaluating the range of incident ions with the MLE method, we must calculate many physical quantities such as the fluence and the energy of both primary ions and fragments as a function of depth in a target. Consequently, by using them we can obtain the dose distribution. Thus, when the mean range of incident ions is determined with the MLE method, the annihilation gamma-ray distribution and the deposited dose distribution can be derived simultaneously. The derived dose distributions in water for the mono-energetic heavy-ion beams of four species were compared with those measured with an

  13. Vacancy-related defects in n-type Si implanted with a rarefied microbeam of accelerated heavy ions in the MeV range

    NASA Astrophysics Data System (ADS)

    Capan, I.; Pastuović, Ž.; Siegele, R.; Jaćimović, R.

    2016-04-01

    Deep level transient spectroscopy (DLTS) has been used to study vacancy-related defects formed in bulk n-type Czochralski-grown silicon after implantation of accelerated heavy ions: 6.5 MeV O, 10.5 MeV Si, 10.5 MeV Ge, and 11 MeV Er in the single ion regime with fluences from 109 cm-2 to 1010 cm-2 and a direct comparison made with defects formed in the same material irradiated with 0.7 MeV fast neutron fluences up to 1012 cm-2. A scanning ion microprobe was used as the ion implantation tool of n-Cz:Si samples prepared as Schottky diodes, while the ion beam induced current (IBIC) technique was utilized for direct ion counting. The single acceptor state of the divacancy V2(-/0) is the most prominent defect state observed in DLTS spectra of n-CZ:Si samples implanted by selected ions and the sample irradiated by neutrons. The complete suppression of the DLTS signal related to the double acceptor state of divacancy, V2(=/-) has been observed in all samples irradiated by ions and neutrons. Moreover, the DLTS peak associated with formation of the vacancy-oxygen complex VO in the neutron irradiated sample was also completely suppressed in DLTS spectra of samples implanted with the raster scanned ion microbeam. The reason for such behaviour is twofold, (i) the local depletion of the carrier concentration in the highly disordered regions, and (ii) the effect of the microprobe-assisted single ion implantation. The activation energy for electron emission for states assigned to the V2(-/0) defect formed in samples implanted by single ions follows the Meyer-Neldel rule. An increase of the activation energy is strongly correlated with increasing ion mass.

  14. Distribution of late Cenozoic volcanic vents in the Cascade Range: volcanic arc segmentation and regional tectonic considerations ( USA).

    USGS Publications Warehouse

    Guffanti, M.; Weaver, C.S.

    1988-01-01

    Spatial, temporal, and compositional distributions of c4000 volcanic vents formed since 16 Ma in Washington, Oregon, N California, and NW Nevada illustrate the evolution of volcanism related to subduction of the Juan de Fuca plate system and extension of the Basin and Range province. Vent data were obtained from published map compilations and include monogenetic and small polygenetic volcanoes in addition to major composite centers. On the basis of the distribution of 2821 vents formed since 5 Ma, the Cascade Range is divided into 5 segments, with vents of the High Lava Plains along the northern margin of the Basin and Range province in Oregon forming a sixth segment. Some aspects of the Cascade Range segmentation can be related to gross structural features of the subducting Juan de Fuca plate.-from Authors

  15. Distribution of Steps with Finite-Range Interactions: Analytic Approximations and Numerical Results

    NASA Astrophysics Data System (ADS)

    GonzáLez, Diego Luis; Jaramillo, Diego Felipe; TéLlez, Gabriel; Einstein, T. L.

    2013-03-01

    While most Monte Carlo simulations assume only nearest-neighbor steps interact elastically, most analytic frameworks (especially the generalized Wigner distribution) posit that each step elastically repels all others. In addition to the elastic repulsions, we allow for possible surface-state-mediated interactions. We investigate analytically and numerically how next-nearest neighbor (NNN) interactions and, more generally, interactions out to q'th nearest neighbor alter the form of the terrace-width distribution and of pair correlation functions (i.e. the sum over n'th neighbor distribution functions, which we investigated recently.[2] For physically plausible interactions, we find modest changes when NNN interactions are included and generally negligible changes when more distant interactions are allowed. We discuss methods for extracting from simulated experimental data the characteristic scale-setting terms in assumed potential forms.

  16. Damage accumulation in neon implanted silicon

    SciTech Connect

    Oliviero, E.; Peripolli, S.; Amaral, L.; Fichtner, P. F. P.; Beaufort, M. F.; Barbot, J. F.; Donnelly, S. E.

    2006-08-15

    Damage accumulation in neon-implanted silicon with fluences ranging from 5x10{sup 14} to 5x10{sup 16} Ne cm{sup -2} has been studied in detail. As-implanted and annealed samples were investigated by Rutherford backscattering spectrometry under channeling conditions and by transmission electron microscopy in order to quantify and characterize the lattice damage. Wavelength dispersive spectrometry was used to obtain the relative neon content stored in the matrix. Implantation at room temperature leads to the amorphization of the silicon while a high density of nanosized bubbles is observed all along the ion distribution, forming a uniform and continuous layer for implantation temperatures higher than 250 deg.C. Clusters of interstitial defects are also present in the deeper part of the layer corresponding to the end of range of ions. After annealing, the samples implanted at temperatures below 250 deg.C present a polycrystalline structure with blisters at the surface while in the other samples coarsening of bubbles occurs and nanocavities are formed together with extended defects identified as (311) defects. The results are discussed in comparison to the case of helium-implanted silicon and in the light of radiation-enhanced diffusion.

  17. Dental Implants

    MedlinePlus

    ... Procedures Dental Implants Dentures Direct Bonding Implants versus Bridges Orthodontics and Aligners Periodontal Plastic Surgery Porcelain Crowns Porcelain Fixed Bridges Porcelain Veneers Repairing Chipped Teeth Teeth Whitening Tooth- ...

  18. Reaction mechanisms in the system {sup 20}Ne+{sup 165}Ho: Measurement and analysis of forward recoil range distributions

    SciTech Connect

    Singh, D.; Ali, R.; Ansari, M. Afzal; Rashid, M. H.; Guin, R.; Das, S. K.

    2009-05-15

    Keeping in view the study of complete and incomplete fusion of heavy ions with a target, the forward recoil range distributions of several evaporation residues produced at 164 MeV {sup 20}Ne-ion beam energy have been measured for the system {sup 20}Ne+{sup 165}Ho. The recoil catcher activation technique followed by off-line gamma spectroscopy has been employed. Measured forward recoil range distributions of these evaporation residues show evidence of several incomplete fusion channels in addition to complete fusion. The entire and partial linear momentum transfers inferred from these recoil range distributions were used to identify the evaporation residues formed by complete and incomplete fusion mechanisms. The results indicate the occurrence of incomplete fusion involving the breakup of {sup 20}Ne into {sup 4}He+{sup 16}O and/or {sup 8}Be+{sup 12}C followed by fusion of one of the fragments with target nucleus {sup 165}Ho. Complete and incomplete fusion reaction channels have been identified in the production of various evaporation residues and an attempt has been made to separate out relative contributions of complete and incomplete fusion components from the analysis of the measured recoil range distribution data. The total contribution of complete and incomplete fusion channels has also been estimated.

  19. Nanotechnology and dental implants.

    PubMed

    Lavenus, Sandrine; Louarn, Guy; Layrolle, Pierre

    2010-01-01

    The long-term clinical success of dental implants is related to their early osseointegration. This paper reviews the different steps of the interactions between biological fluids, cells, tissues, and surfaces of implants. Immediately following implantation, implants are in contact with proteins and platelets from blood. The differentiation of mesenchymal stem cells will then condition the peri-implant tissue healing. Direct bone-to-implant contact is desired for a biomechanical anchoring of implants to bone rather than fibrous tissue encapsulation. Surfaces properties such as chemistry and roughness play a determinant role in these biological interactions. Physicochemical features in the nanometer range may ultimately control the adsorption of proteins as well as the adhesion and differentiation of cells. Nanotechnologies are increasingly used for surface modifications of dental implants. Another approach to enhance osseointegration is the application of thin calcium phosphate (CaP) coatings. Bioactive CaP nanocrystals deposited on titanium implants are resorbable and stimulate bone apposition and healing. Future nanometer-controlled surfaces may ultimately direct the nature of peri-implant tissues and improve their clinical success rate.

  20. Nanotechnology and Dental Implants

    PubMed Central

    Lavenus, Sandrine; Louarn, Guy; Layrolle, Pierre

    2010-01-01

    The long-term clinical success of dental implants is related to their early osseointegration. This paper reviews the different steps of the interactions between biological fluids, cells, tissues, and surfaces of implants. Immediately following implantation, implants are in contact with proteins and platelets from blood. The differentiation of mesenchymal stem cells will then condition the peri-implant tissue healing. Direct bone-to-implant contact is desired for a biomechanical anchoring of implants to bone rather than fibrous tissue encapsulation. Surfaces properties such as chemistry and roughness play a determinant role in these biological interactions. Physicochemical features in the nanometer range may ultimately control the adsorption of proteins as well as the adhesion and differentiation of cells. Nanotechnologies are increasingly used for surface modifications of dental implants. Another approach to enhance osseointegration is the application of thin calcium phosphate (CaP) coatings. Bioactive CaP nanocrystals deposited on titanium implants are resorbable and stimulate bone apposition and healing. Future nanometer-controlled surfaces may ultimately direct the nature of peri-implant tissues and improve their clinical success rate. PMID:21253543

  1. Climate change may alter breeding ground distributions of eastern migratory monarchs (Danaus plexippus) via range expansion of Asclepias host plants.

    PubMed

    Lemoine, Nathan P

    2015-01-01

    Climate change can profoundly alter species' distributions due to changes in temperature, precipitation, or seasonality. Migratory monarch butterflies (Danaus plexippus) may be particularly susceptible to climate-driven changes in host plant abundance or reduced overwintering habitat. For example, climate change may significantly reduce the availability of overwintering habitat by restricting the amount of area with suitable microclimate conditions. However, potential effects of climate change on monarch northward migrations remain largely unknown, particularly with respect to their milkweed (Asclepias spp.) host plants. Given that monarchs largely depend on the genus Asclepias as larval host plants, the effects of climate change on monarch northward migrations will most likely be mediated by climate change effects on Asclepias. Here, I used MaxEnt species distribution modeling to assess potential changes in Asclepias and monarch distributions under moderate and severe climate change scenarios. First, Asclepias distributions were projected to extend northward throughout much of Canada despite considerable variability in the environmental drivers of each individual species. Second, Asclepias distributions were an important predictor of current monarch distributions, indicating that monarchs may be constrained as much by the availability of Asclepias host plants as environmental variables per se. Accordingly, modeling future distributions of monarchs, and indeed any tightly coupled plant-insect system, should incorporate the effects of climate change on host plant distributions. Finally, MaxEnt predictions of Asclepias and monarch distributions were remarkably consistent among general circulation models. Nearly all models predicted that the current monarch summer breeding range will become slightly less suitable for Asclepias and monarchs in the future. Asclepias, and consequently monarchs, should therefore undergo expanded northern range limits in summer months

  2. Climate change may alter breeding ground distributions of eastern migratory monarchs (Danaus plexippus) via range expansion of Asclepias host plants.

    PubMed

    Lemoine, Nathan P

    2015-01-01

    Climate change can profoundly alter species' distributions due to changes in temperature, precipitation, or seasonality. Migratory monarch butterflies (Danaus plexippus) may be particularly susceptible to climate-driven changes in host plant abundance or reduced overwintering habitat. For example, climate change may significantly reduce the availability of overwintering habitat by restricting the amount of area with suitable microclimate conditions. However, potential effects of climate change on monarch northward migrations remain largely unknown, particularly with respect to their milkweed (Asclepias spp.) host plants. Given that monarchs largely depend on the genus Asclepias as larval host plants, the effects of climate change on monarch northward migrations will most likely be mediated by climate change effects on Asclepias. Here, I used MaxEnt species distribution modeling to assess potential changes in Asclepias and monarch distributions under moderate and severe climate change scenarios. First, Asclepias distributions were projected to extend northward throughout much of Canada despite considerable variability in the environmental drivers of each individual species. Second, Asclepias distributions were an important predictor of current monarch distributions, indicating that monarchs may be constrained as much by the availability of Asclepias host plants as environmental variables per se. Accordingly, modeling future distributions of monarchs, and indeed any tightly coupled plant-insect system, should incorporate the effects of climate change on host plant distributions. Finally, MaxEnt predictions of Asclepias and monarch distributions were remarkably consistent among general circulation models. Nearly all models predicted that the current monarch summer breeding range will become slightly less suitable for Asclepias and monarchs in the future. Asclepias, and consequently monarchs, should therefore undergo expanded northern range limits in summer months

  3. Stress distribution in bone: single-unit implant prostheses veneered with porcelain or a new composite material.

    PubMed

    Juodzbalys, Gintaras; Kubilius, Ricardas; Eidukynas, Valdas; Raustia, Aune M

    2005-06-01

    The purpose of this study was to simulate dynamic and static occlusal loading on one unit fixed, implant-supported prostheses veneered with porcelain and with GRADIA in a 3-dimensional finite element model of the human mandible to analyze and compare the resultant stresses in the superstructures and in the supporting bone. Calculation and visualization of stress, deformation, and displacement of complex structures under simulated forces were evaluated by finite element analysis (FEA) using ANSYS. The device employed was from the OSTEOFIX Dental Implant System (Oulu, Finland), and the veneering materials used were standard dental porcelain and GC GRADIA (Tokyo, Japan), a new composite material. Two different loading conditions were considered: static and transitional or impact, each delivered in three different directions: horizontal (Fh) at 0 degrees , vertical (Fv) at 90 degrees , and oblique (Fo) at 120 degrees . The proportion of the force: magnitude was fh:fv:fo = 1:3.5:7. A vertical load of 500 N, a horizontal load of 143 N, and an oblique load of 1000 N were applied. The results showed that the highest stresses in the bone-implant interface occurred in the region of cortical bone adjacent to the first thread of implants in all models and varied within 6.5%. Maximum stresses and displacements were higher (7%) in those models with statically loaded implants as compared with those that had been dynamically loading. The direction of loading played a major role in determining stress levels and they varied at up to 85%. It was shown that with dynamic loads, the peak of 1.568 mm was registered in the model with the GRADIA veneering material. This displacement was 6.5% higher than that found with the Vita VMK 68 veneers. These results suggest that the implant superstructure-fixed single crown veneering materials-porcelain and GRADIA played minor influences to the displacements and stresses in the implant supported bone with a 1% variance. One of the reasons for this

  4. Modeling of long-range memory processes with inverse cubic distributions by the nonlinear stochastic differential equations

    NASA Astrophysics Data System (ADS)

    Kaulakys, B.; Alaburda, M.; Ruseckas, J.

    2016-05-01

    A well-known fact in the financial markets is the so-called ‘inverse cubic law’ of the cumulative distributions of the long-range memory fluctuations of market indicators such as a number of events of trades, trading volume and the logarithmic price change. We propose the nonlinear stochastic differential equation (SDE) giving both the power-law behavior of the power spectral density and the long-range dependent inverse cubic law of the cumulative distribution. This is achieved using the suggestion that when the market evolves from calm to violent behavior there is a decrease of the delay time of multiplicative feedback of the system in comparison to the driving noise correlation time. This results in a transition from the Itô to the Stratonovich sense of the SDE and yields a long-range memory process.

  5. Surgeons' knowledge about the costs of orthopaedic implants.

    PubMed

    Rohman, Lebur; Hadi, Saifullah; Whitwell, George

    2014-08-01

    PURPOSE. To investigate consultant surgeons' knowledge about the costs of implants for various joint surgeries. METHODS. Questionnaires were distributed to consultant orthopaedic surgeons at 2 hospitals. Respondents were asked to estimate the implant costs of any brand for low-demand and high-demand total hip replacement (THR), total knee replacement (TKR), uni-compartmental knee replacement, arthroscopy shaver blade, total anterior cruciate ligament (ACL) fixation, and meniscal repair. The actual cost of each implant was obtained from the manufacturer. RESULTS. 16 consultant surgeons completed the questionnaires. The respective mean estimated and actual costs for a low-demand THR implant were £1714 (range, £600-3000) and £1448 (range, £985- 2335), with an overestimation of 18.4%. The respective costs for a high-demand THR implant were £2172 (range, £600-6000) and £1737 (range, £1192-2335), with an overestimation of 25%. The respective costs for a TKR implant were £1550 (range, £600-6000) and £1316 (range, £995-1535), with an overestimation of 17.8%. The respective costs for a uni-compartmental knee replacement implant were £1040 (range, £600-2000) and £1296 (range, £698-1470), with an underestimation of 19.7%. The respective costs for an arthroscopy shaver blade were £110 (range, £75-150) and £94 (range, £80-100), with an overestimation of 16.6%. The respective costs for a total ACL fixation implant were £246 (range, £80-500) and £306 (range, £272-335), with an underestimation of 19.4%. The respective costs for a meniscal repair implant were £153 (range, £50-250) and £242 (range, £170-260), with an underestimation of 37%. CONCLUSION. The knowledge among consultant orthopaedic surgeons about implant costs was poor. To reduce implant costs, cooperation between surgeons and hospital managers and measures to increase surgeons' awareness about cost-reduction programmes are needed. PMID:25163960

  6. Implementation of a long range, distributed-volume, continuously variable turbulence generator.

    PubMed

    DiComo, Gregory; Helle, Michael; Peñano, Joe; Ting, Antonio; Schmitt-Sody, Andreas; Elle, Jennifer

    2016-07-01

    We have constructed a 180-m-long distributed, continuously variable atmospheric turbulence generator to study high-power laser beam propagation. This turbulence generator operates on the principle of free convection from a heated surface placed below the entire propagation path of the beam, similar to the situation in long-distance horizontal propagation for laser communications, power beaming, or directed energy applications. The turbulence produced by this generator has been characterized through constant-temperature anemometry, as well as by the scintillation of a low-power laser beam. PMID:27409209

  7. Implementation of a long range, distributed-volume, continuously variable turbulence generator.

    PubMed

    DiComo, Gregory; Helle, Michael; Peñano, Joe; Ting, Antonio; Schmitt-Sody, Andreas; Elle, Jennifer

    2016-07-01

    We have constructed a 180-m-long distributed, continuously variable atmospheric turbulence generator to study high-power laser beam propagation. This turbulence generator operates on the principle of free convection from a heated surface placed below the entire propagation path of the beam, similar to the situation in long-distance horizontal propagation for laser communications, power beaming, or directed energy applications. The turbulence produced by this generator has been characterized through constant-temperature anemometry, as well as by the scintillation of a low-power laser beam.

  8. Climatic associations of British species distributions show good transferability in time but low predictive accuracy for range change.

    PubMed

    Rapacciuolo, Giovanni; Roy, David B; Gillings, Simon; Fox, Richard; Walker, Kevin; Purvis, Andy

    2012-01-01

    Conservation planners often wish to predict how species distributions will change in response to environmental changes. Species distribution models (SDMs) are the primary tool for making such predictions. Many methods are widely used; however, they all make simplifying assumptions, and predictions can therefore be subject to high uncertainty. With global change well underway, field records of observed range shifts are increasingly being used for testing SDM transferability. We used an unprecedented distribution dataset documenting recent range changes of British vascular plants, birds, and butterflies to test whether correlative SDMs based on climate change provide useful approximations of potential distribution shifts. We modelled past species distributions from climate using nine single techniques and a consensus approach, and projected the geographical extent of these models to a more recent time period based on climate change; we then compared model predictions with recent observed distributions in order to estimate the temporal transferability and prediction accuracy of our models. We also evaluated the relative effect of methodological and taxonomic variation on the performance of SDMs. Models showed good transferability in time when assessed using widespread metrics of accuracy. However, models had low accuracy to predict where occupancy status changed between time periods, especially for declining species. Model performance varied greatly among species within major taxa, but there was also considerable variation among modelling frameworks. Past climatic associations of British species distributions retain a high explanatory power when transferred to recent time--due to their accuracy to predict large areas retained by species--but fail to capture relevant predictors of change. We strongly emphasize the need for caution when using SDMs to predict shifts in species distributions: high explanatory power on temporally-independent records--as assessed using

  9. Nitrogen ion implantation into various materials using 28 GHz electron cyclotron resonance ion source

    NASA Astrophysics Data System (ADS)

    Shin, Chang Seouk; Lee, Byoung-Seob; Choi, Seyong; Yoon, Jang-Hee; Kim, Hyun Gyu; Ok, Jung-Woo; Park, Jin Yong; Kim, Seong Jun; Bahng, Jungbae; Hong, Jonggi; Lee, Seung Wook; Won, Mi-Sook

    2016-02-01

    The installation of the 28 GHz electron cyclotron resonance ion source (ECRIS) ion implantation beamline was recently completed at the Korea Basic Science Institute. The apparatus contains a beam monitoring system and a sample holder for the ion implantation process. The new implantation system can function as a multipurpose tool since it can implant a variety of ions, ranging hydrogen to uranium, into different materials with precise control and with implantation areas as large as 1-10 mm2. The implantation chamber was designed to measure the beam properties with a diagnostic system as well as to perform ion implantation with an in situ system including a mass spectrometer. This advanced implantation system can be employed in novel applications, including the production of a variety of new materials such as metals, polymers, and ceramics and the irradiation testing and fabrication of structural and functional materials to be used in future nuclear fusion reactors. In this investigation, the first nitrogen ion implantation experiments were conducted using the new system. The 28 GHz ECRIS implanted low-energy, multi-charged nitrogen ions into copper, zinc, and cobalt substrates, and the ion implantation depth profiles were obtained. SRIM 2013 code was used to calculate the profiles under identical conditions, and the experimental and simulation results are presented and compared in this report. The depths and ranges of the ion distributions in the experimental and simulation results agree closely and demonstrate that the new system will enable the treatment of various substrates for advanced materials research.

  10. Nitrogen ion implantation into various materials using 28 GHz electron cyclotron resonance ion source.

    PubMed

    Shin, Chang Seouk; Lee, Byoung-Seob; Choi, Seyong; Yoon, Jang-Hee; Kim, Hyun Gyu; Ok, Jung-Woo; Park, Jin Yong; Kim, Seong Jun; Bahng, Jungbae; Hong, Jonggi; Lee, Seung Wook; Won, Mi-Sook

    2016-02-01

    The installation of the 28 GHz electron cyclotron resonance ion source (ECRIS) ion implantation beamline was recently completed at the Korea Basic Science Institute. The apparatus contains a beam monitoring system and a sample holder for the ion implantation process. The new implantation system can function as a multipurpose tool since it can implant a variety of ions, ranging hydrogen to uranium, into different materials with precise control and with implantation areas as large as 1-10 mm(2). The implantation chamber was designed to measure the beam properties with a diagnostic system as well as to perform ion implantation with an in situ system including a mass spectrometer. This advanced implantation system can be employed in novel applications, including the production of a variety of new materials such as metals, polymers, and ceramics and the irradiation testing and fabrication of structural and functional materials to be used in future nuclear fusion reactors. In this investigation, the first nitrogen ion implantation experiments were conducted using the new system. The 28 GHz ECRIS implanted low-energy, multi-charged nitrogen ions into copper, zinc, and cobalt substrates, and the ion implantation depth profiles were obtained. SRIM 2013 code was used to calculate the profiles under identical conditions, and the experimental and simulation results are presented and compared in this report. The depths and ranges of the ion distributions in the experimental and simulation results agree closely and demonstrate that the new system will enable the treatment of various substrates for advanced materials research.

  11. Nitrogen ion implantation into various materials using 28 GHz electron cyclotron resonance ion source.

    PubMed

    Shin, Chang Seouk; Lee, Byoung-Seob; Choi, Seyong; Yoon, Jang-Hee; Kim, Hyun Gyu; Ok, Jung-Woo; Park, Jin Yong; Kim, Seong Jun; Bahng, Jungbae; Hong, Jonggi; Lee, Seung Wook; Won, Mi-Sook

    2016-02-01

    The installation of the 28 GHz electron cyclotron resonance ion source (ECRIS) ion implantation beamline was recently completed at the Korea Basic Science Institute. The apparatus contains a beam monitoring system and a sample holder for the ion implantation process. The new implantation system can function as a multipurpose tool since it can implant a variety of ions, ranging hydrogen to uranium, into different materials with precise control and with implantation areas as large as 1-10 mm(2). The implantation chamber was designed to measure the beam properties with a diagnostic system as well as to perform ion implantation with an in situ system including a mass spectrometer. This advanced implantation system can be employed in novel applications, including the production of a variety of new materials such as metals, polymers, and ceramics and the irradiation testing and fabrication of structural and functional materials to be used in future nuclear fusion reactors. In this investigation, the first nitrogen ion implantation experiments were conducted using the new system. The 28 GHz ECRIS implanted low-energy, multi-charged nitrogen ions into copper, zinc, and cobalt substrates, and the ion implantation depth profiles were obtained. SRIM 2013 code was used to calculate the profiles under identical conditions, and the experimental and simulation results are presented and compared in this report. The depths and ranges of the ion distributions in the experimental and simulation results agree closely and demonstrate that the new system will enable the treatment of various substrates for advanced materials research. PMID:26931931

  12. Effect of zeranol implants in ram and wether lambs on performance traits, carcass characteristics, and subprimal cut yields and distribution.

    PubMed

    Nold, R A; Unruh, J A; Spaeth, C W; Minton, J E

    1992-06-01

    In two separate 2 x 2 factorial arrangements, 69 male, crossbred lambs were allotted randomly to the following treatments: 1) nonimplanted (NI) rams, 2) implanted (I) rams, 3) NI wethers, and 4) I wethers. In Trial 1, 36 lambs were allotted to treatment groups at birth (n = 9) and I lambs were implanted with 12 mg of zeranol between 1 and 3 d of age and again at weaning (average age of 62 d). Lambs were slaughtered at three time-constant end points of 78, 93, and 107 d on feed postweaning (average age of 155 d). Rams grew faster postweaning, were more efficient in their feed conversion, were heavier at slaughter, and had lower numerical yield grades than did wethers (P less than .05). Implanted lambs tended (P = .08) to grow faster and were (P less than .05) more efficient in their feed conversion than NI lambs. Rams produced heavier (P less than .05) trimmed subprimal shoulders, loins, and legs and had (P less than .05) a higher percentage of their carcass weight in the subprimal shoulder than did wethers. During Trial 2, NI rams (n = 8), I rams (n = 8), NI wethers (n = 8), and I wethers (n = 9) were allotted to treatment groups, and I lambs were implanted at average ages of 14, 55, and 98 d. After weaning, lambs were weighed every 14 d and were slaughtered 7 d after reaching a minimum weight of 50 kg (average age of 148 d).(ABSTRACT TRUNCATED AT 250 WORDS)

  13. DISTRIBUTION AND RANGE OF RADIONUCLIDE SORPTIOIN COEFFICIENTS IN A SAVANNAH RIVER SITE SUBSURFACE: STOCHASTIC MODELING CONSIDERATIONS - 10259

    SciTech Connect

    Kaplan, D.

    2010-01-04

    The uncertainty associated with the sorption coefficient, or K{sub d} value, is one of the key uncertainties in estimating risk associated with burying low-level nuclear waste in the subsurface. The objective of this study was to measure >648 K{sub d} values and provide a measure of the range and distribution (normal or log-normal) of radionuclide K{sub d} values appropriate for the E-Area disposal site, within the Savannah River Site, near Aiken South Carolina. The 95% confidence level for the mean K{sub d} was twice the mean in the Aquifer Zone (18-30.5 m depth), equal to the mean for the Upper Vadose Zone (3.3-10 m depth), and half the mean for the Lower Vadose Zone (3.3-18 m depth). The distribution of K{sub d} values was log normal in the Upper Vadose Zone and Aquifer Zone, and normal in the Lower Vadose Zone. To our knowledge, this is the first report of natural radionuclide K{sub d} variability in the literature. Using ranges and distribution coefficients that are specific to the hydrostratigraphic unit improved model accuracy and reduced model uncertainty. Unfortunately, extension of these conclusions to other sites is likely not appropriate given that each site has its own sources of hydrogeological variability. However, this study provides one of the first examples of the development stochastic ranges and distributions of K{sub d} values for a hydrological unit for stochastic modeling.

  14. The geographical distribution of lightning: Forestry and range requirements and interests

    NASA Technical Reports Server (NTRS)

    Vance, D. L.

    1979-01-01

    In an attempt to reduce the response time of the initial attack forces to lightning-caused fire, a lightning detection system that effectively locates accurate directions to lightning discharges to over 200 miles from the detection equipment was developed. The system was first tested in Alaska in 1975. Since that time, further development and operational testing led to the implementation of wide area networks. For the 1979 fire season an eight station network in Alaska is to be implemented that will cover virtually all of the lightning-caused fire areas in the state. In the western United States, an eighteen station network that will cover approximately 85% of eleven states is to be implemented. For the first time, large scale ground discharge lightning distribution information is to be available.

  15. Deep genetic divergence in giant red shrimp Aristaeomorpha foliacea (Risso, 1827) across a wide distributional range

    NASA Astrophysics Data System (ADS)

    Fernández, M. V.; Heras, S.; Maltagliati, F.; Roldán, M. I.

    2013-02-01

    The giant red shrimp, Aristaeomorpha foliacea, is a commercially important species in the Mediterranean Sea (MED), Mozambique Channel (MOZ), and north western Australia (AUS). 685 bp of the mitochondrial COI gene was sequenced in 317 individuals from six Mediterranean and two Indian Ocean localities. Genetic diversity estimates of Indian Ocean samples were higher than those of MED counterparts. AMOVA, phylogenetic tree, haplotype network and Bayesian assignment analyses detected three haplogroups, corresponding to MED, MOZ and AUS, separated by three and 38 mutational steps, respectively. Within MED shallow genetic divergence between populations was dependent on local oceanographical characteristics. Mismatch distribution analysis and neutrality tests provided a consistent indication of past population expansion in each region considered. Our results provide the first evidence of genetic structure in A. foliacea and suggest a scenario of allopatric speciation within the Indian Ocean that, however needs deeper examination.

  16. Effective oscillator strength distributions of spherically symmetric atoms for calculating polarizabilities and long-range atom–atom interactions

    SciTech Connect

    Jiang, Jun; Mitroy, J.; Cheng, Yongjun; Bromley, M.W.J.

    2015-01-15

    Effective oscillator strength distributions are systematically generated and tabulated for the alkali atoms, the alkaline-earth atoms, the alkaline-earth ions, the rare gases and some miscellaneous atoms. These effective distributions are used to compute the dipole, quadrupole and octupole static polarizabilities, and are then applied to the calculation of the dynamic polarizabilities at imaginary frequencies. These polarizabilities can be used to determine the long-range C{sub 6}, C{sub 8} and C{sub 10} atom–atom interactions for the dimers formed from any of these atoms and ions, and we present tables covering all of these combinations.

  17. Effect of type of luting agents on stress distribution in the bone surrounding implants supporting a three-unit fixed dental prosthesis: 3D finite element analysis

    PubMed Central

    Ghasemi, Ehsan; Abedian, Alireza; Iranmanesh, Pedram; Khazaei, Saber

    2015-01-01

    Background: Osseointegration of dental implants is influenced by many biomechanical factors that may be related to stress distribution. The aim of this study was to evaluate the effect of type of luting agent on stress distribution in the bone surrounding implants, which support a three-unit fixed dental prosthesis (FDP) using finite element (FE) analysis. Materials and Methods: A 3D FE model of a three-unit FDP was designed replacing the maxillary first molar with maxillary second premolar and second molar as the abutments using CATIA V5R18 software and analyzed with ABAQUS/CAE 6.6 version. The model was consisted of 465108 nodes and 86296 elements and the luting agent thickness was considered 25 μm. Three load conditions were applied on eight points in each functional cusp in horizontal (57.0 N), vertical (200.0 N) and oblique (400.0 N, θ = 120°) directions. Five different luting agents were evaluated. All materials were assumed to be linear elastic, homogeneous, time independent and isotropic. Results: For all luting agent types, the stress distribution pattern in the cortical bone, connectors, implant and abutment regions was almost uniform among the three loads. Furthermore, the maximum von Mises stress of the cortical bone was at the palatal side of second premolar. Likewise, the maximum von Mises stress in the connector region was in the top and bottom of this part. Conclusion: Luting agents transfer the load to cortical bone and different types of luting agents do not affect the pattern of load transfer. PMID:25709676

  18. Distribution of pseudoexfoliation material on anterior segment structures in human autopsy eyes after cataract surgery with intraocular lens implantation.

    PubMed

    Schmack, Ingo; Auffarth, Gerd Uwe

    2016-06-01

    The purpose of the study was to evaluate the distribution and amount of pseudoexfoliation material (PXM) on anterior segment structures in pseudophakic human autopsy eyes with pseudoexfoliation (PEX) syndrome and to study its impact on fixation and decentration of posterior chamber intraocular lenses (IOLs). Sixteen human autopsy eyes (donor age [mean ± SD] 77.5 ± 8.6 years; range, 70-90 years) with history of cataract surgery and PEX syndrome were analyzed for distribution and accumulation of PXM on structures of the anterior segment by light microscopy. Quantitative IOL decentration measurements were performed using the Miyake-Apple posterior view technique. All 16 eyes displayed IOLs which were either fixed symmetrically in the capsular bag (n = 8) or asymmetrically with one haptic in the sulcus and one in the bag (n = 7) or at the pars plicata of the ciliary body (n = 1). In the majority, PXM was found around the pars plicata (average grade: 1.6 ± 0.53 µm) and the lens capsule (average grade: 1.05 ± 0.46 µm). Minor amounts were detected at the pars plana and the trabecular meshwork. IOL decentration measurements ranged from 0.51 ± 0.35 (symmetrical-fixation) to 0.61 ± 0.43 mm (asymmetrical-fixation). There was only a weak statistically not significant correlation in regard to the amount of PXM and IOL decentration and between PXM distribution and the IOL fixation site. PXM contributes to weakening of the suspensory apparatus of the crystalline lens. Although PXM induced tissue alterations predispose for a broad spectrum of intra- and postoperative complications, the amount and distribution of PXM on different anterior segment structures showed only a weak correlation to IOL decentration or fixation location. PMID:26307751

  19. Measurements and calculations of neutron scattering angular distributions over a wide mass and energy range

    SciTech Connect

    Hansen, L.F.

    1985-05-01

    Neutron elastic and inelastic differential cross sections for targets between /sup 9/Be and /sup 239/Pu at energies, E > 14 MeV have been measured using the Livermore and Ohio University neutron time-of-flight facilities. We review here the data and the analyses based on two local microscopic optical potentials: that of Jeukenne, Lejeune and Mahaux, and that of Brieva and Rook. The results are also compared with calculations using global potentials. Coupled channel formalism has been used in the analysis of targets with strong deformations, such as Be, C, Ta, and actinides. The value of the microscopic optical potentials as a tool to predict elastic and inelastic neutron cross sections over a wide mass and energy range is discussed. The need for neutron measurements up to higher energies and their analysis in conjunction with (p,p) and charge exchange (p,n) data is addressed. 17 refs.

  20. Isolation, tissue distribution, and molecular characterization of Toxoplasma gondii from free-range chickens from Guatemala.

    PubMed

    Dubey, J P; Lopez, B; Alvarez, M; Mendoza, C; Lehmann, T

    2005-08-01

    The prevalence of Toxoplasma gondii in free-ranging chickens is a good indicator of the prevalence of T. gondii oocysts in the soil because chickens feed from the ground. The prevalence of T. gondii in 50 free-range chickens (Gallus domesticus) from Guatemala was determined. Antibodies to T. gondii were assayed by the modified agglutination test (MAT). Antibodies were found in 37 (74%) chickens with titers of 1:5 (11), 1:10 (7), 1:20 (11), 1:40 (1), 1:80 (1), 1:160 (3), 1:1,280 (2), and 1:2,560 (1). Hearts, pectoral muscles, and brains of 19 chickens with MAT titers of 1:20 or more were bioassayed individually in mice. Tissues from the remaining 31 chickens with titers of 1:10 or lower were pooled and fed to 4 T. gondii-free cats (13 chickens with titers of less than 1:5 to 1 cat, 11 chickens with titers of 1:5 to 2 cats, and 7 chickens with titers of 1:10 to 1 cat). Feces of cats were examined for oocysts; they did not shed oocysts. Toxoplasma gondii was isolated from 8 chickens with MAT titers of 1:20 or more (from 1 of 11 chickens with a titer of 1:20 and all 7 chickens with a titer of 1:80 or more) from the heart, brain, and pectoral muscle (3); heart and pectoral muscle (1); and heart alone (4). Genotyping of these 8 isolates with the SAG2 locus indicated that 5 were type III and 3 were type 1. This is the first report of isolation of T. gondii from chickens from Guatemala.

  1. Listening to Brain Microcircuits for Interfacing With External World-Progress in Wireless Implantable Microelectronic Neuroengineering Devices: Experimental systems are described for electrical recording in the brain using multiple microelectrodes and short range implantable or wearable broadcasting units.

    PubMed

    Nurmikko, Arto V; Donoghue, John P; Hochberg, Leigh R; Patterson, William R; Song, Yoon-Kyu; Bull, Christopher W; Borton, David A; Laiwalla, Farah; Park, Sunmee; Ming, Yin; Aceros, Juan

    2010-01-01

    Acquiring neural signals at high spatial and temporal resolution directly from brain microcircuits and decoding their activity to interpret commands and/or prior planning activity, such as motion of an arm or a leg, is a prime goal of modern neurotechnology. Its practical aims include assistive devices for subjects whose normal neural information pathways are not functioning due to physical damage or disease. On the fundamental side, researchers are striving to decipher the code of multiple neural microcircuits which collectively make up nature's amazing computing machine, the brain. By implanting biocompatible neural sensor probes directly into the brain, in the form of microelectrode arrays, it is now possible to extract information from interacting populations of neural cells with spatial and temporal resolution at the single cell level. With parallel advances in application of statistical and mathematical techniques tools for deciphering the neural code, extracted populations or correlated neurons, significant understanding has been achieved of those brain commands that control, e.g., the motion of an arm in a primate (monkey or a human subject). These developments are accelerating the work on neural prosthetics where brain derived signals may be employed to bypass, e.g., an injured spinal cord. One key element in achieving the goals for practical and versatile neural prostheses is the development of fully implantable wireless microelectronic "brain-interfaces" within the body, a point of special emphasis of this paper.

  2. Altitudinal ranging of black-crested gibbons at Mt. Wuliang, Yunnan: effects of food distribution, temperature and human disturbance.

    PubMed

    Fan, Peng-Fei; Jiang, Xue-Long

    2010-01-01

    We studied the altitudinal ranging of one habituated group of black-crested gibbons (Nomascus concolor) at Dazhaizi, Mt. Wuliang, Yunnan, China, between March 2005 and April 2006. The group ranged from 1,900 to 2,680 m above sea level. Food distribution was the driving force behind the altitudinal ranging patterns of the study group. They spent 83.2% of their time ranging between 2,100 and 2,400 m, where 75.8% of important food patches occurred. They avoided using the area above 2,500 m despite a lack of human disturbance there, apparently because there were few food resources. Temperature had a limited effect on seasonal altitudinal ranging but probably explained the diel altitudinal ranging of the group, which tended to use the lower zone in the cold morning and the higher zone in the warm afternoon. Grazing goats, the main disturbance, were limited to below 2,100 m, which was defined as the high-disturbance area (HDA). Gibbons spent less time in the HDA and, when ranging there, spent more time feeding and travelling and less time resting and singing. Human activities directly influenced gibbon behaviour, might cause forest degradation and create dispersal barriers between populations.

  3. Fluvial incision history that controlled the distribution of landslides in the Central Range of Taiwan

    NASA Astrophysics Data System (ADS)

    Tsou, Ching-Ying; Chigira, Masahiro; Matsushi, Yuki; Chen, Su-Chin

    2014-12-01

    Hillslope processes, which are affected by long-term river incision, give rise to the risk of landsliding in active orogens. We studied the river incision history and the subsequent response of rock slopes in the upstream Dahan River catchment, north Taiwan, by analyzing river long profiles, hillslopes, and landslide scars. The results were combined with chronological data from several landform surfaces to reconstruct the history of landscape evolution. At the study area, the landscape comprises three levels of knickpoints and corresponding slope breaks. These knickpoints propagated upstream along trunk and tributary rivers, undercutting and destabilizing nearby slopes, of which the oldest is a paleosurface dated to ca. 150 kyr by cosmogenic nuclide dating. Consequently, three levels of V-shaped inner gorges (up to 600 m deep) are incised into the paleosurface. The inner slopes of the three levels of gorges have mean inclinations of 35.6°, 37.7°, and 39.8°, and steepen from the higher to the lower inner gorges. These three series of knickpoints and corresponding slope breaks suggest the occurrence of three phases of river incision. Based on analyses of the steepness indices of the river long profiles, cosmogenic nuclide dating, and the regional tectonic and climatic history, the two earlier phases of incision are inferred to have been caused by prevailing tectonic uplifts during the middle to late Pleistocene, and the most recent phase by climate change in addition to uplift. The long-term history of river incision has controlled the distribution of deep-seated gravitational slope deformation and landslides. Many areas of deep-seated gravitational slope deformation and deep-seated rockslide-avalanches are aligned along the higher and middle slope breaks, and debris slide avalanches are concentrated along the middle and lower slope breaks.

  4. Genetic diversity, host range, and distribution of tomato yellow leaf curl virus in Iran.

    PubMed

    Shirazi, M; Mozafari, J; Rakhshandehroo, F; Shams-Bakhsh, M

    2014-01-01

    Tomato yellow leaf curl virus (TYLCV) is considered one of the most important tomato pathogens in tropical and subtropical regions including Iran. During the years 2007 to 2009, a total number of 510 symptomatic and asymptomatic vegetable, ornamental and weed samples were collected from fields and greenhouses in ten provinces of Iran. Symptoms included stunting, yellowing, leaf curl and flower senescence. PCR with specific primers showed TYLCV infection in 184 samples (36%) such as cucumber, pepper, tomato and several weeds from seven provinces. Based on the geographical origin, host range and symptoms, twenty three representative isolates were selected for phylogenetic analysis. An amplicon with a size about 608 base pair (bp) comprising partial sequence of the coat (CP) and movement protein (MP) coding regions of the viral genome was sequenced and compared with the corresponding selected sequences available in GenBank for Iran and worldwide. Phylogenetic analyses on the basis of the nucleotide sequences indicated two geographically separated clades. Isolates collected from Hormozgan, Khuzestan and Kerman provinces were grouped together with other Iranian isolates including TYLCV-Ir2, TYLCV-Kahnooj, and an isolate from Oman. It was also revealed that isolates collected from Boushehr, Fars, Tehran, and Isfahan placed close to the Iranian isolate TYLCV-Abadeh and isolates from Israel and Egypt. No correlation was found between the genetic variation and the host species, but selected Iranian isolates were grouped on the basis of the geographical origins. Results of this study indicated a high genetic diversity among Iranian TYLCV isolates. PMID:24957717

  5. Evidence for an increased distribution range of Dermacentor reticulatus in south-west Poland.

    PubMed

    Kiewra, Dorota; Czulowska, Aleksandra

    2013-04-01

    The expansion of Dermacentor reticulatus to new geographical areas has been observed in several countries in Europe, including Poland and it's neighbors. In 2011 and 2012, a total of 148 host-seeking D. reticulatus ticks were collected after flagging the vegetation in Lower Silesia, south-western Poland. Tick monitoring was conducted in mixed and deciduous forest, on meadows, in river valleys and ecotones between forested and grassy areas. The ornate dog ticks were found in 10 out of 33 sites located in five districts: Legnica, Wroclaw, Środa Śląska, Lubin and Boleslawiec County. All sites where D. reticulatus ticks were found are located to the south-west of the Odra River. The greatest distance between these disconnected localities was approximately 90 km. It seems that at present the southern boundary of the range is Wroclaw district. This study indicates that D. reticulatus can be ranked as a typical element of the fauna in Lower Silesia in southwestern Poland.

  6. The effect of topography, latitude, and lithology on rock glacier distribution in the Lemhi Range, central Idaho, USA

    NASA Astrophysics Data System (ADS)

    Johnson, Bradley G.; Thackray, Glenn D.; Van Kirk, Robert

    2007-10-01

    Statistical analysis of rock glaciers in the Lemhi Range demonstrates that their development and preservation is controlled primarily by annual insolation and lithology. We inspected 171 alpine valleys in the Lemhi Range using optical remote sensing techniques, digital topographic analysis, and field examination. In those valleys, we identified 48 rock glaciers and examined them for lichen cover, evidence of ice presence, specific evidence of movement, and distinctive morphological features. In addition to recording the presence or absence of a rock glacier in each alpine valley, existing rock glaciers were classified according to their morphology. Factors such as topographic shading, lithology, relief, aspect, and elevation determine the development and preservation of rock glaciers. Analysis of these factors in the Lemhi Range shows that elevation > 2600 m, a north-facing aspect (300-60°), and < 2300 h of direct sunlight per year are necessary conditions for the existence of rock glaciers in any form. The majority of alpine valleys in the Lemhi Range meet these requirements. Thus, other parameters, including topographic shading and lithology, must determine occurrence of rock glaciers in the Lemhi Range. Multivariate statistical analysis of controlling parameters demonstrates that annual insolation and latitude influence rock glacier occurrence most strongly. Whereas duration of insolation is a logical controlling factor, latitude is more enigmatic. Additional statistical analysis indicates that the latitude factor is likely a reflection of lithologic changes with latitude along the range. Lithology may affect rock glacier distribution through its effects on hydrology or air ventilation. Moreover, statistical analysis shows that rock glacier occurrence correlates with protalus lobe occurrence, suggesting that protalus lobes play a role in the genesis of rock glaciers in the Lemhi Range. Separate analysis of the classification systems shows that each morphologic

  7. Phenotypic traits of Phragmites australis clones are not related to ploidy level and distribution range

    PubMed Central

    Achenbach, Luciana; Lambertini, Carla; Brix, Hans

    2012-01-01

    Background and aims Phragmites australis is a wetland grass with high genetic variability, augmented by its cosmopolitan distribution, clonal growth form and large variation in chromosome numbers. Different ploidy levels and ecotypes differ in morphology and ecophysiological traits, and may possess different levels of phenotypic variation. The aim of this study was to quantify the natural variation in ecophysiological characteristics of P. australis, and to explore whether differences in ecophysiological traits can be related to ploidy levels or to the geographic origin of the clones. Methodology Fifteen clones of P. australis from Europe and Asia/Australia, representing five ploidy levels (4x, 6x, 8x, 10x and 12x), were grown in a common garden design for 119 days. Plant growth and light-saturated rate of photosynthesis (Pmax), stomatal conductance (gs), water use efficiency (WUE) and concentrations of photosynthetic pigments and mineral ions in the leaves were measured. Principal results The growth of the plants and most ecophysiological parameters differed significantly between clones. The mean maximum shoot height varied from 0.9 to 1.86 m, Pmax from 9.7 to 27 µmol m−2 s−1, gs from 0.22 to 1.41 mol m−2 s−1 and WUE from 13 to 47 µmol mol−1. The concentrations of chlorophylls did not vary significantly between clones, but the chlorophyll a/b ratio and the concentrations of total carotenoids did. The observed differences were not explained either by the ploidy level per se or by the geographic origin or phylogenetic relationships of the clones. Conclusions Phylogeographic relationships in P. australis on a global scale do not mirror the environment where the adaptations have evolved, and high phenotypic variation among and within clones complicates comparative studies. Future studies aimed at explaining differences in plant behaviour between P. australis populations should be careful in the selection of target genotypes and/or populations, and should

  8. Long Range Weather Prediction III: Miniaturized Distributed Sensors for Global Atmospheric Measurements

    SciTech Connect

    Teller, E; Leith, C; Canavan, G; Wood, L

    2001-11-13

    involve continuing costs of the order of 1% of GDP, a large fraction of which could be retrieved if high-fidelity predictions of two weeks forward applicability were available. These {approx}$10{sup 2} B annual savings dwarf the <$1 B costs of operating a rational, long-range weather prediction system of the type proposed.

  9. Long Range Weather Prediction III: Miniaturized Distributed Sensors for Global Atmospheric Measurements

    DOE R&D Accomplishments Database

    Teller, E.; Leith, C.; Canavan, G.; Wood, L.

    2001-11-13

    involve continuing costs of the order of 1% of GDP, a large fraction of which could be retrieved if high-fidelity predictions of two weeks forward applicability were available. These{approx}$10{sup 2} B annual savings dwarf the<$1 B costs of operating a rational, long-range weather prediction system of the type proposed.

  10. [Study of fast acquisition technique for heavy ion CT system based on the measurement of residual range distribution].

    PubMed

    Mogaki, Tatsuya; Abe, Shinji; Sato, Hitoshi; Muraishi, Hiroshi; Hara, Hidetake; Hara, Satoshi; Miyake, Shoko; Himukai, Takeshi; Kanai, Tatsuaki

    2012-01-01

    We proposed a new technique for the fast acquisition heavy ion CT (HICT) system based on the measurement of residual range distribution using an intensifying screen and charge coupled device camera. The previously used fast acquisition HICT system had poor electron density resolution. In the new technique, the range shifter thickness is varied over the required dynamic range in the spill of the heavy ion beam at each projection angle and the residual range distribution is determined by a series of acquisition data. We examined the image quality using the contrast noise ratio and the noise power spectrum, and estimated the electron density resolution, using a low-contrast phantom for measurement of electron density resolution. The image quality of the new technique was superior to that of the previous fast acquisition HICT system. Furthermore, the relative electron density resolution was 0.011, which represented an improvement of about 12-fold. Therefore we showed that the new technique was potentially useful in clinical use of HICT, including treatment and quality assurance of heavy ion therapy. PMID:24592673

  11. The taiga tick Ixodes persulcatus (Acari: Ixodidae) in the Sakha Republic (Yakutia) of Russia: distributional and reproductive ranges.

    PubMed

    Uspensky, Igor; Garruto, Ralph M; Goldfarb, Lev

    2003-01-01

    The finding of an unfed adult female of the taiga tick Ixodes persulcatus Schulze is reported from the northern part of Eastern Siberia (the central part of the Sakha Republic [former Yakutia]) of Russia. This finding supplements other reported single findings of the taiga tick in different sites of the central part of the Sakha Republic, thus increasing its distributional range. The reproductive range of the taiga tick is limited to two separate areas in the southern parts of the Republic. The most probable mode of tick introduction northwards from the border of the reproductive range is by spring bird migrations from their wintering areas to breeding sites. The possibility of the establishment of stable tick populations in the areas of introduction is also considered.

  12. The impact of global warming on the range distribution of different climatic groups of Aspidoscelis costata costata.

    PubMed

    Güizado-Rodríguez, Martha Anahí; Ballesteros-Barrera, Claudia; Casas-Andreu, Gustavo; Barradas-Miranda, Victor Luis; Téllez-Valdés, Oswaldo; Salgado-Ugarte, Isaías Hazarmabeth

    2012-12-01

    The ectothermic nature of reptiles makes them especially sensitive to global warming. Although climate change and its implications are a frequent topic of detailed studies, most of these studies are carried out without making a distinction between populations. Here we present the first study of an Aspidoscelis species that evaluates the effects of global warming on its distribution using ecological niche modeling. The aims of our study were (1) to understand whether predicted warmer climatic conditions affect the geographic potential distribution of different climatic groups of Aspidoscelis costata costata and (2) to identify potential altitudinal changes of these groups under global warming. We used the maximum entropy species distribution model (MaxEnt) to project the potential distributions expected for the years 2020, 2050, and 2080 under a single simulated climatic scenario. Our analysis suggests that some climatic groups of Aspidoscelis costata costata will exhibit reductions and in others expansions in their distribution, with potential upward shifts toward higher elevation in response to climate warming. Different climatic groups were revealed in our analysis that subsequently showed heterogeneous responses to climatic change illustrating the complex nature of species geographic responses to environmental change and the importance of modeling climatic or geographic groups and/or populations instead of the entire species' range treated as a homogeneous entity.

  13. Influence of the chemical nature of implanted ions on the structure of a silicon layer damaged by implantation

    SciTech Connect

    Shcherbachev, K. D. Voronova, M. I.; Bublik, V. T.; Mordkovich, V. N. Pazhin, D. M.; Zinenko, V. I.; Agafonov, Yu. A.

    2013-12-15

    The influence of the implantation of silicon single crystals by fluorine, nitrogen, oxygen, and neon ions on the distribution of strain and the static Debye-Waller factor in the crystal lattice over the implanted-layer depth has been investigated by high-resolution X-ray diffraction. The density depth distribution in the surface layer of native oxide has been measured by X-ray reflectometry. Room-temperature implantation conditions have ensured the equality of the suggested ranges of ions of different masses and the energies transferred by them to the target. It is convincingly shown that the change in the structural parameters of the radiation-damaged silicon layer and the native oxide layer depend on the chemical activity of the implanted ions.

  14. Social monogamy in wild owl monkeys (Aotus azarae) of Argentina: the potential influences of resource distribution and ranging patterns.

    PubMed

    Fernandez-Duque, Eduardo

    2016-03-01

    Using published and new data from a population of monogamous owl monkeys in the Argentinean Chaco, I examine the hypothesis that social monogamy is a default social system imposed upon males because the spatial and/or temporal distribution of resources and females makes it difficult for a single male to defend access to more than one mate. First, I examine a set of predictions on ranging patterns, use of space, and population density. This first section is followed by a second one considering predictions related to the abundance and distribution of food. Finally, I conclude with a section attempting to link the ranging and ecological data to demographic and life-history parameters as proxies for reproductive success. In support of the hypothesis, owl monkey species do live at densities (7-64 ind/km(2) ) that are predicted for monogamous species, but groups occupy home ranges and core areas that vary substantially in size, with pronounced overlap of home ranges, but not of core areas. There are strong indications that the availability of food sources in the core areas during the dry season may be of substantial importance for regulating social monogamy in owl monkeys. Finally, none of the proxies for the success of groups were strongly related to the size of the home range or core area. The results I present do not support conclusively any single explanation for the evolution of social monogamy in owl monkeys, but they help us to better understand how it may function. Moreover, the absence of conclusive answers linking ranging, ecology, and reproductive success with the evolution of social monogamy in primates, offer renewed motivation for continuing to explore the evolution of monogamy in owl monkeys.

  15. Evaluating the Significance of Paleophylogeographic Species Distribution Models in Reconstructing Quaternary Range-Shifts of Nearctic Chelonians

    PubMed Central

    Flecks, Morris; Ahmadzadeh, Faraham; Dambach, Johannes; Engler, Jan O.; Habel, Jan Christian; Hartmann, Timo; Hörnes, David; Ihlow, Flora; Schidelko, Kathrin; Stiels, Darius; Polly, P. David

    2013-01-01

    The climatic cycles of the Quaternary, during which global mean annual temperatures have regularly changed by 5–10°C, provide a special opportunity for studying the rate, magnitude, and effects of geographic responses to changing climates. During the Quaternary, high- and mid-latitude species were extirpated from regions that were covered by ice or otherwise became unsuitable, persisting in refugial retreats where the environment was compatible with their tolerances. In this study we combine modern geographic range data, phylogeny, Pleistocene paleoclimatic models, and isotopic records of changes in global mean annual temperature, to produce a temporally continuous model of geographic changes in potential habitat for 59 species of North American turtles over the past 320 Ka (three full glacial-interglacial cycles). These paleophylogeographic models indicate the areas where past climates were compatible with the modern ranges of the species and serve as hypotheses for how their geographic ranges would have changed in response to Quaternary climate cycles. We test these hypotheses against physiological, genetic, taxonomic and fossil evidence, and we then use them to measure the effects of Quaternary climate cycles on species distributions. Patterns of range expansion, contraction, and fragmentation in the models are strongly congruent with (i) phylogeographic differentiation; (ii) morphological variation; (iii) physiological tolerances; and (iv) intraspecific genetic variability. Modern species with significant interspecific differentiation have geographic ranges that strongly fluctuated and repeatedly fragmented throughout the Quaternary. Modern species with low genetic diversity have geographic distributions that were highly variable and at times exceedingly small in the past. Our results reveal the potential for paleophylogeographic models to (i) reconstruct past geographic range modifications, (ii) identify geographic processes that result in genetic

  16. Cochlear Implants

    MedlinePlus

    ... electrodes are inserted. The electronic device at the base of the electrode array is then placed under ... FDA approval for implants The Food and Drug Administration (FDA) regulates cochlear implant devices for both adults ...

  17. Dental Implants.

    PubMed

    Zohrabian, Vahe M; Sonick, Michael; Hwang, Debby; Abrahams, James J

    2015-10-01

    Dental implants restore function to near normal in partially or completely edentulous patients. A root-form implant is the most frequently used type of dental implant today. The basis for dental implants is osseointegration, in which osteoblasts grow and directly integrate with the surface of titanium posts surgically embedded into the jaw. Radiologic assessment is critical in the preoperative evaluation of the dental implant patient, as the exact height, width, and contour of the alveolar ridge must be determined. Moreover, the precise locations of the maxillary sinuses and mandibular canals, as well as their relationships to the site of implant surgery must be ascertained. As such, radiologists must be familiar with implant design and surgical placement, as well as augmentation procedures utilized in those patients with insufficient bone in the maxilla and mandible to support dental implants.

  18. Electrodeposited silk coatings for functionalized implant applications

    NASA Astrophysics Data System (ADS)

    Elia, Roberto

    The mechanical and morphological properties of titanium as well as its biocompatibility and osteoinductive characteristics have made it the material of choice for dental implant systems. Although the success rate of titanium implants exceeds 90% in healthy individuals, a large subset of the population has one or more risk factors that inhibit implant integration. Treatments and coatings have been developed to improve clinical outcomes via introduction of appropriate surface topography, texture and roughness or incorporation of bioactive molecules. It is essential that the coatings and associated deposition techniques are controllable and reproducible. Currently, methods of depositing functional coatings are dictated by numerous parameters (temperature, particle size distribution, pH and voltage), which result in variable coating thickness, strength, porosity and weight, and hinder or preclude biomolecule incorporation. Silk is a highly versatile protein with a unique combination of mechanical and physical properties, including tunable degradation, biocompatibility, drug stabilizing capabilities and mechanical properties. Most recently an electrogelation technique was developed which allows for the deposition of gels which dry seamlessly over the contoured topography of the conductive substrate. In this work we examine the potential use of silk electrogels as mechanically robust implant coatings capable of sequestering and releasing therapeutic agents. Electrodeposition of silk electrogels formed in uniform electric fields was characterized with respect to field intensity and deposition time. Gel formation kinetics were used to derive functions which allowed for the prediction of coating deposition over a range of process and solution parameters. Silk electrogel growth orientation was shown to be influenced by the applied electric field. Coatings were reproducible and tunable via intrinsic silk solution properties and extrinsic process parameters. Adhesion was

  19. The relationship between Holocene cultural site distribution and marine terrace uplift on the coast fringing Coastal Range, Taiwan

    NASA Astrophysics Data System (ADS)

    Yang, Hsiaochin; Chen, Wenshan

    2013-04-01

    According to the collision of Philippine Sea plate and Eurasia plate, a series of left-lateral active faults with reverse sense exists in the Longitudinal Valley of east Taiwan. The Holocene marine terraces along the east coast of the Coastal Range in Taiwan are well known for their very rapid uplift and record tectonic history of this active collision boundary. The Holocene marine terrace sequence resulting from successive sea level change and tectonic activation is subdivided into several steps where the highest and oldest terrace, back to ca 13,000yr BP, reaches up to ca 80 m above sea level, and the lower terraces are mostly erosional ones, overlain by less than 1m thick coral beds in situ. The uplift of the coast is very high, ranging from 5 to 10 m/ka. According to the fabrics of potsherds and geochronological data, the prehistoric cultures in eastern Taiwan could be classified into three stages: Fushan (ca 5000-3500yr BP), Peinan/Chilin (ca3500-2000yr BP), Kweishan (ca2000-1000 yr BP) and Jinpu (ca 1000-400yr BP) cultural assemblages respectively. A great difference exists between the various cultural stage, not only the pottery making techniques, but also the distributions of archaeological sites. Combined with the dynamic geomorphic evolution of marine terraces and the distribution of prehistoric culture sites on the east coast of the Coastal Range, a coastal migration trend could be established.

  20. SU-E-T-324: The Influence of Patient Positioning Uncertainties in Proton Radiotherapy On Proton Range and Dose Distributions

    SciTech Connect

    Liebl, J; Paganetti, H; Winey, B

    2014-06-01

    Purpose: Proton radiotherapy allows radiation treatment delivery with high dose gradients. The nature of such dose distributions increases the influence of patient positioning uncertainties on their fidelity when compared to photon radiotherapy. The present work quantitatively analyzes the influence of setup uncertainties on proton range and dose distributions. Methods: 38 clinical passive scattering treatment fields for small lesions in the head were studied. Dose distributions for shifted and rotated patient positions were Monte Carlo-simulated. Proton range uncertainties at the 50% and 90%-dose falloff position were calculated considering 18 arbitrary combinations of maximal patient position shifts and rotations for two patient positioning methods. Normal tissue complication probabilities (NTCPs), equivalent uniform doses (EUDs) and tumor control probabilities (TCPs) were studied for organs at risk (OARs) and target volumes of eight patients. Results: We identified a median 1σ proton range uncertainty at the 50%-dose falloff of 2.8 mm for anatomy-based patient positioning and 1.6 mm for fiducial-based patient positioning as well as 7.2 mm and 5.8 mm for the 90%-dose falloff position respectively. These range uncertainties were correlated to heterogeneity indices (HIs) calculated for each treatment field (38% < R{sup 2} < 50%). A NTCP increase of more than 10% (absolute) was observed for less than 2.9% (anatomy-based positioning) and 1.2% (fiducial-based positioning) of the studied OARs and patient shifts. TCP decreases larger than 10% (absolute) were seen for less than 2.2% of the target volumes or non-existent. EUD changes were up to 178% for OARs and 35% for target volumes. Conclusion: The influence of patient positioning uncertainties on proton range in therapy of small lesions in the human brain and target and OAR dosimetry were studied. Observed range uncertainties were correlated with HIs. The clinical practice of using multiple compensator

  1. Investigating short-range magnetism in strongly correlated materials via magnetic pair distribution function analysis and ab initio theory

    NASA Astrophysics Data System (ADS)

    Frandsen, Benjamin; Page, Katharine; Brunelli, Michela; Staunton, Julie; Billinge, Simon

    Short-range magnetic correlations are known to exist in a variety of strongly correlated electron systems, but our understanding of the role they play is challenged by the difficulty of experimentally probing such correlations. Magnetic pair distribution function (mPDF) analysis is a newly developed neutron total scattering method that can reveal short-range magnetic correlations directly in real space, and may therefore help ameliorate this difficulty. We present temperature-dependent mPDF measurements of the short-range magnetic correlations in the paramagnetic phase of antiferromagnetic MnO, an archetypal strongly correlated transition-metal oxide. We observe significant correlations on a ~1 nm length scale that differ substantially from the low-temperature long-range-ordered spin arrangement. With no free parameters, ab initio calculations using the self-interaction-corrected local spin density approximation of density functional theory quantitatively reproduce the magnetic correlations to a high degree of accuracy. These results yield valuable insight into the magnetic exchange in MnO and showcase the utility of the mPDF technique for studying magnetic properties of strongly correlated electron systems.

  2. The niche, limits to species' distributions, and spatiotemporal variation in demography across the elevation ranges of two monkeyflowers.

    PubMed

    Angert, Amy L

    2009-11-17

    Understanding the processes that create and maintain species' geographic range limits has implications for many questions in ecology, evolution, and conservation biology. Many expectations for the ecological and evolutionary dynamics of populations at the range margin rest on the concordance of geographic limits and the limits of a species' ecological niche. If range limits are coincident with niche limits, then marginal populations should have lower and/or more variable vital rates and population growth rates than central populations. Using data from 8 annual censuses of marked individuals, I investigated the demography of Mimulus cardinalis and Mimulus lewisii across the species' elevation ranges. Central and marginal populations exhibited striking demographic differences, but only for one species were differences in expected directions. Marginal populations from the M. lewisii lower elevation range limit had lower and more variable survival than central populations and appeared to be demographic sinks. In contrast, marginal populations from the M. cardinalis upper elevation limit had higher fecundity and higher population growth rates than central populations. Although the species differed with respect to central-marginal patterns, they were concordant with respect to elevation; that is, both species had higher fitness in higher reaches of their examined ranges. Potential explanations for these patterns include source-sink dynamics, with asymmetrical gene flow mediated by river currents, and climate change, with recent warming shifting the species' climatic envelopes to higher elevations. Hence, assessment of spatiotemporal variation in both demography and dispersal is necessary to fully understand the relationship between the niche and species' distributions. PMID:19805178

  3. [Hearing implants].

    PubMed

    Stokroos, Robert J; George, Erwin L J

    2013-01-01

    In the Netherlands, more than 1.5 million people suffer from sensorineural hearing loss or deafness. However, fitting conventional hearing aids does not provide a solution for everyone. In recent decades, developments in medical technology have produced implantable and other devices that restore both sensorineural and conductive hearing losses. These hearing devices can be categorized into bone conductive devices, implantable middle ear prostheses, cochlear implants and auditory brainstem implants. Furthermore, new implants aimed at treating tinnitus and loss of vestibular function have recently been developed.

  4. Translationally invariant calculations of form factors, nucleon densities and momentum distributions for finite nuclei with short-range correlations included

    NASA Astrophysics Data System (ADS)

    Shebeko, A. V.; Grigorov, P. A.; Iurasov, V. S.

    2012-11-01

    Relying upon our previous treatment of the density matrices for nuclei (in general, nonrelativistic self-bound finite systems) we are studying a combined effect of center-of-mass motion and short-range nucleon-nucleon correlations on the nucleon density and momentum distributions in light nuclei (4He and 16O). Their intrinsic ground-state wave functions are constructed in the so-called fixed center-of-mass approximation, starting with mean-field Slater determinants modified by some correlator ( e.g., after Jastrow or Villars). We develop the formalism based upon the Cartesian or boson representation, in which the coordinate and momentum operators are linear combinations of the creation and annihilation operators for oscillatory quanta in the three different space directions, and get the own "Tassie-Barker" factors for each distribution and point out other model-independent results. After this separation of the center-of-mass motion effects we propose additional analytic means in order to simplify the subsequent calculations ( e.g., within the Jastrow approach or the unitary correlation operator method). The charge form factors, densities and momentum distributions of 4He and 16O evaluated by using the well-known cluster expansions are compared with data, our exact (numerical) results and microscopic calculations.

  5. The Influence of Hillslope Steepness on Sediment Supply Size Distribution along Rivers Draining the Colorado Front Range

    NASA Astrophysics Data System (ADS)

    Sato, M. M.; Shobe, C. M.; Tucker, G. E.

    2015-12-01

    The dynamics and timing of river incision are controlled by a multitude of factors including climate, topography, lithology, and sediment supply. Sediment size distribution affects fluvial erosion in rapidly incising rivers by setting the spatial frequency and temporal longevity of bed cover. Formulating accurate models of river erosion and landscape evolution requires constraints on the link between hillslope steepness and sediment size distribution supplied to the channel. We explore this relationship along Boulder and Fourmile Creeks, two rivers draining the Colorado Front Range. We extracted hillslope angles from digital elevation models at 8 locations of constant (granitic) lithology. Measured slopes ranged from 2 ± 0.2 to 35 ± 2.9 degrees, increasing with proximity to migratory knickzones on both channels. At each slope measurement location, we recorded the size of the 50 largest blocks with a long axis >0.5 m in a 50 m2 area (10 m along-channel x 5 m up hillslope). Comparison of the sum of long axes (an effective proxy for total mass supplied) from each location on Boulder Creek against the corresponding hillslope angles reveals an abrupt transition at ~34°. Hillslopes below 34° exhibit fewer blocks over 50 cm as well as lower values of total long axis length (3 blocks and 135 cm total long axis) while hillslopes over 34° show sediment size distributions heavily skewed towards large blocks (15 blocks and 1600 cm total long axis). Fourmile Creek showed similar trends, but a low number of sample sites precludes comparison with Boulder Creek. Increases in the sum of long axes may indicate a general abundance of larger sediment or presence of a few very large blocks, both of which may significantly influence river incision. We conclude that hillslope angle influences sediment size distribution in the study channels. Complicating factors include variable fracture density and the presence of pre-existing alluvial fill in some study reaches. Our results

  6. Exploring trophic strategies of exotic caprellids (Crustacea: Amphipoda): Comparison between habitat types and native vs introduced distribution ranges

    NASA Astrophysics Data System (ADS)

    Ros, Macarena; Tierno de Figueroa, José Manuel; Guerra-García, José Manuel; Navarro-Barranco, Carlos; Lacerda, Mariana Baptista; Vázquez-Luis, Maite; Masunari, Setuko

    2014-02-01

    The trophic ecology of non-native species is a key aspect to understand their invasion success and the community effects. Despite the important role of caprellid amphipods as trophic intermediates between primary producers and higher levels of marine food webs, there is very little information on their feeding habits. This is the first comprehensive study on the trophic strategies of two co-occurring introduced caprellids in the Spanish coasts: Caprella scaura and Paracaprella pusilla. The diet of 446 specimens of C. scaura and 230 of P. pusilla was analyzed to investigate whether there were differences in the feeding habits in relation to habitat characteristics (natural vs artificial hard substrata), type of host substrata (bryozoans and hydroids) and native vs introduced distribution ranges (Brazil vs Spain). Results revealed differences in diet preferences of the two species that have important implications for their trophic behaviour and showed a limited food overlap, which may favour their coexistence in introduced areas. In general terms, P. pusilla is a predator species, showing preference by crustacean prey in all of its life stages, while C. scaura feeds mainly on detritus. Although no sex-related diet shifts were observed in either of the species, evidence of ontogenetic variation in diet of C. scaura was found, with juveniles feeding on more amount of prey than adults. No diet differences were found between native and introduced populations within the same habitat type. However, P. pusilla exhibited a shift in its diet when different habitats were compared in the same distribution area, and C. scaura showed a flexible feeding behaviour between different host substrata in the same habitat type. This study shows that habitat characteristics at different scales can have greater influence on the feeding ecology of exotic species than different distribution ranges, and support the hypothesis that a switch between feeding strategies depending on habitat

  7. The effect of implantation conditions on microstructural evolution in oxygen implanted silicon

    NASA Astrophysics Data System (ADS)

    Datta, Ranju

    Ion implantation is used for the fabrication of SIMOX (separation by implanted oxygen). SIMOX is a silicon on insulator structure used for microelectronic devices, where a buried oxide layer insulates a silicon overlayer from the substrate. High energy, high dose oxygen ions are implanted into a heated single crystalline silicon wafer, followed by high temperature annealing to create a uniform buried oxide and eliminate implantation damage. The final quality of SIMOX material depends on the properties of the silicon overlayer and the buried oxide. The dominant defects are threading dislocations in the silicon overlayer and silicon inclusions (silicon islands) within the buried oxide, both of which are detrimental. The objectives of this dissertation were to evaluate the effect of implantation conditions on the formation of these defects, and to understand the underlying physical mechanisms which govern microstructural evolution in this system. The effects of implant dose, energy, substrate temperature and beam current variations on microstructural evolution were investigated, primarily, by transmission electron microscopy and x-ray diffraction. Only specific dose ranges yielded low defect density SIMOX. Threading dislocation densities were low for intermediate doses and were high for very low and very high doses. However, low silicon island densities in the buried oxide were obtained at only one specific low dose and at high doses. These dose windows were affected to different extents by the other implantation parameters. The physical mechanisms for these effects were established. Threading dislocations in the annealed state evolved from dislocation half loops present in the as-implanted state at high doses. The presence of dislocation half loops was a result of strain relief processes in the near surface region during implantation. Threading dislocations at low doses were the result of defect pinning by a bilayer oxide structure. The precipitate distribution in

  8. Distribution of interaural time difference in the barn owl's inferior colliculus in the low- and high-frequency ranges.

    PubMed

    Wagner, Hermann; Asadollahi, Ali; Bremen, Peter; Endler, Frank; Vonderschen, Katrin; von Campenhausen, Mark

    2007-04-11

    Interaural time differences are an important cue for azimuthal sound localization. It is still unclear whether the same neuronal mechanisms underlie the representation in the brain of interaural time difference in different vertebrates and whether these mechanisms are driven by common constraints, such as optimal coding. Current sound localization models may be discriminated by studying the spectral distribution of response peaks in tuning curves that measure the sensitivity to interaural time difference. The sound localization system of the barn owl has been studied intensively, but data that would allow discrimination between currently discussed models are missing from this animal. We have therefore obtained extracellular recordings from the time-sensitive subnuclei of the barn owl's inferior colliculus. Response peaks were broadly scattered over the physiological range of interaural time differences. A change in the representation of the interaural phase differences with frequency was not observed. In some neurons, response peaks fell outside the physiological range of interaural time differences. For a considerable number of neurons, the peak closest to zero interaural time difference was not the behaviorally relevant peak. The data are in best accordance with models suggesting that a place code underlies the representation of interaural time difference. The data from the high-frequency range, but not from the low-frequency range, are consistent with predictions of optimal coding. We speculate that the deviation of the representation of interaural time difference from optimal-coding models in the low-frequency range is attributable to the diminished importance of low frequencies for catching prey in this species. PMID:17428997

  9. Distribution of Late Cenozoic volcanic vents in the Cascade range: Volcanic arc segmentation and regional tectonic considerations

    NASA Astrophysics Data System (ADS)

    Guffanti, Marianne; Weaver, Craig S.

    1988-06-01

    Spatial, temporal, and compositional distributions of approximately 4000 volcanic vents formed since 16 Ma in Washington, Oregon, northern California, and northwestern Nevada illustrate the evolution of volcanism related to subduction of the Juan de Fuca plate system and extension of the Basin and Range province. Vent data were obtained from published map compilations and include monogenetic and small polygenetic volcanoes in addition to major composite centers. On the basis of the distribution of 2821 vents formed since 5 Ma, the Cascade Range is divided into five segments, with vents of the High Lava Plains along the northern margin of the Basin and Range province in Oregon forming a sixth segment. Some aspects of the Cascade Range segmentation can be related to gross structural features of the subducting Juan de Fuca plate. The orientation of the volcanic front of segments one and two changes from NW in northern Washington to NE in southern Washington, paralleling the strike of the subducting Juan de Fuca plate. Segments one and two are separated by a 90-km volcanic gap between Mount Rainier and Glacier Peak that is landward of the portion of the subducting plate having the least average dip to a depth of 60 km. A narrow, N-S trending belt of predominantly andesitic vents in Oregon constitutes a third segment, which is landward of the seismically quiet portion of the subduction zone. The narrowness of this segment may indicate steep dip of the subducting plate beneath the Cascade arc in Oregon. Vents are sparse between segment four (containing the Mount Shasta and Medicine Lake centers) and segment five (containing Lassen Peak), where the Juan de Fuca and Gorda North plates are characterized by differing age, amounts of subcrustal seismicity, and probably geometry. From the relation between seismicity at depth of 60 km and the position of the volcanic front of vents formed since 5 Ma, transitions between subducting-plate segments of varying geometry likely occur

  10. Dosimetric characterization of radionuclides for systemic tumor therapy: Influence of particle range, photon emission, and subcellular distribution

    SciTech Connect

    Uusijaervi, Helena; Bernhardt, Peter; Ericsson, Thomas; Forssell-Aronsson, Eva

    2006-09-15

    Various radionuclides have been proposed for systemic tumor therapy. However, in most dosimetric analysis of proposed radionuclides the charged particles are taken into consideration while the potential photons are ignored. The photons will cause undesirable irradiation of normal tissue, and increase the probability of toxicity in, e.g., the bone marrow. The aim of this study was to investigate the dosimetric properties according to particle range, photon emission, and subcellular radionuclide distribution, of a selection of radionuclides used or proposed for radionuclide therapy, and to investigate the possibility of dividing radionuclides into groups according to their dosimetric properties. The absorbed dose rate to the tumors divided by the absorbed dose rate to the normal tissue (TND) was estimated for different tumor sizes in a mathematical model of the human body. The body was simulated as a 70-kg ellipsoid and the tumors as spheres of different sizes (1 ng-100 g). The radionuclides were either assumed to be uniformly distributed throughout the entire tumor and normal tissue, or located in the nucleus or the cytoplasm of the tumor cells and on the cell membrane of the normal cells. Fifty-nine radionuclides were studied together with monoenergetic electrons, positrons, and alpha particles. The tumor and normal tissue were assumed to be of water density. The activity concentration ratio between the tumor and normal tissue was assumed to be 25. The radionuclides emitting low-energy electrons combined with a low photon contribution, and the alpha emitters showed high TND values for most tumor sizes. Electrons with higher energy gave reduced TND values for small tumors, while a higher photon contribution reduced the TND values for large tumors. Radionuclides with high photon contributions showed low TND value for all tumor sizes studied. The radionuclides studied could be divided into four main groups according to their TND values: beta emitters, Auger electron

  11. Distribution and long-range transport of polyfluoroalkyl substances in the Arctic, Atlantic Ocean and Antarctic coast.

    PubMed

    Zhao, Zhen; Xie, Zhiyong; Möller, Axel; Sturm, Renate; Tang, Jianhui; Zhang, Gan; Ebinghaus, Ralf

    2012-11-01

    The global distribution and long-range transport of polyfluoroalkyl substances (PFASs) were investigated using seawater samples collected from the Greenland Sea, East Atlantic Ocean and the Southern Ocean in 2009-2010. Elevated levels of ΣPFASs were detected in the North Atlantic Ocean with the concentrations ranging from 130 to 650 pg/L. In the Greenland Sea, the ΣPFASs concentrations ranged from 45 to 280 pg/L, and five most frequently detected compounds were perfluorooctanoic acid (PFOA), perfluorohexanesulfonate (PFHxS), perfluorohexanoic acid (PFHxA), perfluorooctane sulfonate (PFOS) and perfluorobutane sulfonate (PFBS). PFOA (15 pg/L) and PFOS (25-45 pg/L) were occasionally found in the Southern Ocean. In the Atlantic Ocean, the ΣPFASs concentration decreased from 2007 to 2010. The elevated PFOA level that resulted from melting snow and ice in Greenland Sea implies that the Arctic may have been driven by climate change and turned to be a source of PFASs for the marine ecosystem.

  12. Innovative use of Distributed Temperature Sensing and Meteorological Data to Understand Thermoregulation of Free-Ranging Howling Monkeys

    NASA Astrophysics Data System (ADS)

    Suarez, F. I.; Vinyard, C. J.; Williams, S. H.; Hausner, M. B.; Tyler, S. W.; Glander, K.

    2011-12-01

    Temperature fluctuations are a major driver of change in natural habitats and influence the lifestyle of all organisms because temperature impacts molecular, physiological, and behavioral processes. However, there is a lack of understanding on how temperature affects metabolism, behavior, and ecology at the organismal level. Even though physiological responses to temperature fluctuations have been well documented in laboratory conditions, it has been challenging to collect the required environmental data to study thermoregulation of free-ranging mammals such as mantled howling monkeys (Alouatta palliata). Fortunately, recent advances in fiber-optic distributed temperature sensing (DTS) now permit the observation of temperature fields in the environment at scales ranging from millimeters to kilometers. This has opened an exciting opportunity for temperature monitoring at scales that were previously not feasible. This study addresses the main limitations of previous studies of primate behavior by integrating real-time environmental data with the behavior and physiological response of free-ranging primates. In this work, we present preliminary DTS data collected in a natural habitat of howling monkeys. Fiber-optic cables were hung between the ground and an elevation of approximately 15 m within the forest canopy, providing continuous profiles of temperature without any disturbance due to the animals and habitat. These measurements were integrated with conventional meteorological data and with the ambient temperature at the location of the animal, as well as with measurements of primate's subcutaneous and core body temperatures. These data will be utilized to determine how environmental conditions relate to primate behavioral and physiological responses in time and space. The methodologies used in this study provide tools to test theories of physiological thermoregulation of other free-ranging animals.

  13. Invasive alien plants in Croatia as a threat to biodiversity of South-Eastern Europe: distributional patterns and range size.

    PubMed

    Nikolić, Toni; Mitić, Božena; Milašinović, Boris; Jelaska, Sven D

    2013-02-01

    During the analysis of alien and invasive flora of Europe, as a threat to biodiversity, data for Croatia were missing. The aim of our research was to analyse distributional patterns and range size of all invasive alien plants (64) for the state area (57,000 km(2)). They were detected on 49% of the state territory, averaging five taxa per 35 km(2). The greatest number of invasive plants (>30 per grid cell) was recorded in the major urban centres, increasing in the south-east direction and reflecting positive correlation with temperature and negative with altitude. The most endangered areas are in the Mediterranean region, especially on islands. The number of invasive plants increased with habitat diversity and almost 75% of all sites with invasive plants are located within a few habitats with direct anthropogenic influence. The results should provide a reliable regional and global basis for strategic planning regarding invasive alien plants management.

  14. Modeling of exclusive parton distributions and long-range rapidity correlations in proton-proton collisions at the LHC energies

    SciTech Connect

    Kovalenko, V. N.

    2013-10-15

    The soft part of proton-proton interaction is considered within a phenomenological model that involves the formation of color strings. Under the assumption that an elementary collision is associated with the interaction of two color dipoles, the total inelastic cross section and the multiplicity of charged particles are estimated in order to fix model parameters. Particular attention is given to modeling of exclusive parton distributions with allowance for the energy-conservation law and for fixing the center of mass, which are necessary for describing correlations. An algorithm that describes the fusion of strings in the transverse plane and which takes into account their finite rapidity width is developed. The influence of string-fusion effects on long-range correlations is found within this mechanism.

  15. Implantable Microimagers

    PubMed Central

    Ng, David C.; Tokuda, Takashi; Shiosaka, Sadao; Tano, Yasuo; Ohta, Jun

    2008-01-01

    Implantable devices such as cardiac pacemakers, drug-delivery systems, and defibrillators have had a tremendous impact on the quality of live for many disabled people. To date, many devices have been developed for implantation into various parts of the human body. In this paper, we focus on devices implanted in the head. In particular, we describe the technologies necessary to create implantable microimagers. Design, fabrication, and implementation issues are discussed vis-à-vis two examples of implantable microimagers; the retinal prosthesis and in vivo neuro-microimager. Testing of these devices in animals verify the use of the microimagers in the implanted state. We believe that further advancement of these devices will lead to the development of a new method for medical and scientific applications.

  16. Tailored ion radius distribution for increased dynamic range in FT-ICR mass analysis of complex mixtures.

    PubMed

    Kaiser, Nathan K; McKenna, Amy M; Savory, Joshua J; Hendrickson, Christopher L; Marshall, Alan G

    2013-01-01

    Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) typically utilizes an m/z-independent excitation magnitude to excite all ions to the same cyclotron radius, so that the detected signal magnitude is directly proportional to the relative ion abundance. However, deleterious space charge interaction between ion clouds is maximized for clouds of equal radius. To minimize ion cloud interactions, we induce an m/z-dependent ion radius distribution (30%-45% of the maximum cell radius) that results in a 3-fold increase in mass spectral dynamic range for complex mixtures, consistent with increased ion cloud lifetime for less-abundant ion clouds. Further, broadband frequency-sweep (chirp) excitation that contains the second and/or third harmonic frequency of an excited ion cloud swept from low-to-high frequency produces systematic variations in accurate mass measurement not observed when the sweep direction is reversed. The ion cyclotron radius distribution induces an m/z-dependent frequency shift that can be corrected to provide a root-mean-square (rms) mass measurement error of <100 ppb on petroleum-based mixtures that contain tens of thousands of identified peaks.

  17. Long-range transport of biomass burning emissions based on organic molecular markers and carbonaceous thermal distribution.

    PubMed

    Bae, Min-Suk; Shin, Ju-Seon; Lee, Kwang-Yul; Lee, Kwon-Ho; Kim, Young J

    2014-01-01

    Semi-continuous organic carbon (OC), elemental carbon (EC), and organic molecular markers were analyzed using the thermal optical transmittance method at the Gosan supersite (on Jeju Island, Korea), which has been widely used as a regional background site for East Asia. The Carbonaceous Thermal Distribution (CTD) method, which can provide detailed carbon signature characteristics relative to analytical temperature, was used to improve the carbon fractionation of the analytical method. Ground-based measurements were conducted from October 25 to November 5, 2010. During the sampling period, one high OC concentration event and two characteristic periods were observed. Considering the thermal distribution patterns, the relationship between the EC and black carbon (BC) by optical measurements, the backward trajectories, the aerosol optical thickness, the PM10 concentrations from the 316 PM-network sites that were operated by the Ministry of Environment in Korea, and the organic molecular markers, such as levoglucosan, PAHs, and organic acids, we concluded that the event was influenced by long-range transport from biomass burning emissions. This study discusses the CTD analysis with organic molecular marker concentrations, extracts and interprets additional carbon fractions from a semi-continuous data set, and provides knowledge regarding the origin of carbon sources and their behaviors. PMID:23892024

  18. The Distribution and Abundance of an Island Population of Koalas (Phascolarctos cinereus) in the Far North of Their Geographic Range

    PubMed Central

    McGregor, Denise C.; Kerr, Sarah E.; Krockenberger, Andrew K.

    2013-01-01

    Koalas are an iconic species of charismatic megafauna, of substantial social and conservation significance. They are widely distributed, often at low densities, and individuals can be difficult to detect, making population surveys challenging and costly. Consequently, koala population estimates have been limited and the results inconsistent. The aims of this study were to estimate the distribution, relative abundance and population size of the koalas on Magnetic Island, far north Queensland. Population densities were estimated in 18 different vegetation types present on the island using a Fecal Standing Crop Method. Koala density ranged from 0.404 ha−1, recorded in forest red gum and bloodwood woodland, to absence from eight of the vegetation types surveyed. The second highest density of 0.297 koalas ha−1 was recorded in mixed eucalypt woodland, which covers 45% of the island. The total abundance of koalas on Magnetic Island, not including those present in urban areas, was estimated at 825±175 (SEM). The large variation in koala density across vegetation types reinforces the need for sampling stratification when calculating abundance over large areas, as uniformity of habitat quality cannot be assumed. In this context, koala populations also occur in low densities in areas generally regarded as poor quality koala habitat. These results highlight the importance of protecting vegetation communities not traditionally considered to have high conservation value to koalas, as these habitats may be essential for maintaining viable, widespread, low-density populations. The results from this study provide a baseline to assess future trends in koala distribution, density and abundance on Magnetic Island. PMID:23527258

  19. SYNCHROTRON POLARIZATION AND SYNCHROTRON SELF-ABSORPTION SPECTRA FOR A POWER-LAW PARTICLE DISTRIBUTION WITH FINITE ENERGY RANGE

    SciTech Connect

    Fouka, M.; Ouichaoui, S. E-mail: souichaoui@usthb.dz

    2011-12-10

    We have derived asymptotic forms for the degree of polarization of the optically thin synchrotron and for synchrotron self-absorption (SSA) spectra assuming a power-law particle distribution of the form N({gamma}) {approx} {gamma}{sup -p} with {gamma}{sub 1} < {gamma} < {gamma}{sub 2}, especially for a finite high-energy limit, {gamma}{sub 2}, in the case of an arbitrary pitch angle. The new results inferred concern more especially the high-frequency range x >> {eta}{sup 2} with parameter {eta} = {gamma}{sub 2}/{gamma}{sub 1}. The calculated SSA spectra concern instantaneous photon emission where cooling effects are not considered. They have been obtained by also ignoring likely effects such as Comptonization, pair creation and annihilation, as well as magnetic photon splitting. To that aim, in addition to the two usual absorption frequencies, a third possible one has been derived and expressed in terms of the Lambert W function based on the analytical asymptotic form of the absorption coefficient, {alpha}{sub {nu}}, for the high-frequency range {nu} >> {nu}{sub 2} (with {nu}{sub 2} the synchrotron frequency corresponding to {gamma}{sub 2}). We have shown that the latter frequency may not have realistic applications in astrophysics, except in the case of an adequate set of parameters allowing one to neglect Comptonization effects. More detailed calculations and discussions are presented.

  20. Energy expenditure of the spotted snow skink, Niveoscincus ocellatus, at two climatic extremes of its distribution range.

    PubMed

    Yuni, Luh P E K; Jones, Susan M; Wapstra, Erik

    2015-08-01

    The study of energy expenditure between populations of a wide ranging ectothermic species may provide an insight into how organisms respond to variation in environmental conditions. In this study, the energy expenditure of male spotted snow skinks, Niveoscincus ocellatus, living at the two extremes of the species' distribution range (warm lowland versus cold alpine site) was measured using the doubly labelled water method. Males at the cold alpine site expended more energy per gram per hour compared to their counterparts living at the warm lowland site. Lizards living at high altitude were active at lower temperatures compared with those at the low altitude site, which resulted in a longer activity time for the highland population. However, the differences in energy expenditure cannot be explained only by these differences in activity time. We further suggest that at the cold alpine site, lizards compensated for the low temperatures by elevating their metabolism which subsequently increased their energy expenditure. An elevated metabolic rate combined with modified thermoregulatory behaviour is likely an important mechanism allowing N. ocellatus to cope with the cold environments at high altitude sites. PMID:26267516

  1. Extended-range forecast for the temporal distribution of clustering tropical cyclogenesis over the western North Pacific

    NASA Astrophysics Data System (ADS)

    Zhu, Zhiwei; Li, Tim; Bai, Long; Gao, Jianyun

    2016-09-01

    Based on outgoing longwave radiation (OLR), an index for clustering tropical cyclogenesis (CTC) over the western North Pacific (WNP) was defined. Around 76 % of total CTC events were generated during the active phase of the CTC index, and 38 % of the total active phase was concurrent with CTC events. For its continuous property, the CTC index was used as the representative predictand for extended-range forecasting the temporal distribution of CTC events. The predictability sources for CTC events were detected via correlation analyses of the previous 35-5-day lead atmospheric fields against the CTC index. The results showed that the geopotential height at different levels and the 200 hPa zonal wind over the global tropics possessed large predictability sources, whereas the predictability sources of other variables, e.g., OLR, zonal wind, and relatively vorticity at 850 hPa and relatively humility at 700 hPa, were mainly confined to the tropical Indian Ocean and western Pacific Ocean. Several spatial-temporal projection model (STPM) sets were constructed to carry out the extended-range forecast for the CTC index. By combining the output of STPMs separately conducted for the two dominant modes of intraseasonal variability, e.g., the 10-30 and the 30-80 day mode, useful forecast skill could be achieved for a 30-day lead time. The combined output successfully captured both the 10-30 and 30-80 day mode at least 10 days in advance. With a relatively low rate of false alarm, the STPM achieved hits for 80 % (69 %) of 54 CTC events during 2003-2014 at the 10-day (20-day) lead time, suggesting a practical value of the STPM for real-time forecasting WNP CTC events at an extended range.

  2. SYNCHROTRON AND SYNCHROTRON SELF-ABSORPTION FOR A POWER-LAW PARTICLE DISTRIBUTION: ASYMPTOTIC FORMS FOR FINITE ENERGY RANGE

    SciTech Connect

    Fouka, M.; Ouichaoui, S.

    2009-12-10

    We calculate and plot the synchrotron power, P {sub n}u, the absorption coefficient, alpha{sub n}u, and the source function, S {sub n}u, for a power-law distribution of charged particles with Lorentz parameter values gamma{sub 1} <= gamma <= gamma{sub 2}. For this purpose, we define parametric functions Z{sub p} (x, eta), H{sub p} (x, eta), and Y{sub p} (x, eta) with eta = gamma{sub 2}/gamma{sub 1}, such that P {sub n}u propor to Z{sub p} (gamma{sup -2} {sub 1}nu/nu{sub 0}, eta), alpha{sub n}u propor to H{sub p} (gamma{sup -2} {sub 1}nu/nu{sub 0}, eta), and S {sub n}u propor to Y{sub p} (gamma{sup -2} {sub 1}nu/nu{sub 0}, eta). Corresponding asymptotic forms are also calculated and plotted for three frequency ranges, i.e., x << 1, 1 << x << eta{sup 2}, and x >> eta{sup 2}, especially in the case of finite parameter eta. Asymptotic forms of the middle range are possible for functions Z{sub p} and Y{sub p} for p>1/3, and for function H{sub p} for all positive values of index p. A characteristic value, eta {sub c}(p, epsilon) (with epsilon << 1), is then defined for each of the above functions so that for eta approx> eta {sub c}(p, epsilon) the middle range asymptotic forms could be considered. Further calculation details are also presented and discussed.

  3. 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

  4. Histrelin Implant

    MedlinePlus

    ... response to histrelin implant. Your blood sugar and glycosylated hemoglobin (HbA1c) should be checked regularly.Ask your pharmacist any questions you have about histrelin implant.It is important for you to keep a written list of all of the prescription and ...

  5. H{sup +} ion-implantation energy dependence of electronic transport properties in the MeV range in n-type silicon wafers using frequency-domain photocarrier radiometry

    SciTech Connect

    Wang Chinhua; Mandelis, Andreas; Tolev, Jordan; Burchard, Bernd; Meijer, Jan

    2007-06-15

    Industrial n-type Si wafers (resistivity of 5-10 {omega} cm) were H{sup +} ion implanted with energies between 0.75 and 2.00 MeV, and the electronic transport properties of the implanted layer (recombination lifetime, carrier diffusion coefficient, and front-surface and implanted-interface recombination velocities s{sub 1} and s{sub 2}) were studied using photocarrier radiometry (PCR). A quantitative fitting procedure to the diffusing photoexcited free-carrier density wave was introduced using a relatively simple two-layer PCR model in lieu of the more realistic but substantially more complicated three-layer model. The experimental trends in the transport properties of H{sup +}-implanted Si layers extracted from the PCR amplitude and phase data as functions of implantation energy corroborate a physical model of the implanted layer in which (a) overlayer damage due to the light H{sup +} ions decreases with increased depth of implantation at higher energies (b) the implanted region damage close to the interface is largely decoupled from the overlayer crystallinity, and (c) the concentration of implanted H{sup +} ions decreases at higher implantation energies at the interface, thus decreasing the degree of implantation damage at the interface proper.

  6. Distribution of Microbial Arsenic Reduction, Oxidation and Extrusion Genes along a Wide Range of Environmental Arsenic Concentrations

    PubMed Central

    Escudero, Lorena V.; Casamayor, Emilio O.; Chong, Guillermo; Pedrós-Alió, Carles; Demergasso, Cecilia

    2013-01-01

    The presence of the arsenic oxidation, reduction, and extrusion genes arsC, arrA, aioA, and acr3 was explored in a range of natural environments in northern Chile, with arsenic concentrations spanning six orders of magnitude. A combination of primers from the literature and newly designed primers were used to explore the presence of the arsC gene, coding for the reduction of As (V) to As (III) in one of the most common detoxification mechanisms. Enterobacterial related arsC genes appeared only in the environments with the lowest As concentration, while Firmicutes-like genes were present throughout the range of As concentrations. The arrA gene, involved in anaerobic respiration using As (V) as electron acceptor, was found in all the systems studied. The As (III) oxidation gene aioA and the As (III) transport gene acr3 were tracked with two primer sets each and they were also found to be spread through the As concentration gradient. Sediment samples had a higher number of arsenic related genes than water samples. Considering the results of the bacterial community composition available for these samples, the higher microbial phylogenetic diversity of microbes inhabiting the sediments may explain the increased number of genetic resources found to cope with arsenic. Overall, the environmental distribution of arsenic related genes suggests that the occurrence of different ArsC families provides different degrees of protection against arsenic as previously described in laboratory strains, and that the glutaredoxin (Grx)-linked arsenate reductases related to Enterobacteria do not confer enough arsenic resistance to live above certain levels of As concentrations. PMID:24205341

  7. In utero transmission and tissue distribution of chronic wasting disease-associated prions in free-ranging Rocky Mountain elk.

    PubMed

    Selariu, Anca; Powers, Jenny G; Nalls, Amy; Brandhuber, Monica; Mayfield, Amber; Fullaway, Stephenie; Wyckoff, Christy A; Goldmann, Wilfred; Zabel, Mark M; Wild, Margaret A; Hoover, Edward A; Mathiason, Candace K

    2015-11-01

    The presence of disease-associated prions in tissues and bodily fluids of chronic wasting disease (CWD)-infected cervids has received much investigation, yet little is known about mother-to-offspring transmission of CWD. Our previous work demonstrated that mother-to-offspring transmission is efficient in an experimental setting. To address the question of relevance in a naturally exposed free-ranging population, we assessed maternal and fetal tissues derived from 19 elk dam-calf pairs collected from free-ranging Rocky Mountain elk from north-central Colorado, a known CWD endemic region. Conventional immunohistochemistry identified three of 19 CWD-positive dams, whereas a more sensitive assay [serial protein misfolding cyclic amplification (sPMCA)] detected CWD prion seeding activity (PrPCWD) in 15 of 19 dams. PrPCWD distribution in tissues was widespread, and included the central nervous system (CNS), lymphoreticular system, and reproductive, secretory, excretory and adipose tissues. Interestingly, five of 15 sPMCA-positive dams showed no evidence of PrPCWD in either CNS or lymphoreticular system, sites typically assessed in diagnosing CWD. Analysis of fetal tissues harvested from the 15 sPMCA-positive dams revealed PrPCWD in 80 % of fetuses (12 of 15), regardless of gestational stage. These findings demonstrated that PrPCWD is more abundant in peripheral tissues of CWD-exposed elk than current diagnostic methods suggest, and that transmission of prions from mother to offspring may contribute to the efficient transmission of CWD in naturally exposed cervid populations. PMID:26358706

  8. Distribution of microbial arsenic reduction, oxidation and extrusion genes along a wide range of environmental arsenic concentrations.

    PubMed

    Escudero, Lorena V; Casamayor, Emilio O; Chong, Guillermo; Pedrós-Alió, Carles; Demergasso, Cecilia

    2013-01-01

    The presence of the arsenic oxidation, reduction, and extrusion genes arsC, arrA, aioA, and acr3 was explored in a range of natural environments in northern Chile, with arsenic concentrations spanning six orders of magnitude. A combination of primers from the literature and newly designed primers were used to explore the presence of the arsC gene, coding for the reduction of As (V) to As (III) in one of the most common detoxification mechanisms. Enterobacterial related arsC genes appeared only in the environments with the lowest As concentration, while Firmicutes-like genes were present throughout the range of As concentrations. The arrA gene, involved in anaerobic respiration using As (V) as electron acceptor, was found in all the systems studied. The As (III) oxidation gene aioA and the As (III) transport gene acr3 were tracked with two primer sets each and they were also found to be spread through the As concentration gradient. Sediment samples had a higher number of arsenic related genes than water samples. Considering the results of the bacterial community composition available for these samples, the higher microbial phylogenetic diversity of microbes inhabiting the sediments may explain the increased number of genetic resources found to cope with arsenic. Overall, the environmental distribution of arsenic related genes suggests that the occurrence of different ArsC families provides different degrees of protection against arsenic as previously described in laboratory strains, and that the glutaredoxin (Grx)-linked arsenate reductases related to Enterobacteria do not confer enough arsenic resistance to live above certain levels of As concentrations. PMID:24205341

  9. In utero transmission and tissue distribution of chronic wasting disease-associated prions in free-ranging Rocky Mountain elk

    PubMed Central

    Selariu, Anca; Powers, Jenny G.; Nalls, Amy; Brandhuber, Monica; Mayfield, Amber; Fullaway, Stephenie; Wyckoff, Christy A.; Goldmann, Wilfred; Zabel, Mark M.; Wild, Margaret A.; Hoover, Edward A.

    2015-01-01

    The presence of disease-associated prions in tissues and bodily fluids of chronic wasting disease (CWD)-infected cervids has received much investigation, yet little is known about mother-to-offspring transmission of CWD. Our previous work demonstrated that mother-to-offspring transmission is efficient in an experimental setting. To address the question of relevance in a naturally exposed free-ranging population, we assessed maternal and fetal tissues derived from 19 elk dam–calf pairs collected from free-ranging Rocky Mountain elk from north-central Colorado, a known CWD endemic region. Conventional immunohistochemistry identified three of 19 CWD-positive dams, whereas a more sensitive assay [serial protein misfolding cyclic amplification (sPMCA)] detected CWD prion seeding activity (PrPCWD) in 15 of 19 dams. PrPCWD distribution in tissues was widespread, and included the central nervous system (CNS), lymphoreticular system, and reproductive, secretory, excretory and adipose tissues. Interestingly, five of 15 sPMCA-positive dams showed no evidence of PrPCWD in either CNS or lymphoreticular system, sites typically assessed in diagnosing CWD. Analysis of fetal tissues harvested from the 15 sPMCA-positive dams revealed PrPCWD in 80 % of fetuses (12 of 15), regardless of gestational stage. These findings demonstrated that PrPCWD is more abundant in peripheral tissues of CWD-exposed elk than current diagnostic methods suggest, and that transmission of prions from mother to offspring may contribute to the efficient transmission of CWD in naturally exposed cervid populations. PMID:26358706

  10. In utero transmission and tissue distribution of chronic wasting disease-associated prions in free-ranging Rocky Mountain elk.

    PubMed

    Selariu, Anca; Powers, Jenny G; Nalls, Amy; Brandhuber, Monica; Mayfield, Amber; Fullaway, Stephenie; Wyckoff, Christy A; Goldmann, Wilfred; Zabel, Mark M; Wild, Margaret A; Hoover, Edward A; Mathiason, Candace K

    2015-11-01

    The presence of disease-associated prions in tissues and bodily fluids of chronic wasting disease (CWD)-infected cervids has received much investigation, yet little is known about mother-to-offspring transmission of CWD. Our previous work demonstrated that mother-to-offspring transmission is efficient in an experimental setting. To address the question of relevance in a naturally exposed free-ranging population, we assessed maternal and fetal tissues derived from 19 elk dam-calf pairs collected from free-ranging Rocky Mountain elk from north-central Colorado, a known CWD endemic region. Conventional immunohistochemistry identified three of 19 CWD-positive dams, whereas a more sensitive assay [serial protein misfolding cyclic amplification (sPMCA)] detected CWD prion seeding activity (PrPCWD) in 15 of 19 dams. PrPCWD distribution in tissues was widespread, and included the central nervous system (CNS), lymphoreticular system, and reproductive, secretory, excretory and adipose tissues. Interestingly, five of 15 sPMCA-positive dams showed no evidence of PrPCWD in either CNS or lymphoreticular system, sites typically assessed in diagnosing CWD. Analysis of fetal tissues harvested from the 15 sPMCA-positive dams revealed PrPCWD in 80 % of fetuses (12 of 15), regardless of gestational stage. These findings demonstrated that PrPCWD is more abundant in peripheral tissues of CWD-exposed elk than current diagnostic methods suggest, and that transmission of prions from mother to offspring may contribute to the efficient transmission of CWD in naturally exposed cervid populations.

  11. Coupling Fluvial Processes and Landslide Distribution Toward Geomorphological Hazard Assessment: Cases in Tectonically Active Mountain Ranges in Taiwan and Japan

    NASA Astrophysics Data System (ADS)

    Tsou, C. Y.; Chigira, M.; Matsushi, Y.; Arai, N.; Chen, S. C.; Feng, Z. Y.

    2015-12-01

    Large-scale destabilization of mountain slopes, which are affected by long-term river incision, give rise to the risk of catastrophic failures in tectonically active ranges. We found deep-seated gravitational slope deformations (DGSDs) induced by these processes in the Chishan River and Dahan River in the Central Range in Taiwan and the Kumano River in the Kii Mts. in Japan. These areas comprise paleosurface remnants with moderate relief at higher elevations and incised V-shaped inner gorges below them, which were made by the recession of knickpoints. Our studies include field surveys, mapping of DGSD and landslide scars, and cosmogenic nuclide exposure dating of several landform surfaces. In the Dahan River catchment, rims of paleosurfaces, which have a minimum age of ca. 150 kyr, are distributed up to 600 m above the present river bed, acting as a proxy of fluvial dissection associated with phases of river incision since the middle to late Pleistocene. The relationships between slope movements and the topography modified by the river incision show that about 53% of all DGSDs, or all large DGSDs (>106 m2) and catastrophic landslides occurred on slopes along the rims of paleosurfaces, suggesting they could be fundamentally controlled by long-term river incision. Catastrophic landslides observed along or below the rims of paleosurfaces were preceded by buckling of alternating beds of sandstone and mudstone on parallel or underdip cataclinal slopes dipped at 50° to 58°. This suggests that the peripheral zones of the paleosurfaces may be most susceptible to future catastrophic landslides, particularly on parallel or underdip cataclinal slopes comprising alternating beds of sandstone and mudstone dipping at 50° to 60°. The 2009 Typhoon Morakot-induced Shiaolin landslide along the Chishan River and the 2011 Typhoon Talas-induced catastrophic landslides along the Kumano River also occurred on the gravitationally deformed slopes along the rims of paleosurfaces.

  12. GRBs Radiative Processes: Synchrotron and Synchrotron Self-Absorption From a Power Law Electrons Distribution with Finite Energy Range

    SciTech Connect

    Fouka, M.; Ouichaoui, S.

    2010-10-31

    Synchrotron emission behind relativistic magnetic internal-external shocks in gamma-ray bursts cosmological explosions is assumed to be the basic emission mechanism for prompt and afterglow emissions. Inverse Compton from relativistic electrons can also have appreciable effects by upscattering initial synchrotron or blackbody photons or other photons fields up to GeV-TeV energies. For extreme physical conditions such as high magnetic fields (e.g., B>10{sup 5} Gauss) self-absorption is not negligible and can hardly affect spectra at least for the low energy range. In this paper we present calculations of the synchrotron power, P{sub {nu}}, and their asymptotic forms, generated by a power law relativistic electron distribution of type N{sub e}({gamma}) = C{gamma}{sup -p} with {gamma}{sub 1}<{gamma}<{gamma}{sub 2}, especially for finite values of the higher limit {gamma}{sub 2}. For this aim we defined the dimensionless parametric function Z{sub p}(x,{eta}) with x = {nu}/{nu}{sub 1} and {eta} = {gamma}{sub 2}/{gamma}{sub 1} so that P{sub {nu}{proportional_to}Zp}({nu}/{nu}{sub 1},{eta}), with {nu}{sub 1} = (3/4{pi}){gamma}{sub 1}{sup 2}qBsin{theta}/mc({theta} being the pitch angle). Asymptotic forms of this later are derived for three different frequency ranges, i.e., x<<1, 1<>{eta}{sup 2}. These results are then used to calculate the absorption coefficient, {alpha}{sub {nu}}, and the source function, S{sub {nu}}, together with their asymptotic forms through the dimensionless parametric functions H{sub p}(x,{eta}) and Y{sub p}(x,{eta}), respectively. Further calculation details are also presented and discussed.

  13. Flat-topped mountain ranges: Their global distribution and value for understanding the evolution of mountain topography

    NASA Astrophysics Data System (ADS)

    Calvet, Marc; Gunnell, Yanni; Farines, Bernard

    2015-07-01

    Extensive tracts of low-gradient topography in steep mountain ranges, either forming rangetop plateaus or terraced pediments on range flanks, are widely distributed in mountain belts around the world. Before the advent of plate tectonics, such populations of planar landforms were interpreted as vestiges of a post-orogenic raised peneplain, i.e., a low-gradient land surface resulting from the decay, during long intervals of base-level stability, of a previous mountain range that was subsequently raised once again to great elevations-thus forming a new mountain range. This two-stage model has been challenged by theories that advocate continuity in tectonic processes and more gradual changes in base level, and thus expect a more immediate and proportionate response of geomorphic systems. Here we present a global survey of erosion surfaces in mountain ranges and put existing theories and empirical evidence into a broad perspective calling for further research into the rates and regimes of long-term mountain evolution. The resulting library of case studies provides opportunities for comparative analysis and helps to classify the landform mosaics that are likely to arise from the interplay between (i) crustal regimes, which at convergent plate margins need be neither uniform nor steady at all times; (ii) radiation-driven and gravity-driven geomorphic regimes, which are mainly determined by crustal boundary conditions and climate; and (iii) paleogeography, through which clues about base-level changes can be obtained. We examine intracratonic and plate-margin settings, with examples from thin-skinned fold belts, thick-skinned fold belts, island-arc and other subduction-related settings, and bivergent collisional orogens. Results reveal that the existence of erosion surfaces is not a simple function of geodynamic setting. Although some erosion surfaces are pre-orogenic, evidence about their predominantly post-orogenic age is supported by apatite fission-track and helium

  14. Pediatric Cochlear Implantation: Why Do Children Receive Implants Late?

    PubMed Central

    Ham, Julia; Whittingham, JoAnne

    2015-01-01

    Objectives: Early cochlear implantation has been widely promoted for children who derive inadequate benefit from conventional acoustic amplification. Universal newborn hearing screening has led to earlier identification and intervention, including cochlear implantation in much of the world. The purpose of this study was to examine age and time to cochlear implantation and to understand the factors that affected late cochlear implantation in children who received cochlear implants. Design: In this population-based study, data were examined for all children who underwent cochlear implant surgery in one region of Canada from 2002 to 2013. Clinical characteristics were collected prospectively as part of a larger project examining outcomes from newborn hearing screening. For this study, audiologic details including age and severity of hearing loss at diagnosis, age at cochlear implant candidacy, and age at cochlear implantation were documented. Additional detailed medical chart information was extracted to identify the factors associated with late implantation for children who received cochlear implants more than 12 months after confirmation of hearing loss. Results: The median age of diagnosis of permanent hearing loss for 187 children was 12.6 (interquartile range: 5.5, 21.7) months, and the age of cochlear implantation over the 12-year period was highly variable with a median age of 36.2 (interquartile range: 21.4, 71.3) months. A total of 118 (63.1%) received their first implant more than 12 months after confirmation of hearing loss. Detailed analysis of clinical profiles for these 118 children revealed that late implantation could be accounted for primarily by progressive hearing loss (52.5%), complex medical conditions (16.9%), family indecision (9.3%), geographical location (5.9%), and other miscellaneous known (6.8%) and unknown factors (8.5%). Conclusions: This study confirms that despite the trend toward earlier implantation, a substantial number of children

  15. Biomaterials in cochlear implants

    PubMed Central

    Stöver, Timo; Lenarz, Thomas

    2011-01-01

    The cochlear implant (CI) represents, for almost 25 years now, the gold standard in the treatment of children born deaf and for postlingually deafened adults. These devices thus constitute the greatest success story in the field of ‘neurobionic’ prostheses. Their (now routine) fitting in adults, and especially in young children and even babies, places exacting demands on these implants, particularly with regard to the biocompatibility of a CI’s surface components. Furthermore, certain parts of the implant face considerable mechanical challenges, such as the need for the electrode array to be flexible and resistant to breakage, and for the implant casing to be able to withstand external forces. As these implants are in the immediate vicinity of the middle-ear mucosa and of the junction to the perilymph of the cochlea, the risk exists – at least in principle – that bacteria may spread along the electrode array into the cochlea. The wide-ranging requirements made of the CI in terms of biocompatibility and the electrode mechanism mean that there is still further scope – despite the fact that CIs are already technically highly sophisticated – for ongoing improvements to the properties of these implants and their constituent materials, thus enhancing the effectiveness of these devices. This paper will therefore discuss fundamental material aspects of CIs as well as the potential for their future development. PMID:22073103

  16. Parasite communities and feeding ecology of the European sprat (Sprattus sprattus L.) over its range of distribution.

    PubMed

    Kleinertz, Sonja; Klimpel, Sven; Palm, Harry W

    2012-03-01

    The metazoan parasite fauna and feeding ecology of 165 Sprattus sprattus (L., 1758) was studied from different geographic regions (Baltic Sea, North Sea, English Channel, Bay of Biscay, Mediterranean Sea). A total of 13 metazoan parasite species were identified including six Digenea, one Monogenea, two Cestoda, two Nematoda and two Crustacea. Didymozoidae indet., Lecithocladium excisum and Bomolochidae indet. represent new host records. The parasite species richness differed according to regions and ranged between 3 and 10. The most species-rich parasite fauna was recorded for sprats from the Bay of Biscay (North Atlantic), and the fishes from the Baltic Sea contained the lowest number of parasite species. More closely connected geographical regions, the North Sea, English Channel and Bay of Biscay, showed more similar parasite component communities compared with more distant regions. From the examined stomachs of S. sprattus, a total of 11 different prey items were identified, including Mollusca, Annelida, Crustacea and Tunicata. The highest number of prey organisms belonged to the crustaceans. The variety of prey items in the stomach was reflected by the parasite community differences and parasite species richness from the different regions. The feeding ecology of the fish at the sampled localities was responsible for the observed parasite composition and, secondarily, the zoogeographical distribution of the parasites, questioning the use of the recorded sprat parasites as biological indicators for environmental conditions and change.

  17. THE INFLUENCE OF SHORT-RANGE INTERACTIONS ON PROTEIN CONFORMATION, III. DIPEPTIDE DISTRIBUTIONS IN PROTEINS OF KNOWN SEQUENCE AND STRUCTURE*

    PubMed Central

    Kotelchuck, D.; Dygert, M.; Scheraga, H. A.

    1969-01-01

    A statistical analysis is made of the distribution into α-helical and non-α-helical regions of the various dipeptide types appearing in a sample of seven proteins of known sequence and structure. By considering as a group all dipeptide types occurring at a given location relative to the reported helix-coil boundaries and examining the percentage of cases in which these appear in non-α-helical regions throughout the protein sample, we find a sharp change in the nature of the observed dipeptide types when the helix-coil boundary is crossed. Furthermore, we find that dipeptide types which occur in the coil region near the C-terminal end of helical segments are non-α-helical in almost 90 per cent of the cases in which they appear throughout the sample. No similar effect is found in the coil region near the N-terminal end of helical segments. These results give evidence for the importance of short-range interactions in determining protein conformation. They are also consistent with predictions based on a model for helix formation given in the second paper of this series.1 PMID:5259754

  18. Final Report for DOE Project: Climate Effects on Plant Range Distributions and Community Structure of Pacific Northwest Prairies

    SciTech Connect

    Bridgham, Scott D.; Johnson, Bart

    2013-09-26

    Pacific Northwest (PNW) prairies are an imperiled ecosystem that contain a large number of plant species with high fidelity to this habitat. The few remaining high-quality PNW prairies harbor a number of sensitive, rare, and endangered plant species that may be further at-risk with climate change. Thus, PNW prairies are an excellent model system to examine how climate change will affect the distribution of native plant species in grassland sites. Our experimental objectives were to determine: (i) how climate change will affect the range distribution of native plant species; (ii) what life history stages are most sensitive to climate change in a group of key indicator native species; (iii) the robustness of current restoration techniques and suites of species to changing climate, and in particular, the relative competitiveness of native species versus exotic invasive species; and (iv) the effects of climate change on carbon and nutrient cycling and soil-microbial-plant feedbacks. We addressed these objectives by experimentally increasing temperature 2.5 to 3.0 ºC above ambient with overhead infrared lamps and increasing wet-season precipitation by 20% above ambient in three upland prairie sites in central-western Washington, central-western Oregon, and southwestern Oregon from fall 2010 through 2012. Additional precipitation was applied within 2 weeks of when it fell so precipitation intensity was increased, particularly during the winter rainy season but with minimal additions during the summer dry season. These three sites also represent a 520-km natural climate gradient of increasing degree of severity of Mediterranean climate from north to south. After removing the extant vegetation, we planted a diverse suite of 12 native species that have their northern range limit someplace within the PNW in each experimental plot. An additional 20 more wide-spread native species were also planted into each plot. We found that recruitment of plant species within their ranges

  19. Development of vertical compact ion implanter for gemstones applications

    NASA Astrophysics Data System (ADS)

    Intarasiri, S.; Wijaikhum, A.; Bootkul, D.; Suwannakachorn, D.; Tippawan, U.; Yu, L. D.; Singkarat, S.

    2014-08-01

    Ion implantation technique was applied as an effective non-toxic treatment of the local Thai natural corundum including sapphires and rubies for the enhancement of essential qualities of the gemstones. Energetic oxygen and nitrogen ions in keV range of various fluences were implanted into the precious stones. It has been thoroughly proved that ion implantation can definitely modify the gems to desirable colors together with changing their color distribution, transparency and luster properties. These modifications lead to the improvement in quality of the natural corundum and thus its market value. Possible mechanisms of these modifications have been proposed. The main causes could be the changes in oxidation states of impurities of transition metals, induction of charge transfer from one metal cation to another and the production of color centers. For these purposes, an ion implanter of the kind that is traditionally used in semiconductor wafer fabrication had already been successfully applied for the ion beam bombardment of natural corundum. However, it is not practical for implanting the irregular shape and size of gem samples, and too costly to be economically accepted by the gem and jewelry industry. Accordingly, a specialized ion implanter has been requested by the gem traders. We have succeeded in developing a prototype high-current vertical compact ion implanter only 1.36 m long, from ion source to irradiation chamber, for these purposes. It has been proved to be very effective for corundum, for example, color improvement of blue sapphire, induction of violet sapphire from low value pink sapphire, and amelioration of lead-glass-filled rubies. Details of the implanter and recent implantation results are presented.

  20. Reconfigurable Resonant Regulating Rectifier With Primary Equalization for Extended Coupling- and Loading-Range in Bio-Implant Wireless Power Transfer.

    PubMed

    Li, Xing; Meng, Xiaodong; Tsui, Chi-Ying; Ki, Wing-Hung

    2015-12-01

    Wireless power transfer using reconfigurable resonant regulating (R(3)) rectification suffers from limited range in accommodating varying coupling and loading conditions. A primary-assisted regulation principle is proposed to mitigate these limitations, of which the amplitude of the rectifier input voltage on the secondary side is regulated by accordingly adjusting the voltage amplitude Veq on the primary side. A novel current-sensing method and calibration scheme track Veq on the primary side. A ramp generator simultaneously provides three clock signals for different modules. Both the primary equalizer and the R(3) rectifier are implemented as custom integrated circuits fabricated in a 0.35 μm CMOS process, with the global control implemented in FPGA. Measurements show that with the primary equalizer, the workable coupling and loading ranges are extended by 250% at 120 mW load and 300% at 1.2 cm coil distance compared to the same system without the primary equalizer. A maximum rectifier efficiency of 92.5% and a total system efficiency of 62.4% are demonstrated. PMID:26742141

  1. Reconfigurable Resonant Regulating Rectifier With Primary Equalization for Extended Coupling- and Loading-Range in Bio-Implant Wireless Power Transfer.

    PubMed

    Li, Xing; Meng, Xiaodong; Tsui, Chi-Ying; Ki, Wing-Hung

    2015-12-01

    Wireless power transfer using reconfigurable resonant regulating (R(3)) rectification suffers from limited range in accommodating varying coupling and loading conditions. A primary-assisted regulation principle is proposed to mitigate these limitations, of which the amplitude of the rectifier input voltage on the secondary side is regulated by accordingly adjusting the voltage amplitude Veq on the primary side. A novel current-sensing method and calibration scheme track Veq on the primary side. A ramp generator simultaneously provides three clock signals for different modules. Both the primary equalizer and the R(3) rectifier are implemented as custom integrated circuits fabricated in a 0.35 μm CMOS process, with the global control implemented in FPGA. Measurements show that with the primary equalizer, the workable coupling and loading ranges are extended by 250% at 120 mW load and 300% at 1.2 cm coil distance compared to the same system without the primary equalizer. A maximum rectifier efficiency of 92.5% and a total system efficiency of 62.4% are demonstrated.

  2. SEM analysis of ion implanted SiC

    NASA Astrophysics Data System (ADS)

    Malherbe, Johan B.; van der Berg, N. G.; Botha, A. J.; Friedland, E.; Hlatshwayo, T. T.; Kuhudzai, R. J.; Wendler, E.; Wesch, W.; Chakraborty, P.; da Silveira, E. F.

    2013-11-01

    SiC is a material used in two future energy production technologies, firstly as a photovoltaic layer to harness the UV spectrum in high efficient power solar cells, and secondly as a diffusion barrier material for radioactive fission products in the fuel elements of the next generation of nuclear power plants. For both applications, there is an interest in the implantation of reactive and non-reactive ions into SiC and their effects on the properties of the SiC. In this study 360 keV Ag+, I+ and Xe+ ions were separately implanted into 6H-SiC and in polycrystalline SiC at various substrate temperatures. The implanted samples were also annealed in vacuum at temperatures ranging from 900 °C to 1600 °C for various times. In recent years, there had been significant advances in scanning electron microscopy (SEM) with the introduction of an in-lens detector combined with field emission electron guns. This allows defects in solids, such as radiation damage created by the implanted ions, to be detected with SEM. Cross-sectional SEM images of 6H-SiC wafers implanted with 360 keV Ag+ ions at room temperature and at 600 °C and then vacuum annealed at different temperatures revealed the implanted layers and their thicknesses. A similar result is shown of 360 keV I+ ions implanted at 600 °C into 6H-SiC and annealed at 1600 °C. The 6H-SiC is not amorphized but remained crystalline when implanting at 600 °C. There are differences in the microstructure of 6H-SiC implanted with silver at the two temperatures as well as with reactive iodine ions. Voids (bubbles) are created in the implanted layers into which the precipitation of silver and iodine can occur after annealing of the samples. The crystallinity of the substrate via implantation temperature caused differences in the distribution and size of the voids. Implantation of xenon ions in polycrystalline SiC at 350 °C does not amorphize the substrate as is the case with room temperature heavy ion bombardment. Subsequent

  3. Geographical differentiation in floral traits across the distribution range of the Patagonian oil-secreting Calceolaria polyrhiza: do pollinators matter?

    PubMed Central

    Cosacov, Andrea; Cocucci, Andrea A.; Sérsic, Alicia N.

    2014-01-01

    Background and Aims The underlying evolutionary processes of pollinator-driven floral diversification are still poorly understood. According to the Grant–Stebbins model speciation begins with adaptive local differentiation in the response to spatial heterogeneity in pollinators. Although this crucial process links the micro- and macroevolution of floral adaptation, it has received little attention. In this study geographical phenotypic variation was investigated in Patagonian Calceolaria polyrhiza and its pollinators, two oil-collecting bee species that differ in body size and geographical distribution. Methods Patterns of phenotypic variation were examined together with their relationships with pollinators and abiotic factors. Six floral and seven vegetative traits were measured in 45 populations distributed across the entire species range. Climatic and edaphic parameters were determined for 25 selected sites, 2–16 bees per site of the most frequent pollinator species were captured, and a critical flower–bee mechanical fitting trait involved in effective pollination was measured. Geographical patterns of phenotypic and environmental variation were examined using uni- and multivariate analyses. Decoupled geographical variation between corolla area and floral traits related to the mechanical fit of pollinators was explored using a Mantel test. Key Results The body length of pollinators and the floral traits related to mechanical fit were strongly correlated with each other. Geographical variation of the mechanical-fit-related traits was decoupled from variation in corolla size; the latter had a geographical pattern consistent with that of the vegetative traits and was mainly affected by climatic gradients. Conclusions The results are consistent with pollinators playing a key role in shaping floral phenotype at a geographical scale and promoting the differentiation of two floral ecotypes. The relationship between the critical floral-fit-related trait and bee

  4. Structure analysis of bimetallic Co-Au nanoparticles formed by sequential ion implantation

    NASA Astrophysics Data System (ADS)

    Chen, Hua-jian; Wang, Yu-hua; Zhang, Xiao-jian; Song, Shu-peng; chen, Hong; Zhang, Ke; Xiong, Zu-zhao; Ji, Ling-ling; Dai, Hou-mei; Wang, Deng-jing; Lu, Jian-duo; Wang, Ru-wu; Zheng, Li-rong

    2016-08-01

    Co-Au alloy Metallic nanoparticles (MNPs) are formed by sequential ion implantation of Co and Au into silica glass at room temperature. The ion ranges of Au ions implantation process have been displayed to show the ion distribution. We have used the atomic force microscopy (AFM) and transmission electron microscopy (TEM) to investigate the formation of bimetallic nanoparticles. The extended X-ray absorption fine structure (EXAFS) has been used to study the local structural information of bimetallic nanoparticles. With the increase of Au ion implantation, the local environments of Co ions are changed enormously. Hence, three oscillations, respectively, Co-O, Co-Co and Co-Au coordination are determined.

  5. A 13µW 87dB dynamic range implantable ΔΣ modulator for full-spectrum neural recording.

    PubMed

    Xu, Jian; Islam, Md Kafiul; Wang, Shuo; Yang, Zhi

    2013-01-01

    Experiment analysis on in-vivo data sequences suggests a wide system dynamic range (DR) is required to simultaneously record local field potentials (LFPs), extra-cellular spikes, and artifacts/interferences. In this paper, we present a 13 µW 87 dB DR ΔΣ modulator for full-spectrum neural recording. To achieve a wide DR and low power consumption, a fully-differential topology is used with multi-bit (MB) quantization scheme and switched-opamp (SO) technique. By adopting a novel fully-clocked scheme, a power-efficient current-mirror SO is developed with 50% power saving, which doubles the figure-of-merit (FOM) over its counterpart. A new static power-less multi-bit quantizer with 96% power and 69% area reduction is also introduced. Besides, instead of metal-insulator-metal (MIM) capacitor, three high-density MOS capacitor (MOSCAP) structures are employed to reduce circuit area. Measurement results show a peak signal-to-noise and distortion ratio (SNDR) of 85 dB with 10 kHz bandwidth at 1.0 V supply, corresponding to an FOM of 45 fJ/conv.-step. which is implemented in a 0.18 µm CMOS. PMID:24110300

  6. Distribution, prevalence and host specificity of avian malaria parasites across the breeding range of the migratory lark sparrow (Chondestes grammacus).

    PubMed

    Swanson, Bethany L; Lyons, Amanda C; Bouzat, Juan L

    2014-06-01

    The lark sparrow (Chondestes grammacus) is a ground-nesting passerine that breeds across much of the central North American steppe and sand barrens. Through genotyping and sequencing of avian malaria parasites we examined levels of malaria prevalence and determined the distribution of Haemoproteus and Plasmodium lineages across the breeding range of the lark sparrow. Analysis of 365 birds collected from five breeding locations revealed relatively high levels of malaria prevalence in adults (80 %) and juveniles (46 %), with infections being primarily of Haemoproteus (91 % of sequenced samples). Levels of genetic diversity and genetic structure of malaria parasites with respect to the avian host populations revealed distinct patterns for Haemoproteus and Plasmodium, most likely as a result of their distinct life histories, host specificity, and transmission vectors. With the exception of one common Haemoproteus haplotype detected in all populations, all other haplotypes were either population-specific or shared by two to three populations. A hierarchical analysis of molecular variance of Haemoproteus sequences revealed that 15-18 % of the genetic variation can be explained by differences among host populations/locations (p < 0.001). In contrast to the regional patterns of genetic differentiation detected for the lark sparrow populations, Haemoproteus parasites showed high levels of population-specific variation and no significant differences among regions, which suggests that the population dynamics of the parasites may be driven by evolutionary processes operating at small spatial scales (e.g., at the level of host populations). These results highlight the potential effects of host population structure on the demographic and evolutionary dynamics of parasites.

  7. The distribution of uranium and thorium in granitic rocks of the basin and range province, Western United States

    USGS Publications Warehouse

    McNeal, J.M.; Lee, D.E.; Millard, H.T.

    1981-01-01

    Some secondary uranium deposits are thought to have formed from uranium derived by the weathering of silicic igneous rocks such as granites, rhyolites, and tuffs. A regional geochemical survey was made to determine the distribution of uranium and thorium in granitic rocks of the Basin and Range province in order to evaluate the potential for secondary uranium occurrences in the area. The resulting geochemical maps of uranium, thorium, and the Th:U ratio may be useful in locating target areas for uranium exploration. The granites were sampled according to a five-level, nested, analysis-of-variance design, permitting estimates to be made of the variance due to differences between:(1) two-degree cells; (2) one-degree cells; (3) plutons; (4) samples; and (5) analyses. The cells are areas described in units of degrees of latitude and longitude. The results show that individual plutons tend to differ in uranium and thorium concentrations, but that each pluton tends to be relatively homogeneous. Only small amounts of variance occur at the two degree and the between-analyses levels. The three geochemical maps that were prepared are based on one-degree cell means. The reproducibility of the maps is U > Th ??? Th:U. These geochemical maps may be used in three methods of locating target areas for uranium exploration. The first method uses the concept that plutons containing the greatest amounts of uranium may supply the greatest amounts of uranium for the formation of secondary uranium occurrences. The second method is to examine areas with high thorium contents, because thorium and uranium are initially highly correlated but much uranium could be lost by weathering. The third method is to locate areas in which the plutons have particularly high Th:U ratios. Because uranium, but not thorium, is leached by chemical weathering, high Th:U ratios suggest a possible loss of uranium and possibly a greater potential for secondary uranium occurrences to be found in the area. ?? 1981.

  8. The effect of authentic metallic implants on the SAR distribution of the head exposed to 900, 1800 and 2450 MHz dipole near field

    NASA Astrophysics Data System (ADS)

    Virtanen, H.; Keshvari, J.; Lappalainen, R.

    2007-03-01

    As the use of radiofrequency (RF) electromagnetic (EM) fields has increased along with increased use of wireless communication, the possible related health risks have also been widely discussed. One safety aspect is the interaction of medical implants and RF devices like mobile phones. In the literature, effects on active implants like pacemakers have been discussed but the studies of passive metallic (i.e. conductive) implants are rare. However, some studies have shown that the EM power absorption in tissues may be enhanced due to metallic implants. In this study, the effect of authentic passive metallic implants in the head region was examined. A half-wave dipole antenna was used as an exposure source and the specific absorption rate (SAR, W kg-1) in the near field was studied numerically. The idea was to model the presumably worst cases of most common implants in an accurate MRI-based phantom. As exposure frequencies GSM (900 and 1800 MHz) and UMTS (2450 MHz) regions were considered. The implants studied were skull plates, fixtures, bone plates and ear rings. The results indicate that some of the implants, under very rare exposure conditions, may cause a notable enhancement in peak mass averaged SAR.

  9. Cochlear implant

    MedlinePlus

    ... implant. These specialists may include: Audiologists Speech therapists Ear, nose, and throat doctors (otolaryngologists) This is a very important part of the process. You will need to work closely with your team of specialists to get ...

  10. Cochlear Implants

    MedlinePlus

    ... additional visits are needed for activating, adjusting, and programming the various electrodes that have been implanted. Also, ... to the center for checkups once the final programming is made to the speech processor. Both children ...

  11. Pulsed Shortwave Diathermy and Joint Mobilizations for Achieving Normal Elbow Range of Motion After Injury or Surgery With Implanted Metal: A Case Series

    PubMed Central

    Draper, David O.

    2014-01-01

    Context: Regaining full, active range of motion (ROM) after trauma to the elbow is difficult. Objective: To report the cases of 6 patients who lacked full ROM in the elbow because of trauma. The treatment regimen was thermal pulsed shortwave diathermy and joint mobilizations. Design: Case series. Setting: University therapeutic modalities laboratory. Patients or Other Participants: Six patients (5 women [83%], 1 man [17%]) lacked a mean active ROM of 24.5° of extension approximately 4.8 years after trauma or surgery. Intervention(s): Treatment consisted of 20 minutes of pulsed shortwave diathermy at 800 pulses per second for 400 microseconds (40–48 W average power, 150 W peak power) applied to the cubital fossa, immediately followed by 7 to 8 minutes of joint mobilizations. After posttreatment ROM was recorded, ice was applied to the area for about 30 minutes. Main Outcomes Measure(s): Changes in extension active ROM were assessed before and after each treatment. Once the patient achieved full, active ROM or failed to improve on 2 consecutive visits, he or she was discharged from the study. Results: By the fifth treatment, 4 participants (67%) achieved normal extension active ROM, and 2 of the 4 (50%) exceeded the norm. Five participants (83%) returned to normal activities and full use of their elbows. One month later, the 5 participants had maintained, on average, (mean ± SD) 92% ± 6% of their final measurements. Conclusions: A combination of thermal pulsed shortwave diathermy and joint mobilizations was effective in restoring active ROM of elbow extension in 5 of the 6 patients (83%) who lacked full ROM after injury or surgery. PMID:25485976

  12. Two-dimensional finite element analysis of the influence of bridge design on stress distribution in bone tissues surrounding fixtures of osseointegrated implants in the lower molar region.

    PubMed

    Arataki, T; Adachi, Y; Kishi, M

    1998-08-01

    This study is a comparison and examination of the stress distribution of the bone tissues surrounding the fixture under a static vertical load condition with regard to an osseointegrated implant bridge (OIB) applied to the lower molar region. It was performed by constructing more than one of two-dimensional finite element models that differ in design conditions. In the case of the bounded type OIB design to the fixture placed in a straight line, a decrease in the maximum stress value of the compact bone surrounding the fixture was recognized with a decrease in the total inter-fixture distance and an increase in the number of placed fixtures. On the other hand, in the case of the free-end type OIB design, there is an increase in the maximum stress value compared with the bounded type OIB design and, in particular, a marked increase with the decrease in the total inter-fixture distance and the extension of the free-end pontic. However, the effect of the number of fixtures placed on the maximum stress value of the surrounding bone tissues was considered to be comparatively small.

  13. Stoichiometric disturbances in compound semiconductors due to ion implantation

    NASA Technical Reports Server (NTRS)

    Avila, R. E.; Fung, C. D.

    1986-01-01

    A method is developed to calculate the depth distribution of the local stoichiometric disturbance (SD) resulting from ion implantation in binary-compound substrates. The calculation includes first-order recoils considering projected range straggle of projectiles and recoils and lateral straggle of recoils. The method uses tabulated final-range statistics to infer the projectile range distributions at intermediate energies. This approach greatly simplifies the calculation with little compromise on accuracy as compared to existing procedures. As an illustration, the SD profile is calculated for implantation of boron, silicon, and aluminum in silicon carbide. The results for the latter case suggest that the SD may be responsible for otherwise unexplained distortions in the annealed aluminum profile. A comparison with calculations by other investigators using the Boltzmann transport equation shows good agreement.

  14. Is the tiger shark Galeocerdo cuvier a coastal species? Expanding its distribution range in the Atlantic Ocean using at-sea observer data.

    PubMed

    Domingo, A; Coelho, R; Cortes, E; Garcia-Cortes, B; Mas, F; Mejuto, J; Miller, P; Ramos-Cartelle, A; Santos, M N; Yokawa, K

    2016-03-01

    The occurrence of tiger shark Galeocerdo cuvier in the Atlantic Ocean was assessed using at-sea observer data from multiple pelagic longline fisheries. Geographic positions of 2764 G. cuvier recorded between 1992 and 2013 and covering a wide area of the Atlantic Ocean were compared with the currently accepted distribution ranges of the species. Most records fell outside those ranges in both the Southern and Northern Hemispheres, which strongly suggests that the distribution range of G. cuvier in the open ocean is considerably larger than previously described.

  15. Is the tiger shark Galeocerdo cuvier a coastal species? Expanding its distribution range in the Atlantic Ocean using at-sea observer data.

    PubMed

    Domingo, A; Coelho, R; Cortes, E; Garcia-Cortes, B; Mas, F; Mejuto, J; Miller, P; Ramos-Cartelle, A; Santos, M N; Yokawa, K

    2016-03-01

    The occurrence of tiger shark Galeocerdo cuvier in the Atlantic Ocean was assessed using at-sea observer data from multiple pelagic longline fisheries. Geographic positions of 2764 G. cuvier recorded between 1992 and 2013 and covering a wide area of the Atlantic Ocean were compared with the currently accepted distribution ranges of the species. Most records fell outside those ranges in both the Southern and Northern Hemispheres, which strongly suggests that the distribution range of G. cuvier in the open ocean is considerably larger than previously described. PMID:26817438

  16. Contraceptive implants.

    PubMed

    McDonald-Mosley, Raegan; Burke, Anne E

    2010-03-01

    Implantable contraception has been extensively used worldwide. Implants are one of the most effective and reversible methods of contraception available. These devices may be particularly appropriate for certain populations of women, including women who cannot use estrogen-containing contraception. Implants are safe for use by women with many chronic medical problems. The newest implant, Implanon (Organon International, Oss, The Netherlands), is the only device currently available in the United States and was approved in 2006. It is registered for 3 years of pregnancy prevention. Contraceptive implants have failure rates similar to tubal ligation, and yet they are readily reversible with a return to fertility within days of removal. Moreover, these contraceptive devices can be safely placed in the immediate postpartum period, ensuring good contraceptive coverage for women who may be at risk for an unintended pregnancy. Irregular bleeding is a common side effect for all progestin-only contraceptive implants. Preinsertion counseling should address possible side effects, and treatment may be offered to women who experience prolonged or frequent bleeding.

  17. Potential effects of climate change on the distribution range of the main silicate sinker of the Southern Ocean

    PubMed Central

    Pinkernell, Stefan; Beszteri, Bánk

    2014-01-01

    Fragilariopsis kerguelensis, a dominant diatom species throughout the Antarctic Circumpolar Current, is coined to be one of the main drivers of the biological silicate pump. Here, we study the distribution of this important species and expected consequences of climate change upon it, using correlative species distribution modeling and publicly available presence-only data. As experience with SDM is scarce for marine phytoplankton, this also serves as a pilot study for this organism group. We used the maximum entropy method to calculate distribution models for the diatom F. kerguelensis based on yearly and monthly environmental data (sea surface temperature, salinity, nitrate and silicate concentrations). Observation data were harvested from GBIF and the Global Diatom Database, and for further analyses also from the Hustedt Diatom Collection (BRM). The models were projected on current yearly and seasonal environmental data to study current distribution and its seasonality. Furthermore, we projected the seasonal model on future environmental data obtained from climate models for the year 2100. Projected on current yearly averaged environmental data, all models showed similar distribution patterns for F. kerguelensis. The monthly model showed seasonality, for example, a shift of the southern distribution boundary toward the north in the winter. Projections on future scenarios resulted in a moderately to negligibly shrinking distribution area and a change in seasonality. We found a substantial bias in the publicly available observation datasets, which could be reduced by additional observation records we obtained from the Hustedt Diatom Collection. Present-day distribution patterns inferred from the models coincided well with background knowledge and previous reports about F. kerguelensis distribution, showing that maximum entropy-based distribution models are suitable to map distribution patterns for oceanic planktonic organisms. Our scenario projections indicate

  18. Distributed Analysis of Hip Implants Using Six National and Regional Registries: Comparing Metal-on-Metal with Metal-on-Highly Cross-Linked Polyethylene Bearings in Cementless Total Hip Arthroplasty in Young Patients

    PubMed Central

    Furnes, Ove; Paxton, Elizabeth; Cafri, Guy; Graves, Stephen; Bordini, Barbara; Comfort, Thomas; Rivas, Moises Coll; Banerjee, Samprit; Sedrakyan, Art

    2014-01-01

    Background: The regulation of medical devices has attracted controversy recently because of problems related to metal-on-metal hip implants. There is growing evidence that metal-on-metal implants fail early and cause local and systemic complications. However, the failure associated with metal-on-metal head size is not consistently documented and needs to be communicated to patients and surgeons. The purpose of this study is to compare implant survival of metal on metal with that of metal on highly cross-linked polyethylene. Methods: Using a distributed health data network, primary total hip arthroplasties were identified from six national and regional total joint arthroplasty registries (2001 to 2010). Inclusion criteria were patient age of forty-five to sixty-four years, cementless total hip arthroplasties, primary osteoarthritis diagnosis, and exclusion of the well-known outlier implant ASR (articular surface replacement). The primary outcome was revision for any reason. A meta-analysis of survival probabilities was performed with use of a fixed-effects model. Metal-on-metal implants with a large head size of >36 mm were compared with metal-on-highly cross-linked polyethylene implants. Results: Metal-on-metal implants with a large head size of >36 mm were used in 5172 hips and metal-on-highly cross-linked polyethylene implants were used in 14,372 hips. Metal-on-metal total hip replacements with a large head size of >36 mm had an increased risk of revision compared with metal-on-highly cross-linked polyethylene total hip replacements with more than two years of follow-up, with no difference during the first two years after implantation. The results of the hazard ratios (and 95% confidence intervals) from the multivariable model at various durations of follow-up were 0.95 (0.74 to 1.23) at zero to two years (p = 0.698), 1.42 (1.16 to 1.75) at more than two years to four years (p = 0.001), 1.78 (1.45 to 2.19) at more than four years to six years (p < 0.001), and 2

  19. Extended geographical distribution and host range of the cactus moth Cactoblastis cactorum (Lepidoptera Pyralidae)in Argentina

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A field exploration was conducted to confirm the southernmost distribution of Cactoblastis cactorum in Argentina. The distribution of the moth was extended to the south (40° 10´S) and west (66° 56´W). The native Opuntia penicilligera was recorded as a host for the first time. These findings should ...

  20. Metal distribution in tissues of free-range chickens near a lead-zinc mine in Kabwe, Zambia.

    PubMed

    Yabe, John; Nakayama, Shouta M M; Ikenaka, Yoshinori; Muzandu, Kaampwe; Choongo, Kennedy; Mainda, Geoffrey; Kabeta, Matthew; Ishizuka, Mayumi; Umemura, Takashi

    2013-01-01

    Concentrations of Pb, Cd, and other metals in tissues of 17 free-range and 32 commercial broiler chickens from the Kabwe mining town in Zambia were determined. Mean concentrations of Pb and Cd exceeded maximum levels for human consumption in some organs including muscle (Pb only) in free-range chickens, in contrast to low levels in broiler chickens. Human consumers in Kabwe could be exposed to Pb and Cd in free-range chickens.

  1. The influence of coarse-scale environmental features on current and predicted future distributions of narrow-range endemic crayfish populations

    USGS Publications Warehouse

    Dyer, Joseph J.; Brewer, Shannon K.; Worthington, Thomas A.; Bergey, Elizabeth A.

    2013-01-01

    1.A major limitation to effective management of narrow-range crayfish populations is the paucity of information on the spatial distribution of crayfish species and a general understanding of the interacting environmental variables that drive current and future potential distributional patterns. 2.Maximum Entropy Species Distribution Modeling Software (MaxEnt) was used to predict the current and future potential distributions of four endemic crayfish species in the Ouachita Mountains. Current distributions were modelled using climate, geology, soils, land use, landform and flow variables thought to be important to lotic crayfish. Potential changes in the distribution were forecast by using models trained on current conditions and projecting onto the landscape predicted under climate-change scenarios. 3.The modelled distribution of the four species closely resembled the perceived distribution of each species but also predicted populations in streams and catchments where they had not previously been collected. Soils, elevation and winter precipitation and temperature most strongly related to current distributions and represented 6587% of the predictive power of the models. Model accuracy was high for all models, and model predictions of new populations were verified through additional field sampling. 4.Current models created using two spatial resolutions (1 and 4.5km2) showed that fine-resolution data more accurately represented current distributions. For three of the four species, the 1-km2 resolution models resulted in more conservative predictions. However, the modelled distributional extent of Orconectes leptogonopodus was similar regardless of data resolution. Field validations indicated 1-km2 resolution models were more accurate than 4.5-km2 resolution models. 5.Future projected (4.5-km2 resolution models) model distributions indicated three of the four endemic species would have truncated ranges with low occurrence probabilities under the low-emission scenario

  2. Astrotischeria neotropicana sp. nov.-a leaf-miner on Sida, Malvaceae, currently with the broadest distribution range in the Neotropics (Lepidoptera, Tischeriidae).

    PubMed

    Diškus, Arūnas; Stonis, Jonas R

    2015-11-05

    This paper describes Astrotischeria neotropicana Diškus & Stonis, sp. nov. (Lepidoptera: Tischeriidae), a new leaf-miner on Sida (Malvaceae) with a broad distribution range in tropical Central & South America. The new species is currently recorded from the Amazon Basin in Peru and Ecuador to tropical lowlands in Guatemala and Belize (including the Caribbean Archipelago). The new species is illustrated with photographs of the adults, male and female genitalia, and the leaf-mines; distribution map is also provided.

  3. Climate-driven range shifts explain the distribution of extant gene pools and predict future loss of unique lineages in a marine brown alga.

    PubMed

    Assis, J; Serrão, E A; Claro, B; Perrin, C; Pearson, G A

    2014-06-01

    The climate-driven dynamics of species ranges is a critical research question in evolutionary ecology. We ask whether present intraspecific diversity is determined by the imprint of past climate. This is an ongoing debate requiring interdisciplinary examination of population genetic pools and persistence patterns across global ranges. Previously, contrasting inferences and predictions have resulted from distinct genomic coverage and/or geographical information. We aim to describe and explain the causes of geographical contrasts in genetic diversity and their consequences for the future baseline of the global genetic pool, by comparing present geographical distribution of genetic diversity and differentiation with predictive species distribution modelling (SDM) during past extremes, present time and future climate scenarios for a brown alga, Fucus vesiculosus. SDM showed that both atmospheric and oceanic variables shape the global distribution of intertidal species, revealing regions of persistence, extinction and expansion during glacial and postglacial periods. These explained the distribution and structure of present genetic diversity, consisting of differentiated genetic pools with maximal diversity in areas of long-term persistence. Most of the present species range comprises postglacial expansion zones and, in contrast to highly dispersive marine organisms, expansions involved only local fronts, leaving distinct genetic pools at rear edges. Besides unravelling a complex phylogeographical history and showing congruence between genetic diversity and persistent distribution zones, supporting the hypothesis of niche conservatism, range shifts and loss of unique genetic diversity at the rear edge were predicted for future climate scenarios, impoverishing the global gene pool. PMID:24766057

  4. Predicting Peri-implant Stresses Around Titanium and Zirconium Dental Implants-A Finite Element Analysis.

    PubMed

    Gujjarlapudi, Manmohan Choudary; Nunna, Narayana Venkata; Manne, Sanjay Dutt; Sarikonda, Varalakshmi Reddy; Madineni, Praveen Kumar; Meruva, Reddi Narasimha Rao

    2013-09-01

    Due to anatomical and surgical constrains the implant placement may not be parallel to each other always. Non-parallel implants are subjected to detrimental stresses at implant bone interface. Also depending on type of implant material i.e. titanium or zirconium, stresses tend to vary due to change in physical and mechanical properties. Hence stress analysis at implant bone interface between different parallel and non-parallel implants becomes significant. Evaluation and comparison of stress distribution in the bone around two parallel and non-parallel titanium and zirconium dental implants on axial and non-axial loading supporting three unit fixed prosthesis. Three dimensional finite element models (M1, M2, M3) were made of three differently angulated implants in ANSYS (11.0 Version) software and P4 processor with a speed of 3 GHz and 3 Gb RAM hardware, common for titanium and zirconium implants. Stress around the implants was analyzed on an axial load of 200 N and a non-axial load of 50 N. In both titanium and zirconium implants on axial loading in cortical bone, higher stresses were observed in M3 followed by M2 and M1. On non-axial loading higher stresses were observed in M2, followed by M3 and M1. In both titanium and zirconium implants on axial and non-axial loading in cancellous bone stresses were higher in M3 followed by M2 and M1. Zirconium implants showed lower stresses in cortical bone and higher stresses in cancellous bone compared to titanium implants. Over all Stresses in the bone were more due to titanium implants than zirconium implants. Zirconium implants led to lower peri-implant stresses than titanium implants.

  5. Frequency Splitting Analysis and Compensation Method for Inductive Wireless Powering of Implantable Biosensors.

    PubMed

    Schormans, Matthew; Valente, Virgilio; Demosthenous, Andreas

    2016-01-01

    Inductive powering for implanted medical devices, such as implantable biosensors, is a safe and effective technique that allows power to be delivered to implants wirelessly, avoiding the use of transcutaneous wires or implanted batteries. Wireless powering is very sensitive to a number of link parameters, including coil distance, alignment, shape, and load conditions. The optimum drive frequency of an inductive link varies depending on the coil spacing and load. This paper presents an optimum frequency tracking (OFT) method, in which an inductive power link is driven at a frequency that is maintained at an optimum value to ensure that the link is working at resonance, and the output voltage is maximised. The method is shown to provide significant improvements in maintained secondary voltage and system efficiency for a range of loads when the link is overcoupled. The OFT method does not require the use of variable capacitors or inductors. When tested at frequencies around a nominal frequency of 5 MHz, the OFT method provides up to a twofold efficiency improvement compared to a fixed frequency drive. The system can be readily interfaced with passive implants or implantable biosensors, and lends itself to interfacing with designs such as distributed implanted sensor networks, where each implant is operating at a different frequency. PMID:27527174

  6. Frequency Splitting Analysis and Compensation Method for Inductive Wireless Powering of Implantable Biosensors

    PubMed Central

    Schormans, Matthew; Valente, Virgilio; Demosthenous, Andreas

    2016-01-01

    Inductive powering for implanted medical devices, such as implantable biosensors, is a safe and effective technique that allows power to be delivered to implants wirelessly, avoiding the use of transcutaneous wires or implanted batteries. Wireless powering is very sensitive to a number of link parameters, including coil distance, alignment, shape, and load conditions. The optimum drive frequency of an inductive link varies depending on the coil spacing and load. This paper presents an optimum frequency tracking (OFT) method, in which an inductive power link is driven at a frequency that is maintained at an optimum value to ensure that the link is working at resonance, and the output voltage is maximised. The method is shown to provide significant improvements in maintained secondary voltage and system efficiency for a range of loads when the link is overcoupled. The OFT method does not require the use of variable capacitors or inductors. When tested at frequencies around a nominal frequency of 5 MHz, the OFT method provides up to a twofold efficiency improvement compared to a fixed frequency drive. The system can be readily interfaced with passive implants or implantable biosensors, and lends itself to interfacing with designs such as distributed implanted sensor networks, where each implant is operating at a different frequency. PMID:27527174

  7. Frequency Splitting Analysis and Compensation Method for Inductive Wireless Powering of Implantable Biosensors.

    PubMed

    Schormans, Matthew; Valente, Virgilio; Demosthenous, Andreas

    2016-08-04

    Inductive powering for implanted medical devices, such as implantable biosensors, is a safe and effective technique that allows power to be delivered to implants wirelessly, avoiding the use of transcutaneous wires or implanted batteries. Wireless powering is very sensitive to a number of link parameters, including coil distance, alignment, shape, and load conditions. The optimum drive frequency of an inductive link varies depending on the coil spacing and load. This paper presents an optimum frequency tracking (OFT) method, in which an inductive power link is driven at a frequency that is maintained at an optimum value to ensure that the link is working at resonance, and the output voltage is maximised. The method is shown to provide significant improvements in maintained secondary voltage and system efficiency for a range of loads when the link is overcoupled. The OFT method does not require the use of variable capacitors or inductors. When tested at frequencies around a nominal frequency of 5 MHz, the OFT method provides up to a twofold efficiency improvement compared to a fixed frequency drive. The system can be readily interfaced with passive implants or implantable biosensors, and lends itself to interfacing with designs such as distributed implanted sensor networks, where each implant is operating at a different frequency.

  8. Influence of Grain Size Distribution on the Mechanical Behavior of Light Alloys in Wide Range of Strain Rates

    NASA Astrophysics Data System (ADS)

    Skripnyak, Vladimir A.; Skripnyak, Natalia V.; Skripnyak, Evgeniya G.; Skripnyak, Vladimir V.

    2015-06-01

    Inelastic deformation and damage at the mesoscale level of ultrafine grained (UFG) Al 1560 aluminum and Ma2-1 magnesium alloys with distribution of grain size were investigated in wide loading conditions by experimental and computer simulation methods. The computational multiscale models of representative volume element (RVE) with the unimodal and bimodal grain size distributions were developed using the data of structure researches aluminum and magnesium UFG alloys. The critical fracture stress of UFG alloys on mesoscale level depends on relative volumes of coarse grains. Microcracks nucleation at quasi-static and dynamic loading is associated with strain localization in UFG partial volumes with bimodal grain size distribution. Microcracks arise in the vicinity of coarse and ultrafine grains boundaries. It is revealed that the occurrence of bimodal grain size distributions causes the increasing of UFG alloys ductility, but decreasing of the tensile strength. The increasing of fine precipitations concentration not only causes the hardening but increasing of ductility of UFG alloys with bimodal grain size distribution. This research carried out in 2014-2015 was supported by grant from ``The Tomsk State University Academic D.I. Mendeleev Fund Program''.

  9. Feasibility of Surgically Implanting Acoustic Tags into Pacific Herring

    USGS Publications Warehouse

    Hershberger, Paul K.; Gregg, Jacob L.; Seitz, A.C.; Norcross, B.L.; Payne, J.C.; Kagley, A.N.; Meloy, B

    2010-01-01

    Internally implanted acoustic tags represent a potentially valuable approach to assessing the seasonal migration and distribution patterns of Pacific herring Clupea palasii. We examined the feasibility of implanting two sizes of dummy acoustic tags (9 mm in diameter × 21 mm long, 1.6 g; and 7 mm in diameter × 18 mm long, 0.7 g) in Pacific herring that had been held in captivity for nearly a year and that ranged from 165 to 215 mm in fork length (FL) and from 41.6 to 142.6 g. Relatively low mortality (4%) and tag shedding (4%), as well as growth similar to that observed in control fish after 135 d, indicate that, with proper handling, Pacific herring are amenable to surgical implantation of acoustic tags.

  10. Intermediate-range order in simple metal-phosphate glasses: The effect of metal cations on the phosphate anion distribution

    SciTech Connect

    Sales, B.C.; Boatner, L.A.; Ramey, J.O.

    1997-06-01

    The technique of high-performance liquid chromatography (HPLC) has been used to probe the phosphate anion distribution in a variety of metal phosphate glasses including glasses made with trivalent metal cations (Al, In, Ga, La). The composition of each glass was chosen so that the average phosphate chain length was between 2 and 4 PO{sub 4} tetrahedra. The widths of the resulting phosphate anion distributions were determined directly from an analysis of the HPLC chromatograms. Literature values for the free energy of formation of the crystalline metal-orthophosphate compounds with respect to P{sub 2}O{sub 5} and the metal oxide, were compared to the chromatogram widths. It was found that the smaller the energy of formation, the wider the distribution of phosphate chains, and the greater the ease of glass formation.

  11. On a growth model for complex networks capable of producing power-law out-degree distributions with wide range exponents.

    PubMed

    Esquivel-Gómez, J; Arjona-Villicaña, P D; Stevens-Navarro, E; Pineda-Rico, U; Balderas-Navarro, R E; Acosta-Elias, J

    2015-01-01

    The out-degree distribution is one of the most reported topological properties to characterize real complex networks. This property describes the probability that a node in the network has a particular number of outgoing links. It has been found that in many real complex networks the out-degree has a behavior similar to a power-law distribution, therefore some network growth models have been proposed to approximate this behavior. This paper introduces a new growth model that allows to produce out-degree distributions that decay as a power-law with an exponent in the range from 1 to ∞. PMID:25765763

  12. On a growth model for complex networks capable of producing power-law out-degree distributions with wide range exponents.

    PubMed

    Esquivel-Gómez, J; Arjona-Villicaña, P D; Stevens-Navarro, E; Pineda-Rico, U; Balderas-Navarro, R E; Acosta-Elias, J

    2015-03-13

    The out-degree distribution is one of the most reported topological properties to characterize real complex networks. This property describes the probability that a node in the network has a particular number of outgoing links. It has been found that in many real complex networks the out-degree has a behavior similar to a power-law distribution, therefore some network growth models have been proposed to approximate this behavior. This paper introduces a new growth model that allows to produce out-degree distributions that decay as a power-law with an exponent in the range from 1 to ∞.

  13. On a growth model for complex networks capable of producing power-law out-degree distributions with wide range exponents

    PubMed Central

    Esquivel-Gómez, J.; Arjona-Villicaña, P. D.; Stevens-Navarro, E.; Pineda-Rico, U.; Balderas-Navarro, R. E.; Acosta-Elias, J.

    2015-01-01

    The out-degree distribution is one of the most reported topological properties to characterize real complex networks. This property describes the probability that a node in the network has a particular number of outgoing links. It has been found that in many real complex networks the out-degree has a behavior similar to a power-law distribution, therefore some network growth models have been proposed to approximate this behavior. This paper introduces a new growth model that allows to produce out-degree distributions that decay as a power-law with an exponent in the range from 1 to ∞. PMID:25765763

  14. Properties of Gallium Disorder and Gold Implants in GaN

    SciTech Connect

    Jiang, Weilin; Weber, William J.; Thevuthasan, Suntharampillai; Shutthanandan, V; DB Poker, SC Moss, K-H Heinig

    2001-04-25

    Epitaxial single-crystal GaN films on sapphire were implanted 60? off the <0001> surface normal with 1 MeV Auor 3 MeV Au over a fluence range from 0.88 to 86.2 ions/nm2 at 180 and 300 K. The implantation damage was studied in-situ using 2 MeV He Rutherford backscattering spectrometry in channeling geometry (RBS/C). The disordering rate in the near-surface region is faster than at the damage peak. In all cases, results show an intermediate stage of Ga disorder saturation at the damage peak. Migration of Au implants in GaN is observed during ion implantation at 300 K. As a result of thermal annealing at 870 K for 20 min, some Au implants in GaN diffuse into the amorphized surface region, while the remaining Au atoms distribute around the mean ion-projected-range. These results suggest a high mobility of both Ga defects and Au implants in GaN. Deeper damage implantation by 3 MeV Au indicates that GaN cannot be completely amorphized up to the highest ion fluence (86.2 ions/nm) applied at 300 K.

  15. Cochlear Implants

    MedlinePlus

    ... outside of the body, behind the ear. A second part is surgically placed under the skin. An implant does not restore normal hearing. It can help a person understand speech. Children and adults can benefit from them. National Institute on Deafness and Other Communication Disorders

  16. Facial implants.

    PubMed

    Arcuri, M R; Rubenstein, J T

    1998-01-01

    The application of endosseous dental implants for the retention and stabilization of extraoral prostheses and hearing aids has been shown to be effective functionally and aesthetically. Implants have reduced the need for adhesive use, simplifying cleaning procedures and thus extending the life of the prosthesis. Implant-retained prostheses have provided patients the opportunity to participate in routine activities such as work, shopping, swimming, and jogging with less fear of losing their prosthesis. The implants' impact on patients has resulted in their ability to function in society with confidence that their defects will be less noticeable and their ability to respond to the environment enhanced. The culmination of these effects have without doubt improved the overall quality of life for patients. As with any new technology, its application will encounter unanticipated problems and some limitations in use. As the art and science of this technique evolve, however, it is anticipated that it will result in the ability to provide improved health care for patients.

  17. Nanoscale morphology and photoemission of arsenic implanted germanium films

    NASA Astrophysics Data System (ADS)

    Petö, G.; Khanh, N. Q.; Horváth, Z. E.; Molnár, G.; Gyulai, J.; Kótai, E.; Guczi, L.; Frey, L.

    2006-04-01

    Germanium films of 140 nm thickness deposited onto Si substrate were implanted with 70 keV arsenic ions with a dose of 2.5×1014 cm-2. The morphology of the implanted films was determined by Rutherford backscattering and cross-sectional transmission electron microscopy. Concentration of oxygen and carbon impurities and their distribution in the implanted layer were detected by secondary-ion-mass spectroscopy and nuclear reaction analysis using the O16(He4,He4)O16 reaction. The depth dependence of the valence band density of states was investigated by measuring the energy distribution curve of photoelectrons using Ar ion etching for profiling. The morphology of As implanted film was dominated by nanosized (10-100 nm) Ge islands separated by empty bubbles at a depth of 20-50 nm under the surface. At depth ranges of 0-20 and 70 to a measured depth of 140 nm, however, morphology of the as-evaporated Ge film was not modified. At a depth of 20-50 nm, photoelectron spectra were similar to those obtained for Ge amorphized with heavy ion (Sb) implantation [implantation induced (I.I.) a-Ge]. The depth profile of the morphology and the photoemission data indicate correlation between the morphology and valence band density of states of the ion I.I. a-Ge. As this regime was formed deep in the evaporated film, i.e., isolated from the environment, any contamination, etc., effect can be excluded. The depth distribution of this I.I. a-Ge layer shows that the atomic displacement process cannot account for its formation.

  18. Sheet resistance monitoring of low dose implants using the double implant technique

    NASA Astrophysics Data System (ADS)

    Smith, A. K.; Johnson, W. H.; Keenan, W. A.; Rigik, Michael; Kleppinger, Rob

    Sheet resistance has become an industry standard for monitoring high and medium dose ion implants. For low dose there are two sheet resistance techniques available, the direct implant technique and the double implant technique. Careful processing has extended the range of direct sheet resistance measurements down to doses of 2E11 ions/cm 2. The double implant technique requires an initial implant to create an easily measured sheet resistance layer that serves as the test vehicle for the second implant. The dose of the second implant is measured by monitoring the change in the sheet resistance due to the implant damage created by the second implant into the first. This double implant technique is not limited to low dose nor to species that are electrically active in the substrate. The sensitivity of any measurement is defined as the percent change in the measured value divided by the percent change with monitored value. The direct sheet resistance technique has a sensitivity of about unity in the low dose region. For the double implant technique, however, the sensitivity can be increased up to 1.5 by varying the initial dose. The sensitivity of the double implant technique can thus be tailored to the particular dose to be monitored. Several double implant experiments will be reviewed to demonstrate the range, repeatability, accuracy, resolution and sensitivity of the technique.

  19. Range distributions of /sup 11/B/sup +/ in Co, CoSi/sub 2/, Ti, and TiSi/sub 2/

    SciTech Connect

    Delfino, M.; Morgan, A.E.; Maillot, P.; Broadbent, E.K.

    1988-07-15

    The range distributions of 10--120 keV /sup 11/B/sup +/ in polycrystalline Co, Ti, CoSi/sub 2/, and TiSi/sub 2/ targets have been measured by secondary ion mass spectrometry. The obtained projected ranges R/sub p/ and projected range stragglings ..delta..R/sub p/ are within 25% and 10%, respectively, of those predicted using the Monte Carlo computer program t-smcapsr-smcapsIm-smcaps. By comparison the one-dimensional Boltzmann transport calculation in Su-smcapsp-smcapsr-smcapsEm-smcaps-3 tends to overestimate R/sub p/ by as much as 300% at the highest ion energies.

  20. Evolutionary history of the little fire ant Wasmannia auropunctata before global invasion: inferring dispersal patterns, niche requirements, and past and present distribution within its native range

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The evolutionary history of invasive species within their native range may involve key processes that allow them to colonize new habitats. We integrated classic and Bayesian phylogeographic methods with a paleodistribution modeling approach to study the demographic patterns that shaped the distribut...

  1. The hydroxyapatite orbital implant: a prospective study.

    PubMed

    Ashworth, J L; Rhatigan, M; Sampath, R; Brammar, R; Sunderland, S; Leatherbarrow, B

    1996-01-01

    The hydroxyapatite orbital implant was first released for use as an orbital implant in humans in August 1989. It has been shown to be well tolerated, providing good motility of the artificial eye with a low complication rate when used as a primary implant. This prospective study evaluated the hydroxyapatite orbital implant used as both a primary and a secondary implant. Sixty patients were implanted between October 1992 and November 1994, 28 being implanted as a primary procedure at the time of enucleation or evisceration, and 32 as a secondary procedure. Seven patients underwent second-stage drilling and pegging of the implant. The mean follow-up time was 13 months (range 2-26 months). A standardised operative and post-operative protocol was followed. The patients were evaluated post-operatively for the amount of enophthalmos, degree of upper lid sulcus deformity, motility of the prosthesis, location of the implant in the socket, socket status and the presence or absence of discharge, position of the drill hole and coverage of the implant. Complications and their management were documented. Both patient and surgeon made a subjective assessment of cosmesis and the patient's satisfaction with the overall result was noted. The results of this study show the hydroxyapatite orbital implant to provide excellent motility of the artificial eye and good cosmesis with a low rate of complications when used both as a primary and as a secondary implant.

  2. Factors and processes shaping the population structure and distribution of genetic variation across the species range of the freshwater snail radix balthica (Pulmonata, Basommatophora)

    PubMed Central

    2011-01-01

    Background Factors and processes shaping the population structure and spatial distribution of genetic diversity across a species' distribution range are important in determining the range limits. We comprehensively analysed the influence of recurrent and historic factors and processes on the population genetic structure, mating system and the distribution of genetic variability of the pulmonate freshwater snail Radix balthica. This analysis was based on microsatellite variation and mitochondrial haplotypes using Generalised Linear Statistical Modelling in a Model Selection framework. Results Populations of R. balthica were found throughout North-Western Europe with range margins marked either by dispersal barriers or the presence of other Radix taxa. Overall, the population structure was characterised by distance independent passive dispersal mainly along a Southwest-Northeast axis, the absence of isolation-by-distance together with rather isolated and genetically depauperated populations compared to the variation present in the entire species due to strong local drift. A recent, climate driven range expansion explained most of the variance in genetic variation, reducing at least temporarily the genetic variability in this area. Other factors such as geographic marginality and dispersal barriers play only a minor role. Conclusions To our knowledge, such a population structure has rarely been reported before. It might nevertheless be typical for passively dispersed, patchily distributed taxa (e.g. freshwater invertebrates). The strong local drift implied in such a structure is expected to erode genetic variation at both neutral and coding loci and thus probably diminish evolutionary potential. This study shows that the analysis of multiple factors is crucial for the inference of the processes shaping the distribution of genetic variation throughout species ranges. PMID:21599918

  3. Friction wear and auger analysis of iron implanted with 1.5-MeV nitrogen ions

    NASA Technical Reports Server (NTRS)

    Ferrante, J.; Jones, W. R., Jr.

    1982-01-01

    The effect of implantation of 1.5-MeV nitrogen ions on the friction and wear characteristics of pure iron sliding against steel was studied in a pin-on disk apparatus. An implantation dose of 5 x 10 to the 17th power ions/sq cm was used. Small reductions in initial and steady-state wear rates were observed for nitrogen-implanted iron riders as compared with unimplanted controls. Auger electron spectroscopy revealed a subsurface Gaussian nitrogen distribution with a maximum concentration of 15 at. % at a depth of 8 x 10 to the -7th m. A similar analysis within the wear scar of an implanted rider after 20 microns of wear yielded only background nitrogen concentration, thus giving no evidence for diffusion of nitrogen beyond the implanted range.

  4. Biomechanical Analysis of Implant-Supported Prostheses with Different Implant-Abutment Connections.

    PubMed

    Dayrell, Andreza Costa; Noritomi, Pedro Yoshito; Takahashi, Jessica Mie; Consani, Rafael Leonardo; Mesquita, Marcelo Ferraz; dos Santos, Mateus Bertolini

    2015-01-01

    This study evaluated the influence of implant-abutment connections on stress distribution through 3D finite element analysis. Three-dimensional models of an implant-supported fixed prosthesis in the jaw retained by four implants with different connection systems (external hex and Morse taper) were analyzed. External hex connection promoted higher microstrain values, which were concentrated on the cervical region of the distal implants extending into the trabecular bone, while Morse taper connection provided a more even distribution of the microstrain on all implants. Implant-supported fixed prostheses with external hex connections tend to concentrate strain in the distal implants, while Morse taper connection promoted a better situation. On the other hand, there was greater demand on the prosthetic screws and abutments of Morse taper connections than on external hex connections. PMID:26523723

  5. Biomechanical Analysis of Implant-Supported Prostheses with Different Implant-Abutment Connections.

    PubMed

    Dayrell, Andreza Costa; Noritomi, Pedro Yoshito; Takahashi, Jessica Mie; Consani, Rafael Leonardo; Mesquita, Marcelo Ferraz; dos Santos, Mateus Bertolini

    2015-01-01

    This study evaluated the influence of implant-abutment connections on stress distribution through 3D finite element analysis. Three-dimensional models of an implant-supported fixed prosthesis in the jaw retained by four implants with different connection systems (external hex and Morse taper) were analyzed. External hex connection promoted higher microstrain values, which were concentrated on the cervical region of the distal implants extending into the trabecular bone, while Morse taper connection provided a more even distribution of the microstrain on all implants. Implant-supported fixed prostheses with external hex connections tend to concentrate strain in the distal implants, while Morse taper connection promoted a better situation. On the other hand, there was greater demand on the prosthetic screws and abutments of Morse taper connections than on external hex connections.

  6. Three dimensional finite element analysis of the stress distribution around the mandibular posterior implant during non-working movement according to the amount of cantilever

    PubMed Central

    Park, Ji-Man; Kim, Hyun-Joo; Park, Eun-Jin; Kim, Myung-Rae

    2014-01-01

    PURPOSE In case of large horizontal discrepancy of alveolar ridge due to severe resorption, cantilevered crown is usually an unavoidable treatment modality. The purpose of this study was to evaluate the clinical criteria for the placement of the aforementioned implant crown. MATERIALS AND METHODS The mandible model with 2 mm thick cortical bone and cancellous bone was fabricated from CT cross-section image. An external connection type implant was installed and cantilevered crowns with increasing offset of 3, 4, 5, 6, and 7 mm were connected. Vertical load and 30° oblique load of 300 N was applied and stress around bone and implant component was analyzed. A total of 14 cases were modeled and finite element analysis was performed using COSMOS Works (Solid works Inc, USA). RESULTS As for the location of the vertical load, the maximum stress generated on the lingual side of the implant became larger according to the increase of offset distance. When the oblique load was applied at 30°, the maximum stress was generated on the buccal side and its magnitude gradually decreased as the distance of the offset load increased to 5 mm. After that point, the magnitude of implant component's stress increased gradually. CONCLUSION The results of this study suggest that for the patient with atrophied alveolar ridge following the loss of molar teeth, von-Mises stress on implant components was the lowest under the 30° oblique load at the 5 mm offset point. Further studies for the various crown height and numbers of occusal points are needed to generalize the conclusion of present study. PMID:25352958

  7. Semiconductor Ion Implanters

    NASA Astrophysics Data System (ADS)

    MacKinnon, Barry A.; Ruffell, John P.

    2011-06-01

    In 1953 the Raytheon CK722 transistor was priced at 7.60. Based upon this, an Intel Xeon Quad Core processor containing 820,000,000 transistors should list at 6.2 billion! Particle accelerator technology plays an important part in the remarkable story of why that Intel product can be purchased today for a few hundred dollars. Most people of the mid twentieth century would be astonished at the ubiquity of semiconductors in the products we now buy and use every day. Though relatively expensive in the nineteen fifties they now exist in a wide range of items from high-end multicore microprocessors like the Intel product to disposable items containing `only' hundreds or thousands like RFID chips and talking greeting cards. This historical development has been fueled by continuous advancement of the several individual technologies involved in the production of semiconductor devices including Ion Implantation and the charged particle beamlines at the heart of implant machines. In the course of its 40 year development, the worldwide implanter industry has reached annual sales levels around 2B, installed thousands of dedicated machines and directly employs thousands of workers. It represents in all these measures, as much and possibly more than any other industrial application of particle accelerator technology. This presentation discusses the history of implanter development. It touches on some of the people involved and on some of the developmental changes and challenges imposed as the requirements of the semiconductor industry evolved.

  8. Semiconductor Ion Implanters

    SciTech Connect

    MacKinnon, Barry A.; Ruffell, John P.

    2011-06-01

    In 1953 the Raytheon CK722 transistor was priced at $7.60. Based upon this, an Intel Xeon Quad Core processor containing 820,000,000 transistors should list at $6.2 billion. Particle accelerator technology plays an important part in the remarkable story of why that Intel product can be purchased today for a few hundred dollars. Most people of the mid twentieth century would be astonished at the ubiquity of semiconductors in the products we now buy and use every day. Though relatively expensive in the nineteen fifties they now exist in a wide range of items from high-end multicore microprocessors like the Intel product to disposable items containing 'only' hundreds or thousands like RFID chips and talking greeting cards. This historical development has been fueled by continuous advancement of the several individual technologies involved in the production of semiconductor devices including Ion Implantation and the charged particle beamlines at the heart of implant machines. In the course of its 40 year development, the worldwide implanter industry has reached annual sales levels around $2B, installed thousands of dedicated machines and directly employs thousands of workers. It represents in all these measures, as much and possibly more than any other industrial application of particle accelerator technology. This presentation discusses the history of implanter development. It touches on some of the people involved and on some of the developmental changes and challenges imposed as the requirements of the semiconductor industry evolved.

  9. Speech Production Intelligibility of Early Implanted Pediatric Cochlear Implant Users

    PubMed Central

    Habib, Mirette G.; Waltzman, Susan B.; Tajudeen, Bobby; Svirsky, Mario A.

    2010-01-01

    Objectives To investigate the influence of age, and age at implantation, on speech production intelligibility in prelingually deaf pediatric cochlear implant recipients. Methods Forty prelingually, profoundly deaf children who received cochlear implants between 8 and 40 months of age. Their age at testing ranged between 2.5 – 18 years. Children were recorded repeating the ten sentences in the Beginner’s Intelligibility Test. These recordings were played back to normal-hearing listeners who were unfamiliar with deaf speech and who were instructed to write down what they heard. They also rated each subject for the intelligibility of their speech production on a 5-point rating scale. The main outcome measures were the percentage of target words correctly transcribed, and the intelligibility ratings, in both cases averaged across three normal-hearing listeners. Results The data showed a strong effect of age at testing, with older children being more intelligible. This effect was particularly pronounced for children implanted in the first 24 months of life, all of whom had speech production intelligibility scores of 80% or higher when they were tested at age 5.5 years or older. This was true for only five out of nine children implanted at age 25 to 36 months. Conclusions Profoundly deaf children who receive cochlear implants in the first two years of life produce highly intelligible speech before age 6. This is also true for most, but not all children implanted in their third year. PMID:20472308

  10. Pressure distribution on a vectored-thrust V/STOL fighter in the transition-speed range. [wind tunnel tests to measure pressure distribution on body and wing

    NASA Technical Reports Server (NTRS)

    Mineck, R. E.; Margason, R. J.

    1974-01-01

    A wind-tunnel investigation has been conducted in the Langley V/STOL tunnel with a vectored-thrust V/STOL fighter configuration to obtain detailed pressure measurements on the body and on the wing in the transition-speed range. The vectored-thrust jet exhaust induced a region of negative pressure coefficients on the lower surface of the wing and on the bottom of the fuselage. The location of the jet exhaust relative to the wing was a major factor in determining the extent of the region of negative pressure coefficients.

  11. Distribution and abundance of anadromous Sea Lamprey Spawners in a fragmented stream: Current status and potential range expansion following barrier removal

    USGS Publications Warehouse

    Zydlewski, Joseph; Gardner, Cory; Coghlan Jr., Stephen M.

    2012-01-01

    Dams fragment watersheds and prevent anadromous fishes from reaching historic spawning habitat. Sedgeunkedunk Stream, a small tributary to the Penobscot River (Maine), has been the focus of efforts to reestablish marine-freshwater connectivity and restore anadromous fishes via the removal of two barriers to fish migration. Currently, Petromyzon marinus (Sea Lamprey) is the only anadromous fish known to spawn successfully in the stream downstream of the lowermost dam. Here, we describe the distribution and abundance of a spawning population of Sea Lamprey in Sedgeunkedunk Stream, prior to and in anticipation of habitat increase after the completion of one barrier removal. In 2008, we estimated the abundance of Sea Lamprey and its nests using daily stream surveys and an open-population mark-recapture model. We captured 47 Sea Lamprey and implanted each with a PIT tag so that we could track movements and nest associations of individual fish. The spawning migration began on 18 June, and the last living individual was observed on 27 June. We located 31 nests, distributed from head-of-tide to the lowermost dam; no spawners or nests were observed in the tidally influenced zone or upstream of this dam. Mean longevity in the stream and the number of nests attended were correlated with arrival date; early migrants were alive longer and attended more nests than later migrants. Males were more likely to be observed away from a nest, or attending three or more nests, than were females, which attended usually one or two nests. We observed a negative association between nest abundance and substrate cover by fine sediment. Based on their observed movements in the system, and the extent of their habitat use, we anticipate that spawning Sea Lamprey will recolonize formerly inaccessible habitat after dam removals.

  12. Genetic diversity and structuring across the range of a widely distributed ladybird: focus on rear-edge populations phenotypically divergent.

    PubMed

    Lecompte, Émilie; Bouanani, Mohand-Ameziane; Magro, Alexandra; Crouau-Roy, Brigitte

    2016-08-01

    Population genetics and phenotypic structures are often predicted to vary along the geographic range of a species. This phenomenon would be accentuated for species with large range areas, with discontinuities and marginal populations. We herein compare the genetic patterns of central populations of Coccinella septempunctata L. with those of two phenotypically differentiated populations considered as rear-edge populations and subspecies based on phenotype (Algeria and Japan). According to the central-marginal model and expected characteristics of rear-edge populations, we hypothesize that these rear-edge populations have (1) a reduced genetic diversity, resulting from their relative isolation over long periods of time, (2) a higher population genetic differentiation, explained by low contemporary gene flow levels, and (3) a relationship between genetic diversity characteristics and phenotypes, due to historical isolation and/or local adaptation. Based on genotyping of 28 populations for 18 microsatellite markers, several levels of regional genetic diversity and differentiation are observed between and within populations, according to their localization: low within-population genetic diversity and higher genetic differentiation of rear-edge populations. The genetic structuring clearly dissociates the Algerian and Eastern Asia populations from the others. Geographical patterns of genetic diversity and differentiation support the hypothesis of the central-marginal model. The pattern observed is in agreement with the phenotypic structure across species range. A clear genetic break between populations of Algeria, the Eastern Asia, and the remaining populations is a dominant feature of the data. Differential local adaptations, absence of gene flow between marginal and central populations, and/or incapacity to mate after colonization, have contributed to their distinct genotypic and phenotypic characteristics. PMID:27551401

  13. The effect of footwear and footfall pattern on running stride interval long-range correlations and distributional variability.

    PubMed

    Fuller, Joel T; Amado, Avelino; Emmerik, Richard E A van; Hamill, Joseph; Buckley, Jonathan D; Tsiros, Margarita D; Thewlis, Dominic

    2016-02-01

    The presence of long-range correlations (self-similarity) in the stride-to-stride fluctuations in running stride interval has been used as an indicator of a healthy adaptable system. Changes to footfall patterns when running with minimalist shoes could cause a less adaptable running gait. The purpose of this study was to investigate stride interval variability and the degree of self-similarity of stride interval in runners wearing minimalist and conventional footwear. Twenty-six trained habitual rearfoot footfall runners, unaccustomed to running in minimalist footwear, performed 6-min sub-maximal treadmill running bouts at 11, 13 and 15 km·h(-1) in minimalist and conventional shoes. Force sensitive resistors were placed in the shoes to quantify stride interval (time between successive foot contacts). Footfall position, stride interval mean and coefficient of variation (CV), were used to assess performance as a function of shoe type. Long-range correlations of stride interval were assessed using detrended fluctuation analysis (α). Mean stride interval was 1-1.3% shorter (P=0.02) and 27% of runners adopted a midfoot footfall (MFF) in the minimalist shoe. There was a significant shoe effect on α and shoe*speed*footfall interaction effect on CV (P<0.05). Runners that adopted a MFF in minimalist shoes, displayed reduced long-range correlations (P<0.05) and CV (P<0.06) in their running stride interval at the 15 km·h(-1) speed. The reduced variability and self-similarity observed for runners that changed to a MFF in the minimalist shoe may be suggestive of a system that is less flexible and more prone to injury. PMID:27004647

  14. Distribution of Quaternary rhyolite domes of the Coso Range, California: implications for extent of the geothermal anomaly.

    USGS Publications Warehouse

    Bacon, C.R.; Duffield, W.A.

    1980-01-01

    38 separate domes and flows of phenocryst-poor, high-silica rhyolite of similar major element chemical composition were erupted over the past 1My from vents arranged in a crudely S-shaped array atop a granitic horst in the Coso Range, California. Most of the extrusions are probably less than about 0.3My old. The central part of the rhyolite field is characterized by high heat flow, low apparent resistivity, and substantial fumarolic activity indicative of an active geothermal system. -from Authors

  15. Metamorphic distributed Bragg reflectors for the 1440–1600 nm spectral range: Epitaxy, formation, and regrowth of mesa structures

    SciTech Connect

    Egorov, A. Yu. Karachinsky, L. Ya.; Novikov, I. I.; Babichev, A. V.; Berezovskaya, T. N.; Nevedomskiy, V. N.

    2015-10-15

    It is shown that metamorphic In{sub 0.3}Ga{sub 0.7}As/In{sub 0.3}Al{sub 0.7}As distributed Bragg reflectors (DBRs) with a reflection band at 1440–1600 nm and a reflectance of no less than 0.999 can be fabricated by molecular beam epitaxy (MBE) on a GaAs substrate. It is demonstrated that mesa structures formed from metamorphic DBRs on a GaAs substrate can be regrown by MBE and microcavities can be locally formed in two separate epitaxial processes. The results obtained can find wide application in the fabrication of vertical-cavity surface-emitting lasers (VCSELs) with a buried tunnel junction.

  16. Short Implants: New Horizon in Implant Dentistry

    PubMed Central

    Gulati, Manisha; Garg, Meenu; Pathak, Chetan

    2016-01-01

    The choice of implant length is an essential factor in deciding the survival rates of these implants and the overall success of the prosthesis. Placing an implant in the posterior part of the maxilla and mandible has always been very critical due to poor bone quality and quantity. Long implants can be placed in association with complex surgical procedures such as sinus lift and bone augmentation. These techniques are associated with higher cost, increased treatment time and greater morbidity. Hence, there is need for a less invasive treatment option in areas of poor bone quantity and quality. Data related to survival rates of short implants, their design and prosthetic considerations has been compiled and structured in this manuscript with emphasis on the indications, advantages of short implants and critical biomechanical factors to be taken into consideration when choosing to place them. Studies have shown that comparable success rates can be achieved with short implants as those with long implants by decreasing the lateral forces to the prosthesis, eliminating cantilevers, increasing implant surface area and improving implant to abutment connection. Short implants can be considered as an effective treatment alternative in resorbed ridges. Short implants can be considered as a viable treatment option in atrophic ridge cases in order to avoid complex surgical procedures required to place long implants. With improvement in the implant surface geometry and surface texture, there is an increase in the bone implant contact area which provides a good primary stability during osseo-integration. PMID:27790598

  17. Prevalence and distribution of gastrointestinal helminths and their effects on weight gain in free-range chickens in Central Zambia.

    PubMed

    Phiri, I K; Phiri, A M; Ziela, M; Chota, A; Masuku, M; Monrad, J

    2007-05-01

    Examination of helminths from gastrointestinal tracts of 125 free-range chickens in Zambia revealed a 95.2% prevalence rate. The species and their prevalences were: Allodapa suctoria (85.6%), Tetrameres americana (80.8%), Ascaridia galli (28.8%), Gonglonema ingluvicola (50.4%), Raillietina spp. (81.6%) and Heterakis gallinarum (32.8%). No trematodes or Syngamus trachea were found. Mixed infections accounted for 88.2% as compared to 7.2% of single infections. Effects of helminthoses on weight gain were investigated in 100 growing chickens randomly assigned to treatment (levamisole) and untreated control groups. There was a significant mean (+/- SEM) weight gain (grams) of 812.8 +/- 51.4 in the treatment group and 623 +/- 57.4 in the control group (p < 0.01). The mean (+/- SEM) worm burdens from the control group and the treatment group were 96.3 +/- 5.61 and 22.05 +/- 2.61, respectively. These results confirm the higher risk of helminth infections in free-range systems and may explain the deleterious effects in chickens.

  18. An echolocation model for range discrimination of multiple closely spaced objects: Transformation of spectrogram into the reflected intensity distribution

    NASA Astrophysics Data System (ADS)

    Matsuo, Ikuo; Kunugiyama, Kenji; Yano, Masafumi

    2004-02-01

    Using frequency-modulated echolocation, bats can discriminate the range of objects with an accuracy of less than a millimeter. However, bats' echolocation mechanism is not well understood. The delay separation of three or more closely spaced objects can be determined through analysis of the echo spectrum. However, delay times cannot be properly correlated with objects using only the echo spectrum because the sequence of delay separations cannot be determined without information on temporal changes in the interference pattern of the echoes. To illustrate this, Gaussian chirplets with a carrier frequency compatible with bat emission sweep rates were used. The delay time for object 1, T1, can be estimated from the echo spectrum around the onset time. The delay time for object 2 is obtained by adding T1 to the delay separation between objects 1 and 2 (extracted from the first appearance of interference effects). Further objects can be located in sequence by this same procedure. This model can determine delay times for three or more closely spaced objects with an accuracy of about 1 μs, when all the objects are located within 30 μs of delay separation. This model is applicable for the range discrimination of objects having different reflected intensities and in a noisy environment (0-dB signal-to-noise ratio) while the cross-correlation method is hard to apply to these problems.

  19. The impact of seasonality on niche breadth, distribution range and species richness: a theoretical exploration of Janzen's hypothesis.

    PubMed

    Hua, Xia

    2016-07-27

    Being invoked as one of the candidate mechanisms for the latitudinal patterns in biodiversity, Janzen's hypothesis states that the limited seasonal temperature variation in the tropics generates greater temperature stratification across elevations, which makes tropical species adapted to narrower ranges of temperatures and have lower effective dispersal across elevations than species in temperate regions. Numerous empirical studies have documented latitudinal patterns in species elevational ranges and thermal niche breadths that are consistent with the hypothesis, but the theoretical underpinnings remain unclear. This study presents the first mathematical model to examine the evolutionary processes that could back up Janzen's hypothesis and assess the effectiveness of limited seasonal temperature variation to promote speciation along elevation in the tropics. Results suggest that trade-offs in thermal tolerances provide a mechanism for Janzen's hypothesis. Limited seasonal temperature variation promotes gradient speciation not due to the reduction in gene flow that is associated with narrow thermal niche, but due to the pleiotropic effects of more stable divergent selection of thermal tolerance on the evolution of reproductive incompatibility. The proposed modelling approach also provides a potential way to test a speciation model against genetic data. PMID:27466445

  20. SU-E-J-58: Dosimetric Verification of Metal Artifact Effects: Comparison of Dose Distributions Affected by Patient Teeth and Implants

    SciTech Connect

    Lee, M; Kang, S; Lee, S; Suh, T; Lee, J; Park, J; Park, H; Lee, B

    2014-06-01

    Purpose: Implant-supported dentures seem particularly appropriate for the predicament of becoming edentulous and cancer patients are no exceptions. As the number of people having dental implants increased in different ages, critical dosimetric verification of metal artifact effects are required for the more accurate head and neck radiation therapy. The purpose of this study is to verify the theoretical analysis of the metal(streak and dark) artifact, and to evaluate dosimetric effect which cause by dental implants in CT images of patients with the patient teeth and implants inserted humanoid phantom. Methods: The phantom comprises cylinder which is shaped to simulate the anatomical structures of a human head and neck. Through applying various clinical cases, made phantom which is closely allied to human. Developed phantom can verify two classes: (i)closed mouth (ii)opened mouth. RapidArc plans of 4 cases were created in the Eclipse planning system. Total dose of 2000 cGy in 10 fractions is prescribed to the whole planning target volume (PTV) using 6MV photon beams. Acuros XB (AXB) advanced dose calculation algorithm, Analytical Anisotropic Algorithm (AAA) and progressive resolution optimizer were used in dose optimization and calculation. Results: In closed and opened mouth phantom, because dark artifacts formed extensively around the metal implants, dose variation was relatively higher than that of streak artifacts. As the PTV was delineated on the dark regions or large streak artifact regions, maximum 7.8% dose error and average 3.2% difference was observed. The averaged minimum dose to the PTV predicted by AAA was about 5.6% higher and OARs doses are also 5.2% higher compared to AXB. Conclusion: The results of this study showed that AXB dose calculation involving high-density materials is more accurate than AAA calculation, and AXB was superior to AAA in dose predictions beyond dark artifact/air cavity portion when compared against the measurements.

  1. Field evidence of colonisation by Holm Oak, at the northern margin of its distribution range, during the Anthropocene period.

    PubMed

    Delzon, Sylvain; Urli, Morgane; Samalens, Jean-Charles; Lamy, Jean-Baptiste; Lischke, Heike; Sin, Fabrice; Zimmermann, Niklaus E; Porté, Annabel J

    2013-01-01

    A major unknown in the context of current climate change is the extent to which populations of slowly migrating species, such as trees, will track shifting climates. Niche modelling generally predicts substantial northward shifts of suitable habitats. There is therefore an urgent need for field-based forest observations to corroborate these extensive model simulations. We used forest inventory data providing presence/absence information from just over a century (1880-2010) for a Mediterranean species (Quercus ilex) in forests located at the northern edge of its distribution. The main goals of the study were (i) to investigate whether this species has actually spread into new areas during the Anthropocene period and (ii) to provide a direct estimation of tree migration rate. We show that Q. ilex has colonised substantial new areas over the last century. However, the maximum rate of colonisation by this species (22 to 57 m/year) was much slower than predicted by the models and necessary to follow changes in habitat suitability since 1880. Our results suggest that the rates of tree dispersion and establishment may also be too low to track shifts in bioclimatic envelopes in the future. The inclusion of contemporary, rather than historical, migration rates into models should improve our understanding of the response of species to climate change.

  2. Sheet Resistance Low Dose Monitoring Using The Double Implant Technique

    NASA Astrophysics Data System (ADS)

    Smith, A. K.; Johnson, W. H.; Keenan, W. A.

    1986-06-01

    Sheet resistance has become an industry standard for monitoring high and medium dose ion implants. For low dose there are two sheet resistance techniques available, the direct implant technique and the double implant technique. Careful processing has extended the range of direct sheet resistance measurements down to doses of 2E11 ions/cm2. The double implant technique requires an initial implant to create an easily measured sheet resistance layer that serves as the test vehicle for the second implant. The dose of the second implant is measured by monitoring the change in the sheet resistance due to the implant damage created by the second implant into the first. This double implant technique is not limited to low dose nor to species that are electrically active in the substrate.

  3. The 'baseball' orbital implant: a prospective study.

    PubMed

    Leatherbarrow, B; Kwartz, J; Sunderland, S; Brammar, R; Nichol, E

    1994-01-01

    The 'baseball' orbital implant was described by Frueh and Felker in 1976. Although this implant was originally described for use as a secondary implant, it has also been widely used as a primary implant at the time of enucleation. This prospective study evaluated the effectiveness of this implant used both primarily and secondarily. Forty-four patients were implanted between April 1990 and May 1991, 19 of the implants being primary and 25 secondary. A standardised operative and post-operative protocol was followed. The mean follow-up time was 31 months (range 24-36 months). The patients were evaluated for the degree of volume replacement, implant and associated prosthesis motility, secondary eyelid and socket problems, patient satisfaction, the need for further surgery and post-operative complications. The overall results achieved by primary implantation were superior to those of secondary implantation. Our results suggest that this implant provides a satisfactory functional and cosmetic rehabilitation of the anophthalmic patient with few complications.

  4. Abnormal pitch perception produced by cochlear implant stimulation.

    PubMed

    Zeng, Fan-Gang; Tang, Qing; Lu, Thomas

    2014-01-01

    Contemporary cochlear implants with multiple electrode stimulation can produce good speech perception but poor music perception. Hindered by the lack of a gold standard to quantify electric pitch, relatively little is known about the nature and extent of the electric pitch abnormalities and their impact on cochlear implant performance. Here we overcame this obstacle by comparing acoustic and electric pitch perception in 3 unilateral cochlear-implant subjects who had functionally usable acoustic hearing throughout the audiometric frequency range in the non-implant ear. First, to establish a baseline, we measured and found slightly impaired pure tone frequency discrimination and nearly perfect melody recognition in all 3 subjects' acoustic ear. Second, using pure tones in the acoustic ear to match electric pitch induced by an intra-cochlear electrode, we found that the frequency-electrode function was not only 1-2 octaves lower, but also 2 times more compressed in frequency range than the normal cochlear frequency-place function. Third, we derived frequency difference limens in electric pitch and found that the equivalent electric frequency discrimination was 24 times worse than normal-hearing controls. These 3 abnormalities are likely a result of a combination of broad electric field, distant intra-cochlear electrode placement, and non-uniform spiral ganglion cell distribution and survival, all of which are inherent to the electrode-nerve interface in contemporary cochlear implants. Previous studies emphasized on the "mean" shape of the frequency-electrode function, but the present study indicates that the large "variance" of this function, reflecting poor electric pitch discriminability, is the main factor limiting contemporary cochlear implant performance. PMID:24551131

  5. Abnormal pitch perception produced by cochlear implant stimulation.

    PubMed

    Zeng, Fan-Gang; Tang, Qing; Lu, Thomas

    2014-01-01

    Contemporary cochlear implants with multiple electrode stimulation can produce good speech perception but poor music perception. Hindered by the lack of a gold standard to quantify electric pitch, relatively little is known about the nature and extent of the electric pitch abnormalities and their impact on cochlear implant performance. Here we overcame this obstacle by comparing acoustic and electric pitch perception in 3 unilateral cochlear-implant subjects who had functionally usable acoustic hearing throughout the audiometric frequency range in the non-implant ear. First, to establish a baseline, we measured and found slightly impaired pure tone frequency discrimination and nearly perfect melody recognition in all 3 subjects' acoustic ear. Second, using pure tones in the acoustic ear to match electric pitch induced by an intra-cochlear electrode, we found that the frequency-electrode function was not only 1-2 octaves lower, but also 2 times more compressed in frequency range than the normal cochlear frequency-place function. Third, we derived frequency difference limens in electric pitch and found that the equivalent electric frequency discrimination was 24 times worse than normal-hearing controls. These 3 abnormalities are likely a result of a combination of broad electric field, distant intra-cochlear electrode placement, and non-uniform spiral ganglion cell distribution and survival, all of which are inherent to the electrode-nerve interface in contemporary cochlear implants. Previous studies emphasized on the "mean" shape of the frequency-electrode function, but the present study indicates that the large "variance" of this function, reflecting poor electric pitch discriminability, is the main factor limiting contemporary cochlear implant performance.

  6. Prevalence of Peri-Implant Mucositis and Peri-Implantitis in Patients Treated with a Combination of Axial and Tilted Implants Supporting a Complete Fixed Denture

    PubMed Central

    Cavalli, Nicolò; Taschieri, Silvio; Francetti, Luca

    2015-01-01

    Objectives. The aim of this retrospective study was to assess the incidence and prevalence of peri-implant mucositis and peri-implantitis in patients with a fixed full-arch prosthesis supported by two axial and two tilted implants. Materials and Methods. Sixty-nine patients were included in the study. Each patient received a fixed full-arch prosthesis supported by two mesial axial and two distal tilted implants to rehabilitate the upper arch, the lower arch, or both. Three hundred thirty-six implants for 84 restorations were delivered. Patients were scheduled for follow-up visits every 6 months in the first 2 years and yearly after. At each follow-up visit peri-implant mucositis and peri-implantitis were diagnosed if present. Results. The overall follow-up range was from 12 to 130 months (mean 63,2 months). Three patients presented peri-implantitis. The prevalence of peri-implant mucositis ranged between 0 and 7,14% of patients (5,06% of implants) while the prevalence of peri-implantitis varied from 0 to 4,55% of patients (3,81% of implants). Conclusions. The prevalence and incidence of peri-implant mucositis and peri-implantitis are lower than most of the studies in literature. Therefore this kind of rehabilitation could be considered a feasible option, on the condition of adopting a systematic hygienic protocol. PMID:26065029

  7. Stratigraphy, regional distribution, and reconnaisance geochemistry of Oligocene and Miocene volcanic rocks in the Paradise Range and northern Pactolus Hills, Nye County, Nevada

    SciTech Connect

    Not Available

    1992-01-01

    In this paper, stratigraphy, geochronology, and geochemistry of about 40 units of Oligocene and Miocene silicic ash-flow tuff, intermediate to silicic lava, and minor sedimentary rock exposed in three stratigraphic sections are described. The distribution and sources of five regionally widespread ash-flow tuff units were delineated. The late Cenozoic volcanic and tectonic history of the Paradise Range and northern Pactolus Hills was compared to other areas in the Great Basin.

  8. Distribution of quaternary rhyolite dome of the Coso Range, California: Implications for extent of the geothermal anomaly

    SciTech Connect

    Bacon, C.R.; Duffield, W.A.; Nakamura, K.

    1980-05-10

    Thirty-eight separate domes and flows of phenocryst-poor, high-silica rhyolite of similar major element chemical composition were erupted over the past 1 m.y. from vents arranged in a crudely S-shaped array atop a granitic horst in the Coso Range, California. Most of the extrusions are probably less than about 0.3 m.y. old. The area is one of Quaternary basaltic volcanism and crustal extension. The central part of the rhyolite field is characterized by high heat flow, low apparent resistivity, and substantial fumarolic activity indicative of an active geothermal system. The immediate source of heat for the surficial geothermal phenomena is probably a silicic magma reservoir that may still contain molten or partially molten material at a depth of at least 8 km beneath the central part of the rhyolite field. Outlying rhyolite extrusions probably reflect the presence of feeder dikes emanating from the reservoir beneath the central region. Azimuths of dikes appear to be parallel to the regional tectonic axis of maximum horizontal compression, analogous to some dike-fed flank eruptions on basaltic shields and andesitic strato-volcanoes. The areal extent of a magma reservoir and the present total heat content of the silicic magma system at Coso may be less than was previously estimated. However, the area is still considered to be one of significant geothermal potential.

  9. Host range and distribution of fruit-infesting pestiferous fruit flies (Diptera, Tephritidae) in selected areas of Central Tanzania.

    PubMed

    Mwatawala, M W; De Meyer, M; Makundi, R H; Maerere, A P

    2009-12-01

    The host range of major fruit fly pests in Central Tanzania was evaluated from October 2004 to October 2006. Samples of 48 potential hosts were collected and incubated for fruit fly emergence. Bactrocera invadens was the dominant species in incidence expressed as the ratio of infested to total number samples collected, as well as infestation rate, expressed as number of flies emerging per unit weight. Eight new host fruits are reported. Infestation by native pests, such as Ceratitis capitata and C. cosyra, was minor compared to B. invadens. Ceratitis rosa was the dominant species in temperate fruits, and Cucurbitaceae were mainly infested by Bactrocera cucurbitae, a specialized cucurbit feeder. Among commercial fruits, high infestation incidences were observed in mango and guava, but they decreased throughout the fruiting season. Low infestation rates were observed in all Citrus species and in avocado, indicating these fruits as poor hosts for the studied fruit fly pests in this region. Widespread availability and abundance of fruit species studied here ensures year-round breeding of B. invadens. Seasonal infestation differs, with mango being the most important host in October to January, while guava being important from February to August. Tropical almond showed very high incidence and infestation rate for B. invadens and might act as an important reservoir host, bridging the fruiting seasons of mango and guava. Soursop acts as an important host for C. cosyra after the mango season. Ceratitis capitata is a pest of minor importance of the commercial fruits studied in this region. PMID:19323850

  10. Population declines lead to replicate patterns of internal range structure at the tips of the distribution of the California red-legged frog (Rana draytonii)

    USGS Publications Warehouse

    Richmond, Jonathan Q.; Backlin, Adam R.; Tatarian, Patricia J.; Solvesky, Ben G.; Fisher, Robert N.

    2014-01-01

    Demographic declines and increased isolation of peripheral populations of the threatened California red-legged frog (Rana draytonii) have led to the formation of internal range boundaries at opposite ends of the species’ distribution. While the population genetics of the southern internal boundary has been studied in some detail, similar information is lacking for the northern part of the range. In this study, we used microsatellite and mtDNA data to examine the genetic structuring and diversity of some of the last remaining R. draytonii populations in the northern Sierra Nevada, which collectively form the northern external range boundary. We compared these data to coastal populations in the San Francisco Bay Area, where the species is notably more abundant and still exists throughout much of its historic range. We show that ‘external’ Sierra Nevada populations have lower genetic diversity and are more differentiated from one another than their ‘internal’ Bay Area counterparts. This same pattern was mirrored across the distribution in California, where Sierra Nevada and Bay Area populations had lower allelic variability compared to those previously studied in coastal southern California. This genetic signature of northward range expansion was mirrored in the phylogeography of mtDNA haplotypes; northern Sierra Nevada haplotypes showed greater similarity to haplotypes from the south Coast Ranges than to the more geographically proximate populations in the Bay Area. These data cast new light on the geographic origins of Sierra Nevada R. draytonii populations and highlight the importance of distinguishing the genetic effects of contemporary demographic declines from underlying signatures of historic range expansion when addressing the most immediate threats to population persistence. Because there is no evidence of contemporary gene flow between any of the Sierra Nevada R. draytonii populations, we suggest that management activities should focus on

  11. Angular distribution of bremsstrahlung produced by electrons with initial energies in the range from 10 to 20 keV incident on thick Ag

    NASA Astrophysics Data System (ADS)

    Gonzales, Daniel; Cavness, Brandon; Williams, Scott

    2012-03-01

    Experimental results are presented comparing the intensities of the thick-target bremsstrahlung produced by electrons with initial energies ranging from 10 to 20 keV incident on Ag, measured at forward angles in the range of 0 to 55 degrees. When the data are corrected for attenuation due to photon absorption within the target, the results indicate that the detected radiation is distributed anisotropically only at photon energies k that are approximately equal to the initial energy of the incident electrons E0. The results of our experiments suggest that, as k/E0->0, the detected radiation essentially becomes isotropic due primarily to the scattering of electrons within the target. Comparison to the theory of Kissel et al. [At. Data Nucl. Data Tables 28, 381 (1983)] suggests that the angular distribution of bremsstrahlung emitted by electrons incident on thick targets is similar to the angular distribution of bremsstrahlung emitted by electrons incident on free-atom targets only when k/E0 1. The experimental data also are in approximate agreement with the angular distribution predictions of the Monte Carlo program PENELOPE.

  12. Plant distributions in the southwestern United States; a scenario assessment of the modern-day and future distribution ranges of 166 Species

    USGS Publications Warehouse

    Thomas, Kathryn A.; Guertin, Patricia P.; Gass, Leila

    2012-01-01

    The authors developed spatial models of the predicted modern-day suitable habitat (SH) of 166 dominant and indicator plant species of the southwestern United States (herein referred to as the Southwest) and then conducted a coarse assessment of potential future changes in the distribution of their suitable habitat under three climate-change scenarios for two time periods. We used Maxent-based spatial modeling to predict the modern-day and future scenarios of SH for each species in an over 342-million-acre area encompassing all or parts of six states in the Southwest--Arizona, California, Colorado, Nevada, New Mexico, and Utah. Modern-day SH models were predicted by our using 26 annual and monthly average temperature and precipitation variables, averaged for the years 1971-2000. Future SH models were predicted for each species by our using six climate models based on application of the average of 16 General Circulation Models to Intergovernmental Panel on Climate Change emission scenarios B1, A1B, and A2 for two time periods, 2040 to 2069 and 2070 and 2100, referred to respectively as the 2050 and 2100 time periods. The assessment examined each species' vulnerability to loss of modern-day SH under future climate scenarios, potential to gain SH under future climate scenarios, and each species' estimated risk as a function of both vulnerability and potential gains. All 166 species were predicted to lose modern-day SH in the future climate change scenarios. In the 2050 time period, nearly 30 percent of the species lost 75 percent or more of their modern-day suitable habitat, 21 species gained more new SH than their modern-day SH, and 30 species gained less new SH than 25 percent of their modern-day SH. In the 2100 time period, nearly half of the species lost 75 percent or more of their modern-day SH, 28 species gained more new SH than their modern-day SH, and 34 gained less new SH than 25 percent of their modern-day SH. Using nine risk categories we found only two

  13. [Evaluation of asymetric implants in breast cancer].

    PubMed

    Fitoussi, A; Couturaud, B; Laki, F; Alran, S; Salmon, R J

    2005-10-01

    Since more than twenty years, methods of breast reconstruction using implants have continued to evolve in order to improve their aesthetic results. Shapes and materials of these implants have also evolved to obtain contours similar to that of the natural opposite breast. Therefore it can be considered that the use of asymmetric implants is the last step in implant technology before using made to measure implants. Asymmetric implants allow obtaining different contours in harmony to the different breast shapes according to the side, left or right, of the reconstructed breast which maximise the naturalness of the result. Such implants have an axis directed towards the exterior and lower part of the chest wall, are wider than high with a thinner part on their inner edge and a concave rear side moulding the curves of the chest wall. In our own experience, we placed more than 500 asymmetric implants. When analysing retrospectively the medical records of 156 patients, no distinctive features were observed when compared to symmetric classic implants in easiness in the surgical procedure or in complications except a slightly higher rate of seroma formation. When compared to usual implants the main benefits of asymmetric implants are: to offer a wider breadth, to slope down gently on their upper and inner sides according to their concave rear side, and therefore to better match subtle curves of a normal breast. Moreover such contours allow a distribution of the volume which fit better to the usual natural breast configuration of patients who underwent surgery for breast carcinoma. At last, such implants are easy to place and a very low rate of secondary rotation has been observed. In summary, for all these reasons, asymmetric implants, can be considered to be the class one in the choice of implants for breast reconstruction after breast surgery. PMID:16198040

  14. Piezosurgery in implant dentistry

    PubMed Central

    Stübinger, Stefan; Stricker, Andres; Berg, Britt-Isabelle

    2015-01-01

    Piezosurgery, or the use of piezoelectric devices, is being applied increasingly in oral and maxillofacial surgery. The main advantages of this technique are precise and selective cuttings, the avoidance of thermal damage, and the preservation of soft-tissue structures. Through the application of piezoelectric surgery, implant-site preparation, bone grafting, sinus-floor elevation, edentulous ridge splitting or the lateralization of the inferior alveolar nerve are very technically feasible. This clinical overview gives a short summary of the current literature and outlines the advantages and disadvantages of piezoelectric bone surgery in implant dentistry. Overall, piezoelectric surgery is superior to other methods that utilize mechanical instruments. Handling of delicate or compromised hard- and soft-tissue conditions can be performed with less risk for the patient. With respect to current and future innovative surgical concepts, piezoelectric surgery offers a wide range of new possibilities to perform customized and minimally invasive osteotomies. PMID:26635486

  15. Stress distribution in fixed-partial prosthesis and peri-implant bone tissue with different framework materials and vertical misfit levels: a three-dimensional finite element analysis.

    PubMed

    Bacchi, Ataís; Consani, Rafael L X; Mesquita, Marcelo F; dos Santos, Mateus B F

    2013-09-01

    The purpose of this study was to evaluate the influence of superstructure material and vertical misfits on the stresses created in an implant-supported partial prosthesis. A three-dimensional (3-D) finite element model was prepared based on common clinical data. The posterior part of a severely resorbed jaw with two osseointegrated implants at the second premolar and second molar regions was modeled using specific modeling software (SolidWorks 2010). Finite element models were created by importing the solid model into mechanical simulation software (ANSYS Workbench 11). The models were divided into groups according to the prosthesis framework material (type IV gold alloy, silver-palladium alloy, commercially pure titanium, cobalt-chromium alloy, or zirconia) and vertical misfit level (10 µm, 50 µm, and 100 µm) created at one implant-prosthesis interface. The gap of the vertical misfit was set to be closed and the stress values were measured in the framework, porcelain veneer, retention screw, and bone tissue. Stiffer materials led to higher stress concentration in the framework and increased stress values in the retention screw, while in the same circumstances, the porcelain veneer showed lower stress values, and there was no significant difference in stress in the peri-implant bone tissue. A considerable increase in stress concentration was observed in all the structures evaluated within the misfit amplification. The framework material influenced the stress concentration in the prosthetic structures and retention screw, but not that in bone tissue. All the structures were significantly influenced by the increase in the misfit levels.

  16. Transcript of the proceedings of the first Albuquerque informal range/energy workshop

    SciTech Connect

    Brice, D.K.

    1981-04-01

    An informal workshop was held to discuss aspects of the calculation of range and energy deposition distributions which are of interest in ion implantation experiments. Topics covered include: problems encountered in using published range and energy deposition tabulations; some limitations in the solutions of range/energy transport equations; the effect of the scattering cross section on straggle; Monte Carlo calculations of ranges and straggling; damage studies in aluminum; simulation of heavy-ion irradiation of gold using MARLOWE; and MARLOWE calculations of range distribution parameters - dependence on input data and calculational model. (GHT)

  17. The characterization of PEEK, PET and PI implanted with Co ions to high fluences

    NASA Astrophysics Data System (ADS)

    Mackova, A.; Malinsky, P.; Miksova, R.; Khaibullin, R. I.; Valeev, V. F.; Svorcik, V.; Slepicka, P.; Slouf, M.

    2013-06-01

    Polyimide (PI), polyetheretherketone (PEEK), and polyethylene terephthalate (PET) foils have been implanted with 40 keV Co+ ions at room temperature to the fluences ranging from 0.2 × 1016 cm-2 to 1.0 × 1017 cm-2. Co depth profiles determined by RBS have been compared to SRIM 2008 calculations. The measured projected ranges RP differ slightly from the SRIM simulation because of the compositional changes in polymers implanted to high fluences; especially the widths of the Co profiles are much larger than those simulated by SRIM. Oxygen and hydrogen depletion has been examined using the RBS and ERDA techniques. The surface morphology of the implanted polymers has been characterized using AFM. The PET polymer exhibits lower oxygen escape than the PI and PEEK, but the surface roughness at PET has been affected most significantly after the implantation. Implanted Co atoms tend to aggregate into nanoparticles, the size and distribution of which has been determined from TEM micrographs and using image analysis. The largest diameter of Co particles has been found in implanted PET.

  18. A simple analysis of extinction spectra of cancerous and normal prostate tissues in near infrared range using a size discrete particle distribution and Mie scattering model

    NASA Astrophysics Data System (ADS)

    Zhou, Kenneth J.; Chen, Jun

    2015-03-01

    The extinction spectra and optical coefficients of human cancerous and normal prostate tissues were investigated in the spectral range of 750 nm - 860 nm. The scattering coefficient (μs) was determined from the extinction measurements on thin prostate tissue and Beer's law. The absorption coefficient (μa) and the reduced scattering coefficient (μs') were extracted from integrate sphere intensity measurements on prostate tissue of which the thickness is in the multiple scattering range. The anisotropy factor (g) was calculated using the extracted values of μs and μs'. A micro-optical model of soft biological tissue was introduced to simulate the numerical computation of the absolute magnitudes of its scattering coefficients from the refractive index and a particle distribution function based on the Mie theory. A key assumption of the model is that the refractive index variations caused by microscopic tissue elements can be treated as particles with sizes distributed according to a skewed log-normal distribution function. The particle distribution and mean particle size of the two types of tissues were then calculated. Results show that the mean diameter of the particle size of cancerous tissue is larger than that of the cancerous tissue, which is responsible for larger reduced scattering coefficient of normal tissue in comparison with cancerous tissue. The results can be explained the change of tissue during prostate cancer evolution defined by Gleason Grade. The difference of the particles distribution and optical coefficients of cancerous and normal prostate tissues may present a potential criterion for prostate cancer detection.

  19. 21 CFR 870.3610 - Implantable pacemaker pulse generator.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Implantable pacemaker pulse generator. 870.3610... pacemaker pulse generator. (a) Identification. An implantable pacemaker pulse generator is a device that has... implantable pacemaker pulse generator device that was in commercial distribution before May 28, 1976, or...

  20. Implant surfaces and interface processes.

    PubMed

    Kasemo, B; Gold, J

    1999-06-01

    The past decades and current R&D of biomaterials and medical implants show some general trends. One major trend is an increased degree of functionalization of the material surface, better to meet the demands of the biological host system. While the biomaterials of the past and those in current use are essentially bulk materials (metals, ceramics, polymers) or special compounds (bioglasses), possibly with some additional coating (e.g., hydroxyapatite), the current R&D on surface modifications points toward much more complex and multifunctional surfaces for the future. Such surface modifications can be divided into three classes, one aiming toward an optimized three-dimensional physical microarchitecture of the surface (pore size distributions, "roughness", etc.), the second one focusing on the (bio) chemical properties of surface coatings and impregnations (ion release, multi-layer coatings, coatings with biomolecules, controlled drug release, etc.), and the third one dealing with the viscoelastic properties (or more generally the micromechanical properties) of material surfaces. These properties are expected to affect the interfacial processes cooperatively, i.e., there are likely synergistic effects between and among them: The surface is "recognized" by the biological system through the combined chemical and topographic pattern of the surface, and the viscoelastic properties. In this presentation, the development indicated above is discussed briefly, and current R&D in this area is illustrated with a number of examples from our own research. The latter include micro- and nanofabrication of surface patterns and topographies by the use of laser machining, photolithographic techniques, and electron beam and colloidal lithographies to produce controlled structures on implant surfaces in the size range 10 nm to 100 microns. Examples of biochemical modifications include mono- or lipid membranes and protein coatings on different surfaces. A new method to evaluate, e

  1. Angular and energy distributions of fragment ions in dissociative double photoionization of acetylene molecules in the 31.9-50.0 eV photon energy range

    NASA Astrophysics Data System (ADS)

    Falcinelli, Stefano; Alagia, Michele; Farrar, James M.; Kalogerakis, Konstantinos S.; Pirani, Fernando; Richter, Robert; Schio, Luca; Stranges, Stefano; Rosi, Marzio; Vecchiocattivi, Franco

    2016-09-01

    The two-body dissociation reactions of the dication C2H2+2, initiated via double ionization of acetylene molecules by photons in the energy range 31.9-50.0 eV, have been studied by coupling photoelectron-photoion-photoion coincidence and ion imaging techniques. The angular distributions and kinetic energy of product ions, measured in the 31.9-50.0 eV energy range, exhibit significant differences for the three leading dissociation reactions with respect to a previous investigation carried out at a fixed energy of 39.0 eV, providing thus new information on the dynamical evolution of the system. The analysis of the results indicates that such dissociation reactions occur with a different mechanism. In particular, the symmetric dissociation in two CH+ ions is characterized by different dynamics, and the anisotropy of the angular distribution of ionic products increases with photon energy in a more pronounced way than the other two reactions. Moreover, the kinetic energy distribution of the symmetric dissociation reaction exhibits several components that change with photon energy. The new experimental findings cast light on the microscopic evolution of the system and can provide a laboratory reference for new theoretical calculations on specific features of the multidimensional potential energy surface, namely, the structure, energy and symmetry of dication states, the electronic state of dissociation products, energy barriers and their dependence on the geometry of the intermediate state.

  2. Finite Element Analysis of Bone Stress for Miniscrew Implant Proximal to Root Under Occlusal Force and Implant Loading.

    PubMed

    Shan, Li-Hua; Guo, Na; Zhou, Guan-jun; Qie, Hui; Li, Chen-Xi; Lu, Lin

    2015-10-01

    Because of the narrow interradicular spaces and varying oral anatomies of individual patients, there is a very high risk of root proximity during the mini implants inserting. The authors hypothesized that normal occlusal loading and implant loading affected the stability of miniscrew implants placed in proximity or contact with the adjacent root. The authors implemented finite element analysis (FEA) to examine the effectiveness of root proximity and root contact. Stress distribution in the bone was assessed at different degrees of root proximity by generating 4 finite element models: the implant touches the root surface, the implant was embedded in the periodontal membrane, the implant touches the periodontal surface, and the implant touches nothing. Finite element analysis was then carried out with simulations of 2 loading conditions for each model: condition A, involving only tooth loading and condition B, involving both tooth and implant loading. Under loading condition A, the maximum stress on the bone for the implant touching the root was the distinctly higher than that for the other models. For loading condition B, peak stress areas for the implant touching the root were the area around the neck of the mini implant and the point of the mini implant touches the root. The results of this study suggest that normal occlusal loading and implant loading contribute to the instability of the mini implant when the mini implant touches the root. PMID:26207429

  3. Peri-Implant Sulcus Fluid (PISF) Matrix Metalloproteinase (MMP) -8 Levels in Peri-Implantitis

    PubMed Central

    Thierbach, René; Maier, Kurt; Sorsa, Timo

    2016-01-01

    Introduction Matrix Metalloproteinase (MMP) -8 plays crucial role in pathogenesis of periodontitis and is also a possible biomarker candidate in peri-implantitis. Aim The aim of the study was to analyse MMP-8 levels in peri-Implant Sulcus Fluid (PISF) from peri-implantitis affected implants in smoking and non-smoking patients with different periodontal health status of natural teeth before and after peri-implantitis treatment. Settings and Design Altogether 29 patients with peri-implantitis were recruited and divided into two study groups (11 with healthy periodontium or gingivitis, i.e. no marginal bone loss, and 18 with chronic periodontitis). Materials and Methods PISF sample from one implant with peri-implantitis from each patient was collected at the baseline and six months after conservative and surgical peri-implantitis treatment, and clinical parameters were registered. Samples were analysed for MMP-8 with dento ELISA method applying a monoclonal antibody. Mucosal cell samples were also analysed for IL-1 gene polymorphism. PISF MMP-8 levels’ differences between periodontal diagnosis groups and between smokers’ and non-smokers’ were analysed. Also, IL-1 polymorphism profiles were compared between study groups. Results PISF MMP-8 levels were higher at the baseline compared to and after the treatment when all sampled implant sites were analysed together (p = 0.001). MMP-8 levels’ distribution was broader in periodontitis patients’ PISF samples, and only in periodontitis patients’ group levels decreased statistically significantly after the treatment (p = 0.005). Smokers’and non-smokers’ PISF MMP-8 was at similar level both at the baseline and after the treatment. No difference between distributions of IL-1 genotypes was found between study groups. Conclusion MMP-8 levels increase in peri-implantitis affected implants both in non-periodontitis and periodontitis patients, but levels still after treatment of the condition reflect intensified host

  4. Physical modification of polyetheretherketone for orthopedic implants

    NASA Astrophysics Data System (ADS)

    Du, Ya-Wei; Zhang, Li-Nan; Hou, Zeng-Tao; Ye, Xin; Gu, Hong-Sheng; Yan, Guo-Ping; Shang, Peng

    2014-12-01

    Polyetheretherketone (PEEK) is regarded as one of the most potential candidates for replacing current implant applications. To obtain good bone-implant interfaces, many modification methods have been developed to enable PEEK and PEEK-based composites from bio-inert to bioactive. Among them, physical methods have aroused significant attention and been widely used to modify PEEK for orthopedic implants. This review summarizes current physical modification techniques of PEEK for orthopedic applications, which include composite strategies, surface coating methods and irradiation treatments. The positive consequences of those modification methods will encourage continuing investigations and stimulate the wide range of applications of PEEK-based implants in orthopedics.

  5. Dental Implants Installed in Irradiated Jaws

    PubMed Central

    Chambrone, L.; Mandia, J.; Shibli, J.A.; Romito, G.A.; Abrahao, M.

    2013-01-01

    The aim of this study was to assess the survival rate of titanium implants placed in irradiated jaws. MEDLINE, EMBASE, and CENTRAL were searched for studies assessing implants that had been placed in nongrafted sites of irradiated patients. Random effects meta-analyses assessed implant loss in irradiated versus nonirradiated patients and in irradiated patients treated with hyperbaric oxygen (HBO) therapy. Of 1,051 potentially eligible publications, 15 were included. A total of 10,150 implants were assessed in the included studies, and of these, 1,689 (14.3%) had been placed in irradiated jaws. The mean survival rate in the studies ranged from 46.3% to 98.0%. The pooled estimates indicated a significant increase in the risk of implant failure in irradiated patients (risk ratio: 2.74; 95% confidence interval: 1.86, 4.05; p < .00001) and in maxillary sites (risk ratio: 5.96; 95% confidence interval: 2.71, 13.12; p < .00001). Conversely, HBO therapy did not reduce the risk of implant failure (risk ratio: 1.28; 95% confidence interval: 0.19, 8.82; p = .80). Radiotherapy was linked to higher implant failure in the maxilla, and HBO therapy did not improve implant survival. Most included publications reported data on machined implants, and only 3 studies on HBO therapy were included. Overall, implant therapy appears to be a viable treatment option for reestablishing adequate occlusion and masticatory conditions in irradiated patients. PMID:24158336

  6. Synergistic effects of dual Zn/Ag ion implantation in osteogenic activity and antibacterial ability of titanium.

    PubMed

    Jin, Guodong; Qin, Hui; Cao, Huiliang; Qian, Shi; Zhao, Yaochao; Peng, Xiaochun; Zhang, Xianlong; Liu, Xuanyong; Chu, Paul K

    2014-09-01

    Zinc (Zn) and silver (Ag) are co-implanted into titanium by plasma immersion ion implantation. A Zn containing film with Ag nanoparticles (Ag NPs) possessing a wide size distribution is formed on the surface and the corrosion resistance is improved due to the micro-galvanic couples formed by the implanted Zn and Ag. Not only are the initial adhesion, spreading, proliferation and osteogenic differentiation of rBMSCs observed from the Zn/Ag implanted Ti in vitro, but also bacteria killing is achieved both in vitro and in vivo. Electrochemical polarization and ion release measurements suggest that the excellent osteogenic activity and antibacterial ability of the Zn/Ag co-implanted titanium are related to the synergistic effect resulting from the long-range interactions of the released Zn ions and short-range interactions of the embedded Ag NPs. The Zn/Ag co-implanted titanium offers both excellent osteogenic activity and antibacterial ability and has large potential in orthopedic and dental implants. PMID:24947228

  7. Synergistic effects of dual Zn/Ag ion implantation in osteogenic activity and antibacterial ability of titanium.

    PubMed

    Jin, Guodong; Qin, Hui; Cao, Huiliang; Qian, Shi; Zhao, Yaochao; Peng, Xiaochun; Zhang, Xianlong; Liu, Xuanyong; Chu, Paul K

    2014-09-01

    Zinc (Zn) and silver (Ag) are co-implanted into titanium by plasma immersion ion implantation. A Zn containing film with Ag nanoparticles (Ag NPs) possessing a wide size distribution is formed on the surface and the corrosion resistance is improved due to the micro-galvanic couples formed by the implanted Zn and Ag. Not only are the initial adhesion, spreading, proliferation and osteogenic differentiation of rBMSCs observed from the Zn/Ag implanted Ti in vitro, but also bacteria killing is achieved both in vitro and in vivo. Electrochemical polarization and ion release measurements suggest that the excellent osteogenic activity and antibacterial ability of the Zn/Ag co-implanted titanium are related to the synergistic effect resulting from the long-range interactions of the released Zn ions and short-range interactions of the embedded Ag NPs. The Zn/Ag co-implanted titanium offers both excellent osteogenic activity and antibacterial ability and has large potential in orthopedic and dental implants.

  8. Not to put too fine a point on it - does increasing precision of geographic referencing improve species distribution models for a wide-ranging migratory bat?

    USGS Publications Warehouse

    Hayes, Mark A.; Ozenberger, Katharine; Cryan, Paul M.; Wunder, Michael B.

    2015-01-01

    Bat specimens held in natural history museum collections can provide insights into the distribution of species. However, there are several important sources of spatial error associated with natural history specimens that may influence the analysis and mapping of bat species distributions. We analyzed the importance of geographic referencing and error correction in species distribution modeling (SDM) using occurrence records of hoary bats (Lasiurus cinereus). This species is known to migrate long distances and is a species of increasing concern due to fatalities documented at wind energy facilities in North America. We used 3,215 museum occurrence records collected from 1950–2000 for hoary bats in North America. We compared SDM performance using five approaches: generalized linear models, multivariate adaptive regression splines, boosted regression trees, random forest, and maximum entropy models. We evaluated results using three SDM performance metrics (AUC, sensitivity, and specificity) and two data sets: one comprised of the original occurrence data, and a second data set consisting of these same records after the locations were adjusted to correct for identifiable spatial errors. The increase in precision improved the mean estimated spatial error associated with hoary bat records from 5.11 km to 1.58 km, and this reduction in error resulted in a slight increase in all three SDM performance metrics. These results provide insights into the importance of geographic referencing and the value of correcting spatial errors in modeling the distribution of a wide-ranging bat species. We conclude that the considerable time and effort invested in carefully increasing the precision of the occurrence locations in this data set was not worth the marginal gains in improved SDM performance, and it seems likely that gains would be similar for other bat species that range across large areas of the continent, migrate, and are habitat generalists.

  9. Vibrationally resolved photoelectron angular distributions for H2 in the range 17 eV<=hν<=39 eV

    NASA Astrophysics Data System (ADS)

    Parr, A. C.; Hardis, J. E.; Southworth, S. H.; Feigerle, C. S.; Ferrett, T. A.; Holland, D. M. P.; Quinn, F. M.; Dobson, B. R.; West, J. B.; Marr, G. V.; Dehmer, J. L.

    1988-01-01

    Vibrationally resolved photoelectron angular distributions have been measured for photoionization of H2 over the range 17 eV<=hν<=39 eV using independent instrumentation at two synchro- tron radiation facilities. The present data greatly extend and add vibrational resolution to earlier variable-wavelength measurements. The average magnitude of the asymmetry parameter continues to lie lower than the best independent-electron calculations. Broad structure is observed for the first time, possibly indicating the effects of channel interaction with dissociative, doubly excited states of H2. Neither the average magnitude nor the gross wavelength-dependent structure vary strongly with the final vibrational channel.

  10. Development of a high dynamic range spectroscopic system for observation of neutral hydrogen atom density distribution in Large Helical Device core plasma

    SciTech Connect

    Fujii, K. Atsumi, S.; Watanabe, S.; Shikama, T.; Hasuo, M.; Goto, M.; Morita, S.

    2014-02-15

    We report development of a high dynamic range spectroscopic system comprising a spectrometer with 30% throughput and a camera with a low-noise fast-readout complementary metal-oxide semiconductor sensor. The system achieves a 10{sup 6} dynamic range (∼20 bit resolution) and an instrumental function approximated by a Voigt profile with Gauss and Lorentz widths of 31 and 0.31 pm, respectively, for 656 nm light. The application of the system for line profile observations of the Balmer-α emissions from high temperature plasmas generated in the Large Helical Device is also presented. In the observed line profiles, emissions are detected in far wings more than 1.0 nm away from the line center, equivalent to neutral hydrogen atom kinetic energies above 1 keV. We evaluate atom density distributions in the core plasma by analyzing the line profiles.

  11. The range of the golden-mantle tamarin, Saguinus tripartitus (Milne-Edwards, 1878): distributions and sympatry of four tamarins in Colombia, Ecuador, and northern Peru [corrected].

    PubMed

    Rylands, Anthony B; Matauschek, Christian; Aquino, Rolando; Encarnación, Filomeno; Heymann, Eckhard W; de la Torre, Stella; Mittermeier, Russell A

    2011-01-01

    A detailed understanding of the range of the golden-mantle tamarin, Saguinus tripartitus (Milne Edwards, 1878), in Amazonian Peru and Ecuador is of particular relevance, not only because it is poorly known but also because it was on the basis of its supposed sympatry with the saddleback tamarin (S. fuscicollis lagonotus) that Thorington (Am J Primatol 15:367-371, 1988) argued that it is a distinct species rather than a saddleback tamarin subspecies, as was believed by Hershkovitz (Living new world monkeys, vol I. The University of Chicago Press, Chicago, 1977). A number of surveys have been carried out since 1988 in the supposed range of S. tripartitus, in both Ecuador and Peru. Here we summarize and discuss these issues and provide a new suggestion for the geographic range of this species; that is, between the ríos Napo and Curaray in Peru and extending east into Ecuador. We also review current evidence for the distributions of Spix's black-mantle tamarin (S. nigricollis nigricollis), Graells' black-mantle tamarin (S. n. graellsi), and the saddleback tamarin (S. fuscicollis lagonotus), which are also poorly known, and examine the evidence regarding sympatry between them. We conclude that despite the existence of a number of specimens with collecting localities that indicate overlap in their geographic ranges, the fact that the four tamarins are [corrected] of similar size and undoubtedly very similar in their feeding habits militates strongly against the occurrence of sympatry among them.

  12. The range of the golden-mantle tamarin, Saguinus tripartitus (Milne Edwards, 1878): distributions and sympatry of four tamarin species in Colombia, Ecuador, and northern Peru

    PubMed Central

    Matauschek, Christian; Aquino, Rolando; Encarnación, Filomeno; Heymann, Eckhard W.; de la Torre, Stella; Mittermeier, Russell A.

    2010-01-01

    A detailed understanding of the range of the golden-mantle tamarin, Saguinus tripartitus (Milne Edwards, 1878), in Amazonian Peru and Ecuador is of particular relevance, not only because it is poorly known but also because it was on the basis of its supposed sympatry with the saddleback tamarin (S. fuscicollis lagonotus) that Thorington (Am J Primatol 15:367–371, 1988) argued that it is a distinct species rather than a saddleback tamarin subspecies, as was believed by Hershkovitz (Living new world monkeys, vol I. The University of Chicago Press, Chicago, 1977). A number of surveys have been carried out since 1988 in the supposed range of S. tripartitus, in both Ecuador and Peru. Here we summarize and discuss these issues and provide a new suggestion for the geographic range of this species; that is, between the ríos Napo and Curaray in Peru and extending east into Ecuador. We also review current evidence for the distributions of Spix’s black-mantle tamarin (S. nigricollis nigricollis), Graells’ black-mantle tamarin (S. n. graellsi), and the saddleback tamarin (S. fuscicollis lagonotus), which are also poorly known, and examine the evidence regarding sympatry between them. We conclude that despite the existence of a number of specimens with collecting localities that indicate overlap in their geographic ranges, the fact that the four tamarin species are of similar size and undoubtedly very similar in their feeding habits militates strongly against the occurrence of sympatry among them. PMID:20878203

  13. Age or Experience? The Influence of Age at Implantation and Social and Linguistic Environment on Language Development in Children with Cochlear Implants

    ERIC Educational Resources Information Center

    Szagun, Gisela; Stumper, Barbara

    2012-01-01

    Purpose: The authors investigated the influence of social environmental variables and age at implantation on language development in children with cochlear implants. Method: Participants were 25 children with cochlear implants and their parents. Age at implantation ranged from 6 months to 42 months (M[subscript age] = 20.4 months, SD = 22.0…

  14. Stress analysis in platform-switching implants: a 3-dimensional finite element study.

    PubMed

    Pellizzer, Eduardo Piza; Verri, Fellippo Ramos; Falcón-Antenucci, Rosse Mary; Júnior, Joel Ferreira Santiago; de Carvalho, Paulo Sérgio Perri; de Moraes, Sandra Lúcia Dantas; Noritomi, Pedro Yoshito

    2012-10-01

    The aim of this study was to evaluate the influence of the platform-switching technique on stress distribution in implant, abutment, and peri-implant tissues, through a 3-dimensional finite element study. Three 3-dimensional mandibular models were fabricated using the SolidWorks 2006 and InVesalius software. Each model was composed of a bone block with one implant 10 mm long and of different diameters (3.75 and 5.00 mm). The UCLA abutments also ranged in diameter from 5.00 mm to 4.1 mm. After obtaining the geometries, the models were transferred to the software FEMAP 10.0 for pre- and postprocessing of finite elements to generate the mesh, loading, and boundary conditions. A total load of 200 N was applied in axial (0°), oblique (45°), and lateral (90°) directions. The models were solved by the software NeiNastran 9.0 and transferred to the software FEMAP 10.0 to obtain the results that were visualized through von Mises and maximum principal stress maps. Model A (implants with 3.75 mm/abutment with 4.1 mm) exhibited the highest area of stress concentration with all loadings (axial, oblique, and lateral) for the implant and the abutment. All models presented the stress areas at the abutment level and at the implant/abutment interface. Models B (implant with 5.0 mm/abutment with 5.0 mm) and C (implant with 5.0 mm/abutment with 4.1 mm) presented minor areas of stress concentration and similar distribution pattern. For the cortical bone, low stress concentration was observed in the peri-implant region for models B and C in comparison to model A. The trabecular bone exhibited low stress that was well distributed in models B and C. Model A presented the highest stress concentration. Model B exhibited better stress distribution. There was no significant difference between the large-diameter implants (models B and C).

  15. Integrating multiple lines of evidence to better understand the evolutionary divergence of humpback dolphins along their entire distribution range: a new dolphin species in Australian waters?

    PubMed

    Mendez, Martin; Jefferson, Thomas A; Kolokotronis, Sergios-Orestis; Krützen, Michael; Parra, Guido J; Collins, Tim; Minton, Giana; Baldwin, Robert; Berggren, Per; Särnblad, Anna; Amir, Omar A; Peddemors, Vic M; Karczmarski, Leszek; Guissamulo, Almeida; Smith, Brian; Sutaria, Dipani; Amato, George; Rosenbaum, Howard C

    2013-12-01

    The conservation of humpback dolphins, distributed in coastal waters of the Indo-West Pacific and eastern Atlantic Oceans, has been hindered by a lack of understanding about the number of species in the genus (Sousa) and their population structure. To address this issue, we present a combined analysis of genetic and morphologic data collected from beach-cast, remote-biopsied and museum specimens from throughout the known Sousa range. We extracted genetic sequence data from 235 samples from extant populations and explored the mitochondrial control region and four nuclear introns through phylogenetic, population-level and population aggregation frameworks. In addition, 180 cranial specimens from the same geographical regions allowed comparisons of 24 morphological characters through multivariate analyses. The genetic and morphological data showed significant and concordant patterns of geographical segregation, which are typical for the kind of demographic isolation displayed by species units, across the Sousa genus distribution range. Based on our combined genetic and morphological analyses, there is convincing evidence for at least four species within the genus (S. teuszii in the Atlantic off West Africa, S. plumbea in the central and western Indian Ocean, S. chinensis in the eastern Indian and West Pacific Oceans, and a new as-yet-unnamed species off northern Australia).

  16. Complete and incomplete fusion reactions in the {sup 16}O+{sup 169}Tm system: Excitation functions and recoil range distributions

    SciTech Connect

    Sharma, Manoj Kumar; Unnati,; Sharma, B.K.; Singh, B.P.; Prasad, R.; Bhardwaj, H.D.; Kumar, Rakesh; Golda, K.S.

    2004-10-01

    With the view to study complete and incomplete fusion in heavy ion induced reactions, experiments have been carried out for measuring excitation functions for several reactions in the system {sup 16}O+{sup 169}Tm at energies near the Coulomb barrier to well above it, using an activation technique. The measured excitation functions have been compared with those calculated theoretically using three different computer codes viz., ALICE-91, CASCADE and PACE2. The enhancement of experimentally measured cross sections for alpha emission channels over their theoretical prediction has been attributed to the fact that these residues are formed not only by complete fusion but also through incomplete fusion. In order to separate out the relative contributions of complete and incomplete fusion, the recoil range distributions of eight residues produced in the interaction of {sup 16}O with {sup 169}Tm at {approx_equal}87 MeV have been measured. The recoil range distributions indicate significant contributions from incomplete fusion at {approx_equal}87 MeV for some of the channels.

  17. Translationally Invariant Calculations of Form Factors, Densities and Momentum Distributions for Finite Nuclei with Short-Range Correlations Included: A Fresh Look

    NASA Astrophysics Data System (ADS)

    Shebeko, A.; Grigorov, P.; Iurasov, V.

    2014-08-01

    The approach proposed in the 70s (Dementiji et al. in Sov J Nucl Phys 22:6-9, 1976), when describing the elastic and inelastic electron scattering off 4 He, and elaborated in (Shebeko et al.in Eur Phys J A27:143-155, 2006) for calculations of the one-body, two-body and more complex density matrices of finite bound systems has been applied (Shebeko and Grigorov in Ukr J Phys 52:830-842, 2007; Shebeko et al. in Eur. Phys. J. A48:153-172, 2012) in studying a combined effect of the center-of-mass motion and nucleon-nucleon short-range correlations on the nucleon density and momentum distributions in light nuclei beyond the independent particle model. Unlike a common practice, suitable for infinite bound systems, these distributions are determined as expectation values of appropriate intrinsic operators that depend upon the relative coordinates and momenta (Jacobi variables) and act on the intrinsic ground-state wave functions (WFs). The latter are constructed in the so-called fixed center-of-mass approximation, starting with a mean-field Slater determinant modified by some correlator (e.g., after Jastrow or Villars). Our numerical calculations of the charge form factors ( F CH ( q)), densities and momentum distributions have been carried out for nuclei 4 He and 16 O choosing, respectively, the 1 s and 1 s-1 p Slater determinants of the harmonic oscillator model as trial, nontranslationally invariant WFs.

  18. Success of multiple endosseous dental implant designs to second-stage surgery across study sites.

    PubMed

    Morris, H F; Manz, M C; Tarolli, J H

    1997-12-01

    A multicenter clinical study of dental implants is being conducted by the Dental Implant Clinical Research Group to investigate the influence of implant design, application, and site on clinical performance and crestal bone. This article reports on the percentage of success up to implant uncovering for different implant designs and the distribution of failures across study sites. Data from 2,847 implants placed at 32 study sites were analyzed. Percentages of success up to implant uncovering were calculated for study implants overall, by implant design, by implant design within study strata, and according to individual study sites and quartile groupings of sites based on success. Comparisons were made, with chi-square and exact tests employed where appropriate. Differences were found between the different implant designs for the study overall, and between implant designs within the different study strata. Although some implant designs were found to have generally high success across study sites, some study sites designated as having surgeons with less experience tended to have higher failure levels, and one implant design failed at higher rates in a subset of study sites. The percentage and distribution of implant failures varied across study sites and by implant design. These differences appeared to be in part related to the level of experience of the surgeons. Further investigation should focus on identification of factors that contribute to higher success in implant placement with different implant designs.

  19. Subspecific affinities and conservation genetics of western big-eared bats (Corynorhinus townsendii pallescens) at the edge of their distributional range

    USGS Publications Warehouse

    Smith, S.J.; Leslie, David M.; Hamilton, M.J.; Lack, Justin B.; Van Den Bussche, Ronald A.

    2008-01-01

    Subspecific affinities, determination of population boundaries, and levels of population connectedness are of critical importance for the development of management and conservation planning. We used variation at a mitochondrial locus and 5 biparentally inherited nuclear loci to determine partitioning of genetic variation of western big-eared bats (Corynorhinus townsendii) within and among caves occurring in a fragmented landscape of gypsum deposits in western Oklahoma. To accomplish this objective, we first performed a phylogenetic analysis based on the mitochondrial locus of western big-eared bats from a large portion of their range. This analysis indicated that western big-eared bats at the periphery of the distribution in western Oklahoma share phylogenetic affinities with the most geographically restricted subspecies, C. t. pallescens. Because C. townsendii is rare in Oklahoma and is listed as a species of special concern, this finding provides additional support for the continued protection of this species in Oklahoma. Within western Oklahoma, we failed to detect significant differentiation among any caves for the biparentally inherited microsatellite data. However, the mitochondrial locus exhibited significant levels of genetic differentiation among caves, with the highest level of differentiation occurring between caves within the disjunct distributions of gypsum (??ST = 38.76%). Although a significant amount of genetic differentiation was detected between populations on the 2 disjunct distributions of gypsum deposits, Analysis with the program Migrate suggested high levels of asymmetric gene flow among some populations. Our results provide a greater understanding of the population dynamics of western big-eared bats on the periphery of their range and highlight the importance of continued monitoring and study of this taxon. ?? 2008 American Society of Mammalogists.

  20. Influence of trophic variables on the depth-range distributions and zonation rates of deep-sea megafauna: the case of the Western Mediterranean assemblages

    NASA Astrophysics Data System (ADS)

    Cartes, Joan E.; Carrassón, Maite

    2004-02-01

    We studied in a deep-sea megafaunal community the relationship of different trophic variables to the depth ranges inhabited by and depth zonation of species, after the ordination of fish and decapod crustaceans in feeding guilds. The variables studied included trophic level of species, food sources exploited, mean weight of predators and prey, feeding intensity and dietary diversity of species. We compiled data on the diets of 18 species of fish and 14 species of decapod crustaceans distributed between 862 and 2261 m in the Catalano-Balearic Basin (Western Mediterranean). Feeding guilds were identified for fish and decapods separately and at two depth strata (862-1400 and 1400-2261 m). The zonation rates (degree of depth overlap) between species within each trophic guild differed by guild and taxon (fish and decapods). The three guilds (G1, G2 and G3) of decapod crustaceans showed quite significantly distinct overlap. G1 (plankton feeders) showed the widest overlap (1326-1381 m) and G3 (benthos feeders) the narrowest (330-476 m). Among the four guilds established for fish, G1, comprising larger predators such as sharks, showed the lowest overlap (between 194 and 382 m). Macrourids overlap ranged between 122 and 553 m, the rest of benthopelagic feeders ranged between 423 and 970 m, and G3 (benthos feeders) gave overlaps between 867 and 1067 m. Significant differences were detected between the depth overlap of most feeding guilds excluding the paired comparisons between G1/macrourids, and G2/G3. Among decapods higher zonation rates (=lower depth overlap) were identified in those guilds occupying higher trophic levels (TL), with a similar, though not as general, trend among fish. In the ordination of species in feeding guilds, TL as indicated by δ15N measurements, was significantly correlated with Dimension 1 (D1) of ordination—MDS-analysis, both in fish and decapods at 862-1400 m. However, deeper (at 1400-2261 m), D1 was not significantly correlated with TL but

  1. Evolutionary history of the little fire ant Wasmannia auropunctata before global invasion: inferring dispersal patterns, niche requirements and past and present distribution within its native range.

    PubMed

    Chifflet, L; Rodriguero, M S; Calcaterra, L A; Rey, O; Dinghi, P A; Baccaro, F B; Souza, J L P; Follett, P; Confalonieri, V A

    2016-04-01

    The evolutionary history of invasive species within their native range may involve key processes that allow them to colonize new habitats. Therefore, phylogeographic studies of invasive species within their native ranges are useful to understand invasion biology in an evolutionary context. Here we integrated classical and Bayesian phylogeographic methods using mitochondrial and nuclear DNA markers with a palaeodistribution modelling approach, to infer the phylogeographic history of the invasive ant Wasmannia auropunctata across its native distribution in South America. We discuss our results in the context of the recent establishment of this mostly tropical species in the Mediterranean region. Our Bayesian phylogeographic analysis suggests that the common ancestor of the two main clades of W. auropunctata occurred in central Brazil during the Pliocene. Clade A would have differentiated northward and clade B southward, followed by a secondary contact beginning about 380,000 years ago in central South America. There were differences in the most suitable habitats among clades when considering three distinct climatic periods, suggesting that genetic differentiation was accompanied by changes in niche requirements, clade A being a tropical lineage and clade B a subtropical and temperate lineage. Only clade B reached more southern latitudes, with a colder climate than that of northern South America. This is concordant with the adaptation of this originally tropical ant species to temperate climates prior to its successful establishment in the Mediterranean region. This study highlights the usefulness of exploring the evolutionary history of invasive species within their native ranges to better understand biological invasions.

  2. Measurement of the isotopic ratio distribution of HD16O and H2 16O in the 20-38 km altitude range from far-infrared spectra

    NASA Astrophysics Data System (ADS)

    Dinelli, Bianca Maria; Lepri, Gianmarco; Carlotti, Massimo; Carli, Bruno; Mencaraglia, Francesco; Ridolfi, Marco; Nolt, Ira G.; Ade, Peter A. R.

    1997-08-01

    The altitude distribution of the isotopic ratio between HD16O and H216O in the stratosphere is derived by retrieving the mixing ratio profiles (from 20 km to 38 km of altitude) of the two isotopic species from far-infrared emission spectra. The measurements were made with a balloon-borne Fourier Transform Spectrometer capable of 0.0025 cm-1 spectral resolution during the IBEX 92 campaign. The retrievals were carried out using the global-fit procedure on a statistically significant number of spectra for each isotope, in the 40-75 cm-1 spectral region. This measurement determines the D/H ratio in stratospheric water over an altitude range larger than that of previous measurements. The value of the HD16O/H216O ratio, normalized to the standard value, ranges from 0.4 to 0.5 (with a 10% random error) in the altitude range studied and is in good agreement with the values previously measured.

  3. Evolutionary history of the little fire ant Wasmannia auropunctata before global invasion: inferring dispersal patterns, niche requirements and past and present distribution within its native range.

    PubMed

    Chifflet, L; Rodriguero, M S; Calcaterra, L A; Rey, O; Dinghi, P A; Baccaro, F B; Souza, J L P; Follett, P; Confalonieri, V A

    2016-04-01

    The evolutionary history of invasive species within their native range may involve key processes that allow them to colonize new habitats. Therefore, phylogeographic studies of invasive species within their native ranges are useful to understand invasion biology in an evolutionary context. Here we integrated classical and Bayesian phylogeographic methods using mitochondrial and nuclear DNA markers with a palaeodistribution modelling approach, to infer the phylogeographic history of the invasive ant Wasmannia auropunctata across its native distribution in South America. We discuss our results in the context of the recent establishment of this mostly tropical species in the Mediterranean region. Our Bayesian phylogeographic analysis suggests that the common ancestor of the two main clades of W. auropunctata occurred in central Brazil during the Pliocene. Clade A would have differentiated northward and clade B southward, followed by a secondary contact beginning about 380,000 years ago in central South America. There were differences in the most suitable habitats among clades when considering three distinct climatic periods, suggesting that genetic differentiation was accompanied by changes in niche requirements, clade A being a tropical lineage and clade B a subtropical and temperate lineage. Only clade B reached more southern latitudes, with a colder climate than that of northern South America. This is concordant with the adaptation of this originally tropical ant species to temperate climates prior to its successful establishment in the Mediterranean region. This study highlights the usefulness of exploring the evolutionary history of invasive species within their native ranges to better understand biological invasions. PMID:26780687

  4. Characterization of drug-release kinetics in trabecular bone from titania nanotube implants

    PubMed Central

    Aw, Moom Sinn; Khalid, Kamarul A; Gulati, Karan; Atkins, Gerald J; Pivonka, Peter; Findlay, David M; Losic, Dusan

    2012-01-01

    Purpose The aim of this study was to investigate the application of the three-dimensional bone bioreactor for studying drug-release kinetics and distribution of drugs in the ex vivo cancellous bone environment, and to demonstrate the application of nanoengineered titanium (Ti) wires generated with titania nanotube (TNT) arrays as drug-releasing implants for local drug delivery Methods Nanoengineered Ti wires covered with a layer of TNT arrays implanted in bone were used as a drug-releasing implant. Viable bovine trabecular bone was used as the ex vivo bone substrate embedded with the implants and placed in the bone reactor. A hydrophilic fluorescent dye (rhodamine B) was used as the model drug, loaded inside the TNT–Ti implants, to monitor drug release and transport in trabecular bone. The distribution of released model drug in the bone was monitored throughout the bone structure, and concentration profiles at different vertical (0–5 mm) and horizontal (0–10 mm) distances from the implant surface were obtained at a range of release times from 1 hour to 5 days. Results Scanning electron microscopy confirmed that well-ordered, vertically aligned nanotube arrays were formed on the surface of prepared TNT–Ti wires. Thermogravimetric analysis proved loading of the model drug and fluorescence spectroscopy was used to show drug-release characteristics in-vitro. The drug release from implants inserted into bone ex vivo showed a consistent gradual release of model drug from the TNT–Ti implants, with a characteristic three-dimensional distribution into the surrounding bone, over a period of 5 days. The parameters including the flow rate of bone culture medium, differences in trabecular microarchitecture between bone samples, and mechanical loading were found to have the most significant influence on drug distribution in the bone. Conclusion These results demonstrate the utility of the Zetos™ system for ex vivo drug-release studies in bone, which can be applied to

  5. Linking land cover and species distribution models to project potential ranges of malaria vectors: an example using Anopheles arabiensis in Sudan and Upper Egypt

    PubMed Central

    2012-01-01

    Background Anopheles arabiensis is a particularly opportunistic feeder and efficient vector of Plasmodium falciparum in Africa and may invade areas outside its normal range, including areas separated by expanses of barren desert. The purpose of this paper is to demonstrate how spatial models can project future irrigated cropland and potential, new suitable habitat for vectors such as An. arabiensis. Methods Two different but complementary spatial models were linked to demonstrate their synergy for assessing re-invasion potential of An. arabiensis into Upper Egypt as a function of irrigated cropland expansion by 2050. The first model (The Land Change Modeler) was used to simulate changes in irrigated cropland using a Markov Chain approach, while the second model (MaxEnt) uses species occurrence points, land cover and other environmental layers to project probability of species presence. Two basic change scenarios were analysed, one involving a more conservative business-as-usual (BAU) assumption and second with a high probability of desert-to-cropland transition (Green Nile) to assess a broad range of potential outcomes by 2050. Results The results reveal a difference of 82,000 sq km in potential An. arabiensis range between the BAU and Green Nile scenarios. The BAU scenario revealed a highly fragmented set of small, potential habitat patches separated by relatively large distances (maximum distance = 64.02 km, mean = 12.72 km, SD = 9.92), while the Green Nile scenario produced a landscape characterized by large patches separated by relatively shorter gaps (maximum distance = 49.38, km, mean = 4.51 km, SD = 7.89) that may be bridged by the vector. Conclusions This study provides a first demonstration of how land change and species distribution models may be linked to project potential changes in vector habitat distribution and invasion potential. While gaps between potential habitat patches remained large in the Green Nile scenario, the

  6. PEEK dental implants: a review of the literature.

    PubMed

    Schwitalla, Andreas; Müller, Wolf-Dieter

    2013-12-01

    The insertion of dental implants containing titanium can be associated with various complications (eg, hypersensitivity to titanium). The aim of this article is to evaluate whether there are existing studies reporting on PEEK (polyetheretherketone) as an alternative material for dental implants. A systematic literature search of PubMed until December 2010 yielded 3 articles reporting on dental implants made from PEEK. One article analyzed stress distribution in carbon fiber-reinforced PEEK (CFR-PEEK) dental implants by the 3-dimensional finite element method, demonstrating higher stress peaks due to a reduced stiffness compared to titanium. Two articles reported on investigations in mongrel dogs. The first article compared CFR-PEEK to titanium-coated CFR-PEEK implants, which were inserted into the femurs and evaluated after 4 and 8 weeks. The titanium-coated implants showed significantly higher bone-implant contact (BIC) rates. In a second study, implants of pure PEEK were inserted into the mandibles beside implants made from titanium and zirconia and evaluated after 4 months, where PEEK presented the lowest BIC. The existing articles reporting on PEEK dental implants indicate that PEEK could represent a viable alternative material for dental implants. However, further experimental studies on the chemical modulation of PEEK seem to be necessary, mainly to increase the BIC ratio and to minimize the stress distribution to the peri-implant bone.

  7. Treatment of Infected Facial Implants.

    PubMed

    Mohan, Kriti; Cox, Joshua A; Dickey, Ryan M; Gravina, Paula; Echo, Anthony; Izaddoost, Shayan A; Nguyen, Anh H

    2016-05-01

    Alloplastic facial implants have a wide range of uses to achieve the appropriate facial contour. A variety of materials such as metals, polymers, ceramics and synthetic injectable fillers are available to the reconstructive and aesthetic surgeon. Besides choosing the right surgical technique and the adequate material, the surgeon must be prepared to treat complications. Infection is an uncommon but serious complication that can cause displeasing consequences for the patient. There are few references in literature regarding treatment and management of facial implant-related infections. This study aims to discuss the role of biofilm in predisposing alloplastic materials to infection, to provide a review of literature, to describe our own institutional experience, and to define a patient care pathway for facial implant-associated infection. PMID:27152100

  8. Studies of hot B subdwarfs. Part 2: Energy distributions of three bright sdB/sdOB stars in the 950-5500 angstrom range

    NASA Technical Reports Server (NTRS)

    Wesemael, F.; Holberg, J. B.; Veilleux, S.; Lamontagne, R.; Fontaine, G.

    1985-01-01

    Voyager ultraviolet spectrometer observations of the subdwarf B or OB stars HD 205805, UV 1758+36 and Feige 66 are presented. All three objects display the H I Layman series in absorption. These observations are combined with low dispersion IUE spectrophotometry and with Stroemgren photometry to construct virtually complete energy distributions, which extend over the range 950-5500 angstroms. Effective temperatures based on model atmosphere calculations for high gravity, hydrogen rich stars are determined. Our analyses yield T Sub e 28,200 + or - 1300 K for HD 205805, T sub e 31, 800 + or - 1100 K for UV 1758+36, and T sub e 35,700 + or - 1500 K for Feige 66. The importance of far ultraviolet observations below L sub alpha in reducing the uncertainties associated with the interstellar extinction and the degradation of the IUE sensitivity is emphasized.

  9. Implant success!!!.....simplified.

    PubMed

    Luthra, Kaushal K

    2009-01-01

    The endeavor towards life-like restoration has helped nurture new vistas in the art and science of implant dentistry. The protocol of "restoration-driven implant placement" ensures that the implant is an apical extension of the ideal future restoration and not the opposite. Meticulous pre-implant evaluation of soft and hard tissues, diagnostic cast and use of aesthetic wax-up and radiographic template combined with surgical template can simplify the intricate roadmap for appropriate implant treatment.By applying the harmony of artistic skill, scientific knowledge and clinical expertise, we can simply master the outstanding implant success in requisites of aesthetics, phonetics and function.

  10. Inferring population connectivity across the range of distribution of the stiletto shrimp Artemesialonginaris Spence Bate, 1888 (Decapoda, Penaeidae) from DNA barcoding: implications for fishery management.

    PubMed

    Carvalho-Batista, Abner; Negri, Mariana; Pileggi, Leonardo G; Castilho, Antonio L; Costa, Rogério C; Mantelatto, Fernando L

    2014-01-01

    Artemesialonginaris is a marine shrimp endemic to the southwestern Atlantic and distributed from Atafona, Rio de Janeiro (Brazil) to Rawson, Chubut (Argentina). In recent years, this species has become an important target of the commercial fishery as a consequence of the decline in the fishery of more traditional and profitable marine shrimps. In addition, phenotypic variations have been documented in populations along its distribution. Therefore, investigations on the genetics of the fishing stocks are necessary for the development of sustainable management strategies and for understanding the possible sources of these variations. The mitochondrial gene Cytochrome Oxidase I (COI) was used to search for evidence of genetic structure among the populations of Artemesialonginaris and to analyze the phylogenetic relationships among them. A total of 60 specimens were collected from seven different localities, covering its geographical range. The final alignment showed 53 haplotypes (48 individuals and 5 shared), with no biogeographical pattern. The low genetic divergence found, with a non-significant FST value, also suggests the absence of population structure for this gene. These findings indicate a continuous gene flow among the populations analyzed, suggesting that the phenotypic variation is a consequence of different environmental conditions among the localities. PMID:25561842

  11. Inferring population connectivity across the range of distribution of the stiletto shrimp Artemesia longinaris Spence Bate, 1888 (Decapoda, Penaeidae) from DNA barcoding: implications for fishery management

    PubMed Central

    Carvalho-Batista, Abner; Negri, Mariana; Pileggi, Leonardo G.; Castilho, Antonio L.; Costa, Rogério C.; Mantelatto, Fernando L.

    2014-01-01

    Abstract Artemesia longinaris is a marine shrimp endemic to the southwestern Atlantic and distributed from Atafona, Rio de Janeiro (Brazil) to Rawson, Chubut (Argentina). In recent years, this species has become an important target of the commercial fishery as a consequence of the decline in the fishery of more traditional and profitable marine shrimps. In addition, phenotypic variations have been documented in populations along its distribution. Therefore, investigations on the genetics of the fishing stocks are necessary for the development of sustainable management strategies and for understanding the possible sources of these variations. The mitochondrial gene Cytochrome Oxidase I (COI) was used to search for evidence of genetic structure among the populations of Artemesia longinaris and to analyze the phylogenetic relationships among them. A total of 60 specimens were collected from seven different localities, covering its geographical range. The final alignment showed 53 haplotypes (48 individuals and 5 shared), with no biogeographical pattern. The low genetic divergence found, with a non-significant FST value, also suggests the absence of population structure for this gene. These findings indicate a continuous gene flow among the populations analyzed, suggesting that the phenotypic variation is a consequence of different environmental conditions among the localities. PMID:25561842

  12. Inferring population connectivity across the range of distribution of the stiletto shrimp Artemesialonginaris Spence Bate, 1888 (Decapoda, Penaeidae) from DNA barcoding: implications for fishery management.

    PubMed

    Carvalho-Batista, Abner; Negri, Mariana; Pileggi, Leonardo G; Castilho, Antonio L; Costa, Rogério C; Mantelatto, Fernando L

    2014-01-01

    Artemesialonginaris is a marine shrimp endemic to the southwestern Atlantic and distributed from Atafona, Rio de Janeiro (Brazil) to Rawson, Chubut (Argentina). In recent years, this species has become an important target of the commercial fishery as a consequence of the decline in the fishery of more traditional and profitable marine shrimps. In addition, phenotypic variations have been documented in populations along its distribution. Therefore, investigations on the genetics of the fishing stocks are necessary for the development of sustainable management strategies and for understanding the possible sources of these variations. The mitochondrial gene Cytochrome Oxidase I (COI) was used to search for evidence of genetic structure among the populations of Artemesialonginaris and to analyze the phylogenetic relationships among them. A total of 60 specimens were collected from seven different localities, covering its geographical range. The final alignment showed 53 haplotypes (48 individuals and 5 shared), with no biogeographical pattern. The low genetic divergence found, with a non-significant FST value, also suggests the absence of population structure for this gene. These findings indicate a continuous gene flow among the populations analyzed, suggesting that the phenotypic variation is a consequence of different environmental conditions among the localities.

  13. Impact of crestal and subcrestal implant placement in peri-implant bone: A prospective comparative study

    PubMed Central

    Pellicer-Chover, Hilario; Peñarrocha-Diago, María; Peñarrocha-Oltra, David; Gomar-Vercher, Sonia; Agustín-Panadero, Rubén

    2016-01-01

    Background To assess the influence of the crestal or subcrestal placement of implants upon peri-implant bone loss over 12 months of follow-up. Material and Methods Twenty-six patients with a single hopeless tooth were recruited in the Oral Surgery Unit (Valencia University, Valencia, Spain). The patients were randomized into two treatment groups: group A (implants placed at crestal level) or group B (implants placed at subcrestal level). Control visits were conducted by a trained clinician at the time of implant placement and 12 months after loading. A previously established standard protocol was used to compile general data on all patients (sex and age, implant length and diameter, and brushing frequency). Implant success rate, peri-implant bone loss and the treatment of the exposed implant surface were studied. The level of statistical significance was defined as 5% (α=0.05). Results Twenty-three patients (8 males and 15 females, mean age 49.8±11.6 years, range 28-75 years) were included in the final data analyses, while three were excluded. All the included subjects were nonsmokers with a brushing frequency of up to twice a day in 85.7% of the cases. The 23 implants comprised 10 crestal implants and 13 subcrestal implants. After implant placement, the mean bone position with respect to the implant platform in group A was 0.0 mm versus 2.16±0.88 mm in group B. After 12 months of follow-up, the mean bone positions were -0.06±1.11 mm and 0.95±1.50 mm, respectively - this representing a bone loss of 0.06±1.11 mm in the case of the crestal implants and of 1.22±1.06 mm in the case of the subcrestal implants (p=0.014). Four crestal implants and 5 subcrestal implants presented peri-implant bone levels below the platform, leaving a mean exposed treated surface of 1.13 mm and 0.57 mm, respectively. The implant osseointegration success rate at 12 months was 100% in both groups. Conclusions Within the limitations of this study, bone loss was found to be greater in

  14. Single tooth replacement by Morse taper connection implants: a retrospective study of 80 implants.

    PubMed

    Mangano, C; Bartolucci, E G

    2001-01-01

    The goal of this study was to provide data relative to the use of a new implant system (Mac System, Cabon, Milan, Italy) with a Morse taper implant-abutment connection for single implant restorations. The implant system is composed of an endosseous screw made of commercially pure titanium grade 2, while the abutment is titanium alloy (Ti-6Al-4V). A total of 80 single implants were placed in 69 patients (36 women and 33 men, mean age 42 years, range 16 to 61). All patients gave their informed consent and received a thorough clinical and radiographic examination. Smokers and diabetics were excluded from the study. Three implants were placed in areas of previous tooth impaction, 5 were placed in posttraumatic edentulous areas, 2 were used in situations involving tooth agenesis, and 60 replaced teeth lost because of caries or periodontal disease. All patients were edentulous for at least 1 year prior to treatment. The implants received a definitive prosthesis and had been in function for a mean period of 3.5 years. At second-stage surgery, 2 implants were removed because of lack of osseointegration. After 2 years of loading, 1 implant showed evidence of peri-implantitis and was removed. In addition, 2 fractured abutments and 1 loosened abutment were observed. Few mechanical or infectious complications were seen, and this may have been the result of high stability of the conical connection.

  15. Influence of Oxygen Ion Implantation on the Damage and Annealing Kinetics of Iron-Implanted Sapphire

    SciTech Connect

    Hunn, J.D.; McHargue, C.J.

    1999-11-14

    The effects of implanted oxygen on the damage accumulation in sapphire which was previously implanted with iron was studied for (0001) sapphire implanted with iron and then with oxygen. The energies were chosen to give similar projected ranges. One series was implanted with a 1:l ratio (4x10{sup 16} ions/cm{sup 2} each) and another with a ratio of 2:3 (4x10{sup 16} fe{sup +}/cm{sup 2}; 6x10{sup 16} O{sup +}/cm{sup 2}). Retained damage, X, in the Al-sublattice, was compared to that produced by implantation of iron alone. The observed disorder was less for the dual implantations suggesting that implantation of oxygen enhanced dynamic recovery during implantation. Samples were annealed for one hour at 800 and 1200 C in an oxidizing and in a reducing atmosphere. No difference was found in the kinetics of recovery in the Al-sublattice between the two dual implant conditions. However, the rate of recovery was different for each from samples implanted with iron alone.

  16. Examining Speech Sound Acquisition for Children with Cochlear Implants Using the GFTA-2

    ERIC Educational Resources Information Center

    Flipsen, Peter, Jr.

    2011-01-01

    This study examines use of the Goldman-Fristoe Test of Articulation-Second Edition (GFTA-2) with children who use cochlear implants to evaluate whether or not it would be appropriate to use this test with this population. Participants included 15 children with cochlear implants who ranged in age of implantation and amount of implant experience.…

  17. Liquid-phase epitaxy grown PbSnTe distributed feedback laser diodes with broad continuous single-mode tuning range

    NASA Technical Reports Server (NTRS)

    Hsieh, H.-H.; Fonstad, C. G.

    1980-01-01

    Distributed feedback (DFB) pulsed laser operation has been demonstrated in stripe geometry Pb(1-x)Sn(x)Te double-heterostructures grown by liquid-phase epitaxy. The grating structure of 0.79 micron periodicity operates in first order near 12.8 microns and was fabricated prior to the liquid-phase epitaxial growth using holographic exposure techniques. These DFB lasers had moderate thresholds, 3.6 kA/sq cm, and the output power versus current curves exhibited a sharp turn-on free of kinks. Clean, single-mode emission spectra, continuously tunable over a range in excess of 20 per cm, centered about 780 per cm (12.8 microns), and at an average rate of 1.2 per cm-K from 9 to 26 K, were observed. While weaker modes could at times be seen in the spectrum, substantially single-mode operation was obtained over the entire operating range and to over 10 times threshold.

  18. ZnO/a-Si distributed Bragg reflectors for light trapping in thin film solar cells from visible to infrared range

    NASA Astrophysics Data System (ADS)

    Chen, Aqing; Yuan, Qianmin; Zhu, Kaigui

    2016-01-01

    Distributed Bragg reflectors (DBRs) consisting of ZnO and amorphous silicon (a-Si) were prepared by magnetron sputtering method for selective light trapping. The quarter-wavelength ZnO/a-Si DBRs with only 6 periods exhibit a peak reflectance of above 99% and have a full width at half maximum that is greater than 347 nm in the range of visible to infrared. The 6-pair reversed quarter-wavelength ZnO/a-Si DBRs also have a peak reflectance of 98%. Combination of the two ZnO/a-Si DBRs leads to a broader stopband from 686 nm to 1354 nm. Using the ZnO/a-Si DBRs as the rear reflector of a-Si thin film solar cells significantly increases the photocurrent in the spectrum range of 400-1000 nm, in comparison with that of the cells with Al reflector. The obtained results suggest that ZnO/a-Si DBRs are promising reflectors of a-Si thin-film solar cells for light trapping.

  19. A two-short-implant-supported molar restoration in atrophic posterior maxilla: A finite element analysis

    PubMed Central

    2016-01-01

    PURPOSE The aim of this study was to investigate the stress distribution of 2-short implants (2SIs) installed in a severely atrophic maxillary molar site. MATERIALS AND METHODS Three different diameters of internal connection implants were modeled: narrow platform (NP), regular platform (RP), and wide platform (WP). The maxillary first molars were restored with one implant or two short implants. Three 2SI models (NP-oblique, NP-vertical, and NP-horizontal) and four single implant models (RP and WP in a centered or cantilevered position) were used. Axial and oblique loadings were applied on the occlusal surface of the crown. The von Mises stress values were measured at the bone-implant, peri-implant bone, and implant/abutment complex. RESULTS The highest stress distribution at the bone-implant interface and the peri-implant bone was noticed in the RP group, and the lowest stress distribution was observed in the 2SI groups. Cantilevered position showed unfavorable stress distribution with axial loading. 2SI types did not affect the stress distribution in oblique loading. The number and installation positions of the implant, rather than the bone level, influenced the stress distribution of 2SIs. The implant/abutment complex of WP presented the highest stress concentration while that of 2SIs showed the lowest stress concentration. CONCLUSION 2SIs may be useful for achieving stable stress distribution on the surrounding bone and implant-abutment complex in the atrophic posterior maxilla. PMID:27555900

  20. [Biomaterials in cochlear implants].

    PubMed

    Stöver, T; Lenarz, T

    2009-05-01

    Cochlear implants (CI) represent the "gold standard" for the treatment of congenitally deaf children and postlingually deafened adults. Thus, cochlear implantation is a success story of new bionic prosthesis development. Owing to routine application of cochlear implants in adults but also in very young children (below the age of one), high demands are placed on the implants. This is especially true for biocompatibility aspects of surface materials of implant parts which are in contact with the human body. In addition, there are various mechanical requirements which certain components of the implants must fulfil, such as flexibility of the electrode array and mechanical resistance of the implant housing. Due to the close contact of the implant to the middle ear mucosa and because the electrode array is positioned in the perilymphatic space via cochleostomy, there is a potential risk of bacterial transferral along the electrode array into the cochlea. Various requirements that have to be fulfilled by cochlear implants, such as biocompatibility, electrode micromechanics, and although a very high level of technical standards has been carried out there is still demand for the improvement of implants as well as of the materials used for manufacturing, ultimately leading to increased implant performance. General considerations of material aspects related to cochlear implants as well as potential future perspectives of implant development will be discussed.

  1. Molecular distributions and stable carbon isotopic compositions of dicarboxylic acids and related compounds in aerosols from Sapporo, Japan: Implications for photochemical aging during long-range atmospheric transport

    NASA Astrophysics Data System (ADS)

    Aggarwal, Shankar G.; Kawamura, Kimitaka

    2008-07-01

    Molecular and stable carbon isotopic (δ13C value) compositions of dicarboxylic acids, ketoacids, and dicarbonyls in aerosol samples (i.e., total suspended particles) collected in Sapporo, northern Japan during spring and summer were determined to better understand the photochemical aging of organic aerosols during long-range transport from East Asia and Siberia. Their molecular distributions were characterized by the predominance of oxalic acid (C2) followed by malonic (C3) or occasionally succinic (C4) acids. Concentrations of total diacids ranged from 106-787 ng m-3 with ketoacids (13-81 ng m-3) and dicarbonyls (2.6-28 ng m-3) being less abundant. Water-soluble organic carbon (WSOC) comprised 23-69% of aerosol organic carbon (OC). OC to elemental carbon (EC) ratios were high (3.6-19, mean: 8.7). The ratios of C3/C4 and WSOC/OC did not show significant diurnal changes, suggesting that the Sapporo aerosols were not seriously affected by local photochemical processes and instead they were already aged. δ13C values of the dominant diacids (C2 - C4) ranged from -14.0 to -25.3‰. Largest δ13C values (-14.0 to -22.4‰, mean: -18.8‰) were obtained for C2, whereas smallest values (-25.1 to -31.4‰, mean: -28.1‰) were for azelaic acid (C9). In general, δ13C values of C2 - C4 diacids became less negative with aerosol aging (i.e., WSOC/OC), presumably due to isotopic fractionation during photochemical degradation of diacids. By comparing the δ13C values of diacids in the Sapporo aerosols with different air mass source regions, we suggest that although initial δ13C values of diacids depend on their precursor sources, the enrichment in 13C can be ascribed to aerosol photochemical aging.

  2. Breast reconstruction - implants

    MedlinePlus

    ... visits, your surgeon injects a small amount of saline (salt water) through the valve into the expander. ... breast implants. Implants may be filled with either saline or a silicone gel. You may have another ...

  3. Expression and distribution of forkhead activin signal transducer 2 (FAST2) during follicle development in mouse ovaries and pre-implantation embryos.

    PubMed

    Wang, Guiping; Liu, Linlin; Guo, Shujuan; Zhang, Cong

    2016-07-01

    Xenopus forkhead activin signal transducer 1 (xFAST 1) was first characterized in Xenopus as the transcriptional partner for Smad proteins. FAST2, which is the xFAST 1 homologues in mouse, is expressed during early developmental stages of the organism. However, the function of FAST2 in mouse ovaries and pre-implantation embryos is unclear. Therefore, we investigated its expression during these processes. In postnatal mice, FAST2 was expressed in oocytes and thecal cells from postnatal day (PD) 1 to PD 21. In gonadotropin-induced immature mice, FAST2 was expressed in oocytes, thecal cells and newly formed corpora lutea (CLs), but was expressed at a lower level in degenerated CLs. Similar results were observed upon western blot analyses. In meloxicam-treated immature mice, ovulation was inhibited and FAST2 was expressed in thecal cells, luteinized granulosa cells and entrapped oocytes. Immunofluorescence results showed that FAST2 was expressed in the cytoplasm and nucleus but not the nucleolus from the zygote to 8-cell embryo stage, after which it was localized to the cytoplasm of the morulae and inner cell mass of the blastocysts. Taken together, these observations suggest that FAST2 is expressed in a cell-specific manner during ovarian follicle development, ovulation, luteinization and early embryonic development, and that FAST2 might play important roles in these physiological processes. PMID:27432806

  4. [Pathology of implants].

    PubMed

    Mittermayer, C; Eblenkamp, M; Richter, H A; Zwadlo-Klarwasser, G; Bhardwaj, R S; Klosterhalfen, B

    2002-01-01

    Progress in the surgery of implants and biomaterials can be accomplished by: 1. Painstakingly analysing and registering of defaulting implants after explantation within a "National Registry of Implant Pathology". 2. Development of a DNA-microarray named "Implantat/Chronic Wound" in order to discover the differential transcriptional activities of cells brought into contact with different foreign surfaces. 3. Predictive cell-engineering combined with custom-made implant surfaces with the aim of optimal patient care.

  5. Survival of Implants in Immediate Extraction Sockets of Anterior Teeth: Early Clinical Results

    PubMed Central

    Sabir, Mohammad

    2015-01-01

    Background The aims and objectives of this study were placement of implants in freshly extracted sockets of anterior teeth and to evaluate the implant stability, peri-implant radiolucency and gingival inflammation around implant over a short period of 30 months. Materials and Methods A total of 12 patients (8 male and 4 female), ranging in the age from 20 to 50 years, from March 2007 to June 2007, were evaluated for immediate implant placement into 22 fresh extraction sockets. Only maxillary and mandibular anterior teeth/roots (central incisors, lateral incisors and canines) were considered for replacement with implants. One piece implant with integrated abutment and integrated surface, non-submerged, threaded and tapered at apical 5 mm, sand-blasted and acid etched surfaced implants (HI-TEC TRX-OP Implants of Life Care Company) were used. Results The mobility was not present in any of the implants at all the follow up visits. There were 2 implants at 6 month, 1 implant at 12 month, 1 implant at 18 month visits, showing peri-implant radiolucency at some sites at bone to implant contact site. Severe gingival inflammation was not observed in any of the implant site. At every follow-up visit, every implant met the criteria of success and none was found to be failed over a 30 months duration i.e. 100% success rate was achieved by implants in immediate extraction socket. Conclusion The success rate of implant survival in this study was found 100%. These implants have fulfilled all the criteria of implant success and based on the defined criteria, the success rate of implants placed in immediate extraction sockets of anterior teeth compared favorably with the conventional implants. The early results of the present study showed that high survival rates with the implants in immediate extraction sockets can be achieved. PMID:26266220

  6. Implantable Heart Aid

    NASA Technical Reports Server (NTRS)

    1984-01-01

    CPI's human-implantable automatic implantable defibrillator (AID) is a heart assist system, derived from NASA's space circuitry technology, that can prevent erratic heart action known as arrhythmias. Implanted AID, consisting of microcomputer power source and two electrodes for sensing heart activity, recognizes onset of ventricular fibrillation (VF) and delivers corrective electrical countershock to restore rhythmic heartbeat.

  7. A preliminary biomechanical study of a novel carbon-fibre hip implant versus standard metallic hip implants.

    PubMed

    Bougherara, Habiba; Zdero, Rad; Dubov, Anton; Shah, Suraj; Khurshid, Shaheen; Schemitsch, Emil H

    2011-01-01

    Total hip arthroplasty is a widespread surgical approach for treating severe osteoarthritis of the human hip. Aseptic loosening of standard metallic hip implants due to stress shielding and bone loss has motivated the development of new materials for hip prostheses. Numerically, a three-dimensional finite element (FE) model that mimicked hip implants was used to compare a new hip stem to two commercially available implants. The hip implants simulated were a novel CF/PA12 carbon-fibre polyamide-based composite hip stem, the Exeter hip stem (Stryker, Mahwah, NJ, USA), and the Omnifit Eon (Stryker, Mahwah, NJ, USA). A virtual axial load of 3 kN was applied to the FE model. Strain and stress distributions were computed. Experimentally, the three hip stems had their distal portions rigidly mounted and had strain gauges placed along the surface at 3 medial and 3 lateral locations. Axial loads of 3 kN were applied. Measurements of axial stiffness and strain were taken and compared to FE analysis. The overall linear correlation between FE model versus experimental strains showed reasonable results for the lines-of-best-fit for the Composite (Pearson R(2)=0.69, slope=0.82), Exeter (Pearson R(2)=0.78, slope=0.59), and Omnifit (Pearson R(2)=0.66, slope=0.45), with some divergence for the most distal strain locations. From FE analysis, the von Mises stress range for the Composite stem was much lower than that in the Omnifit and Exeter implants by 200% and 45%, respectively. The preliminary experiments showed that the Composite stem stiffness (1982 N/mm) was lower than the metallic hip stem stiffnesses (Exeter, 2460 N/mm; Omnifit, 2543 N/mm). This is the first assessment of stress, strain, and stiffness of the CF/PA12 carbon-fibre hip stem compared to standard commercially-available devices.

  8. Carbon, nitrogen, and oxygen ion implantation of stainless steel

    SciTech Connect

    Rej, D.J.; Gavrilov, N.V.; Emlin, D.

    1995-12-31

    Ion implantation experiments of C, N, and O into stainless steel have been performed, with beam-line and plasma source ion implantation methods. Acceleration voltages were varied between 27 and 50 kV, with pulsed ion current densities between 1 and 10 mA/cm{sup 2}. Implanted doses ranged from 0.5 to 3 {times} 10{sup 18}cm{sup -2}, while workpiece temperatures were maintained between 25 and 800 C. Implant concentration profiles, microstructure, and surface mechanical properties of the implanted materials are reported.

  9. Evolutionary Drivers of Diversification and Distribution of a Southern Temperate Stream Fish Assemblage: Testing the Role of Historical Isolation and Spatial Range Expansion

    PubMed Central

    Chakona, Albert; Swartz, Ernst R.; Gouws, Gavin

    2013-01-01

    This study used phylogenetic analyses of mitochondrial cytochrome b sequences to investigate genetic diversity within three broadly co-distributed freshwater fish genera (Galaxias, Pseudobarbus and Sandelia) to shed some light on the processes that promoted lineage diversification and shaped geographical distribution patterns. A total of 205 sequences of Galaxias, 177 sequences of Pseudobarbus and 98 sequences of Sandelia from 146 localities across nine river systems in the south-western Cape Floristic Region (South Africa) were used. The data were analysed using phylogenetic and haplotype network methods and divergence times for the clades retrieved were estimated using *BEAST. Nine extremely divergent (3.5–25.3%) lineages were found within Galaxias. Similarly, deep phylogeographic divergence was evident within Pseudobarbus, with four markedly distinct (3.8–10.0%) phylogroups identified. Sandelia had two deeply divergent (5.5–5.9%) lineages, but seven minor lineages with strong geographical congruence were also identified. The Miocene-Pliocene major sea-level transgression and the resultant isolation of populations in upland refugia appear to have driven widespread allopatric divergence within the three genera. Subsequent coalescence of rivers during the Pleistocene major sea-level regression as well as intermittent drainage connections during wet periods are proposed to have facilitated range expansion of lineages that currently occur across isolated river systems. The high degree of genetic differentiation recovered from the present and previous studies suggest that freshwater fish diversity within the south-western CFR may be vastly underestimated, and taxonomic revisions are required. PMID:23951050

  10. Genetic analysis of Black Tiger shrimp (Penaeus monodon) across its natural distribution range reveals more recent colonization of Fiji and other South Pacific islands

    PubMed Central

    Waqairatu, Salote S; Dierens, Leanne; Cowley, Jeff A; Dixon, Tom J; Johnson, Karyn N; Barnes, Andrew C; Li, Yutao

    2012-01-01

    The Black Tiger shrimp (Penaeus monodon) has a natural distribution range from East Africa to the South Pacific Islands. Although previous studies of Indo-Pacific P. monodon have found populations from the Indian Ocean and Australasia to differ genetically, their relatedness to South Pacific shrimp remains unknown. To address this, polymorphisms at eight shared microsatellite loci and haplotypes in a 418-bp mtDNA-CR (control region) sequence were examined across 682 P. monodon from locations spread widely across its natural range, including the South Pacific islands of Fiji, Palau, and Papua New Guinea (PNG). Observed microsatellite heterozygosities of 0.82–0.91, allele richness of 6.85–9.69, and significant mtDNA-CR haplotype variation indicated high levels of genetic diversity among the South Pacific shrimp. Analysis of microsatellite genotypes using a Bayesian STRUCTURE method segregated Indo-Pacific P. monodon into eight distinct clades, with Palau and PNG shrimp clustering among others from Southeast Asia and eastern Australia, respectively, and Fiji shrimp clustering as a distinct group. Phylogenetic analyses of mtDNA-CR haplotypes delineated shrimp into three groupings, with shrimp from Fiji again being distinct by sharing no haplotypes with other populations. Depending on regional location, the genetic structures and substructures identified from the genotyping and mtDNA-CR haplotype phylogeny could be explained by Metapopulation and/or Member–Vagrant type evolutionary processes. Neutrality tests of mutation-drift equilibrium and estimation of the time since population expansion supported a hypothesis that South Pacific P. monodon were colonized from Southeast Asia and eastern Australia during the Pleistocene period over 60,000 years ago when land bridges were more expansive and linked these regions more closely. PMID:22957205

  11. The range and distribution of murine central nervous system cells infected with the gamma(1)34.5- mutant of herpes simplex virus 1.

    PubMed Central

    Markovitz, N S; Baunoch, D; Roizman, B

    1997-01-01

    Wild-type herpes simplex virus 1 (HSV-1) multiplies, spreads, and rapidly destroys cells of the murine central nervous system (CNS). In contrast, mutants lacking both copies of the gamma(1)34.5- gene have been shown to be virtually lacking in virulence even after direct inoculation of high-titered virus into the CNS of susceptible mice (J. Chou, E. R. Kern, R. J. Whitley, and B. Roizman, Science 250:1262-1266, 1990). To investigate the host range and distribution of infected cells in the CNS of mice, 4- to 5-week-old mice were inoculated stereotaxically into the caudate/putamen with 3 x 10(5) PFU of the gamma(1)34.5- virus R3616. Four-micrometer-thick sections of mouse brains removed on day 3, 5, or 7 after infection were reacted with a polyclonal antibody directed primarily to structural proteins of the virus and with antibodies specific for neurons, astrocytes, or oligodendrocytes. This report shows the following: (i) most of the tissue damage caused by R3616 was at the site of injection, (ii) the virus spread by retrograde transport from the site of infection to neuronal cell nuclei at distant sites and to ependymal cells by cerebrospinal fluid, (iii) the virus infected neurons, astrocytes, oligodendrocytes, and ependymal cells and hence did not discriminate among CNS cells, (iv) viral replication in some neurons could be deduced from the observation of infected astrocytes and oligodendrocytes at distant sites, and (v) infected cells were being efficiently cleared from the nervous system by day 7 after infection. We conclude that the gamma(1)34.5- attenuation phenotype is reflected in a gross reduction in the ability of the virus to replicate and spread from cell to cell and is not due to a restricted host range. The block in viral replication appears to be a late event in viral replication. PMID:9188630

  12. Influence of long-range atmospheric transportation (LRAT) on mono-to octa-chlorinated PCDD/Fs levels and distributions in soil around Qinghai Lake, China.

    PubMed

    Han, Ying; Liu, Wenbin; Hansen, Hans Chr Bruun; Chen, Xuebin; Liao, Xiao; Li, Haifeng; Wang, Mengjing; Yan, Nan

    2016-08-01

    Long-range atmospheric transportation (LRAT) of persistent organic pollutants followed by their deposition in cold, arid regions is of wide concern. This problem occurs at Qinghai Lake in the northeastern Tibetan Plateau, a sparsely populated area with extreme weather conditions and little current or historical anthropogenic pollution. The concentrations and distribution patterns of the mono-to octa-chlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/F) congeners in surface soil samples collected from around Qinghai Lake were quantified. Concentration differences between low-(mono-to tri-) chlorinated PCDD/Fs and high-(tetra-to octa-) chlorinated PCDD/Fs were measured. High PCDD/F levels were detected, with total concentrations of 15,108 ± 6323 pg/g for the 27 PCDD/F congeners and 15,104 ± 6324 pg/g for the low-chlorinated PCDD/Fs. The concentrations of 17 2,3,7,8-substituted PCDD/Fs were only 3.1 ± 4.4 pg/g and the corresponding international toxicity equivalency (I-TEQ) was 0.11 ± 0.22 pg I-TEQ/g. Given their higher vapor pressures and lower boiling points, low-chlorinated PCDD/Fs, were predominantly gaseous, whereas high-chlorinated PCDD/Fs were predominantly solid, indicating that there is a higher potential for long-range transport of low-chlorinated PCDD/Fs. Overall, because of their high LRAT potential, low-chlorinated PCDD/Fs may pose a greater risk to local ecosystems in cold, remote areas than high-chlorinated PCDD/Fs. PMID:27174827

  13. Distribution of sexual and asexual Ostracoda (Crustacea) from different altitudinal ranges in the Ordu region of Turkey: testing the Rapoport Rule.

    PubMed

    Külköylüoğlu, Okan; Sari, Necmettin; Akdemir, Derya; Yavuzatmaca, Mehmet; Altinbağ, Ceren

    2012-06-01

    We evaluated Rapoport's rule which states a negative correlation between species richness and altitude. To understand the relationship between altitude and reproductive modes (a/sexual) of non-marine ostracods, 166 aquatic bodies in Ordu region, Turkey were randomly sampled from July 11 to July 16, 2010. A total of 26 species of ostracods were found from 133 out of 166 sites. Except for one species (Heterocypris incongruens), the other 25 species were new reports for the region. Candona improvisa was also a new report for Turkish ostracod fauna. Three species (Psychrodromus olivaceus, H. incongruens, and C. neglecta) occurred most frequently as 43, 46, and 76 times, respectively. Canonical correspondence analyses exhibited two variables [Habitat type (p=0.014; F=2.171) and water temperature (p=0.018; F=2.248)] as having the most effect on species. Correlation of species' reproductive modes to those of environmental variables measured was not significant. UPGMA dendrogram displayed 15 most frequently occurring species into four clusters where most species (11) were asexual. Although a small group (asexual species without swimming setae) showed a tendency to habitat type and electrical conductivity, such variables are believed to play secondary role on species distribution. Highest species diversity (13 species) was observed at the range of 1200 and 1400 m (a.s.l.), where numbers of stations sampled was not the highest (22). Numbers of asexual species (19) were higher than the sexual (11) but there were no significant differences (p>0.05) between the frequencies of their occurrences at different altitudinal ranges. Accordingly, our findings do not support the Rapoport Rule. Results yield that reproductive modes of species (sexual and asexual) was not directly correlated to altitude or any environmental variables measured during this study. A better explanation of ostracod diversity appears to be suitability of habitats.

  14. Implanting radio transmitters in wintering canvasbacks

    USGS Publications Warehouse

    Olsen, G.H.; Dein, F.J.; Haramis, G.M.; Jorde, D.G.

    1992-01-01

    To conduct telemetry studies of wintering canvasbacks (Aythya valisineria) on Chesapeake Bay [Maryland, USA], we needed to devise a suitable method of radio transmitter attachment. We describe as aseptic, intraabdominal surgical technique, using the inhalation anesthetic isoflurane, to implant 20-g radio transmitters in free-ranging canvasbacks. We evaluated the technique over 3 winters (1987-89), when an annual average of 83 female canvasbacks received implant surgery during a 9-day period in mid-December. Of 253 ducks, 248 (98%) were implanted successfully, and 200 (80.65) completed the 70-day study until early March. No mortality or abnormal behavior from surgery was identified post-release.

  15. Implantation in IVF.

    PubMed

    Busso, Cristiano E; Melo, Marco A B; Fernandez, Manuel; Pellicer, Antonio; Simon, Carlos

    2006-01-01

    The recent advances in assisted reproduction have made it possible to study and interfere in almost every step of the human reproductive process except for implantation. The most complex and important step remains in great part unknown. Implantation in human has proven to be less efficient compared with other species. However, in in vitro fertilization (IVF) patients, it has been evaluated to be even poorer. This paper highlights the factors related to infertile patients and IVF treatments that can affect implantation and implantation's clinical aspects related to these treatments: implantation failure and early pregnancy loss.

  16. EXTERNAL INVERSE COMPTON SPECTRA FOR MONOENERGETIC AND BLACKBODY PHOTON FIELDS UPSCATTERED BY A POWER-LAW ELECTRON DISTRIBUTION WITH A FINITE ENERGY RANGE

    SciTech Connect

    Fouka, M.; Ouichaoui, S. E-mail: souichaoui@usthb.dz

    2011-08-20

    We have calculated the inverse Compton (IC) integrated spectral power within the Thomson limit for a monoenergetic isotropic photon field upscattered off highly relativistic electrons assuming an isotropic power-law distribution of the latter, N({gamma}) = C{gamma}{sup -p}, with Lorentz parameter values {gamma}{sub 1} < {gamma} < {gamma}{sub 2}. Our interest was essentially focused on the case of a finite energy range (finite {gamma}{sub 2}) possibly having realistic applications in high-energy astrophysical sites, mainly relativistic shock regions. To this end, we have defined and derived a dimensionless parametric function, F{sub p} (z{sub 1}, {eta}), with variables z{sub 1} = {epsilon}{sub 1}/4{gamma}{sup 2}{sub 1}{epsilon} and {eta} = {gamma}{sub 2}/{gamma}{sub 1}. This result was used to derive the IC-integrated spectral power for an upscattered blackbody (BB) photon field using a dimensionless parametric function, W{sub p} ({xi}, {eta}), with variable {xi} = {epsilon}{sub 1}/4{gamma}{sup 2}{sub 1} kT. Asymptotic forms of this function have been derived for three energy ranges, i.e., {xi} << 1, 1 << {xi} << {eta}{sup 2}, and {xi} >> {eta}{sup 2}. Then, a characteristic value, {eta}{sub c}(p, {epsilon}) with {epsilon} << 1, of parameter {eta} was defined such that the middle range asymptotic form of W{sub p} ({xi}, {eta}) could be valid and good when {eta} {approx}> {eta}{sub c}(p, {epsilon}), by deriving an approximate expression of this particular value for {epsilon} = 10{sup -3}. The resulting spectra featured by a high-energy cutoff in the case of low values of the ratio {eta} can be discussed at least for a population of short gamma-ray bursts (GRBs), those best described by the cutoff power-law model with a low-energy spectral index, {alpha} {approx} 0. Furthermore, it is suggested that for GRB spectra with {alpha} < -1/2 pertaining to the prompt emission phase, the IC is a likely emission mechanism for both monoenergetic and BB photon fields if one

  17. Angular and energy distribution of Sn ion debris ejected from a laser-produced plasma source, for laser power densities in the range suitable for extreme ultraviolet lithography

    SciTech Connect

    O'Connor, A.; Morris, O.; Sokell, E.

    2011-04-01

    In this paper, experimental results are presented for the spatial and energy distributions of charge-discriminated Sn ions ejected from laser-produced plasmas. The plasmas were formed on solid, planar Sn targets, irradiated with a Nd:YAG laser. Ions were investigated using a calibrated electrostatic sector analyzer, scanning an energy-to-charge ratio range of 0.22 to 2.2 keV/e for emission angles between 20 and 80 degrees relative to target normal. Results were obtained for three laser power densities, in the region suitable for inducing significant extreme ultraviolet emission, of the order 1.5-8.1 x 10{sup 11} W/cm{sup 2}. The fully differentiated data were found to be well characterized by Gaussian fits, which allowed trends in the emission profiles to be readily quantified. Ions of set energy and charge were observed to possess a preferential angle of emission, the superposition of which yields a physical basis for the total angular emission observed previously and in this work. The experimental results obtained have been related to physical processes within the plasma that influence the energy and angle of ejection of ions from laser produced plasmas.

  18. Investigations on the feeding habits of the rocky-shore mite Hyadesia fusca (Acari: Astigmata: Hyadesiidae): diet range, food preference, food quality, and the implications for distribution patterns

    NASA Astrophysics Data System (ADS)

    Bücking, Jens

    1998-06-01

    Within the food web of estuarine and marine rocky shore ecosystems phytophagous mites of terrestrial and marine origin constitute an important part as grazers on algae and as a food source for certain arthropods, especially zoophagous mites. This investigation deals with the feeding biology of Hyadesia fusca taking as an example a population located on an artificial rocky shore of the middle Weser estuary in Northern Germany. The species is characterized by a broad diet range; in feeding experiments diatoms, lichens, detritus as well as blue, red and green algae were accepted. Even analyses of faecal pellets produced by field specimen suggest a non-specific feeding habit. However, the influence of certain diets on mortality, offspring number and rearing success showed that the food quality differs significantly. The most suitable food, the Ulvaceae Blidingia, was clearly preferred in a series of pairwise choice tests. These findings correlate with the vertical zonation of the field population i.e.: higher population densities in the vegetation zone dominated by Blidingia. It can be concluded that in addition to abiotic factors food supply could play an important role for distribution patterns of phytophagous mites.

  19. Range-wide network of priority areas for greater sage-grouse - a design for conserving connected distributions or isolating individual zoos?

    USGS Publications Warehouse

    Crist, Michele R.; Knick, Steven T.; Hanser, Steven E.

    2015-09-08

    The network of areas delineated in 11 Western States for prioritizing management of greater sage-grouse (Centrocercus urophasianus) represents a grand experiment in conservation biology and reserve design. We used centrality metrics from social network theory to gain insights into how this priority area network might function. The network was highly centralized. Twenty of 188 priority areas accounted for 80 percent of the total centrality scores. These priority areas, characterized by large size and a central location in the range-wide distribution, are strongholds for greater sage-grouse populations and also might function as sources. Mid-ranking priority areas may serve as stepping stones because of their location between large central and smaller peripheral priority areas. The current network design and conservation strategy has risks. The contribution of almost one-half (n = 93) of the priority areas combined for less than 1 percent of the cumulative centrality scores for the network. These priority areas individually are likely too small to support viable sage-grouse populations within their boundary. Without habitat corridors to connect small priority areas either to larger priority areas or as a clustered group within the network, their isolation could lead to loss of sage-grouse within these regions of the network. 

  20. Mechanical stresses and amorphization of ion-implanted diamond

    NASA Astrophysics Data System (ADS)

    Khmelnitsky, R. A.; Dravin, V. A.; Tal, A. A.; Latushko, M. I.; Khomich, A. A.; Khomich, A. V.; Trushin, A. S.; Alekseev, A. A.; Terentiev, S. A.

    2013-06-01

    Scanning white light interferometry and Raman spectroscopy were used to investigate the mechanical stresses and structural changes in ion-implanted natural diamonds with different impurity content. The uniform distribution of radiation defects in implanted area was obtained by the regime of multiple-energy implantation of keV He+ ions. A modification of Bosia's et al. (Nucl. Instrum. Meth. B 268 (2010) 2991) method for determining the internal stresses and the density variation in an ion-implanted diamond layer was proposed that suggests measuring, in addition to the surface swelling of a diamond plate, the radius of curvature of the plate. It is shown that, under multiple-energy implantation of He+, mechanical stresses in the implanted layer may be as high as 12 GPa. It is shown that radiation damage reaches saturation for the implantation fluence characteristic of amorphization of diamond but is appreciably lower than the graphitization threshold.

  1. Trends in Cochlear Implants

    PubMed Central

    Zeng, Fan-Gang

    2004-01-01

    More than 60,000 people worldwide use cochlear implants as a means to restore functional hearing. Although individual performance variability is still high, an average implant user can talk on the phone in a quiet environment. Cochlear-implant research has also matured as a field, as evidenced by the exponential growth in both the patient population and scientific publication. The present report examines current issues related to audiologic, clinical, engineering, anatomic, and physiologic aspects of cochlear implants, focusing on their psychophysical, speech, music, and cognitive performance. This report also forecasts clinical and research trends related to presurgical evaluation, fitting protocols, signal processing, and postsurgical rehabilitation in cochlear implants. Finally, a future landscape in amplification is presented that requires a unique, yet complementary, contribution from hearing aids, middle ear implants, and cochlear implants to achieve a total solution to the entire spectrum of hearing loss treatment and management. PMID:15247993

  2. Breast implants. A review.

    PubMed

    Van Zele, D; Heymans, O

    2004-04-01

    Breast implants have been used for about four decades for both reconstructive and aesthetic purposes. In 1963, the quality of the artificial implants was revolutionized by the introduction of the silicone gel-filled implant. Since, this modern prosthesis has gone through an evolution of change and improvement with several types of devices with many variations and styles within each class. Actually, for the last three decades, approximately one million women have received silicone breast implants in the USA. But, in 1992, the American FDA banned silicone from the market, leaving saline implants as the only product generally available as an alternative until now. Other filler materials were introduced, but have never progressed beyond the experimental stage in the USA (in contrast with Europe). The evolution of the different implants through time, with their advantages and disadvantages will be discussed, but also the controversy on silicone implants in the USA and their suspected association with systemic diseases. PMID:15154572

  3. CO2 lasers and temperature changes of titanium implants.

    PubMed

    Oyster, D K; Parker, W B; Gher, M E

    1995-12-01

    Lasers may be useful in uncovering submerged implants or in removing contaminants from "ailing" implants. The purposes of this study were to record temperature changes at the bone-titanium implant interface when using a CO2 laser to: 1) uncover the implant at second stage surgery; and 2) "decontaminate" exposed implant threads. Scanning electron microscopy (SEM) was used to characterize surface changes of lased implants, both uncontaminated or contaminated with blood or saliva. In part one, 28 titanium implants, measuring 3.75 mm by 7 to 20 mm, were placed into room temperature, fresh, resected pig mandibles and covered with a flap of gingiva. The overlying tissue was removed with a CO2 laser at different power levels. Bone-implant interface temperatures were measured with a thermocouple near the top of the implant, and 5 to 7 mm apical to the osseous crest. The effects of implant size, power level, tissue thickness, and operation time were evaluated. In part two, 5 mm by 4 mm bony dehiscences were created on 3 implants in one mandible and the exposed fixture threads lased at varying times and power levels. The results from part one showed temperature increases at the top thermocouple ranged from 4.2 to 16.8 degrees C and increases at the bottom thermocouple ranged from 2.0 to 11.5 degrees C. The results from part two showed temperature increases at the top thermocouple ranged from 1.2 to 11.7 degrees C and increases at the bottom thermocouple from 0.0 to 5.0 degrees C. If baseline ambient temperatures are 37 degrees C, then the temperature at the bone-implant interface might exceed 50 degrees C. SEM revealed no gross surface changes in lased uncontaminated implants, but laser treatment alone of contaminated implants failed to completely remove saliva or blood. Further study is needed regarding temperature increases and surface changes induced by lasers that may adversely affect osseointegration.

  4. Ion implantation of boron in germanium

    SciTech Connect

    Jones, K.S.

    1985-05-01

    Ion implantation of /sup 11/B/sup +/ into room temperature Ge samples leads to a p-type layer prior to any post implant annealing steps. Variable temperature Hall measurements and deep level transient spectroscopy experiments indicate that room temperature implantation of /sup 11/B/sup +/ into Ge results in 100% of the boron ions being electrically active as shallow acceptor, over the entire dose range (5 x 10/sup 11//cm/sup 2/ to 1 x 10/sup 14//cm/sup 2/) and energy range (25 keV to 100 keV) investigated, without any post implant annealing. The concentration of damage related acceptor centers is only 10% of the boron related, shallow acceptor center concentration for low energy implants (25 keV), but becomes dominant at high energies (100 keV) and low doses (<1 x 10/sup 12//cm/sup 2/). Three damage related hole traps are produced by ion implantation of /sup 11/B/sup +/. Two of these hole traps have also been observed in ..gamma..-irradiated Ge and may be oxygen-vacancy related defects, while the third trap may be divacancy related. All three traps anneal out at low temperatures (<300/sup 0/C). Boron, from room temperature implantation of BF/sub 2//sup +/ into Ge, is not substitutionally active prior to a post implant annealing step of 250/sup 0/C for 30 minutes. After annealing additional shallow acceptors are observed in BF/sub 2//sup +/ implanted samples which may be due to fluorine or flourine related complexes which are electrically active.

  5. Microstructure evolution in carbon-ion implanted sapphire

    SciTech Connect

    Orwa, J. O.; McCallum, J. C.; Jamieson, D. N.; Prawer, S.; Peng, J. L.; Rubanov, S.

    2010-01-15

    Carbon ions of MeV energy were implanted into sapphire to fluences of 1x10{sup 17} or 2x10{sup 17} cm{sup -2} and thermally annealed in forming gas (4% H in Ar) for 1 h. Secondary ion mass spectroscopy results obtained from the lower dose implant showed retention of implanted carbon and accumulation of H near the end of range in the C implanted and annealed sample. Three distinct regions were identified by transmission electron microscopy of the implanted region in the higher dose implant. First, in the near surface region, was a low damage region (L{sub 1}) composed of crystalline sapphire and a high density of plateletlike defects. Underneath this was a thin, highly damaged and amorphized region (L{sub 2}) near the end of range in which a mixture of i-carbon and nanodiamond phases are present. Finally, there was a pristine, undamaged sapphire region (L{sub 3}) beyond the end of range. In the annealed sample some evidence of the presence of diamond nanoclusters was found deep within the implanted layer near the projected range of the C ions. These results are compared with our previous work on carbon implanted quartz in which nanodiamond phases were formed only a few tens of nanometers from the surface, a considerable distance from the projected range of the ions, suggesting that significant out diffusion of the implanted carbon had occurred.

  6. Multiscale Analyses of the Bone-implant Interface

    PubMed Central

    Cha, J.Y.; Pereira, M.D.; Smith, A.A.; Houschyar, K.S.; Yin, X.; Mouraret, S.; Brunski, J.B.

    2015-01-01

    Implants placed with high insertion torque (IT) typically exhibit primary stability, which enables early loading. Whether high IT has a negative impact on peri-implant bone health, however, remains to be determined. The purpose of this study was to ascertain how peri-implant bone responds to strains and stresses created when implants are placed with low and high IT. Titanium micro-implants were inserted into murine femurs with low and high IT using torque values that were scaled to approximate those used to place clinically sized implants. Torque created in peri-implant tissues a distribution and magnitude of strains, which were calculated through finite element modeling. Stiffness tests quantified primary and secondary implant stability. At multiple time points, molecular, cellular, and histomorphometric analyses were performed to quantitatively determine the effect of high and low strains on apoptosis, mineralization, resorption, and collagen matrix deposition in peri-implant bone. Preparation of an osteotomy results in a narrow zone of dead and dying osteocytes in peri-implant bone that is not significantly enlarged in response to implants placed with low IT. Placing implants with high IT more than doubles this zone of dead and dying osteocytes. As a result, peri-implant bone develops micro-fractures, bone resorption is increased, and bone formation is decreased. Using high IT to place an implant creates high interfacial stress and strain that are associated with damage to peri-implant bone and therefore should be avoided to best preserve the viability of this tissue. PMID:25628271

  7. The vertical distribution of pollutants during export and long range transport: A comparison of model simulations and A-Train observations

    NASA Astrophysics Data System (ADS)

    Ford, Bonne

    Due to increasing concern over the detrimental effects of pollution on visibility, human health, and agriculture, many countries have begun to set more stringent air quality regulations and to take measures to reduce local emissions. However, recent studies have also shown that long range transport (LRT) of pollution from upwind sources can make a non-negligible contribution to background concentrations and potentially inhibit a region's ability to meet air quality standards. Quantifying this contribution has become an important research initiative; however, a major hindrance in determining the impact of transported plumes on a receptor site lies in a lack of information on the vertical distribution of pollutants during export and transport from a source region. The vertical distribution can determine the efficiency of transport by way of dominant removal processes and wind strength, which will determine the final surface impact at a downwind site. In this study, we integrate aerosol extinction and optical depth observations from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP), aerosol optical depth AOD from the Moderate-resolution Imaging Spectroradiometer (MODIS) along with measurements of carbon monoxide (CO) from the Tropospheric Emission Spectrometer (TES) with simulations of species concentrations from a global chemical transport model (GEOS-Chem) to examine the differences in gas and aerosol phase transport in the Northern Hemisphere. The different vertical structures exhibited by gaseous and particulate phase pollution due to differing sources and sinks provide opportunities to evaluate the model representation of mechanisms that determine the vertical structure, and ultimately the impact of LRT downwind. While CALIOP has unprecedented vertical resolution, it, like TES, has a small footprint and wide distance between scans, with no cross-track scanning. Therefore, comparisons with these satellite observations are particularly susceptible to

  8. Single-crystal sapphire endosseous dental implant loaded with functional stress--clinical and histological evaluation of peri-implant tissues.

    PubMed

    Hashimoto, M; Akagawa, Y; Nikai, H; Tsuru, H

    1988-01-01

    Peri-implant tissues of the single-crystal sapphire implant connected with neighbouring teeth by a metal bridge-work were examined clinically, radiographically, and histologically in ten monkeys. Professional tooth cleaning was performed during the study. At 3-12 months after insertion, most of the implants were firmly connected to the surrounding tissues and peri-implant gingiva was regarded as healthy, based on various periodontal parameter scores. Destructive changes of the peri-implant bone were not found radiographically. Histologically, peri-implant gingiva was revealed to show similar structure to that of the gingiva around natural teeth. Direct bone-implant interface was observed at 3 months after insertion, while a thin loose fibrous connective tissue layer was present between bone and implant at 6 and 12 months. Such different interrelationship between bone and implant might be attributable to the difference in distribution of functional stress.

  9. Mg-Doped Hydroxyapatite/Chitosan Composite Coated 316L Stainless Steel Implants for Biomedical Applications.

    PubMed

    Sutha, S; Dhineshbabu, N R; Prabhu, M; Rajendran, V

    2015-06-01

    In this investigation, ultrasonication process was used for the synthesis of magnesium doped nano-hydroxyapatite (MH) (0, 1, 2, and 3 mol% of Mg concentration) particles with controlled size and surface morphology. The size of the prepared MH particles was in the range of 20-100 nm with narrow distribution. Increase in the concentration of Mg reduced the particle size distribution from 60 to 40 nm. On incorporation of Mg in HAp lattice, an increase of 20-66 nm in specific surface area was observed in microporous HAp particles. XRF and XRD patterns reveal that the particles possess stoichiometric composition with reduced crystallinity with respect to the Mg concentration. Surface morphology of MH/chitosan (CTS) coated implant was found to be uniform without any defects. The corrosion rate of the implant decreased with increase in Mg concentration. The in vitro formation of bonelike apatite layer on the surface of the MH/CTS coated implant was observed from simulated body fluid studies. The antimicrobial activity of the MH/CTS composites against gram-positive and gram-negative bacterial strains indicated that increasing Mg concentration enhanced antimicrobial properties. Nanoindentation analysis of apatite coated implant surface reveals that the mechanical property depends on the concentration of magnesium in HAp. From the cytotoxicity analysis against NIH 3T3 fibroblast, it was observed that the Mg incorporated HAp/CTS composite was less toxic than the MHO/CTS composite. From this result, it was concluded that the MH/CTS nanocomposites coated implant is the excellent material for implants.

  10. Characterization of PEEK, PET and PI implanted with Mn ions and sub-sequently annealed

    NASA Astrophysics Data System (ADS)

    Mackova, A.; Malinsky, P.; Miksova, R.; Pupikova, H.; Khaibullin, R. I.; Slepicka, P.; Gombitová, A.; Kovacik, L.; Svorcik, V.; Matousek, J.

    2014-04-01

    Polyimide (PI), polyetheretherketone (PEEK) and polyethylene terephthalate (PET) foils were implanted with 80 keV Mn+ ions at room temperature at fluencies of 1.0 × 1015-1.0 × 1016 cm-2. Mn depth profiles determined by RBS were compared to SRIM 2012 and TRIDYN simulations. The processes taking place in implanted polymers under the annealing procedure were followed. The measured projected ranges RP differ slightly from the SRIM and TRIDYN simulation and the depth profiles are significantly broader (up to 2.4 times) than those simulated by SRIM, while TRIDYN simulations were in a reasonable agreement up to the fluence 0.5 × 1016 in PEEK. Oxygen and hydrogen escape from the implanted layer was examined using RBS and ERDA techniques. PET, PEEK and PI polymers exhibit oxygen depletion up to about 40% of its content in virgin polymers. The compositional changes induced by implantation to particular ion fluence are similar for all polymers examined. After annealing no significant changes of Mn depth distribution was observed even the further oxygen and hydrogen desorption from modified layers appeared. The surface morphology of implanted polymers was characterized using AFM. The most significant change in the surface roughness was observed on PEEK. Implanted Mn atoms tend to dissipate in the polymer matrix, but the Mn nanoparticles are too small to be observed on TEM micrographs. The electrical, optical and structural properties of the implanted and sub-sequently annealed polymers were investigated by sheet resistance measurement and UV-Vis spectroscopy. With increasing ion fluence, the sheet resistance decreases and UV-Vis absorbance increases simultaneously with the decline of optical band gap Eg. The most pronounced change in the resistance was found on PEEK. XPS spectroscopy shows that Mn appears as a mixture of Mn oxides. Mn metal component is not present. All results were discussed in comparison with implantation experiment using the various ion species (Ni, Co

  11. R-Wave Sensing in an Implantable Cardiac Monitor without ECG-Based Preimplant Mapping: Results from a Multicenter Clinical Trial

    PubMed Central

    Krahn, Andrew D; Pickett, Robert A; Sakaguchi, Scott; Shaik, Naushad; Cao, Jian; Norman, Holly S; Guerrero, Patricia

    2014-01-01

    Introduction Reducing the form factor of an implantable cardiac monitor (ICM) may simplify device implant. This study evaluated R-wave sensing at a range of electrode distances and a preferred device implant location without mapping. Methods Patients scheduled for a Medtronic Reveal® ICM implant (Medtronic Inc., Minneapolis, MN, USA) underwent a preimplant pocket recording using a diagnostic recording catheter. The ICM implant location was left to the discretion of the implanting physician, but a “recommended” position spanned the V2–V3 electrocardiogram electrode location in an oblique 45° angle. R-wave amplitudes were analyzed from ICM follow-up. Results Seventeen of 41 subjects (15 male, age 57 ± 16 years) had the maximum surface-filtered R-wave at the recommended location. Fourteen patients underwent diagnostic recording across the range of electrode spacing. There was a strong correlation between the R-wave amplitude and electrode distance (r2 = 0.97, P < 0.001) with an increase of 29 μV per 2.5 mm. Comparing normalized R-wave distributions between the recommended ICM implant group (Group 1, n = 19) and the remaining patients (Group 2, n = 7), the proportion of ICM R-wave counts of amplitude 0.25–1.2 mV was higher (79% vs 46%, P < 0.05). Of 17 patients in Group 1 who had ≥1-month ICM follow-up (79 ± 45 days), no sensing-related false arrhythmia detection was found in 16 (93%) patients. Conclusions The subcutaneous R-wave amplitude correlates with electrode spacing in the implant zone of ICM patients. Implant locations at the V2–V3 position at a 45° angle offer an adequate R wave for sensing. Preimplant mapping to achieve acceptable R-wave amplitude may not be necessary. PMID:24299115

  12. [Radioactivity of phosphorus implanted TiNi alloy].

    PubMed

    Zhao, Xingke; Cai, Wei; Zhao, Liancheng

    2003-09-01

    Exposed to neutron flow, the phosphorus implanted TiNi alloy gets radioactive. This radioactive material is used in vascular stent for prevention and cure of restenosis. Phosphorus implantation is carried out in a plasma immerged ion implantation system, and the dose of phosphorus implantation is in the range of 2-10 x 10(17) cm-2. After ion implantation, the alloy is exposed to the slow neutron flow in a nuclear reactor, the dose of the slow neutron is 1.39-5.88 x 10(19) n/cm2. The radioactivity of the TiNi alloy was measured by liquid scintillation spectrometry and radio-chromic-film dosimetry. The result shows that whether the phosphorus is implanted or not, the TiNi alloy comes to be radioactive after exposure to neutron flow. Just after neutron irradiation, the radiation dose of phosphorus implanted TiNi alloy is about one hundred times higher than that of un-phosphorus implanted TiNi alloy. The radiation difference between phosphorus and un-phosphorus implanted alloy decreases as time elapses. Within three months after neutron irradiation, the average half-decay period of phosphorus implanted TiNi alloy is about 62 days. The radiation ray penetration of phosphorus implanted TiNi alloy is deeper than that of pure 32P; this is of benefit to making radiation uniformity between stent struts and reducing radiation grads beyond the edge of stent.

  13. Implants in adolescents

    PubMed Central

    Shah, Rohit A.; Mitra, Dipika K.; Rodrigues, Silvia V.; Pathare, Pragalbha N.; Podar, Rajesh S.; Vijayakar, Harshad N.

    2013-01-01

    Implants have gained tremendous popularity as a treatment modality for replacement of missing teeth in adults. There is extensive research present on the use of implants in adults, but there is a dearth of data available on the same in adolescents. The treatment planning and execution of implant placement in adolescents is still in its infancy. This review article is an attempt to bring together available literature. PMID:24174743

  14. The Development of Intonation in Young Children with Cochlear Implants: A Preliminary Study of the Influence of Age at Implantation and Length of Implant Experience

    ERIC Educational Resources Information Center

    Snow, David; Ertmer, David

    2009-01-01

    This study describes the development of emerging intonation in six children who had received a cochlear implant (CI) before the age of 3 years. At the time their implant was activated, the children ranged in age from 11-37 months. Spontaneous longitudinal speech samples were recorded from 30-minute sessions in which the child interacted with his…

  15. Implantable cardioverter defibrillator - discharge

    MedlinePlus

    Baddour LM, Epstein AE, Erickson CC, et al. Update on cardiovascular implantable electronic device infections and their management: a scientific statement from the American Heart Association. Circulation . ...

  16. High-fluence Si-implanted diamond: Optimum implantation temperature for SiC formation

    SciTech Connect

    Weishart, H.; Eichhorn, F.; Heera, V.; Pecz, B.; Barna, A.; Skorupa, W.

    2005-08-15

    In this paper the authors investigate the effect of implantation temperature on the structural properties of diamond implanted with high fluences of Si between 5.3x10{sup 17} Si cm{sup -2} and 1x10{sup 18} Si cm{sup -2}. In order to reduce radiation-induced damage and to enhance SiC formation the implantations were performed at elevated temperatures in the range from 900 to 1200 deg. C. Subsequently, all samples were annealed for 10 min at 1500 deg. C in a rf-heated furnace. X-ray diffraction revealed the formation of cubic SiC nanocrystallites in a buried layer inside the implanted diamond. The implantation-induced damage was assessed by analyzing graphitization of the surface-near layer using Raman spectroscopy. With increasing Si fluence the implantation-induced damage rises and the nearly perfect alignment of the formed SiC crystallites within the host diamond lattice deteriorates. However, raising the implantation temperature from 900 to 1000 deg. C reduces the damage in the diamond and increases the amount, size, and epitaxial alignment of the crystalline SiC precipitates. Further increase of the implantation temperature gives no improvement in the quality of the SiC-rich layer. Instead, the damaged diamond converts into graphite and the formation of SiC crystallites is obstructed.

  17. Tritium implantation in the accelerator production of tritium device

    SciTech Connect

    Kidman, R.B.

    1997-11-01

    We briefly describe the methods we have developed to compute the magnitude and spatial distribution of born and implanted tritons and protons in the Accelerator Production of Tritium (AFT) device. The methods are verified against experimental measurements and then used to predict that 16% of the tritium is implanted in the walls of the APT distribution tubes. The methods are also used to estimate the spatial distribution of implanted tritium, which will be required for determining the possible diffusion of tritium out of the walls and back into the gas stream.

  18. Radiographic dental implants recognition for geographic evaluation in human identification.

    PubMed

    Nuzzolese, E; Lusito, S; Solarino, B; Di Vella, G

    2008-06-01

    Dental implants for prosthetic rehabilitation with fixed crown or mobile partial/total dentures is a very common oral treatment among the population in Italy as elsewhere. There is a great number of implant systems of different designs. However, a catalogue of radiographic images and a description of the dental implants available in Italy would be useful in order to identify the manufacturer and the type of implant encountered in forensic casework. When an unidentified body is found with one or more implants in the jaws, and no dental record is available, clues gleaned from the type of implants used could give direction to the investigation. In this study Italian implant manufactures were contacted and asked to provide specimen implants. Digital radiographs were taken of all the implants donated at 0º, 30º, and 60º horizontal rotation, combined with -20º, -10º, 0º, +10º, and +20º vertical inclination relative to the radiographic beam and the X-ray sensor. A total of 15 images per implant were taken and examined to identify consistent, unique features that would aid in implant recognition. Only those observations made from radiographs between -10º and +10º vertical inclination would ever be used for definite identification of any implant. The information from this study should be considered a survey of the commercial distribution of dental implants in Italy through their digital radiographic images. It is also a starting point for a wider geographical evaluation of different manufacturers in other countries and continents. The radiographic images provided should help both the forensic odontologist and the prosthodontist to identify pre-existing implants which they may discover from their radiographic images. PMID:22689351

  19. [Low frequency-based non-uniform sampling strategy to improve Chinese recognition in cochlear implant].

    PubMed

    Ni, Saihua; Sun, Wenye; Sun, Baoyin; Zhou, Qiang; Wang, Qiang; Wang, Zhenming; Gu, Jihua; Tao, Zhi

    2014-06-01

    To enhance speech recognition, as well as Mandarin tone recognition in noice, we proposed a speech coding strategy called zero-crossing of fine structure in low frequency (LFFS) for cochlear implant based on low frequency non-uniform sampling (LFFS for short). In the range of frequency perceived boundary of human ear, we used zero-crossing time of the fine structure to generate the stimulus pulse sequences based on the frequency selection rule. Acoustic simulation results showed that although on quiet background the performance of LFFS was similar to continuous interleaved sampling (CIS), on the noise background the performance of LFFS in Chinese tones, words and sentences were significantly better than CIS. In addition to this, we also got better Mandarin recognition factors distribution by using the improved index distribution model. LFFS contains more tonal information which was able to effectively improve Mandarin recognition of the cochlear implant. PMID:25219227

  20. Finite element analysis of thumb carpometacarpal joint implants

    SciTech Connect

    Nielsen, C.

    1995-11-01

    The thumb carpometacarpal joint is frequently replaced in women who have developed severe osteoarthritis of the hand. A new, privately developed implant design consists of two components, trapezial and metacarpal, each with a saddle-shaped articulating surface. A three dimensional finite element model of this implant has been developed to analyze stresses on the device. The first simulations using the model involve loading the implant with forces normal to the trapezial component. Preliminary results show contact stress distributions at the particulating surfaces of the implant.

  1. He reemission implanted in metals

    NASA Astrophysics Data System (ADS)

    Tanabe, T.

    2014-10-01

    Helium (He) reemission of Al, Ni and Mo under energetic He implantation (10-30 keV) in wide temperature range is studied to understand behavior of implanted He in correlation with structure changes. The reemission behavior is categorized into 4 different temperature ranges with the normalized temperature (Tm) to the melting point of each metal. At elevated temperatures (well above ∼0.6 Tm), interstitial He atoms and/or He-vacancy (ies) clusters can migrate remaining no structure change and showing smooth reemission without any burst. Between ∼0.25 and 0.6 Tm, He reemission always accompanies significant structure modification. For ∼04-0.6 Tm, implanted He coalesce to make bubbles and the bubbles can move to the surface. Bubble migration accompanies materials flow to the surface resulting in fuzz surface or columnar structure, depending on implantation flux. Slower bubble motion at ∼0.25-0.4 prohibits the material migration. Instead the bubbles coalesce to grow large and multi-layered blistering appears as periodic reemission behavior. Below ∼0.25 Tm, He migration is too slow for bubbles to grow large, but bubble density increases up to a certain fluence, where neighboring bubbles start to coalesce. Accordingly, He release is mostly caused by mechanical failure or blister rapture. With increasing fluence, all defects (bubbles and dislocation loops) tangle or inter connected with neighboring defects and accordingly He migration to the surface along the tangled or connected defects is enhanced, resulting 100% reemission easily without making multilayered blistering.

  2. Defects and diffusion in MeV implanted silicon

    SciTech Connect

    Venezia, V. C.; Haynes, T. E.; Agarwal, Aditya; Gossmann, H.-J.; Pelaz, L.; Jacobson, D. C.; Eaglesham, D. J.; Duggan, J. L.

    1999-06-10

    In this work we demonstrate that the defects that are created by 2-MeV Si ions can interact with dopant atoms both during implantation and during post-implant annealing. We show that the interstitials and vacancies created during MeV Si implantation result in a radiation enhanced diffusion of B and Sb markers, respectively, when the temperature of implantation is above the threshold temperature for formation of mobile dopant complexes. With the use of these dopant markers we also demonstrate that a vacancy-rich near surface region results during post-implant annealing of MeV implanted silicon. The depth distribution and the thermal evolution of clustered vacancies was measured by a Au labeling technique.

  3. Batteryless implanted echosonometer

    NASA Technical Reports Server (NTRS)

    Kojima, G. K.

    1977-01-01

    Miniature ultrasonic echosonometer implanted within laboratory animals obtains energy from RF power oscillator that is electronically transduced via induction loop to power receiving loop located just under animal's skin. Method of powering device offers significant advantages over those in which battery is part of implanted package.

  4. Implantable, Ingestible Electronic Thermometer

    NASA Technical Reports Server (NTRS)

    Kleinberg, Leonard

    1987-01-01

    Small quartz-crystal-controlled oscillator swallowed or surgically implanted provides continuous monitoring of patient's internal temperature. Receiver placed near patient measures oscillator frequency, and temperature inferred from previously determined variation of frequency with temperature. Frequency of crystal-controlled oscillator varies with temperature. Circuit made very small and implanted or ingested to measure internal body temperature.

  5. A baseline analysis of the distribution, host-range, and severity of the rust Puccinia Psidii in the Hawaiian islands, 2005-2010

    USGS Publications Warehouse

    Anderson, Robert C.

    2012-01-01

    Puccinia psidii was first described by Winter (1884) on guava (Psidium guajava L.) in Brazil. The rust is still a major pest of native guava in Brazil and is often referred to as “guava rust” internationally. It is unusual among rust fungi because of its broad and ever-expanding host-range within the Myrtaceae plant family (Simpson et al. 2006). The pathogen is regarded as a major threat to Eucalyptus plantations and other Myrtaceae worldwide (Coutinho et al. 1998, Grgurinovic et al. 2006, Glen et al. 2007). Infections of leaves and meristems are particularly severe on susceptible seedlings, cuttings, young trees, and coppice, causing plants to be stunted and multi-branched, inhibiting normal growth and development, and sometimes causing death to young seedlings (Booth et al. 2000, Rayachhetry et al. 2001). The fungus has expanded its host-range in Brazil, affecting both native and introduced Myrtaceae (Coutinho et al. 1998).


    Since its discovery in 1884, P. psidii has continually been discovered to have an expanding host-range within the Myrtaceae, affecting hosts throughout much of South and Central America and the Caribbean. Spreading out originally from Brazil in 1884, the fungus has been reported on hosts in the following countries (first record in parentheses): Paraguay (1884), Uruguay (1889), Ecuador (1891), Colombia (1913), Puerto Rico (1913), Cuba (1926), Dominican Republic (1933), Venezuela (1934), Jamaica (1936), Argentina (1946), Dominica (1948), Trinidad and Tobago (1951), Guatemala (1968), United States (Florida; 1977), Mexico (1981), El Salvador (1987), and Costa Rica (1998) (Simpson et al. 2006). It is possible that P. psidii was present in El Salvador and Costa Rica prior to 1980, but was not reported until 1987 and 1998, respectively.


    Until recently, Puccinia psidii was restricted to the Neotropics, Mexico, and the

  6. Graphene for Biomedical Implants

    NASA Astrophysics Data System (ADS)

    Moore, Thomas; Podila, Ramakrishna; Alexis, Frank; Rao, Apparao; Clemson Bioengineering Team; Clemson Physics Team

    2013-03-01

    In this study, we used graphene, a one-atom thick sheet of carbon atoms, to modify the surfaces of existing implant materials to enhance both bio- and hemo-compatibility. This novel effort meets all functional criteria for a biomedical implant coating as it is chemically inert, atomically smooth and highly durable, with the potential for greatly enhancing the effectiveness of such implants. Specifically, graphene coatings on nitinol, a widely used implant and stent material, showed that graphene coated nitinol (Gr-NiTi) supports excellent smooth muscle and endothelial cell growth leading to better cell proliferation. We further determined that the serum albumin adsorption on Gr-NiTi is greater than that of fibrinogen, an important and well understood criterion for promoting a lower thrombosis rate. These hemo-and biocompatible properties and associated charge transfer mechanisms, along with high strength, chemical inertness and durability give graphene an edge over most antithrombogenic coatings for biomedical implants and devices.

  7. Effect of Implant Height Differences on Different Attachment Types and Peri-Implant Bone in Mandibular Two-Implant Overdentures: 3D Finite Element Study.

    PubMed

    Ozan, Oguz; Ramoglu, Serhat

    2015-06-01

    Implant-supported overdentures with self-aligning attachment systems are preferred to improve the stability and retention of complete dentures. The positioning of the implant attachments is a very important aspect of two-implant overdentures in obtaining better stress distribution. Therefore, the objective of this study was to compare two different attachment systems in a two-implant overdenture by evaluating the stress distributions in peri-implant bone and stresses on the attachments with positioning at different height levels using the 3D FEA method. Six models with ball attachments and 6 models with locator attachments-totaling 12 models (including 2 controls)-with the left implant positioned unilaterally at different height levels were subjected to 3 loading conditions (anterior, right posterior, and left posterior). Data for Von Misses stresses were produced numerically, color coded, and compared among the models for attachments and peri-implant cortical bone. The configurations in which implants presented 3 mm height differences in the bone level showed the most successful results in the peri-implant bone. When stresses on the attachments were compared, greater stress values were obtained from the ball attachments. As a conclusion, the configurations with a considerable (3 mm) height difference between quadrants of the mandible in the anterior segment showed the most successful results in the peri-implant bone. On the contrary, peak stress values around the implant observed from the models with less (1 mm) bone height difference may require leveling of the bone during surgery. However, these findings should be corroborated with clinical studies.

  8. Surface topographical and structural analysis of Ag+-implanted polymethylmethacrylate

    NASA Astrophysics Data System (ADS)

    Arif, Shafaq; Rafique, M. Shahid; Saleemi, Farhat; Naab, Fabian; Toader, Ovidiu; Sagheer, Riffat; Bashir, Shazia; Zia, Rehana; Siraj, Khurram; Iqbal, Saman

    2016-08-01

    Specimens of polymethylmethacrylate (PMMA) were implanted with 400-keV Ag+ ions at different ion fluences ranging from 1 × 1014 to 5 × 1015 ions/cm2 using a 400-kV NEC ion implanter. The surface topographical features of the implanted PMMA were investigated by a confocal microscope. Modifications in the structural properties of the implanted specimens were analyzed in comparison with pristine PMMA by X-ray diffraction (XRD) and Raman spectroscopy. UV-Visible spectroscopy was applied to determine the effects of ion implantation on optical transmittance of the implanted PMMA. The confocal microscopic images revealed the formation of hillock-like microstructures along the ion track on the implanted PMMA surface. The increase in ion fluence led to more nucleation of hillocks. The XRD pattern confirmed the amorphous nature of pristine and implanted PMMA, while the Raman studies justified the transformation of Ag+-implanted PMMA into amorphous carbon at the ion fluence of ⩾5 × 1014 ions/cm2. Moreover, the decrease in optical transmittance of PMMA is associated with the formation of hillocks and ion-induced structural modifications after implantation.

  9. Dental implants installed in irradiated jaws: a systematic review.

    PubMed

    Chambrone, L; Mandia, J; Shibli, J A; Romito, G A; Abrahao, M

    2013-12-01

    The aim of this study was to assess the survival rate of titanium implants placed in irradiated jaws. MEDLINE, EMBASE, and CENTRAL were searched for studies assessing implants that had been placed in nongrafted sites of irradiated patients. Random effects meta-analyses assessed implant loss in irradiated versus nonirradiated patients and in irradiated patients treated with hyperbaric oxygen (HBO) therapy. Of 1,051 potentially eligible publications, 15 were included. A total of 10,150 implants were assessed in the included studies, and of these, 1,689 (14.3%) had been placed in irradiated jaws. The mean survival rate in the studies ranged from 46.3% to 98.0%. The pooled estimates indicated a significant increase in the risk of implant failure in irradiated patients (risk ratio: 2.74; 95% confidence interval: 1.86, 4.05; p < .00001) and in maxillary sites (risk ratio: 5.96; 95% confidence interval: 2.71, 13.12; p < .00001). Conversely, HBO therapy did not reduce the risk of implant failure (risk ratio: 1.28; 95% confidence interval: 0.19, 8.82; p = .80). Radiotherapy was linked to higher implant failure in the maxilla, and HBO therapy did not improve implant survival. Most included publications reported data on machined implants, and only 3 studies on HBO therapy were included. Overall, implant therapy appears to be a viable treatment option for reestablishing adequate occlusion and masticatory conditions in irradiated patients.

  10. Mechanical properties of carbon-implanted niobium

    SciTech Connect

    Zinkle, S.J. ); Huang, J.S. )

    1990-01-01

    Polycrystalline niobium specimens were implanted with either 200 keV carbon ions or a combination of 50, 100, and 200 keV carbon ions to peak concentrations of 0.6 to 50 at. {percent}. Microindentation techniques were used to measure the hardness and elastic modulus of the implanted layer. Both the hardness (H) and modulus (E) showed dramatic increases due to the carbon implantation. The measured peak hardness and modulus following uniform implantation with 16 at. {percent} C were 15{times} and 3{times} that of niobium, respectively, which is comparable to the literature values for NbC. The peak hardness and modulus for the implanted specimens were observed at an indent depth of {approximately}40 nm, which is about one-eighth of the depth of the implanted carbon layer. The decrease in the indentation mechanical properties at deeper indent depths is due to the interaction of long-ranging strain fields underneath the indenter with the niobium substrate. 17 refs., 6 figs.

  11. Cochlear implants: our experience and literature review

    PubMed Central

    Martins, Mariane Barreto Brandão; de Lima, Francis Vinicius Fontes; Santos, Ronaldo Carvalho; Santos, Arlete Cristina Granizo; Barreto, Valéria Maria Prado; de Jesus, Eduardo Passos Fiel

    2012-01-01

    Summary Introduction: Cochlear Implants are important for individuals with severe to profound bilateral sensorineural hearing loss. Objective: Evaluate the experience of cochlear implant center of Otorhinolaryngology through the analysis of records of 9 patients who underwent cochlear implant surgery. Methods: This is a retrospective study performed with the patients records. Number 0191.0.107.000-11 ethics committee approval. We evaluated gender, etiology, age at surgery, duration of deafness, classification of deafness, unilateral or bilateral surgery, intraoperative and postoperative neural response and impedance of the electrodes in intraoperative and preoperative tests and found those that counter-indicated surgery. Results: There were 6 pediatric and 3 adult patients. Four male and 5 female. Etiologies: maternal rubella, cytomegalovirus, ototoxicity, meningitis, and sudden deafness. The age at surgery and duration of deafness ranged from 2–46 years and 2–18 years, respectively. Seven patients were pre-lingual. All had profound bilateral PA. There were 7 bilateral implants. Intraoperative complications: hemorrhage. Complications after surgery: vertigo and internal device failure. In 7 patients the electrodes were implanted through. Telemetry showed satisfactory neural response and impedance. CT and MRI was performed in all patients. We found enlargement of the vestibular aqueduct in a patient and incudomalleolar malformation. Conclusion: The cochlear implant as a form of auditory rehabilitation is well established and spreading to different centers specialized in otoaudiology. Thus, the need for structured services and trained professionals in this type of procedure is clear. PMID:25991976

  12. Implantation of carbon in GaAs

    SciTech Connect

    Moll, A.J.

    1992-03-01

    Carbon implanted into GaAs and thermally annealed typically exhibits very low (<3%) electrical activity. It has been demonstrated that the electrical activity of C can be significantly enhanced by co-implantation with Ga. Improved activation may result from either additional damage of the crystal lattice or from stoichiometric changes, forcing the C atoms onto As sites. To determine the relative importance of each of these effects, I have undertaken a systematic study of carbon activation in GaAs. A range of co-implants have been used: group III (B, Ga), group V (N, P, As) and noble gases (Ar, Kr). The damage introduced to the substrate will depend on the mass of the ion implanted. The group III and group V co-implants will affect the crystal stoichiometry. The results indicate that both lattice damage and crystal stoichiometry are important for high electrical activity of C. Increasing the damage will increase the activation due to the increased number of As vacancies but maximum activation can be obtained only by a co-implant which not only damages the lattice but also forces the C to occupy an As site.

  13. Surface morphologies of He-implanted tungsten

    NASA Astrophysics Data System (ADS)

    Bannister, M. E.; Meyer, F. W.; Hijazi, H.; Unocic, K. A.; Garrison, L. M.; Parish, C. M.

    2016-09-01

    Surface morphologies of tungsten surfaces, both polycrystalline and single-crystal [1 1 0], were investigated using SEM and FIB/SEM techniques after implantations at elevated surfaces temperatures (1200-1300 K) using well-characterized, mono-energetic He ion beams with a wide range of ion energies (218 eV-250 keV). Nanofuzz was observed on polycrystalline tungsten (PCW) following implantation of 100-keV He ions at a flux threshold of 0.9 × 1016 cm-2 s-1, but not following 200-keV implantations with similar fluxes. No nanofuzz formation was observed on single-crystal [1 1 0] tungsten (SCW), despite fluxes exceeding those demonstrated previously to produce nanofuzz on polycrystalline tungsten. Pre-damaging the single-crystal tungsten with implanted C impurity interstitials did not significantly affect the surface morphologies resulting from the high-flux He ion implantations. The main factor leading to the different observed surface structures for the pristine and C-implanted single-crystal W samples appeared to be the peak He ion flux characterizing the different exposures. It was speculated that nanofuzz formation was not observed for any SCW target exposures because of increased incubation fluences required for such targets.

  14. Dosimetric effects of a high-density spinal implant

    NASA Astrophysics Data System (ADS)

    Kairn, T.; Crowe, S. B.; Kenny, J.; Mitchell, J.; Burke, M.; Schlect, D.; Trapp, J. V.

    2013-06-01

    In this study, a treatment plan for a spinal lesion, with all beams transmitted though a titanium vertebral reconstruction implant, was used to investigate the potential effect of a high-density implant on a three-dimensional dose distribution for a radiotherapy treatment. The BEAMnrc/DOSXYZnrc and MCDTK Monte Carlo codes were used to simulate the treatment using both a simplified, recltilinear model and a detailed model incorporating the full complexity of the patient anatomy and treatment plan. The resulting Monte Carlo dose distributions showed that the commercial treatment planning system failed to accurately predict both the depletion of dose downstream of the implant and the increase in scattered dose adjacent to the implant. Overall, the dosimetric effect of the implant was underestimated by the commercial treatment planning system and overestimated by the simplified Monte Carlo model. The value of performing detailed Monte Carlo calculations, using the full patient and treatment geometry, was demonstrated.

  15. Tissue response to peritoneal implants

    NASA Technical Reports Server (NTRS)

    Picha, G. J.

    1980-01-01

    Peritoneal implants were fabricated from poly 2-OH, ethyl methacrylate (HEMA), polyetherurethane (polytetramethylene glycol 1000 MW, 1,4 methylene disocynate, and ethyl diamine), and untreated and sputter treated polytetrafluoroethylene (PTFE). The sputter treated PTFE implants were produced by an 8 cm diameter argon ion source. The treated samples consisted of ion beam sputter polished samples, sputter etched samples (to produce a microscopic surface cone texture) and surface pitted samples (produced by ion beam sputtering to result in 50 microns wide by 100 microns deep square pits). These materials were implanted in rats for periods ranging from 30 minutes to 14 days. The results were evaluated with regard to cell type and attachment kinetics onto the different materials. Scanning electron microscopy and histological sections were also evaluated. In general the smooth hydrophobic surfaces attracted less cells than the ion etched PTFE or the HEMA samples. The ion etching was observed to enhance cell attachment, multinucleated giant cell (MNGC) formation, cell to cell contact, and fibrous capsule formation. The cell responsed in the case of ion etched PTFE to an altered surface morphology. However, equally interesting was the similar attachment kinetics of HEMA verses the ion etched PTFE. However, HEMA resulted in a markedly different response with no MNGC's formation, minimal to no capsule formation, and sample coverage by a uniform cell layer.

  16. Interfraction patient motion and implant displacement in prostate high dose rate brachytherapy

    SciTech Connect

    Fox, C. D.; Kron, T.; Leahy, M.; Duchesne, G.; Williams, S.; Tai, K. H.; Haworth, A.; Herschtal, A.; Foroudi, F.

    2011-11-15

    Purpose: To quantify movement of prostate cancer patients undergoing treatment, using an in-house developed motion sensor in order to determine a relationship between patient movement and high dose rate (HDR) brachytherapy implant displacement. Methods: An electronic motion sensor was developed based on a three axis accelerometer. HDR brachytherapy treatment for prostate is delivered at this institution in two fractions 24 h apart and 22 patients were monitored for movement over the interval between fractions. The motion sensors functioned as inclinometers, monitoring inclination of both thighs, and the inclination and roll of the abdomen. The implanted HDR brachytherapy catheter set was assessed for displacement relative to fiducial markers in the prostate. Angle measurements and angle differences over a 2 s time base were binned, and the standard deviations of the resulting frequency distributions used as a metric for patient motion in each monitored axis. These parameters were correlated to measured catheter displacement using regression modeling. Results: The mean implant displacement was 12.6 mm in the caudal direction. A mean of 19.95 h data was recorded for the patient cohort. Patients generally moved through a limited range of angles with a mean of the exception of two patients who spent in excess of 2 h lying on their side. When tested for a relationship between movement in any of the four monitored axes and the implant displacement, none was significant. Conclusions: It is not likely that patient movement influences HDR prostate implant displacement. There may be benefits to patient comfort if nursing protocols were relaxed to allow patients greater freedom to move while the implant is in situ.

  17. Long-term decoding of movement force and direction with a wireless myoelectric implant

    NASA Astrophysics Data System (ADS)

    Morel, Pierre; Ferrea, Enrico; Taghizadeh-Sarshouri, Bahareh; Marcel Cardona Audí, Josep; Ruff, Roman; Hoffmann, Klaus-Peter; Lewis, Sören; Russold, Michael; Dietl, Hans; Abu-Saleh, Lait; Schroeder, Dietmar; Krautschneider, Wolfgang; Meiners, Thomas; Gail, Alexander

    2016-02-01

    Objective. The ease of use and number of degrees of freedom of current myoelectric hand prostheses is limited by the information content and reliability of the surface electromyography (sEMG) signals used to control them. For example, cross-talk limits the capacity to pick up signals from small or deep muscles, such as the forearm muscles for distal arm amputations, or sites of targeted muscle reinnervation (TMR) for proximal amputations. Here we test if signals recorded from the fully implanted, induction-powered wireless Myoplant system allow long-term decoding of continuous as well as discrete movement parameters with better reliability than equivalent sEMG recordings. The Myoplant system uses a centralized implant to transmit broadband EMG activity from four distributed bipolar epimysial electrodes. Approach. Two Rhesus macaques received implants in their backs, while electrodes were placed in their upper arm. One of the monkeys was trained to do a cursor task via a haptic robot, allowing us to control the forces exerted by the animal during arm movements. The second animal was trained to perform a center-out reaching task on a touchscreen. We compared the implanted system with concurrent sEMG recordings by evaluating our ability to decode time-varying force in one animal and discrete reach directions in the other from multiple features extracted from the raw EMG signals. Main results. In both cases, data from the implant allowed a decoder trained with data from a single day to maintain an accurate decoding performance during the following months, which was not the case for concurrent surface EMG recordings conducted simultaneously over the same muscles. Significance. These results show that a fully implantable, centralized wireless EMG system is particularly suited for long-term stable decoding of dynamic movements in demanding applications such as advanced forelimb prosthetics in a wide range of configurations (distal amputations, TMR).

  18. Deformation characteristics of the near-surface layers of zirconia ceramics implanted with aluminum ions

    NASA Astrophysics Data System (ADS)

    Ghyngazov, S. A.; Vasiliev, I. P.; Frangulyan, T. S.; Chernyavski, A. V.

    2015-10-01

    The effect of ion treatment on the phase composition and mechanical properties of the near-surface layers of zirconium ceramic composition 97 ZrO2-3Y2O3 (mol%) was studied. Irradiation of the samples was carried out by accelerated ions of aluminum with using vacuum-arc source Mevva 5-Ru. Ion beam had the following parameters: the energy of the accelerated ions E = 78 keV, the pulse current density Ji = 4mA / cm2, current pulse duration equal τ = 250 mcs, pulse repetition frequency f = 5 Hz. Exposure doses (fluence) were 1016 и 1017 ion/cm2. The depth distribution implanted ions was studied by SIMS method. It is shown that the maximum projected range of the implanted ions is equal to 250 nm. Near-surface layers were investigated by X-ray diffraction (XRD) at fixed glancing incidence angle. It is shown that implantation of aluminum ions into the ceramics does not lead to a change in the phase composition of the near-surface layer. The influence of implanted ions on mechanical properties of ceramic near-surface layers was studied by the method of dynamic nanoindentation using small loads on the indenter P=300 mN. It is shown that in ion- implanted ceramic layer the processes of material recovery in the deformed region in the unloading mode proceeds with higher efficiency as compared with the initial material state. The deformation characteristics of samples before and after ion treatment have been determined from interpretation of the resulting P-h curves within the loading and unloading sections by the technique proposed by Oliver and Pharr. It was found that implantation of aluminum ions in the near-surface layer of zirconia ceramics increases nanohardness and reduces the Young's modulus.

  19. Evaluation of the mechanical characteristics of the implant-abutment complex of a reduced-diameter morse-taper implant. A nonlinear finite element stress analysis.

    PubMed

    Akça, Kivanç; Cehreli, Murat Cavit; Iplikçioğlu, Haldun

    2003-08-01

    The purpose of this study was to evaluate the mechanical characteristics of the implant-abutment connection of a reduced-diameter ITI dental implant. A finite element model of a slashed circle 3.3 mm x 10 mm ITI solid-screw implant and a 6 degrees solid abutment 4 mm in height was constructed, and the implant-abutment complex was embedded vertically in the center of a slashed circle 1.5 cm x 1.5 cm acrylic cylinder. Static vertical and oblique loads of 300 N were applied in separate load cases. The contact area was defined between the implant-abutment connection and nonlinear finite element stress analysis was performed. The magnitude and distribution of Von Mises stresses and displacement characteristics were evaluated. In vertical loading, Von Mises stresses concentrated around the implant-abutment connection at the stem of the screw and around the implant collar. Oblique loading resulted in a 2-fold increase in stresses at the implant collar, which was close to the yield strength of titanium. Displacement values under both loading conditions were negligible. We conclude that, in a reduced-diameter ITI dental implant, vertical and oblique loads are resisted mainly by the implant-abutment joint at the screw level and by the implant collar. The neck of this implant is a potential zone for fracture when subjected to high bending forces. The reduced-diameter ITI dental implant might benefit from reinforcement of this region.

  20. Dental Implant Systems

    PubMed Central

    Oshida, Yoshiki; Tuna, Elif B.; Aktören, Oya; Gençay, Koray

    2010-01-01

    Among various dental materials and their successful applications, a dental implant is a good example of the integrated system of science and technology involved in multiple disciplines including surface chemistry and physics, biomechanics, from macro-scale to nano-scale manufacturing technologies and surface engineering. As many other dental materials and devices, there are crucial requirements taken upon on dental implants systems, since surface of dental implants is directly in contact with vital hard/soft tissue and is subjected to chemical as well as mechanical bio-environments. Such requirements should, at least, include biological compatibility, mechanical compatibility, and morphological compatibility to surrounding vital tissues. In this review, based on carefully selected about 500 published articles, these requirements plus MRI compatibility are firstly reviewed, followed by surface texturing methods in details. Normally dental implants are placed to lost tooth/teeth location(s) in adult patients whose skeleton and bony growth have already completed. However, there are some controversial issues for placing dental implants in growing patients. This point has been, in most of dental articles, overlooked. This review, therefore, throws a deliberate sight on this point. Concluding this review, we are proposing a novel implant system that integrates materials science and up-dated surface technology to improve dental implant systems exhibiting bio- and mechano-functionalities. PMID:20480036

  1. Mobility implants: a review.

    PubMed

    Danz, W

    1990-01-01

    We present a brief review of mobility implants, their contribution, and the experiences derived after almost 40 years since the new concepts of full mobility implants were introduced. In early 1940, experiments with a new material for the making of plastic artificial eyes was also being considered for the making of orbital implants. Methyl-methacrylate (MMA) had proven inert and satisfactory for dental products. The Surgeon Generals office of the Armed Services encouraged further research and experimental work in the development of plastic eyes. The success of the new material sponsored the beginning of great expansion with new concepts for orbital implants. Through a period of more than a decade, the design and types of implants went through three stages. First, the buried implant was introduced, then the exposed integrated followed, and the buried integrated subsequently followed. The path of progress was not smooth. Theoretically correct designs and surgical procedures met unexpected practical difficulties for the ophthalmic surgeon, the patient, and the eye maker. Surgical and technical efforts were carefully reviewed to eliminate the problems encountered, only to have further unforeseen complications arise. Infections, extrusions, and migration of the implant were not uncommon. The exposed integrated implant was eventually abandoned. However, there were some extraordinary successes of mobility. A new era introduced fully buried mobility implants that were more successful. However, this procedure also produced some problems, causing infection (or allergy), extrusion, and migration. Tantalum mesh and gauze gave great promise with the inception of their use. Orbital tissue grew into the material in an astonishing way, making it possible to secure the extraocular muscles and tenons.(ABSTRACT TRUNCATED AT 250 WORDS)

  2. Nanotechnology for dental implants.

    PubMed

    Tomsia, Antoni P; Lee, Janice S; Wegst, Ulrike G K; Saiz, Eduardo

    2013-01-01

    With the advent of nanotechnology, an opportunity exists for the engineering of new dental implant materials. Metallic dental implants have been successfully used for decades, but they have shortcomings related to osseointegration and mechanical properties that do not match those of bone. Absent the development of an entirely new class of materials, faster osseointegration of currently available dental implants can be accomplished by various surface modifications. To date, there is no consensus regarding the preferred method(s) of implant surface modification, and further development will be required before the ideal implant surface can be created, let alone become available for clinical use. Current approaches can generally be categorized into three areas: ceramic coatings, surface functionalization, and patterning on the micro- to nanoscale. The distinctions among these are imprecise, as some or all of these approaches can be combined to improve in vivo implant performance. These surface improvements have resulted in durable implants with a high percentage of success and long-term function. Nanotechnology has provided another set of opportunities for the manipulation of implant surfaces in its capacity to mimic the surface topography formed by extracellular matrix components of natural tissue. The possibilities introduced by nanotechnology now permit the tailoring of implant chemistry and structure with an unprecedented degree of control. For the first time, tools are available that can be used to manipulate the physicochemical environment and monitor key cellular events at the molecular level. These new tools and capabilities will result in faster bone formation, reduced healing time, and rapid recovery to function.

  3. Reflections on Rodent Implantation.

    PubMed

    Cha, Jeeyeon M; Dey, Sudhansu K

    2015-01-01

    Embryo implantation is a complex process involving endocrine, paracrine, autocrine, and juxtacrine modulators that span cell-cell and cell-matrix interactions. The quality of implantation is predictive for pregnancy success. Earlier observational studies formed the basis for genetic and molecular approaches that ensued with emerging technological advances. However, the precise sequence and details of the molecular interactions involved have yet to be defined. This review reflects briefly on aspects of our current understanding of rodent implantation as a tribute to Roger Short's lifelong contributions to the field of reproductive physiology. PMID:26450495

  4. Spectroscopy of implants

    NASA Astrophysics Data System (ADS)

    Afanasyeva, Natalia I.

    1994-01-01

    The spectral criteria of selection of soft intraocular lens (IOL) implants of long service in an organism have been defined for ophthalmology. The analysis of Fourier Transform Infrared (FTIR) spectra provides the required and sufficient level of material polymerization for manufacturing non-toxic lenses for the eye. The spectral limits for determining the biocompatibility of samples can be related to the intensity ratio of two bands only in the FTIR spectra of siloxane. Siloxane-poly(urethane) block copolymers and other materials for implants have been studied. Passivated surfaces of implants have been obtained and registered by methods of Fourier Transform Spectroscopy.

  5. Fracture dynamics in implanted silicon

    NASA Astrophysics Data System (ADS)

    Massy, D.; Mazen, F.; Tardif, S.; Penot, J. D.; Ragani, J.; Madeira, F.; Landru, D.; Kononchuk, O.; Rieutord, F.

    2015-08-01

    Crack propagation in implanted silicon for thin layer transfer is experimentally studied. The crack propagation velocity as a function of split temperature is measured using a designed optical setup. Interferometric measurement of the gap opening is performed dynamically and shows an oscillatory crack "wake" with a typical wavelength in the centimetre range. The dynamics of this motion is modelled using beam elasticity and thermodynamics. The modelling demonstrates the key role of external atmospheric pressure during crack propagation. A quantification of the amount of gas trapped inside pre-existing microcracks and released during the fracture is made possible, with results consistent with previous studies.

  6. Fracture dynamics in implanted silicon

    SciTech Connect

    Massy, D.; Tardif, S.; Penot, J. D.; Ragani, J.; Rieutord, F.; Mazen, F.; Madeira, F.; Landru, D.; Kononchuk, O.

    2015-08-31

    Crack propagation in implanted silicon for thin layer transfer is experimentally studied. The crack propagation velocity as a function of split temperature is measured using a designed optical setup. Interferometric measurement of the gap opening is performed dynamically and shows an oscillatory crack “wake” with a typical wavelength in the centimetre range. The dynamics of this motion is modelled using beam elasticity and thermodynamics. The modelling demonstrates the key role of external atmospheric pressure during crack propagation. A quantification of the amount of gas trapped inside pre-existing microcracks and released during the fracture is made possible, with results consistent with previous studies.

  7. Hearing Experience and Receptive Vocabulary Development in Deaf Children with Cochlear Implants

    ERIC Educational Resources Information Center

    Fagan, Mary K.; Pisoni, David B.

    2010-01-01

    This study investigated receptive vocabulary delay in deaf children with cochlear implants. Participants were 23 children with profound hearing loss, ages 6-14 years, who received a cochlear implant between ages 1.4 and 6 years. Duration of cochlear implant use ranged from 3.7 to 11.8 years. "Peabody Picture Vocabulary Test, Third Edition"…

  8. Effect of cochlear implantation on nasality in post-lingually deafened adults.

    PubMed

    Langereis, M C; Dejonckere, P H; van Olphen, A F; Smoorenburg, G F

    1997-01-01

    The present study addresses the effect of cochlear implantation on nasality in 21 post-lingually deafened Dutch subjects. All subjects received the Nucleus 22 implant (MSP version). Speech recordings were made pre-implantation and 3 and 12 months post-implantation with the implant switched on and off. Nasality measurements were performed on a standard text and on two sentences without nasal phonemes. The results show that post-lingual deafness in individuals can result in a deviant degree of nasality in speech production. However, the nasalance value of 86% of the subjects of our study fell within the normative range defined as the mean +/- 2 standard deviations of the normal population. After implantation we found no statistically significant effect of implant use. However, individual nasality values outside the normative range may improve. Furthermore, 12 months post-implantation we found a significant decrease in the variability of the nasalance values obtained for two sentences without nasal phonemes. PMID:9415736

  9. Across-shelf distribution of blue mussel larvae in the northern Gulf of Maine: consequences for population connectivity and a species range boundary.

    PubMed

    Yund, Philip O; Tilburg, Charles E; McCartney, Michael A

    2015-12-01

    Studies of population connectivity have largely focused on along-shelf, as opposed to across-shelf, processes. We hypothesized that a discontinuity in across-shelf mixing caused by the divergence of the Eastern Maine Coastal Current (EMCC) from shore acts as an ecological barrier to the supply of mussel larvae to the coast. Existing data on the relative abundance of two congeneric blue mussels, Mytilus edulis and M. trossulus, were analysed to quantify the association of M. trossulus with the colder temperature signal of the EMCC and generate larval distribution predictions. We then sampled the across-shelf distribution of larvae along two transects during 2011. Larvae were identified using restriction digests of PCR amplicons from the mitochondrial 16S rDNA. Mytilus edulis larvae were consistently abundant on either the inshore and offshore transect ends, but not homogeneously distributed across the shelf, while M. trossulus larvae were less common throughout the study area. The divergence of the EMCC from shore appears to create a break in the connectivity of M. edulis populations by isolating those inshore of the EMCC from upstream larval sources. Across-shelf transport processes can thus produce connectivity patterns that would not be predicted solely on the basis of along-shelf processes.

  10. Across-shelf distribution of blue mussel larvae in the northern Gulf of Maine: consequences for population connectivity and a species range boundary

    PubMed Central

    Yund, Philip O.; Tilburg, Charles E.; McCartney, Michael A.

    2015-01-01

    Studies of population connectivity have largely focused on along-shelf, as opposed to across-shelf, processes. We hypothesized that a discontinuity in across-shelf mixing caused by the divergence of the Eastern Maine Coastal Current (EMCC) from shore acts as an ecological barrier to the supply of mussel larvae to the coast. Existing data on the relative abundance of two congeneric blue mussels, Mytilus edulis and M. trossulus, were analysed to quantify the association of M. trossulus with the colder temperature signal of the EMCC and generate larval distribution predictions. We then sampled the across-shelf distribution of larvae along two transects during 2011. Larvae were identified using restriction digests of PCR amplicons from the mitochondrial 16S rDNA. Mytilus edulis larvae were consistently abundant on either the inshore and offshore transect ends, but not homogeneously distributed across the shelf, while M. trossulus larvae were less common throughout the study area. The divergence of the EMCC from shore appears to create a break in the connectivity of M. edulis populations by isolating those inshore of the EMCC from upstream larval sources. Across-shelf transport processes can thus produce connectivity patterns that would not be predicted solely on the basis of along-shelf processes. PMID:27018654

  11. Computational modeling of the side chain dihedral angle distributions of methionine using hard-sphere repulsive and short-range attractive interactions

    NASA Astrophysics Data System (ADS)

    Virrueta, Alejandro; O'Hern, Corey; Regan, Lynne

    Methionine (Met) is a versatile amino acid found frequently both in protein cores and at protein-protein interfaces. Thus, a complete description of the structure of Met is tantamount to a fundamental understanding of protein structure and design. In previous work, we showed that our hard-sphere dipeptide model is able to recapitulate the side chain dihedral angle distributions observed in high-resolution protein crystal structures for the 8 amino acids we have studied to date: Val, Thr, Ser, Leu, Ile, Cys, Tyr, and Phe. Using the same approach, we can predict the observed Met side chain dihedral angle distributions P (χ1) and P (χ2) , but not P (χ3) . In this manuscript, we investigate the possible origins of the discrepancy and identify the minimal additions to the hard-sphere dipeptide model necessary to quantitatively predict P (χ3) of Met. We find that applying a Lennard-Jones potential with weak attraction between hydrogen atoms is sufficient to achieve predictions that match the observed χ3 side chain dihedral angle probability distributions for Met, Nle, and Mse without negatively affecting our results for the 8 previously studied amino acids. A. V. is supported by an NSF Graduate Research Fellowship and a Ford Foundation Fellowship.

  12. Late implant sepsis after fracture surgery in HIV positive patients.

    PubMed

    Graham, Simon Matthew; Bates, Jes; Mkandawire, Nyengo; Harrison, William J

    2015-04-01

    A prospective cohort study was undertaken to assess the incidence of late-implant sepsis after internal fixation in HIV-positive patients. A total of 91 HIV-positive patients (67 males and 24 females) who underwent 103 procedures (111 implants) were followed up for a mean period of 27 months (range 12-66 months). No occurrences of late implant sepsis were found in 100 implants (94 procedures) in 82 patients at 27 months' follow-up (range 12-66 months). Nine patients (9 procedures, 9 implants) developed early infections within 6 weeks and were treated with antibiotics (6 patients), amputation (1 patient) or removal of metal work (2 patients). There was no evidence of subsequent late implant sepsis in any of these patients, at a mean follow-up of 25 months (range 12-52 months). This study demonstrates that it is safe to perform internal fixation in HIV-positive patients, with no observed increase risk of late implant sepsis. There is no indication to remove implants after fracture union, other than for the general clinical indications that may lead to removal of metal work in any patient.

  13. The evolution of embryo implantation.

    PubMed

    McGowen, Michael R; Erez, Offer; Romero, Roberto; Wildman, Derek E

    2014-01-01

    Embryo implantation varies widely in placental mammals. We review this variation in mammals with a special focus on two features: the depth of implantation and embryonic diapause. We discuss the two major types of implantation depth, superficial and interstitial, and map this character on a well-resolved molecular phylogenetic tree of placental mammals. We infer that relatively deep interstitial implantation has independently evolved at least eight times within placental mammals. Moreover, the superficial type of implantation represents the ancestral state for placental mammals. In addition, we review the genes involved in various phases of implantation, and suggest a future direction in investigating the molecular evolution of implantation-related genes. PMID:25023681

  14. Effects of inter-implant distance and implant length on the response to frontal traumatic force of two anterior implants in an atrophic mandible: three-dimensional finite element analysis.

    PubMed

    Kan, B; Coskunses, F M; Mutlu, I; Ugur, L; Meral, D G

    2015-07-01

    The aim of this three-dimensional finite element analysis study was to examine the biomechanical behaviour of dental implants and the surrounding bone under traumatic frontal force. Models were created of an edentulous atrophic mandible using cone beam computed tomography data from a patient; two titanium alloy implants (Ti-6Al-4V) were virtually inserted into the anterior of the mandible. Six different variations were modelled to represent differences in implant location (lateral incisor vs. canine placement) and implant length (monocortical, bicortical, and long-bicortical). A static force of 10 MPa was applied frontally to the symphysis region of each model, and the maximum equivalent von Mises strain of bone, maximum von Mises stress of implants, and chromatic force distributions in bone and implants were recorded. In general, when compared to lateral incisor placement, canine placement of implants resulted in greater von Mises stress on implants and greater equivalent von Mises strain on bone. The findings of the present study showed the distribution of traumatic force to be affected more by inter-implant distance than by implant length. The insertion of implants in the lateral incisor area was found to be a better solution than canine area placement in terms of frontal plane trauma and fracture risk. PMID:25818310

  15. Pulsed Nd:YAG laser treatment for failing dental implants due to peri-implantitis

    NASA Astrophysics Data System (ADS)

    Nicholson, Dawn; Blodgett, Kris; Braga, Charles; Finkbeiner, Larry; Fourrier, Jeanne; George, John; Gregg, Robert; Honigman, Allen; Houser, Bruce; Lamas, William; Lehrman, Neal; Linden, Eric; McCarthy, Delwin; McCawley, Tom; McCormick, Randy; Marcus, Ed; Noraian, Kirk; Rubelman, Peter; Salama, Maurice; Saunders, Steven; Seamons, Brandon; Thein, David; Toms, Michael; Vassos, George; Harris, David M.

    2014-02-01

    A large percentage of dental implants experience complications, most commonly, infection leading to peri-implantitis and peri-mucositis, inflammatory disease involving pathogen contamination. It presents with radiographic findings of crestal bone loss. At this time there appears to be no compelling evidence for an effective intervention. The LANAP protocol is a FDA cleared surgical protocol that produces new attachment and bone regeneration when applied to periodontally infected natural teeth. The LANAP protocol and laser dosimetry have been modified to treat ailing and failing implants. Twenty-one clinicians who have been trained to perform the LANAP protocol and the LAPIPTM protocol have volunteered 26 LAPIP case reports. The time from implant to intervention ranges from 3 months to 16 years. Post-LAPIP radiographs range from 2-48 months. Ten cases were excluded for technical reasons. All 16 remaining cases provide radiographic evidence of increase in crestal bone mass around the implant and, when reported, probe depth reductions. All treating clinicians report control of the infection, reversal of bone loss and rescue of the incumbent implant. Although the success/failure rate cannot be judged from these data, any successes in this area deserve reporting and further study.

  16. Biomechanical stress in bone surrounding an implant under simulated chewing.

    PubMed

    Ishigaki, Shoichi; Nakano, Tamaki; Yamada, Shinichi; Nakamura, Takashi; Takashima, Fumio

    2003-02-01

    The concept of reducing nonaxial loading of dental implants has been widely regarded as the standard procedure. The aim of this study was to reveal the biomechanical stress distribution in supporting bone around an implant and a natural tooth under chewing function. Three-dimensional finite element models of the mandibular first molar and the titanium implant both with the mandible in the molar region were constructed. The directions of displacement constraints were determined according to the angles of the closing pathways of chopping type and grinding type chewing patterns. The tooth model showed smooth stress distribution in the supporting bone with low stress concentration around the neck of the tooth. The implant model showed stress concentration in the supporting bone around the neck of the implant, especially in the buccal area. The grinding type model of the implant showed higher tensile stress concentration than the chopping type model at the lingual neck of the implant. The results of this study suggested the importance of considering occlusion under chewing function for understanding the biomechanics of oral implants.

  17. Peri-Implant Diseases

    MedlinePlus

    ... and flossing and regular check-ups from a dental professional. Other risks factors for developing peri-implant disease include previous periodontal disease diagnosis, poor plaque control, smoking , and diabetes . It is essential to routinely ...

  18. Superelastic Orthopedic Implant Coatings

    NASA Astrophysics Data System (ADS)

    Fournier, Eric; Devaney, Robert; Palmer, Matthew; Kramer, Joshua; El Khaja, Ragheb; Fonte, Matthew

    2014-07-01

    The demand for hip and knee replacement surgery is substantial and growing. Unfortunately, most joint replacement surgeries will fail within 10-25 years, thereby requiring an arduous, painful, and expensive revision surgery. To address this issue, a novel orthopedic implant coating material ("eXalt") has been developed. eXalt is comprised of super elastic nitinol wire that is knit into a three-dimensional spacer fabric structure. eXalt expands in vivo to conform to the implantation site and is porous to allow for bone ingrowth. The safety and efficacy of eXalt were evaluated through structural analysis, mechanical testing, and a rabbit implantation model. The results demonstrate that eXalt meets or exceeds the performance of current coating technologies with reduced micromotion, improved osseointegration, and stronger implant fixation in vivo.

  19. Risks of Breast Implants

    MedlinePlus

    ... larger and longer than these conducted so far. Breastfeeding Some women who undergo breast augmentation can successfully ... breast implant silicone shell into breast milk during breastfeeding. Although there are currently no established methods for ...

  20. Silver migration and trapping in ion implanted ZnO single crystals

    NASA Astrophysics Data System (ADS)

    Azarov, Alexander; Vines, Lasse; Rauwel, Protima; Monakhov, Edouard; Svensson, Bengt G.

    2016-05-01

    Potentially, group-Ib elements (Cu, Ag, and Au) incorporated on Zn sites can be used for p-type doping of ZnO, and in the present paper, we use ion implantation to introduce Ag atoms in wurtzite ZnO single crystals. Monitoring the Li behavior, being a residual impurity in the crystals, as a tracer, we demonstrate that Zn interstitials assist the Ag diffusion and lead to Ag pile-up behind the implanted region after annealing above 800 °C. At even higher temperatures, a pronounced Ag loss from the sample surface occurs and concurrently the Ag atoms exhibit a trap-limited diffusion into the crystal bulk with an activation energy of ˜2.6 eV. The dominant traps are most likely Zn vacancies and substitutional Li atoms, yielding substitutional Ag atoms. In addition, formation of an anomalous multipeak Ag distribution in the implanted near-surface region after annealing can be attributed to local implantation-induced stoichiometry disturbances leading to trapping of the Ag atoms by O and Zn vacancies in the vicinity of the surface and in the end-of-range region, respectively.

  1. Primary cilia act as mechanosensors during bone healing around an implant

    PubMed Central

    Leucht, P.; Monica, S.D.; Temiyasathit, S.; Lenton, K.; Manu, A.; Longaker, M.T.; Jacobs, C.R.; Spilker, R.L.; Guo, H.; Brunski, J.B.; Helms, J.A.

    2012-01-01

    The primary cilium is an organelle that senses cues in a cell’s local environment. Some of these cues constitute molecular signals; here, we investigate the extent to which primary cilia can also sense mechanical stimuli. We used a conditional approach to delete Kif3a in pre-osteoblasts and then employed a motion device that generated a spatial distribution of strain around an intra-osseous implant positioned in the mouse tibia. We correlated interfacial strain fields with cell behaviors ranging from proliferation through all stages of osteogenic differentiation. We found that peri-implant cells in the Col1Cre;Kif3afl/fl mice were unable to proliferate in response to a mechanical stimulus, failed to deposit and then orient collagen fibers to the strain fields caused by implant displacement, and failed to differentiate into bone-forming osteoblasts. Collectively, these data demonstrate that the lack of a functioning primary cilium blunts the normal response of a cell to a defined mechanical stimulus. The ability to manipulate the genetic background of peri-implant cells within the context of a whole, living tissue provides a rare opportunity to explore mechanotransduction from a multi-scale perspective. PMID:22784673

  2. Implanted telemeter for electrocardiogram and body temperature

    NASA Technical Reports Server (NTRS)

    Barrows, W. F.

    1972-01-01

    Measuring system requiring one blocking oscillator to generate modulated pulse repetition rate is implantable in the bodies of small animals. Device has life of two years and transmission range of about three feet. EKG sensing unit also is used to sense electromyogram or electrooculogram of laboratory animals.

  3. Ion implantation at elevated temperatures

    SciTech Connect

    Lam, N.Q.; Leaf, G.K.

    1985-11-01

    A kinetic model has been developed to investigate the synergistic effects of radiation-enhanced diffusion, radiation-induced segregation and preferential sputtering on the spatial redistribution of implanted solutes during implantation at elevated temperatures. Sample calculations were performed for Al and Si ions implanted into Ni. With the present model, the influence of various implantation parameters on the evolution of implant concentration profiles could be examined in detail.

  4. Implant treatment planning: endodontic considerations.

    PubMed

    Simonian, Krikor; Frydman, Alon; Verdugo, Fernando; Roges, Rafael; Kar, Kian

    2014-12-01

    Implants are a predictable and effective method for replacing missing teeth. Some clinicians have advocated extraction and replacement of compromised but treatable teeth on the assumption that implants will outperform endodontically and/or periodontally treated teeth. However, evidence shows that conventional therapy is as effective as implant treatment. With data on implants developing complications long term and a lack of predictable treatment for peri-implantitis, retaining and restoring the natural dentition should be the first choice when possible. PMID:25928961

  5. Modeling ecological minimum requirements for distribution of greater sage-grouse leks: implications for population connectivity across their western range, U.S.A

    PubMed Central

    Knick, Steven T; Hanser, Steven E; Preston, Kristine L

    2013-01-01

    Greater sage-grouse Centrocercus urophasianus (Bonaparte) currently occupy approximately half of their historical distribution across western North America. Sage-grouse are a candidate for endangered species listing due to habitat and population fragmentation coupled with inadequate regulation to control development in critical areas. Conservation planning would benefit from accurate maps delineating required habitats and movement corridors. However, developing a species distribution model that incorporates the diversity of habitats used by sage-grouse across their widespread distribution has statistical and logistical challenges. We first identified the ecological minimums limiting sage-grouse, mapped similarity to the multivariate set of minimums, and delineated connectivity across a 920,000 km2 region. We partitioned a Mahalanobis D2 model of habitat use into k separate additive components each representing independent combinations of species–habitat relationships to identify the ecological minimums required by sage-grouse. We constructed the model from abiotic, land cover, and anthropogenic variables measured at leks (breeding) and surrounding areas within 5 km. We evaluated model partitions using a random subset of leks and historic locations and selected D2 (k = 10) for mapping a habitat similarity index (HSI). Finally, we delineated connectivity by converting the mapped HSI to a resistance surface. Sage-grouse required sagebrush-dominated landscapes containing minimal levels of human land use. Sage-grouse used relatively arid regions characterized by shallow slopes, even terrain, and low amounts of forest, grassland, and agriculture in the surrounding landscape. Most populations were interconnected although several outlying populations were isolated because of distance or lack of habitat corridors for exchange. Land management agencies currently are revising land-use plans and designating critical habitat to conserve sage-grouse and avoid endangered

  6. Modeling ecological minimum requirements for distribution of greater sage-grouse leks: implications for population connectivity across their western range, U.S.A.

    USGS Publications Warehouse

    Knick, Steven T.; Hanser, Steven E.; Preston, Kristine L.

    2013-01-01

    Greater sage-grouse Centrocercus urophasianus (Bonaparte) currently occupy approximately half of their historical distribution across western North America. Sage-grouse are a candidate for endangered species listing due to habitat and population fragmentation coupled with inadequate regulation to control development in critical areas. Conservation planning would benefit from accurate maps delineating required habitats and movement corridors. However, developing a species distribution model that incorporates the diversity of habitats used by sage-grouse across their widespread distribution has statistical and logistical challenges. We first identified the ecological minimums limiting sage-grouse, mapped similarity to the multivariate set of minimums, and delineated connectivity across a 920,000 km2 region. We partitioned a Mahalanobis D2 model of habitat use into k separate additive components each representing independent combinations of species–habitat relationships to identify the ecological minimums required by sage-grouse. We constructed the model from abiotic, land cover, and anthropogenic variables measured at leks (breeding) and surrounding areas within 5 km. We evaluated model partitions using a random subset of leks and historic locations and selected D2 (k = 10) for mapping a habitat similarity index (HSI). Finally, we delineated connectivity by converting the mapped HSI to a resistance surface. Sage-grouse required sagebrush-dominated landscapes containing minimal levels of human land use. Sage-grouse used relatively arid regions characterized by shallow slopes, even terrain, and low amounts of forest, grassland, and agriculture in the surrounding landscape. Most populations were interconnected although several outlying populations were isolated because of distance or lack of habitat corridors for exchange. Land management agencies currently are revising land-use plans and designating critical habitat to conserve sage-grouse and avoid endangered

  7. Modeling ecological minimum requirements for