Dynamics of a charged particle in a dissipative Fermi-Ulam model

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Influência do espaçamento do feixe de laser Nd: YAG na obtenção de óxidos e nitretos na superfície do titânio em pressão atmosférica

Neste trabalho investigou-se a modificação de superfície do titânio pela irradiação com feixe de Laser Nd:YAG. Os parâmetros do laser como a potência, o comprimento de onda, a frequência, a velocidade de varredura e a área de exposição foram mantidos constantes, exceto o espaçamento da matriz, o qual foi de 0,01 e 0,02 mm. A caracterização da superfície foi realizada por Microscopia Eletrônica de Varredura (MEV) e Difração de Raios X (DRX), sendo que os espectros foram refinados pelo método Rietveld. Pela análise de MEV, observou-se uma mudança na topografia, obtendo uma superfície rugosa produzida pelo fenômeno de ablação. As análises por Rietveld dos espectros de difração de raios X detectaram TiN, Ti2N, TiO2 (anatásio e rutilo), sendo que a amostra com espaçamento 0,01 mm apresentou uma maior quantidade de óxidos e nitretos. Isso pode ser devido à sobreposição do feixe, induzindo à formação de uma superfície com maior estabilidade termodinâmica. Os óxidos e nitretos obtidos são de grande importância, pois são responsáveis por produzir uma maior interação entre o osso-implante.

Incorporation of Ca, P, and Si on bioactive coatings produced by plasma electrolytic oxidation: The role of electrolyte concentration and treatment duration

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Early peri-implant endosseous healing of two implant surfaces placed in surgically created circumferential defects. A histomorphometric and fluorescence study in dogs

Objective Several implant surfaces are being developed, some in the nanoscale level. In this study, two different surfaces had their early healing properties compared in context of circumferential defects of various widths. Material and methods Six dogs had the mandibular premolars extracted. After 8weeks, four implants were placed equicrestally in each side. One acted as control, while the others were inserted into sites with circumferential defects of 1.0, 1.5 and 2.0mm wide and 5mm deep. A nano-modified surface was used on one side and a micro-rough on the other. Bone markers were administered on the third day after implant placement and then after 1, 2, 4weeks to investigate the bone formation dynamic through fluorescence analysis. Ground sections were prepared from 8-week healing biopsies and histomorphometry was performed. Results The fluorescence evaluation of the early healing showed numerically better results for the nano-modified group; however this trend was not followed by the histomorphometric evaluation. A non-significant numerical superiority of the micro-rough group was observed in terms of vertical bone apposition, defect bone fill, bone-to-implant contact and bone density. In the intra-group analysis, the wider defects showed the worse results while the control sites showed the best results for the different parameters, but without statistical relevance. Conclusion Both surfaces may lead to complete fill of circumferential defects, but the gap width has to be considered as a challenge. The nano-scale modification was beneficial in the early stages of bone healing, but the micro-rough surface showed numerical better outcomes at the 8-week final period.

Cytotoxicity tests for nanostructured chitosan/PEO membranes using the agar diffusion method

Electrospinning is used to produce fibers in the nanometer range by stretching a polymeric jet using electric fields of high magnitude. Chitosan is an abundant natural polymer that can be used to obtain biocompatible nanostructured membranes. The objectives of this work were to obtain nanostructured membranes based on blends of chitosan and polyoxyethylene (PEO), and evaluate their thermal and morphological properties, as well as their in vitro biocompatibility by agar diffusion cytotoxicity tests for three different cell lines. A nanostructured fibrous membrane with fiber diameters in the order of 200 nm was obtained, which presented a rough surface and thickness ranging from one to two millimeters. The results of the cytotoxicity tests evidenced that the chitosan/PEO membranes are non-toxic to the cells studied in this work. Further, the electrospinning technique was effective in obtaining nanostructured chitosan/PEO membranes, which showed biocompatibility according to in vitro preliminary tests using the cell lines.

Photocatalytic activity of nanostructured anatase coatings obtained by cold gas spray

[EN] This article describes a photocatalytic nanostructured anatase coating deposited by cold gas spray (CGS) supported on titanium sub-oxide (TiO22x) coatings obtained by atmospheric plasma spray (APS) onto stainless steel cylinders. The photocatalytic coating was homogeneous and preserved the composition and nanostructure of the starting powder. The inner titanium sub-oxide coating favored the deposition of anatase particles in the solid state. Agglomerated nano-TiO2 particles fragmented when impacting onto the hard surface of the APS TiO22x bond coat. The rough surface provided by APS provided an ideal scenario for entrapping the nanostructured particles, which may be adhered onto the bond coat due to chemical bonding; a possible bonding mechanism is described. Photocatalytic experiments showed that CGS nano-TiO2 coating was active for photodegrading phenol and formic acid under aqueous conditions. The results were similar to the performance obtained by competitor technologies and materials such as dip-coating P25 photocatalysts. Disparity in the final performance of the photoactive materials may have been caused by differences in grain size and the crystalline composition of titanium dioxide.

Dynamik unterkühlter Flüssigkeiten in Filmen und Röhren

GERMAN:Im Rahmen der vorliegenden Arbeit soll der Einfluß einerräumlichen Beschränkung auf die Dynamik einer unterkühltenFlüssigkeit charakterisiert werden. Insbesondere sollgeklärt werden, welche Rolle die Kooperativität derTeilchenbewegung bei niedrigen Temperaturen spielt. Hierzuuntersuchen wir mit Hilfe einer Molekulardynamik-Computersimulation die dynamischen Eigenschaften eineseinfachen Modellglasbildners, einer binäre Lennard-Jones-Flüssigkeit, für Systeme mit unterschiedlichen Geometrienund Wandarten. Durch geschickte Wahl der Wandpotentiale konnte erreichtwerden, daß die Struktur der Flüssigkeit mit der im Bulknahezu identisch ist.In Filmen mit glatten Wänden beobachtet man, daß dieDynamik der Flüssigkeit in der Nähe der Wand starkbeschleunigt ist und sich diese veränderte Dynamik bis weitin den Film ausbreitet. Den umgekehrten Effekt erhält man,wenn man eine strukturierte, rauhe Wand verwendet, in derenNähe die Dynamik stark verlangsamt ist.Die kontinuierliche Verlangsamung bzw. Beschleunigung derDynamik vom Verhalten an der Oberfläche zum Bulkverhaltenin genügend großem Abstand zur Wand können wirphänomenologisch beschreiben. Hieraus kann mancharakteristische dynamische Längenskalen ablesen, die mitsinkender Temperatur kontinuierlich anwachsen, d.h. derBereich, in dem die Existenz der Wand einen (indirekten)Einfluß auf die Dynamik eines Flüssigkeitsteilchens hat,breitet sich immer weiter aus. Man kann daher vonBereichen kooperativer Bewegung sprechen, die mit sinkenderTemperatur anwachsen.Unsere Untersuchungen von Röhren zeigen, daß aufgrund desstärkeren Einflusses der Wände die beobachteten Effektegrößer sind als in Filmgeometrie. Bei Reduzierung derSystemgröße zeigen sich immer größere Unterschiede zumBulkverhalten.

Open or submerged healing of implants with platform switching: a randomized, controlled clinical trial

The temporal pattern of bone-level alterations in conventionally restored implants is dependent upon healing mode (open or submerged). This study examined the influence of healing on marginal bone levels at implants with a medium-rough surface including the implant collar and a clearance-fit implant-abutment connection restored according to a platform-switching concept.

A systematic review of the success of sinus floor elevation and survival of implants inserted in combination with sinus floor elevation

OBJECTIVES: The objectives of this systematic review were to assess the survival rate of grafts and implants placed with sinus floor elevation. MATERIAL AND METHODS: An electronic search was conducted to identify studies on sinus floor elevation, with a mean follow-up time of at least 1 year after functional loading. RESULTS: The search provided 839 titles. Full-text analysis was performed for 175 articles resulting in 48 studies that met the inclusion criteria, reporting on 12,020 implants. Meta-analysis indicated an estimated annual failure rate of 3.48% [95% confidence interval (CI): 2.48%-4.88%] translating into a 3-year implant survival of 90.1% (95% CI: 86.4%-92.8%). However, when failure rates was analyzed on the subject level, the estimated annual failure was 6.04% (95% CI: 3.87%-9.43%) translating into 16.6% (95% CI: 10.9%-24.6%) of the subjects experiencing implant loss over 3 years. CONCLUSION: The insertion of dental implants in combination with maxillary sinus floor elevation is a predictable treatment method showing high implant survival rates and low incidences of surgical complications. The best results (98.3% implant survival after 3 years) were obtained using rough surface implants with membrane coverage of the lateral window.

Porous silicon technology for integrated microsystems

With the development of micro systems, there is an increasing demand for integrable porous materials. In addition to those conventional applications, such as filtration, wicking, and insulating, many new micro devices, including micro reactors, sensors, actuators, and optical components, can benefit from porous materials. Conventional porous materials, such as ceramics and polymers, however, cannot meet the challenges posed by micro systems, due to their incompatibility with standard micro-fabrication processes. In an effort to produce porous materials that can be used in micro systems, porous silicon (PS) generated by anodization of single crystalline silicon has been investigated. In this work, the PS formation process has been extensively studied and characterized as a function of substrate type, crystal orientation, doping concentration, current density and surfactant concentration and type. Anodization conditions have been optimized for producing very thick porous silicon layers with uniform pore size, and for obtaining ideal pore morphologies. Three different types of porous silicon materials: meso porous silicon, macro porous silicon with straight pores, and macro porous silicon with tortuous pores, have been successfully produced. Regular pore arrays with controllable pore size in the range of 2µm to 6µm have been demonstrated as well. Localized PS formation has been achieved by using oxide/nitride/polysilicon stack as masking materials, which can withstand anodization in hydrofluoric acid up to twenty hours. A special etching cell with electrolytic liquid backside contact along with two process flows has been developed to enable the fabrication of thick macro porous silicon membranes with though wafer pores. For device assembly, Si-Au and In-Au bonding technologies have been developed. Very low bonding temperature (~200 degrees C) and thick/soft bonding layers (~6µm) have been achieved by In-Au bondi ng technology, which is able to compensate the potentially rough surface on the porous silicon sample without introducing significant thermal stress. The application of the porous silicon material in micro systems has been demonstrated in a micro gas chromatograph system by two indispensable components: an integrated vapor source and an inlet filter, wherein porous silicon performs the basic functions of porous media: wicking and filtration. By utilizing a macro porous silicon wick, the calibration vapor source was able to produce a uniform and repeatable vapor generation for n-decane with less than a 0.1% variation in 9 hours, and less than a 0.5% variation in rate over 7 days. With engineered porous silicon membranes the inlet filter was able to show a depth filtration with nearly 100% collection efficiency for particles larger than 0.3µm in diameter, a low pressure-drop of 523Pa at 20sccm flow rate, and a filter capacity of 500µg/cm2.

Multi-antenna non-line-of-sight identification techniques for target localization in mobile ad-hoc networks

Target localization has a wide range of military and civilian applications in wireless mobile networks. Examples include battle-field surveillance, emergency 911 (E911), traffc alert, habitat monitoring, resource allocation, routing, and disaster mitigation. Basic localization techniques include time-of-arrival (TOA), direction-of-arrival (DOA) and received-signal strength (RSS) estimation. Techniques that are proposed based on TOA and DOA are very sensitive to the availability of Line-of-sight (LOS) which is the direct path between the transmitter and the receiver. If LOS is not available, TOA and DOA estimation errors create a large localization error. In order to reduce NLOS localization error, NLOS identifcation, mitigation, and localization techniques have been proposed. This research investigates NLOS identifcation for multiple antennas radio systems. The techniques proposed in the literature mainly use one antenna element to enable NLOS identifcation. When a single antenna is utilized, limited features of the wireless channel can be exploited to identify NLOS situations. However, in DOA-based wireless localization systems, multiple antenna elements are available. In addition, multiple antenna technology has been adopted in many widely used wireless systems such as wireless LAN 802.11n and WiMAX 802.16e which are good candidates for localization based services. In this work, the potential of spatial channel information for high performance NLOS identifcation is investigated. Considering narrowband multiple antenna wireless systems, two xvNLOS identifcation techniques are proposed. Here, the implementation of spatial correlation of channel coeffcients across antenna elements as a metric for NLOS identifcation is proposed. In order to obtain the spatial correlation, a new multi-input multi-output (MIMO) channel model based on rough surface theory is proposed. This model can be used to compute the spatial correlation between the antenna pair separated by any distance. In addition, a new NLOS identifcation technique that exploits the statistics of phase difference across two antenna elements is proposed. This technique assumes the phases received across two antenna elements are uncorrelated. This assumption is validated based on the well-known circular and elliptic scattering models. Next, it is proved that the channel Rician K-factor is a function of the phase difference variance. Exploiting Rician K-factor, techniques to identify NLOS scenarios are proposed. Considering wideband multiple antenna wireless systems which use MIMO-orthogonal frequency division multiplexing (OFDM) signaling, space-time-frequency channel correlation is exploited to attain NLOS identifcation in time-varying, frequency-selective and spaceselective radio channels. Novel NLOS identi?cation measures based on space, time and frequency channel correlation are proposed and their performances are evaluated. These measures represent a better NLOS identifcation performance compared to those that only use space, time or frequency.

(Table 8.4, Page 220-223) Chemical composition of different growth structures of manganese nodules, SONNE cruise SO78

In the nodule field of the Peru Basin, situated south of the zone of high bioproductivity, a relatively high flux of biogenic matter explains a distinct redox boundary at about 10 cm depth separating very soft oxic surface sediments from stiffer suboxic sediments. Maximum abundance (50 kg/m**2) of diagenetic nodules is found near the calcite compensation depth (CCD), currently at 4250 m. There, the accretion rate of nodules is much higher (100 mm/Ma) than on ridges (5 mm/Ma). Highest accretion rates are found at the bottom of large nodules that repeatedly sink to a level immediately above the redox boundary. There, distinct diagenetic growth conditions prevail and layers of dense laminated Mn oxide of very pure todorokite are formed. The layering of nodules is mainly the result of organisms moving nodules within the oxic surface sediment from diagenetic to hydrogenetic environments. The frequency of such movements is much higher than that of climatic changes. Two types of nodule burial occur in the Peru Basin. Large nodules are less easily moved by organisms and become buried. Consequently, buried nodules generally are larger than surface nodules. This type of burial predominates in basins. At ridges where smaller nodules prevail, burial is mainly controlled by statistical selection where some nodules are not moved up by organisms.

Production of Polyhydroxyalkanoates by Pseudomonas mendocina using vegetable oils and their characterisation

Synthesis of Polyhydroxyalkanoates (PHAs) by Pseudomonas mendocina, using different vegetable oils such as, coconut oil, groundnut oil, corn oil and olive oil, as the sole carbon source was investigated for the first time. The PHA yield obtained was compared with that obtained during the production of PHAs using sodium octanoate as the sole carbon source. The fermentation profiles at shaken flask and bioreactor levels revealed that vegetable oils supported the growth of Pseudomonas mendocina and PHA accumulation in this organism. Moreover, when vegetable oil (coconut oil) was used as the sole carbon source, fermentation profiles showed better growth and polymer production as compared to conditions when sodium octanoate was used as the carbon source. In addition, comparison of PHA accumulation at shaken flask and fermenter level confirmed the higher PHA yield at shaken flask level production. The highest cell mass found using sodium octanoate was 1.8 g/L, whereas cell mass as high as 5.1 g/L was observed when coconut oil was used as the feedstock at flask level production. Moreover, the maximum PHA yield of 60.5% dry cell weight (dcw) was achieved at shaken flask level using coconut oil as compared to the PHA yield of 35.1% dcw obtained using sodium octanoate as the sole carbon source. Characterisations of the chemical, physical, mechanical, surface and biocompatibility properties of the polymers produced have been carried out by performing different analyses as described in the second chapter of this study. Chemical analysis using GC and FTIR investigations showed medium chain length (MCL) PHA production in all conditions. GC-MS analysis revealed a unique terpolymer production, containing 3-hydroxyoctanoic acid, 3-hydroxydecanoic acid and 3-hydroxydodecanoic acid when coconut oil, groundnut oil, olive oil, and corn oil were used as the carbon source. Whereas production of the homopolymer containing 3-hydroxyoctanoic acid was observed when sodium octanoate was used as the carbon source. MCL-PHAs produced in this study using sodium octanoate, coconut oil, and olive oil exhibited melting transitions, indicating that each of the PHA was crystalline or semi-crystalline polymer. In contrast, the thermal properties of PHAs produced from groundnut and corn oils showed no melting transition, indicating that they were completely amorphous or semi-crystalline, which was also confirmed by the X-Ray Diffraction (XRD) results obtained in this study. Mechanical analysis of the polymers produced showed higher stiffness of the polymer produced from coconut oil than the polymer from sodium octanoate. Surface characterisation of the polymers using Scanning Electron Microscopy (SEM) revealed a rough surface topography and surface contact angle measurement revealed their hydrophobic nature. Moreover, to investigate the potential applicability of the produced polymers as the scaffold materials for dental pulp regeneration, multipotent human Mesenchymal stem cells (hMSCs) were cultured onto the polymer films. Results indicated that these polymers are not cytotoxic towards the hMSCs and could support their attachment and proliferation. Highest cell growth was observed on the polymer samples produced from corn oil, followed by the polymer produced using coconut oil. In conclusion, this work established, for the first time, that vegetable oils are a good economical source of carbon for production of MCL-PHA copolymers effectively by Pseudomonas mendocina. Moreover, biocompatibility studies suggest that the produced polymers may have potential for dental tissue engineering application.

Laser beam control, combining, and propagation in atmospheric turbulence

This dissertation is concerned with the control, combining, and propagation of laser beams through a turbulent atmosphere. In the first part we consider adaptive optics: the process of controlling the beam based on information of the current state of the turbulence. If the target is cooperative and provides a coherent return beam, the phase measured near the beam transmitter and adaptive optics can, in principle, correct these fluctuations. However, for many applications, the target is uncooperative. In this case, we show that an incoherent return from the target can be used instead. Using the principle of reciprocity, we derive a novel relation between the field at the target and the scattered field at a detector. We then demonstrate through simulation that an adaptive optics system can utilize this relation to focus a beam through atmospheric turbulence onto a rough surface. In the second part we consider beam combining. To achieve the power levels needed for directed energy applications it is necessary to combine a large number of lasers into a single beam. The large linewidths inherent in high-power fiber and slab lasers cause random phase and intensity fluctuations occurring on sub-nanosecond time scales. We demonstrate that this presents a challenging problem when attempting to phase-lock high-power lasers. Furthermore, we show that even if instruments are developed that can precisely control the phase of high-power lasers; coherent combining is problematic for DE applications. The dephasing effects of atmospheric turbulence typically encountered in DE applications will degrade the coherent properties of the beam before it reaches the target. Finally, we investigate the propagation of Bessel and Airy beams through atmospheric turbulence. It has been proposed that these quasi-non-diffracting beams could be resistant to the effects of atmospheric turbulence. However, we find that atmospheric turbulence disrupts the quasi-non-diffracting nature of Bessel and Airy beams when the transverse coherence length nears the initial aperture diameter or diagonal respectively. The turbulence induced transverse phase distortion limits the effectiveness of Bessel and Airy beams for applications requiring propagation over long distances in the turbulent atmosphere.

Caracterização elementar de ligas metálicas em implantes dentários

An ideal biomaterial for dental implants must have very high biocompatibility, which means that such materials should not provoke any serious adverse tissue response. Also, used metal alloys must have high fatigue resistance due the masticatory force and good corrosion resistance. These properties are rendered by using alpha and beta stabilizers, such as Al, V, Ni, Fe, Cr, Cu, Zn. Commercially pure titanium (TiCP) is used often for dental and orthopedic implants manufacturing. However, sometimes other alloys are employed and consequently it is essential to research the chemical elements present in those alloys that could bring prejudice for the health. Present work investigated TiCP metal alloys used for dental implant manufacturing and evaluated the presence of stabilizing elements within existing limits and standards for such materials. For alloy characterization and identification of stabilizing elements it was used EDXRF technique. This method allows to perform qualitative and quantitative analysis of the materials using the spectra of the characteristic X-rays emitted by the elements present in the metal samples. The experimental setup was based on two X- rays tubes (AMPTEK Mini X model with Ag and Au targets), a X-123SDD detector (AMPTEK) and a 0.5mm Cu collimator, developed due to the sample characteristics. The other experimental setup used as a complementary technique is composed of an X-ray tube with a Mo target, collimator 0.65mm and XFlash (SDD) detector - ARTAX 200 (BRUKER). Other method for elemental characterization by energy dispersive spectroscopy (EDS) applied in present work was based on Scanning Electron Microscopy (SEM) EVO® (Zeeis). This method also was used to evaluate the surface microstructure of the sample. The percentual of Ti obtained in the elementary characterization was among 93.35 ± 0.17% and 95.34 ± 0.19 %. These values are considered below the reference limit of 98.635% to 99.5% for TiCP, established by Association of metals centric materials engineers and scientists Society (ASM). The presence of elements Al and V in all samples also contributed to underpin the fact that are not TiCP implants. The values for Al vary between 6.3 ± 1.3% and 3.7 ± 2.0% and for V, between 0.26 ± 0.09% and 0.112 ± 0.048%. According to the American Society for Testing and Materials (ASTM), these elements should not be present in TiCP and in accordance with the National Institute of Standards and Technology (NIST), the presence of Al should be <0.01% and V should be of 0.009 ± 0.001%. Obtained results showed that implant materials are not exactly TiCP but, were manufactured using Ti-Al-V alloy, which contained Fe, Ni, Cu and Zn. The quantitative analysis and elementary characterization of experimental results shows that the best accuracy and precision were reached with X-Ray tube with Au target and collimator of 0.5 mm. Use of technique of EDS confirmed the results of EDXRF for Ti-Al-V alloy. Evaluating the surface microstructure by SEM of the implants, it was possible to infer that ten of the thirteen studied samples are contemporaneous, rough surface and three with machined surface.