Mikroleakage of Sealants Placed After Enamel Treatment With Self Etching Adhesive

Samojetkajući adhezivni sustavi istodobno s jetkanjem omogućuju penetraciju adheziva u jetkanu površinu cakline. Važne prednosti uporabe smojetkajućih adhezivnih sustava u postupku pečaćenja kao zamjeni za klasično jetkanje fosfornom kiselinom jesu: nema nanošenja kiseline i nema ispiranja. Svrha je istraživanja bila analizirati penetraciju i rubnu propustljivost pečata apliciranih nakon tretmana cakline samojetkajućim adhezivnim sustavom. 45 zuba podijelje nih u 3 skupine zapečaćeno je materijalom Concise White Sealant (3M Dental Products) nakon sljedećeg postupka pripreme površine cakline: Skupina 1: okluzalna površina jetkana je 37% fosfornom kiselinom 30 s, ispirana 15 s i sušena 15 s, nakon sušenja nanesen je materijal za pečaćenje i osvijetljen 20 s; skupina 2: Okluzalna površina tretirana je samojetkajućim adhezivnim sustavom Prompt- L-Pop (Espe Dental AG) 20 s i osvijetljen 10 s (Optilux, Demetron Research Company), materijal za pečaćenje zatim je nanesen i osvijetljen 20 s; skupina 3: Okluzalna površina tretirana ja samojetkajućim adhezivnim sustavom Prompt-L-Pop 20 s i odmah nakon tretmana nanesen je materijal za pečaćenje, oba materijala istodobno su osvijetljena 20 s. Svi su zubi termociklirani 1.800 ciklusa na temperaturi 5 - 55°C s 10 s imerzije u svakoj kupki. Rubna propustljivost ispitana je postupkom bojenja otopinom AgNO3. Zubi su uloženi u akrilnu smolu, prerezani (3-5 rezova po uzorku) i fotografirani pod 10 x povećanjem stereo mikroskopa. Rubna propustljivost mjerena je postupkom po Överböu i Raadalu. Statistička je rašlamba učinjena neparametrijskim testovima Kruskal-Wallis i Mann-Whitney. Penetracija materijala u dubinu fisura bila je između 87,8 - 92,1% bez statistički znatne razlike između skupina. Ustanovljena je statistički znatna razlika između klasičnoga postupka jetkanja i uporabe samojetkajućeg adhezivnog sustava (p = 0,003). Nije ustanovljena statistički znatna razlika u skupinama tretiranim samojetkajućim adhezivnim sustavom s polimerizacijom ili bez nje (p = 0,1234). Muguće je zaključiti da “all in one” samojetkajući adhezivni sustav Prompt-L-Pop nije tako djelotvoran kao kombinacija jetkanja fosfornom kiselinom i materijala za pečaćenje za dobivanje dobroga rubnog zatvaranja.Self-etching adhesives with enamel treatment at the same time as adhesive infiltration offers simplification of the classic technique of placing sealants. Main advantages in clinical work are: non need for applying acid, and no rinsing. Aim of the study was to evaluate both the penetration an sealing ability of a sealant applied after enamel treatment with a self-etching adhesive. The study was performed on forty-five teeth divided into three groups of fifteen teeth sealed with Concise White Sealant (3M Dental Products) after enamel surface was treated as fallows: Group 1: occlusal surface etched with 37% phosphoric acid for 30 s, rinsed for 15 s and air-dried for 15 s. After drying the sealant was applied and polymerized for 20 s. Group 2: The occlusal surface treated with self-etching adhesive Prompt-L-Pop (Espe Dental AG) for 20 s and lightened for 10 s (Optilux, Demetron Research Company). The sealant was then applied and lightened for 20 s. Group 3: The occlusal surface was treated with the selfetching adhesive Promt-L-Pop for 20 s and directly folloved by sealant application, the two materials were then simultaneously lightened 20 s. All teeth were thermocycled between 5 and 55°C for 1800 cycles with dwelling time of 10 s. AgNO3 dye solution was used for microleakage testing. After dyeing the teeth were embedded in acrylic resin, sectioned (3-5 sections per sample) and photographed under a stereo-microscope (10 X). Microleakage scores were recorded using the method of Övrebö and Raadal. Non-parametric Kruskal-Wallis and Mann-Whitney tests were used for statistical analysis. The sealant penetration rate was between 87.8 - 92.1% whatever the batch with no statistical significant difference between groups. Significant statistical difference was established between the classic H3PO4 pre-etch technique and the self-etching conditioning (p = 0.003). No significant difference was found between self-etching batches with or without polymerisation (p = 0.1234). Obtained data lead to the conclusion that the “all in one” self-etching adhesive Prompt-L-Pop is not as efficient as the classic H3PO4 etching + sealant in achieving a good enamel marginal sealing

Selection and 3D-Reconstruction of Gamma-Ray-induced Air Showers with a Stereoscopic System of Atmospheric Cherenkov Telescopes

A simple 3D-reconstruction method for gamma-ray induced air showers is presented, which takes full advantage of the assets of a system of Atmospheric Cherenkov Telescopes combining stereoscopy and fine-grain imaging like the High Energy Stereoscopic System (H.E.S.S.). The rich information collected by the cameras allows to select electromagnetic showers on the basis of their rotational symmetry with respect to the incident direction, as well as of their relatively small lateral spread. In the framework of a 3D-model of the shower, its main parameters -- incident direction, shower core position on the ground, slant depth of shower maximum, average lateral spread of Cherenkov photon origins (or ``photosphere 3D-width'') and primary energy -- are fitted to the pixel contents of the different images. For gamma-ray showers, the photosphere 3D-width is found to scale with the slant depth of shower maximum, an effect related to the variation of the Cherenkov threshold with the altitude; this property allows to define a dimensionless quantity omega (the ``reduced 3D-width''), which turns out to be an efficient and robust variable to discriminate gamma-rays from primary hadrons. In addition, the omega distribution varies only slowly with the gamma-ray energy and is practically independent of the zenith angle. The performance of the method as applied to H.E.S.S. is presented. Depending on the requirements imposed to reconstructed showers, the angular resolution at zenith varies from 0.04 to 0.1 degrees and the spectral resolution in the same conditions from 15% to 20%.Comment: 32 pages including 38 figures. Accepted by AstroParticle Physic

Mechanical analysis of feeding behavior in the extinct "Terror Bird" <i>Andalgalornis steulleti</i> (Gruiformes: phorusrhacidae)

The South American phorusrhacid bird radiation comprised at least 18 species of small to gigantic terrestrial predators for which there are no close modern analogs. Here we perform functional analyses of the skull of the medium-sized (,40 kg) patagornithine phorusrhacid Andalgalornis steulleti (upper Miocene-lower Pliocene, Andalgalá Formation, Catamarca, Argentina) to assess its mechanical performance in a comparative context. Based on computed tomographic (CT) scanning and morphological analysis, the skull of Andalgalornis steulleti is interpreted as showing features reflecting loss of intracranial immobility. Discrete anatomical attributes permitting such cranial kinesis are widespread phorusrhacids outgroups, but this is the first clear evidence of loss of cranial kinesis in a gruiform bird and may be among the best documented cases among all birds. This apomorphic loss is interpreted as an adaptation for enhanced craniofacial rigidity, particularly with regard to sagittal loading. We apply a Finite Element approach to a three-dimensional (3D) model of the skull. Based on regression analysis we estimate the bite force of Andalgalornis at the bill tip to be 133 N. Relative to results obtained from Finite Element Analysis of one of its closest living relatives (seriema) and a large predatory bird (eagle), the phorusrhacid's skull shows relatively high stress under lateral loadings, but low stress where force is applied dorsoventrally (sagittally) and in ''pullback'' simulations. Given the relative weakness of the skull mediolaterally, it seems unlikely that Andalgalornis engaged in potentially risky behaviors that involved subduing large, struggling prey with its beak. We suggest that it either consumed smaller prey that could be killed and consumed more safely (e.g., swallowed whole) or that it used multiple well-targeted sagittal strikes with the beak in a repetitive attack-and-retreat strategy.Facultad de Ciencias Naturales y Muse

Additively Manufactured Carbon Fiber- Reinforced Thermoplastic Composite Mold Plates For Injection Molding Process

Polymer injection molding processes have been used to create high-volume parts quickly and efficiently. Injection molding uses mold plates that are traditionally made of very hard tool steels, such as P20 steel, which is extremely heavy and has very long lead times to build new molds. In this study, composite-based additive manufacturing (CBAM) was used to create mold plates using long-fiber carbon fiber and polyether ether ketone (PEEK). These mold plates were installed in an injection molding machine, and rectangular flat plates were produced using Lustran 348 acrylonitrile butadiene styrene (ABS). Tensile and flexural testing was performed on these parts as well as parts produced using traditional P20 steel mold plates with the same geometry to compare the performance of the different mold plates. The parts produced using the carbon fiber mold plates were within 5% of the tensile strength and 10% of the flexural strength of the traditionally manufactured parts. However, the parts produced using the carbon fiber mold plates required additional cooling time due to the lower conductivity of the carbon fiber composite compared to the P20 steel. This allows additively manufactured composite molds to be a good substitute for conventional molds in low-volume injection molding production

BeppoSAX Observations of Markarian 501 in June 1999

We present the preliminary results of a long BeppoSAX observation of the BL Lac object Mkn501 carried out in June 1999. The source was fainter than found during the BeppoSAX pointings of 1997 and 1998, but is still detected with a good signal-to-noise ratio up to ~40 keV. The X-ray spectrum in the energy range 0.1-40 keV, produced through synchrotron radiation, is steeper than in the previous years, it is clearly curved, and peaks (in nu*F_nu) at ~0.5 keV. This energy is much lower than those at which the synchrotron component was found to peak in 1997 and 1998. Some intraday variability suggests that activity of the source on small time scales accompanies the large long time scale changes of brightness and spectrum.Comment: 4 pages, Latex, 2 PostScript figures, to appear in the Proceedings of the Conference "X-ray Astronomy '999: Stellar Endpoints, AGNs, and the Diffuse X-ray Background" (Bologna, 6-10 September 1999

The effects of skull flattening on suchian jaw muscle evolution

Jaw muscles are key features of the vertebrate feeding apparatus. The jaw musculature is housed in the skull whose morphology reflects a compromise between multiple functions, including feeding, housing sensory structures, and defense, and the skull constrains jaw muscle geometry. Thus, jaw muscle anatomy may be suboptimally oriented for the production of bite force. Crocodylians are a group of vertebrates that generate the highest bite forces ever measured with a flat skull suited to their aquatic ambush predatory style. However, basal members of the crocodylian line (e.g., Prestosuchus) were terrestrial predators with plesiomorphically tall skulls, and thus the origin of modern crocodylians involved a substantial reorganization of the feeding apparatus and its jaw muscles. Here, we reconstruct jaw muscles across a phylogenetic range of crocodylians and fossil suchians to investigate the impact of skull flattening on muscle anatomy. We used imaging data to create 3D models of extant and fossil suchians that demonstrate the evolution of the crocodylian skull, using osteological correlates to reconstruct muscle attachment sites. We found that jaw muscle anatomy in early fossil suchians reflected the ancestral archosaur condition but experienced progressive shifts in the lineage leading to Metasuchia. In early fossil suchians, musculus adductor mandibulae posterior and musculus pterygoideus (mPT) were of comparable size, but by Metasuchia, the jaw musculature is dominated by mPT. As predicted, we found that taxa with flatter skulls have less efficient muscle orientations for the production of high bite force. This study highlights the diversity and evolution of jaw muscles in one of the great transformations in vertebrate evolution.Fil: Sellers, Kaleb C.. University of Missouri; Estados UnidosFil: Nieto, Mauro Nicolas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Degrange, Federico Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Pol, Diego. Museo Paleontológico Egidio Feruglio; ArgentinaFil: Clark, James M.. The George Washington University. Columbian College Of Arts And Sciences. Department Of Biological Sciences.; Estados UnidosFil: Middleton, Kevin M.. University of Missouri; Estados UnidosFil: Holliday, Casey M.. University of Missouri; Estados Unido

Complex Spectral Variability from Intensive Multi-wavelength Monitoring of Mrk421 in 1998

We conducted a multi-frequency campaign for the TeV blazar Mrk~421 in 1998 April. The campaign started from a pronounced high amplitude flare recorded by SAX and Whipple; ASCA observation started three days later. In the X-ray data, we detected multiple flares, occuring on time scales of about one day. ASCA data clearly reveal spectral variability. The comparison of the data from ASCA, EUVE and RXTE indicates that the variability amplitudes in the low energy synchrotron component are larger at higher photon energies. In TeV Gamma-rays, large intra-day variations -- which were correlated with the X-ray flux -- were observed when results from three Cherenkov telescopes are combined. The RMS variability of TeV Gamma--rays was similar to that observed in hard X-rays, above 10 keV. The X-ray light curve reveals flares which are almost symmetric for most of cases, implying the dominant time scale is the light crossing time through the emitting region. The structure function analysis based on the continuous X-ray light curve of seven days indicates that the characteristic time scale is ~0.5 day. The analysis of ASCA light curves in various energy bands appears to show both soft (positive) and hard (negative) lags. These may not be real, as systematic effects could also produce these lags, which are all much smaller than an orbit. If the lags of both signs are real, these imply that the particle acceleration and X-ray cooling time scales are similar.Comment: 10 pages, 4 figures, accepted for publication in ApJ Letter

Searching for TeV dark matter by atmospheric Cerenkov techniques

There is a growing interest in the possibility that dark matter could be formed of weakly interacting particles with a mass in the 100 GeV - 2 TeV range, and supersymmetric particles are favorite candidates. If they constitute the dark halo of our Galaxy, their mutual annihilations produce energetic gamma rays that could be detected using existing atmospheric \u{C}erenkov techniques.Comment: 10 pp, LaTex (3 figures available by e-mail) PAR-LPTHE 92X

Spectrum and Variability of Mrk501 as observed by the CAT Imaging Telescope

The CAT Imaging Telescope has observed the BL Lac object Markarian 501 between March and August 1997. We report here on the variability over this time including several large flares. We present also preliminary spectra for all these data, for the low emission state, and for the largest flare.Comment: 4 pages, 4 figures, Late