Histological evaluation of microfilled and conventional composite resins on monkey dental pulps

The pulpal responses to two micro-filled composite resins and a conventional composite resin were investigated in adult rhesus monkey teeth. All materials were randomly placed in unetched and unlined class V buccal cavity preparations. A total of 90 teeth were used in the study. Each material was evaluated at 3 days, 5 weeks and 8 weeks. Following perfusion, the teeth were prepared using routine histological procedures. The results indicated that the pulpal response to the microfilled and conventional composite resins were similar for all time periods, characterized by an initial slight to moderate response at 3 days, followed at 5 and 8 weeks by a zero to slight response with evidence of reparative dentine formation. Brown and Brenn staining for bacteria indicated positive staining reactions along the cavity wails of all teeth for all materials at each time period.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73366/1/j.1365-2591.1985.tb00453.x.pd

The Effect of Various Restorative Materials on the Microhardness of Reparative Dentin

This study showed a statistically significant difference between the microhardness of reparative and primary dentin at both five- and eight-week intervals. Reparative dentin from occlusal trauma is harder than reparative dentin underlying a cavity preparation at the 99% level. No statistical difference was noted in the hardness of reparative dentin underlying different materials, but trends were observed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66484/2/10.1177_00220345800590020101.pd

Optical Imaging and Spectroscopic Observation of the Galactic Supernova Remnant G85.9-0.6

Optical CCD imaging with H$\alpha$ and [SII] filters and spectroscopic observations of the galactic supernova remnant G85.9-0.6 have been performed for the first time. The CCD image data are taken with the 1.5m Russian-Turkish Telescope (RTT150) at TUBITAK National Observatory (TUG) and spectral data are taken with the Bok 2.3 m telescope on Kitt Peak, AZ. The images are taken with narrow-band interference filters H$\alpha$, [SII] and their continuum. [SII]/H$\alpha$ ratio image is performed. The ratio obtained from [SII]/H$\alpha$ is found to be $\sim$0.42, indicating that the remnant interacts with HII regions. G85.9-0.6 shows diffuse-shell morphology. [SII]$\lambda\lambda 6716/6731$ average flux ratio is calculated from the spectra, and the electron density $N_{e}$ is obtained to be 395 $cm^{-3}$. From [OIII]/H$\beta$ ratio, shock velocity has been estimated, pre-shock density of $n_{c}=14$ $cm^{-3}$, explosion energy of $E=9.2\times10^{50}$ ergs, interstellar extinction of $E(B-V)=0.28$, and neutral hydrogen column density of $N(HI)=1.53\times10^{21}$ $cm^{-2}$ are reported.Comment: 20 pages, 4 tables, 4 figures. Accepted for publication in Astrophysics & Space Scienc

HI Clouds Beyond the Galactic Disk

Recent observations in the 21cm line with the Green Bank Telescope have changed our view of the neutral interstellar medium (ISM) in several ways. The new data show that in the inner parts of the Milky Way the disk-halo interface is composed of many discrete HI clouds. The clouds lie in a layer more than one kpc thick and follow Galactic rotation. Their origin and evolution is unknown. In the outer Galaxy, the new data show that the high-velocity cloud Complex H is likely a satellite on a retrograde orbit interacting with some extended component of the Milky Way's ISM. These observations place new constraints on models of the ISM and are directly related to the work of Don Cox and Ron Reynolds.Comment: 8 pages includes 2 figures. To appear in "How Does the Galaxy Work?", eds. E.J. Alfaro, E. Perez, & J. Franco, Kluwer, Proceedings of a Conference held 23-27 June 2003 in Granada, Spai

Forward Jets and Energy Flow in Hadronic Collisions

We observe that at the Large Hadron Collider, using forward + central detectors, it becomes possible for the first time to carry out calorimetric measurements of the transverse energy flow due to "minijets" accompanying production of two jets separated by a large rapidity interval. We present parton-shower calculations of energy flow observables in a high-energy factorized Monte Carlo framework, designed to take into account QCD logarithmic corrections both in the large rapidity interval and in the hard transverse momentum. Considering events with a forward and a central jet, we examine the energy flow in the interjet region and in the region away from the jets. We discuss the role of these observables to analyze multiple parton collision effects.Comment: 9 pages, 5 figures. Version2: added results on azimuthal distributions and more discussion of energy flow definition using jet clusterin

Topological String Amplitudes, Complete Intersection Calabi-Yau Spaces and Threshold Corrections

We present the most complete list of mirror pairs of Calabi-Yau complete intersections in toric ambient varieties and develop the methods to solve the topological string and to calculate higher genus amplitudes on these compact Calabi-Yau spaces. These symplectic invariants are used to remove redundancies in examples. The construction of the B-model propagators leads to compatibility conditions, which constrain multi-parameter mirror maps. For K3 fibered Calabi-Yau spaces without reducible fibers we find closed formulas for all genus contributions in the fiber direction from the geometry of the fibration. If the heterotic dual to this geometry is known, the higher genus invariants can be identified with the degeneracies of BPS states contributing to gravitational threshold corrections and all genus checks on string duality in the perturbative regime are accomplished. We find, however, that the BPS degeneracies do not uniquely fix the non-perturbative completion of the heterotic string. For these geometries we can write the topological partition function in terms of the Donaldson-Thomas invariants and we perform a non-trivial check of S-duality in topological strings. We further investigate transitions via collapsing D5 del Pezzo surfaces and the occurrence of free Z2 quotients that lead to a new class of heterotic duals.Comment: 117 pages, 1 Postscript figur

What Physical Processes Drive the Interstellar Medium in the Local Bubble?

Recent 3D high-resolution simulations of the interstellar medium in a star form- ing galaxy like the Milky Way show that supernova explosions are the main driver of the structure and evolution of the gas. Its physical state is largely controlled by turbulence due to the high Reynolds numbers of the average flows. For a constant supernova rate a dynam- ical equilibrium is established within 200 Myr of simulation as a consequence of the setup of a galactic fountain. The resulting interstellar medium reveals a typical density/pressure pattern, i.e. distribution of so-called gas phases, on scales of 500–700 pc, with interstellar bubbles being a common phenomenon just like the Local Bubble and the Loop I superbub- ble, which are assumed to be interacting. However, modeling the Local Bubble is special, because it is driven by a moving group, passing through its volume, as it is inferred from the analysis of Hipparcos data. A detailed analysis reveals that between 14 and 19 super- novae have exploded during the last 15 Myr. The age of the Local Bubble is derived from comparison with HI and UV absorption line data to be 14.5±0.7 Myr. We further predict the 0.4merging of the two bubbles in about 3 Myr from now, when the interaction shell starts to fragment. The Local Cloud and its companion HI clouds are the consequence of a dynamical instability in the interaction shell between the Local and the Loop I bubble

Nickel on Lead, Magnetically Dead or Alive?

Two atomic layers of Ni condensed onto Pb films behave, according to anomalous Hall effect measurements, as magnetic dead layers. However, the Ni lowers the superconducting T_{c} of the Pb film. This has lead to the conclusion that the Ni layers are still very weakly magnetic. In the present paper the electron dephasing due to the Ni has been measured by weak localization. The dephasing is smaller by a factor 100 than the pair-breaking. This proves that the T_{c}-reduction in the PbNi films is not due magnetic Ni moments

The Science of Sungrazers, Sunskirters, and Other Near-Sun Comets

This review addresses our current understanding of comets that venture close to the Sun, and are hence exposed to much more extreme conditions than comets that are typically studied from Earth. The extreme solar heating and plasma environments that these objects encounter change many aspects of their behaviour, thus yielding valuable information on both the comets themselves that complements other data we have on primitive solar system bodies, as well as on the near-solar environment which they traverse. We propose clear definitions for these comets: We use the term near-Sun comets to encompass all objects that pass sunward of the perihelion distance of planet Mercury (0.307 AU). Sunskirters are defined as objects that pass within 33 solar radii of the Sun’s centre, equal to half of Mercury’s perihelion distance, and the commonly-used phrase sungrazers to be objects that reach perihelion within 3.45 solar radii, i.e. the fluid Roche limit. Finally, comets with orbits that intersect the solar photosphere are termed sundivers. We summarize past studies of these objects, as well as the instruments and facilities used to study them, including space-based platforms that have led to a recent revolution in the quantity and quality of relevant observations. Relevant comet populations are described, including the Kreutz, Marsden, Kracht, and Meyer groups, near-Sun asteroids, and a brief discussion of their origins. The importance of light curves and the clues they provide on cometary composition are emphasized, together with what information has been gleaned about nucleus parameters, including the sizes and masses of objects and their families, and their tensile strengths. The physical processes occurring at these objects are considered in some detail, including the disruption of nuclei, sublimation, and ionisation, and we consider the mass, momentum, and energy loss of comets in the corona and those that venture to lower altitudes. The different components of comae and tails are described, including dust, neutral and ionised gases, their chemical reactions, and their contributions to the near-Sun environment. Comet-solar wind interactions are discussed, including the use of comets as probes of solar wind and coronal conditions in their vicinities. We address the relevance of work on comets near the Sun to similar objects orbiting other stars, and conclude with a discussion of future directions for the field and the planned ground- and space-based facilities that will allow us to address those science topics

Measurement of the p-pbar -> Wgamma + X cross section at sqrt(s) = 1.96 TeV and WWgamma anomalous coupling limits

The WWgamma triple gauge boson coupling parameters are studied using p-pbar -> l nu gamma + X (l = e,mu) events at sqrt(s) = 1.96 TeV. The data were collected with the DO detector from an integrated luminosity of 162 pb^{-1} delivered by the Fermilab Tevatron Collider. The cross section times branching fraction for p-pbar -> W(gamma) + X -> l nu gamma + X with E_T^{gamma} > 8 GeV and Delta R_{l gamma} > 0.7 is 14.8 +/- 1.6 (stat) +/- 1.0 (syst) +/- 1.0 (lum) pb. The one-dimensional 95% confidence level limits on anomalous couplings are -0.88 < Delta kappa_{gamma} < 0.96 and -0.20 < lambda_{gamma} < 0.20.Comment: Submitted to Phys. Rev. D Rapid Communication