3,660 research outputs found
Der Einfluss von Haftsilan auf den Dentin-Kompositverbund
EinfĂŒhrung: In der vorliegenden Studie sollte untersucht werden, ob der Dentin-
Kompositverbund neben dem Drei-FlaschenâAdhĂ€sivsystem SyntacÂź (Ivoclar Vivadent
AG) mit Hilfe eines zusÀtzlichen Haftsilanes (MonobondŸ Plus; Ivoclar Vivadent AG)beeinflusst wird.
Methode: FĂŒr den experimentellen Versuch wurden 54 extrahierte, fĂŒllungs- und
kariesfreihe humane dritten Molaren verwendet. Die ZĂ€hne sind willkĂŒrlich auf achtzehn Versuchsgruppen zu je drei Proben verteilt worden. Es folgte die PrĂ€paration einer Klasse-I-KavitĂ€t, deren KavitĂ€tenboden vollstĂ€ndig im Dentin lag. AnschlieĂend ist die KavitĂ€t mit EcuSphereÂź-Komposit (DMG) adhĂ€siv mit Syntac und dem Haftsilan Monobond Plus nach einem festgelegten Schema gruppenspezifisch wieder aufgefĂŒllt und die ZĂ€hne mit Hilfe einer wassergekĂŒhlten DiamantsĂ€ge vertikal und horizontal in kleinen StĂ€bchen
zersĂ€gt worden. Diese PrĂŒfkörper wurden einer MikrozugfestigkeitsprĂŒfung in einer UniversalprĂŒfmaschine (Microtensile MTD-500 Plus, SD Mechatronik GmbH,
Feldkirchen-Westerham) unterzogen. Die dabei ermittelten Werte fĂŒr jede Gruppe wurden statistisch mit Hilfe des Programmes SPSS 14.0 (SPSS Inc., Chicago, Illinois, USA)ausgewertet. AbschlieĂend wurde das Dentin-Komposit-Interface
rasterelektonenmikrokopisch qualitativ untersucht (REM Phenom, Phenom-World BV,
Eindhoven, Niederlande) und bewertet.
Ergebnisse: Es konnte gezeigt werden, dass ein Haftsilan den Einfluss auf den Dentin-Kompositverbund, insbesondere des verwendeteten AdhĂ€sivsystems Syntac negativ beeinflusste. In der Versuchsreihe wurde das Haftsilan Monobond Plus sowohl in der AusfĂŒhrung Syntac Etch-and-Rinse (EAR) und Syntac Self-Etch (SE) eingesetzt.
Die Ergebnisse legen dar, dass alle ermittelten Werte der Versuchsgruppen mit Syntac EAR als auch Syntac SE signifikant schlechter waren (p<0,05), als der Mittelwert von Syntac EAR (38,5 MPa) bzw. Syntac SE (16,9 MPa). Folglich fĂŒhrt die Verwendung eines zusĂ€tzlichen Haftsilanes zu keiner Verbesserung der Haftwerte
Searching For Anomalous Couplings
The capability of current and future measurements at low and high energy
colliders to probe for the existence of anomalous, CP conserving,
dipole moment-type couplings is examined. At present, constraints
on the universality of the tau charged and neutral current interactions as well
as the shape of the energy spectrum provide the strongest
bounds on such anomalous couplings. The presence of these dipole moments are
shown to influence, e.g., the extraction of from
decays and can lead to apparent violations of CVC expectations.Comment: 24 pages, 9 figure
A Two-Step Machine Learning Method for Predicting the Formation Energy of Ternary Compounds
Predicting the chemical stability of yet-to-be-discovered materials is an important aspect of the discovery and development of virtual materials. The conventional approach for computing the enthalpy of formation based on ab initio methods is time consuming and computationally demanding. In this regard, alternative machine learning approaches are proposed to predict the formation energies of different classes of materials with decent accuracy. In this paper, one such machine learning approach, a novel two-step method that predicts the formation energy of ternary compounds, is presented. In the first step, with a classifier, we determine the accuracy of heuristically calculated formation energies in order to increase the size of the training dataset for the second step. The second step is a regression model that predicts the formation energy of the ternary compounds. The first step leads to at least a 100% increase in the size of the dataset with respect to the data available in the Materials Project database. The results from the regression model match those from the existing state-of-the-art prediction models. In addition, we propose a slightly modified version of the Adam optimizer, namely centered Adam, and report the results from testing the centered Adam optimizer.Deutsche ForschungsgemeinschaftPeer Reviewe
Causes of the large warm bias in the AngolaâBenguela Frontal Zone in the Norwegian Earth System Model
We have investigated the causes of the sea surface temperature (SST) bias in the AngolaâBenguela Frontal Zone (ABFZ) of the southeastern Atlantic Ocean simulated by the Norwegian Earth System Model (NorESM). Similar to other coupled-models, NorESM has a warm SST bias in the ABFZ of up to 8 °C in the annual mean. Our analysis of NorESM reveals that a cyclonic surface wind bias over the ABFZ drives a locally excessively strong southward (0.05 m/s (relative to observation)) Angola Current displacing the ABFZ southward. A series of uncoupled stand-alone atmosphere and ocean model simulations are performed to investigate the cause of the coupled model bias. The stand-alone atmosphere model driven with observed SST exhibits a similar cyclonic surface circulation bias; while the stand-alone ocean model forced with the reanalysis data produces a warm SST in the ABFZ with a magnitude approximately half of that in the coupled NorESM simulation. An additional uncoupled sensitivity experiment shows that the atmospheric modelâs local negative surface wind curl generates anomalously strong Angola Current at the ocean surface. Consequently, this contributes to the warm SST bias in the ABFZ by 2 °C (compared to the reanalysis forced simulation). There is no evidence that local air-sea feedbacks among wind stress curl, SST, and sea level pressure (SLP) affect the ABFZ SST bias. Turbulent surface heat flux differences between coupled and uncoupled experiments explain the remaining 2 °C warm SST bias in NorESM. Ocean circulation, upwelling and turbulent heat flux errors all modulate the intensity and the seasonality of the ABFZ errors.publishedVersio
Electroweak corrections to hadronic event shapes and jet production in e+e- annihilation
We present a complete calculation of the electroweak O(alpha^3 alpha_s)
corrections to three-jet production and related event-shape observables at
electron--positron colliders. The Z-boson resonance is described within the
complex-mass scheme, rendering the calculation valid both in the resonance and
off-shell regions. Higher-order initial-state radiation is included in the
leading-logarithmic approximation. We properly account for the corrections to
the total hadronic cross section and for the experimental photon isolation
criteria. To this end we implement contributions of the quark-to-photon
fragmentation function both in the slicing and subtraction formalism. The
effects of the electroweak corrections on various event-shape distributions and
on the three-jet rate are studied. They are typically at the few-per-cent
level, and remnants of the radiative return are found even after inclusion of
appropriate cuts.Comment: 47 pages, 20 figure
Spin structure of the nucleon: QCD evolution, lattice results and models
The question how the spin of the nucleon is distributed among its quark and
gluon constituents is still a subject of intense investigations. Lattice QCD
has progressed to provide information about spin fractions and orbital angular
momentum contributions for up- and down-quarks in the proton, at a typical
scale \mu^2~4 GeV^2. On the other hand, chiral quark models have traditionally
been used for orientation at low momentum scales. In the comparison of such
model calculations with experiment or lattice QCD, fixing the model scale and
the treatment of scale evolution are essential. In this paper, we present a
refined model calculation and a QCD evolution of lattice results up to
next-to-next-to-leading order. We compare this approach with the Myhrer-Thomas
scenario for resolving the proton spin puzzle.Comment: 11 pages, 6 figures, equation (9) has been corrected leading to a
revised figure 1b. Revision matches published versio
in the Two Higgs Doublet Model up to Next-to-Next-to-Leading Order in QCD
We compute three-loop matching corrections to the Wilson coefficients
and in the Two Higgs Doublet Model by applying expansions for small,
intermediate and large charged Higgs boson masses. The results are used to
evaluate the branching ratio of to next-to-next-to
leading order accuracy, and to determine an updated lower limit on the charged
Higgs boson mass. We find \mhplus \ge 380 GeV at 95% confidence level when
the recently completed BABAR data analysis is taken into account. Our results
for the charged Higgs contribution to the branching ratio exhibit considerably
weaker sensitivity to the matching scale , as compared to previous
calculations.Comment: 20 pages, 15 figures; v2: minor modifications, matches published
version in JHE
Electroweak corrections to three-jet production in electron-positron annihilation
We compute the electroweak corrections to
three-jet production and related event-shape observables at electron-positron
colliders. We properly account for the experimental photon isolation criteria
and for the corrections to the total hadronic cross section. Corrections to the
three-jet rate and to normalised event-shape distributions turn out to be at
the few-per-cent level.Comment: 5 pages, 4 figures. v2: changed normalisation in Fig. 2, minor text
revisions, version to appear in Phys.Lett.
Status Report of the DPHEP Study Group: Towards a Global Effort for Sustainable Data Preservation in High Energy Physics
Data from high-energy physics (HEP) experiments are collected with
significant financial and human effort and are mostly unique. An
inter-experimental study group on HEP data preservation and long-term analysis
was convened as a panel of the International Committee for Future Accelerators
(ICFA). The group was formed by large collider-based experiments and
investigated the technical and organisational aspects of HEP data preservation.
An intermediate report was released in November 2009 addressing the general
issues of data preservation in HEP. This paper includes and extends the
intermediate report. It provides an analysis of the research case for data
preservation and a detailed description of the various projects at experiment,
laboratory and international levels. In addition, the paper provides a concrete
proposal for an international organisation in charge of the data management and
policies in high-energy physics
Non-Canonical Gauge Coupling Unification in High-Scale Supersymmetry Breaking
The string landscape suggests that the supersymmetry breaking scale can be
high, and then the simplest low energy effective theory is the Standard Model
(SM). Considering grand unification scale supersymmetry breaking, we show that
gauge coupling unification can be achieved at about 10^{16-17} GeV in the SM
with suitable normalizations of the U(1)_Y, and we predict that the Higgs mass
range is 127 GeV to 165 GeV, with the precise value strongly correlated with
the top quark mass m_t and SU(3)_C gauge coupling. For example, if m_t=178\pm1
GeV, the Higgs boson mass is predicted to be between 141 GeV and 154 GeV. We
also point out that gauge coupling unification in the Minimal Supersymmetric
Standard Model (MSSM) does not imply the canonical U(1)_Y normalization. In
addition, we present 7-dimensional orbifold grand unified theories (GUTs) in
which such normalizations for the U(1)_Y and charge quantization can be
realized. The supersymmetry can be broken at the grand unification scale by the
Scherk--Schwarz mechanism. We briefly comment on a non-canonical U(1)_Y
normalization due to the brane localized gauge kinetic terms in orbifold GUTs.Comment: RevTex4, 28 pages, 4 figures, 2 table
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