Physikalisches Institute

Würzburg, Germany

Physikalisches Institute

Würzburg, Germany

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Lieberherr M.,Physikalisches Institute
Physics Teacher | Year: 2011

The centripetal acceleration has been known since Huygens' (1659) and Newton's (1684) time.1,2 The physics to calculate the acceleration of a simple pendulum has been around for more than 300 years, and a fairly complete treatise has been given by C. Schwarz in this journal.3 But sentences like "the acceleration is always directed towards the equilibrium position" beside the picture of a swing on a circular arc can still be found in textbooks, as e.g. in Ref. 4. Vectors have been invented by Grassmann (1844)5 and are conveniently used to describe the acceleration in curved orbits, but acceleration is more often treated as a scalar with or without sign, as the words acceleration/deceleration suggest. The component tangential to the orbit is enough to deduce the period of the simple pendulum, but it is not enough to discuss the forces on the pendulum, as has been pointed out by Santos-Benito and A. Gras-Marti.6 A suitable way to address this problem is a nice figure with a catch for classroom discussions or homework. When I plotted the acceleration vectors of the simple pendulum in their proper positions, pictures as in Fig. 1 appeared on the screen. The endpoints of the acceleration vectors, if properly scaled, seemed to lie on a curve with a familiar shape: a cardioid. Is this true or just an illusion?.


Dreiner H.K.,Physikalisches Institute | Kim J.S.,University of Adelaide | Lebedev O.,German Electron Synchrotron
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2012

The ATLAS and CMS Collaborations have recently reported tantalizing hints of the existence of a 125 GeV Higgs-like particle, whose couplings appear to match well the Standard Model (SM) expectations. In this work, we study implications of this observation for the neutralino sector of supersymmetric models, assuming that the Higgs signal gets confirmed. In general, the Higgs decay into neutralinos can be one of its dominant decay channels. Since a large invisible Higgs decay branching ratio would be in conflict with the data, this possibility is now constrained. In particular, we find that most of the region μ<170 GeV, M 1<70 GeV at tanβ~10 and μ<120 GeV, M 1<70 GeV at tanβ~40 is disfavored. © 2012 Elsevier B.V.


Brommel F.,Albert Ludwigs University of Freiburg | Stille W.,Physikalisches Institute | Finkelmann H.,Albert Ludwigs University of Freiburg | Hoffmann A.,Albert Ludwigs University of Freiburg
Soft Matter | Year: 2011

To gain insight into the origins of phase biaxiality in nematic polymers and elastomers the relation of molecular dynamics and biaxiality is studied. 2H-NMR investigations of various nematic polymers differing in the attachment geometry of the mesogens to the polymer (side-chain side-on, end-on and main-chain attachment) are presented. The mesogens are 2H- labelled at specific positions of their spacers and in the aromatic core. The NMR experiments are supplemented by dielectric relaxation measurements of polymers labelled with dipole groups. Only minor differences are found for the molecular dynamics of polymers and elastomers and comparing the various labelling positions suggests that the mesogenic moiety rotates as a whole. We find broad biaxial nematic phases for all investigated systems and a slowing down of the rotational diffusion around the mesogens′ long axes upon approaching the glass transition. It seems that in nematic polymers and elastomers phase biaxiality sets in when the rotational diffusion around the long axis gets hindered enough to allow biaxial nematic order. Comparing different attachment geometries we find that the side-on attachment of the mesogens seems to hinder the rotation of the molecules around their long axes considerably more than the other geometries. © 2011 The Royal Society of Chemistry.


Qing G.,Wuhan University of Technology | Sun T.,Wuhan University of Technology | Sun T.,Physikalisches Institute
NPG Asia Materials | Year: 2012

The ability to transform the chiral signals of molecules into the macroscopic properties of a material will offer significant advantages in the development of chiral functional devices and chirality-related applications. Chirality-responsive polymers provide an excellent platform to realize this objective, which often involves two basic strategies. The first strategy is to utilize various external stimuli to directly mediate the chiral conformations of a polymer, through which the energy input is transformed into a macroscopic change in the properties of a material. The second strategy is to utilize the enantioselective interaction between polymers and guest chiral molecules to trigger a stepwise conformational change in smart polymers, which then results in transformation of the macroscopic properties. This review summarizes recent progress in generating chirality-responsive polymers based on these strategies and discusses advances in their applications as chiral sensors, liquid crystals, optical and electrical devices, nanomachines and so on. We then introduce the emerging field of chiral bio-interface materials, in which chiral signals are transformed into changes in the macroscopic behavior of cells and biomacromolecules based on the stereo-specific interactions between biological systems and artificial materials. © Nature Japan K.K. All rights reserved.


Hartmann F.,Physikalisches Institute | Forchel A.,Physikalisches Institute | Neri I.,University of Perugia | Gammaitoni L.,University of Perugia | Worschech L.,Physikalisches Institute
Applied Physics Letters | Year: 2011

The authors have fabricated branched resonant tunneling diodes (RTDs). Using two branches as inputs, universal logic-gate operation was investigated as a function of noise added to the input signal. The difference in the output voltage, used as a measure for logic operation, shows a peak in the noise power characteristic associated with logic stochastic resonance. The split RTD allows morphing between universal logic-gates solely controlled by the noise level with power differences in the nanowatt range. © 2011 American Institute of Physics.


Busch O.,Physikalisches Institute
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2013

The ALICE Transition Radiation Detector (TRD) is one of the largest TRDs ever built. The TRD Detector Controls (DCS) System was conceived to maintain safe detector conditions and allow failsafe, reliable and consistent operation of such a highly complex detector. We present the design and implementation of TRD DCS with emphasis on practical aspects of detector operation at the Large Hadron Collider. © 2012 CERN. Published by Elsevier B.V. All rights reserve.


Messi F.,Physikalisches Institute
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2013

The BGO-OD experiment is intended for the systematic investigation of the photo-production of mesons off the nucleon. The experiment will use bremsstrahlung photons from an e- beam incident upon a thin radiator. The photon energy will be measured via the deflection of the electrons in the magnetic field of a photon tagger. The B-FrED is a 16 channel double-threshold discriminator and shaper board designed as Front-End Electronics for the newTagger detector of the experiment. It is a 6U-VME form factor card.The analog input stage has 1.7 GHz bandwidth. The output stage provides two LVDS signals with an expected jitter of ∼ 8 ps with respect to the input signal. The threshold settings are managed by a micro-controller which is remotely accessible through Ethernet. © 2012 Elsevier B.V.All rights reserved.


Jakobs K.,Physikalisches Institute
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2011

Over the coming years the experiments at the Large Hadron Collider (LHC) will explore the TeV energy scale and will most likely answer fundamental questions of particle physics. In the focus of the experiments are the search for physics beyond the Standard Model and the investigation of the nature of electroweak symmetry breaking. In order to fully exploit the physics potential of the LHC facility a high luminosity upgrade with luminosities of 10 35 cm-2 s-1 is envisaged. In the present article the physics potential of the LHC is summarized. For various physics scenarios it is also discussed how an upgraded high luminosity collider, the so called super-LHC (sLHC), could extend the physics reach of the LHC. © 2010 Elsevier B.V.


Kossacki K.J.,University of Warsaw | Portyankina G.,Physikalisches Institute | Thomas N.,Physikalisches Institute
Icarus | Year: 2011

Recent observations of the surface of Mars have shown several fresh mid-latitude craters. Some of these craters show exposed ice (Byrne, S. et al. [2009]. Science 325, 1674-1676.). In some craters, albedo of ice slowly decreases, while in others, it remains nearly constant. We attempt to determine influence of the regolith structure on the rate of sublimation of ice. For this purpose we performed numerical simulations describing evolution of the exposed ice in model craters located at middle latitudes.We consider a new model for the structure and evolution of the material at- and beneath the crater floors. In contrast to the previous study by Dundas and Byrne (Dundas, C.M., Byrne, S. [2010]. Icarus 206, 716-728.) we do not investigate sublimation of dirty ice, and the related formation of a sublimation lag. Instead, we consider sublimation of a pure ice layer on top of layered regolith. In our model the observed reflectivity decreases due to the sublimation-driven changes of the optical properties of thinning clean ice. This offers an alternative to the deposition of the dust embedded in ice (sublimation lag).We have shown that in our model among many parameters affecting ice sublimation rate, volumetric fraction of water ice in the subsurface beneath the crater has the strongest influence. Hence observed darkening of the ice patch on the crater floor might be sufficient to determine the content of water ice in the subsurface. Our calculations show that an albedo decrease of fresh ice patches in mid-latitude craters can be explained by either strong dust sedimentation or, if this is excluded, by sublimation of a thin layer of water ice from the regolith with large thermal inertia. This is consistent with a large volumetric fraction of water ice beneath the crater floor and contributes to evidence for an extended subsurface water reservoir on Mars.The overall conclusion of our work is that a thin post-impact surface ice coating over ice-rich ground beneath the crater floors is consistent with the observations. © 2010 Elsevier Inc.


Reidt F.,Physikalisches Institute
AIP Conference Proceedings | Year: 2013

A double-gap topology is used for filtering central-diffractive events from a protonproton minimum-bias data sample at a centre-of-mass energy Central diffraction in proton-proton collisions at √s=7TeV. This topology is defined by particle activity in the ALICE central barrel and absence of particle activity outside. The fraction of events satisfying the double-gap requirement RDG is found to be 7.63±0.02(st at.)±0.87(syst.) ×10-4. The background of this double-gap fraction is estimated by studying the contributions of non-diffractive, single-and double-diffractive dissociation processes as modelled by Monte Carlo event generators, and is found to be about 10%. © 2013 AIP Publishing LLC.

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