February 1948

·

7 Reads

Published by Wiley

Online ISSN: 1521-3889

·

Print ISSN: 0003-3804

February 1948

·

7 Reads

February 1948

·

14 Reads

13 Reads

19 Reads

10 Reads

18 Reads

12 Reads

16 Reads

November 2012

·

37 Reads

We present a new plasmonic device architecture based on ultrasmooth metallic surfaces with buried plasmonic nanostructures. Using template-stripping techniques, ultrathin gold films with less than 5 Å surface roughness are optically coupled to an arbitrary arrangement of buried metallic gratings, rings, and nanodots. As a prototypical example, we present linear plasmonic gratings buried under an ultrasmooth 20 nm thick gold surface for biosensing. The optical illumination and collection are completely decoupled from the microfluidic delivery of liquid samples due to the backside, reflection-mode geometry. This allows for sensing with opaque or highly scattering liquids. With the buried nanostructure design, we maintain high sensitivity and decoupled backside (reflective) optical access as with traditional prism-based surface plasmon resonance (SPR) sensors. In addition, we also gain the benefits offered by nanoplasmonic sensors such as spectral tunability and high-resolution, wide-field SPR imaging with normal-incidence epi-illumination that is simple to construct and align. Beyond sensing, our buried plasmonic nanostructures with ultrasmooth metallic surfaces can benefit nanophotonic waveguides, surface-enhanced spectroscopy, nanolithography, and optical trapping.

November 2011

·

69 Reads

In my reply I present a re-analysis of the data of the Smithsonian Astrophysical Observatory (SAO). For this, a new data reduction method is introduced, allowing a drastic lowering of data scatter, so that the time series of the reduced data clearly shows the ≈ 1 % variation of the terrestric solar irradiance in parallel with solar activity. The implications are discussed. In his reply the author present a re-analysis of the data of the Smithsonian Astrophysical Observatory (SAO). For this, a new data reduction method is introduced, allowing a drastic lowering of data scatter, so that the time series of the reduced data clearly shows the ≈ 1 % variation of the terrestric solar irradiance in parallel with solar activity. The implications are discussed.

November 2011

·

65 Reads

An analysis of ground-based observations of solar irradiance was recently published in this journal, reporting an apparent increase of solar irradiance on the ground of the order of 1% between solar minima and maxima [1]. Since the corresponding variations in total solar irradiance on top of the atmosphere are accurately determined from satellite observations to be of the order of 0.1% only [2], the one order of magnitude stronger effect in the terrestrial insolation data was interpreted as evidence for cosmic-ray induced aerosol formation in the atmosphere. In my opinion, however, this result does not reflect reality. Using the energy budget of Earth's surface, I show that changes of ground-based insolation with the solar cycle of the order of 1% between solar minima and maxima would result in large surface air temperature variations which are inconsistent with the instrumental record. It would appear that the strong variations of terrestrial irradiance found by [1] are due to the uncorrected effects of volcanic or local aerosols and seasonal variations. Taking these effects into account, I find a variation of terrestrial insolation with solar activity which is of the same order as the one measured from space, bringing the surface energy budget into agreement with the solar signal detected in temperature data.

November 2012

·

59 Reads

This study demonstrates the proof-of-principle of rapid surface modification of plasmonic nanostructured materials with oligonucleotides using low power microwave heating. Due to their interesting optical and electronic properties, silver nanoparticle films (SNFs, 2 nm thick) deposited onto glass slides were used as the model plasmonic nanostructured materials. Rapid surface modification of SNFs with oligonucleotides was carried out using two strategies (1) Strategy 1: for ss-oligonucleotides, surface hybridization and (2) Strategy 2: for ds-oligonucleotides, solution hybridization), where the samples were exposed to 10, 15, 30 and 60 seconds microwave heating. To assess the efficacy of our new rapid surface modification technique, identical experiments carried out without the microwave heating (i.e., conventional method), which requires 24 hours for the completion of the identical steps. It was found that SNFs can be modified with ss- and ds-oligonucleotides in 10 seconds, which typically requires several hours of incubation time for the chemisorption of thiol groups on to the planar metal surface using conventional techniques.

January 1998

·

25 Reads

This work deals with the overdamped motion of a particle in a fluctuating one-dimensional periodic potential. If the potential has no inversion symmetry and its fluctuations are asymmetric and correlated in time, a net flow can be generated at finite temperatures. We present results for the stationary current for the case of a piecewise linear potential, especially for potentials being close to the case with inversion symmetry. The aim is to study the stationary current as a function of the potential. Depending on the form of the potential, the current changes sign once or even twice as a function of the correlation time of the potential fluctuations. To explain these current reversals, several mechanisms are proposed. Finally, we discuss to what extent the model is useful to understand the motion of biomolecular motors.

March 2013

·

96 Reads

In 1912, Otto Sackur and Hugo Tetrode independently put forward an equation
for the absolute entropy of a monoatomic ideal gas and published it in "Annalen
der Physik." The grand achievement in the derivation of this equation was the
discretization of phase space for massive particles, expressed as \delta q
\delta p = h, where q and p are conjugate variables and h is Planck's constant.
Due to the dependence of the absolute entropy on Planck's constant, Sackur and
Tetrode were able to devise a test of their equation by applying it to the
monoatomic vapor of mercury; from the satisfactory numerical comparison of h
obtained from thermodynamic data on mercury with Planck's value from black-body
radiation, they inferred the correctness of their equation. In this review we
highlight this almost forgotten episode of physics, discuss the arguments
leading to the derivation of the Sackur--Tetrode equation and outline the
method how this equation was tested with thermodynamic data.

August 1999

·

33 Reads

Using Raman spectroscopy and transport measurements we investigate thin epitaxial films of Y{1-x}(Pr,Ca)xBa2Cu3O{6+y}. We explore the electronic Raman responses obtained after subtraction of phononic excitations, and the 2Delta peaks that form out of the electronic background below Tc. We find that the energy of the B1g 2Delta peak increases monotonically with decreasing doping until the peaks become unresolvable. In contrast, the peaks in A1g symmetry follow Tc being resolvable in the Pr-doped films. The B2g responses are weak and a 2Delta peak is only detected at the highest doping level. As a consequence of strong electron-phonon coupling, the B1g phonon at 340 cm^-1 exhibits a pronounced Fano-type line shape. We use a phenomenological model to describe the line shape that takes into account real and imaginary part of the electronic response. It allows us to obtain the self-energy corrections and the mass- enhancement factor lambda as a measure of the coupling. In the normal state we find lambda=0.015 around optimal doping and decreasing values with decreasing doping. The electron-phonon coupling increases strongly below T_c in overdoped samples in which the B1g 2Delta peaks appear in the vicinity of the phonon. Self-energy effects observed in the superconducting state can only partly be assigned to the redistributing electronic response. Anomalies with respect to frequency, linewidth, and intensity remain. They appear at increasing tempera- tures with decreasing doping and we provide evidence that they are connected to the presence of the pseudogap. We supplement our study by a comparison with single crystal data and investigate the influence of site-substitutional disorder on the electronic response and the electron-phonon interaction. Comment: 46 pages including 20 figures, accepted for publication in Annalen der Physik to appear August 1999. Figures and PDF-document are available under http://www.physnet.uni-hamburg.de/home/vms/bock/annalen.htm

December 2011

·

172 Reads

We review the work and life of Otto Stern who developed the molecular beam
technique and with its aid laid the foundations of experimental atomic physics.
Among the key results of his research are: the experimental determination of
the Maxwell-Boltzmann distribution of molecular velocities (1920), experimental
demonstration of space quantization of angular momentum (1922), diffraction of
matter waves comprised of atoms and molecules by crystals (1931) and the
determination of the magnetic dipole moments of the proton and deuteron (1933).

January 2015

·

35 Reads

Anderson localization of Bogoliubov excitations is studied for disordered
lattice Bose gases in planar quasi-one-dimensional geometries. The inverse
localization length is computed as function of energy by a numerical
transfer-matrix scheme, for strips of different widths. These results are
described accurately by analytical formulas based on a weak-disorder expansion
of backscattering mean free paths.

October 2007

·

25 Reads

We review recent advances in the field of full counting statistics (FCS) of charge transfer through impurities imbedded into strongly correlated one-dimensional metallic systems, modelled by Tomonaga-Luttinger liquids (TLLs). We concentrate on the exact analytic solutions for the cumulant generating function (CGF), which became available recently and apply these methods in order to obtain the FCS of a non-trivial contact between two crossed TLL.

December 2010

·

23 Reads

We discuss the generalization of Doubly Special Relativity to a curved de Sitter background. The model has three fundamental observer-independent scales, the velocity of light c, the de Sitter radius α, and the Planck energy κ, and can be realized through a nonlinear action of the de Sitter group on a noncommutative position space. We consider different choices of coordinates on the de Sitter hyperboloid that, although equivalent, may be more suitable for treating different problems. Also the momentum space can be described as a hyperboloid embedded in a five-dimensional space, but in this case different choices of coordinates lead to inequivalent models. We investigate the kinematics and the Hamiltonian dynamics of some specific models and describe some of their phenomenological consequences. Finally, we show that it is possible to construct a model exhibiting a duality for the interchange of positions and momenta together with the interchange of α and κ.

September 2007

·

50 Reads

The h index was introduced by Hirsch to quantify an individual's scientific research output. It has been widely used in different fields to show the relevance of the research work of prominent scientists. I have worked out 26 practical cases of physicists which are not so prominent. Therefore this case study should be more relevant to discuss various features of the Hirsch index which are interesting or disturbing or both for the more average situation. In particular, I investigate quantitatively some pitfalls in the evaluation and the influence of self-citations.

April 2010

·

37 Reads

We develop a quasiclassical method based on the path integral formalism, to study the influence of disorder on magnetooscillations of the density of states and conductivity. The treatment is appropriate for electron systems in the presence of a random potential with large correlation length or a random magnetic field, which are characterisitic features of various 2D electronic systems presently studied in experiment. In particular, we study the system of composite fermions in the fractional quantum Hall effect device, which are coupled to the Chern--Simons field and subject to a long--range random potential.

November 1999

·

28 Reads

The negative magnetoresistance due to weak localization is investigated in the two-dimensional metallic state of Si-MOS structures for high conductance values between 35 and 120 e^2/h. The extracted phase coherence time is equal to the momentum relaxation time at 10 K but nearly 100 times longer at the lowest temperature. Nevertheless, only weak logarithmic corrections to the conductivity are present in the investigated temperature and concentration range thus proving the absence of strong quantum effects due to electron-electron interaction. From saturation effects of the phase coherence time a lower boundary for spin-orbit scattering of about 200 ps is estimated. Comment: 4 pages, 3 figures, Conf. on "Localization: Disorder and Interaction in Transport Phenomena" July 29 - August 2, 1999, Hamburg, Germany

March 2014

·

61 Reads

The article provides full-analytic gravitational wave (GW) forms for
eccentric nonspinning compact binaries of arbitrary mass ratio in the time
Fourier domain. The semi-analytical property of recent descriptions, i.e. the
demand of inverting the higher-order Kepler equation numerically but keeping
all other computations analytic, is avoided for the first time. The article is
a completion of a previous one (Tessmer and Sch\"afer, Phys. Rev. D 82, 124064
(2010)) to second post-Newtonian (2PN) order in the harmonic GW amplitude and
conservative orbital dynamics. A fully analytical inversion formula of the
Kepler equation in harmonic coordinates is provided, as well as the analytic
time Fourier expansion of trigonometric functions of the eccentric anomaly in
terms of sines and cosines of the mean anomaly. Tail terms are not considered.

November 2004

·

43 Reads

We present a generating functional producing quark wave functions of all Fock states in the octet, decuplet and antidecuplet baryons in the mean field approximation, both in the rest and infinite momentum frames. In particular, for the usual octet and decuplet baryons we get the SU(6)-symmetric wave functions for their 3-quark component but with specific corrections from relativism and from additional quark-antiquark pairs. For the exotic antidecuplet baryons we obtain the 5-quark wave function. Comment: 20 p., 6 figs

December 2010

·

35 Reads

We investigate the dynamics of electrons in the vicinity of the Anderson transition in $d=3$ dimensions. Using the exact eigenstates from a numerical diagonalization, a number of quantities related to the critical behavior of the diffusion function are obtained. The relation $\eta = d-D_{2}$ between the correlation dimension $D_{2}$ of the multifractal eigenstates and the exponent $\eta$ which enters into correlation functions is verified. Numerically, we have $\eta\approx 1.3$. Implications of critical dynamics for experiments are predicted. We investigate the long-time behavior of the motion of a wave packet. Furthermore, electron-electron and electron-phonon scattering rates are calculated. For the latter, we predict a change of the temperature dependence for low $T$ due to $\eta$. The electron-electron scattering rate is found to be linear in $T$ and depends on the dimensionless conductance at the critical point.