TY  - JOUR
A1  - Grass, T. D.
A1  - dos Santos, Francisca E. A.
A1  - Pelster, Axel
T1  - Real-time Ginzburg-Landau theory for bosons in optical lattices
JF  - Laser physics
N2  - Within the Schwinger-Keldysh formalism we derive a Ginzburg-Landau theory for the Bose-Hubbard model which describes the real-time dynamics of the complex order parameter field. Analyzing the excitations in the vicinity of the quantum phase transitions it turns out that particle/hole dispersions in the Mott phase map continuously onto corresponding amplitude/phase excitations in the superfluid phase. Furthermore, in the superfluid phase we find a sound mode, which is in accordance with recent Bragg spectroscopy measurements in the Bogoliubov regime, as well as an additional gapped mode, which seems to have been detected via lattice modulation.
Y1  - 2011
U6  - https://doi.org/10.1134/S1054660X11150096
SN  - 1054-660X
SN  - 1555-6611
VL  - 21
IS  - 8
SP  - 1459
EP  - 1463
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Draude, F.
A1  - Galla, S.
A1  - Pelster, Axel
A1  - Tentschert, J.
A1  - Jungnickel, H.
A1  - Haase, Alfred
A1  - Mantion, Alexandre
A1  - Thuenemann, Andreas F.
A1  - Taubert, Andreas
A1  - Luch, A.
A1  - Arlinghaus, H. F.
T1  - ToF-SIMS and Laser-SNMS analysis of macrophages after exposure to silver nanoparticles
JF  - Surface and interface analysis : an international journal devoted to the development and application of techniques for the analysis surfaces, interfaces and thin films
N2  - Silver nanoparticles (SNPs) are among the most commercialized nanoparticles because of their antibacterial effects. Besides being employed, e. g. as a coatingmaterial for sterile surfaces in household articles and appliances, the particles are also used in a broad range of medical applications. Their antibacterial properties make SNPs especially useful for wound disinfection or as a coating material for prostheses and surgical instruments. Because of their optical characteristics, the particles are of increasing interest in biodetection as well. Despite the widespread use of SNPs, there is little knowledge of their toxicity. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and laser post-ionization secondary neutral mass spectrometry (Laser-SNMS) were used to investigate the effects of SNPs on human macrophages derived from THP-1 cells in vitro. For this purpose, macrophages were exposed to SNPs. The SNP concentration ranges were chosen with regard to functional impairments of the macrophages. To optimize the analysis of the macrophages, a special silicon wafer sandwich preparation technique was employed; ToF-SIMS was employed to characterize fragments originating from macrophage cell membranes. With the use of this optimized sample preparation method, the SNP-exposed macrophages were analyzed with ToF-SIMS and with Laser-SNMS. With Laser-SNMS, the three-dimensional distribution of SNPs in cells could be readily detected with very high efficiency, sensitivity, and submicron lateral resolution. We found an accumulation of SNPs directly beneath the cell membrane in a nanoparticular state as well as agglomerations of SNPs inside the cells.
KW  - Laser-SNMS
KW  - ToF-SIMS
KW  - life sciences
KW  - imaging
KW  - nanoparticles
KW  - three-dimensional depth profiling
Y1  - 2013
U6  - https://doi.org/10.1002/sia.4902
SN  - 0142-2421
VL  - 45
IS  - 1
SP  - 286
EP  - 289
PB  - Wiley-Blackwell
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Balaž, Antun
A1  - Vidanovic, Ivana
A1  - Bogojević, Aleksandar
A1  - Pelster, Axel
T1  - Ultra-fast converging path-integral approach for rotating ideal Bose-Einstein condensates
N2  - A recently developed efficient recursive approach for analytically calculating the short-time evolution of the one-particle propagator to extremely high orders is applied here for numerically studying the thermodynamical and dynamical properties of a rotating ideal Bose gas of Rb-87 atoms in an anharmonic trap. At first, the one-particle energy spectrum of the system is obtained by diagonalizing the discretized short-time propagator. Using this, many-boson properties such as the condensation temperature, the ground-state occupancy, density profiles, and time-of-flight absorption pictures are calculated for varying rotation frequencies. The obtained results improve previous semiclassical calculations, in particular for smaller particle numbers. Furthermore, we find that typical time scales for a free expansion are increased by an order of magnitude for the delicate regime of both critical and overcritical rotation.
Y1  - 2010
UR  - http://www.sciencedirect.com/science/journal/03759601
U6  - https://doi.org/10.1016/j.physleta.2010.01.034
SN  - 0375-9601
ER  -