926 research outputs found
How Freud Explains the Tudors: Psychological Motivations and Historical Understanding of Tutor England\u27s Religious Schism
My thesis fuses several scholastic and intellectual interests that have been a part of me for many years now. History, religion, and literature are all fields I contemplated studying seriously. Furthermore, examining the motivations and reasons behind actions - a more psychological slant - has been an angle that has accompanied my fixation with these three fields. In Tudor England, I found the glorious intersection of these four paths, and I think what captivated me more than anything about this thesis, was the way in which they all worked together to create an overarching paradigm for a whole era
Quantum Brownian motion at strong dissipation probed by superconducting tunnel junctions
We have studied the temporal evolution of a quantum system subjected to
strong dissipation at ultra-low temperatures where the system-bath interaction
represents the leading energy scale. In this regime, theory predicts the time
evolution of the system to follow a generalization of the classical
Smoluchowski description, the quantum Smoluchowski equation, thus, exhibiting
quantum Brownian motion characteristics. For this purpose, we have investigated
the phase dynamics of a superconducting tunnel junction in the presence of high
damping. We performed current-biased measurements on the small-capacitance
Josephson junction of a scanning tunneling microscope placed in a low impedance
environment at milli-Kelvin temperatures. We can describe our experimental
findings by a quantum diffusion model with high accuracy in agreement with
theoretical predications based on the quantum Smoluchowski equation. In this
way we experimentally demonstrate that quantum systems subjected to strong
dissipation follow quasi-classical dynamics with significant quantum effects as
the leading corrections.Comment: 5 pages, 4 figure
Viscous behavior in a quasi-1D fractal cluster glass
Journal ArticleThe spin glass transition of a quasi-1D organic-based magnet ([MnTPP][TCNE]) is explored using both ac and dc measurements. A scaling analysis of the ac susceptibility shows a spin glass transition near 4 K, with a viscous decay of the thermoremanent magnetization recorded above 4 K.We propose an extension to a fractal cluster model of spin glasses that determines the dimension of the spin clusters (D) ranging from _x0001_o-0.8 to over 1.5 as the glass transition is approached. Long-range dipolar interactions are suggested as the origin of this low value for the apparent lower critical dimension
Recommended from our members
Kinetic analysis of protein aggregation monitored by real-time 2D solid-state NMR spectroscopy
It is shown that real-time 2D solid-state NMR can be used to obtain kinetic and structural information about the process of protein aggregation. In addition to the incorporation of kinetic information involving intermediate states, this approach can offer atom-specific resolution for all detectable species. The analysis was carried out using experimental data obtained during aggregation of the 10.4 kDa Crh protein, which has been shown to involve a partially unfolded intermediate state prior to aggregation. Based on a single real-time 2D 13C–13C transition spectrum, kinetic information about the refolding and aggregation step could be extracted. In addition, structural rearrangements associated with refolding are estimated and several different aggregation scenarios were compared to the experimental data
Anomalous relaxation in a quasi-one-dimensional fractal cluster glass
Journal ArticleThe low-temperature spin glass state of the quasi-1D organic-based magnet [MnTPP]+[TCNE]- .x(1,3-C6H4Cl2) has unusually long relaxation times due to frustration induced by dipole-dipole interactions between fractal spin clusters. This long relaxation is investigated with in-field relaxation measurements. The extremely long relaxation process enables probing of time-dependent phenomena using conventional magnetic measurements, including sweep rate-dependent hysteresis curves, even for temperatures well above the spin glass transition temperature (Tg). For a temperature of (-)1.3Tg, the coercive field increased by 170% for differing sweep rates, while below Tg the change was less than 5%. A study of the temperature dependence of the coercive field reveals detailed information on the behavior of fractal spin clusters within the system. For temperatures above Tg, the largely single-chain spin clusters act independently during magnetic reversal. As the spin clusters branch out below Tg, magnetic reversal is more cooperative, reflecting an enhancement of the magnetic interaction in the interpenetrating fractal cluster system
Single charge and exciton dynamics probed by molecular-scale-induced electroluminescence
Excitons and their constituent charge carriers play the central role in
electroluminescence mechanisms determining the ultimate performance of organic
optoelectronic devices. The involved processes and their dynamics are often
studied with time-resolved techniques limited by spatial averaging that
obscures the properties of individual electron-hole pairs. Here we overcome
this limit and characterize single charge and exciton dynamics at the nanoscale
by using time-resolved scanning tunnelling microscopy-induced luminescence
(TR-STML) stimulated with nanosecond voltage pulses. We use isolated defects in
C thin films as a model system into which we inject single charges and
investigate the formation dynamics of a single exciton. Tuneable hole and
electron injection rates are obtained from a kinetic model that reproduces the
measured electroluminescent transients. These findings demonstrate that TR-STML
can track dynamics at the quantum limit of single charge injection and can be
extended to other systems and materials important for nanophotonic devices
- …