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Using Molecular Design to Influence Intermolecular Interactions
This thesis describes the impact of molecular design on intermolecular interactions. Chapter 2 explores tuning the properties of contorted hexabenzocoronene (HBC) derivatives to improve photovoltaic performance. First, the interaction between contorted HBC derivatives with varying degrees of "bowl" character and fullerenes are explored in solution. Association constants were determined by fluorescence quenching experiments with fullerenes C70, C60, and Phenyl-C61-butyric acid methyl ester (PCBM). NMR titration experiments mimic fluorescence quenching results that suggest that association in solution increases with shape-complementarity between donor and acceptor. Second, efforts towards the synthesis of azulene HBC, an HBC derivative with red-shifted absorption, are discussed. Calculations of this target molecule and a selected intermediate are compared to those of the parent contorted HBC. Finally, an azulene HBC synthetic intermediate is explored as a potential sensor. Chapter 3 presents a study of the single molecule conductance of cobalt chalcogenide clusters. The synthesis of cobalt chalcogenide clusters decorated with a variety of conjugated molecular connectors was developed. Single molecule conductance of these clusters was shown to take place through the molecular connectors, and was tunable by controlling the substitution of the connectors. The tunability of cluster conductance that was demonstrated in the single molecule experiments was shown to extend to thin film experiments in chapter 4. Preliminary investigation into the mechanism of conductance of these films is discussed. In chapter 5, a family of nickel telluride clusters with a variety of ligands is synthesized. The X-ray crystal structures of these clusters are analyzed and insight into how ligand sterics and electronics influence the final cluster structure is discussed
A Case Illustrating the Efficiency of Dr. Senn's Hydrogen-Gas Test for Perforation of the Alimentary Canal.
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Critical slowing down near the multiferroic phase transition in MnWO
By using broadband dielectric spectroscopy in the radiofrequency and
microwave range we studied the magnetoelectric dynamics in the multiferroic
chiral antiferromagnet MnWO. Above the multiferroic phase transition at
K we observe a critical slowing down of the corresponding
magnetoelectric fluctuations resembling the soft-mode behavior in canonical
ferroelectrics. This electric field driven excitation carries much less
spectral weight than ordinary phonon modes. Also the critical slowing down of
this mode scales with an exponent larger than one which is expected for
magnetic second order phase transition scenarios. Therefore the investigated
dynamics have to be interpreted as the softening of an electrically active
magnetic excitation, an electromagnon.Comment: 5 pages, 4 figures, appendi
Testing the global star formation relation: An HCO+ (3-2) mapping study of Red MSX sources in the Bolocam Galactic Plane Survey
We present an analysis of the relation between the star formation rate (SFR)
and mass of dense gas in Galactic clumps and nearby galaxies. Using the
bolometric luminosity as a measure of SFR and the molecular line luminosity of
HCO+ (3-2) as a measure of dense gas mass, we find that the relation between
SFR and M_{dense} is approximately linear. This is similar to published results
derived using HCN (1-0) as a dense gas tracer. HCO+ (3-2) and HCN (1-0) have
similar conditions for excitation. Our work includes 16 Galactic clumps that
are in both the Bolocam Galactic Plane Survey and the Red MSX Survey, 27 water
maser sources from the literature, and the aforementioned HCN (1-0) data. Our
results agree qualitatively with predictions of recent theoretical models which
state that the nature of the relation should depend on how the critical density
of the tracer compares with the mean density of the gas.Comment: 38 pages (with full table), 3 figure
Nonlocality of cluster states of qubits
We investigate cluster states of qubits with respect to their non-local
properties. We demonstrate that a Greenberger-Horne-Zeilinger (GHZ) argument
holds for any cluster state: more precisely, it holds for any partial, thence
mixed, state of a small number of connected qubits (five, in the case of
one-dimensional lattices). In addition, we derive a new Bell inequality that is
maximally violated by the 4-qubit cluster state and is not violated by the
4-qubit GHZ state.Comment: 5 pages; paragraph V.B contains a comparison with Guehne et al.,
quant-ph/041005
Muon-spin-rotation measurements of the penetration depth in Li_2Pd_3B
Measurements of the magnetic field penetration depth in the ternary
boride superconductor LiPdB ( K) have been carried out by
means of muon-spin rotation (SR). The absolute values of , the
Ginzburg-Landau parameter , and the first and the second
critical fields at T=0 obtained from SR were found to be
nm, , mT, and
T, respectively. The zero-temperature value of the
superconducting gap 1.31(3) meV was found, corresponding to the
ratio . At low temperatures saturates and
becomes constant below , in agreement with what is expected for
s-wave BCS superconductors. Our results suggest that LiPdB is a s-wave
BCS superconductor with the only one isotropic energy gap.Comment: 6 pages, 7 figure
Standard model plethystics
We study the vacuum geometry prescribed by the gauge invariant operators of the minimal supersymmetric standard model via the plethystic program. This is achieved by using several tricks to perform the highly computationally challenging Molien-Weyl integral, from which we extract the Hilbert series, encoding the invariants of the geometry at all degrees. The fully refined Hilbert series is presented as the explicit sum of 1422 rational functions. We found a good choice of weights to unrefine the Hilbert series into a rational function of a single variable, from which we can read off the dimension and the degree of the vacuum moduli space of the minimal supersymmetric standard model gauge invariants. All data in Mathematica format are also presented
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