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Structured High-Harmonic Light Sources for Enhanced Extreme Ultraviolet Microscopy
Lensless imaging techniques such as ptychography have revolutionized short-wavelength metrology by enabling photon-efficient, diffraction limited, robust phase-contrast imaging of nanostructured samples. At the same time, light sources based on the extreme nonlinear optical process of high harmonic generation have enabled these and other short-wavelength metrology techniques to be carried out on a tabletop. However, due to the lack of refractive optics for manipulating extreme ultraviolet and X-ray light, short-wavelength imaging currently lacks the vast flexibility of visible light microscopy, which in part is made possible by the many optical elements available for tailoring the illumination. This thesis aims to fill this gap by integrating amplitude, phase, and polarization structured light into the high harmonic generation process to produce a great deal of flexibility in the light source at its generation, and giving initial demonstrations of how using such tailored light sources can expand the capabilities of tabletop EUV microscopy techniques.</p
Lepton Flavor Violating Muon Decays in a Model of Electroweak-Scale Right-Handed Neutrinos
The small neutrino mass observed in neutrino oscillations is nicely explained
by the seesaw mechanism. Rich phenomenology is generally expected if the heavy
neutrinos are not much heavier than the electroweak scale. A model with this
feature built in has been suggested recently by Hung. The model keeps the
standard gauge group but introduces chirality-flipped partners for the
fermions. In particular, a right-handed neutrino forms a weak doublet with a
charged heavy lepton, and is thus active. We analyze the lepton flavor
structure in gauge interactions. The mixing matrices in charged currents (CC)
are generally non-unitary, and their deviation from unitarity induces flavor
changing neutral currents (FCNC). We calculate the branching ratios for the
rare decays \mu\to e\gamma and \mu\to ee\bar e due to the gauge interactions.
Although the former is generally smaller than the latter by three orders of
magnitude, parameter regions exist in which \mu\to e\gamma is reachable in the
next generation of experiments even if the current stringent bound on \mu\to
ee\bar e is taken into account. If light neutrinos dominate for \mu\to e\gamma,
the latter cannot set a meaningful bound on unitarity violation in the mixing
matrix of light leptons due to significant cancelation between CC and FCNC
contributions. Instead, the role is taken over by the decay \mu\to ee\bar e.Comment: 11 pages, 2 figures. v2: added 2 refs and improved a comment on
previous work; no other changes. v3: proofread version for PLB; added a few
clarifying sentences in paragraph before eq (17) plus minor editting change
Surface Polymer Network Model and Effective Membrane Curvature Elasticity
A microscopic model of a surface polymer network - membrane system is
introduced, with contact polymer surface interactions that can be either
repulsive or attractive and sliplinks of functionality four randomly
distributed over the supporting membrane surface anchoring the polymers to it.
For the supporting surface perturbed from a planar configuration and a small
relative number of surface sliplinks, we investigate an expansion of the free
energy in terms of the local curvatures of the surface and the surface density
of sliplinks, obtained through the application of the Balian - Bloch -
Duplantier multiple surface scattering method. As a result, the dependence of
the curvature elastic modulus, the Gaussian modulus as well as of the
spontaneous curvature of the "dressed" membrane, ~{\sl i.e.} polymer network
plus membrane matrix, is obtained on the mean polymer bulk end to end
separation and the surface density of sliplinks.Comment: 15 pages with one included compressed uuencoded figure
Vaughan-Jackson-like syndrome as an unusual presentation of Kienböck's disease: a case report
<p>Abstract</p> <p>Introduction</p> <p>Kienböck's disease is a condition of osteonecrosis of the lunate bone in the hand, and most patients present with a painful and sometimes swollen wrist with a limited range of motion in the affected wrist. Vaughan-Jackson syndrome is characterized by the disruption of the digital extensor tendons, beginning on the ulnar side with the extensor digiti minimi and extensor digitorum communis tendon of the small finger. It is most commonly associated with rheumatoid arthritis. We describe a case of a patient with an unusual presentation of Kienböck's disease with symptoms similar to those of Vaughan-Jackson syndrome.</p> <p>Case presentation</p> <p>A 40-year-old man of Indian ethnic origin with no known history of trauma presented to our clinic with a ten-day history of an inability to extend his right little and ring fingers with associated pain in his right wrist. He was being treated with long-term steroids but had no other significant medical history. His examination revealed an inability to extend the metacarpal and phalangeal joints of the right ring and little fingers with localized tenderness over the lunate bone. Spontaneous disruption of the extensor tendons was diagnosed clinically and, after radiological investigation, was confirmed to be secondary to dorsal extrusion of the fragmented lunate bone. The patient underwent surgical repair of the tendons and had a full recovery afterward.</p> <p>Conclusion</p> <p>Kienböck's disease, though rare, is an important cause of spontaneous extensor tendon rupture. The original description of Vaughan-Jackson syndrome was of rupture of the extensor tendons of the little and ring fingers caused by attrition at an arthritic inferior radioulnar joint. We describe a case of a patient with Kienböck's disease that first appeared to be a Vaughan-Jackson-like syndrome.</p
Influence of a Uniform Current on Collective Magnetization Dynamics in a Ferromagnetic Metal
We discuss the influence of a uniform current, , on the
magnetization dynamics of a ferromagnetic metal. We find that the magnon energy
has a current-induced contribution proportional to
, where is the spin-current, and
predict that collective dynamics will be more strongly damped at finite . We obtain similar results for models with and without local moment
participation in the magnetic order. For transition metal ferromagnets, we
estimate that the uniform magnetic state will be destabilized for . We discuss the relationship of this effect to
the spin-torque effects that alter magnetization dynamics in inhomogeneous
magnetic systems.Comment: 12 pages, 2 figure
Recalculation of Proton Compton Scattering in Perturbative QCD
At very high energy and wide angles, Compton scattering on the proton (gamma
p -> gamma p) is described by perturbative QCD. The perturbative QCD
calculation has been performed several times previously, at leading twist and
at leading order in alpha_s, with mutually inconsistent results, even when the
same light-cone distribution amplitudes have been employed. We have
recalculated the helicity amplitudes for this process, using contour
deformations to evaluate the singular integrals over the light-cone momentum
fractions. We do not obtain complete agreement with any previous result. Our
results are closest to those of the most recent previous computation, differing
significantly for just one of the three independent helicity amplitudes, and
only for backward scattering angles. We present results for the unpolarized
cross section, and for three different polarization asymmetries. We compare the
perturbative QCD predictions for these observables with those of the handbag
and diquark models. In order to reduce uncertainties associated with alpha_s
and the three-quark wave function normalization, we have normalized the Compton
cross section using the proton elastic form factor. The theoretical predictions
for this ratio are about an order of magnitude below existing experimental
data.Comment: Latex, 23 pages, 13 figures. Checked numerical integration one more
way; added results for one more proton distribution amplitude; a few other
minor changes. Version to appear in Phys. Rev.
Orbital selective coupling in CeRhB: co-existence of high Curie and high Kondo temperature
We investigated the electronic structure of the enigmatic CeRhB using
resonant inelastic scattering and x-ray absorption spectroscopy in combination
with density functional calculations. We find that the Rh 4
states are irrelevant for the high-temperature ferromagnetism and the Kondo
effect. We also find that the Ce 4 crystal-field strength is too small to
explain the strong reduction of the Ce magnetic moment. The data reveal instead
the presence of two different active Ce 4 orbitals, with each coupling
selectively to different bands in CeRhB. The inter-site hybridization
of the |J=5/2,Jz=+/-1/2> crystal-field state and Ce 5 band combined with the
intra-site Ce 4-5 exchange creates the strong ferromagnetism, while
hybridization between the |J=5/2,Jz=+/-5/2> and the B in the -plane
contributes to the Kondo interaction which causes the moment reduction. This
orbital selective coupling explains the unique and seemingly contradictory
properties of CeRhB.Comment: 15 pages, 14 figure
Synthetic organisms and living machines: Positioning the products of synthetic biology at the borderline between living and non-living matter
The difference between a non-living machine such as a vacuum cleaner and a living organism as a lion seems to be obvious. The two types of entities differ in their material consistence, their origin, their development and their purpose. This apparently clear-cut borderline has previously been challenged by fictitious ideas of âartificial organismâ and âliving machinesâ as well as by progress in technology and breeding. The emergence of novel technologies such as artificial life, nanobiotechnology and synthetic biology are definitely blurring the boundary between our understanding of living and non-living matter. This essay discusses where, at the borderline between living and non-living matter, we can position the future products of synthetic biology that belong to the two hybrid entities âsynthetic organismsâ and âliving machinesâ and how the approaching realization of such hybrid entities affects our understanding of organisms and machines. For this purpose we focus on the description of three different types of synthetic biology products and the aims assigned to their realization: (1) synthetic minimal cells aimed at by protocell synthetic biology, (2) chassis organisms strived for by synthetic genomics and (3) genetically engineered machines produced by bioengineering. We argue that in the case of synthetic biology the purpose is more decisive for the categorization of a product as an organism or a machine than its origin and development. This has certain ethical implications because the definition of an entity as machine seems to allow bypassing the discussion about the assignment and evaluation of instrumental and intrinsic values, which can be raised in the case of organisms
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