383 research outputs found
Machara and Kodori Valleys (historical Apsilia) of NW Georgia in Caucasia in the 1st to 7th centuries AD
The dissertation concerns the historical Apsilia and offers a new theoretical approach to the nature of Apsilian material culture, which covers the period from the 1st to the early 7th centuries. Reasons are reflected in critical evaluation of the past scholarly contribution, where all problems have been analyzed.
Three studies are conducted in this thesis that moves over two historical timescale Roman and early medieval periods. The author aims for her achievements and presents a background for new arguments and theories. First is a descriptive-analytical study of cremated minorities of Olginskoe cemetery. This attempts to reveal the full potential of acts, changes, and the purpose of individual choices, leading to distinctive practices and diversifying grave structures. They are patterns rarely considered in past studies of burial customs and drawing on this author’s new research, vision and imaginations. It sets out a new approach to the regional context of cremated minorities. New typo-chronology and relevant content of applied specifics (some are resistant to local origin) attempt to reconcile the components of the cultural definition (‘Tsebeldian culture’) of Apsilian material culture. They are unique components and a new context of hypothesis which can be tested in archaeological evidence.
The other two issues derive from past scholarly contributions concerning the potential, perspectives, and functions of the geo-strategically significant NW region-Apsilia within Colchis/Lazica. It seeks to provide a broader understanding of the evolution of late Roman and early Byzantine Apsilian sites. This is a new approach to the study, which makes accessible the introduction of time-relative pieces of evidence and attempts to encompass existing knowledge about the studied material, but with a different perspective. It explores the possibility of new narratives by investigating broad features of trade and regional militarization that led to a global political establishment in Apsilia
Single-particle imaging reveals intraflagellar transport–independent transport and accumulation of EB1 in \u3cem\u3eChlamydomonas\u3c/em\u3e flagella
The microtubule (MT) plus-end tracking protein EB1 is present at the tips of cilia and flagella; end-binding protein 1 (EB1) remains at the tip during flagellar shortening and in the absence of intraflagellar transport (IFT), the predominant protein transport system in flagella. To investigate how EB1 accumulates at the flagellar tip, we used in vivo imaging of fluorescent protein–tagged EB1 (EB1-FP) in Chlamydomonas reinhardtii. After photobleaching, the EB1 signal at the flagellar tip recovered within minutes, indicating an exchange with unbleached EB1 entering the flagella from the cell body. EB1 moved independent of IFT trains, and EB1-FP recovery did not require the IFT pathway. Single-particle imaging showed that EB1-FP is highly mobile along the flagellar shaft and displays a markedly reduced mobility near the flagellar tip. Individual EB1-FP particles dwelled for several seconds near the flagellar tip, suggesting the presence of stable EB1 binding sites. In simulations, the two distinct phases of EB1 mobility are sufficient to explain its accumulation at the tip. We propose that proteins uniformly distributed throughout the cytoplasm like EB1 accumulate locally by diffusion and capture; IFT, in contrast, might be required to transport proteins against cellular concentration gradients into or out of cilia
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Structured illumination microscopy for in-vivo human retinal imaging: a theoretical assessment
Structured illumination microscopy applied to in-vivo retinal imaging has the potential to provide a low-cost and powerful diagnostic tool for retinal disease. In this paper the key parameters that affect performance in structured illumination ophthalmoscopy are studied theoretically. These include the number of images that need to be acquired in order to generate a sectioned image, which is affected by the non-stationary nature of the retina during acquisition, the choice of spatial frequency of the illuminating sinusoid, the effect of typical ocular aberrations on axial resolution and the nature of the sinusoidal pattern produced by the illumination system. The results indicate that structured illumination ophthalmoscopy can be a robust technique for achieving axial sectioning in retinal imaging without the need for complex optical systems
Surface collective excitations in ultrafast pump-probe spectroscopy of metal nanoparticles
The role of surface collective excitations in the electron relaxation in
small metal particles is studied. It is shown that the dynamically screened
electron-electron interaction in a nanoparticle contains a size-dependent
correction induced by the surface. This leads to new channels of quasiparticle
scattering accompanied by the emission of surface collective excitations. In
noble-metal particles, the dipole collective excitations (surface plasmons)
mediate a resonant scattering of d-holes to the conduction band. The role of
this effect in the ultrafast optical dynamics of small nanoparticles is
studied. With decreasing nanoparticle size, it leads to a strong change in the
differential absorption lineshape and a strong frequency dependence of the
relaxation near the surface plasmon resonance. The experimental implications of
these results in ultrafast pump-probe spectroscopy are addressed. The
size-dependence of conduction electron scattering rates is also discussed.Comment: 26 pages including 10 figures. Invited paper for Special Issue of
Chemical Physics on "Electron Dynamics in Metals
Signatures of the excitonic memory effects in four-wave mixing processes in cavity polaritons
We report the signatures of the exciton correlation effects with finite
memory time in frequency domain degenerate four-wave mixing (DFWM) in
semiconductor microcavity. By utilizing the polarization selection rules, we
discriminate instantaneous, mean field interactions between excitons with the
same spins, long-living correlation due to the formation of biexciton state by
excitons with opposite spins, and short-memory correlation effects in the
continuum of unbound two-exciton states. The DFWM spectra give us the relative
contributions of these effects and the upper limit for the time of the
exciton-exciton correlation in the unbound two-exciton continuum. The obtained
results reveal the basis of the cavity polariton scattering model for the DFWM
processes in high-Q GaAs microcavity.Comment: 11 pages, 1 figur
Ultrafast Spin Dynamics in Nickel
The spin dynamics in Ni is studied by an exact diagonalization method on the
ultrafast time scale. It is shown that the femtosecond relaxation of the
magneto-optical response results from exchange interaction and spin-orbit
coupling. Each of the two mechanisms affects the relaxation process
differently. We find that the intrinsic spin dynamics occurs during about 10 fs
while extrinsic effects such as laser-pulse duration and spectral width can
slow down the observed dynamics considerably. Thus, our theory indicates that
there is still room to accelerate the spin dynamics in experiments.Comment: 4 pages, Latex, 4 postscript figure
Ultrafast Coulomb-induced dynamics of 2D magnetoexcitons
We study theoretically the ultrafast nonlinear optical response of quantum
well excitons in a perpendicular magnetic field. We show that for
magnetoexcitons confined to the lowest Landau levels, the third-order
four-wave-mixing (FWM) polarization is dominated by the exciton-exciton
interaction effects. For repulsive interactions, we identify two regimes in the
time-evolution of the optical polarization characterized by exponential and
{\em power law} decay of the FWM signal. We describe these regimes by deriving
an analytical solution for the memory kernel of the two-exciton wave-function
in strong magnetic field. For strong exciton-exciton interactions, the decay of
the FWM signal is governed by an antibound resonance with an
interaction-dependent decay rate. For weak interactions, the continuum of
exciton-exciton scattering states leads to a long tail of the time-integrated
FWM signal for negative time delays, which is described by the product of a
power law and a logarithmic factor. By combining this analytic solution with
numerical calculations, we study the crossover between the exponential and
non-exponential regimes as a function of magnetic field. For attractive
exciton-exciton interaction, we show that the time-evolution of the FWM signal
is dominated by the biexcitonic effects.Comment: 41 pages with 11 fig
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