28 research outputs found
Ultrastructural characteristics of the vascular wall components of ruptured atherosclerotic abdominal aortic aneurysm
The aim of this study was to determine the ultrastructural characteristics of cell populations and extracellular matrix components in the wall of ruptured atherosclerotic abdominal aortic aneurysm (AAA). We analyzed 20 samples of ruptured AAA. For orientation to the light microscopy, we used routine histochemical techniques by standard procedures. For ultrastructural analysis, we applied transmission electron microscopy (TEM). Our results have shown that ruptured AAA is characterized by the remains of an advanced atherosclerotic lesion in the intima followed by a complete absence of endothelial cells, the disruption of basal membrane and disruption of internal elastic lamina. On plaque margins as well as in the inner media we observed smooth muscle cells (SMCs) that posses a euchromatic nucleus, a well-developed granulated endoplasmic reticulum around the nucleus and reduced myofilaments. The remains of the ruptured lipid core were acellular in all samples; however, on the lateral sides of ruptured plaque we observed a presence of two types of foam cells (FCs), spindle- and star-shaped. Fusiform FCs possess a well-differentiated basal lamina, caveolae and electron dense bodies, followed by a small number of lipid droplets in the cytoplasm. Star-shaped FCs contain a large number of lipid droplets and do not possess basal lamina. On the inner margins of the plaque, we observed a large number of cells undergoing apoptosis and necrosis, extracellular lipid droplets as well as a large number of lymphocytes. The media was thinned out with disorganized elastic lamellas, while the adventitia exhibited leukocyte infiltration. The presented results suggest that atherosclerotic plaque in ruptured AAA contains vascular SMC synthetic phenotype and two different types of FCs: some were derived from monocyte/macrophage lineage, while others were derived from SMCs of synthetic phenotype. The striking plaque hypocellularity was the result of apoptosis and necrosis of different cell populations
Coexistence of Single and Double-Quantum Vortex Lines
We discuss the configurations in which singly and doubly quantized vortex
lines may coexist in a rotating superfluid. General principles of energy
minimization lead to the conclusion that in equilibrium the two vortex species
segregate within a cylindrical vortex cluster in two coaxial domains where the
singly quantized lines are in the outer annular region. This is confirmed with
simulation calculations on discrete vortex lines. Experimentally the
coexistence can be studied in rotating superfluid He-A. With cw NMR
techniques we find the radial distribution of the two vortex species to depend
on how the cluster is prepared: (i) By cooling through in rotation,
coexistence in the minimum energy configuration is confirmed. (ii) A glassy
agglomerate is formed if one starts with an equilibrium cluster of
single-quantum vortex lines and adds to it sequentially double-quantum lines,
by increasing the rotation velocity in the superfluid state. This proves that
the energy barriers, which separate different cluster configurations, are too
high for metastabilities to anneal.Comment: 12 pages, 11 figures; Changed content, 15 pages, 14 figure
Calculation of NMR Properties of Solitons in Superfluid 3He-A
Superfluid 3He-A has domain-wall-like structures, which are called solitons.
We calculate numerically the structure of a splay soliton. We study the effect
of solitons on the nuclear-magnetic-resonance spectrum by calculating the
frequency shifts and the amplitudes of the soliton peaks for both longitudinal
and transverse oscillations of magnetization. The effect of dissipation caused
by normal-superfluid conversion and spin diffusion is calculated. The
calculations are in good agreement with experiments, except a problem in the
transverse resonance frequency of the splay soliton or in magnetic-field
dependence of reduced resonance frequencies.Comment: 15 pages, 10 figures, updated to the published versio
Periodic Vortex Structures in Superfluid 3He-A
We discuss the general properties of periodic vortex arrangements in rotating
superfluids. The different possible structures are classified according to the
symmetry space-groups and the circulation number. We calculate numerically
several types of vortex structures in superfluid 3He-A. The calculations are
done in the Ginzburg-Landau region, but the method is applicable at all
temperatures. A phase diagram of vortices is constructed in the plane formed by
the magnetic field and the rotation velocity. The characteristics of the six
equilibrium vortex solutions are discussed. One of these, the locked vortex 3,
has not been considered in the literature before. The vortex sheet forms the
equilibrium state of rotating 3He-A at rotation velocities exceeding 2.6 rad/s.
The results are in qualitative agreement with experiments.Comment: 13 pages, 7 figures,
http://boojum.hut.fi/research/theory/diagram.htm
Vortices in Rotating Superfluid He3
For about a century now, physicists have been working hard to extend the temperature range accessible to experimental investigations closer and closer to absolute zero. This endeavor has been amply rewarded by new and fundamentally important discoveries. Completely novel continuous vortices in He3‐A and spontaneously magnetized singular vortices in He3‐B are just two of the many interesting peculiarities of rotating superfluid He3.Peer reviewe
Stable population structure in Europe since the Iron Age, despite high mobility
Ancient DNA research in the past decade has revealed that European population structure changed dramatically in the prehistoric period (14,000–3000 years before present, YBP), reflecting the widespread introduction of Neolithic farmer and Bronze Age Steppe ancestries. However, little is known about how population structure changed from the historical period onward (3000 YBP - present). To address this, we collected whole genomes from 204 individuals from Europe and the Mediterranean, many of which are the first historical period genomes from their region (e.g. Armenia and France). We found that most regions show remarkable inter-individual heterogeneity. At least 7% of historical individuals carry ancestry uncommon in the region where they were sampled, some indicating cross-Mediterranean contacts. Despite this high level of mobility, overall population structure across western Eurasia is relatively stable through the historical period up to the present, mirroring geography. We show that, under standard population genetics models with local panmixia, the observed level of dispersal would lead to a collapse of population structure. Persistent population structure thus suggests a lower effective migration rate than indicated by the observed dispersal. We hypothesize that this phenomenon can be explained by extensive transient dispersal arising from drastically improved transportation networks and the Roman Empire’s mobilization of people for trade, labor, and military. This work highlights the utility of ancient DNA in elucidating finer scale human population dynamics in recent history