Cluster-Based Solidification and Growth Algorithm for Decagonal Quasicrystals.

A novel approach is used for the simulation of decagonal quasicrystal (DQC) solidification and growth. It is based on the observation that in well-ordered DQCs the atoms are largely arranged along quasiperiodically spaced planes parallel to the tenfold axis, running throughout the whole structure in five different directions. The structures themselves can be described as quasiperiodic arrangements of decagonal columnar clusters (cluster covering) that partially overlap in a systematic way. Based on these findings, we define a cluster interaction model within the mean field approximation, with effectively asymmetric interactions ranging beyond the nearest neighbors. In our Monte Carlo simulations, this leads to a long-range ordered quasiperiodic ground state. Indications of two finite-temperature unlocking phase transitions are observed, and are related to the two fundamental length scales that are characteristic for the system.

Cardiovascular Risk Factors and Markers of Atherosclerosis in Stable Kidney Transplant Recipients.

BACKGROUND: There is limited evidence regarding the risk factors influencing vascular injury in kidney transplant recipients, except for accelerated vasculopathy and endothelial dysfunction in the pre-transplantation period of end-stage renal failure. Therefore, we performed a cross-sectional study to evaluate the role of traditional and novel or potential nontraditional risk factors in vascular and endothelial dysfunction in a cohort of stable kidney transplant recipients. METHODS: One hundred forty-two kidney transplant recipients at 8.4 ± 1.8 years after transplantation were enrolled into the study. Different markers of vascular injury, such as carotid intima-media thickness (IMT), pulse wave velocity (PWV), and peripheral arterial tonometry (PAT), were assessed. Inflammatory markers, oxidative stress and endothelial function surrogate markers, adhesion molecules, and parathormone and osteoprotegerin levels were measured. RESULTS: Among traditional risk factors, only age, pre-transplantation diabetes, left ventricular hypertrophy (LVH) and cardiovascular disease (CVD) were related to increased IMT and PWV, whereas PAT values were significantly decreased only in diabetics and patients with CVD and were similar in patients with and without LVH. In multivariate regression analysis, IMT was explained by age, previous CVD episodes, and higher high-sensitivity C-reactive protein levels, and PWV by age and pre-transplantation diabetes. The regression analysis failed to find any significant explanatory variables for PAT. CONCLUSIONS: 1. In stable kidney transplant recipients, age, pre-transplantation diabetes, previous cardiovascular episode, and systemic microinflammation were predictors of vascular injury. 2. PAT is poorly associated with traditional CV risk factors and does not correspond with levels of biochemical markers of endothelial dysfunction in those patients.

Frequency of renal artery stenosis and variants of renal vascularization in hypertensive patients: analysis of 1550 angiographies in one centre.

Renal artery stenosis (RAS) is an important cause of arterial hypertension and chronic kidney disease. The aims of our study were to assess the prevalence of RAS and to examine the frequency of variants of renal vasculature, that is, multiple and/or accessory renal arteries in hypertensive patients referred to renal angiography. We evaluated retrospectively 1554 arteriographies of hypertensive patients. Angiograms were evaluated to find RAS, significant RAS (>60% stenosis of the lumen), radiological signs of atherosclerosis, aneurysms of the renal arteries or aorta and variants of kidney vascularization. The frequency of RAS including occlusions was 15.1% (21.3% of them were significant and suitable for revascularization). Variants of renal arterial vascularization were found in 26.5% of patients (multiple renal arteries-11.2% and accessory renal arteries-15.3%). Significant RAS was found more frequently in patients older than 60 years-OR 4.76 (2.08-10.86). Coronary artery disease, history of myocardial infarction or stroke significantly increased the chance of RAS detection. The frequency of renal accessory arteries was lower in patients older than 60 years and in patients with the radiological signs of atherosclerosis. Results of this study indicate that haemodynamically important RAS is found more frequently in hypertensive patients older than 60 years. Symptomatic atherosclerotic disease found in the peripheral and/or coronary arteries and diabetes mellitus increases the chance of RAS detection. Decreased occurrence of renal accessory arteries was found in hypertensive patients with radiological signs of atherosclerosis.