Bitcoin i inne kryptowaluty - dokąd zmierzają?

The article presents contemporary issues in the field of digital currency. It analyzes the economic factors that led to the exchange of digital indicating that it is a natural step in the development of means of payment. A review of the main types of digital currencies discusses the impact of their design on the popularity of individual currencies. It outlines the competition in the market of cryptocurrencies

TVWS policies to enable efficient spectrum sharing

The transition from analogue to the Digital Terrestrial Television (DTV) in Europe is planned to be completed by the end of the year 2012. The DTV spectrum allocation is such that there are a number of TV channels which cannot be used for additional high power broadcast transmitters due to mutual interference and hence are left unused within a given geographical location, i.e. the TV channels are geographically interleaved. The use of geographically interleaved spectrum provides for the so-called TV white spaces (TVWS) an opportunity for deploying new wireless services. The main objective of this paper is to present the spectrum policies that are suitable for TVWS at European level, identified within the COGEU project. The COGEU project aims the efficient exploitation of the geographical interleaved spectrum (TVWS). COGEU is an ICT collaborative project supported by the European Commission within the 7th Framework Programme. Nine partners from seven EU countries representing academia, research institutes and industry are involved in the project. The COGEU project is a composite of technical, business, and regulatory/policy domains, with the objective of taking advantage of the TV digital switchover by developing cognitive radio systems that leverage the favorable propagation characteristics of the UHF broadcast spectrum through the introduction and promotion of real-time secondary spectrum trading and the creation of new spectrum commons regimes. COGEU will also define new methodologies for compliance testing and certification of TVWS equipment to ensure non-interference coexistence with the DVB-T European standard. The innovation brought by COGEU is the combination of cognitive access to TV white spaces with secondary spectrum trading mechanisms.telecommunications,spectrum management,secondary spectrum market,regulation,TV white spaces,cognitive radio

The growth and differentiation of aortal smooth muscle cells after calcitriol treatment are associated with microtubule reorganisation - an in vitro study

The smooth muscle cells (SMCs) of the arterial media play a predominant role in functional and structural alterations of the arterial wall. The transition from the “contractile” to the “synthetic” phenotype appears to be an early critical event in the development of atherosclerotic disease. A number of observations suggest that 1,25(OH)2D3 (calcitriol) is of importance in maintaining normal cardiovascular function through its receptors in cardiac myocytes or aortal SMCs. The present study has focused on the microtubular (MT) network reorganisation after exposure to calcitriol. SMCs isolated by enzymatic digestion from the aortal media of neonatal rats were cultured on glass cover slips. 1 μM of 1,25(OH)2D3 was added to the culture medium every second day. The cytoskeletal features of SMCs after calcitriol were visualised by the immunofluorescence staining of α-tubulin. The alterations in α-tubulin expression and the distribution of microtubules related to the activities of the vascular smooth muscle cells, namely adhesion, migration, multilayer formation and cell division, were observed. A spindle shape, decreased cell adhesion, low expression of α-tubulin and a longitudinally arranged microtubular network manifested the high rate of SMC differentiation in the calcitriol-treated culture. A flat stellate morphology, high expression of α-tubulin and a radially distributed three-dimensional microtubular network were observed in the SMCs of the control culture. Destructive changes in the microtubular architecture which altered the cellular shape were evident in SMCs undergoing apoptosis. Cells with apoptotic features were more frequent in calcitriol-exposed culture. In contrast to the regular SMC divisions observed in the control culture, some of the mitotic cells exposed to calcitriol contained broader bipolar, multipolar or disordered spindles. These alterations in the SMCs’ microtubular cytoskeleton after calcitriol treatment were concomitant with changes in cell growth, differentiation and apoptosis, and may suggest a similarity to atherosclerotic plaque formation

A scanning electron microscopic study of phenotypic plasticity and surface structural changes of aortal smooth muscle cells in primary culture

Phenotypic modulation of smooth muscle cells (SMCs) from a contractile to a synthetic state characterised by active proliferation appears to be an early event in the pathogenesis of atherosclerosis. A similar transition occurs when SMCs are established in culture. In this study the phenotypic plasticity and surface structural changes of aortal smooth muscle cells during the transition from the contractile to the synthetic state and during maturation have been structurally assessed by scanning electron microscope (SEM). The experiments were performed on SMCs obtained from aorta of neonatal rats after enzymatic digestion and then cultured on glass cover slips. SEM observations revealed a three-dimensional appearance characteristic for different stages of SMCs. Intensively proliferating cells from monolayer region were large, polygonal in shape with lamellipodia and well spread. Long, uniform in diameter, finger-like microvilli were densely arranged on the surface of these cells. In the thickened region of culture, the cells were rather small, generally spindle-shaped, not well spread, with low density of short, bubble-like microvilli on the surface. Numerous plasma membrane structural alterations in apoptotic cells were observed by SEM: loss of cellular adhesion, smoothing, shrinkage and outpouching of membrane segments have been recognised as markers associated with the cell injury and death. It was concluded that scanning microscopy observations would allow a more complete understanding of SMCs and their changes in culture and atherosclerotic disease

Exercise stress test and comparison of ST change with cardiac nucleotide catabolite production in patients with coronary artery disease

Background: Uridine (Ur) and hypoxanthine (Hx) are the major end products of ischemic nucleotide breakdown in the human heart. Hypoxanthine is further metabolized to uric acid (UA). The aim of the study was the evaluation of whether changes in nucleotide concentrations during exercise correlate with electrocardiography (ECG) changes, and the severity of coronary artery disease (CAD). Methods: Twenty-nine males with CAD and 11 controls without CAD (mean age 56.1 vs. 51.45) were subjected to treadmill exercise. The test was considered positive if ECG showed more then 1 mm ST segment depression. Venous blood samples taken before and 10 minut after the exercise were analysed by high performance liquid chromatography. Results: Twenty-two out of 29 patients with CAD and 6 of 11 in the control group had abnormal exercise stress tests according to ECG criteria only. Mean &#8710;Ur was positive in the CAD group and negative in the control group (0.45 SEM &#177; 0.09 &#181;M/L vs. -0.43 SEM &#177; 0.21 &#181;M/L, p < 0.0001). &#8710;UA was positive in the CAD group (15.31 SEM &#177; 5.52 &#181;M/L) and negative in the control group (15.31 SEM &#177; 5.52 &#181;M/L vs. -48.18 SEM &#177; 13,8 &#181;M/L, p < 0.00001); Hx increased in both groups, and the change was not significantly different. Correlations of CAD-index with ST depression, &#8710;Ur and &#8710;UA, were: r = 0.43 (p < 0.005), r = 0.62 (p < 0.001), and r = 0.39 (p < 0.01), respectively. Sensitivity of any increase of uridine was superior to 1.5 mm ST depression during exercise. Conclusions: Blood Ur and UA concentration changes during exercise correlate with severity of CAD. We observed slightly greater accuracy of uridine change in comparison to ST changes, thus being a possible new tool in diagnosis of CAD. (Cardiol J 2007; 14: 573-579)

Telecommunication Economics — Summary on the Dagstuhl Perspectives Seminar No. 08043

The telecommunications sector and the Internet section of Internet Service Providers (ISP) have become a dynamic key area for the economic development of industrialized nations in the world. It is in constant evolution. Because of intense competition, telecommunications companies and ISPs are forced to diversify their offers and thus to propose an increasing number of services. However, economic analysis often ignores important technical aspects of telecommunications and is not aware of new developments. Engineering models often ignore economic factors. Thus, the design and deployment of future networks that incorporate new services are subject to uncertainties such as equipment and capacity prices (due to technological innovation), demand and supply for services (due to competition). Seeing leading researchers bringing together with various backgrounds, all working on innovative aspects of technical, techno-economic, social, and regulatory issues, lead to the following four main areas that have been partially tackled in an integrated manner: Architectural side, Social side, Economic and business side, and Regulatory side