203 research outputs found
Impact of European Integration on the Functioning of the Insurance Market in Poland
The transformation process, that has begun 20 years ago, generated significant changes in the structure and organization of Polish economy. It stimulated development of particular market's segments, especially of the insurance sector. Poland's accession to the European Union required conformity to Its regulations, fulfillment of several conditions connected with the membership in the European Community. The purpose of this article is to present the main consequences of Poland's integration with EU in the field of insurance market. Joining the common market was an important challenge for this sector in our country.Rok 1990 stanowił początek procesu transformacji systemu społeczno - gospodarczego i ustrojowego. Ostatnie 20 lat to okres intensywnych przemian o charakterze strukturalnym i organizacyjnym, w wyniku których ukształtowały się warunki rozwoju poszczególnych segmentów systemu finansowego państwa, zwłaszcza sektora ubezpieczeń. Przystąpienie Polski do Unii Europejskiej wymagało wprowadzenia szeregu zmian, dostosowujących polski porządek prawny do uregulowań wspólnotowych regulujących funkcjonowanie rynku ubezpieczeń. Celem artykułu jest zaprezentowanie szans i zagrożeń, jakie wynikają dla tego segmentu gospodarki z przystąpienia Polski do UE. Niewątpliwie proces integracji stanowił poważne wyzwanie dla polskiego rynku ubezpieczeń
The Origin of the Electromagnetic Interaction in Einstein's Unified Field Theory with Sources
Einstein's unified field theory is extended by the addition of matter terms
in the form of a symmetric energy tensor and of two conserved currents. From
the field equations and from the conservation identities emerges the picture of
a gravoelectrodynamics in a dynamically polarizable Riemannian continuum.
Through an approximate calculation exploiting this dynamical polarizability it
is argued that ordinary electromagnetism may be contained in the theory.Comment: 8 pages. Misprint in eq. 15 correcte
Diversity of segetal weeds in pea (Pisum sativum L.) depending on crops chosen for a crop rotation system
This study, lasting from 1999 to 2006, was conducted at the Research Station in Tomaszkowo, which belongs to the University of Warmia and Mazury in Olsztyn. The experiment was set up on brown rusty soil classified as good rye complex 5 in the Polish soil valuation system. The analysis comprised weeds in fields sown with pea cultivated in two four-field crop rotation systems with a different first crop: A. potato – spring barley – pea – spring barley; B. mixture of spring barley with pea – spring barley – pea – spring barley. Every year, at the 2–3 true leaf stage of pea, the species composition and density of individual weed species were determined; in addition, before harvesting the main crop, the dry matter of weeds was weighed. The results were used to analyze the constancy of weed taxa, species diversity, and the evenness and dominance indices, to determine the relationships between all biological indicators analyzed and weather conditions, and to calculate the indices of similarity, in terms of species composition, density and biomass of weeds, between the crop rotations compared.The species richness, density and biomass of weeds in fields with field pea were not differentiated by the choice of the initial crop in a given rotation system. In the spring, the total number of identified taxa was 28 and it increased to 36 before the harvest of pea plants. Chenopodium album and Echinochloa crus-galli were the most numerous. Chenopodium album, Echinochloa crus-galli, Sonchus arvensis, Fallopia convolvulus and Viola arvensis were constant in all treatments, regardless of what the first crop in rotation was or when the observations were made.The species diversity and the evenness and species dominance indices varied significantly between years and dates of observations. Species diversity calculated on the basis of the density of weed species was higher in the rotation with a mixture of cereals and legumes, while that calculated on the basis of weed biomass was higher in the system with potato. The similarity indices, which express the convergence of floristic composition as well as of the density and biomass of weeds growing in pea fields in the two crop rotation systems compared, were within a broad range (42–86%). The biodiversity of weed communities was more closely correlated to total precipitation than to air temperature
Age-related delay in visual and auditory evoked responses is mediated by white- and grey-matter differences
Slowing is a common feature of ageing, yet a direct relationship between neural slowing and brain atrophy is yet to be established in healthy humans. We combine magnetoencephalo-graphic (MEG) measures of neural processing speed with magnetic resonance imaging (MRI) measures of white and grey matter in a large population-derived cohort to investigate the relationship between age-related structural differences and visual evoked field (VEF) and auditory evoked field (AEF) delay across two different tasks. Here we use a novel technique to show that VEFs exhibit a constant delay, whereas AEFs exhibit delay that accumulates over time. White-matter (WM) microstructure in the optic radiation partially mediates visual delay, suggesting increased transmission time, whereas grey matter (GM) in auditory cortex partially mediates auditory delay, suggesting less efficient local processing. Our results demonstrate that age has dissociable effects on neural processing speed, and that these effects relate to different types of brain atrophy.Peer reviewe
The effect of interspecies interactions and water deficit on spring barley and red clover biomass accumulation at successive growth stages
A pot experiment was conducted in a greenhouse in Olsztyn, Poland, in the period 2010–2012. The aim of the study was to examine whether soil water deficit would change biomass volume and distribution of pure sown spring barley and red clover as well as growth rate during their joint vegetation and mutual interactions. The interactions between spring barley and red clover were of a competitive character, and the cereal was the stronger crop. The strength of this competition increased in time with the growing season. Through most of the growing season, the competition was poorer in water deficit conditions.The impact of clover on barley before the heading stage showed facilitation symptoms. Interspecific competition reduced the rate of barley biomass accumulation and decreased stem and leaf biomass towards the end of the growing season. Intensified translocation of assimilates from the vegetative parts to grain minimized the decrease in spike biomass.Water deficit stress had a more inhibitory effect on the biomass and growth rate of barley than competition, and competition did not exacerbate the adverse influence of water deficit stress on barley. Competition from barley significantly reduced the biomass and biomass accumulation rate of clover. Water deficit stress did not exacerbate barley’s competitive effect on clover, but it strongly inhibited the growth of aboveground biomass in pure-sown clover
A fully relativistic radial fall
Radial fall has historically played a momentous role. It is one of the most
classical problems, the solutions of which represent the level of understanding
of gravitation in a given epoch. A {\it gedankenexperiment} in a modern frame
is given by a small body, like a compact star or a solar mass black hole,
captured by a supermassive black hole. The mass of the small body itself and
the emission of gravitational radiation cause the departure from the geodesic
path due to the back-action, that is the self-force. For radial fall, as any
other non-adiabatic motion, the instantaneous identity of the radiated energy
and the loss of orbital energy cannot be imposed and provide the perturbed
trajectory. In the first part of this letter, we present the effects due to the
self-force computed on the geodesic trajectory in the background field.
Compared to the latter trajectory, in the Regge-Wheeler, harmonic and all
others smoothly related gauges, a far observer concludes that the self-force
pushes inward (not outward) the falling body, with a strength proportional to
the mass of the small body for a given large mass; further, the same observer
notes an higher value of the maximal coordinate velocity, this value being
reached earlier on during infall. In the second part of this letter, we
implement a self-consistent approach for which the trajectory is iteratively
corrected by the self-force, this time computed on osculating geodesics.
Finally, we compare the motion driven by the self-force without and with
self-consistent orbital evolution. Subtle differences are noticeable, even if
self-force effects have hardly the time to accumulate in such a short orbit.Comment: To appear in Int. J. Geom. Meth. Mod. Phy
The Electrostatics of Einstein's Unified Field Theory
When sources are added at their right-hand sides, and g_{(ik)} is a priori
assumed to be the metric, the equations of Einstein's Hermitian theory of
relativity were shown to allow for an exact solution that describes the general
electrostatic field of n point charges. Moreover, the injunction of spherical
symmetry of g_{(ik)} in the infinitesimal neighbourhood of each of the charges
was proved to yield the equilibrium conditions of the n charges in keeping with
ordinary electrostatics. The tensor g_{(ik)}, however, cannot be the metric of
the theory, since it enters neither the eikonal equation nor the equation of
motion of uncharged test particles. A physically correct metric that rules both
the behaviour of wave fronts and of uncharged matter is the one indicated by
H\'ely. In the present paper it is shown how the electrostatic solution
predicts the structure of the n charged particles and their mutual positions of
electrostatic equilibrium when H\'ely's physically correct metric is adopted.Comment: 15 pages. Misprints corrected. To appear in General Relativity and
Gravitatio
Activity and Connectivity Differences Underlying Inhibitory Control Across the Adult Life Span.
Inhibitory control requires precise regulation of activity and connectivity within multiple brain networks. Previous studies have typically evaluated age-related changes in regional activity or changes in interregional interactions. Instead, we test the hypothesis that activity and connectivity make distinct, complementary contributions to performance across the life span and the maintenance of successful inhibitory control systems. A representative sample of healthy human adults in a large, population-based life span cohort performed an integrated Stop-Signal (SS)/No-Go task during functional magnetic resonance imaging (n = 119; age range, 18-88 years). Individual differences in inhibitory control were measured in terms of the SS reaction time (SSRT), using the blocked integration method. Linear models and independent components analysis revealed that individual differences in SSRT correlated with both activity and connectivity in a distributed inhibition network, comprising prefrontal, premotor, and motor regions. Importantly, this pattern was moderated by age, such that the association between inhibitory control and connectivity, but not activity, differed with age. Multivariate statistics and out-of-sample validation tests of multifactorial functional organization identified differential roles of activity and connectivity in determining an individual's SSRT across the life span. We propose that age-related differences in adaptive cognitive control are best characterized by the joint consideration of multifocal activity and connectivity within distributed brain networks. These insights may facilitate the development of new strategies to support cognitive ability in old age.SIGNIFICANCE STATEMENT The preservation of cognitive and motor control is crucial for maintaining well being across the life span. We show that such control is determined by both activity and connectivity within distributed brain networks. In a large, population-based cohort, we used a novel whole-brain multivariate approach to estimate the functional components of inhibitory control, in terms of their activity and connectivity. Both activity and connectivity in the inhibition network changed with age. But only the association between performance and connectivity, not activity, differed with age. The results suggest that adaptive control is best characterized by the joint consideration of multifocal activity and connectivity. These insights may facilitate the development of new strategies to maintain cognitive ability across the life span in health and disease
The Relativistic Electrodynamics Least Action Principles Revisited: New Charged Point Particle and Hadronic String Models Analysis
The classical relativistic least action principle is revisited from the
vacuum field theory approach. New physically motivated versions of relativistic
Lorentz type forces are derived, a new relativistic hadronic string model is
proposed and analyzed in detail.Comment: n/
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