Eigenvalue density of empirical covariance matrix for correlated samples

We describe a method to determine the eigenvalue density of empirical covariance matrix in the presence of correlations between samples. This is a straightforward generalization of the method developed earlier by the authors for uncorrelated samples (Z. Burda, A. Görlich, J. Jurkiewicz, B. Waclaw, cond-mat/0508341). The method allows for exact determination of the experimental spectrum for a given covariance matrix and given correlations between samples in the limit $N\rightarrow \infty$ and N/T = r = const with N being the number of degrees of freedom and T being the number of samples. We discuss the effect of correlations on several examples

Spectral properties of empirical covariance matrices for data with power-law tails

We present an analytic method for calculating spectral densities of empirical covariance matrices for correlated data. In this approach the data is represented as a rectangular random matrix whose columns correspond to sampled states of the system. The method is applicable to a class of random matrices with radial measures including those with heavy (power-law) tails in the probability distribution. As an example we apply it to a multivariate Student distribution.Comment: 9 pages, 3 figures, references adde

Oświadczenie

My niżej podpisani stanowczo protestujemy przeciwko tezom dra hab. prof. UKW Macieja Glogera, zamieszczonym we wstępie do tomu Między pozytywizmem i nacjonalizmem. Przemiany kultury polskiej w latach 1886-1918. W 2016 roku wzięliśmy udział w identycznie zatytułowanej konferencji w Sopocie, licząc na stricte naukowy, obiektywny kształt zarówno obrad, jak i późniejszej publikacji. Jak jednak wynika z przedmowy do książki, zamiar organizatora był wyraźnie podporządkowany celom ideologicznym. Mac..

Paradoxical and pulmonary embolism in a patient with superficial venous thrombosis as the first manifestation of patent foramen ovale

Zator skrzyżowany dotyczy stanu, kiedy zator z układu żylnego przedostaje się do układu tętniczego przez otwór pomiędzy lewą i prawą częścią serca, powodując udar mózgu, zator naczyń trzewnych lub ostre niedokrwienie kończyn. Celem pracy było przedstawienie przypadku zatoru tętniczego kończyny górnej i zatorowości płucnej jako pierwszej manifestacji przetrwałego otworu owalnego, ze źródłem materiału zatorowego w układzie żylnym powierzchownym. U chorych, u których rozpoznaje się zatorowość tętnic obwodowych, poszukując źródła zatorowości, zawsze należy uwzględnić możliwość wystąpienia zatoru skrzyżowanego. W poszukiwaniu źródła mate­riału zatorowego konieczne jest wdrożenie diagnostyki ultrasonograficznej układu żylnego, w tym także powierzchownego, oraz echokardiografii serca.Paradoxical embolism concerns the state when a venous thrombus gets into the arterial system through an intracardiac defect between the left and right part of heart causing stroke, visceral artery occlusion or acute limb ischemia. The purpose of this report is to present the case of paradoxical and pulmonary embolism as the first manifestation of patent foramen ovale in which the source of embolic material originates from the superficial venous system. In all arterial embolism events the possibility of the occurrence of paradoxical embolism should be consi­dered. In searching for the source of a thrombus, diagnostic ultrasonography of the deep and superficial venous system is needed, as well as echocardiography

The role of mechanical forces in the planar-to-bulk transition in growing Escherichia coli microcolonies

Mechanical forces are obviously important in the assembly of three-dimensional multicellular structures, but their detailed role is often unclear. We have used growing microcolonies of the bacterium \emph{Escherichia coli} to investigate the role of mechanical forces in the transition from two-dimensional growth (on the interface between a hard surface and a soft agarose pad) to three-dimensional growth (invasion of the agarose). We measure the position within the colony where the invasion transition happens, the cell density within the colony, and the colony size at the transition as functions of the concentration of the agarose. We use a phenomenological theory, combined with individual-based computer simulations, to show how mechanical forces acting between the bacterial cells, and between the bacteria and the surrounding matrix, lead to the complex phenomena observed in our experiments - in particular a non-trivial dependence of the colony size at the transition on the agarose concentration. Matching these approaches leads to a prediction for how the friction coefficient between the bacteria and the agarose should vary with agarose concentration. Our experimental conditions mimic numerous clinical and environmental scenarios in which bacteria invade soft matrices, as well as shedding more general light on the transition between two- and three-dimensional growth in multicellular assemblies

Metody analizy i oceny bezpieczeństwa oraz jakości informacji

Praca recenzowana / Peer-reviewed paperTematyka monografii koncentruje się na metodach zapewnienia bezpieczeństwa informacji, procedurach wspomagających podnoszenie jakości danych oraz narzędziach zwiększających możliwości pozyskiwania z dostępnych informacji wartościowych i rzetelnych wniosków analitycznych. Publikacja podzielona jest na trzy części. Pierwsza część zawiera 3 rozdziały, w których podjęto kwestie zapewnienia bezpieczeństwa informacji. Druga część monografii, ujęta w kolejnych trzech rozdziałach, prezentuje wybrane narzędzia i modele organizacji zasobów cyfrowych mających na celu zapewnienie wysokiej jakości, użyteczności oraz wiarygodności zbiorów danych zawartych w repozytoriach. Ostatnia część pracy przedstawia problematykę związaną z prawem Benforda, pozwalającym ocenić stopień rzetelności danych na podstawie analizy rozkładów cyfr w liczbach weryfikowanego zbioru danych

Mechanical thrombectomy in acute stroke – Five years of experience in Poland

Objectives Mechanical thrombectomy (MT) is not reimbursed by the Polish public health system. We present a description of 5 years of experience with MT in acute stroke in Comprehensive Stroke Centers (CSCs) in Poland. Methods and results We retrospectively analyzed the results of a structured questionnaire from 23 out of 25 identified CSCs and 22 data sets that include 61 clinical, radiological and outcome measures. Results Most of the CSCs (74%) were founded at University Hospitals and most (65.2%) work round the clock. In 78.3% of them, the working teams are composed of neurologists and neuro-radiologists. All CSCs perform CT and angio-CT before MT. In total 586 patients were subjected to MT and data from 531 of them were analyzed. Mean time laps from stroke onset to groin puncture was 250±99min. 90.3% of the studied patients had MT within 6h from stroke onset; 59.3% of them were treated with IV rt-PA prior to MT; 15.1% had IA rt-PA during MT and 4.7% – emergent stenting of a large vessel. M1 of MCA was occluded in 47.8% of cases. The Solitaire device was used in 53% of cases. Successful recanalization (TICI2b–TICI3) was achieved in 64.6% of cases and 53.4% of patients did not experience hemorrhagic transformation. Clinical improvement on discharge was noticed in 53.7% of cases, futile recanalization – in 30.7%, mRS of 0–2 – in 31.4% and mRS of 6 in 22% of cases. Conclusion Our results can help harmonize standards for MT in Poland according to international guidelines

Experimental verification of a CFD model intended for the determination of restitution coefficients used in erosion modelling

Erosion caused by solid particles transported with the steam or flue gas has a negative impact on the power unit reliability and availability. The erosion rate depends inter alia on the restitution of the particle velocity upon impact. The restitution coefficients determine the angle of the particle reflection off the tube surface and the particle post-impingement velocity, i.e., they determine the direction of the particle path, which has a substantial impact on the erosion phenomenon inside the tube. An attempt is made herein to develop a method of determination of restitution coefficients by means of numerical modelling assisted by experimental testing on physical models that will be implemented further in the Ansys Fluent code. Such a numerical procedure will verify the model of erosion caused by particles of iron oxides. The erodent impingement angle α1, the impingement velocity w1, and the reflection velocity w2 are measured using the Casio High-Speed Exilim EX-F1 camera, which enables filming at a high rate. The film is then processed graphically for “frame-by-frame” tracking. The following erodents were used in the testing: iron oxides, quartz sand with a different grain size (490, 1000, 1500, 2000 μm), and 1000 μm-diameter steel balls. The steel balls, due to their ideal shape, were treated as the comparative analysis reference standard. Erosion of three types of 5x10 cm plates was tested: a plasma-coated plate with an anti-erosion layer, an aluminium plate; and a steel sheet plate. Based on the restitution coefficient testing results, numerical simulations were performed of the particle reflection off the surface