A note on minimax rates of convergence in the Spektor-Lord-Willis problem

In this note, attainable lower bounds are constructed for the convergence rates in a stereological problem of unfolding spheres size distribution from linear sections, which shows that a spectral type estimator is strictly rate minimax over some Sobolev-type classes of functions

A comparison of the clinical course of preexcitation syndrome in children and adolescents and in adults

Background: Atrioventricular reentrant tachycardia (AVRT) in patients with preexcitation syndrome (PS) is the main cause of paroxysmal regular arrhythmias in children and adolescents. While the previously published data most commonly concern clinical consequences of PS in adults, few researchers have evaluated the problem in children and adolescents. The aim of the study was to compare the clinical course of PS between the population of children and adolescents below 19 years of age and the population of adult patients. Method: The study population consisted of 302 consecutive PS patients managed between January 2001 and June 2005 with radiofrequency catheter ablation (RFCA). The study population was divided into two groups: Group 1 consisting of 52 patients aged 15.38 years on average (7-18 &#177; 2.53) and Group 2 consisting of 250 adult patients aged 38.67 years on average (19-72 &#177; 13.1). Results: Patients from Groups 1 and 2 experienced their first episode of AVRT at the mean age of 13.3 years and 29.1 years, respectively (p < 0.05). The mean annual numbers of AVRT episodes in Groups 1 and 2 were 12.97 (range, 2-96; median, 8) and 8.86 (range, 2-25; median, 6), respectively (p = non-significant). Two patients from Group 1 (3.85%) and 42 patients from Group 2 (16.8%) experienced episodes of atrial fibrillation (AF) (p < 0.05). Location of the accessory pathways (AP): In Group 1, the right free wall and anteroseptal AP locations were significantly more common [11 (21.15%) and 9 (17.31%) patients, respectively, vs.q 19 (7.6%) and 13 (5.2%) patients in Group 2; p < 0.01]. In Group 2, the left anterolateral AP location was more common [81 (32.4%) vs. 4 (7.69%) in Group 1; p < 0.01]. Conclusions: In children and adolescents with PS, a significantly lower incidence of AF was found. In Group 1, RFCA was performed significantly more frequently due to the development of AVRT caused by right free wall and right anteroseptal AP, while in the group of adults, the left anterolateral AP location was found more commonly. (Cardiol J 2007; 14: 384-390

Porównanie przebiegu klinicznego zespołu preekscytacji u dzieci i młodzieży z pacjentami dorosłymi

Wstęp: Nawrotny częstoskurcz przedsionkowo-komorowy (AVRT) u chorych z zespołem preekscytacji (PS) stanowi główną przyczynę napadowych miarowych arytmii u dzieci i młodzieży. Publikowane dane najczęściej dotyczą następstw klinicznych PS u dorosłych, w niewielu natomiast ocenia się ten problem u dzieci i młodzieży. Celem pracy była analiza porównawcza przebiegu klinicznego PS między populacją dzieci i młodzieży w wieku poniżej 19 lat a chorymi dorosłymi. Metoda: Badaniem objęto 302 kolejnych chorych z PS leczonych w okresie od stycznia 2001 do czerwca 2005 roku za pomocą ablacji prądem o wysokiej częstotliwości (RFCA). Z badanej populacji wyodrębniono dwie grupy: grupę I (52 chorych w wieku średnio 15,38 roku; 7-18 &#177; 2,53) i grupę II (250 chorych dorosłych w wieku średnio 38,67 roku; 19-72 &#177; 13,1). Wyniki: W grupie I wiek, w którym pierwszy raz wystąpił AVRT, wynosił średnio 13,3 roku, w grupie II - 29,1 roku (p < 0,05). Częstość występowania epizodów AVRT w skali rocznej wynosiła w grupie I średnio 12,97 (zakres 2-96, mediana 8), w grupie II - średnio 8,86 (zakres 2-25, mediana 6), p = NS. Epizody migotań przedsionków przebyło 2 chorych (3,85%) z grupy I i 42 pacjentów (16,8%) z grupy II (p < 0,05). W grupie I istotnie częściej stwierdzono lokalizację dróg dodatkowych (AP) prawostronną boczną (11 chorych; 21,15%) oraz przednioprzegrodową (9 chorych; 17,31%), natomiast w grupie II odpowiednio - u 19 (7,6%) i 13 pacjentów (5,2%; p < 0,01). W grupie II częściej występowała lokalizacja lewostronna przednio-boczna (81 chorych; 32,4%), w grupie I - u 4 pacjentów (7,69%; p < 0,01). Wnioski: U dzieci i młodzieży z PS istotnie rzadziej stwierdzano migotanie przedsionków. Częściej w grupie I wykonywano RFCA z powodu ujawnienia się AVRT zależnych od prawostronnych bocznych i prawostronnych przednio-przegrodowych AP, w grupie dorosłych natomiast częściej obserwowano lewostronną przednio-boczną lokalizację AP. (Folia Cardiologica Excerpta 2007; 2: 537-543

Mechanisms of attenuation of pulmonary V'O_{2} slow component in humans after prolonged endurance training

In this study we have examined the effect of prolonged endurance training program on the pulmonary oxygen uptake (V'O2 ) kinetics during heavy-intensity cycling-exercise and its impact on maximal cycling and running performance. Twelve healthy, physically active men (mean\ub1SD: age 22.33\ub11.44 years, V'O2peak 3198\ub1458 mL \ub7 min-1 ) performed an endurance training composed mainly of moderate-intensity cycling, lasting 20 weeks. Training resulted in a decrease (by 3c5%, P = 0.027) in V'O2 during prior low-intensity exercise (20 W) and in shortening of \u3c4 p of the V'O2 on-kinetics (30.1\ub15.9 s vs. 25.4\ub11.5 s, P = 0.007) during subsequent heavy-intensity cycling. This was accompanied by a decrease of the slow component of V'O2 on-kinetics by 49% (P = 0.001) and a decrease in the end-exercise V'O2 by 3c5% (P = 0.005). An increase (P = 0.02) in the vascular endothelial growth factor receptor 2 mRNA level and a tendency (P = 0.06) to higher capillary-to-fiber ratio in the vastus lateralis muscle were found after training (n = 11). No significant effect of training on the V'O2peak was found (P = 0.12). However, the power output reached at the lactate threshold increased by 19% (P = 0.01). The power output obtained at the V'O2peak increased by 14% (P = 0.003) and the time of 1,500-m performance decreased by 5% (P = 0.001). Computer modeling of the skeletal muscle bioenergetic system suggests that the training-induced decrease in the slow component of V'O2 on-kinetics found in the present study is mainly caused by two factors: an intensification of the each-step activation (ESA) of oxidative phosphorylation (OXPHOS) complexes after training and decrease in the "additional" ATP usage rising gradually during heavy-intensity exercise

Unfolding spheres size distribution from linear sections with B-splines and EMDS algorithm

The stereological problem of unfolding spheres size distribution from linear sections is formulated as a problem of inverse estimation of a Poisson process intensity function. A singular value expansion of the corresponding integral operator is given. The theory of recently proposed $B$-spline sieved quasi-maximum likelihood estimators is modified to make it applicable to the current problem. Strong $L^2$-consistency is proved and convergence rates are given. The estimators are implemented with the recently proposed EMDS algorithm. Promising performance of this new methodology in finite samples is illustrated with a numerical example. Data grouping effects are also discussed