Polish Group Research Articles

Ordered structures and large conjugacy classes

This article is a contribution to the following problem: does there exist a Polish non-archimedean group (equivalently: automorphism group of a Fraïssé limit) that is extremely amenable, and has ample generics. As Fraïssé limits whose automorphism groups are extremely amenable must be ordered, i.e., equipped with a linear ordering, we focus on ordered Fraïssé limits. We prove that automorphism groups of the universal ordered boron tree, and the universal ordered poset have a comeager conjugacy class but no comeager 2-dimensional diagonal conjugacy class. We formulate general conditions implying that there is no comeager conjugacy class, comeager 2-dimensional diagonal conjugacy class or non-meager 2-dimensional topological similarity class in the automorphism group of an ordered Fraïssé limit. We also provide a number of applications of these results.

The Influence of Level of Proficiency in the L2 and L3 on the Production of the L3 Spanish Apico-alveolar Sibilant

Current Third Language Acquisition research has traditionally focused on the L2 status (e.g. Hammarberg 2001, Bardel & Falk 2007) or linguistic proximity (e.g. Cenoz 2001, Westergaard, Mitrofanova, Mykhaylyk & Rodina 2016). Limited research has been conducted on the influence of the potentially significant factor of level of proficiency, and particularly where proficiency in both the L2 (Tremblay 2006, Woll 2016) and the L3 (Hammarberg 2001, Wrembel 2010) may be considered as a conditioning factor for the shape of the L3. The aim of the current study was thus to determine the influence of L2 and L3 level of proficiency (L2LoP and L3LoP) and the interaction of the two factors on the production of the L3 Spanish apico-alveolar sibilant in a group of L1 Polish, L2 English and L3 Spanish trilinguals who had different levels of overall proficiency in the two foreign languages. The parameters of the sibilant under analysis were spectral moments: centre of gravity (M1), standard deviation (M2), skewness (M3) and kurtosis (M4) in intervocalic position in two-syllable words with initial stress. The results point to the influential role of both L2LoP and L3LoP as well as their interaction on the production of the L3 Spanish sibilant. When the level of proficiency in one of the languages was low, it allowed the other language with a higher level of proficiency to exert influence on the values of the spectral moments in the L3 sibilant. This interplay of factors furthers the understanding of how levels of proficiency in the L2 and the L3 condition the developing L3.

$\sigma $-lacunary actions of Polish groups

We show that every essentially countable orbit equivalence relation induced by a continuous action of a Polish group on a Polish space is $ \sigma $-lacunary. In combination with Gao and Jackson [Invent. Math. 201 (2015), pp. 309-383] we obtain a straightforward proof of the result from Ding and Gao [Adv. Math. 307 (2017), pp. 312-343] that every essentially countable equivalence relation that is induced by an action of an abelian nonarchimedean Polish group is Borel reducible to $ \mathbb{E}_0$, i.e., it is essentially hyperfinite.

Galois groups as quotients of Polish groups

We present the (Lascar) Galois group of any countable theory as a quotient of a compact Polish group by an [Formula: see text] normal subgroup: in general, as a topological group, and under NIP, also in terms of Borel cardinality. This allows us to obtain similar results for arbitrary strong types defined on a single complete type over [Formula: see text]. As an easy conclusion of our main theorem, we get the main result of [K. Krupiński, A. Pillay and T. Rzepecki, Topological dynamics and the complexity of strong types, Israel J. Math. 228 (2018) 863–932] which says that for any strong type defined on a single complete type over [Formula: see text], smoothness is equivalent to type-definability. We also explain how similar results are obtained in the case of bounded quotients of type-definable groups. This gives us a generalization of a former result from the paper mentioned above about bounded quotients of type-definable subgroups of definable groups.

The Effect of Thermocycling and Surface Treatments on the Surface Roughness and Microhardness of Three Heat-Pressed Ceramics Systems

Dental ceramic restorations are widely used in restorative dentistry. However, these restorations can be affected once cemented in the oral cavity by several factors. How can conventional surface treatments, such as glazing and mechanical polishing, diminish the effects of aging? The purpose of this in vitro study was to evaluate the effect of thermocycling and conventional surface treatments on the surface roughness and microhardness of three types of glass-ceramics by using a profilometer, scanning electron microscopy (SEM), atomic force microscopy (AFM), and a microhardness tester. Three types of ceramic systems (zirconia reinforced lithium silicate glass-ceramic, lithium disilicate glass-ceramic, and feldspathic glass-ceramic) (n = 48) were prepared. The samples were subjected to thermocycling for 10,000 cycles. Surface roughness was evaluated numerically using a profilometer and visually by using SEM and AFM. Microhardness was performed using a microhardness tester. The data were interpreted using the ANOVA test, and the results were correlated using Pearson’s correlation formula (r). Significant differences were found before and after thermocycling for the Ra (p < 0.01) and Rz (p < 0.05) parameters. As well, differences between glazed and polished surfaces were significant before and after thermocycling for surface roughness and microhardness (p < 0.05). A correlation was made between average surface roughness and microhardness (r = −460) and for the maximum surface roughness and microhardness (r = −606). Aging increases the roughness and decreases in time the microhardness. The tested ceramic systems behaved differently to the aging and surface treatments. Surface treatments had a significant impact on the microhardness and surface characteristics. The glazed groups were reported with higher surface roughness and lower microhardness when compared to the polished groups before and after thermocycling. The measuring roughness techniques determine the scale-dependent values for the Ra (Sa) and Rz (Sq) parameters. Thermocycling almost doubled the surface roughness for all the tested samples. Microhardness decreased only for the Celtra glazed samples. Nano-roughness increased the values for Vita and slightly for Emax. Thermocycling had little effect on Emax ceramic and a more significant impact on Celtra Press ceramic.

Comparison of bacterial adhesion and biofilm formation on zirconia fabricated by two different approaches: an in vitro and in vivo study

ABSTRACT Prepared by dry and wet approaches, respectively, the surface properties and bacterial adhesion of conventional zirconia (CZ) and self-glazed zirconia (SGZ) were investigated. Each zirconia was divided into unpolished and polished groups. Our results revealed that SGZ showed significantly lower surface roughness than CZ (P < 0.05) and lower surface-free energy (P < 0.05) in both polished and unpolished groups. The number of bacteria attached to SGZ was less than CZ in vitro (P < 0.05), but no significant difference was found between two kinds of zirconia in vivo (P > 0.05). Our findings suggest that SGZ, due to its excellent surface characteristics, is superior to CZ in bacterial adhesion and zirconia polishing serves as an indispensable procedure in clinics.

Profile kompetencji społecznych studentów przygotowujących się do sprawowania opieki nad osobami starszymi – badania polsko-niemieckie

The ageing of people is one of the most important social issues of the modern world. This is a global phenomenon, concerning all regions and almost all countries. This problem pertains also to Poland and Germany. The following article is based on empirical studies whose subject were the social competencies profiles of Polish and German students preparing for caregiving of the elderly people. The method of the study was a diagnostic survey, whereas the research instruments used in the study were PROKOS. Social Competencies Profile by A. Matczak and K. Martowska and The questionnaire for the analysis of motivation to work with elderly people for students of social wellbeing majors (self-constructed questionnaire). Research studies were carried out between October and December 2018. In Poland, they involved students from Maria Curie-Skłodowska University in Lublin and the University of Rzeszów, while in Germany, students from universities of Münster, Osnabrück, Bielefeld and Wolfsburg. German students (200 people) constituted the main group, whereas the comparative group consisted of 167 Polish students. The results of the research demonstrated significant statistic differences in the range of all distinguished types of social competencies between the examined Polish and German groups of students (p &lt; 0,001).

Tribology, Characterization, and Surface Roughness Study of a CAD/CAM-Fabricated Zirconia

The aim of the study is to evaluate the tribological behavior of dental Zirconia as it undergoes surface and subsurface damages during CAD/CAM milling. These damages cannot be healed in the subsequent fabrication processes leading to shortened lifetime of dental restorations. Four groups based on pre- and post-processing combinations are selected for the study. The groups included milling of pre-sintered blocks followed by sintering and polishing (Group A), polishing of pre-sintered block followed by sintering (Group B), sintering followed by sandblasting with aluminum oxide (Al2O3) and polishing (Group C), and polishing of pre-sintered blocks followed by sintering and sandblasting with aluminum oxide (Al2O3) (Group D). Each of the specimens is tested for wear using an antagonist Zirconia ball of 6 mm diameter and abraded for 7200 cycles at 2 Hz with 15 mm stroke length on a reciprocating tribometer. A load of 10 N was applied and the test is performed in the presence of artificial saliva. The surfaces are evaluated before and after wear using scanning electron microscopy (SEM), elemental-dispersive X-ray analysis (EDX), Micro-Vickers hardness test, and contact profilometer. Results show that Group C has the highest hardness value of 1487 ± 126.1 Hv and surface roughness of 1.319 ± 0.3 µm with coefficient of friction being 0.4. SEM analysis revealed that the wear observed on the surfaces of Group B and Group D was due to fatigue rather than abrasion. It was concluded from this study that friction and wear performances of Group A had no visible wear track with coefficient of friction being 0.38 and hardness value of 1408.5 ± 135.4 Hv. These results indicate that Group A and Group C are more favorable for clinical applications.

The influence of the central warehouse on the functioning of Polish small and medium-sized enterprises operating in group purchasing organizations

Growing competition in the market forces primarily small and medium enterprises (SMEs) to implement certain mechanisms that will allow them to build an advantage over the competition. Most often, SMEs try to work together as part of multi-stakeholder organizations and organize themselves into group purchasing organizations (GPOs) with the central warehouse to improve the financial state of enterprises. The article aims to assess and analyze the impact of the central warehouse on the performance of Polish SMEs operating in group purchasing organizations. The research group comprised of 172 trading enterprises operating in Polish group purchasing organizations. The investigated companies were divided into two groups. In the first group, there were companies operating within GPOs, which have a central warehouse. In the second group, there were companies in which central unit does not have a central warehouse. The analysis and research showed that the central warehouse has a positive impact on financial security of small and medium enterprises operating in group purchasing organizations. The use of central warehouse optimizes the most costly current assets component – inventories. This is confirmed by better results of inventory turnover ratios in days, reduced share of inventories in the structure of current assets, and optimization of financial liquidity ratios.

Some Results on Polish Groups

We prove that no quantifier-free formula in the language of group theory can define the ℵ1-half graph in a Polish group, thus generalising some results from [6]. We then pose some questions on the space of groups of automorphisms of a given Borel complete class, and observe that this space must contain at least one uncountable group. Finally, we prove some results on the structure of the group of automorphisms of a locally finite group: firstly, we prove that it is not the case that every group of automorphisms of a graph of power λ is the group of automorphism of a locally finite group of power λ; secondly, we conjecture that the group of automorphisms of a locally finite group of power λ has a locally finite subgroup of power λ, and reduce the problem to a problem on p-groups, thus settling the conjecture in the case λ = ℵ0.

An in vitro study to compare the surface roughness of glazed and chairside polished dental monolithic zirconia using two polishing systems.

Aim:To evaluate the efficiency of two commercially available polishing systems in reducing surface roughness of a monolithic zirconia after clinical adjustment and to compare them to glazed zirconia.Setting and Design:In vitro study.Material and Methods:This in vitro study was conducted on 25 discs (10mm in diameter and 2mm in thickness) using monolithic zirconia (Ceramill Zolid). From 25 specimens, 5 specimens were randomly selected as the positive control. The remaining discs were abraded for 15 secs with a red band diamond finishing bur using an air rotor handpiece. Then the specimens were randomly divided into 5 equal groups of 5 specimens each. Group 1: Roughened, unpolished and unglazed. Group 2 (Positive Control): Glazed without prior roughening,Group 3: Roughened and polished with eZr polishing kit, Group 4: Roughened and polished with Optra fine ceramic polishing kit and Group 5: Roughened and glazed. The surface roughness (Ra) values (μm) were measured quantitatively by a surface analyzer. The mean values were compared using one-way ANOVA and Post Hoc Test. One specimen of each group was evaluated qualitatively under a scanning electron microscope(SEM) for surface topography.Statistical Analysis Used:One-way ANOVA and Post Hoc Test.Results:The lowest Ra value was found in Group 4-Roughened and polished with Optrafine ceramic polishing kit (Ra=0.47μm) as compared to Group 3-Roughened and polished with eZr polishing kit (Ra=0.49μm) and Group 5-Roughened and glazed (Ra=0.59μm). There was no stastistically significant difference between two polishing systems. SEM analysis of surfaces polished with Optrafine polishing kit revealed smoother and regular morphology as compared to surfaces polished with eZr polishing kit.Conclusion:The Optrafine polishing kit created more smoother and uniform surfaces as compared to surfaces polished with eZr polishing kit both quantitatively and qualitatively. Also, lowest surface roughness values were produced by optrafine ceramic polishing kit on monolithic zirconia as compared to glazed monolithic zirconia after their clinical adjustments.Thus Optrafine ceramic polishing kit can be used as alternative to glazing.

Impact of anterior capsular polishing on capsule opacification rate in eyes undergoing femtosecond laser-assisted cataract surgery.

Purpose:To evaluate the impact of anterior capsular polishing on capsule opacification and contraction in eyes undergoing femtosecond laser-assisted cataract surgery (FLACS).Methods:This prospective interventional comparative analysis included patients undergoing FLACS between August 2016 and May 2017. The eyes were subdivided into three groups based on the extent of intraoperative anterior capsular polishing performed: complete 360-degree polishing; inferior 180-degree polishing; and no polishing. Visual acuity, posterior capsular opacification (PCO) score, anterior capsular opacification (ACO) grade, and capsulorhexis diameter were evaluated at 1-week, 6-months, and 1-year postoperative visits.Results:The study included 99 eyes of 90 patients. No significant differences were observed between the three groups in ACO grade and capsulorhexis contraction at all follow-up visits. There was a statistically significant difference in PCO grade among the groups at 6-month and 1-year follow-up but it was found to be clinically insignificant. One eye in the no polishing group underwent neodymium:yttrium-aluminum-garnet (Nd:YAG) capsulotomy at the 1-year follow-up visit.Conclusion:A lower incidence of PCO was demonstrated in the 360-degree polishing group, although it was visually insignificant. No significant difference in postoperative capsular contraction was demonstrated between the cohorts up to one-year follow-up.

Commentary: Anterior capsule polishing: The present perspective.

Commentary: Anterior capsule polishing: The present perspective.

Polishability of some groups of interval and circle diffeomorphisms

Let $M=I$ or $M=\mathbb{S}^1$ and let $k\geq 1$. We exhibit a new infinite class of Polish groups by showing that each group $\mathop{\rm Diff}_+^{k+AC}(M)$, consisting of those $C^k$ diffeomorphisms whose $k$-th derivative is absolutely continuous, admits a natural Polish group topology which refines the subspace topology inherited from $\mathop{\rm Diff}_+^k(M)$. By contrast, the group $\mathop{\rm Diff}_+^{1+BV}(M)$, consisting of $C^1$ diffeomorphisms whose derivative has bounded variation, admits no Polish group topology whatsoever.

Generalized Problematic Internet Use Scale 2: Results of Validation on Polish Sample

This study aims to adapt the Problematic Internet Use Scale. The scale of Generalized Problematic Internet Use is an important tool for measuring the intensity of the problem. Widely used in English, Portuguese or Italian, it indicates the importance of the obtained result. Validation of the Polish group will allow to use it in Polish conditions. In order to validate the results, the 523 (516 after data cleaning) group of Internet users was surveyed. The study covered people of Polish origin aged 18-47, 304 women and 212 men. The original tool was translated two times, into Polish and then into English by independent translators. There were conducted Exploratory Factor Analysis that showed five-factor structure, which explained 73.9% of variance; chi 2 /df = 1.21; Confirmatory Factor Analysis showed good fitness of proposed model, chi 2 /df = 1.66, RMSEA = 0.035 and reliability measured by Cronbach alpha was 0.89. The obtained results indicate satisfactory psychometric values of the Polish version of Generalized Problematic Internet Use Scale 2. The conducted validation may contribute to a wider application in the Polish group, also in further research and constitute an important tool for scientific purpose s. Due to the theoretical background of the Problematic Use of the Internet, the adapted questionnaire can be used as well for preventive actions.

Every Beginning is Difficult. From Linke-Hofmann-Werke to PAFAWAG

The conclusion of the World War II in 1945 saw the region of Lower Silesia transferred to Polish administration. Although economic and industrial reconstruction was an important task, the issue of how this process took place and the reasons for the successes and failures of reconstruction have rarely been discussed in historiography. To date there is no historical research on the beginnings of the PAFAWAG company. This paper addresses this research gap, partly by focusing on the turbulent history of the biggest rolling stock producer in Lower Silesia, Linke-Hofmann-Werke AG, which was the predecessor of PAFAWAG. The paper focuses on the evacuation of the company by the Wehrmacht at the beginning of 1945, the dismantling of machinery and devices by Soviet “trophy battalions”, the takeover of the factories by the Polish KERM protection groups, and the reactivation of their production.

Effect of surface finishing treatments on the color stability of CAD/CAM materials.

PURPOSEThe aim of this study was to evaluate the effect of different surface finishing processes on the color stabilities of lithium disilicate glass-ceramics, zirconia-reinforced lithium silicate ceramics, and resin nanoceramics after artificial ageing.MATERIALS AND METHODS216 samples were prepared from 3 different CAD/CAM materials (LAVA Ultimate, IPS e.max CAD, VITA Suprinity) with A1 HT color at a size of 14 × 12 mm and a thickness of 0.5 ± 0.05 mm. Color measurements of the samples were performed with a spectrophotometer using color parameters and CIE Lab color system on a gray backing between baseline color and after 5000 cycles of artificial ageing in 4 stages (i.e. the first measurement before the treatment, the second measurement after polishing, the third measurement after cement application, and the fourth measurement after artificial ageing). The results were evaluated using the Variance analysis and Fisher's LSD test.RESULTSResin nanoceramics (LU) exhibited higher color change values than zirconia-reinforced lithium silicate (VS) and lithium disilicate (EC) ceramics after artificial ageing. Manual polishing and glazing resulted in similar color change for LU and VS (P>.05). In the EC group, glazing provided statistically different results as compared to the manual polishing and control groups (P<.05). Among the ceramic groups, color change values of the subgroup, which was treated by glazing, of the zirconia-reinforced lithium silicate (VS) and lithium disilicate (EC) samples were below the clinically acceptable level (ΔE < 3.5).CONCLUSIONThe lowest color change for all stages was observed in Vita Suprinity.

Recommendations of the Polish Group of Experts for HCV for the treatment of hepatitis C in 2020.

The recommendations set out the principles of diagnosis and treatment of hepatitis C virus (HCV) infections according to the most recent knowledge. The main goal of therapy for HCV infection is to eliminate the virus from the body, which consequently leads to arrest of progress or regression of changes in the liver. Current version of the recommendations prioritise pangenotypic regimens and provide guidelines in special populations of patients, such as children, cirrhotics, human immunodeficiency virus (HIV) and hepatitis B virus (HBV) coinfected, those with renal failure, hepatic decompensation and non-responders to previous therapies.

Effect of Different Surface Finishing Procedures on the Color and Translucency of two CAD/CAM Monolithic Glass Ceramics

Purpose: The purpose of this study was to investigate the effects of different surface finishing procedures, storage solutions, and prophylactic polishing on the color and translucency parameters (TPs) of two machinable glass ceramics; lithium silicate glass-ceramic (Obsidian)and lithium disilicate reinforced glass-ceramic (IPS e-max CAD). Materials and Methods: Obsidian and e-max milling blocks were sectioned with a low speed cutting machineunder water cooling into square specimens (10×10×1 mm3)(N=60). The specimens were divided into 3 groups (n=10 each) according to the received surface treatment; finishing and polishing, glaze, and staining and glaze in accordance with manufacturers’ instructions. Then, each group was further subdivided into 2 storage subgroups, coffee and distilled water as a control (n =5 for each subgroup). Color and translucency values were measured in CIELAB color space with spectrophotometer at the initial stage, and following 18 days, and after fine-grit prophylactic polishing paste application. Color changes (ΔE) and translucency (ΔTPs) were calculated and statistically analyzed using One-way ANOVA for comparing surface treatment followed by Tukey’s pair-wise if showed significant. Student t-test was used within material type to show effect of staining. Multifactorial analysis of variance ANOVA was performed to detect significance between variables (material type, surface treatment, immersion solution and re-polish).Results: There was a statistically significant difference between the ΔE values of both immersion solutions as (p = water) for both ceramics tested. Obsidian and e-max, glaze procedure showed lower color change values than finishing and polishing and staining and glazing surface(p > 0.05) following coffee storage. It was found that re-polish decreased color change significantly for both tested ceramics. The translucency was affected according the monolithic CAD/CAM ceramic type. The translucency of the e-max was found to be higher than that of obsidian glass-ceramic. Colorant coffee solution decreased the translucency of both obsidian and e-max ceramics. According to the results of this study, mechanical polishing exhibited highest translucency than stained and glazed and glazed groups. The re-polishing procedure decreased translucency parameter non-significantly for both tested ceramics. Conclusions: Within the limitations of this study, the following conclusions could be drawn: Staining drinks as coffee had a negative effect on the color stability and translucency of both obsidian and e-max glass ceramic materials tested. Glaze procedure led to more color stability with respect to finishing and polishing and stained and glaze for both ceramics after 18 days coffee storage. Polishing paste led to a decrease in color changes for both ceramics tested. The translucency was affected according the monolithic CAD/CAM ceramic type. The translucency of the e-max lithium disilicate glass-ceramic was found to be higher than that of obsidian lithium silicate glass ceramic after different finishing procedure, after coffee storage and after re-polish. Finished and polished groups presented the highest translucency than stained and glazed and glazed for both ceramics tested. Re-polish decreased translucency parameters non-significantly for both tested ceramics.

Polacy w Berlinie i Londynie: różne oblicza sukcesu migracyjnego. Część 1

The article concerns Poles living in Berlin and London, who managed to deal with the integration process and achieved personal success on various levels. Although the research used in the text concerned migrations that began in the 1980s and continue to this day, it particularly focuses on post-accession migrants. At the beginning, I have presented the research assumptions on which the studies were based and the conclusions drawn on their basis. I also have included methodological foundations of research. Next, I have discussed the situation of two West European cities, Berlin and London, in a migration context, and the specificity of the Polish group as seen against this background. The article is the first, introductory part of an integrated cycle. It isdeveloped in the text Poles in Berlin and London: different faces of migration success. Part 2 by Anna Szymoszyn, published in the same issue of JUE.