Polish Group Research Articles

Letters to the Editor

Letters to the Editor

Opposition in Hungary and Poland during the State-Socialist Period: An Attempt at Comparing and Mapping Relations

Abstract The aim of this study is to describe the different political and social conditions of opposition activity in Hungary and Poland between 1956 and 1989, and to map the relations between the various opposition groups. It starts from the premise that after 1956 radically different political, economic, and social conditions developed in the two countries. While in Poland the situation was relatively favorable for opposition activity, in Hungary the possibilities were limited; and only in the late 1970s, and especially after the birth of the Polish Solidarity movement, did the scope for action increase. In this article, I argue that the political, ideological, and generational determinants of Hungarian opposition groups in Hungarian-Polish opposition relations have been decisive in their choice of Polish partners. Hungarian opposition groups contacted Polish groups whose worldview corresponded to their own as this aspect was more important to them than the oppositional attitude itself. The article points out that the East-Central European opposition movement was a transnational phenomenon—not only because the task of all oppositions was to formulate and represent responses and reactions to the socialist system but also because they converged and interacted through their internal relations, channels, and mutual interactions.

Changes in psychological distress among Polish medical university teachers during the COVID-19 pandemic.

Our study aims to update knowledge about psychological distress and its changes in the Polish group of academic medical teachers after two years of a global pandemic. During the coronavirus disease, teachers were challenged to rapidly transition into remote teaching and adapt new assessment and evaluation systems for students, which might have been a completely novel situation that was not addressed before, especially in medical universities in Poland. We conducted a cross-sectional study at Poznan University of Medical Sciences from March to April 2022. The questionnaire included self-reported information on anxiety, stress, and depression. We found that post-pandemic levels of anxiety, stress, and depression have significantly (p<0.001) improved compared to initial levels at the beginning of coronavirus disease. In multivariate models, females had higher odds of improving levels of anxiety (OR = 0.46; 95% CI = -1.58-(-0.03); p = 0.04), stress (OR = 0.36; 95% CI = -1.83-(-0.22); p = 0.01), and depression (OR = 0.0.37; 95% CI = -1.58-(-0.12); p = 0.03). Anxiety, stress, or depression were not significantly associated with years of experience, the number of taught subjects, and weekly teaching hours, but only with the academic work during COVID-19 (Spearman ranxiety = 0.37, rstress = 0.32, rdepression = 0.37, p<0.001). For the virtual learning concerns, 79% of teachers reported that students might engage less; and it was correlated with higher weekly teaching hours (r = 0.19, p<0.05). Even though only 29.8% reported cheating as a concern, it was correlated with a higher number of taught subjects (r = 0.2, p<0.05). Levels of anxiety, stress, and depression have improved as time passed, not affecting teachers' academic performance. Concerns about virtual learning have been raised, suggesting it may be conjoined with classroom learning but not as an alternative. Universities should highlight the importance of seeking psychological support and provide essential programs to employees. Teachers' coping skills with psychological distress should be further studied.

Well-being on supportive techniques in amyotrophic lateral sclerosis: from neurologists' perspective.

To investigate intercultural neurologists' perception of well-being in patients with amyotrophic lateral sclerosis (ALS) using gastrostomy (PEG), non-invasive, and/or invasive ventilation (NIV/IV) and to analyse the determinants and impact on the management of the above medical interventions (MIs). The study was based on anonymous questionnaires addressing the clinical approach and personal attitude towards the use of PEG, NIV and IV in ALS patients completed by 465 neurologists: 228 from Germany and 237 from Poland. The German and Polish neurologists estimated the quality of life in ALS patients using PEG and NIV as neutral, whilst low in individuals using IV. A regression model revealed an independent influence of palliative care training (PCT) and age on that attitude in the German group. Higher values of estimated patients' depressiveness on PEG, NIV and IV were found amongst the Polish neurologists. Marital status, experience in ALS and being a parent independently influenced the perception of patients' depressiveness in the German, whilst marital status, age and PCT were factors in the Polish group. Amongst German neurologists, a higher perception of patients' depressiveness in individuals using PEG, NIV and IV was linked to the later timing of the MIs discussion. In the Polish group, it was a lower estimation of QoL in patients using PEG. Neurologists' perception of ALS patients' well-being on MIs reflects their demographic status, professional experience and potentially their cultural background. This perception plays an important role in the timing of MIs discussion, possibly influencing the decision-making process.

Surface characteristics assessment among layers of different translucent multilayered dental zirconia related to aging

Considering that the surface characteristics and microstructure are relevant factors that may affect the appearance and strength of a material, this study aims to analyse the differences regarding surface roughness and microhardness among layers of three types of dental zirconia: super-high translucent zirconia Ceramill Zolid fx ML (5Y-TZP), super-translucent zirconia STML (4Y-TZP), and IPS e.max ZirCAD CEREC/in Lab MT Multi (4Y + 5Y-TZP), also evaluating the influence of the surface treatment performed by glazing and polishing-before, respectively after aging-by thermocycling. Forty plate-shape specimens were sectioned from the ceramic blocks with a precision disc, polished and sintered according to the manufacturer’s instructions and then, equally divided - the surface of some was finished by polishing and the others by glazing; from each category was formed a control (polished/glazed) group and one subjected to termocycling (polished/glazed) − 30.0000 cycles in a 5˚C and a 55˚C bath with distilled water in a thermocycler, resulting four groups of ten samples, for a material. The assessment of surface roughness (Ra, Rz) was performed with a contact profilometer, with Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM); Vickers hardness (VH) values were recorded with a microhardness tester. The evaluations of the surfaces were achieved in each area: incisal, medium, cervical. For statistical analyses, paired sample t-Test, unpaired sample t-Test, two-way ANOVA test (α = 0.05), Pearson's correlations were used. Both before and after thermocycling, polishing and glazing, as surface treatment have a significant effect on roughness, respectively on microhardness; no statistical differences were observed among areas, on each polished or glazed surface. On the glazed samples, the values recorded for surface roughness were significant higher and for microhardness-lower, compared with those of the polished group. After thermocycling, microrougness increased for STML and all polished specimens and decreased on glazed surfaces of Ceramill Zolid fx ML and IPS e.max ZirCAD CEREC/in Lab MT Multi. Concerning microhardness, the thermocycling procedure had no significant influence. The super-high translucent material was less affected by aging than the super-high translucent zirconia.

Osteoblast behaviour on zirconia fabricated by additive and subtractive technology

Zirconia is an attractive material for the manufacturing of oral implants and patient-individual barriers for guided bone regeneration. This study compared osteoblast behaviour on additive manufactured and milled 3-mol% yttria-stabilized tetragonal polycrystal zirconia (ZrO2).Two groups of samples (Ø5 × 2 mm) were manufactured by stereolithography (LithaCon 230, Lithoz, Vienna, Austria) and subsequently heat-treated and sintered. One group remained superficially unmodified (AM-ZrO2-unmod.), while the other was polished according to DIN EN ISO 6872 standard using automated grinding (AM-ZrO2-pol.). For comparison, milled samples (e.max ZirCAD LT, Ivoclar Vivadent, Schaan, Liechtenstein) were sintered and polished similarly (Mil-ZrO2-pol.). Surface roughness was characterized using tactile profilometry. Adhesion, proliferation and coverage of human fetal osteoblasts (hFOB 1.19) as well as expression of osteogenic marker genes ALPL and RUNX2 were determined (and statistically compared using Kruskal-Wallis-analyses and Dunn's Post-hoc-tests).The surface roughness of AM-ZrO2-unmod. Was 45 times higher than that of the polished groups. No significant differences were detected between the three groups regarding cell adhesion and proliferation. With regard to cell coverage, AM-ZrO2-pol. Significantly outperformed the two other groups (p < 0.05). ALPL- and RUNX2-mRNA expression was insignificantly superior for AM-ZrO2-unmod. Compared to the two other groups. Therefor no detrimental effect on osteoblast behaviour caused by the investigated, acrylic binder-based 3D printing workflow was observed.

SOCIAL RESPONSIBILITY OF PUBLIC CULTURAL INSTITUTIONS – THE EXAMPLE OF MUSEOLOGY. OBSERVATIONS, REFLECTIONS AND PRELIMINARY ANALYSIS – SUMMARY OF THE FOCUS GROUP STAGE

The term ‘social responsibility of museums’ implies various associations, most frequently referring to the sphere of management and the activities of commercial entities in accordance with the ISO 26000 standard. In this article, we report on some of the tasks performed in connection with a project based on a sociological perspective and addressing the social responsibility of public cultural institutions such as museums. As this concept is relatively new, we decided to check how it is understood in the social world of Polish museum professionals. The research was therefore carried out using elements of the grounded theory methodology, i.e., the concepts (categories) were not defined at the outset, but defined and characterised in the course of the research according to the understanding of the respondents. Using a triangulation of methods, an analysis of found data, individual interviews in Polish museums (IDI) and focus group interviews (FGI) in Polish and international groups were conducted. A particularly interesting strand of the Project was museum education and its growing importance. This article focuses on the conducted focus group interviews (FGI). A specific commentary on the findings is provided by the reflections given during a guest lecture by Dr Bernadette Lynch organised as part of the Project.

Sex differences in clinico-pathologic characteristics and long-term survival among 17,192 surgically treated NSCLC patients: Nationwide population-based propensity score-matching study

IntroductionMore information is needed on gender differences in lung cancer surgery. Thus, we conducted a retrospective study on thoracic treatment of non-small cell lung cancer (NSCLC) patients between 2007 and 2020 in Poland. The aim was to characterize sex differences in survival after complete surgical resection and to compare postoperative complications between Polish men and women. The main aspects that were compared between women and men were as follows: type of surgery and postoperative staging, morbidity and mortality, thoracic surgery complications, comorbidities, and overall survival based on a univariate analysis including propensity score matching (PSM) and a multivariate analysis. Materials and MethodsData were collected retrospectively from the Polish Lung Cancer Study Group database. Patients who were surgically treated for NSCLC between 2007 and 2020 (n = 17,192) were included in the study. ResultsThe univariate analysis showed significantly better survival in women than in men. Women had better 5-year survival compared to men both for adenocarcinoma and squamous cell carcinoma (66% vs. 53%, p < 0.0001 and 65% vs. 51%, p<0.0001%, respectively), for both smokers and non-smokers (65% vs. 52%, p < 0.0001 and 65% vs. 51%, p < 0.0001, respectively), all age groups, and all stages (IA1 to III B). In the PSM analysis, statistically significant differences in favor of women were found for lower lobectomy (67% vs. 50%, p < 0.0001) and upper lobectomy (67% vs. 56%, p < 0.0001). Overall, postoperative complications occurred in 33.1% of patients and were observed more often in men than in women (35.8% vs. 28.6%, p < 0.001). ConclusionsWomen with NSCLC who were treated surgically had a better long-term outcome compared to men, with no significant difference in disease severity. In addition to gender, the histological type, comorbidities, and type of surgery and surgical approach are also important.

Influence of anterior capsule polishing on capsular bag and IOL position after phacoemulsification

Background- Phacoemulsification is considered not only as a cataract surgery but also as a refractive surgery due to negligible astigmatism following micro incision and refractive error correcting/ presbyopia correcting IOLs. Objective- To evaluate the effect of anterior capsule polishing on capsular bag and IOL position after phacoemulsification. Methods- In this prospective randomized clinical trial comprised of 120 eyes of 60 consecutive patients with bilateral age related cataract who undergoes phacoemulsification in VMKVMCH, Salem is evaluated. The ACD was measured 1 week, 1 month, 3 months and 6 months and1 year after surgery. The actual axial movement of IOL was defined as the root mean square (RMS) of the change in ELP at each visit. Results- A total of 120 eyes of 60 patients were included, and 60 patients (50%) were men. All the patients underwent uneventful surgeries with­out intra-operative or postoperative complica­tions, and returned on time for measurements. The mean age of them was 70.4±7.2 years (range 54 to 78 years). Mean ELP among differ­ent visits of the polished group was more stable than that of the control group.

Computable topological abelian groups

We study the algorithmic content of Pontryagin - van Kampen duality. We prove that the process of dualization is computable in the important cases of compact and locally compact totally disconnected Polish abelian groups. The applications of our main results include solutions to questions of Kihara and Ng about presentations of connected Polish spaces, and an unexpected arithmetical characterisation of direct products of solenoid groups among all Polish groups.

The Effect of Glazing, Reglazing, and Polishing on Zirconia Biaxial Flexural Strength

Zirconia restorations are usually coated with glazing to provide an aesthetic and reduce wear on opposing teeth. Occlusal adjustments such as grinding and polishing to eliminate occlusal or internal interferences can affect the mechanical properties of zirconia. The purpose of this study was to evaluate the effect of glazing, reglazing, and polishing procedures on the biaxial flexural strength of zirconia ceramic. This experimental study used 20 samples of zirconia discs (12x1,2 mm), which were divided into fourth groups (n=5). The first group was zirconia discs without treatment as control, the second group with glazing treatment, the third group with reglazing treatment, and the fourth group with polishing treatment. Biaxial flexural strength was determined using a piston on three balls technique. The data were analyzed using 1-way ANOVA and t-test. The results of this study showed no statistically significant difference between the group with glazing, reglazing, polishing and the control group (p&gt;0.05). The highest zirconia biaxial flexural strength was found in the polished group but not significant statistically (1913.64 ± 594.28 MPa). The reglazing group with the lowest average biaxial flexural strength was (1413.01 ± 365.66 MPa). It can be concluded that there were no differences in biaxial flexural strength between the polishing, glazing, and reglazing group. The use of polishing can be an alternative technique to improve aesthetics besides glazing and reglazing because it does not impair the biaxial flexural strength of zirconia.

Polish Contribution to Global Research on Somatic Embryogenesis

AbstractSomatic embryogenesis (SE) is a complex process that begins with regaining totipotency in some somatic cells, proceeds through embryo development and maturation, and ends with the formation of a whole plant. Since the first publications on SE in 1958, this regeneration process has been applied to the in vitro propagation of many plant species and has led to the development of some specific model systems. SE has been used to expand our understanding of the cytomorphological, physiological, biochemical, and genetic processes that govern the earliest developmental events in the life of plants. This paper summarizes the achievements of Polish research groups working on SE systems established for several plants (gentians, the tree fernCyathea delgadiiSternb., and conifers) and three model species (Arabidopsis thaliana,Medicagosativa, andM. truncatula). SE systems have used a broad spectrum of experimental approaches involving genomic tools (transcriptomics, proteomics, and chromatin analyses), physiological methods which focus on phytohormones, and cytological techniques. Studies on the experimental models ofA. thalianaandMedicagospp. have resulted in the identification of new genetic and epigenetic elements of the complex regulatory network controlling embryogenic induction in plant somatic cells. The protocol developed for ferns has provided a unique and simple system for cytological analysis of early SE events that occur in a single cell of initial explants. Gentian embryogenic suspension cultures have successfully been used in broad biotechnological applications, including plant transformation, protoplast isolation, culture, and fusion. Systems described for coniferous species effectively produced many vigorous somatic seedlings and cost-efficient storage of genotypes during clonal field-testing. The research undertaken by Polish scientists has resulted in developing experimental systems that have enabled significant advances in SE knowledge.

Evaluation of the Effect of Different Polishing Systems on the Color Change of the New Alkasite Restorative Material

Amaç: Bu çalışmanın amacı, farklı sistemlerle polisajlanmış diş dolgularında kullanılan alkasitin bir renklendirici ajana maruz kalmasının ardından 24. saat ve yedinci gününde oluşan renk değişimlerinin incelenmesidir. Yöntem: 8 mm çapında ve 2 mm yüksekliğinde teflon kalıplar içerisine yerleştirilen alkasit materyali mylar strip uygulaması altında polimerize edildi ve toplam 30 adet örnek elde edildi (n=10). Materyaller rastgele 3 gruba ayrıldı; Grup 1: Elmas grenli polisaj lastikleri (Twist Dia; Kuraray, Japan), Grup 2: Alüminyum oksit diskleri (Sof-Lex; 3M ESPE, MN, USA) uygulanarak polisaj işlemi tamamlandı. Grup 3’te polisaj sistemi uygulanmadı. İlk renk ölçümü bir spektrofotometre kullanılarak gerçekleştirildi. Kahve içerisine daldırıldıktan 24. saat ve 7. gün sonra ikinci ve üçüncü renk ölçümleri aynı cihaz ile tamamlandı. CIEDE2000 renk formülü kullanılarak renk değişimleri (ΔE00) belirlendi. Bulgular tek yönlü ANOVA ve Tukey testi kullanılarak %95 güven aralığında analiz edildi. Bulgular: ΔE00 değerleri 24 saat ile 7. gün arasında alınan ölçümlerde tüm gruplar için istatistiksel olarak anlamlı bir artış gözlenmiştir. 24 saat sonunda en düşük ortalama renk değişimi değerleri Grup 2’de gözlenirken (p0,05). Kontrol grubu ise en yüksek renk değişim değerlerini göstermiştir (p

Adherence of Obese Patients from Poland and Germany and Its Impact on the Effectiveness of Morbid Obesity Treatment.

: ObjectivesThis study aimed to investigate and compare the adherence of patients treated for morbid obesity living in Poland and Germany. Methods: A cross-sectional international multicenter survey design was adopted. The study involved 564 adult subjects treated for morbid obesity at selected healthcare facilities in Germany (210 participants) and Poland (354 participants). A validated, custom-made questionnaire based on the literature related to this issue was used. Results: The degree of adherence was higher, but not statistically significant, among Polish patients (83.82% vs. 78.33%, p = 0.26140). Patient adherence was associated with gender, age, level of education, duration of obesity, number of health professionals involved in obesity treatment, and type of obesity treatment (p < 0.05). A positive correlation was observed in the case of age, level of education, and a growing number of health professionals involved in obesity treatment, whereas a negative correlation was observed in the case of the duration of obesity. Patients who underwent bariatric surgery significantly more often followed medical recommendations regarding lifestyle changes, compared to obese participants treated only conservatively. Adherence in the field of obesity treatment significantly increases the percentage of total weight loss and excess weight loss due to applied obesity treatment among both Polish and German groups (p < 0.001). Both the percentage of total weight loss and that of excess weight loss were significantly higher in the group of adherent patients compared to the nonadherent patients (p < 0.00001). The levels of perceived anxiety, stress, and depression were significantly higher in nonadherent patients in both countries. Conclusions: These findings confirm the role of adherence in the effective and satisfactory treatment of morbid obesity. There is a great need to improve patient adherence to overcome the consequences of the obesity pandemic.

Effect of Polishing on Lead and Cadmium Bioavailability in Rice and Its Health Implications.

Rice polishing is an important approach to reducing the concentrations of heavy metals in rice, but knowledge of its effect on the Pb and Cd bioavailability in produced rice and the related health risk remains limited. In this study, the effects of rice polishing on the bioaccessibility (BAC) and bioavailability (RBA) of Pb and Cd in rice are assessed using an in vitro method and an in vivo mouse bioassay. The Pb removal rate in brown rice (40%), lightly processed brown rice (62%), germinated rice (74%), and polished rice (79%) gradually enhanced with an increase in the polishing degree, while Cd was difficult to remove by polishing. The Pb and Cd BAC in germinated rice was the highest, while that in brown rice was the lowest. The polished rice Pb and Cd RBA in the liver and kidneys were significantly higher than those in the brown rice group. The Pb RBA in the livers and kidneys in the polished rice group was 26.6% ± 1.68% and 65.3% ± 0.83%, respectively, which was 1.6- and 2.6-times higher than that in the brown rice group, respectively. The Cd RBA values in both the livers and kidneys of the polished rice group were 1.3-times higher than those in the brown rice group. Although polishing reduced the total Pb in the polished rice, it was not enough to offset the increase in bioavailability, and its consumption risk was not weakened. This study highlighted the value of the oral-bioavailability-corrected health risk assessment for assessing the influence of rice polishing on Pb and Cd exposure via rice consumption.

Comparison of Surface Roughness and Color Stability of Different Denture Characterizing Composite Resins: The Effect of Different Surface Treatments.

This study aimed to investigate the effect of surface treatment and type of composite resin material on the color stability and surface roughness of different denture characterizing composites. Two nanohybrids [Gradia Plus Gum, (GP) and SR Nexco Paste Gingiva, (SR)] and one microhybrid gingiva-colored composite resin [Amaris Gingiva, (AG)] were investigated. A total of 120 disk-shaped samples were prepared, 40 of each material. Samples were divided into two groups (n = 20) for each material according to the surface treatmentapplied: conventional polishing (control) and coated with a sealant in addition to the surface polishing. All groups were thermocycled. The surface roughness (Ra) was measured using a profilometer after thermal cycling. The samples were then divided into 2 subgroups (n = 10) and stored for 7 days in distilled water or coffee solution. Color differences (ΔE00 ) were calculated with a spectrophotometer. Results were evaluated with Kruskal-Wallis and Mann-Whitney U statistical analysis. The type of denture characterizing composite material and surface treatment method revealed statistically significant differences for the ΔE00 (after immersion both in coffee and distilled water) and the Ra values of denture characterizing composite (p < 0.001 for both). All sealed groups showed significantly higher Ra than the all polished groups. Both in the polished groups and the sealant applied groups, the GP had the highest mean Ra values (0.29 ±0.05μm and 0.47 ±0.09μm, respectively). It was followed by SR (0.23 ±0.06μm and 0.41 ±0.10μm, respectively), and AG groups (0.20 ±0.06μm and 0.39 ±0.09μm, respectively). According to the mean ΔE00 results, all composite groups showed significantly higher ΔE00 values immersed in coffee solutions compared to distilled water. In coffee solutions, the highest ΔE00 was observed in the polished GP (1.90 ±0.40), and the lowest ΔE00 was observed in the polished SR (0.97 ±0.36). The sealed groups showed higher ΔE00 than the polished groups, except for GP. The surface roughness value of sealant applied groups were significantly higher than those of the polished groups. The surface sealant applicationsignificantly increased the staining of all composite groups compared to conventional polishing, except for GP.

In-lab simulation of CAD/CAM grinding and intaglio surface treatments of 4YSZ monolithic restorations: Effect on its load-bearing capacity under fatigue

ObjectivesTo evaluate the effect of in-lab simulation of CAD/CAM grinding and intaglio surface treatments on the surface characteristics (topography and roughness) and fatigue behavior of adhesively luted 4YSZ simplified restorations. MethodsCeramic discs (Ø = 10 mm, thickness = 1 mm) were randomly allocated into 6 groups considering: “In-lab simulation of CAD/CAM grinding” (ground or polished) and “intaglio surface treatments”: Ctrl (without surface treatment), AlOx (aluminum oxide air abrasion) or GLZ (glaze spray application). The surface roughness of all samples was measured, the treated discs received a ceramic primer, were luted with resin cement onto a dentin analogue material (woven glass-reinforced epoxy resin) and tested under a cyclic fatigue test (step-stress approach, n = 15; 1.4 Hz, 10,000 cycles/step, step-size of 100N starting at 200N until failure). A complementary analysis was performed to corroborate the findings in the fatigue test that the glaze fill defects increase the mechanical properties of the ceramic. To do so, bars (n= 10; 1.0 × 1.0 × 12 mm; considering the groups: N-ID: non-indented; ID: indented; ID-GLZ: indented plus glaze spray application) were indented in a vickers hardness tester to produce a crack pattern, treated with glaze or not, and then submitted to flexural strength tests (FS). Fractographic and topographic analysis were performed. ResultsIn-lab simulation of CAD/CAM grinding decreased the fatigue failure load of the 4YSZ ceramic when comparing polished and ground groups, regardless of surface treatment. GLZ induced better fatigue performance compared to the air abrasion, regardless of the grinding condition (ground or polished surface). The results of the flexural strength test corroborated the findings in the fatigue test, as the ID-GLZ group presented superior FS than the ID group, however both had inferior FS than N-ID. There is an inverse association between roughness and fatigue failure load, as the higher the surface roughness, the lower the fatigue failure load. Failures in the fatigue and flexural strength tests started from the face subjected to tensile stresses. ConclusionIn-lab simulation of CAD/CAM grinding had a detrimental effect on the fatigue behavior of 4YSZ and glaze spray induced better 4YSZ performance compared to the air abrasion. The intaglio surface treatments differently influenced the 4YSZ fatigue performance, however, only glaze spray can reverse the damage caused by the grinding.

Universal minimal flows of extensions of and by compact groups

Abstract Every topological group G has, up to isomorphism, a unique minimal G-flow that maps onto every minimal G-flow, the universal minimal flow $M(G).$ We show that if G has a compact normal subgroup K that acts freely on $M(G)$ and there exists a uniformly continuous cross-section from $G/K$ to $G,$ then the phase space of $M(G)$ is homeomorphic to the product of the phase space of $M(G/K)$ with K. Moreover, if either the left and right uniformities on G coincide or G is isomorphic to a semidirect product $G/K\ltimes K$ , we also recover the action, in the latter case extending a result of Kechris and Sokić. As an application, we show that the phase space of $M(G)$ for any totally disconnected locally compact Polish group G with a normal open compact subgroup is homeomorphic to a finite set, the Cantor set $2^{\mathbb {N}}$ , $M(\mathbb {Z})$ , or $M(\mathbb {Z})\times 2^{\mathbb {N}}.$

Haar null closed and convex sets in separable Banach spaces.

Haar null sets were introduced by Christensen in 1972 to extend the notion of sets with zero Haar measure to nonlocally compact Polish groups. In 2013, Darji defined a categorical version of Haar null sets, namely Haar meagre sets. The present paper aims to show that, whenever is a closed, convex subset of a separable Banach space, is Haar null if and only if is Haar meagre. We then use this fact to improve a theorem of Matoušková and to solve a conjecture proposed by Esterle, Matheron and Moreau. Finally, we apply the main theorem to find a characterisation of separable Banach lattices whose positive cone is not Haarnull.

Nonsingular Poisson Suspensions

The classical Poisson functor associates to every infinite measure preserving dynamical system (X, μ, T) a probability preserving dynamical system (X*, μ*, T*) called the Poisson suspension of T. In this paper we generalize this construction: a subgroup Aut2(X, μ) of μ-nonsingular transformations T of X is specified as the largest subgroup for which T* is μ*-nonsingular. The topological structure of this subgroup is studied. We show that a generic element in Aut2(X, μ) is ergodic and of Krieger type III1. Let G be a locally compact Polish group and let A: G → Aut2(X, μ) be a G-action. We investigate dynamical properties of the Poisson suspension A* of A in terms of an affine representation of G associated naturally with A. It is shown that G has property (T), if and only if each nonsingular Poisson G-action admits an absolutely continuous invariant probability. If G does not have property (T), then for each generating probability κ on G and t > 0, a nonsingular Poisson G-action is constructed whose Furstenberg κ-entropy is t.