Amphibians in an urban environment: a case study from a central European city (Wrocław,Poland)

Urban Ecosystems - In 2016, we studied the occurrence of amphibians in 231 selected ponds in the city of Wroc?aw (Lower Silesia, Poland) and confirmed the occurrence of 10 species: Bombina...     

Estimation in singular partitioned,reduced or transformed linear models

A singular partitioned linear model, i.e. the singular model comprising the main parameters and the nuisance parameters, can be reduced, or transformed to the form in which only linear functions concerning main parameters are involved. In the paper some properties of the best linear unbiased estimators of these functions following from these models are considered.     

An association between bone mineral density and anabolic hormones in middle-aged and elderly men with prediabetes

Introduction: Prediabetes (PD) leads to reduced testosterone (T) in males, but the association between the anabolic hormones and bone mineral density (BMD) remains unknown.

Objectives: We investigated an association between the anabolic hormones and BMD in middle-aged and elderly men with PD.

Methods: We investigated 84 prediabetic and 56 control men. Total T (TT), calculated free T (cFT), and dehydroepiandrosterone sulfate (DHEAS) were measured, and BMD was assessed using DXA methods.

Results: Patients with PD had lower TT (p?p?<?.005), and DHEAS (p?<?.02) than control group. BMD values of the lower lumbar spine (p?<?.02) and total body (p?<?.05) in prediabetic men were lower than in control group. Lumbar spine BMD correlated with TT (r?=?0.376), cFT (r?=?0.235), and HbA1c (r?=??0.368); femoral neck BMD correlated with TT (r?=?0.412) and cFT (r?=?0.421). The high lumbar spine and femur neck BMD was associated with high TT, cFT, and low HbA1c, while the high total body BMD with high TT, cFT, and low HbA1c.

Conclusion: The anabolic hormones significantly affect BMD in male with PD, and screening for low BMD is necessary in these patients.     

Packing <Emphasis Type="Bold">[1, Δ]</Emphasis>-factors in graphs of small degree

Given an undirected, connected graph G with maximum degree Δ, we introduce the concept of a [1, Δ]-factor k-packing in G, defined as a set of k edge-disjoint subgraphs of G such that every vertex of G has an incident edge in at least one subgraph. The problem of deciding whether a graph admits a [1,Δ]-factor k-packing is shown to be solvable in linear time for k = 2, but NP-complete for all k≥ 3. For k = 2, the optimisation problem of minimising the total number of edges of the subgraphs of the packing is NP-hard even when restricted to subcubic planar graphs, but can in general be approximated within a factor of by reduction to the Maximum 2-Edge-Colorable Subgraph problem. Finally, we discuss implications of the obtained results for the problem of fault-tolerant guarding of a grid, which provides the main motivation for research.     

Effects of human-related disturbance on breeding success of urban and non-urban blue tits (<Emphasis Type="Italic">Cyanistes caeruleus</Emphasis>)

There is a need to study the effects of urbanization on wildlife in order to understand the ecological implications of increasing urbanization and find out how to reduce its threats to biodiversity. The blue tit evolved as a forest species and prefers deciduous and mixed forests, whereas its nesting in urban habitats is a more recent phenomenon. Our long-term study of blue tit populations has been conducted in two habitats: an urban parkland (frequently visited by people) and a deciduous forest outside of the city. Using linear mixed modeling, we revealed that a relationship of blue tit breeding success (and the number of fledglings) with thermal conditions in May differed between the urban parkland and the forest. While the relationship was positive in the forest, it was negative in the parkland. In addition, breeding success in the parkland increased with increasing number of rainy days in May. We argue that the main possible reason for such patterns is human activity in the parkland, which interferes with tit parental care, especially the regular feeding of nestlings, whereas it is evidently associated with weather conditions. Human disturbance in the forest is likely to be negligible.     

On the robustness of the linear hypothesis test procedure in the singular linear model with implied restrictions

The linear hypothesis test procedure is considered in the restricted linear modelsM _r = {y, Xβ |Rβ = 0, σ ²V} andM _r ^* = {y, Xβ |ARβ = 0, σ ²V}. Necessary and sufficient conditions are derived under which the statistic providing anF-test for the linear hypothesisH ₀:Kβ=0 in the modelM _r ^* (M_r) continues to be valid in the modelM _r (M _r ^* ); the results obtained cover the case whereM _r ^* is replaced by the general Gauss-Markov modelM = {y, Xβ, σ ²V}.     

Allocation Constraints in Stratification

When a finite population is to be stratified, one of constraints in stratification is that sample sizes from strata may not be greater than the corresponding stratum sizes and may not be smaller than two. There are several ways of treating this allocation constraint, each providing an alternative approach to stratification. In this article, it is shown that a choice of the approach has a bearing on stratification efficiency. Unfortunately, no particular approach out of the four compared is shown to be the most efficient for each population studied. In addition, the approaches are applied to stratify a real population.     

Variability of bumblebee communities (Apidae,Bombini) in urban green areas

Based on current research the agglomerations are potentially desirable habitats for bumblebees. However, the relationship between the biodiversity of these bees and the green areas where they live is poorly understood. The aim of the study was to estimate the influence of green areas (ranging from 8 to 102 ha) of big cities on bumblebee species richness, composition, and the relative number of these insects. The studies were conducted within the administrative borders of the city of Wroc?aw (Poland) in 2011–2012 in 12 green areas such as parks, cemeteries and other places with trees and shrubs. Species richness and abundance of bumblebees was determined by direct observation during 30 min. The gathered materials were used to calculate how areas of urban green space affected qualitative and quantitative bumblebee community structure. In total, 13 species of bumblebees (Bombus Latr.) were recorded, of which 3 belonged to cuckoo bumblebees (Psithyrus subgenus). The share of the most similar groups was congregated in green areas not smaller than 30 ha. This was proved by analysis of qualitative structure (Sørensen index), quantitative structure (Renkonen index), and qualitative-quantitative structure (Cody’s index). The number of bumblebee species in the surveyed green areas (r = 0.7497) was decisive for the arrangement of the mutual similarity of group structure. Green urban areas should be created in a size of at least 30 ha. Such sites provide conditions for the most diversified bumblebee species communities. Sites smaller than 30 ha can play an important role as refuges, and allow migration to all pollinators.     

Emigration of Poles to the United Kingdom: history,present state and future prospects

The history of Polish immigration within the United Kingdom is several centuries old. Yet never in its history was such a mass migration as that after the Polish accession to the EU in 2004. During the over ten years that followed, almost a million Poles chose to settle in the United Kingdom. This article reviews and analyses past and present Polish emigration to the United Kingdom. It provides answers to questions regarding who the Polish immigrants are, what work they perform and how they have integrated within British society. It also considers the factors that have influenced the future dynamics of migration from Poland. Based on these, we have formed the hypothesis that while the years of 2004‐2016 saw, statistically, the largest emigration from Poland to the United Kingdom in recorded history, in the future, the number of Polish expatriates living in the United Kingdom will drop or at least the number of newcomers will decrease.     

Recoverable robust spanning tree problem under interval uncertainty representations

This paper deals with the recoverable robust spanning tree problem under interval uncertainty representations. A strongly polynomial time, combinatorial algorithm for the recoverable spanning tree problem is first constructed. This problem generalizes the incremental spanning tree problem, previously discussed in literature. The algorithm built is then applied to solve the recoverable robust spanning tree problem, under the traditional interval uncertainty representation, in polynomial time. Moreover, the algorithm allows to obtain several approximation results for the recoverable robust spanning tree problem under the Bertsimas and Sim interval uncertainty representation and the interval uncertainty representation with a budget constraint.