By a sign pattern (matrix) we mean an array whose entries are from the set $\lbrace +,-,0\rbrace $. The sign patterns $A$ for which every real matrix with sign pattern $A$ has the property that its inverse has sign pattern $A^T$ are characterized. Sign patterns $A$ for which some real matrix with sign pattern $A$ has that property are investigated. Some fundamental results as well as constructions concerning such sign pattern matrices are provided. The relation between these sign patterns and the sign patterns of orthogonal matrices is examined.
Large veteran trees are key structures sustaining biodiversity in wooded landscapes. Many organisms associated with
such trees are, however, also able to inhabit suitable trees with smaller diameters or other surrogate habitats. Understanding the
mechanisms behind the importance of veteran trees and the conditions enabling veteran tree specialists to exploit smaller trees
might help conservation efforts targeted at the diverse and highly endangered biota associated with veteran trees. To investigate
this, we studied local patterns in the exploitation of trees by a veteran tree specialist, the great capricorn beetle (Cerambyx cerdo),
at three sites with different soil characteristics, namely fl oodplain, dry-sandy and dry-rocky sites, where this beetle exploits oaks
of large (~1.5 m), medium (~0.75 m) and small (~0.25 m) diameters, respectively. We recorded the presence and number of exit
holes made by C. cerdo on each tree and related these to the characteristics of the trees: their diameters, openness of the canopy
around them and their state of health. The probability of occurrence and the number of exit holes increased with tree diameter,
canopy openness, and decreasing tree health, but these relationships differed considerably among the study sites. In dry conditions, trees of small diameters were more likely to be exploited by the beetle than in the fl oodplain. The number of exit holes, on
the other hand, was a function of tree diameter, with large trees sustaining more beetles and thus acting as larger habitat patches.
The species of oak affected the probability of exit hole presence as the sessile oak (Quercus petraea) and pedunculate oak (Q.
robur) were preferred over Turkey oak (Q. cerris). The slope orientation also affected the presence of exit holes as trees on slopes
with either an eastern or northern orientation were not exploited by the beetle. This study revealed a high level of between-site
variability in the tree characteristics relevant to predicting the occurrence of C. cerdo, mainly with respect to diameter. Therefore,
while the general patterns of habitat use and the fundamental niche of this beetle are well known, survival and protection of local
populations is dependent on site-specifi c characteristics. The realized niche of this beetle must therefore be carefully considered
when planning conservation management for a particular site. The results also signify that at some sites, small trees can, at least
temporarily, substitute for scarce large trees if the state of their health is managed using proper conservation measures.
Leucorrhinia caudalis is a dragonfly species threatened throughout Europe. Despite evidence of the recent extension of its distribution range, it is unknown whether L. caudalis regularly or hardly ever migrates among ponds. The contemporary migration patterns of the species were investigated using Bayesian assignment tests and the migration rates related to landscape structural and thematic variables (distance between ponds, forest area, area of water body, area of hedgerow). Migration rates of L. caudalis are independent of any landscape element. Thus, landscape structure is not a barrier or corridor for migration in this species. The tendency of L. caudalis to disperse is largely independent of the nature of the landscape, at least at the scale of the present study. and Janine Bolliger, Daniela Keller, Rolf Holderegger.
Let X be a completely regular Hausdorff space and, as usual, let C(X) denote the ring of real-valued continuous functions on X. The lattice of z-ideals of C(X) has been shown by Martínez and Zenk (2005) to be a frame. We show that the spectrum of this lattice is (homeomorphic to) βX precisely when X is a P-space. This we actually show to be true not only in spaces, but in locales as well. Recall that an ideal of a commutative ring is called a d-ideal if whenever two elements have the same annihilator and one of the elements belongs to the ideal, then so does the other. We characterize when the spectrum of the lattice of d-ideals of C(X) is the Stone-Čech compactification of the largest dense sublocale of the locale determined by X. It is precisely when the closure of every open set of X is the closure of some cozero-set of X.
The study stems from the author’s long-time interest in the history of the Czechoslovak foreign resistance during the Great War, particularly in Russia. As to its sources, it draws from a collection of published recollections of Czechoslovak legionnaires and their autobiographic novels and other texts of prose. The author attempts to reconstruct the picture of the return of Czechoslovak legions from Russia to their home country; due to the nature of his sources, however, his intention is not to convey an authentic experience of the return in the fi rst days and weeks, but rather to examine the construct created by the legionnaires’ memories and novels. In this respect, he makes use of, in particular, Anglo-Saxon historical literature dealing with similar topics. The key issues include how individuals or whole social groups were coping with the reality of the newborn republic, which was rather different from the visions of the home country they had been dreaming about while away. An important factor affecting their refl ections was also the required political nonaffi liation of organizations of legionnaires, as well as the criticism of the situation not just among the veterans, but in the entire society. The extent of the idealization of Russia, which was a fairly frequent phenomenon among them, was directly proportional to the disillusionment after their return, and was a mirror image of their previous idealization of home while they had been in Russia. In the author’s opinion, the topic of the return of Czechoslovak legions home and their life in their home country is far from exhausted; this is why the present study should be just a springboard to further broadly conceived research. and Přeložil Jiří Mareš
Socialisation in a single-parent family has been associated with negative consequences both in previous research and popular discourse. This article investigates whether this association may be different in a society with a high rate of divorce and extramarital fertility. Using data from the Czech contribution to the EU-SILC survey, it tests hypotheses concerning the difference between the current situation of adults who grew up in single-parent families and those who were raised in intact families. We look for the influence of socialisation on single-parent families in three areas—educational attainment, current partnership situation, and current family income. The results of regression analyses show that the differences between children from single-parent families and those from intact ones are very small in the area of education (the influence is apparent only at the secondary school graduation level, no difference is present at the tertiary education level), relatively weak in the area of partnership situation, and imperceptible from the viewpoint of family income. These results exclude a causal explanation for the influence of single-parent families on outcomes, cast doubt on selective principles, and open space for interpretation in terms of mechanisms of family de-institutionalisation.
Suppose F ⊂ [0, 1] is closed. Is it true that the typical (in the sense of Baire category) function in C 1 [0, 1] is one-to-one on F? If dimBF < 1/2 we show that the answer to this question is yes, though we construct an F with dimB F = 1/2 for which the answer is no. If Cα is the middle-α Cantor set we prove that the answer is yes if and only if dim(Cα) ≤ 1/2. There are F’s with Hausdorff dimension one for which the answer is still yes. Some other related results are also presented.