Can forest structural diversity be a response to anthropogenic stress? A case study in old-growth fir Abies alba Mill. stands

International audienceAbstractKey messageFrom 1973 to 1991, Polish SO2emissions above 3250 Gg/year resulted in a decline of firAbies albaMill. After stresses connected with these emissions, five main diameter at breast height (DBH) structural types were described. This type of heterogeneous forest structure is supposed to increase forest resistance and resilience to abiotic, biotic and anthropogenic disturbances.ContextThe analyses of forest structure are important under the current scenario of global change, since heterogeneous structures allow for better responses to disturbances. Forests with more complex structures should present greater vitality.AimsThe main hypotheses were as follows: (1) the temporal changes of atmospheric SO2 emissions caused (a) the abrupt changes in the tree DBH radial increment and (b) the death of fir trees; and (2) atmospheric SO2 emissions and related fir decline and recovery processes ultimately result in the development of stands characterised by diverse DBH structures.MethodsRadial growth trends of 49 and 215 fir trees in the older and younger generations, respectively, and 85 dead fir trees were evaluated. Using data collected in 32 stands, the DBH structural types were identified, and the shapes of these types were illustrated.ResultsThe structural diversification of forest patches may influence forest resistance and resilience to disturbances; five main structural types were identified: ML1 and ML2 represent DBH distributions of multi-layered stands, and OS, TS1 and TS2 represent DBH distributions of one- and two-storied stands.ConclusionStructural diversity of forests was a response to SO2 emissions; fir trees had the ability to increase their radial growth, although there were still high SO2 emissions

Tendencje w europejskim i polskim wyższym szkolnictwie rolniczym

In most European countries the number of students taking agricultural courses will continue to decline. In Poland, however, the arrival of new agricultural courses in public vocational schools of higher education as well as in private schools of higher education will lead to a gradual increase in the number of students studying agriculture. In “old” European countries as well as in Poland individuals who choose agricultural studies will have fewer job opportunities. In the USA and in Europę narrowly-defined technological agricultural education is clearly being abandoned in favour of education in natural resources protection and rural development management. In Poland, however, this process is barely noticeable, particularly in traditional agricultural departments. In the short-term, agricultural schools of higher education should modify their organisation, curricula and the teaching processes, otherwise they will face gradual exclusion from the global tertiary agricultural education system.W większości krajów europejskich liczba studentów kierunków rolniczych będzie ulegać zmniejszeniu. W Polsce natomiast - dzięki otwieraniu nowych kierunków rolniczych zarówno w państwowych wyższych szkołach zawodowych, jak i w uczelniach niepublicznych - liczba studentów szeroko rozumianych kierunków rolniczych będzie się stopniowo zwiększać. Zarówno w krajach „starej” Unii Europejskiej, jak i w Polsce wybór kierunków rolniczych będzie skutkował osiąganiem mniejszych możliwości samorealizacji w życiu zawodowym. W Stanach Zjednoczonych i w Europie następuje wyraźne odejście od wąsko pojętego, technologicznego kształcenia rolniczego w stronę kształcenia w zakresie ochrony zasobów naturalnych (natural resources) oraz zarządzania rozwojem obszarów wiejskich (rural development management). W Polsce ten proces jest słabo zauważalny, zwłaszcza na tradycyjnych wydziałach rolniczych. W najbliższej przyszłości uczelnie rolnicze powinny zmodyfikować swoją organizację, programy studiów i sposób realizacji procesu dydaktycznego. Jeśli tego nie uczynią, będą stopniowo wyłączane z globalnego kształcenia rolniczego na poziomie wyższym

Idempotents of Clifford Algebras

A classification of idempotents in Clifford algebras C(p,q) is presented. It is shown that using isomorphisms between Clifford algebras C(p,q) and appropriate matrix rings, it is possible to classify idempotents in any Clifford algebra into continuous families. These families include primitive idempotents used to generate minimal one sided ideals in Clifford algebras. Some low dimensional examples are discussed

Results on system size dependence of strangeness production in the CERN SPS energy range from NA61/SHINE

NA61/SHINE is a multipurpose fixed-target facility at the CERN Super Proton Synchrotron. The main goals of the NA61/SHINE strong interactions program are to discover the critical point of strongly interacting matter and study the properties of the onset of deconfinement. To reach these goals, hadron production measurements are performed in the form of a two-dimensional scan by varying collision energy and system size. The Collaboration has recently finished data acquisition for its original program on strong interactions, accumulating broad data samples on hadron production in various systems in the SPS energy range.\\ In this contribution, the NA61/SHINE results on identified charged kaon and pion production in p+p, Be+Be and Ar+Sc collisions at the SPS energy range ($\sqrt{s_{NN}}$=5.1--17.3 GeV) are presented. The NA61/SHINE measurements of small and intermediate-mass ion collisions establish an interesting system size dependence, showing a rapid change of hadron production properties that starts when moving from Be+Be to Ar+Sc system. In particular, Ar+Sc is the smallest system for which a significant enhancement of $K^+/\pi^+$ ratio with respect to $p$+$p$ collisions is observed. Obtained energy and system size dependence of the measured charged hadron multiplicities are compared with available world data and various theoretical models

Approximating nonlinear functions with latent boundaries in low-rank excitatory-inhibitory spiking networks

Deep feedforward and recurrent rate-based neural networks have become successful functional models of the brain, but they neglect obvious biological details such as spikes and Dale's law. Here we argue that these details are crucial in order to understand how real neural circuits operate. Towards this aim, we put forth a new framework for spike-based computation in low-rank excitatory-inhibitory spiking networks. By considering populations with rank-1 connectivity, we cast each neuron's spiking threshold as a boundary in a low-dimensional input-output space. We then show how the combined thresholds of a population of inhibitory neurons form a stable boundary in this space, and those of a population of excitatory neurons form an unstable boundary. Combining the two boundaries results in a rank-2 excitatory-inhibitory (EI) network with inhibition-stabilized dynamics at the intersection of the two boundaries. The computation of the resulting networks can be understood as the difference of two convex functions, and is thereby capable of approximating arbitrary non-linear input-output mappings. We demonstrate several properties of these networks, including noise suppression and amplification, irregular activity and synaptic balance, as well as how they relate to rate network dynamics in the limit that the boundary becomes soft. Finally, while our work focuses on small networks (5-50 neurons), we discuss potential avenues for scaling up to much larger networks. Overall, our work proposes a new perspective on spiking networks that may serve as a starting point for a mechanistic understanding of biological spike-based computation

Samogłoska y w językach słowiańskich: geneza i ewolucja (przegląd)

The article concerns the origin and development of the Slavic vowel *y in Slavic languages. At the starting point I present the articulatory characteristics of contemporary Polish y, and then move on to the late Indo-European vocal system - the primordial source of the discussed sound. Then I move on to the analysis of the circumstances of the creation of the phoneme y including phonetics - delabialisation *ū1, and phonology - change *ū1 → y as a consequence of the creation of ū2 from the monophthongisation of diphthongs. I also present the views of researchers on the old pronunciation of y. In the main part of the article I focus on the analysis of the occurrence and functioning of y in various Slavic languages, including dialects, without losing sight of the accompanying historical perspectiv

Training deep neural density estimators to identify mechanistic models of neural dynamics

Mechanistic modeling in neuroscience aims to explain observed phenomena in terms of underlying causes. However, determining which model parameters agree with complex and stochastic neural data presents a significant challenge. We address this challenge with a machine learning tool which uses deep neural density estimators-- trained using model simulations-- to carry out Bayesian inference and retrieve the full space of parameters compatible with raw data or selected data features. Our method is scalable in parameters and data features, and can rapidly analyze new data after initial training. We demonstrate the power and flexibility of our approach on receptive fields, ion channels, and Hodgkin-Huxley models. We also characterize the space of circuit configurations giving rise to rhythmic activity in the crustacean stomatogastric ganglion, and use these results to derive hypotheses for underlying compensation mechanisms. Our approach will help close the gap between data-driven and theory-driven models of neural dynamics

Multi-objective optimization of vehicle routing problem using evolutionary algorithm with memory

The idea of a new evolutionary algorithm with memory aspect included is proposed to find multiobjective optimized solution of vehicle routing problem with time windows. This algorithm uses population of agents that individually search for optimal solutions. The agent memory incorporates the process of learning from the experience of each individual agent as well as from the experience of the population. This algorithm uses crossover operation to define agents evolution. In the paper we choose as a base the Best Cost Route Crossover (BCRC) operator. This operator is well suited for VPRTW problems. However it does not treat both of parent symmetrically what is not natural for general evolutionary processes. The part of the paper is devoted to find an extension of the BCRC operator in order to improve inheritance of chromosomes from both of parents. Thus, the proposed evolutionary algorithm is implemented with use of two crossover operators: BCRC and its extended-modified version. We analyze the results obtained from both versions applied to Solomon’s and Gehring & Homberger instances. We conclude that the proposed method with modified version of BCRC operator gives statistically better results than those obtained using original BCRC. It seems that evolutionary algorithm with memory and modification of Best Cost Route Crossover Operator lead to very promising results when compared to the ones presented in the literature