A note on the algebraic growth rate of Poincar\'e series for Kleinian groups

In this note we employ infinite ergodic theory to derive estimates for the algebraic growth rate of the Poincar\'e series for a Kleinian group at its critical exponent of convergence.Comment: 8 page

Optical characterization of marine phytoplankton assemblages within surface waters of the western Arctic Ocean.

An extensive data set of measurements within the Chukchi and Beaufort Seas is used to characterize the optical properties of seawater associated with different phytoplankton communities. Hierarchical cluster analysis of diagnostic pigment concentrations partitioned stations into four distinct surface phytoplankton communities based on taxonomic composition and average cell size. Concurrent optical measurements of spectral absorption and backscattering coefficients and remote-sensing reflectance were used to characterize the magnitudes and spectral shapes of seawater optical properties associated with each phytoplankton assemblage. The results demonstrate measurable differences among communities in the average spectral shapes of the phytoplankton absorption coefficient. Similar or smaller differences were also observed in the spectral shapes of nonphytoplankton absorption coefficients and the particulate backscattering coefficient. Phytoplankton on average, however, contributed only 25% or less to the total absorption coefficient of seawater. Our analyses indicate that the interplay between the magnitudes and relative contributions of all optically significant constituents generally dampens any influence of varying phytoplankton absorption spectral shapes on the total absorption coefficient, yet there is still a marked discrimination observed in the spectral shape of the ratio of the total backscattering to total absorption coefficient and remote-sensing reflectance among the phytoplankton assemblages. These spectral variations arise mainly from differences in the bio-optical environment in which specific communities were found, as opposed to differences in the spectral shapes of phytoplankton optical properties per se. These results suggest potential approaches for the development of algorithms to assess phytoplankton community composition from measurements of seawater optical properties in western Arctic waters

On a problem of A. Weil

A topological invariant of the geodesic laminations on a modular surface is constructed. The invariant has a continuous part (the tail of a continued fraction) and a combinatorial part (the singularity data). It is shown, that the invariant is complete, i.e. the geodesic lamination can be recovered from the invariant. The continuous part of the invariant has geometric meaning of a slope of lamination on the surface.Comment: to appear Beitr\"age zur Algebra und Geometri

The effect of neural adaptation of population coding accuracy

Most neurons in the primary visual cortex initially respond vigorously when a preferred stimulus is presented, but adapt as stimulation continues. The functional consequences of adaptation are unclear. Typically a reduction of firing rate would reduce single neuron accuracy as less spikes are available for decoding, but it has been suggested that on the population level, adaptation increases coding accuracy. This question requires careful analysis as adaptation not only changes the firing rates of neurons, but also the neural variability and correlations between neurons, which affect coding accuracy as well. We calculate the coding accuracy using a computational model that implements two forms of adaptation: spike frequency adaptation and synaptic adaptation in the form of short-term synaptic plasticity. We find that the net effect of adaptation is subtle and heterogeneous. Depending on adaptation mechanism and test stimulus, adaptation can either increase or decrease coding accuracy. We discuss the neurophysiological and psychophysical implications of the findings and relate it to published experimental data.Comment: 35 pages, 8 figure

Design and competitive advantage: collaborative strategies enabling radical innovations of meanings

This seminar was delivered on 30th April 2012 by Dr Claudio Dell'Era, Assistant Professor in the Department of Management, Economics and Industrial Engineering at the Politecnico di Milano, where he also serves as Co-Director of MaDe In Lab, the Laboratory of Management of Design and Innovation of MIP Politecnico di Milano. Research activities developed by Claudio Dell’Era are concentrated in the area of Management of Innovation. Specifically research interests are about two main streams: the former concentrates on innovation strategies developed by leading companies that operate in design-intensive industries where symbolic and emotional values represents critical success factors to generate competitive advantage (Management of Design-Driven Innovation); while the latter analyzes approaches and practices adopted during innovation processes by high-tech companies that face turbulent environments (Management of Technological Innovations in Turbulent Environments). He has published in relevant international journals, such as the Journal of Product Innovation Management, Long Range Planning, R&D Management, International the Journal of Operations & Production Management, Industry & Innovation and the International Journal of Innovation Management. The presentation was hosted at Brunel University as part of the Human Centred Design Institute (HCDI) Research Seminar Series. HCDI is a University Research Centre (URC) that brings together expertise in Human-centred Design which combines methodologies and technologies from design, engineering, computer science, artificial intelligence and philosophy. Human-centred Design leads to machines, systems and products which are physically, cognitively and emotionally intuitive to their users. The Human Centre Design seminar series are events designed to encourage communication and teamwork with colleagues across the university and experts leaders in human-centred related topics.Customers are paying increasing attention to product design, whether the aesthetic, symbolic or emotional meanings of products. Designers can support companies in exploring customers’ needs and the appropriate signs (such as form, colours, materials, etc) that give meaning to products. Managing collaborations with designers is therefore a critical issue for companies that operate in design-intensive industries. The seminar discusses how a company may develop a proper collaborative strategy by identifying an effective portfolio of designers. It shows that companies that innovate collaborate with a broad range of external designers. Most important, innovativeness does not depend on diversity brought by an individual designer, but on diversity brought by the entire portfolio of designers of a firm. The implication is that companies should not focus only on the characteristics of single external parties when developing a collaborative innovation strategy, but, rather, manage carefully a balanced portfolio of collaborators