A hierarchical model to estimate the abundance and biomass of salmonids by using removal sampling and biometric data from multiple locations

We present a Bayesian hierarchical model to estimate the abundance and the biomass of brown trout (Salmo trutta fario) by using removal sampling and biometric data collected at several stream sections. The model accounts for (i) variability of the abundance with fish length (as a distribution mixture), (ii) spatial variability of the abundance, (iii) variability of the catchability with fish length (as a logit regression model), (iv) spatial variability of the catchability, and (v) residual variability of the catchability with fish. Model measured variables are the areas of the stream sections as well as the length and the weight of the caught fish. We first test the model by using a simulated dataset before using a 3-location, 2-removal sampling dataset collected in the field. Fifteen model alternatives are compared with an index of complexity and fit by using the field dataset. The selected model accounts for variability of the abundance with fish length and stream section and variability of the catchability with fish length. By using the selected model, 95% credible interval estimates of the abundances at the three stream sections are (0.46,0.59), (0.90,1.07), and (0.56,0.69) fish/m2. Respective biomass estimates are (9.68, 13.58), (17.22, 22.71), and (12.69, 17.31) g/m2

On inversion sets and the weak order in Coxeter groups

In this article, we investigate the existence of joins in the weak order of an infinite Coxeter group W. We give a geometric characterization of the existence of a join for a subset X in W in terms of the inversion sets of its elements and their position relative to the imaginary cone. Finally, we discuss inversion sets of infinite reduced words and the notions of biconvex and biclosed sets of positive roots.Comment: 22 pages; 10 figures; v2 some references were added; v2: final version, to appear in European Journal of Combinatoric

Creating Products in the Absence of Markets: A Robust Design Approach

The purpose of this study is to examine how firms deal with a situation of true uncertainty about their potential markets and technologies. Specifically, we ask how firms can create products when the corresponding market does not exist. Design/methodology/approach : This paper is based on a longitudinal study of a high-tech firm, combined with analysis of existing theory in Product Design and Entrepreneurship. Findings – Markets and products are usually a defining choice made early on by firms in their strategic process. Such a choice guides their development by providing a ‘stable concept' to which decisions can be related to. When markets do not exist yet, however, this approach is not effective: Early choice of products and markets limits firms' flexibility by constraining their ability and willingness to adapt, while fundamental new technical and market information is likely to emerge during the project that will prove the initial assumptions wrong."New Product Development";"uncertainty";"high-technology venture"

Creating Products in the Absence of Markets: A Robust Design Approach

Purpose - The purpose of this study is to examine how firms deal with a situation of true uncertainty about their potential markets and technologies. Specifically, we ask how firms can create products when the corresponding market does not exist. Design/methodology/approach – This paper is based on a longitudinal study of a high-tech firm, combined with analysis of existing theory in Product Design and Entrepreneurship. Findings – Markets and products are usually a defining choice made early on by firms in their strategic process. Such a choice guides their development by providing a ‘stable concept' to which decisions can be related to. When markets do not exist yet, however, this approach is not effective: Early choice of products and markets limits firms' flexibility by constraining their ability and willingness to adapt, while fundamental new technical and market information is likely to emerge during the project that will prove the initial assumptions wrong. We show an alternative approach where products and markets actually result from a generic process of products and markets exploration driven by the firm. We suggest that this approach forms a robust design in that it allows the firm to deal with the uncertainty by simultaneously developing its products and exploring markets, while preserving the flexibility to adapt to the changing environment. Practical implications – The practical implication of this paper is to suggest an alternative approach to deliberate planning in high-tech ventures. With this approach, rather than markets and products, strategy defines a market and technology exploration process. Originality/value – The paper is original in three ways: 1) It links the product design and market exploration processes in high-tech firm development; 2) It is based on an in-depth longitudinal study; and 3) It results from an academic-practitioner collaborative work.New Product Development; uncertainty; high-technology venture.

Automata, reduced words, and Garside shadows in Coxeter groups

In this article, we introduce and investigate a class of finite deterministic automata that all recognize the language of reduced words of a finitely generated Coxeter system (W,S). The definition of these automata is straightforward as it only requires the notion of weak order on (W,S) and the related notion of Garside shadows in (W,S), an analog of the notion of a Garside family. Then we discuss the relations between this class of automata and the canonical automaton built from Brink and Howlett's small roots. We end this article by providing partial positive answers to two conjectures: (1) the automata associated to the smallest Garside shadow is minimal; (2) the canonical automaton is minimal if and only if the support of all small roots is spherical, i.e., the corresponding root system is finite.Comment: 21 pages, 7 figures; v2: 23 pages, 8 figures, Remark 3.15 added, accepted in Journal of Algebra, computational sectio

Dual-mobility socket in challenging total hip arthroplasty : 2-6 years follow-up.

The success of dual-mobility sockets in achieving implant stability in primary hip replacement is already well established. However, stability cannot always be achieved, especially when dealing with more difficult indications. At our department, 104 dual-mobility sockets (92 uncemented and 12 cemented) were implanted for primary total hip arthroplasty in 97 patients between 2009 and 2013. Indications for hip arthroplasty included primary and secondary coxarthrosis, acetabular and subcapital fractures, avascular necrosis, tumor surgery and metastatic fractures. Although no loosenings were observed, 2 dislocations and 1 infection occurred shortly after surgery. In this challenging group of patients no fixation problems or intraprosthetic dislocations have been observed. The design therefore seems to be a valid alternative to constrained implants, especially in high-risk cases, although dislocation cannot be prevented at all times. Although the findings are very promising, long-term survival studies are mandatory to evaluate intraprosthetic stability and fixation longevity of dual-mobility sockets