1,017 research outputs found
On permanents of Sylvester Hadamard matrices
It is well-known that the evaluation of the permanent of an arbitrary
-matrix is a formidable problem. Ryser's formula is one of the fastest
known general algorithms for computing permanents. In this paper, Ryser's
formula has been rewritten for the special case of Sylvester Hadamard matrices
by using their cocyclic construction. The rewritten formula presents an
important reduction in the number of sets of distinct rows of the matrix to
be considered. However, the algorithm needs a preprocessing part which remains
time-consuming in general
On an inequivalence criterion for cocyclic Hadamard matrices
Given two Hadamard matrices of the same order, it can be quite difficult
to decide whether or not they are equivalent. There are some criteria to determine
Hadamard inequivalence. Among them, one of the most commonly used is the
4-profile criterion. In this paper, a reformulation of this criterion in the cocyclic
framework is given. The improvements obtained in the computation of the 4-profile
of a cocyclic Hadamard matrix are indicated.Ministerio de Ciencia e Innovación MTM2008-06578Junta de Andalucía FQM–296Junta de Andalucía P07-FQM-0298
Self-Dual codes from -matrices of skew symmetric type
Previously, self-dual codes have been constructed from weighing matrices, and
in particular from conference matrices (skew and symmetric). In this paper,
codes constructed from matrices of skew symmetric type whose determinants reach
the Ehlich-Wojtas' bound are presented. A necessary and sufficient condition
for these codes to be self-dual is given, and examples are provided for lengths
up to 52
Using seam to better understand born globals. A spanish case
This work presents a systematic overview of the opportunities and challenges for international ventures. Moreover, it seeks to reflect on success-factors of launching a venture in international context and how Socio-Economic Approach to Management (SEAM) can help.
Using a practical case study, we discuss the limitations of the “state of art” in BGs and reflect on what SEAM can provide in understanding the main managerial complexities faced by BGs and in leading BGs change in order that they develop the dynamic capabilities to succeed in International markets.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
Internal orientation in the growth of Born-Globals. Learning from inside
Este paper ha recibido dos premios en el congreso:
1. Thomson South-Western Award OUTSTANDING RESEARCH-BASED PAPER ON MANAGEMENT CONSULTING
2. FINALIST CAROLYN DEXTER AWARD FOR BEST INTERNATIONAL PAPERBased on a longitudinal case study in a young BG by means of action-research, that allows the participation of all employees in the co-creation of internal knowledge, we identify organisational dysfunctions during the early phase that affect the development of entrepreneurial and market orientation. Using the Socio-Economic Approach to Management (Savall, 1974), we propose that the entrepreneurs need to adopt an Internal Orientation (aiming at developing a cohesive organisation), and that the ‘right time’ for doing so is not after a few years, as the literature suggests, but much earlier.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
Generalized binary arrays from quasi-orthogonal cocycles
Generalized perfect binary arrays (GPBAs) were used by Jedwab to
construct perfect binary arrays. A non-trivial GPBA can exist only if its energy
is 2 or a multiple of 4. This paper introduces generalized optimal binary arrays
(GOBAs) with even energy not divisible by 4, as analogs of GPBAs. We give a
procedure to construct GOBAs based on a characterization of the arrays in terms
of 2-cocycles. As a further application, we determine negaperiodic Golay pairs
arising from generalized optimal binary sequences of small length.Junta de Andalucía FQM-01
On quasi-orthogonal cocycles
We introduce the notion of quasi-orthogonal cocycle. This
is motivated in part by the maximal determinant problem for square
{±1}-matrices of size congruent to 2 modulo 4. Quasi-orthogonal cocycles
are analogous to the orthogonal cocycles of algebraic design theory.
Equivalences with new and known combinatorial objects afforded by this
analogy, such as quasi-Hadamard groups, relative quasi-difference sets,
and certain partially balanced incomplete block designs, are proved.Junta de Andalucía FQM-01
Self-Dual codes from (−1,1)-matrices of skew symmetric type
Previously, self-dual codes have been constructed from weighing matrices,
and in particular from conference matrices (skew and symmetric). In this paper, codes
constructed from matrices of skew symmetric type whose determinants reach the Ehlich-
Wojtas’ bound are presented. A necessary and sufficient condition for these codes to be
self-dual is given, and examples are provided for lengths up to 52.Ministerio de Ciencia e Innovación MTM2008-06578Junta de Andalucía FQM-016Junta de Andalucía P07-FQM-0298
Severe Atopic Dermatitis In Spain: A Real-Life Observational Study
Objective: To determine the epidemiology and characterize the treatment prescribed for severe atopic dermatitis (AD) in children/adults in usual clinical practice.
Methods: Observational, retrospective study made through review of medical records of Spanish patients aged >= 6 years. Patients diagnosed with severe AD who required care between 2013 and 2017 were included. The study groups were: 6-12 years; 13-18 years; and > 18 years. Patients were followed for 5 years. The main measurements were the prevalence of AD, comorbidity and treatment duration. Statistical significance was established as p <0.05.
Results: We included 2323 patients with severe AD. The overall prevalence was 0.10% (95% CI: 0.09-0.11%) and was 0.39%, 0.23% and 0.07% in the 6-12 years, 13-18 years and >18 years age groups, respectively (p <0.001), the percentage of males was 58%, 48.6% and 39%, respectively, and general comorbidity was 0.1, 0.2 and 0.9 points, respectively (p <0.001).The most frequent comorbidities were asthma in 49.0%, 44.9% and 20.8%, respectively (p <0.001), and anxiety in 79.7%, 65.8% and 67.3%, respectively (p <0.001). Oral corticosteroids were administered in 97.3%, 90.9% and 81.7%, respectively (concomitant-medication). Cyclosporine (45.3%), azathioprine (15.9%) and methotrexate (9.0%) were the most frequently prescribed drugs; biologic agents were administered in 5.8% of patients (for AD).
Conclusion: In AD the presence of comorbidities was significant, especially in the psychological, immunoallergic and cardiovascular areas. Cyclosporine was the most widely used immunosuppressant. There was a degree of variability in the use and duration of the treatments prescribed
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