DigitUMa
Repositório Institucional da Universidade da Madeira
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Stock market effects of CrowdStrike IT outage on largest listed hotel companies
Publication . Albuquerque, Bruno; Cró, Susana; Moutinho, Nuno; Martins, António Miguel; Albuquerque, Bruno; Martins, António
This study analyses the short-term market effect of CrowdStrike IT outage in the 100 largest worldwide listed hotel companies. Using an event study methodology, the paper analyses how hotel companies are penalized by the market to the biggest IT disruption in history. Our results evidence a statistically significant negative reaction around the event date. This result is explained by the adverse impact caused by IT failures in the hotel’s business operations (reservation, payment, technical systems) and supply chain processes, which result in financial losses. We also observe a highest negative stock market reaction for hotel companies located in Western countries and for hotels with a low cyber risk rating. Finally, this study identifies hotel-specific characteristics that drive value during an IT outage. The research evidence that larger and more profitable hotel companies, with lower leverage and higher cyber risk ratings are more resilient to the adverse effects of IT outages.
Bioinspired hybrid DNA/dendrimer-based films with supramolecular chirality
Publication . Castro, Rita; Granja, Pedro L.; Rodrigues, João; Pêgo, Ana Paula; Tomás, Helena; Castro, Rita; Rodrigues, João; Pêgo, Ana Paula; Tomás, Helena
Bioinspired hybrid DNA/dendrimer films were obtained by heating long double-stranded DNA (dsDNA)
above its melting temperature and, while in the denatured state, mixing it with poly(amidoamine) (PAMAM)
dendrimers, followed by controlled cooling. The formation of these new types of films was found to be
dependent on several parameters, including the initial heating temperature, pH, buffer composition,
dendrimer generation, amine/phosphate (N/P) ratio, and cooling speed. In addition to the PAMAM
dendrimers (generations 3, 4, and 5), films could also be produced with branched poly(ethylenimine) with
a molecular weight of 25 kDa. The results indicated that these films were formed not only through
electrostatic interactions established between the negatively charged DNA molecules and the positive
dendrimers, as expected, but also through random rehybridization of the single-stranded DNA (ssDNA)
during the cooling process. The resulting films are water-insoluble, transparent when thin, highly elastic
when air-dried, exceptionally stable over extended periods, cytocompatible, and easily scalable. Notably,
the slow cooling process allowed for the establishment of at least a partially ordered structure in the films,
as revealed by circular dichroism, providing evidence of supramolecular chirality. It is envisioned that these
films may have significant potential in biomedical applications, such as drug/gene delivery systems,
platforms for cell-free DNA transcription and components in biosensors.
Numerical investigation of stability of low-current needle-to-plane negative corona discharges in air
Publication . Ferreira, N. G. C.; Almeida, P. G. C.; Taher, A. Eivazpour; Naidis, G. V.; Benilov, M. S .; Ferreira, Nuno; Almeida, Pedro G C; Benilov, Mikhail; Benilov, Mikhail
Abstract
Negative DC corona discharges are known for their self-pulsing regime: the Trichel pulses. In some works, pulsed regimes, stochastic or periodic, have been observed immediately upon the inception of the discharge, while in other works the discharge was found to be ignited in a steady-state (pulseless) mode, with the Trichel pulses developing at higher voltages. Recent theoretical and modeling work showed that the stationary negative corona between concentric cylinders in atmospheric-pressure air is stable immediately after the ignition. The pulseless mode was found also in the modeling of the needle-to-plane geometry, however in a quite narrow voltage range. This work studies conditions for a pulseless negative corona discharge in a needle-to-plane geometry to occur over a wide range of voltages, which will facilitate its unambiguous observation in the experiment. After the negative corona loses stability, the current evolution shows, after a small region of quasi-harmonic oscillations, pulses. These can be of small amplitude or regular Trichel pulses, which develop via standing-wave or ionization-wave mechanisms. Modeling results agree with available experimental data, both for the current–voltage characteristics and the stability limit of the pulseless negative corona discharge. An insight is given into stochastic Trichel pulses, which have been observed in experiments under certain conditions.
Intelligent visibility forecasting at airports: a systematic review
Publication . Alves, Décio; Belo-Pereira, Margarida; Mendonça, Fábio; Morgado-Dias, Fernando; Alves, Decio; Silva Mendonça, Fábio Rúben; Morgado-Dias, Fernando
Abstract
Low visibility conditions caused by phenomena such as fog, heavy rain, or snowfall impose major operational and safety challenges at airports. Conventional numerical weather prediction models, although improved over time, still struggle to forecast low visibility accurately due to scale mismatches and uncertainties in physical parameterizations, among other factors. This review synthesizes findings on data-driven solutions, including machine learning and deep learning, that harness large datasets to reveal hidden patterns, offering better performance and adaptability. Ensemble methods and the integration of multiple data sources further enhance accuracy, particularly for short lead times. Several methods achieve correlation coefficients above 0.90 and root mean square error below 1 km, yet generalization and integration into real-time airport operations remain underexplored. Future work should focus on transferability across diverse climates, integration with advanced operational tools, and bridging gaps between model complexity and user interpretability. The next generation of hybrid forecasting frameworks has the potential to enhance safety, limit economic losses, and improve resilience in airport operations.
Organizational emergence theory: addressing invisible conflicts and emerging dynamics in entrepreneurship
Publication . Leite, Eduardo Manuel de Almeida; Audretsch, David; Leite, Eduardo
Abstract
This study presents the Theory of Organisational Emergence (TOE), an interdisciplinary framework for understanding non-linear dynamics, emergent resilience, and invisible conflicts in entrepreneurial settings. TOE integrates Interacting Q’s and the PIE model (Politics, Ideology, Economy) to address gaps in established theories like Dynamic Capabilities and Effectuation. Through a qualitative analysis of the House of Mendes and Tesla Inc., TOE demonstrates how organisations adapt under systemic pressures. The framework also provides a practical diagnostic toolkit to detect tensions, simulate disruptions, and inform strategic action. By bridging theory and application, TOE offers a novel and actionable perspective for navigating uncertainty, fostering innovation, and enhancing resilience in complex environments. It equips organisations with tools to thrive amid systemic volatility and institutional complexity.