Impact of Covid-19 on the aviation industry: an overview of global and some local effects

The COVID-19 pandemic temporarily paralysed demand for air travel causing long-term implications for all industry stakeholders involved. Nobody was spared, and without government support, many airlines, airports and air navigation service providers (ANSP), would have gone out of business already in the first year of the pandemic. In order to assess the global impact of COVID-19 on the aviation industry, this paper reviewed data from publications by various international aviation organizations, academic papers, and annual reports by airlines, airports and ANSPs, etc. The findings show that the global aviation industry was severely hit by the pandemic, pushing all stakeholders to adopt countermeasures, with the most common response by airlines being the reconfiguring their networks and capacity or switching to cargo operations, airports and other operators reacted by reducing staff numbers, while passengers had to adapt to the new travel rules and the new normality.Peer ReviewedPostprint (published version

Methodological framework for a deeper understanding of airline profit cycles in the context of disruptive exogenous impacts

This paper combines the k-means clustering method in combination with PCA and the system dynamic modeling approach to derive a better insight into the behavior of airline profitability during the time span of 1995 until 2020. The model includes various explanatory variables that capture different aspects of airline economic and operational metrics, whose fluctuations may affect the airline profitability. By forecasting these exogenous variables, the system dynamic model is used to predict airline profitability through 2025 and answer the question of whether the US airline industry will return to its pre-COVID 19 pandemic state. The latter research question can be agreed with, as the effect of introducing a fourth dimension derived from Principal Component Analysis (PCA) to sufficiently cover the variation within the dataset during the years of COVID-19 pandemic diminishes towards the end of the forecast period. Furthermore, the key measures from PCA imply that under the assumption of continuous growth and a non-exogenous shock, future years will not cluster in past years. The six different clusters from 2019 to 2025 showed how the system stays in a certain state for a few years and then drifts further to a new state. There are only a few variables that change to transfer from one cluster to the next.Postprint (published version

Influence of PANI Layer Protonation Degree on Corrosion Protection of Steel

The aim of this work was to study the protective properties of polyaniline (PANI) layers of different degrees of protonation on stainless steel immersed in c = 0.1 mol dm–3 NaCl solution. Methods of testing were open circuit potential monitoring, and electrochemical impedance spectroscopy. Different degrees of PANI protonation were obtained by keeping stainless steel covered with PANI layer during one day time in solutions of different pH values. The testing solutions were c = 3 mol dm–3 phosphoric acid solution (pH 0.4), and buffer solutions of pH 4.3 and pH 7.8. Although all PANI layers were tested in the same solution of c = 0.1 mol dm–3 NaCl, depending on a degree of previously achieved protonation, different protection time of steel samples was obtained. The best protective properties were obtained for steel covered with the PANI layer kept one day in the buffer solution of pH 7.8, before testing, where a complete deprotonation was achieved. The results obtained point out that PANI, under those conditions, presents a physical barrier to the ingress of chloride ions into the passive film, and the electrochemical mechanism of protection is not significantly involved

Fish-derived low molecular weight components modify bronchial epithelial barrier properties and release of pro-inflammatory cytokines

The prevalence of fish allergy among fish-processing workers is higher than in the general population, possibly due to sensitization via inhalation and higher exposure. However, the response of the bronchial epithelium to fish allergens has never been explored. Parvalbumins (PVs) from bony fish are major sensitizers in fish allergy, while cartilaginous fish and their PVs are considered less allergenic. Increasing evidence demonstrates that components other than proteins from the allergen source, such as low molecular weight components smaller than 3 kDa (LMC) from pollen, may act as adjuvants during allergic sensitization. We investigated the response of bronchial epithelial cells to PVs and to LMC from Atlantic cod, a bony fish, and gummy shark, a cartilaginous fish. Polarized monolayers of the bronchial epithelial cell line 16HBE14owere stimulated apically with fish PVs and/-or the corresponding fish LMC. Barrier integrity, transport of PVs across the monolayers and release of mediators were monitored. Intact PVs from both the bony and the cartilaginous fish were rapidly internalized by the cells and transported to the basolateral side of the monolayers. The PVs did not disrupt the epithelial barrier integrity nor did they modify the release of proinflammatory cytokines. In contrast, LMC from both fish species modified the physical and immunological properties of the epithelial barrier and the responses differed between bony and cartilaginous fish. While the barrier integrity was lowered by cod LMC 24 h after cell stimulation, it was increased by up to 2.3-fold by shark LMC. Furthermore, LMC from both fish species increased basolateral and apical release of IL 6 and IL-8, while CCL2 release was increased by cod but not by shark LMC. In summary, our study demonstrated the rapid transport of PVs across the epithelium which may result in their availability to antigen presenting cells required for allergic sensitization. Moreover, different cell responses to LMC derived from bony versus cartilaginous fish were observed, which may play a role in different allergenic potentials of these two fish classes

Collagen-an important fish allergen for improved diagnosis

Background Fish collagen is widely used in medicine, cosmetics, and the food industry. However, its clinical relevance as an allergen is not fully appreciated. This is likely due to collagen insolubility in neutral aqueous solutions, leading to low abundance in commercially available in vitro and skin prick tests for fish allergy. Objective To investigate the relevance of fish collagen as an allergen in a large patient population (n = 101). Methods Acid-soluble collagen type I was extracted from muscle and skin of Atlantic salmon, barramundi, and yellowfin tuna. IgE binding to collagen was analyzed by ELISA for 101 fish-allergic patients. Collagen-sensitized patients' sera were tested for IgE binding to parvalbumin from the same fish species. IgE cross-linking was analyzed by rat basophil leukemia assay and basophil activation test. Protein identities were confirmed by mass spectrometry. Results Purified fish collagen contained type I α1 and α2 chains and their multimers. Twenty-one of 101 patients (21%) were sensitized to collagen. Eight collagen-sensitized patients demonstrated absence of parvalbumin-specific IgE to some fish species. Collagen induced functional IgE cross-linking, as shown by rat basophil leukemia assay performed using 6 patients' sera, and basophil activation test using fresh blood from 1 patient. Collagen type I α chains from barramundi and Atlantic salmon were registered at www.allergen.org as Lat c 6 and Sal s 6, respectively. Conclusions IgE sensitization and IgE cross-linking capacity of fish collagen were demonstrated in fish-allergic patients. Inclusion of relevant collagen allergens in routine diagnosis is indicated to improve the capacity to accurately diagnose fish allergy

Clinical management of seafood allergy

Seafood plays an important role in human nutrition and health. A good patient workup and sensitive diagnostic analysis of IgE antibody reactivity can distinguish between a true seafood allergy and other adverse reactions generated by toxins or parasites contaminating ingested seafood. The 2 most important seafood groupings include the fish and shellfish. Shellfish, in the context of seafood consumption, constitutes a diverse group of species subdivided into crustaceans and mollusks. The prevalence of shellfish allergy seems to be higher than that of fish allergy, with an estimate of up to 3% in the adult population and fin fish allergy prevalence of approximately 1%. Clinical evaluation of the seafood-allergic patient involves obtaining a detailed history and obtaining in vivo and/or in vitro testing with careful interpretation of results with consideration of cross-reactivity features of the major allergens. Oral food challenge is useful not only for the diagnosis but also for avoiding unnecessary dietary restrictions. In this review, we highlight some of the recent reports to provide solid clinical and laboratory tools for the differentiation of fish allergy from shellfish allergy, enabling best treatment and management of these patients

Withering Triad: an Examination of the Modernization Programs For the Strategic Nuclear Forces of the United States

The strategic nuclear triad was the foundation of the American military posture for the duration of the Cold War. During this period, the United States developed detailed roles, missions, and requirements for these forces. With the pronounced termination of the Cold War, the forces that compose the triad have significantly diminished, and their roles and missions have been reduced. This thesis reviews the triad policies of the United States and examines the current modernization programs that are applicable to the three legs of the triad. It also addresses the need for maintenance of triad forces in the post-Soviet world

Modelling the estimation of the airline profit in case of purchasing new slots for increasing flight frequency

AbstractTo achieve network optimization, most airlines depend on slot allocation process. The secondary slot market enables airlines to get additional slots for improving their networks and flight schedules. The idea of developing the model presented in this paper was not just to help in selecting the flight(s) for new slot(s) that maximizes the airline‟s revenue, but to estimating the number of years necessary for refunding the initial outlay for purchasing that slot. The essence of the model is to help an airline to check if the purchasing of new slot(s) is profitable or not in the case when new slot(s) is used for increasing the flight frequency on existing route