Browsing by Issue Date, starting with "2024-04"
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- Spectrum sharing for LTE and 5G-NR coexistencePublication . Busari, Sherif Adeshina; Correia, Noélia; Saghezchi, Firooz B.; Mumtaz, Shahid; Rodriguez, JonathanSpectrum sharing provides a rapid migration pathway toward 5G by enabling the coexistence of 4G LTE and 5G new radio (NR) that share the same spectrum. Due to significant differences in the LTE and 5G-NR air interfaces, several enablers are required to facilitate the spectrum sharing. In this study, we explore the coexistence features and investigate their impacts on network performance. For static and dynamic spectrum sharing scenarios, we assess the impacts of different spectrum sharing ratios, user ratios, MIMO configurations, mixed numerology profiles and traffic patterns on the user throughput and network capacities of spectrum sharing networks, compared with the LTE only and 5G-NR only networks with exclusive spectrum access. The key results show that spectrum sharing leads to a marginal capacity gain over LTE only network and achieves considerably lower capacity than the 5G-NR only network. Also, the results show that mixed numerology profiles between the LTE and 5G-NR lead to capacity losses due to inter-numerology interference. In addition, user and spectrum sharing ratios between LTE and 5G-NR have critical impacts on performance. Reduced spectrum per device as the number of 5G devices increases, higher signaling overhead and higher scheduling complexity are other limiting factors for spectrum sharing networks. The results show limited capacity benefits and reinforce spectrum sharing between LTE and 5G-NR as mainly an evolutionary path to accommodate 5G users in the same LTE spectrum while migrating to the fully-fledged 5G networks. For significant capacity increase, other features such as carrier aggregation, overlay of small cells and higher order MIMO would need to be incorporated into the network.
- Comparison of different pretreatment processes envisaging the potential use of food waste as microalgae substratePublication . Marques, Fabiana; Pereira, Francisco; Machado, Luís; Martins, Joana T.; Pereira, Ricardo N.; Costa, Monya; Genisheva, Zlatina; Pereira, Hugo; Vicente, António A.; Teixeira, José A.; Geada, PedroA significant fraction of the food produced worldwide is currently lost or wasted throughout the supply chain, squandering natural and economic resources. Food waste valorization will be an important necessity in the coming years. This work investigates the ability of food waste to serve as a viable nutritional substrate for the heterotrophic growth of Chlorella vulgaris. The impact of different pretreatments on the elemental composition and microbial contamination of seven retail food waste mixtures was evaluated. Among the pretreatment methods applied to the food waste formulations, autoclaving was able to eliminate all microbial contamination and increase the availability of reducing sugars by 30%. Ohmic heating was also able to eliminate most of the contaminations in the food wastes in shorter time periods than autoclave. However, it has reduced the availability of reducing sugars, making it less preferable for microalgae heterotrophic cultivation. The direct utilization of food waste containing essential nutrients from fruits, vegetables, dairy and bakery products, and meat on the heterotrophic growth of microalgae allowed a biomass concentration of 2.2 x 108 cells center dot mL-1, being the culture able to consume more than 42% of the reducing sugars present in the substrate, thus demonstrating the economic and environmental potential of these wastes.
- Empirical evidence for the validity of the job crafting scale (JCS) in a Portuguese settingPublication . Viseu, João; Santos, Joana; Semedo, Carla Santarém; Bakker, Arnold B.; Tims, Maria; Agrela, Sara; Lagareiro, BeatrizPurpose - This study aims to adapt and validate the Job Crafting Scale (JCS), a measure based on the conceptualization of job crafting of the job demands-resources theory, for a sample of Portuguese workers and to test its psychometric properties regarding validity (factor, convergent, discriminant, and criterion) and reliability. Design/methodology/approach - Two subsamples (n1 = 315 and n2 = 329) of Portuguese workers aged 18 years old and over participated in this research. Exploratory factor analysis and confirmatory factor analysis were used to assess the factor structure. Findings - The results indicated that the Portuguese version of the JCS, with 18 items, has a factor structure composed of four-correlated factors. Furthermore, the results demonstrated the existence of factor, discriminant, and criterion validity, as well as reliability. Originality/value - This study provides a job crafting measure adapted to the Portuguese language that can serve as a diagnostic tool for workers and organizations.
- Smart management of tourist coastal areas in a reborn tourism era: transitioning from safe to sustainable beaches within the spanish sun and sand modelPublication . Martínez del Vas, Ginesa; Puig-Cabrera, Miguel; Cádiz-Gómez, Maricruz; Diego, Asier Amilibia deThe aim of this work is the reconceptualisation of beaches as internal objects of smart tourist destinations and to offer a means to capitalize pandemic distintictives such as the Safe Tourism Certification (STC) on the physical pressure of the coastal tourist space to contribute to the natural recovery of these settings. The methodology of this work consisted of analyzing the spatial management of tourist coastal areas according to their congestion level before and after the implementation of the STC. The research technique used for data collection was an online survey with a sample of 64 certified Spanish beaches. One of the main findings of this work is that despite Spanish beaches holding several quality distinctives based on international standards, none of these distinctives guaranteed their decongestion with a minimum surface of 5 m2 per user in the sample, as literature suggests. Thus, the STC implementation and the efforts related to managing physical pressure on coastal resources show the main existing bottlenecks in the sun and sand destinations to transit from safe to physically and ecologically sustainable tourist coastal areas. Also, practical implications to Destination Management Organisations are shared regarding the transition from traditional to smart sun and sand destinations.
- Parabolic turbulence k-epsilon model with applications in fluid flows through permeable mediaPublication . de Oliveira, H.B.In this work, we study a one-equation turbulence k-epsilon model that governs fluid flows through permeable media. The model problem under consideration here is derived from the incompressible Navier-Stokes equations by the application of a time-averaging operator used in the k-epsilon modeling and a volume-averaging operator that is characteristic of modeling unsteady porous media flows. For the associated initial- and boundary-value problem, we prove the existence of suitable weak solutions (average velocity field and turbulent kinetic energy) in the space dimensions of physics interest.
- NaCl elicitation enhances metabolite accumulation and stress resilience in Inula crithmoides L. shoot cultures: implications for its nutritional and medicinal valuePublication . Rodrigues, Maria João; Neng, Nuno; Custódio, LuísaThis study explored the impact of sodium chloride (NaCl) elicitation on the accumulation of primary and secondary metabolites and the oxidative stress responses of Inula crithmoides L. (golden samphire) in vitro shoot cultures. Elicitation involved applying different concentrations of NaCl (0, 50, 100, and 200 mM) for 4 weeks. This was followed by assessing its impact on plant growth, physiological parameters (pigments, hydrogen peroxide content, total soluble sugars and proteins, and proline), and secondary metabolism (phenylalanine ammonia-lyase activity, shikimic acid, phenolics, flavonoids, and hydroxycinnamic acids) in the shoots. The extracts were also analysed using high-performance liquid chromatography (HPLC). The NaCl elicitation did not affect shoot growth but increased physiological functions such as photosynthesis and oxidative stress management under moderate salinity levels. In addition, NaCl treatments increased the synthesis of soluble sugars and proteins, particularly proline, as well as bioactive phenolics such as gentisic acid, chlorogenic acid, 4-hydroxybenzoic acid, luteolin-7-O-glucoside, and naringenin-7-O-glucoside. The NaCl elicitation in golden samphire shoot cultures offers a significant method for enhancing the production of important nutritional and bioactive compounds. This underscores the species' potential for cultivation in saline environments and provides valuable prospects for its utilization in the health and nutrition sectors.
- Public Spaces: Socioeconomic ChallengesPublication . De Noronha, Maria TeresaThis Special Issue, entitled ‘Public Spaces: Socioeconomic Challenges’ considers the concept of general well-being from the point of view of collective achievements and/or external conditions that can favorably impact the individual when implemented within an urban structure. The generality of the presented papers prioritizes the use of objective, measurable and scientifically proven foundations to confirm that including certain urban or environmental contexts within an urban structure has the potential to provide benefits to the well-being of citizens, and, eventually, lead to better conditions to improve their life quality and the architecture of well-being. As for the series of articles presented herein, the goal of this SI is to merely open the field up to a particularly wide range of possible reflections, which we expect to inspire future publications that can drive the creation even more focused contributions to clearly define the frontiers of a promising field of study. We ask the question how can measures related to urban or environmental architecture contribute to citizens well-being and how far can we expect such a contribution to be the aim of future public policy decisions? Naturally, despite the fact that is not a totally new concern, the consideration of these complex phenomena under a new umbrella and using innovative analysis techniques may bring some original approaches and new dimensions to the discussion.
- Trans-Arctic asymmetries, melting pots and weak species cohesion in the low-dispersal amphiboreal seaweed Fucus distichusPublication . Neiva, J.; Assis, Jorge; Fragkopoulou, Eliza; Pearson, Gareth; Raimondi, Peter T.; Anderson, Laura; Krause-Jensen, Dorte; Marbà, Núria; Want, Andrew; Selivanova, Olga; Nakaoka, Masahiro; Grant, W. Stewart; Konar, Brenda; Roleda, Michael Y.; Sejr, Mikael K.; Paulino, Cristina; Serrao, EsterAmphiboreal taxa are often composed of vicariant phylogroups and species complexes whose divergence and phylogeographic affinities reflect a shared history of chronic isolation and episodic trans-Arctic dispersal. Ecological filters and shifting selective pressures may also promote selective sweeps, niche shifts and ecological speciation during colonization, but these are seldom considered at biogeographical scales. Here we integrate genetic data and Ecologic Niche Models (ENMs) to investigate the historical biogeography and cohesion of the polymorphic rockweed Fucus distichus throughout its immense amphiboreal range, focusing on trans-Arctic asymmetries, glacial/interglacial dynamics, and integrity of sympatric eco-morphotypes. Populations were sampled throughout the Pacific and the Atlantic, from southern rear-edges to the high-Arctic. They were genotyped for seven microsatellites and an mtDNA spacer, and genetic diversity and structure were assessed from global to local scales. ENMs were used to compare niche divergence and magnitude of post-glacial range shifts in Pacific versus Atlantic sub-ranges. Haplotypic and genotypic data revealed distinct and seemingly isolated Pacific vs Arctic/Atlantic gene-pools, with finer-scale regional sub-structuring pervasive in the Pacific. MtDNA diversity was highly structured and overwhelmingly concentrated in the Pacific. Regionally, Alaska showed the highest intra-population diversity but the lowest levels of endemism. Some sympatric/parapatric ecotypes exhibited distinct genotypic/haplotypic compositions. Strikingly, niche models revealed higher Pacific tolerance to maximum temperatures and predicted a much more consolidated presence in the NE Atlantic. Glacial and modern ranges overlapped extensively in the Pacific, whereas the modern Atlantic range was largely glaciated or emerged during the Last Glacial Maximum. Higher genetic and ecogeographic diversity supports a primary Pacific diversification and secondary Atlantic colonization, also likely reflecting the much larger and more stable climatic refugia in the Pacific. The relic distribution and reduced ecological/morphological plasticity in the NE Atlantic are hypothesized to reflect functional trans-Arctic bottlenecks, recent colonization or competition with congeners. Within the Pacific, Alaska showed signatures of a post-glacial melting pot of eastern and southern populations. Genetic/ecotypic variation was generally not sufficiently discontinuous or consistent to justify recognizing multiple taxonomic entities, but support a separate species in the eastern Pacific, at the southern rear-edge. We predict that layered patterns of phylogeographic structure, incipient speciation and niche differences might be common among widespread low-dispersal amphiboreal taxa.
- Assessing the vulnerability of food supply chains to climate change-induced disruptionsPublication . Ngameni Tchonkouang, Rose Daphnee; Onyeaka, Helen; Nkoutchou, HugueClimate change is one of the most significant challenges worldwide. There is strong evidence from research that climate change will impact several food chain-related elements such as agricultural output, incomes, prices, food access, food quality, and food safety. This scoping review seeks to outline the state of knowledge of the food supply chain's vulnerability to climate change and to identify existing literature that may guide future research, policy, and decision-making aimed at enhancing the resilience of the food supply chain. A total of 1526 publications were identified using the SCOPUS database, of which 67 were selected for the present study. The vulnerability assessment methods as well as the adaptation and resilience measures that have been employed to alleviate the impact of climate change in the food supply chain were discussed. The results revealed a growing number of publications providing evidence of the weakening of the food supply chain due to climate change and extreme weather events. Our assessment demonstrated the need to broaden research into the entire food supply chain and various forms of climatic variability because most studies have concentrated on the relationships between climatic fluctuations (especially extreme rainfall, temperatures, and drought) and production. A lack of knowledge about the effects of climate change on the food supply chain and the underlying socio-economic consequences could result in underperformance or failure of the food supply chain.
- Clinical outcomes of percutaneous coronary intervention in chronic total occlusion in patients with type 2 diabetes mellitusPublication . Costa, Hugo; Espírito-Santo, Miguel; Bispo, João; Guedes, João; Mimoso, Jorge; Palmeiro, Hugo; Gonçalves, Rui Baptista; Vinhas, HugoIntroduction and Objectives: Coronary chronic total occlusions (CTOs) are relatively common findings in patients with type 2 diabetes mellitus (T2DM). However, the indication for percutaneous coronary intervention (PCI) and its clinical benefit in these patients remain controversial. Methods: A single-center retrospective cohort study with prospectively collected outcomes was carried out with CTO patients undergoing PCI in 2019 and 2020. Patients were divided into two groups according to previous T2DM diagnosis (T2DM and non-T2DM). The primary outcome was recurrence of angina and/or heart failure symptoms and secondary outcomes were myocardial infarction and all -cause mortality. Results: A total of 177 patients (82.5% male) were included in the analysis, with a mean age of 65 +/- 11 years. The primary outcome (total symptom recurrence) occurred in 16.6% of the sample, with no difference between groups (non-T2DM 13.6% vs. T2DM 21.2%, p=0.194) in a two-year follow-up. Angina recurrence was significantly more frequent in T2DM patients (15.2%, p=0.043). The presence of T2DM was not an independent predictor of symptom recurrence (p=0.429, HR 1.37, 95% CI 0.62 - 2.98). Myocardial infarction and all -cause mortality were also not different between groups (T2DM 1.5%, p=0.786 and 4.5%, p=0.352, respectively, on survival analysis). Independent predictors of all -cause mortality were left ventricular function and creatine clearance (p=0.039, HR 0.92, 95% CI 0.85 - 0.99 and p=0.013, HR 0.96, 95% CI 0.93 - 0.99, respectively). Conclusions: T2DM did not influence outcomes in CTO patients undergoing PCI, and its presence should not be a limiting factor in deciding on CTO revascularization.