13 research outputs found
The effects of upcoming emission regulations on the selection of suitable prime mover combinations for the future harbour/terminal Rotortug: A decision-support tool
No full textNowadays the interest for environmental issues is steadily gaining ground. Inescapably, the shipping industry, is also called to contribute its fair share towards the reduction of air pollution. Harbour tugboats need to comply both with international but also with local exhaust air emission regulations, which are anticipated to become more stringent in the future. Kotug, is interested to proactively explore suitable powering solutions, which can be applied at its Rotortugs’ newbuilding scheme, to comply with upcoming regulations of the intended port of operation. The goal of this thesis is to develop a decision-support tool to facilitate the selection process between alternative prime mover combinations, based on what is needed in terms of operation while considering technical challenges, environmental performance and economic returns. The effect of a variety of promising alternative fuels matched with suitable prime movers was investigated for the period 2018-2033, which was set as the study’s time horizon. LNG, Methanol, Biodiesel and DME were assessed as feasible solutions. The first two were associated with gas-burning engines, whereas the rest were associated with conventional 4-stroke compression ignition engines, similar to the ones already installed in the existing Rotortugs running on MGO. The environmental performance differs substantially to a conventional prime mover running on MGO. However, to adhere to future stricter regulations in certain sea areas, additional after-treatment systems are necessary. Research indicated three post-treatment solutions are the most effective in limiting the majority of the combustion-related emissions; Selective catalytic reduction, diesel particulate filter and oxidation catalysts. The total environmental fingerprint of a vessel can be however assessed only under the context of its propulsion configuration layout. The operational profile of a tugboat is highly variable, allowing room for the exploitation of different drivetrains than the traditional diesel-direct layout, which could lead in benefits mainly in terms of fuel efficiency and maintenance savings. Three drivetrains were selected; a diesel-electric and two hybrid, based on AC and DC topology. Before deciding to invest on a future boat a ship-owner is expected to be eager to comprehend the cost-related issues between alternatives. Moreover, the already proven design of the diesel-direct Rotortug, complemented by the necessary after-treatment technologies, makes sense to be the first option to consider, provided it complies with the anticipated regulations. This option is considered the baseline case. It is reasonable to compare all other options against the baseline case. To this end, a decision framework based on a techno-economic evaluation is proposed for supporting ship-owners to take informative decisions on investment considerations; Three objectives were set; economic performance, environmental performance and cost-effectiveness. To quantify economic performance a comparative TCO analysis was implemented, while for environmental performance the emission output of alternatives is compared. Last, cost-effectiveness adds valuable insight into how good money are allocated towards emission reduction targets and provides a methodology to compete for funding from a regulatory authority. Two case studies are presented that demonstrate the utility of these methods and enhance the understanding of the impact of decisive factors in decision-making. It is concluded that the proposed decision-support tool enables decision-support at an early-stage; nonetheless can still be improved, by incorporating additional factors and expanding certain modules with more details.Marine Technolog
Cross-National Field Research in Developing Countries
No full textCross-national field research performed in developing countries presents researchers with a number of obstacles. Challenges include creating equivalent samples, countering biases, and managing linguistic and cultural issues. In this article the author reviews the conduct of a cross-national study focusing on small tourism operators and the adoption of information communication technologies. He presents the research process, the issues encountered and how they were addressed are discussed, and a number of lessons. This article adds to our understanding of cross-national field research in developing countries and presents a number of implications for social science researchers
Cross-National Field Research in Developing Countries
No full textCross-national field research performed in developing countries presents researchers with a number of obstacles. Challenges include creating equivalent samples, countering biases, and managing linguistic and cultural issues. In this article the author reviews the conduct of a cross-national study focusing on small tourism operators and the adoption of information communication technologies. He presents the research process, the issues encountered and how they were addressed are discussed, and a number of lessons. This article adds to our understanding of cross-national field research in developing countries and presents a number of implications for social science researchers
Covid-19 infection in children and adolescents and its association with type 1 diabetes mellitus (T1d) presentation and management
No full textChildren seem to be affected by the new SARS-CoV-2 virus less severely than adults, with better prognosis and low mortality. Serious complications of COVID-19 infection in children include multisystem inflammatory response syndrome in COVID-19 infection (MIS-C), myo-or pericarditis and, less frequently, long COVID syndrome. On the other hand, adults with type 1 (T1D) or type 2 diabetes (T2D) are among the most vulnerable groups affected by COVID-19, with increased morbidity and mortality. Moreover, an association of SARS-CoV-2 with diabetes has been observed, possibly affecting the frequency and severity of the first clinical presentation of T1D or T2D, as well as the development of acute diabetes after COVID-19 infection. The present review summarizes the current data on the incidence of T1D among children and adolescents during the COVID-19 pandemic, as well as its severity. Moreover, it reports on the types of newly diagnosed diabetes after COVID infection and the possible pathogenetic mechanisms. Additionally, this study presents current data on the effect of SARS-CoV-2 on diabetes control in patients with known T1D and on the severity of clinical presentation of COVID infection in these patients. Finally, this review discusses the necessity of immunization against COVID 19 in children and adolescents with T1D. © 2022, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature
Predictors of the clinical severity of T1DM presentation at diagnosis in children and adolescents with type 1 diabetes mellitus (T1DM)
No full textPurpose: We aimed to assess factors associated with the presence and severity of ketoacidosis (DKA) at pediatric type 1 diabetes (T1DM) diagnosis, in relation to pancreatic, associated and familial autoimmunity. Methods: Antibodies against pancreatic beta-cells, organ specific autoantibodies (thyroid, celiac, and parietal) and family history of autoimmunity were retrospectively evaluated in 116 T1DM patients aged 11.9 ± 4.6 (mean ± SD) years, with disease duration 7.62 ± 3.67 years (mean ± SD). Results: Most patients (67.2%) presented with DKA at diagnosis. Younger children (< 2 years) had tenfold risk of DKA, compared to older children (12.1–15 years) (OR = 10.8, 95% CI: 1.0–116.9, P = 0.05). Fasting c-peptide levels were lower in the DKA group (OR = 0.26, 95% CI = 0.07–0.89, P = 0.033). The number of anti-pancreatic antibodies at disease onset did not show any significant correlations with the presence (p = 0.889) or severity of DKA (p = 0.863). All patients with multiple autoimmunity (> 2 autoimmune diseases plus T1DM) presented with DKA. Familial autoimmunity acted protectively against DKA manifestation (OR = 0.40, 95% CI = 0.16–1.0, P = 0.051). Conclusions: Among newly diagnosed T1DM patients, 67.2% presented with DKA. Younger age, lower c-peptide and the presence of associated autoimmunity were predictive factors of the presence and severity of DKA at diagnosis. High degree of suspicion, due to family history, may prevent DKA development and severity. © The Author(s) 2023
SARS-CoV-2 vaccination in children and adolescents with and without type 1 diabetes mellitus
No full textAdults with Diabetes Mellitus (DM) have increased risk of severe clinical presentation during COVID-19 infection, while children and adolescents with type 1 diabetes (T1D) have the same mild clinical course as their healthy peers, especially those with optimal glycemic control. The present review focuses on the necessity of COVID-19 vaccination among children and adolescents with T1D, and also in their non-diabetic peers. The efficacy and safety of COVID-19 vaccines are also discussed, as well as their various side-effects, ranging from common mild to very rare and serious ones. Furthermore, the results of COVID-19 vaccination of adolescents with and without T1D are reported, as well as the efficacy and concerns about childhood vaccination. It is concluded that patients with DM of all age groups should maintain optimal diabetic control in order to avoid glycemic deterioration during COVID-19 infection. Furthermore, despite the very rare and serious complications of COVID-19 vaccines, vaccination against COVID-19 is recommended for children and adolescents with T1D to prevent glycemic deterioration and rare but serious complications of COVID-19 infection. © 2023, The Author(s)
The Effect of Carbon Content on Methanol Oxidation and Photo-Oxidation at Pt-TiO2-C Electrodes
No full textThe oxidation of methanol is studied at TiO2-supported Pt electrodes of varied high surface area carbon content (in the 30-5% w/w range) and C÷Ti atom ratio (in the 3.0-0.4 ratio). The Pt-TiO2 catalyst is prepared by a photo-deposition process and C nanoparticles (Vulcan XC72R) are added by simple ultrasonic mixing. The optimum C÷Ti atom ratio of the prepared catalyst for methanol electro-oxidation is found to be 1.5, resulting from the interplay of C properties (increased electronic conductivity and methanol adsorption), those of TiO2 (synergistic effect on Pt and photo-activity), as well as the catalyst film thickness. The intrinsic catalytic activity of the best Pt-TiO2/C catalyst is better than that of a commercial Pt/C catalyst and could be further improved by nearly 25% upon UV illumination, whose periodic application can also limit current deterioration
Challenges in the management of patients with HNF1B MODY and multisystem manifestations: the cases of two adolescent boys
No full textIntroduction: Hepatocyte nuclear factor-1 beta (HNF1B) encodes a homeodomain-containing transcription factor, which is expressed early in embryogenesis and is involved in the development of multiple tissues and organs. HNF1B mutations cause complex multisystem disorders, with renal developmental disease and maturity onset diabetes of the young (HNF1B MODY), a rare cause of diabetes mellitus, being representative features. Methods: We present two adolescent boys from different socioeconomic backgrounds who were diagnosed with genetically confirmed HNF1B MODY following hospitalization for diabetic ketoacidosis in the first case and after diagnostic work-up due to impaired glucose tolerance in the second case. Multisystem manifestations, including pancreatic hypoplasia and early-onset diabetes mellitus (DM), renal cysts, hypomagnesemia, hyperuricemia, liver and biliary impairment, genital tract malformations, and primary hyperparathyroidism were also present, strongly suggesting HNF1B MODY. Results: The first patient was treated with subcutaneous insulin but was lost to follow-up due to social reasons. Conversely, early diagnosis in the second patient allowed the management of multisystem defects by a multidisciplinary team of experts. Moreover, manifestation of HNF1B MODY in the form of diabetic ketoacidosis was prevented and a structured diabetes training program has proven successful in regulating glycemic control, postponing the necessity for insulin treatment. Conclusion: Early genetic work-up of patients with dysglycemia associated with a specific phenotype suggestive of HNF1B MODY is extremely important in the care of children and adolescents with diabetes since it ensures that early and optimal management is initiated, thereby preventing the onset of life-threatening diabetic ketoacidosis and other multisystem complications and/or comorbidities. © The Author(s), under exclusive licence to Hellenic Endocrine Society 2024
Magnetic resonance angiography isequivalent to X-Ray coronary angiography for the evaluation of coronary arteries in kawasaki disease
No full textAbstractObjectivesThe purpose of this study was to compare the results of magnetic resonance angiography (MRA) with X-ray coronary angiography (XCA) in a pediatric population.BackgroundCoronary artery abnormalities in Kawasaki disease (KD) develop in about 15% to 25% of young patients, mostly in the form of aneurysms.MethodsThirteen patients (12 male), age three to eight years, were studied. The maximal diameter and length of the aneurysm were recorded. Coronary MRA was performed using a 1.5 T Philips Intera CV magnetic resonance scanner with an electrocardiographically triggered pulse sequence. It was a three-dimensional segmented k-space gradient–echo sequence (TE = 2.1 ms, TR = 7.5 ms, flip angle = 30°, slice thickness = 1.5 mm) employing a T2-weighted preparation pre-pulse and a frequency selective fat-saturation pre-pulse. Data acquisition was performed in mid-diastole. All scans were carried out with the patient free breathing using a two-dimensional real-time navigator beam. All patients underwent XCA within a week.ResultsIn six patients, aneurysms of the coronary arteries were identified, while coronary ectasia alone was present in the remaining seven patients. Magnetic resonance angiography and XCA diagnosis of coronary artery aneurysm agreed completely. Maximal aneurysm diameter and length and ectasia diameter by MRA and XCA were similar. No stenotic lesion was identified by either technique.ConclusionsIn conclusion, MRA is a reliable diagnostic tool, equivalent to XCA for coronary artery aneurysm identification in patients with KD. Magnetic resonance angiography may prove to be of great value for the serial non-invasive evaluation of these patients
EP Elements in Rings with Involution
Get PDF[EN] Let R be a unital ring with involution. We first show that the EP elements in R can be characterized by three equations. Namely, let a. R, then a is EP if and only if there exists x. R such that (xa)* = xa, xa(2) = a and ax(2) = x. Any EP element in R is core invertible and Moore-Penrose invertible. We give more equivalent conditions for a core (Moore-Penrose) invertible element to be an EP element. Finally, any EP element is characterized in terms of the n-EP property, which is a generalization of the bi-EP property.This research is supported by the National Natural Science Foundation of China (No. 11771076). The first author is grateful to China Scholarship Council for giving him a purse for his further study in Universitat Politecnica de Valencia, Spain.Xu, S.; Chen, J.; Benítez López, J. (2019). EP Elements in Rings with Involution. Bulletin of the Malaysian Mathematical Sciences Society. 42(6):3409-3426. https://doi.org/10.1007/s40840-019-00731-xS34093426426Baksalary, O.M., Trenkler, G.: Core inverse of matrices. Linear Multilinear Algebra 58(6), 681–697 (2010)Benítez, J.: Moore–Penrose inverses and commuting elements of -algebras. J. Math. Anal. Appl. 345(2), 766–770 (2008)Bhaskara Rao, K.P.S.: The Theory of Generalized Inverses Over Commutative Rings. Taylor and Francis, London (2002)Boasso, E.: On the Moore–Penrose inverse, EP Banach space operators, and EP Banach algebra elements. J. Math. Anal. Appl. 339(2), 1003–1014 (2008)Chen, W.X.: On EP elements, normal elements and partial isometries in rings with involution. Electron. J. Linear Algebra 23, 553–561 (2012)Drivaliaris, D., Karanasios, S., Pappas, D.: Factorizations of EP operators. Linear Algebra Appl. 429, 1555–1567 (2008)Hartwig, R.E.: Block generalized inverses. Arch. Retion. Mech. Anal. 61(3), 197–251 (1976)Hartwig, R.E., Spindelböck, K.: Matrices for which and commute. Linear Multilinear Algebra 14(3), 241–256 (1983)Koliha, J.J., Patrício, P.: Elements of rings with equal spectral idempotents. J. Aust. Math. Soc. 72(1), 137–152 (2002)Mosić, D., Djordjević, D.S., Koliha, J.J.: EP elements in rings. Linear Algebra Appl. 431, 527–535 (2009)Mosić, D., Djordjević, D.S.: New characterizations of EP, generalized normal and generalized Hermitian elements in rings. Appl. Math. Comput. 218, 6702–6710 (2012)Patrício, P., Puystjens, R.: Drazin–Moore–Penrose invertiblity in rings. Linear Algebra Appl. 389, 159–173 (2004)Rakić, D.S., Dinčić, Nebojša Č., Djordjević, D.S.: Group, Moore–Penrose, core and dual core inverse in rings with involution. Linear Algebra Appl. 463, 115–133 (2014)von Neumann, J.: On regular rings. Proc. Natl. Acad. Sci. USA 22(12), 707–713 (1936
