Structural design of a vertical antenna boresight 18.3 by 18.3-m planar near-field antenna measurement system

A large very precise near-field planar scanner was proposed for NASA Lewis Research Center. This scanner would permit near-field measurements over a horizontal scan plane measuring 18.3 m by 18.3 m. Large aperture antennas mounted with antenna boresight vertical could be tested up to 60 GHz. When such a large near field scanner is used for pattern testing, the antenna or antenna system under test does not have to be moved. Hence, such antennas and antenna systems can be positioned and supported to simulate configuration in zero g. Thus, very large and heavy machinery that would be needed to accurately move the antennas are avoided. A preliminary investigation was undertaken to address the mechanical design of such a challenging near-field antenna scanner. The configuration, structural design and results of a parametric NASTRAN structural optimization analysis are contained. Further, the resulting design was dynamically analyzed in order to provide resonant frequency information to the scanner mechanical drive system designers. If other large near field scanners of comparable dimensions are to be constructed, the information can be used for design optimization of these also

Development and application of a self-referencing glucose microsensor for the measurement of glucose consumption by pancreatic ?-cells

Glucose gradients generated by an artificial source and ?-cells were measured using an enzyme-based glucose microsensor, 8-?m tip diameter, as a self-referencing electrode. The technique is based on a difference measurement between two locations in a gradient and thus allows us to obtain real-time flux values with minimal impact of sensor drift or noise. Flux values were derived by incorporation of the measured differential current into Fick's first equation. In an artificial glucose gradient, a flux detection limit of 8.2 ± 0.4 pmol·cm-2·s-1 (mean ± SEM, n = 7) with a sensor sensitivity of 7.0 ± 0.4 pA/mM (mean ± SEM, n = 16) was demonstrated. Under biological conditions, the glucose sensor showed no oxygen dependence with 5 mM glucose in the bulk medium. The addition of catalase to the bulk medium was shown to ameliorate surface-dependent flux distortion close to specimens, suggesting an underlying local accumulation of hydrogen peroxide. Glucose flux from ?-cell clusters, measured in the presence of 5 mM glucose, was 61.7 ± 9.5 fmol·nL-1·s-1 (mean ± SEM, n = 9) and could be pharmacologically modulated. Glucose consumption in response to FCCP (1 ?M) transiently increased, subsequently decreasing to below basal by 93 ± 16 and 56 ± 6%, respectively (mean ± SEM, n = 5). Consumption was decreased after the application of 10 ?M rotenone by 74 ± 5% (mean ± SEM, n = 4). These results demonstrate that an enzyme-based amperometric microsensor can be applied in the self-referencing mode. Further, in obtaining glucose flux measurements from small clusters of cells, these are the first recordings of the real-time dynamic of glucose movements in a biological microenvironment. <br/

A Machine Learning-Based Method for Modelling a Proprietary SO2 Removal System in the Oil and Gas Sector

The aim of this study is to develop a model for a proprietary SO2 removal technology by using machine learning techniques and, more specifically, by exploiting the potentialities of artificial neural networks (ANNs). This technology is employed at the Eni oil and gas treatment plant in southern Italy. The amine circulating in this unit, that allows for a reduction in the SO2 concentration in the flue gases and to be compliant with the required specifications, is a proprietary solvent; thus, its composition is not publicly available. This has led to the idea of developing a machine learning (ML) algorithm for the unit description, with the objective of becoming independent from the licensor and more flexible in unit modelling. The model was developed in MatLab® by implementing ANNs and the aim was to predict three targets, namely the flow rate of SO2 that goes to the Claus unit, the emissions of SO2, and the flow rate of steam sent to the regenerator reboiler. These represent, respectively, the two physical outputs of the unit and a proxy variable of the amine quality. Three different models were developed, one for each target, that employed the Levenberg–Marquardt optimization algorithm. In addition, the ANN topology was optimized case by case. From the analysis of the results, it emerged that with a purely data-driven technique, the targets can be predicted with good accuracy. Therefore, this model can be employed to better manage the SO2 removal system, since it allows for the definition of an optimal control strategy and the maximization of the plant’s productivity by not exceeding the process constraints

Enamel fluorosis in rat’s incisor: S.E.M. and T.E.M. investigation

Findings on the alterations taking place in the enamel have demonstrated that they are generally caused by a daily use of highly fluoritic drinking waters.According to that, the Authors have carried out an ultrastructural study on lower incisors of albino rats after administering for 60 days water with a fluorine concentration five times the normal one.The samples, studied under the S.E.M., showed a general slowing of both the deposition and the maturation phase as well as the presence of some hypomineralized areas even after eruption.All this suggested the possibility that the damages observed were not due to the direct effect of fluorine on the enamel, but to the interaction between fluorine and ameloblasts.The Authors have then carried out an ultrastructural study on the enamel organ using the S.E.M.The results showed the presence of a well-evident endoplasmic reticulum, the lack in dense granules during the secretion phase, the lack in ruffle ended webs during the modulation phase, and the mitochondrial damage in the ameloblast.All this could justify the slowing of the enamel mineralization caused by fluorine effect on the ameloblasts.Il a été démontré que des altérations de l’émail sont généralement dues à l’absorption quotidienne d’eaux de boissons riches en fluor.Les auteurs ont entrepris une étude ultrastructurale des incisives inférieures du rat ayant reçu pendant 60 jours de l’eau dont la concentration en fluor est 5 fois supérieure à la normale.Les échantillons étudiés en microscopie électronique à balayage ont montré un ralentissement global de la déposition et de la phase de maturation ainsi que la présence de territoires hypominéralisés même après l’éruption.Toutes ces constatations suggèrent la possibilité que les dommages observés ne sont pas dus à l’effet direct du fluor sur l’émail, mais aux interactions entre le fluor et les améloblastes.Les auteurs ont mené une étude ultrastructurale de l’émail en utilisant le microscope électronique à balayage.Les résultats ont montré la présence d’un réticulum endoplasmique bien apparent, l’absence de grains denses au cours de la phase secrétoire, l’absence d’extrémités membranaires rugueuses au cours de la phase de modulation, et des altérations des mitochondries dans les améloblastes.Toutes ces constatations pourraient expliquer le ralentissement de la minéralisation de l’émail causé par les effets du fluor sur les améloblastes

Validation of a Risk Scoring System to Predict Life Expectancy after CEA in Patient with Asymptomatic Carotid Artery Stenosis

n/

Endovascular stenting of the ascending aorta for type A aortic dissections in patients at high risk for open surgery

Background: Open repair is the gold standard for type A aortic dissection (TAAD). Endovascular option has been proposed in very limited and selected TAAD patients. We report our experience with endovascular TAAD repair. Methods: Inclusion criteria were: (1) entry tear in the ascending aorta; (2) proximal landing zone of at least 2 cm; (3) distance between entry tear and brachio-cephalic trunk of at least 0.5 cm; (4) no signs of cardiac tamponade or severe aortic regurgitation and (5) no signs of aortic branches ischaemia. Patients with cardiac revascularisation from ascending aorta were excluded. Results: From April 2009 to June 2012, 37 patients with TAAD were admitted to our hospital. As many as 28 underwent surgical repair and 9 were considered at high surgical risk in a multidisciplinary meeting. Four met our inclusion criteria for an endovascular approach. Two of them had previous ascending aortic repair for TAAD and one had aortic valve replacement. Technical success was achieved in 100% of the patients. No mortality was registered during a median follow-up of 15 months (range 4-39 months), no migration of the graft and complete false lumen thrombosis of the ascending aorta in three patients. Conclusion: Endovascular treatment of TAAD is challenging but feasible in a selected subset of patients. Further research remains mandatory. © 2013 European Society for Vascular Surgery. Published by Elsevier Ltd. All rights reserved

Open fenestration for complicated acute aortic B dissection

Acute type B aortic dissection (ABAD) is a serious cardiovascular emergency in which morbidity and mortality are often related to the presence of complications at clinical presentation. Visceral, renal, and limb ischemia occur in up to 30% of patients with ABAD and are associated with higher in-hospital mortality. The aim of the open fenestration is to resolve the malperfusion by creating a single aortic lumen at the suprarenal or infrarenal level. This surgical procedure is less invasive than total aortic replacement, thus not requiring extracorporeal support and allowing preservation of the intercostal arteries, which results in decreased risk of paraplegia. Surgical aortic fenestration represents an effective and durable option for treating ischemic complications of ABAD, particularly for patients with no aortic dilatation. In the current endovascular era, this open technique serves as an alternative option in case of contraindications or failure of endovascular management of complicated ABAD

The tyrosine kinase receptor c-met, its cognate ligand HGF and the tyrosine kinase receptor trasducers STAT3, PI3K and RHO in thyroid nodules associated with Hashimoto's thyroiditis: an immunohisto-chemical characterization

Hepatocyte growth factor (HGF) exerts proliferative activities in thyrocytes upon binding to its tyrosine kinase receptor c-met and is also expressed in benign thyroid nodules as well as in Hashimoto's thyroiditis (HT)

Single-Center Experience with Simultaneous Mural Aortic Thrombosis and Peripheral Obstructive Disease in Pre-COVID-19 and COVID-19 Era

Background: Mural aortic thrombosis associated with chronic peripheral obstruction of the lower limbs is an unusual event. Repeated embolism of instability aortic mural thrombosis caused acute limb ischemia (Rutherford 2 classification) in patients with peripheral arterial disease (PAD). We report a single-center experience for patients with transmural aortic thrombosis and peripheral artery disease. Methods: We retrospectively analyzed data of 54 patients with aortic mural thrombus disease with PAD presentation, treated at our center between 2013 and 2022. Results: Thirty patients (six with proven SARS-CoV-2 infection) underwent hybrid or staged treatment for an aortic lesion and for lower limb ischemia, by the placement of an endovascular aortic stent graft and a femoro-distal or a popliteal-distal bypass graft. The remaining 24 cases were only subjected to an intravascular treatment of the thoracic or abdominal aorta. Transient renal failure occurred in three patients. No embolic events were detected during the procedures. Aortic-related mortality was reported in just one patient who died from multiple organ failure. There was an embolic stroke in one patient with proven SARS-CoV-2 infection, three major amputations in patients with proven SARS-CoV-2 infection and no aortic-related mortality. Conclusions: Stent coverage of complex aortic lesions, alone or in association with a distal bypass graft, supports this approach in a variety of settings. The COVID-19 pandemic caused an increased mortality and amputation rate