Abstract It has recently emerged that endothelial dysfunction is an early step in the development of atherosclerosis and is mainly characterised by a reduction in the bioavailability of nitric oxide. ...All of the traditional cardiovascular (CV) risk factors (dyslipidemia, arterial hypertension, hyperglycemia and diabetes) are associated with endothelial dysfunction, and oxidised low-density lipoproteins, the renin-angiotensin axis and insulin resistance play important roles in the pathogenesis of impaired endothelial function. The increased expression of adhesion molecules and pro-inflammatory cytokines leads to abnormal endothelium-dependent vasodilation which could be investigated using vasoreactivity tests such as flow-mediated dilation in the brachial artery. Recently, new evidences showed that the immune system plays an important role in the pathogenesis of endothelial dysfunction and atherosclerosis with a particular regard towards autoimmunity. The high prevalence of the atherosclerotic process in systemic autoimmune diseases supports the hypothesis of the immune pathogenesis. Evaluating coronary microvascular dysfunction by means of transthoracic echocardiography with non-invasive coronary flow reserve assessment is particularly interesting as it could detect preclinical impairment of coronary microvascular function. The discovery that the mechanisms responsible for endothelial damage have a genetic basis could improve the approach to CV diseases. This review summarises the most important aspects of the pathogenesis and development of endothelial dysfunction, with particular attention to the role of traditional CV risk factors, the usefulness of vasoreactivity tests, and the future perspectives opened by genetic studies.
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Type 2 diabetes mellitus and arterial hypertension are major cardiovascular risks factors which shares metabolic and haemodynamic abnormalities as well as pathophysiological ...mechanisms. The simultaneous presence of diabetes and arterial hypertension increases the risk of left ventricular hypertrophy, congestive heart failure, and stroke, as compared to either condition alone. A number of guidelines recommend lifestyle measures such as salt restriction, weight reduction and ideal body weight mainteinance, regular physical activity and smoking cessation, together with moderation of alcohol consumption and high intake of vegetables and fruits, as the basis for reduction of blood pressure and prevention of CV diseases. Despite the availability of multiple drugs effective for hypertension, BP targets are reached in only 50 % of patients, with even fewer individuals with T2DM-achieving goals. It is established that new emerging classes of type 2 diabetes mellitus treatment, SGLT2 inhibitors and GLP1-receptor agonists, are efficacious on glucose control, and safe in reducing HbA1c significantly, without increasing hypoglycemic episodes. Furthermore, in recent years, many CVOT trials have demonstrated, using GLP1-RA or SGLT2-inihibitors compared to placebo (in combination with the usual diabetes medications) important benefits on reducing MACE (cardio-cerebral vascular events) in the diabetic population. In this hypothesis-driven review, we have examined the anti-hypertensive effects of these novel molecules of the two different classes, in the diabetic population, and suggest that they could have an interesting ancillary role in controlling blood pressure in type 2 diabetic patients.
Tropical forests are recognized for their role in providing diverse ecosystem services (ESs), with carbon uptake the best recognized. The capacity of tropical forests to provide ESs is strongly ...linked to their enormous biodiversity. However, causal relationships between biodiversity and ESs are poorly understood. This may be because biodiversity is often translated into species richness. Here, we argue that focusing on multiple attributes of biodiversity—structure, composition, and function—will make relationships between biodiversity and ESs clearer. In this review, we discuss the ecological processes behind ESs from tropical humid and subhumid forests of South America. Our main goal is to understand the links between the ESs and those three biodiversity attributes. While supporting and regulating services relate more closely to forest structure and function, provisioning services relate more closely to forest composition and function, and cultural services are more related to structure and composition attributes. In this sense, ESs from subhumid forests (savannas) differ from those provided by the Amazon Forest, although both ecosystems are recognized as harboring tremendous biodiversity. Given this, if anthropogenic drivers of change promote a shift in the Amazon Forest toward savanna—the savannization hypothesis—the types of services provided will change, especially climate regulating services. This review emphasizes the importance of deeply understanding ecosystem structure, composition, and function to better understand the services ecosystems provide. Understanding that anthropogenic impacts on biodiversity occur through these three main attributes, it becomes easier to anticipate how humans will impact ESs.
Key Points
Tropical forests' biodiversity promotes diverse ecosystem services (ESs), but relationships between biodiversity and ESs are not obvious
Different ES types are related to different attributes of biodiversity: structure, composition, and functions
Savannization of Amazonia could impact the types of ESs provided by rain forests, particularly climate regulating services
Stainless steel vessels see widespread use in superconducting magnets for particle accelerator applications. Their function varies in different magnet designs: they always provide the necessary ...liquid helium containment, but in some cases are also used to provide azimuthal prestress and can also be welded to the magnet end plate to provide additional longitudinal stiffness. A magnet designed with the bladder and key technology does not rely on the structural role of the vessel. They are structurally supported using azimuthally prestressed aluminum shells, and the longitudinal constraint by rods. In this case, the magnet designer would generally like to minimize the interaction between the magnet and the stainless-steel vessel and to minimize the coil stress variation due to the vessel. The stress state in the vessel and in the coil is a function of the circumferential interference, defined as the vessel azimuthal length minus the magnet circumference. The vessel and the magnet azimuthal length machining tolerances are relatively large resulting in significant stress variations in the superconducting coils. In this paper we introduce an interference-control shim, which can significantly limit the stress variation of the coils for a given variation of the interference. The effectiveness of the interference-control shim is evaluated numerically on the MQXF, the low-<inline-formula><tex-math notation="LaTeX">\beta</tex-math></inline-formula> quadrupole for the High Luminosity LHC.
The high-luminosity LHC upgrade requires stronger than LHC low-beta quadrupole magnets to reach the luminosity goals of the project. The project is well advanced and HL-LHC quadrupole magnets are ...currently being commissioned in US Labs (MQXFA magnets) and CERN (MQXFB magnets). Those are the first Nb 3 Sn magnets to be used in any large particle accelerator. At development stages, many Nb 3 Sn accelerator sub-scale models showed relatively slow training and MQXFA magnets were projected to have low tens of quenches before reaching operational field. Recently it was shown that dedicated capacitor-based de-vices can affect Nb 3 Sn magnet training, and it was suggested that CLIQ, a capacitor-based device intended for quench protection, can do too. The present paper investigates effects on training likely induced by CLIQ, using the base fact that only half the coils in a quadrupole experience upward current modulation at quench because of capacitor discharge. The study encompasses all MQXFA production magnets trained at BNL to date. No other high-statistics data from identical magnets (series) with CLIQ protection exist so far. Implications and opportunities stemming from data analysis are discussed and conclusions drawn.
Towards 20 T Hybrid Accelerator Dipole Magnets Ferracin, P.; Ambrosio, G.; Arbelaez, D. ...
IEEE transactions on applied superconductivity,
09/2022, Letnik:
32, Številka:
6
Journal Article
Recenzirano
The most effective way to achieve very high collision energies in a circular particle accelerator is to maximize the field strength of the main bending dipoles. In dipole magnets using Nb-Ti ...superconductor the practical field limit is considered to be 8-9 T. When Nb 3 Sn superconductor material is utilized, a field level of 15-16 T can be achieved. To further push the magnetic field beyond the Nb 3 Sn limits, High Temperature Superconductors (HTS) need to be considered in the magnet design. The most promising HTS materials for particle accelerator magnets are Bi2212 and REBCO. However, their outstanding performance comes with a significantly higher cost. Therefore, an economically viable option towards 20 T dipole magnets could consist in an "hybrid" solution, where both HTS and Nb 3 Sn materials are used. We discuss in this paper preliminary conceptual designs of various 20 T hybrid magnet concepts. After the definition of the overall design criteria, the coil dimensions and parameters are investigated with finite element models based on simple sector coils. Preliminary 2D cross-section computation results are then presented and three main layouts compared: cos-theta, block, and common-coil. Both traditional designs and more advanced stress-management options are considered.
The high luminosity LHC (HL-LHC) project is aimed at studying and implementing the necessary changes in the LHC to increase its luminosity by a factor of five. Among the magnets that will be upgraded ...are the 16 superconducting low-β quadrupoles placed around the two high luminosity interaction regions (ATLAS and CMS experiments). In the current baseline scenario, these quadrupole magnets will have to generate a gradient of 140 T/m in a coil aperture of 150 mm. The resulting conductor peak field of more than 12 T will require the use of Nb 3 Sn superconducting coils. We present in this paper the HL-LHC low-β quadrupole design, based on the experience gathered by the US LARP program, and, in particular, we describe the support structure components to pre-load the coils, withstand the electro-magnetic forces, provide alignment and LHe containment, and integrate the cold mass in the LHC IRs.
MQXFA production series quadrupole magnets are being built for the Hi-Lumi (HL) LHC upgrade by the U.S. Accelerator Upgrade Project (US-HL-LHC AUP). These magnets are being placed in pairs, as a cold ...mass, within cryostats at Fermilab, and are being tested to assess alignment and magnetic performance at Fermilab's horizontal test stand facility. The ∼10 m - long assembly must meet stringent specifications for quadrupole strength and harmonic field integrals determination, magnetic axis position, and for magnet variations in positioning and local field profile. This paper describes the results of the magnetic and alignment measurements which characterize the first LQXFA/B assembly.
New high field and large-aperture quadrupole magnets for the low-beta inner triplets (Q1, Q2, Q3) have been built and tested as part of the high-luminosity upgrade of the Large Hadron Collider ...(HL-LHC). These new quadrupole magnets are based on Nb3Sn superconducting technology. The US Accelerator Upgrade Project (US-AUP) is producing the Q1 and Q3 Cryo-Assemblies: a pair of ∼5 m long magnet structures installed in a stainless-steel helium vessel (Cold Mass) and surrounded by cryostat shields, piping, and a vacuum vessel. This paper gives an overview of the design, production, and the results of the horizontal test of the first pre-series Q1/Q3 Cryo-Assembly.
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