Search results for "ASYM"
showing 10 items of 2151 documents
[3 + 2] Cycloadditions in Asymmetric Synthesis of Spirooxindole Hybrids Linked to Triazole and Ferrocene Units: X-ray Crystal Structure and MEDT Stud…
2022
Derivatization of spirooxindole having triazole and ferrocene units was achieved by the [3 + 2] cycloaddition (32CA) reaction approach. Reacting the respective azomethine ylide (AY) intermediate generated in situ with the ethylene derivative produced novel asymmetric cycloadducts with four contiguous asymmetric carbons in an overall high chemical yield with excellent regioselectivity and diastereoselectivity. X-Ray single-crystal structure analyses revealed, with no doubt, the success of the synthesis of the target compounds. The 32CA reaction of AY 5b with ferrocene ethylene 1 has been studied within MEDT. This 32CA reaction proceeds via a two-stage one-step mechanism involving a high asyn…
N-Heterocyclic Carbene Catalyzed Asymmetric Synthesis of Pentacyclic Spirooxindoles via [3+3] Annulations of Isatin-Derived Enals and Cyclic N-Sulfon…
2019
A convenient enantioselective route to new types of pentacyclic spirooxindoles via [3+3] annulation reactions of isatin-derived enals and cyclic N-sulfonyl ketimines, using N-heterocyclic carbene (NHC) catalysis has been developed. The new protocol leads to pentacyclic spirooxindoles bearing a quaternary spirostereocenter in good yields and good to high enantiomeric ratios. peerReviewed
Coronary artery fistulas: symptoms may not correlate to size. An emblematic case and literature review
2015
<p>Coronary artery fistulas are rare anatomic abnormalities of the coronary arteries present in 0.002% of the general population and represent 14% of all anomalies of coronary arteries. Their clinical relevance focuses mainly on the mechanism of "coronary steal phenomenon”, causing myocardial functional ischemia even in the absence of stenosis, hence common symptoms are angina or dyspnea. Small size fistulas are mostly asymptomatic and have excellent prognosis if managed medically with regular follow-up consisting also in echocardiography every 2-5 years. Big-sized and symptomatic fistulas, on the contrary, should undergo invasive closure, either with a transcatheter approach or with …
Multiplicity results for asymmetric boundary value problems with indefinite weights
2004
We prove existence and multiplicity of solutions, with prescribed nodal properties, to a boundary value problem of the formu″+f(t,u)=0,u(0)=u(T)=0. The nonlinearity is supposed to satisfy asymmetric, asymptotically linear assumptions involving indefinite weights. We first study some auxiliary half-linear, two-weighted problems for which an eigenvalue theory holds. Multiplicity is ensured by assumptions expressed in terms of weighted eigenvalues. The proof is developed in the framework of topological methods and is based on some relations between rotation numbers and weighted eigenvalues.
CT imaging findings of abdominopelvic vascular compression syndromes: what the radiologist needs to know.
2020
AbstractAbdominopelvic vascular compression syndromes include a variety of uncommon conditions characterized by either extrinsic compression of blood vessels by adjacent anatomical structures (i.e., median arcuate ligament syndrome, nutcracker syndrome, May-Thurner syndrome) or compression of hollow viscera by adjacent vessels (i.e., superior mesenteric artery syndrome, ureteropelvic junction obstruction, ureteral vascular compression syndromes, portal biliopathy). These syndromes can be unexpectedly diagnosed even in asymptomatic patients and the predisposing anatomic conditions can be incidentally discovered on imaging examinations performed for other indications, or they can manifest wit…
Endovascular treatment of spontaneous isolated abdominal aortic dissection
2016
Isolated abdominal aortic dissection is a rare clinical disease representing only 1.3% of all dissections. There are a few case series reported in the literature. The causes of this pathology can be spontaneous, iatrogenic, or traumatic. Most patients are asymptomatic and symptoms are usually abdominal or back pain, while claudication and lower limb ischemia are rare. Surgical and endovascular treatment are two valid options with acceptable results. We herein describe nine cases of symptomatic spontaneous isolated abdominal aortic dissection, out of which four successfully were treated with an endovascular approach between July 2003 and July 2013. All patients were men, smokers, symptomati…
Phenotypic Buffering in a Monogenean: Canalization and Developmental Stability in Shape and Size of the Haptoral Anchors of Ligophorus cephali (Monog…
2015
Phenotypic variation results from the balance between sources of variation and counteracting regulatory mechanisms. Canalization and developmental stability are two such mechanisms, acting at two different levels of regulation. The issue of whether or not they act concurrently as a common developmental buffering capacity has been subject to debate. We used geometric morphometrics to quantify the mechanisms that guarantee phenotypic constancy in the haptoral anchors of Ligophorus cephali. Canalization and developmental stability were appraised by estimating inter- and intra-individual variation, respectively, in size and shape of dorsal and ventral anchors. The latter variation was estimated…
Leadership in internationalization strategies
2022
This paper examines leadership in internationalization strategies for an asymmetric cost duopoly where firms choose between exports and foreign direct investment (FDI) in a sequential setting. The incentive to lead and to engage in FDI is stronger for the more efficient firm. With sequential choices and the efficient firm playing in advance, it is less likely that firms pick identical internationalization strategies in equilibrium, as compared with simultaneous choices; this is more so for greater cost asymmetry. It also happens for large enough oligopoly profitability when the inefficient firm plays in advance. Follow-the-leader behaviour in FDI arises for low values of the setup cost. Alt…
Asymptotic expansions and causal representations through the loop-tree duality
2022
Large-scale particle physics experiments have provided a vast amount of high-quality data during the last decades. A leading role has been played by the Large Hadron Collider where the evaluation and analysis of its second run is currently still in progress while the third run is about to start, promising ever higher precision data of particle collisions and subsequent decays. The agreement between experimental observations and theoretical predictions using the Standard Model of Particle Physics is excellent. Indeed, this is a problem since there are currently few clues for how genuine shortcomings of the model can be overcome. New physics phenomena can appear either at higher energies, whi…