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  • Author: Radu Constantinescu x
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Seismic Isolation of Bridges Using the Principle of Electromagnetic Attraction and Repulsion

Abstract

This paper presents a new type of seismic isolator that uses the principle of electromagnetic attraction and repulsion, to control the friction force between two electromagnets during earthquakes. The two electromagnets are used in conjunction with a secondary high friction dissipating and damping mechanism composed from a 10mm thick neoprene ring layer and two steel surfaces coated with Si3N4 that are used to dissipate the kinetic energy in the bridge deck at some maximum ground accelerations. The isolator utilizes tri-axial accelerometers embedded in the abutments, high current rechargeable batteries and an automated controlling unit. The presented isolator was developed specifically for a concrete bridge deck with a span of 36 meters and simple supported on two abutments, using time history electromagnetic and structural analyses. The paper presents the advantages of using this active seismic isolation system, compared to classical passive devices and the important results obtained in terms of decreasing internal forces on the substructure elements cross sections together with the reduction of relative displacements between the two electromagnets.

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Retrospective study of 37 Cavalier King Charles Spaniel dogs diagnosed with Chiari-like malformation and Syringomyelia

Abstract

Chiari-like malformation represents a congenital anomaly that affects the bony cranial base and the hindbrain, leading to fluid filled cavities formation in the spinal cord, condition named Syringomyelia. This paper aims to assess the variety of the clinical signs and to evaluate the magnetic resonance imaging findings in thirty- seven Cavalier King Charles Spaniel dogs. The study was performed over a four-year period, from 2013 to 2017, all cases underwent neurological examination, full diagnostic work-up, including magnetic resonance imaging scans of the brain, cervical and upper thoracic spinal cord. Thirty-seven dogs were included in this study, 23 females and 14 males, with a mean age of 3.6±2.1years. The commonest clinical findings encountered were neuropathic pain and vocalization, seen in all 37 cases, followed by scratching, facial rubbing, paw licking, air licking, tail chasing, seizures and unilateral facial paralysis. Different grades of cerebellar herniation and cervical syrinxes were noted in all cases, other magnetic resonance imaging findings encountered were medullary kinking, presyrinx and ventriculomegaly. In establishing the diagnosis of the Chiari-like malformation and Syringomyelia, the breed, clinical history and the symptomatology are very important, but only magnetic resonance imaging technique can provide quantitative assessment of the nervous system lesions.

Open access
Behaviour of Epoxy Silica Nanocomposites Under Static and Creep Loading

Abstract

Specific manufacturing technologies were applied for the fabrication of epoxy-based nanocomposites with silica nanoparticles. For dispersing the fillers in the epoxy resin special equipment such as a shear mixer and a high energy sonicator with temperature control were used. Both functionalized and unfunctionalized silica nanoparticles were added in three epoxy resins. The considered filling fraction was in most cases 0.1, 0.3 and 0.5 wt%.. The obtained nanocomposites were subjected to monotonic uniaxial and creep loading at room temperature. The static mechanical properties were not significantly improved regardless the filler percentage and type of epoxy resin. Under creep loading, by increasing the stress level, the nanocomposite with 0.1 wt% silica creeps less than all other materials. Also the creep rate is reduced by adding silica nanofillers.

Open access
Pulmonary Arterial Hypertension In A Female Patient With Systemic Lupus Erythematosus

Abstract

Introduction. Systemic lupus erythematosus (SLE) is a chronic autoimmune disease of unknown origin, characterized by multisystemic involvement and a potentially severe evolution. Pulmonary arterial hypertension (PAH) is a rare complication of SLE, with low 5-year survival.

Case presentation. We are presenting the case of a female patient, aged 56 years old, diagnosed in 1992 with SLE with cutaneous manifestations (butterfly-shaped erythematous rash), joint manifestations (polyarthritis), serositis manifestations (massive pleuropericarditis), and immunological manifestations (positive anti-dsDNA antibodies, decreased C3), ignored therapeutically for a long time. In 2010 she complained of dyspnea on medium exertion and leg edemas, with marked increase of PAPs by echocardiography. She was diagnosed with severe PAH (confirmed by right heart catheterization) and in the “Marius Nasta” National Institute of Pneumology she started a treatment with an endothelin receptor antagonist (Bosentan) in combination with a prostacyclin receptor agonist (Selexipag). Since 2013 the patient is on oral anticoagulant treatment for permanent atrial fibrillation.

In 2015 she was referred back to out clinic as she complained of recurrent episodes of massive ascites with evacuatory paracenteses in amounts of about 6-9L per paracentesis. After excluding other causes, ascites was considered to be secondary to the SLE, and a treatment was initiated with Hydroxychloroquine (HCQ) and pulse therapy with Methylprednisolone, on which the remission of the ascites was achieved during the following months. Currently, the SLE is well controlled without recurrence of ascites on treatment with HCQ and gradual decrease until stopping of cortisone doses, and the PAH is stable.

Conclusion. PAH is a rare complication of the SLE, with a complex pathophysiological immune mechanism, for which - together with the specific vasodilator treatment - the increase of immune suppression is recommended.

Open access