79,419 research outputs found
Free and forced vibrations of damped locally-resonant sandwich beams
No full textThis paper addresses the dynamics of locally-resonant sandwich beams, where multi-degree-of-freedom viscously-damped resonators are periodically distributed within the core matrix. On adopting an established model in the literature, which consists of an equivalent single-layer Timoshenko beam coupled with mass-spring-dashpot subsystems representing the resonators, novel and exact analytical expressions are presented for the frequency response and modal response under arbitrary loads. Specifically, the frequency response is built by a direct integration method, while the modal impulse and frequency response functions are derived by a complex modal analysis approach, upon introducing orthogonality conditions pertinent to the complex modes. The expressions obtained for frequency response and modal response hold for any number of resonators and degrees of freedom within the resonators, any number of loads and positions of the loads relative to the resonators. In the proposed complex modal analysis approach, the challenging issue of calculating all complex eigenvalues, without missing anyone, is solved applying a recently-introduced contour-integral algorithm to an exact dynamic stiffness matrix that, here, is built with size depending only on the number of degrees of freedom at the beam ends, regardless of the number of resonators and degrees of freedom within the resonators. Numerical applications prove exactness and robustness of the proposed framework
A dynamic-stiffness approach for damped locally-resonant Timoshenko beams
No full textA dynamic-stiffness matrix approach is presented for locally-resonant Timoshenko beams with a periodic array of viscously-damped multi-degree-of-freedom resonators. First, an exact dynamic condensation of the resonator degrees of freedom is pursued, expressing the resonator reaction forces in terms of the deflections of the attachment points via pertinent frequency-dependent stiffness terms. On this basis, a direct integration deriving from the theory of generalized functions provides the exact dynamic-stiffness matrix of the beam, whose size is 4 × 4 for any the number of resonators and degrees of freedom within the resonators. The dynamic-stiffness matrix is used to calculate the complex eigenvalues of the beam by a recently introduced contour-integral algorithm, without missing anyone. Further, it provides the transmittance for an insight into the elastic wave attenuation properties of the beam
On the Free Vibrations of Non-Classically Damped Locally Resonant Metamaterial Plates
No full textIn this paper, the focus is on the free vibrations of locally resonant metamaterial plates with viscously damped resonators. Upon formulating a dynamic-stiffness model where the resonators are represented via pertinent reaction forces depending on the deflections of the attachment points, the complex eigenvalues are calculated by a contour-integral algorithm introduced in the literature for general nonlinear eigenvalue problems. The interest in the proposed approach is twofold. The dynamic-stiffness model involves a limited number of generalised coordinates compared to the nodal degrees of freedom of a standard finite-element model, and the contour-integral algorithm proves successful in evaluating all complex eigenvalues, without missing any one, with remarkable computational efficiency. Numerical results are presented for Lévy plates, but are readily extendible to other plate theories. Finally, an ad hoc dynamic-stiffness approach is formulated to calculate the frequency response of the plate under arbitrarily placed loads, which is of particular interest to investigate its elastic wave attenuation properties
Cone-morse implant connection system significantly reduces bacterial leakage between implant and abutment : an in vitro study
No full textOsseointegrated implants are very popular dental treatments today in the world. In osseointegrated implants, the occlusal forces are transmitted from prosthesis through an abutment to a dental implant. The abutment is connected to the implant by mean of a screw. A screw is the most used mean for connecting an implant to an abutment. Frequently the screws break and are lost. There is an alternative to screw retained abutment systems: the cone-morse connection (CMC). The CMC, thanks to the absence of the abutment screw, guarantees no micro-gaps, no micro-movements, and a reduction of bacterial leakage between implant and abutment. As P. gingivalis and T. forsythia penetration might have clinical relevance, it was the purpose of this investigation to evaluate molecular leakage of these two bacteria in a new CMC implants systems (Leone Spa®, Florence, Italy). To identify the capability of the implant to protect the internal space from the external environment, the passage of genetically modified Escherichia coli across implant-abutment interface was evaluated. Four cone-morse Leone implants (Leone® Spa, Florence, Italy) were immerged in a bacterial culture for 24 h and bacteria amount was then measured inside implant-abutment interface with Real-time PCR. Bacteria were detected inside all studied implants, with a median percentage of 3% for P. gingivalis and 4% for T. forsythia. Cone-morse connection implant system has very low bacterial leakage percentage and is similar to one-piece implants
Association between oral cleft and transcobalamin 2 polymorphism in a sample study from Nassiriya, Iraq
No full textOrofacial clefts are common congenital defects whose prevalence differs between geographical regions and ethnic groups. The inheritance is complex, involving the contribution of both genetic and environmental factors. The involvement of genes belonging to the folate pathway is still matter of debate, with strong evidences of association and conflicting results. After demonstrating the contribution, for a sample from the Italian population, of common mutations mapping on three genes of the folate pathway, our group tried to unravel their contribution in independent sample studies with different ethnicity. In the present investigation a set of 34 triads with oral cleft from Nassiriya, Iraq, has been genotyped for rs1801133 of MTHFR, rs1801198 of TCN2, and rs4920037 of CBS polymorphisms. Association analysis evidenced a decreased risk of cleft for children carrying the 667G allele at TCN2 gene (P = 0.02). This evidence further supported the relationship between polymorphisms of folate related genes and oral clefts, and outlined the relevance of studying populations having different ethnicity
ODArC – Opend Digital Archive of Catalogues. Centocinquant’anni di esposizioni e collezionismo a Napoli dal 1826 al 1970
No full textIl portale Open Digital ARchive of Catalogues (ODArC), creato dall'autrice, nasce per soddisfare le esigenze della ricerca scientifica nel settore degli studi dedicati all'arte dei secoli XIX e XX. Offre, infatti, agli studiosi la possibilità di consultare i cataloghi delle esposizioni d'arte dell'epoca e quelli delle grandi collezioni disperse. Il portale, già attivo, mette a disposizione del pubblico in maniera libera una prima catalogazione delle mostre sviluppatesi a Napoli in tutto l'Ottocento e nel primo Novecento. Lo scopo ultimo sarà quello d'immettere l'intero patrimonio di cataloghi di mostre pubbliche nazionali e internazionali e delle collezioni d'arte italiane dei secoli XIX e XX
Impressive long-term response with pertuzumab and trastuzumab in HER2-positive breast cancer with brain metastasis
No full textThis is a case report of a 40-year-old woman who, after conservative breast cancer treatment, developed a HER2 positive solitary brain metastasis in the left temporal lobe, without extracranial disease. She underwent surgery resection followed by stereotactic radiotherapy and, because of early brain progression, she was submitted to the first line therapy with pertuzumab, trastuzumab and weekly paclitaxel. After six months of treatment, a brain magnetic resonance imaging revealed a complete disappearance of brain recurrence, which persisted for more than 24 months
Replica-guided trauma surgery
No full textThe aim of this study is to present a new approach to the surgical treatment of fractures of the middle third of the face, based on the use of resorbable materials and stereolithographic models. From 2009 to 2014, we treated 10 cases of orbitozygomatic trauma mostly as secondary surgery. For each case, an anatomical replica had been produced simulating the expected result and was then used to contour the resorbable plates on its surface, even before the beginning of the surgical procedure itself. The plates and meshes already bended act as a guide to bony reduction procedure. No complications occurred: all patients healed well, without inflammatory reactions. The results obtained corresponded to the expected results. This technique has been employed for primary or secondary treatment of fracturesof the middle third facial, where it is not always easy to understand the displacement of bony segments and where the use of resorbables plates could be particularly beneficial, as they do not interfere with the maxillofacial skeleton physiology and avoid the necessity to remove plates and screws. Combined use of stereolithographic model and resorbable materials allow a new surgical approach based on the realization of the surgical procedure on the model, then transferred from the patient to the model, thanks to plates and meshes. This technique helps to overcome many of the limits of the conventional technique: the need of minimal surgical access, in order to minimize facial scarring and the vasculo-nervous structures that cross the head and neck district and the obligation to restore not only the morphology but also the biological functions
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