Robust optimum design of MTMD for control of footbridges subjected to human-induced vibrations via the CIOA

Letícia Fleck Fadel Miguel,Otávio Augusto Peter de Souza 국제구조공학회 2023 Structural Engineering and Mechanics, An Int'l Jou Vol.86 No.5

It is recognized that the installation of energy dissipation devices, such as the tuned mass damper (TMD), decreases the dynamic response of structures, however, the best parameters of each device persist hard to determine. Unlike many works that perform only a deterministic optimization, this work proposes a complete methodology to minimize the dynamic response of footbridges by optimizing the parameters of multiple tuned mass dampers (MTMD) taking into account uncertainties present in the parameters of the structure and also of the human excitation. For application purposes, a steel footbridge, based on a real structure, is studied. Three different scenarios for the MTMD are simulated. The proposed robust optimization problem is solved via the Circle-Inspired Optimization Algorithm (CIOA), a novel and efficient metaheuristic algorithm recently developed by the authors. The objective function is to minimize the mean maximum vertical displacement of the footbridge, whereas the design variables are the stiffness and damping constants of the MTMD. The results showed the excellent capacity of the proposed methodology, reducing the mean maximum vertical displacement by more than 36% and in a computational time about 9% less than using a classical genetic algorithm. The results obtained by the proposed methodology are also compared with results obtained through traditional TMD design methods, showing again the best performance of the proposed optimization method. Finally, an analysis of the maximum vertical acceleration showed a reduction of more than 91% for the three scenarios, leading the footbridge to acceleration values below the recommended comfort limits. Hence, the proposed methodology could be employed to optimize MTMD, improving the design of footbridges.

Transmission electron microscopy for characterization of acrosomal damage after Percoll gradient centrifugation of cryopreserved bovine spermatozoa

Letícia Z. Oliveira,Vera F. M. Hossepian de Lima,Marcelo A. Levenhagen,Ricarda M. dos Santos,Terezinha I. Assumpção,José O. Jacomini,André F. C. de Andrade,Rubens P. de Arruda,Marcelo E. Beletti 대한수의학회 2011 Journal of Veterinary Science Vol.12 No.3

The objective of this study was to characterize acrosomal ultrastructure following discontinuous Percoll gradient centrifugation of cryopreserved bovine sperm. Semen was collected from six bulls of different breeds and three ejaculates per bull were evaluated. Frozen semen samples were thawed and the acrosomal region of sperm cells was evaluated by transmission electron microscopy (TEM) before (n = 18) and after (n = 18) Percoll centrifugation. The evaluation of 20 sperm heads from each of the 36 samples analyzed ensured that a large number of cells were investigated. The data were subjected to analysis of variance at a level of significance of 5%. Percoll centrifugation reduced the percentage of sperm exhibiting normal acrosomes (from 61.77 to 30.24%), reduced the percentage of sperm presenting atypical acrosome reactions (from 28.38 to 4.84%) and increased the percentage of sperm exhibiting damage in the acrosome (from 6.14 to 64.26%). The percentage of sperm with typical acrosome reactions was not significantly different before (3.70%) and after (0.67%) centrifugation. TEM distinguished four different types of acrosomal status and enabled ultrastructural characterization of acrosomal injuries. The percentage of sperm exhibiting normal acrosomes decreased and damage in the acrosome was the most frequent acrosomal injury with the Percoll gradient centrifugation protocol utilized.

O uso de tarefas comunicativas para avaliar alunos de português como língua estrangeira

( Letícia Grubert Dos Santos ) 한국포르투갈-브라질학회 2007 포르투갈-브라질 연구 Vol.4 No.2

This article presents a reading and writing communicative task which makes part of a placement test of the Portuguese for Foreigners Program (PPE)/UFRGS. The task was developed to evaluate different levels of students’ achievement in the same situation of language use (Schlatter, et tal 2003), according to the PPE proficiency orientation (Bakhtin, 1992) and the assessed levels Basic Ⅰ, Basic Ⅱ, Intermediate Ⅰ and Intermediate Ⅱ. In order to analyze the utility of this Test (Bachman e Palmer, 1996) and the operationally of the adopted assessment criteria, two examples of students of different levels are shown and discussed. We hope to contribute to the discussion regarding to the elaboration of assessment tasks and to the teaching training of Portuguese as a foreign language.

Empréstimos lexicais no português do Brasil: análise de ocorrências em textos jornalísticos

Letícia Soares Bortolini 한국 포르투갈-브라질 학회 2010 포르투갈-브라질 연구 Vol.7 No.2

Linguists accept that no language is completely pure and free of transferred and loaned language forms. This paper aims to discuss the incorporation of new words in the current Brazilian Portuguese. A member of the Brazilian Federal Parliament, Aldo Rebelo, passed a bill which aims to protect the Portuguese language from foreign words. It states that Portuguese, and no other language, must be used in public documents and events and also in mass media, product handling and shipping. In order to debate about the pertinence of such idea, firstly, I present the approaches of four Brazilian linguists on the topic of transferred and loaned words to Brazilian Portuguese. Next, I present the occurrence of loan-words in Brazilian newspapers through the analyses of three issues of Zero Hora and two issues of Correio do Povo. The article concludes that control and punishment are certainly undesirable and negative practices when we deal with complex cultural phenomena, as is the case of linguistic contacts and exchanges in our modern societies.

Production, Partial Characterization, and Immobilization in Alginate Beads of an Alkaline Protease from a New Thermophilic Fungus Myceliophthora sp.

Letícia Maria Zanphorlin,Fernanda Dell Antonio Facchini,Filipe Vasconcelos,Rafaella Costa Bonugli-Santos,André Rodrigues,Lara Durães Sette,Eleni Gomes,Gustavo Orlando Bonilla-Rodriguez 한국미생물학회 2010 The journal of microbiology Vol.48 No.3

Thermophilic fungi produce thermostable enzymes which have a number of applications, mainly in biotechnological processes. In this work, we describe the characterization of a protease produced in solidstate (SSF) and submerged (SmF) fermentations by a newly isolated thermophilic fungus identified as a putative new species in the genus Myceliophthora. Enzyme-production rate was evaluated for both fermentation processes, and in SSF, using a medium composed of a mixture of wheat bran and casein, the proteolytic output was 4.5-fold larger than that obtained in SmF. Additionally, the peak of proteolytic activity was obtained after 3 days for SSF whereas for SmF it was after 4 days. The crude enzyme obtained by both SSF and SmF displayed similar optimum temperature at 50°C, but the optimum pH shifted from 7 (SmF) to 9 (SSF). The alkaline protease produced through solid-state fermentation (SSF), was immobilized on beads of calcium alginate, allowing comparative analyses of free and immobilized proteases to be carried out. It was observed that both optimum temperature and thermal stability of the immobilized enzyme were higher than for the free enzyme. Moreover, the immobilized enzyme showed considerable stability for up to 7 reuses.

Letramento e ensino de línguas adicionais: uma proposta de prática pedagógica

Letícia Soares Bortolini 한국 포르투갈-브라질 학회 2009 포르투갈-브라질 연구 Vol.6 No.2

This paper aims to suggest that literacy should be one of the objectives of second language teaching. The proposal is based on New Literacies Studies (Barton 1994; Gee 1990, 2004; Street 1984, 1985) theoretical framework. According to this perspective, literacy, or literacy practices (Street, 1984), is defined as collective practices which are socially and culturally organized (Cole & Scribner, 1981), and which have writing technology as their foundation. First, I define the concept of language use and present the concept of literacy as essential to the development of second language learners’ communicative competence and sociolinguistic proficiency. Relying on previous study (Bortolini, 2006), first I suggest steps for the preparation of didactic material that focus on language use. Next, I present a didactic lesson where the main aim is literacy in the second language. This article concludes that having literacy as a pedagogical objective promotes the language education of more than just language students, but of citizens in general. In the classroom, the study of the target language through activities that focus different social practices encourage students to participate in real contexts of language use (in his/her own society or in a foreign one) in a more autonomous and confident way.

Cytocompatibility and cell proliferation evaluation of calcium phosphate-based root canal sealers

Letícia Boldrin Mestieri,Ivana Maria Zaccara,Lucas Siqueira Pinheiro,Fernando Branco Barletta,Patrícia Maria Polli Kopper,Fabiana Soares Grecca 대한치과보존학회 2020 Restorative Dentistry & Endodontics Vol.45 No.1

Objectives: This study aimed to evaluate the cell viability and migration of Endosequence Bioceramic Root Canal Sealer (BC Sealer) compared to MTA Fillapex and AH Plus. Materials and Methods: BC Sealer, MTA Fillapex, and AH Plus were placed in contact with culture medium to obtain sealers extracts in dilution 1:1, 1:2 and 1:4. 3T3 cells were plated and exposed to the extracts. Cell viability and migration were assessed by 3-(4,5-dimethyl-thiazoyl)-2,5-diphenyl-tetrazolium bromide (MTT) and Scratch assay, respectively. Data were analyzed by Kruskal-Wallis and Dunn's test (p < 0.05). Results: The MTT assay revealed greater cytotoxicity for AH Plus and MTA Fillapex at 1:1 dilution when compared to control (p < 0.05). At 1:2 and 1:4 dilutions, all sealers were similar to control (p > 0.05) and MTA Fillapex was more cytotoxic than BC Sealer (p < 0.05). Scratch assay demonstrated the continuous closure of the wound according to time. At 30 hours, the control group presented closure of the wound (p < 0.05). At 36 hours, only BC Sealer presented the closure when compared to AH Plus and MTA Fillapex (p < 0.05). At 42 hours, AH Plus and MTA Fillapex showed a wound healing (p > 0.05). Conclusions: All tested sealers demonstrated cell viability highlighting BC Sealer, which showed increased cell migration capacity suggesting that this sealer may achieve better tissue repair when compared to other tested sealers.

Evaluation of bone substitutes for treatment of peri-implant bone defects: biomechanical, histological, and immunohistochemical analyses in the rabbit tibia

Pâmela Letícia dos Santos,Rafael Scaf de Molon,Thallita Pereira Queiroz,Roberta Okamoto,Ana Paula de Souza Faloni,Jéssica Lemos Gulinelli,Eloá Rodrigues Luvizuto,Idelmo Rangel Garcia Junior 대한치주과학회 2016 Journal of Periodontal & Implant Science Vol.46 No.3

Purpose: We sought to evaluate the effectiveness of bone substitutes in circumferential periimplant defects created in the rabbit tibia. Methods: Thirty rabbits received 45 implants in their left and right tibia. A circumferential bone defect (6.1 mm in diameter/4 mm depth) was created in each rabbit tibia using a trephine bur. A dental implant (4.1 mm × 8.5 mm) was installed after the creation of the defect, providing a 2-mm gap. The bone defect gaps between the implant and the bone were randomly filled according to the following groups: blood clot (CO), particulate Bio-Oss® (BI), and Bio-Oss® Collagen (BC). Ten animals were euthanized after periods of 15, 30, and 60 days. Biomechanical analysis by means of the removal torque of the implants, as well as histologic and immunohistochemical analyses for protein expression of osteocalcin (OC), Runx2, OPG, RANKL, and TRAP were evaluated. Results: For biomechanics, BC showed a better biological response (61.00±15.28 Ncm) than CO (31.60±14.38 Ncm) at 30 days. Immunohistochemical analysis showed significantly different OC expression in CO and BC at 15 days, and also between the CO and BI groups, and between the CO and BC groups at 60 days. After 15 days, Runx2 expression was significantly different in the BI group compared to the CO and BC groups. RANKL expression was significantly different in the BI and CO groups and between the BI and BC groups at 15 days, and also between the BI and CO groups at 60 days. OPG expression was significantly higher at 60 days postoperatively in the BI group than the CO group. Conclusions: Collectively, our data indicate that, compared to CO and BI, BC offered better bone healing, which was characterized by greater RUNX2, OC, and OPG immunolabeling, and required greater reversal torque for implant removal. Indeed, along with BI, BC presents promising biomechanical and biological properties supporting its possible use in osteoconductive grafts for filling peri-implant gaps.

Can different agents reduce the damage caused by bleaching gel to pulp tissue? A systematic review of basic research

Batista Letícia Aparecida Silva,dos Reis-Prado Alexandre Henrique,Chaves Hebertt Gonzaga dos Santos,de Arantes Lara Cancella,Morgan Luís Fernando Santos Alves,André Carolina Bosso,Suzuki Thaís Yumi,Be 대한치과보존학회 2023 Restorative Dentistry & Endodontics Vol.48 No.4

Objectives: This study aimed to investigate the effectiveness of different topical/systemic agents in reducing the damage caused by bleaching gel to pulp tissue or cells. Materials and Methods: Electronic searches were performed in July 2023. In vivo and in vitro studies evaluating the effects of different topical or systemic agents on pulp inflammation or cytotoxicity after exposure to bleaching agents were included. The risk of bias was assessed. Results: Out of 1,112 articles, 27 were included. Nine animal studies evaluated remineralizing/anti-inflammatories agents in rat molars subjected to bleaching with 35%– 38% hydrogen peroxide (HP). Five of these studies demonstrated a significant reduction in inflammation caused by HP when combined with bioglass or MI Paste Plus (GC America), or following KF-desensitizing or Otosporin treatment (n = 3). However, orally administered drugs did not reduce pulp inflammation (n = 4). Cytotoxicity (n = 17) was primarily assessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay on human dental pulp cells and mouse dental papilla Cell-23 cells. Certain substances, including sodium ascorbate, butein, manganese chloride, and peroxidase, were found to reduce cytotoxicity, particularly when applied prior to bleaching. The risk of bias was high in animal studies and low in laboratory studies. Conclusions: Few in vivo studies have evaluated agents to reduce the damage caused by bleaching gel to pulp tissue. Within the limitations of these studies, it was found that topical agents were effective in reducing pulp inflammation in animals and cytotoxicity. Further analyses with human pulp are required to substantiate these findings.

Deposition of hybrid structures of reduced graphene oxide and tin dioxide thin films, and persistent photoconductivity observation

de Oliveira Letícia da S.,Fonseca Lucas P.,de Souza Renato D.,Bueno Cristina de F.,Martins Lucas M.,Scalvi Luis V.A. 한국물리학회 2022 Current Applied Physics Vol.41 No.-

Reduced graphene oxide (rGO) is deposited on glass substrate by dripping and sol-gel-coating methods giving rise to nanostructures. When in combination with thin films of SnO2, they form a heterostructure SnO2:2 at% Eu/ rGO, which alters the surface electrical conductivity. SnO2 and rGO were also combined as a composite, with conductivity strongly affected by ultraviolet excitation, and shows persistent photoconductivity (PPC) phenomenon even very close to room temperature. Both sort o hybrid structures can be applied in electronic devices. The SnO2 films are deposited via chemical route by sol-gel or by a mixed technique that combines powders generated by drying the sol-gel solution with resistive evaporation of this powder. Resistivity measured as a function of temperature show that the SnO2:2 at%Eu sample behaves very similarly to the SnO2:2 at%Eu/rGO heterostructure sample, with the same energy level for the dominant defect, 172 meV, coincident with ionization of oxygen vacancies. Despite not changing the position of this level, the presence of rGO on the surface of the SnO2 film induces a decrease in conductivity in vacuum, demonstrating the surface interaction.