Fractoluminescence characterization of the energy dissipated during fast fracture of glass

Fractoluminescence experiments are performed on two kinds of silicate glasses. All the light spectra collected during dynamic fracture reveal a black body radiator behaviour, which is interpreted as a crack velocity-dependent temperature rise close to the crack tip. Crack velocities are estimated to be of the order of 1300 m.s$^{-1}$ and fracture process zones are shown to extend over a few nanometers.Comment: Accepted for publication in Europhysics Letters; 5 pages; 4 figure

Development of plasmonic nanomaterial‐based biosensors and bioresponsive materials for diagnostics and molecular‐scale technologies

Anisotropic metal nanoparticles have been successful used in a wide range of biomedical applications, such as diagnostics and therapy, because of their unique optical and electronic properties. Even though there is a wide range of morphologies synthetically available, the understanding of the mechanism behind the anisotropic growth of the nanoparticles is still incomplete. Regarding their application in diagnostics, metallic nanoparticle-based biosensors are facing new challenges, such as the discovery of novel circulating cancer biomarkers (e.g. cell-free DNA), which require sensitivities that cannot be achieved by traditional approaches. The research of this thesis covers current challenges in three specific areas found in the interface between bio- and nanoscience. (1) Colloidal synthesis, where a novel synthesis of gold nanorods (AuNRs) has been developed by the addition of Hofmeister salts into the growth solution. The thorough characterization of the surfactant micelles in the growth solution provided a better understanding of the role of the surfactant as symmetry breaking component in the anisotropic growth. (2) Diagnostics and disease prevention, where two new metal nanoparticle-based biosensors have been developed. The first one exploits the control of a photoresponsive fluid over the dimensions of anisotropic gold nanoparticles for UV exposure sensing and erythema prediction, where the nanoparticles are synthesized and used for sensing purpose at the same time. The second one is a AuNR-based biosensor for circulating cell-free DNA with inverse sensitivity, i.e. the lower the analyte concentration, the higher the response intensity. (3) Bio-inspired materials, where a hybrid system made of AuNR-DNA has been designed to study the sequence-specific binding between transcription factors and DNA. This system has been further expanded to build a versatile multi-logic gate platform, capable of performing six different logic operations. Finally, the use of alternative plasmonic nanomaterials for sensing and bio-inspired materials has also been explored

A new methodology using beam elements for the analysis of steel frames subjected to non-uniform temperatures due to fires

[EN] Non-uniform heating in structures under fire involves the appearance of 3D-phenomena and typically requires the use of complex models built with finite elements shell or solid. Although different procedures have been developed to model the complex thermo-mechanical phenomenon, there is no simple, accurate, and low-cost computational methodology involving the space-time variation of the temperature and displacement fields that opens the path advancing more easily towards modeling more complex structural problems in a fire situation. To overcome this knowledge-gap, this paper presents a new methodology that fulfills those conditions, making it possible to carry out more complex analyses that require many simulations in a short time and at low computational costs. The new methodology to obtain the thermo-mechanical response to non-uniform heating and mechanical loads is general, simple, accurate, and avoids using complex and high-cost finite elements, simplifying the structural modeling, and reducing the computational analysis cost. As a result, complex structural fire engineering problems such as probabilistic and optimization analysis can be handled much more easily, representing a significant step toward the generalized application of performance-based approaches to deal with fire effects on structures. The procedure uses simple but advanced Timoshenko¿s beam-type finite elements and represents the non-uniform temperature space-time field through a mean value of the temperature and the two mean values of the section thermal gradients which are variable in time during the fire. The methodology is satisfactorily validated with results (experimental and numerical) of the Cardington frame test and captures 3D-phenomena such as buckling, flexural-torsional buckling, and warping.Thanks are due to the Fundación Carolina, the Universitat Politècnica de València, and the Universidad Surcolombiana for the support given to this research through the 2018-2019 Ph.D. scholarship.Pallares-Muñoz, MR.; Paya-Zaforteza, I.; Hospitaler Pérez, A. (2021). A new methodology using beam elements for the analysis of steel frames subjected to non-uniform temperatures due to fires. Structures. 31:462-483. https://doi.org/10.1016/j.istruc.2021.02.008S46248331Shan, S., & Li, S. (2020). Fire-induced progressive collapse mechanisms of steel frames with partial infill walls. Structures, 25, 347-359. doi:10.1016/j.istruc.2020.03.023Shakib, H., Zakersalehi, M., Jahangiri, V., & Zamanian, R. (2020). Evaluation of Plasco Building fire-induced progressive collapse. Structures, 28, 205-224. doi:10.1016/j.istruc.2020.08.058Horová, K., Jána, T., & Wald, F. (2013). Temperature heterogeneity during travelling fire on experimental building. Advances in Engineering Software, 62-63, 119-130. doi:10.1016/j.advengsoft.2013.05.001Xu, L., & Zhuang, Y. (2012). Storey-based stability of unbraced steel frames at elevated temperature. Journal of Constructional Steel Research, 78, 79-87. doi:10.1016/j.jcsr.2012.06.010Jacques, L., Béchet, E., & Kerschen, G. (2017). Finite element model reduction for space thermal analysis. Finite Elements in Analysis and Design, 127, 6-15. doi:10.1016/j.finel.2017.01.001B.D. R, M. SK. Behaviour of steel columns with realistic boundary restraints under standard fire. Structures 2020;28:626–37. https://doi.org/https://doi.org/10.1016/j.istruc.2020.08.028.Alos-Moya, J., Paya-Zaforteza, I., Hospitaler, A., & Loma-Ossorio, E. (2019). Valencia bridge fire tests: Validation of simplified and advanced numerical approaches to model bridge fire scenarios. Advances in Engineering Software, 128, 55-68. doi:10.1016/j.advengsoft.2018.11.003Jeffers, A. E., & Beata, P. A. (2014). Generalized shell heat transfer element for modeling the thermal response of non-uniformly heated structures. Finite Elements in Analysis and Design, 83, 58-67. doi:10.1016/j.finel.2014.01.003Rigobello, R., Coda, H. B., & Munaiar Neto, J. (2014). A 3D solid-like frame finite element applied to steel structures under high temperatures. Finite Elements in Analysis and Design, 91, 68-83. doi:10.1016/j.finel.2014.07.005Alos-Moya, J., Paya-Zaforteza, I., Hospitaler, A., & Rinaudo, P. (2017). Valencia bridge fire tests: Experimental study of a composite bridge under fire. Journal of Constructional Steel Research, 138, 538-554. doi:10.1016/j.jcsr.2017.08.008Peris-Sayol, G., Paya-Zaforteza, I., Alos-Moya, J., & Hospitaler, A. (2015). Analysis of the influence of geometric, modeling and environmental parameters on the fire response of steel bridges subjected to realistic fire scenarios. Computers & Structures, 158, 333-345. doi:10.1016/j.compstruc.2015.06.003Quiel, S. E., Moreyra Garlock, M. E., & Paya-Zaforteza, I. (2011). Closed-Form Procedure for Predicting the Capacity and Demand of Steel Beam-Columns under Fire. Journal of Structural Engineering, 137(9), 967-976. doi:10.1061/(asce)st.1943-541x.0000443Davidson, M. T., Harik, I. E., & Davis, D. B. (2013). Fire Impact and Passive Fire Protection of Infrastructure: State of the Art. Journal of Performance of Constructed Facilities, 27(2), 135-143. doi:10.1061/(asce)cf.1943-5509.0000295Allam, A., Nassif, A., & Nadjai, A. (2019). Behaviour of restrained steel beam at elevated temperature – parametric studies. Journal of Structural Fire Engineering, 10(3), 324-339. doi:10.1108/jsfe-11-2018-0036Santiago A, Haremza C, Simões da Silva L, Rodrigues JP. Numerical behaviour of steel columns subject to localized fire loading. In: Topping BH V., Costa Neves LF, Barros RC, editors. Proc. Twelfth Int. Conf. Civil, Struct. Environ. Eng. Comput., Stirlingshire, Scotland: Civil-Comp Press; 2009.Burges I, Alexandrou M. Composite beams. In: Ed. Wald F, Burgess I, Kwasniewski L, Horová K, Caldová E, editors. Benchmark Stud. Verif. Numer. Model. fire Eng. 1st ed., Prague: CTU Publishing House; 2014.Burges I, Alexandrou M. Steel beams. In: Ed. Wald F, Burgess I, Kwasniewski L, Horová K, Caldová E, editors. Benchmark Stud. Verif. Numer. Model. fire Eng. 1st ed., Prague: CTU Publishing House; 2014.Burgess I, Plank R, Shephered P. Vulcan 2019.Santiago A, Haremza C, Lopes F, Franssen JM. Numerical behaviour of steel columns under localized fire loading. In: Ed. Wald F, Burgess I, Kwasniewski L, Horová K, Caldová E, editors. Benchmark Stud. Exp. Valid. Numer. Model. fire Eng. 1st ed., Prague: CTU Publishing House; 2014.Franssen, J. M., Cooke, G. M. E., & Latham, D. J. (1995). Numerical simulation of a full scale fire test on a loaded steel framework. Journal of Constructional Steel Research, 35(3), 377-408. doi:10.1016/0143-974x(95)00010-sSrivastava, G., & Ravi Prakash, P. (2017). An integrated framework for nonlinear analysis of plane frames exposed to fire using the direct stiffness method. Computers & Structures, 190, 173-185. doi:10.1016/j.compstruc.2017.05.013EN 1993-1-2. Eurocode 3: Design of steel structures - Part 1-2: General rules - Structural fire design. Brussels: European Committee for Standardization; 2005.EN 1992-1-2. Eurocode 2: Design of concrete structures - Part 1-2: General rules - Structural fire design. Brussels: European Committee for Standardization; 2004.Purkiss JA, Li LY. Fire safety engineering design of structures. 3rd Editio. Boca Raton: CRC Press; 2013. https://doi.org/10.1201/b16059.Ansys. ANSYS Engineering Analysis System. User manual. Canonsburg, Pensilvania: Houston, Pa. : Swanson Analysis Systems, 2019; 2019.Oñate E. Structural Analysis with the Finite Element Method Linear Statics: Volume 2. Beams, Plates and Shells. 1st ed. Barcelona: Springer; 2013.Magisano, D., Liguori, F., Leonetti, L., de Gregorio, D., Zuccaro, G., & Garcea, G. (2019). A quasi-static nonlinear analysis for assessing the fire resistance of reinforced concrete 3D frames exploiting time-dependent yield surfaces. Computers & Structures, 212, 327-342. doi:10.1016/j.compstruc.2018.11.005Kiakojouri, F., De Biagi, V., Chiaia, B., & Sheidaii, M. R. (2020). Progressive collapse of framed building structures: Current knowledge and future prospects. Engineering Structures, 206, 110061. doi:10.1016/j.engstruct.2019.11006

New modeling strategies for analyzing lateral-torsional buckling in class-4 steel structural members at elevated temperatures using beam-type elements

[EN] Fire is one of the main hazards that can affect steel buildings and bridges and was responsible, e.g., for the collapse of the Plasco building in Tehran, Iran, and the I-65 bridge in Birmingham, Alabama, USA. This vulnerability has motivated the development of advanced computational models to predict the response of steel structures to fire accurately. The mechanical response of slender steel members to fire is especially important because they fail prematurely by buckling at load values below their elastic strength. However, the structural analysis of these members typically requires advanced and complex FE models with shell elements, including initial geometric and material imperfections. These shell models are computationally expensive, complicating the carrying out of parametric and probabilistic studies. Therefore, there is a need to develop simple, accurate, and low-cost computational models as reliable as shell-type models. To overcome this knowledge gap, this paper presents two new modeling strategies that simulate the mechanical response of class-4 steel members subjected to lateral-torsional buckling in fire using Timoshenko beam-type finite elements, which significantly simplify the structural modeling. These strategies are called Fiber Beam Model (FBM) and Cruciform Frame Model (CFM) and include initial geometric and material imperfections and thermal strains. In the FBM, the steel member is represented by a single fiber of I-section beam elements, whereas in the CFM, a cruciform arrangement of rectangular beam finite element fibers idealizes it, making the CFM more complex to build than FBM. Both strategies were satisfactorily validated with experimental and numerical results of Test-1 and Test-3 carried out in the ¿Fire design of steel members with welded or hot-rolled class-4 cross-section¿ (FIDESC4) research project on a slender beam of class-4 section. Although both FBM and CFM correctly captured the LTB resistance of the tested beam, CFM can, in addition, adequately reproduce the local buckling failure and significantly reduced the computational time. That means complex fire engineering problems such as probabilistic and optimization analyses of thin-walled beams can be addressed more easily and accurately, representing an important step towards applying performance-based approaches in slender steel structures under fire.Thanks are due to the Fundacion Carolina for the support given to this research through a Ph.D. scholarship.Pallares-Muñoz, MR.; Paya-Zaforteza, I.; Hospitaler Pérez, A. (2021). New modeling strategies for analyzing lateral-torsional buckling in class-4 steel structural members at elevated temperatures using beam-type elements. Structures. 34:3508-3532. https://doi.org/10.1016/j.istruc.2021.09.087S350835323

Acute-Onset Central Serous Retinopathy After Immunization with COVID-19 mRNA Vaccine

Purpose We report the case of a 33-year-old male who presented with unilateral central serous retinopathy three days after the injection of a COVID-19 vaccine. Observations A 33-year-old healthy Hispanic male referred to the ophthalmology service due to blurry vision and metamorphopsia in the right eye without any flashes, floaters, eye redness or pain. The patient reported that 69 hours prior to presentation he received the first dose of the Pfizer-BioNTech BNT162b2 mRNA COVID-19 vaccine. He denied any past ocular history or pertinent medical history. He does not take any medicines and denies stressful factors in his life. The clinical examination and imaging tests were consistent with central serous retinopathy that resolved in three months. Conclusions and importance This is the first report of an ocular complication potentially associated with a COVID-19 vaccination. Our case contributes information of a side effect potentially related to this new vaccine

ENOBIO - First tests of a dry electrophysiology electrode using carbon nanotubes

We describe the development and first tests of Enobio, a dry electrode sensor concept for biopotential applications. In the proposed electrodes, the tip of the electrode is covered with a forest of multi-walled CNTs that can be coated with Ag/AgCl to provide ionic-electronic transduction. The CNT brush-like structure is to penetrate the outer layers of the skin improving electrical contact as well as increae the contact surface area. In this paper, we report the results of the first tests of this concept -- immersion on saline solution and pig skin signal detection. These indicate performance on a par with state of the art research-oriented wet electrodes.Comment: Submitted and accepted at the 28th IEEE EMBS International Conference, New York City, August 31st-September 3rd, 2006. Figures updated with proper filtering and averagin

Risk Factors for Nosocomial Bacterremia Due to Methicillin-Resistant Staphylococcus Aureus

In a prospective surveillance study (February 1990–December 1991) performed at a 1000-bed teaching hospital to identify risk factors for nosocomial methicillin-resistantStaphylococcus aureus (MRSA) bacteremia, 309 patients were found to be colonized (n=103; 33 %) or infected (n=206; 67 %) by MRSA. Sixty-three of them developed bacteremia. Compared with 114 patients who had nosocomial bacteremia caused by methicillin-sensitiveStaphylococcus aureus during the same period of time, MRSA bacteremic patients had more severe underlying diseases (p<0.01), were more often in intensive care units (p<0.01) and had received prior antibiotic therapy more frequently (p<0.01). To further identify risk factors for MRSA bacteremia, univariate and multivariate analyses of this series of 309 patients were performed using the occurrence of MRSA bacteremia as the dependent variable. Among 14 variables analyzed, intravascular catheterization, defined as one or more intravascular catheters in place for more than 48 h, was the only variable selected by a logistic regression model as an independent risk factor (OR=2.7, CI=1.1–6.6). The results of this study reinforce the concept that recent antibiotic therapy may predispose patients to MRSA infection and suggest that among patients colonized or infected by MRSA, those with intravascular catheters are at high risk of developing MRSA bacteremia

An evaluation of management strategies for Atlantic tuna stocks

International agreements for the International Commission for the Conservation of Atlantic Tunas (ICCAT) convention area imply that Atlantic tuna stocks should be managed by strategies based on maximum sustainable yield (MSY); however, there is concern whether this will actually ensure sustainability with sufficiently high probability consistent with the principals of the precautionary approach. Therefore, the performance of MSY management strategies based on current assessment procedures was evaluated using a computer simulation framework. The framework includes the data collection, assessment, prediction, and management processes, as well as the implementation of management regulations. It therefore provides an integrated way to evaluate the relative importance of and the interactions between each component of the system with regard to the overall success of the management strategy. The study elucidates guidelines about assessment and management that are general enough to be applied to all tunas in the Atlantic Ocean. It does so by comparing different hypotheses about management and assessment for three stocks (North Atlantic albacore, Atlantic bigeye and East Atlantic skipjack), which are representative of the variety encountered (i.e. from data rich to poor and tropical to temperate waters) in ICCAT stocks. Management performance was especially sensitive to the carrying capacity of the stock. The type of proxy used for MSY was more important to the success of the procedure than the frequency of assessment or the number of indices used in the assessment. Whilst the procedure was successful at achieving the management objectives for albacore, it was only partially successful for bigeye and was too conservative for skipjack.No disponibl