Abstract
Reinforced concrete structures are prevalent in infrastructure and are of significant economic and social importance to humanity. However, they are prone to decay from cement paste carbonation. pH sensors have been developed to monitor cement paste carbonation, but their adoption by the industry remains limited. This work introduces two new methods for monitoring cement paste carbonation in real time that have been validated through the accelerated carbonation of cement paste samples. Both configurations depart from traditional pH monitoring. In the first configuration, the carbonation depth of a cement paste sample is measured using two CO2 optical fiber sensors. One sensor is positioned on the surface of the sample, while the other is embedded in the middle. As the carbonation depth progresses and reaches the embedded CO2 sensor, the combined response of the sensors changes. In the second configuration, a multimode fiber is embedded within the paste, and its carbonation is monitored by observing the increase in reflected light intensity (1.6-18%) resulting from the formation of CaCO3. Its applicability in naturally occurring carbonation is tested at concentrations of 3.2% CO2, and the influence of water is positively evaluated; thus, this setup is suitable for real-world testing and applications.

Abstract
The increasing demand for precise chemical and biological sensing has led to the development of highly efficient plasmonic optical fiber sensors. Therefore, it is essential to optimize and match the operating wavelength region of both the optical fiber configuration and localized surface plasmon resonance of nanoparticles (NPs). This can be achieved by developing NPs that can reach resonance at near-infrared wavelengths, where refractive index sensitivity is enhanced, and silica optical fibers have lower losses. High aspect-ratio bimetallic Au@Ag nanorods and different side-polished fiber structures are tested using numerical simulations. The selected optical fiber configuration was based on a side-polished fiber with a 1 mm polished section. It is compared power losses and power at the NP interface for two configurations: a step-index single-mode fiber (SMF) with core/cladding diameters of 8.2/125 µm and a multimode graded-index fiber (GIF) with 62.5/125 µm at various polishing depths. The results showed that the best performance for both configurations was achieved at similar polishing depths, namely 59.5 and 55.2 µm for the SMF and GIF, respectively. The optical impact of retardation effects due to the proximity with the fiber structure were also observed, which caused a reduction in sensitivity from 1750 nm/RIU to 1500 nm/RIU and a red-shift of around 70 nm. © 2023 SPIE.

Abstract
The aim of this study was to assess the antimicrobial effects of myrtle (Myrtus communis L.) essential oil (EO) on pathogenic (E. coli O157:H7 NCTC 12900; Listeria monocytogenes ATCC BAA-679) and spoilage microbiota in beef and determine its minimum inhibitory concentration (MIC) and antioxidant activity. The behavior of LAB, Enterobacteriaceae, Pseudomonas spp., and fungi, as well as total mesophilic (TM) and total psychotropic (TP) counts, in beef samples, was analyzed during storage at 2 and 8 C-degrees in two different packaging systems (aerobiosis and vacuum). Leaves of myrtle were dried, its EO was extracted by hydrodistillation using a Clevenger-type apparatus, and the chemical composition was determined using chromatographical techniques. The major compounds obtained were myrtenyl acetate (15.5%), beta-linalool (12.3%), 1,8-cineole (eucalyptol; 9.9%), geranyl acetate (7.4%), limonene (6.2%), alpha-pinene (4.4%), linalyl o-aminobenzoate (5.8%), alpha-terpineol (2.7%), and myrtenol (1.2%). Myrtle EO presented a MIC of 25 mu L/mL for E. coli O157:H7 NCTC 12900, E. coli, Listeria monocytogenes ATCC BAA-679, Enterobacteriaceae, and E. coli O157:H7 ATCC 35150 and 50 mu L/mL for Pseudomonas spp. The samples packed in aerobiosis had higher counts of deteriorative microorganisms than samples packed under vacuum, and samples with myrtle EO presented the lowest microbial contents, indicating good antimicrobial activity in beef samples. Myrtle EO is a viable natural alternative to eliminate or reduce the pathogenic and deteriorative microorganisms of meat, preventing their growth and enhancing meat safety.

Abstract
Long-term stability and high scalability are significant issues in plasmonic optical fiber sensors. This work presents a highly scalable and low-cost all-chemical approach for production of gold-coated silver thin-films, ensuring high performance and chemical stability. © Optica Publishing Group 2023, © 2023 The Authors.

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