Abstract
The ocean has a huge impact on our way of life; therefore, there is a need to monitor and protect its biodiversity [...].

Abstract
Bone cements based on poly(methylmethacrylate) (PMMA) are primarily used in joint replacement surgeries. In the fixation of joint replacement, the self-curing cement fills constitutes a very important interface. To under-stand and improve the interaction between cortical bone and bone cement it is essential to characterize the mechanical properties of cement-bone bonded joints in full detail. In this study, the end-notched flexure test was used in the context of pure mode II fracture characterisation of cement-bone bonded joints. A data reduction scheme based on crack equivalent concept was employed to overcome the difficulties inherent to crack length monitoring during damage propagation. A finite element method combined with a cohesive zone model was first used to validate numerically the adopted method. The procedure was subsequently applied to experimental results to determine the fracture toughness of cement-bone bonded joints under pure mode II loading. The consistency of the obtained results leads to the conclusion that the adopted procedure is adequate to carry out fracture characterisation of these joints under pure mode II loading. The innovative aspect of the present work lies in the application of cohesive zone modelling approach to PMMA-based cement-bone bonded joints.

Abstract
Biofouling is the major factor that limits long-term monitoring studies with automated optical instruments. Protection of the sensing areas, surfaces, and structural housing of the sensors must be considered to deliver reliable data without the need for cleaning or maintenance. In this work, we present the design and field validation of different techniques for biofouling protection based on different housing materials, biocides, and transparent coatings. Six optical turbidity probes were built using polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), PLA with copper filament, ABS coated with PDMS, ABS coated with epoxy and ABS assembled with a system for in situ chlorine production. The probes were deployed in the sea for 48 days and their anti-biofouling efficiency was evaluated using the results of the field experiment, visual inspections, and calibration signal loss after the tests. The PLA and ABS were used as samplers without fouling protection. The probe with chlorine production outperformed the other techniques, providing reliable data during the in situ experiment. The copper probe had lower performance but still retarded the biological growth. The techniques based on transparent coatings, epoxy, and PDMS did not prevent biofilm formation and suffered mostly from micro-biofouling.

Abstract
Oceans all over the world are an important way of sustainability in the lives of many people and have a high impact on the economy of most of the coastal countries. With the growth of underwater activity provided by the development of autonomous and remotely controlled vehicles and with the appearance of new underwater sensors, there is also a need to develop and design more robust underwater wireless networks to provide better and faster communications among the devices connected to the network. Nowadays several technologies provide wireless underwater communications. In this work, we address acoustic technology and the implementation of an acoustic communication system which applies a version of frequency modulation. The main goal of this work is to study the 4-FSK modulation technique and verify the efficiency of the communication system according to variables such as communication distance and baud rate. This implementation uses FPGA systems and Xilinx Vitis Model Composer software and MATLAB Simulink software for simulation. The developed communication system was tested in a controlled environment at two stages: aquarium and pool. The tests were carried out transmitting at 3 different baud rates (40, 100 and 200 kbps) in a distance of 100 cm in the aquarium and 5 meters in the pool.

Abstract
Implementing Artificial Reefs (AR) is seen as a worldwide strategy to overcome the problematic environmental impacts due to climate change, overfishing and other activities that damage natural habitats and ecosystems. The production and deployment of ARs involve a series of technical challenges and this work explores a possible alternative solution to overcome some of these challenges. This work addresses a new system for building underwater modular structures integrating monitoring sensors, exploring the potential that Flat Knitted textiles have when specifically designed and used as Knitted Textile Preforms (KTPs) for concrete filling. The casting of AR modules directly in their final position, underwater, brings new paradigms to the design and production of ARs clusters with more complex geometries and geometrical continuity between modules. This manuscript is dedicated to the analysis of variables such as injection pressure and its variations during filling and curing, respectively, as well as the textile structure and geometrical design. It also addresses the possibilities of the technology to embed environmental sensors, which will add functions to the AR structure.