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The Hong Kong Zhuhai Macao Bridge (HZMB) link is currently one of the largest fixed links ever realised. The link comprises various bridges, causeways, artificial islands and tunnels and has a total length of more than 55 km with an investment of about RMB 120billion (approx. €15 billion). The Link accommodates a dual carriageway with three traffic lanes in each direction. The construction of the Link started at the end of 2010 and was opened to traffic in October 2018. The HZMB Link is internationally regarded as one of the most challenging sea crossing projects in China and a demonstration of China's comprehensive breakthrough in technology, scientific research and other related fields. The offshore part of the HZMB Link, crossing the Pearl River Estuary involves one of the world's longest and deepest immersed tunnels. The tunnel was designed and constructed to meet state-of-the-art requirements and challenging structural, geotechnical and marine/offshore conditions. The HZMB tunnel won the ITA Tunnelling Award Major Project of the Year 2018. This paper presents the project from the Client perspective. The paper will give a general introduction of the project, will provide information regarding the challenging environment in which the tunnel had to be realized and the high demanding design criteria that were applicable. Furthermore, the evaluation of the various technical options will be discussed, ultimately leading to the selection of the immersed tunnel option. The paper will also look into the background of selecting the Design & Build contract approach for this project and the experiences that were built up using this type of contract, new to China on this scale. Finally, the paper introduces how operation and maintenance of the tunnel is planned and executed so as to guarantee the 120-year design lifetime. In Ref. (The Islands and Tunnel Project of HZM Link et al., 2022) more details of the project are discussed from the D&B contractors' perspective. [ABSTRACT FROM AUTHOR]

Intracellular trafficking of ionotropic glutamate receptors is controlled by multiple discrete determinants in receptor subunits. Most such determinants have been localized to the cytoplasmic carboxyl-terminal domain, but other domains in the subunit proteins can play roles in modulating receptor surface expression. Here we demonstrate that formation of an intact glutamate binding site also acts as an additional quality-control check for surface expression of homomeric and heteromeric kainate receptors. A key ligand-bindlng residue in the KA2 subunit, threonine 675, was mutated to either alanine or glutamate, which eliminated affinity for the receptor ligands kainate and glutamate. We found that plasma membrane expression of heteromeric GluR6/KA2(T675A) or GluR6/ KA2(T675E) kainate receptors was markedly reduced compared with wild-type GluR6/KA2 receptors in transfected HEK 293 and COS-7 cells and in cultured neurons. Surface expression of homomeric KA2 receptors lacking a retention/retrieval determinant (KA2R/A) was also reduced upon mutation of Thr-675 and elimination of the ligand binding site. KA2 Thr-675 mutant subunits were able to co-assemble with GluR5 and GluR6 subunits and were degraded at the same rate as wild-type KA2 subunit protein. These results suggest that glutamate binding and associated conformational changes are prerequisites for forward trafticking of intracellular kainate receptors following multimeric assembly. [ABSTRACT FROM AUTHOR]