Application of micropolar theory to the description of the skin effect due to hydrogen saturation

A model is proposed for the description of a highly inhomogeneous distribution of hydrogen within a saturated metal specimen (the so-called skin effect due to hydrogen saturation). The model is based on the micropolar continuum approach and results in a nonuniform stress–strain state of a cylindrical metal specimen due to distributed couples or microrotations. The dependence of the diffusion coefficient on the strain energy is considered in order to model stress-induced diffusion. Accumulation of hydrogen within a thin boundary layer results in a highly nonuniform distribution of hydrogen across the specimen. The mutual influence of the stress–strain state and hydrogen accumulation is taken into account. The estimated thickness of the surface layer containing hydrogen is comparable to the thickness observed in experiments. The predicted average concentration coincides with experimental data.

Habitar una bóveda metálica. Quonset Huts en la Base Aeronaval de Rota

During World War II, and even in the years that followed, thousands of American soldiers lived in prefabricated semi-cylindrical metal huts that could be dismantled and reused: Quonset Huts. Their singular design and their multiple uses made Quonset Huts an American military design icon. The daring construction system made it possible to manufacture them in the United States and take them across the Atlantic, armed with a comprehensive instruction manual. The Seabees, American soldiers posted to Spain to build the Naval Station Rota, set up a provisional camp in 1959 comprising fifty-three Quonset Huts. Assembling them in Spain provided housing for 500 soldiers and they were fitted with all types of facilities for their functions. This text aims to shed light on this unknown case of prefabricated dwellings in our country, contextualising the history of their design, construction and installation, and analysing the repercussion of this constructive experiment in the early days of prefabricated construction in Spain.

672 OESOPHAGOGASTRIC ANASTOMOTIC LEAK IN THE THORAX TREATED WITH COVERED METAL STENTS: SAFE AND HIGHLY SUCCESSFUL

Anastomotic leak (AL) develops in 5–22% of cases following oesophagectomy, and results in additional morbidity, and reduction in overall survival. The management of AL has evolved significantly with advances in endoscopic therapies. Covered cylindrical metal stents have been increasingly used, and insertion techniques have improved over time. We aimed to investigate the effectiveness and safety of modern metal stents in the management of AL. Methods All patients who underwent oesophagectomy with thoracic anastomosis between 2006–2020, and subsequently developed AL were retrospectively identified. Initially, treatment details and patient outcomes were assessed for the subgroup of patients where the AL was initially managed using a stent. In all cases, these were cylindrical covered metal stents. Those patients that progressed to surgery after treatment with a stent were then excluded, with the remainder compared to the subgroup of patients that underwent conservative (i.e., non-interventional) treatment for AL. Results Of 63 patients with AL, primary management was with stents in 32 (57%). Technical success was achieved in all stenting procedures, although three patients (9%) developed complications (stent migration). After stenting, six cases (19%) subsequently required escalation to operative management (thoracotomy). The remainder (N = 23) were then compared to those managed conservatively (N = 26) and were found to have a significantly longer length of hospital stay (median: 37 vs. 20 days, p = 0.003). The AL healing rate was 96% in both groups (p = 1.000); one conservatively managed patient died before healing, and one stented patient refused further treatment. Conclusion Endoscopic treatment of oesophageal AL with cylindrical covered metal stents is safe, with a high technical success rate, and low rates of stent-related morbidity. Treatment with stents also avoids the need for operative management including oesophageal disconnection in the majority of cases, whilst leading to successful healing of the AL. However, treatment with stents does significantly increase hospital stay over conservative management, particularly where multiple procedures are required.

FOCUSING OF POSITRON BUNCH WHEN MOVING IN ELECTRON BUNCH WAKEFIELD IN THE DIELECTRIC WAVEGUIDE FILLED WITH PLASMA

The results of numerical PIC-simulation of focusing accelerated (test) positron and drive electron bunches in the dielectric waveguide filled with radially heterogeneous plasma with the vacuum channel are given in the paper. The wakefield was excited by electron bunch in quartz dielectric tube, inserted into cylindrical metal waveguide. The internal area of dielectric tube has been filled with plasma different transverse density profiles, heterogeneous on radius, with the vacuum channel along waveguide axis. Plasma density for all studied cases was so low that plasma frequency was less, than the frequency of the main dielectric mode. Results of numerical PIC simulation have shown that possibility of simultaneous acceleration and focusing of the test positron bunch are possible in the wakefield. The best acceleration happens in case of plasma absence, however at that there is no focusing of test positron bunch.