Modeling Micro-Porous Surfaces for Secondary Electron Emission Control to Suppress Multipactor

This work seeks to understand how the topography of a surface can be engineered to control secondary electron emission (SEE) for multipactor suppression. Two unique, semi-empirical models for the secondary electron yield (SEY) of a micro-porous surface are derived and compared. The first model is based on a two-dimensional (2D) pore geometry. The second model is based on a three-dimensional (3D) pore geometry. The SEY of both models is shown to depend on two categories of surface parameters: chemistry and topography. An important parameter in these models is the probability of electron emissions to escape the surface pores. This probability is shown by both models to depend exclusively on the aspect ratio of the pore (the ratio of the pore height to the pore diameter). The increased accuracy of the 3D model (compared to the 2D model) results in lower electron escape probabilities with the greatest reductions occurring for aspect ratios less than two. In order to validate these models, a variety of micro-porous gold surfaces were designed and fabricated using photolithography and electroplating processes. The use of an additive metal-deposition process (instead of the more commonly used subtractive metal-etch process) provided geometrically ideal pores which were necessary to accurately assess the 2D and 3D models. Comparison of the experimentally measured SEY data with model predictions from both the 2D and 3D models illustrates the improved accuracy of the 3D model. For a micro-porous gold surface consisting of pores with aspect ratios of two and a 50% pore density, the 3D model predicts that the maximum total SEY will be one. This provides optimal engineered surface design objectives to pursue for multipactor suppression using gold surfaces

Nanopillar Arrays on Semiconductor Membranes as Electron Emission Amplifiers

A new transmission-type electron multiplier was fabricated from silicon-on-insulator (SOI) material by integrating an array of one dimensional (1D) silicon nanopillars onto a two dimensional (2D) silicon membrane. Primary electrons are injected into the nanopillar-membrane system from the flat surface of the membrane, while electron emission from the other side is probed by an anode. The secondary electron yield (SEY) from nanopillars is found to be about 1.8 times that of plane silicon membrane. This gain in electron number is slightly enhanced by the electric field applied from the anode. Further optimization of the dimensions of nanopillars and membrane and application of field emission promise an even higher gain for detector applications and allow for probing of electronic/mechanical excitations in nanopillar-membrane system excited by incident particles or radiation.Comment: 4 figure

Exocrine and endocrine pancreatic function in patients with pancreatico-jejunostomy or pancreatic duct occlusion after pancreaticoduodenectomy

Pancreatic duct occlusion (PDO) is performed in some centres to avoid complications of pancreaticojejunostomy (PJ) after pancreaticodudodenectomy. The aim of our study was to study the exo- and endocrine pancreatic function, nutritional status and quality of life in patients with a PJ or PDO after a pancreatico-duodenectomy (PD)

Optimized Preoperative Planning of Double Outlet Right Ventricle Patients by 3D Printing and Virtual Reality:A Pilot Study

OBJECTIVES: In complex double outlet right ventricle (DORV) patients, the optimal surgical approach may be difficult to assess based on conventional two-dimensional (2D) ultrasound (US) and computed tomography (CT) imaging. The aim of this study is to assess the added value of 3D printed and 3D Virtual Reality (VR) models of the heart used for surgical planning in DORV patients, supplementary to the gold standard 2D imaging modalities.METHODS: Five patients with different DORV-subtypes and high-quality CT scans were selected retrospectively. 3D prints and 3D-VR models were created. Twelve congenital cardiac surgeons and paediatric cardiologists, from three different hospitals, were shown 2D-CT first, after which they assessed the 3D print and 3D-VR models in random order. After each imaging method, a questionnaire was filled in on the visibility of essential structures and the surgical plan.RESULTS: Spatial relationships were generally better visualized using 3D methods (3D printing/3D-VR) than in 2D. The feasibility of VSD patch closure could be determined best using 3D-VR reconstructions (3D-VR 92%, 3D print 66%, and US/CT 46%, P &lt; 0.01). The percentage of proposed surgical plans corresponding to the performed surgical approach was 66% for plans based on US/CT, 78% for plans based on 3D printing, and 80% for plans based on 3D-VR visualization.CONCLUSIONS: This study shows that both 3D printing and 3D-VR have additional value for cardiac surgeons and cardiologists over 2D imaging, because of better visualization of spatial relationships. As a result, the proposed surgical plans based on the 3D visualizations matched the actual performed surgery to a greater extent.</p

Risks and benefits of sharing patient information on social media:a digital dilemma

Social media (SoMe) has witnessed remarkable growth and emerged as a dominant method of communication worldwide. Platforms such as Facebook, X (formerly Twitter), LinkedIn, Instagram, TikTok, and YouTube have become important tools of the digital native generation. In the field of medicine, particularly, cardiology, attitudes towards SoMe have shifted, and professionals increasingly utilize it to share scientific findings, network with experts, and enhance teaching and learning. Notably, SoMe is being leveraged for teaching purposes, including the sharing of challenging and intriguing cases. However, sharing patient data, including photos or images, online carries significant implications and risks, potentially compromising individual privacy both online and offline. Privacy and data protection are fundamental rights within European Union treaties, and the General Data Protection Regulation (GDPR) serves as the cornerstone of data protection legislation. The GDPR outlines crucial requirements, such as obtaining 'consent' and implementing 'anonymization', that must be met before sharing sensitive and patient-identifiable information. Additionally, it is vital to consider the patient's perspective and prioritize ethical and social considerations when addressing challenges associated with sharing patient information on SoMe platforms. Given the absence of a peer-review process and clear guidelines, we present an initial approach, a code of conduct, and recommendations for the ethical use of SoMe. In conclusion, this comprehensive review underscores the importance of a balanced approach that ensures patient privacy and upholds ethical standards while harnessing the immense potential of SoMe to advance cardiology practice and facilitate knowledge dissemination.</p

Risks and benefits of sharing patient information on social media:a digital dilemma

Social media (SoMe) has witnessed remarkable growth and emerged as a dominant method of communication worldwide. Platforms such as Facebook, X (formerly Twitter), LinkedIn, Instagram, TikTok, and YouTube have become important tools of the digital native generation. In the field of medicine, particularly, cardiology, attitudes towards SoMe have shifted, and professionals increasingly utilize it to share scientific findings, network with experts, and enhance teaching and learning. Notably, SoMe is being leveraged for teaching purposes, including the sharing of challenging and intriguing cases. However, sharing patient data, including photos or images, online carries significant implications and risks, potentially compromising individual privacy both online and offline. Privacy and data protection are fundamental rights within European Union treaties, and the General Data Protection Regulation (GDPR) serves as the cornerstone of data protection legislation. The GDPR outlines crucial requirements, such as obtaining 'consent' and implementing 'anonymization', that must be met before sharing sensitive and patient-identifiable information. Additionally, it is vital to consider the patient's perspective and prioritize ethical and social considerations when addressing challenges associated with sharing patient information on SoMe platforms. Given the absence of a peer-review process and clear guidelines, we present an initial approach, a code of conduct, and recommendations for the ethical use of SoMe. In conclusion, this comprehensive review underscores the importance of a balanced approach that ensures patient privacy and upholds ethical standards while harnessing the immense potential of SoMe to advance cardiology practice and facilitate knowledge dissemination.</p

Impact of analyzing fewer image frames per segment during offline volumetric radiofrequency-based intravascular ultrasound measurements of target lesions prior to percutaneous coronary interventions

In the present study, we evaluated the impact of a 50% reduction in number of image frames (every second frame) on the analysis time and variability of offline volumetric radiofrequency-based intravascular ultrasound (RF-IVUS) measurements in target lesions prior to percutaneous coronary interventions (PCI). Volumetric RF-IVUS data of vessel geometry and plaque composition are generally obtained by a semi-automated analysis process that includes time-consuming manual contour editing. A reduction in the number of frames used for volumetric analysis may speed up the analysis, but could increase measurement variability. We repeatedly performed offline volumetric analyses in RF-IVUS image sets of 20 mm-long coronary segments that contained 30 de novo lesions prior to PCI. A 50% reduction in frames decreased the analysis time significantly (from 57.5 ± 7.3 to 35.7 ± 3.7 min; P < 0.0001) while geometric and compositional RF-IVUS measurements did not differ significantly from measurements obtained from all frames. The variability between measurements on the reduced number of frames versus all frames was comparable to the intra-observer measurement variability. In target lesions prior to PCI, offline volumetric RF-IVUS analyses can be performed using a reduced number of image frames (every second frame). This reduces the time of analysis without substantially increasing measurement variability