Large-scale phenotyping of patients with long COVID post-hospitalization reveals mechanistic subtypes of disease

One in ten severe acute respiratory syndrome coronavirus 2 infections result in prolonged symptoms termed long coronavirus disease (COVID), yet disease phenotypes and mechanisms are poorly understood1. Here we profiled 368 plasma proteins in 657 participants ≥3 months following hospitalization. Of these, 426 had at least one long COVID symptom and 233 had fully recovered. Elevated markers of myeloid inflammation and complement activation were associated with long COVID. IL-1R2, MATN2 and COLEC12 were associated with cardiorespiratory symptoms, fatigue and anxiety/depression; MATN2, CSF3 and C1QA were elevated in gastrointestinal symptoms and C1QA was elevated in cognitive impairment. Additional markers of alterations in nerve tissue repair (SPON-1 and NFASC) were elevated in those with cognitive impairment and SCG3, suggestive of brain–gut axis disturbance, was elevated in gastrointestinal symptoms. Severe acute respiratory syndrome coronavirus 2-specific immunoglobulin G (IgG) was persistently elevated in some individuals with long COVID, but virus was not detected in sputum. Analysis of inflammatory markers in nasal fluids showed no association with symptoms. Our study aimed to understand inflammatory processes that underlie long COVID and was not designed for biomarker discovery. Our findings suggest that specific inflammatory pathways related to tissue damage are implicated in subtypes of long COVID, which might be targeted in future therapeutic trials

Open-ended Coaxial Cavities with Corrugated Inner and Outer Walls

In this work an open-ended coaxial cavity with a corrugated insert and a relatively small number of corrugations on the outer wall is studied. In particular, the Spatial Harmonics Method (SHM) is employed in order to derive the TE modes characteristic equation, which is then solved by truncation for the calculation of the corresponding eigenvalues. Special care is given in the expansion functions used in order to avoid numerical instabilities in the calculation of high-order spatial terms. Various cases of outer wall corrugations are studied numerically in order to identify the effect of the outer corrugations and understand the mode coupling mechanism. © 2015, Springer Science+Business Media New York

Selectivity Properties of Coaxial Gyrotron Cavities With Mode Converting Corrugations

Longitudinally corrugated inserts have been proposed as an additional mean to enhance the selectivity properties of coaxial gyrotron cavities. However, when increasing the frequency and the output power, the corrugated insert may not be sufficient to ensure mode stability. Vane loaded cavities with corrugated inserts seem to have the potential for superior mode selectivity and could be employed to facilitate the development of multimegawatt gyrotrons. In this paper, a numerical code based on the spatial harmonics method is used to study the spectrum rearrangement of a typical coaxial cavity with corrugated insert in which additional wedge-shaped corrugations are introduced on the outer wall. A general design procedure for the upgrade of the mode selectivity is presented. Its merits are demonstrated for a 140-GHz gyrotron cavity. © 2016 IEEE

Improved Suppression of Parasitic Oscillations in Gyrotron Beam Tunnels by Proper Selection of the Lossy Ceramic Material

Lossy dielectric materials are used in gyrotron beam tunnels to suppress possible parasitic oscillations by raising their starting currents. The dependence of the overall losses of the structure on the dielectric properties of the material is theoretically and numerically investigated and it is shown that materials with high values of the loss tangent are not suitable for the suppression of the parasitics. The beam tunnel is studied parametrically with a full-wave code, which calculates the diffraction and dielectric losses of the cold-cavity modes. A simplified geometry involving analytic relations is used to verify the results and investigate the underlying physics. It is shown that the proper selection of the material properties and its radial thickness can improve the absorption of the fields significantly. © 2018 IEEE

A comparative study on the modeling of dynamic after-cavity interaction in gyrotrons

There are cases where gyrotron interaction simulations predict dynamic After-Cavity Interaction (ACI). In dynamic ACI, a mode is excited by the electron beam at a dominant frequency in the gyrotron cavity and, at the same time, this mode is also interacting with the beam at a different frequency in the non-linear uptaper after the cavity. In favor of dynamic ACI being a real physical effect, there are some experimental findings that could be attributed to it, as well as some physical rationale indicating the possibility of a mode being resonant with the beam at different frequencies in different regions. However, the interaction codes used in dynamic ACI prediction up to now are based on simplifications that put questions on their capability of correctly simulating this effect. In this work, the shortcomings of the usual simplifications with respect to dynamic ACI modeling, namely, the trajectory approach and the single-frequency boundary condition, are identified. Extensive simulations of dynamic ACI cases are presented, using several "in-house" as well as commercial codes. We report on the comparison and the assessment of different modeling approaches and their results and we discuss whether, in some cases, dynamic ACI can be a numerical artifact or not. Although the possibility of existence of dynamic ACI in gyrotrons is not disputed, it is concluded that the widely used trajectory approach for gyrotron interaction modeling is questionable for simulating dynamic ACI and can lead to misleading results. © 2015 EURATOM