Effect of the COVID-19 pandemic on surgery for indeterminate thyroid nodules (THYCOVID): a retrospective, international, multicentre, cross-sectional study

Background Since its outbreak in early 2020, the COVID-19 pandemic has diverted resources from non-urgent and elective procedures, leading to diagnosis and treatment delays, with an increased number of neoplasms at advanced stages worldwide. The aims of this study were to quantify the reduction in surgical activity for indeterminate thyroid nodules during the COVID-19 pandemic; and to evaluate whether delays in surgery led to an increased occurrence of aggressive tumours.Methods In this retrospective, international, cross-sectional study, centres were invited to participate in June 22, 2022; each centre joining the study was asked to provide data from medical records on all surgical thyroidectomies consecutively performed from Jan 1, 2019, to Dec 31, 2021. Patients with indeterminate thyroid nodules were divided into three groups according to when they underwent surgery: from Jan 1, 2019, to Feb 29, 2020 (global prepandemic phase), from March 1, 2020, to May 31, 2021 (pandemic escalation phase), and from June 1 to Dec 31, 2021 (pandemic decrease phase). The main outcomes were, for each phase, the number of surgeries for indeterminate thyroid nodules, and in patients with a postoperative diagnosis of thyroid cancers, the occurrence of tumours larger than 10 mm, extrathyroidal extension, lymph node metastases, vascular invasion, distant metastases, and tumours at high risk of structural disease recurrence. Univariate analysis was used to compare the probability of aggressive thyroid features between the first and third study phases. The study was registered on ClinicalTrials.gov, NCT05178186.Findings Data from 157 centres (n=49 countries) on 87 467 patients who underwent surgery for benign and malignant thyroid disease were collected, of whom 22 974 patients (18 052 [78 center dot 6%] female patients and 4922 [21 center dot 4%] male patients) received surgery for indeterminate thyroid nodules. We observed a significant reduction in surgery for indeterminate thyroid nodules during the pandemic escalation phase (median monthly surgeries per centre, 1 center dot 4 [IQR 0 center dot 6-3 center dot 4]) compared with the prepandemic phase (2 center dot 0 [0 center dot 9-3 center dot 7]; p<0 center dot 0001) and pandemic decrease phase (2 center dot 3 [1 center dot 0-5 center dot 0]; p<0 center dot 0001). Compared with the prepandemic phase, in the pandemic decrease phase we observed an increased occurrence of thyroid tumours larger than 10 mm (2554 [69 center dot 0%] of 3704 vs 1515 [71 center dot 5%] of 2119; OR 1 center dot 1 [95% CI 1 center dot 0-1 center dot 3]; p=0 center dot 042), lymph node metastases (343 [9 center dot 3%] vs 264 [12 center dot 5%]; OR 1 center dot 4 [1 center dot 2-1 center dot 7]; p=0 center dot 0001), and tumours at high risk of structural disease recurrence (203 [5 center dot 7%] of 3584 vs 155 [7 center dot 7%] of 2006; OR 1 center dot 4 [1 center dot 1-1 center dot 7]; p=0 center dot 0039).Interpretation Our study suggests that the reduction in surgical activity for indeterminate thyroid nodules during the COVID-19 pandemic period could have led to an increased occurrence of aggressive thyroid tumours. However, other compelling hypotheses, including increased selection of patients with aggressive malignancies during this period, should be considered. We suggest that surgery for indeterminate thyroid nodules should no longer be postponed even in future instances of pandemic escalation.Funding None.Copyright (c) 2023 Published by Elsevier Ltd. All rights reserved

Step-over in the structure controlling the regional west tilt of the Sierra Nevada microplate: eastern escarpment system to Kern Canyon system

The Sierra Nevada and Great Valley are coupled, and behave as a semi-rigid microplate. The microplate formed as it was calved off the western edge of the Nevadaplano in the late Miocene, at which time westward regional tilting began. Tilting is controlled by west-side-up normal faulting primarily along the eastern Sierra escarpment system. Uplift and exhumation along the eastern Sierra are balanced by subsidence and sedimentation along the western Great Valley. The west tilt of the microplate is expressed by the west slope of a regional relict landscape surface that developed across much of the Sierra Nevada basement, and by the westward continuation of the surface as the basal Eocene nonconformity of the west-dipping Great Valley Tertiary section. The rigid behaviour of the microplate breaks down along its southern ~100-150 km segment as expressed by seismicity, pervasive faulting and the development of a deep marine basin, the San Joaquin Basin (SJB), whose facies and palaeogeographic patterns diverge from regional patterns of the rest of the Great Valley. The disrupted state of the southern segment of the microplate resulted from its Late Cretaceous position above a regional lateral ramp in the underlying Franciscan-related subduction megathrust. The Kern Canyon fault system began its polyphase history as a complex oblique dextral shear zone above the megathrust lateral ramp. It was remobilized in the Neogene as an oblique transfer structure partitioning differential extension between the southern Sierra Nevada and the SJB. In Quaternary time, the Kern Canyon zone was again remobilized as a west-side-up normal fault system whose geomorphic and structural expressions are best developed south of ~36.4° N. This normal fault system controls the west tilt of the relict landscape surface in the southern Sierra region, as well as the west dip pattern in the strata of the adjacent SJB. To the east of the Kern Canyon normal fault system, the relict landscape surface slopes continuously southwards from the high eastern Sierra into a low-lying, multiply extended terrane. Thus, from ~36.4° N southwards, the west tilt along the western Sierra and the west dip of the adjacent Great Valley strata are controlled by the Kern Canyon system. Fresh normal scarps along the eastern Sierra escarpment system become more subdued and ultimately die out southwards from ~36.4° N. Thus, currently, the controlling structure for the west tilt of the microplate steps westwards in the south from the eastern escarpment system over to the Kern Canyon system

The non-equilibrium landscape of the Sierra Nevada, California: Reply

We thank H.F. Garner for calling attention to an important factor governing fluvial erosion: the role of variable stream discharge caused by climatic fluctuations. We agree that climatic variations affect erosion rates and stream morphology by altering stream discharge, altering bed state such as armoring of channel bottoms and changing sedimentary flux, and can vary local base levels during glacial/interglacial cycles. These processes have most likely played a role in changing river profile form and erosion rates to some degree at various times throughout the Cenozoic in the Sierra Nevada. However, Garner argues that climatically driven changes in erosion rate led to elevation change through isostatic adjustment without any need to call on tectonic forces to explain the modern elevation of the range. This is where we disagree

The non-equilibrium landscape of the Sierra Nevada, California: Reply

We thank H.F. Garner for calling attention to an important factor governing fluvial erosion: the role of variable stream discharge caused by climatic fluctuations. We agree that climatic variations affect erosion rates and stream morphology by altering stream discharge, altering bed state such as armoring of channel bottoms and changing sedimentary flux, and can vary local base levels during glacial/interglacial cycles. These processes have most likely played a role in changing river profile form and erosion rates to some degree at various times throughout the Cenozoic in the Sierra Nevada. However, Garner argues that climatically driven changes in erosion rate led to elevation change through isostatic adjustment without any need to call on tectonic forces to explain the modern elevation of the range. This is where we disagree

Degradation of high loaded oscillating bearings: Numerical analysis and comparison with experimental observations

Nowadays mechanical systems are expected to sustain extreme working conditions, due to the increase of the involved power and the optimized design. Moreover special applications like aeronautics, space engineering and robotics require the reduction of the contact area in the contact pairs, which allow the relative motion between components, by increasing the power transmitted per unit of contact area. As a consequence the joint degradations are between the main issues, resulting in possible failures or increase of consumption and maintenance costs. This paper addresses the analysis of the degradation mechanism of oscillating ball bearings subjected to high loads. These bearings, needed to assure the repetitive relative rotation between two members of the mechanical system (e.g. repetitive motions of assembling and manufacturing robots, ship helms, aircraft flaps, etc.), can reach extreme contact pressures at the ball-race contact surfaces; the oscillations of the bearings provide a fatigue loading of the contact area due to the repetitive rotation of the balls between the races. This work is aimed to calculate the contact stress distributions due to the specific boundary conditions, in order to relate them with the bearing degradation. A numerical model is presented to reproduce the loading conditions and calculate the contact stress and strain distributions in order to correlate them with the damages observed experimentally; results obtained by 2D modelling and 3D modelling, for both elastic and plastic properties of the bearing material, are reported and compared. The numerical results and the comparison with tribological observations of a degraded bearing, after cyclic load application, suggest a possible degradation scenario that brings to the failure of the bearing due to subsurface damages. © 2014 Elsevier B.V

Experimental damage analysis in high loaded oscillating bearings

Several industrial applications require rolling bearings to operate under both high load and oscillating motion. While the oscillating motion does not allow for EHD regime, the high load applied induces high contact pressures. Even if many works in the literature deal with rotating bearings, few works address high loaded oscillating bearings. The degradation scenario of high loaded oscillating bearings is here analysed step by step for both greased and ungreased bearings. Subsurface plastic damage of the balls was found to be at the origin of greased bearing degradation, while progressive superficial degradation lead to a faster degradation of ungreased bearings

The South Tibet detachment shear zone in the Dinggye area Time constraints on extrusion models of the Himalayas

International audienceWe investigate the timing of end of motion along the South Tibet Detachment System (STDS), a major normal fault system that runs parallel to the Himalayan range for more than 1500 km. Near Dinggye (similar to 28 degrees 10'N, 87 degrees 40'E), the STD dips similar to 10 +/- 5 degrees to the North and separates Paleozoic Tethyan series from Upper Himalayan Crystalline Series (UHCS). Immediately below the STD, the UHCS is highly deformed in the STD shear zone, lineations trend NNE and the shear senses are top to the NE. In micaschist, the P-T path constrained by pseudosection and garnet chemistry, shows successive metamorphic conditions of similar to 0.6 GPa and similar to 550 degrees C and 0.5 GPa and 625 degrees C. U/Pb dating of monazites and zircons in deformed and undeformed leucogranites suggests that ductile deformation lasted until at least similar to 16 Ma but ended prior to similar to 15 Ma in the STD shear zone similar to 100 m below the detachment. Ar/Ar micas ages in the footwall span between similar to 14.6 and 13.6 Ma, indicating rapid cooling down to similar to 320 degrees C, and suggesting persistence of normal faulting, at that time. The STDS is cut and offset by the N-S trending Dinggye active normal fault which initiated prior to 11 Ma thus providing a minimum bound for the end of STDS motion. These data are interpreted as reflecting 0.3 GPa (11 km) to 0.6 GPa (22 km) of exhumation along the STDS starting prior to similar to 16 Ma, ending between 13.6 and 11 Ma. The 1000 km long stretch of the STDS east of the Gurla Mandata probably stopped almost synchronously between 13 and 11 Ma ago, coevally with a sudden switch from NNE-SSW to E-W extension at the top of the accretionary prism, with a jump of the major thrust from the lower Main Central Thrust (MCTI) to the Main Boundary Thrust (MBT), and with a change in the India and Asia convergence direction. This synchronism is probably better explained in the frame of a thrust wedge or thrust system model than a lower channel flow model. West of the Gurla Mandata the STDS appears to stop 5 to 3 Ma earlier, possibly related to local interactions with the Karakorum fault in a way that needs to be understood

Roller bearing under high loaded oscillations: Life evolution and accommodation mechanisms

High loaded oscillating bearings are used on several industrial fields such as robotics, wind power, aeronautics and aerospace. These bearings are subjected to extremely high local contact pressures and relatively low oscillatory speed. In this work, endurance tests on commercial single row spherical roller bearings enable to propose a degradation scenario for the bearing lifecycle. Topographical analyses carried out at each phase of the bearing life allowed to understand the degradation evolution at the interface between the inner-ring raceway and rolling elements. The analysis of the experimental results, with the support of numerical stress analysis, led to the understanding of the involved accommodation mechanisms. Then, a comparison with the wear processes in deep-groove ball bearings is provided