A Dual Hybrid Virtual Element Method for Plane Elasticity Problems

A dual hybrid Virtual Element scheme for plane linear elastic problems is presented and analysed. In particular, stability and convergence results have been established. The method, which is first order convergent, has been numerically tested on two benchmarks with closed form solution, and on a typical microelectromechanical system. The numerical outcomes have proved that the dual hybrid scheme represents a valid alternative to the more classical low-order displacement-based Virtual Element Method

Geological characterization of sand-prone subaqueous delta systems: a case study of the Upper Jurassic Sognefjord Formation (Troll Field, Northern North Sea, offshore Norway) and global examples

Core sedimentology, stratigraphic architecture and 3D seismic geomorphology are integrated in order to: (a) demonstrate the criteria for recognition of coarse-grained subaqueous deltas in the stratigraphic record; (b) compare them with modern examples; (c) develop a new method to extract progradation rates from ancient shallow-marine clinoforms; and (d) refine the depositional model of the Upper Jurassic Sognefjord Formation, which forms the main reservoir in the super-giant Troll Field (Norwegian North Sea). The Sognefjord Formation is a 10-200 m thick clastic wedge, deposited in ca. 6 Myr, by a fully marine deltaic system that was sourced from the Norwegian mainland. A series of 10-60 m thick, westerly-dipping subaqueous clinoform sets are developed within this unit and can be mapped for several tens of kilometres along strike. Within each clinoform set, clinothems are formed by regressively stacked sandstone-rich bedsets, devoid of subaerial facies and separated by thin mudstone intervals. Near-horizontal trajectories are observed in each clinoform set, and the sets are stacked vertically. In the eastern half of the field, individual clinoforms are relatively gently dipping (1-6°) and bound thin (10-30 m) clinothems dominated by fine-grained, hummocky cross-stratified sandstones. Towards the west, clinoforms gradually become steeper (5-14°) and bound thicker (15-60 m) clinothems that comprise medium-grained sandstones in their upper parts. Topsets are usually well developed. Quantification of clinoform age and progradation rates is constrained by regionally correlatable bioevents, and relies on exponential age-depth interpolations. The facies break that mirrors the foreset-to-bottomset transition, which represents storm wave base, is subsequently dated, and progradation rates are measured along transects tied to well correlations and seismic interpretations. The results indicate falls in progradation rate (from 500 to 30 km/Myr) and net sediment flux (from 90 to 10 km2/Myr), and a simultaneous rise in vertical sedimentation rate (from 15 to 70 m/Myr) towards the basin; these variations are attributed to the progradation of the subaqueous delta into progressively deeper waters associated with along-shore currents that provide net sediment transport out of the study area, as well as sculpting the linear, elongated clinoforms. Coarse-grained subaqueous deltas provide a new interpretative template that may be applicable to other ancient clinoform-bearing shallow-marine sandstones with reservoir potential, whilst calculation of progradation rates provides a tool to improve reservoir characterisation and near-field exploration by enhancing prediction of reservoir distribution and character.Open Acces

In Situ Force Microscopy to Investigate Fracture in Stretchable Electronics: Insights on Local Surface Mechanics and Conductivity

Stretchable conductors are of crucial relevance for emerging technologies such as wearable electronics, low-invasive bioelectronic implants, or soft actuators for robotics. A critical issue for their development regards the understanding of defect formation and fracture of conducting pathways during stress−strain cycles. Here we present a combination of atomic force microscopy (AFM) methods that provides multichannel images of surface morphology, conductivity, and elastic modulus during sample deformation. To develop the method, we investigate in detail the mechanical interactions between the AFM tip and a stretched, free-standing thin film sample. Our findings reveal the conditions to avoid artifacts related to sample bending modes or resonant excitations. As an example, we analyze strain effects in thin gold films deposited on a soft silicone substrate. Our technique allows one to observe the details of microcrack opening during tensile strain and their impact on local current transport and surface mechanics. We find that although the film fractures into separate fragments, at higher strain a current transport is sustained by a tunneling mechanism. The microscopic observation of local defect formation and their correlation to local conductivity will provide insight into the design of more robust and fatigue resistant stretchable conductors

Atomic Force Microscopy Nanomechanics of Hard Nanometer-Thick Films on Soft Substrates: Insights into Stretchable Conductors

The nanomechanical properties of ultrathin and nanostructured films of rigid electronic materials on soft substrates are of crucial relevance to realize materials and devices for stretchable electronics. Of particular interest are bending deformations in buckled nanometer-thick films or patterned networks of rigid materials as they can be exploited to compensate for the missing tensile elasticity. Here, we perform atomic force microscopy indentation experiments and electrical measurements to characterize the nanomechanics of ultrathin gold films on a polydimethylsiloxane (PDMS) elastomer. The measured force-indentation data can be analyzed in terms of a simple analytical model describing a bending plate on a semi-infinite soft substrate. The resulting method enables us to quantify the local Young’s modulus of elasticity of the nanometer-thick film. Systematic variation of the gold layer thickness reveals the presence of a diffuse interface between the metal film and the elastomer substrate that does not contribute to the bending stiffness. The effect is associated with gold clusters that penetrate the silicone and are not directly connected to the ultrathin film. Only above a critical layer thickness, percolation of the metallic thin film happens, causing a linear increase in bending stiffness and electrical conductivity

Erythema multiforme and COVID-19. what do we know

Background: Erythema multiforme (EM) is an acute cutaneous eruption often associated with infections and more rarely with drugs. This review aimed to evaluate the association between erythema multiforme and coronavirus disease 2019 (COVID-19). Methods: A systematic search of PubMed/MEDLINE, Scimago Scopus, and ISI/Web of Science was performed. Original articles, case series, or case reports were evaluated and selected. Results: Fourteen articles were selected, describing a total of 70 patients. EM is a cutaneous eruption rarely occurring in COVID-19 and is, in most cases, associated with a hypersensitivity reaction to the virus. In these cases, EM seems to affect patients younger than 30 years or older than 55 years. Infrequently, some drugs used in the management of COVID-19 may induce EM, especially hydroxychloroquine. The three groups of patients seem to have different clinical characteristics and courses. Conclusions: From these data, it is possible to preliminarily propose that EM or EM-like eruptions linked to COVID-19 might be divided into three types: the virus-related juvenile type (affecting patients <30-year-old), the virus-related older type (affecting patients >55 years), and the drug-induced type. The occurrence of a skin rash does not seem to be related to the severity and clinical course of COVID-19

Clinical evaluation on the performance and safety of a non-ablative fractional 1340 nm laser for the treatment of stretch marks in adolescents and young adults. a case series

A large part of the world's population suffers from Striae distensae (SD) or stretch marks, which create physical and psychological discomfort in people. We evaluate the SD clinical improvement by using a non-ablative fractional Nd:YAP 1340 nm laser. The research was performed on 25 patients of both sexes, with a mean age of 31 ± 13.09 years. Each patient underwent from a minimum of 3 to a maximum of 4 treatments, with an Nd:YAP (1340 nm) medical device, every four weeks, with 3- and 6-month follow-up, in these areas: back, abdomen, breast, flanks, lower limbs, buttocks, and thighs. Manchester Scar Scale assessed stretch marks improvement. Side effects, patient pain, and SD overall appearance improvement were also recorded for all patients. Digital photographs measured the aesthetic results. Treatment was well-tolerated (pain score 1.08 ± 0.76) by all patients. There were no long-term side effects, and 88% of patients revealed an SD excellent improvement showing good aesthetic results achieved by the treatment. The total mean pretreatment Manchester Scar Scale score decreased from 13.80 (±1.58) to 10.36 (±1.70) after 3 months (p < 0.01) and to 8.36 (±1.07) after 6 months (p < 0.01). An Nd:YAP (1340 nm) laser seems to be a safe and effective treatment, showing a higher security profile with no side effects

Discovery of a Second Transient Low-Mass X-ray Binary in the Globular Cluster NGC 6440

We have identified a new transient luminous low-mass X-ray binary, NGC 6440 X-2, with Chandra/ACIS, RXTE/PCA, and Swift/XRT observations of the globular cluster NGC 6440. The discovery outburst (July 28-31, 2009) peaked at L_X~1.5*10^36 ergs/s, and lasted for <4 days above L_X=10^35 ergs/s. Four other outbursts (May 29-June 4, Aug. 29-Sept. 1, Oct. 1-3, and Oct. 28-31 2009) have been observed with RXTE/PCA (identifying millisecond pulsations, Altamirano et al. 2009a) and Swift/XRT (confirming a positional association with NGC 6440 X-2), with similar peak luminosities and decay times. Optical and infrared imaging did not detect a clear counterpart, with best limits of V>21, B>22 in quiescence from archival HST imaging, g'>22 during the August outburst from Gemini-South GMOS imaging, and J>~18.5$ and K>~17 during the July outburst from CTIO 4-m ISPI imaging. Archival Chandra X-ray images of the core do not detect the quiescent counterpart, and place a bolometric luminosity limit of L_{NS}< 6*10^31 ergs/s (one of the lowest measured) for a hydrogen atmosphere neutron star. A short Chandra observation 10 days into quiescence found two photons at NGC 6440 X-2's position, suggesting enhanced quiescent emission at L_X~6*10^31 ergs/s . NGC 6440 X-2 currently shows the shortest recurrence time (~31 days) of any known X-ray transient, although regular outbursts were not visible in the bulge scans before early 2009. Fast, low-luminosity transients like NGC 6440 X-2 may be easily missed by current X-ray monitoring.Comment: 13 pages (emulateapj), 8 (color) figures, ApJ in press. Revised version adds 5th outburst (Oct./Nov. 2009), additional discussion of possible causes of short outburst recurrence time

Patients' perceptions of quality of care delivery by urology residents: A nationwide study

Objective To present the results of a nationwide survey among urological patients to evaluate their perception of the quality of care provided by residents. Methods An anonymous survey was distributed to patients who were referred to 22 Italian academic institutions. The survey aimed to investigate the professional figure of the urology resident as perceived by the patient. Results A total of 2587 patients were enrolled in this study. In all, 51.6% of patients were able to correctly identify a urology resident; however, almost 40% of respondents discriminated residents from fully trained urologists based exclusively on their young age. Overall, 98.2% patients rated the service provided by the resident as at least sufficient. Urology trainees were considered by more than 50% of the patients interviewed to have good communication skills, expertise and willingness. Overall, patients showed an excellent willingness to be managed by urology residents. The percentage of patients not available for this purpose showed an increasing trend that directly correlated with the difficulty of the procedure. Approximately 5-10% of patients were not willing to be managed by residents for simple procedures such as clinical visits, cystoscopy or sonography, and up to a third of patients were not prepared to undergo any surgical procedure performed by residents during steps in major surgery, even if the residents were adequately tutored. Conclusions Our data showed that patients have a good willingness to be managed by residents during their training, especially for medium- to low-difficulty procedures. Furthermore, the majority of patients interviewed rated the residents' care delivery as sufficient. Urology trainees were considered to have good communication skills, expertise and willingness