24 research outputs found
Three terminal capacitance technique for magnetostriction and thermal expansion measurements
An instrument has been constructed to measure a large range of
magnetostriction and thermal expansion between room temperature and 4 K in a
superconductive split-coil magnet, that allows investigation in magnetic fields
up to 12 T. The very small bulk samples (up to 1 mm in size) as well as big
ones (up to 13 mm) of the irregular form can be measured. The possibility of
magnetostriction investigation in thin films is shown. A general account is
given of both electrical and the mechanical aspects of the design of
capacitance cell and their associated electronic circuitry. A simple lever
device is proposed to increase the sensitivity twice. The resulting obtained
sensitivity can be 0.5 Angstrom. The performance of the technique is
illustrated by some preliminary measurements of the magnetostriction of
superconducting MgB2, thermal expansion of (La0.8Ba0.2)0.93MnO3 single crystal
and magnetoelastic behavior of the Ni/Si(111) and
La0.7Sr0.3CoO3/SAT0.7CAT0.1LA0.2(001) cantilevers.Comment: 6 pages, 6 figures, journal pape
Planned peri-extubation fasting in critically ill children: an international survey of practice
Introduction: Cumulative energy/protein deficit is associated with impaired outcomes in pediatric intensive care Units (PICU). Enteral nutrition is the preferred mode, but its delivery may be compromised by periods of feeding interruptions around procedures, with peri-extubation fasting the most common procedure. Currently, there is no evidence to guide the duration of the peri-extubation fasting in PICU. Therefore, we aimed to explore current PICU fasting practices around the time of extubation and the rationales supporting them.
Material and methods: A cross sectional electronic survey was disseminated via the European Paediatric Intensive Care Society (ESPNIC) membership. Experienced senior nurses, dieticians or doctors were invited to complete the survey on behalf of their unit, and to describe their practice on PICU fasting prior to and after extubation.
Results: We received responses from 122 PICUs internationally, mostly from Europe. The survey confirmed that fasting practices are often extrapolated from guidelines for fasting prior to elective anaesthesia. However, there were striking differences in the duration of fasting times, with some units not fasting at all (in patients considered to be low risk), while others withheld feeding for all patients. Fasting following extubation also showed large variations in practice, with some units withholding nutrition for many hours, and others starting oral feeding based on child demand. The risk of vomiting/aspiration and reducing nutritional deficit were the main reasons for fasting children or reducing fasting times respectively.
Discussion: This variability in practices suggests that shorter fasting times might be safe. Shortening the duration of unnecessary fasting, as well as accelerating the extubation process could potentially be achieved by using other methods of assessing gastric emptiness, such as gastric point of care ultrasonography (POCUS). Yet only half of the units were aware of this technique, and very few used it
Magnetostrictive behaviour of thin superconducting disks
Flux-pinning-induced stress and strain distributions in a thin disk
superconductor in a perpendicular magnetic field is analyzed. We calculate the
body forces, solve the magneto-elastic problem and derive formulas for all
stress and strain components, including the magnetostriction . The
flux and current density profiles in the disk are assumed to follow the Bean
model. During a cycle of the applied field the maximum tensile stress is found
to occur approximately midway between the maximum field and the remanent state.
An effective relationship between this overall maximum stress and the peak
field is found.Comment: 8 pages, 6 figures, submitted to Supercond. Sci. Technol., Proceed.
of MEM03 in Kyot
Shape Distortion by Irreversible Flux-Pinning-Induced Magnetostriction
Exact analytical results are obtained for the flux-pinning-induced
magnetostriction in cylindrical type-II superconductors placed in parallel
magnetic field. New modes of irreversible deformation are found: In contrast to
the circular cylinder where shape is conserved, it is shown that a square
cross-section deforms with considerable distortion. During a field cycle both
concave, convex, and even more complicated distortions are predicted. Strong
implications for dilatometric measurements on crystals are emphasized. The main
results are valid for any critical-state model, j_c = j_c(B).Comment: 4 pages, 4 graph
Gastric point-of-care ultrasound in acutely and critically ill children (POCUS-ped): a scoping review
Point-of-care ultrasound (POCUS) use is increasing in pediatric clinical settings. However, gastric POCUS is rarely used, despite its potential value in optimizing the diagnosis and management in several clinical scenarios (i.e., assessing gastric emptying and gastric volume/content, gastric foreign bodies, confirming nasogastric tube placement, and hypertrophic pyloric stenosis). This review aimed to assess how gastric POCUS may be used in acute and critically ill children. An international expert group was established, composed of pediatricians, pediatric intensivists, anesthesiologists, radiologists, nurses, and a methodologist. A scoping review was conducted with an aim to describe the use of gastric POCUS in pediatrics in acute and critical care settings. A literature search was conducted in three databases, to identify studies published between 1998 and 2022. Abstracts and relevant full texts were screened for eligibility, and data were extracted, according to the JBI methodology (Johanna Briggs Institute). A total of 70 studies were included. Most studies ( = 47; 67%) were conducted to assess gastric emptying and gastric volume/contents. The studies assessed gastric volume, the impact of different feed types (breast milk, fortifiers, and thickeners) and feed administration modes on gastric emptying, and gastric volume/content prior to sedation or anesthesia or during surgery. Other studies described the use of gastric POCUS in foreign body ingestion ( = 6), nasogastric tube placement ( = 5), hypertrophic pyloric stenosis ( = 8), and gastric insufflation during mechanical ventilatory support ( = 4). POCUS was performed by neonatologists, anesthesiologists, emergency department physicians, and surgeons. Their learning curve was rapid, and the accuracy was high when compared to that of the ultrasound performed by radiologists (RADUS) or other gold standards (e.g., endoscopy, radiography, and MRI). No study conducted in critically ill children was found apart from that in neonatal intensive care in preterms. Gastric POCUS appears useful and reliable in a variety of pediatric clinical settings. It may help optimize induction in emergency sedation/anesthesia, diagnose foreign bodies and hypertrophic pyloric stenosis, and assist in confirming nasogastric tube placement, avoiding delays in obtaining confirmatory examinations (RADUS, x-rays, etc.) and reducing radiation exposure. It may be useful in pediatric intensive care but requires further investigation. [Abstract copyright: Copyright © 2022 Valla, Tume, Jotterand Chaparro, Arnold, Alrayashi, Morice, Nabialek, Rouchaud, Cercueil and Bouvet.
Obtaining a Rough Flux Front in Type-II Superconductors Using a Critical State Model
In this work we numerically modelled a periodic magnetic flux pattern which qualitatively reproduces the so-called sand avalanches scenario in type-II superconductors. To model these sand-pile patterns we consider a perturbation on the critical current which, as a first approximation, follows a periodic function which depends on the position
Bioactive Sphingolipids, Complement Cascade, and Free Hemoglobin Levels in Stable Coronary Artery Disease and Acute Myocardial Infarction
Background. Acute myocardial infarction (AMI) and coronary artery bypass graft (CABG) surgery are associated with a pathogen-free inflammatory response (sterile inflammation). Complement cascade (CC) and bioactive sphingolipids (BS) are postulated to be involved in this process. Aim. The aim of this study was to evaluate plasma levels of CC cleavage fragments (C3a, C5a, and C5b9), sphingosine (SP), sphingosine-1-phosphate (S1P), and free hemoglobin (fHb) in AMI patients treated with primary percutaneous coronary intervention (pPCI) and stable coronary artery disease (SCAD) undergoing CABG. Patients and Methods. The study enrolled 37 subjects (27 male) including 22 AMI patients, 7 CABG patients, and 8 healthy individuals as the control group (CTRL). In the AMI group, blood samples were collected at 5 time points (admission to hospital, 6, 12, 24, and 48 hours post pPCI) and 4 time points in the CABG group (6, 12, 24, and 48 hours post operation). SP and S1P concentrations were measured by high-performance liquid chromatography (HPLC). Analysis of C3a, C5a, and C5b9 levels was carried out using high-sensitivity ELISA and free hemoglobin by spectrophotometry. Results. The plasma levels of CC cleavage fragments (C3a and C5b9) were significantly higher, while those of SP and S1P were lower in patients undergoing CABG surgery in comparison to the AMI group. In both groups, levels of CC factors showed no significant changes within 48 hours of follow-up. Conversely, SP and S1P levels gradually decreased throughout 48 hours in the AMI group but remained stable after CABG. Moreover, the fHb concentration was significantly higher after 24 and 48 hours post pPCI compared to the corresponding postoperative time points. Additionally, the fHb concentrations increased between 12 and 48 hours after PCI in patients with AMI. Conclusions. Inflammatory response after AMI and CABG differed regarding the release of sphingolipids, free hemoglobin, and complement cascade cleavage fragments