Search results for "element"
showing 10 items of 13601 documents
Nuclear magnetic resonance imaging with hyperpolarised helium-3
1996
Abstract Summary Background Magnetic resonance imaging (MRI) relies on magnetisation of hydrogen nuclei (protons) of water molecules in tissue as source of the signal. This technique has been valuable for studying tissues that contain significant amounts of water, but biological settings with low proton content, notably the lungs, are difficult to image. We report use of spin-polarised helium-3 for lung MRI. Methods A volunteer inhaled hyperpolarised 3 He to fill the lungs, which were imaged with a conventional MRI detector assembly. The nuclear spin polarisation of helium, and other noble gases, can be greatly enhanced by laser optical pumping and is about 10 5 times larger than the polari…
Scanning electron microscopic and X ray microanalysis study of the mineral deposits in pseudoxanthoma elasticum.
1977
A skin biopsy of a 37 year old man with typical lesions of pseudoxanthoma clasticum (P.E.) associated with angioid streaks (Groenblad-Strandberg Syndrom) was examined with a scanning E. M. (SEM) and a SEM provided with a X ray micro-analyser. The SEM provided with X ray microanalyser enabled us to see the correspondence between the crystalline deposits and a calcium salt. The potassium, sodium and magnesium analysis of the specimen permits us to verify that the P.E. dermis is rich in K and poor in Mg.
Dual-Energy CT Material Density Iodine Quantification for Distinguishing Vascular From Nonvascular Renal Lesions: Normalization Reduces Intermanufact…
2019
OBJECTIVE. The purpose of this study was to determine whether a single, uniform normalized iodine threshold reduces variability and enables reliable differentiation between vascular and nonvascular renal lesions independent of the dual-energy CT (DECT) platform used. MATERIALS AND METHODS. In this retrospective, HIPAA-compliant, institutional review board-approved study, 247 patients (156 men, 91 women; mean age ± SD, 67 ± 12 years old) with 263 renal lesions (193 nonvascular, 70 vascular) underwent unenhanced single- energy and contrast-enhanced DECT scans. One hundred and six nonvascular and 38 vascular lesions were scanned on two dual-source DECT (dsDECT) scanners, and 87 nonvascular and…
Quantification of Regional Intrapulmonary Oxygen Partial Pressure Evolution during Apnea by 3He MRI
1999
We present a new method to determine in vivo the temporal evolution of intrapulmonary oxygen concentrations by functional lung imaging with hyperpolarized (3)Helium ((3)He-->). Single-breath, single-bolus visualization of (3)He--> administered to the airspaces is used to analyze nuclear spin relaxation caused by the local oxygen partial pressure p(O(2))(t). We model the dynamics of hyperpolarization in the lung by rate equations. Based hereupon, a double acquisition technique is presented to separate depolarization by RF pulses and oxygen induced relaxation. It permits the determination of p(O(2)) with a high accuracy of up to 3% with simultaneous flip angle calibration using no additional …
Nocturnal oxygen enrichment in sleep apnoea.
2000
We hypothesized that a modest oxygen enrichment, rather than 100% oxygen supplementation as used in previous trials, could result in improvement in ventilatory and cardiac symptoms, in patients with obstructive sleep apnoea (OSA), without jeopardizing the chemostimulant ventilatory drive. This hypothesis was tested in five male patients with OSA in a single-blinded trial consisting of one night spent sleeping in control room air (control night), followed by one night spent sleeping while exposed to air with a 9% enriched oxygen content (oxygen-enriched night). Oxygen enrichment resulted in a significant shift in the oxygen saturation profile towards values of ≥ 95% and to decrease desatura…
The Use of Testosterone/Cortisol Ratio in Response to Acute Stress as an Indicator of Propensity to Anger in Informal Caregivers
2016
AbstractCaring for an offspring diagnosed with a psychological chronic disorder is used in research as a model of chronic stress. Indeed, it is usually associated with disturbances in the salivary cortisol (Csal) levels of the caregiver. An imbalance between salivary testosterone (Tsal) and Csal levels is a marker of proneness to social aggression. Given this, we aimed to establish whether the salivary testosterone/cortisol (Tsal/Csal) ratio response to acute stress could be employed as a marker of proneness to anger in informal caregivers of offspring with autism spectrum (ASD). Tsal/Csal ratio and anger responses to a set of different cognitive tasks as well as anger trait and expression …
Clinical supervision as an interaction between the clinical educator and the student.
2007
The interaction between clinical educators and students is regarded as the strongest element in developing expertise and in forming students' professional identity in clinical education. Although clinical education has been studied in physiotherapy, the natural interaction between clinical educators and students has remained unanalyzed. The aim of this study was to examine how supervised learning sessions during patient treatment were constructed. The focus was on the forms of interaction between clinical educators and students in natural contexts. By videotaping 12 natural patient treatment sessions, which simultaneously comprised part of the clinical education of physiotherapy students, a…
Mechanical work and efficiency in ergometer bicycling at aerobic and anaerobic thresholds
1987
Internal and external mechanical work, energy consumption and mechanical efficiency were studied in constant-load ergometer bicycling at five different power outputs below, equal to, and above the aerobic (AerT) and anaerobic (AnT) thresholds. The gross, net and true efficiencies of the whole body in five male subjects were calculated. The work against the external load was defined as the external mechanical work. The internal mechanical work was calculated as the sum of the increments of kinetic and potential energy in all body segments by using methods of film analysis. Total energy consumption was measured by combining aerobic and anaerobic energy production. When the power output of the…
Influence of ultra-long-term fatigue on the oxygen cost of two types of locomotion.
2000
The aim of this study was to examine the effects of fatigue induced by a 65-km ultramarathon on the oxygen cost of running (Cr) and cycling (Ccycl). The day before and immediately after the race, a group of nine well-trained male subjects performed two sub-maximal 4-min exercise bouts: one cycling at a power corresponding to 1.5 W · kg−1 body mass on an electromagnetically braked ergometer, and one running at 11 km · h−1 on a flat asphalt roadway. Before oxygen cost determinations, the subjects performed 12 “ankle” jumps at a given frequency that was fixed by an electronic metronome (2.5 Hz). From the non-fatigued to the fatigued condition, there was a significant increase in minute ventila…
Soft tissue cell adhesion to titanium abutments after different cleaning procedures: preliminary results of a randomized clinical trial
2013
Objectives: A randomized controlled trial was performed to assess soft tissue cell adhesion to implant titanium abutments subjected to different cleaning procedures and test if plasma cleaning can enhance cell adhesion at an early healing time. Study Design: Eighteen patients with osseointegrated and submerged implants were included. Before re-opening, 18 abutments were divided in 3 groups corresponding to different clinical conditions with different cleaning processes: no treatment (G1), laboratory customization and cleaning by steam (G2), cleaning by plasma of Argon (G3). Abutments were removed after 1 week and scanning electron microscopy was used to analyze cell adhesion to the abutment…