Search results for "Dynamo"
showing 10 items of 85 documents
Assessment of quadriceps muscle weakness in patients after total knee arthroplasty and total hip arthroplasty: methodological issues.
2013
The aim of this exploratory study was to verify whether the evaluation of quadriceps muscle weakness is influenced by the testing modality (isometric vs. isokinetic vs. isoinertial) and by the calculation method (within-subject vs. between-subject comparisons) in patients 4-8months after total knee arthroplasty (TKA, n=29) and total hip arthroplasty (THA, n=30), and in healthy controls (n=19). Maximal quadriceps strength was evaluated as (1) the maximal voluntary contraction (MVC) torque during an isometric contraction, (2) the peak torque during an isokinetic contraction, and (3) the one repetition maximum (1-RM) load during an isoinertial contraction. Muscle weakness was calculated as the…
Intra- and Inter-Rater Reliability of Strength Measurements Using a Pull Hand-Held Dynamometer Fixed to the Examiner's Body and Comparison with Push …
2021
Hand held dynamometers (HHDs) are the most used method to measure strength in clinical sitting. There are two methods to realize the assessment: pull and push. The purpose of the present study was to evaluate the intra- and inter-rater reliability of a new measurement modality for pull HHD and to compare the inter-rater reliability and agreement of the measurements. Forty healthy subjects were evaluated by two assessors with different body composition and manual strength. Fifteen isometric tests were performed in two sessions with a one-week interval between them. Reliability was examined using the intra-class correlation (ICC) and the standard error of measurement (SEM). Agreement between …
Investigation of a tunnel pasteurizer for “Nocellara del Belice” table olives processed according to the “Castelvetrano method”
2014
The influence of pasteurization temperature and time of treatment on the flesh firmness and the evolution of microbial communities was studied for table olives Cv. Nocellara del Belice, packed in glass jars and processed with a tunnel pasteurizer. The experiment was first carried out on the laboratory level in order to select the optimal combination of pasteurization time/temperature so as to obtain the proper balance between the consistency of the pulp and the microbiological quality of the final product. Pasteurization at industrial scale was then carried out in a tunnel pasteurizer applying the treatment at 75 °C for 8 min in the thermal center of the jars. Besides flesh firmness and mic…
Search for Low-mass Companions to X-ray Emitting A-type Stars
2007
There is no obvious theory that would explain X-ray emission from main-sequence A-type stars. Therefore, the X-ray emission identified with these stars on basis of low spatial resolution X-ray observations is usually attributed to magnetic activity from unknown late-type companion stars. We systematically study the literature and public 2MASS data in search for binaries among A stars. This way, we identify new candidate counterparts for the X-ray sources in at least 60% of the A-type stars claimed to be detected in the ROSAT All-Sky Survey. There is marginal evidence that this fraction decreases from early to late A spectral type, possibly indicating the onset of intrinsic X-ray emission fo…
A large X-ray flare from the Herbig Ae star V892 Tau
2003
We report the XMM-Newton observation of a large X-ray flare from the Herbig Ae star V892 Tau. The apparent low mass companion of V892 Tau, V892 Tau NE, is unresolved by XMM-Newton. Nevertheless there is compelling evidence from combined XMM-Newton and Chandra data that the origin of the flare is the Herbig Ae star V892 Tau. During the flare the X-ray luminosity of V892 Tau increases by a factor of ~15, while the temperature of the plasma increases from kT ~ 1.5 keV to kT ~ 8 keV. From the scaling of the flare event, based on hydrodynamic modeling, we conclude that a 500 G magnetic field is needed in order to confine the plasma. Under the assumptions that a dynamo mechanism is required to ge…
On the origin of the X-ray emission from Herbig Ae/Be stars
2006
We performed a systematic search for Chandra archival observations of Herbig Ae/Be stars. These stars are fully radiative and not expected to support dynamo action analogous to their convective lower-mass counterparts, the T Tauri stars. Their X-ray emission has remained unexplained. The superior spatial resolution of Chandra with respect to previous X-ray instrumentation has allowed us to examine the possible role of late-type companions in generating the observed X-rays. In the total sample of 17 Herbig Ae/Be stars, 8 are resolved from X-ray emitting faint companions or other unrelated X-ray bright objects within 10". The detection fraction of Herbig Ae/Be stars is 76 %, but lowers to 35 …
SADE: The starspot and dynamo explorer
2003
We propose a mission called SADE, the Starspot And Dynamo Explorer, to study dynamo activity in nearby late-type stars. The onboard instruments will be a Ca-K telescope for magnetically dominated chromospheric emission, and an X-ray grazing incidence telescope to study coronal emission. We design the mission for a life-time of 15 years or longer to capture a full activity cycle for most solar-type stars. We aim to firmly establish the spectrum of the relation between chromospheric and coronal emission in late-type stars, and capture one or more stars going into or coming out of a Maunder type minimum. Operation costs will be kept to a minimum by automating mission operations to a maximum, a…
X-ray emission from early-type stars in the Orion Nebula Cluster
2005
The X-ray properties of twenty ~1 Myr old O, B, and A stars of the Orion Trapezium are examined with data from the Chandra Orion Ultradeep Project (COUP). On the basis of simple theories for X-ray emission, we define two classes separated at spectral type B4: hotter stars have strong winds that may give rise to X-ray emission in small- or large-scale wind shocks, and cooler stars that should be X-ray dark due to their weaker winds and absence of outer convection zones where dynamos can generate magnetic fields. Only two of the massive stars show exclusively the constant soft-spectrum emission expected from the standard model for X-ray emission from hot stars involving many small shocks in a…
Energy oscillations and a possible route to chaos in a modified Riga dynamo
2010
Starting from the present version of the Riga dynamo experiment with its rotating magnetic eigenfield dominated by a single frequency we ask for those modifications of this set-up that would allow for a non-trivial magnetic field behaviour in the saturation regime. Assuming an increased ratio of azimuthal to axial flow velocity, we obtain energy oscillations with a frequency below the eigenfrequency of the magnetic field. These new oscillations are identified as magneto-inertial waves that result from a slight imbalance of Lorentz and inertial forces. Increasing the azimuthal velocity further, or increasing the total magnetic Reynolds number, we find transitions to a chaotic behaviour of th…
Influence of electromagnetic boundary conditions onto the onset of dynamo action in laboratory experiments
2009
We study the onset of dynamo action of the Riga and Karlsruhe experiments with the addition of an external wall, the electro-magnetic properties of which being different from those of the fluid in motion. We consider a wall of different thickness, conductivity and permeability. We also consider the case of a ferro-fluid in motion.