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Rotating Frame (rotating + frame)
Selected AbstractsRotating Frame for the In-situ Fixation of Large AnimalsANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 1 2009F.-V. Salomon Summary The frame for the in-situ fixation of large animals can be rotated around its longtitudinal axis. Thereby the fixing procedure is improved and the anatomical preparation is easier. [source] Spin-lattice relaxation of spin-½ nuclei in solids containing diluted paramagnetic impurity centers.CONCEPTS IN MAGNETIC RESONANCE, Issue 1 2003Abstract Dynamic nuclear polarization of nuclei by means of paramagnetic electron spin locking (Hartmann-Hahn cross-polarization between paramagnetic electrons and nuclei, or NOVEL) is discussed. The theory is demonstrated by experiments executed at 2.4 and 9.6 GHz on a natural type Ib diamond. It is shown that the 13C polarization rate is independent of the microwave frequency, in agreement with theory. NOVEL polarization takes place only while the spin-locking pulse is on. The rate at which the nuclei are polarized is proportional to the electron polarization in the rotating frame. Therefore, the length of the spin-locking pulse is limited by the value of T1,(e), and because T1,(e) , T1(e) for diamond the effective NOVEL polarization rate of 13C nuclei is usually relatively low. A comparison between the relative effectiveness of 13C polarization rates between NOVEL and the solid-state effect is made for high and low paramagnetic impurity concentrations. The dependence of the 13C polarization rate on the paramagnetic impurity concentration has been determined for a suite of natural diamonds. © 2003 Wiley Periodicals, Inc. Concepts Magn Reson 19A: 44,49, 2003. [source] An objective incremental formulation for the solution of anisotropic elastoplastic problems at finite strainINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 12 2001S. Chatti Abstract This paper presents an objective formulation for the anisotropic elastic,plastic problems at large strain plasticity. The constitutive equations are written in a rotating frame. The multiplicative decomposition of the deformation gradient is adopted and the formulation is hyperelastic based. Since no stress rates are present and the incremental constitutive law was formulated in a rotating frame, the formulation is numerically objective in the time integration. Explicit algorithm was proposed and has been optimized with regard to stability and accuracy. The incremental law was integrated in fast Lagrangian analysis of continua (FLAC) method to model anisotropic elastic,plastic problems at finite strain. Structural tests are carried out for isotropic and orthotropic materials. Copyright © 2001 John Wiley & Sons, Ltd. [source] Water spin dynamics during apoptotic cell death in glioma gene therapy probed by T1, and T2,MAGNETIC RESONANCE IN MEDICINE, Issue 6 2008A. Sierra Abstract Longitudinal and transverse relaxations in the rotating frame, with characteristic time constants T1, and T2,, respectively, have potential to provide unique MRI contrast in vivo. On-resonance spin-lock T1, with different spin-lock field strengths and adiabatic T2, with different radiofrequency-modulation functions were measured in BT4C gliomas treated with Herpes Simplex Virus thymidine kinase (HVS-tk) gene therapy causing apoptotic cell death. These NMR tools were able to discriminate different treatment responses in tumor tissue from day 4 onward. An equilibrium two-site exchange model was used to calculate intrinsic parameters describing changes in water dynamics. Observed changes included increased correlation time of water associated with macromolecules and a decreased fractional population of this pool. These results are consistent with destructive intracellular processes associated with cell death and the increase of extracellular space during the treatment. Furthermore, association between longer exchange correlation time and decreased pH during apoptosis is discussed. In this study, we demonstrated that T1, and T2, MR imaging are useful tools to quantify early changes in water dynamics reflecting treatment response during gene therapy. Magn Reson Med 59:1311,1319, 2008. © 2008 Wiley-Liss, Inc. [source] Rapid 3D-T1, mapping of the knee joint at 3.0T with parallel imagingMAGNETIC RESONANCE IN MEDICINE, Issue 3 2006S. Kubilay Pakin Abstract Three-dimensional spin-lattice relaxation time in the rotating frame (3D-T1,) with parallel imaging at 3.0T was implemented on a whole-body clinical scanner. A 3D gradient-echo sequence with a self-compensating spin-lock pulse cluster was combined with generalized autocalibrating partially parallel acquisitions (GRAPPA) to acquire T1, -weighted images. 3D-T1, maps of an agarose phantom and three healthy subjects were constructed using an eight-channel phased-array coil without parallel imaging and with parallel imaging acceleration factors of 2 and 3, in order to assess the reproducibility of the method. The coefficient of variation (CV) of the median T1, of the agarose phantom was 0.44%, which shows excellent reproducibility. The reproducibility of in vivo 3D-T1, maps was also investigated in three healthy subjects. The CV of the median T1, of the patellar cartilage varied between ,1.1% and 4.3%. Similarly, the CV varied between ,2.1,5.8%, ,1.4,8.7%, and ,1.5,4.1% for the biceps femoris and lateral and medial gastrocnemius muscles, respectively. The preliminary results demonstrate that 3D-T1, maps can be constructed with good reproducibility using parallel imaging. 3D-T1, with parallel imaging capability is an important clinical tool for reducing both the total acquisition time and RF energy deposition at 3T. Magn Reson Med, 2006. © 2006 Wiley-Liss, Inc. [source] Electromagnetic waves in a rotating frame of referenceANNALEN DER PHYSIK, Issue 5 2003J.C. Hauck Abstract We discuss the electromagnetic measurements of rotating observers and study the propagation of electromagnetic waves in a uniformly rotating frame of reference. The phenomenon of helicity-rotation coupling is elucidated and some of the observational consequences of the coupling of the spin of a particle with the rotation of a gravitational source are briefly examined. [source] Mean electromotive force proportional to mean flow in MILD turbulenceASTRONOMISCHE NACHRICHTEN, Issue 1 2010K.-H. Rädler Abstract In mean-field magnetohydrodynamics the mean electromotive force due to velocity and magnetic-field fluctuations plays a crucial role. In general it consists of two parts, one independent of and another one proportional to the mean magnetic field. The first part may be nonzero only in the presence of mhd turbulence, maintained, e.g., by small-scale dynamo action. It corresponds to a battery, which lets a mean magnetic field grow from zero to a finite value. The second part, which covers, e.g., the , effect, is important for large-scale dynamos. Only a few examples of the aforementioned first part of the mean electromotive force have been discussed so far. It is shown that a mean electromotive force proportional to the mean fluid velocity, but independent of the mean magnetic field, may occur in an originally homogeneous isotropic mhd turbulence if there are nonzero correlations of velocity and electric current fluctuations or, what is equivalent, of vorticity and magnetic field fluctuations. This goes beyond the Yoshizawa effect, which consists in the occurrence of mean electromotive forces proportional to the mean vorticity or to the angular velocity defining the Coriolis force in a rotating frame and depends on the cross-helicity defined by the velocity and magnetic field fluctuations. Contributions to the mean electromotive force due to inhomogeneity of the turbulence are also considered. Possible consequences of the above findings for the generation of magnetic fields in cosmic bodies are discussed (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Microsecond Protein Dynamics Measured by 13C, Rotating-Frame Spin RelaxationCHEMBIOCHEM, Issue 9 2005Patrik Lundström Abstract NMR spin relaxation in the rotating frame (R1,) is a unique method for atomic-resolution characterization of conformational (chemical) exchange processes occurring on the microsecond timescale. We present a rotating-frame13C,relaxation dispersion experiment for measuring conformational dynamics in uniformly13C-labeled proteins. The experiment was validated by using the E140Q mutant of the C-terminal fragment of calmodulin, which exhibits significant conformational exchange between two major conformations, as gauged from previous15N and1H relaxation studies. Consistent with previous work, the present13C, R1,experiment detects conformational-exchange dynamics throughout the protein. The average correlation time of ,,ex,=25±8 ,s is in excellent agreement with those determined previously from1H and15N R1,relaxation data: ,,ex,=19±7 and 21±3 ,s, respectively. The extracted chemical-shift differences between the exchanging states reveal significant fluctuations in dihedral angles within single regions of Ramachandran ,,, space, that were not identified from the1H and15N relaxation data. The present results underscore the advantage of using several types of nuclei to probe exchange dynamics in biomolecules. [source] Complex 1H,13C-NMR relaxation and computer simulation study of side-chain dynamics in solid polylysineBIOPOLYMERS, Issue 3 2005Alexey Krushelnitsky Abstract The side-chain dynamics of solid polylysine at various hydration levels was studied by means of proton spin,lattice relaxation times measurements in the laboratory and tilted (off-resonance) rotating frames at several temperatures as well as Monte Carlo computer simulations. These data were analyzed together with recently measured carbon relaxation data (A. Krushelnitsky, D. Faizullin, and D. Reichert, Biopolymers, 2004, Vol. 73, pp. 1,15). The analysis of the whole set of data performed within the frame of the model-free approach led us to a conclusion about three types of the side-chain motion. The first motion consists of low amplitude rotations of dihedral angles of polylysine side chains on the nanosecond timescale. The second motion is cis,trans conformational transitions of the side chains with correlation times in the microsecond range for dry polylysine. The third motion is a diffusion of dilating defects described in (W. Nusser, R. Kimmich, and F. Winter, Journal of Physical Chemistry, 1988, Vol. 92, pp. 6808,6814). This diffusion causes almost no reorientation of chemical bonds but leads to a sliding motion of side chains with respect to each other in the nanosecond timescale. This work evidently demonstrates the advantages of the simultaneous quantitative analysis of data obtained from different experiments within the frame of the same mathematical formalism, providing for the detailed description of the nature and geometry of the internal molecular dynamics. © 2005 Wiley Periodicals, Inc. Biopolymers 78: 129,139, 2005 This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] | ||||||||||||||||