20 research outputs found
Theory and modeling of molecular modes in the NMR relaxation of fluids
Traditional theories of the NMR autocorrelation function for intramolecular
dipole pairs assume single-exponential decay, yet the calculated
autocorrelation of realistic systems display a rich, multi-exponential behavior
resulting in anomalous NMR relaxation dispersion (i.e., frequency dependence).
We develop an approach to model and interpret the multi-exponential
autocorrelation using simple, physical models within a rigorous statistical
mechanical development that encompasses both rotational and translational
diffusion in the same framework. We recast the problem of evaluating the
autocorrelation in terms of averaging over a diffusion propagator whose
evolution is described by a Fokker-Planck equation. The time-independent part
admits an eigenfunction expansion, allowing us to write the propagator as a sum
over modes. Each mode has a spatial part that depends on the specified
eigenfunction, and a temporal part that depends on the corresponding eigenvalue
(i.e., correlation time) with a simple, exponential decay. The spatial part is
a probability distribution of the dipole-pair, analogous to the stationary
states of a quantum harmonic oscillator. Drawing inspiration from the idea of
inherent structures in liquids, we interpret each of the spatial contributions
as a specific molecular mode. These modes can be used to model and predict NMR
dipole-dipole relaxation dispersion of fluids by incorporating phenomena on the
molecular level. We validate our statistical mechanical description of the
distribution in molecular modes with molecular dynamics simulations interpreted
without any relaxation models or adjustable parameters: the most important
poles in the Pad{\'e}-Laplace transform of the simulated autocorrelation agree
with the eigenvalues predicted by the theory
Data digitization techniques used in the analysis of free oscillation of human lower limb
In biomechanics, the ability to manipulate the video data of the desired human motion using computer vision is as important as obtaining the numerical solutions from mathematical modeling. This paper covers both of these requirements equally. The proposed model presents the concept of data digitizing of recorded video films of free in vivo oscillation of human lower limb. The analysis is carried out using an interactive Graphical User Interface (GUI) object oriented analyzing software
Morphological, anatomical and palynological study of centaurea calcitrapa L. ssp. cilicica (Boiss. & Bal.) Wagenitz and centaurea solstitialis L. ssp. carneola (Boiss.) Wagenitz endemic for Turkey
In this study, morphological, anatomical and palynological properties of Centaurea calcitrapa L. ssp. cilicica (Boiss. & Bal.) Wagenitz and C. solstitialis L. ssp. carneola (Boiss.) Wagenitz which are endemic for Turkey were investigated. In the morphological studies, the properties of these endemic subspecies were determined and measurements made on the materials and compared with floristic-systematical references. The morphology of capitula, involucra, involucral leaves (phyllaries) and achene have been investigated. In the anatomical studies; the transverse sections were taken from the root, stem, phyllaries and leaves of the subspecies. In the palynological researches Polar diameter, equatorial length and apertures were measured in detailed. Microphotographs of pollen and anatomical structures are also presented
Arrhythmic effects of Ivabradine in patients with coronary artery disease
Objectives: Ivabradine is the first specific heart rate-lowering agent that has completed clinical development for stable angina pectoris. The aim of the present study was to investigate the effects of ivabradine therapy on P-wave duration, dispersion and QT duration, dispersion in coronary artery disease patients.
Methods and Results: The study population consisted of 21 patients with CAD who have confirmed by coronary angiography previously. Written informed consent was obtained in all patients. Twelve-lead electrocardiogram was recorded for each subject at a rate of 50mm/s on admission and repeated after 1 month ivabradine therapy. QT duration, QT dispertion, maximum and minimum QT duration calculated. Maximum and minimum P wave and P wave dispersion has been calculated. Heart rate was decreased after ivabradine therapy. (75±15 and 63±10, P=0.02).There was no difference between Pmax, Pmin and Pdis values before and after treatment. QTmax value was prolonged after treatment. (410±43 and 431±14, P=0,005) but there was no difference between cQTmax value.(455±38 and 439±21) There was no difference between QTdis and cQTdis values before and after treatment. (44±18 & 49±14; and 49±22 & 48±15). QTmax was prolonged after ivabradine therapy but cQTmax, Pdis, QTdis and cQTdis were not prolonged.
Conclusion: There is no relationship between ivabradine therapy and increased risk of ventricular and atrial arrhythmia in coronary artery disease patient