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Ellipsoid
Kinds of Ellipsoid Selected AbstractsEchocardiographic Assessment of Left Ventricular Mass in Neonatal and Adult Mice: Accuracy of Different Echocardiographic MethodsECHOCARDIOGRAPHY, Issue 10 2006Alexander Ghanem M.D. Echocardiography is an established method to estimate left-ventricular mass (LVM) in mice. Accuracy is determined by cardiac size and morphology and influenced by mathematical models. We investigated accuracy of three common algorithms in three early developmental stages. High-resolution echocardiography was performed in 35 C57/BL6-mice. Therefore, two-dimensional-guided M-mode echocardiography and parasternal short- and long-axis views in B-mode were obtained. LVM was assessed in vivo applying Penn (P), Area Length (AL), and Truncated Ellipsoid (TE) algorithms and validated with histomorphometry. Regression analysis of all mice showed fair estimation of LVM assessed with M-mode-based Penn algorithm (y = 0.6*x , 0.12, r: 0.71). In contrast two-dimensional assessment of LVM revealed close linear relationship with histomorphometry (yAL= 1.21*x , 12.1, r: 0.88, yTE= 1.38*x , 2.88, r: 0.86). Bias was lowest for LVM-AL at diastole underestimating 3.2%. In concordance with the summarized data, LVM-P revealed lower regression coefficients and significant underestimation in all three subgroups. Small hearts (<50 mg, n = 12) correlated best with LVM-AL at systole. Hearts of adolescent (50,75 mg, n = 13) and adult (75,100 mg, n = 10) mice revealed close linear relationship with LVM-AL and LVM-TE at diastole. Echocardiographic assessment of LVM is feasible in hearts weighting less than 50 mg and can be estimated best in systole. Hearts weighting more than 50 mg are estimated most accurately by means of LVM-AL at diastole. [source] The Presence of Megamitochondria in the Ellipsoid of Photoreceptor Inner Segment of the Zebrafish RetinaANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 6 2005J. Kim Summary Although the megamitochondria (MM) were localized in various pathological conditions, normal retina of some mammalian species was reported to include MM for various physiological roles. However, it was not clearly confirmed whether the MM is present in the retina of lower vertebrate as well. In this study, we tried to show the presence of the MM in the zebrafish retina using electron microscopic technique. In all the photoreceptors including rods, cones and double cones of the zebrafish retina, MM were observed in the ellipsoid of inner segment. In the photoreceptor epllipsoid of the zebrafish retina, the mitochondria located in the central portion of the ellipsoid had a highly electron-dense matrix, which were accompanied by the mitochondria with electron-lucent matrix in the apical portion of the ellipsoid. The presence of MM was more clearly discernable in the rods, which were localized under the double cones. This finding is somewhat different from those observed in the previous studies because MM were localized in the inner segment of cones, but were not in those of rods in the case of mammalian retina. Although the exact physiological meaning for the presence of MM in some vertebrate species should be further studied, the present study could show that the MM in the ellipsoid of the retinal photoreceptors was not only restricted in some mammalian species. [source] Fabrication of 3D Photonic Crystals of Ellipsoids: Convective Self-Assembly in Magnetic FieldADVANCED MATERIALS, Issue 19 2009Tao Ding Three-dimensional photonic crystals of ellipsoidal colloidal particles are prepared by direct convective self-assembly from suspension with the aid of a magnet. The magnetic field provides the orientational order, which is additionally needed for these colloidal particles with symmetry lower than spherical. The positional order is provided by the convection, just as for spherical colloids. [source] Robust principal component analysis and outlier detection with ecological dataENVIRONMETRICS, Issue 2 2004Donald A. Jackson Abstract Ecological studies frequently involve large numbers of variables and observations, and these are often subject to various errors. If some data are not representative of the study population, they tend to bias the interpretation and conclusion of an ecological study. Because of the multivariate nature of ecological data, it is very difficult to identify atypical observations using approaches such as univariate or bivariate plots. This difficulty calls for the application of robust statistical methods in identifying atypical observations. Our study provides a comparison of a standard method, based on the Mahalanobis distance, used in multivariate approaches to a robust method based on the minimum volume ellipsoid as a means of determining whether data sets contain outliers or not. We evaluate both methods using simulations varying conditions of the data, and show that the minimum volume ellipsoid approach is superior in detecting outliers where present. We show that, as the sample size parameter, h, used in the robust approach increases in value, there is a decrease in the accuracy and precision of the associated estimate of the number of outliers present, in particular as the number of outliers increases. Conversely, where no outliers are present, large values for the parameter provide the most accurate results. In addition to the simulation results, we demonstrate the use of the robust principal component analysis with a data set of lake-water chemistry variables to illustrate the additional insight available. We suggest that ecologists consider that their data may contain atypical points. Following checks associated with normality, bivariate linearity and other traditional aspects, we advocate that ecologists examine their data sets using robust multivariate methods. Points identified as being atypical should be carefully evaluated based on background information to determine their suitability for inclusion in further multivariate analyses and whether additional factors explain their unusual characteristics. Copyright © 2004 John Wiley & Sons, Ltd. [source] A structural model for the seismicity of the Arudy (1980) epicentral area (Western Pyrenees, France)GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2007Noalwenn Dubos-Sallée SUMMARY The Western Pyrenees presents a diffuse and moderate (M, 5.7) instrumental seismicity. It nevertheless historically suffered from strong earthquakes (I = IX MSK). The seismic sources of these events are not yet clearly identified. We focus on the Arudy (1980) epicentral area (M= 5.1) and propose here the reactivation of early Cretaceous normal faults of the Iberian margin as a potential source. The late Cretaceous inversion of this basin, first in a left-lateral strike-slip mode and then in a more frontal convergence, resulted in a pop-up geometry. This flower structure attests of the presence of a deep crustal discontinuity. The present-day geodynamic arrangement suggests that this accident is reactivated in a right lateral mode. This reactivation leads to a strain partitioning between the deep discontinuity that accommodates the lateral component of the motion and shallow thrusts, rooted on this discontinuity. These thrusts accommodate the shortening component of the strain. The distribution of the instrumental seismicity fits well the structural model of the Arudy basin. Whatever the compressive regional context, the structural behaviour of the system explains too the extensive stress tensor determined for the Arudy crisis if we interpret it in terms of strain ellipsoid. Indeed numerical modelling has shown that this concomitant activity of strike-slip and thrust faulting results in an extensive component that can rise 50 per cent of the finite strain. We identify too a 25,30 km long potential seismic source for the Arudy area. The size of the structure and its potential reactivation in a strike-slip mode suggest that a maximum earthquake magnitude of ,6.5 could be expected. The extrapolation of this model at the scale of the Western Pyrenees allows to propose other potential sources for major regional historical earthquakes. [source] A two-grid fictitious domain method for direct simulation of flows involving non-interacting particles of a very small sizeINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 11 2010A. Dechaume Abstract The full resolution of flows involving particles whose scale is hundreds or thousands of times smaller than the size of the flow domain is a challenging problem. A naive approach would require a tremendous number of degrees of freedom in order to bridge the gap between the two spatial scales involved. The approach used in the present study employs two grids whose grid size fits the two different scales involved, one of them (the micro-scale grid) being embedded into the other (the macro-scale grid). Then resolving first the larger scale on the macro-scale grid, we transfer the so obtained data to the boundary of the micro-scale grid and solve the smaller size problem. Since the particle is moving throughout the macro-scale domain, the micro-scale grid is fixed at the centroid of the moving particle and therefore moves with it. In this study we combine such an approach with a fictitious domain formulation of the problem resulting in a very efficient algorithm that is also easy to implement in an existing CFD code. We validate the method against existing experimental data for a sedimenting sphere, as well as analytical results for motion of an inertia-less ellipsoid in a shear flow. Finally, we apply the method to the flow of a high aspect ratio ellipsoid in a model of a human lung airway bifurcation. Copyright © 2009 John Wiley & Sons, Ltd. [source] Aligned Gold Nanorods in Silica Made by Ion Irradiation of Core,Shell Colloidal Particles,ADVANCED MATERIALS, Issue 3 2004S. Roorda Colloidal particles with a 14,nm diameter Au core surrounded by a 72,nm thick silica shell have been irradiated with 30,MeV heavy ions. The shell deforms into an oblate ellipsoid, while the core becomes rod-shaped (aspect ratio up to 9) with the major axis along the beam. Optical extinction measurements show evidence for split plasmon bands, characteristic for anisotropic metal nanoparticles. [source] Signal reconstruction in the presence of finite-rate measurements: finite-horizon control applicationsINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 1 2010Sridevi V. Sarma Abstract In this paper, we study finite-length signal reconstruction over a finite-rate noiseless channel. We allow the class of signals to belong to a bounded ellipsoid and derive a universal lower bound on a worst-case reconstruction error. We then compute upper bounds on the error that arise from different coding schemes and under different causality assumptions. When the encoder and decoder are noncausal, we derive an upper bound that either achieves the universal lower bound or is comparable to it. When the decoder and encoder are both causal operators, we show that within a very broad class of causal coding schemes, memoryless coding prevails as optimal, imposing a hard limitation on reconstruction. Finally, we map our general reconstruction problem into two important control problems in which the plant and controller are local to each other, but are together driven by a remote reference signal that is transmitted through a finite-rate noiseless channel. The first problem is to minimize a finite-horizon weighted tracking error between the remote system output and a reference command. The second problem is to navigate the state of the remote system from a nonzero initial condition to as close to the origin as possible in finite-time. Our analysis enables us to quantify the tradeoff between time horizon and performance accuracy, which is not well studied in the area of control with limited information as most works address infinite-horizon control objectives (e.g. stability, disturbance rejection). Copyright © 2009 John Wiley & Sons, Ltd. [source] Comparison of prostate and transition zone volume measured by the ellipsoid and planimetric methods with transrectal ultrasonography before seed implantation of prostate cancerINTERNATIONAL JOURNAL OF UROLOGY, Issue 2 2008Tetsuhiro Ikeda Abstract: A total of 122 men who were diagnosed with localized prostatic cancer underwent transrectal ultrasound and the volumes of their prostates and transitional zones were obtained using the planimetric method and the ellipsoid method. Mean age was 64.2 ±13.4 (48.2,85.8), and mean preimplant prostate specific antigen was 6.01 ± 2.35 mg/mL (0.92,15.5). The clinical stage was T1c in 70 patients, T2a in 46 and T2b in 6. Prostatic volumes and transitional zone volumes obtained by the planimetric method were 18 % and 39% greater than those obtained by the ellipsoid method, respectively. There were significant differences between the volumes obtained by the two different methods. However, there was a good correlation between the prostatic volume and the transitional zone volume obtained by both the ellipsoid method (r = 0.851) and the planimetric method (r = 0.908). The regression line of the prostate volume between these two methods was calculated as OLEX: new software for visualization and analysis of extended crystal structuresJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 5 2003Oleg V. Dolomanov We have developed new software (OLEX) for the visualization and analysis of extended crystal structures. This software has a Windows-compatible mouse-driven graphical interface which gives full control over all structural elements. OLEX provides the user with tools to construct topological networks, visualize interpenetrating or overlapping fragments, and analyse networks constructed fully or partially by exploiting short interactions. It is also easy to generate conventional ellipsoid, ball-and-stick or packing plots. [source] Timing of Depolarization and Contraction in the Paced Canine Left Ventricle:JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 2003Experiment, Model Introduction: For efficient pump function, contraction of the heart should be as synchronous as possible. Ventricular pacing induces asynchrony of depolarization and contraction. The degree of asynchrony depends on the position of the pacing electrode. The aim of this study was to extend an existing numerical model of electromechanics in the left ventricle (LV) to the application of ventricular pacing. With the model, the relation between pacing site and patterns of depolarization and contraction was investigated. Methods and Results: The LV was approximated by a thick-walled ellipsoid with a realistic myofiber orientation. Propagation of the depolarization wave was described by the eikonal-diffusion equation, in which five parameters play a role: myocardial and subendocardial velocity of wave propagation along the myofiber cm and ce; myocardial and subendocardial anisotropy am and ae; and parameter k, describing the influence of wave curvature on wave velocity. Parameters cm, ae, and k were taken from literature. Parameters am and ce were estimated by fitting the model to experimental data, obtained by pacing the canine left ventricular free wall (LVFW). The best fit was found with cm= 0.75 m/s, ce= 1.3 m/s, am= 2.5, ae= 1.5, and k= 2.1 × 10,4 m2/s. With these parameter settings, for right ventricular apex (RVA) pacing, the depolarization times were realistically simulated as also shown by the wavefronts and the time needed to activate the LVFW. The moment of depolarization was used to initiate myofiber contraction in a model of LV mechanics. For both pacing situations, mid-wall circumferential strains and onset of myofiber shortening were obtained. Conclusion: With a relatively simple model setup, simulated depolarization timing patterns agreed with measurements for pacing at the LVFW and RVA in an LV. Myocardial cross-fiber wave velocity is estimated to be 0.40 times the velocity along the myofiber direction (0.75 m/s). Subendocardial wave velocity is about 1.7 times faster than in the rest of the myocardium, but about 3 times slower than as found in Purkinje fibers. Furthermore, model and experiment agreed in the following respects. (1) Ventricular pacing decreased both systolic pressure and ejection fraction relative to natural sinus rhythm. (2) In early depolarized regions, early shortening was observed in the isovolumic contraction phase; in late depolarized regions, myofibers were stretched in this phase. Maps showing timing of onset of shortening were similar to previously measured maps in which wave velocity of contraction appeared similar to that of depolarization. (J Cardiovasc Electrophysiol, Vol. 14, pp. S188-S195, October 2003, Suppl.) [source] Gray-scale sonography of solid breast masses: Diagnosis of probably benign masses and reduction of the number of biopsiesJOURNAL OF CLINICAL ULTRASOUND, Issue 1 2007Luciano Chala MD Abstract Purpose. To identify probably benign breast masses using gray-scale sonography and to see if this strategy could reduce the number of biopsies of breast masses. Methods. This retrospective study included 229 masses in 203 women who underwent sonographically guided percutaneous biopsy. Masses with a negative predictive value for malignancy >98% were retrospectively considered probably benign, and the potential impact of gray-scale sonography in reducing the number of biopsies if these masses were not biopsied was assessed. Assessments were performed considering all masses as a group as well as various subgroups. Results. Round, ellipsoid, or lobulated masses with 3 or fewer lobulations, circumscribed margins, a longitudinal,anteroposterior diameter ratio ,1.0 and no marked hypoechogenicity, posterior acoustic shad owing, internal microcalcifications, or altered surrounding breast tissue were considered probably benign. The sensitivity of gray-scale sonography to identify this subgroup was 98%, with a negative predictive value of 99%. If these masses were not biopsied, there would be a 42% reduction in the number of biopsies considering all masses, a 36% reduction for masses classified as Breast Imaging Reporting and Data System category 4, and a 59% reduction for masses exclusively analyzed with sonography. Conclusions. It is possible to identify probably benign breast masses using gray-scale sonography, and thereby to reduce the number of biopsies performed. © 2006 Wiley Periodicals, Inc. J Clin Ultrasound 2007 [source] Design and control of a planar haptic device with passive actuators based on passive force manipulability ellipsoid (FME) analysisJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 9 2005Changhyun Cho In this paper, we propose an optimal design for a passive haptic device with brakes and its control method. The inability of a brake to generate torque significantly affects the performance of a multi-DOF haptic device, in that a desired force can be generated only approximately in some workspace and, in some cases, the device may become stuck contrary to the user's intention. In this research, these limitations are analyzed by means of the so-called passive force manipulability ellipsoid. Through the analysis, performance indices are developed for evaluating the limitations associated with passive haptic devices. Optimization is conducted for a 5-bar mechanism with redundant actuation, and a coercive force approximation scheme is developed to avoid unsmooth motion during the wall-following task along the virtual wall. It is experimentally shown that the performance in relation to the limitations is greatly improved for the optimized mechanism. © 2005 Wiley Periodicals, Inc. [source] Sample Size Determination for Categorical ResponsesJOURNAL OF FORENSIC SCIENCES, Issue 1 2009Dimitris Mavridis Ph.D. Abstract:, Procedures are reviewed and recommendations made for the choice of the size of a sample to estimate the characteristics (sometimes known as parameters) of a population consisting of discrete items which may belong to one and only one of a number of categories with examples drawn from forensic science. Four sampling procedures are described for binary responses, where the number of possible categories is only two, e.g., licit or illicit pills. One is based on priors informed from historical data. The other three are sequential. The first of these is a sequential probability ratio test with a stopping rule derived by controlling the probabilities of type 1 and type 2 errors. The second is a sequential variation of a procedure based on the predictive distribution of the data yet to be inspected and the distribution of the data that have been inspected, with a stopping rule determined by a prespecified threshold on the probability of a wrong decision. The third is a two-sided sequential criterion which stops sampling when one of two competitive hypotheses has a probability of being accepted which is larger than another prespecified threshold. The fifth procedure extends the ideas developed for binary responses to multinomial responses where the number of possible categories (e.g., types of drug or types of glass) may be more than two. The procedure is sequential and recommends stopping when the joint probability interval or ellipsoid for the estimates of the proportions is less than a given threshold in size. For trinomial data this last procedure is illustrated with a ternary diagram with an ellipse formed around the sample proportions. There is a straightforward generalization of this approach to multinomial populations with more than three categories. A conclusion provides recommendations for sampling procedures in various contexts. [source] Three-dimensional sonographic volume measurement of the fetal spleenJOURNAL OF OBSTETRICS AND GYNAECOLOGY RESEARCH (ELECTRONIC), Issue 5 2007Toshiyuki Hata Abstract Aim:, The objective of this longitudinal study was to evaluate the growth of the fetal spleen in normal pregnancies, using three-dimensional ultrasound. Methods:, Three-dimensional sonographic examinations were performed on 14 appropriate-for-gestational-age fetuses. Fetal splenic volume was measured every 2,3 weeks after 20 weeks of gestational age until delivery. Results:, Curvilinear relationships were found between the gestational age and splenic volume (R2 = 80.2%, P < 0.0001), and normal ranges of splenic volume measurements for estimating the growth of the fetal spleen during normal pregnancy were generated. We found that the splenic volume calculation based on the equation for the volume of the ellipsoid by conventional two-dimensional ultrasound in previous investigations is about twice as large as that using three-dimensional ultrasound in our study, whereas the present data described in this study is quite comparable with previous data from an autopsy series. Conclusion:, Our findings suggest that the standard curve for the fetal splenic volume using three-dimensional ultrasound provides a superior means for evaluating the normal splenic growth in the fetus and for identifying splenic abnormalities in utero. However, the data and its interpretation in our study should be taken with some degree of caution because of the small number of subjects studied. Further studies involving a larger sample size would be needed to confirm these findings. [source] Computer modeling of optical properties of gold ellipsoidal nanoparticles at laser radiation wavelengthsLASER PHYSICS LETTERS, Issue 2 2005V. K. Pustovalov Abstract Processes of laser interaction with metal (gold) nanoparticles are of great interest for laser applications in nanotechnology, engineering, and medicine. Optical properties of nanoparticles determine photophysical and photochemical processes during laser treatment. Computer calculation of efficiency factors of absorption, scattering and extinction of radiation by ellipsoidal gold nanoparticles (two-dimensional ellipsoids of revolution) with small semiaxes in the range 5,100 nm, for some values of aspect ratio and angle of orientation of ellipsoid with respect to direction of laser radiation propagation and for some laser wavelengths is performed. The estimation of absorbed and scattered laser radiation energy by gold ellipsoidal nanoparticles, their maximal temperatures and comparison with experimental data is made. (© 2005 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Retrospective measurement of the diffusion tensor eigenvalues from diffusion anisotropy and mean diffusivity in DTIMAGNETIC RESONANCE IN MEDICINE, Issue 1 2006Khader M. Hasan Abstract A simple theoretical framework to compute the eigenvalues of a cylindrically symmetric prolate diffusion tensor (D) from one of the rotationally-invariant diffusion anisotropy indices and average diffusivity is presented and validated. Cylindrical or axial symmetry assumes a prolate ellipsoid shape (,, = ,1 > ,, = (,2 + ,3)/2; ,2 = ,3). A prolate ellipsoid with such symmetry is largely satisfied in a number of white matter (WM) structures, such as the spinal cord, corpus callosum, internal capsule, and corticospinal tract. The theoretical model presented is validated using in vivo DTI measurements of rat spinal cord and human brain, where eigenvalues were calculated from both the set of diffusion coefficients and a tensor analysis. This method was used to retrospectively analyze literature data that reported tensor-derived average diffusivity, anisotropy, and eigenvalues, and similar eigenvalue measurements were obtained. The method provides a means to retrospectively reanalyze literature data that do not report eigenvalues. Other potential applications of this method are also discussed. Magn Reson Med, 2006. © 2006 Wiley-Liss, Inc. [source] Models of the Cosmic Horseshoe gravitational lens J1004+4112MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2008S. Dye ABSTRACT We model the extremely massive and luminous lens galaxy in the Cosmic Horseshoe Einstein ring system J1004+4112, recently discovered in the Sloan Digital Sky Survey. We use the semilinear method of Warren & Dye, which pixelizes the source surface brightness distribution, to invert the Einstein ring for sets of parametrized lens models. Here, the method is refined by exploiting Bayesian inference to optimise adaptive pixelization of the source plane and to choose between three differently parametrized models: a singular isothermal ellipsoid, a power-law model and a Navarro, Frenk & White (NFW) profile. The most probable lens model is the power law with a volume mass density ,,r,1.96±0.02 and an axis ratio of ,0.8. The mass within the Einstein ring (i.e. within a cylinder with projected distance of ,30 kpc from the centre of the lens galaxy) is (5.02 ± 0.09) × 1012 M ,, and the mass-to-light ratio is ,30. Even though the lens lies in a group of galaxies, the preferred value of the external shear is almost zero. This makes the Cosmic Horseshoe unique amongst large separation lenses, as almost all the deflection comes from a single, very massive galaxy with little boost from the environment. [source] A deep kinematic survey of planetary nebulae in the Andromeda galaxy using the Planetary Nebula SpectrographMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2006H. R. Merrett ABSTRACT We present a catalogue of positions, magnitudes and velocities for 3300 emission-line objects found by the Planetary Nebula Spectrograph in a survey of the Andromeda galaxy, M31. Of these objects, 2615 are found likely to be planetary nebulae (PNe) associated with M31. The survey area covers the whole of M31's disc out to a radius of . Beyond this radius, observations have been made along the major and minor axes, and the Northern Spur and Southern Stream regions. The calibrated data have been checked for internal consistency and compared with other catalogues. With the exception of the very central, high surface brightness region of M31, this survey is complete to a magnitude limit of m5007, 23.75, 3.5 mag into the PN luminosity function. We have identified emission-line objects associated with M31's satellites and other background galaxies. We have examined the data from the region tentatively identified as a new satellite galaxy, Andromeda VIII, comparing it to data in the other quadrants of the galaxy. We find that the PNe in this region have velocities that appear to be consistent with membership of M31 itself. The luminosity function of the surveyed PNe is well matched to the usual smooth monotonic function. The only significant spatial variation in the luminosity function occurs in the vicinity of M31's molecular ring, where the luminosities of PNe on the near side of the galaxy are systematically ,0.2 mag fainter than those on the far side. This difference can be explained naturally by a modest amount of obscuration by the ring. The absence of any difference in luminosity function between bulge and disc suggests that the sample of PNe is not strongly populated by objects whose progenitors are more massive stars. This conclusion is reinforced by the excellent agreement between the number counts of PNe and the R -band light. The number counts of kinematically selected PNe also allow us to probe the stellar distribution in M31 down to very faint limits. There is no indication of a cut-off in M31's disc out to beyond four scalelengths, and no signs of a spheroidal halo population in excess of the bulge out to 10 effective bulge radii. We have also carried out a preliminary analysis of the kinematics of the surveyed PNe. The mean streaming velocity of the M31 disc PNe is found to show a significant asymmetric drift out to large radii. Their velocity dispersion, although initially declining with radius, flattens out to a constant value in the outer parts of the galaxy. There are no indications that the disc velocity dispersion varies with PN luminosity, once again implying that the progenitors of PNe of all magnitudes form a relatively homogeneous old population. The dispersion profile and asymmetric drift results are shown to be mutually consistent, but require that the disc flares with radius if the shape of its velocity ellipsoid remains invariant. [source] On the kinematic deconvolution of the local neighbourhood luminosity functionMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2002C. Pichon A method for inverting the statistical star counts equation, including proper motions, is presented; in order to break the degeneracy in that equation, it uses the supplementary constraints required by dynamical consistency. The inversion gives access to both the kinematics and the luminosity function of each population in three régimes: the singular ellipsoid, the constant ratio Schwarzschild ellipsoid plane-parallel models and the epicyclic model. This more realistic model is tailored to account for the local neighbourhood density and velocity distribution. The first model is fully investigated, both analytically and by means of a non-parametric inversion technique, while the second model is shown to be formally its equivalent. The effect of noise and incompleteness in apparent magnitude is investigated. The third model is investigated by a non-parametric inversion technique where positivity of the underlying luminosity function is explicitly accounted for. It is argued that its future application to data such as the Tycho catalogue (and in the upcoming satellite GAIA) could lead , provided that the vertical potential and or the asymmetric drift or w, are known , to a non-parametric determination of the local neighbourhood luminosity function without any reference to stellar evolution tracks. It should also yield the proportion of stars for each kinematic component and a kinematic diagnostic to split the thin disc from the thick disc or the halo. [source] A new quadruple gravitational lens system: CLASS B0128+437MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2000P. M. Phillips High-resolution MERLIN observations of a newly discovered four-image gravitational lens system, B0128+437, are presented. The system was found after a careful re-analysis of the entire CLASS data set. The MERLIN observations resolve four components in a characteristic quadruple-image configuration; the maximum image separation is 542 mas and the total flux density is 48 mJy at 5 GHz. A best-fitting lens model with a singular isothermal ellipsoid results in large errors in the image positions. A significantly improved fit is obtained after the addition of a shear component, suggesting that the lensing system is more complex and may consist of multiple deflectors. The integrated radio spectrum of the background source indicates that it is a gigahertz peaked spectrum source. It may therefore be possible to resolve structure within the radio images with deep VLBI observations and thus to constrain the lensing mass distribution better. [source] Effects of composition distribution on electronic structures of self-assembled InGaN/GaN quantum dotsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 7 2010Wei-Yi Tsai Abstract In this study, we investigate the influences of different composition distributions on the electronic structures of truncated cone-shaped InGaN quantum dots (QDs). A varying parameter, , is defined as , in which w1 and w2 are the top and base diameter of QD, respectively. This factor is set to study the role of similar truncated cones with the same base diameter and height on electronic structures of QD. Three indium composition distributions are considered: ellipsoid, uniform, and linear. The single-band effective-mass equation and six-band k·p theory are used to calculate the transition energies of electrons and holes, respectively. The numerical results reveal that the parameter plays an important role in changing the piezoelectric potential. In addition, an InGaN quantum dot with a linear distribution of indium has the maximum transition energy, whereas one with an ellipsoidal distribution has the minimum value. It is noteworthy that the binding energy greatly decreases as increases for different indium distributions. [source] A further proteomic study on the effect of iron in the human pathogen Trichomonas vaginalisPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 12 2007Jose Batista De Jesus Dr. Abstract Iron is an essential element to support the growth and survival of Trichomonas vaginalis. It plays a critical role in the host,parasite interaction, and modulates the expression of virulence factors in this protozoan. In this work, parasites grown in iron-rich and iron-depleted media were analyzed by (i) light and scanning electron microscopy and (ii) 2-DE and MS. Withdrawal of iron from the culture medium resulted in dramatic changes in both the morphology and in the proteome pattern of T. vaginalis. Trophozoites underwent transformation from ellipsoid or amoeboid forms to rounded cells, whose flagella and axostyle were internalized. Forty-five proteins differentially expressed in parasites cultivated in the absence of iron were identified. In iron-depleted parasites, enzymes involved in energetic metabolism, proteolysis and hydrogenosomal iron-sulfur (Fe-S) proteins were down-regulated or even suppressed. Among up-regulated proteins, six isoforms of actin were detected. In addition, phosphoenolpyruvate carboxykinase, putative lactate dehydrogenase, and putative adenosine triphosphatase were also up-regulated or were exclusively observed in gels related to iron-depleted parasites. Our data demonstrate that iron has a pivotal role in the regulation of the morphological transformation of T. vaginalis and modulates the expression of both Fe-S and non-Fe-S proteins in the parasite. [source] Architecture of the Blood-Spleen Barrier in the Soft-Shelled Turtle, Pelodiseus SinensisTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 8 2009Hui-Jun Bao The soft-shelled turtle, Pelodiseus sinensis, and its spleen section showing carbon particles of injected Indian ink mainly in the ellipsoid which composed the blood-spleen barrier. See Bao et al, on page 1079, in this issue. Anatomical Record 292:1079,1087. [source] Giant mitochondria in the retina cone inner segments of shrews of genus Sorex (Insectivora, Soricidae)THE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 2 2003Sara Lluch Abstract The retinas of three species of shrews (Sorex araneus, S. coronatus, and S. minutus) were analyzed. Two kinds of photoreceptors were identified according to (among other characteristics) the traits of the mitochondria of their inner segments. The rod inner segments contained several round or oval mitochondria distributed longitudinally inside the ellipsoid. The cone inner segment showed a few mitochondria, which we classified as megamitochondria (maximum length = 4.22 ,m in S. araneus, 5.68 ,m in S. coronatus, and 2.42 ,m in S. minutus). An analysis of serial thin sections in S. coronatus showed that these large organelles occurred in the apical and central portions of the ellipsoid. In the peripheral and basal regions of the ellipsoid, megamitochondria were frequently accompanied by smaller mitochondria. The giant mitochondria were irregular in form and densely packed, and a reduced cytosol was observed between each mitochondria. In general, they exhibited an electron-dense matrix and a complex system of cristae, which varied in length and array. In mammalian retina, megamitochondria have only been described in the ellipsoid of the tree shrews Tupaia glis and T. belangeri, two diurnal Scandentia with a rich-cone retina. In general terms, Sorex megamitochondria are morphologically very similar to those reported for Tupaia, especially in their arrangement in the cone ellipsoid. However, they differ in the orientation of the cristae. We propose that the ellipsoid of Sorex may serve two functions: as a source of energy for receptor cells, and as a device for improving the cone outer segment optics. Anat Rec Part A 272A:484,490, 2003. © 2003 Wiley-Liss, Inc. [source] Dynamic proton disorder and the II,I structural phase transition in (NH4)3H(SO4)2ACTA CRYSTALLOGRAPHICA SECTION B, Issue 1 2009Yoo Jung Sohn X-ray powder diffraction, differential scanning calorimetry (DSC)/thermogravimetry (TG) and single-crystal neutron diffraction methods were used to investigate triammonium hydrogen disulfate (NH4)3H(SO4)2 (TAHS) in the temperature range between 293 and 493,K. The temperature-dependent X-ray powder diffraction measurements show a clear hysteresis of the I II phase transition of TAHS with transition temperatures of Tup = 412.9,(1),K on heating and of Tdown = 402.6,(1),K on cooling. From the existence of hysteresis and from the jump-like changes of the lattice parameters, the I II phase transition of TAHS is considered to be first order. With DSC/TG measurements we confirmed that there is only one phase transition between 293 and 493,K. Through careful investigation on single crystals of TAHS using neutron diffraction, the correct space group (C2/c) of room-temperature TAHS-II phase was confirmed. Crystal structure analysis by single-crystal neutron diffraction showed a strongly elongated displacement ellipsoid of the proton which lies in the middle of the (SO4)H(SO4) dimer with local symmetry. The protons of the NH4 groups also show strongly enlarged anisotropic mean-square displacements. These findings are interpreted in terms of a characteristic proton disorder in the TAHS-II phase. [source] The Presence of Megamitochondria in the Ellipsoid of Photoreceptor Inner Segment of the Zebrafish RetinaANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 6 2005J. Kim Summary Although the megamitochondria (MM) were localized in various pathological conditions, normal retina of some mammalian species was reported to include MM for various physiological roles. However, it was not clearly confirmed whether the MM is present in the retina of lower vertebrate as well. In this study, we tried to show the presence of the MM in the zebrafish retina using electron microscopic technique. In all the photoreceptors including rods, cones and double cones of the zebrafish retina, MM were observed in the ellipsoid of inner segment. In the photoreceptor epllipsoid of the zebrafish retina, the mitochondria located in the central portion of the ellipsoid had a highly electron-dense matrix, which were accompanied by the mitochondria with electron-lucent matrix in the apical portion of the ellipsoid. The presence of MM was more clearly discernable in the rods, which were localized under the double cones. This finding is somewhat different from those observed in the previous studies because MM were localized in the inner segment of cones, but were not in those of rods in the case of mammalian retina. Although the exact physiological meaning for the presence of MM in some vertebrate species should be further studied, the present study could show that the MM in the ellipsoid of the retinal photoreceptors was not only restricted in some mammalian species. [source] Five-dimensional structure refinement of natural melilite, (Ca1.89Sr0.01Na0.08K0.02)(Mg0.92Al0.08)(Si1.98Al0.02)O7ACTA CRYSTALLOGRAPHICA SECTION B, Issue 6 2001Luca Bindi The structure of a crystal of natural melilite from San Venanzo, Umbria (Italy) of the general formula X2T1(T2)2O7, where X = Ca0.945Sr0.005Na0.04K0.01, T1 = Mg0.92Al0.08 and T2 = Si0.99Al0.01, has been solved and refined as an incommensurate structure in five-dimensional superspace. The structure is tetragonal, superspace group P21m:p4mg, cell parameters a = 7.860,(1), c = 5.024,(1),Å, modulation vectors q1 = 0.2815,(3)(a* + b*), q2 = 0.2815,(3)(,a* + b*). The data collection was performed on a KumaCCD diffractometer. The structure was refined from 7606 reflections to final R = 0.0481. A special modification of the refinement program Jana2000 was necessary to take into account overlapping of satellite reflections m×n = ±1, which could not be properly separated in the integration procedure. The final model includes modulations of the atomic positions as well as modulations of the thermal parameters. The latter are induced by strong differences in the neighbourhood of the actual modulated positions. The occupational modulation was neither significant for X nor for T1 sites and the sites were supposed to be occupied only by Ca and Mg, respectively. As a consequence of the Ca and O positional modulations six-, seven- and eightfold Ca coordination occur throughout the structure and the thermal ellipsoid changes its shape correspondingly. The positional modulation of the atoms causes variations in the interatomic distances which, however, do not affect bond-valence sums considerably, but induce flattening and rotation in T1 and T2 tetrahedra, respectively. [source] Atomic resolution structure of pseudoazurin from the methylotrophic denitrifying bacterium Hyphomicrobium denitrificans: structural insights into its spectroscopic propertiesACTA CRYSTALLOGRAPHICA SECTION D, Issue 1 2009Daisuke Hira The crystal structure of native pseudoazurin (HdPAz) from the methylotrophic denitrifying bacterium Hyphomicrobium denitrificans has been determined at a resolution of 1.18,Å. After refinement with SHELX employing anisotropic displacement parameters and riding H atoms, Rwork and Rfree were 0.135 and 0.169, respectively. Visualization of the anisotropic displacement parameters as thermal ellipsoids provided insight into the atomic motion within the perturbed type 1 Cu site. The asymmetric unit includes three HdPAz molecules which are tightly packed by head-to-head cupredoxin dimer formation. The shape of the Cu-atom ellipsoid implies significant vibrational motion diagonal to the equatorial xy plane defined by the three ligands (two His and one Cys). The geometric parameters of the type 1 Cu site in the HdPAz structure differ unambiguously from those of other pseudoazurins. It is demonstrated that their structural aspects are consistent with the unique visible absorption spectrum. [source] Kinematics and metallicity analysis for nearby F, G and K starsASTRONOMISCHE NACHRICHTEN, Issue 1 2009S. Vidojevi Abstract A sample containing 1 026 stars of spectral types F, G, and K, mainly dwarfs, from the solar neighbourhood with available space velocities and metallicities is treated. The treatment comprises a statistical analysis of the metallicity and velocity data and calculation of galactocentric orbits. Sample stars identified as members of the galactic halo are detached from the rest of the sample based on the values of their metallicities, velocity components and galactocentric orbits. In identifying halo stars a new, kinematical, criterion is proposed. Except one, these halo stars are the metal-poorest ones in the sample. Besides, they have very high velocities with respect to LSR. On the other hand, the separation between the thin disc and thick one is done statistically based on LSR space velocities, membership probability (Schwarzschild distribution with assumed parameters) and galactocentric orbits. In the metallicity these two groups are not much different. For each of the three subsamples the mean motion and velocity ellipsoid are calculated. The elements of the velocity ellipsoids agree well with the values found in the literature, especially for the thin disc. The fractions of the subsystems found for the present sample are: thin disc 93%, thick disc 6%, halo 1%. The sample stars established to be members of the thin disc are examined for existence of star streams. Traces of both, known and unknown, star streams are not found (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]
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