Spherical Samples Research Articles

Limitations of three-dimensional power Doppler angiography in preoperative evaluation of ovarian tumors.

BackgroundThis study describes the accuracy of three-dimensional power Doppler (3D-PD) angiography as secondary method for differential diagnosis of ovarian tumors.MethodSeventy-five women scheduled for surgical removal of adnexal masses were assessed by transvaginal ultrasound. Ovarian tumors were classified by IOTA simple rules and two three-dimensional blocks were recorded. In a second step analyses, a 4 cm3 spherical sample was obtained from the highest vascularized solid area of each stored block. Vascularization index (VI), flow index (FI) and vascularization-flow index (VFI) were calculated. The repeatability was assessed by concordance correlation coefficient (CCC) and limits of agreement (LoA), and diagnostic accuracy by area under ROC curve.ResultsIOTA simple rules classified 26 cases as benign, nine as inconclusive and 40 as malignant. There were eight false positive and no false negative. Among the masses classified as inconclusive or malignant by IOTA simple rules, the CCCs were 0.91 for VI, 0.70 for FI, and 0.86 for VFI. The areas under ROC curve were 0.82 for VI, 0.67 for FI and 0.81 for VFI.Conclusions3D-PD angiography presented considerable intraobserver variability and low accuracy for identifying false positive results of IOTA simple rules.

Effects of citric acid and urea on the structural and morphological characteristics of BiVO4 synthesized by the sol–gel combustion method

Micro-sized spherical BiVO4 photocatalysts composed of nanoparticles were synthesized by the sol–gel combustion method. The effects of citric acid and urea on the structural and morphological characteristics of samples were studied by X-ray diffraction, field emission scanning electron microscopy, N2 adsorption and desorption and UV–Vis spectroscopy. The photocatalytic activity was evaluated by the photocatalytic degradation of rhodamine B under visible light. The results showed the sphere-shaped BiVO4 sample to have excellent photocatalytic performance compared with the bulk sample prepared by solid-state reaction. This enhancement could be attributed to the special spherical morphology, which enhanced the absorption ability, increased the separation efficiency of photon-generated carriers and improved surface reaction sites for consumption of photon-generated carriers. Uniform micro-sized spherical BiVO4 samples composed of nanoparticles were successfully synthesized by the sol–gel combustion method. The relationships between the morphologies and citric acid with urea contents were studied by using the field emission scanning electron microscopy (FE-SEM) technology.

Synthesis and Electrochemical Properties of Spherical Nano-Structured and Nano-Agglomerated Li1.2Mn0.6Ni0.2O2 Cathode Materials for Lithium-Ion Batteries

Spherical nano-structured and nano-agglomerated Li1.2Mn0.6Ni0.2O2 cathode materials were prepared by simple blending and mechanical ball-milling process, respectively. The phase structure of Li1.2Mn0.6Ni0.2O2 cathodes were determined by X-ray diffraction (XRD), and the surface morphology was observed by scanning electron microscopy (SEM). Electrochemical tests of the cathodes were performed to examine the effect of particle morphology on the cycle performance, as well as the rate capability. The results show that spherical nano-structured sample prepared by simple blending process exhibits an initial discharge capacity of ∼234.0 mAh g−1 and remains ∼98.0% of that after 50 cycles. In contrast, the nano-agglomerated cathode synthesized by mechanical ball milling process retains only ∼84.0% of its initial discharge capacity after 50 cycles although it shows a better rate performance than the spherical nano-structured cathode. The good rate performance for the nano-agglomerated cathode can be attributed to the fine nano-scale particles which greatly shorten the lithium-ion diffusion distance. Furthermore, the better structure stability for the spherical nano-structured cathode can be responsible for its superior cycling performance.

Improving neutron multiplicity counting for the spatial dependence of multiplication: Results for spherical plutonium samples

The fissile mass deduced from a neutron multiplicity counting measurement of high mass dense items is underestimated if the spatial dependence of the multiplication is not taken into account. It is shown that an appropriate physics-based correction successfully removes the bias. It depends on four correction coefficients which can only be exactly determined if the sample geometry and composition are known. In some cases, for example in warhead authentication, available information on the sample will be very limited. MCNPX-PoliMi simulations have been performed to obtain the correction coefficients for a range of spherical plutonium metal geometries, with and without polyethylene reflection placed around the spheres. For hollow spheres, the analysis shows that the correction coefficients can be approximated with high accuracy as a function of the sphere׳s thickness depending only slightly on the radius. If the thickness remains unknown, less accurate estimates of the correction coefficients can be obtained from the neutron multiplication. The influence of isotopic composition is limited. The correction coefficients become somewhat smaller when reflection is present.

Application of a modified method of ultrasonic measurements for determination of elastic moduli of rocks

The velocities of elastic waves with quasi-longitudinal and quasi-transverse polarizations in a spherical rock sample have been measured. The experimental values of velocities are used to calculate 21 elastic moduli of the sample. For comparison, the effective elastic properties of the sample are simulated based on the data on the crystallographic textures of rock-forming minerals obtained by neutron diffraction. It is shown that the largest discrepancy between the model predictions and experimental velocity values is observed for transversely polarized waves.

High-density Na-doped LiFePO4 synthesised by co-precipitation for lithium ion battery

To improve the density and electrochemical performance of LiFePO4, Na-doping modified Li0·95Na0·05FePO4 cathode material was synthesised through co-precipitation method, using a spherical sample prepared by microwave heating as precursor. The morphology, structure, electrochemical performance and the tap density of the materials were characterised by scanning electron microscope, x-ray diffraction, cyclic voltammetry, constant current charge–discharge experiment and the tap density measurement. The results indicated that the samples have rules spherical or similar spherical morphology and simple pure olive-type phase. The Na-doped Li0·95Na0·05FePO4 material showed excellent performance with a tap density of 1·63 g cm−3. At room temperature, its initial discharge capacities reached 164·2, 151·5 and 130·5 mAh g−1 at 0·2, 1 and 2 C current rates, respectively.

Temperature dependence of the heat capacity and times of the establishment of vacancy equilibrium in simple crystals

The concentration range of vacancies that affect the temperature dependence of the heat capacity at constant volume C v has been determined. The times of the establishment of vacancy equilibrium in spherical samples of simple crystals with different radii due to the thermal motion of atoms have been calculated for the process as close as possible to the equilibrium one with a decrease in the temperature from the melting point to the current value T. The free energy of an imperfect crystal has been determined taking into account contributions from interatomic interactions in terms of the Lennard-Jones potential functions and vibrational energies. The properties of an imperfect crystal have been calculated within the Lifshitz approximation linear in the density of vacancies with the frequency distribution function of the perfect crystal with the corresponding corrections, which reflect local vibrations of atoms around vacancies. The free energy of a defect-free perfect crystal has been determined from the calculated frequencies of normal vibrations with the inclusion of up to four nearest neighbors. It has been shown that disregard of acoustic (out-of-phase) parts of the spectrum in the calculation of the heat capacity C v with increasing temperature leads to a decrease (increase) in C v from the values calculated for the total vibrational spectrum. A nonequilibrium state of the imperfect crystal can lead to negative values of the heat capacity at constant volume.

Fragmentation processes in two-phase materials.

We investigate the fragmentation process of solid materials with crystalline and amorphous phases using the the discrete element method. Damage initiates inside spherical samples above the contact zone in a region where the circumferential stress field is tensile. Cracks initiated in this region grow to form meridional planes. If the collision energy exceeds a critical value which depends on the material's internal structure, cracks reach the sample surface resulting in fragmentation. We show that this primary fragmentation mechanism is very robust with respect to the internal structure of the material. For all configurations, a sharp transition from the damage to the fragmentation regime is observed, with smaller critical collision energies for crystalline samples. The mass distribution of the fragments follows a power law for small fragments with an exponent that is characteristic for the branching merging process of unstable cracks. Moreover this exponent depends only on the dimensionally of the system and not on the microstructure.

Y2O3: Eu3+, Tb3+ spherical particles based anti-reflection and wavelength conversion bi-functional films: Synthesis and application to solar cells

In this study, Eu3+ and Tb3+ co-doped Y2O3 particles were prepared via the simple, cost-effective urea homogeneous precipitation method without additives. The chosen particles were added in the SiO2 sols to get anti-reflection (AR) and wavelength conversion bi-functional films. Careful investigations were carried out to find the optimum preparation conditions and proper morphology. SEM images showed that the particle sizes reduced as metal ion/urea ratio decreased. Additionally, the extracted particles turned from sphere to lamellar type when the deionized water, which was used as solvent, reduced to a certain extent. The mechanisms of the morphology formation and diversification were proposed as well. The as prepared materials can convert UV region photos to visible photons between 460nm and 640nm, which just matched the spectral response of most solar cells. The spherical sample showed better luminescence performance than the one with lamellar morphology. In addition, the optical transmittance spectra indicated that the films adding spherical particles had better anti-reflective performance, and the best adding amount was 0.08g. Finally, As a proof-of-concept application, the as prepared bi-functional films were used to test the standard monocrystalline silicon solar cell assembled with anti-reflection and wavelength conversion bi-functional films photoelectric conversion properties. As a result, the as prepared bi-functional films could effectively improve the photoelectric conversion efficiency by0.23% compared to pure SiO2 AR coating film and 0.55% compared to glass.

Structure and properties of Cu-37%Zn alloy during quasi-spherical explosive loading

The relations between the parameters of loading by powerful convergent shock waves (such as high pressure 40-300 GPa, high-speed deformation 106-107 с-1, tensile stress 0.25-1.75 GPa at unloading and temperature 100-2500°С ) and structural changes (main of which are effects of localized deformation, beta–alpha–beta transformation, the melting and crystallization) in alloy Cu-37%Zn were investi-gated. The investigations were performed with ball samples with diameter 60 and 40 mm. The balls were subjected to the explosion of a spherical explosive charge 10 и 20 mm thick from the surface at twelve points spread uniformly over the charge’s surface. The calculated pressure was 40 и 70 GPa on a ball’s surface and 180 и 300 GPa at its center. A correlation between macrostructural and microstructural changes and the geometrical conditions of shock-wave loading according to various schemes has been found. Effects of the interaction of converging shock waves at loading by and the related phenomena of localization of plastic deformation and the fracture were studied. The initiation of the radial cracks in the spherical samples occurs where the tensile stresses at unloading begin to exceeds the dynamic yield strength of the material. It is determined, that in the spherical sample of brass this distance corresponds to a half of radius of the sample, and the value of the tensile stress is approximately 1.3 GPa, that is close to the spall dynamic strength of brass - 1.75 GPa and exceeds the ultimate static strength of brass by a factor of 5.

Studies of Thermal Behavior on Activated Carbons for the Selection of Regeneration Scheme

Activated carbon is the most potential candidate for the sorption of various gases including hydrogen and helium. Because of its large internal surface area greater than 1000 m2/gm, activated carbons in different forms are widely used in many industries like gas and liquid purification, fuel storage and chemisorption. Recent progress of vacuum and cryogenic technologies leads to the wide application of activated carbons in sorption cryopumps. Cryopump is defined as a kind of entrapment vacuum pump which captures the gas by surfaces cooled to temperatures below 120K and hence after a certain operational time there is a need of regeneration. To define the regeneration scheme of the newly developed sorbents thermo-gravimetric analysis were carried out to study their thermal behavior. Based on the thermal behavior and the regeneration gas loads the required regeneration temperature needs to be fixed. Hence a system is established and experiments were carried out to know the thermal behavior of different forms of activated carbons. Before performing thermal degassing the sample chamber with activated carbon samples are also evacuated to a pressure less than 10-3 mbar for the natural desorption to take place. Studies were carried out for knitted fabric, granular and spherical charcoal samples. It was observed that evacuation increases desorption by 1.5 to 2 times. From the thermal studies it was estimated that after heating till 1000C followed by continuous evacuation 80-95% of gases are removed from the sorbent. Therefore degassing or regeneration above 1000C will not be much effective for regeneration.

Surfactant-assisted crystallization of porous Mn2O3anode materials for Li-ion batteries

MnCO3 precursors with different morphologies were crystallized using three kinds of surfactants as soft templates, i.e., cation surfactant cetyl trimethyl ammonium bromide (CTAB), anion surfactant sodium dodecyl sulfate (SDS) and neutral poly(vinyl pyrrolidone) (PVP). When PVP was used, the reaction manner was changed from only stirring at room temperature to a hydrothermal route. Under hydrothermal conditions, different ethanol/water ratios and sources of CO32− (NaHCO3 and urea) were used. Porous cubic, regular spherical and nut-like spherical Mn2O3 samples can be obtained by a simple post-annealing process. The correlation between the morphology of Mn2O3 and its performance as an anode material for Li-ion batteries was evaluated. The nut-like spherical Mn2O3 sample has the best cycling performance, with a specific discharge capacity of 925 mA h g−1 at a current density of 100 mA g−1 after 180 cycles. The sample composed of cubes and spheres has superior rate performance. The specific discharge capacity decreases with increasing current density from ~872 mA h g−1 at 100 mA g−1 to ~361 mA h g−1 at 2000 mA g−1.

An experimental investigation on the drying kinetics of a single coarse particle of Belchatow lignite in an atmospheric superheated steam condition

The efficiency of lignite-fired power plants is sacrificed by the high moisture content of this energy carrier. The most adequate effort for upgrading the potential of lignite is the drying process, influenced by both the drying conditions and the physicochemical features of lignite. This paper presents studies on the drying kinetic of the Belchatow lignite originating from the biggest Polish lignite mine. Experimental attempts were conducted for spherical lignite samples dried in a superheated steam atmosphere at the temperature range of 110–170°C. Each experiment includes the simultaneous measurements of changes in weight and temperature profiles for a single sample. Additionally, the drying process was recorded to observe the cracking on the surface of the sample and its shrinkage. The kinetics were described in the form of moisture content, drying rate and temperature profiles over the drying process. The time and rate of the superheated steam drying process depending on the sample size and steam temperature were estimated. Those parameters are essential for the design of an effective industrial coal drying system, which allows for the latent heat recovery of water evaporation from the lignite, which in turn will improve the thermal efficiency of the lignite-fired power generation.

The resonant ultrasound spectroscopy method for determining the Poisson׳s ratio of spheres over the full range

The method for determining the Poisson׳s ratio of isotropic spheres was studied via resonant ultrasound spectroscopy (RUS). To that end, The mode structure maps for freely vibrating isotropic spheres were obtained via finite element method over the full range of Poisson׳s ratio (−1 to+0.5). RUS measurements for spherical samples (indium, steel, SiO2, 13.5wt% In–Sn, and copper foam) were compared with the numerical results and the Poisson׳s ratios were determined as +0.4, +0.3, +0.2, −0.08, and −0.3, respectively. The effects of slight shape imperfection upon the first 12 modes were analyzed for various Poisson׳s ratios, and were found to be negligible in interpretation of the experimental results.

Three-dimensional Power Doppler Ultrasound Study of the Placenta

ABSTRACT Advanced ultrasound technology has been a valuable tool in the assessment of placental anatomy and physiology. Conventional two-dimensional (2D) sonography reveals placental morphological characteristics, 2D color Doppler can assess blood flow in the placenta, 2D power Doppler can evaluate placental vascular trees, and three-dimensional (3D) ultrasound gives more detailed information on the surface anatomy. Recent advances, such as 3D power Doppler with virtual organ computer aided-analysis (VOCAL) and histogram analysis can measure the placental volume, and assess uteroplacental and fetoplacental perfusions. In particular, ‘placental vascular sonobiopsy’ can specifically evaluate the second- and thirdtrimester placental blood flow and vascularity by obtaining several spherical samples from the placenta that will represent the entire placenta. This article presents normal placental development and pathological findings of the placenta using 3D power Doppler ultrasound, and discusses 3D power Doppler assessments of placental perfusion in high-risk pregnancies, such as fetal growth restriction, pregnancy-induced hypertension and preeclampsia, and, from this basis, re-establishes the importance of 3D power Doppler ultrasound as a screening, diagnostic, and surveillance tool in normal and abnormal pregnancies. How to cite this article Tanaka H, Cajusay-Velasco S, Noguchi J, Hata T. Three-dimensional Power Doppler Ultrasound Study of the Placenta. Donald School J Ultrasound Obstet Gynecol 2014;8(4):400-409.

A dynamic ball compression test for understanding rock crushing.

During crushing, rock particles are subjected to complicated loading. It is desired to establish the relation between the loading and the fragmentation parameters for better understanding rock crushing mechanism. In this work, a split Hopkinson pressure bar system in combination with high speed cameras is utilized in the dynamic ball compression test, in which the spherical rock sample is adopted to avoid the shape effect. Using elasticity theory, the loading rate and the dynamic indirect tensile strength are first calculated. With the aid of the moment-trap technique and high speed cameras, the surface energy is determined for each sample. The relations between the loading rate and the fragmentation parameters, i.e., the number of fragments and the surface energy are established. The application of this method to a granitic rock shows that it is flexible and can be applied to the crushing study of generic brittle solids.

Ultrasensitive 3He magnetometer for measurements of high magnetic fields

We describe a 3He magnetometer capable to measure high magnetic fields (B > 0.1 Tesla) with a relative accuracy of better than 10^-12. Our approach is based on the measurement of the free induction decay of gaseous, nuclear spin polarized 3He following a resonant radio frequency pulse excitation. The measurement sensitivity can be attributed to the long coherent spin precession time T2* being of order minutes which is achieved for spherical sample cells in the regime of motional narrowing where the disturbing influence of field inhomogeneities is strongly suppressed. The 3He gas is spin polarized in-situ using a new, non-standard variant of the metastability exchange optical pumping. We show that miniaturization helps to increase T2* further and that the measurement sensitivity is not significantly affected by temporal field fluctuations of order 10^-4.

2D and 3D numerical modeling of experimental magnetization cycles in disks and spheres

The use of FEM models to simulate the Bean critical state is used in two particular geometries: the disk and the sphere exposed to a uniform magnetic field. Two FEM approaches have been used, the Adaptive Resistivity Algorithm under the ANSYS framework, and the H-Formulation using the COMSOL software. In this work, the validity of these methods to solve two-dimensional and three-dimensional models is proven through the comparison to the existing theories. In order to reproduce the experimental magnetization cycles, the critical current density dependence on magnetic field has been derived from measurements in YBCO thin disk at 65 K and a Nb spherical samples at 6.0 K. While the YBCO disk critical state is well reproduced by our models, the Nb sample shows more complicated response which cannot be simulated just considering a critical state model.

Laboratory measurement of elastic anisotropy on spherical rock samples by longitudinal and transverse sounding under confining pressure

Knowledge of shear wave velocities in loaded rocks is important in describing elastic anisotropy. A new high-pressure measuring head was designed and constructed for longitudinal and traversal ultrasonic sounding of spherical rock samples in 132 independent directions under hydrostatic pressure up to 60MPa. The velocity is measured using a pair of P-wave sensors and two pairs of S-wave sensors (TV/RV and TH/RH) with perpendicular polarization. An isotropic glass sphere was used to calibrate the experimental setup. A fine-grained anisotropic quartzite sample was examined using the P- and S-wave ultrasonic sounding. Waveforms are recorded by pairs of TP/RP, TV/RV and TH/RH transducers in a range of confining pressure between 0.1 and 60MPa. The recorded data showed a shear wave splitting in three basic structural directions of the sample. The measurements proved to be useful in investigating oriented micro-cracks, lattice (LPO) and shape-preferred orientation (SPO) for the bulk elastic anisotropy of anisotropic rocks subjected to hydrostatic pressure.

Approaching Ultimate Intrinsic SNR in a Uniform Spherical Sample with Finite Arrays of Loop Coils.

We investigated to what degree and at what rate the ultimate intrinsic (UI) signal-to-noise ratio (SNR) may be approached using finite radiofrequency detector arrays. We used full-wave electromagnetic field simulations based on dyadic Green's functions to compare the SNR of arrays of loops surrounding a uniform sphere with the ultimate intrinsic SNR (UISNR), for increasing numbers of elements over a range of magnetic field strengths, voxel positions, sphere sizes, and acceleration factors. We evaluated the effect of coil conductor losses and the performance of a variety of distinct geometrical arrangements such as "helmet" and "open-pole" configurations in multiple imaging planes. Our results indicate that UISNR at the center is rapidly approached with encircling arrays and performance is substantially lower near the surface, where a quadrature detection configuration tailored to voxel position is optimal. Coil noise is negligible at high field, where sample noise dominates. Central SNR for practical array configurations such as the helmet is similar to that of close-packed arrangements. The observed trends can provide physical insights to improve coil design.