Spherical Degree Research Articles

Seismic comparison of the 11‐ and 2‐year cycle signatures in the Sun

AbstractThe solar magnetic activity consists of two periodic components: the main cycle with a period of 11 yr and a shorter cycle with a period of ≈2 yr. The origin of this second periodicity is still not well understood. We use almost 15 years of long high‐quality resolved data provided by the Global Oscillation Network Group (GONG) to investigate the solar cycle changes in p‐mode oscillations with spherical degree Ł = 0–120 and in the range of 1600 µHz ≤ ν ≤ 3500 µHz. For both periodic components of solar magnetic activity our findings locate the origin of the frequency shift in the subsurface layers with a sudden enhancement in the amplitude of the shift in the last few hundred kilometers. We also show that the size of the shift increases towards equatorial latitudes and from minimum to maximum of solar activity. On the other hand, the signatures of the 2‐yr cycle differ from the one of the 11‐yr cycle in the magnitude of the shift, as the 2‐yr cycle causes a weaker shift in mode frequencies and a slower enhancement in the last few hundred kilometers. Based on these findings we speculate that a possible physical mechanism behind the quasi biennial periodicity (QBP) could be the beating between different dynamo modes (dipole and quadrupole mode) (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Effect of mixed solvent on fabrication, morphology and monodispersity of microspheres with hydrophobic poly(butyl methacrylate) shells

Monodisperse microspheres (mean diameter 200–300 nm) with polystyrene cores and poly(acrylamide-co-butyl methacrylate) shells were prepared by using a free radical polymerization method. Moreover, the effect of mixed solvent on the preparation, morphology and monodispersity was investigated. The experimental results showed that solubility parameter of butyl methacrylate and solvent affected mainly the molding of monodisperse core-shell microspheres. When the microspheres were fabricated in a sequential synthesis process, addition of hydrophilic and organic solvent including butyl methacrylate led to spherical degree of the particles becoming worse, and the mean diameter of the microspheres decreased and the monodispersity became better with increasing the crosslinker methylenebisacrylamide dosage.

The Calculation of Circularity for Floating Beads Based on Image Processing Method of Powder Particles

Particle morphology which affects the packed state of particles is a factor that cannot be ignored in the study of gradation model. Floating beads, as the most commonly lightweight additive used in cement slurry, are always regarded as ideal spherical particles, thus the effects of its circular degree on close packing are overlooked. In order to quantitatively characterize the circularity of floating beads , based on image processing methods of powder particles, combined with image processing software(Photoshop and MATLAB), replaced the watershed segmentation method with removing linking particles, the calculating method of the circularity of powder particles was put forward, and finally the average circularity of floating beads was obtained (about 0.929＜1). Although floating beads have high spherical degree, they still aren’t ideal spherical particles, so their morphology feature should not be ignored in the study of particle size distribution.

Mechanical Properties and Tensile Fracture Mechanism of Rheocast A356 Al Alloy Using Cooling Slope

A356 aluminium alloy has a wide applicability in the manufacturing of automotive parts. Cooling slope (CS) rheocasting process has been used in the present work to produce A356 billets having near spherical morphology of primary Al phase. Absence of dendritic primary phase, observed in case conventionally cast A356 alloy, and finer distribution of secondary eutectic Si phase within the matrix establishes the usefulness of the CS casting route. Near spherical primary phase in the rheocast alloy ensures better strength, elongation properties and structural integrity in the produced billets. The liquid melt is allowed to flow through the cooling slope after pouring at 6500C. Rapid heat exchange between the flowing melt and slope wall and the atmosphere facilitates heterogeneous nucleation of α-Al phase on the cooling slope wall. Shear driven flow of the solidifying melt is found responsible for separation of α-Al phase from the slope wall and generation of nearly spherical morphology of the primary phase in the microstructure. Grain refiner addition in the melt leads to enhance the primary α-Al percentage in the microstructure and also aids to the improvement of degree of sphericity and reduction of spheroid size. So, grain refining helps to improve the strength, elongation and fracture properties of rheocast billets further.

Start-up of the anammox process from the conventional activated sludge in a hybrid bioreactor

The anaerobic ammonium oxidation (anammox) process was successfully started up from conventional activated sludge using a hybrid bioreactor within 2 months. The average removal efficiencies of ammonia and nitrite were both over 80%, and the maximum total nitrogen removal rate of 1.85 kg N/(m3·day) was obtained on day 362 with the initial sludge concentration of 0.7 g mixed liquor suspended solids (MLSS)/L. Scanning electron microscope (SEM) observation of the granular sludge in the hybrid reactor clearly showed a high degree of compactness and cell sphericity, and the cell size was quite uniform. Transmission electron microscope photos showed that cells were round or oval, the cellular diameter was 0.6-1.0 μm, and the percentage of the anammoxosome compartment was 51%–85% of the whole cell volume. Fluorescence in situ hybridization analysis (FISH) indicated that anammox bacteria became the dominant population in the community (accounting for more than 51% of total bacteria on day 250). Seven planctomycete 16S rRNA gene sequences were present in the 16S rRNA gene clone library generated from the biomass and affiliated to Candidatus Kuenenia stuttgartiensis and Candidatus Brocadia sp., a new anammox species. In addition, the average effluent suspended solid (MLSS) concentrations of outlets I (above the non-woven carrier) and II (below the non-woven carrier) were 0.0009 and 0.0035 g/L, respectively. This showed that the non-woven carrier could catch the biomass effectively, which increased biomass and improved the nitrogen removal rate in the reactor.

Preparation of ultrafine spherical AlOOH and Al2O3 powders by aqueous precipitation method with mixed surfactants

Abstract Ultrafine spherical boehmite (AlOOH) particles were prepared from aluminum sulfate and aluminum chloride solution with urea as precipitant at 90 °C. It was observed that mixed surfactants tween80 - sodium stearate could improve dispersion of AlOOH particles. While the concentrations of tween80 and sodium stearate were 0.75 wt.% and 0.14 wt.% respectively, particles with spherical degree of 1.1 and size of 0.36 μm could be achieved. The thermogravimetric (TG) and Fourier transform infrared spectroscopy (FTIR) showed that sodium stearate molecules were bonded upon the surface of particles forming a coating layer to prevent agglomeration. Addition of NaCl could further improve dispersion of particles, spherical AlOOH particles with average size of 0.38 μm and nanosized spherical particles could be obtained when the concentration of NaCl was 0.05 M and 0.1 M. At the same time, Al 2 O 3 powders obtained from precursor with NaCl showed much better sintering behavior.

EMPIRICAL DETERMINATION OF CONVECTION PARAMETERS IN WHITE DWARFS. I. WHOLE EARTH TELESCOPE OBSERVATIONS OF EC14012-1446

We report on analysis of 308.3 hrs of high speed photometry targeting the pulsating DA white dwarf EC14012-1446. The data were acquired with the Whole Earth Telescope (WET) during the 2008 international observing run XCOV26. The Fourier transform of the light curve contains 19 independent frequencies and numerous combination frequencies. The dominant peaks are 1633.907, 1887.404, and 2504.897 microHz. Our analysis of the combination amplitudes reveals that the parent frequencies are consistent with modes of spherical degree l=1. The combination amplitudes also provide m identifications for the largest amplitude parent frequencies. Our seismology analysis, which includes 2004--2007 archival data, confirms these identifications, provides constraints on additional frequencies, and finds an average period spacing of 41 s. Building on this foundation, we present nonlinear fits to high signal-to-noise light curves from the SOAR 4.1m, McDonald 2.1m, and KPNO 2m telescopes. The fits indicate a time-averaged convective response timescale of 99.4 +/- 17 s, a temperature exponent 85 +/- 6.2 and an inclination angle of 32.9 +/- 3.2 degrees. We present our current empirical map of the convective response timescale across the DA instability strip.

Preparation and Properties of PB-1/PP Blends

Crystallization behavior, dynamic mechanical properties, mechanical properties and rheological properties of isotactic polybutene-1/polypropylene (PB-1/PP) blends prepared by melt-blending the two components through Brabender extruder were mainly studied via POM, DSC, DMA, capillary rheometer and so on, respectively. The results indicated that after adding PP in PB-1: size of the spherical crystal and degree of crystallization of PB-1 in the blends decreased, its melt temperature and crystallization temperature unchanged; tensile property of the blends was decreased, but impact and flexural properties were improved; change of the melt viscosity of the blends with the shear rate was more sensitive than pure PB-1.

Control of size dispersity of chitosan biopolymer microparticles and nanoparticles to influence vaccine trafficking and cell uptake

Structurally related surfactant molecules were exploited to generate chitosan emulsions to provide systematic variation in micelle radii of curvature and size. These compositions provide precise control of chitosan particle dispersity, that is, size distribution according to three quantitative distribution parameters as well as shape distribution. This resulted in a suite of particle size distributions spanning 71 nm to 3.7 μm and a very high degree of particle sphericity, allowing the influence of particle size to be isolated in two in vivo studies relating biopolymer particle size to cellular uptake and trafficking to lymph nodes. Flow cytometry and fluorescence microscopy indicated that the three cell lines examined preferentially internalized chitosan microparticles to a greater extent than nanoparticles over a 24 h period. In an in vivo mouse model, nanoparticles initially trafficked rapidly to lymph nodes draining the site of inoculation followed by further slower uptake. Microparticles trafficked to the lymph nodes with a similar pattern except that the initial discharge was ∼50-fold less than that observed with nanoparticles indicating a profound difference in the physiological transport properties of the two particle types.

The quasi-biennial periodicity (QBP) in velocity and intensity helioseismic observations

We looked for signatures of Quasi-Biennial Periodicity (QBP) over different phases of solar cycle by means of acoustic modes of oscillation. Low-degree p-mode frequencies are shown to be sensitive to changes in magnetic activity due to the global dynamo. Recently have been reported evidences in favor of two-year variations in p-mode frequencies. Long high-quality helioseismic data are provided by BiSON (Birmingham Solar Oscillation Network), GONG (Global Oscillation Network Group), GOLF (Global Oscillation at Low Frequency) and VIRGO (Variability of Solar IRradiance and Gravity Oscillation) instruments. We determined the solar cycle changes in p-mode frequencies for spherical degree l=0, 1, 2 with their azimuthal components in the frequency range 2.5 mHz < nu < 3.5 mHz. We found signatures of QBP at all levels of solar activity in the modes more sensitive to higher latitudes. The signal strength increases with latitude and the equatorial component seems also to be modulated by the 11-year envelope. The persistent nature of the seismic QBP is not observed in the surface activity indices, where mid-term variations are found only time to time and mainly over periods of high activity. This feature together with the latitudinal dependence provides more evidences in favor of a mechanism almost independent and different from the one that brings up to the surface the active regions. Therefore, these findings can be used to provide more constraints on dynamo models that consider a further cyclic component on top of the 11-year cycle.

Singularity Free Revolute–Prismatic–Revolute and Spherical–Prismatic–Spherical Chains for Actuating Planar and Spherical Single Degree of Freedom Mechanisms

Given a single degree of freedom mechanism, a moving reference frame attached to any link has a motion that can be described with a single parameter. A point relative to this moving frame is sought such that it either continually increases or decreases in distance from a point in the fixed frame over the entire motion. These points can be used to define a revolute–prismatic–revolute (RPR) chain for a planar mechanism or a spherical–prismatic–spherical (SPS) chain for a spherical mechanism capable of actuating the device over its entire range of motion. Moreover, the singularities relative to the joints in the original mechanism are not a concern and the dimensional synthesis can focus on creating the set of circuit-defect free solutions. From this analysis, a unique fixed point is determined in the planar case relative to two positions and their velocities with the following characteristic. All points in the moving reference frame that are moving away from it in the first position are approaching it in the second position, and vice versa. This point is as critical to the identification of singularity-free driving chains as the centrodes or the poles.

A novel method to synthesize homogeneous and mono-dispersible CeO2 nanospheres: two-step hydrothermal process

In this study, homogeneous mono-disperse CeO2 nanosphere was successfully synthesized through two-step hydrothermal process, and the degree of sphericity was also improved comparing with the sample synthesized through one-step hydrothermal process. In the whole reaction, crystallization and ripening were regarded as two independent stages. Upper-layer transparent solution obtained through centrifugation after first-step hydrothermal process contained a large number of CeO2 crystal seeds, indicating that crystallization has taken place in this stage. Then, these seeds participated in the second hydrothermal process and ripened into homogeneous spheres finally. In addition, poly(vinylpyrrolidone) was applied as surfactant to facilitate the oriented aggregation of small CeO2 nanoparticles into nanospheres. The formation mechanism was discussed through scanning electron microscopy and transmission electron microscopy.

CONSTRAINING THE PROPERTIES OF DELTA SCUTI STARS USING SPECTROSCOPIC ECLIPSING BINARY SYSTEMS

Many stars exhibit stellar pulsations, favoring them for asteroseismic analyses. Interpreting the oscillations requires some knowledge of the oscillation mode geometry (spherical degree, radial and azimuthal orders). The delta Scuti stars (1.5 - 2.5 M_sol) often show just one or few pulsation frequencies. Although this may promise a successful seismological analysis, we may not know enough about either the mode or the star to use the oscillation frequency to improve the determination of the stellar model, or probe the star's structure. For the observed frequencies to be used successfully as seismic probes of these objects, we need to concentrate on stars for which we can reduce the number of free parameters in the problem, such as binary systems or open clusters. We investigate how much our understanding of a delta Scuti star is improved when it is in a detached eclipsing binary system instead of being a single field star. We use singular value decomposition to explore the precision we expect in stellar parameters (mass, age and chemical composition) for both cases. We examine how the parameter uncertainties propagate to the luminosity - effective temperature diagram and determine when the effort of obtaining a new measurement is justified. We show that for the single star, a correct identification of the oscillation mode is necessary to produce strong constraints on the stellar model properties, while for the binary system the observations without the pulsation mode provide the same or better constraints on the stellar parameters. In the latter case, ...

Diallel analysis of cowpea (Vigna unguiculata (L.) Walp.) for some physical properties of seed under the Sudano-guinean conditions

The present study was undertaken at Dang (soudano-guinean zone of Cameroon) to determine the variability of 100-seed weight, geometric surface, porosity and sphericity of the seeds of 10 cowpea (Vigna unguiculata) genotypes and investigate the genetic basis of these characters through a 5x5 half-diallel cross mating. Knowledge of the physical properties of the seed of cowpea was necessary for the design of equipment for transporting, sorting, cleaning, separating, smashing and processing it into different foods. The experimental design was a randomized complete block with three replicates. Analysis of results showed that these genotypes presented a significant variability for the four physical properties. The average properties of seed were found to be a hundred seed mass of 20.46g, a surface area of 0.84 cm, a sphericity of 35.50% and a porosity of 0.65. Genetic analysis demonstrated that the parents differed for their general combining ability (GCA) and the crosses showed specific combining ability (SCA). These physical parameters were highly heritable with broad-sense heritability (h) values ranged from 0.76 to 0.96 suggesting that genetic advance was expected. Both dominant and additive gene effects were significant for all traits with a predominance of additive genes for seed mass and dominant genes for degree of sphericity. The alleles for seed weight, degree of porosity and sphericity were mostly recessive whereas the higher performances for seed surface where due to the presence of dominant alleles. Heterosis in F1 over best parent was recorded for some combinations. For these traits, recurrent selection might be a useful breeding strategy.

SOLAR-LIKE OSCILLATIONS AND ACTIVITY IN PROCYON: A COMPARISON OF THE 2007MOSTAND GROUND-BASED RADIAL VELOCITY CAMPAIGNS

We compare the simultaneous 2007 space-based MOST photometry and ground-based radial velocity observations of the F5 star Procyon. We identify slow variations in the MOST data that are similar to those reported in the radial velocity (RV) time series, and confirm by comparison with the Sun that these variations are likely the signature of stellar activity. The MOST power spectrum yields clear evidence for individual oscillation frequencies that match those found in the radial velocity data by Bedding et al. (2010). We identify the same ridges due to modes of different spherical degree in both datasets, but are not able to confirm a definite ridge identification using the MOST data. We measure the luminosity amplitude per radial mode A_{l=0, phot} = 9.1 +/- 0.5 ppm. Combined with the estimate for the RV data by Arentoft et al. (2008) this gives a mean amplitude ratio of A_{l=0, phot}/A_{l=0, RV} = 0.24 +/- 0.02 ppm cm^{-1} s, considerably higher than expected from scaling relations but in reasonable agreement with theoretical models by Houdek (2010). We also compare the amplitude ratio as a function of frequency, and find that the maximum of the oscillation envelope is shifted to higher frequencies in photometry than in velocity.

How Spherical Are the Archimedean Solids and Their Duals?

SummaryThe Isoperimetric Quotient, or IQ, introduced by G. Polya, characterizes the degree of sphericity of a convex solid. This paper obtains closed form expressions for the surface area and volume of any Archimedean polyhedron in terms of the integers specifying the type and number of regular polygons occurring around each vertex. Similar results are obtained for the Catalan solids, which are the duals of the Archimedeans. These results are used to compute the IQs of the Archimedean and Catalan solids and it is found that nine of them have greater sphericity than the truncated icosahedron, the solid which serves as the geometric framework for a molecule of C-60, or “Buckyball.”

Polymerization of Electric Field-Centered Double Emulsion Droplets to Create Polyacrylate Shells

Porous and hollow particles are widely used in pharmaceuticals, as solid phases for chromatography, as catalyst supports, in bioanalytical assays and medical diagnostics, and in many other applications. By controlling size, shape, and chemistry, it is possible to tune the physical and chemical properties of the particles. In some applications of millimeter-scale hollow shells, such as in high energy density physics, controlling the shell thickness uniformity (concentricity) and roundness (sphericity) becomes particularly important. In this work, we demonstrate the feasibility of using electric field-driven droplet centering to form highly spherical and concentric polymerizable double emulsion (DE) droplets that can be subsequently photopolymerized into polymer shells. Specifically, when placed under the influence of an ∼6 × 10(4) V(rms)/m field at 20 MHz, DE droplets, consisting of silicone oil as the inner droplet and tripropylene glycol diacrylate with a photoinitiator in N,N-dimethylacetamide as the outer droplet, suspended in ambient silicone oil, were found to undergo electric field-driven centering into droplets with ≥98% sphericity and ∼98% concentricity. The centered DE droplets were photopolymerized in the presence of the electric field. The high degrees of sphericity and concentricity were maintained in the polymerized particles. The poly(propylene glycol diacrylate) capsules are just within the sphericity requirements needed for inertial confinement fusion experiments. They were slightly outside the concentricity requirement. These results suggest that electric field-driven centering and polymerization of double emulsions could be very useful for synthesizing hollow polymer particles for applications in high energy density physics experiments and other applications of concentric polymer shells.

Asteroseismology of red giants from the first four months ofKeplerdata: Fundamental stellar parameters

Clear power excess in a frequency range typical for solar-type oscillations in red giants has been detected in more than 1000 stars, which have been observed during the first 138 days of the science operation of the NASA Kepler satellite. This sample includes stars in a wide mass and radius range with spectral types G and K, extending in luminosity from the bottom of the giant branch up to high-luminous red giants. The high-precision asteroseismic observations with Kepler provide a perfect source for testing stellar structure and evolutionary models, as well as investigating the stellar population in our Galaxy. We fit a global model to the observed frequency spectra, which allows us to accurately estimate the granulation background signal and the global oscillation parameters, such as the frequency of maximum oscillation power. We find regular patterns of radial and non-radial oscillation modes and use a new technique to automatically identify the mode degree and the characteristic frequency separations between consecutive modes of the same spherical degree. In most cases, we can also measure the small separation. The seismic parameters are used to estimate stellar masses and radii and to place the stars in an H-R diagram by using an extensive grid of stellar models that covers a wide parameter range. Using Bayesian techniques throughout our analysis allows us to determine reliable uncertainties for all parameters. We provide accurate seismic parameters and their uncertainties for a large sample of red giants and determine their asteroseismic fundamental parameters. We investigate the influence of the stars' metallicities on their positions in the H-R diagram. We study the red-giant populations in the red clump and bump and compare them to a synthetic population and find a mass and metallicity gradient in the red clump and clear evidence of a secondary-clump population.

Second operation after laser in situ keratomileusis

To compare clinical results between the laser in situ keratomileusis (LASIK) surgery and the laser subepithelial keratomileusis (LASEK) surgery as the second operation after an unsuccessful LASIK surgery. Thirty one patients (62 eyes) with refractive regression or under-correction after LASIK operation received the second surgery. Thirty eyes received LASIK surgery (group A) and 32 eyes received LASEK surgery (group B). The follow-up period was one year. The main parameters included visual acuity, refraction, corneal curvature, and the total value of high-aberration. The difference in visual acuity in one week postoperation between both group was statistically significant (t = 5.21, P < 0.01), the acuity of LASEK group (0.57 ± 0.11) was obviously lower LASIK group (0.79 ± 0.21). There is no difference in acuity between both group in 1 month and 1 year postop. The difference in uncorrected visual acuity, average spherical equivalent refractive degree, average corneal curvature, and the total value of high-aberration between both group 1 year after operation was statistically not significant. Uncorrected visual acuity (A group 0.84 ± 0.15, B group 0.82 ± 0.11, t = 0.60), average spherical equivalent refractive degree (A group -0.34 ± 1.15, B group -0.32 ± 1.13, t = -0.07), average corneal curvature (A group 37.87 ± 1.95, B group 38.47 ± 2.15, t = -1.15), the total value of high-aberration (A group 0.45 ± 0.11, B group 0.48 ± 0.13, t = -0.98). One patient developed epithelium ingrowth after LASIK surgery. One patient suffered from 2+ haze after LASEK surgery. Both LASIK and LASEK surgery can obtain satisfactory therapeutic results after an unsuccessful LASIK surgery.

Identification of vegetable leaf-eating pests based on image analysis

To achieve the computer recognition of vegetable leaf-eating pests and the scientific evaluation of pest level's,the paper proposed a reverse identification method through the eaten leaves to determine the pests.After image pre-processing of the eaten leaves by pests,seven spherical shape feature values of eaten leaves could be automatically extracted: roundness degree,complexity degree,and spherical degree,etc.,and then the BP neural network model for recognition could be built up.The results show that the method is good at recognizing the pest species by the geometric feature of eaten leaves by pests,and give a scientific evaluation for the leaf's harm degree.