Spherical Degree Research Articles

Comparison of visual quality after EVO-ICL implantation and SMILE to select the appropriate surgical method for high myopia

BackgroundThis study sought to compare the visual quality between intraocular collamer lens (EVO-ICL) implantation and small-incision lenticule extraction (SMILE) and determine the appropriate surgical method to treat patients with high myopia (− 6.25 to − 10 D).MethodsA total of 48 eyes underwent EVO-ICL implantation and another 48 eyes underwent SMILE. The uncorrected distance visual acuity (UDVA), best-corrected distance visual acuity (BCVA) and equivalent spherical degree were compared across the SMILE (− 6.25 to − 10 D) and EVO-ICL (− 6.25 to − 10 D) implantation groups. Preoperative and postoperative visual quality parameters were compared between and within groups.ResultsThe OQAS II values (OV 100%) one week and one month after surgery and the modulation transfer function (MTF), OV 20% and OV 9% values one week after surgery in the SMILE group were lower than the respective preoperative values. The objective scatter index (OSI) value increased one week as well as one month after surgery compared with the preoperative values. The MTF cut-off value of the SMILE group was lower than that of the EVO-ICL implantation group three months after surgery.ConclusionsFor patients with high myopia, the postoperative visual quality of EVO- ICL implantation was slightly better than that of SMILE.

Structural characterization and mechanical properties of rotary melting furnace processed aluminium alloyed ductile irons

ABSTRACTThe microstructural characteristics and mechanical properties of rotary melting furnace processed aluminium alloyed ductile irons were investigated in this study. This was aimed at developing high performance – low material and processing cost ductile irons, suitable for the production of automobile components. Different compositions of the alloys were processed containing 1–4 wt.% aluminium. X-ray diffractometry, optical, scanning electron microscopy and mechanical properties measurements, were used to characterize the alloys. The results show that the ductile irons consists essentially, nodular and vermicular graphite-type distributed in a predominantly pearlite – ferrite matrix structures which attest to the viability of rotary furnace melt processing for ductile iron production. The nodule count were observed to increase with increase in Al wt.% but nodule sizes and degree of sphericity decreased with increase in Al wt.%. The mechanical properties of the ductile irons increased with increase in Al wt.%, except the ductility which decreased slightly with increase in Al wt.%.

Experimental Study of the Mixing and Segregation Behavior in Binary Particle Fluidized Bed with Wide Size Distributions

Abstract Detailed understanding the particle mixing and segregation dynamic is essential in successfully designing and reasonably operating multicomponent fluidized bed. In this work, a novel fluorescent tracer technique combining image processing method has been used to investigate the mixing and segregation behavior in a binary fluidized bed with wide size distributions. The particle number percentage in each layer for different gas velocities is obtained by an image processing method. Fluidization, mixing and segregation behavior has been discussed in terms of bed pressure drop, gas velocity and mixing index. Different types of binary particle systems, including the jetsam and the flotsam-rich system, are analyzed and compared. The mixing indexes at different minimum fluidization velocities are also analyzed and compared with other work. The results show that the theoretical minimum fluidization velocity calculated from the bed pressure drop cannot represent the whole fluidization for a wide size distribution binary particle system. The effect of a wide size distribution is an inflection point in the mixing index curve. There is also a dead region in the bottom of the bed that consists of particles with large size and a low degree of sphericity. The particles in the dead region are extraordinarily difficult to fluidize and should be considered in the design of fluidized beds in industrial applications.

Evaluation of the Bioavailability and Translocation of Selected Heavy Metals by Brassica juncea and Spinacea oleracea L for a South African Power Utility Coal Fly Ash.

This study evaluated the physicochemical and mineralogical properties, mobile chemical species bioavailability and translocation in Brassica juncea and Spinacea oleracea L. plants of a South African coal-fired power utility. Coal-fly-ash (CFA) disposal is associated with various environmental and health risks, including air, soil, surface, and groundwater pollution due to the leaching of toxic heavy metals; these ends up in food webs affecting human health, while repeated inhalation causes bronchitis, silicosis, hair loss, and lung cancer. The morphology and chemical and mineralogical composition of CFA were determined using Scanning Electron Microscopy (SEM), X-ray fluorescence (XRF), and X-ray diffraction, respectively. In pot-culture experiments, S. oleracea L. and B. juncea plants were grown in three sets of pots containing CFA (Set 1), soil (Set 2), and a mixture of CFA plus soil at a ratio of 1:1 (50% CFA: 50% soil, Set 3), while no plants were grown in Set 4 as a control for the leachate samples. SEM showed that the surface morphology of CFA has a lower degree of sphericity with the irregular agglomerations of many particles. XRF results revealed that CFA contains 43.65%, 22.68%, and 10.89% of SiO2, Al2O3, and Fe2O3, respectively, which indicates that CFA is an aluminosilicate material. X-ray diffraction (XRD) showed that CFA contains mullite as a major phase, followed by quartz mineral phases. Chemical species such as B, Ba, Mo, and Cr were occurring at higher concentrations in the leachates for most weeks in the pot-culture experiments, especially for CFA and soil + CFA growth media. However, there was a common trend for all growth media of chemical-species concentrations declining with time, which might have been caused by plant uptake or wash-off with water during irrigation; even for the growth media as well, where no plants were grown. Chemical species, such as Fe, Mn, B, Ba, and Zn, accumulated highly in most parts of the plant species. However, B. juncea showed higher potential to accumulate chemical species as compared to S. oleracea L. Bioconcentration and translocation factors (BF and TF) showed that B. juncea was the most effective in terms of bioconcentration and translocation of most of the chemical species. This indicates that B. juncea has potential in application for the phytoremediation of CFA dumps, and could contribute to the remediation of CFA dumps and the reduction of potential health and environmental impact associated with CFA.

The structure and properties of Inconel 718 superalloy powder prepared by vacuum induction melting gas atomization for laser direct metal deposition

Inconel 718 superalloy powder is one of the main materials for laser direct metal deposition aero parts, and the characteristics of alloy powder have an important impact on the microstructure and properties of the formed parts. In this paper, Inconel 718 superalloy powder for laser direct metal deposition was prepared by vacuum induction melting gas atomization. The results show that the degree of sphericity of the prepared alloy powder is 98% and the particle size distributed within the scope of 1–150 μm. The flowability is 15.2 s/50 g, the apparent density is 4.93 g cm−3, the rate of hollow sphere is 4%, the matrix phase of the alloy powder is γ phase and the strengthening phase consists of the main strengthening phase γ′, the auxiliary strengthening phase γ′ and a small amount of carbide MC. After laser forming, the microstructure is dense with few defects, the phase composition is consistent with the powder phase composition. The tensile strength of laser direct metal deposited samples is 822.3 MPa. The elongation is 12.8%, and the hardness is about 275 HV0.2. The Inconel 718 superalloy powder prepared by VIGA has good powder characteristics and meets the requirements of alloy powder characteristics required for laser direct metal deposition.

Ventricular mechanics in adolescent and adult patients with a Fontan circulation: Relation to geometry and wall stress.

Patients with single ventricle physiology and Fontan circulation are at increased risk for late complications and reduced survival. The aim of the study was to investigate the correlation between ventricular geometry and systolic regional function in different underlying anatomic conditions in adolescent and adult Fontan-palliated patients. In a retrospective cross-sectional study, we measured 2D strain, ventricular diameters, ventricular volumes, ejection fraction (EF), global and segmental wall stress, and sphericity index. The same analyses were performed in 99 age- and gender-matched healthy individuals. One hundred and one patients were included at a mean age of 21 (range 14-59) years. In comparison with healthy subjects, patients with Fontan circulation displayed larger ventricular volumes (153±78mL vs 116±38mL P<0.05), reduced EF (43%±15% vs 55%±8% P<0.05), reduced longitudinal (-13%±6% vs -21%±4% P<0.05) and circumferential strain values (-15%±7% vs -22%±4% P<0.05). Functionally single ventricles were more spherical (ratio of longitudinal to short-axis diameters 1.3±0.3 vs 1.7±0.2 P<0.05). Circumferential strain correlated well with global wall stress and the degree of sphericity (R2 =0.320), while segmental strain did not correlate with segmental wall stress. The percentage of segments with akinesia was relatively high (16±16% vs 0±0% P<0.05) indicating reduced segmental contractile function. Functionally single ventricles after Fontan palliation have significantly reduced systolic regional and global function with a high intersegmental inhomogeneity. The underlying pathological mechanisms might be multifactorial, including ventricular geometry, sphericity, and regional contractile properties. Future studies are needed to investigate the role of ventricular geometry for clinical performance and outcome.

Using a 2-shock 1D platform at NIF to measure the effect of convergence on mix and symmetry

We describe the use of a robust new 1-D like implosion platform at the National Ignition Facility [G. H. Miller et al., Opt. Eng. 43, 2841 (2004)] to study the effect of convergence on mix and shape. Previous experiments suggest that nuclear yields and ion temperature degrade with increased convergence [M. D. Cable et al., Phys. Rev. Lett. 73, 2316 (1994)] due to enhanced perturbation growth and mix, but little has been reported on the distortion of the shape with time. The 2-shock platform was developed [S. F. Khan et al., Phys. Plasmas 23, 042708 (2016)] to maintain a high degree of sphericity during the whole implosion phase and has a thick, uniformly doped (1% Si) plastic CH shell to minimize the effect of mixing due to hydrodynamic feed-through from the outer ablator surface. An inner layer of deuterated plastic (CD) and hydrogen-tritium (DT) gas fill allows for the measurement of DT neutrons produced by the mix between the gas and ablator. DD neutrons provide information about the hot, unmixed CD region. By changing the fill gas density while keeping the capsule diameter, ablator thickness, and Au hohlraum conditions fixed, the x-ray hot spot convergence ratio was varied from 14 to 22. We find that the atomic mix (DT yield) grows linearly as a function of convergence, but since Tion changes as well, it does not necessarily mean that the amount or extent of mix grows linearly as well. We also find the DD yield, which is a measurement of the shell heating, saturates above a certain convergence.

Magnetic and microwave properties of Fe18Ni82 nanoparticles with close to zero magnetostriction

Magnetic nanoparticles (MNPs) with nominal Fe18Ni82 composition were prepared by the electrophysical technique of the electrical explosion of wire. Although we were not able to experimentally estimate the magnetostriction coefficient for MNPs, this iron–nickel ratio is usually associated to close to zero magnetostriction. Different values of the overheating rate K between 0.9 and 2.0, where K is the ratio between the electrical energy ejected into the wire and the sublimation energy of Fe18Ni82 alloy, were used for the fabrication of the MNPs. Structural characterization (X-ray diffraction, scanning electron microscopy, low temperature nitrogen adsorption), magnetic and microwave measurements were used for the comparative analysis of the properties of MNPs. The increase of the overheating rate led to the increase of the specific surface value (Ssp) of the MNPs and the decrease of their average size. The fabricated MNPs were spherical in shape with a very high degree of sphericity and very weakly aggregated with the average weighted diameter in the range of 94–301 nm depending on the specific surface value for each batch. For 0.9 ≤ K ≤ 1.2 the MNPs were in the γ-phase, cubic (S.G: Fm-3 m) face-centered cubic lattice and very a small amount of material had a cubic Pm-3 m structure with lost symmetry. For 1.2 < K ≤ 2.0 they were single γ-phase, cubic (S.G: Fm-3 m) face cubic centered structure. Magnetic measurements and microwave absorption showed that the MNPs of all batches have high saturation magnetization and exhibit both microwave phenomena: significant zero field microwave absorption and resonant absorption in the vicinity of the ferromagnetic resonance field. Contrary to previous studies of FeNi MNPs with non-zero magnetostriction, the field for ferromagnetic resonance was very close to the one expected for MNPs with small contributions arising from magnetocrystalline anisotropy, strains and the deviations from sphericity. The magnetic and microwave characteristics in combination with a very high value of the single batch are promising for technological applications of these MNPs including the development of composites consisting of a polymer matrix filled with MNPs.

Optimization of processing parameters of cooling slope process for semi-solid casting of ADC 12 Al alloy

In the present work, the effect of processing parameters of cooling slope techniques (pouring temperature, slope angle and slope length) of ADC 12 Al alloy on its microstructural evolution has been studied in detail. A series of cooling slope casting experiments were conducted by varying the pouring temperature (580, 585 and 590 °C), slope length (400, 500 and 600 mm) and slope angle (30°, 45° and 60°). The effect of processing parameters on the response factors, viz. degree of sphericity and particle size, has been investigated by applying analysis of variance (ANOVA), interaction graphs obtained using response surface methodology. The obtained results infer that optimum values of the degree of sphericity (0.865) and particle size (49.30) are observed for the following set of processing parameters, namely 585 °C pouring temperature, 500 mm slope length and 45° slope angle. ANOVA results show that the pouring temperature is the most significant input variables that influence degree of sphericity and particle size followed by slope length and slope angle. The values of output variables obtained from confirmation experiment, performed at 95% confidence level, ensure that they are well within the permissible limits.

Simple Preparation of Spherical Activated Carbon with Mesoporous Structure from Phenolic Resol and Associated Catalytic Performance in Isobutane Dehydrogenation

This study provides a detailed report on the synthesis of spherical activated carbon with mesoporous structure using a soluble low molecular weight phenolic resol precursor through an ammonium alginate assisted sol–gel method. The effects of calcinating temperature and the addition of CaCO3 as a pore-enlarging agent on texture structure and catalytic performance in isobutane dehydrogenation to isobutene were investigated. Characterization of N2 sorption, mechanical strength tests, and optical photographs confirmed that the obtained carbon materials had high mechanical strength, a good degree of sphericity, and a large surface area. Introducing CaCO3 as a pore-enlarging agent during the preparation process promoted the formation of a mesoporous structure of carbon spheres and evidently increased the surface area and oxygen content, which can improve isobutane conversion and isobutene selectivity of these carbon spheres. The conversion of isobutane reached up to 28% for this spherical activated carbon, and the selectivity of isobutene reached up to 96%. Isobutane conversion increased with an increase in calcination temperature due to an increase in the oxygen content, whereas the selectivity of isobutene decreased due to the slight decrease in the specific surface area.

Effect of simplified and traditional Chinese character on accommodative microfluctuation in young adult myopes and emmetropes

Objective: This study investigates the effect of simplified and traditional Chinese character on accommodative microfluctuation in young adult myopes and emmetropes. Methods: Prospective cohort study. Based on refractive errors, Young adult candidates (18-28 years) were classified into two groups based on their spherical equivalent degrees: emmetropes (n=18), myopes (n=18). Four different reading targets (12pt size simplified and traditional Chinese characters, and 8pt size simplified and traditional Chinese characters) were displayed on computer screen collectively for 135s. The accommodative microfluctuation of the candidates were measured using the free space Grand-Seiko WAM-5500 autorefractor. Results: The results indicated that the type of character (simplified and traditional) had significant influence on accommodative microfluctuation. For myopic candidates, the accommodative microfluctuation for traditional Chinese character was greater than that for simplified Chinese character [traditional Chinese character: (0.35±0.17) D, vs. simplified Chinese character: (0.29±0.11) D, t=2.556, P=0.017], however as for emmetropic candidates, the difference between the accommodative microflucuation for the two types of characters was of no statistical significance [traditional Chinese character: (0.24±0.11) D, vs. simplified Chinese character: (0.24±0.12) D, t=0.004, P=0.996]. There was a difference between emmetropic and myopic candidates in terms of accommodative microfluctuation for traditional Chinese character, myopes had greater accommodative microfluctuation than emmetropes (t=3.140, P=0.02). However the difference between emmetropic and myopic candidates in terms of accommodative microfluctuation for simplified Chinese character was of no statistical significance (t=1.866, P=0.066). Conclusions: The results of the study indicated that myopes were more susceptible than emmetropic in accommodative microfluctuation when reading traditional Chinese character of high spatial frequency. (Chin J Ophthalmol, 2018, 54: 288-293).

Local order and crystallization of dense polydisperse hard spheres

Computer simulations give precious insight into the microscopic behavior of supercooled liquids and glasses, but their typical time scales are orders of magnitude shorter than the experimentally relevant ones. We recently closed this gap for a class of models of size polydisperse fluids, which we successfully equilibrate beyond laboratory time scales by means of the swap Monte Carlo algorithm. In this contribution, we study the interplay between compositional and geometric local orders in a model of polydisperse hard spheres equilibrated with this algorithm. Local compositional order has a weak state dependence, while local geometric order associated to icosahedral arrangements grows more markedly but only at very high density. We quantify the correlation lengths and the degree of sphericity associated to icosahedral structures and compare these results to those for the Wahnström Lennard-Jones mixture. Finally, we analyze the structure of very dense samples that partially crystallized following a pattern incompatible with conventional fractionation scenarios. The crystal structure has the symmetry of aluminum diboride and involves a subset of small and large particles with size ratio approximately equal to 0.5.

Three-Dimensional Physical and Optical Characteristics of Aerosols over Central China from Long-Term CALIPSO and HYSPLIT Data

Aerosols greatly influence global and regional atmospheric systems, and human life. However, a comprehensive understanding of the source regions and three-dimensional (3D) characteristics of aerosol transport over central China is yet to be achieved. Thus, we investigate the 3D macroscopic, optical, physical, and transport properties of the aerosols over central China based on the March 2007 to February 2016 data obtained from the Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission and the hybrid single-particle Lagrangian integrated trajectory (HYSPLIT) model. Our results showed that approximately 60% of the aerosols distributed over central China originated from local areas, whereas non-locally produced aerosols constituted approximately 40%. Anthropogenic aerosols constituted the majority of the aerosol pollutants (69%) that mainly distributed less than 2.0 km above mean sea level. Natural aerosols, which are mainly composed of dust, accounted for 31% of the total aerosols, and usually existed at an altitude higher than that of anthropogenic aerosols. Aerosol particles distributed in the near surface were smaller and more spherical than those distributed above 2.0 km. Aerosol optical depth (AOD) and the particulate depolarization ratio displayed decreasing trends, with a total decrease of 0.11 and 0.016 from March 2007 to February 2016, respectively. These phenomena indicate that during the study period, the extinction properties of aerosols decreased, and the degree of sphericity in aerosol particles increased. Moreover, the annual anthropogenic and natural AOD demonstrated decreasing trends, with a total decrease of 0.07 and 0.04, respectively. This study may benefit the evaluation of the effects of the 3D properties of aerosols on regional climates.

Experimental tumbling of Dreissena polymorpha: implications for recognizing durophagous predation in the fossil record

Shell damage left by predators constitutes an important source of information on predator–prey interactions. However, recognition of the origins of shell damage can often be controversial, and needs to be assessed cautiously. More specifically, differentiation between predation- and abiotic-induced shell damage remains challenging. Here, we show the results of tumbling experiments using a bivalve species Dreissena polymorpha in order to determine rates and patterns of shell damage induced by physical forces in high-energy conditions. It is demonstrated that, in contrast to durophagous fish and crab predation, abiotic-induced fragmentation and damage are typically characterized by the presence of distinct abrasive scratches and wear scars on the surface of shell fragments. Furthermore, fragmented shells typically reveal a wide size distribution, and a different degree of sphericity and roundness resulting from abrasion. Importantly, large shell fragments commonly display smooth edges. These data suggest that durophagous predation, which typically induces fragmentation into large and angular shell fragments bearing no wear scars, can be reliably recognized both in present-day environments and in the fossil record.

Biocompatible porous titanium scaffolds produced using a novel space holder technique.

We describe a new fabrication strategy for production of porous titanium scaffolds for skeletal implants which provides a promising new approach to repair and remodel damaged bone tissue. The new strategy involves powder sintering of titanium powder, employing pharmaceutical sugar pellets as temporary space holders, to facilitate production of porous scaffolds with structures optimized for mechanical performance and osseointegration of implants. The spherical sugar pellets, with controlled size fractions and excellent biocompatibility, are easily removed by dissolution prior to sintering providing an ideal space holder material for controlled synthesis of titanium scaffolds with desired porosities and pore sizes. The scaffolds contain pores with high degrees of sphericity and interconnectivity which impart excellent mechanical properties and superior biocompatibility to the structures. Scaffolds with 40% porosity and a pore size range of 300-425 µm exhibited an effective Young's modulus of 16.4 ± 3.5 GPa and strength of 176 ± 6 MPa, which closely mimics the properties of human bone, and were also able to support cell adhesion, viability and spreading in cell culture tests. Porous titanium scaffolds manufactured by this approach have excellent potential for hard tissue engineering applications. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2796-2806, 2018.

One‐step synthesis of oxidation‐resistant Cu@Ag core–shell nanoparticles

One-step synthesis of wet chemical method is proposed for the preparation of core–shell nanostructures of copper and silver. This facile and environment friendly fabrication simplifies the surface treatment of copper particles to avoid copper core to be oxidised before coating silver. The thermal stability against oxidation and electrical properties of Cu@Ag core–shell nanoparticles are investigated. The results show that Cu@Ag core–shell nanoparticles possess high spherical degree, and the silver is evenly coated on the surface of copper nanoparticles. The synthesised spherical Cu@Ag core–shell nanoparticles exhibit excellent thermal stability at the high temperature of 300°C. After annealing at 200°C for 30 min, the sheet resistance of the spherical Cu@Ag core–shell nanoparticles (Ag content 7.68 wt%) is extremely low (69.82 μΩ cm).

Effect of particle shape on the apparent viscosity of liquid–solid suspensions

The viscosities of liquid–solid suspensions were experimentally determined for castor oil-paraffin and acrylonitrile butadiene styrene (ABS) plastic particle systems at room temperature and for a FeC melt at various temperatures. The degree of sphericity of the particles was introduced as a parameter for characterizing the effect of the particle shape on the apparent viscosity of liquid–solid systems. The results indicated that with an increase in the degree of sphericity of the particles, the apparent viscosity decreased. However, the presented well-known prediction models, such as Krieger-Dougherty's model and Batchelor's model only consider the effect of the particle fraction on the apparent viscosity of liquid–solid suspensions, whereas the effect of the particle shape is neglected. Based on the experimental data, the particle shape was introduced to modify Krieger-Dougherty's and Batchelor's models. The apparent viscosity can be successfully predicted using the modified model.

Behaviors of Oxide Film during Semisolid Brazing of SiCp/6063Al Composite Materials

The semisolid brazing of SiCp/6063Al under an applied pressure using Zn‐Al‐Cu filler metal was investigated. The samples to be joined were heated from 380°C to 382°C, 386°C, 392°C, and 410°C under a constant pressure of 10 MPa, respectively. Effects of the temperature on microstructural evolution and deformation behavior of the filler metal, interfacial structure, and shear strength of the bonded joint were discussed, and the disruption behavior of the surface oxide film was studied. The results show that, after heating, the solid grains of the filler metal transform into a globular structure surrounded by liquid. The degree of sphericity and the liquid fraction tend to improve with increasing temperature. During the heating process, the deformation of the filler metal is first accomplished by plastic deformation of solid grains and then by intergrain sliding and liquid flow. The surface oxides are broken and stripped by a cocontribution of compressive and shear stress which is caused by depressing and sliding of solid grains along the composites. It is found that the heating of 380°C to 392°C under pressure is the optimum condition to disrupt the surface oxide films and obtain sound bonds. The mechanical test results show that the maximum shear strength of the bond joints is as high as 105 MPa, reaching 78% that of the parent materials.

Doping effects of cerium ion on structure and electrochemical properties of polyaniline

AbstractPolyaniline (PANI)/Ce3+ and PANI/Ce4+ composites were successfully prepared by in situ polymerization in an aqueous solution of poly(2‐acrylamido‐2‐methylpropane sulfonic acid) and characterized by Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, X‐ray photoelectron spectroscopy, SEM, TEM and electrochemical methods. The results showed that the PANI/Ce ion composites had a high degree of sphericity, high electrical conductivity and good electrochemical performance. The conductivity of PANI/Ce(NO3)3 reaches a maximum of 46.76 S cm−1 at 20 wt% of Ce(NO3)3. It is increased by 377% by comparison with that of pure PANI. In particular, the polarization results showed that the corrosion current density (0.47 µA cm−2) and the inhibition efficiency (97%) of PANI/Ce(NO3)3 were better than the results for PANI and PANI/Ce(SO4)2 composite. This suggested that the PANI/Ce(NO3)3 composite has promising applications in conductive materials, anticorrosion coatings and other related fields. © 2017 Society of Chemical Industry

Oceanic Residual Topography Agrees With Mantle Flow Predictions at Long Wavelengths

AbstractDynamic topography, the surface deflection induced by sublithosheric mantle flow, is an important prediction made by geodynamic models, but there is an apparent disparity between geodynamic model predictions and estimates of residual topography (total topography minus lithospheric and crustal contributions). We generate synthetic global topography fields with different power spectral slopes and spatial patterns to investigate how well the long‐wavelength (spherical degrees 1 to 3) components can be recovered from a discrete set of samples where residual topography has been recently estimated. An analysis of synthetic topography, along with observed geoid and gravity anomalies, demonstrates the reliability of signal recovery. Appropriate damping factors, which depend on the maximum degree in the spherical harmonic expansion that is used to fit the samples, must be applied to recover the long‐wavelength topography correctly; large damping factors smooth the model excessively and suppress residual topography amplitude and power spectra unrealistically. Recovered long‐wavelength residual topographies based on recent oceanic point‐wise estimates with different spherical expansion degrees agree with each other and with the predicted dynamic topography from mantle flow models. The peak amplitude of the long‐wavelength residual topography from oceanic observations is about 1 km, suggesting an important influence of large‐scale deep mantle flow.