Homogeneous Density Research Articles

Design and construction of a Maxwell-type induction coil for magnetic nanoparticle hyperthermia

Purpose We describe a modified Helmholtz induction coil, or Maxwell coil, that generates alternating magnetic fields (AMF) having field uniformity (≤10%) within a = 3000 cm3 volume of interest for magnetic hyperthermia research. Materials and methods Two-dimensional finite element analysis (2D-FEA) was used for electromagnetic design of the induction coil set and to develop specifications for the required matching network. The matching network and induction coil set were fabricated using best available practices and connected to a 120 kW industrial induction heating power supply. System performance was evaluated by magnetic field mapping with a magnetic field probe, and tests were performed using gel phantoms. Results Tests verified that the system generated a target peak AMF amplitude along the coil axis of ∼35 kA/m (peak) at a frequency of 150 ± 10 kHz while maintaining field uniformity to >90% of peak for a volume of ∼3000 cm3. Conclusions The induction coil apparatus comprising three independent loops, i.e., Maxwell-type improves upon the performance of simple solenoid and Helmholtz coils by providing homogeneous flux density fields within a large volume while minimizing demands on power and stray fields. Experiments with gel phantoms and analytical calculations show that future translational research efforts should be devoted to developing strategies to reduce the impact of nonspecific tissue heating from eddy currents; and, that an inductor producing a homogeneous field has significant clinical potential for deep-tissue magnetic fluid hyperthermia.

Local degradation effects in automotive size membrane electrode assemblies under realistic operating conditions

In automotive applications, the operational parameters for fuel cell (FC) systems can vary over a wide range. To analyze their impact on fuel cell degradation, an automotive size single cell was operated under realistic working conditions. The parameter sets were extracted from the FC system modeling based on on-road customer data. The parameter variation included simultaneous variation of the FC load, gas pressures, cell temperature, stoichiometries and relative humidity. Current density distributions and the overall cell voltage were recorded in real time during the tests. The current densities were low at the geometric anode gas outlet and high at the anode gas inlet. After electrochemical tests, post mortem analysis was conducted on the membrane electrode assemblies using scanning electron microscopy. The ex-situ analysis showed significant cathode carbon corrosion in areas associated with low current densities. This suggests that fuel starvation close to the anode outlet is the origin of the cathode electrode degradation. The results of the numerical simulations reveal high relative humidity at that region and, therefore, water flooding is assumed to cause local anode fuel starvation. Even though the hydrogen oxidation reaction has low kinetic overpotentials, “local availability” of H2 plays a significant role in maintaining a homogeneous current density distribution and thereby in local degradation of the cathode catalyst layer. The described phenomena occurred while the overall cell voltage remained above 0.3 V. This indicates that only voltage monitoring of fuel cell systems does not contain straightforward information about this type of degradation.

“Osteopoikilosis–Benign Osteosclerotic Dysplasia”―A Case Report

Osteopoikilosis is a rare autosomal dominant or sporadic osteosclerotic dysplasias characterised by homogenous, small, multiple, discrete, symmetric round or ovoid radio densities in cancellous bones. Recognition of this asympomatic condition by plain radiograph makes other expensive investigations unnecessary. Here we present a case report of 28 yrs-old male incidentally found to have osteopoikilosis.

Rigorous Calibration of UAV-Based LiDAR Systems with Refinement of the Boresight Angles Using a Point-to-Plane Approach.

Advances in micro-electro-mechanical navigation systems and lightweight LIDAR (light detection and ranging) sensors onboard unmanned aerial vehicles (UAVs) provide the feasibility of deriving point clouds with very high and homogeneous point density. However, the deformations caused by numerous sources of errors should be carefully treated. This work presents a rigorous calibration of UAV-based LiDAR systems with refinement of the boresight angles using a point-to-plane approach. Our method is divided into a calibration and a parameter mounting refinement part. It starts with the estimation of the calibration parameters and then refines the boresight angles. The novel contribution of the paper is two-fold. First, we estimate the calibration parameters conditioning the centroid of a plane segmented to lie on its corresponding segmented plane without an additional surveying campaign. Second, we refine the boresight angles using a new point-to-plane model. The proposed method is evaluated by analyzing the accuracy assessment of the adjusted point cloud to point/planar features before and after the proposed method. Compared with the state-of-the-art method, our proposed method achieves better positional accuracy.

Wetting of single crystalline and amorphous silicon surfaces: effective range of intermolecular forces for wetting

ABSTRACTWetting at nanoscale is a property of a three-dimensional region with a finite length into the solid domain from the surface. Understanding the extent of the solid region effective on wetting is important for recent coating applications as well as for both crystalline and amorphous solids of different atomic ordering. For such a case, we studied the wetting behaviour of silicon surfaces at various crystalline and amorphous states. Molecular distributions of amorphous systems were varied by changing the amorphisation conditions of silicon. Semi-cylindrical water droplets were formed on the surfaces to be large enough to remain independent of line tension and Tolman length effects. Contact angles showed up to 38% variation by the change in the atomic orientation of silicon. Instead of a homogeneous solid density definition, we calculated different solid densities for a given surface measured inside different extents from the interface. We correlated the observed wetting variation with each of these different solid densities to determine which extent governs the wetting variation. We observed that the variation of solid density measured inside a 0.13 nm extent from the surface reflected the variation of wetting angle better for both single crystalline and amorphous silicon surfaces.

Reliability of charge carrier recombination data determined with charge extraction methods

Charge extraction methods are popular for measuring the charge carrier density in thin film organic solar cells and to draw conclusions about the order and coefficient of nongeminate charge recombination. However, results from such studies may be falsified by inhomogeneous steady state carrier profiles or surface recombination. Here, we present a detailed drift-diffusion study of two charge extraction methods, bias-assisted charge extraction (BACE) and time-delayed collection field (TDCF). Simulations are performed over a wide range of the relevant parameters. Our simulations reveal that both charge extraction methods provide reliable information about the recombination order and coefficient if the measurements are performed under appropriate conditions. However, results from BACE measurements may be easily affected by surface recombination, in particular for small active layer thicknesses and low illumination densities. TDCF, on the other hand, is more robust against surface recombination due to its transient nature but also because it allows for a homogeneous high carrier density to be inserted into the active layer. Therefore, TDCF is capable to provide meaningful information on the order and coefficient of recombination even if the model conditions are not exactly fulfilled. We demonstrate this for an only 100 nm thick layer of a highly efficient nonfullerene acceptor (NFA) blend, comprising the donor polymer PM6 and the NFA Y6. TDCF measurements were performed as a function of delay time for different laser fluences and bias conditions. The full set of data could be consistently fitted by a strict second order recombination process, with a bias- and fluence-independent bimolecular recombination coefficient k2 = 1.7 × 10−17 m3 s−1. BACE measurements performed on the very same layer yielded the identical result, despite the very different excitation conditions. This proves that recombination in this blend is mostly through processes in the bulk and that surface recombination is of minor importance despite the small active layer thickness.

Primary solid lung cancerous nodules with different sizes: computed tomography features and their variations

BackgroundThe computed tomography (CT) features of small solid lung cancers and their changing regularity as they grow have not been well studied. The purpose of this study was to analyze the CT features of solid lung cancerous nodules (SLCNs) with different sizes and their variations.MethodsBetween February 2013 and April 2018, a consecutive cohort of 224 patients (225 nodules) with confirmed primary SLCNs was enrolled. The nodules were divided into four groups based on tumor diameter (A: diameter ≤ 1.0 cm, 35 lesions; B: 1.0 cm < diameter ≤ 1.5 cm, 60 lesions; C: 1.5 cm < diameter ≤ 2.0 cm, 63 lesions; and D: 2.0 cm < diameter ≤ 3.0 cm, 67 lesions). CT features of nodules within each group were summarized and compared.ResultsMost nodules in different groups were located in upper lobes (groups A − D:50.8%–73.1%) and had a gap from the pleura (groups A − D:89.6%–100%). The main CT features of smaller (diameter ≤ 1 cm) and larger (diameter > 1 cm) nodules were significantly different. As nodule diameter increased, more lesions showed a regular shape, homogeneous density, clear but coarse tumor–lung interface, lobulation, spiculation, spinous protuberance, vascular convergence, pleural retraction, bronchial truncation, and beam-shaped opacity (p < 0.05 for all). The presence of halo sign in all groups was similar (17.5%–22.5%; p > 0.05).ConclusionsThe CT features vary among SLCNs with different sizes. Understanding their changing regularity is helpful for identifying smaller suspicious malignant nodules and early determining their nature in follow-up.

A discrete Nambu bracket for 2D extended Magnetohydrodynamics

In this note we propose a trilinear bracket formulation for the Hamiltonian extended Magnetohydrodynamics (XMHD) model with homogeneous mass density. The corresponding two-dimensional representation is derived by performing spatial reduction on the three-dimensional bracket, upon introducing a symmetric representation for the field variables. Subsequently, the trilinear bracket of the resulting two-dimensional, four-field model is discretized using a finite difference scheme, which results in semi-discrete dynamics that involve the Arakawa Jacobian. Simulations of planar dynamics show that this scheme respects the desired conservation properties to high precision.

Asymmetric optical vortex in plasma density gradient

A vortex laser pulse is incident on a plasma with a density gradient along one transverse direction and a homogeneous density along the other one. As the laser pulse propagates in the plasma, the transverse energy distribution becomes asymmetric along the direction with the homogeneous density, which is shown from particle-in-cell simulations. We demonstrate theoretically that the asymmetric energy distribution results from the rate of plasma density change along the transverse energy flow of the vortex beam. Meanwhile, the degree of asymmetry is found to be positively related to the topological charge of the vortex beam as well as the density gradient of the plasma. Our finding provides a new approach for measuring the topological charge of a vortex beam, and also implies an available probe of the inhomogeneity of an optical medium.

Cell Seeding Technology for Microarray-Based Quantitative Human Primary Skeletal Muscle Cell Analysis.

Pipetting techniques play a crucial role in obtaining reproducible and reliable results, especially when seeding cells on small target areas, such as on microarrays, biochips or microfabricated cell culture systems. For very rare cells, such as human primary skeletal muscle cells (skMCs), manual (freehand) cell seeding techniques invariably result in nonuniform cell spreading and heterogeneous cell densities, giving rise to undesirable variations in myogenesis and differentiation. To prevent such technique-dependent variation, we have designed and fabricated a simple, low-cost pipet guidance device (PGD), and holder that works with hand-held pipettes. This work validates the accuracy and reproducibility of the PGD platform and compares its effectiveness with manual and robotic seeding techniques. The PGD system ensures reproducibility of cell seeding, comparable to that of more expensive robotic dispensing systems, resulting in a high degree of cell uniformity and homogeneous cell densities, while also enabling cell community studies. As compared to freehand pipetting, PGD-assisted seeding of C2C12 mouse myoblasts showed 5.3 times more myotube formation and likewise myotubes derived from PGD-seeded human primary skMCs were 3.6 times thicker and 2.2 times longer. These results show that this novel, yet simple PGD-assisted pipetting technique provides precise cell seeding on small targets, ensuring reproducible and reliable high-throughput cell assays.

Stability analysis of ground states in a one-dimensional trapped spin-1 Bose gas

In this work we study the stability properties of the ground states of a spin-1 Bose gas in presence of a trapping potential in one spatial dimension. To set the stage we first map out the phase diagram for the trapped system by making use of a, so-called, continuous-time Nesterov method. We present an extension of the method, which has been previously applied to one-component systems, to our multi-component system. We show that it is a powerful and robust tool for finding the ground states of a physical system without the need of an accurate initial guess. We subsequently solve numerically the Bogoliubov de-Gennes equations in order to analyze the stability of the ground states of the trapped spin-1 system. We find that the trapping potential retains the overall structure of the stability diagram, while affecting the spectral details of each of the possible ground state waveforms. It is also found that the peak density of the trapped system is the characteristic quantity describing dynamical instabilities in the system. Therefore replacing the homogeneous density with the peak density of the trapped system leads to good agreement of the homogeneous Bogoliubov predictions with the numerically observed maximal growth rates of dynamically unstable modes. The stability conclusions in the one-dimensional trapped system are independent of the spin coupling strength and the normalized trap strength over several orders of magnitude of their variation.

A systematic development of Jeans’ criterion with rotation for gravitational instabilities

An inviscid fluid model of a self-gravitating infinite expanse of a uniformly rotating adiabatic gas cloud consisting of the continuity, Euler’s, and Poisson’s equations for that situation is considered. There exists a static homogeneous density solution to this model relating that equilibrium density to the uniform rotation. A systematic linear stability analysis of this exact solution then yields a gravitational instability criterion equivalent to that developed by Sir James Jeans in the absence of rotation instead of the slightly more complicated stability behavior deduced by Subrahmanyan Chandrasekhar for this model with rotation, both of which suffered from the same deficiency in that neither of them actually examined whether their perturbation analysis was of an exact solution. For the former case, it was not and, for the latter, the equilibrium density and uniform rotation were erroneously assumed to be independent instead of related to each other. Then this gravitational instability criterion is employed in the form of Jeans’ length to show that there is very good agreement between this theoretical prediction and the actual mean distance of separation of stars formed in the outer arms of the spiral galaxy Andromeda M31. Further, the uniform rotation determined from the exact solution relation to equilibrium density and the corresponding rotational velocity for a reference radial distance are consistent with the spectroscopic measurements of Andromeda and the observational data of the spiral Milky Way galaxy.

Development of a Cold-Pressing Process for the Production of Brake Pads with Uniform Density

This study aims to reduce brake pad thickness and density variations by pressure equalization in the preforming process. Brake pads consist of fillers, lubricants, abrasives, reinforcing fibers, and binders. These are compacted together as raw materials. Each component is responsible for a different specific property to help the brake pad reduce the speed of the vehicle. The forming of a brake pad begins with compression of friction powder in a rigid mold with a complicated contour. It is then compacted by vertically pressing punches to form a body of complicated shape and homogeneous density. The strength of the brake pad, which is a main property in the compacted material, primarily depends on the type of fiber reinforcing material. Since the ability of fiber to flow is poor due to its high internal friction and its random arrangement. These two characteristics cause non uniformity in density and elastic modulus. Pressure equalization is an adjustment of the filling depth of the powder which otherwise would have an uneven fill inf the cavity of the mold. The pressure equalization of the filled powder is shown to correlate with the brake pad dimensional accuracy and uniformity of density.

Analytical Calculation of the Numerical Results of Khatami and Kasen for Transient Peak Time and Luminosity

The diffusion approximation is often used to study supernovae light-curves around peak light, where it is applicable. By analytic arguments and numerical studies of toy models, Khatami & Kasen (2019) recently argued for a new approximate relation between peak bolometric Luminosity, $L_p$, and the time of peak since explosion, $t_p$, for transients involving homologous expansion: $L_p=2/(\beta t_p)^2\int_0 ^{\beta t_{p}} t'Q(t')dt'$, where $Q(t)$ is the heating rate of the ejecta, and $\beta$ is an order unity parameter that is calibrated from numerical calculations. Khatami & Kasen (2019) demonstrated its validity using Monte-Carlo radiation transfer simulations of ejecta with homogenous density and (for most cases considered) constant opacity. Interestingly, constant values of $\beta$ accurately reproduce the numerical calculations for different heating distributions and over a wide range of energy release times. Here we show that the diffusion and the adiabatic loss of energy in homologous expansion is equivalent to a static diffusion equation and provide an analytic solution for the case of uniform density and opacity (extending the results of Pinto & Eastman 2000). Our accurate analytical solutions reproduce and extend the results of Khatami & Kasen (2019) for this case, allowing clarification for the universality of their peak time-luminosity relation as well as new limitations to its use.

Meadow-ploughing timing as an integrated pest management tactic to prevent soil-pest damage to maize

Abstract The management of soil-pests still largely relies on conventional chemical insecticides despite the provisions of Integrated Pest Management (IPM). Long-term research was carried out in north-eastern Italy to assess the potential of meadow ploughing just before maize sowing to prevent wireworm damage. The research was based on the observation that no serious wireworm damage occurred in 20 years when meadows were ploughed just before maize sowing. The research hypothesis was that soil-incorporated fresh meadow turf would be a more attractive wireworm food source than seeds, emerging seedlings and young plants. Meadow plots with a sufficiently homogeneous wireworm density were alternately ploughed the previous autumn and a few days before maize sowing. The same conditions were simulated in pots into which known numbers of cage-reared wireworms had been introduced. Results showed very consistently that plant damage in plots ploughed just before maize sowing was much lower than the damage in plots ploughed in autumn-winter, and always below the economic risk threshold (15% of damaged plants). In controlled conditions, plant damage in pots with soil-incorporated fresh meadow turf was significantly lower than that observed in pots without. In both field and controlled conditions, this major effect on plant protection is likely to be caused by the incorporation of meadow turf living plant parts into the soil. Therefore, the ploughing timing of meadows in rotation may be a viable alternative to chemical insecticides when rotation includes meadow.

Microstructure of novel SiCp/Al-Si-Mg composites fabricated by high pressure sintering

Three kinds of SiCp/Al-Si-Mg composites, containing 20%, 40% and 60% volume fraction of silicon carbide particles (SiCp) were respectively sintered at high cubic anvil pressure, using SiC powders prepackaged by aluminum. Then microstructures of the composites were investigated, and the influences of pressure, sintering temperature and volume fraction of SiCp on the microstructures were analyzed. Results show that the composites own homogeneous microstructures, high density and few porosities. In the composites, SiCp and Al matrix were bounded to each other tightly and few agglomeration of SiCp or aluminum was observed. With the volume fraction of SiCp increased, the pinning effect of the reinforcement on the Al matrix is enhanced. With the sintering temperature and pressure increased, densities of the samples are also increased. Energy Dispersive Spectrometer (EDS) and X-ray diffraction (XRD) results show that there are transition layers and Al4C3 phases formed at the interface between SiCp and Al matrix when fabricated under pressure of 3.0GPa and temperature of 620 °C.

Analytical prediction of heat transfer by unsteady natural convection at vertical flat plates in air

The following study presents an analytical calculation procedure which allows a prediction of the heat transfer by unsteady natural convection at vertical flat plates in air. The development of this procedure relies on experimental investigations and phenomenological observations of a previous elaboration, which included laminar, transitional and turbulent flow regimes with Grashof numbers of up to 5.5×1010 (isothermal surface) or 2.0×1013 (homogeneous heat flux density). Thereby, the mean deviation of heat transfer by unsteady natural convection from a quasi-stationary approach is approximated for cyclic and step-like variations of the boundary conditions. Furthermore, the model allows to predict the temporal development of the momentary convective heat transfer in the unsteady case. The calculation procedure is based on a physical model in which a variable proportion of potential and kinetic energy of the fluid molecules is assumed for the unsteady case. A validation of the prediction results shows a good overall agreement with the referenced measurement data both for the mean deviations of the unsteady heat transfer from a quasi-stationary approach and for the corresponding momentary values.

Solid Electrolyte for Li-Ion Batteries: Synthesis, Characterization and Solid-State Cell Integration

Combining nebulized spray pyrolysis (NSP) with field assisted sintering technology (FAST) provides a novel strategy for the preparation of ceramic electrolytes, e.g., garnet-type Li7-3xLa3Zr2AlxO12, with a homogeneous elemental distribution and high density. Utilizing FAST for ceramic preparation shows major impact on the structure and microstructure of the material. By varying the pressure during sintering, for instance, strong straining of the lattice can be induced, providing a high conductivity of 0.42 mScm-1. Therefore, this phenomenon might open a new field of research for garnet type electrolytes examining an enhancement of the electrochemical performance by introducing lattice strain. In this contribution, a detailed mechanism for the lattice distortion and resulting microstrain during FAST treatment of the garnet-type electrolyte is proposed. Furthermore, the charge transfer resistance of Li-ions at the interface, between the solid electrolyte and Li electrodes (characterized using AC impedance spectroscopy) is in the order of 37 Ωcm-2 and is among the best reported values to date. The ceramic electrolyte is fully functional and is integrated into both, an all-solid-state battery cell as well as a hybrid cell, the latter providing a practical approach to combine the advantages of the solid electrolyte with the good wetting behaviour of a liquid electrolyte to the slurry-based cathode material.

Comparison of Clinical and Radiologic Characteristics and Prognosis of Patients with Chronic Subdural Hematoma with and without a History of Head Trauma

To compare clinical and radiologic characteristics and prognosis of patients with chronic subdural hematoma (CSDH) with and without a history of head trauma. Clinical and radiologic characteristics and prognosis of patients with CSDH with a history of head trauma (HT group) and without a history of head trauma (WHT group) were comparatively analyzed. Mean age in the WHT group was 70.23 ± 11.53 years, which was significantly older than mean age 67.56 ± 11.18 years in the HT group (P= 0.008). Stroke, uremia, anticoagulant therapy, and antiplatelet therapy were encountered more often in the WHT group than the HT group. Motor weakness was more prevalent in the WHT group (P= 0.011). Modified Rankin Scale score of 2-3 was more common in the WHT group (P= 0.03), whereas a score of 4-5 was more common in the HT group (P=0.014). Hematoma density on CT was mainly homogeneous in the 2 groups, with significantly more homogeneous density in the HT group compared with the WHT group (P= 0.014). There was significantly more mixed density in the WHT group (P= 0.001). Patients with CSDH in the WHT group had higher mortality (P= 0.026) and lower Glasgow Outcome Scale score (P= 0.033). Patients with CSDH with or without a history of head trauma presented with different clinical and radiologic characteristics. Patients with CSDH without a history of head trauma had a higher mortality and lower GOS score, which indicates these patients warrant more attention.

Effects of high oil viscosity on oil-gas upward flow behavior in deviated pipes

Two-phase flow models play a fundamental role in the design, improvement, and operation of oil and gas production systems. Considering very large high-viscosity oil reserves around the world, the understanding of two-phase flow systems, which involves high-viscosity-liquids (>100 mPa s), becomes a relevant topic. The behavior of this kind of flows is expected to be significantly different as compared with low viscosity oils. In this work, we report a new experimental data on high viscosity oil-gas flow. A set of 170 upward flow experiments were carried out using a mixture of air and mineral oil (213 mPa s, 50.8 mm ID, 21.5 m long) for five different elevations: 45°, 60°, 70°, 80°, and 85°. Superficial liquid and gas velocities were varied from 0.05 m/s to 0.7 m/s and from 0.5 m/s to 6 m/s, respectively. We measured and analyzed: flow pattern, pressure gradient, and average liquid holdup. These variables helped evaluate (a) the implications of a buoyancy-like term in the mechanical energy balance, and (b) the performance of two-phase flow models under the experimental conditions. As a result, we propose a practical relationship between the actual and homogenous densities through the slip and no-slip holdup fractions. This approach, supported by experimental evidence, shows that considering a buoyancy-like term is congruent with the physics that results from the interaction of gravitational and friction forces in inclined pipes. Moreover, the comparison of the present data with prediction models shows a performance which varies significantly depending on the predicted variable, the existing flow pattern as well as the inclination angle. In general, the model performance is good when the observed flow pattern is well predicted but fails when it is not, which typically falls into churn flow. This justifies the need to further understand churn flow and develop models consistent with the physics of transport.