Spheres Of Different Sizes Research Articles

Forward-Scattering and Multiple-Scattering Sources of Errors in UV-Visible Spectroscopy of Microspheres.

Conventional UV-visible spectroscopy instruments measure the extinction spectrum of solutions in a transmission configuration. Because of the finite (nonzero) acceptance angle in detection, errors due to forward scattering and multiple scattering can be introduced when measuring scattering samples. We here experimentally quantify these errors using polystyrene spheres of different sizes for two representative analytical/research UV-visible instruments, one based on a single-beam diode array and the other on a double-beam scanning configuration. The measured spectra for particles larger than 1 μm are shown to differ between the two instruments, even at low concentrations, and also vary with concentration (in contradiction with the Beer-Lambert law). We show that systematic errors in the range of 10-40% are common in such measurements. We propose a model accounting for both forward- and multiple-scattering errors and demonstrate its agreement with our experimental results. This model could reduce systematic errors in measurements of scattering samples by up to 40%.

Gel polymer electrolytes containing SiO2 spheres with tuned sizes to increase rechargeability of quasi-solid-state Zn-air batteries

Rechargeable zinc–air batteries (RZABs) with high energy densities and low costs have attracted tremendous interest for meeting the ever-growing demand for flexible and portable applications. In these batteries, the quasi-solid/solid-state electrolyte plays a critical role in the battery performance, such as the cycling performance rate and power output. In this study, porous poly (vinyl alcohol) (PVA) and poly (acrylic acid) (PAA) composite gel polymer electrolytes (GPEs) were modified by incorporating SiO2 as a water retainer. For this reason, SiO2 spheres of different sizes were synthesized by varying the temperature (5, 20, 60, and 80 °C) and reaction time (2, 6, 18, and 24 h). According to the SEM micrographs, the average size ranged from 107 to 710 nm depending on the conditions. The porous PVA/PAA–SiO2 GPEs obtained by selecting three SiO2 sizes (107, 425, and 630 nm) exhibited higher water retention capability than the unmodified GPE. Among them, the GPE with SiO2–630 nm displayed the highest battery performance (1.46 V, 85 mWcm−2 @ 0.8 V). This was achieved using CoMn2O4 spinel as a bifunctional electrocatalyst, with a catalyst loading of 2 mg cm−2. The quasi-solid-state RZAB displayed twice the rechargeability of the RZAB assembled with Pt/C+IrO2/C (120 vs. 62 cycles). According to post-mortem tests, this can be related to the improved water retention, the decrease in the size of the formed Zn dendrites, and the stability of the bifunctional material. Thus, fine-tuning of the electrocatalyst/electrolyte interface strongly affects the rechargeability.

Photocatalyst Au@Ni-MOFs with Different Plasmonic Coverages for Improved Hydrogen Evolution from Water.

Plasmonic materials are fundamental photosensitizer materials for photocatalytic reactions. Various structures, including core-shell types, satellite types, and distribution types, have been designed and prepared for the optimization of photocatalytic reactions. However, understanding the profound enhancement mechanism of various structures is still challenging. Thus, the plasmonic coverage is considered to be an index for analyzing the influence mechanism. Here, Au@Ni-MOF core-shell flower sphere-like photocatalysts are prepared, and the size of the flower sphere can be precisely regulated by varying the amount of Au. Thus, different plasmonic coverages are realized through the tuning of spheres of different sizes. The high plasmonic coverage of catalysts can enhance visible light absorption, facilitate the generation of photogenerated electron-hole pairs, and shorten the photogenerated carrier transport distance. Moreover, the exponential relationship between the photocatalytic hydrogen production performance and the plasmonic coverage can also be used as a guide for material design. As a result, a photocatalytic hydrogen production rate of 3389 μmol·g-1·h-1 is achieved in the Au@Ni-MOF sample with high plasmonic coverage, which will advance the plasmonic application in photocatalytic reactions.

New Functional Orbital-free Within DFT for Metallic Systems

I present the continuation of a study on Laplacian Level Kinetic Energy (KE) functionals applied to metallic nanosystems. The development of novel Kinetic Energy functionals is an important topic in density functional theory (DFT). The nanoparticles are patterned using gelatin spheres of different sizes, background density and number of electrons. To reproduce the correct kinetic and potential energy density of the various nanoparticles, the use of semilocal descriptors is necessary. Need an explicit density functional expression for the kinetic energy of electrons, including the first e second functional derivative, i.e. the kinetic potential and the kinetic kernel, respectively. The exact explicit form of the non interacting kinetic energy, as a functional of the electron density, is known only for the homogeneous electron gas (HEG), i.e., the Thomas-Fermi (TF) local functional and for 1 and 2 electron systems, i.e., the von Weizsacker (VW) functional. In between these two extreme cases, different semilocal or non local approximations were developed in recent years. Most semilocal KE functionals are based on modifications of the second-order gradient expansion (GE2) or fourth-order gradient expansion (GE4). I find that the Laplacian contribute is fundamental for the description of the energy and the potential of nanoparticles. I propose a new LAP2 semilocal functional which, better than the previous ones, allows us to obtain fewer errors both of energy and potential. More details of the previous calculations can be found in my 2 previous works which will be cited in the text.

Electrolytic reduction in LiCl-Li2O of titania microspheres synthesized via vibrational droplet coagulation: Effect of feed morphology

In this work, an electrolytic reduction route of TiO2 microspheres with a well-defined morphology is reported. The TiO2 microspheres are synthesized via a vibrational droplet coagulation method and are electrochemically reduced in LiCl-Li2O molten salt. The reduction process of the spheres of different size and morphology is investigated. The electrolytic reduction kinetics, the product chemistry and morphological parameters such as outer diameter, total surface area and pore size are investigated and benchmarked to a conventional TiO2 powder feed. Moreover, the reduced TiO2 spheres were investigated by X-ray diffraction, scanning electron microscope and BET method. A core–shell structure was observed in the spheres as an intermediate form during electrolysis when charges below 100 % of the theoretical charge were applied. Raman spectroscopy was performed to identify the composition of the core and the shell to further elucidate the reduction pathway of these TiO2 spheres throughout the electrolysis process. After full electrolytic conversion of the feed material, LiTiO2 microspheres were obtained. The presented reduction route provides a novel pathway to synthesize high purity LiTiO2 for practical applications.

Flexible multiscale cavity with omnidirectionality and high stability for in-site SERS detection of nanoplastics on oyster

Nanoplastics are widespread and pose a potential threat to human health. In this work, we designed a flexible multiscale cavity structured (MCS) surface-enhanced Raman scattering (SERS) substrate decorating Ni3S2 nanocavity on a modified polyvinylidene fluoride (PVDF) microcavity. The dense two-dimensional Ni3S2 nanosheets can provide a large surface area for the deposition of plasmonic silver nanoparticles (Ag NPs), increasing the density and strength of the “hotspots”. Additionally, the nanocavity (width ∼500 nm), formed by the nanosheet surroundings, offers not only electromagnetic enhancement of the cavity mode for SERS but also a crucial detection site for nanoplastics attachment. This effectively addresses the challenge of SERS detection due to the scale mismatch between nanoplastics (>50 nm) and conventional “hotspots” (<10 nm). Moreover, the flexible imprinted PVDF microcavity endows the proposed substrate with omnidirectional “hotspots” enhancement, ensuring the signal stability and the feasibility of in-site detection of the actual sample. As a result, we achieved the successful in-site detection of polystyrene (PS) spheres of different sizes on the surface of oysters, with a detection limit of 10-3 mg/mL for 50 nm diameter. The flexible multiscale cavity SERS substrate is expected to show great potential in food safety and environmental monitoring.

Preparation of gradient refractive index films on glass surface and its anti-reflection properties

This study presents the creation of a gradient refractive index film on the surface of aluminosilicate glass using a two-step process involving chemical etching and subsequent multilayer sol-gel coating with hollow silica nanospheres. The primary objective was to achieve effective anti-reflection properties. Various analytical techniques such as FESEM, TEM, UV-Vis-NIR spectrophotometry, ellipsometer, and FT-IR spectrometry were employed to investigate the impact of glass surface morphology and refractive index on optical characteristics. The results revealed the successful formation of a porous structure on the glass surface through chemical etching. Subsequently, this porous structure was uniformly filled and layered with hollow silica spheres of different sizes, resulting in a stepwise gradient refractive index coating. Notably, the pore size of the hollow spherical silica colloidal particles progressively increased from 0 nm to 23 nm, corresponding to distinct film thicknesses and refractive indices. This stepwise modulation contributed to the establishment of a gradient refractive index within the coating. By transitioning the refractive index of the film layer from that of glass to air, the film acted as a matching layer, thereby achieving broadband anti-reflection. The efficiency of this anti-reflection was demonstrated by an increase in transmittance from an initial value of 91.8–95.32% following the two-step etching process. With the subsequent SiO2 coating, the transmittance continued to improve, ultimately reaching a high value of 97.47%. This improvement in transmittance was attributed to the gradual enhancement of the film layer.

Non-etching and controllable fabrication of hollow carbon spheres for high-performance supercapacitor

Due to their unique hollow sphere structure and good graded porous framework, hollow carbon spheres have potential applications in energy conversion and storage. In this study, hollow polymer spheres with regular morphology, uniform size and good dispersion were prepared by one-step hydrothermal reaction without complicated etching process. The formation process of hollow polymer spheres was also studied, and hollow carbon spheres of different sizes were prepared. HCSs20 possessed the largest specific surface area of 1603.28 m2·g−1. The HCSs20 electrode exhibited a high specific capacitance of 261 F·g−1 at a current density of 0.5 A·g−1. Moreover, the symmetric supercapacitor assembled with HCSs20, as the active material, possessed an energy density of 13.34 Wh·kg−1at a power density of 1 kW·kg−1 in a 3 M KOH electrolyte. It exhibited a good performance in the cycle life test at low current density (91 % specific capacitance retention after 9000 cycles).

PET imaging and quantification of small animals using a clinical SiPM-based camera

BackgroundSmall-animal PET imaging is an important tool in preclinical oncology. This study evaluated the ability of a clinical SiPM-PET camera to image several rats simultaneously and to perform quantification data analysis.MethodsIntrinsic spatial resolution was measured using 18F line sources, and image quality was assessed using a NEMA NU 4-2018 phantom. Quantification was evaluated using a fillable micro-hollow sphere phantom containing 4 spheres of different sizes (ranging from 3.95 to 7.86 mm). Recovery coefficients were computed for the maximum (Amax) and the mean (A50) pixel values measured on a 50% isocontour drawn on each sphere. Measurements were performed first with the phantom placed in the centre of the field of view and then in the off-centre position with the presence of three scattering sources to simulate the acquisition of four animals simultaneously. Quantification accuracy was finally validated using four 3D-printed phantoms mimicking rats with four subcutaneous tumours each. All experiments were performed for both 18F and 68Ga radionuclides.ResultsRadial spatial resolutions measured using the PSF reconstruction algorithm were 1.80 mm and 1.78 mm for centred and off-centred acquisitions, respectively. Spill-overs in air and water and uniformity computed with the NEMA phantom centred in the FOV were 0.05, 0.1 and 5.55% for 18F and 0.08, 0.12 and 2.81% for 68Ga, respectively. Recovery coefficients calculated with the 18F-filled micro-hollow sphere phantom for each sphere varied from 0.51 to 1.43 for Amax and from 0.40 to 1.01 for A50. These values decreased from 0.28 to 0.92 for Amax and from 0.22 to 0.66 for A50 for 68 Ga acquisition. The results were not significantly different when imaging phantoms in the off-centre position with 3 scattering sources. Measurements performed with the four 3D-printed phantoms showed a good correlation between theoretical and measured activity in simulated tumours, with r2 values of 0.99 and 0.97 obtained for 18F and 68Ga, respectively.ConclusionWe found that the clinical SiPM-based PET system was close to that obtained with a dedicated small-animal PET device. This study showed the ability of such a system to image four rats simultaneously and to perform quantification analysis for radionuclides commonly used in oncology.

Tumor dosimetry using 177Lu: influence of background activity, measurement method and reconstruction algorithm

BackgroundImage-based tumor dosimetry after radionuclide therapy, using the isotope 177Lu, finds application e.g., for tumor-to-organ dose comparison and for dose response evaluation. When the tumor extent is not much larger than the image resolution, and when 177Lu is found in nearby organs or other tumors, an accurate determination of tumor dose is particularly challenging. Here a quantitative evaluation of three different methods for determining the 177Lu activity concentration in a phantom is performed, and the dependence on a variety of parameters is described. The phantom (NEMA IEC body phantom) has spheres of different size in a background volume, and sphere-to-background 177Lu activity concentration ratios of infinity, 9.5, 5.0 and 2.7 are applied. The methods are simple to implement and well-known from the literature. They are based on (1) a large VOI encompassing the whole sphere, without background activity and with volume information from other sources, (2) a small VOI located in the sphere center, and (3) a VOI consisting of voxels with voxel value above a certain percentage of the maximum voxel value.ResultsThe determined activity concentration varies significantly with sphere size, sphere-to-background ratio, SPECT reconstruction method and method for determining the concentration. Based on the phantom study, criteria are identified under which the activity concentration can be determined with a maximal error of 40% even in the presence of background activity.ConclusionsTumor dosimetry is feasible in the presence of background activity using the above-mentioned methods, provided appropriate SPECT reconstructions are applied and tumors are selected for dosimetry analysis according to the following criteria for the three methods: (1) solitary tumor with diameter > 15 mm, (2) tumor diameter > 30 mm and tumor-to-background ratio > 2, and (3) tumor diameter > 30 mm and tumor-to-background ratio > 3.

Investigating the inflow into a granular bed using a locally resolved method

Discrete Element Method – Computational Fluid Dynamics (DEM/CFD) simulations of industrial-scale granular systems employ spatial averaging (porous media approach) for the fluid-particle interaction in the whole domain, which can lead to poor accuracy, for instance at flow inlets, as local particle bulk morphology is not resolved. This paper presents an approach where the interstitial flow in crucial areas with large gradients can be resolved locally in an otherwise unresolved domain, so that a mixed resolved-unresolved method is realized.As a generic example to show the feasibility and performance of the new approach, the inflow of ambient air into a flat-bottom hopper through a narrow orifice is investigated. In an experimental setup, the vertical profile of the pressure decay through the inlet and across the packing is chosen for comparison with respective simulations. Results obtained with the conventional porous media method and the locally resolved approach are compared to these experiments for varying volume flow rates and for two different particle shapes. Spheres of different size as well as dodecahedrons are examined.It is found that although averaging methods already provide good approximations, the locally resolved method can improve the result especially when conventional drag laws are not applicable due to wall effects or if large velocity gradients exist.

Interframe Echo Intensity Variation of Subregions and Whole Plaque in Two-Dimensional Carotid Ultrasonography: Simulations and In Vivo Observations.

The risk of cardiovascular disease is associated with the echo intensity of carotid plaques in ultrasound images and their cardiac cycle-induced intensity variations. In this study, we aimed to 1) explore the underlying origin of echo intensity variations by using simulations and 2) evaluate the association between the two-dimensional (2D) spatial distribution of these echo intensity variations and plaque vulnerability. First, we analyzed how out-of-plane motion and compression of simulated scattering spheres of different sizes affect the ultrasound echo intensity. Next, we propose a method to analyze the features of the 2D spatial distribution of interframe plaque echo intensity in carotid ultrasound image sequences and explore their associations with plaque vulnerability in experimental data. The simulations showed that the magnitude of echo intensity changes was similar for both the out-of-plane motion and compression, but for scattering objects smaller than 1 mm radius, the out-of-plane motion dominated. In experimental data, maps of the 2D spatial distribution of the echo intensity variations had a low correlation with standard B-mode echo intensity distribution, indicating complementary information on plaque tissue composition. In addition, we found the existence of ∼1 mm diameter subregions with pronounced echo intensity variations associated with plaque vulnerability. The results indicate that out-of-plane motion contributes to intra-plaque regions of high echo intensity variation. The 2D echo intensity variation maps may provide complementary information for assessing plaque composition and vulnerability. Further studies are needed to verify this method's role in identifying vulnerable plaques and predicting cardiovascular disease risk.

Gravitational lensing by black holes with multiple photon spheres

We study gravitational lensing of light by hairy black holes, which, in a certain parameter regime, can possess two photon spheres of different size outside the event horizon. In particular, we focus on higher-order images of a point-like light source and a luminous celestial sphere produced by strong gravitational lensing near photon spheres. Two photon spheres usually triple the number of high-order images of a point-like light source. When a hairy black hole is illuminated by a celestial sphere, two photon spheres would give rise to two critical curves in the black hole image, and the smaller critical curve coincides with the shadow edge. In addition to a set of higher-order images of the celestial sphere outside the shadow edge, two more sets of higher-order images are observed inside and outside the larger critical curve, respectively.

Quantitative Acoustophoresis.

Studying cellular mechanics allows important insights into its cytoskeletal composition, developmental stage, and health. While many force spectroscopy assays exist that allow probing of mechanics of bioparticles, most of them require immobilization of and direct contact with the particle and can only measure a single particle at a time. Here, we introduce quantitative acoustophoresis (QAP) as a simple alternative that uses an acoustic standing wave field to directly determine cellular compressibility and density of many cells simultaneously in a contact-free manner. First, using polymeric spheres of different sizes and materials, we verify that our assay data follow the standard acoustic theory with great accuracy. We furthermore verify that our technique not only is able to measure compressibilities of living cells but can also sense an artificial cytoskeleton inside a biomimetic vesicle. We finally provide a thorough discussion about the expected accuracy our approach provides. To conclude, we show that compared to existing methods, our QAP assay provides a simple yet powerful alternative to study the mechanics of biological and biomimetic particles.

Developing the Nondevelopable: Creating Curved‐Surface Electronics from Nonstretchable Devices (Adv. Mater. 22/2022)

Conformal Films In article number 2106683, Kenjiro Fukuda, Takao Someya, and co-workers demonstrate how a variety of ultrathin, ultraflexible organic photovoltaics that differ in layout, active area, and active material can be laminated to glass spheres of different sizes using a thermally activated shrink film. The wrinkling pattern that occurs in these ultrathin sheets allows even nonstretchable devices to conform to surfaces with a 3D curvature.

Heat transfer to a sphere immersed in a fluidized bed of coarse particles with transition from bubbling to turbulent flow regime

The present work concerns an experimental study on heat transfer in gas-solid fluidized bed of coarse (Geldart D) particles to a larger immersed sphere at high superficial velocities from 2 to 5.5 U mf. The heat transfer coefficient was determined by measuring the temperature of the test sphere during its heating in a fluidized bed in the temperature range of 65–175 °C. The test spheres of different sizes and different materials were utilized. For the given gas-particles system the flow regime changes from rapidly growing bubbles to turbulent fluidization at superficial velocity U c ≈ 3Umf. It has been found that in rapidly growing bubbles regime, the heat transfer coefficient is higher for smaller test spheres while it is almost independent of the superficial gas velocity. In turbulent regime, the heat transfer coefficient increases with increase of gas velocity while the size of the test sphere exhibits less influence. In the rapidly growing bubbles regime, experimental data for heat transfer coefficient can be predicted adequately with correlation of Scott et al.. For the turbulent flow regime a new correlation for prediction of the heat transfer coefficient has been proposed.

A low-cost, portable, two-dimensional bioimpedance distribution estimation system based on the AD5933 impedance converter

This study proposes a low-cost, portable, eight-channel electrical impedance tomograph based on the AD5933 impedance converter. The patterns for current injection and voltage measurement are managed by an Arduino Mega 2560 board and four 74HC4067 Texas Instruments multiplexers. Regarding the experimental results, the errors in the impedance estimates of an electrical circuit that represents a Cole model were less than 1.14% for the magnitude and 4.15% for the phase. Furthermore, the signal-to-noise ratio measured in a resistive phantom was 55.23 dB. Additional experiments consisted of placing five spheres of different size and conductivity in a saline tank, measuring their impedance through eight electrodes, and then generating impedance maps using the Electrical Impedance Tomography and Diffuse Optical Tomography Reconstruction Software (EIDORS). These maps were different for each sphere, suggesting the proposed prototype as a promising alternative for medical applications.

Development of novel kinetic energy functional for orbital-free density functional theory applications

The development of novel Kinetic Energy (KE) functionals is an important topic in density functional theory (DFT). In particular, this happens by means of an analysis with newly developed benchmark sets. Here, I present a study of Laplacian-level kinetic energy functionals applied to metallic nanosystems. The nanoparticles are modeled using jellium sph eres of different sizes, background densities, and number of electrons. The ability of different functionals to reproduce the correct kinetic energy density and potential of various nanoparticles is investigated and analyzed in terms of semilocal descriptors. Most semilocal KE functionals are based on modifications of the second-order gradient expansion GE2 or GE4. I find that the Laplacian contribute is fundamental for the description of the energy and the potential of nanoparticles.

Microstructure and mechanical properties of bimodal syntactic foams with different size combination and volume fraction of alumina hollow spheres

In this study, the stir casting method was used to prepare aluminum matrix bimodal syntactic foams by mixing alumina hollow spheres of different size ranges. Alumina hollow spheres of 1.0–4.0 mm were divided into six size ranges. In bimodal syntactic foams, the hollow spheres of different size ranges were mixed in equal volume to ensure that their average diameter was almost the same, or the hollow spheres of 1.5–2.0 mm and 3.0–3.5 mm were mixed in different volume ratios. The bimodal syntactic foams under quasi-static compression first fractured along the small-sized hollow spheres, presenting brittle fracture characteristics. When mixing hollow spheres with different size ranges in equal volume, the mechanical properties of bimodal syntactic foams strongly depended on the average diameter of hollow spheres. The mechanical properties of bimodal syntactic foams with 1.5–2.0 mm and 3.0–3.5 mm hollow spheres decreased linearly with the increase of 3.0–3.5 mm hollow sphere content.

Photon spheres and spherical accretion image of a hairy black hole

In this paper, we first consider null geodesics of a class of charged, spherical and asymptotically flat hairy black holes in an Einstein-Maxwell-scalar theory with a non-minimal coupling for the scalar and electromagnetic fields. Remarkably, we show that there are two unstable circular orbits for a photon in a certain parameter regime, corresponding to two unstable photon spheres of different sizes outside the event horizon. To illustrate the optical appearance of photon spheres, we then consider a simple spherical model of optically thin accretion on the hairy black hole, and obtain the accretion image seen by a distant observer. In the single photon sphere case, only one bright ring appears in the image, and is identified as the edge of the black hole shadow. Whereas in the case with two photon spheres, there can be two concentric bright rings of different radii in the image, and the smaller one serves as the boundary of the shadow, whose radius goes to zero at the critical charge.