Concentric Spheres Research Articles

Assessment of the Probability of Tumour Control for Prescribed Doses Based on Imaging of Oxygen Partial Pressure.

In radiotherapy, hypoxia is a known negative factor, occurring especially in solid malignant tumours. Nitroimidazole-based positron emission tomography (PET) tracers, due to their selective binding to hypoxic cells, could be used as surrogates to image and quantify the underlying oxygen distributions in tissues. The spatial resolution of a clinical PET image, however, is much larger than the cellular spatial scale where hypoxia occurs. A question therefore arises regarding the possibility of quantifying different hypoxia levels based on PET images, and the aim of the present study is the prescription of corresponding therapeutic doses and its exploration.A tumour oxygenation model was created consisting of two concentric spheres with different oxygen partial pressure (pO2) distributions. In order to mimic a PET image of the simulated tumour, given the relation between uptake and pO2, fundamental effects that limit spatial resolution in a PET imaging system were considered: the uptake distribution was processed with a Gaussian 3D filter, and a re-binning to reach a typical PET image voxel size was performed. Prescription doses to overcome tumour hypoxia and predicted tumour control probability (TCP) were calculated based on the processed images for several fractionation schemes. Knowing the underlying oxygenation at microscopic scale, the actual TCP expected after the delivery of the calculated prescription doses was evaluated. Results are presented for three different dose painting strategies: by numbers, by contours and by using a voxel grouping-based approach.The differences between predicted TCP and evaluated TCP indicate that careful consideration must be taken on the dose prescription strategy and the selection of the number of fractions, depending on the severity of hypoxia.

Effect of earth curvature on long range sound propagation

Since the earth is approximately a sphere, the sound speed equivalent surface on the range-depth plane is not a parallel plane, but a concentric sphere at a long distance. Therefore, for a long-range sound propagation, the effect of the curvature of the earth cannot be ignored. In this paper, conformal mapping is used to propose a method of earth curvature correction without changing the existing sound field calculation model, and has the characteristics of good portability and simple calculation. The simulation results in a typical environment show that because of the earth curvature, the location of the convergence zone moves toward the sound source, and its movement can reach 10 km at 1000 km in distance. Before and after the earth curvature correction, the transmission loss difference can reach up to 15 dB at a particular location. Through the analysis of the simulation results in four typical sound speed profiles in Northwest Pacific Ocean, it is found that the movement of the convergence zone and the distance change are approximately linear, and the movement of the convergence zone increases by about 1km for every increase of the propagation distance by 100 km. For deep-sea channel propagation, the earth curvature will cause the arrival structure to move forward as a whole on the time axis, and the degree of the forward motion will gradually increase with the distance increasing. At 1000 km, the amplitude of the forward motion can reach 136 ms. In addition, the earth curvature will also cause the depth and time extension of the arrival structure. For the received time-domain waveform at a certain depth, there is a big difference between before and after the earth curvature correction. The modified results from different earth approximation models show that the accuracy of the calculation can be satisfied by approximating the earth as a standard sphere.

Anionic/nonionic surfactants for controlled synthesis of highly concentrated sub-50 nm polystyrene spheres.

Polystyrene nanospheres are of great importance in 3D hard templating along with many other fields like pharmaceuticals and coatings. Therefore, it is important to be able to prepare polystyrene beads with different sphere sizes that suit each application. In this work, the emulsion polymerization method was used to prepare monodispersed polystyrene (PS) spheres with an average size of 50 nm, using styrene monomer, sodium dodecyl sulfate (SDS) and polyvinylpyrrolidone (PVP) as surfactants, and potassium persulfate (KPS) as the initiator. The average size and size distribution of the PS spheres were controlled by optimizing the synthesis parameters such as the concentration of the monomer, initiator, and surfactant, the type of surfactant, and the time and temperature of polymerization. The shape, size, and size distribution of the prepared PS spheres were characterized using dynamic light scattering (DLS) and scanning electron microscopy (SEM). The preparation of perfectly spherical PS spheres as small as 50 nm with a narrow size distribution is obtained using 8% styrene with (5% SDS and 2% KPS of the styrene amount) at 90 °C, with the monomer and surfactant molar ratio and concentration and the polymerization temperature being the dominating factors that affect the PS bead size.

An Approach to Diversity and Inclusion in Cardiothoracic Surgery

While the United States (US) population at large is rapidly diversifying, cardiothoracic surgery is among the least diverse specialties in terms of racial and gender diversity. Lack of diversity is detrimental to patient care, physician well-being, and the relevance of cardiothoracic surgery on our nation's health. Recent events, including the coronavirus disease 2019 pandemic and the Black Lives Matter protests, have further accentuated the gross inequities that underrepresented minorities face in our country and have reignited conversations on how to address bias and systemic racism within our institutions. The field of cardiothoracic surgery has a responsibility to adopt a culture of diversity and inclusion. This kind of systemic change is daunting and overwhelming. With bias ubiquitously entangled with everyday experiences, it can be difficult to know where to start. The Society of Thoracic Surgeons Workforce on Diversity and Inclusion presents this approach for addressing diversity and inclusion in cardiothoracic surgery. This framework was adapted from a model developed by the National Institute on Minority Health and Health Disparities and includes information and recommendations generated from our literature review on diversity and inclusion. A MEDLINE search was conducted using keywords "diversity," "inclusion," and "surgery," and approaches to diversity and inclusion were drawn from publications in medicine as well as non-healthcare fields. Recommendations were generated and approved by The Society of Thoracic Surgeons Executive Committee. We present an overarching framework that conceptualizes diversity and inclusion efforts in a series of concentric spheres of influence, from the global environment to the cardiothoracic community, institution, and the individual surgeon. This framework organizes the approach to diversity and inclusion, grouping interventions by level while maintaining a broader perspective of how each sphere is interconnected. We include the following key recommendations within the spheres of influence: It is important to note that each of the spheres of influence is interconnected. Interventions to improve diversity must be coordinated across spheres for concerted change. Altogether, this multilevel framework (global environment, cardiothoracic community, institution, and individual) offers an organized approach for cardiothoracic surgery to assess, improve, and sustain progress in diversity and inclusion.

Cellular dosimetry of 197Hg, 197mHg and 111In: comparison of dose deposition and identification of the cell and nuclear membrane as important targets

Purpose To examine the reliability to model cellular S-values for the Auger electron (AE) emitters, 111In, 197Hg and 197mHg with MCNP6 and their relative dose deposition in subcellular targets. Methods A model cell was defined as four concentric spheres consisting of the nucleus (N), cytoplasm (Cy), cell and nuclear membranes (CM, NM) in which radionuclides distributed homogeneously. The transport of AE, conversion electrons and photons were simulated by MCNP6 to calculate cellular S values (SN←CM, SN←Cy, SN←NM, SN←N, SCM←CM, SNM←NM). SN←CM, SN←Cy and SN←N were also calculated with MIRDcell. Results MIRDcell and MCNP6-calculated SN←N were in excellent agreement, but a slight discrepancy on SN←Cy and SN←CM was observed. The ratios of SCM←CM or SNM←NM vs. SN←N were 9.7–51.0 or 10.5–37.4, 7.9–41.8 or 8.4–31.8 and 7.2–36.9 or 8.0–28.1 for 111In, 197Hg, 197mHg, respectively. The mean S(197Hg)/S(111In) and S(197mHg)/S(111In) were 2.5 ± 0.5 and 2.5 ± 0.6, respectively. Conclusions Cellular S-values were reliably calculated with MCNP6. 197Hg and 197mHg deposit two-fold more doses than 111In at the subcellular scale. All AE emitters deposit a higher self-dose in the CM and NM than in the N, which warrants studies on the effects of targeting the CM and NM by AE emitters.

Hawking Radiation is Nothing: Developed Correlation of Entropy with Black Hole Area

Read is the first word and divine order in the Holy Quran. My lovely physics does not answer many mysteries in the universe including black holes. The observed ordinary matter in the universe is only ~5 %. The remaining is 27% dark matter and approximately 68% dark energy of. This paper introduces a developed model and concept to black hole anatomy and entropy-surface area correlation. It considers the stationary black hole a one entity of 4 concentric spheres around the singularity. They are the event horizon, photon sphere at 1.5Rs, unstable light sphere at 2.6Rs and innermost stable particle sphere at 3Rs. An equation (Sayed Ts formula) was derived excluded heuristics of Professor S. Hawking. This formula is based on different proportional constant between entropy and black hole surface area; not ¼ as He conjectured. In spite of my respect and humanity sympathy with Prof. Hawking, his tombstone equation should be corrected. There is neither radiation escape from black holes nor any signal detected due to micro black holes evaporation. Finally, it can be stated that Hawking radiation is Nothing.

Stiffness of Three-Phase Concentric Composite Solids

There are numerous examples of three-phase concentric composites, including coated fiber-reinforced materials and syntactic foams. The stiffness of such three-phase materials is usually investigated by micromechanical methods specified for this particular case. For example, Luo and Weng presented solutions for three-phase concentric spheres [1] and for three-phase concentric cylinders models [2] of an inclusion, a coating (“intermediate matrix”), and a matrix using the Mori–Tanaka method. Among numerous studies of three-phase or multi-phase composites one can mention [3-6].

Nearest Neighbor and Contact Distance Distribution for Binomial Point Process on Spherical Surfaces

This letter characterizes the statistics of the contact distance and the nearest neighbor (NN) distance for binomial point processes (BPP) spatially-distributed on spherical surfaces. We consider a setup of $n$ concentric spheres, with each sphere $S_{k}$ has a radius $r_{k}$ and $N_{k}$ points that are uniformly distributed on its surface. For that setup, we obtain the cumulative distribution function (CDF) of the distance to the nearest point from two types of observation points: (i) the observation point is not a part of the point process and located on a concentric sphere with a radius $r_{e} , which corresponds to the contact distance distribution, and (ii) the observation point belongs to the point process, which corresponds to the nearest-neighbor (NN) distance distribution.

Monte Carlo track-structure for the radionuclide Copper-64: characterization of S-values, nanodosimetry and quantification of direct damage to DNA

TOPAS-nBio was used to simulate, collision-to-collision, the complete trajectories of electrons in water generated during the explicit simulation of 64Cu decay. S-values and direct damage to the DNA were calculated representing the cell (C) and the cell nucleus (N) with concentric spheres of 5 μm and 4 μm in radius, respectively. The considered ‘target’←‘source’ configurations, including the cell surface (Cs) and cytoplasm (Cy), were: C←C, C←Cs, N←N, N←Cy and N←Cs. Ionization cluster size distributions were also calculated in a cylinder immersed in water corresponding to a DNA segment of 10 base-pairs in length (diameter 2.3 nm, length 3.4 nm), modeling a radioactive point source moving from the central axis to the edge of the cylinder. For that, the first moment (M1) and cumulative probability of having a cluster size of 2 or more ionizations in the cylindrical volume (F2) were obtained. Finally, the direct damage to the DNA was estimated by quantifying double-strand breaks (DSBs) using the clustering algorithm DBSCAN.The S-values obtained with TOPAS-nBio for 64Cu were 7.879 × 10−4 ± 5 × 10−7, 4.351 × 10−4 ± 6 × 10−7, 1.442 × 10−3 ± 1 × 10−6, 2.596 × 10−4 ± 8 × 10−7, 1.127 × 10−4 ± 4 × 10−7 Gy Bq-s−1 for the configurations C←C, C←Cs, N←N, N←Cy and N←Cs, respectively. The difference of these values, compared with previously reported S-values for 64Cu with the code MNCP and software MIRDCell, ranged from −4% to −25% for the configurations N←N and N←Cs, respectively. On the other hand, F2 was maximum with the source at the center of the cylinder 0.373 ± 0.001, and monotonically decreased until reaching a value of 0.058 ± 0.001 at 2.3 nm. The same behavior was observed for M1 with values ranging from 2.188 ± 0.004 to 0.242 ± 0.002. Finally, the DBSCAN algorithm showed that the mean number of DNA DSBs per decay were 0.187 ± 0.001, 0.0317 ± 0.0005, and 0.0125 ± 0.0002 DSB-(Bq-s)−1 for the configurations N←N, N←Cs, and N←Cy, respectively.In conclusion, the results of the S-values show that the absorbed dose strongly depends on the distribution of the radionuclide in the cell, the dose being higher when 64Cu is internalized in the cell nucleus, which is reinforced by the nanodosimetric study by the presence of DNA DSBs attributable to the Auger electrons emitted during the decay of 64Cu.

Dynamics of Gas Bubbles Inside a Ball-like Area at the Nodes of a Uniform Cubic Mesh Under Sudden Liquid Pressure Rise

The influence of hydrodynamic interaction between spherical gas bubbles inside a ball-like area at the nodes of a uniform cubic mesh on their dynamics under sudden liquid pressure rise has been investigated. Main attention is payed to the dynamics of a bubble located in the center of such a cluster of cubic structure. Prior to the pressure rise, the liquid and the bubbles are at rest, the liquid pressure is 1 bar, the radii of the bubbles are 0.25 mm, the size of the cubic mesh cells is 5 mm. The increase in the liquid pressure is 3 bar. For the sake of comparison, ball-like clusters with spherical and stochastic structures are also considered, with similar position of the central bubble and with initial minimum distance between the centers of bubbles not exceeding 5 mm. In the clusters of spherical structure, the non-central bubbles are located on concentric spheres with radii of 5 and 10 mm at the nodes of equally-oriented regular polyhedra (icosahedra and dodecahedra). In the clusters of stochastic structure, the non-central bubbles are distributed stochastically in a sphere with radius of 10 mm. A mathematical model is applied, in which the dynamics of bubbles is governed by the ordinary differential equations in the radii of bubbles and the position-vectors of their centers. It is shown that in the case of a cluster with cubic structure, the interaction between the bubbles leads to strengthening the collapse rate of the central bubble and to non-monotonic decay of oscillations of their pressure. Similar features are characteristic of the clusters with spherical and stochastic structures.

Numerical analysis of local non-equilibrium heat transfer in layered spherical tissue during magnetic hyperthermia

A solid multi-layered concentric sphere with Gaussian space source is considered as the tissue model for magnetic hyperthermia treatment. The generalized dual-phase-lag model of bioheat transfer is used to describe the behavior of heat transport in tissue in the hyperthermia treatment process for accounting the local non-equilibrium effect. The effects of blood perfusion with the transient temperature are included in the tissue model. The hybrid numerical scheme based on Laplace transform, change of variables, and the modified discretization technique is extended to solve the present problem. The analytical solution for constant heat generation in the inner sphere is presented and evidences the accuracy and rationality of the present numerical results. In an ideal hyperthermia treatment, all the diseased tissues should be selectively heated without affecting any healthy tissue. Attempting to achieve the ideal temperature distribution, the thermal dose is estimated at the specified condition. The corresponding thermal efficacy of tumor damage has also been assessed based on the Arrenius equation.

A study on remotely-changeable moderators in Bonner sphere spectrometer for irradiation-field characterization in boron neutron capture therapy

As part of the advancements in the characterization of the irradiation field for boron neutron capture therapy, we are developing a Bonner-sphere neutron energy spectrometer for which the liquid moderator is changed remotely. Simulations were performed to find the best combination of liquid moderators and composition of the Bonner spheres. The combination finally adopted was five-layered concentric acrylic spheres with two different liquid moderators and six optimal patterns for moderator injection.

End-to-End Learning for Omnidirectional Stereo Matching With Uncertainty Prior.

In this paper, we propose a novel end-to-end deep neural network model for omnidirectional depth estimation from a wide-baseline multi-view stereo setup. The images captured with ultra-wide field-of-view cameras on an omnidirectional rig are processed by the feature extraction module, and then the deep feature maps are warped onto the concentric spheres swept through all candidate depths using the calibrated camera parameters. The 3D encoder-decoder block takes the aligned feature volume to produce an omnidirectional depth estimate with regularization on uncertain regions utilizing the global context information. For more accurate depth estimation we also propose an uncertainty prior guidance in two ways: depth map filtering and guiding regularization. In addition, we present large-scale synthetic datasets for training and testing omnidirectional multi-view stereo algorithms. Our datasets consist of 13K ground-truth depth maps and 53K fisheye images in four orthogonal directions with various objects and environments. Experimental results show that the proposed method generates excellent results in both synthetic and real-world environments, and it outperforms the prior art and the omnidirectional versions of the state-of-the-art conventional stereo algorithms.

Optimization of water-pumping-injection multi-homocentric sphere neutron spectrometer

The self-developed pumping water multi-layer concentric neutron spectrometer response function exists a ladder shape, which is not conducive to the subsequent neutron spectrum. The FLUKA program is used to optimize the structure of the multi-layer concentric sphere neutron spectrometer. The response functions of stainless steel, aluminum, lead and leaded glass (divided into sandwich and double-layer combination) to the 3He detector were obtained by simulating the inner shell materials with energy in the interval of 0.01 eV–1 GeV. The results show that when the shell material is aluminum and lead glass, the response function does not appear stepped, and the response functions of the other materials appear stepped. Therefore, the use of aluminum and lead glass instead of stainless steel as the casing of the pumped water multi-layer concentric neutron spectrometer can make its energy spectrum measurement more accurate.

Influence of the Homochronism Number of the Liquid in a Spherical Layer on the Heat Exchange in it and its Magnetic Hydrodynamics

Results of numerical simulation of the nonstationary convective heat exchange in the electrically conducting liquid flowing in the space between two concentric isothermal spheres are presented. The influence of the homochronism number of the liquid on the structure of its flow, the temperature and magneto-induction fields in it, and the distribution of local Nusselt numbers in the spherical liquid layer was investigated.

Ultrastructure of spinal anterior horn cells in human Niemann‐Pick type C (NPC) patient and mouse model of NPC with retroposon insertion in NPC1 genes

Niemann-Pick disease type C (NPC) is a neurovisceral lipid-storage disease. Although NPC patients show lipid storage in anterior horn cells of the spinal cord, little information is available regarding the electron microscopic analyses of the morphologies of intra-endosomal lipid like-materials in the anterior horn cells of NPC patients. In this study, we elucidated the intra-endosomal ultrastructures in spinal anterior horn cells in an NPC patient, as well as in mutant BALB/c NPC1-/- mice with a retroposon insertion in the NPC1 gene. These morphologies were classified into four types: vesicle, multiple concentric sphere (MCS), membrane, and rose flower. The percentages of the composition in the NPC patient and NPC1-/- mice were: vesicle (55.5% and 14.9%), MCS (15.7% and 3.4%), membrane (23.6% and 57.1%), and rose flower (5.2% and 24.6%), respectively. Formation of the intra-endosomal structures could proceed as follows: (i) a vesicle or MCS buds off the endosome into the lumen; (ii) when a vesicle breaks down, a membrane is formed; and (iii) after an MCS breaks down, a rose flower structure is formed. Our new finding in this study is that ultrastructural morphology is the same between the NPC patient and NPC1-/- mice, although there are differences in the composition.

H2 production from methane decomposition by fullerene at low temperature

Carbon materials have previously been reported to work as catalysts for hydrogen (H2) production from hydrocarbons. Mechanisms of the catalytic behavior of graphite and carbon black (CB) have often been discussed in literature. Graphite and CB is constructed from mainly 6-membered rings with sp2 bonds. To understand the catalytic behavior of carbon materials for H2 production by methane (CH4) decomposition, the catalytic behavior of fullerenes with 6-membered rings and also those comprising 5- and 7-membered rings with sp2 bonds and their associated mechanisms should be investigated. In this study, the fullerene catalyst activity has been investigated using gas chromatography and the electronic states and nanoscale structures have been analyzed.H2 production started at 400 °C and the H2 production rate gradually increased with time, and the activation energy of the fullerene for H2 production by CH4 decomposition was found to be 166 kJ/mol. Moreover, in situ heating X-ray photon spectroscopy (XPS) measurements showed that the π-π∗ transition signal becomes stronger with increasing temperature above the threshold of 300 °C. The transition of the π electrons to π∗ orbitals upon heating is expected to decompose CH4 absorbed on fullerene. Moreover, transmission electron microscopy (TEM) analysis revealed that the generated carbon atoms from the CH4 decomposition were deposited onto the surfaces of the fullerenes, forming amorphous and layered concentric sphere carbon. Amorphous carbon is reported to not work as a catalyst for CH4 decomposition at around 400 °C. From XPS analysis and TEM observations of these two structures, it is anticipated that the ring structures without 6-membered rings in carbon materials with sp2 bonding contribute to this catalytic behavior for CH4 decomposition at a low temperature of 400 °C.

Chaotic wave dynamics in weakly magnetized spherical Couette flows.

Direct numerical simulations of a liquid metal filling the gap between two concentric spheres are presented. The flow is governed by the interplay between the rotation of the inner sphere (measured by the Reynolds number Re) and a weak externally applied axial magnetic field (measured by the Hartmann number Ha). By varying the latter, a rich variety of flow features, both in terms of spatial symmetry and temporal dependence, is obtained. Flows with two or three independent frequencies describing their time evolution are found as a result of Hopf bifurcations. They are stable on a sufficiently large interval of Hartmann numbers where regions of multistability of two, three, and even four types of these different flows are detected. The temporal character of the solutions is analyzed by means of an accurate frequency analysis and Poincaré sections. An unstable branch of flows undergoing a period doubling cascade and frequency locking of three-frequency solutions is described as well.

Characterising mass-resolved mixing state of black carbon in Beijing using a morphology-independent measurement method

Abstract. Refractory black carbon (rBC) in the atmosphere is known for its significant impacts on climate. The relationship between the microphysical and optical properties of rBC remains poorly understood and is influenced by its size and mixing state. Mixing state also influences its cloud scavenging potential and thus atmospheric lifetime. This study presents a coupling of a centrifugal particle mass analyser (CPMA) and a single-particle soot photometer (SP2) for the morphology-independent quantification of the mixing state of rBC-containing particles, used in the urban site of Beijing as part of the Air Pollution and Human Health–Beijing (APHH-Beijing) project during winter (10 November–10 December 2016) and summer (18 May–25 June 2017). This represents a highly dynamic polluted environment with a wide variety of conditions that could be considered representative of megacity area sources in Asia. An inversion method (used for the first time on atmospheric aerosols) is applied to the measurements to present two-variable distributions of both rBC mass and total mass of rBC-containing particles and calculate the mass-resolved mixing state of rBC-containing particles, using previously published metrics. The mass ratio between non-rBC material and rBC material (MR) is calculated to determine the thickness of a hypothetical coating if the rBC and other material followed a concentric sphere model (the equivalent coating thickness). The bulk MR (MRbulk) was found to vary between 2 and 12 in winter and between 2 and 3 in summer. This mass-resolved mixing state is used to derive the mass-weighted mixing state index for the rBC-containing particles (χrBC). χrBC quantifies how uniformly the non-rBC material is distributed across the rBC-containing-particle population, with 100 % representing uniform mixing. The χrBC in Beijing varied between 55 % and 70 % in winter depending on the dominant air masses, and χrBC was highly correlated with increased MRbulk and PM1 mass concentration in winter, whereas χrBC in summer varied significantly (ranging 60 %–75 %) within the narrowly distributed MRbulk and was found to be independent of air mass sources. In some model treatments, it is assumed that more atmospheric ageing causes the BC to tend towards a more homogeneous mixture, but this leads to the conclusion that the MRbulk may only act as a predictor of χrBC in winter. The particle morphology-independent and mass-based information on BC mixing used in this and future studies can be applied to mixing-state-aware models investigating atmospheric rBC ageing.

Development of stress on quartz grain in illite ceramics during cooling stage of firing

If the volume fraction of quartz in traditional ceramics is higher than 10% then the use of Selsing’s formula is questionable. A model of two concentric spheres, in which the inner sphere is a quartz grain and its spherical cladding is glassy phase, is proposed. The development of the stress on the grain surface during cooling stage of the firing and its influence on the microcracking is described. The tensile tangential stress which is developed between the glass transformation temperature and β → α transition of quartz can be a source of the first microcracking. After this transition, the tangential stress becomes compressive. The radial stress on the grain surface, which is compressive before the β → α transition of quartz, turns into tensile after this transition as a steep change of 40–80 MPa (for 10–50% of quartz content). These changes are in a narrow temperature interval around the β → α transition of quartz passing through zero value and no cracks are expected. This is confirmed with acoustic emission (AE) and short recovery of Young’s modulus. When the β → α transition of quartz is finished and the temperature decreases, the creation of the cracks continues. The radial tensile stress on the grain and in its close vicinity reaches 100–180 MPa, consequently, circumferential cracks can be formed. This is indirectly confirmed with a decrease of Young’s modulus and weak AE activity.