Spherical Mass Research Articles

Modelling self-interacting dark matter substructures – I. Calibration with N-body simulations of a Milky-Way-sized halo and its satellite

ABSTRACT We study evolution of single subhaloes with their masses of ∼109 M⊙ in a Milky Way-sized host halo for self-interacting dark matter (SIDM) models. We perform dark-matter-only N-body simulations of dynamical evolution of individual subhaloes orbiting its host by varying self-scattering cross-sections (including a velocity-dependent scenario), subhalo orbits, and internal properties of the subhalo. We calibrate a gravothermal fluid model to predict time evolution in spherical mass density profiles of isolated SIDM haloes with the simulations. We find that tidal effects of SIDM subhaloes can be described with a framework developed for the case of collision-less cold dark matter (CDM), but a shorter typical time-scale for the mass loss due to tidal stripping is required to explain our SIDM simulation results. As long as the cross-section is less than $\sim \! 10\, \mathrm{cm}^2\,\mathrm{g}^{ -1}$ and initial states of subhaloes are set within a 2σ-level scatter at redshifts of ∼2 predicted by the standard ΛCDM cosmology, our simulations do not exhibit a prominent feature of gravothermal collapse in the subhalo central density for 10 Gyr. We develop a semi-analytic model of SIDM subhaloes in a time-evolving density core of the host with tidal stripping and self-scattering ram pressure effects. Our semi-analytic approach provides a simple, efficient, and physically intuitive prediction of SIDM subhaloes, but further improvements are needed to account for baryonic effects in the host and the gravothermal instability accelerated by tidal stripping effects.

Event‐triggered prescribed performance robust collision‐free capturing control for drag‐free spacecraft system

This paper addresses the capturing control problem of a plug-and-play modularized drag-free spacecraft system, including two spherical proof masses, where the performance constraints, collision risk, uncertain model parameters, unknown external disturbances, and limited communication are considered simultaneously. First, a nonlinear relative dynamics of spherical proof masses with respect to spacecraft is formulated for the capture process. Second, two different prescribed performance event-triggered robust collision-free capturing control strategies are developed to capture the free-floating proof masses successfully. Suppose only the performance metrics on the relative position are considered, and an event-triggered adaptive terminal sliding mode capturing controller is implemented to achieve the capture process within a finite time. Suppose more performance constraints, such as the user predefined capture duration and the performance bounds on both the relative position and the relative velocity, are taken into account, and an event-triggered appointed-time prescribed performance capturing controller is proposed to solve the above issues. In particular, an artificial potential function is utilized to avoid the collision, and a relative threshold event-triggered rule is employed to save the communication source between the controller and the actuator without any Zeno behaviour. The simulation results demonstrate the efficacy and superiority of the proposed method.

Epidermal Cyst on the Head of a Leopard Gecko (Eublepharis macularius)

Abstract An estimated 6-yr-old female leopard gecko (Eublepharis macularius) presented with a raised spherical mass on the head. Grossly, the skin overlying the mass was smooth, with a focal area of ulceration. Histologically, the dermis was expanded by a well-demarcated, poorly cellular single expansile cyst. The cyst was lined by stratified squamous epithelium and was filled with an accumulation of tightly packed lamellar keratin with regular folding, resembling keratinization of the epidermis. Neither cellular nor nuclear atypia was observed, and there were no mitotic figures in the lining epithelium. The histopathological findings were consistent with an epidermal cyst. To the best of the authors' knowledge, an epidermal cyst in the dermis of the head has not been documented previously in a captive leopard gecko.

Forecasting cosmological parameter constraints using multiple sparsity measurements as tracers of the mass profiles of dark matter haloes

ABSTRACT The dark matter halo sparsity, i.e. the ratio between spherical halo masses enclosing two different overdensities, provides a non-parametric proxy of the halo mass distribution that has been shown to be a sensitive probe of the cosmological imprint encoded in the mass profile of haloes hosting galaxy clusters. Mass estimations at several overdensities would allow for multiple sparsity measurements, which can potentially retrieve the entirety of the cosmological information imprinted on the halo profile. Here, we investigate the impact of multiple sparsity measurements on the cosmological model parameter inference. For this purpose, we analyse N-body halo catalogues from the Raygal and M2Csims simulations and evaluate the correlations among six different sparsities from spherical overdensity halo masses at Δ = 200, 500, 1000, and 2500 (in units of the critical density). Remarkably, sparsities associated to distinct halo mass shells are not highly correlated. This is not the case for sparsities obtained using halo masses estimated from the Navarro-Frenk-White (NFW) best-fitting profile, which artificially correlates different sparsities to order one. This implies that there is additional information in the mass profile beyond the NFW parametrization and that it can be exploited with multiple sparsities. In particular, from a likelihood analysis of synthetic average sparsity data, we show that cosmological parameter constraints significantly improve when increasing the number of sparsity combinations, though the constraints saturate beyond four sparsity estimates. We forecast constraints for the CHEX-MATE cluster sample and find that systematic mass bias errors mildly impact the parameter inference, though more studies are needed in this direction.

Spatial dependency of lesion detectability in digital breast tomosynthesis.

X-ray imaging results in inhomogeneous irradiation of the detector and distortion of structures in the periphery of the image; yet the spatial dependency of tomosynthesis image-quality metrics has not been extensively investigated. In this study, we use virtual clinical trials to quantify the spatial dependency of lesion detectability in our lab's next-generation tomosynthesis (NGT) system. Two geometries were analyzed: a conventional geometry with mediolateral source motion, and a NGT geometry with T-shaped motion. Breast parenchymal texture was simulated using an open-source library with Perlin noise using 400 random seeds and three breast densities. Spherical mass lesions were inserted in the central slice of the phantoms using the voxel additive method. Image acquisition was simulated using in-house ray-tracing software and simple backprojection was performed using commercial reconstruction software. Lesion detectability with Channelized Hotelling Observers (CHOs) was analyzed using receiver operating characteristic curves to measure the detectability index (d') at 154 unique locations for the lesions. We also divided images into three non-overlapping regions (differing in terms of distance from the chest wall). At the 0.05 level of significance, there was a statistically significant difference between the geometries in terms of d' in one of the three regions, with the T geometry offering superior detectability. Examining all 154 lesion locations, the T geometry was found to offer lower spread (standard deviation) in d' values throughout the image area, and superior d' at 83 of 154 locations (53.9%). In summary, the T geometry enables superior lesion detection and mitigates anisotropies.

Effect of finite mass on phononic band structure of face centered pentamodal lattice

Owing to the unique and fascinating property of very high resistance to compressibility in comparison to relatively very small resistance to shear deformation, pentamode lattice has become a coveted form of the metamaterial. Ideally, the connection points in the pentamode lattice are infinitely small which renders it impractical to realize physically. In the present paper, a new pentamode lattice is proposed having a finite spherical mass at the connection point. Effect of added mass at the connection points on the phononic band structure of the proposed pentamode lattice is investigated. Numerical modeling of the proposed lattice is done using COMSOL Multiphysics and dispersion relation of the proposed model is obtained using appropriate boundary conditions. From the dispersion diagram of the proposed pentamode lattice, relative band gap is identified. Effect of various parameters such as Young’s Modulus, density, Poisson’s ratio and geometry of the lattice unit cell on the dispersion relation is studied. It is observed that the relative bandwidth is not affected by the material variation; however, the geometric properties have slight influence on it.

Acoustic Method for Multiple Free Metallic Particle Recognition in GIS/GIL

Free metallic particles are the main factor inducing flashover incidents and threatening the safety of gas-insulated switchgear (GIS) and gas-insulated transmission line (GIL) devices. Acoustic diagnosis is widely used to detect free metal particles due to its high sensitivity, but it generally fails under multiple particle conditions because of the overlap of acoustic signals. This paper proposes a new method of acoustically recognizing multiple free metallic particles. The pattern of t-Normalized N that can be used to distinguish single/multi-particles is determined first. Second, each particles neighboring collision signals are extracted from raw data by the established physical relation between adjacent collision signals. Finally, the free metal spherical double-particles mass and density values are calculated as per the numerical connection between adjacent collision signals. The proposed method is validated in a scale concentric hemisphere platform. The results of this work may provide a workable reference for GIS free metal multi-particle monitoring.

Tumor ósseo multilobular sinonasal em uma égua jovem - relato de caso

ABSTRACT A two-year old mare was referred to the veterinary hospital because of an increase in the volume of the head on the frontal and left side as well as dyspnoea. Radiographic examination showed an osseous radiopaque spherical mass, with a granular aspect, affecting the left frontal, maxillary, and nasal bones. A frontal sinusotomy was performed, and the frontal sinus was found to be totally obliterated by a granular, yellowish, and hard mass containing multiple spicules. Histologically, it was a multilobulated osseous neoplasia diagnosed as a multilobular osseous tumour. Because of poor prognosis, the animal was euthanized. Necropsy showed that the left nasal cavity was totally effaced as were the nasal sinuses and that the nasal turbinate disappeared because of the hard, yellowish, and granular mass measuring 20 × 14 × 14 cm that surrounded the molar teeth and extended to the cribriform plate. This tumour, which was described only once in horses, is more frequently observed in older dogs’ skulls, and must be considered as a differential diagnosis in horses with sinonasal diseases.

Dosimetric dependencies on target geometry and size in radioiodine therapy for differentiated thyroid cancer

Purpose Radioiodine therapy is used in most disease stages for differentiated thyroid cancer. Its success depends on several factors, such as lesion size, completeness of surgery, extent of metastasis and tumoural iodine avidity. We aimed to investigate the importance of non-spherical geometries and size of metastases and thyroid remnants for the absorbed dose delivered. Methods Absorbed doses and energy depositions from homogeneously distributed iodine-131 in clinically relevant geometries and sizes were calculated using Monte Carlo simulations with MCNP6. A total of 162 volumes with different sizes and geometries corresponding to spheres, and prolate or oblate spheroids were simulated. Results Oblate and prolate spheroids had worse radiation coverage compared to spheres for equal masses, up to a difference of 38% for the most eccentric oblate spheroids and smallest masses simulated (a micrometastasis of mass 0.005 g). The differences in coverage could be explained by different volume - to - surface - area ratios of the spheroids. The impact of size alone caused up to 71% lower absorbed doses per decay in a spherical target mass of 0.005 g compared to 50 g. Conclusions While the iodine avidity, and therefore the total amount of decays, is the predominant contributing factor to absorbed dose in radioiodine therapy, eccentric spheroids and small target sizes can receive substantially lower absorbed doses from the same administration of radioiodine.

The First Isospora Species (Apicomplexa: Eimeriidae) Described from the Northern Yellow-Shafted Flicker (Colaptes auratus luteus) in Ontario, Canada.

Members of the genus Isospora commonly infect a wide variety of wild birds. By combining morphometric and genetic data, we are able to differentiate and describe a new apicomplexan parasite, Isospora picoflavae n. sp., from the Northern Yellow-shafted Flicker (Colaptes auratus luteus) in Ontario, Canada. Unsporulated oocysts were observed in intestinal contents obtained during necropsy; these oocysts completed exogenous sporulation within 7days at room temperature. Complete nuclear 18S rDNA and complete mitochondrial genome sequences were obtained from this previously undescribed Isospora sp. to compare with related coccidia. Sporulated oocysts were subspherical in shape measuring an average of 22.7 × 21.7μm (n = 53; mean shape index 1.05) containing a near-spherical polar granule. Sporocysts were ovoidal to ellipsoidal in shape, measuring an average size of 17.0 × 10.5μm (n = 9; mean shape index 1.62). Sporocyst residuum was concentrated in an irregular, spherical mass in the middle of each sporocyst. The isolated oocysts differed morphologically from other Isospora species reported to infect members of the family Picidae. Based on phylogenetic analyses using either combined nuclear 18S rDNA and mitochondrial cytochrome c oxidase I (COI) sequences or complete mitochondrial genome sequences, this Isospora sp. n. isolated from the Northern Flicker grouped within a clade containing Isospora species described from various passeriform hosts. Based on combined morphological and molecular data, the oocysts found in the gastrointestinal contents of Colaptes auratus luteus represent a new species of Isospora named herein as Isospora picoflavae n. sp.

Interferometric sphere surface metrology with cylindrical reference for precision topography.

We demonstrate a method for measuring a surface map of a spherical body with interferometric optical point sensors while rotating the test subject. The setup takes advantage of the excellent performance of heterodyne interferometry at nanometer levels and suppression of common-mode errors, as a cylindrical mirror mounted adjacent to the sphere is used as a reference. Future space based missions for gravitational wave research demand an improved inertial reference sensor with reduced acceleration noise levels. Spherical test masses can enable increased performance by suspension-free operation, contrary to cuboid solutions suffering from cross-coupling of attitude control noise into test mass position. However, interferometric readout is affected by surface irregularities and test mass attitude. An accurate surface map for compensation of the center of gravity readout should be established, by characterization either a priori or in-flight, when optical path length changes due to the surface occur in the measurement bandwidth.

Multiple cardiac metastases from urothelial carcinoma case report

BackgroundCardiac metastases are rare and frequently remain undiagnosed due to the absence of clinical signs in the majority of cases. Malignancies found to most commonly metastasise to the heart include lung carcinoma, breast carcinoma and lymphoma, while urothelial carcinoma is a rare cause of cardiac metastasis. The patient presented with pyrexia, a rare presentation of metastatic cardiac involvement. Single metastatic lesions are mainly reported in the literature, while multiple metastatic deposits such as in this case are less common.Case presentationA 74-year-old gentleman presented with frequent febrile spikes, a month after undergoing a nephroureterectomy for poorly differentiated urothelial carcinoma. No febrile source was identified, and a computed tomography identified two cardiac lesions. A transthoracic echocardiogram could not detect the cardiac lesions; therefore, cardiac magnetic resonance (CMR) imaging was performed. Three spherical intramyocardial masses were noted at the basal septum, LV apex and the anteromedial papillary muscle. The lesions demonstrated signal characteristics suggestive of cardiac metastases (high fluid content, absence of fat, presence of a surrounding rim of increased extravascular space, absence of deformation within the masses) from the previously resected urothelial carcinoma. The patient was palliated, and he shortly succumbed to his condition.ConclusionsUrothelial carcinoma is an exceedingly rare cause of cardiac metastasis. CMR is an important imaging modality for localisation and characterisation of suspicious cardiac lesions, aiding in the diagnosis of cardiac metastasis.

Physics-informed regularisation procedure in neural networks: An application in blast protection engineering

Machine learning offers the potential to enable probabilistic-based approaches to engineering design and risk mitigation. Application of such approaches in the field of blast protection engineering would allow for holistic and efficient strategies to protect people and structures subjected to the effects of an explosion. To achieve this, fast-running engineering models that provide accurate predictions of blast loading are required. This paper presents a novel application of a physics-guided regularisation procedure that enhances the generalisation ability of a neural network (PGNN) by implementing monotonic loss constraints to the objective function due to specialist prior knowledge of the problem domain. The PGNN is developed for prediction of specific impulse loading distributions on a rigid target following close-in detonation of a spherical mass of high explosive. The results are compared to those from a traditional neural network (NN) architecture and stress-tested through various data holdout approaches to evaluate its generalisation ability. In total the results show five statistically significant performance premiums, with four of these being achieved by the PGNN. This indicates that the proposed methodology can be used to improve the accuracy and physical consistency of machine learning approaches for blast load prediction.

Black to white transition of a charged black hole

We present an exact solution of the Maxwell-Einstein equations, which describes the exterior of a charged spherical mass collapsing into its own trapping horizon and then bouncing back from an anti-trapping horizon at the same space location of the same asymptotic region. The solution is locally but not globally isometric to the maximally extended Reissner-Nordstr\"{o}m metric and depends on seven parameters. It is regular, and defined everywhere except for a small region, where quantum tunnelling is expected. This region lies outside the mass: the mass-bounce and its near exterior are governed by classical general relativity. We discuss the relevance of this result for the fate of realistic black holes. We comment on possible effects of the classical instabilities and the Hawking radiation.

Event-triggered adaptive terminal sliding mode tracking control for drag-free spacecraft inner-formation with full state constraints

This paper investigates the reconstruction and maintenance of the inner-formation system for an innovative drag-free spacecraft with double spherical test masses in consideration of unknown model uncertainties, external disturbances, and actuator saturation. First, spherical test mass 1 is prescribed as the ‘leader’ of the inner-formation system, which is freely floating in the nearly pure gravitational orbit without any control. The nonlinear relative orbit dynamics of the outer spacecraft and spherical test mass 2 with respect to spherical test mass 1 is deduced and the micro configuration of the inner-formation system is introduced. For the outer spacecraft, the aim is to track the spherical test mass 1 in real-time, such that both the center of masses coincided with each other. For the spherical test mass 2, the goal is tracking the reference trajectory, which is designed as a space circular fly-around spherical test mass 1 based on the Clohessy-Wiltshire equation. The state constraints caused by the limit cavity size are analyzed. Second, to achieve these goals with satisfied performance, an event-triggered adaptive terminal sliding mode tracking control strategy is developed for the inner-formation. The adaptive terminal sliding mode technique is implemented to overcome the model uncertainties and external disturbances and to accomplish the reconstruction process in a finite time. Two kinds of barrier functions are utilized to tackle the state constraints. The relative threshold event-triggered mechanism is embedded to save the computation source onboard, evidently. The simulation results demonstrate the efficacy and superiority of the proposed method.

Nanoscale trace-element zoning in pyrite framboids and implications for paleoproxy applications

Abstract Pyrite framboids (spherical masses of nanoscale pyrite) are among the earliest textures of pyrite to form in sediments. It has been proposed that their trace-element (TE) contents can be used to track the TE composition of the water column in which they formed. However, it is not clear how these TEs are associated with the framboidal pyrite grains. For instance, it is important to know whether they are incorporated uniformly or are enriched in different regions of the framboid. We used high-resolution scanning transmission electron microscopy to identify chemical zoning within pyrite framboids. We found that initial, nanoscale pyrite euhedral crystals, which make up the volumetric majority of the framboids, are covered/infilled by later pyrite that templates on the earlier pyrite. Further, this later pyrite is enriched in TEs, suggesting that many TEs are incorporated in pyrite relatively late (during early diagenesis; not in the water column). This observation suggests that although chemical analyses of pyrite framboids may provide ocean-water chemistry trends through time, the details are complex. Specifically, the TEs found in pyrite may be linked to adsorption onto organic matter, detrital material, and authigenic minerals such as Fe- and Mn-oxide phases followed by desorption in the sediments or release via dissolution and incorporation into pyrite as overgrowths on the initial nanoscale euhedral crystals that make up framboids. While the use of pyrite chemistry to understand past ocean conditions remains promising, and even diagenetic additions may not preclude the utility of pyrite for reconstructing ancient ocean conditions, care must be taken in interpretations because the end concentration may be influenced by diagenesis.

A Case of a Giant Sublingual Epidermoid Cyst Removed by Content Reducing Surgery

The frequency of epidermoid cysts in the maxillofacial region is relatively low. Reported: a case of a giant sublingual epidermoid cyst on the floor of the mouth. Case: 38-year-old woman. Chief complaint: oral swelling and respiratory distress. History of present illness: no special notes. Current medical history: she was aware of swelling of the floor of the mouth six months before visiting our department and was referred to our department because of increasing size. Present symptoms: at the time of examination, forced respiration and dysarthria were observed and a spherical soft elastic and well-defined mass was observed on the floor of the mouth. Due to the lesion, the tongue was displaced to the pharyngeal side and the tip of the tongue could not be confirmed. Imaging tests revealed a 65 mm × 76 mm × 54 mm well-defined mass on the mylohyoid muscle, and a dermoid or epidermoid cyst was suspected. Based on the clinical diagnosis of the cyst, the bulk of the cyst contents was reduced under general anesthesia, and the cyst was removed by intraoral surgery. The pathological diagnosis was an epidermoid cyst. For sublingual giant epidermoid cysts, removal by content reducing surgery was considered to be effective.

Rare as hen’s teeth: laparoscopic management of primary pelvic hydatid cyst

Hydatid disease is a zoonotic parasitic disease most frequently caused by echinococcus granulose Primary peritoneal hydatidosis is very rare. We report a case of primary hydatid disease of the intraperitoneal pelvic space. A 22-year-old male patient presented with a history of abdominal pain since 5 months. Abdominal examination revealed a smooth, firm, mildly tender, non-mobile lump in suprapubic region, on digital rectal examination, a smooth spherical mass was felt anteriorly and laterally outside the rectal wall, rectal mucosa was normal. All routine investigations including liver function tests were within normal limits Computed tomography scan of the whole abdomen showed giant cyst of 10×10 cm with multiple well-defined cysts in rectovesical pouch. Diagnostic laparoscopy was performed. The liver, spleen, mesentery, omentum was found to be normal. A large tense hydatid cyst was noted in the pelvic cavity. Partial peri-cystectomy with endo-cystectomy was performed. Postoperative period was uneventful and patient was discharged on 4th postoperative day. Primary intra-abdominal but extra-peritoneal localization has been reported in only 0.2-2% cases making it a very rare entity. The treatment of choice for pelvic hydatid cyst is principally a careful surgical excision. Here with minimum invasive technique this case was operated and results were excellent.

Octet lattice-based plate for elastic wave control

Motivated by the importance of lattice structures in multiple fields, we numerically investigate the propagation of flexural waves in a thin reticulated plate augmented with two classes of metastructures for wave mitigation and guiding, namely metabarriers and metalenses. The cellular architecture of this plate invokes the well-known octet topology, while the metadevices rely on novel customized octets either comprising spherical masses added to the midpoint of their struts or variable node thickness. We numerically determine the dispersion curves of a doubly-periodic array of octets, which produce a broad bandgap whose underlying physics is elucidated and leveraged as a design paradigm, allowing the construction of a metabarrier effective for inhibiting the transmission of waves. More sophisticated effects emerge upon parametric analyses of the added masses and node thickness, leading to graded designs that spatially filter waves through an enlarged bandgap via rainbow trapping. Additionally, Luneburg and Maxwell metalenses are realized using the spatial modulation of the tuning parameters and numerically tested. Wavefronts impinging on these structures are progressively curved within the inhomogeneous media and steered toward a focal point. Our results yield new perspectives for the use of octet-like lattices, paving the way for promising applications in vibration isolation and energy focusing.

A Hypermetabolic Subclavian Artery Aneurysm

(A) Chest computed tomography (CT) was performed in a 75 year old man who complained of dyspnoea. CT revealed a 43 mm diameter left subclavian artery aneurysm (arrow). As kidney cancer was also suspected in this patient, 18F-fluorodeoxyglucose (18FFDG) positron emission tomography CT was performed, which revealed unexpected focal and intense 18FFDG uptake of the suspected aneurysm. (B) Magnetic resonance imaging showed a well encapsulated heterogeneous spherical mass (arrow), hyperintense on T2 attenuated images, impinging on the subclavian artery, which allowed for a diagnosis of pleural schwannoma. This rare tumour should be kept in mind for differential diagnosis of an intrathoracic peri-arterial lesion.Image 1