Surface Of Pebbles Research Articles

Metabasite Artefacts from the Neolithic Settlement at Brno-Holásky/Tuřany Compared to the Potential Source Rocks within the Želešice Metabasite Body Based on Petrography and Mineralogy

The Želešice metabasite body served as a significant area for the exploitation of raw material for the production of polished stone tools in the Neolithic. This study is based on petrographical and mineralogical comparisons of the artefacts from the Želešice-type metabasite collected in the Neolithic settlement (and workshop) at Brno-Holásky/Tuřany with the various rock types occurring around the Želešice metabasite body. The determination of the most probable locations of Neolithic exploitation within the Želešice metabasite body is given. The three main rock varieties of the artefacts from Želešice metabasite have been specified. They match well in their petrography and mineralogy with the rock types determined in the source region. The artefacts with pebble surfaces were most likely obtained from the nearby Bobrava riverbed.

Characterization of aged Li4SiO4 pebbles performance

Many studies and research have been carried out in the recent years to identify which breeder material and (in which) form, solid or liquid, are most suitable to be used in the Breeder Blanket (BB) modules. Nonetheless, the choice of a stable material, with high thermal conductivity and melting point remains unsolved and becomes even more complex when durability is considered. The breeder material must guarantee that the thermo-mechanical properties change as little as possible under environmental and operating conditions. The aim of this study is to investigate the ageing effects on the mechanical behaviour of lithium orthosilicate (Li4SiO4) in form of pebbles. The pebbles had been produced at the University of Pisa at room temperature by a hydrolytic sol-gel supported drip casting method and subsequently stored for 4 years in an environment simulating normal storage (i.e., standard condition). These pebbles of about 1.2–1.4 mm diameter have been subjected to uniaxial compression tests, without radial constraints, and SEM analysis. The results obtained were compared to those of non-aged pebbles to highlight the degradation caused by the ageing. SEM examination of aged pebbles showed increased porosity and a pebble surface that was not entirely homogeneous and uniform. This affected the crack shapes on the contact surface and the crushing load.

Oral Lymphatic Malformations: A 21-Year Retrospective Study in a Single Institution.

Introduction. Oral lymphatic malformations are uncommon lesions. This study assessed the clinicopathological and sociodemographic features of oral lymphatic malformations in a Brazilian oral pathology service. Methods. Between 2000 and 2021, all oral lymphatic malformations diagnosed in a single oral pathology service were selected for the study. Clinical data, such as age, sex, site of the lesion, clinical presentation, diagnosis clinical, and the type of biopsy were recorded from the patient's clinical charts. Results. From 7554 oral lesions, 17 (0.22%) were oral lymphatic malformations. This lesion similarly affected both sexes, and the mean age of the patients was 16.5 years. The tongue was the most common site (n = 13; 76%). The mean size of the lesions was 17 mm. Oral lymphatic malformations were asymptomatic for 29% of the patients. Clinically, most lesions appeared as a reddish, sessile nodule, with a pebbly surface. In addition, the clinical and histopathological diagnoses agreed for most lesions (n = 11; 64%). The type of biopsy performed was excisional in 41% of lesions. Conclusions. In summary, oral lymphatic malformations present a low prevalence among the oral lesions diagnosed in an oral pathology service. Moreover, they affect equally both sexes, especially young patients, and usually appear as an asymptomatic or symptomatic nodular swelling on the tongue.

ORAL LYMPHATIC MALFORMATIONS: A 21-YEAR RETROSPECTIVE STUDY IN AN ORAL PATHOLOGY SERVICE

Objective This study aimed to analyze the clinicopathological and sociodemographic features of oral lymphatic malformations (OLM) in a Brazilian oral pathology service. Study Design Between 2000 and 2021, all cases of OLM diagnosed in a single oral pathology service were selected for the study. Clinical data, such as age, sex, site of the lesion, clinical presentation, clinical diagnosis, and type of biopsy were recorded from the patients' clinical charts. Results From 7,565 lesions, 17 (0.22%) were OLM. The cases similarly affected both genders, and the mean age of the patients was 16.5 years. The tongue was the most involved site (n = 13; 76.5%). The mean size of the lesions was 17.3 mm. OLM were asymptomatic for 29.4% of the patients. Clinically, most cases appeared as a reddish, sessile nodule, with a pebbly surface. In addition, the clinical and histopathological diagnosis agreed in most cases (n = 11; 64.7%). The type of biopsy performed was excisional in 41.2% of the cases. Conclusion Thus, this study indicates that OLM are rarely diagnosed in this population. Moreover, they affect equally both sexes, especially young patients, and usually appear as nodular and asymptomatic swellings on the tongue. This study aimed to analyze the clinicopathological and sociodemographic features of oral lymphatic malformations (OLM) in a Brazilian oral pathology service. Between 2000 and 2021, all cases of OLM diagnosed in a single oral pathology service were selected for the study. Clinical data, such as age, sex, site of the lesion, clinical presentation, clinical diagnosis, and type of biopsy were recorded from the patients' clinical charts. From 7,565 lesions, 17 (0.22%) were OLM. The cases similarly affected both genders, and the mean age of the patients was 16.5 years. The tongue was the most involved site (n = 13; 76.5%). The mean size of the lesions was 17.3 mm. OLM were asymptomatic for 29.4% of the patients. Clinically, most cases appeared as a reddish, sessile nodule, with a pebbly surface. In addition, the clinical and histopathological diagnosis agreed in most cases (n = 11; 64.7%). The type of biopsy performed was excisional in 41.2% of the cases. Thus, this study indicates that OLM are rarely diagnosed in this population. Moreover, they affect equally both sexes, especially young patients, and usually appear as nodular and asymptomatic swellings on the tongue.

Pebble tools and colored rocks in the collection of the Late Palaeolithic site of Eliseevitchi 1 stored in Kustkamera Museum

The article presents a functional definition of several finds made by K.M. Polikarpovich at the initial stage of studying the most interesting and complex site of the Late Upper Paleolithic — Eliseevichi 1. Previously, a large number of stones found in the ash lens in the excavation area 2 (1936) were noted only as a specific feature of the cultural layer, but their categorical analysis was not carried out. This study focuses on the tools identified in the assemblage of «crystalline rocks» (hammerstones and tools for crushing raw materials for mineral colorants, including those with painted surfaces), and probably non-utilitarian objects — stones with colored blurs. Although the described groups consist of a small number of finds (see Table 1), they display high level of homogeneity of features on intra-group level, and the tools inclusion in the general production context of the industry as well as. This represents, on the one hand, a full cycle of the production of tools from local cretaceous flint, and on the other hand, all stages of the production of mineral colorants, from splitting pieces and burning them to “pencils” with traces of use, also founded in the collection. While the previous long-term interdisciplinary studies of the Eliseevichi 1 site established the complex character of the cultural layer formation, its accumulation over repeated visits to the cape by ancient groups, possibly even within several millennia, however, the assemblage of artifacts of granular rocks from the excavation space 2 (1936) seems to be a rather homogeneous complex, characterized by the stylistic unity, manifested through the coloring of individual surfaces of tools and split pebbles.

Tools for Stone Raw Material Treatment in the Initial and Early Upper Palaeolithic Industries of the Ust-Karakol-1 Site (Excavation Area, 1986)

Purpose. This article studies tools for stone raw material treatment found in the Ust-Karakol-1 site collection in Altai (excavation area, 1986).Results. We have established that the latest industry of this site, tentatively correlated with the Middle stage of the Upper Palaeolithic, includes one hammer made of the endcore of fine-grained sedimentary rock. We have identified a pebble hammer flake and retouchers made of coarse-grained sedimentary rocks in the Ust-Karakolian horizon of the Early Upper Palaeolithic. The site inhabitants used flattened and end natural surfaces of pebbles’ fragments for retouching, in some cases the base was additionally modified by flakes. We only recorded tools for pecking on the horizons of the Early Upper Palaeolithic Kara-Bomian tradition. These tools are distinguished by the secondary use of cores and technical flakes as bases, the choice of workpieces from homogeneous fine-grained volcanic and sedimentary rocks, and the use of subrectangular sections of the flaked surface with pronounced edges. These tools are characterized by several working zones and intensive modification of the original relief as a result of utilization.Conclusion. We consider the noted features of percussive-abrasive tools at different stages of site settlement are conditioned by technological and raw material strategies of the bearers of the Early and Initial Upper Palaeolithic traditions, their economic and cultural stereotypes.

Multifocal Gingival Squamous Cell Papilloma: A Case Report and Literature Review

Squamous Cell Papilloma (SCP) is a benign, asymptomatic, exophytic cauliflower-like growth of mucosal mass. It is mostly associated with Human Papilloma Virus (HPV) subtypes 6 and 11, and has a very low virulence and infectivity rate. The papillomas are commonly known as warts or verrucas when found on the skin. The typical lesion is a single mass with finger-like extensions, resembling a soft, pedunculated growth supported by a stem or stalk. If keratin, a skin protein, accumulates around the lesion, the projections can be long and pointed or short and rounded. Intraorally, the most common sites of occurrence are the tongue, lips, buccal mucosa, palate, and uvula. Hereby, the author present a case report of 25-year-old male patient with a 4x9 mm exophytic growth exhibiting a pebbled surface in the upper left first premolar region, with no signs of radiographic bone loss. Additionally, smaller pinpoint lesions were observed bilaterally in the interdental region of the first and second maxillary molars. A nevus on the right side of the face was also noted. Histological analysis confirmed the diagnosis of SCP. The presence of multifocal gingival squamous papilloma, along with an extraoral nevus, represents a novel finding that warrants reporting. The gingival lesion in the maxillary left first premolar region was surgically excised, along with 1 mm of healthy surrounding gingiva. This resulted in complete healing, and no recurrence was observed during the 12-month follow-up period.

Granulomatosis with polyangiitis in gingiva: A rare case of isolated presentation.

Granulomatosis with polyangiitis (GPA) is a rare autoimmune disease characterized by necrotising granulomatous inflammation of upper and lower respiratory tract, vasculitis and glomerulonephritis. This ailment may present with cough, haemoptysis, sinusitis, nasal deformity, skin lesions, malaise, fever, anorexia, and weight loss. Oral manifestation includes strawberry gingivitis, which is a pathognomonic clinical presentation. Here, we present a case of GPA in gingiva as the first manifestation. Clinical examination of the oral cavity revealed granular, erythematous gingival enlargement in the lower anterior teeth region involving papilla, marginal and attached gingiva with shiny and pebbled surface. Histopathological examination showed pseudoepitheliomatous hyperplasia with vasculitis and inflammation in the connective tissue, neutrophilic infiltration and abscess formation with haemorrhage were noted. Laboratory investigations revealed Proteinase 3 (PR3) antigen and Glomerular basement membrane (GBM) antigen were positive. Clinical, histopathological and laboratory investigations enabled the diagnosis of Granulomatosis with Polyangiitis. We present this rare case report of GPA with primary manifestation in gingiva.

Explicit modeling of pebble temperature in the porous-media model for pebble-bed reactors

In this study, a multiscale model has been developed to include an explicit pebble-temperature model nested in the porous-media model for pebble-bed reactor applications. The multiscale solid-phase energy balance model, including the pebble surface energy balance equation and an explicit modeling of pebble temperature, can predict the macroscopic (pebble bed) and microscopic (pebble) temperature distributions under both steady-state and transient conditions. The proposed multiscale model is solved in a fully coupled manner using the Newton-Krylov method, and therefore iterations between the macroscopic (pebble-bed-scale) and microscopic (pebble-scale) model are avoided. Extensive code verifications, validation, and demonstrations have been performed for this newly developed model. By explicitly modeling pebble temperatures, this new model addresses a major deficiency of the basic porous-media model, which assumes homogeneous solid-phase temperature and is not appropriate for pebble-bed reactor design and safety analyses.

Verrucous carcinoma of the conjunctiva – A rare variant of squamous cell carcinoma

Verrucous carcinoma is a rare and indolent variant of squamous cell carcinoma. We report the first histopathologically confirmed case of verrucous carcinoma of the conjunctiva. An 85-year-old male presented with complaint of mass in interpalpebral region in the left eye. Examination revealed a single, sessile, pale-colored exophytic mass with a pebble surface approximately 15 mm × 10 mm in size. Patient did not respond to topical therapy and underwent complete excision of the lesion with biopsy. Histopathological examination of the excisional biopsy revealed a diagnosis of verrucous carcinoma. The patient was healthy with no signs of recurrence at 2 years follow-up.

HTR-10 OTTO Cycle Depletion Simulation Using Discrete Element Method Coupled Monte Carlo

Pebble bed reactor core contains 27,000 pebbles placed in a random position. Since the pebble insertion relies on gravity, the pebble placement pattern is irregular. Discrete Element Method used to simulate the pebble interaction and pebble movement during HTR-10 operation. Even though pebbles distributed randomly, the random generation of pebble positions used in most research does not mimic the actual pebble position and pebble surface contact. The Discrete Element Method provides a realistic interpretation of the pebble position by considering the pebble surface contact and gravity force. Each pebble coordinates from the Discrete Element Method obtained to construct Monte Carlo geometry of the HTR-10 core realistically. By coupling the DEM simulation with Monte Carlo simulation, it is possible to calculate the depletion while considering the core dynamic characteristic. The OTTO recirculation depletion calculation scheme with steady 10MW power for 368 days was constructed and demonstrated in this work. The DEM coupled Monte Carlo method allow one to track and predict each depleted fuel composition. Although the flux distribution change is slight in every timestep, the relation between flux and depleted U235 and Xe135 composition deserves to be taken into account. The calculation model in this work is comparable with the other calculation, but the timestep adjustment is needed to provide more accurate and representative results. Flux calculation and depletion simulation performed using the OpenMC program with ENDF/B-VIII.0 cross-section data. Please refer to digital version to view graph.

Evaluation of pebble scanning strategies for fuel qualification by simple simulated radiography

Reactor designs using tristructural-isotropic (TRISO) particles in pebble fuel forms have been developed in multiple programs and are now being designed and deployed by several companies around the world. Fuel pebbles for these designs commonly contain an inner fueled zone packed with TRISO particles and a fuel-free zone on the surface of the pebble to protect the particles within. Therefore, qualification of pebbles for use in a reactor commonly requires determination that there are no TRISO particles within a given minimum distance to the pebble surface. This determination may be made non-destructively by pebble radiography, in which a series of x-ray projections of the pebble are acquired. In this work, a method to create and image representative digital pebbles was developed to allow for rapid testing of various pebble radiography strategies to evaluate their effectiveness in detecting escapee particles. Using this method, imaging strategies in two and three dimensions were tested with fixed and adaptive angular distributions. It was found that an adaptive two-dimensional pebble scanning strategy was the most effective for fuel pebble qualification.

English

Lymphangioma is a rare developmental hamartomatous malformation of the lymphatic vessels. It usually occurs in the dorsum of the tongue resulting in macroglossia that can interfere with speech and mastication. About 10 % of lymphangiomas can occur in the buccal mucosa resulting in multiple discrete vesicle like structures resembling frogs-egg or pebbly surface or Tapioca pudding like appearance containing clear proteinaceous rich fluid. They also can appear reddish or reddish - purple coloured pebbly surface and are completely asymptomatic. In due course can result in painless, asymptomatic soft tissue swelling on the face resulting in facial disfigurement. Such a rare occurrence of lymphangioma reported in the cheek of a 52-year-old female and treated by ultrasonographic guided Bleomycin sclerotherapy is discussed here. A lymphangioma is a misnomer as it is not a tumour of lymphatic vessels. It is a developmental hamartomatous malformation of the lymphatic vessels that usually clinically becomes more apparent only after second year of age. Clinically they appear as painless soft swellings of the face resulting in facial asymmetry. Patients affected by lymphangioma usually report to the physician or a dentist and complain only of cosmetic defect.1

Sub-lithic photosynthesis in hot desert habitats.

In hyper-arid soil environments, photosynthetic microorganisms are largely restricted to hypolithic (sub-lithic) habitats: i.e., on the ventral surfaces of translucent pebbles in desert pavements. Here, we combined fluorometric, spectroscopic, biochemical and metagenomic approaches to investigate in situ the light transmission properties of quartz stones in the Namib Desert, and assess the photosynthetic activity of the underlying hypolithic cyanobacterial biofilms. Quartz pebbles greatly reduced the total photon flux to the ventral surface biofilms and filtered out primarily the short wavelength portion of the solar spectrum. Chlorophylls d and f were not detected in biofilm pigment extracts; however, hypolithic cyanobacterial communities showed some evidence of adaptation to sub-lithic conditions, including the prevalence of genes encoding Helical Carotenoid Proteins, which are associated with desiccation stress. Under water-saturated conditions, hypolithic communities showed no evidence of light stress, even when the quartz stones were exposed to full midday sunlight. This initial study creates a foundation for future in-situ and laboratory exploration of various adaptation mechanisms employed by photosynthetic organisms forming hypolithic microbial communities.

The importance of the surface roughness and running band area on the bottom of a stone for the curling phenomenon

Curling is a sport in which players deliver a cylindrical granite stone on an ice sheet in a curling hall toward a circular target located 28.35 m away. The stone gradually moves laterally, or curls, as it slides on ice. Although several papers have been published to propose a mechanism of the curling phenomenon for the last 100 years, no established theory exists on the subject, because detailed measurements on a pebbled ice surface and a curling stone sliding on ice and detailed theoretical model calculations have yet to be available. Here we show using our precise experimental data that the curl distance is primarily determined by the surface roughness and the surface area of the running band on the bottom of a stone and that the ice surface condition has smaller effects on the curl distance. We also propose a possible mechanism affecting the curling phenomena of a curing stone based on our results. We expect that our findings will form the basis of future curling theories and model calculations regarding the curling phenomenon of curling stones. Using the relation between the curl distance and the surface roughness of the running band in this study, the curl distance of a stone sliding on ice in every curling hall can be adjusted to an appropriate value by changing the surface roughness of the running band on the bottom of a stone.

Preparation of Li4TiO4-Li2TiO3 core-shell ceramic pebbles with thick shells and high strength through an improved granulation method

The instability of Li4TiO4 to carbon dioxide (CO2) and moisture (H2O) was considered to be the main obstacle to its practical application as a tritium breeding material. Using Li2TiO3 ceramic coating as a physical barrier wrapped on the surface of Li4TiO4 pebbles was still considered to be the optimal solution. At present, increasing the thickness and strength of the Li2TiO3 coating to increase the service life of this core-shell pebble has become an urgent problem to be solved. In this study, we successfully wrapped a thick and uniform Li2TiO3 coating on the Li4TiO4 pebble by an optimized granulation method assisted only by polyvinylpyrrolidone (PVP). The Li4TiO4-Li2TiO3 core-shell pebbles have high shell thickness (∼370 µm), relatively high wall thickness uniformity (78.86±3.07%) and good sphericity (90.72±1.88%) with a crush load of 47.73±1.49 N. It was demonstrated that PVP not only plays the role of bridge bonding between powders but also serves as a template to induce powder to be assembled layer by layer to form a uniform core-shell structure.

Keep your head down: Maintaining gait stability in challenging conditions.

Peripheral vision often deteriorates with age, disrupting our ability to maintain normal locomotion. Laboratory based studies have shown that lower visual field loss, in particular, is associated with changes in gaze and gait behaviour whilst walking and this, in turn, increases the risk of falling in the elderly. Separately, gaze and gait behaviours change and fall risk increases when walking over complex surfaces. It seems probable, but has not yet been established, that these challenges to stability interact. How does loss of the lower visual field affect gaze and gait behaviour whilst walking on a variety of complex surfaces outside of the laboratory? Specifically, is there a synergistic interaction between the effects on behaviour of blocking the lower visual field and increased surface complexity? We compared how full vision versus simulated lower visual field loss affected a diverse range of behavioural measures (head pitch angle, eye angle, muscle coactivation, gait speed and walking smoothness as measured by harmonic ratios) in young participants. Participants walked over a range of surfaces of different complexity, including pavements, grass, steps and pebbles. In both full vision and blocked lower visual field conditions, surface complexity influenced gaze and gait behaviour. For example, more complex surfaces were shown to be associated with lowered head pitch angles, increased leg muscle coactivation, reduced gait speed and decreased walking smoothness. Relative to full vision, blocking the lower visual field caused a lowering of head pitch, especially for more complex surfaces. However, crucially, muscle coactivation, gait speed and walking smoothness did not show a significant change between full vision and blocked lower visual field conditions. Finally, head pitch angle, muscle coactivation, gait speed and walking smoothness were all correlated highly with each other. Our study showed that blocking the lower visual field did not significantly change muscle coactivation, gait speed or walking smoothness. This suggests that young people cope well when walking with a blocked lower visual field, making minimal behavioural changes. Surface complexity had a greater effect on gaze and gait behaviour than blocking the lower visual field. Finally, head pitch angle was the only measure that showed a significant synergistic interaction between surface complexity and blocking the lower visual field. Together our results indicate that, first, a range of changes occur across the body when people walk over more complex surfaces and, second, that a relatively simple behavioural change (to gaze) suffices to maintain normal gait when the lower visual field is blocked, even in more challenging environments. Future research should assess whether young people cope as effectively when several impairments are simulated, representative of the comorbidities found with age.

Exploration of Designed Robot in Non Linear Movement Using EKF SLAM and Its Stability on Loose Concrete Surface

The paper analyze the pressure exerted during movement of robot on path (marble flooring and Pebbled surface) using Gmapping based EKF (Extended Kalman Filter) for SLAM (Simultaneous Localization and Mapping). The experiments were carried out using meta software (vMicro) and Arduino BSP on.Net framework, which was not discussed in collaborative SLAM. In this paper, pressure and physical information captured by various sensors are analyzed and concludes robot’s behavior at different surface type with various angles.

Various surfaces challenge gait characteristics of ambulatory patients with spinal cord injury.

A cross-sectional study. To assess the influence of various surfaces on the gait characteristics of ambulatory participants with incomplete spinal cord injury (SCI) as compared to data from able-bodied participants. A tertiary rehabilitation center and communities. Seventy participants (35 ambulatory individuals with incomplete SCI and 35 able-bodied individuals with gender- and age-matched) were assessed for their spatiotemporal gait variables while walking over a 10-m walkway of different surfaces (including hard, artificial grass, soft, and pebble surfaces) at a self-selected and fastest speed. The findings were analyzed using the method of manual digitization. The data among the surfaces were compared using Kruskal-Wallis test and Mann-Whitney U test, with a level of statistical significance at P < 0.05. Participants with incomplete SCI could safely walk over every surface without any adverse events. Their average stride length, cadence, and walking speed, but not percent step length symmetry, were significantly decreased while walking on the artificial grass, soft, and particularly pebble surfaces as compared to those found on a hard surface. These changes were found particularly in those with SCI, resulting in a walking speed decreased from 0.11 to 0.35 m/s, whereas the reduction of walking speed of able-bodied participants ranged from 0.04 to 0.20 m/s. The spatiotemporal characteristics of ambulatory participants with SCI were dramatically affected by the surfaces as compared to the data found in able-bodied participants. The findings have potential clinical implications for the incorporation of various surfaces to promote the functional outcomes and safety for ambulatory individuals with SCI.

Современное минералообразование в месте разгрузки рассолов Людмилинской скважины (г. Соликамск, Пермский край)

The minerals formed from cold (4°C) sodium chloride solutions discharged between 1923 and 2019 from the Lyudmilinskaya brine-producing well were studied. During this time, the mineralization dropped from 260 to 9 g/dc3, and, at the wellhead area, an ecosystem presented by invertebrate animals, diatoms, iron and sulfur bacteria has been formed. Minerals, such as calcite and pyrite, and micron precipitates of native phases (sulfur, copper, silver, nickel, bronze), sulphides (series chalcocite- covelline, marcasite, argentopentlandite, acantite, millerite, chalcopyrite), sulfochlorides ((Ag,Cu,Ni)3(Cl,S)), chlorides (Ag3Cl), iron hydroxides, barite and sahamalit(Ce), were deposited both on the surface of pebbles and in clay-sand alluvial sediments. The studied brines are enriched with respect to sea water by siderophilic (Co, Ni), chalcophilic (Zn, Ge, As, Se, Sn, Sb, Bi, Pb, Tl (Cu?), and lithophilic elements (Be, Al, Ti, Cr, Mn, Y, Zr, Nb, W, Th). The increased concentration of these elements is explained by the hydrolysis and metal leaching the suprasalt clayey rocks with chlorides and sulfates. It is shown that the deposition of minerals occurs both chemically and biochemically.