Cylindrical Shape Research Articles

Rho1 and Rgf1 establish a new actin-dependent signal to determine growth poles in yeast independently of microtubules and the Tea1-Tea4 complex.

Cellular asymmetry begins with the selection of a discrete point on the cell surface that triggers Rho-GTPases activation and localized assembly of the cytoskeleton to establish new growth zones. The cylindrical shape of fission yeast is organized by microtubules (MT) that deliver the landmark Tea1-Tea4 complex at the cell tips to define the growth poles. However, only a few tea1Δ cells mistaken the direction of growth, indicating that they manage to detect their growth sites. Here, we show that Rgf1 (Rho1-GEF) and Tea4 are components of the same complex and that Rgf1 activity toward Rho1 is required for strengthen Tea4 at the cell tips. Moreover, in cells lacking Tea1, selection of the correct growth site depends on Rgf1 and on a correctly polarized actin cytoskeleton, both necessary for Rho1 activation at the pole. We propose an actin-dependent mechanism driven by Rgf1-Rho1 that marks the poles independently of MTs and the Tea1-Tea4 complex.

Varying the Core Topology in All-Glycidol Hyperbranched Polyglycerols: Synthesis and Physical Characterization.

In the present study, low molecular weight cyclic polyglycidol is used as a macroinitiator for hypergrafting glycidol and producing cyclic graft hyperbranched polyglycerol (cPG-g-hbPG) in the molecular weight range of 103-106gmol-1. Linear graft hyperbranched polyglycerol (linPG-g-hbPG) and hyperbranched polyglycerol (hbPG) are prepared as reference samples. This creates a family of hbPG structures with cyclic, linear, and star cores, allowing to evaluate their properties in solution and in bulk. The morphology study of the high molecular weight structures using atomic force microscopy revealed a spherical shape for cPG-g-hbPG and hbPG, and a cylindrical shape for linPG-g-hbPG in the nanometric range. Small angle X-ray scattering confirmed the compact particle-like structure of this family of hbPG architectures. Interestingly, the glass transition temperature showed a structure dependence, with cPG-g-hbPG having the highest values and hbPG having the lowest values for the same molecular weight. This study is a step forward in the generation of water-soluble polymers with tailored structure and functionality for advanced applications.

Ultrasonic Production of Chitosan Nanoparticles and Their Application Against Colletotrichum gloeosporioides Present in the Ataulfo Mango.

In Mexico, the Ataulfo mango crop faces significant challenges due to anthracnose, a disease caused by the fungus Colletotrichum gloeosporioides. The need to use eco-friendly fungicides is crucial to avoid the use of harmful synthetic chemicals. This study aimed to prepare chitosan nanoparticles through a simple and effective ultrasound-assisted top-down method, with high antifungal efficiency. The nanoparticles were prepared from chitosan (DD = 85%, MW = 553 kDa) and Tween 20 under constant sonication. The formation of the nanoparticles was initially confirmed by Fourier-transform infrared (FTIR) spectroscopy; and their physicochemical properties were subsequently characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The antifungal potential of the chitosan nanoparticles against the phytopathogen Colletotrichum gloeosporioides was evaluated with isolated fungi obtained directly from mango tissues showing anthracnose symptoms in the state of Guerrero, Mexico. The fungus was identified through SEM imaging, showing a regular and smooth conidial layer, with cylindrical shape (r = 2 µm, h = 10 µm). In vitro tests were conducted with three different concentrations of chitosan nanoparticles to assess their inhibitory effects. After seven days of incubation, a maximum inhibition rate of 97% was observed with the 0.5% nanoparticle solution, corresponding to a fungal growth rate of 0.008 cm/h. At this time, the control mycelial growth was 7 cm, while the treated sample reached a radius of 0.55 mm. These results demonstrated the antifungal effect of the nanoparticles on the membrane and cell wall of the fungus, suggesting that their composition could induce a resistance response. The inhibitory effect was also influenced by the particle size (30 nm), as the small size facilitated penetration into fungal cells. Consequently, the parent compound could be formulated and applied as a natural antifungal agent in nanoparticle form to enhance its activity. The method described in this study offers a viable alternative for the preparation of chitosan nanoparticles, by avoiding the use of toxic reagents.

Melting of olive oil in immiscible surroundings: experiments and theory

We report on the melting dynamics of frozen olive oil in quiescent water for Rayleigh numbers up to $10^9$ . The density difference results in an upward buoyancy-driven flow of liquid oil forming a thin film around the frozen oil. We experimentally investigate flat, cylindrical and spherical shapes and we derive theoretical expressions for the local film thickness, velocity and the local melt rate for these three canonical geometries. Our theoretical models predict the correct order of magnitude and the correct scaling as compared with our experimental findings.

Impact of nanoparticle shape on the thermal performance of eco-friendly soybean-based nanofluids in cooling titanium alloys

Ecofriendly soybean coolant offers a sustainable alternative to conventional coolants, providing excellent thermal performance while reducing environmental impact. Its biodegradable nature and low toxicity make it a safe choice for various cooling applications, promoting greener industrial practices. This study investigates the thermal performance of eco-friendly soybean nanofluids dispersed with alumina and molybdenum disulfide (MoS2) nanoparticles for cooling a titanium alloy block. The investigations are conducted using single and dual nozzle setup to assess the impact of nanoparticle shape, volume fraction and Reynolds number on heat transfer characteristics of ecofriendy coolant. The discretization is conducted using the finite volume method, and the Nusselt number is calculated from the convective heat transfer coefficient. Results show that platelet-shaped nanoparticles exhibit superior thermal conductivity and heat transfer performance compared to spherical and cylindrical shapes. Increasing the volume fraction of MoS2 platelet-shaped nanoparticles from 0.5% to 6% results in a reduction of the average temperature distribution of the titanium block by 26.53% in the single-nozzle setup and 28.87% in the dual-nozzle configuration. The dual nozzle arrangements significantly enhance heat dissipation, with MoS2 nanoparticles decreasing the temperature distribution by 9.24% in the single-nozzle setup and 15.78% in the dual-nozzle setup compared to alumina nanoparticles. Optimal thermal performance is observed at elevated Reynolds numbers, where platelet-shaped MoS2 nanoparticles achieve the highest Nusselt numbers. Specifically, incorporating MoS2 cylindrical-shaped nanoparticles into soybean oil at higher Reynolds numbers improves average heat transfer by up to 29.16% when compared to cylindrical alumina nanoparticles. The enhancements in heat transfer for spherical and platelet-shaped MoS2 nanoparticles are 37.51% and 46.66%, respectively, relative to cylindrical alumina particles. This research offers crucial guidance on developing and enhancing sustainable coolants, revealing the significance of nanoparticle shape in optimizing thermal performance and paving the way for cleaner production processes that prioritize environmental responsibility.

Modeling of Cutting Mechanics Analysis of Diamond Core Bits

Diamond core bits are essential tools for coring operations in deep formations during oil and gas drilling projects. By establishing a cutting mechanics calculation model for diamond core bits, this study investigates the changes in bit load and torque under the influence of key factors such as bit cutting structure, rock strength, and diamond distribution density. This research is significant for optimizing bit structure, enhancing coring drilling efficiency, and prolonging bit lifespan. This paper conducts modeling analysis of the cutting element loads for various shaped diamond particles, including rectangular, triangular, cylindrical, and spherical shapes. Based on this, a cutting mechanics calculation model for axial and tangential forces of granular spherical diamonds is established using the fundamental principles of elastoplastic mechanics. Consequently, a set of methods for calculating and analyzing the working loads of diamond core bits is developed. The findings of this paper provide a theoretical basis for studying the rock-breaking mechanism of diamond core bits, evaluating drilling efficiency, and optimizing tooth arrangement structures.

Metal Hydride Storage Systems: Approaches to Improve Their Performances

AbstractMetal hydrides provide a safe and efficient way to store hydrogen. However, current metal hydride storage systems, i.e., hydrides incorporated within a storage tank, are far from efficient. Depending on the design, (dis)charging rates may be very long. However, this can be significantly improved by implementing strategies tackling the issue of heat management at the level of: i) the metal hydride bed, and ii) the overall storage system design. This review summarises recent progress in tackling heat management of hydride systems. In this respect, modeling has emerged as a powerful tool. In particular, simulation results show that the compaction of hydride powders with binders and the use of metal foams are both effective in lifting the poor thermal conductivity of hydride beds. For tank designs, cylindrical shapes remain the preferred choice because of the flexibility and ease of supplementing heat management with fins and tubular heat exchangers. The addition of phase change materials to the hydride tank can lead to further heat storage, but any add‐on to simple hydride tanks can only lead to cumbersome systems. It is still a fine art to tune the thermal conductivity of hydride beds while selecting a suitable metal hydride alloy composition.

Strong spherical V2O5/TiO2–SiO2 composites obtained by template combined with sol-gel method

This study is devoted to the preparation of strong spherical composites V2O5/TiO2–SiO2 by a combined template and sol-gel method. The composition, size and shape of the colloidal particles in butanol ash with tetrabutoxytitanium and tetraethoxysilane, as well as the physicochemical processes leading to the strengthening of the spherical agglomerates obtained using an anion exchanger with a gel structure, have been determined. Electrophoresis, small-angle X-ray scattering, and viscometry were used to demonstrate the presence in the sol of positively charged colloidal particles of lenticular and cylindrical shape, whose size, when the sol is stabilised, reaches 53 Å. The absorption of the sol by the anion exchanger in vanadium form is due to the equalisation of the osmotic pressure in the anion exchanger/sol system. Spherical composites with a diameter of 300 µm were obtained. It was shown by X-ray diffraction that the composites consist of V2O5 with an orthorhombic structure, TiO2 with an anatase structure, and amorphous silicon dioxide. The interaction at the interface between the phases of V2O5 with TiO2 and SiO2, which leads to the strengthening of the sphere of the V2O5/TiO2–SiO2 composite, has been demonstrated by IR and Raman spectroscopy. The results obtained can be used for the synthesis of MxOy/TiO2–SiO2 oxide composites with spherical agglomerates.

SUPERSOFT SPONGE-LIKE CRYOGEL AS AN IMPLANT TO TREAT GLIOBLASTOMA

Abstract AIMS Create cylindrical cryogels with well-defined size. Investigate clemastine drug loading capicaty and drug release patterns. Investigate in vitro and in vivo safety and antitumor efficacy. METHOD A 3D printed template was designed and printed to make cylindrical shape cryogels. The morphology of cryogels was characterized by bright field photos, SEM, FTIR and confocal microscopy photos. The mechanical property was evaluated by uniaxial compression tests. The orthotropic glioblastoma tumor model was established by engrafting BT12 human glioblastoma stem cells intracerebrally into immunocompromised nude mice. The tumor was surgically removed after two weeks and the cryogel was implanted into the resection cavity. Animals were euthanized after two weeks, and their brains were collected for the immunohistochemistry. RESULTS Cylindrical cryogels were prepared to exactly fit the biopsy resection cavity in the mouse glioblastoma tumor resected model. The macropore structure in the cryogel was observed under confocal microscopy. Young’s modulus of the cryogel was only 1.6 kPa. The loading capacity of clemastine in one cryogel was more than 100 μg. Clemastine could be sustained released for around a week. In vitro cell viability studies showed that empty cryogels were not toxic to the tumor cells and drug loaded cryogels killed the tumor cells in a time and concentration dependent manner. In vivo studies further confirmed that cryogels could be safely implanted into the brain. Although the implantation of clemastine loaded cryogels did not prevent the growth of the primary tumor, it reduced the amount of invasion tumor cells compared with the mice only resected the tumor. CONCLUSION Cryogels were easily created by the 3D printed templates. The soft material avoided mechanical mismatch with the brain tissue. The cryogel did not show any toxicity in in vitro and in vivo studies, which indicated it would be a promising material to be implanted into the brain.

Computational analysis of heat transport dynamics in viscous dissipative blood flow within a cylindrical shape artery through influence of autocatalysis and magnetic field orentation

Nanofluids consisting of tetra nanoparticles are crucial in bio medical sciences due to their improved thermal transport characteristics. The advanced tailored properties of tera nanoparticles make them useful in several medical interventions, such as hyperthermia treatment, where the targeted tissue can be heated more efficiently, leading to better treatment outcomes. The current study investigates the heat transfer enhancement in a hemodynamic system using tetra nanoparticles. The physical configuration of the blood flow is assumed with in a permeable cylindrical shape stenosed artery. The model incorporates the Carreau model with inclusion of diverse factors such as, exponential space-based heat source, viscous dissipation, infinite shear rate and permeability of surface. Additionally, impact of chemical reaction (autocatalysis) and magnetohydrodynamic (MHD) consequences is also integrated into the system. The framed partial differential equations (PDEs) generated by physical problem are converted into new dimensionless form of an ordinary differential system (ODEs). Bvp4c MATLAB procedure is fetched for numerical investigation. It is observed that, velocity profile of the fluid is reduced due to intensification in inclined magnetic effect, whereas autocatalysis effect promotes the concentration of nanoparticles in blood flow mixture, which increases the temperature field of fluid. Furthermore, augmentation in the values of Wassenberg number increased the elasticity in blood which enables it to deform and stretch more readily in reaction to alterations in flow conditions and hence reduction is seen in overall blood flow rate. The results revealed the significance of these integrated factors for accurate modelling of blood flow passing through a stenosed artery, which is crucial in medical interventions.

Fusion of visible and fluorescence imaging through deep neural network for color value prediction of pelletized red peppers.

A non-destructive method for determining the color value of pelletized red peppers is crucial for pepper processing factories. This study aimed to investigate the potentiality of visible and fluorescence images for the determination of color value of pelletized red pepper. The imaging problem, caused by the cylindrical shape and irregular cross-sectional features of the pelletized red peppers, was reduced through the extraction of an approximate plane region. To integrate the information in the visible and fluorescence images, a baseline convolutional neural network (CNN) architecture was designed and low level, middle level, and high level fusion models (denoted as LL-CNN, ML-CNN, and HL-CNN, respectively) were developed upon the baseline CNN. The effects of input image size and color space were examined. According to the training result, CNN fusion models were developed using visible image in L*a*b* color space and fluorescence image in RGB color space using 56×56 input image size. Among the three types of CNN fusion models, the HL-CNN obtained the best performance, resulting in Rv 2 of 0.828 and RMSEV of 0.351. This study suggests that the fusion of visible and fluorescence image through CNN is a practical approach to save testing time and replace traditional destructive method. The low cost and compact structure of the imaging systems can maintain the commercial appeal of pepper industry.

Behind Amor Blunt Trauma Lung and Liver Strains from Indenter Loading via Finite Element Modeling

Abstract To determine behind armor blunt trauma injury criteria, experiments have been conducted to launch projectiles at live swine at velocities ranging up to 65 m/s using one type of indenter design. To ensure the generalizability of the developed injury criteria, tests are needed with other indenter designs. The objectives of this study were to evaluate the kinematics and injury parameters from two indenter designs using human body finite element modeling. The simulation matrix consisted of indenter designs of chord and cylindrical shape, and 150 and 230 grams (g) mass, with impacts to liver and lung regions at 30 and 60 m/s. Rib and lung strains from lung impacts, and rib strains and liver strain energy densities from liver impacts were used to evaluate the design variables of mass and shape. Both designs played a role in skeletal and organ injury parameters. Analysis revealed the increased susceptibility for skeletal and organ traumas with the high mass indenter at high velocity impacts. The cylindrical indenter may be protective for organ injuries due to the larger area of loading on the ribcage compared to the chord indenter. Results from the chord indenter may serve as a conservative estimate of injury criteria.

Leaf Rust Pathogens on Hypericum pseudohenryi: Describing Melampsora danbaensis sp. nov. and M. hyperici-pseudohenryi sp. nov. from China.

Based on morphological and phylogenetic evidence, two novel species of Melampsora were discovered on Hypericum pseudohenryi in China and have been thoroughly characterized. One of these species, designated as M. danbaensis, exhibits distinct features such as aecia of Uredo-type, typically appearing in gregarious or grouped arrangements, and presenting a shallowly pulvinate structure. Aeciospores exhibit tremendous variations in size, ranging in shape from globose to ellipsoidal and bearing pronounced verrucose texture. Telia resemble crusts one-spore deep, covering nearly the entire abaxial leaf surface, with sessile teliospores reaching sizes of up to 65.8 µm, and exhibiting a clavate to cylindrical shape. Another species, designated as M. hyperici-pseudohenryi, is distinguished by Uredo-type uredinia, which are hypophyllous, scattered or grouped, and interspersed with numerous paraphyses. Its urediniospores tend to be globose, ellipsoidal or obovoid, echinulate, and are accompanied by clavate to capitate paraphyses reaching lengths up to 77.6 µm. Phylogenetically, both species form a novel monophyletic clade within the Melampsora genus, with robust support demonstrated by a high Maximum likelihood bootstrap support (MLBS) value of 100% and a Bayesian posterior probability (BPP) of 1. This study enriches our understanding of the diversity and geographical distribution of Melampsora species that infect Hypericum plants in China.

How porosity can reduce the sound radiation of electrical coils?

High-power electrical coils used in the electricity transmission network can create a noise nuisance for local residents. These industrial coils are made up of a multi-strand cable winding, giving them a cylindrical shell shape. Electromagnetic excitation by Lorentz forces induces coil vibration, creating an undesirable sound field. In this study, we investigate analytically and by numerical simulation the reduction of acoustic radiation using regularly spaced apertures. As the shell becomes porous (with a porosity of less than 10%), acoustic short-circuits appear. We show a reduction in radiation efficiency and the impact of apertures on the structure vibration. Our results offer insights into the design and optimization of apertured electrical coils to mitigate noise generation.

On the hydrothermal features of MHD nanofluid flow over a differently shaped thin needle influenced by Hall current with nonlinear thermal radiation

PurposeThe investigation has appraised the problem of an incompressible laminar steady magnetohydrodynamic (MHD) nanofluid stream over three distinct slendering thin isothermal needles of paraboloid, cylindrical and cone shapes. Water as a base liquid is assumed in this flow model. The influences of the Hall current and variable sorts of magnetic forces have enriched our investigation. Energy and concentration expressions consist of thermophoresis and Brownian migration phenomena. The analysis of thermal and mass slips of the presumed model has also been performed.Design/methodology/approachA relevant transformation is implemented for the alteration of the leading partial differential equations (PDEs) to the equations with nonlinear ordinary form. Due to the strong nonlinearity of the foremost equations, the problem is solved numerically by embedding the well-known RK-4 shooting practice. The software MAPLE 2017 has been exploited in reckoning the entire computation. To enunciate the investigated upshots, some graphical diagrams have been regarded here. According to technological interest, we measured the engineering quantities like the Sherwood number, the coefficient of drag friction and the Nusselt number in tabular customs.FindingsThe obtained consequences support that Hall current intensifies fluid movement when the needle is in a cone shape, while the superior velocity is noticed for cylindrical-shaped needles. The transference of heat responds inversely along with the growths of thermal and mass slip factors.Originality/valueNo work has been performed on the flow model of radiated nanofluid over a variable-shaped thin needle under Hall current, the variable magnetic field and different slip factors.

Measurement of muon flux behind the beam dump of the J-PARC Hadron Experimental Facility

A muon-flux measurement behind the beam dump of the J-PARC Hadron Experimental Facility was performed with a compact muon detector that can be inserted into a vertical observing hole with 81 mm in diameter which was dug underground. The detector consists of 12 plastic scintillation strips with a length of 80 mm each, which are arranged with cylindrical shape and contained inside an aluminum housing with an outer diameter of 75 mm. A silicon photomultiplier is coupled to the end of each strip to collect the scintillating light. The flux of the muons penetrating the beam dump was scanned vertically at intervals of 0.5 m, showing a wide distribution with a maximum at the beam level. The muon flux was consistent with the expectation from a Monte-Carlo simulation at more than 1 m away from the beam axis, which is expected to be used for signal-loss evaluation in the future KOTO II experiment for measuring rare kaon decays. The data can also be used in improving the accuracy of shielding calculations in the radiation protection.

Development, process optimization and assessment of sustainable mobile biochar kiln for agricultural use

A novel and energy-efficient biochar kiln that can be operated in the field with few requirements has been developed. The generated syngas are recirculated into the combustion chamber to heat biomass. This study optimized the feedstock parameters, biochar yield, and economics of producing biochar from soybean straw using the Response Surface Methodology (RSM) based on Central Composite Design (CCD). The biochar kilns had an energy conversion efficiency of 47.02% and an overall kiln efficiency of 41.03% at steady-state operation over 500 °C. It produced an average of 29.43 ± 1.42% biochar with a minimal fuel-to-biochar ratio of 0.19 ± 0.02 and a payback period of 4.02 months. The statistical analysis confirmed that the characteristics of the feedstock affect the biochar output and economic aspects of the biochar production process. Based on the optimization studies, it was concluded that the feedstock's moisture content should be 8% and particle size should be 15 mm for higher biochar yield with maximum energy efficiency and benefit-cost ratio. Biochar produced at optimal conditions obtained from the optimization process was also characterized. Physical-chemical analysis reveals that biochar has a higher carbon content (79.38 ± 1.04 %) and a lower atomic ratio of H/C (0.696), O/C (0.14), and (N + O)/C (0.08), indicating higher carbon stability and aromaticity. The TGA analysis demonstrated the high thermal stability of biochar by showing a lower (2.15%) mass loss between the 343.8 and 407.1 °C temperature range. The SEM and TEM micrographs showed the microporous structure of the soybean straw biochar with a worm-like pattern and a cylindrical shape.

Particles reinforcement via friction stir processing (FSP): A Review

Abstract Friction stir processing (FSP) is a variant of friction stir welding (FSW) follows the same principle of operation as that of FSW; however, its purpose is very much different. FSP can be employed for the reinforcement of particulate filler in materials to form surface composites. FSP carries a tool of cylindrical shape with shoulder and pin. Being mounted with the spindle of the machine, it can rotate with high speed as well as exert vertical force and hence plunges the pin in to the materials. Heat originated due to friction softens the material beneath shoulder and as tool passed through ahead the material is processed and consolidated. During processing, materials experience severe deformation and mixing. Also, the temperature of the materials goes high significantly due to the synergetic effect of friction and plastic deformation. Due to the material mixing and thermo-mechanical nature, the process opens the door for the possible incorporation of second phase particles in the processed region. In this review, firstly processing/reinforcement approaches will be discussed which will be followed by effect of process parameters. After that, microstructure evolution and related mechanical properties will be discussed in detail. The synergism among process parameters, microstructure and mechanical properties will also be discussed.

Дослідження процесів самозаймання у насипі з прямокутним перерізом методами Роте та двобічних наближень

Self-ignition of a stockpile of material (coal, peat, grain) occurs as a result of the accumulation of heat released by an exothermic reaction of oxidation, which makes it possible to consider the stockpile as a body with an internal heat source. The research of self-ignition processes using mathematical modeling methods leads to the need to find a solution to the initial boundary value problem for a two-dimensional semilinear heat conduction equation. This cannot always be done analytically, so it makes sense to use numerical analysis methods. The aim of this article is to apply Rothe’s method in combination with the method of two-sided approximations based on the use of the Green's function to find the solution of the initial boundary value problem for the two-dimensional semilinear heat conduction equation that arises during the mathematical modeling of self-ignition processes of an stockpile of bulk material of cylindrical shape with a rectangular base. To achieve the goal, after the discretization of the heat conduction equation by the time variable, a sequence of boundary value problems was obtained by the Rothe’s method, each of which was reduced to the Hammerstein equation. For this nonlinear operator equation, an iterative process of the two-way method was constructed with its stopping condition obtained through a posteriori error estimation. The power of the internal heat source was approximated using an exponential dependence. As a result of the computational experiment, a sequence of approximate solutions was obtained. The graphs of heat maps constructed for them made it possible to examine over time the course of the self-ignition process in the cross-section of a stockpile of cylindrical shape with a rectangular base and to identify areas of heat accumulation

OS FULGURITOS DE ARACATI, NO ESTADO DO CEARÁ

This work describes the first known occurrence of fulgurites in Ceará coastline found in the Aracati county. Fulgurites are the result of the natural process of the incidence of electrical discharges of lightning on sand, soil and rocks. The product of this process in sand and soil is a new rock with unique recrystallization characteristics of the material exposed to the discharge. In some occurrences around the world, there is a record of vitrification observed with the naked eye, which was not possible in Aracati. Here, the samples collected are representative of two predominant shapes: oblong and cylindrical. The first form presents cohesion of sand grains in the central part of the sample and friability on the crests, without presenting the cavities characteristic of the cylindrical shape. This, in turn, presents differences in density, fragility and color in relation to the oblong shape. These characteristics are very similar to those of the petrified roots described in the municipality of Itarema as rhizoconcretions, however, Prof. Dr. Marcondes Lima da Costa in Aracati, in March 2024, made it possible to investigate the material with a focus on fulgurites.