Synthetic Sponge Research Articles

Circular RNAs in Cardiovascular Diseases: Molecular Mechanisms, Therapeutic Advances, and Innovations

Circular RNAs (circRNAs) have emerged as promising therapeutic targets due to their unique covalently closed-loop structures and their regulatory roles in gene expression. Despite their potential, challenges in circRNA-based therapies include ensuring stability, tissue specificity, and efficient intracellular delivery. This review explores the implications of circRNAs in cardiovascular diseases (CVDs), providing an overview of their biogenesis, molecular mechanisms, and roles in disease pathology. In addition to discussing molecular features, this review highlights therapeutic advances, including small-molecule drugs targeting circRNAs, synthetic circRNA sponges, and innovations in drug delivery systems that enhance the effectiveness of these therapies. Finally, current challenges and future directions are addressed, emphasizing the need for continued research to fully unlock the therapeutic potential of circRNA-based strategies in cardiovascular medicine.

Wet-Stable Lamellar Wood Sponge with High Elasticity and Fatigue Resistance Enabled by Chemical Cross-Linking.

The excessive consumption of fossil-based plastics and the associated environmental concerns motivate the increasing exploitation of sustainable biomass-based materials for advanced applications. Natural wood-derived lamellar wood sponges via a top-down approach have recently attracted significant attention; however, the insufficient compressive fatigue resistance and lack of structural stability in water limit their wide applications. Here, we report a facile chemical cross-linking strategy to tackle these challenges, by which the cellulose fibrils in the lamellas are covalently bridged to enhance their connectivity. The cross-linked wood sponges demonstrate high compressibility up to 70% strain and exceptional compressive fatigue resistance (∼5% plastic deformation after 10,000 cycles at 50% strain). The interfibrillar cross-linking inhibits the swelling of cellulose fibrils and preserves the arch-shaped lamellas of the sponge in water, endowing the wood sponge with excellent wet stability. Such highly elastic and wet-stable lamellar wood sponges offer a sustainable alternative to synthetic polymer-based sponges used in diverse applications.

Evaluation of synthetic sponge to control wave-induced currents in coastal waters

Based on National Oceanic and Atmospheric Administration (NOAA) Coral Reef Conservation Program, climate change causes coral bleaching. In response to the high roughness of coral colonies and reduced current velocity, coral reefs in near-shore regions are susceptible to accumulation of pollutants or sediments. This threatens coral reef ecosystems and causes several challenges. Controlling the wave velocity, Turbulent Kinetic Energy (TKE), and vortical structures help enhance advection/diffusion of particles from coral reef zones.In the current study, a device inspired by a marine sponge (synthetic sponge), was designed. A suction/pumping function was devised through two concentric perforated cylinders to simulate this mechanism in the synthetic sponge. Several physical and numerical experiments (using OpenFOAM software considering RANS modeling) were carried out to investigate the effects of geometrical characteristics (i.e., cylinder and perforation diameters) of synthetic sponge on wave hydrodynamics. Accordingly, wave attenuation, mean horizontal and orbital velocities, turbulent kinetic energy, and vortex structures were evaluated. In summary, the results indicated that the pumping flow can act as an energy recovery downstream of the sponge, and the horizontal velocity and TKE growing in the water column due to generation of special vortices. Therefore, the current synthetic sponge can improve momentum transfer.

High-aspect-ratio nanostructured hydroxyapatite: towards new functionalities for a classical material.

Hydroxyapatite-based materials have been widely used in countless applications, such as bone regeneration, catalysis, air and water purification or protein separation. Recently, much interest has been given to controlling the aspect ratio of hydroxyapatite crystals from bulk samples. The ability to exert control over the aspect ratio may revolutionize the applications of these materials towards new functional materials. Controlling the shape, size and orientation of HA crystals allows obtaining high aspect ratio structures, improving several key properties of HA materials such as molecule adsorption, ion exchange, catalytic reactions, and even overcoming the well-known brittleness of ceramic materials. Regulating the morphogenesis of HA crystals to form elongated oriented fibres has led to flexible inorganic synthetic sponges, aerogels, membranes, papers, among others, with applications in sustainability, energy and catalysis, and especially in the biomedical field.

Inspiration of marine sponges to design a structure for managing the coastal hydrodynamics and protection: numerical study

Climate changes and sediment discharge within the oceans trigger many problems, such as coastline erosion and coral reef extinction hazards. Therefore, it is crucial to control wave hydrodynamics in the desired manner to protect marine environments. To prevent the promotion of sedimentation, nature has its response. The tubular sponge is a marvelous animal. It has a perforated body and sucks nutrition and water from these perforations; then, it pumps the undigested materials out from the top outlet. In the current study, an apparatus inspired by natural tubular sponges (synthetic sponges) was designed. The computational fluid dynamics derived from the Reynolds-averaged Navier-Stokes equations and image processing technique (surfaceLIC) was deployed to study how the synthetic sponge affects the wave hydrodynamics. The results revealed that the suction of the body and outflow shielding phenomenon of one sponge reduces the wave transmission by up to ≈7%. In addition, the swing motion of the jet by wave train and effluent cloud generation causes the shear on the sponge. Therefore, the momentum exchange enhances through the water column (≈46% increase of turbulent kinetic energy). It is similar to the swing behavior of flexible vegetation. Furthermore, the surfaceLIC result revealed that the effluent cloud shape changes to a pear shape, symmetric, stretched (transition), and asymmetric by increasing the pumping discharge to 600 L/h. Observing the chute–jet phenomenon by surfaceLIC also proved the diffraction and creation of a low-velocity zone in the shadow region, which is proof of a breaking wave due to the sponge’s suction/pumping and perforated body. Consequently, it can be concluded that a synthetic sponge can act as both rigid and flexible vegetation. The synthetic sponge is anticipated to mitigate sedimentation by creating unique vortices, circulating flow, and its body shape.

Three-dimensional modeling of dilute sediment concentration around the synthetic sponge inspired by the tubular sponge mechanism

Marine tubular sponges use horizontal suction to receive the nutrients from the perforated body and pump the undigested materials from the top mouth. The idea of a synthetic sponge was inspired by the tubular one. It was introduced to manage the sediment-flow hydrodynamics for enhancing sediment transport in coral reefs and access channels. In the current study, synthetic sponge effects on the dilute sediment concentration were investigated numerically. The Mixture method based on Three-Fluids Modeling (TFM) was selected. The effects of pore area distributions (0–0.42) and jet flow discharges (0–7500 L/h) on the sediment concentration were evaluated. The surface Line Integral Convolution (surfaceLIC) was used as an image processing technique to assess the fluid hydrodynamics. The results indicate that the effects of perforation area distribution are more significant than suction/pumping discharges on the sediment concentration (94.87% vs. 5.13% contribution). So increasing the distribution of perforation areas can effectively reduce water turbidity (between 20% and 50%). The combination of the wide re-circulation zone, Counter Rotating Vortex Pair (CRVP), spiral flow, and dipole formation are the reasons for this. Therefore, the combination of vortices facilitates sediment transport due to the unique shape and mechanism of synthetic sponge.

Numerical Modeling of Sediment-flow around Obstacle Inspired by Marine Sponges: Considering Body Configurations

Coral reefs are exposed to extinction due to the sediment blocking through coral colonies. In this condition, there is no practical solution that originates from nature. Among all aquatic animals, marine tubular sponges have marvelous mechanisms. These natural creatures can inspire the design of a device for managing sediment-flow hydrodynamics. They suck flow from body perforation and pump water and undigested materials from the top outlet. Therefore, coinciding with receiving nutrients, the flow becomes circulated. This may help the momentum transfer through the coral colonies. In the current study, a synthetic sponge by motivating the tubular sponges was designed. Synthetic sponges’ suction/pumping discharge was constant at 150 L/h. They have a body diameter of 8 and 15 cm and a height of 20 cm. The perforation area distribution changes to understand how it may influence sediment-flow hydrodynamics. The numerical modeling based on Reynolds Averaged Navier Stokes (RANS) equations and image processing technique (surface LIC) were deployed to determine the vortical flow patterns. Results confirmed that choosing the best body perforation configuration and area distribution can generate the dipole vortex. In this condition, a tornado combines with dipole and erodes the sediments to ≈ 30% near the bed. Moreover, the sediment concentration reduces to ≈ 20% in the water column at X/D =1. In this condition, it can be observed that the emergence of specific vorticities and re-circulations develops the suspension of particles. Therefore, the synthetic sponge with precise design can be practical for enhancing the momentum transferring and preventing pollutant blockage among coral colonies.

A cytotoxic survey on 2-amino-1H-imidazol based synthetic marine sponge alkaloid analogues.

Here, we describe the synthesis and biologic activity evaluation of 20 novel synthetic marine sponge alkaloid analogues with 2-amino-1H-imidazol (2-AI) core. Cytotoxicity was tested on murine 4T1 breast cancer, A549 human lung cancer, and HL-60 human myeloid leukemia cells by the resazurin assay. A total of 18 of 20 compounds showed cytotoxic effect on the cancer cell lines with different potential. Viability of healthy human fibroblasts and peripheral blood mononuclear cells upon treatment was less hampered compared to cancer cell lines supporting tumor cell specific cytotoxicity of our compounds. The most cytotoxic compounds resulted the following IC50 values 28: 2.91 µM on HL-60 cells, and 29: 3.1 µM on 4T1 cells. The A549 cells were less sensitive to the treatments with IC50 15 µM for both 28 and 29. Flow cytometry demonstrated the apoptotic effect of the most active seven compounds inducing phosphatidylserine exposure and sub-G1 fragmentation of nuclear DNA. Cell cycle arrest was also observed. Four compounds caused depolarization of the mitochondrial membrane potential as an early event of apoptosis. Two lead compounds inhibited tumor growth in vivo in the 4T1 triple negative breast cancer and A549 human lung adenocarcinoma xenograft models. Novel marine sponge alkaloid analogues are demonstrated as potential anticancer agents for further development.

Economical alternatives for the production of fungal β-1,3-glucanase using easily obtainable industrial substrates

The β-1,3-glucanases synthesized by filamentous fungi have wide applicability in the food, chemical, and pharmaceutical industries. However, its obtainment can be costly, especially due to substrates used to induce its synthesis. Therefore, the objective of this work was to produce β-1,3-glucanase by T. harzianum Rifai using free and immobilized cells in synthetic and plant sponges, using different inducing substrates that could provide better cost-effectiveness for the industrial production of the enzyme. The Petri dish zymogram technique proved to be efficient for screening substrates inducing β -1,3-glucanases against species of filamentous fungi. It was possible to perform the immobilization of T. harzianum in a synthetic sponge allowing the realization of repetitive batches for enzymatic production. All tested substrates resulted in the synthesis of β-1,3-glucanase, including succinoglycan, proposed innovatively in this study. Fungal biomass resulted in the best inducing substrate under conditions of free and immobilized cells, with a production of β-1,3-glucanases of 0.73 U and 0.80 U of β -1,3-glucanases. The substrates corn starch and cassava showed promise in the production of β-1,3-glucanase and maintained production until the fourth batch was evaluated, with values of 0.51 U and 0.46 U of β-1.3-glucanases, respectively. The results obtained in this study showed that the zymogram is a practical method for screening substrates induced by the fungus T. harzianum. Corn starch and cassava are accessible and low-cost sources for β-1,3-glucanase synthesis in repetitive batches, including the use of immobilized and free cells.

Comparative Study of Different Sampling Methods of Biofilm Formed on Stainless-Steel Surfaces in a CDC Biofilm Reactor.

The formation of biofilms in dairy processing plants can reduce equipment efficiency, contribute to surface deterioration, and contaminate dairy products by releasing the microorganisms they contain, which may cause spoilage or disease. However, a more representative identification of microbial communities and physico-chemical characterization requires to detach and recover adequately the entire biofilm from the surface. The aim of this study is to develop an efficient technique for in-plant biofilm sampling by growing a strain of Pseudomonas azotoformans PFl1A on stainless-steel surface in a dynamic CDC biofilm reactor system using tryptic soy broth (TSB) and milk as growth media. Different techniques, namely, swabbing, scraping, sonic brushing, synthetic sponge, and sonicating synthetic sponge were used and the results were compared to a standard ASTM International method using ultrasonication. Their efficiencies were evaluated by cells enumeration and scanning electron microscopy. The maximum total viable counts of 8.65 ± 0.06, 8.75 ± 0.08, and 8.71 ± 0.09 log CFU/cm2 were obtained in TSB medium using scraping, synthetic sponge, and sonicating synthetic sponge, respectively, which showed no statistically significant differences with the standard method, ultrasonication (8.74 ± 0.02 log CFU/cm2). However, a significantly (p < 0.05) lower cell recovery of 8.57 ± 0.10 and 8.60 ± 0.00 log CFU/cm2 compared to ultrasonication were achieved for swabbing and sonic brushing, respectively. Furthermore, scanning electron microscopy showed an effective removal of biofilms by sonic brushing, synthetic sponge, and sonicating synthetic sponge; However, only the latter two methods guaranteed a superior release of bacterial biofilm into suspension. Nevertheless, a combination of sonication and synthetic sponge ensured dislodging of sessile cells from surface crevices. The results suggest that a sonicating synthetic sponge could be a promising method for biofilm recovery in processing plants, which can be practically used in the dairy industries as an alternative to ultrasonication.

An environmentally friendly method to fabricate superhydrophobic cellulose fiber for oil absorption

The complex preparation process, high cost, and use of non-renewable materials limit the marketization of most synthetic superhydrophobic oil-absorbing sponges. This work provides a preparation method of superhydrophobic and nontoxic oil absorbents by surface modification of pulp cellulose fibers. A simple hydrothermal method was used to in situ grow micron-scale petal-like γ-AlOOH layers on the surface of cellulose fibers pretreated with ultrasonication and swelled with urea, and then modified with low surface energy to prepare superhydrophobic cellulose fibers. The obtained cellulose fibers have high oil absorption property, fast absorption speed and high recyclability. The fibers exhibit excellent superhydrophobic stability in boiling water, various corrosive solutions and even high-temperature combustion environments, proving that it has the ability to absorb oil in harsh environments. In addition, after being connected to a vacuum filtration device, the as-prepared fibers can continuously separate the n-hexane solution of 200 quilts of its own weight within 15 s. And in the experiment of simulating turbulent water flow, they can still effectively remove oil from oil-water mixture. More importantly, the fiber can separate micro-nano scale oil droplets from the oil (n-hexane)-in-water emulsion with a separation rate up to 93.15% (solution transparency). All these excellent properties show that the prepared fibers have high application value in the fields of marine oil spill absorption and oil-water separation.

Synthetic Circular miR-21 Sponge as Tool for Lung Cancer Treatment.

Lung cancer is the most common cancer in the world and several miRNAs are associated with it. MiRNA sponges are presented as tools to inhibit miRNAs. We designed a system to capture miRNAs based on circular RNAs (circRNA). To demonstrate its usefulness, we chose miR-21, which is upregulated and implicated in lung cancer. We constructed a miR-21 sponge and inserted it into a vector that facilitates circular RNA production (Circ-21) to study its effect on growth, colony formation, and migration in lung cancer cell lines and multicellular tumor spheroids (MTS). Circ-21 induced a significant and time-dependent decrease in the growth of A549 and LL2 cells, but not in L132 cells. Furthermore, A549 and LL2 cells transfected with Circ-21 showed a lower number of colonies and migration than L132. Similar findings were seen in A549 and LL2 Circ-21 MTS, which showed a significant decrease in volume growth, but not in L132 Circ-21 MTS. Based on this, the miR-21 circular sponge may suppress the processes of tumorigenesis and progression. Therefore, our system based on circular sponges seems to be effective, as a tool for the capture of other miRNAs.

Highly Elastic and Fatigue-Resistant Graphene-Wrapped Lamellar Wood Sponges for High-Performance Piezoresistive Sensors

Three-dimensional (3D) conductive aerogels with structural robustness and mechanical resilience are highly attractive for sensitive and stable pressure sensing. However, the fabrication of such 3D aerogels often relies on complicated bottom-up assembly processes that involve costly raw materials or intensive energy consumption or directly coating synthetic polymer sponges (e.g., polyurethane) with conductive materials, which may pose environmental concerns for their disposal. Herein, a simple and sustainable strategy is proposed to fabricate a reduced graphene oxide-coated wood sponge (RGO@WS) with a lamellar structure for high-performance piezoresistive sensors. The introduced RGO nanosheets endow the RGO@WS not only with high conductivity but also with high elasticity and excellent fatigue resistance. These features make it an ideal piezoresistive sensor with a high sensitivity of 0.32 kPa–1 (superior to most polymeric sponge-based sensors), high working stability over 10 000 cycles, and excellent sensing reproducibility at ultralow temperatures. Thanks to its prominent sensing performance, the RGO@WS-based sensor can serve as a wearable device for detecting human motions and physiological signals and allows for spatially resolved pressure mapping via integrating the sensors into a large-area sensing array. The developed highly elastic and fatigue-resistant RGO@WS represents a promising and sustainable alternative to the synthetic polymer-based piezoresistive sensors.

MiR-221/222 sponge abrogates tamoxifen resistance in ER-positive breast cancer cells through restoring the expression of ER\u03b1

Tamoxifen resistance (TamR) prevents ER-positive breast cancer patients from benefitting from endocrine therapy, and miR-221 or miR-222 plays vital roles in inducing TamR. In this study, we designed synthetic sponges to reverse TamR by targeting these two miRs. First, we established a tamoxifen resistant breast cancer cell line (MCF-7TamR), we verified the high expressing level of these two miRs in TamR cells. miR-221 or miR-222 inhibitors rendered MCF-7TamR cells responsive to tamoxifen. Next, we designed a miR-221/222 sponge, which contains total 8 multi-antisense binding sites (MBSs) for these two onco-miRs, and inserted it into CMV promoter- or hTERT promoter-driven expressing vectors. After transfected miR-221/222 sponge expressing vectors into MCF-7TamR cells, we identified a strong interaction between miR-221/222 sponge and endogenous miR-221 or miR-222 by RNA pulldown assay. We also found that miR-221/222 sponge restored the expression of ERα and PTEN, arrested cells in G1 phase, and finally resulted in reduced cell growth and cell migration. Notably, miR-221/222 sponge expressing cells abrogates tamoxifen resistance through restoring the expression of ERα, suggesting that miR-221/222 sponge gene therapy especially driven by tumor specific promoter could provide an effective therapeutic approach against TamR in breast cancer.

Disentangling the independent effects of vegetation cover and pattern on runoff and sediment yield in dryland systems – Uncovering processes through mimicked plant patches

There is strong empirical evidence on the importance of the spatial pattern of vegetation in dryland hydrologic and geomorphologic dynamics. However, changes in vegetation cover and spatial pattern are often linked, making it difficult to disentangle and assess their independent hydro-geomorphologic roles. We used synthetic sponges placed on the soil surface to mimic the aboveground structure of vegetation patches, and manipulated patch cover and pattern as well as the sink capacity of the patches on a set of 24 (2 × 1 m) runoff plots. Combining natural-rainfall and simulated-rainfall experiments, we aimed to test that (1) both vegetation cover and pattern independently control runoff and sediment yield; (2) for any given cover, coarsening the vegetation pattern entails increasing runoff and sediment yield; and (3) pattern effect is mostly exerted by modulating the source-sink dynamics of the system. We found that increasing either patch cover or patch density decreased runoff and sediment yields from natural rainfalls, yet the effect of patch density largely disappeared when the effect of the co-varying patch cover was removed. Simulated-rainfall experiments on plots with equal medium-low patch cover showed however that coarser patterns (lower patch density; higher patch size) increased runoff coefficients and reduced time to runoff as compared with finer patterns. The effect of patch density was particularly clear when the sink function of vegetation patches was also mimicked. Rainfall interception and direct soil protection proved to be critical mechanisms underlying the effects of patch cover, yet they barely contributed to the effects of patch pattern. The control of overland flow by patch pattern was exerted through changes in the level of runoff disruption. However, physical obstructions to runoff hardly reduced runoff unless coupled to mimicked soil sinks. Overall this work demonstrates the independent effects of patch cover and pattern on the hydro-geomorphologic functioning of patchy landscapes, with patch cover being the primary hydrologic control factor and patch pattern exhibiting its full potential for low and medium low patch cover values. Our findings provide useful information for modelling and understanding dryland vegetation dynamics, and for designing management and restoration measures that take into account the critical role played by source-sink dynamics and hydrological connectivity in dryland landscapes.

EFFECT OF CASEARIA SYLVESTRIS OIL IN CHRONIC INFLAMMATION INDUCED BY SYNTHETIC IMPLANTS IN MICE

Inflammation is a natural body’s event that starts immediately when the body suffers a tissue injury. Its goal is to exterminate the noxious agent, however when the noxious agent is not removed and stands much longer, it is succeeded into a chronic inflammation, what is characterized by the persistence of the harmful agent that can go on for days, months or years. When the chronic inflammation ends, it forms a fibrous tissue. This study we evaluated the effect of the essential oil of Casearia sylvestris used on the traditional medicine. Itis rich in a type of chemical class called sesquiterpene, which is characterized for its anti-inflammatory effect. The inflammatory componentwas measured by myeloperoxidase activity (MPO) and N-acetyl-β-D-glicosaminidase (NAG) and mast cells account. For this purpose, 61 male mices C57∕B1∕6 (control group (saline), DMSO1%, 10 ng, 100 ng, and 1000 ng, of C. sylvestris essential oil) underwent to a chronic inflammatory response induced by synthetic sponge and treated with these dosages. The results have showed that the inflammatory component, represented by the evaluation of MPO and NAG activity, had no significant difference between the three doses evaluated compared to the control group. According to the results, the chronic inflammation treated with C. sylvestris essential oil had no effect on the inflammatory process.

Daily monitoring of vaginal interleukin 6 as a predictor of intraamniotic inflammation after preterm premature rupture of membranes- a new method of sampling studied in a prospective multicenter trial.

(A) To introduce a new technique for vaginal fluid sampling (biocompatible synthetic fiber sponge) and (B)evaluate the collected vaginal fluid interleukine-6 (IL-6vag)-concentration as a new diagnostic tool for daily monitoring of intrauterine inflammation after preterm premature rupture of membranes (PPROM). Secondary objectives were to compare the potential to predict an intrauterine inflammation with established inflammation parameters (e.g., maternal white blood cell count). This prospective clinical case-control diagnostic accuracy multicenter study was performed with women after PPROM (gestational age 24.0/7- 34.0/7weeks). Sampling of vaginal fluid was performed once daily. IL-6vag was determined by electrochemiluminescence-immunoassay-kit. Neonatal outcome and placental histology results were used to retrospectively allocate the cohort into two subgroups: 1) inflammation and 2) no inflammation (controls). A total of 37 cases were included in the final analysis. (A): Measurement of IL-6 was successful in 86% of 172 vaginal fluid samples. (B): Median concentration of IL-6vag in the last vaginal fluid sample before delivery was significantly higher within the inflammation group (17,085pg/mL) compared to the controls (1,888pg/mL; p=0.01). By Youden's index an optimal cut-off for prediction an intrauterine inflammation was: 6,417pg/mL. Two days before delivery, in contrast to all other parameters IL-6vag remained the only parameter with a sufficient AUC of 0.877, p<0.001, 95%CI [0.670-1.000]. This study established a new technique for vaginal fluid sampling, which permits assessment of IL-6vag concentration noninvasively in clinical daily routine monitoring.

Synthetic protein-binding DNA sponge as a tool to tune gene expression and mitigate protein toxicity

Versatile tools for gene expression regulation are vital for engineering gene networks of increasing scales and complexity with bespoke responses. Here, we investigate and repurpose a ubiquitous, indirect gene regulation mechanism from nature, which uses decoy protein-binding DNA sites, named DNA sponge, to modulate target gene expression in Escherichia coli. We show that synthetic DNA sponges can be designed to reshape the response profiles of gene circuits, lending multifaceted tuning capacities including reducing basal leakage by >20-fold, increasing system output amplitude by >130-fold and dynamic range by >70-fold, and mitigating host growth inhibition by >20%. Further, multi-layer DNA sponges for decoying multiple regulatory proteins provide an additive tuning effect on the responses of layered circuits compared to single-layer sponges. Our work shows synthetic DNA sponges offer a simple yet generalizable route to systematically engineer the performance of synthetic gene circuits, expanding the current toolkit for gene regulation with broad potential applications.

Structural anisotropy in three dimensional macroporous graphene: A polarized XANES investigation

Three-dimensional macroporous graphene sponges with different densities were investigated by angular dependent carbon K-edge X-ray Absorption Near Edge Spectroscopy (XANES) with a linearly polarized beam. The C K-edge XANES analysis shows an unexpected anisotropic behavior of the macroporous graphene random networks. The macroporous graphene sponges expectedly show an exceedingly lower dichroic ratio compared with that of the highly oriented pyrolytic graphite, but spectra clearly points out the occurrence of oriented hexagonal carbon planes. The anisotropy of the investigated samples exhibits a linear dependence with the measured density. The XANES analysis supports the presence of graphene-like, two-dimensional planar structures inside these synthetic sponges and correlates it with different structural networks and/or density in graphene sponges.

Determination of the coefficient of rolling friction of a hollow cylinder rolling on a curved track using a smartphone’s sensors

This paper demonstrated a simple experiment for determining the coefficient of rolling friction of a hollow cylinder rolling on a curved track using a smartphone’s sensors. We studied theoretically and experimentally the rolling motion of a hollow cylinder uncovered and covered with various materials (synthetic leather and sponge sheets). The smartphone (iPhone 4s) was attached to the end of the hollow cylinder for recording the angular position and angular velocity via the Rolling Cylinder application. The results showed that the coefficient of rolling friction depends on the velocity of the hollow cylinder. We expect that the experiment can be an alternative method for determining the coefficient of rolling friction and will help students better understand rolling motion.