When a tunnel catches fire, temperatures inside the concrete lining can soar to 800 or 900 degrees Celsius, and the emergency response almost always involves dousing the structure with water. A new study suggests that this familiar firefighting image—flames followed by a torrent of cooling water—may be doing far more damage to the concrete than engineers have typically accounted for. Researchers investigating basalt fiber-reinforced concrete have found that how a fire-damaged structure is cooled can be as important as how hot it got in the first place, with water quenching consistently inflicting greater strength loss than slow, natural cooling across every temperature they tested.

The research, published in Case Studies in Construction Materials, systematically examined how heating temperature, cooling regime, fiber content, and impact loading combine to determine whether concrete survives a fire with its load-bearing capacity intact. The team, led by Yang Liu and colleagues including Delin Li, Jinyue Dong, Yingda Zhang, Xianliang Zhou, and Qiong Zhou, chose basalt fiber-reinforced concrete, or BFRC, as their test material because of the fiber’s unusual combination of properties. Basalt fibers, drawn from volcanic rock, offer high tensile strength, thermal stability up to melting points between 1350 and 1450 degrees Celsius, and a cost profile far more attractive than premium alternatives such as carbon fiber. This makes them an appealing candidate for tunnel linings, where fire resistance and economy must be balanced.

The experimental design was exhaustive. The researchers prepared a C35-grade concrete mix—the grade commonly recommended for tunnel design—using ordinary Portland cement, medium sand, and continuously graded gravel between 5 and 10 millimeters. Into this base mix they incorporated chopped basalt fibers, 12 millimeters long with a monofilament diameter of 17 micrometers, at volume fractions of 0, 0.1, and 0.2 percent. The fibers were added in small batches during dry mixing to prevent agglomeration, and the fresh concrete was cast into cylindrical specimens measuring 50 millimeters in diameter and 25 millimeters in height, then cured under standard conditions at 20 degrees Celsius and 95 percent relative humidity.

The thermal assault began in a high-temperature electric oven capable of reaching 1200 degrees Celsius. Specimens were heated at a controlled rate of 5 degrees Celsius per minute to target temperatures of 200, 400, 600, and 800 degrees Celsius, then held at temperature for a full hour to ensure the heat penetrated the interior. Half the specimens were then removed and allowed to cool naturally in ambient air, mimicking a structure left to cool on its own after a fire. The other half were plunged immediately into a tank of tap water, replicating the thermal shock of firefighting operations. After cooling, the water-immersed specimens were conditioned in air for seven days to return them to a natural moisture state before testing.

The dynamic mechanical properties were then probed using a split Hopkinson pressure bar, the workhorse instrument for measuring how materials behave under the extreme strain rates produced by impacts and blasts. The apparatus used bars 75 millimeters in diameter, made of high-strength steel with an elastic modulus of 210 gigapascals, with a striker bar propelled by compressed gas striking an incident bar that transmitted stress waves through the specimen. Three impact velocities—3.5, 4.4, and 5.2 meters per second—were tested, achieved by varying the operating gas pressure, with three specimens per condition. A thin pulse shaper was pasted at the impact end of the incident bar to smooth out high-frequency oscillations, and stress equilibrium between the two faces of each specimen was verified from strain-gauge signals, confirming the reliability of the data. Fragments from each impact were sieved through meshes ranging from 4.75 millimeters down to 75 micrometers so that a fractal dimension could be calculated, providing a quantitative measure of how thoroughly each specimen shattered.

The visual evidence of thermal damage followed a familiar but telling progression. At 200 degrees Celsius, the concrete surfaces turned bluish-gray, with no cracking. By 400 degrees, the color shifted to yellowish-gray, still structurally sound. At 600 degrees, fine cracks appeared along with slight surface peeling, and by 800 degrees the specimens showed severe cracking, spalling, and edge breakage. Water-cooled specimens generally exhibited more pronounced surface damage than their naturally cooled counterparts, and at 800 degrees the concave shape at the start of the stress-strain curve—evidence of pre-existing microcracks being closed under compression—was especially marked in the water-quenched samples.

The strength data told a stark quantitative story. For naturally cooled specimens containing 0.2 percent basalt fiber, the dynamic peak stress at an impact velocity of 3.5 meters per second fell from 51.1 megapascals at room temperature to 18.6 megapascals at 800 degrees—a reduction of 63.6 percent. Water cooling made matters worse across the board: at the same impact velocity, the reductions reached 23.9 percent at just 200 degrees and climbed to 64.9 percent at 800 degrees. Averaged across the temperature range, each 100-degree increment cost naturally cooled specimens roughly 6.7 to 8.0 percent of their strength, while water-cooled specimens lost about 7.5 to 8.1 percent per 100 degrees. The gap between the two cooling regimes widened at higher impact velocities: at 5.2 meters per second and 800 degrees, the water-cooled specimens suffered 6.4 percent greater strength loss than the naturally cooled ones, whereas at the lowest velocity the difference was a mere 1.3 percent. The explanation lies in competing timescales—at slow loading rates, cracks have time to propagate and dissipate energy, blunting the effect of water-induced damage, but at high rates the loading outpaces the material’s energy dissipation, and the microcracks created by thermal shock propagate catastrophically.

Against this backdrop of degradation, the basalt fibers demonstrated genuine protective power. At every temperature from 200 to 800 degrees, specimens with 0.2 percent fiber content outperformed both plain concrete and the 0.1 percent mix. At 400 degrees and an impact velocity of 3.5 meters per second, the naturally cooled fiber-reinforced specimens reached peak stresses of 40.1 megapascals, some 16.9 percent above plain concrete, while at 200 degrees under water cooling the 0.2 percent mix achieved 38.8 megapascals—a remarkable 32.4 percent improvement over unreinforced concrete. The mechanism, the authors explain, is architectural: randomly distributed fibers form a three-dimensional network that binds tightly with the cementitious matrix, reduces internal pores and cracks, and bridges microcracks before they can coalesce into fracture surfaces. But this protection has a ceiling. Above roughly 600 degrees, the fibers begin to degrade and lose their reinforcing capability, and the fiber-matrix interface—already weakened by thermal mismatch between fiber and paste—becomes a liability during water quenching.

Fractal analysis of the impact debris added another layer of insight. The fractal dimension of the fragments rose steadily with temperature, from around 1.82 at 200 degrees to above 2.3 at 800 degrees under the highest loading rate, indicating progressively finer and more complex fragmentation. Water-cooled specimens consistently shattered into finer pieces than naturally cooled ones, particularly at 600 and 800 degrees, confirming that the steep thermal gradients during quenching seed dense populations of microcracks that later explode into fracture networks under impact.

Microstructural investigation grounded these observations in chemistry and physics. X-ray diffraction of specimens heated to 800 degrees showed the disappearance of calcium hydroxide peaks and weakened calcium carbonate signals, evidence that these phases had thermally decomposed—reactions that release vapor, increase porosity, and weaken the matrix. Scanning electron microscopy revealed the deterioration in vivid detail: an unheated specimen showed a dense microstructure with abundant calcium-silicate-hydrate gel and a compact interfacial transition zone around each aggregate, while specimens heated to 800 degrees contained no detectable C-S-H gel at all, their structure riddled with pores and cracks and hosting instead a dicalcium silicate-like phase. Comparing cooling regimes at 400 degrees, the naturally cooled sample remained relatively dense and rich in hydration products, whereas its water-quenched twin displayed obvious cracks at the interfacial transition zone and a loosened surrounding matrix—the fingerprint of thermal shock stress racing through the cooling material.

The practical implications reach well beyond the laboratory. Tunnel linings that survive a fire are routinely assessed and, if necessary, repaired, but this study shows that the assessment itself must account for the cooling history. A lining quenched by firefighting water may be significantly weaker than its peak temperature alone would suggest, particularly if it subsequently faces dynamic loads from traffic vibration, rockfall impacts, or secondary events. Conversely, the results give engineers a positive tool: specifying basalt fiber reinforcement at around 0.2 percent by volume can meaningfully bolster the impact resistance of fire-exposed concrete below 600 degrees, at a modest material cost. The authors frame their work as a theoretical foundation for post-fire safety assessment of tunnel linings and for the wider engineering adoption of basalt fiber-reinforced concrete—a reminder that in structural fire engineering, what happens in the minutes after the flames matter almost as much as the fire itself.

As populations age, scientists are looking more closely at a hidden biological process that may help explain why some older adults remain mobile and independent while others experience a rapid decline in strength, balance, and endurance. A systematic review by A. Boshnjaku, R. Obërtinca, M. Hoxha, and colleagues examines whether five inflammation-related biomarkers—CRP, high-sensitivity CRP, interleukin-6, interleukin-10, and tumor necrosis factor-alpha—are linked to physical performance in older adults living in the community. Published in BMC Geriatrics, the review focuses on a question with major implications for healthy aging: can signals circulating in the blood reveal who is at greater risk of losing physical function?

The study centers on chronic, low-grade inflammation, a biological condition often associated with aging and commonly described as “inflammaging.” Unlike the intense inflammation triggered by an infection or injury, inflammaging can persist quietly over years. It may be influenced by immune-system changes, excess body fat, physical inactivity, chronic disease, and cellular stress. Although inflammation is essential for repairing tissue and fighting pathogens, prolonged activation can affect muscle metabolism, blood-vessel function, nervous-system signaling, and energy production. These changes could, in theory, make everyday movements such as walking, rising from a chair, or climbing stairs increasingly difficult.

C-reactive protein, or CRP, is one of the most widely used indicators of systemic inflammation. It is produced primarily by the liver in response to inflammatory signals, especially interleukin-6. Standard CRP testing is useful for detecting relatively pronounced inflammatory activity, while high-sensitivity CRP, known as hs-CRP, can measure much lower concentrations. That distinction matters in research on older adults, where subtle inflammatory differences may exist even when there is no obvious acute illness. However, neither CRP nor hs-CRP identifies a single disease or proves that inflammation itself caused a decline in physical ability.

The review also considers three signaling proteins known as cytokines. Interleukin-6, or IL-6, can promote inflammation but also participates in muscle adaptation and energy regulation, making its effects highly dependent on timing, tissue, and physiological context. Tumor necrosis factor-alpha, or TNF-α, is a potent inflammatory mediator that can influence muscle protein breakdown and interfere with insulin signaling. Interleukin-10, or IL-10, generally acts as an anti-inflammatory regulator, helping restrain excessive immune activation. Examining these markers together offers a more nuanced picture than relying on a single laboratory value.

Physical performance is a crucial measure of aging because it reflects how effectively multiple systems work together. Muscle strength alone does not determine whether a person can remain independent. Walking speed, repeated chair stands, balance, grip strength, endurance, and composite tests such as the Short Physical Performance Battery can reveal the combined effects of the muscular, cardiovascular, neurological, and skeletal systems. For people living outside hospitals and care facilities, these measures may also provide a practical snapshot of resilience in everyday life. A small difference in performance can translate into a major difference in fall risk, mobility, and the ability to manage daily activities.

By bringing together evidence from studies of community-dwelling older adults, the authors address an important gap between laboratory research and real-world aging. Older people living independently are not a uniform group: some have multiple chronic conditions, while others remain highly active; some take anti-inflammatory medications, and others do not. Diet, smoking, obesity, socioeconomic conditions, sleep, recent infections, and exercise can all alter cytokine levels and physical performance. A systematic review can help determine whether associations between biomarkers and function appear consistently across this complex population or whether they vary substantially from one study to another.

The review’s importance lies not only in asking whether inflammatory markers are associated with poorer performance, but also in highlighting the limitations of interpreting such relationships. A high biomarker level may be a consequence of frailty, reduced activity, obesity, or an undiagnosed illness rather than the original cause of decline. Conversely, a single blood sample may fail to capture fluctuations in inflammation over time. Differences in laboratory methods, cutoff values, participant health, medication use, and performance tests can make studies difficult to compare. These issues are central when translating population-level associations into decisions about an individual patient.

The findings may ultimately support a broader approach to healthy aging in which inflammation is considered alongside strength, nutrition, cardiovascular health, cognition, and social environment. The biomarkers discussed in the review are not presented as standalone tests that can predict the future with certainty. Instead, they may help researchers understand why physical function changes and identify biological pathways that could be targeted through exercise, weight management, treatment of chronic disease, or other interventions. The study also underscores the need for longitudinal research capable of separating cause from consequence and for standardized testing that can connect laboratory signals with meaningful improvements in daily life.

For now, the review places a spotlight on the immune system as a possible contributor to the physical changes associated with later life. Its focus on CRP, hs-CRP, IL-6, IL-10, and TNF-α reflects the growing recognition that aging is not simply the result of muscles becoming weaker, but of interconnected changes across the body. Understanding how these inflammatory signals relate to mobility could help scientists develop more precise strategies for preserving independence—while reminding clinicians and the public that a blood test is most informative when interpreted together with a person’s functional ability, medical history, and lived environment.

Subject of Research: The relationship between inflammatory biomarkers and physical performance in community-dwelling older adults.

Article Title: What is the impact of CRP, hs-CRP, IL-6, IL-10, and TNFα in physical performance in community-dwelling older adults: a systematic review.

Article References: Boshnjaku, A., Obërtinca, R., Hoxha, M. et al. What is the impact of CRP, hs-CRP, IL-6, IL-10, and TNFα in physical performance in community-dwelling older adults: a systematic review. BMC Geriatrics (2026). https://doi.org/10.1186/s12877-026-08080-8

Image Credits: AI Generated

DOI: 10.1186/s12877-026-08080-8

Keywords: aging, older adults, inflammation, CRP, hs-CRP, IL-6, IL-10, TNF-α, physical performance, inflammaging, systematic review

The elephant’s trunk is one of the animal world’s most formidable facial appendages; it is capable of tearing a tree limb from its base and, moments later, carefully lifting a single blade of grass.

Now, this combination of strength and precision is also helping to drive robotics research.

A boneless appendage that can both move heavy logs and peel fruit like a banana, the elephant’s trunk has long been studied by engineers seeking to understand how it can perform both powerful and delicate tasks effectively. Now, in a new study published in PNAS Nexus, researchers have identified the skin, rather than the underlying muscle, as a key factor in the versatility of this pachyderm appendage. 

Lucia Beccai and colleagues at the Istituto Italiano di Tecnologia studied the trunk of an adult Asian elephant that died of natural causes at Zurich Zoo in 2020. They collected 35 samples from different regions of the trunk and analyzed them using biomechanical testing, histology, various imaging techniques, and computational modeling. The team’s analysis revealed a trunk that combines two very different mechanical strategies within a single structure.

One Trunk, Two Skins

The elephant trunk acts as a muscular hydrostat, similar to an octopus tentacle or the human tongue. With no bones and over 100,000 muscles, the trunk can stretch, compress, twist, and bend in any direction. The trunk achieves this flexibility through a combination of muscle power and specialized skin architecture. The study found that the trunk’s outer surface varies in structure depending on location and the types of forces it encounters.

The researchers identified clear differences between the upper and lower surfaces of the trunk, reflecting what scientists call functional anisotropy. The trunk’s upper surface serves as a tough, protective layer, which is over three times stiffer than the underside. In contrast, the trunk’s lower surface remains soft and flexible, allowing the elephant to grip objects with delicacy and precision.

The way elephants use their trunks reflects this structural difference. The upper surface faces the environment and absorbs impacts and abrasions. The underside is used for gripping objects. Its lower stiffness allows it to adapt to the shape of objects and hold them securely. The design of the elephant trunk may offer a solution to a persistent challenge that has stumped soft-robotics engineers in balancing protection and precision by assigning each function to a different layer of skin.

A Lens Made of Tissue

Another significant finding was made beneath the gripping surface. The researchers identified dome-shaped structures known as dermal papillae. Finite element modeling suggested that these structures act as subsurface mechanical lenses, concentrating mechanical stress in regions where sensory nerves are located.

This design could solve an additional problem in robotics: touch sensors are often fragile and require protective coatings that can reduce their sensitivity. The tissue in the elephant trunk appears to protect sensory structures while still allowing mechanical signals to reach them.

The Biomimetic Blueprint

For Beccai’s group, which specializes in soft robotics, the possible design template represents a huge opportunity for their field. A robotic gripping device built on this idea would feature a stiff outer shell over a flexible inner layer, with structures underneath to direct pressure to protected sensors. This setup would keep sensitive electronics shielded while still allowing for mechanical feedback from touch.

This research adds to the growing scientific interest in the elephant trunk as a model for engineering. Another 2024 study in Communications Biology found that the trunk’s dermis is reinforced by tangled collagen fibers, creating skin armor thicker than an armadillo’s shell. Together, these studies show a structure optimized at every level, from the protein fibers in the dermis to the clear split between the upper and lower surfaces.

Today’s robotic hands still struggle to balance durability with sensitivity. The elephant trunk offers biological inspiration for this challenge, providing a model for future engineering designs.

Austin Burgess is a writer and researcher with a background in sales, marketing, and data analytics. He holds an MBA, a Bachelor of Science in Business Administration, and a data analytics certification. His work focuses on breaking scientific developments, with an emphasis on emerging biology, cognitive neuroscience, and archaeological discoveries.