Biological exoskeletons, in particular those with unusually robust and multifunctional properties, hold enormous potential for the development of improved load-bearing and protective engineering materials. Here, we report new materials and mechanical design principles of the iron-plated multilayered structure of the natural armor of Crysomallon squamiferum, a recently discovered gastropod mollusc from the Kairei Indian hydrothermal vent field, which is unlike any other known natural or synthetic engineered armor. We have determined through nanoscale experiments and computational simulations of a predatory attack that the specific combination of different materials, microstructures, interfacial geometries, gradation, and layering are advantageous for penetration resistance, energy dissipation, mitigation of fracture and crack arrest, reduction of back deflections, and resistance to bending and tensile loads. The structure-property-performance relationships described are expected to be of technological interest for a variety of civilian and defense applications.exoskeleton | mollusc | biomechanics | nanomechanics | nanoindentation M any organisms have evolved robust protective exterior structures over millions of years to maximize survivability in their specific environments. Biological exoskeletons or "natural armor" must fulfill various performance requirements such as wear resistance, dissolution prevention, thermal and hydration regulation, and accommodations for feeding, locomotion, and reproduction. Another critical function of these systems is mechanical protection from predators that can induce damage from, for example, penetration, fatigue, drilling, peeling, chipping, hammering, crushing, and kinetic attacks (1). Hence, a diverse array of macroscopic geometries, sizes, and hierarchical, multilayered composite structures exist (2). The shells of gastropod molluscs have long provided key insights into the mechanical performance of biological armor materials. Early on, Wainwright carried out macroscopic mechanical experiments on bivalve shells and formulated important questions on the contributions of different crystal textures to their strength and other functional properties (3). Soon after, Currey and Taylor characterized the properties of numerous mollusc shell microstructures and determined that the inner nacreous layer had superior mechanical properties (4). Subsequently, three decades of investigations ensued on nacre (5-9), leading to the generalized concept of "mechanical property amplification;" i.e., order of magnitude increases in strength and toughness exhibited by biological composites compared to their individual constituent materials beyond simple rule of mixture formulations (10-12). These discoveries engendered numerous efforts to produce nacre-mimetic composite materials that also exhibit mechanical property amplification (12-15). Design, inspired by nature, of engineering materials with robust and multifunctional mechanical properties [i.e., those which sustain a variety of loading condi...

Bloating in English is defined as the subjective sensation of an increase in abdominal girth, while abdominal distension is the visible or true increase in abdominal girth. 1 The first one is a symptom, while the second one is both a symptom and a clinical sign. In addition, bloating and distension can coexist and they are very commonly reported by patients and subjects in the general population. 2 Their underlying mechanism is not completely elucidated; however, bloating may be related to gut hypersensitivity, while abdominal distension can be related to an increment in intraluminal gas, as well as a behavioral response, featuring a diaphragmatic contraction and descent with anterior wall protrusion known as abdomino-phrenic dyssynergia. 2 Earlier epidemiological studies in North America

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