Identification of N-pyrrolidino protonitazene in powders sold as heroin and associated with overdose clusters in Dublin and Cork, Ireland.

Synthetic opioids have been associated globally with adverse effects in drug users. The nitazene group of drugs is a relatively new addition to the synthetic opioid class emerging in Europe in 2019. Some nitazenes have been shown to be more potent than fentanyl.

Nonclassical Chiral Elasticity of the Gyroid Lattice.

The gyroid lattice is a metamaterial which allows chirality that is tunable by geometry. Gyroid lattices were made in chiral and nonchiral form by 3D printing. The chiral lattices exhibited nonclassical elastic effects including coupling between compressive stress and torsional deformation.

Author Correction: Poisson's ratio and modern materials.

In the version of this Review Article originally published, parentheses were misplaced and the longitudinal and transverse speeds were inverted in two expressions for Poisson's ratio in Box 2; the expressions should have read, respectively, ν = (3B/G - 2)/(6B/G + 2) and ν = [½(V/V) - 1]/[(V/V) - 1].

Attraction of Female (L.) to Aphid Honeydew.

Plant sugar is an essential dietary constituent for mosquitoes, and hemipteran honeydew is one of the many forms of plant sugar that is important to mosquitoes. Many insects rely on volatile honeydew semiochemicals to locate aphids or honeydew itself. Mosquitoes exploit volatile semiochemicals to locate sources of plant sugar but their attraction to honeydew has not previously been investigated.

Strong Cosserat Elasticity in a Transversely Isotropic Polymer Lattice.

Large size effects are experimentally measured in lattices of triangular unit cells: about a factor of 36 in torsion rigidity and 29 in bending rigidity. This nonclassical phenomenon is consistent with Cosserat elasticity, which allows for the rotation of points and distributed moments in addition to the translation of points and force stress of classical elasticity. The Cosserat characteristic length for torsion is ℓ_{t}=9.

Chiral behavior in rat tail tendon fascicles.

Ex vivo tendon mechanical behavior has been well described under rotationally constrained uniaxial tensile testing. During standard loading of rat tail tendon (RTT) fascicles, apparent axial twist has been observed. To quantify this behavior, we designed a custom testing setup, utilizing magnetic suspension, to allow unconstrained axial rotation during tensile loading.

Viscoelastic properties, creep behavior and degree of conversion of bulk fill composite resins.

Objectives: The aim of this study was to investigate the viscoelastic properties and creep behavior of bulk fill composites under different conditions and evaluate their degree of conversion.

Methods: Seven bulk fill composites were examined: everX Posterior (EV), SDR (SD), SonicFill (SF), Tetric EvoCeram Bulk Fill (TE), Venus Bulk Fill (VE), x-tra base (XB) and x-tra fil (XF). Each material was tested at 21°C, 37°C and 50°C under dry and wet conditions by applying a constant torque for static and creep testing and dynamic torsional loading for dynamic testing.

Shear loads induce cellular damage in tendon fascicles.

Tendon is vital to musculoskeletal function, transferring loads from muscle to bone for joint motion and stability. It is an anisotropic, highly organized, fibrous structure containing primarily type I collagen in addition to tenocytes and other extracellular matrix components contributing to maintenance and function. Tendon is generally loaded via normal stress in a longitudinal direction.

Shear load transfer in high and low stress tendons.

Background: Tendon is an integral part of joint movement and stability, as it functions to transmit load from muscle to bone. It has an anisotropic, fibrous hierarchical structure that is generally loaded in the direction of its fibers/fascicles. Internal load distributions are altered when joint motion rotates an insertion site or when local damage disrupts fibers/fascicles, potentially causing inter-fiber (or inter-fascicular) shear.

Evaluation of global load sharing and shear-lag models to describe mechanical behavior in partially lacerated tendons.

The mechanical effect of a partial thickness tear or laceration of a tendon is analytically modeled under various assumptions and results are compared with previous experimental data from porcine flexor tendons. Among several fibril-level models considered, a shear-lag model that incorporates fibril-matrix interaction and a fibril-fibril interaction defined by the contact area of the interposed matrix best matched published data for tendons with shallow cuts (less than 50% of the cross-sectional area). Application of this model to the case of many disrupted fibrils is based on linear superposition and is most successful when more fibrils are incorporated into the model.

Comparison of approaches to quantify arterial damping capacity from pressurization tests on mouse conduit arteries.

Large conduit arteries are not purely elastic, but viscoelastic, which affects not only the mechanical behavior but also the ventricular afterload. Different hysteresis loops such as pressure-diameter, pressure-luminal cross-sectional area (LCSA), and stress-strain have been used to estimate damping capacity, which is associated with the ratio of the dissipated energy to the stored energy. Typically, linearized methods are used to calculate the damping capacity of arteries despite the fact that arteries are nonlinearly viscoelastic.

Changes in large pulmonary arterial viscoelasticity in chronic pulmonary hypertension.

Conduit pulmonary artery (PA) stiffening is characteristic of pulmonary arterial hypertension (PAH) and is an excellent predictor of mortality due to right ventricular (RV) overload. To better understand the impact of conduit PA stiffening on RV afterload, it is critical to examine the arterial viscoelastic properties, which require measurements of elasticity (energy storage behavior) and viscosity (energy dissipation behavior). Here we hypothesize that PAH leads to frequency-dependent changes in arterial stiffness (related to elasticity) and damping ratio (related to viscosity) in large PAs.

Mechanical viscoelastic behavior of dental adhesives.

Objectives: The purpose of the study was to evaluate the mechanical properties of dental adhesive materials at different testing temperatures after dry and wet storage.

Methods: Specimens (d=1 mm, l=18 mm) from six materials were tested: Silorane Adhesive System (SL), Heliobond (HE), One-Step Plus (OS), Optibond Solo Plus (OP), cmf Adhesive System (CF) and Protobond (PR). Static and creep testing was performed by applying a constant torque below the proportional limit of the materials, while dynamic testing consisted of dynamic torsional loading.

Relationship between tendon stiffness and failure: a metaanalysis.

Tendon is a highly specialized, hierarchical tissue designed to transfer forces from muscle to bone; complex viscoelastic and anisotropic behaviors have been extensively characterized for specific subsets of tendons. Reported mechanical data consistently show a pseudoelastic, stress-vs.-strain behavior with a linear slope after an initial toe region.

Effect of age and exercise on the viscoelastic properties of rat tail tendon.

Tendon mechanical properties are thought to degrade during aging but improve with exercise. A remaining question is whether exercise in aged animals provides sufficient regenerative, systemic stimulus to restore younger mechanical behaviors. Herein we address that question with tail tendons from aged and exercised rats, which would be subject to systemic effects but not direct loading from the exercise regimen.

Time-dependent ultrasound echo changes occur in tendon during viscoelastic testing.

The viscoelastic behavior of tendons has been extensively studied in vitro. A noninvasive method by which to acquire mechanical data would be highly beneficial, as it could lead to the collection of viscoelastic data in vivo. Our lab has previously presented acoustoelasticity as an alternative ultrasound-based method of measuring tendon stress and strain by reporting a relationship between ultrasonic echo intensity (B mode ultrasound image brightness) and mechanical behavior of tendon under pseudoelastic in vitro conditions [Duenwald, S.

Effects of collagen deposition on passive and active mechanical properties of large pulmonary arteries in hypoxic pulmonary hypertension.

Proximal pulmonary artery (PA) stiffening is a strong predictor of mortality in pulmonary hypertension. Collagen accumulation is mainly responsible for PA stiffening in hypoxia-induced pulmonary hypertension (HPH) in mouse models. We hypothesized that collagen cross-linking and the type I isoform are the main determinants of large PA mechanical changes during HPH, which we tested by exposing mice that resist type I collagen degradation (Col1a1[Formula: see text] and littermate controls (Col1a1[Formula: see text] to hypoxia for 10 days with or without [Formula: see text]-aminopropionitrile (BAPN) treatment to prevent cross-link formation.

Mechanical compromise of partially lacerated flexor tendons.

Tendons function to transmit loads from muscle to move and stabilize joints and absorb impacts. Functionality of lacerated tendons is diminished, however clinical practice often considers surgical repair only after 50% or more of the tendon is lacerated, the "50% rule." Few studies provide mechanical insight into the 50% rule.

Resonant ultrasound spectroscopy of cubes over the full range of Poisson's ratio.

Methods are developed for study of isotropic cubes via resonant ultrasound spectroscopy. To that end, mode structure maps are determined for freely vibrating isotropic cubes via finite element method over the full range of Poisson's ratio ν (-1 to +0.5).

Strain-induced damage reduces echo intensity changes in tendon during loading.

Tendon functionality is related to its mechanical properties. Tendon damage leads to a reduction in mechanical strength and altered biomechanical behavior, and therefore leads to compromised ability to carry out normal functions such as joint movement and stabilization. Damage can also accumulate in the tissue and lead to failure.

Damage mechanics of porcine flexor tendon: mechanical evaluation and modeling.

Porcine flexor tendons underwent cyclic and stress relaxation testing before and after strain exceeding elastic limit ("overstretch") to examine which mechanical parameters undergo changes following subfailure damage. From these data, we developed an "effective strain" damage model (in which the tendon is modeled as if being pulled to a lower strain). Damage was induced at three strain levels to determine the extent to which post-damage parameter changes were affected by overstretch strain level.

Poisson's ratio and modern materials.

In comparing a material's resistance to distort under mechanical load rather than to alter in volume, Poisson's ratio offers the fundamental metric by which to compare the performance of any material when strained elastically. The numerical limits are set by ½ and -1, between which all stable isotropic materials are found. With new experiments, computational methods and routes to materials synthesis, we assess what Poisson's ratio means in the contemporary understanding of the mechanical characteristics of modern materials.

Viscoelastic properties of low-shrinking composite resins compared to packable composite resins.

The aim of this study was to evaluate the viscoelastic properties of novel low-shrinking composites and compare them to those of packable composites. Six materials were tested: Clearfil Majesty Posterior (CM), ELS Extra Low Shrinkage (EL), Filtek P60 (FP), Filtek Silorane (FS), Prodigy (PR) and Surefil (SU). Static and dynamic testing was performed and materials were tested dry and wet at different temperatures (21°C to 50°C).

Effect of storage time on the viscoelastic properties of elastomeric impression materials.

Purpose: The aim of this study was to evaluate creep and viscoelastic properties of dental impression materials after different storage times.

Methods: Six commercially available impression materials (one polyether and five silicones) were tested after being stored for 30 min to 2 weeks under both static and dynamic testing. Shear and Young's moduli, dynamic viscosity, loss tangent and other viscoelastic parameters were calculated.