Suction feeding biomechanics of Polypterus bichir: investigating linkage mechanisms and the contributions of cranial kinesis to oral cavity volume change

Many fishes use substantial cranial kinesis to rapidly increase buccal cavity volume, pulling prey into the mouth via suction feeding. Living polypterids are a key lineage for understanding the evolution and biomechanics of suction feeding due to their phylogenetic position and unique morphology. Polypterus bichir have fewer mobile cranial elements compared to teleosts (e.g., immobile [pre]maxillae) but successfully generate suction through dorsal, ventral, and lateral oral cavity expansion. However, the relative contributions of these motions to suction feeding success have not been quantified. Additionally, extensive body musculature and lack of opercular jaw opening linkages make P. bichir of interest for examining the role of cranial vs. axial muscles in driving mandibular depression. Here we analyze the kinematics of buccal expansion during suction feeding in P. bichir using X-Ray Reconstruction of Moving Morphology (XROMM) and quantify the contributions of skeletal elements to oral cavity volume expansion and prey capture. Mouth gape peaks early in the strike, followed by maximum cleithral and ceratohyal rotations, and finally by opercular and suspensorial abductions, maintaining the anterior-to-posterior movement of water. Using a new method of quantifying bones’ relative contributions to volume change (RCVC) we demonstrate that ceratohyal kinematics are the most significant drivers of oral cavity volume change. All measured cranial bone motions, except abduction of the suspensorium, are correlated with prey motion. Lastly, cleithral retraction is largely concurrent with ceratohyal retraction and jaw depression while the sternohyoideus maintains constant length, suggesting a central role of the axial muscles, cleithrum, and ceratohyal in ventral expansion.

Comparison of the Effectiveness of Chemo-mechanical and Traditional Caries Removal Methods in Primary Teeth Using Micro-Computed Tomography

Purpose: The purpose of this study was to evaluate dentin mineral density before and after caries removal with the traditional caries removal technique and chemo-mechanical method, with or without the use of caries detection dye. Our null hypothesis was that the chemo-mechanical method with minimally invasive treatment would achieve an effect similar to that of conservative pediatric dentistry treatment. Materials & Methods: Forty-eight medium-sized, interfacial decayed primary molar teeth without pulpal perforation were selected. Two groups were formed by Papacarie Duo and conventional method; then four sub-groups were formed by two caries detection dye applied or not applied groups, twelve teeth were randomly divided into each group. The teeth were then treated with chemo mechanical and traditional caries removal approach. Teeth were scanned with the same voxel sizes using micro-computed tomography images to figure out the difference dentin mineral density and to calculate the removed dentinal volume after chemo-mechanical or traditional method application. Results: The results showed increase of cavity volume in the chemo-mechanical and traditional method groups. No significant difference was found for cavity volume and dentinal carious volume in both groups (p>0.05). The mineral density values of demineralized dentin were between 0.52-0.66 g/cm3 before caries removal, and 1.39-1.59 g/cm3 after removing caries. These values were found to be within the range of healthy dentin mineral density values again without any significant difference between groups (p>0.05). Conclusion: In conclusion, chemo-mechanical methods can be used effectively for removing the caries in the primary molar teeth similar to conservative treatments.

Investigation of wheelhouse shapes on the aerodynamic characteristics of a generic car model

As vehicle speed increases, the aerodynamic drag reduction becomes increasingly significant. The aim of this paper is to find out the effects of the wheelhouse shapes on the aerodynamics of an Ahmed body with a 35 slant angle. In this paper, based on the detached-eddy simulation method, the effects of the three classic different wheelhouse on the aerodynamic performance and near wake of the Ahmed body are presented. The mesh resolution and methodology are validated against the published test results. The results show that the front wheelhouse has a significant impact on the aerodynamic performance of the Ahmed body, leading to different aerodynamic drag forces and flow fields. Enlarging the wheelhouse cavity volume could result in a gradual increase in aerodynamic drag coefficients, the ratio of the wheelhouse cavity volume increased by 2.9% and 9.8%, the drag coefficients increased by 2.5% and 4.5% respectively. The increase in aerodynamic drag was primarily caused by flow separation in the large cavity volume wheelhouse.

Transmural Distribution of Coronary Perfusion and Myocardial Work Density Due to Alterations in Ventricular Loading, Geometry and Contractility

Myocardial supply changes to accommodate the variation of myocardial demand across the heart wall to maintain normal cardiac function. A computational framework that couples the systemic circulation of a left ventricular (LV) finite element model and coronary perfusion in a closed loop is developed to investigate the transmural distribution of the myocardial demand (work density) and supply (perfusion) ratio. Calibrated and validated against measurements of LV mechanics and coronary perfusion, the model is applied to investigate changes in the transmural distribution of passive coronary perfusion, myocardial work density, and their ratio in response to changes in LV contractility, preload, afterload, wall thickness, and cavity volume. The model predicts the following: (1) Total passive coronary flow varies from a minimum value at the endocardium to a maximum value at the epicardium transmurally that is consistent with the transmural distribution of IMP; (2) Total passive coronary flow at different transmural locations is increased with an increase in either contractility, afterload, or preload of the LV, whereas is reduced with an increase in wall thickness or cavity volume; (3) Myocardial work density at different transmural locations is increased transmurally with an increase in either contractility, afterload, preload or cavity volume of the LV, but is reduced with an increase in wall thickness; (4) Myocardial work density-perfusion mismatch ratio at different transmural locations is increased with an increase in contractility, preload, wall thickness or cavity volume of the LV, and the ratio is higher at the endocardium than the epicardium. These results suggest that an increase in either contractility, preload, wall thickness, or cavity volume of the LV can increase the vulnerability of the subendocardial region to ischemia.

Pressure Adaptations in Deep-Sea Moritella Dihydrofolate Reductases: Compressibility versus Stability

Proteins from “pressure-loving” piezophiles appear to adapt by greater compressibility via larger total cavity volume. However, larger cavities in proteins have been associated with lower unfolding pressures. Here, dihydrofolate reductase (DHFR) from a moderate piezophile Moritella profunda (Mp) isolated at ~2.9 km in depth and from a hyperpiezophile Moritella yayanosii (My) isolated at ~11 km in depth were compared using molecular dynamics simulations. Although previous simulations indicate that MpDHFR is more compressible than a mesophile DHFR, here the average properties and a quasiharmonic analysis indicate that MpDHFR and MyDHFR have similar compressibilities. A cavity analysis also indicates that the three unique mutations in MyDHFR are near cavities, although the cavities are generally similar in size in both. However, while a cleft overlaps an internal cavity, thus forming a pathway from the surface to the interior in MpDHFR, the unique residue Tyr103 found in MyDHFR forms a hydrogen bond with Leu78, and the sidechain separates the cleft from the cavity. Thus, while Moritella DHFR may generally be well suited to high-pressure environments because of their greater compressibility, adaptation for greater depths may be to prevent water entry into the interior cavities.

Dehydration-induced mechanical instabilities in active elastic spherical shells

Active elastic instabilities are common phenomena in the natural world, where they have the character of sudden mechanical morphings. Frequently, the driving force of the instability mechanisms has a chemo-mechanical nature, which makes the instabilities very different from the standard elastic instabilities. In this paper, we describe and study the active elastic instability occurring in a swollen spherical closed shell, confining a water-filled cavity, during a dehydration process. We set up a few numerical experiments based on a stress-diffusion model to give an insight into the phenomenon. Then, we present a study that looks at the chemo-mechanical problem and, through a few simplifying assumptions, allows us to derive a semi-analytical model of the phenomenon. It takes into account both the stress state and the water concentration in the walls of the shell at the onset of the instability. Moreover, it considers the invariance of the cavity volume at the onset of instability, which is due to the impossibility of instantaneously changing the cavity volume filled with water. Eventually, it is shown that the semi-analytic model matches very well the outcomes of the numerical experiments far from the initial regime; the ranges of validity of the approximated analytical model are also discussed.

Postpartum Uterine Ultrasonographic Scale: a novel method to standardize the assessment of uterine postpartum involution

Postpartum hemorrhage is a leading cause of maternal mortality. Various methods can be used to evaluate the postpartum uterine cavity volume. This work aims to introduce a simple method for uterine postpartum cavity volume evaluation, called Postpartum Uterine Ultrasonographic Scale (PUUS), which could be used routinely. In this prospective study, 131 consecutive Caucasian patients were evaluated by using the PUUS method. The mean age was 27.72 years (ranging from 15 to 42). Patients were examined in the same time intervals: within the first 24-48 hours after delivery in case of vaginal delivery, and within the first 48-72 hours, in case of cesarean delivery. Patients with PUUS grades 2, 3, or 4 were reexamined daily until the PUUS grade declined to 1 or 0. The PUUS method evaluated the length of the endometrium of the uterine cavity occupied by blood or debris, from grade 0 (no blood) to grade 4 (over three-quarters of the endometrial length occupied by blood/debris). The PUUS grade of uterine involution varied with the day of examination, gestation, and parity. In this article, a novel method of evaluating uterine postpartum involution titled PUUS is introduced. This method standardized uterine cavity involution in a numerical fashion. We hope that the PUUS scale could further be used to decrease the morbidity and mortality of women due to postpartum hemorrhage.