Mechanical testing of metallic foams for 3d model and simulation of cell distribution effects

Cellular materials have a bulk matrix with a larger number of voids named also cells. Metallic foams made by powder technology represent stochastic closed cells. The related inhomogeneity leads to a scattering of results both in terms of stress–strain curves and maximum strength. Scattering is attributed to relative density variations and local cell discontinuities and it is confirmed also in case of dynamic loading. Finite element simulations through geometrical models that are able to capture the void morphology (named “mesoscale models”), confirm these results and some efforts have been already done to quantify the relationship between shape irregularities and mechanical behavior. The aim of this paper is to present the dynamic characterization of an AA7075 closed cell material and to calibrate its mesoscale finite element model according to the related cell shape distribution. Specimens have been derived from a small ingot (45x45x100 mm) divided along sections so that morphological analysis and experimental tests have been carried out. Specimens extracted from a half of the ingot have been used for dynamic compression tests by means of a split Hopkinson bar, meanwhile specimens extracted from the other half of the ingot have been dissected for porosity distribution analyses carried out by means of image analysis. Stress-strain curves obtained from the mechanical tests have been discussed in terms of strain rate and statistical descriptors of the porosity. Successively a 3D-model of the specimen has been generated starting from the Voronoi algorithm, assigning as input the above-mentioned statistical distribution of the porosity. Due to the peculiarity of the cell morphology (e.g. single larger cells), stress-strain localization has been demonstrated as one of the reasons of the scattering found during the experiments. A material model, to reproduce the investigated foam mechanical behavior, has been calibrated. Despite the difference among experiments the material model is able to reproduce all of them. Difference between the model coefficients quantifies roughly the difference due to the local geometry of the cells

Sex-dependent differences in the activities of acetylsalicylic acid-esterases in mouse kidneys

Acetylsalicylic acid (ASA), the most used drug worldwide, is hydrolyzed to salicylic acid and acetate by esterases present in tissues of several species including humans. Sex differences in drug metabolism by rodent liver are documented in the literature. In this paper we report a difference in the activities of the esterases (ASA-esterase I and II) in the kidneys of male and female mice. In this species there is no difference between males and females in liver ASA-esterases (ASA-esterase I: males 38.5 ± 7.9 (N = 5) and females 31.6 ± 7.6 (N = 5) nmol of salicylic acid formed min-1 mg protein-1, P>0.05; ASA-esterase II: males 77.3 ± 17.4 (N = 5) and females 61.4 ± 15.1 (N = 5) nmol of salicylic acid formed min-1 mg protein-1, P>0.05). However, in the kidneys males presented a much higher enzyme activity than females (ASA-esterase I: males 25.2 ± 6.3 (N = 5) and females 6.8 ± 0.6 (N = 5) nmol of salicylic acid formed min-1 mg protein-1, P<0.0002; ASA-esterase II: males 79.8 ± 10.1 (N = 5) and females 13.0 ± 1.1 (N = 5) nmol of salicylic acid formed min-1 mg protein-1, P<0.0001). The difference between sexes observed in mouse kidneys could serve as a model to study the molecular basis of this sex difference and also to determine the possible involvement of pituitary and gonadal hormones in this difference in ASA-esterase activities since these hormones control the sex differences in rodent liver enzyme activity.Universidade Federal de São Paulo (UNIFESP)Universidade Federal de São Paulo, EPM, São Paulo, BrazilSciEL

Acetylcholinesterase activity in the pons and medulla oblongata of rats after chronic electroconvulsive shock

An imbalance between cholinergic and noradrenergic neurotransmission has been proposed for the etiology of affective disorders. According to this hypothesis, depression would be the result of enhanced cholinergic and reduced noradrenergic neurotransmission. Repeated electroconvulsive shock (ECS) is an effective treatment for depression; moreover, in laboratory animals it induces changes in brain noradrenergic neurotransmission similar to those obtained by chronic treatment with antidepressant drugs (down-regulation of beta-adrenergic receptors). The aim of the present study was to determine whether repeated ECS in rats changes acetylcholinesterase (Achase) activity. Achase controls the level of acetylcholine (Ach) in the synaptic cleft and its levels seem to be regulated by the interaction between Ach and its receptor. Thus, a decrease in Achase activity would suggest decreased cholinergic activity. Adult male Wistar rats received one ECS (80 mA, 0.2 s, 60 Hz) daily for 7 days. Control rats were handled in the same way without receiving the shock. Rats were sacrificed 24 h after the last ECS and membrane-bound and soluble Achase activity was assayed in homogenates obtained from the pons and medulla oblongata. A statistically significant decrease in membrane-bound Achase activity (nmol thiocholine formed min-1 mg protein-1) (control 182.6 ± 14.8, ECS 162.2 ± 14.2, P<0.05) and an increase in soluble Achase activity in the medulla oblongata (control 133.6 ± 4.2, ECS 145.8 ± 12.3, P<0.05) were observed. No statistical differences were observed in Achase activity in the pons. Although repeated ECS induced a decrease in membrane-bound Achase activity, the lack of changes in the pons (control Achase activity: total 231.0 ± 34.5, membrane-bound 298.9 ± 18.5, soluble 203.9 ± 30.9), the region where the locus coeruleus, the main noradrenergic nucleus, is located, does not seem to favor the existence of an interaction between cholinergic and noradrenergic neurotransmission after ECS treatmentUniversidade Federal de São Paulo (UNIFESP)UNIFESPSciEL

Digital design of medical replicas via desktop systems: shape evaluation of colon parts

In this paper, we aim at providing results concerning the application of desktop systems for rapid prototyping of medical replicas that involve complex shapes, as, for example, folds of a colon. Medical replicas may assist preoperative planning or tutoring in surgery to better understand the interaction among pathology and organs. Major goals of the paper concern with guiding the digital design workflow of the replicas and understanding their final performance, according to the requirements asked by the medics (shape accuracy, capability of seeing both inner and outer details, and support and possible interfacing with other organs). In particular, after the analysis of these requirements, we apply digital design for colon replicas, adopting two desktop systems. ,e experimental results confirm that the proposed preprocessing strategy is able to conduct to the manufacturing of colon replicas divided in self-supporting segments, minimizing the supports during printing. ,is allows also to reach an acceptable level of final quality, according to the request of having a 3D presurgery overview of the problems. ,ese replicas are compared through reverse engineering acquisitions made by a structured-light system, to assess the achieved shape and dimensional accuracy. Final results demonstrate that low-cost desktop systems, coupled with proper strategy of preprocessing, may have shape deviation in the range of ±1 mm, good for physical manipulations during medical diagnosis and explanation

COMPARING THE RESPECTIVE EFFECTS OF THREE TYPES OF WARM-UP ON THE COUNTERMOVEMENT JUMP: AN ANALYSIS OF NON-ATHLETE COLLEGE STUDENTS

The purpose of this study was to examine and compare the respective effects of traditional, dynamic, and plyometric warm-ups on non-athlete college students’ performance of the countermovement jump (CMJ). Forty-seven male non-athlete college students were respectively allocated to three separate groups: the traditional warm-up group (TG), dynamic warm-up group (DG), and the plyometric warm-up group (PG). The DG and PG showed statistically significant improvements in push-off, force, and power (p\u3c0.001) when compared to the TG. No statistically significant differences were observed in jump height, flight time and velocity, and the effect sizes were small. The findings of this study showed that dynamic and plyometric warm-up protocols could influence CMJ performance among non-athlete college students

THE INFLUENCE OF DYNAMIC AND PLYOMETRIC EXERCISES ON KNEE JOINT MOTION FOR COUNTERMOVEMENT JUMP PERFORMANCE.

This study aims to analyse the effects of dynamic and plyometric exercises on knee joint motion for countermovement jump (CMJ) performance. The CMJ test was performed on 45 college male non-athletes who were categorised into three groups; a dynamic group (DG) performing dynamic exercises, a plyometric group (PG) performing jumping exercises, a control group (EG) performing traditional exercises for physical education. Motion analysis data from the knee joint angles were obtained during countermovements in the sagittal plane using video recording. The results showed that plyometric and dynamic exercises could improve jumping performance in college non-athletes and enhance the strength, force, and power of lower limb muscles and joints. Furthermore, the motion analysis helped identify a range of motions in knee joints, dynamic, and plyometric exercises that contribute to jumping performance

ANALYSIS ON THE EFFECTS OF WARM UP ON ANKLE JOINT MOTION AND STRIKE PATTERNS FOR 50M SPRINT PERFORMANCE.

The purpose of this study was to analyze the effects of ankle angles and strike pattern on 50m sprint test performance for young non-athletes. Twenty-seven non-athletes were distributed in a control group (CG) using habitual PE warm up exercises and an experimental group (EG) using basic sprint drills, and performed pre, control and post 50m sprint tests. Motion analysis data from the left leg ankle angle (LAA), right leg ankle angle (RAA) and strike pattern were obtained during landing moments in the sagittal plane using video recording. In accordance with our findings, basic sprint drill warm-ups can improve sprinting time in young girls and contribute to the strengthening of ankle muscles and joints. Motion analysis and the implementation of warm-ups with basic sprint exercises could help in the recognition of range of motion in ankle joints, and benefit sprint performance

THE INFLUENCE OF WARM-UP EXERCISES ON KNEE AND ELBOW JOINT MOTION FOR STANDING LONG JUMP PERFORMANCE

The purpose of this study was to analyse the influences of the motion angles of the knee and elbow joints on the standing long jump performance of high school students. Twenty-nine participants were assigned to either a control group to perform static and dynamic joint exercises or an experimental group to perform basic sprinting drill warm-up exercises. Both groups performed pre-, control, and post-standing long jump tests. Motion analysis of the knee and elbow joints was conducted in the sagittal plane by using video recording. Our findings support that basic sprint drill warm-up exercises can enhance the jump length in the youth. The implementation of warm-up exercises with basic sprint drills and motion analysis could be useful for determining the ranges of motion of the elbow and knee joints and improving standing long jump performance