76 research outputs found
Anti-aging activities of extracts from Tunisian medicinal halophytes and their aromatic constituents
Six medicinal halophytes widely represented in North Africa and commonly used in traditional
medicine were screened for pharmacological properties to set out new promising sources of natural
ingredients for cosmetic or nutraceutical applications. Thus, Citrullus colocynthis, Cleome
arabica, Daemia cordata, Haloxylon articulatum, Pituranthos scoparius and Scorzonera undulata were
examined for their in vitro antioxidant (DPPH scavenging and superoxide anion-scavenging,
β-carotene bleaching inhibition and iron-reducing tests), antibacterial (microdi- lution method,
against four human pathogenic bacteria) and anti-tyrosinase activities. Besides, their aromatic
com- position was determined by RP-HPLC. H. articulatum shoot extracts exhibited the strongest
antioxidant activity and inhibited efficiently the growth of Salmonella enterica and Escherichia
coli. P. scoparius and C. arabica inhibited slightly monophenolase, whereas H. articulatum was the
most efficient inhibitor of diphenolase activity. Furthermore, H. articulatum exhibited the highest
aromatic content (3.4 % DW), with dopamine as the major com- pound. These observations suggest that
shoot extract of H. articulatum, and to a lesser extent of C. arabica, could otic as well as new
natural skin lightening agents. Also, possible implication of aromatic compounds in anti-tyrosinase activity is discussed
Assessment of brain injury biomechanics in soccer heading using finite element analysis
This study presents an in silico finite element (FE) model-based biomechanical analysis of brain injury metrics and associated risks of a soccer ball impact to the head for aware and unaware athletes, considering ball impact velocity and direction. The analysis presented herein implements a validated soccer ball and 50th percentile human head computational FE model for quantifying traumatic brain injury (TBI) metrics. The brain's mechanical properties are designated using a viscoelastic-viscoplastic constitutive material model for the white and gray matter within the human head FE model. FE results show a dynamic human head-soccer ball peak contact area of approximately seven times greater than those documented for helmet-to-helmet hits in American Football. Due to the deformable nature of the soccer ball, the impact dynamics are unique depending on the location and velocity of impact. TBI injury risks also depend on the location of impact and the impact velocity. Impacts to the rear (BrIC:0.48, HIC15:180.7), side (BrIC:0.52, HIC15:176.5), and front (BrIC:0.37, HIC15:129.0) are associated with the highest injury risks. Furthermore, the FE results indicate when an athlete is aware of an incoming ball, HIC15-based Abbreviated Injury Scale 1 (AIS 1) injury risks for the front, side, and rear impacts decrease from 10.5%, 18.5%, and 19.3%, respectively, to approximately 1% in front and side impacts and under 6% in a rear impact. Lastly, the unique contact area between the head and soccer ball produces pressure gradients in the ball that translate into distinguishable stress waves in the skull and the cerebral cortex
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A mechanism-based approach to modeling ductile fracture.
Ductile fracture in metals has been observed to result from the nucleation, growth, and coalescence of voids. The evolution of this damage is inherently history dependent, affected by how time-varying stresses drive the formation of defect structures in the material. At some critically damaged state, the softening response of the material leads to strain localization across a surface that, under continued loading, becomes the faces of a crack in the material. Modeling localization of strain requires introduction of a length scale to make the energy dissipated in the localized zone well-defined. In this work, a cohesive zone approach is used to describe the post-bifurcation evolution of material within the localized zone. The relations are developed within a thermodynamically consistent framework that incorporates temperature and rate-dependent evolution relationships motivated by dislocation mechanics. As such, we do not prescribe the evolution of tractions with opening displacements across the localized zone a priori. The evolution of tractions is itself an outcome of the solution of particular, initial boundary value problems. The stress and internal state of the material at the point of bifurcation provides the initial conditions for the subsequent evolution of the cohesive zone. The models we develop are motivated by in-situ scanning electron microscopy of three-point bending experiments using 6061-T6 aluminum and 304L stainless steel, The in situ observations of the initiation and evolution of fracture zones reveal the scale over which the failure mechanisms act. In addition, these observations are essential for motivating the micromechanically-based models of the decohesion process that incorporate the effects of loading mode mixity, temperature, and loading rate. The response of these new cohesive zone relations is demonstrated by modeling the three-point bending configuration used for the experiments. In addition, we survey other methods with the potential to provide more detailed information about the near tip deformation fields
FCS-MPC upravljačka strategija novim trorazinskim izmjenjivačem otpornim na kvarove
In order to meet the high reliability of aviation inverters, the paper established a new three-level inverter which can increase the reliability in safety-critical applications, what\u27s more, the new topology adding assistant leg to control neutral-point voltage independently. On the basis of the new topology, a mixed logic dynamic (MLD) model was established for the new inverter circuits, and takes finite control set model predictive control (FCS-MPC) for the new inverter. The method takes a discrete-time model of inverter to predict the future value of the all possible voltage vectors generated by the inverter. The vector which minimizes objective function in finite control set is selected as the control of inverter, the objective function used in this work evaluates the voltage error and the switch frequency at the next sampling time. The paper explicitly researched the solving algorithm and realization procedure of the new inverter circuit, its feasibility and validity is verified by the experiment.Za postizanje visokog stupnja pouzdanosti avijacijskih izmjenjivača, u radu je postavljena nova topologija trorazinskog izmjenjivača za primjene u sigurnosno kritičnim sustavima koja ima dodatnu pomoćnu granu za nezavisno upravljanje naponom neutralne točke. Zasnivajući se na ovoj novoj topologiji, dinamički model s mješovitom logikom (MLD) postavljen je za električne krugove novog ispravljača koji za upravljanje pretvaračem koriste konačni skup upravljačkih signala dobivenih modelskog prediktivnog upravljanja (FCS-MPC). Metoda koristi vremenski diskretni model izmjenjivača za predviđanje budućih vrijednosti svih mogućih vektora napona koje generira izmjenjivač. Za upravljanje pretvaračem koristi se upravljački vektor iz konačnog skupa upravljačkih signala dobiven minimiziranjem funkcije cilja koja u obzir uzima grešku napona i frekvenciju sklapanja u sljedećem koraku diskretizacije. U radu je izravno razvijen algoritam za rješavanje problema i procedura za realizaciju nove topologije izmjenjivača, a izvedivost i validnost provjereni su eksperimentalno
A multivariant secure framework for smart mobile health application
This is an accepted manuscript of an article published by Wiley in Transactions on Emerging Telecommunications Technologies, available online: https://doi.org/10.1002/ett.3684
The accepted version of the publication may differ from the final published version.Wireless sensor network enables remote connectivity of technological devices such as smart mobile with the internet. Due to its low cost as well as easy availability of data sharing and accessing devices, the Internet of Things (IoT) has grown exponentially during the past few years. The availability of these devices plays a remarkable role in the new era of mHealth. In mHealth, the sensors generate enormous amounts of data and the context-aware computing has proven to collect and manage the data. The context aware computing is a new domain to be aware of context of involved devices. The context-aware computing is playing a very significant part in the development of smart mobile health applications to monitor the health of patients more efficiently. Security is one of the key challenges in IoT-based mHealth application development. The wireless nature of IoT devices motivates attackers to attack on application; these vulnerable attacks can be denial of service attack, sinkhole attack, and select forwarding attack. These attacks lead intruders to disrupt the application's functionality, data packet drops to malicious end and changes the route of data and forwards the data packet to other location. There is a need to timely detect and prevent these threats in mobile health applications. Existing work includes many security frameworks to secure the mobile health applications but all have some drawbacks. This paper presents existing frameworks, the impact of threats on applications, on information, and different security levels. From this line of research, we propose a security framework with two algorithms, ie, (i) patient priority autonomous call and (ii) location distance based switch, for mobile health applications and make a comparative analysis of the proposed framework with the existing ones.Published onlin
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