Investigation of abrasive wear resistance of ferrous-based coatings with scratch tester

Abrasive wear resistance is very important in many applications and in most cases it is directly correlated with hardness of materials. Possible solutions for overcoming poor abrasive wear resistance of light metals, like Al-alloys, is using of coatings. In this paper the investigated results of the two types of ferrous-based coatings were presented and compared with gray cast iron, known as a material with good abrasive wear resistance. Process used for coating deposition on an Al-Si alloy substrate was Atmospheric Plasma Spraying (APS). Scratch tests with diamond indenter were used to simulate abrasive wear process. The indenter velocity of 10 mm/min was used over a wear tracks of 10 mm, with different normal loads applied. Both, coefficient of friction and wear rate of the samples were investigated and analyzed in correlation with its mechanical properties.

Investigation of abrasive wear resistance of ferrous-based coatings with scratch tester

Abrasive wear resistance is very important in many applications and in most cases it is directly correlated with hardness of materials. Possible solutions for overcoming poor abrasive wear resistance of light metals, like Al-alloys, is using of coatings. In this paper the investigated results of the two types of ferrous-based coatings were presented and compared with gray cast iron, known as a material with good abrasive wear resistance. Process used for coating deposition on an Al-Si alloy substrate was Atmospheric Plasma Spraying (APS). Scratch tests with diamond indenter were used to simulate abrasive wear process. The indenter velocity of 10 mm/min was used over a wear tracks of 10 mm, with different normal loads applied. Both, coefficient of friction and wear rate of the samples were investigated and analyzed in correlation with its mechanical properties.

Bilateral fibular fractures in a pre-ambulant infant

Multiple long-bone fractures, particularly bilateral fractures, are of moderate specificity for inflicted injury (physical abuse) in infants and young children. Bilateral healing fractures of the fibulae are rare and, depending on age, raise the suspicion of inflicted injury. We report healing undisplaced fractures of both fibulae, in almost identical positions, in a pre-ambulant infant. The caregivers reported that the infant repeatedly banged his legs against the metal frame of his playpen. A video of this mechanism was provided to the instructed radiology expert and showed that the point of impact of the infant’s legs against the metal frame was at a similar level to the radiographic abnormalities. This mechanism was therefore believed to be consistent with the injuries, resulting in a diagnosis of self-inflicted bilateral fibular fractures and not of inflicted injury

Influence of point defects concentration on optical and photocatalytic properties of ZnO ceramics

Zinc oxide is one of the most studied materials due to its wide bandgap (3.37 eV) and large exciton binding energy (60 meV) which enables application in electronics, optoelectronics and spintronics. In the forms of single crystal and thin-film ZnO are used as UV and blue light emitter, while sintered ZnO-based ceramics are important as varistors, thermistors or semiconductors. It has been found that point defects in the crystal structure of a ZnO strongly influenced its electrical and optical properties. Neutral oxygen vacancies are considered to be a major component of the defect structure of ZnO. Thus, correlation of the oxygen vacancies concentration with band gap energy of ZnO product is important to its application in optoelectronic devices. In this study we investigated the influence of point defects concentration in ZnO crystal structure on its optical and photocatalytic properties. We analyzed ZnO powders prepared by different techniques: (a) microwave processing of precipitate and (b) hydrothermal processing, which yield different ordered crystal structure. To increase a concentration of the point defects in the crystal structure, the powders were sintered in air atmosphere by heating rate of 10 °/min up to 1100 °C, with dwell time of 1 h. The crystal structure, average crystallite size and phase purity of the ZnO ceramics were determined by X-ray diffraction and Raman spectroscopy. The optical properties, in particular, absorption capacity and bang gap energy, were studied using UV–Vis diffuse reflectance spectroscopy. To reveal the role of microstructures and point defects in ZnO crystal lattice, which are receptive for luminescence and photocatalytic activity of this functional oxide, photoluminescence (PL), photoluminescence excitation (PLE) and EPR spectra were analyzed. The influence of point defects concentration in the ZnO crystal structure on photocatalytic properties was examined via decolorization of methylene blue under direct sunlight irradiation. Correlation between amount of the point defects, absorption capacity and photocatalytic efficiency were established. In order to clarify the experimental results ab initio calculations based on density functional theory (DFT) were performed

Point defect-enhanced optical and photoelectrochemical water splitting activity of nanostructured Zn1-xFeyO(1-x+1.5y)

Even has been under study since 1935, zinc oxide (ZnO) based materials still attract a huge scientific attention. Owing to a wide band gap energy (3.37 eV at room temperature) and a large exciton binding energy (60 meV) ZnO has a variety of application, e.g. in electronics, optoelectronics, spintronics and photocatalysis. Besides, it has been shown that zinc oxide-based materials have a great potential as photoelectrocatalysts in the processes of water splitting, yielding an increased both photocurrent density and photoconversion efficiency. However, with a band gap energy of 3.37 eV, ZnO is restricted to absorb UV light only. This restriction can be overcome by modifying optical properties of zinc oxide particles. During the years different approaches have been applied to modify the visible light photocatalytic activity of ZnO materials, for example: (1) metal and nonmetal ion doping, (2) hydrogenation, (3) the incorporation of crystalline defects in the form of vacancies and interstitials, (4) the modification of particles morphology and surface topology, etc. In this study we employed 3d metal ion substitution to improve visible light-driven photoactivity of zinc oxide particles. We investigated the influence of Fe concentration in Zn1-xFeyO(1-x+1.5y) nanoparticles on crystal structure, textural, optical and photoelectrocatalytic properties. Zn1-xFeyO(1-x+1.5y) nanoparticles with nominally 5, 10, 15 and 20 at.% of Fe ions were synthesized by microwave processing of a precipitate. The crystal structure and phase purity of the samples were investigated by X-ray diffraction, Raman and ATR-FTIR spectroscopy. Mössbauer spectroscopy was carried out to clarify the valence state of the iron ions in the ZnO crystal structure. Effects of the iron ions concentration on particles morphology and texture properties were observed with field emission scanning electron microscopy (FE–SEM), transmission electron microscopy (TEM) with elemental mapping, and nitrogen adsorption–desorption isotherm, respectively. The optical properties were studied using UV–Vis diffuse reflectance and photoluminescence (PL) spectroscopy. Photoelectrochemical activity of the Zn1-xFeyO(1-x+1.5y) samples as anode material was evaluated by linear sweep voltammetry in Na2SO4 electrolyte; the oxygen evolution kinetics were determined and compared. In addition, a series of first principles calculations were performed to address the influence of the iron concentration on the electronic structure of Zn1-xFeyO(1-x+1.5y) samples

A Transfer Matrix Method for Resonances in Randall-Sundrum Models

In this paper we discuss in detail a numerical method to study resonances in membranes generated by domain walls in Randall-Sundrum-like scenarios. It is based on similar works to understand the quantum mechanics of electrons subject to the potential barriers that exist in heterostructures in semiconductors. This method was used recently to study resonances of a three form field and lately generalized to arbitrary forms. We apply it to a lot of important models, namely those that contain the Gauge, Gravity and Spinor fields. In many cases we find a rich structure of resonances which depends on the parameters involved.Comment: 25 pages, 17 figure

Fibrinogen is not elevated in the cerebrospinal fluid of patients with multiple sclerosis

<p>Abstract</p> <p>Background</p> <p>Elevated plasma fibrinogen levels are a well known finding in acute infectious diseases, acute stroke and myocardial infarction. However its role in the cerebrospinal fluid (CSF) of acute and chronic central (CNS) and peripheral nervous system (PNS) diseases is unclear.</p> <p>Findings</p> <p>We analyzed CSF and plasma fibrinogen levels together with routine parameters in patients with multiple sclerosis (MS), acute inflammatory diseases of the CNS (bacterial and viral meningoencephalitis, BM and VM) and PNS (Guillain-Barré syndrome; GBS), as well as in non-inflammatory neurological controls (OND) in a total of 103 patients. Additionally, MS patients underwent cerebral MRI scans at time of lumbar puncture.</p> <p>CSF and plasma fibrinogen levels were significantly lower in patients with MS and OND patients as compared to patients with BM, VM and GBS. There was a close correlation between fibrinogen levels and albumin quotient (rho = 0.769, <it>p </it>< 0.001) which strongly suggests passive transfer of fibrinogen through the blood-CSF-barrier during acute inflammation. Hence, in MS, the prototype of chronic neuroinflammation, CSF fibrinogen levels were not elevated and could not be correlated to clinical and neuroradiological outcome parameters.</p> <p>Conclusions</p> <p>Although previous work has shown clear evidence of the involvement of fibrinogen in MS pathogenesis, this is not accompanied by increased fibrinogen in the CSF compartment.</p

Light Relic Neutralinos

The relic abundance and the scalar cross{section o nucleon for light neutralinos (of mass m below about 45 GeV) are evaluated in an e ective MSSM model with R-parity conservation and without GUT{inspired relations among gaugino masses. It is shown that these neutralinos may provide a sizeable contribution to the matter density in the Universe CDM. By requiring that its relic abundance does not exceed the upper bound on CDM based on the new WMAP data, a lower bound on the neutralino mass m > 6 GeV is derived. These light neutralinos can also produce measurable e ects in WIMP direct detection experiments, and in particular could explain the modulation result recently con rmed by DAMA. Uncertainties in direct detection calculations due to the modeling of the WIMP velocity distribution function are also discussed

Direct and Inverse Variational Problems on Time Scales: A Survey

We deal with direct and inverse problems of the calculus of variations on arbitrary time scales. Firstly, using the Euler-Lagrange equation and the strengthened Legendre condition, we give a general form for a variational functional to attain a local minimum at a given point of the vector space. Furthermore, we provide a necessary condition for a dynamic integro-differential equation to be an Euler-Lagrange equation (Helmholtz's problem of the calculus of variations on time scales). New and interesting results for the discrete and quantum settings are obtained as particular cases. Finally, we consider very general problems of the calculus of variations given by the composition of a certain scalar function with delta and nabla integrals of a vector valued field.Comment: This is a preprint of a paper whose final and definite form will be published in the Springer Volume 'Modeling, Dynamics, Optimization and Bioeconomics II', Edited by A. A. Pinto and D. Zilberman (Eds.), Springer Proceedings in Mathematics & Statistics. Submitted 03/Sept/2014; Accepted, after a revision, 19/Jan/201