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Rauckyte T.,University of Technology and Life Sciences in Bydgoszcz | Zak S.,University of Technology and Life Sciences in Bydgoszcz | Pawlak Z.,Tribochemistry Consulting | Pawlak Z.,University of economics | Oloyede A.,Queensland University of Technology
Journal of Environmental Engineering and Landscape Management | Year: 2010

This paper describes a case study of petroleum-contaminated soil/sediment samples which were analyzed using gas chromatography-flame ionization detector (GC-FID) for total petroleum hydrocarbons (TPH), volatile aromatic compounds: benzene, toluene, ethylbenzene, and xylenes (BTEX) and naphthalene by GC-MS, and oil and grease (O/G) content by sonication in hexane. The ratio of (TPH) / (O/G) shows that the hydrocarbon fraction is between 7% and 87%. The content of volatile organic fraction BTEX accounts for only a small proportion of total TPH, and the ratio of (BTEX) / (TPH) ranges from 0.1% to 0.6%. It should be stressed that the use of TPH methods as against gas chromatography must be done with care because the potential risk posed by BTEX compounds may not be adequately addressed.

Yusuf K.Q.,Queensland University of Technology | Motta N.,Queensland University of Technology | Pawlak Z.,Tribochemistry Consulting | Pawlak Z.,University of economics | Oloyede A.,Queensland University of Technology
Connective Tissue Research | Year: 2012

The surface amorphous layer of articular cartilage is of primary importance to its load-bearing and lubrication function. This lipid-filled layer is degraded/disrupted or eliminated when cartilage degenerates due to diseases. This article examines further the characteristic of this surface overlay using a combination of microscopy and imaging methods to evaluate the hypothesis that the surface of articular cartilage can be repaired by exposing degraded cartilage to aqueous synthetic lipid mixtures. The preliminary results demonstrate that it is possible to create a new surface layer of phospholipids on the surface of cartilage following artificial lipid removal, but such a layer does not possess enough mechanical strength for physiological function when created with either unsaturated palmitoyl-oleoyl-phosphatidylcholine or saturated dipalmitoyl-phosphatidylcholine component of joint lipid composition alone. We conclude that this may be due to low structural cohesivity, inadequate time of exposure, and the mix/content of lipid in the incubation environment. Copyright © Informa Healthcare USA, Inc.

Pawlak Z.,Tribochemistry Consulting | Pawlak Z.,University of economics | Petelska A.D.,University of Bialystok | Urbaniak W.,Kazimierz Wielki University in Bydgoszcz | And 2 more authors.
Cell Biochemistry and Biophysics | Year: 2013

The wettability of the articular surface of cartilage depends on the condition of its surface active phospholipid overlay, which is structured as multi-bilayer. Based on a hypothesis that the surface of cartilage facilitates the almost frictionless lubrication of the joint, we examined the characteristics of this membrane surface entity in both its normal and degenerated conditions using a combination of atomic force microscopy, contact angle measurement, and friction test methods. The observations have led to the conclusions that (1) the acid-base equilibrium condition influences the lubrication effectiveness of the surface of cartilage and (2) the friction coefficient is significantly dependent on the hydrophobicity of the surface of the tissue, thereby confirming the hypothesis tested in this paper. Both wettability angle and interfacial energy were obtained for varying conditions of the cartilage surface both in its wet, dry and lipid-depleted conditions. The interfacial energy also increased with mole fraction of the lipid species reaching an asymptotic value after 0. 6. Also, the friction coefficient was found to decrease to an asymptotic level as the wettability angle increased. The result reveal that the interfacial energy increased with pH till pH = 4. 0, and then decreased from pH = 4. 0 to reach equilibrium at pH = 7. 0. © 2012 The Author(s).

Pawlak Z.,Tribochemistry Consulting | Pawlak Z.,University of economics | Urbaniak W.,University of economics | Urbaniak W.,Kazimierz Wielki University in Bydgoszcz | Oloyede A.,Queensland University of Technology
Wear | Year: 2011

In this study, the influence of surface wettability (θ) and interfacial energy (γ) on the coefficient of friction (f) of tribopair surfaces in aqueous environment was investigated using a tribotester. The wettability behaviour of various tribopair surfaces [hydrophilic (HL) and hydrophobic (HB)]: (HL-HL), (HB-HB) and (HB-HL) was characterized by friction properties in water and aqueous two-phase lubricants (water+additive). The results show that the level of wettability of the tribopairs [the so-called delta wettability, Δθ=(θDisc-θPin)] is related to friction coefficient (f) in aqueous environment. In view of recent results, we conclude that both the interfacial energy and wettability of tribopair surfaces adequately characterize the lubrication processes. © 2011 Elsevier B.V.

Pawlak Z.,Tribochemistry Consulting | Pawlak Z.,University of economics | Urbaniak W.,University of economics | Gadomski A.,University of Technology and Life Sciences in Bydgoszcz | And 3 more authors.
Acta of Bioengineering and Biomechanics | Year: 2012

This study aims to determine the effect of progressive loss of the surface active phospholipids on the characteristics, and hence tribological function of articular cartilage. In accordance to Hill's hypothesis, 3-7 lipid bilayers at pH 7.4 operate as the solid lubricant in the cartilage-cartilage interface during physiological function. These bilayers are known to be depleted during cartilage degeneration. This study models this loss of phospholipid bilayers, studying experimentally both wet and dry cartilage surfaces, measuring surface wettability, and friction coefficient under a constant stress of 1.2 MPa. The results demonstrate that the friction coefficient increases gradually with loss of the phospholipid bilayers, and gains in value with decrease in wettability.

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