High pressure viscosity behaviour of tris(2-ethylhexyl) trimellitate up to 150 MPa

This article presents a study on the viscous behaviour at high pressure of a synthetic oil, tris(2-ethylhexyl) trimellitate (TOTM). This fluid is being recommended as potential industrial reference material for high viscosity-high pressure measurements. Here we report new experimental viscosity values for TOTM at temperatures from 278.15 K to 373.15 K and at pressures to 150 MPa with a maximum viscosity of 2570 mPa s. The measurements have been performed using a high pressure falling-body apparatus and a Couette rotational viscometer. The experimental values obtained in this work are included in the database of a multinational project used recently to develop a reference correlation for TOTM (Wakeham et al., 2017). The universal viscosity-pressure coefficient of this fluid has been evaluated and compared with other oils, finding that it is close to the literature values of mineral oils. Moreover, we perform an analysis of the dependency of viscosity on pressure and temperature based on the density scaling concept.This work was supported by both the Spanish Ministry of Economy, Industry and Competitiveness and the European Regional Development Fund through the ENE2014-55489-C2-1-R and ENE2017-86425-C2-2-R projects. Authors acknowledge the financial support by the Xunta de Galicia through GRC ED431C 2016/001 and ED431E 2018/08 grants. The measurements of TOTM were carried out under the auspices of the International Union of Pure and Applied Chemistry (IUPAC) within the framework of the Project No. 2012–051–1–100.S

High Pressure Characterization of the Viscous and Volumetric Behavior of Three Transmission Oils

Measurements of viscosity and density of three lubricating oils (two synthetic and one mineral) were performed. The density of these lubricants was measured at atmospheric pressure by means of a density measuring cell which works on the proven principle of the oscillating tube. Using the same device, the viscosity of these lubricants was measured at 0.1 MPa by using a rotational viscometer. The volumetric behavior of the tested lubricants at high pressure is also reported. Density was measured from 278.15 to 398.15 K up to 120 MPa with a high pressure vibrating tube densimeter. The isobaric thermal expansivity and the isothermal compressibility were determined with a Tammann–Tait equation. A falling body viscometer was used to determine the viscosity behavior at high pressure from 303.15 to 353.15 K up to 150 MPa. From the experimental data obtained in these measurements, the film pressure–viscosity coefficient of these lubricants was calculated and their ability to generate a lubricant film in rolling concentrated contacts was discussed.The authors gratefully acknowledge the funding through several projects and grants without whom this work would not have been possible: IACOBUS exchange program (2017); ENE2014-55489-C2-1-R and ENE2017-86425-C2-2-R cofinanced by the Spanish Ministry of Economy and Competitiveness and the European ERDF program; GRC ED431C 2016/001 financed by Xunta de Galicia (Spain); ED431E 2018/08 financed by Xunta de Galicia (Spain); Principia program JMLR of Xunta de Galicia (Spain); NORTE-01-0145-FEDER-000022—SciTech—Science and Technology for Competitive and Sustainable Industries, cofinanced by Programa Operacional Regional do Norte (NORTE2020), through Fundo Europeu de Desenvolvimento Regional (FEDER); LAETA under the project UID/EMS/50022/2013.S

Thermophysical and tribological properties of dispersions based on graphene and a trimethylolpropane trioleate oil

The objective of this work is to study the tribological and thermophysical properties of nanolubricants composed by a trimethylolpropane trioleate (TMPTO) oil, and graphene nanoplatelets (GnP). For this aim, nanolubricants based on TMPTO with 0.05, 0.10, 0.25 and 0.50 wt% of graphene nanoplatelets were prepared. The dependence on temperature and concentration of the viscosity, density and speed of sound was determined by means of a rotational viscometer and two mechanical oscillation densimeters. Likewise, the antifriction and antiwear properties of these nanolubricants were analyzed. For this purpose, tribological tests were carried out at room temperature in a tribometer operating in ball on plate configuration and in reciprocating mode under a working load of 2.5 N. A 3D optical profilometer was used to analyze the wear track through the width of the scar. As regards thermophysical behavior of density and viscosity, both increase as the concentration of nanoparticles increases, whereas the speed of sound slightly diminishes when the GnP concentration increases. The best antifriction-antiwear performance was obtained for the nanolubricant containing 0.25 wt% in GnP.This work was supported by both the Spanish Ministry of Economy and Competitiveness and the ERDF programme through ENE2014-55489-C2-1-R and ENE2017-86425-C2-2-R projects. Moreover, this work was funded by the Xunta de Galicia (AGRUP2015/11 and GRC ED431C 2016/001). The three last funders also financed the acquisition of the 3D Optical Profile Sensofar S Neox (UNST15-DE-3156). JMLR acknowledges Xunta de Galicia for a Principia contract.S

Thermophysical and Tribological Properties of Highly Viscous Biolubricants

Two new highly viscous biodegradable oils are investigated for use in wind turbine gearboxes (BIO-G00) and in mechanical transmissions of agricultural tractors (BIO-G02). Studies on their thermophysical and tribological properties were performed. High-pressure–viscosity measurements were obtained up to 250 MPa and 363.15 K using a falling-body apparatus. The viscosity of BIO-G00 and BIO-G02 reaches maximum values of 14720 and 7072 mPa·s, respectively. The film thickness and the tribological performance, from boundary to full-fluid lubrication regimes, under a slide-to-roll ratio of 5% obtained in an EHD2 ball-on-disk test rig are reported. Film thickness has also been computed through the Hamrock and Dowson equation, considering the inlet shear heating (thermal correction factor) due to the high viscosity of both biolubricants. Differences between the experimental and theoretical film thicknesses are around 4% at 353.15 K and 14% at 303.15 K for both oils. The universal pressure–viscosity coefficients, αfilm, for both oils are lower than those of other mineral and synthetic oils. Higher friction coefficients are obtained for BIO-G00 in all of the studied lubrication regimes for the different rough disks and in the entire temperature range. A suitable wetting behavior on steel surfaces is observed for both selected oils.Spanish Ministry of Economy and Competitiveness and the Xunta de Galicia have supported this work through GRC ED431C 2020/10 and ENE2017-86425-C2-2-R projects. The authors are grateful to the BIOVESIN (PSE-420000-2008-4) partners for the advice and for providing them the samples of the vegetable formulated oils and the reference lubricants. Dr. M.J.G.G. acknowledges a postdoctoral fellowship (ED481B-2019-015) from the Xunta de Galicia (Spain), and Dr. L.d.R. acknowledges the financial support through the Margarita Salas program (Ministry of Universities, Spain). The authors express their gratitude to Dr. K.R. Harris (University of New South Wales, Australia) for his high-pressure–viscosity study of DiPEiC9 and also to M.A. Marcos from the University of Vigo for his help with rheology tests.S

Modelling Service Level Agreements for Business Process Outsourcing Services

Many proposals to model service level agreements (SLAs) have been elaborated in order to automate different stages of the service lifecycle such as monitoring, implementation or deployment. All of them have been designed for computational services and are not well–suited for other types of services such as business process outsourcing (BPO) services. However, BPO services suported by process–aware information systems could also benefit from modelling SLAs in tasks such as performance monitoring, human resource assignment or process configuration. In this paper, we identify the requirements for modelling such SLAs and detail how they can be faced by combining techniques used to model computational SLAs, business processes, and process performance indicators. Furthermore, our approach has been validated through the modelling of several real BPO SLAsMinisterio de Economía y Competitividad TIN2012-32273Junta de Andalucía TIC-5906Junta de Andalucía P12-TIC-186

Pharmacogenetic prediction of clinical outcome in advanced colorectal cancer patients receiving oxaliplatin/5-fluorouracil as first-line chemotherapy

To determine whether molecular parameters could be partly responsible for resistance or sensitivity to oxaliplatin (OX)-based chemotherapy used as first-line treatment in advanced colorectal cancer (CRC). We studied the usefulness of the excision repair cross-complementing 1 (ERCC1), xeroderma pigmentosum group D (XPD), XRCC1 and GSTP1 polymorphisms as predictors of clinical outcome in these patients. We treated 126 CRC patients with a first-line OX/5-fluorouracil chemotherapeutic regimen. Genetic polymorphisms were determined by real-time PCR on an ABI PRISM 7000, using DNA from peripheral blood. Clinical response (CR), progression-free survival (PFS) and overall survival (OS) were evaluated according to each genotype. In the univariate analysis for CR, ERCC1-118 and XPD 751 polymorphisms were significant (P=0.02 and P=0.05, respectively). After adjustment for the most relevant clinical variables, only ERCC1-118 retained significance (P=0.008). In the univariate analysis for PFS, ERCC1-118 and XPD 751 were significant (P=0.003 and P=0.009, respectively). In the multivariant analysis, only the XPD 751 was significant for PFS (P=0.02). Finally, ERCC1-118 and XPD 751 polymorphisms were significant in the univariate analysis for OS (P=0.006 and P=0.015, respectively). Both genetic variables remained significant in the multivariate Cox survival analysis (P=0.022 and P=0.03). Our data support the hypothesis that enhanced DNA repair diminishes the benefit of platinum-based treatments

Meanings given to algebraic symbolism in problem posing

Some errors in the learning of algebra suggest students have difficulties giving meaning to algebraic symbolism. In this paper, we use problem posing in order to analyze the students’ capacity to assign meaning to algebraic symbolism and the difficulties that students encounter in this process depending on the characteristics of the algebraic statements given. We designed a written questionnaire composed of eight closed algebraic statements expressed symbolically, which was administered to 55 students who had finished their compulsory education and that had some previous experience in problem posing. In our analysis of the data, we examine both syntactic and semantic structures of the problem posed. We note that in most cases students posed problems with syntactic structures different to those given. They did not include computations within variables, and changed the kinds of relationships connecting variables. Students easily posed problems for statements with additive structures. Other differences in the type of problems posed depend on the characteristics of the given statements

Zipf's Law in Short-Time Timbral Codings of Speech, Music, and Environmental Sound Signals

Timbre is a key perceptual feature that allows discrimination between different sounds. Timbral sensations are highly dependent on the temporal evolution of the power spectrum of an audio signal. In order to quantitatively characterize such sensations, the shape of the power spectrum has to be encoded in a way that preserves certain physical and perceptual properties. Therefore, it is common practice to encode short-time power spectra using psychoacoustical frequency scales. In this paper, we study and characterize the statistical properties of such encodings, here called timbral code-words. In particular, we report on rank-frequency distributions of timbral code-words extracted from 740 hours of audio coming from disparate sources such as speech, music, and environmental sounds. Analogously to text corpora, we find a heavy-tailed Zipfian distribution with exponent close to one. Importantly, this distribution is found independently of different encoding decisions and regardless of the audio source. Further analysis on the intrinsic characteristics of most and least frequent code-words reveals that the most frequent code-words tend to have a more homogeneous structure. We also find that speech and music databases have specific, distinctive code-words while, in the case of the environmental sounds, this database-specific code-words are not present. Finally, we find that a Yule-Simon process with memory provides a reasonable quantitative approximation for our data, suggesting the existence of a common simple generative mechanism for all considered sound sources

Forest carbon sequestration:the impact of forest management

In this chapter, we describe alternative ways in which forests and forestry can help to mítigate climate change, along with the potential impact of these activities. The three carbon storage compartments should be considered inall impact estimates. Carbon content in living biomass is easily estimated via species-specific equations or by applying factors to oven-dry biomass weights (e.g.,lbañez et al.,2002, Herrero et al.,2011,Castaño and Bravo, 2012).Litter carbon content has been analysed in many studies on primary forest productivity, though information regarding the influence of forest management on litter carbon content is less abundant (Blanco et al., 2006). In the last decade,efforts have been made to assess soil carbon in forests, but studies on the effect of forest management on soils show discrepancies (Lindner and Karjalainen,2007).Hoover (2011), for example,found no difference in forest floor carbon stocks among stands subjected to partial or complete harvest treatments in the United States.Instituto Universitario de Gestión Forestal Sostenibl