202 research outputs found
Thermophysical properties of functionalized graphene nanoplatelet dispersions for improving efficiency in a wind turbine cooling system
A new generation of heat transfer fluids, nanofluids, can
play a major role in the development of today’s renewable
energies. In the particular case of wind turbines, an undesirable
overheating of electrical and mechanical components can
provoke a noticeable reduction of overall efficiency due to the
temperature is a limiting factor to the electricity generation or
even very expensive repair cost because of an unexpected crash
of generators, or others turbine components. Dispersions of
multiple-layer graphene nanostructures with high thermal
conductivity in conventional working fluids are a promising
type of new heat transfer fluids due to the excellent
performance of nanoadditives in heat transference. Hence,
determining the thermophysical properties of these
nanomaterials under different conditions is the first step and
key issue for analysing and optimizing the dispersions.
Although water-based graphene nanoplatelet nanofluids have
been investigated and some correlations can be found in the
literature, scarce studies were conducted using other industrial
working fluids as base fluids.
The purpose of this study is to carry out a thorough
thermophysical characterization of different loaded samples of
functionalized graphene nanoplatelet dispersions in an
industrial heat transfer fluid, Havoline XLC Pre-mixed 50/50.
Four different nanofluids at mass concentrations (0.25, 0.50,
0.75 and 1.0) wt.% of functionalized graphene nanoplatelets
powder were produced. In order to obtain improved long-term
stabilities, sodium dodecyl benzene sulphonate was added to
the samples at a mass concentration of 0.125 % in relation to
the base fluid without appreciable variations in the pH value.
Stability was assessed through zeta potential and dynamic light
scattering measurements. Tests for determining thermal
conductivity were conducted with a transient hot wire
technique in a wide temperature range. In addition, densities,
dynamic viscosities and specific heat capacities of the samples
were experimentally determined at different temperatures in
order to carry out further studies such as experimental
convective heat transfer coefficients and pressure drops.
Increases in thermal conductivity up to 7.3 % were found with
not very high viscosity rises.Papers presented at the 13th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Portoroz, Slovenia on 17-19 July 2017 .International centre for heat and mass transfer.American society of thermal and fluids engineers
Flow behaviour of glycolated water suspensions of functionalized graphene nanoplatelets
The heat transfer performance of the conventional fluids
used in heat exchange processes improves by dispersing
nanoparticles with high thermal conductivity, as many
researches have shown in the last decades. The heat transfer
capability of a fluid depends on several physical properties
among which the rheological behavior is very relevant, as we
have previously pointed out.
In this study, different samples of nanofluids have been
analyzed by using a DHR-2 rotational rheometer of TA
Instruments with concentric cylinder geometry in the
temperature range from (278.15 to 323.15) K. The used base
fluids were two different binary mixtures of propylene glycol
and water at (10:90)% and (30:70)% mass ratios. Two different
mass concentrations (viz. 0.25 and 0.5 wt.%) of graphene
nanoplatelets functionalized with sulfonic acid (graphenit-
HW6) were dispersed in these two base fluids.
Firstly, with the goal of checking and calibrating the
operation of the rheometer, the viscosity-shear stress curves for
pure propylene glycol, Krytox GPL102 oil, and the two base
fluids were experimentally determined. A detailed comparative
study with those well-known data over the entire range of
temperature was stabilized obtaining deviations in viscosity less
than 3.5%. Then, the flow curves of the different nanofluid
samples were studied at different temperatures to characterize
their flow behavior.Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016
CD28null CD4 T-cell expansions in autoimmune disease suggest a link with cytomegalovirus infection
Immunosenescence is thought to contribute to the increase of autoimmune diseases in older people. Immunosenescence is often associated with the presence of an expanded population of CD4 T cells lacking expression of CD28 (CD28null). These highly cytotoxic CD4 T cells were isolated from disease-affected tissues in patients with rheumatoid arthritis, systemic lupus erythematosus, multiple sclerosis, or other chronic inflammatory diseases and their numbers appeared to be linked to disease severity. However, we recently demonstrated that the common herpes virus, cytomegalovirus (CMV), not ageing, is the major driver of this subset of cytotoxic T cells. In this review, we discuss how CMV might potentiate and exacerbate autoimmune disease through the expansion of CD28null CD4 T cells
Coupling dynamics of a geared multibody system supported by Elastohydrodynamic lubricated cylindrical joints
A comprehensive computational methodology to study the coupling dynamics of a geared multibody system supported by ElastoHydroDynamic (EHD) lubricated cylindrical joints is proposed throughout this work. The geared multibody system is described by using the Absolute-Coordinate-Based (ACB) method that combines the Natural Coordinate Formulation (NCF) describing rigid bodies and the Absolute Nodal Coordinate Formulation (ANCF) characterizing the flexible bodies. Based on the finite-short bearing approach, the EHD lubrication condition for the cylindrical joints supporting the geared system is considered here. The lubrication forces developed at the cylindrical joints are obtained by solving the Reynolds’ equation via the finite difference method. For the evaluation of the normal contact forces of gear pair along the Line Of Action (LOA), the time-varying mesh stiffness, mesh damping and Static Transmission Error (STE) are utilized. The time-varying mesh stiffness is calculated by using the Chaari’s methodology. The forces of sliding friction along the Off-Line-Of-Action (OLOA) are computed by using the Coulomb friction models with a time-varying coefficient of friction under the EHD lubrication condition of gear teeth. Finally, two numerical examples of application are presented to demonstrate and validate the proposed methodology.National Natural Science Foundations of China under Grant
11290151, 11221202 and 11002022, Beijing Higher
Education Young Elite Teacher Project under Grant YETP1201
Brugia malayi Antigen (BmA) inhibits HIV-1 trans-infection but neither BmA nor ES-62 alter HIV-1 infectivity of DC induced CD4+ Th-cells
One of the hallmarks of HIV-1 disease is the association of heightened CD4+ T-cell activation with HIV-1 replication. Parasitic helminths including filarial nematodes have evolved numerous and complex mechanisms to skew, dampen and evade human immune responses suggesting that HIV-1 infection may be modulated in co-infected individuals. Here we studied the effects of two filarial nematode products, adult worm antigen from Brugia malayi (BmA) and excretory-secretory product 62 (ES-62) from Acanthocheilonema viteae on HIV-1 infection in vitro. Neither BmA nor ES-62 influenced HIV-1 replication in CD4+ enriched T-cells, with either a CCR5- or CXCR4-using virus. BmA, but not ES-62, had the capacity to bind the C-type lectin dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin (DC-SIGN) thereby inhibiting HIV-1 trans-infection of CD4+ enriched T-cells. As for their effect on DCs, neither BmA nor ES-62 could enhance or inhibit DC maturation as determined by CD83, CD86 and HLA-DR expression, or the production of IL-6, IL-10, IL-12 and TNF-α. As expected, due to the unaltered DC phenotype, no differences were found in CD4+ T helper (Th) cell phenotypes induced by DCs treated with either BmA or ES-62. Moreover, the HIV-1 susceptibility of the Th-cell populations induced by BmA or ES-62 exposed DCs was unaffected for both CCR5- and CXCR4-using HIV-1 viruses. In conclusion, although BmA has the potential capacity to interfere with HIV-1 transmission or initial viral dissemination through preventing the virus from interacting with DCs, no differences in the Th-cell polarizing capacity of DCs exposed to BmA or ES-62 were observed. Neither antigenic source demonstrated beneficial or detrimental effects on the HIV-1 susceptibility of CD4+ Th-cells induced by exposed DCs
Diagnostic accuracy of non-invasive tests for advanced fibrosis in patients with NAFLD: An individual patient data meta-analysis
Objective Liver biopsy is still needed for fibrosis staging in many patients with non-alcoholic fatty liver disease. The aims of this study were to evaluate the individual diagnostic performance of liver stiffness measurement by vibration controlled transient elastography (LSM-VCTE), Fibrosis-4 Index (FIB-4) and NAFLD (non-alcoholic fatty liver disease) Fibrosis Score (NFS) and to derive diagnostic strategies that could reduce the need for liver biopsies. Design Individual patient data meta-analysis of studies evaluating LSM-VCTE against liver histology was conducted. FIB-4 and NFS were computed where possible. Sensitivity, specificity and area under the receiver operating curve (AUROC) were calculated. Biomarkers were assessed individually and in sequential combinations. Results Data were included from 37 primary studies (n=5735; 45% women; median age: 54 years; median body mass index: 30 kg/m2; 33% had type 2 diabetes; 30% had advanced fibrosis). AUROCs of individual LSM-VCTE, FIB-4 and NFS for advanced fibrosis were 0.85, 0.76 and 0.73. Sequential combination of FIB-4 cut-offs (<1.3; ≥2.67) followed by LSM-VCTE cut-offs (<8.0; ≥10.0 kPa) to rule-in or rule-out advanced fibrosis had sensitivity and specificity (95% CI) of 66% (63-68) and 86% (84-87) with 33% needing a biopsy to establish a final diagnosis. FIB-4 cut-offs (<1.3; ≥3.48) followed by LSM cut-offs (<8.0; ≥20.0 kPa) to rule out advanced fibrosis or rule in cirrhosis had a sensitivity of 38% (37-39) and specificity of 90% (89-91) with 19% needing biopsy. Conclusion Sequential combinations of markers with a lower cut-off to rule-out advanced fibrosis and a higher cut-off to rule-in cirrhosis can reduce the need for liver biopsies
Diagnostic accuracy of non-invasive tests for advanced fibrosis in patients with NAFLD: An individual patient data meta-analysis
Why Are Outcomes Different for Registry Patients Enrolled Prospectively and Retrospectively? Insights from the Global Anticoagulant Registry in the FIELD-Atrial Fibrillation (GARFIELD-AF).
Background: Retrospective and prospective observational studies are designed to reflect real-world evidence on clinical practice, but can yield conflicting results. The GARFIELD-AF Registry includes both methods of enrolment and allows analysis of differences in patient characteristics and outcomes that may result. Methods and Results: Patients with atrial fibrillation (AF) and ≥1 risk factor for stroke at diagnosis of AF were recruited either retrospectively (n = 5069) or prospectively (n = 5501) from 19 countries and then followed prospectively. The retrospectively enrolled cohort comprised patients with established AF (for a least 6, and up to 24 months before enrolment), who were identified retrospectively (and baseline and partial follow-up data were collected from the emedical records) and then followed prospectively between 0-18 months (such that the total time of follow-up was 24 months; data collection Dec-2009 and Oct-2010). In the prospectively enrolled cohort, patients with newly diagnosed AF (≤6 weeks after diagnosis) were recruited between Mar-2010 and Oct-2011 and were followed for 24 months after enrolment. Differences between the cohorts were observed in clinical characteristics, including type of AF, stroke prevention strategies, and event rates. More patients in the retrospectively identified cohort received vitamin K antagonists (62.1% vs. 53.2%) and fewer received non-vitamin K oral anticoagulants (1.8% vs . 4.2%). All-cause mortality rates per 100 person-years during the prospective follow-up (starting the first study visit up to 1 year) were significantly lower in the retrospective than prospectively identified cohort (3.04 [95% CI 2.51 to 3.67] vs . 4.05 [95% CI 3.53 to 4.63]; p = 0.016). Conclusions: Interpretations of data from registries that aim to evaluate the characteristics and outcomes of patients with AF must take account of differences in registry design and the impact of recall bias and survivorship bias that is incurred with retrospective enrolment. Clinical Trial Registration: - URL: http://www.clinicaltrials.gov . Unique identifier for GARFIELD-AF (NCT01090362)
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