A Rare Case of Folate Deficiency-Induced Subacute Combined Degeneration of the Spinal Cord: A Case Report.

Folate deficiency is a rare cause of subacute combined degeneration (SCD). SCD is characterized by demyelination of the dorsal and lateral columns of the cervical and thoracic spine most commonly caused by vitamin B12 deficiency. Folate deficiency, which can be clinically indistinguishable from B12 deficiency, leads to a variety of presentations, including absent vibratory sensation and proprioception, sensory ataxia, and progressive motor weakness. Recognizing the clinical sequelae of SCD is essential for timely diagnosis and treatment. We present a case of a 38-year-old male with progressive ascending bilateral lower extremity numbness and motor weakness in the presence of normal vitamin B12 and methylmalonic acid levels. MRI of the entire neuraxis revealed a diagnosis of SCD, which was managed with oral folate replacement. We aim to highlight this rare cause of SCD, which can lead to permanent neurological deficits if not promptly recognized and treated.

Envisioning Better Healthcare Systems: A Unique and Innovative Journey From Community Hospital to Academic Medical Center.

The transformation from a community hospital to an academic medical center (AMC) presents a unique set of challenges and opportunities. This editorial provides an in-depth analysis of the barriers encountered and solutions developed within a large community hospital in Florida as it embarked on this transition, with a focus on the global relevance of issues experienced such as competition with major markets, the ongoing COVID-19 pandemic, the development of multiple Accreditation Council for Graduate Medical Education (ACGME) programs and balancing the complexities of the United States healthcare system. In alignment with the call for submissions, this editorial highlights the personal experiences of healthcare providers, researchers, and policymakers involved in this transition and explores how the lessons learned can inform the development of better healthcare systems worldwide.

Correction: A time-course comparative clinical and immune response evaluation study between the human pathogenic Orientia tsutsugamushi strains: Karp and Gilliam in a rhesus macaque (Macaca mulatta) model.

[This corrects the article DOI: 10.1371/journal.pntd.0010611.].

Ionogels Derived from Fluorinated Ionic Liquids to Enhance Aqueous Drug Solubility for Local Drug Administration.

Gelatin is a popular biopolymer for biomedical applications due to its harmless impact with a negligible inflammatory response in the host organism. Gelatin interacts with soluble molecules in aqueous media as ionic counterparts such as ionic liquids (ILs) to be used as cosolvents to generate the so-called Ionogels. The perfluorinated IL (FIL), 1-ethyl-3-methylpyridinium perfluorobutanesulfonate, has been selected as co-hydrosolvent for fish gelatin due to its low cytotoxicity and hydrophobicity aprotic polar structure to improve the drug aqueous solubility. A series of FIL/water emulsions with different FIL content and their corresponding shark gelatin/FIL Ionogel has been designed to enhance the drug solubility whilst retaining the mechanical structure and their nanostructure was probed by simultaneous SAXS/WAXS, FTIR and Raman spectroscopy, DSC and rheological experiments. Likewise, the FIL assisted the solubility of the antitumoural Doxorubicin whilst retaining the performing mechanical properties of the drug delivery system network for the drug storage as well as the local administration by a syringe. In addition, the different controlled release mechanisms of two different antitumoral such as Doxorubicin and Mithramycin from two different Ionogels formulations were compared to previous gelatin hydrogels which proved the key structure correlation required to attain specific therapeutic dosages.

A time-course comparative clinical and immune response evaluation study between the human pathogenic Orientia tsutsugamushi strains: Karp and Gilliam in a rhesus macaque (Macaca mulatta) model.

BACKGROUND: Scrub typhus is a vector-borne febrile illness caused by Orientia tsutsugamushi transmitted by the bite of Trombiculid mites. O. tsutsugamushi has a high genetic diversity and is increasingly recognized to have a wider global distribution than previously assumed. METHODOLOGY/PRINCIPLE FINDINGS: We evaluated the clinical outcomes and host immune responses of the two most relevant human pathogenic strains of O. tsutsugamushi; Karp (n = 4) and Gilliam (n = 4) in a time-course study over 80 days post infection (dpi) in a standardized scrub typhus non-human primate rhesus macaque model. We observed distinct features in clinical progression and immune response between the two strains; Gilliam-infected macaques developed more pronounced systemic infection characterized by an earlier onset of bacteremia, lymph node enlargement, eschar lesions and higher inflammatory markers during the acute phase of infection, when compared to the Karp strain. C-reactive protein (CRP) plasma levels, interferon gamma (IFN-γ, interleukin-1 receptor antagonist (IL-1ra), IL-15 serum concentrations, CRP/IL10- and IFN-γ/IL-10 ratios correlated positively with bacterial load in blood, implying activation of the innate immune response and preferential development of a T helper-type 1 immune response. The O. tsutsugamushi-specific immune memory responses in cells isolated from skin and lymph nodes at 80 dpi were more markedly elevated in the Gilliam-infected macaques than in the Karp-infected group. The comparative cytokine response dynamics of both strains revealed significant up-regulation of IFN-γ, tumor necrosis factor (TNF), IL-15, IL-6, IL-18, regulatory IL-1ra, IL-10, IL-8 and granulocyte-colony-stimulating factor (G-CSF). These data suggest that the clinical outcomes and host immune responses to scrub typhus could be associated with counter balancing effects of pro- and anti-inflammatory cytokine-mediated responses. Currently, no data on characterized time-course comparisons of O. tsutsugamushi strains regarding measures of disease severity and immune response is available. Our study provides evidence for the strain-specificity of host responses in scrub typhus, which supports our understanding of processes at the initial inoculation site (eschar), systemic disease progression, protective and/or pathogenic host immune mechanisms and cellular immune memory function. CONCLUSIONS/SIGNIFICANCE: This study characterised an improved intradermal rhesus macaque challenge model for scrub typhus, whereby the Gilliam strain infection associated with higher disease severity in the rhesus macaque model than the previous Karp strain infection. Difficulties associated with inoculum quantitation for obligate-intracellular bacteria were overcome by using functional inoculum titrations in outbred mice. The Gilliam-based rhesus macaque model provides improved endpoint measurements and contributes towards the identification of correlates of protection for future vaccine development.

Characterization of Tuna Gelatin-Based Hydrogels as a Matrix for Drug Delivery.

The skin of yellowfin tuna is one of the fishery industry solid residues with the greatest potential to add extra value to its circular economy that remains yet unexploited. Particularly, the high collagen content of fish skin allows generating gelatin by hydrolysis, which is ideal for forming hydrogels due to its biocompatibility and gelling capability. Hydrogels have been used as drug carriers for local administration due to their mechanical properties and drug loading capacity. Herein, novel tuna gelatin hydrogels were designed as drug vehicles with two structurally different antitumoral model compounds such as Doxorubicin and Crocin to be administrated locally in tissues with complex human anatomies after surgical resection. The characterization by gel permeation chromatography (GPC) of purified gelatin confirmed their heterogeneity composition, exhibiting three major bands that correspond to the ß and α chains along with high molecular weight species. In addition, the Fourier Transform Infrared (FT-IR) spectra of gelatin probed the secondary structure of the gelatin showing the simultaneous existence of α helix, ß sheet, and random coil structures. Morphological studies at different length scales were performed by a multi-technique approach using SAXS/WAXS, AFM and cryo-SEM that revealed the porous network formed by the interaction of gelatin planar aggregates. In addition, the sol-gel transition, as well as the gelation point and the hydrogel strength, were studied using dynamic rheology and differential scanning calorimetry. Likewise, the loading and release profiles followed by UV-visible spectroscopy indicated that the novel gelatin hydrogels improve the drug release of Doxorubicin and Crocin in a sustained fashion, indicating the structure-function importance in the material composition.

Analysis of Heat Transfer Characteristics of a GnP Aqueous Nanofluid through a Double-Tube Heat Exchanger.

The thermal properties of graphene have proved to be exceptional and are partly maintained in its multi-layered form, graphene nanoplatelets (GnP). Since these carbon-based nanostructures are hydrophobic, functionalization is needed in order to assess their long-term stability in aqueous suspensions. In this study, the convective heat transfer performance of a polycarboxylate chemically modified GnP dispersion in water at 0.50 wt% is experimentally analyzed. After designing the nanofluid, dynamic viscosity, thermal conductivity, isobaric heat capacity and density are measured using rotational rheometry, the transient hot-wire technique, differential scanning calorimetry and vibrating U-tube methods, respectively, in a wide temperature range. The whole analysis of thermophysical and rheological properties is validated by two laboratories. Afterward, an experimental facility is used to evaluate the heat transfer performance in a turbulent regime. Convective heat transfer coefficients are obtained using the thermal resistances method, reaching enhancements for the nanofluid of up to 13%. The reported improvements are achieved without clear enhancements in the nanofluid thermal conductivity. Finally, dimensionless analyses are carried out by employing the Nusselt and Péclet numbers and Darcy friction factor.

Enhancing the Thermal Performance of a Stearate Phase Change Material with Graphene Nanoplatelets and MgO Nanoparticles.

The effectiveness of dispersed nanomaterials to improve the thermal performance of phase change materials (PCMs) is well-proven in the literature. The proposal of new engineered nanoenhanced phase change materials (NePCMs) with customized characteristics may lead to more efficient thermal energy storage (TES) systems. This work is focused on the development of new NePCMs based on the dispersions of graphene nanoplatelets (GnPs) or MgO nanoparticles in a stearate PCM. The new proposed materials were synthesized using a two-step method, and acetic acid was selected as a surfactant to improve the stability of the dispersions. An extensive characterization of the constitutive materials and the developed dispersions using different spectroscopy techniques is reported. Also, the GnP nanopowder was explored by using the XPS technique with the aim to characterize the used carbon nanomaterial. The obtained spectra were investigated in terms of the chemical bonds related to the observed peaks. The thermophysical profile (density, thermal conductivity, isobaric heat capacity, and thermal diffusivity) was experimentally determined once the main components of the NePCMs were characterized and dispersions were designed and developed. This discussion focuses on the differentiated and distinguished effects of the dispersed GnPs and MgO on the properties of the NePCMs. A comprehensive analysis of the measurements to elucidate the mechanism that promoted higher improvements using GnPs instead of MgO was performed.

NePCM Based on Silver Dispersions in Poly(Ethylene Glycol) as a Stable Solution for Thermal Storage.

The main objective of this study is to design and characterize silver suspensions based on poly(ethylene glycol) PEG400, Ag/PEG400, as energy storage media for low-temperature applications. A polyvinylpyrrolidone (PVP) treatment was applied to ~22 nm silver nanoparticles to ensure good stability in poly(ethylene glycol). An array of different experimental techniques was utilized to analyze the molecular mass and purity of base poly(ethylene glycol), morphology of dry PVP-capped Ag nanoparticles, hydrodynamic average size of dispersed Ag particles, as well as thermal stability of PEG400 and Ag/PEG400 dispersions. Samples exhibited good temporal stabilities with average hydrodynamic diameter around 50 nm according to dynamic light scattering analyses. Melting and solidification transitions were investigated in terms of temperature and enthalpy from differential scanning calorimeter (DSC) thermograms. The thermophysical characterization was completed with thermal conductivity (k), dynamic viscosity (η), isobaric heat capacity (Cp), density (ρ), and surface tension (σ) measurements of designed materials using a Hot Disk thermal conductivimeter, a rotational rheometer, a DSC calorimeter working with a quasi-isothermal modulated method, a U-tube densimeter and a drop shape analyzer, respectively. For a nanoparticle loading of only 1.1% in mass, sub-cooling reduced by 7.1% and thermal conductive improved by 3.9%, with almost no penalization in dynamic viscosity (less than 5.4% of increase). Maximum modifications in Cp, ρ, and σ were 0.9%, 2.2%, and 2.2%, respectively. Experimental results were compared with the values provided by using different theoretical or semi-empirical equations. In particular, good descriptions of dynamic viscosity as functions of temperature and nanoparticle volume concentration were obtained by using the Vogel-Fulcher-Tammann equation and a first-order polynomial η( ϕ v , n p ) correlation, with absolute average deviations of 2.2% and 0.55%, respectively.

Graphene IoNanofluids, Thermal and Structural Characterization.

Graphene is considered a promising substance in applications related to the capture and reduction of the environmental impact of fluorinated gases. However, further research is still required to explore all related possibilities. In this work, the potential use in this context of nanofluids (NFs), obtained by dispersing graphene nanosheets in fluorinated ionic liquids (FILs) is investigated. As a starting step, a thermal and structural characterization for this type of IoNanofluids (IoNFs) is presented. The highly nanostructured nature of FILs has been recently demonstrated. The presence of fluorinated moieties is responsible for enhancing the accommodation of solutes such as small gases. The strong tendency to self-assemble forming continuous and supramolecular structures, and the versatility to rearrange in several conformational features allows the stabilization of nano colloidal systems. It is essential to perform a comprehensive study of their structural features to understand the behavior of this type of heterogeneous systems. Therefore, we present screening on the phase and structural behavior of these novel IoNFs to discover and develop optimized systems where FILs turn out to be advantageous. Thermogravimetric analysis (TGA) was employed to evaluate IoNFs mass losses with temperature, and their solid-fluid phase transitions were located using a differential scanning calorimeter (DSC). Their rheological properties were also determined through oscillatory experiments, obtaining the viscous and loss moduli. In addition, the structural percolation transition was also identified.

Experimental Convection Heat Transfer Analysis of a Nano-Enhanced Industrial Coolant.

Convection heat transfer coefficients and pressure drops of four functionalized graphene nanoplatelet nanofluids based on the commercial coolant Havoline® XLC Pre-mixed 50/50 were experimentally determined to assess its thermal performance. The potential heat transfer enhancement produced by nanofluids could play an important role in increasing the efficiency of cooling systems. Particularly in wind power, the increasing size of the wind turbines, up to 10 MW nowadays, requires sophisticated liquid cooling systems to keep the nominal temperature conditions and protect the components from temperature degradation and hazardous environment in off-shore wind parks. The effect of nanoadditive loading, temperature and Reynolds number in convection heat transfer coefficients and pressure drops is discussed. A dimensionless analysis of the results is carried out and empirical correlations for the Nusselt number and Darcy friction factor are proposed. A maximum enhancement in the convection heat transfer coefficient of 7% was found for the nanofluid with nanoadditive loading of 0.25 wt %. Contrarily, no enhancement was found for the nanofluids of higher functionalized graphene nanoplatelet mass fraction.

Influence of Six Carbon-Based Nanomaterials on the Rheological Properties of Nanofluids.

Nanofluids, dispersions of nanosized solid particles in liquids, have been conceived as thermally-improved heat transfer fluids from their conception. More recently, they have also been considered as alternative working fluids to improve the performance of direct absorption solar thermal collectors, even at low nanoadditive concentrations. Carbon-based nanomaterials have been breaking ground in both applications as nanoadditives during the last decade due to their high thermal conductivities and the huge transformation of optical properties that their addition involves. In any application field, rheological behavior became a central concern because of its implications in the pumping power consumption. In this work, the rheological behavior of four different loaded dispersions (0.25, 0.50, 1.0, and 2.0 wt%) of six carbon-based nanomaterials (carbon black, two different phase content nanodiamonds, two different purity graphite/diamond mixtures, and sulfonic acid-functionalized graphene nanoplatelets) in ethylene glycol:water mixture 50:50 vol% have been analysed. For this purpose, a rotational rheometer with double cone geometry was employed, which included a special cover to avoid mass losses due to evaporation at elevated temperatures. The flow curves of the twenty-four nanofluids and the base fluid were obtained by varying the shear rate between 1 and 1000 s-1 for seven different temperatures in the range from 283.15 to 353.15 K. The shear-thinning behaviors identified, as well as their dependences on carbon-based nanomaterial, concentration, and temperature, were analyzed. In addition, oscillatory tests were performed for samples with the clearest Non-Newtonian response, varying the deformation from 0.1 to 1000% with constant frequency and temperature. The dependence of the behaviors identified on the employed carbon-based nanomaterial was described.

Cruciferous Vegetables as Antioxidative, Chemopreventive and Antineoplasic Functional Foods: Preclinical and Clinical Evidences of Sulforaphane Against Prostate Cancers.

BACKGROUND: Sulforaphane (SF, 1-isothiocyanato-4-(methyl-sulfinyl)-butane) is found in broccoli, cabbage and cauliflower. METHODS: we performed a critical review on the antioxidative, chemopreventive and antitumor effects of SF from cruciferous vegetables against prostate cancers and molecular pathways. For a complete and reliable review, primary and secondary resources were used, including original and review articles, books and government documents published until March 2018. Articles that are in duplicity and disconnected are not considered for review. SF is derived from glucoraphanin (4-methyl-sulfinyl-butyl-glucosinate), being one of the most commonly found isothiocyanates in vegetables from Brassica spp., especially in broccoli samples. In vitro studies indicate that SF induces apoptosis in a dependent or non-dependent method of androgens by transcription of tumor suppressor genes, oxidation response and higher expression of phase II enzymes in prostate cancer cells. Sulforaphane also decreases transcription of the nuclear factor kB and antiapoptotic proteins, expression of cyclin D2 and survivin and DNA synthesis, increases Nrf2 gene activity, interferes with genome compacting by inhibition of histone deacetylases and disrupts Hsp90 complexes, which cause cell cycle arrest, mitosis interruption, activation of caspases and mitochondria depolarization. CONCLUSION: SF and cruciferous vegetables play antioxidative and chemopreventive role, delaying or blocking in vivo carcinogenesis, causing biochemical and epigenetic changes, preventing, delaying, or reversing preneoplastic or advanced prostate lesions, and frequently activating tumor cell death by intrinsic methods of apoptosis. These outcomes encourage the consumption of Brassica specimens, which could be easily achieved by the incorporation of food and vegetables rich in cruciferous isothiocyanates in the diet.

PEG 400-Based Phase Change Materials Nano-Enhanced with Functionalized Graphene Nanoplatelets.

This study presents new Nano-enhanced Phase Change Materials, NePCMs, formulated as dispersions of functionalized graphene nanoplatelets in a poly(ethylene glycol) with a mass-average molecular mass of 400 g·mol-1 for possible use in Thermal Energy Storage. Morphology, functionalization, purity, molecular mass and thermal stability of the graphene nanomaterial and/or the poly(ethylene glycol) were characterized. Design parameters of NePCMs were defined on the basis of a temporal stability study of nanoplatelet dispersions using dynamic light scattering. Influence of graphene loading on solid-liquid phase change transition temperature, latent heat of fusion, isobaric heat capacity, thermal conductivity, density, isobaric thermal expansivity, thermal diffusivity and dynamic viscosity were also investigated for designed dispersions. Graphene nanoplatelet loading leads to thermal conductivity enhancements up to 23% while the crystallization temperature reduces up to in 4 K. Finally, the heat storage capacities of base fluid and new designed NePCMs were examined by means of the thermophysical properties through Stefan and Rayleigh numbers. Functionalized graphene nanoplatelets leads to a slight increase in the Stefan number.

Heat Transfer Performance of Functionalized Graphene Nanoplatelet Aqueous Nanofluids.

The low thermal conductivity of fluids used in many industrial applications is one of the primary limitations in the development of more efficient heat transfer systems. A promising solution to this problem is the suspension of nanoparticles with high thermal conductivities in a base fluid. These suspensions, known as nanofluids, have great potential for enhancing heat transfer. The heat transfer enhancement of sulfonic acid-functionalized graphene nanoplatelet water-based nanofluids is addressed in this work. A new experimental setup was designed for this purpose. Convection coefficients, pressure drops, and thermophysical properties of various nanofluids at different concentrations were measured for several operational conditions and the results are compared with those of pure water. Enhancements in thermal conductivity and in convection heat transfer coefficient reach 12% (1 wt %) and 32% (0.5 wt %), respectively. New correlations capable of predicting the Nusselt number and the friction factor of this kind of nanofluid as a function of other dimensionless quantities are developed. In addition, thermal performance factors are obtained from the experimental convection coefficient and pressure drop data in order to assess the convenience of replacing the base fluid with designed nanofluids.

Factores relacionados al uso inadecuado del Servicio de Emergencias del Hospital Nacional Daniel Alcides Carrión durante Julio del 2012 a Julio 2013 / Factors related with the inappropriate use of the Emergency Service at the National Hospital Daniel Alcides Carrion during July 2012 to July 2013

Objetivo: Determinar los factores relacionados al uso inadecuado del servicio de Emergencias del Hospital Nacional Daniel Alcides Carrión durante Julio del 2012 a Julio del 2013. Metodología: El estudio es analítico, prospectivo, observacional y transversal. El muestreo es no probabilístico, se realizó una encuesta a 336 pacientes del servicio de Emergencias del Hospital Nacional Daniel Alcides Carrión durante julio del 2012 a julio del 2013. Para medir la relación de variables se utilizó la prueba estadística Chi-cuadrado con una significancia del 5 por ciento. Resultados: Los 336 pacientes estudiados, tuvieron como edad promedio 47±7.3 años, fueron de sexo femenino (52.7 por ciento) y convivientes (29.2 por ciento). Entre los factores predisponentes, la mayoría tienen grado de instrucción secundaria (34.2 por ciento) y con tipo de familia extensa (49.1 por ciento), tenían actividad laboral informal en la mayoría de los casos (45.8 por ciento). Con respecto a los factores facilitadores, el 33.3 por ciento de los pacientes tenía un ingreso menor a S/. 750 nuevos soles, la mayoría tenía un seguro SIS (73.8 por ciento), los pacientes mayormente acuden de día al centro de salud (70.5 por ciento). Por otro lado, el 76.2 por ciento acude de lunes a viernes al centro de salud, el tiempo de demora fue entre 16 a 45 minutos (46.7 por ciento) mientras que el 58.9 por ciento acude a su atención con un acompañante y la mayoría provenían del Callao. En cuanto a los factores de necesidad, el 60.7 por ciento manifestó reconocer el problema o percibe la gravedad de la realidad, mientras la decisión de buscar asistencia médica en la mayoría fue por su propia cuenta (76.2) y el 85.4 por ciento de los pacientes demandaron asistencia urgente o inmediata. El 78.6 por ciento de los pacientes que acuden al Servicio de Emergencia fueron clasificados inadecuadamente (Prioridad III, IV y V), solo el 21.4 por ciento fueron clasificados adecuadamente (Prioridad I y II)...

Objective: To determine the factors related to inappropriate use of Emergency service of Daniel Alcides Carrion National Hospital during July 2012 to July 2013. Methodology: Analytical, prospective, observational and transversal study. Sampling was not probabilistic; it was applied a survey to 336 patients from the Emergency service of Daniel Alcides Carrion National Hospital during July 2012 to July 2013. To measure the ratio of variables, Chi-square test statistical with a significance of 5 per cent was used. Results: Of 336 patients studied, the average age was 47±7.3 years old, female (52.7 per cent) and cohabiting marital status (29.2 per cent). Among the predisposing factors, most had secondary level education (34.2 per cent) and extended family type (49.1 per cent). They had informal labor activity in most cases (45.8 per cent). Regarding the enabling factors, 33.3 per cent of patients had an income of less than S/.750, most had SIS insurance (73.8 per cent); patients mostly come in day to the health center (70.5 per cent). On the other hand, 76.2 per cent attend Monday to Friday at the health center; the delay time was between 16 to 45 minutes (46.7 per cent), while 58.9 per cent goes to their attention with a companion and most carne from Callao. As for the need factors, 60.7 per cent stated recognize the problem or perceived severity of reality, while the decision to seek medical care in most was their own (76.2) and 85.4 per cent of patients demanded assistance urgent or immediate. The 78.6 per cent of patients attending to Emergency Services were classified improperly (Priority III, IV and V), only 21.4 per cent were classified properly (Priority I and II). It was evaluated the re1ationship between the priority of the patient and the associated factors, yielding results that race was related to the priority of the patients (p=0.01), work activity or job type (p=0.023), the monthly income level (p=0.035), type of insurance (p=0.001), the time they...

Rheological and volumetric properties of TiO2-ethylene glycol nanofluids.

Homogeneous stable suspensions obtained by dispersing dry TiO2 nanoparticles in pure ethylene glycol were prepared and studied. Two types of nanocrystalline structure were analyzed, namely anatase and rutile phases, which have been characterized by scanning electron microscopy. The rheological behavior was determined for both nanofluids at nanoparticle mass concentrations up to 25%, including flow curves and frequency-dependent storage and loss moduli, using a cone-plate rotational rheometer. The effect of temperature over these flow curve tests at the highest concentration was also analyzed from 283.15 to 323.15 K. Furthermore, the influence of temperature, pressure, nanocrystalline structure, and concentration on the volumetric properties, including densities and isobaric thermal expansivities, were also analyzed.

Rheological non-Newtonian behaviour of ethylene glycol-based Fe2O3 nanofluids.

The rheological behaviour of ethylene glycol-based nanofluids containing hexagonal scalenohedral-shaped α-Fe2O3 (hematite) nanoparticles at 303.15 K and particle weight concentrations up to 25% has been carried out using a cone-plate Physica MCR rheometer. The tests performed show that the studied nanofluids present non-Newtonian shear-thinning behaviour. In addition, the viscosity at a given shear rate is time dependent, i.e. the fluid is thixotropic. Finally, using strain sweep and frequency sweep tests, the storage modulus G', loss modulus G″ and damping factor were determined as a function of the frequency showing viscoelastic behaviour for all samples.

Thermal conductivity and viscosity measurements of ethylene glycol-based Al2O3 nanofluids.

The dispersion and stability of nanofluids obtained by dispersing Al2O3 nanoparticles in ethylene glycol have been analyzed at several concentrations up to 25% in mass fraction. The thermal conductivity and viscosity were experimentally determined at temperatures ranging from 283.15 K to 323.15 K using an apparatus based on the hot-wire method and a rotational viscometer, respectively. It has been found that both thermal conductivity and viscosity increase with the concentration of nanoparticles, whereas when the temperature increases the viscosity diminishes and the thermal conductivity rises. Measured enhancements on thermal conductivity (up to 19%) compare well with literature values when available. New viscosity experimental data yield values more than twice larger than the base fluid. The influence of particle size on viscosity has been also studied, finding large differences that must be taken into account for any practical application. These experimental results were compared with some theoretical models, as those of Maxwell-Hamilton and Crosser for thermal conductivity and Krieger and Dougherty for viscosity.