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Due to the potential hazard of deepwater oil exploration, the Brazilian industry has an ever-increasing concern for reliability during hydrocarbon production. A major source of concern is mechanical failure in devices, such as safety valves, which can fail without warning, putting both the operation and the environment at risk. A possible reason for malfunction and failure could be the permanent occurrence of vibrations induced by internal two-phase flow during the extraction of fluids from the well. An experimental campaign is proposed to better understand these phenomena. Twenty two-phase flow conditions were tested, with superficial velocities ranging from 0.1 m/s to 2.0 m/s for water, and 0.33 m/s to 7.47 m/s for compressed air. The experiments were carried out in a restricted pipe and a pipe without any restriction to evaluate and compare the vibrations produced by two-phase flow (2-FIV). Three accelerometers positioned downstream of the restriction were used to collect vibrational amplitude spectral density data, 2-D acceleration magnitudes, and RMS values of acceleration. Among the main findings are the roles played by the gas volumetric fraction and the mixture velocity, which strongly influence the vibrational amplitude of both tubes, and the observation that the gas phase is the main responsible for vibrational amplitudes at low frequencies, while the liquid phase acts mainly at high frequencies. Furthermore, the flow pattern is also considered a key feature in determining the vibration level, as 20- and 12-fold increments have been observed for the same volumetric fraction when comparing elongated bubbles and severe slug patterns. Finally, it was demonstrated that the presence of an internal restriction strongly influences the structural response. • The presence of an internal restriction affects a pipe's dynamic response significantly. • Large changes in vibratory response are found between single-phase and two-phase flow. • It is suggested that the gas phase is responsible for the vibration amplitudes at low frequencies. • It is suggested that the liquid phase is responsible for the vibration amplitudes at high frequencies. • Two-phase flow parameters directly influence the structural response to vibration. [ABSTRACT FROM AUTHOR]

• A restriction affects the pressure of a two-phase flow, representing large differences compared to an unrestricted pipe. • Downstream of the restriction there is an increase in the void fraction due to the breaking of bubbles and loss of pressure. • Upstream of the restriction there is an increase in the length and velocity of the liquid slugs due to bubble coalescence. • 14 models from the literature, between pressure gradient, void fraction, and frequency of passage of liquid slugs are used to compare with experimental data. Subsurface safety valves play an important role in the hydrocarbon production process. The Brazilian industry is suffering significant losses due to the reduction of the useful life of this device, not to mention the risks associated with the operation and the environment. One possible reason for the failure of the subsurface safety valve's reliability prediction may be the occurrence of two-phase flow in the well. For this reason, a set of twenty horizontal two-phase flow experiments was carefully designed to evaluate the influence of a simplified internal reduction in a steel pipe. Superficial velocities were considered in the range of 0.1 m/s and 2.0 m/s for water and, 0.33 m/s and 7.47 m/s for compressed air. The experiments were carried out in 2″-i.d. and 2-m-long steel pipes, being a tube with restriction and another without restriction. Both tubes have an upstream development length of 126 pipe diameters. Gamma-ray densitometry and a differential pressure transducer were used to measure void fraction and pressure drop, and a visualization window was used to observe the flow patterns. Among the main findings are the effects of void fraction and mixture velocity on pressure gradient, with different impacts on the restricted pipe (RP) compared to the unrestricted pipe (UP). The presence of the restriction generated significant changes in the upstream flow: the lengths of the liquid slugs were increased, appeased by the increase in local pressure necessary to overcome the resistance produced by the restriction. Downstream, the change was reflected in the rise of void fraction and decrease of slip ratio between the phases. [ABSTRACT FROM AUTHOR]

For a system, a priori identifiability is a theoretical property depending only on the model and guarantees that its parameters can be uniquely determined from observations. This paper provides a survey of the various and numerous definitions of a priori identifiability given in the literature, for both deterministic continuous and discrete-time models. A classification is done by distinguishing analytical and algebraic definitions as well as local and global ones. Moreover, this paper provides an overview on the distinct methods to test the parameter identifiability. They are classified into the so-called output equality approaches, local state isomorphism approaches and differential algebra approaches. A few examples are detailed to illustrate the methods and complete this survey. [ABSTRACT FROM AUTHOR]

Abstract An array of gold interdigitated microelectrodes (Au-IDA) has been modified by casting herringbone carbon nanotubes (hCNTs) producing a new electrochemical sensor suitable for the simultaneous determination of ascorbic acid (AA) and uric acid (UA) in PBS (0.25 M, pH 7.0). The sensor showed good electrocatalytic properties for both analytes with low working potentials, linear ranges between 0 and 600 μM for AA, and between 0 and 420 μM for UA. The empirical limits of detection (LODs) and the limits of quantification (LOQs) for both analytes were 15 μM and 50 μM, respectively. Moreover, UA does not interfere in the measurement of AA and vice versa. Furthermore, the presence of common analytes in physiological fluids as glucose, dopamine and epinephrine do not interfere in the quantification neither AA nor UA. [ABSTRACT FROM AUTHOR]

Resumen Objetivo El Standardized uptake value (SUV) y los parámetros volumétricos volumen metabólico tumoral (MTV) y glicolisis total de la lesión (TLG) de la 18 F-FDG PET/TC son útiles para determinar el pronóstico preoperatorio y postratamiento del cáncer epitelial de ovario (CEO). El Ki67 es otro marcador pronóstico en el CEO asociado con la agresividad tumoral. El objetivo fue estudiar la asociación entre los parámetros de la 18 F-FDG PET/TC y el Ki67 en el CEO pretratamiento para determinar si la PET/TC puede predecir la agresividad tumoral de forma no invasiva. Material y métodos Se realizó una PET/TC a 18 pacientes con sospecha o recién diagnóstico de CEO. Se obtuvo el SUV máximo (SUVmax), SUV medio (SUVmean) y el MTV y la TLG corporal (wbMTV y wbTLG, respectivamente), con un dintel del 30%-40% del SUVmax. Se estimó el índice de Ki67 (medio y máximo) en muestras del tejido tumoral, y se correlacionó con los parámetros de la PET. Resultados La edad media fue 57,0 años (desviación estándar 13,6 años). Se observó una moderada correlación entre el Ki67 medio y el SUVmax (r = 0.392), SUVmean 30% (r = 0.437) y SUVmean 40% (r = 0.443), así como entre el Ki67 máximo y el SUVmax (r = 0.360), SUVmean 30% (r = 0.362) y SUVmean 40% (r = 0.319). La correlación fue más débil, e inversamente negativa, entre el Ki67 medio y máximo y los parámetros volumétricos de la PET. No hubo diferencias estadísticamente significativas entre las correlaciones. Conclusiones SUVmax y SUVmean se correlacionaron moderadamente con el Ki67 mientras que los parámetros volumétricos mostraron una correlación débil. SUVmax y SUVmean podrían utilizarse para predecir la agresividad tumoral en el CEO pretratamiento. Objective Standardised uptake value (SUV) and volumetric parameters such as metabolic tumour volume (MTV) and total lesion glycolysis (TLG) from 18 F-FDG PET/CT are useful criteria for disease prognosis in pre-operative and post-treatment epithelial ovarian cancer (EOC). Ki67 is another prognostic biomarker in EOC, associated with tumour aggressiveness. The aim of this study is to evaluate the association between 18 F-FDG PET/CT measurements and Ki67 in pre-treatment EOC to determine if PET/CT parameters could non-invasively predict tumour aggressiveness. Material and methods A pre-treatment PET/CT was performed on 18 patients with suspected or newly diagnosed EOC. Maximum SUV (SUVmax), mean SUV (SUVmean), whole-body MTV (wbMTV), and whole-body TLG (wbTLG) with a threshold of 30% and 40% of the SUVmax were obtained. Furthermore, Ki67 index (mean and hotspot) was estimated in tumour tissue specimens. Immunohistochemical findings were correlated with PET parameters. Results The mean age was 57.0 years old (standard deviation 13.6 years). A moderate correlation was observed between mean Ki67 index and SUVmax (r = 0.392), SUVmean 30% (r = 0.437), and SUVmean 40% (r = 0.443), and also between hotspot Ki67 index and SUVmax (r = 0.360), SUVmean 30% (r = 0.362) and SUVmean 40% (r = 0.319). There was a weaker correlation, which was inversely negative, between mean and hotspot Ki67 and volumetric PET parameters. However, no statistical significant differences were found for any correlations. Conclusions SUVmax and SUVmean were moderately correlated with Ki67 index, whereas volumetric PET parameters overall, showed a weaker correlation. Thus, SUVmax and SUVmean could be used to assess tumour aggressiveness in pre-treatment EOC. [ABSTRACT FROM AUTHOR]

This paper presents results from experimental studies on the thermal resistance and dilatometry analysis of various geopolymer formulations, which were prepared by mixing alkaline solutions, metakaolin and reinforcements. Nine compositions were tested by dilatometric analysis and thermal resistance at high temperature (800 °C). Structural and microstructural analysis was conducted to verify the geopolymerization, and differential thermogravimetric analysis was performed to evaluate the nature of water, depending on the formulation. Some key parameters were identified as critical parameters that influenced the geopolymer properties, such as the nature (Na or K) and the molar concentration of the alkaline cation ([M] < 16 mol/L), the molar concentration of silicon ([Si] < 39 mol/L) and the alkaline metal to aluminum ratio (M/Al < 0.65). Finally, it was possible to arrange the various formulations in a ternary scheme as functions of the metal, aluminum and silicon concentrations. This scheme may represent a roadmap for controlling the thermal resistance of geopolymer materials. [ABSTRACT FROM AUTHOR]

An electrochemical sensor based on graphene oxide decorated with gold nanoparticles has been prepared for the simultaneous quantification of uric acid (UA) and ascorbic acid (AA) in urine samples. The gold interdigitated microelectrodes array (Au-IDA) has been modified using graphene oxide doped with gold nanoparticles (AuNPs-GO/Au-IDA), which was characterized by TEM, FE-SEM, XPS and cyclic voltammetry. Excellent results were obtained for the separate quantification of UA and AA by chronoamperometry. The electrochemical sensor exhibits limits of detection (LODs) of 1.4 μM and 0.62 μM for AA and UA, respectively, limits of quantification (LOQs) of 4.6 μM (AA) and 2.0 μM (UA), and the working ranges obtained were between 4.6 μM and 193 μM for AA and between 2 μM and 1.05 mM for UA. The repeatability was studied at 20 μM providing coefficients of variation of 16% for AA and 13% for UA. Moreover, UA does not interfere in the measurement of AA and viceversa (provided that the concentration of UA is equal to or higher than 450 μM in the latter case). For lower concentrations of UA, an easy and fast strategy to quantify both analytes is presented. The good electrocatalytic activity achieved with this material makes it useful for the quantification of AA and UA in biological fluids. Other analytes like glucose, dopamine and epinephrine have been investigated. The results allow us to conclude that they do not interfere in the quantification of AA and UA in PBS (0.25 M, pH 7.0). Human urine samples have been analyzed using the method proposed, contaning AA and UA concentration levels of (0.588 ± 0.002) mM and (1.43 ± 0.02) mM, respectively, which are in the concentration range of these analytes in urine samples for healthy people. [ABSTRACT FROM AUTHOR]

Currently, many applications require the assembly of different materials to improve their properties in use. This work focuses on the production of a geopolymer binder coating based on metal or agglomerated sand. For this, several compositions based on sodium or potassium and different reactivities of metakaolin and their interactions in the presence of different types of support were studied. The interactions between the binder and substrate were analysed by measurements of the wetting angles. Coating trials conducted over tin-plated copper and bonded sand highlighted the influences of the binder composition and the drying and deposition parameters. Scanning electronic and optical microscopy observations confirm the chemical adhesion between the various components. FTIR spectroscopic analyses have also identified the parameters for obtaining a geopolymer network such as the reactive aluminium concentration (5 a.u.) and the molar Si/Al and M/Al (M=K or Na) ratios (2 and 1.2, respectively). It is therefore possible, by determining the wetting angle, to control the deposition on either a metal or silica sand. [ABSTRACT FROM AUTHOR]

Geopolymers are new binders resulting from the activation of an aluminosilicate source by an alkaline solution. These binders are economically and environmentally profitable since they have the advantage of reusing recycled waste and industrial by-products as aluminosilicate sources. In this context, this paper focuses on the geopolymer wastes incorporation in different formulations and their effect on geopolymer formation and the properties of the final materials. For this purpose, the geopolymer wastes were at first characterized. Three compositions differing in the used alkaline solution and the amount of metakaolin added were investigated. A feasibility study allowed retaining 20% as the waste percentage added or substituted to the metakaolin to still obtain geopolymer materials. Moreover, it was shown that the incorporation of the geopolymer waste may disturb the polycondensation rate which was proven to strongly depend on the solid to liquid ratio and the Si/K ratio of the alkaline solution. Finally, relationships were demonstrated between the compressive strengths and the chemical compositions of the different samples. The low reactivity of geopolymer waste can be compensated with the use of highly reactive alkaline solution or the increase of the amount of metakaolin in the mixture. [ABSTRACT FROM AUTHOR]

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This paper focuses on the influence of the addition of ammonium molybdate to geopolymer mixtures to better understand the formation of geopolymer structural networks and the effect of Mo-based additive on the thermal behavior of material. Several geopolymers were synthesized between two metakaolins and various amounts of ammonium molybdate. The microstructure of samples was determined by SEM, the structural evolution (depending on the amount of molybdenum added) was investigated using Raman spectroscopy and XRD analyses, and the temperature behaviors of materials by DTA–TGA and dilatometric analyses. The results showed that (i) both metakaolins react differently in the presence of ammonium molybdate, (ii) molybdenum induces decrease of shrinkage value at high temperatures, and (iii) the crystallization seems to be favored with ammonium molybdate. This work shows that ammonium molybdate controls polycondensation reactions highlighting the modifier or former role played by the molybdenum atoms depending on the amount of ammonium molybdate added. [ABSTRACT FROM AUTHOR]

Abstract: Nanosized chromium (Cr2O3) oxide was prepared by the common thermal decomposition of Cr(NO3)3·9H2O chromium (III) nitrate nonahydrate. Prior to the heat treatment at 550°C, the commercial reagent was first dissolved in a colloidal silica solution and then dried at a low temperature to slowly evaporate the aqueous solvent. The SiO2/Cr(NO3)3·9H2O weight ratio (R) was changed from 0 to 2. The various Cr2O3 powders were characterized by XRD, FTIR, nitrogen adsorption, SEM and TEM techniques. A maximum specific surface area of 113m2 g−1, associated with a pore volume of 0.72cm3 g−1, was obtained for the Cr2O3 powder prepared with R =2. These pristine chromium oxide nanoparticles, with a slightly sintered sphere-shaped morphology, exhibited a 10nm particle size with a monocrystalline character as demonstrated by the TEM and XRD correlation. [Copyright &y& Elsevier]

OBJECTIVE: To compare available antifungal treatments for invasive candidiasis, a leading cause of nosocomial bloodstream infections. METHODS: We performed a systematic review and meta-analysis of randomized controlled trials that compared different antifungal agents for the treatment of candidemia and other forms of invasive candidiasis. Two reviewers independently appraised the quality of trials and extracted data. The primary outcome was all-cause mortality, and secondary outcomes were microbiological failure, treatment failure, and adverse events. Relative risks (RRs) with 95% confidence intervals (CIs) were pooled. RESULTS: Of the 15 included trials, 9 compared fluconazole with other drugs (amphotericin B, itraconazole, or a combination of fluconazole and amphotericin B), 4 compared echinocandins with other drugs (fluconazole, amphotericin B, liposomal amphotericin B), 1 compared micafungin and caspofungin, and 1 compared amphotericin B plus fluconazole and voriconazole. No difference in mortality was observed with fluconazole vs amphotericin B (RR, 0.92; 95% CI, 0.72-1.17); however, the rate of microbiological failure increased in the fluconazole arm (RR, 1.52; 95% CI, 1.12-2.07). Anidulafungin decreased the rate of microbiological failure compared with fluconazole (RR, 0.50; 95% CI, 0.29-0.86) with fewer adverse events. Caspofungin was comparable to amphotericin B in mortality and efficacy, with fewer adverse events requiring discontinuation (RR, 0.11; 95% CI, 0.04-0.36). Micafungin was comparable to liposomal amphotericin B in mortality. CONCLUSION: All assessed antifungal agents showed similar efficacy, but the rate of microbiological failure increased with fluconazole vs amphotericin B or anidulafungin. Amphotericin B is associated with a higher rate of adverse events than fluconazole and echinocandins. [ABSTRACT FROM AUTHOR]

Abstract: The hypocretins (Hcrt; also known as orexins) and melanin-concentrating hormone comprise distinct families of neuropeptides synthesized in cells located in the lateral hypothalamus and adjacent areas. The Hcrts are thought to modulate food intake and sleep/wake patterns in mammals. Melanin-concentrating hormone has a well-documented role in energy metabolism. A moderate plexus of Hcrt immunoreactive terminals has been described in the hamster intergeniculate leaflet, part of the circadian rhythm system. This study investigated the origin of Hcrt-immunoreactive terminals in the intergeniculate leaflet and determined whether melanin-concentrating hormone neurons also project to the intergeniculate leaflet. The tracer, cholera toxin β-subunit, was injected into the intergeniculate leaflet of the golden hamster. Double-label fluorescent immunohistochemistry for cholera toxin β-subunit and Hcrt or melanin-concentrating hormone was then performed to identify retrogradely labeled cells also containing immunoreactive peptide. Most cholera toxin β-subunit-labeled cells were detected in the medial zona incerta and sub-incertal zone, with few observed in the lateral hypothalamus. Hcrt-immunoreactive cells were abundant and found largely in the lateral hypothalamus and adjacent nuclei. Melanin-concentrating hormone cells were also abundant in the medial zona incerta, in close proximity to cholera toxin β-subunit-labeled cells, but ventral to them. Cells containing both cholera toxin β-subunit and Hcrt-immunoreactive, were present in the dorsal aspect of the lateral hypothalamus. The number observed was small, ≤1% of the total number of Hcrt cells counted in the hamster. No cholera toxin β-subunit-immunoreactive cells also contained melanin-concentrating hormone and no melanin-concentrating hormone-immunoreactive processes were evident in the intergeniculate leaflet. The results show that a small number of lateral hypothalamus cells containing Hcrt-immunoreactivity project to the intergeniculate leaflet, but they are scattered rather than collected into a discrete group. At the present time there is no information regarding the function of these cells, although they may contribute to the regulation of sleep/arousal, circadian rhythmicity, or vestibulo-oculomotor function. [Copyright &y& Elsevier]

An ultrastructural and quantitative study of age-related changes in the capillaries of the dorsal lateral geniculate nucleus was carried out using male Wistar rats aged 3, 24, and 28 months. The most important structural changes were found in the basal lamina: thickenings either homogeneously distributed or in specific points; spurs towards the astrocyte sheath; and osmiophilic membrane-like inclusions located within the basal lamina. Endothelial cells and pericytes showed an increase in inclusions and dense bodies in the cytoplasm. The quantitative study showed that the most pronounced alteration was the thickening of the basal lamina, which existed at 24 months. Later, at 28 months, thinning of the endothelial cells was observed together with an increase in mitochondria size and the number of pinocytic vesicles. These changes could be an endothelial cell response to compensate for the increasing transport difficulties caused by the thickening of the basal lamina.The progressive age-related changes observed in the structure of the capillaries might have an effect on the regulation of blood and brain tissue exchanges, and thus might contribute to the development of degenerative alterations in surrounding aging neurones. [Copyright &y& Elsevier]

To evaluate the pathologic findings in liver explants of patients with hepatocellular carcinoma (HCC) who received radiation segmentectomy. Patients were excluded if the treatment angiosome did not provide complete tumor coverage per mapping angiography or the target lesion could not be correlated with gross pathology. After 2 patients were excluded, a total of 32 patients and 34 tumors were analyzed. [Extracted from the article]