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This paper presents an experimental study carried out in an industrial furnace for frits production using different configurations of burners based on different combustion techniques such as enriched air combustion, flat-flame oxy-combustion and preheater air combustion. The residence time of combustion gases inside the furnace also was modified. Several combustion configurations were tested and its effects on productivity and thermal energy specific consumption and efficiency were determined. The results show that higher residence time of the combustion gases can decrease significantly the specific consumption of fuel, while the change of the burners and combustion techniques did not show significant effects on decreasing the energy consumption. However, it is highlighted that the oxy-combustion flat-flame burners produced the lowest specific consumption of fuel. Even though the experiments were conducted in a furnace for frit production, the corresponding results can also be applied to guide or improve other industrial high temperature processes. [ABSTRACT FROM AUTHOR]

Abstract In this work, a study to evaluate the effect of the concentration of nanoparticles of an Al 2 O 3 /water nanofluid on the capillary limit of a heat pipe with a screen mesh wick was performed. For the first time, a numerical model has been developed to couple the hydrodynamical equations that describe the flow and the phase change of the working fluid in the wick of a screen mesh heat pipe, with a population balance which account for the agglomeration of Al 2 O 3 nanoparticles and the deposition of them on the surface of the wick. The model has been validated with experimental data of temperature and capillary limit. Experimental results showed that capillary limit is reached at higher heat input when nanoparticles are added to the working fluid. The best improvement of the capillary limit was around 30–40%. At high nanoparticle concentration, the improvement of the capillary limit was more variable, and the thermal resistance was higher than even the working fluid without nanoparticles. The improvement of the capillary limit has been found to be due to the modification of the wettability of the wick instead of reduction of effective pore radius or enhancing of the thermal conductivity. Numerical results fitted in good agreement the experimental data, but some limitations were found when high nanoparticle concentration was simulated because model can not predict the non-uniform deposition observed at microscopic level. Finally, it was found that there is an optimal concentration of nanoparticles to delay the occurrence of capillary limit. In this work, that optimal concentration was Al 2 O 3 /water 0.5% w/w. Highlights • The wetting angle is reduced by nanoparticles deposition. • Population balance in the model allows for considering wettability variation. • Capillary limit is higher when nanoparticles are added to the working fluid. • There is an optimal concentration of nanoparticles to reduce the thermal resistance. [ABSTRACT FROM AUTHOR]

The cement industry is one of the world’s largest energy consumers. In this work, a walk-through study of representative cement companies was carried out to characterize the energy profile of the cement industry in Colombia, with emphasis on evaluating the degree of obsolescence of the technology used in the processes, as well as identifying the main barriers that prevent the adaptation of more efficient technologies. Perception-surveys were performed among the energy managers to determine the barriers that hinder the implementation of energy efficiency measures. A factor that quantifies the influence of each type of barrier was defined according to the results of the survey. The results show that the Colombian cement industry has a specific energy consumption that is competitive with the largest cement producers in the world, while the technological obsolescence found is at a medium - low level. Furthermore, the main barrier to the penetration of energy efficiency technologies and measures is identified as the hidden costs associated with the implementation of these technologies. Finally, some conventional and emerging technologies are proposed to improve the efficiency of thermal energy use in the processes studied. [ABSTRACT FROM AUTHOR]

We explore the strategies implemented by Research Groups' Leaders while coping with unstable contexts, characterized by incoherence and lack of coordination among different policy discourses and instruments, and scarce resources. We focus on a country where these conditions are present: Colombia. In doing so, we study two cases, one in nanotechnology and another one in biomedical engineering. Interviews, focus groups and workshops allowed us to identify and validate strategies grouped in four popular sayings, proper to local idiosyncrasy, highlighting the role of home institutions and principal investigators in facing such situations with resilience and resourcefulness, and even taking advantage of them. We find that Research Groups' Leaders use strategies such as: adapting, balancing agendas and funding sources, networking, and taking advantage of the support programs available at their home institution to continue functioning. These are setting the ground for a further survey which could pretend some generalization. However, policymakers could consider these findings when defining policy instruments or for assessing their effectiveness or impacts. [ABSTRACT FROM AUTHOR]

The purpose of this article is to analyze the mediation efforts of the university in innovation processes in social networks. The article is based on the sociology of innovation by dissociation. It explains how the work of two groups of university research passes from one process of accompaniment to another of distance, in the constitution of a cooperative in a neighborhood of Bogotá, Colombia. The guidelines of the analysis are the types of workshops applied in the transition from economic development approaches and local economic management to learning communities approach. For university mediation to be directed toward Socio Technological System, it is necessary to understand innovation not as a process of change, but as one of exchange based on vital vocations, this requires going beyond scientific inquiry as the only source of innovation. [ABSTRACT FROM AUTHOR]

Objective: To study the response to posterior tibial nerve stimulation in patients with overactive bladder refractory to medical treatment. Methods: A cohort of 53 patients were treated by posterior tibial nerve stimulation and followed up for a maximum of 24 months. All patients completed the International Consultation on Incontinence Modular Questionnaire-Short Form quality of life questionnaire and kept a urination diary to record the daytime urination frequency and night-time urination frequency. Urodynamic studies were also conducted. Results: At 6 months of follow-up, a cure/improvement rate of 92.4% (49 of 53 cases) had been achieved. Ten patients were given additional treatment and were excluded from subsequent follow-up analysis. At 12 months of follow-up, a cure/improvement rate of 91.69% had been achieved (39 of 43). At 24 months of follow-up, of the 16 patients initially included during the first year, a cure/improvement rate of 62.5% had been achieved (10 of 16). The first sensation of bladder filling had increased by the end of treatment, with differences observed before and after posterior tibial nerve stimulation (P ≤ .001). The average post-treatment bladder capacity had increased by 72.7 mL compared with the initial value (P ≤ .001). At 24 months of follow-up, the group of 16 patients evaluated recorded a significant worsening of night-time urination frequency (P ≤ .05) and quality of life (P ≤ .01). Conclusion: Posterior tibial nerve stimulation is a good option for the treatment of overactive bladder. In our series, the optimal point to start retreatment would be at 24 months after therapy completion. [ABSTRACT FROM AUTHOR]

A methodology to design flameless combustion heating equipment is presented. The design of flameless combustion devices requires an appropriate methodology to guarantee the necessary conditions to obtain this combustion mode. Nevertheless, such methodologies are not available in the scientific literature. For this, a combination of dynamic scaling, based on air/gas impulse ratio, and numerical simulation with FLUENT® has been employed to get suitable geometric configurations and dimensions for discharging fuel and comburent air. The proposed methodology has been applied to the design of a 20 kW experimental furnace using natural gas as fuel. The validity of the methodology has been verified with stable flameless combustion operation in the furnace. [ABSTRACT FROM AUTHOR]

La meta en este paper es probar existencia y unicidad de soluciones para la ecuación de Enskog con término fuerza The goal in this paper is prove existence and uniqueness of solutions for the Enskog equation with force term. [ABSTRACT FROM AUTHOR]

In this article the author discusses the state of freedom of expression in Venezuela in 2006. The author asserts that the freedom of expression and the press are alive and well in the country. The manifestations of this observation are given. The author also explores the impact of political conflict on freedom of expression.

This study evaluates the effect of using alumina (Al2O3)-water nanofluids stabilized by sodium dodecylbenzene sulfonate (SDBS) on the thermal performance and capillary limit of a screen mesh heat pipe. Nanofluids were prepared using three Al2O3 concentrations (0.1 mass/%, 0.5 mass/%, and 1.0 mass/%) and two SDBS concentrations (0.064 mass/% and 0.32 mass/%). The stability of the nanofluids was studied by means of UV-absorbance measurements prior to the experimental test. The results show that the thermal resistance of the heat pipe decreased by up to 50% with Al2O3 and SDBS at concentrations of 0.5 mass/% and 0.32 mass/%, respectively. Nevertheless, the capillary limit was reduced between 25 and 45 W compared to the operation with water. Finally, the capillary limit was improved by 5 W (compared to water) using an Al2O3 concentration of 0.1 mass/% and no surfactant. [ABSTRACT FROM AUTHOR]

In this study, the effects of pristine carbon nanotubes (CNTs), sodium dodecylbenzene sulfonate (SDBS), and diesel blends on the ignition delay and burning rate are examined experimentally. For this purpose, single-droplet combustion tests were conducted in a combustion system for 21 days using CNTs at concentrations of 50 ppm and 100 ppm, which were dispersed in Colombian commercial diesel and stabilized by SDBS. Videos of the diesel droplet burning were obtained using a high-speed camera, and the Shadowgraph optical technique was used to observe the development of the droplet size during combustion. Thus, records of the process were collected, and the treatment was carried out using a MATLAB algorithm. The measurements and processing were carried out along with a stability study, which included measurements of dynamic light scattering (DLS), pH, potential Zeta, and properties such as thermal conductivity and surface tension. The results demonstrated that the temporal stability has a direct impact on the single-droplet combustion tests because a concentration of CNTs of 100 ppm showed a higher stability than those achieved by 50 ppm. Consequently, improvements were found with a concentration of 100 ppm—for instance, the thermal conductivity increased by about 20%, the ignition delay time increased by 16.2%, and the burning rate increased by 30.5%. [ABSTRACT FROM AUTHOR]

• An experimental study of nanofluids stability was carried out. • The effects of Al 2 O 3 -SDBS over the thermos-physical properties were investigated. • The nanofluid with higher temporal stability was Al 2 O 3 0.5 wt% and SDBS 0.32 wt%. • Surface tension increased as the concentration of the Al 2 O 3 nanoparticles increased. • Newtonian behaviour and values close to those of water were found with SDBS. Nanofluids are thermo-fluids engineered by dispersing nanosized particles in conventional base fluids used in heat transfer applications. In this experimental study, the temporal stability and thermophysical properties of water-based alumina nanofluids, such as thermal conductivity, surface tension and viscosity, were evaluated at three different concentrations (0.1 wt%, 0.5 wt%, and 1.0 wt%) using sodium dodecyl benzene sulfonate (SDBS) as dispersant agent. The results showed that the nanofluid prepared with 1.0 wt% exhibits thermal conductivity enhancements between 11% and 15% compared to deionized water. Additionally, a pseudoplastic behaviour was identified by means of a rheological study, which increased as the nanoparticle concentration increased. Nevertheless, the nanofluids with SDBS showed a Newtonian behaviour and viscosity values close to those of water, which is suitable to avoid frictional losses in pump processes. In turn, surface tension increases with the amount of DI-water in Al 2 O 3 concentrations, but it decreases with the addition of SDBS, which has an important effect on the boiling applications of nanofluids. This work was carried out to highlight the importance of nanofluids stability in function of the surfactant added and the nanoparticle concentration, in the measurement of significant thermophysical properties such as surface tension, viscosity and thermal conductivity, which could be used to explain the nanofluids behaviour in different thermal devices. [ABSTRACT FROM AUTHOR]

Nanofluids have been introduced as an alternative to conventional fluids to improve energy efficiency in heat transfer systems. However, their stability problems before and after operation cycles can produce inconsistent results in different heat transfer technologies that use them. This review summarizes different experimental results obtained using nanofluids in heat pipes, particularly in two-phase closed thermosyphons, and it focuses on the role of preparation and stability issues of nanofluids before and after their use in these devices. Additionally, the effects of nanofluids on heat pipes' thermal performance were compiled and compared from available experimental studies in the literature. Nanoparticles' deposition on the evaporator surface and wick or groove structures were the most common mechanism to explain the reported increase or decrease in the thermal performance of heat pipes. This review also identifies the research problems that need to be solved in order to use nanofluids that outperform conventional fluids in heat pipes. [ABSTRACT FROM AUTHOR]

Analyses of ancient DNA typically involve sequencing the surviving short oligonucleotides and aligning to genome assemblies from related, modern species. Here, we report that skin from a female woolly mammoth († Mammuthus primigenius) that died 52,000 years ago retained its ancient genome architecture. We use PaleoHi-C to map chromatin contacts and assemble its genome, yielding 28 chromosome-length scaffolds. Chromosome territories, compartments, loops, Barr bodies, and inactive X chromosome (Xi) superdomains persist. The active and inactive genome compartments in mammoth skin more closely resemble Asian elephant skin than other elephant tissues. Our analyses uncover new biology. Differences in compartmentalization reveal genes whose transcription was potentially altered in mammoths vs. elephants. Mammoth Xi has a tetradic architecture, not bipartite like human and mouse. We hypothesize that, shortly after this mammoth's death, the sample spontaneously freeze-dried in the Siberian cold, leading to a glass transition that preserved subfossils of ancient chromosomes at nanometer scale. [Display omitted] • 3D genome architecture is preserved in a 52,000-year-old woolly mammoth sample • PaleoHi-C makes it possible to assemble the woolly mammoth's genome • Chromatin compartments also persist, enabling study of mammoth gene expression • We propose that dehydration led to a glass transition arresting molecular movement Three-dimensional genome architecture is shown to be preserved in a 52,000-year-old woolly mammoth sample, enabling genome assembly and analysis of gene expression. Spontaneous freeze-drying of the mammoth carcass in the cold Siberian environment potentially led to a glass transition that preserved sample morphology across eight orders of magnitude in length, from the 3-m carcass to 50-nm chromatin loops. [ABSTRACT FROM AUTHOR]

Background: Despite most metastatic castration-resistant prostate cancer (mCRPC) patients benefit from abiraterone acetate plus prednisone 5 mg bid (AA + P), resistance eventually occurs. Long-term use of prednisone has been suggested as one of the mechanisms driving resistance, which may be reversed by switching to another steroid.Methods: SWITCH was a single-arm, open-label, single-stage phase II study. The primary objective was to evaluate the antitumour activity of abiraterone acetate plus dexamethasone 0.5 mg daily (AA + D) in mCRPC patients progressing to AA + P. Clinically stable mCRPC patients who had prostate-specific antigen (PSA) and/or limited radiographic progression after at least 12 weeks on AA + P, were eligible. The primary endpoint was measured as the proportion of patients achieving a PSA decline of  ≥ 30% (PSA30) from baseline after 6 weeks on AA + D. Secondary endpoints included: PSA50 response rate at 12 weeks, time to biochemical and radiological progression, overall survival, safety profile evaluation, benefit from subsequent treatment lines and the identification of biomarkers of response (AR copy number, TMPRSS2-ERG status and PTEN expression).Results: Twenty-six patients were enrolled. PSA30 and PSA50 were 46.2% and 34.6%, respectively. Median time to biochemical and radiological progression were 5.3 and 11.8 months, respectively. Two radiological responses were observed. Median overall survival was 20.9 months. Patients with AR gain detected in plasma circulating tumour DNA did not respond to switch, whereas patients with AR normal status benefited the most. No significant toxicities were observed and PSA50 response rate to subsequent taxane was 50%.Conclusions: In selected clinical stable mCRPC patients with limited disease progression on AA + P, a steroid switch from prednisone to dexamethasone can lead to PSA and radiological responses. [ABSTRACT FROM AUTHOR]

A characterization of the energy profile of certain ceramic industry enterprises in Colombia was carried out. An emphasis was placed on the barriers that prevent the implementation of energy efficiency actions, the degree of obsolescence of their production equipment, and the potential for energy efficiency savings. The barrier with the greatest impact in this sector was found to be hidden costs , followed by corporate values . There was a positive correlation between the potential savings and the degree of equipment obsolescence and the total barrier factor to the implementation of energy efficiency measures. Finally, it was concluded that the creation of programs that allow for more certainty in the appropriation of new technologies could help to overcome the barriers in Colombia's ceramic industry. [ABSTRACT FROM AUTHOR]

Nanofluids have been introduced as new-generation fluids able to improve energy efficiency in heat exchangers. However, stability problems related to both agglomeration and sedimentation of nanoparticles have limited industrial-level scaling. A fractional factorial experimental 2 k−1 design was applied in order to evaluate the effects of nanoparticle concentration, surfactant type and concentration, ultrasonic amplitude as well as ultrasonic time on the stability of alumina (Al 2 O 3 ) nanofluids. Commercial alumina nanoparticles (particle diameter <50 nm) were dispersed in deionized water using ultrasonic probe dispersion equipment. Sodium dodecylbenzenesulfonate (SDBS) and cetyltrimethylammonium bromide (CTAB) were used as surfactants. The stability of the nanofluids in static mode was monitored by visual inspection and UV visible spectroscopy. The results of the experimental design showed that the coupled effects between surfactant type and surfactant concentration and between ultrasonication tip amplitude and ultrasonication time had the most pronounced effects on nanofluid stability. The experimental conditions providing the best stability were 0.5 wt% of Al 2 O 3 , CTAB, critical micelle surfactant concentration, 30% ultrasonic amplitude and 30 min of ultrasonication. [ABSTRACT FROM AUTHOR]

• Diesel-biodiesel-carbon nanotube droplets expand before ignition. • Functionalized and non-functionalized CNT reduces the ignition delay. • Functionalized CNT in biodiesel had a greater effect on ignition delay reduction. • Functionalized and non-functionalized CNT affect equally the diesel ignition delay. The wide use of diesel in transport and industry demands actions to reduce the emissions of harmful pollutants in the scenario of the energy transition to renewable energy, which is currently the trend in most countries around the world. Carbon nanomaterials added to diesel have been identified as a promising alternative for reducing particulate matter and NO x emissions. However, the stability of the dispersions of these nanomaterials in liquid fuels is an issue of major concern because it determines the applicability of nanofuels to internal combustion engines. That is why some alternatives, like carbon nanomaterial functionalization, have been explored to increase the stability of nanofuels, but the addition of these functionalized nanomaterials could have an effect on the combustion properties of the blends. This work explores for the first time the effect of using amide-functionalized carbon nanotubes on the ignition delay of blends of these nanomaterials (50 and 100 ppm) and Colombian commercial diesel (90 % petroleum diesel and 10 % palm-oil biodiesel) and palm-oil biodiesel. The characterization of the ignition delay was conducted on a droplet scale through the shadowgraph technique since this property is an indicator of the performance of real compression ignition engines in terms of combustion efficiency and pollutant emissions. Results showed that the addition of carbon nanotubes, either functionalized or not, increased the volumetric expansion of the droplets before ignition by up to 1.6 % in comparison with the raw fuels. Also, the addition of carbon nanotubes reduced the ignition delay of the blends in comparison to the raw fuels by about 18.3 % and 13.1 % for biodiesel with functionalized carbon nanotubes at 50 ppm and 100 ppm, respectively; 9.4 % and 11.8 % for biodiesel with no-functionalized carbon nanotubes at 50 ppm and 100 ppm, respectively; 12.3 % and 18.3 % for commercial diesel with functionalized carbon nanotubes at 50 ppm and 100 ppm, respectively; and 14.9 % and 14.7 % for commercial diesel with no-functionalized carbon nanotubes at 50 ppm and 100 ppm, respectively. However, the reduction for biodiesel with functionalized carbon nanotubes at 100 ppm was not significantly different from that of the biodiesel added with no-functionalized carbon nanotubes at 50 and 100 ppm. In the case of commercial diesel, despite the reduction of the ignition delay for all the nanofuels in comparison with the raw fuel, there was not a significant difference between the functionalized and no-functionalized blends. [ABSTRACT FROM AUTHOR]

Nanofluids stability on rest is important to characterize the nanofluids thermophysical properties before being used on different thermal systems. However, this stability can be modified during devices operation because of different thermal loads, fluid movements and phase changes. Particularly, in Two Phase Closed-Thermosyphon (TPCT), nanoparticle deposition on the evaporator surface is one of the most important issues that affects their thermal performance, this deposition indicates a lost in the nanofluids stability during operation and also a modification in their thermophysical properties. In addition, surfactants are commonly employed to improve nanoparticles dispersion and nanofluids stability and its effect on the TPCT thermal performance has been little studied. Surfactant presence modifies the surface tension of the base fluid, affecting the boiling heat transfer in the TPCT evaporator, which contributes also with the thermal performance variations. In this study, the stability of Al 2 O 3 -water nanofluids was evaluated on rest exploiting different surfactants. After that, nanofluids with high and low stability were used as working fluid in a thermosyphon in order to evaluate the effect of stability and the presence of surfactant on the TPCT thermal performance. Stability after several operation cycles was also studied and results show that the nanofluid with Sodium Dodecylbenzene Sulfonate SDBS at critical micelle concentration as surfactant was stable after several operation cycles. On the contrary, nanoparticles were completed sedimented after operation for nanofluids without surfactant and with Cetyl Trimethyl Ammonium Bromide CTAB. Decrease in the thermal resistance was up to 24% for the different nanofluids (stable and unstable) and surfactant solutions in comparison with water, but no effects of nanofluid stability on rest in the final thermal performance were not found. Moreover, interesting phenomena during operation were observed such as a dry path with water and high bubble formation with surfactant presence. Image 1 • Al 2 O 3 -SDBS nanofluid was stable before and after thermosyphon operation cycles. • Thermal resistance decreased with Al 2 O 3 nanofluids and surfactant solutions. • The thermal resistance of thermosyphon was not affected by nanofluids stability. • Surfactant solutions presented similar thermal performance compared to nanofluids. • Nanoparticle deposition and surfactant presence play an important role in heat transfer. [ABSTRACT FROM AUTHOR]

Nanofluids are complex fluids, mainly proposed to improve the efficiency of thermal systems. However, their poor stability, caused by the agglomeration and sedimentation of nanoparticles over time, has limited their practical application. A common technique to increase the stability of nanofluids is to add surfactants, which produce electrostatic or steric repulsion between nanoparticles, thus avoiding their agglomeration. This work evaluated the effects of surfactants and their concentration on the zeta potential and hydrodynamic diameter at different pH values as an indicator of nanofluids stability. Commercial alumina nanoparticles (0.1 wt.%) were dispersed in deionized water using two surfactants (cetyltrimethylammonium bromide, CTAB and sodium dodecylbenzenesulfonate, SDBS) at different concentrations, and the pH values were varied (2–12) by adding hydrochloric acid and sodium hydroxide. The results show the importance of the critical micelle concentration value in the nanofluids stabilization by electrostatic repulsion between nanoparticles and indicate that SDBS at a concentration of 0.064 wt.% (critical micelle concentration) offers the best dispersion conditions according with their zeta potential values, allowing high stability regardless of the pH value of the suspension. [ABSTRACT FROM AUTHOR]

Background: Despite most metastatic castration-resistant prostate cancer (mCRPC) patients benefit from abiraterone acetate plus prednisone 5 mg bid (AA + P), resistance eventually occurs. Long-term use of prednisone has been suggested as one of the mechanisms driving resistance, which may be reversed by switching to another steroid.Methods: SWITCH was a single-arm, open-label, single-stage phase II study. The primary objective was to evaluate the antitumour activity of abiraterone acetate plus dexamethasone 0.5 mg daily (AA + D) in mCRPC patients progressing to AA + P. Clinically stable mCRPC patients who had prostate-specific antigen (PSA) and/or limited radiographic progression after at least 12 weeks on AA + P, were eligible. The primary endpoint was measured as the proportion of patients achieving a PSA decline of  ≥ 30% (PSA30) from baseline after 6 weeks on AA + D. Secondary endpoints included: PSA50 response rate at 12 weeks, time to biochemical and radiological progression, overall survival, safety profile evaluation, benefit from subsequent treatment lines and the identification of biomarkers of response (AR copy number, TMPRSS2-ERG status and PTEN expression).Results: Twenty-six patients were enrolled. PSA30 and PSA50 were 46.2% and 34.6%, respectively. Median time to biochemical and radiological progression were 5.3 and 11.8 months, respectively. Two radiological responses were observed. Median overall survival was 20.9 months. Patients with AR gain detected in plasma circulating tumour DNA did not respond to switch, whereas patients with AR normal status benefited the most. No significant toxicities were observed and PSA50 response rate to subsequent taxane was 50%.Conclusions: In selected clinical stable mCRPC patients with limited disease progression on AA + P, a steroid switch from prednisone to dexamethasone can lead to PSA and radiological responses. [ABSTRACT FROM AUTHOR]