Search

Purpose The purpose of this paper is to investigate the impact of semi-circular zigzag-channel printed circuit heat exchanger (PCHE) design parameters on heat transfer and pressure drop of flows under high Reynolds numbers and provide new thermal-hydraulic correlations relevant to conditions encountered in natural gas processing plants. Design/methodology/approach The correlations were developed using three-dimensional steady-state computational fluid dynamics simulations with varying semicircular channel diameter (from 1 to 5 mm), zigzag angle (from 15° to 45°) and Reynolds number (from 40,000 to 100,000). The simulation results were validated by comparison with experimental results and existing correlations. Findings The results revealed that the thermal-hydraulic performance was mostly affected by the zigzag angle, followed by the ratio of the zigzag channel length to the hydraulic diameter. Overall, smaller zigzag angles favored heat transfer intensification while keeping reasonably low pressure drops. Originality/value This study is, to date, the only one providing thermal-hydraulic correlations for PCHEs with zigzag channels under high Reynolds numbers. Besides, the broad range of parameters considered makes the proposed correlations valuable PCHE design tools.

Common rare earth (RE) minerals, such as bastnasite and monazite, may be formed in deposits associated with carbonate gangue, such as calcite and dolomite. Sodium oleate is a widely used collector for the flotation of both RE and gangue minerals, which might, therefore, be an inefficient process due to the lack of selectivity of this collector. Since these minerals are also sparingly soluble in solution, they could release their constituent ions into the solution, which could affect the floatability of other minerals. In this study, the interactions of sodium oleate with bastnasite and monazite in the presence of dissolved dolomite species have been investigated. Microflotation tests were carried out to explore the effects of these dissolved species on the floatability of the RE minerals. Zeta potential measurements and XPS characterization were carried out to understand how the species affect the collector adsorption. To complement these characterizations, density functional theory (DFT) simulations were conducted to investigate the collector-mineral and collector-adsorbed species (on the mineral surface) interactions. The results show that collector-dolomite interaction energy is greater than that of collector-adsorbed species, but lower than collector-monazite interaction energy, explaining the decrease in the minerals' recovery upon exposure to the dissolved mineral species. It is also shown that oleate ions (Ol–) have the strongest interaction with the minerals compared to other oleate species such as acid soap (HOl2–) and oleate dimer (Ol22−). The behavior (strength and selectivity) of sodium oleate towards RE minerals and dolomite, as compared to other RE mineral collectors (such as aromatic hydroxamate), is attributed mainly to the collector's and the minerals' structure. The long hydrocarbon chain of sodium oleate which imparts hydrophobic characteristic to the minerals, makes it stronger collector than benzohydroxamate. Moreover, sodium oleate (with linear structure), unlike the aromatic hydroxamate, can approach the mineral easier due to lesser steric hindrance effect and higher reactivity of O involved in the interaction, making it less selective. In addition, it can interact easily with dolomite due to the presence of more exposed active sites than RE minerals.

Research into the application of microwave irradiation in the comminution of ores has made great progress in recent years, creating a demand to understand the effects of this technique on downstream processes, especially flotation. The present work investigated the floatability of untreated and microwave-treated chalcopyrite, pentlandite and pyrrhotite samples using potassium amyl xanthate and sodium oleate as collectors. The effects of the exposure time on each mineral’s recovery at different concentrations, pH and particle sizes were studied through microflotation, and the adsorption of the collectors was analyzed by electrophoretic zeta potential measurements. Microwave irradiation led to the decrease in the floatability of chalcopyrite and pyrrhotite in the presence of xanthate, at the pH values investigated, whereas no significant change was observed for pentlandite. The flotation of the microwave-treated minerals required greater sodium oleate concentration. The treated and non-treated pentlandite and pyrrhotite samples did not float at pH 10. Although the treated chalcopyrite and pentlandite displayed low recoveries at all pH values, the treated pyrrhotite displayed high floatability at acidic and neutral pH. The recovery of the microwave-treated sulphide minerals was more affected by the particle size in the tests with potassium amyl xanthate than with sodium oleate. The overall results presented by this work indicate potential conditions to achieve selectivity between the microwave-treated chalcopyrite, pentlandite and pyrrhotite.

The application of microwave radiation as an assisted grinding technique has shown great potential to improve comminution. Besides fracturing, the treatment also leads to phase transformations at the grain boundaries of the minerals, changing their surface properties and affecting downstream processes, such as flotation. Therefore, the study of the effects of microwave treatment on a mineral’s surface properties is important for the industrial application of microwave assisted grinding. In this work, the surface properties of untreated and microwave-treated chalcopyrite were investigated by XRD, XPS, ATR-FTIR, SEM, BET/BJH, IGC, ELS (zeta potential) and microflotation. While short exposure times were found to favor the formation of copper polysulphides (CuxFeySn) at the mineral surface, longer treatments converted CuFeS2 into iron oxides/ hydroxides/oxyhydroxides and sulfate at the surface and, enriched CuxFeySn underneath the oxidation layer. A shift in the zeta potential curves to less negative values was observed after treatment, reaching an IEP around pH 4.5. The collectorless floatability of chalcopyrite initially improved after exposure as its surface energy decreased. However, the samples’ surface became energetically more active after longer treatment times, and the flotation recovery decreased. Microwave treatment also increased the mineral’s specific surface area (SSA) and porosity; and changed the pore size distribution.

Aims A new L-asparaginase produced by Streptomyces ansochromogenes UFPEDA 3420 actinobacteria was used in this study against human lymphocyte cultures to evaluate the immunological profile induced by this enzyme. Methods and results Cultures of lymphocytes were stimulated with S. ansochromogenes L-asparaginase, and cytotoxicity, cell viability, cell stimulation and cytokine production were analysed. This new S. ansochromogenes L-asparaginase induced activation and proliferation of the TCD8+ lymphocyte subset and produced higher TNF-α, IFN-γ, IL-2 and IL-10 levels in a 24-h assay. Conclusion Streptomyces ansochromogenes L-asparaginase is a promising molecule to be used in in vivo models and to deepen preclinical tests against acute lymphoblast leukaemia. Significance and impact of study L-asparaginase is an indispensable component of the chemotherapeutic treatment of acute lymphoblast leukaemia (ALL) and acute myeloid leukaemia (AML). Currently, drugs such as Asparaginase® , Kidrolase® , and Elspar® and Erwinase® are efficient against leukemic disease, but promote immunosuppression and other side effects in human organisms. Our purified S. ansochromogenes L-asparaginase showed promissory results inducing, in vitro, higher immunostimulation in human PBMC, especially in T CD8+ lymphocyte subsets.

Flotation is the most commonly used beneficiation method for rare earth (RE) ores. Due to the dissolution characteristics of the RE minerals and the gangue minerals, they may behave similarly in a flotation system. Previous work has shown that dissolved mineral species from gangue could precipitate/adsorb at the mineral surface affecting the minerals’ flotation behavior. In this work, the effect of dolomite supernatant on the surface of bastnasite, monazite and dolomite are presented. Zeta potential measurements, complemented with flotation tests, were conducted with and without the presence of the supernatant using benzohydroxamate as the collector. XPS results confirmed the surface speciation, and DFT simulations detail the possible mineral - collector, mineral - precipitated species and precipitated species - collector interactions. The results show that carbonate precipitates and Ca2+ from the supernatant could adsorb onto the mineral surface through covalent bonding, both affecting the zeta potential and reducing collector adsorption. Another important finding of this study is the potential loss of the collector in the solution due to complexation with ions from the supernatant. These findings confirm that an effective rare earth mineral separation through flotation does not rely solely on the strength of collector-mineral interaction, but rather is highly dependent on the chemistry of the flotation solution. Taking advantage of, or controlling, the surface reactions should be the main target to developing a more efficient and cost-effective flotation process. Different measures have been proposed to reverse/reduce the detrimental effects of the dolomite supernatant to RE mineral flotation.

Cellulose is a very common component of foods, such as fruits and vegetables, although not digestible by the human intestinal tract. Its fibers and their capacity of water intake play a vital role in the digestive transit, besides a helper effect in the mouth feel. A few cellulose producer bacterial strains biosynthesize “Nata de Coco,” a food/dessert that has been appreciated historically by many Asian people. Here we describe some experiences of blending bacterial cellulose with many other colored and tasteful bioactive food ingredients to further valorize their aspect, flavor, and taste. The remaining descriptions refer to other nonfood, bacterial cellulose applications from our historical and pioneering application as a temporary skin substitute with wound healing efficacy and a few other several physical, chemical, and biotechnological goods from bacterial cellulose.

Interesting aspects and products of the program are presented. The program, that was presented in the paper SPE 69468 (VII LACPEC), is now in the middle of its development. Brazilian oil and gas industry data and also the regulatory strategy for the facilities' operational safety are updated. Focus is given in the principal obstacles and in the most important conquests of a innovative and complex project, specially considering its "multiple interfaces" characteristics. Finally, it is presented, the revised planning for development and implantation of the Program, including its stages, in an outlined 5W + 2H method (WHAT - WHY - WHO - WHERE - WHEN - HOW and HOW MUCH).

Firstly, some of the principal challenges for ANP-the Brazilian Regulatory Agency for the petroleum industrial segment - are presented: a) the diversity and the great number of Plants / Facilities and Economical Agents; b) the peculiar context after a monopolistic scenario, in evolution to a liberal one, regulated in a efficient way by the Brazilian Government. Secondly, the bases, the guidelines and the expected results of a Conformity Assessment Program are showed; in a simply overview, the program consider that Authorized Entities by the National Accreditation Organism - INMETRO - would evaluate the expected performance of the petroleum "Players", according to international rules and to specific Regulations. Finally, it is presented a Planning for development and implantation of the Program, including its stages, in an outlined 5W + 2H method (WHAT - WHY - WHO - WHERE - WHEN - HOW and HOW MUCH).

With the aim to study potential risk factors for the development of microalbuminuria and retinopathy, baseline characteristics were examined in 50 Brazilian IDDM patients followed for 4.48 years with a 2-year reexamination. During the study, 3 patients (6%) aged 25.9 +/- 4.4 years, duration of diabetes 8.1 +/- 4.2 years, died from acute complications without microalbuminuria and retinopathy after a follow-up of 2.1 +/- 0.7 years. The standardized mortality rate for the group was 0.84 per 1000 (95% CL, 0.31, 1.83) in comparison to 0.14 per 1000 in the general population. From 34 normoalbuminuric individuals at baseline (urinary albumin excretion rate (AER)or = 20 micrograms/min inor = 2 overnight urine collections), 10 developed microalbuminuria with an incidence density of 6.5 cases per 100 person-years (95% CL, 2.23, 10.16). Spontaneous normalization of AER was found in 2 of 4 patients with microalbuminuria at cycle 2. Multiple stepwise regression analysis demonstrated that baseline AER (p = 0.03), but not glycated hemoglobin, blood pressure or duration of diabetes, predicted end-of-study AER. From 36 patients without retinopathy, 10 developed nonproliferative retinopathy with an incidence density of 6.6 cases per 100 person-years (95% CL, 2.75, 10.54). Retinopathy was associated with duration (p = 0.05) and age at diagnosis of diabetes (p = 0.01). A tendency with baseline AER (p = 0.06) was also noted. No patient developed macroalbuminuria, proliferative retinopathy or hypertension. By the end of our study, in a cohort of young IDDM patients followed in a developing country, 6% died from acute complications and 15 patients (44.1%) developed retinopathy and/or microalbuminuria. Our results suggest that the only predictor of end-of-study AER was baseline AER. Also, duration of diabetes and age at diagnosis appear to be risk factors for retinopathy.