Quantiles via moments Machado, José A.F.; Santos Silva, J.M.C.
Journal of econometrics,
11/2019, Letnik:
213, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We study the conditions under which it is possible to estimate regression quantiles by estimating conditional means. The advantage of this approach is that it allows the use of methods that are only ...valid in the estimation of conditional means, while still providing information on how the regressors affect the entire conditional distribution. The methods we propose are not meant to replace the well-established quantile regression estimator, but provide an additional tool that can allow the estimation of regression quantiles in settings where otherwise that would be difficult or even impossible. We consider two settings in which our approach can be particularly useful: panel data models with individual effects and models with endogenous explanatory variables. Besides presenting the estimator and establishing the regularity conditions needed for valid inference, we perform a small simulation experiment, present two simple illustrative applications, and discuss possible extensions.
Salinity reduces feijão-caupi production, and the search for tolerant varieties becomes important within the agricultural context, as, in addition to being used in the field, they can be used in ...genetic improvement. The objective was to for a identify variety that is tolerant to salinity considering the physiological quality of seeds and seedling growth. A 2 × 4 factorial scheme was used, referring to the varieties Pingo-de-ouro and Coruja, and four electrical conductivities of water (0; 3.3; 6.6 and 9.9 dS m-1). The physiological quality of seeds and the growth of seedlings were analyzed, in addition to the cumulative germination. The Pingo-de-ouro variety showed no germination, length of the shoot and root, dry mass of the shoot and root compromised up to electrical conductivity of 6 dS m-1 in relation to 0.0 dS m-1. On the other hand, the Coruja variety showed reduced germination, increased shoot and root length. The creole variety Pingo-de-ouro proved to be tolerant to salinity.
The aim of this work was to assess the uptake of citrate-coated magnetite nanoparticles (NPs) by wheat plants and its effect on the bioaccumulation and toxicity of individual and joint Cd2+ and Cr6+ ...levels. Seven-day assays were conducted using quartz sand as the plant growth substrate. The endpoints measured were seed germination, root and shoot lengths, and heavy metal accumulation. Magnetite exhibited very low toxicity, regardless of the wheat seedling NP uptake and distribution into roots and shoots. The seed germination and shoot length were not sensitive enough, while the root length was a more sensitive toxicity endpoint. The root length of wheat seedlings exposed to individual metals decreased by 50% at 2.67mgCd2+kg−1 and 5.53mgCr6+kg−1. However, when magnetite NPs (1000mgkg−1) were added, the root length of the plants increased by 25 and 50%. Cd2+ and Cr6+ showed similar and noninteractive joint action, but strongly impaired the wheat seedlings. In contrast, an interactive infra-additive or antagonistic effect was observed upon adding magnetite NPs. Thus, cadmium and chromium accumulation in vegetable tissues was considerately diminished and the toxicity alleviated.
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•We assessed the effect of nanomagnetite on heavy metal toxicity in wheat plants.•Citrate-coated magnetite nanoparticles (NPs) exerted very low toxicity to plants.•Cadmium was more toxic than chromium and toxicity was mitigated by magnetite NPs.•Cadmium and chromium had a similar and noninteractive joint action on plants.•Metals showed an interactive infra-additive joint effect by adding magnetite NPs.
Brazil major probiotics and bioremediators have proven their effectiveness in the cultivation of exotic species. The aim of the study was to evaluate the effects of a commercial multi‐species ...probiotic suitable for shrimp and fish in the feed and as biocontrol in tambaqui rearing through zootechnical performance, water quality, clinical and laboratory alterations and innate immunity evaluations. Colossoma macropomum juveniles were used, distributed: Control (C)—without any probiotic addition; Probiotics added to water (G2)—.004 g/L of probiotics added to each experimental unit; Probiotics in feed (G3)—5 g/kg of probiotics added to the feed. The use of probiotics during the tambaqui breeding phase was proven safe. However, the use of multi‐species did not result in any complementary benefit when added to the water or to the feed for 60 consecutive days regarding zootechnical performance, water quality and tambaqui health under the applied experimental conditions. The findings demonstrate the need for further in vitro and in vivo tests regarding microorganism screening and protocols analyses for each culture species, since several factors influence the effects of the administration of probiotics on aquaculture production and health.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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•Extrusion optimization of PP and GRPP filaments for 3D printing.•3D printing vs. compression molding benchmark with the same raw material.•Optimal 3D printing conditions for PP and ...GRPP.•3D printing deposition orientation with minimum mechanical performance impact.•Reinforcing role of glass fibers is maintained with 3D printing.
This paper addresses the potential of polypropylene (PP) as a candidate for fused deposition modeling (FDM)-based 3D printing technique. The entire filament production chain is evaluated, starting with the PP pellets, filament production by extrusion and test samples printing. This strategy enables a true comparison between parts printed with parts manufactured by compression molding, using the same grade of raw material. Printed samples were mechanically characterized and the influence of filament orientation, layer thickness, infill degree and material was assessed. Regarding the latter, two grades of PP were evaluated: a glass-fiber reinforced and a neat, non-reinforced, one. The results showed the potential of the FDM to compete with conventional techniques, especially for the production of small series of parts/components; also, it was showed that this technique allows the production of parts with adequate mechanical performance and, therefore, does not need to be restricted to the production of mockups and prototypes.
This study aimed to analyze how meteorological conditions such as temperature, humidity and rainfall can affect the spread of COVID-19 in five Brazilian (São Paulo, Rio de Janeiro, Brasília, Manaus ...and Fortaleza) cities. The cities selected were those with the largest number of confirmed cases considering data of April 13. Variables such as number of cumulative cases, new daily cases and contamination rate were employed for this study. Our results showed that higher mean temperatures and average relative humidity favored the COVID-19 transmission, differently from reports from coldest countries or periods of time under cool temperatures. Thus, considering the results obtained, intersectoral policies and actions are necessary, mainly in cities where the contamination rate is increasing rapidly. Thus, prevention and protection measures should be adopted in these cities aiming to reduce transmission and the possible collapse of the health system.
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•This study attempts to model the effects of meteorological factors in COVID-19 spread in Brazil•High mean temperatures influenced the COVID-19 transmission rate•Intermediate relative humidity influenced the COVID-19 transmission rate•Correlation of meteorological conditions with COVID-19 spread is presented for five Brazilian cities•This study aims to support decision-makers to avoid deaths by the collapse of health-care systems
Schistosomiasis is one of the most significant neglected tropical diseases, affecting around 260 million people worldwide, and Praziquantel is currently the only available drug for the treatment of ...infected persons. Thus, the search for new schistosomicidal compounds is urgent. The objective of this study was to investigate of the schistosomicidal effect of barbatic acid, a lichen metabolite, on adult worms of Schistosoma mansoni. The in vitro schistosomicidal effect was evaluated through the assessment of motility and mortality, cellular viability of the worms and ultrastructural analysis through scanning electron microscopy. To evaluate the cytotoxicity of barbatic acid, a cell viability assay was performed with human peripheral blood mononuclear cells. Barbatic acid showed a schistosomicidal effect after 3 h of exposure. At the end of 24 h the concentrations of 50–200 μM presented lethality on the worms. Motility changes were observed at sublethal concentrations. The IC50 obtained by the cell viability assay for S. mansoni was 99.43 μM. Extensive damage to the worm's tegument was observed from 25 μM. No cytotoxicity was observed on human peripheral blood mononuclear cells. This report provides data showing the schistosomicidal effect of barbatic acid on S. mansoni, causing death, motility changes and ultrastructural damage to worms. In addition, barbatic acid was shown to be non-toxic to human peripheral blood mononuclear cells at concentrations that are effective against S. mansoni.
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•Barbatic acid exhibited schistosomicidal effect against adult S. mansoni.•Motility changes were observed in S.mansoni at all concentrations after 24 h.•Tegumentary damages were caused by the barbatic acid in Schistosoma mansoni.•No cytotoxicity was observed on PBMC exposed to barbatic acid after 72 h.
Sugarcane cultivation stands out in Brazilian agribusiness, covering more than eight million hectares for the production of sugar, ethanol, and by-products. Fertilization is one of the limiting ...factors in sugarcane yield, for which filter cake is a viable solution to meet plant nutritional needs. This study aimed to assess the effect of enriched filter cake on gas exchange and yield in RB041443 sugarcane, cultivated in soils of the coastal tablelands of Paraíba, Brazil. The experiment was conducted in the Monte Alegre S/A sugarcane mill, in the municipality of Mamanguape, using a randomized blocks experimental design, with 12 treatments (T1- cake, T2- cake + MAP, T3- cake + gypsum, T4 - cake + phosphate, T5- cake + bagasse, T6- cake + MAP + gypsum, T7- cake + MAP + phosphate, T8- cake + MAP + bagasse, T9- cake + gypsum + phosphate, T10- cake + gypsum + bagasse, T11- cake + phosphate + bagasse, and T12- control (only MAP)), and 4 replications, totaling 48 plots. A significant effect (5% probability) was also observed for the variables number of leaves and tons of stem per hectare (TSH). T1- cake, T4- cake + phosphate, T6- cake + MAP + gypsum and T10- cake + gypsum + bagasse, had the best results for TSH, with yields greater than 140 t ha-1. Regarding stomatal conductance, the highest values were obtained in T6 and T8, which, together with T11, had the highest gs values. Concerning the internal carbon concentration, T1, T2, T6, and T8 stood out. T6 also had a significant effect on transpiration. From this study, it was concluded that the use of enriched filter cake as a base fertilizer in sugarcane culture contributes to increasing the yield of the RB041443 variety, generating positive responses for plant gas exchange, being T1 and T10 indicated to increase the production in the sugar-energy sector.
In this work, we demonstrate for the first time the design and fabrication of microchip electrophoresis devices containing cross-shaped channels and spiral electrodes around the separation channel ...for microchip electrophoresis and capacitively coupled contactless conductivity detection. The whole device was prepared in a digital light processing–based 3D printer in poly(ethylene glycol) diacrylate resin. Outstanding X-Y resolution of the customized 3D printer ensured the fabrication of 40-μm cross section channels. The spiral channels were filled with melted gallium to form conductive electrodes around the separation channel. We demonstrate the applicability of the device on the separation of sodium, potassium, and lithium cations by microchip electrophoresis.
Graphical abstract
Superoxide, a naturally produced reactive oxygen species (ROS) in the human body, is involved in many pathological and physiological signaling processes. However, if superoxide formation is left ...unregulated, overproduction can lead to oxidative damage to important biomolecules, such as DNA, lipids, and proteins. Superoxide can also lead to the formation of peroxynitrite, an extremely hazardous substance, through its reaction with endogenously produced nitric oxide. Despite its importance, quantitative information regarding superoxide production is difficult to obtain due to its high reactivity and low concentrations in vivo. MitoHE, a fluorescent probe that specifically reacts with superoxide, was used in conjunction with microchip electrophoresis (ME) and laser-induced fluorescence (LIF) detection to investigate changes in superoxide production by RAW 264.7 macrophage cells following stimulation with phorbol 12-myristate 13-acetate (PMA). Stimulation was performed in the presence and absence of the superoxide dismutase (SOD) inhibitors, diethyldithiocarbamate (DDC) and 2-metoxyestradiol (2-ME). The addition of these inhibitors resulted in an increase in the amount of superoxide specific product (2-OH-MitoE⁺) from 0.08 ± 0.01 fmol (0.17 ± 0.03 mM) in native cells to 1.26 ± 0.06 fmol (2.5 ± 0.1 mM) after PMA treatment. This corresponds to an approximately 15-fold increase in intracellular concentration per cell. Furthermore, the addition of 3-morpholino-sydnonimine (SIN-1) to the cells during incubation resulted in the production of 0.061 ± 0.006 fmol (0.12 ± 0.01 mM) of 2-OH-MitoE⁺ per cell on average. These results demonstrate that indirect superoxide detection coupled with the use of SOD inhibitors and a separation method is a viable method to discriminate the 2-OH-MitoE⁺ signal from possible interferences.
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