ABSTRACT
Objective: To investigate the preparation process of polylactic acid-glycolic acid copolymer/ hydroxyapatite (PLGA/HA) microcarriers by electrostatic spraying method, and to elucidate the superiority of PLGA/HA microcarriers. Methods: The PLGA/HA microcarriers were prepared by electrostatic spraying method using nano-HA (20 nm, 99.9%) and PLGA (LA/GA = 50/50, Mw30k), and the influence of different concentrations (1%, 3%, 5%) and different voltages (4. 0, 4. 5, > 5. 0 kV) of HA in the morphology of the microcarriers was investigated and the best ball making parameters were obtained. The PLGA microcarriers were used as PLGA group, PLGA+1%HA as 1% PLGA/HA group, PLGA + 3% HA as 3% PLGA/HA group, PLGA+ 5% HA as 5% PLGA/HA group, and the simple cells were used as blank control group. The characteristics of PLGA/HA microcarriers were detected by scanning electron microscope (SEM), cell proliferation test, cell fluorescence staining experiment, and Fourier transform infrared spectroscopy (FTIR). Results: The SEM results showed that the microcarrier particles were uniform, all of them were elliptical or circular, without abnormal shape spheres, with smooth surface, without sharp edges, adhesion between the spheres and aggregation, and there were no significant differences between the different concentrations of microcarriers. The cell proliferation test results showed that the order of adhesion cells was 5% PLGA/HA group > 3% PLGA/HA group > 1% PLGA/HA group > PLGA group > blank control group (P<0. 05); the number of cells was increased with the increasing of HA concentration; the microcarriers in 5% PLGA/HA group had the best cell affinity and the microcarriers had no cytotoxity. The cell fluorescence staining experiment showed that the MC3T3-E1 cells adhered well on the microcarriers. The FTIR analysis results showed that HA characteristic absorption peak was observed, indicating that the composite microcarrier contained PLGA and HA. Conclusion: The preparation process of PLGA/ HA microcarriers is successfully established by electrostatic spraying method. The method is simple and convenient to operate, and has excellent ball-making effect. It has broadly application prospects in bone tissue engineering.
ABSTRACT
ABSTRACT: Despite all advances obtained with the pesticide use worldwide and in Brazilian agriculture, there is still a lack of technologies for agricultural aircrafts. The objective of this study was to evaluate the drift produced by the use of conical nozzles and electrostatic system in aircraft application. The experimental design was completely randomized with a factorial arrangement and four replications. Treatments included two spraying equipment: electrostatic system with 5L ha-1 of spray volume and conical nozzle with 15 and 20L ha-1. In all treatments, azoxystrobin fungicide was used at a dose of 100g a.i. ha-1 and paraffinic mineral oil at a dose of 0.5% v.v. Volume median diameter (VMD) and droplet density were estimated using water sensitive paper. Evaluations of drift distance were performed with glass collectors distributed horizontally on the soil surface, 50m before the application band, at the application site and 12,5, 25, 50, 75, 100, 150, 200 and 300m after the application site, along the wind direction. Azoxystrobin concentration in glasses were quantified by UHPLC-MS/MS. Results indicated that the drift distance can reach more than 300 meters away from the application site, with variable concentrations according to the equipment used. Electrostatic system reduced drift when compared to hydraulic conical nozzles.
RESUMO: Apesar dos avanços obtidos no uso de agrotóxicos na agricultura mundial e brasileira, ainda existe carência em tecnologias voltadas para aviação agrícola. O objetivo deste estudo foi avaliar a deriva ocorrida com a utilização de bicos hidráulicos com pontas cônicas e sistema eletrostático em aplicação aérea. O delineamento experimental adotado foi inteiramente casualizado com quatro repetições. Os tratamentos foram compostos por dois equipamentos de pulverização: sistema eletrostático com volume de aplicação de 5L ha-1 e bicos hidráulicos com pontas cônicas, utilizando volumes de aplicação de 15 e 20L ha-1. Em todos os tratamentos, foi utilizado o fungicida azoxistrobina na dose de 100g i.a. ha-1 e óleo mineral parafínico na dose de 0,5% v.v. As avaliações de diâmetro mediano volumétrico e densidade de gotas foram realizadas através de papéis hidrossensíveis na faixa de aplicação. As avaliações de distância de deriva foram realizadas com coletores de vidro distribuídos horizontalmente sobre a superfície do solo, 50m antes da faixa, na faixa de aplicação e aos 12,5, 25, 50, 75, 100, 150, 200 e 300m após a faixa de aplicação, no sentido da direção de vento. Azoxistrobina foi quantificada por UHPLC-MS/MS. Os resultados indicam que a distância de deriva pode alcançar mais de 300 metros do local de aplicação, com concentrações variáveis de acordo com o equipamento utilizado. O sistema eletrostático reduz a deriva, quando comparado aos bicos hidráulicos com pontas cônicas.
ABSTRACT
Este trabalho teve como objetivo desenvolver um dispositivo para promover a atração de gotas carregadas eletricamente para o interior do dossel de plantas cítricas, visando reduzir o impacto ambiental causado pelos agrotóxicos. Foram distribuídos condutores metálicos no interior do dossel das plantas da laranja Pêra, com o propósito de atrair as gotas. Assim como etiquetas hidrossensíveis nos terços superiores, médios e inferiores, em três profundidades do dossel. As pulverizações foram realizadas com e sem carga, combinadas com a presença e ausência do dispositivo proposto. A eficiência da pulverização eletrostática e do dispositivo proposto foi baseada na densidade de gotas que variou de 112 a 147 gotas cm-2 sem e com carga, respectivamente, e na cobertura que variou de 10,7% a 12, 1% na parte inferior e superior, nas diferentes regiões da planta, não ocorrendo diferenças significativas entre os tratamentos. Em todas as condições estudadas, a maior densidade de gotas e a maior cobertura foram obtidas na parte externa do dossel.
This study aimed to develop a device to promote the attraction of electrically charged droplets to the inner part of the citrus plants, to reduce the environmental impact caused by pesticides. Metallic conductors were distributed in the inner part of the orange Pear canopy, in order to attract the droplets. Water sensitive papers were distributed onto the upper, middle and bottom part of the plant, at three different depths of the canopy. The spraying was performed with and without charging, combined with the presence and absence of the proposed device. The efficiency of electrostatic spraying and the mechanism proposed was based onto the droplets density ranging from 112.08 to 146.76 cm- 2 droplets with and without charging, respectively, and onto the coverage ranged from 10.75 to 12.12 % in the inner and superior part, in different regions of the plant, not occurring significant difference between the treatments. In all conditions studied, the highest droplets density and coverage were obtained on the outer part of the canopy.