Highly selective transport of mercury(II) ion through a bulk liquid membrane

In this work carrier-facilitated transport of mercury(II) against its concentration gradient from aqueous 0.04 M hydrochloric acid solution across a liquid membrane containing isopropyl 2-[(isopropoxycarbothiolyl)disulfanyl]ethane thioate (IIDE) as the mobile carrier in chloroform has been investigated. Sodium thiocyanate solution (1.6 M) was the most efficient receiving phase agent among several aqueous reagents tested. Various parameters such as investigated. Under optimum conditions the transport of Hg(II) across the liquid membrane is more than 97% after 2.5 h. The carrier, IIDE, selectively and efficiently could able to transport Hg (II) ions in the presence of other associated metal ions in binary systems.

Mathematical equation correction to spectral and transport interferences in high-resolution continuum source flame atomic absorption spectrometry: determination of lead in phosphoric acid

In this work, a new mathematical equation correction approach for overcoming spectral and transport interferences was proposed. The proposal was applied to eliminate spectral interference caused by PO molecules at the 217.0005 nm Pb line, and the transport interference caused by variations in phosphoric acid concentrations. Correction may be necessary at 217.0005 nm to account for the contribution of PO, since Atotal217.0005 nm = A Pb217.0005 nm + A PO217.0005 nm. This may be easily done by measuring other PO wavelengths (e.g. 217.0458 nm) and calculating the relative contribution of PO absorbance (A PO) to the total absorbance (Atotal) at 217.0005 nm: A Pb217.0005 nm = Atotal217.0005 nm - A PO217.0005 nm = Atotal217.0005 nm - k (A PO217.0458 nm). The correction factor k is calculated from slopes of calibration curves built up for phosphorous (P) standard solutions measured at 217.0005 and 217.0458 nm, i.e. k = (slope217.0005 nm/slope217.0458 nm). For wavelength integrated absorbance of 3 pixels, sample aspiration rate of 5.0 ml min-1, analytical curves in the 0.1 - 1.0 mg L-1 Pb range with linearity better than 0.9990 were consistently obtained. Calibration curves for P at 217.0005 and 217.0458 nm with linearity better than 0.998 were obtained. Relative standard deviations (RSD) of measurements (n = 12) in the range of 1.4 - 4.3% and 2.0 - 6.0% without and with mathematical equation correction approach were obtained respectively. The limit of detection calculated to analytical line at 217.0005 nm was 10 µg L-1 Pb. Recoveries for Pb spikes were in the 97.5 - 100% and 105 - 230% intervals with and without mathematical equation correction approach, respectively.

Harvesting and wood transport planning with SNAP III program (Scheduling and Network Analysis Program) in a pine plantation in Southeast Brazil

The objective of this study was to verify the potential of SNAP III (Scheduling and Network Analysis Program) as a support tool for harvesting and wood transport planning in Brazil harvesting subsystem definition and establishment of a compatible route were assessed. Initially, machine operational and production costs were determined in seven subsystems for the study area, and quality indexes, construction and maintenance costs of forest roads were obtained and used as SNAP III program input data. The results showed, that three categories of forest road occurrence were observed in the study area: main, secondary and tertiary which, based on quality index, allowed a medium vehicle speed of about 41, 30 and 24 km/hours and a construction cost of about US$ 5,084.30, US$ 2,275.28 and US$ 1,650.00/km, respectively. The SNAP III program used as a support tool for the planning, was found to have a high potential tool in the harvesting and wood transport planning. The program was capable of defining efficiently, the harvesting subsystem on technical and economical basis, the best wood transport route and the forest road to be used in each period of the horizon planning.

Temperature effect in potassium and nitrate ions in soil transport

When doing researches on solute dynamics in porous medium, the knowledge of medium characteristics and percolating liquids, as well as of external factors is very important. An important external factor is temperature and, in this sense, our purpose was determining potassium and nitrate transport parameters for different values of temperature, in miscible displacement experiments. Evaluated parameters were retardation factor (R), diffusion/dispersion coefficient (D) and dispersivity, at ambient temperature (25 up to 28 ºC), 40 ºC and 50 ºC. Salts used were potassium nitrate and potassium chlorate, prepared in a solution made up of 5 ppm nitrate and 2.000 ppm potassium, with Red-Yellow Latosol porous medium. Temperature exhibited a positive influence upon porous medium solution and upon dispersion coefficient.

Agricultural engineering at UNICAMP: undergraduate student dropout analysis

Nowadays, dropping out in B.Sc. courses practically occurs in all Universities of the contemporary world. Undergraduate student withdraw could means several losses as, to the student, not to graduate, to the teacher, for not accomplishing his goal as educator, to the university, for not attending its mission, to the society, economic and social losses and also to the family for unfulfilling the dreams. The objective of this research is to present a quantitative study on the dropping out rate in the Agricultural Engineering B.Sc. program (BSAGENG) at State University of Campinas (UNICAMP), seeking to contribute to the understanding of this issue. It has been determined the dropping out rate from 1995 to 2006 based on the university official data, by employing four different methods of calculation. Three of the methods revealed that dropping out rate is very close to the graduation index, i.e., close to 50%. Regardless of the adopted method for the dropping rate estimation and the statistics demonstrating that the agricultural engineering undergraduate course at UNICAMP figures falls within similar courses normality in Brazil, it should be recognized that a public institution of education should be concerned in presenting such figures. A detailed and deep analysis must be outlined in further studies seeking for specific actions aiming to reduce dropping out process.

Nutrient loss in composting of agroindustrial residues

The management of composting may influence the characteristics of the produced compounds. The experiment used three frequencies of plowing, combined with the conditions: with and without coverage of the composting patio, with and without the use of commercial inoculant, resulting in 12 furrows, installed on the Experimental Center of Agricultural Engineering (NEEA), of the STATE UNIVERSITY OF WEST PARANÁ (UNIOESTE), Campus of Cascavel city - state of Paraná (PR), in Brazil. The waste and quantities used in kg were: corn cob (7.5); hatchery residue (5); floater sludge (31); ash (1); wheat cleaning residue (120); wheat pre-cleaning residue (120); corn peel (7.5); solid fraction of wash trucks used to transport chickens (2); solid fraction of pig manure (1) and coal (5), totaling 300kg of natural matter. The aim of this study was to evaluate the influence of plowings, patio coverage and inoculation in losses of N, P, K, Ca, Mg, Na, Cu, Zn, Mn, Fe. The furrows plowed three times a week in the first month showed significant higher losses of N (p<0.05). The coverage of the composting patio influenced significantly the losses of N, K, Mg and Na (p<0.05). The produced compounds had a high agronomic value in relation to macro and micronutrients. It is recommended the use of patio coverage and plowing twice a week in the first month and once a week in the subsequent months for a compound with higher concentrations of nutrients.

Transport of broilers: load microclimate during Brazilian summer

The objective of this study was to characterize the microclimatic profile of broiler transport trucks under commercial conditions, in the summer, by continuous monitoring of environmental variables (temperature and air relative humidity). Three loads were monitored from farm to slaughterhouse, considering factors such as distance and day periods (morning, afternoon, and night). To obtain the profile of the environmental variables during journey, data loggers, that determined the microclimate to which birds were submitted, were installed in the trucks; data loggers also allowed visualization of the Enthalpy Comfort Index (ECI) so that load regions could be classified according to heat comfort limits for 6-week old poultries. Temperature, relative humidity, and ECI in the truck were analyzed, using geostatistics, by the ordinary kriging method. The afternoon was the most critical period, and truck central and rear regions were most problematic for chickens, thus most susceptible to losses.