Geometric Mean Diameter Values Research Articles

Microscopy techniques and image analysis for evaluation of some chemical and physical properties and morphological features for seeds of the castor oil plant ( Ricinus communis)

Ricinus communis seed is a source of protein and oil with a high potential to use as animal's feedstock and biodiesel production. However, the oil yield and the extraction efficiency depend on the process conditions applied, as well as on the physical, chemical and structural properties of the seed, which have not been fully investigated. Hence, the objective of this study was to evaluate some chemical and physical properties of R. communis seed as well as to describe and quantify the macro and microstructure of this raw material by microscopy techniques and image analysis. Chemical analysis confirmed the seeds’ high contents of protein (28.48 ± 0.25%) and fat (51 ± 0.31%). On the other hand, the values of geometric mean diameter (8.95 ± 0.05 mm), bulk density (538 ± 11 kg/m 3), and true density (1458 ± 27 kg/m 3), among others, were higher than the ones reported about similar oils seeds. Microstructural studies showed that the endosperm cells presented an ovoid shape, as obtained from the aspect ratio results (AR = 1.28 ± 0.17), and a cell density of 570 ± 10 cell/mm 2, resulting in a porous structure, while the embryo cells had a cell density of 4903 ± 2 cell/mm 2, and an AR of 2.41 ± 0.48, related to a more compact structure (rectangular form) in this part of the seed. Regarding to lipids bodies (lb), they were only visible in the endosperm cells, showing a circular shape (AR = 1.16 ± 0.1), and a mean cell density of 9.57 ± 2.40 lipid bodies/μm 2, associated to protein as observed by the mineral presence (K, P, Mg and S) as determined by the energy dispersive X-ray analysis. Microscopy techniques and images analysis were efficient tools for the characterization of macro and microstructure of seeds and the data obtained integrate numerical information that could be useful for thermal and mechanical processing of R. communis seed, as well as for the design process equipment.

Aggregate stability as affected by short and long-term tillage systems and nutrient sources of a hapludox in southern Brazil

The ability of a soil to keep its structure under the erosive action of water is usually high in natural conditions and decreases under frequent and intensive cultivation. The effect of five tillage systems (NT = no-till; CP = chisel plowing and one secondary disking; CT = primary and two secondary distings; CTb = CT with crop residue burning; and CTr = CT with removal of crop residues from the field), combined with five nutrient sources (C = control, no nutrient application; MF = mineral fertilizers according to technical recommendations for each crop; PL = 5 Mg ha-1 y-1 fresh matter of poultry litter; CM = 60 m³ ha-1 y-1 slurry cattle manure; and SM = 40 m³ ha-1 y-1 slurry swine manure) on wet-aggregate stability was determined after nine years (four sampled soil layers) and on five sampling dates in the 10th year (two sampled soil layers) of the experiment. The size distribution of the air-dried aggregates was strongly affected by soil bulk density, and greater values of geometric mean diameter (GMD AD) found in some soil tillage or layer may be partly due to the higher compaction degree. After nine years, the GMD AD on the surface was greater in NT and CP compared to conventional tillage systems (CT, CTb and CTr), due to the higher organic matter content, as well as less soil mobilization. Aggregate stability in water, on the other hand, was affected by the low variation in previous gravimetric moisture of aggregates, which contributed to a high coefficient of variation of this attribute. The geometric mean diameter of water-stable aggregates (GMD WS) was highest in the 0.00-0.05 m layer in the NT system, in the layers 0.05-0.10 and 0.12-0.17 m in the CT, and values were intermediate in CP. The stability index (SI) in the surface layers was greater in treatments where crop residues were kept in the field (NT, CP and CT), which is associated with soil organic matter content. No differences were found in the layer 0.27-0.32 m. The effect of nutrient sources on GMD AD and GMD WS was small and did not affect SI.

Physical Properties and Compositional Changes of two Cultivars of Cantaloupe Fruit During Various Maturity Stages

Some physical properties and chemical compositions of two cultivars (Semsouri and Shahabadi) of cantaloupe studied during four different stages of maturity from fruit set to completely ripe. The physical properties investigated were the geometric mean diameter (GMD), specific gravity (SG), mean firmness (MF), rind, seed (%) and flesh (%). The chemical compositions were Brix, Titrable Acidity (TA), moisture content, pH, and ash. The results showed that the GMD, flesh (%), Brix, and pH values of both cultivars increased in the full-ripe stage of maturity whereas there was concurrent decrease in SG, rind (%), seed (%), moisture content, TA, and ash values obtained in the same period. There were also significant differences (using GLM-multivariate analysis) in all measured variables apart from ash, seed (%), rind (%), and flesh (%) between the two cultivars. Overall, the linear relationships were obtained between sugar content and GMD, SG, and MF respectively, correlation coefficients being higher than 0.87.

Tillage affects soil aggregation parameters linked with wind erosion

Geometric mean diameter (GMD), erodible fraction (EF), and dry aggregate stability (DASt) are soil parameters deduced by dry sieving that are used to identify soil susceptibility to wind erosion. Values of GMD, EF, and DASt have been calculated for different soil types but limited information is available on the effects of tillage on these parameters. In order to asses this influence we analyzed their variation in an Entic Haplustoll of Argentina during a 2 year sampling period. This soil was submitted to three tillage systems during the 7 years prior to sampling: no-till (NT), vertical tillage (VT) and conventional tillage (CT). We also analyzed the dry stability of each aggregate size fraction coarser than 0.84 mm (DASi). Results showed that tillage produced significant differences in all analyzed parameters. Average parameter values were, by treatment: GMD (2.37 mm) and DASt (88%) the highest and EF (20%) the lowest in NT, and GMD (0.88 mm) and DASt (49%) the lowest and EF the highest (49%) in CT. VT showed intermediate values of these parameters. As a consequence of soil disturbance by tillage, variations with time in CT were higher for GMD (SD = 0.42), EF (SD = 8.26) and DASt (SD = 16.31) than in VT (SD = 0.31, 5.71 and 8.00, respectively) and NT (SD = 0.31, 2.75, and 1.99, respectively). GMD calculated with a regression equation based on soil textural fractions, OM and CaCO 3 contents (Hagen, pers. comm.), was similar to the measured GMD in soils with low tillage disturbance (NT and VT) but it was much higher than the measured GMD in highly disturbed soils (CT). WEQ overestimated the wind erosion of the studied soil by 25 t ha − 1 year − 1 in NT and 9 t ha − 1 year − 1 in VT when the potential wind erosion (I factor) was calculated with an EF value obtained from the regression equation given by Fryrear et al. [Fryrear, D.W., Krammes C.A., Williamson D.L., Zobeck T.M. 1994. Computing the wind erosion fraction of soils. Soil Water Conserv. 49:183-188.]. NT exhibited greater quantities of aggregates coarser 19.2 and 6.4 mm than VT and CT, and lesser quantities of fine aggregates (0.84 and 2 mm) than CT on most sampling dates. The variability of the 19.2 mm sized aggregates between sampling dates was greater in NT (SD = 18) than in VT (SD = 6) and CT (SD = 4), while the variability of the 6.4 mm sized aggregates (SD = 5.5) was similar in all tillage systems. A time-dependent trend toward an increase of the 0.84 mm sized aggregates and a decrease of the 19.2 mm sized was observed in CT, indicating that tillage was degrading 19.2 mm aggregates into 0.84 mm aggregates. DASi of all sized aggregates was lower in NT (8.1%) than in VT (14.1%) and CT (23.1%), and was also less variable between sampling dates in NT (SD = 1.1), than in VT (SD = 4) and CT (SD = 7.6). A negative relationship between aggregate size and DASi was found ( y = − 1.755 × + 86.46, R 2 = 0.56, P < 0.001). Aggregates formed in NT were 5 to 7% more stable than VT aggregates and 13 to 16% more stable than CT aggregates. We concluded that tillage practices affect the parameters deduced from dry aggregate size distribution at different rates in the studied soil. Therefore, further studies should be developed to obtain reliable correction factors for these parameters on the basis of previous management conditions.

Some Physical Properties of Gilaburu Seed

In this study, the physical properties of gilaburu (Viburnum opulus L.) seed have been investigated. The average length, width, thickness and geometric mean diameter values in 54% of moisture content of gilaburu seed were between 6.56 and 8.44 mm, 6.24 and 8.57 mm, 1.62 and 2.52 mm, 4.19 and 5.31 mm, respectively. Sphericity, surface area, thousand seed mass and terminal velocity values in the same moisture content increased from 0.59 to 0.68, from 55.22 to 88.65 mm 2 , from 75.00 to 78.30 kg, from 4.52 to 5.15 m s -1 ; the bulk density, true density, porosity and angle of repose values changed betweeen 524.82 and 546.81 kg m -3 , 981.45 and 1046.15 kg m -3 , % 45.46 and 50.14%, 22.60 o and 26.78 o , respectively. The physical properties of gilaburu seed are necessary for the design of equipments for planting, harvesting, seperating,transporting, storage and other processing.

Winter and summer time size distributions and densities of traffic-related aerosol particles at a busy highway in Helsinki

Abstract. Number concentrations and size distributions of traffic related aerosol particles were measured at a roadside in Helsinki during two winter campaigns (10–26 February 2003, 28 January–12 February 2004) and two summer campaigns (12–27 August 2003, 6–20 August 2004). The measurements were performed simultaneously at distances of 9 m and 65 m from the highway. Total number concentrations were measured by a condensation particle counter (CPC) and particle size distributions by a scanning mobility particle sizer (SMPS) and an electrical low pressure impactor (ELPI). This study concentrates on data that were measured when the wind direction was from the road to the measurement site. The total concentrations in the wintertime were 2–3 times higher than in the summertime and the concentrations were dominated by nucleation mode particles. The particles smaller than 63 nm (aerodynamic diameter) constituted ~90% of all particles in the wintertime and ~80% of particles in the summer time. The particle total concentration increased with increasing traffic rate. The effect of traffic rate on particles smaller than 63 nm was stronger than on the larger particles. The particle distributions at the roadside consisted of two distinguishable modes. The geometric mean diameter (GMD) of nucleation mode (Mode 1) was 20.3 nm in summer and 18.9 nm in winter. The GMD of the larger mode consisting mostly of traffic related soot particles (Mode 2) was 72.0 nm in summer and 75.1 nm in winter. The GMD values of the modes did not depend on the traffic rate. The average particle density for each mode was determined by a parallel density fitting method based on the size distribution measurement made by ELPI and SMPS. The average density value for Mode 1 particles was 1.0±0.13 g/cm3 and 1.0±0.07 g/cm3 both in summer and winter respectively, while the average density value for Mode 2 was 1.5±0.1 g/cm3 and 1.8±0.3 g/cm3 for summer and winter, respectively.

Soil Fragment Size Distribution and Compactive Effort Effects on Maize Root Seedling Elongation in Moist Soil

Distributions of soil fragments (a mixture of primary aggregates resulting from tillage fragmentation) in seedbeds are known to influence emergence and early shoot and root growth of crops. However, it is not clearly understood which distribution model parameters the roots are responding to when water imbibition and nutrient availability are not limiting factors. The objective of this study was to determine the effect(s) of variation in geometric mean diameter (GMD) and log of the geometric standard deviation (LogGSD) taken from a log‐normal model of soil fragment size distribution on maize (Zea mays L.) root elongation over a range of soil bulk density (ρb) and air‐filled porosity (AFP) levels. Root growth, determined 48 h after seedling emergence, was evaluated in a greenhouse experiment with artificially packed soil fragments sieved from a Maury silt loam (fine, mixed, semiactive, mesic Typic Paleudalf) under sod. Two experiments were conducted. The first consisted of a complete factorial combination of four compactive efforts (CEs) (0.0, 26.8, 53.5, and 107.0 kJ m−3) applied over four GMDs (4.3, 5.1, 6.8, and 9.0 mm) at a uniform LogGSD of 0.22. The second experiment was a complete factorial combination of the same four CE treatments applied over three LogGSD (0.22, 0.31, and 0.48) values at a uniform GMD of 5.1 mm. Increasing CE, GMD, or LogGSD caused the ρb to increase. Maximum root elongation occurred at intermediate (5.1–6.8 mm) GMD values when 26.8 kJ m−3 of CE was applied, corresponding to an average ρb of 1.15 Mg m−3 There was no direct effect of the spread in soil fragment size (LogGSD) on root elongation. Total root length density (RLD) showed a quadratic response to ρb, relative bulk density (ρbr), bulk density divided by maximum Proctor density), or AFP levels reaching maximum elongation at values of 1.12 Mg m−3, 0.78 m3 m−3, or 0.187 m3 m−3, respectively. These results suggest that maximum radicle elongation depends more on the size of soil fragments rather than on the spread in their size distribution. Bulk density seems to be a more relevant parameter than size or distribution of soil fragments in characterizing compacted seedbeds. Loose or highly compacted seedbeds are inadequate for maximal early growth of maize roots.

Fallow Management and Overwinter Effects on Wind Erodibility in Southern Alberta

AbstractAggregate size distribution (ASD) is influenced by tillage and climate and greatly affects wind erodibility of soils. This study determined the effects of fallow management and winter effects on ASD in the chinook belt of Alberta. Geometric mean diameter (GMD), geometric standard deviation (GSD), and erodible fraction (EF) &lt;0.84 mm were determined in fall and spring on five fallow systems on a Lethbridge clay loam soil (fine‐loamy, mixed, Typic Haploboroll). The fallow systems were (i) tillage only, (ii) minimum tillage (herbicides and tillage), and (iii) zero tillage (herbicides only). In fall, one‐way disk and heavy‐duty cultivator fallow treatments had GMD values about 1 mm higher than blade cultivator or zero tillage treatments. The 1989–1990 winter with 90 cm of snowfall, 67 d of snow cover, and 101 d with a mean 2‐cm soil temperature between +2 and −2°C resulted in greater aggregate breakdown than the 1988–1989 winter, which had 129 cm of snowfall, 104 d of snow cover, and 68 d with 2‐cm soil temperatures between +2 and −2°C. Estimates of initiating wind velocities for erosion, based on residue cover and EF, were 13.3 m s−1 for the tillage treatments, 13.7 m s−1 for the minimum tillage treatment, and 15.4 m s−1 for the zero tillage treatment. However, the minimum and zero tillage systems had EF values &gt;60% at more sampling times than the tilled treatments, indicating that wind erosion problems may occur if the residue cover was jeopardized.

Soil Physical Properties as Affected by Soybean and Other Cropping Sequences

AbstractInfiltration, water stability of soil aggregates, and water retention characteristics were measured on a Sharpsburg silty clay loam (Typic Argiudolls) in a 4‐year cropping sequence. The cropping systems include soybean (Glycine max L. Merr.), sorghum (Sorghum bicolor L. Moench), corn (Zea mays L.), and fallow, in various sequential cropping combinations.The influence of cropping systems on size distribution of water‐stable aggregates is indicated by the values of geometric mean diameter (GMD). The rank order of GMD for the soybean sequences was: soybean after fallow &gt; soybean after sorghum &gt; soybean after corn &gt; continuous soybean. The low GMD of continuous soybean reflected the negative effect of soybean roots in building a stable soil structure. Cumulative infiltration after 4 hours of water application was 6, 13, 29, and 41 cm for continuous soybean, sorghum after soybean, fallow after soybean, and corn after sorghum, respectively. The low infiltration was associated with low macroporosity and decreased aggregate stability. Both Kostiakov's and Philip's equations fitted the infiltration data reasonably well statistically, but Kostiakov's equation was a better fit for the early and late stages of infiltration.

Effect of Sodium Ion on Synthetic Water‐stable Aggregates

AbstractParticles of diameter &lt;0.15µ were separated from Hesperia sandy loam (micaceous soil) and electrodialyzed. Proper quantities of 0.1 N NaOH were added to the electrodialzed suspensions so that the symmetry‐concentrations, S, of Na+ were 0.0625, 0.125, 0.25, 0.50, 1.0, and 2.0. Each suspension was dried to induce aggregation. The dry synthetic aggregates were then analyzed for their water‐stability by shaking them in water for 2‐, 20‐, 200‐, and 2,000‐minutes. After each shaking period a size distribution of aggregates was obtained.The cumulative weight percentage curves for aggregates with Na+ showed two distinct types of size distribution. Those for aggregates formed with electrodialyzed particles and with Na+ of 0.25‐S and less showed a sigmoid type of size distribution, while those for aggregates formed with Na+ of 0.50‐, 1.0‐, and 2.0‐S showed a bimodal type. The aggregates formed with electrodialyzed particles were more stable in water than any of the aggregates with Na+. The order of water‐stability of aggregates for each of the four shaking periods, as shown by the geometric mean diameters, was: electrodialyzed particles &gt; 0.0625‐S Na+ &gt; 0.125‐S Na+ &gt; 0.25‐S Na+ &gt; 0.50‐S Na+ &gt; 1.0‐S Na+ &gt; 2.0‐S Na+.The effect of Na+ on the values of geometric mean diameter of water‐stable aggregates was not a linear function, but rather some power function.