Sections Of Grain Research Articles

Geology and ore-forming fluids of the Dayingezhuang gold deposit, Jiaodong Peninsula, eastern China: Implications for mineral exploration

The Dayingezhuang deposit is a representative large gold deposit within the Zhao-Ping fault zone in Jiaodong Peninsula, eastern China, and contains gold reserves of 170 t with an average grade of 3.10 g/t. The orebodies are hosted in the Late Jurassic Linglong granite intrusion and are Jiaojia-type (disseminated- or stockwork-style) ores. Mineralization and alteration are structurally controlled by the NE- to NNE-striking Linglong detachment fault located near the central section of the regional Zhao-Ping fault zone. Mineralization can be divided into primary and supergene periods. The primary period can be further divided into four hydrothermal stages: I) pyrite–(K-feldspar)–sericite–quartz; II) auriferous quartz–pyrite; III) quartz–gold–polymetallic sulfides; and IV) quartz–carbonate. Gold was mainly deposited in the second and third stages. Three types of fluid inclusion were observed (in decreasing order of abundance): AC-type (aqueous–carbonic), A-type (aqueous), and PC-type (pure carbonic). Based on petrographic, microthermometric, and laser Raman spectroscopic analyses of these fluid inclusions, three types of fluid inclusion assemblage (FIA) were identified in the quartz grains: FIA1 (AC- and PC-type), FIA2 (AC-, PC- and A-type), and FIA3 (A-type). First stage quartz grains contain mainly FIA1-type inclusions, with trapping temperatures of 305–388 °C and salinities of 4.28–8.51 wt% NaCl equivalent. Quartz grains that formed in the second and third mineralization stages contain all three types of FIA. Second stage inclusions homogenize completely at temperatures of 219–317 °C and have salinities of 1.56–11.12 wt% NaCl equivalent, while third stage inclusions homogenize completely at temperatures of 195–319 °C and have salinities of 2.73–13.33 wt% NaCl equivalent. In contrast, quartz grains that formed during the last mineralization stage contain mainly FIA3-type inclusions that yield homogenization temperatures of 126–233 °C and salinities of 0.48–6.72 wt% NaCl equivalent. The microthermometric data indicate that the ore-forming system evolved from a CO2-rich mesothermal fluid into a CO2-poor fluid. The existence and microthermometric characteristics of AC-, PC-, and A-type inclusion assemblages (FIA2) within a single thin section of grains that formed during the second and third stages show that ore fluids underwent unmixing during the syn-ore mineralization stages, due to pressure and temperature fluctuations. The microstructural deformation of auriferous samples indicates that both ductile and brittle deformation occurred during the syn-ore mineralization. Based on the inference that fluids were immiscible in FIA2, trapping pressures during ore formation are estimated at 127–276 MPa. Assuming a fluid pressure regime controlled by fault-valve activity, these pressures are equivalent to a mineralization depth of 9.2–14.0 km. The depth to which erosion occurred in the study area has been calculated as ~10.3 km since the formation of the deposit at 130 Ma, which suggests good prospecting potential for gold at depth in Dayingezhuang.

Modification of Copper

The requirement of modification of copper is proved in the article. As a modifier for copper the misch metal is proposed. The misch metal contains rare earth elements having greatest modifying ability. The results of experiments of the influence of misch metal in an amount from 0.0025 to 0.0125 wt. % on the formation of crystal structure of cast copper with different impurity content are presented. The metallographic analysis of macrostructure of copper is made and the average area of cross section of grains in the structure of copper is determined. The average area of cross section of grains in the structure of copper of brand M00 decreases from 5 to 0.9 mm2 with addition of 0.005 wt. % of misch metal. The average area of cross section of grains in the structure of copper of brand M1 decreases from 6 to 0.45 mm2 with addition of 0.005 wt. % of misch metal. An increase of quantity of added misch metal more than 0.005 wt. % dose does not lead to significant decrease of average area of cross section of grain in the structure of copper. The investigation of microstructure of samples of cast copper of brands of M00 and M1 is made. It is established that the addition of misch metal in the copper dose does not lead to increase in the thickness of the grain boundaries. The results of experiments are shown that addition of misch metal in the copper leads to increase of stregth and plastic properties of copper. Based on the results of experiments the mechanism of modification of copper is proposed.

Austenite Grain Size Estimtion from Chord Lengths of Logarithmic-Normal Distribution

AbstractLinear section of grains in polyhedral material microstructure is a system of chords. The mean length of chords is the linear grain size of the microstructure. For the prior austenite grains of low alloy structural steels, the chord length is a random variable of gamma- or logarithmic-normal distribution. The statistical grain size estimation belongs to the quantitative metallographic problems. The so-called point estimation is a well known procedure. The interval estimation (grain size confidence interval) for the gamma distribution was given elsewhere, but for the logarithmic-normal distribution is the subject of the present contribution. The statistical analysis is analogous to the one for the gamma distribution.

Austenite Grain Size Estimation in Structural Steels by Linear Section Method / Ocena Wielkości Ziarna Austenitu Metodą Przekrojów Liniowych

Linear section of grains in polyhedral material microstructure is a system of chords on a test line. The mean chord length is the linear grain size of the material. In the prior austenite microstructure of low alloy structural steels, the chord length is a random variable which has the gamma distribution. The distribution parameters are closely related to the austenite linear grain size. Because the sequent chord lengths are statistically independent, the grain size interval estimation (confidence interval) may be performed by the chi-square distribution.

RNA Interference Suppression of Genes in Glycosyl Transferase Families 43 and 47 in Wheat Starchy Endosperm Causes Large Decreases in Arabinoxylan Content

The cell walls of wheat (Triticum aestivum) starchy endosperm are dominated by arabinoxylan (AX), accounting for 65% to 70% of the polysaccharide content. Genes within two glycosyl transferase (GT) families, GT43 (IRREGULAR XYLEM9 [IRX9] and IRX14) and GT47 (IRX10), have previously been shown to be involved in the synthesis of the xylan backbone in Arabidopsis, and close homologs of these have been implicated in the synthesis of xylan in other species. Here, homologs of IRX10 TaGT47_2 and IRX9 TaGT43_2, which are highly expressed in wheat starchy endosperm cells, were suppressed by RNA interference (RNAi) constructs driven by a starchy endosperm-specific promoter. The total amount of AX was decreased by 40% to 50% and the degree of arabinosylation was increased by 25% to 30% in transgenic lines carrying either of the transgenes. The cell walls of starchy endosperm in sections of grain from TaGT43_2 and TaGT47_2 RNAi transgenics showed decreased immunolabeling for xylan and arabinoxylan epitopes and approximately 50% decreased cell wall thickness compared with controls. The proportion of AX that was water soluble was not significantly affected, but average AX polymer chain length was decreased in both TaGT43_2 and TaGT47_2 RNAi transgenics. However, the long AX chains seen in controls were absent in TaGT43_2 RNAi transgenics but still present in TaGT47_2 RNAi transgenics. The results support an emerging picture of IRX9-like and IRX10-like proteins acting as key components in the xylan synthesis machinery in both dicots and grasses. Since AX is the main component of dietary fiber in wheat foods, the TaGT43_2 and TaGT47_2 genes are of major importance to human nutrition.

Spectroscopic Analysis of Diversity of Arabinoxylan Structures in Endosperm Cell Walls of Wheat Cultivars (Triticum aestivum) in the HEALTHGRAIN Diversity Collection

Fifty bread wheat (Triticum aestivum L.) cultivars were selected from the HEALTHGRAIN germplasm collection based on variation in their contents of total and water-extractable arabinoxylan. FT-IR spectroscopic mapping of thin transverse sections of grain showed variation in cell wall arabinoxylan composition between the cultivars, from consisting almost entirely of low-substituted arabinoxylan (e.g., T.aestivum 'Claire') to almost entirely of highly substituted arabinoxylan (e.g., T.aestivum 'Manital') and a mixture of the two forms (e.g., T.aestivum 'Hereward'). Complementary data were obtained using endoxylanase digestion of flour followed by HP-AEC analysis of the arabinoxylan oligosaccharides. This allowed the selection of six cultivars for more detailed analysis using FT-IR and (1)H NMR spectroscopy to determine the proportions of mono-, di-, and unsubstituted xylose residues. The results of the two analyses were consistent, showing that variation in the composition and structure of the endosperm cell wall arabinoxylan is present between bread wheat cultivars. The heterogeneity and spatial distribution of the arabinoxylan in endosperm cell walls may be exploited in wheat processing as it may allow the production of mill streams enriched in various arabinoxylan fractions which have beneficial effects on health.

Pressure effects on the charge carrier transportation of polycrystalline LiCr0.35Mn0.65O2

AbstractLiCr0.35Mn0.65O2 powders were investigated by using in situ impedance spectroscopy under high pressure. The impedance spectroscopy of the Nyquist representation showed two overlapped arcs in the complex impedance plane which corresponded to the electrical transportation of grain and grain boundary respectively. By using the representation of Z ″/f versus Z ′, the resistance and the relaxation frequency of grain and grain boundary were obtained under different pressures. It was found that at every phase transition region, both the resistance and the relaxation frequency of grain and grain boundary changed discontinuously. Pressure decreases the effective scattering section of grain and grain boundary to the charge carriers obviously and makes their transport easier. The variation of defects in the grain boundary region leads the sample resistance in the decompression process is much lower than that in the compression process. This indicates the pressure treatment has a positive contribution to the electrochemical performance of LiCr0.35Mn0.65O2. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Diffusion and reaction in whole wheat grains during boiling

AbstractThe boiling of whole wheat grains was studied using magnetic resonance imaging (MRI) and pulsed‐gradient‐spin‐echo nuclear magnetic resonance (NMR) (PGSE NMR). MRI was used to image moisture distributions across a central section of grains boiled for different times at either 100 or 120°C. A moisture front gradually moved into the grain, although some moisture did penetrate ahead of the front. PGSE NMR, which measures self‐diffusion, indicated that two pools of water with differing diffusion characteristics may exist within the grain. Diffusion models suggested from the PGSE results were incorporated into finite‐element simulations along with the Thomas‐Windle model for diffusion/relaxation in polymers. Simulation results were compared to the MRI data, and the best fit was achieved using the Thomas‐Windle model with a step‐change in diffusivity above a critical moisture content. This behavior is similar to that of diffusion in polymers undergoing a glass transition, a phenomenon widely accepted to occur when starch gelatinizes.

NMR imaging of the wheat grain cooking process

NMR imaging has been used to study the boiling and steaming of intact wheat grains by mapping the distribution of water on the central cross section of grains after various cooking times. The results show different distributions of water occurring with boiling and steaming. Boiled grains showed a front of moisture which gradually moved towards the centre of the grain, although some water was able to diffuse ahead of the front. Steamed grains showed no such front, but showed a homogeneous distribution of water which gradually increases with cooking time. The different results for boiling and steaming imply that different mechanisms control the influx of water in each case, and provide important data for modelling these processes. It is postulated that absorption of water during steaming is slowed by the grain temperature rising above that of the steam temperature as a result of the latent heat associated with the condensation of steam being taken up by the grain.

SOME BARLEY GRAIN AND GREEN MALT PROPERTIES AND THEIR INFLUENCE ON MALT HOT-WATER EXTRACT: I. β-GLUCAN, β-GLUCAN SOLUBILASE AND ENDO-β-GLUCANASE

A study has been made of the variation between varieties in some properties of barley and malt and how this variation relates to malt hot water extract (HWE). The development of enzyme activity along the grain during germination was investigated. In this first paper we have examined β-glucan-related characters and found significant varietal variation in maximum enzyme activities and in the activities in different sections of grain during germination. Varietal variation was greater than environmental variation for each character. The fraction of β-glucan soluble in acid was the character most highly correlated with HWE.

The Absorption Cross Section for Light of the Silver Grains in Photographic Deposits

AbstractEstimations of projection area of silver grains in photographic deposits were made on photomicrographs as well as counts of grains per unit area. Density of the deposit was calculated from these data employing known formulae. These were found smaller by a factor of 2-3 when compared with densities measured in diffuse light. The absorption cross section of grains for light considerably greater than their projective area is concluded. The results are in agreement with those obtained by other authors, which were, however, interpreted in a different way.