Native Grain Research Articles

Deriving the ideal ore texture for microwave treatment of metalliferous ores

High power density microwave treatments on metalliferous ores have historically been shown to reduce ore competency prior to beneficiation at economically feasible energy inputs. However, the relationship between mineralogical textural features and the extent of the microwave-induced fracturing had previously been limited to qualitative descriptions or simplistic two-phase numerical models, which could not account for the complex mineral assemblages in real ores. In this paper, mineralogy, grain size, dissemination, textural consistency and mineral associations were determined for 13 commercially exploited nickel, copper and lead–zinc ores using a Mineral Liberation Analyser (MLA). The ores were subjected to high power density microwave treatments at up to 25kW in a single mode cavity with microwave energy inputs of approximately 0.5–10kWh/t, and the subsequent reductions in ore competency were measured by the Point Load Test. The ores that demonstrated the greatest reductions in strength typically contained between approximately 2wt% and 20wt% of highly microwave-absorbing minerals, with a native grain size d50 greater than approximately 500μm, constrained by hard matrix minerals such as quartz and feldspar. Texturally consistent ores with a high proportion of amenable textures also demonstrated the highest average reductions in strength. These findings support the qualitative descriptions and numerical modelling results available in the literature and provide a baseline for selecting likely candidate ores for microwave treatments in the future.

Effects of dietary starch content and rate of fermentation on methane production in lactating dairy cows

The objective of this study was to investigate the effects of starch varying in rate of fermentation and level of inclusion in the diet in exchange for fiber on methane (CH4) production of dairy cows. Forty Holstein-Friesian lactating dairy cows of which 16 were rumen cannulated were grouped in 10 blocks of 4 cows each. Cows received diets consisting of 60% grass silage and 40% concentrate (dry matter basis). Cows within block were randomly assigned to 1 of 4 different diets composed of concentrates that varied in rate of starch fermentation [slowly (S) vs. rapidly (R) rumen fermentable; native vs. gelatinized corn grain] and level of starch (low vs. high; 270 vs. 530g/kg of concentrate dry matter). Results of rumen in situ incubations confirmed that the fractional rate of degradation of starch was higher for R than S starch. Effective rumen degradability of organic matter was higher for high than low starch and also higher for R than S starch. Increased level of starch, but not starch fermentability, decreased dry matter intake and daily CH4 production. Milk yield (mean 24.0±1.02kg/d), milk fat content (mean 5.05±0.16%), and milk protein content (mean 3.64±0.05%) did not differ between diets. Methane expressed per kilogram of fat- and protein-corrected milk, per kilogram of dry matter intake, or as a fraction of gross energy intake did not differ between diets. Methane expressed per kilogram of estimated rumen-fermentable organic matter (eRFOM) was higher for S than R starch–based diets (47.4 vs. 42.6g/kg of eRFOM) and for low than high starch–based diets (46.9 vs. 43.1g/kg of eRFOM). Apparent total-tract digestibility of neutral detergent fiber and crude protein were not affected by diets, but starch digestibility was higher for diets based on R starch (97.2%) compared with S starch (95.5%). Both total volatile fatty acid concentration (109.2 vs. 97.5mM) and propionate proportion (16.5 vs. 15.8mol/100mol) were higher for R starch– compared with S starch–based diets but unaffected by the level of starch. Total N excretion in feces plus urine and N retained were unaffected by dietary treatments, and similarly energy intake and output of energy in milk expressed per unit of metabolic body weight were not affected by treatments. In conclusion, an increased rate of starch fermentation and increased level of starch in the diet of dairy cattle reduced CH4 produced per unit of eRFOM but did not affect CH4 production per unit of feed dry matter intake or per unit of milk produced.

Effets d'un stress hydrique appliqué à différents stades de développement sur l'aspect quantitatif et qualitatif des semences chez un écotype autochtone de sorgho grain (<i>Sorghum bicolor</i>)

Effects of water stress applied at different stages of development on the quantity and quality of autochthonous sorghum seed ecotype (Sorghum bicolor ) Objective: The effects of water stress applied at different stages of development on the quantity and quality of seeds were studied in native grain sorghum ecotype. Methodology and Results: The trial was conducted in plant pots. The irrigation of the plants was made together with the successive weighing pots. During each weighing, the control was returned to the same weight corresponding to 70% of the UWR (useful water reserve), whereas stress treatment (SI, S2 and S3) maintained the water content to 30% of the UWR for 10 days. At the end of the cycle of water shortage, irrigation was taken Jour nal of Applied Biosciences 74:6 149 – 6156

Historical Analysis of Beach Nourishment and Its Impact on the Morphological Modal Beach State in the North Reach of Brevard County, Florida

The beach and nearshore in the North Reach of Brevard County, Florida was the subject of 14 fill projects between 1972 and 2010. Historical data was analyzed to determine how those projects may have impacted the morphological modal beach state. The borrow site sediments used prior to 2001 did not modify the typically dissipative morphological modal beach state. The borrow site sediment used in 2001 and 2005 was significantly coarser than the composite native beach profile grain size distribution. The coarser fill changed the modal beach state from dissipative to intermediate with transverse bars and rips. Analysis of sediment data collected in 2011 and 2013 indicates that some combination of fill template equilibration, natural sorting, and the addition of finer sediment to updrift portions of the reach in 2007 and 2010, has returned the North Reach to a dissipative modal beach state. A more robust post-fill physical monitoring program is needed to capture the sediment equili- bration process, assess the impact on the modal beach state, assess the impact on the surfing wave environment, and better un- derstand the coastal processes involved in the North Reach of Brevard County, Florida.

Synthesis and Characterization of Ba0.96Sr0.04Zr0.04Y0.005Ti0.955O2.9975 Nano-powders via Polyacrylamide-Gel Method

Pure tetragonal phase Ba0.96Sr0.04Zr0.04Y0.005Ti0.955O2.9975 nano-powders were synthesized via a simple, fast and low cost method: polyacrylamide gel (PAG) method. The effects of processing parameters on the polymerization reaction and the sizes of as-prepared powder were investigated. The results reveal that the critical value of monomer / cross-linking agent ratio is 4.5:1 for the tightest network structure and the smallest average particle size of nano-powder correspondingly due to the smallest grid of gel. The monomer/cross-linking agent ratio and the concentration of cross-linking agent have significant influence on the gel quality and particle. In the investigation range we have probed into, the nano-dispersed BSZYT powders is obtained. The average native grain size of as-prepared powder is ∼27 and ∼45 nm after calcined at 900°C and 1200°C, respectively.

Detecting ancient wild rice (Zizania spp. L.) using phytoliths: a taphonomic study of modern wild rice in Minnesota (USA) lake sediments

Wild rice (Zizania spp. L.) is a North American native grain with spiritual and dietary significance to many native people. Wild rice is also an important aquatic plant that provides critical habitat to wetland and aquatic wildlife. Past distribution of wild rice in North America is poorly understood, largely because of the limited taxonomic resolution of Poaceae pollen. A novel technique for detecting diagnostic Zizania silica phytoliths allows unambiguous identification of this taxon in lake sediments. We need to better understand modern depositional patterns of phytoliths in lake sediments, however, before attempting detailed paleoreconstructions. We analyzed distributions of diagnostic Zizania and other Poaceae phytoliths in modern sediments from three lakes with variable percent cover of wild rice and a non-wild rice control lake in central Minnesota. Absolute counts of phytoliths per gram sediment were achieved using an exotic diatom marker. Non-Zizania short-cell phytoliths, i.e. phytoliths from wetland grasses Phragmites australis and Muhlenbergia glomerata, dominate the assemblages in all lakes. Most Poaceae short-cell phytoliths appear to be derived locally, with little evidence for regional inheritance from eolian or alluvial processes. Because of anatomical differences in decay of plant debris and other taphonomic issues, Zizania inflorescence rondel phytoliths were most abundant, with morphotypes from other parts rarely encountered. Even in sediments under the densest wild rice stands, Zizania phytoliths contributed a maximum of 9 % to total Poaceae phytolith abundance. Lake morphology also affects the depositional pattern of phytoliths in modern sediments, so coring locations should be considered carefully. At least 500 phytoliths should be counted to detect a sufficient number of wild rice phytolith morphotypes. Diagnostic Zizania phytoliths are a reliable tool for wild rice detection in paleolake sediments.

Folate in oats and its milling fractions

Total folate content in oat varieties from three harvesting years (2006–2008), and in oats milling fractions, was determined using microbiological assay. Furthermore, folate vitamer distribution in milling fractions were examined with the UPLC method, which was taken in use and validated. The total folate content of the cultivars varied moderately within each year. The average content in the 2008 samples was 685ng/gdm. The UPLC method proved fast and sensitive for determining seven folate monoglutamates in cereal samples. Folate content in fractions, which are normally discarded, such as flour from oat cutting and flaking, were 1.5- to 2.5-fold higher than in native grain. The main folate vitamers found in the oat fractions were 5-CH3-H4folate, 5-HCO-H4folate, and 5,10-CH+-H4folate. The UPLC results more closely matched the microbiological results compared to those that are usually achieved with HPLC methods. This study illustrates that oats and, especially, by-products of milling are good sources of folate.

Gold in the Beach Placer Sands of Chavakkad-Ponnani, Kerala Coast, India

Abstract Although sporadic mining of placer gold from river beds is not uncommon in India, there is no documented literature on the occurrence of gold in the beach placer sand deposits of the country. While characterizing the heavy minerals of the Chavakkad-Ponnani (CP) beach placer sands along the North Kerala coast, the association of gold with the pyriboles in these sands has been observed. A native gold grain of about 25 μm was seen to occur as an inclusion within an amphibole of hornblendic composition. The pyriboles of the CP deposit are angular to sub-angular indicating a nearby provenance that may be in the upstream reaches of the Ponnani River in the districts of Malappuram and Palakkad or further north in the auriferous tracts of the Wynad-Nilambur or Attapadi regions. It is argued that the occurrence of native gold in CP deposit is not a freak occurrence and that it warrants thorough investigation of all the pyribole-ilmenite-rich placers to examine the possible presence of gold and its abundance in the beach placers of northern Kerala coast.

Manipulation of polycrystalline TiO2 carrier concentration via electrically active native defects

There is good reason to believe that the properties of semiconducting metal oxides for catalytic applications can be improved when designed according to the principles of microelectronic devices. Nevertheless, defect engineering of polycrystalline TiO2 is complicated by native charged point defects and grain boundaries that alter bulk carrier concentration in a manner that depends on synthesis and post-treatment protocols. These influences are difficult to decouple with standard electrical characterization methods, which typically induce rectifying Schottky barriers to wide-bandgap semiconductors like TiO2. Here, TiO2 donor carrier concentration (Nd) is investigated as a function of film thickness and annealing time using a rigorous Schottky diode-based electrical characterization approach. Nd scales inversely with film thickness due to a reduction in the concentration of electrically active grain boundaries in the bulk. Annealing of polycrystalline TiO2 at 550 °C induces film densification that reduces the void volume surface area available for charge trapping. Strategies for defect engineering polycrystalline metal oxides must focus on tuning electrical activity of grain boundaries and intergranular voids for successful control and manipulation of Nd.

Locally diagnostic phytoliths of wild rice (Z izania palustris L.) from Minnesota, USA: comparison to other wetland grasses and usefulness for archaeobotany and paleoecological reconstructions

Wild rice ( Zizania spp.) is an important native grain of north-central North America, with spiritual and subsistence significance to many native peoples. Due to lack of suitable proxies, its past distribution and pattern of use are poorly known. This study demonstrates the diagnostic value of silica phytoliths from Z. palustris as a proxy tool to detect its past occurrence in a variety of paleoenvironmental and archaeological contexts. Our main findings are: 1) Dominant wetland grass species in Minnesota produce phytoliths distinct from Zizania phytoliths; 2) Closely related Leersia oryzoides produces a few Zizania-like phytolith morphotypes; however, these potential confusers can be identified based on 2-D and 3-D morphologies; 3) Z. palustris produces a wide variety of phytolith morphotypes, many of which are only found in certain parts of the plant (e.g., Inflorescence Type 1 from the spikelet); 4) Z. palustris produces 23 locally diagnostic phytolith morphotypes that can be used to determine the presence and abundance of wild rice in modern and paleo lake sediments; and 5) Wild rice phytolith Inflorescence Type 1 is the morphotype most likely to be observed in archaeological contexts, and may be unequivocally diagnostic for the genera Zizania.

The time for CIGS

This special issue of Progress in Photovoltaics (PIP) is completely devoted to the state of the art in chalcopyrite Cu(In,Ga)(Se,S)2 (CIGS)-based solar cells research and technology. We made the choice to ask for in-depth review papers with joint authorship by scientists from internationally leading research institutions involved in different areas in the field of CIGS solar cells and modules. These invited reviews are devoted to key aspects and specificities of the CIGS photovoltaics (PV) field with an aim to provide to the interested reader a snapshot of the 2010 CIGS's technological landscape and perspectives. The paper from Siebentritt et al. describes fundamental aspects of electronic properties of chalcopyrites and how they are influenced by native defects and grain boundaries. Naghavi et al. summarize the current status of research and development in buffer layers and transparent conducting oxides with special focus of novel and alternative materials and deposition processes. And, influences on solar cell efficiency and metastability are also addressed in this special issue of PIP. While CIGS solar cell technologies based on vacuum deposited absorber layers have driven the advancements with the highest efficiency records and heading towards industrial maturity, the non-vacuum processes are drawing considerable attention because of the attractive inherent features related to large area scale up and low cost processing. Hibberd et al. provide a comprehensive review of various deposition methods and current status of this approach for the fabrication of CIGS solar cells. On the other hand, the review paper from Niki et al. is focused on solar cell and module technologies based on vacuum deposited absorber layers describing aspects of manufacturing and performance stability. The topics of process monitoring and control are very important for the development of reproducible manufacturing processes and also to enhance the production yield. Scheer et al. provide a critical assessment of various techniques and tools to study fundamental physical properties of CIGS PV materials and solar cells with special emphasis on the application of laser light scattering, Raman scattering and time resolved photoluminescence. Editors accept that some important topics might be missing and could have been addressed, and also contributions from several other leading groups could have further enhanced the value of the special issue. By the way the special issue comes timely in a key transition period for PV, not only regarding the global acceleration of the growth of PV production towards large scale deployment in the near future, but also strengthening the position of thin film PV technologies with respect to traditional wafer-based silicon PV. At the beginning of the decade, the share of thin film PV, mostly a-Si based, was decreasing in relative value, from 12.5% in 2000 to 6% in 2005, giving the impression that contrary to the expectations thin film technologies will not become competitive. However, 2005 saw the start of large scale industrial commercial development of thin film CdTe with ever growing success in increasing production volume and decreasing production costs to the ‘benchmark value of below one dollar’ for the first time. Thin film PV production is increasing in volume as well as in terms of relative contribution to the global PV production with an incredibly high growth rate. In 2009, a CdTe thin film company became for the first time in PV history the number 1 in the field: who would have expected this revolution? After 30 years of R&D, the ‘potential’ of chalcogenide compound semiconductors had finally been demonstrated! But this may be only the beginning of the success story for chalcogenide materials. As in the case of CdTe, CIGS has progressed step by step, reaching an incredible level of efficiency of 20% while the industrial production of CIGS modules crossed the symbolic value of 1% in market share in 2008. Does it means that CIGS share will be of 9% within 4 years of the total PV production? Maybe yes, many indicators point that way, but one thing is certain: CIGS technology is here to stay and will successfully contribute to the solar revolution. We hope that this special issue, giving an example of very dynamic worldwide research networks and collaborations, will be useful for making this challenge a reality. It is the right time for CIGS!

Dietary fiber and other functional components in two varieties of crude and extruded kiwicha ( Amaranthus caudatus)

Two varieties (Centenario and Oscar Blanco) of Andean native grain, kiwicha ( Amaranthus caudatus), were evaluated as sources of dietary fiber and of some bioactive compounds. The impact of low-cost extrusion on the content of these components was studied for technological applications. The content of total dietary fiber in Centenario was higher (16.4%) than in Oscar Blanco (13.8%). In both varieties, the content of total and insoluble dietary fiber decreased during the extrusion process. In Centenario, the content of soluble dietary fiber increased, from 2.5 to 3.1% during the extrusion process. The content of phytic acid in raw kiwicha was 0.3% for both varieties, and the content of total phenolic compounds was 98.7 and 112.9 mg GAE/100 g of sample, for Centenario and Oscar Blanco, respectively. Antioxidant activity with the DPPH method for the raw kiwicha of the two varieties was 410.0 μmol trolox/g sample for Centenario and 398.1 μmol trolox/g sample for Oscar Blanco. With ABTS method those values were 827.6 and 670.1 μmol trolox/g sample for Centenario and Oscar Blanco, respectively. The content of total phenolics, phytic acid and the antioxidant activity decreased in both varieties during the extrusion process. The in vitro digestibility of protein and starch was improved after the extrusion process in both varieties, demonstrating potential for nutritional applications.

A New Analytical Approach to Reveal the Mechanisms of Grain Refinement

AbstractThis paper presents an overview of a new methodology for investigating the grain refinement performance of alloys and master alloys and then uses this methodology to shed new light on the mechanisms occurring during superheating and native grain refinement, and the effect of iron and manganese on grain refinement in magnesium alloys. The methodology also describes changes in grain size upon Zr grain refinement of Mg and has been used to analyse the potential for the use of SiC to grain refine Mg‐Al alloys. With this new methodology, and the knowledge it generates, the potential for the discovery of new or improved refiners is significantly enhanced.

New approach to analysis of grain refinement

Grain refinement of aluminium and magnesium alloys has been a challenging topic for decades and this is partly due to the complex nature of the mechanisms occurring during solidification and the lack of a common experimental method allowing comparison of data from different research groups. A new analytical approach that plots grain size versus the inverse of the growth restriction factor Q enables additional valuable information to be revealed about the efficiency and potency of grain refiner particles and master alloys. The present paper describes the new analytical approach and then gives examples where insights into the grain refinement mechanisms have been achieved. For aluminium alloys, the new analytical approach compares the effectiveness of different master alloys and examines the mechanism of poisoning of grain refinement by Zr. For magnesium alloys, the new analytical approach is applied to explain phenomena such as superheating and native grain refinement. With this new analytical approach and the knowledge it generates, the potential for the discovery of new or improved refiners is significantly enhanced.

Nanostructure development in wet amorphous amylopectin as revealed by in situ X‐ray scattering methods

AbstractCompletely amorphous, transparent bars of amylopectin were prepared by injection molding of pure native semicrystalline samples (Waxy Maize). The formation of a semicrystalline morphology was studied during annealing treatment at various temperatures in a wet atmosphere, using simultaneous WAXS and SAXS. Amylopectin samples crystallized during 20 days in a humid atmosphere at room temperature and subjected to a successive melting process were also studied by X‐ray scattering. Results indicate that individual molecules crystallize independently from each other, similar to the case of native amylopectin grains. During the first stages of crystallization, the changes in the SAXS pattern suggest that uncorrelated crystal blocks are formed, which may arrange to lamellae (if a secondary network of double‐helix net‐points is hydrothermally dissociated). At the beginning of the crystallization process, only few amylopectin molecules (about 10%) are incorporated into the nanostructure. A shell‐like structure of semicrystalline layers, comparable to that of a native grain, develops. When crystallization proceeds further, the initially thin shell layers thicken. This causes the amorphous interlayers to be subjected to inner tensions, leading to a decrease in the melt temperature. After a storage time of 20 days in a humid atmosphere, amylopectin reaches a crystallinity level of 54%, only slightly lower than that of the initial native grains. Upon heating the retrograded amylopectin, immediately before complete melting, the long‐period shows a value of 15 nm with a crystal thickness, derived from WAXS, of only 4 nm. Such a structure, which has not been reported before, is due to the relaxations of the inner tensions during melting, which lead to a disappearance of inserted interlamellar crystals. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3832‐3839, 2006

Native grain refinement of magnesium alloys

High purity Mg-Al type alloys have a naturally fine grain size compared to commercial purity alloys with the same basic composition. This is referred to as native grain refinement. It is shown that native grain refinement occurs only in magnesium alloys containing aluminium. The mechanism is attributed to the Al4C3 particles existing in these alloys. (c) 2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

A study of refractories from baddeleyite stabilized with magnesium oxide

It is shown that refractory articles can be produced from ZrO2 on a forsterite binder based on natural baddeleyite with native grain composition. The articles have a high density (4.71 – 4.72 g/cm3), ultimate compressive strength (257.6 MPa), heat resistance (6 – 8 water heat cycles from 1300°C), and a low porosity (12.2%).

Morphological Properties of Acid-modified Tapioca Starch

Highly crystalline tapioca starch was prepared by partial hydrolysis of tapioca starch in hydrochloric acid at room temperature for various lengths of time. The crystallinity of the starch increased while its amylose content decreased with increasing reaction time. Scanning electron micrographs of these natural and highly crystalline starches were taken in order to study the morphological changes and mode of acid attack during hydrolysis. Exocorrosion all over the surface was observed after 96 h of hydrolysis. Further hydrolysis caused the outer layer of the starch grain surface to erode away. After complete erosion was accomplished, an inner layer or underlayer was revealed with a smooth surface similar to that of the native starch grain surface. Endocorrosion was not observed at any time in this study.

Molecular-beam epitaxial growth of high electron mobility AlGaN/GaN heterostructures

We report the growth of high quality AlGaN/GaN heterostructures on sapphire by ammonia gas-source molecular-beam epitaxy. By inserting a low-temperature-grown AlN interlayer during the growth of the thick GaN buffer, the piezoelectrically-induced two-dimensional electron gas (2DEG) in the unintentional doped AlGaN/GaN heterostructures exhibited substantially increased mobility. With the optimized AlN interlayer thickness of 30 nm, electron mobilities as high as 1500, 10 310, and 12 000 cm2/V s were obtained at room temperature, 77 and 0.3 K respectively. Sheet densities of 9×1012 and 6×1012 cm−2 were measured at room temperature and 77 K, respectively. The 2DEG was confirmed by strong and well resolved Shubnikov–de Haas oscillations starting at 2.8 T. Photoluminescence measurements and atomic force microscopy revealed that the densities of native donors and grain boundaries were effectively reduced in the AlGaN/GaN heterostructures with AlN interlayers.

High electron mobility AlGaN/GaN heterostructures grown on sapphire substrates by molecular-beam epitaxy

High-quality AlGaN/GaN heterostructures have been grown by ammonia gas-source molecular-beam epitaxy on sapphire substrates. Incorporation of a low-temperature-grown AlN interlayer during the growth of a thick GaN buffer is shown to substantially increase the mobility of the piezoelectrically induced two-dimensional electron gas (2DEG) in unintentionally doped AlGaN/GaN heterostructures. For an optimized AlN interlayer thickness of 30 nm, electron mobilities as high as 1500 cm2/V s at room temperature, 10 310 cm2/V s at 77 K, and 12 000 cm2/V s at 0.3 K were obtained with sheet densities of 9×1012 cm−2 and 6×1012 cm−2 at room temperature and 77 K, respectively. The 2DEG was confirmed by strong and well-resolved Shubnikov–de Haas oscillations starting at 3.0 T. Photoluminescence measurements and atomic force microscopy revealed that the densities of native donors and grain boundaries were effectively reduced in the AlGaN/GaN heterostructures incorporating low-temperature-grown AlN interlayers.