Role Of Grains Research Articles

Electrical modulus and dielectric behavior of Cr3+ substituted Mg–Zn nanoferrites

The dielectric parameters and ac electrical conductivity of Mg0.8Zn0.2CrxFe2−xO4; (0≤x≤0.025) nanoferrites synthesized citrate–nitrate auto-combustion method were studied using the complex impedance technique in the frequency and temperature ranges 4Hz–5MHz and 303–873K respectively. Hopping of charge carriers plus interfacial polarization could interpret the behaviors of dielectric constant (ε′), dielectric loss tangent (tanδ) and ac electrical conductivity (σac) with frequency, temperatures and composition. The up-normal behavior observed in tanδ trend with temperatures confirms the presence of relaxation loss (dipoles losses). Correlated barrier hopping (CBH) of electron is the conduction mechanism of the investigated nanoferrites. Cole-Cole plots at different temperatures emphasize the main role of grain and grain boundaries in the properties of the investigated nanoferrites. Cr3+ substitution can control the dielectric parameters and ac electrical conductivity of Mg-Zn nanoferrites making it candidates for versatile applications.

On the Role of Grains in Plastic Deformation and Low Cycle Fatigue of Polycrystalline Metal

In the previous papers, the author discussed the role of r-value (anisotropic parameter in plasticity) on the surface roughening after plastic deformation. In the present paper, discussion is made on the effects of mutual constraint of deformation between neighboring grains at the grain boundary on the surface roughening. A characteristic parameter called constraint ratio is introduced to express the degree of the mutual restriction between grains. The well-known Coffin-Manson relation in low cycle fatigue is deduced considering to the surface roughening after cyclic deformation.

Dielectric and impedance behavior of neodymium substituted strontium hexaferrite

In this study, dielectric behavior and complex impedance of neodymium (Nd) substituted strontium hexaferrite system: Sr1−xNdxFe12O19 (x = 0.0, 0.05, 0.1, 0.15, 0. 20), synthesized by citrate precursor technique, have been evaluated as a function of applied frequency and temperature. Variation of dielectric constant and dielectric loss with frequency shows the identical behavior for all the compositions. The value of dielectric constant increases with Nd doping. Relaxation process is observed in the composition x = 0.20, and the peaks in this composition shift toward the higher-frequency region as the temperature increases. The dielectric constants show temperature-independent behavior at low temperature, whereas at higher temperatures it increases for all the frequencies. The AC conductivity follows Jonscher’s power law, showing that conduction mechanism is due to polaron hopping. Complex impedance as a function of composition and temperature is used to examine the role of grain and grain boundary in the prepared material. Cole–cole plot shows only one semicircle up to x = 0.15, while as for x = 0.20 two semicircles are observed. The conduction mechanism is explained on the basis of both grain and grain boundary.

Effect of Removing Superior Spikelets on Grain Filling of Inferior Spikelets in Rice.

Large-panicle rice cultivars often fail to reach their yield potential due to the poor grain filling of inferior spikelets (IS). Thus, it is important to determine the causes of poor IS grain filling. In this study, we attempted to identify whether inferior grain filling of large panicles is restricted by superior spikelets (SS) and their physiological mechanism. SS were removed from two homozygous japonica rice strains (W1844 and WJ165) during flowering in an attempt to force photosynthate transport to the IS. We measured the effects of SS removal on seed setting rate, grain weight, grain filling rate, sucrose content, as well as hormone levels, activities of key enzymes, and expression of genes involved in sucrose to starch metabolism in rice IS during grain filling. The results showed that SS removal improved IS grain filling by increasing the seed setting rate, grain weight, sucrose content, and hormone levels. SS removal also enhanced the activities of key enzymes and the expression levels of genes involved in sucrose to starch metabolism. These results suggest that sucrose and several hormones act as signal substances and play a vital role in grain filling by regulating enzyme activities and gene expression. Therefore, IS grain filling is restricted by SS, which limit assimilate supply and plant hormones, leading to poor grain filling of IS.

Structural, electrical and magneto-electric characteristics of complex multiferroic perovskite Bi0.5Pb0.5Fe0.5Ce0.5O3

The polycrystalline sample of bismuth based-complex multiferroic of a composition Bi0.5Pb0.5Fe0.5Ce0.5O3 was prepared by a high-temperature solid-state reaction technique (calcinations temperature = 900 °C, sintering temperature = 960 °C, time = 4 h). Preliminary structural analysis using XRD data exhibits the formation of a single-phase compound. Studies of surface morphology of the ceramic sample of the compound, recorded at room temperature using a scanning electron microscope, show uniform distribution of grains of different size with few voids. Detailed studies of dielectric properties (er, tan δ) supported the existence of multiferroic properties in the above complex system. The analysis of impedance parameters, recorded in a wide frequency (1 kHz–1 MHz) and temperature (room temperature to 450 °C) range of the material provide better understanding of (a) role of grains and grain boundaries in resistive and capacitative characteristics, (c) structure-properties relationship and (b) type of relaxation process occurred in the material. Study of temperature dependence of dc conductivity of the compound shows the existence of negative temperature coefficient of resistance in it. The nature of variation of ac conductivity with temperature of the material follows the Josher’s universal power law. Study of magneto-electric characteristics of the sample at room temperature has provided many useful and new data on magneto-electric coupling coefficient of different orders.

Structural and electrical properties of Bi3La2Ti3FeO15 ceramics

This research article reports structural and electrical (dielectric, impedance and conductivity) characteristics of La3+ modified Bi5Ti3FeO15 multiferroic (i.e., Bi3La2Ti3FeO15). Preliminary structural analysis of the prepared material using room temperature X-ray diffraction (XRD) data confirmed the formation of a single-phase compound in the orthorhombic crystal. The nature of scanning electron micrograph of the compound showed the uniform distribution of grains on the sample surface with less voids (high density) Detailed studies of dielectric, impedance and conduction characteristics of the material, carried out in a wide frequency range (100 Hz–1000 kHz) at different temperatures (room temperature to 500 °C) using a complex impedance spectroscopy technique, have provided vital information on dielectric relaxation, conduction mechanism and role of grains, grain boundary and interface in understanding of structure–property relationship of the material.

EFFECT OF COARSE-TO-FINE WC GRAIN RATIO ON MECHANICAL PROPERTIES AND ABRASIVE WEAR OF WC-8Co CEMENTED CARBIDES

This study performs a comprehensive analysis concerning the amount of fine tungsten carbide (WC) grains needed for the appropriate reinforcement of the cobalt (Co) metallic binder in WC-8Co cemented carbides. The goal is to investigate the balance of coarse-to-fine grain distribution to achieve overall improvement of the material’s mechanical and wear properties. All samples possessed the same WC-8Co binder content, therefore, allowing the role of grain size distribution to be tested. It was found that a ratio of 8:1 wt% of coarse to ultrafine grain WC yielded an appropriate balance between material hardness, fracture toughness, and rupture strength. Upon adding grain growth inhibitors vanadium carbide (VC) and chromium carbide (Cr3C2), the overall wear resistance is further improved compared to undoped composites when samples are tested under abrasive wear conditions.

Local analysis of the grain and grain boundary contributions to the bulk dielectric properties of Ca(Cu3−yMgy)Ti4O12 ceramics: Importance of the potential barrier at the grain boundary

The present work focuses on two aspects related to the synthesis and the dielectric properties of CaCu3Ti4O12 (CCTO) ceramics. Effective strategies able to synthesize high quality CCTO, with reduced dielectric losses and high relative permittivity, are achieved by the substitution of Cu ion by Mg one in the crystal. Ca(Cu3−yMgy)Ti4O12 ceramics have been synthesized by conventional mixed oxide method involving CCTO and MgO. This approach is found to drastically reduce the synthesis time by lowering the eutectic point of CCTO as a result of the small fraction (1–3wt%) of MgO added to the mixture. Experimental data have been used to successfully confirm this substitution and the only presence of CuO at grain-boundaries. The role of grain and grain boundary contributions on the dielectric properties of ceramics are investigated. It is found that samples containing 1% MgO lead to excellent relative permittivity values of the order of 3.5×104. In these substituted ceramics, extracted relative permittivity values are found to be extremely stable, with low loss tangent (<0.06), up to 100kHz at room temperature. From the various samples investigated, the optimized ceramics are found to contain large grains (≥15μm). Local intra-grain and inter-grain electrical transport measurements show that the grains and their respective grain boundaries exhibit metallic and semiconducting behaviors, respectively. This approach confirms the crucial role of the potential barrier at the grain boundary in determining the dielectric properties of such Ca(Cu3−yMgy)Ti4O12 ceramics.

Cadres, Grain, and Sexual Abuse in Wuwei County, Mao’s China

Primarily based on official archives produced from Mao’s China in the mid-1950s to 1963 in Wuwei County, Anhui Province, this article explores sexual abuse carried out by local cadres of the Chinese Communist Party around the time of Mao’s Great Famine (1958–1961). It first clarifies key concepts of sexual abuse and then reviews the crucial role of grain in many sexual cases. Further efforts are made to discuss the female victims, male perpetrators, and institutional factors of these crimes. A series of political, economic, and social policies, systems, and movements of highly centralized governance set up institutional traps for disadvantaged female victims who were “liberated” from traditional households. Supplemented with other local cases, the article argues that the overlap of state patriarchy and the authoritarian party-state made women vulnerable to local cadres and institutionalized sexual abuse. The case of Wuwei indicates that Mao’s regime was yet another form of gender domination.

Biochemical and molecular characterisation of salt-induced poor grain filling in a rice cultivar.

Despite the prevalence of poor grain filling in rice (Oryza sativa L.) under abiotic stress, the reason for this is largely unexplored. Application of 0.75% NaCl to a salt-sensitive rice cultivar at late booting resulted in a >20% yield loss. Spikelets per panicle and the percentage of filled grain decreased significantly in response to NaCl application. The inhibitory effect of NaCl on grain filling was greater in basal than in apical spikelets. Sucrose synthase (SUS) activity was positively correlated with grain weight. The transcript levels of the SUS isoforms differed greatly: the levels of SUS2 increased significantly in response to salt; those of SUS4 decreased drastically. Gene expression studies of starch synthase and ADP-glucose pyrophosphorylase showed that the decreased transcript levels of one isoform was compensated by an increase in those of the other. Salt application also significantly increased the gene expression of the ethylene receptors and the ethylene signalling proteins. The increase in their transcript levels was comparatively greater in basal than in apical spikelets. Significant enhancement in the transcript levels of the ethylene receptors and the increase in the production of ethylene indicated that the salt-induced inhibition of grain filling might be mediated by ethylene. Additionally, the inhibition of chromosomal endoreduplication mediated by decreased transcript levels of B-type cyclin could explain poor grain filling under salt stress. A significant increase in the transcript levels of the ethylene-responsive factors in the spikelets during grain filling in response to salt indicated their possible protective role in grain filling under stress.

Erratum to: Genetic variation of stem characters in wheat and their relation to kernel weight under drought and heat stresses

The frequency, duration, and severity of heat and drought stresses singly or in combination can be aggravated by climate change. Under these stresses, the stored carbohydrates in stems play an important role in grain filling in wheat (Triticum aestivum L.) post-anthesis. This study examines the genetic variation of stem characters in wheat and their role in supporting grain weight under favorable and drought, combined drought, and heat conditions. Field experiments were conducted with seven spring wheat genotypes along with their F1 and F2 progenies. Stem diameter (SD), stem density (SDN), and stem weight (SW) were measured in 21 F1 (half-diallel analysis) and 12 F2 (3 x 4 North Carolina Design II) crosses. Among stem characters, SD was significantly correlated with thousand kernel weight (TKW) and grain yield per spike (GYPS) in all environments in F1 and F2. All characters showed high heritability estimates. For stem characters, the highest heritability was found for SD in both generations. High positive phenotypic and genotypic correlations were found between stem characters and both TKW and GYPS. The correlation between reductions due to stress (%) in stem characters and reduction due to stress in TKW and GYPS confirmed the strong relationships between stem characters and yield attributes in the stressed environments. We conclude that stem characters, especially SD, may play an important role in sustaining grain filling under such conditions. This is possibly due to a greater stem capacity for assimilates storage post-anthesis and subsequent remobilization to the grains.

Formation of the eutecticum with multilayer structure during solidification in as-cast Al–Mg alloy containing a high level of Sc

An addition of a high level of 0.6wt% Sc imposed a remarkable grain refining effect on Al-5Mg alloy for as-cast condition, changing typical dendritic microstructure into fine equiaxed grains. Such effect was found to be related to the extensively formed Sc-rich particles. Electron back-scatter diffraction (EBSD), Atomic force microscopy (AFM) and SEM-elemental mapping were employed to investigate the inner structure of these particles and their role in grain refining. They could be identified as some eutectic structure consist of multilayer of ‘Al3Sc+α-Al+Al3Sc····’, which shows good consistency in orientation both in the particle and matrix.

Good Food, Bad Food: Where Do Grains Land?

In this column, Slavin discusses the role of grains in a health-promoting diet. The general recommendation made in the dietary guidelines report published by the 2015 DGAC is that more whole grains be consumed as part of a nutritious, health-promoting diet and that consumption of refined grain should be limited. What is lost in this recommendation is that in the United States refined grains are enriched with thiamin, riboflavin, niacin, and iron and fortified with folic acid to aid in preventing pellagra, improving iron stores, and reducing neural tube birth defects caused by nutrient deficiencies. Gluten content, genetic modification, and their association with products high in saturated fat, added sugar, and sodium all negatively affect the perception of grains. In addition, all grains consumed by humans are processed, which helps maintain a safe, sustainable food supply. “Processed” has become a bad word, however. To maintain and promote the reputation of grains, those involved in the production of gra...

Abscisic acid and the key enzymes and genes in sucrose-to-starch conversion in rice spikelets in response to soil drying during grain filling.

Abscisic acid mediates the effect of post-anthesis soil drying on grain filling through regulating the activities of key enzymes and expressions of genes involved in sucrose-to-starch conversion in rice spikelets. This study investigated if abscisic acid (ABA) would mediate the effect of post-anthesis soil drying on grain filling through regulating the key enzymes in sucrose-to-starch conversion in rice (Oryza sativa L.) spikelets. Two rice cultivars were field-grown. Three treatments, well-watered (WW), moderate soil drying (MD), and severe soil drying (SD), were imposed from 6 days after full heading until maturity. When compared with those under the WW, grain filling rate, grain weight, and sink activity, in terms of the activities and gene expression levels of sucrose synthase, ADP glucose pyrophosphorylase, starch synthase, and starch branching enzyme, in inferior spikelets were substantially increased under the MD, whereas they were markedly decreased in both superior and inferior spikelets under the SD. The two cultivars showed the same tendencies. Both MD and SD increased ABA content and expression levels of its biosynthesis genes in spikelets, with more increase under the SD than the MD. ABA content was significantly correlated with grain filling rate and sink activities under both WW and MD, while the correlations were not significant under the SD. Application of a low concentration ABA to WW plants imitated the results under the MD, and applying with a high concentration ABA showed the effect of the SD. The results suggest that ABA plays a vital role in grain filling through regulating sink activity and functions in a dose-dependent manner. An elevated ABA level under the MD enhances, whereas a too high level of ABA under the SD decreases, sink activity.

Surface Oxidation as a Cause of High Open‐Circuit Voltage in CdSe ETA Solar Cells

TiO2/CdSe/CuSCN extremely thin absorber (ETA) solar cells are found to give relatively high values of open‐circuit voltage (&gt;0.8 V) but low currents upon annealing the cadmium selenide (CdSe) in air (500 ºC). Annealing in N2 produces much lower photovoltages and slightly lower photocurrents. Band structure measurements show differences between the two annealing regimes that, however, appear to favor the N2‐annealed CdSe. On the other hand, chemically resolved electrical measurements (CREM) of the cells reveal marked differences in photo‐induced charge trapping, in particular at absorber grain boundaries of the air versus N2‐annealed systems, correlated with the formation of Cd–O species at the CdSe surface. Using transient absorption and photovoltage decay, pronounced lifetime differences are also observed, in agreement with the strong suppression of charge recombination. The results point to a multiple role of grain surface‐oxidation, which both impedes electron injection from the CdSe to the TiO2, but, much more significantly, enhances hole injection to the CuSCN via passivation of hole traps that act as efficient recombination centers.

Constitutive expression and silencing of a novel seed specific calcium dependent protein kinase gene in rice reveals its role in grain filling

Ca2+ sensor protein kinases are prevalent in most plant species including rice. They play diverse roles in plant signaling mechanism. Thirty one CDPK genes have been identified in rice and some are functionally characterized. In the present study, the newly identified rice CDPK gene OsCPK31 was functionally validated by overexpression and silencing in Taipei 309 rice cultivar. Spikelets of overexpressing plants showed hard dough stage within 15d after pollination (DAP) with rapid grain filling and early maturation. Scanning electron microscopy of endosperm during starch granule formation confirmed early grain filling. Further, seeds of overexpressing transgenic lines matured early (20–22 DAP) and the average number of maturity days reduced significantly. On the other hand, silencing lines showed more number of unfilled spikelet without any difference in maturity duration. It will be interesting to further decipher the role of OsCPK31 in biological pathways associated with distribution of photosynthetic assimilates during grain filling stage.

OsAlba1, a dehydration-responsive nuclear protein of rice (Oryza sativa L. ssp. indica), participates in stress adaptation

Alba proteins have exhibited great functional plasticity through the course of evolution and constitute a superfamily that spans across three domains of life. Earlier, we had developed the dehydration-responsive nuclear proteome of an indica rice cultivar, screening of which led to the identification of an Alba protein. Here we describe, for the first time, the complete sequence of the candidate gene OsAlba1, its genomic organization, and possible function/s in plant. Phylogenetic analysis showed its close proximity to other monocots as compared to dicot Alba proteins. Protein–DNA interaction prediction indicates a DNA-binding property for OsAlba1. Confocal microscopy showed the localization of OsAlba1–GFP fusion protein to the nucleus, and also sparsely to the cytoplasm. Water-deficit conditions triggered OsAlba1 expression suggesting its function in dehydration stress, possibly through an ABA-dependent pathway. Functional complementation of the yeast mutant ΔPop6 established that OsAlba1 also functions in oxidative stress tolerance. The preferential expression of OsAlba1 in the flag leaves implies its role in grain filling. Our findings suggest that the Alba components such as OsAlba1, especially from a plant where there is no evidence for a major chromosomal role, might play important function in stress adaptation.

QTL Mapping for Hull Thickness and Related Traits in Hybrid Rice Xieyou 9308

We conducted a quantitative trait locus (QTL) analysis of 165 rice recombinant inbred lines derived from a cross between Zhonghui 9308 (Z9308) and Xieqingzao B (XB) in Hainan and Hangzhou, China. Grain thickness (GT), brown rice thickness (BRT), hull thickness (HT) and milling quality were used for QTL mapping. HT was significantly and positively correlated with GT and BRT. Twenty-nine QTLs were detected with phenotypic effects ranging from 2.80% to 21.27%. Six QTLs, qGT3, qBRT3, qBRT4, qHT6.1, qHT8 and qHT11, were detected repeatedly across two environments. Inherited from XB, qHT6.1, qHT8 and qHT11 showed stable expression, explaining 9.92%, 21.27% and 10.83% of the phenotypic variances in Hainan and 9.61%, 6.40% and 6.71% in Hangzhou, respectively. Additionally, the QTL cluster between RM5944 and RM5626 on chromosome 3 was probably responsible for GT and milling quality. The cluster between RM6992 and RM6473 on chromosome 4 played an important role in grain filling. Three near isogenic lines (NILs), X345, X338 and X389, were selected because they contained homozygous fragments from Zhonghui 9308, corresponding to qHT6.1, qHT8 and qHT11, respectively. The hull of XB was thicker than those of X345, X338 and X389. In all the lines, qHT6.1, qHT8 and qHT11 that regulated rice HT were stably inherited with obvious genetic effects.

Investigation of structural and electrical properties of CuO modified SnO2 nanoparticles

Nanocrystalline SnO2 was prepared by the co-precipitation method and doped with CuO. Crystallite sizes were estimated by Scherrer formula to be of the order of 90nm and lesser. A.C. conduction behaviour of the samples has been described by the different hopping processes. From impedance analysis multi-relaxation processes in the samples are evident. Shrinkage of Cole–Cole plots with increase in temperature is also observed in our case which shows role of grain and grain boundary effects in the conduction mechanism with rise in temperature. Dielectric constant decreases with frequency but increases with rise in temperature which is governed by different components of polarizability (deformational and relaxational polarization). Dielectric constant increases with rise in temperature but at higher frequency range it takes constant value. Impedance analysis is used to explain the effects of grain and grain boundary on transport mechanism of undoped and CuO modified SnO2 nanoparticles.

Leakage current through the poly-crystalline HfO2: Trap densities at grains and grain boundaries

We investigate the role of grains and grain boundaries (GBs) in the electron transport through poly-crystalline HfO2 by means of conductive atomic force microscopy (CAFM) measurements and trap-assisted tunneling simulations. CAFM experiments demonstrate that the leakage current through a thin dielectric film preferentially flows via the GBs. The current I-V characteristics measured on both types of sites, grains, and GBs are successfully simulated by utilizing the multiphonon trap-assisted tunneling model, which accounts for the inelastic charge transport via the electron traps. The extracted density of electrically active traps, whose energy parameters match those of the positively charged oxygen vacancies in hafnia, is ∼3 × 1019 cm−3 at the grains, whereas a much higher value of (0.9÷2.1) × 1021 cm−3 is required to reproduce the leakage current through the GBs.