Size distribution of heavy mineral grains in some modern Nile Delta coastal sands, Egypt

This study includes determination and discussion of the texture and heavy mineral compositions of some modem Nile Delta coastal sands (river, coastal dune, beach-face, and nearshore marine) in order to delineate the process and factors that regulate the size distribution of heavy mineral grains comprising these coastal sands. Textural analysis of unseparated bulk samples indicate that the examined four types of sands differ in their mean grain sizes and degree of sorting. However, analysis of size distribution curves of 10 heavy mineral species or group of species in the four environments having the same general shape and nearly similar in that general order of arrangement. However, these curves vary both in median sizes and sorting. The size distribution of a heavy mineral in the Nile Delta coastal sands appear to depend on: (1) range of grain size fractions in each sample, (2) relative availability of heavy mineral in each size grade of the sample, (3) specific gravity of minerals comprising these sands, and (4) some other unknown factor or factors. Results of size measurement of heavy minerals indicated that increasing specific gravity is accompanied by increasing fineness of the heavy minerals. This study may be useful in search for marine placers and understanding the processes of grain-sorting on the sea beaches.

Mapping forces in a 3D elastic assembly of grains

Our understanding of the elasticity and rheology of disordered materials, such as granular piles, foams, emulsions or dense suspensions relies on improving experimental tools to characterise their behaviour at the particle scale. While 2D observations are now routinely carried out in laboratories, 3D measurements remain a challenge. In this paper, we use a simple model system, a packing of soft elastic spheres, to illustrate the capability of X-ray microtomography to characterise the internal structure and local behaviour of granular systems. Image analysis techniques can resolve grain positions, shapes and contact areas; this is used to investigate the materials microstructure and its evolution upon strain. In addition to morphological measurements, we develop a technique to quantify contact forces and estimate the internal stress tensor. As will be illustrated in this paper, this opens the door to a broad array of static and dynamical measurements in 3D disordered systems. © 2011 Elsevier Ltd. All rights reserved.

YBCO single grains seeded by 45° - 45° bridge-seeds of different lengths

Single grain, (RE)BCO bulk superconductors in large or complicated geometries are required for a variety of potential applications, such as motors and generators and magnetic shielding devices. As a result, top, multi-seeded, melt growth (TMSMG) has been investigated over the past two years in an attempt to enlarge the size of (RE)BCO single grains specifically for such applications. Of these multi-seeding techniques, so-called bridge seeding provides the best alignment of two seeds in a single grain growth process. Here we report, for the first time, the successful growth of YBCO using a special, 45{\deg} - 45{\deg}, arrangement of bridge-seeds. The superconducting properties, including trapped field, of the multi-seeded YBCO grains have been measured for different bridge lengths of the 45{\deg}- 45{\deg} bridge-seeds. The boundaries at the impinging growth front and the growth features of the top, multi-seeded surface and cross-section of the multi-seeded, samples have been analysed using optical microscopy. The results suggest that an impurity-free boundary between the two seeds of each leg of the bridge-seed can form when 45{\deg}- 45{\deg} bridge-seeds are used to enlarge the size of YBCO grains.

A comparison of 0°-0° and 45°-45° bridge-seeded, YBCO single grains

A variety of multiseeding techniques have been investigated over the past 20 yr in an attempt to enlarge bulk (RE)BCO superconducting samples fabricated by the top-seeded melt growth (TSMG) process for practical applications. Unfortunately, these studies have failed to establish whether technically useful values of trapped field can be achieved in multiseeded bulk samples. In this work specially designed, 0°-0° and 45°-45° bridge seeds of different lengths have been employed to produce improved alignment of the seeds during the TSMG process. The ability of these bridge-seeded samples to trap magnetic field, which is the key superconducting property for practical applications of bulk (RE)BCO, is compared for the samples seeded using 0°-0° and 45°-45° bridge seeds of different lengths. The grain boundaries produced by these bridge seeds are analyzed in detail, and the similarities and differences between the two bridge-seeding processes are discussed. © 2013 The American Ceramic Society.

Effect of high dietary starch levels on the growth performance, blood chemistry and body composition of gibel carp (Carassius auratus var. gibelio)

An 8-week growth trial was carried out in a semi-recirculation system to investigate the effect of high dietary starch levels on the growth performance, blood chemistry, starch utilization and body composition of gibel carp (Carassius auratus var. gibelio). Five isonitrogenous and isocarloric experimental diets were formulated to contain different starch levels (24%, 28%, 32%, 36% and 40% respectively). Triplicate groups of fish (24 fish per tank with an average body weight, of 8.5 g) were assigned to each diet. The results showed that dietary carbohydrate levels significantly affected the growth performance, hepatopancreatic lipid content, pyruvate kinase (PK) activity and whole-body lipid content. Growth performance, body crude lipid and plasma glucose concentrations showed a decreasing trend with an increase in dietary starch from 24% to 40%. Pyruvate kinase activities and hepatopancreatic lipid content showed an increasing trend with the dietary starch increasing from 24% to 32%, and then a decreasing trend with the dietary starch increasing from 32% to 40%. No significant difference in the hepatopancreatic hexokinase (HK) activity, plasma triglyceride contents, body crude protein, ash and calcium (Ca) and phosphorus (P) contents was observed between different treatments. In conclusion, higher dietary starch levels (32-40%) significantly (P < 0.05) decreased the growth of gibel carp in the present study.

Strong visible photoluminescence from amorphous silicon grains in a-SiOx:H films

Two strong luminescence bands were observed from a-SiOx:H in the spectral range of 550-900 nm at room temperature. One is a main broad peak which blueshifts with oxygen content and the other is a shoulder fixed at about 835 nm. In conjunction with TR and micro-Raman spectra, we have proposed that the main band may originate from the amorphous silicon grains embedded in SiOx network, while the shoulder might be due to some defects induced by excess-silicon in these films. (C) 1997 Elsevier Science Ltd.

Fabrication of nano-sized grains by pulsed laser surface melting

In this work, the formation and characterization of nano-sized grains on the modified surfaces of GCr15 and H13 steels have been investigated. The material was processed by pulsed laser surface melting (LSM) under different depths of de-ionized water. The microstructures and phases of the melted zones were examined by x-ray diffraction, environmental field emission scanning electron microscopy and high resolution transmission electron microscopy. The results indicate that LSM under water can successfully fabricate nano-scaled grains on the surfaces of steel, due to the rapid solidification and crystallization by heterogeneous nucleation. The elemental segregation of chromium and activated heterogeneous nucleation mechanism of austenite in liquid metal play a key role in the formation of nano-sized grains at high cooling rates. This one-step technique provides us a new way to prepare uniform nano-scaled grains, and is of great importance for further understanding the growth of nano-materials under extreme conditions.

糯小麦杂交后代的基因型鉴定及Wx基因的效应研究

糯小麦在食品加工业、淀粉加工业及其它工业上有着重要用途，是近年来许多国家小麦研究的重要课题。国外糯小麦选育尚未突破高产与糯性相结合的难点，国内目前还没有培育出高蛋白强筋型的糯小麦品种，这在一定程度上与缺乏合适的育种方法和高效、实用的糯小麦分子标记辅助育种技术有关。国内外对Wx基因效应的研究主要利用缺体－四体系、重组自交系或近等基因系，还未见有利用遗传背景相同的BC5F2代回交改良群体的报道。 糯性位点近等基因系是小麦淀粉品质育种的重要材料，而我国目前还没有一套中国栽培小麦遗传背景的糯性位点近等基因系。为了选育部分糯小麦、全糯小麦和中国栽培小麦遗传背景的糯性位点近等基因系，我们利用Wx蛋白电泳和高效实用的分子标记技术体系来鉴定糯小麦杂交后代的基因型，结果证明该体系能有效地用于糯小麦的分子标记辅助育种。以中国春糯性位点全套近等基因系为研究材料，对小麦Wx基因的6个STS标记和1个CAPS标记进行了筛选，改良PCR扩增条件以及产物检测方式后，从这些标记中筛选出3个标记，包括鉴定Wx-A1、Wx-D1位点的2个共显性STS标记和Wx-B1位点的1个显性STS标记。利用上述3个分子标记从BC5F2 代回交改良群体中筛选出了8种Wx基因型，经卡方检验，其分离比符合3对基因的分离比例，其中基因型为aabbdd的植株有2株，直链淀粉含量分别为1.81%和0.82%，为全糯小麦；基因型为AAbbdd，aabbDD的部分糯性植株各有1株，直链淀粉含量分别为15.24%和17.57%。以上4株植株的农艺性状和品质性状接近回交亲本“川育12”，并明显优于全糯材料“98Y1441”，表明采用回交法与Wx基因分子标记辅助选择相结合，有助于培育高产、优质的全糯和部分糯小麦。同时，本研究中建立的分子标记技术体系，也为选育具有中国栽培小麦遗传背景的糯性位点近等基因系奠定了基础。 在基因型鉴定的基础上，利用糯小麦杂交后代BC5F2代回交改良群体研究了各基因缺失降低直链淀粉含量的效果和各基因合成直链淀粉的能力，以及直链淀粉含量与农艺性状、品质性状、淀粉糊化特性等的相关性。缺失不同Wx基因的8种基因型，直链淀粉含量差异显著。研究单缺失基因型发现，减少效应最大的是Wx-B1b基因，Wx-B1b和Wx-D1b基因没有显著差异，减少效应最小的是Wx-A1b基因。研究双缺失基因型发现，Wx基因合成直链淀粉的能力，Wx-B1a基因最高，Wx-A1a基因最低，而Wx-B1a和Wx-D1a基因差异很小；直链淀粉含量与株高、穗长、小穗数、穗粒数、千粒重等农艺性状相关不显著，表明淀粉品质育种可以与高产育种实现有机结合；直链淀粉含量与SDS-沉降值呈显著负相关(r=-0.726)，说明直链淀粉含量降低在一定程度上有利于提高小麦营养与加工品质，这一结果至今未见有文献报道；全糯类型的淀粉糊化特性与其他类型显著不同，具有最高的峰值粘度和稀懈值，最低的低谷粘度、最终粘度、反弹值、峰值时间、糊化温度、起始糊化温度，表明糯小麦淀粉在食品和工业上具有特殊用途；稀懈值与直链淀粉含量呈极显著负相关(r=-0.969)，其他粘度参数与直链淀粉含量呈显著正相关(最终粘度r=0.797，低谷粘度r=0.910、反弹值r=0.954、峰值时间r=0.970、糊化温度r=0.962、起始糊化温度r=0.932)。以上结论可为糯小麦品种选育和淀粉品质改良提供理论依据。 Waxy wheat is very important in food processing industry, starch processing industry and the other industries, so it is a focus of wheat research in many countries these years. Foreign wheat breeders have not conquered the difficulty of high yield combined with waxy character, and there is no waxy wheat variety with high protein and strong gluten in China at present，all of which were caused by lacking proper breeding methods and effective, applied molecular markers-assisted selection technique at a certain extent. Until now, research about the effect of waxy genes mainly depended on nullisomic-tetrasomic lines, recombinant lines or near-isogenic lines, and it is lacking the reports of using improved BC5F2 backcross progenies under the common genetic background. Near-isogenic lines at the Wx loci are important materials for wheat starch quality breeding. However, there are no such lines under the Chinese cultivated wheat genetic background. To develop partial waxy wheats, waxy wheats and near-isogenic lines at the Wx loci under the Chinese cultivated wheat genetic background, we use SDS-PAGE of waxy proteins and effective, applied molecular marker-assisted selection technical system to identify the genotype of waxy wheat’s progenies. The results indicated that such a system is applicable in waxy wheat’s molecular marker-assisted selection effectively. A series of Chinese Spring Wx loci near-isogenic lines were used to identify the specific bands of six STS markers and one CAPS marker of Wx genes. After optimizing PCR amplification and separating of PCR products, three co-dominant and dominant STS-markers were identified at the Wx-A1, Wx-D1 and Wx-B1 loci, respectively, which were used to identify the genotype of waxy wheat’s progenies. Eight Wx genotypes were developed from the improved BC5F2 backcross progenies, which follows Mendelian segregation. Among them, there were two aabbdd waxy plants whose amylose content in the BC5F3 seeds were 1.81% and 0.82%, respectively. In addition, there were partial waxy plants (AAbbdd and aabbDD) whose amylose content in the BC5F3 seeds were 15.24 % and 17.57%, respectively. Most agronomic and quality traits of these four plants resembled those of the recurrent parent “Chuanyu 12”, and superior to waxy wheat parent “98Y1441”. This shows that backcross approach in combination with molecular marker-assisted selection of waxy genes is helpful to develop partial and full waxy wheat with good traits in the waxy wheat breeding program. At the same time, molecular marker-assisted selection technical system in this paper, also establish the base for breeding the near-isogenic lines at the Wx loci under the Chinese cultivated wheat genetic background. According to the results of genotype identification, we use waxy wheat’s improved BC5F2 backcross progenies to verify the effects of null alleles on reducing amylose content and determine the amylose synthesis capacity of each Wx gene independently, and investigate the relativity among amylose content with agonomic traits, quality traits, starch pasting properties respectively. There was significant difference in amylose content of the eight genotypes carrying different null Wx alleles. The reducing effect of the single null alleles was the most significant in Wx-B1b, followed by Wx-D1b and Wx-A1b, and there was no significant difference between Wx-B1b and Wx-D1b. The results of the double null lines further demonstrated that for the capacity of amylose synthesis, Wx-B1a was the highest, followed by Wx-D1a and Wx-A1a, and there was no significant difference between Wx-B1a and Wx-D1a. Amylose contents of the eight genotypes were not significantly correlated with plant height, spike length, spikelets per spike, grains per spike, 1000-grain weight, which showed that starch quality breeding could integrate with high yield breeding. Amylose contents of the eight genotypes were negatively significantly correlated with SDS-sedimentation value(r=-0.726), which suggested that reduction in amylose content is propitious to improve quality at a certain extent. Starch pasting properties of the full waxy type was significantly different from the other seven types, with the highest peak viscosity and breakdown, and lowest valley viscosity, final viscosity, setback, peak time, pasting temperature and starting pasting temperature. It indicated that waxy wheat starch has special use in food and industry. Breakdown was negatively significantly correlated with amylose contents (r=-0.969), and the other parameters were positively significantly correlated with amylose contents (r=0.797 for final viscosity, r=0.910 for trough viscosity, r =0.954 for setback, r =0.970 for peak time, r=0.962 for pasting temperature and r=0.932 for starting pasting temperature ). The results of the study are very useful for waxy wheat variety breeding and starch quality improvement.

Study on structure and molecular dynamics of starch/poly(sodium acrylate)grafted superabsorbent by C-13 solid state NMR

The domain-structure of samples containing a series of starch/poly(sodium acrylate)-grafted superabsorbents, pure starch, pure poly(sodium acrylate), and blend of starch/poly(sodium acrylate) has been studied by high-resolution solid-state C-13 NMR spectroscopy at room temperature. The result shows that the crystallinity of starch decreases greatly in the grafted and blended samples.