Microstructure and Mechanical Properties of TiC Nanoparticle-Reinforced Iron-Matrix Composites

Uniformly distributed TiC nanoparticle-reinforced iron-based composites were successfully fabricated by planetary milling in argon and subsequent hot pressing procedures. Nearly full density composite specimens could be obtained via 6-hour milling and hot pressing at 1100° C under 50 MPa. Spherical TiC particles and fine fibrous Fe₃C phases were observed to form the iron-matrix composites and subjected to comparative analysis. Microstructural analysis results show that theaverage diameter of TiC particles and the length of Fe₃C phases tend to decrease with an increase in a TiC volume content. The compression yield strength of hot-pressed composites increased in proportion to the TiC content, resulting in 1.3 GPa for 7.5% TiC. The relationship between the microstructural characteristics and the yield strength of TiC-reinforced composites was also investigated. Based on the Orowan strengthening mechanism, a higher strength is observed for a high TiC content, mainly due to reduced distance between reinforcing TiC nanoparticles.Композитные материалы на основе железа, армированные равномерно распространенными наночастицами TiC, получены с помощью планетарного фрезерования в аргоне и последующего горячего прессования. Путем измельчения в течение 6 часов и горячего прессования материала при температуре 1100° C и давлении 50 MПa оказалось возможным получить образцы композитных материалов с почти максимальной плотностью. Исследованы сферические частицы TiC и волокнистые мелкодисперсные Fe₃C фазы, которые образуют матрицу композитного материала на основе железа. Микроструктурный анализ показал, что усредненный диаметр частиц TiC и длина Fe₃C фаз уменьшаются с увеличением объемного содержания частиц TiC. Значение предела текучести при сжатии композитных материалов, полученных горячим прессованием, увеличивается пропорционально содержанию частиц TiC: 1,3 ГПа для 7,5% TiC. Исследована взаимосвязь между микроструктурными характеристиками и пределом текучести композитных материалов, армированных частицами TiC. На основе механизма упрочнения Орована можно предположить, что более высокое значение прочности имеет место при большем содержании частиц TiC, в основном вследствие сокращения расстояния между армирующими наночастицами TiC.Композитні матеріали на основі заліза, армовані рівномірно розповсюдженими нано-частинками ТіС, отримано за допомогою планетарного фрезерування в аргоні і подальшого гарячого пресування. Шляхом подрібнення протягом 6 годин і гарячого пресування матеріалу за температури 1100° C і тиску 50 МПа можна отримати зразки композитних матеріалів із майже максимальною щільністю. Досліджено сферичні частинки ТіС і волокнисті дрібнодисперсні Fe₃C фази, які сприяють виникненню матриці композитного матеріалу на основі заліза. Мікроструктурний аналіз показав, що усереднений діаметр частинок ТіС і довжина Fe₃C фаз зменшуються зі збільшенням об’ємного вмісту частинок ТіС. Значення границі текучості при стисканні композитних матеріалів, отриманих гарячим пресуванням, збільшується пропорційно вмісту ТіС частинок: 1,3 ГПа для 7,5% ТіС. Досліджено взаємозв’язок між мікроструктурними характеристиками і границею текучості композитних матеріалів, армованих частинками ТіС. На основі механізму зміцнення Орована можна припустити, що більш високі значення міцності відмічаються за більшого вмісту частинок ТіС, в основному внаслідок скорочення відстані між армуючими наночастинками ТіС

Influence of season of birth, sex and paternal line on growth performance and carcass traits in pigs

Participants in the pig production industry focus on feed and feed additives to improve growth performance and meat quality of pigs. Consequently, the Rural Development Administration of the Republic of Korea produced a new paternal line to improve economic traits in pigs. However, there is an absence of information on pig traits with regard to season and sex, and a comparison between the new paternal line and past paternal lines. Therefore, the authors conducted this study to investigate the influence of season of birth, sex and paternal line on growth performance and carcass traits in pigs. A total of 2888 piglets ((Landrace × Yorkshire) × Darby Duroc (DD) or Chookjin Duroc (CD)) with an average age of three weeks were tested for 22 weeks during the four season of the year (spring 608 piglets, summer 404 piglets, autumn 576 piglets and winter 1300 piglets). The bodyweights (BW) of individual pig were recorded, and feed consumption was recorded at weeks 2, 12 and 22, to determine growth performance. At reaching market weight, backfat thickness was determined at the last rib area. Meat was graded according to the criteria of the slaughterhouse. There were no significant differences in growth performance and carcass traits between sexes. The CD line crossbred pig had a significant higher BW at 16 weeks, and higher carcass trait values at 22 weeks than the DD line. During weeks 8 to 16 the CD line crossbred pigs showed a tendency of an increased average daily gain (ADG) and gain : feed (G : F) ratio compared with the DD line. Furthermore, pigs born in spring had significant lower ADG, average daily feed intake (ADFI) and carcass trait values than born in the other seasons. In conclusion, the new paternal line (Chookjin Duroc) improved growth performance and carcass traits compare with the DD line.Keywords: sex, growth, terminal sire, meat quality, backfat thicknes

The influence of ionic strength on the adhesive bond stiffness of oral streptococci possessing different surface appendages as probed using AFM and QCM-D

Bacterial adhesion to surfaces poses threats to human-health, not always associated with adhering organisms, but often with their detachment causing contamination elsewhere. Bacterial adhesion mechanisms may not be valid for their detachment, known to proceed according to a visco-elastic mechanism. Here we aimed to investigate influences of ionic strength on the adhesive bond stiffness of two spherically shaped Streptococcus salivarius strains with different lengths of fibrillar surface appendages. The response of a Quartz-Crystal-Microbalance-with-Dissipation (QCM-D) upon streptococcal adhesion and changes in the ionic strength of the surrounding fluid indicated that the bond stiffness of S. salivarius HB7, possessing a dense layer of 91 nm long fibrils, was unaffected by ionic strength. Atomic-force-microscopic (AFM) imaging in PeakForce-QNM mode showed a small decrease in bond stiffness from 1200 to 880 kPa upon decreasing ionic strength from 57 to 5.7 mM, while Total-Internal-Reflection-Microscopy suggested a complete collapse of fibrils. S. salivarius HBV51, possessing a less dense layer of shorter (63 nm) fibrils, demonstrated a strong decrease in bond stiffness both from QCM-D and AFM upon decreasing the ionic strength, and a partial collapse of fibrils. Probably, the more hydrophobic and less negatively charged long fibrils on S. salivarius HB7 collapse side-on to the cell surface, while the more hydrophilic and negatively charged fibrils of S. salivarius HBV51 remain partially stretched. In summary, we demonstrate how a combination of different methods can yield a description of the structural changes occurring in the interfacial region between adhering, fibrillated streptococci and a substratum surface upon changing the ionic strengt

Parameterization and Reconstruction of Quasi Static Universe

We study a possibility of the fate of universe, in which there is neither the rip singularity, which results in the disintegration of bound systems, nor the endless expansion, instead the universe will be quasi static. We discuss the parameterization of the corresponding evolution and the reconstruction of the scalar field model. We find, with the parameterization consistent with the current observation, that the current universe might arrive at a quasi static phase after less than 20Gyr.Comment: minor changes and Refs. added, publish in EPJ

A New Upper Limit for the Tau-Neutrino Magnetic Moment

Using a prompt neutrino beam in which a nu_tau component was identified for the first time, the nu_tau magnetic moment was measured based on a search for an anomalous increase in the number of neutrino-electron interactions. One such event was observed when 2.3 were expected from background processes, giving an upper 90% confidence limit of 3.9x10^-7 Bohr magnetons.Comment: 9 pages; 1 figur

A Note on Inflation with Tachyon Rolling on the Gauss-Bonnet Brane

In this paper we study the tachyonic inflation in brane world cosmology with Gauss-Bonnet term in the bulk. We obtain the exact solution of slow roll equations in case of exponential potential. We attempt to implement the proposal of Lidsey and Nunes, astro-ph/0303168, for the tachyon condensate rolling on the Gauss-Bonnet brane and discuss the difficulties associated with the proposal.Comment: RevTex4, 5 pages, no figures, Minor clarifications added and references updated, To appear in PR

Physical Characterization of an Unlensed, Dusty Star-forming Galaxy at z = 5.85

We present a physical characterization of MM J100026.36+021527.9 (a.k.a. "Mambo-9"), a dusty star-forming galaxy (DSFG) at z = 5.850 \ub1 0.001. This is the highest-redshift unlensed DSFG (and fourth most distant overall) found to date and is the first source identified in a new 2 mm blank-field map in the COSMOS field. Though identified in prior samples of DSFGs at 850 \u3bcm to 1.2 mm with unknown redshift, the detection at 2 mm prompted further follow-up as it indicated a much higher probability that the source was likely to sit at z > 4. Deep observations from the Atacama Large Millimeter and submillimeter Array (ALMA) presented here confirm the redshift through the secure detection of 12CO(J = 6\u21925) and p-H2O (21,1 \u2192 20,2). Mambo-9 is composed of a pair of galaxies separated by 6 kpc with corresponding star formation rates of 590 M o\u2d9 yr-1 and 220 M o\u2d9 yr-1, total molecular hydrogen gas mass of (1.7 \ub1 0.4) 7 1011 M o\u2d9, dust mass of (1.3 \ub1 0.3) 7 109 M o\u2d9, and stellar mass of (3.2-1.5+1.0) 7 109 M o\u2d9. The total halo mass, (3.3 \ub1 0.8) 7 1012 M o\u2d9, is predicted to exceed 1015 M o\u2d9 by z = 0. The system is undergoing a merger-driven starburst that will increase the stellar mass of the system tenfold in \u3c4 depl = 40-80 Myr, converting its large molecular gas reservoir (gas fraction of 96-2+1) into stars. Mambo-9 evaded firm spectroscopic identification for a decade, following a pattern that has emerged for some of the highest-redshift DSFGs found. And yet, the systematic identification of unlensed DSFGs like Mambo-9 is key to measuring the global contribution of obscured star formation to the star formation rate density at z \u2a86 4, the formation of the first massive galaxies, and the formation of interstellar dust at early times ( 721 Gyr)

Transverse Beam Spin Asymmetries in Forward-Angle Elastic Electron-Proton Scattering

We have measured the beam-normal single-spin asymmetry in elastic scattering of transversely-polarized 3 GeV electrons from unpolarized protons at Q^2 = 0.15, 0.25 (GeV/c)^2. The results are inconsistent with calculations solely using the elastic nucleon intermediate state, and generally agree with calculations with significant inelastic hadronic intermediate state contributions. A_n provides a direct probe of the imaginary component of the 2-gamma exchange amplitude, the complete description of which is important in the interpretation of data from precision electron-scattering experiments.Comment: 5 pages, 3 figures, submitted to Physical Review Letters; shortened to meet PRL length limit, clarified some text after referee's comment