Magnetic anisotropy of YbNi4P2

We report on transport and magnetic measurements between 1.8 and 400 K on single crystalline YbNi4P2, which was recently reported to be a heavy fermion system with a low lying ferromagnetic transition at T_C=0.17 K, based on data from polycrystals. The tetragonal crystal structure of YbNi4P2 presents quasi-one-dimensional Yb chains along the c direction. Here we show that at high temperatures, the magnetic anisotropy of YbNi4P2 is dominated by the crystal electrical field effect with an Ising-type behaviour, which gets more pronounced towards lower temperatures. The electrical resistivity also reflects the strong anisotropy of the crystal structure and favours transport along c, the direction of the Yb chains.Comment: SCES 2011 proceedings, in pres

Characterization of Marble-Clay Composite as Alternative To Conventional Bricks in Building

The usability of marble as an additive material with clay in industrial brick has been investigated. Marble was collected from the marble deposit located at Igbeti (latitude 80 451 longitude 40 81 E.), and the red clay was collected at University of Ilorin, Ilorin (latitude 80 321 N and longitude 40 341 E), both in Nigeria. Marble and Clay were processed for the preparation of the composite. The two materials were mixed in varying proportion of marble, ranging from 0 wt. % to 45 %. The mixture was made into bricks with size 6.0 x 7.0 x 2.0 cm. Ten sample bricks of different marble composition were prepared. These bricks were compressed and heated at a temperature of 950 0C for 2 hours. Water absorption and thermal conductivity tests were carried out on the samples. It was observed that the amount of marble added had positive effect on the physical and mechanical strength of the produced brick. The results also show that increase in percentage of marble will be of good advantage in keeping the house warm during raining season as observed from the thermal conductivity test.Keywords: Marble, Clay, Physico-mechanical, Thermal conductivity, Water Absorptio

Internal conversion with 4-(azetidinyl)benzonitriles in alkane solvents. Influence of fluoro substitution

The introduction of a fluoro-substituent in the phenyl ring of 4-(1-azetidinyl)benzonitrile (P4C) leads to smaller fluorescence quantum yields Phi (f) and shorter decay times tau in alkane solvents (cyclopentane, n-hexadecane, n-hexane and 2-methylpentane). In cyclopentane at 25 degreesC, Phi (f) and tau equal 0.02 and 0.14 ns for 2-fluoro-4-(1-azetidinyl)benzonitrile (P4CF2) and 0.11 and 0.85 ns for 3-fluoro-4-(1-azetidinyl)benzonitrile (P4CF3), as compared with 0.27 and 4.55 ns for P4C. The fluorescence originates from a locally excited (LE) state and dual fluorescence due to intramolecular charge transfer is not observed for the three aminobenzonitriles at any temperature in the alkane solvents. By measuring the yields of intersystem crossing Phi (ISC), it follows that this enhancement of the radiationless deactivation of the first excited singlet state S-1 is due to thermally activated internal conversion (IC). The IC yield Phi (IC) in cyclopentane at 25 degreesC, as an example, is considerably larger for P4CF2 (0.93) than for P4CF3 (0.35) and of minor importance for P4C (0.03). The IC activation energies E-IC of P4CF2 (12.6 kJ mol(-1)), P4CF3 (19.3 kJ mol(-1)) and P4C (38.1 kJ mol(-1)) in cyclopentane were determined by fitting tau measured as a function of temperature, together with data for Phi (f) and Phi (ISC). Similar E-IC values were obtained in n-hexane and n-hexadecane. These data show that the increase in IC efficiency from P4C via P4CF3 to P4CF2 is caused by a decrease in E-IC. The radiative rate constants k(f) in cyclopentane of P4CF2 and P4CF3 are about twice that of P4C, probably due to the mixing of the S-2(L-1(a),CT) and S-1(L-1(b)) states of P4C caused by the molecular asymmetry introduced by the F-substituents. It is assumed that the lowering of the IC barriers in P4CF2 and P4CF3 is governed by an F-substituent-dependent difference in the energies of the molecular configuration of the azetidinylbenzonitriles that can be reached in S-1 as compared with those in S-0

Type Ia Supernova Explosion Models

Because calibrated light curves of Type Ia supernovae have become a major tool to determine the local expansion rate of the Universe and also its geometrical structure, considerable attention has been given to models of these events over the past couple of years. There are good reasons to believe that perhaps most Type Ia supernovae are the explosions of white dwarfs that have approached the Chandrasekhar mass, M_ch ~ 1.39 M_sun, and are disrupted by thermonuclear fusion of carbon and oxygen. However, the mechanism whereby such accreting carbon-oxygen white dwarfs explode continues to be uncertain. Recent progress in modeling Type Ia supernovae as well as several of the still open questions are addressed in this review. Although the main emphasis will be on studies of the explosion mechanism itself and on the related physical processes, including the physics of turbulent nuclear combustion in degenerate stars, we also discuss observational constraints.Comment: 38 pages, 4 figures, Annual Review of Astronomy and Astrophysics, in pres

Graphene plasmonics

Two rich and vibrant fields of investigation, graphene physics and plasmonics, strongly overlap. Not only does graphene possess intrinsic plasmons that are tunable and adjustable, but a combination of graphene with noble-metal nanostructures promises a variety of exciting applications for conventional plasmonics. The versatility of graphene means that graphene-based plasmonics may enable the manufacture of novel optical devices working in different frequency ranges, from terahertz to the visible, with extremely high speed, low driving voltage, low power consumption and compact sizes. Here we review the field emerging at the intersection of graphene physics and plasmonics.Comment: Review article; 12 pages, 6 figures, 99 references (final version available only at publisher's web site

Thermal Properties of Carbon Nanotube–Copper Composites for Thermal Management Applications

Carbon nanotube–copper (CNT/Cu) composites have been successfully synthesized by means of a novel particles-compositing process followed by spark plasma sintering (SPS) technique. The thermal conductivity of the composites was measured by a laser flash technique and theoretical analyzed using an effective medium approach. The experimental results showed that the thermal conductivity unusually decreased after the incorporation of CNTs. Theoretical analyses revealed that the interfacial thermal resistance between the CNTs and the Cu matrix plays a crucial role in determining the thermal conductivity of bulk composites, and only small interfacial thermal resistance can induce a significant degradation in thermal conductivity for CNT/Cu composites. The influence of sintering condition on the thermal conductivity depended on the combined effects of multiple factors, i.e. porosity, CNTs distribution and CNT kinks or twists. The composites sintered at 600°C for 5 min under 50 MPa showed the maximum thermal conductivity. CNT/Cu composites are considered to be a promising material for thermal management applications

The Effects of Seed Size on Hybrids Formed between Oilseed Rape (Brassica napus) and Wild Brown Mustard (B. juncea)

Background : Seed size has significant implications in ecology, because of its effects on plant fitness. The hybrid seeds that result from crosses between crops and their wild relatives are often small, and the consequences of this have been poorly investigated. Here we report on plant performance of hybrid and its parental transgenic oilseed rape (Brassica napus) and wild B. juncea, all grown from seeds sorted into three seed-size categories.[br/] Methodology/Principal Findings : Three seed-size categories were sorted by seed diameter for transgenic B. napus, wild B. juncea and their transgenic and non-transgenic hybrids. The seeds were sown in a field at various plant densities. Globally, small-seeded plants had delayed flowering, lower biomass, fewer flowers and seeds, and a lower thousand-seed weight. The seed-size effect varied among plant types but was not affected by plant density. There was no negative effect of seed size in hybrids, but it was correlated with reduced growth for both parents.[br/] Conclusions : Our results imply that the risk of further gene flow would probably not be mitigated by the small size of transgenic hybrid seeds. No fitness cost was detected to be associated with the Bt-transgene in this study

Breeding histories and selection criteria for oilseed rape in Europe and China identified by genome wide pedigree dissection

Selection breeding has played a key role in the improvement of seed yield and quality in oilseed rape (Brassica napus L.). We genotyped Tapidor (European), Ningyou7 (Chinese) and their progenitors with the Brassica 60 K Illumina Infinium SNP array and mapped a total of 29,347 SNP markers onto the reference genome of Darmor-bzh. Identity by descent (IBD) refers to a haplotype segment of a chromosome inherited from a shared common ancestor. IBDs identified on the C subgenome were larger than those on the A subgenome within both the Tapidor and Ningyou7 pedigrees. IBD number and length were greater in the Ningyou7 pedigree than in the Tapidor pedigree. Seventy nine QTLs for flowering time, seed quality and root morphology traits were identified in the IBDs of Tapidor and Ningyou7. Many more candidate genes had been selected within the Ningyou7 pedigree than within the Tapidor pedigree. These results highlight differences in the transfer of favorable gene clusters controlling key traits during selection breeding in Europe and China