Comparison of physicochemical properties of soils under contrasting land use systems in Southwestern Nigeria

Soil physicochemical properties were determined for soils under cropland and forest at the headquarters of the International Institute of Tropical Agriculture in Ibadan, Southwestern Nigeria to examine the 30-year effects of different land use on the fertility of five soil series toposequences underlain by a Basement Complex. The cropland had been under cultivation for 30 years, during which mainly maize and yams had been cultivated in rotation with application of chemical fertilizer and intermittent fallow, while the forest had secondary vegetation that had been regenerated during a 30-year period under protection. The findings for cropland indicated an accumulation of available phosphorus and exchangeable potassium, soil compaction and slight depletion of topsoil organic carbon content; and the findings for forest indicated soil acidification and accumulation of exchangeable Ca at the surface soil horizon. These findings suggest the possibility of maintaining soil fertility with a long-term intensive and continuous crop farming system in kaolinitic Alfisol soil over the inland valley toposequences of tropical Africa

Role of dipolar interactions in a system of Ni nanoparticles studied by magnetic susceptibility measurements

The role of dipolar interactions among Ni nanoparticles (NP) embedded in an amorphous SiO2/C matrix with different concentrations has been studied performing ac magnetic susceptibility Chi_ac measurements. For very diluted samples, with Ni concentrations < 4 wt % Ni or very weak dipolar interactions, the data are well described by the Neel-Arrhenius law. Increasing Ni concentration to values up to 12.8 wt % Ni results in changes in the Neel-Arrhenius behavior, the dipolar interactions become important, and need to be considered to describe the magnetic response of the NPs system. We have found no evidence of a spin-glasslike behavior in our Ni NP systems even when dipolar interactions are clearly present.Comment: 7 pages, 5 figures, 3 table

Increase in the magnitude of the energy barrier distribution in Ni nanoparticles due to dipolar interactions

The energy barrier distribution Eb of five samples with different concentrations x of Ni nanoparticles using scaling plots from ac magnetic susceptibility data has been determined. The scaling of the imaginary part of the susceptibility Chi"(nu, T) vs. Tln(t/tau_0) remains valid for all samples, which display Ni nanoparticles with similar shape and size. The mean value increases appreciably with increasing x, or more appropriately with increasing dipolar interactions between Ni nanoparticles. We argue that such an increase in constitutes a powerful tool for quality control in magnetic recording media technology where the dipolar interaction plays an important role.Comment: 3 pages, 3 figures, 1 tabl

From Molecular Cores to Planet-forming Disks with SIRTF

The SIRTF mission and the Legacy programs will provide coherent data bases for extra-galactic and Galactic science that will rapidly become available to researchers through a public archive. The capabilities of SIRTF and the six legacy programs are described briefly. Then the cores to disks (c2d) program is described in more detail. The c2d program will use all three SIRTF instruments (IRAC, MIPS, and IRS) to observe sources from molecular cores to protoplanetary disks, with a wide range of cloud masses, stellar masses, and star-forming environments. The SIRTF data will stimulate many follow-up studies, both with SIRTF and with other instruments.Comment: 6 pages, from Fourth Cologne-Bonn-Zermatt-Symposium, The Dense Interstellar Matter in Galaxie

Protostellar Jet and Outflow in the Collapsing Cloud Core

We investigate the driving mechanism of outflows and jets in star formation process using resistive MHD nested grid simulations. We found two distinct flows in the collapsing cloud core: Low-velocity outflows (sim 5 km/s) with a wide opening angle, driven from the first adiabatic core, and high-velocity jets (sim 50 km/s) with good collimation, driven from the protostar. High-velocity jets are enclosed by low-velocity outflow. The difference in the degree of collimation between the two flows is caused by the strength of the magnetic field and configuration of the magnetic field lines. The magnetic field around an adiabatic core is strong and has an hourglass configuration. Therefore, the low-velocity outflow from the adiabatic core are driven mainly by the magnetocentrifugal mechanism and guided by the hourglass-like field lines. In contrast, the magnetic field around the protostar is weak and has a straight configuration owing to Ohmic dissipation in the high-density gas region. Therefore, high-velocity jet from the protostar are driven mainly by the magnetic pressure gradient force and guided by straight field lines. Differing depth of the gravitational potential between the adiabatic core and the protostar cause the difference of the flow speed. Low-velocity outflows correspond to the observed molecular outflows, while high-velocity jets correspond to the observed optical jets. We suggest that the protostellar outflow and the jet are driven by different cores (the first adiabatic core and protostar), rather than that the outflow being entrained by the jet.Comment: To appear in the proceedings of the "Protostellar Jets in Context" conference held on the island of Rhodes, Greece (7-12 July 2008

Tumour enhancement with newly developed Mn-metalloporphyrin (HOP-9P) in magnetic resonance imaging of mice

The purpose of the study is to evaluate the tumour enhancing characteristics and biodistribution of a newly developed metalloporphyrin derivative, HOP-9P (13, 17-bis (1-carboxypropionyl) carbamoylethyl-3, 8-bis (1-phenylpropyloxyethyl)-2,7,12,18-tetra- methyl-porphynato manganese (III)). Seven mice bearing SCC VII tumours were imaged using T1-weighted conventional spin echo magnetic resonance images before and 5 min, 2 h and 24 h after intravenous injection of 0.1 mmol/kg of HOP-9P. For the acquired images, signal intensities of the tumour, muscle and oil-phantom were measured. Then, tumor/oil and tumor/muscle signal intensity ratios were calculated. Nineteen mice were sacrificed before or after the administration of HOP-9P (at 5 min, 2 h and 24 h), and the biodistribution of manganese in the tumour, muscle, liver, blood and kidneys was measured using optical emission spectrometers and was expressed as micrograms of manganese per gram of tissue. The tumour/muscle signal intensity ratio at 24 h (3.18 ± 0.34) was significantly higher than precontrast ratio (1.77 ± 0.20) (P < 0.05). The biodistribution assessment of manganese demonstrated that HOP-9P gradually and consistently accumulated in the tumour to reach the highest concentration at 24 h (3.49 ± 1.22 μ gMn/g). It is concluded that HOP-9P is a potential tumour-specific MR contrast agent. © 2001 Cancer Research Campaign http://www.bjcancer.co

Effect of draw ratio on fiber structure development of polyethylene terephthalate

Fiber properties are decided by its structure, and the structure are mainly formed in the fiber drawing process. In this study, the effects of the draw ratio on the fiber structure development of polyethylene terephthalate after continuous neck-drawing were investigated using simultaneous WAXD/SAXS measurements. Low-oriented amorphous as-spun fibers were drawn to a draw ratio of 3.0-4.5, at which the fiber can be stably neck drawn. WAXD and SAXS images were obtained up to 2.0 ms when the structure was mainly developed. The smectic (0010) diffraction intensity and long period increased with increasing draw ratio up to 4.2, and a larger (0010) diffraction d-spacing was observed at a draw ratio of 4.5. The results suggest that more fibrillar structures were formed with increasing draw ratio up to 4.2, and more constrained molecular bundles were formed at a draw ratio of 4.5. A larger amount of constrained fibrillar structures can bear a greater tensile force in tensile tests, therefore the drawn fibers have higher tensile strengths. (C) 2017 Elsevier Ltd. All rights reserved.ArticlePOLYMER.116:357-366(2017)journal articl

Effect of melt spinning conditions on the fiber structure development of polyethylene terephthalate

The effects of spinning conditions on fiber properties are not well explained by the fiber structures because the birefringence, crystallinity, and SAXS patterns are often similar. In this study, the effects on the fiber structure development of polyethylene terephthalate after necking was analyzed by simultaneous WAXD/SAXS measurements. An X-shaped SAXS pattern was observed for all fibers drawn at the minimum draw ratio. In contrast, by drawing under a drawing stress of 100 MPa, the strong diffraction of the smectic phase and an obviously larger long period less than 1 ms after necking were observed for fibers spun at 500-1500 m/min, while almost no smectic phase was observed for fibers spun at 2000 m/min. A higher crystallization rate and clear draw ratio dependence of crystallization rate were also observed for the fiber spun at 2000 m/min. The clear differences in structure development can explain their differences in tensile strength and thermal shrinkage. (C) 2017 Elsevier Ltd. All rights reserved.ArticlePOLYMER.116:367-377(2017)journal articl