2,580 research outputs found
Multiferroic properties of an \aa kermanite SrCoSiO single crystal in high magnetic fields
The magnetic and dielectric properties of \aa kermanite SrCoSiO
single crystals in high magnetic fields were investigated. We have observed
finite induced electric polarization along the c axis in high fields, wherein
all Co spins were forcibly aligned to the magnetic field direction. Existence
of the induced polarization in the spin-polarized state accompanied with the
finite slope in the magnetization curve suggests the possible role of the
orbital angular momenta in the excited states as its microscopic origin. The
emergence of the field-induced polarization without particular magnetic order
can be regarded as the magnetoelectric effects of the second order from the
symmetry point of view. A low magnetic field-driven electric polarization flip
induced by a rotating field, even at room temperature, has been successfully
demonstrated.Comment: 12 pages, 4 figure
Five-dimensional Monopole Equation with Hedge-Hog Ansatz and Abel's Differential Equation
We review the generalized monopole in the five-dimensional Euclidean space. A
numerical solution with the Hedge-Hog ansatz is studied. The Bogomol'nyi
equation becomes a second order autonomous non-linear differential equation.
The equation can be translated into the Abel's differential equation of the
second kind and is an algebraic differential equation.Comment: 4 pages, 4 figures, typos correcte
Scale Invariance in a Perturbed Einstein-de Sitter Cosmology
This paper seeks to check the validity of the "apparent fractal conjecture"
(Ribeiro 2001ab: gr-qc/9909093, astro-ph/0104181), which states that the
observed power-law behaviour for the average density of large-scale
distribution of galaxies arises when some observational quantities, selected by
their relevance in average density profile determination, are calculated along
the past light cone. Implementing these conditions in the proposed set of
observational relations profoundly changes the behaviour of many observables in
the standard cosmological models. In particular, the average density becomes
observationally inhomogeneous, even in the spatially homogeneous spacetime of
standard cosmology, change which was already analysed by Ribeiro (1992b, 1993,
1994, 1995: astro-ph/9910145) for a non-perturbed model. Here we derive
observational relations in a perturbed Einstein-de Sitter cosmology by means of
the perturbation scheme proposed by Abdalla and Mohayaee (1999:
astro-ph/9810146), where the scale factor is expanded in power series to yield
perturbative terms. The differential equations derived in this perturbative
context, and other observables necessary in our analysis, are solved
numerically. The results show that our perturbed Einstein-de Sitter cosmology
can be approximately described by a decaying power-law like average density
profile, meaning that the dust distribution of this cosmology has a scaling
behaviour compatible with the power-law profile of the density-distance
correlation observed in the galaxy catalogues. These results show that, in the
context of this work, the apparent fractal conjecture is correct.Comment: 18 pages, 1 figure, LaTeX. Final version (small changes in the figure
plus some references update). Fortran code included with the LaTeX source. To
be published in "Fractals
Use of rapid diagnostic tests in malaria school surveys in Kenya: does their under-performance matter for planning malaria control?
Malaria rapid diagnostic tests (RDTs) are known to yield false-positive results, and their use in epidemiologic surveys will overestimate infection prevalence and potentially hinder efficient targeting of interventions. To examine the consequences of using RDTs in school surveys, we compared three RDT brands used during a nationwide school survey in Kenya with expert microscopy and investigated the cost implications of using alternative diagnostic approaches in identifying localities with differing levels of infection. Overall, RDT sensitivity was 96.1% and specificity was 70.8%. In terms of classifying districts and schools according to prevalence categories, RDTs were most reliable for the 40% categories and least reliable in the 1-4.9% category. In low-prevalence settings, microscopy was the most expensive approach, and RDT results corrected by either microscopy or polymerase chain reaction were the cheapest. Use of polymerase chain reaction-corrected RDT results is recommended in school malaria surveys, especially in settings with low-to-moderate malaria transmission
Soil structural degradation and nutrient limitations across land use categories and climatic zones in Southern Africa
Although soil degradation is a major threat to food security and carbon sequestration, our knowledge of the spatial extent of the problem and its drivers is very limited in Southern Africa. Therefore, this study aimed to quantify the risk of soil structural degradation and determine the variation in soil stoichiometry and nutrient limitations with land use categories (LUCs) and climatic zones. Using data on soil clay, silt, organic carbon (SOC), total nitrogen (N), available phosphorus (P), and sulfur (S) concentrations collected from 4,468 plots on 29 sites across Angola, Botswana, Malawi, Mozambique, Zambia and Zimbabwe, this study presents novel insights into the variations in soil structural degradation and nutrient limitations. The analysis revealed strikingly consistent stoichiometric coupling of total N, P, and S concentrations with SOC across LUCs. The only exception was on crop land where available P was decoupled from SOC. Across sample plots, the probability (φ) of severe soil structural degradation was 0.52. The probability of SOC concentrations falling below the critical value of 1.5% was 0.49. The probabilities of soil total N, available P, and S concentrations falling below their critical values were 0.95, 0.70, and 0.83, respectively. N limitation occurred with greater probability in woodland (φ = .99) and forestland (φ = .97) than in cropland (φ = .92) and grassland (φ = .90) soils. It is concluded that soil structural degradation, low SOC concentrations, and N and S limitations are widespread across Southern Africa. Therefore, significant changes in policies and practices in land management are needed to reverse the rate of soil structural degradation and increase soil carbon storage
Randomised control trial on immediate post-operative outcomes on patients done either closure or non-closure of peritoneum at caesarean delivery at the Kenyatta national hospital
Objectives: To assess effects of non-closure as compared to closure of the peritoneum at caesarean delivery on the intra-operative and early post-operative outcomes.Design: Randomised controlled trial.Setting: Kenyatta National Hospital (KNH), Nairobi, Kenya.Subjects: One hundred and thirty (130) women undergoing first elective or emergency caesarean delivery.Main outcome measure: Primary outcome measures were operation time, number of sutures used, post-operative pain, febrile morbidity, wound dehiscence and hospital stay.Results: The mean duration of Caesarean Section (CS) was 42.8 minutes ± SD12.5. The closure group took longer than non-closure group (45.7±15Vs. 39.6 ±8, P<0.05). The number of sutures used was on average were 4.7 ± SD 0.8, the closure group more compared with the non-closure group (5.2 ±0.7 Vs. 4.2 ±0.7, p<0.05). Post-operative pain was generally not a problem to the patients with a mean Visual analogue score of 1.4 ± SD 1.0 on a scale of 0-10. The non-closure group however indicated slightly more pain (1.5± SD0.93) compared with the closure group (1.2 ±1.1), but this difference was not significant. The adverse outcomes like febrile morbidity and wound complications at Caesarean section were rare and not different whether peritoneum was closed or not during Caesarean section.Conclusion: Non-closure of peritoneum during CS took less time (42.8± SD 8) and number of sutures used (4.2±0.7) can result in cost savings. There were no statistically significant differences in post-operative pain scores, febrile morbidity, wound complications and length of hospital stay. Obstetricians and Medical institutions should consider adoption of non-closure of peritoneum at Caesarean delivery as part of the standard operating procedures
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