True polar wander driven by late-stage volcanism and the distribution of paleopolar deposits on Mars

The areal centroids of the youngest polar deposits on Mars are offset from those of adjacent paleopolar deposits by 5-10 degrees. We test the hypothesis that the offset is the result of true polar wander (TPW), the motion of the solid surface with respect to the spin axis, caused by a mass redistribution within or on the surface of Mars. In particular, we consider TPW driven by late-stage volcanism during the late Hesperian to Amazonian. There is observational and qualitative support for this hypothesis: in both North and South, observed offsets lie close to a great circle 90 degrees from Tharsis, as expected for polar wander after Tharsis formed. We calculate the magnitude and direction of TPW produced by mapped late-stage lavas for a range of lithospheric thicknesses, lava thicknesses, eruption histories, and prior polar wander events. If Tharsis formed close to the equator, the stabilizing effect of a fossil rotational bulge located close to the equator leads to predicted TPW of <2 degrees, too small to account for observed offsets. If, however, Tharsis formed far from the equator, late-stage TPW driven by low-latitude, late-stage volcanism would be 6-33 degrees, similar to that inferred from the location of paleopolar deposits. 4.4+/-1.3x10^19 kg of young erupted lava can account for the offset of the Dorsa Argentea Formation from the present-day south rotation pole. This mass is consistent with prior mapping-based estimates and would imply a mass release of CO2 by volcanic degassing similar to that in the atmosphere at the present time. The South Polar Layered Deposits are offset from the spin axis in the opposite sense to the other paleopolar deposits. This can be explained by an additional contribution from a plume beneath Elysium. We conclude with a list of observational tests of the TPW hypothesis.Comment: Accepted by Earth and Planetary Science Letters. 3 tables, 8 figure

Formation of Box Canyon, Idaho, by megaflood: implications for seepage erosion on Earth and Mars

Amphitheater- headed canyons have been used as diagnostic indicators of erosion by groundwater seepage, which has important implications for landscape evolution on Earth and astrobiology on Mars. Of perhaps any canyon studied, Box Canyon, Idaho, most strongly meets the proposed morphologic criteria for groundwater sapping because it is incised into a basaltic plain with no drainage network upstream, and approximately 10 cubic meters per second of seepage emanates from its vertical headwall. However, sediment transport constraints, ^4He and ^14C dates, plunge pools, and scoured rock indicate that a megaflood (greater than 220 cubic meters per second) carved the canyon about 45,000 years ago. These results add to a growing recognition of Quaternary catastrophic flooding in the American northwest, and may imply that similar features on Mars also formed by floods rather than seepage erosion

Cascading parallel fractures on Enceladus

Active eruptions from the south polar region of Saturn's small (~500 km diameter) moon Enceladus are concentrated along a series of lineaments known as the `tiger stripes', thought to be partially open fissures that connect to the liquid water ocean beneath the ice shell. Whereas aspects of the tiger stripes have been addressed in previous work, no study to date simultaneously explains why they should be located only at the south pole, why there are multiple approximately parallel and regularly spaced fractures, and what accounts for their spacing of ~35 km. Here we propose that secular cooling and the resulting ice shell thickening and global tensile stresses cause the first fracture to form at one of the poles, where the ice shell is thinnest due to tidal heating. The tensile stresses are thereby partially relieved, preventing a similar failure at the opposite pole. We propose that subsequent activity then concentrates in the vicinity of the first fracture as the steadily erupted water ice loads the flanks of the open fissure, causing bending in the surrounding elastic plate and further tensile failure in bands parallel to the first fracture, leading to a cascading sequence of parallel fissures until the conditions no longer permit through-going fractures.Comment: 18 pages, 9 figure

Sensitivity Analysis of a Mathematical Modeling of Ebola Virus Population Dynamics in the Presence of Vaccine

The virus (Ebola virus) (EBV) belongs to the Filoviri-dae family which is a filovirus and is a serious disease which&nbsp; leads to hemorrhagic disease in human and non human such as chimpanzee, gorilla, porcupine, fruit bats etc. In&nbsp; this paper, a mathematical modeling for the population dynamics of EBV diseases in the presence of vaccination&nbsp; was developed. The research shows that, using the human control reproduction number ( Rc )as response and&nbsp; infectious individual as response function, that the sensitive parameters in the formulated system (1) are the&nbsp; personal hygiene (ε ), humans to human contact rate ( β1 ), modification parameter (η ), human vaccination rate ( ρ ), proper burial (φ ) and humans natural mortality rate (μh ). The study shows that personal hygiene rate, effective&nbsp; contact rate of humans, natural mortality of humans’ rate, vaccination rate and proper burial rate are very sensitive&nbsp; to both reproduction number and infectious humans.&nbsp

Optimal control of mathematical modelling for Ebola virus population dynamics in the presence of vaccination

Ebola virus is a severe often fatal illness in human, which is known to be very dangerous and highly infectious disease that seized many lives in west African countries. In this paper, a mathematical model for the population dynamics of Ebola virus diseases incorporating bats compartment, recovery due to immune response and vaccination was constructed. Pontryagin’s maximum principle has been applied on the model to determine the necessary conditions for the optimal control of the Ebola virus in the presence of vaccination and fruit bats population, the optimality of most of the controls have been analyzed to use a small resources available in other to maximize the performance of the controls. The numerical simulation shows that with small resources if 0.1 percent of the people in a society can be vaccinated daily, Ebola can be mitigated in the environment

Le paludisme urbain à Yaoundé, Cameroun : 1. Etude entomologique dans deux quartiers centraux

Une étude entomologique longitudinale sur les moustiques agressifs pour l'homme et la transmission du paludisme a été réalisée dans deux quartiers centraux de la ville de Yaoundé (Cameroun) d'avril 1989 à mars 1990. Le quartier Essos borde un bas-fond marécageux. Le quartier Obili est comparable à Essos, mais il y a beaucoup de bassins de pisciculture mal entretenus et couverts de végétation aquatique. Les moustiques furent échantillonnés de nuit, dans les maisons, sur appât humain, deux fois par mois dans chaque quartier. A Essos, un habitant reçoit annuellement près de 4000 piqûres de moustiques. Quatre espèces de moustiques sont capturées : #Culex #quinquefasciatus (84%), #Mansonia$(9$ #gambiae$(6$. #Funestus$(1$. #gambiae$est de 78$. #Funestus est absent et la proportion d'#A. #gambiae$est très basse (1$. #gambiae$, sur 11 dissections, sont pares. Aucune glande salivaire sur 16 dissections n'a été trouvée positive; cependant, l'indice sporozoïtique peut être estimé à 4$ (49% de la faune culicidienne agressive) est liée à l'abondance de la végétation aquatique due au manque d'entretien des bassins. (Résumé d'auteur

Control of superluminal transit through a heterogeneous medium

We consider pulse propagation through a two component composite medium (metal inclusions in a dielectric host) with or without cavity mirrors. We show that a very thin slab of such a medium, under conditions of localized plasmon resonance, can lead to significant superluminality with detectable levels of transmitted pulse. A cavity containing the heterogeneous medium is shown to lead to subluminal-to-superluminal transmission depending on the volume fraction of the metal inclusions. The predictions of phase time calculations are verified by explicit calculations of the transmitted pulse shapes. We also demonstrate the independence of the phase time on system width and the volume fraction under specific conditions.Comment: 21 Pages,5 Figures (Published in Journal of Modern Optics

Types of albinism in the black Southern Africa population

Background: Oculocutaneous albinism (OCA) is the most common inherited disorder in Southern African blacks and several types have been described. Molecular techniques, where available, can be used to confirm a clinical diagnosis and the type of OCA, if necessary, and for prenatal diagnosis.Objectives: To investigate and classify the different types of albinism commonly found and to determine the clinical implications for each type.Design: A descriptive survey.Setting: Gauteng province, South Africa, and Lesotho.Subjects: Three groups of subjects with OCA (96 from a genetics clinic, 62 from a dermatology clinic, and 31 from community surveys) from the black African population participated.Main outcome measures: Subjects underwent clinical and/or dermatological examinations and were then classified according to type of OCA.Results: Four forms of OCA were identified: most (82%) subjects had OCA2 (a tyrosinasepositive type) with three sub-types: those without large freckles (ephelides) on exposed areas (named OCA 2a in this study), those with such freckles (named OCA 2b), and those with brown albinism (BOCA); the remainder had red/ rufous albinism, ROCA (OCA 3). The four forms could be distinguished from each other clinically without using molecular genetic testing.Conclusion: The most common types of albinism found in the black population of Southern Africa are OCA 2 and OCA 3. Given the high prevalence of the disorder, together with the high risk of skin cancer, and the recent persecution of affected individuals in certain East African countries, these findings and their clinical implications have significance in terms of both education and awareness for health professionals andlay people caring for those with albinism

Assessment of agro-ecological influence on the seed quality of groundnut (Arachis hypogaea) in The Gambia

A survey was conducted to assess the quality of groundnut seed produced and stored under ambient environment across various agro-ecologies of The Gambia, with a view to understanding regions with comparative advantage for its production and storage. Seed production activities of 60 seed growers in 26 communities were collected using structured questionnaires, interviews and observations. The Global Positioning System (GPS) coordinates of the communities were geo-referenced to identify the geographical positioning of the production sites. Samples of the groundnut pods were taken from the seed stores, threshed and subjected to seed quality analysis. Descriptive analysis was used to categorize the seed sources, hectarage cultivated, while seed quality data were subjected to analysis of variance of Nested Design. Means of significant factors were separated using Duncan Multiple Range Test (DMRT) at 5% significant level. The study showed that groundnut seed production is better concentrated in regions with optimum and sustainable rainfall that will reduce abiotic stress during seed development like the Lower River Region, West Coast Region and Central River Region. Fleur-11 variety was identified as one of the most promising varieties for groundnut cultivation in The Gambia and Tropical Africa