Herders and Wetland Degradation in Northern Cameroon

Livestock rearing in Northern Cameroon is carried out under two majors systems: the nomadic and the transhumance production systems (Pamo & Pamo, 1991). Nomadism is the practice of wandering from place to place, while transhumance involves seasonal displacement of flocks from one area to another by herders. These production systems involved large grazing areas, which may encompass different ecosystems. The Yaére, the only wetland of the northern Cameroon, is the major dry season grazing lands for livestock and wildlife. The main characteristic of this wetland is that the whole area is excluded from grazing during the growing season as a result of large scale flooding. Thus the major forage species (i.e. Echinochloa pyramidalis, Oryza longistaminata, Hyparrhenia rufa, Echinochloa stagnina) can set seed thereby ensuring their continued dispersal, establishment, and survival during the subsequent rainy season. In 1979, an upstream dam of 28 km with an additional 20 km embankment along the Logone river was build to store water for a rice irrigation project. This suppressed flooding over some 60 000 ha, and seriously affected the hydrological regime over another 200 000 ha. Major perennial forage species were gradually replaced by less palatable annual species such as Sorghum arundinaceum. This paper investigates how herders coped with the induced degradation of this dry season grazing land

Herders and Wetland Degradation in Northern Cameroon

Livestock rearing in Northern Cameroon is carried out under two majors systems: the nomadic and the transhumance production systems (Pamo & Pamo, 1991). Nomadism is the practice of wandering from place to place, while transhumance involves seasonal displacement of flocks from one area to another by herders. These production systems involved large grazing areas, which may encompass different ecosystems. The Yaére, the only wetland of the northern Cameroon, is the major dry season grazing lands for livestock and wildlife. The main characteristic of this wetland is that the whole area is excluded from grazing during the growing season as a result of large scale flooding. Thus the major forage species (i.e. Echinochloa pyramidalis, Oryza longistaminata, Hyparrhenia rufa, Echinochloa stagnina) can set seed thereby ensuring their continued dispersal, establishment, and survival during the subsequent rainy season. In 1979, an upstream dam of 28 km with an additional 20 km embankment along the Logone river was build to store water for a rice irrigation project. This suppressed flooding over some 60 000 ha, and seriously affected the hydrological regime over another 200 000 ha. Major perennial forage species were gradually replaced by less palatable annual species such as Sorghum arundinaceum. This paper investigates how herders coped with the induced degradation of this dry season grazing land

West African Dwarf Goat Response to Supplementary Feeding in Cameroon

The production of the West African Dwarf goat (WADG) in Cameroon is very low, because of lack of proper nutrition. Nitrogen content is generally very low and fibre content is high, both in the grass and the crop residues which form the basis of their diet particularly during the dry season. Supplementation of these roughages is a promising way of alleviating nutrient deficiencies. Different types of supplementary feeding have been advocated to boost goat production (Leng, 2003), of which supplementary feeding with leguminous tree leaves is of high merit. The present study was undertaken to evaluate the effects of supplementary feeding of Calliandra calothyrsus and Leucaena leucocephala leaves on growth and reproduction of WADG

System-level investigation of multi-MW direct-drive wind power PM vernier generators

Surface mounted permanent magnet Vernier (SPM-V) machines are known for their high torque density but relatively poor power factor compared to conventional SPM machines. The high torque density feature of the SPM-V machines is desirable for direct-drive offshore wind power applications as it leads to reduced generator size, mass and cost. However, their poor power factor can negatively affect the converter cost and efficiency. This paper compares the system-level performance, including generator active and structural components and converter, between the SPM-V and the conventional SPM generator systems. Four different power ratings, i.e. 0.5MW, 3MW, 5MW and 10MW, have been considered to study the trend of system-level performance with increasing power rating. The study shows that the SPM-V generators can be lighter and cheaper than their conventional SPM counterparts. However, after the consideration of converter cost and efficiency, the conventional SPM generator exhibited slightly better overall performance. Nonetheless, with the development of novel Vernier topologies and reduction in converter costs in the future due to emerging technologies, the Vernier generators can still be competitive for direct-drive offshore wind power applications

Nutrient Accumulation in Leaves and Soft Twigs of \u3ci\u3eMoringa oleifera\u3c/i\u3e Lam. at Different Growth Stages in Western Highland of Cameroon

Moringa oleifera belongs to the Moringaceae family and is considered to have its origin in the south of the Himalayan mountains. The species is being introduced into the highland zone of Cameroon. It is a tree which has many valuable properties and it is of great nutritional and scientific interest. The objective of this experiment was to evaluate nutrient composition in leaves and soft twigs of M. oleifera at different growth heights when grown in the Western Highland of Cameroon

Constraints on Galaxy Density Profiles from Strong Gravitational Lensing: The Case of B 1933+503

We consider a wide range of parametric mass models for B 1933+503, a ten-image radio lens, and identify shared properties of the models with the best fits. The approximate rotation curves varies by less than 8.5% from the average value between the innermost and the outermost image (1.5h^{-1} kpc to 4.1h^{-1} kpc) for models within 1 \sigma of the best fit, and the radial dependence of the shear strength and angle also have common behavior for the best models. The time delay between images 1 and 6, the longest delay between the radio cores, is \Delta t = (10.6^{+2.4}_{-1.1})h^{-1} days (\Omega_0=0.3, \lambda_0=0.7) including all the modeling uncertainties. Deeper infrared observations, to more precisely register the lens galaxy with the radio images and to measure the properties of the Einstein ring image of the radio source's host galaxy, would significantly improve the model constraints and further reduce the uncertainties in the mass distribution and time delay.Comment: 24 pages, 10 figures, final version to appear in ApJ. Some minor corrections (e.g. constraint on central unseen image was stronger than intended earlier, now agrees with text, conventions on angles fixed in text/plots). Resulting model fits have some change in chi squareds and best parameters (e.g. cores, flatness of rotation curve) have some changes. Properties of model families and trends for best fitting models very close to earlier results; general conclusions the sam

Detection of Bronchial Neoplasia in Uranium Miners by Autofluorescence Endoscopy (SAFE-1000)

The increase in the detection rate for premalignant changes of bronchial epithelium was studied in 56 symptom-free volunteers from the risk group of Czech uranium miners (mean age 50.69 years, mean WLM 21.06 (1 Working Level Month is equal to the absorption of latent energy of 2.08 × 10–5 J/m3 in one month, i.e. 170 working hours)) by the additional employment of the System of Autofluorescence Endoscopy (SAFE-1000 Pentax) to conventional white-light bronchoscopy, comparing results with those of bronchial biopsy histopathology examination. Histopathology using hematoxylin and eosin staining confirmed intraepithelial neoplasias in 15 areas in 10 persons. White-light bronchoscopy sensitivity was 21.05%, and specificity 93.7% which an autofluorescence bronchoscopy sensitivity was 78.95% and specificity 81.89%

Determination of Inflationary Observables by Cosmic Microwave Background Anisotropy Experiments

Inflation produces nearly Harrison-Zel'dovich scalar and tensor perturbation spectra which lead to anisotropy in the cosmic microwave background (CMB). The amplitudes and shapes of these spectra can be parametrized by $Q_S^2$, $r\equiv Q_T^2/Q_S^2$, $n_S$ and $n_T$ where $Q_S^2$ and $Q_T^2$ are the scalar and tensor contributions to the square of the CMB quadrupole and $n_S$ and $n_T$ are the power-lawspectral indices. Even if we restrict ourselves to information from angles greater than one third of a degree, three of these observables can be measured with some precision. The combination $130^{1-n_S}Q_S^2$ can be known to better than $\pm 0.3\%$. The scalar index $n_S$ can be determined to better than $\pm 0.02$. The ratio $r$ can be known to about $\pm 0.1$ for $n_S \simeq 1$ and slightly better for smaller $n_S$. The precision with which $n_T$ can be measured depends weakly on $n_S$ and strongly on $r$. For $n_S \simeq 1$ $n_T$ can be determined with a precision of about $\pm 0.056(1.5+r)/r$. A full-sky experiment with a $20'$beam using technology available today, similar to those being planned by several groups, can achieve the above precision. Good angular resolution is more important than high signal-to-noise ratio; for a given detector sensitivity and observing time a smaller beam provides significantly more information than a larger beam. The uncertainties in $n_S$ and $r$ are roughly proportional to the beam size. We briefly discuss the effects of uncertainty in the Hubble constant, baryon density, cosmological constant and ionization history.Comment: 28 pages of uuencoded postscript with 8 included figures. A postscript version is also available by anonymous ftp at ftp://astro.uchicago.edu/pub/astro/knox/fullsim.p

Limits on a Stochastic Background of Gravitational Waves from Gravitational Lensing

We compute the effects of a stochastic background of gravitational waves on multiply imaged systems or on weak lensing. There are two possible observable effects, a static relative deflection of images or shear, and an induced time dependent shift or proper motion. We evaluate the rms magnitude of these effects for a COBE normalized, scale-invariant spectrum, which is an upper limit on spectra produced by inflation. Previous work has shown that large-scale structure may cause a relative deflection large enough to affect observations, but we find that the corresponding effect of gravity waves is smaller by $\sim 10^4$ and so cannot be observed. This results from the oscillation in time as well as the redshifting of the amplitude of gravity waves. We estimate the magnitude of the proper motion induced by deflection of light due to large-scale structure, and find it to be $\sim 10^{-8}$ arcsec per year. This corresponds to $\sim 50$ km/s at cosmological distances, which is quite small compared to typical peculiar velocities. The COBE normalized gravity wave spectrum produces motions smaller still by $\sim 10^2$. We conclude that light deflection due to these cosmological perturbations cannot produce observable proper motions of lensed images. On the other hand, there are only a few known observational limits on a stochastic background of gravity waves at shorter, astrophysical wavelengths. We calculate the expected magnitudes of the effects of lensing by gravity waves of such wavelengths, and find that they are too small to yield interesting limits on the energy density of gravity waves.Comment: 14 pages, LaTex + 1 PS Figure, accepted version to be published in Phys. Rev. D15, Dec. 1996. An incorrect assumption was removed, also various other minor change