Recycling Hybrid Maize Varieties: Is It Backward Practice or Innovative Response to Adverse Conditions in Kenya?

Hybrid varieties have significantly contributed to increased maize proclivity in Kenya and other SSA countries. A number of factors limit access of farmers to maize varieties, smallholder farmers have sort an alternative option of recycling the hybrid maize seeds. Seeds are carefully selected based on cob and grain size during or before harvest after which they are preserved. hybrid yielding maize varieties (HYMV) developers and disseminators observe that there is a progressive yield decrease of recycling HYMV. The question is Is it economical to recycle HYMV or an innovation that farmers can practice?. This study was designed to evaluate the yield losses and benefits of hybrid maize recycling in Kenya. Through key informants, farmers who grew both certified seed and recycled maize were identified. For on farm trial (OFT), sixty two (62) farmers who recycled hybrid maize varieties and 30 who grew certified seeds were randomly selected while for the On station trial (OST), the trial was laid out in a completely randomized block design replicated four time with plots measuring 100M square. For the OFT, two plots of 100 square meters were superimposed on farmers fields both on recycled and fresh seed. Input and output levels in the plots were identified and valued. The results showed that the yield decreases at an increasing rate. Yield losses for Double crosses low compared to the Top crosses. The yield levels of recycled Top cross reduced by 16%, 17% and 32 while that for double crosses decreased by 20%, 37% and 46% for the first, second and third recycling generations respectively. However, positive net benefits are attained in recycling HYMV. This implies that it is beneficial to recycle HYMV up-to the third generation level. However at regional and national level food security objectives is comprised. This demands that incentives to discourage farmers from recycling may be sought through development of OPVs which can be recycled if national objective of food security has to be enhanced. From the logit results the major significantly influencing factors in recycling HYMVs are amount of credit, fertilizer, wealth and extension contact.Crop Production/Industries,

Prehistory of the British Isles: A tale of coming and going

It is now recognised that Britain has not always been geographically isolated from Europe and, for most of the last one million years, formed an extension of the northwest European landmass. During most of this time, Britain was accessible to migrating humans and animals, although climatic conditions varied greatly from Mediterranean-like through to glaciations and extreme cold, making Britain a difficult place to settle for any length of time. The oldest evidence for humans in Britain dates to between about 850,000 and 1 million years ago. Recovered lithic artefacts suggest that hominin species occupied and deserted the British Isles at least nine times. This article reviews the prehistory of the British Isles and presents the main sites and time periods

Ecology and biogeography of free-living nematodes associated with chemosynthetic environments in the deep sea: A review

Background: Here, insight is provided into the present knowledge on free-living nematodes associated with chemosynthetic environments in the deep sea. It was investigated if the same trends of high standing stock, low diversity, and the dominance of a specialized fauna, as observed for macro-invertebrates, are also present in the nematodes in both vents and seeps.Methodology: This review is based on existing literature, in combination with integrated analysis of datasets, obtained through the Census of Marine Life program on Biogeography of Deep-Water Chemosynthetic Ecosystems (ChEss).Findings: Nematodes are often thriving in the sulphidic sediments of deep cold seeps, with standing stock values ocassionaly exceeding largely the numbers at background sites. Vents seem not characterized by elevated densities. Both chemosynthetic driven ecosystems are showing low nematode diversity, and high dominance of single species. Genera richness seems inversely correlated to vent and seep fluid emissions, associated with distinct habitat types. Deep-sea cold seeps and hydrothermal vents are, however, highly dissimilar in terms of community composition and dominant taxa. There is no unique affinity of particular nematode taxa with seeps or vents.Conclusions: It seems that shallow water relatives, rather than typical deep-sea taxa, have successfully colonized the reduced sediments of seeps at large water depth. For vents, the taxonomic similarity with adjacent regular sediments is much higher, supporting rather the importance of local adaptation, than that of long distance distribution. Likely the ephemeral nature of vents, its long distance offshore and the absence of pelagic transport mechanisms, have prevented so far the establishment of a successful and typical vent nematode fauna. Some future perspectives in meiofauna research are provided in order to get a more integrated picture of vent and seep biological processes, including all components of the marine ecosystem

Root grooves on two adjacent anterior teeth of Australopithecus africanus

Tooth root grooves and other ante-mortem dental tissue loss, not associated with caries found on or near the cementoenamel junction (CEJ), are commonly termed non-carious cervical lesions. Three main processes are implicated in forming these lesions: abrasion, dental erosion, and abfraction. As yet, these lesions have not been described in non-Homo hominins. In this study, South African fossil hominin collections were examined for evidence of any type of non-carious cervical lesion. Only one individual shows ante-mortem root grooves consistent with non-carious cervical lesions. Two teeth, a mandibular right permanent lateral incisor (STW 270) and canine (STW 213), belonging to the same Australopithecus africanus individual, show clear ante-mortem grooves on the labial root surface. These lesions start below the CEJ, extend over a third of the way toward the apex, and taper to a point towards the lingual side. The characteristics of these grooves suggest the predominant aetiology was erosive wear. In addition, they are extremely similar to clinical examples of dental erosion. These are the oldest hominin examples of non-carious cervical lesions and the first described in a genus other than Homo. Further, the lesions suggest that this individual regularly processed and consumed acidic food items. © 2018 Elsevier Inc

Insights into muscle metabolic energetics: Modelling muscle-tendon mechanics and metabolic rates during walking across speeds

Prior studies have produced models to predict metabolic rates based on experimental observations of isolated muscle contraction from various species. Such models can provide reliable predictions of metabolic rates in humans if muscle properties and control are accurately modeled. This study aimed to examine how muscle-tendon model calibration and metabolic energy models influenced estimation of muscle-tendon states and time-series metabolic rates, to evaluate the agreement with empirical data, and to provide predictions of the metabolic rate of muscle groups and gait phases across walking speeds. Three-dimensional musculoskeletal simulations with prescribed kinematics and dynamics were performed. An optimal control formulation was used to compute muscle-tendon states with four levels of individualization, ranging from a scaled generic model and muscle controls based on minimal activations, to calibration of passive muscle forces, personalization of Achilles and quadriceps tendon stiffnesses, to finally informing muscle controls with electromyography. We computed metabolic rates based on existing models. Simulations with calibrated passive forces and personalized tendon stiffness most accurately estimate muscle excitations and fiber lengths. Interestingly, the inclusion of electromyography did not improve our estimates. The whole-body average metabolic cost was better estimated using Bhargava et al. 2004 and Umberger 2010 models. We estimated metabolic rate peaks near early stance, pre-swing, and initial swing at all walking speeds. Plantarflexors accounted for the highest cost among muscle groups at the preferred speed and was similar to the cost of hip adductors and abductors combined. Also, the swing phase accounted for slightly more than one-quarter of the total cost in a gait cycle, and its relative cost decreased with walking speed.Comment: 33 pages, 7 figure

Economics of Insecticide use and Potential for Bt Maize Varieties in the Control of Stalkborer in Kenya.

Maize is the staple food crop and source of income for majority of the Kenyan population and many sub-Saharan African countries. The increasing Kenyan population demands an increase in maize production if intermittent food deficits have to be averted. Since the introduction of improved maize varieties in mid-1960, the start of Green Revolution period, maize yields increased drastically up to 1970s and started declining from 1980s to-date. The key contributory factors are nutrient mining, sub-optimal input use and insect pest damage. Of the insect pests, stalk borer is of economic importance. Currently, KARI and CIMMYT are developing maize varieties that are tolerant to stalk borer damage. In order to evaluate the potential impact of these interventions economics of stalk borer control at farm level was evaluated. Surveys complemented with on-farm trials were executed in six major maize growing zones of Kenya. Farmers were randomly selected and a sample-frame established after which a total of 1854 households were randomly selected using random sampling technique. Each household was interviewed using structured questionnaire. Data on method of stalk borer control and the type insecticides used was collected. Partial budget and economic surplus models were used. The results indicated that very few farmers control stalk borer in maize despite significant stalk borer losses of about 15%. Therefore if Bt maize is introduced in Kenya it is likely to reduce these losses. This will benefit many hungry and poor Kenyans with improved household food supply and on farm incomes, in line with Government policy of food security and poverty eradication.Crop Production/Industries,