ADOPTION OF MAIZE AND WHEAT TECHNOLOGIES IN EASTERN AFRICA: A SYNTHESIS OF THE FINDINGS OF 22 CASE STUDIES

This paper synthesizes the findings of 22 micro-level studies on technology adoption carried out by the International Maize and Wheat Improvement Center (CIMMYT) with national agricultural research systems in Ethiopia, Kenya, Tanzania, and Uganda from 1996-1999. The authors found that technology adoption is taking place across Eastern Africa but considerable scope remains to improve the productivity of smallholder agriculture in higher potential regions with high levels of adoption. Extension was the variable most highly correlated with technology adoption, and extension services continue to play an important role in disseminating information on new varieties and how to manage them. Despite the usefulness of the micro-study results, especially for priority setting and impact assessment, future adoption studies can be improved by standardizing definitions across studies and using sampling techniques that allow results to be generalized across wider areas. Finally, the paper suggests that maize and wheat breeding research should be made more relevant to the preferences and circumstances of farmers, that the link between research and extension should be strengthened and include the private sector and non-governmental organizations, that policies should support the development and expansion of efficient markets for inputs and outputs, and that rural credit systems should be strengthened.Maize, Wheat, Innovation adoption, Technology transfer, Plant Breeding, Small farms, Case studies, Fertilizers, Private sector, Nongovernmental organizations, Research institutions, International organizations, Kenya, Tanzania, Uganda, Farm Management,

Folk Theorems on the Correspondence between State-Based and Event-Based Systems

Kripke Structures and Labelled Transition Systems are the two most prominent semantic models used in concurrency theory. Both models are commonly believed to be equi-expressive. One can find many ad-hoc embeddings of one of these models into the other. We build upon the seminal work of De Nicola and Vaandrager that firmly established the correspondence between stuttering equivalence in Kripke Structures and divergence-sensitive branching bisimulation in Labelled Transition Systems. We show that their embeddings can also be used for a range of other equivalences of interest, such as strong bisimilarity, simulation equivalence, and trace equivalence. Furthermore, we extend the results by De Nicola and Vaandrager by showing that there are additional translations that allow one to use minimisation techniques in one semantic domain to obtain minimal representatives in the other semantic domain for these equivalences.Comment: Full version of SOFSEM 2011 pape

Participatory Evaluation of Integrated Pest and Soil Fertility Management Options Using Ordered Categorical Data Analysis

During participatory rural appraisals, farmers at the Lake Victoria basin of Kenya and Uganda identified Striga, stemborer and declining soil fertility as three major constraints to maize production To reduce food insecurity, several innovative integrated technologies to address these constraints have been developed, including push-pull (maize intercropped with Desmodium and surrounded by napier grass), maize-soybean and maize-crotalaria rotations, and Imazapyrresistant (IR) maize seed coated with the herbicide. To let farmers evaluate the new technologies, 12 demonstration trials, comparing the different technologies, were established in four villages in Siaya and Vihiga districts (Western Kenya) and two villages in Busia (Uganda). These evaluations, where farmers' appreciation and feedback on the technology are captured, are an important step in technology development. During field days at the end of short rainy seasons of 2003 and 2004, 504 farmers individually observed and rated each treatment under the different cropping systems, with and without IR maize, and with and without fertilizer, with a maize continuous monocrop as control. Farmers scored each of the 16 treatments on an ordered scale of five categories: very poor, poor, average, good, and very good. The treatments were scored for each of the criteria farmers has previously determined (including yield, resistance to Striga and stemborer, and improvement of soil fertility). Analysis of the evaluation, using ordinal regression, show significant differences in farmers' preference by year and site. There was, however, little effect of farm and farmer characteristics such as farm size and gender of the observer. Ordinal regression of farmers' scores are not as intuitive and also bit cumbersome to use, but they have a better theoretical foundation than other methods, in particular the use of means. This paper shows how the method can be used, and concludes that, with some effort, it is a convenient way to analyse farmers' ranking of a large number of options.farmers' preference, technologies, ordinal regression, Crop Production/Industries,

The Maize Green Revolution in Kenya Revisited

The maize green revolution, which increased maize yields through the use of improved varieties and fertilizer, has stalled since the mid-eighties in Kenya. This paper examines whether the stagnation of yields continued in the 1990s in spite of the implementation of the maize liberalization policies by the Kenya Government. Analysis of farm level surveys from 1992 and 2002 indicates slight increases in the use of improved maize varieties and fertilizer, but a substantial decrease in the intensity of fertilizer use. The econometric analysis suggests that the intensity of fertilizer use has a major effect on yield. The use of improved maize varieties, however, did not affect yield, suggesting that there are local varieties for some areas that do as well as improved varieties. Research is needed to develop improved varieties for some areas, and also needed for the development of alternative affordable soil fertility measures.green revolution, maize, adoption, soil fertility, Kenya, Crop Production/Industries, International Development,

Purely radiative perfect fluids with degenerate shear tensor

We consider non-rotating geodesic perfect fluid spacetimes which are purely radiative in the sense that the gravitational field satisfies the covariant transverse conditions div H = div E = 0. We show that when the shear tensor S is degenerate, H, E and S necessarily commute and hence the resulting spacetimes are hypersurface homogeneous of Bianchi class A (modulo some purely electric exceptions).Comment: 8 pages, references added, typos corrected, simplified some algebraic manipulation

Concurrent constraint programming with process mobility

We propose an extension of concurrent constraint programming with primitives for process migration within a hierarchical network, and we study its semantics. To this purpose, we first investigate a "pure " paradigm for process migration, namely a paradigm where the only actions are those dealing with transmissions of processes. Our goal is to give a structural definition of the semantics of migration; namely, we want to describe the behaviour of the system, during the transmission of a process, in terms of the behaviour of the components. We achieve this goal by using a labeled transition system where the effects of sending a process, and requesting a process, are modeled by symmetric rules (similar to handshaking-rules for synchronous communication) between the two partner nodes in the network. Next, we extend our paradigm with the primitives of concurrent constraint programming, and we show how to enrich the semantics to cope with the notions of environment and constraint store. Finally, we show how the operational semantics can be used to define an interpreter for the basic calculus.

Management of intractable bladder neck strictures following radical prostatectomy using the Memokath®045 stent

The incidence of vesicourethral anastomotic stenosis (VUAS) post radical prostatectomy varies from 1 to 26%. Current treatment can be challenging and includes a variety of different procedures. These range from endoscopic dilations to bladder neck reconstruction to urinary diversion. We investigated a 2-stage endoscopic treatment, using the thermo-expandable Memokath®045 bladder neck stent to manage patients with VUAS post radical prostatectomy. We retrospectively reviewed 30 patients, between 2013 and 2017, who underwent a Memokath®045 stent insertion following failed primary treatment (dilation and clean intermittent catheterisation) for VUAS. The mean interval time between prostatectomy and Memokath®045 stent insertion was 13 months. The mean follow-up time was 3.6 years with all patients having a minimum of 12-month follow-up. All patients had two previous attempts at endoscopic dilatation with or without incision and a trial of clean intermittent catheterisation. During stage 1, the anastomotic stricture is dilated/incised to diameter of 30 Fr, the stricture length is measured, and a catheter is left in situ. One to 2 weeks later, post haemostasis and healing, an appropriately sized Memokath®045 stent is inserted. The stent is then removed 1-year post-op. Our series of patients had a median age of 62 (54–72). Most patients (26) had a robot-assisted radical prostatectomy (RARP) or salvage procedure. Results showed improvement in IPSS scores, IPSS quality of life scores, Qmax and PVR after the Memokath®045 stent was removed compared to pre-operation. With a minimum of 12 months post stent removal, 93% of patients were fully continent, whilst 7% of patients were socially continent. 2 (7%) patients had their stents removed and not replaced due to re-stricturing and stone formation. However, no urinary tract infections, stricture recurrence or urinary retention was observed in the rest of the cohort (93%). Overall, the Memokath®045 stent was successful in treating 93% of our patients with VUAS. Our series had minimal complications that were managed with conservative measures and in three patients’ re-operation was needed. In conclusion, the Memokath®045 stent is a minimally invasive technique with faster recovery time compared to other techniques such as bladder neck reconstruction or urinary diversion. Additionally, it provides superior patency results compared to other techniques such as bladder neck incision and injection of Mitomycin C. Therefore, this management option should be considered in the management of VUAS

Management of intractable bladder neck strictures following radical prostatectomy using the Memokath\uae045 stent

The incidence of vesicourethral anastomotic stenosis (VUAS) post radical prostatectomy varies from 1 to 26%. Current treatment can be challenging and includes a variety of different procedures. These range from endoscopic dilations to bladder neck reconstruction to urinary diversion. We investigated a 2-stage endoscopic treatment, using the thermo-expandable Memokath\uae045 bladder neck stent to manage patients with VUAS post radical prostatectomy. We retrospectively reviewed 30 patients, between 2013 and 2017, who underwent a Memokath\uae045 stent insertion following failed primary treatment (dilation and clean intermittent catheterisation) for VUAS. The mean interval time between prostatectomy and Memokath\uae045 stent insertion was 13\ua0months. The mean follow-up time was 3.6\ua0years with all patients having a minimum of 12-month follow-up. All patients had two previous attempts at endoscopic dilatation with or without incision and a trial of clean intermittent catheterisation. During stage 1, the anastomotic stricture is dilated/incised to diameter of 30\ua0Fr, the stricture length is measured, and a catheter is left in situ. One to 2\ua0weeks later, post haemostasis and healing, an appropriately sized Memokath\uae045 stent is inserted. The stent is then removed 1-year post-op. Our series of patients had a median age of 62 (54\u201372). Most patients (26) had a robot-assisted radical prostatectomy (RARP) or salvage procedure. Results showed improvement in IPSS scores, IPSS quality of life scores, Qmax and PVR after the Memokath\uae045 stent was removed compared to pre-operation. With a minimum of 12\ua0months post stent removal, 93% of patients were fully continent, whilst 7% of patients were socially continent. 2 (7%) patients had their stents removed and not replaced due to re-stricturing and stone formation. However, no urinary tract infections, stricture recurrence or urinary retention was observed in the rest of the cohort (93%). Overall, the Memokath\uae045 stent was successful in treating 93% of our patients with VUAS. Our series had minimal complications that were managed with conservative measures and in three patients\u2019 re-operation was needed. In conclusion, the Memokath\uae045 stent is a minimally invasive technique with faster recovery time compared to other techniques such as bladder neck reconstruction or urinary diversion. Additionally, it provides superior patency results compared to other techniques such as bladder neck incision and injection of Mitomycin C. Therefore, this management option should be considered in the management of VUAS