Ex-ante Evaluation of Cassava Research for Development in Malawi: A Farm Household and Random Utility Modeling Approach

Ex ante evaluation of agricultural research for development projects has become important in recent years for priority setting, ex post impact assessment and learning about generalizability to other populations and contexts. We apply farm household and random utility modeling to baseline survey data and evaluate the impact of a cassava research for development project in Malawi prior to its implementation. The project is being implemented to unlock the potential of cassava in response to the global food crisis. We find that a high proportion of farm households are not self-sufficient in food production and can be assisted by increasing the productivity of land and labor in production, processing and marketing of cassava to reduce deficits and increase marketed surplus. The research for development embeds research in an innovation systems network and speeds up exposure, awareness, adoption and diffusion. This increases the likelihood that incremental benefits will be generated and accrue earlier compared to the counterfactual without the project.Resource /Energy Economics and Policy,

Farmers perception of coconut mite damage and crop diversification alternatives in the coastal belt of Tanzania

Published online: 30 May 2012This article analysed farmers' perceptions of the effects of coconut mite in their livelihood and assessed crop diversification as a copping strategy for reduced coconut production. A socio-economic model of farmers' decisions on intercropping as an indicator for overall crop diversity was developed. The study was conducted between November 2009 and March 2010 in five districts in Tanzania, which were selected on the basis of the coconut's economic importance, using structured questionnaires which were administered to 200 household heads. Respondents were categorized in three groups – resource-poor farmers (43% of sample), medium-level farmers (50%) and well-off farmers (7%) according to six criteria. More than 80% of farmers were aware of the negative effects of the coconut mite. The result further indicated that the damaged nuts cause a loss of more than 30% of the cash income from coconut. Intercropping coconut with cassava, maize, cashew nut, sorghum and pineapples were the alternatives used by farmers to cope with declining coconut production caused by coconut mite and lethal yellowing disease. Land ownership and size, income from crops, non-farm income and family size were the main factors that influenced the farmer's decision to diversify crops. Although farmers diversify their cropping systems in order to be self-reliant, there is still a need to promote policies and programmes that will address coconut production constraints such pests and diseases such as rehabilitation of old plantations

Assessing the technical efficiency of maize producers with Imazapyrresistant maize for Striga control in Western Kenya

Imazapyr-Resistant Maize (IRM) is a weed control technology, not yet well adopted in the Striga prone area in Western Kenya. The adoption may expand in the future because it enhances maize production via efficiency gains. As to help farmers maximize the maize output affected by Striga for so long in time, research and development initiatives with substantial participation of the private sector to shift to this novel technology have been made in Western Kenya. A multistage random sampling technique was used to select a total of 600 households from Nyanza and Western provinces for this study. Stochastic production frontier analysis was the analytical method and the study revealed that the mean technical efficiency in the maize production sector is 70% indicating some inefficiencies of maize production. Technical inefficiency effects were influenced by household size along with farm size. Enhancing the technical efficiency will increase net returns of maize production enterprises, hence, improving livelihoods of maize producers

Effect of head-upright tilt on the dynamic of cerebral autoregulation.

The effect of head-upright tilting on the rate of cerebral autoregulation was studied in 12 healthy volunteers (nine men and three women; age range 20-36 years). The dynamics of cerebral autoregulation was determined from the rate of change in cerebral resistance (RoR) during a drop in arterial blood pressure induced by rapid deflation of a 3-min ischaemic thigh cuff and from the ratio of changes in cerebral blood flow and arterial blood pressure (CAI) during the recovery period after the drop in arterial blood pressure. The test was performed supine and with 40 degrees head-up tilt (40 degrees HUT). Middle cerebral artery mean blood flow velocity was measured by transcranial Doppler simultaneously with peripheral arterial blood pressure using Finapres. The thigh cuff deflation induced a larger drop in arterial pressure during 40 degrees HUT [median -28% (25 percentile -36, 75 percentile -19)] than in the supine position [-16% (-23, -15)] (P < 0.01) and in cerebral resistance [supine: -12% (-15, -6); 40 degrees HUT: -15% (-20, -12); P < 0.05]. There was no significant change in RoR [15% s-1 (12, 15)] and CAI [1.9 (1.5, 3.1)] measured supine and during 40 degrees HUT [RoR: 13% s-1 (12, 15); CAI: 1.3 (0.99, 1.9)]. During the drop in arterial pressure, the relationship between arterial blood pressure and systolic peak-to-peak interval exhibited an hysteresis loop, indicating a cardiopulmonary and/or baroreflex activation that was not observed with cerebral resistance. The rate of autoregulation is an intrinsic property of the cerebral vascular bed and is not affected by the vasodilator state in the range of arterial blood pressure changes induced by the tight cuff method

Experimental study of damping flexural vibrations in tapered turbofan blades

In this paper, the results of the experimental investigations into damping of flexural vibrations in turbofan blades with trailing edges tapered according to a power-law profile are reported. Edges of power-law profile (wedges), with small pieces of attached absorbing layers, materialise one-dimensional acoustic black holes for flexural waves that can absorb a large proportion of the incident flexural wave energy. The NACA 1307 aerofoil was used as a base model for experimental samples. This model was modified to form four samples of non-enginespecific model fan blades. Two of them were then twisted, so that a more realistic fan blade could be considered. All model blades, the ones with tapered trailing edges and the ones of traditional form, were excited by an electromagnetic shaker, and the corresponding frequency response functions have been measured. The results show that the fan blades with power-law tapered edges have the same pattern of damping that can be seen for plates with attached wedges of power-law profile, when compared to their respective reference samples. The resonant peaks are reduced substantially once a power-law tapering is introduced to the sample. The obtained results demonstrate that power-law tapering of trailing edges of turbofan blades can be a viable method of reduction of blade vibrations

Isomorphously Substituted [Fe,Al]ZSM-5 Catalysts for Methane Dehydroaromatization

Dehydroaromatization of methane (MDA) under non-oxidative conditions is a promising reaction for direct valorization of natural gas and biogas. Typically, Fe-modified ZSM-5 catalysts display low aromatic productivity and high coke selectivity in the MDA reaction. Herein, we show the benefit of starting from isomorphously substituted Fe-sites in [Fe,Al]ZSM-5 zeolites prepared by direct hydrothermal synthesis. Upon calcination, these samples contain predominantly isolated Fe3+ species, either atomically dispersed within the zeolite framework or anchored at exchange sites inside zeolite channels. In terms of the integral hydrocarbon productivity, [Fe,Al]ZSM-5 catalysts outperform Fe/ZSM-5, prepared by impregnation, as well as Mo/ZSM-5 catalysts with the same Si/Al ratio and molar metal loading. Operando X-ray absorption spectroscopy coupled with mass spectrometry (XANES-MS) demonstrates that the initial tetrahedral Fe3+ within the zeolite framework or at exchange sites are transformed into octahedral extraframework Fe2+ active sites during the MDA reaction and form small Fe2O3 clusters during oxidative regeneration. Combining activity measurements and operando thermogravimetry shows that the duration of the induction period, related to the formation of active hydrocarbon pool intermediates, strongly depends on the Fe dispersion and loading and can be used as a suitable descriptor for the MDA activity of [Fe,Al]ZSM-5. The shorter induction period of [Fe,Al]ZSM-5 in comparison to impregnated Fe/ZSM-5 can be linked to the higher methane conversion rate over highly dispersed Fe-sites and faster formation of active hydrocarbon pool intermediates.</p

Symptoms associated with an abnormal echocardiogram in elderly primary care hypertension patients

Background The prevalence and diagnostic value of heart failure symptoms in elderly primary care patients with hypertension is unknown. Aim To assess the prevalence, sensitivity, specificity, positive and negative predictive value of symptoms in association with an abnormal echocardiogram. Design and setting Cross-sectional screening study in five general practices in the south-east of the Netherlands. Method Between June 2010 and January 2013, 591 primary care hypertension patients aged between 60 and 85 years were included, without known heart failure and not treated by a cardiologist. All patients underwent an echocardiogram and a structured interview including assessment of heart failure symptoms: shortness of breath, fatigue, oedema, cold extremities, and restless sleep. Results and conclusion Restless sleep was reported by 25 %, cold extremities by 23%, fatigue by 19 %, shortness of breath by 17 %, and oedema by 13 %. Oedema was the only symptom significantly associated with an abnormal echocardiogram (positive predictive value was 45 %, sensitivity 20 %, and specificity 90 %, OR 2.12; 95 % CI=1.23-3.64), apart from higher age (OR 1.06; 95 % CI=1.03-1.09), previous myocardial infarction (OR 3.00; 95 % CI=1.28-7.03), and a systolic blood pressure of >160 mmHg (OR 1.62; 95 % CI= 1.08-2.41). Screening with echocardiography might be considered in patients with oedema

Neutral perfect fluids of Majumdar-type in general relativity

We consider the extension of the Majumdar-type class of static solutions for the Einstein-Maxwell equations, proposed by Ida to include charged perfect fluid sources. We impose the equation of state $\rho+3p=0$ and discuss spherically symmetric solutions for the linear potential equation satisfied by the metric. In this particular case the fluid charge density vanishes and we locate the arising neutral perfect fluid in the intermediate region defined by two thin shells with respective charges $Q$ and $-Q$. With its innermost flat and external (Schwarzschild) asymptotically flat spacetime regions, the resultant condenser-like geometries resemble solutions discussed by Cohen and Cohen in a different context. We explore this relationship and point out an exotic gravitational property of our neutral perfect fluid. We mention possible continuations of this study to embrace non-spherically symmetric situations and higher dimensional spacetimes.Comment: 9 page

Stabilization of Hydrodynamic Flows by Small Viscosity Variations

Motivated by the large effect of turbulent drag reduction by minute concentrations of polymers we study the effects of a weakly space-dependent viscosity on the stability of hydrodynamic flows. In a recent Letter [Phys. Rev. Lett. {\bf 87}, 174501, (2001)] we exposed the crucial role played by a localized region where the energy of fluctuations is produced by interactions with the mean flow (the "critical layer"). We showed that a layer of weakly space-dependent viscosity placed near the critical layer can have a very large stabilizing effect on hydrodynamic fluctuations, retarding significantly the onset of turbulence. In this paper we extend these observation in two directions: first we show that the strong stabilization of the primary instability is also obtained when the viscosity profile is realistic (inferred from simulations of turbulent flows with a small concentration of polymers). Second, we analyze the secondary instability (around the time-dependent primary instability) and find similar strong stabilization. Since the secondary instability develops around a time-dependent solution and is three-dimensional, this brings us closer to the turbulent case. We reiterate that the large effect is {\em not} due to a modified dissipation (as is assumed in some theories of drag reduction), but due to reduced energy intake from the mean flow to the fluctuations. We propose that similar physics act in turbulent drag reduction.Comment: 10 pages, 17 figs., REVTeX4, PRE, submitte