Vision-based localization of a wheeled mobile robot for greenhouse applications: A daisy-chaining approach

The Euclidean position and orientation of a wheeled mobile robot (WMR) is typically required for autonomous selection and control of agricultural operations in a greenhouse. A vision-based localization scheme is formulated as a desire to identify the position and orientation of a WMR navigating in a greenhouse by utilizing the image feedback of the above-the-aisle targets from an on-board camera. An innovative daisy chaining strategy is used to find the local coordinates of the above-the-aisle targets in order to localize a WMR. In contrast to typical camera configurations used for vision-based control problems, the localization scheme in this paper is developed using a moving on-board camera viewing reseeding targets. Multi-view photogrammetric methods are used to develop relationships between different camera frames and WMR coordinate systems. Experimental results demonstrate the feasibility of the developed geometric model.     

Evaluation of a cassava germplasm collection for reaction to three major diseases and the effect on yield

Thirty-five cassava (Manihot esculenta Crantz) genotypes from the International Institute of Tropical Agriculture (IITA), germplasm collection were planted in May 1992 under natural disease infection conditions, at the IITA field plots at Ibadan, Nigeria. The genotypes were evaluated at monthly intervals for six months, for incidence and severity of cassava anthracnose disease (CAD), cassava bacterial blight (CBB) and African cassava mosaic virus (ACMV). The effect of the pathogens on yield was also evaluated twelve months after planting (MAP). CAD, CBB and ACMV incidence and severity were significantly different (P<0.05) among the cassava genotypes at 3 and 6 months after planting. ACMV incidence and severity reached the maximum levels at 3 MAP while CAD and CBB had a low incidence and severity at that period but exhibited a high disease symptom expression at 6 MAP. Yield parameters (plant stand, tuber number, tuber weight and tuber dry matter) differed significantly (P<0.05) between the cassava genotypes. ACMV and CBB severity was negatively correlated with tuber number (r = –0.54 and r = –0.62 respectively). CAD severity was negatively correlated with tuber number (r = –0.46) and tuber weight (r = –0.63). Percentage dry matter was significantly correlated with ACMV severity (r = 0.71), CBB severity (r = 0.63) and CAD severity (r = 0.42). There was also a significant correlation between CBB and ACMD severity (r=0.46) and CBB and CAD severity (r=0.62). Tuber number and yield were significantly correlated (r=0.60), while% dry matter content and root rot showed a significant negative correlation (–0.42).     

How successful are plant species reintroductions?

Reintroduction of native species has become increasingly important in conservation worldwide for recovery of rare species and restoration purposes. However, few studies have reported the outcome of reintroduction efforts in plant species. Using data from the literature combined with a questionnaire survey, this paper analyses 249 plant species reintroductions worldwide by assessing the methods used and the results obtained from these reintroduction experiments. The objectives were: (1) to examine how successful plant species reintroductions have been so far in establishing or significantly augmenting viable, self-sustaining populations in nature; (2) to determine the conditions under which we might expect plant species reintroductions to be most successful; (3) to make the results of this survey available for future plant reintroduction trials. Results indicate that survival, flowering and fruiting rates of reintroduced plants are generally quite low (on average 52%, 19% and 16%, respectively). Furthermore, our results show a success rate decline in individual experiments with time. Survival rates reported in the literature are also much higher (78% on average) than those mentioned by survey participants (33% on average). We identified various parameters that positively influence plant reintroduction outcomes, e.g., working in protected sites, using seedlings, increasing the number of reintroduced individuals, mixing material from diverse populations, using transplants from stable source populations, site preparation or management effort and knowledge of the genetic variation of the target species. This study also revealed shortcomings of common experimental designs that greatly limit the interpretation of plant reintroduction studies: (1) insufficient monitoring following reintroduction (usually ceasing after 4 years); (2) inadequate documentation, which is especially acute for reintroductions that are regarded as failures; (3) lack of understanding of the underlying reasons for decline in existing plant populations; (4) overly optimistic evaluation of success based on short-term results; and (5) poorly defined success criteria for reintroduction projects. We therefore conclude that the value of plant reintroductions as a conservation tool could be improved by: (1) an increased focus on species biology; (2) using a higher number of transplants (preferring seedlings rather than seeds); (3) taking better account of seed production and recruitment when assessing the success of reintroductions; (4) a consistent long-term monitoring after reintroduction.     

India: a perspective on the food situation

Four major points emerge from this brief survey of the evidence: 1) The food crisis in 1974 seems to have been largely a result of distributional factors. The per capita availability of food grains from all sources, including imports, although below 1971 and 1972 levels, was probably above the average for 1963 to 1973. Comparison of available food supplies with estimated caloric and protein requirements of the population indicates that, on average, enough food was available to meet minimal requirements, with a small margin to spare. Supplies obtained through the government procurement and distribution program were especially short since the program depends primarily on the winter harvest, which failed badly in 1974. Thus, urban areas and some pockets of rural areas were badly hit. The poorest third of the population, who receive 20 to 30 percent less food than the national average even in normal times, were severely affected by higher prices, and there is little doubt that a sizable fraction of the population received inadequate diets. 2) The food supply for 1975 depends heavily on the winter harvest. If this is good, as it promises to be, widespread starvation, but not hunger, should be averted. Since the main shortfall was in the summer crop, the nature of the distribution problem will be different and shortages may be spread more evenly over the population. Nevertheless, the situation seems to forebode considerable hardship for the poorer segments of the population. 3) Food requirements will continue to grow over the foreseeable future as a result of rising population and incomes. India's agricultural resources are still relatively poorly exploited. In the short run, output can probably be increased substantially by increased fertilizer use on traditional as well as new varieties. In the longer run, increased production can be obtained from more intensive cropping, expansion of surface and groundwater irrigation, improved water management, and improved cultural practices brought about by more active agricultural research and appropriate land and pricing policies. These measures will need buttressing by an expanded food storage program if extreme hardships due to periodic drought are to be avoided. 4) India's farmers have shown considerable willingness to innovate under favorable conditions. The rate of adoption of HYV's in the first few years after their introduction was impressive. The same was true for tubewells and fertilizers. Nevertheless, many of the easy gains may already have been made. Fragmentary information on the quality of irrigation indicates that the acreage sown to wheat and rice HYV's may be approaching an upper limit in many areas because of the requirements of these varieties for a high degree of water control. Further gains will require more aggressive and coordinated policies for agricultural development. A major change in development strategy may be required if scarcities and hardships such as those currently being experienced are to be avoided in the future, and some hard political decisions on land reform and consolidation may have to be made. It is to be hoped that bold and imaginative agricultural policies will be followed, and that they will be accompanied by greater efforts to reduce population growth to manageable levels.     

True polar wander as a mechanism for second-order sea-level variations

Long-term wander of the rotation pole can be a significant contributor to second-order (time scales of approximately 100 million years) sea-level variations. Numerical predictions based on realistic viscoelastic Earth models and paleomagnetically constrained polar motion yield global-scale, differential sea-level trends that can be as large as approximately 200 meters. From the results presented here, it is argued that the well-documented, second-order, Cretaceous-Tertiary sea-level cycle should be reinterpreted as some combination of a eustatic and a regionally varying rotational signal.     

Disruption of signaling by Yersinia effector YopJ, a ubiquitin-like protein protease

Homologs of the Yersinia virulence effector YopJ are found in both plant and animal bacterial pathogens, as well as plant symbionts. These YopJ family members were shown to act as cysteine proteases. The catalytic triad of the protease was required for inhibition of the mitogen-activated protein kinase (MAPK) and nuclear factor kappaB (NF-kappaB) signaling in animal cells and for induction of localized cell death in plants. The substrates for YopJ were shown to be highly conserved ubiquitin-like molecules, which are covalently added to numerous regulatory proteins. YopJ family members exert their pathogenic effect on cells by disrupting this posttranslational modification.     

Regeneration of ammonia borane spent fuel by direct reaction with hydrazine and liquid ammonia

Ammonia borane (H(3)N-BH(3), AB) is a lightweight material containing a high density of hydrogen (H(2)) that can be readily liberated for use in fuel cell-powered applications. However, in the absence of a straightforward, efficient method for regenerating AB from dehydrogenated polymeric spent fuel, its full potential as a viable H(2) storage material will not be realized. We demonstrate that the spent fuel type derived from the removal of greater than two equivalents of H(2) per molecule of AB (i.e., polyborazylene, PB) can be converted back to AB nearly quantitatively by 24-hour treatment with hydrazine (N(2)H(4)) in liquid ammonia (NH(3)) at 40°C in a sealed pressure vessel.     

Improving Map Accuracy of Soil Variables Using Soil Electrical Conductivity as a Covariate

Accurate characterization of soil properties across a field can be difficult, especially when compounded with the diverse landscapes used for pastureland. Indirect methods of data collection have the advantage of being rapid, noninvasive, and dense; they may improve mapping accuracy of selected soil parameters. The objective of this study was to determine if the use of soil electrical conductivity (EC) as a covariate improved mapping accuracy of five soil variables across four sampling schemes and two sampling densities in a central Iowa, USA pasture. In this study, cokriging methods were compared to kriging methods for the measured soil properties of soil pH, available P and K, organic matter and moisture. Maps resulting from cokriging each of the soil variables with soil EC exhibited more local detail than the kriged maps of each soil variable. A small, but inconsistent, improvement occurred in kriging variance and prediction accuracy of non-sampled sites when cokriging was implemented. The improvement was generally greater for soil variables more highly correlated with soil EC. This work indicates that cokriging of EC with less densely and invasively collected soil parameters of P, K, pH, organic matter (OM) and moisture does not consistently and substantially improve the characterization accuracy of pasture soil variability.     

Role of anthocyanidin reductase,encoded by BANYULS in plant flavonoid biosynthesis

Condensed tannins (CTs) are flavonoid oligomers, many of which have beneficial effects on animal and human health. The flavanol (-)-epicatechin is a component of many CTs and contributes to flavor and astringency in tea and wine. We show that the BANYULS (BAN) genes from Arabidopsis thaliana and Medicago truncatula encode anthocyanidin reductase, which converts anthocyanidins to their corresponding 2,3-cis-flavan-3-ols. Ectopic expression of BAN in tobacco flower petals and Arabidopsis leaves results in loss of anthocyanins and accumulation of CTs.