In crop/weed interactions a method is needed to reduce the complex data derived from interference research to a simple form which can be utilized immediately. A response surface technique was utilized in analyses involving densities, duration of interference, interference abilities of different species, and weed growth rates. At high weed densities interfering for long durations, multispecies interference is not additive but at low densities additiveness is approached. Soybean [Glycine max (L.) Merr.] yield loss from multispecies weed interference was calculated by subtracting the percent yield loss from the most competitive weed and then repeating the same procedure for remaining weeds. Interference data for weed species in which fewer data were available were determined by linear interpolation for densities of more comprehensively researched, closely related species. Polynominal regression curves were utilized to predict weed age and future weed size from weed height. These analyses can produce information to assist soybean producers in recognizing economically detrimental threshold levels of weed infestations which require the initiation of control measures.

Bioeconomic sugarbeet weed management models for preplant, postemergence, and layby herbicides, and late-season handweeding decisions are presented. The personal computer/spreadsheet models are based on number of weed seed in soil, field survey of weed populations, growth stages of weeds and sugarbeets, expected yield loss from weeds, herbicide weed control, weed control cost, and sugarbeet price. The models incorporate two producer risk levels. Several weed scenarios were used to verify the models for reasonable recommendations.

The inductive category formation framework, an influential set of theories of learning in psychology and artificial intelligence, is deeply flawed. In this framework a set of necessary and sufficient features is taken to define a category. Such definitions are not functionally justified, are not used by people, and are not inducible by a learning system. Inductive theories depend on having access to all and only relevant features, which is not only impossible but begs a key question in learning. The crucial roles of other cognitive processes (such as explanation and credit assignment) are ignored or oversimplified. Learning necessarily involves pragmatic considerations that can only be handled by complex cognitive processes.

We provide an alternative framework for learning according to which category definitions must be based on category function. The learning system invokes other cognitive processes to accomplish difficult tasks, makes inferences, analyses and decides among potential features, and specifies how and when categories are to be generated and modified. We also examine the methodological underpinnings of the two approaches and compare their motivations.

Cognitivism in psychology and philosophy is roughly the position that intelligent behavior can (only) be explained by appeal to internal “cognitive processes,” that is, rational thought in a very broad sense. Sections 1 to 5 attempt to explicate in detail the nature of the scientific enterprise that this intuition has inspired. That enterprise is distinctive in at least three ways: It relies on a style of explanation which is different from that of mathematical physics, in such a way that it is not basically concerned with quantitative equational laws; the states and processes with which it deals are “interpreted,” in the sense that they are regarded as meaningful or representational; and it is not committed to reductionism, but is open to reduction in a form different from that encountered in other sciences. Spelling these points out makes it clear that the Cognitivist study of the mind can be rigorous and empirical, despite its unprecedented theoretical form. The philosophical explication has another advantage as well: It provides a much needed framework for articulating questions about whether the Cognitivist approach is right or wrong. The last three sections take that advantage of the account, and address several such questions, pro and con.

The objective of this study was to investigate the normal distribution of cartilage thickness in the major joints of the lower limb in elderly individuals. A 12.5 MHz ultrasound transducer was used to measure the cartilage thickness in the right and left hip, knee and ankle joint of 10 individuals aged between 62 and 99 y. Distribution patterns of cartilage thickness were derived by b-spline interpolation and the average distribution computed in each surface. The maximum cartilage thickness in the hip joint was 2.6 (±0.36) mm and the mean thickness 1.3 (±0.17) mm. The CV% (a measure of thickness inhomogeneity within the joint surface) was 32%. In the knee, the maximal and mean values were 3.8 (±0.46) mm and 1.9 mm (±0.24) mm, respectively (CV%=34%), and in the ankle 1.7 (±0.25) mm and 1.0 (±0.16) mm (CV%=32%). Systematic differences existed between both sides in the knee, the distal femur showing a significantly greater thickness on the right. While the mean and maximal thicknesses were systematically higher in the knee than in the hip, and in the hip higher than in the ankle (P<0.05), there were no systematic differences in the thickness inhomogeneity of the 3 joints. Only the malleolus showed a somewhat more uniform thickness than the other joint surfaces. The variablity between individuals was similar for all joints for mean thickness, but the interindividual variability of the maximal thickness values was highest in the knee and lowest in the ankle. Whereas the cartilage thickness distributions in the joints of the lower limb have been suggested to reflect the pressure distribution within the articular surface, the absolute thickness is proposed to be a function of dynamic loading (range of motion) during gait, rather than being a reflection of the static articular pressure.

Boophilus microplus is Brazil's outstanding livestock ectoparasitic pest (annual losses, US$ 1B), affecting, to varying extents, all its States, with a national herd of some 130 M cattle. The country's 8.5 M sq km and 23,000 km of land frontier with 10 tick infested countries complicate any concepts of national campaigns. Whereas Brazil is increasingly climatically suitable for B. microplus from south (three generations annually) to central (four) to north (potentially up to five), direct problems caused are incidentally decreased due to greater use of Bos indicus cattle at lower stocking rates; five tick population survival mechanisms are suggested. Voluntary, empirical chemical tick control remains the tradition, with little government involvement. Formamidine and synthetic pyrethroid acaricides dominate the market, due to former tick resistance to arsenicals, organochlorines and organophosphates, and market forces. Plunge dips, various sprayers, and “pour-on” formulations are used; first suspicions of tick resistance to synthetic pyrethroids have been reported. Various ecologically based “improved” tick control schemes produced promising results experimentally, but require a complementary vaccine against babesiosis/anaplasmosis before wide recommendation. Intensive use of synthetic pyrethroid acaricides has created tick-borne diseases and heightened demand for a live, frozen “vaccine”, in its pre-commercialization phase in Brazil. A strategic research and development approach has been adopted for widespread improvement to cattle ticks and tick-borne disease control in Brazil.