Psychological distance to reward in monkeys

A concurrent-chains schedule was employed to examine crab-eating macaques' choice between segmented and unsegmented fixed-interval 30-s schedules. A stimulus change occurred during one of the fixed-interval schedules (segmented schedule), while no stimulus change occurred during the other (unsegmented schedule). The subjects were exposed to three consecutive stimulus-change conditions, in an attempt to explore whether correlation of the stimulus changes with a fixed interval of nonreinforcement affects the preference between the alternatives. When the stimulus change always occurred at a half point of the segmented schedule (the first and third conditions), all subjects preferred the fixed-interval schedule without stimulus changes. This replicated previous findings with pigeons and humans. On the other hand, when the intervals before and after the stimulus change varied on every entry to the segmented schedule with the sum of them being constant (the second condition), the subjects were indifferent to the alternatives. These results are consistent with the view that the preference for unsegmented schedules over segmented ones might be due to aversiveness which the initial component in the segmented schedule possesses as a result of its correlation with a fixed interval of nonreinforcement.     

A subject-specific finite element musculoskeletal framework for mechanics analysis of a total knee replacement

Concurrent use of finite element (FE) and musculoskeletal (MS) modeling techniques is capable of considering the interactions between prosthetic mechanics and subject dynamics after a total knee replacement (TKR) surgery is performed. However, it still has not been performed in terms of favorable prediction accuracy and systematic experimental validation. In this study, we presented a methodology to develop a subject-specific FE-MS model of a human right lower extremity including the interactions among the subject-specific MS model, the knee joint model with ligament bundles, and the deformable FE prosthesis model. In order to evaluate its accuracy, the FE-MS model was compared with a traditional hinge-constraint MS model and experimentally verified over a gait cycle. Both models achieved good temporal agreement between the predicted muscle force and the electromyography results, though the magnitude on models is different. A higher predicted accuracy, quantified by the root-mean-square error (RMSE) and the squared Pearson correlation coefficient (r²), was found in the FE-MS model (RMSE = 177.2 N, r² = 0.90) when compared with the MS model (RMSE = 224.1 N, r² = 0.81) on the total tibiofemoral contact force. The contact mechanics, including the contact area, pressure, and stress were synchronously simulated, and the maximum contact pressure, 22.06 MPa, occurred on the medial side of the tibial insert without exceeding the yield strength of the ultra-high-molecular-weight polyethylene, 24.79 MPa. The approach outlines an accurate knee joint biomechanics analysis and provides an effective method of applying individualized prosthesis design and verification in TKR.     

猪繁殖与呼吸综合征与伪狂犬病混合感染的分子生物学快速诊断

猪繁殖与呼吸综合征自1987年发现至今,已在世界大多数养猪国家和地区普遍存在[1,2].而伪狂犬病作为仅次于口蹄疫、猪瘟的危害养猪业的重要疫病,一直引起人们的高度重视[3,4].     

Effect of artemether administered alone or in combination with praziquantel to mice infected with Plasmodium berghei or Schistosoma mansoni or both

The artemisinins have become key drugs for the treatment and control of malaria, particularly within artemisinin-based combination therapies. Since the artemisinins also exhibit antischistosomal properties, their use in areas where malaria and schistosomiasis are co-endemic may have an effect on both diseases and co-infection might alter drug efficacy. We assessed the antimalarial and antischistosomal efficacies of artemether in mice infected with Plasmodium berghei or Schistosoma mansoni or both parasites concurrently. Three oral doses of 400 mg/kg artemether at 14-day intervals reduced total and female S. mansoni worm burdens by 98.7-100%, regardless of a concurrent P. berghei infection. When four daily doses of 55 mg/kg artemether were administered, which is a standard treatment schedule to cure P. berghei-infected mice, significantly lower total and female S. mansoni worm burden reductions were observed (73.1-89.2%). Artemether, administered at both of the above-mentioned treatment schemes, showed excellent antimalarial efficacy with no indications of delayed clearance of P. berghei or recrudescence, also in mice co-infected with S. mansoni. Co-infection with P. berghei had no effect on S. mansoni worm burden reductions following artemether-praziquantel combinations. Our findings point to the need for epidemiological studies in areas where malaria and schistosomiasis co-exist and where artemisinin-based combination therapies are introduced, since artemisinin-based combination therapies as part of a malaria control package may have ancillary benefits against schistosomiasis.     

Effects of initial-link duration on preference and resistance to change in concurrent-chains schedules

Previous studies with concurrent-chains procedures have shown that preference for a terminal-link signaling a higher reinforcement rate decreases as initial-link durations increase. Using a concurrent-chains procedure, the present experiment examined the effects of manipulating initial-link duration on preference and resistance to disruption with rats nose poking for different rates of food reinforcement in the terminal links. Consistent with previous findings, preference for a terminal link with a higher reinforcement rate decreased with longer initial links. Conversely, relative resistance to disruption in the terminal link with a higher reinforcement rate increased with longer initial links. These findings are counter to the prediction of behavioral momentum theory that preference and resistance to change should be positively related.     

Some effects of procedural variables on operant choice behavior

Procedural variables are concerned with the way subjects contact stimulus, response, and reinforcer variables and relations in an experiment. Procedural variables may therefore be understood as tools that allow researchers and theorists to explore the generality of their conceptions of independent variables, behavioral processes, and quantitative laws of behavior. The present article reviews data from several studies showing how procedural variables can influence the outcome of operant choice experiments, even when nominal independent variables remain constant. An important theoretical issue raised by these data is whether researchers have most usefully identified the independent variables that they incorporate into their quantitative models. Particular attention is paid to how procedural variables can influence the measure of reinforcement frequency over time that best correlates with the distribution of choice responding over time.     

Concurrent application of ethyl formate and 1‐methylcyclopropene to control Tetranychus urticae on exported sweet persimmons (Diospyros kaki Thunb. ‘Fuyu’)

Extending the shelf life of fruits during post‐harvest storage and eradicating pests associated with quarantine issues could together comprise the key steps toward expanding the exportation of sweet persimmon in South Korea. Here we firstly investigated the concurrent application of ethyl formate (EF), a methyl bromide alternative fumigant, which is currently considered a beneficial and safe fumigant in quarantine use, and 1‐methylcyclopropene (1‐MCP), an anti‐ethylene compound that is broadly used in post‐harvest systems, on sweet persimmon. We also suggest the proper fumigation methods to be follow when using these compounds. Tetranychus urticae, an important quarantine pest, was inoculated under the calyx of sweet persimmon, and the fruits were then fumigated using 35.0 mg L^?1 of EF for 6 h before and after treating with 1.0 μL L^?1 of 1‐methylcyclopropene for 24 h under storage conditions of 5°C. Our results showed that concurrent treatments with 1‐MCP and EF could be suitable for commercial purposes by extending shelf life, delaying color changes and softening, and offering complete control of the target pest, Tetranychus urticae.     

Human choice among five alternatives when reinforcers decay

Human participants played a computer game in which choices among five alternatives were concurrently reinforced according to dependent random-ratio schedules. "Dependent" indicates that choices to any of the wedges activated the random-number generators governing reinforcers on all five alternatives. Two conditions were compared. In the hold condition, once scheduled, a reinforcer - worth a constant five points - remained available until it was collected. In the decay condition, point values decreased with intervening responses, i.e., rapid collection was differentially reinforced. Slopes of matching functions were higher in the decay than hold condition. However inter-subject variability was high in both conditions.     

The stay/switch model describes choice among magnitudes of reinforcers

The stay/switch model is an alternative to the generalized matching law for describing choice in concurrent procedures. The purpose of the present experiment was to extend this model to choice among magnitudes of reinforcers. Rats were exposed to conditions in which the magnitude of reinforcers (number of food pellets) varied for staying at alternative 1, switching from alternative 1, staying at alternative 2 and switching from alternative 2. A changeover delay was not used. The results showed that the stay/switch model provided a good account of the data overall, and deviations from fits of the generalized matching law to response allocation data were in the direction predicted by the stay/switch model. In addition, comparisons among specific conditions suggested that varying the ratio of obtained reinforcers, as in the generalized matching law, was not necessary to change the response and time allocations. Other comparisons suggested that varying the ratio of obtained reinforcers was not sufficient to change response allocation. Taken together these results provide additional support for the stay/switch model of concurrent choice.