Modelisation connexioniste de 1'apprentissage social : le cas de 1'apprentissage par observation d'une tache simple.

This article proposes a Connectionist model of the social learning theory developed by Bandura (1977). The theory posits that an individual in an interactive situation is capable of learning new behaviours merely by observing them in others. Such learning is acquired through an initial phase in which the individual memorizes what he has observed (observation phase), followed by a second phase where he puts the recorded observations to use as a guide for adjusting his own behaviour (reproduction phase). We shall refer to the two above-mentioned phases to demonstrate that it is conceivable to simulate learning by observation other than through the recording of perceived information using symbolic representation. To this end we shall rely on the formalism of ecological neuron networks to implement an agent provided with the major processes identified as essential to learning through observation. Connectionist model architecture appears valid for modeling learning through observation as defined by Bandura (1977). However, certain limitations appear during implementation, especially in terms of the observed behaviour's availability and the planning of produced behaviours that future developments are liable to counter. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Possible induction by estrous cows of pheromone production in penmates

The primary attractive odors of estrous cows apparently induced production of secondary attractive odors in penmates. Presence of both odors was reflected by the bull's olfactory behavior. The inducing effect was strongest on the day of estrus and the day before. The information content of the primary and secondary odors was different since a sexually experienced bull was able to distinguish olfactorily between estrous and nonestrous cows. The secondary odors attracted at least transient bull's interest, resulting in sniffing, urine tasting, and flehmen reactions, but not mounting attempts. The induced production of attractive odors and lack of precise smell discrimination in penmates may lead to erroneous detection of estrus in cows and heifers that show false estrous signs without corresponding changes in their reproductive organs. Similar factors may be involved in triggering mounting among feedlot steers (buller steer syndrome).     

关于节水型社会建设的几点思考

全面节约和高效利用水资源是缓解我国水资源短缺局面的根本出路。从贯彻循环经济理念，加强制度建设，形成有效的节水体系；促进节水领域的科技进步，提高水资源的利用效率；调整经济结构和产业结构，实现发展与节水的双赢等几方面提出了推动节水型社会建设和区域经济可持续发展的思路和措施。     

Characterization of and male adaptation to pheromone of femaleTrichostrongylus colubriformis (Nematoda)

Males of the ruminant nematodeTrichostrongylus colubriformis were significantly attracted to an incubate from their females during in vitro assay. Exposure of males to sera from uninfected and infected animals or selected neurotransmitters had no effect on their subsequent responsiveness to the female's pheromone. In contrast, exposure to 1500 female-hours of pheromone decreased male responsiveness after moderate rinsing prior to bioassay. Rinsing of the males with larger volumes of Tyrode's solution prior to in vitro assay increased their subsequent response to the female's pheromone. High-performance liquid chromatography yielded a presumptive pheromone peak with a fivefold increase in biological activity. This peak was soluble in alcohols and tetrahydrofuran, based on elution from reverse-phase Sep-Pak cartridges. Stability of the peak was increased by EDTA or ascorbic acid (10 mM). Storage for six weeks in ascorbic acid at 4 °C allowed recovery of 47.3% of the original material.Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products or vendors that may also be suitable.     

Considering the surround in device-independent color imaging

When viewing images, the relative luminance of the surround has a profound impact on the apparent contrast of the image. For this reason, photographic transparencies intended for projection in a darkened room are produced with an objective contrast substantially higher than that necessary for optimum reproduction as prints viewed in an illuminated surround. the dark surround causes the image elements to appear lighter and this effect is stronger for darker colors resulting in a loss in perceived contrast. This effect is also of great importance in deviceindependent color imaging since resultant images might be observed in a wide variety of media and viewing conditions. Research on psychophysical scaling of brightness and lightness and the effects of background and surround relative luminance on lightness and chroma is reviewed. the importance of this research for device-independent color imaging systems is described along with the prediction of these effects using the RLAB color-appearance model. Finally, experiments testing the use of RLAB and other color-appearance models in cross-media color reproduction applications are described.     

Effect of grazing and fat supplementation on production and reproduction of Holstein cows

The objective of this trial was to investigate the effects of feeding a soybean oil refining by-product (SORB), made up mainly of sodium salts of long-chain fatty acids, on reproductive performance and productivity of 36 early lactation Holstein cows managed in a free-stall barn or on annual rye-ryegrass pasture. In this 2 × 2 factorial arrangement of treatments, cows consumed 0 or 0.5 kg/d of SORB as part of a total mixed ration for barn cows or as part of a grain supplement fed to cows on intensively, rotationally stocked pasture. Blood was sampled 3 times weekly and plasma was measured for progesterone to assess ovarian activity. Estrus activity was recorded using the HeatWatch estrus detection system. Although average 14-wk milk production (37.2 kg/d) was not different among treatments, barn cows had more persistent lactations than did grazing cows. Cows housed in the barn lost less body weight and returned to initial body weight sooner and had lower mean concentrations of plasma nonesterified fatty acids (464 vs. 261 mEq/L) than those managed on pasture. The milk fat of cows on pasture contained greater proportions of conjugated linoleic acid and linolenic acid but a corresponding 0.22 percentage unit decrease in milk fat concentration (3.39 vs. 3.16%). Cows managed on pasture had greater peak concentrations of plasma progesterone during the first estrous cycle. Cows managed on pasture and fed SORB had the greatest accumulation of plasma progesterone over the 14 wk of the study (SORB × housing interaction). These cows experienced the most mounts during their first estrus (9.3) and pregnancy rate was also greatest for this treatment (62.5%). Feeding SORB did not affect production of milk, fat, or protein. Loss of body condition was less in cows fed SORB. Ruminal fluid concentration of propionate increased and ruminal pH decreased in cows fed SORB. A lower proportion of fatty acids less than 18 carbons in length was found in the milk fat of cows fed SORB, thus indicating lower de novo synthesis of fatty acids. Higher proportions of C18:2n-6 and conjugated C18:2 were found in the milk fat of cows fed SORB. Based on concentrations of plasma progesterone, cows fed SORB experienced their first ovulation earlier (26.7 vs. 42.4 d postpartum) than did cows not supplemented with SORB. Neither housing system nor SORB supplementation influenced detection of first estrus (50.5 d) or the mean length of each estrus period (447 min).     

A spreadsheet-based model demonstrating the nonuniform economic effects of varying reproductive performance in Ohio dairy herds

A spreadsheet-based model was developed to estimate the economic effect of varying reproductive performance in dairy herds. Scenarios were created to model an average cow with respect to production, herd lifetime, and reproductive events. Average milk yield per day of life as well as lifetime calf and replacement heifer production were examined. Additional inputs representing milk, feed, semen, calf, and salvage prices were used to calculate net cash flow for each day of herd life for the average cow in a scenario. Economic comparison of different scenarios was accomplished using an equivalent annual cash flow (annuity) methodology.Herd performance measures and prices representative of Ohio dairy herds were used to establish a baseline average cow that had a 160-d calving-to-conception interval [days open (DO)]. Alternative scenarios that differed from baseline in DO, annual culling rate, and feed and milk prices were created to characterize the effects of changes. Under scenario inputs representative of typical Ohio dairy herds, the model indicated that a lower annual culling rate (25%) was preferable to higher annual culling rates (34 or 45%). The model estimated maximum average milk yield per day of life to occur at 110 DO. At 34% annual culling rate, calves and replacement heifers produced per lifetime declined as DO increased; beyond 150 DO, the modeled cow produced less than 1 replacement heifer per lifetime. The model also estimated a loss of $1.37 per cow per year for a 1-d increase in DO beyond 160 d. At 20% higher feed and milk prices, the model estimated a loss of $1.52 per cow per year; at 20% lower feed and milk prices, the model estimated a loss of $1.23 per cow per year. Furthermore, the model suggested that the loss associated with a 1-d increase in DO changed as DO changed. Using baseline inputs, the model calculated losses for a 1-d increase of $0.44 per cow per year at 130 DO and $1.71 per cow per year at 190 DO. The nonuniform nature of the cost of additional DO is important to veterinarians and producers. The implication is that inefficient reproduction becomes marginally more costly to producers as performance declines and warrants increased attention. Conversely, marginal benefits of improved reproduction decrease as performance improves. Herds with strong reproductive performance have less opportunity to capture economic benefits of improvement.     

Effects of an acute feed restriction at the onset of the seasonal breeding period on reproductive performance and milk production in pasture-grazed dairy cows

Reproduction and milk production responses were compared between dairy cows offered a high (HPA; n = 453 in 4 replicates) or low (LPA; n = 317 in 3 replicates) pasture allowance for the first 14 d after the planned start of mating (d 0 of experiment) in 2 seasonal, pasture-based dairy herds. Estimated pasture dry matter intake (DMI) between d −1 and 13 were 14.3 ± 2.8 and 8.0 ± 1.7 kg of DM/cow per day for HPA and LPA cows, respectively. The LPA cows produced 22% less energy-corrected milk during the 14-d feeding treatment period, and milk yield remained less in LPA cows at d 53 despite all cows receiving pasture allowances to support DMI of 16 kg of dry matter/cow per day from d 14 onwards. The 3-wk submission rate (percentage of cows inseminated at least once from d 0 to 20) and the 3- and 6-wk pregnancy rates of LPA cows (88, 45, and 71%, respectively) were lower than those of HPA cows (94, 53, and 78%, respectively), but conception rates to first (50%) or second (47%) service and final pregnancy rates (93%) did not differ between treatments. These results quantify the immediate and subsequent responses in reproductive performance and milk production to a severe restriction in DMI at the onset of a seasonal breeding period in pasture-grazed dairy cows.     

Polymorphisms in the bovine lactoferrin promoter are associated with reproductive performance and somatic cell count

Lactoferrin plays an important role in the innate immune system, with well-characterized antibacterial, antiviral, and immune modulatory properties. The objective of this study was to determine the allele and haplotype frequency of polymorphisms at positions −586, −190, and −28 of the bovine lactoferrin promoter in Holstein-Friesians and to quantify their association with performance using phenotypic data on progeny from 848 sires. Associations between genotypes and performance were quantified using weighted mixed models with genotyped individuals included as a random effect, and average expected relationships among individuals accounted for through a numerator relationship matrix. The dependent variables were daughter yield deviation for production traits and deregressed predicted transmitting ability for calving interval and functional survival. The C to T polymorphism at −586, which distorts a putative activating protein 2 (AP-2) binding site, was associated with a shorter calving interval and higher somatic cell score. The G to A polymorphism at −190, located in a putative selective promoter factor 1 (SP-1) binding site, was associated with a longer calving interval and decreased functional survival. A third polymorphism (A to C) at position −28, found within the noncanonical TATA box, had a tendency to associate with functional survival. On the basis of the data we proposed a haplotype combination that was associated with improved reproductive performance in the Holstein-Friesian breed. We hypothesized that the observable phenotypic associations with lactoferrin promoter polymorphisms can potentially be explained by allele-specific differences in constitutive or inducible levels of gene expression. The lack of a pleiotropic effect of the single nucleotide polymorphisms studied on both fertility and milk production traits strengthens the importance of these polymorphisms, or at least the lactoferrin promoter, in selection for improved fertility.     

Toxicological and ecotoxic impact of secondary and tertiary treated sewage effluents

Secondary sewage effluents are discharged in significant quantities in aquatic environments delivering pollutants that were not removed during treatment; yet advanced treated effluents are not lacking of contaminants. In this study, biochemical biomarkers were measured in liver and kidney of rainbow trout (Oncorynchus mykiss) exposed to unchlorinated, chlorinated and tertiary treated secondary sewage effluents. In addition, organic matter, nitrogen and suspended solids were assayed, while a common bioassay, Daphnia magna 21d reproduction test was also applied in order to examine potential relation between the performed bioassay and the biomarkers. Processes using oxidative conditions, such as ozonation and chlorination, resulted in significantly increased breeding rate (up to 74%) of the organism. Biomarkers measurements incorporated the determination of total glutathione (GSH), glutathione S-transferases (GST), glutathione peroxidase (GPX), lipid peroxidation (LPO) and an innovative biomarker in such applications, haem peroxidase. In general, the response of biomarkers was dependent upon the treatment method and it was tissue specific. Secondary effluents inhibited liver GST and haem peroxidase, while GSH levels and LPO were significantly provoked in liver. Ozonation provoked hepatic peroxidation, in terms of haem peroxidase and LPO, and GST; while the protective (to Reactive Oxidant Species – ROS) GSH was depleted, suggesting extended ROS attack to the organism. Similar response of biomarkers (but to a lesser extend) was observed after exposure of trout to effluents submitted to both coagulation and ozonation, emphasizing the significance of removing the residual organic matter by other methods than oxidative ones. Ozonation also enhanced renal LPO and GPX; however the former employment of coagulation limited the peroxidation phenomena. Chlorination mainly affected the levels of total GSH in both tissues.