Home About us Contact
|
Home About us Contact | ||
|
|
||
First Experiment (first + experiment)
Selected AbstractsINLINE RADIOFREQUENCY ABLATION-ASSISTED LAPAROSCOPIC LIVER RESECTION: FIRST EXPERIMENT WITH STAPLING DEVICEANZ JOURNAL OF SURGERY, Issue 6 2007Peng Yao Background: In liver surgery, the increase in advancement of laparoscopic equipment has allowed the feasibility and safety of complex laparoscopic liver resection. However, blood loss and the potential risk of gas embolism seem to be the main obstacles. In this study, we successfully used the InLine radiofrquency ablation (RFA) device to carry out laparoscopic hand-assisted liver resection in pigs. Methods: Under general anaesthesia with tracheal intubation, pigs underwent InLine RFA-assisted laparoscopic liver resection. After installation of Hand Port and trocars, the InLine RFA device was introduced through Hand Port system and inserted into the premarked resection line. Then the generator was turned on and the power was applied according to the power setting. The resection was finally carried out using diathermy or stapler. For the control group, resection was simply carried out by diathermy or stapler. Results: Eight Landrace pigs underwent 23 liver resections. Blood loss was reduced significantly in the InLine group (P < 0.001) when compared with control group in both surgical methods (diathermy and stapler). Conclusion: In this study, we successfully carried out InLine RFA-assisted laparoscopic liver resection in both stapled and diathermy group. We showed that there was a highly significant difference between InLine and other liver resection techniques laparoscopically. [source] Synthesis of Enantiopure Tricarbonyl(indan-1,2-dione)chromiumEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 24 2005Dirk Leinweber Abstract A multistep synthesis of the planar chiral tricarbonyl(,6 -indan-1,2-dione)chromium, based on acetal protection of the keto groups, is presented. Since common deacetalization procedures failed, an oxidative deprotection with triphenylcarbenium tetrafluoroborate was used. Tricarbonyl(,6 -indan-1,2-dione)chromium is regarded as a potential precursor for dianionic oxy-Cope rearrangements upon alkenyllithium diaddition. As an unexpected side product in the synthesis, an indan-1,2-dione complex with a triphenylmethyl substituent at C-3 was obtained. Attempts directed towards the formation of enantiomerically pure material include the first reported investigation into an enantioselective ketone reduction with two methoxy substituents present in the , position. Although enantiomeric excesses of up to 84.5,% were achieved, the chemical yields decreased with increasing ee. A classical resolution was therefore undertaken, giving access to the enantiomerically pure title compound (99.4,% ee). The absolute configuration was verified by an X-ray structure analysis of an intermediate. First experiments concerning the alkenyllithium addition showed that a single addition is possible while a second one does not occur, presumably due to enolate formation. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] First experiments on diffraction-enhanced imaging at LNLSJOURNAL OF SYNCHROTRON RADIATION, Issue 6 2003C. Giles Diffraction-enhanced images have been obtained using two silicon crystals in a non-dispersive set-up at the XRD2 beamline at the Brazilian Synchrotron Light Laboratory (LNLS). A first asymmetrically cut silicon crystal using the (333) reflection vertically expanded the monochromated beam from 1,mm to 20,mm allowing the imaging of the whole sample without movements. A symmetrically cut Si(333) second crystal was used as a Bragg analyzer. Images of biological samples including human tissue were recorded using a direct-conversion CCD detector resulting in enhancement of the contrast compared with absorption-contrast images. [source] Experimental investigation of transient and thermal effects on lubricated non-conformal contactsLUBRICATION SCIENCE, Issue 4 2007R. Bassani Abstract In this work, thermal and transient effects on non-conformal lubricated contacts are investigated through experimental analyses. Experiments between a ball and a plane surface of a disc are described. Friction coefficients and film thicknesses are measured (the film thickness only for the glass-on-steel contact). A paraffin base mineral oil is used as a lubricant. First experiments are carried out under steady-state conditions. To include effects due to different thermal properties of contacting materials, a steel-on-steel and a glass-on-steel contact with different slide-to-roll ratios are tested. If the contacting materials have different thermal properties, as in the case of a glass-on-steel contact, thermal effects like the temperature,viscosity wedge action could clearly be shown. It is found that the friction coefficients are influenced by the slide-to-roll ratio and the thermal properties of the contacting materials. Under transient conditions, the entraining velocity is varied with a sinusoidal law. Squeeze effects explain ,loops' of friction and film thickness found also in previous works. The formation of friction loops is related to the measured film thickness differences. However, also under non-steady-state conditions, thermal effects, like the temperature,viscosity wedge action, influence the friction coefficients. Copyright © 2007 John Wiley & Sons, Ltd. [source] Supported Membranes with Well-Defined Polymer Tethers,Incorporation of Cell ReceptorsCHEMPHYSCHEM, Issue 3 2004Oliver Purrucker Abstract We report the design of supported lipid membranes attached to the surface by tailored lipopolymer tethers. A series of well-defined lipopolymers were synthesized by means of living cationic polymerization of 2-methyl-2-oxazolines. The polymers were equipped with a silane coupling group on the proximal, and lipid anchors on the distal chain ends. The length of the intermediate hydrophilic polymer tether was varied (n=14, 18, 33) to change the distance between the membrane and the substrate. Supported membranes have been prepared in two-steps. First, a suitable lipopolymer/lipid mixture was deposited by Langmuir,Blodgett transfer, and annealed to establish the covalent coupling to the surface. On the dry lipopolymer/lipid monolayer, the upper leaflet was deposited by vesicle fusion. Optimization of both preparation steps resulted in the formation of stable and defect-free membranes. Impacts of the spacer length and the lipopolymer fraction upon the lateral diffusivity of the lipids were systematically compared by fluorescence recovery after photobleaching (FRAP). First experiments on the incorporation of a large transmembrane cell receptor (integrin ,IIb,3) into the polymer-tethered membrane suggested that the length of the polymer tether plays a crucial role in distribution of the proteins on the surface. [source] Social context affects testosterone-induced singing and the volume of song control nuclei in male canaries (Serinus canaria)DEVELOPMENTAL NEUROBIOLOGY, Issue 10 2006Géraldine Boseret Abstract The contribution of social factors to seasonal plasticity in singing behavior and forebrain nuclei controlling song, and their interplay with gonadal steroid hormones are still poorly understood. In many songbird species, testosterone (T) enhances singing behavior but elevated plasma T concentrations are not absolutely required for singing to occur. Singing is generally produced either to defend a territory or to attract a mate and it is therefore not surprising that singing rate can be influenced by the sex and behavior of the social partner. We investigated, based on two independent experiments, the effect of the presence of a male or female partner on the rate of song produced by male canaries. In the first experiment, song rate was measured in dyads composed of one male and one female (M-F) or two males (M-M). Birds were implanted with T-filled Silastic capsules or with empty capsules as control. The number of complete song bouts produced by all males was recorded during 240 min on week 1, 2, 4, and 8 after implantation. On the day following each recording session, brains from approximately one-fourth of the birds were collected and the volumes of the song control nuclei HVC and RA were measured. T increased the singing rate and volume of HVC and RA but these effects were affected by the social context. Singing rates were higher in the M-M than in the M-F dyads. Also, in the M-M dyads a dominance-subordination relationship soon became established and dominant males sang at higher rates than subordinates in T-treated but not in control pairs. The differences in song production were not reflected in the size of the song control nuclei: HVC was larger in M-F than in M-M males and within the M-M dyads, no difference in HVC or RA size could be detected between dominant and subordinate males. At the individual level, the song rate with was positively correlated with RA and to a lower degree HVC volume, but this relationship was observed only in M-M dyads, specifically in dominant males. A second experiment, carried out with castrated males that were all treated with T and exposed either to another T-treated castrate or to an estradiol-implanted female, confirmed that song rate was higher in the M-M than in the M-F condition and that HVC volume was larger in heterosexual than in same-sex dyads. The effects of T on singing rate and on the volume of the song control nuclei are thus modulated by the social environment, including the presence/absence of a potential mate and dominance status among males. 2006 Wiley Periodicals, Inc. J Neurobiol, 2006 [source] Twenty-two-month-olds discriminate fluent from disfluent adult-directed speechDEVELOPMENTAL SCIENCE, Issue 5 2007Melanie Soderstrom Deviation of real speech from grammatical ideals due to disfluency and other speech errors presents potentially serious problems for the language learner. While infants may initially benefit from attending primarily or solely to infant-directed speech, which contains few grammatical errors, older infants may listen more to adult-directed speech. In a first experiment, Post-verbal infants preferred fluent speech to disfluent speech, while Pre-verbal infants showed no preference. In a second experiment, Post-verbal infants discriminated disfluent and fluent speech even when lexical information was removed, showing that they make use of prosodic properties of the speech stream to detect disfluency. Because disfluencies are highly correlated with grammatical errors, this sensitivity provides infants with a means of filtering ungrammaticality from their input. [source] Selective glucocorticoid receptor (type II) antagonist prevents and reverses olanzapine-induced weight gainDIABETES OBESITY & METABOLISM, Issue 6 2010J. K. Belanoff Use of antipsychotic medications has been associated consistently with weight gain and metabolic disturbances, and a subsequent increased risk for diabetes and cardiovascular disease. Two experiments tested whether CORT 108297, a newly identified selective glucocorticoid antagonist could (i) reduce and (ii) prevent olanzapine-induced weight gain in rats. In the first experiment, rats dosed only with olanzapine gained a statistically significant amount of weight. When vehicle was added to their olanzapine dose, they continued to gain weight; when CORT 108297 was added to their regimen, they lost a significant amount of weight. Rats administered CORT 108297 plus olanzapine had significantly less abdominal fat than those who received olanzapine alone. In the second experiment, rats receiving olanzapine plus CORT 108297 gained significantly less weight than rats receiving only olanzapine. Increasing doses of CORT 108297 were associated with less weight gain. [source] Dropping behaviour of larvae of aphidophagous ladybirds and its effects on incidence of intraguild predation: interactions between the intraguild prey, Adalia bipunctata (L.) and Coccinella septempunctata (L.), and the intraguild predator, Harmonia axyridis PallasECOLOGICAL ENTOMOLOGY, Issue 2 2005Satoru Sato Abstract., 1.,Two experiments were performed in the laboratory to assess the behaviour of dropping from a host plant as a defence against intraguild predation in aphidophagous ladybird larvae. 2.,In the first experiment, encounters were observed on bean plants between fourth instars of the intraguild predator species, Harmonia axyridis, and first instars of two other ladybird species, Adalia bipunctata (L.) and Coccinella septempunctata (L.). The percentages of first instars of the latter two species that dropped from the plant in response to attack differed dramatically, with 47.5% of C. septempunctata first instars dropping vs. 0% of A. bipunctata. 3.,In the second experiment, first instars of A. bipunctata or C. septempunctata and a fourth instar of H. axyridis were allowed to forage together on bean plants for 3 h. During this time, 44.3% of C. septempunctata larvae dropped from the plant, but less than 2% of A. bipunctata larvae did so. In contrast, 95.0% of A. bipunctata larvae fell victim to intraguild predation by H. axyridis vs. only 54.5% of C. septempunctata larvae. 4.,The significance of dropping behaviour of ladybird larvae as a defence against intraguild predation, and the relationship of dropping behaviour to species-specific habitat affinity of ladybirds, is discussed. [source] Behavioural changes in Schistocerca gregaria following infection with a fungal pathogen: implications for susceptibility to predationECOLOGICAL ENTOMOLOGY, Issue 3 2001Steven Arthurs Summary 1. Field observations have indicated that infection of locusts and grasshoppers by the fungal entomopathogen Metarhizium anisopliae var. acridum may result in a substantial increase in the host's susceptibility to predation, before death is caused directly by the disease. 2. Laboratory experiments were conducted to examine how the behaviour of the desert locust Schistocerca gregaria Forskål changes following infection by M. anisopliae var. acridum to explore some potential mechanisms underlying this phenomenon. 3. In the first experiment, which involved monitoring general locust activity in small cages throughout the disease incubation period, infected locusts were observed to increase locomotion and bodily movement from 3 days after infection until death (average survival time of 11 days). There was some evidence of reduced feeding and mating behaviour following infection. 4. In a second experiment, locusts were exposed individually to a simulated predator attack and the initiation and strength of any escape responses were measured. Infected locusts were observed to have a reduced escape capability (both the propensity to escape and the strength of the response). In contrast to the relatively early changes in general activity observed in the first experiment, this was only apparent at the late stages of infection shortly before death. 5. Both an increase in movement and general apparency early in the infection process, and reduced escape capability late on, suggest mechanisms whereby the susceptibility of locusts and grasshoppers to predation might be enhanced following infection with M. anisopliae var. acridum. [source] Vulnerability of larvae of two species of aphidophagous ladybirds, Adalia bipunctata Linnaeus and Harmonia axyridis Pallas, to cannibalism and intraguild predationENTOMOLOGICAL SCIENCE, Issue 2 2009Satoru SATO Abstract Vulnerability of larvae of two species of aphidophagous ladybirds, Adalia bipunctata Linnaeus and Harmonia axyridis Pallas, to cannibalism and intraguild predation was assessed in the laboratory. In the first experiment, a first instar of one of the two above species was kept with a fourth instar of the other species in a Petri dish. The number of times each first instar larva was encountered by the fourth instar larva and the fate of the first instar was determined over a period of 10 min. The fourth instar larvae captured and killed all the first instar larvae of their own species at the first encounter. However, when presented with fourth instar larvae of the other species the first instar larvae of A. bipunctata and H. axyridis were encountered 6.4 ± 1.3 (n = 10) and 19.4 ± 2.1 (n = 10), respectively. In this experiment no first instar larvae of H. axyridis, whereas all those of A. bipunctata, were killed. [source] Effects of 17 ,-estradiol exposure on Xenopus laevis gonadal histopathologyENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2010Jeffrey C. Wolf Abstract The natural estrogen 17 ,-estradiol (E2) is a potential environmental contaminant commonly employed as a positive control substance in bioassays involving estrogenic effects. The aquatic anuran Xenopus laevis is a frequent subject of reproductive endocrine disruptor research; however, histopathological investigations have tended to be less than comprehensive. Consequently, a study was designed to characterize gross and microscopic changes in the gonads of X. laevis as a result of E2 exposure. Additional goals of this study, which consisted of three separate experiments, included the standardization of diagnostic terminology and criteria, the validation of statistical methodology, and the establishment of a half maximal effective concentration (EC50) for E2 as defined by an approximately 50% conversion of presumptive genotypic males to phenotypic females. In the first experiment, frogs were exposed to nominal concentrations of 0, 0.2, 1.5, or 6.0,µg/L E2. From these experimental results and those of a subsequent range finding trial, the EC50 for E2 was determined to be approximately 0.2,µg/L. This E2 concentration was utilized in the other two experiments, which were performed at different facilities to confirm the reproducibility of results. Experiments were conducted according to Good Laboratory Practice guidelines, and the histopathologic evaluations were peer reviewed by an independent pathologist. Among the three trials, the histopathological findings that were strongly associated with E2-exposure (p,<,0.001 to 0.0001) included an increase in the proportion of phenotypic females, mixed sex, dilated testis tubules, dividing gonocytes in the testis, and dilated ovarian cavities in phenotypic ovaries. A comparison of the gross and microscopic evaluations suggested that some morphologic changes in the gonads may potentially be missed if studies rely entirely on macroscopic assessment. Environ. Toxicol. Chem. 2010;29:1091,1105. © 2010 SETAC [source] Metamorphic inhibition of Xenopus laevis by sodium perchlorate: Effects on development and thyroid histologyENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2005Joseph E. Tietge Abstract The perchlorate anion inhibits thyroid hormone (TH) synthesis via inhibition of the sodium-iodide symporter. It is, therefore, a good model chemical to aid in the development of a bioassay to screen chemicals for affects on thyroid function. Xenopus laevis larvae were exposed to sodium perchlorate during metamorphosis, a period of TH-dependent development, in two experiments. In the first experiment, stage 51 and 54 larvae were exposed for 14 d to 16, 63, 250, 1,000, and 4,000 ,g perchlorate/L. In the second experiment, stage 51 larvae were exposed throughout metamorphosis to 8, 16, 32, 63, and 125 ,g perchlorate/L. Metamorphic development and thyroid histology were the primary endpoints examined. Metamorphosis was retarded significantly in the first study at concentrations of 250 ,g/L and higher, but histological effects were observed at 16 ,g/L. In the second study, metamorphosis was delayed by 125 ,g/L and thyroid size was increased significantly at 63 ,g/L. These studies demonstrate that inhibition of metamorphosis readily can be detected using an abbreviated protocol. However, thyroid gland effects occur at concentrations below those required to elicit developmental delay, demonstrating the sensitivity of this endpoint and suggesting that thyroidal compensation is sufficient to promote normal development until perchlorate reaches critical concentrations. [source] Conspecifics and Their Posture Influence Site Choice and Oviposition in the Damselfly Argia moestaETHOLOGY, Issue 8 2009Catherine J. Byers Finding a suitable oviposition site can be costly because of energy and time requirements, and ovipositioning can be dangerous because of the risk of predation and harassment by males. The damselfly Argia moesta oviposits, contact-guarded by her mate, on vegetation in streams. Oviposition aggregations are commonly observed in this species, despite their territorial nature during other behaviors. We conducted experiments in the field to test the hypothesis that aggregations are the result of conspecific attraction. In the first experiment, two oviposition sites (sycamore leaves) were provided, one with models of ovipositing pairs, and one without. In the second experiment, one leaf again had ovipositing models, while the other had models of uncoupled males and females in a resting posture. In both experiments, damselfly pairs preferred the site with ovipositing models. In general, they visited the ovipositing models first more often than expected by chance, stayed longer there, were more likely to oviposit there, and laid a greater total number of eggs there. These results support the hypothesis that conspecific attraction is responsible for ovipositing aggregations in A. moesta and that posture is an important cue for attraction. Using conspecific cues could be a beneficial strategy to save in search costs while taking advantage of the presence of ovipositing conspecifics to dilute the effects of harassment and predation. [source] Effects of Male Vocal Learning on Female Behavior in the Budgerigar, Melopsittacus undulatusETHOLOGY, Issue 10 2005Arla G. Hile Parrots are unusual among birds and animals in general in the extent of their ability to learn new vocalizations throughout life and irrespective of season. The budgerigar (Melopsittacus undulatus), a small parrot that is well suited for laboratory studies, has been the subject of numerous studies investigating the neurobiology of vocal learning. To date, few studies have focused on the function of vocal imitation by parrots. Previous work from our research group has shown that vocal imitation in budgerigars is sex-biased, as males paired with females learn vocalizations from their new mates, but not vice versa. This bias led us to hypothesize that vocal learning has a reproductive function. To test this hypothesis, we conducted two experiments. In the first experiment, we tutored males so that they could produce a call similar to one shared by a group of experimental females. The experimental females were then presented with one of the tutored males and another, equally unfamiliar, male that had not been tutored. We found that the females spent a greater proportion of time in proximity of, and made more affiliative displays toward, the tutored males. In the second experiment, seven males received small bilateral brain lesions that disrupt vocal learning. These males and an equal number of control males were then released into an aviary containing females and reproductive resources. We found that lesioned and control males were equally successful in obtaining social mates, but females mated to lesioned males were more likely to engage in extra-pair activities. These experiments indicate that a male's ability to imitate a female's call can influence the sexual behavior of the female even though lack of imitation ability does not appear to influence social pairing. We hypothesize that mate choice in budgerigars has multiple stages. Upon meeting a strange male, a female quickly assesses its ability for social acquisition of calls by the presence or absence of a call type similar to its own in its repertoire. As courtship proceeds into pair formation, the female assesses the ability of male to learn more directly by the extent of the male's perfection of imitation. [source] Fruit Colour Preferences of Redwings (Turdus iliacus): Experiments with Hand-Raised Juveniles and Wild-Caught AdultsETHOLOGY, Issue 6 2004Johanna Honkavaara Certain fruit colours and their contrast with the background coloration are suggested to attract frugivorous birds. To test the attractiveness of different colours, we performed three experiments in laboratory with controlled light conditions. In the first two experiments, we studied the fruit colour preferences of naive juvenile redwings. In the third experiment, we continued to investigate whether the contrast of the fruit colour with the background coloration affects the preference of both naive juveniles and experienced adult redwings. In the first experiment, juvenile birds preferred black, UV-blue and red berries, to white ones. In pairwise trials, a new set of juveniles still preferred red berries to white ones. When testing the effect of contrasts on their choice, juveniles preferred UV-blue berries to red ones on a UV-blue background. However, no preference was found, when the background was either red or green. Adult redwings preferred UV-blue berries to red ones on all backgrounds. According to these results, juveniles seem to have an innate avoidance of white berries. Furthermore, the foraging decisions of fruit-eating birds are affected more by fruit colour than its contrast with background coloration, at least when contrasting displays are encountered from relatively short distances. Differences in preferences of adult and juvenile birds also indicate that learning seems to play a role in fruit choices. [source] Parasitized Salamanders are Inferior Competitors for Territories and Food ResourcesETHOLOGY, Issue 4 2000Daria S. Maksimowich Parasites have been shown to impair the behaviour of their hosts, compromising the host's ability to exploit and compete for resources. We conducted two experiments to determine whether infestation with an ectoparasitic mite (Hannemania eltoni) was associated with changes in aggressive and foraging behaviour in the Ozark zigzag salamander, Plethodon angusticlavius. In a first experiment, male salamanders with high parasite loads were less aggressive overall than males with low parasite loads during territorial disputes. In addition, males with high parasite loads were more aggressive toward opponents with high parasite loads (symmetric contests) than toward opponents with low parasite loads (asymmetric contests). In contrast, males with low parasite loads did not adjust their level of aggression according to the parasite load of the opponent. In a second experiment, foraging behaviour of females was tested in response to ,familiar' (Drosophila) prey and ,novel' (termite) prey. Latency to first capture was significantly longer for parasitized than non-parasitized females when tested with ,familiar' prey, but not for ,novel' prey. Our results suggest that parasite-mediated effects may have profound influences on individual fitness in nature. [source] Predictive and reactive co-ordination of grip and load forces in bimanual lifting in manEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2003R. Martyn Bracewell Abstract We investigated the intra- and inter-manual coordination of grip force (GF) and load force (LF) during bimanual lifting and holding of a single object. In a voluntary task involving lifting a predictable load (Experiment 1), we showed scaling of GF to LF generated by either hand, similar to effects seen in previous unimanual studies. Moreover, the GF rates generated by the two hands were correlated. In part this correlation was due to the correlation between the LF rates. However, the GF rates remained correlated when the effects of the correlation in LF rates were partialled out. This novel finding suggests an additional co-ordinative constraint at the level of specification of GFs. As a contrast to the predictable loading in the first experiment, in the second experiment loading was temporally unpredictable and elicited reactive increases in GF. In Experiment 2, the intermanual correlation of GF rates was stronger than in Experiment 1. We speculate that this result reflects greater degrees of co-ordinative constraint at lower levels in the motor control hierarchy. [source] The effects of genetic and pharmacological blockade of the CB1 cannabinoid receptor on anxietyEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2002J. Haller Abstract The aim of this study was to compare the effects of the genetic and pharmacological disruption of CB1 cannabinoid receptors on the elevated plus-maze test of anxiety. In the first experiment, the behaviour of CB1-knockout mice and wild-type mice was compared. In the second experiment, the cannabinoid antagonist SR141716A (0, 1, and 3 mg/kg) was administered to both CB1-knockout and wild type mice. Untreated CB1-knockout mice showed a reduced exploration of the open arms of the plus-maze apparatus, thus appearing more anxious than the wild-type animals, however no changes in locomotion were noticed. The vehicle-injected CB1-knockout mice from the second experiment also showed increased anxiety as compared with wild types. Surprisingly, the cannabinoid antagonist SR141716A reduced anxiety in both wild type and CB1 knockout mice. Locomotor behaviour was only marginally affected. Recent evidence suggests the existence of a novel cannabinoid receptor in the brain. It has also been shown that SR141716A binds to both the CB1 and the putative novel receptor. The data presented here supports these findings, as the cannabinoid receptor antagonist affected anxiety in both wild type and CB1-knockout mice. Tentatively, it may be suggested that the discrepancy between the effects of the genetic and pharmacological blockade of the CB1 receptor suggests that the novel receptor plays a role in anxiety. [source] Majority versus minority influence: the role of message processing in determining resistance to counter-persuasionEUROPEAN JOURNAL OF SOCIAL PSYCHOLOGY, Issue 1 2008Robin Martin Two experiments examined the extent to which attitudes changed following majority and minority influence are resistant to counter-persuasion. In both experiments participants' attitudes were measured after being exposed to two messages, delayed in time, which argued opposite positions (initial message and counter-message). In the first experiment, attitudes following minority endorsement of the initial message were more resistant to a second counter-message only when the initial message contained strong versus weak arguments. Attitudes changed following majority influence did not resist the second counter-message and returned to their pre-test level. Experiment 2 varied whether memory was warned (i.e., message recipients expected to recall the message) or not, to manipulate message processing. When memory was warned, which should increase message processing, attitudes changed following both majority and minority influence resisted the second counter-message. The results support the view that minority influence instigates systematic processing of its arguments, leading to attitudes that resist counter-persuasion. Attitudes formed following majority influence yield to counter-persuasion unless there is a secondary task that encourages message processing. Copyright © 2007 John Wiley & Sons, Ltd. [source] Attitude-behaviour consistency: the role of group norms, attitude accessibility, and mode of behavioural decision-makingEUROPEAN JOURNAL OF SOCIAL PSYCHOLOGY, Issue 5 2003Joanne R. Smith The interplay between two perspectives that have recently been applied in the attitude area,the social identity approach to attitude-behaviour relations (Terry & Hogg, 1996) and the MODE model (Fazio, 1990a),was examined in the present research. Two experimental studies were conducted to examine the role of group norms, group identification, attitude accessibility, and mode of behavioural decision-making in the attitude-behaviour relationship. In Study 1 (N,=,211), the effects of norms and identification on attitude-behaviour consistency as a function of attitude accessibility and mood were investigated. Study 2 (N,=,354) replicated and extended the first experiment by using time pressure to manipulate mode of behavioural decision-making. As expected, the effects of norm congruency varied as a function of identification and mode of behavioural decision-making. Under conditions assumed to promote deliberative processing (neutral mood/low time pressure), high identifiers behaved in a manner consistent with the norm. No effects emerged under positive mood and high time pressure conditions. In Study 2, there was evidence that exposure to an attitude-incongruent norm resulted in attitude change only under low accessibility conditions. The results of these studies highlight the powerful role of group norms in directing individual behaviour and suggest limited support for the MODE model in this context. Copyright © 2003 John Wiley & Sons, Ltd. [source] QUANTITATIVE GENETICS OF SEXUAL PLASTICITY: THE ENVIRONMENTAL THRESHOLD MODEL AND GENOTYPE-BY-ENVIRONMENT INTERACTION FOR PHALLUS DEVELOPMENT IN THE SNAIL BULINUS TRUNCATUSEVOLUTION, Issue 5 2000Marie-France Ostrowski Abstract Sexual polymorphisms are model systems for analyzing the evolution of reproductive strategies. However, their plasticity and other binary traits have rarely been studied, with respect to environmental variables. A possible reason is that, although threshold models offer an adequate quantitative genetics framework for binary traits in a single environment, analyzing their plasticity requires more refined empirical and theoretical approaches. The statistical framework proposed here, based on the environmental threshold model (ETM), should partially fill this gap. This methodology is applied to an empirical dataset on a plastic sexual polymorphism, aphally, in the snail Bulinus truncatus. Aphally is characterized by the co-occurrence of regular hermaphrodites (euphallics) together with hermaphrodites deprived of the male copulatory organ (aphallics). Reaction norms were determined for 40 inbred lines, distributed at three temperatures, in a first experiment. A second experiment allowed us to rule out maternal effects. We confirmed the existence of high broad-sense heritabilities as well as a positive effect of high temperatures on aphally. However a significant genotype-by-environment interaction was detected for the first time, suggesting that sexual plasticity itself can respond to selection. A nested series of four ETM-like models was developed for estimating genetical effects on both mean aphally rate and plasticity. These models were tested using a maximum-likelihood procedure and fitted to aphally data. Although no perfect fit of models to data was observed, the refined versions of ETM models conveniently reduce the analysis of complex reaction norms of binary traits into standard quantitative genetics parameters, such as genetic values and environmental variances. [source] Thyroid hormones determine developmental mode in sand dollars (Echinodermata: Echinoidea)EVOLUTION AND DEVELOPMENT, Issue 6 2004Andreas Heyland Summary Evolutionary transitions in larval nutritional mode have occurred on numerous occasions independently in many marine invertebrate phyla. Although the evolutionary transition from feeding to nonfeeding development has received considerable attention through both experimental and theoretical studies, mechanisms underlying the change in life history remain poorly understood. Facultative feeding larvae (larvae that can feed but will complete metamorphosis without food) presumably represent an intermediate developmental mode between obligate feeding and nonfeeding. Here we show that an obligatorily feeding larva can be transformed into a facultative feeding larva when exposed to the thyroid hormone thyroxine. We report that larvae of the subtropical sand dollar Leodia sexiesperforata (Echinodermata: Echinoidea) completed metamorphosis without exogenous food when treated with thyroxine, whereas the starved controls (no thyroxine added) did not. Leodia sexiesperforata juveniles from the thyroxine treatment were viable after metamorphosis but were significantly smaller and contained less energy than sibling juveniles reared with exogenous food. In a second starvation experiment, using an L. sexiesperforata female whose eggs were substantially larger than in the first experiment (202±5 vs. 187±5 ,m), a small percentage of starved L. sexiesperforata larvae completed metamorphosis in the absence of food. Still, thyroxine-treated larvae in this experiment completed metamorphosis faster and in much higher numbers than in the starved controls. Furthermore, starved larvae of the sand dollar Mellita tenuis, which developed from much smaller eggs (100±2 ,m), did not complete metamorphosis either with or without excess thyroxine. Based on these data, and from recent experiments with other echinoids, we hypothesize that thyroxine plays a major role in echinoderm metamorphosis and the evolution of life history transitions in this group. We discuss our results in the context of current life history models for marine invertebrates, emphasizing the role of egg size, juvenile size, and endogenous hormone production for the evolution of nonfeeding larval development. [source] Host,parasite interactions and competition between tubificid species in a benthic communityFRESHWATER BIOLOGY, Issue 8 2009L. C. STEINBACH ELWELL Summary 1. Parasites can be important determinants of host community structure while host community structure can influence the success of parasites, although both are often overlooked. In two laboratory experiments, we examined interactions among Myxobolus cerebralis syn Myxosoma cerebralis Höfer, the myxozoan parasite that causes salmonid whirling disease, and two coexisting tubificid species: Tubifex tubifex (Müller), which is the alternate host of the parasite, and Limnodrilus hoffmeisteri Claparède, which is not susceptible. In the first experiment, we examined T. tubifex infection prevalence when exposed to nine doses of spores. In the second experiment, we examined tubificid and parasite success under three spore doses when tubificids were combined in a response surface experimental design used to detect interactions among species. 2. The outcomes of interactions between tubificid species were complex. The number and biomass of offspring of both tubificid species were density dependent when in monoculture or in combination with the other species. Adult growth of T. tubifex was also density dependent in monoculture, but when L. hoffmeisteri replaced one-half of the T. tubifex in the high-density treatment, adult growth of T. tubifex was higher than in monoculture. Adult growth of L. hoffmeisteri was always density independent. Whether T. tubifex was exposed to the parasite or not did not change the outcome of these interactions. However, adult growth of T. tubifex, but not L. hoffmeisteri, was highest when M. cerebralis was present. 3. Infection prevalence of T. tubifex increased with increasing spore dose. Infection prevalence was lowest in the high-density T. tubifex monoculture and highest in the low-density T. tubifex monoculture and when T. tubifex was in combination with L. hoffmeisteri. 4. Both intraspecific and interspecific competition influenced tubificid success, but T. tubifex gained some competitive advantage through increased adult growth when in combination with L. hoffmeisteri. Whether T. tubifex was exposed to the parasite or not did not change the outcome of the interactions between the tubificid species. 5. The presence of L. hoffmeisteri did not decrease the prevalence of infection in T. tubifex, suggesting that parasite success was unaltered by the presence of this non-susceptible species. [source] Flow-substrate interactions create and mediate leaf litter resource patches in streamsFRESHWATER BIOLOGY, Issue 3 2006TRENT M. HOOVER Summary 1. The roles that streambed geometry, channel morphology, and water velocity play in the retention and subsequent breakdown of leaf litter in small streams were examined by conducting a series of field and laboratory experiments. 2. In the first experiment, conditioned red alder (Alnus rubra Bongard) leaves were released individually in three riffles and three pools in a second-order stream. The transport distance of each leaf was measured. Several channel and streambed variables were measured at each leaf settlement location and compared with a similar number of measurements taken at regular intervals along streambed transects (,reference locations'). Channel features (such as water depth) and substrate variables (including stone height, stone height-to-width ratio, and relative protrusion) were the most important factors in leaf retention. 3. In the second experiment, the role of settlement location and reach type in determining the rate of leaf litter breakdown was examined by placing individual conditioned red alder leaves in exposed and sheltered locations (on the upper and lower edges of the upstream face of streambed stones, respectively) in riffle and pool habitats. After 10 days, percent mass remaining of each leaf was measured. Generally, leaves broke down faster in pools than in riffles. However, the role of exposure in breakdown rate differed between reach types (exposed pool > sheltered pool > sheltered riffle > exposed riffle). 4. In the third experiment, the importance of substrate geometry on leaf litter retention was examined by individually releasing artificial leaves upstream of a series of substrate models of varying shape. Substrates with high-angle upstream faces (were vertical or close to vertical), and that had high aspect ratios (were tall relative to their width), retained leaves more effectively. 5. These results show that streambed morphology is an important factor in leaf litter retention and breakdown. Interactions between substrate and flow characteristics lead to the creation of detrital resource patchiness, and may partition leaf litter inputs between riffles and pools in streams at baseflow conditions. [source] Bumble bee preference for flowers arranged on a horizontal plane versus inclined planesFUNCTIONAL ECOLOGY, Issue 6 2008T. T. Makino Summary 1Determining factors affecting pollinator visitation is the key to understanding the reproductive success of animal-pollinated plants. The inclination of the ground where plants grow, which has been little studied, could be one such factor. There may be differences in foraging performance when visiting flowers on horizontal planes compared with flowers on inclines planes. And if this is the case, pollinators may have a preference for horizontal or inclined planes. To test these possibilities, a series of laboratory experiments with bumble bees and arrays of artificial flowers were conducted. 2In the first experiment, bees were presented with a pair of floral arrays, one on a horizontal plane and one sloping. The bees preferred visiting flowers on the horizontal array. 3In the second experiment, bees were allowed to forage on a flower array tilted at various angles ranging from 0° (horizontal) to 90° (vertical). It was found that their foraging performance decreased with increasing angles, showing a 9·1% reduction from 0° to 90° arrays. This reduction was caused by an increased travel time between flowers, when moving upslope or downslope. 4These results suggest that plants growing on steep slopes may be less preferred by pollinators. Future studies are needed to clarify how slopes affect pollinator behaviour in field conditions and the ecological influences on plant reproduction. [source] Social and sexual incentive properties of estrogen receptor ,, estrogen receptor ,, or oxytocin knockout miceGENES, BRAIN AND BEHAVIOR, Issue 1 2008A. Ågmo Social and sexual incentive motivation, defined as the intensity of approach to a social and a sexual incentive, respectively, were studied in female Swiss Webster mice. In the first experiment, the social incentive was a castrated mouse of the same strain as the females, whereas the sexual incentive was an intact male mouse of the same strain. Ovariectomized females were first tested after oil treatment and then after administration of estradiol benzoate + progesterone in doses sufficient to induce full receptivity. The hormones increased sexual incentive motivation while leaving social incentive motivation unaffected. This suggests that sexual incentive motivation in the female mouse is dependent on ovarian hormones. In the next experiment, ovariectomized females were tested with an intact, male estrogen receptor , knockout and its wild type as incentives, first without hormones and then when fully receptive. There were no differences in incentive properties between the wild type and the knockout. In a similar experiment, we used an intact male estrogen receptor , knockout and its corresponding wild type as incentives. The wild type turned out to be a more attractive social incentive than the knockout, while they were equivalent as sexual incentives. Finally, an intact male oxytocin knockout and its wild type were used as incentives. The knockout turned out to be a superior incentive, particularly a superior sexual incentive. The fact that the estrogen receptor , and oxytocin knockouts have incentive properties different from their wild types may be important to consider in studies of these knockouts' sociosexual behaviors. [source] The influence of sward canopy structure on foraging decisions by grazing cattle.GRASS & FORAGE SCIENCE, Issue 2 2003Abstract Patch selection by grazing dairy cows in response to simultaneous variation in combinations of sward structural characteristics was examined in three experiments in which four mature dairy cows were offered a choice of patches (typically 0.9 m × 0.9 m) of perennial ryegrass (Lolium perenne) presented in a linear arrangement. Treatments involved combinations of variations in sward height, stubble height and/or depth of regrowth, prepared by preliminary cutting treatments. They were arranged in balanced sets of four to nine treatments, which were arranged in linear sequences of eighteen to twenty-seven patches. Within experiments, sequences were balanced across replicate sets of patches, which were grazed separately by individual cows. The number of bites removed and the residence time for each patch were highly correlated in all three experiments, and the results are reported using number of bites per patch as an estimator of foraging behaviour. In the first experiment, with vegetative swards, cows preferentially selected the tallest swards. When swards comprising reproductive stem were offered in Experiment 2, cows selectively grazed short-stubble swards rather than tall-stubble swards, although both offered a similar depth of regrowth. Cows did not exhibit preference for swards comprising the greatest quantity of leaf mass, indicating that the spatial distribution of plant components assumed greater importance. In the third experiment, the number of bites removed increased with increasing depth of regrowth, and was negatively correlated with sward height. The three patch-appraisal cues investigated were broadly ranked in order of importance as (i) depth of regrowth, (ii) sward maturity and (iii) sward height. There was no evidence, at least at a short temporal scale, that patch behaviour was influenced by conditions in adjacent patches, suggesting that the cows assessed grazing opportunities on a patch-by-patch basis. [source] A fuzzy logical vigilance alarm system for improving situation awareness and trust in supervisory controlHUMAN FACTORS AND ERGONOMICS IN MANUFACTURING & SERVICE INDUSTRIES, Issue 4 2006Cheng-Li Liu An automation system's operating performance is judged by how well an automation unit is monitored and maintained by its supervisors. Previous research has shown that situation awareness (SA) and trust are critical factors in automation. The purpose of this study was to evaluate and improve supervisory performance in automation manufacturing. First, a conceptual structure of the relationship among SA, trust, and vigilance was developed. Second, a quantitative vigilance performance-measuring model (, value) was proposed. Third, a matrix experiment based on orthogonal arrays through a simulated system of an auxiliary feed-water system (AFWS) was conducted to verify the effect of the measuring model. Finally, according to the vigilance performance-measuring model, a fuzzy logical vigilance alarm system was constructed to improve operating performance. The results of the first experiment indicated that the , value on human dynamic decision-making characteristics was easy and objective in the measurement of operators' vigilance. With greater vigilance, there is a greater likelihood of making appropriate SA and acquiring more trust in automation. The results of the second experiment indicated that applying the , value to the design of the fuzzy logical vigilance alarm system could improve supervisory performance efficiently. Therefore, an adaptive vigilance performance-measuring model combined with a fuzzy technique applied to the design of a human,machine interface for the improvement of cognitive decision making and operating performance is an important new direction in automation manufacturing. © 2006 Wiley Periodicals, Inc. Hum Factors Man 16: 409,426, 2006. [source] The effects of delaying the start of moult on the duration of moult, primary feather growth rates and feather mass in Common Starlings Sturnus vulgarisIBIS, Issue 3 2004Alistair Dawson In many species of birds there is a close relationship between the end of breeding and the start of moult. Late-breeding birds therefore often start to moult late, but then moult more rapidly. This is an adaptive mechanism mediated by decreasing day lengths that allows late-breeding birds to complete moult in time. This study asked how these birds complete moult of the primary feathers more rapidly, and the consequences of this on the mass of primary feathers. Common Starlings Sturnus vulgaris were induced to moult rapidly in one of two ways. In the first experiment, one group was exposed to artificially decreasing photoperiods from the start of moult, whereas the control group remained on a constant long photoperiod. The second experiment was a more realistic simulation. Two groups were allowed to moult in an outdoor aviary. One group started to moult at the normal time. In the other, the start of moult was delayed by 3 weeks with an implant of testosterone. The duration of moult was significantly reduced in both the group experiencing artificially decreasing photoperiods and the group in which the start of moult was delayed. The faster moult rate was achieved by moulting more feathers concurrently. The rate of increase in length of each of the primary feathers, and their final length, did not differ between groups. The rate at which total new primary feather mass was accumulated was greater in more rapidly moulting birds, but this was insufficient to compensate for the greater numbers of feathers being grown concurrently. Consequently, the rate of increase in mass of individual feathers, and the final feather mass, were less in the rapidly moulting birds. A 3-week delay in the start of moult is not an unrealistic scenario. That this caused a measurable decrease in feather mass suggests that late-breeding birds are indeed likely to suffer a real decrease in the quality of plumage grown during the subsequent moult. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||