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Timing
Kinds of Timing Terms modified by Timing Selected AbstractsTHE TIMING AND MECHANISMS OF THE OFFENDING-DEPRESSION LINK,CRIMINOLOGY, Issue 3 2007SONJA E. SIENNICK Why is juvenile delinquency associated with depression in young adulthood? One possibility is that delinquency interferes with socioeco-nomic attainment and disrupts entry into adult roles, perhaps because of official labeling processes or adolescent socialization into deviance, and these repercussions of delinquency lead to depression. Another possibility is that grown delinquents may show high levels of depression because they tend to offend in adulthood, and adult offenders tend to be depressed. I use data from the National Longitudinal Study of Adolescent Health to examine the timing and mechanisms of the offending-depression relationship. The results suggest that delinquency is negatively associated with later status attainment and that the status attainment deficits of grown delinquents are not fully explained by justice system contacts or by adolescent delinquent peer influence. A portion of the longitudinal delinquency-depression link is explained by the low levels of education of grown delinquents and by their involvement with the justice system. Still, young adult depression is more closely tied to recent offending than it is to juvenile delinquency, official labeling, or the status attainment consequences of delinquency. [source] THE TIMING OF DELINQUENT BEHAVIOR AND ITS IMPLICATIONS FOR AFTER-SCHOOL PROGRAMS,CRIMINOLOGY AND PUBLIC POLICY, Issue 1 2001DENISE C. GOTTFREDSON Research Summary: This study examines self-reports from two samples to assess the timing of delinquency. Results imply that the after-school hours are a time of elevated delinquency, but that the peak is modest compared with that observed in official records. Additionally, children who are unsupervised during the after-school hours - the primary target population for after-school programs - are found to be more delinquent at all times, not only after-school. Policy Implications: This finding suggests that factors (including social competencies and social bonding) in addition to inadequate supervision produce delinquency during the after-school hours and that the effectiveness of after-school programs for reducing delinquency will depend upon their ability to address these other factors through appropriate and high quality services. [source] EVOLUTION OF TEMPORAL ISOLATION IN THE WILD: GENETIC DIVERGENCE IN TIMING OF MIGRATION AND BREEDING BY INTRODUCED CHINOOK SALMON POPULATIONSEVOLUTION, Issue 4 2000Thomas P. Quinn Abstract. The timing of migration and breeding are key life-history traits; they are not only adaptations of populations to their environments, but can serve to increase reproductive isolation, facilitating further divergence among populations. As part of a study of divergence of chinook salmon, Oncorhynchus tshawytscha, populations, established in New Zealand from a common source in the early 1900s, we tested the hypotheses that the timing of migration and breeding are under genetic control and that the populations genetically differ in these traits despite phenotypic overlap in timing in the wild. Representatives of families from two populations were collected within a day or two of each other, reared in a common environment, and then released to sea from each of two different rivers, while other family representatives were retained in fresh water to maturity. The date of maturation of fish held in fresh water and the dates of return from the ocean and maturation of fish released to sea all showed significant differences between the two populations and among families within populations. The very high heritabilities and genetic correlations estimated for migration and maturation date indicated that these traits would respond rapidly to selection. Combined with the results of related studies on these chinook salmon populations, it appears that spawning time may not only evolve during the initial phases of divergence, but it may play an important role in accelerating divergence in other traits. [source] MATTER(S) OF INTEREST: ARTEFACTS, SPACING AND TIMINGGEOGRAFISKA ANNALER SERIES B: HUMAN GEOGRAPHY, Issue 1 2007Tim Schwanen ABSTRACT. This paper argues that time-geography can make a contribution to contemporary ,rematerialized' geographies, because the interconnections among social processes, human corporeality and inanimate material artefacts within the landscape were among Hägerstrand's central concerns. Time-geography needs none the less to be extended in several ways to make it more reconcilable with current thinking about materiality in geography. The possibility of combining Hägerstrand's framework with notions from (post) actor-network approaches is therefore explored. It is suggested that concepts and notions from the latter may contribute to the advancement of the conceptualization of action at a distance and agency in general in time-geography, as well as the incorporation of the immaterial realm into space,time diagrams. The resulting materially heterogeneous time-geography is a framework for studying the spacing and timing of different material entities that is sensitive to the role of artefacts and their local connectedness with other material forms. Some of its elements are illustrated briefly through an empirical study of the roles played by a few mundane artefacts in working parents ,coping with child-care responsibilities on working days. The case study suggest that these artefacts not only enable goal fulfilment and routinization but also result in further spacing and timing practices, and can introduce uncertainty and novelty to existing orders. [source] THE TIMING OF SIGNALING: TO STUDY IN HIGH SCHOOL OR IN COLLEGE?,INTERNATIONAL ECONOMIC REVIEW, Issue 3 2007Sanghoon Lee American students study harder in college than in high school, whereas East Asian students study harder in high school than in college. This article proposes a signaling explanation. Signaling may occur over time both in high school and in college, and societies may differ in the timing of signaling. Students work harder in the signaling stage determined by the society as a whole. A testable implication is that high ability workers in East Asia are more concentrated among a few colleges than their U.S. counterparts. This implication is confirmed by top CEO education profile data in the United States and Korea. [source] TIMING AND MODES OF DEFORMATION IN THE WESTERN SICILIAN THRUST SYSTEM, SOUTHERN ITALYJOURNAL OF PETROLEUM GEOLOGY, Issue 2 2001L. Tortorici Imbricate units in the western Sicilian fold-and-thrust belt originated on the southern continental margin of Neotethys, and were deformed during the Neogene-Recent in response to convergence between the African and European Plates. Neogene-Pleistocene synorogenic sediments, deposited in flexural foredeeps and satellite piggy-back basins, contain a record of the belt's evolution. Progressive migration of the thrust front southwards into the foreland has been documented, beginning in the Tortonian and continuing to the present-day particularly in western parts of the belt. In the eastern part, activity on Quaternary strike-slip fault zones has produced asymmetric flower structures and other interference structures. In this paper, we present two regional sections across the western Sicilian foreland-thrust belt system. These structural cross-sections extend down as far as the top of the Hercynian basement and integrate our field observations with previously-acquired well log, magnetic and seismic data. We show that complex interactions between the foreland-migrating thrust belt, which developed between the Late Miocene and the Pleistocene, and Pleistocene strike-slip faults led to the development of structural traps which constitute potential targets for hydrocarbon exploration. [source] HABITAT DIFFERENCES IN THE TIMING OF REPRODUCTION OF THE INVASIVE ALGA SARGASSUM MUTICUM (PHAEOPHYTA, SARGASSACEAE) OVER TIDAL AND LUNAR CYCLES,JOURNAL OF PHYCOLOGY, Issue 1 2009Carla Monteiro Sargassum muticum (Yendo) Fensholt is an invasive species that is firmly established on intertidal and subtidal rocky shores of Europe and the Pacific coast of North America. Local success and spread of S. muticum is thought to rely on its reproductive potential that seems dependent on exogenous factors like tidal and lunar cycles. This study is the first to compare the reproductive patterns (periodicity of egg expulsion and embryo settlement) of this invader in two different habitats: the middle and low intertidal. The combination of monthly, daily, and tidal samples at triplicate sites within each habitat showed a semilunar periodicity of egg expulsion and embryo settlement coincident with increasing tidal amplitude just before full and new moons. In both habitats, duration of each egg expulsion event was ,1 week, and embryo settlement occurred during the first daily low tide and with the incoming high tide during spring tides. However, both expulsion and settlement started 1,2 d earlier, expulsion saturation was faster, and settlement was higher in the mid- compared to the low intertidal. Our results suggest that the exact timing of gamete expulsion and embryo release of S. muticum responds to local factors, including tidal cues, which result in differences between mid- and low-intertidal habitats. [source] PARTICIPATION IN INTERNATIONAL ENVIRONMENTAL AGREEMENTS: THE ROLE OF TIMING AND REGULATIONNATURAL RESOURCE MODELING, Issue 2 2006MICHAEL FINUS ABSTRACT. We analyze the formation of self-enforcing international environmental agreements under the assumption that countries announce their participation either simultaneously or sequentially. It is shown that a sequential formation process opens up possibilities for strategic behavior of countries that may lead to inferior outcomes in terms of global abatement and welfare. We then analyze whether and under which conditions a regulator like an international organization, even without enforcement power, can improve upon globally suboptimal outcomes through coordination and moderation, given that recommendations must be Pareto-improving to all parties. [source] The CCAAT binding factor can mediate interactions between CONSTANS-like proteins and DNATHE PLANT JOURNAL, Issue 3 2006Orna Ben-Naim Summary CONSTANS-Like (COL) proteins are plant-specific nuclear regulators of gene expression but do not contain a known DNA-binding motif. We tested whether a common DNA-binding protein can deliver these proteins to specific cis-acting elements. We screened for proteins that interact with two members of a subgroup of COL proteins. These COL proteins were Tomato COL1 (TCOL1), which does not seem to be involved in the control of flowering time, and the Arabidopsis thaliana CONSTANS (AtCO) protein which mediates photoperiodic induction of flowering. We show that the C-terminal plant-specific CCT (CO, CO-like, TIMING OF CAB EXPRESSION 1) domain of both proteins binds the trimeric CCAAT binding factor (CBF) via its HAP5/NF-YC component. Chromatin immunoprecipitation demonstrated that TCOL is recruited to the CCAAT motifs of the yeast CYC1 and HEM1 promoters by HAP5. In Arabidopsis, each of the three CBF components is encoded by several different genes that are highly transcribed. Under warm long days, high levels of expression of a tomato HAP5 (THAP5a) gene can reduce the flowering time of Arabidopsis. A mutation in the CCT domain of TCOL1 disrupts the interaction with THAP5 and the analogous mutation in AtCO impairs its function and delays flowering. CBFs are therefore likely to recruit COL proteins to their DNA target motifs in planta. [source] A MODEL OF ENDOGENOUS PAYOFF MOTIVES AND ENDOGENOUS TIMING IN A MIXED DUOPOLY,AUSTRALIAN ECONOMIC PAPERS, Issue 3 2009KANGSIK CHOI A model of endogenous payoff motives and endogenous order of moves is analysed in a mixed duopoly. We find that, when a non-negative price constraint is imposed on public and private firms' quantity choice, both firms always choose to be relative-payoff-maximisers, and both simultaneous move and sequential move can be sustained in equilibrium. In contrast, when non-negative absolute profit constraint is imposed, public and private firms always choose to be absolute-payoff-maximisers, and only sequential move can be sustained in equilibrium. [source] ENDOGENOUS TIMING IN A MIXED DUOPOLY AND PRIVATE DUOPOLY ,,CAPACITY-THEN-QUANTITY' GAME: THE LINEAR DEMAND CASE,AUSTRALIAN ECONOMIC PAPERS, Issue 2 2009YUANZHU LU We consider a game of endogenous timing of sequential choice of capacity and quantity with observable delay in a mixed duopoly and a private duopoly. In mixed duopoly, we find that a simultaneous play at the capacity stage or at the quantity stage can never be supported as subgame perfect Nash equilibrium (SPNE); whereas a simultaneous play at each stage turns out to be the unique SPNE in a private duopoly. In mixed duopoly there is multiplicity of equilibria and all SPNEs require sequentiality at the capacity as well as quantity stage. [source] Pulmonary Regurgitation after Tetralogy of Fallot Repair: Clinical Features, Sequelae, and Timing of Pulmonary Valve ReplacementCONGENITAL HEART DISEASE, Issue 6 2007Naser M. Ammash MD ABSTRACT Pulmonary regurgitation following repair of tetralogy of Fallot is a common postoperative sequela associated with progressive right ventricular enlargement, dysfunction, and is an important determinant of late morbidity and mortality. Although pulmonary regurgitation may be well tolerated for many years following surgery, it can be associated with progressive exercise intolerance, heart failure, tachyarrhythmia, and late sudden death. It also often necessitates re-intervention. Identifying the appropriate timing of such intervention could be very challenging given the risk of prosthetic valve degeneration and the increased risk of reoperation. Comprehensive informed and regular assessment of the postoperative patient with tetralogy of Fallot, including evaluation of pulmonary regurgitation, right heart structure and function, is crucial to the optimal care of these patients. Pulmonary valve replacement performed in an experienced tertiary referral center is associated with low operative morbidity and mortality and very good long-term results. Early results of percutaneous pulmonary valve replacement are also promising. [source] Types and Timing of Inter,organizational Communication in New Product DevelopmentCREATIVITY AND INNOVATION MANAGEMENT, Issue 4 2001Marjan Hummel Managing the communication between the participants involved in inter,organizational product development is complex. The traditional models of new product development are not sufficient to gain insight in effective management practices in this respect. Our study explored the inter,organizational communication in a research and development project. Our results confirm Gersick's model that looks upon new product development as being punctuated by periods of rapid change. In these periods, including the start,up, explorative prototype stage, and completion of the project, inter,organizational communication is essential about design objectives and project planning, contextual factors and the required resources, skills and knowledge. [source] Timing and duration of developmental nicotine exposure contribute to attenuation of the tadpole hypercapnic neuroventilatory responseDEVELOPMENTAL NEUROBIOLOGY, Issue 7 2009Cord M. Brundage Abstract The ability for air-breathing vertebrates to adjust ventilation in response to increased CO2 (hypercapnia) is fundamental to maintaining pH homeostasis. Developmental nicotine exposure has been shown to impair tadpole neuroventilatory responses to hypercapnia following 8,12 weeks of exposure. It is not clear, however, to what extent the timing of exposure during development and/or the duration over which the exposure takes place contribute to this impairment. Here, tadpoles were exposed to 30 ,g/L of nicotine for 3- or 10-week durations, either early or late in tadpole development. Correlates of tadpole lung neuroventilation were monitored during normocapnic (1.5% CO2) and hypercapnic (5% CO2) conditions of isolated brainstems. Preparations derived from early metamorphic tadpoles failed to increase lung neuroventilation in response to hypercapnia whether they had been exposed to nicotine for 3 or 10 weeks. Preparations derived from late metamorphic tadpoles failed to respond to hypercapnia after being exposed to nicotine for 10 weeks. These results suggest that both the developmental timing and duration of exposure are important when considering nicotine's effect on the hypercapnic neuroventilatory response. © 2009 Wiley Periodicals, Inc. Develop Neurobiol 2009 [source] Profiles in Patient Safety: Antibiotic Timing in Pneumonia and Pay-for-performanceACADEMIC EMERGENCY MEDICINE, Issue 7 2006Jesse M. Pines MD The delivery of antibiotics within four hours of hospital arrival for patients who are admitted with pneumonia, as mandated by the Joint Commission for the Accreditation of Healthcare Organizations and the Centers for Medicare and Medicaid Services, has gained considerable attention recently because of the plan to implement pay-for-performance for adherence to this standard. Although early antibiotic administration has been associated with improved survival for patients with pneumonia in two large retrospective studies, the effect on actual patient care and outcomes for patients with pneumonia and other emergency department patients of providing financial incentives and disincentives to hospitals for performance on this measure currently is unknown. This article provides an in-depth case-based description of the evidence behind antibiotic timing in pneumonia, discusses potential program effects, and analyzes how the practical implementation of pay-for-performance for pneumonia conforms to American Medical Association guidelines on pay-for-performance. [source] Timing of fetal exposure to stress hormones: Effects on newborn physical and neuromuscular maturationDEVELOPMENTAL PSYCHOBIOLOGY, Issue 3 2008Lauren M. Ellman Abstract The purpose of the study was to determine the specific periods during pregnancy in which human fetal exposure to stress hormones affects newborn physical and neuromuscular maturation. Blood was collected from 158 women at 15, 19, 25, and 31 weeks' gestation. Levels of placental corticotropin-releasing hormone (CRH) and maternal cortisol were determined from plasma. Newborns were evaluated with the New Ballard Maturation Score. Results indicated that increases in maternal cortisol at 15, 19, and 25 weeks and increases in placental CRH at 31 weeks were significantly associated with decreases in infant maturation among males (even after controlling for length of gestation). Results also suggested that increases in maternal cortisol at 31 weeks were associated with increases in infant maturation among females, although these results were not significant after controlling for length of gestation. Findings suggest that stress hormones have effects on human fetal neurodevelopment that are independent of birth outcome. © 2008 Wiley Periodicals, Inc. Dev Psychobiol 50: 232,241, 2008. [source] The Accuracy and Completeness of Data Collected by Prospective and Retrospective MethodsACADEMIC EMERGENCY MEDICINE, Issue 9 2005J. Tobias Nagurney MD Abstract Objectives: To describe and test a model that compares the accuracy of data gathered prospectively versus retrospectively among adult emergency department patients admitted with chest pain. Methods: The authors developed a model of information flow from subject to medical record to the clinical study case report form, based on a literature review. To test this model, a bidirectional (prospective and retrospective) study was conducted, enrolling all eligible adult patients who were admitted with a chief complaint of chest pain. The authors interviewed patients in the emergency department to determine their chest pain history and established a prospective database; this was considered the criterion standard. Then, patient medical records were reviewed to determine the accuracy and completeness of the information available through a retrospective medical record review. Results: The model described applies the concepts of reliability and validity to information passed on by the study subject, the clinician, and the medical record abstractor. This study was comprised of 104 subjects, of which 63% were men and the median age was 63 years. Subjects were uncertain of responses for 0,8% of questions and responded differently upon reinterview for subsets of questions 0,30% of the time. The sensitivity of the medical record for risk factors for coronary artery disease was 0.77 to 0.93. Among the 88 subjects (85%) who indicated that their chest pain was substernal or left chest, the medical record described this location in 44%. Timing of the chest pain was the most difficult item to accurately capture from the medical record. Conclusions: Information obtained retrospectively from the abstraction of medical records is measurably less accurate than information obtained prospectively from research subjects. For certain items, more than half of the information is not available. This loss of information is related to the data types included in the study and by the assumptions that a researcher performing a retrospective study makes about implied versus explicitly stated responses. A model of information flow that incorporates the concepts of reliability and validity can be used to measure some of the loss of information that occurs at each step along the way from subject to clinician to medical record abstractor. [source] Females of the European beewolf preserve their honeybee prey against competing fungiECOLOGICAL ENTOMOLOGY, Issue 2 2001Erhard Strohm Summary 1. Females of the European beewolf Philanthus triangulum (Hymenoptera, Sphecidae) provision brood cells with paralysed honeybees as larval food. Because brood cells are located in warm, humid locations there is a high risk of microbial decomposition of the provisions. Low incidence of fungus infestation (Aspergillus sp.) in nests in the field suggested the presence of an anti-fungal adaptation. 2. To test whether the paralysis caused the protection from fungus infestation, the timing of fungus growth on bees that were freeze-killed, paralysed but not provisioned, and provisioned regularly by beewolf females was determined. Fungus growth was first detected on freeze-killed bees, followed by paralysed but not provisioned bees. By contrast, fungus growth on provisioned bees was delayed greatly or even absent. Thus, paralysis alone is much less efficient in delaying fungus growth than is regular provisioning. 3. Observations of beewolves in their nests revealed that females lick the body surface of their prey very thoroughly during the period of excavation of the brood cell. 4. To separate the effect of a possible anti-fungal property of the brood cell and the licking of the bees, a second experiment was conducted. Timing of fungus growth on paralysed bees did not differ between artificial and original brood cells. By contrast, fungus growth on bees that had been provisioned by a female but were transferred to artificial brood cells was delayed significantly. Thus, the treatment of the bees by the female wasp but not the brood cell caused the delay in fungus growth. 5. Beewolf females most probably apply anti-fungal chemicals to the cuticle of their prey. This is the first demonstration of the mechanism involved in the preservation of provisions in a hunting wasp. Some kind of preservation of prey as a component of parental care is probably widespread among hunting wasps and might have been a prerequisite for the evolution of mass provisioning. [source] Timing of foetal growth spurts can explain sex ratio variation in polygynous mammalsECOLOGY LETTERS, Issue 1 2000M.C. Forchhammer The prediction from sex ratio theory that natural selection on sexually dimorphic mammals should favour an excess of male offspring only when mothers are in good condition, has been tested extensively but with little consistency in results. Although recent studies have shown that environmental variations may cause some of the discrepancy, there have also been reports of contrasting sex ratios under similar environmental settings. Here it is suggested that variation in timing of environmental stress and sex-specific differences in foetal growth pattern in relation to maternal condition, may explain such seeming contradictions in sex ratio variation of polygynous mammals. [source] Movements of Murray cod (Maccullochella peelii peelii) in a large Australian lowland riverECOLOGY OF FRESHWATER FISH, Issue 4 2009J. D. Koehn Abstract,,, This study of Murray cod (Maccullochella peelii peelii) movements in a large lowland river in south-eastern Australia indicated that the species was not sedentary, but undertook complex movements that followed a seasonal pattern. While there were sedentary periods with limited home ranges and high site fidelity, Murray cod also under took larger movements for considerable portions of the year coinciding with its spawning schedule. This generally comprised movements (up to 130 km) from a home location in late winter and early spring to a new upstream position, followed by a rapid downstream migration typically back to the same river reach. Timing of movements was not synchronous amongst individuals and variation in the scale of movements was observed between individuals, fish size, original location and years. [source] Does timing of daily feeding affect growth rates of juvenile three-spined sticklebacks, Gasterosteus aculeatus L?ECOLOGY OF FRESHWATER FISH, Issue 3 2001M. Ali Abstract , To assess the consequences of unpredictability in the availability of food, this study measured the effect of timing of the daily feeding on food consumption and growth rates of juvenile Gasterosteus aculeatus. The experiment lasted 21 days at 14 °C and a photoperiod of 10 hours of light and 14 hours of dark. Fish were housed individually and allocated at random to three treatments. The mean initial weight of fish was 0.402 g. Group 1 were fed live enchytraeid worms for 2 h after lights came on ("morning"), group 2 was offered food for 2 h randomly at any time of the day ("random") during the light period and group 3 received food for 2 h before the lights went off ("evening"). There was no significant effect of timing of feeding on mean daily food consumption, which was 0.052 g day,1. Daily consumption on the random schedule was more irregular than on the two fixed schedules. Timing of feeding had no significant effect on mean specific growth rate (G) (2.42% day,1), gross growth efficiency (23.3%), white muscle RNA:DNA ratio (5.6), carcase lipid content (31.7% dry wt) and carcase dry matter content (27.4% wet wt). Thus, a lack of predictability in the availability of food during the light period of the day did not impose a detectable cost on the growth performance of the stickleback., [source] Timing of first alcohol use and alcohol dependence: evidence of common genetic influencesADDICTION, Issue 9 2009Carolyn E. Sartor ABSTRACT Aims To estimate the magnitude of genetic and environmental influences on timing of first alcohol use and alcohol dependence (AD) and to quantify the overlap in these influences across the two alcohol-related outcomes. Participants The sample consisted of 5382 twins (2691 complete pairs), aged 24,36 years, from the Australian Twin Registry. Measurements History of alcohol use and DSM-IV alcohol dependence were assessed by structured telephone interview. Findings In both sexes, the relationship between age at first alcohol use and risk for AD followed a linear trend, such that the highest rates of AD were observed in individuals who began drinking at an earlier than average age (14 years or younger). Heritability estimates for timing of first alcohol use and AD were 36% and 53%, respectively. Shared environmental factors accounted for 15% of variance in initiation. There was no evidence of shared environmental influences on AD. The genetic correlation between timing of first alcohol use and AD was 0.59. Conclusions Findings highlight the substantial role of genetics in the development of AD and the early manifestation of that genetic risk in the timing of alcohol use initiation which, unlike AD, is also influenced to a modest degree by shared environmental factors. The considerable overlap in heritable influences,and the virtual absence of overlap in individual-specific environmental influences,on initiation of alcohol use and AD indicates that the association between age at first drink and AD is attributable in large part to common genetic sources of variance. [source] Reproductive responses to photoperiod and temperature by artificially hibernated bumblebee (Bombus terrestris) queensENTOMOLOGICAL RESEARCH, Issue 4 2008Md. Ruhul AMIN Abstract Post-hibernated bumblebee (Bombus terrestris) queens were kept for 1 week under photoperiodic conditions of 8 h light : 16 h dark, and at four different temperatures (24, 28, 32 and 36°C). The reproductive performance of the queens was then observed. It was found that exposure temperature and hibernation duration did not affect the oviposition rate. The pre-oviposition period was found to be shortest (3.8 ± 0.7 days) for queens that had hibernated for 4.0 months and had been activated at 28°C. Timing of the initiation of the switch-point was not affected by exposure temperature and hibernation duration. Significantly higher numbers of workers (268.0 ± 31.4) and sexual queens (119.3 ± 16.8) were produced by the queens that had hibernated for 3.0 months and had been activated at 28 and 36°C, respectively. The queens that had hibernated for 4.0 months and had been activated at 36°C produced the highest number of males (296.2 ± 32.3). [source] Effects of carbaryl on green frog (Rana clamitans) tadpoles: Timing of exposure versus multiple exposuresENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 11 2003Michelle D. Boone Abstract The majority of studies on pesticide impacts have evaluated the effects of single exposures. However, multiple exposures to a pesticide may be more prevalent. The objective of our study was to determine how multiple exposures versus single exposure at different times during development affected survival to metamorphosis, tadpole survival, tadpole mass, and tadpole developmental stage of green frog (Rana clamitans) tadpoles reared at low and high density in outdoor cattle tank ponds. Tadpoles were exposed to carbaryl zero, one, two, or three times at 14-d intervals. We applied single doses of carbaryl at one of three times, specifically during early, mid, or late development. Overall, we found that multiple exposures had a greater impact than single exposures during development. More individuals reached metamorphosis in ponds exposed to multiple doses of carbaryl compared with controls, indicating that the presence of carbaryl stimulated metamorphosis. The presence of carbaryl in the aquatic environment also resulted in more developed tadpoles compared with controls. Tadpoles in control ponds did not reach metamorphosis and were less developed than individuals exposed to carbaryl; this effect indicates that, under ideal conditions, green frogs could overwinter in ponds so that greater size could be attained before metamorphosis in the following spring or summer. Our study demonstrated the importance of including realistic application procedures when evaluating the effects of a pesticide and that multiple exposures to a short-lived pesticide are more likely to affect an amphibian population. [source] Timing of exposure to a pulp and paper effluent influences the manifestation of reproductive effects in rainbow troutENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 11 2002Michael R. Van den Heuvel Abstract Rainbow trout were exposed to a secondary treated, thermomechanical/bleached kraft pulp and paper effluent in 12,000-L, flow-through exposure tanks at an environmental research facility located at a pulp and paper mill in Kawerau, New Zealand. Trout (age, 2+ years) were obtained from a local hatchery and exposed either to upstream river water or a nominal concentration of 12% (v/v) effluent diluted in upstream river water. Three treatment groups were used: Effluent exposure that started approximately three months before gonadal growth (eight-month total exposure), effluent exposure that started approximately halfway through gonadal development (two-month total exposure), and trout exposed to reference water alone for the total duration of the experiment. Trout were sacrificed just before spawning; exposure, growth, and reproductive endpoints were assessed during and at the termination of the experiment. Reduction in growth was observed in both sexes in the eight-month treatment group relative to the river water reference treatment group. No differences were observed in condition factor or liver size in either treatment. Females in the eightmonth exposure group also had significantly lower ovary weight. The two-month exposure group showed no differences from the reference group in growth or somatic indices. Estradiol and testosterone were reduced in blood samples taken from the eight-month exposure group by four months into the experiment as compared to the reference treatment. Steroid and vitellogenin levels in individual female trout from this treatment were significantly correlated with gonadosomatic indices (GSI) measured at the termination of the experiment. The GSI was not correlated strongly or consistently with pregnenolone, nor were any treatment-related pregnenolone differences observed, indicating that the steroid hormone reductions likely were not related to cholesterol side-chain cleavage. Male trout showed significant induction of vitellogenin and lower 11-ketotestosterone during the experiment (only the eight-month group was examined), but this did not result in any significant differences in testes development. Thus, this study has shown an impact of pulp mill effluent exposure on the reproductive physiology of female trout that appeared to be hormonally mediated. Furthermore, the effect could only be manifest when the exposure was initiated before the start of gonad development. [source] SELECTION AGAINST LATE EMERGENCE AND SMALL OFFSPRING IN ATLANTIC SALMON (SALMO SALAR)EVOLUTION, Issue 2 2000Sigurd Einum Abstract., Timing of breeding and offspring size are maternal traits that may influence offspring competitive ability, dispersal, foraging, and vulnerability to predation and climatic conditions. To quantify the extent to which these maternal traits may ultimately affect an organism's fitness, we undertook laboratory and field experiments with Atlantic salmon (Salmo salar). To control for confounding effects caused by correlated traits, manipulations of the timing of fertilization combined with intraclutch comparisons were used. In the wild, a total of 1462 juveniles were marked at emergence from gravel nests. Recapture rates suggest that up to 83.5% mortality occurred during the first four months after emergence from the gravel nests, with the majority (67.5%) occurring during the initial period ending 17 days after median emergence. Moreover, the mortality was selective during this initial period, resulting in a significant phenotypic shift toward an earlier date of and an increased length at emergence. However, no significant selection differentials were detected thereafter, indicating that the critical episode of selection had occurred at emergence. Furthermore, standardized selection gradients indicated that selection was more intense on date of than on body size at emergence. Timing of emergence had additional consequences in terms of juvenile body size. Late-emerging juveniles were smaller than early-emerging ones at subsequent samplings, both in the wild and in parallel experiments conducted in seminatural stream channels, and this may affect success at subsequent size-selective episodes, such as winter mortality and reproduction. Finally, our findings also suggest that egg size had fitness consequences independent of the effects of emergence time that directly affected body size at emergence and, in turn, survival and size at later life stages. The causality of the maternal effects observed in the present study supports the hypothesis that selection on juvenile traits may play an important role in the evolution of maternal traits in natural populations. [source] Insider Trading after Repurchase Tender Offer Announcements: Timing versus Informed TradingFINANCIAL MANAGEMENT, Issue 1 2010Henock Louis Abnormally high net insider selling is commonly observed after repurchase tender offer (RTO) announcements although, on average, firms experience positive abnormal returns in the years after the repurchases. We explore two potential explanations: liquidity trade timing and informed trading. Consistent with the notion that fixed price RTOs are more likely than Dutch-auction RTOs to signal undervaluation, the results suggest that insider selling after fixed price RTO announcements are driven largely by insiders who time their trades with the repurchase announcements. In contrast, selling after Dutch-auction RTOs seems to be driven primarily by informed traders who exploit mispricing associated with the repurchase announcements. [source] Ecological effects of regime shifts in the Bering Sea and eastern North Pacific OceanFISH AND FISHERIES, Issue 2 2002Ashleen J Benson Abstract Large-scale shifts occurred in climatic and oceanic conditions in 1925, 1947, 1977, 1989 and possibly 1998. These shifts affected the mix and abundance of suites of coexisting species during each period of relative environmental stability,from primary producers to apex predators. However, the 1989 regime shift was not a simple reversal of the 1977 shift. The regime shifts occurred abruptly and were neither random variations nor simple reversals to the previous conditions. Timing of these anomalous environmental events in the North Pacific Ocean appears to be linked to physical and biological responses in other oceanic regions of the world. Changes in the atmospheric pressure can alter wind patterns that affect oceanic circulation and physical properties such as salinity and depth of the thermocline. This, in turn, affects primary and secondary production. Data from the North Pacific indicate that regime shifts can have opposite effects on species living in different domains, or can affect similar species living within a single domain in opposite ways. Climatic forcing appears to indirectly affect fish and marine mammal populations through changes in the distribution and abundance of their predators and prey. Effects of regime shifts on marine ecosystems are also manifested faster at lower trophic levels. Natural variability in the productivity of fish stocks in association with regime shifts indicates that new approaches to managing fisheries should incorporate climatic as well as fisheries effects. [source] Night stocking facilitates nocturnal migration of hatchery-reared Atlantic salmon, Salmo salar, smoltsFISHERIES MANAGEMENT & ECOLOGY, Issue 1 2009L. J. ROBERTS Abstract, Hatchery-reared salmon, Salmo salar L., smolts are generally stocked during daylight hours, but the natural migration of smolts tends to occur at night. Recapture rates and timing of migration were compared between Atlantic salmon smolts stocked during the day and during the evening. Timing of release had no significant effect on the number of smolts recaptured, but had a strong effect on nocturnal behaviour. When stocked in the evening (but not during the day) hatchery-reared smolts moved almost exclusively during the night. This study suggests that timing the release to coincide with the natural time of smolt migration may provide valuable acclimatisation and facilitate nocturnal smolt passage. [source] Life histories of Eucalanus bungii and Neocalanus cristatus (Copepoda: Calanoida) in the western subarctic Pacific OceanFISHERIES OCEANOGRAPHY, Issue 2004ATSUSHI TSUDA Abstract Life cycles of the large suspension-feeding copepods, Eucalanus bungii and Neocalanus cristatus were investigated by seasonal sampling in the western subarctic Pacific. Eucalanus bungii has a diapause from August to March at copepodite stages between copepodite 3 (C3) and C6 female. We propose that individuals with early birth dates are young of overwintering C5 and C6-females that develop to C4 in their birth year, while individuals with late birth dates are young of overwintering C4 that develop to C3 in their birth year. Thus, a majority of the population has annual generations alternating with biennial generations. Neocalanus cristatus showed life history almost identical to the population in the Alaskan gyre. Timing of the life cycle in N. cristatus is very close to that in the eastern subarctic gyre, but that of E. bungii is 2 months earlier than in the eastern subarctic. This difference is probably caused by the timing difference in the maximum primary production in the two areas and the plasticity of the life cycle strategy in E. bungii. [source] | |||||||||||||||||||||||||||||||||||||||||||