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Selected AbstractsWhy health expectations and hopes are different: the development of a conceptual modelHEALTH EXPECTATIONS, Issue 4 2009Karen K. Leung BA (Hons) Abstract Background, In the literature, ,hope' has often been thought of as an ideal expectation. However, we believe the classification of hope as a type of expectation is problematic. Although both hopes and expectations are future-oriented cognitions, expectations are distinct in that they are an individual's probability-driven assessment of the most likely outcomes, while hopes are an assessment of the most desirable , but not necessarily the most probable , outcomes. Aim, This paper presents a conceptual model of the factors that may serve as common antecedents of hopes and expectations, and a mechanism that may mediate their differentiation. Method, Ovid Healthstar and PsycINFO database searches from January 1967 to October 2008 were conducted. An integrative literature review, synthesis and conceptual model development were carried out. Outcome, Our model envisages the differentiation of hope from expectation as a dynamic, longitudinal process consisting of three phases: appraisal of possible outcomes, cognitive analysis for achieving hopes and goal pursuit. Key variables such as temporal proximity, controllability, external resources, goals, affect, agency and pathways may moderate the extent of divergence by influencing the perceived probability of achieving desired outcomes. Conclusion, Hopes and expectations are distinct, but linked, constructs. This preliminary conceptual model presents how hopes and expectations develop, become differentiated and how social-cognitive factors may moderate this relationship. A better understanding of hopes and expectations may assist health professionals in communicating illness-related expectations while maintaining the integrity of patient hopes. [source] Standardized procedure for measurement of nasal potential difference: An outcome measure in multicenter cystic fibrosis clinical trials,PEDIATRIC PULMONOLOGY, Issue 5 2004Thomas A. Standaert PhD Abstract Patients with cystic fibrosis (CF) can be discriminated from healthy subjects by measurement of the nasal potential difference, which has become a useful outcome measure for therapies directed toward correcting defective electrolyte transport in CF. A standard operating procedure was developed by a CF Foundation clinical trials network, to be followed by all sites performing collaborative studies. Key variables in the measurement included type of voltmeter, exploring probe, reference electrodes, and solutions used to assess both sodium transport and chloride conductance. Eight sites submitted data on 3,8 normal and 4,5 CF subjects. Baseline voltage, an index of sodium transport, was ,18.2,±,8.3 mV (mean,±,SD) for normals, and ,45.3,±,11.4 mV for CF patients. There was no CFTR-mediated chloride secretion in CF subjects, as evidenced by the lack of response to perfusion with zero chloride,+,beta agonist solutions (+3.2,±,3.5 mV) vs. that in normals (,23.7,±,10.2 mV). The standardized nasal potential difference measurement minimizes variability between operators and study sites. Valid and consistent results can be attained with trained operators and attention to technical details. These data demonstrate the procedure to be sufficient for multicenter studies in the CF Foundation network. Pediatr Pulmonol. 2004; 37:385,392. © 2004 Wiely-Liss, Inc. [source] Sampling from Dirichlet partitions: estimating the number of speciesENVIRONMETRICS, Issue 7 2009Thierry Huillet Abstract The Dirichlet partition of an interval can be viewed as the generalization of several classical models in ecological statistics. We recall the unordered Ewens sampling formulae -ESF) from finite Dirichlet partitions. As this is a key variable for estimation purposes, focus is on the number of distinct visited species in the sampling process. These are illustrated in specific cases. We use these preliminary statistical results on frequencies distribution to address the following sampling problem: what is the estimated number of species when sampling is from Dirichlet populations? The obtained results are in accordance with the ones found in sampling theory from random proportions with Poisson,Dirichlet -PD) distribution. To conclude with, we apply the different estimators suggested to two different sets of real data. Copyright © 2009 John Wiley & Sons, Ltd. [source] The effect of tree height and light availability on photosynthetic leaf traits of four neotropical species differing in shade toleranceFUNCTIONAL ECOLOGY, Issue 1 2000T. Rijkers Abstract 1.,Light-saturated rate of photosynthesis (Amax), nitrogen (N), chlorophyll (Chl) content and leaf mass per unit area (LMA) were measured in leaves of trees of different heights along a natural light gradient in a French Guiana rain forest. The following four species, arranged in order from most shade-tolerant to pioneer, were studied: Duguetia surinamensis, Vouacapoua americana, Dicorynia guianensis and Goupia glabra. Light availability of trees was estimated using hemispherical photography. 2.,The pioneer species Goupia had the lowest LMA and leaf N on both an area and mass basis, whereas Duguetia had the highest values. In general, leaf variables of Vouacapoua and Dicorynia tended to be intermediates. Because Amax/area was similar among species, Goupia showed both a much higher light-saturated photosynthetic nitrogen-use efficiency (PNUEmax) and Amax/mass. Leaves of Vouacapoua demonstrated the greatest plasticity in Amax/area, particularly in small saplings. 3.,A distinction could be made between the effect of tree height and light availability on the structural, i.e. LMA, and photosynthetic leaf characteristics of all four species. The direction and magnitude of the variation in variables were similar among species. 4.,LMA was the key variable that mainly determined variation in the other leaf variables along tree height and light availability gradients, with the exception of changes in chlorophyll concentration. Amax/area, N/area, LMA and stomatal conductance to water vapour (gs) increased, whereas Chl/mass decreased, with both increasing tree height and canopy openness. Amax/mass, PNUEmax and Amax/Chl increased with increasing openness only. N/mass and Chl/area were independent of tree height and openness, except for small saplings of Goupia which had a much lower Chl/area. [source] Wind erosion and intensive prehistoric agriculture: A case study from the Kalaupapa field system, Moloka'i Island, Hawai'iGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 5 2007Mark D. McCoy Wind erosion is a major problem for modern farmers, a key variable affecting nutrient levels in ecosystems, and a potentially major force impacting archaeological site formation; however, it has received scant consideration in geoarchaeological studies of agricultural development compared with more easily quantifiable environmental costs, such as vegetation change or fluvial erosion. In this study, soil nutrient analysis is used in the Kalaupapa field system, Moloka'i Island, Hawai'i, to detect an increase in wind erosion attributable to intensive agriculture following the burning of endemic forest. This practice began on a small scale in the 13th century A.D., expanded around cal A.D. 1450,1550, and continued until the near total abandonment of the fields after European contact in the 18th century. Nutrients that naturally occur in high amounts in coastal windward areas due to the long-term, cumulative effect of sea spray were especially impacted. However, thanks to the unique landform of the Kalaupapa Peninsula, nutrient depletion in windward areas was offset by downwind enrichment and likely contributed to the long-term sustainability of the system as a whole. Future research on tropical and arid agriculture should consider the cumulative environmental cost of increased eolian erosion attributable to anthropogenic landscape modification. © 2007 Wiley Periodicals, Inc. [source] The formation of spores in biofilms of Anoxybacillus flavithermusJOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2009S.A. Burgess Abstract Aims:, To examine the rate and the extent of spore formation in Anoxybacillus flavithermus biofilms and to test the effect of one key variable , temperature , on spore formation. Methods and Results:, A continuous flow laboratory reactor was used to grow biofilms of the typical dairy thermophile A. flavithermus (strain CM) in skim milk. The reactor was inoculated with either a washed culture or a spore suspension of A. flavithermus CM, and was run over an 8·5 h period at three different temperatures of 48, 55 and 60°C. Change in impedance was used to determine the cell numbers in the milk and on the surface of the stainless steel reactor tubes. The biofilm developed at all three temperatures within 6,8 h. Spores formed at 55 and 60°C and amounted to approx. 10,50% of the biofilm. No spores formed at 48°C. Conclusions:, The results suggest that both biofilm formation and spore formation of A. flavithermus can occur very rapidly and simultaneously. In addition, temperature variation has a considerable effect on the formation of spores. Significance and Impact of the Study:, This information will provide direction for developing improved ways in which to manipulate conditions in milk powder manufacturing plants to control biofilms and spores of A. flavithermus. [source] Life satisfaction of people with intellectual disability living in community residences: perceptions of the residents, their parents and staff membersJOURNAL OF INTELLECTUAL DISABILITY RESEARCH, Issue 2 2003C. Schwartz Abstract Background Within the literature on quality of life (QoL), life satisfaction (LS) has emerged as a key variable by which to measure perceived well-being, which is referred to as subjective QoL. The LS self-reports of 93 residents with intellectual disability (ID) living in community-based residences were compared with reports about their LS completed by their staff and parents. Method The residents were interviewed on their LS by social workers who did not belong to the staff of the interviewee's residence. The instrument used was the Life Satisfaction Scale (LSS). Staff and parents completed the short version of the LSS. Results Residents and staff's LS reports were positively correlated. However, significant differences were found between these two groups of informants when the residents were characterized as high functioning, had a low score in challenging behaviour, worked in an integrative employment setting and lived in an apartment. As opposed to staff/resident discrepancies, no differences were found between parents' and residents' LS reports. Conclusions If residents cannot to be interviewed about their LS, then the parent is the preferred person to respond on behalf of the resident. The current study highlights the importance of including both objective measures (e.g. functional assessment characteristics) and subjective measures (e.g. LS) in order to get a better understanding of the QoL of people with ID. [source] Swimming speed and foraging strategies of New Zealand sea lions (Phocarctos hookeri)JOURNAL OF ZOOLOGY, Issue 2 2001D. E. Crocker Abstract Lactating New Zealand sea lions (Phocarctos hookeri) have recently been reported to be the longest and deepest-diving otariid. An unusually large proportion of dives exceeded a theoretical aerobic dive limit, predicted from estimated oxygen stores and measurements of diving metabolic rate. We investigated swimming speed, a key variable in both the management of oxygen stores and foraging strategies, and its relation to diving behaviour in New Zealand sea lions. Diving behaviour was nearly continuous with short inter-dive intervals. Mean diving swimming speeds ranged from 1.6 to 2.4 m/s. Mean surface swimming speeds ranged from 0.9 to 1.8 m/s and were significantly lower than diving speeds in all subjects. New Zealand sea lions spend significant but variable amounts of time resting at the surface. Diving and swimming speed patterns were consistent with foraging on the benthos. Time in the foraging zone was maintained in deeper dives by increasing dive duration. This increased duration cannot be accounted for by a decreased metabolic rate resulting from slower swimming speeds, as speeds increased with the maximum depth of dives. Patterns of swimming speed and acceleration suggest the use of a gliding phase during descent. For most females, the extended duration of deeper dives did not impact on surface times, suggesting the use of aerobic metabolism. Females exhibited significantly slower swim speeds during the bottom segments of foraging dives than during descent or ascent. These findings suggest that swimming behaviour should be considered a critical component when modelling energetic costs for diving animals. [source] In vivo delivery of fluoresceinated dextrans to the murine growth plate: Imaging of three vascular routes by multiphoton microscopyTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 1 2006Cornelia E. Farnum Abstract Bone elongation by endochondral ossification occurs through the differentiation cascade of chondrocytes of cartilaginous growth plates. Molecules from the systemic vasculature reach the growth plate from three different directions: epiphyseal, metaphyseal, and a ring vessel and plexus associated with the perichondrium. This study is an analysis of the real-time dynamics of entrance of fluoresceinated tracers of different molecular weights into the growth plate from the systemic vasculature and tests the hypothesis that molecular weight is a key variable in the determination of both the directionality and the extent of tracer movement into the growth plate. Multiphoton microscopy was used for direct in vivo imaging of the murine proximal tibial growth plate in anesthetized 4- to 5-week-old transgenic mice with green fluorescent protein linked to the collagen II promoter. Mice were given an intracardiac injection of either fluorescein (332.3 Da) or fluoresceinated dextrans of 3, 10, 40, 70 kDa, singly or sequentially. For each tracer, directionality and rate of arrival, together with extent of movement within the growth plate, were imaged in real time. For small molecules (up to 10 kDa), vascular access from all three directions was observed and entrance was equally permissive from the metaphyseal and the epiphyseal sides. Within our detection limit (a few percent of vascular concentration), 40 kDa and larger dextrans did not enter. These results have implications both for understanding systemic and paracrine regulation of growth plate chondrocytic differentiation, as well as variables associated with effective drug delivery to growth plate chondrocytes. © 2005 Wiley-Liss, Inc. [source] Principal Stratification Designs to Estimate Input Data Missing Due to DeathBIOMETRICS, Issue 3 2007Constantine E. Frangakis Summary We consider studies of cohorts of individuals after a critical event, such as an injury, with the following characteristics. First, the studies are designed to measure "input" variables, which describe the period before the critical event, and to characterize the distribution of the input variables in the cohort. Second, the studies are designed to measure "output" variables, primarily mortality after the critical event, and to characterize the predictive (conditional) distribution of mortality given the input variables in the cohort. Such studies often possess the complication that the input data are missing for those who die shortly after the critical event because the data collection takes place after the event. Standard methods of dealing with the missing inputs, such as imputation or weighting methods based on an assumption of ignorable missingness, are known to be generally invalid when the missingness of inputs is nonignorable, that is, when the distribution of the inputs is different between those who die and those who live. To address this issue, we propose a novel design that obtains and uses information on an additional key variable,a treatment or externally controlled variable, which if set at its "effective" level, could have prevented the death of those who died. We show that the new design can be used to draw valid inferences for the marginal distribution of inputs in the entire cohort, and for the conditional distribution of mortality given the inputs, also in the entire cohort, even under nonignorable missingness. The crucial framework that we use is principal stratification based on the potential outcomes, here mortality under both levels of treatment. We also show using illustrative preliminary injury data that our approach can reveal results that are more reasonable than the results of standard methods, in relatively dramatic ways. Thus, our approach suggests that the routine collection of data on variables that could be used as possible treatments in such studies of inputs and mortality should become common. [source] Phylogenetic Age is Positively Correlated with Sensitivity to Timber Harvest in Bornean MammalsBIOTROPICA, Issue 1 2008Erik Meijaard ABSTRACT The reasons that forest vertebrates differ in their response to selective timber extraction in tropical forests remain poorly characterized. Understanding what determines response and sensitivity can indicate how forest management might yield greater conservation benefits, and help us identify which lesser-known species may be especially vulnerable. We assessed the response of 41 Bornean mammals to selective timber harvest and tested eight hypotheses regarding the correlation between those responses and a range of species characteristics. Multivariate analyses show that phylogenetic species age is a key variable determining sensitivity. Older species are less able to cope with the effects of selective timber harvest. Most of these species are endemic to insular southeast Asia, and do not occur on the Asian mainland. These species are more specialized, and appear less able to cope with habitat change. In contrast, species tolerant to logging evolved more recently. This group tends to be omnivorous or herbivorous, to use all vegetation strata, and to be regionally widespread. This finding allows the sensitivity to habitat disturbance of lesser-known species to be predicted, and therefore has important conservation implications. These new insights also help in the design of large-scale forest landscapes that combine sustainable forest management and species conservation requirements. We recognize that these functions can be compatible, but that some species still need completely protected areas for their survival. RINGKASAN Hingga saat ini belum banyak penelitian mengungkapkan bagaimana berbagai vertebrata hutan akan bereaksi ketika dilakukan pembalakan hutan secara selektif. Dengan mempelajari tingkat reaksi dan kepekaan vertebrata, maka dapat diketahui bagaimana pengelolaan hutan dapat memberikan manfaat konservasi yang lebih besar. Penelitian demikian dapat membantu kami mengidentifikasi spesies mana saja yang biologinya sedikit diketahui namun termasuk rentan kepunahan. Kami mengevaluasi tanggapan 41 spesies mamalia Kalimantan/Borneo terhadap pemanenan kayu secara selektif, dan selanjutnya menguji 8 hipotesa berkaitan dengan hubungan atau korelasi antara tanggapan yang terjadi dengan berbagai karakteristik dari masing-masing spesies yang diteliti. Berdasarkan analisis multivarian disimpulkan bahwa umur filogenetik dari masing-masing spesies merupakan penentu kelentingan masing-masing spesies tersebut terhadap dampak pemanenan selektif. Spesies yang berumur lebih tua cenderung kurang dapat mentolerir dampak pemanenan kayu. Kebanyakan spesies ini merupakan endemik kepulauan di Asia Tenggara. Spesies ini cenderung merupakan spesialis (memiliki niche yang lebih sempit), serta tampaknya tidak seberapa kuat menerima dampak perubahan habitat. Sebaliknya spesies yang lebih toleran terhadap pembalakan cenderung baru berevolusi belakangan ini. Kelompok ini cenderung bersifat omnivora atau herbivora, serta mampu menggunakan seluruh lapisan vegetasi yang ada, serta tersebar meluas. Berdasarkan penelitian ini, dimungkinkan dilakukan prakiraan terhadap kepekaan dan dengan demikian terdapat berbagai manfaat praktis dalam hal metodologi. Analisis ini juga dapat membantu perancangan lanskap hutan berskala besar, dengan menggabungkan pengelolaan hutan berkelanjutan serta kebutuhan konservasi spesies. Kami melihat bahwa kedua kebutuhan pengelolaan tersebut dapat dipadu-serasikan, namun untuk beberapa spesies akan mutlak dibutuhkan kawasan yang dilindungi penuh demi kelanjutan spesies-spesies tersebut. [source] Psychological factors, immune function and recovery from major surgeryACTA NEUROPSYCHIATRICA, Issue 4 2009Ute Vollmer-Conna Objective: This study used a prospective design and the technique of structural modelling to examine the complex interrelations between psychological factors, immune status and complications after major surgery. Methods: Twenty-nine women scheduled for elective cholecystectomy were studied prospectively. Information regarding medical history, health practices, life stressors, and coping strategies was obtained two weeks prior to admission. At this initial meeting, as well as three days after surgery, and at one month follow-up immunological tests were performed and the level of psychological distress was assessed. The study additionally included measures of post-operative complications, and infections and negative effect during follow-up. Results: Pre-operative immune status emerged as a key variable exerting strong effects on subsequent immune function and, thereby producing significant, indirect effects on every recovery variable. Pre-operative distress was directly linked to increased mood disturbance at follow-up. Moreover, distress significantly influenced immune function both before and after surgery, which mediated a significant impact on most recovery variables. Active coping behaviour directly increased the risk of a complicated recovery. Conclusions: The study demonstrated that distress-induced changes in immune functioning have clinical relevance. Overall, the present findings suggest that recovery from surgery is facilitated in patients with a well-functioning immune system, a low-level of pre-operative distress and a passive coping disposition. [source] Are regulatory problems in infancy precursors of later hyperkinetic symptoms?ACTA PAEDIATRICA, Issue 11 2004K Becker Aim: To examine whether regulatory problems in infancy predict later hyperkinetic symptoms in childhood and pre-adolescence. Methods: In a prospective longitudinal study of 319 children at risk of later developmental problems and psychopathology, hyperkinetic behaviour problems were assessed at the ages of 2, 4.5, 8 and 11 y by means of a standardized parent interview. Infant regulatory problems at the age of 3 mo were determined from multiple sources of information. An observational procedure was used to assess the quality of mother-infant interaction. Results: At the age of 3 mo, 17% of the infants (n= 55; 27 boys, 28 girls) suffered from multiple regulatory problems. Compared to a control group (n= 264), these children presented more hyperkinetic symptoms throughout childhood. Negativity in the mother-infant interaction and early family adversity each contributed to later hyperkinetic symptoms. When controlling for family adversity, the association between infant multiple regulatory problems and later hyperkinetic problems was rendered insignificant. Conclusions: These findings suggest that multiple regulatory problems may not be a key variable for later hyperkinetic problems. The impact of early family adversity factors clearly outweighed that of infant psychopathology on later behaviour disorder. [source] Socio-economic status, obesity and prevalence of Type 1 and Type 2 diabetes mellitusDIABETIC MEDICINE, Issue 6 2000J. M. M. Evans Summary Aims ,The influence of socio-economic status on the prevalence of Type 1 and Type 2 diabetes mellitus, and on obesity, was explored using routinely collected healthcare data for the population of Tayside, Scotland. Methods ,Among 366 849 Tayside residents, 792 and 5474 patients with Type 1 and Type 2 diabetes, respectively, were identified from a diabetes register. The Carstairs Score was used as a proxy for socio-economic status. This is a material deprivation measure derived from the UK census, using postcode data for four key variables. Odds ratios for diabetes prevalence, adjusted for age, were determined for each of six deprivation categories (1 , least deprived, 6/7 , most deprived). The mean body mass index (BMI) in each group was also determined, and the effect of deprivation category explored by analysis of covariance, adjusting for age and sex. Results ,The prevalence of Type 2 diabetes, but not Type 1 diabetes, varied by deprivation. People in deprivation category 6 and 7 were 1.6-times (95% confidence interval 1.4,1.8) more likely to have Type 2 diabetes than those least deprived. There was no relationship between deprivation and BMI in Type 1 diabetes (P = 0.36), but there was an increase in BMI with increasing deprivation in Type 2 diabetes (P < 0.001; test of linearity P < 0.001). Conclusions ,The study confirms the relationship between deprivation and the prevalence of Type 2 diabetes. There are more obese, diabetic patients in deprived areas. They require more targeted resources and more primary prevention. [source] Is dyslexia necessarily associated with negative feelings of self-worth?DYSLEXIA, Issue 3 2008A review, implications for future research Abstract This paper will provide an overview of research in the past 20 years into the relationship between dyslexia and various aspects of self-perception, including self-concept, self-esteem, self-efficacy and locus of control. Problems are identified relating to the measurement of some of the most widely used constructs, as is the need for more precise identification of key variables relating to them. Critical issues concerning the assumptions that can be drawn from largely correlational data are highlighted also. The conclusion is drawn that an alternative approach to research in this area is required to enhance our understanding of how those suffering from learning disabilities of a dyslexic nature develop a positive or negative sense of identity. Suggestions are made as to how this can be achieved by drawing upon attribution theory and other aspects of social psychology. Copyright © 2008 John Wiley & Sons, Ltd. [source] Error estimation of closed-form solution for annual rate of structural collapseEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 15 2008Brendon A. Bradley Abstract With the increasing emphasis of performance-based earthquake engineering in the engineering community, several investigations have been presented outlining simplified approaches suitable for performance-based seismic design (PBSD). Central to most of these PBSD approaches is the use of closed-form analytical solutions to the probabilistic integral equations representing the rate of exceedance of key performance measures. Situations where such closed-form solutions are not appropriate primarily relate to the problem of extrapolation outside of the region in which parameters of the closed-form solution are fit. This study presents a critical review of the closed-form solution for the annual rate of structural collapse. The closed-form solution requires the assumptions of lognormality of the collapse fragility and power model form of the ground motion hazard, of which the latter is more significant regarding the error of the closed-form solution. Via a parametric study, the key variables contributing to the error between the closed-form solution and solution via numerical integration are illustrated. As these key variables cannot be easily measured, it casts doubt on the use of such closed-form solutions in future PBSD, especially considering the simple and efficient nature of using direct numerical integration to obtain the solution. Copyright © 2008 John Wiley & Sons, Ltd. [source] The Impact of Vertical Scaling Decisions on Growth InterpretationsEDUCATIONAL MEASUREMENT: ISSUES AND PRACTICE, Issue 4 2009Derek C. Briggs Most growth models implicitly assume that test scores have been vertically scaled. What may not be widely appreciated are the different choices that must be made when creating a vertical score scale. In this paper empirical patterns of growth in student achievement are compared as a function of different approaches to creating a vertical scale. Longitudinal item-level data from a standardized reading test are analyzed for two cohorts of students between Grades 3 and 6 and Grades 4 and 7 for the entire state of Colorado from 2003 to 2006. Eight different vertical scales were established on the basis of choices made for three key variables: Item Response Theory modeling approach, linking approach, and ability estimation approach. It is shown that interpretations of empirical growth patterns appear to depend upon the extent to which a vertical scale has been effectively "stretched" or "compressed" by the psychometric decisions made to establish it. While all of the vertical scales considered show patterns of decelerating growth across grade levels, there is little evidence of scale shrinkage. [source] The influence of pH and salinity on the toxicity of heavy metals in sediment to the estuarine clam Ruditapes philippinarum,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2004Inmaculada Riba Abstract An approach is presented for determining the influence of two key variables, pH and salinity(S), on the toxicity of four common heavy metals bound to sediments in estuaries. Two samples of environmental sediment taken from two estuaries in southern Spain (the Huelva estuary and the Guadalquivir River estuary), together with a dilution of toxic mud from the Aznalcóllar (Spain) mining spill (April 1998) were used to determine their toxicity at different values of pH (6.5, 7.5, and 8.5) and salinity (10, 20, and 30) on the estuarine clam Ruditapes philippinarum. Two different endpoints, sublethal, indicated by clam reburial (median effective burial time [ET50]), and relative mortality (median lethal concentration [LC50]), were used to quantify the toxicity associated with the heavy metals. Neither salinity nor pH was found to influence the toxic responses measured by the behavioral endpoint (ET50). However, a strong effect on the LC50 related to pH and salinity was detected, with the toxicity of the heavy metals being increased at low values of both variables (pH = 6.5 and S = 10). The mechanism of heavy metals uptake through water may explain this influence of pH and salinity on the lethal toxicity detected. The results show differences in the toxicity of these heavy metals bound to sediments depending on whether the origin of metal contamination is chronic or acute. [source] Rational Pricing of Internet Companies RevisitedFINANCIAL REVIEW, Issue 4 2001Eduardo S. Schwartz G12 Abstract In this article we expand and improve the Internet company valuation model of Schwartz and Moon (2000) in numerous ways. By using techniques from real options theory and modern capital budgeting, the earlier paper demonstrated that uncertainty about key variables plays a major role in the valuation of high growth Internet companies. Presently, we make the model more realistic by providing for stochastic costs and future financing, and also by including capital expenditures and depreciation in the analysis. Perhaps more importantly, we offer insights into the practical implementation the model. An important challenge to implementing the original model was estimating the various parameters of the model. Here, we improve the procedure by setting the speed of adjustment parameters equal to one another, by tying the implied half-life of the revenue growth process to analyst forecasts, and by inferring the risk-adjustment parameter from the observed beta of the company's stock price. We illustrate these extensions in a valuation of the company eBay. [source] Second Language Reading Research on Passage Content and Gender: Challenges for the Intermediate-Level CurriculumFOREIGN LANGUAGE ANNALS, Issue 4 2001Cindy Brantmeier PhD Howevel, a careful examination of available studies reveals disparities among research methods and procedures, thus making it difficult to formulate theories for re-examining the intermediate-level course, where the reading of lengthy, authentic texts begins. To complicate matters further, females begin to outnumber males at the intermediate level, and this gap widens at the advanced levels (Chavez, 2001). This article , through a careful review of the relevant literature , shows that much of the L2 reading process at the intermediate level remains unexplained. Finally, a call for more research at the intermediate level that examines key variables, such as passage content and gender, is made. [source] Impact of the fish Garra on the ecology of reservoirs and the occurrence of Microcystis blooms in semi-arid tropical highlands: an experimental assessment using enclosuresFRESHWATER BIOLOGY, Issue 8 2009TADESSE DEJENIE Summary 1.,Many man-made reservoirs in the semi-arid highlands of Northern Ethiopia (Tigray) are characterised by the occurrence of intensive blooms of cyanobacteria and a dominance of small riverine fishes belonging to the genus Garra. 2.,We carried out enclosure experiments to test for the effect of these small fish on abiotic characteristics, phytoplankton biomass and zooplankton community structure in the pelagic of two reservoirs (Gereb Awso and Tsinkanet). Two experiments were carried out in each of the reservoirs, one at the end of the rainy season (highest water level) and one at the end of the dry season (lowest water level). 3.,The presence of Garra in general increased the amount of suspended matter, nutrient concentrations (total nitrogen and total phosphorus), phytoplankton and Microcystis biomass (including the proportion of Microcystis in the phytoplankton community), and reduced water transparency. The positive effect of the presence of Garra on nutrient concentrations and phytoplankton productivity indicate that Garra has the potential to affect food web functioning indirectly through bottom-up effects, by enhancing nutrient concentrations through sediment resuspension and excretion of nutrients. Indeed, population densities of the cladoceran zooplankton taxa Ceriodaphnia and Diaphanosoma also showed an overall increase in enclosures with Garra. 4.,However, our data also provide some evidence for a potential of Garra to exert top-down control on large bodied daphnids (Daphnia carinata, D. barbata), although such effect varied among experiments. The limited capability of Garra to control zooplankton communities mainly reflects the low efficiency of these small, riverine and benthos-oriented fish in foraging on zooplankton and suggests the existence of an unoccupied niche for zooplanktivorous fish in the majority of the reservoirs. 5.,Although the main effects of Garra on the pelagic food web seemed to be mediated by bottom-up mechanisms, our results also indicate that one of the key variables, the relative abundance of Microcystis, was impacted by Daphnia -mediated trophic cascade effects. [source] Effects of increased temperature and nutrient enrichment on the stoichiometry of primary producers and consumers in temperate shallow lakesFRESHWATER BIOLOGY, Issue 7 2008M. VENTURA Summary 1. We studied the effects of increased water temperatures (0,4.5 °C) and nutrient enrichment on the stoichiometric composition of different primary producers (macrophytes, epiphytes, seston and sediment biofilm) and invertebrate consumers in 24 mesocosm ecosystems created to mimic shallow pond environments. The nutrient ratios of primary producers were used as indicative of relative nitrogen (N) or phosphorus (P) limitation. We further used carbon stable isotopic composition (,13C) of the different primary producers to elucidate differences in the degree of CO2 limitation. 2. Epiphytes were the only primary producer with significantly higher ,13C in the enriched mesocosms. No temperature effects were observed in ,13C composition of any primary producer. Independently of the treatment effects, the four primary producers had different ,13C signatures indicative of differences in CO2 limitation. Seston had signatures indicating negligible or low CO2 limitation, followed by epiphytes and sediment biofilm, with moderate CO2 limitation, while macrophytes showed the strongest CO2 limitation. CO2 together with biomass of epiphytes were the key variables explaining between 50 and 70% of the variability in ,13C of the different primary producers, suggesting that epiphytes play an important role in carbon flow of temperate shallow lakes. 3. The ratio of carbon to chlorophyll a decreased with increasing temperature and enrichment in both epiphytes and seston. The effects of temperature were mainly attributed to changes in algal Chl a content, while the decrease with enrichment was probably a result of a higher proportion of algae in the seston and epiphytes. 4. Macrophytes, epiphytes and seston decreased their C : N with enrichment, probably as an adaptation to the different N availability levels. The C : N of epiphytes and Elodea canadensis decreased with increasing temperature in the control mesocosms. Sediment biofilm was the only primary producer with lower C : P and N : P with enrichment, probably as a result of higher P accumulation in the sediment. 5. Independently of nutrient level and increased temperature effects the four primary producers had significantly different stoichiometric compositions. Macrophytes had higher C : N and C : P and, together with epiphytes, also the highest N : P. Seston had no N or P limitation, while macrophytes and epiphytes may have been P limited in a few mesocosms. Sediment biofilm indicated strong N deficiency. 6. Consumers had strongly homeostatic stoichiometric compositions in comparison to primary producers, with weak or no significant treatment effects in any of the groups (insects, leeches, molluscs and crustaceans). Among consumers, predators had significantly higher N content and lower C : N than grazers. [source] Dealing with Timing and Synchronization in Opportunities for Joint Activity ParticipationGEOGRAPHICAL ANALYSIS, Issue 3 2010Tijs Neutens The ability of people to access opportunities offered by the built environment is circumscribed by various sets of space,time constraints, including the requirements to meet other persons at particular times and places to undertake activities together. While models of space,time accessibility recognize that joint activities may constrain the performance of activities in space and time, their specifications do not explicitly acknowledge the opportunities that individuals of a group have for joint activity participation. Therefore, this article focuses on joint activity participation and argues that collective activity decisions are the outcome of a complex process involving various aspects of timing, synchronization, and social hierarchy. The utility-theoretic model proposed here quantifies the extent to which opportunities can be jointly accessed by a particular group of people within a specific time period. Central to the approach are three key variables: the attractiveness of an opportunity, the time available for activity participation, and the travel time to an activity location. Because of the multiperson character of joint activities, the determination of these variables is subject to individual preferences, privileges, and power differentials within a group. Specific attention is given to how time-of-day and synchronization effects influence the opportunities accessible to a group of individuals. The impact of these factors on joint accessibility is illustrated by a real-world example of an everyday rendezvous scenario. The outcomes of a simulation exercise suggest that time-of-day and synchronization effects significantly affect the benefits that can be gained from opportunities for joint activities. La capacidad de acceso a las oportunidades que los entornos construidos (como las ciudades) ofrecen a las personas, está limitada por un conjunto diverso de restricciones espacio-temporales. Entre ellas se incluyen los requisitos para coincidir y encontrarse con otras personas en determinados momentos y lugares con el fin de realizar actividades conjuntas. Los modelos de accesibilidad comunes reconocen que las actividades conjuntas pueden limitar el ejercicio de actividades en el espacio y el tiempo. Sin embargo, sus especificaciones no reconocen explícitamente las oportunidades disponibles a todos los individuos de un grupo para participar de una actividad conjunta. Es en este contexto y dadas las limitaciones descritas que este artículo se centra en la participación de individuos en actividades conjuntas y propone el argumento que la toma de decisiones relacionadas con dichas actividades son el resultado de un proceso complejo que involucra varios aspectos de temporización (programación temporal), sincronización, y jerarquía social. El modelo teórico de utilidad que se propone aquí cuantifica el grado en que las oportunidades pueden ser evaluadas en forma conjunta por un grupo de personas particular dentro de un período de tiempo específico. El marco general propuesto por los autores se basa en tres variables fundamentales: el atractivo de una oportunidad, el tiempo disponible para la participación de la actividad, y el tiempo de desplazamiento al lugar donde se lleva a cabo actividad. Debido al carácter particular de estas actividades (que involucran múltiples participantes), la determinación de estas variables está sujeta a preferencias individuales, a privilegios y a diferencias de poder dentro de un grupo. El presente estudio además presta atención especial a la forma en la que la hora del día y los efectos de sincronización pueden influenciar la disponibilidad de oportunidades para un grupo determinado de individuos. El impacto de estos factores sobre la accesibilidad agregada de actividades conjuntas es ejemplificado por los autores mediante un caso del mundo real que utiliza escenarios de encuentros diarios entre personas. Los resultados de este ejercicio de simulación sugieren que los efectos de la hora del día y la sincronización afectan significativamente los beneficios que se pueden obtener a partir las oportunidades disponibles para acceder a y realizar actividades conjuntas. [source] Reshaping the State: Administrative Reform and New Public Management in FranceGOVERNANCE, Issue 4 2005ALISTAIR COLE This essay examines the administrative reform process in France since the late 1980s. The key reforms undertaken during this period have sought to delegate greater managerial autonomy to the ministerial field-service level. We undertook semistructured interviews with officials in the field services of three French ministries (Education, Agriculture, and Infrastructure) in the Champagne-Ardennes region, as well as with members of the wider policy communities. The capacity of the field services to adopt a proactive approach to management reform depended on five key variables: internal organizational dynamics; the attitude of the central services to mesolevel autonomy; the degree of institutional receptivity to change; the type of service delivery, and the extent of penetration in local networks. The Infrastructure Ministry was more receptive to management change than either Education or (especially) Agriculture, a receptivity that reflects the institutional diversity of the French administrative system, and that supports new institutionalist arguments. The essay rejects straightforward convergence to the New Policy Management norm. Changes in public management norms require either endogenous discursive shifts or else need to be interpreted in terms of domestic registers that are acceptable or understandable to those charged with implementing reform. [source] When is Commuting Desirable to the Individual?GROWTH AND CHANGE, Issue 3 2004David T. Ory ABSTRACT Commuting is popularly viewed as a stressful, costly, time-wasting experience from the individual perspective, with the attendant congestion imposing major social costs as well. However, several authors have noted that commuting can also offer benefits to the individual, serving as a valued transition between the home and work realms of personal life. Using survey data collected from about 1,300 commuting workers in three San Francisco Bay Area neighborhoods, empirical models are developed for four key variables measured for commute travel, namely: Objective Mobility, Subjective Mobility, Travel Liking, and Relative Desired Mobility. Explanatory variables include measures of general travel-related attitudes, personality traits, lifestyle priorities, and sociodemographic characteristics. Both descriptive statistics and analytical models indicate that commuting is not the unmitigated burden that it is widely perceived to be. About half of the sample were relatively satisfied with the amount they commute, with a small segment actually wanting to increase that amount. Both the psychological impact of commuting, and the amounts people want to commute relative to what they are doing now, are strongly influenced by their liking for commuting. An implication for policy is that some people may be more resistant than expected toward approaches intended to induce reductions in commuting (including, for example, telecommuting). New creativity may be needed to devise policies that recognize the inherent positive utility of travel, while trying to find socially beneficial ways to fulfill desires to maintain or increase travel. [source] Cost-effectiveness of HIV nonoccupational post-exposure prophylaxis in AustraliaHIV MEDICINE, Issue 4 2009D Guinot Objective The aim of the study was to determine the cost-effectiveness of HIV nonoccupational post-exposure prophylaxis (NPEP) in Australia. Methods A retrospective cost analysis of a population-based observational cohort of 1601 participants eligible for NPEP in Australia between 1998 and 2004 was carried out. We modelled NPEP treatment costs and combined them with effectiveness outcomes to calculate the cost per seroconversion avoided. We estimated the cost-utility of the programme, and sensitivity and threshold analysis was performed on key variables. Results The average NPEP cost per patient was A$1616, of which A$848 (52%) was for drugs, A$331 (21%) for consultations, A$225 (14%) for pathology and A$212 (13%) for other costs. The cost per seroconversion avoided in the cohort was A$1 647 476 in our base case analysis, and A$512 410 when transmission rates were set at their maximal values. The cost per quality-adjusted life-year (QALY) was between A$40 673 and A$176 772, depending on the risks of HIV transmission assumed. Conclusions In our base case, NPEP was not a cost-effective intervention compared with the widely accepted Australian threshold of A$50 000 per QALY. It was only cost-effective after receptive unprotected anal intercourse exposure to an HIV-positive source. Although NPEP was a relatively well-targeted intervention in Australia, its cost-effectiveness could be improved by further targeting high-risk exposures. [source] Energy budget above a temperate mixed forest in northeastern ChinaHYDROLOGICAL PROCESSES, Issue 18 2007Jiabing Wu Abstract Components of the energy budget were measured continuously above a 300-year-old temperate mixed forest at the Changbaishan site, northeastern China, from 1 January to 31 December 2003, as a part of the ChinaFlux programme. The albedo values above the canopy were lower than most temperate forests, and the values for snow-covered canopy were over 50% higher than for the snow-free canopy. In winter, net radiation Rn was generally less than 5% of the summer value due to high albedo and low incoming solar radiation. The annual mean latent heat LE was 37·5 W m,2, accounting for 52% of Rn. The maximum daily evaporation was about 4·6 mm day,1 in summer. Over the year, the accumulated precipitation was 578 mm; this compares with 493 mm of evapotranspiration, which shows that more than 85% of water was returned to the atmosphere through evapotranspiration. The LE was strongly affected by the transpiration activity and increased quickly as the broadleaved trees began to foliate. The sensible heat H dropped at that time, although Rn increased. Consequently, the seasonal variation in the Bowen ratio , was clearly U-shaped, and the minimum value (0·1) occurred on a sunny day just after rain, when most of the available energy was used for evapotranspiration. Negative , values occurred occasionally in the non-growing season as a result of intensive radiative cooling and the presence of water on the surface. The , was very high (up to 13·0) in snow-covered winter, when evapotranspiration was small due to low surface temperature and available soil water. Vegetation phenology and soil moisture were the key variables controlling the available energy partitioning between H and LE. Energy budget closure averaged better than 86% on a half-hourly basis, with slightly greater closure on a daily basis. The degree of closure showed a dependence on friction velocity u*. Copyright © 2006 John Wiley & Sons, Ltd. [source] Assessing burn severity and comparing soil water repellency, Hayman Fire, ColoradoHYDROLOGICAL PROCESSES, Issue 1 2006Sarah A. Lewis Abstract An important element of evaluating a large wildfire is to assess its effects on the soil in order to predict the potential watershed response. After the 55 000 ha Hayman Fire on the Colorado Front Range, 24 soil and vegetation variables were measured to determine the key variables that could be used for a rapid field assessment of burn severity. The percentage of exposed mineral soil and litter cover proved to be the best predictors of burn severity in this environment. Two burn severity classifications, one from a statistical classification tree and the other a Burned Area Emergency Response (BAER) burn severity map, were compared with measured ,ground truth' burn severity at 183 plots and were 56% and 69% accurate, respectively. This study also compared water repellency measurements made with the water drop penetration time (WDPT) test and a mini-disk infiltrometer (MDI) test. At the soil surface, the moderate and highly burned sites had the strongest water repellency, yet were not significantly different from each other. Areas burned at moderate severity had 1·5 times more plots that were strongly water repellent at the surface than the areas burned at high severity. However, the high severity plots most likely had a deeper water repellent layer that was not detected with our surface tests. The WDPT and MDI values had an overall correlation of r = ,0·64(p < 0·0001) and appeared to be compatible methods for assessing soil water repellency in the field. Both tests represent point measurements of a soil characteristic that has large spatial variability; hence, results from both tests reflect that variability, accounting for much of the remaining variance. The MDI is easier to use, takes about 1 min to assess a strongly water repellent soil and provides two indicators of water repellency: the time to start of infiltration and a relative infiltration rate. Copyright © 2005 John Wiley & Sons, Ltd. [source] Missile defence and the transatlantic security relationshipINTERNATIONAL AFFAIRS, Issue 3 2001Wyn Q. Bowen This article examines the re-emergence of ballistic missile defence (BMD) as a contentious issue in US-European security relations since 1999. It begins by outlining three phases in the recent evolution of US missile defence policy from 1995 to mid-2001. The article then examines five key factors that have dominated European views and concerns in relation to BMD: a divergence between European and American assessments of the emerging ballistic missile threat; concern over the implications for nuclear arms control stemming from Russian and Chinese opposition to BMD; the impact of missile defence on deterrence and the Atlantic alliance; scepticism about the technological feasibility of BMD; and the potential opportunity costs associated with resource allocation to missile defence. It is shown that European anxieties have been exacerbated by a perception of a growing unilateralism in American security policy in recent years. The article proceeds by arguing that the US-European debate over BMD looks set to evolve in one of two directions. The more likely and most desirable scenario would involve the US reaching an understanding with its European allies on the way forward. The less desirable scenario would involve key European countries, such as France and Germany, deciding ultimately to withhold their political support for BMD, which would have the potential of causing significant rifts in both transatlantic and intra-European security relations. In both cases, it is argued that the BMD debate will be defined by the interaction of several key variables. These include the extent to which the Bush administration engages in meaningful consultations with the Europeans; the administration's ability or otherwise to reach an agreement with Russia on the way ahead; the architecture options of a future allied or global BMD system; the related issues of technological feasibility and financial cost; and the evolving missile threat. [source] Experimental modelling and intelligent control of a wood-drying kilnINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 8 2001Givon Chuen Kee Yan Abstract Proper control of the wood-drying kiln is crucial in ensuring satisfactory quality of dried wood and in minimizing drying time. This paper presents the development, implementation, and evaluation of a control system for a lumber drying kiln process incorporating sensory feedback from in-wood moisture content sensors and intelligent control such that the moisture content of lumber will reach and stabilize at the desired set point without operator interference. The drying process is difficult to model and control due to complex dynamic nonlinearities, coupling effects among key variables, and process disturbances caused by the variation of lumber sizes, species, and environmental factors. Through system identification scheme using experimental data and recursive least-squares algorithm for parameter estimation, appropriate models are developed for simulation purpose and controller design. Two different control methodologies are employed and compared: a conventional proportional-integral-derivative (PID) controller and a direct fuzzy logic controller (FLC), and system performance is evaluated through simulations. The developed control system is then implemented in a downscaled industrial kiln located at the Innovation Centre of National Research Council (NRC) of Canada. This experimental set-up is equipped with a variety of sensors, including thermocouples for temperature feedback, an air velocity transmitter for measuring airflow speed in the plenum, relative humidity sensors for measuring the relative humidity inside the kiln, and in-wood moisture content sensors for measuring the moisture content of the wood pieces. For comparison, extensive experimental studies are carried out on-line using the two controllers, and the results are evaluated to tune the controller parameters to achieve good performance in the wood-drying kiln. The combination of conventional control with the intelligent control promises improved performance. The control system developed in this study may be applied in industrial wood-drying kilns, with a clear potential for improved quality and increased speed of drying. Copyright © 2001 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||||||||||||||