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Threshold Level (threshold + level)
Selected AbstractsLate Preterm Birth and Neonatal Outcome: Is 37 Weeks' Gestation a Threshold Level or a Road Marker on the Highway of Perinatal Risk?BIRTH, Issue 2 2010Russell S. Kirby PhD No abstract is available for this article. [source] Biomarkers for exposure to estrogenic compounds: Gene expression analysis in zebrafish (Danio rerio)ENVIRONMENTAL TOXICOLOGY, Issue 1 2008Ulf Kausch Abstract Gene expression analyses in male zebrafish (Danio rerio) were carried out using microarray technique and quantitative polymerase chain reaction. Genes responding to the exposure to 17,-estradiol, bisphenol A and genistein were identified, among them genes involved in metabolism, reproductional and developmental processes. Threshold levels of 17,-estradiol (200 ng/L), bisphenol A (2000 ,g/L), and genistein (5000 ,g/L) for the upregulation of the vtg1 gene in short-time exposures (11 days) were determined by qPCR. 14k microarrays were used to generate complete lists of genes regulated by these estrogenic compounds. For this purpose, liver samples from 10 exposed zebrafish and 10 controls were processed. In this case the expressions of 211 genes were significantly regulated by 17,-estradiol, 47 by bisphenol A and 231 by genistein. Furthermore, it is shown that fish exposed to 17,-estradiol and genistein have similarities in their gene expression patterns, whereas bisphenol A apparently affected gene expression in a different way. Only genes coding for egg-yolk precursor protein vitellogenin were found to be regulated by all three compounds, which shows that these genes are the only suitable markers for exposure to different estrogenic compounds. The regulated genes were assigned to gene ontology classes. All three estrogenic compounds regulated genes mainly involved in primary and cellular metabolism, but genistein regulated several genes involved in cell cycle-regulation and bisphenol A several genes involved in protein biosynthesis. Genistein also upregulated the expression of four eggshell proteins, which can be used as biomarkers for exposure to this chemical. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2008. [source] Effects of lambda-cyhalothrln in two ditch microcosm systems of different trophic statusENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2005Ivo Roessink Abstract The fate and effects of the pyrethroid insecticide lambda-cyhalothrin were compared in mesotrophic (macrophyte-dominated) and eutrophic (phytoplankton-dominated) ditch microcosms (,0.5 m3). Lambda-cyhalothrin was applied three times at one-week intervals at concentrations of 10, 25, 50, 100, and 250 ng/L. The rate of dissipation of lambda-cyhalothrin in the water column of the two types of test systems was similar. After 1 d, only 30% of the amount applied remained in the water phase. Initial, direct effects were observed primarily on arthropod taxa. The most sensitive species was the phantom midge (Chaoborus obscuripes). Threshold levels for slight and transient direct toxic effects were similar (10 ng/L) between types of test systems. At treatment levels of 25 ng/L and higher, apparent population and community responses occurred. At treatments of 100 and 250 ng/L, the rate of recovery of the macroinvertebrate community was lower in the macrophyte-dominated systems, primarily because of a prolonged decline of the amphipod Gammarus pulex. This species occurred at high densities only in the macrophyte-dominated enclosures. Indirect effects (e.g., increase of rotifers and microcrustaceans) were more pronounced in the plankton-dominated test systems, particularly at treatment levels of 25 ng/L and higher. [source] Threshold levels of purified natural Bos d 2 for inducing bronchial airway response in asthmatic patientsCLINICAL & EXPERIMENTAL ALLERGY, Issue 10 2002T. Zeiler Summary Background Provocation tests are invaluable in establishing threshold levels and a causal relationship between atopic asthma and a certain allergen source, especially in relation to work-associated exposure. Purified major allergens open possibilities for a more accurate assessment of sensitization. Objective To determine the threshold dose of purified major bovine dander allergen Bos d 2 in bronchial provocation in comparison with the standard allergen and a set of other parameters of allergy. Method Nine consecutive patients referred to hospital for confirming the bovine origin of their occupational asthma were subjected to bronchial provocation tests with purified natural Bos d 2 and a standard bovine dander allergen. Additional tests included bronchial histamine challenge, measurements of total IgE, specific IgE antibody determinations and skin prick tests (SPT) with both allergens. Results In the provocation tests with Bos d 2, a 15% decrease in the forced expiratory volume in 1 s (FEV1) and/or peak expiratory flow (PEF) values in eight out of nine patients confirmed the predominant role of Bos d 2 in the sensitization. The threshold dose of Bos d 2 varied from 0.1 µg to > 100 µg (median ± median absolute deviation = 4.5 ± 3.9 µg). A positive SPT was induced by a median dose of 13.9 ± 9.8 µg of Bos d 2. Bronchial response to histamine and IgE antibodies against Bos d 2 showed the highest correlations to the provocations results. Conclusions The efficacy of Bos d 2 in bronchial provocation in patients with occupational cattle-associated asthma was confirmed and the range of the threshold level was determined. There were individual variations, but the response in provocation remains the reference method for identification of the cause of occupational atopic asthma. SPT and the measurement of specific IgE antibodies, preferably with purified or recombinant major allergens, increase the accuracy of the diagnosis. [source] Further studies on knockout mice lacking a functional dynein heavy chain (MDHC7).CYTOSKELETON, Issue 2 2005Abstract Male mice had been previously generated in which the inner dynein arm heavy chain 7 gene (MDHC7) was disrupted. MDHC7,/, animals show asthenozoospermia and are sterile. Very few of their spermatozoa can achieve forward progression, but for those that can, we add here the information (1) that the three-dimensional aspects of their movement are normal; (2) that their maximum velocity is less than that of wild-type controls; and (3) that they are entirely unable to penetrate media of raised viscosity (25,4,000 cP). However, the large majority of the spermatozoa can achieve only a low amplitude vibration. In these sperm we find, using electron microscopy, that the outer dense fibres retain attachments to the inner surface of the mitochondria. Such attachments are present in normal epididymal mouse spermatozoa but are broken down as soon as the sperm become motile on release from the epididymis. The attachments are presumed to be essential during midpiece development and, afterwards, to require a threshold level of force to loosen them and so permit the sliding displacements necessary for normal bending. We presume that the disruption of the inner dynein arm heavy chain gene, MDHC7, means that there is insufficient force to overcome the attachments, for all but a few spermatozoa. Cell Motil. Cytoskeleton 61:74,82, 2005. © 2005 Wiley-Liss, Inc. [source] Close range digital photogrammetric analysis of experimental drainage basin evolutionEARTH SURFACE PROCESSES AND LANDFORMS, Issue 3 2003J. Brasington Abstract Despite the difficulties of establishing formal hydraulic and geometric similarity, small-scale models of drainage basins have often been used to investigate the evolution and dynamics of larger-scale landforms. Historically, this analysis has been restricted to planform basin characteristics and only in the last decade has the topographic similarity of experimental landscapes been explored through explicitly three-dimensional parameters such as the distributions of cumulative drainage area, area,slope and catchment elevation. The current emphasis on three-dimensional morphometry reflects a growing awareness of the descriptive paucity of planform data and the need for more robust analysis of spatial scaling relationships. This paradigm shift has been significantly facilitated by technological developments in topographic survey and digital elevation modelling (DEM) which now present the opportunity to acquire and analyse high-resolution, distributed elevation data. Few studies have, however, attempted to use topographic modelling to provide information on the changing pattern and rate of sediment transport though an evolving landscape directly by using multitemporal DEM differencing techniques. This paper reports a laboratory study in which digital photogrammetry was employed to derive high-resolution DEMs of a simulated landscape in declining equilibrium at 15 minute frequency through a 240 minute simulation. Detailed evaluation of the DEMs revealed a vertical precision of 1·2 mm and threshold level of change detection between surfaces of ±3 mm at the 95 per cent confidence level. This quality assurance set the limits for determining the volumetric change between surfaces, which was used to recover the sediment budget through the experiment and to examine local - and basin-scale rates of sediment transport. A comparison of directly observed and morphometric estimates of sediment yield at the basin outlet was used to quantify the closure of the sediment budget over the simulation, and revealed an encouragingly small 6·2 per cent error. The application of this dynamic morphological approach has the potential to offer new insights into the controls on landform development, as demonstrated here by an analysis of the changing pattern of the basin sediment delivery ratio during network growth. Copyright © 2003 John Wiley & Sons, Ltd. [source] Seismic reliability of V-braced frames: Influence of design methodologiesEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 14 2009Alessandra Longo Abstract According to the most modern trend, performance-based seismic design is aimed at the evaluation of the seismic structural reliability defined as the mean annual frequency (MAF) of exceeding a threshold level of damage, i.e. a limit state. The methodology for the evaluation of the MAF of exceeding a limit state is herein applied with reference to concentrically ,V'-braced steel frames designed according to different criteria. In particular, two design approaches are examined. The first approach corresponds to the provisions suggested by Eurocode 8 (prEN 1998,Eurocode 8: design of structures for earthquake resistance. Part 1: general rules, seismic actions and rules for buildings), while the second approach is based on a rigorous application of capacity design criteria aiming at the control of the failure mode (J. Earthquake Eng. 2008; 12:1246,1266; J. Earthquake Eng. 2008; 12:728,759). The aim of the presented work is to focus on the seismic reliability obtained through these design methodologies. The probabilistic performance evaluation is based on an appropriate combination of probabilistic seismic hazard analysis, probabilistic seismic demand analysis (PSDA) and probabilistic seismic capacity analysis. Regarding PSDA, nonlinear dynamic analyses have been carried out in order to obtain the parameters describing the probability distribution laws of demand, conditioned to given values of the earthquake intensity measure. Copyright © 2009 John Wiley & Sons, Ltd. [source] Subcellular distribution of zinc in Daphnia magna and implication for toxicityENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2010Wen-Xiong Wang Abstract We examined the subcellular partitioning of zinc (Zn) in Daphnia magna both under acute and chronic exposures. In the acute Zn toxicity tests, the daphnids were exposed to different Zn concentrations for 48,h or to one lethal concentration (1,000,µg/L) for different durations (time to death for up to 47,h). Significant mortality of daphnids was observed when the newly accumulated Zn concentration reached a threshold level of approximately 40,µg/g wet weight (or 320,µg/g dry wt), approximately 3.5 times higher than the background tissue concentration (92,µg/g dry wt). Chronic exposure (14 d) to Zn resulted in nonobservable effect on survivorship and growth at newly accumulated tissue concentration of over 40,µg/g wet weight. With increasing Zn acute exposure, more Zn was partitioned into the cellular debris fraction, indicating that this fraction was presumably the first targeted site of binding for Zn upon entering the animals. The importance of other subcellular fractions either decreased accordingly or remained comparable. We found that the metal-sensitive fraction (Zn distribution in the organelles and heat-denatured proteins) did not predict the acute Zn toxicity in Daphnia. During chronic exposure, however, no major change of the subcellular partitioning of Zn with increasing Zn exposure was documented. Zinc was mainly found in the organelles and heat-stable protein fractions during chronic exposure, suggesting that any subcellular repartitioning occurred primarily during acute exposure. Metallothioneins were induced upon chronic Zn exposure, but its induction evidently lagged behind the Zn accumulation. Our present study showed that the subcellular fractionation approach could not be readily used to predict the acute and chronic toxicities of Zn in Daphnia. A tissue-based Zn accumulation approach with a threshold Zn tissue concentration was better in predicting acute Zn toxicity. Environ. Toxicol. Chem. 2010; 29:1841,1848. © 2010 SETAC [source] An evaluation of the etiology of reduced CYP1A1 messenger RNA expression in the Atlantic tomcod from the Hudson River, New York, USA, using reverse transcriptase polymerase chain reaction analysisENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2001Nirmal K. Roy Abstract Adult Atlantic tomcod, Microgadus tomcod, from the Hudson River, New York State, USA, exhibit reduced inducibility of hepatic cytochrome P4501A1 (CYP1A1) mRNA compared with adult tomcod from the cleaner Miramichi River, New Brunswick, Canada, when treated with coplanar polychlorinated biphenyl (PCB) congeners or 2,3,7,8-tetrachlorodibenzo- p -dioxin. In contrast, little difference in CYP1A1 inducibility is observed between tomcod from these two rivers when treated with polycyclic aromatic hydrocarbons (PAHs). We sought to determine if impaired hepatic CYP1A1 inducibility in Hudson River tomcod results from a multigenerational, genetic adaptation or a single generational, physiological acclimation. Embryos and larvae from controlled experimental crosses of Hudson River and Miramichi River parents were exposed for 24 h to water-borne PCB congener 77 (10 ppm), benzo[a]pyrene (BaP; 10 ppm), or dimethysulfoxide, and CYP1A1 expression was assessed in individual larva using competitive reverse transcriptase polymerase chain reaction (RT-PCR) analysis. The CYP1A1 mRNA was significantly induced in larvae from both populations by BaP (47- and 52-fold) and PCB 77 (9- and 22-fold), although levels of expression were higher in offspring of Miramichi matings. Most important, CYP1A1 mRNA was significantly induced by PCB 77 in larvae from Hudson River parents. Concentrations of dioxin, furan, and PCB congeners were measured in livers and eggs of female tomcod from these two locales to quantify the extent of maternal transfer of contaminants. For both rivers, wet-weight contaminant concentrations were significantly higher (4,7 times) in livers than in eggs of the same females, suggesting that a threshold level of contaminants may have to be reached before CYP1A1 transcription is impaired. We conclude that reduced inducibility of hepatic CYP1A1 mRNA in adult tomcod from the Hudson River is most consistent with single-generational acclimation. [source] INAR(1) modeling of overdispersed count series with an environmental applicationENVIRONMETRICS, Issue 4 2008Harry Pavlopoulos Abstract This paper is concerned with a novel version of the INAR(1) model, a non-linear auto-regressive Markov chain on ,, with innovations following a finite mixture distribution of Poisson laws. For , the stationary marginal probability distribution of the chain is overdispersed relative to a Poisson, thus making INAR(1) suitable for modeling time series of counts with arbitrary overdispersion. The one-step transition probability function of the chain is also a finite mixture, of m Poisson-Binomial laws, facilitating likelihood-based inference for model parameters. An explicit EM-algorithm is devised for inference by maximization of a conditional likelihood. Alternative options for inference are discussed along with criteria for selecting m. Integer-valued prediction (IP) is developed by a parametric bootstrap approach to ,coherent' forecasting, and a certain test statistic based on predictions is introduced for assessing performance of the fitted model. The proposed model is fitted to time series of counts of pixels where spatially averaged rain rate exceeds a given threshold level, illustrating its capabilities in challenging cases of highly overdispersed count data. Copyright © 2007 John Wiley & Sons, Ltd. [source] Performance analysis of optical code switching routerEUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 2 2010F. R. Durand In this work we study and evaluate the performance of an optical code switching router (OCSR), intended to be utilised in hybrid wavelength-division multiplexing/optical code-division multiplexing (WDM/OCDM) networks. This OCSR can transport and route efficiently user data over optical code paths without departing from the optical domain. Limitations of the proposed OCSR are investigated and its superior performance demonstrated based on non-coherent prime codes. Our results indicate that our solution is useful in showing the effects of the optimum threshold level on the OCSR performance. We propose a continuous adjustment of the optimum threshold level based on the measurement of the mean optical power before the decoder. The influence of various parameters of the optical codes on the OCSR performance are also considered and evaluated. Copyright © 2009 John Wiley & Sons, Ltd. [source] Ranking State Environmental Outputs: Evidence from Panel DataGROWTH AND CHANGE, Issue 1 2000John A. List This paper uses state-level pollution data from 1986,1997 to construct two indices that rank U.S. states according to environmental outputs. A major finding is that marginal performers in other indices, such as Wyoming, garner top spots in these ranking systems. The paper also presents findings from fixed and random effects models of panel data that imply state income levels are positively associated with environmental outputs after a threshold level of income is obtained. [source] A re-examination of distance as a proxy for severity of illness and the implications for differences in utilization by race/ethnicity ,,HEALTH ECONOMICS, Issue 7 2007Jayasree Basu Abstract The study analyzes the hospitalization patterns of elderly residents to examine whether the relation between distant travel and severity of illness is uniform across racial/ethnic subgroups. A hypothesis is made that severity thresholds could be higher for minorities than whites. Hospital discharge data from the Healthcare Cost and Utilization Project (HCUP-SID) of the Agency for Health Care Research and Quality for New York residents is used, with a link to the Area Resource File and American Hospital Association's survey files. Logistic models compare the association of distant admission with severity corresponding to each local threshold level, race, and type of hospital admission. The study uses four discrete distance thresholds in contrast to recent work. Also, an examination of severity thresholds for distant travel for different types of admission may clarify different sources of disparities in health care utilization. The findings indicate that minorities are likely to have higher severity thresholds than whites in seeking distant hospital care, although these conclusions depend on the type of condition. The study results imply that if costly elective services were regionalized to get the advantages of high volume for both cost and quality of care, some extra effort at outreach may be desirable to reduce disparities in appropriate care. Published in 2006 by John Wiley & Sons, Ltd. [source] Effects of spatial grid resolution on river flow and surface inundation simulation by physically based distributed modelling approachHYDROLOGICAL PROCESSES, Issue 4 2009Dushmanta Dutta Abstract Grid-based distributed hydrological models are considered to be a very effective flood modelling tool for basin-wide flood risk analysis because of their capabilities of simulating river and surface inundations at high spatio-temporal resolutions by taking advantages of grid-based data from meteorological models, radar and satellite remote sensing. Selecting an appropriate grid size is critically important for any application of a grid-based model, which requires proper understanding of effects of grid sizes on simulated outcomes. The paper presents the outcomes of a study conducted to analyse the effects of grid resolution on simulated river peak flows and surface inundation in two selected river basins using a process-based distributed hydrological model. The outcomes show that grid resolution significantly affects the simulated river peak flows and surface inundation characteristics. In both cases, it has been found that the effects are mainly caused by changes of the topographic parameters as a result of changes of grid sizes. The reduction of average surface slope with the increase of grid size affects the simulated surface inundation extents and heights. There is a threshold resolution of digital elevation model (DEM) in the simulated flood inundation and beyond that the model outcomes become arbitrary. Averaged topographic values at coarse resolution beyond this threshold level do not represent any characteristics of locally elevated topographic features such as dykes, highways, etc. and their influence on flood inundation characteristics can be no more captured by the model. Copyright © 2008 John Wiley & Sons, Ltd. [source] Propagation of drought through groundwater,a new approach using linear reservoir theoryHYDROLOGICAL PROCESSES, Issue 15 2003E. Peters Abstract The effect of drought on groundwater heads and discharge is often complex and poorly understood. Therefore the propagation of a drought from groundwater recharge to discharge and the influence of aquifer characteristics on the propagation was analysed by tracking a drought in recharge through a linear reservoir. The recharge was defined as a sinusoid function with a period of 1 year. The decrease in recharge owing to drought was simulated by multiplying the recharge during 1 year with a drought fraction between 0 and 1, which represents a decrease in the recharge of 100 to 0%, respectively. The droughts were identified using the threshold level approach, with a threshold that is constant in time. For this case analytical formulations were derived, which express the drought duration and deficit in the groundwater discharge in terms of the decrease in recharge, the reservoir coefficient that characterizes aquifer properties and the height of the threshold level. The results showed that the delay in the groundwater system caused a shift of the main part of the decrease in recharge from the high-flow to the low-flow period. This resulted in an increase in drought deficit for discharge compared with the drought deficit for recharge. Also the development of multiyear droughts caused an increase in drought deficit. The attenuation in the groundwater system caused a decrease in drought deficit. In most cases the net effect of these processes was an increase of drought deficit as a result of the propagation through groundwater. Only for small droughts the deficit decreased from recharge to discharge. The amount of increase or decrease depends on the reservoir coefficient and the severity of the drought. Under most conditions a maximum in the drought deficit occurred for a reservoir coefficient of around 200 days. Copyright © 2003 John Wiley & Sons, Ltd. [source] Outcome prediction and risk assessment by quantitative pyrosequencing methylation analysis of the SFN gene in advanced stage, high-risk, neuroblastic tumor patientsINTERNATIONAL JOURNAL OF CANCER, Issue 3 2010Barbara Banelli Abstract The aim of our study was to identify threshold levels of DNA methylation predictive of the outcome to better define the risk group of stage 4 neuroblastic tumor patients. Quantitative pyrosequencing analysis was applied to a training set of 50 stage 4, high risk patients and to a validation cohort of 72 consecutive patients. Stage 4 patients at lower risk and ganglioneuroma patients were included as control groups. Predictive thresholds of methylation were identified by ROC curve analysis. The prognostic end points of the study were the overall and progression-free survival at 60 months. Data were analyzed with the Cox proportional hazard model. In a multivariate model the methylation threshold identified for the SFN gene (14.3.3,) distinguished the patients presenting favorable outcome from those with progressing disease, independently from all known predictors (Training set: Overall Survival HR 8.53, p = 0.001; Validation set: HR 4.07, p = 0.008). The level of methylation in the tumors of high-risk patients surviving more than 60 months was comparable to that of tumors derived from lower risk patients and to that of benign ganglioneuroma. Methylation above the threshold level was associated with reduced SFN expression in comparison with samples below the threshold. Quantitative methylation is a promising tool to predict survival in neuroblastic tumor patients. Our results lead to the hypothesis that a subset of patients considered at high risk,but displaying low levels of methylation,could be assigned at a lower risk group. [source] Dimensioning and optimization of push-to-talk over cellular serverINTERNATIONAL JOURNAL OF NETWORK MANAGEMENT, Issue 1 2008M. T. Alam The PoC (push-to-talk over cellular) application allows point-to-point or point-to-multipoint voice communication between mobile network users. The related work over PoC focuses on the performance analysis only and is ignorant about dimensioning a PoC controller to optimize revenue for service providers. In this paper, we dimension a PoC service with the assumption that the network grade of service is provided. The on-demand sessions should have access priority over pre-established sessions. A PoC controller should be able to terminate a PoC session based on an optimal timer. Moreover, the number of simultaneous session initiations by a PoC client is also a configurable parameter. We derived relations to provide access priority to special PoC sessions based on available transmit/receive units (TRU) and threshold level. Load sharing expressions are reported for a PoC controller using the Lagrange multiplier technique. A simple relation to control the PoC session timer is proposed. Finally, the derivation of maximum number of allowable simultaneous sessions is depicted using two-state Markov models. Numerical results have been computed with the corresponding derivation to provide a useful insight into the system behaviour. A PoC service can benefit from these optimal values of our work during the busy hour. Copyright © 2007 John Wiley & Sons, Ltd. [source] Effect of filter parameters on the phase noise of RF MEMS tunable filters employing shunt capacitive switchesINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 1 2010Vikram Sekar Abstract The effect of filter parameters on the phase noise of RF MEMS tunable filters employing shunt capacitive switches is investigated in this article. It is shown that the phase noise of a tunable filter is dependent on the input power, fractional bandwidth, filter order, resonator quality factor, and tuning state. Phase noise is higher for filters with smaller fractional bandwidth. In filters with high fractional bandwidth (>3%), phase noise increases as the input power approaches the power-handling capability of the filter. In filters with smaller bandwidths, phase noise increases with input power upto a threshold level of input power, but begins to decrease thereafter. The unloaded quality factor of the filter has a noticeable effect on the phase noise of filters with narrow bandwidths. The phase noise changes with the filter tuning state and is maximum when all the switches are in the up-state position. It is also shown that the phase noise increases with the filter order, due to increase in the number of noisy elements in the filter structure. This article provides a methodology to evaluate the phase noise of a tunable filter and proves that RF MEMS filters are suitable for high performance applications without considerable phase-noise penalty. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010. [source] Are weed population dynamics chaotic?JOURNAL OF APPLIED ECOLOGY, Issue 5 2002Robert P. Freckleton Summary 1There have been suggestions that the population dynamics of weeds may show chaotic dynamics, and that therefore it will not be possible to predict the impact of changing management regimes on weed abundance. The instability of weed populations is presumed to result either from overcompensating yield,density responses or from threshold management. 2Using theoretical arguments and empirical evidence we argue that this contention is likely to be incorrect. 3Overcompensating yield,density responses are unlikely in plant populations and this point has been extensively discussed. Such responses have only been observed in high-density artificially sown stands of weed populations. The form of chaos that results from threshold management is a consequence of high population growth resulting from the cessation of management when weed densities are lower than a threshold level. Consequently the dynamics of such populations may be argued to be extrinsically rather than intrinsically driven. 4There are many studies that have shown weed populations to be dynamically stable, both spatially and temporally. Here we present an analysis of data from the Broadbalk experiment that demonstrates long-term stability of 12 species of common weeds over a 12-year period. Using parameter estimates derived from the literature we show that the stability of these populations is similar to other annual species, both weedy and non-weedy. 5We argue that weed population dynamics are more generally better viewed as resulting from the impacts of broad-scale types of management, as well as temporal variability in population numbers. The significance of chaotic dynamics is likely to be minimal. [source] Laboratory and field studies on the integrated pest management of Helicoverpa armigera (Hübner) in cotton, based on pheromone trap catch threshold levelJOURNAL OF APPLIED ENTOMOLOGY, Issue 5-6 2000G. V. P. Reddy Results revealed that egg parasitism in the laboratory by Trichogramma chilonis was 75.6%. Among the insecticides tested against T. chilonis and the predator Chrysoperla carnea, nimbecidine (neem product) and dipel resulted in zero mortality, with only a low level of mortality by dimethoate, cypermethrin, fenvalerate, alphamethrin and monocrotophos. Combinations of nimbecidine 2% + NPV at 250 larval equivalents (LE)/ha and dipel 8 l + NPV @250 LE/ha were the most effective treatments against H. armigera. The integrated pest management components (T. chilonis, C. carnea, NPV, nimbecidine, dipel and synthetic chemicals) were imposed at different intervals on the basis of pheromone trap threshold level (7 moths/trap per night) on a consolidated block of 40 ha cotton (MCU-1) fields at two locations, Shankarabanda and Korlagundi. The results demonstrated a significant superiority of the IPM strategy in terms of both cost versus benefit and environmental safety over that used in the farmer's fields where only conventional control methods were followed. [source] Relevance of the developmental toxicity of ethanol in the occupational setting: a review,JOURNAL OF APPLIED TOXICOLOGY, Issue 5 2003Lorraine F. H. Irvine Abstract Numerous studies have been conducted investigating the reproductive toxicology of ethanol, the overwhelming majority concerning the adverse effects of consuming alcohol in beverages during pregnancy. Because many of the in vivo studies were designed to model alcoholism, they used comparatively high doses and assessed relatively few endpoints. Outcomes may have been affected by disturbances of metabolism at such high exposures, giving rise to secondary effects on development. The available data on ethanol from ,conventional' developmental toxicity study test methods of the type used for regulatory hazard assessment of chemicals are limited. It is in this context, however, i.e. the use of ethanol as an industrial chemical rather than as a component of beverages, that this review is based. Using the usual criteria applied for the purpose of hazard assessment of industrial chemicals, it is concluded that there is no evidence that industrial exposure to ethanol is a developmental toxicity hazard. Developmental toxicity may result from drinking alcoholic beverages, the threshold level for all aspects of which has yet to be de,ned. This is not, however, considered relevant to the low blood alcohol concentrations resulting from any conceivable inhalation or dermal exposure in the workplace or through the directed use of any consumer product containing ethanol. Copyright © 2003 John Wiley & Sons, Ltd. [source] The number of CD34+ cells in peripheral blood as a predictor of the CD34+ yield in patients going to autologous stem cell transplantationJOURNAL OF CLINICAL APHERESIS, Issue 2 2006A.L. Basquiera Abstract The number of CD34+ cells in peripheral blood (PB) is a guide to the optimal timing to harvest peripheral blood progenitor cells (PBPC). The objective was to determine the number of CD34+ cells in PB that allows achieving a final apheresis product containing ,1.5 × 106 CD34+ cells/kg, performing up to three aphereses. Between March 1999 and August 2003, patients with hematological and solid malignancies who underwent leukapheresis for autologous bone marrow transplantation were prospectively evaluated. Seventy-two aphereses in 48 patients were performed (mean 1.45 per patient; range 1,3). PBPC were mobilized with cyclophosphamide plus recombinant human granulocyte-colony stimulating factor (G-CSF) (n = 40), other chemotherapy drugs plus G-CSF (n = 7), or G-CSF alone (n = 1). We found a strong correlation between the CD34+ cells count in peripheral blood and the CD34+ cells yielded (r = 0.903; P < 0.0001). Using receiver-operating characteristic (ROC) curves, the minimum number of CD34+ cells in PB to obtain ,1.5 × 106/kg in the first apheresis was 16.48 cells/,L (sensitivity 100%; specificity 95%). The best cut-off point necessary to obtain the same target in the final harvest was 15.48 cells/,L, performing up to three aphereses (sensitivity 89%; specificity 100%). In our experience, ,15 CD34+ cells/,L is the best predictor to begin the apheresis procedure. Based on this threshold level, it is possible to achieve at least 1.5 × 106/kg CD34+ cells in the graft with ,3 collections. J. Clin. Apheresis 2005. © 2005 Wiley-Liss, Inc. [source] Threshold changes in vegetation along a grazing gradient in Mongolian rangelandsJOURNAL OF ECOLOGY, Issue 1 2008Takehiro Sasaki Summary 1The concept of threshold has become important in ecology, but the nature of potential threshold responses of vegetation to grazing in rangeland ecosystems remains poorly understood. We aimed to identify ecological thresholds in vegetation changes along a grazing gradient and to examine whether threshold changes were expressed similarly at a variety of ecological sites. 2To accomplish this, we surveyed the vegetation along grazing gradients at 10 ecological sites, each located at different landscape positions in Mongolia's central and southern rangelands. Evidence for a threshold in changes in floristic composition along the grazing gradient was examined by comparing linear models of the data with nonlinear models fitted using an exponential curve, an inverse curve, a piecewise regression and a sigmoid logistic curve. 3Three nonlinear models (piecewise, exponential and sigmoid) provided a much better fit to the data than the linear models, highlighting the presence of a discontinuity in vegetation changes along the grazing gradient. The shapes of the best-fit models and their fit to the data were generally similar across sites, indicating that the changes in floristic composition were relatively constant below a threshold level of grazing, after which the curve changed sharply. 4Except for two sites, the best-fit models had relatively narrow bootstrap confidence intervals (95% CI), especially around threshold points or zones where the rate of change accelerated, emphasizing that our results were robust and conclusive. 5Synthesis. Our study provided strong evidence for the existence of ecological thresholds in vegetation change along a grazing gradient across all ecological sites. This suggests that vegetation responses to grazing in the study areas are essentially nonlinear. The recognition that real threshold changes exist in real grazing gradients will help land managers to prevent the occurrence of undesirable states and promote the occurrence of desirable states, and will therefore permit a major step forward in the sustainable management of rangeland ecosystems. [source] Pikeperch Sander lucioperca trapped between niches: foraging performance and prey selection in a piscivore on a planktivore dietJOURNAL OF FISH BIOLOGY, Issue 4 2008A. Persson The foraging behaviour of planktivorous pikeperch Sander lucioperca during their first growing season was analysed. Field data showed that S. lucioperca feed on extremely rare prey at the end of the summer, suggesting the presence of a bottleneck. In experiments, foraging ability of planktivorous S. lucioperca was determined when fish were feeding on different prey types (Daphnia magna or Chaoborus spp.) and sizes (D. magna of lengths 1 or 2·5 mm) when they occurred alone. From these results, the minimum density requirement of each prey type was analysed. The energy gain for three different foraging strategies was estimated; a specialized diet based on either large D. magna or Chaoborus spp. or a generalist diet combining both prey types. Prey value estimates showed that Chaoborus spp. should be the preferred prey, assuming an energy maximizing principle. In prey choice experiments, S. lucioperca largely followed this principle, including D. magna in the diet only when the density of the Chaoborus spp. was below a threshold value. Splitting the foraging bout into different sequences, however, resulted in a somewhat different pattern. During an initial phase, S. lucioperca captured both prey as encountered and then switched to Chaoborus spp. if prey density was above the threshold level. The prey selection observed was mainly explained by sampling behaviour and incomplete information about environmental quality, whereas satiation only had marginal effects. It was concluded that the observed diet based on rare prey items was in accordance with an optimal foraging strategy and may generate positive growth in the absence of prey fish in suitable sizes. [source] Catastrophic payments for health care among households in urban Tamil Nadu, IndiaJOURNAL OF INTERNATIONAL DEVELOPMENT, Issue 2 2009Salem Deenadayalan Vaishnavi Abstract Urban residents in India face important health problems due to unhygienic conditions, excessive crowding and lack of proper sanitation. The private sector has started occupying the centre stage of the health system and households are burdened with increasing levels of health expenditure. This paper aims to study out-of-pocket expenditure (OOPE) and the extent of catastrophic payments for health care among households in a highly urbanised state, Tamil Nadu. The study used data on morbidity and health care for the year 2004 collected by the National Sample Survey Organization, India. Care was sought for 84 per cent of illness episodes in urban areas, and the majority used private sector providers (67 per cent for inpatients and 78 per cent for outpatients). Mean OOPE for inpatients and outpatients was higher for households with higher income. The average cost burden per visit was higher among those who sought care from private providers for inpatient services (29 per cent of household consumption expenditure) and outpatient services (20% of household consumption expenditure) compared with the burden associated with public health service use (3,4 per cent of consumption expenditure). About 60 per cent of households which used private health services faced catastrophic payments at the 10 per cent threshold level. To avoid catastrophic expenditure, greater use of the public sector which is providing services at an affordable cost is needed. Improving access to public health services, better gate-keeping systems, stronger controls on drug prices and increasing the quality of services are required to reduce the incidence of catastrophic expenditure both on inpatients and outpatients. Greater use of risk pooling mechanisms would encourage the poor to seek health care and also to protect households from all socio-economic groups from catastrophic expenditure. Copyright © 2009 John Wiley & Sons, Ltd. [source] Therapeutic immunization with Modified Vaccinia Virus Ankara (MVA) vaccines in SIV-infected rhesus monkeys undergoing antiretroviral therapyJOURNAL OF MEDICAL PRIMATOLOGY, Issue 1 2007Klaus Überla Abstract Background, The long-term benefits of highly active antiretroviral therapy in HIV-infected patients are limited by emergence of drug-resistant variants and side effects. Therefore, we studied the concept of therapeutic immunization in 18 rhesus monkeys infected with a highly pathogenic simian immunodeficiency virus (SIV) swarm. Methods, Monkeys were treated with the reverse transcriptase inhibitor (R)-9-(2-phosphonylmethoxypropyl)adenine (PMPA) for 19 weeks starting 10 days after infection. After suppression of viremia, one group of monkeys was immunized with recombinant modified vaccinia virus Ankara (MVA) vectors expressing gag-pol and env. A second group received MVA vectors expressing the regulatory genes tat, rev and nef, while a third group was not immunized. Results, Immunization with gag-pol and env expressing MVA enhanced SIV antibody titers. Following discontinuation of PMPA treatment, a rebound in viral load was observed. However, in three of six monkeys immunized with MVA gag-pol and MVA env, and two of six monkeys immunized MVA expressing regulatory genes set point RNA levels were below or close to a threshold level of 104 RNA copies/ml, while only one of six unvaccinated monkeys maintained such low RNA levels. Conclusions, Although a subset of animals seem to benefit from therapeutic immunization with MVA vectors, the difference in set point RNA levels between the groups did not reach statistical significance. [source] Oral mucosal versus cutaneous sensory testing: a review of the literatureJOURNAL OF ORAL REHABILITATION, Issue 10 2002R. Jacobs summary, The innervation of skin and oral mucosa plays a major physiological role in exteroception. It also has a clinical interest as illustrated by sensory changes after neurosurgical procedures. These sensory changes often rely only on the patients' subjective reports, although objective assessments are possible. This review compares the neurophysiological features of the trigeminal sensory pathways with those of cutaneous sensory innervation. In this review, three receptor groups will be discussed: mechanoreceptors, thermoreceptors and nociceptors. Differences between receptors in the glabrous skin, the hairy skin and the oral mucosa will be highlighted. Sensory testing devices have been developed to quantify psychophysiological parameters such as the threshold level for receptor activation upon mechanical stimulation, but such devices have been merely developed to determine the threshold of skin receptors (tactile, thermal). Later on, some have been adapted to suit the particularities of the oral environment. This review attempts to compare the available literature on test devices for oral versus cutaneous tactile function. It summarizes what is common or rather particular to the devices used to study either cutaneous or oral receptors. [source] Combined use of crystalline salt forms and precipitation inhibitors to improve oral absorption of celecoxib from solid oral formulationsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 10 2007Héctor R. Guzmán Abstract Biopharmaceutical evaluation of crystalline celecoxib salts in novel solid formulations, which were designed to simultaneously facilitate dissolution and inhibit precipitation in vitro, showed fast and complete absorption in beagle dogs at doses up to 7.5 mg/kg orally. In contrast, 5 mg/kg celecoxib in the form of Celebrex® showed approximately 40% absolute bioavailability in a cross-over experiment. An in vitro,in vivo correlation was observed in dog, and a threshold level of in vitro dissolution needed to maximize in vivo performance was highlighted. Oral bioavailability was limited in the absence of excipient combinations that delayed precipitation of celecoxib free acid as the salt neutralized in the GI fluid. Formulations of crystal forms having high energy (a ,spring'), thus transiently increasing solubility in aqueous solution relative to the free acid, combined with excipients functioning as precipitation inhibitors (,parachutes') were shown to provide both enhanced dissolution and high oral bioavailability. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 96: 2686,2702, 2007 [source] INTERREGIONAL KNOWLEDGE SPILLOVERS AND OCCUPATIONAL CHOICE IN A MODEL OF FREE TRADE AND ENDOGENOUS GROWTH,JOURNAL OF REGIONAL SCIENCE, Issue 5 2009Colin R. Davis ABSTRACT A two region model of horizontal innovation with free trade and occupational choice is used to examine the spatial patterns of innovation and manufacturing industry in interior and core-periphery long-run equilibria. The inclusion of skill heterogeneity among workers creates a tension between stabilizing productivity effects that coincide with reallocations of workers across industries, and destabilizing productivity effects that arise with localized stocks of knowledge capital. We find that while core-periphery equilibria are always saddlepath stable, interior equilibria are saddlepath stable when knowledge spillovers exceed a threshold level but are unstable otherwise. In addition, incorporating skill heterogeneity into the model allows for interior equilibria with asymmetric shares for innovation and industry. [source] Discovering EFL learners' perception of prior knowledge and its roles in reading comprehensionJOURNAL OF RESEARCH IN READING, Issue 2 2002Zheng Lin This paper investigates EFL learners' perception of prior knowledge and its roles in reading comprehension. It is based on a survey conducted among 400 EFL students studying at secondary and tertiary levels in China. Through the analysis of the ranked multiple responses to the questions posed in the questionnaire, the paper shows that EFL students in mainland China believe that their command of English vocabulary plays a crucial role in their reading comprehension. However as their linguistic knowledge increases, they tend to attach less importance to their linguistic knowledge, especially the knowledge of English syntax and formal structures. At the same time, conceptual and sociocultural knowledge seems to gain greater importance. Furthermore, the perceived importance of linguistic knowledge seems to start diminishing around the end of secondary education, when EFL students have acquired a vocabulary of about 3000 words and the basic knowledge of English syntax and formal structures. The final replacement of linguistic knowledge by conceptual or sociocultural knowledge as the top factor that affects their reading comprehension seems to take place one year after the beginning of the tertiary EFL course. This may well be considered as an indication of the EFL threshold level for EFL students in China. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||