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Zero
Terms modified by Zero Selected AbstractsIn Pursuit of Zero: Polymer Brushes that Resist the Adsorption of ProteinsADVANCED MATERIALS, Issue 23 2009Angus Hucknall Abstract Protein resistant or "non-fouling" surfaces are of great interest for a variety of biomedical and biotechnology applications. This article briefly reviews the development of protein resistant surfaces, followed by recent research on a new methodology to fabricate non-fouling surfaces by surface-initiated polymerization. We show that polymer brushes synthesized by surface-initiated polymerization that present short oligo(ethylene glycol) side chains are exceptionally resistant to protein adsorption and cell adhesion. The importance of the protein and cell resistance conferred by these polymer brushes is illustrated by their use as substrates for the fabrication of antibody microarrays that exhibit femtomolar limits of detection in complex fluids such as serum and blood with relaxed requirements for intermediate wash steps. This example highlights the important point that the reduction in background noise afforded by protein-resistant surfaces can greatly simplify the development of ultrasensitive heterogeneous, surface-based clinical and proteomic assays with increased sensitivity and utility. [source] Discussion of Positive (Zero) NPV Projects and the Behavior of Residual EarningsJOURNAL OF BUSINESS FINANCE & ACCOUNTING, Issue 1-2 2003Peter Pope First page of article [source] Caffeine Content of Prepackaged National-Brand and Private-Label Carbonated BeveragesJOURNAL OF FOOD SCIENCE, Issue 6 2007K.-H. Chou ABSTRACT:, Caffeine is a well-known stimulant that is added as an ingredient to various carbonated soft drinks. Due to its stimulatory and other physiological effects, individuals desire to know the exact amount of caffeine consumed from these beverages. This study analyzed the caffeine contents of 56 national-brand and 75 private-label store-brand carbonated beverages using high-performance liquid chromatography. Caffeine contents ranged from 4.9 mg/12 oz (IGA Cola) to 74 mg/12 oz (Vault Zero). Some of the more common national-brand carbonated beverages analyzed in this study with their caffeine contents were Coca-Cola (33.9 mg/12 oz), Diet Coke (46.3 mg/12 oz), Pepsi (38.9 mg/12 oz), Diet Pepsi (36.7 mg/12 oz), Dr Pepper (42.6 mg/12 oz), Diet Dr Pepper (44.1 mg/12 oz), Mountain Dew (54.8 mg/12 oz), and Diet Mountain Dew (55.2 mg/12 oz). The Wal-Mart store-brand beverages with their caffeine contents were Sam's Cola (12.7 mg/12 oz), Sam's Diet Cola (13.3 mg/12 oz), Dr Thunder (30.6 mg/12 oz), Diet Dr Thunder (29.9 mg/12 oz), and Mountain Lightning (46.5 mg/12 oz). Beverages from 14 other stores were also analyzed. Most store-brand carbonated beverages were found to contain less caffeine than their national-brand counterparts. The wide range of caffeine contents in carbonated beverages indicates that consumers would benefit from the placement of caffeine values on food labels. [source] The aesthetics of absence: Rebuilding Ground ZeroAMERICAN ETHNOLOGIST, Issue 3 2004Marita Sturken ABSTRACT In this article, I examine the narratives and meanings that have been projected onto the space of Ground Zero in New York City since September 11, 2001, how they have been deployed for various political agendas, and how they have informed the ways in which the site will be rebuilt and memorialized. I investigate the changing meanings attributed to the dust and the footprints of the World Trade Center buildings and the debates over architectural designs and the proposed memorial. [source] A Two-Level Model for Evidence Evaluation in the Presence of Zeros,JOURNAL OF FORENSIC SCIENCES, Issue 2 2010Grzegorz Zadora Ph.D. Abstract:, Likelihood ratios (LRs) provide a natural way of computing the value of evidence under competing propositions. We propose LR models for classification and comparison that extend the ideas of Aitken, Zadora, and Lucy and Aitken and Lucy to include consideration of zeros. Instead of substituting zeros by a small value, we view the presence of zeros as informative and model it using Bernoulli distributions. The proposed models are used for evaluation of forensic glass (comparison and classification problem) and paint data (comparison problem). Two hundred and sixty-four glass samples were analyzed by scanning electron microscopy, coupled with an energy dispersive X-ray spectrometer method and 36 acrylic topcoat paint samples by pyrolysis gas chromatography hyphened with mass spectrometer method. The proposed LR model gave very satisfactory results for the glass comparison problem and for most of the classification tasks for glass. Results of comparison of paints were also highly satisfactory, with only 3.0% false positive answers and 2.8% false negative answers. [source] Modeling Data with Excess Zeros and Measurement Error: Application to Evaluating Relationships between Episodically Consumed Foods and Health OutcomesBIOMETRICS, Issue 4 2009Victor Kipnis Summary Dietary assessment of episodically consumed foods gives rise to nonnegative data that have excess zeros and measurement error. Tooze et al. (2006,,Journal of the American Dietetic Association,106, 1575,1587) describe a general statistical approach (National Cancer Institute method) for modeling such food intakes reported on two or more 24-hour recalls (24HRs) and demonstrate its use to estimate the distribution of the food's usual intake in the general population. In this article, we propose an extension of this method to predict individual usual intake of such foods and to evaluate the relationships of usual intakes with health outcomes. Following the regression calibration approach for measurement error correction, individual usual intake is generally predicted as the conditional mean intake given 24HR-reported intake and other covariates in the health model. One feature of the proposed method is that additional covariates potentially related to usual intake may be used to increase the precision of estimates of usual intake and of diet-health outcome associations. Applying the method to data from the Eating at America's Table Study, we quantify the increased precision obtained from including reported frequency of intake on a food frequency questionnaire (FFQ) as a covariate in the calibration model. We then demonstrate the method in evaluating the linear relationship between log blood mercury levels and fish intake in women by using data from the National Health and Nutrition Examination Survey, and show increased precision when including the FFQ information. Finally, we present simulation results evaluating the performance of the proposed method in this context. [source] Functional magnetic resonance imaging of the human brain and spinal cord by means of signal enhancement by extravascular protonsCONCEPTS IN MAGNETIC RESONANCE, Issue 1 2003P.W. Stroman Abstract A review of functional magnetic resonance imaging (fMRI) signal changes in spin,echo image data is presented. Spin,echo fMRI data from the human brain and spinal cord show a consistent departure from that expected with blood oxygen level dependent (BOLD) contrast. Studies to investigate this finding demonstrate fMRI signal changes of 2.5% in the spinal cord and 0.7% in the brain at 1.5 T, which is extrapolated to an echo time of zero. Consistent evidence of a non-BOLD contrast mechanism arising from a proton-density change at sites of neuronal activation is demonstrated. A mathematical model and physiological explanation for signal enhancement by extravascular protons is also presented. © 2003 Wiley Periodicals, Inc. Concepts Magn Reson 16A: 28,34, 2003 [source] Indirect evidence for increased mechanosensitivity of jejunal secretomotor neurones in patients with idiopathic bile acid malabsorptionACTA PHYSIOLOGICA, Issue 2 2009A. Bajor Abstract Aim:, The interdigestive motor rhythm, the migrating motor complex (MMC), is accompanied by active secretion of chloride during periods of distally propagating maximal motor activity (MMC phase III). We studied the behaviour of this system in bile acid malabsorption (BAM), a relative common cause of chronic diarrhoea. We measured motor activity and transmucosal potential difference (PD, reflecting active chloride secretion), in the proximal jejunum in healthy controls (n = 18) and in a group of patients with BAM (n = 11). The phase III-generated voltage was related to the degree of BAM quantified by the 75SeHCAT test. Methods:, We used a multi-channel intestinal infusion system to simultaneously measure jejunal pressure and PD. Saline passing calomel half-cells was infused into the jejunum and subcutaneously. Pressure and PD were recorded in the fasting state and after a test meal. Results:, In the absence of motor activity, jejunal PD was not significantly different from zero in either group. During MMC phase III, PD reached significantly higher mean and peak levels in BAM patients. The product of MMC phase III length multiplied by voltage, over 3 h, was also significantly higher in BAM patients (controls: median 307 mV × cm, range 70,398; BAM: median 511, range 274,2271, P < 0.01). This value was also significantly correlated with the degree of BAM as reflected by the 75SeHCAT test (P < 0.05). Conclusion:, Phase III induced jejunal secretion may be upregulated in BAM patients, resulting in overload of colonic reabsorption capacity. [source] WAL-MART, LEISURE, AND CULTURECONTEMPORARY ECONOMIC POLICY, Issue 4 2009ART CARDEN This essay contributes to the debate about the alleged spillover effects associated with Wal-Mart's growth. Combining county-level data on Wal-Mart entry and location from 1985 through 1998 with individual-level data on leisure activities, we estimate a positive relationship between Wal-Mart penetration and participation in activities involving inputs that can be bought at Wal-Mart. The relationship between Wal-Mart penetration and activities that do not involve inputs that can be bought at Wal-Mart is negative in most cases but may be positive or zero for "cultural" activities such as attending classical music concerts and visiting art galleries. The evidence is consistent with the thesis that deeper Wal-Mart penetration expands consumption possibilities.(JELA13, D00, C12, Z11, Z13) [source] The emptiness of zero: representations of loss, absence, anxiety and desire in the late twentieth centuryCRITICAL QUARTERLY, Issue 1 2004Kathy Smith As the new millenium approached, the anxiety which this moment generated found resonance in various cultural representations, and the appearance of spectral imagery seemed to indicate an anxiety about subjectivity, and about its fragmentation or complete loss. Unable to comtemplate a state beyond this loss, there came into being a crisis in subjectivity itself, and the existence of the destabilized millenium subject. This subject approached the moment by both fixating on the threshold and by disavowing what lay beyond. These strategies, and the underlying anxiety which brought them into existence, were resonated through many of the cultural representations of the time. This paper argues that it is through nachträglichkeit - a 'making sense' in retrospect of earlier disparate experiences - that we can begin to examine, contextualise and account for the phenomenon of 'millenium frenzy' which came about at the end of 1999. It constructs a reading of this moment, and of two particular filmic representations which resonate the concerns of the time, examining in the process how - from a psychoanalytic perspective - culture might be understood through its representations, and how these representations can be understood through culture. [source] Frequency of intrusive luxation in deciduous teeth and its effectsDENTAL TRAUMATOLOGY, Issue 4 2010Vivian Carvalho Second, to investigate the sequelae of total and partial intrusive luxation in the primary anterior teeth and in their successors and finally, to establish whether the sequelae on both deciduous and permanent teeth were related to the child's age at the time of the intrusion. Data collected from records of 169 boys and 138 girls, all between the ages of zero and 10 years, who were undergoing treatment during the period of March 1996 to December 2004. The sample was composed of 753 traumatized deciduous teeth, of which 221 presented intrusive luxation injury. Children with ages ranging from one to 4 years were the most affected with falls being the main cause of intrusion. Of all intruded teeth 128 (57.9%) were totally intruded and 93 (42.1%) partially. Pulp necrosis/premature loss and color change were the most frequent sequelae in both total and partial intrusions. Concerning permanent dentition, the most common disturbances were color change and/or enamel hypoplasia. Both types of intrusion caused eruption disturbance. Total intrusion was the most frequent type of intrusive luxation. There was no significant correlation between the child's age at the time of intrusion and the frequency of subsequent sequela on primary injured teeth (P = 0.035), between the age at the time of injury and the developmental disturbances on permanent teeth (P = 0.140). [source] A one-dimensional model for simulating armouring and erosion on hillslopes: 2.EARTH SURFACE PROCESSES AND LANDFORMS, Issue 10 2007Long term erosion, armouring predictions for two contrasting mine spoils Abstract This paper investigates the dynamics of soil armouring as a result of fluvial erosion for a non-cohesive sandy gravel spoil from the Ranger Mine, Australia, and a cohesive silt loam spoil from the Northparkes Mine, Australia, using a model for hillslope soil armouring. These long term predictions concentrate on the temporal and spatial changes of the spoil grading and erosion over 100,200 years for the flat cap regions (1,2%) and steep batter edges (10,30%) typically encountered on waste rock dumps. The existence of a significant rock fragment fraction in the Ranger spoil means that it armours readily, while Northparkes does not. For Ranger the waste rock showed reductions in (1) cumulative erosion of up to 81% from that obtained by extrapolating the initial erosion rate out 100 years and (2) the erosion/year by more than 10-fold. For Northparkes reductions were less marked, with the maximum reduction in erosion/year being 37% after 200 years. For Ranger the reductions were greatest and fastest for intermediate gradient hillslopes. For the steepest hillslopes the armouring decreased because the flow shear stresses were large enough to mobilize all material in the armour layer. Model uncertainty was assessed with probabilistic confidence limits demonstrating that these erodibility reductions were statistically significant. A commonly used hillslope erosion model (sediment flux = ,1 discharge m1 slope n1) was fitted to these predictions. The erodibility, ,1, and m1 decreased with time, which was consistent with our physical intuition about armouring. At Ranger the parameter m1 asymptoted to 1·5,1·6 while at Northparkes it asymptoted to 1·2,1·3. At Ranger transient spatial trends in armouring led to a short term (50,200 years in the future) reduction in n1, to below zero under certain circumstances, recovering to an asymptote of about 0·5,1. At Northparkes n1 asymptoted to about 0·6, with no negative transients predicted. The m1 and n1 parameters predicted for Ranger were shown to be consistent with field data from a 10-year-old armoured hillslope and consistent with published relationships between erodibility and rock content for natural hillslopes. Copyright © 2007 John Wiley & Sons, Ltd. [source] Unanticipated impacts of spatial variance of biodiversity on plant productivityECOLOGY LETTERS, Issue 8 2005Lisandro Benedetti-Cecchi Abstract Experiments on biodiversity have shown that productivity is often a decelerating monotonic function of biodiversity. A property of nonlinear functions, known as Jensen's inequality, predicts negative effects of the variance of predictor variables on the mean of response variables. One implication of this relationship is that an increase in spatial variability of biodiversity can cause dramatic decreases in the mean productivity of the system. Here I quantify these effects by conducting a meta-analysis of experimental data on biodiversity,productivity relationships in grasslands and using the empirically derived estimates of parameters to simulate various scenarios of levels of spatial variance and mean values of biodiversity. Jensen's inequality was estimated independently using Monte Carlo simulations and quadratic approximations. The median values of Jensen's inequality estimated with the first method ranged from 3.2 to 26.7%, whilst values obtained with the second method ranged from 5.0 to 45.0%. Meta-analyses conducted separately for each combination of simulated values of mean and spatial variance of biodiversity indicated that effect sizes were significantly larger than zero in all cases. Because patterns of biodiversity are becoming increasingly variable under intense anthropogenic pressure, the impact of loss of biodiversity on productivity may be larger than current estimates indicate. [source] Nominal Wage Rigidity in Contract Data: A Parametric ApproachECONOMICA, Issue 280 2003Louis N. Christofides Using wage agreements reached in the Canadian unionized sector during 1976,99, a period of high as well as exceptionally low inflation, we consider how histograms of wage adjustment changed as inflation reached the low levels of the 1990s. The histograms and parametric tests suggest that wage adjustment is characterized by downward nominal rigidity and significant spikes at zero. There is some evidence of modest menu-cost effects. We examine whether the rigidity features of wage adjustment are sensitive to indexation provisions, and investigate whether the distinction between short and long contracts is useful. [source] Radii of Redox Components from Absolute Redox Potentials Compared with Covalent and Aqueous Ionic RadiiELECTROANALYSIS, Issue 9 2010Raji Heyrovska Abstract Aqueous standard potentials, referred to that of the SHE as zero, were recently shown to vary linearly with gaseous ionization potentials, with the absolute potential of SHE as the intercept. This enabled arriving at the absolute redox potentials of elements. Here, the distances between the oxidized and reduced forms in aqueous solutions have been evaluated. From the linear dependence of these distances on the covalent radii of atoms, the radii of the redox components have been obtained. The latter also vary linearly with the aqueous ionic radii estimated earlier from ion-water distances, and indicate the presence of aqueous molecular anions. [source] Electrophoretic collision of a DNA molecule with a small elliptical obstacleELECTROPHORESIS, Issue 5 2010Jaeseol Cho Abstract We present a Brownian dynamics study of the collision and unhooking of a ,-DNA molecule with an elliptical obstacle. The semi-major and semi-minor axes of the obstacle are comparable to the radius of gyration of the DNA, and the field is sufficiently strong to cause frequent hairpin formation upon collision. We focus on how the dynamics of a head-on collision (impact parameter of zero) are affected by the angle between the major axis of the ellipse and the direction of the electric field far from the elliptical surface. When this orientation angle breaks the symmetry of the system, we find that the collision dynamics are considerably more complicated than the cylindrical obstacle case. In particular, a higher strain rate at the stagnation point on an elliptical surface does not always lead to a higher hooking probability. As a result, elliptical obstacles should be less effective than cylindrical obstacles for DNA separations based on hairpin formation. [source] Chiral CE of aromatic amino acids by ligand-exchange with zinc(II),L -lysine complexELECTROPHORESIS, Issue 15 2007Li Qi Abstract A novel method of chiral ligand-exchange CE was developed with either L - or D -lysine (Lys) as a chiral ligand and zinc(II) as a central ion. This type of chiral complexes was explored for the first time to efficiently separate either individual pairs of or mixed aromatic amino acid enantiomers. Using a running buffer of 5,mM ammonium acetate, 100,mM boric acid, 3,mM ZnSO4·7H2O and 6,mM L -Lys at pH,7.6, unlabeled D,L -tryptophan, D,L -phenylalanine, and D,L -tyrosine were well separated, giving a chiral resolution of up to 7.09. The best separation was obtained at a Lys-to-zinc ratio of 2:1, zinc concentration of 2,4,mM and running buffer pH,7.6. The buffer pH was determined to have a strong influence on resolution, while buffer composition and concentration impacted on both the resolution and peak shape. Boric acid with some ammonium acetate was an adoptable buffer system, and some additives like ethylene diamine tetraacetic acid capable of destroying the complex should be avoided. Fine-tuning of the chiral resolution and elution order was achieved by regulating the ratio of L -Lys to D -Lys; i.e. the resolution increased from zero to its highest value as the ratio ascended from 1:0 to 1:infinitive, and L -isomers eluted before or after D -isomers in excessive D - or L -Lys, respectively. [source] Sutured wounds: Factors associated with patient-rated cosmetic scoresEMERGENCY MEDICINE AUSTRALASIA, Issue 3 2006Tatiana Lowe Abstract Objective: To determine the association between wound characteristics, wound management in the ED and patient-rated cosmetic appearance of sutured wounds. Our hypothesis was that practitioner seniority would most strongly predict outcome. Methods: Prospective recruitment of patients with lacerations sutured at the primary ED visit was performed. Data collected included patient demographics, wound characteristics and wound management. A standardized telephone questionnaire was administered 14 days and 3 months later. Scar appearance was scored using a verbal rating scale from zero to 10. Data were obtained about suture removal, antibiotic compliance, infection and dehiscence rates at 2 weeks. Associations of variables with cosmetic scores were analysed using multivariate linear regression. Results: One hundred and thirty-two patients were evaluated. Mean cosmetic scores were not significantly associated with seniority (P = 0.07). Lacerations repaired by senior practitioners were more likely to result from glass or general trauma (P = 0.007), be shorter (P = 0.03), be cleaned with antiseptic (P = 0.03), not to re-open (P = 0.01) or require re-suturing (P = 0.03). Following multivariate regression factors significantly associated with cosmetic scores at 14 days and 3 months were site of injury (P < 0.003) and time from injury to repair (P < 0.009). Wounds of the torso, leg or foot had lower cosmetic scores at both time-points. An association with age (P = 0.04) was present at 3 months. Conclusions: Previous research found improvement between short-term doctor-rated cosmesis and training beyond internship. Our study demonstrated a non-significant trend relationship between seniority and patient-rated outcome, both short and long-term. However, staff seniority was overshadowed by the site of laceration and time from injury to repair. [source] Ancestral feeding and survival of offspring in European corn borerENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 2 2002D.A. Andow Abstract Experiments were conducted to evaluate the influence of ancestral adult feeding by European corn borer, Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae), on larval survival in the field and neonate movement behavior in laboratory. Larval survival was higher when either the grandparental or parental generation had fed, but the feeding sites of the surviving larvae were not affected by ancestral feeding condition. This is the first evidence that grandparental feeding could influence larval survival in the field. Larval movement was observed in the laboratory. Silking speed of neonates was faster when either grandparents or parents had fed, while walking speed was faster only when parents had fed. No broad-sense genetic correlation was found between silking speed and walking speed. Broad-sense heritability among feeding histories were not significant for silking speed, but was significantly greater than zero for walking speed when grandparents fed and parents did not. These intergenerational effects could induce complex population dynamics in this species. [source] Genetic structure of Japanese populations of an ambrosia beetle, Xylosandrus germanus (Curculionidae: Scolytinae)ENTOMOLOGICAL SCIENCE, Issue 3 2008Masaaki ITO Abstract We examined the genetic structures of 13 Japanese populations of an ambrosia beetle, Xylosandrus germanus (Curculionidae: Scolytinae), to understand the effects of geographical barriers on the colonization dynamics of this species. The genetic structure was studied using portions of the mitochondrial cytochrome oxidase I (COI) gene. A phylogenetic analysis revealed three distinct lineages (clades A, B and C) within X. germanus. Clade A contained 21 haplotypes from all 13 populations; whereas clade B contained eight haplotypes from Hokkaido (Sapporo and Furano), Iwate and Nagano populations; and clade C contained only a single a haplotype from the Hokkaido (Furano) population. In the analysis of molecular variance (amova), the greatest amount of genetic variation was detected between populations in Hokkaido and those in Honshu and other southern islands. Between these two groups of populations, all the values of the coefficient of gene differentiation were significantly larger than zero, except for the Hokkaido (Sapporo) versus Nagano comparison. Our results confirm that for X. germanus, gene flow has been interrupted between Hokkaido and Honshu since the last glacial maximum. [source] Arsenic, lead, and other trace elements in soils contaminated with pesticide residues at the Hanford site (USA)ENVIRONMENTAL TOXICOLOGY, Issue 2 2003Jerry Yokel Abstract The primary purpose of this study was to characterize arsenic (As) and lead (Pb) concentrations in former orchard soils contaminated with lead arsenate pesticides at the Hanford site in Washington state (USA). Surface samples (n = 31) were collected from former orchard soils (in cultivation during the pre-Hanford period) at five locations at the 100 Areas and at one location at the Old Hanford Townsite (OHT). Another set of samples (n = 17) was collected over a soil depth interval of 10,50 cm at the four locations with the highest As and Pb surface concentrations. All samples were analyzed for 22 trace elements (including As and Pb) with inductively coupled plasma,atomic emission spectrometry (ICP,AES). The mean, standard deviation, and range for As in the surface soils were 30, 61, and 2.9,270 mg/kg dry wt, respectively. The corresponding statistics for Pb were 220, 460, and 6.5,1900 mg/kg dry wt, respectively. As and Pb concentrations in the surface soils were positively and significantly correlated (r = 0.91, Bonferroni p < 0.05). Descriptive statistics and bivariate correlations were also computed for other trace elements. As and Pb mean concentrations in the surface soils each differed significantly (p < 0.05) among Hanford locations, with the highest concentrations at the 100-H and 100-F Areas. Although both As and Pb mean concentrations decreased with soil depth, regression and correlation coefficients only, for Pb significantly differed from zero (b = ,0.0372, r = ,0.805, Bonferroni p < 0.05). Compared with data in the literature As and Pb concentrations found in this study exceeded background levels but were typical of orchard soils. Furthermore, mean As and Pb soil concentrations were in the range of various toxicological benchmarks derived for protection of human and ecological receptors. © 2003 Wiley Periodicals, Inc. Environ Toxicol 18: 104,114, 2003 [source] Predicting the toxicity of chromium in sedimentsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2004Walter J. Berry Abstract Chromium exists in sediments in two oxidation states: Cr(III), which is relatively insoluble and nontoxic, and Cr(VI), which is much more soluble and toxic. Chromium(VI) is thermodynamically unstable in anoxic sediments, and acid-volatile sulfide (AVS) is formed only in anoxic sediments; therefore sediments with measurable AVS concentrations should not contain toxic Cr(VI). If this hypothesis holds true, measuring AVS could form the basis for a theoretically based guideline for Cr in sediments. Ten-day water-only and spiked sediment toxicity tests with the amphipod Ampelisca abdita were performed with Cr(VI) and Cr(III), along with sediments collected from a site contaminated with high concentrations of Cr. In sediments where AVS exceeded analytical detection limits, Cr concentrations in interstitial water were very low (<100 ,g/L) and no significant toxicity to A. abdita was observed. In sediments in which AVS was not significantly greater than zero, Cr concentrations in interstitial waters increased significantly, with greater than 90% of the Cr present as Cr(VI), and mortality of A. abdita was elevated. These results demonstrate that measurements of AVS and interstitial water chromium can be useful in predicting the absence of acute effects from Cr contamination in sediments. [source] Speciation of heavy metals in recent sediments of three coastal ecosystems in the Gulf of Cadiz, Southwest Iberian PeninsulaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2003Veronica Sáenz Abstract A five-step sequential extraction technique was used to determine the partitioning of Cr, Mn, Fe, Cu, Zn, Cd, and Pb among the operative sedimentary phases (exchangeable ions, carbonates, manganese and iron oxides, sulfides and organic matter, and residual minerals) in coastal sediment from three locations in the southwest Iberian Peninsula. Two sites are located close to industrial areas, the salt marshes of the Odiel River and Bay of Cádiz, and one in a nonindustrial area, the Barbate River salt marshes. The Odiel River salt marshes also receive the drainage from mining activities in the Huelva region. In the sediments from the Bay of Cádiz and Barbate River salt marshes, Cr, Cu, Fe, and Zn were extracted from the residual fraction at percentages higher than 60%. In the sediments from the Odiel River salt marshes, concentrations of all the metals, except Cu, zn, and cd, exceeded 60% in the residual fraction as well. In the sediments from the Bay of Cádiz and Barbate River salt marshes, the main bioavailable metals were Mn and Cd; in those from the Odiel River salt marshes, the main bioavailable metals were Zn and Cd, respectively. The environmental risk was determined by employing the environmental risk factor (ERF), defined as ERF = (CSQV , Ci/CSQV), where Ci is the heavy metal concentration in the first four fractions and CSQV is concentration sediment quality value (the highest concentration with no associated biological effect). Our results showed that the sediments from the Cádiz Bay and Barbate River salt marshes do not constitute any environmental risk under the current natural conditions. In contrast, in the Odiel River salt marshes, Cu, Zn, and Pb yielded ERFs of less than zero at several sampling stations and, consequently, pose a potential threat for the organisms in the area. This is a consequence of the high levels of metals in the area derived from the mining activity (pyrite) and industrial activities and the association of these heavy metals with more labile fractions of the sediments. [source] Incidence and impact of axial malformations in larval bullfrogs (Rana catesbeiana) developing in sites polluted by a coal-burning power plantENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2000William A. Hopkins Abstract Amphibian malformations have recently received much attention from the scientific community, but few studies have provided evidence linking environmental pollution to larval amphibian malformations in the field. We document an increased incidence of axial malformations in bullfrog larvae (Rana catesbeiana) inhabiting two sites contaminated with coal combustion wastes. In the polluted sites, 18 and 37% of larvae exhibited lateral curvatures of the spine, whereas zero and 4% of larvae from two reference sites had similar malformations. Larvae from the most heavily polluted site had significantly higher tissue concentrations of potentially toxic trace elements, including As, Cd, Se, Cu, Cr, and V, compared with conspecifics from the reference sites. In addition, malformed larvae from the most contaminated site had decreased swimming speeds compared with those of normal larvae from the same site. We hypothesize that the complex mixture of contaminants produced by coal combustion is responsible for the high incidence of malformations and associated effects on swimming performance. [source] Space,time modeling of rainfall dataENVIRONMETRICS, Issue 6 2004Luis Guillermo Coca Velarde Abstract Climate variables assume non-negative values and are often measured as zero. This is just the case when the rainfall level, in the dry season, is measured in a specified place. Then, the stochastic modeling demands the inclusion of a probability mass point at the zero level, and the resulting model is a mixture of a continuous and a Bernoulli distribution. In this article, spatial conditional autoregressive effects dealing with the idea that neighbors present similar responses is considered and the response level is modeled in two stages. The aim is to consider spatial interpolation and prediction of levels in a Bayesian context. Data on weekly rainfall levels measured in different stations at the central region of Brazil, an area with two well-marked seasons, will be used as an example. A method for comparing models, based on the deviance function, is also implemented. The main conclusion is that the use of space,time models improves the modeling of hydrological and climatological variables, allowing the inclusion of real life considerations such as the influence of other covariates, space dependence and time effects such as seasonality. Copyright © 2004 John Wiley & Sons, Ltd. [source] Non-medical use of prescription stimulants among US college students: prevalence and correlates from a national surveyADDICTION, Issue 1 2005Sean Esteban McCabe ABSTRACT Aims To examine the prevalence rates and correlates of non-medical use of prescription stimulants (Ritalin, Dexedrine or Adderall) among US college students in terms of student and college characteristics. Design A self-administered mail survey. Setting One hundred and nineteen nationally representative 4-year colleges in the United States. Participants A representative sample of 10 904 randomly selected college students in 2001. Measurements Self-reports of non-medical use of prescription stimulants and other substance use behaviors. Findings The life-time prevalence of non-medical prescription stimulant use was 6.9%, past year prevalence was 4.1% and past month prevalence was 2.1%. Past year rates of non-medical use ranged from zero to 25% at individual colleges. Multivariate regression analyses indicated non-medical use was higher among college students who were male, white, members of fraternities and sororities and earned lower grade point averages. Rates were higher at colleges located in the north-eastern region of the US and colleges with more competitive admission standards. Non-medical prescription stimulant users were more likely to report use of alcohol, cigarettes, marijuana, ecstasy, cocaine and other risky behaviors. Conclusions The findings of the present study provide evidence that non-medical use of prescription stimulants is more prevalent among particular subgroups of US college students and types of colleges. The non-medical use of prescription stimulants represents a high-risk behavior that should be monitored further and intervention efforts are needed to curb this form of drug use. [source] Divergence of US and Local Returns in the After-market for Equity Issuing ADRsEUROPEAN FINANCIAL MANAGEMENT, Issue 3 2004Padma Kadiyala F30; G12; G14 Abstract We study one-year post-listing prices and returns to equity issuing ADRs that listed in the US between January 1991 and October 2000. ADRs from countries that impose restrictions on capital flows are priced at a premium to their home market ordinaries. While the mean premium for the full sample is statistically indistinguishable from zero, after an adjustment for asynchronous trading, the magnitude of the premium to ADRs from restricted markets is 11.33% at the 300-day post listing interval, which is statistically significant. In the short run (30 days) following listing, the magnitude of the premium is larger for ADRs with larger excess demand from US investors. At the longer 300-day horizon, Nasdaq listed ADRs earn a larger premium than their NYSE/AMEX listed counterparts. Time-series regressions and two-stage cross-sectional regressions establish that the premium to foreign equity issuers is greater if the US listing attracts liquidity and if US returns have a lower correlation with the local country index. [source] Long-Lived Luminescent Dendrimers with a [Ru(dpp)3]2+ -Type Core: Synthesis and Photophysical PropertiesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 18 2009Uwe Hahn Abstract Metallodendrimers built around a [Ru(dpp)3]2+ -type core (dpp = 4,7-diphenyl-1,10-phenanthroline) were prepared containing peripheral phenyl moieties. The convergent synthesis of the ligands was accomplished by coupling dendritic branches with a focal amino function to the chelating phenanthroline precursor under the formation of sulfonamide linkages. Complexation of ruthenium ions afforded the corresponding metallodendrimers with up to 24 peripheral phenyl units in the case of the largest dendritic structure. The absorption spectra and luminescence properties of the four new dendrimers are reported. The dendritic effect is clearly visible, going from zero to second generation, as demonstrated by an elongation in the excited-state lifetime in aerated acetonitrile and improved emission quantum yields relative to the reference complex containing a [Ru(dpp)3]2+ core. Interestingly, the use of rigid and conjugated ruthenium-based cores results, for all dendritic structures, in luminescence lifetimes that are several microseconds long in deaerated solutions, even at room temperature.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Factors influencing the fatty acid determination in fats and oils using Fourier transform near-infrared spectroscopyEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 9 2007Hormoz Azizian Abstract Fourier transform near-infrared (FT-NIR) technology is matrix dependent and thus highly dependent on factors that influence the absorption spectra. Ignoring these factors during the development of FT-NIR models will affect the accuracy and reliability of the classification of fats and oils and the determination of their fatty acid (FA) composition. Four factors were studied: the temperature at which samples are scanned, differences in FA chain length and number of double bonds, and the presence of non-triacylglycerol components. The results showed that an increase in the recording temperature decreased the absorption peak intensity, but not the position. FT-NIR spectral differences were linked to variations in molecular vibrations resulting from the number of carbon atoms or double bonds in the FA. The FT-NIR method could clearly differentiate between chain lengths from 10:0 to 18:0 and numbers of double bonds from zero (18:0) to three (18:3). Contaminants in triacylglycerols altered the FT-NIR spectra, resulting in increased errors in the FA content. An increased concentration of ,-sitosterol in triolein decreased or increased the observed contents of cis9-18:1 and cis11-18:1, respectively. An FT-NIR model adjusted for the phytosterol content corrected this discrepancy. The revised FT-NIR model was successfully used to provide the accurate FA compositions of commercial sunflower oils. [source] Lignin turnover in an agricultural field: from plant residues to soil-protected fractionsEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 4 2006D. P. Rasse Summary Lignin has long been suspected to be a major source of stable carbon in soils, notably because of the recalcitrant nature of its polyphenolic structure relative to other families of plant molecules. However, lignin turnover studies have produced conflicting results, most of them suggesting that large proportions of plant-residue lignin decompose within a year of incorporation into soils. Here, we propose a two-reservoir model where lignin in undecomposed plant residue (Lp) can either reach soil fractions where it is somewhat protected from further decomposition (Ls) or is transformed to non-lignin products. Model calibration data were obtained through compound-specific 13C isotopic analyses conducted in a zero- to 9-year chronosequence of maize monoculture after wheat in a temperate loam soil of the Paris basin. Lignin was quantified by CuO oxidation as VSC-lignin, i.e. the sum of vanillil- (V), syringyl- (S) and coumaryl-type (C) phenols. Model calibrations indicate that Lp has a turnover rate faster than 1 year and that 92% is mineralized as CO2 or transformed into other non-lignin products, while only 8% reaches the Ls fraction. Estimated turnover rate of the Ls fraction was 0.05 years,1. The model also suggested that about half of Lp was not measured because it had been excluded from the samples in the process of sieving at 5 mm. In conclusion, the model indicates that chemical recalcitrance alone is not sufficient to explain VSC-lignin turnover in soils, and that, functionally, the most relevant mechanism appears to be the transfer of VSC-lignin molecules and fragments from decomposing plant tissues to soil-protected fractions. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||