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Deviation
Kinds of Deviation Terms modified by Deviation Selected AbstractsLARGE DEVIATIONS IN MULTIFACTOR PORTFOLIO CREDIT RISKMATHEMATICAL FINANCE, Issue 3 2007Paul Glasserman The measurement of portfolio credit risk focuses on rare but significant large-loss events. This paper investigates rare event asymptotics for the loss distribution in the widely used Gaussian copula model of portfolio credit risk. We establish logarithmic limits for the tail of the loss distribution in two limiting regimes. The first limit examines the tail of the loss distribution at increasingly high loss thresholds; the second limiting regime is based on letting the individual loss probabilities decrease toward zero. Both limits are also based on letting the size of the portfolio increase. Our analysis reveals a qualitative distinction between the two cases: in the rare-default regime, the tail of the loss distribution decreases exponentially, but in the large-threshold regime the decay is consistent with a power law. This indicates that the dependence between defaults imposed by the Gaussian copula is qualitatively different for portfolios of high-quality and lower-quality credits. [source] Twenty-two-month-olds discriminate fluent from disfluent adult-directed speechDEVELOPMENTAL SCIENCE, Issue 5 2007Melanie Soderstrom Deviation of real speech from grammatical ideals due to disfluency and other speech errors presents potentially serious problems for the language learner. While infants may initially benefit from attending primarily or solely to infant-directed speech, which contains few grammatical errors, older infants may listen more to adult-directed speech. In a first experiment, Post-verbal infants preferred fluent speech to disfluent speech, while Pre-verbal infants showed no preference. In a second experiment, Post-verbal infants discriminated disfluent and fluent speech even when lexical information was removed, showing that they make use of prosodic properties of the speech stream to detect disfluency. Because disfluencies are highly correlated with grammatical errors, this sensitivity provides infants with a means of filtering ungrammaticality from their input. [source] Temporal and spatial variation of annual rainfall on the island of Crete, GreeceHYDROLOGICAL PROCESSES, Issue 10 2003S. Naoum Abstract Annual rainfall records from the island of Crete in Greece were used with the aid of a geographical information system (GIS) to study the temporal and spatial rainfall characteristics. The GIS was used to produce a digital elevation model, delineate watersheds and estimate the areal rainfall from a network of raingauges by using different interpolation schemes. The rainfall,elevation correlation was significant, suggesting an orographic type of precipitation for the island. The rainfall records for the majority of the stations were found to fit the normal distribution. Deviation from normal for the rest of the records was attributed to the wettest year of 1977,1978. The year 1989,1990 was the driest, and most rainfall records showed a decrease in rainfall over 30 years with higher negative rainfall gradients at the higher elevations. Frequency analysis of the rainfall records was used to estimate areal rainfall for the island of Crete and its main watersheds for return periods of 2, 5 and 10 years. Copyright © 2003 John Wiley & Sons, Ltd. [source] Numerical simulation of the vertical structure of discontinuous flowsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 1 2001Guus S. Stelling Abstract A numerical method to solve the Reynolds-averaged Navier,Stokes equations with the presence of discontinuities is outlined and discussed. The pressure is decomposed into the sum of a hydrostatic component and a hydrodynamic component. The numerical technique is based upon the classical staggered grids and semi-implicit finite difference methods applied for quasi- and non-hydrostatic flows. The advection terms in the momentum equations are approximated in order to conserve mass and momentum following the principles recently developed for the numerical simulation of shallow water flows with large gradients. Conservation of these properties is the most important aspect to represent near local discontinuities in the solution, following from sharp bottom gradients or hydraulic jumps. The model is applied to reproduce the flow over a step where a hydraulic jump forms downstream. The hydrostatic pressure assumption fails to represent this type of flow mainly because of the pressure deviation from the hydrostatic values downstream the step. Fairly accurate results are obtained from the numerical model compared with experimental data. Deviation from the data is found to be inherent to the standard k,, model implemented. Copyright © 2001 John Wiley & Sons, Ltd. [source] Deviation of Fiber Tracts in the Vicinity of Brain Lesions: Evaluation by Diffusion Tensor ImagingISRAEL JOURNAL OF CHEMISTRY, Issue 1-2 2003Yaniv Assaf Diffusion Tensor Imaging (DTI) is used to characterize the diffusion properties of deviated white matter caused by brain tumors. DTI was recently shown to be very helpful in delineating white matter both within brain lesions and surrounding them. Displacement of white matter fibers may be one of the consequences of tumor growth adjacent to white matter. The combination of white matter mapping with DTI and gray matter mapping using functional MRI, in some cases, facilitated assessment of the relation between the shifted cortical areas and the corresponding white matter tracts. We found that the fractional anisotropy extracted from DTI is increased by 38% in areas of non-edematous shifted white matter fibers. By contrast, trace apparent diffusion coefficient (ADC) values in those areas were found to be similar to contralateral side and normal control values. Analysis of the three diffusion tensor eigenvalues revealed that the increase in the fractional anisotropy is a result of two processes. The first is the increase in the diffusion parallel to the fibers,,1 (by 18%), and the second is the decrease in the diffusion perpendicular to fibers,,3 (by 34%) as compared with the contralateral side. These opposing changes cause an increase in the diffusion anisotropy but no change in the trace ADC. It is suggested that the pressure caused by the tumor may lead to an increase in white matter fiber tension, thus causing an increase in ,1. On the other hand, the same pressure causes increased fiber density per unit area, leading to a higher degree of restricted diffusion in the extracellular space and, hence, a reduction in ,3. [source] The shifting trajectory of growth in femur length during gestationJOURNAL OF BONE AND MINERAL RESEARCH, Issue 5 2010Åshild Bjørnerem Abstract Bone size is a determinant of bone strength and tracks in its percentile of origin during childhood and adolescence. We hypothesized that the ranking of an individual's femur length (FL) is established in early gestation and tracks thereafter. Fetal FL was measured serially using 2D ultrasound in 625 Norwegian fetuses. Tracking was assessed using Pearson correlation, a generalized estimating equation model, and by calculating the proportion of fetuses whose FL remained within the same quartile. Baseline FL Z -score (weeks 10 to 19) and later measurements correlated, but more weakly as gestation advanced: r,=,0.59 (weeks 20 to 26); r,=,0.45 (weeks 27 to 33); and r,=,0.32 (weeks 34 to 39) (p,<,0.001). Tracking within the same quartile throughout gestation occurred in 13% of fetuses. Of the 87% deviating, 21% returned to the quartile of origin, so 34% began and ended in the same quartile, 38% deviated by one quartile, and 28% deviated by two or more quartiles by the end of gestation. A standard deviation higher baseline FL Z -score, placental weight (150,g), maternal height (5,cm), and weight (10,kg), was associated with a 0.25, 0.15, 0.10, and 0.05 SD higher FL Z -score at the end of gestation, respectively (p ranging from <0.001 to 0.02). Tracking within the same percentile throughout the whole of gestation, as suggest by growth charts, is uncommon. Deviation from tracking is more common and is the result of changes in growth velocity within and between fetuses and is partly influenced by maternal, fetal, and placental factors. © 2010 American Society for Bone and Mineral Research [source] Wet chemical synthesis of low bulk density aluminium hydroxide powderJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2003JK Pradhan Abstract Fine, low bulk density aluminium hydroxide powdered gel was prepared by the mild base hydrolysis of an aqueous solution of aluminium sulfate with hydrazine hydrate. Parameters such as method of addition of reactant, initial concentration of Al3+, mole ratio, final pH and hydrolysis temperature have a profound effect on the lightness and particle size of the powder. Optimized conditions showed that the final pH, Al3+ concentration and method of addition of reactant have a major contribution on the formation of lighter grade powder. Experiments conducted using other bases also produced lighter particles under similar conditions. Deviation from the optimized conditions led to formation of a higher bulk density product. Copyright © 2003 Society of Chemical Industry [source] Protein purification using chromatography: selection of type, modelling and optimization of operating conditionsJOURNAL OF MOLECULAR RECOGNITION, Issue 2 2009J. A. Asenjo Abstract To achieve a high level of purity in the purification of recombinant proteins for therapeutic or analytical application, it is necessary to use several chromatographic steps. There is a range of techniques available including anion and cation exchange, which can be carried out at different pHs, hydrophobic interaction chromatography, gel filtration and affinity chromatography. In the case of a complex mixture of partially unknown proteins or a clarified cell extract, there are many different routes one can take in order to choose the minimum and most efficient number of purification steps to achieve a desired level of purity (e.g. 98%, 99.5% or 99.9%). This review shows how an initial 'proteomic' characterization of the complex mixture of target protein and protein contaminants can be used to select the most efficient chromatographic separation steps in order to achieve a specific level of purity with a minimum number of steps. The chosen methodology was implemented in a computer- based Expert System. Two algorithms were developed, the first algorithm was used to select the most efficient purification method to separate a protein from its contaminants based on the physicochemical properties of the protein product and the protein contaminants and the second algorithm was used to predict the number and concentration of contaminants after each separation as well as protein product purity. The application of the Expert System approach was experimentally tested and validated with a mixture of four proteins and the experimental validation was also carried out with a supernatant of Bacillus subtilis producing a recombinant , -1,3-glucanase. Once the type of chromatography is chosen, optimization of the operating conditions is essential. Chromatographic elution curves for a three-protein mixture (, -lactoalbumin, ovalbumin and , -lactoglobulin), carried out under different flow rates and ionic strength conditions, were simulated using two different mathematical models. These models were the Plate Model and the more fundamentally based Rate Model. Simulated elution curves were compared with experimental data not used for parameter identification. Deviation between experimental data and the simulated curves using the Plate Model was less than 0.0189 (absorbance units); a slightly higher deviation [0.0252 (absorbance units)] was obtained when the Rate Model was used. In order to optimize operating conditions, a cost function was built that included the effect of the different production stages, namely fermentation, purification and concentration. This cost function was also successfully used for the determination of the fraction of product to be collected (peak cutting) in chromatography. It can be used for protein products with different characteristics and qualities, such as purity and yield, by choosing the appropriate parameters. Copyright © 2008 John Wiley & Sons, Ltd. [source] Comparison of the Bayer VERSANT HCV RNA 3.0 and the Roche COBAS Amplicor HCV Monitor, Version 2.0, assays in HCV genotype 4 infectionJOURNAL OF VIRAL HEPATITIS, Issue 11 2007W. Jessner summary Prediction of treatment response is clinically important in chronic hepatitis C virus (HCV) genotype 4 infection. Early viral kinetics is useful in this respect for genotype 1 but interpretation is dependent on assay linearity and reproducibility. The VERSANT HCV RNA 3.0 (bDNA-3.0) and the COBAS Amplicor HCV Monitor 2.0 (HCM-2.0) have been widely used quantitative assays. We wanted to comparatively evaluate the two tests in a large genotype 4 sample. Genotyping was performed by NS5b sequencing. Viral load was tested in parallel in 32 patients at least six times on antiviral therapy with interferon , (IFN,). Totally, 198 samples within a quantitative range from undetectable to about 7 × 106 IU/mL (bDNA-3.0) were obtained and compared. Twenty-two samples with viral load above 500 000 IU/mL tested by HCM-2.0 were 1:100 diluted and retested. Quantitative values were fitted to a third order polynomial (M = 0.118303 + 1.07503 × V+ 0.0112128 × V2 , 0.0055504 × V3; M,HCM-2.0, V,bDNA-3.0, both log IU/mL) showing progressive nonlinearity of HCM-2.0 above 100 000 IU/mL but better clinical sensitivity with respect to bDNA-3.0. Dilution lead to a gain of at least a factor of 2.7 and thus, overestimation compared with bDNA-3.0. Deviation from linearity and overestimation upon dilution by HCM-2.0 are similar with HCV genotype 4, compared with other HCV genotypes. Differences in test performance were not detected for subtypes but for individual patients possibly related to specific quasispecies patterns. The interpretation of viral kinetic data becomes difficult due to overestimation upon dilution of baseline values by HCM-2.0. [source] Effect of Suppression of FSH with a GnRH Antagonist (Acyline) Before and During Follicle Deviation in the MareREPRODUCTION IN DOMESTIC ANIMALS, Issue 3 2009CM Checura Contents A GnRH antagonist (Acyline) was used to study the role of FSH in early development of a follicular wave in 61 mares. In Experiment 1, a single dose of 3 mg per mare, compared with 0 and 1 mg, suppressed both the FSH and follicle responses to exogenous GnRH. In Experiment 2, high concentrations of FSH were induced by two successive ablations of all follicles , 6 mm on days 10 and 13 (day 0 = ovulation). A single treatment with Acyline resulted in significantly greater suppression of plasma concentrations of FSH than a single treatment with charcoal-extracted follicular fluid (source of inhibin) or oestradiol. Suppression of FSH was not significantly different between the group treated with Acyline alone and a group treated with a combination of Acyline, inhibin and oestradiol. In Experiment 3, all follicles were ablated on day 10 to induce an FSH surge and a new follicular wave. Acyline treatment on day 10 resulted in an immediate decrease in FSH, without a significant effect on day of emergence of a new wave or growth of follicles from 7 to 11 mm on days 11,13. Treatment on day 15, a day before expected follicle deviation and after the peak of the wave-stimulating FSH surge, resulted in an immediate decrease in FSH and cessation of follicle growth. Results indicated that growth of follicles for about 2 days after wave emergence was independent of FSH. In contrast, during the decline in the wave-stimulating FSH surge and before follicle deviation, growth of follicles was dependent on FSH. [source] Influence of Itraconazole on T-cell Immune DeviationTHE LARYNGOSCOPE, Issue S3 2010Elizabeth W. Chance MD No abstract is available for this article. [source] N. Femoralis, N. Obturatorius and N. Ischiadicus: Deviation in Creation in the DogsANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 6 2007D. Miheli Summary Two hundred and twelve dog cadavers belonging to different breeds were examined, to investigate the formation of the femoral, obturator and the sciatic nerve. Besides the commonly described formation patterns of the mentioned nerves, some variations were also found. These variations were not gender-related, but on the other hand we discovered a certain correlation between the variations appearing in the formation of the femoral, obturator and the sciatic nerve. In 74.05% of cases, the femoral nerve was formed from ventral branches of the 4th, 5th and 6th lumbar nerve, and 16.98% of the dogs had the nerve formed from ventral branches of the 3rd, 4th and 5th lumbar nerve. Many dogs (i.e. 2.30%) had the femoral nerve formed from the ventral branches of the 5th, 6th and 7th, the 3rd, 4th, 5th and 6th or the 4th, 5th, 6th and 7th lumbar nerve, respectively. In 1.88% of dogs in particular, the femoral nerve was formed from ventral rami of the 4th and 5th lumbar nerve. In 66.98% of the examined dogs, the obturator nerve was formed from the ventral branches of the 4th, 5th and 6th lumbar nerve, followed by 16.59% of the dogs with the obturator nerve formed from the ventral rami of the 4th and 5th lumbar nerve and 9.43% of dogs in which the nerve was formed from the ventral branches of the 5th and 6th lumbar nerve. In 4.71% of dogs, the obturator nerve was formed from the ventral rami of the 4th, 5th, 6th and 7th lumbar nerve, while only 2.30% of the examined dogs had the same nerve formed from the ventral branches of the 5th, 6th and 7th lumbar nerve. The sciatic nerve was formed from ventral branches of the 6th and 7th lumbar nerve and the 1st sacral nerve in 86.79% of the dogs. In 5.18% of cases, the same nerve was formed from a junction of the ventral branches of the 7th lumbar and the 1st and 2nd sacral nerve, and, in the same percentage of cases, it was formed from a junction of ventral branches of the 6th and 7th lumbar nerve and the 1st and 2nd sacral nerve. In 2.83% of the dogs, it was formed from a junction of the ventral branches of the 6th and 7th lumbar and the 1st sacral nerve. The correlation of variations established in the formation of the femoral, obturator and the sciatic nerve was not statistically significant. [source] Deviation from Purchasing Power Parity: Evidence from Malaysia, 1973,1997ASIAN ECONOMIC JOURNAL, Issue 1 2000Goh Soo Khoon This paper presents an empirical test of Purchasing Power Parity (PPP) applied to the Malaysia ringgit for the period from 1973 (CPI) and 1984 (WPI) to 1997. Consistent with other research findings, it is detected that real exchange rate follows a random walk. Using multivariate cointegration methodology for the long-run relationship between real exchange rate and certain macro-economic variables, the study provides evidence supporting a long-run relationship between the real exchange rate and the current account balance and government spending, the last two variables have been not included in previous studies of this economy. The causality test between real exchange rate with the current account balance and government spending, however, does not receive support from the error-correction model. This suggests that both government spending and current account balance are not adequate to explain the changes in ringgit real exchange rate. The puzzle still remains unsolved. [source] 4351: Using the OHTS-EGPS risk calculator with OctopusTM visual field testingACTA OPHTHALMOLOGICA, Issue 2010AM STEVENS Purpose Assessing risk in ocular hypertensive (OHT)patients is not only of clinical importance for the patients with regard to their possible glaucomatous field damage but has major repercussions on their quality of life when making decisions about the use of eye drops for longer periods. Clinicians are not that good in estimating the risk hence the need for instruments to help them make a more evidence-based decision. The EGPS group states that a methodological difference " of using in a quarter of the patients another type of perimeter could explain the Hasard Ratio for the Pattern Standard Deviation (PSD) of 1.66 in EGPS and 1.27 in OHTS . Hence our interest to recalculate a conversion of the Octopus G1 program ( mostly used for glaucoma ) to the Humphrey 30-2 in a Group of ocular hypertensives conform the inclusions of the OHTS thus providing a way to use the calculator more accurately. Methods 50 OHT patients recruited using the OHTS criteria were tested both with the Humphrey 30-2 program and the Octopus G1 program. The Humphrey PSD values were plotted against the square root of the Loss of Variance (sLV) and a conversion formula was calculated Results Our data generated the following conversion formula: Y = 0.4X + 1.1 Conclusion Our conversion permits a proper use of the risk calculator in OHT patients. There has been an attempt to convert the values from Humphrey 30-2 to Octopus 32 by Monhart based on the results of a study by Langerhorst. Another approach could be based on the algorithm described by Zeyen using HFA 24-2 and G1 Octopus but proves difficult to use in daily practice. EGPS simply used "converted" indices by taking the square root of LV for PSD. Our formula is based on the same population as OHTS but yields different results [source] The retinal nerve fiber layer and the optic nerve head morphology after glaucoma surgeryACTA OPHTHALMOLOGICA, Issue 2009T GRACNER Purpose To detect and quantify changes in the retinal nerve fiber layer (RNFL) and the optic nerve head (ONH) morphology after glaucoma surgery. Methods 13 eyes of 13 patients with open-angle glaucoma in which goniotrephining with scleral flap without intraoperative antimetabolites for progressive glaucoma damage was done were included in this prospective study. Before and 6 months after the surgery: the intraocular pressure (IOP) was measured, the thicknes of the RNFL was measured with a scanning laser polarimeter (GDx VCC), the confocal scanning laser ophthalmoscopy measurements of ONH with Heidelberg retina tomograph (HRT 3) were performed and the visual field was tested with Humphrey Field Analyser. Results The mean IOP before surgery was 24.5 ? 2.3 mmHg decreasing 6 months after to a mean of 13.9 ? 3.0 mmHg (p<0.05). The RNFL measurements with GDx VCC revealed no differences between the mean TSNIT Avarage (p=0.383), mean Superior Avarage (p=0.756) and mean Inferior Avarage (p=0.269) before and after surgery. The ONH measurements with HRT 3 revealed postoperatively a significant increase in the mean Rim Area, Rim Volume and Cup Shape Measure, whereas Cup Area, Cup Volume and Linear Cup/Disc Ratio decreased (p<0.05). There were no differences between the mean Height Variation Contour (p=0.678) and Mean RNFL Thickness (p=0.064) before and after surgery. Preoperatively the mean value of the Mean Deviation on automated perimetry was ,18.82 ? 8.5 dB improving 6 months postoperatively to a mean of ,16.63 ? 7.9 dB (p<0.05). Conclusion Our study demonstrated the beneficial effect of IOP reduction obtained with glaucoma surgery on visual field indices and ONH parameters evaluated by HRT 3. [source] Acoustical Properties of Binary Mixtures of Heptane with Ethyl Acetate or Butyl AcetateCHINESE JOURNAL OF CHEMISTRY, Issue 3 2010Divya Shukla Abstract Mixed solvents rather than single pure liquids are of utmost practical importance in chemical and industrial processes as they provide an ample opportunity for the continuous adjustment of desired properties of the medium. Therefore, ultrasonic velocity (u) and density (,) were measured for the binary mixtures formed by heptane with ethyl acetate or butyl acetate at temperatures 293, 298 and 303 K over the entire composition range. Deviation in ultrasonic velocity (,u), deviation in isentropic compressibility (,,s), and excess intermolecular free length (LEf) have been evaluated using the ultrasonic velocity data and the computed results were fitted to the Redlich-Kister polynomial equation. The values of ,u, ,,s and LEf were plotted against the molar fraction of heptane. The observed positive and negative values of excess parameters were discussed in terms of molecular interaction between the components of the mixtures. Experimental values of ultrasonic velocity and density were compared with the results obtained by theoretical estimation procedures. The results were discussed in terms of average absolute deviation (AAD). [source] Correlations of ELM Frequency with Pedestal Plasma CharacteristicsCONTRIBUTIONS TO PLASMA PHYSICS, Issue 2 2005G. Kamberov Abstract JET and ASDEX data for the correlations of ELM's frequency with pedestal plasma temperature and density are compared with a corresponding functional dependence predicted by a classical Fokker-Planck approach. Deviations of the predicted relaxation time from the experimental data are found to increase with the input power. They are discussed in relation with a possible non-diffusional transport of plasma into the SOL. This approach gives opportunity to express the impact of the main engineering factors on ELM's frequency and to extrapolate it for ITER scenaria. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Deviations in the emergence of representations: a neuroconstructivist framework for analysing developmental disordersDEVELOPMENTAL SCIENCE, Issue 1 2000Andrew Oliver A common way of studying developmental disorders is to adopt a static neuropsychological deficit approach, in which the brain is characterized in terms of a normal brain with some parts or ,modules' impaired. In this paper we outline a neuroconstructivist approach in which developmental disorders are viewed as alternative developmental trajectories in the emergence of representations within neural networks. As a concrete instantiation of the assumptions underlying this general approach, we present a number of simulations in an artificial neural network model. The representations that emerge under different architectural, input and developmental timing conditions are then analysed within a multi-dimensional state space. We explore alternative developmental trajectories in these simulations, demonstrating how initial differences in the same parameter can lead to very different outcomes, and conversely how different starting states can sometimes result in similar end states (phenotypes). We conclude that the assumptions of the neuroconstructivist approach are likely to be more appropriate for analysing developmental deviations in complex dynamic neural networks, such as the human brain. [source] Autopodial skeleton evolution in side-necked turtles (Pleurodira)ACTA ZOOLOGICA, Issue 3 2007Marcelo R. Sánchez-Villagra Abstract Carpal and tarsal anatomy was documented based on the observation of dry skeletons of adult specimens representing 25 species in 15 genera and on data taken from the literature. In addition, histological sections and cleared and double-stained autopodia of recently hatched and juvenile specimens representing seven chelid and pelomedusoid species were studied. There is much more morphological diversity in the manus than in the pes. Variation in autopodial skeletons includes: the astragalus and calcaneum are either separated or fused; fusion of distal carpals 3,4,5 or just 4,5; number of centralia in the carpus; and presence/absence of a pisiform and of an accessory radial element. The widespread and probably basal phalangeal formula for Pleurodira is 2.3.3.3.3. Deviations are Pelomedusa subrufa, exhibiting a reduction to 2.2.2.2.2, Pelusios spp. with one phalanx less in digit I and for one species in digit V as well, and Acanthochelys pallidipectoris with an additional phalanx in the fourth finger. Six discrete characters itemizing some of the morphological variation observed were plotted on a composite pleurodire phylogeny, revealing not only homoplastic patterns but also the utility of some characters in supporting the monophyly of several clades. The pisiform is the last carpal element to ossify in Chelus fimbriatus. We hypothesize that the so-called fifth hooked metatarsal represents the fusion of distal tarsal 5 with metatarsal V. The accessory radial element that was occasionally present in the turtles examined may represent an atavism of the otherwise lost radiale of turtles. [source] The micro-topography of the wetlands of the Okavango Delta, BotswanaEARTH SURFACE PROCESSES AND LANDFORMS, Issue 1 2005T. Gumbricht Abstract The surface of the 40 000 km2 Okavango alluvial fan is remarkably smooth, and almost everywhere lies within two to three metres of a perfectly smooth theoretical surface. Deviations from this perfect surface give rise to islands in the Okavango wetlands. This micro-topography was mapped by assigning empirical elevations to remotely sensed vegetation community classes, based on the observation that vegetation is very sensitive to small, local differences in elevation. Even though empirical, the method produces fairly accurate results. The technique allows estimation of depths of inundation and therefore will be applicable even when high resolution radar altimetry becomes available. The micro-topography has arisen as a result of clastic sedimentation in distributary channels, which produces local relief of less than two metres, and more importantly as a result of chemical precipitation in island soils, which produces similar local relief. The micro-topography is, therefore, an expression of the non-random sedimentation taking place on the fan. Volume calculations of islands extracted from the micro-topography, combined with estimates of current sediment in,ux, suggest that the land surface of the wetland may only be a few tens of thousands of years old. Constant switching of water distribution, driven by local aggradation, has distributed sediment widely. Mass balance calculations suggest that over a period of c. 150 000 years all of the fan would at one time or other have been inundated, and thus subject to sedimentation. Coalescing of islands over time results in net aggradation of the fan surface. The amount of vertical aggradation on islands and in channels is restricted by the water depth. Restricted vertical relief, in turn, maximizes the distribution of water, limiting its average depth. Aggradation in the permanent swamps occurs predominantly by clastic sedimentation. Rates of aggradation here are very similar to those in the seasonal swamps, maintaining the overall gradient, possibly because of the operation of a feedback loop between the two. The limited amount of local aggradation arising from both clastic and chemical sedimentation, combined with constant changes in water distribution, has resulted in a near-perfect conical surface over the fan. In addition to providing information on sedimentary processes, the micro-topography has several useful hydrological applications. Copyright © 2004 John Wiley & Sons, Ltd. [source] Best Nonparametric Bounds on Demand ResponsesECONOMETRICA, Issue 6 2008Richard Blundell This paper uses revealed preference inequalities to provide the tightest possible (best) nonparametric bounds on predicted consumer responses to price changes using consumer-level data over a finite set of relative price changes. These responses are allowed to vary nonparametrically across the income distribution. This is achieved by combining the theory of revealed preference with the semiparametric estimation of consumer expansion paths (Engel curves). We label these expansion path based bounds on demand responses as E-bounds. Deviations from revealed preference restrictions are measured by preference perturbations which are shown to usefully characterize taste change and to provide a stochastic environment within which violations of revealed preference inequalities can be assessed. [source] Adenylyl cyclase Rv0386 from Mycobacterium tuberculosis H37Rv uses a novel mode for substrate selectionFEBS JOURNAL, Issue 12 2005Lucila I. Castro Class III adenylyl cyclases usually possess six highly conserved catalytic residues. Deviations in these canonical amino acids are observed in several putative adenylyl cyclase genes as apparent in several bacterial genomes. This suggests that a variety of catalytic mechanisms may actually exist. The gene Rv0386 from Mycobacterium tuberculosis codes for an adenylyl cyclase catalytic domain fused to an AAA-ATPase and a helix-turn-helix DNA-binding domain. In Rv0386, the standard substrate, adenine-defining lysine-aspartate couple is replaced by glutamine-asparagine. The recombinant adenylyl cyclase domain was active with a Vmax of 8 nmol cAMP·mg,1·min,1. Unusual for adenylyl cyclases, Rv0386 displayed 20% guanylyl cyclase side-activity with GTP as a substrate. Mutation of the glutamine-asparagine pair either to alanine residues or to the canonical lysine-aspartate consensus abolished activity. This argues for a novel mechanism of substrate selection which depends on two noncanonical residues. Data from individual and coordinated point mutations suggest a model for purine definition based on an amide switch related to that previously identified in cyclic nucleotide phosphodiesterases. [source] Liquidity: Considerations of a Portfolio ManagerFINANCIAL MANAGEMENT, Issue 1 2009Laurie Simon Hodrick This paper examines liquidity and how it affects the behavior of portfolio managers, who account for a significant portion of trading in many assets. We define an asset to be perfectly liquid if a portfolio manager can trade the quantity she desires when she desires at a price not worse than the uninformed expected value. A portfolio manager is limited by both what she needs to attain and the ease with which she can attain it, making her sensitive to three dimensions of liquidity: price, timing, and quantity. Deviations from perfect liquidity in any of these dimensions impose shadow costs on the portfolio manager. By focusing on the trade-off between sacrificing on price and quantity instead of the canonical price-time trade-off, the model yields several novel empirical implications. Understanding a portfolio manager's liquidity considerations provides important insights into the liquidity of many assets and asset classes. [source] A Monitoring Role for Deviations from Absolute Priority in Bankruptcy ResolutionFINANCIAL MARKETS, INSTITUTIONS & INSTRUMENTS, Issue 5 2003By Dina Naples Layish Firms that have successfully reorganized under Chapter 11 of the bankruptcy laws of the United States frequently award shares of common stock in the reorganized firm to pre-bankruptcy shareholders, even though pre-bankruptcy creditors' claims are not fully satisfied. Using a sample of large publicly traded firms, these deviations from absolute priority (DAPR) are found to be positively related to the severity of agency costs within a financially distressed firm. US bankruptcy laws may exacerbate these agency costs by granting exclusivity to management during the reorganization period. Firms in which outside shareholders are more concentrated have a lower occurrence of DAPR indicating that blockholders provide an effective monitoring mechanism for controlling managerial behavior during reorganization. On the other hand, firms without this monitoring mechanism have a higher probability of DAPR indicating that creditors attempt to control managerial behavior by providing them with some sort of financial compensation via their equity holding in the firm. Finally, the evidence indicates that DAPR can be used to mitigate the hold-up problem resulting from voting rights granted to both junior and senior claimants of the firm by US bankruptcy laws. [source] Preparation of a Synthetic Titanite Glass Calibration Material for In Situ Microanalysis by Direct Fusion in Graphite Electrodes: A Preliminary Characterisation by EPMA and LA-ICP-MSGEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 2 2005Magne Ødegård matériaux de calibration; microanalyse; fusion directe; électrodes de graphite; verre de titanite This paper describes a technique for the preparation of a titanite (CaTiSiO5) glass calibration material for use in in situ microanalysis of major, minor, and trace elements in geological materials. The starting composition was a titanite matrix doped with minor and trace elements at , 200 ,g g -1. The elements Sc, Y, REEs, Th and U were added in the form of nitrates in solution, and the elements V, Cr, Mn, Fe, Co, Ni, Zr, Nb, Hf and W were added as solid oxides. The synthetic titanite glass was produced by direct fusion by resistance heating in graphite electrodes at 1600-1700 °C, and quenched in air. Backscattered electron images indicate good homogeneity, with no signs of separate phases or vesicles, and analysis of the major elements Ca, Ti and Si by electron microprobe showed relative standard deviations between 0.5 and 0.7%, based on six independent measurements. Deviations from nominal concentrations for Ca, Si and Ti were measured to -1.2, -3.3 and -0.8%, respectively. The homogeneity of the trace elements in the glass was assessed by LA-ICP-MS analyses, using NIST SRM 610, 612 and 616 as external calibrators, and Ca as the internal standard element. Determinations were made both with a quadrupole mass spectrometer and a sector field instrument, and both raster and spot modes of analysis were used. For the majority of doped elements, precision was better than 10%, and relative deviations from nominal values were, with few exceptions, between 5 and 10%. Cet article décrit une technique de préparation d'un verre de composition CaTiSiO5 (titanite) pour l'utiliser comme matériau de calibration lors de microanalyses in situ des éléments majeurs, mineurs et en trace dans des matériaux géologiques. La composition de départ a une matrice de titanite, dopée avec des éléments mineurs et en trace à une concentration de , 200 ,g g-1. Les éléments Sc, Y, REE, Th et U ont été ajoutés sous forme de nitrates en solution et les éléments V, Cr, Mn, Fe, Co, Ni, Zr, Nb, Hf et W sous forme d'oxydes solides. Le verre synthétique de titanite a été produit par fusion directe avec un chauffage par des résistances dans des électrodes de graphite à 1600-1700 °C suivi d'un refroidissement rapide à l'air. Les images obtenues par électrons rétrodiffusés montrent que le verre présente une bonne homogénéité, sans aucun signe de phases individualisées ou de vésicules, et l'analyse des éléments majeurs Ca, Ti et Si par microsonde électronique a des déviations standard relatives (RSD) entre 0.5 et 0.7% provenant de six mesures indépendantes. Les déviations par rapport aux concentrations calculées, pour Ca, Si et Ti, sont de -1.2, -3.3 et -0.8% respectivement. L'homogénéité de répartition des éléments en trace dans le verre a été vérifiée par des analyses LA-ICP-MS, en utilisant les matériaux de référence NIST SRM 610, 612 et 616 pour la calibration externe et Ca comme élément standard interne. Les déterminations ont été faites avec un spectromètre de masse de type quadrupôle et un autre de type secteur magnétique, par des analyses à la fois en mode balayage et en mode ponctuel. Pour la majorité des éléments dopés, la précision est meilleure que 10% et les déviations standard relatives par rapport aux valeurs calculées sont, à quelques exceptions près, entre 5 et 10%. [source] The conservation management of upland hay meadows in Britain: a reviewGRASS & FORAGE SCIENCE, Issue 4 2005R. G. Jefferson Abstract Upland hay meadows conforming to MG3 in the National Vegetation Classification of the UK are a rare habitat in Britain and are largely confined to upland valleys in northern England. Agricultural intensification, particularly ploughing and reseeding and a shift from hay-making to silage production over the last 50 years, has resulted in large losses of species-rich upland hay meadows. Remaining species-rich meadows have been the focus of much nature conservation effort resulting in many of the species-rich sites being protected by statutory designations or through voluntary agri-environment scheme agreements. Research and monitoring has tended to confirm that species richness is maximized by management involving spring and autumn grazing, a mid-July hay cut, no inorganic fertilizer and possibly low levels of farmyard manure. Deviations from this regime result in a loss of species richness. Restoration of semi-improved grassland to swards resembling species-rich MG3 also requires a similar regime but is also dependent on the introduction of seed of appropriate species. The role of Rhinanthus minor as a tool for manipulating meadow biodiversity during restoration management is discussed. Suggestions for future research are outlined. [source] Apparent/spurious multifractality of data sampled from fractional Brownian/Lévy motionsHYDROLOGICAL PROCESSES, Issue 15 2010Shlomo P. Neuman Abstract Many earth and environmental variables appear to be self-affine (monofractal) or multifractal with spatial (or temporal) increments having exceedance probability tails that decay as powers of , , where 1 < , , 2. The literature considers self-affine and multifractal modes of scaling to be fundamentally different, the first arising from additive and the second from multiplicative random fields or processes. We demonstrate theoretically that data having finite support, sampled across a finite domain from one or several realizations of an additive Gaussian field constituting fractional Brownian motion (fBm) characterized by , = 2, give rise to positive square (or absolute) increments which behave as if the field was multifractal when in fact it is monofractal. Sampling such data from additive fractional Lévy motions (fLm) with 1 < , < 2 causes them to exhibit spurious multifractality. Deviations from apparent multifractal behaviour at small and large lags are due to nonzero data support and finite domain size, unrelated to noise or undersampling (the causes cited for such deviations in the literature). Our analysis is based on a formal decomposition of anisotropic fLm (fBm when , = 2) into a continuous hierarchy of statistically independent and homogeneous random fields, or modes, which captures the above behaviour in terms of only E + 3 parameters where E is Euclidean dimension. Although the decomposition is consistent with a hydrologic rationale proposed by Neuman (2003), its mathematical validity is independent of such a rationale. Our results suggest that it may be worth checking how closely would variables considered in the literature to be multifractal (e.g. experimental and simulated turbulent velocities, some simulated porous flow velocities, landscape elevations, rain intensities, river network area and width functions, river flow series, soil water storage and physical properties) fit the simpler monofractal model considered in this paper (such an effort would require paying close attention to the support and sampling window scales of the data). Parsimony would suggest associating variables found to fit both models equally well with the latter. Copyright © 2010 John Wiley & Sons, Ltd. [source] Temporal variability of phytoplankton in a salt wedge estuary, the Swan,Canning Estuary, Western AustraliaHYDROLOGICAL PROCESSES, Issue 13 2001Peter A. Thompson Abstract The temporal cycles of variation in salinity, temperature and river flow in the Swan,Canning Estuary plus rainfall in the vicinity are examined. A ,normal' pattern is defined for rainfall and river flow based on long-term median monthly values from available historical data. Long-term monthly median rainfall and median monthly river flow were highly correlated. Deviations from the ,normal' patterns of rainfall and river flow are documented. Three years of detailed data on the temporal distribution of the algal biomass and phytoplankton community composition from the Swan,Canning Estuary are presented and discussed. Significant interannual variability in the phytoplankton biomass was observed with 1996 having a significantly lower median chlorophyll a concentration than 1995 or 1997. Different years also had pronounced differences in the timing, persistence and occurrence of algal blooms. Links with, and between, rainfall, river flow, nutrient concentrations and phytoplankton biomass are made by careful examination of the temporal patterns. Deviations from the proposed ,normal' temporal pattern of physical and chemical environmental factors relevant to the growth of phytoplankton biomass are assessed. Deviations from ,normal' rainfall and river flow, depending upon their timing and intensity, appear to be associated with occurrence of algal blooms. For example, the lack of a dinoflagellate bloom in December 1996 or January 1997 appears to be associated with a wetter than normal spring. Based upon the observed data, published reports and basic principles of algal ecology a set of predicted responses to variation in the major environmental variables (rainfall and river flow) are tabulated. The tabulated predictions are proposed as a useful tool for resource managers. Copyright © 2001 John Wiley & Sons, Ltd. [source] Reconstructing impairment of secretory ameloblast function in porcine teeth by analysis of morphological alterations in dental enamelJOURNAL OF ANATOMY, Issue 1 2006Carsten Witzel Abstract We studied the relationship between the macroscopic appearance of hypoplastic defects in the dental enamel of wild boar and domestic pigs, and microstructural enamel changes, at both the light and the scanning electron microscopic levels. Deviations from normal enamel microstructure were used to reconstruct the functional and related morphological changes of the secretory ameloblasts caused by the action of stress factors during amelogenesis. The deduced reaction pattern of the secretory ameloblasts can be grouped in a sequence of increasingly severe impairments of cell function. The reactions ranged from a slight enhancement of the periodicity of enamel matrix secretion, over a temporary reduction in the amount of secreted enamel matrix, with reduction of the distal portion of the Tomes' process, to either a temporary or a definite cessation of matrix formation. The results demonstrate that analysis of structural changes in dental enamel allows a detailed reconstruction of the reaction of secretory ameloblasts to stress events, enabling an assessment of duration and intensity of these events. Analysing the deviations from normal enamel microstructure provides a deeper insight into the cellular changes underlying the formation of hypoplastic enamel defects than can be achieved by mere inspection of tooth surface characteristics alone. [source] Comparison of estimated breeding values, daughter yield deviations and de-regressed proofs within a whole genome scan for QTLJOURNAL OF ANIMAL BREEDING AND GENETICS, Issue 6 2001H. Thomsen An important issue in quantitative trait loci (QTL) detection is the use of phenotypic measurement as a dependent variable. Daughter yield deviations (DYDs) as the unit of choice are not available for all traits of interest. The use of de-regressed proofs (DRPFs) of estimated breeding values (EBVs) is an alternative to using daughter yield deviations. The objective of this study was to examine possible differences between DYDs and DRPFs within the use of QTL detection. The pedigree used was part of the granddaughter design of the German QTL effort. Consisting marker maps for livestock species were derived from all available data of 16 German Holstein paternal half-sib families with a total of 872 sires. The number of progeny ranged from 19 to 127. A whole genome scan was performed using weighted and unweighted multimarker regression with DYDs, DRPFs and EBVs as dependent variables for the traits milk, fat and protein yields. Results were compared with respect to the number of QTL detected. A similar number of QTL was detected with DRPFs and DYDs. Also, when dependent variables were weighted according to the variance of the trait, a higher number of QTL was detected at the desired level of significance as compared to using unweighted variables. Vergleich von Zuchtwerten, Daughter Yield Deviation und deregressierten Zuchtwerten bei der Genomanalyse zum Nachweis für QTL Ein bedeutender Einflussfaktor in der QTL-Analyse (QTL: Genorte für quantitativemarkmale) ist die Wahl der abhängigen Leistungsvariablen. Da Daughter Yield Deviations (DYDs) aber nicht für jedes Leistungsmerkmal zur Verfügung stehen, sollte untersucht werden, ob die De-regression von Zuchtwerten als alternative Variable in der QTL Analyse verwendet werden kann. Für die Untersuchung wurde ein Teil des Tiermaterials verwendet, das im Rahmen des Genomanalyseprojektes der Arbeitsgemeinschaft Deutscher Rinderzüchter untersucht wurde. Es standen 872 Bullen aus 16 väterlichen Halbgeschwisterfamilien der Rasse Deutsche Holsteins zur Verfügung. Die Zahl der Nachkommen pro Familie variierte von 19 bis 127. Unter Verwendung eines gewichteten als auch ungewichteten Multi-Marker Regressionsansatzes wurde ein Genomscan für die Leistungsmerkmale Milch-kg, Fett-kg und Eiweiss-kg durchgeführt, wobei als abhängige Variablen Zuchtwerte (EBV), Daughter Yield Deviations (DYD) und de-regressierte Zuchtwerte (DRPF) verwendet wurden. Die De-regression wurde auf der Basis der effektiven Töchterzahl, der Heritabilität des Merkmals und der additiv genetischen Verwandtschaftsmatrix durchgeführt. Alle Ergebnisse wurden in Hinblick auf die Anzahl der entdeckten QTL verglichen. Es zeigten sich dabei keine wesentlichen Unterschiede bei der Verwendung von DYDs und DRPFs. Die Rate der QTL Entdeckungen war bei beiden verwendeten Zuchtwerten annähernd gleich. Über den Vergleich unterschiedlicher Leistungsvariablen hinaus wurden die Ergebnisse der ungewichteten und gewichteten Analyse einander gegenübergestellt. Es konnte gezeigt werden, dass bei einer Gewichtung des Merkmals die Rate der QTL-Entdeckungen bei einem bestimmten Signifikanzniveau deutlich höher ist. [source] | ||||||||||||||||||||||||||||||||||||||||||||||||||||