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Selected AbstractsTowards non-linear inversion for characterization of time-lapse phenomena through numerical modellingGEOPHYSICAL PROSPECTING, Issue 4 2003A. Abubakar ABSTRACT We compare two geophysical survey measurements of the same type made at different times in order to characterize the change in the geological medium during the elapsed time. The aim of this study is to develop a strategy using a full non-linear inversion algorithm as the interpretation tool. In this way, not only the location and the form of the changes are recovered, but also the changes in the material parameters of the geological medium can be estimated. In order to solve this fully non-linear problem, the so-called ,multiplicative regularized contrast source inversion' (MR-CSI) method is employed. The unique property of this iterative method is that it does not solve the forward problem at each iterative step. This makes it possible to use the non-linear inversion algorithm for large-scale computation problems. The numerical results show that by taking into account the non-linear nature of the problem, interpretation of the time-lapse data can be significantly improved, compared with that obtained using linear inversion. [source] Does the organization of care processes affect outcomes in patients undergoing total joint replacement?JOURNAL OF EVALUATION IN CLINICAL PRACTICE, Issue 1 2010Kris Vanhaecht RN MSc PhD Abstract Background, Surgeons realize that safe and efficient care processes for total joint replacement requires more than just well-performed operations. Orthopaedic teams are reorganizing care process to improve efficacy and shorten length of stay. Little is known on the impact of organizational changes on patient outcome. This paper studies the relation between the organization of care processes and patient outcomes in hip and knee. Clinical pathways are used as one of the methods to structure the care process. Although evidence is available on the effect of pathways in total joint replacement, their impact with the organization of the care process has not been studied previously. Methods, A cross-sectional multicentre study was performed on 39 care processes and 737 consecutive patients. Regression models were used to analyse the relation between the organization of the care process and risk-adjusted patient outcomes. The use of pathways and the organization of the care process, measured by the Care Process Self Evaluation Tool (CPSET), were measured at organizational level. Length of stay, pain, mobility and elapsed time to discharge were measured at patient level. Results, The use of pathways had a positive effect on four out of five subscales and the overall CPSET score. Using pathways decreased length of stay (P = 0.014), pain (P = 0.052) and elapsed time to discharge (P = 0.003). The CPSET subscale communication was related with three risk adjusted outcomes. Multivariate analysis demonstrated a significant effect by three different variables on the length of stay; (1) use of pathways; (2) coordination of care processes; and (3) communication with patients and family. Both the use of pathways and coordination of the care process were determinants for the elapsed time to discharge. A significant interaction effect was found between use of pathways and coordination of the care process. Conclusion, This large multicentre study revealed the relation between the use of pathways, organization of the care process and patient outcomes. This information is important for both clinicians and managers to understand and further improve the organization of orthopaedic care. Level of evidence, Level I prognostic study. [source] A hybrid N -body code incorporating algorithmic regularization and post-Newtonian forcesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2008S. Harfst ABSTRACT We describe a novel N -body code designed for simulations of the central regions of galaxies containing massive black holes. The code incorporates Mikkola's ,algorithmic' chain regularization scheme including post-Newtonian terms up to PN2.5 order. Stars moving beyond the chain are advanced using a fourth-order integrator with forces computed on a GRAPE board. Performance tests confirm that the hybrid code achieves better energy conservation, in less elapsed time, than the standard scheme and that it reproduces the orbits of stars tightly bound to the black hole with high precision. The hybrid code is applied to two sample problems: the effect of finite- N gravitational fluctuations on the orbits of the S-stars, and inspiral of an intermediate-mass black hole into the Galactic Centre. [source] Predicting moisture dynamics of fine understory fuels in a moist tropical rainforest system: results of a pilot study undertaken to identify proxy variables useful for rating fire dangerNEW PHYTOLOGIST, Issue 3 2010David Ray Summary ,The use of fire as a land management tool in the moist tropics often has the unintended consequence of degrading adjacent forest, particularly during severe droughts. Reliable models of fire danger are needed to help mitigate these impacts. ,Here, we studied the moisture dynamics of fine understory fuels in the east-central Brazilian Amazon during the 2003 dry season. Drying stations established under varying amounts of canopy cover (leaf area index (LAI) = 0 , 5.3) were subjected to a range of water inputs (5,15 mm) and models were developed to forecast litter moisture content (LMC). Predictions were then compared with independent field data. ,A multiple linear regression relating litter moisture content to forest structure (LAI), ambient vapor pressure deficit (VPDM) and an index of elapsed time since a precipitation event (d,1) was identified as the best-fit model (adjusted R2 = 0.89). Relative to the independent observations, model predictions were relatively unbiased when the LMC was , 50%, but consistently underestimated the LMC when the observed values were higher. ,The approach to predicting fire danger based on forest structure and meteorological variables is promising; however, additional information to the LAI, for example forest biomass, may be required to accurately capture the influence of forest structure on understory microclimate. [source] Are cortisol profiles a stable trait during child development?AMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 6 2009Mark V. Flinn Exposure to stressful experiences can increase vulnerability to adverse health outcomes. A potential neuroendocrine mechanism mediating the link between stress and health is the hypothalamic-pituitary-adrenal (HPA) system, with a key role attributed to the glucocorticoid hormone cortisol. Retrospective and cross sectional clinical studies of humans and experimental studies with nonhuman primates and rodents suggest that traumatic experiences during critical periods in development may have permanent effects on HPA regulation, which in turn can have deleterious effects on health. Here I report results from a continuous 20-year study (1988,2009) of children in a rural community on Dominica. Sequential data on cortisol levels, social stressors, and health in naturalistic, everyday conditions are examined to assess developmental trajectories of HPA functioning. Saliva aliquots were assayed for cortisol in concert with monitoring of growth, morbidity, and social environment. Analyses here include data from 1989 to 1999 for 147 children aged 3,16 years with >100 saliva samples each. Cortisol values were standardized by elapsed time since wake-up. Results do not support the hypothesis that traumatic stress during childhood causes permanent general elevation of cortisol levels. Am. J. Hum. Biol., 2009. © 2009 Wiley-Liss, Inc. [source] Assessment of the plasma desorption time-of-flight mass spectrometry technique for pesticide adsorption and degradation on ,as-received' treated soil samplesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 17 2005J. P. Thomas The assessment of the plasma desorption time-of-flight mass spectrometry (PD-TOFMS) technique as a tool for direct characterization of pesticides adsorbed on agricultural soil is made for the first time in this study. Pellets of soils impregnated by solutions of three pesticides, namely norflurazon, malathion and oxyfluorfen, as well as deposits of these solutions onto aluminum surfaces, were investigated to this end. The yield values of the most characteristic peaks of the negative ion mass spectra were used to determine both the lowest concentrations detected on soils and limits of detection from thin films. The lowest values on soils are for malathion (1000,ppm range), and the largest for norflurazon (20,000,ppm), which is close to the limit of detection (LOD) found for the pesticide on the aluminum substrate (,0.2,µg,·,cm,2). Different behaviors were observed as a function of time of storage in the ambient atmosphere or under vacuum; norflurazon adsorbed on soil exhibited high stability for a long period of time, and a rapid degradation of malathion with the elapsed time was clearly observed. The behavior of oxyfluorfen was also investigated but segregation processes seem to occur after several days. Although by far less sensitive than conventional methods based on extraction processes and used for real-world analytical applications, this technique is well suited to the study of the transformations occurring at the sample surface. A discussion is presented of the future prospects of such experiments in degradation studies. Copyright © 2005 John Wiley & Sons, Ltd. [source] Infection of Gymnodinium sanguineum by the Dinoflagellate Amoebophryasp.: Effect of Nutrient Environment on Parasite Generation Time, Reproduction, and InfectivityTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 5 2000WONHO YIH ABSTRACT. Preliminary attempts to culture Amoebophrya sp., a parasite of Gymnodinium sanguineum from Chesapeake Bay, indicated that success may be influenced by water quality. To explore that possibility, we determined development time, reproductive output, and infectivity of progeny (i.e. dinospores) for Amoebophrya sp. maintained on G. sanguineum grown in four different culture media. The duration of the parasite's intracellular growth phase showed no significant difference among treatments; however, the time requiredfor completion of multiple parasite generations did, with elapsed time to the middle of the third generation being shorter in nutrient-repletemedia. Parasites of hosts grown in nutrient-replete medium also produced three to four times more dinospores than those infectinghosts under low-nutrient conditions, with mean values of 380 and 130 dinospores/host, respectively. Dinospore production relative tohost biovolume also differed, with peak values of 7.4 per 1,000 ,m3 host for nutrient-replete medium and 4.8 per 1,000 ,m3 host fornutrient-limited medium. Furthermore, dinospores produced by "high-nutrient" parasites had a higher success rate than those formedby "low-nutrient" parasites. Results suggest that Amoebophrya sp. is well adapted to exploit G. sanguineum populations in nutrient-enrichedenvironments. [source] Evolution of magnetic fields in stars across the upper main sequence: II.ASTRONOMISCHE NACHRICHTEN, Issue 6 2007Observed distribution of the magnetic field geometry Abstract We re-discuss the evolutionary state of upper main sequence magnetic stars using a sample of Ap and Bp stars with accurate Hipparcos parallaxes and definitely determined longitudinal magnetic fields. We confirm our previous results obtained from the study of Ap and Bp stars with accurate measurements of the mean magnetic field modulus and mean quadratic magnetic fields that magnetic stars of mass M < 3 M, are concentrated towards the centre of the main-sequence band. In contrast, stars with masses M > 3 M, seem to be concentrated closer to the ZAMS. The study of a few known members of nearby open clusters with accurate Hipparcos parallaxes confirms these conclusions. Stronger magnetic fields tend to be found in hotter, younger and more massive stars, as well as in stars with shorter rotation periods. The longest rotation periods are found only in stars which spent already more than 40% of their main sequence life, in the mass domain between 1.8 and 3 M, and with log g values ranging from 3.80 to 4.13. No evidence is found for any loss of angular momentum during the main-sequence life. The magnetic flux remains constant over the stellar life time on the main sequence. An excess of stars with large obliquities , is detected in both higher and lower mass stars. It is quite possible that the angle , becomes close to 0. in slower rotating stars of mass M > 3 M, too, analog to the behaviour of angles , in slowly rotating stars of M < 3 M,. The obliquity angle distribution as inferred from the distribution of r -values appears random at the time magnetic stars become observable on the H-R diagram. After quite a short time spent on the main sequence, the obliquity angle , tends to reach values close to either 90. or 0. for M < 3 M,. The evolution of the obliquity angle , seems to be somewhat different for low and high mass stars. While we find a strong hint for an increase of , with the elapsed time on the main sequence for stars with M > 3 M,, no similar trend is found for stars with M < 3 M,. However, the predominance of high values of , at advanced ages in these stars is notable. As the physics governing the processes taking place in magnetised atmospheres remains poorly understood, magnetic field properties have to be considered in the framework of dynamo or fossil field theories. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Regression Analysis of Doubly Censored Failure Time Data Using the Additive Hazards ModelBIOMETRICS, Issue 3 2004Liuquan Sun Summary Doubly censored failure time data arise when the survival time of interest is the elapsed time between two related events and observations on occurrences of both events could be censored. Regression analysis of doubly censored data has recently attracted considerable attention and for this a few methods have been proposed (Kim et al., 1993, Biometrics49, 13,22; Sun et al., 1999, Biometrics55, 909,914; Pan, 2001, Biometrics57, 1245,1250). However, all of the methods are based on the proportional hazards model and it is well known that the proportional hazards model may not fit failure time data well sometimes. This article investigates regression analysis of such data using the additive hazards model and an estimating equation approach is proposed for inference about regression parameters of interest. The proposed method can be easily implemented and the properties of the proposed estimates of regression parameters are established. The method is applied to a set of doubly censored data from an AIDS cohort study. [source] Apnea testing for the diagnosis of brain deathACTA NEUROLOGICA SCANDINAVICA, Issue 6 2005C. J. G. Lang Objectives,,, A review is given on various methods, preconditions and pitfalls of apnea testing for the diagnosis of brain death. Materials and methods,,, An extensive medical data base search was implemented by information gathered from books and our own experience with more than 2000 apnea tests. Results,,, While testing for apnea (AT) is considered indispensable worldwide, recommendations and handling differ. Rather than relying on elapsed time, a specific target value for the partial arterial pressure of carbon dioxide (PaCO2) should be aimed at being the maximum physiological stimulus for respiration. Methodological points are elaborated upon in detail for apneic oxygenation and hypoventilation. Conclusion,,, AT is an indispensable element of diagnosing brain death. Although with proper handling and adequate precautions AT is safe, it should be performed as a last resort. An international agreement on target values for the PaCO2 is desirable. [source] | ||||||||||||||||