| 3551. |
- Arheimer, Berit, et al.
(författare)
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Using catchment models to establish measure plans according to the Water Framework Directive
- 2007
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Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 56:1, s. 21-28
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Tidskriftsartikel (refereegranskat)abstract
- A participatory modelling process (DEMO) has been developed and applied in a 350 km(2) catchment in southern Sweden. The overall goal is to improve the dialogues between experts and local stakeholders by using numerical models as a platform for discussions. The study is focused on reducing nutrient load and on the development of a locally established measure plan, which is requested by the European Water Framework Directive. The HBV-NP model was chosen as it can calculate effects and costs for different allocations of several combined measures in a catchment. This paper shows the impact of including local data in the modelling process vs. using more general data. It was found that modelled diffuse nutrient pollution was highly modified when including local know-how, soft information and more detailed field investigations. Leaching from arable land was found to be 35% higher using more detailed information on for instance, agricultural practices, crop and soil distribution. Moreover, the stakeholders' acceptance of model results and reliance on experts was increased by applying the participatory process and involving stakeholders in the modelling procedure.
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| 3552. |
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| 3553. |
- Ariano, R E, et al.
(författare)
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An evaluation of an optimal sampling strategy for meropenem in febrile neutropenics
- 2005
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Ingår i: Journal of Clinical Pharmacology. - : Wiley. - 0091-2700. ; 45:7, s. 832-835
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Tidskriftsartikel (refereegranskat)abstract
- Optimal sampling design with nonparametric population modeling offers the opportunity to determine pharma-cokinetic parameters for patients in whom blood sampling is restricted. This approach was compared to a standard individualized modeling method for meropenem pharmacokinetics in febrile neutropenic patients. The population modeling program, nonparametric approach of expectation maximization (NPEM), with a full data set was compared to a sparse data set selected by D-optimal sampling design. The authors demonstrated that the D-optimal sampling strategy, when applied to this clinical population, provided good pharmacokinetic parameter estimates along with their variability. Four individualized and optimally selected sampling time points provided the same parameter estimates as more intensive sampling regimens using traditional and population modeling techniques. The different modeling methods were considerably consistent, except for the estimation of CLd with sparse sampling. The findings suggest that D-optimal sparse sampling is a reasonable approach to population pharmacokinetic/pharmacodynamic studies during drug development when limited sampling is necessary.
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| 3554. |
- Ariano, RE, et al.
(författare)
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Pharmacokinetics and pharmacodynamics of meropenern in febrile neutropenic patients with bacteremia
- 2005
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Ingår i: Annals of Pharmacotherapy. - 1060-0280. ; 39:1, s. 32-38
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Tidskriftsartikel (refereegranskat)abstract
- Background: Pharmacodynamic investigations with antimicrobials define the relationship between the infecting organism and achievable drug concentrations with clinical outcome. Objective: To examine this relationship for meropenem in a population of patients who are at high risk of infection-related morbidity and mortality. Methods: The study was a retrospective analysis of a multicenter, randomized, blinded clinical trial. A population-based predictive model was created using data from adults with febrile neutropenia and the nonparametric modeling program, NPEM. Patient age, body weight, and serum creatinine level were covariates in the model used to predict unbound concentrations for each patient. Pathogen susceptibility was estimated using product literature minimum inhibitory concentrations for effectiveness against 50% of microorganisms (MIC50) for specific organisms. The pharmacodynamic index of percent time above MIC (% T>MIC) was analyzed for its association with clinical outcome. Results: A 2-compartment pharmacokinetic model using patient covariates of body weight and renal function best described the pharmacokinetics of meropenem in febrile neutropenic patients. Sixty patients with confirmed gram-positive or -negative bacteremia were studied. An average of 83% T>MIC was identified for the 42 clinical responders compared with 59% T>MIC for the 18 nonresponders (p=0.04). An 80% clinical response rate was evident when the % T>MIC for meropenem exceeded 75% of the dosing interval (p=0.01). Conclusions: To our knowledge, this is the first published report of a relationship between a pharmacodynamic index and clinical outcome in a febrile neutropenic population. Based on this relationship, dosing with intravenous meropenem 500 mg every 6 hours is predicted to be comparable to the currently recommended 1 g every 8 hours for serious infections. Our model provides further justification for a prospective clinical trial to evaluate a pharmacodynamically targeted meropenem dosing schedule as to its ability to improve clinical outcome in these patients.
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| 3555. |
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| 3556. |
- Arias, Marvin, et al.
(författare)
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A Generalized Angle Domain Clusters PDF and Its Application in Geometrically Based Channel Models
- 2005
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Ingår i: Procedings de IEEE ICICS 2005 Conf. Bangkok, Tailandia. ; , s. 1339-1343
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Konferensbidrag (refereegranskat)abstract
- In this paper we present analytical expressions for the angle-of-arrival (AOA) power density function (PDF) and its application in geometrically based channel models for urban environments. We make comparisons with experimental results for wideband channel models, published in the open literature, in order to evaluate the theoretical clusters PDF in angle domain proposed. The comparison with experimental results shows good agreement. The generalized clusters PDF derived in this paper can be used to simulate a power-delay-angle profile and to quantify second order statistics, i.e., angle spread for a given elliptical shape of the cluster.
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| 3557. |
- Arias, Marvin, et al.
(författare)
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Clusters PDF in Angle and Time Domain for Geometrically Based Channel Model
- 2004
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Ingår i: Proceedings of International Symposium on Intelligent Signal Processing and Communication Systems. - 0780386396 ; , s. 433-438
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Konferensbidrag (refereegranskat)abstract
- Advanced radio system designs have been proposed that are intended to overcome or even take advantage of the radio channel caused by multipath effects in urban environments to achieve even higher performance. We present analytical expressions for the angle-of-arrival power density function (PDF) and general analysis for time of arrival (expressed in terms of distance) respectively, for the channel model based on geometry for urban environments. Then we make comparisons with experimental results published in the open literature, in order to evaluate the theoretical PDF proposed. The comparison with experimental results shows good agreement. The derived PDF can be used to simulate a power-delay-angle profile and to quantify angle spread and delay spread for a given elliptical shape of the cluster.
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| 3558. |
- Arias, M R, et al.
(författare)
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An approach of the geometrical-based single bounce elliptical channel model for mobile environments
- 2002
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Ingår i: 8th International Conference on Communication Systems. ICCS 2002 (Cat. No.02EX585). - 0780375106 ; 1, s. 11-16
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Konferensbidrag (refereegranskat)abstract
- The simulation approach is an important tool used for the design and implementation of mobile radio systems with an emphasis on the propagation modeling for wireless channel. We carried out simulations for three different street positions scenarios of the receiver, (mobile station), using the geometrical-based single bounce elliptical channel model, as might be appropriate for microcellular applications and mobile-to-mobile communication. From the simulation results we use the parameters time-of-arrival (TOA) and angle-of-arrival (AOA), (delay and angular domain, respectively), to estimate the higher order channel statistics, such as the delay spread (DS) and the angle spread (AS), respectively
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| 3559. |
- Arias, Marvin R., et al.
(författare)
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Clustering approach for geometrically based channel model in urban environments
- 2006
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Ingår i: IEEE Antennas and Wireless Propagation Letters. - 1548-5757. ; 5, s. 290-293
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Tidskriftsartikel (refereegranskat)abstract
- Advanced radio system designs have been proposed to overcome the radio channel caused by multipath effects in urban environments or even take advantage of it to achieve higher performance.. In this letter, we present a clustering approach to represent the power delay angle profiles (PDAPs) of the multipath components in urban environments. A cluster in an urban area originates from scattering points such as street apertures, large buildings, roof edges, or building corners. Unlike the previous geometrical models based only on single bounce reflection, our model represents the PDAPs by clusters plus background single bounce scatter components, i.e., waves that arrive at the receiver by double bounce at least. We present a numerical example for a typical outdoor scenario using the approach proposed for urban environments and including both temporal and spatial properties regarding path delay and angle-of-arrival (AOA).
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| 3560. |
- Arias, Marvin, et al.
(författare)
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Time Domain Cluster PDF and Its Application in Geometry-Based Statistical Channel Models
- 2007
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Ingår i: Annual IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC 2007). - 9781424411443 ; , s. 1-5
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Konferensbidrag (refereegranskat)abstract
- This paper presents an approach to derivate the Time of Arrival (TOA) power density function (PDF) and its application in geometry-based statistical channel models for urban environments. The cluster PDF derived can be used to simulate temporal dispersion of the multipath signal grouped in clusters in a variety of urban propagation conditions to quantify second order statistics, i.e., delay spread for a given elliptical shape of the cluster. We propose a clustering approach channel model, and employ it to derive the PDF of TOA of the multipath signal. In order to evaluate the theoretical clusters PDF in time domain proposed, we make computer simulations for the geometry-based channel model proposed and compared it with experimental results published in the open literature. The comparison with experimental results shows good agreement.
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