264 research outputs found
Strong electrostatic interactions in spherical colloidal systems
We investigate spherical macroions in the strong Coulomb coupling regime
within the primitive model in salt-free environment. We first show that the
ground state of an isolated colloid is naturally overcharged by simple
electrostatic arguments illustrated by the Gillespie rule. We furthermore
demonstrate that in the strong Coulomb coupling this mechanism leads to ionized
states and thus to long range attractions between like-charged spheres. We use
molecular dynamics simulations to study in detail the counterion distribution
for one and two highly charged colloids for the ground state as well as for
finite temperatures. We compare our results in terms of a simple version of a
Wigner crystal theory and find excellent qualitative and quantitative
agreement.Comment: 30 pages and 17 PS figures. REVTEX. Minor changes. To appear in Phys
Rev
Evaluering af 10 trængselspletprojekter: Resultater og anbefalinger
Vejdirektoratet har efter anlæg af en række mindre projekter på statsvejnettet med det formål at forbedre fremkommeligheden i kryds gennemført evalueringer af disse på en ensartet og systematisk måde via et egenudviklet evalueringskoncept. Formålet er, at undersøge om projekterne virker efter hensigten og at sikre vej- og trafikfaglig læring, som kan bruges i den fremadrettede vejplanlægning
Usefulness of the Beagle Model in the Evaluation of Paracetamol and Ibuprofen Exposure after Oral Administration to Pediatric Populations:An Exploratory Study
The present study aimed to explore the usefulness of beagle dogs in combination with physiologically based pharmacokinetic (PBPK) modeling in the evaluation of drug exposure after oral administration to pediatric populations at an early stage of pharmaceutical product development. An exploratory, single-dose, crossover bioavailability study in six beagles was performed. A paracetamol suspension and an ibuprofen suspension were coadministered in the fasted-state conditions, under reference-meal fed-state conditions, and under infant-formula fed-state conditions. PBPK models developed with GastroPlus v9.7 were used to inform the extrapolation of beagle data to human infants and children. Beagle-based simulation outcomes were compared with published human-adult-based simulations. For paracetamol, fasted-state conditions and reference-meal fed-state conditions in beagles appeared to provide adequate information for the applied scaling approach. Fasted-state and/or reference-meal fed-state conditions in beagles appeared suitable to simulate the performance of ibuprofen suspension in pediatric populations. Contrary to human-adult-based translations, extrapolations based on beagle data collected under infant-formula fed-state conditions appeared less useful for informing simulations of plasma levels in pediatric populations. Beagle data collected under fasted and/or reference-meal fed-state conditions appeared to be useful in the investigation of pediatric product performance of the two investigated highly permeable and highly soluble drugs in the upper small intestine. The suitability of the beagle as a preclinical model to understand pediatric drug product performance under different dosing conditions deserves further evaluation with a broader spectrum of drugs and drug products and comparisons with pediatric in vivo data.</p
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