Search results for "Radius"
showing 10 items of 708 documents
Untersuchungen über das Reibungsverhalten von Polymethacrylsäuremethylestern in verschiedenen Lösungsmitteln
1963
An drei Polymethacrylsauremethylester-Fraktionen wurden Sedimentationskoeffizienten, Diffusionskoeffizienten und Viskositatszahlen im Θ-Losungsmittel n-Butylchlorid und in den guten Losungsmitteln Aceton und Dioxan gemessen. Die Reibungszahl [f] = kT/Dη0 ist der Ausdehnung des Knauels proportional. Mit dem Tragheitsradius R gilt [f] = Ψ·R, worin der Faktor Ψ von der Gute des Losungsmittels abhangt. Experimentell wurde am Θ-Punkt ΨΘ = 15,5 gefunden. Hydrodynamische Rechnungen verschiedener Autoren ergeben dagegen ΨΘ = 12,5. In den beiden guten Losungsmitteln fanden wir Ψ ≈ 13. Fur alle Losungsmittel last sich Ψ als Funktion des Exponenten a der Viskositats-Molekulargewichtsbeziehung [η] = Kη…
On the phase dependence of the interconversion of the motional modes in a Penning trap by quadrupolar excitation
2012
Abstract The interconversion of the radial motional modes in a Penning trap (magnetron and cyclotron modes) by an external quadrupolar rf-field with a frequency near the true cyclotron frequency ω c plays an important role in the measurement cycle of Penning trap mass spectrometry. Ions to be measured are prepared in a state of magnetron motion which is then resonantly converted into cyclotron motion. The data analysis is usually carried out under the assumption that the initial motional state of the ions has been a pure magnetron state. In reality, however, a small component of cyclotron motion is always present in the ion's initial motional state. This component introduces a dependence on…
A critical assessment of methods for the determination of the shear stress amplitude in multiaxial fatigue criteria belonging to critical plane class
2015
Abstract Multiaxial high cycle fatigue criteria based on the critical plane approach necessitate unambiguous definitions of the amplitude and mean value of the shear stress (τa and τm) acting on the material planes. Four of the existing definitions relate the values of τa and τm to a geometrical element of the curve described by the tip of the shear stress vector (curve Ψ), respectively, the radius of the Minimum Circumscribed Circle, the Longest Chord, the Longest Projection, the diagonal of the Maximum Rectangular Hull (MRH). In this paper a critical assessment of the above definitions is proposed, focusing on that based on the concept of MRH, which is the most recently developed. The mai…
Separation of selected peptides by capillary electroendoosmotic chromatography using 3 μm reversed-phase bonded silica and mixed-mode phases
1999
The retention behaviour and selectivity of selected basic, neutral and acidic peptides have been studied by capillary electroendoosmotic chromatography (CEC) with Hypersil C8, C18, Hypersil mixed-mode, and Spherisorb C18/SCX columns, 250 (335) mm x 100 microns, packed with 3 microns particles, and eluted with mobile phases composed of acetonitrile-triethylamine-phosphoric acid (TEAP) at pH 3.0 using a Hewlett-Packard Model HP3DCE capillary electrophoresis system. The selected peptides were desmopressin (D), two analogues (A and B) of desmopressin, oxytocin (O) and carbetocin (C). The peptides eluted either before or after the electroendoosmotic flow (EOF) marker, depending on the concentrat…
Fractal Dimension of Transdermal-Delivery Drug Models: 4-Alkylanilines
2008
Abstract The pathways that exist in porous membranes used to deliver drugs form fractal percolating paths. For a homologous series of 4-alkylanilines, the fractal dimension D is calculated as a model for transdermal-delivery drugs. Program TOPO is used for the calculation of the solvent-accessible surface AS, which is denoted by the centre of a probe, which is allowed to roll on the outside while maintaining contact with the bare molecular surface S. AS depends on the probe radius R. For 4-alkylanilines, the quadrupole moment Θ is doubled. The hydrophobic contribution to AS is doubled while its hydrophilic part remains constant. D increases 11%. Geometric descriptor and topological index re…
Ferricytochrome c encapsulated in silica nanoparticles: structural stability and functional properties.
2004
Using a modified sol-gel technique, we have succeeded in encapsulating ferric cytochrome c in silica nanoparticles obtained from hydrolysis and polycondensation of tetramethylorthosilicate. Particles dimensions have been determined with dynamic light scattering; this technique yields an hydrodynamic radius of about 100 nm, each nanoparticle containing about 10(2)-10(3) proteins. If stored in the cold at low ionic strength, nanoparticles are stable for more than one week, even if a slow radius increase with time is observed. CD measurements show that encapsulated proteins exhibit substantially increased stability against guanidinium hydrochloride induced denaturation. Reduction kinetics of e…
A lower bound for the Bloch radius of 𝐾-quasiregular mappings
2004
We give a quantitative proof to Eremenko’s theorem (2000), which extends Bloch’s classical theorem to the class of n n -dimensional K K -quasiregular mappings.
A numerical model of the cloud-topped planetary boundary-layer: Impact of aerosol particles on the radiative forcing of stratiform clouds
1997
In a numerical sensitivity study, the microphysical model of stratus MISTRA, is used to investigate the impact of aerosol particles on the evolution of stratiform clouds. Four model runs are presented, each for a different type of background aerosol. Two include aerosol particle size-distributions which are typical of marine and rural continental air masses; a third represents a mixture of marine and rural continental aerosol particles, and the fourth rural continental aerosol particles with a reduced solubility in water. The results show that the microphysical structure of layer clouds was strongly affected by the physico-chemical properties of the aerosol particles from which the cloud dr…
A numerical model of the cloud-topped planetary boundary-layer: radiative forcing of aerosols in stratiform clouds
1998
In a numerical sensitivity study with the microphysical stratus model MISTRA the impact of aerosol particles on the time evolution of stratiform clouds is investigated. Four model runs with different aerosol size distributions are presented. Two size distributions are typical for maritime and continental air masses. The third model run consists of a mixture of maritime and rural aerosol particles, while in the fourth case study rural aerosol particles with a reduced water solubility are utilized. The numerical results show that the microphysical structure of the clouds is strongly affected by the physico-chemical properties of the aerosol particles. In the maritime case, with a relatively l…
Linear relationship between effective radius and precipitation water content near the top of convective clouds
2021
Quantifying the precipitation within clouds is a crucial challenge to improve our current understanding of the Earth’s hydrological cycle. We have investigated the relationship between the effective radius of droplets and ice particles (re) and precipitation water content (PWC) measured by cloud probes near the top of growing convective cumuli. The data for this study were collected by aircraft measurements in clean and polluted conditions over the Amazon Basin and over the western tropical Atlantic in September 2014. Our results indicate a threshold of re ∼ 13 μm for warm rain initiation in convective clouds, which is in agreement with previous studies. In…