16,244 research outputs found
A stochastic design rainfall generator based on copulas and mass curves
The use of design storms can be very useful in many hydrological and hydraulic practices. In this study, the concept of a copula-based secondary return period in combination with the concept of mass curves is used to generate point-scale design storms. The analysis is based on storms selected from the 105 year rainfall time series with a 10 min resolution, measured at Uccle, Belgium. In first instance, bivariate copulas and secondary return periods are explained, together with a focus on which couple of storm variables is of highest interest for the analysis and a discussion of how the results might be affected by the goodness-of-fit of the copula. Subsequently, the fitted copula is used to sample storms with a predefined secondary return period for which characteristic variables such as storm duration and total storm depth can be derived. In order to construct design storms with a realistic storm structure, mass curves of 1st, 2nd, 3rd and 4th quartile storms are developed. An analysis shows that the assumption of independence between the secondary return period and the internal storm structure could be made. Based on the mass curves, a technique is developed to randomly generate an intrastorm structure. The coupling of both techniques eventually results in a methodology for stochastic design storm generation. Finally, its practical usefulness for design studies is illustrated based on the generation of a set of statistically identical design storm and rainfall-runoff modelling
The limits of filopodium stability
Filopodia are long, finger-like membrane tubes supported by cytoskeletal
filaments. Their shape is determined by the stiffness of the actin filament
bundles found inside them and by the interplay between the surface tension and
bending rigidity of the membrane. Although one might expect the Euler buckling
instability to limit the length of filopodia, we show through simple energetic
considerations that this is in general not the case. By further analyzing the
statics of filaments inside membrane tubes, and through computer simulations
that capture membrane and filament fluctuations, we show under which conditions
filopodia of arbitrary lengths are stable. We discuss several in vitro
experiments where this kind of stability has already been observed.
Furthermore, we predict that the filaments in long, stable filopodia adopt a
helical shape
Histologically Measured Cardiomyocyte Hypertrophy Correlates with Body Height as Strongly as with Body Mass Index
Cardiac myocytes are
presumed to enlarge with left ventricular
hypertrophy (LVH). This study correlates
histologically measured myocytes with lean and
fat body mass. Cases of LVH without coronary
heart disease and normal controls came from
forensic autopsies. The cross-sectional widths
of myocytes in H&E-stained paraffin sections
followed log normal distributions almost to
perfection in all 104 specimens, with constant
coefficient of variation across the full range
of ventricular weight, as expected if myocytes
of all sizes contribute proportionately to
hypertrophy. Myocyte sizes increased with
height. By regression analysis,
height2.7 as a proxy for lean body
mass and body mass index (BMI) as a proxy for
fat body mass, exerted equal effects in the
multiple correlation with myocyte volume, and
the equation rejected race and sex. In summary,
myocyte sizes, as indexes of LVH, suggest that
lean and fat body mass may contribute
equally
Developing the MRI (Mediation Receptivity Index)
Published in cooperation with the American Bar Association Section of Dispute Resolutio
Introduction
Published in cooperation with the American Bar Association Section of Dispute Resolutio
An investigation of some thermal and mechanical properties of a low-density phenolic-nylon ablation material Final report
Thermal and mechanical properties of phenolic nylon ablation material
Sulfonium Salts as Leaving Groups for Aromatic Labelling of Drug-like Small Molecules with Fluorine-18.
Positron emission tomography (PET) is unique in that it allows quantification of biochemical processes in vivo, but difficulties with preparing suitably labelled radiotracers limit its scientific and diagnostic applications. Aromatic [(18)F]fluorination of drug-like small molecules is particularly challenging as their functional group compositions often impair the labelling efficiency. Herein, we report a new strategy for incorporation of (18)F into highly functionalized aromatic compounds using sulfonium salts as leaving groups. The method is compatible with pharmacologically relevant functional groups, including aliphatic amines and basic heterocycles. Activated substrates react with [(18)F]fluoride at room temperature, and with heating the reaction proceeds in the presence of hydrogen bond donors. Furthermore, the use of electron rich spectator ligands allows efficient and regioselective [(18)F]fluorination of non-activated aromatic moieties. The method provides a broadly applicable route for (18)F labelling of biologically active small molecules, and offers immediate practical benefits for drug discovery and imaging with PET
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