69 research outputs found
Non-coordinating anions assemble cyanine amphiphiles into ultra-small fluorescent nanoparticles
A non-coordinating anion, fluorinated tetraphenylborate, assembles specially designed cationic cyanine amphiphiles into 7â8 nm fluorescent nanoparticles that are >40-fold brighter than a single cyanine dye. This kind of anion, combining hydrophobic and electrostatic forces in aqueous media, constitutes promising building blocks in the self-assembly of functional nanomaterials
Understanding the Cool DA White Dwarf, G29-38
The white dwarfs are promising laboratories for the study of cosmochronology
and stellar evolution. Through observations of the pulsating white dwarfs, we
can measure their internal structures and compositions, critical to
understanding post main sequence evolution, along with their cooling rates,
allowing us to calibrate their ages directly. The most important set of white
dwarf variables to measure are the oldest of the pulsators, the cool DAVs,
which have not previously been explored through asteroseismology due to their
complexity and instability. Through a time-series photometry data set spanning
ten years, we explore the pulsation spectrum of the cool DAV, G29-38 and find
an underlying structure of 19 (not including multiplet components) normal-mode,
probably l=1 pulsations amidst an abundance of time variability and linear
combination modes. Modelling results are incomplete, but we suggest possible
starting directions and discuss probable values for the stellar mass and
hydrogen layer size. For the first time, we have made sense out of the
complicated power spectra of a large-amplitude DA pulsator. We have shown its
seemingly erratic set of observed frequencies can be understood in terms of a
recurring set of normal-mode pulsations and their linear combinations. With
this result, we have opened the interior secrets of the DAVs to future
asteroseismological modelling, thereby joining the rest of the known white
dwarf pulsators.Comment: 29 pages including 5 figures To appear in ApJ 1 Mar 9
Tuning color and photostability of perylene diimides inside polymer nanoparticles: towards biodegradable substitutes of quantum dots
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