1,458 research outputs found
Odour and colour polymorphism in the food-deceptive orchid Dactylorhiza romana
The food deceptive orchid, Dactylorhiza romana (Sebastiani) SoĂł exhibits a colour polymorphism with yellow, red, and intermediate orange morphs. In this study we tested if floral odour differed among the three distinct colour morphs. We identified 23 odour compounds in D. romana, and all of them occurred in the three colour morphs. Monoterpenes dominated the floral scent. On the basis of Euclidean distances of relative amounts of compounds, yellow morphs were closer to each other than to orange or red morphs. Differentiation of the morphs was mainly due to linalool and benzaldehyde. Linalool occurred in low relative amounts in the yellow morphs, but in high amounts in some of the red individuals, whereas benzaldehyde occurred in higher relative amounts in yellow morphs. Linalool and benzaldehyde are known to be important signal-substances in plant-insect communication, however, it remains to be shown whether insects can discriminate between flower morphs on the basis of the here shown odour difference
Benchmarking acid and base dopants with respect to enabling the ice V to XIII and ice VI to XV hydrogen-ordering phase transitions
Doping the hydrogen-disordered phases of ice V, VI and XII with hydrochloric
acid (HCl) has led to the discovery of their hydrogen-ordered counterparts ices
XIII, XV and XIV. Yet, the mechanistic details of the hydrogen-ordering phase
transitions are still not fully understood. This includes in particular the
role of the acid dopant and the defect dynamics that it creates within the
ices. Here we investigate the effects of several acid and base dopants on the
hydrogen ordering of ices V and VI with calorimetry and X-ray diffraction. HCl
is found to be most effective for both phases which is attributed to a
favourable combination of high solubility and strong acid properties which
create mobile H3O+ defects that enable the hydrogen-ordering processes.
Hydrofluoric acid (HF) is the second most effective dopant highlighting that
the acid strengths of HCl and HF are much more similar in ice than they are in
liquid water. Surprisingly, hydrobromic acid doping facilitates hydrogen
ordering in ice VI whereas only a very small effect is observed for ice V.
Conversely, lithium hydroxide (LiOH) doping achieves a performance comparable
to HF-doping in ice V but it is ineffective in the case of ice VI. Sodium
hydroxide, potassium hydroxide (as previously shown) and perchloric acid doping
are ineffective for both phases. These findings highlight the need for future
computational studies but also raise the question why LiOH-doping achieves
hydrogen-ordering of ice V whereas potassium hydroxide doping is most effective
for the 'ordinary' ice Ih.Comment: 18 pages, 7 figures, 1 tabl
Timing of CaseâBased Discussions and Educational Outcomes for Dental Students
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/153714/1/jddjde018056.pd
Complex nanostructures in diamond
Meteoritic diamonds and synthesized diamond-related materials contain a wide variety of complex nanostructures. This Comment highlights and classifies this structural complexity by a systematic hierarchical approach, and discusses the perspectives on nanostructure and properties engineering of diamond-related materials
Theoretical model for ultracold molecule formation via adaptive feedback control
We investigate pump-dump photoassociation of ultracold molecules with
amplitude- and phase-modulated femtosecond laser pulses. For this purpose a
perturbative model for the light-matter interaction is developed and combined
with a genetic algorithm for adaptive feedback control of the laser pulse
shapes. The model is applied to the formation of 85Rb2 molecules in a
magneto-optical trap. We find for optimized pulse shapes an improvement for the
formation of ground state molecules by more than a factor of 10 compared to
unshaped pulses at the same pump-dump delay time, and by 40% compared to
unshaped pulses at the respective optimal pump-dump delay time. Since our model
yields directly the spectral amplitudes and phases of the optimized pulses, the
results are directly applicable in pulse shaping experiments
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