Phylogenetics of Cucumis (Cucurbitaceae)

Background: Melon, Cucumis melo, and cucumber, C. sativus, are among the most widely cultivated crops worldwide. Cucumis, as traditionally conceived, is geographically centered in Africa, with C. sativus and C. hystrix thought to be the only Cucumis species in Asia. This taxonomy forms the basis for all ongoing Cucumis breeding and genomics efforts. We tested relationships among Cucumis and related genera based on DNA sequences from chloroplast gene, intron, and spacer regions (rbcL, matK, rpl20-rps12, trnL, and trnL-F), adding nuclear internal transcribed spacer sequences to resolve relationships within Cucumis. Results: Analyses of combined chloroplast sequences (4,375 aligned nucleotides) for 123 of the 130 genera of Cucurbitaceae indicate that the genera Cucumella, Dicaelospermum, Mukia, Myrmecosicyos, and Oreosyce are embedded within Cucumis. Phylogenetic trees from nuclear sequences for these taxa are congruent, and the combined data yield a well-supported phylogeny. The nesting of the five genera in Cucumis greatly changes the natural geographic range of the genus, extending it throughout the Malesian region and into Australia. The closest relative of Cucumis is Muellerargia, with one species in Australia and Indonesia, the other in Madagascar. Cucumber and its sister species, C. hystrix, are nested among Australian, Malaysian, and Western Indian species placed in Mukia or Dicaelospermum and in one case not yet formally described. Cucumis melo is sister to this Australian/Asian clade, rather than being close to African species as previously thought. Molecular clocks indicate that the deepest divergences in Cucumis, including the split between C. melo and its Australian/Asian sister clade, go back to the mid-Eocene. Conclusion: Based on congruent nuclear and chloroplast phylogenies we conclude that Cucumis comprises an old Australian/Asian component that was heretofore unsuspected. Cucumis sativus evolved within this Australian/Asian clade and is phylogenetically far more distant from C. melo than implied by the current morphological classification

Coupling nitrogen-vacancy centers in diamond to fiber-based Fabry-Pérot microcavities

This thesis investigates the coupling of the fluorescence of nitrogen-vacancy (NV) centers in diamond to tunable optical microresonators at ambient conditions, in particular in the regime of Purcell enhancement. We use fiber-based, open-access Fabry-Pérot cavities optimized for high finesse and ultra-small mode volume. Different regimes of cavity enhancement are studied that are complementary to each other: A first experiment relies on a high-finesse cavity with dielectric mirrors. The scaling laws of Purcell enhancement are explicitly demonstrated by a large-range variation of both the cavity mode volume (V = 16 − 600 µm^3 ) and the quality factor (Q = 6 · 10^3 − 2 · 10^6). We detect an enhancement of the emission spectral density by up to a factor of 300. The full potential of this resonator can be exploited with emitters having a linewidth which is narrower than the resonance linewidth of the cavity. This concept holds promise for the implementation of wavelength-tunable, narrow-band single-photon sources as well as the generation of indistinguishable single-photons at ambient conditions. However, for broad-band emitters like the NV center at room temperature, the emission lifetime is not affected noticeably in this configuration. In order to directly observe lifetime changes and Purcell-enhanced single-photon emission, we manufacture fiber-based cavities with silver-coated mirrors having ultra-small mode volumes, as small as V = 1.0 λ^3 = 0.34 µm^3. We demonstrate cavity-enhanced fluorescence imaging, which allows to locate and analyze several single NV centers with one cavity. The Purcell effect is evidenced by an enhanced fluorescence collection of up to 1.6 · 10^6 photons per second from single-NV centers and a tunable variation of the emission lifetime corresponding to an effective Purcell factor of up to 2. We furthermore investigate a benefcial regime of optical confinement where the Fabry-Pérot cavity mode is combined with additional mode confinement by the diamond nanocrystal itself, enabling sub-λ^3 mode volumes. We perform simulations that predict effective Purcell factors of up to 11 for NV centers and of up to 63 for silicon-vacancy centers, revealing a great potential for bright single-photon sources and effcient spin readout at ambient conditions.Diese Arbeit erforscht die Kopplung der Fluoreszenz von Stickstoff-Fehlstellen-Zentren (NV-Zentren) in Diamant mit durchstimmbaren optischen Mikroresonatoren bei Umgebungsbedingungen, insbesondere im Regime der Purcell Verstärkung. Hierzu benutzen wir faserbasierte, offen zugängliche Fabry-Pérot Resonatoren, die für hohe Finesse und ultrakleine Modenvolumen optimiert sind. Verschiedene, komplementäre Bereiche der Resonatorverstärkung werden untersucht. Ein erstes Experiment basiert auf einem Resonator mit hoher Finesse und dielektrischen Spiegeln. Das Skalierungsverhalten der Purcell Verstärkung wird ausführlich ausgewertet, indem man sowohl das Modenvolumen des Resonators (V = 16 − 600 µm^3 ) als auch dessen Güte (Q = 6 · 10^3 − 2 · 10^6) über einen weiten Bereich verändert. Die spektrale Leistungsdichte der Emission kann durch den Resonator um einen Faktor von bis zu 300 überhöht werden. Das gesamte Leistugsvermögen dieses Resonators kann mit schmalbandigen Emittern ausgenutzt werden, deren Emissionslinienbreite kleiner als die Linienbreite des Resonators ist. Dies ist ein vielversprechender Ansatz für die Umsetzung von schmalbandigen Einzelphotonenquellen mit durchstimmbarer Wellenlänge und für die Erzeugung ununterscheidbarer Einzelphotonen bei Umgebungsbedingungen. Jedoch bleibt die Lebenszeit der Emission für breitbandige Emitter, wie dem NV-Zentrum bei Raumtemperatur, in dieser Anordnung nahezu unbeeinflusst. Um eine Veränderung der Lebenszeit und durch den Purcell-Effekt verstärkte Einzelphotonenemission direkt zu beobachten, stellen wir Faserresonatoren mit silberbeschichteten Spiegeln und ultrakleinen Modenvolumen, bis hinab zu V = 1.0 λ^3 = 0.34 µm^3, her. Wir demonstrieren resonatorverstärkte Fluoreszenzbildgebung, die das Auffinden und Untersuchen von verschiedenen einzelnen NV-Zentren mit einem Resonator erlaubt. Der Purcell-Effekt wird über eine gesteigerte Aufsammlung der Fluoreszenz nachgewiesen, mit einer Rate von bis zu 1.6 · 10^6 Photonen pro Sekunde von einzelnen NV-Zentren und außerdem durch die abstimmbare Veränderung der Emissionslebenszeit, entsprechend einem effektiven Purcell Faktor von bis zu 2. Des Weiteren untersuchen wir ein vorteilhaftes Regime, in dem der Diamant Nanokristall selbst eine zusätzliche Einschränkung der optischen Mode bewirkt, die sich mit der Mode des Fabry-Pérot Resonators verbindet und Modenvolumen unter 1 λ^3 ermöglicht. Simulationen ergeben effektive Purcell Faktoren von bis zu 11 für NV-Zentren und von bis zu 63 für Silizium-Fehlstellen-Zentren, wodurch das große Potenzial für helle Einzelphotonenquellen und für effzientes Spin-Auslesen bei Umgebungsbedingungen aufgezeigt wird

Photothermal effects in ultra-precisely stabilized tunable microcavities

We study the mechanical stability of a tunable high-finesse microcavity under ambient conditions and investigate light-induced effects that can both suppress and excite mechanical fluctuations. As an enabling step, we demonstrate the ultra-precise electronic stabilization of a microcavity. We then show that photothermal mirror expansion can provide high-bandwidth feedback and improve cavity stability by almost two orders of magnitude. At high intracavity power, we observe self-oscillations of mechanical resonances of the cavity. We explain the observations by a dynamic photothermal instability, leading to parametric driving of mechanical motion. For an optimized combination of electronic and photothermal stabilization, we achieve a feedback bandwidth of $500\,$kHz and a noise level of $1.1 \times 10^{-13}\,$m rms

Evolution and loss of long-fringed petals

Background: The Cucurbitaceae genus Trichosanthes comprises 90–100 species that occur from India to Japan and southeast to Australia and Fiji. Most species have large white or pale yellow petals with conspicuously fringed margins, the fringes sometimes several cm long. Pollination is usually by hawkmoths. Previous molecular data for a small number of species suggested that a monophyletic Trichosanthes might include the Asian genera Gymnopetalum (four species, lacking long petal fringes) and Hodgsonia (two species with petals fringed). Here we test these groups’ relationships using a species sampling of c. 60% and 4759 nucleotides of nuclear and plastid DNA. To infer the time and direction of the geographic expansion of the Trichosanthes clade we employ molecular clock dating and statistical biogeographic reconstruction, and we also address the gain or loss of petal fringes. Results: Trichosanthes is monophyletic as long as it includes Gymnopetalum, which itself is polyphyletic. The closest relative of Trichosanthes appears to be the sponge gourds, Luffa, while Hodgsonia is more distantly related. Of six morphology-based sections in Trichosanthes with more than one species, three are supported by the molecular results; two new sections appear warranted. Molecular dating and biogeographic analyses suggest an Oligocene origin of Trichosanthes in Eurasia or East Asia, followed by diversification and spread throughout the Malesian biogeographic region and into the Australian continent. Conclusions: Long-fringed corollas evolved independently in Hodgsonia and Trichosanthes, followed by two losses in the latter coincident with shifts to other pollinators but not with long-distance ispersal events. Together with the Caribbean Linnaeosicyos, the Madagascan Ampelosicyos and the tropical African Telfairia, these cucurbit lineages represent an ideal system for more detailed studies of the evolution and function of petal fringes in plant-pollinator mutualisms

Dynamical Backreaction in Robertson-Walker Spacetime

The treatment of a quantized field in a curved spacetime requires the study of backreaction of the field on the spacetime via the semiclassical Einstein equation. We consider a free scalar field in spatially flat Robertson-Walker space time. We require the state of the field to allow for a renormalized semiclassical stress tensor. We calculate the sigularities of the stress tensor restricted to equal times in agreement with the usual renormalization prescription for Hadamard states to perform an explicit renormalization. The dynamical system for the Robertson Walker scale parameter $a(t)$ coupled to the scalar field is finally derived for the case of conformal and also general coupling.Comment: Obtained equation of motion for non-conformal coupling, not just counter terms as in previous version. Typos fixed, renormalization term proportional to R adde

Gender-specific profiles of adverse childhood experiences, past year mental and substance use disorders, and their associations among a national sample of adults in the United States

Purpose: This study examined profiles of adverse childhood experiences (ACEs) and mental and substance use disorders (MSUDs), and associations between distinct profiles of ACEs and MSUDs. Methods: Participants were adults (N = 34, 652) involved in the National Epidemiologic Survey on Alcohol and Related Conditions. Latent class analysis was used to examine both profiles of ten ACEs and ten past year MSUDs. Dual latent class analysis regression was used to examine associations between profiles of ACEs and MSUDs. Given gender differences in ACEs and MSUDs, analyses were conducted separately for females and males. Results: Four profiles of ACEs and three profiles of MSUDs were selected for both genders. The four profiles of ACEs were characterized by the following probabilities: high multiple ACEs, high parental substance abuse, high childhood physical abuse, and low ACEs. The three profiles of MSUDs were characterized by the following probabilities: high multiple MSUDs for females and low MSUDs except alcohol use disorders for males, moderate-to-high major depressive episode, and low MSUDs. When compared to the low ACEs and MSUDs profiles, members in the higher ACEs profiles had 3.71–89.75 times greater odds of also being members in the higher MSUDs profiles. However, more than one-third of members in the high multiple ACEs profiles were also in the low MSUDs profiles. Conclusions: Study findings suggest four profiles of the ACEs widely studied as part of the Adverse Childhood Experiences study and risk and resilience for recent MSUDs among men and women nationally affected by ACEs