1,318 research outputs found
Reconstructing Dryopteris “semicristata” (Dryopteridaceae): Molecular profiles of tetraploids verify their undiscovered diploid ancestor
This is the publisher's version, also available electronically from http://www.amjbot.org.• Premise of the study: Discovering missing ancestors is essential to understanding the evolutionary history of biodiversity on Earth. Evidence from extinct species can provide links for reconstructing intricate patterns of reticulate relationships among extant descendents. When fossils are unavailable and other evidence yields competing hypotheses to explain species ancestry, data from proteins and DNA can help resolve conflicts and generate novel perspectives. The identity of a parent shared by two tetraploid species in the cosmopolitan fern genus Dryopteris has remained elusive for more than 50 years. Based on available data, four hypotheses were developed previously, each providing a different resolution to this uncertainty.
• Methods: New molecular evidence from studies of isozymes and restriction site analysis of chloroplast DNA tested the competing hypotheses about the diploid ancestors of these two extant Dryopteris polyploids.
• Key results: The results falsify two of the hypotheses, resolve the uncertainty in the third, and support the fourth.
• Conclusions: Our data validate the prior existence of Dryopteris “semicristata,” which was proposed 38 years ago as a diploid progenitor of the allotetraploids D. cristata and D. carthusiana but has never been collected. After developing a phylogeny using the new molecular data, we describe a plausible morphology for D. “semicristata” by extrapolating likely character states from related extant species
Abnormal activity in hypothalamus and amygdala during humour processing in human narcolepsy with cataplexy
Narcolepsy with cataplexy (NC) is a complex sleep-wake disorder, which was recently found to be associated with a reduction or loss of hypocretin (HCRT, also called orexin). HCRT is a hypothalamic peptide implicated in the regulation of sleep/wake, motor and feeding functions. Cataplexy refers to episodes of sudden and transient loss of muscle tone triggered by strong, mostly positive emotions, such as hearing or telling jokes. Cataplexy is thought to reflect the recruitment of ponto-medullary mechanisms that normally underlie muscle atonia during REM-sleep. In contrast, the suprapontine brain mechanisms associated with the cataplectic effects of emotions in human narcolepsy with cataplexy remain essentially unknown. Here, we used event-related functional MRI to assess brain activity in 12 NC patients and 12 controls while they watched sequences of humourous pictures. Patients and controls were similar in humour appreciation and activated regions known to contribute to humour processing, including limbic and striatal regions. A direct statistical comparison between patients and controls revealed that humourous pictures elicited reduced hypothalamic response together with enhanced amygdala response in the patients. These results suggest (i) that hypothalamic HCRT activity physiologically modulates the processing of emotional inputs within the amygdala, and (ii) that suprapontine mechanisms of cataplexy involve a dysfunction of hypothalamic-amygdala interactions triggered by positive emotion
Penning traps as a versatile tool for precise experiments in fundamental physics
This review article describes the trapping of charged particles. The main
principles of electromagnetic confinement of various species from elementary
particles to heavy atoms are briefly described. The preparation and
manipulation with trapped single particles, as well as methods of frequency
measurements, providing unprecedented precision, are discussed. Unique
applications of Penning traps in fundamental physics are presented.
Ultra-precise trap-measurements of masses and magnetic moments of elementary
particles (electrons, positrons, protons and antiprotons) confirm
CPT-conservation, and allow accurate determination of the fine-structure
constant alpha and other fundamental constants. This together with the
information on the unitarity of the quark-mixing matrix, derived from the
trap-measurements of atomic masses, serves for assessment of the Standard Model
of the physics world. Direct mass measurements of nuclides targeted to some
advanced problems of astrophysics and nuclear physics are also presented
Combined ion and atom trap for low temperature ion-atom physics
We report an experimental apparatus and technique which simultaneously traps
ions and cold atoms with spatial overlap. Such an apparatus is motivated by the
study of ion-atom processes at temperatures ranging from hot to ultra-cold.
This area is a largely unexplored domain of physics with cold trapped atoms. In
this article we discuss the general design considerations for combining these
two traps and present our experimental setup. The ion trap and atom traps are
characterized independently of each other. The simultaneous operation of both
is then described and experimental signatures of the effect of the ions and
cold-atoms on each other are presented. In conclusion the use of such an
instrument for several problems in physics and chemistry is briefly discussed.Comment: 24 pages, 13 figures. Figures Fixe
High-accuracy Penning trap mass measurements with stored and cooled exotic ions
The technique of Penning trap mass spectrometry is briefly reviewed
particularly in view of precision experiments on unstable nuclei, performed at
different facilities worldwide. Selected examples of recent results emphasize
the importance of high-precision mass measurements in various fields of
physics
HITRAP: A facility at GSI for highly charged ions
An overview and status report of the new trapping facility for highly charged
ions at the Gesellschaft fuer Schwerionenforschung is presented. The
construction of this facility started in 2005 and is expected to be completed
in 2008. Once operational, highly charged ions will be loaded from the
experimental storage ring ESR into the HITRAP facility, where they are
decelerated and cooled. The kinetic energy of the initially fast ions is
reduced by more than fourteen orders of magnitude and their thermal energy is
cooled to cryogenic temperatures. The cold ions are then delivered to a broad
range of atomic physics experiments.Comment: 8 pages, 11 figure
Sodium oxybate in narcolepsy with cataplexy: Zurich sleep center experience
Sodium oxybate (SO; Xyrem®) has been approved in most countries for treatment of narcolepsy and cataplexy. In this study, we present a single-center experience of a series of 18 patients with narcolepsy with cataplexy (18/18 DQB1*0602 positive, 17/17 with low/absent cerebrospinal fluid hypocretin) in whom SO was prescribed. After 26 ± 13 months, 13/18 patients were still on SO at a mean dosage of 6.1 ± 1.2 g (in 8 of them in combination with stimulants). The following significant effects were observed: improved subjective sleepiness (12/13), cataplexy (13/13; median number of attacks from 20 to 1/month), hallucinations (8/10) and sleep paralysis (8/8); increase in mean sleep latency on the Maintenance of Wakefulness Test (from 5.5 to 17.4 min) and sleep/rest efficiency on actigraphy (from 61 to 76%); decrease in Epworth Sleepiness Scale score (from 18 to 14), sleep onset REM periods on the Multiple Sleep Latency Test (from 3.6 to 2.4) and errors in the Steer-Clear Test (from 11 to 2%). Five patients discontinued SO because of insufficient compliance (n = 2), lack of efficiency (n = 1) and side effects (n = 1). These data confirm and expand previous reports on the good effects and tolerability of SO as a treatment for narcolepsy with cataplexy
Ultraviolet Irradiation Induces the Accumulation of Chondroitin Sulfate, but Not Other Glycosaminoglycans, in Human Skin
Ultraviolet (UV) light alters cutaneous structure and function. Prior work has shown loss of dermal hyaluronan after UV-irradiation of human skin, yet UV exposure increases total glycosaminoglycan (GAG) content in mouse models. To more fully describe UV-induced alterations to cutaneous GAG content, we subjected human volunteers to intermediate-term (5 doses/week for 4 weeks) or single-dose UV exposure. Total dermal uronyl-containing GAGs increased substantially with each of these regimens. We found that UV exposure substantially increased dermal content of chondroitin sulfate (CS), but not hyaluronan, heparan sulfate, or dermatan sulfate. UV induced the accumulation of both the 4-sulfated (C4S) and 6-sulfated (C6S) isoforms of CS, but in distinct distributions. Next, we examined several CS proteoglycan core proteins and found a significant accumulation of dermal and endothelial serglycin, but not of decorin or versican, after UV exposure. To examine regulation in vitro, we found that UVB in combination with IL-1α, a cytokine upregulated by UV radiation, induced serglycin mRNA in cultured dermal fibroblasts, but did not induce the chondroitin sulfate synthases. Overall, our data indicate that intermediate-term and single-dose UVB exposure induces specific GAGs and proteoglycan core proteins in human skin in vivo. These molecules have important biologic functions and contribute to the cutaneous response to UV
Fabrication of a planar micro Penning trap and numerical investigations of versatile ion positioning protocols
We describe a versatile planar Penning trap structure, which allows to
dynamically modify the trapping conguration almost arbitrarily. The trap
consists of 37 hexagonal electrodes, each with a circumcirle-diameter of 300 m,
fabricated in a gold-on-sapphire lithographic technique. Every hexagon can be
addressed individually, thus shaping the electric potential. The fabrication of
such a device with clean room methods is demonstrated. We illustrate the
variability of the device by a detailed numerical simulation of a lateral and a
vertical transport and we simulate trapping in racetrack and articial crystal
congurations. The trap may be used for ions or electrons, as a versatile
container for quantum optics and quantum information experiments.Comment: 10 pages, 7 figures, pdflatex, to be published in New Journal of
Physics (NJP) various changes according to the wishes of the NJP referees.
Text added and moved around, title changed, abstract changed, references
added rev3: one reference had a typo (ref 15), fixed (phys rev a 72, not 71
g factor of Li-like ions with nonzero nuclear spin
The fully relativistic theory of the g factor of Li-like ions with nonzero
nuclear spin is considered for the (1s)^2 2s state. The magnetic-dipole
hyperfine-interaction correction to the atomic g factor is calculated including
the one-electron contributions as well as the interelectronic-interaction
effects of order 1/Z. This correction is combined with the
interelectronic-interaction, QED, nuclear recoil, and nuclear size corrections
to obtain high-precision theoretical values for the g factor of Li-like ions
with nonzero nuclear spin. The results can be used for a precise determination
of nuclear magnetic moments from g factor experiments.Comment: 20 pages, 5 figure
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