28,357 research outputs found
Efficient spin control in high-quality-factor planar micro-cavities
A semiconductor microcavity embedding donor impurities and excited by a laser
field is modelled. By including general decay and dephasing processes, and in
particular cavity photon leakage, detailed simulations show that control over
the spin dynamics is significally enhanced in high-quality-factor cavities, in
which case picosecond laser pulses may produce spin-flip with high-fidelity
final states.Comment: 6 pages, 4 figure
Ni3TeO6 - a collinear antiferromagnet with ferromagnetic honeycomb planes
We report a comprehensive study of magnetic properties of Ni3TeO6. The system
crystallizes in a noncentrosymmetric rhombohedral lattice, space group R3.
There are three differently coordinated Ni atoms in the unit cell. Two of them
form an almost planar honeycomb lattice, while the third one is placed between
the layers. Magnetization and specific heat measurements revealed a single
magnetic ordering at TN = 52 K. Below TN the susceptibility with the magnetic
field parallel to the c-axis drops towards zero while the perpendicular
susceptibility remains constant, a characteristic of antiferromagnetic
materials. Neutron diffraction confirmed that the system is antiferromagnet
below TN with ferromagnetic ab-planes stacked antiferromagnetically along the
c-axis. All Ni moments are in the S = 1 spin state and point along the c-axis.Comment: accepted for publication in Journal of Physics Condensed Matte
Integrated optics for astronomical interferometry. I. Concept and astronomical applications
We propose a new instrumental concept for long-baseline optical single-mode
interferometry using integrated optics which were developed for
telecommunication. Visible and infrared multi-aperture interferometry requires
many optical functions (spatial filtering, beam combination, photometric
calibration, polarization control) to detect astronomical signals at very high
angular resolution. Since the 80's, integrated optics on planar substrate have
become available for telecommunication applications with multiple optical
functions like power dividing, coupling, multiplexing, etc. We present the
concept of an optical / infrared interferometric instrument based on this new
technology. The main advantage is to provide an interferometric combination
unit on a single optical chip. Integrated optics are compact, provide
stability, low sensitivity to external constrains like temperature, pressure or
mechanical stresses, no optical alignment except for coupling, simplicity and
intrinsic polarization control. The integrated optics devices are inexpensive
compared to devices that have the same functionalities in bulk optics. We think
integrated optics will fundamentally change single-mode interferometry.
Integrated optics devices are in particular well-suited for interferometric
combination of numerous beams to achieve aperture synthesis imaging or for
space-based interferometers where stability and a minimum of optical alignments
are wished.Comment: 11 pages, 8 figures, accpeted by Astronomy and Astrophysics
Supplement Serie
Fringe tracking performance monitoring: FINITO at VLTI
Since April 2011, realtime fringe tracking data are recorded simultaneously
with data from the VLTI/AMBER interferometric beam combiner. Not only this
offers possibilities to post-process AMBER reduced data to obtain more accurate
interferometric quantities, it also allows to estimate the performance of the
fringe tracking a function of the conditions of seeing, coherence time, flux,
etc. First we propose to define fringe tracking performance metrics in the
AMBER context, in particular as a function of AMBER's integration time. The
main idea is to determine the optimal exposure time for AMBER: short exposures
are dominated by readout noise and fringes in long exposures are completely
smeared out. Then we present this performance metrics correlated with Paranal
local ASM (Ambient Site Monitor) measurements, such as seeing, coherence time
or wind speed for example. Finally, we also present some preliminary results of
attempts to model and predict fringe tracking performances, using Artificial
Neural Networks.Comment: SPIE conference, Optical and Infrared Interferometry II
Ferrimagnetism of the magnetoelectric compound CuOSeO probed by Se NMR
We present a thorough Se NMR study of a single crystal of the
magnetoelectric compound CuOSeO. The temperature dependence of the
local electronic moments extracted from the NMR data is fully consistent with a
magnetic phase transition from the high-T paramagnetic phase to a low-T
ferrimagnetic state with 3/4 of the Cu ions aligned parallel and 1/4
aligned antiparallel to the applied field of 14.09 T. The transition to this
3up-1down magnetic state is not accompanied by any splitting of the NMR lines
or any abrupt modification in their broadening, hence there is no observable
reduction of the crystalline symmetry from its high-T cubic \textit{P}23
space group. These results are in agreement with high resolution x-ray
diffraction and magnetization data on powder samples reported previously by Bos
{\it et al.} [Phys. Rev. B, {\bf 78}, 094416 (2008)]. We also develop a mean
field theory description of the problem based on a microscopic spin Hamiltonian
with one antiferromagnetic ( K) and one ferromagnetic
( K) nearest-neighbor exchange interaction
Magnetic-field-induced transition in BaVS3
The metal-insulator transition (MIT) of BaVS3 is suppressed under pressure
and above the critical pressure of p~2GPa the metallic phase is stabilized. We
present the results of detailed magnetoresistivity measurements carried out at
pressures near the critical value, in magnetic fields up to B=12T. We found
that slightly below the critical pressure the structural tetramerization --
which drives the MIT -- is combined with the onset of magnetic correlations. If
the zero-field transition temperature is suppressed to a sufficiently low value
(T_MI<15K), the system can be driven into the metallic state by application of
magnetic field. The main effect is not the reduction of T_MI with increasing B,
but rather the broadening of the transition due to the applied magnetic field.
We tentatively ascribe this phenomenon to the influence on the magnetic
structure coupled to the bond-order of the tetramers.Comment: 5 pages, 5 figure
The development of a menthol solution for use during sport and exercise
Menthol mouth-swilling has been shown to improve performance across differing exercise modalities, yet no work has been conducted to ascertain the preferred concentration of menthol within a swill. Colour has also been shown to influence psychophysiological outcomes, and may influence the efficacy of ergogenic aids.
We conducted two experiments: one to ascertain preferred menthol concentration (0.005–0.105% menthol), the second to assess colour preference (Light Blue,Dark Blue, Light Green, Dark Green, Red). Participants rated swills for Smell, Taste, Freshness, Mouth Feel and Irritation (plus Appearance in the second trial) via 15 cm Visual Analogue Scales (VAS), having swilled and expectorated 25 mL of fluid. Both trials employed a crossover design, with tasting order assigned by Latin squares. Differences were assessed for statistical significance (p < 0.05) using one-way repeated measures ANOVAs. Standardised mean differences �90% confidence intervals were calculated to assess the magnitude of any observed differences. No significant differences were found between concentrations for total VAS score, but higher concentrations demonstrated a greater number of small effects. Similarly, no significant differences between colours were found. Small effects were found when Light Green was compared to Dark Green and Red. Effects were trivial when Light Green was compared to Light Blue (0.05 � 0.20) and Dark Blue (0.19 � 0.32). We recommend athletes employ a Light Green or Light Blue 0.1% menthol mouth-swill
Parent-child play and the emergence of externalizing and internalizing behavior problems in childhood: A systematic review
It has widely been accepted that play has a major role in human development. The play situation is considered a save and controlled space in which children can learn to express their problems and to regulate their emotions, thus promoting emotional and behavioral adjustment. In early childhood, this process is thought to emerge in close interaction with caregivers. Parent-child play is thus viewed as an ideal window for parents to connect with their children and to support them in their social-emotional development. In this preregistered systematic review, we sought to integrate evidence from developmental and clinical psychology to shed more light on the role of parents in the relationship between parent-child play and children's behavioral adjustment as expressed in internalizing or externalizing behavior. Our review revealed that increased harsh control during play interactions as well as a lack of parental responsiveness, warmth and sensitivity were found to be associated with increased behavioral problems. Yet, no protective effect of warmth or responsiveness could be found in the context of risk groups. Moreover, the included studies indicated that positive affect expressed by parents during parent-child play was associated with fewer behavior problems in children, while negative affect was associated with more behavior problems. In general, this review revealed that quality and quantity of playful parent-child interactions were reduced in children with behavioral problems of both domains compared to children without behavioral problems. These findings illustrate the important role of parental characteristics during play interactions and their possible impact on children's behavioral adjustment
Humor in psychiatry: Lessons from neuroscience, psychopathology, and treatment research
Humor is a ubiquitous human characteristic that is socially motivated at its core and has a broad range of significant positive effects on emotional well-being and interpersonal relationships. Simultaneously, however, impairments in humor abilities have often been described in close association with the occurrence and course of neuropsychiatric disorders, such as schizophrenia, social anxiety, or depression. In the past decade, research in the neuroimaging and psychiatric domain has substantially progressed to (i) characterize impaired humor as an element of psychopathology, and (ii) shed light on the neurobiological mechanisms underlying the role of humor in neuropsychiatric diseases. However, (iii) targeted interventions using concepts of positive psychology have revealed first evidence that a systematic training and/or a potential reactivation of humor-related skills can improve rehabilitative outcome in neuropsychiatric patient groups. Here, we sought to integrate evidence from neuroscience, as well as from psychopathology and treatment research to shed more light on the role of humor in psychiatry. Based on these considerations, we provide directions for future research and application in mental health services, focusing on the question of how our scientific understanding of humor can provide the basis for psychological interventions that foster positive attitudes and well-being
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