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In this paper, we provide support for the Rayleigh-Taylor-(RT)-based subgrid model used in full-star simulations of deflagrations in Type Ia supernovae explosions. We use the results of a parameter study of two-dimensional direct numerical simulations of an RT unstable model flame to distinguish between the two main types of subgrid models (RT or turbulence dominated) in the flamelet regime. First, we give scalings for the turbulent flame speed, the Reynolds number, the viscous scale, and the size of the burning region as the non-dimensional gravity (G) is varied. The flame speed is well predicted by an RT-based flame speed model. Next, the above scalings are used to calculate the Karlovitz number (Ka) and to discuss appropriate combustion regimes. No transition to thin reaction zones is seen at Ka = 1, although such a transition is expected by turbulence-dominated subgrid models. Finally, we confirm a basic physical premise of the RT subgrid model, namely, that the flame is fractal, and thus self-similar. By modeling the turbulent flame speed, we demonstrate that it is affected more by large-scale RT stretching than by small-scale turbulent wrinkling. In this way, the RT instability controls the flame directly from the large scales. Overall, these results support the RT subgrid model. [ABSTRACT FROM AUTHOR]

Behavioural responses of an animal are variable even when the animal experiences the same sensory input several times. This variability can arise from stochastic processes inherent to the nervous system. Also, the internal state of an animal may influence a particular behavioural response. In the present study, we analyse the variability of visually induced head pitch responses of tethered blowflies by high-speed cinematography. We found these optomotor responses to be highly variable in amplitude. Most of the variability can be attributed to two different internal states of the flies with high and low optomotor gain, respectively. Even within a given activity state, there is some variability of head optomotor responses. The amount of this variability differs for the two optomotor gain states. Moreover, these two activity states can be distinguished on a fine timescale and without visual stimulation, on the basis of the occurrence of peculiar head jitter movements. Head jitter goes along with high gain optomotor responses and haltere oscillations. Halteres are evolutionary transformed hindwings that oscillate when blowflies walk or fly. Their main function is to serve as equilibrium organs by detecting Coriolis forces and to mediate gaze stabilisation. However, their basic oscillating activity was also suggested to provide a gain-modulating signal. Our experiments demonstrate that halteres are not necessary for high gain head pitch to occur. Nevertheless, we find the halteres to be responsible for one component of head jitter movements. This component may be the inevitable consequence of their function as equilibrium and gaze-stabilising organs. [ABSTRACT FROM AUTHOR]

High-cadence TRACE observations show that outward-propagating intensity disturbances are a common feature in large, quiescent coronal loops. Analysis of the frequency distribution of these modes shows peaks at both three- and five-minute periods, indicating that they may be driven by the solar surface oscillations ( p modes). The energy flux contained within the coronal intensity disturbances is of the order of (1.1±0.4)×103 ergs cm−2 s−1. A simple order-of-magnitude estimate of the damping rate of the relevant p modes allows us to put an observational constraint on the damping of p modes and shows that leakage into the overlying coronal atmosphere might be able to account for a significant fraction of p-mode damping. [ABSTRACT FROM AUTHOR]

Investigates the accretion flow penetration of magnetosphere. Occurrence of the penetration without turbulent mixing caused by charge polarization effect; Influence of ambient medium on plasma propagation across the stellar magnetic field; Criteria for deep magnetosphere penetration.

Proposes an alternative mechanism of magnetic-field generation in galaxies. Generation of a seed field; Effect of strong shear flows in the rotating gas.

The conjecture is presented that the gap in the distribution of the orbital periods of cataclysmic variables is related to a particular kind of hydromagnetic dynamo, called an interface dynamo, operating near the base of the convective envelope of their secondary components. Such a dynamo is characterized by the spatial separation of the regions where differential rotation and the α effect operate. Unlike conventional dynamos, the linear growth rate of an interface dynamo becomes negative for highly supercritical dynamo numbers, leading to the disappearance of the dynamo action. If such a result, from linear theory, is confirmed by non-linear calculations, it may provide a physical basis for the so-called disrupted magnetic braking hypothesis, invoked to explain the existence of the period gap by several evolutionary models of cataclysmic variables. [ABSTRACT FROM AUTHOR]

Among minors, posttraumatic stress symptoms (PTSS) are a common consequence of traumatic events requiring trauma-focused treatment. This meta-analysis quantified treatment effects of trauma-focused cognitive behavioral therapy (TF-CBT) with PTSS as primary outcome and symptoms of depression, anxiety, and grief as secondary outcomes. Inclusion criteria for individual settings: (1) patients aged between 3 and 21, (2) at least one traumatic event, (3) minimum 8 sessions of (4) TF-CBT according to Cohen, Mannarino and Deblinger (2006, 2017), (5) a quantitative PTSS measure at pre- and post-treatment, (6) original research only. Inclusion criteria for group settings: had to involve (1) psychoeducation, (2) coping strategies, (3) exposure, (4) cognitive processing/restructuring, (5) contain some reference to the manual and no minimum session number was required. Searched databases were PsychInfo, MEDLINE, Cochrane Library, PTSDPubs, PubMed, Web of Science, and OpenGrey. 4523 participants from 28 RCTs and 33 uncontrolled studies were included. TF-CBT showed large improvements across all outcomes from pre- to post-treatment (PTSS: g = 1.14, CI 0.97–1.30) and favorable results compared to any control condition including wait-list, treatment as usual, and active treatment at post-treatment (PTSS: g = 0.52, CI 0.31–0.73). Effects were more pronounced for group settings. We give pooled estimates adjusted for risk of bias and publication bias, which initially limited the quality of the analyzed data. TF-CBT is an effective treatment for pediatric PTSS as well as for depressive, anxiety, and grief symptoms. It is superior to control conditions, supporting international guidelines recommending it as a first-line treatment. [ABSTRACT FROM AUTHOR]

BACKGROUND: Hypersensitivity to electromagnetic fields (EMF) is frequently claimed to be linked to a variety of non-specific somatic and neuropsychological complaints. Whereas provocation studies often failed to demonstrate a causal relationship between EMF exposure and symptom formation, recent studies point to a complex interplay of neurophysiological and cognitive alterations contributing to symptom manifestation in electromagnetic hypersensitive patients (EHS). However, these studies have examined only small sample sizes or have focused on selected aspects. Therefore this study examined in the largest sample of EHS EMF-specific cognitive correlates, discrimination ability and neurobiological parameters in order to get further insight into the pathophysiology of electromagnetic hypersensitivity.MethodIn a case-control design 89 EHS and 107 age- and gender-matched controls were included in the study. Health status and EMF-specific cognitions were evaluated using standardized questionnaires. Perception thresholds following single transcranial magnetic stimulation (TMS) pulses to the dorsolateral prefrontal cortex were determined using a standardized blinded measurement protocol. Cortical excitability parameters were measured by TMS. RESULTS: Discrimination ability was significantly reduced in EHS (only 40% of the EHS but 60% of the controls felt no sensation under sham stimulation during the complete series), whereas the perception thresholds for real magnetic pulses were comparable in both groups (median 21% versus 24% of maximum pulse intensity). Intra-cortical facilitation was decreased in younger and increased in older EHS. In addition, typical EMF-related cognitions (aspects of rumination, symptom intolerance, vulnerability and stabilizing self-esteem) specifically differentiated EHS from their controls. CONCLUSIONS: These results demonstrate significant cognitive and neurobiological alterations pointing to a higher genuine individual vulnerability of electromagnetic hypersensitive patients. [ABSTRACT FROM AUTHOR]

BackgroundHypersensitivity to electromagnetic fields (EMF) is frequently claimed to be linked to a variety of non-specific somatic and neuropsychological complaints. Whereas provocation studies often failed to demonstrate a causal relationship between EMF exposure and symptom formation, recent studies point to a complex interplay of neurophysiological and cognitive alterations contributing to symptom manifestation in electromagnetic hypersensitive patients (EHS). However, these studies have examined only small sample sizes or have focused on selected aspects. Therefore this study examined in the largest sample of EHS EMF-specific cognitive correlates, discrimination ability and neurobiological parameters in order to get further insight into the pathophysiology of electromagnetic hypersensitivity.MethodIn a case-control design 89 EHS and 107 age- and gender-matched controls were included in the study. Health status and EMF-specific cognitions were evaluated using standardized questionnaires. Perception thresholds following single transcranial magnetic stimulation (TMS) pulses to the dorsolateral prefrontal cortex were determined using a standardized blinded measurement protocol. Cortical excitability parameters were measured by TMS.ResultsDiscrimination ability was significantly reduced in EHS (only 40% of the EHS but 60% of the controls felt no sensation under sham stimulation during the complete series), whereas the perception thresholds for real magnetic pulses were comparable in both groups (median 21% versus24% of maximum pulse intensity). Intra-cortical facilitation was decreased in younger and increased in older EHS. In addition, typical EMF-related cognitions (aspects of rumination, symptom intolerance, vulnerability and stabilizing self-esteem) specifically differentiated EHS from their controls.ConclusionsThese results demonstrate significant cognitive and neurobiological alterations pointing to a higher genuine individual vulnerability of electromagnetic hypersensitive patients. [ABSTRACT FROM AUTHOR]

In the turbulent Rayleigh–Taylor instability, the light fluid penetrates the heavy fluid as bubbles with a diameter Db and amplitude hb that grow self-similarly Db∝hb∼αbA gt2 where A is Atwood number, g is acceleration, and t is time. Experiments measure an acceleration constant αb∼0.04–0.08 whereas the highest resolution three-dimensional numerical simulations obtain αb∼0.02–0.03 with idealized initial conditions. This paper reconciles this apparent discrepancy with new simulations that quantify the importance of initial conditions on αb. The results compare favorably with experiments and a model based on self-similar bubble dynamics. [ABSTRACT FROM AUTHOR]

We present a study of wind-driven nonlinear interfacial gravity waves using numerical simulations in two dimensions. We consider a case relevant to mixing phenomenon in astrophysical events such as novae in which the density ratio is approximately 1:10. Our physical setup follows the proposed mechanism of Miles [ J. Fluid Mech. 3, 185 (1957) ] for the amplification of such waves. Our results show good agreement with linear predictions for the growth of the waves. We explore how the wind strength affects the wave dynamics and the resulting mixing in the nonlinear stage. We identify two regimes of mixing, namely, the overturning and the cusp-breaking regimes. The former occurs when the wind is strong enough to overcome the gravitational potential barrier and overturn the wave. This result is in agreement with the common notion of turbulent mixing in which density gradients are increased to diffusion scales by the stretching of a series of vortices. In the latter case, mixing is the result of cusp instabilities. Although the wind is not strong enough to overturn the wave in this case, it can drive the wave up to a maximum amplitude where a singular structure at the cusp of the wave forms. Such structures are subject to various instabilities near the cusp that result in breaking the cusp. Mixing then results from these secondary instabilities and the spray-like structures that appear as a consequence of the breaking. [ABSTRACT FROM AUTHOR]

The turbulent Rayleigh–Taylor instability is investigated in the limit of strong mode-coupling using a variety of high-resolution, multimode, three dimensional numerical simulations (NS). The perturbations are initialized with only short wavelength modes so that the self-similar evolution (i.e., bubble diameter Db∝amplitude hb) occurs solely by the nonlinear coupling (merger) of saturated modes. After an initial transient, it is found that hb∼αbAgt2, where A=Atwood number, g=acceleration, and t=time. The NS yield Db∼hb/3 in agreement with experiment but the simulation value αb∼0.025±0.003 is smaller than the experimental value αb∼0.057±0.008. By analyzing the dominant bubbles, it is found that the small value of αb can be attributed to a density dilution due to fine-scale mixing in our NS without interface reconstruction (IR) or an equivalent entrainment in our NS with IR. This may be characteristic of the mode coupling limit studied here and the associated αb may represent a lower bound that is insensitive to the initial amplitude. Larger values of αb can be obtained in the presence of additional long wavelength perturbations and this may be more characteristic of experiments. Here, the simulation data are also analyzed in terms of bubble dynamics, energy balance and the density fluctuation spectra. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]