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Turbulent convection systems are known to give rise to prominent large-scale circulation. At the same time, the ‘background’ (or ‘small-scale’) turbulence is also highly relevant and e.g. carries the majority of the heat transport in the bulk of the flow. Here, we investigate how the small-scale turbulence is interlinked with the large-scale flow organization of Rayleigh–Bénard convection. Our results are based on a numerical simulation at Rayleigh number $Ra = 10^8$ in a large aspect ratio ($\varGamma =32$) cell to ensure a distinct scale separation. We extract local magnitudes and wavenumbers of small-scale turbulence and find significant correlation of large-scale variations in these quantities with the large-scale signal. Most notably, we find stronger temperature fluctuations and increased small-scale transport (by about 10 % of the global Nusselt number $Nu$) in plume impacting regions and opposite trends in the plume emitting counterparts. This concerns wall distances up to $2\delta _\theta$ (thermal boundary layer thickness). Local wavenumbers are generally found to be higher on the plume emitting side compared to the impacting one. A second independent approach by means of conditional averages confirmed these findings and yields additional insight into the large-scale variation of small-scale properties. Our results have implications for the modelling of small-scale turbulence.
To identify attention profiles at 7 and 13 years, and transitions in attention profiles over time in children born very preterm (VP; <30 weeks’ gestation) and full term (FT), and examine predictors of attention profiles and transitions.
Participants were 167 VP and 60 FT children, evaluated on profiles across five attention domains (selective, shifting and divided attention, processing speed, and behavioral attention) at 7 and 13 years using latent profile analyses. Transitions in profiles were assessed with contingency tables. For VP children, biological and social risk factors were tested as predictors with a multinomial logistic regression.
At 7 and 13 years, three distinct profiles of attentional functioning were identified. VP children were 2–3 times more likely to show poorer attention profiles compared with FT children. Transition patterns between 7 and 13 years were stable average, stable low, improving, and declining attention. VP children were two times less likely to have a stable average attention pattern and three times more likely to have stable low or improving attention patterns compared with FT children. Groups did not differ in declining attention patterns. For VP children, brain abnormalities on neonatal MRI and greater social risk at 7 years predicted stable low or changing attention patterns over time.
VP children show greater variability in attention profiles and transition patterns than FT children, with almost half of the VP children showing adverse attention patterns over time. Early brain pathology and social environment are markers for attentional functioning.
A delayed detached eddy simulation of an overexpanded nozzle flow with shock-induced separation is carried out at a Reynolds number of
, based on nozzle throat diameter and stagnation chamber properties. In this flow, self-sustained shock oscillations induce local unsteady loads on the nozzle wall as well as global off-axis forces. Despite several studies in the last few decades, a clear physical understanding of the factors driving this unsteadiness is still lacking. The geometry under investigation is a subscale truncated ideal contour nozzle, which was experimentally tested at the University of Texas at Austin at a nozzle pressure ratio of 30. Under these conditions, the nozzle operates in a highly overexpanded state and comprises a conical separation shock that merges to form a Mach disk at the nozzle centre. The delayed detached eddy simulation model agrees well with the experimental results in terms of mean and fluctuating wall-pressure statistics. Wall-pressure spectra reveal a large bump at low frequencies associated with an axisymmetric (piston-like) motion of the shock system, followed by a broad and high-amplitude peak at higher frequencies associated with the Mach waves produced by turbulent eddies convecting through the detached shear layer. Moreover, a distinct peak at an intermediate frequency (
) persists in the wall-pressure spectra downstream of the separation shock. A Fourier-based analysis performed in both time and space (azimuthal wavenumber) reveals that this intermediate-frequency peak is associated with the
(non-symmetric) pressure mode and is thus related to the generation of aerodynamic side loads. It is then shown how the unsteady Mach disk motion is characterized by an intense vortex shedding activity that, together with the vortical structures of the annular shear layer, contributes to the sustainment of an aeroacoustic feedback loop occurring within the nozzle.
Functional transcranial Doppler sonography (fTCD) of basal cerebral arteries is a non-invasive technique that allows monitoring of cerebral hemodynamics during cognitive performance with a high temporal resolution. There is ample evidence that age impacts on performance and cerebral hemodynamics. This study investigated those associations between a sample of young adult healthy subjects performing the Trail Making Test (TMT), a means of selective attention and complex cognitive functioning.
We examined cerebral hemodynamic parameters in the middle cerebral arteries (MCA) using fTCD while healthy subjects (mean age 31.5 years) simultaneously performed the TMT.
There was a significant slowing with older age (age 30 years or older) for both selective attention and complex cognitive functioning, and older age was associated with significantly lower mean cerebral blood flow velocity (MFV) in males during complex functioning. Young age (younger than 30 years) was associated with initially bilateral and then significantly left sided lateralization, and older age with a bilateral pattern.
These novel results suggest that, in a relatively young age continuum sample, older age results in slowing and decreased brain perfusion, though in a diverse manner. Younger age is associated with alternating pattern of lateralization implying a diverse cognitive style with age as covariate. It adds to the notion that fTCD is a substantial tool to significantly link age related modulation of performance with dedicated parameters of brain perfusion.
Scalings of the streamwise velocity energy spectra in turbulent boundary layers were considered in Part 1 (Baars & Marusic, J. Fluid Mech., vol. 882, 2020, A25). A spectral decomposition analysis provided a means to separate out attached and non-attached eddy contributions and was used to generate three spectral sub-components, one of which is a close representation of the spectral signature induced by self-similar, wall-attached turbulence. Since sub-components of the streamwise turbulence intensity
follow from an integration of the velocity energy spectra, we here focus on the scaling of the former. Wall-normal profiles and Reynolds-number trends of the three individual, additive sub-components of the streamwise turbulence intensity are examined. Based on universal trends across all Reynolds numbers considered, some evidence is given for a Townsend–Perry constant of
, which would describe the wall-normal logarithmic decay of the turbulence intensity per Townsend’s attached-eddy hypothesis. It is also demonstrated how this constant can be consistent with the Reynolds-number increase of the streamwise turbulence intensity in the near-wall region.
In wall-bounded turbulence, a multitude of coexisting turbulence structures form the streamwise velocity energy spectrum from the viscosity- to the inertia-dominated range of scales. Definite scaling-trends for streamwise spectra have remained empirically elusive, although a prominent school of thought stems from the works of Perry & Abell (J. Fluid Mech., vol. 79, 1977, pp. 785–799) and Perry et al. (J. Fluid Mech., vol. 165, 1986, pp. 163–199), which were greatly inspired by the attached-eddy hypothesis of Townsend (The Structure of Turbulent Shear Flow, Cambridge University Press, 1976). In this paper, we re-examine the turbulence kinetic energy of the streamwise velocity component in the context of the spectral decompositions of Perry and co-workers. Two universal spectral filters are derived via spectral coherence analysis of two-point velocity signals, spanning a Reynolds-number range
and form the basis for our decomposition of the logarithmic-region turbulence into stochastically wall-detached and wall-attached portions of energy. The latter is composed of scales larger than a streamwise/wall-normal ratio of
. If the decomposition is accepted, a
scaling region can only appear for
, at a wall-normal position of
. Following Perry and co-workers, it is hypothesized that spectral contributions from turbulence structures other than attached eddies obscure a
scaling. When accepting the idea of different spectral contributions it is furthermore shown that a broad outer-spectral peak is present even at low
Cognitive strategies that adolescents use to cope with negative emotions might show distinct profiles of cognitive emotion regulation strategies, which could be differentially associated with depressive symptoms. In total, 411 Dutch adolescents who had experienced at least one stressful life event that required some coping strategy participated in this study, including 334 nonclinical and 77 clinically depressed adolescents (12–21 years). A person-centered approach with Latent Profile Analysis was used to identify underlying profiles of cognitive emotion regulation based on the adolescents’ reports of their use of cognitive emotion regulation strategies when they were confronted with stressful life events. Nine different strategies, five adaptive and four maladaptive, were used as indicators. Four profiles with distinct features were found in the nonclinical sample, as well as in the combined sample of nonclinical and clinically depressed adolescents: Low Regulators, High Regulators, Maladaptive Regulators, and Adaptive Regulators. In both samples, the High Regulators profile was most commonly used, followed by the Adaptive, Maladaptive, and Low Regulators profile. Maladaptive Regulators endorsed higher levels of depressive symptoms relative to Low, High, and Adaptive Regulators. The findings underscore the utility of using a person-centered approach in order to identify patterns of cognitive emotion regulation deficits in psychopathology.
Streamwise velocity and wall-shear stress are acquired simultaneously with a hot-wire and an array of azimuthal/spanwise-spaced skin friction sensors in large-scale pipe and boundary layer flow facilities at high Reynolds numbers. These allow for a correlation analysis on a per-scale basis between the velocity and reference skin friction signals to reveal which velocity-based turbulent motions are stochastically coherent with turbulent skin friction. In the logarithmic region, the wall-attached structures in both the pipe and boundary layers show evidence of self-similarity, and the range of scales over which the self-similarity is observed decreases with an increasing azimuthal/spanwise offset between the velocity and the reference skin friction signals. The present empirical observations support the existence of a self-similar range of wall-attached turbulence, which in turn are used to extend the model of Baars et al. (J. Fluid Mech., vol. 823, p. R2) to include the azimuthal/spanwise trends. Furthermore, the region where the self-similarity is observed correspond with the wall height where the mean momentum equation formally admits a self-similar invariant form, and simultaneously where the mean and variance profiles of the streamwise velocity exhibit logarithmic dependence. The experimental observations suggest that the self-similar wall-attached structures follow an aspect ratio of
in the streamwise, spanwise and wall-normal directions, respectively.
An assessment of the turbulent boundary layer flow structure, which is coherent with the near-wall region, is carried out through a spectral coherence analysis. This spectral method is applied to datasets comprising synchronized two-point streamwise velocity signals at a near-wall reference position and a range of wall-normal positions spanning a Reynolds-number range
. Within each dataset, a self-similar structure is identified from the coherence between the turbulence in the logarithmic region and at the near-wall reference position. This self-similarity is described by a streamwise/wall-normal aspect ratio of
are the streamwise wavelength and wall-normal distance respectively.
The success of scaling out depends on a clear understanding of the factors that affect adoption of grain legumes and account for the dynamism of those factors across heterogeneous contexts of sub-Saharan Africa. We reviewed literature on adoption of grain legumes and other technologies in sub-Saharan Africa and other developing countries. Our review enabled us to define broad factors affecting different components of the scaling out programme of N2Africa and the scales at which those factors were important. We identified three strategies for managing those factors in the N2Africa scaling out programme: (i) testing different technologies and practices; (ii) evaluating the performance of different technologies in different contexts; and (iii) monitoring factors that are difficult to predict. We incorporated the review lessons in a design to appropriately target and evaluate technologies in multiple contexts across scales from that of the farm to whole countries. Our implementation of this design has only been partially successful because of competing reasons for selecting activity sites. Nevertheless, we observe that grain legume species have been successfully targeted for multiple biophysical environments across sub-Saharan Africa, and to social and economic contexts within countries. Rhizobium inoculant and legume specific fertiliser blends have also been targeted to specific contexts, although not in all countries. Relatively fewer input and output marketing models have been tested due to public–private partnerships, which are a key mechanism for dissemination in the N2Africa project.
Epidemiological studies have demonstrated protective effects of breast-feeding on childhood obesity. Differences between human milk and infant milk formula (IMF) in dietary lipid structure may contribute to this effect. In our mouse model, feeding a diet containing large lipid droplets coated with phospholipids (PL) (Nuturis®; PL of milk fat globule membrane (MFGM) fraction origin) in early life protected against excessive body fat accumulation following a diet challenge in adult life. We now set out to determine the relevance of increased droplet size and/or MFGM lipid droplet coating to the observed anti-obesogenic effects in adult life. From day 16 to 42, male mouse pups were exposed to diets with small (S) or large (L) lipid droplets (0·3 v. 2·9 µm average mode diameter, respectively), either without MFGM or with MFGM coating around the lipid droplet, resulting in four groups: S (control diet), L, Scoating and Lcoating (Nuturis® IMF diet). Mice were subsequently challenged with a Western-style diet until dissection at postnatal day 98. A non-challenged group served as reference (REF). We repeatedly determined body composition between postnatal day 42 and 98. At day 98 plasma and gene expression measurements were performed. Only the Nuturis® IMF diet (Lcoating) in early life containing MFGM-coated large lipid droplets reduced body fat mass to a level comparable with the REF group. These data support the notion that the structural aspects of lipids in human milk, for example, both lipid droplet size as well as the MFGM coating, may contribute to its reported protective effect against obesity in later life.
A model is proposed for predicting the presence of cumulative nonlinear distortions in the acoustic waveforms produced by high-speed jet flows. The model relies on the conventional definition of the acoustic shock formation distance and employs an effective Gol’dberg number
for diverging acoustic waves. The latter properly accounts for spherical spreading, whereas the classical Gol’dberg number
is restricted to plane wave applications. Scaling laws are then derived to account for the effects imposed by jet exit conditions of practical interest and includes Mach number, temperature ratio, Strouhal number and an absolute observer distance relative to a broadband Gaussian source. Surveys of the acoustic pressure produced by a laboratory-scale, shock-free and unheated Mach 3 jet are used to support findings of the model. Acoustic waveforms are acquired on a two-dimensional grid extending out to 145 nozzle diameters from the jet exit plane. Various statistical metrics are employed to examine the degree of local and cumulative nonlinearity in the measured waveforms and their temporal derivatives. This includes a wave steepening factor (WSF), skewness, kurtosis and the normalized quadrature spectral density. The analysed data are shown to collapse reasonably well along rays emanating from the post-potential-core region of the jet. An application of the generalized Burgers equation is used to demonstrate the effect of cumulative nonlinear distortion on an arbitrary acoustic waveform produced by a high-convective-Mach-number supersonic jet. It is advocated that cumulative nonlinear distortion effects during far-field sound propagation are too subtle in this range-restricted environment and over the region covered, which may be true for other laboratory-scale jet noise facilities.
Carruthers claims that “our knowledge of our own attitudes results from turning our mindreading capacities upon ourselves” (target article, Abstract). This may be true in many cases. But like other constructivist claims, it fails to explain occasions when constructed knowledge is accurate, like a well-supported scientific theory. People can know their surrounding world and to some extent themselves. Accurate self-knowledge is firmly established for both somatosensory and social pain.
Target-controlled infusion, via the calculated effect compartment concentrations, may help anaesthesiologists to titrate anaesthetic depth and to shorten recovery from anaesthesia.
In this prospective, randomized clinical study, we compared the performance of six inexperienced anaesthesiologists with <1 yr of training when using target- or manually controlled infusion of propofol, combined with manual dosing of fentanyl. Ninety-two premedicated ASA I–III patients undergoing minor elective urological or gynaecological surgery were assigned to the manual- or target-controlled infusion group. Bispectral index was recorded in a blinded manner. Subjective assessment of anaesthetic depth on a 10 point numerical scale (1 = very deep anaesthesia, 10 = awake) was asked at regular intervals and the correlation with the blinded bispectral index was analysed using the prediction probability, PK. The propofol concentration profile was calculated post hoc.
Propofol administration was similar in both groups with no significant difference for the administered amount and concentrations of propofol. Recovery times were also not different. In both groups, a large percentage of the bispectral index data points recorded during surgery showed bispectral index values below the recommended value of 40, but in the target-controlled infusion group there were significantly less bispectral index values above the recommended upper limit of 60 (2.5% vs. 5.1%).
A target-controlled infusion system does not help inexperienced anaesthesiologists to assess anaesthetic depth or to shorten recovery times, but may reduce episodes of overly light anaesthesia and thus help to prevent awareness.
This introduction provides an overview of the concepts discussed in the various chapters of this volume on consciousness. This volume attempts to survey the major developments in a wide range of intellectual domains to give the reader an appreciation of the state of the field and where it is heading. The development of new techniques has made it possible to treat consciousness in a more rigorous and scientifically respectable fashion. These techniques include electrophysiological methods, such as magneto-encephalography (MEG), and various types of functional neuroimaging, including functional magnetic resonance imaging (fMRI). There is currently considerable interest in exploring the neural correlates of consciousness. The volume covers philosophical approaches to consciousness from a variety of cultural perspectives, including continental phenomenology and Asian philosophy. It is organized mainly around a broad (sometimes untenable) distinction between cognitive scientific approaches and neuroscientific approaches.
The aim of this study was to describe a systematic process of record-linkage, cross-validation, case-ascertainment and capture–recapture analysis to assess the quality of tuberculosis registers and to estimate the completeness of notification of incident tuberculosis cases in The Netherlands in 1998. After record-linkage and cross-validation 1499 tuberculosis patients were identified, of whom 1298 were notified, resulting in an observed under-notification of 13·4%. After adjustment for possible imperfect record-linkage and remaining false-positive hospital cases observed under-notification was 7·3%. Log-linear capture–recapture analysis initially estimated a total number of 2053 (95% CI 1871–2443) tuberculosis cases, resulting in an estimated under-notification of 36·8%. After adjustment for possible imperfect record-linkage and remaining false-positive hospital cases various capture–recapture models estimated under-notification at 13·6%. One of the reasons for the higher than expected estimated under-notification in a country with a well-organized system of tuberculosis control might be that some tuberculosis cases, e.g. extrapulmonary tuberculosis, are managed by clinicians less familiar with notification of infectious diseases. This study demonstrates the possible impact of violation of assumptions underlying capture–recapture analysis, especially the perfect record-linkage, perfect positive predictive value and absent three-way interaction assumptions.
Background and objective: Derived parameters of the electroencephalogram and auditory evoked potentials can be used to determine depth of anaesthesia and sedation. However, it is not known whether any parameter can identify the occurrence of awareness in individual patients. We have compared the performance of bispectral index and a new composite index derived from auditory evoked potentials and the electroencephalogram (AAI 1.61) in predicting consciousness, explicit and implicit memory during moderate sedation with propofol. Methods: Twenty-one patients with spinal anaesthesia received intraoperatively propofol at the age-corrected C50 for loss of consciousness and were presented test words via headphones. Bispectral index and AAI 1.61 (auditory evoked potentials, AEP-Monitor2) were recorded in parallel as well as the Observer's Assessment of Alertness/Sedation-score. Postoperatively, testing for explicit and implicit memory formation was performed. Results: Bispectral index and AAI 1.61 correlated well with loss of consciousness defined by an Observer's Assessment of Alertness/Sedation-score of 2 (identical PK of 0.87), but did not allow a prediction of postoperative explicit or implicit recall. Conclusions: Both bispectral index and AAI may be indices of depth of sedation rather than indicators of memory formation, which persists during propofol sedation even after loss of consciousness.
van der Velde & de Kamps make a case for neural blackboard architectures to address four questions raised by human language. Unfortunately, they neglect a sizable literature relating blackboard architectures to other fundamental cognitive questions, specifically consciousness and voluntary control. Called “global workspace theory,” this literature integrates a large body of brain and behavioral evidence to come to converging conclusions.