The evolution of a turbulent boundary layer over truncated cones in staggered and random configurations is investigated using direct numerical simulations. Three random planform densities and one staggered, which closely match the configuration in the recent experiment by Womack et al. (J. Fluid Mech., vol. 933, 2022, A38), are considered. The experiment is also used to validate the present computations which are found to reproduce the flow measurements very accurately. Spanwise heterogeneity in the mean streamwise velocity in the form of high and low momentum pathways was detected in both the staggered and random arrangements, indicating the presence of secondary flows in the cross-stream plane. The momentum pathways found in the staggered arrangements are much weaker and confined near the roughness crest, while in the random arrangements they approach the edge of the boundary layer. We found a clear correlation of the momentum pathways with the leading edge of the roughness, while the correlation to the local topography was very weak for all the cases studied. Vorticity transport analysis is also employed to explore the nature of the secondary flows formed, highlighting the strong presence of vortex stretching near the leading edge of the roughness. The impact of the momentum pathways on the flow statistics, especially in the random arrangements, is demonstrated by the breakdown of outer-layer similarity.

Measurements were made in rough-wall boundary layers subject to favourable, zero and adverse pressure gradients. Profiles of mean velocity and turbulence quantities were acquired and velocity fields were measured in multiple planes to document flow structure. Comparisons were made to equivalent smooth-wall cases with the same free stream velocity distributions. Outer layer similarity was observed between the rough- and smooth-wall cases in all quantities in the favourable and zero pressure gradient regions, but large differences were observed with adverse pressure gradients. In both the smooth- and rough-wall cases, the favourable pressure gradient reduced the turbulence in the boundary layer, and increased the size of turbulence structures relative to the boundary layer thickness in both the streamwise and spanwise directions, while lowering their inclination angle with respect to the wall. When the boundary layer was returned to a zero pressure gradient following the favourable pressure gradient region, the turbulence level and the size and inclination of the structures returned to their canonical zero pressure gradient condition. The response of the boundary layer was somewhat faster in the rough-wall case, causing it to reach equilibrium in a shorter streamwise distance after the changes in pressure gradient than in the smooth-wall case. The adverse pressure gradient increased turbulence levels relative to the wall friction velocity, reduced the size of turbulence structures relative to the boundary layer thickness and increased their inclination angle. The changes with the adverse pressure gradient were significantly larger with the rough wall than the smooth. The results suggest that similarity might be achieved with adverse pressure gradients if smooth- and rough-wall cases with the same Clauser pressure gradient parameter history are compared.

Aiming to study the rough-wall turbulent boundary layer structure over differently arranged roughness elements, an experimental study was conducted on flows with regular and random roughness. Varying planform densities of truncated cone roughness elements in a square staggered pattern were investigated. The same planform densities were also investigated in random arrangements. Velocity statistics were measured via two-component laser Doppler velocimetry and stereoscopic particle image velocimetry. Friction velocity, thickness, roughness length and zero-plane displacement, determined from spatially averaged flow statistics, showed only minor differences between the regular and random arrangements at the same density. Recent a priori morphometric and statistical drag prediction methods were evaluated against experimentally determined roughness length. Observed differences between regular and random surface flow parameters were due to the presence of secondary flows which manifest as high-momentum pathways and low-momentum pathways in the streamwise velocity. Contrary to expectation, these secondary flows were present over the random surfaces and not discernible over the regular surfaces. Previously identified streamwise-coherent spanwise roughness heterogeneity does not seem to be present, suggesting that such roughness heterogeneity is not necessary to sustain secondary flows. Evidence suggests that the observed secondary flows were initiated at the front edge of the roughness and sustained over irregular roughness. Due to the secondary flows, local turbulent boundary layer profiles do not scale with local wall shear stress but appear to scale with local turbulent shear stress above the roughness canopy. Additionally, quadrant analysis shows distinct changes in the populations of ejection and sweep events.

A fine-grained, up to 3-m-thick tephra bed in southwestern Saskatchewan, herein named Duncairn tephra (Dt), is derived from an early Pleistocene eruption in the Jemez Mountains volcanic field of New Mexico, requiring a trajectory of northward tephra dispersal of ~1500 km. An unusually low CaO content in its glass shards denies a source in the closer Yellowstone and Heise volcanic fields, whereas a Pleistocene tephra bed (LSMt) in the La Sal Mountains of Utah has a very similar glass chemistry to that of the Dt, supporting a more southerly source. Comprehensive characterization of these two distal tephra beds along with samples collected near the Valles caldera in New Mexico, including grain size, mineral assemblage, major- and trace-element composition of glass and minerals, paleomagnetism, and fission-track dating, justify this correlation. Two glass populations each exist in the Dt and LSMt. The proximal correlative of Dt1 is the plinian Tsankawi Pumice and co-ignimbritic ash of the first ignimbrite (Qbt1g) of the 1.24 Ma Tshirege Member of the Bandelier Tuff. The correlative of Dt2 and LSMt is the co-ignimbritic ash of Qbt2. Mixing of Dt1 and Dt2 probably occurred during northward transport in a jet stream.

We present a Newtonian, one-dimensional, differential analysis for capillary breakup rheometry (CBR) to determine the surface tension to viscosity ratio $\unicode[STIX]{x1D6FC}$. Our local differential analysis does not require specific assumptions for the axial force to preclude its measurement. Our analysis indicates that measuring gradients in filament curvature is necessary to accurately determine $\unicode[STIX]{x1D6FC}$ when axial force is not measured. CBR experiments were performed on five silicone oils ($0.35~\text{Pa}~\text{s}<\unicode[STIX]{x1D707}<10~\text{ Pa}~\text{s}$), three sample volumes, and three strains to evaluate the operating range of the differential analysis and compare its performance to that of a standard integral method from literature. We investigate the role of filament asymmetry, caused mainly by gravity, on the performance of the differential method for the range of conditions studied. Experimental and analytical details for resolving gradients of curvature are also given.

Attention-deficit hyperactivity disorder (ADHD) is currently recognized as a neurobiological, genetically based disorder in both children and adults. In this article we examine whether, by using a sample of middle-aged male twin veterans, the phenotypic characterization, prevalence, heritability and the longitudinal course of the illness is comparable to results observed in samples of children and adolescents. We evaluated the utility of adult reports of lifetime ADHD symptoms by examining the heritability of retrospectively reported childhood symptoms, using both symptom-based and discrete classification- based approaches, as well as examining the persistence of ADHD symptoms into adulthood for that subsample of individuals who were judged to possibly have ADHD as children. Our results showed prevalence rates that were approximately similar to those observed in other studies, demonstrable familiality, similar item endorsement patterns, a strong genetic association between hyperactive and inattentive subtypes, and a longitudinal decline in symptom severity. We concluded that while assessing ADHD in adult probands may be less accurate than with children or adolescents, since it demonstrates several characteristics in common with other assessment techniques it remains a viable diagnostic and research strategy, even with population samples.

Measurements are presented from turbulent boundary layers over periodic two- and three-dimensional roughness. Cases with transverse rows of staggered cubes and cases with solid square transverse bars of two sizes were considered. Previous results by Volino, Schultz & Flack (J. Fluid Mech. vol. 635, 2009, p. 75) showed outer-layer similarity between cases with three-dimensional roughness and smooth walls, and deviations from similarity in cases with large two-dimensional transverse bars. The present results show that differences also occur with small two-dimensional bars and to a lesser extent when the bars are replaced with rows of staggered cubes. Differences are most apparent in correlations of turbulence quantities, which are of larger spatial extent for the rough-wall cases. The results with the staggered cubes indicate that part of the periodic roughness effect is caused by the repeated disturbance and recovery of the boundary layer as it encounters a row of roughness followed by a smooth surface. A larger effect, however, is due to the blockage caused by the two-dimensional transverse bars, which extend across the entire width of the boundary layer. The small two-dimensional bars have a larger effect than the staggered cubes, in spite of the bar height being only 11 viscous units and 1/7 of the cube height. The effect of the small bars extends well into the outer flow, indicating that effects observed previously with larger bars were not due only to a thickening of the roughness sublayer. The observed differences between the rough- and smooth-wall results are believed to be caused by large-scale attached eddies which extend from the roughness elements to the edge of the boundary layer.

Two-point hot-wire measurements of streamwise velocity were performed in the logarithmic and wake regions of turbulent pipe flow for Reynolds numbers, based on pipe diameter, ranging from 7.6 × 104 to 8.3 × 106 at four wall-normal positions with azimuthal probe separation. The azimuthal correlations were found to be consistent with the presence of very large-scale coherent regions of low-wavenumber, low-momentum fluid observed in previous studies of wall-bounded flows and were found to be independent of changing Reynolds number and surface roughness effects. At the edge of the logarithmic layer the azimuthal scale determined from the correlations was found to be similar to that observed for channel flows but larger than that observed for boundary layers, inconsistent with the concept of a universal logarithmic region. As the wall-normal position increased outside the logarithmic layer, there was a decrease in azimuthal scale relative to that of channel flow. Using cross-spectral analysis, high-wavenumber motion was found to grow azimuthally with wall-normal distance at a faster rate than the low-wavenumber motions.

The NASA Discovery mission EPOXI, utilizing the Deep Impact flyby spacecraft, comprises two phases: EPOCh (Extrasolar Planet Observation and Characterization) and DIXI (Deep Impact eXtended Investigation). With EPOCh, we use the 30-cm high resolution visible imager to obtain ultraprecise photometric light curves of known transiting planet systems. We will analyze these data for evidence of additional planets, via transit timing variations or transits; for planetary moons or rings; for detection of secondary eclipses and the constraint of geometric planetary albedos; and for refinement of the system parameters. Over a period of four months, EPOCh observed four known transiting planet systems, with each system observed continuously for several weeks. Here we present an overview of EPOCh, including the spacecraft and science goals, and preliminary photometry results.

EPOXI (EPOCh + DIXI) is a NASA Discovery Program Mission of Opportunity using the Deep Impact flyby spacecraft. The EPOCh (Extrasolar Planet Observation and Characterization) Science Investigation will gather photometric time series of known transiting exoplanet systems from January through August 2008. Here we describe the steps in the photometric extraction of the time series and present preliminary results of the first four EPOCh targets.

Bulged nucleotides play a variety of important roles in RNA structure and function, frequently forming tertiary interactions and sometimes even participating in RNA catalysis. In pre-mRNA splicing, the U2 snRNA base pairs with the intron branchpoint sequence (BPS) to form a short RNA duplex that contains a bulged adenosine that ultimately serves as the nucleophile that attacks the 5′ splice site. We have determined a 2.18-Å resolution crystal structure of a self-complementary RNA designed to mimic the highly conserved yeast (Saccharomyces cerevisiae) branchpoint sequence (5′-UACUAACGUAGUA with the BPS italicized and the branchsite adenosine underlined) base paired with its complementary sequence from U2 snRNA. The structure shows a nearly ideal A-form helix from which two unpaired adenosines flip out. Although the adenosine adjacent to the branchsite adenosine is the one bulged out in the structure described here, either of these adenosines can serve as the nucleophile in mammalian but not in yeast pre-mRNA splicing. In addition, the packing of the bulged RNA helices within the crystal reveals a novel RNA tertiary interaction in which three RNA helices interact through bulged adenosines in the absence of any divalent metal ions.

This study developed a method for measuring subjective costs and benefits of psychiatric treatments. Forty-one patients rated the relative bothersomeness of symptoms of schizophrenia and side effects of neuroleptics. Thirty-four psychiatrists made parallel ratings from the perspective of the average patient (individual utility) and of the patient's family and society (institutional utility). Psychiatrists predicted patients' ratings moderately well, but misjudged the bothersomeness to patients of 24% of side effects and 20% of symptoms. When considering the patient's perspective, both schizophrenic patients and psychiatrists rated symptoms as no more bothersome than side effects. However, psychiatrists saw side effects as significantly less bothersome than symptoms when considering costs to society. The subjective utility of neuroleptic medications for schizophrenia is most justifiable from an institutional perspective.