Mechanical and hydrodynamic analyses of helical strake-like ridges in a glass sponge

From the discovery of functionally graded laminated composites, to near-structurally optimized diagonally reinforced square lattice structures, the skeletal system of the predominantly deep-sea sponge Euplectella aspergillum has continued to inspire biologists, materials scientists and mechanical engineers. Building on these previous efforts, in the present study, we develop an integrated finite element and fluid dynamics approach for investigating structure–function relationships in the complex maze-like organization of helical ridges that surround the main skeletal tube of this species. From these investigations, we discover that not only do these ridges provide additional mechanical reinforcement, but perhaps more significantly, provide a critical hydrodynamic benefit by effectively suppressing von Kármán vortex shedding and reducing lift forcing fluctuations over a wide range of biologically relevant flow regimes. By comparing the disordered sponge ridge geometry to other more symmetrical strake-based vortex suppression systems commonly employed in infrastructure applications ranging from antennas to underwater gas and oil pipelines, we find that the unique maze-like ridge organization of E. aspergillum can completely suppress vortex shedding rather than delaying their shedding to a more downstream location, thus highlighting their potential benefit in these engineering contexts.

Clues to primary vismodegib resistance lie in histology and genetics

Basal cell carcinoma (BCC) is the most common human malignant neoplasm. However, there are multiple BCC subtypes that share clinical features while demanding different management. We present a case of a woman with hundreds of BCCs throughout her body that were resistant to vismodegib and without other features of basal cell nevus syndrome. Histological results of biopsies taken from various sites revealed three lesions characteristic of infundibulocystic BCCs (IBCCs) and two BCCs. Paired whole-exome sequencing performed using DNA isolated from blood and one of her IBCCs uncovered a germline heterozygous SUFU (Suppressor of Fused) mutation. The downstream location of SUFU in the hedgehog pathway explains why its mutation results in IBCCs that will not respond to any therapeutics that target upstream components of SUFU. These results capture the significance of histological and genetic analysis in directing treatment.

Plasma transport into the duskside magnetopause caused by Kelvin–Helmholtz vortices in response to the northward turning of the interplanetary magnetic field observed by THEMIS

A train of likely Kelvin–Helmholtz (K–H) vortices with plasma transport across the magnetopause has been observed by the Time History of Events and Macroscale Interactions during Substorms (THEMIS) at the duskside of the magnetopause. This unique event occurs when the interplanetary magnetic field (IMF) abruptly turns northward, which is the immediate change to facilitate the K–H instability. Two THEMIS spacecraft, TH-A and TH-E, separated by 3 RE, periodically encountered the duskside magnetopause and the low-latitude boundary layer (LLBL) with a period of 2 min and tailward propagation of 212 km s−1. Despite surface waves also explaining some of the observations, the rotations in the bulk velocity observation, a distorted magnetopause with plasma parameter fluctuations and the magnetic field perturbations, as well as a high-velocity low-density feature indicate the possible formation of rolled-up K–H vortices at the duskside of the magnetopause. The coexistence of magnetosheath ions with magnetospheric ions and enhanced energy flux of hot electrons is identified in the K–H vortices. These transport regions appear more periodic at the upstream spacecraft and more dispersive at the downstream location, indicating significant transport can occur and evolve during the tailward propagation of the K–H waves. There is still much work to do to fully understand the Kelvin–Helmholtz mechanism. The observations of the direct response to the northward turning of the IMF, the possible evidence of plasma transport within the vortices, involving both ion and electron fluxes, can provide additional clues as to the K–H mechanism.

Overview of Current Immunotherapies Targeting Mutated KRAS Cancers

: The occurrence of somatic substitution mutations of the KRAS proto-oncogene is highly prevalent in certain cancer types, which often leads to constant activation of proliferative pathways and subsequent neoplastic transformation. It is often seen as a gateway mutation in carcinogenesis and has been commonly deemed as a predictive biomarker for poor prognosis and relapse when conventional chemotherapeutics are employed. Additionally, its mutational status also renders EGFR targeted therapies ineffective owing to its downstream location. Efforts to discover new approaches targeting this menacing culprit have been ongoing for years without much success, and with incidences of KRAS positive cancer patients being on the rise, researchers are now turning towards immunotherapies as the way forward. In this scoping review, recent immunotherapeutic developments and advances in both preclinical and clinical studies targeting K-ras directly or indirectly via its downstream signal transduction machinery will be discussed. Additionally, some of the challenges and limitations of various K-ras targeting immunotherapeutic approaches such as vaccines, adoptive T cell therapies, and checkpoint inhibitors against KRAS positive cancers will be deliberated.

Performance Improvement of a Fin-Tube Heat Exchanger Using Rectangular Winglet as Vortex Generator

Heat transfer performance of fin-tube heat exchanger can be augmented by using longitudinal vortex generators. Numerical simulations have been performed in the present work for investigating the effect of punching a rectangular winglet having hole from fin surface, on the heat transfer and flow resistance characteristics in a fin-tube heat exchanger. The concept of punching out a rectangular winglet having hole from the fin-plate surface is being proposed here and studied in two configurations namely, common flow down and common flow up. Comparisons on the basis of heat transfer and flow resistance characteristics have been drawn for all the configurations under consideration using Colburn’s factor (j), friction factor (f) and performance evaluation criterion (PEC) also known as area goodness factor (j/f). Investigations have been performed considering Reynolds number in the range of 1500 to 9000 and angle of attack as 45°. The result clearly indicates that punched out rectangular winglet with hole having common flow down configuration at upstream location as exhibiting the best thermal performance, followed by common flow up at upstream location and, common flow down at downstream location.

Investigations of Trenched Film Hole Orientation Angle on Film Cooling Effectiveness

The effect of altering the orientation angle of trenched film hole on film cooling effectiveness (ƞ) is analyzed through numerical investigation. The film holes were oriented at 6 different angles viz., 0°, 30°, 45°, 90°, 135° and 180° with a fixed inclination angle 30° and with a pitch to diameter (P/D) ratio 5.The length and depth of the trench embedding the film hole are fixed at 3D and 0.75D respectively. Three different blowing ratios M=0.5, 1 and 1.5 were studied. Results from the study reveal that changing the orientation angle of film hole with in trench offered a considerable improvement on ƞ from near film hole region to far downstream location on test surface. For a low blowing ratio of 0.5, the film cooling effectiveness distribution changes with respect to film hole orientation angle and higher ƞ zones are distributed along the corresponding film hole orientation angle. The film hole oriented at 90° with respect to stream wise direction delivered highest ƞ at all three different blowing ratios due to better lateral spreading and uniform coverage of injected coolant. Except near film hole region, 30° and 45° hole orientation produced uniform lateral effectiveness compared to 0° hole orientation.

Rivers and reciprocity: perceptions and policy on international watercourses

The paper analyses geopolitical dimensions of the 1997 United Nations Convention on the Law of the Non-Navigational Uses of International Watercourses (UNWC) using quantitative data on transboundary flows and qualitative data on basin State location within a watercourse. The UNWC has had a long and difficult history. A tendency for downstream support for, and upstream ambivalence/opposition to, the UNWC is identified. It appears not widely recognized that adverse effects can be caused by any State on other States, regardless of their upstream or downstream location. Thus downstream States consider that their actions cannot harm upstream States, and upstream States consider that the UNWC provides them with greater obligations than downstream States. Clarification of the UNWC with the principle of reciprocal obligations on all States, both upstream and downstream, will remove any ambiguity, correct misperceptions, have clear policy implications for all States, promote UNWC engagement of upstream States, and contribute to long-term global water security.

Perturbing vortex packets in a turbulent boundary layer

A zero pressure gradient turbulent boundary layer of $\textit {Re}_{\tau }=2500$ was perturbed by a single spanwise array of finite cylinders mounted on the bounding surface and extending through the logarithmic region. The cylinder height was $H/\delta =0.2$ ($H^{+}=500$), where $\delta $ is the boundary layer thickness, with an aspect ratio ($AR$) (height/diameter) of four. Streamwise–spanwise ($x\text {--}y$) planes of the flow were examined by particle image velocimetry (PIV) up to $7\delta $ downstream at a wall-normal location of $z^{+}=300$ for cylinder array spacings ranging from $0.2\delta $ to $0.8\delta $. Average streamwise velocity fields showed a splitting, then merging pattern of cylinder wakes which occurred further downstream as the cylinder spacing increased. Based on measurements at the furthest downstream location, both the spanwise variation of average streamwise velocity and the Fourier content in the instantaneous fields suggested that the case with $0.6\delta $ cylinder spacing, which matched the dominant spanwise scale in the unperturbed flow, yielded the most persistent downstream flow organization. A flying PIV method was implemented to track specific packet structures over a range $-2<x/\delta <7$ with respect to the cylinder array, corresponding to a time scale of $12.4\delta /U_{\infty }$. Packets approaching the $0.2\delta $ spacing array first lost their organization but then regained it a distance $2\delta $ downstream, suggesting that a persistent outer layer organization propagated inwards into the log region. For arrays with larger spanwise spacing, approaching packets were generally redirected into the spanwise location midway between cylinders and sometimes enhanced.

Mean and Turbulent Velocity Profile Measurements on the Suction Side of a Film Cooled Turbine Vane

Boundary layer velocity and turbulence profiles were measured on the suction side of a scaled up, film-cooled turbine vane airfoil. There have been a number of previous studies of the velocity profile on a turbine vane, but few have taken velocity profile data with film cooling, and none have taken such data on the suction side of the vane. Velocity and turbulence profile data were taken at two locations on the suction side of the vane — one at a high curvature region and one further downstream in a low curvature region. Data were collected for high (20%) and low (0.5%) mainstream turbulence conditions. For the upstream, high curvature location, velocity and turbulence profiles were found with and without the showerhead blowing and within and outside of the merged showerhead coolant jet. The data for the low curvature, downstream location was taken with injection from the showerhead alone, a second upstream row of holes alone, and the combination of the two cases. It was found that the presence of an active upstream row of holes thickens the boundary layer and increases urms both within and beyond the extent of the boundary layer. Span-wise variations showed that these effects are strongest within the core of the coolant jets. At the downstream location, the boundary layer velocity profile was most strongly influenced by the row of holes immediately upstream of that location. Finally, turbulence integral length scale data showed the effect of large scale mainstream turbulence penetrating the boundary layer. The increase in turbulence, thickening of the boundary layer, and large scale turbulence all play important roles in row to row coolant interactions and affect the film cooling effectiveness.