Experimental investigation of the subsonic high-altitude operation of the NASA Lewis 10- by 10-foot supersonic wind tunnel

An experimental investigation was conducted in the NASA Lewis 10- by 10-Foot Supersonic Wind Tunnel during subsonic tunnel operation in the aerodynamic cycle to determine the test section flow characteristics near the Advanced Turboprop Project propeller model plane of rotation. The investigation used an eight-probe pitot static flow survey rake to measure total and static pressures at two locations in the wind tunnel: the test section and the bellmouth section (upstream of the two-dimensional flexible-wall nozzle). A cone angularity probe was used to measure any flow angularity in the test section. The evaluation was conducted at tunnel Mach numbers from 0.10 to 0.35 and at three operating altitudes from 2,000 to 50,000 ft. which correspond to tunnel reference total pressures from 1960 to 245 psfa, respectively. The results of this experimental investigation indicate a total-pressure loss area in the center of the test section and a static-pressure gradient from the test section centerline to the wall. These total and static pressure differences were observed at all tunnel operating altitudes and diminished at lower tunnel velocities. The total-pressure loss area was also found in the bellmouth section, which indicates that the loss mechanism is not the tunnel flexible-wall nozzle. The flow in the test section is essentially axial since very small flow angles were measured. The results also indicate that a correction to the tunnel total and static pressures must be applied in order to determine accurate freestream conditions at the test section centerline

Enantioselective synthesis and application to the allylic imidate rearrangement of amine-coordinated palladacycle catalysts of cobalt sandwich complexes

The reaction of (η5-(N,N-dimethylaminomethyl)cyclopentadien-yl)(η4-tetraphenylcyclobutadiene)cobalt with sodium tetrachloropalladate and (R)-N-acetylphenylalanine gave planar chiral palladacycle di-μ-chloridebis[(η5-(Sp)-2-(N,N-dimethylaminomethyl)cyclopentadienyl,1-C,3′-N)(η4-tetraphenylcyclobutadiene)cobalt]dipalladium [(Sp)-Me2-CAP-Cl] in 92 % ee and 64 % yield. Enantiopurity (>98 % ee) was achieved by purification of the monomeric (R)-proline adducts and conversion back to the chloride dimer. Treatment with AgOAc gave (Sp)-Me2-CAP-OAc which was applied to asymmetric transcyclopalladation (up to 78 % ee). The (R)-N-acetylphenylalanine mediated palladation methodology was applicable also to the corresponding N,N-diethyl (82 % ee, 39 % yield) and pyrrolidinyl (>98 % ee, 43 % yield) cobalt sandwich complexes. A combination of 5 mol % of the latter [(Sp)-Pyrr-CAP-Cl] and AgNO3 (3.8 equiv) is a catalyst for the allylic imidate rearrangement of an (E)-N-aryltrifluoroacetimidate (up to 83 % ee), and this catalyst system is also applicable to the rearrangement of a range of (E)-trichloroacetimidates (up to 99 % ee). This asymmetric efficiency combined with the simplicity of catalyst synthesis provides accessible solutions to the generation of non-racemic allylic amine derivatives

An isogeometric finite element formulation for phase transitions on deforming surfaces

This paper presents a general theory and isogeometric finite element implementation for studying mass conserving phase transitions on deforming surfaces. The mathematical problem is governed by two coupled fourth-order nonlinear partial differential equations (PDEs) that live on an evolving two-dimensional manifold. For the phase transitions, the PDE is the Cahn-Hilliard equation for curved surfaces, which can be derived from surface mass balance in the framework of irreversible thermodynamics. For the surface deformation, the PDE is the (vector-valued) Kirchhoff-Love thin shell equation. Both PDEs can be efficiently discretized using $C^1$-continuous interpolations without derivative degrees-of-freedom (dofs). Structured NURBS and unstructured spline spaces with pointwise $C^1$-continuity are utilized for these interpolations. The resulting finite element formulation is discretized in time by the generalized-$\alpha$ scheme with adaptive time-stepping, and it is fully linearized within a monolithic Newton-Raphson approach. A curvilinear surface parameterization is used throughout the formulation to admit general surface shapes and deformations. The behavior of the coupled system is illustrated by several numerical examples exhibiting phase transitions on deforming spheres, tori and double-tori.Comment: fixed typos, extended literature review, added clarifying notes to the text, added supplementary movie file

Acute Effects of Increased Joint Mobilization Treatment Duration on Ankle Function and Dynamic Postural Control in Female Athletes With Chronic Ankle Instability

Background:: Chronic ankle instability (CAI) is linked to mechanical and functional insufficiencies. Joint mobilization is purported to be effective at treating these deficits. Purpose:: To examine the effect of different treatment durations of a grade IV anterior-to-posterior ankle joint mobilization on weightbearing dorsiflexion range of motion (WB-DFROM), posterior talar glide (PG), and dynamic postural control in individuals with CAI. Study Design:: Controlled laboratory study. Methods:: A total of 48 female athletes (mean age, 22.8 ± 4.8 years) with unilateral CAI participated in this study. Participants were randomly assigned to 1 of 3 treatment conditions: 30 seconds, 60 seconds, and 120 seconds. Treatment was provided to the injured limb on 3 separate occasions 48 hours apart and consisted of a Maitland grade IV anterior-to-posterior talar joint mobilization based on the participant’s initial group assignment. WB-DFROM; PG; and the anterior (ANT), posteromedial (PM), and posterolateral (PL) reach directions of the Star Excursion Balance Test were measured bilaterally before and after each treatment. The uninjured limb acted as a control. Data were analyzed using 2-way mixed-model analyses of variance, and effect sizes were calculated through use of Hedges g. Results:: Significant differences were detected after all treatment sessions for all outcome measures (P ≤ .001) and between treatment groups after sessions 1, 2, and 3 for all outcome measures (P ≤ .001). Effect sizes were very large or huge for all treatment groups for WB-DFROM, PG, and ANT reach direction. Substantial variation was found in effect sizes for PM and PL measures. Conclusion:: Accessory mobilization is an effective treatment to induce acute changes in ankle motion and dynamic postural control in patients with CAI, with longer treatment durations conferring greater improvements. Clinical Relevance:: This study adds clarity to the use of joint mobilization treatments and will add to the current clinical practice strategy for patients with CAI

IMP: Indirect Memory Prefetcher

Machine learning, graph analytics and sparse linear algebra-based applications are dominated by irregular memory accesses resulting from following edges in a graph or non-zero elements in a sparse matrix. These accesses have little temporal or spatial locality, and thus incur long memory stalls and large bandwidth requirements. A traditional streaming or striding prefetcher cannot capture these irregular access patterns. A majority of these irregular accesses come from indirect patterns of the form A[B[i]]. We propose an efficient hardware indirect memory prefetcher (IMP) to capture this access pattern and hide latency. We also propose a partial cacheline accessing mechanism for these prefetches to reduce the network and DRAM bandwidth pressure from the lack of spatial locality. Evaluated on 7 applications, IMP shows 56% speedup on average (up to 2.3×) compared to a baseline 64 core system with streaming prefetchers. This is within 23% of an idealized system. With partial cacheline accessing, we see another 9.4% speedup on average (up to 46.6%).Intel Science and Technology Center for Big Dat

Planar chiral palladacycle precatalysts for asymmetric synthesis

Chiral non-racemic palladacycles were employed as precatalysts for Pd(0) mediated asymmetric synthesis. Addition of HPAr2/base to a ferrocenyloxazoline planar chiral palladacycle resulted in ligand synthesis and palladium capture to give a bidentate Phosferrox/Pd(0) complex. A series of these complexes were generated in situ and applied successfully as catalysts for asymmetric allylic alkylation

Enantiopure planar chiral and chiral-at-metal iridacycles derived from bulky cobalt sandwich complexes

Reaction of (η5-(S)-2-(4-methylethyl)oxazolinylcyclopentadienyl)(η4-tetraphenylcyclobutadiene)cobalt with [IrCp*Cl2]2 in acetonitrile with KPF6 and KOt-Bu resulted in S,Sp,SIr and S,Rp,RIr configured acetonitrile and Cp* coordinated cationic iridacycles (d.r. up to 4.8 : 1 – kinetic control), the planar chiral configuration dictating the configuration of the pseudo-tetrahedral iridium-based stereogenic centre. Addition of water to the cycloiridation reaction resulted in an increase in yield (up to 78%) at the cost of diastereoselectivity. Use of the corresponding substrate containing a t-Bu rather than an i-Pr substituted oxazoline gave exclusively the S,Sp,SIr diastereoisomer, and under the same conditions (S)-2-ferrocenyl- 4-(1,1-dimethylethyl)oxazoline cycloiridated to give only the S,Sp,SIr diastereoisomer. Substitution reactions of the title complexes at iridium proceeded with retention of configuration, a computational study revealing the proposed coordinatively unsaturated intermediate of a dissociative mechanism to display a relatively weak Co-Ir interaction, and a pronounced steric effect as the basis of stereocontrol

Following the Sand Grains

When longshore transport systems encounter tidal inlets, complex mechanisms are involved in bypassing sand to downdrift barriers. Here, this process is examined at Plum Island Sound and Essex Inlets, Massachusetts, USA. One major finding from this study is that sand is transferred along the coast—especially at tidal inlets—by parcels, in discrete steps, and over decadal-scale periods. The southerly orientation of the main-ebb channel at Plum Island Sound, coupled with the landward migration of bars from the ebb delta to the central portion of the downdrift Castle Neck barrier island, have formed a beach protuberance. During the constructional phase, sand is sequestered at the protuberance and the spit-end of the barrier becomes sediment starved, leading to shoreline retreat and a broadening of the spit platform at the mouth to Essex Bay (downdrift side of Castle Neck). Storm-induced sand transport from erosion of the spit and across the spit platform is washed into Essex Bay, filling channels and enlarging flood deltas. This study illustrates the pathways and processes of sand transfer along the shoreline of a barrier-island/tidal-inlet system and provides an important example of the processes that future hydrodynamic and sediment-transport modeling should strive to replicate

Rapid, Semi-Automated Fractionation of Freshwater Dissolved Organic Carbon Using DAX 8 (XAD 8) and XAD 4 Resins in Tandem

Natural dissolved organic carbon (DOC) consists of different bio-molecular classes of compounds that are currently very difficult and time-consuming to isolate as individual compounds. However, it is possible to separate natural DOC into hydrophobic and hydrophilic fractions. Such characterisation approaches are becoming increasingly important because, over the past 20 years natural DOC concentrations have been rising rapidly in many parts of the world, most likely influenced by climate change. Higher DOC concentrations in drinking water catchments present a serious problem for the water industry because DOC can form disinfection by-products DBPs during water treatment (e.g. chlorination). Hence, there is an urgent need to better characterise natural DOC before, during and after water treatment. However, current DOC fractionation procedures are extremely laborious requiring days and continual manual monitoring to separate sufficient quantities of DOC for subsequent analysis. This seriously limits sample throughput and the parameter space which can be studied. In this paper, we propose a much more rapid semi-automated method (12.5 hours/litre/sample) which utilises readily available equipment, i.e., HPLC pump or similar and sequential columns of Amberlite DAX 8 and XAD 4 resins. The method reduces the manual input from continual attention to minutes. This paper describes the development of the method and its application in the fractionation of natural DOC from reservoir and lake samples fed from upland peat-land catchments. Recoveries are found to be comparable to those using the manual technique, with the dominant component being hydrophobic acid accounting for 35% - 40% of the natural DOC with the second largest, being hydrophilic acid at 20% - 27%