Acoustically shielded exhaust system for high thrust jet engines

A flade exhaust nozzle for a high thrust jet engine is configured to form an acoustic shield around the core engine exhaust flowstream while supplementing engine thrust during all flight conditions, particularly during takeoff. The flade airflow is converted from an annular 360.degree. flowstream to an arcuate flowstream extending around the lower half of the core engine exhaust flowstream so as to suppress exhaust noise directed at the surrounding community

Technology Readiness Level Assessment Process as Applied to NASA Earth Science Missions

Technology assessments of fourteen science instruments were conducted within NASA using the NASA Technology Readiness Level (TRL) Metric. The instruments were part of three NASA Earth Science Decadal Survey missions in pre-formulation. The Earth Systematic Missions Program (ESMP) Systems Engineering Working Group (SEWG), composed of members of three NASA Centers, provided a newly modified electronic workbook to be completed, with instructions. Each instrument development team performed an internal assessment of its technology status, prepared an overview of its instrument, and completed the workbook with the results of its assessment. A team from the ESMP SEWG met with each instrument team and provided feedback. The instrument teams then reported through the Program Scientist for their respective missions to NASA's Earth Science Division (ESD) on technology readiness, taking the SEWG input into account. The instruments were found to have a range of TRL from 4 to 7. Lessons Learned are presented; however, due to the competition-sensitive nature of the assessments, the results for specific missions are not presented. The assessments were generally successful, and produced useful results for the agency. The SEWG team identified a number of potential improvements to the process. Particular focus was on ensuring traceability to guiding NASA documents, including the NASA Systems Engineering Handbook. The TRL Workbook has been substantially modified, and the revised workbook is described

Caracterización de la dehiscencia bilateral del conducto semicircular superior

In the superior canal dehiscence syndrome, patients can have sound- or pressure-induced vertigo and oscillopsia. They may also present conductive hearing loss or higher than normal bone conduction thresholds. Clinical manifestations are due to the effect of a third mobile window in the inner ear created by the dehiscence. Diagnosis is based on clinical manifestations, vertical and rotatory nystagmus induced by sound and pressure reflecting SSC stimulation, reduced threshold and increased amplitude of vestibular evoked myogenic potentials (VEMP) and temporal bone CT scan images showing the SSC dehiscence. Characteristic eye movements can be recorded with the scleral search coil technique

Vestibulo-Oculomotor Reflex Recording Using the Scleral Search Coil Technique. Review of Peripheral Vestibular Disorders

Our goal is to review vestibulo-oculomotor reflex (VOR) studies on several peripheral vestibular disorders (Ménière’s disease, vestibular neuritis, benign paroxysmal positional vertigo, superior canal dehiscence syndrome, and vestibular neuroma), using the scleral search coil (SSC) technique. Head movements are detected by vestibular receptors and the elicited VOR is responsible for compensatory 3 dimensional eye movements. Therefore, to study the VOR it is necessary to assess the direction and velocity of 3 dimensional head, and eye movements. This can be achieved using the SSC technique. Interaction between a scleral search coil and an alternating magnetic field generates an electrical signal that is proportional to eye position. Ideally, eye rotation axis is aligned with head rotation axis and VOR gain (eye velocity/head velocity) for horizontal and vertical head rotations is almost 1. The VOR gain, however, for torsional head rotations is smaller and about 0.

Vestibular Evoked Myogenic Potential Testing Payment Policy Review for Clinicians and Payers

Purpose of review A recent American Academy of Neurology Evidence-Based Practice Guideline on vestibular myogenic evoked potential (VEMP) testing has described superior canal dehiscence syndrome (SCDS) and evaluated the merits of VEMP in its diagnosis. SCDS is an uncommon but now well-recognized cause of dizziness and auditory symptoms. This article familiarizes health care providers with this syndrome and the utility and shortcomings of VEMP as a diagnostic test and also explores payment policies for VEMP. Recent findings In carefully selected patients with documented history compatible with the SCDS, both high-resolution temporal bone CT scan and VEMP are valuable aids for diagnosis. Payers might be unfamiliar with both this syndrome and VEMP testing. Summary It is important to raise awareness of VEMP and its possible indications and the rationale for coverage of VEMP testing. Payers may not be readily receptive to VEMP coverage if this test is used in an undifferentiated manner for all common vestibular and auditory symptoms

Diverse and Variable Community Structure of Picophytoplankton across the Laurentian Great Lakes

The Laurentian Great Lakes provide economic support to millions of people, drive biogeochemical cycling, and are an important natural laboratory for characterizing the fundamental components of aquatic ecosystems. Small phytoplankton are important contributors to the food web in much of the Laurentian Great Lakes. Here, for the first time, we reveal and quantify eight phenotypically distinct picophytoplankton populations across the Lakes using a multilaser flow cytometry approach, which distinguishes cells based on their pigment phenotype. The distributions and diversity of picophytoplankton flow populations varied across lakes and depths, with Lake Erie standing out with the highest diversity. By sequencing sorted cells, we identified several distinct lineages of Synechococcales spanning Subclusters 5.2 and 5.3. Distinct genotypic clusters mapped to phenotypically similar flow populations, suggesting that there may not be a clear one-to-one mapping between genotypes and phenotypes. This suggests genome-level differentiation between lakes but some degree of phenotypic convergence in pigment characteristics. Our results demonstrate that ecological selection for locally adapted populations may outpace homogenization by physical transport in this interconnected system. Given the reliance of the Lakes on in situ primary production as a source for organic carbon, this work sets the foundation to test how the community structure of small primary producers corresponds to biogeochemical and food web functions of the Great Lakes and other freshwater systems

Relative stability and significance of dawsonite and aluminum minerals in geologic carbon sequestration

[1] Computer simulations predict dawsonite, NaAlCO 3 (OH) 2 , will provide l ong -term mineral sequestration of anthropogenic CO 2 whereas dawsonite rarely occurs in nature or in laboratory experiments that emulate a carbon repository. Resolving this discrepancy is important to determining the significance of dawsonite mineralization to the long-term security of geologic carbon sequestration. This study is an equilibrium-based experimental and modeling evaluation of underlying causes for inconsistencies between predicted and observed dawsonite stability. Using established hydrothermal methods, 0.05 molal NaHCO 3 aqueous solution and synthetic dawsonite were reacted for 18.7 days (449.2 hours) at 50°C, 20 MPa. Temperature was increased to 75°C and the experiment continued for an additional 12.3 days (295.1 hours). Incongruent dissolution yielded a dawsonite-gibbsite-nordstrandite assemblage. Geochemical simulations using Geochemist's Workbench and the resident database thermo.com.V8.R6 + incorrectly predicted a dawsonite-diaspore assemblage and underestimated dissolved aluminum by roughly 100 times. Higher aqueous aluminum concentrations in the experiment suggest that dawsonite or diaspore is less stable than predicted. Simulations employing an alternate database, thermo.dat, correctly predict dawsonite and dawsonitegibbsite assemblages at 50 and 75°C, respectively, although dissolved aluminum concentrations are still two to three times lower than experimentally measured values. Correctly reproducing dawsonite solubility in standard geochemical simulations requires an as yet undeveloped internally consistent thermodynamic database among dawsonite, gibbsite, boehmite, diaspore, aqueous aluminum complexes and other Al-phases such as albite and kaolinite. These discrepancies question the ability of performance assessment models to correctly predict dawsonite mineralization in a sequestration site. Citation: Kaszuba, J. P., H. S. Viswanathan, and J. W. Carey (2011), Relative stability and significance of dawsonite and aluminum minerals in geologic carbon sequestration, Geophys. Res. Lett., 38, L08404

Hole Polaron Migration in Bulk Phases of TiO2 Using Hybrid Density Functional Theory

[Image: see text] Understanding charge-carrier transport in semiconductors is vital to the improvement of material performance for various applications in optoelectronics and photochemistry. Here, we use hybrid density functional theory to model small hole polaron transport in the anatase, brookite, and TiO(2)-B phases of titanium dioxide and determine the rates of site-to-site hopping as well as thermal ionization into the valance band and retrapping. We find that the hole polaron mobility increases in the order TiO(2)-B < anatase < brookite and there are distinct differences in the character of hole polaron migration in each phase. As well as having fundamental interest, these results have implications for applications of TiO(2) in photocatalysis and photoelectrochemistry, which we discuss