Highlights of experience with a flexible walled test section in the NASA Langley 0.3-meter transonic cryogenic tunnel

The unique combination of adaptive wall technology with a contonuous flow cryogenic wind tunnel is described. This powerful combination allows wind tunnel users to carry out 2-D tests at flight Reynolds numbers with wall interference essentially eliminated. Validation testing was conducted to support this claim using well tested symmetrical and cambered airfoils at transonic speeds and high Reynolds numbers. The test section hardware has four solid walls, with the floor and ceiling flexible. The method of adapting/shaping the floor and ceiling to eliminate top and bottom wall interference at its source is outlined. Data comparisons for different size models tested and others in several sophisticated 2-D wind tunnels are made. In addition, the effects of Reynolds number, testing at high lift with associated large flexible wall movements, the uniqueness of the adapted wall shapes, and the effects of sidewall boundary layer control are examined. The 0.3-m TCT is now the most advanced 2-D research facility anywhere

Increased Natural Ventilation Flow Rates through Ventilation Shafts

Buoyancy-driven natural ventilation in ventilation shafts is investigated with a small scale physical experiment within a duct and CFD simulations of an office building. For a fixed exhaust opening, smaller shafts lead to higher flow rates in upper floors of a multi-storey building with a shared ventilation shaft. These higher flow rates are caused by increased vertical momentum within the smaller shafts that induce flow through upper floors, an effect referred to as the “ejector effect”. In the small scale duct, a 0.5 m by 0.5 m shaft leads to a slight reverse flow of 0.0029 m[superscript 3]/s through the upper floor. Holding all other parameters constant and reducing the shaft to 0.25 m by 0.5 m leads to a positive flow rate of 0.012 m[superscript 3]/s through the upper floor. In the CFD simulations of a three storey office building, this same pattern is observed. A 3 m by 2 m shaft leads to a flow rate of 0.0168 m[superscript 3]/s through the third floor, while the reduced shaft of 2 m by 2 m leads to a flow rate of 0.766 m[superscript 3]/s through the same floor. This increased airflow rate from the ejector effect can allow natural ventilation to be used in buildings where it may otherwise have been deemed inappropriate. Most airflow network models neglect air momentum and fail to account for the ejector effect. To improve these models, an empirical model is incorporated into the airflow network model CoolVent in a manner easily transferable to most airflow network models.Hulic Co., Ltd

Swift Follow-Up of Reported Radio Pulsars at Fermi 4FGL Unassociated Sources

Following the discovery of radio pulsars at the position of Fermi-LAT unassociated sources by the TRAPUM group, we conduct Swift-XRT observations of six of those 4FGL sources to determine if any pulsar-like X-ray sources are present and to confirm the reported detection of an X-ray counterpart via eROSITA at 4FGL J1803.1-6708. At two of the six targets, we detect no X-ray sources at the TRAPUM radio position, placing an upper limit on the 0.3-10.0 keV flux. At 4FGL J1803.1-6708 we find an X-ray source at the TRAPUM and eROSITA position. At 4FGL J1858.3-5424 we find a new X-ray counterpart at the TRAPUM position with S/N=4.17, but also detect a distinct and separate X-ray source. At 4FGL J1823.8-3544 and 4FGL J1906.4-1757 we detect no X-ray flux at the TRAPUM positions, but we do detect separate X-ray sources elsewhere in the Fermi error ellipse. At these last two targets, our newly detected Swift sources are possible alternatives to the radio pulsar associations proposed by TRAPUM. Our findings confirm several of the discoveries reported by the TRAPUM group but suggest that further observations and investigations are necessary to confirm the low-energy counterpart of several unassociated sources.Comment: 10 pages main text, 6 figures, 2 table

Modeling buoyancy-driven airflow in ventilation shafts

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 185-191).Naturally ventilated buildings can significantly reduce the required energy for cooling and ventilating buildings by drawing in outdoor air using non-mechanical forces. Buoyancy-driven systems are common in naturally ventilated commercial buildings because of their reliable performance in multi-story buildings. Such systems rely on atria or ventilation shafts to provide a pathway for air to rise through the building. Although numerous modeling techniques are used to simulate naturally ventilated buildings, airflow network tools (AFNs) are most commonly used for annual simulations. These AFNs, however, assume minimal momentum within each zone, which is a reasonable approximation in large atria, but is inappropriate in smaller ventilation shafts. This thesis improves AFNs by accounting for momentum effects within ventilation shafts. These improvements are validated by Computation Fluid Dynamics (CFD) models that haven been validated by small scale and full scale experiments. The full scale experiment provides a detailed data set of an actual atrium that can be used in further validations and demonstrates the first use of a neutrally buoyant bubble generator for flow visualization and particle image velocimetry within a buoyancy driven naturally ventilated space. Small scale experiments and CFD simulations indicate an "ejector effect" within the shaft that uses momentum from lower floors to induce flow through upper floors. In some configurations, upper floors achieve higher flow rates than lower floors. Existing AFNs do not predict this "ejector effect" and are shown to significantly under predict flow rates through ventilation shafts by 30-40%. Momentum effects are accounted for in AFNs using empirical relationships for discharge coefficients. This approach maintains the current structure of AFNs while enhancing their ability to simulate airflow through ventilation shafts. These improvements are shown to account for the "ejector effect" and predict airflow rates that agree with CFD simulations to within 1-25%.by Stephen Douglas Ray.Ph.D

Energy saving potential of various roof technologies

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 159-168).Unconventional roof technologies such as cool roofs and green roofs have been shown to reduce building heating and cooling load. Although previous studies suggest potential for energy savings through such technologies, many factors affect potential savings. To further investigate these factors, a tool has been developed to allow architects and designers the ability to quickly assess the energy saving potential of different roof technologies and roof constructions for various sites around the world. A first principles heat transfer model is developed for each of the roof technologies, with particular care for green roof heat and mass transfer. Two sets of experimental data from Japan and Florida validate the models by predicting roof surface temperature. The predicted roof surface temperatures in Japan agree with measured values within 10 and 26% of peak roof temperature fluctuations for the cool and green roof respectively, while the same models in Florida agree with measured values there within 7.2 and 14% for the cool and green roof respectively. The models have been integrated into a free online building simulation tool, MIT's Design Advisor, available at http : //designadvisor.mit.edu. Numerous simulations are run, showing that potential energy savings are found to strongly vary with many parameters, particularly roof type, climate, and amount of insulation. For example, a one-story building in Boston with an uninsulated modified-bitumen roof can save 82% in cooling and heating energy by adding 3 m 2K/W of roof insulation, whereas only 34% if an uninsulated green roof is installed instead. However, in Lisbon, the same addition of roof insulation to the same building results in 54% savings, while the installation of an uninsulated green roof results in a 67% reduction. Such findings and their implications are discussed for other locations and design parameters.by Stephen Douglas Ray.S.M

Development of laboratory class experiment to characterize magneto-rheological fluid

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.Includes bibliographical references (p. 39).An experimental apparatus has been developed that characterizes magneto-rheological (MR) fluid for an MIT Mechanical Engineering laboratory class by charting the fluid's yield stress versus magnetic field strength. The apparatus consists of a cantilevered beam that is damped using MR fluid, through which a magnetic field is varied. Unique functional requirements for a class experiment as well as experimental design rationale are also discussed. Lord's MRF-336AG MR fluid is characterized at low magnetic field strengths and compared to the company provided data. Experimental data suggest the magnetic field strength affects the fluid yield stress more greatly than the company data, though both data show similar general trends. This discrepancy likely comes from approximations for damper velocity made in the analysis. Both a Bingham plastic and Newtonian model are used to describe the fluid and based on the similarity of the results from both models at low field strengths, it is concluded that MR fluid can be modeled as a Newtonian fluid for field strengths between 0 and 4 kAmp/m.by Stephen D. Ray.S.B

GSK-3 inhibitors induce chromosome instability

<p>Abstract</p> <p>Background</p> <p>Several mechanisms operate during mitosis to ensure accurate chromosome segregation. However, during tumour evolution these mechanisms go awry resulting in chromosome instability. While several lines of evidence suggest that mutations in <it>adenomatous polyposis coli </it>(<it>APC</it>) may promote chromosome instability, at least in colon cancer, the underlying mechanisms remain unclear. Here, we turn our attention to GSK-3 – a protein kinase, which in concert with APC, targets β-catenin for proteolysis – and ask whether GSK-3 is required for accurate chromosome segregation.</p> <p>Results</p> <p>To probe the role of GSK-3 in mitosis, we inhibited GSK-3 kinase activity in cells using a panel of small molecule inhibitors, including SB-415286, AR-A014418, 1-Azakenpaullone and CHIR99021. Analysis of synchronised HeLa cells shows that GSK-3 inhibitors do not prevent G1/S progression or cell division. They do, however, significantly delay mitotic exit, largely because inhibitor-treated cells have difficulty aligning all their chromosomes. Although bipolar spindles form and the majority of chromosomes biorient, one or more chromosomes often remain mono-oriented near the spindle poles. Despite a prolonged mitotic delay, anaphase frequently initiates without the last chromosome aligning, resulting in chromosome non-disjunction. To rule out the possibility of "off-target" effects, we also used RNA interference to selectively repress GSK-3β. Cells deficient for GSK-3β exhibit a similar chromosome alignment defect, with chromosomes clustered near the spindle poles. GSK-3β repression also results in cells accumulating micronuclei, a hallmark of chromosome missegregation.</p> <p>Conclusion</p> <p>Thus, not only do our observations indicate a role for GSK-3 in accurate chromosome segregation, but they also raise the possibility that, if used as therapeutic agents, GSK-3 inhibitors may induce unwanted side effects by inducing chromosome instability.</p

SOLUTION STRUCTURE OF THE TOXIC E. COLI PEPTIDE, TISB

poster abstractAntibiotics act by interfering in bacterial metabolism. Thus, antibiotics are only effective against metabolically active bacteria while dormant cells are highly tolerant to antibiotics. Such persistent bacterial cells may be the main culprits in chronic infectious diseases resistance to antimicrobial thera-py. In Escherichia coli, expression of a toxic peptide, TisB, sends cells into dormancy by decreasing the proton motive force thus decreasing ATP levels. TisB is a 29 amino acid residue peptide with 70% hydrophobic residues. It has a predicted alpha helical transmembrane domain spanning residues 6 - 28. In membrane channel studies, ion transport is observed with TisB and with some TisB mutants. As a preliminary to combining multi-dimensional NMR spectroscopy with circular dichroism to determine the structure of the TisB membrane ion transport complex in lipid micelles, NMR spectroscopy is used to determine the structure of TisB in ethanol

The mPower Study, Parkinson Disease Mobile Data Collected Using Researchkit

Current measures of health and disease are often insensitive, episodic, and subjective. Further, these measures generally are not designed to provide meaningful feedback to individuals. The impact of high-resolution activity data collected from mobile phones is only beginning to be explored. Here we present data from mPower, a clinical observational study about Parkinson disease conducted purely through an iPhone app interface. The study interrogated aspects of this movement disorder through surveys and frequent sensor-based recordings from participants with and without Parkinson disease. Benefitting from large enrollment and repeated measurements on many individuals, these data may help establish baseline variability of real-world activity measurement collected via mobile phones, and ultimately may lead to quantification of the ebbs-and-flows of Parkinson symptoms. App source code for these data collection modules are available through an open source license for use in studies of other conditions. We hope that releasing data contributed by engaged research participants will seed a new community of analysts working collaboratively on understanding mobile health data to advance human health

Overview of Hybrid Ventilation Control System and Full Scale Monitoring

Mix-mode or hybrid ventilation systems have been previously shown to reduce cooling and ventilation energy consumption. This paper presents a case study of a new ten story 83,700 ft² (7,780 m²) office building in downtown Tokyo with a hybrid ventilation system that uses only 1.7% of the building footprint for ventilation shafts. The control system design is presented as an example of balancing the comfort expectations of multiple tenants in a mix-mode system. On-site measurements are presented from a three week commissioning project to show: modest temperature differences within the occupied zone with a maximum difference of 1.5 °F (0.83 °C), large differences of up to 6.1 °F (3.4 °C) between the measured outdoor temperature in the control system and the actual inlet temperature for the natural ventilation system, the importance of smooth integration of various design teams, and the use of low-power fans, 1.2-0.60 hp (900-450 W), that leverage the low pressure drop through the building when natural driving forces are insufficient for pure natural ventilation. Practical lessons learned from the design and commissioning of the building are also shared.Hulic Co., Ltd