Experimental Investigation of Transverse Supersonic Gaseous Injection Enhancement into Supersonic Flow

In pursuit of more efficient and effective fuel-air mixing for a SCRAMJET combustor, this study was conducted to investigate relative near field enhancements of penetration and mixing of a discrete low-angled (25°) injected air jet into a supersonic (M=2.9) cross flow. The enhancements were achieved by injecting the transverse air jet parallel to the compression face of eight different ramp geometries. The jet-ramp interactions created collinear shock structures, baroclinic torque vorticity enhancement, ramp spillage enhanced vorticity, magnus effect penetration enhancement, and increased total pressure loss. Shadowgraph photography was used to identify the shock structures and interactions in the flow field. Measurements of mean flow properties were used to establish the jet plume size, jet plume penetration and to quantify the total pressure loss created by the ramps. Rayleigh-Mie scattering images were used for both qualitative flow field assessments and quantitative analysis of the plume trajectory and mixing rate. Results indicate that up to a 20% increase in penetration height and plume expansion can be achieved by injection over a ramp compared to simple transverse injection. This increase in penetration and mixing incurs up to a 15% loss in total pressure. The most critical geometric aspects that affect the flow are the ramp compression face shape and frontal aspect, and the location and strength of ramp generated expansion

Molecular free volume and viscosity changes in non-Newtonian fluids probed with molecular rotors

Abstract only availableAn empirical relationship between molecular free volume and viscosity has been established (Doolittle AK, J Appl. Phys. 1952; 23: 236-9). Non-Newtonian fluids hold much importance to scientific study because of their ubiquity in nature - from gelatins to starches to blood. The purpose of this study was to examine the relationship between molecular free volume and viscosity in non-Newtonian fluids under shear-thinning conditions. Molecular rotors are fluorescent probes for free volume. After photoexcitation, these molecules can decay from their singlet state either through radiation (fluorescence) or torsional relaxation (intramolecular rotation). In environments with low free volume, intramolecular rotation is hindered, and the radiative deexcitation pathway becomes dominant. This behavior is accompanied by a measurable increase in fluorescence intensity. Molecular rotors have been used successfully as viscosity probes in various fluids and polymers. Two molecular rotors, CCVJ (9-(2-carboxy-2-cyano)-vinyl-julolidine) and CCVJ-TEG (CCVJ-triethyleneglycol ester), were dissolved at 10µM in an aqueous solution of KelcoGelF (gellan gum) and subjected to shear forces both in a tube shear apparatus for fluorescence measurements and in a Haake VT-550 rheometer to determine the shear-thinning behavior. The gellan solution exhibited power-law behavior with an exponent n=0.48. In spite of this strong shear-thinning behavior, no change in rotor emission intensity was observed. Additionally, a novel behavior of some molecular rotors, a sensitivity towards fluid flow (Haidekker MA et al, Sensor Lett. 2005; 3: 42-8), was exploited to observe shear-thinning behavior by probing flow velocity in a tube. Under application of sufficiently high shear rates to cause shear thinning, molecular rotors revealed no change in free volume as observed with fluorescence intensity. This preliminary study suggests that molecular free volume and shear thinning are independent properties. Further studies will be needed to corroborate that the free volume of a fluid is not related to its viscosity in shear-thinning environments.NSF-REU Program in Biosystems Modeling and Analysi

Examination of the robustness of viscosity sensitive molecular rotors against chemical modification

Abstract only availableMolecular rotors, a special class of compounds which form twisted intramolecular charge transfer complexes (TICT), have dual deexcitation processes - intramolecular rotation and fluorescence emission. Molecular rotors exhibit a quantum yield that is sensitive to changes in solution viscosity; this property makes molecular rotors highly suitable for optical measurements of viscosity. The goal of this study was to test the idea that increasing the chain length of the molecular rotor increases its viscosity sensitivity. Molecular rotors of varying chain length were selected for experimentation; DCVJ, a thoroughly studied molecular rotor, was chosen as the control. Mixtures of differing ratios of ethylene glycol and glycerol were created to vary viscosity. Fluorescence emission intensity data for the six molecular rotors was measured with a Jobin Yvon Fluoromax-3 spectrofluorometer. Logarithmic graphs of fluorescence intensity versus viscosity were created and displayed a linear relationship with regression values exceeding 0.99. However, the slopes for the various molecular rotors were not significantly different. The results demonstrate that increasing the molecular rotor's chain length does not significantly increase viscosity sensitivity, indicating that additional elements can be attached to the molecular rotor without changing its functionality.NSF-REU Biosystems Modelin

Evolutionary history of the ADRB2 gene in humans

No abstract available

Dextran preserves native corneal structure during decellularization

Corneal decellularization has become an increasingly popular technique for generating scaffolds for corneal regeneration. Most decellularization procedures result in tissue swelling, thus limiting their application. Here, the use of a polysaccharide, dextran, to reduce swelling and conserve the native corneal structure during decellularization was investigated. Corneas were treated with 1% Triton X-100, 0.5% sodium dodecyl sulfate, and nucleases under constant rotation followed by extensive washing. To reduce swelling, decellularization solutions were supplemented with 5% dextran either throughout the whole decellularization process or during the washing cycles only. Quantitative analysis of DNA content showed a 96% reduction after decellularization regardless of the addition of dextran. Dextran resulted in a significant reduction in swelling from 3.85 ± 0.43 nm without to 1.94 ± 0.29-2.01 ± 0.37 nm (p 0.05. Dextran can counteract the detrimental effects of decellularizing agents on the biomechanical properties of the tissue resulting in similar compressive moduli (mean before decellularization: 5.40 ± 1.18 kPa; mean after decellularization with dextran: 5.64 ± 1.34 kPa, p > 0.05). Cells remained viable in the presence of decellularized scaffolds. The findings of this study indicate that dextran not only prevents significant corneal swelling during decellularization but also enhances the maintenance of the native corneal ultrastructure

Characterizing the role of dextran in the decellularization of porcine corneas [Abstract]

Characterizing the role of dextran in the decellularization of porcine corneas [Abstract