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Experimental ablation cooling

Description: Report presenting the results of an experimental investigation on the ablation of a number of promising materials for heating conditions comparable to those which maybe encountered by unmanned reentry satellite vehicles or heating conditions associated with reentry ballistic missiles. Results regarding exploratory tests, further Teflon tests, and graphite testing are provided.
Date: July 15, 1958
Creator: Bond, Aleck C.; Rashis, Bernard & Levin, L. Ross
Partner: UNT Libraries Government Documents Department

Synthesis and rheological properties of cation-exchanged Laponite suspensions

Description: In this paper we report our new approach to synthesize cation-exchanged Laponite suspensions. General observations of the prepared samples indicated that an aqueous suspension of 1 wt% Laponite retained its free flowing liquid phase characteristics even after aging for several weeks. When bivalent cationic metals (Cu, Co, Ni) were ablated into the suspension, the strong charge of the crystal face was reduced and, on standing, the suspension gelled becoming highly viscous. This sol-gel transition was induced by the formation of a space-filled structure due to both van derWaals and electrostatic bonds between the positively charged rims and negatively charged faces. Rheological properties of such prepared suspensions were measured using a Brookfield DV-H Pro Viscometer with a small sample adapter{SSA18/13RPY). The yield strengths of2.2 N/m2, 3.2 N/m2, and 1.7 N/m2 were measured for Ni-, Co-, and Cu-modified Laponite suspensions, respectively. These yield strengths are sufficiently high for suspending weighting materials such as barite which requires the gel strength of about 0.5 N/m2.
Date: January 1, 2009
Creator: Tran, X.P.; Howard, B. & Chyu, M.K.
Partner: UNT Libraries Government Documents Department

Time Resolved Shadowgraph Images of Silicon during Laser Ablation:Shockwaves and Particle Generation

Description: Time resolved shadowgraph images were recorded of shockwaves and particle ejection from silicon during laser ablation. Particle ejection and expansion were correlated to an internal shockwave resonating between the shockwave front and the target surface. The number of particles ablated increased with laser energy and was related to the crater volume.
Date: May 6, 2006
Creator: Liu, C.Y.; Mao, X.L.; Greif, R. & Russo, R.E.
Partner: UNT Libraries Government Documents Department

Laser Ablated Carbon Nanodots for Light Emission

Description: This article reports the synthesis of fluorescent carbon dots-like nanostructures obtained through the laser ablation of a carbon solid target in liquid environment is reported.
Date: September 22, 2016
Creator: Reyes, Delfino; Camacho, Marco; Camacho, Miguel; Mayorga, Miguel; Weathers, Duncan L.; Salamo, Greg et al.
Partner: UNT College of Arts and Sciences

Qualitative measurements of the effective heats of ablation of several materials in supersonic air jets at stagnation temperatures up to 11,000 F

Description: Report presenting testing on the effective heats of ablation of a number of materials using supersonic arc jets at stagnation temperatures ranging from 2000 degrees F to 11,000 degrees F. Materials examined included Teflon, nylon, Lucite, polystyrene, ammonium chloride, sodium carbonate, several phenolic resins, and melamine-fiber glass laminate.
Date: July 7, 1958
Creator: Rashis, Bernard; Witte, William G. & Hopko, Russell N.
Partner: UNT Libraries Government Documents Department

AnGa{sub 2}O{sub 4} Thin-Film Phosphors Grown by Pulsed Laser Ablation

Description: The growth and properties of undoped and Mn-doped ZnGa{sub 2}O{sub 4} thin-film phosphors on (100) MgO and glass substrates using pulsed laser ablation were investigated. Blue-white and green emission were observed for as-deposited undoped and Mn-doped films, respectively. Luminescent properties as well as crystallinity were considerably affected by processing conditions and film stoichiometry. Films with enhanced luminescent characteristics were obtained on single crystal substrates without post-annealing.
Date: April 5, 1999
Creator: Lee, Y. E.; Rouleau, C. M.; Park, C. & Norton, D. P.
Partner: UNT Libraries Government Documents Department

Momentum Transfer by Laser Ablation of Irregularly Shaped Space Debris

Description: Proposals for ground-based laser remediation of space debris rely on the creation of appropriately directed ablation-driven impulses to either divert the fragment or drive it into an orbit with a perigee allowing atmospheric capture. For a spherical fragment, the ablation impulse is a function of the orbital parameters and the laser engagement angle. If, however, the target is irregularly shaped and arbitrarily oriented, new impulse effects come into play. Here we present an analysis of some of these effects.
Date: February 4, 2010
Creator: Liedahl, D A; Libby, S B & Rubenchik, A
Partner: UNT Libraries Government Documents Department

Design Calculations For NIF Convergent Ablator Experiments

Description: The NIF convergent ablation tuning effort is underway. In the early experiments, we have discovered that the design code simulations over-predict the capsule implosion velocity and shock flash rhor, but under-predict the hohlraum x-ray flux measurements. The apparent inconsistency between the x-ray flux and radiography data implies that there are important unexplained aspects of the hohlraum and/or capsule behavior.
Date: October 25, 2011
Creator: Olson, R E; Hicks, D G; Meezan, N B; Callahan, D A; Landen, O L; Jones, O S et al.
Partner: UNT Libraries Government Documents Department

Thermo-Chemical Ablation During Reentrant and High Altitude Skipping Flight

Description: Thermo-chemical ablation during reentrant and high altitude skipping flights is treated using a variety of techniques. The solid material response is computed using heat-balance integrals, finite differences, and finite elements. The surface mass loss is computed using curve fits to the standard transport coefficient approach and by a surface kinetic model. Agreement between the approaches, when using the curve fits, is good. All approaches concur that for the skipping trajectory studied there is very little mass loss and surface temperatures remain in a range where the thermal protection system can be reused.
Date: March 28, 2000
Creator: Havstad, M. & Carter, P.
Partner: UNT Libraries Government Documents Department

A Theoretical Study of Stagnation-Point Ablation

Description: "A simplified analysis is made of the shielding mechanism which reduces the stagnation-point heat trasnfer when ablation takes place at the surface. The ablation process considered is that in which the material changes directly from the solid to the gaseous state. The automatic shielding mechanism is discussed and the significant thermal properties of a good ablation material are given. The results of the analysis are given in terms of dimensionless parameters" (p. 1).
Date: September 1958
Creator: Roberts, Leonard
Partner: UNT Libraries Government Documents Department

Synthesis of Mg(OH)2, MgO, and Mg nanoparticles using laser ablation of magnesium in water and solvents

Description: laser ablation of magnesium in deionized water (OW), solutions of OW and sodium dodecyl sulfate (50S) with different concentrations, acetone and 2-propanol has been conducted, The results showed that ablation in acetone and 2-propanol yielded MgO and Mg nanocrystallites as isolated particles and agglomerated chains probably intermixed with organic residues resulting from the alterationj decomposition of the solvents under the high-energy conditions. Brucite-like Mg(OH)2 particles were mainly produced by laser ablation of Mg in either OW or OW~SOS solutions. Ablation in OW yielded particles of fiber-like shapes having a diameter of about 5-lOnm and length as long as 150nm. Materials produced in DW-SOS solutions were composed of various size and shape particles, Some had rough surfaces with irregular shapes. Small particles were about 20-30nm and larger particles were about 120 nm. Particles with rod-like, triangular, and plate-like shapes were also observed.
Date: January 1, 2008
Creator: Tran, P.X.; Howard, B.H.; Martello, D.V.; Soong, Y. & Chyu, M.K.
Partner: UNT Libraries Government Documents Department

Expansion of radiative cooling of the laser induced plasma

Description: To study the expansion and cooling process of the laser induced plasma generated by nanosecond pulsed laser ablation, experiments have been conducted which measure the position of the external shockwaves and the temperature of the vapor plumes. The positions of external shockwaves were determined by a femtosecond laser time-resolved imaging system. Vapor plume temperature was determined from spectroscopic measurements of the plasma emission lines. A model which considers the mass, momentum, and energy conservation of the region affected by the laser energy was developed. It shows good agreement to the experimental data.
Date: May 5, 2006
Creator: Wen, Sy-Bor; Mao, Xianglei; Liu, Chunyi; Greif, Ralph & Russo,Richard
Partner: UNT Libraries Government Documents Department

IFE thick liquid wall chamber dynamics: Governing mechanisms andmodeling and experimental capabilities

Description: For thick liquid wall concepts, it is important to understand the different mechanisms affecting the chamber dynamics and the state of the chamber prior to each shot a compared with requirements from the driver and target. These include ablation mechanisms, vapor transport and control, possible aerosol formation, as well as protective jet behavior. This paper was motivated by a town meeting on this subject which helped identify the major issues, assess the latest results, review the capabilities of existing modeling and experimental facilities with respect to addressing remaining issues, and helping guide future analysis and R&D efforts; the paper covers these exact points.
Date: January 24, 2005
Creator: Raffray, A.R.; Meier, W.; Abdel-Khalik, S.; Bonazza, R.; Calderoni, P.; Debonnel, C.S. et al.
Partner: UNT Libraries Government Documents Department

Low-Energy Electron Irradiation of Preheated and Gas-Exposed Single-Wall Carbon Nanotubes

Description: We investigate the conditions under which electron irradiation of single-walled carbon nanotube (SWCNT) bundles with 2 keV electrons produces an increase in the Raman D peak. We find that an increase in the D peak does not occur when SWCNTs are preheated in situ at 600 C for 1 h in ultrahigh vacuum (UHV) before irradiation is performed. Exposing SWCNTs to air or other gases after preheating in UHV and before irradiation results in an increase in the D peak. Small diameter SWCNTs that are not preheated or preheated and exposed to air show a significant increase in the D and G bands after irradiation. X-ray photoelectron spectroscopy shows no chemical shifts in the C1s peak of SWCNTs that have been irradiated versus SWCNTs that have not been irradiated, suggesting that the increase in the D peak is not due to chemisorption of adsorbates on the nanotubes.
Date: December 2016
Creator: Ecton, Philip
Partner: UNT Libraries

Real time assessment of RF cardiac tissue ablation with optical spectroscopy

Description: An optical spectroscopy approach is demonstrated allowing for critical parameters during RF ablation of cardiac tissue to be evaluated in real time. The method is based on incorporating in a typical ablation catheter transmitting and receiving fibers that terminate at the tip of the catheter. By analyzing the spectral characteristics of the NIR diffusely reflected light, information is obtained on such parameters as, catheter-tissue proximity, lesion formation, depth of penetration of the lesion, formation of char during the ablation, formation of coagulum around the ablation site, differentiation of ablated from healthy tissue, and recognition of micro-bubble formation in the tissue.
Date: March 20, 2008
Creator: Demos, S G & Sharareh, S
Partner: UNT Libraries Government Documents Department

Experimental Studies of ICF Indirect-Drive Be and High Density C Candidate Ablators

Description: To validate our modeling of the macroscopic and microscopic hydrodynamic and equation of state response of these candidate ablators to NIC-relevant x-ray drive, a multi-lab experimental program has been verifying the behavior of these new ablators. First, the pressures for onset and termination of melt for both Be and HDC under single or double shock drive has been measured at the Z and Omega facilities. Second, the level and effect of hard x-ray preheat has been quantified in scaled experiments at the Omega facility. Third, a long planar x-ray drive has been developed to check 2D and 3D perturbation growth at the ablation front upon acceleration. The concept has been extended to study growth at and near the ablator-ice interface upon deceleration. In addition, experimental designs for validating the expected low level of perturbation seeding due to possible residual microstructure after melt during first and second shock transit in Be and HDC have been completed. Results so far suggest both Be and HDC can remain ablator choices and have guided pulse shaping designs.
Date: September 5, 2007
Creator: Landen, O L; Bradley, D K; Braun, D G; A.Smalyuk, V; Hicks, D G; Celliers, P M et al.
Partner: UNT Libraries Government Documents Department

Dystroglycan loss disrupts polarity and beta-casein induction inmammary epithelial cells by perturbing laminin anchoring

Description: Precise contact between epithelial cells and their underlying basement membrane is critical to the maintenance of tissue architecture and function. To understand the role that the laminin receptor dystroglycan (DG) plays in these processes, we assayed cell responses to laminin-111 following conditional ablation of DG expression in cultured mammary epithelial cells (MECs). Strikingly, DG loss disrupted laminin-111-induced polarity and {beta}-casein production, and abolished laminin assembly at the step of laminin binding to the cell surface. DG re-expression restored these deficiencies. Investigations of mechanism revealed that DG cytoplasmic sequences were not necessary for laminin assembly and signaling, and only when the entire mucin domain of extracellular DG was deleted did laminin assembly not occur. These results demonstrate that DG is essential as a laminin-111 co-receptor in MECs that functions by mediating laminin anchoring to the cell surface, a process that allows laminin polymerization, tissue polarity, and {beta}-casein induction. The observed loss of laminin-111 assembly and signaling in DG-/-MECs provides insights into the signaling changes occurring in breast carcinomas and other cancers, where DG's laminin-binding function is frequently defective.
Date: February 17, 2006
Creator: Weir, M. Lynn; Oppizzi, Maria Luisa; Henry, Michael D.; Onishi,Akiko; Campbell, Kevin P.; Bissell, Mina J. et al.
Partner: UNT Libraries Government Documents Department

BOLIDE PHYSICAL THEORY WITH APPLICATION TO PN AND EN FIREBALLS.

Description: Using data on 22 'precise bolides' with up to 882 individual points on their trajectories and using data on 29 'bright bolides' and on 10 artificial meteors, we tried to derive dependence of ablation and shape-density coefficients, and of luminous efficiency on various time dependent parameters. The only significant dependence we found was that on v{sub {infinity}} - v (on difference of initial and instantaneous velocities). We present the results as Eq. 3, 4 and 8, with coefficients a{sub 1}, a{sub 2}, a{sub 3}, a{sub 4}, b{sub 1}, b{sub 2}, a{sub 3}, c{sub 1}, c{sub 2}, computed for different bolide types. Also average values of ablation, and shape-density coefficients as well as average luminous efficiencies for individual bolide types are given.
Date: January 1, 2001
Creator: ReVelle, D. O. (Douglas O.)
Partner: UNT Libraries Government Documents Department

Rapid Fabrication of Disposable Micromixing Arrays Using Xurography and Laser Ablation

Description: This article presents a novel split-and-recombine (SAR) array design adapted for interfacing standardized dispensing (handheld micropipette) and sampling (microplate reader) equipment.
Date: February 28, 2017
Creator: Martínez-López, J. Israel; Betancourt, H. A.; García-López, Erika; Rodríguez, Ciro A. & Siller, Héctor R.
Partner: UNT College of Engineering

Investigating Molecular Structures: Rapidly Examining Molecular Fingerprints Through Fast Passage Broadband Fourier Transform Microwave Spectroscopy

Description: Microwave spectroscopy is a gas phase technique typically geared toward measuring the rotational transitions of Molecules. The information contained in this type of spectroscopy pertains to a molecules structure, both geometric and electronic, which give insight into a molecule's chemistry. Typically this type of spectroscopy is high resolution, but narrowband ≤1 MHz in frequency. This is achieved by tuning a cavity, exciting a molecule with electromagnetic radiation in the microwave region, turning the electromagnetic radiation o, and measuring a signal from the molecular relaxation in the form of a free induction decay (FID). The FID is then Fourier transformed to give a frequency of the transition. "Fast passage" is defined as a sweeping of frequencies through a transition at a time much shorter (≤10 s) than the molecular relaxation (≈100 s). Recent advancements in technology have allowed for the creation of these fast frequency sweeps, known as "chirps", which allow for broadband capabilities. This work presents the design, construction, and implementation of one such novel, high-resolution microwave spectrometer with broadband capabilities. The manuscript also provides the theory, technique, and motivations behind building of such an instrument. In this manuscript it is demonstrated that, although a gas phase technique, solids, liquids, and transient species may be studied with the spectrometer with high sensitivity, making it a viable option for many molecules wanting to be rotationally studied. The spectrometer has a relative correct intensity feature that, when coupled with theory, may ease the difficulty in transition assignment and facilitate dynamic chemical studies of the experiment. Molecules studied on this spectrometer have, in turn, been analyzed and assigned using common rotational spectroscopic analysis. Detailed theory on the analysis of these molecules has been provided. Structural parameters such as rotational constants and centrifugal distortion constants have been determined and reported for most molecules in ...
Date: May 2011
Creator: Grubbs, Garry Smith, II
Partner: UNT Libraries