Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Using”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,459 records · Page 81
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Tracking Tumor Colonization in Xenograft Mouse Models Using Accelerator Mass Spectrometry [Tracking Tumor Colonization in vivo Using Accelerator Mass Spectrometry]

Here we propose an Accelerator Mass Spectrometry (AMS)-based high precision method for quantifying the number of cancer cells that initiate metastatic tumors, in xenograft mice. Quantification of 14 C per cell prior to injection into animals, and quantification of 14 C in whole organs allows us to extrapolate the number of cancer cells available to initiate metastatic tumors. The 14 C labeling was optimized such that 1 cancer cell was detected among 1 million normal cells. We show that ~1–5% of human cancer cells injected into immunodeficient mice form subcutaneous tumors, and even fewer cells initiate metastatic tumors. Comparisons of metastatic site colonization between a highly metastatic (PC3) and a non-metastatic (LnCap) cell line showed that PC3 cells colonize target tissues in greater quantities at 2 weeks post-delivery, and by 12 weeks post-delivery no 14 C was detected in LnCap xenografts, suggesting that all metastatic cells were cleared. The 14 C-signal correlated with the presence and the severity of metastatic tumors. AMS measurements of 14 C-labeled cells provides a highly-sensitive, quantitative assay to experimentally evaluate metastasis and colonization of target tissues in xenograft mouse models. This method can potentially be used to evaluate tumor aggressiveness and assist in making informed decisions regarding treatment.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Solid matrix transformation and tracer addition using molten ammonium bifluoride salt as a sample preparation method for laser ablation inductively coupled plasma mass spectrometry

Solid sampling and analysis methods, such as laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), are challenged by matrix effects and calibration difficulties. Matrix-matched standards for external calibration are seldom available and it is difficult to distribute spikes evenly into a solid matrix as internal standards. While isotopic ratios of the same element can be measured to high precision, matrix-dependent effects in the sampling and analysis process frustrate accurate quantification and elemental ratio determinations. Here we introduce a potentially general solid matrix transformation approach entailing chemical reactions in molten ammonium bifluoride (ABF) salt that enables the introduction of spikes as tracers or internal standards. Proof of principle experiments show that the decomposition of uranium ore in sealed PFA fluoropolymer vials at 230 °C yields, after cooling, new solids suitable for direct solid sampling by LA. When spikes are included in the molten salt reaction, subsequent LA-ICP-MS sampling at several spots indicate that the spikes are evenly distributed, and that U-235 tracer dramatically improves reproducibility in U-238 analysis. Precisions improved from 17% relative standard deviation for U-238 signals to 0.1% for the ratio of sample U-238 to spiked U-235, a factor of over two orders of magnitude. These results introduce the concept of solid matrix transformation (SMT) using ABF, and provide proof of principle for a new method of incorporating internal standards into a solid for LA-ICP-MS. This new approach, SMT-LA-ICP-MS, provides opportunities to improve calibration and quantification in solids based analysis. Finally, looking forward, tracer addition to transformed solids opens up LA-based methods to analytical methodologies such as standard addition, isotope dilution, preparation of matrix-matched solid standards, external calibration, and monitoring instrument drift against external calibration standard

47 OTHER INSTRUMENTATION↗
DOE OSTI2017

A structural examination and collision cross section database for over 500 metabolites and xenobiotics using drift tube ion mobility spectrometry

The confident identification of metabolites and xenobiotics in biological and environmental studies is an analytical challenge due to their immense dynamic range, vast chemical space and structural diversity. Ion mobility spectrometry (IMS) is widely used for small molecule analyses since it can separate isomeric species and be easily coupled with front end separations and mass spectrometry for multidimensional characterizations. However, to date IMS metabolomic and exposomic studies have been limited by an inadequate number of accurate collision cross section (CCS) values for small molecules, causing features to be detected but not confidently identified. In this work, we utilized drift tube IMS (DTIMS) to directly measure CCS values for over 450 small molecules including primary metabolites, secondary metabolites and xenobiotics. Since DTIMS measurements do not need calibrates, they avoid calibration errors which can cause CCS accuracy problems and difficulties identifying structurally similar molecules. Furthermore, all measurements were performed in triplicate in both positive and negative polarities with nitrogen gas and seven different electric fields, so that relative standard deviations (RSD) could be assessed for each molecule and structural differences studied. The primary metabolites selected for the database are from key metabolism pathways such as glycolysis, the pentose phosphate pathway, and the tricarboxylic acid (TCA) cycle, while the secondary metabolites consist of classes such as terpenes and flavonoids, and the xenobiotics represent a range of molecules from antibiotics to polycyclic aromatic hydrocarbons. Different CCS trends were observed for several of the diverse small molecule classes, allowing insight in their separations and a possible why of classifying unknowns. This CCS database and structural information are freely available for download at http://panomics.pnnl.gov/metabolites/ with new molecules being added monthly.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

A new non-diffusional gas bubble production route in used nuclear fuel: Implications for fission gas release, cladding corrosion, and next generation fuel design

The relationship between noble metal phase particles and fission gas bubble production in used nuclear fuel is described. The majority of Te atoms within noble metal phase undergo radioactive decay to form stable Xe within a few hours after particle formation. This results in the production of clusters of Xe atoms contained within the solid metal matrix exhibiting an equivalent gas bubble pressure approaching 1 GPa. These high pressure bubbles are stabilized by the UO2 within the bulk of the fuel. However, when these bubbles form near the fuel / cladding interface, in combination with local and temporal damage caused by fission recoil, they are capable of overcoming the fracture strength of the UO2 and rupturing catastrophically. The force of the resulting bubble rupture is sufficient to eject noble metal phase particles several microns into the cladding. This proposed mechanism explains the observance of noble metal phase in cladding and is consistent with a host of morphological features found near the fuel / cladding interface.

Schwantes, Jon M.↗
DOE OSTI2011

Nanostructured Electrodes For Organic Bulk Heterojunction Solar Cells: Model Study Using Carbon Nanotube Dispersed Polythiophene-fullerene Blend Devices

We test the feasibility of using nanostructured electrodes in organic bulk heterojunction solar cells to improve their photovoltaic performance by enhancing their charge collection efficiency and thereby increasing the optimal active blend layer thickness. As a model system, small concentrations of single wall carbon nanotubes are added to blends of poly(3-hexylthiophene): [6,6]-phenyl-C{sub 61}-butyric acid methyl ester in order to create networks of efficient hole conduction pathways in the device active layer without affecting the light absorption. The nanotube addition leads to a 22% increase in the optimal blend layer thickness from 90 nm to 110 nm, enhancing the short circuit current density and photovoltaic device efficiency by as much as {approx}10%. The associated incident-photon-to-current conversion efficiency for the given thickness also increases by {approx}10% uniformly across the device optical absorption spectrum, corroborating the enhanced charge carrier collection by nanostructured electrodes.

14 SOLAR ENERGY↗
DOE OSTI2012

Elemental and magnetic sensitive imaging using x-ray excited luminescence microscopy

We demonstrate the potential of x-ray excited luminescence microscopy for full-field elemental and magnetic sensitive imaging using a commercially available optical microscope, mounted on preexisting synchrotron radiation (SR) beamline end stations. The principal components of the instrument will be described. Bench top measurements indicate that a resolution of 1 {mu}m or better is possible; this value was degraded in practice due to vibrations and/or drift in the end station and associated manipulator. X-ray energy dependent measurements performed on model solar cell materials and lithographically patterned magnetic thin film structures reveal clear elemental and magnetic signatures. The merits of the apparatus will be discussed in terms of conventional SR imaging techniques.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

Communication: A vibrational study of propargyl cation using the vacuum ultraviolet laser velocity-map imaging photoelectron method

By employing the vacuum ultraviolet (VUV) laser velocity-map imaging photoelectron (VUV-VMI-PE) method, we have obtained a vibrationally resolved photoelectron spectrum of gaseous propargyl radical [C{sub 3}H{sub 3}(X{sup 2}B{sub 1})] in the energy range of 0-4600 cm{sup -1} above its ionization energy. The cold C{sub 3}H{sub 3} radicals were produced from a supersonically cooled radical beam source based on 193 nm ArF photodissociation of C{sub 3}H{sub 3}Cl. The VUV-VMI-PE spectrum of C{sub 3}H{sub 3} thus obtained reveals a Franck-Condon factor (FCF) pattern with a highly dominant origin band along with weak vibrational progressions associated with excitations of the C-C {nu}{sub 5}{sup +}(a{sub 1}) and C{identical_to}C {nu}{sub 3}{sup +}(a{sub 1}) symmetric stretching modes and the CCH {nu}{sub 7}{sup +}(b{sub 1}) out-of-plane bending mode of C{sub 3}H{sub 3}{sup +}(X{sup 1}A{sub 1}). The {nu}{sub 5}{sup +}(a{sub 1}) vibrational frequency of 1120 cm{sup -1} determined in the present study is lower than the value deduced from the recent Ar-tagged infrared photodissociation study by 102 cm{sup -1}, confirming the highly accurate vibrational frequency predictions obtained by the most recent state-of-the-art ab initio quantum calculations. The observation of the FCF disallowed {nu}{sub 7}{sup +}(b{sub 1}) mode is indicative of vibronic interactions. The discrepancy observed between the FCF pattern determined in the present study and that predicted by a recent high-level quantum theoretical investigation can be taken as evidence that the potential energy surfaces used in the latter theoretical study are in need of improvement in order to provide a reliable FCF prediction for the C{sub 3}H{sub 3}/C{sub 3}H{sub 3}{sup +} photoionization system.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Real time x-ray studies during nanostructure formation on silicon via low energy ion beam irradiation using ultrathin iron films

Real time grazing incidence small angle x-ray scattering and x-ray fluorescence (XRF) are used to elucidate nanodot formation on silicon surfaces during low energy ion beam irradiation of ultrathin iron-coated silicon substrates. Four surface modification stages were identified: (1) surface roughening due to film erosion, (2) surface smoothing and silicon-iron mixing, (3) structure formation, and (4) structure smoothing. The results conclude that 2.5 Multiplication-Sign 10{sup 15} iron atoms in a 50 nm depth triggers surface nanopatterning with a correlated nanodots distance of 25 nm. Moreover, there is a wide window in time where the surface can have correlated nanostructures even after the removal of all the iron atoms from the sample as confirmed by XRF and ex-situ x-ray photoelectron spectroscopy (XPS). In addition, in-situ XPS results indicated silicide formation, which plays a role in the structure formation mechanism.

77 NANOSCIENCE AND NANOTECHNOLOGY↗