Future water resource shifts in the high desert Southwest of Northern New Mexico, USA
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54 ENVIRONMENTAL SCIENCES↗
SEARCH · Engineering Papers
Results for “GRETA”
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.
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Potential for Improved Intelligence Quotient Using Volumetric Modulated Arc Therapy Compared With Conventional 3-Dimensional Conformal Radiation for Whole-Ventricular Radiation in Children
Purpose: To compare volumetric modulated arc therapy (VMAT) with 3-dimensional conformal radiation therapy (3D-CRT) in the treatment of localized intracranial germinoma. We modeled the effect of the dosimetric differences on intelligence quotient (IQ). Method and Materials: Ten children with intracranial germinomas were used for planning. The prescription doses were 23.4 Gy to the ventricles followed by 21.6 Gy to the tumor located in the pineal region. For each child, a 3D-CRT and full arc VMAT was generated. Coverage of the target was assessed by computing a conformity index and heterogeneity index. We also generated VMAT plans with explicit temporal lobe sparing and with smaller ventricular margin expansions. Mean dose to the temporal lobe was used to estimate IQ 5 years after completion of radiation, using a patient age of 10 years. Results: Compared with the 3D-CRT plan, VMAT improved conformality (conformity index 1.10 vs 1.85), with slightly higher heterogeneity (heterogeneity index 1.09 vs 1.06). The averaged mean doses for left and right temporal lobes were 31.3 and 31.7 Gy, respectively, for VMAT plans and 37.7 and 37.6 Gy for 3D-CRT plans. This difference in mean temporal lobe dose resulted in an estimated IQ difference of 3.1 points at 5 years after radiation therapy. When the temporal lobes were explicitly included in the VMAT optimization, the mean temporal lobe dose was reduced 5.6-5.7 Gy, resulting in an estimated IQ difference of an additional 3 points. Reducing the ventricular margin from 1.5 cm to 0.5 cm decreased mean temporal lobe dose 11.4-13.1 Gy, corresponding to an estimated increase in IQ of 7 points. Conclusion: For treatment of children with intracranial pure germinomas, VMAT compared with 3D-CRT provides increased conformality and reduces doses to normal tissue. This may result in improvements in IQ in these children.
62 RADIOLOGY AND NUCLEAR MEDICINE↗
A noncollinear density functional theory ansatz for the phononic and thermodynamic properties of α -Pu
Plutonium's phase diagram is host to complex structures and interactions that make the description of its ground state properties elusive. Using all-electron density functional theory calculations, we study the thermodynamic properties of α-Pu. To do this, we build on recent work in the literature by introducing a novel noncollinear magnetic ansatz for α-Pu's ground state. We show that the noncollinear ansatz improves the description of the experimental phonon density of states, heat capacity, and thermal expansion over previous results obtained with a collinear ansatz. Here, despite lacking a bond-equivalent picture of the bonding, these new results for α-Pu, along with recent results on δ-Pu, demonstrate the efficacy of noncollinear ansatzes for the description of plutonium.
36 MATERIALS SCIENCE↗
A green chemical approach to the synthesis of photoluminescent ZnO hollow spheres with enhanced photocatalytic properties
ZnO hollow spheres have been synthesized by a simple and environmentally friendly template assisted route. Starch-derived carbonaceous spheres were used as template, impregnated with Zn(CH{sub 3}COO){sub 2}{center_dot}2H{sub 2}O to obtain zinc-containing precursor spheres and thermally treatment at 600 Degree-Sign C, yielding hollow ZnO spherical shells. The precursor spheres and hollow shells were characterized by X-ray diffraction, FTIR spectroscopy, scanning electron microscopy, thermal analysis and room-temperature photoluminescence measurements. The hollow spherical shells with diameters of {approx}150 nm and wall thickness of {approx}20 nm, are polycrystalline, with a mean crystallite size of 22 nm, exhibiting interesting emission features, with a wide multi-peak band covering blue and green regions of the visible spectrum. The photocatalytic activities (under UV and visible light irradiations) of the ZnO spherical shells evaluated for the phenol degradation reaction in aqueous solutions are outstanding, a total phenol conversion being registered in the case of UV irradiation experiments. - Graphical abstract: The photocatalytic reaction initiated by the photoexcitation of the semiconductor (ZnO), leads to the formation of electron-hole, while part of the electron-hole pairs recombine, some holes combine with water to form {center_dot}OH radicals and some electrons convert oxygen to super oxide radical ({center_dot}O{sub 2}{sup -}). Highlights: Black-Right-Pointing-Pointer Green synthesis of ZnO hollow spheres. Black-Right-Pointing-Pointer Starch-derived carbonaceous spheres as spherical hard template. Black-Right-Pointing-Pointer ZnO hollow spheres with notable visible photoluminescence properties. Black-Right-Pointing-Pointer ZnO hollow spheres with photocatalytical activity in degradation/mineralization of phenol.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Carbonaceous spheres—an unusual template for solid metal oxide mesoscale spheres: Application to ZnO spheres
A green template route for the synthesis of mesoscale solid ZnO spheres was ascertained. The protocol involves a double coating of the carbonaceous spheres with successive layers of zinc-containing species by alternating a non-ultrasound and ultrasound-assisted deposition, followed by calcination treatments. The composites were characterized by FTIR spectroscopy, thermal analysis, scanning electron microscopy while the obtained ZnO spheres by X-ray diffraction, Raman spectroscopy, scanning and transmission electron microscopy, N{sub 2} adsorption–desorption isotherms and photoluminescence investigations. A growth mechanism of the solid spheres is advanced based on these results. While the spheres' diameters and the mean size values of ZnO are independent on deposition order, the surface area and the external porosity are fairly dependent. The photoluminescence measurements showed interesting emission features, with emission bands in the violet to orange region. The spheres present high photocatalytical activity towards the degradation of phenol under UV irradiation, the main reaction being its mineralization. - Graphical abstract: A novel and eco-friendly methodology for the synthesis of mesoscale solid ZnO spheres was developed. The protocol involves a double coating of the starch-derived carbonaceous spheres with successive layers of zinc-containing species by alternating a non-ultrasound and ultrasound-assisted deposition, followed by calcination treatments. - Highlights: • ZnO solid spheres are obtained via a template route using carbonaceous spheres. • Two-step coatings of interchangeable order are used as deposition procedure. • The coating procedure influences the porosity and surface area. • ZnO spheres exhibited interesting visible photoluminescence properties. • Solid spheres showed photocatalytical activity in degradation of phenol.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Systematic study on the influence of the morphology of α-MoO{sub 3} in the selective oxidation of propylene
A variety of morphologically different α-MoO{sub 3} samples were prepared by hydrothermal synthesis and applied in the selective oxidation of propylene. Their catalytic performance was compared to α-MoO{sub 3} prepared by flame spray pyrolysis (FSP) and a classical synthesis route. Hydrothermal synthesis from ammonium heptamolybdate (AHM) and nitric acid at pH 1–2 led to ammonium containing molybdenum oxide phases that were completely transformed into α-MoO{sub 3} after calcination at 550 °C. A one-step synthesis of α-MoO{sub 3} rods was possible starting from MoO{sub 3}·2H{sub 2}O with acetic acid or nitric acid and from AHM with nitric acid at 180 °C. Particularly, if nitric acid was used during synthesis, the rod-like morphology of the samples could be stabilized during calcination at 550 °C and the following catalytic activity tests, which was beneficial for the catalytic performance in propylene oxidation. Characterization studies using X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman spectroscopy showed that those samples, which retained their rod-like morphology during the activity tests, yielded the highest propylene conversion. - Graphical abstract: Hydrothermal synthesis from MoO{sub 3}·2H{sub 2}O in the presence of HNO{sub 3} led to rod-shaped particles which mainly expose (1 0 0) facets which are the most active surfaces. - Highlights: • Hydrothermal synthesis of MoO3 resulted in either rod or slab shaped particles depending on pH. • At pH<0 rods stable towards calcination and catalytic activity testing were formed. • Rod shaped particles had significantly higher activity than slab shaped ones. • The rod shaped particles mainly expose the (1 0 0) facets which are the most active surfaces. • Total surface area is not main determining factor for catalytic activity.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
UCGretina geant4 simulation of the GRETINA Gamma-Ray Energy Tracking Array
UCGretina, a geant4 simulation of the GRETINA gamma-ray tracking array of highly-segmented high-purity germanium detectors is described. We have developed a model of the array, in particular of the Quad Module and the capsules, that gives good agreement between simulated and measured photopeak efficiencies over a broad range of gamma-ray energies and reproduces the shape of the measured Compton continuum. Both of these features are needed in order to accurately extract gamma-ray yields from spectra collected in in-beam gamma-ray spectroscopy measurements with beams traveling at v / c ≳0.3 at the National Superconducting Cyclotron Laboratory and the Facility for Rare Isotope Beams. In the process of developing the model, we determined that millimeter-scale layers of passive germanium surrounding the active volumes of the simulated crystals must be included in order to reproduce measured photopeak efficiencies. In conclusion, we adopted a simple model of effective passive layers and developed heuristic methods of determining passive-layer thicknesses by comparison of simulations and measurements for a single crystal and for the full array. Prospects for future development of the model are discussed.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Thermodynamics of the S–Sn system: Implication for synthesis of earth abundant photovoltaic absorber materials
Not Available
Lindwall, Greta (ORCID:0000000342218510)↗
Noonan syndrome patient-specific induced cardiomyocyte model carrying SOS1 gene variant c.1654A>G
Noonan syndrome (NS) is a dominant autosomal genetic disorder, associated with mutations in several genes that exhibit multisystem abnormal development including cardiac defects. NS associated with the Son of Sevenless homolog 1 (SOS1) gene mutation attributes to the development of cardiomyopathy and congenital heart defects. Since the treatment option for NS is very limited, an in vitro disease model with SOS1 gene mutation would be beneficial for exploring therapeutic possibilities for NS. We reprogrammed cardiac fibroblasts obtained from a NS patient and normal control skin fibroblasts (C-SF) into induced pluripotent stem cells (iPSCs). We identified NS-iPSCs carry a heterozygous single nucleotide variation in the SOS1 gene at the c.1654A > G. Furthermore, the control and NS-iPSCs were differentiated into induced cardiomyocytes (iCMCs), and the electron microscopic analysis showed that the sarcomeres of the NS-iCMCs were highly disorganized. FACS analysis showed that 47.5% of the NS-iCMCs co-expressed GATA4 and cardiac troponin T proteins, and the mRNA expression levels of many cardiac related genes, studied by qRT-PCR array, were significantly reduced when compared to the control C-iCMCs. We report for the first time that NS-iPSCs carry a single nucleotide variation in the SOS1 gene at the c.1654A>G were showing significantly reduced cardiac genes and proteins expression as well as structurally and functionally compromised when compared to C-iCMCs. These iPSCs and iCMCs can be used as a modeling platform to unravel the pathologic mechanisms and also the development of novel drug for the cardiomyopathy in patients with NS.
60 APPLIED LIFE SCIENCES↗
Approximating the particle distribution in rotating and tandem mirror traps
Steady-state distribution functions can be used to calculate stability conditions for modes, radiation energy losses and particle loss rates. Heuristic analytic approximations to these distributions can capture key behaviors of the true distributions such as the relative speeds of different transport processes while possessing computational advantages over their numerical counterparts. In this paper, we motivate and present a closed-form analytic model for a distribution of particles in a centrifugal or tandem mirror. We find that our model outperforms other known models in approximating numerical steady-state simulations outside of a narrow range of low confining potentials. We demonstrate the model’s suitability in the high confining potential regime for applications such as loss-cone stability thresholds, fusion yields and available energy.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Diffusion Monte Carlo Study of the Structure and Spectroscopy of H 3 O –
A potential energy surface for H 3 O – has been developed based on the NN+(MOB-ML) approach we developed for studies of complexes of OH – with two or three water molecules. Unlike those systems, H 3 O – has two low-energy isomers, H – ·H 2 O and OH – ·H 2 , which differ in energy by less than 2.5 kcal mol –1 , and which are separated by a barrier of roughly 4.5 kcal mol –1 . We find that by training the NN+(MOB-ML) model using structures based on diffusion Monte Carlo (DMC) simulations initiated in the two potential minima, we are able to obtain a potential surface that describes both isomers. Using these potentials, the structure and spectra of H 3 O – and its deuterated analogues are investigated using DMC. These calculations show that the ground state wave function for H 3 O – is mainly localized in the H – ·H 2 O minimum in the potential, with a small amount of the probability amplitude (<5%) in the region of the OH – ·H 2 minimum. The delocalization of the wave function into the secondary minimum is lowered by deuteration of the water molecule, while replacing H – with D – increases the isomerization due to the shortening of the average distance between the hydride ion and the hydrogen atom in water to which it is bound. Introducing one quantum of excitation in the H – ···H 2 O stretching vibration increases the amount of isomerization, while the isomerization decreases with additional excitation of this mode. Excitation of the free OH stretch in the water molecule also increases the amount of isomerization, while excitation of the out-of-plane bending vibration suppresses the isomerization. Furthermore, the effects of partial deuteration on the frequencies for these vibrations are also explored.
Chemical structure↗
Molecular Vibration Induced Plasmon Decay
Noble metal nanoparticles, when interacting with an external electric field, give rise to a phenomenon called surface plasmon resonance characterized by collective valence electron oscillations, and because of this unique feature these systems are employed for a large and heterogeneous number of applications. To improve their performance, it is necessary to develop a deep knowledge of the main factors affecting the plasmon lifetime. In order to answer this question, in this work a linear silver chain is investigated as a simplified model for silver nanorods. Through a non-adiabatic molecular dynamics approach the role of nuclear dynamics on transverse plasmon lifetime is investigated. A strong dependence of plasmon dynamics on the specific nature of nuclear motions is found: nuclear motions along the chain do not affect the transverse plasmon lifetime while motions causing a deviation from linearity of the wire have an important impact on the plasmon dynamics causing its decay. As the vibrational energy increases, the decay becomes faster because of an accelerated loss of symmetry and shows a weak Landau-like mechanism. The unveiled molecular nature of the plasmon decay on a linear wire can be representative of possible decay mechanisms taking place in larger systems. Finally, these results improve the knowledge of plasmon dynamics, and can be helpful for an efficient design of more performing materials.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
In Situ Surface Reconstruction via Lithium Residue Regulation for Direct Recycling of Ni-Rich Cathodes
Surface stability is crucial for the long cycling performance of Ni-rich cathodes, as it dictates and governs side reactions, preserves crystal integrity, and mitigates capacity degradation during cycling. For spent Ni-rich cathodes targeted for one-step direct recycling, constructing a robust and stable surface is particularly challenging because prior cycling induces severe structural and morphological degradation. Here, in this study, we introduce an in situ surface reconstruction strategy that converts surface lithium residues into a protective layer via a direct liquid-phase coating with ammonium dihydrogen phosphate (ADP). During the process, residual lithium remaining after the hydrothermal relithiation is removed, while a conformal lithium phosphate (Li 3 PO 4 , LPO) layer is formed to act as both a chemical barrier and a structural stabilizer. This dual function enhances cycling stability and rate capability in regenerated cathodes, and the approach is applicable to various Ni-rich compositions including spent LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622) and scrap LiNi 0.866 Mn 0.066 Co 0.05 Al 0.018 O 2 (NCMA). Its scalability and compositional versatility make it a promising route for sustainable regeneration of high-performance cathode materials.
36 MATERIALS SCIENCE↗
Multimodal interference-based imaging of nanoscale structure and macromolecular motion uncovers UV induced cellular paroxysm
Understanding the relationship between intracellular motion and macromolecular structure remains a challenge in biology. Macromolecular structures are assembled from numerous molecules, some of which cannot be labeled. Most techniques to study motion require potentially cytotoxic dyes or transfection, which can alter cellular behavior and are susceptible to photobleaching. Here in this paper, we present a multimodal label-free imaging platform for measuring intracellular structure and macromolecular dynamics in living cells with a sensitivity to macromolecular structure as small as 20 nm and millisecond temporal resolution. We develop and validate a theory for temporal measurements of light interference. In vitro, we study how higher-order chromatin structure and dynamics change during cell differentiation and ultraviolet (UV) light irradiation. Finally, we discover cellular paroxysms, a near-instantaneous burst of macromolecular motion that occurs during UV induced cell death. With nanoscale sensitive, millisecond resolved capabilities, this platform could address critical questions about macromolecular behavior in live cells.
59 BASIC BIOLOGICAL SCIENCES↗
Mechanistic insight into the active centers of single/dual-atom Ni/Fe-based oxygen electrocatalysts
Single-atom catalysts with maximum metal utilization efficiency show great potential for sustainable catalytic applications and fundamental mechanistic studies. We here provide a convenient molecular tailoring strategy based on graphitic carbon nitride as support for the rational design of single-site and dual-site single-atom catalysts. Catalysts with single Fe sites exhibit impressive oxygen reduction reaction activity with a half-wave potential of 0.89 V vs. RHE. We find that the single Ni sites are favorable to promote the key structural reconstruction into bridging Ni-O-Fe bonds in dual-site NiFe SAC. Meanwhile, the newly formed Ni-O-Fe bonds create spin channels for electron transfer, resulting in a significant improvement of the oxygen evolution reaction activity with an overpotential of 270 mV at 10 mA cm –2 . We further reveal that the water oxidation reaction follows a dual-site pathway through the deprotonation of *OH at both Ni and Fe sites, leading to the formation of bridging O 2 atop the Ni-O-Fe sites.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗