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At least 1,207 records · Page 67
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Superbalance of holographic entropy inequalities

The domain of allowed von Neumann entropies of a holographic field theory carves out a polyhedral cone — the holographic entropy cone — in entropy space. Such polyhedral cones are characterized by their extreme rays. For an arbitrary number of parties, it is known that the so-called perfect tensors are extreme rays. In this work, we constrain the form of the remaining extreme rays by showing that they correspond to geometries with vanishing mutual information between any two parties, ensuring the absence of Bell pair type entanglement between them. This is tantamount to proving that besides subadditivity, all non-redundant holographic entropy inequalities are superbalanced, i.e. not only do UV divergences cancel in the inequality itself (assuming smooth entangling surfaces), but also in the purification thereof.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Simple holographic models of black hole evaporation

Several recent papers have shown a close relationship between entanglement wedge reconstruction and the unitarity of black hole evaporation in AdS/CFT. The analysis of these papers however has a rather puzzling feature: all calculations are done using bulk dynamics which are essentially those Hawking used to predict information loss, but applying ideas from entanglement wedge reconstruction seems to suggest a Page curve which is consistent with information conservation. Why should two different calculations in the same model give different answers for the Page curve? In this note we present a new pair of models which clarify this situation. Our first model gives a holographic illustration of unitary black hole evaporation, in which the analogue of the Hawking radiation purifies itself as expected, and this purification is reproduced by the entanglement wedge analysis. Moreover a smooth black hole interior persists until the last stages the evaporation process. Our second model gives an alternative holographic interpretation of the situation where the bulk evolution leads to information loss: unlike in the models proposed so far, this bulk information loss is correctly reproduced by the entanglement wedge analysis. This serves as an illustration that quantum extremal surfaces are in some sense kinematic: the time-dependence of the entropy they compute depends on the choice of bulk dynamics. In both models no bulk quantum corrections need to be considered: classical extremal surfaces are enough to do the job. We argue that our first model is the one which gives the right analogy for what actually happens to evaporating black holes, but we also emphasize that any complete resolution of the information problem will require an understanding of non-perturbative bulk dynamics.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Multipartite reflected entropy

We discuss two methods that, through a combination of cyclically gluing copies of a given n-party boundary state in AdS/CFT and a canonical purification, creates a bulk geometry that contains a boundary homologous minimal surface with area equal to 2 or 4 times the n-party entanglement wedge cross-section, depending on the parity of the party number and choice of method. The areas of the minimal surfaces are each dual to entanglement entropies that we define to be candidates for the n-party reflected entropy. In the context of AdS 3 /CFT 2 , we provide a boundary interpretation of our construction as a multiboundary wormhole, and conjecture that this interpretation generalizes to higher dimensions.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2019

Beyond toy models: distilling tensor networks in full AdS/CFT

We present a general procedure for constructing tensor networks that accurately reproduce holographic states in conformal field theories (CFTs). Given a state in a large-N CFT with a static, semiclassical gravitational dual, we build a tensor network by an iterative series of approximations that eliminate redundant degrees of freedom and minimize the bond dimensions of the resulting network. We argue that the bond dimensions of the tensor network will match the areas of the corresponding bulk surfaces. For “tree” tensor networks (i.e., those that are constructed by discretizing spacetime with nonintersecting Ryu-Takayanagi surfaces), our arguments can be made rigorous using a version of one-shot entanglement distillation in the CFT. Using the known quantum error correcting properties of AdS/CFT, we show that bulk legs can be added to the tensor networks to create holographic quantum error correcting codes. These codes behave similarly to previous holographic tensor network toy models, but describe actual bulk excitations in continuum AdS/CFT. By assuming some natural generalizations of the “holographic entanglement of purification” conjecture, we are able to construct tensor networks for more general bulk discretizations, leading to finer-grained networks that partition the information content of a Ryu-Takayanagi surface into tensor-factorized subregions. While the granularity of such a tensor network must be set larger than the string/Planck scales, we expect that it can be chosen to lie well below the AdS scale. However, we also prove a no-go theorem which shows that the bulk-to-boundary maps cannot all be isometries in a tensor network with intersecting Ryu-Takayanagi surfaces.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Synthesis and antitumor activity of cyclic octapeptide, samoamide A, and its derivatives

Using 2-chloro-trityl chloride resin as a solid phase carrier, a linear peptide was synthesized by Fmoc solid phase synthesis followed by liquid phase cyclization. After separation and purification by high-performance liquid chromatography (HPLC), cyclic octapeptide samoamide A was prepared. The synthesis yield was 54.5%. The structure of cyclic octapeptide samoamide A was characterized by electrospray ionization–mass spectrometry (ESI-MS) and nuclear magnetic resonance (NMR) spectrometry. The biological activity was evaluated by the CCK-8 assay and DPP4 enzyme activity inhibition assay. This compound exhibited high antitumor activity. Using samoamide A as a lead compound, eight cyclic octapeptide samoamide A derivatives (a, b, c, d, e, f, g, and h) were designed and synthesized using the alanine scanning method. The molecular weight and chemical structure of these derivatives were verified by ESI-MS and NMR, and the antitumor activity of the derivatives was analyzed. The antitumor activity of compound f was similar to that of samoamide A, and its replacement site is the non-active site of samoamide A, providing a theoretical basis for further modification and transformation of samoamide A.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2024

Beyond the Holographic Entropy Cone via Cycle Flows

Motivated by bit threads, we introduce a new prescription for computing entropy vectors outside the holographic entropy cone. By utilizing cycle flows on directed graphs, we show that the maximum cycle flow associated to any subset of vertices, which corresponds to a subsystem, manifestly obeys purification symmetry. Furthermore, by restricting ourselves to a subclass of directed graphs, we prove that the maximum cycle flow obeys both subadditivity and strong subadditivity, thereby establishing it as a viable candidate for the entropy associated to the subsystem. Lastly, we demonstrate how our model generalizes the entropy vectors obtainable via conventional flows in undirected graphs, as well as conjecture that our model similarly generalizes the entropy vectors arising from hypergraphs.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Influence of Intermolecular Interactions and Axial Ligands on the Absorption Spectra of Metallophthalocyanines in Solid-State Matrices

The influences of the structure of the anionic axial ligands in Group-IIIA and -IVA metal–phthalocyanine complexes and intermolecular interactions on the absorption spectra of the macroheterocycles in solutions, an organic polymer, and nanoporous silicate gel matrices were studied. It was shown that anionic Cl – ligands of the central metal ion were effectively substituted for hydroxyls (OH –) during the synthesis and purification of the metallophthalocyanines. Studies of solid-state nanoporous samples obtained by the sol-gel method showed that activator hydroxoaluminumphthalocyanine molecules were incorporated as monomers into the organo-inorganic silicate material. The optically homogeneous luminescent xerogel could be used in optical devices for the wavelength range adjacent to the near-IR region.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Development of Holmium-163 electron-capture spectroscopy with transition-edge sensors

Calorimetric decay energy spectroscopy of electron-capture-decaying isotopes is a promising method to achieve the sensitivity required for electron neutrino mass measurement. The very low total nuclear decay energy (Q EC < 3 keV) and short half-life (4570 years) of 163 Ho make it attractive for high-precision electron-capture spectroscopy (ECS) near the kinematic endpoint, where the neutrino momentum goes to zero. In the ECS approach, an electron-capture-decaying isotope is embedded inside a microcalorimeter designed to capture and measure the energy of all the decay radiation except that of the escaping neutrino. We have developed a complete process for proton irradiation-based isotope production, isolation, and purification of 163 Ho. We have developed transition-edge sensors for this measurement and methods for incorporating 163 Ho into high-resolution microcalorimeters, and have measured the electron-capture spectrum of 163 Ho. Finally, we present our work in these areas and discuss the measured spectrum and its comparison to current theory.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Thermo-Chemical Decomposition Study of Polyurethane Elastomer Through Glycerolysis Route with Using Crude and Refined Glycerine as a Transesterification Agent

Due to the increasing amount of polyurethane waste, chemical recycling of these materials is a topic of growing interest for many researchers. The primary purpose of polyurethane feedstock recycling is to recover the starting polyol. In this study glycerolysis using glycerine from two sources and two purity grades is proposed as a method of chemical recycling. The main effort of this paper focuses on the employment of commercial glycerine of analytical grade and waste glycerine without purification derived from the biodiesel production, as a decomposing agent for polyurethane recycling. In this study, the influence of polyurethane to glycerine mass ratio (PU/GL) and the type of decomposing agent on the chemical structure by FTIR, {sup 1}H NMR and GPC was examined. FTIR analysis of the glycerolysates showed absorption peaks similar to the virgin polyol. Those results are in compliance with GPC chromatograms, which showed for all samples, well-defined peak at ca. 13 min of retention time. The molecular weight of glycerolysates was ranging from 800 to 1300 g mol{sup −1} depending on PU/GL mass ratio. The novel decomposition agent, namely waste glycerine derived from biodiesel production was successfully used in glycerolysis process.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Synthesis of N-Guanidinium-Chitosan/Silica Hybrid Composites: Efficient Adsorbents for Anionic Pollutants

A new chitosan derivative, N-guanidinium chitosan acetate, has been synthesized by direct guanylation of chitosan by cyanamide in presence of scandium(III) triflate under mild acidic condition. Starting from this material, N-guanidinium chitosan/silica microhybrids were prepared via a sol gel method using 3-glycidoxypropyl trimethoxysilane as silica precursor. Both N-guanidinium chitosan and the N-guanidinium chitosan/silica hybrid were characterized by a range of analytical techniques such as {sup 29}Si/{sup 13}C solid state NMR, FT-IR, scanning electron microscopy, thermogravimetry and elemental analysis. The characterization of the chitosan/silica hybrid indicated that this material is a highly hydrophilic nanocomposite material containing an organic core and a highly condensed silica shell. The N-guanidinium chitosan/silica microhybrids display excellent adsorption properties for anionic dyes such as methyl orange (MO) with very high capacities up to 917 mg/g. The fixation of MO as anionic dye was investigated in detail as a function of contact time, pH and the MO concentration. The adsorption kinetics of MO on N-guanidinium chitosan/silica microhybrids was more accurately described by pseudo second-order model. Langmuir isotherm model exhibited a better fit with adsorption data than Freundlich isotherm model. This work opens new possibilities for using N-guanidinium chitosan as a reusable adsorbent for water purification. Graphical Abstract: .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Tailored Natural Polysaccharides Beads as Green Sorbents for Efficient Lysozyme Adsorption

Herein, we prepared alginate (SA)/carboxymethyl cellulose (CMC) gel beads through Ca{sup 2+} and glutaraldehyde (GA) crosslinking and investigated their adsorption performance on lysozyme from aqueous solution. Taking advantage of the abundant active carboxyl groups on SA and CMC, the obtained SA/CMC gel beads present an excellent integrated lysozyme adsorption performance with a high capacity of 236.34 mg g{sup −1}, short equilibrium time of 8 h, ease of elution, and good reusability. Furthermore, the resultant SA/CMC gel beads also possess unique selectivity for positively charged proteins, confirmed by the method of sodium dodecyl sulfate polyacrylamide gel electrophoresis. Considering the nature of biopolymers and advantages of favorable physical properties, high efficiency, cost-effectiveness, intriguing adsorption capacity and easier separation from the reaction system, the SA/CMC gel beads may find more potential in protein separation and purification than that of synthetic material.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Efficient Acetylation of Xylans by Exploiting the Potassium Acetate Formed During the Alkaline Extraction

Isolation of hemicelluloses through alkaline extraction results in formation of salts, which usually necessitates additional salt removal steps. In this study, acetylation of xylans was studied without the removal of potassium acetate (KAc), a commonly produced salt during the alkaline extraction, to find a facile method to alter the hydrophilic characteristics of hemicelluloses. The acetylation reaction was carried out solely with acetic anhydride without any catalysts or solvents added. The weight gain and ATR–FTIR analyses verified the acetylation of xylans in the presence of KAc. A significant decrease in water solubility and moisture uptake was observed upon acetylation in the presence of KAc which is also accompanied by an increase in thermal stability, disclosing an easy, efficient and environmentally friendly method to obtain hydrophobically modified xylans without the use of toxic catalysts and costly salt purification steps.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Equilibrium, Kinetic and Thermodynamic Studies on Methylene Blue Adsorption by Konjac Glucomannan/Activated Carbon Aerogel

Activated carbon (AC) is a common adsorbent used for the purification of aqueous solutions, yet its poor aqueous dispersion may negatively affects its practicability significantly. In the present study, the fabrication of an AC aerogel immobilized with konjac glucomannan (KGM/AC) for environmental protection was reported, and the parameters (e.g. AC content in aerogel, solution pH, adsorption duration, adsorption temperature and adsorbent dosage) were analyzed systematically using methylene blue (MB) as a model adsorbate. Further, to explore the adsorption equilibrium isotherm at equilibrium, the adsorption data were respectively fitted to Langmuir and Freundlich models, while kinetics study was conducted to explain the adsorption mechanism and predict the adsorption efficiency. Besides, the effect of temperature on the adsorption behavior was assessed using Van’t Hoff equation. According to the experimental and calculative results, the adsorption data at equilibrium could be well geared into the Langmuir model, and the adsorption kinetics behavior was better consistent with the pseudo-second-order expression as well as the intra-particle diffusion model. The Brunauer, Emmett and Teller surface area of KGM/AC aerogel was 352.44 m{sup 2}/g. KGM/AC aerogel exhibited the maximal capacity of adsorption of 416.67 mg/g at 323 K, and its adsorption behavior toward MB was endothermic and spontaneous in nature.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

One-Pot Depolymerization and Polycondensation of PET Based Random Oligo- and Polyesters

The glycolysis of PET is a promising well-developed technique that could be utilized in a wide range of processes. Due to its equilibrial nature, the high ratio of reagents and the purification steps it is an expensive process. In this study our goal was to modify the standard glycolysis to an easily modulateable method (acido-alcoholysis) suited for one-pot oligoester, polyester synthesis. Adipic acid was added to the depolymerization reaction to connect low molecular weighed components into oligoesters. PET depolymerization reaction series were carried out with ethylene–glycol/adipic acid and butane-1,4-diol/adipic acid to demonstrate the tuneability of these systems. The reaction products were thoroughly characterized with NMR, FTIR, TGA, DSC and functional group analysis. One-pot depolymerization-polycondensation reactions were engineered to produce unsaturated and saturated polyesters. The unsaturated polyesters were dissolved in styrene, cross-linked and moulded to be characterized with DMA. A decreasing tendency of the glass transition temperature and cross-link density were found in the function of the ratio of adipic acid used during the depolymerization step. Acido-alcoholysis proved to be a versatile technique that could be used to engineer oligoesters and polyesters. The reagent use can be minimalized, and the raw reaction products can be directly applied as mid-products.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Californium Electrodepositions at Oak Ridge National Laboratory

Electrodepositions of californium isotopes were successfully performed at Oak Ridge National Laboratory (ORNL) during the past year involving two different types of deposition solutions, ammonium acetate (NH 4 C 2 H 3 O 2 ) and isobutanol ((CH 3 ) 2 CHCH 2 OH). A californium product that was decay enriched in 251 Cf was recovered for use in super-heavy element (SHE) research. This neutron-rich isotope, 251 Cf, provides target material for SHE research for the potential discovery of heavier isotopes of Z=118. The californium material was recovered from aged 252 Cf neutron sources in storage at ORNL. These sources have decayed for over 30 years, thus providing material with a very high 251 Cf-to- 252 Cf ratio. After the source capsules were opened, the californium was purified and then electrodeposited using the isobutanol method onto thin titanium foils for use in an accelerator at the Joint Institute for Nuclear Research in Dubna, Russia. Another deposition method, ammonium acetate, was used to produce a deposition containing 1.7 0.1 Ci of 252 Cf onto a stainless steel substrate. This was the largest single electrodeposition of 252 Cf ever prepared. The 252 Cf material was initially purified using traditional ion exchange media, such as AG50-AHIB and AG50-HCl, and further purified using a TEVA-NH 4 SCN system to remove any lanthanides, resulting in the recovery of 3.6 0.1 mg of purified 252 Cf. The ammonium acetate deposition was run with a current of 1.0 amp, resulting in a 91.5% deposition yield. Purification and handling of the highly radioactive californium material created additional challenges in the production of these sources.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2015

Production of ⁶¹Cu by the nat Zn(p,α) reaction: Improved separation and specific activity determination by titration with three chelators

In this study, the cyclotron-based production of position-emitting ⁶¹Cu using the (p,α) reaction at 11.7 MeV was investigated starting from natural-zinc ( nat Zn) and enriched ⁶⁴Zn-foil targets, as well as its subsequent purification. For nat Zn, a combination of three resins were assessed to separate ⁶¹Cu from contaminating 66,67,68 Ga and nat Zn. The specific activity of the purified ⁶¹Cu determined using ICP-MS analysis ranged from 143.3±14.3(SD) to 506.2±50.6 MBq/μg while the titration method using p-SCN-Bn-DOTA, p-SCN-Bn-NOTA and diamsar gave variable results (4.7±0.2 to 412.5±15.3 MBq/μg), with diamsar lying closest to the ICP-MS values. Results suggest that the p-SCN-Bn-DOTA and p-SCN-Bn-NOTA titration methods are significantly affected by the presence of trace-metal contaminants.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2015

Developing 226 Ra and 227 Ac age-dating techniques for nuclear forensics to gain insight from concordant and non-concordant radiochronometers

The model age or ‘date of purification’ of a nuclear material is an important nuclear forensic signature. In this study, chemical separation and MC-ICP-MS measurement techniques were developed for 226 Ra and 227 Ac: grand-daughter nuclides in the 238 U and 235 U decay chains respectively. The 230 Th- 234 U, 226 Ra- 238 U, 231 Pa- 235 U, and 227 Ac- 235 U radiochronometers were used to calculate model ages for CRM-U100 standard reference material and two highly-enriched pieces of uranium metal from the International Technical Working Group Round Robin 3 Exercise. In conclusion, the results demonstrate the accuracy of the 226 Ra- 238 U and 227 Ac- 235 U chronometers and provide information about nuclide migration during uranium processing.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2016

Measurement Background and the Sediment Age-Dating Reach of 32Si

Silicon-32 has been identified as an isotope that fills the sediment geochronology gap created between Pb-210 at <150 years and C-14 at >1000 years. However, detector sensitivity and chemical isolation challenges of radiometric Si-32 for age dating have resulted in a fairly limited number of applications of this technique to real-world sediment studies. The significance of targeting the intermediate age bracket is to provide accurate geochronological reconstructions of paleoindicators that identify human and large-scale, climate-induced shifts in coastal areas. Therefore, we targeted Puget Sound, Washington, United States, to demonstrate the application of Si-32 age dating to determine the relative importance of climate cycles versus human activities in an in-land sea. The enhanced reconstructions will be achieved through the design of new detectors, chemical separation of biogenic silica from kilogram-scale sediment samples, and demonstration of the viable age-dating reach of Si-32. Implications of detector background on the duration of required measurements and the age-dating reach are considered. The design of a low-background, gas-proportional beta counter for measurement of the daughter isotope P-32 is discussed; detector background goals for these new detectors are based on the sensitivity study.

Keillor, Martin E.↗