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1
Rampho, G. J., S. A. Sofianos, S. Oryu, and T. Watanabe. "Nuclear Electro-disintegration with Antisymmetrized Molecular Dynamics." Few-Body Systems 54, no. 1-4 (March 30, 2012): 455–58. http://dx.doi.org/10.1007/s00601-012-0412-4.
2
Benhar, Omar. "Extracting Hypernuclear Properties from the (e, e′K+) Cross Section." Particles 4, no. 2 (May 11, 2021): 194–204. http://dx.doi.org/10.3390/particles4020018.
Анотація:
Experimental studies of hypernuclear dynamics, besides being essential for the understanding of strong interactions in the strange sector, have important astrophysical implications. The observation of neutron stars with masses exceeding two solar masses poses a serious challenge to the models of hyperon dynamics in dense nuclear matter, many of which predict a maximum mass incompatible with the data. In this paper, it is argued that valuable new insight can be gained from the forthcoming extension of the experimental studies of kaon electro production from nuclei to include the 208Pb(e,e′K+)Λ208Tl process. A comprehensive framework for the description of kaon electro production, based on factorization of the nuclear cross section and the formalism of the nuclear many-body theory, is outlined. This approach highlights the connection between the kaon production and proton knockout reactions, which will allow us to exploit the available 208Pb(e,e′p)207Tl data to achieve a largely model-independent analysis of the measured cross section.
3
SARGSIAN, MISAK M. "SELECTED TOPICS IN HIGH ENERGY SEMI-EXCLUSIVE ELECTRO-NUCLEAR REACTIONS." International Journal of Modern Physics E 10, no. 06 (December 2001): 405–57. http://dx.doi.org/10.1142/s0218301301000617.
Анотація:
We review the present status of the theory of high energy reactions with semi-exclusive nucleon electro-production from nuclear targets. We demonstrate how the increase of transferred energies in these reactions opens a completely new window for study of the microscopic nuclear structure at small distances. The simplifications in theoretical descriptions associated with the increase in the energies are discussed. The theoretical framework for calculation of high energy nuclear reactions based on the effective Feynman diagram rules is described in detail. The result of this approach is the generalized eikonal approximation (GEA), which is reduced to the Glauber approximation when nucleon recoil is neglected. The method of GEA is demonstrated in the calculation of high energy electro-disintegration of the deuteron and A=3 targets. Subsequently, we generalize the obtained formulae for A>3 nuclei. The relation of GEA to the Glauber theory is analyzed. Then, based on the GEA framework we discuss some of the phenomena which can be studied in exclusive reactions: nuclear transparency and short-range correlations in nuclei. We illustrate how light-cone dynamics of high-energy scattering emerge naturally in high energy electro-nuclear reactions.
4
Alyokhina, S., I. Nevliudov, and Yu Romashov. "Safe Transportation of Nuclear Fuel Assemblies by Means of Wheeled Robotic Platforms." Nuclear and Radiation Safety, no. 3(91) (September 17, 2021): 43–50. http://dx.doi.org/10.32918/nrs.2021.3(91).05.
Анотація:
Certain engineering problems concerning safety of the technological operations of the horizontal transportation of nuclear fuel within the enterprises’ sites were considered. Taking into account current trends in the introduction of robotic systems to reduce the impact of hazardous nuclear materials on personnel, the issue of automated control of the movement of the wheeled robotic platform, which can be used for horizontal transportation of nuclear fuel was studied. The major attention was paid to minimizing the transportation loads on nuclear fuel by means of decreasing the accelerations under its horizontal movement on the robotic wheeled transportation platform, which is a separate issue of the comprehensive safety problem of nuclear materials management.
The research of horizontal movement safety of nuclear fuel by means of the robotic wheeled platforms was limited to defining transportation accelerations and was performed by computer simulations using mathematical models of dynamics and electro-mechanics. The mathematical model of the robotic transport wheeled platform loaded with nuclear fuel with the on-board accelerometer ensuring the required measurements necessary for an automated safe movement control system was built in the form of the Lagrange equations of the second kind and the electro-mechanics equations of the direct current electric motors. The issue of ensuring smooth running during the displacement of a wheeled platform loaded with nuclear fuel was investigated, since especially in this mode the maximum accelerations are observed, which can lead to nuclear fuel damage. Computer simulation was performed using free Scilab software with open program code. It was demonstrated that due to the proper choice of the time algorithm of the voltage of electric motors, it is possible to ensure a small acceleration during the displacement of a robotic wheeled transport platform loaded with nuclear fuel. The obtained result substantiated the possibility of safe horizontal transportation of nuclear fuel on robotic wheeled platforms within the territories of enterprises, which will significantly reduce the harmful impact of hazardous nuclear materials on industrial personnel.
5
Lenske, Horst, Jessica Bellone, Maria Colonna, and Danilo Gambacurta. "Theory of Majorana-Type Heavy Ion Double Charge Exchange Reactions by Pion–Nucleon Isotensor Interactions." Universe 10, no. 5 (April 30, 2024): 202. http://dx.doi.org/10.3390/universe10050202.
Анотація:
The theory of heavy ion double charge exchange (DCE) reactions proceeding by effective rank-2 isotensor interactions is presented. Virtual pion–nucleon charge exchange interactions are investigated as the source for induced isotensor interactions, giving rise to the Majorana DCE (MDCE) reaction mechanism. MDCE is of a generic character, proceeding through pairs of complementary (π±,π∓) reactions in the projectile and target nucleus. The dynamics of the elementary processes is discussed, where the excitation of pion–nucleon resonances are of central importance. Investigations of initial and final state ion–ion interactions show that these effects are acting as vertex renormalizations. In closure approximation, well justified by the finite pion mass, the second-order transition matrix elements reduce to pion potentials and effective two-body isotensor DCE interactions, giving rise also to two-body correlations in either of the participating nuclei. Connections to neutrinoless Majorana double beta decay (MDBD) are elucidated at various levels of the dynamics, from the underlying fundamental electro-weak and QCD scales to the physical scales of nuclear MDBD and MDCE physics. It is pointed out that heavy ion MDCE reactions may also proceed by competing electro-weak charge exchange processes, leading to lepton MDCE by electrons, positrons, and neutrinos.
6
Kalegaev, Vladimir, Mikhail Panasyuk, Irina Myagkova, Yulia Shugay, Natalia Vlasova, Wera Barinova, Evgenia Beresneva, et al. "Monitoring, analysis and post-casting of the Earth’s particle radiation environment during February 14–March 5, 2014." Journal of Space Weather and Space Climate 9 (2019): A29. http://dx.doi.org/10.1051/swsc/2019029.
Анотація:
Internet-based system of Space Monitoring Data Center (SMDC) of Skobeltsyn Institute of Nuclear Physics of Moscow State University (SINP MSU) has been developed to predict and analyze radiation conditions in near-Earth space. This system contains satellite measurement databases and operational models and devoted to collect, store and process space weather monitoring data in the near real-time. SMDC operational services acquire data from ACE, SDO, GOES, Electro-L, Meteor-M satellites and use them for forecasting, now-casting and post-casting of space weather factors. This paper is intended to give overview of operational services of SMDC Internet-based system and demonstrate their possibilities and limitations to analyze space weather phenomena and predict radiation and geomagnetic conditions in the near-Earth space during February 14–March 5, 2014. This prolonged period of high level solar and geomagnetic activity demonstrates various manifestations of the space weather: solar proton events, geomagnetic storms and outer radiation belt (RB) dynamics. Solar sources of interplanetary space disturbances and their influence on geomagnetic and radiation state of the Earth’s magnetosphere were described using output coming from SMDC’ Web-based applications. Validation of SMDC’s operational models was performed based on the quality of description of the physical conditions in near-Earth space during space weather events observed from February 14 to March 5, 2014. The advantages and disadvantages of SMDC operational services are illustrated and discussed based on comparison with data obtained from satellites.
7
King, W. A., B. G. Jeon, and D. H. Betts. "47 BLASTOCYST DEVELOPMENT RATE OF CLONED BOVINE EMBRYOS USING SERIAL NUCLEAR TRANSFER OF CELLS CONTAINING AN X-AUTOSOME-TRANSLOCATED CHROMOSOME t(Xp+;23q-)." Reproduction, Fertility and Development 18, no. 2 (2006): 132. http://dx.doi.org/10.1071/rdv18n2ab47.
Анотація:
Somatic cell nuclear transfer (SCNT) has been utilized to study various genetic and epigenetic contributions of specific biomedical diseases and developmental events by using various donor cell types such as mature lymphocytes, brain tumor cells, and other unique genotypes. Previously, we produced cloned fetuses and offspring derived from SCNT of adult ear skin fibroblasts obtained from a sub-fertile cow harboring an X-autosome translocation as a model to study X-inactivation and chromosome dynamics during female meiosis. The aim of this study was to assess the cloning efficiency of the fibroblasts derived from a cloned calf with the X-autosome translocation t(Xp+;23q-) compared to the original adult fibroblast donor containing the same chromosome translocation. Primary cultures of cells were established in DMEM +15% fetal calf serum (FCS). To serve as nuclear donors, cells at 5-7 passages were cultured for 5 days until confluent. Oocytes matured for 18 h in TCM-199 with hormones were removed of their chromatin, and reconstructed by transfer of donor cells and fusion with two DC pulses (1.2 kV/cm, 15 �s), delivered by a BTX 2000 Electro Cell Minupulator (BTX, Inc., San Diego, CA, USA), in 0.28 M mannitol containing 0.01 mM MgCl2. After 1 h of fusion, the eggs were activated with 5.5 �M ionomycin for 5 min, followed by 11 �g/mL cyclohexamide for 5 h. The eggs were cultured for 9 days in L-SOF at 39�C in a humidified atmosphere of 5% CO2, 5% O2, 90% N2. Chi-square analysis revealed no significant (P > 0.05) differences in the rates of cleavage, blastocyst frequencies, and cell numbers between the 1st and 2nd generation cloned embryos. Cleavage rates were 87.4% and 85.4% for 1st and 2nd generation cloned embryos, respectively. The frequencies of blastocyst development and hatched blastocyst formation on Day 9 were 41.4% (91/220) and 38.7% (92/238), and 26.4% (58/220) and 22.7% (54/238) for the 1st and 2nd generation cloned embryos, respectively. The numbers of total cells and inner cell mass (ICM) cells of Day 9 blastocysts were 183 and 52, respectively, in the 1st generation embryos and 167 and 51 cells in the 2nd-generation cloned embryos. In summary, 2nd generation cloned embryos derived from fibroblasts of a cloned calf with an X-autosome translocated chromosome showed embryo development and cell numbers similar to those of the 1st generation clones. These results demonstrate that serial nuclear transfer does not improve the blastocyst development rate of cloned embryos containing the X-autosome translocation t(Xp+;23q-). This work was funded by OCAG, OMAF, and CRC.
8
Krivtchik, G. "COSI7: THE NEW CEA REFERENCE ELECTRO-NUCLEAR SIMULATION TOOL." EPJ Web of Conferences 247 (2021): 13001. http://dx.doi.org/10.1051/epjconf/202124713001.
Анотація:
Nuclear fuel cycle scenario studies are used as a prospective analysis tool in order to provide stakeholders with decision aid. Nuclear fuel cycle simulation tools model the deployment of reactor fleets, the mass flows in the fuel cycle, and track the nuclear materials. The CEA has been developing for more than 30 years the nuclear fuel cycle tool COSI. The latest version, COSI7, was designed in order to model dynamic systems of ever-increasing complexity with improved user experience. The new developments include functionalities designed to improve the user experience as well as new physical models and post-processing capabilities. COSI7 supersedes COSI6 as the CEA reference nuclear fuel cycle simulation code starting January 2020.
9
Fathirad, Fariba, Ali Mostafavi, and Daryoush Afzali. "Conductive Polymeric Ionic Liquid/Fe3O4 Nanocomposite as an Efficient Catalyst for the Voltammetric Determination of Amlodipine Besylate." Journal of AOAC INTERNATIONAL 100, no. 2 (March 1, 2017): 406–13. http://dx.doi.org/10.5740/jaoacint.16-0216.
Анотація:
Abstract A novel conductive polymeric ionic liquid (IL)-Fe3O4 nanocomposite (represented as PIL-Fe3O4) based on inorganic-organic hybrid material was synthesized using two different methods. Nuclear magnetic resonance, Fourier transform infrared, X-ray diffraction, and field emission scanning electron microscopy characterized the structures of IL, Fe3O4 nanoparticles, and PIL-Fe3O4. The electrochemical sensors based on PIL-Fe3O4-modified glassy carbon electrode were fabricated, and each of these nanocomposites was examined for the ability to determine amlodipine besylate (AMD). The electrochemical study of the modified electrodes, as well as its efficiency for the electro-oxidation of AMD, was described in 0.1 M phosphate-buffered solution (pH 7.0) using voltammetric methods. The results exhibit a linear dynamic range from 1 to 500 nM and a detection limit of 0.36 nM. Finally, the modified electrode was used for the determination of AMD in pharmaceutical and biological samples.
10
CAMPBELL-SMITH, A. "COMPOSITE OPERATOR EFFECTIVE POTENTIAL APPROACH TO QED3." Modern Physics Letters A 13, no. 29 (September 21, 1998): 2337–46. http://dx.doi.org/10.1142/s0217732398002485.
Анотація:
The composite operator effective potential is compared with the conventional Dyson–Schwinger method as a calculational tool for (2+1)-dimensional quantum electro-dynamics. It is found that when the fermion propagator ansatz is put directly into the effective potential, it reproduces exactly the usual gap equations derived in the Dyson–Schwinger approach.
11
Kohno, Masahiro, Toshiaki Kamachi, and Koji Fukui. "Intermolecular binding between bulk water and dissolved gases in earth’s magnetic field." PLOS ONE 17, no. 5 (May 12, 2022): e0267391. http://dx.doi.org/10.1371/journal.pone.0267391.
Анотація:
Elucidation of the static states and dynamic behavior of oxygen and nitrogen dissolved in water is one of the most important issues in the life sciences. In the present study, experimental trials and theoretical calculations were performed based on the hypothesis that the dissolution of gas molecules in water is related to excitation by the Earth’s magnetic field. Using quantum theories such as those used to describe electro magnetic resonance and nuclear magnetic resonance, this study investigated the states of oxygen, nitrogen and hydrogen dissolved in water. The results indicate that the Earth’s magnetic field is involved in the bonding and dissociation of molecules at the gas-liquid interface. These calculations assessed the effect of a field strength of 1.0 x 10−4 T and reproduced the influences of temperature changes on dissolved gas concentrations. Molecular interactions caused by electromagnetic properties and the external geomagnetic field were found to affect intermolar bonding associated with water cluster structures. It is concluded that the binding between molecules typically attributed to Coulomb coupling by magnetic charge and van der Waals forces results from excitation in the Earth’s magnetic field.
12
Nishimura, Ryouichi, Masa-yuki Yamamoto, Takayuki Otsu, Takuma Oi, and Taira Itoh. "Evolving infrasound measurement and growing infrasound monitoring network." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 268, no. 4 (November 30, 2023): 4484–94. http://dx.doi.org/10.3397/in_2023_0640.
Анотація:
Infrasound carries information useful for detecting a strong natural phenomenon such as volcanic eruption and tsunami, which may cause catastrophic disaster. Therefore, infrasound measurement is gathering attention for potential applications in disaster prevention and life protection. However, the methodology of its measurement has not been well established except a few specific applications such as Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO). Some sensor devices employ Micro Electro Mechanical Systems (MEMS) sensors, which are, in general, small and available at a low price. This advantage enables us to increase the number of locations where infrasound can be monitored at multiple observation points. Another attempt is to assemble multiple sensors of different characters for widening dynamic range and frequency coverage of the sensor. These progress in infrasound measurement would make it possible to utilize infrasound in various purposes. In this respect, infrasound measurement needs to be standardized because one may want to analyze infrasound data together with those acquired using different devices by other organizations. At the same time, a platform for sharing infrasound data is becoming important to accelerate such usage. This paper overviews recent development of sensor devices for infrasound measurement and sensor deployment on going in Japan.
13
Albertini, Francesca, and Domenico D'Alessandro. "Symmetric states and dynamics of three quantum bits." Quantum Information and Computation 22, no. 7&8 (May 2022): 541–68. http://dx.doi.org/10.26421/qic22.7-8-1.
Анотація:
The unitary group acting on the Hilbert space ${\cal H}:=(C^2)^{\otimes 3}$ of three quantum bits admits a Lie subgroup, $U^{S_3}(8)$, of elements which permute with the symmetric group of permutations of three objects. Under the action of such a Lie subgroup, the Hilbert space ${\cal H}$ splits into three invariant subspaces of dimensions $4$, $2$ and $2$ respectively, each corresponding to an irreducible representation of $su(2)$. The subspace of dimension $4$ is uniquely determined and corresponds to states that are themselves invariant under the action of the symmetric group. This is the so called {\it symmetric sector.} The subspaces of dimension two are not uniquely determined and we parametrize them all. We provide an analysis of pure states that are in the subspaces invariant under $U^{S_3}(8)$. This concerns their entanglement properties, separability criteria and dynamics under the Lie subgroup $U^{S_3}(8)$. As a physical motivation for the states and dynamics we study, we propose a physical set-up which consists of a symmetric network of three spin $\frac{1}{2}$ particles under a common driving electro-magnetic field. {For such system, we solve the control theoretic problem of driving a separable state to a state with maximal distributed entanglement.
14
Rego, L. G. C., S. G. Abuabara, and V. S. Batista. "Coherent optical control of electronic excitations in functionalized semiconductor nanostructures." Quantum Information and Computation 5, no. 4&5 (July 2005): 318–34. http://dx.doi.org/10.26421/qic5.45-4.
Анотація:
The feasibility of creating and manipulating coherent quantum states on surfaces of functionalized semiconductor nanostructures is computationally investigated. Quantum dynamics simulations of electron-hole transfer between catechol molecules adsorbed on TiO_2 -anatase nanostructures under cryogenic and vacuum conditions indicate that laser induced coherent excitations can be prepared and manipulated to exhibit controllable spatial Rabi oscillations. The presented computational methods and results are particularly relevant to explore the basic model components of quantum-information electro-optic devices based on inexpensive and readily available semiconductor materials.
15
Rozhina, Elvira, Ilnur Ishmukhametov, Läysän Nigamatzyanova, Farida Akhatova, Svetlana Batasheva, Sergey Taskaev, Carlos Montes, Yuri Lvov, and Rawil Fakhrullin. "Comparative Toxicity of Fly Ash: An In Vitro Study." Molecules 26, no. 7 (March 30, 2021): 1926. http://dx.doi.org/10.3390/molecules26071926.
Анотація:
Fly ash produced during coal combustion is one of the major sources of air and water pollution, but the data on the impact of micrometer-size fly ash particles on human cells is still incomplete. Fly ash samples were collected from several electric power stations in the United States (Rockdale, TX; Dolet Hill, Mansfield, LA; Rockport, IN; Muskogee, OK) and from a metallurgic plant located in the Russian Federation (Chelyabinsk Electro-Metallurgical Works OJSC). The particles were characterized using dynamic light scattering, atomic force, and hyperspectral microscopy. According to chemical composition, the fly ash studied was ferro-alumino-silicate mineral containing substantial quantities of Ca, Mg, and a negligible concentration of K, Na, Mn, and Sr. The toxicity of the fly ash microparticles was assessed in vitro using HeLa cells (human cervical cancer cells) and Jurkat cells (immortalized human T lymphocytes). Incubation of cells with different concentrations of fly ash resulted in a dose-dependent decrease in cell viability for all fly ash variants. The most prominent cytotoxic effect in HeLa cells was produced by the ash particles from Rockdale, while the least was produced by the fly ash from Chelyabinsk. In Jurkat cells, the lowest toxicity was observed for fly ash collected from Rockport, Dolet Hill and Muscogee plants. The fly ash from Rockdale and Chelyabinsk induced DNA damage in HeLa cells, as revealed by the single cell electrophoresis, and disrupted the normal nuclear morphology. The interaction of fly ash microparticles of different origins with cells was visualized using dark-field microscopy and hyperspectral imaging. The size of ash particles appeared to be an important determinant of their toxicity, and the smallest fly ash particles from Chelyabinsk turned out to be the most cytotoxic to Jukart cells and the most genotoxic to HeLa cells.
16
Tikhonova, Ol’ga, Igor’ Malygin, and Anatoliy Plastun. "THE EQUIVALENT CIRCUIT PARAMETERS CALCULATION OF INDUCTION MOTORS WITH RING WINDINGS." Bulletin of the South Ural State University series "Power Engineering" 22, no. 1 (March 2022): 21–35. http://dx.doi.org/10.14529/power220103.
Анотація:
Induction motors with ring windings (IMRW) are designed for the processing of nuclear waste. The sta-tor winding coils are covered with ceramic insulation to allow for long-term operation in conditions of increased radiation. The stator coils are ring shaped, in order to reduce the bend angle. The stator has a specific design consisting of tooth tips located around the axis of rotation and tooth cores placed over the tooth tips in a spiral. The first IMRW prototype was manufactured by UrFU together with “Uralelectromash”. It was designed to the same diameters as an induction motor of a classical design with a power P = 2.2 kW, with a synchronous rotation speed n = 1000 rpm. The fundamentally new ar-mature design involves the search for new solutions for determining machine parameters, such as inductances, electro-magnetic torques. The article discusses a method of equivalent circuit parameter calculation for IMRW using the “ANSYS Maxwell” in 3D mode. In order to determine stator winding leakage inductances, a static analysis of the model with the ro-tor removed was used. Mutual inductance is defined as the difference between stator winding phase impedance and leak-age inductance. The active resistance of the magnetizing circuit and the impedance of the motor can be determined using the IMRW no-load and short-circuit characteristics obtained in ANSYS Maxwell. The paper also provides an example of calculating the mechanical characteristics of a motor using the analytical method (AM).This involves the use of equivalent circuit parameters, and the finite element method (FEM). The use of FEM for calculating the mechanical characteristics implies the analysis of IMRW in a dynamic mode. This allows the electromagnetic torque to be determined at a user-specified rotor speed. In conclusion, a comparative analysis of the parameters of a classic engine and IMRW engine, of the same size, is given. Recommendations are given for further improvement of the design of IMRW engines.
17
Wang, Xiaohua, Jinfeng Zhang, Kunpeng Feng, Yu Yang, Wenwei Qi, Pablo Martinez-Vazquez, Guoguang Zhao, and Tianlong Wang. "The effect of hypothermia during cardiopulmonary bypass on three electro-encephalographic indices assessing analgesia and hypnosis during anesthesia: consciousness index, nociception index, and bispectral index." Perfusion 35, no. 2 (August 7, 2019): 154–62. http://dx.doi.org/10.1177/0267659119864821.
Анотація:
The depth of anesthesia is commonly assessed in clinical practice by the patient’s clinical signs. However, during cardiopulmonary bypass and hypothermia, common symptoms of nociception such as tachycardia, hypertension, sweating, or movement have low sensitivity and specificity in the description of the patient nociception and hypnosis, in particular, detecting nociceptive stimuli. Better monitoring of the depth of analgesia during hypothermia under cardiopulmonary bypass will avoid underdosage or overdosage of analgesia, especially opioids. Induced hypothermia has a multifactorial effect on the level of analgesia and hypnosis. Thermoregulatory processes appear essential for the activation of analgesic mechanisms, ranging from a physiological strong negative affiliation between nerve conduction velocity and temperature, until significant repercussions on the pharmacological dynamics of the analgesic drugs, the latter decreasing the clearance rate with a subsequent increase in the effect-site concentrations. Under the hypothesis that deep hypothermia induces massive effects on the analgesia and hypnosis levels of the patient, we studied whether hypothermia effects were mirrored by several neuromonitoring indices: two hypnosis indices, consciousness index and bispectral index, and a novel nociception index designed to evaluate the analgesic depth. In this clinical trial, 39 patients were monitored during general anesthesia with coronary atherosclerosis cardiopathy who were elective for on-pump coronary artery bypass graft surgery under hypothermia. The changes and correlation between the consciousness index, bispectral index, and nociception index with respect to the temperature were compared in different timepoints at basic state, during cardiopulmonary bypass and after cardiopulmonary bypass. While the three neuromonitoring indices showed significant correlations with respect to the temperature, the nociception index and consciousness index showed the strongest sensitivities, indicating that these two indices could be an important means of intraoperative neuromonitoring during induced hypothermia under cardiopulmonary bypass.
18
Lee, Doohee, Guodong Wu, Wonhyeong Kim, Yoolim Cha, and Dong-Joo Kim. "(Digital Presentation) Paper-Based Sensor for Monitoring Urea Oxidation Using Hierarchical Nickel Cobalt Oxide." ECS Meeting Abstracts MA2022-01, no. 52 (July 7, 2022): 2173. http://dx.doi.org/10.1149/ma2022-01522173mtgabs.
Анотація:
Urea has attracted attention because of its various potential applications such as hydrogen production, fuel cells, fertilizers, and electrochemical sensors. [1] Their long-term usages can lead to soil acidification and eutrophication, disturbing the ecosystem.[2] As an end-product of human metabolism, urea is a crucial biomarker that can access various human disorders such as kidney and renal function. Thus, the rapid sensing of the urea level in urine can play an important role in diagnostic areas, especially point-of-care testing devices. Most electrochemical biosensors rely on the enzymatic method. However, the utilization of the enzyme for the sensors appears to be limited due to complex processes of enzyme immobilization, high cost, short shelf life from the denaturation of the enzyme. [3] To overcome the limitations from using enzyme, non-enzymatic catalyst, especially nickel oxide, has been attracted with the advantage of good stability re-usability, high sensitivity, simplicity, low cost, and an excellent catalytic activity on detection of urea by the formation of the redox couple of Ni(II) and Ni(III).[4] Despite many efforts to achieve a higher catalytic effect with bimetallic oxides with Co[5], Mo[6], and Mn[7], the improvement of electrochemical response of oxidation of urea is still challenging due to the low exposure of active sites. Therefore, the formation of hollow structured hierarchical catalysts can be considered to improve the sensitivity of urea detection besides exploration of highly performing compositions. Such a hierarchical structure will provide structural stability and facile transport channels for electrolytes by exploiting its inner and outer surface as active sites. For a flexible and disposable sensor platform, the paper has merit due to a porous cellulose matrix. The paper naturally allows a liquid sample to infiltrate the paper matrix by capillary force. Furthermore, the capillary force-driven transport can be utilized in the catalyst loading process to distribute the catalyst and conductive network uniformly within the paper, which made the fabrication process simpler and enhanced performance. In this study, the combination of the hierarchical structure of nickel oxide and the paper matrix has demonstrated an increase in the sensitivity toward electrochemical sensing of urea. A filter paper and CNTs were used for the porous matrix and the conductive network, respectively. The hierarchical nickel cobalt oxide was synthesized with a one-pot hydrothermal method with the variation of Ni:Co atomic ratio, and then applied to the paper substrate. The structure and morphology of paper-based electrodes were characterized by XRD, SEM, and EDS, and the electrochemical response was measured by a potentiostat. A detailed description of the fabrication of paper-based sensors and the effect of hierarchical structure and bimetallic composition will be presented. [1] B. K. Boggs, R. L. King, and G. G. Botte, “Urea electrolysis: direct hydrogen production from urine,” Chem. Commun., no. 32, pp. 4859–4861, Aug. 2009, doi: 10.1039/B905974A. [2] L. Liu, H. Mo, S. Wei, and D. Raftery, “Quantitative analysis of urea in human urine and serum by 1 H nuclear magnetic resonance,” Analyst, vol. 137, no. 3, pp. 595–600, 2012, doi: 10.1039/C2AN15780B. [3] K. Kim et al., “Fabrication of a Urea Biosensor for Real-Time Dynamic Fluid Measurement,” Sensors, vol. 18, no. 8, Art. no. 8, Aug. 2018, doi: 10.3390/s18082607. [4] Nie, Huagui, et al. "Non-enzymatic electrochemical detection of glucose using well-distributed nickel nanoparticles on straight multi-walled carbon nanotubes." Biosensors and Bioelectronics 30.1 (2011): 28-34. [5] Ding, Rui, et al. "Facile synthesis of mesoporous spinel NiCo2O4 nanostructures as highly efficient electrocatalysts for urea electro-oxidation." Nanoscale 6.3 (2014): 1369-1376. [6] Liang, Yanhui, et al. "Enhanced electrooxidation of urea using NiMoO4· xH2O nanosheet arrays on Ni foam as anode." Electrochimica Acta 153 (2015): 456-460. [7] Periyasamy, Sivakumar, et al. "Exceptionally active and stable spinel nickel manganese oxide electrocatalysts for urea oxidation reaction." ACS applied materials & interfaces 8.19 (2016): 12176-12185.
19
Sazinas, Rokas, Mattia Saccoccio, Katja Li, Suzanne Zamany Andersen, Shaofeng Li, Jakob B. Pedersen, Jakob Kibsgaard, Peter Vesborg, Debasish Chakraborty, and Ib Chorkendorff. "Role and Control of Solid-Electrolyte Interphase in Lithium-Mediated Electrochemical Ammonia Synthesis." ECS Meeting Abstracts MA2022-02, no. 49 (October 9, 2022): 1927. http://dx.doi.org/10.1149/ma2022-02491927mtgabs.
Анотація:
Lithium-mediated electrochemical ammonia synthesis (LiMEAS) is a way-to-go to reduce nitrogen at ambient pressure and temperature, thus avoiding harsh conditions of industrial standard Haber-Bosch process.1 Inspired by Tsuneto,2 we showed how the choice of electrolyte solvent has a considerable effect both in terms of ammonia yield and electrolyte degradation, which affects the long term stability.3 Recently, we introduced a strategy to improve LiMEAS by pulsed instead of constant current over time leading to considerably higher Faradaic efficiency.4 The pulsed current kept the electrode cleaner from deposit, which allowed the system to run for a longer time. The thinner deposit decreased the ohmic losses, thus increasing the energy efficiency of the electrosynthesis process. Including our discovery that small amounts of oxygen (O2) added to nitrogen (N2) enhance Faradaic efficiency of LiMEAS,5 the role of the solid-electrolyte interphase (SEI) has to be understood, in order to make LiMEAS stable, reliable, and more efficient. The SEI is responsible for performance and stability of Li-ion batteries (LIB).6 It grows on the working electrode (WE) once the deposited lithium contacts the electrolyte resulting in the materials from electrolyte decomposition. Inorganic, organic and polymeric compounds are the main components of this layer, which can be controlled. The same is expected in LiMEAS, since the organic byproducts in electrolyte are formed during electrosynthesis.3 In an ideal case, only Li+ and H+ should diffuse through this layer, shielding the reactive electrode against further reduction reactions.7 However, the composition, behavior and specific role of SEI in LiMEAS is not known, and the field lacks of studies on it. In this work we show what SEI in LiMEAS is and how its formation and properties can be tuned. An operando electrochemical quartz crystal microbalance (EQCM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), gas chromatography-mass spectrometry (GCMS) and nuclear magnetic resonance (NMR) were employed to determine dynamic, mechanical and chemical SEI properties as a function of time, electrolyte, gases, and additives. We focus on the physical behavior and chemical composition changes on the electrodes and in the electrolyte. The role of SEI was elaborated in detail by comparing electrochemical operation conditions, constant and pulsed current, introducing additives to the electrolyte or exchanging electrolyte components. When the current is pulsed, electrolyte decomposition triggers slower and more controllable interphase growth with some mass stripping during relaxation compared to rapid growth in constant current LiMEAS. Due to these (electro-)chemical processes, the interphase formed on cathodes with pulsed current is thinner, less rigid and more viscous than formed with constant current. Furthermore, addition of O2 to N2 suppresses the electrolyte degradation and chemical side reactions, leading to a more efficient and chemically stable LiMEAS. High performance of LiMEAS with optimal O2 was attributed to the formation of a stable and efficient SEI on the surface of the working electrode, and the subsequent suppression of HER from electrolyte. The main phases in SEI were lithium hydroxides (LiOH∙xH2O), carbonate (LiCO3), and ethoxide (LiOEt). However, larger masses in EQCM and NMR describe polytetrahydrofuran (polyTHF) network formation. This work additionally elaborates on the effect of LiMEAS and consequent SEI on the electrolyte decomposition. Our results point towards efficient, stable and robust LiMEAS with highly dynamic structure–activity–stability relationship of the electrode interphase for, but not limited to, LiMEAS. C. Li, T. Wang and J. Gong, Transactions of Tianjin University, 2020, 26, 67-91. A. Tsuneto, A. Kudo and T. Sakata, Chem. Lett., 1993, 22, 851-854. R. Sažinas, S. Z. Andersen, K. Li, M. Saccoccio, K. K., J. B. Pedersen, J. Kibsgaard, P. K. K. Vesborg, D. Chakraborty and I. Chorkendorff, Submitted, 2021. S. Z. Andersen, M. J. Statt, V. J. Bukas, S. G. Shapel, J. B. Pedersen, K. Krempl, M. Saccoccio, D. Chakraborty, J. Kibsgaard, P. C. K. Vesborg, J. Nørskov and I. Chorkendorff, Energy & Environ. Sci., 2020, 13, 4291-4300. K. Li, S. Z. Andersen, M. J. Statt, M. Saccoccio, V. J. Bukas, K. Krempl, R. Sažinas, J. B. Pedersen, V. Shadravan, Y. Zhou, D. Chakraborty, J. Kibsgaard, P. C. K. Vesborg, J. K. Nørskov and I. Chorkendorff, Science (New York, N.Y.), 2021, 374, 1593-1597. S. K. Heiskanen, J. Kim and B. L. Lucht, Joule, 2019, 3, 2322–2333. L. Wang, A. Menakath, F. Han, Y. Wang, P. Y. Zavalij, K. J. Gaskell, O. Borodin, D. Iuga, S. P. Brown, C. Wang, K. Xu and B. W. Eichhorn, Nat. Chem., 2019, 11, 789-796.
20
Wellnitz, David, Guido Pupillo, and Johannes Schachenmayer. "Disorder enhanced vibrational entanglement and dynamics in polaritonic chemistry." Communications Physics 5, no. 1 (May 17, 2022). http://dx.doi.org/10.1038/s42005-022-00892-5.
Анотація:
AbstractCollectively coupling molecular ensembles to a cavity has been demonstrated to modify chemical reactions akin to catalysis. Theoretically understanding this experimental finding remains an important challenge. In particular the role of quantum effects in such setups is an open question of fundamental and practical interest. Theoretical descriptions often neglect quantum entanglement between nuclear and electro-photonic degrees of freedom, e.g., by computing Ehrenfest dynamics. Here we discover that disorder can strongly enhance the build-up of this entanglement on short timescales after incoherent photo-excitation. We find that this can have direct consequences for nuclear coordinate dynamics. We analyze this phenomenon in a disordered Holstein-Tavis-Cummings model, a minimal toy model that includes all fundamental degrees of freedom. Using a numerical technique based on matrix product states we simulate the exact quantum dynamics of more than 100 molecules. Our results highlight the importance of beyond Born-Oppenheimer theories in polaritonic chemistry.
21
Vigneau, Jean-Nicolas, Thanh-Tung Nguyen Dang, and Eric Charron. "Electro-Nuclear Dynamics of Single and Double Ionization of H2 in Ultrafast Intense Laser Pulses." Journal of Physical Chemistry A, February 13, 2024. http://dx.doi.org/10.1021/acs.jpca.3c06525.
22
Li, Shenghao, Jing Lin, Mareen Schaller, Sylvio Indris, Xin Zhang, Torsten Brezesinski, Ce-Wen Nan, Shuo Wang, and Florian Strauss. "High‐Entropy Lithium Argyrodite Solid Electrolytes Enabling Stable All‐Solid‐State Batteries." Angewandte Chemie, October 30, 2023. http://dx.doi.org/10.1002/ange.202314155.
Анотація:
Superionic solid electrolytes (SEs) are essential for bulk‐type solid‐state battery (SSB) applications. Multicomponent SEs are recently attracting attention for their favorable charge‐transport properties, however a thorough understanding of how configurational entropy (ΔSconf) affects ionic conductivity is lacking. Here, we successfully synthesized a series of halogen‐rich lithium argyrodites with the general formula Li5.5PS4.5ClxBr1.5−x (0 ≤ x ≤ 1.5). Using neutron powder diffraction and 31P magic‐angle spinning nuclear magnetic resonance spectroscopy, the S2−/Cl−/Br− occupancy on the anion sublattice was quantitatively analyzed. We show that disorder positively affects Li‐ion dynamics, leading to a room‐temperature ionic conductivity of 22.7 mS cm−1 (9.6 mS cm−1 in cold‐pressed state) for Li5.5PS4.5Cl0.8Br0.7 (ΔSconf = 1.98R). To the best of our knowledge, this is the first experimental evidence that configurational entropy of the anion sublattice correlates with ion mobility. Our results indicate the possibility of improving ionic conductivity in ceramic ion conductors by tailoring the degree of compositional complexity. Moreover, the Li5.5PS4.5Cl0.8Br0.7 SE allowed for stable cycling of single crystal LiNi0.9Co0.06Mn0.04O2 (s‐NCM90) composite cathodes in SSB cells, underscoring the unique opportunity to achieve both high ionic conductivity paired with (electro)chemical stability with dual‐substituted lithium argyrodites.
23
Li, Shenghao, Jing Lin, Mareen Schaller, Sylvio Indris, Xin Zhang, Torsten Brezesinski, Ce-Wen Nan, Shuo Wang, and Florian Strauss. "High‐Entropy Lithium Argyrodite Solid Electrolytes Enabling Stable All‐Solid‐State Batteries." Angewandte Chemie International Edition, October 30, 2023. http://dx.doi.org/10.1002/anie.202314155.
Анотація:
Superionic solid electrolytes (SEs) are essential for bulk‐type solid‐state battery (SSB) applications. Multicomponent SEs are recently attracting attention for their favorable charge‐transport properties, however a thorough understanding of how configurational entropy (ΔSconf) affects ionic conductivity is lacking. Here, we successfully synthesized a series of halogen‐rich lithium argyrodites with the general formula Li5.5PS4.5ClxBr1.5−x (0 ≤ x ≤ 1.5). Using neutron powder diffraction and 31P magic‐angle spinning nuclear magnetic resonance spectroscopy, the S2−/Cl−/Br− occupancy on the anion sublattice was quantitatively analyzed. We show that disorder positively affects Li‐ion dynamics, leading to a room‐temperature ionic conductivity of 22.7 mS cm−1 (9.6 mS cm−1 in cold‐pressed state) for Li5.5PS4.5Cl0.8Br0.7 (ΔSconf = 1.98R). To the best of our knowledge, this is the first experimental evidence that configurational entropy of the anion sublattice correlates with ion mobility. Our results indicate the possibility of improving ionic conductivity in ceramic ion conductors by tailoring the degree of compositional complexity. Moreover, the Li5.5PS4.5Cl0.8Br0.7 SE allowed for stable cycling of single crystal LiNi0.9Co0.06Mn0.04O2 (s‐NCM90) composite cathodes in SSB cells, underscoring the unique opportunity to achieve both high ionic conductivity paired with (electro)chemical stability with dual‐substituted lithium argyrodites.
24
Huang, Miaosen, Yiwei Peng, Qida He, Linyu Lian, Yichen Wang, Longbin Zhang, Yuan Zhang, Jiacheng Shen, and Zongbao Yang. "NMR-based metabonomics reveals the dynamic effect of electro-acupuncture on central nervous system in gastric mucosal lesions (GML) rats." Chinese Medicine 17, no. 1 (March 21, 2022). http://dx.doi.org/10.1186/s13020-022-00593-9.
Анотація:
Abstract Background Gastric mucosal lesions (GML) are common in gastric diseases and seriously affect the quality of life. There are inevitable side effects in drug therapy. Acupuncture is an important part of traditional Chinese medicine. Electro-acupuncture (EA) has unique curative effect in treatment of GML. However, there are still few reports on the central mechanism of electro-acupuncture in treatment of GML. In this study, NMR metabonomics was used to explore the central metabolic change mechanism of electro-acupuncture in treatment of GML. Methods SD rats were randomly divided into Control, GML and EA groups. According to different intervention time, each group was further divided into 3 subgroups. This study mainly established GML model rats by 75% ethanol. Dynamic expressions of metabolites in cerebral cortex and medulla were observed by 1D 1H Nuclear Magnetic Resonance (NMR) metabolomics, combined with gastric mucosal histopathological examination to evaluate the time-effect relationship of electro-acupuncture at Zusanli (ST36) and Liangmen (ST21) points for 1 day, 4 days and 7 days treatment of GML. Results The results showed that the repair effect of electro-acupuncture on gastric mucosal injury was the most obvious in 4 days and stable in 7 days, and 4 days electro-acupuncture can effectively inhibit GML gastric mucosal inflammation and the expression of inflammatory cells. Meanwhile, the NMR spectrum results of medulla and cerebral cortex showed that, 21 potential metabolites were identified to participate in the mechanism of pathogenesis of GML and the regulation of electro-acupuncture, including 15 in medulla and 10 in cerebral cortex. Metabolic pathway analysis showed that the differential metabolites involved 19 metabolic pathways, which could be divided into energy, neurotransmitters, cells and cell membrane and antioxidation according to their functions. The correlation analysis of stomach, medulla and cerebral cortex shows that the stimulation signal of GML may reach the cerebral cortex from the stomach through medulla, and electro-acupuncture can treat GML by regulating the central nervous system (CNS). Conclusions 4 days electro-acupuncture treatment can significantly improve gastric mucosal injury, and the curative effect tends to be stable in 7 days treatment. Meanwhile, the pathogenesis of GML and the efficacy of electro-acupuncture involve metabolic pathways such as energy, neurotransmitters, cells and antioxidation, and electro-acupuncture can treat GML by regulating CNS.
25
Murillo, Edwin A., Pedro P. Vallejo, and Betty L. López. "Characterization of hydroxylated hyperbranched polyesters of fourth and fifth generation." e-Polymers 10, no. 1 (December 1, 2010). http://dx.doi.org/10.1515/epoly.2010.10.1.1347.
Анотація:
AbstractHydroxylated hyperbranched polyester (HBPs) of fourth and fifth generation were obtained by three methods; one step (HBP4, HBP5), step by step (HBP4P, HBP5P) and combinations of one step and step by step (HBP1-4, HBP1- 5). The HBPs were synthesized in bulk from 2,2-bis(hydroxymethyl)propionic acid (DMPA) and pentaerythritol (PE) using acid catalysis (p-toluenesulfonic acid) and characterized by infrared analysis, 1H and 13C nuclear magnetic resonance, gel permeation chromatography, vapor pressure osmometry, electro spray ionizationmass spectrometry, dynamic light scattering, refractive index, thermogravimetric and differential scanning calorimetric analysis. The refractive index of HBPs were low, the infrared and nuclear magnetic resonance analysis showed evidence of the occurrence of reaction between from 2,2-bis(hydroxymethyl) propionic acid (DMPA) and pentaerythritol (PE). The molar mass values of the HBPs determined by gel permeation chromatography were different to vapor pressure osmometry measurements due to small hydrodynamic volume of the HBPs. The mass spectrometry analysis showed different acyclic and cyclic units in the HBPs. The distributions of HBPs studied by dynamic light scattering were monomodal in number and volume and bimodal in intensity. The thermal stability of the fifth generation HBPs was higher than that the fourth generation. All HBPs presented amorphous behavior
26
Patkós, A. "Electromagnetic energy transfer processes in effective electro-magneto dynamics of axions." Modern Physics Letters A, October 18, 2023. http://dx.doi.org/10.1142/s0217732323501377.
Анотація:
Oscillating and dissipative energy exchange between the electromagnetic and axion fields is investigated in an effective electro-magneto dynamical (EEMD) model theory, implying the coexistence of axions with hypothetic magnetic charges. An exact formula is presented for the energy transfer between the electromagnetic and axionic sectors. In a first example, we compute analytically the homogeneously oscillating electric and magnetic field configurations generated by the combined action of a constant static magnetic field and a periodically oscillating axion condensate. In the second example, the electromagnetic radiative energy loss of a gravitationally bound axion configuration is computed in the EEMD model. As a result, an asymptotic [Formula: see text] temporal increase of the clump size is found also in EEMD.
27
Liu, Yi, Stefano Moretti, and Harri Waltari. "Measuring neutrino dynamics in NMSSM with a right-handed sneutrino LSP at the ILC." Journal of High Energy Physics 2022, no. 1 (January 2022). http://dx.doi.org/10.1007/jhep01(2022)034.
Анотація:
Abstract We study the possibility of measuring neutrino Yukawa couplings in the Next-to-Minimal Supersymmetric Standard Model with right-handed neutrinos (NMSSMr) when the lightest right-handed sneutrino is the Dark Matter (DM) candidate, by exploiting a ‘dijet + dilepton + Missing Transverse Energy’ (MET or "Image missing") signature. We show that, contrary to the miminal realisation of Supersymmetry (SUSY), the MSSM, wherein the DM candidate is typically a much heavier (fermionic) neutralino state, this extended model of SUSY offers one with a much lighter (bosonic) state as DM that can then be produced at the next generation of e+e− colliders with energies up to 500 GeV or so. The ensuing signal, energing from chargino pair production and subsequent decay, is extremely pure so it also affords one with the possibility of extracting the Yukawa parameters of the (s)neutrino sector. Altogether, our results serve the purpose of motivating searches for light DM signals at such machines, where the DM candidate can have a mass around the Electro-Weak (EW) scale.
28
Kaselouris, Evaggelos, Alexandros Skoulakis, Vasilis Menelaos Dimitriou, Ioannis Fitilis, John Chatzakis, Makis Bakarezos, Nektarios Andrea Papadogiannis, and Michael Tatarakis. "Progress on the electro-thermo-mechanical instability and its role as seed on plasma instabilities." Plasma Physics and Controlled Fusion, August 16, 2022. http://dx.doi.org/10.1088/1361-6587/ac8a15.
Анотація:
Abstract Ιt was recently demonstrated that a newly explored instability, which was named Electro-Thermo-Mechanical (ETM) instability, was developed in the solid elastic phase in the case of an electrically exploded conductor in the skin effect mode. Here we present new advances in the exploration of the role of the ETM instability as seed of the Magneto-Hydro-Dynamic (MHD) instabilities that are later observed in the plasma phase. Our study, through analytical calculations, simulations and experiments, demonstrates the whole evolution dynamics of the instability amplitude, from the solid to the plasma phase, including the phase transitions. It is validated that the sustained axial wavelength modes in the plasma phase lie in the range of values of those of the ETM instability developed in the solid phase. The results are of significant importance for understanding the role of the ETM instability as seeding for the later observed instabilities in the plasma phase.
29
Ononye, Onyekachi E., Christopher W. Sausen, Matthew W. Bochman, and Lata Balakrishnan. "Lysine Acetylation of Nuclear Pif1 Regulates Its Helicase Function." FASEB Journal 31, S1 (April 2017). http://dx.doi.org/10.1096/fasebj.31.1_supplement.lb51.
Анотація:
Petite integration frequency 1 (Pif1) is a 5′‐3′ helicase which plays a significant role in maintaining the fidelity of nuclear and mitochondrial DNA. Pif1 preferentially unwinds RNA‐DNA hybrids during key metabolic processes such as DNA replication, repair and telomere maintenance. Regulation of Pif1 activity by phosphorylation modulates the role of this helicase in telomere maintenance. Our current work is focused on understanding how lysine acetylation modifies the protein's activity. Lysine acetylation of proteins is a dynamic modification that is regulated by the activity of acetyltransferases and deacetylases. Using biochemical assays we characterized the enzymatic activity of acetylated Pif1, which was modified in vitro using the Gcn5/Ada2/Ada3 and Rtt109/Vps75 acetyltransferase complexes. Helicase assays revealed an enhanced unwinding function of Pif1 upon protein acetylation. Additionally, the ATPase activity of acetylated Pif1 was also significantly stimulated compared to the unmodified form. In concert, the binding function of acetylated Pif1 to its cognate substrates was also improved when assessed using gel electro‐mobility shift assay (EMSA) in tandem with Bio‐layer interferometry technology (BLI). Mass spectrometric analysis of the in vitro acetylated Pif1 protein revealed some acetylated lysine residues on the N‐terminus of the protein. Current work is focused on understanding how acetylation based Pif1 regulation impacts its role in the maintenance of genome fidelity.Support or Funding InformationIUPUI New Faculty Start Up GrantNIH R00 GM98328
30
Khatsymovsky, V. M. "On the discrete version of the Reissner–Nordström solution." International Journal of Modern Physics A 37, no. 11n12 (April 30, 2022). http://dx.doi.org/10.1142/s0217751x22500646.
Анотація:
This paper generalizes our previous work on the discrete Schwarzschild-type solution in Regge calculus to the case of a charge. The known in the literature simplicial electro-dynamics retaining like Regge calculus geometric features of the continuum counterpart is incorporated into the formalism. The functional integral provides a loose fixation of edge lengths around some scale and a perturbative expansion, for which we consider, in essence, finding the optimal starting (background) metric/field from the skeleton Regge and electro-dynamic equations. The simplest periodic simplicial structure and the expansion over metric/field variations between 4-simplices are considered. In the leading order of this expansion, the electromagnetic action, as we found earlier for the Regge action, is reducible to a finite-difference form of the continuum counterpart. Instead of infinite continuous metric/field variables at the center, we have finite discrete variables; the discrete metric in the Schwarzschild-type coordinates turns out to change the sign of its variation when approaching the center from the nearest vertices, so that [Formula: see text] is positive at the center (the continuum [Formula: see text] tends to [Formula: see text] at the center). The metric/field in the neighborhood of the center and the curvature and the Kretschmann scalar at the center are estimated.
31
Schwarz, Nina, Francisco Javier Artola, Matthias Hoelzl, Matthias Bernert, Dominik Brida, Louis Giannone, Marc Maraschek, et al. "Experiments and non-linear MHD simulations of hot vertical displacement events in ASDEX-Upgrade." Plasma Physics and Controlled Fusion, March 10, 2023. http://dx.doi.org/10.1088/1361-6587/acc358.
Анотація:
Abstract Hot Vertical Displacement Events (VDEs) are one of the worst case scenarios for high current tokamaks as they are associated with large heat loads and electro-magnetic forces. 
Non-linear magneto-hydrodynamic (MHD) simulations of the thermal and current quench can help to understand their dynamics and consequences. 
In order to make predictions for future devices, the validation of codes against present machines is crucial.
Dedicated experiments were performed in ASDEX Upgrade to provide a basis for simulations with the non-linear extended MHD code JOREK. 
2D as well as non-axisymmetric simulations at realistic parameters can reproduce quantities like the edge safety factor $q_{95}$ at the thermal quench (TQ) onset, the halo current magnitude and the level of vertical forces, while the exact width of the halo current area requires more sophisticated boundary conditions and is left for future work. Small horizontal forces are observed during the hot VDEs in the experiment as well as in the simulations.
32
Bourquard, Claire, and Nicolas Noiray. "Stability and Limit Cycles of a Nonlinear Damper Acting on a Linearly Unstable Thermoacoustic Mode." Journal of Engineering for Gas Turbines and Power 141, no. 5 (December 17, 2018). http://dx.doi.org/10.1115/1.4042080.
Анотація:
The resonant coupling between flames and acoustics is a growing issue for gas turbine manufacturers, which can be reduced by adding acoustic dampers on the combustion chamber walls. Nonetheless, if the engine is operated out of the stable window, the damper is exposed to high-amplitude acoustic levels, which trigger unwanted nonlinear effects. This work provides an overview of the dynamics of this coupled system using a simple analytical model, where a perfectly tuned damper is coupled to the combustion chamber. The damper, crossed by a purge flow in order to prevent hot gas ingestion, is modeled as a nonlinearly damped harmonic oscillator. The combustion chamber featuring a linearly unstable thermoacoustic mode is modeled as a Van der Pol oscillator. Analyzing the averaged amplitude equations gives the limit cycle amplitudes as function of the growth rate of the unstable mode and the mean velocity through the damper neck. Experiments are also performed on a simple rectangular cavity, where the thermoacoustic instability is mimicked by an electro-acoustic instability. A feedback loop is built, through which the growth rate of the instability can be controlled. A Helmholtz damper is added to the cavity and tuned to the mode of interest. The stabilization capabilities of the damper and the amplitude of the limit cycle in the unstable cases are in good agreement between the experiments and the analytical and numerical predictions, underlining the potentially dangerous behavior of the system, which should be taken into account for real engine cases.
33
Sato, S., S. Jovanovic, J. Lang, and Z. Spakovszky. "Demonstration of a Palm-Sized 30 W Air-to-Power Turbine Generator." Journal of Engineering for Gas Turbines and Power 133, no. 10 (May 2, 2011). http://dx.doi.org/10.1115/1.4002826.
Анотація:
A compact, high power density turbo-generator system was conceived, designed, and experimentally tested. The air-to-power (A2P) device with a nominal design point of 50 W electric power output operates on high pressure air such as from a plant pneumatic system or from a portable bottle of pressurized air. A concept design study was first carried out to explore the design space for a range of output power at cost efficiency levels specified in collaboration with industry. The cost efficiency is defined as the cost of electrical power over the cost of pressurized air. The key challenge in the design is the relatively low power demand of 50 W while operating at high supply pressures of nominally 5–6 bars. To meet the cost efficiency goal under these conditions, a high-speed turbine and generator (∼450,000 rpm) are required with small blade span (∼200 μm), minimizing the mass flow while achieving the highest possible turbine performance. Since turbines with such small turbomachinery blading are not commercially available, a silicon-based micro electro mechanical systems (MEMS) turbine was designed using 2D and 3D computational fluid dynamics (CFD) computations. To reduce the development time, existing and previously demonstrated custom-made generator and ceramic ball bearing technology were used, resulting in a compact A2P proof-of-concept demonstration. The cylindrical device of 35 mm diameter resembles a tube fitting with a standard M24 adapter. Without load, a top turbine speed of 475,000 rpm was demonstrated, exceeding the design specification. Using load resistors, the proof-of-concept A2P device achieved 30 W of electrical power at 360,000 rpm and a turbine efficiency of 47%, meeting the cost efficiency goal. Higher speeds under load could not be achieved due to thrust load limitations of the off-shelf ball bearings. The demonstrated performance is in good agreement with the projected CFD based predictions. To the authors’ knowledge, this is the first successful demonstration of a self-contained, 50 W class turbo-generator of hybrid architecture where a MEMS turbine disk is joined with a precision machined titanium shaft and aluminum housing.