bluuebunny/crossref_metadata_2025 huggingface dataset:
Withanone Ameliorates Stress Symptoms in Caenorhabditis Elegans by Acting through Serotonin Receptors
Authors: Naß Janine , Efferth Thomas
Published: May 2021

Introduction Depression is responsible for 800 000 deaths
worldwide, a number that will rise significantly due to the COVID-19
pandemic. Affordable novel drugs with less severe side effects are urgently
required. We investigated the effect of withanone (WN) from Withania
somnifera on the serotonin system of wild-type and knockout Caenorhabditis
elegans strains using in silico, in vitro, and in vivo methods.

Methods WN or fluoxetine (as positive control drug) was administered
to wild-type (N2) and knockout C. elegans strains (AQ866, DA1814, DA2100,
DA2109, and MT9772) to determine their effect on oxidative stress (Trolox,
H2DCFDA, and juglone assays) on osmotic stress and heat
stress and lifespan. Quantitative real-time RT-PCR was applied to
investigate the effect of WN or fluoxetine on the expression of serotonin
receptors (ser-1, ser-4, ser-7) and serotonin transporter
(mod-5). The binding affinity of WN to serotonin receptors and
transporter was analyzed in silico using AutoDock 4.2.6.

Results WN scavenged ROS in wild-type and knockout C. elegans and
prolonged their lifespan. WN upregulated the expression of serotonin
receptor and transporter genes. In silico analyses revealed high binding
affinities of WN to Ser-1, Ser-4, Ser-7, and Mod-5.

Limitations Further studies are needed to prove whether the results
from C. elegans are transferrable to mammals and human beings.

Conclusion WN ameliorated depressive-associated stress symptoms by
activating the serotonin system. WN may serve as potential candidate in
developing new drugs to treat depression.
Acute Response of Sclerostin to Whole-body Vibration with Blood Flow
Restriction
Authors: Gapper Kyle S , Stevens Sally , Antoni Rona , Hunt Julie , Allison Sarah J
Published: May 2021

Blood flow restriction may augment the skeletal response to whole-body
vibration. This study used a randomised, crossover design to investigate the
acute response of serum sclerostin and bone turnover biomarkers to
whole-body vibration with blood flow restriction. Ten healthy males
(mean±standard deviation; age: 27±8 years) completed two
experimental conditions separated by 7 days: (i) whole-body vibration (10
1-minute bouts of whole-body vibration with 30 s recovery) or (ii)
whole-body vibration with lower-body blood flow restriction (10 cycles of
110 mmHg inflation with 30 s deflation during recovery). Fasting blood
samples were obtained immediately before and immediately after exercise,
then 1 hour, and 24 hours after exercise. Serum samples were analysed for
sclerostin, cross-linked C-terminal telopeptide of type I collagen, and
bone-specific alkaline phosphatase. There was a significant time ×
condition interaction for bone-specific alkaline phosphatase
(p=0.003); bone-specific alkaline phosphatase values at 24 hours
post-exercise were significantly higher following whole-body vibration
compared to combined whole-body vibration and blood flow restriction
(p=0.028). No significant time × condition interaction
occurred for any other outcome measure (p>0.05). These findings
suggest that a single session of whole-body vibration combined with blood
flow restriction does not significantly affect serum sclerostin or bone
turnover biomarkers.
Iridium-Catalyzed Site-Selective Borylation of 8-Arylquinolines
Authors: Chattopadhyay Buddhadeb , Hassan Mirja Md Mahamudul , Hoque Md Emdadul , Dey Sayan , Guria Saikat , Roy Brindaban
Published: May 2021

We report a convenient method for the highly site-selective borylation of 8-arylquinoline. The reaction proceeds smoothly in the presence of a catalytic amount of [Ir(OMe)(cod)]2 and 2-phenylpyridine derived ligand using bis(pinacolato)diborane as the borylating agent. The reactions occur with high selectivity with many functional groups, providing a series of borylated 8-aryl quinolines with good to excellent yield and excellent selectivity. The borylated compounds formed in this method can be transformed into various important synthons by using known transformations.
Diastereoselective Synthesis of Spiropyrazolones via 1,3-Dipolar [3+2] Cycloadditions between Pyrazolone-Based Olefins and N,N′-Cyclic Azomethine Imines
Authors: Zhao Hong-Wu , Tang Zhe , Wu Hui-Hui , Fan Xiao-Zu , Zhang Heng , Cai Lu-Yu , Bi Xiao-Fan
Published: May 2021

Under the catalysis of PhCO2H, the 1,3-dipolar [3+2] cyclo­addition between pyrazolone-based olefins and N,N′-cyclic azomethine imines proceeded readily, thus delivering structurally novel spiropyrazolones with up to 98% yield and >20:1 dr. The relative stereochemical configuration of the obtained spiropyrazolones was unambiguously ­assigned by X-ray single-crystal structure analysis. The diastereoselective formation of the title spiropyrazolones was interpreted by the hypothesized reaction mechanism.
Chromium-Catalyzed Cross-Coupling Reactions by Selective Activation of Chemically Inert Aromatic C–O, C–N, and C–H Bonds
Authors: Zeng Xiaoming , Cong Xuefeng
Published: May 2021

Transition-metal-catalyzed cross-coupling has emerged as one of the most powerful and useful tools for the formation of C–C and C–heteroatom bonds. Given the shortage of resources of precious metals on Earth, the use of Earth-abundant metals as catalysts in developing cost-effective strategies for cross-coupling is a current trend in synthetic chemistry. Compared with the achievements made using first-row nickel, iron, cobalt, and even manganese catalysts, the group 6 metal chromium has rarely been used to promote cross-coupling. This perspective covers recent advances in chromium-catalyzed cross-coupling reactions in transformations of chemically inert C(aryl)–O, C(aryl)–N, and C(aryl)–H bonds, offering selective strategies for molecule construction. The ability of low-valent Cr with a high-spin state to participate in two-electron oxidative addition is highlighted; this is different from the mechanism involving single-electron transfer that is usually assigned to chromium-mediated transformations.

1 Introduction

2 Chromium-Catalyzed Kumada Coupling of Nonactivated C(aryl)–O and C(aryl)–N Bonds

3 Chromium-Catalyzed Reductive Cross-Coupling of Two Nonactivated C(aryl)–Heteroatom Bonds

4 Chromium-Catalyzed Functionalization of Nonactivated C(aryl)–H Bonds

5 Conclusions and Outlook
Cesium Carbonate Mediated Cyclization of Oxotryptamines with Allenoates: An Approach to Spiro[azepane-4,3′-indol]-2′(1′H)-ones
Authors: Shi Min , Yang Ze-ren
Published: May 2021

A new method was developed for the synthesis of spiro[azepane-4,3′-indol]-2′(1′H)-ones in yields of up to 96% with a broad substrate scope by using oxotryptamines as dual-nucleophilic reagents to react with allenoates in the presence of cesium carbonate under mild conditions. In accord with previous works and a deprotonation-tracing experiment, a plausible reaction mechanism is proposed.
Transcavernous Approach to the Anteromedial Triangle for Residual Functional Pituitary Adenoma
Authors: Starnoni Daniele , Cossu Giulia , Messerer Mahmoud , Daniel Roy Thomas
Published: May 2021

Surgical treatment of functional pituitary adenomas is as rule performed by transsphenoidal approach. However, when then lesion invades the parasellar structures and the cavernous sinus, the transsphenoidal removal of these adenomas is usually incomplete. In this video, we present the technical nuances of a transcavernous approach to the anterio-medial triangle for the resection of a residual functional pituitary adenoma. The patient is a 40-year-old male who was diagnosed with growth hormone secreting pituitary macroadenoma. He underwent two transsphenoidal resections in 2013 and 2016 with a small residue in the left cavernous sinus. Subsequently, due to a failure of biochemical remission despite medical management, a transcranial transcavernous surgery was performed. Brain magnetic resonance imaging showed a mass in the roof of the left cavernous sinus, located at the level of the anteromedial triangle, adherent to the clinoidal segment of the internal carotid artery (ICA). The computed tomographic scan showed an osteolysis of the inferior surface of the anterior clinoidal process. After performing an extended pterional craniotomy and an extradural clinoidectomy, the cleavage plane is extended between the temporal dura and the inner layer of the lateral wall of the cavernous sinus. Intraoperative Doppler and stimulation are used to localize the clinoidal segment of the ICA and the third cranial nerve, delimiting the anteromedial triangle. The lesion is progressively dissected and removed. An optic neuropexy with the previously harvested fat is performed in case of a complementary radio surgical treatment. The patient had an uneventful postoperative course and showed a biochemical remission at the 3-month follow-up.

The link to the video can be found at: https://youtu.be/oHfugVtU-Nc.
Transcavernous Approach for Microsurgical Clipping of Ruptured Right Superior Cerebellar Artery Aneurysm with Cadaveric Stepwise Video Illustration
Authors: Najera Edinson , Muhsen Baha'eddin A. , Borghei-Razavi Hamid , obrzut Michal , Adada Badih
Published: May 2021

Superior cerebellar artery (SCA) aneurysms are rare. The management options are not well defined. There is increasing role of endovascular treatment for all aneurysms, especially for aneurysms of the posterior circulation. However in some situations (wide base, dysmorphic features) coiling is not feasible. The surgical management of these aneurysms has its own distinct complexity and requires careful planning. The classic pterional or subtemporal approaches had its own limitation in proper visualization of the neurovascular anatomy.

In this video, we describe the technical nuances of transcavernous sinus approach for microsurgical clipping SCA and A-comm aneurysms. We present the case of a 67-year-old RHF who presented with ruptured right-sided SCA aneurysm. She complained of Headache, confusion, and double vision. On physical examination, she had no focal deficits and was Hunt and Hess grade 3. A brain computed tomography (CT) scan revealed a subarachnoid hemorrhage Fisher's grade 4. A brain CT angiography (CTA) demonstrated an aneurysm at the origin of right SCA. The patient had failed attempt of endovascular coiling and she underwent microsurgical clipping.

Stepwise demonstration of the approach with cadaveric anatomical dissection is illustrated. The technique presented here allows for safe clipping of the aneurysm through the cavernous sinus. The approach allows for good exposure of the aneurysm and the surrounding structures. Care is taken to visualize the perforators to avoid any devastating brain stem infarction during the clipping.

The transcavernous sinus is a robust approach with good visualization of the neurovascular structures allowing safe aneurysm clipping in this location.

The link to the video can be found at: https://youtu.be/oE-HyDASiKM.
Leveraging Artificial Intelligence to Improve Chronic Disease Care: Methods and Application to Pharmacotherapy Decision Support for Type-2 Diabetes Mellitus
Authors: Tarumi Shinji , Takeuchi Wataru , Chalkidis George , Rodriguez-Loya Salvador , Kuwata Junichi , Flynn Michael , Turner Kyle M. , Sakaguchi Farrant H. , Weir Charlene , Kramer Heidi , Shields David E. , Warner Phillip B. , Kukhareva Polina , Ban Hideyuki , Kawamoto Kensaku
Published: May 2021

Objectives Artificial intelligence (AI), including predictive analytics, has great potential to improve the care of common chronic conditions with high morbidity and mortality. However, there are still many challenges to achieving this vision. The goal of this project was to develop and apply methods for enhancing chronic disease care using AI.

Methods Using a dataset of 27,904 patients with diabetes, an analytical method was developed and validated for generating a treatment pathway graph which consists of models that predict the likelihood of alternate treatment strategies achieving care goals. An AI-driven clinical decision support system (CDSS) integrated with the electronic health record (EHR) was developed by encapsulating the prediction models in an OpenCDS Web service module and delivering the model outputs through a SMART on FHIR (Substitutable Medical Applications and Reusable Technologies on Fast Healthcare Interoperability Resources) web-based dashboard. This CDSS enables clinicians and patients to review relevant patient parameters, select treatment goals, and review alternate treatment strategies based on prediction results.

Results The proposed analytical method outperformed previous machine-learning algorithms on prediction accuracy. The CDSS was successfully integrated with the Epic EHR at the University of Utah.

Conclusion A predictive analytics-based CDSS was developed and successfully integrated with the EHR through standards-based interoperability frameworks. The approach used could potentially be applied to many other chronic conditions to bring AI-driven CDSS to the point of care.
Pulmonary Support of Infants with Tracheotomies in a Regional Neonatal Intensive Care Unit
Authors: Attar Mohammad A. , Pace Rachael A. , Schumacher Robert E.
Published: May 2021

Objective We evaluate patient characteristics, hospital course, and outcome by type discharge pulmonary support; mechanical ventilation (MV) or with tracheotomy masks (TM).

Study Design We reviewed records of infants admitted to the neonatal intensive care unit (NICU) that underwent tracheotomy within their first year of life between 2006 and 2017. We evaluated patient characteristics, referral pattern, destination of discharge, and outcome by type of pulmonary support at discharge (MV vs. TM).

Results Of the 168 patients, 63 (38%) were inborn, 91 (54%) transferred to our NICU, and 5 (3%) were readmitted after being home. Median gestational age at birth was 34 weeks. Twenty-three (14%) infants were transferred to hospitals closer to their homes (13 with MV and 10 with TM), and 125 (74%) were discharged home (75 on MV and 50 on TM). Twenty patients (12%) died in the regional center (RC). Among those discharged home from our RC, infants on MV were of lower birth weight and younger gestational age, had tracheostomies later in life, had longer duration between tracheostomy to discharge to home, and had longer total duration of hospitalization at the RC. In addition, infants in the MV group were more frequently dependent on MV at time of placement of tracheostomies, less frequently had congenital airway anomalies and more frequently having possibly acquired airway anomalies and more frequently having major congenital anomalies, more frequently treated with diuretics, inhaled medications and medications for pulmonary hypertension, and more frequently had gastrostomies for feeding compared with the TM group.

Conclusion Patients with tracheostomies in the NICU and discharged from RC on MV or TM vary by patient characteristic, timing of tracheostomy placement, timing of discharge from RC, type of upper airway anomalies, duration of stay in the hospital, and complexity of medical condition at discharge.

Key Points
Clinicoradiological Features and Treatment Outcome of Supratentorial Intraparenchymal Epidermoid Cyst: A Report of Five Cases and Literature Review
Authors: Kumar Ashutosh , Maurya Ved Prakash , Kanjilal Soumen , Bhaisora Kamlesh Singh , Sardhara Jayesh , Das Kuntal Kanti , Mehrotra Anant , Srivastava Arun Kumar , Jaiswal Awadhesh Kumar , Behari Sanjay
Published: May 2021

Objectives Intraparenchymal epidermoid cysts (IECs) are rare lesions. They represent less than 1% of the intracranial epidermoid cysts. The supratentorial IEC is a clinically and prognostically distinct subset. Given the rarity, most of the articles are case reports. We present a series of five cases of supratentorial IEC to characterize their clinical presentation and outcome, with emphasis on the surgical features.

Materials and Methods We searched our database for all cases of intracranial epidermoid cysts operated between January 2005 and January 2020. Five patients were identified having IEC from the hospital information system and the neurosurgical operation record book. Standard craniotomy and decompression of the lesion were performed in all these patients. Standard postoperative care includes computed tomography scan of head on the day of surgery and magnetic resonance imaging of brain after 6 weeks to look for the residual lesion, if any. Subsequent follow-up visits in outpatient department to look for resolution of the presurgical symptoms.

Results The mean age of the patients in our series was 28.8 years (range: 28–40 years.). All the five patients were male. Four patients had IEC involving frontal lobe and one in parietal lobe with a small occipital lobe extension. Seizure was the most common presenting complaint followed by headache. Complete excision was achieved in all the cases. All the three patients with seizure attained seizure freedom postlesionectomy. Focal neurological deficits resolved gradually in postoperative period. There was no recurrence of lesion during follow-up.

Conclusion Supratentorial IEC most commonly affects young males, involve frontal lobe and present clinically with seizure. Complete surgical excision offers best outcome in the form of remission of seizure disorder.
Geometric model of the fracture as a manifold immersed in porous media
Authors: Paranamana Pushpi , Aulisa Eugenio , Toda Magdalena
Published: May 2021

In this work, we analyze the flow filtration process of slightly compressible fluids in porous media containing fractures with complex geometries. We model the coupled fracture-porous media system where the linear Darcy flow is considered in porous media and the nonlinear Forchheimer equation is used inside the fracture. We develop a model to examine the flow inside fractures with complex geometries and variable thickness on a Riemannian manifold. The fracture is represented as the normal variation of a surface immersed in R3. Using operators of Laplace–Beltrami type and geometric identities, we model an equation that describes the flow in the fracture. A reduced model is obtained as a low dimensional boundary value problem. We then couple the model with the porous media. Theoretical and numerical analyses have been performed to compare the solutions between the original geometric model and the reduced model in reservoirs containing fractures with complex geometries. We prove that the two solutions are close and, therefore, the reduced model can be effectively used in large scale simulators for long and thin fractures with complicated geometry.
Patterns produced in water-oil-block copolymer systems
Authors: Larter Raima
Published: May 2021

Phase diagrams for a ternary system consisting of water, oil and ABA triblock copolymers reveal a variety of ordered structures and patterns.
The movement of a particle according to the Gurevich–Zybin dark matter model
Authors: Sarrico C. O. R.
Published: May 2021

We consider the nonlinear 2 × 2 Gurevich–Zybin system as a model for the one-dimensional dynamics of dark matter. In this setting, we evaluate the movement of a particle of mass subjected to a possible jump discontinuity in the hydrodynamic speed. This problem is solved by extending the concept of usual solution to the framework of a product of distributions. A brief survey of the ideas and formulas used for multiplying distributions is included, as well as a physical interpretation of the results involving the observed speed of rotation of stars in galaxies.
Silicon cantilevers locally heated from 300 K up to the melting point: Temperature profile measurement from their resonances frequency shift
Authors: Pottier Basile , Aguilar Sandoval Felipe , Geitner Mickaël , Esteban Melo Francisco , Bellon Ludovic
Published: May 2021

When heated, micro-resonators present a shift of their resonance frequencies. We study specifically silicon cantilevers heated locally by laser absorption and evaluate theoretically and experimentally their temperature profile and its interplay with the mechanical resonances. We present an enhanced version of our earlier model [Sandoval et al., J. Appl. Phys. 117, 234503 (2015)], including both elasticity and geometry temperature dependency, showing that the latter can account for 20% of the observed shift for the first flexural mode. The temperature profile description takes into account thermal clamping conditions, radiation at high temperature, and lower conductivity than bulk silicon due to phonon confinement. Thanks to space–power equivalence in the heat equation, scanning the heating point along the cantilever directly reveals the temperature profile. Finally, frequency shift measurement can be used to infer the temperature field with a few percent precision.
Magnetic and morphological properties of Ca substituted M-type hexaferrite powders synthesized by the molten salt method
Authors: Kim Minyeol , Lee Kwiyoung , Bae Cheoljun , Kim Jongryoul
Published: May 2021

The doping element and morphology are important factors for improving the magnetic properties of M-type hexaferrite powder. As the demand for electromagnetic absorber and magnetic sensors increases in the market, it is required to develop hexaferrite powder with a homogenous shape and excellent magnetic properties. In this study, Ca substituted strontium hexaferrite powders were synthesized by the molten salt method under various calcination conditions. The morphology and magnetic properties of the synthesized powders were successfully controlled according to the Ca content and calcination conditions. As a result, single-crystalline Sr0.90Ca0.10Fe12O19 powders with an average thickness of 0.4 µm were successfully obtained by calcining at 950 °C for 1 h. The synthesized powders had a magnetic saturation of 74.9 emu/g and a coercivity of 3397 Oe.
Long duration x-ray source development for x-ray diffraction at the National Ignition Facility
Authors: Werellapatha K. , Hall G. N. , Coppari F. , Kemp G. E. , Palmer N. E. , Krauland C. , Khan S. F. , Lazicki A. , Gorman M. G. , Nagel S. R. , Heinbockel C. , Bhandarkar N. , Masters N. , Bradley D. K. , Eggert J. H. , Benedetti L. R.
Published: May 2021

We present the results of experiments to produce a 10 ns-long, quasi-monochromatic x-ray source. This effort is needed to support time-resolved x-ray diffraction (XRDt) measurements of phase transitions during laser-driven dynamic compression experiments at the National Ignition Facility. To record XRDt of phase transitions as they occur, we use high-speed (∼1 ns) gated hybrid CMOS detectors, which record multiple frames of data over a timescale of a few to tens of ns. Consequently, to make effective use of these imagers, XRDt needs the x-ray source to be narrow in energy and uniform in time as long as the sensors are active. The x-ray source is produced by a laser irradiated Ge foil. Our results indicate that the x-ray source lasts during the whole duration of the main laser pulse. Both time-resolved and time-integrated spectral data indicate that the line emission is dominated by the He-α complex over higher energy emission lines. Time-integrated spectra agree well with a one-dimensional Cartesian simulation using HYDRA that predicts a conversion efficiency of 0.56% when the incident intensity is 2 × 1015 W/cm2 on a Ge backlighter.
First spatially resolved measurements of the D–3He α-particle source with the upgraded JET gamma-ray camera
Authors: Panontin E. , Rigamonti D. , Nocente M. , Dal Molin A. , Broslawski A. , Craciunescu T. , Croci G. , Cruz N. , Figueiredo J. , Giacomelli L. , Gorini G. , Gosk M. , Kaveney G. , Kazakov Ye. O. , Kiptily V. , Korolczuk S. , Marcer G. , Murari A. , Perelli Cippo E. , Salewski M. , Urban A. , Zychor I. , Tardocchi M. ,   JET Contributors
Published: May 2021

The Joint European Torus (JET) gamma-ray camera has been recently upgraded with the installation of new gamma-ray detectors, based on LaBr3(Ce) scintillation crystals, which add spectroscopic capability to the existing system allowing measurements with good energy resolution (5% at 0.622 MeV), a dynamic range from hundreds of keV up to about 30 MeV, and high counting rate capabilities of MCps. First gamma-ray measurements during the C38 campaign of the JET have been successfully carried out, in particular, in D–3He plasmas from three-ion ion cyclotron resonance heating experiments, where the detection of 16.4 MeV γ-rays from D + 3He → γ + 5Li reactions with the gamma-ray camera upgrade allowed determining the spatial profile of alpha particles born in D + 3He fusion reactions.
Development of an ultrafast charge exchange spectroscopy system on the KSTAR tokamak
Authors: Jang Jae Young , Ko Won-Ha , Li Yingying , von Hellermann Manfred , Shi Yuejiang , Hwang Y. S.
Published: May 2021

An ultrafast charge exchange spectroscopy (UFCES) system has been designed for measuring fluctuations in ion temperature and toroidal rotation velocity. The UFCES on the KSTAR tokamak is a powerful tool for investigating plasma instabilities and long-wavelength turbulence related to ion temperature gradient and flow. The UFCES system is designed to measure the C VI line (n = 8 → 7, λ0 = 529.05 nm) from the charge exchange reaction between a deuterium-heating neutral beam and the intrinsic carbon impurity in KSTAR. The ion temperature and toroidal rotation velocity at two radial positions will be observed simultaneously with UFCES. The key difference between the UFCES system and conventional charge exchange spectrometers is the application of high-throughput collection optics, a high-efficiency transmission grating combined with prisms, and a high-speed detector. We use a comprehensive spectrum simulation code with input parameters of KSTAR’s plasmas and a neutral beam injection system to estimate the performance of the designed UFCES system. The results simulated with the code show that the diagnostic achieves a turbulence-relevant time resolution of 10 µs with a high enough signal-to-noise ratio. Furthermore, a preliminary test is performed using a complementary metal–oxide semiconductor camera and Ne spectral lamp to confirm the linear dispersion and curvature radius.
A wafer-like apparatus for two-dimensional measurement of plasma parameters and temperature distribution in low-temperature plasmas
Authors: Lim Yeong-Min , Eo Hyundong , Kim Kyung-Hyun , Lee Moo-Young , Chung Chin-Wook
Published: May 2021

A wafer-type monitoring apparatus that can simultaneously measure the two-dimensional (2D) distributions of substrate temperature and plasma parameters is developed. To measure the temperature of the substrate, a platinum resistance temperature detector is used. The plasma density and electron temperature are obtained using the floating harmonics method, and incoming heat fluxes from the plasma to the substrate are obtained from the plasma density and electron temperature. In this paper, 2D distributions of the substrate temperature, plasma density, and electron temperature are obtained simultaneously for the first time in inductively coupled plasma. The shapes of the 2D distributions of the substrate temperature and incoming heat flux are similar to each other, but some differences are found. To understand that, an energy balance equation for the substrate is established, which shows good agreement with the experimental results. This apparatus will promote the understanding of surface reactions, which are very sensitive to the temperatures and plasma densities in plasma processing.
Particle simulation of streamer discharges on surface of DC transmission line in presence of raindrops
Authors: Zhang Xin-chun , Wang Feng , Liu Nan-nan , Li An-qi , Fan Wei-li
Published: May 2021

The streamer discharge occurring on the surface of a conductor in rain is one of the critical problems associated with the design of high voltage direct current (HVDC) transmission lines. In this paper, the streamer discharges on the conductor surface in the presence of raindrops at atmospheric pressure are studied by use of two-dimensional particle-in-cell simulations with Monte Carlo collisions included. The influences of the drop angles, volumes, and spatial distributions of raindrops on the development of streamer discharges have been demonstrated. The formation of streamer discharges and the involved electric fields, plasma densities, propagation velocities, and discharge currents are presented. It is found that the discharge intensity decreases significantly with an increasing of the drop angle. The dividing point at the 95° angle is suggested. With an increase of the raindrop volume and the distance of raindrops, strong discharges with the advanced discharge time, faster propagation velocity, larger electric field, and higher plasma density are initiated. Moreover, the electron energy probability functions of different discharges have been studied, which are nonequilibrium and reveal kinetic behavior of the discharges. The simulation results, which are qualitatively in agreement with the previous experimental observations, bring new insight into the discharge dynamics and provide useful references for the protection of HVDC transmission lines in rainy days.
Comment on “The Gibbs free energy of cavity formation in a diverse set of solvents”[J. Chem. Phys. 153, 134501 (2020)]
Authors: Graziano Giuseppe
Published: May 2021

It is pointed out that the unexpected result that the magnitude of the reversible work of cavity creation in ethylene glycol proves to be larger than that in water [I. Sedov and T. Magsumov, J. Chem. Phys. 153, 134501 (2020)] could be due to that (a) the density of the used computational model of this liquid is “significantly” larger than the experimental one and (b) the procedure adopted to perform the comparison among the different liquids is not “strictly” correct. It is also indicated that several lines of evidence suggest that the magnitude of the reversible work of cavity creation in water can be larger than that in ethylene glycol.
Magnetic control of particle trapping in a hybrid plasmonic nanopore
Authors: Maccaferri Nicolò , Vavassori Paolo , Garoli Denis
Published: May 2021

Plasmonic nanopores are extensively investigated as single molecules detectors. The main limitations in plasmonic nanopore technology are the too fast translocation velocity of the molecule through the pore and the consequent very short analysis times, as well as the possible instabilities due to local heating. An interesting approach to enable longer acquisition times is represented by the ability to stably trap the nanoparticles used to tag molecules close to the nanopore. Here, we theoretically investigate the performance of a magneto-plasmonic nanopore prepared with a thin layer of cobalt sandwiched between two gold layers. A nanopore is then coupled with a bifunctional (magnetic and plasmonic) core–shell nanoparticle made of magnetite (core) covered with a thin layer of gold (shell). By setting the magnetic configuration of the cobalt layer around the pore by an external magnetic field, it is possible to generate a nanoscale magnetic tweezer to trap the nanoparticle at a specific point. Considering a ∼10 nm diameter magnetite nanoparticle, we calculate a trapping force up to 28 pN, an order of magnitude above the force that can be obtained with standard optical or plasmonic trapping approaches. Moreover, the magnetic force pulls the nanoparticle in close contact with the plasmonic nanopore's wall, thus enabling the formation of a nanocavity enclosing a sub-10 nm3 confined electromagnetic field with an average field intensity enhancement up to 230 at near-infrared wavelengths. The presented hybrid magneto-plasmonic system points toward a strategy to improve nanopore-based biosensors for single-molecule detection and potentially for the analysis of various biomolecules.
Evolutionary inverse design of defects at graphene 2D lateral interfaces
Authors: Zhang Jianan , Srinivasan Srilok , Sankaranarayanan Subramanian K. R. S. , Lilley Carmen M.
Published: May 2021

Grain boundaries (GBs) in two-dimensional (2D) materials often have a profound impact on various material properties from mechanical to optical to electronic, yet predicting all possible GB formations is a challenge. Here, we introduce a workflow based on an evolutionary algorithm for exploring possible GBs formed at a lateral 2D interface. In a departure from conventional genetic algorithm based structure optimization methods, we perform genetic operations in the near interface region that allow us to be computationally efficient. We benchmark our method using graphene, which is a well-studied 2D material with a wide range of point defects. An empirical potential was used as the surrogate of the evolutionary search. More than 11.5 × 106 structures in total were evaluated for 128 GB orientations, and for each orientation, the ten best structures are recorded. A subset of low energy GBs predicted by empirical potential based search was relaxed by first-principles calculations and used to validate the energetic rank order. With the validated formation energy, we rank-ordered the best 128 GB structures and performed a detailed statistical analysis of primitive rings to find the correlation between the ring distribution and the formation energy. We found that for low energy GBs (below 0.5eV/Å), Stone–Wales defects will dominate, while structures with a higher energy (0.5–1.1eV/Å) show an increasing population of heptagons and nine-membered rings to form seven-nine defect pairs. For structures with energy higher than 1.1eV/Å, the percentage of octagons and nine-membered rings increases, which indicates that these two types of rings are not energetically favorable. Our proposed methodology is broadly applicable to explore defective low dimensional materials and represents a powerful tool that enables a systematic search of GBs of lateral interfaces for 2D materials.
In situ monitoring of electrosprayed water microdroplets using laser and LED light attenuation technique: Comparison with ultra-high-speed camera imaging
Authors: Janda Mário , Hassan Mostafa E. , Martišovitš Viktor , Hensel Karol , Kwiatkowski Michal , Terebun Piotr , Pawłat Joanna , Machala Zdenko
Published: May 2021

An electrostatic spray (ES) of liquids is a simple way to generate microdroplets with a high surface-to-volume ratio. The ES generated by electrical discharges enables a fast transfer of reactive species from plasma into the liquid for an efficient generation of plasma-activated water. Here, we present a relatively simple, versatile, and cost-effective diagnostic technique for online monitoring of ES microdroplets which enables simultaneous and synchronized electrical and optical diagnostics of an electrical discharge. This technique is based on planar laser light attenuation monitored by a large area photo-detector covered by a slit. Two variants were tested and compared—one with two lasers and another with one laser and a broadband LED lamp. This technique enables estimations of the speed and size of microdroplets (down to ∼10 μm) and allows for monitoring the dripping frequency or studying fragmentation of microdroplets and water filaments. The ES characteristics obtained by this technique were successfully verified by ultra-high-speed camer:a imaging.
Machine learning phase space quantum dynamics approaches
Authors: Liu Xinzijian , Zhang Linfeng , Liu Jian
Published: May 2021

Derived from phase space expressions of the quantum Liouville theorem, equilibrium continuity dynamics is a category of trajectory-based phase space dynamics methods, which satisfies the two critical fundamental criteria: conservation of the quantum Boltzmann distribution for the thermal equilibrium system and being exact for any thermal correlation functions (even of nonlinear operators) in the classical and harmonic limits. The effective force and effective mass matrix are important elements in the equations of motion of equilibrium continuity dynamics, where only the zeroth term of an exact series expansion of the phase space propagator is involved. We introduce a machine learning approach for fitting these elements in quantum phase space, leading to a much more efficient integration of the equations of motion. Proof-of-concept applications to realistic molecules demonstrate that machine learning phase space dynamics approaches are possible as well as competent in producing reasonably accurate results with a modest computation effort.
Magnetism-induced ideal Weyl state in bulk van der Waals crystal MnSb2Te4
Authors: Huan Shuchun , Wang Dinghui , Su Hao , Wang Hongyuan , Wang Xia , Yu Na , Zou Zhiqiang , Zhang Haijun , Guo Yanfeng
Published: May 2021

We have unveiled a magnetic exchange-induced topological phase transition in a bulk natural van der Waals crystal MnSb2Te4, based on magnetization and magnetotransport measurements and first principles calculations. At the A-type antiferromagnetic ground state, MnSb2Te4 is a topologically trivial insulator with a bandgap of ∼ 42 meV at the Γ point of the Brillouin zone. A small magnetic field less than 1.4 T along the c axis can drive the system into a spin fully polarized state, which hosts only a single pair of Weyl points setting near the Γ point at the Fermi level without other band mixing, supported by both the first principles calculations and the measured anomalous Hall effect. The results would setup an excellent paradigm for the study of interplay between magnetism and nontrivial topology of the electronic band structure.
Coexistence of band-like and thermally activated charge transport through nuclear tunneling effect in organic semiconductors
Authors: Xu Feng
Published: May 2021

In this study, the coexistence of band-like and thermally activated charge transport in organic semiconductors is demonstrated through the first-principles calculation of the electric field dependent charge mobilities of TIPS-pentacene, which strongly deviates from the semi-classical Marcus theory. The nuclear tunneling hopping rates simultaneously exhibit band-like and thermally activated conduction for the downward and upward hoppings, respectively, which explains the puzzling observation of the transition from thermally activated transport to band-like transport with increasing field strength. As the hopping rates are very sensitive to the site-energy fluctuations induced by defect configurations, the transition from band-like transport to thermally activated transport with increasing energetic disorder is found. The results suggest that the interplay of the quantum-mechanical effect and disorder is of particular importance in the understanding of the temperature and field dependence of mobility in organic materials.
Operating modes of a magnetized direct-current discharge in helium at pressures ∼10 Pa
Authors: Levko Dmitry , Upadhyay Rochan R. , Raja Laxminarayan L.
Published: May 2021

A high-pressure direct current magnetron discharge is analyzed using a self-consistent two-dimensional fluid model. This discharge has potential interest in plasma switching applications due to its ability to generate rather dense (plasma density of ∼1019 m−3) stable nonequilibrium plasmas at pressures of ∼13.3 Pa (100 mTorr). This discharge has several advantages over nanosecond pulsed high pressure discharges used in conventional plasma switchers since it operates at much lower voltages and lower gas pressures, with the advantage of much longer cathode lifetime. In the present paper, we analyze the operating modes of this magnetron discharge for conditions close to that of Sommerer et al. [J. Phys. D: Appl. Phys. 52, 435202 (2019)]. We observe the subnormal and normal modes of the magnetron operation whose physics differs from that typical for unmagnetized plasmas.
Constant amplitude driving of a radio frequency excited plasmonic tunnel junction
Authors: Doležal Jiří , Merino Pablo , Švec Martin
Published: May 2021

Constant amplitude bias modulation over a broad range of microwave frequencies is a prerequisite for application in high-resolution spectroscopic techniques in a tunnel junction, e.g., electron spin resonance spectroscopy or optically detected paramagnetic resonance. Here, we present an optical method for determining the frequency-dependent magnitude of the transfer function of a dedicated high-frequency line integrated with a scanning probe microscope. The method relies on determining the energy cutoff of the plasmonic electroluminescence spectrum, which is linked to the energies of the electrons inelastically tunneling across the junction. We develop an easy-to-implement procedure for effective compensation of an radio frequency line and determination of the transfer function magnitude in the GHz range. We compare our method with conventional fully electronic calibration and find a perfect agreement.
Characteristics of surface discharging and gas desorption of PTFE due to electron beam irradiation
Authors: Feng Guobao , Liu Lu , Li Xiaojun , Li Yun
Published: May 2021

PTFE (Polytetrafluoroethylene) with a low dielectric constant and less microwave loss is widely applied in dielectric microstrip antenna and has a significant prospect on low-cost miniaturization satellite cluster. In contrast, the surface discharging induced by space electron beam irradiation degrade antenna radiation efficiency and generate pulse interference signal, which comes to be the critical challenge for employing in orbit. In this paper, we use an experiment and simulation combined method for avoiding surface discharging current path to figure out the charging states and gas desorption phenomenon. The charging state numerical simulation calculates secondary electron emission and deposited electron-hole pair distribution with the Monte Carlo simulation. In addition, we investigate the surface gas desorption, chemical state, as well as morphology of PTFE film under different irradiation situations in situ. We find that the electron irradiation with a higher energy can result in a more frequent discharging, meanwhile, coming with a lower surface discharging potential yet. In spite of a less incident current, the gas desorption rate under the satisfied discharging irradiation presents to be larger than the none discharging irradiation situation. Under the 20 keV E-beam irradiation, the F1s spectrum translates more remarkably, and the C1s spectrum presents a greater promotion on breakage of C–F bond. The presented results and numerical simulation method in this study can offer a comprehensive insight into researches and developments on dielectric microstrip antenna in space.
Thermal expansion characterization of thin films using harmonic Joule heating combined with atomic force microscopy
Authors: Chaikasetsin Settasit , Kodama Takashi , Bae Kiho , Jung Jun Young , Shin Jeeyoung , Lee Byung Chul , Kim Brian S. Y. , Seo Jungju , Sim Uk , Prinz Fritz B. , Goodson Kenneth E. , Park Woosung
Published: May 2021

Characterizing coefficient of thermal expansion (CTE) for thin films is often challenging as the experimental signal is asymptotically reduced with decreasing thickness. Here, we present a method to measure CTE of thin films by locally confining an active thermal volume using harmonic Joule heating. Importantly, we simultaneously probe the harmonic expansion at atomic-scale thickness resolution using atomic force microscopy. We use a differential method on lithographically patterned thin films to isolate the topographical and harmonic thermal expansion contributions of the thin films. Based on the measured thermal expansion, we use numerical simulations to extract the CTE considering the stress induced from neighboring layers. We demonstrate our method using poly(methyl methacrylate), and the measured CTE of 55.0 × 10−6 ± 6.4 × 10−6 K−1 shows agreement with previous works. This work paves an avenue for investigating thermo-mechanical characterization in numerous materials systems, including both organic and inorganic media.
Effect of airflow pressure on the droplet breakup in the shear breakup regime
Authors: Zhu Wanli , Zhao Ningbo , Jia Xiongbin , Chen Xiang , Zheng Hongtao
Published: May 2021

In this paper, the coupled level set volume of fluid and the large eddy simulation methods are adopted to perform three-dimensional simulations of the shear breakup of a water droplet. We investigate the effect of airflow pressure (1–3 atm) on the temporary deformation and breakup characteristics, including the breakup initiations, the cross-stream, and streamwise deformations. In addition, special attention is paid to subsequent sub-droplet size distributions, which are generally ignored by many researchers. The results indicate that different morphologies on the surface of the droplets in the shear breakup regime are in relatively good agreement with the available experimental visualizations. Based on the present method, the physical mechanism for the variations in the wake recirculation with the development of Rayleigh–Taylor instability waves is discussed. Furthermore, higher airflow pressures can significantly increase cross-stream and streamwise deformations. However, the corresponding breakup initiations at high airflow pressures are much earlier than those of parent droplets at low airflow pressures. Specifically, a reduction of 12.17% in the mean sub-droplet sizes is obtained as the airflow pressure increases from 1 atm to 2 atm, while a reduction of less than 0.1% in the mean sub-droplet sizes is obtained at higher airflow pressures from 2 atm to 3 atm. Eventually, there are linear growths of the aggregate superficial area ratios (0.996–28.2) and the mass ratios (3.55%–64.29%) of the sub-droplets to the parent droplet.
Quantitative evaluation of local permittivity of semiconductor nanomaterials using microwave atomic force microscopy
Authors: Zhao Minji , Tong Bo , Kimura Yasuhiro , Toku Yuhki , Morita Yasuyuki , Ju Yang
Published: May 2021

In this paper, we report a non-contact and quantitative method to evaluate the permittivity of semiconductor nanomaterials. A microwave atomic force microscopy (M-AFM) was used to obtain the topography and microwave images of nanomaterials in one scanning process. Morphology and microwave images of ZnO and CuO nanowires, and SnO2 nanobelts with high spatial resolution were obtained in the non-contact mode of M-AFM. The local relative permittivity of these one-dimensional metal oxide nanomaterials was quantitatively evaluated.
A durable microsecond solid-state pulsed power system
Authors: Chen Rong , Qian Baoliang , Yang Jianhua , Cheng Xinbing , Geng Jiuyuan
Published: May 2021

An all-solid-state microsecond pulsed power system has been tested in this paper. It can produce larger than 50 kV and microsecond-range pulses continuously for more than 9 × 104 shots into a resistive load at a repetition rate of 10 pps. The whole device has accumulatively operated more than 15 000 pulses at 100 Hz and 3 × 105 pulses at 10 Hz. This all-solid-state pulsed power system consists of a repetitive power supply, a four-stage Marx generator, a pulse forming network, and a resistive load. The repetitive power supply of the pulsed power system is calculated and analyzed first, followed by the introduction of the Marx generator and the three-section anti-resonance network. A polymer box of sodium chloride solution is applied as a resistive load with an impedance of 200 Ω. Repetitive experiments showed that this system is able to operate stably at 100 Hz repetition rate without failure.