bluuebunny/crossref_metadata_2025 huggingface dataset:
Task-Specific Iconic Gesturing During Spoken Discourse in Aphasia
Authors: Stark Brielle C. , Cofoid Caroline
Published: May 2021

Purpose:

In persons living with aphasia, we will explore the relationship between iconic gesture production during spontaneous speech and discourse task, spoken language, and demographic information.

Method:

Employing the AphasiaBank database, we coded iconic gestures in 75 speakers with aphasia during two spoken discourse tasks: a procedural narrative, which involved participants telling the experimenter how to make a sandwich (“Sandwich”), and a picture sequence narrative, which had participants describe the picture sequence to the experimenter (“Window”). Forty-three produced a gesture during both tasks, and we further evaluate data from this subgroup as a more direct comparison between tasks.

Results:

More iconic gestures, at a higher rate, were produced during the procedural narrative. For both tasks, there was a relationship between iconic gesture rate, modeled as iconic gestures per word, and metrics of language dysfluency extracted from the discourse task as well as a metric of fluency extracted from a standardized battery. Iconic gesture production was correlated with aphasia duration, which was driven by performance during only a single task (Window), but not with other demographic metrics, such as aphasia severity or age. We also provide preliminary evidence for task differences shown through the lens of two types of iconic gestures.

Conclusions:

While speech-language pathologists have utilized gesture in therapy for poststroke aphasia, due to its possible facilitatory role in spoken language, there has been considerably less work in understanding how gesture differs across naturalistic tasks and how we can best utilize this information to better assess gesture in aphasia and improve multimodal treatment for aphasia. Furthermore, our results contribute to gesture theory, particularly, about the role of gesture across naturalistic tasks and its relationship with spoken language.

Supplemental Material

https://doi.org/10.23641/asha.14614941
Raman analysis of chemisorbed tribofilm for metal‐on‐polyethylene hip joint prostheses
Authors: Rufaqua Risha , Vrbka Martin , Hemzal Dušan , Choudhury Dipankar , Rebenda David , Křupka Ivan , Hartl Martin
Published: May 2021

The biochemical reaction during the formation of lubricant film the in case of a cobalt‐chromium ball on an ultrahigh‐molecular weight polyethylene cup was studied. Three types of model synovial fluids and hyaluronic acid (HA) at physiologic concentrations were used in the experiment. The coefficient of friction was measured using a pendulum hip simulator, and Raman spectroscopy was used to perceive chemical reactions between the synovial fluid and implant material. Raman spectra evidenced that the three model fluids and HA chemisorbed onto the cobalt‐chromium surface. An α‐helix structure of the model fluid components was detected on the surface of the prosthesis.
Intelligent anti‐epidemic mask based on KF and ECF fusion algorithm
Authors: Xia Kun , Li Xiang , Li Xueyong , Liu Yiren , Zhang Hongwei , Hou Ruifeng
Published: May 2021

In response to environmental pollution and the spread of Coronavirus Disease 2019 (COVID‐19), this paper proposes a new type of smart mask design, and specifically proposes an optimized double closed‐loop control method, especially an improved filtering fusion algorithm. Using the filtering fusion algorithm proposed in this paper, after the Kalman filter (KF) filters the raw data of the attitude sensor, explicit complementary filtering and data fusion are used to obtain the attitude angle of the body. At the same time, the obtained attitude angle is combined with acceleration and blood oxygen concentration to obtain the behaviour characteristic value. On this basis, the speed of the oxygen supply fan captured by the photoelectric sensor is used to form a closed loop with the characteristic value of the behaviour. Finally, the structure of the mask is upgraded and optimized through fluid mechanics simulation, and experiments have verified that the combination of the replaceable filter cloth, the intelligent control system and the ultraviolet disinfection device can effectively protect people's health.
Design of metallic nanocylinder array waveguide for controlling resonant wavelength shift
Authors: Ando Yuki , Endo Motohiro , Wu Di , Yamaguchi Takashi , Kishimoto Seiya , Ohnuki Shinichiro
Published: May 2021

A metallic nanocylinder array was previously proposed for the propagation of localized light generated in nanosized objects. However, the plasmon resonant wavelength for each cylinder shifts significantly with the propagation of light. In this study, a metallic nanoelliptic cylinder waveguide is investigated to control the plasmon resonant wavelength shift. The finite‐difference frequency‐domain (FDFD) electromagnetic solver is used to reduce the computational time. The relationship between the cross‐section of the cylinder and the plasmon resonance for the metal is described with the hydrodynamic Drude model. The effectiveness of the proposed waveguide in controlling the resonant wavelength shifts is confirmed by examining the plasmon propagation for 30 nanocylinders.
Fast and efficient lossless encoder in image compression with low computation and low memory
Authors: Karthikeyan N. , Saravanakumar N. M. , Sivakumar M.
Published: May 2021

This research focuses on frequency‐based lossless new encoding technique with low computation and low memory scheme. This encoding technique doesn't require, any table similar to Huffman and Golomb Rice encoder, and doesn't take high computation time like an arithmetic encoder. For better comparative results, nearly 200 standard images were tested with the proposed encoder and their results were compared with the standard encoders. Based on the analysis of results reported in the experimental part, the proposed scheme in Discrete Cosine Transformation (DCT) achieves a high Compression Ratio (CR) of 97.68 %, Bits Per Pixel (BPP) of 0.19, Peak Signal To Noise Ratio (PSNR) of 27.62 dB for pepper image, CR of 98.65%, BPP of 0.11 and PSNR of 29.24 dB for house image, CR of 98.58 %, BPP of 0.11, PSNR of 30.59 dB for pepper image, CR of 98.37%, BPP of 0.13, PSNR of 31.37dB for house image in Discrete Wavelet Transformation (DWT) than compared to other encoders. It consumes less computation time to attain superior CR with a better quality of reconstructed picture than DCT based Huffman, Golomb‐ Rice (GR) coder and Low Complexity, Low memory Entropy Coder (LLEC), DWT based Arithmetic, GR code, LLEC.
Energy storage properties of P(VDF‐TrFE‐CTFE)‐based composite dielectrics with uniform and gradient‐doped boron nitride nanosheets
Authors: Shang Yanan , Feng Yu , Li Changming , Zhang Changhai , Zhang Tiandong , Zhang Yongquan , Zhang Yue , Song Chunhui , Chi Qingguo
Published: May 2021

Dielectric capacitors play an important role in advanced electronic and power systems such as portable electronic devices, hybrid electric vehicles and electronic weapon systems, and the improvement of energy storage density will have a positive effect on reducing the volume and weight of equipment. Here, a series of single‐layer dielectrics with boron nitride nanosheets (BNNSs) uniformly dispersed and multilayer dielectrics with BNNSs showing a positive gradient distribution (PGD) and inverse gradient distribution (IGD) in the poly(vinylidene fluoride‐trifluoroethylene‐chlorotrifluoroethylene) (P[VDF‐TrFE‐CTFE]) matrix were prepared by high‐speed electrospinning and hot press technology. It is found that the best performance is observed inthe lowest interlayer gradient component in both PGD and IGD composite dielectrics. However, the performance of PGD is better than that of IGD, and the 3‐5‐3 multilayer dielectric in the positive gradient structure has the best electrical performance. Its maximum energy storage density of the 3‐5‐3 composite dielectrics is 12.93 J/cm3 at the applied electric field of 380 kV/mm. The above research results show that the gradient structure design plays an important role in optimising the breakdown strength and energy storage characteristics of composite dielectrics.
Islanding detection method for multi‐terminal renewable power DC distribution system
Authors: Ke Jia , Jin Sun , Zhiming Shi , Zhengxuan Zhu , Qijuan Zhao , Tianshu Bi
Published: May 2021

Most of the traditional islanding detection methods are designed for renewable sources in AC systems and cannot be directly applied in multi‐terminal DC renewable power distribution systems. Moreover, the attenuation effect of multi‐branches makes it difficult for active methods to effectively detect complex islanding operations with multiple renewable power sources. To address the above problems, this paper proposes an active high‐frequency impedance estimation based DC islanding detection method. The impedance of converters is proved to be a constant value at high‐frequencies, and the high‐frequency impedance of the system changes significantly after islanding. Therefore, islanding operations can be accurately detected through impedance characteristics with a negligible none detection zone. The proposed islanding detection method uses DC/DC converters to inject non‐characteristic harmonics to perform high‐frequency impedance calculations without additional injection equipment. The high‐frequency impedance directly reflects structural changes of the DC system. In this case, this method has lower requirements on the disturbance intensity and will not be influenced by the attenuation effect. The injected harmonic voltage is used as an auxiliary criterion to detect complex DC islanding operations with multiple renewable sources. Simulation results prove that the proposed method has high detection accuracy and is not affected by transient conditions.
Consensus active power sharing for islanded microgrids based on distributed angle droop control
Authors: Xu Tao , Zhou Jiaxin , Liang Lemeng , Wu Yuhan , Cai Shuqi , Liu Zuozheng , Li Peng , Yu Li
Published: May 2021

The implementation of synchronous phasor measurement units (PMUs) in distribution networks provide accurate and GPS‐based synchronous data which support the grid flexible reconfiguration, such as island partition and island reconnection. Utilizing the high resolution PMU data, the phase angle droop control can be implemented on islanded microgrids (MGs) without causing the deviation on frequency brought from traditional frequency droop control, consequently support the synchronous and seamless transition. In this paper, a phase angle droop control method considering the incremental cost of distributed generation (DG) is proposed utilizing distributed finite‐time protocol to realize cost minimization and consensus active power sharing of DG units. In addition, an observer‐based voltage controller with finite‐time convergence velocity is implemented to meet the target of DG units’ voltage recovery and the accuracy of reactive power sharing. The proposed method is implemented through a sparse communication topology and exchange information with their own neighbours only. The effectiveness, robustness and scalability of the proposed distributed control method are verified through case studies.
A new approach for the statistical denoising of Planck interstellar dust polarization data
Authors: Regaldo-Saint Blancard Bruno , Allys Erwan , Boulanger François , Levrier François , Jeffrey Niall
Published: May 2021

Dust emission is the main foreground for cosmic microwave background polarization. Its statistical characterization must be derived from the analysis of observational data because the precision required for a reliable component separation is far greater than what is currently achievable with physical models of the turbulent magnetized interstellar medium. This Letter takes a significant step toward this goal by proposing a method that retrieves non-Gaussian statistical characteristics of dust emission from noisy Planck polarization observations at 353 GHz. We devised a statistical denoising method based on wavelet phase harmonics (WPH) statistics, which characterize the coherent structures in non-Gaussian random fields and define a generative model of the data. The method was validated on mock data combining a dust map from a magnetohydrodynamic simulation and Planck noise maps. The denoised map reproduces the true power spectrum down to scales where the noise power is an order of magnitude larger than that of the signal. It remains highly correlated to the true emission and retrieves some of its non-Gaussian properties. Applied to Planck data, the method provides a new approach to building a generative model of dust polarization that will characterize the full complexity of the dust emission. We also release PyWPH, a public Python package, to perform GPU-accelerated WPH analyses on images.
Current Insights in the Age-related Decline in Sports Performance of the Older Athlete
Authors: Ganse Bergita , Degens Hans
Published: May 2021

The higher performance level of master athletes compared to non-athletes is often associated with better health throughout life. However, even the physical performance of master athletes declines with age, and this decline accelerates from about the age of 70 years onwards. A progressive loss of muscle mass, declines in force- and power-generating capacity, decreased flexibility, and the concomitant decline in specific tension characterize the muscular changes underlying performance declines. In the cardiovascular system, declines in stroke volume and cardiac output, and cardiac and vascular stiffness contribute to decreasing performance. Recent studies have shown that long-term endurance exercise in master athletes does not only have positive effects, but is associated with an increased incidence of atrial fibrillation, atherosclerotic plaques, and aortic dilation, and even more so in men than in women. Recently, larger longitudinal datasets were analysed and showed that the age-related decline in performance was similar in longitudinal and cross-sectional data. In conclusion, regular physical activity enhances the exercise capacity, and hence quality of life in old age, but it is not without risks.
Exploring Azatidinone Moiety: An Insight into its Anti-tubercular Potency
Authors: Das Rina , Mehta Dinesh Kumar , Dhanawat Meenakshi
Published: May 2021

TB is becoming a worldwide problem and it was declared since 1993 by the World Health Organization (WHO), a global health emergency. The current problem of tuberculosis therapy is the emergence of multi-drug resistant (MDR) strains, caused by the improper use of antibiotics in chemotherapy of TB patients. Azatidinones, a β-lactam cyclic amide with four atoms in a ring, has been considered as a magic moiety (wonder nucleus) which possesses almost all types of biological activities. This diversity in the biological response profile has attracted the attention of many researchers to explore this skeleton to its multiple potential against several activities. Present article is sincere attempt to review chemistry, method of synthesis of azatidinones and to study azatidinones synthesized in last few years which have shown potent antitubercular activity.
Radiological CT Patterns and Distribution of Invasive Pulmonary Aspergillus, Non-Aspergillus, Cryptococcus and Pneumocystis Jirovecii Mold Infections – A Multicenter Study
Authors: Obmann Verena C. , Bickel Flurina , Hosek Nicola , Ebner Lukas , Huber Adrian T. , Damonti Lauro , Zimmerli Stefan , Christe Andreas
Published: May 2021

Purpose Clinical signs and symptoms related to invasive fungal disease are nonspecific and need to be followed up by appropriate diagnostic procedures. The goal of this study was to analyze CT imaging patterns in invasive fungal infections and their correlation with the immune status and clinical outcome.

Materials and Methods We performed a retrospective multicenter study including 85 consecutive patients with invasive pulmonary fungal infection (2011–2014). Lung patterns on computed tomography (CT) scans were classified according to the Fleischner Society glossary. The patients were grouped according to immune status (neutropenia, steroid therapy, organ transplant recipient, and other cause) and outcome (positive outcome, progressive disease, and death). The Chi square test or Fisher exact test was used. Bonferroni correction was applied.

Results The total number of patients with invasive Aspergillus and non-Aspergillus infection (IANA), Pneumocystis jirovecii pneumonia (PCP), and Cryptococcus (CRY) was 60, 22, and 3, respectively. Patients with IANA demonstrated significantly more nodules (93 % vs. 59 %, p = 0.001), significantly fewer ground glass opacities (58 % vs. 96 %, p = 0.005), and significantly fewer positive lymph nodes (5 % vs. 41 %, p < 0.001) than patients with PCP. All patients with PCP and CRY had a favorable outcome. Patients with IANA and an adverse outcome demonstrated significantly more nodules with halo sign than patients with IANA and a favorable outcome (42.5 % vs. 15.9 %, p < 0.0001). Interestingly, patients with IANA and a favorable outcome had a higher prevalence of pulmonary infarction than patients with an adverse outcome (8 % vs. 1 %, p = 0.047). Patients with neutropenia showed significantly more consolidations (66 %) than organ transplant recipients (27 %, p = 0.045).

Conclusion Patients with IANA showed a higher prevalence of nodules and a lower prevalence of ground glass opacities than patients with PCP. In patients with IANA, nodules with halo sign were associated with an adverse outcome. Patients with neutropenia showed generally more consolidations, but the consolidations were not associated with an adverse outcome.

Key Points: 

Citation Format
Examining the Role of Exercise Timing in Weight Management: A
Review
Authors: Blankenship Jennifer M. , Rosenberg Rebecca C. , Rynders Corey A. , Melanson Edward L. , Catenacci Victoria A. , Creasy Seth A.
Published: May 2021

Many adults cite exercise as a primary strategy for losing weight, yet exercise
alone is modestly effective for weight loss and results in variable weight loss
responses. It is possible that some of the variability in weight loss may be
explained by the time of day that exercise is performed. Few studies have
directly compared the effects of exercise performed at different times of the
day (i. e., morning versus evening exercise). Results from these
existing studies are mixed with some studies demonstrating superior weight and
fat mass loss from morning exercise, while other studies have found that evening
exercise may be better for weight management. Exercise timing may alter
modifiable lifestyle behaviors involved in weight management, such as
non-exercise physical activity, energy intake, and sleep. The purpose of this
review is to summarize evidence for and against time-of-day dependent effects of
exercise on weight management. Although limited, we also review studies that
have examined the effect of exercise timing on other lifestyle behaviors linked
to body weight regulation. While exercise at any time of day is beneficial for
health, understanding whether there is an optimal time of day to exercise may
advance personalized treatment paradigms for weight management.
C(sp3)–H Activation Enabled by (η3-Indolylmethyl)palladium Complexes: Synthesis of Monosubstituted Tetrahydrocarbazoles
Authors: Ramasastry S. S. V. , Kumar Ketan , Vivekanand T. , Singh Bara
Published: May 2021

The synthesis of monosubstituted tetrahydrocarbazoles is achieved via the palladium-catalyzed formal [4+2] cycloaddition of 2-alkyl-3-indolylmethyl carbonates and monosubstituted olefins. The transformation demonstrates an unusual C(sp3)–H activation enabled by (η3-indolylmethyl)palladium complexes. The regioselectivity is found to be dependent on the nature of the substituent across the olefin component. Elaborate mechanistic studies are performed, and the synthetic utility of the products is also demonstrated.
Surgical Management of Gallstone Ileus in Low-Settings Hospital during COVID-19 Outbreak: A Case Report
Authors: Al-Abbasi Ghaith , Alhilfy Ali Adil , Al-Jasim Ameer
Published: May 2021

Introduction Gallstone ileus is a very infrequent complication of cholelithiasis in which single or multiple stones pass through an abnormal fistula to the lumen of the intestine leading to a true mechanical obstruction. We are reporting a case of a female who developed intestinal obstruction due to gallstones during the coronavirus disease 2019 (COVID-19) outbreak and was managed urgently surgically in a low-settings hospital.

Case Presentation An 85-year-old white female with 40 years history of gallstone disease, hypertension, and type-2 diabetes presented to the accidents and emergency unit with upper central crampy abdominal pain for 5 days associated with green color vomiting and absolute constipation. On examination, she was barely stable, dehydrated, had a distended abdomen, and guarding in the epigastric region. Her electrolytes were disturbed and had elevated serum creatinine and blood urea. Imaging studies confirmed gallstone ileus. Management was surgical despite the lack of facilities and equipment including COVID-19 personal protective equipment.

Conclusion Despite being an infrequent complication, gallstone ileus might present at the most unexpected time and in the least equipped hospital where the surgeon's suspicion, risk stratification, and improvisation by utilizing what is available are the keys for successful management and saving lives.
Analysis of Homeopathic Genus Epidemicus for COVID-19 Patients in Spain
Authors: Clapers Marc Lluís , Velat Manuela , Clapers Josep Maria , Vidal-Jové Joan , Mora Joan
Published: May 2021

Background Homeopathy has had documented success treating epidemics in the last two centuries. We aimed to obtain a clear homeopathic clinical picture of coronavirus disease 2019 (COVID-19) and postulate the genus epidemicus of the disease in order to inform and enhance future treatment and prophylaxis options.

Methods We conducted a prospective case series study, collecting data from 19 homeopaths in Catalonia, Spain, from patients who presented with fever and/or cough and/or breathlessness and/or confirmed COVID-19 infection or close contact with a confirmed case. We included 107 patients, and data were recorded through a checklist questionnaire on the day of the case analysis and at day 10–15 after commencing treatment. Symptoms were collected and analyzed with the help of homeopathic repertories.

Results A total of 103 cases were mild or moderate; four were severe. The severe cases were excluded from the analysis and the 103 mild and moderate cases were analyzed and a clear overall clinical picture with mental, general, and particular symptoms was achieved. Eighty-eight cases had a complete recorded follow-up. The most prescribed medicines were Bry, Ars, Phos and Gels, whilst those with the best rates of good response were Sulph, Puls and Bry. Time to full recovery after homeopathic treatment ranged from 3.5 to 14.4 days, depending on the medicine used. The potency 200c was associated with faster rates of full recovery and a lesser need to change remedy.

Conclusion We have defined the symptomatic homeopathic characteristics of mild and moderate COVID-19 in Spain and established a set of medicines that might be useful to consider as effective genus epidemicus.
Nicolau Syndrome: An Unforeseen Yet Evadable Consequence of Intramuscular Injection
Authors: Sasmal Prakash K. , Sahoo Ankit , Singh Pradeep Kumar , VS Vikram
Published: May 2021

An intramuscular (IM) injection is one of the common routes for administering drugs, commonly analgesics and vaccines. Nicolau syndrome refers to the rapid-onset painful, extensive cutaneous discoloration progressing to necrosis and ulceration, reported after IM injections. This case report highlights a rare but avoidable complication of such injections. An elderly man presented with extensive cutaneous necrosis and discoloration over the buttocks extending to the thigh, within few days after receiving a single shot of IM injection of diclofenac. Management involved wound care, biopsy, and cultures with supportive antibiotics to control superadded infection. After multiple sittings of extensive surgical debridement, the wound showed signs of healing and was ultimately amicable for skin grafting in a month.

Health care workers need sensitization toward such a complication that can occur out of a routine procedure like an IM injection. They should follow standard IM injections techniques and take precautions to avoid this mishap, which adds to the patient's morbidity.
Endoscopic Management of Gastroesophageal Reflux Disease
Authors: DeLong Colin G. , Winder Joshua S.
Published: May 2021

Gastroesophageal reflux disease (GERD) occurs in up to 20% of the population. Effective management of the condition is essential to reduce both symptoms and the risk for dysplastic changes of esophageal mucosa. Although lifestyle and diet modification and proton-pump inhibitors (PPIs) remain the standard of therapy, approximately 30% of patients experience persistent or recurrent symptoms with this therapy, which has been labeled PPI-refractory GERD. Surgical antireflux procedures have long been the standard therapy for PPI-refractory GERD, but drawbacks include cost and surgical morbidity. Endoscopic techniques for GERD management have been developed over the past 20 years including transoral incisionless fundoplication, the Stretta procedure, and antireflux mucosectomy. This article will review the current literature on each of these endoscopic procedures as well as highlight areas where further research is needed to fully understand the best practices for use of these endoscopic techniques for the management of PPI-refractory GERD.
Art films foster theory of mind
Authors: Castano Emanuele
Published: May 2021

Research shows that reading literary but not popular fiction enhances the Theory of Mind (ToM). This article builds on the symmetry between literary theory and film theory and investigates whether exposure to art films, but not Hollywood films, enhances ToM. Participants (N = 232) were randomly assigned to view either art or Hollywood films and then answered questions about the film and its characters before completing two separate measures of ToM (the Read the Mind in the Eyes Test and the Moral Judgement Task). Results showed that art film viewers scored higher on both ToM measures and that the effect was sequentially mediated by perception of complexity and predictability of the characters. The findings are discussed in the context of the emerging literature on the impact of fiction on social cognition.
Complex networks reveal emergent interdisciplinary knowledge in Wikipedia
Authors: Schwartz Gustavo A.
Published: May 2021

In the last 2 decades, a great amount of work has been done on data mining and knowledge discovery using complex networks. These works have provided insightful information about the structure and evolution of scientific activity, as well as important biomedical discoveries. However, interdisciplinary knowledge discovery, including disciplines other than science, is more complicated to implement because most of the available knowledge is not indexed. Here, a new method is presented for mining Wikipedia to unveil implicit interdisciplinary knowledge to map and understand how different disciplines (art, science, literature) are related to and interact with each other. Furthermore, the formalism of complex networks allows us to characterise both individual and collective behaviour of the different elements (people, ideas, works) within each discipline and among them. The results obtained agree with well-established interdisciplinary knowledge and show the ability of this method to boost quantitative studies. Note that relevant elements in different disciplines that rarely directly refer to each other may nonetheless have many implicit connections that impart them and their relationship with new meaning. Owing to the large number of available works and to the absence of cross-references among different disciplines, tracking these connections can be challenging. This approach aims to bridge this gap between the large amount of reported knowledge and the limited human capacity to find subtle connections and make sense of them.
Multi-signal spectroscopy of qubit-resonator systems
Authors: Nakonechnyi M. A. , Karpov D. S. , Omelyanchouk A. N. , Shevchenko S. N.
Published: May 2021

Some unique properties of superconducting devices are promising for the development of modern quantum technologies. Superconducting quantum circuits use large coupling constants and provide good scalability and controllability due to their macroscopic dimensions. Still, micro-fabrication methods have some hardship with reproducibility of identical superconducting quantum circuits. The dressed state approach presents some possibility to reduce influence of non-identity of qubits. We study a qubit-resonator system, when the qubit interacts with three signals. Such system configuration adds additional flexibility for circuit tunability. A particular realization of such a system is a superconducting flux qubit coupled to a transmission-line resonator driven by three signals. We describe this triply-driven system in terms of the dressed qubit states and conclude that using several signals can be beneficial for both system spectroscopy and tunability. Such study of a qubit-based system, coupled to both classical and quantum fields, can be useful for detection of individual itinerant microwave photons.
Majorana zero modes in the interacting fermion chain without pairing
Authors: Zvyagin A. A.
Published: May 2021

The ground state behavior of the spinless fermion chain with an interaction between fermions at neighboring sites is studied for free open boundaries. For the strong enough repulsion boundary gapless states (bound state of Majorana operators from opposite sites of the chain) can exist inside the gap for bulk excitations, i.e., in the topological insulator regime. We propose to use those Majorana zero modes as topological qubits, similar to the ones in one-dimensional topological superconductors. Possible physical realizations of the considered model are discussed.
Exciton absorption spectra of thin films of RbCu2Cl3 and Rb2Cu3Cl5 ternary compounds
Authors: Kovalenko E. N. , Yunakova O. N. , Yunakov N. N.
Published: May 2021

The absorption spectra of RbCu2Cl3 and Rb2Cu3Cl5 thin films were studied in the 2−6 eV spectral and 90−450 K temperature ranges. The localization of excitons in CuCl43− structural elements of crystal lattice of compounds, three-dimensional nature of excitons in RbCu2Cl3 and two-dimensional nature of excitons in Rb2Cu3Cl5 were established. The exciton spectra of RbCu2Cl3 and Rb2Cu3Cl5 thin films were interpreted based on the transitions in the Cu+ ion.
Design and development of a compact ion implanter and plasma diagnosis facility based on a 2.45 GHz microwave ion source
Authors: Swaroop Ram , Kumar Narender , Rodrigues G. , Kanjilal D. , Banerjee I. , Mahapatra S. K.
Published: May 2021

A project on developing a 2.45 GHz microwave ion source based compact ion implanter and plasma diagnostic facility has been taken up by the Central University of Punjab, Bathinda. It consists of a double-wall ECR plasma cavity, a four-step ridge waveguide, an extraction system, and an experimental beam chamber. The mechanical design has been carried out in such a way that both types of experiments, plasma diagnosis and ion implantation, can be easily accommodated simultaneously and separately. To optimize microwave coupling to the ECR plasma cavity, a four-step ridge waveguide is designed. Microwave coupling simulation for the ECR plasma cavity has been performed at different power inputs using COMSOL Multiphysics. An enhanced electric field profile has been obtained at the center of the ECR plasma cavity with the help of a four-step ridge waveguide compared to the WR284 waveguide. The magnetic field distribution for two magnetic rings and the extraction system’s focusing properties have been simulated using the computer simulation technique. A tunable axial magnetic field profile has been obtained with a two permanent magnetic ring arrangement. The dependency of the beam emittance and beam current on accelerating voltages up to 50 kV has been simulated with different ions. It shows that ion masses have a great impact on the beam emittance and output current. This facility has provision for in situ plasma diagnosis using a Langmuir probe and optical emission spectroscopy setups. This system will be used for ion implantation, surface patterning, and studies of basic plasma sciences.
Exergy and exergoeconomic investigations of the secondary reflectors effect on the linear Fresnel concentrator applied to an organic Rankine cycle
Authors: Chavoshi M. , Minaeian A.
Published: May 2021

Loss of solar rays in linear Fresnel concentrators (LFCs) through the width difference of primary reflectors and absorber tube led the scientists to add secondary reflectors to these concentrators. This secondary reflector increases the optical efficiency, as it is mentioned in the literature. In this paper, the effect of the secondary reflector on energy and exergy efficiencies was investigated. To find the most efficient design, four orientations of secondary reflectors including circular, flat, few segmented, and parabolic were studied. The reference values for the thermodynamic properties for all types of secondary reflectors were considered, and the systems were simulated in the EES environment by applying the supposed parameters at the base point. The results showed that lack of secondary reflectors decreased the thermal efficiency of the system. It is found that the flat geometry increased the energy and exergy efficiencies, while the cost was increased. However, the low manufacturing cost makes it acceptable as it was appropriate in optical aspects. The energy and exergy efficiencies were enhanced in circular and parabolic designs less than that in the flat design. The few flat segmented model has the most energy efficiency. However, much increment in efficiencies justifies growth in costs. The parabolic secondary reflector had the least cost increment. Effects of the variations of the temperature of the inlet flow to the collector, the pressure of the inlet flow to turbine, and the pressure of the inlet flow to the first pump on the design parameters were investigated. The results demonstrated that the only benefit increasing the temperature of the inlet flow to the collector and the pressure of the inlet flow to the first pump is cost reduction. Also, the increment of the pressure of the inlet flow to the turbine increases the exergy efficiency.
New local electrical diagnostic tool for dielectric barrier discharge (DBD)
Authors: Tyl Clémence , Martin Stéphane , Combettes Céline , Brillat Gilles , Bley Vincent , Belinger Antoine , Dap Simon , Brandenburg Ronny , Naudé Nicolas
Published: May 2021

A new diagnostic tool to study dielectric barrier discharges (DBDs) at atmospheric pressure by local electrical measurements is introduced. The square ground electrode is divided into 64 square segments (3.44 mm side length) so as to measure the discharge currents and gas voltages with spatial resolutions, which allows a 2D mapping. The electrical measurement results are validated by a comparison with short exposure time photographs taken from the top view of the discharge cell. For this purpose, we changed the local discharge behavior by varying locally the gas gap and the barrier capacitance and also by using a gas flow. Then, in both situations, the breakdown voltage depends on the position, and the discharge current and gas voltage are different as well. The measurements performed for a planar DBD in nitrogen with admixed nitrous oxide gas show that even if the discharge operates in a diffuse regime, the discharge does not behave exactly homogeneously on the whole surface area. The resulting electrical parameters allow us to refine the understanding of planar DBDs. The discharge activity changes the gas composition and thus, the level of preionization in the direction of the gas flow. This influences the local breakdown voltage and thus, the discharge morphology and local power density on the surface. The use of this new electrical diagnostic tool will allow us to refine the analysis of the spatial development of the discharge. This work gives some clues to improve the spatial resolution of this tool in the future.
Effect of pilot hydrogen on the formation of dynamic flame in an ethylene-fueled scramjet with a cavity
Authors: Shi Wen , Tian Ye , Le Jialing , Zhong Fuyu
Published: May 2021

Pilot hydrogen is used for the ignition of gaseous ethylene to improve combustion efficiency at low flight Mach numbers. The process of dynamic flame stabilization has been investigated experimentally in a scramjet equipped with a cavity by using a variety of fuel injection strategies involving the injection of pure hydrogen, pure ethylene, and combinations of fuels to understand the effects of pilot hydrogen on supersonic combustion. This study reports experiments conducted in a direct-connected facility that simulated flight conditions at a Mach number of 4, a total temperature of 953 K, and a total pressure of 0.82 MPa. The data were collected by using hydroxyl planar laser-induced fluorescence (OH-PLIF), methylene (CH), luminosity images, and 10-kHz static pressure transducers. The results show that the internal flow oscillated at a dominant frequency of approximately 450 Hz without fuel injection. Oscillation in internal flow was suppressed when pilot hydrogen was injected into the cavity, whereas the influence of other injection strategies was minor. The OH-PLIF images indicate that the pilot flame was unstable, with different locations and occupying different areas. The normalized pressure was apparently higher when pilot hydrogen was injected ahead of the cavity step. The pure ethylene flame was difficult to stabilize without the application of pilot hydrogen. Once the pilot hydrogen had been turned off, the ethylene flame moved toward the cavity ramp and its area expanded. Thus, pilot hydrogen is a precondition for the stabilization of the ethylene flame.
Ammonium fluoride’s analogy to ice: Possibilities and limitations
Authors: Conway L. J. , Brown K. , Loveday J. S. , Hermann A.
Published: May 2021

Ammonium fluoride, NH4F, is often seen as an analog to ice, with several of its solid phases closely resembling known ice phases. While its ionic and hydrogen-ordered nature puts topological constraints on the ice-like network structures it can form, it is not clear what consequences these constraints have for NH4F compound formation and evolution. Here, we explore computationally the reach and eventual limits of the ice analogy for ammonium fluoride. By combining data mining of known and hypothetical ice networks with crystal structure prediction and density functional calculations, we explore the high-pressure phase diagram of NH4F and host–guest compounds of its hydrides. Pure NH4F departs from ice-like behavior above 80 GPa with the emergence of close-packed ionic structures. The predicted stability of NH4F hydrides shows that NH4F can act as a host to small guest species, albeit in a topologically severely constraint configuration space. Finally, we explore the binary NH3–HF chemical space, where we find candidate structures for several unsolved polyfluoride phases; among them is the chemical analog to H2O2 dihydrate.
Mechanistic insights into carbon–carbon coupling on NiAu and PdAu single-atom alloys
Authors: Kress Paul , Réocreux Romain , Hannagan Ryan , Thuening Theodore , Boscoboinik J. Anibal , Stamatakis Michail , Sykes E. Charles H.
Published: May 2021

Carbon–carbon coupling is an important step in many catalytic reactions, and performing sp3–sp3 carbon–carbon coupling heterogeneously is particularly challenging. It has been reported that PdAu single-atom alloy (SAA) model catalytic surfaces are able to selectively couple methyl groups, producing ethane from methyl iodide. Herein, we extend this study to NiAu SAAs and find that Ni atoms in Au are active for C–I cleavage and selective sp3–sp3 carbon–carbon coupling to produce ethane. Furthermore, we perform ab initio kinetic Monte Carlo simulations that include the effect of the iodine atom, which was previously considered a bystander species. We find that model NiAu surfaces exhibit a similar chemistry to PdAu, but the reason for the similarity is due to the role the iodine atoms play in terms of blocking the Ni atom active sites. Specifically, on NiAu SAAs, the iodine atoms outcompete the methyl groups for occupancy of the Ni sites leaving the Me groups on Au, while on PdAu SAAs, the binding strengths of methyl groups and iodine atoms at the Pd atom active site are more similar. These simulations shed light on the mechanism of this important sp3–sp3 carbon–carbon coupling chemistry on SAAs. Furthermore, we discuss the effect of the iodine atoms on the reaction energetics and make an analogy between the effect of iodine as an active site blocker on this model heterogeneous catalyst and homogeneous catalysts in which ligands must detach in order for the active site to be accessed by the reactants.
Anomalous diffusion of cosmic rays: A geometric approach
Authors: Buonocore Salvatore , Sen Mihir
Published: May 2021

In this work, we analyze the process leading to the occurrence of anomalous transport phenomena associated with galactic cosmic rays propagating through the interstellar space. The origin of non-conventional transport is found in the dynamics of cosmic rays dominated by long uninterrupted flights interspersed with interactions with magnetized scattering clouds. The process is analyzed via a geometric Monte Carlo model that is able to mimic the intrinsic non-local character of the investigated transport phenomena. Numerical results show the existence of ranges of density and re-emission strengths of the interstellar magnetic clouds leading to heavy-tailed (Lévy α-stable) distributions of the propagating cosmic rays denoting a marked superdiffusive character. The correspondence between the geometric Monte Carlo integration method proposed in this work and the fractional Green’s functions suggests a novel approach to efficiently performing integration in higher dimensional spaces.
The dependence of medium refractive index on optical properties of gold nanorods and their SERS application
Authors: Hue Do Thi , Thu Huong Tran Thi , Thu Ha Pham Thi , Trang Tran Thu , Ha Lien Nghiem Thi , Xuan Hoa Vu
Published: May 2021

In this article, the influence of the medium refractive index on optical properties of gold nanorods (GNRs) and their surface enhanced Raman spectroscopy application were studied. In particular, GNRs have been applied in biomedical sensors to detect diseases by monitoring the changes in the environment. In this study, the changes in optical properties of GNRs were investigated according to the medium refractive index changes in the cationic surfactant cetyltrimethylammonium bromide (CTAB) during synthesis processes as well as GNR dispersion in different medium refractive indices. For instance, in the solutions with different concentrations of CTAB, GNRs were coated by biomolecules [such as PEG, bovine serum albumin (BSA), and glutathione (GSH)], which have different refractive indices. The fundamental reason for the change in optical properties of GNRs is also elucidated. GNRs have been used to enhance surface Raman scattering to detect indigo molecules. The results showed that due to the surface plasmon resonance effect, the GNRs could strongly enhance the scattering signal of indigo dyes, with the lowest detectable concentration of up to 10−8 M and with an enhancement coefficient of over 2000 times.
Crowding breaks the forward/backward symmetry of transition times in biased random walks
Authors: Shin Jaeoh , Berezhkovskii Alexander M. , Kolomeisky Anatoly B.
Published: May 2021

Microscopic mechanisms of natural processes are frequently understood in terms of random walk models by analyzing local particle transitions. This is because these models properly account for dynamic processes at the molecular level and provide a clear physical picture. Recent theoretical studies made a surprising discovery that in complex systems, the symmetry of molecular forward/backward transition times with respect to local bias in the dynamics may be broken and it may take longer to go downhill than uphill. The physical origins of these phenomena remain not fully understood. Here, we explore in more detail the microscopic features of the symmetry breaking in the forward/backward transition times by analyzing exactly solvable discrete-state stochastic models. In particular, we consider a specific case of two random walkers on a four-site periodic lattice as the way to represent the general systems with multiple pathways. It is found that the asymmetry in transition times depends on several factors that include the degree of deviation from equilibrium, the particle crowding, and methods of measurements of dynamic properties. Our theoretical analysis suggests that the asymmetry in transition times can be explored experimentally for determining the important microscopic features of natural processes by quantitatively measuring the local deviations from equilibrium and the degrees of crowding.
Approaching meV level for transition energies in the radium monofluoride molecule RaF and radium cation Ra+ by including quantum-electrodynamics effects
Authors: Skripnikov Leonid V.
Published: May 2021

Highly accurate theoretical predictions of transition energies in the radium monofluoride molecule, 226RaF, and radium cation, 226Ra+, are reported. The considered transition X2Σ1/2 → A2Π1/2 in RaF is one of the main features of this molecule and can be used to laser-cool RaF for a subsequent measurement of the electron electric dipole moment. For molecular and atomic predictions, we go beyond the Dirac–Coulomb Hamiltonian and treat high-order electron correlation effects within the coupled cluster theory with the inclusion of quadruple and ever higher amplitudes. The effects of quantum electrodynamics (QED) are included non-perturbatively using the model QED operator that is now implemented for molecules. It is shown that the inclusion of the QED effects in molecular and atomic calculations is a key ingredient in resolving the discrepancy between the theoretical values obtained within the Dirac–Coulomb–Breit Hamiltonian and the experiment. The remaining deviation from the experimental values is within a few meV. This is more than an order of magnitude better than the “chemical accuracy,” 1 kcal/mol = 43 meV, that is usually considered as a guiding thread in theoretical molecular physics.
Spreading and epigenetic inheritance of heterochromatin require a critical density of histone H3 lysine 9 tri-methylation
Authors: Cutter DiPiazza Amber R. , Taneja Nitika , Dhakshnamoorthy Jothy , Wheeler David , Holla Sahana , Grewal Shiv I. S.
Published: May 2021

Significance

In multicellular organisms, a single genome gives rise to a multitude of cell types by enforcing appropriate gene expression patterns. Epigenetic mechanisms involving modification of histones, including tri-methylation of histone H3 lysine 9 (H3K9me3), assemble and propagate repressive heterochromatin to prevent untimely gene expression. Dysregulation of epigenetic gene-silencing mechanisms is a hallmark of a variety of diseases including cancer. However, the requirements for epigenetic transmission of heterochromatin are not well understood. This study reveals the mechanism by which methylated histones provide an epigenetic template for heterochromatin propagation. We discover that a critical threshold of H3K9me3 is required for effective chromatin-association of the histone methyltransferase, which binds to and catalyzes additional H3K9me to propagate heterochromatin and enforce stable gene silencing.