bluuebunny/crossref_metadata_2025 huggingface dataset:
The A3 Redox-Neutral C1-Alkynylation of Tetrahydroisoquinolines: A Comparative Study between Visible Light Photocatalysis and Transition-Metal Catalysis
Authors: Kouznetsov Vladimir V. , Ortiz Villamizar Marlyn C. , Puerto Galvis Carlos E.
Published: September 2020

Considering the current challenges of the A3 redox-neutral C1-alkynylation of tetrahydroisoquinolines (THIQs), we studied this synthetic tool under visible light photocatalysis and transition-metal catalysis in order to describe alternative reaction conditions and discuss possible improvements to this process. We demonstrated that 1-alkynylated THIQs can be readily obtained by three different approaches: iridium-based photocatalysis and copper ([CuBr(PPh3)3]) and silver (AgNO3) catalysis under mild, selective and accessible reaction conditions. Among these approaches, the copper(I)-based methodology resulted in the most robust, optimal reaction conditions for the synthesis of a series of 18 1-alkynylated THIQs in moderate to excellent yields and with high selectivity for the endo-alkynylated products. Moreover, this reaction can be accelerated by microwave irradiation (120 °C, 15 min) affording a novel library of diverse THIQs with alkyne and N-substituent moieties, from unreactive and uncommon substrates, that could be further transformed into new compounds of interest.
Clinical Outcomes after Minimally Invasive Trans-Psoas Lateral Lumbar Interbody Fusion for the Treatment of Adult Degenerative Scoliosis: Four Years’ Multicenter Study
Authors: Asad Sheikh , Dubey Arjun , Dubey Arvind , Sutterlin Chester
Published: September 2020

The use of minimally invasive transpsoas lateral lumbar interbody fusion (LLIF) surgery for treatment of adult degenerative scoliosis is rapidly increasing in popularity. However, limited data is available regarding its use in adult degenerative lumbar scoliosis surgery. The objective of this study was to evaluate the clinical outcomes of adults with degenerative lumbar scoliosis who were treated with minimally invasive LLIF. Thirty-two consecutive patients with adult degenerative scoliosis treated by a single surgeon at two spine centers were followed up for an average of 13.2 months. Interbody fusion was completed using the minimally invasive LLIF technique with supplemental 360 degrees’ posterior instrumentation. Oswestry disability index (ODI) scores were obtained preoperatively and at most recent follow-up. Complications were recorded. The study group demonstrated improvement in clinical outcome scores. ODI scores improved from 36.8 to 23.4 (p < 0.00001). A total of four complications (12%) were recorded, and two patients (6%) required additional surgery. Based on the significant improvement in validated clinical outcome scores, minimally invasive LLIF can be considered an effective procedure in the treatment of adult degenerative scoliosis.
The Utility of Cinematherapy for Stuttering Intervention: An Exploratory Study
Authors: Azios Michael , Irani Farzan , Bellon-Harn Monica , Swartz Eric , Benson Cristiana
Published: September 2020

This preliminary study explored the feasibility and benefits of using cinematherapy with adults who stutter to address affective and cognitive reactions to stuttering and their impact on the persons' life. A mixed methods research design was used to explore the impact of cinematherapy. Four clients completed a 4-week structured cinematherapy program. All clients completed two questionnaires: Unhelpful Thoughts and Beliefs about Stuttering and Overall Experience of the Speaker's Experience of Stuttering, before starting and after completing the program. At the end of the program, clients also completed a semistructured interview. The semistructured interviews provide insight on clients' perceptions of cinematherapy, and questionnaires provided quantitative insights on the clients' perceptions of change. Qualitative data analysis indicated that clients reported five themes related to perceptions of cinematherapy: Promoted Vulnerability; Nurtured Empowerment; Stimulated Self-Reflection; Incited Feelings of Belonging; and Diminished Self-Stigma. Overall, clients reported a clinically significant decrease in scores on both questionnaires after completion of the 4-week cinematherapy program. Results indicate that cinematherapy was well received and had a positive impact on cognitive and affective aspects of stuttering in the four adult clients. These results provide preliminary support for larger scale clinical trials of cinematherapy as an adjuvant to traditional stuttering therapy.
Fulminant Acute Disseminated Encephalomyelitis: A Remarkable Outcome with Cyclophosphamide
Authors: Meirson Hadas , Shiran Shelly I. , Raz Michal , Roth Jonathan , Fattal-Valevski Aviva
Published: September 2020

Acute disseminated encephalomyelitis (ADEM) is an inflammatory demyelinating disease of the central nervous system which occurs predominantly in the pediatric population. Acute treatment is high-dose intravenous glucocorticoids. Alternative treatment is usually intravenous immune globulin and/or plasma exchange. Fulminant ADEM is rare in children. Only a few cases of cyclophosphamide use in refractory ADEM have been reported. Here, we report a case of a 12-year-old girl with fulminant ADEM who was comatose and improved dramatically after cyclophosphamide administration. Cyclophosphamide treatment should be considered as a therapy in children with fulminant ADEM nonresponsive to standard therapies.
Bone Union Enhancement by bFGF-Containing HAp/Col in Prefabricated Vascularized Allo-Bone Grafts
Authors: Yamaguchi Konosuke , Kaji Yoshio , Nakamura Osamu , Tobiume Sachiko , Nomura Yumi , Oka Kunihiko , Yamamoto Tetsuji
Published: September 2020

Background We have developed a prefabricated vascularized allo-bone graft (PVAG) by implanting the saphenous vascular bundles of recipient rats into transplanted donor bones in a flow-through manner. We previously demonstrated that the angiogenetic and bone formative abilities of the PVAG are stimulated by the addition of a basic fibroblast growth factor (bFGF)-containing hydroxyapatite/collagen (HAp/Col). This study aimed to demonstrate that the bone union ability of the PVAG is similarly stimulated by the bFGF-containing HAp/Col composite.

Methods Sprague-Dawley donor rats (n = 32) and Wistar recipient rats (n = 32) were used in this study. The PVAG was fixed to the femur of the recipient rat using K-wire (dimeter: 0.7 mm) pinning, followed by suturing with a 4–0 nylon suture. Recipients were divided into four groups: with or without vascular bundles, and with or without bFGF-containing HAp/Col. Rats were sacrificed 6 weeks after transplantation, and bone union, bone resorption, and angiogenesis were radiologically and histologically evaluated.

Results Radiological analysis revealed a significant increase in callus formation and union rate, while histological analysis showed a significant increase in bone formation and angiogenesis in the group treated with both vascular bundles and bFGF. Bone resorption did not significantly increase in any of the evaluated groups.

Conclusion Osteogenic cells, osteoconductive scaffolds, growth factors, and mechanical environment are known to be important factors in the process of fracture healing. The PVAG developed herein contains osteogenic cells, osteoconductive scaffolds, and growth factors. In addition, the PVAG is rigidly fixed to the fracture site, providing a stable mechanical environment. Together, these four factors contributed to a good bone union. Furthermore, this method did not promote bone resorption. Thus, the addition of a vascular bundle and bFGF-containing HAp/Col makes it possible to create an ideal vascularized allo-bone graft for the reconstruction of massive bone defects.
The Blue-Blood Porcine Chest Wall: A Novel Microsurgery Training Simulator for Internal Mammary Vessel Dissection and Anastomosis
Authors: Zeng Weifeng , Gunderson Kirsten A. , Sanchez Ruston J. , Albano Nicholas J. , Nkana Zeeda H. , Thadikonda Kishan M. , Dingle Aaron M. , Poore Samuel O.
Published: September 2020

Background Preparation of the internal mammary artery (IMA) is a critical step in autologous breast reconstruction. Intraoperatively, there is limited opportunity for residents to practice this skill. Porcine models provide highly realistic simulation for vascular surgery; however, use of live laboratory pigs is expensive, inconvenient, and offers limited opportunity for repetitive training. We aimed to develop an inexpensive and effective training model for IMA preparation. This article describes creation of a novel microsurgical model using cadaveric chest walls of Wisconsin Miniature Swine embedded in a modified mannequin thorax and augmented with a blue-blood perfusion system.

Methods Anatomic comparison: five porcine chest walls were dissected, and various anatomic measurements were made for anatomic comparison to existing human data in the literature. Model assembly: the chest wall is prepared by cannulating the proximal and distal ends of the internal mammary vessels with angiocatheters, which are then connected to the blue-blood perfusion system. The model is assembled in four layers including: (1) a mannequin thorax with a window removed to expose the first to fourth intercostal spaces, bilaterally, (2) a layer of foam simulating fat, (3) the perfused pig chest wall, and (4) a second mannequin shell placed posteriorly for support.

Results The porcine chest walls are similar to humans with regards to vessel size and location. This model can be assembled quickly, with a one-time approximate cost of $55.00, and allows for six training sessions per specimen. The model allows residents to practice the key steps of IMA preparation including dissection, elevation of perichondria, and vascular anastomosis while working at a depth that closely simulates the human thorax. Continuous blue-blood perfusion provides immediate feedback on anastomosis quality.

Conclusion Overall, this novel model can provide inexpensive and realistic simulation of internal mammary vessel preparation and anastomosis.
Employment Opportunities for Pediatric Critical Care Fellowship Trained Physicians in the United States
Authors: Dalabih Abdallah R. , Prodhan Parthak , Harris Zena L. , Bone Meredith F.
Published: September 2020

Pediatric Critical Care Medicine (PCCM) training programs and trained fellows in the United State increased steadily without a corresponding increase in population growth. PCCM trainees worry about limited employment prospects. This study aimed to quantify the demand for PCCM trained physicians in the United States by prospectively tracking full-time employment opportunities over 12 months. The number of advertised opportunities identified was low compared with number of fellows likely to be seeking jobs during same time period. If market demand remains stable, there is risk of excess supply if number of newly fellowship-trained PCCM physicians continues to rise.
Unanswered questions about the application of Casimir forces
Authors: Patrick Chris
Published: September 2020

This perspective discusses potential applications of Casimir forces in micro and nanosystems, focusing mainly on actuation and adhesion.
The development of a screen valve for reciprocating heat pump/engine applications
Authors: Ameen Muhammad Tahir , Smallbone Andrew , Roskilly Anthony Paul , Carpenter Edward
Published: September 2020

A novel screen valve with rectilinear ports is presented for use in advanced high-efficiency compressors, expanders, heat pumps, or engines. The novel design aims to minimize the pumping losses generated as the working gas flows through the valve by maximizing the effective opening cross-sectional area. In this work, various screen valve configurations have been investigated through a series of experimental tests conducted on a heavily modified research engine for high-speed, high-pressure valve testing. The valves were designed and tested to operate efficiently at both low and high engine speeds ranging between 1500 and 3000 rpm. The valve dynamics were optimized to meet two high-level criteria for performance—namely (1) high speed metrics quantified by its percentage of “maximum dynamic pressure” and (2) low speed metrics quantified by the valve “minimum closure angle.” The valves were tested to meet the objective of avoiding any friction-locking issues associated with the valve retainer design. Multiple tests were carried out in pursuit of attaining an improved design. The work concluded that by including a carrier frame (rather than a retainer frame) and upstands on the valve seat, the valve performance was improved significantly. The best design yielded results of 50.4% of maximum dynamic pressure and 25.1° as the minimum closure angle.
Highly efficient meta-radiators with circular polarization
Authors: Rajabalipanah Hamid , Nadi Morteza , Abdolali Ali , Cheldavi Ahmad
Published: September 2020

In this paper, circularly polarized metasurface radiators (meta-radiator) are elaborately designed with low-profile, small footprint, and highly efficient specifications. The proposed array consists of single-feed dense radiating meta-atoms that overall occupies a small area of 1.57λ0×1.57λ0 at f=5.8 GHz. The inter-element coupling is involved by analyzing the contributing meta-atoms with Floquet boundary conditions. For demonstration purposes, an 8×8 sample of meta-radiators excited by an isolated network beneath the ground plane is fabricated. Both numerical and experimental results demonstrate that the meta-radiator exposes a pure left-hand circularly polarized radiation with a peak broadside directivity, a realized gain, and an axial ratio of 14.9 dBi, 14.2 dB, and 1.28 dB, respectively. Numerical simulations indicate that the aperture, radiation, and total efficiencies are as high as 99%, 97.5%, and 84.3%, respectively. In comparison with the conventional array antennas with similar performances, the proposed meta-radiator provides a higher aperture efficiency, in a simpler manner to achieve circular polarization, and more compact size as discussed throughout the paper. This new class of radiating architectures may find great potential applications in target detection systems and wireless communications.
Mask-MRNet: A deep neural network for wind turbine blade fault detection
Authors: Zhang Chao , Wen Chuanbo , Liu Jihui
Published: September 2020

In this paper, a deep neural network named Mask-MRNet is proposed to detect wind turbine (WT) blade fault based on images taken by unmanned aerial vehicles. Two datasets of the blade image are built for training and optimizing. Based on the proposed network, the blade images can intuitively express the mask, bounding box, and type of fault. In the detection, the network is stacked with Mask R-CNN-512 and MRNet. Optimized Mask R-CNN, Mask R-CNN-512, can significantly reduce inference time when performing large object detection such as WT blade fault. MRNet is proposed to correct the fault mask angle for cropping the low noise fault image from the original image and classify the fault type. Compared with more than 20 classification models based on indices including training and testing accuracy, the f1-score, and detection efficiency, DenseNet-121 was chosen as the classification model for Mask-MRNet. In addition, it is better to choose the classifier according to specific application demands in practical environments. A computational study was performed to further demonstrate that Mask-MRNet can not only achieve the multifunctional WT blade fault detection but also dynamic monitoring during the running of the WT.
InGaAs-InP core–shell nanowire/Si junction for vertical tunnel field-effect transistor
Authors: Tomioka Katsuhiro , Ishizaka Fumiya , Motohisa Junichi , Fukui Takashi
Published: September 2020

Tunnel field-effect transistors (TFETs) have attracted much attention as building blocks for low-power integrated circuits because they can lower the subthreshold slope (SS) below the physical limitation of conventional FETs. There, however, remains a difficulty in increasing the tunnel current in TFETs since the energy gap at the tunnel junction has a unique probability. Here, we investigated the strain effect stemming from the InGaAs-InP core–shell (CS) structure on the tunneling current in a vertical TFET using an InGaAs nanowire (NW)/Si heterojunction. We found that the TFET demonstrated a 10-fold enhancement in current while achieving a steep SS (minimum SS = 41 mV/dec). Strain analysis for the InGaAs NW/Si tunnel junction revealed that specific strain induced at the junction affected the increase in the on-state current.
Optimization of atomic density-fitting basis functions for molecular two-electron integral approximations
Authors: Laikov Dimitri N.
Published: September 2020

A general procedure for the optimization of atomic density-fitting basis functions is designed with the balance between accuracy and numerical stability in mind. Given one-electron wavefunctions and energies, weights are assigned to the product densities, modeling their contribution to the exchange and second-order correlation energy, and a simple weighted error measure is minimized. Generally contracted Gaussian auxiliary basis sets are optimized to match the wavefunction basis sets [D. N. Laikov, Theor. Chem. Acc. 138, 40 (2019)] for all 102 elements in a scalar-relativistic approximation [D. N. Laikov, J. Chem. Phys. 150, 061103 (2019)].
On the size-dependence of CdSe nanocrystals for photon upconversion with anthracene
Authors: Rigsby Emily M. , Miyashita Tsumugi , Jaimes Paulina , Fishman Dmitry A. , Tang Ming Lee
Published: September 2020

In triplet–triplet annihilation based photon upconversion, controlling triplet energy transfer (TET) through the system is key to unlocking higher efficiencies. In this work, we vary the size of colloidally synthesized CdSe nanocrystals (NCs) to examine the effects on TET during photon upconversion, using steady-state measurements and transient absorption spectroscopy. As the CdSe NC size increases, the photon upconversion quantum yield (QY) decreases due to the decrease in the rate of TET from CdSe to the surface bound anthracene transmitter ligand, as expected for the Marcus description of energy transfer from the transmitter to the NC. Long microsecond transmitter lifetimes are critical to high photon upconversion QYs.
Route to logical strange nonchaotic attractors with single periodic force and noise
Authors: Sathish Aravindh M. , Venkatesan A. , Lakshmanan M.
Published: September 2020

Strange nonchaotic attractors (SNAs) have been identified and studied in the literature exclusively in quasiperiodically driven nonlinear dynamical systems. It is an interesting question to ask whether they can be identified with other types of forcings as well, which still remains an open problem. Here, we show that robust SNAs can be created by a small amount of noise in periodically driven nonlinear dynamical systems by a single force. The robustness of these attractors is tested by perturbing the system with logical signals, leading to the emulation of different logical elements in the SNA regions.
Scaling law for the propagation speed of domino toppling
Authors: Sun Bo-Hua
Published: September 2020

It is essential for domino game players to have a quick estimate of dominoes’ propagation speed without engaging in complicated multi-body dynamics simulation. This research article uses directed dimensional analysis to propose a universal scaling law, v=λghf(δλ), for the speed of domino toppling motion. As an application, two approximate power laws were formulated by curve fitting of both theoretical and experimental data. The fitted power laws, v∼δλhg, show that the domino propagation speed is proportional to the square root of the domino separation λ, thickness δ, and the reciprocation of the domino height h. The obtained scaling law might not only be useful for players but also help them understand domino toppling energy transfer cascades.
Development of a five-stage solid-state linear transformer driver
Authors: Wang Li-min , Zhang Zheng-quan , Liu Qing-xiang , Zhang Tong-xin
Published: September 2020

In this paper, the development of a five-stage solid-state linear transformer driver (LTD) is described. Each stage consists of eight compact pulse generating modules and a magnetic core. The pulse generating modules contain a multilayer-ceramic-capacitor-based pulse-forming network (PFN) and an insulated-gate bipolar transistor (IGBT) switch array, as well as magnetic switches, which are used to speed up the pulse front. To prevent damage from the reverse voltage to the IGBT switch, a reverse voltage absorption circuit was added to the PFN. For this study, a larger cross-sectional core with improved output characteristics was adopted. The developed five-stage LTD has the advantages of long life, low jitter, fast rising edge, and so on. The device can provide a 35 kV, 119 ns, 4.3 kA square pulse train with a maximum frequency of 50 Hz. On this basis, a 50-stage LTD of output 500 kV, which would serve as a high-power microwave driver source, is under development.
Mathematical modeling and cellular automata simulation of infectious disease dynamics: Applications to the understanding of herd immunity
Authors: Mondal Sayantan , Mukherjee Saumyak , Bagchi Biman
Published: September 2020

The complexity associated with an epidemic defies any quantitatively reliable predictive theoretical scheme. Here, we pursue a generalized mathematical model and cellular automata simulations to study the dynamics of infectious diseases and apply it in the context of the COVID-19 spread. Our model is inspired by the theory of coupled chemical reactions to treat multiple parallel reaction pathways. We essentially ask the question: how hard could the time evolution toward the desired herd immunity (HI) be on the lives of people? We demonstrate that the answer to this question requires the study of two implicit functions, which are determined by several rate constants, which are time-dependent themselves. Implementation of different strategies to counter the spread of the disease requires a certain degree of a quantitative understanding of the time-dependence of the outcome. Here, we compartmentalize the susceptible population into two categories, (i) vulnerables and (ii) resilients (including asymptomatic carriers), and study the dynamical evolution of the disease progression. We obtain the relative fatality of these two sub-categories as a function of the percentages of the vulnerable and resilient population and the complex dependence on the rate of attainment of herd immunity. We attempt to study and quantify possible adverse effects of the progression rate of the epidemic on the recovery rates of vulnerables, in the course of attaining HI. We find the important result that slower attainment of the HI is relatively less fatal. However, slower progress toward HI could be complicated by many intervening factors.
Nano-second exciton-polariton lasing in organic microcavities
Authors: Putintsev A. , Zasedatelev A. , McGhee K. E. , Cookson T. , Georgiou K. , Sannikov D. , Lidzey D. G. , Lagoudakis P. G.
Published: September 2020

Organic semiconductors are a promising platform for ambient polaritonics. Several applications, such as polariton routers, and many-body condensed matter phenomena are currently hindered due to the ultra-short polariton lifetimes in organics. Here, we employ a single-shot dispersion imaging technique, using 4 ns long non-resonant excitation pulses, to study polariton lasing in a λ/2 planar organic microcavity filled with BODIPY-Br dye molecules. At a power threshold density of 1.5 MW/cm2, we observe the transition to a quasi-steady state, 1.2 ns long-lived, single-mode polariton lasing and the concomitant superlinear increase in photoluminescence, spectral line-narrowing, and energy blueshift.
Parameter identification and performance estimation for PV modules based on reduced forms model
Authors: Lang Zhe , Zhang Yunpeng
Published: September 2020

Many methods are proposed for parameter identification and performance estimation of photovoltaic (PV) modules, including analytical methods, numerical methods, and optimization methods. In this paper, a hybrid method based on analysis expressions and optimization algorithms is proposed to determine the parameters of the single-diode model and the double-diode model for PV modules. The method is based on the reduced forms and combines the analytical method and the optimization method. By using three key points in I–V curves and making some approximations or simplifying assumptions without sacrificing accuracy, the dimensions of the search space are reduced to only one independent parameter, which reduces the computational complexity and cost. After identifying the parameters under certain conditions, the parameters under any operating conditions are estimated based on the dependence of parameters on environmental conditions. The proposed method is validated by massive experimental data of I–V curves under varying operating conditions. Comparing with other methods with high accuracy, the proposed method shows similar accuracy in parameter identification under certain conditions. Using the proposed method, the output performance estimation is found to be better than the results of other methods. Moreover, the influence of condition selection on the accuracy of output power performance estimation is investigated thoroughly.
Toward ultrathin ferromagnetic metal of (110) La2/3Sr1/3MnO3 thin films
Authors: Li Lin , Ji Yaoyao , Diao Zhenyu , Zhang Jiandi , Liao Zhaoliang
Published: September 2020

The ferromagnetic metal La2/3Sr1/3MnO3 (LSMO) is an important correlated oxide material for oxide spintronics. However, the existence of a dead layer not only degrades device performance but also hinders the ultimate miniaturization of devices. Intense research has been made to eliminate the dead layer and understand its origin. Here, we have investigated the dead layer of (110)-oriented LSMO films on SrTiO3 (STO) substrates in which there is no polar discontinuity across the interface, in contrast to the (001)-oriented LSMO/STO interface. Our results reveal an 8 unit cell (u.c.) dead layer for (110) LSMO. Angle resolved x-ray photoemission demonstrating Sr segregation at the surface. Additionally, the broken symmetry at LSMO/vacuum interfaces also degrades the transport property. By introducing a capping layer, the film conductivity is enhanced. Finally, an ultrathin limit dead layer of 5 u.c. (=1.36 nm) has been obtained by introducing both the LaMnO3 capping layer and the buffer layer to compensate the excess holes at both LSMO/STO and Vacuum/LSMO interfaces and also to reduce the structural distortion at the top surface of LSMO. Our work paves the way toward eliminating the LSMO dead layer for spintronics application and provides a route to engineer the intriguing physical properties of oxide heterointerfaces.
Wave amplitude decay driven by anharmonic potential in nonlinear mass-in-mass systems
Authors: Fiore S. , Finocchio G. , Zivieri R. , Chiappini M. , Garescì F.
Published: September 2020

Periodic or quasi-periodic arrangements of artificial structures can be used to design a class of materials, i.e., metamaterials, with intriguing properties. Recently, it has been proposed to use periodic systems with internal resonances for the attenuation of acoustic/seismic waves. However, large input displacements due to seismic waves can drive the working point of these systems in a nonlinear regime. Here, we have studied the nonlinear dynamics of periodic chain of mass-in-mass systems, which can be used to model composite foundations, where the external spring is characterized by an anharmonic potential. The main finding of this work is the identification of two attenuation mechanisms, one is characterized by an exponential amplitude decay and is observed in the strongly anharmonic regime, whereas the other has a linear decay pattern and characterizes the weak anharmonic dynamics. This result has a direct impact in the design of low frequency seismic metamaterials.
All-optical probe of magnetization precession modulated by spin–orbit torque
Authors: Ishibashi Kazuaki , Iihama Satoshi , Takeuchi Yutaro , Furuya Kaito , Kanai Shun , Fukami Shunsuke , Mizukami Shigemi
Published: September 2020

Laser-induced magnetization precession modulated by an in-plane direct current was investigated in a W/CoFeB/MgO micron-sized strip using an all-optical time-resolved magneto-optical Kerr effect microscope. We observed a relatively large change in the precession frequency, owing to a current-induced spin–orbit torque. The generation efficiency of the spin–orbit torque was evaluated as −0.35 ± 0.03, which was in accordance with that evaluated from the modulation of damping. This technique may become an alternate method for the evaluation of spin–orbit torque.
Enhanced stability of bulk heterojunction organic solar cells by application of few layers of electrochemically exfoliated graphene
Authors: Subramanyam B. V. R. S. , Alam I. , Subudhi S. , Mandal M. , Patra S. , Mahanandia P.
Published: September 2020

Few layers of electrochemically exfoliated graphene (FLECEG) of high quality have been synthesized by a modest method, and their composites with PEDOT:PSS and P3HT have been prepared by a simple solution process. The increase in filler FLECEG wt. % in the polymer has been observed to cause attractive modifications in the physical properties of all the composites, encouraging for their applications in energy systems. Conventional bulk heterojunction organic solar cells (OSCs) have been fabricated by separately using the composites as additional electrode layers and in the active layer of the device. A significant enhancement in the magnitude of device parameters of the OSCs due to the incorporation of FLECEG has been perceived compared with the corresponding reference devices. The caustic effects of intrinsic and additional extrinsic degradation processes on the output of the OSCs have been studied by periodically measuring the device's electrical properties under different environmental conditions. When compared with the performance of reference devices, OSCs manufactured by the application of the composites in both the charge transport layer and the active layer have been noticed to be sustaining with a remarkable stability, while the increment in power conversion efficiency is well maintained. This report has the potential to provide motivation for concentrating advanced research towards the development of composite materials for their applications in manufacturing more stable and efficient organic optoelectronic devices.
Highly sensitive heat flux sensor based on the transverse thermoelectric effect of YBa2Cu3O7−
δ
thin film
Authors: Song Shijin , Wang Yong , Yu Lan
Published: September 2020

Thin film heat flux sensors with the size of 5 mm × 3 mm have been fabricated by growing c-axis tilted YBa2Cu3O7−δ thin films on miscut SrTiO3 (001) substrates. The Seebeck coefficient anisotropy between the ab-plane and the c-axis of the YBa2Cu3O7−δ thin film is utilized to generate the output voltage of the heat flux sensor via the transverse thermoelectric effect. The sensitivities of 104.9, 174.1, and 220.9 μV cm2/W have been achieved in nominal 5°, 10°, and 15° inclined thin films, respectively. Such a sensitivity of 220.9 μV cm2/W exceeds a sensitivity of 180.3 μV cm2/W from a standard and water-cooled Gardon gauge. In addition, the fast response time in the range of 15–40 ms has been identified in these sensors based on the transverse thermoelectric effect, which is significantly superior to 400 ms of the Gardon gauge. These results may provide an approach to manufacture highly sensitive heat flux sensors with a low cost, in contrast to the traditional thin film heat flux sensors with complicated micro-fabrication processes.
Nonlinear magnetoelectric effects in Y-type hexaferrite microwave resonators
Authors: Popov Maksym , Liu Ying , Zavislyak Igor , Qu Hongwei , Zhang T. , Page M. R. , Srinivasan G.
Published: September 2020

The nature of the nonlinear magnetoelectric effect is investigated in platelets of single-crystal Y-type hexaferrite with a collinear ferrimagnetic structure. The effect was observed at room temperature as a shift of 1.1-to-1.4 GHz in the ferromagnetic resonance frequency of Ba2Zn2Fe12O22 (Zn2Y) rectangular resonator with the application of an in-plane DC voltage. The shift amounted to 10%–12% of the central frequency which ranged from 8 to 17 GHz (X and Ku-bands). From the experimental results, we estimated the magnetoelectric modification of effective saturation magnetization and found that it scales almost linearly with the applied DC electric power. A phenomenological model for the nonlinear magnetoelectric effect, which considers the hexaferrite magnetic symmetry, is proposed and qualitatively accounts for the observed dependence of magnetic parameters on input power. It is shown that the resonator can operate as an electrically controlled discrete phase shifter with almost π/4 phase shift and <4 dB insertion losses. These results are of importance for the use of Y-type hexaferrites in electrically tunable planar microwave signal processing devices.
Finite element analysis of hybrid nanofluid flow and heat transfer in a split lid-driven square cavity with Y-shaped obstacle
Authors: Khan Z. H. , Khan W. A. , Hamid M. , Liu Hongtao
Published: September 2020

The constructal design-based model is reported to analyze the thermal control and heat augmentation inside a split lid-driven square cavity. A Y-shaped obstacle is placed within the cavity, which is filled with Al2O3–Cu–water hybrid nanofluids. The concept of the split-lid-driven cavity is utilized for the first time. The governing flow mathematical structure is obtained in terms of a system of partial differential equations and converted to a non-dimensional form through dimensionless variables. The numerical experiments are performed by employing a Galerkin finite element scheme for different values of involved physical parameters. The effects of pertinent parameters on the streamlines, isotherms, dimensionless temperature, and Nusselt numbers are investigated for different values of the Richardson number. Due to the simultaneous motion of the split-lids, the streamlines and isotherms show symmetrical distribution. The local Nusselt number increases with the moving split-lids and attains the maximum value when both lids meet. The average Nusselt number decreases with an increase in the Richardson number. It is important to note that the Y-shaped obstacle enhances the heat transfer rate in the cavity.
Transition to chaos in the wake of a circular cylinder near a moving wall at low Reynolds numbers
Authors: Wang Rui , Zhu Hongbo , Zhou Dai , Bao Yan , Ping Huan , Han Zhaolong , Xu Hui
Published: September 2020

Floquet stability analysis has been employed to identify modes of three-dimensional (3D) instability in the flow over a circular cylinder of diameter D above a moving wall at a gap height of G = 0.2D, beyond the onset of two-dimensional vortex shedding. Two subharmonic modes (mode C1 and mode C2) and one long-wavelength quasi-periodic mode (mode QPL) are revealed. The characteristics of these 3D modes are discussed in detail. The results of 3D direct simulations show that it is the intensively nonlinear modal interactions that lead to a chaotic final flow state at higher Reynolds numbers, rather than the interference of the shear layer caused by the no-slip moving wall.
Different mechanism of response of asymmetric lone pair electrons around ns2 cations to birefringence and second harmonic generation
Authors: Shi Xuerui , Jing Qun , Chen Zhaohui , Lee Ming-Hsien , Duan Haiming , Ding Hanqin
Published: September 2020

The 6s2 lone-pair electrons (Pb2+, Bi3+) and 5s2 lone-pair electrons (Sn2+, Sb3+) show different responses to birefringence than they do to second harmonic generation (SHG). In the current work, different mechanisms of birefringence and SHG responses induced by Pb2+/Sn2+ cations were investigated using the first-principles method on AB2O3F2 (A = Ba, Sn, Pb). The obtained birefringence and SHG coefficients were in good agreement with the experimental values. The anisotropic lone-pair electron distribution was found at the states near the Fermi level containing cation sp-oxygen p states. Our analyses showed the birefringences of the AB2O3F2 (A = Ba, Sn, Pb) compounds to be directly affected by the anisotropic lone-pair electron distribution, however, the SHG responses of these three compounds have a more complicated relationship with the hybrid cation-oxygen states. The expanded hybrid cation-oxygen states including the lone-pair states were concluded to endow the PbB2O3F2 compound with a stronger SHG response than those displayed by the other compounds.
Dynamical correction to the Bethe–Salpeter equation beyond the plasmon-pole approximation
Authors: Loos Pierre-François , Blase Xavier
Published: September 2020

The Bethe–Salpeter equation (BSE) formalism is a computationally affordable method for the calculation of accurate optical excitation energies in molecular systems. Similar to the ubiquitous adiabatic approximation of time-dependent density-functional theory, the static approximation, which substitutes a dynamical (i.e., frequency-dependent) kernel by its static limit, is usually enforced in most implementations of the BSE formalism. Here, going beyond the static approximation, we compute the dynamical correction of the electron–hole screening for molecular excitation energies, thanks to a renormalized first-order perturbative correction to the static BSE excitation energies. The present dynamical correction goes beyond the plasmon-pole approximation as the dynamical screening of the Coulomb interaction is computed exactly within the random-phase approximation. Our calculations are benchmarked against high-level (coupled-cluster) calculations, allowing one to assess the clear improvement brought by the dynamical correction for both singlet and triplet optical transitions.
Intercalated ion tuning of the cross-plane thermal transport properties of graphite
Authors: Ju Wenjing , Zhu Chongming , Wei Zhiyong
Published: September 2020

The effects of the intercalated ion concentration on the cross-plane thermal conductivity and the thermal boundary conductance in the graphite/lithiated graphite interface are investigated from molecular dynamics simulations. At low ion concentration, the cross-plane thermal conductivity of the lithiated graphite is lower than that of the pristine graphite. However, as the intercalated ion concentration increases, the cross-plane thermal conductivity increases rapidly, even exceeding that of the pristine graphite at high ion concentration. By analyzing the variations of the cross-plane elastic constants and phonon dispersion relation with the intercalated ion concentration, it is found that the intercalated ions significantly increase the phonon irradiation heat flux along the cross-plane direction. Our study further shows that the variation of the intercalated ion concentrations can also modulate the thermal boundary conductance in the graphite/lithiated graphite interface. The non-equilibrium molecular dynamics simulations show that the thermal boundary conductance between graphite and lithiated graphite decreases as the lithiation level increases, which would worsen the thermal performance of Li-ion batteries. A one-dimensional atomic chain model is proposed to elaborate on how the effective spring stiffness of material influences the interfacial transmission of phonons with different frequencies. This work provides a quantitative calculation of the cross-plane thermal conductivity and thermal boundary conductance in intercalated graphite samples and is also extremely important for the thermal management and structural design of lithium-ion batteries.
Drop impacting on a surface with adjustable wettability based on the dielectrowetting effect
Authors: Zheng Jiangen , Cheng Yang , Huang Yingzhou , Wang Shuxia , Liu Liyu , Chen Guo
Published: September 2020

The dielectrowetting technique is an important method for controlling surface wettability. Herein, by combining the dielectrowetting technique with high-speed photography, the impact of a water drop on a surface with adjustable wettability is studied. Four different impact phenomena of the drop are identified, and the corresponding phase diagram is provided. As the surface wettability changes, the drop spreading factor and the dynamic contact angle differ for the same Weber number, exhibiting diverse drop behavior. A bubble entrapped on the surface is the most commonly observed phenomenon, and its maximum spreading factor and spreading time are dominated by the Weber number. However, its oscillation period and damping rate are independent of the Weber number. Moreover, a jet occurs on the surface with high hydrophobicity, and the inverse relationship between the jet velocity and radius is in good agreement with the theoretical model. Our work on drop impact based on the dielectrowetting effect can provide a new direction for the study of drop dynamics. Furthermore, the preparation method of the substrate with adjustable surface wettability could be applied in industrial fields such as inkjet printing and coating preparation.
Defect filtering for thermal expansion induced dislocations in III–V lasers on silicon
Authors: Selvidge Jennifer , Norman Justin , Hughes Eamonn T. , Shang Chen , Jung Daehwan , Taylor Aidan A. , Kennedy M. J. , Herrick Robert , Bowers John E. , Mukherjee Kunal
Published: September 2020

Epitaxially integrated III–V semiconductor lasers for silicon photonics have the potential to dramatically transform information networks, but currently, dislocations limit performance and reliability even in defect-tolerant InAs quantum dot (QD)-based lasers. Despite being below the critical thickness, QD layers in these devices contain previously unexplained misfit dislocations, which facilitate non-radiative recombination. We demonstrate here that these misfit dislocations form during post-growth cooldown due to the combined effects of (1) thermal-expansion mismatch between the III–V layers and silicon and (2) mechanical hardening in the active region. By incorporating an additional sub-critical thickness, indium-alloyed “misfit dislocation trapping layer,” we leverage these mechanical hardening effects to our advantage, displacing 95% of misfit dislocations from the QD layer in model structures. Unlike conventional dislocation mitigation strategies, the trapping layer reduces neither the number of threading dislocations nor the number of misfit dislocations. It simply shifts the position of misfit dislocations away from the QD layer, reducing the defects' impact on luminescence. In full lasers, adding a misfit dislocation trapping layer both above and below the QD active region displaces misfit dislocations and substantially improves performance: we measure a twofold reduction in lasing threshold currents and a greater than threefold increase in output power. Our results suggest that devices employing both traditional threading dislocation reduction techniques and optimized misfit dislocation trapping layers may finally lead to fully integrated, commercially viable silicon-based photonic integrated circuits.
Crystalline anharmonicity and ultralow thermal conductivity in layered Bi2GeTe4 for thermoelectric applications
Authors: Singh Niraj Kumar , Soni Ajay
Published: September 2020

Anharmonicity related to crystal structures strongly affects the phonon propagation and reduces lattice thermal conductivity (κl). Associated with a higher order of anharmonicity, thermoelectric (TE) materials with a large Grüneisen parameter (γ) possess ultralow thermal conductivity (κtotal), which plays a decisive role in engineering of their TE performances. We report on the structural and TE transport properties of layered Bi2GeTe4, which belongs to the Bi2Te3 family of TE materials albeit with a larger unit cell. Bi2GeTe4 shows the electron dominated metallic nature throughout the temperature range with a carrier density of n = 8.23 × 1019 cm−3 at 300 K. Bi2GeTe4 exhibits an ultralow κtotal ∼ 0.52 W m−1 K−1 at 350 K with a high degree of anharmonicity as estimated by a large value of γ ∼ 4.24. Here, the calculated average phonon speed (νavg = 1.54 km s−1) and larger bond lengths support the observations of ultralow κtotal. The sufficiently lower value of κtotal makes Bi2GeTe4 a good candidate for high performance TE materials through appropriate electronic transport modulation.
Modern trends in controlled synthesis of functional polymers: fundamental aspects and practical applications
Authors: Grishin Dmitry F. , Grishin Ivan D.
Published: September 2020

Major trends in controlled radical polymerization (CRP) or reversible-deactivation radical polymerization (RDRP), the most efficient method of synthesis of well-defined homo- and copolymers with specified parameters and properties, are critically analyzed. Recent advances associated with the three classical versions of CRP: nitroxide mediated polymerization, reversible addition-fragmentation chain transfer polymerization and atom transfer radical polymerization, are considered. Particular attention is paid to the prospects for the application of photoinitiation and photocatalysis in CRP. This approach, which has been intensively explored recently, brings synthetic methods of polymer chemistry closer to the light-induced processes of macromolecular synthesis occurring in living organisms. Examples are given of practical application of CRP techniques to obtain industrially valuable, high-tech polymeric products.

The bibliography includes 429 references.
An explorative analysis of the perception of guns and gun laws in Azerbaijan using a mixed-methods approach
Authors: Shahbazov Ingilab , Afandiyev Zaur
Published: September 2020

Despite being a post-conflict society, Azerbaijan now enjoys relatively low levels of gun crime and firearm ownership. Adopting a data triangulation approach, this study explored the attitude of the self-select sample (n= 589) in Azerbaijan on guns and gun laws regulating the acquisition of guns, in addition to qualitative interviews. The majority of the participants were content with the current restrictive gun control policies and legislation. Firearms were viewed mostly as an instrument for hunting and self-defence. Qualitative interviews among experts and respondents with experience of the Nagorno-Karabakh conflict (n= 19) largely supplemented the findings obtained through the online survey and provided in-depth insights into the meanings attached to firearms. This explorative study contributes to our understanding of the gunscape in the post-communist and post-conflict society that does not suffer from a gun epidemic. From a comparative perspective, the perceptions of Azerbaijani respondents indicate the absence of “conflict mentality” observed in some other conflict-stricken regions, as well as an extremely limited degree of cultural acceptance of guns as honourable and symbolic items to possess.