bluuebunny/crossref_metadata_2025 huggingface dataset:
Ca–Si mesoporous nanoparticles with the optimal Ag–Zn ratio inhibit the Enterococcus faecalis infection of teeth through dentinal tubule infiltration: an in vitro and in vivo study
Authors: Sun Qing , Duan Mengting , Fan Wei , Fan Bing
Published: December 2020

Ca–Si mesoporous nanoparticles with the optimal Ag–Zn ratio showed better color, excellent antibacterial activity, good biocompatibility, and could infiltrate into the dentinal tubules.
Polyimide-based graphene composite foams with hierarchical impedance gradient for efficient electromagnetic absorption
Authors: Pu Lei , Li Shuangshuang , Zhang Yawei , Zhu Haiyan , Fan Wei , Ma Piming , Dong Weifu , Wang Zicheng , Liu Tianxi
Published: December 2020

Excellent electromagnetic absorption performance can be controllably adjusted by optimizing impedance gradient of polyimide-based graphene composite foam with hierarchical structure.
Mathematical description of the groundwater pumping process during the design of the automatic drainage system
Authors: Shtykova I. , Shinkevich T. , Ybytayeva G.
Published: December 2020

The main structure of any building is the foundation. It takes on itself and transfers all its load to the ground. When choosing the type of foundation, the decisive factor is considered to be the characteristics of the soil, the depth of freezing, as well as the level of groundwater, which gives the developer a lot of problems. The foundation under high groundwater level greatly affects the strength and load-bearing capacity of the building and requires a big investment. The groundwater level will be the fundamental criteriawhen calculating the cost of development, construction technology, durability of the structure and operating conditions of the building. The process of designing such systems is significantly complicated by multidimensionality, non-stationarity, as well as the non-linear nature of control objects. When developing an automatic drainage system, it is necessary to build a high-quality mathematical model of the pumping station. The article discusses the process of building an automatic system of groundwater regulation in a drainage tank based on a given control value and disturbing effect. The mathematical description is developed for the control circuit “water level - speed of the drainage pump” with the main disturbing effect - a change in the groundwater supply Mathematical model of the pumping station is implemented using a virtual simulation program - ViSSim.Based on the obtained model, an automatic drainage system can be developed to prevent flooding of the foundation with ground water during the construction of buildings and structures.
Development of information support for the technological production process of drinks based on plant roughage
Authors: Pachkin Sergey , Ivanov Pavel , Maytakov Anatoliy , Beryazeva Liliya , Kotlyarov Roman
Published: December 2020

Today, SCADA is the main and advanced method for automated management of complex dynamic systems (processes). Supervisory control of technological processes in various branches of the agro-industrial complex is an essential factor in improving their effectiveness and fulfilling the tasks of increasing productivity, competitiveness, and profitability of production. Due to the introduction of SCADA, the company manages to facilitate and improve the production process. The article deals with an example of supervisory control of the production of a drink based on plant roughages. In order to decrease capital costs and further maintenance costs during automation, the functions of the controller level are united with the operator level, and dispatching functions are combined with the level of the administrative automated process control system. SCADA TRACE MODE was selected as the development framework for the technological process information support of the drink. The structure of the SCADA project and the key screen forms allowing dispatching the technological production process of a drink based on plant roughage were designed.
Features of growing chickpea in the foothill zone of the Kabardino-Balkarian Republic
Authors: Tarasheva Zalina , Khanieva Irina , Boziev Aliy , Chapaev Takhir , Odizhev Andemirkan
Published: December 2020

In the foothill zone of the Kabardino-Balkarian Republic in 2013-2015, studies were carried out in order to study the effect of growth regulators and rhizotorfin on the formation of elements of the structure of the chickpea crop. The objects of research were the varieties of chickpeas “Golden Jubilee” and “Privo 1”. The background for testing biological preparations was pre-sowing inoculation of seeds with rhizotorphin based on nitrogen-fixing bacteria and their treatment with microelements (P120K60MoV). The following drugs were used: Albit, Alfastim, Potassium / sodium humate with microelements. The use of growth regulators and rhizotorfin has a positive effect on field germination, the duration of the growing season and the yield of chickpea. The analysis of the data in our studies showed that the cultivation of the chickpea variety “Golden Jubilee” in the foothill zone of the Kabardino-Balkarian Republic is more profitable.
The effect of antioxidant drugs on veterinary and sanitary parameters of cow’s milk
Authors: Kashirina Lidia , Ivanischev Konstantin , Romanov Kirill
Published: December 2020

The article presents the results of experimental studies to determine the effect of antioxidant drugs “Butofan” and “E-selenium” on veterinary and sanitary parameters of cows’ milk obtained in the period after calving. Childbirth is characterized by a stressful physiological state of the body and a large amount of lipid peroxidation (LPO) products are formed in the blood of cows, which have a negative depleting effect on the body and, naturally, on the quality of milk, since it is a blood product. To enhance the work of the body’s own antioxidant system, since it is not always enough to neutralize LPO products, antioxidant drugs are used. It is necessary to determine veterinary and sanitary parameters in milk obtained under the influence of any drugs, since it is used in human nutrition. For this purpose, experimental studies were carried out on analogous dairy cows in one of the farms of Ryazan region. The cows were divided into three groups: the control and two experimental ones. The control group of animals was intact, the cows of the experimental groups received antioxidant preparations: the first one got “E-selenium” and the second one got “Butofan”. The research results showed that the milk yield of cows in the experimental groups was higher compared to the control. The quality parameters of milk in the experimental groups of cows were better in terms of fat content, protein content, density and acidity. Cow’s milk under the influence of antioxidant drugs was biologically complete and environmentally friendly.
The influence of the vegetative stage of Galega orientalis on the quality of haylage prepared from it
Authors: Starkovskiy Boris , Simonov Gennadiy , Malinovskaya Yuliya , Simonov Aleksandr
Published: December 2020

Studying the effect of plant raw materials on the quality of the finished haylage made of Galega orientalis when preparing it at different vegetative stages of plants. Special attention is paid to haylage in the livestock ration structure because compared to silage it has higher nutritive value and contains more dry matter, protein, sugars, macro- and microelements, as well as biologically active substances. It is worth to note that haylage rations have a beneficial impact on the animal body and the productivity of animals, which, in turn, reduces production costs. it has been proved that the green mass of Galega orientalis is a good raw material for making haylage if the technological requirements for feed preparation are met.
Development of new methods for increasing the germination of licorice (Glycyrrhiza uralensis Fisch.) seeds: preliminary data
Authors: Kruglikov Nikolai , Bystrushkin Andrey , Belyaev Alexander
Published: December 2020

The licorice (Glycyrrhiza uralensis Fisch.) is cultivated as a valuable medicinal plant. It is grown from seeds, but 70-90% of its seeds are in deep physical dormancy (hard seeds) – do not swell and do not germinate without special treatment (scarification). We are searching for the most effective methods of such processing. We have studied the effect of hydrostatic pressure from 10 to 40 MPa (pressure treatment) on the licorice seeds to improve the swelling and germination of them, which belong to a pair of visually distinguished groups by the color of the seed coat. For the first time, it was found that olive-colored seeds do not germinate after pressure treatment (the number of hard seeds is 80% or more). At the same time, very high content (up to 90%) of swollen but non-viable seeds was detected in the group with a light brown color of the seed coat. Hydrostatic pressure levels used did not significantly reduce hard seeds proportion in studied licorice seed material. A weak positive effect of hydrostatic pressure treatment was found. Further search for optimal pressure treatment modes for licorice seeds germination increasing looks promising.
The importance of internal control for agricultural organizations and ways to improve it
Authors: Panferova Liya
Published: December 2020

The article reveals the important role and importance of internal control for agricultural organizations, its purpose and objectives are given. It is noted that the internal control system is a set of methods and techniques that ensure compliance with regulatory legal acts, the safety of assets, the timely reflection of business transactions in the accounting, prevention of abuse by staff, and the formation of reliable financial statements. The higher the level of organization of internal control, the lower the risk of material distortion of the data in the financial statements of agricultural organizations. At this stage of development, internal control is not only a verification of the accuracy of accounting, but also is a control function of management. In the process of its implementation, the risks of the organization and their consequences are assessed. The article focuses on the risks that distort the financial statements of the organization, and also provides ways to minimize them.
Formulation and Characterization of Losartan Loaded Chitosan Microspheres: Effect of Crosslinking Agents
Authors: Pahuja Sonia , Aggarwal Shweta , Sarup Prerna
Published: December 2020

Objective The present investigation entailed determination of effect of diverse cross-linking agents on Losartan Potassium loaded chitosan microspheres. The emulsion cross-linking method was employed to formulate the microspheres with an endeavour to achieve maximum sustained effect.

Methods The FTIR studies revealed absence of any interaction between Losartan and chitosan. The emulsion cross linking method was accomplished in three steps encompassing formation of an aqueous and oily phase, emulsification and cross-linking. A total of eighteen Losartan formulations were developed using six different cross-linkers at three varying level were screened for optimum parameters. The in vitro drug release parameters of optimum formulations (LC3, LE3, LF3, LG3, LS3 and LV3) containing citric acid, epichlorohydrin, formaldehyde, glutaraldehyde, suphuric acid and vanillin as cross-linkers were assessed to determine the sustained effect.

Results The values of evaluated parameters including percent yield (94.67%), average particle size (51.19 µm), drug content (44.38 mg) and entrapment efficiency (88.77%) connoted LG3 as the best formulation. Additionally, the values of relative measure of skewness (β1=0.01 and γ1=0.10) and platykurtic (β2=1.26) size distribution were least for LG3 with spherical shape and smooth surface as revealed by SEM studies.

Conclusion The outcome of in vitro release and other characterizations of microspheres explicitly revealed glutaraldehyde as the best cross-linker amongst the cross-linkers used herewith. The maximum sustained effect (lasting over a period of 24 h) accompanied with higher MDT and t50% with lower%DE and Q14h values thus corroborated the objective of attaining sustained release of Losartan.
Resorcylic Acid Lactones Produced by an Endophytic Penicillium ochrochloron Strain from Kadsura angustifolia
Authors: Song Hong Chuan , Qin Dan , Liu Hai Yang , Dong Jin Yan , You Chuan , Wang Yu Meng
Published: December 2020

Four new β-resorcylic acid lactones, including penochrochlactone A (2), 4-O-desmethyl-aigialomycin B (4), and penochrochlactones C and D (5 and 6), two compounds isolated from a natural source for the first time, 5α, 6β-acetonide-aigialomycin B (1) and penochrochlactone B (3), together with six known compounds, aigialomycin F (7), aigialomycins A, B, and D (8–10), zeaenol (11), and oxozeaenol (12), were isolated from a mycelial solid culture of the endophytic fungus Penicillium ochrochloron SWUKD4.1850 from the medicinal plant Kadsura angustifolia by sequential purification over silica gel, Sephadex LH-20 column chromatography, and preparative HPLC. Their structures were elucidated by extensive spectroscopic analysis and chemical conversions. In addition, all the new compounds were evaluated for their cytotoxic and antibacterial activities in vitro.
Penochrochlactone C (5) displayed moderate cytotoxicity against the HeLa tumor cell line with an IC50 value of 9.70 µM. In the antibacterial assays, compounds 4 – 6 exhibited moderate activities against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa with MIC values between 9.7 and 32.0 µg/mL.
Endoscopic management of enteral tubes in adult patients – Part 2: Peri- and post-procedural management. European Society of Gastrointestinal Endoscopy (ESGE) Guideline
Authors: Gkolfakis Paraskevas , Arvanitakis Marianna , Despott Edward J. , Ballarin Asuncion , Beyna Torsten , Boeykens Kurt , Elbe Peter , Gisbertz Ingrid , Hoyois Alice , Mosteanu Ofelia , Sanders David S. , Schmidt Peter T. , Schneider Stéphane M. , van Hooft Jeanin E.
Published: December 2020

Main recommendations

ESGE recommends the “pull” technique as the standard method for percutaneous endoscopic gastrostomy (PEG) placement.

Strong recommendation, low quality evidence.

ESGE recommends the direct percutaneous introducer (“push”) technique for PEG placement in cases where the “pull” method is contraindicated, for example in severe esophageal stenosis or in patients with head and neck cancer (HNC) or esophageal cancer.

Strong recommendation, low quality evidence.

ESGE recommends the intravenous administration of a prophylactic single dose of a beta-lactam antibiotic (or appropriate alternative antibiotic, in the case of allergy) to decrease the risk of post-procedural wound infection.

Strong recommendation, moderate quality evidence.

ESGE recommends that inadvertent insertion of a nasogastric tube (NGT) into the respiratory tract should be considered a serious but avoidable adverse event (AE).

Strong recommendation, low quality evidence.

ESGE recommends that each institution should have a dedicated protocol to confirm correct positioning of NGTs placed “blindly” at the patient’s bedside; this should include: radiography, pH testing of the aspirate, and end-tidal carbon dioxide monitoring, but not auscultation alone.

Strong recommendation, low quality evidence.

ESGE recommends confirmation of correct NGT placement by radiography in high-risk patients (intensive care unit [ICU] patients or those with altered consciousness or absent gag/cough reflex).

Strong recommendation, low quality evidence.

ESGE recommends that EN may be started within 3 – 4 hours after uncomplicated placement of a PEG or PEG-J.

Strong recommendation, high quality evidence.

ESGE recommends that daily tube mobilization (pushing inward) along with a loose position of the external PEG bumper (1 – 2 cm from the abdominal wall) could mitigate the risk of development of buried bumper syndrome.

Strong recommendation, low quality evidence.
Why, Whom, and How to Screen for Chronic Thromboembolic Pulmonary Hypertension after Acute Pulmonary Embolism
Authors: Boon Gudula J.A.M. , Huisman Menno V. , Klok Frederikus A.
Published: December 2020

Chronic thromboembolic pulmonary hypertension (CTEPH) is considered a long-term complication of acute pulmonary embolism (PE). Diagnosing CTEPH is challenging, as demonstrated by a considerable diagnostic delay exceeding 1 year, which has a negative impact on the patient's prognosis. Dedicated screening CTEPH strategies in PE survivors could potentially help diagnosing CTEPH earlier, although the optimal strategy is unknown. Recently published updated principles for screening in medicine outline the conditions that must be considered before implementation of a population-based screening program. Following these extensive principles, we discuss the pros and cons of CTEPH screening, touching on the epidemiology of CTEPH, the prognosis of CTEPH in the perspective of emerging treatment possibilities, and potentially useful tests and test combinations for screening. This review provides a modern perspective on CTEPH screening including a novel approach using a simple noninvasive algorithm of sequential diagnostic tests applied to all PE survivors.
Measurement of thermal properties of bulk materials and thin films by modulated thermoreflectance (MTR)
Authors: Fournier D. , Marangolo M. , Fretigny C.
Published: December 2020

Thermal conductivity and thermal diffusivity of materials must be known at high accuracy for thermal engineering applications, in order to understand energy dissipation in devices and engines. Thermal conductivity libraries can be unreliable since their reported values may not reflect the complexities of the samples under investigation, and new materials may not yet be listed. Over the past three decades, modulated thermoreflectance (MTR) has emerged and evolved as a reliable, non-contact, and noninvasive technique to measure the thermal properties of a wide range of bulk and thin film materials and their interfaces. This Tutorial discusses the basis of, and recent advances in, the MTR technique, and its applications in the thermal characterization of a variety of materials. MTR experiments use two micrometer-wide laser beams. Experimental data (amplitude and phase vs the offset between the pump and the probe) give information about heat diffusion around the heat source along several tens of micrometers. Heat diffusion equations are used to fit the experimental data and extract the required thermal properties. Importantly, best fit procedures are not always needed because some analytical approximations provide evidence of the required thermal properties. We present many examples (bulk materials, layered sample, etc.) which illustrate this.
Measurements of a quantum bulk acoustic resonator using a superconducting qubit
Authors: Chou M.-H. , Dumur É. , Zhong Y. P. , Peairs G. A. , Bienfait A. , Chang H.-S. , Conner C. R. , Grebel J. , Povey R. G. , Satzinger K. J. , Cleland A. N.
Published: December 2020

Phonon modes at microwave frequencies can be cooled to their quantum ground state using conventional cryogenic refrigeration, providing a convenient way to study and manipulate quantum states at the single phonon level. Phonons are of particular interest because mechanical deformations can mediate interactions with a wide range of different quantum systems, including solid-state defects, superconducting qubits, and optical photons when using optomechanically active constructs. Phonons, thus, hold promise for quantum-focused applications as diverse as sensing, information processing, and communication. Here, we describe a piezoelectric quantum bulk acoustic resonator (QBAR) with a 4.88 GHz resonant frequency, which, at cryogenic temperatures, displays large electromechanical coupling strength combined with a high intrinsic mechanical quality factor, Qi≈4.3×104. Using a recently developed flip-chip technique, we couple this QBAR resonator to a superconducting qubit on a separate die and demonstrate the quantum control of the mechanics in the coupled system. This approach promises a facile and flexible experimental approach to quantum acoustics and hybrid quantum systems.
A non-linear elastic approach to study the effect of ambient humidity on sandstone
Authors: Khajehpour Tadavani Somayeh , Poduska Kristin M. , Malcolm Alison E. , Melnikov Andrey
Published: December 2020

We demonstrate that strong elastic pump wave pulses soften sandstone more in humidified conditions than they do in dry conditions and that this effect is repeatable and reversible. We assess these changes via the non-linear interactions of a strong pump wave with a weaker probe wave. We find that there is an exponential time constant (τ≈13days) associated with this process that is independent of the amplitudes of the pump and the probe, the phase delay between the two waves (the time between transmission of the pump and probe waves), the sampling rate, and whether the sample is being dried or humidified. We demonstrate that the humidity-dependent differences in the amount of softening are induced by only a very small amount of absorbed water vapor and argue that this water is intercalated within clay particles. We also show that our pump–probe experiments detect these humidity-dependent differences in the amount of softening easily and repeatably using an experimental design that does not rely on resonance conditions. This means that, in principle, our experiments could be more easily generalized to other experimental geometries to investigate non-linear elastic properties in complex or irregular sample geometries. Our method and findings have potential relevance in oil and gas exploration, civil engineering, and understanding of the mechanism of earthquakes.
Microscopic origin of inhomogeneous transport in four-terminal tellurene devices
Authors: Kupp Benjamin M. , Qiu Gang , Wang Yixiu , Casper Clayton B. , Wallis Thomas M. , Atkin Joanna M. , Wu Wenzhuo , Ye Peide D. , Kabos Pavel , Berweger Samuel
Published: December 2020

Tellurene—the 2D form of elemental tellurium—provides an attractive alternative to conventional 2D semiconductors due to its high bipolar mobilities, facile solution processing, and the possibility of dopant intercalation into its 1D van der Waals lattice. Here, we study the microscopic origin of transport anisotropy in lithographically defined four-terminal tellurene devices using spatially resolved near-field scanning microwave microscopy (SMM). Our conductivity- and carrier type-sensitive SMM imaging reveals that the overall p-type transport measured between adjacent and opposite terminals originates from strong p-type character at the device edges. Despite using an atomic layer deposition-grown conformal overcoat that n-dopes the device interior, we observe only weak n-type transport along the main device channel at positive backgate voltages. This weak n-type transport along the device channel is shown to arise from local p-doping within a few micrometers of the electrodes, which produces a transport barrier from the n-type interior to the electrodes. These results reveal how the backgate-dependent conduction anisotropy could be leveraged to weigh different inputs for non-von Neumann architectures.
A gas-insulated mega-ampere-class linear transformer driver with pluggable bricks
Authors: Jiang Xiaofeng , Sun Fengju , Wang Zhiguo , Jiang Hongyu , Qiu Aici , Li Xingwen , Wu Jian , Chen Li , Li Penghui , Jia Shenli
Published: December 2020

This paper presents the design and test of a gas-insulated linear transformer driver (LTD) cavity aimed at the Z-pinch experimental device CZ-34. The LTD cavity has a diameter of 2290 mm and a height of 346 mm. It consists of 23 main bricks and 1 trigger brick. Each main brick is comprised of two 100 nF capacitors connected electrically in series with a field-distortion gas switch. The trigger brick is comprised of two 50 nF capacitors connected in series with a compact multi-gap gas switch. All bricks are placed in the cavity filled with compressed SF6 and are pluggable like drawers. The trigger pulse generated by the trigger brick passes through an azimuthal transmission line to the trigger ring and makes the main bricks discharge synchronously. The LTD cavity can deliver ∼1 MA current pulse with a rise time of 115 ns to 0.08 Ω liquid resistance load when the charging voltage is ±100 kV, which is in good agreement with the circuit simulation results. Experimental results demonstrate the successful application of using gas insulation and pluggable bricks. The technical feasibility of the charging configuration, triggering method, and isolation resistors is verified. There is little difference in output performance as return-current rods replaced the outside metal cylinder, which provides a new path for the design of LTD cavities in series.
Vortex breakdown of the swirling flow in a Lean Direct Injection burner
Authors: Shen Yazhou , Ghulam Mohamad , Zhang Kai , Gutmark Ephraim , Duwig Christophe
Published: December 2020

This paper presents a comprehensive study of the unsteady flow field in a new concept lean direct injection gas turbine burner, which aims at a clean and efficient combustion with application to sustainable aviation and pollution abatement. Large Eddy Simulation (LES) and planar particle image velocimetry are employed to capture the characteristics of the swirling flow issued from the multiple-jet swirler under both the confined and unconfined conditions. The results are compared, and good agreement shows the capability of LES in capturing the large-scale flow structures. The iso-contour of axial and swirl velocities shows that the swirling flow is featured by multiple jets. These jets interact with the central recirculation zone (CRZ) and reform it into a “starfish” shape. Under the effect of the confinement, the flow displays a larger spreading angle of the jets and an outer recirculation zone (ORZ). A distinctive connection between the CRZ and the ORZ is evidenced to occur through the channels between the multiple jets. The outward flow in the channels is identified to oscillate at a Strouhal number of 0.1. To characterize the evolution, the unsteady large-scale structures, proper orthogonal decomposition (POD), and spectra POD (SPOD) analyses are performed. It is found that a single helix and a double helix are manifestations of two independent global modes in the SPOD analysis. The former shares the same frequency with the outward flow, and the latter is solely affected by the confinement.
Frequency-comb response of a parametrically driven Duffing oscillator to a small added ac excitation
Authors: Batista Adriano A. , Lisboa de Souza A. A.
Published: December 2020

Here, we present a one-degree-of-freedom model of a nonlinear parametrically driven resonator in the presence of a small added ac signal that has spectral responses similar to a frequency comb. The proposed nonlinear resonator has a spread spectrum response with a series of narrow peaks that are equally spaced in frequency. The system displays this behavior most strongly after a symmetry-breaking bifurcation at the onset of parametric instability. We further show that the added ac signal can suppress the transition to parametric instability in the nonlinear oscillator. We also show that the averaging method is able to capture the essential dynamics involved.
Directionality of growth and kinetics of branched fibril formation
Authors: Razbin Mohammadhosein , Benetatos Panayotis , Mirabbaszadeh Kavoos
Published: December 2020

The self-assembly of fibrils is a subject of intense interest, primarily due to its relevance to the formation of pathological structures. Some fibrils develop branches via the so-called secondary nucleation. In this paper, we use the master equation approach to model the kinetics of formation of branched fibrils. In our model, a branched fibril consists of one mother branch and several daughter branches. We consider five basic processes of fibril formation, namely, nucleation, elongation, branching, fragmentation, and dissociation of the primary nucleus of fibrils into free monomers. Our main focus is on the effect of the directionality of growth on the kinetics of fibril formation. We consider several cases. At first, the mother branch may elongate from one or from both ends, while the daughter branch elongates only from one end. We also study the case of branched fibrils with bidirectionally growing daughter branches, tangentially to the main stem, which resembles the intertwining process. We derive a set of ordinary differential equations for the moments of the number concentration of fibrils, which can be solved numerically. Assuming that the primary nucleus of fibrils dissociates with the fragmentation rate, in the limit of the zero branching rate, our model reproduces the results of a previous model that considers only the three basic processes of nucleation, elongation, and fragmentation. We also use the experimental parameters for the fibril formation of Huntingtin fragments to investigate the effect of unidirectional vs bidirectional elongation of the filaments on the kinetics of fibrillogenesis.
Vibronic exciton model for low bandgap donor–acceptor polymers
Authors: Balooch Qarai Mohammad , Chang Xin , Spano F. C.
Published: December 2020

A vibronic exciton model is introduced to describe the excited state band structure and associated absorption spectra of low bandgap donor–acceptor conjugated polymers. The Hamiltonian is represented in a diabatic basis consisting of Frenkel-like donor and acceptor fragment excitations as well as charge-transfer (CT) excitations between neighboring fragments. States are coupled to each other through electron and hole transfer as well as Coulombically, through interacting fragment transition dipole moments. Local vibronic coupling involving the prominent aromatic-quinoidal vibrational mode, which is responsible for pronounced vibronic progressions in most conjugated oligomers and polymers, is also included. The DAD repeat unit is shown to behave like a J-aggregate trimer, driven by both the sizable in-phase electron and hole transfer integrals between donor and acceptor fragments as well as negative Coulomb coupling between donor and acceptor fragment excitations. The J-aggregate behavior is enhanced in the polymer limit through inter-repeat unit coupling, with the 0–0 vibronic peak significantly enhanced in the lowest-energy near-IR band. In addition, the radiative rate is enhanced by the number of coherently connected repeat units. The near-IR band is shown to possess roughly equal admixtures of CT and Frenkel-like excitations. Applications are made to the polymer PffBT4T-2DT, with the simulated absorption spectrum quantitatively capturing the salient features of the measured spectrum.
Charge transfer states impact the triplet pair dynamics of singlet fission polymers
Authors: He Guiying , Busby Erik , Appavoo Kannatassen , Wu Qin , Xia Jianlong , Campos Luis M. , Sfeir Matthew Y.
Published: December 2020

Polymers are desirable optoelectronic materials, stemming from their solution processability, tunable electronic properties, and large absorption coefficients. An exciting development is the recent discovery that singlet fission (SF), the conversion of a singlet exciton to a pair of triplet states, can occur along the backbone of an individual conjugated polymer chain. Compared to other intramolecular SF compounds, the nature of the triplet pair state in SF polymers remains poorly understood, hampering the development of new materials with optimized excited state dynamics. Here, we investigate the effect of solvent polarity on the triplet pair dynamics in the SF polymer polybenzodithiophene-thiophene-1,1-dioxide. We use transient emission measurements to study isolated polymer chains in solution and use the change in the solvent polarity to investigate the role of charge transfer character in both the singlet exciton and the triplet pair multiexciton. We identify both singlet fluorescence and direct triplet pair emission, indicating significant symmetry breaking. Surprisingly, the singlet emission peak is relatively insensitive to solvent polarity despite its nominal “charge-transfer” nature. In contrast, the redshift of the triplet pair energy with increasing solvent polarity indicates significant charge transfer character. While the energy separation between singlet and triplet pair states increases with solvent polarity, the overall SF rate constant depends on both the energetic driving force and additional environmental factors. The triplet pair lifetime is directly determined by the solvent effect on its overall energy. The dominant recombination channel is a concerted, radiationless decay process that scales as predicted by a simple energy gap law.
A robust in-motion attitude alignment method for odometer-aided strapdown inertial navigation system
Authors: Sun Yiding , Yang Gongliu , Cai Qingzhong , Wen Zeyang
Published: December 2020

A significant issue of land vehicle navigation is in-motion attitude alignment of the odometer (OD)-aided strapdown inertial navigation system (SINS). The consecutive OD outliers can occur due to sudden wheel slipping and skidding while vehicle maneuvering. They seriously reduce the robustness and precision of attitude alignment. In this paper, we investigate a robust in-motion attitude alignment method for the OD-aided SINS. The method consists of in-motion coarse alignment and in-motion fine alignment. In the in-motion coarse alignment process, we developed Huber’s M-estimation and integral formula based robust Kalman filter (HRKF/IF-CA), which can restrain the interference of consecutive OD outliers on reconstructed observation vectors. Thus, HRKF/IF-CA can contribute to better coarse attitude results. The next process is in-motion fine alignment. Under the popular repeated backtracking scheme, we investigate HRKF based fine alignment (HRKF-FA) with the SINS/OD summed measurement model. HRKF-FA can refine attitude alignment and restrain the interference of consecutive OD outliers simultaneously. Finally, the proposed method is evaluated by simulation and vehicle test. The attitude alignment results show that this method can achieve reasonable attitude results, and the interference of consecutive OD outliers caused by sudden wheel slipping and skidding can be greatly restrained.
Engineering visible light emitting point defects in Zr-implanted polycrystalline AlN films
Authors: Aghdaei A. , Pandiyan R. , Ilahi B. , Chicoine M. , El Gowini M. , Schiettekatte F. , Fréchette L. G. , Morris D.
Published: December 2020

We have investigated the impact of thermal annealing gaseous atmosphere of argon, nitrogen, and forming gas on the structural and optical properties of thin polycrystalline AlN films subjected to high-energy zirconium ions implantation. X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and atomic force microscopy measurements show that the structural and morphological properties of the Zr-implanted AlN films depend on the annealing gaseous environment. Post-implantation annealing under argon atmosphere yields the lowest structured surface roughness with increased grain size. Photoluminescence spectroscopy revealed multiple point defects and defect complexes related emission bands in the visible range. A series of absorption bands have been observed using photoluminescence excitation spectroscopy. The origin of the emission or absorption bands is identified and attributed to various types of point defects and defect complexes, theoretically reported for AlN. New emission and absorption peaks at 1.7eV (730nm) and 2.6eV (466nm), respectively, have been identified and attributed to the (ZrAl–VN)0 defect complexes.
Direct visualization of the photovoltaic effect in a single-junction GaAs cell via in situ electron holography
Authors: Anada Satoshi , Hirayama Tsukasa , Sasaki Hirokazu , Yamamoto Kazuo
Published: December 2020

The nanoscale electric potential distribution in a gallium arsenide single p–n junction cell under artificial illumination, or the photovoltaic (PV) effect, was investigated using in situ electron holography with a transmission electron microscope. A custom-made specimen holder with biasing and illumination capabilities was used for this purpose. To determine the practical potential of the specimen prepared by a focused ion beam (FIB), the thickness of active layers that directly contribute to the PV effect was accurately derived by analyzing the results of in situ biasing electron holography. In situ light-illumination electron holography directly visualized the PV effect in the cell, where the potential difference between the p and n regions decreased with the increase in the intensity of light illumination. Using PV simulations, in conjunction with some reasonable assumptions regarding the practical specimen parameters in the FIB-milled specimen, we can generate a credible explanation of the experimental result. These findings will help to fully understand the PV effect in various types of solar cells, including perovskite and quantum dot cells.
Three-dimensional flip-flopping flow around a pair of dual-stepped circular cylinders in a side-by-side arrangement
Authors: Yan Yuhao , Ji Chunning , Srinil Narakorn
Published: December 2020

Three-dimensional direct numerical simulations of flow around a pair of dual-stepped circular cylinders in a side-by-side arrangement and a proximity interference region are presented. The dual-stepped cylinders consist of two coaxial cylinders with a larger-to-smaller diameter ratio of 2. The Reynolds number and the side-by-side gap ratio, based on the larger (smaller) diameter, are 200 (100) and 1 (3), respectively. Two flip-flopping flow regimes A and B are observed behind the dual-stepped cylinders, exhibiting temporal variations of hydrodynamic drag and lift force coefficients. The flow regime B is featured by the flip-flopping, higher vortex-shedding frequencies and greater flow instability than those in the flow regime A. Half-loop and direct connections of vortices take place frequently in the narrower wake, while the vortex reconnection and multiple connection predominate the wider wake. This suggests that the dual-stepped cylinder with the narrower wake behaves similarly to a single dual-stepped cylinder. The dynamic mode decomposition analysis reveals pitchfork and Hopf bifurcation (in-phase and anti-phase synchronization) modes in the larger cylinder wake, with the interaction of these bifurcations originating from the flip-flopping flow pattern. However, the pitchfork mode is not found in the smaller cylinder wake, suggesting that its flip-flopping flow behavior is not self-originated but triggered by the flip-flopping flow mechanism of the larger cylinder.
Estimates of electron correlation based on density expansions
Authors: Whitten Jerry L.
Published: December 2020

Two methods for estimating the correlation energy of molecules and other electronic systems are discussed based on the assumption that the correlation energy can be partitioned between atomic regions. In the first method, the electron density is expanded in terms of atomic contributions using rigorous electron repulsion bounds, and in the second method, correlation contributions are associated with basis function pairs. These methods do not consider the detailed nature of localized excitations but instead define a correlation energy per electron factor that is unique to a specific atom. The correlation factors are basis function dependent and are determined by configuration interaction (CI) calculations on diatomic and hydride molecules. The correlation energy estimates are compared with the results of high-level CI calculations for a test set of 27 molecules representing a wide range of bonding environments (average error of 2.6%). An extension based on truncated CI calculations in which d-type and hydrogen p-type functions are eliminated from the virtual space combined with estimates of dynamical correlation contributions using atomic correlation factors is discussed and applied to the dissociation of several molecules.
Tunable power factor in fluorine-doped single-walled carbon nanotubes
Authors: Sakyi-Arthur D. , Mensah S. Y. , Mensah N. G. , Adu K. W. , Dompreh K. A. , Edziah R.
Published: December 2020

Herein, we present a tunable axial power factor (Pzz) in a nondegenerate fluorine-doped single-walled carbon nanotube (FSWCNT) using a tractable analytical approach. We derived the expressions for the electrical conductivity (σ), thermopower (α), and power factor (P) as a function of temperature. Additionally, we investigated the influence of doping concentration (no), constant electric field (Eo), and overlapping integrals (Δs and Δz) on their behavior. The intensity of the axial power factor (Pzz) and the operational temperature range can be tuned using the constant electric field, doping (carrier), and overlapping integrals, respectively. Applying the temperature field to the FSWCNT induces high-frequency carrier dynamics that critically depend on the magnitude of the temperature gradient. There exist two dynamic regimes that depend on the temperature gradient and carrier’s initial position. The carrier drifts through the FSWCNT and is allowed to perform drifting periodic orbits (in THz frequencies), resulting in the resonant enhancement of Pzz. Alternatively, inducing Bloch-like oscillations (in THz frequencies) cause ultra-high negative differential velocity without domain formation using an adequate temperature field. Moreover, we compare the Pzz of the FSWCNT to that of the superlattice (SL) (PzzSL), which shows that the Pzz of the FSWCNT is 8 orders of magnitude greater than that of the SL. It is worth noting that the large Pzz obtained and the ability to tune the FSWCNT to operate at high temperatures make the FSWCNT a potential candidate for thermoelectric applications.
SnO/β-Ga2O3 vertical pn heterojunction diodes
Authors: Budde Melanie , Splith Daniel , Mazzolini Piero , Tahraoui Abbes , Feldl Johannes , Ramsteiner Manfred , von Wenckstern Holger , Grundmann Marius , Bierwagen Oliver
Published: December 2020

As a contribution to (transparent) bipolar oxide electronics, vertical pn heterojunction diodes were prepared by plasma-assisted molecular beam epitaxy of unintentionally doped p-type SnO layers with hole concentrations ranging from p=1018 to 1019 cm−3 on unintentionally doped n-type β-Ga2O3(−201) substrates with an electron concentration of n=2.0×1017 cm−3. The SnO layers consist of (001)-oriented grains without in-plane epitaxial relation to the substrate. After subsequent contact processing and mesa-etching (which drastically reduced the reverse current spreading in the SnO layer and associated high leakage), electrical characterization by current–voltage and capacitance–voltage measurement was performed. The results reveal a type-I band alignment and junction transport by thermionic emission in forward bias. A rectification of 2×108 at ±1 V, an ideality factor of 1.16, a differential specific on-resistance of 3.9 m Ω cm2, and a built-in voltage of 0.96 V were determined. The pn-junction isolation prevented parallel conduction in the highly conductive Ga2O3 substrate during van-der-Pauw Hall measurements of the SnO layer on top, highlighting the potential for decoupling the p-type functionality in lateral transport devices from that of the underlying n-type substrate. The measured maximum reverse breakdown voltage of the diodes of 66 V corresponds to a peak breakdown field of 2.2 MV/cm in the Ga2O3-depletion region and suggests the low bandgap of the SnO (≈0.7 eV) not to be the limiting factor for breakdown. Higher breakdown voltages that are required in high-voltage devices could be achieved by reducing the donor concentration in the β-Ga2O3 toward the interface to increase the depletion width, as well as improving the contact geometry to reduce field crowding.
Structural and electronic properties of monodomain ultrathin PbTiO3/SrTiO3/PbTiO3/SrRuO3 heterostructures: A first-principles approach
Authors: Mahjoub Reza , Nagarajan Valanoor , Junquera Javier
Published: December 2020

First-principles calculations within the local density approximation were carried out to explain the ground state and electronic properties of a vacuum/PbTiO3/SrTiO3/PbTiO3/SrRuO3 multilayer in a monodomain phase. Open-circuit boundary conditions were assumed, considering the electric displacement field, D, as the fundamental electrical variable. The direction and the magnitude of D can be monitored by proper treatment of the PbO surface layer, introducing external fractional charges Q in the surface atomic layers by means of virtual crystal approximation. Different excess or deficit surface charges (from Q=±0.05 to Q=±0.15) were considered, corresponding to small values of the polarization (up to ±0.16C/m2) in both directions. The layer-by-layer electric polarization, tetragonality, and the profile of the electrostatic potential were computed, as well as the projected density of states, as a function of electric displacement field. The magnitude of D is preserved across the dielectric layers, which translates into a polarization of the SrTiO3 spacer layer. The tetragonality of the two PbTiO3 layers is different, in good agreement with experimental x-ray diffraction techniques, with the layer closer to the free surface exhibiting a smaller value. This is attributed to the interplay with surface effects that tend to contract the material in order to make the remaining bonds stronger. Our calculations show how the final structure in this complex oxide heterostructure comes from a delicate balance between electrical, mechanical, and chemical boundary conditions.
Band offsets of (100)
β
-(AlxGa1−x)2O3/
β
-Ga2O3 heterointerfaces grown via MOCVD
Authors: Bhuiyan A F M Anhar Uddin , Feng Zixuan , Johnson Jared M. , Huang Hsien-Lien , Hwang Jinwoo , Zhao Hongping
Published: December 2020

The valence and conduction band offsets at (100) β-(AlxGa1−x)2O3/β-Ga2O3 heterointerfaces with the increasing Al composition are determined via x-ray photoelectron spectroscopy. The (100) β-(AlxGa1−x)2O3 thin films with the Al composition of 0.10 < x < 0.52 are grown on (100) β-Ga2O3 substrates by the metalorganic chemical vapor deposition method. By examining the onset of inelastic energy loss in core-level atomic spectra, the bandgaps of β-Ga2O3 and β-(AlxGa1−x)2O3 alloys with different Al compositions are measured from 4.83 ± 0.12 eV (x = 0) to 5.85 ± 0.08 eV (x = 0.52). The valence band offsets are determined to be −0.06 ± 0.06 eV (x = 0.10), −0.11 ± 0.06 eV (x = 0.33), and −0.19 ± 0.06 eV (x = 0.52). The conduction band offsets of 0.34 ± 0.17 eV (x = 0.10), 0.62 ± 0.17 eV (x = 0.33), and 1.21 ± 0.16 eV (x = 0.52) are determined from the extracted bandgaps of β-(AlxGa1−x)2O3 alloys. The determined band alignments at β-(AlxGa1−x)2O3/β-Ga2O3 interfaces reveal the formation of type-II (staggered gap) heterojunctions for all Al compositions investigated. The bowing parameters obtained from the quadratic fitting of both conduction band minimum and valence band maximum values are estimated to be 1.25 eV and 0.005 eV, respectively.