bluuebunny/crossref_metadata_2025 huggingface dataset:
A comparative study on the effect of disks geometrical features on the drag torque of a wet friction clutch
Authors: Rogkas Nikolaos , Almpani Despoina , Vasileiou Georgios , Tsolakis Eustratios , Vakouftsis Christos , Zalimidis P. , Spitas Vasilios
Published: August 2020

In recent years, the need for highly efficient automatic and semiautomatic powertrains has led to the wide use of wet friction clutches as power transmission systems. While wet friction clutches surpass their counterparts dry-friction clutches in the engagement process as they provide higher efficient torque and smoother torque and speed transmission, yet they fall behind in their disengaged state where the clutch acts as a power loss to the system due to the drag torque developed on the disks from fluid’s viscous shear stresses. Shear stresses are developed due to the relative speed difference of coaxial disks distanced at a prescribed axial clearance and rotating independently, yielding to a torsional Couette shear flow. This matter has been investigated thoroughly in the literature with experimental and numerical approaches for the case of flat disks admitting the complex flow pattern, which is augmented even more from the presence of geometrical features (grooves) on the surface of the disks. It becomes clear that the efficient calculation and understanding of drag torque can lead to its minimization and therefore to further establishing the use of wet clutches. In this work the effect of various disks geometrical features on the drag torque of a wet clutch is examined. The results are obtained via FEA (Finite Element Analysis) using the commercial software ANSYS.
Investigation of the influence of gear milling modes of cylindrical gears on the quality parameters of tooth surfaces
Authors: Kane Mark , Sheleg Valery , Kravchuk Marina , Kot Pavel
Published: August 2020

Summary. The current state of the problem of studying the influence of gear milling modes of cylindrical gears on the quality parameters of the tooth surfaces is considered. Insufficient study of this problem and inconsistency of the available results is shown. The relevance and possible areas of application of this research are shown. The research objects are described (the effect of the cutting speed V and feed S during hobbing of cylindrical gears on the roughness parameter Ra, microhardness Hμ, residual stresses 1 and 2, σ1 and σ2 in the tooth surfaces), the accepted methods of planning experiments and presenting results. The results obtained are presented. It is established that the considered relationships can be modeled with sufficient accuracy by statistical methods and can be described by polynomials of the first or second degree. Shows the nature of the change Ra, Hμ, σ1 and σ2, with changes of V and S. Given are calculated according to Ra, Hμ, σ1 and σ2 from V and S.
Stab resistance of bulletproof vests. A conceptual model of test bench
Authors: Yaneva Svetlana
Published: August 2020

This paper presents a conceptual model of a stand to test the physico-mechanical characteristics of materials used in the soft panels of bulletproof vests for their stab resistance to cold weapons having a sharpened blade portion firmly and rigidly attached to handle. In the process of conceptual design of the model, the requirements and norms set out in two of the leading standardization documents used to determine the stab resistance of the bulletproof vests: the standard of the US National Institute of Justice -NIJ 0115.00, Stab Resistance of Personal Body Armor, and the UK Police Standard - HOSDB 2007. Part 3 -Knife and Spike Resistance, have been taken into account. 3D models of the stand and its individual constructive elements were developed, on the basis of which were offered real elements and devices for its elaboration. The designed stand is technologically accessible, inexpensive and easy to manufacture and install. It can be used to pre-determine the stab resistance of different types of materials and their combinations used in the soft panels of the bulletproof vests in the process of improving their structure. Availability of such stands in the equipment of the producers laboratories involved in this type of activity would reduce costs and shorten the evaluation time of the tested materials in order to verify their compliance with standard requirements since only samples showing the highest stab resistance will have to be sent for testing in certified and accredited laboratories.
Computer-Sensation
Authors: Ziehaus Otto
Published: August 2020

Dieser Fall besticht durch die Fähigkeit des Patienten, das benötigte Mittel im Lauf der Anamnese zu beschreiben.
Indications of Okoubaka aubrevillei in oncological supportive care
Authors: MD Jean-Lionel Bagot
Published: August 2020

Der Ende des letzten Jahrhunderts entdeckte Okoubaka-aubrevillei-Stamm ist in homöopathischen Kreisen immer noch unzureichend bekannt. Ursprünglich bei der Behandlung von Lebensmittelvergiftungen angezeigt, ist seine Verwendung in der begleitenden onkologischen Behandlung neu. Die Synthese verschiedener existierender Prüfungen ermöglichte es uns, eine Materia medica für Okoubaka zusammenzustellen, in der es ähnliche Symptome zu Nux vomica und Arsenicum album zeigt. Die Ätiologie „nach einer Vergiftung“ und die Nähe zum Verdauungssystem haben uns in den letzten 10 Jahren veranlasst, es zur Verhinderung von chemotherapeutischen Nebenwirkungen zu verwenden. Wir haben es kurz vor und während jeder Chemotherapie bei ca. 1000 Patienten eingesetzt. Unsere klinische Erfahrung bestätigt die onkologische Indikation zur Vorbeugung der gastroenterologischen Toxizität einer Chemotherapie, wie Übelkeit oder Durchfall. Die Veröffentlichung klinischer Fälle oder sogar klinischer Studien sollte es ermöglichen, die Verwendung in der Onkologie zu spezifizieren.
Materiovigilance: Concept, Structure and Emerging Perspective for Patient’s Safety in India
Authors: Hoda Farazul , Verma Rishabh , Arshad Mawrah , Siddiqui Ali Nasir , Khan Mohammad Ahmed , Akhtar Mohammad , Najmi Abul Kalam
Published: August 2020

There has been an escalation in the number, diversity, and complexity of medical devices. Regulation of these devices has also advanced due to the requirement of better regulatory perspective induced due to elevation in the number of adverse events associated with medical devices. All over the globe, various measures are undertaken to provide better safety to the patients along with attempts to improve the standard of medical devices. The initial and ultimate objective of the concept happens to be unfailingly to ensure patient safety as well as impart required guidance for both manufacturers and adept authorities enabling them to superintend cases coherently and appropriately. Materiovigilance programme of India (MvPI) was launched by the Drug Controller General of India at the Indian Pharmacopoeia commission (IPC) in Ghaziabad in 2015. The main purpose of this initiative is to monitor adverse events associated with medical devices in order to generate safety data, create awareness among the various stakeholders, and prescribe best practices for patient safety. Whilst the reforms in regulations have proposed policies and designs to elucidate, consolidate and accelerate the processes involved in manufacturing and importing medical devices to India, they consistently carry their challenges and limitations. To eliminate such complications the guidelines and regulations are anticipated to be implemented appropriately with the efficacious conclusion. India has been evident in matching with advancements in the World Medical Device regulation scenario, the current review at hand takes upon the question of ‘how successful has it been so far’?
A Comprehensive Review on Physiological Effects of Curcumin
Authors: Ahsan Rabiya , Arshad Md , Khushtar Mohammad , Ahmad Mohd Afroz , Muazzam Mohammad , Akhter Md Sohel , Gupta Gudiya , Muzahid Mohd
Published: August 2020

Turmeric (Curcuma longa Linn) is an herbal medicine which is traditionally used as a spice, food colouring or flavouring agent and widely used for several diseases such as biliary disorders, cough, hepatic disorders, rheumatism, wound healing, sinusitis, diabetes, cardiac disorders and neurological disorder. It belongs to the Zingiberaceae family. Turmeric is a popular domicile remedy used in Indian food, is mainly a native of south-east Asia, is widely cultivated in India, Sri Lanka, Indonesia, China, Jamaica , Peru, Haiti and Taiwan and it is very less expensive. Curcumin is the main principle of turmeric. Curcumin has shown various biological properties pre-clinically and clinically. Curcumin is a highly pleiotropic molecule which can be modulators of various intracellular signalling pathways that maintain cell growth. It has been reported as anti-inflammatory, anti-angiogenic, antioxidant, wound healing, anti-cancer, anti-Alzheimer and anti-arthritis and possesses an excellent safety profile. All previous review articles on curcumin have collected the biological/pharmacological activities but this review article summarises the most interesting in vitro and in vivo studies of curcumin on most running diseases around the whole world.
Prognostic Factors and Survival in Resected T4 Non-small Cell Lung Cancer: Is There Any Difference in the T4 Subgroups?
Authors: Aksoy Yunus , Citak Necati , Obuz Cigdem , Acikmese Baris , Pekcolaklar Atilla , Metin Muzaffer , Sayar Adnan
Published: August 2020

Introduction The eighth edition of the TNM classification revised the subgroups of T4 non-small cell lung cancer (NSCLC). This study aimed to compare the T4-NSCLC subgroups that underwent surgical treatment in terms of mortality, morbidity, survival, and prognostic factors based on the new classification.

Materials and Methods Between 2000 and 2014, a total of 284 T4-NSCLC patients who underwent lung resection (mediastinal organ invasion, n = 114; ipsilateral different lobe tumors, n = 32; and tumors larger than 7 cm, n = 138) were included in the present study.

Results Surgical mortality and morbidity were 5.6% (n = 16) and 23.9% (n = 68), respectively. The 5-year survival rates were 46% for ipsilateral different lobe tumors, 45.4% for tumours larger than 7 cm, and 36.6% for mediastinal organ invasion (28% for patients with heart/atrium invasion, 43.3% for carina invasion, 37.5% for large vessel invasion) (p = 0.223). Age above 65 (p = 0.002, HR = 1.781), pN2 versus pN0/1 (p < 0.0001, HR = 2.564), incomplete resection (p = 0.003, HR = 2.297), and pneumonectomy (p = 0.02, HR = 1.524) were identified as poor prognostic survival factors. According to multivariate analysis, mediastinal lymph node metastasis (p = 0.001) and incomplete resection (p = 0.0026) were the independent negative risk factors for survival.

Conclusion According to the results of our study, surgical treatment is a good option in T4-NSCLC patients who have no mediastinal lymph node metastasis and are completely resectable. There is no difference in terms of survival among the T4 subgroups. The eighth edition of the TNM classification has a better prognostic definition than the previous version.
Population Pharmacokinetic Modeling of von Willebrand Factor Activity in von Willebrand Disease Patients after Desmopressin Administration
Authors: de Jager Nico C. B. , Heijdra Jessica M. , Kieboom Quincy , Kruip Marieke J. H. A. , Leebeek Frank W. G. , Cnossen Marjon H. , Mathôt Ron A. A. ,   for the OPTI-CLOT Group
Published: August 2020

Objective Most von Willebrand disease (VWD) patients can be treated with desmopressin during bleeding or surgery. Large interpatient variability is observed in von Willebrand factor (VWF) activity levels after desmopressin administration. The aim of this study was to develop a pharmacokinetic (PK) model to describe, quantify, and explain this variability.

Methods Patients with either VWD or low VWF, receiving an intravenous desmopressin test dose of 0.3 µg kg−1, were included. A PK model was derived on the basis of the individual time profiles of VWF activity. Since no VWF was administered, the VWF dose was arbitrarily set to unity. Interpatient variability in bioavailability (F), volume of distribution (V), and clearance (Cl) was estimated.

Results The PK model was developed using 951 VWF activity level measurements from 207 patients diagnosed with a VWD type. Median age was 28 years (range: 5–76), median predose VWF activity was 0.37 IU/mL (range: 0.06–1.13), and median VWF activity response at peak level was 0.64 IU/mL (range: 0.04–4.04). The observed PK profiles were best described using a one-compartment model with allometric scaling. While F increased with age, Cl was dependent on VWD type and sex. Inclusion resulted in a drop in interpatient variability in F and Cl of 81.7 to 60.5% and 92.8 to 76.5%, respectively.

Conclusion A PK model was developed, describing VWF activity versus time profile after desmopressin administration in patients with VWD or low VWF. Interpatient variability in response was quantified and partially explained. This model is a starting point toward more accurate prediction of desmopressin dosing effects in VWD.
Invasive Mechanical Ventilation in Chronic Obstructive Pulmonary Disease Exacerbations
Authors: Peñuelas Óscar , Frutos-Vivar Fernando , Mancebo Jordi
Published: August 2020

Chronic obstructive pulmonary disease (COPD) continues to be an important cause of morbidity, mortality, and health care costs worldwide. Although there exist some heterogeneity between patients, the course of COPD is characterized by recurrent acute exacerbations, which are among the most common causes of medical admission to hospital. Patients with frequent exacerbations have accelerated lung function decline, worse quality of life, and greater mortality. Therefore, interest is growing in assessing the effectiveness of interventions used to treat exacerbations. The present review summarizes the current evidence regarding the use of ventilatory management to treat COPD and the implementation of novel cost-effective strategies, such as high-flow oxygenation or extracorporeal carbon dioxide removal to improve clinical outcomes and functional recovery in this disease and to reduce the associated costs.
Pandemie Schärft Prozesse und Logistik: Covid-19-Pandemie erfordert logistische Innovationen im Krankenhaus
Authors: Kriegel Johannes
Published: August 2020

Die Covid-19-Pandemie wirkt sich auf alle gesellschaftlichen, wirtschaftlichen und versorgungsbezogenen Bereiche und Sektoren aus. Das Krankenhaus steht im Zentrum der Patientenversorgung und wird mit unterschiedlichen Herausforderungen konfrontiert. Die Logistik kann dabei, insbesondere hinsichtlich der Prozessgestaltung und Ressourcenbereitstellung, erfolgskritische Unterstützungen und Innovationen ermöglichen.
Zentrale Versorgung von Covid-19-Patienten: Patientenstromgestaltung und Infektionsschutz in Zeiten der Corona-Pandemie
Authors: Reckwitz Nanni , Reckwitz Sybille Christine , Thra Marcel
Published: August 2020

Krankenhäuser mussten sich zu Beginn der Covid-19-Pandemie innerhalb kürzester Zeit auf die Versorgung von zum Teil schwer erkrankten Covid-19-Patienten vorbereiten. Das St. Willibrord-Spital Emmerich-Rees verfolgte dabei ein konzeptionelles Vorgehen. Hierbei standen insbesondere die Prozessgestaltung und die Mitarbeiterqualifikation im Vordergrund.
Digitale Transformation: Digital Opportunities im Procurement: Wo liegen große Optimierungspotenziale?
Authors: Süme Christoph , Rong Oliver
Published: August 2020

Die Corona-Krise hat deutlich gezeigt, dass es großen Nachholbedarf bei der Digitalisierung gibt. Der Artikel setzt auf den aktuellen Herausforderungen im daily business auf und fokussiert praxisrelevante Verbesserungspotenziale inklusive digitaler Lösungen. Ein Must-Read für jeden zukunftsgerichteten Klinikeinkäufer und Geschäftsführer.
Eggstraordinary artefacts: decorated ostrich eggs in the ancient Mediterranean world
Authors: Hodos Tamar
Published: August 2020

Decorated ostrich eggs were luxury items in antiquity. They were engraved, painted, and embellished with ivory, precious metals and faience fittings. They have been found primarily in elite funerary contexts from Mesopotamia and the Levant to the wider Mediterranean throughout the region’s Bronze and Iron Ages (third-first millennia BCE). Most scholarship has assessed their iconography to determine craftsman origin, equating decorative style with cultural identity. This is tenuous at best, given how readily motifs can be copied or adapted, and especially challenging for periods in which artisans were reliant on royal/elite patronage and known to migrate between regions, as during these eras. Furthermore, the full extent of the roles of non-elites in the production and distribution of these elite artefacts has never been considered directly. Thus, the role these luxuries played as social actors across a spectrum of society has been overlooked. It is this aspect that the present work addresses. It does so by building upon a recently concluded study that has used isotopic analyses and scanning electron microscopy to assess where and how eggs were acquired in the ancient Mediterranean and the working techniques used to decorate them. The results allow us to consider the role these objects played as social actors upon more than just their elite consumers. This suggests that, as scholars, we must adopt different questions, methodologies, and thus perspectives, to recognise the wider social effects of luxury material culture and its impact upon diverse groups and individuals beyond wealthy consumers.
Unraveling the origin of resistive switching behavior in organolead halide perovskite based memory devices
Authors: Wu Xiaojing , Yu Hui , Cao Jie
Published: August 2020

This study investigates the operation mechanisms of organolead halide perovskite based resistive memory cells and explores the device architectures that could ensure high memory endurance and high fabrication reproducibility. By introducing thin polyethyleneimine (PEI) interfacial layers to separate the direct contact of the perovskite layer with the top and bottom electrodes, thus producing a device structure of ITO/PEI/CH3NH3PbI3/PEI/metal, we achieved endurance cycles of more than 4000 times while maintaining a low operation voltage around 0.25 V. Furthermore, reproducible memory switching behavior was demonstrated among 180 devices fabricated from eight different device batches. To study the memory mechanism, we varied the top electrode (TE) metal materials and found three distinctively different resistive switching characteristics for InGa, Ag, and Al electrodes, respectively. The results suggest that the memory switching originates from a concerted effect of defect motion in the perovskite film and metal ion diffusion from the TE and that the switching mechanism is associated with the substitutionality of the metal ion in the Pb–I cage. For Ag ions with high substitutionality, the memory turn-on is dominated by interface vacancies, whereas for Al ions with low substitutionality, filament formation governs the memory switching.
Study on thermal expansion characteristics of mixed systems of flaky dust and alkane liquid
Authors: Bai Chunhua , Liu Wenjie , Yao Jian , Sun Binfeng
Published: August 2020

To obtain the cubical coefficients of thermal expansion of a mixed system of flaky dust and alkane liquid, the volume and pressure of the mixed system under different temperatures and volume fractions of aluminum powder were measured. On the basis of the experimental results, the cubical coefficients of thermal expansion under the corresponding conditions were calculated and the effect of each influencing factor was obtained. The results show that since the volume of each phase component in the system increases with temperature, the volume of the mixed system also increases with temperature. With increasing temperature, the cubical coefficients of thermal expansion of the mixed system generally increase. Affected by the increase in mass concentration of low-expansion-coefficient substances, an increase in the volume fraction of aluminum powder results in a decrease in the volume thermal expansion coefficient of the mixed system. At the same time, due to the changes in the state of the mixed system, the mass fraction of aluminum powder decreased sharply within a certain range. The low mass fraction of aluminum powder weakens the supporting effect of the metal particle skeleton, the thermal expansion properties of the liquid dominate the mixed system, and the volume thermal expansion coefficient is high. The high aluminum powder mass fraction creates the metal particle skeleton, the metal thermal expansion properties dominate the mixed system, and the volume thermal expansion coefficient is low.
Laser-induced anharmonicity vs thermally induced biaxial compressive strain in mono- and bilayer MoS2 grown via CVD
Authors: Madapu Kishore K. , Dhara Sandip
Published: August 2020

We studied the role of biaxial compressive strain in laser-induced anharmonicity effects of mono- and bilayer MoS2 grown by chemical vapor deposition. With the increased laser powers, the A1g phonon mode was strongly affected by the anharmonicity, whereas the E12g mode was negligibly affected by the anharmonic effects, which is attributed to the dominant nature of biaxial compressive strain over the effects of anharmonicity. In the case of the A1g phonon mode, anharmonicity effects dominated over the biaxial compressive strain owing to its large out-of-plane thermal expansion coefficient. The origin of biaxial compressive strain was explained by invoking the difference in linear thermal expansion coefficients of MoS2 and the substrate. Moreover, thermally induced biaxial compressive strain also influenced the exciton emission energy. The role of the substrate thermal conductivity was discussed in the light of anharmonicity of the MoS2 monolayer. In addition, the polarizability of Raman modes was found to be dependent on the second layer arrangement over the monolayer.
Effect of a thin (doped) PZT interfacial layer on the properties of epitaxial PMN-PT films
Authors: Boota Muhammad , Houwman Evert P. , Lanzara Giulia , Rijnders Guus
Published: August 2020

Pure perovskite phase, (001)-oriented, epitaxial thin films of (Pb(Mg1/3Nb2/3)O3)0.67-(PbTiO3)0.33 (PMN-PT) were fabricated on single crystal, (001)-oriented SrTiO3 substrates using a hard (Fe-doped) and soft doped (Nb-doped) PZT(52/48) interfacial layer. The effect of different interface layers on the structural and ferroelectric properties of the PMN-PT films was investigated in detail. A significant self-bias voltage in the PMN-PT films can be introduced by using an appropriate interfacial layer. There are significant differences in polarization for different types of doped and undoped interface layers and a doubling of the relative dielectric constant was observed for the Nb-doped interfacial layer. Device properties remain stable up to at least 108 cycles.
Nonlocal Raman response in Kerr resonators: Moving temporal localized structures and bifurcation structure
Authors: Clerc M. G. , Coulibaly S. , Parra-Rivas P. , Tlidi M.
Published: August 2020

A ring resonator made of a silica-based optical fiber is a paradigmatic system for the generation of dissipative localized structures or dissipative solitons. We analyze the effect of the non-instantaneous nonlinear response of the fused silica or the Raman response on the formation of localized structures. After reducing the generalized Lugiato–Lefever to a simple and generic bistable model with a nonlocal Raman effect, we investigate analytically the formation of moving temporal localized structures. This reduction is valid close to the nascent bistability regime, where the system undergoes a second-order critical point marking the onset of a hysteresis loop. The interaction between fronts allows for the stabilization of temporal localized structures. Without the Raman effect, moving temporal localized structures do not exist, as shown in M. G. Clerc, S. Coulibaly, and M. Tlidi, Phys. Rev. Res. 2, 013024 (2020). The detailed derivation of the speed and the width associated with these structures is presented. We characterize numerically in detail the bifurcation structure and stability associated with the moving temporal localized states. The numerical results of the governing equations are in close agreement with analytical predictions.
Explicitly correlated ab initio potential energy surface and predicted rovibrational spectra for H2O–N2 and D2O–N2 complexes
Authors: Wang Lu , Zhang Xiao-Long , Zhai Yu , Nooijen Marcel , Li Hui
Published: August 2020

An ab initio intermolecular potential energy surface (PES) for the van der Waals complex of H2O–N2 that explicitly incorporates the intramolecular Q2 bending normal mode of the H2O monomer is presented. The electronic structure computations have been carried out at the explicitly correlated coupled cluster theory [CCSD(T)-F12] with an augmented correlation-consistent triple zeta basis set and an additional bond function. Analytic five-dimensional intermolecular PESs for ν2(H2O) = 0 and 1 are obtained by fitting to the multi-dimensional Morse/long-range potential function form. These fits to 40 890 points have the root-mean-square (rms) discrepancy of 0.88 cm−1 for interaction energies less than 2000.0 cm−1. The resulting vibrationally averaged PESs provide good representations of the experimental microwave and infrared data: for microwave transitions of H2O–N2, the rms discrepancy is only 0.0003 cm−1, and for infrared transitions of the A1 symmetry of the H2O(ν2 = 1 ← 0)–N2, the rms discrepancy is 0.001 cm−1. The calculated infrared band origin shifts associated with the ν2 bending vibration of water are 2.210 cm−1 and 1.323 cm−1 for H2O–N2 and D2O–N2, respectively, in good agreement with the experimental values of 2.254 cm−1 and 1.266 cm−1. The benchmark tests and comparisons of the predicted spectral properties are carried out between CCSD(T)-F12a and CCSD(T)-F12b approaches.
Enhancing the settling time estimation of fixed-time stability and applying it to the predefined-time synchronization of delayed memristive neural networks with external unknown disturbance
Authors: Lin Lixiong , Wu Peixin , Chen Yanjie , He Bingwei
Published: August 2020

This paper concentrates on the global predefined-time synchronization of delayed memristive neural networks with external unknown disturbance via an observer-based active control. First, a global predefined-time stability theorem based on a non-negative piecewise Lyapunov function is proposed, which can obtain more accurate upper bound of the settling time estimation. Subsequently, considering the delayed memristive neural networks with disturbance, a disturbance-observer is designed to approximate the external unknown disturbance in the response system with a Hurwitz theorem and then to eliminate the influence of the unknown disturbance. With the help of global predefined-time stability theorem, the predefined-time synchronization is achieved between two delayed memristive neural networks via an active control Lyapunov function design. Finally, two numerical simulations are performed, and the results are given to show the correctness and feasibility of the predefined-time stability theorem.
Interconversion of complementary resistive switching from graphene oxide based bipolar multilevel resistive switching device
Authors: Pal Parthasarathi , Wang Yeong Her
Published: August 2020

In this work, organic material-based resistive switching mechanisms were studied by using graphene oxide as the switching layer. With the insertion of a charge trapping graphene layer, the device showed good stability and good electrical bipolar switching properties, with an ON/OFF ratio about 102–103. The device gradually shifted toward complementary switching behavior while maintaining an ON/OFF ratio of ∼102 from bipolar switching behavior after a specific number of consecutive DC switching cycles with increases in the SET-RESET voltage. The conduction mechanisms for bipolar (P–F conduction) and the complementary switching were verified based on the electrical characteristics and curve fittings. Rapid increases in the injected electrons due to increased voltage in complementary switching facilitated the formation of an intermediate charge reservoir region that, in turn, enhanced performance. The device showed a retention period as high as 104 s at 85 °C and good DC endurance. The device is also capable of multi-resistance states to obtain multi-bit (4-bit) data storage, leading to high density memory realization.
Ab initio quantum dynamics of charge carriers in graphitic carbon nitride nanosheets
Authors: Agrawal Sraddha , Lin Wei , Prezhdo Oleg V. , Trivedi Dhara J.
Published: August 2020

Graphitic carbon nitride (g-C3N4), a metal-free and visible light responsive photocatalyst, has garnered much attention due to its wide range of applications. In order to elucidate the role of dimensionality on the properties of photo-generated charge carriers, we apply nonadiabatic (NA) molecular dynamics combined with time-domain density functional theory to investigate nonradiative relaxation of hot electrons and holes, and electron–hole recombination in monolayer and bulk g-C3N4. The nonradiative charge recombination occurs on a nanosecond timescale and is faster in bulk than the nanosheet, in agreement with the experiment. The difference arises due to the smaller energy gap and participation of additional vibrations in the bulk system. The long carrier lifetimes are favored by small NA coupling and rapid phonon-induced loss of quantum coherence between the excited and ground electronic states. Decoherence is fast because g-C3N4 is soft and undergoes large scale vibrations. The NA coupling is small since electrons and holes are localized on different atoms, and the electron–hole overlap is relatively small. Phonon-driven relaxation of hot electrons and holes takes 100–200 fs and is slightly slower at higher initial energies due to participation of fewer vibrational modes. This feature of two-dimensional g-C3N4 contrasts traditional three-dimensional semiconductors, which exhibit faster relaxation at higher energies due to larger density of states, and can be used to extract hot carriers to perform useful functions. The ab initio quantum dynamics simulations present a comprehensive picture of the photo-induced charge carrier dynamics in g-C3N4, guiding design of photovoltaic and photocatalytic devices.
The vacuum ultraviolet spectrum of cyclohepta-1, 3, 5-triene: Analysis of the singlet and triplet excited states by ab initio and density functional methods
Authors: Palmer Michael H. , Hoffmann Søren Vrønning , Jones Nykola C. , Coreno Marcello , de Simone Monica , Grazioli Cesare , Aitken R. Alan
Published: August 2020

The vacuum ultraviolet (VUV) spectrum for cyclohepta-1,3,5-triene up to 10.8 eV shows several broad bands, which are compared with electron impact spectra. Local curve fitting exposed groups of sharp vibrational peaks, which are assigned to Rydberg states. The vertical excitation profile of the VUV spectrum, reproduced by time dependent density functional theory (TDDFT), gives a good interpretation of the principal regions of absorption. Fourth order Möller–Plessett perturbation theory, including single, double, and quadruple excitations, showed that the lowest singlet and triplet states retain CS symmetry. This contrasts with TDDFT where several low-lying excited states are planar. Detailed vibrational analysis of the first UV band was performed by Franck–Condon, Herzberg–Teller, and their combined methods. These show the dominance of mid-range frequencies, while the lowest frequency (75 cm−1) has negligible importance. In contrast, the second excited (Rydberg) state shows a major progression with separations of 115 (6) cm−1. This is interpreted by re-analysis of the X2A′ ionic state at the anharmonic level. Extremely low exponent Gaussian functions enabled several low-lying Rydberg state energies to be determined theoretically; extrapolation of the 3s-, 4s-, and 5s-Rydberg state calculated energies gives the adiabatic ionization energy as 7.837 eV (4) with δ 0.964 (2). Similarly, extrapolation of the centroids of the observed Rydberg states gave the vertical ionization energy (VIE) as VIE1 = 8.675 ± 0.077, close to the photoelectron spectroscopy VIE value [8.55 (1) eV].
H2O vapor assisted growth of β-Ga2O3 by MOCVD
Authors: Alema Fikadu , Zhang Yuewei , Mauze Akhil , Itoh Takeki , Speck James S. , Hertog Brian , Osinsky Andrei
Published: August 2020

The role of water (H2O) vapor in reducing background impurity concentration in epitaxial Ga2O3 thin films grown by metalorganic chemical vapor deposition (MOCVD) was studied. Adding H2O vapor to oxygen was found to increase the surface roughness and decrease the carrier concentration but have no effect on the structural quality and RT electron mobility of both the UID and doped films. The H2O vapor promotes the growth of the stable (110) and 1¯10 facets elongated along the [001] direction. Using [H2O] of 250 ppm, the β-Ga2O3 films showed a RMS roughness of >13 nm, which is much higher than that measured for similar films grown without H2O (RMS = 0.8 nm). The electron mobility of the UID Ga2O3 layers grown with and without water vapor was ∼150 cm2/V s, while the carrier concentration dropped by ∼2.5× after increasing the [H2O] to 6000 ppm. Similarly, for the lightly Si doped films, the RT carrier concentration dropped from 5.4 × 1015 cm−3 ([H2O] = 0 ppm) to 3.4 × 1015 cm−3 ([H2O] = 250 ppm), leaving the mobility unaffected. The results offer a new method of using water vapor assisted growth of Ga2O3 films with low RT carrier concentration that are required for the realization of high-performance electronic power devices with high breakdown voltages.
Stable polynomials and crystalline measures
Authors: Kurasov P. , Sarnak P.
Published: August 2020

Explicit examples of positive crystalline measures and Fourier quasicrystals are constructed using pairs of stable polynomials, answering several open questions in the area.
Current driven chiral domain wall motions in synthetic antiferromagnets with Co/Rh/Co
Authors: Cohen Alexander , Jonville Alexis , Liu Zhentao , Garg Chirag , Filippou Panagiotis Ch. , Yang See-Hun
Published: August 2020

Spin–orbit torque that originates from spin Hall effect and Dzyaloshinskii–Moriya interaction (DMI) can efficiently move chiral magnetic domain walls in perpendicularly magnetized wires. It has been shown that antiferromagnetically coupled composite domain walls across a ruthenium layer can be driven even faster by exchange coupling torque that is proportional to exchange coupling strength. Here, we report a current-driven motion of composite chiral domain walls in synthetic antiferromagnets with a rhodium spacer layer. It is found that the domain walls in the wire with a rhodium layer do not move as fast as that with a ruthenium layer although the exchange coupling in Co|Rh|Co is stronger than Co|Ru|Co, which is due to the formation of a large DMI at the Rh|Co interface. The Dzyaloshinskii–Moriya interaction at the Co/Rh interface has the same sign and comparable strength to the Pt|Co interface, thus negating the exchange coupling torque. The spin Hall effect from rhodium is found to be as small as ruthenium. Our findings show that rhodium can be used to tailor the DMI strengths in the current-driven motion of chiral domain walls in various magnetic nanostructures.
Output facet heating mechanism for uncoated high power long wave infrared quantum cascade lasers
Authors: Hathaway Dagan , Shahzad Monas , Sakthivel Tamil S. , Suttinger Matthew , Go Rowel , Sanchez Enrique , Seal Sudipta , Shu Hong , Lyakh Arkadiy
Published: August 2020

Output facet temperatures of an uncoated high power continuous-wave quantum cascade laser (QCL) emitting at 8.5 μm were measured by using micro-Raman thermometry. The rate of the measured temperature changes with the injected electrical power increased from 6.5 K/W below the laser threshold to 12.3 K/W above the threshold. In addition, the measured temperature rise exceeded 220 K at an optical power of 0.9 W, well above the model projections based only on Joule heating. Facet oxidation was characterized via x-ray photoelectron spectroscopy measurements at incremental etch depths. While the oxidation reactions of InP and Ga were observed only at the surface level, the measured penetration of native Al2O3 was ∼24 nm. COMSOL thermal modeling demonstrated that light reabsorption by the native Al2O3 layer could well explain the additional temperature rise above the threshold. These results suggest that facet oxidation must be addressed to ensure the reliability of high-power long wave infrared QCLs.
On the origin of red luminescence from iron-doped β-Ga2O3 bulk crystals
Authors: Sun Rujun , Ooi Yu Kee , Dickens Peter T. , Lynn Kelvin G. , Scarpulla Michael A.
Published: August 2020

Currently, Fe doping in the ∼1018 cm−3 range is the most widely available method for producing semi-insulating single crystalline β-Ga2O3 substrates. Red luminescence features have been reported from multiple types of Ga2O3 samples, including Fe-doped β-Ga2O3, and attributed to Fe or NO. Herein, however, we demonstrate that the high-intensity red luminescence from Fe-doped β-Ga2O3 commercial substrates consisting of two sharp peaks at 689 nm and 697 nm superimposed on a broader peak centered at 710 nm originates from Cr impurities present at a concentration near 2 ppm. The red emission exhibiting a twofold symmetry, peaks in intensity for excitation near the absorption edge, seems to compete with the Ga2O3 emission at a higher excitation energy and appears to be intensified in the presence of Fe. Based on the polarized absorption, luminescence observations, and the Tanabe–Sugano diagram analysis, we propose a resonant energy transfer of photogenerated carriers in the β-Ga2O3 matrix to octahedrally coordinated Cr3+ to give red luminescence, possibly also sensitized by Fe3+.
Fluorescent diamond microparticle doped glass fiber for magnetic field sensing
Authors: Bai D. , Huynh M. H. , Simpson D. A. , Reineck P. , Vahid S. A. , Greentree A. D. , Foster S. , Ebendorff-Heidepriem H. , Gibson B. C.
Published: August 2020

Diamond containing the nitrogen-vacancy (NV) center is emerging as a significant sensing platform. However, most NV sensors require microscopes to collect the fluorescence signals and therefore are limited to laboratory settings. By embedding micron-scale diamond particles at an annular interface within the cross section of a silicate glass fiber, we demonstrate a robust fiber material capable of sensing magnetic fields. Luminescence spectroscopy and electron spin resonance characterization reveal that the optical properties of NV centers in the diamond microcrystals are well preserved throughout the fiber drawing process. The hybrid fiber presents a low propagation loss of ∼4.0 dB/m in the NV emission spectral window, permitting remote monitoring of the optically detected magnetic resonance signals. We demonstrate NV-spin magnetic resonance readout through 50 cm of fiber. This study paves a way for the scalable fabrication of fiber-based diamond sensors for field-deployable quantum metrology applications.
Distributed Bragg reflectors for the colorimetric detection of bacterial contaminants and pollutants for food quality control
Authors: Paternò Giuseppe M. , Manfredi Giovanni , Scotognella Francesco , Lanzani Guglielmo
Published: August 2020

Real-time monitoring of bacterial contaminants and pollutants in food is of paramount importance nowadays, owing to the impressive extension of the food production/supply chain and the consequent increase in foodborne outbreaks worldwide. This represents a serious risk for consumers’ health and accounts for a large fraction of food wastage, especially in the developed countries. Therefore, modern sensors for food quality control should possibly afford low-cost, portability, and easiness of readout to enable widespread diffusion of the technology, thus allowing food quality monitoring from the production/supply chain to the consumers’ table. In these regards, one-dimensional photonic crystals, also known as Distributed Bragg Reflectors (DBRs), can represent simple yet efficient all-optical and label-free colorimetric sensors, given their relatively high color purity, easiness of integration with a large number of stimulus responsive materials, and low-cost fabrication from scalable processes. In this perspective article, we discuss the development of DBRs-based colorimetric sensors for the monitoring of bacterial contaminants and pollutants of interest in the food quality sector. We aim at providing a systematic overview on the main approaches that have been employed to achieve selectivity and sensitivity in DBRs-based sensors, with the view to enable widespread use of this technology at both the industry/supply chain and customers’ level.
Roles of bandgrading, lifetime, band alignment, and carrier concentration in high-efficiency CdSeTe solar cells
Authors: Zheng X. , Colegrove E. , Duenow J. N. , Moseley J. , Metzger W. K.
Published: August 2020

CdSeTe alloying has significantly increased the efficiency of CdTe-based solar technology. Here, computational modeling compares how different CdSeTe bandgrading, carrier lifetimes, band alignment, and carrier concentrations contribute to transport, recombination, and performance. We find that the gain in photocurrent caused by bandgap narrowing alone is insufficient to describe experimental efficiency gains. Performance can be increased by adjusting CdSeTe compositions and bandgrading depths. However, these performance gains are small relative to the contributions of enhanced lifetime by Se alloying, which can explain record cell efficiency gains with minimal open-circuit voltage loss despite significant bandgap narrowing. Similarly, CdSeTe band alignment shifts can significantly increase performance if front interface recombination is prevalent. For a wide range of CdSeTe grading profiles, the hole density is a critical component to achieve efficiencies exceeding 25%.
Laser cooling in a chip-scale platform
Authors: McGilligan J. P. , Moore K. R. , Dellis A. , Martinez G. D. , de Clercq E. , Griffin P. F. , Arnold A. S. , Riis E. , Boudot R. , Kitching J.
Published: August 2020

Chip-scale atomic devices built around micro-fabricated alkali vapor cells are at the forefront of compact metrology and atomic sensors. We demonstrate a micro-fabricated vapor cell that is actively pumped to ultra-high-vacuum (UHV) to achieve laser cooling. A grating magneto-optical trap (GMOT) is incorporated with a 4 mm-thick Si/glass vacuum cell to demonstrate the feasibility of a fully miniaturized laser cooling platform. A two-step optical excitation process in rubidium is used to overcome surface-scatter limitations to the GMOT imaging. The unambiguous miniaturization and form-customizability made available with micro-fabricated UHV cells provide a promising platform for future compact cold-atom sensors.
Airflow driven fluid–structure interaction subjected to aqueous-based liquid spraying
Authors: Bouvet A. , Pelorson X. , Van Hirtum A.
Published: August 2020

Artificial saliva sprays are commonly used to remedy vocal folds surface hydration. Vocal folds surface hydration and its effect on their auto-oscillation are studied experimentally using artificial vocal folds. The airflow is used to excite the vocal folds into auto-oscillation after which the vocal folds surface is sprayed with a liquid. The validity of the findings described in a previous study [A. Bouvet, X. Pelorson, and A. Van Hirtum, “Influence of water spraying on an oscillating channel,” J. Fluids Struct. 93, 102840 (2020)] concerning the effect of water spraying is further investigated. First, artificial saliva sprays (up to 5 ml) are sprayed instead of water. It is shown that this allows us to address the effect of increased dynamic viscosity (up to 8 times compared to water) as other artificial saliva properties affecting air–liquid mixing and surface wettability remain similar to water. Second, the Reynolds number in the dry stage is systematically increased (with 60%) for constant spraying volume ≥3 ml. Regardless of the sprayed liquid and Reynolds number, oscillation cycles are characterized by an increase in mean upstream pressure, cycle-to-cycle variability, and a decrease in oscillation frequency due period doubling. Increasing the dynamic viscosity tends to reduce the magnitude of these tendencies for spraying volumes smaller than 3 ml, indicating that viscous liquid–gas mixing affects the flow regime. Systematic Reynolds number variation shows that liquid spraying increases the oscillation onset threshold pressure and that the magnitude of general tendencies is reduced. The assessed conditions and features are pertinent to human voice production after hydration with an artificial saliva spray burst.
Improved nucleation of AlN on in situ nitrogen doped graphene for GaN quasi-van der Waals epitaxy
Authors: Chen Yang , Zang Hang , Jiang Ke , Ben Jianwei , Zhang Shanli , Shi Zhiming , Jia Yuping , Lü Wei , Sun Xiaojuan , Li Dabing
Published: August 2020

In the present work, improved crystal quality of GaN on a graphene-covered sapphire substrate was achieved compared to GaN grown on a bare sapphire substrate, and the growth mechanism of GaN quasi-van der Waals epitaxy with an AlN nucleation layer was clarified using metal-organic chemical vapor deposition. The in situ N-doping of graphene by an NH3 source during AlN growth was responsible for AlN nucleation. The first-principles calculation indicated that N atoms doped initially at the step edges of graphene and subsequently at its center and AlN nuclei followed the same sequence, which is consistent with experimental observations of nucleation. The lower migration barrier of Al atoms (0.07 eV) on graphene created larger AlN nuclei compared to that on bare sapphire (0.21 eV), leading to improved quality of the upper GaN epilayer with lower defect density. This work offers guidance for precisely controlling the nucleation morphology and density of GaN base materials and thus realizing high-quality epitaxial materials and related high-performance devices by quasi-van der Waals epitaxy.
Nuclear quantum effects on the hydrogen bond donor–acceptor exchange in water–water and water–methanol dimers
Authors: Méndez Emilio , Laria Daniel
Published: August 2020

We present results from path integral molecular dynamics simulations that describe effects from the explicit incorporation of nuclear quantum fluctuations on the topology of the free energy associated with the geared exchange of hydrogen bonds in the water–water dimer. Compared to the classical treatment, our results reveal important reductions in the free energy barriers and changes at a qualitative level in the overall profile. Most notable are those manifested by a plateau behavior, ascribed to nuclear tunneling, which bridges reactant and product states, contrasting with the usual symmetric double-well profile. The characteristics of the proton localizations along the pathway are examined. An imaginary time analysis of the rotational degrees of freedom of the partners in the dimer at the vicinities of transition states shows a clear “anticorrelation” between intermolecular interactions coupling beads localized in connective and dangling basins of attractions. As such, the transfer is operated by gradual concerted inter-basin migrations in opposite directions, at practically no energy costs. Modifications operated by partial deuteration and by the asymmetries in the hydrogen bonding characteristics prevailing in water–methanol heterodimers are also examined.