bluuebunny/crossref_metadata_2025 huggingface dataset:
Bamboo-structured N-doped CNTs/FeF3·0.33H2O derived from melamine as a high-performance cathode for Li-ion batteries
Authors: Ding Jing , Zhou Xiangyang , Luo Chucheng , Yang Juan , Tang Jingjing
Published: August 2021

The N-doped CNTs/FeF3·0.33H2O composite with a bamboo-like morphology was prepared via catalyzed pyrolysis and fluorination–annealing and used as a high-performance cathode for Li-ion batteries.
Co-embedded sulfur vacant MoS2 monolayer as a promising catalyst for formaldehyde oxidation: a theoretical evaluation
Authors: Jitwatanasirikul Thanadol , Roongcharoen Thantip , Chitpakdee Chirawat , Jungsuttiwong Siriporn , Poldorn Preeyaporn , Takahashi Kaito , Namuangruk Supawadee
Published: August 2021

In this work, we theoretically evaluated the complete catalytic oxidation of formaldehyde (HCHO) catalyzed by a cobalt embedded sulfur vacant MoS2 (COSv–MoS2) monolayer.
Studies of cyanomethylcarbamoyl-bridged anthracene and pyrene fluorophores
Authors: Younes Eyad A. , Issa Maram J. , Abdollahi Maryam F. , Ding Yuan-Fu , Rasras Anas J. , Mok Greta S. P. , Lin Jian-Bin , Zhao Yuming
Published: August 2021

Cyanomethylcarbamoyl-bridged anthracene and pyrene derivatives were prepared as functional fluorophores with diverse structural, electronic, and fluorescence properties.
MOF-derived porous TiO2 decorated with n-type Cu2O for efficient photocatalytic H2 evolution
Authors: Bai Xue , Liu Bo , Zhang Wei , Wang Yang , Yu Yu , Yang Yang , Guo Jianping
Published: August 2021

Type-I Cu2O/TiO2 with a porous structure has excellent photocatalytic activity for hydrogen production because of the effectively separated electron–hole pairs.
Quality grade evaluation and the related research ofForsythia suspensafrom different places on the market
Authors: Pang Xinyue , Zhang Jianglei , Yu Yue , Sun Guoxiang
Published: August 2021

Quality grade evaluation, content determination and antioxidant activityin vitroresearch ofForsythia suspensaand seeds from different places.
Transition-metal-free and facile synthesis of 3-alkynylpyrrole-2,4-dicarboxylates from methylene isocyanides and propiolaldehyde
Authors: Huo Xiaoli , Chen Xiaojuan , Yu Liya , Zhang Chong , Zeng Linghui , Zhu Huajian , Shao Jiaan , Fu Liping , Zhang Jiankang
Published: August 2021

A transition-metal-free, facile and efficient method for the synthesis of 3-alkynylpyrrole-2,4-dicarboxylates was developed.
Effect of the reduced graphene oxide (rGO) compaction degree and concentration on rGO–polymer composite printability and cell interactions
Authors: Cámara-Torres María , Sinha Ravi , Eqtesadi Siamak , Wendelbo Rune , Scatto Marco , Scopece Paolo , Sanchez Alberto , Villanueva Sara , Egizabal Ainhoa , Álvarez Noelia , Patelli Alessandro , Mota Carlos , Moroni Lorenzo
Published: August 2021

rGO densification prior to polymer compounding affects the composite printability and physicochemical properties, which also depend on rGO concentration. The resulting scaffolds support cell viability and osteogenesis, and possess antibacterial properties.
Diverse privileged N-polycyclic skeletons accessed from a metal-free cascade cyclization reaction
Authors: Li Wenzhong , Wang Yu , Qi Huijing , Shi Ran , Li Jiazhu , Chen Si , Xu Xin-Ming , Wang Wei-Li
Published: August 2021

Metal-free cascade cyclization of 2-acylbenzoic acids with amines provided a one-pot synthesis of diverse isoindoloisoquinoline and benzoindolizinoindole derivatives, which were subsequently used to produce nitrogen-containing nine-membered ring compounds.
Organocatalytic controlled/living ring-opening polymerization of 1,3,5-triphenyl-1,3,5-tri-p-tolylcyclotrisiloxane for the precise synthesis of fusible, soluble, functionalized, and solid poly[phenyl(p-tolyl)siloxane]s
Authors: Fuchise Keita , Sato Kazuhiko , Igarashi Masayasu
Published: August 2021

An organocatalytic controlled/living ring-opening polymerization (ROP) of 1,3,5-triphenyl-1,3,5-tri(p-tolyl)cyclotrisiloxane (PT3) produced linear poly[phenyl(p-tolyl)siloxane] (PPTS) with controlled structures.
Thiol ligand capped quantum dot as an efficient and oxygen tolerance photoinitiator for aqueous phase radical polymerization and 3D printing under visible light
Authors: Zhu Yifan , Ramadani Emira , Egap Eilaf
Published: August 2021

We report here a rapid visible-light-induced radical polymerization in aqueous media photoinitiated by only ppm level thiol ligand capped cadmium selenide quantum dots. The photoinitiation system could be readily employed for photo 3D printing.
Insight into the function of active site residues in the catalytic mechanism of human ferrochelatase
Authors: Medlock Amy E. , Najahi-Missaoui Wided , Shiferaw Mesafint T. , Albetel Angela N. , Lanzilotta William N. , Dailey, Harry A.
Published: August 2021

Ferrochelatase catalyzes the insertion of ferrous iron into a porphyrin macrocycle to produce the essential cofactor, heme. In humans this enzyme not only catalyzes the terminal step, but also serves a regulatory step in the heme synthesis pathway. Over a dozen crystal structures of human ferrochelatase have been solved and many variants have been characterized kinetically. In addition, hydrogen deuterium exchange, resonance Raman, molecular dynamics, and high level quantum mechanic studies have added to our understanding of the catalytic cycle of the enzyme. However, an understanding of how the metal ion is delivered and the specific role that active site residues play in catalysis remain open questions. Data are consistent with metal binding and insertion occurring from the side opposite from where pyrrole proton abstraction takes place. To better understand iron delivery and binding as well as the role of conserved residues in the active site, we have constructed and characterized a series of enzyme variants. Crystallographic studies as well as rescue and kinetic analysis of variants were performed. Data from these studies are consistent with the M76 residue playing a role in active site metal binding and formation of a weak iron protein ligand being necessary for product release. Additionally, structural data support a role for E343 in proton abstraction and product release in coordination with a peptide loop composed of Q302, S303 and K304 that act a metal sensor.
Examining Social Networks in Older Adults: What Predicts Communicative Participation?
Authors: Meeker Melanie , McCullough Kimberly C. , McCullough Gary H. , Akpanudo Usenime
Published: August 2021

Purpose

Social isolation is linked to cognitive decline and depression, which can be risk factors for developing dementia. The purpose of this study was to determine which of a variety of factors were associated with communicative participation as measured by social network size.

Method

Three hundred thirty-seven adults aged 65 years or older were administered assessments to evaluate social network size, cognition, hearing handicap, and quality of communicative participation.

Results

Cognition, education, living setting, and quality of communication life were associated to varying degrees with the construct of communicative participation as measured by social network size.

Conclusion

Assessment of these variables, along with early identification of cognitive decline, could play an important role in identifying elderly individuals at risk for limitations in communicative participation and associated consequences.
Uncertainties in the pasta-phase properties of catalysed neutron stars
Authors: Dinh Thi H. , Carreau T. , Fantina A. F. , Gulminelli F.
Published: August 2021

Context. The interior of a neutron star is expected to exhibit different states of matter. In particular, complex non-spherical configurations known as ‘pasta’ phases may exist at the highest densities in the inner crust, potentially having an impact on different neutron-star phenomena.

Aims. We study the properties of the pasta phase and the uncertainties in the pasta observables which are due to our incomplete knowledge of the nuclear energy functional.

Methods. To this aim, we employed a compressible liquid-drop model approach with surface parameters optimised either on experimental nuclear masses or theoretical calculations. To assess the model uncertainties, we performed a Bayesian analysis by largely varying the model parameters using uniform priors, and generating posterior distributions with filters accounting for both our present low-density nuclear physics knowledge and high-density neutron-star physics constraints.

Results. Our results show that the nuclear physics constraints, such as the neutron-matter equation of state at very low density and the experimental mass measurements, are crucial in determining the crustal and pasta observables. Accounting for all constraints, we demonstrate that the presence of pasta phases is robustly predicted in an important fraction of the inner crust. We estimate the relative crustal thickness associated with pasta phases as Rpasta/Rcrust = 0.128 ± 0.047 and the relative moment of inertia as Ipasta/Icrust = 0.480 ± 0.137.

Conclusions. Our findings indicate that the surface and curvature parameters are more influential than the bulk parameters for the description of the pasta observables. We also show that using a surface tension that is inconsistent with the bulk functional leads to an underestimation of both the average values and the uncertainties in the pasta properties, thus highlighting the importance of a consistent calculation of the nuclear functional.
A Domino Heck Coupling–Cyclization–Dehydrogenative Strategy for the One-Pot Synthesis of Quinolines
Authors: Ghora Santanu , Sreenivasulu Chinnabattigalla , Satyanarayana Gedu
Published: August 2021

An efficient, one-pot, domino synthesis of quinolines via the coupling of iodoanilines with allylic alcohols facilitated by palladium catalysis is described. The overall synthetic process involves an intermolecular Heck coupling between 2-iodoanilines and allylic alcohols, intramolecular condensation of in situ generated ketones with an internal amine functional group, and a dehydrogenation sequence. Notably, this protocol occurs in water as a green solvent. Significantly, the method exhibits broad substrate scope and is applied for the synthesis of deuterated quinolines through a deuterium-exchange process.
Recent Progress in Amination Enabled by Transition-Metal-Free C(sp2)–O/C(sp2)–S Bond Cleavage Strategy
Authors: Yang Xin-Ge , Wang Xue-Qiang , Li Shen-Huan , Long Cheng-Yu
Published: August 2021

Recently, intense efforts have been dedicated to the development of novel synthetic strategies to access aromatic amines due to their importance in the pharmaceuticals, agrochemicals, materials, and natural product areas. Although numerous transition-metal-catalyzed C–N formation strategies have been described for the preparation of aromatic amines in the past few decades, complementary methods under transition-metal-free conditions are still required. We present the recent advances in the exploration of innovative amination approaches via C(sp2)–O/C(sp2)–S bond cleavage in this review.

1 Introduction

2 Stoichiometric Base-Promoted Amination

3 Base-Catalyzed Amination

4 Photoredox-Catalyzed Amination

5 Acid-Promoted Amination

6 Conclusion and Perspectives
Depressor Anguli Oris Myectomy versus Transfer to Depressor Labii Inferioris for Facial Symmetry in Synkinetic Facial Paralysis
Authors: Halani Sameer H. , Sanchez Cristina V. , Hembd Austin S. , Mohanty Ahneesh J. , Reisch Joan , Rozen Shai M.
Published: August 2021

Background Postparalytic synkinesis presents with a combination of hypo- and hypertonic muscles, leading to facial asynchrony with animation and at rest. One ubiquitous finding is a hypertonic depressor anguli oris (DAO) muscle and a weak depressor labii inferioris (DLI) muscle. The goal of this study was to evaluate the utility of DAO myectomy with or without its transfer to the weakened DLI in improving critical components of the dynamic smile.

Methods From 2018 to 2020, this single-center, prospective study included of postparetic facial synkinetic patients with evidence of DAO hypertonicity who underwent DAO myectomy with or without transfer to DLI. Objective facial measurements were used to compare the effectiveness of DAO to DLI transfer to pure DAO myectomy in improving asymmetry of the synkinetic hemiface.

Results Twenty-one patients with unilateral postparetic facial synkinesis with DAO hypertonicity were included; 11 underwent DAO myectomy, while 10 underwent DAO to DLI transfer. Baseline demographics and facial measurements were similar between the groups. DAO myectomy resulted in increased modiolus resting position, closed-mouth smile modiolus angle and excursion, open-mouth smile modiolus angle, excursion, dental show, and decreased lower lip height deviation. DAO to DLI transfer demonstrated similar findings but lacked significant increase in excursion and resulted in worsened lower lip height deviation.

Conclusion These findings illustrate the utility of DAO myectomy in improving imbalance in the synkinetic patient and necessitate further technical refinements for DAO transfers or a different approach for improving lower lip depression in this subgroup of patients.
A Wireless Near-Infrared Spectroscopy Device for Flap Monitoring: Proof of Concept in a Porcine Musculocutaneous Flap Model
Authors: Wu Changsheng , Rwei Alina Y. , Lee Jong Yoon , Ouyang Wei , Jacobson Lauren , Shen Haixu , Luan Haiwen , Xu Yameng , Park Jun Bin , Kwak Sung Soo , Ni Xiaoyue , Bai Wubin , Franklin Daniel , Li Shuo , Liu Yiming , Ni Xinchen , Westman Amanda M. , MacEwan Matthew R. , Rogers John A. , Pet Mitchell A.
Published: August 2021

Background Current near-infrared spectroscopy (NIRS)-based systems for continuous flap monitoring are highly sensitive for detecting malperfusion. However, the clinical utility and user experience are limited by the wired connection between the sensor and bedside console. This wire leads to instability of the flap–sensor interface and may cause false alarms.

Methods We present a novel wearable wireless NIRS sensor for continuous fasciocutaneous free flap monitoring. This waterproof silicone-encapsulated Bluetooth-enabled device contains two light-emitting diodes and two photodetectors in addition to a battery sufficient for 5 days of uninterrupted function. This novel device was compared with a ViOptix T.Ox monitor in a porcine rectus abdominus myocutaneous flap model of arterial and venous occlusions.

Results Devices were tested in four flaps using three animals. Both devices produced very similar tissue oxygen saturation (StO2) tracings throughout the vascular clamping events, with obvious and parallel changes occurring on arterial clamping, arterial release, venous clamping, and venous release. Small interdevice variations in absolute StO2 value readings and magnitude of change were observed. The normalized cross-correlation at zero lag describing correspondence between the novel NIRS and T.Ox devices was >0.99 in each trial.

Conclusion The wireless NIRS flap monitor is capable of detecting StO2 changes resultant from arterial vascular occlusive events. In this porcine flap model, the functionality of this novel sensor closely mirrored that of the T.Ox wired platform. This device is waterproof, highly adhesive, skin conforming, and has sufficient battery life to function for 5 days. Clinical testing is necessary to determine if this wireless functionality translates into fewer false-positive alarms and a better user experience.
Are “Free Flaps” “Free” Flaps?
Authors: Hallock Geoffrey G.
Published: August 2021

Background Even standard microvascular tissue transfers are time consuming, require great skill and intensity, and can be stressful. Not surprisingly, work-related relative value units are considered by many microsurgeons to be suboptimal. Some might even say that “free flaps” indeed really are “free” flaps.

Methods A retrospective review of related finances was undertaken for all free flaps performed in a single surgeon private practice during the latest possible year (2014) that included a complete 5-year follow-up to insure receipt of all expected reimbursements from accounts receivable. There were 61 free flaps available; but arbitrarily 12 free flaps were excluded since postmastectomy breast reconstruction always received mandatory insurance payment, as were additional two cases done pro bono as part of an international educational service. This left 47 free flaps to permit determination of gross payments, if any.

Results Compensation summated for three distinct time intervals for all free flaps was preoperative: $10,855.92 (mean: $230.98/flap); intraoperative: $117,015.46 (mean: $2,489.69/flap); and postoperative: $45,296.28 (mean: $963.75/flap). Range of gross payment for the free flap portion only was 529.65 to $4,503.71. Total overall revenue received was $173,167.66 (mean: $3,684.42/flap).

Conclusion A true benefit cost-analysis even if microsurgery specific expenses could be estimated would be inaccurate, so that mean net income for each free flap could not be determined. Albeit a minimal gross payment was obtained for some free flap procedures, in no instance was there zero reimbursement. Based on that fact, there were no truly “free” free flaps in this private practice experience, which should encourage the younger surgeon to realize that economic viability is possible so that their enthusiasm for reconstructive microsurgery can be sustained.
The Need to Reassess the Diagnosis of Polycystic Ovary Syndrome (PCOS): A Review of Diagnostic Recommendations from the International Evidence-Based Guideline for the Assessment and Management of PCOS
Authors: Kiconco Sylvia , Teede Helena J. , Azziz Ricardo , Norman Robert J. , Joham Anju E.
Published: August 2021

Polycystic ovary syndrome (PCOS) is a common endocrine disorder that is associated with negative metabolic, reproductive, endocrine, and psychological consequences among women of reproductive age. The diagnosis of PCOS remains challenging due to limited and conflicting evidence regarding definitions for each of the diagnostic features. This review of the recommended PCOS assessment criteria from the international evidence-based guideline highlights the crucial need to reassess, redefine, and optimize the diagnosis of PCOS. Notably, normal values and cut-offs need to be defined for each diagnostic feature across the lifespan and diverse ethnic groups. Understanding how these features cluster together and relate to short- and long-term health outcomes in PCOS is also vital. Ultimately, greater knowledge of the natural history of PCOS is needed through well-characterized, community-based longitudinal studies, which will inform future PCOS diagnosis guidelines and optimize women's health in reproductive life.
Method could quicken the characterization of single-nanoparticle catalysts
Authors: Lim Alane
Published: August 2021

Microwell arrays allow for the high-throughput characterization of single-nanoparticle catalysis in real working conditions.
Re-engineering transition layers in AlGaN/GaN HEMT on Si for high voltage applications
Authors: Remesh Nayana , Chandrasekar Hareesh , Venugopalrao Anirudh , Raghavan Srinivasan , Rangarajan Muralidharan , Nath Digbijoy N.
Published: August 2021

We report on the study of step-graded AlGaN transition layers (TLs) in metalorganic chemical vapor deposition-grown GaN HEMT-on-silicon toward improving the breakdown field while minimizing buffer-induced current dispersion. The transition layers include three AlGaN epi-layers of 75%, 50%, and 25% Al-content, downgraded from bottom to top. The growth temperature and carbon doping are varied independently to assess the transition layer's role in reducing current collapse and leakage current. We observe that the introduction of High Temperature (HT) AlGaN increases the lateral but decreases the vertical leakage, the latter being attributed to the reduction of V-pit density. Temperature-dependent data indicate that the increased lateral (mesa) leakage current in HT AlGaN layers is due to space charge limited current, the activation energy of which yields the positions of the defect states within the bandgap. The increase in mesa leakage current in HT AlGaN layers is attributed to the formation of point defects such as oxygen in nitrogen site (ON) and VGa–ON complexes. The introduction of C-doping in the top AlGaN transition layer with 25% Al-content helps reduce lateral leakage in both mesa and 3-terminal configurations. The combination of HT AlGaN (75% Al-content) with C-doped AlGaN (25% Al-content) is found to be the optimal TL design that yielded a minimum buffer-induced current dispersion with a 65% channel recovery when the substrate was swept to −300 V and back; moreover, it also enabled a vertical breakdown field of 2.05 MV/cm defined at 1 A/cm2 for a buffer thickness of 1.65 μm.
Rapid diagnosis and continuous monitoring of intracerebral hemorrhage with magnetic induction tomography based on stacked autoencoder
Authors: Chen Ruijuan , Song Yixiang , Huang Juan , Wang Jinhai , Sun Hongsheng , Wang Huiquan
Published: August 2021

Magnetic induction tomography (MIT) is a promising approach in rapid diagnosis and continuous monitoring of cerebral hemorrhage. A new algorithm for the reconstruction of intracerebral hemorrhage with MIT, including the location and volume of hemorrhage, is proposed in this study. First, 2D magnetic resonance imaging and computed tomography images of patients with cerebral hemorrhage were used for the development of simulation models. The Stacked Autoencoder (SAE) network was then used to predict the location and volume of hemorrhage by conductivity reconstruction. Finally, the one-dimensional quantitative monitoring index is proposed as an auxiliary diagnostic indicator for assessment of real-time intracranial electrical characteristics. The 2D simulation results showed that the SAE was able to quickly image the location and volume of the hemorrhages. Compared with the back-projection algorithm, the prediction speed of each frame was improved 15-fold, and the accuracy improved by 90.53%. The extracted one-dimensional quantitative monitoring indicators can describe the bleeding status. The diagnostic accuracy and the imaging speed of cerebral hemorrhage were both improved by constructing a realistic head section model and using the proposed SAE network. This research provides a new alternative for dynamic monitoring of hemorrhages and shows the potential advantages of MIT in noninvasive detection.
Flexoelectricity in compositionally graded Ba1−xSrxTiO3 ceramics
Authors: Wen X. , Yang G. , Ma Q. , Tian Y. , Liu X. , Xue D. , Deng Q. , Shen S.
Published: August 2021

Flexoelectricity, the coupling between electric polarization and strain gradients in dielectrics, attracts growing research interest because of its potential to replace/complement piezoelectricity in electromechanical applications. Thanks to the large dielectric permittivity, ferroelectrics exhibit enhanced flexoelectricity and usually serve as the functional ingredient in flexoelectric devices. However, ferroelectric flexoelectricity usually suffers from poor temperature stability, which adversely affects practical applications. In this work, compositional gradients are introduced into Ba1−xSrxTiO3 systems to enhance the temperature stability of flexoelectric behavior. Experimental results show that the drastic variations of flexoelectricity (up to 100 times) from 20 to 120 °C in single component ceramics (such as Ba0.67Sr0.33TiO3 and BaTiO3) can be significantly reduced in graded Ba1−xSrxTiO3 ceramics, in which the flexoelectric coefficient is in the range from 13 to 26 μC/m. The improved stability results from the engineered sequential Curie temperatures of individual layers in graded ceramics and the positive correlation between dielectric constant and flexoelectricity. Our work provides a method to enable the robust performance of flexoelectric devices in an ambient environment with large temperature fluctuations.
Spalling fracture of Ni/Al nanolaminates influenced by chemical reaction
Authors: Tian Xia , Xiang Meizhen , Cui Junzhi , Ji Guangyu , Fu Zhuojia
Published: August 2021

We investigate spalling behaviors of Ni/Al nanolaminates by molecular dynamics simulations. First, we discuss spalling damage distributions in shocked Ni/Al nanolaminates. Voids nucleate in Al layers, while no voids are located in Ni layers or along the Ni/Al interfaces. This is because the spall strength of single-crystalline Ni is higher than that of single-crystalline Al. We reveal influences of a shock-induced chemical reaction on dynamic spalling damage and fracture processes. An abnormal “decrease → increase → decrease” zigzag variation tendency of the spall strength of Ni/Al nanolaminates as the impact velocity increase is observed in our simulations, which resulted from combining effects of micro-structures, chemical reactions, and temperature softening. When the impacting intensity is relatively low, the spall strength of Ni/Al nanolaminates decreases as the impact velocity increases due to micro-structure effects. However, when the loading velocity increases to a certain magnitude (2.5 km/s), the intimate contact of liquid Al with amorphous Ni near the interface makes the chemical reaction rate increase rapidly to form a large amount of Ni/Al alloys and enhances the spall strength.
Onset of dynamic stall of tubercled wings
Authors: Zhao Ming , Xu Lianchao , Tang Zhanqi , Zhang Xiaolu , Zhao Bo , Liu Zhengxian , Wei Zhaoyu
Published: August 2021

In the present study, numerical simulation of the flow field of the tubercled NACA0021 (National Advisory Committee for Aeronautics) wing has been conducted with the large eddy simulation model. Then, proper orthogonal decomposition (POD) analysis has been carried out at trough and peak sections. According to the spatial distributions and temporal coefficients in the case of αA=5°, the physical backgrounds of corresponding POD modes could be identified, including flow attachment, separation, and the dynamic stall vortex (DSV). The onsets of local dynamic stall could be indicated with the extremum values of the DSV mode coefficients, which stay almost synchronized at trough and peak. Actually, the DSV is originally generated at trough and then moves to peak due to the spanwise convection induced by streamwise vorticity. The generation of the secondary vortex at trough is triggered with the streamwise pressure gradient, the development of which pinches off the feeding vorticity of the DSV and results in the detachment of the DSV. Eventually, the influence of pitching amplitude has also been discussed. The strength of the DSV at peak is increased with a larger pitching amplitude, which could be interpreted with the feeding sheet connected with the leading edge.
Effect of surface heat exchange on phase change materials melting with thermocapillary flow in microgravity
Authors: Martínez N. , Salgado Sánchez P. , Porter J. , Ezquerro J. M.
Published: August 2021

A numerical analysis of the melting of n-octadecane in microgravity is presented for a small aspect ratio rectangular container. The container is bounded above by an air layer that exchanges heat with the phase change material (PCM) and supports thermocapillary convection in the liquid phase. The air temperature is assumed to match the applied temperatures at the lateral walls and to change linearly between them. The effect of key dimensionless parameters is investigated including the Marangoni number (Ma), which quantifies the heat transport due to the thermocapillary flow, and the Biot (Bi) number, which characterizes the heat exchanged across the PCM/air interface. Several different dynamic regimes are distinguished according to whether the flow is quasi-steady or oscillatory; the latter may be characterized by an oscillatory standing wave (OSW), a hydrothermal traveling wave, or a novel type of thermal traveling wave (TTW). The results are summarized with a stability map in terms of Bi and Ma. Notably, there are parameters where the flow undergoes transitions between distinct regimes during melting, including a transition between the TTW and OSW modes and other regions where the oscillatory flow undergoes a homoclinic bifurcation. The effect of Bi on heat transport is also investigated and shown to be particularly relevant for small Ma.
Kinetically driven island morphology in growth on strained Cu(100)
Authors: Khatri Indiras , Sabbar Ehsan H. , Shim Yunsic , Amar Jacques G.
Published: August 2021

We study the effects of strain on the monomer and dimer diffusion mechanisms and island morphology during the growth of Cu on a biaxially strained Cu(100) substrate. We find an approximately linear dependence of the activation barriers on strain. In particular, while hopping is favored for compressive and/or small (<2%) tensile strain, for greater than 2% tensile strain, the exchange mechanism is favored. We then present the results of temperature-accelerated dynamics simulations of submonolayer growth at 200 K. For the case of 2% compressive strain we find that, as in previous kinetic Monte Carlo simulations of Cu/Ni(100) growth, the competition between island growth and multi-atom relaxation (“pop-out”) events leads to an island morphology with a mixture of open and closed steps. At slightly higher coverage, island coalescence then leads to elongated islands. However, annealing leads to a significant decrease in the number of open steps. In contrast, for the case of 8% tensile strain, only one large strongly anisotropic island is formed. Surprisingly, we find that despite the large strain, the island anisotropy is not due to energetics but is instead due to anisotropic attachment barriers that favor the exchange-mediated attachment of monomers to corners over close-packed step-edges. An explanation for the asymmetry in attachment barriers is provided. Our results provide a new general kinetic mechanism for the formation of anisotropic islands in the presence of isotropic diffusion and tensile strain.
Photovoltaic behavior of polymerizable ionic liquid based fixed-junction light-emitting electrochemical cells
Authors: Hayes A. N. , Sampson C. R. , Garcia A. A. , Leger J. M.
Published: August 2021

Since their initial demonstration in 1995, light-emitting electrochemical cells (LECs) have received attention due to potential advantages over traditional polymer optoelectronic devices. A standard LEC consists of two electrodes surrounding an active layer that contains polymer and mobile ions. When a bias is applied, the ions separate and move toward the electrodes, creating a reversible p–n junction analog. Immobilizing the ions after ion dissociation using one of several demonstrated methods to create a “fixed-junction LEC” allows the device to produce a significant photovoltaic response. Recently, our group demonstrated chemically fixed junction LECs using a polymerizable ionic liquid (ATOA-AS) that conferred important advantages over first-generation chemically fixed junction devices, including improved phase compatibility and turn-on time. Early tests showed improvements in the performance of these devices over the first chemically fixed junctions in terms of light-emitting properties. However, their photovoltaic behavior has not been previously investigated. In this paper, we demonstrate photovoltaic behavior in chemically fixed junction LECs based on the polymerizable ionic liquid ATOA-AS as the ion source. While further improvements in the photovoltaic performance of fixed-junction devices still need to be made before they are considered a commercially viable technology, we find that the devices reported here compare well to other single-layer polymer homojunction solar cells and demonstrate an exceptionally high VOC (>1.8 V for some configurations). We also explore the effects that changes to various aspects of device composition and testing procedures have on device performance.
Effect of cavity on hypersonic flat-plate boundary layer instability
Authors: Chen Shuo , Lee Cunbiao
Published: August 2021

The effects of a cavity on hypersonic boundary layer instabilities are investigated experimentally. First- and second-mode wave amplitude evolution is determined using pressure sensors and high-resolution Schlieren technology. The results indicate that when a cavity is located downstream of the fast- and slow-mode synchronization points, it suppresses the second-mode wave and promotes first-mode wave growth. In contrast, when the cavity is located upstream of the synchronization point, the growth of the second-mode wave is promoted while that of the first-mode wave is suppressed. During disturbance evolution, nonlinear interactions are observed due to the phase-locked mechanism that relates the two unstable modes. The transition locations for various cases are confirmed using temperature-sensitive paint technology, and the influences of the cavity on the transition are explained from the perspective of unstable mode amplitude evolution.
Micro-PL analysis of high current density resonant tunneling diodes for THz applications
Authors: Cito M. , Cimbri D. , Childs D. , Baba R. , Harrison B. A. , Watt A. , Mukai T. , Wasige E. , Hogg R. A.
Published: August 2021

Low-temperature micro-photoluminescence (μPL) is used to evaluate wafer structural uniformity of current densities >5mA/μm2 InGaAs/AlAs/InP resonant tunneling diode (RTD) structures on different length scales. Thin, highly strained quantum wells (QWs) are subject to monolayer fluctuations, leading to a large statistical distribution in their electrical properties. This has an important impact on the RTD device performance and manufacturability. The PL spot size is reduced using a common photolithography mask to reach a typical high Jpeak for a given RTD mesa size (1 ∼ 100 μm2). We observe that for lower strain-budget samples, the PL line shape is essentially identical for all excitation/collection areas. For higher strain-budget samples, there is a variation in the PL line shape that is discussed in terms of a variation in long-range disorder brought about by strain relaxation processes. The RTD operating characteristics are discussed in light of these findings, and we conclude that strain model limits overestimate the strain budget that can be incorporated in these devices. We also highlight μPL as a powerful nondestructive characterization method for RTD structures.
A modified nudged elastic band algorithm with adaptive spring lengths
Authors: Mandelli D. , Parrinello M.
Published: August 2021

We present a modified version of the nudged elastic band (NEB) algorithm to find minimum energy paths connecting two known configurations. We show that replacing the harmonic band-energy term with a discretized version of the Onsager–Machlup action leads to a NEB algorithm with adaptive spring lengths that automatically increase the resolution of the minimum energy path around the saddle point of the potential energy surface. The method has the same computational cost per optimization step of the standard NEB algorithm and does not introduce additional parameters. We present applications to the isomerization of alanine dipeptide, the elimination of hydrogen from ethane, and the healing of a 5-77-5 defect in graphene.
Modulation of π-stacking modes and photophysical properties of an organic semiconductor through isosteric cocrystallization
Authors: Campillo-Alvarado Gonzalo , Bernhardt Michael , Davies Daniel W. , Soares Julio A. N. T. , Woods Toby J. , Diao Ying
Published: August 2021

We report on the control of π-stacking modes (herringbone vs slipped-stack) and photophysical properties of 9,10-bis((E)-2-(pyridin-4-yl)vinyl)anthracene (BP4VA), an anthracene-based organic semiconductor (OSC), by isosteric cocrystallization (i.e., the replacement of one functional group in a coformer with another of “similar” electronic structure) with 2,4,6-trihalophenols (3X-ph-OH, where X = Cl, Br, and I). Specifically, BP4VA organizes as slipped-stacks when cocrystallized with 3Cl-ph-OH and 3Br-ph-OH, while cocrystallization with 3I-ph-OH results in a herringbone mode. The photoluminescence and molecular frontier orbital energy levels of BP4VA were effectively modulated by the presence of 3X-ph-OH through cocrystallization. We envisage that the cocrystallization of OSCs with minimal changes in cocrystal formers can provide access to convenient structural and property diversification for advanced single-crystal electronics.
Onset of instability in Hadley–Prats flow in a weakly heterogeneous porous layer with viscous dissipation
Authors: Roy Kamalika
Published: August 2021

The stability of a flow subjected to an inclined temperature gradient (Hadley-type flow) in a horizontal porous media is studied in the presence of a basic horizontal mass flow (Prats flow). Therefore, the basic flow is called the Hadley–Prats flow. A weak vertical heterogeneity in permeability and conductivity is considered. The effect of viscous dissipation is taken to be non-negligible. The Rayleigh number corresponding to the vertical thermal gradient RaC is considered as an eigenvalue. Other parameters are the Péclet number (Pe) associated with the horizontal through flow, horizontal Rayleigh number (RaH) associated with the horizontal temperature gradient, Gebhart number (Ge) associated with viscous dissipation; parameters γ1 and γ2 represent the changes in permeability and conductivity, respectively. A linear stability analysis is done and the governing equations are solved numerically to obtain the critical Rayleigh number and wave number. Longitudinal and transverse rolls are discussed. Longitudinal rolls are the preferred modes for instability in most scenarios. It is found that when throughflow is present, the heterogeneity in permeability can show a stabilizing effect for longitudinal rolls but destabilizing effect for transverse rolls and vice versa depending on the direction of the throughflow. Increase in conductivity also may stabilize or destabilize the flow depending on the mass flow and viscous heating. The horizontal thermal gradient shows interesting effects in the presence of weak heterogeneity and horizontal throughflow. Significant change in the critical Rayleigh number is observed even for small values of the horizontal Rayleigh number.
Mechanical reading of ferroelectric polarization
Authors: Stefani Christina , Langenberg Eric , Cordero-Edwards Kumara , Schlom Darrell G. , Catalan Gustau , Domingo Neus
Published: August 2021

Flexoelectricity is a property of dielectric materials whereby they exhibit electric polarization induced by strain gradients; while this effect can be negligible at the macroscale, it can become dominant at the nanoscale, where strain gradients can turn out to be tremendous. Previous works have demonstrated that flexoelectricity coupled with piezoelectricity enables the mechanical writing of ferroelectric polarization. When considering ferroelectric materials with out-of-plane polarization, the coupling of piezoelectricity with flexoelectricity can insert a mechanical asymmetry to the system and enable the distinction of oppositely polarized domains, based on their nanomechanical response. Using atomic force microscopy and, more specifically, contact resonance techniques, the coupling of flexoelectricity to piezoelectricity can be exploited to mechanically read the sign of ferroelectric polarization in a non-destructive way. We have measured a variety of ferroelectric materials, from a single crystal to thin films, and domains that are polarized down always appear to be stiffer than oppositely polarized domains. In this article, we demonstrate experimentally that the phenomenon is size-dependent and strongly enhanced when the dimension of the material is reduced to nanoscale in thin films. Ultimately, we demonstrate how the sensitivity in mechanical reading of ferroelectric polarization can be improved by appropriately tuning the mechanical stiffness of the cantilevers.
On dispersion of solute in a hydromagnetic flow between two parallel plates with boundary absorption
Authors: Dhar Subham , Poddar Nanda , Mondal Kajal Kumar , Mazumder Bijoy Singha
Published: August 2021

It is well known that the widely applied Taylor diffusion model predicts the longitudinal distribution of tracers. Some recent studies indicate that the transverse concentration distribution is highly significant for large dispersion times. The present study describes an analytical approach to explore the two-dimensional concentration dispersion of a solute in the hydromagnetic laminar flow between two parallel plates with boundary absorption. The analytical expressions for the transverse concentration distribution and the mean concentration distribution of the tracers up to second-order approximation are derived using Mei's homogenization technique. The effects of the Péclet number and Hartmann number on the Taylor dispersivity are shown. It is also observed how the transverse and longitudinal mean concentration distributions are influenced by the magnetic effect, dispersion times, and boundary absorption. It is remarkable to note that the boundary absorption creates a large non-uniformity on the transverse concentration in a hydromagnetic flow between two parallel plates.
Numerical study on the drag characteristics of rigid submerged vegetation patches
Authors: Liu Mengyang , Huai Wenxin , Ji Bin , Han Peng
Published: August 2021

Aquatic plants play a crucial role in the hydrodynamic and material transport processes within the aquatic environments due to the additional flow resistance induced by vegetation stems. In this study, high-resolution numerical experiments were performed to investigate the drag characteristics of circular vegetation patches fully immersed in a turbulent open channel flow. The submerged vegetation patch was modeled as a rigid cylinder array with a diameter D composed of N cylinder elements with a diameter d. The effects of vegetation density Φ (0.023 ≤ Φ ≤ 1) and relative diameter d/D (d/D = 0.051 and 0.072) were tested. The simulation results show that Φ and d/D affect the flow resistance exerted by the vegetation patch by modifying the bleeding flow intensity. With the increase in Φ, the drag forces acting on the individual cylinder elements decrease, whereas the total drag forces of the patch increase. The oscillation strength of the drag force of individual cylinders depends on Φ and the fixed positions within the patch. The presence of the free end of submerged cylinder array leads to enhanced wake entrainment with the increase in Φ. The drag coefficient of the submerged patch is smaller than that of the emergent patch when the dimensionless frontal area aD > 3. However, the two patches exhibit comparable drag coefficients for smaller aD values.
The shape of a falling jet formed by concentrated polymer solutions
Authors: Subbotin A. V. , Skvortsov I. Yu. , Kuzin M. S. , Gerasimenko P. S. , Kulichikhin V. G. , Malkin A. Ya.
Published: August 2021

We studied the shape of free-falling stable jets created by viscoelastic concentrated poly(acrylonitrile) solutions that were pressed out of a capillary at different outputs. The viscosity of the solutions varied by more than 1000 times, and the elasticity increased along with growing concentration. The main goal of the study was to compare theoretical predictions with experimental data. The theoretical argumentations were based on the momentum and rheological equations. We analyzed the superposition of viscoelastic, capillary, and inertial forces for fluids with different rheological properties flowing with different velocities changing more than 100 times. Although elasticity is definitely present, the Weissenberg number in all cases under study appeared less than one and, respectively, played a secondary role except for the most concentrated solution. Then we discussed the applicability of two main models based on the combination of visco-inertial and capillary-inertial forces. The best fitting and dominant input of different forces appeared dependent on the properties of the fluids and conditions of flow. At low polymer concentration, the jet profile corresponds better to the capillary-inertial model, while the visco-inertial regime of flow becomes dominant at higher velocities and highly viscous solutions. At very high concentrations (25% in our case), both of the considered models do not allow describing the complete experimental data due to the increasing role of elasticity.
Coupling response of flow-induced oscillating cylinder with a pair of flow-induced rotating impellers
Authors: Zhu Hongjun , Chu Xin , Yan Zhiyin , Gao Yun
Published: August 2021

An innovative device transforming the active control of rotating rods to passive control with a pair of impellers is proposed and numerically examined in this paper. The coupling response of a vortex-induced vibrating (VIV) circular cylinder symmetrically equipped with two impellers that are free to rotate is analyzed based on the results of computations that carried out for a reduced velocity range of Ur = 2–14 at a low Reynolds number of 150. In comparison with the bare cylinder, both the in-line and cross-flow responses are significantly augmented in the VIV initial branch with the introduction of a pair of passively rotating impellers, which is mainly attributed to the unstable rotation response in both direction and speed and the wake adjustment including the reduction in vortex formation length and broadening of flow wake. In the VIV lower branch, although the response amplitude is close to that of a bare cylinder, the strong interaction between two directional responses occurs with the same dominant frequency locking on the natural one. Nevertheless, the coexistence of multiple vibration frequencies leads to irregular oscillation trajectories and irregular vortex shedding. Moreover, the secondary vortex street is observed in the whole Ur range, but the number of merged vortices for the formation of secondary vortex street varies with Ur, depending on the response amplitude and the interaction between the shear layers of the main cylinder and impellers. In terms of time-averaged rotation, the symmetrical inward counter-rotating pattern is achieved despite the intermittent alteration of rotation direction. Furthermore, the vibration–rotation coupling is demonstrated from the variation of time-averaged rotation speed that closely follows the variation of vibration amplitude against Ur.
Unravelling the most diverse lance lacewing genus from the New World,
Authors: Califre Martins Caleb , Ardila-Camacho Adrian , Pires Machado Renato Jose , Flint Oliver S. , Stange Lionel A.
Published: August 2021

The genus Isostenosmylus Krüger, 1913 (Neuroptera: Osmylidae) is the most species-rich genus of lance lacewings in the Neotropical region. Seven species are newly described here (Isostenosmylus angustipennis, sp. nov., Isostenosmylus apaapensis sp. nov., Isostenosmylus barbatus, sp. nov., Isostenosmylus inca, sp. nov., Isostenosmylus jaguar, sp. nov., Isostenosmylus penai, sp. nov., Isostenosmylus triangulatus, sp. nov.). A neotype of Oedosmylus morenoi Navás, 1928 is proposed, the male of Isostenosmylus irroratus Ardila-Camacho et al., 2016 is newly described, and identification keys to males and females of Isostenosmylus species are provided. A morphological phylogeny and biogeographical analysis of the genus are also presented. Isostenosmylus is recovered as a monophyletic genus and species are divided in two main clades (named here as ‘bifurcatus’ and ‘pulverulentus’ clades); the greatest diversity of this genus is located in the Andean mountain range, where new studies should be focused on. http://zoobank.org/urn:lsid:zoobank.org:pub:7AA1CED6-D30D-4DE5-A45A-86C2F038B915