bluuebunny/crossref_metadata_2025 huggingface dataset:
Co-Modification of Bentonite by CTAB and Silane and its Performance in Oil-Based Drilling Mud
Authors: Guo Miao , Yang Guangbin , Zhang Shengmao , Zhang Yujuan , Gao Chuanping , Zhang Chunli , Zhang Pingyu
Published: January 2021

The stability, dispersion, and rheological properties of clay suspensions are important in the process of drilling. Organic clays were obtained traditionally by cation exchange, which is thermally unstable due to weak electrostatic interaction between the cationic surfactant and clay minerals. The purpose of the present study was to yield a stable and well dispersed organic bentonite (OBent) as a rheological additive for oil-based drilling mud. The co-modified method was used to modify bentonite by a cationic surfactant (cetyltrimethoxyammonium bromide: CTAB) and a silane coupling agent (hexadecyltrimethoxysilane: HDTMS). Firstly, the basal spacing of bentonite was enlarged by intercalation of CTAB, and the thermal stability of bentonite was improved by covalent bonds of HDTMS onto the bentonite platelets. The as-prepared OBent was characterized by infrared analysis, X-ray diffraction analysis, thermogravimetric analysis, and scanning electron microscopy. The hydrophobicity, solubility, viscosity, and tribological performance of the OBent were also recorded. The test results showed that the hydrophobicity of the co-modified bentonite was improved significantly, and was greater than that of bentonite modified with single surfactant CTAB or HDTMS. The bentonite modified by the surfactant together with the silane coupling agent had stable rheology and a lower coefficient of friction than the single surfactant-modified bentonite because more HDTMS entered into the interlayer spaces and formed chemical bonds at the inner surface of platelets.
Why Composition Matters
Authors: Bailey Andrew M. , Brenner Andrew
Published: January 2021

Many say that ontological disputes are defective because they are unimportant or without substance. In this paper, we defend ontological disputes from the charge, with a special focus on disputes over the existence of composite objects. Disputes over the existence of composite objects, we argue, have a number of substantive implications across a variety of topics in metaphysics, science, philosophical theology, philosophy of mind, and ethics. Since the disputes over the existence of composite objects have these substantive implications, they are themselves substantive.
Efficacy of artemisinin–lumefantrine for treatment of uncomplicated malaria after more than a decade of its use in Kenya
Authors: Kishoyian Gabriel , Njagi Eliud N. M. , Orinda George O. , Kimani Francis T. , Thiongo Kevin , Matoke-Muhia Damaris
Published: January 2021

Background

The resistance of Plasmodium falciparum to antimalarial drugs remains a major impairment in the treatment and eradication of malaria globally. Following the introduction of artemisinin-based combination therapy (ACT), there have been reports of delayed parasite clearance. In Kenya, artemether–lumefantrine (AL) is the recommended first-line treatment of uncomplicated malaria. This study sought to assess the efficacy of AL after a decade of use as the preferred method of managing malarial infections in Kenya. We assessed clinical and parasitological responses of children under 5 years between May and November 2015 in Chulaimbo sub-County, Kisumu, Kenya. Patients aged between 6 and 60 months with uncomplicated P. falciparum mono-infection, confirmed through microscopy, were enrolled in the study. The patients were admitted at the facility for 3 days, treated with a standard dose of AL, and then put under observation for the next 28 days for the assessment of clinical and parasitological responses. Of the 90 patients enrolled, 14 were lost to follow-up while 76 were followed through to the end of the study period. Seventy-five patients (98.7%) cleared the parasitaemia within a period of 48 h while one patient (1.3%) cleared on day 3. There was 100% adequate clinical and parasitological response. All the patients cleared the parasites on day 3 and there were no re-infections observed during the stated follow-up period. This study, therefore, concludes that AL is highly efficacious in clearing P. falciparum parasites in children aged ≥6 and ≤60 months. The study, however, underscores the need for continued monitoring of the drug to forestall both gradual ineffectiveness and possible resistance to the drug in all target users.
Michigan Court Enjoins Statute Limiting Abortions Covered by Medicaid
Authors: A.S.
Published: January 2021

In Planned Parenthood Affiliates of Michigan v. Engler (73 F.3d 634 (6th Cir. 1996)), the United States Court of Appeals for the Second Circuit held that § 400.109(a) of the Social Welfare Act of Michigan (Mich. Comp. Laws Ann. § 400.109(a) (1994)) impermissibly conflicts with the Medicaid Act (Social Security Act tit. XIX, 42 U.S.C. §§ 1396 et seq. (1988)) as modified by the 1994 Hyde Amendment (Pub. L. No. 103-112, § 509, 107 Stat. 1082-1113 (1994)), insofar as the § 400.109(a) only provides state funding for abortions necessary to save the life of a mother, and not for abortions resulting from rape or incest. The court held that the Hyde Amendment defines medically necessary abortions that must be funded by states participating in the federal Medicaid program, and that the amendment is not merely a federal appropriations bill.
Fourth Circuit Upholds Hospital's Right to Terminate HIV-Positive Surgeon
Authors: J.K.T.
Published: January 2021

On April 3, 1995, the Fourth Circuit upheld the right of a Maryland hospital to terminate a surgeon who was HIV-positive (John Doe v. University of Maryland Medical System Corp. (50 F.3d 1261 (4th Cir. 1995)). A resident in the University of Maryland Neurosurgical Training Program was dismissed when hospital administrators learned of his infection with HIV. The resident, known as Dr. Doe, claimed that his termination violated federal laws protecting persons with disabilities. The court upheld the hospital's actions as lawful and affirmed the trial court's grant of summary judgment for the hospital.

Dr. Doe charged that his dismissal from the training program violated the Rehabilitation Act and the Americans with Disabilities Act (ADA).
The Eleventh Circuit Holds that Agreements in which Pharmaceutical Companies Pay Generic Companies Not to Compete May be Valid
Authors: Garrigues Amy
Published: January 2021

On September 15, 2003, the US. Court of Appeals for the Eleventh Circuit held that agreements between pharmaceutical and generic companies not to compete are not per se unlawful if these agreements do not expand the existing exclusionary right of a patent. The Valley DrugCo.v.Geneva Pharmaceuticals decision emphasizes that the nature of a patent gives the patent holder exclusive rights, and if an agreement merely confirms that exclusivity, then it is not per se unlawful. With this holding, the appeals court reversed the decision of the trial court, which held that agreements under which competitors are paid to stay out of the market are per se violations of the antitrust laws. An examination of the Valley Drugtrial and appeals court decisions sheds light on the two sides of an emerging legal debate concerning the validity of pay-not-to-compete agreements, and more broadly, on the appropriate balance between the seemingly competing interests of patent and antitrust laws.
Emergency Contraception: Legal Consequences of Medical Classification
Authors: Gerber Elizabeth
Published: January 2021

Pharmacists with religious or ethical objections to prescribing emergency contraception won the latest round in the fight over conscience clauses in a case that could have broader implications for attempts to restrict access to contraception. In Stormans, Inc. v. Selecky, a federal District Court in Washington State granted an injunction to block the enforcement of regulations that would have forbidden pharmacists to refuse to dispense emergency contraception on the grounds of religious or ethical objections. In its decision, the court applied Supreme Court abortion precedent without explicitly ruling whether emergency contraception should be legally categorized as a form of abortion or as contraception. However, the legal status of emergency contraception affects the strength of the defendants’ claims that the law was justified on the grounds of preventing sex discrimination. In neglecting to rule one way or the other, the court not only failed to adequately consider the sex discrimination claim but also may have opened the door to more restrictive regulation on contraceptives generally.
Antitrust: U.S. Supreme Court Affirms FTC Jurisdiction but Vacates Scope of Analysis on CDA Policy
Authors: Zakhary Joseph R.
Published: January 2021

In California Dental Association v. FTC, 119 S. Ct. 1604 (1999), the U.S. Supreme Court reviewed a decision by the U.S. Court of Appeals for the Ninth Circuit that a nonprofit affiliation of dentists violated section 5 of the Federal Trade Commission Act (FTCA), 15 U.S.C.A. § 45 (1998), which prohibits unfair competition. The Court examined two issues: (1) the Federal Trade Commission's (FTC) jurisdiction over the California Dental Association (CDA); and (2) the proper scope of antitrust analysis. The Court unanimously held that CDA was subject to FTC's jurisdiction, but split 5-4 in its finding that the district court's use of abbreviated rule-of-reason analysis was inappropriate.

CDA is a voluntary, nonprofit association of local dental societies. It boasts approximately 19,000 members, who constitute roughly threequarters of the dentists practicing in California. Although a nonprofit, CDA includes for-profit subsidiaries that financially benefit CDA members. CDA gives its members access to insurance and business financing, and lobbies and litigates on their behalf. Members also benefit from CDA marketing and public relations campaigns.
Constitutional Law: U.S. Supreme Court Clarifies Procedural Requirements for Workers’ Compensation Benefits Claim
Authors: Collins Kathleen A.
Published: January 2021

The U.S. Supreme Court held, in American Manufacturers Mutual Insurance Co. v. Sullivan, 119 S. Ct. 988 (1999), that state workers’ compensation system insurers cannot be sued for withholding health care benefits for work-related injuries while they decide whether the treatment is “reasonable” and “necessary.” The respondents, ten employees and two organizations representing employees who received medical benefits under the Workers’ Compensation Act, brought a 42 U.S.C. § 1983 action against state officials, the Pennsylvania State Workers’ Insurance Fund, private insurers, and the school district, alleging that their due process rights were violated by provisions of the Pennsylvania Workers’ Compensation Act (Act), 77 Pa. Cons. Stat. Ann. § 1 et seq. (West 1992 & Supp. 1998). The Act permits suspension of benefits without notice or opportunity to be heard pursuant to a “utilization review” process.

To control costs, Pennsylvania amended its workers’ compensation system in 1993. Under the Act, an employer or its insurer must pay for all reasonable and necessary medical treatment.
Author Correction: A large-scale binding and functional map of human RNA-binding proteins
Authors: Van Nostrand Eric L. , Freese Peter , Pratt Gabriel A. , Wang Xiaofeng , Wei Xintao , Xiao Rui , Blue Steven M. , Chen Jia-Yu , Cody Neal A. L. , Dominguez Daniel , Olson Sara , Sundararaman Balaji , Zhan Lijun , Bazile Cassandra , Bouvrette Louis Philip Benoit , Bergalet Julie , Duff Michael O. , Garcia Keri E. , Gelboin-Burkhart Chelsea , Hochman Myles , Lambert Nicole J. , Li Hairi , McGurk Michael P. , Nguyen Thai B. , Palden Tsultrim , Rabano Ines , Sathe Shashank , Stanton Rebecca , Su Amanda , Wang Ruth , Yee Brian A. , Zhou Bing , Louie Ashley L. , Aigner Stefan , Fu Xiang-Dong , Lécuyer Eric , Burge Christopher B. , Graveley Brenton R. , Yeo Gene W.
Published: January 2021

A Correction to this paper has been published: https://doi.org/10.1038/s41586-020-03067-w
Palladium-catalyzed functionalizations of acidic and non-acidic C(sp3)–H bonds – recent advances
Authors: Saini Gaurav , Kapur Manmohan
Published: January 2021

This feature article discusses some of the recent reports on direct as well as indirect C(sp3)–H arylations and alkenylations via cross-coupling reactions under palladium catalysis.
Rapid access to Asp/Glu sidechain hydrazides as thioester precursors for peptide cyclization and glycosylation
Authors: Barnes Natalie G. , Nyandoro Kudakwashe , Jin Hanzhang , Macmillan Derek
Published: January 2021

We present a streamlined approach to sidechain acyl hydrazides of aspartic and glutamic acids – user friendly precursors to peptide macrocycles and glycopeptide analogues.
Recent progress of zero-dimensional luminescent metal halides
Authors: Li Mingze , Xia Zhiguo
Published: January 2021

This review provides in-depth insight into the structure–luminescence–application relationship of 0D all-inorganic/organic–inorganic hybrid metal halide luminescent materials.
Embedded homogeneous ultra-fine Pd nanoparticles within MOF ultra-thin nanosheets for heterogeneous catalysis
Authors: Guo Taolian , Mo Kaili , Zhang Nannan , Xiao Lipengcheng , Liu Wenlong , Wen Lili
Published: January 2021

Owing to the synergetic effects of ultra-small Pd NPs and the intrinsic characteristics of two-dimensional supports, the obtained Pd@NMOF-Ni showed high catalytic activity and size-selectivity in olefin hydrogenation with easy recovery.
Co3O4@NiCo2O4 double-shelled nanocages with hierarchical hollow structure and oxygen vacancies as efficient bifunctional electrocatalysts for rechargeable Zn–air batteries
Authors: Yu Neng-Fei , Huang Wen , Bao Kai-Lin , Chen Hui , Hu Kai , Zhang Yi , Huang Qing-Hong , Zhu Yusong , Wu Yu-Ping
Published: January 2021

Co3O4@NiCo2O4double-shelled nanocages with hierarchical hollow structure and oxygen vacancies provide efficient reactive sites and charge/mass transport environmen, demonstrating excellent bifunctional oxygen electrocatalytic performance.
Coincident angle-resolved state-selective photoelectron spectroscopy of acetylene molecules: a candidate system for time-resolved dynamics
Authors: Mandal S. , Gopal R. , Srinivas H. , D’Elia A. , Sen A. , Sen S. , Richter R. , Coreno M. , Bapat B. , Mudrich M. , Sharma V. , Krishnan S. R.
Published: January 2021

We focus on detailed investigations of the molecular acetylene-vinylidene system in the photon energy range 19–40 eV where extreme-ultraviolet pulses can probe the dynamics effectively.
A distance-based capillary biosensor using wettability alteration
Authors: Li Yansheng , Men Xiujin , Gao Guowei , Tian Ye , Wen Yongqiang , Zhang Xueji
Published: January 2021

A visual quantitative distance-based biosensor through capillary action is proposed, which converts the wettability changes caused by the target molecules into a capillary rise height signal without any manufacturing technology.
Towards designing globular antimicrobial peptide mimics: role of polar functional groups in biomimetic ternary antimicrobial polymers
Authors: Rani Garima , Kuroda Kenichi , Vemparala Satyavani
Published: January 2021

Using atomistic molecular dynamics simulations, we study the interaction of ternary methacrylate polymers, composed of charged cationic, hydrophobic and neutral polar groups, with model bacterial membrane.
Onsager's variational principle in active soft matter
Authors: Wang Haiqin , Qian Tiezheng , Xu Xinpeng
Published: January 2021

Onsager's variational principle is extended and applied to the dynamic modeling of active soft matter such as the directional motion of individual self-propelled units and the dynamics of active polar droplets on solid substrates.
The Galactic center chimneys: the base of the multiphase outflow of the Milky Way
Authors: Ponti G. , Morris M. R. , Churazov E. , Heywood I. , Fender R. P.
Published: January 2021

Context.Outflows and feedback are key ingredients of galaxy evolution. Evidence for an outflow arising from the Galactic center (GC) – the so-called GC chimneys – has recently been discovered at radio, infrared, and X-ray bands.

Aims.We undertake a detailed examination of the spatial relationships between the emission in the different bands in order to place constraints on the nature and history of the chimneys and to better understand their impact on the GC environment and their relation with Galactic scale outflows.

Methods.We compare X-ray, radio, and infrared maps of the central few square degrees.

Results.The X-ray, radio, and infrared emissions are deeply interconnected, affecting one another and forming coherent features on scales of hundreds of parsecs, therefore indicating a common physical link associated with the GC outflow. We debate the location of the northern chimney and suggest that it might be located on the front side of the GC because of a significant tilt of the chimneys toward us. We report the presence of strong shocks at the interface between the chimneys and the interstellar medium, which are traced by radio and warm dust emission. We observe entrained molecular gas outflowing within the chimneys, revealing the multiphase nature of the outflow. In particular, the molecular outflow produces a long, strong, and structured shock along the northwestern wall of the chimney. Because of the different dynamical times of the various components of the outflow, the chimneys appear to be shaped by directed large-scale winds launched at different epochs. The data support the idea that the chimneys are embedded in an (often dominant) vertical magnetic field, which likely diverges with increasing latitude. We observe that the thermal pressure associated with the hot plasma appears to be smaller than the ram pressure of the molecular outflow and the magnetic pressure. This leaves open the possibility that either the main driver of the outflow is more powerful than the observed hot plasma, or the chimneys represent a “relic” of past and more powerful activity.

Conclusions.These multiwavelength observations corroborate the idea that the chimneys represent the channel connecting the quasi-continuous, but intermittent, activity at the GC with the base of theFermibubbles. In particular, the prominent edges and shocks observed in the radio and mid-infrared bands testify to the most powerful, more recent outflows from the central parsecs of the Milky Way.
The Effect of Hydrogen-Charging on Mechanical Properties of Austenitic CrNi Steel Fabricated by Wire-Feed Electron Beam Additive Manufacturing
Authors: Panchenko Marina , Melnikov Eugeny , Moskvina Valentina , Astafurov Sergey , Maier Galina , Reunova Kseniya , Rubtsov Valery , Kolubaev Evgeny , Astafurova Elena
Published: January 2021

A comparative study of the mechanical properties, fracture mechanisms and hydrogen embrittlement peculiarities was carried out using the specimens of austenitic CrNi steel produced by two different methods: wire-feed electron beam additive manufacturing and conventional casting followed by solid-solution treatment. Hydrogen-induced reduction of ductility and the increase in the yield strength are observed in steel specimens produced by both methods. Despite hydrogen embrittlement index is comparable in them, the increase in the yield strength after hydrogen-charging is different: 25 MPa for cast steel and 175 MPa for additively manufactured steel. This difference is associated with the peculiarities of phase composition and phase distribution in steels produced by different methods.
The Basic Problems of Breakdown of Oil Refining Equipment
Authors: Taube Aleksandr , Storozheva Ekaterina , Dyachenko Denis
Published: January 2021

The paper describes typical cases of failure of elements of oil refining equipment, including the destruction of welded joints made by austenitic electrodes, furnace coil pipes cracking, hydrogen cracking, metallurgical cases and corrosion. The causes of destruction and depressurization are classified with the identification of the main problems and the relations between them.
Complex treatment of erosion-corrosion issues for piping
Authors: Antonov Mikhail , Kalyutik Aleksandr , Karyakin Yury , Arzhaev Alexandr , Arzhaev Alexey , Makhanev Valentin
Published: January 2021

Erosion-corrosion damages piping sufficiently affect safety and economic efficiency of NPP long-term operation up. Due to the multifactorial nature of the damage mechanism under consideration, an integrated approach is required to minimize its negative effects.
Increased operational reliability tubing from steel 25CrMnNb grade
Authors: Laev Konstantin , Devyaterikova Nataya , Aleksandrov Sergey , Shcherbakov Igor , Rogova Kseniya , Oshurkov Georgiy , Radionova Irina , Pavlov Aleksandr , Alekseeva Ekaterina , Strekalovskaya Darya
Published: January 2021

The conventional tubing supplied to oilfields with low aggressive environments: with pCO2 up to 0.3 atm and pH2S up to 0.005 atm often shows signs of pitting carbon dioxide corrosion after operation. To solve the problem, a new sparingly alloyed steel of 25KhGB was developed for K steel grade tubing with increased set of performance characteristics obtained after thermomechanical treatment.
Durian Rind Micro Composter Model: A Case of Kampung Durian, Ngrogung, Ponorogo, Indonesia
Authors: Setyaningrum Haris , Rukminastiti Masrifah Atika , Susilo Adib , Haryadi Imam
Published: January 2021

The case of waste from durian rind in Ngrogung, Ngebel, Ponorogo, Indonesia increased significantly per year. Agglomerations and decomposition of durian rind surrounding agro park caused air pollution and bad view in park areas. The decomposition of durian rind is very important to reduce those impacts. The micro composter model in Kampung Durian consisted of three main components. The first component was drying area with cemented ground. The drying area was set to accommodate 1 t fresh durian rind per day. The materials come from surrounding areas of agro park. The second was a machine house with one ton material capacity per day. The third was a composter house consisted of composter tube and packing area. The result of the micro composter house showed a cleaning agglomeration of durian rind from Ngebel lake and surrounding areas. In addition, the model produced liquid organic fertilizer and compost. A cycle of composting was 30 d in the dry season. Amount 1 t of durian rind decomposition resulted of 100 L liquid organic fertilizers and 50 kg compost. The result of composter had a direct impact to control waste problems in Ngebel and surrounding areas.
Adoption Level of Integrated Farming System Based on Rice–Cattle and Its Determinants Related to Sustainable Agriculture
Authors: Kurniati Novitri , Sukiyono Ketut , Purmini Purmini , Oryza Sativa Mutyarsih
Published: January 2021

A way to restore the fertility of rice fields is through improving soil structure and microbes by using organic fertilizer derived from livestock waste. Therefore it is necessary to implement an Integrated Farming System (IFS) particularly rice and cattle. The study aimed to analyze the determinants of farmers’ decisions in adopting IFS of rice in Bengkulu Province, Indonesia. This research applied a survey method, which was conducted in Seluma and Rejang Lebong Regencies, Bengkulu Province, Indonesia. The data included primary and secondary and analyzed with the use of Multinomial Logistic Regression. The results indicated that simultaneously all the predictor variables had a significant effect on the response variable, while the income, land area, number of cattle and farmers’ perceptions had a very significant effect on the adoption of the integration system while the variable costs of production, farming experience and labor did not have a significant effect on the decision to adopt a rice and cattle integration system.
Economic pricing of complex products in a competitive closed-loop supply chain network under uncertainty: A case study of CoPS industry
Authors: Solgi Omid , Taromi Alireza , Gheidar-Kheljani Jafar , Dehghani Ehsan
Published: January 2021

The development of technology, globalization of the economy and the unpredictable behavior of customers have eventuated in a dynamic and competitive environment in the complex product systems (CoPS) market. Besides, CoPS economic pricing is one of the key factors that dramatically reduces production costs and increases competitiveness. In this regard, this paper unveils a hybrid data envelopment analysis (DEA)-fuzzy mathematical model for economic pricing of CoPS in a competitive closed-loop supply chain network under uncertainty. In the first stage, different CoPS suppliers are evaluated exploiting a DEA model based on a set of economic, technical, and geographical criteria. The advantage of this evaluation is choosing appropriate suppliers, and reducing the complexity of the original model. Next, using a robust optimization model, the strategic and tactical decisions are simultaneously determined, providing a fully optimal solution to the model. In the concerned model, the costs and capacities of facilities are considered to be hemmed in by uncertainty. Eventually, to evaluate the proposed approach, a case study is conducted to derive the important managerial results. The numerical results corroborate that the presented robust model is capable of providing a stable structure under different realizations.
COVID-19 als Berufskrankheit oder Arbeitsunfall: Überlegungen zu Versicherungsschutz und Meldepflicht in der gesetzlichen Unfallversicherung
Authors: Nowak Dennis , Ochmann Uta , Brandenburg Stephan , Nienhaus Albert , Woltjen Michael
Published: January 2021

Eine COVID-19-Erkrankung kann Berufskrankheit oder Arbeitsunfall sein. Eine Anerkennung als Berufskrankheit 3101 kann erfolgen, wenn die Erkrankung bei versicherten Personen auftritt, die infolge der Ausübung ihrer beruflichen Tätigkeit in einem von vier Bereichen einer gegenüber der Allgemeinbevölkerung wesentlich erhöhten Infektionsgefahr ausgesetzt waren: (1) Gesundheitsdienst, (2) Wohlfahrtspflege, (3) Laboratorium oder (4) bei anderer Tätigkeit mit ähnlich wie bei (1) bis (3) erhöhter Infektionsgefahr. Der Versicherungsschutz bezieht sich auf Arbeitnehmerinnen und Arbeitnehmer, Selbständige – soweit nicht befreit – und Ehrenamtliche. Gesetzlich meldepflichtig ist die COVID-19-Erkrankung, meist in Verbindung mit zeitnahem SARS-CoV-2-Erregernachweis. Eine COVID-19-Erkrankung kann dann als Arbeitsunfall vorliegen, wenn sich der intensive und direkte Kontakt zu infizierten Personen nicht bestimmungsgemäß wie bei der Berufskrankheit 3101, sondern anderweitig situativ aus der versicherten Tätigkeit ergibt.
Numerical investigation of plasma characteristics for an ion thruster discharge chamber
Authors: Guo S. L. , Jin X. L. , Lei L. , Zhang X. Y. , Li B.
Published: January 2021

A 2D fully kinetic particle-in-cell plus Monte Carlo collision model is developed to simulate the plasma characteristics of the ion thruster discharge chamber. The interaction between charged particles and the dynamic electric field, the confinement of the static magnetic field, and the particle collisions are simulated. The self-similar scaling method, the multigrid method, sub-cycle time, and neutral particle pre-distribution techniques work together to perform the full-particle and full-kinetic simulation. The steady-state results such as particle number, current flows, static magnetic field, electric potential, particle density, and energy distributions are obtained and discussed. Moreover, the plasma generation and transport, the dynamic behavior of neutral particles, and the influence of the gas flow rate on the plasma are analyzed. The density distribution of charged particles indicates that the electrons are strongly constrained by the magnetic field, and the magnetization characteristics are distinguished from that of ions. Neutral particles are heavily ionized and are depleted along the central line, which is consistent with the area with a higher ionization rate. At last, it is found that the energy and density of charged particles are sensitive to the change of the gas flow rate.
Inelastic scattering and cooling of photoexcited electrons through coupling with acoustic, optic, and surface polar optic phonons in graphene
Authors: Arshia Khatoon S. , Ansari Meenhaz , Ashraf S. S. Z. , Obaidurrahman M.
Published: January 2021

The acoustic, optic, and surface polar optic phonons are the three important intrinsic and extrinsic phononic modes that increasingly populate graphene on a substrate with rising temperatures; the coupling of the three phononic modes with photoexcited hot carriers in the equipartition regime provides significant pathways for electron-phonon relaxation. In this paper, we theoretically investigate the relative significance of the three phononic modes in electron scattering and cooling phenomena in single layer graphene, including their comparison with supercollision driven power loss, and obtain analytical formulas on the energy dependence of electron–phonon scattering rates and cooling power in the Boltzmann transport formalism. The obtained analytical solutions not only closely reproduce the results for scattering rates and cooling power, as that obtained from the earlier reported numerically tractable integral forms, but also enable us to derive closed-form formulas of the cooling time and thermal conductance. The important role of Pauli blocking that prevents transition to filled energy states has also been elucidated in the estimation of the scattering rate and cooling power density for all three modes. The obtained formulas provide better insight into the dynamics of hot electron phenomena giving an explicit view of the interplay of the different variables that affect the transport quantities under investigation. The formulas can also be potentially useful for performance optimization of transport quantities in numerical optimization methods since the first and second-order derivatives are easily deducible from these formulas.
Tri-directional piezoelectric energy harvester based on U-shaped beam-pendulum structure
Authors: Mo Shuting , Liu Yan , Shang Siyao , Wang Hai , Yang Keyuan
Published: January 2021

This Note proposed a multi-direction piezoelectric energy harvester with a wide bandwidth and low working frequency, which is distinguished by the multiple working modes of the U-shaped beam and the high capacity of the pendulum in collecting arbitrary vibrations. The structural features are evaluated by finite element simulation and verified by experiments. At least three voltage peaks are generated in the frequency range of 0 Hz–25 Hz, and favorable harvesting consistency in different directions is achieved. The designed structure is adaptable in collecting energy from arbitrary vibration in ambient environments.
Spatially resolved photoluminescence brightening in individual single-walled carbon nanotubes
Authors: Hou Zhentao , Tumiel Trevor M. , Krauss Todd D.
Published: January 2021

Single-molecule microscopy was used to image photoluminescence (PL) brightening of individual sodium-dodecyl-sulfate (SDS)-wrapped single-walled carbon nanotubes (SWCNTs) upon the addition of dithiothreitol (DTT). PL enhancement varied for each nanotube (NT), with some brightening by 16% and others by a factor of about 7. Interestingly, NTs that displayed lower initial QY values showed the largest increases in PL enhancement. SDS-SWCNTs longer than the diffraction limit were studied in order to spatially resolve the brightening phenomenon. Quite unexpectedly, a uniform, single-step PL brightening along the NT was consistently observed, suggesting that the PL enhancement is the result of a non-localized process. The even PL brightening seen over SWCNTs that are micrometers long implies that single point defect sites, which are known to be largely responsible for exciton nonradiative decay, play no significant role in the brightening process. Interestingly, affixing the SWCNT strongly to the substrate surface mitigated the PL brightening response, consistent with a hypothesis that surfactant reorganization upon the addition of DTT is responsible for exciton PL brightening.
Demonstration of highly repeatable room temperature negative differential resistance in large area AlN/GaN double-barrier resonant tunneling diodes
Authors: Zhang HePeng , Xue JunShuai , Fu YongRui , Li LanXing , Sun ZhiPeng , Yao JiaJia , Liu Fang , Zhang Kai , Ma XiaoHua , Zhang JinCheng , Hao Yue
Published: January 2021

Here, we present a systematical investigation of AlN/GaN double-barrier resonant tunneling diodes (RTDs) grown by plasma-assisted molecular beam epitaxy on metal-organic chemical vapor deposition GaN-on-sapphire templates. The processed devices featured an active region composed of 2.5 nm GaN quantum well sandwiched by two 1.5 nm AlN barriers and RTD mesa diameter ranging from 1 to 20 μm. Room temperature current–voltage characteristics exhibited a repeatable negative differential resistance (NDR) free of degradation and hysteresis after 1000 times subsequently up-to-down voltage sweeps across different sizes. High peak-to-valley current ratios of 1.93 and 1.58 were obtained at room temperature for 1 and 12 μm diameter devices, respectively, along with peak current densities of 48 and 36 kA/cm2 corresponding to peak voltages of 4.65 and 5.9 V. The peak current density decreased quickly initially and then was less susceptible to this averaging effect with increasing the device diameter. Temperature-dependent measurements revealed that the valley current density displayed a positive relationship to the temperature, and an abruptly increasement was observed for the devices with a diameter of 20 μm when the temperature rose over 230 K. We attributed this abnormal phenomenon to the increased contribution from acoustic and longitudinal optical (LO) phonon scattering, especially for the LO phonon scattering. The area dependence of electrical performance suggested that the leakage pathway through dislocations played a vital role for charge transport and there existed a threshold of dislocation density for NDR characteristics. These results promote further study for future implementation of III-nitride-based RTD oscillators into high-frequency and high-power terahertz radiation.
Study on shallow donor-type impurities of GaN epilayer regrown by epitaxial lateral overgrowth technique
Authors: Tang Wenxin , Chen Fu , zhang Li , Xu Kun , Zhang Xuan , Deng Xuguang , Wei Xing , Sun Chi , Cai Yong , Zhang Xiaodong , Yu Guohao , Zhang Baoshun
Published: January 2021

p-doped gallium nitride (GaN) regrowth by epitaxial lateral overgrowth using a SiO2 mask is studied. A comparison between SiO2 and Al2O3 masked p-GaN by cathodoluminescence spectroscopy and scanning electron microscopy indicates that donor-type impurities are related to the SiO2 mask. A domain peak of 3.25 eV induced by shallow-donor and acceptor transitions and the dark contrast of obtuse triangles have been detected in SiO2 masked p-type GaN. Secondary ion mass spectroscopy is simultaneously employed for the analysis of SiO2 and Al2O3 masked p-GaN and identifies that the source of donor-type impurities is from Si atoms. Furthermore, the experimental results of cross-sectional microstructures at different regrowth times have been investigated. It is found that the donor-type impurities tend to cluster in semi-polar 112¯2 facets before the coalescence at the bottom of adjacent triangular stripes starts. The explanation for the non-uniform distribution of impurities is that semi-polar 112¯2 facets exhibit more dangling bond densities than the (0001) plane, and the SiO2 mask exposed to the vapor phase would likely introduce more impurities before the coalescence of GaN stripes.
Nitrogen-displacement-related electron traps in n-type GaN grown on a GaN freestanding substrate
Authors: Horita Masahiro , Narita Tetsuo , Kachi Tetsu , Suda Jun
Published: January 2021

Energy levels due to intrinsic point defects are identified by deep-level transient spectroscopy (DLTS). Electron-beam (EB) irradiation created nitrogen vacancies (VN) and nitrogen interstitials (NI) in n-type GaN layers grown via metalorganic vapor phase epitaxy on freestanding GaN substrates, where the irradiation energies were selected to be within 100–401 keV to displace only nitrogen atoms in GaN. Two electron traps, EE1 (0.13 eV) and EE2 (0.98 eV), were observed in the DLTS spectra. The production rates of EE1 and EE2 were 0.093 and 0.109 cm−1 under 401 keV irradiation, which were nearly equal values. In the DLTS spectra recorded for EB-irradiated samples at the energy ranging from 100 to 401 keV, EE1 and EE2 were found to appear simultaneously at an irradiation energy of 137 keV and were observed at energies greater than 137 keV. On the basis of a comparison with the results of recent first-principles calculations, we attributed the EE1 and EE2 peaks to nitrogen vacancies VN (+/0) and nitrogen interstitials NI (0/−), respectively. Furthermore, annealing led to reductions of the densities of these traps at the same rate. The reduction of the densities of EE1 and EE2 can be explained by the migration of NI and the subsequent recombination with VN. The displacement energy of 21.8 eV for nitrogen in GaN was obtained from the irradiation-energy dependence of EE1.
Instability of large-scale riverbed patterns
Authors: Ali Sk Zeeshan , Dey Subhasish
Published: January 2021

In this paper, we explore the instability of large-scale riverbed patterns, performing a linear stability analysis of a zero-pressure gradient free-surface flow in a wide straight channel with an erodible bed. The local depth-averaged turbulence state is governed by two key parameters: namely, the turbulent kinetic energy (TKE) and its dissipation rate. A depth-averaged flow model coupled with the transport equations of the TKE and its dissipation rate and the particle transport model are developed to examine the formation of large-scale patterns. Both the modes of particle transport as bedload and suspended load are considered herein, allowing for the extension of the conventional theories to cover from hydraulically smooth to transitional flow regimes. The classical Exner equation of the bed evolution is modified in the presence of suspended particles, whose concentration is coupled with the steady-state advection–diffusion equation. Applying a standard linearization technique, the periodic perturbations in both streamwise and spanwise directions are imposed on the bed to find the dispersion relationship. The stability maps for the growth rate of large-scale patterns are obtained as a function of streamwise and spanwise wavenumbers and of key parameters associated with the flow and particles.
Grid-point and time-step requirements for direct numerical simulation and large-eddy simulation
Authors: Yang Xiang I. A. , Griffin Kevin P.
Published: January 2021

We revisit the grid-point requirement estimates in Choi and Moin [“Grid-point requirements for large eddy simulation: Chapman’s estimates revisited,” Phys. Fluids 24, 011702 (2012)] and establish more general grid-point requirements for direct numerical simulations (DNS) and large-eddy simulations (LES) of a spatially developing turbulent boundary layer. We show that by allowing the local grid spacing to scale with the local Kolmogorov length scale, the grid-point requirement for DNS of a spatially developing turbulent boundary layer is N∼ReLx2.05 rather than N∼ReLx2.64, as suggested by Choi and Moin, where N is the number of grid points and Lx is the length of the plate. In addition to the grid-point requirement, we estimate the time-step requirement for DNS and LES. We show that for a code that treats the convective term explicitly, the time steps required to get converged statistics are Nt∼ReLx/Rex06/7 for wall-modeled LES and Nt∼ReLx/Rex01/7 for wall-resolved LES and DNS (with different prefactors), where Rex0 is the inlet Reynolds number. The grid-point and time-step requirement estimates allow us to estimate the overall cost of DNS and LES. According to the present estimates, the costs of DNS, wall-resolved LES, and wall-modeled LES scale as ReLx2.91, ReLx2.72, and ReLx1.14, respectively.
Breakthrough instruments and products: Near infrared spectral sensing: Advances in portable instrumentation and implementations
Authors: Gilmore John
Published: January 2021

The breakthrough MEMS-Fabry–Perot interferometry spectral analyzer (C15712) offers engineers and scientists a compact, inexpensive and versatile module to expand the range of applications in near infrared spectroscopy.
Occupancy modelling reveals a highly restricted and fragmented distribution in a threatened montane frog (Philoria kundagungan) in subtropical Australian rainforests
Authors: Bolitho Liam J. , Rowley Jodi J. L. , Hines Harry B. , Newell David
Published: January 2021

In the last several decades, habitat loss, overexploitation, invasive organisms, disease, pollution and, more recently, climate change have led to catastrophic declines in amphibian biodiversity. Montane amphibian species, particularly those with narrow distributions and specific habitat requirements are likely to be at particular risk under future climate change scenarios. Despite this, fundamental ecological data are lacking for most of these species. Philoria kundagungan is a poorly known representative of a range-restricted genus of montane amphibians from eastern Australia. Using an occupancy framework, we conducted repeated call playback surveys at 32 sites across the mountainous regions of south-east Queensland and north-eastern New South Wales, Australia, to investigate: (1) the current extent of this species’ geographic range, and (2) environmental predictors of this species’ presence. We found that P. kundagungan has a highly restricted and fragmented distribution, being limited to ~11 km2 of potentially suitable habitat, and that its presence is strongly associated with high elevation (>800 m). Our survey protocol resulted in a high probability of detection (>70%) at occupied sites from relatively few visits. From these baseline data, future studies will have the ability to determine changes in this species’ geographic range and occupancy rate in response to the ever-increasing threats faced by P. kundagungan, thereby supporting more effective conservation strategies and policy decisions.
Using R2L pedagogy in teaching practical writing to non-Chinese speaking students in Hong Kong
Authors: Shum Mark Shiu-kee , Shi Dan
Published: January 2021

Since Hong Kong handover, the language policy in Hong Kong shifts from diglossic bilingualism to bi-literacy and trilingualism policy, balancing the status of English and Chinese with the mother tongue education policy. This policy shift has inadvertently impacted non-Chinese speaking (NCS) students’ enrollment, whose limited mastery of Chinese language prevents them from the mainstream schooling. Faced with this ethnically diverse and multilingual population, Applied Learning Chinese (ApL(C)) motivating practical reading and writing in an applied learning context was proposed by Hong Kong Education Bureau as an alternative for second language education. This study examines the effectiveness of “Reading to Learn, Learning to Write, R2L” pedagogy (Rose, 2012) in teaching Chinese practical writing to NCS students in Hong Kong with pedagogic interventions and Systemic Functional analytical perspective. Semi-structured interviews were conducted to perceive students’ learning experiences with R2L pedagogy. The finding suggests an increased meta-linguistic awareness of genre-specific writings after interventions to be empowered with a voice against social inequity and be empathized with humanistic reflections.
High spin expansion for null geodesics
Authors: Li Peng-Cheng , Guo Minyong , Chen Bin
Published: January 2021

We consider the high spin expansion for the null geodesics in the Kerr spacetime. We expand the null geodesic equation successively to higher orders in deviation from extremality. Via the method of matched asymptotic expansion, the radial integrals are obtained analytically. It turns out that the analytic expressions are very sensitive to the value of the shifted Carter constant q. We show that for a large q, the analytic expressions can be used to study observational electromagnetic signatures for astrophysical black holes like M87*. However, for a small q, the high spin expansion method can only be applied to (near-) extreme black holes.
Observing the polarization of cosmic-ray muons in student physics laboratory
Authors: Xu Jisi , Chu Anjun , Yuan Zi , Song Xinliang , Cheng Tianle , Yi Han , Wang Yijie , Chang Ying , Zhang Zhao , Xiao Zhigang
Published: January 2021

An undergraduate-level student experiment has been designed and implemented to measure the forward–backward asymmetry of the decay of the cosmic-ray muons, offering a pedagogical view to the parity violation in weak interactions. The detector system consists of six plastic scintillators installed vertically in row. The backward–forward asymmetry of the decay e−  and  e+ with respect to the muon motion direction is correlated with the incident depth of the muon stopped in the scintillator. MC simulations have been carried out in order to better interpret the data and optimize the data analysis. The forward–backward asymmetry of 0.051 ± 0.027 is deduced for the decay of cosmic-ray muons in the energy range being studied. The results are consistent with the picture of parity violation in weak interactions. The experiment can be constructed by the senior undergraduate students under the guidance of the course teacher.
Convergence of proximal gradient algorithm in the presence of adjoint mismatch
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Authors: Chouzenoux Emilie , Pesquet Jean-Christophe , Riddell Cyril , Savanier Marion , Trousset Yves
Published: January 2021

We consider the proximal gradient algorithm for solving penalized least-squares minimization problems arising in data science. This first-order algorithm is attractive due to its flexibility and minimal memory requirements allowing to tackle large-scale minimization problems involving non-smooth penalties. However, for problems such as x-ray computed tomography, the applicability of the algorithm is dominated by the cost of applying the forward linear operator and its adjoint at each iteration. In practice, the adjoint operator is thus often replaced by an alternative operator with the aim to reduce the overall computation burden and potentially improve conditioning issues. In this paper, we propose to analyze the effect of such an adjoint mismatch on the convergence of the proximal gradient algorithm in an infinite-dimensional setting, thus generalizing the existing results on PGA. We derive conditions on the step-size and on the gradient of the smooth part of the objective function under which convergence of the algorithm to a fixed point is guaranteed. We also derive bounds on the error between this point and the solution to the original minimization problem. We illustrate our theoretical findings with two image reconstruction tasks in computed tomography.
Bending behavior and its effect on switching performance of an all-optical switch
Authors: Wang K F , Wang B L , Zheng L , Zhang Y , Zhang C W
Published: January 2021

The all-optical switch is one of the key elements of all-optical high speed information networks and computing systems. Their bending behavior, actuated by optical gradient forces, dramatically influences their switching performance and is therefore the research topic of this paper. The coupled behavior between optical gradient forces and the bending deflection is taken into account in the present model. The effects of the effective refractive index and the stretching induced by bending are included and their influences on the resonance wavelength shift of the signal light are discussed. Results show that the resonance wavelength shift increases almost linearly at first, and then increases suddenly as the circulating power increases. The resonance wavelength shift increases as the central angle of the suspended part increases, while it decreases with the initial gap. The present theoretical model may be helpful when designing all-optical switches.