bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of innovative and traditional physical education classes on motor skills of young school children
Authors: Škrkar Stanislav , Madić Dejan , Popović Boris , Radanović Danilo
Published: May 2021

The aim of this study was to determine the effects of innovative and traditional physical education classes on motor abilities of children of younger school age. The sample consisted of 42 students (26 males and 16 females), aged 8 (M = 8.54), second grade of the Elementary School "Laza Kostić" in Kovilj near Novi Sad. The experimental group consisted of 22 students (52.3%) involved in a twelve-week innovative exercise program whose characteristics were changing the content of the class and the fact that it consisted of teaching units that with their form, scope and intensity focus on development of these abilities, while the control group consisted of 20 (47.7%) students who attended traditional physical education classes in accordance with the current curriculum of the Ministry of Education of the Republic of Serbia. Motor skills were assessed using six tests (Sprint from a high start at 20 meters - speed; Long jump from the board - explosive power of the lower extremities; Backwards polygon and Skipping and pulling - whole body coordination; Test T for agility and Running 4x10 meters - agility). The results showed that there is a statistically significant effect on all tested variables of motor skills in students who attended innovative classes (Sprint from a high start at 20 meters) (p = .00, ES = -.14); Long jump from the board (p = .,00, ES = .,71); Back polygon (p = .00 ES = -.44); Skipping and dragging (p = .00, ES = -.20); T test for agility (p = .01, ES = -0,22); Running 4x10 meters (p = .00; ES = -.43), while this was not the case with students who attended traditional physical education classes.
Sailing Yacht Performance in Calm Water and in Waves
Authors: Gerritsma J. , Keuning J. A. , Versluis A.
Published: May 2021

The Delft systematic Yatch Hull Series has been extended to a total of 39 hull form variations, covering a wide range of length displacement ratios and other form of parameters. The total set of model experiment results, upright and heeled resistance as well as sideforce and stability, had been analysed and polynomial expressions to approximate these quantities are presented. In view of the current interest in the performance of sailing yachts in waves, the added resistance in irregular waves of 8 widely different hull variations has been calculated. Analysis of the results shows that the added resistance in waves strongly depends on the product of displacement-length ratio and the gyradius of the pitching motion.
Seakeeping and Added Resistance of IACC Yachts by a Three-Dimensional Panel Method
Authors: Sclavounos P. D. , Nakos D. E.
Published: May 2021

A three-dimensional panel method developed for the prediction of the seakeeping properties of conventional ships has been extended to predict the motions and added resistance of IACC Yachts. The method solves the three dimensional unsteady potential flow around the yacht in monochromatic oblique waves. Predicted quantities include the heave and pitch motion amplitudes and phases and added resistance over a broad range of wave frequencies yacht speeds. Computations have been carried out for a series of IACC hull shapes studied by PACT (Partnership for America's Cup Technology) and correlations with experimental measurements are found to be very satisfactory. The same method was also used to study the added-resistance properties of hull shapes supplied by the America3 Foundation. A sensitivity analysis was carried out of the added resistance on the principal yacht hull shape parameters, including the slenderness, displacement, LCB­LCF separation and pitch radius of gyration.
IACC Appendage Studies
Authors: Tinoco E. N. , Gentry A. E. , Bogataj P. , Sevigny E. G. , Chance B.
Published: May 2021

Experimental and computational studies of several representative IACC appendage geometries were carried out to establish baseline data and verify computational models and methods.

Wind tunnel tests of an unheeled, unswept, constant section, rectangular planform keel mounted on a ground plane included force and moment measurements, and wake surveys at various angles of attack. Test configurations (all at constant draft) included the addition of ballast bulbs and winglets.

Correlations of computational results with experimental wind tunnel data were made. A502/PAN AIR potential flow induced drag predictions proved to be in good agreement with the wind tunnel data. Comparisons are also presented between A598 (A502 + boundary layer), wind tunnel results and empirical predictions. Again good agreement was shown for cases within the limitations of the boundary layer method.
How to Go Cruising
Authors: Hays James O. , Hays Anne M.
Published: May 2021

What follows is based upon our own experience and observations while cruising to the Hudson River and the Great Lakes, up and down the East Coast to Maine and around to the west coast of Florida, and across the Gulf stream to the Bahamas and twice to the Caribbean. We are well aware that we have not learned everything that the cruising life has to teach -and we hope to go back for further lessons. our goal is simply to pass along whatever we have learned that might be of interest to others who may wish to go cruising, and we ask you to read it in that context.
Tacking Simulation of Sailing Yachts - Numerical Integration of Equations of Motion and Application of Neural Network Technique
Authors: Masayuma Yutaka , Fukasawa Toichi , Sasagawa Hiroshi
Published: May 2021

The question, "What is the best tacking procedure?", has challenged sailors for a long time. In order to answer this question, it might be best to clarify the mechanism of tacking motions of sailing boats theoretically. However, tacking is a complicated maneuvering motion. Many factors affect tacking, including maneuverability, rolling characteristics, sail performance, etc. The first step to tackle this problem, therefore, is to make a proper model which represents tacking motions. In the present paper, two models are proposed to represent the tacking motions of sail boats. One is a mathematical model and another is a neural network model.

In the mathematical model, the tacking motion of the boat is described by partial differential equations with the coordinate system using the horizontal body axes. The hydrodynamic derivatives of the equations are mainly given by model test results and/or full scale measurements. Such coefficients as added mass and added moment of inertia are calculated using the strip method. These equations are integrated using an integration method.

In the neural network model, on the other hand, the tacking motion of the boat is regarded as a neural network system consisting of several layers. In the present paper, two hidden layers are used besides the input and output layers. The network constants are tuned using back-propagation procedure. If the rudder angle is inputted, the boat motion can be obtained step by step using the network.

Comparing the results obtained by these two methods with the full-scale experiments of a sailing boat, the merit and the demerit of these models are discussed.
Scoring IMS Regattas - An Empirical Study of Alternative Methods
Authors: Cane John W.
Published: May 2021

The International Measurement System (IMS) uses a computerized velocity prediction program (VPP) to calculate the performance of a meas­ured hull and rig in winds from six to twenty knots, at any sailing angle. A regatta is scored by comparing a yacht's performance with pre­dictions of the VPP. The winner is the yacht whose performance, relative to its VPP predic­tions, is the best, compared to all other yachts in its class or division.

This paper discusses different methods of malc­ing the comparison and accounting for various factors in the race such as wind shifts and cur­rent on the course. Decisions made by race man­agers and/or developers of scoring programs can significantly impact results. Illustrative examples show the effects that these decisions can have.

In 1994 the number of data points available for use in scoring yachts in custom courses doubled. Alternative ways of using these data are illus­trated by application to a sample regatta.
The Alexandria Class Dinghy - A Design For Change
Authors: Hunley William H.
Published: May 2021

The trade and skills of wooden boatbuilding began to die with the development of fiberglass reinforced plastic boats, and long before 1992 wooden boatbuilding was considered a dead industry. Still, the building of a wooden boat was something that could catch a child's attention; to build and sail a boat of one's own could be a consuming project that would set a pattern for life. In 1990 a program began to build on this premise: to reach out to the troubled youth of the inner cities, teach useable skills, self confidence, and pride of accomplishment by teaching youths to build small wooden boats, then teaching them to sail the boats that they built.
Imagine - An Open Class 60 BOC Racer -Design and Program Management - Lessons Learned
Authors: Court Kenneth E. , Kaufman F. Michael , Whitacre Harold M.
Published: May 2021

This paper describes the creation of the Open Class 60 (BOC 60) racing yacht "Imagine". She was conceived to win the 1994 BOC singlehanded round the world race, an ambitious goal since the French sailors have dominated the race since its inception. This paper will examine the design of this complex racing machine, and the management of the project. The project produced a boat that was capable of attaining the goal of winning, but when the project management office failed to adhere to the project plan, the project unravelled and collapsed.

In a squall at sea, at night, off Cape May, New Jersey, "Imagine's" boom failed, the main sail was dropped, and in the resultant short steep seas, "Imagine" slammed badly, dishing plating at both ends of the vessel, causing two forward frames to trip, and resulting in other structural damage to forward deck longitudinals and in the cockpit. "Imagine's" hull remained watertight, and she returned to Norfolk under short sail. Upon arrival she was inspected, and the necessary repair steps were outlined. These were discussed the following day with the project office and the ABS inspector. Within days drawings were provided to the project office for repair and to ABS for review. At that point matters stalled, no repair was started and within two week-; the project office announced their intent to abandon the project.

The project plan will be reviewed, the basis for the design will be discussed, the incident at sea which precipitated the project's disbanding will be examined, and an analysis of the resultant damage given. Lessons learned from the project will be discussed.

The actual design of the boat was interesting and rewarding, but it was a small part of the goal of the project. The goal was not attained, and when the BOC race started from Charleston in September 94, "Imagine" remained at the dock, her outfit and development incomplete. This paper will attempt to evaluate the reasons why. Two central themes repeat: lack of funds; and lack of sea trials.

In our opinion it was this lack of funds, that led the project office to eliminate carefully planned steps in "Imagine's" development, specifically the sea trials. This also lead them to attempt an offshore voyage from Norfolk, Virginia to Newport, Rhode Island in November 1993, prior to sea trials, with a known defective boom, and a jury rigged boom vang.
The entanglement of knowing and being: Hegel, ontology and education in the 21st century
Authors: Hyde Brendan
Published: May 2021

There has been a revived interest Georg Wilhelm Friedrich Hegel. Notions emanating from his philosophy concerning the human person and that human beings together create and sustain phenomena through social practice speaks of a relational ontology that has relevance for contemporary
education. This article argues that such ontology needs to be considered alongside the epistemological concerns of education. From Hegel’s writing, five interdependent ideas are delineated which have relevance for a relational ontology appropriate for contemporary education ‐
consciousness, self-consciousness, social space, recognition and identity. From these, three propositions for a social ontology of education ‐ learning as a socially constructed activity, learning as the formation of identity and learning as recognition ‐ are posited and discussed.
Thermal conductivity of Si/Ge superlattices containing tilted interface
Authors: Liu Ying-Guang , Ren Guo-Liang , Hao Jiang-Shuai , Zhang Jing-Wen , Xue Xin-Qiang ,   School of Energy, Power and Mechanical Engineering, North China Electric Power University, Baoding 071003, China
Published: May 2021

The non-equilibrium molecular dynamics (NEMD) method is used to study the thermal conductivities of Si/Ge superlattices with tilted interface under different period lengths, different sample lengths, and different temperatures. The simulation results are as follows. The thermal conductivity of Si/Ge superlattices varies nonmonotonically with the increase of interface angle: when the period length is 4–8 atomic layers, the thermal conductivity for the interface angle of 45° is one order of magnitude larger than those for other interface angles, and the thermal conductivity increases linearly with the sample length increasing and decreases with the temperature increasing. However, when the period length is 20 atomic layers, the thermal conductivity is weakly dependent on sample length and temperature due to the existence of phonon localization.
Thirst interneurons that promote water seeking and limit feeding behavior in Drosophila
Authors: Landayan Dan , Wang Brian P , Zhou Jennifer , Wolf Fred W
Published: May 2021

Thirst is a motivational state that drives behaviors to obtain water for fluid homeostasis. We identified two types of central brain interneurons that regulate thirsty water seeking in Drosophila, that we term the Janu neurons. Janu-GABA, a local interneuron in the subesophageal zone, is activated by water deprivation and is specific to thirsty seeking. Janu-AstA projects from the subesophageal zone to the superior medial protocerebrum, a higher order processing area. Janu-AstA signals with the neuropeptide Allatostatin A to promote water seeking and to inhibit feeding behavior. NPF (Drosophila NPY) neurons are postsynaptic to Janu-AstA for water seeking and feeding through the AstA-R2 galanin-like receptor. NPF neurons use NPF to regulate thirst and hunger behaviors. Flies choose Janu neuron activation, suggesting that thirsty seeking up a humidity gradient is rewarding. These findings identify novel central brain circuit elements that coordinate internal state drives to selectively control motivated seeking behavior.
Augmenting the technology acceptance model with trust model for the initial adoption of a blockchain-based system
Authors: Shrestha Ajay K. , Vassileva Julita , Joshi Sandhya , Just Jennifer
Published: May 2021

Background

In the collaborative business environment, blockchain coupled with smart contract removes the reliance on a central system and offers data integrity which is crucial when the transacting parties rely on the shared data. The acceptance of such blockchain-based systems is necessary for the continued use of the services. Despite many extensive studies evaluating the performance of blockchain-based systems, few have focused on users’ acceptance of real-life applications.

Objective

The main objective of this research is to evaluate the user acceptance of a real-life blockchain-based system (BBS) by observing various latent variables affecting the development of users’ attitudes and intention to use the system. It also aims to uncover the dimensions and role of trust, security and privacy alongside the primary Technology Acceptance Model (TAM)-based predictors and their causal relationship with the users’ behavior to adopt such BBS.

Methods

We tested the augmented TAM with Trust Model on a BBS that comprises two subsystems: a Shopping Cart System (SCS), a system oriented towards end-users and a Data Sharing System (DSS), a system oriented towards system administrators. We set research questions and hypotheses, and conducted online surveys by requesting each participant to respond to the questionnaire after using the respective system. The main study comprises two separate sub-studies: the first study was performed on SCS and the second on DSS. Furthermore, each study data comprises initial pre-test and post-test data scores. We analyzed the research model with partial least square structural equation modelling.

Results

The empirical study validates our research model and supports most of the research hypotheses. Based on our findings, we deduce that TAM-based predictors and trust constructs cannot be applied uniformly to BBS. Depending on the specifics of the BBS, the relationships between perceived trust antecedents and attitudes towards the system might change. For SCS, trust is the strongest determinant of attitudes towards system, while DSS has perceived privacy as the strongest determinant of attitudes towards system. Quality of system shows the strongest total effect on intention to use SCS, while perceived usefulness has the strongest total effect on intention to use DSS. Trust has a positive significant effect on users’ attitudes towards both BSS, while security does not have any significant effect on users’ attitudes toward BBS. In SCS, privacy positively affects trust, but security has no significant effect on trust, whereas, in DSS, both privacy and security have significant effects on trust. In both BBS, trust has a moderating effect on privacy that correlates with attitudes towards BBS, whereas security does not have any mediating role between privacy and attitudes towards BBS. Hence, we recommend that while developing BBS, particular attention should be paid to increasing user trust and perceived privacy.
Destabilization of EpCAM dimer is associated with increased susceptibility towards cleavage by TACE
Authors: Žagar Tomaž , Pavšič Miha , Gaber Aljaž
Published: May 2021

The cell-surface protein EpCAM is a carcinoma marker utilized in diagnostics and prognostics, and a promising therapeutic target. It is involved in nuclear signaling via regulated intramembrane proteolysis (RIP). Many aspects of this process are not fully understood, including the events at the molecular level leading to the exposure of cleavage sites, buried at the dimerization interface. To investigate the effect of dimer stability on cleavage susceptibility we prepared two mutants of human EpCAM ectodomain: a monomeric form, and a disulfide-stabilized dimeric form. We show that the disulfide-stabilized dimer is resistant to tumor necrosis factor-α-converting enzyme (TACE) cleavage, while the monomeric form is more susceptible than the predominantly dimeric wild type. This provides experimental evidence that the oligomeric state of EpCAM is a determinant in RIP and demonstrates the usefulness of the oligomeric state-specific mutants in investigations of EpCAM biological function.
Мемориальные запонки представителей Дома Романовых, "Природа"
Authors: Прыгов В.И.
Published: May 2021

Бесспорно, наиболее яркие произведения ювелирного искусства — это, прежде всего, женские костюмные украшения. Мужские же украшения и аксессуары весьма редко привлекают внимание исследователей. На рубеже XIX–XX вв. запонки стали непременным аксессуаром парадного мужского костюма. Функциональное назначение такого аксессуара диктовало определенные требования к конструктивным решениям и накладывало известные ограничения на возможности декоративного оформления. Из общего ряда, благодаря редкой композиции декора, необычным самоцветным вставкам, символике изображения, чаще всего выделяются мемориальные запонки. Для них характерно использование дорогостоящих материалов и трудоемких ручных ювелирных техник. Мемориальные запонки из частных коллекций, выполненные ведущими мастерами последней трети XIX — начала ХХ в. и принадлежавшие некогда Великому князю Владимиру Александровичу, опосредовано характеризуют степень государственных и военных заслуг, рафинированный художественный вкус, широкий круг интересов, а также этапы семейной жизни их прежнего владельца.
«Ожившее» ископаемое: история желтой пеструшки, "Природа"
Authors: Прокопов К.П.
Published: May 2021

Желтая пеструшка (Eolagurus luteus) впервые была обнаружена Э.А.Эверсманном 9 февраля 1826 г. недалеко от Северо-Западного Устюрта и описана им в 1840 г. Около миллиона лет назад желтая пеструшка обитала на огромных просторах от Западной Румынии до Забайкалья. Однако в западной части ареала она исчезла, как и некоторые другие животные. К середине ХIХ в. желтая пеструшка населяла полупустыни от низовий Урала до Восточного Казахстана и была всюду многочисленна. Во второй половине ХIХ в. она полностью вымерла в большинстве районов Казахстана. В середине 1960-х годов мы обнаружили желтую пеструшку на востоке Зайсанской котловины, где до сих пор этот грызун обитает на щебнисто-глинистых и щебнисто-песчаных участках, в ковыльной степи, в пойме и в разнотравных долинах пересыхающих ручьев. Питаются зверьки преимущественно вегетативными частями полыней и злаков. Размножаются с марта по октябрь, в выводке у взрослых и сеголеток до восьми детенышей. Активны круглосуточно и круглогодично. Периодически наблюдаются вспышки численности пеструшки и ее зимние миграции, во время которых бесчисленные полчища желтых пеструшек устремляются через оз.Зайсан. Не всем из них удается преодолеть большие расстояния (ширина озера в местах миграции составляет 30 км), и на льду погибает невероятное количество животных.
Коуровка – обсерватория и астероид, "Земля и Вселенная"
Authors: Горда С.Ю. , Соболев А.М. , Кузнецов Э.Д.
Published: May 2021

В январе далекого 1965 года в 85 километрах к западу от Свердловска, ныне Екатеринбурга, была открыта Коуровская астрономическая обсерватория Уральского государственного университета им. А.М. Горького. Наименование обсерватории было выбрано по названию ближайшей железнодорожной станции Коуровки, поскольку добраться тогда до нее можно было исключительно по железной дороге. Своим появлением обсерватория обязана профессору Клавдии Александровне Бархатовой, возродившей в 1960 году кафедру астрономии в Уральском университете. Ее неутомимая энергия, а также царивший в те годы в нашей стране и в мире настоящий бум покорения космического пространства позволили основать новую астрономическую обсерваторию как загородную станцию наблюдений искусственных спутников Земли. Строительство станции было задумано с целью практического обучения студентов кафедры навыкам наблюдений ИСЗ и естественных небесных тел. Не обошлось и без некоторого парадокса. Так, находясь на одном материке, обсерватория и Уральский университет, которому она принадлежит, находятся в разных частях света. Обсерватория – в Европе, а университет – в Азии. Виной всему Уральский хребет, по которому проходит граница между этими частями света, поскольку город Екатеринбург располагается восточнее хребта, а обсерватория – западнее. Таким образом, она является самой восточной в Европе обсерваторией.
Determination of Genetic Diversity of Four Guppy Strains Using the Random Amplified Polymorphic DNA-PCR
Authors: Hafidah Riva , Yustiati Ayi , Mulyani Yuniar , Suryadi Ibnu Bangkit Bioshina
Published: May 2021

This research aims to determine genetic diversity of four strains guppy, respectively are japan blue double sword (JBD), japan blue tiger double sword (JBTD), blue moscow (BM), and panda guppy (PG) with RAPD-PCR method. The obtained genetic diversity data is used as guide reference for hybridization between four strains. The research was conducted in September 2020 to April 2021 with explorative methods and in qualitative and quantitative descriptive analysis. The research was carried out in biotechnology Laboratory, Fishery and Marine Sciences Faculty and Central Laboratory,Padjadjaran University, Indonesia.Strains of JBD, JBTD, BM obtained fromCilengkrangSubdistrict, Bandung and PG strain obtained from Parung market, Bogor. Primary OPA-03 (AGTCAGCCAC) is used for standard parameters to interpret genetic diversity among four strains of guppy. Based on results, amplification with OPA-03 primary visualize 25 bands that include five polymorphic bands and 20 monomorphic bands. The phylogenetic tree result show that there are two relationship groups. The first group are JBD, JBTD, and BM with similarity index in the range of 80-89%The first group consist two sub groups of relationship. The first sub group are JBD and JBTD with similarity index of 89%. The second sub group is BM with similarity index of 80%. The second group isPG with similarity index of 65.5%.
Cardioprotective effect of Butanol Fraction of Rivea ornata against H2O2 Induced Oxidative Stress in H9c2 Cells: Role of its Phenolic Content and Antioxidant Effect
Authors: Sudheer Akkiraju , Jyothi M. V. , Devanna N.
Published: May 2021

Rivea ornata used traditionally for various disease of heart. However, its protective effect against oxidative stress induced injury is unclear and unproved. So, we attempted to investigate the protective role of butanol fraction of Rivea ornata on H9c2 cardiomyocytes against oxidative stress induced by H2O2. Ethanol extract and its fractions such as n-hexane, ethyl acetate and butanol fractions were assessed for its phytochemical composition, total phenolic and flavonoid content and assessed in vitro antioxidant activity by using established assays such as DPPH, H2O2 neutralization activity, ferric reduction assays and total antioxidant capacity. Among all the extracts/fractions butanol fraction found with high phenolic (82.4 ± 4.61 mg of GAE/g) and flavonoid (105 ± 4.09 mg of QE/g) content as well as possess strong antioxidant abilities evident by comparative lowest IC50 values for DPPH (41.80 µg/mL), H2O2 neutralization assay (35.39 µg/m), highest ferric reduction at 120µg/mL and high antioxidant capacity equivalent to quercetin (72.5±2.98 µg/mL). By considering these results, only butanol fraction assessed for its protective effect H2O2 induced oxidative stress on H9c2 cardiac cell lines was assessed by MTT, LDH assay and ROS expression studies. Butanol fraction at 25µg/mL maintain H9c2 cell lines viability (in MTT assay), cell integrity (decreased LDH release) and decreased ROS expression (decrease in percentage mean fluorescence). These findings are proved antioxidant rich polyphenolic butanol fraction protective effect against oxidative stress injury observed with H2O2 by maintain cell viability, cell integrity and ROS expression.
REVISITING STUDENTS’ ENTREPRENEURIAL INTENTION IN INDONESIA: A THEORY OF PLANNED BEHAVIOR APPROACH
Authors: Purusottama Ambara
Published: May 2021

The purpose of this study is to verify and measure entrepreneurial intentions among uni­ver­sity students as affected by changes in the entrepreneurial environment in Indonesia. The re­searchers use the Theory of Planned Behavior and the concept of entrepreneurial intention to support the study. The unit of analysis is university students who are currently exposed to changes in the entrepreneurial environment. This study uses a quantitative approach with pur­posive sampling as the sampling technique. The questionnaire was distributed, and 631 sample responses were received from several universities. The findings show that attitude and perceived control behavior have a significant role in entrepreneurial intention. In addition, subjective norm plays no role in entrepreneurial intention
Ternary‐Responsive Field‐Effect Transistors and Multilevel Memories Based on Asymmetrically Functionalized Janus Few‐Layer WSe2
Authors: Qiu Haixin , Herder Martin , Hecht Stefan , Samorì Paolo
Published: May 2021

Hybrids composed of 2D transition metal dichalcogenides with stimuli‐responsive molecules are prototypical components for the development of multifunctional field‐effect transistors (FETs), whose output currents can be remotely controlled by external inputs. Herein, ternary‐responsive FETs based on a few‐layer WSe2 are realized by decorating the two opposite surfaces of the 2D semiconductor with different stimuli‐responsive molecules in an asymmetric fashion: the bottom surface is interfaced with a photochromic diarylethene film and the top surface with a ferroelectric poly(vinylidene fluoride–trifluoroethylene) layer. This novel Janus ternary device architecture shows superior functional complexity compared with normal mono‐stimuli‐responsive FETs. The synergy between the two molecularly induced effects enables the devices to respond orthogonally to an electric field and light irradiation, with an enhanced output current modulation efficiency of 87%. The 9 ferroelectric and 84 photo‐generated states ensure 756 current levels in a single device. The over 10 cycles of cyclic endurance and more than 1000 h of retention time confirm the reliability of each state, implementing the demand for high‐density non‐volatile memories, as well as enriching the diversification in “More than Moore” technologies.
Structuring of Si into Multiple Scales by Metal‐Assisted Chemical Etching
Authors: Srivastava Ravi P. , Khang Dahl‐Young
Published: May 2021

Structuring Si, ranging from nanoscale to macroscale feature dimensions, is essential for many applications. Metal‐assisted chemical etching (MaCE) has been developed as a simple, low‐cost, and scalable method to produce structures across widely different dimensions. The process involves various parameters, such as catalyst, substrate doping type and level, crystallography, etchant formulation, and etch additives. Careful optimization of these parameters is the key to the successful fabrication of Si structures. In this review, recent additions to the MaCE process are presented after a brief introduction to the fundamental principles involved in MaCE. In particular, the bulk‐scale structuring of Si by MaCE is summarized and critically discussed with application examples. Various approaches for effective mass transport schemes are introduced and discussed. Further, the fine control of etch directionality and uniformity, and the suppression of unwanted side etching are also discussed. Known application examples of Si macrostructures fabricated by MaCE, though limited thus far, are presented. There are significant opportunities for the application of macroscale Si structures in different fields, such as microfluidics, micro‐total analysis systems, and microelectromechanical systems, etc. Thus more research is necessary on macroscale MaCE of Si and their applications.
Kinetic 2D Crystals via Topochemical Approach
Authors: Bae Jihong , Kim Minjung , Kang Hyeonsoo , Kim Taeyoung , Choi Hong , Kim Bokyeong , Do Hyung Wan , Shim Wooyoung
Published: May 2021

The designing of novel materials is a fascinating and innovative pathway in materials science. Particularly, novel layered compounds have tremendous influence in various research fields. Advanced fundamental studies covering various aspects, including reactants and synthetic methods, are required to obtain novel layered materials with unique physical and chemical properties. Among the promising synthetic techniques, topochemical approaches have afforded the platform for widening the extent of novel 2D materials. Notably, the synthesis of binary layered materials is considered as a major scientific breakthrough after the synthesis of graphene as they exhibit a wide spectrum of material properties with varied potential applicability. In this review, a comprehensive overview of the progress in the development of metastable layered compounds is presented. The various metastable layered compounds synthesized from layered ternary bulk materials through topochemical approaches are listed, followed by the descriptions of their mechanisms, structural analyses, characterizations, and potential applications. Finally, an essential research direction concerning the synthesis of new materials is indicated, wherein the possible application of topochemical approaches in unprecedented areas is explored.
High‐Density Lignin‐Derived Carbon Nanofiber Supercapacitors with Enhanced Volumetric Energy Density
Authors: Hérou Servann , Bailey Josh J , Kok Matt , Schlee Philipp , Jervis Rhodri , Brett Dan J. L. , Shearing Paul R. , Ribadeneyra Maria Crespo , Titirici Magdalena
Published: May 2021

Supercapacitors are increasingly used in short‐distance electric transportation due to their long lifetime (≈15 years) and fast charging capability (>10 A g−1). To improve their market penetration, while minimizing onboard weight and maximizing space‐efficiency, materials costs must be reduced (<10 $ kg−1) and the volumetric energy‐density increased (>8 Wh L−1). Carbon nanofibers display good gravimetric capacitance, yet their marketability is hindered by their low density (0.05–0.1 g cm−3). Here, the authors increase the packing density of low‐cost, free‐standing carbon nanofiber mats (from 0.1 to 0.6 g cm−3) through uniaxial compression. X‐ray computed tomography reveals that densification occurs by reducing the inter‐fiber pore size (from 1–5 µm to 0.2–0.5 µm), which are not involved in double‐layer capacitance. The improved packing density is directly proportional to the volumetric performances of the device, which reaches a volumetric capacitance of 130 F cm−3 and energy density of 6 Wh L−1 at 0.1 A g−1 using a loading of 3 mg cm−2. The results outperform most commercial and lab‐scale porous carbons synthesized from bioresources (50–100 F cm−3, 1–3 Wh L−1 using 10 mg cm−2) and contribute to the scalable design of sustainable electrodes with minimal ‘dead volume’ for efficient supercapacitors.
Repression of Interlayer Recombination by Graphene Generates a Sensitive Nanostructured 2D vdW Heterostructure Based Photodetector
Authors: Wang Huide , Gao Shan , Zhang Feng , Meng Fanxu , Guo Zhinan , Cao Rui , Zeng Yonghong , Zhao Jinlai , Chen Si , Hu Haiguo , Zeng Yu‐Jia , Kim Sung Jin , Fan Dianyuan , Zhang Han , Prasad Paras N.
Published: May 2021

Great success in 2D van der Waals (vdW) heterostructures based photodetectors is obtained owing to the unique electronic and optoelectronic properties of 2D materials. Performance of photodetectors based 2D vdW heterojunctions at atomic scale is more sensitive to the nanointerface of the heterojunction than conventional bulk heterojunction. Here, a nanoengineered heterostructure for the first‐time demonstration of a nanointerface using an inserted graphene layer between black phosphorus (BP) and InSe which inhibits interlayer recombination and greatly improves photodetection performances is presented. In addition, a transition of the transport characteristics of the device is induced by graphene, from diffusion motion of minority carriers to drift motion of majority carriers. These two reasons together with an internal photoemission effect make the BP/G/InSe‐based photodetector have ultrahigh specific detectivity at room temperature. The results demonstrate that high‐performance vdW heterostructure photodetectors can be achieved through simple structural manipulation of the heterojunction interface on nanoscale.
Neurocutaneous syndromes in art and antiquities
Authors: Ruggieri Martino , Gentile Amalia Egle , Ferrara Vincenza , Papi Massimo , Praticò Andrea D. , Mudry Albert , Taruscio Domenica , Micali Giuseppe , Polizzi Agata
Published: May 2021

Neurocutaneous syndromes are a group of genetic disorders affecting the skin, the central and peripheral nervous system, and the eye with congenital abnormalities and/or tumors. Manifestations may also involve the heart, vessels, lungs, kidneys, endocrine glands and bones. When people with these disorders are portrayed in works of art, physicians have speculated on possible diagnoses. In particular, many figures have been labeled as possibly having a neurocutaneous disorder, sometimes distorting the popular conception of these diseases. We review numerous documents, drawings, prints, lithographs, xylographs, and portraits which span the ages from antiquity to the era of the pioneers behind the eponyms, depicting a large spectrum of neurocutaneous disorders.
Selective N‐Arylation of p‐Aminophenylalanine in Unprotected Peptides with Organometallic Palladium Reagents
Authors: Mallek Aaron J. , Pentelute Bradley L. , Buchwald Stephen L.
Published: May 2021

The selective N‐arylation of p‐aminophenylalanine in polypeptides with pre‐formed palladium oxidative addition complexes is described. The depressed pKa of the aniline NH2 group enables chemoselective C−N bond formation on peptides containing multiple other aliphatic amino groups at lysines or the N‐terminus via Curtin–Hammett control under mild conditions. Using palladium complexes derived from electron‐poor aryl halides, p‐aminophenylalanine is fully arylated in aqueous buffer in as little as one hour at micromolar concentrations. A complementary protocol using the non‐nucleophilic, organic base 1,5‐diazabicyclo(4.3.0)non‐5‐ene (DBN), expands the substrate scope to tolerate electron‐rich functional groups provides up to 97 % conversion. These procedures enable the chemoselective conjugation of functionally diverse small molecule pharmaceuticals to p‐aminophenylalanine containing derivatives of cell‐penetrating peptides.
Marquesan ceramics, palaeotsunami, and megalithic architecture: Ho‘oumi Beach site (NHo‐3) in regional perspective
Authors: ALLEN MELINDA S. , McALISTER ANDREW , PETCHEY FIONA , HUEBERT JENNIFER M. , MAEVA MA’ARA , JONES BENJAMIN D.
Published: May 2021

The iconic Ho‘oumi Beach site (NHo‐3), Nuku Hiva Island (Marquesas), was excavated by Robert Suggs in the late 1950s. It figured importantly in his island‐wide reconstruction of settlement patterns, socio‐political organisation, material culture and subsistence change – a cultural historical framework that has guided Marquesan archaeology for six decades. Ho‘oumi is also one of four Marquesan localities where prehistoric ceramics have been found. We revisited Ho‘oumi to acquire chronological and palaeoenvironmental context for two cultural occupations reported by Suggs. Eight 14C determinations on short‐lived materials and new marine reservoir corrections are reported, and the overall series evaluated using Bayesian modelling. A single ceramic sherd, previously assigned to a Fijian source, is attributed to the thirteenth to fourteenth centuries AD – a period when Marquesans engaged in long‐distance voyaging. A significant marine inundation disrupted the associated occupation, leading to sustained coastal abandonment. Stratigraphic and historical evidence suggests this was a palaeotsunami, which may also be represented at Hane (Ua Huka Island). House pavements of the early occupation were replaced by raised megalithic house foundations, probably around the late seventeenth to mid‐eighteenth centuries AD, but material culture changes were modest. By late prehistory, mature native forest was largely replaced by secondary species and Polynesian introductions.
Enantioselective Synthesis of Quaternary Carbon Stereocenters by Asymmetric Allylic Alkylation: A Review
Authors: Wu Gengxin , Wu Jia‐Rui , Huang Yan , Yang Ying‐Wei
Published: May 2021

Quaternary stereocenters are of great importance to the three‐dimensionality and enhanced properties of new molecules, but the synthetic challenges in creating quaternary stereocenters greatly hinder their wide use in drug discovery, organic material design, and natural product synthesis. The asymmetric allylic alkylation (AAA) of allylic substrates has proven to be a powerful methodology for enantioselective formation of structure skeletons bearing single or more quaternary carbon centers in modern asymmetric organocatalysis. AAA has certain advantages in constructing the tetrasubstituted stereocenters, including but not limited to mild reactive conditions, effective reaction rates, new functional group introduction, and carbon chains length extension. This review outlines the key considerations in the application of AAA reactions and summarizes the recent progress of AAA reactions in the enantioselective synthesis of products containing quaternary stereocenters. Meanwhile, a detailed discussion of the AAA reactions such as ligands, scope of substrates, transformations and the general reaction mechanisms is also provided. We hope this review could stimulate further advances in much broader areas, including organic synthesis, asymmetric catalysis, C−H activation, and symmetrical pharmaceutical chemistry.
Microwave‐assisted combustion synthesis and luminescence properties of colour‐tunable Eu3+/Tb3+ co‐doped BaLaB9O16
Authors: Palan Chetan B. , Bajaj Nikhilesh S. , Bhagat Suresh P. , Omanwar Shrinivas K.
Published: May 2021

In the present study, hexagonal structured borate phosphors BaLaB9O16 were prepared using a combustion method with colour‐tunable emission properties achieved by varying the doping concentration of Eu3+ and Tb3+ in the cluster. The as‐prepared materials were analyzed for structural and morphological parameters through X‐ray diffraction (XRD) and field emission scanning electron microscopy (FE‐SEM) studies. Tuning of colour was predicted through the photoluminescence and photoluminescence excitation spectra of the materials that showed good green and red emissions when doped with Tb3+ and Eu3+, respectively, whereas the emission of the co‐doped sample (Eu3+ and Tb3+) can be varied from the green region to red region by varying the excitation range from 207 to 254  nm.
Relevance of π‐Backbonding for the Reactivity of Electrophilic Anions [B12X11]− (X=F, Cl, Br, I, CN)
Authors: Mayer Martin , Rohdenburg Markus , Kawa Sebastian , Horn Francine , Knorke Harald , Jenne Carsten , Tonner Ralf , Asmis Knut R. , Warneke Jonas
Published: May 2021

Electrophilic anions of type [B12X11]− posses a vacant positive boron binding site within the anion. In a comparatitve experimental and theoretical study, the reactivity of [B12X11]− with X=F, Cl, Br, I, CN is characterized towards different nucleophiles: (i) noble gases (NGs) as σ‐donors and (ii) CO/N2 as σ‐donor‐π‐acceptors. Temperature‐dependent formation of [B12X11NG]− indicates the enthalpy order (X=CN)>(X=Cl)≈(X=Br)>(X=I)≈(X=F) almost independent of the NG in good agreement with calculated trends. The observed order is explained by an interplay of the electron deficiency of the vacant boron site in [B12X11]− and steric effects. The binding of CO and N2 to [B12X11]− is significantly stronger. The B3LYP 0 K attachment enthapies follow the order (X=F)>(X=CN)>(X=Cl)>(X=Br)>(X=I), in contrast to the NG series. The bonding motifs of [B12X11CO]− and [B12X11N2]− were characterized using cryogenic ion trap vibrational spectroscopy by focusing on the CO and N2 stretching frequencies
and
, respectively. Observed shifts of
and
are explained by an interplay between electrostatic effects (blue shift), due to the positive partial charge, and by π‐backdonation (red shift). Energy decomposition analysis and analysis of natural orbitals for chemical valence support all conclusions based on the experimental results. This establishes a rational understanding of [B12X11]− reactivety dependent on the substituent X and provides first systematic data on π‐backdonation from delocalized σ‐electron systems of closo‐borate anions.
A Disulfide Switch Providing Absolute Handedness Control in Double Helices via Conversion from the Antiparallel to Parallel Helical Pattern
Authors: Li Dongyao , Ma Chunmiao , Xiang Junfeng , Zhang Kai , Yang Ling , Gan Quan
Published: May 2021

A strategy to reversibly switch the parallel/antiparallel helical conformation of aromatic double helices through the formation/breakage of a disulfide bond is presented. Single‐crystal X‐ray structures, NMR, and circular dichroism spectroscopy demonstrate that the double helices with terminal thiol groups favor an antiparallel helical arrangement both in the solid state and in solution, while the P/M bias of helicity induced by chiral segments from another extremity of the sequence is weak in this structural motif. The antiparallel helices can be rearranged to parallel helices through the disulfide connection of the sequences. This change enhances the bias of helical handedness and results in absolute chirality control of the double helices. The handedness‐mediated process can be governed by the oxidation‐reduction cycle, thereby switching the structural arrangement and the enhancement of chiral bias. In addition, we find that the sequences can dimerize into an intermolecular double helix with the disulfide connection. And the helical handedness is also fully controlled due to the head‐to‐head structural motif.
Dual Plasmonic Au−Cu2−xS Nanocomposites: Design Strategies and Photothermal Properties
Authors: Hans Earl Adrian D. R. , Regulacio Michelle D.
Published: May 2021

Coupling two different materials to create a hybrid nanostructured system is a powerful strategy for achieving synergistically enhanced properties and advanced functionalities. In the case of Au and Cu2−xS, their combination on the nanoscale results in dual plasmonic Au−Cu2−xS nanocomposites that exhibit intense photon absorption in both the visible and the near‐infrared spectral ranges. Their strong light‐absorbing properties translate to superior photothermal transduction efficiency, making them attractive in photothermal‐based applications. There are several nanostructure configurations that are possible for the Au−Cu2−xS system, and the successful fabrication of a particular architecture often requires a carefully planned synthetic strategy. In this Minireview, the different synthetic approaches that can be employed to produce rationally designed Au−Cu2−xS nanocomposites are presented, with a focus on the experimental protocols that can lead to heterodimer, core–shell, reverse core–shell, and yolk–shell configurations. The photothermal behavior of these materials is also discussed, providing a glimpse of their potential use as photothermally active agents in therapeutic and theranostic applications.
Highly Active Halogen Bonding and Chalcogen Bonding Chloride Transporters with Non‐Protonophoric Activity
Authors: Bickerton Laura E. , Docker Andrew , Sterling Alistair J. , Kuhn Heike , Duarte Fernanda , Beer Paul D. , Langton Matthew J.
Published: May 2021

Synthetic anion transporters show much promise as potential anti‐cancer agents and therapeutics for diseases associated with mis‐regulation of protein anion channels. In such applications high activity and anion selectivity are crucial to overcome competing proton or hydroxide transport which dissipates cellular pH gradients. Here, highly active bidentate halogen bonding and chalcogen bonding anion carriers based on electron deficient iodo‐ and telluromethyl−triazole derivatives are reported. Anion transport experiments in lipid bilayer vesicles reveal record nanomolar chloride transport activity for the bidentate halogen bonding anion carrier, and remarkably high chloride over proton/hydroxide selectivity for the chalcogen bonding anionophore. Computational studies provide further insight into the role of sigma‐hole mediated anion recognition and desolvation at the membrane interface. Comparison with hydrogen bonding analogues demonstrates the importance of employing sigma‐hole donor motifs in synthetic anionophores for achieving both high transport activity and selectivity.
New semiparametric regression method with applications in selection‐biased sampling and missing data problems
Authors: Diao Guoqing , Qin Jing
Published: May 2021

We propose a new method to estimate a regression function based on the semiparametric density ratio model, which can be viewed as a generalized linear model with a canonical link function and an unspecified baseline distribution function. Under this model, the distribution of the observed data retains the same structure in the presence of selection‐biased sampling or when the predictors are missing at random. In particular, in the latter case, the new method utilizes all the available information and does not need to specify the distribution of the predictors or the probability of observing the predictors. We establish large sample properties of the proposed regression estimators. Simulation studies demonstrate that the proposed estimators perform well in practical situations. Empirical data from the National Health and Nutrition Examination Survey are presented.