bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetically driven short-range order can explain anomalous measurements in CrCoNi
Authors: Walsh Flynn , Asta Mark , Ritchie Robert O.
Published: March 2021

Significance

High-entropy alloys, an exciting new class of structural materials involving many concentrated elements, are generally assumed to be chemically disordered. This work reveals how magnetic interactions can drive atomic-scale ordering in a mechanically interesting system that has been widely studied as a model for many promising alloys. The formation of short-range order in this manner is used to explain experimental anomalies, suggesting that many related materials could contain similarly impactful ordering under standard conditions. This possibility offers solutions to outstanding questions concerning CrCoNi and emphasizes the importance of magnetism and short-range order in related high-entropy alloys.
Virus-specific NK cell memory
Authors: Sheppard Sam , Sun Joseph C.
Published: March 2021

NK cells express a limited number of germline-encoded receptors that identify infected or transformed cells, eliciting cytotoxicity, effector cytokine production, and in some circumstances clonal proliferation and memory. To maximize the functional diversity of NK cells, the array and expression level of surface receptors vary between individual NK cell “clones” in mice and humans. Cytomegalovirus infection in both species can expand a population of NK cells expressing receptors critical to the clearance of infected cells and generate a long-lived memory pool capable of targeting future infection with greater efficacy. Here, we discuss the pathways and factors that regulate the generation and maintenance of effector and memory NK cells and propose how this understanding may be harnessed therapeutically.
Nuclear DEK preserves hematopoietic stem cells potential via NCoR1/HDAC3-Akt1/2-mTOR axis
Authors: Chen Zhe , Huo Dawei , Li Lei , Liu Zhilong , Li Zhigang , Xu Shuangnian , Huang Yongxiu , Wu Weiru , Zhou Chengfang , Liu Yuanyuan , Kuang Mei , Wu Feng , Li Hui , Qian Pengxu , Song Guanbin , Wu Xudong , Chen Jieping , Hou Yu
Published: March 2021

The oncogene DEK is found fused with the NUP214 gene creating oncoprotein DEK-NUP214 that induces acute myeloid leukemia (AML) in patients, and secreted DEK protein functions as a hematopoietic cytokine to regulate hematopoiesis; however, the intrinsic role of nuclear DEK in hematopoietic stem cells (HSCs) remains largely unknown. Here, we show that HSCs lacking DEK display defects in long-term self-renew capacity, eventually resulting in impaired hematopoiesis. DEK deficiency reduces quiescence and accelerates mitochondrial metabolism in HSCs, in part, dependent upon activating mTOR signaling. At the molecular level, DEK recruits the corepressor NCoR1 to repress acetylation of histone 3 at lysine 27 (H3K27ac) and restricts the chromatin accessibility of HSCs, governing the expression of quiescence-associated genes (e.g., Akt1/2, Ccnb2, and p21). Inhibition of mTOR activity largely restores the maintenance and potential of Dek-cKO HSCs. These findings highlight the crucial role of nuclear DEK in preserving HSC potential, uncovering a new link between chromatin remodelers and HSC homeostasis, and have clinical implications.
Investigation of plant leaf-derived graphene quantum dot clusters via magnetic force microscopy
Authors: Chuang Chiashain , Matsunaga Masahiro , Wang Tian-Hsin , Roy Prathik , Ravindranath Rini , Ananthula Meenakshi , Aoki Nobuyuki
Published: March 2021

Magnetic force microscopy (MFM) is utilized to characterize the magnetic moment in nanostructured plant leaf-derived graphene quantum dot clusters (GQDCs). The MFM signal reveals that the magnetic response of the GQDCs depends on the height and width of the GQDCs. However, individual GQDs, and smaller clusters with widths of less than 20 nm, have not shown any observable magnetic signal. Importantly, experimental analyses suggest that the magnetic signal of GQDCs distributed in a plane can be effectively detected at room temperature. These results could pave the way for future graphene-based magnetic storage media and spin manipulation quantum devices.
Bead on a uniformly rotating rod: why does the bead move out if there is no force in the radial direction?
Authors: Joseph Toby
Published: March 2021

Problems involving rotating systems analysed from an inertial frame, without invoking fictitious forces, is something that freshman students find difficult to understand in an introductory mechanics course. In this article we try to see what could be the factors that lead to this difficulty and propose a set of arguments that could be used to resolve the confusion. We take a specific example of a bead sliding without friction on a rotating rod to address the issues involved. After solving the problem in the inertial reference frame by integrating the equations of motion expressed in the plane polar coordinate system, we carry out a consistency check on how the radial motion can be accounted for by the force that the rod exerts on the bead. We hope that going through this exercise would help students to get more comfortable with understanding problems in a similar mould.
Freeze-in produced dark matter in the ultra-relativistic regime
Authors: Biondini Simone , Ghiglieri Jacopo
Published: March 2021

When dark matter particles only feebly interact with plasma
constituents in the early universe, they never reach thermal
equilibrium. As opposed to the freeze-out mechanism, where the dark
matter abundance is determined at T ≪ M, the energy density of a
feebly interacting state builds up and increases over T ≳
M. In this work, we address the impact of the high-temperature
regime on the dark matter production rate, where the dark and
Standard Model particles are ultra-relativistic and nearly
light-like. In this setting, multiple soft scatterings, as well as
2 → 2 processes, are found to give a large contribution to the
production rate. Within the model we consider in this work, namely a
Majorana fermion dark matter of mass M accompanied by a heavier
scalar — with mass splitting Δ M — which shares
interactions with the visible sector, the energy density can be
dramatically underestimated when neglecting the high-temperature
dynamics. We find that the overall effective 1 ↔ 2
and 2 →2 high-temperature contributions to dark-matter
production give 𝒪(10) (20%) corrections for
Δ M /M =0.1 (Δ M /M =10) to the Born production rate
with in-vacuum masses and matrix elements. We also assess the
impact of bound-state effects on the late-time annihilations of the
heavier scalar, in the context of the super-WIMP mechanism.
Vacuum decay constraints on the Higgs curvature coupling from inflation
Authors: Mantziris Andreas , Markkanen Tommi , Rajantie Arttu
Published: March 2021

We derive lower bounds for the Higgs-curvature coupling from
vacuum stability during inflation in three inflationary models:
quadratic and quartic chaotic inflation, and Starobinsky-like
power-law inflation. In contrast to most previous studies we take
the time-dependence of the Hubble rate into account both in the
geometry of our past light-cone and in the Higgs effective
potential, which is approximated with three-loop renormalisation
group improvement supplemented with one-loop curvature
corrections. We find that in all three models, the lower bound is
ξ≳ 0.051… 0.066 depending on the top quark mass. We
also demonstrate that vacuum decay is most likely to happen a few
e-foldings before the end of inflation.
High-resolution three-dimensional atomic microscopy via double electromagnetically induced transparency
Authors: Wahab Abdul
Published: March 2021

We aim to present a new scheme for high-dimensional atomic microscopy via double electromagnetically induced transparency in a four-level tripod system. For atom–field interaction, we construct a spatially dependent field by superimposing three standing-wave fields (SWFs) in 3D-atom localization. We achieve a high precision and high spatial resolution of an atom localization by appropriately adjusting the system variables such as field intensities and phase shifts. We also see the impact of Doppler shift and show that it dramatically deteriorates the precision of spatial information on 3D-atom localization. We believe that our suggested scheme opens up a fascinating way to improve the atom localization that supplies some practical applications in atom nanolithography, and Bose–Einstein condensation.
Convolutional neural network for transient grating frequency-resolved optical gating trace retrieval and its algorithm optimization*
Authors: Xu Siyuan , Zhu Xiaoxian , Wang Ji , Li Yuanfeng , Gao Yitan , Zhao Kun , Zhu Jiangfeng , Zhang Dacheng , Chen Yunlin , Wei Zhiyi
Published: March 2021

A convolutional neural network is employed to retrieve the time-domain envelop and phase of few-cycle femtosecond pulses from transient-grating frequency-resolved optical gating (TG-FROG) traces. We use theoretically generated TG-FROG traces to complete supervised trainings of the convolutional neural networks, then use similarly generated traces not included in the training dataset to test how well the networks are trained. Accurate retrieval of such traces by the neural network is realized. In our case, we find that networks with exponential linear unit (ELU) activation function perform better than those with leaky rectified linear unit (LRELU) and scaled exponential linear unit (SELU). Finally, the issues that need to be addressed for the retrieval of experimental data by this method are discussed.
Pressure-induced anomalous insulating behavior in frustrated iridate La3Ir3O11
*
Authors: Chen Chun-Hua , Zhou Yong-Hui , Zhou Ying , Yuan Yi-Fang , An Chao , Chen Xu-Liang , Tian Zhao-Ming , Yang Zhao-Rong
Published: March 2021

The geometrically frustrated iridate La3Ir3O11 with strong spin–orbit coupling and fractional valence was recently predicted to be a quantum spin liquid candidate at ambient conditions. Here, we systematically investigate the evolution of structural and electronic properties of La3Ir3O11 under high pressure. Electrical transport measurements reveal an abnormal insulating behavior rather than metallization above a critical pressure P
c ∼ 38.7 GPa. Synchrotron x-ray diffraction (XRD) experiments indicate the stability of the pristine cubic KSbO3-type structure up to 73.1 GPa. Nevertheless, when the pressure gradually increases across P
c, the bulk modulus gets enhanced and the pressure dependence of bond length d
Ir – Ir undergoes a slope change. Consistent with the XRD data, detailed analyses of Raman spectra reveal an abnormal redshift of Raman mode and a change of Raman intensity around P
c. Our results demonstrate that the pressure-induced insulating behavior in La3Ir3O11 can be assigned to the structural modification, such as the distortion of IrO6 octahedra. These findings will shed light on the emergent abnormal insulating behavior in other 5d iridates reported recently.
Resistance fluctuations in superconducting K
x
Fe2 – y
Se2 single crystals studied by low-frequency noise spectroscopy*
Authors: Zi Hai , Yao Yuan , He Ming-Chong , Ke Di , Zhan Hong-Xing , Zhao Yu-Qing , Wen Hai-Hu , Ren Cong
Published: March 2021

Low-frequency resistance noise spectroscopy is applied to investigate bulk single crystals of the intercalated iron-selenide K
x
Fe2 – y
Se2 superconductors with different iron vacancy orders. Based on a generalized fluctuation model, the well-observed resistance hump above 100 K is interpreted as an insulator–metal phase transition with a characteristic transition energy of 0.1–0.6 eV, indicating a highly inhomogeneous energy distribution configuration. In the superconducting transition regime, we find that the normalized resistance noise scales with resistance R excellently as SR
/R
2 ∝ R

l
rs
with the noise exponent l
rs ≈ 1.4. With reduced iron vacancy disordering in enhanced superconductivity K
x
Fe2 – y
Se2 crystals, the level of resistance fluctuations is greatly suppressed, suggesting a geometrical phase transition for conduction channel, which is directly related to the microstructure of the crystals.
Integrated silicon-based suspended racetrack micro-resonator for biological solution sensing with high-order mode*
Authors: Ma Tao , Tian Yong-Sheng , Liu Shao-Hui , Ma Jia-He , Liu Heng , Wang Fang
Published: March 2021

A biological sensing structure with a high-order mode (

E

21

y

) is designed, which is composed of a suspended racetrack micro-resonator (SRTMR) and a microfluidic channel. The mode characteristics, coupling properties, and sensing performances are simulated by using the finite element method (FEM). To analyze the mode confinement property, the confinement factors in the core and cladding of the suspended waveguide for the

E

11

x

,

E

11

y

, and

E

21

y

are calculated. The simulation results show that the refractive index (RI) sensitivity of the proposed sensing structure can be improved by using the high-order mode (

E

21

y

). The RI sensitivity for the

E

21

y

mode is ∼ 201 nm/RIU, which is twice to thrice higher than those for the

E

11

x

mode and the

E

11

y

mode. Considering a commercial spectrometer, the proposed sensing structure based on the SRTMR achieves a limit of detection (LOD) of ∼ 4.7 × 10−6 RIU. Combined with the microfluidic channel, the SRTMR can possess wide applications in the clinical diagnostic assays and biochemical detections.
Molecular dynamics study of coupled layer thickness and strain rate effect on tensile behaviors of Ti/Ni multilayered nanowires*
Authors: Su Meng-Jia , Deng Qiong , Liu Lan-Ting , Chen Lian-Yang , Su Meng-Long , An Min-Rong
Published: March 2021

Novel properties and applications of multilayered nanowires (MNWs) urge researchers to understand their mechanical behaviors comprehensively. Using the molecular dynamic simulation, tensile behaviors of Ti/Ni MNWs are investigated under a series of layer thickness values (1.31, 2.34, and 7.17 nm) and strain rates (

1.0
×

10

8

s

−
1

≤

ε
.

≤
5.0
×

10

10

s

−
1

). The results demonstrate that deformation mechanisms of isopachous Ti/Ni MNWs are determined by the layer thickness and strain rate. Four distinct strain rate regions in the tensile process can be discovered, which are small, intermediate, critical, and large strain rate regions. As the strain rate increases, the initial plastic behaviors transform from interface shear (the shortest sample) and grain reorientation (the longest sample) in small strain rate region to amorphization of crystalline structures (all samples) in large strain rate region. Microstructure evolutions reveal that the disparate tensile behaviors are ascribed to the atomic fractions of different structures in small strain rate region, and only related to collapse of crystalline atoms in high strain rate region. A layer thickness-strain rate-dependent mechanism diagram is given to illustrate the couple effect on the plastic deformation mechanisms of the isopachous nanowires. The results also indicate that the modulation ratio significantly affects the tensile properties of unequal Ti/Ni MNWs, but barely affect the plastic deformation mechanisms of the materials. The observations from this work will promote theoretical researches and practical applications of Ti/Ni MNWs.
Negative tunnel magnetoresistance in a quantum dot induced by interplay of a Majorana fermion and thermal-driven ferromagnetic leads*
Authors: Niu Peng-Bin , Cui Bo-Xiang , Luo Hong-Gang
Published: March 2021

We investigate the spin-related currents and tunnel magnetoresistance through a quantum dot, which is side-coupled with a Majorana fermion zero mode and two thermal-driven ferromagnetic electrodes. It is found that the interplay of Majorana fermion and electrodes’ spin polarization can induce a nonlinear thermal-bias spin current. This interplay also decreases the total magnitude of spin or charge current, in either parallel or antiparallel configuration. In addition, a thermal-driven negative tunnel magnetoresistance is found, which is an unique feature to characterize Majorana fermion. With large temperature difference, a step phenomenon is observed in gate tuned spin-up current. When the coupling between quantum dot and topological superconductor is strong enough, this step will evolve into a linear relation, revealing Majorana fermion’s robustness.
Enhanced absorption process in the thin active region of GaAs based p–i–n structure*
Authors: Yue Chen , Tang Xian-Sheng , Li Yang-Feng , Wang Wen-Qi , Li Xin-Xin , Zhang Jun-Yang , Deng Zhen , Du Chun-Hua , Jia Hai-Qiang , Wang Wen-Xin , Lu Wei , Jiang Yang , Chen Hong
Published: March 2021

The optical absorption is the most important macroscopic process to characterize the microscopic optical transition in the semiconductor materials. Recently, great enhancement has been observed in the absorption of the active region within a p–n junction. In this paper, GaAs based p–i–n samples with the active region varied from 100 nm to 3 μm were fabricated and it was observed that the external quantum efficiencies are higher than the typical results, indicating a new mechanism beyond the established theories. We proposed a theoretical model about the abnormal optical absorption process in the active region within a strong electric field, which might provide new theories for the design of the solar cells, photodetectors, and other photoelectric devices.
Two–dimensional PC3 as a promising anode material for potassium-ion batteries: First–principles calculations*
Authors: Zhou Chun , Huang Junchao , Duan Xiangmei
Published: March 2021

With the diversified development of the battery industry, potassium-ion batteries (PIBs) have aroused widespread interest due to their safety and high potassium reserves on earth. However, the lack of suitable anode materials limits their development and application to a certain extent. Based on first-principles calculations, we investigate the possibility of using PC3 monolayer as the anode material for PIBs. PC3 sheet has excellent electrical properties and meets the prerequisite of anode materials. The storage capacity of potassium is as high as 1200 mAh⋅g−1, which is better than many other reported potassium-ion anode materials. In addition, the outstanding advantages of PC3 sheet, such as low diffusion barrier and moderate open-circuit voltage, make it a potential anode candidate for PIBs.
Hydrogen-induced dynamic slowdown of metallic glass-forming liquids*
Authors: Gao Jin-Ai , Huang Hai-Shen , Lü Yong-Jun
Published: March 2021

Dynamics of hydrogen doped Cu50Zr50 glass-forming liquids are investigated by using the newly developed modified embedded atomic method (MEAM) potential based on molecular dynamics simulations. We find that the doping of hydrogen atoms slows down the relaxation dynamics, reduces the fragility of supercooled melts, and promotes the occurrence of glass transitions. The dynamic slowdown is suggested to be closely related to the effect of hydrogen atoms on locally ordered structure of melts. With increasing concentration of hydrogen, the five-fold symmetry associated with Cu- and Zr-centered polyhedrons is lowered, on the other hand, the local order featuring metal hydrides is enhanced. The latter dominates the dynamic behaviors of glass-forming liquids, especially for Zr atoms, and results in the dynamic slowdown.
Fabrication of microresonators by using photoresist developer as etchant*
Authors: Song Shu-Qing , Xu Jian-Wen , Han Zhi-Kun , Yang Xiao-Pei , Sun Yu-Ting , Wang Xiao-Han , Li Shao-Xiong , Lan Dong , Zhao Jie , Tan Xin-Sheng , Yu Yang
Published: March 2021

In superconducting circuit, microwave resonators and capacitors are crucial components, and their quality has a strong impact on circuit performance. Here we develop a novel wet etching process to define these two components using common photoresist developer as etchant. This method reduces subsequent steps and can be completed immediately after development. By measuring the internal quality factor of resonators, we show that it is possible to achieve similar or better performance when compared with samples made by standard etching processes. This easy-to-implement method may boost the yield hence providing an alternative fabrication process for microwave resonators and capacitors.
Automatic control of desflurane concentration in surgical procedures using laparoscopic technique
Authors: Dominikowski B , Gaszyński T
Published: March 2021

Currently computer programs are known to predict what value of desflurane concentration will be required during general anesthesia. None of them are coupled with the vaporizer of this anesthetic. The authors of the article presented the possibilities of automating the selection of desflurane concentration for vaporizers equipped with an adjustable knob during the conduction phase of balanced anesthesia. The value of the delivered concentration of the volatile anesthetic should be such as to ensure the hemodynamic stability of the anesthetized patient. The above-mentioned solution is based on the values of circulatory parameters such as: mean blood arterial pressure (MAP) and heart rate (HR). The proposed system is equipped with limiters containing upper and lower limits to prevent decrease or excessive deepening of anesthesia which resulting in hemodynamic instability. The system also reacts to rapid changes in blood circulation values adjusting the concentration of anesthetic to the strength of the surgical stimulus and the circulatory response to the course of anesthesia and the surgical procedure. The authors of the article showed the usefulness of automating the selection of desflurane concentration in low-flow anesthesia. The algorithm controlling the setting of the desflurane vaporizer knob does not bind the input and output spaces with mathematical relationships.
Textronics Interdigitate Electrodes for Staphylococcus Aureus bacteria detecting
Authors: Korzeniewska E , Szczesny A , Lipinski P , Dróżdż T , Kiełbasa P , Miernik A , Politowski K
Published: March 2021

The aim of the paper is to investigate the changes in electrical parameters of the interdigitated electrodes (IDEs) due to the development of Staphylococcus aureus. More precisely, the article presents the results of electrode’s resistance, capacitance and inductance changes in the function of bacteria density. The electrodes are made in the process of physical vacuum deposition on composite textile substrates. This allows to apply them in textronic applications. Changes in the electrical parameters of the produced IDEs were observed during microbial cell culture growing. The results of the research have demonstrated that the bacteria density influences the electrical parameters of the electrode. The greatest changes in these parameters are observed at the frequencies of 100 and 120 Hz after the day of inoculating staphylococcal cells into the medium, where the measuring electrodes were placed.
System construction based on a wire-mesh sensor for flow analysis
Authors: Szumowski J , Rymarczyk T , Rymarczyk P , Adamkiewicz P , Kowalski M , Bednarczuk P
Published: March 2021

Wire-mesh sensor (WMS, mesh sensor) is a device for invasive imaging of vertical and horizontal flows of liquids and gases. Visualisation of the measurement results does not require any complicated software reconstruction. The device consists of two parts: the wire-mesh acquisition module and the wire-mesh sensor. The device allows for testing of multiphase flows as well as air bubbles in air-lift reactors. The sensors are also suitable for testing various types of surface flows and the movement of bulk materials along the bottom of a pipeline. This paper describes the goals and results of construction of the system for flow analysis based on a wire-mesh sensor.
The effect of scientific inquiry learning model and scientific attitude on students’ science process skills
Authors: Pulungan Mailita Sari , Nasution Derlina , Rahmatsyah
Published: March 2021

This study aims to analyze how science process skills use scientific inquiry, to analyze how science process skills with high scientific attitude and low scientific attitude, to analyze the interaction between scientific inquiry and scientific attitude. This type of research is a quasi experiment with a pretest-posttest control group design. Data analysis was performed using descriptive analysis which aims to be able to explain and predict the symptoms that apply on the basis of data obtained in the field. Based on the results of the study it was found that the science process skills using scientific inquiry on the temperature and heat material experienced a significant increase, the skills that had a high scientific attitude were better than the science process skills which had a low scientific attitude, and there was an interaction between scientific inquiry and scientific attitude.
Analysis of linear motion kinematics on student’s critical thinking skillsbased on scientific inquiry
Authors: Pulungan Nurul Hidayah , Sirait Makmur , Ginting Eva M
Published: March 2021

This purpose of this studywas to analyze students’ critical thinking skills on linear motion kinematics material using the Scientific Inquiry model. This type of research is a quasi-experimental. The data analysis was carried out through 7 critical thinking skills test in essay form. Before the test instruments are tested on students, expert validation tests were carried outfirst. The critical thinking skill test indicators used consist of elementary indicators of clarification, basic support, inference, advanced clarification and indicators of strategies and tactics. The results of the study showed that the average value of students’ critical thinking skills on linear motion material was 60.02 and included in the sufficient category.
Model of quality control station allocation with consider work in process, and defect probability of final product
Authors: Regent Montororing Yuri Delano , Nurprihatin Filscha
Published: March 2021

Planning is needed in quality control for the target output produced is good. Quality control in the production line is carried out based on the inspection with acceptance of products that meet the requirements. This quality control method is carried out by allocating the quality control station flexibly to separate the rework products to be reworked and scrap to dispose of. The number of acceptable product proportions will depend on the ability of the production line to produce the product expressed in the probability of the product defect. The probability of a production line defect product will be affected to the probability at each work station, where the proportion of product defects that occur will also determine the allocation of the number of quality control stations. Research that discusses the allocation of quality control stations by considering the probability of the final product on the production line and the proportion of work in process does not yet exist, therefore researchers intend to do so. The development of this model is done by developing an objective function to minimize the total production cost. The total cost consists of processing costs, inspection costs, waiting costs, quality control station assignation costs, rework costs, and scrap costs. The aim is to find the configuration of the quality control station allocation in the production line at a minimum cost. From the results of the study obtained a quality control station allocation model that can minimize assembly costs and be flexible to changes in demand parameters, costs, defect probability of final product.
Investigation of chaos behaviour on damped and driven nonlinear simple pendulum motion simulated by mathematica
Authors: Rahayu Siti Utari , Tamba Takdir , Tarigan Kerista
Published: March 2021

This study aimed to investigate the chaos behavior resulted from damped driven nonlinear simple pendulum motion, which was simulated by using Mathematica. The method used to solve the equation of the pendulum was the 4th order of Runge-Kutta. The solution was obtained by setting some parameters to be determined at a certain value (dimensionless), namely the gravitational acceleration (g) was 9.8; the length of rope (l) was 9.8, the dumpling coefficient (q) was 0.4; the initial conditions (θ

0
and ω

0
) were 0.8 for both; the frequency of driving force (Ω

D
) was 0.6; and the mass of pendulum (m) was 1. Due to these settings, the natural frequency of the pendulum (Ω

2
) was calculated to be 1. Still, the driving force (a) was varied in order to analyze the chaos clearly. The solution was then plotted as θ vs t graphs, phase space, and Poincaré section. The results showed that the chaotic motion occurs when the driving force was in the range of 1.36-3.0, in which 3.0 was the maximum value in this simulation. In this range, the slight change in the initial condition resulted in significant differences of θ vs t graph, implying sensitivity to initial conditions. The phase space depicted a chaotic attractor, while the Poincaré section resulted in many dots forming stretching and folding patterns. Based on these results, it can be said that the chaos behavior could arise from damped and driven nonlinear simple pendulum motion by varying parameters, such as driving force.
Identification of mother plant for in vitro propagation of sumatra benzoin as a strategy to improve non-timber forest product
Authors: Nurwahyuni Isnaini , Situmorang Manihar , Sinaga Riyanto
Published: March 2021

Efforts to increase non-timber forest products need to be made to prevent illegal logging. One of the strategy is increasing the production of frankincense sap, which has high economic value as a raw material for medicine and cosmetics. This study aims to choose the best Sumatra Benzoin (Styrax benzoin Dryander) mother plant that qualifies as a source of explants for in vitro propagation, in an effort to provide seeds for forest conservation and at the same time to increase non-timber products. The research was conducted in the forest area of Pakpak Bharat Regency, North Sumatra, Indonesia. The research stages included surveying the Sumatran Benzoin plants in forest areas, identifying plant quality phenotically, and determining the best plants based on the production of incense sap. The production of incense sap at each harvest period is determined based on the quantity and quality of the sap produced by using traditional tapping techniques. The best parent plants was chosen as the source of explants for in vitro propagation. The mature and productive Sumatra Benzoin trees had been identified and marked as good quality plants that met the criteria as mother plants for in vitro propagation. The traditional technique used by the farmers to extract frankincense sap from mature trees is described in this study which guarantees the production of gum in large quantities and with very good quality of sap. The best quality mother plant has been selected, namely plant of Styrax benzoin Dryander that is phenotically very fertile, dense, bearing fruit, relatively resistant to various forest plant diseases, and productive produce lagrge quantity accompany with very good quality incense sap. This mother plant has been determined as the source of explantsin the in vitro propagation of Sumatra Benzoin.
The Development of Physics Objective Tests Based on PISA for Sound Wave Topics in High School
Authors: Sari Bestrica Kurnia , Sahyar  , Sani Ridwan Abdullah
Published: March 2021

The purpose of this study is to develop a PISA-based physics objective test instrument for sound wave material in high school according to good test qualification standards in terms of index validity, reliability, discrimination, level of difficulty, and distractor effectiveness. This study is a type of research and development (R&D). The model used is Analysis, Design, Development, Implement and Evaluation (ADDIE). The analysis stage resulted in minimal variation in the assessment and students still lacking PISA-based physics questions, especially on sound wave material. The material for developed physics problems includes the magnitude of sound waves, reflection and refraction, resonance, sound intensity, and the Doppler effect. The design stage resulted in 45 items based on the PISA scientific literacy competency which were classified into three competency standards, namely: explaining scientific phenomena; evaluate and design scientific research; interpret scientific data and evidence. The development stage obtained 44 items in the very valid category based on content validation by 5 experts, both in terms of material, construct, and language. The results of the implementation and evaluation stages show that of the 45 questions developed, 38 questions have met the criteria for good test quality, based on index validity, reliability, discrimination, difficulty level, and distractor effectiveness in small group trials and large group trials.
Study development of digital teaching materials support online learning during Covid-19
Authors: Lubis Fitriani , Yudhi Achmad
Published: March 2021

The implementation of education activity policy conducted at home by applying work from home (WFH) demand all of the each education institutions to perform the online learning by using any platforms provided in internet web. For college education, it is hoped to develop the information system of online learning based on learning management system. This research is intended to find out the information about the college students responds related to the online learning activity conducted in the Study Program of Language and Literature of Bahasa Indonesia Unimed since March 2020 until June 2020. The data obtained by answering the questionnaire submitted to the college students randomly. The results showed that 81.6% was in the very positive category related to the college students’ responses to the implementation of online learning. Besides that, there are some obstacles in the implementation of online learning as well, they are a small proportion of instructors and the college students who have not mastered the use of IT in the online learning process. The college students highly hope that the instructors can transform the teaching materials into digital form based on the applications so that it makes easier for them to understand the materials and can save any costs as complained by the college students when the online learning is carried out.
Performance test of an aerosol concentration measurement system based on quartz crystal microbalance
Authors: Budianto A , Wardoyo A Y P , Masruroh  , Dharmawan H A , Nurhuda M
Published: March 2021

QCM or quartz crystal microbalance is a well-known sensor technology that generates cycles of oscillation related to mass change on the crystal’s surface. This crystal works well when it has a frequency counter and an oscillator to drive the crystal and count the oscillation, and a good airflow regulator. This study developed a measurement system for aerosol concentrations with a diameter of less than 2.5 micrometers. The system consists of QCM sensors, an oscillator, a frequency counter, and an airflow regulator. The system was tested inside an exposure chamber with a constant emission source for the different velocity speeds, namely v

1
, v

2
, v

3
, v

4
, and v

5
. The test was conducted every10seconds due to the saturated time of the QCM related to the mass loading effect of aerosol. The results show that the system can drive the QCM sensor with a frequency of 5MHz. The measurement system works well to measure aerosol concentrationafter the preload duration often seconds and every sixty seconds in which the durations are related to the optimum QCM’s response at v

1
and v

2
. The optimum performance was found to be in the laminar regime, with the sample rate of 0.6 m/s to 1.0 m/s.
Evaluating the stock volatility of service companies in the rise of COVID-19 using ARMAX-GARCHX
Authors: Setiarno Putera Muhammad Luthfi
Published: March 2021

This study evaluates the impact of Covid-19 variables which has attracted huge attention from whole countries. The service companies listed in IDX are being the main issue while many are struggling amidst the economy slowdown due to pandemy. By comparing the time series regression (TSR) - GARCHX and ARMAX - GARCHX of stock return of 4 companies listed in service sub-sector since early March 2020, proposed GARCHX models are able to assess the volatility of stock return. As a proxy of the volatility, Value-at-Risk (VAR) is analyzed at 1% and 5% quantiles. It is found that ARMAX-GARCHX is more accurate than TSR-GARCHX in evaluating the volatility in lower risk, particularly that of medical service stock. Through ARMAX-GARCHX model, it is indicated that JCI return and lagged Covid-19 daily death cases have significant impact to the stock volatility, particularly that of transportation and medical service companies.
Synthesis and characterization of natural zeolite-clay as resistive humidity detection
Authors: Susilawati  , Balyan Muhammad
Published: March 2021

Zeolite-clay was successfully employed in as resistance type humidity sensor. Zeolite-clay humidity sensor was synthesized by crushing into powder and soaked into 6% H2SO4while stirred for two hours using a magnetic stirrer. The solution was filtered, washed using aquadest and dried at 100°C for 5 hours with the mixture process of zeolite and clay were varied into 10%:0%, 9.5%:0.5%, 9%:1%, 8.5%:1.5%, and 8%:2%. The result pressed with a size of 3x3x1 cm3 using a hydraulic under 3 tons pressure for 10 minutes and heated at temperatures of 800°C.Zeolite-clay was placed in a testing chamber equipped with the electrode that connected to an electrical supply of 3 Volt. The electrical resistance was recorded using Multimeter Hydra Series III Fluke when exposed with humidity in range of 18.5-99% RH. Zeolite 8%-clay 2% sensor exhibits the highest sensitivity properties, which indicate saturated resistance value at 99% RH.Meanwhile, Zeolite 8.5 gr-clay 1.5 gr revealed the highest response value at 54.3 Mega Ohm. Based on SEM and EDX characterization, the ratio of Si/Al and microstructure surface have an effect towards humidity detection process. The results indicate enhancement than previous research on zeolite as a sensor, and therefore Zeolite-Clay has proved the capability to detect humidity.
An introduction of scada-based based back pressure vessel (BPV) at palm oil factory with biomass energy
Authors: Ulum Zahrul , Hasan Syafrudin , Sinulingga Emerson P. , Latifah Siti , Fachrudin Khaira Amalia
Published: March 2021

Empty bunches, shells and fibers are waste biomass for renewable energy in steam power plants. The automatic control system provides many advantages for industrial use. Apart from speeding up time, work productivity is also able to reduce human error. The SCADA system includes a number of RTUs (Remote Terminal Units), Main Station / RCC (Area Control Center) and a data telecommunication network between the RTU and the Main Station. Application of scada, BPV can be controlled easily. This study introduces the application of scada to the BPV regulation in the biomass power plant at the Gunung Melayu palm oil mill
The Toxicity of n-Hexane, Ethyl Acetate and Ethanol Extracts of SarangBanua (Clerodendrumfragrans Vent Willd) Leaves by Brine Shrimp Lethality Test (BSLT) Method
Authors: Simorangkir Murniaty , Nainggolan Bajoka , Juwitaningsih Tita , Silaban Saronom
Published: March 2021

Sarangbanua traditional medicinal plant is found in Simalungunand NorthTapanuli Regencies, Sumatera, Indonesia. The result of plant determination, sarangbanuais Clerodendrumfragrans Vent Willd, including the Verbenaceae family. This study aims to determine the toxicity of the three types of leaf extracts of C. fragrans Vent Will. The Brine Shrimp Lethality Test (BSLT) method was used to determine the toxicity of the extracts. The mortality data were then analyzed by Probit SAS to obtain LC50 values. The results showed that the three types of C. fragrans leaf extracts had LC50 values below 1000 µg/mL, so they were classified as toxic and potentially bioactive. The LC50 values of each of the ethanol, ethyl acetate and ethanol extracts were 26.25; 37.50 and 41.97 µg/mL
Ring-opening Polymerization Reaction Mechanism of ε-Caprolactone Catalyzed by Bis(dibenzoylmethanato) zirconium(IV) Using PM3 Semi-Empirical Method
Authors: Yusuf Muhammad , Pulungan Ahmad Nasir , Irmala Sari Rizki Dwi , Fitri Amne Dinda Prihatini , Siregar Rahmayani , Rahmah Mawaddatur
Published: March 2021

Polycaprolactone (PCL) is a semi-crystalline polymer and belongs to a biodegradable plastic. PCL also can naturally degraded, has a high degree of adjustment with other polymer, and has great mechanical and thermal properties. By using the Lewis acid catalyst, PCL can be yielded through the ring opening polymerization (ROP) of caprolactone (ε-CL). The objective of this study was to explore the most likely reaction mechanism of the ROP of ε-CL using bis(dibenzoylmethanato) zirconium(IV) chloride as a catalyst. Here, the Hyper Chem 8.0 program was performed to compute the monomer molecule, intermediate molecules, and polymer molecule. The program can be launch on the Windows 07 systems. The method used was the PM3 semi-empirical method. This program also used to show the results of optimized structures. The calculation results show that to generate PCL required bis(dibenzoylmethanato) zirconium (IV) catalyst. The ROP reaction mechanism of ε-CL can be occurs through direct coordination ε-CL on the Zr complex. After that, deprotonation and insertion monomer. Last step was chain propagation of the χ–CL.
Development of Chemistry Practicum Guidelines with the Support of STEM (Science, Technology, Engineering, and Mathematics) Integrating Character Education
Authors: Sinaga Mahniar , Silaban Ramlan , Jahro Iis Siti
Published: March 2021

The implementation of the STEM-based learning approach is able to shape student character. One of them is using a chemistry lab guide based on the STEM approach. The purpose of this study was to determine the feasibility level of a chemistry lab guide based on the integrated STEM approach to character education based on the criteria of the National Education Standards Agency (BSNP) and the character level of students after using a validated practicum guide. This type of research uses the Research and Development (R & D) method with the ADDIE model development stages (Analysis, Design, Development, Implementation, and Evaluation). The data collection instrument consisted of a practicum guide validation sheet based on BSNP criteria and student character observation sheets. The data source in this study was 40 students of class XII SMA N 1 Tanjungbalai academic year 2020/2021 using purposive sampling technique of collecting samples. The results showed that the validation test for chemistry lab guides by expert validators stated that the chemistry practicum guidance based on the integrated STEM approach to character education was valid with an average value of 3.53 from a maximum scale of 4 which means it is feasible and does not need to be revised. Furthermore, the results of observations of the character level of students using a practical guide based on the STEM integrated approach to character education are very good with an average of 85.8%. Based on the results of character validation and observation, it shows that chemistry practicum speakers based on the STEM integrated approach to character education are feasible to be implemented in schools.
The Quality of Learning System by Using Online Learning Technology based on SIPDA during Covid-19 Pandemic
Authors: Atmojo Wahyu Tri , Adisaputera Abdurahman , Masitowarni  , Marice
Published: March 2021

One impact of the Covid 19 Pandemic on the education is the implementation of online learning policy. All the educational institutions are encouraged to develop any online learning platforms and continue to socialize the use of the online learning system to all the academic community. This research aims to assess the quality of online learning conducted by the instructors and college students at the Language and Arts Faculty. The data were obtained through a response questionnaire that distributed to the college students. There are 3294 respondents who took part in this research that consist of the college students who are from the study program of Bahasa Indonesia, Indonesian literature, English literature, Educations of English language, German language, French language, arts, dance, music and performing arts. The research results showed that the implementation of the online learning has a good quality based on the results of the college students’ responses. However, there are several weaknesses in the implementation of the online learning process, such as there are still a small proportion of the instructors (15 percent) who have not been able to use the Unimed online learning information system (SIPDA), and the low feedback provided by the instructors to the college students. The findings of this research then become an input for the head of the Language and Arts Faculty to arrange the online learning policy which will later become a standard guideline for the online learning at the Faculty of Language and Arts, Universitas Negeri Medan.
VECM and Bayesian VECM for Overparameterization Problem
Authors: Hapsari Meilina Retno , Astutik Suci , Soehono Loekito Adi
Published: March 2021

Overparameterization is the amount of data used in the study is less than the number of estimated parameters. Overparameterization problems can cause the forecasting ability to be weak because the model is not suitable. This problem often occurs in complex models such as Vector Error Correction Model (VECM). This study discusses VECM and Bayesian VECM (BVECM), which aims to analyze the relationship between macroeconomic variables in Indonesia. First, estimate parameters of VECM with Maximum Likelihood Estimation. Second, estimate parameters of VECM with a Bayesian approach (BVECM). The variables used in this study are six macroeconomic variables in Indonesia in 2010 quarter 1 to 2019 quarter 4 are GDP, the money supply, exchange rate of rupiah to US dollar, exports, imports and interest rates. The amount of data in this study is less than the number of estimated parameters that causing overparameterization problems. Based on literature, Bayesian method can avoid overparameterization problems which can not be overcome by Maximum Likelihood Estimation. The model obtained from this study is the VECM(3) and BVECM(3). In the VECM analysis, the residuals did not meet the assumptions of diagnostic model. However, diagnostics of BVECM models show that it has been proven that the model is suitable. This conclusion is relevant to the statement that the Bayesian method can solve the problem of overparameterization.
Analysis of Students Critical Thinking Ability using Models Scientific Inquiry
Authors: Ginting Samson , Sinulingga Karya , Tampubolon Togi , Rajagukguk Juniastel
Published: March 2021

This study aims to analyze students critical thinking ability in Static Fluid material. This type of research is a quantitative descriptive study. The research subjects were students of class XI MIPA 1 in Senior High School 1 Kerajaan for the 2020/2021 academic year, totaling 30 students. Data analysis was carried out through a test of critical thinking ability in the form of description questions. The test instrument used was 7 items based on the indicators of Ennis ‘critical thinking ability (1995) which had been validated by expert lecturers. From the analysis of the results of students’ critical thinking ability using a model scientific inquiry In the Static Fluid material the average value was 79.52, and after being converted it was in the good category. Of the 30 students of class XI MIPA 1, 15 students (50%) have very good critical thinking ability; as many as 14 students (46.7%) have good critical thinking ability; and as many as 1 student (3.3%) had enough critical thinking ability. Thus it can be concluded that the use of the scientific inquiry model can improve the critical thinking ability sof class XI MIPA 1 SMAN 1 Kerajaan students.