bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cytotoxicity, antioxidant and phytochemical screening of propolis extracts from four different Malaysian stingless bee species
Authors: Mat Nafi Nor Elani , Md Zin Nur Basyirah , Pauzi Norzilawati , Abdul Khadar Ammira Shafiqha , Anisava Aulia Rani , Mohd Badiazaman Ainur Awanis , Mohd Khamsah Suryati 
Published: April 2020

Propolis is a plant-derived substance collected by stingless bee’s product from various sources, including plant resins with combination of bee’s saliva and wax. Propolis has been used to treat several diseases since ancient times and it is an important source of bioactive natural compound and drug derivatives. The aim of this study was to evaluate biological and chemical profiles of ethanolic extracts from propolis produced by Heterotrigona itama (HI), Geniotrigona thoracica (GT), Lepidotrigona terminate (LT), and Tretrigona apicalis (TA). Cytotoxicity activity was evaluated by using 3-(4,5-Dimethylthiazol-2-YI)-2,5-Diphenyltetrazolium Bromide (MTT) assay against three cancer cell lines. H. itama extracts showed the highest cytotoxicity effect with of 5 µg/mL, 4 µg/mL and 8 µg/mL for MDA-MB-231, SK-UT-1 and HeLa, respectively. Other species only possessed moderate to weak cytotoxicity effect against tested cells. Phytochemical screening was carried out by thin layer chromatography (TLC) analysis and visualized by derivatives agents in order to detect the presence of terpenoids, steroids, saponins, essential oils and phenol. It was found that H. itama (HI) possessed the highest antioxidant activity with the lowest of 30 µg/mL with percetange of inhibition at 85.69 % evaluated by (2,2-diphenyl-1-picryl-hydrazyl-hydrate) DPPH scaveging assay. In conclusion, bee species was considered as important factor in selecting the quality of propolis. It was found that H. itama produced the most active extract compared to other species. The data obtained from this study would be the basis for further investigation on therapeutic application especially for cytotoxic activity, antioxidant and phytochemical screenings for four Malaysian stingless bees of propolis.
Antioxidant and antibacterial activities of Ischaemum indicum leaves extracted using different solvents
Authors: Auwaliyah Fithrotul , Rizqi Hamdan Dwi , Purnomo Adi Setyo , Fatmawati Sri 
Published: April 2020

The aim of this study was to evaluate antioxidant and antibacterial activities of Ischaemum indicum leaves extracts based on different polarity solvents: water, methanol, ethyl acetate, dichloromethane, and n-hexane. The antioxidant activity was evaluated using ABTS and DPPH methods, while the antibacterial activity was determined by broth dilution method against Pseudomonas aeruginosa and Bacillus subtilis. The results showed that water and methanol extracts of I. indicum gave the highest antioxidant activity in ABTS assay with an IC50 73.80 and 46.32 µg/mL, respectively. On the other hand, The IC50 on DPPH assay for water extracts was 117.51 µg/mL, this value was higher than that of methanol extract with no inhibition. Methanol and water extracts showed the antibacterial activity against B. subtilis with inhibition of 48.62 and 45.11%, whereas inhibition of P. aeruginosa were 31.95 and 30.31%, respectively. This study denoted that I. indicum is a new potential candidate as antioxidant source.
Zeolite templated carbon: Preparation, characterization and performance as filler material in co-polyimide membranes for CO2/CH4 separation
Authors: Gunawan Triyanda , Romadiansyah Taufik Qodar , Wijiyanti Rika , Wan Salleh Wan Norharyati , Widiastuti Nurul 
Published: April 2020

Zeolite templated carbon (ZTC), a structurally unique carbon material was used as new fillers for the preparation of composite polymeric membrane derived from BTDA-TDI/MDI (P84) co-polyimide. The thermal stability of membrane, the structure evolution, morphology and topology, as well as gas separation performance of modified membranes were investigated. Zeolite-Y, a hard template for ZTC, was synthesized via hydrothermal method. The ZTC was synthesized via impregnation of sucrose as carbon precursor into zeolite pore and followed by carbonization at 800°C. The zeolite template was removed through acid treatment to obtain ZTC, which was used as fillers for membrane preparation. The membrane was prepared using P84 co-polyimide as membrane precursor via phase inversion process. Synthesized materials were characterized using SEM, XRD, N2 adsorption-desorption isotherm and TEM. The thermal stability of membrane was improved by the addition of ZTC. As the result of ZTC loading into P84 co-polyimide membrane, the gas permeability of CO2 increased thirty-four times, as well as the CO2/CH4 selectivity boosted from 0.76 to 5.23. The ordered pore structure in ZTC plays important role in increasing the permeability and selectivity performances of the P84 co-polyimide membrane.
A Modeling Study of Discharging Li-O2 Batteries With Various Electrolyte Concentrations
Authors: Wang Fangzhou , Li Xianglin , Hao Xiaowen , Tan Jianyu 
Published: April 2020

Abstract
The mass transfer in the cathode electrode plays an important role in operating Li-O2 batteries. In this study, a two-dimensional, transient, and isothermal model is developed to investigate the mass transfer in discharging Li-O2 batteries. This model simulates the discharge performance of Li-O2 batteries with various electrolyte concentrations (0.1−1.0M) at various current densities (0.1, 0.3, and 0.5 mA/cm2). The O2 diffusivity and the ionic conductivity and diffusivity of Li+ are altered as the bis(trifluoromethane)sulfonimide lithium salt (LiTFSI) concentration in the electrolyte of tetraethylene glycol dimethyl ether (TEGDME) changes. The distributions of O2, Li+, and lithium peroxide (Li2O2) in the cathode electrode after discharge are calculated using this model. Modeling results show that when the concentration decreases from 0.5 to 0.25M, the discharge capacity of Li-O2 sharply drops at various current densities. The mass transfer of Li+ determines the discharge capacity of Li-O2 batteries with dilute electrolytes (≤0.25 M). In contrast, the O2 supply is dominant regarding the discharge capacity when the electrolyte concentration is larger than 0.5M. The highest discharge capacity (e.g., 6.09 mAh at 0.1 mA/cm2) is achieved using 0.5M electrolyte since it balances mass transfer of O2 and Li+.
Measurement of Natural Vibrations and Resonant Second Higher-Harmonics Due to a Fatigue Crack
Authors: Kanda Kosuke , Lin Shan 
Published: April 2020

Abstract
Nonlinear ultrasonic testing is considered a more promising technique for evaluating closed cracks than conventional ultrasonic testing. However, the mechanism of the generation of nonlinear ultrasonic waves has not been sufficiently explained. We first set up a system to measure the frequency–response characteristics of ultrasonic waves and experimentally investigated the mechanism of second higher-harmonic (HH) wave generation for a fatigue crack. Sweeping the frequencies of incident waves impinging on a fatigue crack introduced to a specimen, we obtained a frequency–response characteristic curve for the crack. From the curve, resonance phenomena resulting from local defect resonance were observed. We then measured the frequency response characteristics of second HH waves using the same system and consequently confirmed that second HH waves resonated when their frequencies corresponded to the eigenfrequencies of the crack. Finally, we theoretically showed that the resonant second HH waves were generated by local defect resonance and nonlinearity.
Assessment of Photovoltaic Capabilities in Urban Environments: A Case Study of Islamabad, Pakistan
Authors: Zubair Muhammad , Ghuffar Sajid , Shoaib Muhammad , Awan Ahmed Bilal , Bhatti Abdul Rauf 
Published: April 2020

Abstract
Photovoltaic (PV) estimation in an urban environment requires detection of rooftop area, design of PV system based on optimization on PV placement distance and the study of additional benefit of lower cooling load of building by shading provided by PV panels. The study is aimed at policymakers to introduce renewable energy policy toward net-zero energy buildings in urban areas. In this research, the capital city of Pakistan, Islamabad, is analyzed for rooftop PV capabilities using deep learning algorithms. The area of the rooftop is calculated by extracting buildings in high-resolution satellite imagery using a deep learning algorithm. The site location is analyzed for available solar energy resources. The distance between the rooftop-PV array is optimized based on self-shading losses, coefficient of performance, energy yield, net-zero energy analysis, and reduction of cooling load of the building provided by PV arrays as shading devices. The 40-km2 area of Islamabad considered in this research can generate 1038 GWh of solar energy annually from its 4.3-km2 rooftop area by installed capacity of 447 MW PV panels rows placed at 0.75 m apart. The electricity generated by Islamabad can curtail residential load from the national grid and form a near net-zero energy zone while the electrical energy from the grid can be provided to the industries to enhance the economy and reduce unemployment in Pakistan.
Numerical and Experimental Studies of Pendulum Dynamic Vibration Absorber for Structural Vibration
Authors: Ha Seon Il , Yoon Gil Ho 
Published: April 2020

AbstractThis research presents a pendulum dynamic vibration absorber (PDVA) consisting of a spring and a mass in order to attenuate structural vibrations at two frequencies of hosting structure. It is a convention to attach several dynamic absorbers to hosting structure for the sake of the attenuations of structural vibrations at multiple frequencies with enlarged bandwidth and often it increases the total mass and the installation cost. Therefore, the reduction of the number of vibration absorbers for multiple excitation frequencies is an important issue from an engineering point of view. To resolve these difficulties, this study proposes to adopt the vibration absorber framework of the spring-mass vibration as well as the pendulum vibration simultaneously with the present PDVA system. It is composed of a spring and a mass but being allowed to swing circumferentially, the structural vibrations at the two resonance frequencies, i.e., the square root of stiffness over mass and the square root of a length over gravidity, can be simultaneously attenuated. As the length of the spring of the present PDVA is varied, the effective ranges for the pendulum dynamic vibration absorber become widen. To prove the concept of the present PDVA, this research conducts several numerical simulations and experiments.
On the Characterization of Nonlinearities in Assembled Structures
Authors: Smith Scott A. , Brake Matthew R. W. , Schwingshackl Christoph W. 
Published: April 2020

Abstract
This work refines a recently formalized methodology proposed by D.J. Ewins consisting of ten steps for model validation of nonlinear structures. This work details, through a series of experimental studies, that many standard test setup assumptions that are made when performing dynamic testing are invalid and need to be evaluated for each structure. The invalidation of the standard assumptions is due to the presence of nonlinearities, both known and unrecognized in the system. Complicating measurements, many nonlinearities are currently characterized as constant properties instead of variables that exhibit dependency on system hysteresis and actuation amplitude. This study reviews current methods for characterizing nonlinearities and outlines gaps in the approaches. A brief update to the CONCERTO method, based on the accelerance of a system, is derived for characterizing a system’s nonlinearities. Finally, this study ends with an updated methodology for model validation and the ramifications for modeling assemblies with nonlinearities are discussed.
Contact Stress and Linearized Modal Predictions of As-Built Preloaded Assembly
Authors: Brink Adam R. , Kuether Robert J. , Fronk Matthew D. , Witt Bryan L. , Nation Brendan L. 
Published: April 2020

Abstract
The member stiffness and pressure distribution in a bolted joint is significantly influenced by the contact area of the mechanical interface under a prescribed preload force. This research explores the influence of as-built surface profiles for nominally flat interfaces of a C-Beam assembly with two well-defined contact regions. A high-fidelity finite element model is created such that the model uncertainty is minimized by updating and calibrating the piece parts prior to the preload assembly procedure. The model is then assembled and preloaded to evaluate the contact stresses and contact area for both nominally flat and perturbed non-flat surfaces based on three-dimensional surface topography measurements. The predicted pressures are validated with digitized pressure-sensitive film measurements. The high-fidelity modeling reveals how the compliance and thickness of the pressure-sensitive film alter the measured pressures, leading to incorrect evaluations of the stresses and contact area in the joint. The resulting low-level dynamic behavior of the preloaded assembly is shown to be sensitive to the true contact area by linearizing the nonlinear finite element model about the preloaded equilibrium and performing a computational modal analysis. The resonant frequencies are validated with experimental measurements to demonstrate the effect of the contact area on the modal characteristics of the bolted assembly. Vibration modes and loading patterns exhibit varying levels of sensitivity to the contact area in the joint, leading to an improved physical understanding of the influence of contact mechanics on the low-level linear vibration modes of jointed assemblies.
Nonlinear Visco-Poroelasticity of Gels With Different Rheological Parts
Authors: He Dongjing , Hu Yuhang 
Published: April 2020

Abstract
A polymeric gel contains a crosslinked polymer network and solvent. Gels can swell or shrink in response to external stimuli. Two typical kinetic processes are involved during the deformation of gels: the viscoelastic and poroelastic responses. Viscoelasticity of gels is generated from local rearrangement of the polymers, while poroelasticity is generated from solvent migration. The coupled time-dependent behaviors of gels can be formulated by coupling a spring-dashpot model with a diffusion–deformation model. Different combinations of spring and dashpot and different ways of dealing with the coupling between solvent migration and rheological models—either through the spring or dashpot—induce significantly different constitutive behaviors and characteristic time-dependent responses of gels. In this work, we quantitatively study how different rheological models coupled with solvent migration affect the transient behavior of gels. We formulate the visco-poroelastic gel theory for the Maxwell model, the Kelvin–Voigt model, and the generalized standard viscoelastic model. In addition, for generalized standard viscoelastic model, we also discuss the different coupling through the secondary spring or the dashpot. The models are implemented into finite element codes, and the transient-state simulations are performed to investigate the time-dependent deformation and frequency-dependent energy dissipation of different rheologically implemented gel models. The result shows that different combinations of spring and dashpot give the gel solid-like properties and liquid-like properties under different time scales; in addition, the coupling of solvent migration with the dashpot in the rheological model results in restrictions of solvent migration under certain length scales.
Improving the Drell–Yan probe of small x partons at the LHC via an azimuthal angle cut
Authors: Yamasaki M. Kendi , de Oliveira Emmanuel G. 
Published: April 2020

AbstractPredictions for Drell–Yan lepton pair production at low dilepton mass and small x at the LHC usually have a large scale dependence. This can be decreased by determining an optimal factorization scale. In this paper, we reduce this scale by imposing a cutoff in azimuthal angle between the transverse momentum of the leptons, properly taking into account Sudakov effects. This allows one to probe the parton distributions at smaller scales eliminating most of the current theoretical uncertainty.
Prognostic Implications of Resistive Reserve Ratio in Patients With Coronary Artery Disease
Authors: Lee Seung Hun , Lee Joo Myung , Park Jonghanne , Choi Ki Hong , Hwang Doyeon , Doh Joon‐Hyung , Nam Chang‐Wook , Shin Eun‐Seok , Hoshino Masahiro , Murai Tadashi , Yonetsu Taishi , Mejía‐Rentería Hernán , Kakuta Tsunekazu , Escaned Javier ,   the International Collaboration of Comprehensive Physiologic Assessment Investigators
Published: April 2020

Background

Resistive reserve ratio is a thermodilution‐based index which integrates both coronary flow and pressure. Resistive reserve ratio represents the vasodilatory capacity of interrogated vessels including both epicardial coronary artery and microvascular circulation. We evaluated the prognostic potential of resistive reserve ratio compared with pressure‐derived index (fractional flow reserve [
FFR
]) or flow‐derived index (coronary flow reserve [
CFR
]).

Methods and Results

A total of 1245 patients underwent coronary pressure and flow measurement using pressure‐temperature wire. Resistive reserve ratio was calculated by
CFR
adjusted using the ratio between resting and hyperemic distal coronary pressure ([resting mean transit time/hyperemic mean transit time]×[resting distal coronary pressure/hyperemic distal coronary pressure]). Clinical outcome was assessed by patient‐oriented composite outcome (
POCO
), a composite of any death, myocardial infarction, and revascularization at 5 years. At 5 years, the cumulative incidence of
POCO
was significantly different according to quartiles of resistive reserve ratio (9.9%, 11.3%, 17.2%, and 22.7% in quartiles 1 to 4, respectively, log rank
P
<0.001). Among patients with deferred revascularization, those with depressed resistive reserve ratio (<3.5) showed a significantly higher risk of
POCO
than those with preserved resistive reserve ratio (≥3.5) in patients with
FFR
>0.80 or patients with
CFR
>2.0. (
FFR
>0.80 group: 14.8% versus 6.0%; log rank
P
=0.001;
CFR
>2.0 group: 13.5% versus 7.1%; log rank
P
=0.045). Adding resistive reserve ratio into the model for 5‐year
POCO
showed significantly higher global Chi square value than
FFR
or
CFR
(
P
<0.001, respectively, for
FFR
and
CFR
). Resistive reserve ratio <3.5 was significantly associated with the risk of
POCO
at 5 years in multivariable model (adjusted hazard ratio 1.597, 95%
CI
, 1.098–2.271,
P
=0.014).

Conclusions
Resistive reserve ratio, which integrated both coronary flow and pressure, showed incremental prognostic implications in patients with coronary artery disease undergoing elective percutaneous coronary intervention guided by invasive physiologic evaluation.

Registration

URL
:
https://www.clini​caltr​ials.gov
; Unique identifier:
NCT
03690713.
Regionalizing Tourism through Transfrontier Conservation: Implications for Local Development in Southern Africa
Authors: Noe Christine 
Published: April 2020

Abstract
The term ‘region’ no longer functions to denote a strictly geographical or spatial reference (Söderbaum, 2003). Owing to the radical shift in the conception of regions, their role in promoting local development has likewise changed drastically over time. Nowadays regions are conceived as multi-dimensional networks that emerge through partnerships between states and non-state actors, linking together local and foreign individuals and companies, powerful and powerless individuals and their communities. Rather than existing as bounded spatial expanses per se, regions in this expanded sense are fluid, continually constructed and deconstructed by the practices of these different partners and therefore their parameters are in perpetual flux. This paper explores how the practices of nature conservation and the promotion of nature-based tourism have contributed to the creation of new regions in this sense. The paper applies the case of Transfrontier Conservation Areas (TFCAs) in the Southern African Development Community (SADC) and their constructions as cross-border regions of significance for promoting tourism. The paper draws some insights from studies that have examined transfrontier tourism to demonstrate how different actors have acquired political support and legitimacy for promoting cross-border tourism but that on-the-ground experiences have not matched the claims that tourism promotes local development. The main argument of the paper is that regional-wide conservation initiatives through which cross-border tourism is promoted by different partners have had spatial implications that are largely associated with various kinds of local livelihood (in) securities.
Ultrastructural X-ray scattering studies of tropical and temperate hardwoods used as tonewoods
Authors: Viljanen Mira , Ahvenainen Patrik , Penttilä Paavo , Help Hanna , Svedström Kirsi 
Published: April 2020

Abstract
The structure of hardwoods representing eight tropical and five temperate species was characterized from the atomistic level up to the cellular level using X-ray scattering, X-ray microtomography and light microscopy. The species were chosen for this study based on their popularity as tonewoods. The ultrastructure of wood cell walls, including crystallite size, orientation and close-range order of cellulose microfibrils were determined by small- and wide-angle X-ray scattering (SAXS, WAXS). The SAXS patterns were interpreted by using an analytical model of cylinders packed in a hexagonal close-range order with paracrystalline distortion. The values for the cylinder diameters given by this model were compared to the average crystallite widths obtained by WAXS using the Scherrer equation. In six out of 26 samples, all of these representing tropical species used especially in fretboard parts of electric guitars, large differences between these two sizes were obtained. The WAXS and microscopy results of these samples corresponded to tension wood structures. These comparisons and interpretations of SAXS results have not been previously presented for any tropical hardwoods, especially related to those containing tension wood tissue. The importance of the ultrastructural characterization was highlighted in this study in the case of tropical hardwood samples.
Philology for an Enchanted World: Motoori Norinaga and the Study of Japanese Language and Literature in Early Modern Japan
Authors: Bushelle Emi Foulk 
Published: April 2020

Abstract
This article focuses on a pioneering figure in the philological study of language and literature in early modern Japan, Motoori Norinaga 本居宣長 (1730–1801). In his studies of Japan’s “ancient Way,” Norinaga describes the correct understanding of the syntactical elements of the ancient Japanese language as a way to restore a lost sense of the world as enchanted, the abode of powerful presences known as kami. For Norinaga, the study of Japan’s ancient literature and language was thus situated within a broader interpretive framework. This article will show how philology contributed to the configuration of this framework as the method by which the disciplined individual was empowered to retrieve a lost sense of enchantment. As such, it takes the position that Norinaga’s philological restoration of enchantment is best understood as a re-enchantment, an attempt to transcend (early) modern disenchantment.