bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of Gut Microbiome in Korean Patients with Metabolic Associated Fatty Liver Disease
Authors: Oh Joo Hyun , Lee Je Hee , Cho Min Seok , Kim Hyeree , Chun Jongsik , Lee Joon Hyeok , Yoon Yeup , Kang Wonseok
Published: March 2021

Metabolic associated fatty liver disease (MAFLD) is a new concept where the presence of both fatty liver and metabolic abnormality are necessary for diagnosis. Several studies have reported that altered gut microbiome is closely associated with metabolic diseases and non-alcoholic fatty liver disease. However, the studies on MAFLD population are scarce. This prospective study aimed to identify differences in gut microbiome between patients with MAFLD and healthy controls in Korean population. In this study, patients with MAFLD and age, sex-matched healthy controls were included, and their stool samples were collected. Taxonomic composition of gut microbiota was analyzed using 16S ribosomal ribonucleic acid pyrosequencing. Twenty-two MAFLD patients and 44 healthy controls were included. Taxonomic diversity was lower in patients with MAFLD in the aspect of alpha and beta diversity. The differences were also found at phylum, class, family, and genus levels between the two groups. Phylum Proteobacteria, family Enterobactereriaceae, genus Citrobacter abundance was significantly increased and genus Faecalibacterium was significantly decreased in patients with MAFLD. In addition, butyrate-producing bacteria were decreased and ethanol-producing bacteria were increased in patients with MAFLD. The composition of gut microbiome was different between MAFLD and healthy controls in Korean population. This could offer potential targets for therapeutic intervention in MAFLD.
Vitamin D and Allergy Susceptibility during Gestation and Early Life
Authors: Briceno Noriega Daniela , Savelkoul Huub F. J.
Published: March 2021

Worldwide, the prevalence of allergies in young children, but also vitamin D deficiency during pregnancy and in newborns is rising. Vitamin D modulates the development and activity of the immune system and a low vitamin D status during pregnancy and in early life might be associated with an increased risk to develop an allergy during early childhood. This review studies the effects of vitamin D during gestation and early life, on allergy susceptibility in infants. The bioactive form of vitamin D, 1,25(OH)2D, inhibits maturation and results in immature dendritic cells that cause a decreased differentiation of naive T cells into effector T cells. Nevertheless, the development of regulatory T cells and the production of interleukin-10 was increased. Consequently, a more tolerogenic immune response developed against antigens. Secondly, binding of 1,25(OH)2D to epithelial cells induces the expression of tight junction proteins resulting in enhanced epithelial barrier function. Thirdly, 1,25(OH)2D increased the expression of anti-microbial peptides by epithelial cells that also promoted the defense mechanism against pathogens, by preventing an invasive penetration of pathogens. Immune intervention by vitamin D supplementation can mitigate the disease burden from asthma and allergy. In conclusion, our review indicates that a sufficient vitamin D status during gestation and early life can lower the susceptibility to develop an allergy in infants although there remains a need for more causal evidence.
Hepatoprotective Effect of Mixture of Dipropyl Polysulfides in Concanavalin A-Induced Hepatitis
Authors: Arsenijevic Dragana , Stojanovic Bojana , Milovanovic Jelena , Arsenijevic Aleksandar , Simic Milos , Pergal Marija , Kodranov Igor , Cvetkovic Olga , Vojvodic Danilo , Ristanovic Elizabeta , Manojlovic Dragan , Milovanovic Marija , Arsenijevic Nebojsa
Published: March 2021

The main biologically active components of plants belonging to the genus Allium, responsible for their biological activities, including anti-inflammatory, antioxidant and immunomodulatory, are organosulfur compounds. The aim of this study was to synthetize the mixture of dipropyl polysulfides (DPPS) and to test their biological activity in acute hepatitis. C57BL/6 mice were administered orally with DPPS 6 h before intravenous injection of Concanavalin A (ConA). Liver inflammation, necrosis and hepatocytes apoptosis were determined by histological analyses. Cytokines in liver tissue were determined by ELISA, expression of adhesive molecules and enzymes by RT PCR, while liver mononuclear cells were analyzed by flow cytometry. DPPS pretreatment significantly attenuated liver inflammation and injury, as evidenced by biochemical and histopathological observations. In DPPS-pretreated mice, messenger RNA levels of adhesion molecules and NADPH oxidase complex were significantly reduced, while the expression of SOD enzymes was enhanced. DPPS pretreatment decreased protein level of inflammatory cytokines and increased percentage of T regulatory cells in the livers of ConA mice. DPPS showed hepatoprotective effects in ConA-induced hepatitis, characterized by attenuation of inflammation and affection of Th17/Treg balance in favor of T regulatory cells and implicating potential therapeutic usage of DPPS mixture in inflammatory liver diseases.
L-Glutamine Supplementation Enhances Strength and Power of Knee Muscles and Improves Glycemia Control and Plasma Redox Balance in Exercising Elderly Women
Authors: Amirato Gislene R. , Borges Juliana O. , Marques Daniella L. , Santos Juliana M. B. , Santos Carlos A. F. , Andrade Marilia S. , Furtado Guilherme E. , Rossi Marcelo , Luis Lais N. , Zambonatto Raquel F. , Silva Eliane B. da , Poma Sarah O. , Almeida Mariana M. de , Pelaquim Renato L. , Santos-Oliveira Laiane C. dos , Diniz Vinicius L. Sousa , Passos Maria E. P. , Levada-Pires Adriana C. , Gorjão Renata , Barros Marcelo P. , Bachi André L. L. , Pithon-Curi Tania C.
Published: March 2021

We investigated the effects of oral L-glutamine (Gln) supplementation, associated or not with physical exercises, in control of glycemia, oxidative stress, and strength/power of knee muscles in elderly women. Physically active (n = 21) and sedentary (n = 23) elderly women aged 60 to 80 years were enrolled in the study. Plasma levels of D-fructosamine, insulin, reduced (GSH) and oxidized (GSSG) glutathione, iron, uric acid, and thiobarbituric acid-reactive substances (TBARs) (lipoperoxidation product), as well as knee extensor/flexor muscle torque peak and average power (isokinetic test), were assessed pre- and post-supplementation with Gln or placebo (30 days). Higher plasma D-fructosamine, insulin, and iron levels, and lower strength/power of knee muscles were found pre-supplementation in the NPE group than in the PE group. Post-supplementation, Gln subgroups showed higher levels of GSH, GSSG, and torque peak, besides lower D-fructosamine than pre-supplementation values. Higher muscle average power and plasma uric acid levels were reported in the PE + Gln group, whereas lower insulin levels were found in the NPE + Gln than pre-supplementation values. TBARs levels were diminished post-supplementation in all groups. Gln supplementation, mainly when associated with physical exercises, improves strength and power of knee muscles and glycemia control, besides boosting plasma antioxidant capacity of elderly women.
Acinetobacter baumannii Antibiotic Resistance Mechanisms
Authors: Kyriakidis Ioannis , Vasileiou Eleni , Pana Zoi Dorothea , Tragiannidis Athanasios
Published: March 2021

Acinetobacter baumannii is a Gram-negative ESKAPE microorganism that poses a threat to public health by causing severe and invasive (mostly nosocomial) infections linked with high mortality rates. During the last years, this pathogen displayed multidrug resistance (MDR), mainly due to extensive antibiotic abuse and poor stewardship. MDR isolates are associated with medical history of long hospitalization stays, presence of catheters, and mechanical ventilation, while immunocompromised and severely ill hosts predispose to invasive infections. Next-generation sequencing techniques have revolutionized diagnosis of severe A. baumannii infections, contributing to timely diagnosis and personalized therapeutic regimens according to the identification of the respective resistance genes. The aim of this review is to describe in detail all current knowledge on the genetic background of A. baumannii resistance mechanisms in humans as regards beta-lactams (penicillins, cephalosporins, carbapenems, monobactams, and beta-lactamase inhibitors), aminoglycosides, tetracyclines, fluoroquinolones, macrolides, lincosamides, streptogramin antibiotics, polymyxins, and others (amphenicols, oxazolidinones, rifamycins, fosfomycin, diaminopyrimidines, sulfonamides, glycopeptide, and lipopeptide antibiotics). Mechanisms of antimicrobial resistance refer mainly to regulation of antibiotic transportation through bacterial membranes, alteration of the antibiotic target site, and enzymatic modifications resulting in antibiotic neutralization. Virulence factors that may affect antibiotic susceptibility profiles and confer drug resistance are also being discussed. Reports from cases of A. baumannii coinfection with SARS-CoV-2 during the COVID-19 pandemic in terms of resistance profiles and MDR genes have been investigated.
The Impact of Angiotensin-Converting Enzyme 2 (ACE2) Expression on the Incidence and Severity of COVID-19 Infection
Authors: Kaseb Ahmed O. , Mohamed Yehia I. , Malek Alexandre E. , Raad Issam I. , Altameemi Lina , Li Dan , Kaseb Omar A. , Kaseb Safa A. , Selim Abdelhafez , Ma Qing
Published: March 2021

The novel coronavirus disease 2019 (COVID-19) pandemic has led to an unprecedented threat to the international community and raised major concerns in terms of public health safety. Although our current understanding of the complexity of COVID-19 pathogenesis remains limited, the infection is largely mediated by the interaction of viral spike protein and angiotensin-converting enzyme 2 (ACE2). The functional importance of ACE2 in different demographic and comorbid conditions may explain the significant variation in incidence and mortality of COVID-19 in vulnerable groups, and highlights its candidacy as a potential therapeutic target. We provide evidence supporting the idea that differences in incidence and severity of COVID-19 infection may be related to ACE2. Emerging data based on the prevalence and severity of COVID-19 among those with established high levels of ACE2 expression strongly support our hypothesis. Considering the burden of COVID-19 infection in these vulnerable groups and the impact of the potential therapeutic and preventive measures that would result from adopting ACE2-driven anti-viral strategies, our hypothesis may expedite global efforts to control the current COVID-19 pandemic.
Marine-Derived Natural Products as ATP-Competitive mTOR Kinase Inhibitors for Cancer Therapeutics
Authors: Parate Shraddha , Kumar Vikas , Lee Gihwan , Rampogu Shailima , Hong Jong Chan , Lee Keun Woo
Published: March 2021

The mammalian target of rapamycin (mTOR) is a serine/threonine kinase portraying a quintessential role in cellular proliferation and survival. Aberrations in the mTOR signaling pathway have been reported in numerous cancers including thyroid, lung, gastric and ovarian cancer, thus making it a therapeutic target. To attain this objective, an in silico investigation was designed, employing a pharmacophore modeling approach. A structure-based pharmacophore (SBP) model exploiting the key features of a selective mTOR inhibitor, Torkinib directed at the ATP-binding pocket was generated. A Marine Natural Products (MNP) library was screened using SBP model as a query. The retrieved compounds after consequent drug-likeness filtration were subjected to molecular docking with mTOR, thus revealing four MNPs with better scores than Torkinib. Successive refinement via molecular dynamics simulations demonstrated that the hits formed crucial interactions with key residues of the pocket. Furthermore, the four identified hits exhibited good binding free energy scores through MM-PBSA calculations and the subsequent in silico toxicity assessments displayed three hits deemed essentially non-carcinogenic and non-mutagenic. The hits presented in this investigation could act as potent ATP-competitive mTOR inhibitors, representing a platform for the future discovery of drugs from marine natural origin.
Barriers to Biosimilar Prescribing Incentives in the Context of Clinical Governance in Spain
Authors: Lobo Félix , Río-Álvarez Isabel
Published: March 2021

Incentives contribute to the proper functioning of the broader contracts that regulate the relationships between health systems and professionals. Likewise, incentives are an important element of clinical governance understood as health services’ management at the micro-level, aimed at achieving better health outcomes for patients. In Spain, monetary and non-monetary incentives are sometimes used in the health services, but not as frequently as in other countries. There are already several examples in European countries of initiatives searching the promotion of biosimilars through different sorts of incentives, but not in Spain. Hence, this paper is aimed at identifying the barriers that incentives to prescribe biosimilars might encounter in Spain, with particular interest in incentives in the framework of clinical governance. Both questions are intertwined. Barriers are presented from two perspectives. Firstly, based on the nature of the barrier: (i) the payment system for health professionals, (ii) budget rigidity and excessive bureaucracy, (iii) little autonomy in the management of human resources (iv) lack of clinical integration, (v) absence of a legal framework for clinical governance, and (vi) other governance-related barriers. The second perspective is based on the stakeholders involved: (i) gaps in knowledge among physicians, (ii) misinformation and distrust among patients, (iii) trade unions opposition to productivity-related payments, (iv) lack of a clear position by professional associations, and (v) misalignment of the goals pursued by some healthcare professionals and the goals of the public system. Finally, the authors advance several recommendations to overcome these barriers at the national level.
Current Pharmacological Intervention and Medical Management for Diabetic Kidney Transplant Recipients
Authors: Klangjareonchai Theerawut , Eguchi Natsuki , Tantisattamo Ekamol , Ferrey Antoney J. , Reddy Uttam , Dafoe Donald C. , Ichii Hirohito
Published: March 2021

Hyperglycemia after kidney transplantation is common in both diabetic and non-diabetic patients. Both pretransplant and post-transplant diabetes mellitus are associated with increased kidney allograft failure and mortality. Glucose management may be challenging for kidney transplant recipients. The pathophysiology and pattern of hyperglycemia in patients following kidney transplantation is different from those with type 2 diabetes mellitus. In patients with pre-existing and post-transplant diabetes mellitus, there is limited data on the management of hyperglycemia after kidney transplantation. The following article discusses the nomenclature and diagnosis of pre- and post-transplant diabetes mellitus, the impact of transplant-related hyperglycemia on patient and kidney allograft outcomes, risk factors and potential pathogenic mechanisms of hyperglycemia after kidney transplantation, glucose management before and after transplantation, and modalities for prevention of post-transplant diabetes mellitus.
Anticonvulsant Action of GluN2A-Preferring Antagonist PEAQX in Developing Rats
Authors: Mares Pavel , Tsenov Grygoriy , Kubova Hana
Published: March 2021

The GluN2A subunit of N-methyl-D-aspartate (NMDA) receptors becomes dominant during postnatal development, overgrowing the originally dominant GluN2B subunit. The aim of our study was to show changes of anticonvulsant action of the GluN2A subunit-preferring antagonist during postnatal development of rats. Possible anticonvulsant action of GluN2A-preferring antagonist of NMDA receptors P = [[[(1S)-1-(4-bromophenyl)ethyl]amino](1,2,3,4-tetrahydro-2,3-dioxo-5-quinoxalinyl)methyl]phosphonic acid tetrasodium salt (PEAQX) (5, 10, 20 mg/kg s.c.) was tested in 12-, 18-, and 25-day-old rats in three models of convulsive seizures. Pentylenetetrazol-induced generalized seizures with a loss of righting reflexes generated in the brainstem were suppressed in all three age groups in a dose-dependent manner. Minimal clonic seizures with preserved righting ability exhibited only moderately prolonged latency after the highest dose of PEAQX. Anticonvulsant action of all three doses of PEAQX against cortical epileptic afterdischarges (generated in the forebrain) was found in the 25-day-old animals. The highest dose (20 mg/kg) was efficient also in the two younger groups, which might be due to lower specificity of PEAQX and its partial affinity to the GluN2B subunit. Our results are in agreement with the postero-anterior maturation gradient of subunit composition of NMDA receptors (i.e., an increase of GluN2A representation). In spite of the lower selectivity of PEAQX, our data demonstrate, for the first time, developmental differences in comparison with an antagonist of NMDA receptors with a dominant GluN2B subunit.
Biocompatible DNA/5-Fluorouracil-Gemini Surfactant-Functionalized Gold Nanoparticles as Promising Vectors in Lung Cancer Therapy
Authors: Giráldez-Pérez Rosa M. , Grueso Elia , Domínguez Inmaculada , Pastor Nuria , Kuliszewska Edyta , Prado-Gotor Rafael , Requena-Domenech Francisco
Published: March 2021

The design and preparation of novel nanocarriers to transport cancer drugs for chemotherapy purposes is an important line of research in the medical field. A new 5-fluorouracil (5-Fu) transporter was designed based on the use of two new biocompatible gold nanosystems: (i) a gold nanoparticle precursor, Au@16-Ph-16, stabilized with the positively charged gemini surfactant 16-Ph-16, and (ii) the compacted nanocomplexes formed by the precursor and DNA/5-Fu complexes, Au@16-Ph-16/DNA–5-Fu. The physicochemical properties of the obtained nanosystems were studied by using UV–visible spectroscopy, TEM, dynamic light scattering, and zeta potential techniques. Method tuning also requires the use of circular dichroism, atomic force microscopy, and fluorescence spectroscopy techniques for the prior selection of the optimal relative Au@16-Ph-16 and DNA concentrations (R = CAu@16-Ph-16/CDNA), biopolymer compaction/decompaction, and 5-Fu release from the DNA/5-Fu complex. TEM experiments revealed the effective internalization of the both precursor and Au@16-Ph-16/DNA–5-Fu-compacted nanosystems into the cells. Moreover, cytotoxicity assays and internalization experiments using TEM and confocal microscopy showed that the new strategy for 5-Fu administration enhanced efficacy, biocompatibility and selectivity against lung cancer cells. The differential uptake among different formulations is discussed in terms of the physicochemical properties of the nanosystems.
Analysis of Dispensing Errors Made by First-Year Pharmacy Students in a Virtual Dispensing Assessment
Authors: Chuang Sara , Grieve Kate Lorraine , Mak Vivienne
Published: March 2021

Pharmacists have a crucial role in the supply of medications and ensuring optimal patient outcomes. However, with the increased use of prescription medications, there is a potential for dispensing errors to occur. Some dispensing errors can result in patient harm, with some leading to death. The development of safe and accurate dispensing skills in pharmacy students is an essential part of the pharmacy curriculum to prevent such dispensing errors from occurring. A retrospective study was conducted on a virtual dispensing assessment completed by first-year pharmacy students using MyDispense at Monash University. Students were assessed on their ability to safely and accurately dispense four prescriptions. The students’ answers in the assessment were then analyzed using qualitative and quantitative methods. Errors in drug quantity, number of repeats, product, patient and prescriber selection were quantitatively analyzed. Through the development of a codebook, frequency of errors was determined for label directions and appropriate use of ancillary labels. In this study, the dispensing errors that were identified depended on the class of medication. Errors in label directions were most common, with the majority of errors displaying incorrect route of administration, drug formulation and/or frequency of dosing. Identified errors were then further categorized into potential severity of harm, ranging from “no harm” to “severe harm”. The findings from this study show the types of errors made by students that are preventable and the potential for first-year pharmacy students to benefit from more comprehensive introductions to dispensing guides and safe environments to practice.
The Overlap Factor Model of Spin-Polarised Coupled Lasers
Authors: Vaughan Martin , Susanto Hadi , Henning Ian , Adams Mike
Published: March 2021

A general model for the dynamics of arrays of coupled spin-polarised lasers is derived. The general model is able to deal with waveguides of any geometry with any number of supported normal modes. A unique feature of the model is that it allows for independent polarisation of the pumping in each laser. The particular geometry is shown to be introduced via ’overlap factors’, which are a generalisation of the optical confinement factor. These factors play an important role in determining the laser dynamics. The model is specialised to the case of a general double-guided structure, which is shown to reduce to both the spin flip model in a single cavity and the coupled mode model for a pair of guides in the appropriate limit. This is applied to the particular case of a circular-guide laser pair, which is analysed and simulated numerically. It is found that increasing the ellipticity of the pumping tends to reduce the region of instability in the plane of pumping strength versus guide separation.
Coherence Stokes Parameters in the Description of Electromagnetic Coherence
Authors: Setälä Tero , Saastamoinen Kimmo , Friberg Ari
Published: March 2021

The two-point counterparts of the traditional Stokes parameters, which are called the coherence Stokes parameters, have recently been extensively used for assessing the coherence properties of random electromagnetic light beams. In this work, we highlight their importance by emphasizing two features associated with them. First, the role of polarization in electromagnetic coherence is significantly elucidated when the coherence Stokes parameters are used. Second, the normalized coherence Stokes parameters should be regarded as the true electromagnetic counterparts of the normalized scalar-field correlation coefficient.
The Short-Term Metabolic Modulation of Basil (Ocimum basilicum L. cv. ‘Genovese’) after Exposure to Cold or Heat
Authors: Jakovljević Dragana , Momčilović Jovana , Bojović Biljana , Stanković Milan
Published: March 2021

Chilling stress in spring and mid-season heat stress are important environmental stresses that can significantly affect plant productivity. The objectives of this study were to understand the effects of cold (4 and 10 °C) or heat (30 and 40 °C) stress on biochemical and physiological traits in leaves and roots of basil (Ocimum basilicum L. cv. ‘Genovese’) young plants. After short-time exposure to mild and severe temperature stresses, both photosynthetic pigments’ and protein, as well as enzymatic and non-enzymatic defense components in basil leaves and roots, were quantified and compared with the control non-stressed plants. It was shown that both cold and heat treatment increase the content of chlorophyll a, chlorophyll b, and carotenoids. Chilling correlated with higher content of soluble proteins in leaves, whereas the concentration of these osmoprotectants in roots was higher under both cold and heat stress. For all tested antioxidant enzymes, higher activity was measured in leaves, and activity was related to temperature stress. SOD, CAT, A-POX, and P-POX activities was induced under heat stress, while the higher activity of SOD, CAT, P-POX, and G-POX was recorded under cold stress, compared to the control. In addition to the induced activity of enzymatic components, the content of secondary metabolites including total phenolics, flavonoids, and total anthocyanins, was several times higher compared to the non-stressed plants. Furthermore, total phenolic content was higher in roots than in leaves. Significant positive correlation can be seen among photosynthetic pigments, SOD, total phenolics, and flavonoids under severe temperature stress (4 or 40 °C) in basil leaves, while for roots, positive correlation was found in the content of secondary metabolites and activity of CAT or peroxidases. Obtained results are discussed in terms of phenotyping of O. basilicum cv. ‘Genovese’ response to heat and chilling stress, which should contribute to a better understanding of merged responses to cold and heat tolerance of this valuable crop.
Physical Aging Behavior of a Glassy Polyether
Authors: Monnier Xavier , Marina Sara , Lopez de Pariza Xabier , Sardón Haritz , Martin Jaime , Cangialosi Daniele
Published: March 2021

The present work aims to provide insights on recent findings indicating the presence of multiple equilibration mechanisms in physical aging of glasses. To this aim, we have investigated a glass forming polyether, poly(1-4 cyclohexane di-methanol) (PCDM), by following the evolution of the enthalpic state during physical aging by fast scanning calorimetry (FSC). The main results of our study indicate that physical aging persists at temperatures way below the glass transition temperature and, in a narrow temperature range, is characterized by a two steps evolution of the enthalpic state. Altogether, our results indicate that the simple old-standing view of physical aging as triggered by the α relaxation does not hold true when aging is carried out deep in the glassy state.
Effects of Counter Anions on AC and DC Electrical Conductivity in Poly(Dimethylsiloxane) Crosslinked by Metal-Ligand Coordination
Authors: Wrzesińska Angelika , Wypych-Puszkarz Aleksandra , Bobowska Izabela , Ulański Jacek
Published: March 2021

There is an urgent need for the development of elastic dielectric materials for flexible organic field effect transistors (OFETs). In this work, detailed analysis of the AC and DC electrical conductivity of a series of flexible poly(dimethylsiloxane) (PDMS) polymers crosslinked by metal-ligand coordination in comparison to neat PDMS was performed for the first time by means of broadband dielectric spectroscopy. The ligand was 2,2-bipyridine-4,4-dicarboxylic amide, and Ni2+, Mn2+, and Zn2+ were introduced for Cl−, Br−, and I− salts. Introduction of metal salt and creation of coordination bonds resulted in higher permittivity values increasing in an order: neat PDMS < Ni2+ < Mn2+ < Zn2+; accompanied by conductivity values of the materials increasing in an order: neat PDMS < Cl− < I− < Br−. Conductivity relaxation time plot as a function of temperature, showed Vogel-Fulcher–Tammann dependance for the Br− salts and Arrhenius type for the Cl− and I− salts. Performed study revealed that double-edged challenge can be obtained, i.e., dielectric materials with elevated value of dielectric permittivity without deterioration too much the non-conductive nature of the polymer. This opens up new perspectives for the production of flexible dielectrics suitable for gate insulators in OFETs. Among the synthesized organometallic materials, those with chlorides salts are the most promising for such applications.
Thermochemical Mechanism of the Epoxy-Glutamic Acid Reaction with Sn-3.0 Ag-0.5 Cu Solder Powder for Electrical Joining
Authors: Choi Gwang-Mun , Jang Ki-Seok , Choi Kwang-Seong , Joo Jiho , Yun Ho-Gyeong , Lee Chanmi , Eom Yong-Sung
Published: March 2021

An epoxy-based solder paste (ESP) is a promising alternative to conventional solder pastes to improve the reliability of fine-pitch electrical joining because the epoxy encapsulates the solder joint. However, development of an appropriate epoxy formulation and investigation of its reaction mechanism with solder powder is challenging. In this study, we demonstrate a newly designed ESP consisting of diglycidyl ether of bisphenol F (DGEBF) resin, Sn-3.0 Ag-0.5 Cu (SAC305) solder powder, and L-glutamic acid (Glu), which is a proteinogenic amino acid for biosynthesis of proteins in living systems. The mechanism of the thermochemical reaction was explored and tentatively proposed, which reveals that the products of the reaction between SAC305 and Glu function as catalysts for the etherification of epoxides and alcohols produced by chemical bonding between DGEBF and Glu, consequently leading to highly crosslinked polymeric networks and an enhancement of impact resistance. Our findings provide further insight into the mechanism of the reaction between various formulations comprising an epoxy, amino acid, and solder powder, and their potential use as ESPs for electrical joining.
Adsorption of Cu(II) by Poly-γ-glutamate/Apatite Nanoparticles
Authors: Chen Kuo-Yu , Zeng Wei-Yu
Published: March 2021

Poly-γ-glutamate/apatite (PGA-AP) nanoparticles were prepared by chemical coprecipitation method in the presence of various concentrations of poly-γ-glutamate (γ-PGA). Powder X-ray diffraction pattern and energy-dispersive spectroscopy revealed that the main crystal phase of PGA-AP was hydroxyapatite. The immobilization of γ-PGA on PGA-AP was confirmed by Fourier transform infrared spectroscopy and the relative amount of γ-PGA incorporation into PGA-AP was determined by thermal gravimetric analysis. Dynamic light scattering measurements indicated that the particle size of PGA-AP nanoparticles increased remarkably with the decrease of γ-PGA content. The adsorption of aqueous Cu(II) onto the PGA-AP nanoparticles was investigated in batch experiments with varying contact time, solution pH and temperature. Results illustrated that the adsorption of Cu(II) was very rapid during the initial adsorption period. The adsorption capacity of PGA-AP nanoparticles for Cu(II) was increased with the increase in the γ-PGA content, solution pH and temperature. At a pH of 6 and 60 °C, a higher equilibrium adsorption capacity of about 74.80 mg/g was obtained. The kinetic studies indicated that Cu(II) adsorption onto PGA-AP nanoparticles obeyed well the pseudo-second order model. The Langmuir isotherm model was fitted well to the adsorption equilibrium data. The results indicated that the adsorption behavior of PGA-AP nanoparticles for Cu(II) was mainly a monolayer chemical adsorption process. The maximum adsorption capacity of PGA-AP nanoparticles was estimated to be 78.99 mg/g.
Steady and Oscillatory Shear Flow Behavior of Different Polysaccharides with Laponite®
Authors: Blanco-López Marcos , González-Garcinuño Álvaro , Tabernero Antonio , Martín del Valle Eva M.
Published: March 2021

The rheological behavior, in terms of steady and oscillatory shear flow, of Laponite® with different polysaccharides (alginate, chitosan, xanthan gum and levan) in salt-free solutions was studied. Results showed that a higher polymer concentration increased the zero-rate viscosity and decreased the critical strain rate (Cross model fit) as well as increasing the elastic and viscous moduli. Those properties (zero-rate viscosity and critical strain rate) can be a suitable indicator of the effect of the Laponite® on the shear flow behavior for the different solutions. Specifically, the effect of the Laponite® predominates for solutions with large critical strain rate and low zero-rate viscosity, modifying significantly the previous parameters and even the yield stress (if existing). On the other hand, larger higher polymeric concentration hinders the formation of the platelet structure, and polymer entanglement becomes predominant. Furthermore, the addition of high concentrations of Laponite® increases the elastic nature, but without modifying the typical mechanical spectra for polymeric solutions. Finally, Laponite® was added to (previously crosslinked) gels of alginate and chitosan, obtaining different results depending on the material. These results highlight the possibility of predicting qualitatively the impact of the Laponite® on different polymeric solutions depending on the solutions properties.
Review and Suggestion of Failure Theories in Voids Scenario for VARTM Processed Composite Materials
Authors: Dhimole Vivek Kumar , Serrao Pruthvi , Cho Chongdu
Published: March 2021

Fiber-reinforced composite structures are used in different applications due to their excellent strength to weight ratio. Due to cost and tool handling issues in conventional manufacturing processes, like resin transfer molding (RTM) and autoclave, vacuum-assisted resin transfer molding (VARTM) is the best choice among industries. VARTM is highly productive and cheap. However, the VARTM process produces complex, lightweight, and bulky structures, suitable for mass and cost-effective production, but the presence of voids and fiber misalignment in the final processed composite influences its strength. Voids are the primary defects, and they cannot be eliminated completely, so a design without considering void defects will entail unreliability. Many conventional failure theories were used for composite design but did not consider the effect of voids defects, thus creating misleading failure characteristics. Due to voids, stress and strain uncertainty affects failure mechanisms, such as microcrack, delamination, and fracture. That’s why a proper selection and understanding of failure theories is necessary. This review discusses previous conventional failure theories followed by work considering the void’s effect. Based on the review, a few prominent theories were suggested to estimate composite strength in the void scenario because they consider the effect of the voids through crack density, crack, or void modeling. These suggested theories were based on damage mechanics (discrete damage mechanics), fracture mechanics (virtual crack closure technique), and micromechanics (representative volume element). The suggested theories are well-established in finite element modeling (FEM), representing an effective time and money-saving tool in design strategy, with better early estimation to enhance current design practices’ effectiveness for composites. This paper gives an insight into choosing the failure theories for composites in the presence of voids, which are present in higher percentages in mass production and less-costly processes (VARTM).
Advances in Molecularly Imprinted Polymers Based Affinity Sensors (Review)
Authors: Ramanavicius Simonas , Jagminas Arunas , Ramanavicius Arunas
Published: March 2021

Recent challenges in biomedical diagnostics show that the development of rapid affinity sensors is very important issue. Therefore, in this review we are aiming to outline the most important directions of affinity sensors where polymer-based semiconducting materials are applied. Progress in formation and development of such materials is overviewed and discussed. Some applicability aspects of conducting polymers in the design of affinity sensors are presented. The main attention is focused on bioanalytical application of conducting polymers such as polypyrrole, polyaniline, polythiophene and poly(3,4-ethylenedioxythiophene) ortho-phenylenediamine. In addition, some other polymers and inorganic materials that are suitable for molecular imprinting technology are also overviewed. Polymerization techniques, which are the most suitable for the development of composite structures suitable for affinity sensors are presented. Analytical signal transduction methods applied in affinity sensors based on polymer-based semiconducting materials are discussed. In this review the most attention is focused on the development and application of molecularly imprinted polymer-based structures, which can replace antibodies, receptors, and many others expensive affinity reagents. The applicability of electrochromic polymers in affinity sensor design is envisaged. Sufficient biocompatibility of some conducting polymers enables to apply them as “stealth coatings” in the future implantable affinity-sensors. Some new perspectives and trends in analytical application of polymer-based semiconducting materials are highlighted.
Mechanical, Wear and Thermal Behavior of Polyethylene Blended with Graphite Treated in Ball Milling
Authors: Visco Annamaria , Grasso Antonio , Recca Giuseppe , Carbone Domenico Carmelo , Pistone Alessandro
Published: March 2021

Additive manufacturing, civil, and biomechanical applications are among the most important sectors, where the filler’s presence can significantly improve the quality of polymeric products blends. The high market demand of new low-cost material to be used as shock absorbers and mechanical joints arouses our curiosity to study a relatively common commercial polymer and filler. The possible improvement by blending high-density polyethylene (HDPE) and graphite was investigated for these sectors. To achieve this objective, we have prepared HDPE/graphite nanocomposites following mechanical treatment to understand which parameter provides the researched properties. As widely reported in the literature, milling treatment leads to the decrease of the particle size and the exfoliation of graphitic layers. Therefore, graphite has been previously treated with a ball mill for different times (1–16 h) to enhance its lubricating action. We checked an improvement in stiffness, yielding strength, thermal stability, and, in particularly, wear resistance that increased by 65% with respect to that of polyethylene (PE). A treatment time of eight hours in ball milling could be enough to give an appreciable improvement. The wear behavior of HDPE with treated graphite has not been deeply investigated so far, and it could be important because HDPE is considered a “carrier polymer” for different low-friction applications.
Development of Polyvinylidene Fluoride Membrane via Assembly of Tannic Acid and Polyvinylpyrrolidone for Filtration of Oil/Water Emulsion
Authors: Nawi Normi Izati Mat , Ong Amat Syasya , Bilad Muhammad Roil , Nordin Nik Abdul Hadi Md , Shamsuddin Norazanita , Prayogi Saiful , Narkkun Thanitporn , Faungnawakij Kajornsak
Published: March 2021

Wastewater containing oil/water emulsion has a serious ecological impact and threatens human health. The impact worsens as its volume increases. Oil/water emulsion needs to be treated before it is discharged or reused again for processing. A membrane-based process is considered attractive in effectively treating oil/water emulsion, but progress has been dampened by the membrane fouling issue. The objective of this study is to develop polyvinylidene fluoride (PVDF) membranes customized for oil/water emulsion separation by incorporating assembly of tannic acid (TA) and polyvinylpyrrolidone (PVP) in the polymer matrix. The results show that the assembly of TA/PVP complexation was achieved as observed from the change in colour during the phase inversion and as also proven from the characterization analyses. Incorporation of the TA/PVP assembly leads to enhanced surface hydrophilicity by lowering the contact angle from 82° to 47°. In situ assembly of the TA/PVP complex also leads to enhanced clean water permeability by a factor of four as a result of enhanced mean flow pore size from 0.2 to 0.9 µm. Owing to enhanced surface chemistry and structural advantages, the optimum hydrophilic PVDF/TA/PVP membrane poses permeability of 540.18 L/(m2 h bar) for oil/water emulsion filtration, three times higher than the pristine PVDF membrane used as the reference.
The Suitability of Methylene Blue Discoloration (MB Method) to Investigate the Fe0/MnO2 System
Authors: Cao Viet , Alyoussef Ghinwa , Gatcha-Bandjun Nadège , Gwenzi Willis , Noubactep Chicgoua
Published: March 2021

The typical time-dependent decrease of the iron corrosion rate is often difficult to consider while designing Fe0-based remediation systems. One of the most promising approaches is the amendment with manganese dioxide (Fe0/MnO2 system). The resulting system is a very complex one where characterization is challenging. The present communication uses methylene blue discoloration (MB method) to characterize the Fe0/MnO2 system. Shaken batch experiments (75 rpm) for 7 days were used. The initial MB concentration was 10 mg L−1 with the following mass loading: [MnO2] = 2.3 g L−1, [sand] = 45 g L−1, and 0 < [Fe0] (g L−1) ≤ 45. The following systems where investigated: Fe0, MnO2, sand, Fe0/MnO2, Fe0/sand, and Fe0/MnO2/sand. Results demonstrated that MB discoloration is influenced by the diffusive transport of MB from the solution to the aggregates at the bottom of the test-tubes. Results confirm the complexity of the Fe0/MnO2/sand system, while establishing that both MnO2 and sand improve the efficiency of Fe0/H2O systems in the long-term. The mechanisms of water decontamination by amending Fe0-based systems with MnO2 is demonstrated by the MB method.
Novel Numerical Spiking Neural P Systems with a Variable Consumption Strategy
Authors: Yin Xiu , Liu Xiyu , Sun Minghe , Ren Qianqian
Published: March 2021

A novel variant of NSN P systems, called numerical spiking neural P systems with a variable consumption strategy (NSNVC P systems), is proposed. Like the spiking rules consuming spikes in spiking neural P systems, NSNVC P systems introduce a variable consumption strategy by modifying the form of the production functions used in NSN P systems. Similar to the delay feature of the spiking rules, NSNVC P systems introduce a postponement feature into the production functions. The execution of the production functions in NSNVC P systems is controlled by two, i.e., polarization and threshold, conditions. Multiple synaptic channels are used to transmit the charges and the production values in NSNVC P systems. The proposed NSNVC P systems are a type of distributed parallel computing models with a directed graphical structure. The Turing universality of the proposed NSNVC P systems is proved as number generating/accepting devices. Detailed descriptions are provided for NSNVC P systems as number generating/accepting devices. In addition, a universal NSNVC P system with 66 neurons is constructed as a function computing device.
Effect of Alumina Additives on Mechanical and Fresh Properties of Self-Compacting Concrete: A Review
Authors: Shokravi Hoofar , Mohammadyan-Yasouj Seyed Esmaeil , Koloor Seyed Saeid Rahimian , Petrů Michal , Heidarrezaei Mahshid
Published: March 2021

Self-compacting concrete (SCC) has been increasingly used in the construction sector due to its favorable characteristics in improving various durability and rheology aspects of concrete such as deformability and segregation resistance. Recently, the studies on the application of nano-alumina (NA) produced from factory wastes have been significantly considered to enhancing the performance, and mechanical strength, of SCC. Many experimental works show that NA can be used in SCC with appropriate proportion to enjoy the benefits of improved microstructure, fresh and hardened properties, durability, and resistance to elevated temperature. However, a limited detailed review is available to particularly study using NA to improve the performance of SCC, so far. Hence, the present study is conducted to fill the existing gap of knowledge. In this study, the effect of using NA in improving rheological, mechanical parameters, and elevated temperature resistance of SCC is reviewed. This research summarized the studies in this area, which have been different from the previous researches, and provided a discussion on limitations, practical implications, and suggestions for future studies.
Cucumis melo Enhances Enalapril Mediated Cardioprotection in Rats with Isoprenaline Induced Myocardial Injury
Authors: Asdaq Syed Mohammed Basheeruddin , Venna Saidareddy , Mohzari Yahya , Alrashed Ahmed , Alajami Hamdan Najib , Aljohani Awad Othman , Mushtawi Abdullah Ali Al , Alenazy Majed Sultan , Alamer Rakan Fahad , Alanazi Abdulmajead Khalid , Nayeem Naira
Published: March 2021

This study sought to investigate the cardioprotective potency and interaction of muskmelon (Cucumis melo) with enalapril (ENA) against myocardial damage caused by acute and chronic isoprenaline (ISO) treatments in rats. In the acute model, 150 mg/kg (s.c) of ISO was administered for two consecutive days at the end of pretreatment with either ENA, muskmelon, or both in their respective groups. ISO was introduced into the chronic therapy of ENA/muskmelon/ENA + muskmelon groups during the last 10 days at 3 mg/kg. Muskmelon was tested at three doses (100, 200, and 500 mg/kg, p.o., 30 days), and one normal dose of ENA (10 mg/kg) was used. Blood samples were taken at the end of treatment, and the animals were sacrificed. Biochemical markers such as LDH and CK-MB, as well as antioxidant (superoxide dismutase (SOD) and catalases) and thiobarbituric acid reactive species (TBARS) were measured in both serum and heart tissue homogenate (HTH). To confirm the biochemical findings, histological slides of heart tissue were prepared. ISO administration induced an elevation in the amount of TBARS, which was increased in all groups in which it was administered. Prior treatment with muskmelon and ENA in animals resulted in a rise in biomarker activity in homogenated heart tissue and a decrease in serum. In terms of alleviating the abnormal conditions caused by ISO, the group given a high dose of muskmelon and combined therapy had the best outcomes. The activities of SOD and catalase were substantially higher in the treated classes. Histological findings showing the cytoprotective actions of the high dose of muskmelon and ENA have confirmed the biochemical outcomes of both models. It is therefore concluded that the high dose of muskmelon (500 mg/kg) has a promising cardioprotective potential that is improved more efficiently in the acute injury model in the presence of ENA.
Numerical Analysis of Hydrodynamic Loads on Passing and Moored Ships in Shallow Water
Authors: Park Ji-Yong , Nam Bo Woo , Kim Yonghwan
Published: March 2021

In this study, hydrodynamic interactions between passing and moored ships were studied by applying a time-domain numerical simulation method. The boundary value problem for a fluid domain was formulated based on a potential flow theory. A numerical method was developed based on a finite element method with an efficient re-mesh algorithm. Regarding the free-surface boundary conditions, both double-body and free-surface models were considered for examining the free-surface effect on the hydrodynamic forces due to the passing ship. First, numerical results were validated by comparison with the model test results of Kriebel et al. (2005), where generic Series 60 hulls were considered as the target model for the passing and moored ships. In addition, hydrodynamic pressure fields and force time-series were investigated to understand the passing ship problem. Second, a series of numerical simulations were performed to study the effects of the passing ship speed, separation distance, water depth, and relative vessel size, which were used to compare the peak values of hydrodynamic forces. The applicability and limitations of the double-body and free-surface models are discussed for predicting passing ship loads.