bluuebunny/crossref_metadata_2025 huggingface dataset:
Confidence Intervals for Assessing Non-Inferiority with Assay Sensitivity in a Three-Arm Trial with Normally Distributed Endpoints
Authors: Tang Niansheng , Liang Fan
Published: January 2022

Various approaches including hypothesis test and confidence interval (CI) construction have been proposed to assess non-inferiority and assay sensitivity via a known fraction or pre-specified margin in three-arm trials with continuous or discrete endpoints. However, there is little work done on the construction of the non-inferiority margin from historical data and simultaneous generalized CIs (SGCIs) in a three-arm trial with the normally distributed endpoints. Based on the generalized fiducial method and the square-and-add method, we propose two simultaneous CIs for assessing non-inferiority and assay sensitivity in a three-arm trial. For comparison, we also consider the Wald-type Bonferroni simultaneous CI and parametric bootstrap simultaneous CI. An algorithm for evaluating the optimal sample size for attaining the pre-specified power is given. Simulation studies are conducted to investigate the performance of the proposed CIs in terms of their empirical coverage probabilities. An example taken from the mildly asthmatic study is illustrated using the proposed simultaneous CIs. Empirical results show that the proposed generalized fiducial method and the square-and-add method behave better than other two compared CIs.
Study on Overlying Strata Movement and Surface Subsidence of Coal Workfaces with Karst Aquifer Water
Authors: Wang Yuliang , Wu Guiyi , Liu Yang , Cheng Zhanbo
Published: January 2022

The overlying strata layers of coal workfaces with karst aquifer water normally causes serious safety problems due to the precipitation, drainage and water inrush, such as a wide range and long term of surface subsidence. In this study, by taking 10,301 working faces of the Daojiao coal mine in Guizhou Province as the engineering background, the numerical model of water-bearing strata with fluid-solid coupling was established by using UDEC to illustrate the laws of overlying strata movement and surface subsidence. A theory model was proposed to calculate the surface settlement caused by the drainage of aquifer based on the principle of effective stress modified by the Biot coefficient αb. The results showed that the corresponding maximum value (0.72 m) and the range of the surface subsidence with the occurrence of karst aquifer water were larger than that of the overlying strata without karst aquifer water (e.g., the maximum value of surface subsidence with 0.1 m). Moreover, the surface subsidence caused by the drainage of aquifer accounted for 17.8% of the total surface subsidence caused by coal mining. According to the field monitoring of surface subsidence in 10,301 working faces, the maximum value was 0.74 m, which was highly consistent with the results of numerical simulation and theoretical analysis. It verified the accuracy and reliability of the numerical model and the theory model in this study.
Approaches to Efficiency Assessing of Regional Knowledge-Intensive Services Sector Development Using Data Envelopment Analysis
Authors: Firsova Anna , Chernyshova Galina , Tugusheva Ryasimya
Published: January 2022

The sector of knowledge-intensive services is one of the fastest-growing sectors in the present-day economy of knowledge, which explains the scientific interest in developing methods of its quantitative assessment. The object of the research is the development of new approaches to the mathematical modeling of the efficiency of the regional knowledge-intensive services sector, based on a distance function approach to assess productivity changes. An approach was proposed to analyze the efficiency of this sector using data envelopment analysis and Malmquist productivity index and its components. The article presents the results of the assessment of indicators characterizing the development of knowledge-intensive services in education, innovation, and ICT obtained from 80 Russian regions for the period 2010–2020. To perform the analysis, the following input variables were used: volume of investments in fixed assets in ICT; share of personnel employed in the ICT; share of internal expenditures on R&D in GRP; the number of personnel engaged in R&D; share of innovative-active organizations and registered patents; funding for higher education institutions; and the number of higher education institutions graduated. Output variables were number of used advanced production technologies in the region; share of innovative goods, works, and services in GRP, and use of the intellectual property. As a result of applying the data envelopment analysis, Malmquist productivity index and its components, data were obtained on the positive dynamics of the development of the knowledge-intensive services sector in Russian regions and conclusions were drawn about the sector’s growth sources due to economies of scale.
Bounds for Statistical Curvatures of Submanifolds in Kenmotsu-like Statistical Manifolds
Authors: Siddiqui Aliya Naaz , Siddiqi Mohd Danish , Alkhaldi Ali Hussain
Published: January 2022

In this article, we obtain certain bounds for statistical curvatures of submanifolds with any codimension of Kenmotsu-like statistical manifolds. In this context, we construct a class of optimum inequalities for submanifolds in Kenmotsu-like statistical manifolds containing the normalized scalar curvature and the generalized normalized Casorati curvatures. We also define the second fundamental form of those submanifolds that satisfy the equality condition. On Legendrian submanifolds of Kenmotsu-like statistical manifolds, we discuss a conjecture for Wintgen inequality. At the end, some immediate geometric consequences are stated.
Study on Mechanical Characteristics and Failure Modes of Coal–Mudstone Combined Body with Prefabricated Crack
Authors: Lv Huayong , Wang Defeng , Cheng Zhanbo , Zhang Yaning , Zhou Tao
Published: January 2022

There are normally pre-existing cracks that can be observed in the coal seam and immediate roof that influences the stability of the rib spalling and the movement law of overlying strata. In this study, comprehensive research methods (e.g., theory analysis, experimental tests and numerical simulations) were adopted to reveal the mechanical characteristics, acoustic emission behaviors and failure modes of a coal–mudstone combined body with a single prefabricated non-penetrating crack. The results show that the influence of the crack angle on the elastic modulus of the coal–mudstone combined body samples was limited. With the increase in the crack angle, the unconfined compressive strength of samples decreased first and then increased in a V-shaped trend. In addition, the minimum unconfined compressive strength could be observed at a crack angle of 45°. Moreover, the number of acoustic emissions significantly increased with the process of continuous loading. In addition, the stress reduction zone could be observed in both ends of the prefabricated cracks at the initial stage of loading. The high- and low-stress zones were transformed with the process of continuous loading. Under an unconfined compression test, the failure models of the coal body part in the samples were mainly caused by shear failure, and only a few cracks occurred in the upper tip of the prefabricated cracks of the mudstone part. Therefore, airfoil cracks could be observed in the samples due to the strength difference of the coal mass and mudstone.
Symbolic Computation Applied to Cauchy Type Singular Integrals
Authors: Conceição Ana C. , Pires Jéssica C.
Published: January 2022

The development of operator theory is stimulated by the need to solve problems emerging from several fields in mathematics and physics. At the present time, this theory has wide applications in the study of non-linear differential equations, in linear transport theory, in the theory of diffraction of acoustic and electromagnetic waves, in the theory of scattering and of inverse scattering, among others. In our work, we use the computer algebra system Mathematica to implement, for the first time on a computer, analytical algorithms developed by us and others within operator theory. The main goal of this paper is to present new operator theory algorithms related to Cauchy type singular integrals, defined in the unit circle. The design of these algorithms was focused on the possibility of implementing on a computer all the extensive symbolic and numeric calculations present in the algorithms. Several nontrivial examples computed with the algorithms are presented. The corresponding source code of the algorithms has been made available as a supplement to the online edition of this article.
Bacillimidazoles A−F, Imidazolium-Containing Compounds Isolated from a Marine Bacillus
Authors: Yan Jia-Xuan , Wu Qihao , Helfrich Eric J. N. , Chevrette Marc G. , Braun Doug R. , Heyman Heino , Ananiev Gene E. , Rajski Scott R. , Currie Cameron R. , Clardy Jon , Bugni Tim S.
Published: January 2022

Chemical investigations of a marine sponge-associated Bacillus revealed six new imidazolium-containing compounds, bacillimidazoles A–F (1–6). Previous reports of related imidazolium-containing natural products are rare. Initially unveiled by timsTOF (trapped ion mobility spectrometry) MS data, extensive HRMS and 1D and 2D NMR analyses enabled the structural elucidation of 1–6. In addition, a plausible biosynthetic pathway to bacillimidazoles is proposed based on isotopic labeling experiments and invokes the highly reactive glycolytic adduct 2,3-butanedione. Combined, the results of structure elucidation efforts, isotopic labeling studies and bioinformatics suggest that 1–6 result from a fascinating intersection of primary and secondary metabolic pathways in Bacillus sp. WMMC1349. Antimicrobial assays revealed that, of 1–6, only compound six displayed discernible antibacterial activity, despite the close structural similarities shared by all six natural products.
Interactions of Nereistoxin and Its Analogs with Vertebrate Nicotinic Acetylcholine Receptors and Molluscan ACh Binding Proteins
Authors: Kem William , Andrud Kristin , Bruno Galen , Xing Hong , Soti Ferenc , Talley Todd , Taylor Palmer
Published: January 2022

Nereistoxin (NTX) is a marine toxin isolated from an annelid worm that lives along the coasts of Japan. Its insecticidal properties were discovered decades ago and this stimulated the development of a variety of insecticides such as Cartap that are readily transformed into NTX. One unusual feature of NTX is that it is a small cyclic molecule that contains a disulfide bond. In spite of its size, it acts as an antagonist at insect and mammalian nicotinic acetylcholine receptors (nAChRs). The functional importance of the disulfide bond was assessed by determining the effects of inserting a methylene group between the two sulfur atoms, creating dimethylaminodithiane (DMA-DT). We also assessed the effect of methylating the NTX and DMA-DT dimethylamino groups on binding to three vertebrate nAChRs. Radioligand receptor binding experiments were carried out using washed membranes from rat brain and fish (Torpedo) electric organ; [3H]-cytisine displacement was used to assess binding to the predominantly high affinity alpha4beta2 nAChRs and [125I]-alpha-bungarotoxin displacement was used to measure binding of NTX and analogs to the alpha7 and skeletal muscle type nAChRs. While the two quaternary nitrogen analogs, relative to their respective tertiary amines, displayed lower α4β2 nAChR binding affinities, both displayed much higher affinities for the Torpedo muscle nAChR and rat alpha7 brain receptors than their respective tertiary amine forms. The binding affinities of DMA-DT for the three nAChRs were lower than those of NTX and MeNTX. An AChBP mutant lacking the C loop disulfide bond that would potentially react with the NTX disulfide bond displayed an NTX affinity very similar to the parent AChBP. Inhibition of [3H]-epibatidine binding to the AChBPs was not affected by exposure to NTX or MeNTX for up to 24 hr prior to addition of the radioligand. Thus, the disulfide bond of NTX is not required to react with the vicinal disulfide in the AChBP C loop for inhibition of [3H]-epibatidine binding. However, a reversible disulfide interchange reaction of NTX with nAChRs might still occur, especially under reducing conditions. Labeled MeNTX, because it can be readily prepared with high specific radioactivity and possesses relatively high affinity for the nAChR-rich Torpedo nAChR, would be a useful probe to detect and identify any nereistoxin adducts.
Mid-Term Outcomes of Laparoscopic Gastric Greater Curvature Plication versus Roux-en-Y Gastric Bypass: Weight Loss, Gastrointestinal Symptoms, and Health-Related Quality of Life
Authors: Gudaityte Rita , Kavaliauskaite Agne , Maleckas Almantas
Published: January 2022

Background and Objectives: Laparoscopic gastric greater curvature plication (LGGCP) is considered to be less invasive, technically simpler, and less costly. Few studies have compared LGGCP to gastric bypass. The aim of this prospective study was to evaluate the mid-term outcomes of LGGCP such as weight loss, gastrointestinal symptoms, and health-related quality of life (HRQoL) in comparison to laparoscopic Roux-en-Y gastric bypass (LRYGB). Materials and Methods: Between 2017 April and 2018 December, 112 patients were included in the study. Fifty patients had LGGCP, and sixty-two patients underwent LRYGB. Demographics, comorbidities, complications, percentage of excess body mass index loss (%EBMIL), gastrointestinal symptoms (GSRS questionnaire), and HRQoL (EQ-5D-3L questionnaire) were analysed. Gastrointestinal symptoms and HRQoL data are presented as the mean and median with the interquartile range (25th–75th percentile). Follow-up at 1 year and 3 year was performed. Results: The follow-up rate was 96.4% and 92.9%, 1 year and 3 year after surgery, respectively. Mean (SD) %EBMIL 1 year after surgery was 59.05 (25.34) in the LGGCP group and 82.40 (19.03) in the LRYGB group (p < 0.001) and 3 year after was 41.44 (26.74) and 75.59 (19.14), respectively (p < 0.001). The scores of all gastrointestinal symptoms measured by the GSRS questionnaire significantly decreased 3 year after both procedures, except reflux after LGGCP. Patients 3 year after LGGCP had a significantly lower abdominal pain score as compared to patients after LRYGB (1.01; 1.0 (1.0–1.0) and 1.20; 1.0 (1.0–1.33), respectively (p < 0.001); however, LGGCP resulted in significantly more GERD symptoms (1.79; 1.25 (1.0–2.5) and 1.18; 1.0 (1.0–1.0), respectively (p < 0.001)). Three years after surgery, the quality of life was significantly lower in the LGGCP group (0.762; 0.779 (0.690–0.794) and 0.898; 1.000 (0.783–1.000), respectively (p < 0.001)). Conclusions: Three years after surgery, LGGCP patients lost significantly less weight, had less abdominal pain and more reflux symptoms, and a lower quality of life as compared to LRYGB patients.
Personal and Social Consequences of Psychotropic Substance Use: A Population-Based Internet Survey
Authors: Ballestar-Tarín María Luisa , Ibáñez-del-Valle Vanessa , Cauli Omar , Navarro-Martínez Rut
Published: January 2022

Background and objectives: Drug abuse has become a major worldwide health concern among all age groups. The present study analyses substance misuse and its social and personal consequences using a population-based internet survey in Spain. Materials and Methods: Screening for drug abuse (of alcohol, marijuana/hashish and psychostimulants) and its related risks and problems was performed using the Car, Relax, Alone, Forget, Friends, Trouble (CRAFFT) score. Socio-demographic factors, depressive, anxiety and stress symptoms as well as health habits were also evaluated. We used Linear regression methods to compare each variable’s individual contribution so as to determine which one best explains the results. Results: In this population-based study, 1224 people completed and returned the online survey. Of all participants, 57% reported consuming at least one substance based on the CRAFFT scale. While increasing age reduces the probability of personal and social consequences of consumption, people who smoke receive up to three times more (OR = 3.370) recommendations from family and friends to reduce their consumption. As for the type of substance, the consumption of marijuana increases the risk of forgetting (OR = 2.33) and the consumption of other psychostimulant substances almost triples the risk of consuming alone (OR = 2.965). Combining substances can increase the rate of driving a vehicle after consumption by 3.4 times. Conclusions: Although age, smoking and the type of substances used increase the risk of suffering from social and personal consequences of the use or abuse of substances, future studies are needed to determine the influence of new variables as a potential tool for treating and minimizing the adverse consequences of drug abuse.
Light Transmission of Various Aesthetic Posts at Different Depths and Its Effect on Push-Out Bond Strength, Microhardness of Luting Cement
Authors: Haralur Satheesh B. , Alasmari Turki Abdullah , Alasmari Mohammed Hussin , Hakami Hafiz Mohammed
Published: January 2022

Background and Objectives: One requirement for the cemented post is the light transmittance on its entire length up to the deepest portion of a root canal to ensure the complete polymerization of resin cement. This study aimed to determine the light transmission ability in different aesthetic posts at different depths and its effect on the push-out bond strength and microhardness of luting cement at the corresponding interface. Materials and Methods: Twenty endodontic posts from glass fiber posts (GFP), zirconia ceramic posts (ZCP), and highly translucent zirconium oxide posts (HTZP) were sequentially sectioned into 12.8 and 4 mm lengths after recording the light intensity using a dental radiometer. Sixty single rooted premolar teeth root canals were treated and implanted vertically in a resin block. The post space was prepared and cemented with GFP, ZCP, and HTZP posts with twenty samples each. The root portion of teeth samples were sectioned into cervical, middle, and apical portion. A universal testing machine was utilized for the push-out bond strength test for the first ten samples from each group. The remaining ten samples from each group were used for the microhardness test using a micro-indenter instrument. The data were statistically analyzed using one-way Analysis of variance and Tukey HSD tests at p < 0.05. Results: The GFP endodontic postpresented with significant highest light translucency compared to HTZP, which was significantly higher than ZCP. GFP posts showed significantly higher bond strength per unit area compared to ZCP at analogous cross sections. The hardness of luting cement was also significantly higher amongst all tested endodontic posts. Conclusions: GFP high light translucency enhanced the curing of the luting resin cement that resulted in harder cement and a stronger bond supported by hardness and push-out tests. These findings suggest that GFP is preferred to be used with light-cured luting cements for restoration of endodontically treated teeth.
Challenges and Solutions for Musculoskeletal Disorders in Athletes
Authors: Iolascon Giovanni , Tarantino Umberto , Moretti Antimo
Published: January 2022

The etymology of the word “athlete” derives from the ancient Greek ἀθλητής (athletés, from âthlos that is, fight, competition) [...]
Comment on Ramos-Rincon et al. Palliative Sedation in COVID-19 End-of-Life Care. Retrospective Cohort Study. Medicina 2021, 57, 873
Authors: Twycross Robert Geoffrey , Wong Aaron Kee Yee , Vivat Bella
Published: January 2022

We read with interest the article by Ramos-Rincon and colleagues about patients with COVID-19 dying in acute medical wards in a Spanish University hospital [...]
Current Status and Future Therapeutic Options for Fecal Microbiota Transplantation
Authors: Tkach Sergii , Dorofeyev Andrii , Kuzenko Iurii , Boyko Nadiya , Falalyeyeva Tetyana , Boccuto Luigi , Scarpellini Emidio , Kobyliak Nazarii , Abenavoli Ludovico
Published: January 2022

The intestinal microbiota plays an important role in maintaining human health, and its alteration is now associated with the development of various gastrointestinal (ulcerative colitis, irritable bowel syndrome, constipation, etc.) and extraintestinal diseases, such as cancer, metabolic syndrome, neuropsychiatric diseases. In this context, it is not surprising that gut microbiota modification methods may constitute a therapy whose potential has not yet been fully investigated. In this regard, the most interesting method is thought to be fecal microbiota transplantation, which consists of the simultaneous replacement of the intestinal microbiota of a sick recipient with fecal material from a healthy donor. This review summarizes the most interesting findings on the application of fecal microbiota transplantation in gastrointestinal and extraintestinal pathologies.
Intravesical Therapy for Non-Muscle-Invasive Bladder Cancer: What Is the Real Impact of Squamous Cell Carcinoma Variant on Oncological Outcomes?
Authors: Mantica Guglielmo , Chierigo Francesco , Malinaric Rafaela , Smelzo Salvatore , Ambrosini Francesca , Beverini Martina , Guano Giovanni , Caviglia Alberto , Rigatti Lorenzo , De Rose Aldo Franco , Tafuri Alessandro , De Marchi Davide , Gaboardi Franco , Suardi Nazareno , Terrone Carlo
Published: January 2022

Background and Objectives: To evaluate the oncological impact of squamous cell carcinoma (SCC) variant in patients submitted to intravesical therapy for non-muscle-invasive bladder cancer (NMIBC). Materials and Methods: Between January 2015 and January 2020, patients with conventional urothelial NMIBC (TCC) or urothelial NMIBC with SCC variant (TCC + SCC) and submitted to adjuvant intravesical therapies were collected. Kaplan–Meier analyses targeted disease recurrence and progression. Uni- and multivariable Cox regression analyses were used to test the role of SCC on disease recurrence and/or progression. Results: A total of 32 patients out of 353 had SCC at diagnosis. Recurrence was observed in 42% of TCC and 44% of TCC + SCC patients (p = 0.88), while progression was observed in 12% of both TCC and TCC + SCC patients (p = 0.78). At multivariable Cox regression analyses, the presence of SCC variant was not associated with higher rates of neither recurrence (p = 0.663) nor progression (p = 0.582). Conclusions: We presented data from the largest series on patients with TCC and concomitant SCC histological variant managed with intravesical therapy (BCG or MMC). No significant differences were found in term of recurrence and progression between TCC and TCC + SCC. Despite the limited sample size, this study paves the way for a possible implementation of the use of intravesical BCG and MMC in NMIBC with histological variants.
Impact of Drug Pressure versus Limited Access to Drug in Malaria Control: The Dilemma
Authors: Egwu Chinedu , Obasi Nwogo , Aloke Chinyere , Nwafor Joseph , Tsamesidis Ioannis , Chukwu Jennifer , Elom Sunday
Published: January 2022

Malaria burden has severe impact on the world. Several arsenals, including the use of antimalarials, are in place to curb the malaria burden. However, the application of these antimalarials has two extremes, limited access to drug and drug pressure, which may have similar impact on malaria control, leading to treatment failure through divergent mechanisms. Limited access to drugs ensures that patients do not get the right doses of the antimalarials in order to have an effective plasma concentration to kill the malaria parasites, which leads to treatment failure and overall reduction in malaria control via increased transmission rate. On the other hand, drug pressure can lead to the selection of drug resistance phenotypes in a subpopulation of the malaria parasites as they mutate in order to adapt. This also leads to a reduction in malaria control. Addressing these extremes in antimalarial application can be essential in maintaining the relevance of the conventional antimalarials in winning the war against malaria.
The Potential Impact of Blood System on Dietary Habits and Smoking
Authors: Tsamesidis Ioannis , Stalika Evangelia , Egwu Chinedu , Pritsa Agathi , Parpori Maria , Gkinoudis Argyrios , Samara Diana , Lymperaki Evgenia
Published: January 2022

The ‘Blood-Type’ diet advises individuals to eat according to their ABO blood group to improve their health and decrease the risk of chronic diseases. However, the food preferences of individuals with different blood groups have not been examined. The aim of our study was to investigate, in healthy regular blood donors (rBDs), the associations of smoke, alcohol, caffeine, vitamin and fat intake with their different blood groups and if ABO groups could be a potential predictor tool for disease prevention. A total of 329 volunteers were divided into four groups according to their ABO types: Group 1 (A) comprised 141 rBDs; Group 2 (B), 65 rBDs; Group 3 (O), 96 rBDs; and Group 4, 27 rBDs. Additionally, they were divided into two groups according to their rhesus types and their preferences for smoke, too. Dietary intake was assessed using 3-day food recall and the Food Processor computer program for nutrient analysis. Alcohol, caffeine, sugar and Vitamin D consumption were significantly (p < 0.05) higher in the O group. The A group presented statistically significantly (p < 0.05) greater preferences for cholesterol intake and a higher trend for smoking (25%) habits compared with all the other groups, whereas Group B preferred more fatty foods. The blood group AB appeared to be the most controlled food intake group. Regarding the rhesus comparisons, alcohol; caffeine; and Vitamin C, D, E and K consumptions were significantly (p < 0.05) higher in rhesus-positive individuals than their rhesus-negative counterparts. For the non-smoker group, compared with the smokers, a higher consumption of Vitamin D and fibers was found. In conclusion, in the present study, statistically significant correlations of the ABO and rhesus system with some dietary parameters were found, indicating a consequent influence of these preferences on the progression of different diseases.
Removal of Emerging Contaminants from Wastewater Streams Using Membrane Bioreactors: A Review
Authors: Sengupta Arijit , Jebur Mahmood , Kamaz Mohanad , Wickramasinghe S. Ranil
Published: January 2022

Water is a very valuable natural resource. As the demand for water increases the presence of emerging contaminants in wastewater has become a growing concern. This is particularly true when one considers direct reuse of wastewater. Obtaining sufficient removal of emerging contaminants will require determining the level of removal for the various unit operations in the wastewater treatment process. Membrane bioreactors are attractive as they combine an activated sludge process with a membrane separation step. They are frequently used in a wastewater treatment process and can operate at higher solid loadings than conventional activated sludge processes. Determining the level of removal of emerging contaminants in the membrane bioreactor step is, therefore, of great interest. Removal of emerging contaminants could be by adsorption onto the biomass or membrane surface, biotransformation, size exclusion by the membrane, or volatilization. Given the fact that most emerging contaminants are low molecule weight non-volatile compounds, the latter two methods of removal are usually unimportant. However, biotransformation and adsorption onto the biomass are important mechanisms of removal. It will be important to determine if the microorganisms present at given treatment facility are able to remove ECs present in the wastewater.
Mass Transfer Characteristics of Haemofiltration Modules—Experiments and Modeling
Authors: Moschona Alexandra , Kostoglou Margaritis , Karabelas Anastasios J.
Published: January 2022

Reliable mathematical models are important tools for design/optimization of haemo-filtration modules. For a specific module, such a model requires knowledge of fluid- mechanical and mass transfer parameters, which have to be determined through experimental data representative of the usual countercurrent operation. Attempting to determine all these parameters, through measured/external flow-rates and pressures, combined with the inherent inaccuracies of pressure measurements, creates an ill-posed problem (as recently shown). The novel systematic methodology followed herein, demonstrated for Newtonian fluids, involves specially designed experiments, allowing first the independent reliable determination of fluid-mechanical parameters. In this paper, the method is further developed, to determine the complete mass transfer module-characteristics; i.e., the mass transfer problem is modelled/solved, employing the already fully-described flow field. Furthermore, the model is validated using new/detailed experimental data on concentration profiles of a typical solute (urea) in counter-current flow. A single intrinsic-parameter value (i.e., the unknown effective solute-diffusivity in the membrane) satisfactorily fits all data. Significant insights are also obtained regarding the relative contributions of convective and diffusive mass-transfer. This study completes the method for reliable module simulation in Newtonian-liquid flow and provides the basis for extension to plasma/blood haemofiltration, where account should be also taken of oncotic-pressure and membrane-fouling effects.
A Biofouling Resistant Zwitterionic Polysulfone Membrane Prepared by a Dual-Bath Procedure
Authors: Maggay Irish Valerie B. , Aini Hana Nur , Lagman Mary Madelaine G. , Tang Shuo-Hsi , Aquino Ruth R. , Chang Yung , Venault Antoine
Published: January 2022

This study introduces a zwitterionic material to modify polysulfone (PSf) membranes formed by a dual bath procedure, in view of reducing their fouling propensity. The zwitterionic copolymer, derived from a random polymer of styrene and 4-vinylpyrridine and referred to as zP(S-r-4VP), was incorporated to the PSf solution without any supplementary pore-forming additive to study the effect of the sole copolymer on membrane-structuring, chemical, and arising properties. XPS and mapping FT-IR provided evidence of the modification. Macrovoids appeared and then disappeared as the copolymer content increased in the range 1–4 wt%. The copolymer has hydrophilic units and its addition increases the casting solution viscosity. Both effects play an opposite role on transfers, and so on the growth of macrovoids. Biofouling tests demonstrated the efficiency of the copolymer to mitigate biofouling with a reduction in bacterial and blood cell attachment by more than 85%. Filtration tests revealed that the permeability increased by a twofold factor, the flux recovery ratio was augmented from 40% to 63% after water/BSA cycles, and irreversible fouling was reduced by 1/3. Although improvements are needed, these zwitterionic PSf membranes could be used in biomedical applications where resistance to biofouling by cells is a requirement.
Endogenous Nitric Oxide-Releasing Microgel Coating Prevents Clot Formation on Oxygenator Fibers Exposed to In Vitro Blood Flow
Authors: Winnersbach Patrick , Hosseinnejad Aisa , Breuer Thomas , Fechter Tamara , Jakob Felix , Schwaneberg Ulrich , Rossaint Rolf , Bleilevens Christian , Singh Smriti
Published: January 2022

Background: Clot formation on foreign surfaces of extracorporeal membrane oxygenation systems is a frequent event. Herein, we show an approach that mimics the enzymatic process of endogenous nitric oxide (NO) release on the oxygenator membrane via a biomimetic, non-fouling microgel coating to spatiotemporally inhibit the platelet (PLT) activation and improve antithrombotic properties. This study aims to evaluate the potential of this biomimetic coating towards NO-mediated PLT inhibition and thereby the reduction of clot formation under flow conditions. Methods: Microgel-coated (NOrel) or bare (Control) poly(4-methyl pentene) (PMP) fibers were inserted into a test channel and exposed to a short-term continuous flow of human blood. The analysis included high-resolution PLT count, pooled PLT activation via β-Thromboglobulin (β-TG) and the visualization of remnants and clots on the fibers using scanning electron microscopy (SEM). Results: In the Control group, PLT count was significantly decreased, and β-TG concentration was significantly elevated in comparison to the NOrel group. Macroscopic and microscopic visualization showed dense layers of stable clots on the bare PMP fibers, in contrast to minimal deposition of fibrin networks on the coated fibers. Conclusion: Endogenously NO-releasing microgel coating inhibits the PLT activation and reduces the clot formation on PMP fibers under dynamic flow.
Cobalt-Doped Carbon Nitride Frameworks Obtained from Calcined Aromatic Polyimines as Cathode Catalyst of Anion Exchange Membrane Fuel Cells
Authors: Hsieh Tar-Hwa , Chen Sin-Nan , Wang Yen-Zen , Ho Ko-Shan , Chuang Jung-Kuan , Ho Lin-Chia
Published: January 2022

Cobalt-doped carbon nitride frameworks (CoNC) were prepared from the calcination of Co-chelated aromatic polyimines (APIM) synthesized from stepwise polymerization of p-phenylene diamine (PDA) and o-phthalaldehyde (OPAl) via Schiff base reactions in the presence of cobalt (II) chloride. The Co-chelated APIM (Co-APIM) precursor converted to CoNC after calcination in two-step heating with the second step performed at 100 °C lower than the first one. The CoNCs demonstrated that its Co, N-co-doped carbonaceous framework contained both graphene and carbon nanotube, as characterized by X-ray diffraction pattern, Raman spectra, and TEM micropictures. CoNCs also revealed a significant ORR peak in the current–voltage polarization cycle and a higher O2 reduction current than that of commercial Pt/C in a linear scanning voltage test in O2-saturated KOH(aq). The calculated e-transferred number even reaches 3.94 in KOH(aq) for the CoNC1000A900 cathode catalyst, which has the highest BET surface area of 393.94 m2 g−1. Single cells of anion exchange membrane fuel cells (AEMFCs) are fabricated using different CoNCs as the cathode catalysts, and CoNC1000A900 demonstrates a peak power density of 374.3 compared to the 334.7 mW cm−2 obtained from the single cell using Pt/C as the cathode catalyst.
On the Potential of Gallium- and Indium-Based Liquid Metal Membranes for Hydrogen Separation
Authors: Rosseau Leon R. S. , Medrano José A. , Bhardwaj Rajat , Goetheer Earl L. V. , Filot Ivo A. W. , Gallucci Fausto , van Sint Annaland Martin
Published: January 2022

The concept of liquid metal membranes for hydrogen separation, based on gallium or indium, was recently introduced as an alternative to conventional palladium-based membranes. The potential of this class of gas separation materials was mainly attributed to the promise of higher hydrogen diffusivity. The postulated improvements are only beneficial to the flux if diffusion through the membrane is the rate-determining step in the permeation sequence. Whilst this is a valid assumption for hydrogen transport through palladium-based membranes, the relatively low adsorption energy of hydrogen on both liquid metals suggests that other phenomena may be relevant. In the current study, a microkinetic modeling approach is used to enable simulations based on a five-step permeation mechanism. The calculation results show that for the liquid metal membranes, the flux is limited by the dissociative adsorption over a large temperature range, and that the membrane flux is expected to be orders of magnitude lower compared to the membrane flux through pure palladium membranes. Even when accounting for the lower cost of the liquid metals compared to palladium, the latter still outperforms both gallium and indium in all realistic scenarios, in part due to the practical difficulties associated with making liquid metal thin films.
Effects of Graphene on the Wear and Corrosion Resistance of Micro-Arc Oxidation Coating on a Titanium Alloy
Authors: Zhang Ruifang , Lv Kai , Du Zhaoxin , Chen Weidong , Ji Pengfei , Wang Mingli
Published: January 2022

In order to improve the wear and corrosion resistance of micro-arc oxidation (MAO) coating on a Ti-5Al-1V-1Sn-1Zr-0.8Mo alloy, 0–0.20 g/L graphene was added to the electrolyte to prepare micro-arc oxidation coating. The thickness, roughness, micro-morphology, and composition of the MAO coating were characterized, and the wear and corrosion resistance of the coating was tested and analyzed. The results show that with 0.05 g/L of graphene in the electrolyte, the roughness of the coating decreased from 56.76 μm to 31.81 μm. With the increase in the addition of graphene, the microstructure of the coating became more compact, the diameter of micro-holes and micro-cracks decreased, and the corrosion resistance of the coating improved. The wear tests showed that the mass loss of the coating at the early wear stage (0~100 revolutions) was greater than that at the later stage (100~250 revolutions), and the wear resistance of the coating obtained by the addition of 0.10 g/L of graphene was the highest. With 0.10 g/L of graphene, the adhesion force between the coating and the substrate alloy is the largest, reaching 57.1 N, which is 9.98 N higher than that without graphene. After salt spray corrosion for 480 h, the coating with graphene has better corrosion resistance than that of a graphene-free coating.
Mixed Oxides NiO/ZnO/Al2O3 Synthesized in a Single Step via Ultrasonic Spray Pyrolysis (USP) Method
Authors: Yeşiltepe Özcelik Duygu , Ebin Burçak , Stopic Srecko , Gürmen Sebahattin , Friedrich Bernd
Published: January 2022

Mixed oxides have received remarkable attention due to the many opportunities to adjust their interesting structural, electrical, catalytic properties, leading to a better, more useful performance compared to the basic metal oxides. In this study, mixed oxides NiO/ZnO/Al2O3 were synthesized in a single step via the ultrasonic spray pyrolysis method using nitrate salts, and the temperature effects of the process were investigated (400, 600, 800 °C). The synthesized samples were characterized by means of scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction and Raman spectroscopy analyses. The results showed Al2O3, NiO–Al2O3 and ZnO–Al2O3 systems with spinel phases. Furthermore, the Raman peaks supported the coexistence of oxide phases, which strongly impact the overall properties of nanocomposite.
Stress Corrosion Analysis and Direct Cell Viability of Biodegradable Zn-Fe-Ca Alloy in In-Vitro Conditions
Authors: Avior Orit , Ben Ghedalia-Peled Noa , Ron Tomer , Goldman Jeremy , Vago Razi , Aghion Eli
Published: January 2022

Due to the excellent biocompatibility of Zn and Zn-based alloys, researchers have shown great interest in developing biodegradable implants based on zinc. Furthermore, zinc is an essential component of many enzymes and proteins. The human body requires ~15 mg of Zn per day, and there is minimal concern for systemic toxicity from a small zinc-based cardiovascular implant, such as an arterial stent. However, biodegradable Zn-based implants have been shown to provoke local fibrous encapsulation reactions that may isolate the implant from its surrounding environment and interfere with implant function. The development of biodegradable implants made from Zn-Fe-Ca alloy was designed to overcome the problem of fibrous encapsulation. In a previous study made by the authors, the Zn-Fe-Ca system demonstrated a suitable corrosion rate that was higher than that of pure Zn and Zn-Fe alloy. The Zn-Fe-Ca system also showed adequate mechanical properties and a unique microstructure that contained a secondary Ca-reach phase. This has raised the promise that the tested alloy could serve as a biodegradable implant metal. The present study was conducted to further evaluate this promising Zn alloy. Here, we assessed the material’s corrosion performance in terms of cyclic potentiodynamic polarization analysis and stress corrosion behavior in terms of slow strain rate testing (SSRT). We also assessed the ability of cells to survive on the alloy surface by direct cell culture test. The results indicate that the alloy develops pitting corrosion, but not stress corrosion under phosphate-buffered saline (PBS) and air environment. The direct cell viability test demonstrates the successful adherence and growth of cells on the alloy surface.
Effect of Magnesium Addition and High Energy Processing on the Degradation Behavior of Iron Powder in Modified Hanks’ Solution for Bioabsorbable Implant Applications
Authors: Estrada Rafael G. , Multigner Marta , Lieblich Marcela , Fajardo Santiago , Rams Joaquín
Published: January 2022

This paper shows the results of applying a combination of high energy processing and magnesium (Mg) as an alloying element in a strategy for enhancing the degradation rate of iron (Fe) for applications in the field of non-permanent medical implants. For this purpose, Fe powder was milled with 5 wt% of Mg (Fe5Mg) and its microstructure and characterized degradation behavior. As-received Fe powder was also milled in order to distinguish between the effects due to high energy processing from those due to the presence of Mg. The powders were prepared by high energy planetary ball milling for 16 h. The results show that the initial crystallite size diminishes from >150 nm to 16 nm for Fe and 46 nm for Fe5Mg. Static degradation tests of loose powder particles were performed in Hanks’ solution. Visual inspection of the immersed powders and the X-ray diffraction (XRD) phase quantification indicate that Fe5Mg exhibited the highest degradation rate followed by milled Fe and as received Fe, in this order. The analysis of degradation products of Fe5Mg showed that they consist on magnesium ferrite and pyroaurite, which are known to present good biocompatibility and low toxicity. Differences in structural features and degradation behaviors of milled Fe and milled Fe5Mg suggest the effective dissolution of Mg in the Fe lattice. Based on the obtained results, it can be said that Fe5Mg powder would be a suitable candidate for non-permanent medical implants with a higher degradation rate than Fe.
The Microstructure and Mechanical Properties of Ferritic-Martensitic Steel EP-823 after High-Temperature Thermomechanical Treatment
Authors: Litovchenko Igor , Almaeva Kseniya , Polekhina Nadezhda , Akkuzin Sergey , Linnik Valeria , Moskvichev Evgeny , Chernov Vyacheslav , Leontyeva-Smirnova Maria
Published: January 2022

The effect of high-temperature thermomechanical treatment (HTMT) with plastic deformation by rolling in austenitic region on the microstructure and mechanical properties of 12% chromium ferritic-martensitic steel EP-823 is investigated. The features of the grain and defect microstructure of steel are studied by Scanning Electron Microscopy with Electron Back-Scatter Diffraction (SEM EBSD) and Transmission Electron Microscopy (TEM). It is shown that HTMT leads to the formation of pancake structure with grains extended in the rolling direction and flattened in the rolling plane. The average sizes of martensitic packets and ferrite grains are approximately 1.5–2 times smaller compared to the corresponding values after traditional heat treatment (THT, which consists of normalization and tempering). The maximum grain size in the section parallel to the rolling plane increases up to more than 80 µm. HTMT leads to the formation of new sub-boundaries and a higher dislocation density. The fraction of low-angle misorientation boundaries reaches up to ≈68%, which exceeds the corresponding value after HTMT (55%). HTMT does not practically affect the carbide subsystem of steel. The mechanical properties are investigated by tensile tests in the temperature range 20–700 °C. It is shown that the values of the yield strength in this temperature range after HTMT increase relative to the corresponding values after THT. As a result of HTMT, the elongation decreases. A significant decrease is observed in the area of dynamic strain aging (DSA). The mechanisms of plastic deformation and strengthening of ferritic-martensitic steel under the high-temperature thermomechanical treatments are also discussed.
The Effect of Ultraviolet Treatment on TiO2 Nanotubes: A Study of Surface Characteristics, Bacterial Adhesion, and Gingival Fibroblast Response
Authors: Kobayashi Masahiko , Abdulmajeed Aous A. , Moon Jongyun , Shahramian Khalil , Punkkinen Risto , Shimada Jun , Vallittu Pekka K. , Lassila Lippo V.
Published: January 2022

Titanium dioxide (TiO2) nanotubes are emerging as a provocative target for oral implant research. The aim of this study was to evaluate the effect of UV on the wettability behavior, bacterial colonization, and fibroblast proliferation rate of TiO2 nanotube surfaces prepared using different anodization voltages and aimed for use as implant abutment materials. Four different experimental materials were prepared: (1) TiO2 nanotube 10 V; (2) TiO2 nanotube 15 V; (3) TiO2 nanotube 20 V; and (4) commercial pure titanium as a control group. TiO2 nanotube arrays were prepared in an aqueous electrolyte solution of hydrofluoric acid (HF, 0.5 vol.%). Different anodization voltages were used to modify the morphology of the TiO2 nanotubes. Equilibrium contact angles were measured using the sessile drop method with a contact angle meter. The investigated surfaces (n = 3) were incubated at 37 °C in a suspension of Streptococcus mutans (S. mutans) for 30 min for bacterial adhesion and 3 days for biofilm formation. Human gingival fibroblasts were plated and cultured on the experimental substrates for up to 7 days and the cell proliferation rate was assessed using the AlamarBlue assayTM (BioSource International, Camarillo, CA, USA). The data were analyzed using one-way ANOVA followed by Tukey’s post-hoc test. Water contact angle measurements on the TiO2 after UV treatment showed an overall hydrophilic behavior regardless of the anodization voltage. The ranking of the UV-treated surfaces of experimental groups from lowest to highest for bacterial adhesion was: TiO2 nanotube 20 V < Ti and TiO2 nanotube 15 V < TiO2 nanotube 10 V (p < 0.05), and for bacterial biofilm formation was: TiO2 nanotube 20 V-TiO2 nanotube 10 V < Ti-TiO2 nanotube 15 V (p < 0.05). Fibroblast cell proliferation was lower on TiO2 nanotube surfaces throughout the incubation period and UV light treatment showed no enhancement in cellular response. UV treatment enhances the wettability behavior of TiO2 nanotube surfaces and could result in lower bacterial adhesion and biofilm formation.
Process Parameter Optimization in Metal Laser-Based Powder Bed Fusion Using Image Processing and Statistical Analyses
Authors: Ahsan Faiyaz , Razmi Jafar , Ladani Leila
Published: January 2022

The powder bed fusion additive manufacturing process has received widespread interest because of its capability to manufacture components with a complicated design and better surface finish compared to other additive techniques. Process optimization to obtain high quality parts is still a concern, which is impeding the full-scale production of materials. Therefore, it is of paramount importance to identify the best combination of process parameters that produces parts with the least defects and best features. This work focuses on gaining useful information about several features of the bead area, such as contact angle, porosity, voids, melt pool size and keyhole that were achieved using several combinations of laser power and scan speed to produce single scan lines. These features are identified and quantified using process learning, which is then used to conduct a comprehensive statistical analysis that allows to estimate the effect of the process parameters, such as laser power and scan speed on the output features. Both single and multi-response analyses are applied to analyze the response parameters, such as contact angle, porosity and melt pool size individually as well as in a collective manner. Laser power has been observed to have a more influential effect on all the features. A multi-response analysis showed that 150 W of laser power and 200 mm/s produced a bead with the best possible features.