bluuebunny/crossref_metadata_2025 huggingface dataset:
Plasma Levels of Apelinergic System Components in Patients with Chronic and Acute Coronary Syndromes—A Pilot Study
Authors: Diakowska Dorota , Wyderka Rafal , Krzystek-Korpacka Małgorzata , Osuch Łukasz , Leśków Anna , Sołtowska Alicja , Stanek Marta , Rosińczuk Joanna , Jaroch Joanna
Published: September 2021

The effects of the apelinergic system components apelin (AP) and elabela (ELA) in the regulation of human cardiovascular homeostasis, and data concerning the relationship between ELA and AP and coronary artery disease (CAD) are yet unknown. The aim of the study was the evaluation of AP, ELA and APJ-receptor levels in the plasma of patients with chronic coronary syndromes (CCS) and acute coronary syndromes (ACS). The study group consisted of 114 patients with CAD and 33 healthy controls. Patients were divided into two groups: with CCS (n = 30) and ACS (n = 84). Routine laboratory tests and plasma ELA, AP-17, AP-13 and APJ receptor levels were measured. Echocardiographic data were analyzed in all patients. Levels of AP-17 and ELA were significantly lower in CCS than in healthy controls and ACS patients. We demonstrated significant increase of levels of plasma apelinergic system peptides, especially ELA and AP-17 in ACS patients compared with healthy controls and CCS, suggestive of compensating up-regulation mechanisms. There is a relationship between circulating ELA and AP-17 levels and classical, biochemical markers of ischemia and left ventricular ejection faction as well.
Predictors of Treatment Requirements in Women with Gestational Diabetes: A Retrospective Analysis
Authors: Weschenfelder Friederike , Lohse Karolin , Lehmann Thomas , Schleußner Ekkehard , Groten Tanja
Published: September 2021

The diagnosis of gestational diabetes is usually very stressful for pregnant women, especially because they fear that insulin treatment may become necessary. Knowledge about personal risk factors predicting the probability of insulin treatment could therefore help to improve acceptance of the diagnosis and therapy adherence. The aim of this study was to find potential risk factors for insulin dependency and treatment requirements using information available at the time of diagnosis of gestational diabetes during pregnancy. We included 454 singleton pregnancies diagnosed ≥24 weeks of gestation. Multivariate regression analysis was used to evaluate independent associations of metabolic, anthropometric and fetal ultrasound parameters with the general need for insulin treatment and further stratified treatment options: diet (n = 275), bolus insulin only (n = 45), basal insulin only (n = 73) and multiple daily injections (n = 61). Receiver operator characteristics and cut-off values for independent variables were generated. Treatment groups differed significantly concerning pre-pregnancy weight and BMI as well as fasting glucose and 1 h glucose test values. Significant cut-offs for insulin dependency were HbA1c level of 5.4%, FPG of 5.5 mmol/L and 1 h glucose of 10.6 mmol/L. At time of diagnosis, certain patient characteristics and measurements can help to predict treatment necessities and therefore improve individualized counselling.
Evidence-Based Practices and Use among Employees and Students at an Austrian Medical University
Authors: Haluza Daniela , Jungwirth David , Gahbauer Susanne
Published: September 2021

Developed in the pre-internet era in the early 1980s, empirical medical practice, i.e., evidence-based practice (EBP) has become crucial in critical thinking and statistical reasoning at the point-of-care. As little evidence is available so far on how EBP is perceived in the Austrian academic context, we conducted a cross-sectional online survey among a nonrandom purposive sample of employees and students at the Medical University Vienna, Austria (total n = 1247, 59.8% females). The German questionnaire assessed both EBP capability beliefs and EBP use, with the respective indices both yielding good internal consistency. We conducted subgroup comparisons between employees (n = 638) and students (n = 609). In line with Bandura’s self-efficacy theory, we found a correlation between EBP capability beliefs and EBP use, with higher scores reported in the employee group. The results indicated that the participants did not strictly follow the sequential EBP steps as grounded in the item-response theory. Since its emergence, EBP has struggled to overcome the dominating traditional way of conducting medicine, which is also known as eminence-based medicine, where ad hoc decisions are based upon expert opinions, and nowadays frequently supplemented by quick online searches. Medical staff and supervisors of medical students should be aware of the existing overlaps and synergies of these potentially equivalent factors in clinical care. There is a need for intensifying the public and scientific debate on how to deal with the divergence between EBP theory and EBP practice.
A Systematic Review of the Cyclooxygenase-2 (COX-2) Expression in Rectal Cancer Patients Treated with Preoperative Radiotherapy or Radiochemotherapy
Authors: Berbecka Monika , Forma Alicja , Baj Jacek , Furtak-Niczyporuk Marzena , Maciejewski Ryszard , Sitarz Robert
Published: September 2021

The main objective of this systematic review is to investigate the expression level of the cyclooxygenase-2 (COX-2) in rectal cancer treated with either preoperative radiotherapy or radiochemotherapy. In addition, we have summarized the effects of preoperative treatment of rectal cancer with regards to the expression levels of COX-2. A systematic literature review was performed in The Cochrane Library, PubMed, Web of Science, and Scopus databases on 1 January 2021 with the usage of the following search string—(cyclooxygenase-2) OR (COX-2) AND (rectal cancer) AND (preoperative radiochemotherapy) OR (preoperative radiotherapy). Among the 176 included in the analysis, only 13 studies were included for data extraction with a total number of 2095 patients. The results of the analysis are based on the articles concerning the expression of COX-2 in rectal cancer among patients treated with preoperative radiotherapy or radiochemotherapy. A COX-2 expression is an early event involved in rectal cancer development. In cases of negative COX-2 expression, radiotherapy and radiochemotherapy might contribute to the reduction of a local recurrence. Therefore, COX-2 may be considered as a biologic factor while selecting patients for more effective, less time-consuming and less expensive preoperative treatment. However, the utility of the administration of COX-2 inhibitors to patients with COX-2 overexpression, in an attempt to improve the patients’ response rate to the neoadjuvant treatment, needs an assessment in further clinical trials.
Neutrophil-to-Lymphocyte Ratio as a Factor Predicting Radiotherapy Induced Oral Mucositis in Head Neck Cancer Patients Treated with Radiotherapy
Authors: Homa-Mlak Iwona , Brzozowska Anna , Mlak Radosław , Szudy-Szczyrek Aneta , Małecka-Massalska Teresa
Published: September 2021

Background: The objective of this research conducted in head and neck cancer (HNC) patients was the assessment of the relationship between neutrophil-to-lymphocyte ratio (NLR) and the incidence of severe radiotherapy (RT) induced oral mucositis (OM), as well as overall survival (OS). Methods: The study involved 207 patients in advanced stages (III–IV) of HNC. RTOG/EORTC scale was used to assess OM. The pre-treatment NLR was specified as the absolute neutrophil count divided by the absolute lymphocyte count. Results: Starting from second to seventh week of RT, we observed a significant, positive correlation between NLR values and OM grade. From the second to seventh week of RT, higher NLR values were related with significant increases (from 2- to over 24-fold) in the risk of occurrence of more severe OM (multivariate analysis confirmed its independent influence). Moreover, multivariate analysis for survival revealed that both higher TNM stage (HR = 1.84; p = 0.0043) and higher NLR values (HR = 1.48; p = 0.0395) were independent prognostic factors. Conclusion: NLR is a simple and accurate parameter that is useful in the evaluation of the risk of more severe OM, as well as an independent prognostic factor of OS in patients subjected to RT due to HNC.
Effect of Ce Content on Properties of Al-Ce-Based Composites by Powder-in-Tube Method
Authors: Vázquez Mairym , Suárez Oscar Marcelo , Thompson Michael , Jang Haneul , Gong Na , Weiss David , Rios Orlando
Published: September 2021

Al-Ce based alloys have gained recent interest and have proven to have excellent strength without heat treatment and high thermal stability. Challenges with the production of Al-Ce samples from elemental powders arise due to the elemental material before alloying being susceptible to rapid oxidation. The methodology for making superconductive wire, powder-in-tube, was used as a consolidate Al and Ce elemental powder, and Al-8 wt % Ce-10 wt % Mg composite powder into bulk nanostructured material. Powder samples are fabricated in an inert controlled atmosphere, then sealed in a tube to avoid oxidation of powders. Therefore, most of the powder is used without much loss. We used 316 stainless-steel tubes as a sheathing material. For Al-xCe wt % (x = 8 to 14) samples of elemental powder, liquid phase sintering was used and for Al-Ce-Mg powder solid-state sintering. Characterization of the bulk consolidated material after sintering, and before and after heat treatment, was made using optical and Scanning Electron Microscope imaging, Energy Dispersive Spectroscopy, Microhardness and Rockwell Hardness test. We demonstrated that microstructure stability in Al-Ce-based specimens can be retained after thermomechanical processing. Densification was achieved and oxidation of powder was avoided in most samples. In addition, we found that Fe and Ni in the sheathing material react with Al in the process, and Ce concentration modifies the reactivity the sheath.
Influence of the Shape of Gear Wheel Bodies in Marine Engines on the Gearing Deformation and Meshing Stiffness
Authors: Maláková Silvia , Puškár Michal , Frankovský Peter , Sivák Samuel , Harachová Daniela
Published: September 2021

The basic properties of gears must be considered: the shape of their gearing, their load capacity, and the meshing stiffness, which affects the noise and vibration. When designing large gears, it is important to choose the correct shape of the gear body. Large gears used in marine gearboxes must be designed with as little weight as possible. The requirements of sufficient stiffness of the gear wheel body, as well as the meshing stiffness, must be met. This paper is devoted to the influence of spur gear wheel body parameters on gearing deformation and meshing stiffness. The stiffness of the gear is solved on the basis of the deformation of the gearing teeth, which is determined by the finite element method. Examples of the simulation and subsequent processing of results demonstrates how the individual parameters of the gear wheel body influence the stiffness of the gearing teeth. At the same time, the results point to designs of suitable shape and dimensions to achieve the required stiffness of the gearing teeth, but with the lowest possible weight of the spur gear wheel body.
1D–3D Coupling Algorithm of Gas Flow for the Valve System in a Compression Ignition Engine
Authors: Kong Kyeong-Ju
Published: September 2021

Emission control devices such as selective catalytic reduction (SCR), exhaust gas recirculation (EGR), and scrubbers were installed in the compression ignition (CI) engine, and flow analysis of intake air and exhaust gas was required to predict the performance of the CI engine and emission control devices. In order to analyze such gas flow, it was inefficient to comprehensively analyze the engine’s cylinder and intake/exhaust systems because it takes a lot of computation time. Therefore, there is a need for a method that can quickly calculate the gas flow of the CI engine in order to shorten the development process of emission control devices. It can be efficient and quickly calculated if only the parts that require detailed observation among the intake/exhaust gas flow of the CI engine are analyzed in a 3D approach and the rest are analyzed in a 1D approach. In this study, an algorithm for gas flow analysis was developed by coupling 1D and 3D in the valve systems and comparing with experimental results for validation. Analyzing the intake/exhaust gas flow of the CI engine in a 3D approach took about 7 days for computation, but using the developed 1D–3D coupling algorithm, it could be computed within 30 min. Compared with the experimental results, the exhaust pipe pressure occurred an error within 1.80%, confirming the accuracy and it was possible to observe the detailed flow by showing the contour results for the part analyzed in the 3D zone. As a result, it was possible to accurately and quickly calculate the gas flow of the CI engine using the 1D–3D coupling algorithm applied to the valve system, and it was expected that it can be used to shorten the process for analyzing emission control devices, including predicting the performance of the CI engine.
Identification of Promising Antifungal Drugs against Scedosporium and Lomentospora Species after Screening of Pathogen Box Library
Authors: Rollin-Pinheiro Rodrigo , Borba-Santos Luana Pereira , da Silva Xisto Mariana Ingrid Dutra , de Castro-Almeida Yuri , Rochetti Victor Pereira , Rozental Sonia , Barreto-Bergter Eliana
Published: September 2021

Fungal infections have been increasing during the last decades. Scedosporium and Lomentospora species are filamentous fungi most associated to those infections, especially in immunocompromised patients. Considering the limited options of treatment and the emergence of resistant isolates, an increasing concern motivates the development of new therapeutic alternatives. In this context, the present study screened the Pathogen Box library to identify compounds with antifungal activity against Scedosporium and Lomentospora. Using antifungal susceptibility tests, biofilm analysis, scanning electron microscopy (SEM), and synergism assay, auranofin and iodoquinol were found to present promising repurposing applications. Both compounds were active against different Scedosporium and Lomentospora, including planktonic cells and biofilm. SEM revealed morphological alterations and synergism analysis showed that both drugs present positive interactions with voriconazole, fluconazole, and caspofungin. These data suggest that auranofin and iodoquinol are promising compounds to be studied as repurposing approaches against scedosporiosis and lomentosporiosis.
Uncertainty, Anxiety and Isolation: Experiencing the COVID-19 Pandemic and Lockdown as a Woman with Polycystic Ovary Syndrome (PCOS)
Authors: Atkinson Lou , Kite Chris , McGregor Gordon , James Tamsin , Clark Cain C. T. , Randeva Harpal S. , Kyrou Ioannis
Published: September 2021

Background: The COVID-19 pandemic and the related lockdown measures presented a significant risk to physical and mental wellbeing in affected populations. Women with polycystic ovary syndrome (PCOS) are predisposed to several cardio-metabolic risk factors which increase the susceptibility to severe COVID-19 and also exhibit increased likelihood of impaired mental health wellbeing. Therefore, these women who usually receive care from multiple primary and specialist healthcare services may be disproportionately impacted by this pandemic and the related restrictions. This study aimed to explore the lived experience of the first UK national lockdown as a woman with PCOS. Methods: As part of a larger cross-sectional study, 12 women with PCOS living in the UK during the first national COVID-19 lockdown were recruited to a qualitative study. Telephone interviews were conducted in June/July of 2020, and data collected were subjected to thematic analysis. Results: Five themes were identified. “My PCOS Journey” describes participants’ experiences of diagnosis, treatment and ongoing management of their PCOS. “Living Through Lockdown” describes the overall experience and impact of the lockdown on all aspects of participants’ lives. “Self-care and Managing Symptoms” describe multiple challenges to living well with PCOS during the lockdown, including lack of access to supplies and services, and disruption to weight management. “Healthcare on Hold” describes the uncertainty and anxiety associated with delays in accessing specialised healthcare for a range of PCOS aspects, including fertility treatment. “Exacerbating Existing Issues” captures the worsening of pre-existing mental health issues, and an increase in health anxiety and feelings of isolation. Conclusion: For the women with PCOS in this study, the COVID-19 pandemic and the first national lockdown was mostly experienced as adding to the pre-existing challenges of living with their condition. The mental health impact experienced by the study participants was increased due to lack of access to their normal support strategies, limitations on healthcare services and uncertainty about their risk of COVID-19.
Comparative Assessment of Robotic versus Classical Physical Therapy Using Muscle Strength and Ranges of Motion Testing in Neurological Diseases
Authors: Major Zoltán Zsigmond , Vaida Calin , Major Kinga Andrea , Tucan Paul , Brusturean Emanuela , Gherman Bogdan , Birlescu Iosif , Craciunaș Raul , Ulinici Ionut , Simori Gábor , Banica Alexandru , Pop Nicoleta , Burz Alin , Carbone Giuseppe , Pisla Doina
Published: September 2021

The use of robotic systems in physical rehabilitation protocols has become increasingly attractive and has been given more focus in the last decade as a result of the high prevalence of motor deficits in the population, which is linked to an overburdened healthcare system. In accordance with current trends, three robotic devices have been designed, called ParReEx Elbow, ParReEx Wrist, and ASPIRE, which were designed to improve upper-limb medical recovery (shoulder, elbow, forearm, and wrist). The three automated systems were tested in a hospital setting with 23 patients (12 men and 11 women) suffering from motor deficits caused by various neurological diseases such as stroke, Parkinson’s disease, and amyotrophic lateral sclerosis (ALS). The patients were divided into three groups based on their pathology (vascular, extrapyramidal, and neuromuscular). Objective clinical measures, such as the Medical Research Council (MRC) scale, goniometry, and dynamometry, were used to compare pre- and post-rehabilitation assessments for both robotic-aided and manual physical rehabilitation therapy. The results of these tests showed that, with the exception of a few minor differences in muscular strength recovery, the robotic-assisted rehabilitation methods performed equally as well as the manual techniques, though only minor improvements were validated during short-term rehabilitation. The greatest achievements were obtained in the goniometric analysis where some rehabilitation amplitudes increased by over 40% in the vascular group, but the same analysis returned regressions in the neuromuscular group. The MRC scale analysis returned no significant differences, with most regressions occurring in the neuromuscular group. The dynamometric analysis mostly returned improvements, but the highest value evolution was 19.07%, which also in the vascular group. While the results were encouraging, more research is needed with a larger sample size and a longer study period in order to provide more information regarding the efficacy of both rehabilitation methods in neurological illnesses.
Serotonin after β-Adrenoreceptors’ Exposition: New Approaches for Personalized Data in Breast Cancer Cells
Authors: Correia Ana Salomé , Duarte Diana , Silva Isabel , Reguengo Henrique , Oliveira José Carlos , Vale Nuno
Published: September 2021

Serotonin is an important monoamine in the human body, playing crucial roles, such as a neurotransmitter in the central nervous system. Previously, our group reported that β-adrenergic drugs (ICI 118,551, isoprenaline, and propranolol) influence the proliferation of breast cancer cells (MCF-7 cells) and their inherent production of adrenaline. Thus, we aimed to investigate the production of serotonin in MCF-7 cells, clarifying if there is a relationship between this production and the viability of the cells. To address this question, briefly, we treated the MCF-7 cells with ICI 118,551, isoprenaline, and propranolol, and evaluated cellular viability and serotonin production by using MTT, Sulforhodamine B (SRB) and Neutral Red (NR) assays, and HPLC-ECD analysis, respectively. Our results demonstrate that isoprenaline promotes the most pronounced endogenous synthesis of serotonin, about 3.5-fold greater than control cells. Propranolol treatment also increased the synthesis of serotonin (when compared to control). On the other hand, treatment with the drug ICI 118,551 promoted a lower endogenous synthesis of serotonin, about 1.1-fold less than what was observed in the control. Together, these results reveal that MCF-7 cells can produce serotonin, and the drugs propranolol, isoprenaline and ICI 118,551 influence this endogenous production. For the first time, after modulation of the β-adrenergic system, a pronounced cellular growth can be related to higher consumption of serotonin by the cells, resulting in decreased levels of serotonin in cell media, indicative of the importance of serotonin in the growth of MCF-7 cells.
Graphical Trajectory Comparison to Identify Errors in Data of COVID-19: A Cross-Country Analysis
Authors: Yao Lan , Dong Wei , Wan Jim Y. , Howard Scott C. , Li Minghui , Graff Joyce Carolyn
Published: September 2021

Data from the early stage of a novel infectious disease outbreak provide vital information in risk assessment, prediction, and precise disease management. Since the first reported case of COVID-19, the pattern of the novel coronavirus transmission in Wuhan has become the interest of researchers in epidemiology and public health. To thoroughly map the mechanism of viral spreading, we used the patterns of data at the early onset of COVID-19 from seven countries to estimate the time lag between peak days of cases and deaths. This study compared these data with those of Wuhan and estimated the natural history of disease across the infected population and the time lag. The findings suggest that comparative analyses of data from different regions and countries reveal the differences between peaks of cases and deaths caused by COVID-19 and the incomplete and underestimated cases in Wuhan. Different countries may show different patterns of cases peak days, deaths peak days, and peak periods. Error in the early COVID-19 statistics in Brazil was identified. This study provides sound evidence for policymakers to understand the local circumstances in diagnosing the health of a population and propose precise and timely public health interventions to control and prevent infectious diseases.
Patient-Specific Instrument Guided Double Chevron-Cut Distal Femur Osteotomy
Authors: Huang Yen-Chun , Chen Kuan-Jung , Lin Kuan-Yu , Lee Oscar Kuang-Sheng , Yang Jesse Chieh-Szu
Published: September 2021

The risk of non-union and prolonged periods of protected weight-bearing still remain unsolved issues after distal femur osteotomy (DFO). To improve the stability, we developed the double chevron-cut technique, which is a modified medial closing-wedge DFO guided by a patient-specific instrument. The purpose of this study was to investigate the feasibility and outcome of this operative approach. Twenty-five knees in twenty-three consecutive patients with genu valgum and lateral compartment osteoarthritis that received double chevron-cut DFO were included. The target of correction was 50% on the weight-bearing line (WBL) ratio. Patient-reported outcomes included the Oxford Knee Score (OKS) and the 2011 Knee Society Score (KSS). The mean of the WBL ratio was corrected from 78.7% ± 12.0% to 48.7% ± 2.9% postoperatively. The mean time to full weight bearing was 3.7 ± 1.4 weeks. Union of the osteotomy was achieved at 11.3 ± 2.8 weeks. At a mean follow-up of 17 months, the OKS improved from a mean of 27.6 ± 11.7 to 39.1 ± 7.5 (p = 0.03), and the KSS from a mean of 92.1 ± 13.0 to 143.9 ± 10.2 (p < 0.001). Three patients developed complications, including one case of peri-implant fracture, one of loss of fixation, and one of non-union. The double chevron-cut DFO followed by immediate weight-bearing as tolerated is effective in treating genu valgum deformity and associated lateral compartment osteoarthritis.
Impact of Improved Corporate Governance and Regulations on Earnings Management Practices—Analysis of 7 Industries from the Indian National Stock Exchange
Authors: Thoppan Jose Joy , Nathan Robert Jeyakumar , Victor Vijay
Published: September 2021

This study investigates discretionary earnings management practices, tracing the changes over the years in selected top performing and highly liquid listed Indian firms. It empirically measures the impact of corporate governance, financial legislation and global reporting standards on the firms’ earnings management practices. The study analyses a sample of 712 firm-year data comprising 89 listed Indian companies across 7 different sectoral indices of the National Stock Exchange of India (NSE) over 8 years (2011–2018). The Modified Jones model was used to compute Discretionary Accruals to measure Earnings Management based on data obtained using Bloomberg terminals. Statistical results and plots generated in Stata offer evidence that instances of earnings management have significantly reduced after the enactment of the Companies Act 2013 and the adoption of Indian Accounting standards which are converged with the IFRS. Findings suggest that services firms are engaging in relatively higher levels of earnings management compared to manufacturing firms. This study reveals the positive impact of improved corporate governance, regulation, and enforcement by significantly reducing the levels of earnings management among listed firms in India.
Succession as a Risk Process in the Survival of a Family Business—Case of Slovakia
Authors: Rumanko Boris , Lušňáková Zuzana , Moravanská Monika , Šajbidorová Mária
Published: September 2021

Generational transfer is a risky point in the life cycle of any family business, and thus the succession process should not be underestimated. Family businesses in Slovakia began to appear after 1989, and therefore many of them await the process of generational exchange in the coming years. For this reason, research on generational exchange has been limited. The aim of this paper was to evaluate the attitude of the owners of Slovak family businesses to the succession process and to reveal the key factors that positively or negatively affect this process. A semi-structured interview was selected as a tool for data collection, in which 74 family business owners took part. The findings were evaluated by the text mining method and afterwards transferred to a scatter diagram in concepts. Based on the clusters in the scatter plot, we revealed the key factors that the current owners consider to be a risk in successfully managing generational exchange. We found that only 48.64% of owners started the succession process, which proves the importance of solving the problem in Slovakia.
Surface Topography Analysis of Mg-Based Composites with Different Nanoparticle Contents Disintegrated Using Abrasive Water Jet
Authors: Mardi Kumari Bimla , Dixit Amit Rai , Pramanik Alokesh , Hvizdos Pavol , Mallick Ashis , Nag Akash , Hloch Sergej
Published: September 2021

This study investigated the effect of abrasive water jet kinematic parameters, such as jet traverse speed and water pressure, on the surface of magnesium-based metal matrix nanocomposites (Mg-MMNCs) reinforced with 50 nm (average particle size) Al2O3 particles at concentrations of 0.66 and 1.11 wt.%. The extent of grooving caused by abrasive particles and irregularities in the abrasive waterjet machined surface with respect to traverse speed (20, 40, 250 and 500 mm/min), abrasive flow rate (200 and 300 g/min) and water pressure (100 and 400 MPa) was investigated using surface topography measurements. The results helped to identify the mode of material disintegration during the process. The nanoindentation results show that material softening was decreased in nanocomposites with higher reinforcement content due to the presence of a sufficient amount of nanoparticles (1.11 wt.%), which protected the surface from damage. The values of selected surface roughness profile parameters—average roughness (Ra), maximum height of peak (Rp) and maximum depth of valleys (Rv)—reveal a comparatively smooth surface finish in composites reinforced with 1.11 wt.% at a traverse speed of 500 mm/min. Moreover, abrasive waterjet machining at high water pressure (400 MPa) produced better surface quality due to sufficient material removal and effective cleaning of debris from the machining zone as compared to a low water pressure (100 MPa), low traverse speed (5 mm/min) and low abrasive mass flow rate (200 g/min).
Electrical Resistivity of Cu and Au at High Pressure above 5 GPa: Implications for the Constant Electrical Resistivity Theory along the Melting Curve of the Simple Metals
Authors: Ezenwa Innocent C. , Yoshino Takashi
Published: September 2021

The electrical resistivity of solid and liquid Cu and Au were measured at high pressures from 6 up to 12 GPa and temperatures ∼150 K above melting. The resistivity of the metals was also measured as a function of pressure at room temperature. Their resistivity decreased and increased with increasing pressure and temperature, respectively. With increasing pressure at room temperature, we observed a sharp reduction in the magnitude of resistivity at ∼4 GPa in both metals. In comparison with 1 atm data and relatively lower pressure data from previous studies, our measured temperature-dependent resistivity in the solid and liquid states show a similar trend. The observed melting temperatures at various fixed pressure are in reasonable agreement with previous experimental and theoretical studies. Along the melting curve, the present study found the resistivity to be constant within the range of our investigated pressure (6–12 GPa) in agreement with the theoretical prediction. Our results indicate that the invariant resistivity theory could apply to the simple metals but at higher pressure above 5 GPa. These results were discussed in terms of the saturation of the dominant nuclear screening effect caused by the increasing difference in energy level between the Fermi level and the d-band with increasing pressure.
The Use of Copper Oxides as Cross-Linking Substances for Chloroprene Rubber and Study of the Vulcanizates Properties. Part I
Authors: Kobędza Piotr , Smejda-Krzewicka Aleksandra , Strzelec Krzysztof
Published: September 2021

The purpose of this work was to verify the ability to cross-link the chloroprene rubber (CR) by using copper oxides: copper(I) oxide or copper(II) oxide. The use of copper oxides arises from the need to limit the application of ZnO as a cross-linking agent of CR. The obtained results indicate that CR compositions cross-linked with copper oxides are characterized by good mechanical properties and a high cross-linking degree. The results show that the type and the amount of copper oxides influence the cross-linking of the CR and the properties of the vulcanizates. For compositions containing copper(II) oxide, the properties are linearly dependent on the amount of CuO. Such a relationship is difficult to notice in the case of the use of copper(I) oxide—when analyzing individual parameters, the best results are obtained for different samples. Infrared spectroscopy (IR) studies confirmed the possibility of cross-linking of chloroprene rubber with copper oxides. This is evidenced by the characteristic changes in the intensity of the bands. Structural changes in the material during heating were determined by the thermal analysis—differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Regardless of the type and amount of copper oxide, all compositions exhibit similar characteristics, and there are no significant changes in the glass transition temperature of the material.
Effect of Loading Angles and Implant Lengths on the Static and Fatigue Fractures of Dental Implants
Authors: Sun Fei , Lv Li-Tao , Cheng Wei , Zhang Jia-Le , Ba De-Chun , Song Gui-Qiu , Lin Zeng
Published: September 2021

Mechanical properties play a key role in the failure of dental implants. Dental implants require fatigue life testing before clinical application, but this process takes a lot of time. This study investigated the effect of various loading angles and implant lengths on the static fracture and fatigue life of dental implants. Implants with lengths of 9 mm and 11 mm were prepared. Static fracture tests and dynamic fatigue life tests were performed under three loading angles (30°, 40°, and 50°), and the level arm and bending moment were measured. After that, the fracture morphology and fracture mode of the implant were observed. The results showed that 9 mm length implants have a higher static failure load and can withstand greater bending moments, while 11 mm length implants have a longer fatigue life. In addition, as the loading angle increases, the static strength and bending moment decrease linearly, and the fatigue life shows an exponential decrease at a rate of three times. Increasing the loading angle reduces the time of the implant fatigue test, which may be an effective method to improve the efficiency of the experiment.
Humidity-Sensing Properties of an 1D Antiferromagnetic Oxalate-Bridged Coordination Polymer of Iron(III) and Its Temperature-Induced Structural Flexibility
Authors: Burazer Sanja , Molčanov Krešimir , Šantić Ana , Klaser Teodoro , Wenger Emmanuel , Pajić Damir , Jagličić Zvonko , Popović Jasminka , Jurić Marijana
Published: September 2021

A novel one-dimensional (1D) oxalate-bridged coordination polymer of iron(III), {[NH(CH3)(C2H5)2][FeCl2(C2O4)]}n (1), exhibits remarkable humidity-sensing properties and very high proton conductivity at room temperature (2.70 × 10−4 (Ω·cm)−1 at 298 K under 93% relative humidity), in addition to the independent antiferromagnetic spin chains of iron(III) ions bridged by oxalate groups (J = −7.58(9) cm−1). Moreover, the time-dependent measurements show that 1 could maintain a stable proton conductivity for at least 12 h. Charge transport and magnetic properties were investigated by impedance spectroscopy and magnetization measurements, respectively. Compound 1 consists of infinite anionic zig-zag chains [FeCl2(C2O4)]nn− and interposed diethylmethylammonium cations (C2H5)2(CH3)NH+, which act as hydrogen bond donors toward carbonyl oxygen atoms. Extraordinarily, the studied coordination polymer exhibits two reversible phase transitions: from the high-temperature phase HT to the mid-temperature phase MT at T ~213 K and from the mid-temperature phase MT to the low-temperature phase LT at T ~120 K, as revealed by in situ powder and single-crystal X-ray diffraction. All three polymorphs show large linear thermal expansion coefficients.
Structures, Bonding and Sensor Properties of Some Alkaline o-Phthalatocuprates
Authors: Gladnev Sergey V. , Grigoryev Mikhail V. , Kryukova Mariya A. , Khairullina Evgenia M. , Tumkin Ilya I. , Bogachev Nikita A. , Mereshchenko Andrey S. , Skripkin Mikhail Y.
Published: September 2021

Comprehensive study of the structure and bonding of disodium, dipotassium and diammonium di-o-phthalatocuprates(II) dihydrates has been undertaken. The crystal structure of ammonium o-phthalatocuprate has been determined. The identity of structures of phthalatocuprate chains in potassium and ammonium salts has been revealed. Vibrational spectra of all three compounds have been recorded, and the assignment of vibrational bands has been made. Force field calculations have shown a minor effect of outer-sphere cations (Na+, K+, NH4+) on both intraligand (C-O) and metal–ligand bond strengths. Synthesized compounds have been tested as electrochemical sensors on D-glucose, dopamine and paracetamol. Their sensitivity to analytes varied in the order of Na+ > K+ > NH4+. This effect has been explained by the more pronounced steric hindrance of copper ions in potassium and ammonium salts.
Modeling and Optimization of Cut Quality Responses in Plasma Jet Cutting of Aluminium Alloy EN AW-5083
Authors: Peko Ivan , Marić Dejan , Nedić Bogdan , Samardžić Ivan
Published: September 2021

The plasma jet cutting process has a high potential for the machining of aluminium and its alloys. Aluminium is well known as a highly thermally conductive and sensitive material, and because of that there exist uncertainties in defining process parameters values that lead to the best possible cut quality characteristics. Due to that, comprehensive analysis of process responses as well as defining optimal cutting conditions is necessary. In this study, the effects of three main process parameters—cutting speed, arc current, and cutting height—on the cut quality responses: top kerf width, bevel angle, surface roughness Ra, Rz, and material removal rate were analyzed. Experimentations were conducted on aluminium EN AW-5083. In order to model relations between input parameters and process responses and to conduct their optimization, a novel hybrid approach of response surface methodology (RSM) combined with desirability analysis was presented. Prediction accuracy of developed responses regression models was proved by comparison between experimental and predicted data. Significance of process parameters and their interactions was checked by analysis of variance (ANOVA). Desirability analysis was found as an effective way to conduct multi-response optimization and to define optimal cutting area. Due to its simplicity, the novel presented approach was demonstrated as a useful tool to predict and optimize cut quality responses in plasma jet cutting process of aluminium alloy.
Finite Model Analysis and Practical Design Equations of Circular Concrete-Filled Steel Tube Columns Subjected to Compression-Torsion Load
Authors: Gong Yongzhi , Ding Faxing , Wang Liping , Huang Borong , Shan Yingjie , Lyu Fei
Published: September 2021

The objective of this study is to investigate the mechanical properties and the composite action of circular concrete-filled steel tube (CFST) columns subjected to compression-torsion load using finite element model analysis. Load–strain (T–γ) curves, normal stress, shear stress, and the composite action between the steel tubes and the interior concrete were analyzed based on the verified 3D finite element models. The results indicate that with the increase of axial force, the maximum shear stress at the core concrete increased significantly, and the maximum shear stress of the steel tubes gradually decreased. Meanwhile, the torsional bearing capacity of the column increased at first and then decreased. The torque share in the columns changed from the tube-sharing domain to the concrete-sharing domain, while the axial force of the steel tube remained unchanged. Practical design equations for the torsional capacity of axially loaded circular CFST columns were proposed based on the parametric analysis. The accuracy and validity of the proposed equations were verified against the collected experimental results.
Processing and Thermal Conductivity of Bulk Nanocrystalline Aluminum Nitride
Authors: Duarte Matthew A. , Mishra Vivek , Dames Chris , Kodera Yasuhiro , Garay Javier E.
Published: September 2021

Producing bulk AlN with grain sizes in the nano regime and measuring its thermal conductivity is an important milestone in the development of materials for high energy optical applications. We present the synthesis and subsequent densification of nano-AlN powder to produce bulk nanocrystalline AlN. The nanopowder is synthesized by converting transition alumina (δ-Al2O3) with <40 nm grain size to AlN using a carbon free reduction/nitridation process. We consolidated the nano-AlN powder using current activated pressure assisted densification (CAPAD) and achieved a relative density of 98% at 1300 °C with average grain size, d¯~125 nm. By contrast, high quality commercially available AlN powder yields densities ~75% under the same CAPAD conditions. We used the 3-ω method to measure the thermal conductivity, κ of two nanocrystalline samples, 91% dense, d¯ = 110 nm and 99% dense, d¯ = 220 nm, respectively. The dense sample with 220 nm grains has a measured κ = 43 W/(m·K) at room temperature, which is relatively high for a nanocrystalline ceramic, but still low compared to single crystal and large grain sized polycrystalline AlN which can exceed 300 W/(m·K). The reduction in κ in both samples is understood as a combination of grain boundary scattering and porosity effects. We believe that these are finest d¯ reported in bulk dense AlN and is the first report of thermal conductivity for AlN with ≤220 nm grain size. The obtained κ values are higher than the vast majority of conventional optical materials, demonstrating the advantage of AlN for high-energy optical applications.
Laser Heating Study of the High-Temperature Interactions in Nanograined Uranium Carbides
Authors: Chowdhury Sanjib , Manara Dario , Dieste-Blanco Oliver , Robba Davide , Gonçalves António Pereira
Published: September 2021

Nanograined nuclear materials are expected to have a better performance as spallation targets and nuclear fuels than conventional materials, but many basic properties of these materials are still unknown. The present work aims to contribute to their better understanding by studying the effect of grain size on the melting and solid–solid transitions of nanograined UC2−y. We laser-heated 4 nm–10 nm grain size samples with UC2−y as the main phase (but containing graphite and UO2 as impurities) under inert gas to temperatures above 3000 K, and their behavior was studied by thermal radiance spectroscopy. The UC2−y solidification point (2713(30) K) and α-UC2 to β-UC2 solid–solid transition temperature (2038(10) K) were observed to remain unchanged when compared to bulk crystalline materials with micrometer grain sizes. After melting, the composite grain size persisted at the nanoscale, from around 10 nm to 20 nm, pointing to an effective role of carbon in preventing the rapid diffusion of uranium and grain growth.
Research on the Effect of Desert Sand on Pore Structure of Fiber Reinforced Mortar Based on X-CT Technology
Authors: Shi Fangying , Li Tianyu , Wang Weikang , Liu Ruidan , Liu Xiaoyan , Tian Huiwen , Liu Nazhen
Published: September 2021

Concrete is a multi-phase, porous system. The pore structure has an important influence on the properties of the concrete. In this paper, a kind of fiber reinforced mortar was prepared with desert sand and its pore structure was studied. The MIP technique was used to investigate the pore structure characteristics between 1 nm and 500 μm (in diameter). Meanwhile, the μX-CT technique was used to study the pore structure characteristics above 200 μm. It was found that the total porosity tends to decrease first and then increase as the dosage of desert sand increased. The porosity decreased gradually from the upper to bottom area inside the sample, and the diameter of the air voids near the upper area became larger. After curing for 28 days, the compressive strength of fiber reinforced mortar reached the maximum when the content of desert sand was 50%. In conclusion, the appropriate amount of desert sand can reduce the porosity of the fiber reinforced mortar to some extent and the number of large size air voids can be significantly reduced, which improves the pore structure and the mechanical properties of the fiber reinforced mortar.
Basalt/Glass Fiber Polypropylene Hybrid Composites: Mechanical Properties at Different Temperatures and under Cyclic Loading and Micromechanical Modelling
Authors: Kufel Anna , Para Slawomir , Kuciel Stanisław
Published: September 2021

Basalt/glass fiber polypropylene hybrid composites were developed as subjects of investigation, with the aim to characterize their properties. An injection molding machine was used to produce the test samples. The following three different tests, at various specimen temperatures, were conducted: tensile test, three-point flexural test, and Charpy impact test. To determine fatigue behavior, the samples were uniaxially loaded and unloaded. Mechanical hysteresis loops were recorded and the dissipation energy of each loop was calculated. To determine the adhesion and dispersion between the fibers and the matrix, the fractured surfaces of the various specimens, after the tensile test, were investigated using a scanning electron microscope. The results show that the production of a composite with both basalt and glass fibers, in a polypropylene matrix with maleic anhydride-grafted polypropylene, can be successfully achieved. The addition of the two types of fibers increased the tensile strength by 306% and the tensile modulus by 333% for a composition, with 20% by weight, of fibers. The material properties were estimated with the help of a simulation software, and validated with a FEA. A satisfactory correlation between the simulation and measurement data was achieved. The error lays in a range of 2% between the maximum stress values. At a lower strain (up to 0.02), the stress values are very well matched.
Evolution of Microstructure, Texture and Mechanical Properties for Multilayered Al Matrix Composites by Accumulative Roll Bonding
Authors: Wang Wen-Jing , Yung Kam-Chuen , Tang An-Dong , Choy Hang-Shan , Lv Zheng
Published: September 2021

Carbon nanotubes (CNTs) reinforced aluminum matrix nanocomposites were fabricated by Accumulative Roll Bonding (ARB). The surface morphologies, mechanical properties, grains texture and orientation of the Al/CNTs nanocomposites were characterized, and the mechanisms and influences of CNTs contents and ARB cycles on the mechanical performance and grain textures of Al/CNTs were investigated and revealed. The strength of the composites rose with increase of the CNTs content, and the ARB cycles showed a 26% improvement when the CNTs content varied from 0 to 1 volume percent (vol.%). The increase in the mass fraction of the carbon nanotubes made the grain distribution in the Al/CNTs nanocomposite samples more diffuse. Besides, the stable texture of the hot rolled crystal grains on the α orientation are constantly turning to {011}< 011> with the mass fraction of the reinforcing phase increased.
Time-Dependent Shrinkage Model for Recycled Fine Aggregate Thermal Insulation Concrete
Authors: Zang Xuhang , Zhu Pinghua , Chen Chunhong , Yan Xiancui , Wang Xinjie
Published: September 2021

In this study, the shrinkage performance of recycled aggregate thermal insulation concrete (RATIC) with added glazed hollow beads (GHB) was investigated and a time-dependent shrinkage model was proposed. Two types of recycled fine aggregate (RFA) were used to replace natural fine aggregate in RATIC: RFA from waste concrete (RFA1) and waste clay brick (RFA2). Besides, the mechanical properties and thermal insulation performance of RATIC were also studied. Results showed that the pozzolanic reaction caused by RFA2 effectively improved the mechanical properties of RATIC; 75% was the optimal replacement ratio of RATIC prepared by RFA2. Added RFA decreased the thermal conductivity of thermal insulation concrete (TIC). The total shrinkage strain of RATIC increased with the increase of the replacement ratio of RFA. The 150d total shrinkage of RATIC prepared by RFA1 was 1.46 times that of TIC and the 150d total shrinkage of RATIC prepared by RFA2 was 1.23 times. The addition of GHBs led to the increase of early total shrinkage strain of concrete. Under the combined action of the higher elastic modulus of RFA2 and the pozzolanic components contained in RFA2, the total shrinkage strain of RATIC prepared by RFA2 with the same replacement ratio was smaller than that of RATIC prepared by RFA1. For example, the final total shrinkage strain of RATIC prepared by RFA2 at 100% replacement ratio was about 18.6% less than that of RATIC prepared by RFA1. A time-dependent shrinkage model considering the influence of the elastic modulus of RFA and the addition of GHB on the total shrinkage of RATIC was proposed and validated by the experimental results.