Search results for: rock mechanical studies

Authors: Solomon Huluka, Akrum Abdul-Latif, Rachid Baleh

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Metal foams have been developed intensively as a new class of materials for the last two decades due to their unique structural and multifunctional properties. The aim of this experimental work was to characterize the effect of biaxial loading complexity (combined compression-torsion) on the plastic response of highly uniform architecture open-cell aluminum foams of spherical porous with a density of 80%. For foam manufacturing, the Kelvin cells model was used to generate the generally spherical shape with a cell diameter of 11 mm. A patented rig called ACTP (Absorption par Compression-Torsion Plastique), was used to investigate the foam response under quasi-static complex loading paths having different torsional components (i.e. 0°, 45° and 60°). The key mechanical responses to be examined are yield stress, stress plateau, and energy absorption capacity. The collapse mode was also investigated. It was concluded that the higher the loading complexity, the greater the yield strength and the greater energy absorption capacity of the foam. Experimentally, it was also noticed that there were large softening effects that occurred after the first pick stress for both biaxial-45° and biaxial-60° loading.

Keywords: aluminum foam, loading complexity, characterization, biaxial loading

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Authors: Tei Kim, Brooklynn McNeil, Kathryn Dunn, Douglas I. Walker

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To better characterize the relationship between complex chemical exposures and disease, our laboratory uses an approach that combines low-cost, polydimethylsiloxane (silicone) wristband samplers that absorb many of the chemicals we are exposed to with untargeted high-resolution mass spectrometry (HRMS) to characterize 1000’s of chemicals at a time. In studies with human populations, these wristbands can provide an important measure of our environment: however, there is a need to use this approach in large cohorts to study exposures associated with the disease. To facilitate the use of silicone samplers in large scale population studies, the goal of this research project was to establish automated sample preparation methods that improve throughput, robustness, and scalability of analytical methods for silicone wristbands. Using the Opentron OT2 automated liquid platform, which provides a low-cost and opensource framework for automated pipetting, we created two separate workflows that translate the manual wristband preparation method to a fully automated protocol that requires minor intervention by the operator. These protocols include a sequence generation step, which defines the location of all plates and labware according to user-specified settings, and a transfer protocol that includes all necessary instrument parameters and instructions for automated solvent extraction of wristband samplers. These protocols were written in Python and uploaded to GitHub for use by others in the research community. Results from this project show it is possible to establish automated and open source methods for the preparation of silicone wristband samplers to support profiling of many environmental exposures. Ongoing studies include deployment in longitudinal cohort studies to investigate the relationship between personal chemical exposure and disease.

Keywords: bioinformatics, automation, opentrons, research

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Authors: Lingxia Li, Frédéric Schnell, Shuzhe Ding, Solène Le Douairon Lahaye

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Background: The risk of sudden cardiac arret/death (SCA/D) in athletes is controversial. There is a lack of meta-analyses assessing the sex differences in the risk of SCA/D in competitive athletes. Purpose: The aim of the present study was to evaluate sex differences in the incidence of SCA/D in competitive athletes using meta-analyses. Methods: The systematic review was registered in the PROSPERO database (registration ID: CRD42023432022) and was conducted according to the PRISMA guidelines. PubMed, Embase, Scopus, SPORT Discus and Cochrane Library were searched up to July 2023. To avoid systematic bias in data pooling, only studies with data for both sexes were included. Results: From the 18 included studies, 2028 cases of SCA/D were observed (males 1821 (89.79%), females 207 (10.21%)). The age ranges from the adolescents (<26 years) to the elderly (>45 years). The incidence in male athletes was 1.32/100,000 AY (95% CI: [0.90, 1.93]) and in females was 0.26/100,000 AY (95% CI: [0.16, 0.43]), the incidence rate ratio (IRR) was 6.43 (95% CI: [4.22, 9.79]). The subgroup synthesis showed a higher incidence in males than in females in both age groups <25 years and ≤35 years, the IRR was 5.86 (95% CI: [4.69, 7.32]) and 5.79 (95% CI: [4.73, 7.09]), respectively. When considering the events, the IRR was 6.73 (95%CI: [3.06, 14.78]) among studies involving both SCA/D events and 7.16 (95% CI: [4.93, 10.40]) among studies including only cases of SCD. The available clinical evidence showed that cardiac events were most frequently seen in long-distance running races (26, 35.1%), marathon (16, 21.6%) and soccer (10, 13.5%). Coronary artery disease (14, 18.9%), hypertrophic cardiomyopathy (8, 10.8%), and arrhythmogenic right ventricular cardiomyopathy (7, 9.5%) are the most common causes of SCA/D in competitive athletes. Conclusion: The meta-analysis provides evidence of sex differences in the incidence of SCA/D in competitive athletes. The incidence of SCA/D in male athletes was 6 to 7 times higher than in females. Identifying the reasons for this difference may have implications for targeted the prevention of fatal evets in athletes.

Keywords: incidence, sudden cardiac arrest, sudden cardiac death, sex difference, athletes

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Authors: Hazel Ann Gianelli Cu, Stephanie Co, Radcliff Cobankiat

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Objectives: TRC101/Veverimer is an orally administered, non absorbed, sodium- and counterion-free hydrochloric acid binder for the treatment of metabolic acidosis associated with chronic kidney disease. The main objective of this study is to determine the efficacy of TRC 101/ Veverimer 6g/day in increasing serum bicarbonate levels of chronic kidney disease patients with metabolic acidosis. In this meta analysis, we also aim to look at safety outcomes, adverse effects and if the level of serum bicarbonate reached metabolic alkalosis when given TRC101/Veverimer. Methodology: Pubmed, Cochrane, Google Scholar and Science direct were used to search for randomized controlled trials about TRC101/Veverimer use in Chronic kidney disease patients with metabolic acidosis. Search strategy according to the Prisma checklist was done with evaluation of biases and synthesis of results using the Cochrane Review Manager software 5.4. Results: Two randomized controlled trials involving 371 chronic kidney disease patients were included in this study. Results show there was a significant increase in the serum bicarbonate level when given TRC101/Veverimer compared to the placebo. Both studies had a significant number of participants who completed the studies until the end. P value of <0.00001 was used in both studies with a confidence interval of 95%. Conclusion: TRC101/Veverimer 6g/day was shown to effectively and safely increase serum bicarbonate or achieve normalization in chronic kidney disease patients with metabolic acidosis as compared with a placebo. This was associated with delayed progression of kidney disease with improvement of physical functioning, however longer duration of future studies is ideal in order to assess further the long advantages and consequences of TRC 101/Veverimer.

Keywords: chronic kidney disease, metabolic acidosis, Veverimer, TRC101

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Authors: D. Castillo T., Luis F. Jimenez

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The compressed earth blocks (CEBs) constitute an alternative as a constructive element for building homes in regions with high levels of poverty and marginalization. Such is the case of Southeastern Mexico, where the population, predominantly indigene, build their houses with feeble materials like wood and palm, vulnerable to extreme weather in the area, because they do not have the financial resources to acquire concrete blocks. There are several advantages that can provide BTCs compared to traditional vibro-compressed concrete blocks, such as the availability of materials, low manufacturing cost and reduced CO2 emissions to the atmosphere for not be subjected to a burning process. However, to improve its mechanical properties and resistance to adverse weather conditions in terms of humidity and temperature of the sub-humid climate zones, it requires the use of a chemical stabilizer; in this case we chose Ca(OH)2. The stabilization method Eades-Grim was employed, according to ASTM C977-03. This method measures the optimum amount of lime required to stabilize the soil, increasing the pH to 12.4 or higher. The minimum amount of lime required in this experiment was 1% and the maximum was 10%. The employed material was clay unconsolidated low to medium plasticity (CL type according to the Unified Soil Classification System). Based on these results, the CEBs manufacturing process was determined. The obtained blocks were from 10x15x30 cm using a mixture of soil, water and lime in different proportions. Later these blocks were put to dry outdoors and subjected to several physical and mechanical tests, such as compressive strength, absorption and drying shrinkage. The results were compared with the limits established by the Mexican Standard NMX-C-404-ONNCCE-2005 for the construction of housing walls. In this manner an alternative and sustainable material was obtained for the construction of rural households in the region, with better security conditions, comfort and cost.

Keywords: calcium hydroxide, chemical stabilization, compressed earth blocks, sub-humid warm weather

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Authors: M. Murmu, Govardhan, J. Satya Eswari

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Concrete is the most common and widely used building material. Concrete is basically made of aggregates, both fine and coarse, glued by a cement paste which is made of cement and water. Each one of these constituents of concrete has a negative environmental impact and gives rise to different sustainability issues. The current concrete construction practice is unsustainable because, not only it consumes enormous quantities of stones, sand, and drinking water, but also one billion tons a year of cement, which is not an environment friendly material. Preventing the reduction of natural resources and enhancing the usage of waste materials has become a challenge to the scientist and engineers. A number of studies have been conducted concerning the protection of natural resources, prevention of environmental pollution and contribution to the economy by using this waste material. This paper outlines the influence of Ground Granulated Blast furnace Slag (GGBS) as partial replacement of fine aggregate on mechanical properties of concrete. The strength of concrete is determined having OPC binder, replaced the fine aggregate with15%, 30%, 45% respectively. For this purpose, characteristics concrete mix of M25 with partial replacement of cement with GGBS is used and the strength of concrete cubes and cylinder have determined. The strength of concrete specimens has been compared with the reference specimen. Also X-ray diffraction (XRD) and scanning electron microscope (SEM) tests have been performed to examine the hydration products and the microstructure of the tested specimens. A correlation has been established between the developmental strength concrete with and without GGBS through analysis of hydration products and the microstructure.

Keywords: GGBS, sand, concrete, workability

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Authors: S. Vignesh, N. Vishnu, S. Vigneshwaran, M. Vishnu Anand, Dinesh Kumar Babu, V. R. Sanal Kumar

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The study of the primary flow velocity and the self impinging secondary jet flow mixing is important from both the fundamental research and the application point of view. Real industrial configurations are more complex than simple shear layers present in idealized numerical thrust-vectoring models due to the presence of combustion, swirl and confinement. Predicting the flow features of self impinging secondary jets in a supersonic primary flow is complex owing to the fact that there are a large number of parameters involved. Earlier studies have been highlighted several key features of self impinging jets, but an extensive characterization in terms of jet interaction between supersonic flow and self impinging secondary sonic jets is still an active research topic. In this paper numerical studies have been carried out using a validated two-dimensional k-omega standard turbulence model for the design optimization of a thrust vector control system using shock induced self impinging secondary flow sonic jets using non-reacting flows. Efforts have been taken for examining the flow features of TVC system with various secondary jets at different divergent locations and jet impinging angles with the same inlet jet pressure and mass flow ratio. The results from the parametric studies reveal that in addition to the primary to the secondary mass flow ratio the characteristics of the self impinging secondary jets having bearing on an efficient thrust vectoring. We concluded that the self impinging secondary jet nozzles are better than single jet nozzle with the same secondary mass flow rate owing to the fact fixing of the self impinging secondary jet nozzles with proper jet angle could facilitate better thrust vectoring for any supersonic aerospace vehicle.

Keywords: fluidic thrust vectoring, rocket steering, supersonic to sonic jet interaction, TVC in aerospace vehicles

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Authors: Niladri Sekhar Barma, Satish Dhandole

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Damage identification in the context of safety, nowadays, has become a fundamental research interest area in the field of mechanical, civil, and aerospace engineering structures. The following research is aimed to identify damage in a mechanical beam structure and quantify the severity or extent of damage in terms of loss of stiffness, and obtain an updated analytical Finite Element (FE) model. An FE model is used for analysis, and the location of damage for single and multiple damage cases is identified numerically using the modal strain energy method and mode shape curvature method. Experimental data has been acquired with the help of an accelerometer. Fast Fourier Transform (FFT) algorithm is applied to the measured signal, and subsequently, post-processing is done in MEscopeVes software. The two sets of data, the numerical FE model and experimental results, are compared to locate the damage accurately. The extent of the damage is identified via modal frequencies using a mixed numerical-experimental technique. Mode shape comparison is performed by Modal Assurance Criteria (MAC). The analytical FE model is adjusted by the direct method of model updating. The same study has been extended to some real-life structures such as plate and GARTEUR structures.

Keywords: damage identification, damage quantification, damage detection using modal analysis, structural damage identification

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Authors: Maria Reznakova, Michala Strnadova, Lukas Reznak

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Successful achievement of strategic goals requires an effective performance management system, i.e. determining the appropriate indicators measuring the rate of goal achievement. Assuming that the goal of the owners is to grow the assets they invested in, it is vital to identify the key performance indicators, which contribute to value creation. These indicators are known as value drivers. Based on the undertaken literature search, a value driver is defined as any factor that affects the value of an enterprise. The important factors are then monitored by both financial and non-financial indicators. Financial performance indicators are most useful in strategic management, since they indicate whether a company's strategy implementation and execution are contributing to bottom line improvement. Non-financial indicators are mainly used for short-term decisions. The identification of value drivers, however, is problematic for companies which are not publicly traded. Therefore financial ratios continue to be used to measure the performance of companies, despite their considerable criticism. The main drawback of such indicators is the fact that they are calculated based on accounting data, while accounting rules may differ considerably across different environments. For successful enterprise performance management it is vital to avoid factors that may reduce (or even destroy) its value. Among the known factors reducing the enterprise value are the lack of capital, lack of strategic management system and poor quality of production. In order to gain further insight into the topic, the paper presents results of the research identifying factors that adversely affect the performance of mechanical engineering enterprises in the Czech Republic. The research methodology focuses on both the qualitative and the quantitative aspect of the topic. The qualitative data were obtained from a questionnaire survey of the enterprises senior management, while the quantitative financial data were obtained from the Analysis Major Database for European Sources (AMADEUS). The questionnaire prompted managers to list factors which negatively affect business performance of their enterprises. The range of potential factors was based on a secondary research – analysis of previously undertaken questionnaire surveys and research of studies published in the scientific literature. The results of the survey were evaluated both in general, by average scores, and by detailed sub-analyses of additional criteria. These include the company specific characteristics, such as its size and ownership structure. The evaluation also included a comparison of the managers’ opinions and the performance of their enterprises – measured by return on equity and return on assets ratios. The comparisons were tested by a series of non-parametric tests of statistical significance. The results of the analyses show that the factors most detrimental to the enterprise performance include the incompetence of responsible employees and the disregard to the customers‘ requirements.

Keywords: business value, financial ratios, performance measurement, value drivers

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Authors: H. Yilmaz Atay

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Huntite and hydromagnesite minerals have been used as additive materials to achieve incombustible material due to their inflammability property. Those fire retardants materials can help to extinguish in the early stages of fire. Thus dispersion of the flame can be prevented even if the fire started. Huntite and hydromagnesite minerals are known to impart fire-proofing of the polymer composites. However, the additives used in the applications led to deterioration in the mechanical properties due to the usage of high amount of the powders in the composites. In this study, by enriching huntite and hydromagnesite, it was aimed to use purer minerals to reinforce the polymer composites. Thus, predictably, using purer mineral will lead to use lower amount of mineral powders. By this manner, the minerals free from impurities by various processes were added to the polymer matrix with different loading level and grades. Different types of samples were manufactured, and subsequently characterized by XRD, SEM-EDS, XRF and flame-retardant tests. Tensile strength and elongation at break values were determined according to loading levels and grades. Besides, a comparison on the properties of the polymer composites produced by using of minerals with and without impurities was performed. As a result of the work, it was concluded that it is required to use beneficiated minerals to provide better fire-proofing behaviors in the polymer composites.

Keywords: flame retardant, huntite and hydromagnesite, mechanical property, polymer composites

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Authors: Keping Zuo, Jia Yin Chia, Gideon Praveen Kumar Vijayakumar, Foad Kabinejadian, Fangsen Cui, Pei Ho, Hwa Liang Leo

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Carotid artery is the major vessel supplying blood to the brain. Carotid artery stenosis is one of the three major causes of stroke and the stroke is the fourth leading cause of death and the first leading cause of disability in most developed countries. Although there is an increasing interest in carotid artery stenting for treatment of cervical carotid artery bifurcation therosclerotic disease, currently available bare metal stents cannot provide an adequate protection against the detachment of the plaque fragments over diseased carotid artery, which could result in the formation of micro-emboli and subsequent stroke. Our research group has recently developed a novel preferential covered-stent for carotid artery aims to prevent friable fragments of atherosclerotic plaques from flowing into the cerebral circulation, and yet retaining the ability to preserve the flow of the external carotid artery. The preliminary animal studies have demonstrated the potential of this novel covered-stent design for the treatment of carotid therosclerotic stenosis. The purpose of this study is to evaluate the biomechanical property of PU membrane of different concentration configurations in order to refine the stent coating technique and enhance the clinical performance of our novel carotid covered stent. Results from this study also provide necessary material property information crucial for accurate simulation analysis for our stents. Method: Medical grade Polyurethane (ChronoFlex AR) was used to prepare PU membrane specimens. Different PU membrane configurations were subjected to uniaxial test: 22%, 16%, and 11% PU solution were made by mixing the original solution with proper amount of the Dimethylacetamide (DMAC). The specimens were then immersed in physiological saline solution for 24 hours before test. All specimens were moistened with saline solution before mounting and subsequent uniaxial testing. The specimens were preconditioned by loading the PU membrane sample to a peak stress of 5.5 Mpa for 10 consecutive cycles at a rate of 50 mm/min. The specimens were then stretched to failure at the same loading rate. Result: The results showed that the stress-strain response curves of all PU membrane samples exhibited nonlinear characteristic. For the ultimate failure stress, 22% PU membrane was significantly higher than 16% (p<0.05). In general, our preliminary results showed that lower concentration PU membrane is stiffer than the higher concentration one. From the perspective of mechanical properties, 22% PU membrane is a better choice for the covered stent. Interestingly, the hyperelastic Ogden model is able to accurately capture the nonlinear, isotropic stress-strain behavior of PU membrane with R2 of 0.9977 ± 0.00172. This result will be useful for future biomechanical analysis of our stent designs and will play an important role for computational modeling of our covered stent fatigue study.

Keywords: carotid artery, covered stent, nonlinear, hyperelastic, stress, strain

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Authors: Khulud Alhussain, Anna Gavine, Stephen Macgillivray, Sushila Chowdhry

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Background: Estimates show that by the year 2030, mental illness will account for more than half of the global economic burden, second to non-communicable diseases. Often, the perinatal period is characterised by psychological ambivalence and a mixed anxiety-depressive condition. Maternal mental disorder is associated with perinatal anxiety and depression and affects breastfeeding behaviors. Studies also indicate that maternal mental health can considerably influence a baby's health in numerous aspects and impact the newborn health due to lack of adequate breastfeeding. However, studies reporting factors associated with breastfeeding behaviors are predominantly quantitative. Therefore, it is not clear what literature is available to understand the factors affecting breastfeeding and perinatal women’s perspectives and experiences. Aim: This review aimed to explore the perceptions and experiences of women with perinatal anxiety and depression, as well as how these experiences influence their breastfeeding behaviours. Methods: A systematic literature review of qualitative studies in line with the Enhancing Transparency in Reporting the Synthesis of Qualitative Research (ENTREQ). Four electronic databases (CINAHL, PsycINFO, Embase, and Google Scholar) were explored for relevant studies using a search strategy. The search was restricted to studies published in the English language between 2000 and 2022. Findings from the literature were screened using a pre-defined screening criterion and the quality of eligible studies was appraised using the Walsh and Downe (2006) checklist. Findings were extracted and synthesised based on Braun and Clark. The review protocol was registered on PROSPERO (Ref: CRD42022319609). Result: A total of 4947 studies were identified from the four databases. Following duplicate removal and screening 16 studies met the inclusion criteria. The studies included 87 pregnant and 302 post-partum women from 12 countries. The participants were from a variety of economic, regional, and religious backgrounds, mainly from the age of 18 to 45 years old. Three main themes were identified: Barriers to breastfeeding, breastfeeding facilitators, emotional disturbance, and breastfeeding. Seven subthemes emerged from the data: expectation versus reality, uncertainly about maternal competencies, body image and breastfeeding, lack of sufficient breastfeeding support for family and caregivers’ support, influences positive breastfeeding practices, breastfeeding education, and causes of mental strain among breastfeeding women. Breastfeeding duration is affected in women with mental health disorders, irrespective of their desire to breastfeed. Conclusion: There is significant empirical evidence that breastfeeding behaviour and perinatal mental disturbance are linked. However, there is a lack of evidence to apply the findings to Saudi women due to lack of empirical qualitative information. To improve the psychological well-being of mothers, it is crucial to explore and recognise any concerns with their mental, physical, and emotional well-being. Therefore, robust research is needed so that breastfeeding intervention researchers and policymakers can focus on specifically what needs to be done to help mentally distressed perinatal women and their new-born.

Keywords: pregnancy, perinatal period, anxiety, depression, emotional disturbance, breastfeeding

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Authors: Andreas Stollwitzer, Lara Bettinelli, Josef Fink

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The expansion of the high-speed rail network over the past decades has resulted in new challenges for engineers, including traffic-induced resonance vibrations of railway bridges. Excessive resonance-induced speed-dependent accelerations of railway bridges during high-speed traffic can lead to negative consequences such as fatigue symptoms, distortion of the track, destabilisation of the ballast bed, and potentially even derailment. A realistic prognosis of bridge vibrations during high-speed traffic must not only rely on the right choice of an adequate calculation model for both bridge and train but first and foremost on the use of dynamic model parameters which reflect reality appropriately. However, comparisons between measured and calculated bridge vibrations are often characterised by considerable discrepancies, whereas dynamic calculations overestimate the actual responses and therefore lead to uneconomical results. This gap between measurement and calculation constitutes a complex research issue and can be traced to several causes. One major cause is found in the dynamic properties of the ballasted track, more specifically in the persisting, substantial uncertainties regarding the consideration of the ballasted track (mechanical model and input parameters) in dynamic calculations. Furthermore, the discrepancy is particularly pronounced concerning the damping values of the bridge, as conservative values have to be used in the calculations due to normative specifications and lack of knowledge. By using a large-scale test facility, the analysis of the dynamic behaviour of ballasted track has been a major research topic at the Institute of Structural Engineering/Steel Construction at TU Wien in recent years. This highly specialised test facility is designed for isolated research of the ballasted track's dynamic stiffness and damping properties – independent of the bearing structure. Several mechanical models for the ballasted track consisting of one or more continuous spring-damper elements were developed based on the knowledge gained. These mechanical models can subsequently be integrated into bridge models for dynamic calculations. Furthermore, based on measurements at the test facility, model-dependent stiffness and damping parameters were determined for these mechanical models. As a result, realistic mechanical models of the railway bridge with different levels of detail and sufficiently precise characteristic values are available for bridge engineers. Besides that, this contribution also presents another practical application of such a bridge model: Based on the bridge model, determination equations for the damping factor (as Lehr's damping factor) can be derived. This approach constitutes a first-time method that makes the damping factor of a railway bridge calculable. A comparison of this mathematical approach with measured dynamic parameters of existing railway bridges illustrates, on the one hand, the apparent deviation between normatively prescribed and in-situ measured damping factors. On the other hand, it is also shown that a new approach, which makes it possible to calculate the damping factor, provides results that are close to reality and thus raises potentials for minimising the discrepancy between measurement and calculation.

Keywords: ballasted track, bridge dynamics, damping, model design, railway bridges

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Authors: Yehya Abdellatif, Ahmed Alsalaymeh, Iyad Muslih, Ali Alshduifat

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Photovoltaic (PV) power generation systems, mainly small scale, are rapidly being deployed in Jordan. The impact of these systems on the grid has not been studied or analyzed. These systems can cause many technical problems such as reverse power flows and voltage rises in distribution feeders, and real and reactive power transients that affect the operation of the transmission system. To fully understand and address these problems, extensive research, simulation, and case studies are required. To this end, this paper studies the cloud shadow effect on the power generation of a ground mounted PV system installed at the test field of the Renewable Energy Center at the Applied Science University.

Keywords: photovoltaic, cloud effect, MPPT, power transients

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Authors: Taehoon Kwon, Hyeongrae Cho, Dirk Henkensmeier, Youngjong Kang, Chong Min Koo

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Ionic polymer actuators have been of interest in the bio-inspired artificial muscle devices. However, the relatively slow response and low power density were the obstacles for practical applications. In this study, ionic polymer actuators are fabricated with ionic polymer composite membranes based on sulfonated poly(arylene ether sulfone) (SPAES) and copper(II) phthalocyanine tetrasulfonic acid (CuPCSA). CuPCSA is an organic filler with very high ion exchange capacity (IEC, 4.5 mmol H+/g) that can be homogeneously dispersed on the molecular scale into the SPAES membrane. SPAES/CuPCSA actuators show larger ionic conductivity, mechanical properties, bending deformation, exceptional faster response to electrical stimuli, and larger mechanical power density (3028 W m–3) than Nafion actuators. This outstanding actuation performance of SPAES/CuPCSA composite membrane actuators makes them attractive for next generation transducers with high power density, which are currently developed biomimetic devices such as endoscopic surgery.

Keywords: actuation performance, composite membranes, ionic polymer actuators, organic filler

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Authors: Selen Demirtas Zorbaz, Ozlem Ulas

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Examining the reasons of child behaviour problems has been one of the focus of psychology and related disciplines for so long. It can be said there is a lot of reasons of child behaviour problems and familial factors might be the leading ones. When taking into account the prevalence of the children having behaviour problems in Turkey, it can be said that it is important to carry out studies putting forward the reasons of behaviour problems. From this point of view, the aim of this study is to examine dissertations and thesis putting forward the relationship between problem behaviour of the children (12-year-old and younger) and teenagers (12-18 years old), and familial factors. For that purpose, 46 dissertations that were chosen according to the study criteria out of 141 dissertations scanned by using the keywords of ‘behaviour problems’ and ‘behaviour disorder’ at Higher Education Thesis Centre between the years of 1989 and 2016 have been taken into the scope of the study. ‘Thesis Examination Draft Form’ has been prepared for the purpose of being used for data collecting tool. For the analysis of the data, percentage, and frequency analysis methods have been used. When the results of these studies are evaluated on the whole, it is seen that all the dissertations and thesis done are descriptive study, and it was not encountered any studies designed as experimental. When looked at the distribution of dissertations by years, it is seen that the first thesis was done in 1989 and the most number of dissertations were done in the years of 2014 and 2016. When looked at the department in which the dissertations were done, it can be said that dissertations and thesis were done in many different fields of disciplines ranging from psychology and special education. In addition to this, when investigated the group taken into the scope of dissertations and thesis research, it is seen that the children mostly worked with are below the age of 12 and types of studies are master’s thesis. When the dissertations and thesis are examined by means of topics, it is seen that mostly-studied topics are demographic variables such as gender, whether the family is fragmented or not, education level of the family and the parents’ attitude. Obtained findings have been examined in the light of literature.

Keywords: family, child behaviour problem, dissertations, thesis

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Authors: David Kriebel, Jan Edgar Mehner

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The paper introduces a method to efficiently simulate nonlinear changing electrostatic fields occurring in micro-electromechanical systems (MEMS). Large deflections of the capacitor electrodes usually introduce nonlinear electromechanical forces on the mechanical system. Traditional finite element methods require a time-consuming remeshing process to capture exact results for this physical domain interaction. In order to accelerate the simulation process and eliminate the remeshing process, a formulation of a strongly coupled electromechanical transducer element will be introduced, which uses a combination of finite-element with an advanced mesh morphing technique using radial basis functions (RBF). The RBF allows large geometrical changes of the electric field domain while retaining the high element quality of the deformed mesh. Coupling effects between mechanical and electrical domains are directly included within the element formulation. Fringing field effects are described accurately by using traditional arbitrary shape functions.

Keywords: electromechanical, electric field, transducer, simulation, modeling, finite-element, mesh morphing, radial basis function

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Authors: Chandra Gupt Porwal, Preeti C. Porwal

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Transient data reveals much about the machine's condition that steady-state data cannot. New technologies make this information much more available for evaluating the mechanical integrity of a machine train. Recent surveys at various stations indicate that simplicity is preferred over completeness in machine audits throughout the power generation industry. This is most clearly shown by the number of rotating machinery predictive maintenance programs in which only steady-state vibration amplitude is trended while important transient vibration data is not even acquired. Efforts have been made to explain what transient data is, its importance, the types of plots used for its display, and its effective utilization for analysis. In order to demonstrate the value of measuring transient data and its practical application in rotating machinery for resolving complex and persistent issues with turbine generators, the author presents a few case studies that highlight the presence of rotor instabilities due to the shaft moving towards the bearing centre in a 100 MM LMZ unit located in the Northern Capital Region (NCR), heavy misalignment noticed—especially after 2993 rpm—caused by loose coupling bolts, which prevented the machine from being synchronized for more than four months in a 250 MW KWU unit in the Western Region (WR), and heavy preload noticed at Intermediate pressure turbine (IPT) bearing near HP- IP coupling, caused by high points on coupling faces at a 500 MW KWU unit in the Northern region (NR), experienced at Indian power plants.

Keywords: transient data, steady-state-data, intermediate -pressure-turbine, high-points

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Authors: Moncayo Donoso Miguelangel, Guevara Morales Johana, Kalenia Flores Kalenia, Barrera Avellaneda Luis Alejandro, Garzon Alvarado Diego Alexander

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In mammals, long bones are formed by ossification of a cartilage mold during early embryonic development, forming structures called secondary ossification centers (SOCs), a primary ossification center (POC) and growth plates. This last structure is responsible for long bone growth. During the femur growth, the morphology of the growth plate and the SOCs may vary during different developmental stages. So far there are no detailed morphological studies of the development process from embryonic to adult stages. In this work, we carried out a morphological characterization of femur development from embryonic period to adulthood in mice. 15, 17 and 19 days old embryos and 1, 7, 14, 35, 46 and 52 days old mice were used. Samples were analyzed by a computational approach, using 3D images obtained by micro-CT imaging. Results obtained in this study showed that femur, its growth plates and SOCs undergo morphological changes during different stages of development, including changes in shape, position and thickness. These variations may be related with a response to mechanical loads imposed for muscle development surrounding the femur and a high activity during early stages necessary to support the high growth rates during first weeks and years of development. This study is important to improve our knowledge about the ossification patterns on every stage of bone development and characterize the morphological changes of important structures in bone growth like SOCs and growth plates.

Keywords: development, femur, growth plate, mice

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Authors: Samvel H. Sargsyan

Abstract:

Together with the study of electron-optical properties of nanostructures and proceeding from experiment-based data, the study of the mechanical properties of nanostructures has become quite actual. For the study of the mechanical properties of fullerene, carbon nanotubes, graphene and other nanostructures one of the crucial issues is the construction of their adequate mathematical models. Among all mathematical models of graphene or carbon nano-tubes, this so-called discrete-continuous model is specifically important. It substitutes the interactions between atoms by elastic beams or springs. The present paper demonstrates the construction of the discrete-continual beam model for carbon nanotubes or graphene, where the micropolar beam model based on the theory of moment elasticity is accepted. With the account of the energy balance principle, the elastic moment constants for the beam model, expressed by the physical and geometrical parameters of carbon nanotube or graphene, are determined. By switching from discrete-continual beam model to the continual, the models of micropolar elastic cylindrical shell and micropolar elastic plate are confirmed as continual models for carbon nanotube and graphene respectively.

Keywords: carbon nanotube, discrete-continual, elastic, graphene, micropolar, plate, shell

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Authors: Bilal Ahmad

Abstract:

Alzheimer’s disease (AD) is one of the most common neurodegenerative illnesses. However, how Gut-microbiota plays a role in the pathogenesis of AD is not well elucidated. The purpose of this literature review is to summarize and understand the current findings that may elucidate the gut microbiota's role in the development of AD. Methods: A literature review of all the relevant papers known to the author was conducted. Relevant articles, abstracts and research papers were collected from well-accepted web sources like PubMed, PMC, and Google Scholar. Results: Recent studies have shown that Gut-microbiota has an important role in the progression of AD via Gut-Microbiota-Brain Axis. The onset of AD supports the ‘Hygiene Hypothesis’, which shows that AD might begin in the Gut, causing dysbiosis, which interferes with the intestinal barrier by releasing pro-inflammatory cytokines and making its way up to the brain via the blood-brain barrier (BBB). Molecular mechanisms lipopolysaccharides and serotonin kynurenine (tryptophan) pathways have a direct association with inflammation, the immune system, neurodegeneration, and AD. Conclusion: The studies helped to analyze the molecular basis of AD, other neurological conditions like depression, autism, and Parkinson's disease and how they are linked to Gut-microbiota. Further, studies to explore the therapeutic effects of probiotics in AD and cognitive enhancement should be warranted to provide significant clinical and practical value.

Keywords: gut-microbiota, Alzheimer’s disease, second brain aging, lipopolysaccharides, short-chain fatty acids

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Authors: Gopi Kerekere Rangaraju, Madhu Puttegowda

Abstract:

Natural fibres composites include coir, jute, bagasse, cotton, bamboo, and hemp. Natural fibers come from plants. These fibers contain lingo cellulose in nature. Natural fibers are eco-friendly; lightweight, strong, renewable, cheap, and biodegradable. The natural fibers can be used to reinforce both thermosetting and thermoplastic matrices. Thermosetting resins such as epoxy, polyester, polyurethane, and phenolic are commonly used composites requiring higher performance applications. They provide sufficient mechanical properties, in particular, stiffness and strength at acceptably low-price levels. Recent advances in natural fibers development are genetic engineering. The composites science offers significant opportunities for improved materials from renewable resources with enhanced support for global sustainability. Natural fibers composites are attractive to industry because of their low density and ecological advantages over conventional composites. These composites are gaining importance due to their non-carcinogenic and bio-degradable nature. Natural fibers composites are a very costeffective material, especially in building and construction, packaging, automobile and railway coach interiors, and storage devices. These composites are potential candidates for the replacement of high- cost glass fibers for low load bearing applications. Natural fibers have the advantages of low density, low cost, and biodegradability

Keywords: PMC, basalt, coir, carbon fibers

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Authors: Chi Zhang, Hua-Peng Chen

Abstract:

With the increasingly demanding resources in the word, renewable and clean energy has been considered as an alternative way to replace traditional ones. Thus, one of practical examples for using wind energy is wind turbine, which has gained more attentions in recent research. Like most offshore structures, the blades, which is the most critical components of the wind turbine, will be subjected to millions of loading cycles during service life. To operate safely in marine environments, the blades are typically made from fibre reinforced composite materials to resist fatigue delamination and harsh environment. The fatigue crack development of blades is uncertain because of indeterminate mechanical properties for composite and uncertainties under offshore environment like wave loads, wind loads, and humid environments. There are three main delamination failure modes for composite blades, and the most common failure type in practices is subjected to mixed mode loading, typically a range of opening (mode 1) and shear (mode 2). However, the fatigue crack development for mixed mode cannot be predicted as deterministic values because of various uncertainties in realistic practical situation. Therefore, selecting an effective stochastic model to evaluate the mixed mode behaviour of wind turbine blades is a critical issue. In previous studies, gamma process has been considered as an appropriate stochastic approach, which simulates the stochastic deterioration process to proceed in one direction such as realistic situation for fatigue damage failure of wind turbine blades. On the basis of existing studies, various Paris Law equations are discussed to simulate the propagation of the fatigue crack growth. This paper develops a Paris model with the stochastic deterioration modelling according to gamma process for predicting fatigue crack performance in design service life. A numerical example of wind turbine composite materials is investigated to predict the mixed mode crack depth by Paris law and the probability of fatigue failure by gamma process. The probability of failure curves under different situations are obtained from the stochastic deterioration model for comparisons. Compared with the results from experiments, the gamma process can take the uncertain values into consideration for crack propagation of mixed mode, and the stochastic deterioration process shows a better agree well with realistic crack process for composite blades. Finally, according to the predicted results from gamma stochastic model, assessment strategies for composite blades are developed to reduce total lifecycle costs and increase resistance for fatigue crack growth.

Keywords: Reinforced fibre composite, Wind turbine blades, Fatigue delamination, Mixed failure mode, Stochastic process.

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Authors: Benn Van Den Ende

Abstract:

Over the last three decades, there has been an exponential increase in developments in implantable technologies such as the cardiac pacemaker, bionic prosthesis, and implantable chips. The effect of these technologies has been well researched in many areas. However, there is a lack of critical research in security studies. This paper will provide preliminary findings to an ongoing research project which aims to examine how implantable technologies effect the practices of governmentality in the context of security. It will do this by looking at the practices and techniques of governmentality along with different implantable technologies which increase, change or otherwise affect governmental practices. The preliminary research demonstrates that implantable technologies have a profound effect on the practices of governmentality, while also paving the way for further research into a potential ‘new’ form of governmentality in relation to these implantable technologies.

Keywords: critical security studies, governmentality, security theory, political theory, Foucault

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Authors: Benzerara Mohammed, Redjel Bachir, Kebaili Bachir

Abstract:

The cracking of the concrete is a more crucial problem with the development of the complex structures related to technological progress. The projections in the knowledge of the breaking process make it possible today for better prevention of the risk of the fracture. The breaking strength brutal of a quasi-fragile material like the concrete called Toughness, is measured by a breaking value of the factor of intensity of the constraints K1C for which the crack is propagated, it is an intrinsic property of material. Many studies reported in the literature treating of the concrete were carried out on specimens which are in fact inadequate compared to the intrinsic characteristic to identify. We started from this established fact, in order to compare the evolution of the parameter of toughness K1C measured by calling upon ordinary concrete specimens of three prismatics geometries different (10*10*84) cm³ and (5*20*120) cm³ &(12*20*120) cm³ containing from the side notches various depths simulating of the cracks was set up. The notches are carried out using triangular pyramidal plates into manufactured out of sheet coated placed at the centre of the specimens at the time of the casting, then withdrawn to leave the trace of a crack. The tests are carried out in 3 points bending test in mode 1 of fracture, by using the techniques of mechanical fracture. The evolution of the parameter of toughness K1C measured with the three geometries specimens gives almost the same results. They are acceptable and return in the beach of the results determined by various researchers (toughness of the ordinary concrete turns to the turn of the 1 MPa √m). These results inform us about the presence of an economy on the level of the geometrie specimen (5*20*120) cm³, therefore to use plates specimens later if one wants to master the toughness of this material complexes, astonishing but always essential that is the concrete.

Keywords: elementary representative volume, concrete, fissure, toughness

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Authors: Meshal Al-Samhan, Abdullah Al-Marshed

Abstract:

Recently, there has been a tremendous increase in interest in nanotechnology applications and nanomaterials in the oilfield. In the last decade, the global increase in oil production resulted in large amounts of produced water, causing a significant problem for all producing countries and companies. This produced water deserves special attention and a study of its characteristics to understand and determine how it can be treated and later used for suitable applications such as water injection for Enhance Oil Recovery (EOR) without harming the environment. This work aims to investigate the prepared compatible mixed water (seawater and effluent water) response to nanoparticles for EOR water injection. The evaluation of different mix seawater/effluent water ratios (60/40,70/30) for their characteristics prior to nanofluid preparation using Inductive Couple Plasma (ICP) analysis, potential zeta test, and OLI software (the OLI Systems is a recognised leader in aqueous chemistry). This step of the work revealed the suitability of the water mix with a lower effluent-water ratio. Also, OLI predicted that the 60:40 mix needs to be balanced around temperatures of 70 ºC to avoid the mass accumulation of calcium sulfate and strontium sulfate. Later the prepared nanofluid was tested for interfacial tension (IFT) and wettability restoration in the sandstone rock; the Al2O3 nanofluid at 0.06 wt% concentration reduced the IFT by more than 16% with moderate water wet contact angle. The study concluded that the selected nanoparticle Al2O3 had demonstrated excellent performance in decreasing the interfacial tension with respect to the selected water mix type (60/40) at low nanoparticles wt%.

Keywords: nano AL2O3, sanstone, nanofluid, IFT, wettability

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Authors: Amir Asadi, Karim Habib, Robert J. Moon, Kyriaki Kalaitzidou

Abstract:

There has been considerable interest in cellulose nanomaterials (CN) as polymer and polymer composites reinforcement due to their high specific modulus and strength, low density and toxicity, and accessible hydroxyl side groups that can be readily chemically modified. The focus of this study is making lightweight composites for better fuel efficiency and lower CO2 emission in auto industries with no compromise on mechanical performance using a scalable technique that can be easily integrated in sheet molding compound (SMC) manufacturing lines. Light weighting will be achieved by replacing part of the heavier components, i.e. glass fibers (GF), with a small amount of cellulose nanocrystals (CNC) in short GF/epoxy composites made using SMC. CNC will be introduced as coating of the GF rovings prior to their use in the SMC line. The employed coating method is similar to the fiber sizing technique commonly used and thus it can be easily scaled and integrated to industrial SMC lines. This will be an alternative route to the most techniques that involve dispersing CN in polymer matrix, in which the nanomaterials agglomeration limits the capability for scaling up in an industrial production. We have demonstrated that incorporating CNC as a coating on GF surface by immersing the GF in CNC aqueous suspensions, a simple and scalable technique, increases the interfacial shear strength (IFSS) by ~69% compared to the composites produced by uncoated GF, suggesting an enhancement of stress transfer across the GF/matrix interface. As a result of IFSS enhancement, incorporation of 0.17 wt% CNC in the composite results in increases of ~10% in both elastic modulus and tensile strength, and 40 % and 43 % in flexural modulus and strength respectively. We have also determined that dispersing 1.4 and 2 wt% CNC in the epoxy matrix of short GF/epoxy SMC composites by sonication allows removing 10 wt% GF with no penalty on tensile and flexural properties leading to 7.5% lighter composites. Although sonication is a scalable technique, it is not quite as simple and inexpensive as coating the GF by passing through an aqueous suspension of CNC. In this study, the above findings are integrated to 1) investigate the effect of CNC content on mechanical properties by passing the GF rovings through CNC aqueous suspension with various concentrations (0-5%) and 2) determine the optimum ratio of the added CNC to the removed GF to achieve the maximum possible weight reduction with no cost on mechanical performance of the SMC composites. The results of this study are of industrial relevance, providing a path toward producing high volume lightweight and mechanically enhanced SMC composites using cellulose nanomaterials.

Keywords: cellulose nanocrystals, light weight polymer-matrix composites, mechanical properties, sheet molding compound (SMC)

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Authors: Peter Jurči, Jana Ptačinová, Mária Hudáková, Mária Dománková, Martin Kusý, Martin Sahul

Abstract:

The strength, hardness, and toughness (ductility) are in strong conflict for the metallic materials. The only possibility how to make their simultaneous improvement is to provide the microstructural refinement, by cold deformation, and subsequent recrystallization. However, application of this kind of treatment is impossible for high-carbon high-alloyed ledeburitic tool steels. Alternatively, it has been demonstrated over the last few years that sub-zero treatment induces some microstructural changes in these materials, which might favourably influence their complex of mechanical properties. Commercially available PM ledeburitic steel Vanadis 6 has been used for the current investigations. The paper demonstrates that sub-zero treatment induces clear refinement of the martensite, reduces the amount of retained austenite, enhances the population density of fine carbides, and makes alterations in microstructural development that take place during tempering. As a consequence, the steel manifests improved wear resistance at higher toughness and fracture toughness. Based on the obtained results, the key question “can the wear performance be improved by sub-zero treatment simultaneously with toughness” can be answered by “definitely yes”.

Keywords: ledeburitic tool steels, microstructure, sub-zero treatment, mechanical properties

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Authors: Madeline Phillips, Luis Mendez

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The 21st century has seen an increase in the amount and variety of psychological research on Latinx, the largest minority group in the U.S., with great variability from the individual’s cultural origin (e.g., ethnicity) to region (e.g., nationality). We were interested in exploring how scientists recruit, conduct and report research on Latinx samples. Ethnicity and race are important components of individuals and should be addressed to capture a broader and deeper understanding of psychological research findings. In order to explore Latinx/Hispanic work, the Journal of Latinx Psychology (JLP) and Hispanic Journal of Behavioral Sciences (HJBS) were analyzed for 1) measures of ethnicity and race in empirical studies 2) nationalities represented 3) how researchers reported ethnic-racial demographics. The analysis included publications from 2013-2018 and revealed two common themes of reporting ethnicity and race: overrepresentation/underrepresentation and overgeneralization. There is currently not a systematic way of reporting ethnicity and race among Latinx/Hispanic research, creating a vague sense of what and how ethnicity/race plays a role in the lives of participants. Second, studies used the Hispanic/Latinx terms interchangeably and are not consistent across publications. For the purpose of this project, we were only interested in publications with Latinx samples in the U.S. Therefore, studies outside of the U.S. and non-empirical studies were excluded. JLP went from N = 118 articles to N = 94 and HJBS went from N = 174 to N = 154. For this project, we developed a coding rubric for ethnicity/race that reflected the different ways researchers reported ethnicity and race and was compatible with the U.S. census. We coded which ethnicity/race was identified as the largest ethnic group in each sample. We used the ethnic-racial breakdown numbers or percentages if provided. There were also studies that simply did not report the ethnic composition besides Hispanic or Latinx. We found that in 80% of the samples, Mexicans are overrepresented compared to the population statistics of Latinx in the US. We observed all the ethnic-racial breakdowns, demonstrating the overrepresentation of Mexican samples and underrepresentation and/or lack of representation of certain ethnicities (e.g., Chilean, Guatemalan). Our results showed an overgeneralization of studies that cluster their participants to Latinx/Hispanic, 23 for JLP and 63 for HJBS. The authors discuss the importance of transparency from researchers in reporting the context of the sample, including country, state, neighborhood, and demographic variables that are relevant to the goals of the project, except when there may be an issue of privacy and/or confidentiality involved. In addition, the authors discuss the importance to recognize the variability within the Latinx population and how it is reflected in the scientific discourse.

Keywords: Latinx, Hispanic, race and ethnicity, diversity

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Authors: Ilirian Laçi, Alketa Spahiu

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Ageing causes an increase in the number of patients with spinal canal stenosis. Most of the patients have back pain, leg pain, numbness of the legs, as well as urinary incontinence as a very common symptoms. Urinary incontinence impairs the quality of life. Correction of the symptom of urinary incontinence is possible in the early and adequate treatment of spinal stenosis. Methods: This study observed patients with urinary incontinence and spinal canal stenosis. These patients underwent mechanical decompression of the spinal stenosis through surgery. At the same time, these patients were observed clinically with clinical consultations. Cystoscopy and urodynamic tests were conducted at intervals of 2 and 6 months. As a result of treatment, 60% of patients did recover. The patients in this group who benefit from treatment were the patients who were early diagnosed and treated. Conclusions: An important factor in the prognosis of this pathology is the early diagnosis and treatment. The proper treatment of this pathology makes it curable in most cases. An important role in this pathology is played by the neurosurgeon. Surgery accompanied by laminotomy and mechanical decompression is the best way of treatment. Other factors that played a role in this pathology are also a large number of childbirths for women, obesity, etc.

Keywords: urinary incontinence, quality of life, spinal canal stenosis, early diagnosis, treatment

Procedia PDF Downloads 92