Search results for: shear stress correlations

Authors: V. Fuis, P. Janicek, T. Navrat

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The global solved problem is the calculation of the parameters of ceramic material from a set of destruction tests of ceramic heads of total hip joint endoprosthesis. The standard way of calculation of the material parameters consists in carrying out a set of 3 or 4 point bending tests of specimens cut out from parts of the ceramic material to be analysed. In case of ceramic heads, it is not possible to cut out specimens of required dimensions because the heads are too small (if the cut out specimens were smaller than the normalized ones, the material parameters derived from them would exhibit higher strength values than those which the given ceramic material really has). A special destruction device for heads destruction was designed and the solved local problem is the modification of this destructive device based on the analysis of tensile stress in the head for two different values of the depth of the conical hole in the head. The goal of device modification is a shift of the location with extreme value of 1 max from the region of head’s hole bottom to its opening. This modification will increase the credibility of the obtained material properties of bio ceramics, which will be determined from a set of head destructions using the Weibull weakest link theory.

Keywords: ceramic heads, depth of the conical hole, destruction test, material parameters, principal stress, total hip joint endoprosthesis

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Authors: Noa Nelson, Meitar Moshe, Dana Cohen

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Work-family conflict (WFC) is a significant source of stress for contemporary employees, with research indicating its heightened severity for women. The conservation of resources theory argues that individuals experience stress when their resources fall short of demands, and attempt to reach balance by obtaining resources. Presumably then, to achieve work-family balance women would need to negotiate for resources such as spouse support, employer support and work flexibility. The current research tested the hypotheses that competent negotiation at home and at work associated with increased family and job resources and with decreased WFC, as well as with higher work, marital and life satisfaction. In the first study, 113 employed mothers, married or cohabiting, reported to what extent they conducted satisfactory negotiation with spouse over division of housework, and their actual housework load compared to spouse. They answered a WFC questionnaire, measuring how much work interferes with family (WIF) and how much family interferes with work (FIW), and finally, measurements of satisfaction. In the second study, 94 employed mothers, married or cohabiting reported to what extent they conducted satisfactory negotiation with their boss over balancing work demands with family needs. They reported the levels of three job resources: flexibility, control and family-friendly organizational culture. Finally, they answered the same WFC and satisfaction measurements from study 1. Statistical analyses –t-tests, correlations, and hierarchical linear regressions- showed that in both studies, women reported higher WIF than FIW. Negotiations associated with increased resources: support from spouse, work flexibility and control and a family-friendly culture; negotiation with spouse associated also with satisfaction measurements. However, negotiations or resources (except family-friendly culture) did not associate with reduced conflict. The studies demonstrate the role of negotiation in obtaining family and job resources. Causation cannot be determined, but the fact is that employed mothers who enjoyed more support (at both home and work), flexibility and control, were more likely to keep active interactions to increase them. This finding has theoretical and practical implications, especially in view of research on female avoidance of negotiation. It is intriguing that negotiations and resources generally did not associate with reduced WFC. This finding might reflect the severity of the conflict, especially of work interfering with family, which characterizes many contemporary jobs. It might also suggest that employed mothers have high expectations from themselves, and even under supportive circumstances, experience the challenge of balancing two significant and demanding roles. The research contributes to the fields of negotiation, gender, and work-life balance. It calls for further studies, to test its model in additional populations and validate the role employees have in actively negotiating for the balance that they need. It also calls for further research to understand the contributions of job and family resources to reducing work-family conflict, and the circumstances under which they contribute.

Keywords: sork-family conflict, work-life balance, negotiation, gender, job resources, family resources

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Authors: Abhishek Mukherjee, Juan C. Cajas, Jenny Suckale, Guillaume Houzeaux, Oriol Lehmkuhl, Simone Marras

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The investigation of tsunami flow characteristics and the quantification of tsunami energy reduction through the coastal vegetation is important to understand the protective benefits of nature-based mitigation parks. In the present study, a three-dimensional non-hydrostatic incompressible Computational Fluid Dynamics model with a two-way coupling enabled fluid-structure interaction approach (FSI) is used. After validating the numerical model against experimental data, tsunami flow characteristics have been investigated by varying vegetation density, modulus of elasticity, the gap between stems, and arrangement or distribution of vegetation patches. Streamwise depth average velocity profiles, turbulent kinetic energy, energy flux reflection, and dissipation extracted by the numerical study will be presented in this study. These diagnostics are essential to assess the importance of different parameters to design the proper coastal defense systems. When a tsunami wave reaches the shore, it transforms into undular bores, which induce scour around offshore structures and sediment transport. The bed shear stress, instantaneous turbulent kinetic energy, and the vorticity near-bed will be presented to estimate the importance of vegetation to prevent tsunami-induced scour and sediment transport.

Keywords: coastal defense, energy flux, fluid-structure interaction, natural hazards, sediment transport, tsunami mitigation

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Authors: Junior Nomani

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This paper presents a novel approach to modelling the metal cutting of duplex stainless steels, a two-phase alloy regarded as a difficult-to-machine material. Calculation and control of shear strain and stresses during cutting are essential to achievement of ideal cutting conditions. Too low or too high leads to higher required cutting force or excessive heat generation causing premature tool wear failure. A 2D finite element cutting model was created based on electron backscatter diffraction (EBSD) data imagery of duplex microstructure. A mesh was generated using ‘object-oriented’ software OOF2 version V2.1.11, converting microstructural images to quadrilateral elements. A virtual workpiece was created on ABAQUS modelling software where a rigid body toolpiece advanced towards workpiece simulating chip formation, generating serrated edge chip formation cutting. Model results found calculated stress strain contour plots correlated well with similar finite element models tied with austenite stainless steel alloys. Virtual chip form profile is also similar compared experimental frozen machining chip samples. The output model data provides new insight description of strain behavior of two phase material on how it transitions from workpiece into the chip.

Keywords: Duplex stainless steel, ABAQUS, OOF2, Chip formation

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Authors: Hossein Alimohammadi, Mohsen Amirmojahedi, Mehrdad Rowhani

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Soil properties are used by geotechnical engineers to evaluate and analyze site conditions for designing purposes. Although basic soil classification tests are easy to perform and provide useful information to determine the properties of soils, it may take time to get the result and add some costs to the projects. Standard Penetration Test (SPT) provides an opportunity to evaluate soil parameters without performing laboratory tests. In addition to its simplicity and cheapness, the results become available immediately. This research provides a guideline on the application of the SPT test method, reliability of adapting the SPT test results in evaluating soil physical and mechanical properties such as Atterberg limits, shear strength, and compressive strength compressibility parameters. A total of 70 boreholes were investigated in this study by taking soil samples between depths of 1.2 to 15.25 meters. The project site was located in Morrow County, Ohio. A regression-based formula was proposed based on Tobit regression with a stepwise variable selection analysis conducted between SPT and other typical soil properties obtained from soil tests. The results of the research illustrated that the shear strength and physical properties of the soil affect the SPT number. The proposed correlation can help engineers to use SPT test results in their design with higher accuracy.

Keywords: standard penetration test, soil properties, soil classification, regression method

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Authors: H. Hosseini, B. V. Berdyshev, I. Iskopintsev

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This paper presents a rheological model for producing shape-memory thermoplastic polymers. Shape-memory occurs as a result of internal rearrangement of the structural elements of a polymer. A non-linear viscoelastic model was developed that allows qualitative and quantitative prediction of the stress-strain behavior of shape-memory polymers during heating. This research was done to develop a technique to determine the maximum possible change in size of heat-shrinkable products during heating. The rheological model used in this work was particularly suitable for defining process parameters and constructive parameters of the processing equipment.

Keywords: elastic deformation, heating, shape-memory polymers, stress-strain behavior, viscoelastic model

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Authors: A. Bahieldin, A. Atef, S. Edris, N. O. Gadalla, S. M. Hassan, M. A. Al-Kordy, A. M. Ramadan, A. S. M. Al- Hajar, F. M. El-Domyati

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The idea of this work is based on a natural exciting phenomenon suggesting that suppression of genes related to the program cell death (or PCD) mechanism might help the plant cells to efficiently tolerate abiotic stresses. The scope of this work was the detection of PCD-related transcription factors (TFs) that might also be related to salt stress tolerance in plant. Two model plants, e.g., tobacco and Arabidopsis, were utilized in order to investigate this phenomenon. Occurrence of PCD was first proven by Evans blue staining and DNA laddering after tobacco leaf discs were treated with oxalic acid (OA) treatment (20 mM) for 24 h. A number of 31 TFs up regulated after 2 h and co-expressed with genes harboring PCD-related domains were detected via RNA-Seq analysis and annotation. These TFs were knocked down via virus induced gene silencing (VIGS), an RNA interference (RNAi) approach, and tested for their influence on triggering PCD machinery. Then, Arabidopsis SALK knocked out T-DNA insertion mutants in selected TFs analogs to those in tobacco were tested under salt stress (up to 250 mM NaCl) in order to detect the influence of different TFs on conferring salt tolerance in Arabidopsis. Involvement of a number of candidate abiotic-stress related TFs was investigated.

Keywords: VIGS, PCD, RNA-Seq, transcription factors

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Authors: M. Abdollahi, S. N. Moghaddas Tafreshi

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Expanded polystyrene (EPS) geofoam is often used in below ground applications in geotechnical engineering. A most recent configuration system implemented in roadways to protect lifelines such as buried pipes, electrical cables and culvert systems could be consisted of two EPS geofoam blocks, “posts” placed on each side of the structure, an EPS block capping, “beam” put atop two posts, and soil cover on the beam. In this configuration, a rectangular void space will be built atop the lifeline. EPS blocks will stand all the imposed vertical forces due to their strength and deformability, thus the lifeline will experience no vertical stress. The present paper describes the results of a numerical study on the post and beam configuration subjected to the static loading. Three-dimensional finite element analysis using ABAQUS software is carried out to investigate the effect of different parameters such as beam thickness, soil thickness over the beam, post height to width ratio, EPS density, and free span between two posts, on the stress distribution and the deflection of the beam. The results show favorable performance of EPS geofoam for protecting sensitive infrastructures.

Keywords: beam, EPS block, numerical analysis, post, stress distribution

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Authors: Nicholas Bayfield, Liam Bibo, Charley Budgeon, Robert Larbalestier, Tom Briffa

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Introduction: Stress hyperglycaemia is common following cardiac surgery. Its optimal management is uncertain and may differ by diabetic status. This study assesses the in-hospital glycaemic management of cardiac surgery patients and associated postoperative outcomes. Methods: A retrospective cohort analysis of all patients undergoing cardiac surgery at Fiona Stanley Hospital from February 2015 to May 2019 was undertaken. Management and outcomes of hyperglycaemia following cardiac surgery were assessed. Follow-up was assessed to 1 year postoperatively. Multivariate regression modelling was utilised. Results: 1050 non-diabetic patients and 689 diabetic patients were included. In the non-diabetic cohort, patients with mild (peak blood sugar level [BSL] < 14.3), transient stress hyperglycaemia managed without insulin were not at an increased risk of wound-related morbidity (P=0.899) or mortality at 1 year (P=0.483). Insulin management was associated with wound-related readmission to hospital (P=0.004) and superficial sternal wound infection (P=0.047). Prolonged or severe stress hyperglycaemia was predictive of hospital re-admission (P=0.050) but not morbidity or mortality (P=0.546). Diabetes mellitus was an independent risk factor 1-year mortality (OR; 1.972 [1.041–3.736], P=0.037), graft harvest site wound infection (OR; 1.810 [1.134–2.889], P=0.013) and wound-related readmission (OR; 1.866 [1.076–3.236], P=0.026). In diabetics, postoperative peak BSL > 13.9mmol/L was predictive of graft harvest site infections (OR; 3.528 [1.724-7.217], P=0.001) and wound-related readmission OR; 3.462 [1.540-7.783], P=0.003) regardless of modality of management. A peak BSL of 10.0-13.9 did not increase the risk of morbidity/mortality compared to a peak BSL of < 10.0 (P=0.557). Diabetics with a peak BSL of 13.9 or less did not have significantly increased morbidity/mortality outcomes compared to non-diabetics (P=0.418). Conclusion: In non-diabetic patients, transient mild stress hyperglycaemia following cardiac surgery does not uniformly require treatment. In diabetic patients, postoperative hyperglycaemia with peak BSL exceeding 13.9mmol/L was associated with wound-related morbidity and hospital readmission following cardiac surgery.

Keywords: cardiac surgery, pulmonary embolism, pulmonary embolectomy, cardiopulmonary bypass

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Authors: Mark T. Hanson, Alan T. Varughese

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Osteoporosis is a disease affecting bone quality which in turn can increase the risk of low energy fractures. Treatment of osteoporosis using Bisphosphonates has the beneficial effect of increasing bone mass while at the same time has been linked to the formation of atypical femoral fractures. This has led to the increased study of micro-fractures in bones of patients using Bisphosphonate treatment. One of the mechanics related issues which have been identified in this regard is the loss in stiffness of bones containing one or many micro-fractures. Different theories have been put forth using fracture mechanics to determine the effect of crack presence on elastic properties such as modulus. However, validation of these results in a deterministic way has not been forthcoming. The present analysis seeks to provide this deterministic evaluation of fracture’s effect on the elastic modulus. In particular, the effect of crack size, crack orientation and crack number on elastic modulus is investigated. In particular, the Finite Element method is used to explicitly determine the elastic modulus reduction caused by the presence of cracks in a representative volume element. Single cracks of various lengths and orientations are examined as well as cases of multiple cracks. Cracks in tension as well as under shear stress are considered. Although the focus is predominantly two-dimensional, some three-dimensional results are also presented. The results obtained show the explicit reduction in modulus caused by the parameters of crack size, orientation and number noted above. The present results allow the interpretation of the various theories which currently exist in the literature.

Keywords: cracks, elastic, fracture, modulus

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Authors: Pui-Lai To, Chechen Liao, Ming-Chi Sung

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Work and family life are the most important areas for men and women today. Every professional is required to meet and fulfill the responsibilities of work and family roles. Although the development and popularity of communication technology bring a lot of benefits, including effective and efficient communication, may also generate conflicts between work and family life. Since mobile devices and the applications of mobile devices, such as instant messages, are ubiquitous, the boundaries of work and family roles are increasingly blurred. Professionals may be in the risk of work over-loading and work-family conflict. This study examines the impact of work stress on professionals’ life and health in the context of instant messaging application of smart phone. This study uses a web-based questionnaire to collect samples. The questionnaires are sent via virtual community sites, instant messaging applications, and e-mail. The study develops and empirically validates a work-family conflict model by integrating the pressure theory and technostress factors. The causal relationship between variables in the research model is tested. In terms of data analysis, Partial Least Square (PLS) in Structural Equation Modeling (SEM) is used for sample analysis and research model testing. The results of this study are as follows. First, both the variables of work-related stress and technological violations positively affect the work-family conflict. Second, both the variables of work-loading and technology-overloading have no effect on work-family conflict. Third, work-family conflict has negative effect on job satisfaction, family satisfaction, physical health, and mental health.

Keywords: mental health, physical health, technostress, work-family conflict, work-related stress

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Authors: Seyed Ali Mohammad, Modarres Sanavy, Hamed Keshavarz, Ali Mokhtassi-Bidgoli

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One of the biggest challenges for the current and future generations is to produce sufficient food for the world population with the existing limited available water resources. Peppermint is a specialty crop used for food and medicinal purposes. Its main component is menthol. It is used predominantly for oral hygiene, pharmaceuticals, and foods. Although drought stress is considered as a negative factor in agriculture, being responsible for severe yield losses; medicinal plants grown under semi-arid conditions usually produce higher concentrations of active substances than same species grown under moderate climates. Nitrogen (N) fertilizer management is central to the profitability and sustainability of forage crop production. Sub-optimal N supply will result in poor yields, and excess N application can lead to nitrate leaching and environmental pollution. In order to determine the response of peppermint to drought stress and different fertilizer treatments, a field experiment with peppermint was conducted in a sandy loam soil at a site of the Tarbiat Modares University, Agriculture Faculty, Tehran, Iran. The experiment used a complete randomized block design, with six rates of fertilizer strategies (F1: control, F2: Urea, F3: 75% urea + 25% vermicompost, F4: 50% urea + 50% vermicompost, F5: 25% urea + 75% vermicompost and F6: vermicompost) and three irrigation regime (S1: 45%, S2: 60% and S3: 75% FC) with three replication. The traits such as nitrogen, chlorophyll, carotenoids, anthocyanin, flavonoid and fresh biomass were studied. The results showed that the treatments had a significant effect on the studied traits as drought stress reduced photosynthetic pigment concentration. Also, drought stress reduced fresh yield of peppermint. Non stress condition had the greater amount of chlorophyll and fresh yield more than other irrigation treatments. The highest concentration of chlorophyll and the fresh biomass was obtained in F2 fertilizing treatments. Sever water stress (S1) produced decreased photosynthetic pigment content fresh yield of peppermint. Supply of N could improve photosynthetic capacity by enhancing photosynthetic pigment content. Perhaps application of vermicompost significantly improved the organic carbon, available N, P and K content in soil over urea fertilization alone. To get sustainable production of peppermint, application of vermicompost along with N through synthetic fertilizer is recommended for light textured sandy loam soils.

Keywords: fresh yield, peppermint, synthetic nitrogen, vermicompost, water stress

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Authors: Maxime Alex Junior Kuitche, Ruxandra Mihaela Botez, Jean-Chirstophe Maunand

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The evolution of aircraft is closely linked to the study and improvement of propulsion systems. Determining the propulsion performance is a real challenge in aircraft modeling and design. In addition to theoretical methodologies, experimental procedures are used to obtain a good estimation of the propulsion performances. For piston-propeller propulsion, the propeller needs several experimental tests which could be extremely demanding in terms of time and money. This paper presents a new procedure to estimate the performance of a propeller from a numerical approach using computational fluid dynamic analysis. The propeller was initially scanned, and then, its 3D model was represented using CATIA. A structured meshing and Shear Stress Transition k-ω turbulence model were applied to describe accurately the flow pattern around the propeller. Thus, the Partial Differential Equations were solved using ANSYS FLUENT software. The method was applied on the UAS-S45’s propeller designed and manufactured by Hydra Technologies in Mexico. An extensive investigation was performed for several flight conditions in terms of altitudes and airspeeds with the aim to determine thrust coefficients, power coefficients and efficiency of the propeller. The Computational Fluid Dynamics results were compared with experimental data acquired from wind tunnel tests performed at the LARCASE Price-Paidoussis wind tunnel. The results of this comparison have demonstrated that our approach was highly accurate.

Keywords: CFD analysis, propeller performance, unmanned aerial system propeller, UAS-S45

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Authors: A. Yazdanmehr, H. Jahed

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Being made with the lightest commercially available industrial metal, Magnesium (Mg) alloys are of interest for light-weighting. Expanding their application to different material processing methods requires Mg properties at large strains. Several room-temperature processes such as shot and laser peening and hole cold expansion need compressive large strain data. Two methods have been proposed in the literature to obtain the stress-strain curve at high strains: 1) anti-buckling guides and 2) small cubic samples. In this paper, an anti-buckling fixture is used with the help of digital image correlation (DIC) to obtain the compression-tension (C-T) of AZ31B-H24 rolled sheet at large strain values of up to 10.5%. The effect of the anti-bucking fixture on stress-strain curves is evaluated experimentally by comparing the results with those of the compression tests of cubic samples. For testing cubic samples, a new fixture has been designed to increase the accuracy of testing cubic samples with DIC strain measurements. Results show a negligible effect of anti-buckling on stress-strain curves, specifically at high strain values.

Keywords: large strain, compression-tension, loading-unloading, Mg alloys

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Authors: Ntokozo Dambuza, Maryna Van De Venter, Trevor Koekemoer

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Oxidative stress contributes to the pathogenesis of many diseases and consequently antioxidant therapy has attracted much attention as a potential therapeutic strategy. Regardless of the quantities ingested, antioxidants need to reach the diseased tissues at concentrations sufficient to combat oxidative stress. Bioavailability is thus a defining criterion for the therapeutic efficacy of antioxidants. In addition, therapeutic antioxidants must possess biologically relevant characteristics which can target the specific molecular mechanisms responsible for disease related oxidative stress. While many chemical antioxidant assays are available to quantify antioxidant capacity, they relate poorly to the biological environment and provide no information as to the bioavailability. The present comparative study thus aims to characterise green and fermented rooibos extracts, well recognized for their exceptional antioxidant capacity, in terms of antioxidant bioavailability and efficacy in a disease relevant cellular setting. Chinese green tea antioxidant activity was also evaluated. Chemical antioxidant assays (FRAP, DPPH and ORAC) confirmed the potent antioxidant capacity of both green and fermented rooibos, with green rooibos possessing antioxidant activity superior to that of fermented rooibos and Chinese green tea. Bioavailability was assessed using the PAMPA assay and the results indicate that green and fermented rooibos have a permeation coefficient of 5.7 x 10-6 and 6.9 x 10-6 cm/s, respectively. Chinese green tea permeability coefficient was 8.5 x 10-6 cm/s. These values were comparable to those of rifampicin, which is known to have a high permeability across intestinal epithelium with a permeability coefficient of 5 x 10 -6 cm/s. To assess the antioxidant efficacy in a cellular context, U937 and red blood cells were pre-treated with rooibos and Chinese green tea extracts in the presence of a dye DCFH-DA and then exposed to oxidative stress. Green rooibos exhibited highest activity with an IC50 value of 29 μg/ml and 70 μg/ml, when U937 and red blood cells were exposed oxidative stress, respectively. Fermented rooibos and Chinese green tea had IC50 values of 61 μg/ml and 57 μg/ml for U937, respectively, and 221 μg/ml and 405 μg/ml for red blood cells, respectively. These results indicate that fermented and green rooibos extracts were able to permeate the U937 cells and red blood cell membrane and inhibited oxidation of DCFH-DA to a fluorescent DCF within the cells.

Keywords: rooibos, antioxidants, permeability, bioavailability

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Authors: Lintle Mohase, Ninikoe Lebusa, Mpho Stephen Mafa

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Wheat is an economically important cereal crop. However, the changing climatic conditions that intensify drought in production areas, and additional pest infestation, such as the Russian wheat aphid (RWA, Diuraphis noxia), severely hamper its production. Drought and pest management require an additional water supply through irrigation and applying inorganic nutrients (including silicon) as alternative strategies to mitigate the stress effects. Therefore, other approaches are needed to enhance wheat productivity during drought stress and aphid abundance. Two wheat cultivars were raised under greenhouse conditions, exposed to drought stress, and treated with silicon before infestation with the South African RWA biotype 2 (RWASA2). The morphological evaluations showed that severe drought or a combination of drought and infestation significantly reduced the plant height of wheat cultivars. Silicon treatment did not alleviate the growth reduction. The biochemical responses were measured using spectrophotometric assays with specific substrates. An evaluation of the enzyme activities associated with oxidative stress and defence responses indicated that drought stress increased NADPH oxidase activity, while silicon treatment significantly reduced it in drought-stressed and infested plants. At 48 and 72 hours sampling periods, a combination of silicon, drought and infestation treatment significantly increased peroxidase activity compared to drought and infestation treatment. The treatment also increased β-1,3-glucanase activity 72 hours after infestation. In addition, silicon and drought treatment increased glucose but reduced sucrose accumulation. Furthermore, silicon, drought, and infestation treatment combinations reduced the sucrose content. Finally, silicon significantly increased the trehalose content under severe drought and infestation, evident at 48 and 72-hour sampling periods. Our findings shed light on silicon’s ability to induce protective biochemical responses during drought and aphid infestation.

Keywords: drought, enzyme activity, silicon, soluble sugars, Russian wheat aphid, wheat

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Authors: Supriya Mahida, Sangita, Yogesh U. Shah, Shanta Kumar

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The global production of thermocol increasing day by day, due to vast applications of the use of thermocole in many sectors. Thermocol being non-biodegradable and more toxic than plastic leads towards a number of problems like its management into value-added products, environmental damage and landfill problems due to weight to volume ratio. Utilization of waste thermocol for modification of bitumen binders resulted in waste thermocol modified bitumen (WTMB) used in road construction and maintenance technology. Modification of bituminous mixes through incorporating thermocol into bituminous mixes through a dry process is one of the new options besides recycling process which consumes lots of waste thermocol. This process leads towards waste management and remedies against thermocol waste disposal. The present challenge is to dispose the thermocol waste under different forms in road infrastructure, either through the dry process or wet process to be developed in future. This paper focuses on the use of thermocol wastes which is mixed with VG 10 bitumen in proportions of 0.5%, 1%, 1.5%, and 2% by weight of bitumen. The physical properties of neat bitumen are evaluated and compared with modified VG 10 bitumen having thermocol. Empirical characterization like penetration, softening, and viscosity of bitumen has been carried out. Thermocol and waste thermocol modified bitumen (WTMB) were further analyzed by Fourier Transform Infrared Spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), and Dynamic Shear Rheometer (DSR).

Keywords: DSR, FESEM, FT-IR, thermocol wastes

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Authors: Shian-Ling Keng, Onn Siong Yim, Poh San Lai, Soo Chong Chew, Anne Chong, Richard Ebstein

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Research has demonstrated a positive association between mindfulness meditation and physical health. Little work, however, has examined the association between trait mindfulness and leukocyte telomere length (LTL), an emerging marker of cellular aging. The present study aimed to examine whether facets of trait mindfulness are correlated with longer LTL in a Singaporean Han Chinese sample and whether these facets may mediate the association between psychological symptoms and LTL. 158 adults (mean age = 27.24 years) completed measures assessing trait mindfulness and psychological symptoms (i.e., depression and stress) and provided blood samples for analyses of LTL using qPCR. Multiple regression analyses were conducted to assess the association between facets of trait mindfulness and LTL. Bootstrapping-based mediational analyses were run to examine the role of trait mindfulness as a mediator of the association between psychological symptoms and LTL. Of five facets of trait mindfulness (describe, act with awareness, observe, nonreactivity, and nonjudging), nonreactivity was significantly associated with LTL, after controlling for the effects of age, gender, and education, β = .21, p = .006. Further, there was a trend for overall trait mindfulness, β = .15, p = .06, and nonjudging, β = .13, p = .095, to each predict longer LTL. Nonreactivity significantly mediated the association between depression and LTL, BCa 95% CI [-.004, -.0004], p=.03, as well as the association between stress and LTL, BCa 95% CI [-.004, -.0004], p=.04. The results provide preliminary evidence for a positive association between selected facets of trait mindfulness and slower cellular aging, indexed by LTL. The findings suggest that individuals who are high on equanimity may experience slower aging at the cellular level, presumably through engaging in more effective coping mechanisms and modulation of stress. The findings also highlight the role of nonreactivity as a potential mechanism that underlies the association between LTL and psychological symptoms.

Keywords: depression, mindfulness, stress, telomere length

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Authors: Marek Pawlikowski, Krzysztof Jankowski, Konstanty Skalski, Anna Makuch

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Nanoindentation or depth-sensing indentation (DSI) technique has proven to be very useful to measure mechanical properties of various tissues at a micro-scale. Bone tissue, both trabecular and cortical one, is one of the most commonly tested tissues by means of DSI. Most often such tests on bone samples are carried out to compare the mechanical properties of lamellar and interlamellar bone, osteonal bone as well as compact and cancellous bone. In the paper, a relation between stress and strain for human trabecular bone is presented. The relation is based on the results of nanoindentation tests. The formulation of a constitutive model for human trabecular bone is based on nanoindentation tests. In the study, the approach proposed by Olivier-Pharr is adapted. The tests were carried out on samples of trabecular tissue extracted from human femoral heads. The heads were harvested during surgeries of artificial hip joint implantation. Before samples preparation, the heads were kept in 95% alcohol in temperature 4 Celsius degrees. The cubic samples cut out of the heads were stored in the same conditions. The dimensions of the specimens were 25 mm x 25 mm x 20 mm. The number of 20 samples have been tested. The age range of donors was between 56 and 83 years old. The tests were conducted with the indenter spherical tip of the diameter 0.200 mm. The maximum load was P = 500 mN and the loading rate 500 mN/min. The data obtained from the DSI tests allows one only to determine bone behoviour in terms of nanoindentation force vs. nanoindentation depth. However, it is more interesting and useful to know the characteristics of trabecular bone in the stress-strain domain. This allows one to simulate trabecular bone behaviour in a more realistic way. The stress-strain curves obtained in the study show relation between the age and the mechanical behaviour of trabecular bone. It was also observed that the bone matrix of trabecular tissue indicates an ability of energy absorption.

Keywords: constitutive model, mechanical behaviour, nanoindentation, trabecular bone

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Authors: Vinod Kumar, Navin Kumar, Surjit Angra, Prince Sharma

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This paper presents the design analysis of saddle support of a horizontal pressure vessel. Since saddle have the vital role to support the pressure vessel and to maintain its stability, it should be designed in such a way that it can afford the vessel load and internal pressure of the vessel due to liquid contained in the vessel. A model of horizontal pressure vessel and saddle support is created in Ansys. Stresses are calculated using mathematical approach and Ansys software. The analysis reveals the zone of high localized stress at the junction part of the pressure vessel and saddle support due to operating conditions. The results obtained by both the methods are compared with allowable stress value for safe designing.

Keywords: ANSYS, pressure vessel, saddle, support

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Authors: Emmanuel Kamal Aziz Saba, Hussein Al-Moghazy Sultan

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The aim of this study was to evaluate clinically and electro physiologically the autonomic nervous system changes associated with rheumatoid arthritis (RA). The present study included 25 patients with RA [22 women (88%)] and 30 apparently healthy control subjects [27 women (90%)]. A thorough clinical examination was carried out. Disease activity and functional disability were assessed. Tests for assessment of autonomic functions include active and passive orthostatic stress tests, and sympathetic skin response (SSR). The presence of abnormality in 2 tests or more was a clue for the presence of autonomic neuropathy (AN). Sural sensory nerve conduction study and posterior tibial motor nerve conduction study were done. There was a statistically significant decrease in standing systolic and diastolic blood pressure (BP) components of the active orthostatic stress test and SSR amplitude as well as statistically significant prolongation of SSR latency of RA patients when compared to control. Three patients (12%) had clinical symptoms suggestive of AN; increased to 14 patients (56 %) when orthostatic stress tests and SSR were utilized. There were no statistically significant differences between patients with different disease activity score 28 with 4 variables grades of RA activity and SSR latency and amplitude. There were no statistically significant differences between patients with different Stanford Health Assessment Questionnaire Disability Index grades of RA functional disability and SSR latency and amplitude. In conclusion, autonomic neuropathy is a common extra-articular manifestation of RA affecting sympathetic and parasympathetic fibers.

Keywords: autonomic neuropathy, orthostatic stress test, rheumatoid arthritis, sympathetic skin response

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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: Jyothi Nagraj, Sudeshna Mukherjee, Rajdeep Chowdhury

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Autophagy has recently been linked with cancer cell survival post drug insult contributing to acquisition of resistance. However, the molecular signaling governing autophagic survival response is poorly explored. In our study, in osteosarcoma (OS) cells cisplatin shock was found to activate both MAPK and autophagy signaling. An activation of JNK and autophagy acted as pro-survival strategy, while ERK1/2 triggered apoptotic signals upon cisplatin stress. An increased sensitivity of the cells to cisplatin was obtained with simultaneous inhibition of both autophagy and JNK pathway. Furthermore, we observed that the autophagic stimulation upon drug stress regulates other developmentally active signaling pathways like the Hippo pathway in OS cells. Cisplatin resistant cells were thereafter developed by repetitive drug exposure followed by clonal selection. Basal levels of autophagy were found to be high in resistant cells to. However, the signaling mechanism leading to autophagic up-regulation and its regulatory effect differed in OS cells upon attaining drug resistance. Our results provide valuable clues to regulatory dynamics of autophagy that can be considered for development of improved therapeutic strategy against resistant type cancers.

Keywords: JNK, autophagy, drug resistance, cancer

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Authors: Hannah Gutmann, Rick Richardson, Richard Bryant

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Intrusive memories following a traumatic event are not uncommon. However, in some individuals, these memories become maladaptive and lead to prolonged stress reactions. A seminal model of PTSD explains that aberrant processing during trauma may lead to prolonged stress reactions and intrusive memories. This model explains that elevated arousal at the time of the trauma promotes data driven processing, leading to fragmented and intrusive memories. This study investigated the role of elevated arousal on the development of intrusive memories. We measured salivary markers of arousal and investigated what impact this had on data driven processing, memory fragmentation, and subsequently, the development of intrusive memories. We assessed 100 healthy participants to understand their processing style, arousal, and experience of intrusive memories. Participants were randomised to a control or experimental condition, the latter of which was designed to increase their arousal. Based on current theory, participants in the experimental condition were expected to engage in more data driven processing and experience more intrusive memories than participants in the control condition. This research aims to shed light on the mechanisms underlying the development of intrusive memories to illustrate ways in which therapeutic approaches for PTSD may be augmented for greater efficacy.

Keywords: stress, cortisol, SAA, PTSD, intrusive memories

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Authors: Mohamed Trigui, Fatma Masmoudi, Imen Zouari

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Massive utilizations of chemical fertilizer and chemical pesticides in agriculture sector to improve the farming productivity have created increasing environmental damages. Then, agriculture must become sustainable, focusing on production systems that respect the environment and help to reduce climate change. Isolation and microbial identification of new bacterial strains from naturally saline habitats and compost extracts could be a prominent way in pest management and crop production under saline conditions. In this study, potential mechanisms involved in plant growth promotion and suppressive activity against fungal diseases of a compost extract produced from poultry manure/olive husk compost and halotolerant and halophilic bacterial strains under saline stress were investigated. On the basis of the antimicrobial tests, different strains isolated from Sfax solar saltern (Tunisia) and from compost extracts were selected and tested for their plant growth promoting traits, such as siderophores production, nitrogen fixation, phosphate solubilization and the production of extracellular hydrolytic enzymes (protease and lipase) under in-vitro conditions. Among 450 isolated bacterial strains, 16 isolates showed potent antifungal activity against the tested plant pathogenic fungi. Their identification based on 16S rRNA gene sequence revealed they belonged to different species. Some of these strains were also characterized for their plant growth promoting capacities. Obtained results showed the ability of four strains belonging to Bacillus genesis to ameliorate germination rate and root elongation compared to the untreated positive controls. Combinatorial capacity of halotolerant bacteria with antimicrobial activity and plant growth promoting traits could be promising sources of interesting bioactive substances under saline stress.

Keywords: abiotic stress, biofertilizer, biotic stress, compost extract, halobacteria, plant growth promoting (PGP), soil fertility

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Authors: Markéta Chmelíková, David Ullrich, Iva Burešová

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The paper maps the possibilities and limits of diagnosing selected personality and performance characteristics of military leadership and psychology students in the context of coping with challenging situations. Individuals vary greatly inter-individually in their ability to effectively manage extreme situations, yet existing diagnostic tools are often criticized mainly for their low predictive power. Nowadays, every modern army focuses primarily on the systematic minimization of potential risks, including the prediction of desirable forms of behavior and the performance of military commanders. The context of military leadership is well known for its life-threatening nature. Therefore, it is crucial to research stress load in the specific context of military leadership for the purpose of possible anticipation of human failure in managing extreme situations of military leadership. The aim of the submitted pilot study, using an experiment of 24 hours duration, is to verify the possibilities of a specific combination of psychodiagnostic to predict people who possess suitable equipment for coping with increased stress load. In our pilot study, we conducted an experiment of 24 hours duration with an experimental group (N=13) in the bomb shelter and a control group (N=11) in a classroom. Both groups were represented by military leadership students (N=11) and psychology students (N=13). Both groups were equalized in terms of study type and gender. Participants were administered the following test battery of personality characteristics: Big Five Inventory 2 (BFI-2), Short Dark Triad (SD-3), Emotion Regulation Questionnaire (ERQ), Fatigue Severity Scale (FSS), and Impulsive Behavior Scale (UPPS-P). This test battery was administered only once at the beginning of the experiment. Along with this, they were administered a test battery consisting of the Test of Attention (d2) and the Bourdon test four times overall with 6 hours ranges. To better simulate an extreme situation – we tried to induce sleep deprivation - participants were required to try not to fall asleep throughout the experiment. Despite the assumption that a stay in an underground bomb shelter will manifest in impaired cognitive performance, this expectation has been significantly confirmed in only one measurement, which can be interpreted as marginal in the context of multiple testing. This finding is a fundamental insight into the issue of stress management in extreme situations, which is crucial for effective military leadership. The results suggest that a 24-hour stay in a shelter, together with sleep deprivation, does not seem to simulate sufficient stress for an individual, which would be reflected in the level of cognitive performance. In the context of these findings, it would be interesting in future to extend the diagnostic battery with physiological indicators of stress, such as: heart rate, stress score, physical stress, mental stress ect.

Keywords: bomb shelter, extreme situation, military leadership, psychodiagnostic

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Authors: Zhuoneng Li, Zeeshan A. Rana, Karl W. Jenkins

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In industry, to validate a case, often a multitude of simulation are required and in order to demonstrate confidence in the process where users tend to use a coarser mesh. Therefore, it is imperative to establish the coarsest mesh that could be used while keeping reasonable simulation accuracy. To date, the two most reliable, affordable and broadly used advanced simulations are the hybrid RANS (Reynolds Averaged Navier Stokes)/LES (Large Eddy Simulation) and wall modelled LES. The potentials in these two simulations will still be developed in the next decades mainly because the unaffordable computational cost of a DNS (Direct Numerical Simulation). In the wall modelled LES, the turbulence model is applied as a sub-grid scale model in the most inner layer near the wall. The RANS turbulence models cover the entire boundary layer region in a hybrid RANS/LES (Detached Eddy Simulation) and its variants, therefore, the RANS still has a very important role in the state of art simulations. This research focuses on the turbulence model mesh sensitivity analysis where various turbulence models such as the S-A (Spalart-Allmaras), SSG (Speziale-Sarkar-Gatski), K-Omega transitional SST (Shear Stress Transport), K-kl-Omega, γ-Reθ transitional model, v2f are evaluated within the OpenFOAM. The simulations are conducted on a fully developed turbulent flow over a flat plate where the skin friction coefficient as well as velocity profiles are obtained to compare against experimental values and DNS results. A concrete conclusion is made to clarify the mesh sensitivity for different turbulence models.

Keywords: mesh sensitivity, turbulence models, OpenFOAM, RANS

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Authors: Caglayan Pinar Demirtas, Mustafa Koc

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Objective: This study was carried out in order to find out; the methods which are used by primary school teachers to cope with stress, their psychological health, and the direction of controlling focus. The study was carried out by using the ‘school survey’ and ‘society survey’ methods. Method: The study included primary school teachers. The study group was made up of 1066 people; 511 women and 555 men who accepted volunteerly to complete; ‘the inventory for collecting data, ‘the Scale for Attitude of Overcoming Stress’ (SBTE / SAOS), ‘Rotter’s Scale for the Focus of Inner- Outer Control’ (RİDKOÖ / RSFIOC), and ‘the Symptom Checking List’ (SCL- 90). The data was collected by using ‘the Scale for Attitude of Overcoming Stress’, ‘the Scale for the Focus of Inner- Outer Control’, ‘the Symptom Checking List’, and a personal information form developed by the researcher. SPSS for Windows packet programme was used. Result: The age variable is a factor in interpersonal sensitivity, depression, anxciety, hostality symptoms but it is not a factor in the other symptoms. The variable, gender, is a factor in emotional practical escaping overcoming method but it is not a factor in the other overcoming methods. Namely, it has been found out that, women use emotional practical escaping overcoming method more than men. Marital status is a factor in methods of overcoming stress such as trusting in religion, emotional practical escaping and biochemical escaping while it is not a factor in the other methods. Namely, it has been found out that married teachers use trusting in religion method, and emotional practical escaping method more than single ones. Single teachers generally use biochemical escaping method. In primary school teachers’ direction of controlling focus, gender variable is a factor. It has been found out that women are more inner controlled while the men are more outer controlled. The variable, time of service, is a factor in the direction of controlling focus; that is, teachers with 1-5 years of service time are more inner controlled compared with teachers with 16-20 years of service time. The variable, age, is a factor in the direction of controlling focus; that is, teachers in 26-30 age groups are more outer controlled compared with the other age groups and again teachers in 26-30 age group are more inner controlled when compared with the other age groups. Direction of controlling focus is a factor in the primary school teachers’ psychological health. Namely, being outer controlled is a factor but being inner controlled is not. The methods; trusting in religion, active plannıng and biochemical escaping used by primary school teachers to cope with stress act as factors in the direction of controlling focus but not in the others. Namely, it has been found out that outer controlled teachers prefer the methods of trusting in religion and active planning while the inner controlled ones prefer biochemical escaping.

Keywords: coping with, controlling focus, psychological health, stress

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Authors: Hae Jeong Park, Joo-Ho Chung

Abstract:

In this study, the effect of essential oil from Chamaecyparis obtuse (EOCO) on early life stress using maternal separation (MS) rats was investigated. Anxiety-related behaviors were examined in MS rats using the elevated plus-maze (EPM) test. The changes of gene expressions by EOCO in the hippocampus of MS rats were analyzed using a microarray method. Rats in the MS groups were separated from their respective mothers from postnatal day (pnd) 14 to 28. Rats in the EOCO-treated groups were exposed to EOCO for 1 h or 2 h by inhalation from pnd 21 to 28. The EOCO-treated MS rats showed decreased anxiety-related behaviors compared to the MS rats in the EPM test. In the microarray analysis, EOCO downregulated the expressions of cytokine genes such as Ccl2, Il6, Cxcl10, Ccl19, and Il1rl in the hippocampus of MS rats, and it was also confirmed through RT-PCR. In particular, the expressions of Ccl2 and Il6 were predominantly decreased by EOCO in the hippocampus of MS rats. Interestingly, their protein expressions were also reduced by EOCO in MS rats. These results indicate that EOCO decreases MS-induced anxiety-related behaviors, and modulate cytokines, particularly Ccl2 and Il6, in the hippocampus of MS rats.

Keywords: anxiety-related behavior, Chamaecyparis obtuse, cytokine gene, early-life stress, maternal separation

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Authors: Rahaf Alasiri, Tarek Alghamdi, Abdullah Zarkan

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Background: Due to measures such as school closure, social distancing, and virtual teaching during the pandemic, primary school children's psychological well-being is greatly affected. These measures have short and long-term consequences on the children's well-being and mental health. Identifying these consequences is important. Aim: This study aimed to evaluate mood and behavior changes in children who attended school virtually. Subjects and methods: This is a cross-sectional study conducted among children and their parents who visited the outpatient clinic. A self-administered questionnaire was given to the parents of children aged between 6 to 14 years. The questionnaire includes socio-demographic characteristics, Conor's modifies scale to assess the attention deficit hyperactivity disorder (ADHD) of children, and the parental stress scale (PSS) to assess the stress symptoms of the parents. Results: Of the 66 surveyed children, 60.6% were aged between 10 to 14 years old, with the female being dominant (77.3%). The most common medical condition was asthma (7.6%), and nearly two-thirds (63.6%) indicated good health conditions during the pandemic. There was a significant inverse correlation observed between ADHD score and PSS score (r=-0.387). No significant differences are in ADHD and PSS scores in relation to the socio-demographic characteristics of the children, including age, gender, and having an associated medical condition (p>0.05). Conclusion: During the pandemic, children who attended virtual classes did not seem to affect even with restrictions. Most children indicated good health conditions during the pandemic. However, it is surprising to know that in spite of children’s high spirits during the pandemic, their parents were seen to have an increased level of stress. Strategies to address parents’ psychological disorders during the pandemic are warranted.

Keywords: children's mood, COVID-19, ADHD, parental stress

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