George Youssef | Egypt 1 (original) (raw)
Papers by George Youssef
Materials Horizons, 2020
A concentric multiferroic cylinder composite exhibit a sustained and frequency-modulated magnetoe... more A concentric multiferroic cylinder composite exhibit a sustained and frequency-modulated magnetoelectric coupling at magnetic fields above saturation due to delayed magnetization around the circumference of the magnetostrictive material.
Archives of Women's Mental Health, 2020
Early maternal-infant bonding problems are often forerunners of later emotional and behavioural d... more Early maternal-infant bonding problems are often forerunners of later emotional and behavioural difficulties. Interventions typically target the perinatal period but many risks may be established well before pregnancy. Here we examine the extent to which adolescent and young adult depression and anxiety symptoms predict perinatal maternal-infant bonding difficulties. The Victorian Intergenerational Health Cohort Study (VIHCS, est. 2006) is following offspring born to the Victorian Adolescent Health Cohort Study (VAHCS; est. 1992). VAHCS participants were assessed for depression and anxiety symptoms nine times during adolescence and young adulthood (age 14–29 years), and then contacted bi-annually (from age 29–35 years) to identify pregnancies. The Postpartum Bonding Questionnaire (PBQ) was administered to mothers at 2 and 12 months postpartum. A total of 395 women (606 infants) completed the 2-month and/or 12-month postpartum interviews. For most infants (64%), mothers had experienced depression and/or anxiety before pregnancy. Preconception depression and anxiety symptoms that persisted from adolescence into young adulthood predicted maternal-infant bonding problems at 2 months ( β = 0.30, 95% CI 0.04, 0.55) and 12 months postpartum ( β = 0.40, 95% CI 0.16, 0.63). Depression and anxiety symptoms occurring in young adulthood only, also predicted bonding problems at 12 months postpartum ( β = 0.37, 95% CI 0.02, 0.71). Associations between preconception depression and anxiety symptoms and anxiety-related maternal-infant bonding problems at 12 months postpartum remained after adjustment for antenatal and concurrent postpartum depressive symptoms. This study puts forward a case for extending preconception health care beyond contraception and nutrition to a broader engagement in supporting the mental health of young women from adolescence.
Applied Mechanics of Polymers, 2022
Applied Mechanics of Polymers, 2022
Applied Mechanics of Polymers, 2022
The Coping with Children's Negative Emotion Scale (CCNES) is a self-report measure of parent ... more The Coping with Children's Negative Emotion Scale (CCNES) is a self-report measure of parent reactions to negative child emotions. It was originally designed to measure parenting behaviours in accordance with Lazarus & Folkman's Transactional Model of Stress and Coping but has been commonly used to assess parent emotion socialisation, and specifically, theory of meta-emotion. However, while many of the CCNES items and subscales appear to fit with this purpose, the theoretical alignment has never been formally tested. Further, the scale is lengthy, limiting wider research use, given that longer measures increase participant burden and result in poorer quality response data. To address these issues, the current study will develop a short-form version of the CCNES, via two processes. The first process will involve a theoretical evaluation of the individual items, in line with Gottman and colleagues meta-emotion theory. We will also evaluate items from an additional 'empathy...
Supplemental material, Supplementary_material for The Role of Sleep in the Relationship Between A... more Supplemental material, Supplementary_material for The Role of Sleep in the Relationship Between ADHD Symptoms and Stop Signal Task Performance by Brittany Mann, Emma Sciberras, Jason He, George Youssef, Vicki Anderson and Timothy J. Silk in Journal of Attention Disorders
Maternal sensitivity is a modifiable determinant of infant attachment security and a precursor to... more Maternal sensitivity is a modifiable determinant of infant attachment security and a precursor to optimal child development. Contextual stressors undermine sensitivity, but research was yet to be synthesized. We aimed to identify i) types of stress associations analyzed in studies of maternal sensitivity and ii) the strength of effects of various stress factors. A systematic search identified all studies that used the Maternal Behavior Q-Sort (MBQS) to code sensitivity in dyadic observations and that reported a coefficient for MBQS associations with contextual stress. Identified stressors cohered around three spheres: sociodemography (maternal education, family income, composite SES, maternal age and cohabitation status); parenting stress (perceived maternal stress related to parenting); and mental health (specifically maternal internalizing symptoms). Seven meta-analyses (combined ns range 223-1239) of a subset of 30 effects from 20 articles, and a multi-level meta-analysis (N=1324...
Macromolecular Materials and Engineering, 2021
Section A Table S1. Patterns of alcohol use by partners across pregnancy. Table S2. Paternal fact... more Section A Table S1. Patterns of alcohol use by partners across pregnancy. Table S2. Paternal factors associated with alcohol use by mothers. Table S3. Regression results for maternal alcohol use and infant gross motor outcomes; women with partner in study only. Table S4. Marginal means for maternal alcohol use and infant gross motor outcomes; women with partner in study only. (DOCX 24 kb)
Table S1. Terms used in the electronic search strategy, adjusted as required for each database. (... more Table S1. Terms used in the electronic search strategy, adjusted as required for each database. (DOCX 12 kb)
Journal of Engineering Materials and Technology, 2022
The residual effect of thermally and mechanically loaded polyurea samples was investigated in thi... more The residual effect of thermally and mechanically loaded polyurea samples was investigated in this study using terahertz time-domain spectroscopy (THz-TDS). Samples of different thicknesses were submerged in liquid nitrogen and allowed to reach cryogenic isothermal conditions while another set of samples were extracted from quasi-statically loaded strips. All samples were interrogated using THz-TDS since terahertz waves exhibit non-ionizing, nondestructive interactions with polymers. The time-domain terahertz signals were used to extract the optical and electrical properties as a function of sample thickness and loading conditions. The residual effect was prominent in the mechanically loaded samples compared to a nearly negligible presence in thermally loaded polyurea. On average, the results of the thermally loaded samples were subtle when compared to the virgin samples, whereas samples that were mechanically stretched showed a considerable difference in the characteristics of the ...
Biomed. Signal Process. Control., 2021
Background and objective Transfer functions could model biomechanical parameters to conveniently ... more Background and objective Transfer functions could model biomechanical parameters to conveniently analyze the system dynamics of the lower limb during daily activities, e.g., walking. The current study evaluates the feasibility of transfer functions as a means of predicting surface electromyography (sEMG) of lower limb muscles based on axial tibial (ATA) and femoral (FA) accelerations. Since the transfer functions are comparable in accuracy to commonly used long short-term memory models (LSTM), the transfer function-based methodology can assist in the design of novel prostheses while being competitive with mainstream models. Methods Data were collected from eight participants with no medical history that would alter their gait cycles. The data included the sEMG of four primary muscle groups, ATA and FA, and heel-strike triggering signal, while the subjects walked at 5.28 km/h on a treadmill. A fast Fourier transform (FFT) was performed on the filtered ensemble averages of the ATA, FA...
Rationale and Objectives: Vascular calcification independently predicts cardiovascular disease (C... more Rationale and Objectives: Vascular calcification independently predicts cardiovascular disease (CVD), and computed tomography (CT) is a useful tool to evaluate and quantify not only coronary but also thoracic aortic calcification (TAC). Previous TAC progression reports were limited to dialysis and renal transplant patients. This is the first study to evaluate TAC progression in a large multiethnic cohort without clinically evident CVD at entry. Methods: Non-contrast-enhanced cardiac CTs were obtained in 5886 of 6814 Multi-Ethnic Study of Atherosclerosis (MESA) participants (mean age, 62 years; 48% males; 40% white, 27% black, 21% Hispanic, and 12% Chinese). Baseline and follow-up TAC scores were derived. Results: Overall, 4308 (73%) participants had no detectable baseline TAC. Mean follow-up duration was 2.4 AE 0.8 years, during which 12% developed TAC. The overall incidence rate was 4.8%/year and was greater with age across gender and ethnic groups; TAC incidence was significantly lower in blacks than whites. After adjustment for follow-up duration, regression analyses showed age, systolic blood pressure, antihypertensives, and smoking were associated with incident TAC. A total of 1578 (27%) participants had TAC at baseline with a positive association between average annual TAC change and baseline age. Although the overall median change was 32.9 (À1.4 to 112.2) Agatston units, 27% showed an annual score change of $100 and blacks showed the lowest median across ethnic groups; 22.7 (À3 to 86.8). Age, systolic blood pressure, lipid-lowering medication, diabetes, and smoking were associated with TAC progression. Conclusions: In MESA, traditional CV risk factors were related to both TAC incidence and progression. Blacks had the lowest incidence and median change across ethnic groups, consistent with previous findings for coronary calcification.
International Journal of Mechanical Sciences, 2021
Strain-mediated multiferroic composite structures are gaining scientific and technological attrac... more Strain-mediated multiferroic composite structures are gaining scientific and technological attractions because of the promise of low power consumption and greater flexibility in material and geometry choices. In here, the direct magnetoelectric coupling coefficient (DME) of composite multiferroic cylinders, consisted of two mechanically bonded concentric cylinders, was analytically modeled under the influence of a radially emanating magnetic field. The analysis framework emphasized the effects of shear lag and demagnetization on the overall performance. The shear lag effect was analytically proven to have no bearing on the DME since it has no effect on the induced radial displacement due to the conditions imposed on the composite cylinder. The demagnetization effect was also thoroughly considered as a function of the imposed mechanical boundary conditions, geometrical dimensions of the composite cylinder, and the introduction of a thin elastic layer at the interface between the inne...
Introduction Hypertensive disorders of pregnancy (HDP) are associated with increased post-partum ... more Introduction Hypertensive disorders of pregnancy (HDP) are associated with increased post-partum cardiovascular risk in comparison to normal pregnancy (NP). Changes in cardiac structure and function following an HDP have been described previously but whether such changes are useful in identifying women at increased cardiovascular risk is not known. Echocardiography is a non-invasive tool used in the detection of early systolic and diastolic dysfunction. Objectives To assess cardiac structure and function by echocardiography in women, 6 months after NP or pregnancy complicated by either gestational HT or pre-eclampsia (HDP group). Methods The study enrolled a prospective cohort of women recruited to the ongoing P4 (Postpartum Physiology, Psychology, and Paediatric follow up) study at St George Hospital, Kogarah, Sydney. Echocardiography was performed six months after either NP or HDP. Trained cardiac sonographers were blinded to whether women had a NP or an HDP. All studies were perf...
Bones self-optimize their mechanical behavior in response to mechanical stimulus. The objective o... more Bones self-optimize their mechanical behavior in response to mechanical stimulus. The objective of this research was to develop an integrated bone remodeling and stress binning algorithms into a finite element environment to elucidate the evolution of the bone properties as a function of loading. The bone remodeling algorithm was used to calculate the change in the density and elastic modulus based on the strain energy stimulus. The stress-binning procedure seeks to assign the properties to each element based on the levels of stress from the previous cycle, eliminating pseudo-lazy-zoning and stress dilation effects. The developed algorithms were used to analyze the response skull to loading associated with orthodontic devices. Specifically, a load was applied between the roots of the canine teeth and the first premolars while constraining the foramen magnum. Full-field contours of the displacement, strain, and strain energy were extracted after each remodeling cycle at nine commonly...
Multiferroic composite materials operating under the principle of strain mediation across the int... more Multiferroic composite materials operating under the principle of strain mediation across the interfaces separating different material boundaries address many limitations of single-phase magnetoelectric materials. Although significant research has been conducted to explore their responses relating to the topography and directionality of material polarization and magnetic loading, there remain unanswered questions regarding the long-term performance of these multiferroic structures. In this study, a multiferroic composite structure consisting of an inner Terfenol-D magnetostrictive cylinder and an outer lead zirconate titanate (PZT) piezoelectric cylinder was investigated. The composite was loaded over a 45-day period with an AC electric field (20 kV/m) at a near-resonant frequency (32.5 kHz) and a simultaneously applied DC magnetic field of 500 Oe. The long-term magnetoelectric and thermal responses were continuously monitored, and an extensive micrographic analysis of pretest and p...
Materials Horizons, 2020
A concentric multiferroic cylinder composite exhibit a sustained and frequency-modulated magnetoe... more A concentric multiferroic cylinder composite exhibit a sustained and frequency-modulated magnetoelectric coupling at magnetic fields above saturation due to delayed magnetization around the circumference of the magnetostrictive material.
Archives of Women's Mental Health, 2020
Early maternal-infant bonding problems are often forerunners of later emotional and behavioural d... more Early maternal-infant bonding problems are often forerunners of later emotional and behavioural difficulties. Interventions typically target the perinatal period but many risks may be established well before pregnancy. Here we examine the extent to which adolescent and young adult depression and anxiety symptoms predict perinatal maternal-infant bonding difficulties. The Victorian Intergenerational Health Cohort Study (VIHCS, est. 2006) is following offspring born to the Victorian Adolescent Health Cohort Study (VAHCS; est. 1992). VAHCS participants were assessed for depression and anxiety symptoms nine times during adolescence and young adulthood (age 14–29 years), and then contacted bi-annually (from age 29–35 years) to identify pregnancies. The Postpartum Bonding Questionnaire (PBQ) was administered to mothers at 2 and 12 months postpartum. A total of 395 women (606 infants) completed the 2-month and/or 12-month postpartum interviews. For most infants (64%), mothers had experienced depression and/or anxiety before pregnancy. Preconception depression and anxiety symptoms that persisted from adolescence into young adulthood predicted maternal-infant bonding problems at 2 months ( β = 0.30, 95% CI 0.04, 0.55) and 12 months postpartum ( β = 0.40, 95% CI 0.16, 0.63). Depression and anxiety symptoms occurring in young adulthood only, also predicted bonding problems at 12 months postpartum ( β = 0.37, 95% CI 0.02, 0.71). Associations between preconception depression and anxiety symptoms and anxiety-related maternal-infant bonding problems at 12 months postpartum remained after adjustment for antenatal and concurrent postpartum depressive symptoms. This study puts forward a case for extending preconception health care beyond contraception and nutrition to a broader engagement in supporting the mental health of young women from adolescence.
Applied Mechanics of Polymers, 2022
Applied Mechanics of Polymers, 2022
Applied Mechanics of Polymers, 2022
The Coping with Children's Negative Emotion Scale (CCNES) is a self-report measure of parent ... more The Coping with Children's Negative Emotion Scale (CCNES) is a self-report measure of parent reactions to negative child emotions. It was originally designed to measure parenting behaviours in accordance with Lazarus & Folkman's Transactional Model of Stress and Coping but has been commonly used to assess parent emotion socialisation, and specifically, theory of meta-emotion. However, while many of the CCNES items and subscales appear to fit with this purpose, the theoretical alignment has never been formally tested. Further, the scale is lengthy, limiting wider research use, given that longer measures increase participant burden and result in poorer quality response data. To address these issues, the current study will develop a short-form version of the CCNES, via two processes. The first process will involve a theoretical evaluation of the individual items, in line with Gottman and colleagues meta-emotion theory. We will also evaluate items from an additional 'empathy...
Supplemental material, Supplementary_material for The Role of Sleep in the Relationship Between A... more Supplemental material, Supplementary_material for The Role of Sleep in the Relationship Between ADHD Symptoms and Stop Signal Task Performance by Brittany Mann, Emma Sciberras, Jason He, George Youssef, Vicki Anderson and Timothy J. Silk in Journal of Attention Disorders
Maternal sensitivity is a modifiable determinant of infant attachment security and a precursor to... more Maternal sensitivity is a modifiable determinant of infant attachment security and a precursor to optimal child development. Contextual stressors undermine sensitivity, but research was yet to be synthesized. We aimed to identify i) types of stress associations analyzed in studies of maternal sensitivity and ii) the strength of effects of various stress factors. A systematic search identified all studies that used the Maternal Behavior Q-Sort (MBQS) to code sensitivity in dyadic observations and that reported a coefficient for MBQS associations with contextual stress. Identified stressors cohered around three spheres: sociodemography (maternal education, family income, composite SES, maternal age and cohabitation status); parenting stress (perceived maternal stress related to parenting); and mental health (specifically maternal internalizing symptoms). Seven meta-analyses (combined ns range 223-1239) of a subset of 30 effects from 20 articles, and a multi-level meta-analysis (N=1324...
Macromolecular Materials and Engineering, 2021
Section A Table S1. Patterns of alcohol use by partners across pregnancy. Table S2. Paternal fact... more Section A Table S1. Patterns of alcohol use by partners across pregnancy. Table S2. Paternal factors associated with alcohol use by mothers. Table S3. Regression results for maternal alcohol use and infant gross motor outcomes; women with partner in study only. Table S4. Marginal means for maternal alcohol use and infant gross motor outcomes; women with partner in study only. (DOCX 24 kb)
Table S1. Terms used in the electronic search strategy, adjusted as required for each database. (... more Table S1. Terms used in the electronic search strategy, adjusted as required for each database. (DOCX 12 kb)
Journal of Engineering Materials and Technology, 2022
The residual effect of thermally and mechanically loaded polyurea samples was investigated in thi... more The residual effect of thermally and mechanically loaded polyurea samples was investigated in this study using terahertz time-domain spectroscopy (THz-TDS). Samples of different thicknesses were submerged in liquid nitrogen and allowed to reach cryogenic isothermal conditions while another set of samples were extracted from quasi-statically loaded strips. All samples were interrogated using THz-TDS since terahertz waves exhibit non-ionizing, nondestructive interactions with polymers. The time-domain terahertz signals were used to extract the optical and electrical properties as a function of sample thickness and loading conditions. The residual effect was prominent in the mechanically loaded samples compared to a nearly negligible presence in thermally loaded polyurea. On average, the results of the thermally loaded samples were subtle when compared to the virgin samples, whereas samples that were mechanically stretched showed a considerable difference in the characteristics of the ...
Biomed. Signal Process. Control., 2021
Background and objective Transfer functions could model biomechanical parameters to conveniently ... more Background and objective Transfer functions could model biomechanical parameters to conveniently analyze the system dynamics of the lower limb during daily activities, e.g., walking. The current study evaluates the feasibility of transfer functions as a means of predicting surface electromyography (sEMG) of lower limb muscles based on axial tibial (ATA) and femoral (FA) accelerations. Since the transfer functions are comparable in accuracy to commonly used long short-term memory models (LSTM), the transfer function-based methodology can assist in the design of novel prostheses while being competitive with mainstream models. Methods Data were collected from eight participants with no medical history that would alter their gait cycles. The data included the sEMG of four primary muscle groups, ATA and FA, and heel-strike triggering signal, while the subjects walked at 5.28 km/h on a treadmill. A fast Fourier transform (FFT) was performed on the filtered ensemble averages of the ATA, FA...
Rationale and Objectives: Vascular calcification independently predicts cardiovascular disease (C... more Rationale and Objectives: Vascular calcification independently predicts cardiovascular disease (CVD), and computed tomography (CT) is a useful tool to evaluate and quantify not only coronary but also thoracic aortic calcification (TAC). Previous TAC progression reports were limited to dialysis and renal transplant patients. This is the first study to evaluate TAC progression in a large multiethnic cohort without clinically evident CVD at entry. Methods: Non-contrast-enhanced cardiac CTs were obtained in 5886 of 6814 Multi-Ethnic Study of Atherosclerosis (MESA) participants (mean age, 62 years; 48% males; 40% white, 27% black, 21% Hispanic, and 12% Chinese). Baseline and follow-up TAC scores were derived. Results: Overall, 4308 (73%) participants had no detectable baseline TAC. Mean follow-up duration was 2.4 AE 0.8 years, during which 12% developed TAC. The overall incidence rate was 4.8%/year and was greater with age across gender and ethnic groups; TAC incidence was significantly lower in blacks than whites. After adjustment for follow-up duration, regression analyses showed age, systolic blood pressure, antihypertensives, and smoking were associated with incident TAC. A total of 1578 (27%) participants had TAC at baseline with a positive association between average annual TAC change and baseline age. Although the overall median change was 32.9 (À1.4 to 112.2) Agatston units, 27% showed an annual score change of $100 and blacks showed the lowest median across ethnic groups; 22.7 (À3 to 86.8). Age, systolic blood pressure, lipid-lowering medication, diabetes, and smoking were associated with TAC progression. Conclusions: In MESA, traditional CV risk factors were related to both TAC incidence and progression. Blacks had the lowest incidence and median change across ethnic groups, consistent with previous findings for coronary calcification.
International Journal of Mechanical Sciences, 2021
Strain-mediated multiferroic composite structures are gaining scientific and technological attrac... more Strain-mediated multiferroic composite structures are gaining scientific and technological attractions because of the promise of low power consumption and greater flexibility in material and geometry choices. In here, the direct magnetoelectric coupling coefficient (DME) of composite multiferroic cylinders, consisted of two mechanically bonded concentric cylinders, was analytically modeled under the influence of a radially emanating magnetic field. The analysis framework emphasized the effects of shear lag and demagnetization on the overall performance. The shear lag effect was analytically proven to have no bearing on the DME since it has no effect on the induced radial displacement due to the conditions imposed on the composite cylinder. The demagnetization effect was also thoroughly considered as a function of the imposed mechanical boundary conditions, geometrical dimensions of the composite cylinder, and the introduction of a thin elastic layer at the interface between the inne...
Introduction Hypertensive disorders of pregnancy (HDP) are associated with increased post-partum ... more Introduction Hypertensive disorders of pregnancy (HDP) are associated with increased post-partum cardiovascular risk in comparison to normal pregnancy (NP). Changes in cardiac structure and function following an HDP have been described previously but whether such changes are useful in identifying women at increased cardiovascular risk is not known. Echocardiography is a non-invasive tool used in the detection of early systolic and diastolic dysfunction. Objectives To assess cardiac structure and function by echocardiography in women, 6 months after NP or pregnancy complicated by either gestational HT or pre-eclampsia (HDP group). Methods The study enrolled a prospective cohort of women recruited to the ongoing P4 (Postpartum Physiology, Psychology, and Paediatric follow up) study at St George Hospital, Kogarah, Sydney. Echocardiography was performed six months after either NP or HDP. Trained cardiac sonographers were blinded to whether women had a NP or an HDP. All studies were perf...
Bones self-optimize their mechanical behavior in response to mechanical stimulus. The objective o... more Bones self-optimize their mechanical behavior in response to mechanical stimulus. The objective of this research was to develop an integrated bone remodeling and stress binning algorithms into a finite element environment to elucidate the evolution of the bone properties as a function of loading. The bone remodeling algorithm was used to calculate the change in the density and elastic modulus based on the strain energy stimulus. The stress-binning procedure seeks to assign the properties to each element based on the levels of stress from the previous cycle, eliminating pseudo-lazy-zoning and stress dilation effects. The developed algorithms were used to analyze the response skull to loading associated with orthodontic devices. Specifically, a load was applied between the roots of the canine teeth and the first premolars while constraining the foramen magnum. Full-field contours of the displacement, strain, and strain energy were extracted after each remodeling cycle at nine commonly...
Multiferroic composite materials operating under the principle of strain mediation across the int... more Multiferroic composite materials operating under the principle of strain mediation across the interfaces separating different material boundaries address many limitations of single-phase magnetoelectric materials. Although significant research has been conducted to explore their responses relating to the topography and directionality of material polarization and magnetic loading, there remain unanswered questions regarding the long-term performance of these multiferroic structures. In this study, a multiferroic composite structure consisting of an inner Terfenol-D magnetostrictive cylinder and an outer lead zirconate titanate (PZT) piezoelectric cylinder was investigated. The composite was loaded over a 45-day period with an AC electric field (20 kV/m) at a near-resonant frequency (32.5 kHz) and a simultaneously applied DC magnetic field of 500 Oe. The long-term magnetoelectric and thermal responses were continuously monitored, and an extensive micrographic analysis of pretest and p...