The Experts below are selected from a list of 300 Experts worldwide ranked by ideXlab platform
Carolyn B. Mervis - One of the best experts on this subject based on the ideXlab platform.
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Methodological Issues in Group-Matching Designs: α Levels for Control Variable Comparisons and Measurement Characteristics of Control and Target Variables
Journal of Autism and Developmental Disorders, 2004Co-Authors: Carolyn B. Mervis, Bonita P. Klein-tasmanAbstract:Group-matching designs are commonly used to identify the diagnosis-specific characteristics of children with developmental disabilities. In this paper, we address three issues central to the use of this design. The first concerns the α level to be used for considering groups to be matched on the control variable(s). The second involves the measurement characteristics of the control and target variables. We discuss the properties of standard scores, raw scores, and age equivalents and argue against the use of age equivalents. In addition, we consider the appropriateness of the commonly made prediction that groups that are matched for a control variable such as language ability or nonverbal reasoning ability but are not matched for chronological age should perform at equivalent levels on the target variable. Finally, we discuss issues related to the interpretation of significant between-group differences on the target variable, assuming groups are well-matched on the control variables, and describe the benefits of a method that focuses on characterizing a disorder on a case-by-case basis and then aggregating the cases, using the measures of sensitivity and specificity from signal detection theory.
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methodological issues in group matching designs alpha levels for control variable comparisons and measurement characteristics of control and target variables
Journal of Autism and Developmental Disorders, 2004Co-Authors: Carolyn B. Mervis, Bonita P KleintasmanAbstract:Group-matching designs are commonly used to identify the diagnosis-specific characteristics of children with developmental disabilities. In this paper, we address three issues central to the use of this design. The first concerns the α level to be used for considering groups to be matched on the control variable(s). The second involves the measurement characteristics of the control and target variables. We discuss the properties of standard scores, raw scores, and age equivalents and argue against the use of age equivalents. In addition, we consider the appropriateness of the commonly made prediction that groups that are matched for a control variable such as language ability or nonverbal reasoning ability but are not matched for chronological age should perform at equivalent levels on the target variable. Finally, we discuss issues related to the interpretation of significant between-group differences on the target variable, assuming groups are well-matched on the control variables, and describe the benefits of a method that focuses on characterizing a disorder on a case-by-case basis and then aggregating the cases, using the measures of sensitivity and specificity from signal detection theory.
Bonita P. Klein-tasman - One of the best experts on this subject based on the ideXlab platform.
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Methodological Issues in Group-Matching Designs: α Levels for Control Variable Comparisons and Measurement Characteristics of Control and Target Variables
Journal of Autism and Developmental Disorders, 2004Co-Authors: Carolyn B. Mervis, Bonita P. Klein-tasmanAbstract:Group-matching designs are commonly used to identify the diagnosis-specific characteristics of children with developmental disabilities. In this paper, we address three issues central to the use of this design. The first concerns the α level to be used for considering groups to be matched on the control variable(s). The second involves the measurement characteristics of the control and target variables. We discuss the properties of standard scores, raw scores, and age equivalents and argue against the use of age equivalents. In addition, we consider the appropriateness of the commonly made prediction that groups that are matched for a control variable such as language ability or nonverbal reasoning ability but are not matched for chronological age should perform at equivalent levels on the target variable. Finally, we discuss issues related to the interpretation of significant between-group differences on the target variable, assuming groups are well-matched on the control variables, and describe the benefits of a method that focuses on characterizing a disorder on a case-by-case basis and then aggregating the cases, using the measures of sensitivity and specificity from signal detection theory.
Bonita P Kleintasman - One of the best experts on this subject based on the ideXlab platform.
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methodological issues in group matching designs alpha levels for control variable comparisons and measurement characteristics of control and target variables
Journal of Autism and Developmental Disorders, 2004Co-Authors: Carolyn B. Mervis, Bonita P KleintasmanAbstract:Group-matching designs are commonly used to identify the diagnosis-specific characteristics of children with developmental disabilities. In this paper, we address three issues central to the use of this design. The first concerns the α level to be used for considering groups to be matched on the control variable(s). The second involves the measurement characteristics of the control and target variables. We discuss the properties of standard scores, raw scores, and age equivalents and argue against the use of age equivalents. In addition, we consider the appropriateness of the commonly made prediction that groups that are matched for a control variable such as language ability or nonverbal reasoning ability but are not matched for chronological age should perform at equivalent levels on the target variable. Finally, we discuss issues related to the interpretation of significant between-group differences on the target variable, assuming groups are well-matched on the control variables, and describe the benefits of a method that focuses on characterizing a disorder on a case-by-case basis and then aggregating the cases, using the measures of sensitivity and specificity from signal detection theory.
Maxim Zhadobov - One of the best experts on this subject based on the ideXlab platform.
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Thermal Model of Electromagnetic Skin-Equivalent Phantom at Millimeter Waves
IEEE Transactions on Microwave Theory and Techniques, 2017Co-Authors: Carole Leduc, Maxim ZhadobovAbstract:This paper reports the first thermal model and detailed analysis of the heating of an electromagnetic (EM) skinequivalent phantom with a finite thickness at 60 GHz. The 1-D heat transfer equation is solved analytically for homogeneous phantoms with finite thicknesses. The temperature rise dynamics and heating distribution within the phantom are calculated for several phantom thicknesses (5, 10, and 15 mm) using measured thermal properties of the phantom. Analytical results are confirmed by numerical analysis based on EM-thermal cosimulations. Furthermore, the numerical model is validated by measurements using an experimental setup based on the high-resolution infrared thermometry. The impact of uncertainty of EM and the thermal parameters of the numerical model upon heat deposition is also studied. Our results reveal that, for short exposure durations (i.e., less than 1 min), the surface temperature is well described by the semi-infinite and finite-thickness phantom models, whereas, for longer exposures (more than 1 min), finite-thickness models must be used to properly account for heating accumulation close to the phantom boundaries. While the reported results cannot be directly used for predicting temperature increase in skin, they are of importance for temperature-based dosimetric assessment in the millimeter-wave band using currently available homogeneous phantoms.
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Thermal model of skin-equivalent phantoms at 60 GHz
2015Co-Authors: Carole Leduc, Maxim Zhadobov, Ronan SauleauAbstract:This paper reports the first analytical thermal model of a finite millimeter-wave phantom emulating the electromagnetic properties of human skin at 60 GHz. This model is obtained by solving the one-dimensional (1D) heat transfer equation (HTE). The analytical results calculated for several phantom thicknesses (5mm, 10mm, and 15mm) have been compared to the 1D analytical solution of the bio-heat transfer equation (BHTE) for a semi-infinite phantom model as well as to electromagnetic-thermal co-simulation results obtain using CST Microwave Studio. An excellent agreement is observed between the analytical and numerical results (deviations around 1%), and, as expected, a convergence toward the BHTE result is observed when increasing the phantom thickness.
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broadband tissue equivalent phantom for ban applications at millimeter waves
IEEE Transactions on Microwave Theory and Techniques, 2012Co-Authors: Nacer Chahat, Maxim Zhadobov, Ronan SauleauAbstract:The extension of body area networks from microwaves to millimeter waves requires to develop experimental phantoms emulating the dielectric properties of human skin for the accurate, reproducible, and well-controlled characterization of wearable antennas, on-body propagation channel, and absorption of the electromagnetic power by the human body. Here we introduce a broadband skin-equivalent semisolid phantom whose composition is optimized to coincide with measured values of the human skin permittivity in the 55-65-GHz range. To confirm the accuracy of this phantom, specific absorption rate measurements are performed at 60 GHz using a temperature-based approach. An excellent agreement between the experimental and numerical results is demonstrated.
Verónica Mericq - One of the best experts on this subject based on the ideXlab platform.
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Ultrasensitive estrogen levels at 7 years of age predict earlier thelarche: evidence from girls of the growth and obesity Chilean cohort.
European journal of endocrinology, 2015Co-Authors: Ana Pereira, Karen O Klein, Camila Corvalán, Ricardo Uauy, Verónica MericqAbstract:Objective: Prepubertal estradiol equivalents have been inconsistently linked to age at thelarche; elucidating this relationship becomes relevant given the worldwide decline in the age of puberty onset. Thus, our aim is to assess whether prepubertal girls with higher serum levels of estradiol equivalents at age 7 have a greater risk of presenting early thelarche (ET). Design: Nested case‐control study within the Growth and Obesity Cohort Study of 1196 low-middle income children (w50% girls) from Santiago, Chile. Girls were defined as cases (ET; nZ61) if breast bud appeared prior to 8 years of age; controls (nZ91) had thelarche O8 years. Methods: At 6.7 years, weight, height and waist circumference were measured and a fasting blood sample was obtained for measuring estrogen equivalent (ultrasensitive recombinant cell bioassay), DHEAS, leptin, insulin and IGF1. Beginning at 7 years old, Tanner staging was assessed prospectively twice a year and the appearance of breast bud was assessed by palpation. Results: Mean serum estradiol-equivalent at 6.7 years was 3.9G3.6 pg/ml for cases and 3.6G2.3 pg/ml for controls. Girls with ET had a higher risk of presenting elevated estradiol-equivalent (R5 pg/ml) at 7 years (ORZ2.05, 95% CI: 0.96‐4.36) than controls that was borderline significant. However, after adjusting by BMI, insulin and IGF1 at age 7, the association between estradiol-equivalent and ET was significant (ORZ2.29 (95% CI: 1.05‐5.01)). Conclusions: Chilean girls from low to middle socioeconomic status with ETexhibited double the risk of having high levels of estradiol-equivalent at 7 years than girls with a later age of thelarche. Whole-body adiposity and increased adrenal activity did not explain the observed prepubertal estrogen increase.