Alexandre Carra - Academia.edu (original) (raw)
Uploads
Papers by Alexandre Carra
Using a physically-based approach, we set up a dynamical model for cell deformation during moveme... more Using a physically-based approach, we set up a dynamical model for cell deformation during movement. Our description is based on the behavior observed in motile mammalian cells during which the front and rear of the cell periodically exchange signals. Our simulations show that very simple dynamics, based on coupled autonomous Van der Pol oscillators, help to understand the interaction between the mechanical properties of the cell structures (membrane, actin cables, focal adhesion) and the activation/deactivation of Rho and Rac-dependent protein cascades. In addition, the physically-based approach proves its relevance in the context of complex systems, where physical and chemical processes together build up the cell response to external perturbation.
The modeling of needle insertion into tissues is important for simulation of this procedure and f... more The modeling of needle insertion into tissues is important for simulation of this procedure and for robotic technologies applied to percutaneous therapy. In this article, we present a first attempt to develop a general force model for the needle insertion throw different tissue layers (skin, fat and muscle) to reach an internal organ (the liver, for instance) with objectives of control, looking for an optimal (less invasive and more accurate) puncture task. The forces are divided into three parts: stiffness, a nonlinear model; friction, a modified Dahl model; and cutting, a constant for a given tissue. Results show that the overall shape of forces presents the main phases of a needle insertion through several tissue layer.
The modeling of needle insertion into tissues is important for simulation of this procedure and f... more The modeling of needle insertion into tissues is important for simulation of this procedure and for robotic technologies applied to percutaneous therapy. In this article, we present a first attempt to develop a general force model for the needle insertion throw different tissue layers (skin, fat and muscle) to reach an internal organ (the liver, for instance) with objectives of control, looking for an optimal (less invasive and more accurate) puncture task. The forces are divided into three parts: stiffness, a nonlinear model; friction, a modified Dahl model; and cutting, a constant for a given tissue. Results show that the overall shape of forces presents the main phases of a needle insertion through several tissue layers.
Pediatric Neurology, 1992
Although methylphenidate has been demonstrated to be useful in ADHD, scant research has been devo... more Although methylphenidate has been demonstrated to be useful in ADHD, scant research has been devoted to predictors of medication response. We examined a series of 30 children meeting DSM III-R criteria for ADHD, in a randomized, doubleblind, placebo-controlled study using methylphenidate. The outcome measure was the continuous paired-associate learning task (CPALT), which is a computerized task developed at the Behavioral Neurology Department at Boston University, which measures children's learning and attention, and is sensitive to medication effects. All children received the Raven test, the Wisconsin card sorting test (WCST), and the matching familiar figures test (MFFT) on their placebo day. Twenty-five children (85%) showed a significant medication response on CPALT. Responders and nonresponders did not differ on any of the other measures, including the CPALT on placebo. There was a significant correlation between responder status and clinical improvement as measured by the DSM III-R-based snap rating scale. It is likely that responder status can only be predicted based on measurements on and off methylphenidate such as we performed.
Pediatric Neurology, 1992
Although methylphenidate has been demonstrated to be useful in ADHD, scant research has been devo... more Although methylphenidate has been demonstrated to be useful in ADHD, scant research has been devoted to predictors of medication response. We examined a series of 30 children meeting DSM III-R criteria for ADHD, in a randomized, doubleblind, placebo-controlled study using methylphenidate. The outcome measure was the continuous paired-associate learning task (CPALT), which is a computerized task developed at the Behavioral Neurology Department at Boston University, which measures children's learning and attention, and is sensitive to medication effects. All children received the Raven test, the Wisconsin card sorting test (WCST), and the matching familiar figures test (MFFT) on their placebo day. Twenty-five children (85%) showed a significant medication response on CPALT. Responders and nonresponders did not differ on any of the other measures, including the CPALT on placebo. There was a significant correlation between responder status and clinical improvement as measured by the DSM III-R-based snap rating scale. It is likely that responder status can only be predicted based on measurements on and off methylphenidate such as we performed.
Pediatric Neurology, 1992
Although methylphenidate has been demonstrated to be useful in ADHD, scant research has been devo... more Although methylphenidate has been demonstrated to be useful in ADHD, scant research has been devoted to predictors of medication response. We examined a series of 30 children meeting DSM III-R criteria for ADHD, in a randomized, doubleblind, placebo-controlled study using methylphenidate. The outcome measure was the continuous paired-associate learning task (CPALT), which is a computerized task developed at the Behavioral Neurology Department at Boston University, which measures children's learning and attention, and is sensitive to medication effects. All children received the Raven test, the Wisconsin card sorting test (WCST), and the matching familiar figures test (MFFT) on their placebo day. Twenty-five children (85%) showed a significant medication response on CPALT. Responders and nonresponders did not differ on any of the other measures, including the CPALT on placebo. There was a significant correlation between responder status and clinical improvement as measured by the DSM III-R-based snap rating scale. It is likely that responder status can only be predicted based on measurements on and off methylphenidate such as we performed.
Using a physically-based approach, we set up a dynamical model for cell deformation during moveme... more Using a physically-based approach, we set up a dynamical model for cell deformation during movement. Our description is based on the behavior observed in motile mammalian cells during which the front and rear of the cell periodically exchange signals. Our simulations show that very simple dynamics, based on coupled autonomous Van der Pol oscillators, help to understand the interaction between the mechanical properties of the cell structures (membrane, actin cables, focal adhesion) and the activation/deactivation of Rho and Rac-dependent protein cascades. In addition, the physically-based approach proves its relevance in the context of complex systems, where physical and chemical processes together build up the cell response to external perturbation.
The modeling of needle insertion into tissues is important for simulation of this procedure and f... more The modeling of needle insertion into tissues is important for simulation of this procedure and for robotic technologies applied to percutaneous therapy. In this article, we present a first attempt to develop a general force model for the needle insertion throw different tissue layers (skin, fat and muscle) to reach an internal organ (the liver, for instance) with objectives of control, looking for an optimal (less invasive and more accurate) puncture task. The forces are divided into three parts: stiffness, a nonlinear model; friction, a modified Dahl model; and cutting, a constant for a given tissue. Results show that the overall shape of forces presents the main phases of a needle insertion through several tissue layer.
The modeling of needle insertion into tissues is important for simulation of this procedure and f... more The modeling of needle insertion into tissues is important for simulation of this procedure and for robotic technologies applied to percutaneous therapy. In this article, we present a first attempt to develop a general force model for the needle insertion throw different tissue layers (skin, fat and muscle) to reach an internal organ (the liver, for instance) with objectives of control, looking for an optimal (less invasive and more accurate) puncture task. The forces are divided into three parts: stiffness, a nonlinear model; friction, a modified Dahl model; and cutting, a constant for a given tissue. Results show that the overall shape of forces presents the main phases of a needle insertion through several tissue layers.
Pediatric Neurology, 1992
Although methylphenidate has been demonstrated to be useful in ADHD, scant research has been devo... more Although methylphenidate has been demonstrated to be useful in ADHD, scant research has been devoted to predictors of medication response. We examined a series of 30 children meeting DSM III-R criteria for ADHD, in a randomized, doubleblind, placebo-controlled study using methylphenidate. The outcome measure was the continuous paired-associate learning task (CPALT), which is a computerized task developed at the Behavioral Neurology Department at Boston University, which measures children's learning and attention, and is sensitive to medication effects. All children received the Raven test, the Wisconsin card sorting test (WCST), and the matching familiar figures test (MFFT) on their placebo day. Twenty-five children (85%) showed a significant medication response on CPALT. Responders and nonresponders did not differ on any of the other measures, including the CPALT on placebo. There was a significant correlation between responder status and clinical improvement as measured by the DSM III-R-based snap rating scale. It is likely that responder status can only be predicted based on measurements on and off methylphenidate such as we performed.
Pediatric Neurology, 1992
Although methylphenidate has been demonstrated to be useful in ADHD, scant research has been devo... more Although methylphenidate has been demonstrated to be useful in ADHD, scant research has been devoted to predictors of medication response. We examined a series of 30 children meeting DSM III-R criteria for ADHD, in a randomized, doubleblind, placebo-controlled study using methylphenidate. The outcome measure was the continuous paired-associate learning task (CPALT), which is a computerized task developed at the Behavioral Neurology Department at Boston University, which measures children's learning and attention, and is sensitive to medication effects. All children received the Raven test, the Wisconsin card sorting test (WCST), and the matching familiar figures test (MFFT) on their placebo day. Twenty-five children (85%) showed a significant medication response on CPALT. Responders and nonresponders did not differ on any of the other measures, including the CPALT on placebo. There was a significant correlation between responder status and clinical improvement as measured by the DSM III-R-based snap rating scale. It is likely that responder status can only be predicted based on measurements on and off methylphenidate such as we performed.
Pediatric Neurology, 1992
Although methylphenidate has been demonstrated to be useful in ADHD, scant research has been devo... more Although methylphenidate has been demonstrated to be useful in ADHD, scant research has been devoted to predictors of medication response. We examined a series of 30 children meeting DSM III-R criteria for ADHD, in a randomized, doubleblind, placebo-controlled study using methylphenidate. The outcome measure was the continuous paired-associate learning task (CPALT), which is a computerized task developed at the Behavioral Neurology Department at Boston University, which measures children's learning and attention, and is sensitive to medication effects. All children received the Raven test, the Wisconsin card sorting test (WCST), and the matching familiar figures test (MFFT) on their placebo day. Twenty-five children (85%) showed a significant medication response on CPALT. Responders and nonresponders did not differ on any of the other measures, including the CPALT on placebo. There was a significant correlation between responder status and clinical improvement as measured by the DSM III-R-based snap rating scale. It is likely that responder status can only be predicted based on measurements on and off methylphenidate such as we performed.