Lighting Up and Slimming Down: The Effects of Body Weight and Cigarette Prices on Adolescent Smoking Initiation

This paper examines the influence of body weight, body image, and cigarette prices in determining adolescent smoking initiation. Adolescents who desire to lose weight may initiate smoking as a method of appetite control. Such behavior may undermine the goals of tobacco control policies that seek to prevent smoking initiation. Using a nationally representative panel of adolescents, we show that smoking initiation is more likely among females who are overweight, who report trying to lose weight, or who describe themselves as overweight. In contrast, neither objective nor subjective measures of weight predict smoking initiation by males. Higher cigarette prices decrease the probability of smoking initiation among males but have no impact on female smoking initiation. These gender-specific differences may help explain the mixed and inconclusive evidence of the impact of price on smoking initiation found in previous literature

Isopropylphenidate: An Ester Homolog of Methylphenidate with Sustained and Selective Dopaminergic Activity and Reduced Drug Interaction Liability

Objective: The most widely utilized pharmacological treatment of attention-deficit/hyperactivity disorder (ADHD) is the psychostimulant methylphenidate (MPH). Most MPH formulations consist of the racemic mixture of d-threo-(R, R)-MPH and l-threo-(S, S)-MPH isomers. MPH is characterized by its low bioavailability and short half-life (2?3 hours). Additionally, significant inter-individual variability in MPH pharmacokinetics has been consistently documented. Accordingly, efforts have been directed at developing alternatives to MPH as therapeutic agents. A wide range of MPH analogues (dl-α-[2-piperidyl]-phenylacetic acid esters) have been synthesized with the dopamine transporter (DAT) and norepinephrine transporter (NET) as principle neuropharmacological targets. The present study investigated the metabolic profiles and pharmacological activity of the isopropyl ester derivative of MPH, dl-isopropylphenidate (IPH), both in vitro and in vivo. Methods: The synthesis, monoaminergic transporter binding, cellular uptake profiles, and assessment of metabolic hydrolysis and transesterification in the presence of ethanol are described using MPH as a comparator. Additionally, an in vivo assessment of IPH stimulant effects (vs. saline) in rats was performed with locomotor activity as a pharmacodynamic outcome. Results: IPH displayed unique pharmacological characteristics including greater DAT than NET binding and cellular uptake activity, and greater resistance to hydrolysis and transesterification via carboxylesterase 1 relative to MPH. Further, sustained psychostimulant properties offer the prospect of an enhanced duration of action. Conclusions: Our findings are consistent with IPH exhibiting attributes distinguishing it from MPH and warranting further study and development of IPH as a novel psychotherapeutic agent.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140321/1/cap.2013.0074.pd

A data-driven neuromuscular model of walking and its application to prosthesis control

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (pages 119-123).In this thesis we present a data-driven neuromuscular model of human walking and its application to prosthesis control. The model is novel in that it leverages tendon elasticity to more accurately predict the metabolic consumption of walking than conventional models. Paired with a reflex-based neural drive the model has been applied in the control of a robotic ankle-foot prosthesis, producing speed adaptive behavior. Current neuromuscular models significantly overestimate the metabolic demands of walking. We believe this is because they do not adequately consider the role of elasticity; specifically the parameters that govern the force-length relations of tendons in these models are typically taken from published values determined from cadaver studies. To investigate this issue we first collected kinematic, kinetic, electromyographic (EMG), and metabolic data from five subjects walking at six different speeds. The kinematic and kinetic data were used to estimate muscle lengths, muscle moment arms, and joint moments while the EMG data were used to estimate muscle activations. For each subject we performed a kinematically clamped optimization, varying the parameters that govern the force-length curve of each tendon while simultaneously seeking to minimize metabolic cost and maximize agreement with the observed joint moments. We found a family of parameter sets that excel at both objectives, providing agreement with both the collected kinetic and metabolic data. This identification allows us to accurately predict the metabolic cost of walking as well as the force and state of individual muscles, lending insight into the roles and control objectives of different muscles throughout the gait cycle. This optimized muscle-tendon morphology was then applied with an optimized linear reflex architecture in the control of a powered ankle-foot prosthesis. Specifically, the model was fed the robot's angle and state and used to command output torque. Clinical trials were conducted that demonstrated speed adaptive behavior; commanded net work was seen to increase with walking speed. This result supports both the efficacy of the modeling approach and its potential utility in controlling life-like prosthetic limbs.by Jared Markowitz.Ph.D

A Utility Based Approach to Energy Hedging

A key issue in the estimation of energy hedges is the hedgers' attitude towards risk which is encapsulated in the form of the hedgers' utility function. However, the literature typically uses only one form of utility function such as the quadratic when estimating hedges. This paper addresses this issue by estimating and applying energy market based risk aversion to commonly applied utility functions including log, exponential and quadratic, and we incorporate these in our hedging frameworks. We find significant differences in the optimal hedge strategies based on the utility function chosen

Role of disclinations in determining the morphology of deformable fluid interfaces

We study the equilibrium shapes of vesicles, with an in-plane nematic order, using a Monte-Carlo scheme and show that highly curved shapes, like tubes and discs, with a striking similarity to the structures engendered by certain curvature sensing peripheral membrane proteins, can be spontaneously generated by anisotropic directional curvature with nematic disclinations playing and important role. We show that the coupling between nematic order and local curvature could lead to like defects moving towards each other and unlike defects moving away, in turn leading to tube formation. Thermally induced defect pair production lead to branched tubular structures. It is also shown that helical arrangement of the membrane tubes, with nematic field spiraling around it, is a dominant soft mode of the system.Comment: 6 Figures; Soft Matter, Advance Article 201

The Emerging Role of HTLV-I/II and HIV-1 Among Intravenous Drug Users in Detroit

During 1987-1988, a seroprevalence study of the human immunodeficiency virus (HIV-1) and the human T-cell lymphoma/leukemia virus (HTLV-l/II) was performed among Detroit intravenous drug users unaffiliated with substance abuse programs. Seroprevalence data along with patient demographic information were compared to a similar study performed in 1985-1986. In the earlier study, 12 (12.5%) of 96 individuals tested positive for HIV-1. Of the 74 available negative samples retested in 1987-1988 for retroviruses, 7 (9.5%) tested positive for HTLV-I/II. Thus, the overall retroviral (HIV-1, HTLV-I/II) seropositive rate for 1985-1986 was 22%. In 1987-1988, 11 (15.7%) of 70 individuals tested positive for HIV-1 and 7 (10%) tested positive for HTLV-I/II. Concomitant infection with both viruses was found in 2 (2.9%) of the 70 individuals. Thus, retrovirus seroprevalence in 1987-1988 was 22.9%. In 1987-1988, significant differences between the retroviral-positive group and the retroviral-negative group consisted of intravenous drug use greater than 16 years (P = 0.059) for an odds ratio of 3.80 (Cl 1.12-12.89) and sex with female prostitutes (P = 0.029) for an odds ratio of 5.38 (Cl 1.38-20.95)