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D Kandel

Publications and source records attributed to D Kandel.

At least 19 recordsLinked to original sources
PubMed2001

Coiling instability of multilamellar membrane tubes with anchored polymers.

We study experimentally a coiling instability of cylindrical multilamellar stacks of phospholipid membranes, induced by polymers with hydrophobic anchors grafted along their hydrophilic backbone. Our system is unique in that coils form in the absence of both twist and adhesion. We interpret our experimental results in terms of a model in which local membrane curvature and polymer concentration are coupled. The model predicts the occurrence of maximally tight coils above a threshold polymer occupancy. A proper comparison between the model and experiment involved imaging of projections from simulated coiled tubes with maximal curvature and complicated torsions.

Journal Article↗
PubMed2001

Pearling instabilities of membrane tubes with anchored polymers.

We have studied the pearling instability induced on hollow tubular lipid vesicles by hydrophilic polymers with hydrophobic side groups along the backbone. The results show that the polymer concentration is coupled to local membrane curvature. The relaxation of a pearled tube is characterized by two different well-separated time scales, indicating two physical mechanisms. We present a model, which explains the observed phenomena and predicts polymer segregation according to local membrane curvature at late stages.

Fluorescent Dyes↗
PubMed2000

Wetting layer thickness and early evolution of epitaxially strained thin films

We propose a physical model which explains the existence of finite thickness wetting layers in epitaxially strained films. The finite wetting layer is shown to be stable due to the variation of the nonlinear elastic free energy with film thickness. We show that anisotropic surface tension gives rise to a metastable enlarged wetting layer. The perturbation amplitude needed to destabilize this wetting layer decreases with increasing lattice mismatch. We observe the development of faceted islands in unstable films.

Journal Article↗
PubMed1998

Measurement of risk for mental disorders and competence in a psychiatric epidemiologic community survey: the National Institute of Mental Health Methods for the Epidemiology of Child and Adolescent Mental Disorders (MECA) Study.

This paper describes the implementation of the National Institute of Mental Health Methods for the Epidemiology of Child and Adolescent Mental Disorders (MECA) study's goals of measuring risk factors and competence. The emphasis is on the development and testing of the measures. Relevant constructs for measurement of risk and competence in relation to psychopathology were selected and pilot tested prior to the field trials. A structured interview was developed and field tested using lay interviewers. Using the full sample from the field trials (n = 1285 caretaker-youth pairs), sample means, standard deviations, internal consistencies, parent-youth agreement, and associations with childhood disorder were computed. Descriptive statistics reveal a range of scores and means consistent with norming samples, when available, Internal consistencies were moderate to high. Parent-youth agreement on factual items was excellent and on scales was consistent with the literature. Several strong associations were found between risk factors and disorder, although most were related to disorder in general and not specific to a diagnostic category. This instrument provides a means of obtaining data that will be useful to researchers conducting epidemiologic and clinical studies designed to contribute to the understanding of mental disorders in children and adolescents, including nosology, risk factors, context, adaptive functioning, and treatment.

Adolescent↗
PubMed1997

Prevalence and demographic correlates of symptoms of last year dependence on alcohol, nicotine, marijuana and cocaine in the U.S. population.

The prevalence of last year use of alcohol, cigarettes, marijuana and cocaine in the U.S. population and conditional prevalence of a proxy measure of last year dependence among last year users of each drug class were assessed as a function of age, gender and ethnicity. Analyses were based on three aggregated waves (1991, 1992 and 1993) of the nationally representative samples of the general population aged > or = 12 interviewed in the National Household Surveys on Drug Abuse (n = 87915). An approximation of DSM-IV drug-specific last year dependence for each drug class was derived from self-reported symptoms of dependence, data on frequency and quantity of use and drug-related problems reported for the last year. Descriptive and multivariate analyses were conducted. The inclusion of cigarettes among the drugs, the large number of cases and the wide age range of respondents (> or = 12) enable us to make drug, age, gender and ethnic comparisons not otherwise possible in any other data set. The proxy measure of dependence, however, has limitations. The five major findings are that: (1) nicotine is the most addictive of the four drugs we examined; (2) among female last year users of alcohol and marijuana, adolescents are significantly more at risk for dependence than any other age group of women; (3) conditional prevalences of last year dependence on alcohol, marijuana and cocaine are higher among adolescent females than adolescent males but significantly different only for cocaine; (4) among adults, the rates of dependence are higher among males than among females for alcohol and marijuana, but lower for nicotine; and (5) among last year users, whites are more likely than any other ethnic group to be dependent on nicotine and blacks to be dependent on cocaine.

Adolescent↗
PubMed1997

In the eye of the beholder? Parental ratings of externalizing and internalizing symptoms.

Variations in ratings of externalizing and internalizing symptoms may contain a trait (i.e., shared view) component when behavioral symptoms that generalize across context are perceived and an individual view component when they are misperceived of when each informant has access to different symptoms. Using a LISREL model, we estimated that the trait and the important-specific, individual view components in parental ratings of externalizing and internalizing symptoms of adolescent siblings. This model demonstrated that mothers' and fathers' ratings contained a substantial individual view component (from 21% to 50% of total rating variance, depending on rater and trait). Except for fathers' ratings of internalizing symptoms (13%), parental ratings also contained a substantial trait component (42% to 58%). Mother's, fathers', and child's ratings may be averaged to estimate a trait of externalizing. To estimate an internalizing trait, it may be best to combine just the mother's rating with the child's self-rating.

Adolescent↗
PubMed1993

From beer to crack: developmental patterns of drug involvement.

OBJECTIVES: Prior research has identified developmental stages in drug use in adolescence, from substances that are legal for adults to illicit drugs. The position of crack in patterns of drug involvement remains to be established. METHODS: The analyses are based on a sample (n = 1108) representative of 12th graders attending New York State public and private schools. From reported ages of first use of five classes of drugs (alcoholic beverages, cigarettes, marijuana, cocaine but not crack, crack), alternate models of progression were tested for their goodness of fit through log-linear models. RESULTS: The sequence involves at the earliest stage the use of at least one licit drug, alcohol or cigarettes. Subsequent stages involve marijuana and cocaine; crack is the last drug in the sequence. The results confirm the more important role of alcohol among males and cigarettes among females in the progression into various drug classes. Age of first drug use at a lower stage is a strong predictor of further progression. CONCLUSIONS: The developmental pattern of drug involvement identified in the early 1970s still characterizes adolescent pathways of drug involvement in the late 1980s.

Adolescent↗