The Size-Frequency Distribution of the Zodiacal Cloud: Evidence from the Solar System Dust Bands

Recent observations of the size-frequency distribution of zodiacal cloud particles obtained from the cratering record on the LDEF satellite (Love and Brownlee 1993) reveal a significant large particle population (100 micron diameter or greater) near 1 AU. Our previous modeling of the Solar System dust bands (Grogan et al 1997), features of the zodiacal cloud associated with the comminution of Hirayama family asteroids, has been limited by the fact that only small particles (25 micron diameter or smaller) have been considered. This was due to the prohibitively large amount of computing power required to numerically analyze the dynamics of larger particles. The recent availability of cheap, fast processors has finally made this work possible. Models of the dust bands are created, built from individual dust particle orbits, taking into account a size-frequency distribution of the material and the dynamical history of the constituent particles. These models are able to match both the shapes and amplitudes of the dust band structures observed by IRAS in multiple wavebands. The size-frequency index, q, that best matches the observations is approximately 1.4, consistent with the LDEF results in that large particles are shown to dominate. However, in order to successfully model the `ten degree' band, which is usually associated with collisional activity within the Eos family, we find that the mean proper inclination of the dust particle orbits has to be approximately 9.35 degrees, significantly different to the mean proper inclination of the Eos family (10.08 degrees).Comment: 49 pages total, including 27 figure pages. Submitted to Icaru

Family and parenting characteristics associated with marijuana use by Chilean adolescents

OBJECTIVE: Family involvement and several characteristics of parenting have been suggested to be protective factors for adolescent substance use. Some parenting behaviors may have stronger relationships with adolescent behavior while others may have associations with undesirable behavior among youth. Although it is generally acknowledged that families play an important role in the lives of Chilean adolescents, scant research exists on how different family and parenting factors may be associated with marijuana use and related problems in this population which has one of the highest rates of drug use in Latin America. METHODS: Using logistic regression and negative binomial regression, we examined whether a large number of family and parenting variables were associated with the possibility of Chilean adolescents ever using marijuana, and with marijuana-related problems. Analyses controlled for a number of demographic and peer-related variables. RESULTS: Controlling for other parenting and family variables, adolescent reports of parental marijuana use showed a significant and positive association with adolescent marijuana use. The multivariate models also revealed that harsh parenting by fathers was the only family variable associated with the number of marijuana-related problems youth experienced. CONCLUSION: Of all the family and parenting variables studied, perceptions of parental use of marijuana and harsh parenting by fathers were predictors for marijuana use, and the experience of marijuana-related problems. Prevention interventions need to continue emphasizing the critical socializing role that parental behavior plays in their children's development and potential use of marijuana.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3109755/https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3109755/Accepted manuscrip

Abnormal infant islet morphology precedes insulin resistance in PCOS-like monkeys.

Polycystic ovary syndrome (PCOS) is prevalent in reproductive-aged women and confounded by metabolic morbidities, including insulin resistance and type 2 diabetes. Although the etiology of PCOS is undefined, contribution of prenatal androgen (PA) exposure has been proposed in a rhesus monkey model as premenopausal PA female adults have PCOS-like phenotypes in addition to insulin resistance and decreased glucose tolerance. PA female infants exhibit relative hyperinsulinemia, suggesting prenatal sequelae of androgen excess on glucose metabolism and an antecedent to future metabolic disease. We assessed consequences of PA exposure on pancreatic islet morphology to identify evidence of programming on islet development. Islet counts and size were quantified and correlated with data from intravenous glucose tolerance tests (ivGTT) obtained from dams and their offspring. Average islet size was decreased in PA female infants along with corresponding increases in islet number, while islet fractional area was preserved. Infants also demonstrated an increase in both the proliferation marker Ki67 within islets and the beta to alpha cell ratio suggestive of enhanced beta cell expansion. PA adult females have reduced proportion of small islets without changes in proliferative or apoptotic markers, or in beta to alpha cell ratios. Together, these data suggest in utero androgen excess combined with mild maternal glucose intolerance alter infant and adult islet morphology, implicating deviant islet development. Marked infant, but subtle adult, morphological differences provide evidence of islet post-natal plasticity in adapting to changing physiologic demands: from insulin sensitivity and relative hypersecretion to insulin resistance and diminished insulin response to glucose in the mature PCOS-like phenotype

Contributors to the March Issue/Notes

Notes by Joseph F. Nigro, Francis E. Bright, Edward F. Grogan, James H. Graham, Jr., John C. O\u27Connor, and William P. Mahoney

Contributors to the March Issue/Notes

Notes by Joseph F. Nigro, Francis E. Bright, Edward F. Grogan, James H. Graham, Jr., John C. O\u27Connor, and William P. Mahoney

Contributors to the January Issue/Notes

Notes by Leon L. Lancaster, Edwin Daniel O\u27Leary, Richard F. Sullivan, Edward F. Grogan, Jr., and Samuel L. Devine