Does the continuum theory of dynamic fracture work?

We investigate the validity of the Linear Elastic Fracture Mechanics approach to dynamic fracture. We first test the predictions in a lattice simulation, using a formula of Eshelby for the time-dependent Stress Intensity Factor. Excellent agreement with the theory is found. We then use the same method to analyze the experiment of Sharon and Fineberg. The data here is not consistent with the theoretical expectation.Comment: 4 page

Nonlinear lattice model of viscoelastic Mode III fracture

We study the effect of general nonlinear force laws in viscoelastic lattice models of fracture, focusing on the existence and stability of steady-state Mode III cracks. We show that the hysteretic behavior at small driving is very sensitive to the smoothness of the force law. At large driving, we find a Hopf bifurcation to a straight crack whose velocity is periodic in time. The frequency of the unstable bifurcating mode depends on the smoothness of the potential, but is very close to an exact period-doubling instability. Slightly above the onset of the instability, the system settles into a exactly period-doubled state, presumably connected to the aforementioned bifurcation structure. We explicitly solve for this new state and map out its velocity-driving relation

Infrared Space Observatory Polarimetric Imaging of the Egg Nebula (RAFGL 2688)

We present polarimetric imaging of the protoplanetary nebula RAFGL 2688 obtained at 4.5 microns with the Infrared Space Observatory (ISO). We have deconvolved the images to remove the signature of the point spread function of the ISO telescope, to the extent possible. The deconvolved 4.5 micron image and polarimetric map reveal a bright point source with faint, surrounding reflection nebulosity. The reflection nebula is brightest to the north-northeast, in agreement with previous ground- and space-based infrared imaging. Comparison with previous near-infrared polarimetric imaging suggests that the polarization of starlight induced by the dust grains in RAFGL 2688 is more or less independent of wavelength between 2 microns and 4.5 microns. This, in turn, indicates that scattering dominates over thermal emission at wavelengths as long as ~5 microns, and that the dust grains have characteristic radii < 1 micron.Comment: 27 pages, 9 figures; to appear in the Astronomical Journal, May 2002 issu

Steady-State Cracks in Viscoelastic Lattice Models II

We present the analytic solution of the Mode III steady-state crack in a square lattice with piecewise linear springs and Kelvin viscosity. We show how the results simplify in the limit of large width. We relate our results to a model where the continuum limit is taken only along the crack direction. We present results for small velocity, and for large viscosity, and discuss the structure of the critical bifurcation for small velocity. We compute the size of the process zone wherein standard continuum elasticity theory breaks down.Comment: 17 pages, 3 figure

Steady-State Cracks in Viscoelastic Lattice Models

We study the steady-state motion of mode III cracks propagating on a lattice exhibiting viscoelastic dynamics. The introduction of a Kelvin viscosity $\eta$ allows for a direct comparison between lattice results and continuum treatments. Utilizing both numerical and analytical (Wiener-Hopf) techniques, we explore this comparison as a function of the driving displacement $\Delta$ and the number of transverse sites $N$. At any $N$, the continuum theory misses the lattice-trapping phenomenon; this is well-known, but the introduction of $\eta$ introduces some new twists. More importantly, for large $N$ even at large $\Delta$, the standard two-dimensional elastodynamics approach completely misses the $\eta$-dependent velocity selection, as this selection disappears completely in the leading order naive continuum limit of the lattice problem.Comment: 27 pages, 8 figure

Diabetes status and post-load plasma glucose concentration in relation to site-specific cancer mortality: findings from the original Whitehall study

ObjectiveWhile several studies have reported on the relation of diabetes status with pancreatic cancer risk, the predictive value of this disorder for other malignancies is unclear. Methods: The Whitehall study, a 25year follow-up for mortality experience of 18,006 men with data on post-challenge blood glucose and self-reported diabetes, allowed us to address these issues. Results: There were 2158 cancer deaths at follow-up. Of the 15 cancer outcomes, diabetes status was positively associated with mortality from carcinoma of the pancreas and liver, while the relationship with lung cancer was inverse, after controlling for a range of potential covariates and mediators which included obesity and socioeconomic position. After excluding deaths occurring in the first 10years of follow-up to examine the effect of reverse causality, the magnitude of the relationships for carcinoma of the pancreas and lung was little altered, while for liver cancer it was markedly attenuated. Conclusions: In the present study, diabetes status was related to pancreatic, liver, and lung cancer risk. Cohorts with serially collected data on blood glucose and covariates are required to further examine this area

Cross-national epidemiology of DSM-IV major depressive episode

Background: Major depression is one of the leading causes of disability worldwide, yet epidemiologic data are not available for many countries, particularly low- to middle-income countries. In this paper, we present data on the prevalence, impairment and demographic correlates of depression from 18 high and low-to middle-income countries in the World Mental Health Survey Initiative. Methods: Major depressive episodes (MDE) as defined by the Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DMS-IV) were evaluated in face-to-face interviews using the World Health Organization Composite International Diagnostic Interview (CIDI). Data from 18 countries were analyzed in this report (n = 89,037). All countries surveyed representative, population-based samples of adults. Results: The average lifetime and 12-month prevalence estimates of DSM-IV MDE were 14.6% and 5.5% in the ten high-income and 11.1% and 5.9% in the eight low- to middle-income countries. The average age of onset ascertained retrospectively was 25.7 in the high-income and 24.0 in low- to middle-income countries. Functional impairment was associated with recency of MDE. The female: male ratio was about 2: 1. In high-income countries, younger age was associated with higher 12-month prevalence; by contrast, in several low-to middle-income countries, older age was associated with greater likelihood of MDE. The strongest demographic correlate in high-income countries was being separated from a partner, and in low- to middle-income countries, was being divorced or widowed. Conclusions: MDE is a significant public-health concern across all regions of the world and is strongly linked to social conditions. Future research is needed to investigate the combination of demographic risk factors that are most strongly associated with MDE in the specific countries included in the WMH.(NIH/NIMH) United States National Institute of Mental Health[R01MH070884]John D. and Catherine T. MacArthur FoundationPfizer FoundationUSA Public Health Service[R13-MH066849]USA Public Health Service[R01-MH069864]USA Public Health Service[R01 DA016558](NIH) Fogarty International Center[FIRCA R03-TW006481]PAHO Pan American Health OrganizationEli Lilly & Company FoundationOrtho-McNeil Pharmaceutical, Inc.GlaxoSmithKlineSanofi-AventisBristol-Myers SquibbState of Brazil Research Foundation (FAPESP)[03/00204-3]Ministry of Social ProtectionEuropean Commission[QLG5-1999-01042]European Commission[SANCO 2004123]Piedmont Region (Italy)Fondo de Investigacion Sanitaria, Instituto de Salud Carlos III, Spain[FIS 00/0028]Spanish Ministerio de Ciencia y Tecnologia[SAF 2000-158-CE]Departament de Salut, Generalitat de Catalunya, SpainInstituto de Salud Carlos III[CIBER CB06/02/0046]Instituto de Salud Carlos III[RETICS RD06/0011 REM-TAP]Government of IndiaWHOMinistry of HealthIsrael National Institute for Health Policy and Health Services ResearchNational Insurance Institute of IsraelJapan Ministry of Health, Labour and Welfare[H13-Shogai-023]Japan Ministry of Health, Labour and Welfare[H14-Tokubetsu-026]Japan Ministry of Health, Labour and Welfare[H16-Kokoro-013]Lebanese Ministry of Public HealthWHO (Lebanon)(NIH) Fogarty International, anonymous private donations to IDRAAC, LebanonJanssen CilagEli LillyRocheNovartisNational Institute of Psychiatry Ramon de la Fuente[INPRFMDIES 4280]CNPq National Council on Science and Technology[CONACyT-G30544-H]PanAmerican Health Organization (PAHO)New Zealand Ministry of Health, Alcohol Advisory CouncilHealth Research Council(NIH/NIMH) USA National Institute of Mental Health[R01-MH059575](NIH/NIMH) USA National Institute of Mental Health[RO1-MH61905]National Institute of Drug AbuseSouth African Department of HealthUniversity of MichiganNational Institute of Mental Health (NIH/NIMH)[U01-MH60220]National Institute of Drug Abuse (NIDA)Substance Abuse and Mental Health Services Administration (SAMHSA)Robert Wood Johnson Foundation (RWJF)[044708]John W. Alden TrustsAnalysis Group Inc.Eli Lilly CompanyEPI-QJohnson & Johnson PharmaceuticalsOrtho-McNeil Janssen Scientific AffairsPfizer Inc.Shire USA, Inc