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Instability
Kinds of Instability Selected AbstractsINSTABILITY AND THE INCENTIVES FOR CORRUPTIONECONOMICS & POLITICS, Issue 1 2009FILIPE R. CAMPANTE We investigate the relationship between corruption and political stability, from both theoretical and empirical perspectives. We propose a model of incumbent behavior that features the interplay of two effects: a horizon effect, whereby greater instability leads the incumbent to embezzle more during his short window of opportunity, and a demand effect, by which the private sector is more willing to bribe stable incumbents. The horizon effect dominates at low levels of stability, because firms are unwilling to pay high bribes and unstable incumbents have strong incentives to embezzle, whereas the demand effect gains salience in more stable regimes. Together, these two effects generate a non-monotonic, U-shaped relationship between total corruption and stability. On the empirical side, we find a robust U-shaped pattern between country indices of corruption perception and various measures of incumbent stability, including historically observed average tenures of chief executives and governing parties: regimes that are very stable or very unstable display higher levels of corruption when compared with those in an intermediate range of stability. These results suggest that minimizing corruption may require an electoral system that features some re-election incentives, but with an eventual term limit. [source] RESWITCHING AS A CAUSE OF INSTABILITY OF INTERTEMPORAL EQUILIBRIUMMETROECONOMICA, Issue 4 2005Article first published online: 16 NOV 200, Bertram Schefold ABSTRACT It is generally recognized that the paradoxes of capital, of which reswitching is the most striking example, are a reason to question the existence of aggregate production functions. It is here shown that they affect intertemporal general equilibrium as well as causes of instabilities. [source] FORECASTING VOLATILITY IN THE PRESENCE OF MODEL INSTABILITYAUSTRALIAN & NEW ZEALAND JOURNAL OF STATISTICS, Issue 2 2010John M. Maheu Summary Recent advances in financial econometrics have allowed for the construction of efficient,ex post,measures of daily volatility. This paper investigates the importance of instability in models of realised volatility and their corresponding forecasts. Testing for model instability is conducted with a subsampling method. We show that removing structurally unstable data of a short duration has a negligible impact on the accuracy of conditional mean forecasts of volatility. In contrast, it does provide a substantial improvement in a model's forecast density of volatility. In addition, the forecasting performance improves, often dramatically, when we evaluate models on structurally stable data. [source] STABILITY AND INSTABILITY OF THE COUCRNOT EQUILIBRIUM,AUSTRALIAN ECONOMIC PAPERS, Issue 3 2008EIICHI CHUMAN Conditions for the Cournot equilibrium to be locally asymptotically stable or unstable are explored, which are still compatible with the second-order condition for the optimum. The Cournot equilibrium may not be stable even if the condition owing to Fisher (1961), Hahn (1962), and Okuguchi (1964, 1976, 1999) is satisfied, which was given as a sufficient condition for the Cournot equilibrium to be stable. However, as long as a game by symmetric players is concerned, the Cournot equilibrium is unstable whenever F-H-O condition is not satisfied. In this sense, that F-H-O condition is not satisfied is sufficient for the Cournot equilibrium to be unstable. [source] A 61-YEAR-OLD MAN WITH INSTABILITY OF GAIT AND RIGHT HAND CLUMSINESSBRAIN PATHOLOGY, Issue 1 2010Anne Vital MD No abstract is available for this article. [source] Acute management,How should we intervene?CLINICAL CARDIOLOGY, Issue S1 2000Frederic Kontny M.D., PH.D. Abstract A crucial question in the acute management of the patient with unstable coronary artery disease (UCAD) is whether to carry out early intervention, performing angiography soon after presentation and following this with revascularization where appropriate, or whether to follow a noninvasive medical strategy as far as possible unless symptoms necessitate intervention. The body of literature addressing this question is sparse, but the recent Fast Revascularization during InStability in Coronary artery disease (FRISC II) study has provided new insights into the problem. Using a factorial design to randomize patients to invasive or noninvasive management strategies, and to short- or long-term treatment with the low-molecular-weight heparin (LMWH) dalteparin sodium (Fragmin®), it was shown in FRISC II that early invasive treatment (within 7 days), when combined with optimal medical pretreatment with dalteparin sodium, aspirin, and appropriate antianginal medication, is associated with improved clinical outcomes, relative to a "watchful waiting" approach based on noninvasive therapy. Thus, an early invasive approach following aggressive medical pretreatment should be the preferred strategy for patients with UCAD who present with signs of ischemia on the electrocardiogram or raised biochemical markers of myocardial damage at admission. [source] Effect of Energetic-Ion-Driven MHD Instabilities on Energetic-Ion-Transport in Compact Helical System and Large Helical DeviceCONTRIBUTIONS TO PLASMA PHYSICS, Issue 6-7 2010M. Isobe Abstract This paper describes 1) representative results on excitation of energetic-particle mode (EPM) and toroidicity-induced Alfvén eigenmode (TAE) and consequent beam-ion losses in CHS, and 2) recent results on beam-ion transport and/or losses while EPMs are destabilized in LHD. Bursting EPMs and TAEs are often excited by co-injected beam ions in the high-beam ion pressure environment and give a significant effect on co-going beam ions in both experiments. It seems that in CHS, resonant beam ions are lost within a relatively short-time scale once they are anomalously transported due to energetic-ion driven MHD modes, whereas unlike CHS, redistribution of beam ions due to energetic-ion driven MHD modes is seen in LHD, suggesting that not all anomalously transported beam ions escape from the plasma (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Mitigation of Electromagnetic Instabilities in Fast Ignition ScenarioCONTRIBUTIONS TO PLASMA PHYSICS, Issue 3-4 2005C. Deutsch Abstract We address the issues of collective stopping for intense relativistic electron beams (REB) used to selectively ignite precompressed deuterium + tritium (DT) fuels. We investigate the subtle interplay of electron collisions in target as well as in beam plasmas with quasi-linear electromagnetic growth rates. Intrabeam scattering is found effective in taming those instabilities, in particular for high transverse temperatures. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Nanopatterning via Pressure-Induced Instabilities in Thin Polymer FilmsADVANCED MATERIALS, Issue 20 2009Ximin He The residual stresses in spin-coated films can be exploited to produce highly controlled nanoscale patterns via pressure-induced local rupturing and dewetting of thin films. Residue-free holes as small as 28,nm in diameter formed over large areas by pressing sharp stamps into polymer films at temperatures well below the glass transition temperature. [source] Instabilities of Boussinesq models in non-uniform depthINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 6 2009F. Løvholt Abstract The von Neumann method for stability analysis of linear waves in a uniform medium is a widely applied procedure. However, the method does not apply to stability of linear waves in a variable medium. Herein we describe instabilities due to variable depth for different Boussinesq equations, including the standard model by Peregrine and the popular generalization by Nwogu. Eigenmodes are first found for bathymetric features on the grid scale. For certain combinations of Boussinesq formulations and bottom profiles stability limits are found in closed form, otherwise numerical techniques are used for the eigenvalue problems. Naturally, the unstable modes in such settings must be considered to be as much a result of the difference method as of the underlying differential (Boussinesq) equations. Hence, modes are also computed for smooth depth profiles that are well resolved. Generally, the instabilities do not vanish with refined resolution. In some cases convergence is observed and we thus have indications of unstable solutions of the differential equations themselves. The stability properties differ strongly. While the standard Boussinesq equations seem perfectly stable, all the other formulations do display unstable modes. In most cases the instabilities are linked to steep bottom gradients and small grid increments. However, while a certain formulation, based on velocity potentials, is very prone to instability, the Boussinesq equations of Nwogu become unstable only under quite demanding conditions. Still, for the formulation of Nwogu, instabilities are probably inherent in the differential equations and are not a result of the numerical model. Copyright © 2008 John Wiley & Sons, Ltd. [source] Instabilities during batch sedimentation in geometries containing obstacles: A numerical and experimental study,INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 8 2007Rekha R. Rao Abstract Batch sedimentation of non-colloidal particle suspensions is studied with nuclear magnetic resonance flow visualization and continuum-level numerical modelling of particle migration. The experimental method gives particle volume fraction as a function of time and position, which then provides validation data for the numerical model. A finite element method is used to discretize the equations of motion, including an evolution equation for the particle volume fraction and a generalized Newtonian viscosity dependent on local particle concentration. The diffusive-flux equation is based on the Phillips model (Phys. Fluids A 1992; 4:30,40) and includes sedimentation terms described by Zhang and Acrivos (Int. J. Multiphase Flow 1994; 20:579,591). The model and experiments are utilized in three distinct geometries with particles that are heavier and lighter than the suspending fluid, depending on the experiment: (1) sedimentation in a cylinder with a contraction; (2) particle flotation in a horizontal cylinder with a horizontal rod; and (3) flotation around a rectangular inclusion. Secondary flows appear in both the experiments and the simulations when a region of higher density fluid is above a lower density fluid. The secondary flows result in particle inhomogeneities, Rayleigh,Taylor-like instabilities, and remixing, though the effect in the simulations is more pronounced than in the experiments. Published in 2007 by John Wiley & Sons, Ltd. [source] Stress-Driven Morphological Instabilities in Rocks, Glass, and CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2007M. A. Grinfeld The purpose of this study is to further investigate the classical Gibbs analysis of the heterogeneous system "stressed crystal,melt." It is demonstrated that each equilibrium configuration is stable with respect to a special class of variations introduced by Gibbs. This basic result is compared with the opposite result on the universal morphological instability of phase interface separating a stressed crystal with its melt. Some plausible manifestations of the instabilities implied by the Gibbs model are qualitatively discussed. [source] In situ Pressure Fluctuations of Polymer Melt Flow Instabilities: Experimental Evidence about their Origin and DynamicsMACROMOLECULAR RAPID COMMUNICATIONS, Issue 21 2009Humberto Palza Abstract Despite the practical importance of polymer melt instabilities, there is still a lack of experiments able to characterize in situ the origin and behavior of these phenomena. In this context, a new set-up consisting of high sensitive pressure transducers located inside a slit-die and an advanced mathematical framework to process in situ measurements of polymer melt instabilities, are developed and applied. Our results show for the first time that pressure oscillations can actually be detected inside the die under sharkskin conditions. This originates from a factor of 103 and 102 improvement in terms of time and pressure resolution. Furthermore, new evidence towards the propagation of the slip phenomena along the die in spurt instabilities are found. [source] Instabilities in two-fluid magnetized media with inter-component driftMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2002P. V. Tytarenko Abstract We analyse the stability of a magnetized medium consisting of a neutral fluid and a fluid of charged particles, coupled to each other through a drag force and exposed to differential body forces (for example, as the result of radiation forces on one phase). We consider a uniform equilibrium and simple model input physics, but do not arbitrarily restrict the relative orientations of the magnetic field, slip velocity and wavevector of the disturbance. We find several instabilities and classify these in terms of wave resonances. We briefly apply our results to the structure of SiO maser regions appearing in the winds from late-type stars. [source] Instabilities and bifurcations in lid-driven cavity flowsPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2003Hendrik C. Kuhlmann Dr. The three-dimensional flow of an incompressible Newtonian fluid in a rectangular slab is calculated numerically using a pseudo-spectral method. The fluid motion is driven by two facing sidewalls which can move in parallel or anti-parallel directions. Examples for bifurcations from two-dimensional to three-dimensional flows are given for spanwise periodic systems. For a comparison with previous experimental results rigid end walls are also considered. Differences between periodic and rigid end conditions are highlighted. [source] Dynamic Chemical Instabilities in Living Cells May Provide a Novel Route in Drug DevelopmentCHEMBIOCHEM, Issue 10 2004Howard R. Petty Dr. Chemical waves, such as the NAD(P)H (green) and Ca2+(white-orange) waves of neutrophils, are emergent properties of living cells that represent the collective behavior of proteins that constitute intracellular subsystems. Studies of these waves suggest novel approaches in drug development and fresh insights into several clinical issues. [source] Stabilization of Radiation-Condensation Instability by Light Impurity InjectionCONTRIBUTIONS TO PLASMA PHYSICS, Issue 3-5 2010A. A. Pshenov Abstract As it has been shown in [1,2], Radiation-Condensation Instability (RCI) may initiate Microfaceted Asymmetric Radiation from the Edge (MARFE) in tokamaks (see also review papers [3-5]). Nevertheless, experiments demonstrate the stable regimes with strongly radiated edge plasmas after Ne injection [6-8] or in siliconized discharges. Two effects destabilize radiative plasmas, the decrease of radiation losses Q with the electron temperature Te increase, and the increase of Q with electron and impurity densities rise. The finite relaxation time of impurity distribution over ionization states [6] as well as the thermal force acting on the growth rate doesn't shift the instability margin. Hence, one can examine the stability margin using the approximation of the coronal equilibrium. Radiation losses of intrinsic impurities like beryllium, carbon and nitrogen usually decrease with the temperature increase at the temperature range typical for the edge (see Fig. 1, curve 1). The situation may be significantly different for impurity mixtures. Radiation losses L , Q /(nenI)normalized by electron and impurity densities ne and nI for the mixture of carbon and neon are shown in Fig. 1, curves 2-5. One can see that ,Q/,T > 0 for practically any temperature at the edge if the concentration ratio nNe/nC , 5. Hence, one can expect the stabilization of RCI by injection of additional impurity and achievement of stable regime with the strongly radiated edge plasmas. The stability of plasmas with few impurity mixtures is examined in the present paper numerically (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Tests for Parameter Instability and Structural Change with Unknown Change Point: A CorrigendumECONOMETRICA, Issue 1 2003Donald W. K. Andrews No abstract is available for this article. [source] The Role of Political Instability in Stock Market Development and Economic Growth: The Case of GreeceECONOMIC NOTES, Issue 3 2000Dimitrios Asteriou This article examines empirically the relationship between stock market development, political instability and economic growth in Greece. We measure socio-political instability by constructing an index which captures the occurrence of various phenomena of political violence using time-series data. The main advantages of analysing political instability in a case study framework using time-series, in contrast with the widely used cross-country empirical studies, are: (a) a more careful and in-depth examination of institutional and historical characteristics of a particular country; (b) the use of a data set comprised of the most appropriate and highest quality measures; and (c) a more detailed exposition of the dynamic evolution of the economy. The empirical results indicate the existence of a strong negative relationship between uncertain socio-political conditions and the general index of the Athens Stock Exchange (ASE) and support the theoretical hypothesis that uncertain socio-political conditions affect economic growth negatively, is true for the Greek case. (J.E.L.: G10, G14, O40, C32) [source] Aggregate Investment and Political Instability: An Econometric InvestigationECONOMICA, Issue 279 2003Nauro F. Campos Although in theory the long-run effect of uncertainty on investment is ambiguous, available econometric evidence widely supports a negative association between aggregate investment and political instability. A shortcoming of this body of evidence is that it has failed to investigate the existence and direction of causality between these two variables. This paper fills this gap by testing for such causal and negative long-run relationship between political instability and investment. We find there is a causal relation going from instability to investment, but it is positive and particularly strong in low-income countries. This finding is robust to various sensitivity checks. [source] Drunk with the Glitter: Space, Consumption and Sexual Instability in Modern Urban Culture,by Gillian SwansonGENDER & HISTORY, Issue 1 2010ADRIAN BINGHAM No abstract is available for this article. [source] Polyploidy-Associated Genomic Instability in Arabidopsis thalianaGENESIS: THE JOURNAL OF GENETICS AND DEVELOPMENT, Issue 4 2010Yixing Wang Formation of polyploid organisms by fertilization of unreduced gametes in meiotic mutants is believed to be a common phenomenon in species evolution. However, not well understood is how species in nature generally exist as haploid and diploid organisms in a long evolutionary time while polyploidization must have repeatedly occurred via meiotic mutations. Here, we show that the ploidy increased for two consecutive generations due to unreduced but viable gametes in the Arabidopsis cyclin a1;2-2 (also named tardy asynchronousmeiosis-2) mutant, but the resultant octaploid plants produced progeny of either the same or reduced ploidy via genomic reductions during meiosis and pollen mitosis. Ploidy reductions through sexual reproduction were also observed in independently generated artificial octaploid and hexaploid Arabidopsis plants. These results demonstrate that octaploid is likely the maximal ploidy produced through sexual reproduction in Arabidopsis. The polyploidy-associated genomic instability may be a general phenomenon that constrains ploidy levels in species evolution. [source] Talus Instability in a Recent Deglaciation Area and Its Relationship to Buried Ice and Snow Cover Evolution (Picacho Del Veleta, Sierra Nevada, Spain)GEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 2 2003Antonio Gómez The southernmost glacier in Europe formed during the Little Ice Age at the foot of the north wall of Picacho del Veleta (3 398 m) in Sierra Nevada, in the southeast region of the Iberian Peninsula (lat. 37,03,N, long. 3,22,W). The glacier gradually retreated during the last century, leaving a large talus slope at the base of the wall. The unconsolidated material covering the ice masses acted as a thermal insulator. Recent bottom temperature of snow (BTS) analyses and drillings indicate that the ice still exists within the talus. Evidence from field observations made during the period 1995,2001, revealed that large mass movements occurred during the driest summers (1998 and especially, 1999 and 2000) when the talus was snow free. These conditions suggest a direct relationship between talus stability and thermal insulation from the snow cover in areas where buried ice or decaying marginal permafrost exists. [source] Intra-executive Conflict and Cabinet Instability: Effects of Semi-presidentialism in Central and Eastern EuropeGOVERNMENT AND OPPOSITION, Issue 4 2010Thomas Sedelius Comparing eight post-communist semi-presidential systems (Bulgaria, Croatia, Lithuania, Moldova, Poland, Romania, Ukraine and Russia), comprising a total of 65 instances of intra-executive coexistence between 1991 and 2007, this article asks to what extent and in what ways president,cabinet conflicts increase the risk of cabinet instability. Previous studies of intra-executive conflicts in semi-presidential regimes have mainly been occupied with explaining why conflicts occur in the first place, and have neglected the question of how such conflicts are actually related to political outcomes. The present empirical investigation demonstrates that the occurrence of intra-executive conflict in transitional semi-presidential systems is likely to produce high rates of cabinet turnover. [source] Nanocarving of Titania as a Diffusion-Driven Morphological Instability,ADVANCED FUNCTIONAL MATERIALS, Issue 3 2008Doh-Kwon Lee Abstract Under strongly reducing conditions at high temperatures titania develops a specific surface morphology, comprising a regular array of fibers with a diameter in the sub-micrometer range. By a chemical diffusion experiment in a defined oxygen potential gradient it is shown that this surface structuring is caused by a diffusion-driven morphological instability of an advancing reaction front (surface). The kinetics of the process is analyzed in terms of linear transport equations. The conditions for the occurrence of the surface instability are discussed and the required materials properties are analyzed. The observed surface structuring is not restricted to titania, rather it has to occur in all nonstoichiometric compounds with predominant cation mobility. [source] Negative Poisson's Ratio Behavior Induced by an Elastic InstabilityADVANCED MATERIALS, Issue 3 2010Katia Bertoldi Negative Poisson's ratio behavior has been uncovered in cellular solids that comprise a solid matrix with a square array of circular voids. The simplicity of the fabrication implies robust behavior, which is relevant over a range of scales. The behavior results from an elastic instability, which induces a pattern transformation and excellent quantitative agreement is found between calculation and experiment. [source] Instability of wave propagation in saturated poroelastoplastic mediaINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 6 2002Xikui Li Abstract In the present work, stationary discontinuities and fluttery instabilities of wave propagation in saturated poro-elastoplastic media are analysed in the frame of Biot theory. The generalized Biot formulations are particularly employed for simulating non-linear coupled hydro-mechanical behaviour of the media. Inertial coupling effect between the solid and the fluid phases of the media is also taken into account. The non-associated Drucker,Prager criterion to describe non-linear constitutive behaviour of pressure dependent elasto-plasticity for the solid skeleton of the media is particularly considered. With omission of compressibility of solid grains and the pore fluid, the critical conditions of stationary discontinuities and flutter instabilities occurring in wave propagation are given in explicit forms. It is shown that when the stationary discontinuity is triggered at the surface of discontinuity there still may exist real wave speeds. The wave speeds across the stationary discontinuity surface entirely cease to be real only in non-associated plasticity, certain ranges of value of Poisson's ratio and when compression stress normal to the surface of discontinuity dominates the stress state at the surface. It is also indicated that the fluttery instabilities, under which some wave speeds cease to be real even in strain hardening stage, may occur prior to stationary discontinuities only for non-associated plasticity under certain conditions. These conditions are: (1) both the porosity and the Poisson's ratio possess relatively low values and (2) the deviatoric part of the effective stress normal to the surface of discontinuity is compressive. A region in the porosity,Poisson's ratio plot, in which fluttery instabilities are possible to occur, is given. Copyright © 2002 John Wiley & Sons, Ltd. [source] Telomere Higher-Order Structure and Genomic InstabilityIUBMB LIFE, Issue 8 2003Terace Fletcher Abstract Telomeres, nucleoprotein complexes at the end of eukaryotic chromosomes, have vital roles in chromosome integrity. Telomere chromatin structure is both intricate and dynamic allowing for a variety of responses to several stimuli. A critical determinant in telomere structure is the G-strand overhang. Facilitated by telomeric proteins, the G-strand overhang stabilizes telomere higher-order assemblies most likely by adopting unusual DNA structures. These structures influence activities that occur at the chromosome end. Dysfunctional telomeres induce signals resulting in cell growth arrest or death. To overcome telomere dysfunction, cancer cells activate the DNA polymerase, telomerase. The presence of telomerase at the telomere may establish a particular telomeric state. If the chromosome ends of cancer and normal cells exist in different states, cancer-specific telomere structures would offer a unique chemotherapeutic target. IUBMB Life, 55: 443-449, 2003 [source] Femoral Neck BMD Is a Strong Predictor of Hip Fracture Susceptibility in Elderly Men and Women Because It Detects Cortical Bone Instability: The Rotterdam Study,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 11 2007Fernando Rivadeneira Abstract We studied HSA measurements in relation to hip fracture risk in 4806 individuals (2740 women). Hip fractures (n = 147) occurred at the same absolute levels of bone instability in both sexes. Cortical instability (propensity of thinner cortices in wide diameters to buckle) explains why hip fracture risk at different BMD levels is the same across sexes. Introduction: Despite the sexual dimorphism of bone, hip fracture risk is very similar in men and women at the same absolute BMD. We aimed to elucidate the main structural properties of bone that underlie the measured BMD and that ultimately determines the risk of hip fracture in elderly men and women. Materials and Methods: This study is part of the Rotterdam Study (a large prospective population-based cohort) and included 147 incident hip fracture cases in 4806 participants with DXA-derived hip structural analysis (mean follow-up, 8.6 yr). Indices compared in relation to fracture included neck width, cortical thickness, section modulus (an index of bending strength), and buckling ratio (an index of cortical bone instability). We used a mathematical model to calculate the hip fracture distribution by femoral neck BMD, BMC, bone area, and hip structure analysis (HSA) parameters (cortical thickness, section modulus narrow neck width, and buckling ratio) and compared it with prospective data from the Rotterdam Study. Results: In the prospective data, hip fracture cases in both sexes had lower BMD, thinner cortices, greater bone width, lower strength, and higher instability at baseline. In fractured individuals, men had an average BMD that was 0.09 g/cm2 higher than women (p < 0.00001), whereas no significant difference in buckling ratios was seen. Modeled fracture distribution by BMD and buckling ratio levels were in concordance to the prospective data and showed that hip fractures seem to occur at the same absolute levels of bone instability (buckling ratio) in both men and women. No significant differences were observed between the areas under the ROC curves of BMD (0.8146 in women and 0.8048 in men) and the buckling ratio (0.8161 in women and 0.7759 in men). Conclusions: The buckling ratio (an index of bone instability) portrays in both sexes the critical balance between cortical thickness and bone width. Our findings suggest that extreme thinning of cortices in expanded bones plays a key role on local susceptibility to fracture. Even though the buckling ratio does not offer additional predictive value, these findings improve our understanding of why low BMD is a good predictor of fragility fractures. [source] Race/Ethnic Differences in Effects of Family Instability on Adolescents' Risk BehaviorJOURNAL OF MARRIAGE AND FAMILY, Issue 2 2010Paula Fomby We used data from the National Longitudinal Study of Adolescent Health (N = 7,686) to determine whether racial and ethnic differences in socioeconomic stress and social protection explained group differences in the association between family structure instability and three risk behaviors for White, Black, and Mexican American adolescents: delinquent behavior, age at first nonmarital sex, and age at first nonmarital birth. The positive association between mothers' union transitions and each outcome for White adolescents was attenuated by social protection. The association of instability with age at first sex and first nonmarital birth was weaker for Black adolescents but not for Mexican American adolescents. The weaker association was explained by Black adolescents' more frequent exposure to socioeconomic stress in the context of union instability. [source] | ||||||||||||||||||||||||||||||||||||||||||||||||||||