One Out of Every Five: Teen Mothers and Subsequent Childbearing

The birth of a child to a teenager puts the young family at risk for negative social and health consequences; the birth of additional children can further impede the family's financial, academic, and social success. Though there is a national interest in reducing the teen birth rate, strategies designed to achieve this goal often insufficiently target a readily identifiable group -teens who are already mothers. Of those programs that do target teen mothers, few have been able to demonstrate success. Teen mothers should be targeted for pregnancy prevention not only because they contribute to the teen birth rate with its attendant consequences, but also because second and higher-order births to teenaged mothers often limits life options further than having only one child.Compared to a teen mother with one child, a teenager with two or more children typically faces: lower educational attainment;greater likelihood of poverty; andimpaired health for the infant

Determination of complex absorbing potentials from the electron self-energy

The electronic conductance of a molecule making contact to electrodes is determined by the coupling of discrete molecular states to the continuum electrode density of states. Interactions between bound states and continua can be modeled exactly by using the (energy-dependent) self-energy, or approximately by using a complex potential. We discuss the relation between the two approaches and give a prescription for using the self-energy to construct an energy-independent, non-local, complex potential. We apply our scheme to studying single-electron transmission in an atomic chain, obtaining excellent agreement with the exact result. Our approach allows us to treat electron-reservoir couplings independent of single electron energies, allowing for the definition of a one-body operator suitable for inclusion into correlated electron transport calculations.Comment: 11 pages, 8 figures; to be published in the J. Chem. Phy

Modes, Means and Measures: Adapting Sustainability Indicators to Assess Preservation Activity\u27s Impact on Community Equity

Preservation of and reinvestment in the built environment as a redevelopment tool has been used by cities and towns across the country, in many cases providing significant social, economic and environmental benefits. Potential social effects have often been the least explored aspect of sustainable development, especially with regard to preservation, yet they are often the most challenging, particularly given the potential for displacement. This thesis reviews literature where the issues of preservation, redevelopment and sustainability intersect. A set of best practices was developed that can be applied to other cities and towns to help balance preservation- and equity- enhancing activities. Another result of this research is the development of appropriate community indicators to provide means for measuring the effects of preservation on social equity. A selection of the indicators will be applied to two selected case studies (Northampton and Pittsfield, MA) to explore how such indicators can work as a measurement tool, how to best adapt them for a community, and their comparative strengths and weaknesses. The findings section addresses the data at both the fine and coarse grain – for the indicators and best practices as well as for the overall observations from the study process

Mechanical compatibility of sol–gel annealing with titanium for orthopaedic prostheses

Sol–gel processing is an attractive method for large-scale surface coating due to its facile and inexpensive preparation, even with the inclusion of precision nanotopographies. These are desirable traits for metal orthopaedic prostheses where ceramic coatings are known to be osteoinductive and the effects may be amplified through nanotexturing. However there are a few concerns associated with the application of sol–gel technology to orthopaedics. Primarily, the annealing stage required to transform the sol–gel into a ceramic may compromise the physical integrity of the underlying metal. Secondly, loose particles on medical implants can be carcinogenic and cause inflammation so the coating needs to be strongly bonded to the implant. These concerns are addressed in this paper. Titanium, the dominant material for orthopaedics at present, is examined before and after sol–gel processing for changes in hardness and flexural modulus. Wear resistance, bending and pull tests are also performed to evaluate the ceramic coating. The findings suggest that sol–gel coatings will be compatible with titanium implants for an optimum temperature of 500 °C

Fundamental Differences in Mechanical Behavior between Two Types of Crystals at the Nanoscale

We present differences in the mechanical behavior of nanoscale gold and molybdenum single crystals. A significant strength increase is observed as the size is reduced to 100 nm. Both nanocrystals exhibit discrete strain bursts during plastic deformation. We postulate that they arise from significant differences in the dislocation behavior. Dislocation starvation is the predominant mechanism of plasticity in nanoscale fcc crystals, while junction formation and hardening characterize bcc plasticity. A statistical analysis of strain bursts is performed as a function of size and compared with stochastic models

Dynamical Monte Carlo Study of Equilibrium Polymers : Static Properties

We report results of extensive Dynamical Monte Carlo investigations on self-assembled Equilibrium Polymers (EP) without loops in good solvent. (This is thought to provide a good model of giant surfactant micelles.) Using a novel algorithm we are able to describe efficiently both static and dynamic properties of systems in which the mean chain length \Lav is effectively comparable to that of laboratory experiments (up to 5000 monomers, even at high polymer densities). We sample up to scission energies of $E/k_BT=15$ over nearly three orders of magnitude in monomer density $\phi$, and present a detailed crossover study ranging from swollen EP chains in the dilute regime up to dense molten systems. Confirming recent theoretical predictions, the mean-chain length is found to scale as \Lav \propto \phi^\alpha \exp(\delta E) where the exponents approach $\alpha_d=\delta_d=1/(1+\gamma) \approx 0.46$ and $\alpha_s = 1/2 [1+(\gamma-1)/(\nu d -1)] \approx 0.6, \delta_s=1/2$ in the dilute and semidilute limits respectively. The chain length distribution is qualitatively well described in the dilute limit by the Schulz-Zimm distribution \cN(s)\approx s^{\gamma-1} \exp(-s) where the scaling variable is s=\gamma L/\Lav. The very large size of these simulations allows also an accurate determination of the self-avoiding walk susceptibility exponent $\gamma \approx 1.165 \pm 0.01$. ....... Finite-size effects are discussed in detail.Comment: 15 pages, 14 figures, LATE