How Does Adolescent Fertility Affect the Human Capital and Wages of Young Women?

The consequences of teen childbearing for the future well-being of young women remain controversial. In this paper, we model and estimate the relationship between early childbearing and human capital investment, and its effect on wages in early adulthood. Taking advantage of a large set of potential instruments for fertility—principally state- and county-level indicators of the costs of fertility and fertility control—we use instrumental variables procedures to generate unbiased estimates of the effects of early fertility on education and work experience, and the effects of these outcomes on adult wages. For both black and white women, adolescent fertility substantially reduces years of formal education and teenage work experience. White teenage mothers also obtain less early adult work experience than young women who delay childbearing. We also find that, through these human capital effects, teenage childbearing has a significant effect on a young woman’s market wage at age 25. Our results, unlike those of recent “revisionist” studies, suggest that public policies that reduce teenage childbearing are likely to have positive effects on the economic well-being of many young mothers and their families.

Instrument selection: The case of teenage childbearing and women's educational attainment

Recent research has identified situations in which instrumental variables (IV) estimators are severely biased and has suggested diagnostic tests to identify such situations. We suggest a number of alternative techniques for choosing a set of instruments that satisfy these tests from a universe of a priori plausible candidates, and we apply them to a study of the effects of adolescent childbearing on the educational attainment of young women. We find that substantive results are sensitive to instrument choice, and make two recommendations to the practical researcher: First, it is prudent to begin with a large set of potential instruments, when possible, and pare it down through formal testing rather than to rely on a minimal instrument set justified on a priori grounds. Second, the application of more restrictive tests of instrument validity and relevance can yield results very different from those based on less restrictive tests that produce a more inclusive set of instruments, and is the preferred, conservative approach when improper instrument choice can lead to biased estimates.

Studies of an orbital gradiometer mission

The goal of using an orbital gradiometer mission to provide an accurate (1 to 2 mgal), high resolution (1 by 1 deg), global map of the earth's geopotential is currently being investigated. This investigation involves the simulation of the satellite ephemeris and the corresponding gradiometer measurements which can be used in the study of various techniques and methodologies that were proposed to recover the parameters used in modeling the geopotential. Also, the effects on the mission of various time varying forces acting on the spacecraft were included in the studies

Reversible plasticity in amorphous materials

A fundamental assumption in our understanding of material rheology is that when microscopic deformations are reversible, the material responds elastically to external loads. Plasticity, i.e. dissipative and irreversible macroscopic changes in a material, is assumed to be the consequence of irreversible microscopic events. Here we show direct evidence for reversible plastic events at the microscopic scale in both experiments and simulations of two-dimensional foam. In the simulations, we demonstrate a link between reversible plastic rearrangement events and pathways in the potential energy landscape of the system. These findings represent a fundamental change in our understanding of materials--microscopic reversibility does not necessarily imply elasticity.Comment: Revised pape

Experimental f-value and isotopic structure for the Ni I line blended with [OI] at 6300A

We have measured the oscillator strength of the Ni I line at 6300.34 \AA, which is known to be blended with the forbidden [O I] $\lambda$6300 line, used for determination of the oxygen abundance in cool stars. We give also wavelengths of the two isotopic line components of $^{58}$Ni and $^{60}$Ni derived from the asymmetric laboratory line profile. These two line components of Ni I have to be considered when calculating a line profile of the 6300 \AA\ feature observed in stellar and solar spectra. We also discuss the labelling of the energy levels involved in the Ni I line, as level mixing makes the theoretical predictions uncertain.Comment: Accepted for publication in ApJLetter

Laplacian Growth, Elliptic Growth, and Singularities of the Schwarz Potential

The Schwarz function has played an elegant role in understanding and in generating new examples of exact solutions to the Laplacian growth (or "Hele- Shaw") problem in the plane. The guiding principle in this connection is the fact that "non-physical" singularities in the "oil domain" of the Schwarz function are stationary, and the "physical" singularities obey simple dynamics. We give an elementary proof that the same holds in any number of dimensions for the Schwarz potential, introduced by D. Khavinson and H. S. Shapiro [17] (1989). A generalization is also given for the so-called "elliptic growth" problem by defining a generalized Schwarz potential. New exact solutions are constructed, and we solve inverse problems of describing the driving singularities of a given flow. We demonstrate, by example, how \mathbb{C}^n - techniques can be used to locate the singularity set of the Schwarz potential. One of our methods is to prolong available local extension theorems by constructing "globalizing families". We make three conjectures in potential theory relating to our investigation

Heavy metal removal from aqueous solutions by sorption using natural clays from Burkina Faso

The acid-base properties of two raw and purified mixed clays from Burkina Faso were studied, as well as their potential to remove copper(II), lead(II) and chromium(III), and thereby their ability to be used to purify water from heavy metals. The purification procedure of the clays involved removal of carbonates, iron oxides and organic matter. A determination of the elemental composition of the mixed clays revealed the presence of aluminum, iron and silicon as main constituents. The high alkaline pH in one of the samples is attributable to the presence of carbonate in the raw clay. The point of zero charge (pHpzc) values of the clays, as determined by potentiometric titrations, were 6.79 and 9.52 for the raw clays, while after purification they were 6.87 and 6.76, respectively. Metal adsorption to the clay surfaces started at pH values below pHpzc, strongly indicating formation of inner-sphere complexes. With contact time of 48 h, complete removal of copper(II) was achieved at pH 8 for all samples. More than 90% of the lead(II) removal was attributed to adsorption while for chromium(III), it was 85%. Adsorption to organic matter and iron oxides, and precipitation of metal hydroxides gave significant contributions to the removal of metal ions in aqueous systems.Key words: Mixed clays, potentiometric titration, heavy metals, pHpzc

Framework for Testing and Operation of the ATLAS Level-1 MUCTPI and CTP

The ATLAS Level-1 Muon-to-Central-Trigger-Processor Interface (MUCTPI) receives information on muon candidates from the muon trigger sectors and sends multiplicity values to the Central Trigger Processor (CTP). The CTP receives the multiplicity values from the MUCTPI and combines them with information from the calorimeter trigger and other triggers of the experiment and makes the final Level-1 decision. The MUCTPI and CTP are housed in two 9U VME64x crates and are made of nine different types of custom designed modules. This paper will present the framework which is used for debugging, commissioning and operation of all modules of the MUCTPI and CTP. Testing of the modules has been considered right from design. Most types of modules contain diagnostic memories at the input of the module which can be used to capture incoming data or to inject data into the module. Testing of the modules can be achieved by capturing data at input of a down-stream module, by reading out data from a monitoring buffer, or by reading out monitoring counters. A layered software framework using C++ has been developed for configuring and controlling all modules and for testing them independently or grouped into complete subsystems. The lowest level uses the ATLAS VME library and driver. At the next higher level, a compiler translates a description of the VME registers from XML to C++ code. This code together with existing code for some components, e.g. HPTDC, DELAY25, and JTAG, is combined to the lowlevel library of the module. A menu program provides access to all methods of the module low-level library. Generators create data for the test memories. Simulators calculate expected results. Generators, simulators and the low-level library are combined to a suite of test programs which cover the full functionality of the MUCTPI and CTP. The low-level library is also used by the control and monitoring programs which integrate the sub-systems into the ATLAS experiment control and monitoring framework

Hardware studies for the upgrade of the ATLAS Central Trigger Processor

The ATLAS Central Trigger Processor (CTP) is the final stage of the first level trigger system which reduces the collision rate of 40 MHz to a level-1 event rate of 75 kHz. The CTP makes the Level-1 trigger decision based on multiplicity values of various transverse-momentum thresholds as well as energy information received from the calorimeter and muon trigger sub-systems using programmable selection criteria. In order to improve the rejection rate for the first phase of the luminosity upgrade of the LHC to 3∙1034 cm-2 s-1 planned for 2015, one of the options being studied consists of adding a topological trigger processor, using Region-Of-Interest information from the calorimeter and potentially also the muon trigger. This will require an upgrade of the CTP in order to accommodate the additional trigger inputs. The current CTP system consists of a 9U VME64x crate with 11 custom designed modules where the functionality is largely implemented in FPGAs. The constraint for the upgrade study presented here was to reuse the existing hardware as much as possible. This is achieved by operating the backplane at twice the design frequency and required developing new FPGA firmware for several of the CTP modules. We present the design of the newly developed firmware for the input, monitoring and core modules of the CTP as well as results from initial tests of the upgraded system