An Evaluation of Instrumental Variable Strategies for Estimating the Effects of Catholic Schools

Several previous studies have relied on religious affiliation and the proximity to Catholic schools as exogenous sources of variation for identifying the effect of Catholic schooling on a wide variety of outcomes. Using three separate approaches, we examine the validity of these instrumental variables. We find that none of the candidate instruments is a useful source of identification of the Catholic school effect, at least in currently available data sets

Dimensionality Reduction for k-Means Clustering and Low Rank Approximation

We show how to approximate a data matrix $\mathbf{A}$ with a much smaller sketch $\mathbf{\tilde A}$ that can be used to solve a general class of constrained k-rank approximation problems to within $(1+\epsilon)$ error. Importantly, this class of problems includes $k$-means clustering and unconstrained low rank approximation (i.e. principal component analysis). By reducing data points to just $O(k)$ dimensions, our methods generically accelerate any exact, approximate, or heuristic algorithm for these ubiquitous problems. For $k$-means dimensionality reduction, we provide $(1+\epsilon)$ relative error results for many common sketching techniques, including random row projection, column selection, and approximate SVD. For approximate principal component analysis, we give a simple alternative to known algorithms that has applications in the streaming setting. Additionally, we extend recent work on column-based matrix reconstruction, giving column subsets that not only `cover' a good subspace for \bv{A}, but can be used directly to compute this subspace. Finally, for $k$-means clustering, we show how to achieve a $(9+\epsilon)$ approximation by Johnson-Lindenstrauss projecting data points to just $O(\log k/\epsilon^2)$ dimensions. This gives the first result that leverages the specific structure of $k$-means to achieve dimension independent of input size and sublinear in $k$

Parameter-free predictions of the viscoelastic response of glassy polymers from non-affine lattice dynamics

We study the viscoelastic response of amorphous polymers using theory and simulations. By accounting for internal stresses and considering instantaneous normal modes (INMs) within athermal non-affine theory, we make parameter-free predictions of the dynamic viscoelastic moduli obtained in coarse-grained simulations of polymer glasses at non-zero temperatures. The theoretical results show very good correspondence with rheology data collected from molecular dynamics simulations over five orders of magnitude in frequency, with some instabilities that accumulate in the low-frequency part on approach to the glass transition. These results provide evidence that the mechanical glass transition itself is continuous and thus represents a crossover rather than a true phase transition. The relatively sharp drop of the low-frequency storage modulus across the glass transition temperature can be explained mechanistically within the proposed theory: the proliferation of low-eigenfrequency vibrational excitations (boson peak and nearly-zero energy excitations) is directly responsible for the rapid growth of a negative non-affine contribution to the storage modulus.Comment: 10 pages, 7 figure

Selective Inguinal Lymphadenectomy in the Treatment of Invasive Squamous Cell Carcinoma of the Vulva

En bloc radical vulvectomy with bilateral inguinofemoral lymphadenectomy has now been replaced by radical wide excision and selective inguinal lymphadenectomy based on the stage and location of invasive vulvar cancer. Early stage lateral cancers can be effectively treated by radical wide excision and ipsilateral superficial inguinal lymphadenectomy. Lymph node mapping using perilesional injection of radiocolloid and blue dye may identify sentinel lymph nodes which can be removed, thereby avoiding the morbidity of full inguinal lymphadenectomy in selected patients with early stage disease

Oxygen cost of dynamic or isometric exercise relative to recruited muscle mass

BACKGROUND: Oxygen cost of different muscle actions may be influenced by different recruitment and rate coding strategies. The purpose of this study was to account for these strategies by comparing the oxygen cost of dynamic and isometric muscle actions relative to the muscle mass recruited via surface electrical stimulation of the knee extensors. METHODS: Comparisons of whole body pulmonary Δ [Formula: see text] O(2 )were made in seven young healthy adults (1 female) during 3 minutes of dynamic or isometric knee extensions, both induced by surface electrical stimulation. Recruited mass was quantified in T(2 )weighted spin echo magnetic resonance images. RESULTS: The Δ [Formula: see text] O(2 )for dynamic muscle actions, 242 ± 128 ml • min(-1 )(mean ± SD) was greater (p = 0.003) than that for isometric actions, 143 ± 99 ml • min(-1). Recruited muscle mass was also greater (p = 0.004) for dynamic exercise, 0.716 ± 282 versus 0.483 ± 0.139 kg. The rate of oxygen consumption per unit of recruited muscle ([Formula: see text]) was similar in dynamic and isometric exercise (346 ± 162 versus 307 ± 198 ml • kg(-1 )• min(-1); p = 0.352), but the [Formula: see text] calculated relative to initial knee extensor torque was significantly greater during dynamic exercise 5.1 ± 1.5 versus 3.6 ± 1.6 ml • kg(-1 )• Nm(-1 )• min(-1 )(p = 0.019). CONCLUSION: These results are consistent with the view that oxygen cost of dynamic and isometric actions is determined by different circumstances of mechanical interaction between actin and myosin in the sarcomere, and that muscle recruitment has only a minor role

Selection on Observed and Unobserved Variables: Assessing the Effectiveness of Catholic Schools

We develop estimation methods that use the amount of selection on the observables in a model as a guide to the amount of selection on the unobservables. We show that if the observed variables are a random subset of a large number of factors that influence the endogenous variable and the outcome of interest, then the relationship between the index of observables that determines the endogenous variable and the index that determines the outcome will be the same as the relationship between the indices of unobservables that determine the two variables. In some circumstances this fact may be used to identify the effect of the endogenous variable. We also propose an informal way to assess selectivity bias based on measuring the ratio of selection on unobservables to selection on observables that would be required if one is to attribute the entire effect of the endogenous variable to selection bias. We use our methods to estimate the effect of attending a Catholic high school on a variety of outcomes. Our main conclusion is that Catholic high schools substantially increase the probability of graduating from high school and, more tentatively, college attendance. We do not find much evidence for an effect on test scores.

Prenatal Exclusion of Lamellar Ichthyosis Based on Identification of Two New Mutations in the Transglutaminase 1 Gene

Lamellar ichthyosis is a severe, generalized, autosomal recessive genodermatosis characterized clinically by large, parchment-like scales and histologically by acanthosis and marked hyperkeratosis. Genetic heterogeneity in lamellar ichthyosis has been recognized with reports of two linked loci (on chromosomes 14q11 and 2q33–35). In a cohort of four small families with lamellar ichthyosis we found confirmatory evidence for linkage (p ≤ 0.01) to D14S275, a microsatellite marker close to transglutaminase 1 on chromosome 14q11. We also identified two novel transglutaminase 1 mutations in an affected sibling pair from one of these families. The paternal mutation in exon 3, 1387insCAGC, causes a frameshift predicted to result in premature termination of translation within the same exon. The maternal mutation in exon 8, 4561delAC, also causes a frameshift and a premature stop codon in this exon. The mother of these siblings recently became pregnant with twins. Genotyping and direct sequencing of DNA isolated from fetal amniotic fluid cultures revealed the presence of the paternal but the absence of the maternal mutation, thus predicting a normal skin phenotype. Both twins were born with normal-appearing skin. Our findings demonstrate that mutations of both alleles of the transglutaminase 1 gene are the cause of lamellar ichthyosis in this family, and illustrate an emerging clinical application of molecular genetics in dermatology