University of Texas at Austin

About: University of Texas at Austin is a education organization based out in Austin, Texas, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 94352 authors who have published 206297 publications receiving 9070052 citations. The organization is also known as: UT-Austin & UT Austin.

Concept Decompositions for Large Sparse Text Data Using Clustering

Abstract: Unlabeled document collections are becoming increasingly common and availables mining such data sets represents a major contemporary challenge. Using words as features, text documents are often represented as high-dimensional and sparse vectors–a few thousand dimensions and a sparsity of 95 to 99% is typical. In this paper, we study a certain spherical k-means algorithm for clustering such document vectors. The algorithm outputs k disjoint clusters each with a concept vector that is the centroid of the cluster normalized to have unit Euclidean norm. As our first contribution, we empirically demonstrate that, owing to the high-dimensionality and sparsity of the text data, the clusters produced by the algorithm have a certain “fractal-like” and “self-similar” behavior. As our second contribution, we introduce concept decompositions to approximate the matrix of document vectorss these decompositions are obtained by taking the least-squares approximation onto the linear subspace spanned by all the concept vectors. We empirically establish that the approximation errors of the concept decompositions are close to the best possible, namely, to truncated singular value decompositions. As our third contribution, we show that the concept vectors are localized in the word space, are sparse, and tend towards orthonormality. In contrast, the singular vectors are global in the word space and are dense. Nonetheless, we observe the surprising fact that the linear subspaces spanned by the concept vectors and the leading singular vectors are quite close in the sense of small principal angles between them. In conclusion, the concept vectors produced by the spherical k-means algorithm constitute a powerful sparse and localized “basis” for text data sets.

Seven-year wilkinson microwave anisotropy probe (wmap *) observations: sky maps, systematic errors, and basic results

Abstract: New full-sky temperature and polarization maps based on seven years of data from WMAP are presented. The new results are consistent with previous results, but have improved due to reduced noise from the additional integration time, improved knowledge of the instrument performance, and improved data analysis procedures. The improvements are described in detail. The seven-year data set is well fit by a minimal six-parameter flat ?CDM model. The parameters for this model, using the WMAP data in conjunction with baryon acoustic oscillation data from the Sloan Digital Sky Survey and priors on H 0 from Hubble Space Telescope observations, are ? b h 2 = 0.02260 ? 0.00053, ? c h 2 = 0.1123 ? 0.0035, ?? = 0.728+0.015 ?0.016, ns = 0.963 ? 0.012, ? = 0.087 ? 0.014, and ?8 = 0.809 ? 0.024 (68% CL uncertainties). The temperature power spectrum signal-to-noise ratio per multipole is greater that unity for multipoles ? 919, allowing a robust measurement of the third acoustic peak. This measurement results in improved constraints on the matter density, ? m h 2 = 0.1334+0.0056 ?0.0055, and the epoch of matter-radiation equality, z eq = 3196+134 ?133, using WMAP data alone. The new WMAP data, when combined with smaller angular scale microwave background anisotropy data, result in a 3? detection of the abundance of primordial helium, Y He = 0.326 ? 0.075. When combined with additional external data sets, the WMAP data also yield better determinations of the total mass of neutrinos, ?m ? ? 0.58 eV(95%CL), and the effective number of neutrino species, N eff = 4.34+0.86 ?0.88. The power-law index of the primordial power spectrum is now determined to be ns = 0.963 ? 0.012, excluding the Harrison-Zel'dovich-Peebles spectrum by >3?. These new WMAP measurements provide important tests of big bang cosmology.

Aneurysm Syndromes Caused by Mutations in the TGF-β Receptor

Abstract: Background The Loeys–Dietz syndrome is a recently described autosomal dominant aortic-aneurysm syndrome with widespread systemic involvement The disease is characterized by the triad of arterial tortuosity and aneurysms, hypertelorism, and bifid uvula or cleft palate and is caused by heterozygous mutations in the genes encoding transforming growth factor β receptors 1 and 2 (TGFBR1 and TGFBR2, respectively) Methods We undertook the clinical and molecular characterization of 52 affected families Forty probands presented with typical manifestations of the Loeys–Dietz syndrome In view of the phenotypic overlap between this syndrome and vascular Ehlers–Danlos syndrome, we screened an additional cohort of 40 patients who had vascular Ehlers–Danlos syndrome without the characteristic type III collagen abnormalities or the craniofacial features of the Loeys–Dietz syndrome Results We found a mutation in TGFBR1 or TGFBR2 in all probands with typical Loeys–Dietz syndrome (type I) and in 12 probands presenting

Transfer of CVD-Grown Monolayer Graphene onto Arbitrary Substrates

Abstract: Reproducible dry and wet transfer techniques were developed to improve the transfer of large-area monolayer graphene grown on copper foils by chemical vapor deposition (CVD). The techniques reported here allow transfer onto three different classes of substrates: substrates covered with shallow depressions, perforated substrates, and flat substrates. A novel dry transfer technique was used to make graphene-sealed microchambers without trapping liquid inside. The dry transfer technique utilizes a polydimethylsiloxane frame that attaches to the poly(methyl methacrylate) spun over the graphene film, and the monolayer graphene was transferred onto shallow depressions with 300 nm depth. The improved wet transfer onto perforated substrates with 2.7 μm diameter holes yields 98% coverage of holes covered with continuous films, allowing the ready use of Raman spectroscopy and transmission electron microscopy to study the intrinsic properties of CVD-grown monolayer graphene. Additionally, monolayer graphene transfer...

Bacterial Rhodopsin: Evidence for a New Type of Phototrophy in the Sea

Abstract: Extremely halophilic archaea contain retinal-binding integral membrane proteins called bacteriorhodopsins that function as light-driven proton pumps. So far, bacteriorhodopsins capable of generating a chemiosmotic membrane potential in response to light have been demonstrated only in halophilic archaea. We describe here a type of rhodopsin derived from bacteria that was discovered through genomic analyses of naturally occuring marine bacterioplankton. The bacterial rhodopsin was encoded in the genome of an uncultivated gamma-proteobacterium and shared highest amino acid sequence similarity with archaeal rhodopsins. The protein was functionally expressed in Escherichia coli and bound retinal to form an active, light-driven proton pump. The new rhodopsin exhibited a photochemical reaction cycle with intermediates and kinetics characteristic of archaeal proton-pumping rhodopsins. Our results demonstrate that archaeal-like rhodopsins are broadly distributed among different taxa, including members of the domain Bacteria. Our data also indicate that a previously unsuspected mode of bacterially mediated light-driven energy generation may commonly occur in oceanic surface waters worldwide.