Stephen Becker

We establish methods for quantum state tomography based on compressed sensing. These methods are specialized for quantum states that are fairly pure, and they offer a significant performance improvement on large quantum systems. In particular, they are able to reconstruct an unknown density matrix of dimension d and rank r using O(rdlog²d) measurement settings, compared to standard methods that require d² settings. Our methods have several features that make them amenable to experimental implementation: they require only simple Pauli measurements, use fast convex optimization, are stable against noise, and can be applied to states that are only approximately low rank. The acquired data can be used to certify that the state is indeed close to pure, so no a priori assumptions are needed.

Exposure to 17beta-estradiol prior to induction of apoptosis protects skeletal muscle cells against damage. The mechanism involved in this protective action of the hormone is poorly understood. In the present study, using the murine muscle cell line C2C12, evidence was obtained that inhibition of H(2)O(2)-induced apoptosis by the estrogen requires the participation of heat shock protein 27 (HSP27). Reverse transcriptase polymerase chain reaction, Western blot, and immunocytochemistry assays showed that 17beta-estradiol induces a time-dependent (5-60 min) increase in the expression of HSP27. In addition, in presence of quercetin, an inhibitor of HSPs, the antiapoptotic effect of the hormone was diminished. More specifically, blockage experiments with short interference RNA targeting HSP27 confirmed the role of this chaperone in the protective effect of the steroid. 17beta-Estradiol abolished caspase-3 cleavage elicited by H(2)O(2). Coimmunoprecipitation assays suggested physical interaction of HSP27 with caspase-3 in presence of estradiol. Furthermore, we observed that this chaperone interacts with estrogen receptors (ER) beta in mitochondria. Then, this study suggests that HSP27 plays a new role in the antiapoptotic action triggered by 17beta-estradiol by modulating caspase-3 activity and stabilizing ERbeta in skeletal muscle cells.

This article reviews recent advances in convex optimization algorithms for big data, which aim to reduce the computational, storage, and communications bottlenecks. We provide an overview of this emerging field, describe contemporary approximation techniques such as first-order methods and randomization for scalability, and survey the important role of parallel and distributed computation. The new big data algorithms are based on surprisingly simple principles and attain staggering accelerations even on classical problems.

Research Article| July 01, 2010 A 48 m.y. history of fracture opening, temperature, and fluid pressure: Cretaceous Travis Peak Formation, East Texas basin S.P. Becker; S.P. Becker * 1Bureau of Economic Geology, The University of Texas at Austin, University Station Box X, Austin, Texas 78713-8924, USA *Current address: ExxonMobil Upstream Research Company, P.O. Box 2189, Houston, Texas 77252-2189, USA. Search for other works by this author on: GSW Google Scholar P. Eichhubl; P. Eichhubl † 1Bureau of Economic Geology, The University of Texas at Austin, University Station Box X, Austin, Texas 78713-8924, USA †E-mail: peter.eichhubl@beg.utexas.edu Search for other works by this author on: GSW Google Scholar S.E. Laubach; S.E. Laubach 1Bureau of Economic Geology, The University of Texas at Austin, University Station Box X, Austin, Texas 78713-8924, USA Search for other works by this author on: GSW Google Scholar R.M. Reed; R.M. Reed 1Bureau of Economic Geology, The University of Texas at Austin, University Station Box X, Austin, Texas 78713-8924, USA Search for other works by this author on: GSW Google Scholar R.H. Lander; R.H. Lander 2Geocosm LLC, 3311 San Mateo Drive, Austin, Texas 78738, USA Search for other works by this author on: GSW Google Scholar R.J. Bodnar R.J. Bodnar 3Department of Geosciences, 4044 Derring Hall, Virginia Tech, Blacksburg, Virginia 24061, USA Search for other works by this author on: GSW Google Scholar GSA Bulletin (2010) 122 (7-8): 1081–1093. https://doi.org/10.1130/B30067.1 Article history received: 05 Apr 2009 rev-recd: 03 Aug 2009 accepted: 24 Aug 2009 first online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation S.P. Becker, P. Eichhubl, S.E. Laubach, R.M. Reed, R.H. Lander, R.J. Bodnar; A 48 m.y. history of fracture opening, temperature, and fluid pressure: Cretaceous Travis Peak Formation, East Texas basin. GSA Bulletin 2010;; 122 (7-8): 1081–1093. doi: https://doi.org/10.1130/B30067.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Quartz cement bridges across opening-mode fractures of the Cretaceous Travis Peak Formation provide a textural and fluid inclusion record of incremental fracture opening during the burial evolution of this low-porosity sandstone. Incremental crack-seal fracture opening is inferred based on the banded structure of quartz cement bridges, consisting of up to 700 cement bands averaging ∼5 μm in thickness as observed with scanning electron microscope–cathodoluminescence. Crack-seal layers contain assemblages of aqueous two-phase fluid inclusions. Based on fluid inclusion microthermometry and Raman microprobe analyses, we determined that these inclusions contain methane-saturated brine trapped over temperatures ranging from ∼130°C to ∼154°C. Using textural crosscutting relations of quartz growth increments to infer the sequence of cement growth, we reconstructed the fluid temperature and pore-fluid pressure evolution during fracture opening. In combination with published burial evolution models, this reconstruction indicates that fracture opening started at ca. 48 Ma and above-hydrostatic pore-fluid pressure conditions, and continued under steadily declining pore-fluid pressure during partial exhumation until present times. Individual fractures opened over an ∼48 m.y. time span at rates of 16–23 μm/m.y. These rates suggest that fractures can remain hydraulically active over geologically long times in deep basinal settings. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Fluid inclusions that homogenize by disappearance of the halite crystal after the vapor bubble has disappeared have been reported from a wide range of ore-forming systems. While this inclusion type is most commonly observed in porphyry copper and similar magmatichydrothermal ore deposits, they have also been reported from iron oxide copper-gold (IOCG), Mississippi Valley-type, orogenic (lode, greenstone) gold, massive sulfide, unconformity U, and mantotype deposits, as well as from non-ore associated granitoids and oceanic crust. The lack of experimental data to interpret microthermometric data from these inclusions, combined with poor petrographic characterization of inclusion origin, has led to a wide range of inferred PT trapping conditions for the inclusions. The relationship between liquid-vapor homogenization temperature (ThL-V), halite dissolution temperature (Tmhalite) and pressure has been determined using synthetic H2O-NaCl fluid inclusions that homogenize by halite disappearance. The experimental data cover the range ThL-V ≈ 150° to 500°C and Tmhalite ≈ 275° to 550°C. An empirical equation describing the relationship between pressure, ThL-V, and Tmhalite has been developed to estimate formation pressures from microthermometric data and is valid from pressures along the liquid + vapor + halite curve to 300 MPa. A detailed literature review reveals that the results of this study cannot be applied retroactively to estimate pressures of previously reported inclusions that homogenize by halite dissolution for several reasons. First, most workers have not collected and reported the data in a manner that allows one to determine if the inclusions have trapped a single, homogeneous phase and have not leaked or changed volume following trapping. Thus, it is not possible to determine if the inclusions show consistent microthermometric behavior within a group of coeval inclusions. Additionally, many published studies provide only summaries of results from numerous samples or present the data graphically, precluding application of our results to individual inclusions. However, based on our review, it appears that much of the published data for inclusions that homogenize by halite dissolution represent inclusions that have either trapped a halite crystal along with the liquid or have reequilibrated by necking and/or stretching. Results from this study have been used to estimate minimum formation pressures for inclusions from the Ditrau Alkaline Massif, Transylvania, Romania, the Musoshi stratiform copper deposit, Zaire, the Bismark skarn deposit, northern Mexico, the Naica chimneymanto deposit, Mexico, the Questa porphyry molybdenum deposit, New Mexico, and the Bingham Canyon porphyry Cu-Mo deposit, Utah. In each case, pressures estimated using results from the present study are in good agreement with previous pressure estimates. However, in some cases estimated pressures (both our estimates as well as those of other authors) appear to be unreasonably high, based on the geologic setting at the time of formation. These results highlight the currently limited understanding concerning pressures (depths) of ore formation.