cssi/SciSciGPT-SciSciNet huggingface dataset:
Renormalized yukawa couplings from the lattice

Abstract Renormalized Yukawa couplings, yR, are evaluated numerically in the single component lattice λϕ4 theory coupled to staggered fermions. For a wide range of bare couplings, the renormalized yR is found to be “small” (⪅1.5) whenever physical scalar and fermion masses have dropped below about one half the cutoff scale. In these cases Yukawa coupling generated fermion masses are never much larger than the symmetry breaking scale ν = 〈ϕR〉. The simulations have been performed using the hybrid Monte Carlo algorithm for dynamical fermions.
TEDI: the TripleSpec Exoplanet Discovery Instrument

The TEDI (TripleSpec Exoplanet Discovery Instrument) will be the first instrument fielded specifically for finding low-mass stellar companions. The instrument is a near infra-red interferometric spectrometer used as a radial velocimeter. TEDI joins Externally Dispersed Interferometery (EDI) with an efficient, medium-resolution, near IR (0.9 - 2.4 micron) echelle spectrometer, TripleSpec, at the Palomar 200 telescope. We describe the instrument and its radial velocimetry demonstration program to observe cool stars.
Factoring multivariate polynomials over algebraic number fields

We present an algorithm to factor multivariate polynomials over algebraic number fields that is polynomial-time in the degrees of the polynomial to be factored. The algorithm is an immediate generalization of the polynomial-time algorithm to factor univariate polynomials with rational coefficients.
Semi-automatic, octave-spanning optical frequency counter

This work presents and demonstrates a semi-automatic optical frequency counter with octave-spanning counting capability using two fiber laser combs operated at different repetition rates. Monochromators are utilized to provide an approximate frequency of the laser under measurement to determine the mode number difference between the two laser combs. The exact mode number of the beating comb line is obtained from the mode number difference and the measured beat frequencies. The entire measurement process, except the frequency stabilization of the laser combs and the optimization of the beat signal-to-noise ratio, is controlled by a computer running a semi-automatic optical frequency counter.
Predicting and Understanding Order of Heteroepitaxial Quantum Dots

Heteroepitaxial self-assembled quantum dots (SAQDs) will allow breakthroughs in electronics and optoelectronics. SAQDs are a result of Stranski–Krastanow growth, whereby a growing planar film becomes unstable after an initial wetting layer is formed. Common systems are GexSi1� x=Si and InxGa1� xAs/GaAs: For applications, SAQD arrays need to be ordered. The roles of crystal anisotropy, random initial conditions and thermal fluctuations in influencing SAQD order during early stages of SAQD formation are studied through a simple stochastic model of surface diffusion. Surface diffusion is analyzed through a linear and perturbatively non-linear analysis. The role of crystal anisotropy in enhancing SAQD order is elucidated. It is also found that SAQD order is enhanced when the deposited film is allowed to evolve at heights near the critical wetting surface height that marks the onset of non-planar film growth.
Inference with “Difference in Differences” with a Small Number of Policy Changes

Abstract In difference-in-differences applications, identification of the key parameter often arises from changes in policy by a small number of groups. In contrast, typical inference assumes that the number of groups changing policy is large. We present an alternative inference approach for a small (finite) number of policy changers, using information from a large sample of nonchanging groups. Treatment effect point estimators are not consistent, but we can consistently estimate their asymptotic distribution under any point null hypothesis about the treatment. Thus, treatment point estimators can be used as test statistics, and confidence intervals can be constructed using test statistic inversion.
The catalytic asymmetric aldol reaction of aldehydes with unsubstituted and monosubstituted silyl ketene acetals: formation of anti-β-hydroxy-α-methyl esters

Abstract The title reaction with unsubstituted and monosubstituted silyl ketene acetals proceeds with high enantioselectivity, and in the latter case good diastereoselectivity favoring the anti-β-hydroxy-α-methyl esters in all reported cases.
Random measurement bases, quantum state distinction and applications to the hidden subgroup problem

We show that measuring any two low rank quantum states in a random orthonormal basis gives, with high probability, two probability distributions having total variation distance at least a universal constant times the Frobenius distance between the two states. This implies that for any finite ensemble of quantum states there is a single POVM that distinguishes between every pair of states from the ensemble by at least a constant times their Frobenius distance; in fact, with high probability a random POVM, under a suitable definition of randomness, suffices. There are examples of ensembles with constant pairwise trace distance where a single POVM cannot distinguish pairs of states by much better than their Frobenius distance, including the important ensemble of coset states of hidden subgroups of the symmetric group (Moore at al., 2005). We next consider the random Fourier method for the hidden subgroup problem (HSP) which consists of Fourier sampling the coset state of the hidden subgroup using random orthonormal bases for the group representations. In cases where every representation of the group has polynomially bounded rank when averaged over the hidden subgroup, the random Fourier method gives a POVM for the HSP operating on one coset state at a time and using totally a polynomial number of coset states. In particular, we get such POVMs whenever the group and the hidden subgroup form a Gel'fand pair, e.g., Abelian, dihedral and Heisenberg groups. This gives a positive counterpart to earlier negative results about random Fourier sampling when the above rank is exponentially large (Grigni et al., 2004), which happens for example in the HSP in the symmetric group. The drawback of random POVMs is that they are not efficient to implement, since measuring in a random basis takes exponential time as can be seen by a counting argument. This leads us to the open question of efficiently implementable pseudorandom measurement bases.
RF safety of wires in interventional MRI: using a safety index.

With the rapid growth of interventional MRI, radiofrequency (RF) heating at the tips of guidewires, catheters, and other wire-shaped devices has become an important safety issue. Previous studies have identified some of the variables that affect the relative magnitude of this heating but none could predict the absolute amount of heating to formulate safety margins. This study presents the first theoretical model of wire tip heating that can accurately predict its absolute value, assuming a straight wire, a homogeneous RF coil, and a wire that does not extend out of the tissue. The local specific absorption rate (SAR) amplification from induced currents on insulated and bare wires was calculated using the method of moments. This SAR gain was combined with a semianalytic solution to the bioheat transfer equation to generate a safety index. The safety index ( degrees C/(W/kg)) is a measure of the in vivo temperature change that can occur with the wire in place, normalized to the SAR of the pulse sequence. This index can be used to set limits on the spatial peak SAR of pulse sequences that are used with the interventional wire. For the case of a straight resonant wire in a tissue with very low perfusion, only about 100 mW/kg/ degrees C spatial peak SAR may be used at 1.5 T. But for or =30% of the wire radius that are placed in well-perfused tissues, normal operating conditions of 4 W/kg spatial peak SAR are possible at 1.5 T. Further model development to include the influence of inhomogeneous RF, curved wires, and wires that extend out of the sample are required to generate safety indices that are applicable to common clinical situations. We propose a simple way to ensure safety when using an interventional wire: set a limit on the SAR of allowable pulse sequences that is a factor of a safety index below the tolerable temperature increase.
Enzyme-catalyzed regioselective transesterification of peracylated sophorolipids

Abstract Regioselective transesterifications and hydrolysis of peracylated sophorolipid (SL) derivatives catalyzed by lipases was investigated. This study is the first evaluation of the lipase-catalyzed reactions on the non-lactonic SL derivatives. Four lipases, namely from porcine pancreas (PPL, Type II), Candida rugosa (AYS, TypeVII), Pseudomonas cepacia (PS-30), and Candida antarctica (Novozym 435, carrier fixed lipase fraction B) were used in anhydrous THF or in phosphate buffer (pH=7.4, 0.2 M). It was confirmed from the detailed spectral analysis of the products that transesterification failed to furnish any free hydroxyls on the sophorose ring. Instead, transesterification took place on the methyl ester located at the carboxylic end of the 17-hydroxyoctadecenoic acid chain attached to the C-1′ position of the sophorose ring. It is proposed that in absence of the lactonic structural motif, the binding of the peracylated non-lactonic SLs in the lipase binding pocket takes place such that the carboxyl group of the octadecenoic acid, not the sophorose sugar, is preferentially accessible to the active site.
Sudden Flight and True Sudden Stops

A sudden stop is a trading phenomenon that should be framed using a trading model. But in the existing literature sudden stops are described in the context of international macro models that focus on net flows and do not differentiate between global and local investors. We allow crisis episodes to be caused by either the retreat of global investors (true sudden stops), as is assumed but not shown in the extant literature, or the sudden flight of local investors. We find that almost half of the previously defined sudden stop episodes are actually sudden flight. Compared to sudden flight, true sudden stops are bunched and are associated with greater slowdowns in economic activity and sharper currency depreciations. The empirical regularities of sudden flight and true sudden stops are consistent with the well-known Brennan and Cao (1997) model of gross capital flows and information asymmetries.
Deformation Quantization of the Isotropic Rotator

We perform a deformation quantization of the classical isotropic rigid rotator. The resulting quantum system is not invariant under the usual SU(2) × SU(2) chiral symmetry, but instead . We give the energy spectrum for the resulting system.
Flux-period scaling in the Laughlin quasiparticle interferometer

We report experiments on electron interferometer devices in the quantum Hall regime, where edge channels circle a two-dimensional (2D) electron island. The main confinement is produced by etch trenches, into which front-gate metal is deposited. We find a linear dependence of the Aharonov-Bohm period on gate voltage for electrons (integer filling $f=1$) and for Laughlin quasiparticles (fractional 2/5 embedded in 1/3). The capacitance of a large 2D electron island with respect to the front gates is approximately proportional to the island radius. Comparing the experimental data for the integer and the fractional fillings and for two samples, we find the magnetic field period and its slope scale with the radius of the Aharonov-Bohm orbit. Analysis of the directly measured integer and fractional slope data allows us to determine the interferometer area in the fractional regime, and thus the Laughlin quasiparticle flux period of $5h∕e$, within the experimental accuracy.
Reaction of NO2 with Zn and ZnO: Photoemission, XANES, and Density Functional Studies on the Formation of NO3

Synchrotron-based high-resolution photoemission and X-ray absorption near-edge spectroscopy (XANES) have been used to study the interaction of NO2 with polycrystalline surfaces of metallic zinc and zinc oxide. NO2 exhibits a complex chemistry on metallic zinc. After adsorbing nitrogen dioxide, N, O, NO, NO2, and NO3 are present on the surface of the metal. At room temperature the NO2 molecule mainly dissociates into O adatoms and gaseous NO, whereas at low temperatures (<250 K) chemisorbed NO2 and NO3 dominate on the surface. NO2 is a very good oxidizing agent for preparing ZnO from metallic zinc. Zn reacts more vigorously with NO2 than metals, such as Rh, Pd, or Pt which are typical catalysts for the removal of NOx molecules (DeNOx process). At 300 K, the main product of the reaction of NO2 with polycrystalline ZnO is adsorbed NO3 with little NO2 or NO present on the surface of the oxide. No evidence was found for the full decomposition of the NO2 molecule (i.e., no NO2 → N + 2O). The results of density ...
State-of-the-art multichip modules for avionics

The emerging multichip packaging technology offers significant advantages in miniaturization, electrical performance, thermal performance, lower cost, and improved reliability. Newly available materials and processes have stimulated multichip applications ranging from low cost consumer electronics and automotive modules to advanced aerospace and supercomputers. Avionics multichip modules share the same systems integration issues as other applications: optimum partitioning, seamless CAD/CIM tools, testability and repairability strategies, cost-effective manufacturing, availability of vendor support technologies, and reliable packaging for long life in environmental stresses. State-of-the-art avionics multichip modules are detailed. Industry developments required to enable wider utilization are discussed. Evolutionary extensions into next generation technologies are discussed. >
Co-authorship networks in the digital library research community

The field of digital libraries (DLs) coalesced in 1994: the first digital library conferences were held that year, awareness of the World Wide Web was accelerating, and the National Science Foundation awarded $24 Million (US) for the Digital Library Initiative (DLI). In this paper we examine the state of the DL domain after a decade of activity by applying social network analysis to the co-authorship network of the past ACM, IEEE, and joint ACM/IEEE digital library conferences. We base our analysis on a common binary undirectional network model to represent the co-authorship network, and from it we extract several established network measures. We also introduce a weighted directional network model to represent the co-authorship network, for which we define AuthorRank as an indicator of the impact of an individual author in the network. The results are validated against conference program committee members in the same period. The results show clear advantages of PageRank and AuthorRank over degree, closeness and betweenness centrality metrics. We also investigate the amount and nature of international participation in Joint Conference on Digital Libraries (JCDL).
Nonlinear Polarizabilities of Donor-Acceptor Substituted Conjugated Polyenes

The polarizabilities of conjugated polyenes with 8−36 carbon atoms are calculated using the time dependent Hartree−Fock (TDHF) technique. By examining the reduced single-electron density matrix, we explore the relations among the ground state chemical bonding structure and off-resonant and resonant susceptibilities. The effects of a donor−acceptor substitution on oligomers of different sizes are investigated.
A DIELS-ALDER SYNTHESIS OF PYRIDINES

(2003). A DIELS-ALDER SYNTHESIS OF PYRIDINES. Organic Preparations and Procedures International: Vol. 35, No. 6, pp. 623-626.
Periods in missing lengths of rainbow cycles

A cycle in an edge-colored graph is said to be rainbow if no two of its edges have the same color. For a complete, infinite, edge-colored graph G, define \documentclass{article}\usepackage{amssymb}\usepackage[mathscr]{euscript}\footskip=0pc \pagestyle{empty}\begin{document}\begin{eqnarray*} {\mathscr{G}}({G}) = \{ {n} \ge {2} | {\rm {no}}\, {n{-}{\rm {cycle \, of}}} \,{{G}}\, {{\rm {is}\, {\rm {rainbow}}}}\}.\end{eqnarray*}\end{document}Then G(G) is a monoid with respect to the operation ncm=n+ m-2, and thus there is a least positive integer π(G), the period of G(G), such that G(G) contains the arithmetic progression lN+ kπ(G)|kg0r for some sufficiently large N. Given that n∈G(G), what can be said about π(G)? Alexeev showed that π(G)=1 when ng3 is odd, and conjectured that π(G) always divides 4. We prove Alexeev's conjecture: Let p(n)=1 when n is odd, p(n)=2 when n is divisible by four, and p(n)=4 otherwise. If 2 0 there are G, H such that 4k∈G(G), π(G)=2, and 4k+ 2∈G(H), π(H)=4. © 2009 Wiley Periodicals, Inc. J Graph Theory
Optical Damage Threshold of Silicon for Ultrafast Infrared Pulses

We present measurements of the optical damage threshold of crystalline silicon in air for ultrafast pulses in the near infrared. The wavelengths tested span a range from the telecommunications band at 1550 nm, extending to 2260 nm. We discuss the motivation for the measurements and give theoretical context. We then describe the experimental setup, diagnostics, and procedure. The results show a breakdown threshold of 0.2J/cm{sup 2} at 1550 nm and 1.06 ps FWHM pulse duration, and a weak dependence on wavelength.
The GEM MAP algorithm with 3-D SPECT system response

In single photon emission computed tomography (SPECT), every reconstruction algorithm must use some model for the response of the gamma camera to emitted gamma -rays. The true camera response is both spatially variant and object dependent. These two properties result from the effects of scatter, septal penetration, and attenuation, and they forestall determination of the true response with any precision. This motivates the investigation of the performance of reconstruction algorithms when there are errors between the camera response used in the reconstruction algorithm and the true response of the gamma camera. In this regard, the authors compare the filtered backprojection algorithm, the expectation-maximization maximum likelihood algorithm, and the generalized expectation maximization (GEM) maximum a posteriori (MAP) algorithm, a Bayesian algorithm which uses a Markov random field prior. >
Galaxy Form and Spectral Type: a Physical Framework for Measuring Evolution

I outline a quantitative method for characterizing galaxies both by photometric ‘form’ and indices of spectral-type, applicable to both nearby and distant galaxies. Such a characterization provides insight on galaxy evolution because there are physical connections between galaxies’ stellar populations and their light distribution. ‘Normal’ galaxies’ form-parameters (surface-brightness, image concentration and asymmetry) correlate well with spectral-index (color), which in turn correlates only weakly with scale (size or luminosity). Deviations from these normal relations also offer clues to the physical modes of galaxy formation and evolution. As an example, I contrast a puzzling, distant population of compact, but luminous, blue, star-forming galaxies to nearby samples. These distant sources appear to be associated with the bulk of the luminosity increase since z < 1. They have structural properties comparable to low-redshift populations, and photometric properties within the norm for nearby, actively star-forming galaxies. When combined, however, their photometric and structural properties appear to be highly unusual.
Computationally Efficient Sparse Bayesian Learning via Belief Propagation

We present a belief propagation (BP)-based sparse Bayesian learning (SBL) algorithm, referred to as the BP-SBL, to recover sparse transform coefficients in large scale compressed sensing problems. BP-SBL is based on a widely used hierarchical Bayesian model, which is turned into a factor graph so that BP can be applied to achieve computational efficiency. We prove that the messages in BP are Gaussian probability density functions and therefore, we only need to update their means and variances when we update the messages. The computational complexity of BP-SBL is proportional to the number of transform coefficients, allowing the algorithms to deal with large scale compressed sensing problems efficiently. Numerical examples are provided to demonstrate the effectiveness of BP-SBL.
The Role of Intellectual Property Rights in Seed Technology Transfer through Trade – Evidence from U.S. Field Crop Seed Exports

A panel of 134 countries over the period 1985–2010 is used to evaluate the effect of intellectual property rights (IPRs) on field crop seed imports from the United States. Based on estimating a gravity equation using the Heckman selection and Poisson fixed‐effects panel econometric methods, the results indicate that membership of countries in both the International Union for the Protection of New Varieties of Plants and the Trade‐Related Aspects of Intellectual Property Rights Agreement of the World Trade Organization have a positive and statistically significant effect on their imports of U.S. field crop seeds. These results, however, are also sensitive to both income level of importing countries and better enforcement of IPRs by those countries.
Strings in a time dependent orbifold

We consider string theory in a time dependent orbifold with a null singularity. The singularity separates a contracting universe from an expanding universe, thus constituting a big crunch followed by a big bang. We quantize the theory both in light-cone gauge and covariantly. We also compute some tree and one loop amplitudes which exhibit interesting behavior near the singularity. Our results are compatible with the possibility that strings can pass through the singularity from the contracting to the expanding universe, but they also indicate the need for further study of certain divergent scattering amplitudes.
Permutationally invariant codes for quantum error correction

Abstract A permutationally invariant n-bit code for quantum error correction can be realized as a subspace stabilized by the non-Abelian group Sn. The code is spanned by bases for the trivial representation, and all other irreducible representations, both those of higher dimension and orthogonal bases for the trivial representation, are available for error correction. A number of new (non-additive) binary codes are obtained, including two new 7-bit codes and a large family of new 9-bit codes. It is shown that the degeneracy arising from permutational symmetry facilitates the correction of certain types of two-bit errors. The correction of two-bit errors of the same type is considered in detail, but is shown not to be compatible with single-bit error correction using 9-bit codes.
Role of Proton-Coupled Electron Transfer in O–O Bond Activation

The selective reduction of oxygen to water requires four electrons and four protons. The design of catalysts that promote oxygen reduction therefore requires the management of both electron and proton inventories. Pacman and Hangman porphyrins provide a cleft for oxygen binding, a redox shuttle for oxygen reduction, and functionality for tuning the acid–base properties of bound oxygen and its intermediates. With proper control of the proton-coupled electron transfer events, O–O bond breaking of oxygen, and more generally oxygenated substrates, may be achieved with high efficiencies. The rule set developed for oxygen reduction may be applied to a variety of other small molecule activation reactions of consequence to energy conversion.
Two-dimensional resistivity inversion

Resistivity data on a profile often must be interpreted in terms of a complex two‐dimensional (2-D) model. However, trial‐and‐error modeling for such a case can be very difficult and frustrating. To make interpretation easier and more objective, we have developed a nonlinear inversion technique that estimates the resistivities of cells in a 2-D model of predetermined geometry, based on dipole‐dipole resistivity data. Our numerical solution for the forward problem is based on the transmission‐surface analogy. The partial derivatives of apparent resistivity with respect to model resistivities are equal to a simple function of the currents excited in the transmission surface by transmitters placed at receiver and transmitter sites. Thus, for the dipole‐dipole array the inversion requires only one forward problem per iteration. We use the Box‐Kanemasu method to stabilize the parameter step at each iteration. We have tested our inversion technique on synthetic and field data. In both cases, convergence is rapi...
Using 1-Jettiness to Measure 2 Jets in DIS 3 Ways

We predict cross sections in deep inelastic scattering (DIS) for the production of two jets---one along the proton beam direction created by initial-state radiation (ISR) and another created by final-state radiation after the hard collision. Our results include fixed-order corrections and a summation of large logarithms up to next-to-next-to-leading logarithmic accuracy in resummed perturbation theory. We make predictions for three versions of a DIS event shape 1-jettiness, each of which constrains hadronic final states to be well collimated into two jets along the beam and final-state jet directions, but which differ in their sensitivity to the transverse momentum of the ISR from the proton beam. We use the tools of soft collinear effective theory to derive factorization theorems for these three versions of 1-jettiness. The sensitivity to the ISR gives rise to significantly different structures in the corresponding factorization theorems---for example, dependence on either the ordinary or the generalized ${k}_{\ensuremath{\perp}}$-dependent beam function. Despite the differences among 1-jettiness definitions, we show that the leading nonperturbative correction that shifts the tail region of their distributions is given by a single universal nonperturbative parameter ${\ensuremath{\Omega}}_{1}$, even accounting for hadron mass effects. Finally, we give numerical results for ${Q}^{2}$ and $x$ values explored at the HERA collider, emphasizing that the target of our factorization-based analyses is to open the door for higher-precision jet phenomenology in DIS.
It's No Secret. Measuring the Security and Reliability of Authentication via Secret Questions

All four of the most popular webmail providers -- AOL, Google, Microsoft, and Yahoo! -- rely on personal questions as the secondary authentication secrets used to reset account passwords. The security of these questions has received limited formal scrutiny, almost all of which predates webmail. We ran a user study to measure the reliability and security of the questions used by all four webmail providers. We asked participants to answer these questions and then asked their acquaintances to guess their answers. Acquaintances with whom participants reported being unwilling to share their webmail passwords were able to guess 17% of their answers. Participants forgot 20% of their own answers within six months. What's more, 13% of answers could be guessed within five attempts by guessing the most popular answers of other participants, though this weakness is partially attributable to the geographic homogeneity of our participant pool.
StarT-Voyager: A Flexible Platform for Exploring Scalable SMP Issues

This paper describes StarT-Voyager, a machine designed as an experimental platform for research in cluster system communication. The heart of StarT-Voyager is a network interface unit (NIU) that connects the memory bus of a PowerPC-based SMP to the MIT Arctic network. The NIU is highly flexible, with its set of functions easily modified by firmware or by programmable hardware, making it possible to compare different communication interfaces and implementation strategies on a common platform. Its flexibility comes from a fast embedded processor and large, fast FPGAs that surround a high-speed protected communication core. Its efficiency comes from a set of primitive operations that are implemented in hardware and are designed to reduce the firmware overhead. Our initial configuration of StarT-Voyager implements four forms of message passing along with S-COMA and NUMA shared memory support. With experimentation on the machine, it can be reconfigured to introduce new mechanisms improving usability and performance.
Selective screenability in topological groups

Abstract We examine the selective screenability property in topological groups. In the metrizable case we also give characterizations of S c ( O nbd , O ) and Smirnov - S c ( O nbd , O ) in terms of the Haver property and finitary Haver property respectively relative to left-invariant metrics. We prove theorems stating conditions under which S c ( O nbd , O ) is preserved by products. Among metrizable groups we characterize the countable dimensional ones by a natural game.
SecurityCom: a multi-player game for researching and teaching information security teams

A major portion of government and business organizations' attempts to counteract information security threats is teams of security personnel. These teams often consist of personnel of diverse backgrounds in specific specialties such as network administration, application development, and business administration, resulting in conflicts between security, functionality, and availability. This paper discusses the use of games to teach and research information security teams and outlines research to design and build a simple, team-oriented, configurable, information security game, to study how information security teams work together to defend against attacks using a multi-player game, and to study the use of games in training security teams. Studying how information security teams work, especially considering the topic of shared-situational awareness, could lead to better ways of forming, managing, and training teams. Studying the effectiveness of the game as a training tool could lead to better training for security teams. This work will build off of the successful use of a similar multi-player game for studying deception in groups and teaching network-centric warfare.
Advances in daylight statistical colour modelling

In this paper, parametric statistical modelling of distributions of colour camera data is discussed. A review is provided with some analysis of the properties of some common models, which are generally based on an assumption of independence of the chromaticity and intensity components of colour data. Results of an empirical comparison of the performance of various models are also reviewed. These results indicate that such models are not appropriate for situations other than highly controlled environments. In particular, they perform poorly for daylight imagery. Here, a modification to existing statistical colour models is proposed and the resultant new models are assessed using the same methodology as for the previous results. This simple modification, which is based on the inclusion of an ambient term in the underlying physical model, is shown to have a major impact on the performance of the models in less constrained daylight environments.
Heterogeneity of SPECT bull's-eyes in normal dogs: comparison of attenuation compensation algorithms

In normal dogs, SPECT /sup 99m/Tc Sestamibi (MIBI) and /sup 201/Tl myocardial perfusion images reconstructed with filtered backprojection (FBP) show a large decrease of counts in the septal wall (S) compared to the lateral wall (L). We evaluated the iterative method of Chang (1978) at 0 and 1 iterations (Chang0 and Chang1), and the Maximum Likelihood-Expectation Maximization with attenuation compensation (ML-EM-ATN) algorithm on data acquired from 5 normal dogs and from simulated projection data using a homogeneous count-density model of a normal canine myocardium in the attenuation field measured in one dog. Mean counts in the S and L regions were calculated from maximum-count circumferential profile arrays. Our results demonstrate that ML-EM-ATN and Chang1 result in improved uniformity, as measured by the S/L ratio. >
Serum vitamin D, vitamin D binding protein, and risk of colorectal cancer

Background We previously reported a positive association between serum 25-hydroxyvitamin D (25(OH)D) and colorectal cancer risk. To further elucidate this association, we examined the molar ratio of 25(OH)D to vitamin D binding protein (DBP), the primary 25(OH)D transport protein, and whether DBP modified the association between 25(OH)D and colorectal cancer risk. Methods In a nested case-control study within the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study, controls were 1∶1 matched to 416 colorectal cancer cases based on age and date of blood collection. Logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CI) for quartiles of 25(OH)D, DBP, and the molar ratio of 25(OH)D:DBP, a proxy for free, unbound circulating 25(OH)D. Results Comparing highest to lowest quartiles, DBP was not associated with colorectal cancer risk (OR = 0.91; 95% CI: 0.58, 1.42, p for trend = 0.58); however, a positive risk association was observed for the molar ratio of 25(OH)D:DBP (OR = 1.44; 95% CI: 0.92, 2.26, p for trend = 0.04). In stratified analyses, the positive association between 25(OH)D and colorectal cancer was stronger among men with DBP levels above the median (OR = 1.89; 95% CI: 1.07, 3.36, p for trend = 0.01) than below the median (OR = 1.20; 95% CI: 0.68, 2.12, p for trend = 0.87), although the interaction was not statistically significant (p for interaction = 0.24). Conclusion Circulating DBP may influence the association between 25(OH)D and colorectal cancer in male smokers, with the suggestion of a stronger positive association in men with higher DBP concentrations. This finding should be examined in other populations, especially those that include women and non-smokers.
A homological definition of the HOMFLY polynomial

We give a new definition of the knot invariant associated to the Lie algebra suN+1. Knowing these for all N is equivalent to knowing the HOMFLY polynomial. Our definition requires that the knot or link be presented as the plat closure of a braid. The invariant is then a homological intersection pairing between two immersed manifolds in a configuration space of points in a disk. This generalizes previous work on the Jones polynomial, which is the case N = 1.
Is the fear of dioxin cancer more harmful than dioxin

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a proven animal carcinogen. Occupational cohorts with the highest exposures imply that there is a small risk of all cancers combined, but it is difficult to pinpoint the confounding effect of the main chemicals. Studies after major accidents do not unequivocally confirm this risk. The risks to populations at the current dioxin levels seem trivial if present at all. There is increasing evidence that the aryl hydrocarbon receptor (AhR), i.e. the so called "dioxin receptor", is a physiological transcription factor exerting important functions in the body. Consequently a certain level of AhR activation may be beneficial rather than harmful. This challenges the wisdom of excessive regulation of dioxin levels in certain foods and nutrients. This could pose indirect nutritional risks, in fact being more harmful than even the worst case predictions of the putative cancer risks attributable to dioxins.
Carbonaceous chondrites of the Ornans type - A metamorphic sequence

The six identified carbonaceous chondrites classified as C3(O) (also known as the Ornans subtype or ornansites) are studied as a group. The Karoonda meteorite is also examined to determine whether it may be classified as a highly metamorphosed equivalent of the Ornans subtype. Petrographic and chemical similarities among these meteorites are discussed along with such systematic variations as textural, mineralogical, metallurgical, and chemical differences. Three metamorphic grades are delineated, chemical variations are correlated with the grades, and an attempt is made to determine why the Ornans meteorite belongs in a higher metamorphic grade on the basis of its chemical properties than on the basis of its petrographic characteristics. It is concluded that subtle differences among the meteorites may be related to small variations in the thermal metamorphism they have experienced.
Estimating Time Required to Reach Bid Levels in Online Auctions

Sellers in eBay are often small-business owners whose livelihood depends on fast turnaround of their cash flows. Unlike in traditional auctions, these sellers are content to sell as soon as some target price is reached. While a wealth of literature exists on the final rent of the various stakeholders in a traditional auction setting, what is of interest here is to estimate the time required to reach a certain bid level in ongoing auctions. This paper introduces an analytical model to estimate the time it takes an online auction to reach a prespecified price threshold. The motivation for the research is to avoid unnecessary delays in conducting the transaction. Specifying the right duration would benefit small sellers who would realize the revenue proceeds from the sale faster. To this end, we model the bidding process as an infinite quasi-birth-death process, characterized by bursts of rapid bidding and subsequent lulls. We obtain closed-form solutions for the transient probability distribution in the frequency domain of the bid prices in an ongoing auction, which are then used to compute the transient probability distributions in the time domain. Experienced auctioneers can use these results to estimate expected ending times for their auctions. Sample observations from online auctions indicate that there may be potential room for improvement for sellers in setting their auction ending times. Simulations of the quasi-birth-death processes back up the theoretical observations.
Chandra X-ray spectroscopy of the very early O supergiant HD 93129A: constraints on wind shocks and the mass-loss rate

We present an analysis of both the resolved X-ray emission-line profiles and the broad-band X-ray spectrum of the O2 If^* star HD 93129A, measured with the Chandra High Energy Transmission Grating Spectrometer (HETGS). This star is among the earliest and most massive stars in the Galaxy, and provides a test of the embedded wind-shock scenario in a very dense and powerful wind. A major new result is that continuum absorption by the dense wind is the primary cause of the hardness of the observed X-ray spectrum, while intrinsically hard emission from colliding wind shocks contributes less than 10 per cent of the X-ray flux. We find results consistent with the predictions of numerical simulations of the line-driving instability, including line broadening indicating an onset radius of X-ray emission of several tenths of R_*. Helium-like forbidden-to-intercombination line ratios are consistent with this onset radius, and inconsistent with being formed in a wind-collision interface with the star’s closest visual companion at a distance of 100 au. The broad-band X-ray spectrum is fitted with a dominant emission temperature of just kT= 0.6 keV along with significant wind absorption. The broad-band wind absorption and the line profiles provide two independent measurements of the wind mass-loss rate: M = 5.2^(+1.8)_(-1.5) x 10^(-6) and 6.8^(+2.8)_(−2.2) × 10^(−6) M_⊙ yr^(−1), respectively. This is the first consistent modelling of the X-ray line-profile shapes and broad-band X-ray spectral energy distribution in a massive star, and represents a reduction of a factor of 3–4 compared to the standard Hα mass-loss rate that assumes a smooth wind.
Discussion of ''Anomalous stock returns around internet firms' earnings announcements''

Abstract Trueman, Wong, and Zhang (TWZ) investigate an apparent anomaly in the pricing of internet firms around their earnings announcements, which they attribute to price pressure. The discussion addresses three concerns. The paper is unusual in choosing an event (earnings announcements) that does not appear to have an obvious non-information-related reason for triggering unjustified changes in demand for the firm's shares. Relatedly, there are limitations to the tests made of the price pressure hypothesis. Finally, the discussion elaborates on TWZ's brief mention of the difficulties with implementing a profitable trading strategy based on the stock return pattern they document.
X-RAYS AND PROTOSTARS IN THE TRIFID NEBULA

The Tri—d Nebula is a young H II region, recently rediscovered as a ii pre-Orion ˇˇ star-forming region, containing protostars undergoing violent mass ejections visible in optical jets as seen in images from the Infrared Space Observatory and the Hubble Space Telescope. We report the —rst X-ray observations of the Tri—d Nebula using ROSAT and ASCA. The ROSAT image shows a dozen X-ray sources, with the brightest X-ray source being the O7 star, HD 164492, which provides most of the ionization in the nebula. We also identify 85 T Tauri star and young, massive star candidates from near-infrared colors using the color-color diagram from the Two-Micron All-Sky Survey (2MASS). Ten X-ray sources JHK s have counterpart near-infrared sources. The 2MASS stars and X-ray sources suggest there are potentially numerous protostars in the young H II region of the Tri—d. ASCA moderate-resolution spectroscopy of the brightest source shows hard emission up to 10 keV with a clearly detected Fe K line. The best model —t is a two-temperature (T \ 1.2 ] 106 K and 39 ] 106 K) thermal model with additional warm absorbing media. The hotter component has an unusually high temperature for either an O star or an H II region; a typical Galactic H II region could not be the primary source for such hot temperature plasma and the Fe XXV line emission. We suggest that the hotter component originates in either the interaction of the wind with another object (a companion star or a dense region of the nebula) or from —ares from deeply embedded young stars. . . . . . . . . . . . . . . . . . . . . .
Bicrystal YBCO DC SQUIDs with low noise

The authors have fabricated 12 DC superconducting quantum interference devices (SQUIDs) by laser-depositing YBa/sub 2/Cu/sub 3/O/sub 7-x/ on a SrTiO/sub 3/ bicrystal substrate with a misorientation angle of 24 degrees . At 77 K all 12 devices had acceptable values of critical current, resistance, and voltage modulation produced by an external magnetic field. The white noise energy of one device with an estimated inductance of 41 pH was 1.8*10/sup -30/ JHz/sup -1/. The noise power scaled as 1/f at frequencies below about 1 kHz; by using a bias current reversal scheme it was possible to reduce this noise by two orders of magnitude at 1 Hz, to a value of about 1.5*10/sup -29/ JHz/sup -1/. A magnetometer was made by coupling the SQUID to a flux transformer with a 5-turn input coil. The measured magnetic field gain was 60, and the white noise was 36 fT/ square root Hz. However, the transformer produced relatively large levels of 1/f flux noise, not reduced by the bias reversal scheme, that limited the noise at 1 Hz to 1.7 fT/ square root Hz. A single-layer magnetometer with a single-turn pick-up loop is described. >
Palladium(III)-Catalyzed Fluorination of Arylboronic Acid Derivatives

A practical, palladium-catalyzed synthesis of aryl fluorides from arylboronic acid derivatives is presented. The reaction is operationally simple and amenable to multigram-scale synthesis. Evaluation of the reaction mechanism suggests a single-electron-transfer pathway, involving a Pd(III) intermediate that has been isolated and characterized.
PCSK9 inhibitors for LDL lowering.

In 2003, families were described with a rare, autosomal dominant form of familial hypercholesterolemia due to gain-of-function mutations in proprotein convertase subtilisin/kexin type 9 (PCSK9) [1]. Subsequent studies demonstrated that PCSK9 is secreted from liver and accelerates degradation of LDL receptors [2,3]. Heterozygosity for PCSK9 null mutations in 2.6% of African-Americans was found to be associated with 28% reduction in LDL cholesterol (LDL-C) and an 88% reduction in CAD risk [4]. These findings stimulated intense interest in PCSK9 as a pharmaceutical target. In this issue of Trends in Cardiovascular Medicine, Desai and Sabatine [5] thoroughly review recent and ongoing trials of three monoclonal antibodies that disrupt PSCK9 binding to LDL receptors, leading to marked reductions in LDL-C. As detailed in their review, evolocumab (AMG145), alirocumab (SAR236553/REGN727), and bococizumab (RN316) given every 2–4 weeks, reduced LDL-C up to 75% in patients on statin therapy as compared to statin therapy alone, up to 51% in statin-intolerant patients and other patients not in statin therapy, and up to 55% in patients with heterozygous familial hypercholesterolemia, most of whom were on statin therapy. Evolocumab reduced LDL-C up to 31% in patients with homozygous familial hypercholesterolemia, although there was no effect in LDL receptor-negative patients. Ongoing cardiovascular outcome trials that will rigorously test the ability of these agents to reduce major adverse cardiovascular events in high-risk patients are also described. PCSK9 is secretory serine endoprotease [6]. Pro-PCSK9 is autocatalytically cleaved during its maturation in the Golgi, but the prodomain remains tightly bound after secretion, precluding further catalytic activity [6]. Effects of PCSK9 on LDL-C clearance thus do not depend on its protease activity.
Hilbert's 14th problem and Cox rings

Our main result is the description of generators of the total coordinate ring of the blow-up of P n in any number of points that lie on a rational normal curve. As a corollary we show that the algebra of invariants of the action of a two-dimensional vector group introduced by Nagata is finitely generated by certain explicit determinants. We also prove the finite generation of the algebras of invariants of actions of vector groups related to T-shaped Dynkin diagrams introduced by Mukai.
Do organizations have to change to learn? Examining the effects of technological change and learning from failures in the natural gas distribution industry

Failures contain valuable information. However, organizations vary at learning from them. I ask whether failures prompt organizations to make technological investments, and whether these investments help boost performance beyond improvements gained through direct organizational learning. I test hypotheses on natural gas distributors to determine whether they enhance their performance by learning directly, by recognizing failures as prompts to invest in safer technologies, or through a combination. Results suggest that distributors learn directly, though firms, which also invest in related technologies, are able to gain some additional benefits. Copyright 2010 The Author 2010. Published by Oxford University Press on behalf of Associazione ICC. All rights reserved., Oxford University Press.
Organosilicon platforms: bridging homogeneous, heterogeneous, and bioinspired catalysis

Organosilicon compounds, in the form of cubic metallasiloxanes, cage-like silsesquioxanes, macromolecular nanocages, and flexible structures such as dendrimers and linear metallsiloxanes, have found useful applications as catalysts, ligands for metal complexes, and catalyst supports. Illustrative examples of these are presented. The well-defined structures of these compounds make them particularly suitable as molecular analogues of zeolites or silica-supported catalysts. A unique feature of many of these compounds is the presence of flexible siloxane bonds, which accommodate large fluctuations in the framework geometry, reminiscent of the adaptability of enzymes to conformational changes, and distinguish siloxane containing materials from carbon based synthetic materials. New preparative pathways and the use of the versatile silyl ester as a protection group have greatly expanded synthetic possibilities, pointing to the possibility of assembling these structures to form multifunctional catalytic structures. Some nanocage structures, with functionalities organized in close proximity, exhibit nanoconfinement effects.