cssi/SciSciGPT-SciSciNet huggingface dataset:
Nitric oxide catalysis in automotive exhaust systems

Abstract This review covers the literature through 1991 on nitric oxide catalysis as applied to automobile exhaust systems. Attention is given to the threeway catalyst system which simultaneously promotes the reduction of nitrogen oxides and the oxidation of carbon monoxide and hydrocarbons. These systems have been used on most passenger cars in the United States since 1982. Prior to 1980, emission control catalysts were oxidation catalysts, and reduction in exhaust nitric oxide was achieved using engine modifications (i.e., exhaust gas recirculation). This review focuses on catalytic control of NO, for gasoline-fueled vehicles (not diesels and alternate fuels) and primarily on developments reported since 1982. The term NO, refers to both NO and NOz. The reader is referred to an earlier publication by the author for a general review of automobile catalytic converters [1] and to a review by Egelhoff [2] on the nitric oxide literature through 1980. The recent literature on NO, reduction in lean exhaust is c...
Miscible Gas Displacement of Multicomponent Oils

This paper extends the theory of multicontact miscible displacements in four-component systems to displacements by a single gas component of an oil containing any number of components. Multicomponent solutions are developed using the method of characteristics in the absence of dispersion and are shown to consist of a series of successive pseudoternary displacements. Example analytical solutions are constructed and compared to experimental results for a synthetic ten-component oil displaced by CO{sub 2} as given by Metcalfe and Yarborough. The minimum pressure for miscibility (MMP) for the synthetic oil is determined to be substantially below pressures used in the experiments and is below the bubble-point pressure. We show that multi-contact miscibility (MCM) can be achieved even when an oil exists as two phases. The displacement of the synthetic oil by CO{sub 2} is demonstrated to have features of both condensing and vaporizing mechanisms (C/V). Furthermore, the key tie line that controls development of miscibility is the crossover tie line that divides the condensing and vaporizing portions of the displacement path (composition route) - Extension of the theory for displacements of real oils with an arbitrary number of components is also discussed. For displacements by CO{sub 2} of an oil that containsmore » only CH{sub 4}, C{sub 2} and heavier components, we demonstrate that the most down-stream crossover tie line will control the development of miscibility. For displacements by the most volatile component (i.e. pure N{sub 2} or CH{sub 4} injection) of the same oil, however, displacements are purely vaporizing and miscibility is controlled by the tie line that extends through the oil. A procedure is given that can be used to find the key tie line that controls miscibility and also to estimate the MMP from an equation-of-state (EOS).« less
Integer quantization of the Chern-Simons coefficient in a broken phase

Abstract We consider a spontaneously broken nonabelian topologically massive gauge theory in a broken phase possessing a residual nonabelian symmetry. Recently there has been some question concerning the renormalization of the Chern-Simons coefficient in such a broken phase. We show that, in this broken vacuum, the renormalized ratio of the Chern-Simons coupling to the gauge coupling is shifted by 1 4π times an integer, preserving the usual integer quantization condition on the bare parameters.
Absolutely graded Floer homologies and intersection forms for four-manifolds with boundary

Abstract In Ozsvath and Szabo (Holomorphic triangles and invariants for smooth four-manifolds, math. SG/0110169, 2001), we introduced absolute gradings on the three-manifold invariants developed in Ozsvath and Szabo (Holomorphic disks and topological invariants for closed three-manifolds, math.SG/0101206, Ann. of Math. (2001), to appear). Coupled with the surgery long exact sequences, we obtain a number of three- and four-dimensional applications of this absolute grading including strengthenings of the “complexity bounds” derived in Ozsvath and Szabo (Holomorphic disks and three-manifold invariants: properties and applications, math.SG/0105202, Ann. of Math. (2001), to appear), restrictions on knots whose surgeries give rise to lens spaces, and calculations of HF + for a variety of three-manifolds. Moreover, we show how the structure of HF + constrains the exoticness of definite intersection forms for smooth four-manifolds which bound a given three-manifold. In addition to these new applications, the techniques also provide alternate proofs of Donaldson's diagonalizability theorem and the Thom conjecture for CP 2 .
Nonlinear tolerant long-haul WDM transmission over 1200km using 538Gb/s/ch PDM-64QAM SC-FDM signals with pilot tone

We investigate long-haul WDM transmission using 538Gb/s PDM-64QAM single-carrier frequency-division-multiplexing (SC-FDM) signal with pilot tone. Assuming 20% FEC overhead, the longest transmission distance of 1200km at the spectral efficiency of 8.96b/s/Hz is achieved.
Absence of a magnetic-field-induced metal-insulator transition in Kondo insulators.

We investigate whether or not Kondo insulators undergo a magnetic-field-induced metal-insulator transition in one dimension at half filling using both a density matrix formulation of the numerical renormalization group and bosonization. Contrary to expectations, the quasiparticle gap never vanishes at any field and no metal-insulator transition is found. We discuss generalizing our result to the asymmetric Anderson lattice. \textcopyright{} 1996 The American Physical Society.
Multiplier ideals of sums via cellular resolutions

Fix nonzero ideal sheaves $\fa_1,\dots,\fa_r$ and $\fb$ on a normal $\QQ$-Gorenstein complex variety~$X$. For any positive real numbers $\alpha$ and~$\beta$, we construct a resolution of the multiplier ideal $\JJ((\fa_1+\cdots+\fa_r)^\alpha \fb^\beta)$ by sheaves that are direct sums of multiplier ideals $\JJ(\fa_1^{\lambda_1}\cdots\fa_r^{\lambda_r}\fb^\beta)$ for various $\lambda \in \RR^r_{\geq 0}$ satisfying $\sum_{i=1}^r \lambda_i = \alpha$. The resolution is cellular, in the sense that its boundary maps are encoded by the algebraic chain complex of a regular CW-complex. The CW-complex is naturally expressed as a triangulation~$\Delta$ of the simplex of nonnegative real vectors $\lambda \in \RR^r$ with $\sum_{i=1}^r \lambda_i = \alpha$. The acyclicity of our resolution reduces to that of a cellular free resolution, supported on~$\Delta$, of a related monomial ideal. Our resolution implies the multiplier ideal sum formula \[ \JJ(X,(\fa_1+\cdots+\fa_r)^\alpha \fb^\beta) = \sum_{\lambda_1+\cdots+\lambda_r=\alpha} \JJ(X,\fa_1^{\lambda_1}\cdots\fa_r^{\lambda_r}\fb^\beta), \] generalizing Takagi's formula for two summands \cite{Takagi}, and recovering Howald's multiplier ideal formula for monomial ideals~\cite{Howald} as a special case. Our resolution also yields a new exactness proof for the \emph{Skoda complex} \mbox{\cite[Section~9.6.C]{Laz}}.
THE FIRST TOTAL SYNTHESIS OF ROQUEFORTINE D

Abstract The synthesis of roquefortine D (1), an alkaloid isolated from the cultures of Penicillium roqueforti, is described. The absolute stereochemistry of the natural product was determined by comparison of its optical rotation with that of the synthetic product. A photo-cleavable o-nitrobenzyl group was utilized for histidine side chain protection, and the cyclization to the diketopiperazine was carried out under mild conditions.
Efficient rare event simulation for heavy-tailed systems via cross entropy

Abstract The cross entropy method is an iterative technique that is used to obtain a low-variance importance sampling (IS) distribution from a given parametric family, which must satisfy two properties. First, subsequent iterations of the parameters must be easily computable and, second, the family should approximate the zero-variance IS distribution. We obtain parametric families for which these two properties are satisfied for a large class of heavy-tailed systems. Our estimators are shown to be strongly efficient in these settings.
Solar absorber selective paint research

Abstract Research and development effort seeking to develop low cost, high performance solar selective paint has been conducted under government support for approximately eight years. Other investigators have spent many years in bringing various types of selective paint to the market place. This report is intended primarily to focus on the DOE programs that the Los Alamos National Laboratory has the responsibility of monitoring.
Conjugate addition of lithium diorganocuprate reagents to the enol tosylate of a 1,2-diketone

Abstract The conjugate addition of lithium diorganocuprate reagents to the enol tosylate of 1,2-cyclohexanedione has been investigated. The intermediate enolates eliminate para-toluenesulfmate ion to generate the alkylated 1,2-dicarbonyl system.
Principle of corresponding states and equation of state of polymer liquids and glasses

Isotherms and isobars for polymer liquids using corresponding states principle to establish function describing dependence of internal pressure on volume or temperature
ENHANCED CONVERGENCE IN DISTRIBUTED DESIGN PROCESSES

The focus of this paper is on studying the convergence properties of the solution process of decentralized or distributed subsystems, where each subsystem has its own design problem, including objective(s), constraints, and design variables. The challenging aspect of this type of problem comes in the coupling of the subsystems, which create complex research and implementation challenges in modeling and solving these types of problems. We focus on the dynamics of these distributed design problems and attempt to further the understanding of the fundamental mechanics behind these processes in order to support the decisions being made by a network of decision makers. In this work, the domain of attraction, or region where convergence to a stable equilibrium point is guaranteed, of a decentralized design process is studied. Two approaches based on concepts from nonlinear control theory are presented: the first determines the domain of attraction for a specified Lyapunov function and the second optimizes for a Lyapunov function which maximizes the domain of attraction. The two techniques are illustrated on a benchmark pressure vessel design problem.
Behavioral Mechanism Design: Optimal Crowdsourcing Contracts and Prospect Theory

Incentive design is more likely to elicit desired outcomes when it is derived based on accurate models of agent behavior. A substantial literature in behavioral economics, however, demonstrates that individuals systematically and consistently deviate from the standard economic model---expected utility theory---for decision-making under uncertainty, %a central component of which is at the core of the equilibrium analysis necessary to facilitate mechanism design. Can these behavioral biases---as modeled by prospect theory [Kahneman and Tversky 1979]---in agents' decision-making make a difference to the optimal design of incentives in these environments? In this paper, we explore this question in the context of markets for online labor and crowdsourcing where workers make strategic choices about whether to undertake a task, but do not strategize over quality conditional on participation. We ask what kind of incentive scheme---amongst a broad class of contracts, including those observed on major crowdsourcing platforms such as fixed prices or base payments with bonuses (as on MTurk or oDesk), or open-entry contests (as on platforms like Kaggle or Topcoder)---a principal might want to employ, and how the answer to this question depends on whether workers behave according to expected utility or prospect theory preferences. We first show that with expected utility agents, the optimal contract---for any increasing objective of the principal---always takes the form of an output-independent fixed payment to some optimally chosen number of agents. In contrast, when agents behave according to prospect theory preferences, we show that a winner-take-all contest can dominate the fixed-payment contract, for large enough total payments, under a certain condition on the preference functions; we show that this condition is satisfied for the parameters given by the literature on econometric estimation of the prospect theory model [Tversky and Kahneman 1992; Bruhin et al. 2010]. Since these estimates are based on fitting the prospect theory model to extensive experimental data, this result provides a strong affirmative answer to our question for 'real' population preferences: a principal might indeed choose a fundamentally different kind of mechanism---an output-contingent contest versus a 'safe' output-independent scheme---and do better as a result, if he accounts for deviations from the standard economic models of decision-making that are typically used in theoretical design.
A cooperative N-heterocyclic carbene/palladium catalysis system

N-heterocyclic carbenes (NHC) have been extensively studied as organocatalysts and ligands for transition metals, but the successful integration of NHCs and late transition metals in cooperative catalysis remains an underexplored area. We have developed a cooperative palladium-catalyzed allylation of NHC-activated aldehydes to access a variety of 3-allyl dihydrocoumarin derivatives. Kinetic experiments support a cooperative pathway for this transformation.
Formal synthesis of platencin.

Formal synthesis of platencin was achieved by assembling its tricyclic core structure through a Robinson annulation reaction, whose precursor was made from a bicyclo[3.2.2] ring structure, product of a tropone Diels–Alder reaction.
Toward natural interaction in the real world: real-time gesture recognition

Using a new hand tracking technology capable of tracking 3D hand postures in real-time, we developed a recognition system for continuous natural gestures. By natural gestures, we mean those encountered in spontaneous interaction, rather than a set of artificial gestures chosen to simplify recognition. To date we have achieved 95.6% accuracy on isolated gesture recognition, and 73% recognition rate on continuous gesture recognition, with data from 3 users and twelve gesture classes. We connected our gesture recognition system to Google Earth, enabling real time gestural control of a 3D map. We describe the challenges of signal accuracy and signal interpretation presented by working in a real-world environment, and detail how we overcame them.
Highly efficient molybdenum-based catalysts for enantioselective alkene metathesis

Discovery of efficient catalysts is one of the most compelling objectives of modern chemistry. Chiral catalysts are in particularly high demand, as they facilitate synthesis of enantiomerically enriched small molecules that are critical to developments in medicine, biology and materials science. Especially noteworthy are catalysts that promote-with otherwise inaccessible efficiency and selectivity levels-reactions demonstrated to be of great utility in chemical synthesis. Here we report a class of chiral catalysts that initiate alkene metathesis with very high efficiency and enantioselectivity. Such attributes arise from structural fluxionality of the chiral catalysts and the central role that enhanced electronic factors have in the catalytic cycle. The new catalysts have a stereogenic metal centre and carry only monodentate ligands; the molybdenum-based complexes are prepared stereoselectively by a ligand exchange process involving an enantiomerically pure aryloxide, a class of ligands scarcely used in enantioselective catalysis. We demonstrate the application of the new catalysts in an enantioselective synthesis of the Aspidosperma alkaloid, quebrachamine, through an alkene metathesis reaction that cannot be promoted by any of the previously reported chiral catalysts.
Gray codes and overlap cycles for restricted weight words

A Gray code is a listing structure for a set of combinatorial objects such that some consistent (usually minimal) change property is maintained throughout adjacent elements in the list. While Gray codes for m-ary strings have been considered in the past, we provide a new, simple Gray code for fixed-weight m-ary strings. In addition, we consider a relatively new type of Gray code known as overlap cycles and prove basic existence results concerning overlap cycles for fixed-weight and weight-range m-ary words.
“Accordion” rearrangements of cyclobutane α-sulfonyl lactones

Abstract The tricyclic α-sulfonyl lactone 4 is converted by alkoxides to bicyclic acids 5,6; the homologous α-sulfonyl lactone 8 yields bicyclic acid 10 or the cyclononene ketoacid 9. These products arise from a common Grob fragmentation mechanism, in which the fate of the medium-ring trans-cycloalkene intermediates 12 is determined by ring size and by the nature of the nucleophilic base used.
Consumer spending self-control effectiveness and outcome elaboration prompts

Decision making related to finances is of significant importance. A major factor underlying financial decision making involves differences in consumers’ spending self-control (CSSC). We conceptualize CSSC as an individual difference, distinct from general self-control, develop a parsimonious measure to assess it, and demonstrate important related consequences and behaviors. Further, we examine how underlying differences in CSSC impact the effectiveness of a self-control strategy that has recently received attention in public policy legislation—enhancing consumers’ awareness of the future consequences of present behavior through the provision of outcome elaboration prompts. Results from our studies suggest that outcome elaboration prompts (that is, external stimuli used to encourage consumers to consider the future outcomes of their present decisions) differentially impact consumers’ self-control effectiveness depending on their inherent CSSC. Specifically, the presence of outcome elaboration prompts enhances self-control for low CSSC consumers, but does not affect the choices of high CSSC consumers. Furthermore, we provide direct evidence that it is a differential focus on future outcomes that drives the distinct responses of high- versus low-CSSC consumers to the provision of outcome elaboration prompts.
Cyclin‐dependent kinase inhibitors for treating cancer

Cyclin dependent kinases (Cdks) are essential enzymes for the control of cell cycle progression. Inhibitors of cyclin-dependent kinases are anticipated to possess therapeutic utility against a wide variety of proliferative diseases, especially cancer. The field of published small molecule Cdk inhibitors is briefly reviewed here as background to a summary of work on a class of pyrido[2,3-d]pyrimidine Cdk inhibitors. Compounds from this class are described that display potency against cyclin D/Cdk4 up to IC(50) = 0.004 microM. Good to moderate selectivity for cyclin D/Cdk4 is also reported for compounds in this structural class. Structure-activity relationship data are presented for substitution at the C2 and N8 positions and these data are interpreted in the context of a binding model that is based on the Cdk2 crystal structure. A representative cyclin D/Cdk4 inhibitor (compound 56) is demonstrated to selectively inhibit the proliferation of an Rb(+) cell line vs. a matched Rb(-) cell line and to produce a distinct G(1) block consistent with cyclin D/Cdk4 inhibition in cells.
Properties of Pt Schottky type contacts on high-resistivity CdZnTe detectors

In this paper, we present studies of the I- V characteristics of CdZnTe (CZT) detectors with Pt contacts fabricated from high-resistivity single crystals grown by the high-pressure Bridgman process. We have analyzed the experimental I- V curves using a model that approximates the CZT detector as a system consisting of a reversed Schottky contact, in series with the bulk resistance. Least-square fit to the experimental data yields 0.78- 0.79 eV for the Pt-CZT Schottky barrier height, and <20V for the voltage required to deplete a 2mm thick CZT detector. We demonstrate that, at high bias, the thermionic current over the Schottky barrier, the height of which is reduced due to an interfacial layer between the contact and CZT material, controls the leakage current of the detectors. In many cases, the dark current is not determined by the resistivity of the bulk material, but rather the properties of the contacts; namely, by the interfacial layer between the contact and CZT material.
An organocatalytic asymmetric chlorolactonization.

A reagent controlled organocatalytic enantioselective chlorolactonization reaction has been developed. Several 4-aryl pentenoic acids were cyclized in the presence of 0.1 equiv of (DHQD)2PHAL, employing various N-chlorinated hydantoins as the terminal chlorenium source. Ten examples are presented with selectivities ranging from 43 to 90% ee. This work represents the first example of an enantioselective reagent-controlled chlorolactonization that approaches synthetically useful enantioselectivities.
Thoughts on polarimetry for 3He beams at RHIC

The Relativistic Heavy Ions Collider (RHIC) has accelerated polarized proton beams for physics since 2001. As part of the future eRHIC program and in order to enhance access to the down quark, a program to accelerate polarized 3He in the AGS and RHIC is envisioned. To that end, a polarized 3He source is being built at MIT. This will be installed on the BNL EBIS source in preparation for injection into the booster and AGS. As an early exercise, in June 2012, unpolarized 3He beams have been accelerated in the AGS. This paper will peruse some potential ideas for 3He polarimetry and calibration that could be utilized at the AGS as well as RHIC. The current proton polarimetry program serves as a guide.
The North Atlantic Oscillation and regional phenology prediction over Europe

We present an integrated modeling study designed to investigate changes in ecosystem level phenology over Europe associated with changes in climate pattern, by the North Atlantic Oscillation (NAO). We derived onset dates from processed NDVI data sets and used growing degree day (GDD) summations from the NCEP re-analysis to calibrate and validate a phenology model to predict the onset of the growing season over Europe. In a cross-validation hindcast, the model (PHENOM) is able to explain 63% of the variance in onset date for grid cells containing at least 50% mixed and boreal forest. Using a model developed from previous work we performed climate change scenarios, generating synthetic temperature and GDD distributions under a hypothetically increasing NAO. These new distributions were used to drive PHENOM and project changes in the timing of onset for forested cells over Europe. Results from the climate change scenarios indicate that, if the current trend in the NAO continues, there is the potential for a continued advance to the start of the growing season by as much as 13 days in some areas.
Studies on intramolecular Cr(0)-promoted [6π+2π] cycloaddition reactions. Synthesis of β-cedrene

Abstract Intramolecular metal-promoted [6 π +2 π ] cycloaddition followed by Tl(III)-mediated oxidative ring contraction affords β-cedrene.
Rigidly supersymmetric gauge theories on curved superspace

In this note we construct rigidly supersymmetric gauged sigma models and gauge theories on certain Einstein four-manifolds, and discuss constraints on these theories. In work elsewhere, it was recently shown that on some nontrivial Einstein four-manifolds such as AdS4, N = 1 rigidly supersymmetric sigma models are constrained to have target spaces with exact Kahler forms. Similarly, in gauged sigma models and gauge theories, we find that supersymmetry imposes constraints on Fayet-Iliopoulos parameters, which have the effect of enforcing that Kahler forms on quotient spaces be exact. We discuss the ‘background principle’ in this context. We also discuss general aspects of universality classes of gauged sigma models, as encoded by stacks, and also discuss affine bundle structures implicit in these constructions. In an appendix, we discuss how anomalies in four-dimensional gauge theories, such as those which play an important role in our analysis, can be recast in the language of stacks.
Fast monte-carlo algorithms for finding low-rank approximations

We consider the problem of approximating a given m × n matrix A by another matrix of specified rank k, which is smaller than m and n. The Singular Value Decomposition (SVD) can be used to find the "best" such approximation. However, it takes time polynomial in m, n which is prohibitive for some modern applications. In this article, we develop an algorithm that is qualitatively faster, provided we may sample the entries of the matrix in accordance with a natural probability distribution. In many applications, such sampling can be done efficiently. Our main result is a randomized algorithm to find the description of a matrix D* of rank at most k so that holds with probability at least 1 − δ (where v·vF is the Frobenius norm). The algorithm takes time polynomial in k,1/e, log(1/δ) only and is independent of m and n. In particular, this implies that in constant time, it can be determined if a given matrix of arbitrary size has a good low-rank approximation.
Bioinformatic perspectives on NRPS/PKS megasynthases: advances and challenges.

Covering: 1997 to 2008 The increased understanding of both fundamental principles and mechanistic variations of NRPS/PKS megasynthases along with the unprecedented availability of microbial genome sequences has inspired a number of in silico studies of both enzyme families. The insights that can be extracted from these analyses go far beyond a rough classification of data and have turned bioinformatics into a frontier field of natural products research. As databases are flooded with NRPS/PKS gene sequences of microbial genomes and metagenomes, increasingly reliable structural prediction methods can help to uncover hidden treasures. Already, phylogenetic analyses have revealed that NRPS/PKS pathways should not simply be regarded as enzyme complexes, specifically evolved to produce a selected natural product. Rather, they represent a collection of genetic options, allowing biosynthetic pathways to be shuffled in a process of perpetual chemical innovation. Understanding the principles underlying domain specificities, protein–protein interactions and pathway diversification in nature can give impulses for genomic mining approaches and genetic engineering of libraries of novel peptides and polyketides. The successful translation of the knowledge obtained from bioinformatic dissection of NRPS/PKS megasynthases into new techniques for drug discovery and design remain challenges for the future.
Pair-Instability Supernovae, Gravity Waves, and Gamma-Ray Transients

Growing evidence suggests that the first generation of stars may have been quite massive (~100-300 M☉). If they retain their high mass until death, such stars will, after about 3 Myr, make pair-instability supernovae. Models for these explosions have been discussed in the literature for four decades, but very few included the effects of rotation and none employed a realistic model for neutrino trapping and transport. Both turn out to be very important, especially for those stars whose cores collapse into black holes (helium cores above about 133 M☉). We consider the complete evolution of two zero-metallicity stars of 250 and 300 M☉. Despite their large masses, we argue that the low metallicities of these stars imply negligible mass loss. Evolving the stars with no mass loss, but including angular momentum transport and rotationally induced mixing, the two stars produce helium cores of 130 and 180 M☉. Products of central helium burning (e.g., primary nitrogen) are mixed into the hydrogen envelope with dramatic effects on the radius, especially in the case of the 300 M☉ model. Explosive oxygen and silicon burning cause the 130 M☉ helium core (250 M☉ star) to explode, but explosive burning is unable to drive an explosion in the 180 M☉ helium core, and it collapses to a black hole. For this star, the calculated angular momentum in the presupernova model is sufficient to delay black hole formation, and the star initially forms an ~50 M☉, 1000 km core within which neutrinos are trapped. The calculated growth time for secular rotational instabilities in this core is shorter than the black hole formation time, and they may develop. If so, the estimated gravitational wave energy and wave amplitude are EGW ≈ 10-3 M☉ c2 and h+ ≈ 10-21/d(Gpc), but these estimates are very rough and depend sensitively on the nonlinear nature of the instabilities. After the black hole forms, accretion continues through a disk. The mass of the disk depends on the adopted viscosity but may be quite large, up to 30 M☉ when the black hole mass is 140 M☉. The accretion rate through the disk can be as large as 1-10 M☉ s-1. Although the disk is far too large and cool to transport energy efficiently to the rotational axis by neutrino annihilation, it has ample potential energy to produce a 1054 erg jet driven by magnetic fields. The interaction of this jet with surrounding circumstellar gas may produce an energetic gamma-ray transient, but given the probable redshift and the consequent timescale and spectrum, this model may have difficulty explaining typical gamma-ray bursts.
CALIBRATING 100 YEARS OF POLAR FACULAE MEASUREMENTS: IMPLICATIONS FOR THE EVOLUTION OF THE HELIOSPHERIC MAGNETIC FIELD

Although the Sun's polar magnetic fields are thought to provide important clues for understanding the 11 year sunspot cycle, including the observed variations of its amplitude and period, the current database of high-quality polar field measurements spans relatively few sunspot cycles. In this paper, we address this deficiency by consolidating Mount Wilson Observatory polar faculae data from four data reduction campaigns, validating it through a comparison with facular data counted automatically from Michelson Doppler Imager (MDI) intensitygrams, and calibrating it against polar field measurements taken by the Wilcox Solar Observatory and average polar field and total polar flux calculated using MDI line-of-sight magnetograms. Our results show that the consolidated polar facular measurements are in excellent agreement with both polar field and polar flux estimates, making them an ideal proxy to study the evolution of the polar magnetic field. Additionally, we combine this database with sunspot area measurements to study the role of the polar magnetic flux in the evolution of the heliospheric magnetic field (HMF). We find that there is a strong correlation between HMF and polar flux at solar minimum and that, taken together, polar flux and sunspot area are better at explaining the evolution of the HMF during the last century than sunspot area alone.
Ensuring high-quality randomness in cryptographic key generation

The security of any cryptosystem relies on the secrecy of the system's secret keys. Yet, recent experimental work demonstrates that tens of thousands of devices on the Internet use RSA and DSA secrets drawn from a small pool of candidate values. As a result, an adversary can derive the device's secret keys without breaking the underlying cryptosystem. We introduce a new threat model, under which there is a systemic solution to such randomness flaws. In our model, when a device generates a cryptographic key, it incorporates some random values from an "entropy authority" into its cryptographic secrets and then proves to the authority, using zero-knowledge-proof techniques, that it performed this operation correctly. By presenting an entropy-authority-signed public key certificate to a third party (like a certificate authority or SSH client), the device can demonstrate that its public key incorporates randomness from the authority and is therefore drawn from a large pool of candidate values. Where possible, our protocol protects against eavesdroppers, entropy authority misbehavior, and devices attempting to discredit the entropy authority. To demonstrate the practicality of our protocol, we have implemented and evaluated its performance on a commodity wireless home router. When running on a home router, our protocol incurs a $1.7\times$ slowdown over conventional RSA key generation and it incurs a $3.6\times$ slowdown over conventional EC-DSA key generation.
THE STRUCTURE OF HALOS: IMPLICATIONS FOR GROUP AND CLUSTER COSMOLOGY

The dark matter halo mass function is a key repository of cosmological information over a wide range of mass scales, from individual galaxies to galaxy clusters. N-body simulations have established that the friends-of-friends (FOF) mass function has a universal form to a surprising level of accuracy (10%). The high-mass tail of the mass function is exponentially sensitive to the amplitude of the initial density perturbations, the mean matter density parameter, Ω m , and to the dark energy controlled late-time evolution of the density field. Observed group and cluster masses, however, are usually stated in terms of a spherical overdensity (SO) mass which does not map simply to the FOF mass. Additionally, the widely used halo models of structure formation—and halo occupancy distribution descriptions of galaxies within halos—are often constructed exploiting the universal form of the FOF mass function. This again raises the question of whether FOF halos can be simply related to the notion of a spherical overdensity mass. By employing results from Monte Carlo realizations of ideal Navarro-Frenk-White (NFW) halos and N-body simulations, we study the relationship between the two definitions of halo mass. We find that the vast majority of halos (80%-85%) in the mass-range 1012.5-1015.5 h –1 M ☉ indeed allow for an accurate mapping between the two definitions (~5%), but only if the halo concentrations are known. Nonisolated halos fall into two broad classes: those with complex substructure that are poor fits to NFW profiles and those bridged by the (isodensity-based) FOF algorithm. A closer investigation of the bridged halos reveals that the fraction of these halos and their satellite mass distribution is cosmology dependent. We provide a preliminary discussion of the theoretical and observational ramifications of these results.
Cryogenic and elevated temperature hypervelocity impact facility

Abstract The hypervelocity impact facility at Space Research Institute (SRI), Auburn University has recently completed a facility upgrade that permits the impact testing of space materials within the cryogenic and elevated temperature range. Sample temperatures within the range of 40–450 K have been achieved for polymer films. These wide temperature range capabilities add to the facilities current testing experience with impact initiated plasma discharge testing for solar cell arrays. The facility utilizes a plasma drag gun to accelerate a variety simulated micrometeorite materials in the 50–150 μm range to velocities between 5 and 12 km/s. For each test 5–50 particles impact the surface of the target sample within an impact area of approximately 15 cm in diameter. The test chamber can accommodate samples up to a meter wide for ambient and heated tests, and 48 cm for cryogenic samples. The gun and test chambers are evacuated by He cryopumps and dry roughing pumps to produce a clean, oil free environment. Utilizing a streak camera and PMT detection system, the correspondence between individual particle size, speed and impact site can be determined. Standard post-analysis yields: micrographs of each impact site, dimensions of the pertinent impact characteristics, individual particle velocity and size estimates.
An Observation of the Intermediate Polar XY Arietis with Chandra

Chandra serendipitously observed the eclipsing (80° < i < 84°) intermediate polar XY Arietis (=H0253+193) in two separate but continuous observations 5 weeks apart. XY Ari was in a quiescent state during both observations. We pursue the study of phase-resolved spectra for this system by focusing on the Fe K lines. From the combined and separate data sets, we readily detect emission lines of iron near 6.4, 6.7, and 6.9 keV at better than 99% significance, in contrast to previous results. We confirm the orbit-phased sinusoidal absorption column behavior first observed with Ginga, as well as a sinusoid-like behavior as a function of spin phase. The presence of the 6.4, 6.7, and 6.9 keV lines requires different ionization states with ξ < 2 (6.4 keV) and ξ ~ 3.5–4 (6.7 and 6.9 keV) that must vary with phase. We also detect emission lines at 3.25, 4.8, and 5.4 keV that are not instrumental in origin. The 4.8 keV line may be identified as Ca XIX (4.832 keV) and the 3.25 keV line may be Ar I K, but the 5.4 keV line has no obvious identification.
Correlation of paroxysmal supraventricular tachycardia, atrial fibrillation, and sinus rhythm with incidences of new thromboembolic stroke in 1476 old-old patients

The relationship between supraventricular tachycardia and the incidence of thromboembolic stroke has not been previously reported. We investigated in a prospective study the incidence of new thromboembolic stroke in 1476 patients, mean age 81 years, with atrial fibrillation, paroxysmal supraventricular tachycardia, or sinus rhythm detected by 24-hour ambulatory electrocardiograms. New thromboembolic stroke developed at 31-month follow-up in 87 of 201 patients (43%) with atrial fibrillation, at 43-month follow-up in 84 of 493 patients (17%) with paroxysmal supraventricular tachycardia, and at 45-month follow-up in 143 of 782 patients (18%) with sinus rhythm (p<0.0001 comparing atrial fibrillation with paroxysmal supraventricular tachycardia or sinus rhythm). Kaplan-Meier survival curves showed a higher significance of thromboembolic stroke in patients with atrial fibrillation, compared to patients with paroxysmal supraventricular tachycardia or sinus rhythm (log-rank: p<0.0001). Multivariate Cox regression model showed that independent significant predictors of thromboembolic stroke were: a) atrial fibrillation (relative risk = 3.31); b) prior thromboembolic stroke (relative risk = 2.85); c) sex (relative risk for women = 0.75); and d) age (relative risk = 1.02). These data show that atrial fibrillation is an independent predictor of thromboembolic stroke in elderly patients, and that paroxysmal supraventricular tachycardia is not associated with thromboembolic stroke.
Boundary diffraction wave integrals for diffraction modeling of external occulters

An occulter is a large diffracting screen which may be flown in conjunction with a telescope to image extrasolar planets. The edge is shaped to minimize the diffracted light in a region beyond the occulter, and a telescope may be placed in this dark shadow to view an extrasolar system with the starlight removed. Errors in position, orientation, and shape of the occulter will diffract additional light into this region, and a challenge of modeling an occulter system is to accurately and quickly model these effects. We present a fast method for the calculation of electric fields following an occulter, based on the concept of the boundary diffraction wave: the 2D structure of the occulter is reduced to a 1D edge integral which directly incorporates the occulter shape, and which can be easily adjusted to include changes in occulter position and shape, as well as the effects of sources—such as exoplanets—which arrive off-axis to the occulter. The structure of a typical implementation of the algorithm is included.
Coherent Electronic Fringe Structure in Incommensurate Silver-Silicon Quantum Wells

Atomically uniform silver films grown on highly doped n-type Si(111) substrates show fine-structured electronic fringes near the silicon valence band edge as observed by angle-resolved photoemission. No such fringes are observed for silver films grown on lightly doped n-type substrates or p-type substrates, although all cases exhibited the usual quantum-well states corresponding to electron confinement in the film. The fringes correspond to electronic states extending over the silver film as a quantum well and reaching into the silicon substrate as a quantum slope, with the two parts coherently coupled through an incommensurate interface structure.
From short to long scales in the QCD vacuum

Abstract We study approximate decimations in SU(N) LGT that connect the short to long distance regimes, and provide both upper and lower bounds on the exact partition function. This leads to a representation of the exact partition function in terms of successive decimations. The implications for a derivation of confinement from first principles are discussed.
WEIL–PETERSSON GEOMETRY ON MODULI SPACE OF POLARIZED CALABI–YAU MANIFOLDS

In this paper, we define and study the Weil–Petersson geometry. Under the framework of the Weil–Petersson geometry, we study the Weil–Petersson metric and the Hodge metric. Among the other results, we represent the Hodge metric in terms of the Weil–Petersson metric and the Ricci curvature of the Weil–Petersson metric for Calabi–Yau fourfold moduli. We also prove that the Hodge volume of the moduli space is finite. Finally, we proved that the curvature of the Hodge metric is bounded if the Hodge metric is complete and the dimension of the moduli space is 1.
Manganese Abundances in Cluster and Field Stars

We have derived Mn abundances for more than 200 stars in 19 globular clusters. In addition, Mn abundance determinations have been made for a comparable number of halo field and disk stars possessing an overlapping range of metallicities and stellar parameters. Our primary data set was comprised of high-resolution spectra previously acquired at the McDonald, Lick, and Keck Observatories. To enlarge our data pool, we acquired globular and open cluster spectra from several other investigators. Data were analyzed using synthetic spectra of the 6000 A Mn I triplet. Hyperfine structure parameters were included in the synthetic spectra computations. Our analysis shows that for the metallicity range -0.7>[Fe/H]>-2.7, stars of 19 globular clusters have a mean relative abundance of =-0.37+/-0.01 (σ=0.10), a value in agreement with that of the field stars, =-0.36+/-0.01 (σ=0.08). Despite the 2 orders of magnitude span in metallicity, the ratio remains constant in both stellar populations. Our Mn abundance data indicate that there is no appreciable variation in the relative nucleosynthetic contribution from massive stars that undergo core-collapse supernovae and thus no significant change of the associated initial mass function in the specified metallicity range. (Less)
A hierarchical eigenmodel for pooled covariance estimation

Summary. Although the covariance matrices corresponding to different populations are unlikely to be exactly equal they can still exhibit a high degree of similarity. For example, some pairs of variables may be positively correlated across most groups, whereas the correlation between other pairs may be consistently negative. In such cases much of the similarity across covariance matrices can be described by similarities in their principal axes, which are the axes that are defined by the eigenvectors of the covariance matrices. Estimating the degree of across-population eigenvector heterogeneity can be helpful for a variety of estimation tasks. For example, eigenvector matrices can be pooled to form a central set of principal axes and, to the extent that the axes are similar, covariance estimates for populations having small sample sizes can be stabilized by shrinking their principal axes towards the across-population centre. To this end, the paper develops a hierarchical model and estimation procedure for pooling principal axes across several populations. The model for the across-group heterogeneity is based on a matrix-valued antipodally symmetric Bingham distribution that can flexibly describe notions of ‘centre’ and ‘spread’ for a population of orthogonal matrices.
Web servers under overload: How scheduling can help

This article provides a detailed implementation study on the behavior of web serves that serve static requests where the load fluctuates over time (transient overload). Various external factors are considered, including WAN delays and losses and different client behavior models. We find that performance can be dramatically improved via a kernel-level modification to the web server to change the scheduling policy at the server from the standard FAIR (processor-sharing) scheduling to SRPT (shortest-remaining-processing-time) scheduling. We find that SRPT scheduling induces no penalties. In particular, throughput is not sacrificed and requests for long files experience only negligibly higher response times under SRPT than they did under the original FAIR scheduling.
PICARD LATTICES OF FAMILIES OF K3 SURFACES

ABSTRACT Using toric geometry, lattice theory, and elliptic surface techniques, we compute the Picard Lattice of certain K3 surfaces. In particular, we examine the generic member of each of M. Reid's list of 95 families of Gorenstein K3 surfaces which occur as hypersurfaces in weighted projective 3-spaces. As an application, we are able to determine whether the mirror family (in the sense of mirror symmetry for K3 surfaces) for each one is also on Reid's list.
An Analysis of Rising Bubble Experiments to Determine Minimum Miscibility Pressures

We report an analysis of rising bubble experiments for ternary systems. We present experimental evidence that observations of changes in bubble appearance are primarily controlled by changes in interfacial tension (IFT) that occur as components transfer from the surrounding liquid to the rising bubble. We report experimental observations for an analog ternary system (brine/isopropanol/iso-octane) that confirm the influence of IFT on bubble appearance. We also describe a simple diffusion model of composition changes during bubbles rise. A combination of experimental results and model calculations indicates that rising bubble experiments can be used to detect minimum miscibility pressure (or enrichment) for ternary vaporizing drives. Similar analysis shows, however, that falling drop experiments are more appropriate for ternary condensing displacements. Questions that remain to be resolved for systems with more than three components are outlined.
Quantitative seismostratigraphic inversion of a prograding delta from seismic data

Quantitative stratigraphy predicts the geometry of geologic strata and their petrophysical properties based on mathematical models of geological processes and parameters which affect the formation and evolution of geologic strata. Such processes include erosion, sediment transport, and deposition. Quantitative stratigraphic inversion estimates the process parameters from a priori data by systematic modeling until the predictions are compatible with the observations. In the case of quantitative seismostratigraphic inversion, the a priori data are predominantly of the seismic kind. To evaluate feasibility, we designed a preliminary algorithm which we applied in a prograding delta environment. We found that by fixing the sediment influx rate, subaerial transport rate, and the initial topography, we were able to reproduce the basic features of the delta with only three to five parameters which included subaqueous transport rate and its depth-dependent decay rate, base level, and sediment source location and spatial extent.