cssi/SciSciGPT-SciSciNet huggingface dataset:
Data dependency on measurement uncertainties in speaker recognition evaluation

The National Institute of Standards and Technology conducts an ongoing series of Speaker Recognition Evaluations (SRE). Speaker detection performance is measured using a detection cost function defined as a weighted sum of the probabilities of type I and type II errors. The sampling variability can result in measurement uncertainties. In our prior study, the data independency was assumed in using the nonparametric two-sample bootstrap method to compute the standard errors (SE) of the detection cost function based on our extensive bootstrap variability studies in ROC analysis on large datasets. In this article, the data dependency caused by multiple uses of the same subjects is taken into account. The data are grouped into target sets and non-target sets, and each set contains multiple scores. One-layer and two-layer bootstrap methods are proposed based on whether the two-sample bootstrap resampling takes place only on target sets and non-target sets, or subsequently on target scores and non-target scores within the sets, respectively. The SEs of the detection cost function using these two methods along with those with the assumption of data independency are compared. It is found that the data dependency increases both estimated SEs and the variations of SEs. Some suggestions regarding the test design are provided.
DISCONNECTION FROM THE TERMINATION SHOCK: THE END OF THE VOYAGER PARADOX

The most recent Voyager 1 observations show rapidly increasing galactic cosmic ray fluxes with simultaneously decreasing anomalous cosmic ray fluxes. While this has been suggested to somehow herald the imminent crossing of the heliopause, which bounds the heliosphere, we show that such observations should naturally arise from the heliosphere's global magnetic topology. For a blunt termination shock, there must be a region of magnetic flux, still inside the heliopause, but beyond the last magnetic connection point to the termination shock, with poorer access for the shock-accelerated anomalous cosmic rays and better access for the galactic cosmic rays entering the heliosphere.
Deriving the nonlinear cosmological power spectrum and bispectrum from analytic dark matter halo profiles and mass functions

We present an analytic model for the fully nonlinear two- and three-point correlation functions of the cosmological mass density field, and their Fourier transforms, the mass power spectrum and bispectrum. The model is based on physical properties of dark matter halos, with the three main model inputs being analytic halo density profiles, halo mass functions, and halo-halo spatial correlations, each of which has been well studied in the literature. We demonstrate that this new model can reproduce the power spectrum and bispectrum computed from cosmological simulations of both an n = -2 scale-free model and a low-density cold dark matter model. To enhance the dynamic range of these large simulations, we use the synthetic-halo replacement technique of Ma & Fry, in which the original halos with numerically softened cores are replaced by synthetic halos of realistic density profiles. At high wavenumbers, our model predicts a slope for the nonlinear power spectrum different from the often-used fitting formulas in the literature based on the stable-clustering assumption. Our model also predicts a three-point amplitude, Q, that is scale dependent, in contrast to the popular hierarchical clustering assumption. This model provides a rapid way to compute the mass power spectrum and bispectrum over all length scales where the input halo properties are valid. It also provides a physical interpretation of the clustering properties of matter in the universe.
Highly Diastereoselective Chelation-Controlled Additions to α-Silyloxy Ketones

The polar Felkin–Anh, Cornforth−Evans, and Cram-chelation models predict that the addition of organometallic reagents to silyl-protected α-hydroxy ketones proceeds via a nonchelation pathway to give anti-diol addition products. This prediction has held true for the vast majority of additions reported in the literature, and few methods for chelation-controlled additions of organometallic reagents to silyl-protected α-hydroxy ketones have been introduced. Herein, we present a general and highly diastereoselective method for the addition of dialkylzincs and (E)-di-, (E)-tri-, and (Z)-disubstituted vinylzinc reagents to α-silyloxy ketones using alkyl zinc halide Lewis acids, RZnX, to give chelation-controlled products (dr ≥18:1). The compatibility of organozinc reagents with other functional groups makes this method potentially very useful in complex molecule synthesis.
A microfabricated, electrochemiluminescence cell for the detection of amplified DNA

Abstract An electrochemical cell for the generation and detection of electrochemiluminescence of tris (2,2′-bipyridyl) ruthenium(II) has been microfabricated in silicon. The cell has been designed for use in the detection and quantification of DNA which has been amplified by the polymerase chain reaction. The cell is a vertical assembly of micromachined silicon and glass substrates, containing a gold, thin film cathode and an indium tin oxide, thin film anode. The anode is transparent, enabling the detection of the luminescence by an external photodetector. Preliminary tests have yielded the detection of free TBR concentrations from 10−9 M to 10−3 M with a cell volume of 85 μl.
Conversion of 1,3-disubstituted arenes to chiral α,α-diaryl methylammonium chlorides using arene borylation

A two-step conversion of 1,3-disubstituted arenes to chiral α,α-diaryl methylammonium chlorides is described. In this procedure, arenes are converted to aryl boronic esters by iridium-catalyzed borylation, and the aryl boronic esters are converted to enantioenriched amines by subsequent rhodium-catalyzed addition to chiral tert-butanesulfinimes.
On the stereoselectivity of the intramolecular dioxenone photocycloaddition

Abstract The stereoselectivity of the intramolecular photocycloaddition of dioxenone and enone substrates is compared. A mechanistic scheme that is consistent with the striking differences in the observed stereoselectivities is presented.
Transition Region Emission from Very Low Mass Stars

We present results from our Cycle 10 Hubble Space Telescope (HST) program to search for transition region emission in very low mass main-sequence stars in the spectral range M7-M9. Our program is aimed at (1) detecting emission and (2) distinguishing between flaring and quiescent origin for the emission. We have obtained HST/Space Telescope Imaging Spectrograph time series observations of three active, very low mass stars (VB 8, VB 10, and LHS 2065), which show persistent activity in transition region lines including Si IV, C IV, and He II. Emission in transition region lines appears to be variable between exposures but is always observed. A strong flare was also observed in one 10 minute exposure on VB 10. Our results indicate that active, very low mass stars maintain a persistent quiescent chromosphere and transition region that is similar to those observed in active earlier type M dwarfs, in contrast to suggestions that these low-mass main-sequence stars exhibit only relatively strong flares and no quiescent emission.
Improved methods for simulating nearly extremal binary black holes

Astrophysical black holes could be nearly extremal (that is, rotating nearly as fast as possible); therefore, nearly extremal black holes could be among the binaries that current and future gravitational-wave observatories will detect. Predicting the gravitational waves emitted by merging black holes requires numerical-relativity simulations, but these simulations are especially challenging when one or both holes have mass m and spin S exceeding the Bowen–York limit of S/m^2 = 0.93. We present improved methods that enable us to simulate merging, nearly extremal black holes (i.e., black holes with S/m^2 > 0.93) more robustly and more efficiently. We use these methods to simulate an unequal-mass, precessing binary black hole (BBH) coalescence, where the larger black hole has S/m^2 = 0.99. We also use these methods to simulate a non-precessing BBH coalescence, where both black holes have S/m^2 = 0.994, nearly reaching the Novikov–Thorne upper bound for holes spun up by thin accretion disks. We demonstrate numerical convergence and estimate the numerical errors of the waveforms; we compare numerical waveforms from our simulations with post-Newtonian and effective-one-body waveforms; we compare the evolution of the black hole masses and spins with analytic predictions; and we explore the effect of increasing spin magnitude on the orbital dynamics (the so-called ‘orbital hangup’ effect).
Beyond mutation matrices: physical-chemistry based evolutionary models

We describe a model for characterizing site mutations in evolving proteins. By representing the fitness of each of the amino acids as a function of the physical-chemical properties of that amino acid, and constructing mutation matrices based on Boltzmann statistics and Metropolis kinetics, we are able to greatly reduce the number of adjustable parameters. This allows us to include site heterogeneity in the model, as well as to optimize the model for specific protein types. We demonstrate the applicability of the model by investigating the phylogenetic relationship between various subtypes of HIV-1.
A note on the consistency condition of primordial fluctuations

We show that the squeezed limit of (N+1)-point functions of primordial correlation functions in which one of the modes has a very small wavenumber can be inferred from the spatial variation of locally measured N-point function. We then show how in single clock inflation a long wavelength perturbation can be re-absorbed in the background cosmology and how in computing correlation functions the integrals of the interaction Hamiltonian are dominated by conformal times of order of the short wavelength modes, when the long mode is already outside of the horizon. This allows us to generalize the consistency condition for N-point functions to the case in which the short wavelength fluctuations are inside the horizon and derivatives acts on them. We further discuss the consistency condition in the soft internal squeezed limit in which in an (N+M)-point function with (N+M) short modes the sum of the first N modes is a very soft momentum. These results are very useful to study infrared effects in Inflation.
Electrodynamics of the phonon-mediated optical Stark effect

The electrodynamics of three-wave polariton-phonon interactions with spatial dispersion is developed and applied to the phonon-mediated optical Stark effect in bulk polar semiconductors. This electrodynamics is formulated within three macroscopic equations, which describe the coupled probe light field, excitonic polarization, and LO phonons of a semiconductor virtually excited by the pump light. We analyze how the incident probe light reflects (transmits) from a boundary of the crystal in the presence of an intense coherent polariton. A Poynting theorem, which clarifies the structure of the total energy flux of the probe wave resonantly coupled to the pump polariton through Raman interaction, is derived. In order to calculate the reflectivity of the probe light from the boundary of a virtually excited crystal, we apply the recently developed wave-vector-space method [B. Chen and D.F. Nelson, Phys. Rev. B 48, 15 372 (1993)]. The transient excitonic spectra of the phonon-mediated Stark effect are analyzed and calculated numerically for bulk CdS.
Using simulated emergent vegetation to alter stream flow direction within a straight experimental channel

River restoration programs often use vegetation to enhance the biological functionality, recreational opportunities, and aesthetic beauty of degraded stream corridors. Yet, none has used vegetation for the purpose of inducing a straight channel to meander. A flume-based study was designed to alter the flow pattern within a straight, degraded stream corridor by using simulated emergent vegetation of varying density placed at key locations within the channel. Placement of vegetation zones was determined using an empirical relation for equilibrium meander wavelength based on the imposed flow rate. Surface flow velocities were quantified using particle image velocimetry. The study showed that (i) flow velocity can be markedly reduced within and near the vegetation zones, (ii) flow can be diverted toward the opposite bank, and (iii) vegetation density controlled the magnitude of these effects.
Performance of two coupled lasers.

The theory of Spencer and Lamb for the performance of two coupled lasers is generalized to account for intercavity phase shifts (transmitted wave minus reflected wave) other than ±π/2. The results are directly applicable to the case of two coupled single-line Fabry-Perot resonators with intercavity losses. Analytic expressions are given for steady-state performance and for the regions of stable operation. It is concluded that it is generally not possible to achieve stable operation on all potential laser lines for two multiline coupled lasers. Competition between stable and unstable lasing modes, in these devices, may result in stable operation on a reduced number of lines.
Technology, unemployment and efficiency

Abstract This paper analyzes technology choices and unemployment in search equilibrium. In contrast to standard search models, the presence of technology choices makes the decentralized equilibrium inefficient; there is too little investment in skills, too little job creation and there can be multiple equilibria. The paper also shows that technological progress is likely to be slower in labor markets where job tenure is low.
REGIOSELECTIVE REDUCTION OF EPOXIDES AND CONJUGATED CARBONYL COMPOUNDS USING ZEOLITE SUPPORTED ZINC BOROHYDRIDE

Abstract Zeolite supported zinc borohydride is a versatile catalyst for the regeoselective reduction of epoxides, conjugated ketones, and aldehydes to the corresponding alcohols in good yields.
Prospects for mirage mediation

Mirage mediation reduces the fine-tuning in the minimal supersymmetric standard model by dynamically arranging a cancellation between anomaly-mediated and modulus-mediated supersymmetry breaking. We explore the conditions under which a mirage ``messenger scale'' is generated near the weak scale and the little hierarchy problem is solved. We do this by explicitly including the dynamics of the SUSY-breaking sector needed to cancel the cosmological constant. The most plausible scenario for generating a low mirage scale does not readily admit an extra-dimensional interpretation. We also review the possibilities for solving the μ/Bμ problem in such theories, a potential hidden source of fine-tuning.
Design of flexure-based precision transmission mechanisms using screw theory

Abstract This paper enables the synthesis of flexure-based transmission mechanisms that possess multiple decoupled inputs and outputs of any type (e.g., rotations, translations, and/or screw motions), which are linked by designer-specified transmission ratios. A comprehensive library of geometric shapes is utilized from which a multiplicity of feasible concepts that possess the desired transmission characteristics may be rapidly conceptualized and compared before an optimal concept is selected. These geometric shapes represent the mathematics of screw theory and uniquely link a body's desired motions to the flexible constraints that enable those motions. This paper is significant to the design of nano-positioners, motion stages, and optical mounts. It is also significant to the design of transmission-based microstructural architectures for creating new materials with extraordinary mechanical properties. The microstructural architecture for a material that achieves a negative Poisson's ratio as well as a hand-actuated two degree of freedom (DOF) microscopy stage are designed as case studies to demonstrate the utility of this theory.
Partial identification of probability distributions with misclassified data

Abstract This paper addresses the problem of data errors in discrete variables. When data errors occur, the observed variable is a misclassified version of the variable of interest, whose distribution is not identified. Inferential problems caused by data errors have been conceptualized through convolution and mixture models . This paper introduces the direct misclassification approach . The approach is based on the observation that in the presence of classification errors, the relation between the distribution of the ‘true’ but unobservable variable and its misclassified representation is given by a linear system of simultaneous equations, in which the coefficient matrix is the matrix of misclassification probabilities. Formalizing the problem in these terms allows one to incorporate any prior information into the analysis through sets of restrictions on the matrix of misclassification probabilities. Such information can have strong identifying power. The direct misclassification approach fully exploits it to derive identification regions for any real functional of the distribution of interest. A method for estimating the identification regions and construct their confidence sets is given, and illustrated with an empirical analysis of the distribution of pension plan types using data from the Health and Retirement Study.
The Pathophysiology of Stress Urinary Incontinence in Women and Its Implications for Surgical Treatment

Stress urinary incontinence is a symptom that arises from damage to the muscles, nerves, and connective tissue of the pelvic floor. Urethral support, vesical neck function, and function of the urethral muscles are important determinants of continence. The urethra is supported by the action of the levator ani muscles through their connection to the endopelvic fascia of the anterior vaginal wall. Damage to the connection between this fascia and muscle, loss of nerve supply to the muscle, or direct muscle damage can influence continence. In addition, loss of normal vesical neck closure can result in incontinence despite normal urethral support. Although the traditional attitude has been to ignore the urethra as a factor contributing to continence, it does play a role in determining stress continence since in 50% of continent women, urine enters the urethra during increases in abdominal pressure, where it is stopped before it can escape from the external meatus. Perhaps one of the most interesting yet least acknowledged aspects of continence control concerns the coordination of this system. The muscles of the urethra and levator ani contract during a cough to assist continence, and little is known about the control of this phenomenon. That operations cure stress incontinence without altering nerve or muscle function should not be misinterpreted as indicating that these factors are unimportant.
Externalities, incentives, and failure to achieve national objectives in decentralized economies

Abstract This paper studies why decentralized economies often fail to achieve national objectives. We assume that the central government allocates its tax revenues among a large number of decision makers (provincial authorities or ministers). Decision makers are facing a soft budget constraint because of limited monitoring by the central authorities. Spending in excess to allocations fuels inflation. Cooperation to limit aggregate spending occurs when no decision maker can benefit by opportunistic behavior. Adverse macroeconomic shocks are shown to reduce the likelihood that decentralized decision makers will cooperate in order to achieve national objectives. Debt relief can induce higher investment because it can promote a shift from opportunistic behavior to cooperation.
The In Situ Generation and Use of Iodomethyllithium for the One-Carbon Homologation of Boronic Esters and Epoxide Formation from Carbonyl Compounds

Abstract Iodomethyllithium is shown to be an effective reagent for the one-carbon homologation of oxygenated boronic esters. The use of iodomethyllithium for the preparation of pinacol iodomethaneboronate and for the synthesis of epoxides from carbonyl compounds is also discussed.
Quantization of charges and fluxes in warped Stenzel geometry

We examine the quantization of fluxes for the warped Stiefel cone and Stenzel geometries and their orbifolds, and distinguish the roles of three related notions of charge: Page, Maxwell, and brane. The orbifolds admit discrete torsion, and we describe the associated quantum numbers which are consistent with the geometry in its large radius and small radius limits from both the type IIA and the M-theory perspectives. The discrete torsion, measured by a Page charge, is related to the number of fractional branes. We relate the shifts in the Page charges under large gauge transformations to the Hanany-Witten brane creation effect.
The synthesis and anti-hiv activity of pyrimidine dioxolanyl nucleosides

Abstract A series of 5-substituted uracil and cytosine dioxolanyl nucleosides were synthesized as potential anti-HIV agents. Compounds 3a and 3c were found to be extremely in acutely infected human lymphocytes.
Acceleration of pentobarbital metabolism in tolerant mice induced by pentobarbital pellet implantation.

Abstract The time course of inductions of N-demethylation and pentobarbital hydroxylation of hepatic drug metabolizing system in continuous pentobarbital administration by pentobarbital pellet implantation in the mouse is presented. The results also demonstrate that hepatic microsomal drug-metabolizing enzymes in the mouse could be induced much faster by a single pentobarbital pellet implantation than by the ordinary parenteral administration technique. The reduction of pentobarbital half-life ( T 1 2 ) in plasma, brain and liver of the animals which had been implanted with a pentobarbital pellet also substantiates the acceleration of pentobarbital metabolism in the mouse by the pellet implantation method. The results show that the T 1 2 of pentobarbital in plasma, brain and liver of pentobarbital pellet implanted groups is only 1 2 , 1 6 and 1 9 of that of the placebo control group, respectively. The studies on urinary excretion of pentobarbital and its metabolites also reveals that pentobarbital pellet implantation induced much faster rate of metabolism of pentobarbital in the mouse.
Interaction of fundamental parametric resonances with subharmonic resonances of order one-half

Abstract The interaction of fundamental parametric resonances with subharmonic resonances of order one-half in a single-degree-of-freedom system with quadratic and cubic nonlinearities is investigated. The method of multiple scales is used to derive two first-order ordinary differential equations that describe the modulation of the amplitude and the phase of the response with the non-linearity and both resonances. These equations are used to determine the steady state solutions and their stability. Conditions are derived for the quenching or enhancement of a parametric resonance by the addition of a subharmonic resonance of order one-half. The degree of quenching or enhancement depends on the relative amplitudes and phases of the excitations. The analytical results are verified by numerically integrating the original governing differential equation.
Formation of Isolated Nickel-Centered Gallium Clusters in Na10Ga10Ni and a 2-D Network of Gallium Octahedra in K2Ga3

Exploration of the sodium−gallium−nickel system has revealed a new compound containing the isolated gallium clusters Ga10Ni10-. Single-crystal X-ray diffraction studies of Na10Ga10Ni (Pnma, Z = 12, a = 13.908(3) A, b = 28.146(6) A, c = 16.286(4) A) show it to be isostructural with K10In10Ni. The compound contains two similar “naked” gallium clusters as distorted, tetracapped trigonal prismatic units that are centered by nickel. The sodium atoms serve to isolate the clusters from each other as well as to provide the cluster with a closed shell configuration of electrons. This is the first isolated gallium cluster in an alkali-metal system that is centered. Molecular orbital calculations on the cluster are also reported. The crystal structure of K2Ga3 (I4/mmm, Z = 4, a = 6.1382(3) A, c = 14.815(1) A) has also been established to be isostructural with A2In3 (A = Rb, Cs). This contains Ga64- octahedra interconnected through the waist atoms into layers [Ga64-], with octahedra in adjacent layers sitting in the ...
The Supermarxists and Pan-Africanism

I still feel it (Marxism) has been one of the most important phenomena in history and one of the greatest catalysts for change and transformation of society. The mistake of orthodox Marxists was to assume that the Manifesto, published in 1847, contained immutable scientific truth [Djilas, 1976]. I think I have said enough to make it understood that it is neither Marxism or Communism that I renounce, but it is the use that certain people have made of Marxism and Communism of which I disapprove. What I want is Marxism and Communism to be placed in the service of the black peoples and not the black peoples in the service of Marxism and Communism [Cesaire, 1956].
Mechanistic Studies on the Copper-Catalyzed N-Arylation of Amides

The copper-catalyzed N-arylation of amides, i.e., the Goldberg reaction, is an efficient method for the construction of products relevant to both industry and academic settings. Herein, we present mechanistic details concerning the catalytic and stoichiometric N-arylation of amides. In the context of the catalytic reaction, our findings reveal the importance of chelating diamine ligands in controlling the concentration of the active catalytic species. The consistency between the catalytic and stoichiometric results suggests that the activation of aryl halides occurs through a 1,2-diamine-ligated copper(I) amidate complex. Kinetic studies on the stoichiometric N-arylation of aryl iodides using 1,2-diamine ligated Cu(I) amidates also provide insights into the mechanism of aryl halide activation.
A confining quark model and new gauge symmetry

We discuss a confining model for quark–antiquark system with a new color SU3 gauge symmetry. New gauge transformations involve non-integrable phase factors and lead to the fourth-order gauge field equations and a linear potential. The massless gauge bosons have non-definite energies, which are not observable because they are permanently confined in quark systems by the linear potential. We use the empirical potentials of charmonium to determine the coupling strength of the color charge gs and find . The rules for Feynman diagrams involve propagators with poles of order 2 associated with new gauge fields. The confining quark model may be renormalizable by power counting and compatible with perturbation theory.
Parent Stars of Extrasolar Planets. VI. Abundance Analyses of 20 New Systems

The results of new spectroscopic analyses of 20 recently reported extrasolar planet parent stars are presented. The companion of one of these stars, HD 10697, has recently been shown to have a mass in the brown dwarf regime; we find [Fe/H] = +0.16 for it. For the remaining sample, we derive [Fe/H] estimates ranging from -0.41 to +0.37, with an average value of +0.18 ± 0.19. If we add the 13 stars included in the previous papers of this series and six other stars with companions below the 11 MJ limit from the recent studies of Santos et al., we derive [Fe/H] = +0.17 ± 0.20. Among the youngest stars with planets with F or G0 spectral types, [Fe/H] is systematically larger than young field stars of the same Galactocentric distance by 0.15 to 0.20 dex. This confirms the recent finding of Laughlin that the most massive stars with planets are systematically more metal-rich than field stars of the same mass. We interpret these trends as supporting a scenario in which these stars accreted high-Z material after their convective envelopes shrunk to near their present masses. Correcting these young star metallicities by 0.15 dex still does not fully account for the difference in mean metallicity between the field stars and the full parent stars sample. The stars with planets appear to have smaller [Na/Fe], [Mg/Fe], and [Al/Fe] values than field dwarfs of the same [Fe/H]. They do not appear to have significantly different values of [O/Fe], [Si/Fe], [Ca/Fe], or [Ti/Fe], though. The claim made in Paper V that stars with planets have low [C/Fe] is found to be spurious, due to unrecognized systematic differences among published studies. When corrected for these differences, they instead display slightly enhanced [C/Fe] (but not significantly so). If these abundance anomalies are due to the accretion of high-Z matter, it must have a composition different from that of the Earth.
Trinuclear Cuboidal and Heterometallic Cubane-Type Iron–Sulfur Clusters: New Structural and Reactivity Themes in Chemistry and Biology

Publisher Summary This chapter discusses some of the most significant recent findings and unusual properties of native and synthetic Fe4S4 clusters. Certain properties lead to newer types of clusters, viz., the cuboidal and heterometal cubane-type species. These afford new structural and reactivity themes in both inorganic chemistry and biology. This contention is well supported by consideration of just four of the major discoveries in the field in the last decade. With the former clusters, structural definition has advanced to the point where the relative stabilities of oxidation states of conventional Fd versus HP proteins may be sensibly interpreted in terms of the influence of the immediate protein environment, viz., the different numbers of protein-cluster N–H . . . S hydrogen bonds. Equilibrium and kinetic data may be derived with just trace amounts of protein and verified by preparation of appropriate spectroscopic samples.
A convenient procedure for the deprotection of silylated nucleosides and nucleotides using triethylamine trihydrofluoride

Abstract A new procedure for the deprotection of nucleosides and nucleotides bearing silyl protecting groups has been developed based on commercially-available reagent triethylamine trihydrofluoride.
Risk-sensitive real business cycles☆

Abstract This paper considers the business cycle, asset pricing, and welfare effects of increased risk aversion, while holding intertemporal substitution preferences constant. I show that increasing risk aversion does not significantly affect the relative variabilities and co-movements of aggregate quantity variables. At the same time, it dramatically improves the model's asset market predictions. The welfare costs of business cycles increase when preference parameters are chosen to match financial data.
THICK-THIN DECOMPOSITION FOR QUADRATIC DIFFERENTIALS

Quadratic differentials arise naturally in the study of Teichmuller space and Teichmuller geodesics, in particular. A quadratic differential q on a surface S defines a singular Euclidean metric on S. The explicit nature of singular Euclidean metrics often makes estimates simple and combinatorial arguments possible ([GM91], [Mas93]). On the other hand, by the uniformization theorem, there also exists a canonical hyperbolic metric σ in the conformal class of q and the problem of understanding the relationship between the two metrics often arises (see for example [Min92], [Raf05] and [Raf]). There is a well-known decomposition of a hyperbolic surface S into thick and thin parts ([Thu86], [BP92]). The components of the thin part have a simple topology; they are homeomorphic to annuli. The components of the thick part, on the other hand, have bounded geometry, i.e., the diameter and the injectivity radius of a thick piece are bounded both above and below by constants depending on the topology of S only. The geometry of a thick piece Y is coarsely determined by the topology of a short marking (see [MM00] and Section 3.1 below) in Y . For example, the hyperbolic length of a curve α is comparable (up to multiplicative constants depending on the topology of S) to the geometric intersection number between α and a given short marking ([Min93], see also (3)). We are interested in comparing these two metrics restricted to a thick piece Y of S. In general the diameter and the area of Y may be much smaller in the quadratic differential metric compared with the hyperbolic metric (see the example at the end of this paper). However, we show that, after scaling appropriately, Y equipped with the quadratic differential metric has a geometry comparable with the geometry of Y equipped with the hyperbolic metric. The following is our main theorem:
Implementation of universal control on a decoherence-free qubit

We demonstrate storage and manipulation of one qubit encoded into a decoherence-free subspace (DFS) of two nuclear spins using liquid state nuclear magnetic resonance techniques. The DFS is spanned by states that are unaffected by arbitrary collective phase noise. Encoding and decoding procedures reversibly map an arbitrary qubit state from a single data spin to the DFS and back. The implementation demonstrates the robustness of the DFS memory against engineered dephasing with arbitrary strength as well as a substantial increase in the amount of quantum information retained, relative to an un-encoded qubit, under both engineered and natural noise processes. In addition, a universal set of logical manipulations over the encoded qubit is also realized. Although intrinsic limitations prevent maintenance of full noise tolerance during quantum gates, we show how the use of dynamical control methods at the encoded level can ensure that computation is protected with finite distance. We demonstrate noise-tolerant control over a DFS qubit in the presence of engineered phase noise significantly stronger than observed from natural noise sources.
Valley degeneracies in (111) silicon quantum wells

(111) silicon quantum wells have been studied extensively, yet no convincing explanation exists for the experimentally observed breaking of sixfold valley degeneracy into two- and fourfold degeneracies. Here, systematic sp3d5s∗ tight-binding and effective mass calculations are presented to show that a typical miscut modulates the energy levels, which leads to breaking of sixfold valley degeneracy into two lower and four raised valleys. An effective mass based valley-projection model is used to determine the directions of valley minima in tight-binding calculations of large supercells. Tight-binding calculations are in better agreement with experiments compared to effective mass calculations.
DIAGNOSING THE TIME-DEPENDENCE OF ACTIVE REGION CORE HEATING FROM THE EMISSION MEASURE. I. LOW-FREQUENCY NANOFLARES

Observational measurements of active region emission measures contain clues to the time dependence of the underlying heating mechanism. A strongly nonlinear scaling of the emission measure with temperature indicates a large amount of hot plasma relative to warm plasma. A weakly nonlinear (or linear) scaling of the emission measure indicates a relatively large amount of warm plasma, suggesting that the hot active region plasma is allowed to cool and so the heating is impulsive with a long repeat time. This case is called low-frequency nanoflare heating, and we investigate its feasibility as an active region heating scenario here. We explore a parameter space of heating and coronal loop properties with a hydrodynamic model. For each model run, we calculate the slope α of the emission measure distribution EM(T)∝T α. Our conclusions are: (1) low-frequency nanoflare heating is consistent with about 36% of observed active region cores when uncertainties in the atomic data are not accounted for; (2) proper consideration of uncertainties yields a range in which as many as 77% of observed active regions are consistent with low-frequency nanoflare heating and as few as zero; (3) low-frequency nanoflare heating cannot explain observed slopes greater than 3; (4) the upper limit to the volumetric energy release is in the region of 50 erg cm–3 to avoid unphysical magnetic field strengths; (5) the heating timescale may be short for loops of total length less than 40 Mm to be consistent with the observed range of slopes; (6) predicted slopes are consistently steeper for longer loops.
Free radical chain reactions of 3-fluoro-3-iodo-β-lactams

Abstract The iodine atom transfer addition reaction of 3-fluoro-3-iodo-β-lactams under photolytic conditions was found to be a convenient and stereoselective method for functionalization at the C-3 position. The cyclization leading to 1-fluoro-3,6-diazabicyclo[3.2.1]octan-2-one derivatives was achieved using allylamine as an olefin.
The tachyon at the end of the universe

We show that a tachyon condensate phase replaces the spacelike singularity in certain cosmological and black hole spacetimes in string theory. We analyze explicitly a set of examples with flat spatial slices in various dimensions which have a winding tachyon condensate, using worldsheet path integral methods from Liouville theory. In a vacuum with no excitations above the tachyon background in the would-be singular region, we analyze the production of closed strings in the resulting state in the bulk of spacetime. We find a thermal result reminiscent of the Hartle-Hawking state, with tunably small energy density. The amplitudes exhibit a self-consistent truncation of support to the weakly-coupled small-tachyon region of spacetime. We argue that the background is accordingly robust against back reaction, and that the resulting string theory amplitudes are perturbatively finite, indicating a resolution of the singularity and a mechanism to start or end time in string theory. Finally, we discuss the generalization of these methods to examples with positively curved spatial slices.
Association of lipid abnormalities with measures and severity of adiposity and insulin resistance among overweight children and adolescents.

Obesity and lipid abnormalities in children may increase premature cardiovascular disease risk, but the relationship of dyslipidemia with adiposity among obese children is not well defined. The authors performed a cross-sectional analysis of children and adolescents (N=698) in 3 age groups (3–8 years, 9–11 years, and 12–18 years; 53% female, 81% African American, and 16% Hispanic) attending an obesity treatment program. More than 50% of the sample had abnormal levels of triglycerides (TG) or high-density lipoprotein (HDL) cholesterol or both. Only HDL cholesterol and TG were significantly associated with adiposity measures and insulin resistance (measured by homeostasis model assessment [HOMA]) and only in adolescents. All measures of adiposity, adjusted for age and sex, among adolescents were modest predictors of abnormal TG and HDL cholesterol, but these associations were attenuated when adjusting for HOMA. Despite the high prevalence of dyslipidemia in overweight children and adolescents, severity of adiposity appears to be a poor predictor of lipid values except among adolescents. Insulin resistance may in part mediate the relationship of adiposity and dyslipidemia among obese adolescents.
Sequential Ketyl−Olefin Coupling/β-Elimination Reactions Mediated by Samarium(II) Iodide

Samarium(II) iodide (SmI2) has been employed in an intramolecular sequential ketyl−olefin coupling/β-elimination reaction. The overall process results in the net addition of an alkenyl species to a ketone carbonyl. This novel protocol for the intramolecular delivery of an alkenyl moiety avoids the basic reaction conditions typical of nucleophilic additions that are mediated by alkenylmagnesium halides and alkenyllithium reagents. A high degree of stereocontrol is imparted in the SmI2-mediated process as a result of the excellent facial selectivity conveyed in the initial ketyl−olefin coupling reaction. The relative asymmetric induction engendered in these addition reactions is complementary to more traditional nucleophilic addition reactions in that the alkenyl group is directed to the carbonyl center by an attached tether.
Diastereoselective introduction of an EtO2CCF2-group into chiral imide enolates mediated by triethylborane

Abstract The introduction of an EtO 2 CCF 2 - group into lithium enolates of chiral N-acyloxazolidinones with ethyl difluoroiodoacetate mediated by triethylborane proceeds with good diastereomeric excess (86->98% de).
Three-Dimensional Navier–Stokes Analysis and Redesign of an Imbedded Bellmouth Nozzle in a Turbine Cascade Inlet Section

Experimental measurements in the inlet of a transonic turbine blade cascade showed unacceptable pitchwise flow non-uniformity. A three-dimensional, Navier-Stokes computational fluid dynamics (CFD) analysis of the imbedded bellmouth inlet in the facility was performed to identify and eliminate the source of the flow non-uniformity. The blockage and acceleration effects of the blades were accounted for by specifying a periodic static pressure exit condition interpolated from a separate three-dimensional Navier-Stokes CFD solution of flow around a single blade in an infinite cascade. Calculations of the original inlet geometry showed total pressure loss regions consistent in strength and location to experimental measurements. The results indicate that the distortions were caused by a pair of streamwise vortices that originated as a result of the interaction of the flow with the imbedded bellmouth. Computations were performed for an inlet geometry which eliminated the imbedded bellmouth by bridging the region between it and the upstream wall. This analysis indicated that eliminating the imbedded bellmouth nozzle also eliminates the pair of vortices, resulting in a flow with much greater pitchwise uniformity. Measurements taken with an installed redesigned inlet verify that the flow non-uniformity has indeed been eliminated.
“The arrival of the fittest”: Toward a theory of biological organization

The formal structure of evolutionary theory is based upon the dynamics of alleles, individuals and populations. As such, the theory must assume the prior existence of these entities. This existence problem was recognized nearly a century ago, when DeVries (1904, Species and Varieties: Their Origin by Mutation ) stated, “Natural selection may explain the survival of the fittest, but it cannot explain the arrival of the fittest.” At the heart of the existence problem is determining how biological organizations arise in ontogeny and in phylogeny. We develop a minimal theory of biological organization based on two abstractions from chemistry. The theory is formulated using λ-calculus, which provides a natural framework capturing (i) the constructive feature of chemistry, that the collision of molecules generates specific new molecules, and (ii) chemistry's diversity of equivalence classes, that many different reactants can yield the same stable product. We employ a well-stirred and constrained stochastic flow reactor to explore the generic behavior of large numbers of applicatively interacting λ-expressions. This constructive dynamical system generates fixed systems of transformation characterized by syntactical and functional invariances. Organizations are recognized and defined by these syntactical and functional regularities. Objects retained within an organization realize an algebraic structure and possess a grammar which is invariant under the interaction between objects. An organization is self-maintaining, and is characterized by (i) boundaries established by the invariances, (ii) strong self-repair capabilities responsible for a robustness to perturbation, and (iii) a center, defined as the smallest kinetically persistent and self-maintaining generator set of the algebra. Imposition of different boundary conditions on the stochastic flow reactor generates different levels of organization, and a diversity of organizations within each level. Level 0 is defined by self-copying objects or simple ensembles of copying objects. Level 1 denotes a new object class, whose objects are self-maintaining organizations made of Level 0 objects, and Level 2 is defined by self-maintaining metaorganizations composed of Level 1 organizations. These results invite analogy to the history of life, that is, to the progression from self-replication to self-maintaining procaryotic organizations to ultimately yield self-maintaining eucaryotic organizations. In our system self-maintaining organizations arise as a generic consequence of two features of chemistry, without appeal to natural selection. We hold these findings as calling for increased attention to the structural basis of biological order.
Arthroscopic management of refractory shoulder stiffness

Abstract Glenohumeral stiffness is a major cause of shoulder disability and pain. Conventional management strategies often fail to yield consistent or prompt return of comfort and function. Over the past 5 years, we have employed a prospective approach to the evaluation and management of glenohumeral stiffness using arthroscopic release of capsular contractures for the most refractory. This report concerns the first 30 patients who failed at least 6 months (28 month mean) of nonoperative management for unilateral refractory shoulder stiffness and who were managed by arthroscopic capsular release. Fourteen patients were diabetic. Follow-up averaged 33 months (range 12 to 56 months). Each patients' motion and strength was documented according to the American Shoulder and Elbow Surgeons standard examination. Functional outcome measures were patient-assessed using the Simple Shoulder test before and after surgery. Before surgery, active range-of-motion of the affected shoulder averaged 41% of the opposite asymptomatic side. The day after surgery, motion had improved dramatically to a mean of 78%. An additional 15% of motion was gained after discharge from the hospital. The final motion averaged 93% of the opposite side. All Simple Shoulder Test (SST) parameters and six of nine SF-36 health status scores were improved significantly. Only 6% of patients were able to sleep comfortably on their side and 35% could place 1 lb. on a shelf at shoulder height before surgery. After surgery, 73% were able to sleep comfortably on the affected side and 83% were able to place 1 lb. on a shelf at shoulder height. There were no differences among all outcome measures between diabetic or nondiabetic patients. Three patients developed recurrent refractory stiffness. The only complication was a single axillary neuropraxia which resolved spontaneously. No patient developed instability. Arthroscopic capsular release can be a safe and effective tool in the management of refractory shoulder stiffness.
A novel class of zinc-binding inhibitors for the phosphatidylcholine-preferring phospholipase C from Bacillus cereus.

The phospholipase C (PLC) isozymes catalyze the hydrolysis of phospholipids to provide diacylglycerol (DAG) and a phosphorylated headgroup. Because DAG has been implicated in cellular signal transduction cascades in mammalian systems, there has been considerable interest in the development of inhibitors of these enzymes. Toward this end, we have discovered that the cyclic N,N‘-dihydroxyureas 6−10 inhibit the phosphatidylcholine preferring PLC from Bacillus cereus (PLCBc). This class of inhibitors is believed to function by the bidentate chelation of the N,N‘-dihydroxyurea array to one or more of the zinc ions at the active site of the enzyme. Because the affinities of these compounds correlate with the pKas of the N−OH hydroxyl groups, it is apparent that one or both of the hydroxyl groups must be ionized for effective coordination to the zinc ions. It is also apparent that there may be rather strict steric requirements for these inhibitors.