cssi/SciSciGPT-SciSciNet huggingface dataset:
Synthetic Strategies Directed Towards the Cortistatin Family of Natural Products

Since their isolation by Kobayashi and co-workers, the cortistatins have captured the attention both of the synthetic chemistry community and of researchers interested in exploiting the potent anti-angiogenic activity of these natural products. The unique rearranged steroidal cortistatin core has become the target of numerous synthetic efforts, which are detailed herein.
Copper-catalyzed electrophilic amination of diorganozinc reagents.

The copper-catalyzed electrophilic amination of diorganozinc reagents employing O-acyl N,N-dialkyl hydroxylamine derivatives as aminating agents is described. This reaction offers a general method for the preparation of tertiary amines in high yields and is noteworthy for its convenience both in terms of reaction conditions employed (room temperature, ≤1 h) and ease of product isolation (acid/base extractive workup).
Three‐dimensional velocity structure of the polar wind

[1] A three-dimensional, time-dependent, fluid model was used to investigate the velocity structure of the global ionosphere–polar wind system. Each simulation involved following a large number of high-latitude flux tubes (over 1000) as they moved under the influence of convection and corotational electric fields. A flux tube typically traversed various high-latitude regions during the course of a simulation, including the subauroral ionosphere, dayside and nightside auroral ovals, and polar cap. Heating due to auroral electron precipitation was included in the simulations, but “nonclassical” heating mechanisms at high altitudes, such as wave-particle interactions, were not. The model results show the variation of H+ and O+ drift velocities with respect to magnetic latitude and longitude over the northern polar region, as well as variations with altitude and universal time (UT). A simulated geomagnetic storm of moderate intensity was introduced at a particular UT, and the effect of variable geomagnetic activity levels on the two major ion species was studied. Equivalent simulations were performed for four geophysical cases, corresponding to summer and winter solstices at both solar maximum and minimum. These simulations reveal the seasonal and solar cycle dependence of the ion velocities for both quiet and geomagnetically active times. The H+ and O+ populations responded to the varying geophysical conditions in dramatically different ways. These responses provide insight into the role played by the polar wind in the larger and inclusive system of fields and plasmas referred to as the Sun-Earth connection. The self-consistent high-resolution results obtained here reveal structure in the polar wind that cannot be resolved by simpler studies using velocity profiles based on averaged experimental data. The results of this investigation were compared with those of relevant observational studies.
Computing Roadmaps of General Semi-Algebraic Sets

In this paper we study the problem of determining whether two points lie in the same connected component of a semi-algebraic set S. Although we are mostly concerned with sets S⊆R k , our algorithm can also decide if points in an arbitrary set S⊆R k can be joined by a semi-algebraic path, for any real closed field R. Our algorithm computer a one-dimensional semi-algebraic subset R(S) of S (actually of an embedding of S in a space R k for a certain real extension field R of the given field R). R(S) is called the roadmap of S. The basis of this work is the eoadmap algorithm described in [3, 4] which worked only for compact, regularly stratified sets
Minimal intersection of curves on surfaces

This paper is a consequence of the close connection between combinatorial group theory and the topology of surfaces. In the eighties Goldman discovered a Lie algebra structure on the vector space generated by the free homotopy classes of oriented curves on an oriented surface. The Lie bracket [a, b] is defined as the signed sum over the intersection points of a and b of their loop product at the intersection points. If one of the classes has a simple representative we give a combinatorial group theory description of the terms of the Lie bracket and prove that this bracket has as many terms, counted with multiplicity, as the minimal number of intersection points of a and b. In other words the bracket with a simple element has no cancellation and determines minimal intersection numbers. We show that analogous results hold for the Lie bracket (also discovered by Goldman) of unoriented curves. We give three applications: a factorization of Thurston’s map defining the boundary of Teichmuller space, various decompositions of the underlying vector space of conjugacy classes into ad invariant subspaces and a connection between bijections of the set of conjugacy classes of curves on a surface preserving the Goldman bracket and the mapping class group.
The contracting value of tainted reports in cost reduction settings

Abstract While cost accounting is a well-developed discipline with a rich institutional past, it is criticized for being manipulable. This criticism is due, in part, to the existence of multiple , yet equally accepted cost allocation procedures or cost estimation techniques. Employing a principal–agent model, cost accounting is modeled as a menu of alternative methods which, conditional on agent effort, produce noisy, unbiased and independently distributed (i.e., equally defensible) measures from which a single realization is selected ex post as the report used to contract with the agent. Assuming that the report does not indicate which method produced it, the report modeled is “tainted” in that the lowest (most favorable to the agent) outcome is reported, where the “amount” of tainting corresponds to the menu's size. The paper identifies bright-line conditions where the principal's expected net payoff is independent of the amount of tainting, demonstrating that tainting does not necessarily affect the report's incentive value.
Uranyl fluoride luminescence in acidic aqueous solutions

Abstract Luminescence emission spectra and decay rates are reported for uranyl species in acidic aqueous solutions containing HF or added NaF. The longest luminescence lifetime, 0.269±0.006 ms, was observed from uranyl in 1 M HF+1 M HClO4 at 296 K and decreased with increasing temperature. Based on a luminescence dynamics model that assumes equilibrium among electronically excited uranyl fluoride species and free fluoride ion, this long lived uranyl luminescence in aqueous solution is attributed primarily to UO2F2. Studies on the effect of added LiNO3 or Na2WO4·2H2O showed relatively weak quenching of uranyl fluoride luminescence which suggests that high sensitivity determination of the UF6 content of WF6 gas should be feasible via uranyl luminescence analysis of hydrolyzed gas samples of impure WF6.
A generalization of Rado's Theorem for almost graphical boundaries

In this paper, we prove a generalization of Rado's Theorem, a fundamental result of minimal surface theory, which says that minimal surfaces over a convex domain with graphical boundaries must be disks which are themselves graphical. We will show that, for a minimal surface of any genus, whose boundary is ``almost graphical'' in some sense, that the surface must be graphical once we move sufficiently far from the boundary.
A Study of Humidification in the Thermal Life Determination of Motorette Insulation Systems

The moisture conditioning cycle is the most critical factor in the functional evaluation of rotating machinery insulation systems. An analysis is made of some of the humidity problems currently existing, particularly in respect to the use of the now proposed IEEE 117 Test Procedure and the NRL-designed condensation chamber. A time-dependence ratio of surface-to-bulk absorption has been discovered that varies with the degree of thermal aging. This is explored. Cautionary measures are given for use of the condensation chamber with recommendations as to temperature differentials and exposure-time durations needed to ensure stable test conditions.
Evaluation of Simple Rate Expressions for Vibration-Dissociation Coupling

We consider relatively simple expressions for inelastic state-to-state and state-specific dissociative rate coefficients for use in vibrational master equation studies of shock-heated CO, N2, and O2 highly dilute in Ar. Rotationally averaged inelastic rate coefficients are determined using information theory. Rotationally averaged dissociative rate coefficients are computed using an expression we developed earlier and refined in this work. The master equation is linearized by neglecting diatom-diatom collisions and recombination. This allows us to use efficient eigenvector-eigenvalue matrix techniques. We show that the information theoretic rate coefficients are easily formulated and more accurate than commonly used Schwartz, Slawsky, and Herzfeld rate coefficients; they are therefore well suited for engineering solutions of the master equation. Our master equation results indicate that the most significant contribution to dissociation comes from low- and midlying vibrational levels. In addition, we find that the omission of multiquantum transitions results in significant underpredictions of the average vibrational energy and average dissociative rate coefficient.
Quantification in a relational data system

The desire to express interrelationships between symbolic objects has been with us for some time, along with exploration of relationship systems which are operational in a computer. These systems coalesced under the term relational data systems (RDS), and a technology for dealing with this kind of data evolved. Relational systems have been through feasibility tests, experimental usage and should become generally available to the computing community in the near future. The advantages which account for the expanding use of RDSs are a simple, formal definition which allows associative processing, extreme flexibility in both structure and use, an ability to be efficiently implemented, and a notation and conception which is not dependent upon any particular physical data representation.
Going global: the historical contingency of baseball hall of famer developmental networks

Purpose – The purpose of this paper is to investigate how the changing of institutional logics in an established field shapes the developmental networks of high‐achievers.Design/methodology/approach – This research combines time series analysis of more than 80 years of historical data (1922‐2004) with qualitative analysis of induction speeches of 99 hall of fame players from the same period.Findings – Findings indicate that a change in field logics from a more staid “insular” logic to a market or more business‐oriented logic coincided with changes in key players' developmental networks. In particular, the key players' self‐identified developmental relationships become both more numerous and more diverse in nature. Results of the time series analysis connect the shift in logic with the late 1950s which was an important time in Major League Baseball's history. It was during this period that, for the first time, each team had at least one African American player on their roster and each team had an average o...
Distributed-order calculus: An operator-theoretic interpretation

Within the Bochner-Phillips functional calculus and Hirsch functional calculus, we describe the operators of distributed-order differentiation and integration as functions of the classical operators of differentiation and integration, respectively.
Compilation of giant electric dipole resonances built on excited states

Abstract Giant Electric Dipole Resonance (GDR) parameters for γ decay to excited states with finite spin and temperature are compiled. Over 100 original works have been reviewed and from some 70 of them, about 350 sets of hot GDR parameters for different isotopes, excitation energies, and spin regions have been extracted. All parameter sets have been brought onto a common footing by calculating the equivalent Lorentzian parameters. The current compilation is complementary to an earlier compilation by Samuel S. Dietrich and Barry L. Berman (At. Data Nucl. Data Tables 38 (1988) 199–338) on ground-state photo-neutron and photo-absorption cross sections and their Lorentzian parameters. A comparison of the two may help shed light on the evolution of GDR parameters with temperature and spin. The present compilation is current as of July 2006.
A Multidomain spectral method for solving elliptic equations

We present a new solver for coupled nonlinear elliptic partial differential equations (PDEs). The solver is based on pseudo-spectral collocation with domain decomposition and can handle one- to three-dimensional problems. It has three distinct features. First, the combined problem of solving the PDE, satisfying the boundary conditions, and matching between different subdomains is cast into one set of equations readily accessible to standard linear and nonlinear solvers. Second, touching as well as overlapping subdomains are supported; both rectangular blocks with Chebyshev basis functions as well as spherical shells with an expansion in spherical harmonics are implemented. Third, the code is very flexible: The domain decomposition as well as the distribution of collocation points in each domain can be chosen at run time, and the solver is easily adaptable to new PDEs. The code has been used to solve the equations of the initial value problem of general relativity and should be useful in many other problems. We compare the new method to finite difference codes and find it superior in both runtime and accuracy, at least for the smooth problems considered here.
Information-theoretic approaches to branching in search

Deciding what question to branch on at each node is a key element of search algorithms. In this paper, we describe a collection of techniques for branching decisions that are motivated from an information-theoretic perspective. The idea is to drive the search to reduce the uncertainty (entropy) in the current subproblem. We present four families of methods for branch question selection in mixed integer programming that use this idea. In the first, a variable to branch on is selected based on lookahead. This method performs comparably to strong branching on MIPLIB, and better than strong branching on hard real-world procurement optimization instances on which CPLEX's default strong branching outperforms CPLEX's default branching strategy. The second family combines this idea with strong branching. The third family does not use lookahead, but instead exploits the tie between indicator variables and the variables they govern. This significantly outperforms the state-of-the-art branching strategies on both combinatorial procurement problems and facility location problems. The fourth family concerns branching using carefully constructed linear inequality constraints over sets of variables.
IRREVERSIBILITY OF THE RENORMALIZATION GROUP FLOW IN TWO-DIMENSIONAL QUANTUM GRAVITY

We argue that the torus partition sum in 2D (super) gravity, which counts physical states in the theory, is a decreasing function of the renormalization group scale. As an application we chart the space of models coupled to (super) gravity, confirming and extending ideas due to A. Zamolodchikov, and discuss briefly string theory, where our results imply that the number of degrees of freedom decreases with time.
Demand Dynamics in the Seasonal Goods Industry: An Empirical Analysis

This study develops and estimates a dynamic model of consumer choice behavior in markets for seasonal goods, where products are sold over a finite season and availability is limited. In these markets, retailers often use dynamic markdown policies in which an initial retail price is announced at the beginning of the season and the price is subsequently marked down as the season progresses. Strategic consumers face a trade-off between purchasing early in the season, when prices are higher but goods are available, and purchasing later, when prices are lower but the stockout risk is higher. If the good starts providing utility as soon as it is purchased (e.g., apparel), consumers purchasing earlier in the season can also get more use from the product compared to those purchasing later. Our structural model incorporates three features essential for modeling the demand for seasonal goods: changing prices, limited availability, and possible dependence of total consumption utility on the time of purchase. In this model, heterogeneous consumers have expectations about future prices and product availability, and they strategically time their purchases. We estimate the model using aggregate sales and inventory data from a fashion goods retailer. The results indicate that, in the fashion goods context, ignoring consumers' expectations about future availability or the change in total consumption utility over the season can lead to biased demand estimates. We find that strategic consumers delay their purchases to take advantage of markdowns and that these strategic delays hurt the retailer's revenues. Retailer revenues facing strategic consumers are 9% lower than they would have been facing myopic consumers. Limited availability, on the other hand, reduces the extent of strategic delays by motivating consumers to purchase earlier. We find that the impact of strategic delays on retailer revenues would have been as high as 35% if there were no stockout risk. By means of counterfactual experiments, we show that the highest retailer profits are achieved by offering small markdowns early in the season. On the other hand, given current markdown percentages, the retailer can improve profits by carrying less stock as consumers accelerate purchases and purchase at higher prices when they anticipate scarcity in future periods. As long as the reduction in availability is not great, the profit gain from earlier higher-priced sales can overcome the loss resulting from the reduction in overall sales.
A flexible, highly efficient method for the preparation of homochiral oxazaphospholidine-boranes

Abstract An efficient and operationally simple procedure for the synthesis of 2-substituted 3,4-dimethyl-5-phenyloxazaphospholidine derivatives has been develop
Cloud-based Multimedia Conferencing: Business Model, Research Agenda, State-of-the-Art

Multimedia conferencing enables the conversational exchange of media data. It is a critical application in enterprises' settings. Cloud computing is an emerging multi-faceted paradigm (Infrastructure as a Service -- IaaS, Platform as a Service -- PaaS, and Software as a Service -- SaaS). This position paper proposes a business model for cloud-based multimedia conferencing and uses it as a basis to derive a research agenda. We also present the state-of-the-art. The model is introduced, the research agenda articulated, and the state-of-the-art is contrasted to that agenda. A key role in the proposed model is played by the conference substrate provider. Conference substrate providers offer re-usable and sharable virtualized substrates (e.g. audio /video mixers, floor control algorithms) that can be assembled on the fly to build conferencing applications. The research challenges are numerous (e.g. identification, description and control (including composition) of multimedia conferencing substrates, mechanisms for enabling mobile devices to access the conferencing applications built with substrates) and the state-of-the-art still germinal.
Carbon Stripper Foils for Heavy Ion Accelerators

Carbon stripper foils have for many years been successfully used with accelerators because they yield higher average charge states than gas strippers. However, with the development of heavy ion accelerators and the resulting use of heavier ions, the carbon stripper foil lifetimes are greatly reduced. Even when using the new foils changer systems, which typically contain two hundred foils or more, it becomes necessary to have frequent accelerator shutdowns for foil reloading. The rate of experiment interruption makes it clear a new approach is necessary to increase foil lifetimes. Several techniques have been tried with varying degrees of success to strengthen these foils so that they will last longer; the most successful one reported a lifetime increase of the order of a factor of 30 over foils produced in the conventional manner. Methods of producing various types of foils will be presented, a discussion will be given on theories for foil breakage, and some new ideas will be introduced for further increasing foil lifetimes.
Mini Z′ burst from relic supernova neutrinos and late neutrino masses

In models in which neutrinos are light, due to a low scale of symmetry breaking, additional light bosons are generically present. We show that the interaction between diffuse supernova relic neutrinos (SRN) and the cosmic background neutrinos, via exchange of these light scalars, can result in a dramatic change of the supernova (SN) neutrinos flux. Measurement of this effect with current or future experiments can provide a spectacular direct evidence for the low scale models. We demonstrate how the observation of neutrinos from SN1987A constrains the symmetry breaking scale of the above models. We also discuss how current and future experiments may confirm or further constrain the above models, either by detecting the ``accumulative resonance'' that diffuse SRN go through or via a large suppression of the flux of neutrinos from nearby (Mpc) SN bursts.
Acoustic Radiation From Bending Waves of a Plate

In the commonly used definition of acoustic “radiation efficiency” of a plate, it is assumed that the amplitude of a traveling harmonic wave on the plate is kept constant, independent of the acoustic radiation load on the plate. As a result, this definition leads to an infinite value of the radiation efficiency when there is coincidence between the speed U of the traveling wave and the sound speed c in the surrounding fluid. The result of infinite radiation efficiency can be avoided if we consider the more realistic situation in which the plate is driven by a traveling force distribution, in which the amplitude of the force rather than the displacement is independent of the radiation load. This situation is considered here, and a modified definition of radiation efficiency is proposed. The displacement amplitude of the plate will have a maximum when the speed U of the force distribution equals the speed c b of free running bending wave on the plate. Then, if U c , the bulk of the power goes into the plane wave radiated from the plate. Finally, if U → c , the displacement and radiated power → 0 since the radiation impedance → ∞. In regard to the role of the viscothermal effects, it is interesting to find that at the coincidence frequency the contributions to the reactive part of the load impedance on the plate from the viscothermal boundary layer and the viscothermal losses in the bulk of the surrounding fluid almost cancel each other and the contributions to the resistive load are approxiamtely equal when U ∼ c .
Effect of bilayer thickness on membrane bending rigidity.

The bending rigidity kc of bilayer vesicles self-assembled from amphiphilic diblock copolymers has been measured using single- and dual-micropipet techniques. These copolymers are nearly a factor of 5 greater in hydrophobic membrane thickness d than their lipid counterparts and an order of magnitude larger in molecular weight Mn. The macromolecular structure of these amphiphiles lends insight into and extends relationships for traditional surfactant behavior. We find the scaling of kc with thickness to be nearly quadratic, in good agreement with existing theories for bilayer membranes. The results here are key to understanding and designing soft interfaces such as biomembrane mimetics.
Investment under Uncertainty in Dynamic Conflicts

This paper analyses a model in which two groups repeatedly compete with each other for a prize in every time period. We assume that there is a status quo bias: if there is a fight today, yesterday's winner is in a stronger position than the other group. Hence, a change of the status quo has long-term consequences that groups need to take into account. Important applications of this model include lobbying for legislation and political transitions through revolutions. We analyse the strategic timing of attacks on the status quo, which is similar to investment decisions under uncertainty. We find that the attack threshold is considerably lower than in a comparable one-period game, and that the expenditure level necessary to change the status quo is low in comparison to the prize; this provides a possible solution to Tullock's “rent-seeking paradox” in lobbying. Copyright 2006, Wiley-Blackwell.
Visualizing Keyboard Pattern Passwords

Passwords are fundamental security vulnerabilities in many systems. Several researchers have investigated the trade-off between password memorability versus resiliency to cracking and have looked at alternative systems such as graphical passwords and biometrics. To create stronger passwords, many systems enforce rules regarding the required length and types of characters passwords must contain. Another suggested approach is to use passphrases to combat dictionary attacks. One common ‘trick’ used to remember passwords that conform to complex rules is to select a pattern of keys on the keyboard. Although appearing random, the pattern is easy to remember. The purpose of this research was to investigate how often patterns are used, whether patterns could be classified into common categories, and whether those categories could be used to attack and defeat pattern-based passwords. Visualization techniques were used to collect data and assist in pattern categorization. The approach successfully identified 2 out ...
Effects of errors in the solar radius on helioseismic inferences

ABSTRA C T Frequencies of intermediate-degree f modes of the Sun seem to indicate that the solar radius is smaller than what is normally used in constructing solar models. We investigate the possible consequences of an error in radius on results for solar structure obtained using helioseismic inversions. It is shown that solar sound speed will be overestimated if oscillation frequencies are inverted using reference models with a larger radius. Using solar models with a radius of 695.78 Mm and new data sets, the base of the solar convection zone is estimated to be at a radial distance of 0:7135 6 0:0005 of the solar radius. The helium abundance in the convection zone as determined using models with an OPAL equation of state is 0:248 6 0:001, where the errors reflect the estimated systematic errors in the calculation, the statistical errors being much smaller. Assuming that the OPAL opacities used in the construction of the solar models are correct, the surface Z=X is estimated to be 0:0245 6 0:0006.
Analysis for leakage and rotordynamic coefficients of surface-roughened tapered annular gas seals

The present analysis calculates the leakage and rotor-dynamic coefficients for tapered annular gas seals whose rotor and stator have been subjected to different surface roughness treatments. The analysis is demonstrated for the effects of changes in the Space Shuttle Main Engine High Pressure Oxygen Turbopump's turbine interstage seal length, taper, clearance, and fluid prerotation. It is noted that changes in these parameters generally resulted in major changes in leakage and rotordynamic coefficients.
XTAG system: a wide coverage grammar for English

This paper present the XTAG system, a grammar development tool based on the Tree Adjoining Grammar (TAG) formalism that includes a wide-coverage syntactic grammar for English. The various components of the system are discussed and preliminary evaluation results from the parsing of various corpora are given. Results from the comparison of XTAG against the IBM statistical parser and the Alvey Natural Language Tool parser are also given.
Error analysis for circle fitting algorithms

We study the problem of fitting circles (or circular arcs) to data points observed with errors in both variables. A detailed error analysis for all popular circle fitting methods – geometric fit, Kasa fit, Pratt fit, and Taubin fit – is presented. Our error analysis goes deeper than the traditional expansion to the leading order. We obtain higher order terms, which show exactly why and by how much circle fits differ from each other. Our analysis allows us to construct a new algebraic (non-iterative) circle fitting algorithm that outperforms all the existing methods, including the (previously regarded as unbeatable) geometric fit.
The impact of prior heart failure hospitalizations on long-term mortality differs by baseline risk of death.

Abstract Background Hospitalizations for decompensated heart failure (HF) are thought to increase long-term mortality. However, previous reports focus on newly hospitalized HF patients or clinical trial populations and do not always adjust for baseline mortality risk. We hypothesized that the number of HF hospitalizations within the prior 12 months would improve overall mortality risk stratification, particularly in otherwise "low-risk" HF inpatients. Methods We studied 2221 HF patients admitted to 14 Michigan community hospitals during 2002-2004. We estimated 1-year mortality using the multivariable (Enhanced Feedback For Effective Cardiac Treatment [EFFECT]) model and classified patients as low (EFFECT 120). We used logistic regression and stratified Cox proportional hazard modeling to explore the overall EFFECT model performance and the influence of HF hospitalizations within the prior 12 months on mortality risk. Results The EFFECT model adequately predicted and stratified for 1-year mortality (odds ratio 1.35 [95% confidence interval (CI), 1.30-1.40] per 10 points, P P =.04). However, in low-risk patients the number of prior HF hospitalizations progressively increased the hazard for 1-year mortality (none: mortality 13%; 1: mortality 20%, hazard ratio [HR] 1.50 (95% CI, 0.86-2.60), P =.15; 2 or 3: mortality 27%, HR 2.24 (95% CI, 1.39-3.60); P =.001; 4 or more: mortality 31%, HR 2.80 (95% CI, 1.70-4.63); P P Conclusion In otherwise "low-risk" HF inpatients, a history of 2 or more HF hospitalizations within the prior 12 months markedly increases 1-year mortality risk. This easily obtained information could help allocate specialized HF resources to the subset of "low-risk" patients most likely to benefit.
Selective Cleavage of Carboxylic Esters in the Presence of Monosubstituted Malonates

Abstract Aliphatic carboxylic esters containing in the molecule a malonate moiety with an α-hydrogen undergo selective cleavage in the presence of potassium tertbutoxide in wet tetrahydrofuran. Dedicated to Professor Paul Dowd on the occasion of his 60th birthday.
O6-(benzotriazol-1-yl)inosine derivatives: easily synthesized, reactive nucleosides.

A novel class of O6-(benzotriazol-1-yl)inosine as well as the corresponding 2‘-deoxy derivatives can be conveniently prepared by a reaction between sugar-protected or -unprotected inosine or 2‘-deoxyinosine nucleosides and 1H-benzotriazol-1-yloxy-tris(dimethylamino)phosphonium hexafluorophosphate (BOP). The reaction appears to proceed via a nucleoside phosphonium salt, and in the absence of any additional nucleophile, the released 1-hydroxybenzotriazole undergoes reaction with the formed phosphonium salt leading to the requisite O6-(benzotriazol-1-yl)inosine or 2‘-deoxyinosine derivatives. Isolation and characterization of the phosphonium salt as well as analysis by 31P{1H} NMR appear to be consistent with this reaction pathway. The resulting O6-(benzotriazol-1-yl)inosine derivatives are effective as electrophilic nucleosides, undergoing facile reactions with a variety of nucleophiles such as alcohols, phenols, amines, and a thiol. Unusual and challenging nucleoside derivatives such as an aryl-bridged dim...
Dark energy: The observational challenge

Abstract Nearly all proposed tests for the nature of dark energy measure some combination of four fundamental observables: the Hubble parameter H ( z ), the distance-redshift relation d ( z ), the age-redshift relation t ( z ), or the linear growth factor D 1 ( z ). I discuss the sensitivity of these observables to the value and redshift history of the equation of state parameter w , emphasizing where these different observables are and are not complementary. Demonstrating time-variability of w is difficult in most cases because dark energy is dynamically insignificant at high redshift. Time-variability in which dark energy tracks the matter density at high redshift and changes to a cosmological constant at low redshift is relatively easy to detect. However, even a sharp transition of this sort at z c = 1 produces only percent-level differences in d ( z ) or D 1 ( z ) over the redshift range 0.4 ⩽ z ⩽ 1.8, relative to the closest constant- w model. Estimates of D 1 ( z ) or H ( z ) at higher redshift, potentially achievable with the Ly α forest, galaxy redshift surveys, and the CMB power spectrum, can add substantial leverage on such models, given precise distance constraints at z d ( z ) directly, and of weak gravitational lensing, which is sensitive to d ( z ), D 1 ( z ), and H ( z ).
Stein's lemma, Malliavin calculus, and tail bounds, with application to polymer fluctuation exponent

Abstract We consider a random variable X satisfying almost-sure conditions involving G : = 〈 D X , − D L − 1 X 〉 where D X is X ’s Malliavin derivative and L − 1 is the pseudo-inverse of the generator of the Ornstein-Uhlenbeck semigroup. A lower- (resp. upper-) bound condition on G is proved to imply a Gaussian-type lower (resp. upper) bound on the tail P [ X > z ] . Bounds of other natures are also given. A key ingredient is the use of Stein’s lemma, including the explicit form of the solution of Stein’s equation relative to the function 1 x > z , and its relation to G . Another set of comparable results is established, without the use of Stein’s lemma, using instead a formula for the density of a random variable based on G , recently devised by the author and Ivan Nourdin. As an application, via a Mehler-type formula for G , we show that the Brownian polymer in a Gaussian environment, which is white-noise in time and positively correlated in space, has deviations of Gaussian type and a fluctuation exponent χ = 1 / 2 . We also show this exponent remains 1 / 2 after a non-linear transformation of the polymer’s Hamiltonian.
A combined light sheet fluorescence and differential interference contrast microscope for live imaging of multicellular specimens

We describe a microscope capable of both light sheet fluorescence microscopy and differential interference contrast microscopy (DICM). The two imaging modes, which to the best of our knowledge have not previously been combined, are complementary: light sheet fluorescence microscopy provides three-dimensional imaging of fluorescently labelled components of multicellular systems with high speed, large fields of view, and low phototoxicity, whereas differential interference contrast microscopy reveals the unlabelled neighbourhood of tissues, organs, and other structures with high contrast and inherent optical sectioning. Use of a single Nomarski prism for differential interference contrast microscopy and a shared detection path for both imaging modes enables simple integration of the two techniques in one custom microscope. We provide several examples of the utility of the resulting instrument, focusing especially on the digestive tract of the larval zebrafish, revealing in this complex and heterogeneous environment anatomical features, the behaviour of commensal microbes, immune cell motions, and more.
High-pressure U3O8 with the fluorite-type structure

A new high-pressure phase of U3O8, which has a fluorite-type structure, forms at pressures greater than � 8.1 GPa that was confirmed by in situ x-ray diffraction (XRD) measurements. The fluorite-type U3O8 is stable at pressures at least up to � 40 GPa and temperatures to 1700 K, and quenchable to ambient conditions. Based on the XRD analysis, there is a huge volume collapse (420%) for U3O8 during the phase transition and the quenched high-pressure phase is 28% denser than the initial orthorhombic phase at ambient conditions. The high-pressure phase has a very low compressibility comparing with the starting orthorhombic phase.
Feature Detection in Highly Noisy Images using Random Sample Theory

A novel feature detection algorithm utilizing random sample theory is proposed for 2D and 3D images. The proposed method works on both binary and gray-scale images and yields faster results than standard feature detection algorithms, such as the Hough Transform (HT), while keeping the performance level of HT. The proposed method creates random hypothesis features and tests them to select candidate features in the image. The selected candidate features are then re-estimated within a smaller search space around the candidate feature. The proposed algorithm has been tested on both simulated and experimental subsurface seismic and GPR images to locate linear features like pipes or tunnels. Results show that the proposed algorithm can detect features accurately and much faster than conventional methods.
Synthesis and reactions of fluorous carbobenzyloxy (FCbz) derivatives of α-amino acids

Fluorous carbobenzyloxy (FCbz) reagents RfCH2CH2C6H4CH2OC(O)OSu (where Su is succinimidoyl and Rf is C6F13 and C8F17) have been used to make FCbz derivatives of 18 of the 20 natural amino acids. The potential utility of this new family of reagents in both standard fluorous synthesis with spe separation and fluorous quasiracemic synthesis is illustrated with representative reactions of the FCbz-Phe derivatives.
A superior catalyst for low-temperature NO reduction with NH3

Mn-Ce mixed-oxide catalyst yields nearly 100% NO conversion at 100–150 °C at a high space velocity of 42,000 h−1. SO2 and H2O (at high concentrations) have only slight effects on the activity.
Mechanism of Spontaneous Formation of Stable Magnetic Structures on the Sun

One of the puzzling features of solar magnetism is formation of long-living compact magnetic structures, such as sunspots and pores, in the highly turbulent upper layer of the solar convective zone. We use realistic radiative three-dimensional MHD simulations to investigate the interaction between magnetic field and turbulent convection. In the simulations, a weak vertical uniform magnetic field is imposed in a region of fully developed granular convection, and the total magnetic flux through the top and bottom boundaries is kept constant. The simulation results reveal a process of spontaneous formation of stable magnetic structures, which may be a key to understanding the magnetic self-organization on the Sun and formation of pores and sunspots. This process consists of two basic steps: (1) formation of small-scale filamentary magnetic structures associated with concentrations of vorticity and whirlpool-type motions, and (2) merging of these structures due to the vortex attraction, caused by converging downdrafts around magnetic concentration below the surface. In the resulting large-scale structure maintained by the converging plasma motions, the magnetic field strength reaches ~1.5 kG at the surface and ~6 kG in the interior, and the surface structure resembles solar pores. The magnetic structure remains stable for the whole simulation run of several hours with no sign of decay.
Results on the Standard Error of the Coefficient Alpha Index of Reliability

In this research, we investigate the behavior of Cronbach's coefficient alpha and its new standard error. We systematically analyze the effects of sample size, scale length, strength of item intercorrelations, and scale dimensionality. We demonstrate the beneficial effects of sample size on alpha's standard error and of scale length and the strengths of item intercorrelations (effects that are substitutes in their benefits) on both alpha and its standard error. Our findings also speak to this adage: Heterogeneity within the item covariance matrix (e.g., through multidimensionality or poor items) negatively impacts reliability by decreasing the precision of the estimation. We also examined the question of "equilibrium" scale length, showing the conditions for which it is optimal to add no items, or one, or multiple items to a scale. In terms of "best practices," we recommend that researchers report a confidence interval or standard error along with the coefficient alpha point estimate.
svviz: a read viewer for validating structural variants

UNLABELLED Visualizing read alignments is the most effective way to validate candidate structural variants (SVs) with existing data. We present svviz, a sequencing read visualizer for SVs that sorts and displays only reads relevant to a candidate SV. svviz works by searching input bam(s) for potentially relevant reads, realigning them against the inferred sequence of the putative variant allele as well as the reference allele and identifying reads that match one allele better than the other. Separate views of the two alleles are then displayed in a scrollable web browser view, enabling a more intuitive visualization of each allele, compared with the single reference genome-based view common to most current read browsers. The browser view facilitates examining the evidence for or against a putative variant, estimating zygosity, visualizing affected genomic annotations and manual refinement of breakpoints. svviz supports data from most modern sequencing platforms. AVAILABILITY AND IMPLEMENTATION svviz is implemented in python and freely available from http://svviz.github.io/.
The Proper Scope of Government: Theory and an Application to Prisons

When should a government provide a service in-house, and when should it contract out provision? We develop a model in which the provider can invest in improving the quality of service or reducing cost. If contracts are incomplete, the private provider has a stronger incentive to engage in both quality improvement and cost reduction than a government employee has. However, the private contractor's incentive to engage in cost reduction is typically too strong because he ignores the adverse effect on noncontractible quality. The model is applied to understanding the costs and benefits of prison privatization.
Spectral Irradiance Calibration in the Infrared. XIV. The Absolute Calibration of 2MASS

Element by element, we have combined the optical components in the three cameras of the Two Micron All Sky Survey (2MASS), and incorporated detector quantum efficiency curves and site-specific atmospheric transmissions, to create three relative spectral response curves (RSRs). We provide the absolute 2MASS attributes associated with "zero magnitude" in the JHKs bands so that these RSRs may be used for synthetic photometry. The RSRs tie 2MASS to the "Cohen-Walker-Witteborn" framework of absolute photometry and stellar spectra for the purpose of using 2MASS data to support the development of absolute calibrators for the Infrared Array Camera and pairwise cross-calibrators between all three SIRTF instruments. We examine the robustness of these RSRs to changes in water vapor within a night. We compare the observed 2MASS magnitudes of 33 stars (converted from the precision optical calibrators of Landolt and Carter-Meadows into absolute infrared calibrators from 1.2 to 35 μm) with our predictions, thereby deriving 2MASS "zero-point offsets" from the ensemble. These offsets are the final ingredients essential to merge 2MASS JHKs data with our other absolutely calibrated bands and stellar spectra, and to support the creation of faint calibration stars for SIRTF.
Postsynthetic modification of metal–organic frameworks—a progress report

Metal–organic frameworks (MOFs) are an important class of hybrid inorganic–organic materials. In this tutorial review, a progress report on the postsynthetic modification (PSM) of MOFs is provided. PSM refers to the chemical modification of the MOF lattice in a heterogeneous fashion. This powerful synthetic approach has grown in popularity and resulted in a number of advances in the functionalization and application of MOFs. The use of PSM to develop MOFs with improved gas sorption, catalytic activity, bioactivity, and more robust physical properties is discussed. The results reported to date clearly show that PSM is an important approach for the development and advancement of these hybrid solids.
Assessing regional trading arrangements in the Asia-Pacific

Using both a gravity model to consider the natural trading bloc hypothesis and simulation using a computer generated equilibrium (CGE) model to make welfare estimates, this publication examines the potential effect of a subset of the new regional trading arrangement (RTA) proposal in the Asia Pacific Economic Cooperation region. The objective of this paper is to see to what extent the predictions from these two disparate techniques can be correlated in the context of the new Asia-Pacific proposals.
Macronutrients, cholesterol, sodium and fiber intakes of 1-10 year old children by age, gender and race

Abstract Intakes of energy, macronutrients, cholesterol, sodium and dietary fiber were evaluated among 1–10 year old US children stratified by age, gender and race. The USDA's 1989–1991 Continuing Survey of Food Intakes by Individuals (CSFII) data sets supplied the study sample. Caregivers of 1,895 children residing in the 48 conterminous states provided one 24-hour recall and two 1-day food records to describe the children's dietary intake. Blacks compared to Whites and females compared to males consumed less energy. Children consumed 46–52%, 15–17%, 34–38%, 13–15%, 5–6%, 12–15% of energies from carbohydrates, proteins, fats, saturated fat, polyunsaturated fat and monounsaturated fat, respectively. Intakes of fat, saturated fat and cholesterol (mg/1000 Kcal) exceeded current recommendations. Intake ratio of polyunsaturated fat to saturated fat was lower than recommendation. Cholesterol intakes were higher and dietary fiber intakes were lower among Blacks compared to Whites. Dietary patterns of children were less favorable for cardiovascular health. To achieve recommended intake patterns, significant modifications are needed in children's diets concerning fat, sodium and fiber.
What can we learn about financial access from U.S. immigrants? : the role of country of origin institutions and immigrant beliefs

Immigrants from countries with more effective institutions are more likely than other immigrants to have a relationship with a bank and to use formal financial markets more extensively. The evidence that a country's institutional environment shapes beliefs and by extension the use of financial services provides support for policies that focus on institutional reforms in promoting financial access. After holding wealth, education, and other factors constant, the impact of institutional quality in the country of origin affects the financial market participation of all immigrant groups except those who have lived in the United States for more than 28 years. These findings are robust to alternative measures of institutional effectiveness, to controlling for additional country of origin characteristics, and to various methods for addressing potential biases caused by immigrant self-selection.