cssi/SciSciGPT-SciSciNet huggingface dataset:
Discovery of a Magnetic White Dwarf in the Symbiotic Binary Z Andromedae

We report the first result from our survey of rapid variability in symbiotic binaries: the discovery of a persistent oscillation at P=1682.6 ± 0.6 s in the optical emission from the prototype symbiotic Z Andromedae. The oscillation was detected on all eight occasions on which the source was observed over a time span of nearly 1 yr, making it the first such persistent periodic pulse found in a symbiotic binary. The amplitude was typically 2-5 mmag, and it was correlated with the optical brightness during a relatively small outburst of the system. The most natural explanation is that the oscillation arises from the rotation of an accreting magnetic (BS105G) white dwarf. This discovery constrains the outburst mechanisms, since the oscillation emission region near the surface of the white dwarf was visible during the outburst.
Spatial Variation in an Algal Turf Community with Respect to Substratum Slope and Wave Height

A mid-shore colonial algal turf community is described. Samples were analysed to determine if species composition, invertebrate epiphyte density, algal mat biomass, and the amount of sediment trapped among algal thalli differed with respect to substratum slope and wave height.Colonial algal turf was approximately 1–3 cm in height and predominantly composed of a mixture of four species of eurythermal red algae, including Gelidium crinale (Turner) Lamouroux (Rhodophyceae: Gelidiales), Centroceras clavulatum (C. Agardh) Montagne, Polysiphonia denudata (Dillwyn) Kuetzing, and Bryocladia cuspidata (J. Agardh) De Toni (Rhodophyceae: Ceramiales). More delicate algae and algal epiphytes were found at stations with lower mean wave height, while non-epiphytic coralline algae were found only at stations with higher mean wave height. Algal mat mass was significantly greater on horizontal slopes than on vertical slopes, but did not differ with respect to wave-height levels. Algal mats trapped significantly more sediment on horizontal slopes with lower mean wave height.Densities of the three most abundant invertebrate epiphytes appeared to be related to sediment deposition. Like sedimentation patterns, disparities in population densities on different substratum slopes increased with lower mean wave height. The highest densities of the amphipods Elasmopus rapax Costa and Hyale frequens Haswell (Crustacea: Peracarida) occurred on horizontal slopes at stations with significantly lower mean wave height. The highest densities of the tree oyster Isognomon bicolor C.B. Adams (Mollusca: Pterioida) were on vertical slopes at stations with significantly lower mean wave height. Barnacle epiphytes occurred in higher densities at stations receiving greater mean wave height, while dominant species of other crustaceans and molluscs had higher densities at stations with significantly lower mean wave height.
Social search and discovery using a unified approach

We explore new ways of improving a search engine using data from Web 2.0 applications such as blogs and social bookmarks. This data contains entities such as documents, people and tags, and relationships between them. We propose a simple yet effective method, based on faceted search, that treats all entities in a unified manner: returning all of them (documents, people and tags) on every search, and allowing all of them to be used as search terms. We describe an implementation of such a social search engine on the intranet of a large enterprise, and present large-scale experiments which verify the validity of our approach.
Rateless Codes for AVC Models

The arbitrarily varying channel (AVC) is a channel model whose state is selected maliciously by an adversary. Fixed-blocklength coding assumes a worst-case bound on the adversary's capabilities, which leads to pessimistic results. This paper defines a variable-length perspective on this problem, for which achievable rates are shown that depend on the realized actions of the adversary. Specifically, rateless codes are constructed which require a limited amount of common randomness. These codes are constructed for two kinds of AVC models. In the first the channel state cannot depend on the channel input, and in the second it can. As a by-product, the randomized coding capacity of the AVC with state depending on the transmitted codeword is found and shown to be achievable with a small amount of common randomness. The results for this model are proved using a randomized strategy based on list decoding.
Crystal Chemistry of Perovskite-Type Hydride NaMgH3: Implications for Hydrogen Storage

The crystal structure, lattice dynamics, and local metal-hydrogen bonding of the perovskite hydride NaMgH3 were investigated using combined neutron powder diffraction, neutron vibrational spectroscopy, and first-principles calculations. NaMgH3 crystallizes in the orthorhombic GdFeO3-type perovskite structure (Pnma) with a - b + a - octahedral tilting in the temperature range of 4 to 370 K. In contrast with previous structure studies, the refined Mg-H lengths and H-Mg-H angles indicate that the MgH6 octahedra maintain a near ideal configuration, which is corroborated by bond valence methods and our DFT calculations, and is consistent with perovskite oxides with similar tolerance factor values. The temperature dependences of the lattice distortion, octahedral tilting angle, and atomic displacement of H are also consistent with the recently observed high H mobility at elevated temperature. The stability and dynamics of NaMgH3 are discussed and rationalized in terms of the details of our observed perovskite structure. Further experiments reveal that its perovskite crystal structure and associated rapid hydrogen motion can be used to improve the slow hydrogenation kinetics of some strongly bound light-metal-hydride systems such as MgH2 and possibly to design new alloy hydrides with desirable hydrogen-storage properties.
Control constraints, abnormality, and improved performance by periodic control

Second-order conditions for steady-state optimality and nonoptimality in a periodic control problem are presented. The main result is a generalization of the π test, a second-order sufficient condition for improved performance by periodic control. Earlier results are generalized in two distinct ways: 1) the control constraint set is only assumed to be convex (and, hence, possibly nonopen) thus allowing the optimal steady-slate control to be an element of the control constraint set boundary; and 2) auxiliary normality conditions are eliminated. Proofs of the results are based upon second-order necessary, conditions for nonlinear programming and optimal control obtained recently in [43] and [44].
Synthesis of the tetracyclic core of the bisabosquals

Abstract HCl-catalyzed deprotection and cyclization of 8b provided tricycle 9b cleanly. Epoxidation of 9b afforded tetracycle 13 with the wrong stereochemistry at the tertiary alcohol. Selective elimination of the tertiary alcohol to give the exocyclic methylene compound, alkene cleavage to form the ketone with OsO 4 and NaIO 4 , and addition of MeMgBr to the ketone from the least hindered face gave tertiary alcohol 16 with the tetracyclic core of bisabosqual A ( 1 ).
AdS / CFT correspondence and topological field theory

In = 4 super Yang-Mills theory on a four-manifold M, one can specify a discrete magnetic flux valued in H2(M,N). This flux is encoded in the AdS/CFT correspondence in terms of a five-dimensional topological field theory with Chern-Simons action. A similar topological field theory in seven dimensions governs the space of ``conformal blocks'' of the six-dimensional (0,2) conformal field theory.
Underwater Microscope for Measuring Spatial and Temporal Changes in Bed-Sediment Grain Size

For more than a century, studies of sedimentology and sediment transport have measured bed-sediment grain size by collecting samples and transporting them back to the laboratory for grain-size analysis. This process is slow and expensive. Moreover, most sampling systems are not selective enough to sample only the surficial grains that interact with the flow; samples typically include sediment from at least a few centimeters beneath the bed surface. New hardware and software are available for in situ measurement of grain size. The new technology permits rapid measurement of surficial bed sediment. Here we describe several systems we have deployed by boat, by hand, and by tripod in rivers, oceans, and on beaches. Published by Elsevier B.V.
Application of Cost Matrices and Cost Curves to Enhance Diagnostic Health Management Metrics for Gas Turbine Engines

Statistically based metrics, incorporating operating costs, for gas turbine engine diagnostic systems are required to evaluate competing products fairly and to establish a convincing business case. Diagnostic algorithm validation often includes engine testing with implanted faults. The implantation rate is rarely, if ever, representative of the true fault occurrence rate and the sample size is very small. Costs related to diagnostic outcomes have a significant effect on the utility of a given algorithm and need to be incorporated into the assessment. Techniques for assessing diagnostics are drawn from the literature and modified for application to gas turbine applications. The techniques are modified with computational experiments and the application demonstrated through examples. New techniques are compared to the traditional methods and the advantages presented. A technique is presented to convert a confusion matrix with a non-representative fault distribution to one representative of the expected distribution. The small sample size associated with fault implantation studies requires a confidence interval on the results to provide valid comparisons and a method for calculating confidence intervals, including on zero entries, is presented. Receiver operating characteristic (ROC) curves evaluate diagnostic system performance across a range of threshold settings. This allows an algorithm’s ability to be assessed over a range of possible usage. Cost curves are analogous to ROC curves but offer several advantages. The techniques for applying cost curves to diagnostic algorithms are presented and their advantages over ROC curves are outlined. This paper provides techniques for more informed comparison of diagnostic algorithms, possibly preventing incorrect assessment due to small sample sizes.
Quinoline and acridine templates in selective steroid chlorinations

Abstract Steroid esters of quinoline and acridine carboxylic acids can undergo template directed delivery of chlorine atoms to a particular steroid hydrogen even though chlorination selectivity studies with 2,3-dimethylbutane suggest that the bonding in the chlorine complex is probably different from that with pyridine templates.
Using Reproductive Altruism to Evolve Multicellularity in Digital Organisms

The processes by which multicellular organismsfirst emerged from their unicellular ancestors are fundamental to the biology of complex, differentiated life forms. Previous work suggests that reproductive division of labor between specialized germ and soma cells was central to this evolution in some cases. Here, we assess the potential of the digital life platform Avida to examine the trade-off between survival and replication in multicellular organisms. Avida uses a grid of selfreplicating computer programs capable of mutation and evolution to address biological questions computationally. We model our digital organisms after the Volvocales, a flagellated order of photosynthetic green algae that includes both unicellular and multicellular species. We show that, given selective pressures similar to those experienced by the Volvocales in nature, digital organisms are capable of evolving multicellularity within the Avida platform. The strategies we observed that best handled the trade-off between survival and replication involved germ cells producing sterile, somatic offspring. These strategies are similar to those observed in volvocine algae, which suggests that digital platforms, such as Avida, are appropriate to use in the study of reproductive altruism.
Nutrients stimulate leaf breakdown rates and detritivore biomass: bottom-up effects via heterotrophic pathways

Most nutrient enrichment studies in aquatic systems have focused on autotrophic food webs in sys- tems where primary producers dominate the resource base. We tested the heterotrophic response to long- term nutrient enrichment in a forested, headwater stream. Our study design consisted of 2 years of pre- treatment data in a reference and treatment stream and 2 years of continuous nitrogen (N) + phosphorus addition to the treatment stream. Studies were con- ducted with two leaf species that diVered in initial C:N, Rhododendron maximum (rhododendron) and Acer rubrum (red maple). We determined the eVects of nutrient addition on detrital resources (leaf breakdown rates, litter C:N and microbial activity) and tested whether nutrient enrichment aVected macroinverte- brate consumers via increased biomass. Leaf break- down rates were ca. 1.5 and 3£ faster during the Wrst and second years of enrichment, respectively, in the treatment stream for both leaf types. Microbial respira- tion rates of both leaf types were 3£ higher with enrichment, and macroinvertebrate biomass associated with leaves increased ca. 2-3£ with enrichment. The mass of N in macroinvertebrate biomass relative to leaves tended to increase with enrichment up to 6£ for red maple and up to 44£ for rhododendron leaves. Lower quality (higher C:N) rhododendron leaves exhibited greater changes in leaf nutrient content and macroinvertebrate response to nutrient enrichment than red maple leaves, suggesting a unique response by diVerent leaf species to nutrient enrichment. Nutrient concentrations used in this study were moderate and equivalent to those in streams draining watersheds with altered land use. Thus, our results suggest that similarly moderate levels of enrichment may aVect detrital resource quality and subsequently lead to altered energy and nutrient Xow in detrital food webs.
Cu(II)-Catalyzed Functionalizations of Aryl C−H Bonds Using O2 as an Oxidant

Cu(II)-catalyzed acetoxylation and halogenation of aryl C−H bonds are developed. ortho-Selectivity was observed with a wide range of 2-arylpyridine substrates. Both mono- and difunctionalizations are achieved by tuning the reaction conditions. Excellent functional group tolerance and use of O2 as a stoichiometric oxidant are significant advantages over our recently developed Pd-catalyzed C−H functionalization reactions. These newly discovered reaction conditions are also applicable for cyanation, amination, etherification, and thioetherification of aryl C−H bonds. Mechanistic investigations are carried out to gain insights into the Cu(II)-catalyzed C−H functionalization reactions.
A problem with Euclidean preferences in spatial models of politics

Abstract Euclidean public sector preferences can not be induced from a strictly quasiconcave primitive utility function and a linear constraint.
When environmental chemicals act like uncontrolled medicine

In the same way as medicines are delivered to produce effects in the endocrine system, environmental chemicals can be similarly delivered to produce unwanted endocrine effects, resulting in a staggering increase in several diseases. These effects on endocrine and other physiological systems can have significant population-level impacts and thus require public health approaches to disease control.
Demand-side management implications of electrically-based manufacturing technologies

Abstract The energy consequences of 17 industrial electrotechnologies are considered in the context of 14 2-digit SIC (Standard Industrial Classification) industries as a basis for utility demand-side management decision making. A matrix of electrotechnology-industry application combinations is presented in which each entry falls into one of four categories: 1. (i) increased electricity and primary fuel use, but with positive impact on other production factors, 2. (ii) decreased electricity use with negligible end-use fossil fuel impact, 3. (iii) increased electricity use but reduced primary fuel use, and 4. (iv) decreased electricity and primary fuel use. Examples are presented and energy impacts calculated for several cases to illustrate the tradeoffs involved in electrotechnology process substitution. The implications of these tradeoffs in terms of utility demand-side management program strategies are discussed.
Discovery of spin glass behavior in Ln2Fe4Sb5 (Ln = La-Nd and Sm).

Single crystals of Ln2Fe4Sb5 (Ln = La–Nd and Sm) were grown from an inert Bi flux. Measurements of the single crystal X-ray diffraction revealed that these compounds crystallize in the tetragonal space group I4/mmm with lattice parameters of a ≈ 4 A, c ≈ 26 A, V ≈ 500 A3, and Z = 2. This crystal structure consists of alternating LnSb8 square antiprisms and Fe-sublattices composed of nearly equilateral triangles of bonded Fe atoms. These compounds are metallic and display spin glass behavior, which originates from the magnetic interactions within the Fe-sublattice. Specific heat measurements are void of any sharp features that can be interpreted as contributions from phase transitions as is typical for spin glass systems. A large, approximately linear in temperature, contribution to the specific heat of La2Fe4Sb5 is observed at low temperatures that we interpret as having a magnetic origin. Herein, we report the synthesis, structure, and physical properties of Ln2Fe4Sb5 (Ln = La–Nd and Sm).
Shell Model the Monte Carlo Way

The formalism for the auxiliary-field Monte Carlo approach to the nuclear shell model is presented. The method is based on a linearization of the two-body part of the Hamiltonian in an imaginary-time propagator using the Hubbard-Stratonovich transformation. The foundation of the method, as applied to the nuclear many-body problem, is discussed. Topics presented in detail include: (1) the density-density formulation of the method, (2) computation of the overlaps, (3) the sign of the Monte Carlo weight function, (4) techniques for performing Monte Carlo sampling, and (5) the reconstruction of response functions from an imaginary-time auto-correlation function using MaxEnt techniques. Results obtained using schematic interactions, which have no sign problem, are presented to demonstrate the feasibility of the method, while an extrapolation method for realistic Hamiltonians is presented. In addition, applications at finite temperature are outlined.
Convection and AGN Feedback in Clusters of Galaxies

A number of studies have shown that the convective stability criterion for the intracluster medium (ICM) is very differentfromtheSchwarzchildcriterion,duetotheeffectsofanisotropicthermalconductionandcosmicrays.Buildingonthesestudies,wedevelopamodeloftheICMinwhichacentralactivegalacticnucleus(AGN)accreteshotintracluster plasma at the Bondi rate and produces cosmic rays that cause the ICM to become convectively unstable. The resulting convection heats the intracluster plasma and regulates its temperature and density profiles. By adjusting a single parameter in the model (the size of the cosmic-ray acceleration region), we are able to achieve a good match to the observed density and temperature profiles in a sample of eight clusters. Our results suggest that convection is an important process in cluster cores. An interesting feature of our solutions isthat the cooling rate is more sharply peaked abouttheclustercenterthanistheconvectiveheatingrate.Asaresult,inseveraloftheclustersinoursample,acompact coolingflowarisesinthecentralregionwithasizercf thatistypicallyafewkpc.ThecoolingflowmatchesontoaBondi flow at smaller radii. The mass accretion rate in the Bondi flow is equal to, and controlled by, the rate at which mass flowsinthroughthecoolingflow.Oursolutionssuggest thattheAGNregulatesthemassaccretionrateintheseclusters bycontrollingrcf: if the AGN power rises above the equilibrium level,rcf decreases, the mass accretion rate drops, and the AGN power drops back down to the equilibrium level. Subject headingg convection — cooling flows — galaxies: active — galaxies: clusters: general — magnetic fields — turbulence
Causes of Fertilization Failure in Repeat Breeding Cattle

Abstract One hundred and four ova were recovered from 150 cows (69.3%), and 58 of them were fertilized (55.8% of the ova). The fertilization rate was significantly lower (48.5%) for cows bred during the first eight hours of heat than for those bred 16 hours later (68.6%). Breeding twice during the heat period (during the first eight hours and again 16 hours later) did not improve the fertilization rate (66.7%). Abnormalities causing fertilization failure were as follows: ovulation failure, 8.7% of the cows bred; oviduct obstructions, 6.7%; abnormal ova, 3.3%; ovarian adhesions, 2.0%; and endometritis, 3.3%. Ova could not be found in 17.3% of the cows, even though no abnormalities were apparent to account for their absence. In 24.7% of the cows, there was no apparent explanation for fertilization failure. The presence or absence of bacteria in the cervix and uterus had no effect on fertilization rate. When we studied histological sections of the uteri we found that fertilization rates were somewhat lower for cows having cystic uterine glands, thin mucosae, or endometritis. However, arterial elastosis and mucosal edema did not affect fertilization rates.
A 700-MHz switched-capacitor analog waveform sampling circuit

Analog switched-capacitor memory circuits are suitable for use in a wide range of applications where analog waveforms must be captured or delayed, such as the recording of pulse echo events and pulse shapes. Analog sampling systems based on switched-capacitor techniques offer performance superior to that of flash A/D converters and charge-coupled devices with respect to cost, density, dynamic range, sampling speed, and power consumption. This paper proposes an architecture with which sampling frequencies of several hundred megahertz can be achieved using conventional CMOS technology. Issues concerning the design and implementation of an analog memory circuit based on the proposed architecture are presented. An experimental two-channel memory with 32 sampling cells in each channel has been integrated in a 2-/spl mu/m CMOS technology with poly-to-poly capacitors. The measured nonlinearity of this prototype is 0.03% for a 2.5 V input range, and the memory cell gain matching is 0.01% rms. The dynamic range of the memory exceeds 12 b for a sampling frequency of 700 MHz. The power dissipation for one channel operated from a single +5 V supply is 2 mW. >
On weak relative degree and the McGehee transformation

Points where jumps in relative degree occur are presented as singularities in the vector field of the internal dynamics of systems that are candidates for input-output linearization via nonlinear feedback. For a certain class of vector fields, it is shown that the point at which the relative degree is weak can be transformed to a saddle equilibrium point at the origin. >
Entangled-photon coincidence fluorescence imaging.

We describe fluorescence imaging using the second-order correlation of entangled photon pairs. The proposed method is based on the principle that one photon of the pair carries information on where the other photon has been absorbed and has produced fluorescence in a sample. Because fluorescent molecules serve as “detectors” breaking the entanglement, multiply-scattered fluorescence photons within the sample do not cause image blur. We discuss experimental implementations.
The first synthesis of cyclopropanone acetals from the reaction of Fischer carbene complexes with ketene acetals

The reaction of iso-propoxy stabilized Fischer carbene complexes with ketene acetals gives moderate to excellent yields of cyclopropanone acetals when carried out under a carbon monoxide atmosphere. This is in contrast to the known reaction of methoxy substituted complexes which give cyclic ortho esters under the same conditions. A mechanism is proposed which involves a branch point between the two products as the zwitterionic intermediate resulting from nucleophilic addition of the ketene acetal to the carbene carbon. A 1,3-migration of the methoxyl group to the cationic center leads to the ortho ester and a ring closure by backside attack leads to the cyclopropanone acetal. A double-labeling experiment shows that the 1,3-migration occurs by an intramolecular process that is proposed to involve a bridging oxonium ion. The effect of the isopropoxy group is thus interpreted to be to sterically hinder the formation of a bridged oxonium ion.
Structural chemistry and magnetic properties of RE2[SnxGe1−x]5 (RE = Nd, Sm) and RE[SnxGe1−x]2 (RE = Gd, Tb): Four new rare-earth metal intermetallic compounds with germanium zig-zag chains and tin square-nets

Abstract Four new rare-earth metal tin germanides with general formulae RE2[SnxGe1−x]5 (RE = Nd, Sm; x ≈ 0.25–0.3) and RE[SnxGe1−x]2 (RE = Gd, Tb; x ≈ 0.2–0.25) have been synthesized from the corresponding elements by high temperature reactions using Sn flux. Their structures have been established from single-crystal and powder X-ray crystallography: orthorhombic space group Cmcm (No. 63) with cell parameters a = 4.1057(6) A, b = 35.992(5) A, c = 4.2534(6) A for Nd2[SnxGe1−x]5; a = 4.0707(8) A, b = 35.550(7) A, c = 4.2095(8) A for Sm2[SnxGe1−x]5; a = 4.2248(11) A, b = 30.451(8) A, c = 4.0013(11) A for Gd[SnxGe1−x]2, and a = 4.1936(13) A, b = 30.230(9) A, c = 3.9793(12) A for Tb[SnxGe1−x]2, respectively. The structures of the two families can be described as being stacking variants of the ZrSi2 and DyGe3 types, respectively. They represent another example of site preferences between two group 14 elements, where the lighter Ge atoms preferentially form zig-zag chains while the square sheets (or double square sheets) are made up of Sn atoms, respectively. Magnetic susceptibility measurements show that all of the compounds order antiferromagnetically at low temperatures and their respective ordering temperatures are further corroborated by specific heat measurements.
One-pot oligosaccharide synthesis: reactivity tuning by post-synthetic modification of aglycon

Post-synthetic aglycon modification of substituted aryl thioglycosides led to building blocks with multiple levels of anomeric reactivities, which can be used in rapid assembly of oligosaccharides in one-pot syntheses.
The UCLA AGCM in High Performance Computing Environments

General Circulation Models (GCMs) are at the top of the hierarchy of numerical models that are used to study the Earth's climate. To increase the significance of predictions using GCMs requires ensembles of integrations that in turn demand large amounts of computing resources. GCMs codes are particularly difficult to optimize in view of their heterogeneity. In this paper we focus on code optimization for GCMs of the atmosphere (AGCMs), one of the major components of the climate system. In this paper, we present our efforts in optimizing the parallel UCLA AGCM code. The UCLA AGCM is a state-of-the-art finite-difference model of the global atmosphere. Our optimization efforts include the implementation of load balancing schemes, new physical parameterizations of atmospheric processes, code restructuring and use of special mathematical functions. At the beginning of this work, the overall execution time of the code was 459 seconds per simulated day in 256 nodes of a CRAY T3D. At present, the same model configuration requires 51 seconds per simulated day in 256 nodes of a CRAY T3E-900, which is approximately 9 times faster. The peak model performance is about 40 GFLOPs on 512 T3E-900 nodes. We present results in support of our conclusion that major advances in our ability to carry out longer and more detailed climate simulations depend primarily upon development of more powerful supercomputers and that code optimization, for a particular computer architecture, and development of more efficient algorithms can be nearly as important.
A new approach to strong embeddings

We revisit strong approximation theory from a new perspective, culminating in a proof of the Komlos–Major–Tusnady embedding theorem for the simple random walk. The proof is almost entirely based on a series of soft arguments and easy inequalities. The new technique, inspired by Stein’s method of normal approximation, is applicable to any setting where Stein’s method works. In particular, one can hope to take it beyond sums of independent random variables.
Generalized rewrite theories

Since its introduction, more than a decade ago, rewriting logic has attracted the interest of both theorists and practitioners, who have contributed in showing its generality as a semantic and logical framework and also as a programming paradigm. The experimentation conducted in these years has suggested that some significant extensions to the original definition of the logic would be very useful in practice. In particular, the Maude system now supports subsorting and conditions in the equational logic for data, and also frozen arguments to block undesired nested rewritings; moreover, it allows equality and membership assertions in rule conditions. In this paper, we give a detailed presentation of the inference rules, model theory, and completeness of such generalized rewrite theories.
Effects of UV Illumination on Surface Flashover Under Pulsed Excitation

Undesirable surface flashover of high voltage support structures can severely limit the compactness of open air high voltage systems. Only recently, increased effort has been invested in characterizing and quantifying the physical processes involved in surface flashover occurring under atmospheric conditions and under the influence of UV illumination. In this paper, a UV flash lamp and a solid-state UV source, with its much faster turn-off time, were utilized in conjunction with a high temporal resolution testing apparatus. The UV pulse, excitation voltage, discharge current, and flashover self-luminosity were measured with high temporal precision. We relate recent experiments to our experimental findings of surface flashover under atmospheric conditions gained over the past five years. A simple model that describes the observed behavior will be presented. In addition, a more advanced Monte Carlo-type code for electron collision dynamics will be utilized to further analyze the role of UV in surface flashover under atmospheric conditions.
High-resolution velocity spectra using eigenstructure methods

Stacking spectra provide maximum‐likelihood estimates for the stacking velocity, or for the ray parameter, of well separated reflections in additive white noise. However, the resolution of stacking spectra is limited by the aperture of the array and the frequency of the data. Despite these limitations, parametric spectral estimation methods achieve better resolution than does stacking. To improve resolution, the parametric methods introduce a parsimonious model for the spectrum of the data. In particular, when the data are modeled as the superposition of wavefronts, the properties of the eigenstructure of the data covariance matrix can be used to obtain high‐resolution spectra. The traditional stacking spectra can also be expressed as a function of the data covariance matrix and directly compared to the eigenstructure spectra. The superiority of the latter in separating closely interfering reflections is then apparent from a simple geometric interpretation. Eigenstructure methods were originally developed...
The global 21-centimeter background from high redshifts

We consider the evolution of the sky-averaged 21-cm background during the early phases of structure formation. Using simple analytic models, we calculate the thermal and ionization histories, assuming that stellar photons dominate the radiation background. The resulting 21-cm spectra can constrain the properties of the first generations of stars and quasars. If Population II stars dominate, Lyα coupling renders the intergalactic medium (IGM) visible before it is heated by X-rays and long before reionization. Thus the 21-cm background has a strong absorption epoch followed by weaker emission that fades during reionization. The harder spectra of very massive Population III stars compress these transitions into a shorter time interval and decreases the signal amplitude. However, the reionization epoch will remain visible except in extreme cases. The global 21-cm signal will be challenging to observe because of astronomical foregrounds, but it offers an exciting opportunity to study the first sources of light. It also fixes the overall amplitude of the fluctuating background whose detection is a major goal of several next-generation low-frequency radio interferometers.
Adrian E. Gill 1937–1986

On April 19, Adrian Gill, FRS, my former thesis advisor and distinguished friend, died suddenly of cancer. My sadness and disbelief are more strongly felt because the life of this gifted and generous man ended so early. Born in Melbourne, Australia, Adrian was granted his Ph.D. at Cambridge University, Cambridge, U.K., in 1963. After a year at the Massachusetts Institute of Technology (Cambridge, Mass.), he returned to Cambridge in Britain, where he spent most of the rest of his life. In 1984, he left Cambridge to become director and cofounder of the Hooke Institute in Oxford, U.K. During his career he enjoyed many summers working in the United States.
The J3 SCR Model Applied to Resonant Converter Simulation

The J3 SCR model is a continuous topology computer model for the SCR. Its circuit analog and parameter estimation procedure are uniformly applicable to popular computer-aided design and analysis programs such as SPICE2 and SCEPTRE. The circuit analog is based on the intrinsic three pn junction structure of the SCR. The parameter estimation procedure requires only manufacturer's specification sheet quantities as a data base.
Traveling the vitamin B12 pathway: Oral delivery of protein and peptide drugs

Oral routes of administration for therapeutic peptides and proteins face two major barriers: proteolytic degradation in the stomach and an inadequate absorption mechanism for polypeptides within the intestinal lumen. As a result, peptide-based therapeutics are administered by injection, a painful process associated with lower patient compliance. The development of a means of overcoming these two major obstacles and enabling the successful delivery of peptide therapeutics by the oral route of administration has therefore been the target of extensive scientific endeavor. This Minireview focuses on oral peptide/ protein delivery by the dietary uptake pathway for vitamin B 12. Recent progress in this field includes the delivery of erythropoietin, granulocyte-colony-stimulating factor, luteinizing-hormone- releasing hormone, and insulin.
Welfare Reforms, Family Resources, and Child Maltreatment.

This paper examines the impact of welfare reforms on several measures of child maltreatment. The authors use state-level data from 1990 to 1998 to examine whether recent welfare reforms have increased or reduced the incidence of reported and substantiated cases of maltreatment, the incidence of specific types of substantiated maltreatment—physical abuse and neglect—and the number of children living in out-of-home care. The welfare reforms considered are the imposition of: family caps, lifetime limits, work requirements, sanctions for non-compliance, and the restriction of welfare benefits to immigrants. How welfare benefit levels and changes in state Earned Income Tax Credit programs affect reports and substantiated cases of maltreatment are also considered. Evidence strongly indicates that reductions in states' welfare benefit levels increase the number of children in out-of-home care, and some evidence indicates that strict lifetime welfare limits and tougher sanctions for noncompliance are related to higher levels of substantiated maltreatment. The evidence on family caps is mixed: family caps appear to be associated with fewer instances of substantiated maltreatment, but more children in out-of-home care. Because most of the welfare reforms examined have been in effect for only a short time, these results should be considered preliminary. Overall, however, they provide some evidence that the recent welfare reforms in the United States may have increased child maltreatment. © 2003 by the Association for Public Policy and Analysis and Management.
Quantization noise shaping on arbitrary frame expansions

Quantization noise shaping is commonly used in oversampled A/D and D/A converters with uniform sampling. This paper considers quantization noise shaping for arbitrary finite frame expansions based on generalizing the view of first-order classical oversampled noise shaping as a compensation of the quantization error through projections. Two levels of generalization are developed, one a special case of the other, and two different cost models are proposed to evaluate the quantizer structures. Within our framework, the synthesis frame vectors are assumed given, and the computational complexity is in the initial determination of frame vector ordering, carried out off-line as part of the quantizer design. We consider the extension of the results to infinite shift-invariant frames and consider in particular filtering and oversampled filter banks.
Anomaly cancellation in M-theory☆

Abstract We show the complete cancellation of gauge and gravitational anomalies in the M-theory of Horava and Witten using their boundary contribution, and a term coming from the existence of two and five-branes. A factor of three discrepancy noted in an earlier work is resolved. We end with a comment on flux quantization.
Analysis of conjugate gradient algorithms for adaptive filtering

The paper presents and analyzes two approaches to the implementation of the conjugate gradient (CG) algorithm for filtering where several modifications to the original CG method are proposed. The convergence rates and misadjustments for the two approaches are compared. An analysis in the z-domain is used in order to find the asymptotic performance, and stability bounds are established. The behavior of the algorithms in finite word-length computation are described, and dynamic range considerations are discussed. It is shown that in finite word-length computation and close to steady state, the algorithms' behaviors are similar to the steepest descent algorithm, where the stalling phenomenon is observed. Using 16-bit fixed-point number representation, our simulations show that the algorithms are numerically stable.
A Direct Synthesis of O-Methyl Claussequinone

The reaction of a chromene with BH(3) followed by treatment with benzoquinone and air is the key step in a direct entry to O-methyl claussequinone.
Optimal State-Contingent Unemployment Insurance

Since the probability of finding a job is aected not only by individual eort but also by the aggregate state of the economy, designing unemployment insurance payments conditional on the business cycle could be valuable. This paper answers a fundamental question related to this issue: How should the payments vary with the aggregate state of the economy?
Earthquakes Induced by Hydraulic Fracturing in Poland Township, Ohio

Felt seismicity induced by hydraulic fracturing is very rare, with only a handful of reported cases worldwide. Using an optimized multistation cross‐correlation template‐matching routine, 77 earthquakes were identified in Poland Township, Mahoning County, Ohio, that were closely related spatially and temporally to active hydraulic fracturing operations. We identified earthquakes as small as local magnitudes ( M L) ∼1 up to 3, potentially one of the largest earthquakes induced by hydraulic fracturing in the United States. These events all occurred from 4 to 12 March 2014, and the rate decayed once the Ohio Department of Natural Resources issued a shutdown of hydraulic fracturing at a nearby well on 10 March. Using a locally derived velocity model and double‐difference relocation, the earthquakes occurred during six stimulation stages along two horizontal well legs that were located ∼0.8 km away. Nearly 100 stimulation stages in nearby wells at greater distances from the earthquake source region did not coincide with detected seismicity. During the sequence, hypocenters migrated ∼600 m along an azimuth of 083°, defining a vertically oriented plane of seismicity close to the top of the Precambrian basement. The focal mechanism determined for the M L 3 event had a vertically oriented left‐lateral fault plane consistent with the earthquake distribution and the regional stress field. The focal mechanism, orientation, and depth of hypocenters were similar to those of the 2011 Youngstown earthquake sequence that occurred 18 km to the northwest and was correlated with wastewater injection instead of hydraulic fracturing. Considering the relatively large magnitude of the Poland Township events and the b ‐value of 0.89, it appears the hydraulic fracturing induced slip along a pre‐existing fault/fracture zone optimally oriented in the regional stress field.
Entrepreneurship, public policy, and cities

Since the 2008-09 global financial crises, interest among policy makers in promoting innovative, high-potential ventures has exploded. The emerging great hubs of entrepreneurial activity, like Bangalore, Dubai, Shanghai, Silicon Valley, Singapore, and Tel Aviv, bear the unmistakable stamp of the public sector. Enlightened government intervention played a key role in each region's emergence. But for each effective government intervention, dozens, even hundreds, disappointed, with substantial public spending bearing no fruit. This paper sheds light on how governments can avoid mistakes in stimulating entrepreneurship. In recent decades, efforts have increased to provide the world's poorest with financing and other assistance to facilitate their entry into entrepreneurship or the growth of their small ventures. These are typically subsistence businesses offering services like snack preparation or clothing repair. Such businesses typically allow business owners and their families to get by, but little else. The public policy literature, along with academic studies of new ventures, often does not distinguish among the types of businesses being studied. The author will focus here exclusively on high-potential new ventures and the policies that enhance them. This choice, not intended to diminish the importance of efforts to boost microenterprises, reflects the complexity of the field: the dynamics and issues involving micro firms are quite different from those of their high-potential counterparts. A substantial literature suggests that promising entrepreneurial firms can have a powerful effect in transforming industries and promoting innovation.
C–H Bonds as Ubiquitous Functionality: A General Approach to Complex Arylated Imidazoles via Regioselective Sequential Arylation of All Three C–H Bonds and Regioselective N-Alkylation Enabled by SEM-Group Transposition

Imidazoles are an important group of the azole family of heterocycles frequently found in pharmaceuticals, drug candidates, ligands for transition metal catalysts, and other molecular functional materials. Owing to their wide application in academia and industry, new methods and strategies for the generation of functionalized imidazole derivatives are in demand. We here describe a general and comprehensive approach for the synthesis of complex aryl imidazoles, where all three C−H bonds of the imidazole core can be arylated in a regioselective and sequential manner. We report new catalytic methods for selective C5- and C2-arylation of SEM-imidazoles and provide a mechanistic hypothesis for the observed positional selectivity based on electronic properties of C−H bonds and the heterocyclic ring. Importantly, aryl bromides and low-cost aryl chlorides can be used as arene donors under practical laboratory conditions. To circumvent the low reactivity of the C-4 position, we developed the SEM-switch that transf...
Distillation protocols for Fourier states in quantum computing

Fourier states are multi-qubit registers that facilitate phase rotations in fault-tolerant quantum computing. We propose distillation protocols for constructing the fundamental, n-qubit Fourier state with error O(2-n) at a cost of O(n log n) Toffoli gates and Clifford gates, or any arbitrary Fourier state using O(n2) gates. We analyze these protocols with methods from digital signal processing. These results suggest that phase kickback, which uses Fourier states, could be the current lowest-overhead method for generating arbitrary phase rotations.
A Model of Chemical Mechanical Polishing

A model of chemical mechanical polishing is presented which quantitatively correlates the polishing rate with the slurry concentrations of both chemicals and abrasives. The model predicts that as the concentration of either chemicals or abrasives is increased, an initial steep rise in the polishing rate is followed by an asymptotic approach to a maximum rate. The causes and implications of this behavior are discussed.
Role of Cofactors in Protein Folding

Although cofactors are essential components of many proteins to attain biological activity, the role of cofactors in protein folding is not well understood. Biophysical characterization of four types of cofactor-binding proteins (with copper, flavin moiety, iron−sulfur cluster, and heme cofactors, respectively) provides the following insights. (1) The presence of the cofactor often stabilizes the native protein. (2) The cofactor has the ability to interact specifically with the unfolded polypeptide. (3) The presence of the cofactor is sometimes essential for the polypeptide to fold. (4) Coordination of the cofactor prior to polypeptide folding can dramatically accelerate formation of the functional protein.
Preparation and reactivity of β-zinc and copper phosphonates

Abstract Several zinc and copper β-metallated alkylphosphonates of type 2 have been prepared by the insertion of zinc to dialkyl β-bromoalkylphosphonates of type 1 . This new class of d 2 reagents reacts in excellent yields with a broad range of electrophiles such as acyl chlorides, aldehydes, enones, acetylenic esters, allylic and alkynyl halides, trialkyltin halides and nitro olefins.
Exchange rate volatility and domestic consumption: Evidence from Japan

Abstract In 1952, Alexander provided an argument that since inflationary effects of depreciation could shift income from workers to producers it could lead to a decline in aggregate domestic consumption. This was based on the assumption that wages do not adjust fully to inflation and labor has a high MPC relative to that of the producers. In this paper, we argue that in addition to the exchange rate itself, exchange rate uncertainty could also affect domestic consumption. We demonstrate our conjecture by using quarterly data from Japan and a bounds testing approach that distinguishes the short run from the long run.
FARMERS' PERCEPTIONS OF SPATIAL YIELD VARIABILITY AS INFLUENCED BY PRECISION FARMING INFORMATION GATHERING TECHNOLOGIES

This study evaluated how farmers' perceptions of spatial yield variability are influenced by precision technologies. Farmer estimates from a mail survey were regressed on use of alternative information technologies and personal characteristics. Results indicate that farmers who adopted yield monitors with GPS for cotton perceived significantly higher spatial yield variability.
Static Vacuum Einstein Metrics on Bounded Domains

We study the existence and uniqueness of solutions to the static vacuum Einstein equations in bounded domains, satisfying the Bartnik boundary conditions of prescribed metric and mean curvature on the boundary.
Racial Disparities in Life Insurance Coverage

We evaluate the extent to which there are racial disparities in life insurance coverage using multiple years of the Survey of Income and Program Participation between 2001 and 2010. We find that African-Americans hold significantly more life insurance after controlling for other factors, especially employer-sponsored and whole life insurance. We demonstrate that our findings diverge from prior work because we examine all households instead of focusing exclusively on married and cohabitating households. The findings on life insurance coverage and composition imply that earnings shocks due to mortality are not a contributing factor to racial disparities in wealth.