cssi/SciSciGPT-SciSciNet huggingface dataset:
The Void Phenomenon

Advances in theoretical ideas on how galaxies formed have not been strongly influenced by the advances in observations of what might be in the voids between the concentrations of ordinary optically selected galaxies. The theory and observations are maturing, and the search for a reconciliation offers a promising opportunity to improve our understanding of cosmic evolution. I comment on the development of this situation and present an update of a nearest neighbor measure of the void phenomenon that may be of use in evaluating theories of galaxy formation.
Accretion processes in star formation

Our understanding of the formation of stars and planetary systems has changed greatly since the first edition of this book was published. This new edition has been thoroughly updated, and now includes material on molecular clouds, binaries, star clusters and the stellar initial mass function (IMF), disk evolution and planet formation. This book provides a comprehensive picture of the formation of stars and planetary systems, from their beginnings in cold clouds of molecular gas to their emergence as new suns with planet-forming disks. At each stage gravity induces an inward accretion of mass, and this is a central theme for the book. The author brings together current observations, rigorous treatments of the relevant astrophysics, and 150 illustrations, to clarify the sequence of events in star and planet formation. It is a comprehensive account of the underlying physical processes of accretion for graduate students and researchers.
Plutonium transport in the environment.

The recent estimated global stockpile of separated plutonium (Pu) worldwide is about 500 t, with equal contributions from nuclear weapons and civilian nuclear energy. Independent of the United States’ future nuclear energy policy, the current large and increasing stockpile of Pu needs to be safely isolated from the biosphere and stored for thousands of years. Recent laboratory and field studies have demonstrated the ability of colloids (1–1000 nm particles) to facilitate the migration of strongly sorbing contaminants such as Pu. In understanding the dominant processes that may facilitate the transport of Pu, the initial source chemistry and groundwater chemistry are important factors, as no one process can explain all the different field observations of Pu transport. Very little is known about the molecular-scale geochemical and biochemical mechanisms controlling Pu transport, leaving our conceptual model incomplete. Equally uncertain are the conditions that inhibit the cycling and mobility of Pu in the s...
The dynamic cost and persistence of asset inequality in an agrarian economy

Abstract A growing literature suggests that asset inequality can be economically costly in the presence of agency costs that constrain labor and capital markets. Unclear in this literature is whether asset markets and optimal individual accumulation of self-finance capacity suffice to eliminate costly inequality over time. This paper uses numerical dynamic programming methods to explore this question with a model of an initially inegalitarian agrarian economy. While an egalitarian asset distribution emerges over time, the process involves sufficiently great productivity losses along the way, that a redistributive policy could improve on the market's performance by both equity and efficiency criteria.
The Utility of a Standard Composite for Forecasting Academic Performance in Several Liberal Arts Colleges.

In this study, one linear discriminant function of four admissions scores was found to exhaust more than 90% of their predictive power for separating 16 college/level-of-achievement groups — i.e., high- and low-performing freshman women at each of eight liberal arts colleges. Moreover, the corresponding discriminant score yielded validity coefficients vs freshman- and senior-level continuous grade-average criteria within each college comparable to coefficients yielded by group-specific, regression-weighted composites of the four scores in cross-validation samples. Results of the study suggest that multiple-discriminant analysis provides a rigorous and practical basis for adding an important and largely unexplored between-group dimension to studies in the prediction of within-group performance.
Calculation of 3-D free electron laser gain: comparison with simulation and generalization to elliptical cross section

Abstract In a previous paper [Y.H. Chin, K.-J. Kim and M. Xie, Nucl. Instr. and Meth. A318 (1992) 481], we have derived a dispersion relation for the free electron laser (FEL) gain in the exponential regime taking the diffraction and electron's betatron oscillation into account. Here we compare the growth rates obtained by solving the dispersion relation with those obtained by simulation calculation for the waterbag and the Gaussian models for the electron's transverse phase space distribution. The agreement is found to be good except for the limiting case where the Rayleigh length is much longer than the gain length (1-D limit). We also generalize the analysis to the case where the electron beam cross section is elliptical as is usually the case in storage rings, and derive the first-order dispersion relation.
Palladium-Catalyzed Intermolecular Coupling of Aryl Halides and Amides

The first general intermolecular C−N bond-forming reactions between aryl halides and amides were realized using a palladium catalyst with Xantphos as the ligand. Aryl triflates, carbamates, and sulfonamides are also viable substrates for the amidations, which proceed at 45−110 °C with 1−4 mol % of Pd catalyst in 66−99% yields and exhibit good functional group compatibility.
Dynamics of broad emission-line region in NGC 5548: Hydromagnetic wind model versus observations

We analyze the results of long-term observations of the broad-line region (BLR) in the Seyfert 1 galaxy NGC 5548 and provide a critical comparison with the predictions of a hydromagnetically driven outflow model of Emmering, Blandford, & Shlosman. We use this model to generate a time series of C IV line profiles that have responded to a time-varying continuum. Our modifications to the model include cloud emission anisotropy, cloud obscuration, a CLOUDY-generated emissivity function, and a narrow-line component which is added to the BLR component to generate the total line profiles. The model is driven with continuum input based on the monitoring campaigns of NGC 5548 reported in Clavel et al. and Korista et al., and the line strengths, profiles, and lags are compared with the observations. Our model is able to reproduce the basic features of C IV line variability in this active galactic nucleus, i.e., time evolution of the profile shape and strength of the C IV emission line without varying the model parameters. The best-fit model provides the effective size, the dominant geometry, the emissivity distribution, and the three-dimensional velocity field of the C IV BLR and constrains the mass of the central black hole to ~3 × 107 M☉. The inner part of the wind in NGC 5548 appears to be responsible for the anisotropically emitted C IV line, while its outer part remains dusty and molecular, thus having similar spectral characteristics to a molecular torus, although its dynamics is fundamentally different. In addition, our model predicts a differential response across the C IV line profile, producing a red-side-first response in the relative velocity interval of 3000 km s-1 to 6000 km s-1 followed by the blue mid-wing and finally by the line core. Based on the comparison of data and model cross-correlation functions and one- and two-dimensional transfer functions, we find that the rotating outflow model is compatible with observations of the BLR in NGC 5548.
False Spectra from the Rowland Concave Grating

It is proposed to show in the following paper that among the spectra formed by the Rowland concave gratings there are spectra not accounted for by the ordinary theory of the grating ; that such spectra are common, and at times fairly strong and of excellent definition ; that these spectra are diffraction spectra, of much less dispersion than the ordinarily recog nized spectra, and that the errors of ruling to which they are due are not local, but general to the whole surface of the grating. Finally, it is pro posed to explain an experimental method by which these false lines can be sorted out from the regular and calculable overlapping spectra. These lines are especially dangerous in series spectra work, giving a some what systematic reproduction of strong lines and groups, which reproduc tions in actual vibration frequencies do not exist. There is probability and some evidence that such errors have been committed in the past, and it was in the presence of this danger that the false spectra were here discovered. In the year 1893, Schumann showed that the ultra-violet spectrum could be extended to the neighborhood of 1000 /x. He used a spectroscope fitted with a fluorite prism and fluorite lenses. The apparatus was so constructed that it could be enclosed in a case from which the air could be exhausted. According to his investigation, it was chiefly the absorp tion of the air for light of very short wave lengths that had prevented other investigators from extending the spectrum below wave length 1800 p. Owing to the nature of a prism spectrum, it was difficult for Schumann to determine accurately the wave lengths of the lines which he discovered. Since his paper no attempt seems to have been made to measure these lines. It was in an effort to measure these wave lengths that the false spectra above referred to were first observed. It seemed probable that if a concave grating could be used to obtain these ultra-violet lines, an accurate determination of their wave length vol. xxxvi. ?16
Differential equations, duality and modular invariance

We solve the problem of constructing all chiral genus-one correlation functions from chiral genus-zero correlation functions associated to a vertex operator algebra satisfying the following conditions: (i) V(n) = 0 for n < 0 and V(0) = ℂ1, (ii) every ℕ-gradable weak V-module is completely reducible and (iii) V is C2-cofinite. We establish the fundamental properties of these functions, including suitably formulated commutativity, associativity and modular invariance. The method we develop and use here is completely different from the one previously used by Zhu and others. In particular, we show that the q-traces of products of certain geometrically-modified intertwining operators satisfy modular invariant systems of differential equations which, for any fixed modular parameter, reduce to doubly-periodic systems with only regular singular points. Together with the results obtained by the author in the genus-zero case, the results of the present paper solves essentially the problem of constructing chiral genus-one weakly conformal field theories from the representations of a vertex operator algebra satisfying the conditions above.
An expert system to perform on-line controller tuning

An expert system that tunes a proportional-integral-derivative (PID) controller online for a single-input-single-output multiple-lag process with dead time is described. The expert system examines features of each transient response and the corresponding controller parameters. It determines a new set of controller gains to obtain a more desirable time response. This technique can be used to determine and implement a different set of PID gains for each operating regime, and once in steady state, the system can be used to find optimal parameters for load disturbance rejection. The expert system can be applied to any system of the specified form (aerospace, industrial, etc.) and can be expanded to include additional process models. >
Static and dynamic characterization of a magnetoelectric cantilever cutting tool

A magnetoelectric self-sensing cantilever actuator is under investigation for use as a remotely driven self-sensing actuator. The cantilever is fabricated from Galfenol and Lead Zirconate Titanate strips as a laminate composite. An applied magnetic field generates strain in the magnetostrictive layer, thereby creating a bending moment in the composite and generating an electrical signal in the piezoelectric layer. A force-deflection model and equation of motion for the self-sensing magnetoelectric material in cantilever configuration is developed in this paper. An equivalent mass and stiffness matrix derived for the cantilever in terms of generalized coordinates is used to predict the bending behavior of the cantilever in its linear range of operation. In addition, the electrical boundary condition of the piezoelectric layer is varied to determine its influence on the actuation properties of the cantilever tool. Cantilever specimens measuring 40mm x 20mm and 20mm x 10mm are excited using a remote magnetic field of up to 2.8x10 4 A/m and free tip displacements of 200μm and 60 μm are observed, respectively. The model predicts the slope of the magnetic field/tip displacement curve with an error of 7% and 33%, respectively. The sensing current generated by the smaller specimen is 5x10 -7 A.
Garbled RAM From One-Way Functions

Yao's garbled circuit construction is a very fundamental result in cryptography and recent efficiency optimizations have brought it much closer to practice. However these constructions work only for circuits and garbling a RAM program involves the inefficient process of first converting it into a circuit. Towards the goal of avoiding this inefficiency, Lu and Ostrovsky (Eurocrypt 2013) introduced the notion of "garbled RAM" as a method to garble RAM programs directly. It can be seen as a RAM analogue of Yao's garbled circuits such that, the size of the garbled program and the time it takes to create and evaluate it, is proportional only to the running time on the RAM program rather than its circuit size. Known realizations of this primitive, either need to rely on strong computational assumptions or do not achieve the aforementioned efficiency (Gentry, Halevi, Lu, Ostrovsky, Raykova and Wichs, EUROCRYPT 2014). In this paper we provide the first construction with strictly poly-logarithmic overhead in both space and time based only on the minimal assumption that one-way functions exist. Our scheme allows for garbling multiple programs being executed on a persistent database, and has the additional feature that the program garbling is decoupled from the database garbling. This allows a client to provide multiple garbled programs to the server as part of a pre-processing phase and then later determine the order and the inputs on which these programs are to be executed, doing work independent of the running times of the programs itself.
Models for Dense Molecular Cloud Cores

We present a detailed theoretical model for the thermal balance, chemistry, and radiative transfer within quiescent dense molecular cloud cores that contain a central protostar. In the interior of such cores, we expect the dust and gas temperatures to be well coupled, while in the outer regions CO rotational emissions dominate the gas cooling and the predicted gas temperature lies significantly below the dust temperature. Large spatial variations in the gas temperature are expected to affect the gas phase chemistry dramatically; in particular, the predicted water abundance varies by more than a factor of 1000 within cloud cores that contain luminous protostars. Based upon our predictions for the thermal and chemical structure of cloud cores, we have constructed self-consistent radiative transfer models to compute the line strengths and line profiles for transitions of (12)CO, (13)CO, C(18)O, ortho- and para-H2(16)O, ortho- and para-H2(18)O, and O I. We carried out a general parameter study to determine the dependence of the model predictions upon the parameters assumed for the source. We expect many of the far-infrared and submillimeter rotational transitions of water to be detectable either in emission or absorption with the use of the Infrared Space Observatory (ISO) and the Submillimeter Wave Astronomy Satellite. Quiescent, radiatively heated hot cores are expected to show low-gain maser emission in the 183 GHz 3(sub 13)-2(sub 20) water line, such as has been observed toward several hot core regions using ground-based telescopes. We predict the (3)P(sub l) - (3)P(sub 2) fine-structure transition of atomic oxygen near 63 micron to be in strong absorption against the continuum for many sources. Our model can also account successfully for recent ISO observations of absorption in rovibrational transitions of water toward the source AFGL 2591.
Bandpass Dependence of X-Ray Temperatures in Galaxy Clusters

We explore the band dependence of the inferred X-ray temperature of the intracluster medium (ICM) for 192 well-observed galaxy clusters selected from the Chandra Data Archive. If the hot ICM is nearly isothermal in the projected region of interest, the X-ray temperature inferred from a broadband (0.7-7.0 keV) spectrum should be identical to the X-ray temperature inferred from a hard-band (2.0-7.0 keV) spectrum. However, if unresolved cool lumps of gas are contributing soft X-ray emission, the temperature of a best-fit single-component thermal model will be cooler for the broadband spectrum than for the hard-band spectrum. Using this difference as a diagnostic, the ratio of best-fitting hard-band and broadband temperatures may indicate the presence of cooler gas even when the X-ray spectrum itself may not have sufficient signal-to-noise ratio (S/N) to resolve multiple temperature components. To test this possible diagnostic, we extract X-ray spectra from core-excised annular regions for each cluster in our archival sample. We compare the X-ray temperatures inferred from single-temperature fits when the energy range of the fit is 0.7-7.0 keV (broad) and when the energy range is -->2.0/(1 + z)-7.0 keV (hard). We find that the hard-band temperature is significantly higher, on average, than the broadband temperature. On further exploration, we find this temperature ratio is enhanced preferentially for clusters which are known merging systems. In addition, cool-core clusters tend to have best-fit hard-band temperatures that are in closer agreement with their best-fit broadband temperatures. We show, using simulated spectra, that this diagnostic is sensitive to secondary cool components ( -->TX = 0.5-3.0 keV) with emission measures ?10-30% of the primary hot component.
Social resilience: The value of social fitness with an application to the military.

Resilience has been regarded narrowly as a quintessential individual property by most investigators. Social resilience, however, is inherently a multilevel construct, revealed by capacities of individuals, but also groups, to foster, engage in, and sustain positive social relationships and to endure and recover from stressors and social isolation. Emergent levels of organization, ranging from dyads, families, and groups to cities, civilizations, and international alliances have long been apparent in human existence, but identifying the features of individuals, relationships, and group structures and norms that promote social resilience-and determining effective interventions to build social resilience-represent some of the most important challenges facing the military as well as contemporary behavioral science. We identify nine personal resources that foster social resilience, and we describe an educational, computer-based program that builds on these resources in an effort to improve the social resilience among troops in the U.S. Army. Data from this program should provide valuable evidence regarding the challenge of building social resilience.
Recovery and visualization of 3D structure of chromosomes from tomographic reconstruction images

The objectives of this work include automatic recovery and visualization of a 3D chromosome structure from a sequence of 2D tomographic reconstruction images taken through the nucleus of a cell. Structure is very important for biologists as it affects chromosome functions, behavior of the cell, and its state. Analysis of chromosome structure is significant in the detection of diseases, identification of chromosomal abnormalities, study of DNA structural conformation, in-depth study of chromosomal surface morphology, observation of in vivo behavior of the chromosomes over time, and in monitoring environmental gene mutations. The methodology incorporates thresholding based on a histogram analysis with a polyline splitting algorithm, contour extraction via active contours, and detection of the 3D chromosome structure by establishing corresponding regions throughout the slices. Visualization using point cloud meshing generates a 3D surface. The 3D triangular mesh of the chromosomes provides surface detail and allows a user to interactively analyze chromosomes using visualization software.
Sulfur induced selectivity changes for methanol decomposition on Ni(100)

Abstract The adsorption and reactions of methanol on Ni(100), Ni(100)p(2 × 2)S and Ni(100) c(2 × 2)S were studied by temperature programmed reaction spectroscopy. On the clean surface mixed isotopes of dihydrogen and CO were formed in desorption-limited processes above 300 K. Evidence suggestive of the existence of an adsorbed [COD] intermediate was obtained. Similar results were found on the p(2 × 2)S surface. The sulfur decreased the amount of adsorbed methanol which reacted, and it interacted significantly with the high temperature binding state of deuterium produced by decomposition of the [COD] intermediate. On the c(2 × 2)S structure the primary reaction intermediate was methoxy, CH3O. Formaldehyde was formed with an activation energy of 26 kcal gmol . No desorption-limited CO was observed. These results clearly demonstrate the role of structural overlayers in selective poisoning.
Development of porous sintered-ceramic separators for application in a Li-Al, LiCl-KCl, FeS battery

Abstract The procedure for fabrication of porous sintered-ceramic separators and the technical feasibility of using such separators in LiAl/molten LiClKCl/FeS battery cells have been investigated. Processing techniques have been developed to fabricate ∼1.5–2.5 mm thick, ∼35–60% porous, flat, sintered Y2O2 and MgO separator plates with sufficient strength to allow handling prior to and during cell assembly. These separators performed successfully in laboratory-scale cells for up to ∼2000 h and 283 cycles, indicating that the concept of a sintered separator, is viable for LiAl/FeS batteries. The particularly attractive features of these separators are potentially low cost, prefabricated form that allows easy cell assembly, and small pore size (average diameter 0.5–1.0 μm) which provides good particle retention. The test results from the sintered-separator cells indicate that Y2O2 is probably unsuitable for long-term performance in LiAl/FeS cells because of its reaction with the positive active material. This is in agreement with the recently reported data on cells with Y2O2 felt and powder separators. Sintered MgO separators, however, showed good chemical and mechanical stability in the cell environment.
Design and synthesis of new fluorinated ligands for the rhodium-catalyzed hydroformylation of alkenes in supercritical CO2 and fluorous solvents

Abstract Novel fluorous biphenols, 5,5′-[ n -C 4 F 9 (CH 2 ) 3 ] 2 -2,2′-biphenol and 5,5′-[ n -C 4 F 9 (CH 2 ) 3 O] 2 -3,3′-di- tert -butyl-2,2′-biphenol, as well as enantiopure BINOLs, ( S )-6,6′-[ n -C 4 F 9 (CH 2 ) 3 ] 2 -BINOL, ( R )-6,6′-[ n -C 6 F 13 (CH 2 ) 3 ] 2 -BINOL, and ( S )-6,6′-[ n -C 8 F 17 (CH 2 ) 3 ] 2 -BINOL, are synthesized. These compounds serve as key intermediates for the syntheses of a variety of new fluorous ligands for regioselective and enantioselective catalytic reactions. Novel fluorous [Rf(CH 2 ) 3 ] 2 -BINAPHOS ligands (Rf= n -C 4 F 9 , n -C 6 F 13 , and n -C 8 F 17 ) are successfully synthesized. These new fluorous chiral ligands when used with a rhodium catalyst can achieve comparable or even higher regioselectivity and enantioselectivity in the asymmetric hydroformylation of styrene as compared to those by the Rh-BINAPHOS system.
Constraining the littlest Higgs

Little Higgs models offer a new way to address the hierarchy problem, and give rise to a weakly-coupled Higgs sector. These theories predict the existence of new states which are necessary to cancel the quadratic divergences of the Standard Model. The simplest version of these models, the Littlest Higgs, is based on an SU(5)/SO(5) non-linear sigma model and predicts that four new gauge bosons, a weak isosinglet quark, t{prime}, with Q=2/3, as well as an isotriplet scalar field exist at the TeV scale. We consider the contributions of these new states to precision electroweak observables, and examine their production at the Tevatron. We thoroughly explore the parameter space of this model and find that small regions are allowed by the precision data where the model parameters take on their natural values. These regions are, however, excluded by the Tevatron data. Combined, the direct and indirect effects of these new states constrain the ''decay constant'' f {approx}> 3.5 TeV and m{sub t{prime}} {approx}> 10 TeV. These bounds imply that significant fine-tuning be present in order for this model to resolve the hierarchy problem.
Boolean Representation of Manifolds and Functions

It is shown that a smooth n dimensional manifold with a boundary in R^n admits a Boolean representation in terms of closed half spaces defined by the tangent hyperplanes at the points on its boundary. A similar result is established for smooth functions on closed convex domains in R^n. The latter result is considered as a form of the Legendre transformation.
Equilibration of a one-dimensional quantum liquid

We review some of the recent results on equilibration of one-dimensional quantum liquids. The low-energy properties of these systems are described by the Luttinger liquid theory, in which the excitations are bosonic quasiparticles. At low temperatures, the relaxation of the gas of excitations toward full equilibrium is exponentially slow. In electronic Luttinger liquids, these relaxation processes involve backscattering of electrons and give rise to interesting corrections to the transport properties of one-dimensional conductors. We focus on the phenomenological theory of the equilibration of a quantum liquid and obtain an expression for the relaxation rate in terms of the excitation spectrum.
B72.3 immunoreactivity in benign abdominal lymph nodes associated with gastrointestinal disease.

PURPOSE: Immunolocalization of the tumor-associated glycoprotein 72 antigen with the monoclonal antibody B72.3 has been used as a “cancer marker” in radioimmunoscintigraphy and radioimmunoguided surgery (RIGS). Radioimmunoscintigraphy and RIGS have been used to detect occult metastatic deposits from colorectal adenocarcinoma. It has been suggested that RIGS is superior to histologic examination in detecting lymph node metastases from colorectal cancer. To determine the specificity of immunodetection of the tumor-associated glycoprotein -72 antigen as a marker for metastatic adenocarcinoma, we studied benign intraabdominal lymph nodes with B72.3 and an immunohistochemical technique. METHODS: Formaldehyde-fixed, paraffin-embedded sections of 276 benign abdominal lymph nodes, resected with 35 cases of colonic adenocarcinoma and 33 cases of benign gastrointestinal disorders, were evaluated for B72.3 immunoreactivity using an avidin-biotin complex immunohistochemical technique. Lymph nodes from cases of colonic carcinoma were also studied with cytokeratin immunostaining to help eliminate occult micrometastases. RESULTS: B72.3 immunoreactivity was seen in the germinal centers of benign lymph nodes associated with 49 percent of the cases of colonic adenocarcinoma and 12 percent of the cases of benign gastrointestinal disease. CONCLUSIONS: B72.3 immunoreactivity can be seen in benign abdominal lymph nodes associated with gastrointestinal disease. We advise caution in the use of diagnostic techniques that equate B72.3 immunoreactivity with the presence of adenocarcinoma.
Global network alignment in the context of aging

Analogous to sequence alignment, network alignment (NA) can be used to transfer biological knowledge across species between conserved network regions. NA faces two algorithmic challenges: 1) Which cost function to use to capture "similarities" between nodes in different networks? 2) Which alignment strategy to use to rapidly identify "high-scoring" alignments from all possible alignments? We "break down" existing state-of-the-art methods that use both different cost functions and different alignment strategies to evaluate each combination of their cost functions and alignment strategies. We find that a combination of the cost function of one method and the alignment strategy of another method beats the existing methods. Hence, we propose this combination as a novel superior NA method. Then, since human aging is hard to study experimentally due to long lifespan, we use NA to transfer aging-related knowledge from well annotated model species to poorly annotated human. By doing so, we produce novel human aging-related knowledge, which complements currently available knowledge about aging that has been obtained mainly by sequence alignment. We demonstrate significant similarity between topological and functional properties of our novel predictions and those of known aging-related genes. We are the first to use NA to learn more about aging.
Strichartz Estimates on Asymptotically de Sitter Spaces

In this article we prove a family of local (in time) weighted Strichartz estimates with derivative losses for the Klein–Gordon equation on asymptotically de Sitter spaces and provide a heuristic argument for the non-existence of a global dispersive estimate on these spaces. The weights in the estimates depend on the mass parameter and disappear in the “large mass” regime. We also provide an application of these estimates to establish small-data global existence for a class of semilinear equations on these spaces.
Availability of Calibration Sources for Measuring Spacecraft Angular Position with Sub-Nanoradian Accuracy

Precision measurements are now capable of determining the angular position of spacecrafts with accuracies of 2-5 nanoradians. To achieve this level of precision, compact radio sources with flux density of at least a few hundred milli-Jansky (at 8.4 GHz) are used for calibration purposes. Further improvements in position measurement accuracy may be possible with use of appropriate calibrators near the direction of the spacecrafts even if the calibrators are much weaker (a few milli-Jansky) in flux density. In this paper we discuss the calibrator flux density required to achieve sub-nanoradian astrometric accuracy and attempt to estimate the density of suitable calibrators, using existing source count surveys. We point out, however, that the fraction of these sources that are suitable for use as calibrators is not well understood and requires further study.
Constraining Cosmological Parameters Based on Relative Galaxy Ages

We propose to use relative galaxy ages as a means of constraining cosmological parameters. By measuring the age difference between two ensembles of passively evolving galaxies at somewhat different redshifts, one could determine the derivative of redshift with respect to cosmic time, dz/dt. At high redshifts, z ~ 1-2, this measurement would constrain the equation of state of the dark energy, while at low redshifts, z 0.2, it would determine the Hubble constant, H0. Furthermore, we show that d2z/dt2 directly tracks the equation of state of the dark energy; thus, measurements of this quantity at low redshifts can be used to constrain it. The selected galaxies need to be passively evolving on a time much longer than their age difference.
Conformational Analysis of Single DNA Molecules Undergoing Entropically Induced Motion in Nanochannels

We have used the interface between a nanochannel and a microchannel as a tool for applying controlled forces on a DNA molecule. A molecule, with a radius of gyration larger than the nanochannel width, that straddles such an interface is subject to an essentially constant entropic force, which can be balanced against other forces such as the electrophoretic force from an applied electric field. By controlling the applied field we can position the molecule as desired and observe the conformation of the molecule as it stretches, relaxes, and recoils from the nanochannel. We quantify and present models for the molecular motion in response to the entropic, electrophoretic, and frictional forces acting on it. By determining the magnitude of the drag coefficients for DNA molecules in the nanostructure, we are able to estimate the confinement-induced recoil force. Finally, we demonstrate that we can use a controlled applied field and the entropic interfacial forces to unfold molecules, which can then be manipulated and positioned in their simple extended morphology.
Pattern avoidance in compositions and multiset permutations

We show that among the compositions of n into positive parts, the number g(n) that avoid a given pattern @p of three letters is independent of @p. We find the generating function of {g(n)}, and it shows that the sequence {g(n)} is not P-recursive. If S is a given multiset, we show that the number of permutations of S that avoid a pattern @p of three letters is independent of @p. Finally, we give a bijective proof of the fact that if M=1^a^"^1...k^a^"^k is a given multiset then the number of permutations of M that avoid the pattern (123) is a symmetric function of the multiplicities a"1,...,a"k. The bijection uses the Greene-Kleitman symmetric chain decomposition of the Boolean lattice.
Terrestrial Consequences of Spectral and Temporal Variability in Ionizing Photon Events

Gamma-ray bursts (GRBs) directed at Earth from within a few kiloparsecs may have damaged the biosphere, primarily through changes in atmospheric chemistry that admit greatly increased solar UV. However, GRBs are highly variable in spectrum and duration. Recent observations indicate that short (~0.1 s) burst GRBs, which have harder spectra, may be sufficiently abundant at low redshift that they may offer an additional significant effect. A much longer timescale is associated with shock breakout luminosity observed in the soft X-ray (~103 s) and UV (~105 s) emission and radioactive decay gamma-ray line radiation emitted during the light-curve phase of supernovae (~107 s). Here, we generalize our atmospheric computations to include a broad range of peak photon energies and investigate the effect of burst duration while holding total fluence and other parameters constant. The results can be used to estimate the probable impact of various kinds of ionizing events (such as short GRBs, X-ray flashes, and supernovae) on the Earth's atmosphere. We find that the ultimate intensity of atmospheric effects varies only slightly with burst duration from 10-1 to 108 s. Therefore, the effect of many astrophysical events causing atmospheric ionization can be approximated without including time development. Detailed modeling requires specification of the season and latitude of the event. Harder photon spectra produce greater atmospheric effects for spectra with peaks up to about 20 MeV because of greater penetration into the stratosphere.
Lessons from hadron phenomenology

Abstract Meson spectra can be well approximated by a specific form of a nonlinear Regge trajectory which is consistent with a finite number of bound states. This may have important consequences for experiment, and may be a hint for the theory.
Kinetic resolution of alcohols using a 1,2-dihydroimidazo[1,2-a]quinoline enantioselective acylation catalyst.

A new enantioselective acylation catalyst (Cl-PIQ), designed to provide enhanced π-stacking with benzylic and cinnamyl alcohol substrates, was found to give considerably increased reaction rates and selectivities compared with the first-generation catalyst CF3-PIP.
The Cognitive Movement in Instruction

ed from the article of the same title in the Educational Psychologist, Volume 13, 1978. Copyrighted by the Division of Educational Psychology of the American Psychological Association. A cognitive approach implies that learning from instruction is scientifically more productively studied as an internally, cognitively mediated process than as a direct product of the environment, people, or factors external to the learner. The approach involves understanding relations or interactions beween the learners' cognitive processes and aptitudes, such as attribution, motivation, encoding, memory, cognitive styles and cognitive structures, and the characteristics of instructional treatments. The cognitive movement thus brings a unity of interest to people who study individual differences, learning and instruction, and a unifying synthesis to many recent research findings (Bandura, 1969). It also encourages research on comprehension, understanding, and transfer, several areas of fundamental importance to education. In educational research, a cognitive approach implies that it is more useful and meaningful to study, for example, how teaching style influences the learners' attention, motivation, and understanding, which in turn influence behavior, than it is useful and meaningful to study how teaching style directly influences student behavior. A cognitive model emphasizes the active and constructive role of the learner. From this point of view, the art of instruction begins with an understanding and a diagnosis of the cognitive and affective processes and aptitudes of the learners. From these one designs different treatments for different students in different situations to actively induce mental elaborations that relate previous learning and schemata to stimuli. In this conception the learners are active, responsible, and accountable for their role in generative learning. That theme expresses a centrally important part of the cognitive movement in instruction and of the state of the art of instruction.
Comment on ‘Simulation of Bell states with incoherent thermal light’

Recently, Chen et al (2011 New J. Phys. 13 083018) presented experimental results, accompanied by quantum-mechanical analysis, showing that the quantum interference behavior of Bell states could be simulated in a modified Mach?Zehnder interferometer whose inputs are pseudothermal light beams obtained by passing laser light through a rotating ground-glass diffuser. Their experiments and their theory presumed low-flux operation in which the simulated quantum interference is observed via photon-coincidence counting. This work is a comment on the paper by Chen et al (2011). We first show that the Chen et al photon-coincidence counting experiments can be fully explained with semiclassical photodetection theory, in which light is taken to be a classical electromagnetic wave, and the discreteness of the electron charge leads to shot noise as the fundamental photodetection noise. We then use semiclassical photodetection theory to show that the same simulated quantum interference pattern can be observed in high-flux operation when photocurrent cross-correlation is used instead of photon-coincidence counting.
Approximation of analytic functions with prescribed boundary conditions by circle-packing maps

We use recent advances in circle-packing theory to develop a constructive method for the approximation of an analytic functionF: Ω źC by circle packing maps providing we have only been given ΩF'dΩ, and the set of critical points ofF. This extends the earlier results of Carter and Rodin and of Colin de Verdiere and Matheus, for functionsF with no critical points.
A simple modal logic for belief revision

We propose a modal logic based on three operators, representing intial beliefs, information and revised beliefs. Three simple axioms are used to provide a sound and complete axiomatization of the qualitative part of Bayes' rule. Some theorems of this logic are derived concerning the interaction between current beliefs and future beliefs. Information flows and iterated revision are also discussed.
Sectoral Shifts and Cyclical Unemployment Reconsidered

This paper develops a new measure of reallocation shocks based on the variance of industry stock market excess returns to assess the contribution of sectoral reallocation to unemployment in the postwar U. S. economy. The Beveridge Curve relationship is used to establish that this series isolates reallocation shocks. Reallocation shocks are found to explain only a moderate share of the fluctuations in aggregate unemployment on average over the period. However, reallocation accounted for a substantial share of increases in unemployment in several episodes, particularly the mid-1970s. Reallocation shocks also account for a larger share of fluctuations in unemployment of longer durations than of shorter durations.
AMPTE/CCE magnetic field studies of the September 4, 1984 storm

The AMPTE/CCE (active magnetospheric particle tracer explorer/charge composition explorer) magnetic-field observations acquired during the September 4, 1984 geomagnetic storm are described. The observations are used to determine magnetospheric regions and boundaries and are also used as the primary index of the development, evolution, and distribution of the ring current. The results of an analysis of the observations are presented. It is shown that a magnetic compression observed inside the magnetosphere by CCE and outside by ISEE-2 is interpreted as a sudden impulse. From an estimation of magnetopause normals at each crossing, it is concluded that the magnetic variations that occur are due to a contraction and expansion of the entire magnetosphere. Local magnetic-field depressions are observed during two inbound dusk passes, confirming that the ring current never developed in the dawn sector.
Exact Solution of a Many-Fermion System and Its Associated Boson Field

Luttinger’s exactly soluble model of a one-dimensional many-fermion system is discussed. We show that he did not solve his model properly because of the paradoxical fact that the density operator commutators [p(p), p(−p′)], which always vanish for any finite number of particles, no longer vanish in the field-theoretic limit of a filled Dirac sea. In fact the operators p(p) define a boson field which is ipso facto associated with the Fermi-Dirac field. We then use this observation to solve the model, and obtain the exact (and now nontrivial) spectrum, free energy, and dielectric constant. This we also extend to more realistic interactions in an Appendix. We calculate the Fermi surface parameter , and find: (i.e., there exists a sharp Fermi surface) only in the case of a sufficiently weak interaction.
Currency Orders and Exchange Rate Dynamics: An Explanation for the Predictive Success of Technical Analysis

This paper documents clustering in currency stop-loss and take-profit orders, and uses that clustering to provide an explanation for two familiar predictions from technical analysis: (1) trends tend to reverse course at predictable support and resistance levels, and (2) trends tend to be unusually rapid after rates cross such levels. The data are the first available on individual currency stop-loss and take-profit orders. Take-profit orders cluster particularly strongly at round numbers, which could explain the first prediction. Stop-loss orders cluster strongly just beyond round numbers, which could explain the second prediction.
Regioselection in the reaction of 3-amino-5-benzylthio-1,2,4-triazole with unsymmetrical 1,3-diketones

The results of a study of the regioselection in the reaction of 3-amino-5-benzylthio-1,2,4-triazole with several unsymmetrical 1,3-diketones are reported. The 1,3-diketones studied are 1,1,1-trifluoro-2,4-pentanedione, benzoylacetone and 2-acetylcyclopentanone. Chemical, spectroscopic and X-ray crystallographic data are presented to support structural assignments of the major reaction products.
INTRINSIC CHARM FLAVOR AND HELICITY CONTENT IN THE PROTON

Contributions to the quark flavor and spin observables from the intrinsic charm in the proton are discussed in the SU(4) quark meson fluctuation model. Our results suggest that the probability of finding the intrinsic charm in the proton is less than 1%. The intrinsic charm helicity is small and negative, Δc ≃ -(0.003 ~ 0.015). The fraction of the total quark helicity carried by the intrinsic charm is less than 2%. A brief comparison of the quark flavor and spin observables with data and other models or analyses is given.
Worldsheet derivation of a large N duality

We give a worldsheet proof of the equivalence between the U(N) Chern-Simons gauge theory on S-3 and the topological closed string theory on the resolved conifold geometry. When the 't Hooft coupling of the gauge theory is small, the dual closed string worldsheet develops a new branch. We show that the fluctuations of the worldsheet into this branch effectively correspond to "holes" on the worldsheet, generating an open string sector. This leads to a microscopic description of how the 't Hooft expansion of gauge theory amplitudes is reproduced in the closed string computation. We find that the closed string amplitudes also contain terms which are not captured in the 't Hooft expansion but are present in the exact computation in the gauge theory amplitudes. These arise when the whole Riemann surface is in the new branch. We also discuss the cases with SO and Sp gauge groups.
Direct C-arylation of free (NH)-indoles and pyrroles catalyzed by Ar-Rh(III) complexes assembled in situ.

Ar−Rh(III) pivalate complexes assembled in situ from the reaction of [RhCl(coe)2]2 (coe = cis-cyclooctene), [p-(CF3)C6H4]3P, and CsOPiv effectively catalyzed the direct C-arylation of free (NH)-indoles and (NH)-pyrroles in good yields and with high regioselectivity. The reaction displayed excellent functional group compatibility and low moisture sensitivity. Kinetics studies support a mechanism involving phosphine displacement by indole in complex 2 (resting state of the catalyst), followed by a rate-limiting C−H bond metalation.
Hamiltonian description of Vlasov dynamics: Action-angle variables for the continuous spectrum

The linear Vlasov-Poisson system for homogeneous, stable equilibria is solved by means of a novel integral transform that is a generalization of the Hilbert transform. The integral transform provid...
Oxygen atom transfer between rhenium, sulfur, and phosphorus. Characterization and reactivity of Re(O)Cl3(Me2S)(OPPh3) and Re(O)Cl3(CNCMe3)2

Re(O)Cl/sub 3/(PPh/sub 3/)/sub 2/ (I) reacts with Me/sub 2/SO to form OPPh/sub 3/ and Re(O)Cl/sub 3/(Me/sub 2/S)(OPPh/sub 3/) (II), not Re(O)Cl/sub 3/(Me/sub 2/SO)(PPh/sub 3/) as had been previously reported. Compounds I and II are catalysts for oxygen atom transfer from Me/sub 2/SO to PPh/sub 3/. The mechanism of these oxygen atom transfer reactions has been studied with oxygen-18 labeling experiments. The rhenium oxo group does not appear to be involved; rather, the rhenium center acts as a Lewis acid activator for a Me/sub 2/SO ligand. The rhenium oxo group does, however, exchange oxygen atoms with Me/sub 2/S/sup 18/O, probably by a similar mechanism. Compound II is an excellent starting material for compounds of the form Re(O)Cl/sub 3/L/sub 2/, with L = isonitriles, phosphines, bipyridine, etc. The compounds Re(O)Cl/sub 3/-(CNR)/sub 2/ (R = CMe/sub 3/ (IV), CHMe/sub 2/, C/sub 6/H/sub 11/) are rare examples of high-valent isonitrile complexes. Data from an X-ray crystal structure of IV are reported. 36 references, 2 figures, 3 tables.
UBV photometry of asteroid 433 Eros

UBV observations of asteroid 433 Eros were conducted on 17 nights during the winter of 1974/75. The peak-to-peak amplitude of the light curve varied from about 0.3 mag to nearly 1.4 mag. The absolute V magnitude, extrapolated to zero phase, is 10.85. Phase coefficients of 0.0245 mag/degree, 0.0009 mag/degree, and 0.0004 mag/degree were derived for V, B-V, and U-B, respectively. The zero-phase color of Eros (B-V = 0.88, U-B = 0.50) is representative of an S (silicaceous) compositional type asteroid. The color does not vary with rotation. The photometric behavior of Eros can be modeled by a cylinder with rounded ends having an axial ratio of about 2.3:1.