cssi/SciSciGPT-SciSciNet huggingface dataset:
Optimal Formation Reconfiguration of Multiple Spacecraft with Docking and Undocking Capability

Optimal control problems associated with formation reconfiguration of multiple spacecraft with docking and undocking capability are considered. The basic approach is to decompose the optimal formation reconfiguration problem into several simple optimal control problems. Explicit solutions of the minimum-fuel and minimum-energy control problems for reconfiguration of simple formation patterns formed by simultaneous docking of multiple spacecraft are obtained. Simulation results are given to demonstrate the effectiveness of the proposed approach.
Conditional Universal Consistency

Each period, a player must choose an action without knowing the outcome that will be chosen by "Nature," according to an unknown and possibly history-dependent stochastic rule. We discuss have a class of procedures that assign observations to categories, and prescribe a simple randomized variation of fictitious play within each category. These procedures are "conditionally consistent," in the sense of yielding almost as high a time-average payoff as could be obtained if the player chose knowing the conditional distributions of actions given categories. Moreover given any alternative procedure, there is a conditionally consistent procedure whose performance is no more than epsilon worse regardless of the discount factor. Cycles can persist if all players classify histories in the same way; however in an example, where players classify histories differently, the system converges to a Nash equilibrium. We also argue that in the long run the time-average of play should resemble a correlated equilibrium.
Synthesis of 3-Alkoxy-, 3-Aryloxy- and 3-Substituted Amino-2,5-Diarylfurans by Reductive-Furanization of α,β-Unsaturated-1,4-Diketones

Abstract The use of phosphorus trichloride for synthesis of 3-alkoxy, 3-aryloxy and 3-substitutedamino-2,5-diarylfurans from α,β-unsaturated-1,4-diketones by reductive-furanization is reported.
Probing the Ionization Structure of the Narrow-Line Region in the Seyfert 1 Galaxy NGC 4151

We present a study of the distribution of [O III] λ5007 and [O II] λ3727 emission in the narrow-line region (NLR) of the Seyfert 1 galaxy NGC 4151. While the NLR of NGC 4151 exhibits an overall structure consistent with the unified model of Seyfert galaxies, narrowband [O III] and [O II] images obtained with the Wide Field and Planetary Camera 2 aboard the Hubble Space Telescope reveal significant emission from outside the emission-line bicone. The [O III]/[O II] ratios are lower in these regions, consistent with a weaker ionizing flux. We performed a photoionization modeling analysis of the emission-line gas within a series of annuli, centered on the central continuum source, with inner radii from 13 to 90 pc. The gas is ionized by radiation that has been attenuated by a relatively highly ionized absorber (HABS), which completely covers the central source, and a lower ionization absorber (LABS), which has a covering factor ranging from 0 to 1. We found that the [O III]/[O II] ratios are well fit by assuming that, within each segment of an annulus, some fraction of the NLR gas is completely within the shadow of LABS, while the rest is irradiated by the continuum filtered only by HABS. This suggests that the structure of the NLR is due to filtering of the ionizing radiation by ionized gas, consistent with disk-wind models. One possible scenario is that the low-ionization absorbers are dense knots of gas swept up by a wind.
Ultracompact Binaries as Bright X-Ray Sources in Elliptical Galaxies

Chandra observations of distant (D ~ 10 Mpc) elliptical galaxies have revealed large numbers of low-mass X-ray binaries (LMXBs) accreting at > 10-8 M☉ yr-1. The majority of these LMXBs reside in globular clusters (GCs), and it has been suggested that many of the field LMXBs also originated in GCs. We show here that ultracompact (UC) binaries with orbital periods of 8-10 minutes and He or C/O donors of 0.06-0.08 M☉ naturally provide the observed from gravitational radiation losses alone. Such systems are predicted to be formed in the dense GC environment, a hypothesis supported by the 11.4 minute binary 4U 1820-30, the brightest persistent LMXB in a Galactic GC. These binaries have short enough lifetimes ( 1038 ergs s-1) that we calculate their luminosity function under a steady state approximation. This yields a luminosity function slope in agreement with that observed for 6 × 1037 ergs s-1 < L < 5 × 1038 ergs s-1, encouraging us to use the observed numbers of LMXBs per GC mass to calculate the accumulated number of UC binaries. For a constant birthrate over 8 Gyr, the number of UC binaries that have evolved through this bright phase is ~4000 in a 107 M☉ GC, consistent with dynamical interaction calculations. Perhaps most importantly, if all UC binaries become millisecond radio pulsars, then the observed normalization agrees with the inferred number of millisecond radio pulsars in 47 Tuc and Galactic GCs in general.
Automatic aircraft landing using interferometric inverse synthetic aperture radar imaging

This paper presents an interferometric processing of an aircraft's monostatic and bistatic inverse synthetic aperture radar (ISAR) signatures for automatic landing. The aircraft's squint angle in this ISAR imaging problem is near 90/spl deg/. We show that this extreme squint angle does not pose any problem for the ISAR Fourier-based (wavefront) reconstruction algorithm. In fact, the aircraft can be imaged accurately, and without any erroneous shifts in the cross-range domain, within the imposed theoretical resolution. Moreover, the algorithm is accurate enough such that one can utilize the phase of the ISAR monostatic and bistatic measurements for interferometric processing. The resultant interferometric ISAR image is used to detect undesirable rotations in the aircraft's orientation.
COMPETITION BETWEEN GRAVITATIONAL AND SCALAR FIELD RADIATION

Recent astrophysical observations have provided strong evidence that the present expansion of the universe is accelerating, powered by the energy density associated with a cosmological term. Assuming the latter to be not simply a constant term but a quintessence field, we study the radiation of quanta of such a quintessence field (quintons) by binary systems of different types and compare intensities to those of standard tensor gravitational wave emission. We consider both the case in which the quintessence field varies only over cosmological distances and the case in which it is modified spatially by (strong) gravitational fields, a condition that results in bounds on the gradient of the scalar field. We show that, in both the first case and, because of a bound we derive from the Hulse-Taylor pulsar, in the second, there is not sufficient quinton radiation to affect expected LISA and LIGO gravity wave signals from binary systems. We show that in the second case, the Large Hadron Collider is capable of setting a bound similar to that from the binary pulsar.
A limit theorem for particle current in the symmetric exclusion process

Using the recently discovered strong negative dependence properties of the symmetric exclusion process, we derive general conditions for when the normalized current of particles between regions converges to the Gaussian distribution. The main novelty is that the results do not assume any translation invariance, and hold for most initial configurations.
B decay charm counting via topological vertexing

We present a new and unique measurement of the branching fractions of b hadrons to states with 0, 1 and 2 open charm hadrons, using a sample of 350,000 Z's collected during the SLD/SLC 97-98 run. The analysis takes advantage of the excellent vertexing resolution of the VXD3, a pixel-based CCD vertex detector, which allows the separation of B and cascade D decay vertices. Analysis of the decay length distributions for each of the 1-, 2-, and 3-vertex topologies allows the extraction of the inclusive branching fractions. We measure: BR(b → 0D) =5.6% ± 1.1%(stat.) ± 2.0%(syst.), BR(b → 2D)= 24.6% ± 1.4%(stat.)± 4.0%(syst.) (preliminary), where b and D represent mixtures of open b and open c hadrons.
The synthesis and spectral properties of hemins derived from tetra(p-tolyl)-porphyrin

Abstract Some 32 novel hemin alkoxides, aryloxides, hydroxamates, sulfonates, oximates and other derivatives have been prepared and their infrared, visible and Mossbauer spectra measured. Room temperature Mossbauer spectra can be classified into four general types: A, unsymmetrical doublet with lower energy peak broadened; B, singlet (or perhaps symmetrical unresolved doublet); C, unsymmetrical doublet with higher energy peak broadened; and D, well-resolved symmetrical doublet. The type of spectrum, in general, depends upon the σ-basicity of the axial ligand, although this may not be true for every case. A similar dependence upon basicity is shown in the visible spectra of the hemin alkoxides and aryloxides. The infrared data indicate monodenticity even in those ligands which are commonly bidentate, e.g., the hydroxamates, cupferrate and the anion of 2-mercaptopyridine- N -oxide.
Divisibility properties of the Fibonacci entry point

For a prime p, let Z(p) be the smallest positive integer n so that p divides Fn, the nth term in the Fibonacci sequence. Paul Bruckman and Peter Anderson conjectured a formula for �(m), the density of primes p for which m|Z(p) on the basis of numerical evidence. We prove Bruckman and Anderson's conjecture by studying the algebraic group G : x 2 − 5y 2 = 1 and relating Z(p) to the order of � = (3/2,1/2) ∈ G(Fp). We are then able to use Galois theory and the Chebotarev density theorem to compute �(m).
Single-Sex Schools, Student Achievement, and Course Selection: Evidence from Rule-Based Student Assignments in Trinidad and Tobago

Abstract Existing studies on single-sex schooling suffer from biases because students who attend single-sex schools differ in unmeasured ways from those who do not. In Trinidad and Tobago, students are assigned to secondary schools based on an algorithm allowing one to address self-selection bias and estimate the causal effect of attending a single-sex school versus a similar coeducational school. While females with strong expressed preferences for single-sex schools have better 10th grade exam performance due to attending single-sex schools between grades 6 and10, most students perform no better at single-sex schools. Girls at single-sex-schools take fewer sciences courses.
Evidence, preferences, recommendations--finding the right balance in patient care.

Much progress has been made in applying scientific evidence to medical practice; less progress has been made in rendering care “patient-centered.” A five-step framework for reconciling the tension between “evidence-based” and “preference-based” medicine may help.
Eikonal wave functions and model independent exclusive B decays

Abstract In this letter we calculate the proper normalization for the B meson eikonal valence wave function used in exclusive B decays. The normalization appropriate for a hard scattering process renormalized at the scale μ is determined by calculating the short distance contribution to the purely leptonic decay.
Visualization of Pallets

The National Institute of Standards and Technology (NIST) has been studying pallet visualization for the automated guided vehicle (AGV) industry. Through a cooperative research and development agreement with Transbotics, an AGV manufacturer, NIST has developed advanced sensor processing and world modeling algorithms to verify pallet location and orientation with respect to the AGV. Sensor processing utilizes two onboard AGV, single scan-line, laser-range units. The "Safety" sensor is a safety unit located at the base of a forktruck AGV and the "Panner" sensor is a panning laser-ranger rotated 90 degrees, mounted on a rotating motor, and mounted at the top, front of the AGV. The Safety sensor, typically used to detect obstacles such as humans, was also used to detect pallets and their surrounding area such as the walls of a truck to be loaded with pallets. The Panner, was used to acquire many scan-lines of range data which was processed into a 3D point cloud and segment out the pallet by a priori, approximate pallet load or remaining truck volumes. A world model was then constructed and output to the vehicle for pallet/truck volume verification. This paper will explain this joint government/industry project and results of using LADAR imaging methods.
Cartan’s magic formula and soap film structures

A soap film is actually a thin solid fluid bounded by two surfaces of opposite orientation. It is natural to model the film using one polyhedron for each side. Two problems are to get the polyhedra for both sides to be in the same place without canceling each other out and to model triple junctions without introducing extra boundary components. We use chainlet geometry to create dipole cells and mass cells which accomplish these goals and model faithfully all observable soap films and bubbles. We introduce a new norm on chains of these cells and prove lower semicontinuity of area. A geometric version of Carton’s magic formula provides the necessary boundary coherence.
Silicon Surface Barrier Detectors with High Reverse Breakdown Voltages

Surface barrier detectors with essentially no dead layer and with depleted depths up to 1.5 mnm have been achieved by the combination of an inverted edge and a guard ring. The ability of these devices to withstand high reverse bias voltages insures rapid collection of the charge carriers and consequently fast rising pulses even for thick depletion regions. The energy resolution was 9.2 kev for 1-Mev electrons and was 7.5 kev fwhm at 285°K for 0.6-Mev electrons.
Challenges for hospitality and tourism operators: a North American perspective.

Identifies five main themes from the articles published in the Cornell Hotel and Restaurant Administration Quarterly during a five‐year review period from 1990‐1995. The theme areas (hospitality training and education, human resources and organizations, restaurant and food service operations, hotel operations and development and travel and tourism management) serve to identify some of the main challenges that hospitality and tourism operators are currently facing.
Electrode materials for cesium contact ion engines.

Focusing and accelerating electrode materials for cesium contact ion engines, noting advantages of copper, beryllium and molybdenum
Can dileptons reveal the in-medium properties of vector mesons?

Abstract Dilepton production from both pion-pion and kaon-antikaon annihilation in heavy-ion collisions is studied using the relativistic transport model. The formation of a rho meson from pion-pion annihilation and a phi meson from kaon-antikaon annihilation, their propagation in the medium, and their decay into dileptons are explicity treated. Including medium modifications of the masses and widths of vector mesons as predicted by the QCD sum-rule calculations, we study their effects on the dilepton invariant-mass spectra from heavy-ion collisions at SIS/GSI energies.
Computer simulation studies of model biological membranes.

This Account is focused on computer simulation studies of model biological membrane systems with potential applications in biomedical research. In the past decade, classical molecular dynamics has provided novel insights into the properties of model biomembrane systems, including the nature of the DNA-lipid interactions, the effect of pore-forming transmembrane peptides on the lipid environment, and the partitioning of volatile anesthetic molecules. Such simulations, employing full atomic detail, are typically restricted to systems of dimensions less than 10 nm. Simplified models of the coarse-grain type have been intended to bridge the gap between full atomistic detail and the mesoscopic (micron) regime. The use of such models is illustrated with the example of anesthetics in a phospholipid bilayer.
ANTICIPATING A NEW GOLDEN AGE

The standard model of fundamental interactions is remarkably successful, but it leaves an unfinished agenda. Several major questions seem ripe for exploration in the near future. I anticipate that the coming decade will be a Golden Age of discovery in fundamental physics.
Crystal structure of Nd4Fe1.3Ge7.5

Abstract The crystal structure of the ternary rare-earth compound Nd 4 Fe 1.3 Ge 7.5 has been determined from single-crystal X-ray data. The compound crystallizes in tetragonal, space group Cmcm, No. 63), with a =4.121(1) A, b =30.446(8) A, c =4.2180(9) A, V =529.2(4) A 3 and Z =2 at room temperature. The structure refinement ( R =0.024, R w =0.031) showed the compound to be a new structure-type.
Flows of Calogero–Moser Systems

The Calogero-Moser (or CM) particle system and its generalizations appear, in a variety of ways, in integrable systems, nonlinear PDE, representation theory, and string theory. Moreover, the partially completed CM systems--in which dynamics of particles are continued through collisions--have been identified as meromorphic Hitchin systems, giving natural ``geometric action-angle variables'' for the CM system. Motivated by relations of the CM system to nonlinear PDE, we introduce a new class of generalizations of the spin CM particle systems, the framed (rational, trigonometric and elliptic) CM systems. We give two algebro-geometric descriptions of these systems, via meromorphic Hitchin systems with decorations (framing data) on (cuspidal, nodal and smooth) cubic curves and via one-dimensional sheaves on corresponding ``twisted'' ruled surfaces. We also present a simple geometric formulation of the flows of all meromorphic GL_n Hitchin systems (with no regularity assumptions) as tweaking flows on spectral sheaves. Using this formulation, we show that all spin and framed CM systems are identified with hierarchies of tweaking flows on the corresponding spectral sheaves. This generalizes the well-known description of spinless CM systems in terms of tangential covers.
WARS AND FAMINES: ON DIVISIONS AND INCENTIVES

[Up to now, our analysis has pertained largely, if not entirely, to the problems faced by both developed and Eastern European countries. But most of the world's population resides in developing countries elsewhere, where the role and impact of military expenditures is significantly different. In the first of two papers relating to developing countries, Amyrta Sen asks the basic question: how does the preparation for and the execution of wars influence the ability of famine-prone countries to escape mass starvation — a question of perhaps not much significance to highly developed industrialized market economies, but clearly of tremendous significance to developing economies. (eds.)]
Finite-element quantum field theory

Abstract An alternative approach to lattice gauge theory has been under development for the past decade. It is based on discretizing the operator Heisenberg equations of motion in such a way as to preserve the canonical commutation relations at each lattice site. It is now known how to formulate a non-Abelian gauge theory within this framework. The formulation appears to be free of fermion doubling. Since the theory is unitary, a time-development operator (Hamiltonian) can be constructed.
Intermolecular Gold(I)‐Catalyzed Alkyne Carboalkoxylation Reactions for the Multicomponent Assembly of β‐Alkoxy Ketones

A new gold(I)-catalyzed multicomponent synthesis of β-alkoxy ketones from aldehydes, alcohols, and alkynes is described. This atom economical synthesis was achieved through the use of the gold complex (SPhos)AuNTf2 as a catalyst, and allows for the preparation of a diverse array of β-alkoxy ketone products. Mechanistic studies illustrate that these reactions proceed via gold(I)-catalyzed hydrolysis of the alkyne to an aryl ketone, which then undergoes an aldol reaction with an oxocarbenium ion generated in situ from the aldehyde and alcohol components.
Reliability models for almost-series and almost-parallel systems

When assessing system reliability using system, subsystem, and component-level data, assumptions are required about the form of the system structure in order to utilize the lower-level data. We consider model forms which allow for the assessment and modeling of possible discrepancies between reliability estimates based on different levels of data. By understanding these potential conflicts between data, we can more realistically represent the true uncertainty of the estimates and gain understanding about inconsistencies which might guide further improvements to the system model. The new methodology is illustrated with several examples.
An efficient regioselective NBS aromatic bromination in the presence of an ionic liquid

Abstract A simple, efficient, and rapid method was developed for high-yielding regioselective monobromination of activated aromatic compounds using NBS in combination with ionic liquid 1-butyl-1-methylimidazolium bromide ([Bmim]Br) or dioxane. The ionic liquid is recyclable and can be reused with minimal loss in the catalytic efficiency if the ionic liquid is rapidly microwaved prior to reactions.
Theoretical Analysis of a Water Desalination System Using Low Grade Solar Heat

Theoretical analysis of a solar desalination system utilizing an innovative new concept, which uses low-grade solar heat, is presented. The system utilizes natural means of gravity and atmospheric pressure to create a vacuum, under which liquid can be evaporated at much lower temperatures and with less energy than conventional techniques. The uniqueness of the system is in the way natural forces are used to create vacuum conditions and its incorporation in a single system design where evaporation and condensation take place at appropriate locations without any energy input other than low grade heat. The system consists of solar heating system, an evaporator, a condenser, and injection, withdrawal, and discharge pipes. The effect of various operating conditions, namely, withdrawal rate, depth of water body, temperature of the heat source, and condenser temperature were studied. Numerical simulations show that the proposed system may have distillation efficiencies as high as 90% or more. Vacuum equivalent to 3.7 kPa (abs) or less can be created depending on the ambient temperature at which condensation will take place. @DOI: 10.1115/1.1669450#
Eriksson's numbers game and finite Coxeter groups

The numbers game is a one-player game played on a finite simple graph with certain ''amplitudes'' assigned to its edges and with an initial assignment of real numbers to its nodes. The moves of the game successively transform the numbers at the nodes using the amplitudes in a certain way. This game and its interactions with Coxeter/Weyl group theory and Lie theory have been studied by many authors. In particular, Eriksson connects certain geometric representations of Coxeter groups with games on graphs with certain real number amplitudes. Games played on such graphs are ''E-games''. Here we investigate various finiteness aspects of E-game play: We extend Eriksson's work relating moves of the game to reduced decompositions of elements of a Coxeter group naturally associated to the game graph. We use Stembridge's theory of fully commutative Coxeter group elements to classify what we call here the ''adjacency-free'' initial positions for finite E-games. We characterize when the positive roots for certain geometric representations of finite Coxeter groups can be obtained from E-game play. Finally, we provide a new Dynkin diagram classification result of E-game graphs meeting a certain finiteness requirement.
Querying encrypted data

Data security is a serious concern when we migrate data to a cloud DBMS. Database encryption, where sensitive columns are encrypted before they are stored in the cloud, has been proposed as a mechanism to address such data security concerns. The intuitive expectation is that an adversary cannot "learn" anything about the encrypted columns, since she does not have access to the encryption key. However, query processing becomes a challenge since it needs to "look inside" the data. This tutorial explores the space of designs studied in prior work on processing queries over encrypted data. We cover approaches based on both classic client-server and involving the use of a trusted hardware module where data can be securely decrypted. We discuss the privacy challenges that arise in both approaches and how they may be addressed. Briefly, supporting the full complexity of a modern DBMS including complex queries, transactions and stored procedures leads to significant challenges that we survey and open problems which we highlight.
Quantum deformations from toric geometry

We will demonstrate how calculations in toric geometry can be used to compute quantum corrections to the relations in the chiral ring for certain gauge theories. We focus on the gauge theory of the del Pezzo 2, and derive the chiral ring relations and quantum deformations to the vacuum moduli space using Affleck-Dine-Seiberg superpotential arguments. Then we calculate the versal deformation to the corresponding toric geometry using a method due to Altmann, and show that the result is equivalent to the deformation calculated using gauge theory. In an appendix we will apply this technique to a few other examples. This is a new method for understanding the infrared dynamics of certain quiver gauge theories.
Development and Validation of a Thickened Flame Modeling Approach for Large Eddy Simulation of Premixed Combustion

The development of a dynamic thickened flame (TF) turbulence-chemistry interaction model is presented based on a novel approach to determine the subfilter flame wrinkling efficiency. The basic premise of the TF model is to artificially decrease the reaction rates and increase the species and thermal diffusivities by the same amount, which thickens the flame to a scale that can be resolved on the large eddy simulation (LES) grid while still recovering the laminar flame speed. The TF modeling approach adopted here uses local reaction rates and gradients of product species to thicken the flame to a scale large enough to be resolved by the LES grid. The thickening factor, which is a function of the local grid size and laminar flame thickness, is only applied in the flame region and is commonly referred to as dynamic thickening. Spatial filtering of the velocity field is used to determine the efficiency function by accounting for turbulent kinetic energy between the grid-scale and the thickened flame scale. The TF model was implemented into the commercial computational fluid dynamics code FLUENT. Validation in the approach is conducted by comparing model results to experimental data collected in a laboratory-scale burner. The burner is based on an enclosed scaled-down version of the low swirl injector developed at Lawrence Berkeley National Laboratory. A perfectly premixed lean methane-air flame was studied, as well as the cold-flow characteristics of the combustor. Planar laser induced fluorescence of the hydroxyl molecule was collected for the combusting condition, as well as the velocity field data using particle image velocimetry. Thermal imaging of the quartz liner surface temperature was also conducted to validate the thermal wall boundary conditions applied in the LES calculations.
Cooperative bimetallic catalysis in asymmetric transformations

The efficient synthesis of enantioenriched compounds is becoming increasingly important in modern organic, pharmaceutical, and materials chemistry. Recently, chiral cooperative bimetallic catalysts have emerged as a powerful tool to achieve high efficiency and selectivity in asymmetric transformations. This tutorial review highlights strategies and recent advances in cooperative bimetallic catalysts which have been developed for a variety of asymmetric transformations.
Privacy and Confidentiality in an e-Commerce World: Data Mining, Data Warehousing, Matching and Disclosure Limitation

The growing expanse of e-commerce and the widespread availability of online databases raise many fears regarding loss of privacy and many statistical challenges. Even with encryption and other nominal forms of protection for individual databases, we still need to protect against the violation of privacy through linkages across multiple databases. These issues parallel those that have arisen and received some attention in the context of homeland security. Following the events of September 11, 2001, there has been heightened attention in the United States and elsewhere to the use of multiple government and private databases for the identification of possible perpetrators of future attacks, as well as an unprecedented expansion of federal government data mining activities, many involving databases containing personal information. We present an overview of some proposals that have surfaced for the search of multiple databases which supposedly do not compromise possible pledges of confidentiality to the individuals whose data are included. We also explore their link to the related literature on privacy-preserving data mining. In particular, we focus on the matching problem across databases and the concept of “selective revelation” and their confidentiality implications.
The affinity of a permutation of a finite vector space

For a permutation f of an n-dimensional vector space V over a finite field of order q we let k-affinity(f) denote the number of k-flats X of V such that f(X) is also a k-flat. By k-spectrum(n,q) we mean the set of integers k-affinity(f), where f runs through all permutations of V. The problem of the complete determination of k-spectrum(n,q) seems very difficult except for small or special values of the parameters. However, we are able to determine (n-1)-spectrum(n,2) and establish that [email protected]?k-spectrum(n,q) in the following cases: (i) q>=3 and [email protected][email protected]?n-1; (ii) q=2, [email protected][email protected]?n-1; (iii) q=2, k=2, n>=3 odd. For [email protected][email protected]?n-1 and (q,k) (2,1), the maximum of k-affinity(f) is obtained when f is any semiaffine mapping. We conjecture that the next to largest value of k-affinity(f) occurs when f is a transposition, and we are able to prove it when q=2, k=2, n>=3 and when q>=3, k=1, n>=2.
Taxing the rich: Recombinations and bubble growth during reionization

Reionization is inhomogeneous for two reasons: the clumpiness of the intergalactic medium (IGM), and clustering of the discrete ionizing sources. While numerical simulations can in principle take both into account, they are at present limited by small box sizes. On the other hand, analytic models have only examined the limiting cases of a clumpy IGM (with uniform ionizing emissivity) and clustered sources (embedded in a uniform IGM). Here, we present the first analytic model that includes both factors. At first, recombinations can be ignored and ionized bubbles grow primarily through major mergers, because at any given moment the bubbles have a well-defined characteristic size. As a result, reionization resembles ‘punctuated equilibrium,’ with a series of well-separated sharp jumps in the ionizing background. These features are local effects and do not reflect similar jumps in the global ionized fraction. We then combine our bubble model with a simple description of recombinations in the IGM. We show that the bubbles grow until recombinations balance ionizations, when their expansion abruptly halts. If the IGM density structure is similar to that at moderate redshifts, this limits the bubble radii to ∼20 comoving Mpc; however, if the IGM is significantly clumpier at higher redshifts (because of minihalo formation, for example), the limit could be much smaller. Once a bubble reaches saturation, that region of the Universe has for all intents and purposes entered the ‘post-overlap’ stage. Because different H ii regions saturate over a finite time interval, the overlap epoch actually has a finite width. Our model also predicts a mean recombination rate several times larger than expected for a uniformly illuminated IGM. This picture naturally explains the substantial large-scale variation in Lyman-series opacity along the lines of sight to the known z > 6 quasars. More quasar spectra will shed light on the transition between the ‘bubble-dominated’ topology characteristic of reionization and the ‘web-dominated’ topology characteristic of the later Universe.
Going the last mile: a spatial decision support system for wireless broadband communications

High-speed, wireless communication networks are increasing in popularity; however they can be costly and difficult to plan. In this paper we present a spatial decision support system that incorporates expert knowledge of wireless communications, area topography, demographics and propensity to pay for service in order to aid wireless network planners determine optimal placement of equipment to maximize profit or minimize cost. Moreover, the system can be useful in performing policy analysis to determine pricing, governmental subsidy levels, etc. By integrating a GIS tool into the DSS, planners can easily adjust parameters to better understand the problem at hand and move toward bringing broadband connectivity to the last mile.
The Never-Ending Search for High-Temperature Superconductivity

A brief history of the discovery of new superconductors is given. Different types of pairing mechanisms are considered. By comparing Tcs in different cuprate families it is concluded that the pairing in the CuO2 layers must be supplemented by interactions elsewhere in the unit cell. This conclusion is reached simply by considering the significant variations in Tc that are found in structures that have the same sequence of CuO2 layers within the unit cell but have different intervening layers. A quasi-particle is postulated to account for pairing found in the double chain layer of the Pr247 cuprate and may also exist in the CuO2 layers of all the cuprates.
The Growing Skeleton: MR Imaging Appearances of Developing Cartilage

Developing hyaline cartilage at ends of long bones consists of the epiphyseal, physeal, and articular cartilage components, each of which has specific imaging characteristics that reflect biochemical and macromolecular composition. Standard MR imaging protocols used in adults do not provide sufficient information when used for children, and MR imaging techniques need to be tailored to the developmental stage of the child. This article presents the biochemical and histologic features of normal hyaline cartilage and its MR imaging characteristics, followed by a practical approach to optimizing imaging protocols for cartilage imaging. Finally, common abnormalities and advanced hyaline cartilage imaging techniques are described.
A High-Order Markov-Chain-Based Scheduling Algorithm for Low Delay in CSMA Networks

Recently, several CSMA algorithms based on the Glauber dynamics model have been proposed for wireless link scheduling, as viable solutions to achieve the throughput optimality, yet simple to implement. However, their delay performance still remains unsatisfactory, mainly due to the nature of the underlying Markov chains that imposes a fundamental constraint on how the link state can evolve over time. In this paper, we propose a new approach toward better queueing delay performance, based on our observation that the algorithm needs not be Markovian, as long as it can be implemented in a distributed manner. Our approach hinges upon utilizing past state information observed by local link and then constructing a high-order Markov chain for the evolution of the feasible link schedules. We show that our proposed algorithm, named delayed CSMA, achieves the throughput optimality, and also provides much better delay performance by effectively “decorrelating” the link state process (and thus resolves link starvation). Our simulation results demonstrate that the delay under our algorithm can be reduced by a factor of 20 in some cases, compared to the standard Glauber-dynamics-based CSMA algorithm.
GAS-RICH DWARF SPHEROIDALS

We present evidence that 10 of the 21 dwarf spheroidal galaxies (dSph and dSph/dIrr) in the Local Group are associated with large reservoirs of atomic gas, reservoirs that are, in some cases, larger than the stellar mass. The gas is sometimes found at a large distance (~10 kpc) from the center of a galaxy and is not necessarily centered on it. Similarly large quantities of ionized gas could be hidden in these systems as well. The properties of some of the gas reservoirs are similar to the median properties of the high-velocity clouds (HVCs); two of the H I reservoirs are cataloged HVCs. The association of the H I with the dwarf spheroidals might thus provide a link between the HVCs and stars. We show that the H I content of the Local Group dSphs and dIrrs exhibits a sharp decline if the galaxy is within 250 kpc of either the Milky Way or M31. This can be explained if both galaxies have a sufficiently massive X-ray-emitting halo that produces ram-pressure stripping if a dwarf ventures too close to either giant spiral. We also investigate tidal stripping of the dwarf galaxies and find that although it may play a role, it cannot explain the apparent total absence of neutral gas in most dSph galaxies at distances less than 250 kpc. For the derived mean density of the hot gas, n° = 2.5 × 10-5 cm-3, ram-pressure stripping is found to be more than an order of magnitude more effective in removing the gas from the dSph galaxies. The hot halo, with an inferred mass of 1 × 1010 M☉, may represent a reservoir of ~103 destroyed dwarf systems—either HVCs or true dwarf galaxies similar to those we observe now.
A Clue to the Extent of Convective Mixing Inside Massive Stars: The Surface Hydrogen Abundances of Luminous Blue Variables and Hydrogen-Poor Wolf-Rayet Stars

Interior layers of stars that have been exposed by surface mass loss reveal aspects of their chemical and convective histories that are otherwise inaccessible to observation. It must be significant that the surface hydrogen abundances of luminous blue variables (LBVs) show a remarkable uniformity, specifically X(sub surf) = 0.3 - 0.4, while those of hydrogen-poor Wolf-Rayet (WN) stars fall, almost without exception, below these values, ranging down to X(sub surf) = 0. According to our stellar model calculations, most LBVs are post-red-supergiant objects in a late blue phase of dynamical instability, and most hydrogen-poor WN stars are their immediate descendants. If this is so, stellar models constructed with the Schwarzschild (temperature-gradient) criterion for convection account well for the observed hydrogen abundances, whereas models built with the Ledoux (density-gradient) criterion fail. At the brightest luminosities, the observed hydrogen abundances of LBVs are too large to be explained by any of our highly evolved stellar models, but these LBVs may occupy transient blue loops that exist during an earlier phase of dynamical instability when the star first becomes a yellow supergiant. Independent evidence concerning the criterion for convection, which is based mostly on traditional color distributions of less massive supergiants on the Hertzsprung-Russell diagram, tends to favor the Ledoux criterion. It is quite possible that the true criterion for convection changes over from something like the Ledoux criterion to something like the Schwarzschild criterion as the stellar mass increases.
Alkaline degradation product of cephradine.

Abstract Cephradine yields an unique alkaline degradation product, which has been identified by proton magnetic resonance, n C-N.MR, and mass spectrometry as 2-[6-(l,4-cyclohexadine-l- yl) - 2,5 - dioxo - 3 - piperazinyl] - 5,6- dihydro - 5 - methyl - 2//-1.3- thiazine-4-carboxylic acid, sodium salt.
Photochemical SET induced 1,4-conjugate additions of silyl phosphites to cyclic enones

Abstract Irradiation of cyclic enones 5–8 in the presence of Me3SiOP(OMe)2 or Me3SiOP(OEt)2 gives phosphonosilylation products of 1,4-conjugate addition which are hydrolyzed to the phosphonoketones 11–14 in 82–92% isolated yields. An SET process in which the triplet enone accepts an electron from the silyl phosphite is proposed to be the key initiation step in these reactions.
TIME-DOMAIN ULTRA-WIDEBAND MICROWAVE IMAGING RADAR SYSTEM

This paper describes the time-domain (TD) ultrawideband (UWB) microwave imaging radar system developed at the University of Illinois at Urbana-Champaign recently. The TD-UWB imaging radar system successfully combines the UWB impulse radar system and inverse scattering imaging algorithms for nondestructive evaluation (NDE) and remote sensing purposes in the near-field region. Both the system hardware and inverse scattering algorithms of the system will be discussed in this paper. The TD-UWB imaging radar system can detect dielectric or metallic targets located in air or shallow subsurface with a high resolution image reconstruction capability. Reconstructed images of different types of targets are shown to be in good agreement with the target geometry. The experimental results demonstrate the potential of the system as an useful tool for NDE and remote sensing applications.
Conserved gravitational charges from Yano tensors

The defining properties of Yano tensors naturally generalize those of Killing vectors to anti-symmetric tensor fields of arbitrary rank. We show how the Yano tensors of flat spacetime can be used to construct new, conserved gravitational charges for transverse asymptotically flat spacetimes. The relationship of these new charges to Yano tensors parallels that of ordinary ADM conserved charges to Killing vectors. Hence, we call them Y-ADM charges. A rank n Y-ADM charge is given by an integral over a co-dimension n slice of spatial infinity. In particular, a rank (p+1) Y-ADM charge in a p-brane spacetime is given by an integral over only the sphere SD−(p+2) surrounding the brane and may be regarded as an intensive property of the brane.
Cohen factorizations: Weak functoriality and applications

We investigate Cohen factorizations of local ring homomorphisms from three perspectives. First, we prove a “weak functoriality” result for Cohen factorizations: certain morphisms of local ring homomorphisms induce morphisms of Cohen factorizations. Second, we use Cohen factorizations to study the properties of local ring homomorphisms (Gorenstein, Cohen–Macaulay, etc.) in certain commutative diagrams. Third, we use Cohen factorizations to investigate the structure of quasi-deformations of local rings, with an eye on the question of the behavior of CI-dimension in short exact sequences.
H-dyons and S-duality

Abstract We present a relatively simple argument showing that H-dyon states required by S-duality of the heterotic string on T6 are present provided that the BPS dyons required by S-duality of N = 4 supersymmetric Yang-Mills theory are present. We also conjecture and provide evidence that H-dyons at singularities where the non-perturbative gauge symmetry is completely broken behave like BPS dyons.
Numerical Experiments in Boundary-Layer Stability

Numerical solution of the three-dimensional incompressible Navier-Stokes equations is used to study the instability of a flat-plate boundary layer in a manner analogous to the vibrating-ribbon experiments. Flow field structures are observed which are very similar to those found in the vibrating-ribbon experiment to which computational initial conditions have been matched. Stream wise periodicity is assumed in the simulation so that the evolution occurs in time, but the events that constitute the instability are so similar to the spatially occurring ones of the laboratory that it seems clear the physical processes involved are the same. A spectral and finite difference numerical algorithm is employed in the simulation.
Shock/Viscous Interaction Effects on Nonequilibrium-Dissociated Heating Along Arbitrarily Catalytic Surfaces

A fundamental asymptotic analysis of the subject problem is given based on a triple deck model, here generalized to include both gas phase nonequilibrium dissociation and arbitrary surface catalycity. This theory provides several important results. First, the interaction zone gas phase chemistry may be taken as locally frozen, while its upstream history (however arbitrary) can be readily accommodated into the theory. Second, the influence of finite surface catalycity is characterized by a new interactive heterogeneous Dahmkohler number different from that of noninteractive flows. Third, a new Crocco-like integral of the interactive species/energy equations is identified and then used to derive a closed form analytical solution for the local diffusive heating on an arbitrarily-catalytic surface.
A lower bound for Torelli-K-quasiconformal homogeneity

A closed hyperbolic Riemann surface M is said to be K-quasiconformally homogeneous if there exists a transitive family ℱ of K-quasiconformal homeomorphisms. Further, if all [f]⊂ℱ act trivially on H_1(M;ℤ), we say M is Torelli-K-quasiconformally homogeneous. We prove the existence of a uniform lower bound on K for Torelli-K-quasiconformally homogeneous Riemann surfaces. This is a special case of the open problem of the existence of a lower bound on K for (in general non-Torelli) K-quasiconformally homogeneous Riemann surfaces.
Regiospecific synthesis of 2-methyl-4-arylcarbonyl-2H-1,2-benzothiazin-3(4H)-one 1,1-dioxides

Acylation of 2-methyl-2H-1, 2-benzothiazin-3(4H)-one 1, 1-dioxide 3 with aryl anhydrides in the presence of dimethylaminopyridine occurs regiospecifically to afford 2-methyl-4-arylcarbonyl-2H1, 2-benzothiazin-3(4H)-one 1, 1-dioxides 2a-f.
Dimer Statistics on a Bethe Lattice

We discuss the exact solutions of various models of the statistics of dimer coverings of a Bethe lattice. We reproduce the well-known exact result for noninteracting hard-core dimers by both a very simple geometrical argument and a general algebraic formulation for lattice statistical problems. The algebraic formulation enables us to discuss loop corrections for finite dimensional lattices. For the Bethe lattice we also obtain the exact solution when either (a) the dimers interact via a short-range interaction or (b) the underlying lattice is anisotropic. We give the exact solution for a special limit of dimers on a Bethe lattice in a quenched random potential in which we consider the maximal covering of dimers on random clusters at site occupation probability p. Surprisingly the partition function for "maximal coverage" on the Bethe lattice is identical to that for the statistics of branched polymers when the activity for a monomer unit is set equal to -p. Finally we give an exact solution for the number of residual vacancies when hard-core dimers are randomly deposited on a one dimensional lattice.
Elecciones de 1988 en México: crisis del autoritarismo

The elections of 1988 were considered by almost all political actors and observers from Mexico as the key episode of the political moment facing the country at the end of the century.The federal election of 1988, in more than one sense, a critical choice that can be analyzed from many perspectives. In this article, we will focus this process from two of them: institutional and electoral. First, we analyze the 1988 elections as ainstitutionally regulated process, ie, contained in a framework of laws, regulations and public bodies that set the boundaries of the political strategies of the players available and thus induce certain balances. In particular, we will discuss some important aspects of how the rules of electoral competition policy in force in 1988 contributed both to secure the victory of the PRI, as a result of the crisis of the party system. Furthermore, we discuss some of the highlights of the changes observed in the general patterns of voting behavior. In this regard, we postulate queen the 1988 election, it became clear that the patterns of behavior of the electoratehad been observed for many years were significantly modified, to the extent that one can speak of an electoral realignment. This means that not only witnessed a change among the main variables of electoral behavior (participation and party preference), but above all, a change in the relationship between these aspects of electoral behavior and some of the most important social and regional country.