cssi/SciSciGPT-SciSciNet huggingface dataset:
Quantum mechanics and algorithmic randomness

A long sequence of tosses of a classical coin produces an apparently random bit string, but classical randomness is an illusion: the algorithmic information content of a classically-generated bit string lies almost entirely in the description of initial conditions. This letter presents a simple argument that, by contrast, a sequence of bits produced by tossing a quantum coin is, almost certainly, genuinely (algorithmically) random. This result can be interpreted as a strengthening of Bell's no-hidden-variables theorem, and relies on causality and quantum entanglement in a manner similar to Bell's original argument.
Latin Hypercube Sampling and the Identification of the Foreclosure Contagion Threshold

Over the last several years, the U.S. economy has experienced a significant recession brought on by the collapse of the residential real estate market. During this downturn, the number of real estate foreclosures has risen drastically. Recent studies have empirically demonstrated a reduction in real estate values due to neighboring foreclosures, termed the foreclosure contagion effect. The foreclosure contagion effect impacts healthy neighboring properties that surround the foreclosed property as a function of both time and distance. We mathematically specify a precise equation that identifies the foreclosure contagion threshold, that is, the boundary that separates surviving markets from those that crash. Using a new technique to our field known as Latin Hypercube Sampling, we presents the results of a large scale sensitivity analysis to find that beyond the foreclosure discount and disposition time variables, the percentage of adjustable rate mortgages (ARMs) and the foreclosure distance discount weight...
LOCUSTRA: Accurate Prediction of Local Protein Structure Using a Two-Layer Support Vector Machine Approach

Constraint generation for 3d structure prediction and structure-based database searches benefit from fine-grained prediction of local structure. In this work, we present LOCUSTRA, a novel scheme for the multiclass prediction of local structure that uses two layers of support vector machines (SVM). Using a 16-letter structural alphabet from de Brevern et al. (Proteins: Struct., Funct., Bioinf. 2000, 41, 271-287), we assess its prediction ability for an independent test set of 222 proteins and compare our method to three-class secondary structure prediction and direct prediction of dihedral angles. The prediction accuracy is Q16=61.0% for the 16 classes of the structural alphabet and Q3=79.2% for a simple mapping to the three secondary classes helix, sheet, and coil. We achieve a mean phi(psi) error of 24.74 degrees (38.35 degrees) and a median RMSDA (root-mean-square deviation of the (dihedral) angles) per protein chain of 52.1 degrees. These results compare favorably with related approaches. The LOCUSTRA web server is freely available to researchers at http://www.fz-juelich.de/nic/cbb/service/service.php.
Buddy tracking - efficient proximity detection among mobile friends

Global positioning systems (GPS) and mobile phone networks make it possible to track individual users with an increasing accuracy. It is natural to ask whether this information can be used to maintain social networks. In such a network each user wishes to be informed whenever one of a list of other users, called the user's friends, appears in the user's vicinity. In contrast to more traditional positioning based algorithms, the computation here depends not only on the user's own position on a static map, but also on the dynamic position of the user's friends. Hence it requires both communication and computation resources. The computation can be carried out either between the individual users in a peer-to-peer fashion or by centralized servers where computation and data can be collected at one central location. In the peer-to-peer model, a novel algorithm for minimizing the number of location update messages between pairs of friends is presented. We also present an efficient algorithm for the centralized model, based on region hierarchy and quadtrees. The paper provides an analysis of the two algorithms, compares them with a naive approach, and evaluates them on user motions generated by the IBM City Simulator system.
A non-averaging method of determining the rheological properties of traction fluids

Traction machines have been frequently used to study the rheological responses of lubricants in elastohydrodynamic lubrication (EHL) contacts. Fundamental properties are inferred from EHL traction measurements based on the average pressures and temperatures in the contact. This average approach leads to uncertainty in the accuracy of the results due to the highly nonlinear resonse of the fluid such as viscosity to both pressure and temperature. A non-averaging method is developed in this paper to study the elastic and plastic properties of traction fluids operating in EHL contacts at small slide-to-roll ratios. A precision line-contact traction rig is used to measure the EHL traction at a given oil temperature and Hertz pressure. By choosing a sensible pressure-property expression, the parameters of the expression can be determined through the initial slope and peak traction coefficient of the traction measurements. The elastic shear modulus and the limiting shear stress of the lubricant corresponding to a single pressure can then be calculated for a range of pressures and temperatures of practical interest. Two high-traction fluids are studied, and their elastic moduli and limiting shear stresses presented.
Reflectance calibration standard for optical discs

An accurate method for the determination of reflectance of primary reference discs has been developed at National Institute of Standards and Technology. The reference discs can be used as a traceable industry standard in the calibration of optical disc testing equipments and in the manufacturing of secondary calibration discs.
Linear colorings of subcubic graphs

Abstract A linear coloring of a graph is a proper coloring of the vertices of the graph so that each pair of color classes induces a union of disjoint paths. In this paper, we prove that for every connected graph with maximum degree at most three and every assignment of lists of size four to the vertices of the graph, there exists a linear coloring such that the color of each vertex belongs to the list assigned to that vertex and the neighbors of every degree-two vertex receive different colors, unless the graph is C 5 or K 3 , 3 . This confirms a conjecture raised by Esperet, Montassier and Raspaud [L. Esperet, M. Montassier, and A. Raspaud, Linear choosability of graphs, Discrete Math. 308 (2008) 3938–3950]. Our proof is constructive and yields a linear-time algorithm to find such a coloring.
The Synthesis of Substituted 2-Aminophenyl Heterocyclic Ketones

Abstract The synthesis of substituted 2-aminophenyl heterocyclic ketones, key intermediates to the preparation of 1,4-benzodiazepines has been achieved in one step and in good, yield from the corresponding anthranilic acid, by treatment with heterocyclic lithium reagents and chlorotrimethylsilane.
On the effective group‐velocities of low‐frequency radio time‐signals and the apparent variability of velocity with the region of the Earth traversed

This paper is being printed in full in the September 1936 issue of the Journal of Terrestrial Magnetism and Atmospheric Electricity.
Exoelectron emission from a clean, annealed magnesium single crystal during oxygen adsorption

Exoelectron emission has been observed from a clean, annealed Mg (0001) surface during oxygen and chlorine adsorption at pressures of 6.5×10−5 N/m2 and lower. The studies were performed in an ultrahigh vacuum system. The crystals were cleaned by argon ion bombardment and annealed, at 300 C. Auger electron spectroscopy was used to verify cleanliness, and low energy electron diffraction was used to verify that the surface was annealed. The emission was found to be oxygen arrival rate dependent. Two peaks were observed in the electron emission with exposure. Evidence is presented that the formation of the second peak corresponds to oxidation of the Mg surface. No emission was observed from clean aluminum during adsorption. The results verify that electron emission occurs from a strain free surface simply upon adsorption of oxygen. A qualitative explanation for the mechanisms of emission in terms of chemical effects is presented. Presented at the 31st Annual Meeting in Philadelphia, Pennsylvania, May 10–13, 1976
Designing a Conflict Management System for Higher Education: A Case Study for Design in Integrative Organizations

In 1994, the University System of Georgia embarked on an ambitious effort to reduce the costs of disputing by creating what is now possibly the largest comprehensive, integrated conflict management system (ICMS) in higher education. For almost twenty years, the Consortium on Negotiation and Conflict Resolution has provided technical advice and support for this initiative. This article reviews the context, summarizes the ICMS design, draws a few lessons, and speculates on the value of this work. Because of my close personal involvement, I am straying from convention and telling this story from the first-person perspective. Although probably skewed by hindsight, the historical context is important because our decisions and actions reflected the prevailing conditions and our nascent level of knowledge and experience. The overarching lessons are applicable to most organizations and particularly salient for the conflict management challenges facing the diverse colleges and universities in the United States today and any multifaceted, integrative organization.
Hybrid dynamics of two coupled oscillators that can impact a fixed stop

We consider two linearly coupled masses, where one mass can have inelastic impacts with a fixed, rigid stop. This leads to the study of a two degree of freedom, piecewise linear, frictionless, unforced, constrained mechanical system. The system is governed by three types of dynamics: coupled harmonic oscillation, simple harmonic motion and discrete rebounds. Energy is dissipated discontinuously in discrete amounts, through impacts with the stop. We prove the existence of a non-zero measure set of orbits that lead to infinite impacts with the stop in a finite time. We show how to modify the mathematical model so that forward existence and uniqueness of solutions for all time is guaranteed. Existence of hybrid periodic orbits is shown. A geometrical interpretation of the dynamics based on action coordinates is used to visualize numerical simulation results for the asymptotic dynamics.
Supersonic Annular Nozzles

An analytical method is presented for the design of axisymmetric annular nozzles to yield uniform and axial flow. Computed results are used to display typical matched inner and outer contours, the effects of major initial flow variables, and the resulting wall forces. For axial inflow, the inner contour is longer than the matched outer contour, and there is an apparent maximum expansion area ratio. Variations in the initial flow angle can be used to vary the base height required from matching considerations, to effect the relative division of thrust and length between inner and outer contour. Previous plug-type nozzles are simple limiting cases of the annular nozzles described here.
Fluorinated proteins: From design and synthesis to structure and stability

Fluorine is all but absent from biology; however, it has proved to be a remarkably useful element with which to modulate the activity of biological molecules and to study their mechanism of action. Our laboratory's interest in incorporating fluorine into proteins was stimulated by the unusual physicochemical properties exhibited by perfluorinated small molecules. These include extreme chemical inertness and thermal stability, properties that have made them valuable as nonstick coatings and fire retardants. Fluorocarbons also exhibit an unusual propensity to phase segregation. This phenomenon, which has been termed the "fluorous effect", has been effectively exploited in organic synthesis to purify compounds from reaction mixtures by extracting fluorocarbon-tagged molecules into fluorocarbon solvents. As biochemists, we were curious to explore whether the unusual physicochemical properties of perfluorocarbons could be engineered into proteins. To do this, we developed a synthesis of a highly fluorinated amino acid, hexafluoroleucine, and designed a model 4-helix bundle protein, α4H, in which the hydrophobic core was packed exclusively with leucine. We then investigated the effects of repacking the hydrophobic core of α4H with various combinations of leucine and hexafluoroleucine. These initial studies demonstrated that fluorination is a general and effective strategy for enhancing the stability of proteins against chemical and thermal denaturation and proteolytic degradation. We had originally envisaged that the "fluorous interactions", postulated from the self-segregating properties of fluorous solvents, might be used to mediate specific protein-protein interactions orthogonal to those of natural proteins. However, various lines of evidence indicate that no special, favorable fluorine-fluorine interactions occur in the core of the fluorinated α4 protein. This makes it unlikely that fluorinated amino acids can be used to direct protein-protein interactions. More recent detailed thermodynamic and structural studies in our laboratory have uncovered the basis for the remarkably general ability of fluorinated side chains to stabilize protein structure. Crystal structures of α4H and its fluorinated analogues show that the fluorinated residues fit into the hydrophobic core with remarkably little perturbation to the structure. This is explained by the fact that fluorinated side chains, although larger, very closely preserve the shape of the hydrophobic amino acids they replace. Thus, an increase in buried hydrophobic surface area in the folded state is responsible for the additional thermodynamic stability of the fluorinated protein. Measurements of ΔG°, ΔH°, ΔS°, and ΔCp° for unfolding demonstrate that the "fluorous" stabilization of these protein arises from the hydrophobic effect in the same way that hydrophobic partitioning stabilizes natural proteins.
State cancer pain initiatives

Interest and participation in state cancer pain initiatives have grown rapidly in the past 5 yr. Of signal importance to these state efforts is the fact that several national groups have made relief of cancer pain a priority. State cancer pain initiatives will play a key role in disseminating basic pain-management information, in changing practice and ultimately in evaluating the effectiveness of cancer pain control efforts. They are dedicated to making relief of cancer pain a reality. That is a challenge that will occupy them for many years to come.
Synthesis of a novel heterocyclic system: 2-oxo-1,3-dioxolo[4,5-c]pyridine-6-carboxylic acid, phenylmethyl ester

The synthesis of heterobicyclic carbonate 4 and its conversions to the mixed carbonate 5 and carbamate 6 are described.
Advances in molecular design and synthesis of regioregular polythiophenes.

Regioregular poly(3-alkylthiophene)s (rrP3ATs) are an important class of π-conjugated polymers that can be used in plastic electronic devices such as solar cells and field-effect transistors. rrP3ATs can be ordered in three dimensions: conformational ordering along the backbone, π-stacking of flat polymer chains, and lamellar stacking between chains. All of these features lead to the excellent electrical properties of these materials. Creative molecular design and advanced synthesis are critical in controlling the properties of the materials as well as their device performance. This Account reports the advances in molecular design of new functional polythiophenes as well as the associated polymerization methods. Many functionalized regioregular polythiophenes have been designed and synthesized and show fascinating properties such as high conductivity, mobility, chemosensitivity, liquid crystallinity, or chirality. The methods for the synthesis of rrP3ATs are also applicable to other functional side chains...
A Long-lived Accretion Disk around a Lithium-depleted Binary T Tauri Star

We present a high-dispersion optical spectrum of St 34 and identify the system as a spectroscopic binary with components of similar luminosity and temperature (both M3 ± 0.5). Based on kinematics, signatures of accretion, and location on an H-R diagram, we conclude that St 34 is a classical T Tauri star belonging to the Taurus-Auriga T association. Surprisingly, however, neither component of the binary shows Li I λ6708 absorption, the most universally accepted criterion for establishing stellar youth. In this uniquely known instance, the accretion disk appears to have survived longer than the lithium-depletion timescale. We speculate that the long-lived accretion disk is a consequence of the sub-AU separation companion tidally inhibiting, although not preventing, circumstellar accretion. Comparisons with pre-main-sequence evolutionary models imply, for each component of St 34, a mass of 0.37 ± 0.08 M_☉ and an isochronal age of 8 ± 3 Myr, which is much younger than the predicted lithium-depletion timescale of ~25 Myr. Although a distance 38% closer than that of Taurus-Auriga or a hotter temperature scale could reconcile this discrepancy at 21-25 Myr, similar discrepancies in other systems and the implications of an extremely old accreting Taurus-Auriga member suggest instead a possible problem with evolutionary models. Regardless, the older age implied by St 34's depleted lithium is the first compelling evidence of a substantial age spread in this region. Additionally, since St 34's coeval comembers with early M spectral types would likewise fail the lithium test for youth, current membership lists may be incomplete.
Generative programming for embedded systems

Composition and component-based design are key tools of modern software engineering for managing complexity. The concept of component-based design is straightforward: systems are built by composing software components with precisely defined interfaces using standardized interconnection mechanisms. "Plug-and-play" construction is supported by some underlying composition framework, such as CORBA, which facilitates the component interactions by providing standard services such as request broker, interface repository and others. Unfortunately, this solution tends to work only for building systems with a giant component using small "plug-ins" or for very small systems with a few components.The success of building applications based on a giant component is the result of strong restrictions on plug-in-s and their interaction: the dominant component (such as databases or web browsers) preserves the overall design integrity. In case of small systems, the system designers can preserve design integrity without extensive tool support. The problems of software composition for embedded systems are even harder. Embedded computers are surrounded by physical processes: they receive their inputs from sensors and send their outputs to actuators. Embedded computing devices, viewed from their sensor and actuator interfaces, act like physical processes with dynamics, noise, fault, size, power and other physical characteristics.It is not surprising that using current software technology, logical/functional composability does not imply physical composability. In fact, physical properties are not composable, rather, they appear as cross-cutting constraints in the development process. .Our vision with Model-Integrated Computing (MIC) is to answer the composition challenges of embedded systems the following way:.Modeling: The software development paradigm is changing from the use of dominantly imperative programming languages to dominantly declarative, Domain-Specific Modeling Languages (DSML). Complexity is managed by the use of multiple-view modeling and model analysis techniques.Model-Based Generators: The tight relationship between the model-based design and the modeled system is ensured by the extensive use of model-based generators, which translate the synthesized and verified models into code and other artifacts that form the application.The MIC toolset of ISIS has significant progress in implementing this vision.
Solvent-Free Microwave-Assisted Preparation of N-(2-(Pyridin-2-yl)-ethyl)sulfonamides

Abstract Although nitrogen-containing heterocycles and sulfonamides both play crucial roles in the chemical and pharmaceutical industries, surprisingly little research exists that examines the bifunctional N-(2-(pyridin-2-yl)ethyl)sulfonamide scaffold for any potential applications. Retrosynthetic analysis indicates that this skeleton would be well suited for a conjugate addition reaction. However, the ability of 2-vinylpyridine to behave as an acceptor, and of sulfonamides to behave as donors, has very limited literature precedent, and thus required some preliminary investigations into their mutual reactivity. Herein outlines our laboratory's discovery of a novel and efficient solvent-free 1,4-aza-conjugate addition reaction between sulfonamides and 2-vinylpyridines that provides expedient access to various N-(2-(pyridin-2-yl)ethyl)sulfonamide derivatives. The products, possessing multiple sites of Bronsted acidity and basicity in close proximity, could display a wide array of valuable host–guest propert...
Minimizing Neumann fundamental tones of triangles: An optimal Poincaré inequality

Abstract The first nonzero eigenvalue of the Neumann Laplacian is shown to be minimal for the degenerate acute isosceles triangle, among all triangles of given diameter. Hence an optimal Poincare inequality for triangles is derived. The proof relies on symmetry of the Neumann fundamental mode for isosceles triangles with aperture less than π / 3 . Antisymmetry is proved for apertures greater than π / 3 .
Star formation in emission-line galaxies between redshifts of 0.8 and 1.6

Optical spectra of 14 emission-line galaxies representative of the 1999 NICMOS parallel grism Hα survey of McCarthy et al. are presented. Of the 14, 9 have emission lines confirming the redshifts found in the grism survey. The higher resolution of our optical spectra improves the redshift accuracy by a factor of 5. The [O II]/Hα values of our sample are found to be more than 2 times lower than expected from Jansen et al. This [O II]/Hα ratio discrepancy is most likely explained by additional reddening in our Hα-selected sample [on average, as much as an extra E(B-V) = 0.6], as well as by a possible stronger dependence of the [O II]/Hα ratio on galaxy luminosity than is found in local galaxies. The result is that star formation rates (SFRs) calculated from [O II] λ3727 emission, uncorrected for extinction, are found to be on average 4 ± 2 times lower than the SFRs calculated from Hα emission. Classification of emission-line galaxies as starburst or Seyfert galaxies based on comparison of the ratios [O II]/Hβ and [Ne III] λ3869/Hβ is discussed. New Seyfert 1 diagnostics using the Hα line luminosity, H-band absolute magnitude, and Hα equivalent widths are also presented. One galaxy is classified as a Seyfert 1 based on its broad emission lines, implying a comoving number density for Seyfert 1 galaxies of 2.5 × 10-5 Mpc-3. This comoving number density is a factor of 2.4 times higher than estimated by other surveys.
Lost Greek Mathematical Works in Arabic Translation

The works of the ancient Greek mathematicians which we possess represent only a few fragments from the wreck of the great treasure ship of Hellenistic mathematics. What has come down to us is little more than a reflection of the pedagogical interests of the schoolmen of late antiquity and Byzantine times, who caused to be copied only those works which were of some use in the curricula of their institutions of higher education at Alexandria, Antioch, Athens, Constantinople, and a very few other places. Their choice illustrates the impoverished intellectual climate of the Greek world in the millennium from the third to the thirteenth century a.d. Thus the compendium of elementary geometry which goes under the name of Euclid was transmitted through the schoolrooms, but none of the works on higher geometry which Euclid wrote (probably in the early third century b.c.) has been preserved; and only the first four books of Apollonius’ Conics, which treat the elements of the theory, continued to be copied in Byzantine times: The last four books, which deal with more advanced topics, are lost in Greek.
Uncertainty about average profitability and the diversification discount

Abstract The diversification discount (multiple segment firm value below the value imputed using single segment firm multiples) is commonly thought to be generated by agency problems, a lack of transparency, or lackluster future prospects for diversified firms. If multiple segment firms have lower uncertainty about mean profitability than single segment firms, rational learning about mean profitability provides an alternative explanation for the diversification discount that does not rely on suboptimal managerial decisions or a poor firm outlook. Empirical tests which examine changes in firm value across the business cycle and idiosyncratic volatility are consistent with lower uncertainty about mean profitability for multiple segment firms.
Multichannel Analog to Digital Converter and Readout System for the Time Projection Chamber

The Time Projection Chamber (TPC) project involves the characterization of signals arriving at approximately 20,000 separate detector wires and pad electrodes. The characterization requires measurement of the signal amplitudes in 100 ns time slices over a total time of 20 ?s (the total chamber drift time). Charge Coupled Devices (CCD's) are used to store an image of the 20 ?s span of signals and the image is "played back" at a low rate (50 ?s time slices, i.e., a time expansion of 500:1). Digitization of the 20,000 parallel signals at the output of the CCD's must therefore be accomplished in 50 ?s and readout of digital data into the computer system must also be accomplished in this time. Many zeros occur in the data, a fact which reduces the data handling demands on the readout system, but does not reduce the stringent requirements on the digitizer. Therefore, the requirements on the digitizer are highlighted by the need for low cost, low power consumption and by the need to perform 9-bit digitizing in less than 50 ?s. Furthermore, a double buffering scheme must be used to permit interleaving digitizing and digital readout cycles. We describe our implementation of this concept and some possible applications for other experiments which require many Analog to Digital Converter (ADC) channels.
Optimizing password composition policies

A password composition policy restricts the space of allowable passwords to eliminate weak passwords that are vulnerable to statistical guessing attacks. Usability studies have demonstrated that existing password composition policies can sometimes result in weaker password distributions; hence a more principled approach is needed. We introduce the first theoretical model for optimizing password composition policies. We study the computational and sample complexity of this problem under different assumptions on the structure of policies and on users' preferences over passwords. Our main positive result is an algorithm that -- with high probability --- constructs almost optimal policies (which are specified as a union of subsets of allowed passwords), and requires only a small number of samples of users' preferred passwords. We complement our theoretical results with simulations using a real-world dataset of 32 million passwords.
On the coding theorem and its converse for finite-memory channels

A new definition for the capacity C of a (discrete or semicontinuous) channel with finite memory is given. In terms of this definition both the coding theorem and its weak converse are easily established. In particular, all questions of the ergodicity of the source-channel distribution are avoided, and we are able to show for discrete channels that both the ergodic and stationary capacities (as given by the Shannon-McMillan definition) coincide with that given here. Finally, the strong converse of the coding theorem is shown to hold for a particular finite-memory channel recently considered by Wolfowitz.
Electric propulsion activities outside of the United States.

A has been made of electric propulsion activities in countries outside of the United States. The review was confined to electric thruster studies excluding studies of mission analysis, power supplies, or related diagnostic instrumentation. Since much work on plasma acceleration has been, and still is being carried out in connection with thermonuclear fusion studies and MHD power generation, only those papers were examined wherein specific reference was made to electric propulsion. It is recognized that these latter constraints preclude from this survey many basic studies in ion and plasma physics whose results could possibly be of interest to someone engaged in electric thruster studies. The information upon which this survey is based was obtained from a machine literature search (for qualified users) of unclassified material contained on microfilm in the Data Distribution Center, Alexandria, Va., and NASA files and information that was obtained directly from foreign authors. In most cases, foreign reports that have been translated into English are several years old. This time lapse occurs because of the time delay between publication of the original work and the subsequent translation and republication. Recent material, therefore, can only be had by contacting individuals engaged in research or by attending conferences at which recent research results are presented.
The reaction of [I,I-bis(trifluoroacetoxy)iodo]benzene with N-(benzyloxycarbonyl)-1-aminocyclopropane-1-carboxamide

Abstract The treatment of N -(benzyloxycarbonyl)-1-aminocyclopropane-1-carboxamide with [I,I-bis(trifluoroacetyl)iodo]benzene caused cleavage of the cyclopropane ring with the formation of a β-alaninamide derivative.
An Approximate Solver for Riemann and Riemann-like Ellipsoidal Configurations

We introduce a new technique for constructing three-dimensional models of incompressible Riemann S-type ellipsoids and compressible triaxial configurations that share the same velocity field as that of Riemann S-type ellipsoids. Our incompressible models are exact steady-state configurations; our compressible models represent approximate steady-state equilibrium configurations. Models built from this method can be used to study a variety of relevant astrophysical and geophysical problems.
NEW FORMS OF QUANTUM MATTER NEAR ABSOLUTE ZERO TEMPERATURE

In my talk at the workshop on fundamental physics in space I described the nanokelvin revolution which has taken place in atomic physics. Nanokelvin temperatures have given us access to new physical phenomena including Bose–Einstein condensation, quantum reflection, and fermionic superfluidity in a gas. They also enabled new techniques of preparing and manipulating cold atoms. At low temperatures, only very weak forces are needed to control the motion of atoms. This gave rise to the development of miniaturized setups including atom chips. In Earth-based experiments, gravitational forces are dominant unless they are compensated by optical and magnetic forces. The following text describes the work which I used to illustrate the nanokelvin revolution in atomic physics. Strongest emphasis is given to superfluidity in fermionic atoms. This is a prime example of how ultracold atoms are used to create well-controlled strongly interacting systems and obtain new insight into many-body physics.
How Many Numerical Eigenvalues Can We Trust

When using finite element and finite difference methods to approximate eigenvalues of 2mth-order elliptic problems, the number of reliable numerical eigenvalues can be estimated in terms of the total degrees of freedom $$N$$N in resulting discrete systems. The truth is worse than what we used to believe in that the percentage of reliable eigenvalues decreases with an increased $$N$$N, even though the number of reliable eigenvalues increases with $$N$$N.
Superprotonic phase transition in CsH(PO3H)

High-temperature investigations of the compound CsH(PO₃H) (or CsH₂PO₃, cesium hydrogen phosphite) revealed that this material undergoes a transition, with an onset of 137 °C, to a phase of high proton conductivity. The transition is accompanied by a large heat of transformation, ΔH = 58 ± 2 J/g (12.4 ± 0.4 kJ/mol), and exhibits measurable hysteresis, occurring at 96 °C upon cooling. High-temperature X-ray powder diffraction showed that the high-temperature phase is cubic, with a₀ = 4.896(1)A, and likely takes on a CsCl structure, with Cs atoms at the corners of a simple cubic unit cell, and PO₃H groups at the center. The conductivity in the high-temperature phase at 160 °C is 5.5 × 10⁻³ Ω⁻¹ cm⁻¹, and the activation energy for proton transport is 0.40 ± 0.01 eV. These values suggest that proton transport is facilitated by rapid PO₃H group reorientations in the cubic phase of CsH(PO₃H), as is known to occur in the high-temperature, tetragonal phase of CsHSO₄.
Electric field facilitated SN2 reactions in 7-bromonorbornanes

Abstract Ab initio and natural bond orbital calculations on a series of substituted norbornanes show that the nucleophilic displacement of a nucleofuge at C7 can be enhanced when the molecule contains a substituent at C2 or C3 that creates a strong electric field.
The Complementarity Between Cities and Skills

There is a strong connection between per-worker productivity and metropolitan area population, which is commonly interpreted as evidence for the ex- istence of agglomeration economies. This correlation is particularly strong in cities with higher levels of skill and virtually nonexistent in less skilled metropolitan areas. This fact is particularly compatible with the view that urban density is important because prox- imity spreads knowledge, which either makes workers more skilled or entrepreneurs more productive. Bigger cities certainly attract more skilled workers, and there is some evidence suggesting that human capital accumulates more quickly in urban areas. The connection between area size and per worker productivity and income is a core fact at the center of urban economics (Glaeser, 2008). The connection between urban density and earnings is understood to be a primary reason that cities exist. Understanding the connection between city size and productivity is a core task for students of agglomeration. This paper notes that the connection between city size and productivity does not hold for less skilled metropolitan areas in the United States today. In the least well-educated third of metropolitan areas, there is virtually no connection between city size and productivity or income. In the most well- educated third of metropolitan areas, area population can explain 45 percent of the variation in per-worker productivity. Why does productivity increase with area population for skilled places, but not for unskilled places? One hypothesis is that the connection between productivity and area size reflects a tendency of more skilled people to locate in big cities. However, even in the more skilled places, controlling for area- level skills can only explain a quarter of the measured agglomeration effect. If unobserved skills were explaining the correlation, then we would expect
A re-unification of two competing models for document retrieval

The popularity of the World Wide Web and corporate intranets presents information retrieval (IR) researchers with new opportunities to study users' behaviors, and to thereby improve the systems we deploy. While previous work has shown remarkable benefits from using this data, the field has nevertheless been plagued by theoretical difficulties that prevent its full exploitation. This work aims to resolve one of those difficulties. The problem addressed in this work was originally raised by Robertson et al. in their seminal work (Robertson, Maron et al. 1982). Essentially the problem is that it is not clear how to interpret users' feedback regarding the relevance of a document to a query. Shall we learn something about the document, or shall we instead learn something about the user's query? Or both? This work addresses the question of whether to learn from users' feedback about their queries or about our documents. We propose that in order to properly attribute the positive or negative feedback to either the users' queries or to our document database, we must know which artifact is more likely to require correction. This in turn requires that we hypothesize models about how reliably both documents and queries are created by their respective composers. This simple idea has resulted in immediately practical approaches to feedback data and document retrieval. At the same time, to theoretical soundness allows us to renew our interest in previous approaches to feedback, as we can now better understand how and when they work. Lastly, this theory also opens up a new field of immediately important research into the reliability of people's use of language in their various roles of document author, searcher, and assessor of relevance. The first practical methods for document retrieval to come from our approach are reported here. Results are promising and the methods deserve further investigation.
Pricing of seasoned equity offers and earnings management

This study examines the relations between earnings management by firms offering seasoned equity issues and the pricing of their offers. We hypothesize that seasoned equity offering (SEO) firms that employ aggressive accounting decisions also more aggressively push up their offer prices, thereby leading to a decrease in the degree of underpricing. Consistent with our prediction (the issuer's greed hypothesis), evidence indicates that SEO firms that make opportunistic accounting decisions issue new shares at inflated prices. Our findings remain robust after controlling for other determinants of SEO underpricing and the possible endogeneity of pricing and earnings management.
Solving the supersymmetric flavor problem with radiatively generated mass hierarchies

The supersymmetric flavor problem may be solved if the first and second generation scalars are heavy (with multi-TeV masses) and scalars with large Higgs couplings are light (with sub-TeV masses). We show that such an inverted spectrum may be generated radiatively; that is, from initial conditions where all scalar masses are multi-TeV at some high scale, those with large Higgs couplings may be driven asymptotically to the weak scale in the infra-red. The lightness of third generation scalars is therefore a direct consequence of the heaviness of third generation fermions, and fine-tuning is avoided even though the fundamental scale of the soft supersymmetry breaking parameters is multi-TeV. We investigate this possibility in the framework of the usual Yukawa quasi-fixed point solutions. The required high scale boundary conditions are found to be simple and highly predictive. This scenario also alleviates the supersymmetric CP and Polonyi problems.
The crystal structure and absolute configuration of the 3‐p‐iodobenzoate‐11‐acetate of secogorgosterol

The crystal and molecular structure of a cyclopropane containing marine steroid, secogorgosterol and its absolute configuration have been determined by single X-ray diffraction studies on the 3-p-iodobenzoate-11-acetate derivative. The compound crystallizes in space group PI with reduced cell dimensions a = 9.58, b = 16.38, c = 9.80, α = 96.71, β = 139.75, γ = 94.29. There is one formula unit (C39H55O5I) per unit cell (Z = I). Crystal data were obtained on a G.E. XRD-5 diffractometer using the moving-crystal, moving-counter method, and the structure refined by least squares methods to a conventional R of 6.7% on all (2409) data. The structure determination confirms the presence of a cyclopropane ring in the side chain of the gorgosterol system while a trans conformation is observed about the 22-23 bond.
Stereospecific Suzuki Cross-Coupling of Alkyl α-Cyanohydrin Triflates

Scalemic α-cyanohydrin triflates undergo Pd-catalyzed cross-coupling with aryl, heteroaryl, and vinyl boronic acids under mild conditions. Coupling proceeds with complete inversion of configuration at the stereogenic carbon. The resultant nitrile can be easily converted into a variety of alternative functional groups of value in organic synthesis and thus achieves a higher level of molecular complexity than the products of traditional Suzuki reactions.
Hochschild cohomology of group extensions of quantum symmetric algebras

Quantum symmetric algebras (or noncommutative polynomial rings) arise in many places in mathematics. In this article we find the multiplicative structure of their Hochschild cohomology when the coefficients are in an arbitrary bimodule algebra. When this bimodule algebra is a finite group extension (under a diagonal action) of a quantum symmetric algebra, we give explicitly the graded vector space structure. This yields a complete description of the Hochschild cohomology ring of the corresponding skew group algebra.
Galactic twins of the nebula around SN 1987A: Hints that LBVs may be supernova progenitors

I discuss outstanding questions about the formation of the ring nebula around SN1987A and some implications of similar ring nebulae around Galactic B supergiants. There are notable obstacles for the formation of SN1987A's bipolar nebula through interacting winds in a transition from a red supergiant to a blue supergiant. Instead, several clues hint that the nebula may have been ejected in an LBV‐like event. In addition to the previously known example of Sher 25, there are two newly‐discovered Galactic analogs of SN1987A's ringed nebula. Of these three Galactic analogs around blue supergiants, two (Sher 25 and SBW1 ) have chemical abundances indicating that they have not been through a red supergiant phase, and the remaining ringed bipolar nebula surrounds a luminous blue variable (HD168625). Although SK—69 202's initial mass of ∼20 M⊙ is lower than those atributed to most LBVs, it is not far off, and the low‐luminosity end of the LBV phenomenon is not well defined. Furthermore, HD168625's luminosity indicates an initial mass of only ∼25 M⊙, that of SBW1 is consistent with ∼20 M⊙, and there is a B[e] star in the SMC with an initial mass of ∼20 M⊙ that experienced an LBV outburst in the 1990s. These similarities may be giving us important clues about Sk—69 202's pre‐SN evolution and the formation mechanism of its nebula.
A Census of the Chamaeleon I Star-forming Region

I present a new census of the members of the Chamaeleon I star-forming region. Optical spectroscopy has been obtained for 179 objects that have been previously identified as possible members of the cluster, that lack either accurate spectral types or clear evidence of membership, and that are optically visible (I 18). I have used these spectroscopic data and all other available constraints to evaluate the spectral classifications and membership status of a total sample of 288 candidate members of Chamaeleon I that have appeared in published studies of the cluster. The latest census of Chamaeleon I now contains 158 members, eight of which are later than M6 and thus are likely to be brown dwarfs. I find that many of the objects identified as members of Chamaeleon I in recent surveys are actually field stars. Meanwhile, seven of nine candidates discovered by Carpenter and coworkers are confirmed as members, one of which is the coolest known member of Chamaeleon I at a spectral type of M8 (~0.03 M☉). I have estimated extinctions, luminosities, and effective temperatures for the members and used these data to construct an H-R diagram for the cluster. Chamaeleon I has a median age of ~2 Myr according to evolutionary models and hence is similar in age to IC 348 and is slightly older than Taurus (~1 Myr). The measurement of an initial mass function for Chamaeleon I from this census is not possible because of the disparate methods with which the known members were originally selected and must await an unbiased, magnitude-limited survey of the cluster.
High temporal and spatial‐resolution detection of D‐layer fluctuations by using time‐domain lightning waveforms

[1] This paper presents a new method for probing ionospheric D-layer fluctuations with time-domain very-low and low-frequency (VLF/LF) lightning waveforms detected several hundred kilometers away from lightning storms. The technique compares the amplitude and the time delay between the direct ground wave and the first-hop ionospheric reflection of the lightning signal to measure the apparent D-layer reflectivity and height. This time-domain technique allows a higher time and spatial resolution measurement of the D-layer fluctuations compared to previously reported frequency-domain techniques. For a region near a nighttime thunderstorm, results demonstrate that the apparent reflectivity and height exhibit significant variation on spatial scales of tens of kilometers and over time periods of hours. The range of the reflectivity variation was observed as large as 100% away from the averaged reflectivity for some localized regions, and the height varies by as much as 5% (4 km). The time scales and propagation velocities of the fluctuations appear to be consistent with signatures of atmospheric gravity waves at D-layer altitudes, and the direction of the fluctuation propagation suggests that the gravity waves are originated from the storm. Superimposed on the fluctuations, a general decreasing trend (by ∼4–8 km) in reflection height over the nighttime is observed. In some localized ionosphere regions, apparent splitting of the D-layer by 2–4 km is observed to last a short time period of about 10 min.
Level densities of nickel isotopes: Microscopic theory versus experiment

We apply a spin-projection method to calculate microscopically the level densities of a family of nickel isotopes ${}^{59\ensuremath{-}64}$Ni using the shell model Monte Carlo approach in the complete $pf{g}_{9/2}$ shell. Accurate ground-state energies of the odd-mass nickel isotopes, required for the determination of excitation energies, are determined using the Green's function method recently introduced to circumvent the odd particle-number sign problem. Our results are in excellent agreement with recent measurements based on proton evaporation spectra and with level counting data at low excitation energies. We also compare our results with neutron resonance data, assuming equilibration of parity and a spin-cutoff model for the spin distribution at the neutron binding energy, and find good agreement with the exception of ${}^{63}$Ni.
Multiview range-image registration for forested scenes using explicitly-matched tie points estimated from natural surfaces

Abstract Range images collected from terrestrial laser scanners hold promise for characterizing forest canopies and facilitating research into linkages between forest structure and function. Applications that aim to make plot-level or canopy-level assessments may ultimately require combining range imagery from multiple viewpoints, a procedure of image co-registration that poses numerous challenges. We developed a method for simultaneously registering multiple range images using explicitly-matched, computer-estimated tie points from natural ground and tree-stem surfaces in two stages. Stage I involved registration using tie points estimated from ground-surfaces, while stage II involved tie points estimated from tree-stem centers. Eight range images were simultaneously aligned based on more than 3000 tie point pairs from ground surfaces, and more than 4000 tie point pairs from tree stems. Tie points were widely dispersed throughout the scanned volume, spanning a horizontal area of 750 m 2 and heights up to 22 m above ground. Results showed accurate image alignments at heights well above ground, with an average post-registration error, for tree-stem-based tie point pairs, of 0.16 cm. When linked to automated algorithms for identification and extraction of tree stems from point clouds, the method developed here should be useful for delivering an array of products related to the detailed assessment of forest canopies and stand structure.