cssi/SciSciGPT-SciSciNet huggingface dataset:
Taking the pulse of a continent: expanding site???based research infrastructure for regional??? to continental???scale ecology

Many of the most dramatic and surprising effects of global change on ecological systems will occur across large spatial extents, from regions to continents. Multiple ecosystem types will be impacted across a range of interacting spatial and temporal scales. The ability of ecologists to understand and predict these dynamics depends, in large part, on existing site-based research infrastructures developed in response to historic events. Here we review how unevenly prepared ecologists are, and more generally, ecology is as a discipline, to address regional- to continental-scale questions given these pre-existing site-based capacities, and we describe the changes that will be needed to pursue these broad-scale questions in the future. We first review the types of approaches commonly used to address questions at broad scales, and identify the research, cyber-infrastructure, and cultural challenges associated with these approaches. These challenges include developing a mechanistic understanding of the drivers and responses of ecosystem dynamics across a large, diverse geographic extent where measurements of fluxes or flows of materials, energy or information across levels of biological organization or spatial units are needed. The diversity of methods, sampling protocols, and data acquisition technologies make post-hoc comparisons of ecosystems challenging, and data collected using standardized methods across sites require coordination and teamwork. Sharing of data and analytics to create derived data products are needed for multi-site studies, but this level of collaboration is not part of the current ecological culture. We then discuss the strengths and limitations of current site-based research infrastructures in meeting these challenges, and describe a path forward for regional- to continental-scale ecological research that integrates existing infrastructures with emerging and potentially new technologies to more effectively address broad-scale questions. This new research infrastructure will be instrumental in developing an “uber network” to allow users to seamlessly identify and select, analyze, and interpret data from sites regardless of network affiliation, funding agency, or political affinity, to cover the spatial variability and extent of regional-to continental-scale questions. Ultimately, scientists must network across institutional boundaries in order to tap and expand these existing network infrastructures before these investments can address critical broad-scale research questions and needs.
Extended obstruction tensors and renormalized volume coefficients

Abstract The behavior is investigated of the renormalized volume coefficients associated to a pseudo-Riemannian metric under conformal change of the metric. It is shown that the renormalized volume coefficients define second order fully nonlinear operators in the conformal factor whose algebraic structure is elucidated via the introduction of “extended obstruction tensors”. These together with the Schouten tensor constitute building blocks for the coefficients in the ambient metric expansion. The renormalized volume coefficients have recently been considered by Chang and Fang motivated by comparison with the elementary symmetric functions of the eigenvalues of the Schouten tensor.
Discriminating top-antitop resonances using azimuthal decay correlations

Top-antitop pairs produced in the decay of a new heavy resonance will exhibit spin correlations that contain valuable coupling information. When the tops decay, these correlations imprint themselves on the angular patterns of the final quarks and leptons. While many approaches to the measurement of top spin correlations are known, the most common ones require detailed kinematic reconstructions and are insensitive to some important spin interference effects. In particular, spin-1 resonances with mostly-vector or mostly-axial couplings to top cannot be easily discriminated from one another without appealing to mass-suppressed effects or to more model-dependent interference with continuum Standard Model production. Here, we propose to probe the structure of a resonance’s couplings to tops by measuring the azimuthal angles of the tops’ decay products about the production axis. These angles exhibit modulations which are typically O(0.1-1), and which by themselves allow for discrimination of spin-0 from higher spins, measurement of the CP-phase for spin-0, and measurement of the vector/axial composition for spins1and 2. For relativistic tops, the azimuthal decay angles can be well-approximated without detailed knowledge of the tops’ velocities, and appear to be robust against imperfect energy measurements and neutrino reconstructions. We illustrate this point in the highly challenging dileptonic decay mode, which also exhibits the largest modulations. We comment on the relevance of these observables for testing axigluon-like models that explain the top quark A FB anomaly at the Tevatron, through direct production at the LHC.
Total synthesis of d,l-fulvine and d,l-crispatine

Synthese a partir des acides hydroxy-3 methyl-3 pentanedicarboxyliques-2,3 (fulvinique et crispatique) et de retronecine
Partially premixed laminar gas flames from triangular burners

An experimental study of the effects of using triangular burner exit ports in place of the standard circular ports in a laminar partially premixed gas burner is presented. A natural gas burner employed in a small residential-scale heating system rated at 5.86 kW was modie ed. Air entrainment into the nonburning jets, emission indices of nitrogen oxides and carbon monoxide, and ine ame temperature and composition proe les were measured. Flowe eld in the near-nozzle region was visualized by shadowgraphy. Results show that triangular ports increase air entrainment by 30%, decrease nitrogen oxides emission by less than 15%, and increase carbon monoxide emission by 20%. The effects are explained in terms of the changes in e ow structure and instabilities caused by the noncircular geometry and sharp corners of the burner exit port. Nomenclature D = area equivalent diameter of burner exit port EI = emission index HHV = heating value M = molecular weight n = number of moles PA = primary air r = radial distance from the centroid SA = secondary air T = temperature Tri = triangular port X = mole fraction Subscripts a = air f = fuel
Enantioselective synthesis of (-)-terpestacin and (-)-fusaproliferin: clarification of optical rotational measurements and absolute configurational assignments establishes a homochiral structural series.

An enantioselective synthesis of the syncytium formation inhibitor (−)-terpestacin (1, 19 steps, 5.8% yield from the allylation product of (R,R)-pseudoephedrine propionamide, 3) and the fungal metabolite (−)-fusaproliferin (2, 21 steps, 5.3% yield from 3) in their natural configurations is described. The route employs a series of stereoselective enolate alkylation reactions to establish the initial stereogenic center, set the quaternary carbon configuration, close the 15-membered ring, and introduce the side-chain residue with proper stereocontrol. Careful analysis of our synthetic materials alongside natural samples has revealed that several errors were made in the earlier measurements of optical rotation or in the absolute stereochemical assignments of these natural products. Clarifying all discrepancies, we show here that natural terpestacin (1) is levorotatory, not dextrorotatory as originally described, but was correctly assigned as the (1S,11S,15R,23S)-enantiomer. Fusaproliferin (2) is levorotatory,...
The exchange coupling and spin waves in metallic magnets: removal of the long-wave approximation

Abstract A well-known connection between the magnetic susceptibility and the effective exchange parameter is analyzed. It is shown that all current computational schemes use a long-wave approximation which is suitable only for localized moments systems. A corresponding smallness parameter is derived in real and reciprocal space. General ‘inverse susceptibility’ approach is combined with a multiple scattering theory and applied for the studies of elementary metals Fe, Ni and Gd. It is shown how the proposed approach significantly improves the description of the exchange coupling between nearest atoms, the spin wave spectrum at large wave vectors for the itinerant degrees of freedom in metallic magnets. A consistent usage of this method leads to the proper description of magnetic short-range order effects.
Do Sovereign Bonds Benefit Corporate Bonds in Emerging Markets

We analyze the impact of emerging-market sovereign bonds on emerging-market corporate bonds by examining their spanning enhancement, price discovery, and issuance effects. We find that the effect of spanning enhancement is positive and large; over one-fifth of the information in corporate yield spreads is traced to innovations in sovereign bonds; and most of these effects are due to discovery and spanning of systematic risks. Further, issuance of sovereign bonds, controlling for endogeneity of market-timing decisions, lowers corporate yield and bid-ask spreads. Our results indicate that sovereign securities act as benchmarks and suggest they promote a vibrant corporate bond market.
Guiding principles for site selective and stereoselective intermolecular C–H functionalization by donor/acceptor rhodium carbenes

This tutorial review presents a description of the controlling elements of intermolecular C–H functionalization by means of C–H insertion by donor/acceptor rhodium carbenes. These rhodium carbenes, readily derived from the combination of diazo compounds with dirhodium(II) catalysts, are sufficiently reactive to undergo a wide range of C–H insertions. They are also capable of highly selective reactions, controlled by a combination of steric and electronic factors. An overview of the structural factors that influence site selectivity will be given, followed by a description of the exceptional diastereo- and enantioselectivity that can be achieved. Several examples will be shown of how this methodology can be applied to streamline the synthesis of natural products and pharmaceutical targets.
Multi‐year tracking of sediment sources in a small agricultural watershed using rare earth elements

Rare earth elements (REEs) have been successfully used as a sediment tracer, but the REE technique has never been used for studying sediment sources for a multi-year period. A nearly four-year field experiment was conducted on a small agricultural watershed near Coshocton, OH, USA, to assess the applicability of the REE technique for a multi-year period and to evaluate the relative contributions of sediment sources in the watershed. Tracer depletion and tracer enrichment ratio (ratio of the tracer concentrations in sediment to the concentrations in the soil in the areas of application) were evaluated to examine the applicability and accuracy of the technique. A minimum of 91 per cent of the mass of the applied elements was still available on any individual morphological element at the end of the experimental period. The tracer enrichment ratio varied from 0·4 to 2·3, and it was not significantly related to time. The relative contributions of six morphological elements within the watershed were evaluated as proportions to total sediment yield. The relative contribution of the lower channel was significantly increased as a function of the amount of sediment yield, while that of the lower backslope was significantly decreased. The relative contribution of the lower channel significantly decreased as a function of cumulative sediment yield, while the contributions of the shoulder and the upper backslope significantly increased. Our results showed that the REE technique can be used to track sediment sources for a relatively long period with two limitations or potential sources of error associated with a selective depletion of tracers and a contamination of downslope areas with tagged sediments from upslope areas. Copyright © 2006 John Wiley & Sons, Ltd.
GPS-based attitude determination for a spinning rocket

An algorithm is developed for determining the attitude of a spinning sounding rocket. This algorithm is able to track global positioning system (GPS) signals with intermittent availability but with enough accuracy to yield phase observables for the precise, three-axis attitude determination of a nutating rocket. Raw, single-frequency GPS RF front-end data are processed by several filters to accomplish this task. First, a Levenberg-Marquardt algorithm (LMA) estimates GPS observables for multiple satellites by performing a least-squares fit to the accumulation outputs of a bank of correlators. These observables are then used as measurements in a Rauch-Tung-Striebel smoother that optimizes estimates of carrier phase, Doppler shift, and code phase. Finally, attitude determination is carried out by another batch filter that uses the single-differenced optimized carrier phase estimates between two antennas and an Euler dynamics model for the torque-free attitude motion of the spinning rocket. This second batch filter implements a combination of a substantially modified form of the LMA and the least-squares ambiguity decorrelation adjustment (LAMBDA) method. This design enables it to deal with integer ambiguities that change over long data gaps between times of carrier phase availability. The algorithm presented in this paper is applied to recorded RF data from a spinning sounding rocket mission to produce attitude quaternion and spin-rate estimates using a pair of antennas separated by a 0.3-m baseline. These results are confirmed by another set of quaternions and spin-rate vectors independently estimated from magnetometer and horizon crossing indicator data. Attitude precision on the order of several degrees has been demonstrated.
Fluidic Composite Tunable Vibration Isolators

Coupling a fluidic flexible matrix composite (F2MC) to an air-pressurized fluid port produces a fundamentally new class of tunable vibration isolators. This Fluidlastic device provides significant vibration reduction at an isolation frequency that can be tuned over a broad frequency range. The material properties and geometry of the F2MC element, as well as the port inertance, determine the isolation frequency. A unique feature of this device is that the port inertance depends on pressure so the isolation frequency can be adjusted by changing the air pressure. For constant port inertance, the isolation frequency is largely independent of the isolated mass so the device is robust to changes in load. A nonlinear model is developed to predict isolator length and port inertance. The model is linearized and the frequency response calculated. Experiments agree with theory, demonstrating a tunable isolation range from 9 Hz to 36 Hz and transmitted force reductions of up to 60 dB at the isolation frequency.
The role of ocean-atmosphere reorganizations in glacial cycles

Abstract A case is made that glacial-to-interglacial transitions involve major reorganizations of the ocean-atmosphere system. Such reorganizations constitute jumps between stable modes of operation which cause changes in the greenhouse gas content and albedo of the atmosphere. Only in this way can the rapidity of glacial terminations, the hemispheric synchroneity and symmetry of mountain glaciation, and the large polar air temperature and dustiness variations be accounted for. If these reorganizations are driven in some fashion by orbitally induced seasonal insolation changes, then the connection between insolation and climate is most likely through impacts of fresh water transport on the ocean's salinity distribution.
The enigma of malignant melanoma.

Abstract The case histories of two patients with malignant melanoma are presented to illustrate the varied course which this tumor may pursue. The difficulty in determining prognosis for the individual patient afflicted with melanoma is stressed.
Electronic and structural properties of the novel chain compound Ta4Te4Si

Some interesting aspects of the newly synthesized chain structure Ta 4 Te 4 Si are discussed in this paper. A fragment analysis shows that both metal-metal bonding ant Ta-Si bonding are strong and are responsible for the stabilization of the chain. Band structure calculations suggest that the compound is a metallic conductor
Efficient commit protocols for the tree of processes model of distributed transactions

This paper describes two efficient distributed transaction commit protocols, the Presumed Abort (PA) and Presumed Commit (PC) protocols, which have been implemented in the distributed data base system R* [DSHLM82, LHMWY83]. PA and PC are extensions of the well-known two-phase (2P) commit protocol [Gray78, Lamp80, LSGGL80]. PA is optimized for read-only transactions and a class of multi-site update transactions, and PC is optimized for other classes of multi-site update transactions. The optimizations result in reduced inter-site message traffic and log writes, and, consequently, a better response time for such transactions. We derive the new protocols in a step-wise fashion by modifying the 2P protocol.
The Signatures of Voids and the CMBR

We explore the signature of a cold dark matter compensated void in the quasi non-linear regime. We find that this void is entirely a cold spot on the microwave background, in contrast to a non-linear void. On the last scattering surface(LSS), it appears as either a hot or cold spot depending on where this surface cuts the void. In addition, because the usual cancellations do not occur, the void's LSS signature can be very large as it is proportional to $R/H^{-1}$ rather than $(R/H^{-1})^3$. This implies strict limits for voids on the LSS.
Debts and deficits with fragmented fiscal policymaking

Abstract This paper develops a political-economic model of fiscal policy — one in which government resources are a ‘common property’ out of which interest groups can finance expenditures on their preferred items. This setup has striking macroeconomic implications. Transfers are higher than a benevolent planner would choose them to be; fiscal deficits emerge even when there are no reasons for intertemporal smoothing, and in the long run government debt tends to be excessively high; peculiar time profiles for transfers can emerge, with high net transfers early on giving rise to high taxes later on.
Open subgroups of free topological groups

The theory of covering spaces is often used to prove the Nielsen-Schreier theorem, which states that every subgroup of a free group is free. We apply the more general theory of semicovering spaces to obtain analogous subgroup theorems for topological groups: Every open subgroup of a free Graev topological group is a free Graev topological group. An open subgroup of a free Markov topological group is a free Markov topological group if and only if it is disconnected.
On the embedding problem for nonsolvable Galois groups of algebraic number fields: Reduction theorems

Abstract The embedding problem, which is the problem of extending a given Galois extension K ⊃ k to a Galois extension L ⊃ K ⊃ k so that G( L k ) is a prescribed group extension of G( K k ) , is investigated in the case k is a number field and G( L K ) is nonsolvable, with respect to the question of reduction methods. Two general (arbitrary k and G( L K ) reduction theorems are proved, one reducing the general problem to the cases of G( L K ) nilpotent, and split group extensions, resp, and the second reducing the problem in the case G( L K ) having trivial center to the case G( L k )∼ ⊂ aut G( L K ) . The notion of localizability of an embedding problem is formulated and investigated for certain classical groups.
Petroleum Data System: a network of energy information

The Petroleum Data System is a comprehensive computer base of petroleum information. PDS is available worldwide through the General Electric time-sharing network. It has received widespread usage since its release in April, 1976.The software supporting PDS is a group of general purpose software packages. A driver program links the packages together and provides the interface between the packages and the time-sharing network. These packages handle the problems of information storage and retrieval, applications, and graphics. They have proved to be adaptable to a wide variety of applications. In addition to PDS, the University of Oklahoma plans to make available data bases on coal, geothermal, and minerals. These data bases will be accessed via the same operating procedure as PDS, creating a complete energy-information network.
CR structures on open manifolds

We show that the vanishing of the higher dimensional homology groups of a manifold ensures that every almost CR structure of codimension $k$ may be homotoped to a CR structure. This result is proved by adapting a method due to Haefliger used to study foliations (and previously applied to study the relation between almost complex and complex structures on manifolds) to the case of (almost) CR structures on open manifolds.
Theory of unstable growth

Abstract The theory for the growth of order in unstable systems developed previously is reviewed. An effort is made to illuminate the key assumptions underlying the theory and to indicate how the theory can be improved.
Agricultural Extension: Good Intentions and Hard Realities

This article provides a framework outlining farmers demand for information, the public goods character of extensions services, and the organizational and the political attributes affecting the performance of extension systems. This conceptual framework is used to analyze several extensions modalities and their likely and actual effectiveness. The analysis highlights the efficiency gains that can come from locally decentralized delivery system with incentive structures based on largely private provision, although in poorer countries extension services will remain funded. The goals of agricultural extension includes transferring information from the global knowledge base and from local research to farmers, enabling them to clarify their own goals and possibilities, educating them on how to make better decisions, and stimulating desirable agricultural development.
The crystal chemistry of Bi6TP2O15+x, T=Fe, Ni, Zn: Isomorphism and polymorphism, structural relationship to Bi6TiP2O16

Abstract The crystal structures of compounds with nominal compositions Bi6FeP2O15+x (I), Bi6NiP2O15+x (II) and Bi6ZnP2O15+x (III) were determined from single-crystal X-ray diffraction data. They are monoclinic, space group I2, Z=2. The lattice parameters for (I) are a=11.2644(7), b=5.4380(3), c=11.1440(5) A, β=96.154(4)°; for (II) a=11.259(7), b=5.461(4), c=11.109(7) A, β=96.65(1)°; for (III) a=19.7271(5), b=5.4376(2), c=16.9730(6) A, β=131.932(1)°. Least squares refinements on F2 converged for (I) to R1=0.0554, wR2=0.1408; for (II) R1=0.0647, wR2=0.1697; for (III) R1=0.0385, wR2=0.1023. The crystals are complexly twinned by 2-fold rotation about [ 10 1 ¯ ] , by inversion and by mirror reflection. The structures consist of edge-sharing articulations of OBi4 tetrahedra forming layers in the a–c plane that then continue by edge-sharing parallel to the b-axis. The three-dimensional networks are bridged by Fe and Ni octahedra in (I) and (II) and by Zn trigonal bipyramids in (III) as well as by oxygen atoms of the PO4 moieties. Bi also randomly occupies the octahedral sites. Oxygen vacancies exist in the structures of the three compounds due to required charge balances and they occur in the octahedral coordination polyhedron of the transition metal. In compound (III), no positional disorder in atomic sites is present. The Bi–O coordination polyhedra are trigonal prisms with one, two or three faces capped. Magnetic susceptibility data for compound (I) were obtained between 4.2 and 350 K. Between 4.2 and 250 K it is paramagnetic, μeff=6.1 μB; a magnetic transition occurs above 250 K.
Molecular approach to the study of the mechanisms of alkyl reactions on metal surfaces

Abstract The surface chemistry of alkyl species adsorbed on solid transition metal surfaces is contrasted here against the behavior of analog organometallic systems. The several methods developed in recent years for the clean production of alkyl surface moieties on well characterized metal surfaces are described, and the main decomposition pathways observed after thermal activation of those alkyl species, namely, elimination of both hydride and methyl groups from either the alpha or the beta position, reductive elimination processes related to hydrogenation and to carbon—carbon coupling steps, and insertion, homolysis, and displacement reactions, are discussed. A brief outlook on the future of this field is presented.
NEUTRAL-TO-GROUND VOLTAGE MINIMIZATION IN A PWM-RECTIFIER / INVERTER CONFIGURATION

High frequency common mode voltage produced by power converters are a major cause of conducted EMI, creating motor ground currents, bearing currents and other harmful by-products. In this paper a control algorithm for an induction motor fed by a fully controlled rectifier and inverter is developed to reduce the common mode neutral-to-ground voltage of the induction motor. A bearing current model is used to evaluate the effects on the bearing currents of the double bridge modulation scheme when the new algorithm and conventional algorithms are used. Simulation results are shown to demonstrate the benefits of the new PWM approach.
Enrollment Projection Models for Institutional Planning.

This paper examines alternative techniques for projecting freshman enrollment in specific academic departments. Departmental enrollment projections provided by four different projection models are compared to actual departmental enrollments at a selected institution. Two of the models use only historical data, while the other two models are sensitized to current developments as indicated by the expressed major choices of prospective freshmen. The use of discriminant analysis to establish differential enrollment probabilities is also explored. Although different models do a better job for different curricular departments, the smallest mean squared error across all departments was obtained with the simplest projection technique. The use of the preliminary major choice of prospective freshmen did not improve departmental projections, and the student characteristics explored in this study did not differentiate enrolled from non-enrolled students adequately enough to improve enrollment projection accuracy. Based on the results obtained at this one institution, therefore, it would appear that simple and straightforward projection models can be as useful as complex and sophisticated models.
The Earnings of American Jewish Men : Human Capital, Denomination, and Religiosity

This article analyzes the determinants of the earnings of American Jewish men using the 2000/2001 National Jewish Population Survey. Nonresponse to the question on earnings is analyzed. Earnings are related to conventional human capital variables, as well as Jewish-specific variables. Except for the size of place and region variables, the standard human capital variables have similar effects for Jewish men and the general male population. Jewish day schooling as a youth enhances earnings. Earnings vary by denomination, with Jewish men who identify their denomination as Conservative earning the most, with secular and Orthodox Jews earning less. The effect on earnings of religiosity (measured by synagogue attendance) is not monotonic. Earnings are highest for those who attend about once a week, are lower for those who attend daily, and are lowest for those who never attend.
Linear and Circular Polarization from Sagittarius A* and M81*

We describe recent results for Sgr A*, M81* and other low luminosity active galactic nuclei. We have conducted linear and circular polarimetry over a frequency range of 1.4 to 230 GHz and detected a variety of phenomena. The polarization properties of the studied sources are substantially different from higher powered AGN. In the case of Sgr A*, we are able to eliminate ADAFs and Bondi-Hoyle flows as possible models based on mm λ polarimetry. Our success with Sgr A* demonstrates that we can learn about the nature of accretion and outflow in these sources with unprecedented detail. We may also develop probes of general relativity in the strong-field limit.
The impact of the WARN Act on firm value

Abstract The Worker Adjustment and Retraining Notification (WARN) Act of 1989 mandated that at least 60 days advance notice be given to employees. Critics argued that its passage would decrease managerial flexibility in closing plants, subsequently reducing firm values. This study addresses this issue by examining the stock market's reaction to announcements leading to the eventual enactment of the WARN legislation. We find evidence indicating negative effects of the legislation on stock returns of small firms.
Dynamics with Infinitely Many Time Derivatives and Rolling Tachyons

Both in string field theory and in p-adic string theory the equations of motion involve infinite number of time derivatives. We argue that the initial value problem is qualitatively different from that obtained in the limit of many time derivatives in that the space of initial conditions becomes strongly constrained. We calculate the energy-momentum tensor and study in detail time dependent solutions representing tachyons rolling on the p-adic string theory potentials. For even potentials we find surprising small oscillations at the tachyon vacuum. These are not conventional physical states but rather anharmonic oscillations with a nontrivial frequency-amplitude relation. When the potentials are not even, small oscillatory solutions around the bottom must grow in amplitude without a bound. Open string field theory resembles this latter case, the tachyon rolls to the bottom and ever growing oscillations ensue. We discuss the significance of these results for the issues of emerging closed strings and tachyon matter.
Narrow resonances in statistical mechanics

It is shown that when the dynamics of a system is dominated by narrow-resonance formation it behaves like a noninteracting system with added species of free particles, corresponding to all the quantum numbers and the statistics of each of the resonances. This equivalence, widely assumed and used in practice, is established by explicitly constructing many-particle $S$ matrices consistent with unitarity that correspond to purely resonance-dominated dynamics. These are then used in the $S$-matrix formulation of statistical mechanics to obtain the grand partition function, which is seen to reveal the above result. In the following paper, operational criteria are presented for determining when in general narrow resonances and loosely bound states may be treated as "elementary" particles.
The two-dimensional Bose-Einstein condensate

We study the Hartree–Fock–Bogoliubov mean-field theory as applied to a two-dimensional finite trapped Bose gas at low temperatures and find that, in the Hartree–Fock approximation, the system can be described either with or without the presence of a condensate; this is true in the thermodynamic limit as well. Of the two solutions, the one that includes a condensate has a lower free energy at all temperatures. However, the Hartree–Fock scheme neglects the presence of phonons within the system, and when we allow for the possibility of phonons we are unable to find condensed solutions; the uncondensed solutions, on the other hand, are valid also in the latter, more general scheme. Our results confirm that low-energy phonons destabilize the two-dimensional condensate.
Housing vacancies, thin markets, and idiosyncratic tastes

This paper presents a model with rental housing vacancies in equilibrium. Because of the indivisibility and multi-dimensional heterogeneity of housing units, the housing market is thin. As a result, a typical household entering the market is willing to pay a premium for its most-preferred over its second most-preferred available (vacant) unit. This confers monopoly power on landlords, which they exploit by setting rents above costs. Free entry and exit force profits to zero, with vacancies as the equilibrating mechanism. A nice feature of the model is that housing vacancies are socially useful in expanding the choice set of entering households, though there is no presumption that the market vacancy rate is socially optimal. Thin markets are modeled by assuming an idiosyncratic component to households' tastes over housing units.
Organic Synthesis in the Solid State via Hydrogen-Bond-Driven Self-Assembly

This Perspective describes how chemists can control intermolecular [2 + 2] photodimerizations in the solid state using small molecules as linear templates. The templates assemble olefins into positions for the reaction via hydrogen-bond-driven self-assembly. We attach functional groups to the olefins that complement hydrogen bond donor and acceptor groups of the templates. The resulting cyclobutane-based products form stereospecifically, quantitatively, and in gram amounts. The templates are used to direct the formation of a [2.2]paracyclophane and ladderanes. The organic solid state is an exciting medium within which to control chemical reactivity since it is possible to synthesize, or construct, molecules that may be, otherwise, unobtainable from solution. The products form with a high degree of stereocontrol provided by a crystal lattice. The critical covalent-bond-forming process also occurs in a solvent-free environment. That molecules are virtually frozen in position in a solid also means that this ...
On seven-brane and instanton solutions of type IIB

Abstract It is shown that magnetic seven-branes previously considered as different objects are members of a one-parametric family of supersymmetric seven branes. We enlarge the class of seven-branes by constructing new magnetically and also electrically charged seven-branes. The solutions display a kink-like behavior. We also construct a solution that naturally generalizes the D-instanton.
Symbolic dynamics for nonhyperbolic systems

We introduce index systems, a tool for studying isolated invariant sets of dynamical systems that are not necessarily hyperbolic. The mapping of the index systems mimics the expansion and contraction of hyperbolic maps on the tangent space, and they may be used like Markov partitions to generate symbolic dynamics. Every continuous dynamical system satisfying a weak form of expansiveness possesses an index system. Because of their topological robustness, they can be used to obtain rigorous results from computer approximations of a dynamical system.
Spread-F theories—a review

Our understanding of equatorial spread-F (ESF) phenomena has progressed significantly in the past several years. ESF phenomena involves ionospheric irregularities spanning some 5–6 orders of magnitude in scale size. The largest scale sizes, on the order of many kilometers, are thought to be caused by a plasma fluid type Rayleigh-Taylor instability mechanism on the bottomside of the night-time equatorial-F region. Plasma density bubbles (depletions) are formed on the bottomside by these ionospheric irregularities and then they rise nonlinearly to the topside, by E × B polarization motion, causing irregularities above the F-peak. The power spectral density (PSD) of these long wavelength plasma density fluctuations is proportional to k−2, where k is perpendicular to the geomagnetic field and equal to 2μλ. Current theories of the very small scale, ≲ 10 m, radar backscatter observed irregularities (specifically at 3 m, 1 m, 36 cm, and 11 cm), during ESF, indicate that these irregularities are due to various kinetic type plasma drift wave instabilities. These instabilities are formed by a two step process in which they are driven by the steep plasma density gradients created by the primary long wavelength Rayleigh-Taylor type plasma fluid instabilities. Recent theoretical and numerical simulation studies supporting these ideas on ESF phenomena will be presented.
Cooperative Catalysis: A New Development in Heterogeneous Catalysis

Whereas cooperative effect in catalysis, in which multiple chemical interactions participate cooperatively to achieve significant enhancement in catalytic activity and/or selectivity, is common in enzymatic reactions, it has been sparingly employed in heterogeneous catalytic systems. Here, some recent literature examples of abiotic catalysis, with emphasis on heterogeneous systems, that employ cooperation between acid and base and two metal centers are briefly described to demonstrate the principles involved. Since effective cooperation places strict demand on the positions of the different functional groups, new synthetic methods and strategies are needed to design and construct structures useful for cooperative catalysis. Recent progress in our laboratory in synthesizing new nanocage structures that possess molecular-size cavities, atomic layer thick, porous shells with internal functional groups is described. These recent developments suggest possibilities of new catalytic transformations that have not been attempted before. This is illustrated with two speculative examples utilizing cooperative catalysis: oxidative hydrolytic desulfurization and terminal carbon activation of hydrocarbon molecules.
Calculational study of fluoroammonium and related cations and dications.

Structures as well as 15N and 19F NMR chemical shifts of a series of fluoroammonium ions were studied by ab initio/GIAO-SCF, GIAO-MP2 and GIAO-CCSD(T) methods. Calculated 15N and 19F NMR chemical shifts correlate well with the experimental data. The relative stabilities as well as the charge of the central nitrogen atom of fluoro-substituted tetrahedral ammonium ions were found to increase linearly with the increasing number of fluorine substituents due to their strong electron-withdrawing inductive effect. Similarly the magnitude of 15N NMR chemical shifts also increase linearly with the increasing number of fluorine substituents in accord with the strong deshielding effect of fluorine. Structures as well as 15N and 19F NMR chemical shifts of yet experimentally unknown fluoroammonium dications were also computed.
High Quantum Efficiency at Low Bias AlxGa1–xN p–i–n Photodiodes

There has been a growing interest in back-illuminated solar-blind Al x Ga 1-x N photodiodes for flip-chip mounting to silicon read-out circuits. These devices not only need to have high external quantum efficiencies, but these efficiencies must be achieved at, or less than, the operating voltage of the readout display. We report the growth, fabrication, characterization, and comparison of two Al x Ga 1-x N heteroepitaxial back-illuminated p-i-n photodiodes. The first device is visible-blind with an Al 0.20 Ga 0.80 N active region and shows an external quantum efficiency of 53% at zero bias and 64% at 5 V at a wavelength of λ = 290 nm. The second device is solar-blind and has an Al 0.35 Ga 0.65 N active region with 0 V and 5 V external quantum efficiencies of 26% and 32% at 279 nm, respectively. Detectivities of D * = 8.40 × 10 12 cm Hz 1/2 W -1 and D * = 5.30 × 10 12 cm Hz 1/2 W -1 were demonstrated for the Al 0.20 Ga 0.80 N and Al 0.35 Ga 0.65 N devices, respectively.
Magnetic energy production by turbulence in binary neutron star mergers

The simultaneous detection of electromagnetic and gravitational wave emission from merging neutron star binaries would greatly aid in their discovery and interpretation. By studying turbulent amplification of magnetic fields in local high-resolution simulations of neutron star merger conditions, we demonstrate that magnetar-level ( 1016?G) fields are present throughout the merger duration. We find that the small-scale turbulent dynamo converts 60% of the randomized kinetic energy into magnetic fields on a merger timescale. Since turbulent magnetic energy dissipates through reconnection events that accelerate relativistic electrons, turbulence may facilitate the conversion of orbital kinetic energy into radiation. If 10?4 of the ~1053?erg of orbital kinetic available gets processed through reconnection and creates radiation in the 15-150?keV band, then the fluence at 200?Mpc would be 10?7 erg cm?2, potentially rendering most merging neutron stars in the advanced LIGO and Virgo detection volumes detectable by Swift BAT.
Simulation of Flux Emergence from the Convection Zone to the Corona

Here, we present numerical simulations of magnetic flux buoyantly rising from a granular convection zone into the low corona. We study the complex interaction of the magnetic field with the turbulent plasma. The model includes the radiative loss terms, non-ideal equations of state, and empirical corona heating. We find that the convection plays a crucial role in shaping the morphology and evolution of the emerging structure. The emergence of magnetic fields can disrupt the convection pattern as the field strength increases, and form an ephemeral region-like structure, while weak magnetic flux emerges and quickly becomes concentrated in the intergranular lanes, i.e., downflow regions. As the flux rises, a coherent shear pattern in the low corona is observed in the simulation. In the photosphere, both magnetic shearing and velocity shearing occur at a very sharp polarity inversion line. In a case of U-loop magnetic field structure, the field above the surface is highly sheared while below it is relaxed.
Asymptotic Opening Angles for Colliding-Wind Bow Shocks: The Characteristic-Angle Approximation

By considering the advection and interaction of the vector momentum flux in highly supersonic spherically diverging winds, we derive a simple analytic description of the asymptotic opening angle of a wind-collision shock cone, in the approximation that the shocked gas is contained in a cone streaming out along a single characteristic opening angle. Both highly radiative and highly adiabatic limits are treated, and their comparison is the novel result. Analytic closed-form expressions are obtained for the inferred wind momentum ratios as a function of the observed shock opening angle, allowing the conspicuous shape of the asymptotic bow shock to be used as a preliminary constraint on more detailed modeling of the colliding winds. In the process, we explore from a general perspective the limitations in applying to the global shock geometry the so-called Dyson approximation, which asserts a local balance in the perpendicular ram pressure across the shock.
Suzuki and Heck coupling reactions mediated by palladium complexes bearing trans-spanning diphosphines

Palladium complexes of three trans-spanning diphosphines are examined for effecting C–C coupling reactions. Ten aryl halides of varying electron density were screened in Suzuki coupling reactions with phenylboronic acid and in Heck reactions with styrene. The results are discussed in terms of the unique flexibility and shape of the meta-terphenyl backbone upon which the diphosphine ligand is built. 2004 Elsevier B.V. All rights reserved.
Simultaneous independent measurement of splat diameter and cooling time during impact on a substrate of plasma-sprayed molybdenum particles

In thermal spray processes, the coating structure is the result of flattening and cooling of molten droplets on the substrate. The study of the cooling time and evolution of the splat size during impact is then of the highest importance to understand the influence of the spray parameters and substrate characteristics on the coating structure. Measurement of particle temperature during impact requires the use of a high-speed two-color pyrometer to collect the thermal emission of the particle during flattening. Simultaneous measurement of the splat size with this pyrometer is difficult since the size of the particle can change as it cools down. To measure the splat size independently, a new measurement technique has been developed. In this technique, the splat size is measured from the attenuation of the radiation of a laser beam illuminating the particle during impact. Results are presented for plasma-sprayed molybdenum particles impacting on a glass substrate at room temperature. It is shown that the molybdenum splat reaches its maximum extent about 2 µs after the impact. In this work, we show that this increase of the splat surface is followed by a phase during which the splat size decreases significantly during 2 to 3 µs.
Domestic unionization and import competition

We develop a Cournot duopoly model of a domestic unionized firm and a foreign firm. The negotiated wage and employment levels are simultaneously determined through efficient Nash bargaining. A union is employment (wage) oriented if the employment elasticity of its utility is higher (lower) than the corresponding excess wage elasticity. An increase in the bargaining power of an employment oriented union increases domestic output and welfare. If the union is wage oriented, then protection may decrease output and welfare. A credible threat to shift production abroad increases domestic profits and lowers the negotiated wage.
Detector and event visualization with SketchUp at the CMS experiment

We have created 3D models of the CMS detector and particle collision events in SketchUp, a 3D modelling program. SketchUp provides a Ruby API which we use to interface with the CMS Detector Description to create 3D models of the CMS detector. With the Ruby API, we also have created an interface to the JSON-based event format used for the iSpy event display to create 3D models of CMS events. These models have many applications related to 3D representation of the CMS detector and events. Figures produced based on these models were used in conference presentations, journal publications, technical design reports for the detector upgrades, art projects, outreach programs, and other presentations.
A simple economic theory of skill accumulation and schooling decisions

Abstract We propose a model of schooling that can account for the observed heterogeneity in workers' productivity and educational attainment. Identical unskilled agents can get a degree at a cost, but becoming skilled entails an additional unobservable effort cost. Individual labor can then be used as an input in pairwise production matches. Two factors affect students' desire to build human capital: degrees imperfectly signal productivity, and contract imperfections generate holdup problems. Multiple stationary equilibria exist, some of which are market failures characterized by a largely educated workforce of low average skill. Policy implications are explored.