cssi/SciSciGPT-SciSciNet huggingface dataset:
Reduced models for quantum gravity

As outlined in various other lectures given at this meeting, it seems that a quantum theory of gravity can only be constructed in a non perturbative manner (compare, in particular, Ashtekar’s lectures). Because of that, no calculations, as for example cross sections, decay rates and so on, can be done for the full theory of 3+1 gravity unless one has the full solution space of the quantum constraints and, derived from that, the physical Hilbert space. For a non-gravitational quantum field theory that can be attacked via a perturbative approach one can make quantitative predictions and even make estimates of the error due to higher order corrections while for quantum gravity ’one would have to consider all orders’. So for the former theories one does have a very good idea of how the exact quantum theory should look like and this is important because intuition gives rise to new lines of attack. Hence unfortunately, for the quantum theory of gravity, we lack this general picture of how the exact theory should look like completely. The only way that might help to uncover some of the secrets of how to solve the technical and/or conceptual problems of quantum gravity seems to be to study model systems, ideally those that can be solved exactly. Of course, the lessons that models teach us might be totally misleading and extreme care is due when transferring results from the model to the physical theory of full quantum gravity. This is the point of view that we adopt in the sequel : The models that we are going to discuss capture some of the technical and conceptual problems of gravity and we will pin these down. We will attempt at drawing some conclusions from the solutions we found but we stress the limitations that arise from the various special features of the models we choose and which are not shared by the full theory of quantum gravity.
The Importance of Ownership for E-Commerce

This paper examines the nature and characteristics of the ownership relationship between objects in an object-oriented database. The ownership relationship is distinguished from the Part-Whole relationship since these two are often confused. Dimensions of the ownership relationship are detailed and described with clarifying examples from the financial securities markets. These dimensions are: 1) exclusiveness, 2) dependency, 3) limitation, 4) status, 5) settlement, 6) documentation and 7) inheritance. Formal definitions of the dimensions of the ownership relationship are sketched out for the purpose of extending current Object-Oriented Database Models (OODBs).
Within and Across Country Inequality in a Model of Trade and Endogenous Growth

This paper addresses the dynamics of income inequality, both within and across countries. In an endogenous growth model with North-South trade, the dynamics of income inequality depend on the ability of workers to adapt to new technologies, captured by the quality of education. For developing countries with low quality of education, Southern trade liberalization leads to: 1) an overall decline in effective human capital; 2) an inverted U-shape transition of income inequality, where within country inequality increases in the initial periods following a reduction in trade barriers; and 3) divergence in terms of average income in the short and long run. However, in cases where the South has a high quality of education, workers are better equipped to adapt to new technologies, and trade liberalization induces an U-shape dynamic transition of within country income inequality, where income inequality can decline in the transition. This paper highlights the critical role the quality of education plays in explaining the variations in the observed dynamics of income inequality in developing countries.
A Theory of Inferred Causation

Publisher Summary This chapter discusses the theory of inferred causation. The study of causation is central to the understanding of human reasoning. Inferences involving changing environments require causal theories that make formal distinctions between beliefs based on passive observations and those reflecting intervening actions. In applications such as diagnosis, qualitative physics, and plan recognition, a central task is that of finding a satisfactory explanation to a given set of observations, and the meaning of explanation is intimately related to the notion of causation. In some systems, causal ordering is defined as the ordering at which subsets of variables can be solved independently of others; in other systems, it follows the way a disturbance is propagated from one variable to others. An empirical semantics for causation is important for several reasons. The notion of causation is often associated with those of necessity and functional dependence; causal expressions often tolerate exceptions, primarily because of missing variables and coarse description. Temporal precedence is normally assumed essential for defining causation, and it is one of the most important clues that people use to distinguish causal from other types of associations.
Sovereign Debt Risk Premia and Fiscal Policy in Sweden

This paper takes a step toward providing a general equilibrium framework within which to study the nub of the current fiscal debate around the world: what are the tradeoffs between short-run stabilization and long-run sustainability when the perceived riskiness of government debt depends, in part, on the current and expected fiscal environment in place? We calibrate a simple model to Swedish fiscal data in two periods: before and after the financial crisis of the early 1990s. We compute the dynamic fiscal limit, which depends on the peak of the Laffer curve, for the pre-crisis and three alternative post-crisis fiscal policies. The model simulates the macroeconomic consequences of alternative policies in the face of the sequence of bad output shocks that Sweden experienced from 1991–1997.
Implementing means-tested welfare systems in the United States

While targeting can effectively channel resources to the poor, implementation details matter tremendously to distributive outcomes. Several key factors affect performance, including: data collection processes; information management; household assessment mechanisms; institutional arrangements; and monitoring and oversight mechanisms. This report conducts an in-depth assessment of key design and implementation factors and their potential impact on outcomes for the household targeting system used in the United States to target social programs to the poor and vulnerable.
Assessing the durability of formats in a digital preservation environment: The INFORM methodology

Purpose – To describe INFORM, a new methodology for investigating and measuring the risk factors of digital formats and providing guidelines for preservation action plans.Design/methodology/approach – Construction of a model which aims to discover specific threats to preservation and measure their possible impact on preservation decisions. The methodology defines: risk categories of digital formats and their dependencies; risk factors for each category; scales to measure probability of occurrence and impact; and methods to collect, report and interpret the results.Findings – While individuals are biased and subjective in their aversion to risk, collating the assessments of many individuals should generate group‐consensus or group‐averaged objective results. Hence, preservation plans can be based on objective analysis of risk trends instead of individuals’ opinions developed in the relative isolation of their institutions. The methodology takes into consideration individuals’ aversion to risk, therefore re...
On representations and K -theory of the braid groups

Let Γ be the fundamental group of the complement of a K(Γ, 1) hyperplane arrangement (such as Artin's pure braid group) or more generally a homologically toroidal group as defined below. The triviality of bundles arising from orthogonal representations of Γ is characterized completely as follows. An orthogonal representation gives rise to a trivial bundle if and only if the representation factors through the spinor groups. Furthermore, the subgroup of elements in the complex K-theory of BΓ which arises from complex unitary representations of Γ is shown to be trivial. In the case of real K-theory, the subgroup of elements which arises from real orthogonal representations of Γ is an elementary abelian 2-group, which is characterized completely in terms of the first two Stiefel-Whitney classes of the representation. In addition, quadratic relations in the cohomology algebra of the pure braid groups which correspond precisely to the Jacobi identity for certain choices of Poisson algebras are shown to give the existence of certain homomorphisms from the pure braid group to generalized Heisenberg groups. These cohomology relations correspond to non-trivial Spin representations of the pure braid groups which give rise to trivial bundles.
Gamma-ray astronomy and the origin of cosmic rays

New surveys of galactic gamma ray emission together with millimeter wave radio surveys indicated that cosmic rays were produced as the result of supernova explosions in our galaxy with the most intense production occurring in a Great Galactic Ring about 35,000 light years in diameter where supernova remnants and pulsars were concentrated.
Entropy and the Magic Flute

Part One Entropy and the magic flute The perversion of J. Willard Gibbs, les Atomes, Triscentennial, Albertus Magnus, Fundamental laws of nature Part Two jesus, Moses, Aristotle, and Laboratory Animals Tubes Humans, animals, and physicians' waiting rooms The oath Autism and authority the missing volumes he smoking gun Part Three Just say no The fromagification of America Killer cheese a bioenergeticist's revenge A two-coffee culture Deliver us Part Four Roots of a American tail Justice The sidewalks of New York Brighten the corner where you are Nixon and thermodynamics George Mason, one of our really great men Part Five Koobi Fora Clitoridectomy Mammals I have known Daibutsu and Descartes Taitami taxonomy Madan Pele The sociology of Palo Alto coffee shops Part Six Dirty Neoplatonists Quadrivial pursuits Twenty books clad in black and red The litmus test Expertise The afternoon session Literati Potlatch Part Seven What is Life? Brekekekex A rose by any other name.
Cometary Silicates: Interstellar and Nebular Materials

Evidence for interstellar material in comets is deduced from IR spectra, insitu measurements of Halley, and chondritic porous interplanetary dust particles (CP IDPs). IR spectra of comets reveal the spectrally active minerals: amorphous carbon, amorphous silicates, and (in some comets) crystalline silicates. Evidence suggests amorphous silicates are of interstellar origin while crystalline silicates are of nebular origin. 10 microns spectra of comets and submicron amorphous silicate spherules in CP IDPs have shapes similar to lines-of-sight through the ISM. Thermal emission models of cometary IR spectra require Fe-bearing amorphous silicates. Fe-bearing amorphous silicates may be Fe-bearing crystalline silicates formed in AGB outflows that are amorphized through He+ ion bombardment in supernova shocks in the ISM. Crystalline silicates in comets, as revealed by IR spectra, and their apparent absence in the ISM, argues for their nebular origin. The high temperatures (less than l000 K) at which crystals form or are annealed occur in the inner nebula or in nebular shocks in the 5-10 AU region. Oxygen isotope studies of CP IDPs show by mass only 1 % of the silicate crystals are of AGB origin. Together this suggests crystalline silicates in comets are probably primitive grains from the early solar nebula.
Learning shape and texture characteristics of CT tree-in-bud opacities for CAD systems

Although radiologists can employ CAD systems to characterize malignancies, pulmonary fibrosis and other chronic diseases; the design of imaging techniques to quantify infectious diseases continue to lag behind. There exists a need to create more CAD systems capable of detecting and quantifying characteristic patterns often seen in respiratory tract infections such as influenza, bacterial pneumonia, or tuborculosis. One of such patterns is Tree-in-bud (TIB) which presents thickened bronchial structures surrounding by clusters of micro-nodules. Automatic detection of TIB patterns is a challenging task because of their weak boundary, noisy appearance, and small lesion size. In this paper, we present two novel methods for automatically detecting TIB patterns: (1) a fast localization of candidate patterns using information from local scale of the images, and (2) a Mobius invariant feature extraction method based on learned local shape and texture properties. A comparative evaluation of the proposed methods is presented with a dataset of 39 laboratory confirmed viral bronchiolitis human parainfluenza (HPIV) CTs and 21 normal lung CTs. Experimental results demonstrate that the proposed CAD system can achieve high detection rate with an overall accuracy of 90.96%.
Tax and Incentive Trade-Offs in Multinational Transfer Pricing

Multinationals use transfer prices both for tax minimization and for managerial incentives. This paper analyzes two methods of disentangling the tax and incentive roles: setting multiple prices and...
Modeling the Accretion History of Supermassive Black Holes

There is overwhelming evidence for the presence of supermassive black holes (SMBHs) in the centers of most nearby galaxies. The mass estimates for these remnant black holes from the stellar kinematics of local galaxies and the quasar phenomenon at high redshifts point to the presence of assembled SMBHs. The accretion history of SMBHs can be reconstructed using observations at high and low redshifts as model constraints. Observations of galaxies and quasars in the submillimeter, infrared, optical, and X-ray wavebands are used as constraints, along with data from the demography of local black holes. Theoretical modeling of the growth of black hole mass with cosmic time has been pursued thus far in two distinct directions: a phenomenological approach that utilizes observations in various wavebands, and a semi-analytic approach that starts with a theoretical framework and a set of assumptions with a view to matching observations. Both techniques have been pursued in the context of the standard paradigm for structure formation in a Cold Dark Matter dominated universe. In this chapter, we examine the key issues and uncertainties in the theoretical understanding of the growth of SMBHs.
Asymmetric catalysis: An enabling science

Chirality of organic molecules plays an enormous role in areas ranging from medicine to material science, yet the synthesis of such entities in one enantiomeric form is one of the most difficult challenges. The advances being made stem from the convergence of a broader understanding of theory and how structure begets function, the developments in the interface between organic and inorganic chemistry and, most notably, the organic chemistry of the transition metals, and the continuing advancements in the tools to help define structure, especially in solution. General themes for designing catalysts to effect asymmetric induction are helping to make this strategy more useful, in general, with the resultant effect of a marked enhancement of synthetic efficiency.
Measurement of the microwave background radiation

Absolute flux measurements of the 2.7 K background radiation show a blackbody spectrum with good accuracy ( ca . + 5 %) over two orders of magnitude of wavelength (12 cm to 1 mm). This is in agreement with the thermal history of matter and radiation envisaged by the hot Big Bang model. In particular, experimental limits on spectral distortion constrain processes that release energy into the early Universe. The extreme isotropy of the 2.7 K radiation on small angular scales (10" to 1°) sets interesting limits on models for the formation of mass structure. Some types of perturbations can be ruled out because the accompanying spatial fluctuations in radiation temperature are not seen (Δ T / T -4 ). Large-scale (1-90°) anisotropy of the radiation is plausible because at the time of decoupling (z « 1000), regions separated by more than a few degrees in the sky were not in causal contact. Explanation of the observed isotropy is a major feature of inflationary models. Finally, the observed dipole anisotropy is mostly due to the peculiar velocity of the Galaxy with respect to the radiation frame. An interesting question is: how much of this velocity is primordial and how much can be accounted for by local mass attractors?
Efficient fault diagnosis of helicopter gearboxes

Application of a diagnostic system to a helicopter gearbox is presented. The diagnostic system is a nonparametric pattern classifier that uses a multi-valued influence matrix (MVIM) as its diagnostic model and benefits from a fast learning algorithm that enables it to estimate its diagnostic model from a small number of measurement-fault data. To test this diagnostic system, vibration measurements were collected from a helicopter gearbox test stand during accelerated fatigue tests and at various fault instances. The diagnostic results indicate that the MVIM system can accurately detect and diagnose various gearbox faults so long as they are included in training.
Wireless integration, design, modeling, and analysis of nanosensors, networks, and systems: a systems engineering approach

The design of nanosensor networks and systems encompass multiple areas of research, which include: Design of nanosensors and modeling; Design of wireless interfaces; Design of reliable sensor networks that sense and collect data reliably; Design of backbone networks capable of reliably transporting collected data to remote servers; Design of secure servers for data transfer. This paper provides a systems engineering framework and provides insights into the above design issues.
Linear Models Based on Noisy Data and the Frisch Scheme.

We address the problem of identifying linear relations among variables based on noisy measurements. This is a central question in the search for structure in large data sets. Often a key assumption is that measurement errors in each variable are independent. This basic formulation has its roots in the work of Charles Spearman in 1904 and of Ragnar Frisch in the 1930s. Various topics such as errors-in-variables, factor analysis, and instrumental variables all refer to alternative viewpoints on this problem and on ways to account for the anticipated way that noise enters the data. In the present paper we begin by describing certain fundamental contributions by the founders of the field and provide alternative modern proofs to certain key results. We then go on to consider a modern viewpoint and novel numerical techniques to the problem. The central theme is expressed by the Frisch--Kalman dictum, which calls for identifying a noise contribution that allows a maximal number of simultaneous linear relations a...
A model for tsunami flow inversion from deposits (TSUFLIND)

Abstract Modern tsunami deposits are employed to estimate the overland flow characteristics of tsunamis. With the help of the overland-flow characteristics, the characteristics of the causative tsunami wave can be estimated. The understanding of tsunami deposits has tremendously improved over the last decades. There are three prominent inversion models: (a) Moore's advection model (Moore et al., 2007 ), (b) Soulsby's model (Soulsby et al., 2007 ), and (c) TsuSedMod (Jaffe & Gelfenbuam, 2007 ). TSUFLIND incorporates all three models and adds new modules to better simulate tsunami deposit formation and calculate flow condition. TSUFLIND takes grain-size distribution, thickness, water depth and topography information as inputs. TSUFLIND computes sediment concentration, grain-size distribution of sediment source and initial flow condition to match the sediment thickness and grain size distribution from field observation. Furthermore, TSUFLIND estimates the flow speed, Froude number and representative wave amplitude. The model is tested by using field data collected at Ranganathapuram, India after the 2004 India Ocean tsunami. TSUFLIND reproduces the field measurement grain-size distribution with less than 5% error. Tsunami speed in this test case is about 4.7 ms− 1 at 150 m inland and decreases to 3.3 ms− 1 350 m inland from the shoreline. The estimated wave amplitude of the largest wave for this test case is about 5 to 7 m.
The Infinite Latent Events Model

We present the Infinite Latent Events Model, a nonparametric hierarchical Bayesian distribution over infinite dimensional Dynamic Bayesian Networks with binary state representations and noisy-OR-like transitions. The distribution can be used to learn structure in discrete timeseries data by simultaneously inferring a set of latent events, which events fired at each timestep, and how those events are causally linked. We illustrate the model on a sound factorization task, a network topology identification task, and a video game task.
Predictions of Default Probabilities in Structural Models of Debt

The author investigates corporate bond default probabilities associated mainly with two structural models. Although the models offer alternate probability and recovery rate predictions given changes to common inputs such as volatility and debt maturity, the models reasonably describe actual default probability curves across ratings categories for long horizons. At short horizons, however, the models underpredict defaults and yield spreads. Adding a jump condition to the asset value process may provide a solution.
1 – Introduction and General Considerations

This chapter discusses the chemical vapor deposition (CVD) process. CVD is defined as the deposition of a solid on a heated surface from a chemical reaction in the vapor phase. It belongs to the class of vapor-transfer processes, which is atomistic in nature. It has various advantages such as it is not restricted to a line-of-sight deposition, which is a feature of sputtering, evaporation, and other physical vapor deposition (PVD) processes. The CVD equipment does not require ultrahigh vacuum and can be adapted to many process variations. Its flexibility allows many changes in composition during deposition and the codeposition of elements or compounds is readily achieved. CVD is suitable for various processes such as: the manufacturing of coatings, powders, fibers, and monolithic components. The CVD technology is an essential factor in the manufacture of semiconductors and other electronic components and in optoelectronic and corrosion applications.
Elementary Development of the Gravitational Self-Force

The gravitational field of a particle of small mass m moving through curved spacetime, with metric g ab , is naturally and easily decomposed into two parts each of which satisfies the perturbed Einstein equations through O(m). One part is an inhomogeneous field h ab S which, near the particle, looks like the Coulomb m ∕ r field with tidal distortion from the local Riemann tensor. This singular field is defined in a neighborhood of the small particle and does not depend upon boundary conditions or upon the behavior of the source in either the past or the future. The other part is a homogeneous field h ab R. In a perturbative analysis, the motion of the particle is then best described as being a geodesic in the metric g ab + h ab R. This geodesic motion includes all of the effects which might be called radiation reaction and conservative effects as well.
Hyperbolic Manifolds, Harmonic Forms, and Seiberg–Witten Invariants

New estimates are derived concerning the behavior of self-dual harmonic 2-forms on a compact Riemannian 4-manifold with nontrivial Seiberg–Witten invariants. Applications include a vanishing theorem for certain Seiberg–Witten invariants on compact 4-manifolds of constant negative sectional curvature.
Observing the First Stars, One Star at a Time

Gamma-Ray Bursts (GRBs) are believed to originate in compact remnants (black holes or neutron stars) of massive stars. Their high luminosities make them detectable out to the edge of the visible universe. We describe the many advantages of GRB afterglows relative to quasars as probes of the intergalactic medium during the epoch of reionization. The Swift satellite, planned for launch by the end of 2004, will likely open a new era in observations of the high redshift universe.
Virialization of high redshift dark matter haloes

We present results of a study of the virial state of high-redshift dark matter haloes in an N-body simulation. We find that the majority of collapsed, bound haloes are not virialized at any redshift slice in our study (z= 15 − 6) and have excess kinetic energy. At these redshifts, merging is still rampant and the haloes cannot strictly be treated as isolated systems. To assess if this excess kinetic energy arises from the environment, we include the surface pressure term in the virial equation explicitly and relax the assumption that the density at the halo boundary is zero. Upon inclusion of the surface term, we find that the haloes are much closer to virialization; however, they still have some excess kinetic energy. We report trends of the virial ratio including the extra surface term with three key halo properties: spin, environment and concentration. We find that haloes with closer neighbours depart more from virialization and that haloes with larger spin parameters do as well. We conclude that except at the lowest masses (M < 106 M⊙), dark matter haloes at high redshift are not fully virialized. This finding has interesting implications for galaxy formation at these high redshifts, as the excess kinetic energy will impact the subsequent collapse of baryons and the formation of the first discs and/or baryonic structures.
Revisiting kernelized locality-sensitive hashing for improved large-scale image retrieval

We present a simple but powerful reinterpretation of kernelized locality-sensitive hashing (KLSH), a general and popular method developed in the vision community for performing approximate nearest-neighbor searches in an arbitrary reproducing kernel Hilbert space (RKHS). Our new perspective is based on viewing the steps of the KLSH algorithm in an appropriately projected space, and has several key theoretical and practical benefits. First, it eliminates the problematic conceptual difficulties that are present in the existing motivation of KLSH. Second, it yields the first formal retrieval performance bounds for KLSH. Third, our analysis reveals two techniques for boosting the empirical performance of KLSH. We evaluate these extensions on several large-scale benchmark image retrieval data sets, and show that our analysis leads to improved recall performance of at least 12%, and sometimes much higher, over the standard KLSH method.
Gamma-ray burst rate: high-redshift excess and its possible origins

Prompted by various analyses of long (type II) gamma-ray burst (GRB) rates and their relationship to the cosmic star formation history, metallicity and luminosity function evolution, we systematically analyse these effects with a Monte Carlo code. We test various cosmic star formation history models including analytical and empirical models as well as those derived from cosmological simulations. We also explore expressions for metallicity enhancement of the GRB rate with redshift, as presented in the literature, and discuss improvements to these analytic expressions from the point of view of galactic evolution. These are also compared to cosmological simulations on metal enrichment. Additionally, we explore possible evolutionary effects of the GRB rate and luminosity function with redshift. The simulated results are tested with the observed Swift sample including the L, z and peak flux (log N–log P) distributions. The observational data imply that an increase in the GRB rate is necessary to account for the observations at high redshift, although the form of this enhancement is unclear. A rate increase due to lower metallicity at higher redshift may not be the singular cause and is subject to a variety of uncertainties. Alternatively, evolution of the GRB luminosity function break with redshift shows promise as a possible alternative.
Addressing Household Air Pollution : A Case Study in Rural Madagascar

Household air pollution is the second leading cause of disease in Madagascar, where more than 99 percent of households rely on solid biomass, such as charcoal, wood, and crop waste, as the main cooking fuel. Only a limited number of studies have looked at the emissions and health consequences of cook stoves in Africa. This paper summarizes an initiative to monitor household air pollution in two towns in Madagascar, with a stratified sample of 154 and 184 households. Concentrations of fine particulate matter and carbon monoxide in each kitchen were monitored three times using UCB Particle Monitors and GasBadge Pro Single Gas Monitors. The average concentrations of both pollutants significantly exceeded World Health Organization guidelines for indoor exposure. A fixed-effect panel regression analysis was conducted to investigate the effects of various factors, including fuel (charcoal, wood, and ethanol), stove (traditional and improved ethanol), kitchen size, ventilation, building materials, and ambient environment. Judging by its effect on fine particulate matter and carbon monoxide, ethanol is significantly cleaner than biomass fuels and, for both pollutants, a larger kitchen significantly improves the quality of household air. Compared with traditional charcoal stoves, improved charcoal stoves were found to have no significant impact on air quality, but the improved wood stove with a chimney was effective in reducing concentrations of carbon monoxide in the kitchen, as was ventilation.
On the Minimum Induced Drag of Wings

Of all the types of drag, induced drag is associated with the creation and generation of lift over wings. Induced drag is directly driven by the span load that the aircraft is flying at. The tools by which to calculate and predict induced drag we use were created by Ludwig Prandtl in 1903. Within a decade after Prandtl created a tool for calculating induced drag, Prandtl and his students had optimized the problem to solve the minimum induced drag for a wing of a given span, formalized and written about in 1920. This solution is quoted in textbooks extensively today. Prandtl did not stop with this first solution, and came to a dramatically different solution in 1932. Subsequent development of this 1932 solution solves several aeronautics design difficulties simultaneously, including maximum performance, minimum structure, minimum drag loss due to control input, and solution to adverse yaw without a vertical tail. This presentation lists that solution by Prandtl, and the refinements by Horten, Jones, Kline, Viswanathan, and Whitcomb
Incomplete cooling down of Saturn’s A ring at solar equinox: Implication for seasonal thermal inertia and internal structure of ring particles

Abstract At the solar equinox in August 2009, the Composite Infrared Spectrometer (CIRS) onboard Cassini showed the lowest Saturn’s ring temperatures ever observed. Detailed radiative transfer models show that the observed equinox temperatures of Saturn’s A ring are much higher than model predictions as long as only the flux from Saturn is taken into account. In addition, the post-equinox temperatures are lower than the pre-equinox temperatures at the same absolute solar elevation angle. These facts indicate that the A ring was not completely cooled down at the equinox and that it is possible to give constraints on the size and seasonal thermal inertia of ring particles using seasonal temperature variations around the equinox. We develop a simple seasonal model for ring temperatures and first assume that the internal density and the thermal inertia of a ring particle are uniform with depth. The particle size is estimated to be 1–2 m. The seasonal thermal inertia is found to be 30–50 J m−2 K−1 s−1/2 in the middle A ring whereas it is ∼10 J m−2 K−1 s−1/2 or as low as the diurnal thermal inertia in the inner and outermost regions of the A ring. An additional internal structure model, in which a particle has a high density core surrounded by a fluffy regolith mantle, shows that the core radius relative to the particle radius is about 0.9 for the middle A ring and is much less for the inner and outer regions of the A ring. This means that the radial variation of the internal density of ring particles exists across the A ring. Some mechanisms may be confining dense particles in the middle A ring against viscous diffusion. Alternatively, the (middle) A ring might have recently formed (<108 yr) by destruction of an icy satellite, so that dense particles have not yet diffused over the A ring and regolith mantles of particles have not grown thick. Our model results also indicate that the composition of the core is predominantly water ice, not rock.
POVMs and the Two Theorems of Naimark and Sz.-Nagy

In 1940 Naimark showed that if a set of quantum observables are positive semi-definite and sum to the identity then, on a larger space, they have a joint resolution as commuting projectors. In 1955 Sz.-Nagy showed that any set of observables could be so resolved, with the resolution respecting all linear sums. Crucially, both resolutions return the correct Born probabilities for the original observables. Here, an alternative proof of the Sz.-Nagy result is given using elementary inner product spaces. A version of the resolution is then shown to respect all products of observables on the base space. Practical and theoretical consequences are indicated. For example, quantum statistical inference problems that involve any algebraic functionals can now be studied using classical statistical methods over commuting observables. The estimation of quantum states is a problem of this type. Further, as theoretical objects, classical and quantum systems are now distinguished by only more or less degrees of freedom.
The composition of public expenditure and economic growth

Abstract Noting that the literature has focused on the link between the level of public expenditure and growth, we derive conditions under which a change in the composition of expenditure leads to a higher steady-state growth rate of the economy. The conditions depend not just on the physical productivity of the different components of public expenditure but also on the initial shares. Using data from 43 developing countries over 20 years we show that an increase in the share of current expenditure has positive and statistically significant growth effects. By contrast, the relationship between the capital component of public expenditure and per-capita growth is negative. Thus, seemingly productive expenditures, when used in excess, could become unproductive. These results imply that developing-country governments have been misallocating public expenditures in favor of capital expenditures at the expense of current expenditures.
The developing world's bulging (but vulnerable) "middle class"

Summary Western notions of the ‘middle class’ are of little obvious relevance to developing countries. Instead, the middle class is identified here as those living above the median poverty line of developing countries, even if still poor by rich-country standards. Over 1990–2005, economic growth and global distributional shifts allowed an extra 1.2 billion people to join the developing world’s middle class. Four-fifths came from Asia, and half from China. Many of those in this new middle class remain fairly close to poverty. Only 100 million of the 1.2 billion would not be considered poor in any developing county. Economic growth typically came with an expanding middle class.
The Radio Luminosity-Black Hole Mass Correlation for Quasars from the FIRST Bright Quasar Survey and a “Unification Scheme” for Radio-loud and Radio-quiet Quasars

Several independent lines of evidence now point to a correlation between black hole mass Mbh and radio luminosity. In this Letter, we discuss the correlation for quasars from the FIRST Bright Quasar Survey (FBQS) using black hole mass estimates from Hβ line widths. The FBQS objects fill in the gap between the radio-loud and radio-quiet quasars in the radio luminosity-optical luminosity plane, and we find that they fill the corresponding gap in the Mbh-radio luminosity correlation. There is thus a continuous variation of radio luminosity with Mbh, and no evidence for a "switch" at some set of critical parameter values that turns on powerful radio jets. By combining the FBQS data with that for quasars from the Palomar-Green survey, we find evidence for a dependence of radio luminosity on accretion rate relative to the Eddington limit, L/LEdd, as well as on Mbh, consistent with the well-known radio-optical correlation for radio-loud quasars. We therefore suggest a new scheme to "unify" radio-loud and radio-quiet objects in which the radio luminosity scales proportional to M(L/LEdd)1.0 for L/LEdd ~ 0.1, with an apparently weaker accretion rate dependence at low L/LEdd. The scatter about this relation is ±1.1 dex and may well hide significant contributions from other physical effects, such as the black hole spin and radio source environment.
A review of recursive filtering algorithms

The recursive filtering theory introduced scarcely a decade ago by Kalman and Kalman and Bucy has been widely hailed as a major development in data processing, perhaps as important as the work of Weiner on linear filtering.
TUTTE POLYNOMIALS OF TENSOR PRODUCTS OF SIGNED GRAPHS AND THEIR APPLICATIONS IN KNOT THEORY

It is well-known that the Jones polynomial of an alternating knot is closely related to the Tutte polynomial of a special graph obtained from a regular projection of the knot. Relying on the results of Bollobas and Riordan, we introduce a generalization of Kauffman's Tutte polynomial of signed graphs for which describing the effect of taking a signed tensor product of signed graphs is very simple. We show that this Tutte polynomial of a signed tensor product of signed graphs may be expressed in terms of the Tutte polynomials of the original signed graphs by using a simple substitution rule. Our result enables us to compute the Jones polynomials of some large non-alternating knots. The combinatorics used to prove our main result is similar to Tutte's original way of counting "activities" and specializes to a new, perhaps simpler proof of the known formulas for the ordinary Tutte polynomial of the tensor product of unsigned graphs or matroids.
Strain Characteristics Near the Flame Attachment Point in a Swirling Flow

Swirling flows are widely used in industrial burners and gas turbine combustors for flame stabilization. In many cases, the flame is stabilized in the shear layer near the centerbody and/or abrupt expansion, where the high speed nozzle flow transitions into the larger combustor. Several prior studies have shown that the flame position becomes increasingly unsteady as it approaches blowoff, due to local extinction/re-attachment of the flame at one or both of these locations. This is apparently due to the local strain rate irregularly oscillating about the extinction strain rate values near the attachment point. In order to characterize these flame strain characteristics, PIV measurements were obtained of several hydrogen/methane mixtures in this spatial region. The fluid mechanic straining of the flame in this region is dominated by two gradients in velocity – that due to the strong shear near the centerbody and to the bulk flow deceleration as it expands from the smaller diameter nozzle into the combustor. These two velocity gradients cause positive and negative stretching of the flame sheet, respectively. The shearing velocity gradient is an order of magnitude larger than the flow deceleration term but, due to the fact that the flame is essentially parallel to the shear layer, actually has a secondary influence relative to the flow deceleration. As a result, the dominant flame straining term near the attachment point is apparently compressive – a somewhat counter-intuitive result, given that the flame is stabilized in the positively straining shear layer.
Systematic Approach to Cyclic Orbifolds

We introduce an orbifold induction procedure which provides a systematic construction of cyclic orbifolds, including their twisted sectors. The procedure gives counterparts in the orbifold theory of all the current-algebraic constructions of conformal field theory and enables us to find the orbifold characters and their modular transformation properties.
Enantiospecific synthesis of a differentially protected L-chiro-inositol from D-xylose

Abstract A convenient synthesis of differentially protected L-chiro-inositol 7 from 2,3,4-tri-O-benzyl-D-xylopyranose is described. The structure of 7 was confirmed by its transformation to the pentabenzylated derivative of (−)-quebrachitol.
Power management for energy-aware communication systems

System-level power management has become a key technique to render modern wireless communication devices economically viable. Despite their relatively large impact on the system energy consumption, power management for radios has been limited to shutdown-based schemes, while processors have benefited from superior techniques based on dynamic voltage scaling (DVS). However, similar scaling approaches that trade-off energy versus performance are also available for radios. To utilize these in radio power management, existing packet scheduling policies have to be thoroughly rethought to make them energy-aware, essentially opening a whole new set of challenges the same way the introduction of DVS did to CPU task scheduling. We use one specific scaling technique, dynamic modulation scaling (DMS), as a vehicle to outline these challenges, and to introduce the intricacies caused by the nonpreemptive nature of packet scheduling and the time-varying wireless channel.
Silicon photonics: The optical spice rack

Silicon is evolving as a versatile photonic platform with multiple functionalities that can be seamlessly integrated. We have recently demonstrated the ability to guide, detect and switch multiple wavelength sources at GHz bandwidths and fJ powers on a microelectronic chip.
Packet Switching in a Multiaccess Broadcast Channel: Performance Evaluation

In this paper, the rationale and some advantages for multiaccess broadcast packet communication using satellite and ground radio channels are discussed. A mathematical model is formulated for a "slotted ALOHA" random access system. Using this model, a theory is put forth which gives a coherent qualitative interpretation of the system stability behavior which leads to the definition of a stability measure. Quantitative estimates for the relative instability of unstable channels are obtained. Numerical results are shown illustrating the trading relations among channel stability, throughput, and delay. These results provide tools for the performance evaluation and design of an uncontrolled slotted ALOHA system. Adaptive channel control schemes are studied in a companion paper.
Capital income taxation and risk-taking in a small open economy

Abstract How do capital income taxes affect household portfolio choice and growth? We approach this question within the context of a stochastic model of a small open economy in which taxes on income from domestic capital (equity) and foreign bonds affect household portfolio choice, welfare and the growth rate of the economy. The theoretical and numerical analysis demonstrates the important role that risk plays in determining the mean and variability of growth as well as the conditions under which a higher tax rate can be welfare improving. To shed more light on the complex theoretical interaction between taxes and risk-taking we estimate a reduced-form multinomial probit model of household portfolio choice using the method of simulated moments. The empirical evidence is in stark contrast to the conventional wisdom—we find that higher taxes make it less likely that the household will hold risky assets.
Endogenous Business Networks

Business networks are a feature of the organizational landscape of many countries, though they vary in magnitude. This article develops a theory of business networks where they are endogenous to the reliability of the legal system. Networks are a substitute for reliable institutional support that guarantees written contracts. The existence of networks exerts a negative effect on the functioning of the anonymous market. This is because the network absorbs honest individuals, raising the density of dishonest individuals engaged in anonymous market exchange. Since this lowers the payoff from market exchange, larger networks may be easier to enforce. We find that networks are economically inefficient unless they are relatively large. This is consistent with the view that informal contract enforcement institutions may be inefficient in general equilibrium even though they enhance efficiency in partial equilibrium.
Recent progress in geodesy

Let us consider the present status and scope of geodesy and look at its problems with a view to making the best progress possible in the near future. The recent past to be brought under review should not be limited to a single year, but to a few years. Similarly our attempt to look into the future should not be limited to the one year until we meet here again. In recent time there has been a continually increasing application of the results of geodetic surveys to the control of other less accurate surveying and to mapping. There has been a steady improvement in instruments and methods in spite of the fact that these were already very highly developed. Geodesy is once more internationally organized. The available store of fundamental data of geodesy is being increased rapidly. In North America the extension of the area over which there is continuous triangulation all reduced to one datum has been, and is now, very rapid. Geodesy is developing many contacts with other fields of science, by discussion and by action. The discussions of isostasy have been given new life by the realization on the part of many men that isostasy brings new tests to their hypotheses in other fields of thought than geodesy and that their observations in other fields shed light upon the probable mechanism of isostatic readjustment.
LOW VIRIAL PARAMETERS IN MOLECULAR CLOUDS: IMPLICATIONS FOR HIGH-MASS STAR FORMATION AND MAGNETIC FIELDS

Whether or not molecular clouds and embedded cloud fragments are stable against collapse is of utmost importance for the study of the star formation process. Only "supercritical" cloud fragments are able to collapse and form stars. The virial parameter, α=M_(vir)/M, which compares the virial to the actual mass, provides one way to gauge stability against collapse. Supercritical cloud fragments are characterized by α≾2, as indicated by a comprehensive stability analysis considering perturbations in pressure and density gradients. Past research has suggested that virial parameters α≳2 prevail in clouds. This would suggest that collapse towards star formation is a gradual and relatively slow process, and that magnetic fields are not needed to explain the observed cloud structure. Here, we review a range of very recent observational studies that derive virial parameters <<2 and compile a catalogue of 1325 virial parameter estimates. Low values of alpha are in particular observed for regions of high mass star formation (HMSF). These observations may argue for a more rapid and violent evolution during collapse. This would enable "competitive accretion" in HMSF, constrain some models of "monolithic collapse", and might explain the absence of high--mass starless cores. Alternatively, the data could point at the presence of significant magnetic fields ~1 mG at high gas densities. We examine to what extent the derived observational properties might be biased by observational or theoretical uncertainties. For a wide range of reasonable parameters, our conclusions appear to be robust with respect to such biases.