cssi/SciSciGPT-SciSciNet huggingface dataset:
Factoring LP block-angular bases

The total basis D for any simplex solution to a block-angular LP model is factored in the form B E = D, B = Πp D p, where the D p are simple matrix structures of the form $$ \left[ {\begin{array}{*{20}c} I & {A_p } \\ 0 & {B_p } \\ \end{array} } \right] $$ which are fully commutative as are their inverses. The total inverse D −1 = E −1·Πp D p −1 is readily maintainable in piece-meal product-forms with possible additional columns required for E −1. These additional columns are the length of the corresponding columns of B p.
Clinically important body weight gain following knee arthroplasty: a five-year comparative cohort study.

Objective The impact of knee arthroplasty on body weight has not been fully explored. Clinically important weight gain following knee arthroplasty would pose potentially important health risks. Methods We used one of the largest US-based knee arthroplasty registries and a population-based control sample from the same geographic region to determine whether knee arthroplasty increases the risk of clinically important weight gain of ≥5% of baseline body weight over a 5-year postoperative period. Results Of the persons in the knee arthroplasty sample, 30.0% gained ≥5% of baseline body weight 5 years following surgery as compared to 19.7% of the control sample. The multivariable-adjusted (age, sex, body mass index, education, comorbidity, and presurgical weight change) odds ratio (OR) was 1.6 (95% confidence interval [95% CI] 1.2–2.2) in persons with knee arthroplasty as compared to the control sample. Additional arthroplasty procedures during followup further increased the risk for weight gain (OR 2.1, 95% CI 1.4–3.1) relative to the control sample. Specifically, among patients with knee arthroplasty, younger patients and those who lost greater amounts of weight in the 5-year preoperative period were at greater risk for clinically important weight gain. Conclusion Patients who undergo knee arthroplasty are at an increased risk of clinically important weight gain following surgery. The findings potentially have broad implications to multiple members of the health care team. Future research should develop weight loss/maintenance interventions particularly for younger patients who have lost a substantial amount of weight prior to surgery, as they are most at risk for substantial postsurgical weight gain.
The role of cytosine methylation on charge transport through a DNA strand

Cytosine methylation has been found to play a crucial role in various biological processes, including a number of human diseases. The detection of this small modification remains challenging. In this work, we computationally explore the possibility of detecting methylated DNA strands through direct electrical conductance measurements. Using density functional theory and the Landauer-Buttiker method, we study the electronic properties and charge transport through an eight base-pair methylated DNA strand and its native counterpart. We first analyze the effect of cytosine methylation on the tight-binding parameters of two DNA strands and then model the transmission of the electrons and conductance through the strands both with and without decoherence. We find that the main difference of the tight-binding parameters between the native DNA and the methylated DNA lies in the on-site energies of (methylated) cytosine bases. The intra- and inter-strand hopping integrals between two nearest neighboring guanine base and (methylated) cytosine base also change with the addition of the methyl groups. Our calculations show that in the phase-coherent limit, the transmission of the methylated strand is close to the native strand when the energy is nearby the highest occupied molecular orbital level and larger than the native strand by 5 times in the bandgap. The trend in transmission also holds in the presence of the decoherence with the same rate. The lower conductance for the methylated strand in the experiment is suggested to be caused by the more stable structure due to the introduction of the methyl groups. We also study the role of the exchange-correlation functional and the effect of contact coupling by choosing coupling strengths ranging from weak to strong coupling limit.
Antioxidant Decay in Engine Oils During Laboratory Tests and Long Drain Interval Service

A new method for determining antioxidant capacity of lubricants was used for monitoring initial antioxidant capacities in various engine oils and antioxidant decay during laboratory and fleet testing of selected oils. The method involves the quantitative determination of antioxidant species present in oil by titration with peroxy radicals formed at a known and constant rate from the decomposition of a free radical initiator at 60 degrees C in the presence of oxygen. A general correlation between initial antioxidant capacities of engine oils and an oil thickening characteristic from Sequence IIIC testing was obtained for engine oils containing conventional additive technologies. Monitoring the decay of antioxidant capacity during laboratory beaker, Sequence IIIC, and long drain fleet testing provided information on lubricant oxidative deterioration in the early period of testing when no other performance characteristics showed appreciable changes. New insights into the nature of engine oils' oxidative deterioration, as a function of antioxidant type and concentration, base oil type, and test or engine severity, were obtained. This was achieved by combining results derived from the new method with those obtained from conventional analysis.
Partial Pressure Analysis in Space Testing

For vacuum-system or test-article analysis it is often desirable to know the species and partial pressures of the vacuum gases. Residual gas or Partial Pressure Analyzers (PPA's) are commonly used for this purpose. These are mass spectrometer-type instruments, most commonly employing quadrupole filters. These instruments can be extremely useful, but they should be used with caution. Depending on the instrument design, calibration procedures, and conditions of use, measurements made with these instruments can be accurate to within a few percent, or in error by two or more orders of magnitude. Significant sources of error can include relative gas sensitivities that differ from handbook values by an order of magnitude, changes in sensitivity with pressure by as much as two orders of magnitude, changes in sensitivity with time after exposure to chemically active gases, and the dependence of the sensitivity for one gas on the pressures of other gases. However, for most instruments, these errors can be greatly reduced with proper operating procedures and conditions of use. In this paper, data are presented illustrating performance characteristics for different instruments and gases, operating parameters are recommended to minimize some errors, and calibrations procedures are described that can detect and/or correct other errors.
Contingency and behavior analysis

The concept of contingency is central to theoretical discussions of learned behavior and in the application of learning research to problems of social significance. This paper reviews three aspects of the contingency concept as it has been developed by behavior analysts. The first is the empirical analysis of contingency through experimental studies of both human and nonhuman behavior. The second is the synthesis of experimental studies in theoretical and conceptual frameworks to yield a more general account of contingency and to integrate the concept with other behavioral processes. The third aspect is one of practical considerations in the application of the contingency concept in both laboratory and applied settings.
Effects of Volcanic Eruptions on Stratospheric Ozone Recovery

The effects of the stratospheric sulfate aerosol layer associated with the Mt. Pinatubo volcano and future volcanic eruptions on the recovery of the ozone layer is studied with an interactive two-dimensional photochemical model. The time varying chlorine loading and the stratospheric cooling due to increasing carbon dioxide have been taken into account. The computed ozone and temperature changes associated with the Mt. Pinatubo eruption in 1991 agree well with observations. Long model runs out to the year 2050 have been carried out, in which volcanoes having the characteristics of the Mount Pinatubo volcano were erupted in the model at 10-year intervals starting in the year 2010. Compared to a non-volcanic run using background aerosol loading, transient reductions of globally averaged column ozone of 2-3 percent were computed as a result of each of these eruptions, with the ozone recovering to that computed for the non-volcanic case in about 5 years after the eruption. Computed springtime Arctic column ozone losses of from 10 to 18 percent also recovered to the non-volcanic case within 5 years. These results suggest that the long-term recovery of ozone would not be strongly affected by infrequent volcanic eruptions with a sulfur loading approximating Mt. Pinatubo. Sensitivity studies in which the Arctic lower stratosphere was forced to be 4 K and 10 K colder resulted in transient ozone losses of which also recovered to the non-volcanic case in 5 years. A case in which a volcano five times Mt. Pinatubo was erupted in the year 2010 led to maximum springtime column ozone losses of 45 percent which took 10 years to recover to the background case. Finally, in order to simulate a situation in which frequent smaller volcanic eruptions result in increasing the background sulfate loading, a simulation was made in which the background aerosol was increased by 10 percent per year. This resulted in a delay of the recovery of column ozone to 1980 values of more than 10 years.
Economic Reforms and the Agricultural Situation in Russia

The Russian Federation, like other countries of Eastern Europe, is undergoing a complicated period of transition from centralized to democratic methods of management. The main goal of this period is the transition to market relations within the entire national economy. Specifically, the goal of agricultural land reform is to convert the legal structure as it relates to land in order to create favorable conditions for competition among all forms of ownership.
A nested parallel experiment demonstrates differences in intensity-dependence between RNA-seq and microarrays

Understanding the differences between microarray and RNA-Seq technologies for measuring gene expression is necessary for informed design of experiments and choice of data analysis methods. Previous comparisons have come to sometimes contradictory conclusions, which we suggest result from a lack of attention to the intensity-dependent nature of variation generated by the technologies. To examine this trend, we carried out a parallel nested experiment performed simultaneously on the two technologies that systematically split variation into four stages (treatment, biological variation, library preparation and chip/lane noise), allowing a separation and comparison of the sources of variation in a well-controlled cellular system, Saccharomyces cerevisiae. With this novel dataset, we demonstrate that power and accuracy are more dependent on per-gene read depth in RNA-Seq than they are on fluorescence intensity in microarrays. However, we carried out quantitative PCR validations which indicate that microarrays may demonstrate greater systematic bias in low-intensity genes than in RNA-seq.
Electrocardiographic tomographic imaging

We review our recent work on the development of an electrocardiographic tomography imaging (ETI) technology. Three dimensional (3D) distributions of cardiac electrophysiological properties are estimated from body surface EGG signals with the aid of a realistic geometry heart model in which electrophysiological a priori information is incorporated. Computer simulation studies carried in our laboratory demonstrate the feasibility of imaging 3D distributions of activation time and trans-membrane potential using the ETI approach.
Nonlocal cancellation of dispersion in Franson interferometry

Dispersion and its cancellation in entanglement-based nonlocal quantum measurements are of fundamental and practical interests. We report a demonstration of cancellation of femtosecond-level dispersion by inverting the sign of the differential dispersion between the long and short paths in only one arm of a fiber-based Franson interferometer. We restore the otherwise limited quantum visibility to an unprecedented 99.6%, and put time-energy entanglement at the same level of quality as polarization entanglement for use in quantum information processing applications.
Averting the old-age crisis : technical annex

Supporting documentation for the World Bank publication Averting the Old Age Crisis: Policies to Protect the Old and Promote Growth (1994). Averting the Old Age Crisis: Policies to Protect the Old and Promote Growth, the publication for which this technical annex provides supporting documentation, is the third in a series of major World Bank Policy Research Reports. Unlike its predecessors, The East Asian Miracle and Adjustment in Africa, it does not concentrate on a specific region but focuses rather on the general topic of income security for old age. More than two years of research were required to gather data, review the theoretical literature, examine empirical evidence, and write the book that represents the Bank's most important study of the issue to date. This annex explains in detail the data sources, concepts, and definitions used in the book and provides additional information. It describes the demographic data used in the report and discusses data about public and privately managed pension schemes around the world (giving specific sources for individual countries). An attempt has been made to cross-reference the data available on ]STARS] diskettes, which can be downloaded and analyzed in most database or statistical software packages. This paper - a product of the Poverty and Human Resources Division, Policy Research Department - provides supporting documentation for the World Bank publication Averting the Old-Age Crisis: Policies to Protect the Old and Promote Growth (1994), available from the World Bank bookstore.
The great synergy: The european enlightenment as a factor in modern economic growth

The ‘knowledge economy’ is a concept commonly deemed too ambiguous and elusive to hold any significance in current economic debate. This valuable book seeks to refute that myth. Presenting an important collection of views, from a number of leading scholars, this innovative volume visibly demonstrates that knowledge and information are a prime resource in driving the dynamics of an economy.
Toda Systems, Cluster Characters, and Spectral Networks

We show that the Hamiltonians of the open relativistic Toda system are elements of the generic basis of a cluster algebra, and in particular are cluster characters of nonrigid representations of a quiver with potential. Using cluster coordinates defined via spectral networks, we identify the phase space of this system with the wild character variety related to the periodic nonrelativistic Toda system by the wild nonabelian Hodge correspondence. We show that this identification takes the relativistic Toda Hamiltonians to traces of holonomies around a simple closed curve. In particular, this provides nontrivial examples of cluster coordinates on SLn-character varieties for n > 2 where canonical functions associated to simple closed curves can be computed in terms of quivers with potential, extending known results in the SL2 case.
Measurement to error stability: a notion of partial detectability for nonlinear systems

In previous work the notion of input to state stability (ISS) has been generalized to systems with outputs, yielding a number of useful concepts. When considering a system whose output is to be kept small (i.e. an error output), the notion of input to output stability (IOS) arises. Alternatively, when considering a system whose output is meant to provide information about the state (a measurement output), one arrives at the detectability notion of output to state stability (OSS). Combining these concepts, one may consider a system with two outputs, an error and a measurement. This leads naturally to a notion of partial detectability we call measurement to error stability (MES). This property characterizes systems in which the error signal is detectable through the measurement signal. This paper provides a partial Lyapunov characterization of the MES property. A closely related property of stability in three measures (SIT) is introduced, which characterizes systems for which the error decays whenever it dominates the measurement. The SIT property is shown to imply MES, and the two are shown to be equivalent under an additional boundedness assumption. A nonsmooth Lyapunov characterization of the SIT property is provided, which yields the partial characterization of MES. The analysis is carried out on systems described by differential inclusions mplicitly incorporating a disturbance input with compact value-set.
Agricultural Arbitrage, Adjustment Costs, and the Intensive Margin

Farmland and capital are an important and rapidly expanding component of the agricultural economy, and empirical evidence suggests that these assets are quasi-fixed in that adjustment costs are incurred when holdings are altered. Increased interest in the rate of return for investing in farmland suggests that an important consideration is the effect of adjustment costs on this return. A novel theoretical model is developed that ties together contributions from the farmland pricing and adjustment cost literatures, and the first order conditions for a utility maximizing decision maker are rearranged into intertemporal arbitrage equations that are similar in spirit to traditional finance models. The common assumptions that land and capital are quasi-fixed assets, and that production is characterized by constant returns to scale are tested and the evidence supports these assumptions. An empirical application of the arbitrage equations provides evidence that risk aversion and adjustment costs are jointly significant components of agricultural production, and that adjustment costs generate significant changes in the rate of return to farmland. The results have important policy implications as sluggish supply response due to quasi-fixity can lead to dramatically inflated commodity prices, and an accurate measure of the farmland return can help determine how far the extensive margin will expand or contract in response to a variety of policy scenarios, such as the subsidization of corn for ethanol, an increase in the variety of subsidized crop insurance products, or the introduction of new revenue support programs such as ACRE.
Research and Productivity Growth: Theory and Evidence from Patent Data

I use the aggregate behavior of three indicators of technology (employment of research and scientists and enginerrs, patented inventions, and total factor productivity) to identify a model of endogenous technological change. In the United States and several other developed countries, research employment and total factor productivity have both grown substantially while the rate of patenting has remained relatively flat. One interpretation of these facts is that: (i) patentable inventions are becoming increasingly difficult to discover as the quality of techniques in use increases, (ii) inventions that are patented represent percentage improvements on techniques currently in use, and (iii) the size of the economy is growing, making patents increasingly valuable and justifying increased research efforst devoted to discovering them. I develop a general-equilibrium search-theoretic model of invention to formalize this view. I then fit the model to data for the U.S. economy. The calibrated model implies that as much as 25% of U.S. productivity growth can be attributed to industrial research activity and that the equilibrium fraction of resources devoted to research is less than two-thirds of the level that a social planner would choose.
A Hybrid Agent Based and Differential Equation Model of Body Size Effects on Pathogen Replication and Immune System Response

Many emerging pathogens infect multiple host species [1], and multi-host pathogens may have very different dynamics in different host species [2]. This research addresses how pathogen replication rates and Immune System (IS) response times are constrained by host body size. An Ordinary Differential Equation (ODE) model is used to show that pathogen replication rates decline with host body size but IS response rates remain invariant with body size. An Agent-Based Model (ABM) is used to investigate two models of IS architecture that could explain scale invariance of IS response rates. A stage structured hybrid model is proposed that strikes a balance between the detailed representation of an ABM and computational tractability of an ODE, by using them in the initial and latter stages of an infection, respectively.
Don't Confuse a Tool with a Goal: Making Information Technology Serve Higher Education, Rather Than the Other Way Around

This article examines the relationship between information technology (IT) and educational policy and argues that leaders of universities and colleges must do a better job of thinking creatively and strategically about how IT can enrich their institution's basic educational mission. The paper examines five areas of education policy that are deeply affected by IT-library policy, intellectual property, distance education, commercialization, and curricular standards and processes. The paper suggests that the new technology has unleashed such creative, frequently entrepreneurial activity that is so expensive, pervasive and difficult to manage that it has had a negative impact on some of our fundamental practices in teaching and scholarship. It will continue to do so, and it will drive us if we do not drive it. The paper asks, have we established the mechanisms to review, monitor and evaluate these developments? And, have we given enough thought to how we can employ IT thoughtfully and self-consciously to meet our explicit educational policy goals?
Oceanic transport of subpolar climate signals to mid-depth subtropical waters

The spatial distributions of certain sea-surface properties, such as temperature, fluctuate on timescales from months to decades and in synchrony with the main regional atmospheric patterns comprising the global climate system1. Although it has long been assumed that the ocean is submissive to the dictates of the atmosphere, recent studies raise the possibility of an assertive, not merely passive, oceanic role in which water-mass circulation controls the timescales of climate fluctuations2,3,4,5,6. Previously held notions of the immutability of the physical and chemical characteristics of deep water masses are changing as longer time series of ocean measurements indicate that the signatures of varying sea-surface conditions are translated to deep waters4,7. Here we use such time-series measurements to track signals ‘imprinted’ at the sea surface in the North Atlantic Ocean's subpolar Labrador Basin into the deep water of the subtropical basins near Bermuda, and infer an approximately 6-year transit time. We establish a geographic and temporal context for a portion of the long-term warming trend reported for mid-depth subtropical waters over the past 40 or so years8,9, and we predict that waters at these depths will continue to cool well into the next decade.
Introduction to Stellar Astrophysics

This book is the final one in a series of three texts which together provide a modern, complete and authoritative account of our present knowledge of the stars. It discusses the internal structure and the evolution of stars, and is completely self-contained. There is an emphasis on the basic physics governing stellar structure and the basic ideas on which our understanding of stellar structure is based. The book also provides a comprehensive discussion of stellar evolution. Careful comparison is made between theory and observation, and the author has thus provided a lucid and balanced introductory text for the student. As for volumes 1 and 2, volume 3 is self-contained and can be used as an independent textbook. The author has not only taught but has also published many original papers in this subject. Her clear and readable style should make this text a first choice for undergraduate and beginning graduate students taking courses in astronomy and particularly in stellar astrophysics.
Preparation and Epoxidation of Conjugated Lactams: Influence of Ring Size on Epoxidation

Abstract α,β-Epoxy-lactams can be prepared from conjugated lactams by treatment with m-chloroperoxybenzoic acid. Good yields are obtained, however, only with 2-pyrrolidinone derivatives. The yield of epoxy-lactam diminishes dramatically as the size of the lactam ring increases.
Custom VLSI design of efficient low latency and low power finite field multiplier for Reed-Solomon codec

The issue of VLSI design of low latency/low power finite field multipliers is addressed and methods from logic structure, circuit design and physical mapping aspects are presented. With proposed architecture and physical mapping, an irregular balanced-tree parallel multiplier con be implemented as easy as a regular multiplier. The custom VLSI implementations of these multipliers over GF(2/sup m/) show that the irregular multiplier has 53% smaller delay and 58% less power consumption than a regular multiplier.
Ultra-large alignments using phylogeny-aware profiles

Many biological questions, including the estimation of deep evolutionary histories and the detection of remote homology between protein sequences, rely upon multiple sequence alignments and phylogenetic trees of large datasets. However, accurate large-scale multiple sequence alignment is very difficult, especially when the dataset contains fragmentary sequences. We present UPP, a multiple sequence alignment method that uses a new machine learning technique, the ensemble of hidden Markov models, which we propose here. UPP produces highly accurate alignments for both nucleotide and amino acid sequences, even on ultra-large datasets or datasets containing fragmentary sequences. UPP is available at https://github.com/smirarab/sepp .
From weak to strong watermarking

The informal goal of a watermarking scheme is to "mark" a digital object, such as a picture or video, in such a way that it is difficult for an adversary to remove the mark without destroying the content of the object. Although there has been considerable work proposing and breaking watermarking schemes, there has been little attention given to the formal security goals of such a scheme. In this work, we provide a new complexity-theoretic definition of security for watermarking schemes. We describe some shortcomings of previous attempts at defining watermarking security, and show that security under our definition also implies security under previous definitions. We also propose two weaker security conditions that seem to capture the security goals of practice-oriented work on watermarking and show how schemes satisfying these weaker goals can be strengthened to satisfy our definition.
Coordinating tax reforms in the poorest countries : can lost tariffs be recouped ?

A revenue-neutral switch from trade taxes to domestic consumption taxes is fraught with implementation challenges in countries with a large informal sector. It is shown for a sample of low-income countries over 25 years that they have had a mixed record of offsetting reductions in trade tax revenue. The paper then analyzes the specific case of Nepal, using a unique data set compiled from unpublished customs records of imports, tariffs and all other taxes levied at the border. It estimates changes to revenue and domestic production associated with two sets of reforms: i) proportional tariff cuts coordinated with a strictly enforced value-added tax; and ii) proposed tariff cuts under a regional free trade agreement. It is shown that a revenue-neutral tax reform is conditional on the effectiveness with which domestic taxes are enforced. Furthermore, loss of revenue as a result of intra-regional free trade can be minimized through judicious use of Sensitive Lists that still cover substantially all the trade as required by Article XXIV of the GATT.
Finding Anomalous and Suspicious Files from Directory Metadata on a Large Corpus

We describe a tool Dirim for automatically finding files on a drive that are anomalous or suspicious, and thus worthy of focus during digital-forensic investigation, based on solely their directory information. Anomalies are found both from comparing overall drive statistics and from comparing clusters of related files using a novel approach of "superclustering" of clusters. Suspicious file detection looks for a set of specific clues. We discuss results of experiments we conducted on a representative corpus on 1467 drive images where we did find interesting anomalies but not much deception (as expected given the corpus). Cluster comparison performed best at providing useful information for an investigator, but the other methods provided unique additional information albeit with a significant number of false alarms.
Partisan Polarization and the Effect of Congressional Performance Evaluations on Party Brands and American Elections

Scholars of political parties and elections around the globe have devoted extensive study toward understanding how party polarization affects the criteria voters use to determine their party preferences in elections. In American politics, previous empirical research suggests that congressional job performance ratings do not affect public attitudes toward parties and therefore have no significant ramifications for the electoral fortunes of parties. Building on the existing literature from American and comparative traditions, I demonstrate that congressional performance evaluations can be important for American parties and elections, but this depends on the extent of party polarization in Congress. First, when congressional parties are more distinct, congressional performance evaluations have a greater effect on the relative favorability of the majority party brand: when citizens like how Congress is performing under the leadership of the majority party, this boosts the favorability of that party overall. S...
Perspective: semantic data management for the home

Perspective is a storage system designed for the home, with the decentralization and flexibility sought by home users and a new semantic filesystem construct, the view, to simplify management. A view is a semantic description of a set of files, specified as a query on file attributes, and the ID of the device on which they are stored. By examining and modifying the views associated with a device, a user can identify and control the files stored on it. This approach allows users to reason about what is stored where in the same way (semantic naming) as they navigate their digital content. Thus, in serving as their own administrators, users do not have to deal with a second data organization scheme (hierarchical naming) to perform replica management tasks, such as specifying redundancy to increase reliability and data partitioning to address device capacity exhaustion. Experiences with Perspective deployments and user studies confirm the efficacy of view-based data management.
Image Segmentation With Eigenfunctions of an Anisotropic Diffusion Operator

We propose the eigenvalue problem of an anisotropic diffusion operator for image segmentation. The diffusion matrix is defined based on the input image. The eigenfunctions and the projection of the input image in some eigenspace capture key features of the input image. An important property of the model is that for many input images, the first few eigenfunctions are close to being piecewise constant, which makes them useful as the basis for a variety of applications, such as image segmentation and edge detection. The eigenvalue problem is shown to be related to the algebraic eigenvalue problems resulting from several commonly used discrete spectral clustering models. The relation provides a better understanding and helps developing more efficient numerical implementation and rigorous numerical analysis for discrete spectral segmentation methods. The new continuous model is also different from energy-minimization methods such as active contour models in that no initial guess is required for in the current model. A numerical implementation based on a finite-element method with an anisotropic mesh adaptation strategy is presented. It is shown that the numerical scheme gives much more accurate results on eigenfunctions than uniform meshes. Several interesting features of the model are examined in numerical examples, and possible applications are discussed.
Are Newtonian Gravitation and Geometrized Newtonian Gravitation Theoretically Equivalent

I argue that a criterion of theoretical equivalence due to Clark Glymour [Nous 11(3), 227-251 (1977)] does not capture an important sense in which two theories may be equivalent. I then motivate and state an alternative criterion that does capture the sense of equivalence I have in mind. The principal claim of the paper is that relative to this second criterion, the answer to the question posed in the title is "yes", at least on one natural understanding of Newtonian gravitation.
Spending Is Not Easier Than Trading: On the Computational Equivalence of Fisher and Arrow-Debreu Equilibria

It is a common belief that computing a market equilibrium in Fisher's spending model is easier than computing a market equilibrium in Arrow-Debreu's exchange model. This belief is built on the fact that we have more algorithmic success in Fisher equilibria than Arrow-Debreu equilibria. For example, a Fisher equilibrium in a Leontief market can be found in polynomial time, while it is PPAD-hard to compute an approximate Arrow-Debreu equilibrium in a Leontief market. In this paper, we show that even when all the utilities are additively separable, piecewise-linear and concave, computing an approximate equilibrium in Fisher's model is PPAD-hard. Our result solves a long-term open question on the complexity of market equilibria. To the best of our knowledge, this is the first PPAD-hardness result for Fisher's model.
Brownian sheet images and Bessel-Riesz capacity

We show that the image of a 2-dimensional set under d-dimensional, 2-parameter Brownian sheet can have positive Lebesgue measure, if and only if the set in question has positive (d/2)-dimensional Bessel-Riesz capacity. Our methods solve a problem of J.-P. Kahane.
Phase transitions in phylogeny

We apply the theory of Markov random fields on trees to derive a phase transition in the number of samples needed in order to reconstruct phylogenies. We consider the Cavender-Farris-Neyman model of evolution on trees, where all the inner nodes have degree at least 3, and the net transition on each edge is bounded by e. Motivated by a conjecture by M. Steel, we show that if 2(1 - 2∈) 2 > 1, then for balanced trees, the topology of the underlying tree, having n leaves, can be reconstructed from O(logn) samples (characters) at the leaves. On the other hand, we show that if 2(1 - 2∈) 2 < 1, then there exist topologies which require at least n Ω(1) samples for reconstruction. Our results are the first rigorous results to establish the role of phase transitions for Markov random fields on trees, as studied in probability, statistical physics and information theory, for the study of phylogenies in mathematical biology.
The Big Bang and the Infrared Sky as Seen by Cobe

The Cosmic Background Explorer (COBE) was developed by NASA Goddard Space Flight Center to measure the diffuse infrared and microwave radiation from the early universe. It also measured emission from nearby sources such as the stars, dust, molecules, atoms, ions, and electrons in the Milky Way, and dust and comets in the Solar System. It was launched 18 November 1989 on a Delta rocket, carrying one microwave instrument and two cryogenically cooled infrared instruments. The Differential Microwave Radiometers (DMR) measured the fluctuations in the CMBR originating in the Big Bang, with a total amplitude of 11 parts per million on a 10° scale. These fluctuations are consistent with scale-invariant primordial fluctuations. The Far Infrared Absolute Spectrophotometer (FIRAS) mapped the sky at wavelengths from 0.01 to 1 cm, and compared the CMBR to a precise blackbody. The spectrum of the CMBR differs from a blackbody by less than 0.03%. The Diffuse Infrared Background Experiment (DIRBE) spanned the wavelength range from 1.2 to 240 μm and mapped the sky at a wide range of solar elongation angles to distinguish foreground sources from a possible extragalactic Cosmic Infrared Background Radiation (CIBR).
Obesidad infantil: sus características antropométricas y bioquímicas *

Determinar las caracteristicas antropometricas, bioquimicas y sus relaciones en ninos con obesidad exogena. MATERIAL Y METODOS: Se estudio 50 ninos y adolescentes (25 varones y 25 mujeres) comprendidos entre los 6 a 18 anos, que presentaban un indice de masa corporal (IMC) por encima del 95 percentil para la clasificacion de Must y col. A todos se les tomo los pliegues tricipital y subescapular y la cincunferencia de cintura; asimismo se doso por venopuntura colesterol total (CT) y trigliceridos (TG).. Los niveles diagnosticos para determinar dislipidemia fueron 200 mg/dL para CT y 100 mg/dL en menores de 10 anos, y 130 mg/dL en mayores de 10 anos para TG. Al conjunto de ninos se los dividio en dos grupos, de acuerdo al valor encontrado del 50 p para el IMC, PT y CC. En cada grupo se determino el promedio y su desviacion estandar, asi como la correlacion de Pearson, para los indicadores antropometricos, bioquimicos. RESULTADOS: El 32,6% y 55,6% de ninos obesos presentaron hipercolesterolemia e hipertrigliceridemia, respectivamente y 26,1% tuvo dislipidemia mixta. La diferencia de promedio entre los dos grupos presento significacion estadistica (p< 0,05) para los indicadores antropometricos; lo contrario sucedio para los bioquimicos. CONCLUSIONES: El mayor problema que presenta el nino obeso es la hipertrigliceridemia. La obesidad y las dislipidemias pudieran ser factores de riesgo independientes y no necesariamente uno consecuencia del otro
Robust H/sub 2/ and H/sub /spl infin// filters for uncertain LFT systems

In this note, robust H/sub 2/ and H/sub /spl infin// filter design problems are considered. The uncertainties, unstructured or structured, are norm bounded and represented by linear fractional transformation (LFT). The main result is that after upper-bounding the objectives, the problems of minimizing the upper bounds are converted to finite dimensional convex optimization problems involving linear matrix inequalities (LMIs). These are extensions of well-known results for systems with polytopic uncertainty. It is shown that for the unstructured, norm bounded uncertainty case, the upper bounds are directly minimized (without further overbounding), yielding less conservative results than previously available. An elementary numerical example is given to illustrate the results.
Indian Ocean violates conventional plate tectonic theory

A new study of magnetic profiles and other plate tectonic data in the Indian Ocean predicts that India and Australia, previously thought to move in unison as part of the same rigid plate, are approaching each other at about 12 mm/year. According to conventional plate tectonic theory, plates are internally rigid with earthquakes concentrated at plate boundaries and occurring only rarely in plate interiors. However, many large earthquakes occur within the conventionally defined plate interior between Australia and India [Stein and Okal, 1978; Bergman and Solomon, 1985]. The Indian Ocean earthquakes are scattered over many hundreds of kilometers, a region much larger than the ∼1–20 km width of typical ocean plate boundaries. Questions exist concerning how much motion is taken up by the deformation represented by the earthquakes, and whether this shows that tectonic plates deform.
Enlarging the Contracting Space: Collateral Menus, Access to Credit, and Economic Activity

Recent reforms across Eastern European countries have given more flexibility and information to parties to engage in secured debt transactions. The menu of assets legally accepted as collateral was enlarged to include movable assets (e.g., machinery and equipment). Generalized difference-in-differences tests show that firms operating more movable assets borrowed more as a result. Those firms also invested more, hired more, and became more efficient and profitable following the changes in the contracting environment. The financial deepening we document triggered important reallocation effects: firms affected by the reforms increased their share of fixed assets and employment in the economy.
Reinsurance as capital optimization tool under Solvency II

This paper compares solvency capital requirements under Solvency I and Solvency II for a sample mid-size insurance portfolio. According to the results of a study, changing the solvency capital regime from Solvency I to Solvency II will lead to a substantial additional solvency capital requirement that might represent a heavy burden for the company's shareholders. One way to reduce the capital requirement under Solvency II is to increase reinsurance protection, which will reduce the net retained risk exposure and hence also the solvency capital requirement. Therefore, this paper proposes an extended reinsurance structure that, under Solvency II, brings the capital requirement back to the level of that required under Solvency I. In a step-by-step approach, the paper demonstrates the extent of solvency relief attained by the insurer by applying different possible adjustments in the reinsurance structure. To evaluate the efficiency of reinsurance as the solvency capital relief instrument, the authors introduce a cost-of-capital based approach, which puts the achieved capital relief in relation to the costs of extending the reinsurance protection. This approach allows a direct comparison of reinsurance as a capital relief instrument with debt instruments available in the capital market. With the help of the introduced approach, the authors show that the best capital relief efficiency under all examined reinsurance alternatives is achieved when a financial quota share contract is chosen for proportional reinsurance.
Understanding replication fork progression, stability and chromosome fragility by exploiting the Suppressor of Underreplication protein

There are many layers of regulation governing DNA replication to ensure that genetic information is accurately transmitted from mother cell to daughter cell. While much of the control occurs at the level of origin selection and firing, less is known about how replication fork progression is controlled throughout the genome. In Drosophila polytene cells, specific regions of the genome become repressed for DNA replication, resulting in underreplication and decreased copy number. Importantly, underreplicated domains share properties with common fragile sites. The Suppressor of Underreplication protein SUUR is essential for this repression. Recent work established that SUUR functions by directly inhibiting replication fork progression, raising several interesting questions as to how replication fork progression and stability can be modulated within targeted regions of the genome. Here we discuss potential mechanisms by which replication fork inhibition can be achieved and the consequences this has on genome stability and copy number control.
Oil Price Risks and Pump Price Adjustments

Between 1999 and 2008, world oil prices more than quadrupled in real terms. For oil importers, vulnerability to oil price increases, defined as the share of gross domestic product spent on net oil imports, rose considerably. Considering medians, low-income countries had the highest vulnerability in 2008 and the highest increase in vulnerability between 1999 and 2008. When changes in vulnerability were decomposed into several contributing factors, more than two-thirds of 170 countries studied were found to have offset the increase in the value of oil consumption by reducing the oil intensity of gross domestic product. Oil intensity fell in more than half the countries in every income group and in every region of the world, driven by falling energy intensity and, to a lesser extent, the oil share of energy. This study also examines the degree of pass-through to consumers of increases in world prices of gasoline, diesel, kerosene, and liquefied petroleum gas between January 2009 and January 2012, when oil prices in nominal U.S. dollars more than doubled. Retail fuel prices varied by two orders of magnitude in 2012, and oil-exporting countries were far less likely to pass on price increases. Gasoline had the highest pass-through, followed by diesel, liquefied petroleum gas, and kerosene. The median pass-through increased with income for gasoline, diesel, and kerosene, but was highest in low-income countries for liquefied petroleum gas. Despite divergent pricing policies, the pass-through coefficients of different fuels were strongly positively correlated, suggesting that the degrees to which domestic prices tracked world prices were comparable for the four fuels in many countries.
Zeolite acid strength and reaction mechanisms in catalysis

The heterogeneous catalysts of greatest practical importance are acidic zeolites, and these cannot be studied using the traditional methods of UHV surface science. As recently as 1994 there was near universal agreement that zeolites were superacids, and that many of the most important reaction mechanisms in catalysis were based upon simple carbenium ions and other exotic high-energy intermediate species. This Paper reviews a series of investigations, many of them using solid-state NMR, that led to the reclassification of zeolite acidity and a theoretical basis for understanding carbenium ion stability in these fascinating solids. Building on this better understanding of zeolite acid strength and the types of carbenium ions that are reasonable intermediates in zeolites, it was possible to elucidate many of the features of a challenging mechanistic problem: methanol to hydrocarbon catalysis.
Computational extractors and pseudorandomness

Computational extractors are efficient procedures that map a source of sufficiently high min-entropy to an output that is computationally indistinguishable from uniform. By relaxing the statistical closeness property of traditional randomness extractors one hopes to improve the efficiency and entropy parameters of these extractors, while keeping their utility for cryptographic applications. In this work we investigate computational extractors and consider questions of existence and inherent complexity from the theoretical and practical angles, with particular focus on the relationship to pseudorandomness. An obvious way to build a computational extractor is via the "extract-then-prg" method: apply a statistical extractor and use its output to seed a PRG. This approach carries with it the entropy cost inherent to implementing statistical extractors, namely, the source entropy needs to be substantially higher than the PRG's seed length. It also requires a PRG and thus relies on one-way functions. We study the necessity of one-way functions in the construction of computational extractors and determine matching lower and upper bounds on the "black-box efficiency" of generic constructions of computational extractors that use a one-way permutation as an oracle. Under this efficiency measure we prove a direct correspondence between the complexity of computational extractors and that of pseudorandom generators, showing the optimality of the extract-then-prg approach for generic constructions of computational extractors and confirming the intuition that to build a computational extractor via a PRG one needs to make up for the entropy gap intrinsic to statistical extractors. On the other hand, we show that with stronger cryptographic primitives one can have more entropy- and computationally-efficient constructions. In particular, we show a construction of a very practical computational extractor from any weak PRF without resorting to statistical extractors.