cssi/SciSciGPT-SciSciNet huggingface dataset:
Motion planning in the presence of moving obstacles

This paper investigates the computational complexity of planning the motion of a body B in 2-D or 3-D space, so as to avoid collision with moving obstacles of known, easily computed, trajectories. Dynamic movement problems are of fundamental importance to robotics, but their computational complexity has not previously been investigated.We provide evidence that the 3-D dynamic movement problem is intractable even if B has only a constant number of degrees of freedom of movement. In particular, we prove the problem is PSPACE-hard if B is given a velocity modulus bound on its movements and is NP-hard even if B has no velocity modulus bound, where, in both cases, B has 6 degrees of freedom. To prove these results, we use a unique method of simulation of a Turing machine that uses time to encode configurations (whereas previous lower bound proofs in robotic motion planning used the system position to encode configurations and so required unbounded number of degrees of freedom).We also investigate a natural class of dynamic problems that we call asteroid avoidance problems: B, the object we wish to move, is a convex polyhedron that is free to move by translation with bounded velocity modulus, and the polyhedral obstacles have known translational trajectories but cannot rotate. This problem has many applications to robot, automobile, and aircraft collision avoidance. Our main positive results are polynomial time algorithms for the 2-D asteroid avoidance problem, where B is a moving polygon and we assume a constant number of obstacles, as well as single exponential time or polynomial space algorithms for the 3-D asteroid avoidance problem, where B is a convex polyhedron and there are arbitrarily many obstacles. Our techniques for solving these asteroid avoidance problems use “normal path” arguments, which are an intereting generalization of techniques previously used to solve static shortest path problems.We also give some additional positive results for various other dynamic movers problems, and in particular give polynomial time algorithms for the case in which B has no velocity bounds and the movements of obstacles are algebraic in space-time.
Eigenfunctions of Unbounded Support for Embedded Eigenvalues of Locally Perturbed Periodic Graph Operators

It is known that if a locally perturbed periodic self-adjoint operator on a combinatorial or quantum graph admits an eigenvalue embedded in the continuous spectrum, then the associated eigenfunction is compactly supported—that is, if the Fermi surface is irreducible, which occurs generically in dimension two or higher. This article constructs a class of operators whose Fermi surface is reducible for all energies by coupling several periodic systems. The components of the Fermi surface correspond to decoupled spaces of hybrid states, and in certain frequency bands, some components contribute oscillatory hybrid states (corresponding to spectrum) and other components contribute only exponential ones. This separation allows a localized defect to suppress the oscillatory (radiation) modes and retain the exponential ones, thereby leading to embedded eigenvalues whose associated eigenfunctions decay exponentially but are not compactly supported.
In situ Raman spectroscopy as a probe for the effect of power on microwave-promoted Suzuki coupling reactions

We report the use of in situ Raman spectroscopy as a probe for the effect of power on microwave-promoted Suzuki coupling reactions. We find that increased initial microwave power leads to greater acceleration of the reaction but that the product yield obtained is essentially independent of initial microwave power. The application of simultaneous cooling lengthens the reaction time but does not alter the relative rates of the Suzuki coupling and deboronation processes. Performing the reaction at an initial microwave power of 5 W leads to an improvement in product yield.
Algebraic topology and the quantization of fluctuating currents

Abstract We give a new approach to the study of statistical mechanical systems: algebraic topology is used to investigate the statistical distributions of stochastic currents generated in graphs. In the adiabatic and low temperature limits we will demonstrate that quantization of current generation occurs.
Relativistic flows at the hotspots of radio galaxies and quasars

Abstract We review the broad band properties of X-ray detected hotspots in radio galaxies and quasars. We show that their collective spectral properties can be unified in a framework involving frequency dependent relativistic beaming and varying orientations to the observer's line of sight. The simplest dynamic model consistent with this picture is a slowing-down relativistic flow downstream from the hotspot shock, suggesting that the jet flows remain relativistic to the hotspot distances.
Technical and economic feasibility of Ocean Thermal Energy Conversion

Abstract Ocean Thermal Energy Conversion (OTEC) plants will employ the temperature difference ( ΔT ) between the solar-heated surface layer of a tropical ocean (24–29.5°C) and the water at 500–1200 m depth (7-3.5°C) as the source and sink for a Rankine cycle system to generate electric power. An annual average ΔT near 24°C is available to grazing tropical OTEC plants. The resource is tremendous in terms of suitable ocean siting areas and is available 24 hr per day. It could supply a significant fraction of the world's energy needs in the year 2000. The first commercial plants could be deployed in the mid 1980s, and we believe they will be competitive then with fossil fuel and nuclear energy sources for selected applications. Ammonia (for fertilizers) is a particularly attractive product, because 95 per cent of the ammonia produced in the U.S. is now made from natural gas, our scarcest resource. Direct delivery of electric power to shore may also be competitive for, e.g. the southeastern United States. In the late 1980s or early 1990s, ammonia produced by grazing tropical OTEC plants could also be used as a hydrogen carrier for production of electricity by fuel cells anywhere in the world, and production of other chemicals and metals (aluminum, magnesium) should become attractive. Various OTEC plant-ship concepts, their economics, onboard production plants and some of the environmental considerations are discussed.
N = 2 gauged WZW models and the elliptic genus

Abstract Witten recently gave further evidence for the conjectured relationship between the A-series of the N = 2 minimal models and certain Landau-Ginzburg models by computing the elliptic genus for the latter. The results agree with those of the N = 2 minimal models, as can be calculated from the known characters of the discrete series representations of the N = 2 superconformal algebra. The N = 2 minimal models also have a lagrangian representation as supersymmetric gauged WZW models. We calculate the elliptic genera, interpreted as a genus one path integral with twisted boundary conditions, for such models and recover the previously known result.
Testing supersymmetry in the associated production of CP-odd and charged Higgs bosons

Abstract In the Minimal Supersymmetric Standard Model (MSSM), the masses of the charged Higgs boson ( H ± ) and the CP-odd scalar ( A ) are related by M H + 2 = M A 2 + m W 2 . Furthermore, because the coupling of W − – A – H + is fixed by gauge interaction, the tree level production rate of q q ′→W ±∗ →AH ± depends only on one supersymmetry parameter—the mass ( M A ) of A . We show that to a good approximation this conclusion also holds at the one-loop level. Consequently, this process can be used to distinguish MSSM from its alternatives (such as a general two-Higgs-doublet model) by verifying the above mass relation, and to test the prediction of the MSSM on the product of the decay branching ratios of A and H ± in terms of only one single parameter— M A .
A complexity separation between the cache-coherent and distributed shared memory models

We consider asynchronous multiprocessor systems where processes communicate by accessing shared memory. Exchange of information among processes in such a multiprocessor necessitates costly memory accesses called remote memory references (RMRs), which generate communication on the interconnect joining processors and main memory. In this paper we compare two popular shared memory architecture models, namely the ca che-coherent (CC) and distributed shared memory (DSM) models, in terms of their power for solving synchronization problems efficiently with respect to RMRs. The particular problem we consider entails one process sending a "signal" to a subset of other processes. We show that a variant of this problem can be solved very efficiently with respect to RMRs in the CC model, but not so in the DSM model, even when we consider amortized RMR complexity.To our knowledge, this is the first separation in terms of amortized RMR complexity between the CC and DSM models. It is also the first separation in terms of RMR complexity (for asynchronous systems) that does not rely in any way on wait-freedom---the requirement that a process makes progress in a bounded number of its own steps.
Partial density of occupied valence states by x-ray standing waves and high-resolution photoelectron spectroscopy

We introduce an experimental method by which site-specific valence-electronic structure may be obtained. It utilizes the spatial dependence of the electric-field intensity that results from the superposition of the incident and reflected x-ray beams within the vicinity of a crystal x-ray Bragg reflection. Resolution of the anion and cation contributions to the GaAs valence band is demonstrated and compared to an ab initio theoretical calculation of the Ga and As partial density of states.
Boarding School Abuses, Human Rights and Reparations

This article analyzes the Boarding School Healing Project which seeks to build a movement for reparations for American Indian boarding school abuses as part of a larger global reparations strategy for colonialism. This project rearticulates violence within Native communities as the continuing effect of human rights violations perpetrated by state policy in order to frame ending gender violence as an anticolonial strategy.
THE MASS PROFILE OF THE GALAXY TO 80 kpc

The Hypervelocity Star Survey presents the currently largest sample of radial velocity measurements of halo stars out to 80 kpc. We apply spherical Jeans modeling to these data in order to derive the mass profile of the Galaxy. We restrict the analysis to distances larger than 25 kpc from the Galactic center, where the density profile of halo stars is well approximated by a single power law with logarithmic slope between -3.5 and -4.5. With this restriction, we also avoid the complication of modeling a flattened Galactic disk. In the range 25 kpc < r < 80 kpc, the radial velocity dispersion declines remarkably little; a robust measure of its logarithmic slope is between -0.05 and -0.1. The circular velocity profile also declines remarkably little with radius. The allowed range of V{sub c} (80 kpc) lies between 175 and 231 km s{sup -1}, with the most likely value of 193 km s{sup -1}. Compared with the value at the solar location, the Galactic circular velocity declines by less than 20% over an order of magnitude in radius. Such a flat profile requires a massive and extended dark matter halo. The mass enclosed within 80 kpc is 6.9{sup +3.0} {sub -1.2}more » x 10{sup 11} M {sub sun}. Our sample of radial velocities is large enough that the biggest uncertainty in the mass is not statistical but systematic, dominated by the density slope and anisotropy of the tracer population. Further progress requires modeling observed data sets within realistic simulations of galaxy formation.« less
On the Chung-Diaconis-Graham random process

Chung, Diaconis, and Graham considered random processes of the form $X_{n+1}=2X_n+b_n \pmod p$ where $X_0=0$, $p$ is odd, and $b_n$ for $n=0,1,2,\dots$ are i.i.d. random variables on $\{-1,0,1\}$. If $\Pr(b_n=-1)=\Pr(b_n=1)=\beta$ and $\Pr(b_n=0)=1-2\beta$, they asked which value of $\beta$ makes $X_n$ get close to uniformly distributed on the integers mod $p$ the slowest. In this paper, we extend the results of Chung, Diaconis, and Graham in the case $p=2^t-1$ to show that for $0<\beta\le 1/2$, there is no such value of $\beta$.
A Fermionic Top Partner: Naturalness and the LHC

Naturalness demands that the quadratic divergence of the one-loop top contribution to the Higgs mass be cancelled at a scale below 1 TeV. This can be achieved by introducing a fermionic (spin-1/2) top partner, as in, for example, Little Higgs models. In this paper, we study the phenomenology of a simple model realizing this mechanism. We present the current bounds on the model from precision electroweak fits, flavor physics, and direct searches at the LHC. The lower bound on the top partner mass from precision electroweak data is approximately 500 GeV, while the LHC bound with 5 fb−1 of data at $ \sqrt {s} = 7\;TeV $ is about 450 GeV. Given these bounds, the model can incorporate a 125 GeV Higgs with minimal fine-tuning of about 20 %. We conclude that natural electroweak symmetry breaking with a fermionic top partner remains a viable possibility. We also compute the Higgs decay rates into gauge bosons, and find that significant, potentially observable deviations from the Standard Model predictions may occur.
Octonionic representations of Clifford algebras and triality

The theory of representations of Clifford algebras is extended to employ the division algebra of the octonions or Cayley numbers. In particular, questions that arise from the nonassociativity and noncommutativity of this division algebra are answered. Octonionic representations for Clifford algebras lead to a notion of octonionic spinors and are used to give octoninic representations of the respective orthogonal groups. Finally, the triality automorphisms are shown to exhibit a manifest Σ3×SO(8) structure in this framework.
Quantum pump for spin and charge transport in a Luttinger liquid

We study two different parametric pumps---one for pumping spin currents, the other for charge currents---in interacting quantum wires. We find that, as a function of pumping frequency, the spin or charge pumped per cycle has a nonuniversal crossover---depending on pumping details---between two universal fixed point values of 0 and twice the electronic spin or charge quantum number. The direction of flow between these two fixed points depends on whether the interactions are repulsive or attractive, while the quantization itself is a signature of interactions.
Reflectance Spectroscopy of Palagonite and Iron-Rich Montmorillonite Clay Mixtures: Implications for the Surface Composition of Mars

Abstract Mixtures of a Hawaiian palagonite and an iron-rich, montmorillonite clay (15.8 ± 0.4 wt% Fe as Fe 2 O 3 ) were evaluated as Mars surface spectral analogs from their diffuse reflectance spectra. The presence of the 2.2-μm absorption band in the reflectance spectrum of clays and its absence in the Mars spectrum have been interpreted as indicating that highly crystalline aluminous hydroxylated clays cannot be a major mineral component of the soil on Mars. The palagonite sample used in this study does not show this absorption feature in its spectrum. In mixtures of palagonite and iron-rich montmorillonite, the 2.2-μm AlOH clay lattice band is not seen below 15 wt% montmorillonite. This suggests the possibility that iron-rich montmorillonite clay may be present in the soil of Mars at up to 15 wt% in combination with palagonite, and remain undetected in remotely sensed spectra of Mars.
Effect of wave motion on chill cast surfaces

The formation of exterior surface ripples, and their dependence on filling rate and superheat, was studied in bottom-poured ingots of low melting Sn-Pb alloys. It was found that surface waves in the liquid metal during mold filling are the basis for an important mechanism leading to formation of the primary exterior ripples. Imposition of a steady D. C. magnetic field strongly dampens the surface waves in the liquid metal, essentially eliminating the primary ripple marks throughout the bottom two-thirds of the ingots. The magnetic field also enhances columnar grain growth.
Histone Tails: Ideal Motifs for Probing Epigenetics through Chemical Biology Approaches

Post-translational modifications (PTMs) on histone proteins have emerged as a central theme in the regulation of gene expression and other chromatin-associated processes. The discovery that certain protein domains can recognize acetylated and methylated lysine residues of histones has spurred efforts to uncover and characterize histone PTM-binding proteins. In this task, chromatin biology has strongly benefited from synthetic approaches stemming from chemical biology. Peptide-based techniques have been instrumental in identifying histone mark-binding proteins and analyzing their binding specificities. To explore how histone PTMs carry out their function in the context of chromatin, reconstituted systems based on recombinant histones carrying defined modifications are increasingly being used. They constitute promising tools to analyze mechanistic aspects of histone PTMs, including their role in transcription and their transmission in replication. In this review, we present strategies that have been used successfully to investigate the role of histone modifications, concepts that have emerged from their application, and their potential to contribute to current developments in the field.
Quark propagation in the random instanton vacuum

Abstract This is the first of a series of papers devoted to a systematic study of QCD correlation functions. Our aim is to reach a quantitative understanding of the forces between quarks in all channels, and, in particular, the role played by instanton-induced effects. The topic of this first paper is to work out approximate formulae for quark propagators in a multi-instanton environment, which include the 't Hooft interaction to all orders. As an application, we use the simplest possible model of the kind, the so-called “random instanton liquid model” (RILM). The results obtained can also be related to properties of heavy-light mesons, and those are found to be consistent with phenomenology.
Large N matrix mechanics on the light-cone

We report a simplification in the large N matrix mechanics of light-cone matrix field theories. The absence of pure creation or pure annihilation terms in the Hamiltonian formulation of these theories allows us to find their reduced large N Hamiltonians as explicit functions of the generators of the Cuntz algebra. This opens up a free-algebraic playground of new reduced models — all of which exhibit new hidden conserved quantities at large N and all of whose eigenvalue problems are surprisingly simple. The basic tool we develop for the study of these models is the infinite dimensional algebra of all normal-ordered products of Cuntz operators, and this algebra also leads us to a special number-conserving subset of these models, each of which exhibits an infinite number of new hidden conserved quantities at large N.
IMAGE CORRELATION APPLIED TO SINGLE CRYSTAL PLASTICITY EXPERIMENTS AND COMPARISON TO STRAIN GAGE DATA

The results from compression tests on Mo single crystals using the 6DOF apparatus show that at small strains the image correlation system is able to match the data measured using conventional strain gages. In addition, the image correlation technique has several advantages, such as the ability to measure large strains, full-field strains, and displacement gradients, which make it an essential tool in measuring the deformation behavior of single crystals.
Differentially Private Distributed Optimization

In distributed optimization and iterative consensus literature, a standard problem is for N agents to minimize a function f over a subset of Euclidean space, where the cost function is expressed as a sum Σ fi. In this paper, we study the private distributed optimization problem (PDOP) with the additional requirement that the cost function of the individual agents should remain differentially private. The adversary attempts to infer information about the private cost functions from the messages that the agents exchange. Achieving differential privacy requires that any change of an individual's cost function only results in unsubstantial changes in the statistics of the messages. We propose a class of iterative algorithms for solving PDOP, which achieves differential privacy and convergence to a common value. Our analysis reveals the dependence of the achieved accuracy and the privacy levels on the the parameters of the algorithm. We observe that to achieve e-differential privacy the accuracy of the algorithm has the order of O(1/e2).
Development of an approach to the synthesis of the plakortones

Abstract A general synthesis of the plakortones has been developed by the synthesis of two key sections, with a focus on Pd(II)-promoted preparation of a cis-fused tetrahydrofuranolactone. The key intermediates were obtained in homochiral form starting from asymmetric epoxidation of an allylic alcohol.
Design Optimization of Aircraft Engine-Mount Systems

The engine is modeled as a rigid body connected to a flexible isolation base representing the nacelle. The base is modeled with mass and stiffness matrices and strucural damping using finite element modeling. The objective is to select the stiffness coefficients and orientation angles of the individual mounts in order to minimize the transmitted forces from the engine to the nacelle
From Heisenberg to Supersymmetry

There is a little-known connection between Heisenberg’s research in the 1960’s and supersymmetry. First, I try to explain, in laymen terms, what supersymmetry is and why it gives rise to such high expectations in high-energy physics. After a brief excursion into origins of supersymmetry I present evidence that a section in an essentially forgotten Heisenberg’s book, which contained unorthodox ideas, was inspirational for Dmitry Volkov, one of the co-discoverers of supersymmetry.
A method for estimating apparent displacement vectors from time-lapse seismic images

Reliable estimates of vertical, inline, and crossline components of apparent displacements in time-lapse seismic images are difficult to obtain for two reasons. First, features in 3D seismic images tend to be locally planar, and components of displacement within the planes of such features are poorly resolved. Second, searching directly for peaks in 3D crosscorrelations is less robust, more complicated, and computationally more costly than searching for peaks of 1D crosscorrelations. I estimate all three components of displacement with a process designed to mitigate these two problems. I address the first problem by computing for each image sample a local phase correlation instead of a local crosscorrelation. I address the second problem with a cyclic sequence of searches for peaks of correlations computed for lags constrained to one of the three image axes.
Experimental Methodology for Computational Fluid Dynamics Code Validation

Validation of Computational Fluid Dynamics (CFD) codes is an essential element of the code development process. Typically, CFD code validation is accomplished through comparison of computed results to previously published experimental data that were obtained for some other purpose, unrelated to code validation. As a result, it is a near certainty that not all of the information required by the code, particularly the boundary conditions, will be available. The common approach is therefore unsatisfactory, and a different method is required. This paper describes a methodology developed specifically for experimental validation of CFD codes. The methodology requires teamwork and cooperation between code developers and experimentalists throughout the validation process, and takes advantage of certain synergisms between CFD and experiment. The methodology employs a novel uncertainty analysis technique which helps to define the experimental plan for code validation wind tunnel experiments, and to distinguish between and quantify various types of experimental error. The methodology is demonstrated with an example of surface pressure measurements over a model of varying geometrical complexity in laminar, hypersonic, near perfect gas, 3-dimensional flow.
Applications of Automata and Graphs: Labeling-Operators in Hilbert Space I

We show that certain representations of graphs by operators on Hilbert space have uses in signal processing and in symbolic dynamics. Our main result is that graphs built on automata have fractal characteristics. We make this precise with the use of Representation Theory and of Spectral Theory of a certain family of Hecke operators. Let G be a directed graph. We begin by building the graph groupoid G induced by G, and representations of G. Our main application is to the groupoids defined from automata. By assigning weights to the edges of a fixed graph G, we give conditions for G to acquire fractal-like properties, and hence we can have fractaloids or G-fractals. Our standing assumption on G is that it is locally finite and connected, and our labeling of G is determined by the "out-degrees of vertices". From our labeling, we arrive at a family of Hecke-type operators whose spectrum is computed. As applications, we are able to build representations by operators on Hilbert spaces (including the Hecke operators); and we further show that automata built on a finite alphabet generate fractaloids. Our Hecke-type operators, or labeling operators, come from an amalgamated free probability construction, and we compute the corresponding amalgamated free moments. We show that the free moments are completely determined by certain scalar-valued functions. A number of recent papers have addressed an intriguing interplay between Dis- crete Potential Theory on the one hand and Harmonic Analysis / Spectral Theory on an associated family of fractals on the other, with the Sierpinski gasket serving as a preferred model. This is the first of two papers studying representations of graphs by operators in Hilbert space, and their applications. While graph theory is traditionally considered part of discrete mathematics, in this paper we show that applications of tools from automata and operators on Hilbert spaces yield global results for representations of a class of infinite graphs, as well as spin-off applications. We begin with an outline of the use of automata, and more generally, of finite state models (FSMs) in the processing of numbers, or more importantly in sampling and in quantization of digitized information such as speech signals and digital images. In these models, the finite input states of a particular FSM might be frequency-bands (for example a prescribed pair of high-pass and low-pass digital filters), or a choice of subdivision
On Quantum and Classical BCH Codes

Classical Bose-Chaudhuri-Hocquenghem (BCH) codes that contain their (Euclidean or Hermitian) dual codes can be used to construct quantum stabilizer codes; this correspondence studies the properties of such codes. It is shown that a BCH code of length n can contain its dual code only if its designed distance delta=O(radicn), and the converse is proved in the case of narrow-sense codes. Furthermore, the dimension of narrow-sense BCH codes with small design distance is completely determined, and - consequently - the bounds on their minimum distance are improved. These results make it possible to determine the parameters of quantum BCH codes in terms of their design parameters
Intermodel variability of the poleward shift of the austral jet stream in the CMIP3 integrations linked to biases in 20th century climatology.

[1] Future climate predictions by global circulation models in the Coupled Model Intercomparison Project Phase 3 (CMIP3) archive indicate that the recent poleward shift of the eddy-driven jet streams will continue throughout the 21 st century. Here it is shown that differences in the projected magnitude of the trend in the Southern Hemisphere are well correlated with biases in the latitude of the jet in the simulation of 20th century climate. Furthermore, the latitude of the jet in the models' 20th century climatology is correlated with biases in the internal variability of the jet stream, as quantified by the time scale of the annular mode. Thus an equatorward bias in the position of the jet is associated with both enhanced persistence of the annular mode, and an increased poleward shift of the jet. These relationships appear to be robust throughout the year except in the austral summer, when differences in forcing, particularly stratospheric ozone, make it impossible to compare the response of one model with another. These results suggest that the fidelity of a model's simulation of the 20th century climate may be related to its fitness for climate prediction. The cause of this relationship is discussed, as well as the implications for climate change projections.
The [1, 3] O-to-C rearrangement: opportunities for stereoselective synthesis

The relay of stereochemistry of a breaking C–O bond into a forming C–C bond is well-known in the context of [3, 3] sigmatropic shifts; however, this useful strategy is less well-known in other types of molecular rearrangements. Though the first successful example of a [1, 3] O-to-C rearrangement was reported more than 100 years ago, this class of reactions has received less attention than its [3, 3] counterpart. This perspective analyzes the various methods used for the activation and [1, 3] rearrangement of vinyl ethers with an emphasis on mechanism and applications to stereoselective synthesis. We also highlight our own contributions to this area.
Developing asthma in childhood from exposure to secondhand tobacco smoke: insights from a meta-regression

Studies have shown links between household secondhand tobacco smoke (SHS) exposure and induction of childhood asthma. But the true nature of this link remains unclear in many studies. We conducted a meta-analysis of studies published from 1970 to 2005 to uncover consistent patterns of relative risk estimates (RRs), and found substantial heterogeneity within initial summary RRs of 1.48 [95% confidence interval (CI), 1.32-1.65], 1.25 (1.21-1.30), and 1.21 (1.08-1.36), for ever, current, and incident asthma, respectively. Lack of control for type of atopy history (familial or child) and child's own smoking status within studies and age category altered summary RRs in separate metaregressions. After adjustments, consistent patterns of association emerged between SHS exposure and childhood asthma induction. Our summary RR of 1.33 (95% CI, 1.14-1.56) from studies of incident asthma among older children (618 years old) is 1.27 times the estimate from studies of younger children and higher than estimates from earlier meta-analyses. This showns that exposure duration may be a more important factor than previously understood, and suggests that SHS could be a more fundamental cause of childhood asthma than some previous meta-analyses have indicated.
Nonrigid shape and motion from multiple perspective views

We consider the problem of nonrigid shape and motion recovery from point correspondences in multiple perspective views. It is well known that the constraints among multiple views of a rigid shape are multilinear on the image points and can be reduced to bilinear (epipolar) and trilinear constraints among two and three views, respectively. In this paper, we generalize this classic result by showing that the constraints among multiple views of a nonrigid shape consisting of K shape bases can be reduced to multilinear constraints among K + ⌈ (K + 1)/2⌉, ⋯, 2K + 1 views. We then present a closed form solution to the reconstruction of a nonrigid shape consisting of two shape bases. We show that point correspondences in five views are related by a nonrigid quintifocal tensor, from which one can linearly compute nonrigid shape and motion. We also demonstrate the existence of intrinsic ambiguities in the reconstruction of camera translation, shape coefficients and shape bases. Examples show the effectiveness of our method on nonrigid scenes with significant perspective effects.
CORRECT SPECIFICATION AND IDENTIFICATION OF NONPARAMETRIC TRANSFORMATION MODELS

This paper derives necessary and sucient conditions for nonpara- metric transformation models to be (i) correctly specied,
Copper-Catalyzed Aerobic C-H Trifluoromethylation of Phenanthrolines.

Direct C–H trifluoromethylation of heterocycles is a valuable transformation. In particular, nonprecious metal-catalyzed C–H trifluoromethylation processes, which do not proceed through CF3 radical species, have been less developed. In this cluster report, a new copper-catalyzed aerobic C–H trifluoromethylation of phenanthrolines is described. This transformation affords trifluoromethylated phenanthrolines that have not been synthesized and preliminary mechanistic studies suggest that the CF3 group transfer may occur through cooperative activation.
The rise-time distribution of nearby Type Ia supernovae

We present an analysis of the B- and V-band rise-time distributions of nearby Type Ia supernovae (SNe Ia). Drawing mostly from the recently published Lick Observatory Supernova Search sample of SNe Ia , together with other published nearby SNe Ia with data starting at least 1 week before maximum light, we use a two-stretch template-fitting method to measure the rise and decline of BV light curves. Our analysis of 61 SNe with high-quality light curves indicates that the longer the time between explosion and maximum light (i.e. the rise time), the slower the decline of the light curve after maximum. However, SNe with slower post-maximum decline rates have a faster rise than would be expected from a single-parameter family of light curves, indicating that SN Ia light curves are not a single-parameter family of varying widths. Comparison of the B-band rise-time distribution for spectroscopically normal SNe Ia to those exhibiting high-velocity (HV) spectral features indicates that HV SNe Ia have shorter B-band rise times compared to their spectroscopically normal counterparts. After normalizing the
Modular ecosystem modeling

The Library of Hydro-Ecological Modules (LHEM, http://giee.uvm.edu/LHEM) was designed to create flexible landscape model structures that can be easily modified and extended to suit the requirements of a variety of goals and case studies. The LHEM includes modules that simulate hydrologic processes, nutrient cycling, vegetation growth, decomposition, and other processes, both locally and spatially. Where possible the modules are formulated as STELLA models, which adds to transparency and helps reuse. Spatial transport processes are presented as C++ code. The modular approach takes advantage of the spatial modeling environment (http://giee.uvm.edu/SME3) that allows integration of various STELLA models and C++ user code, and embeds local simulation models into a spatial context. Using the LHEM/SME the Patuxent landscape model (PLM) was built to simulate fundamental ecological processes in the watershed scale driven by temporal (nutrient loadings, climatic conditions) and spatial (land use patterns) forcings. Local ecosystem dynamics were replicated across a grid of cells that compose the rasterized landscape. Different habitats and land use types translate into different modules and parameter sets. Spatial hydrologic modules link the cells together. These are also part of the LHEM and define horizontal fluxes of material and information. This approach provides additional flexibility in scaling up and down over a range of spatial resolutions. Model results show good agreement with data for several components of the model at several scales. Other applications include several subwatersheds of the Patuxent, the Gwynns Falls watershed in Baltimore, and others.  2003 Elsevier Ltd. All rights reserved.
Multifrequency Strategies for the Identification of Gamma-Ray Sources

More than half the sources in the Third EGRET (3EG) catalog have no firmly established counterparts at other wavelengths and are unidentified. Some of these unidentified sources have remained a mystery since the first surveys of the γ-ray sky with the COS-B satellite. The unidentified sources generally have large error circles, and finding counterparts has often been a challenging job. A multiwavelength approach, using X-ray, optical, and radio data, is often needed to understand the nature of these sources. This chapter reviews the technique of identification of EGRET sources using multiwavelength studies of the gamma-ray fields.
Hydrodynamics of the double-wave structure of insect spermatozoa flagella

In addition to conventional planar and helical flagellar waves, insect sperm flagella have also been observed to display a double-wave structure characterized by the presence of two superimposed helical waves. In this paper, we present a hydrodynamic investigation of the locomotion of insect spermatozoa exhibiting the double-wave structure, idealized here as superhelical waves. Resolving the hydrodynamic interactions with a non-local slender body theory, we predict the swimming kinematics of these superhelical swimmers based on experimentally collected geometric and kinematic data. Our consideration provides insight into the relative contributions of the major and minor helical waves to swimming; namely, propulsion is owing primarily to the minor wave, with negligible contribution from the major wave. We also explore the dependence of the propulsion speed on geometric and kinematic parameters, revealing counterintuitive results, particularly for the case when the minor and major helical structures are of opposite chirality.
Ethics and governance of global health inequalities

Background: A world divided by health inequalities poses ethical challenges for global health. International and national responses to health disparities must be rooted in ethical values about health and its distribution; this is because ethical claims have the power to motivate, delineate principles, duties and responsibilities, and hold global and national actors morally responsible for achieving common goals. Theories of justice are necessary to define duties and obligations of institutions and actors in reducing inequalities. The problem is the lack of a moral framework for solving problems of global health justice. Aim: To study why global health inequalities are morally troubling, why efforts to reduce them are morally justified, how they should be measured and evaluated; how much priority disadvantaged groups should receive; and to delineate roles and responsibilities of national and international actors and institutions. Discussion and conclusions: Duties and obligations of international and state actors in reducing global health inequalities are outlined. The ethical principles endorsed include the intrinsic value of health to well-being and equal respect for all human life, the importance of health for individual and collective agency, the concept of a shortfall from the health status of a reference group, and the need for a disproportionate effort to help disadvantaged groups. This approach does not seek to find ways in which global and national actors address global health inequalities by virtue of their self-interest, national interest, collective security or humanitarian assistance. It endorses the more robust concept of “human flourishing” and the desire to live in a world where all people have the capability to be healthy. Unlike cosmopolitan theory, this approach places the role of the nation-state in the forefront with primary, though not sole, moral responsibility. Rather shared health governance is essential for delivering health equity on a global scale.
Auction Design and Tacit Collusion in FCC Spectrum Auctions

Abstract The Federal Communications Commission (FCC) has used auctions to award spectrum since 1994. During this time period, the FCC has experimented with a variety of auctions rules including click box bidding and anonymous bidding. These rule changes make the actions of bidders less visible during the auction and also limit the set of bids that can be submitted during a particular round. Economic theory suggests that tacit collusion may be more difficult as a result. We examine this proposition using data from four auctions: the PCS-C Block, the PCS-C&F Block Reauction, the Advanced Wireless Service auction and the 700 MHz auction. We examine the frequency of jump bids, retaliatory bids and straightforward bids across these auctions. While this simple descriptive exercise has a number of limitations, the data suggest that these rule changes have limited firms’ ability to tacitly collude.
Probability Inequalities for sums of Bounded Random Variables

Abstract Upper bounds are derived for the probability that the sum S of n independent random variables exceeds its mean ES by a positive number nt. It is assumed that the range of each summand of S is bounded or bounded above. The bounds for Pr {S – ES ≥ nt} depend only on the endpoints of the ranges of the summands and the mean, or the mean and the variance of S. These results are then used to obtain analogous inequalities for certain sums of dependent random variables such as U statistics and the sum of a random sample without replacement from a finite population.
A comparative evaluation of new silicon carbide diodes and state-of-the-art silicon diodes for power electronic applications

Recent progress in silicon carbide (SiC) material has made it feasible to build power devices of reasonable current density. This paper presents recent results including a comparison with state-of-the-art silicon diodes. Switching losses for two silicon diodes (a fast diode, 600 V, 50 A, 60 ns Trr), an ultra-fast silicon diode (600 V, 50 A, 23 ns Trr) and a 4H-SiC diode (600 V, 50 A) are compared. The effect of diode reverse recovery on the turn-on losses of a fast WARP/sup TM/ IGBT are studied both at room temperature and at 150/spl deg/C. At room temperature, SiC diodes allow a reduction of IGBT turn-on losses by 25% compared to ultra-fast silicon diodes and by 70% compared to fast silicon diodes. At 150/spl deg/C junction temperature, SiC diodes allow a turn-on loss reduction of 35% and 85% compared to ultra-fast and fast silicon diodes respectively. The silicon and SiC diodes are used in a boost power converter with the WARP/sup TM/ IGBT to assess the overall effect of SiC diodes on the power converter characteristics. Efficiency measurements at light load (100 W) and full load (500 W) are reported. Although SiC diodes exhibit very low switching losses, their high conduction losses due to the high forward drop dominate the overall losses, hence reducing the overall efficiency. Since this is an ongoing development, it is expected that future prototypes will have improved forward characteristics.
Efficient Management of Unerupted Teeth: A Time-Tested Treatment Modality

The strategy for managing unerupted teeth has been debated for more than half a century. Duration of treatment, adverse responses, and type of surgical procedure and mechanotherapy to align ectopically positioned teeth has been analyzed, with disparate approaches endorsed. This report will describe the most frequent adverse problems encountered with management of unerupted teeth and suggest a means to prevent them. A recent study will be reviewed that will demonstrate a time-tested evidence-based approach that can prevent these commonly encountered adverse problems as well as reduce treatment time required to position the malposed tooth into the line of occlusion regardless of the patient's age.
Wartime Institutions: A Research Agenda

Theories of civil war usually theorize the choices of civilians and combatants without considering the institutional context in which they interact. Despite common depictions of war as chaotic and ...
New Strategies for the Synthesis of Pyrimidine Derivatives

Recent advances in pyrimidine synthesis are described. Modification of conventional strategies involving N-C-N fragment condensation with 1,3-dicarbonyl derivatives remains a common theme in current literature. Other methods, including N-C fragment condensation strategies, provide reactive intermediates capable of intramolecular cyclization and formation of pyrimidine derivatives. These recently developed methodologies offer a valuable addendum to azaheterocycle synthesis.
Total Synthesis of the Polyether Antibiotic Ionomycin

A convergent asymmetric synthesis of the calcium ionophore ionomycin has been achieved through a route that is outlined below. The four illustrated subunits, which comprise the c,-C,,-,, CI)-&r cI&22, and C=-C32 portions of ionomycin,
A Thermodynamic Hypothesis Regarding Optimality Principles for Flow Processes in Geosystems

While optimality principles have been successfully used in many different areas related to flow processes in geosystems, their thermodynamic base has not been fully established. As an attempt to address this important issue, this chapter presents a thermodynamic hypothesis regarding optimality principles for the flow process. It states that a nonlinear natural system that is not isolated and involves positive feedbacks tends to minimize its resistance to the flow process that is imposed by its environment. Consistence between the hypothesis and typical flow processes in geosystems is demonstrated. In spirit, the hypothesis is consistent with Darwin’s evolution theory. It reconciles the seeming inconsistency between the minimization of energy expenditure rate principle and the maximum entropy production principle. An application of the hypothesis to calculation of inelastic deformation of natural rock is also outlined. The hypothesis is fundamental in nature, but proposed in a phenomenological manner. Further examinations of the usefulness and potential limitations of the hypothesis in describing other processes, distinct from flow processes in geosystems, are needed.
ULTRA-FAINT DWARF GALAXIES AS A TEST OF EARLY ENRICHMENT AND METALLICITY-DEPENDENT STAR FORMATION

The close relation of star formation with molecular gas indicated by observations and assumed in recent models implies that the efficiency with which galaxies convert their gas into stars depends on gas metallicity. This is because abundance of molecular hydrogen is sensitive to abundance of dust, which catalyzes formation of H2 and helps to shield it from dissociating radiation. In this study, we point out that in the absence of significant pre-enrichment by Population III stars forming out of zero metallicity gas, such H2-based star formation is expected to leave an imprint in the form of bi-modality in the metallicity distribution among dwarf galaxies and in the metallicity distribution of stars within individual galaxies. The bi-modality arises because when gas metallicity (and dust abundance) is low, formation of molecular gas is inefficient, the gas consumption timescale is long, and star formation and metal enrichment proceed slowly. When metallicity reaches a critical threshold value star formation and enrichment accelerate, which leads to rapid increase in both stellar mass and metallicity of galaxies. We demonstrate this process both using a simple analytical model and full cosmological simulations. In contrast, the observed metallicity distributions of dwarf galaxies or stars within them are not bi-modal. We argue that this discrepancy points to substantial early stochastic pre-enrichment by Population III stars to levels Z ~ 10–2 Z ☉ in dense, star-forming regions of early galaxies.
K6Cd4Sn3Se13: A polar open-framework compound based on the partially destroyed supertetrahedral [Cd4Sn4Se17]10− cluster

K6Cd4Sn3Se13 forms in superheated water and has a polar open-framework structure that is based on an octahedral topological motif. It forms from the polymerization of a single [Cd4Sn3Se13]6− cluster which formally derives from a [Cd4Sn4Se17]10−via elimination of one [SnSe4]4− anion. K6Cd4Sn3Se13 exhibits facile ion-exchange properties with suitably sized cations.