cssi/SciSciGPT-SciSciNet huggingface dataset:
Piles of Cubes, Monotone Path Polytopes, and Hyperplane Arrangements

Monotone path polytopes arise as a special case of the construction of fiber polytopes, introduced by Billera and Sturmfels. A simple example is provided by the permutahedron, which is a monotone path polytope of the standard unit cube. The permutahedron is the zonotope polar to the braid arrangement. We show how the zonotopes polar to the cones of certain deformations of the braid arrangement can be realized as monotone path polytopes. The construction is an extension of that of the permutahedron and yields interesting connections between enumerative combinatorics of hyperplane arrangements and geometry of monotone path polytopes.
Arts of the states in crisis–Revisiting determinants of state-level appropriations to arts agencies

Abstract Clearly, much has happened to the state of public coffers and their ability to finance the arts in the past decade. This study extends Noonan (2007) into the next decade and the “Great Recession” that hit the U.S. (and world) economy–with state public finances severely exposed to the downward economic shock. The emphasis of the empirical analysis here is answering a twofold question: how well have past models predicted the past decade of funding patterns, and how have the funding determinants shifted in recent years. While the previous work found that some predictable patterns (e.g., there is much momentum in funding, demographics and partisan politics matter), there was insufficient evidence to back the claims that SAAs suffer disproportionately during times of fiscal stress. Further, political culture has changed substantially in the US in recent decades. From today's vantage, we can observe how well the older models predict the changes actually experienced. This comparison shows that the severe budget cuts experienced in the wake of the recession were to be expected, but there are some interesting shortcomings in the previous understanding, which points to a shift in the determinants of public arts funding in the U.S.
Recent progress in first-principles studies of magnetoelectric multiferroics

Materials that combine magnetic and ferroelectric properties have generated increasing interest over the last few years, due to both their diverse properties and their potential utility in new types of magnetoelectric device applications. In this review we discuss recent progress in the study of such magnetoelectric multiferroics which has been achieved using computational first-principles methods based on density functional theory. In particular, we show how first-principles methods have been successfully used to explain various properties of multiferroic materials and to predict novel effects and new systems that exhibit multiferroic properties.
On the escape of ionizing radiation from starbursts

Far-ultraviolet spectra obtained with FUSE show that the strong C II λ1036 interstellar absorption line is essentially black in five of the UV-brightest local starburst galaxies. Because the opacity of the neutral ISM below the Lyman edge will be significantly larger than in the C II line, these data provide strong constraints on the escape of ionizing radiation from these starbursts. Interpreted as a uniform, absorbing slab, the implied optical depth at the Lyman edge is huge (τ0 ≥ 102). Alternatively, the areal covering factor of opaque material is typically ≥94%. Thus, the fraction of ionizing stellar photons that escape the ISM of each galaxy is small: our conservative estimates typically yield fesc ≤ 6%. Inclusion of extinction due to dust will further decrease fesc. An analogous analysis of the rest-UV spectrum of the star-forming galaxy MS 1512-cB58 at z = 2.7 leads to similar constraints on fesc. These new results agree with the constraints provided by direct observations below the Lyman edge in a few other local starbursts. However, they differ from the recently reported properties of star-forming galaxies at z ≥ 3. We assess the idea that the strong galactic winds seen in many powerful starbursts clear channels through their neutral ISM. We show empirically that such outflows may be a necessary—but not sufficient—part of the process of creating a relatively porous ISM. We note that observations will soon document the cosmic evolution in the contribution of star-forming galaxies to the metagalactic ionizing background, with important implications for the evolution of the IGM.
A New pH Oscillator: The Chlorite−Sulfite−Sulfuric Acid System in a CSTR

A new pH oscillator has been discovered involving the system of NaClO2, Na2SO3, and H2SO4 in a continuous-flow stirred tank reactor (CSTR). While ClO2- serves as an oxidant in numerous systems exhibiting nonlinear dynamical behavior, this is the first reported chlorite-based pH oscillator. Large-amplitude oscillations in pH and potential of a platinum electrode were observed over a rather narrow concentration range. Complex dynamical behavior also was observed, including aperiodic oscillations, bistability between steady states, bistability between steady state and oscillatory state, bursting, a possible third steady state, and damped oscillations in batch. Autocatalytic oxidation of HSO3- by ClO2- is a major source of positive feedback in H+. A fast Cl+-transfer reaction between HOCl and SO32- is an important source of negative feedback. Oscillations were also obtained in the presence of Na2CO3, with the dehydration reaction of H2CO3 providing additional negative feedback. Models are proposed to account ...
Forty years of photosynthesis and related activities

AbstractAt the heart of this review are the 10 years of work leading up to the award of the Nobel Prize for Chemistry in 1961 for the elucidation of the multiple steps in the path of carbon during photosynthesis, a process now universally known as the Calvin cycle. Also described are the background to the author's first forays into the brand new terrain of biochemistry, early work on the effects of deuterium oxide on biological systems, and research into hydrocarbon producing plants as sources of energy and the construction of an artificial photosynthetic system.
Slip-Length Scaling in Large Earthquakes: The Role of Deep-Penetrating Slip below the Seismogenic Layer

Coseismic slip is observed to increase with earthquake rupture length for lengths far beyond the length scale set by the seismogenic layer. The observation, when interpreted within the realm of static dislocation theory and the imposed limit that slip be confined to the seismogenic layer, implies that earthquake stress drop increases as a function of rupture length for large earthquakes and, hence, that large earthquakes differ from small earthquakes. Here, a three-dimensional elastodynamic model is applied to show that the observed increase in coseismic slip with rupture length may be satisfied while maintaining a constant stress drop across the entire spectrum of earthquake sizes when slip is allowed to penetrate below the seismogenic layer into an underlying zone characterized by velocity-strengthening behavior. Is this deep coseismic slip happening during large earthquakes? We point to a number of additional associated features of the model behavior that are potentially observable in the Earth. These include the predictions that a substantial fraction, on the order of one-third of the total coseismic moment, is due to slip below the seismogenic layer and that slip below the seismogenic layer should be characterized by long rise times and a dearth of high-frequency motion.
Calabi-Yau mirror symmetry as a gauge theory duality

Using brane set-ups we construct dual gauge theories in two dimensions with calN = (2,2) supersymmetry. Two different dualities are realized. One is basically a consequence of three-dimensional mirror symmetry. The nonlinear sigma model with a Calabi-Yau target space on the Higgs branch of the gauge theory is mapped into an equivalent non-linear sigma model on the Coulomb branch on the dual, realizing a T-dual target space with torsion. The second dual is genuine to two dimensions. In addition to swapping Higgs and Coulomb branches it trades twisted for untwisted multiplets, implying a sign flip of the left-moving U (1)R charge. Successive application of both dualities leads to geometric mirror symmetry for the Calabi-Yau target space.
Using Vertical Fourier Transforms to Invert Potential-Field Data to Magnetization or Density Models in the Presence of Topography

The Fourier transform relationship between a density or magnetization distribution within a volume and the corresponding gravity or magnetic field within the volume can be used to develop a non-linear inversion procedure that performs well in the presence of topography. Previous Fourier-transform-based potential-field inversion routines (Li and Oldenburg, 1996, 2003; Pilkington, 1997, 2009) use Fourier transforms in the horizontal plane, and require sources within horizontal layers and observed data on horizontal surfaces. These previous approaches are not designed for situations that involve topography and data collected on undulating surfaces.
Simplified Building and Air-handling Unit Model Calibration and Applications

Model calibration remains a significant topic for both researchers and practitioners in the HVAC field although calibrated building and air-handling unit (AHU) models have been used for measuring building energy retrofit/commissioning savings, identifying operational problems, and optimizing system operation and control schedules for decades. This paper discusses the modeling and simplification of building and AHU systems used in the simplified model calibration process. The paper presents a two-level calibration procedure integrated with energy signatures for simplified building and AHU heating and cooling energy consumption models. The procedures are demonstrated using a detailed example. This procedure can be implemented into computer simulation programs to allow automatic calibration and fault detection in many HVAC engineering processes.
Dynamic Modeling and Simulation of Impact in Tether Net/Gripper systems

The objective of this paper is to study the dynamic modeling andsimulation of a tether-net/gripper system during an impact, while it isbeing deployed or retrieved by a winch on a satellite orbiting aroundearth. We stick to Tether-Net system but the analysis is applicable toTether-Gripper systems too. We assume that the net is deployed from thesatellite in orbit and the motion is restricted to the orbital plane.This net captures a second satellite and tows it. The motion of atether-net system can be broken down into the following phases: (i)Phase 1: Net is shot out from the satellite with the tether completelyslack, (ii) Phase 2: Net comes to a location where the tether is tautwhile the drum on the orbiter is locked, (iii) Phase 3: Drum is unlockedand the net moves with the tether, (iv) Phase 4: Net captures a body.The continua (tether) is modeled using mode functions and coordinates.The theory of impulse and momentum can be used to model Phases 1, 2, and4 of motion of the tether-net system. The dynamics of the motion of thesystem in phase 3 is characterized by differential and algebraicequations (DAEs). Matlab ODE solvers were used to solve these DAEs.
A multistable transistor circuit

Summary form only given. This paper explains a multistable circuit which appears to be well suited to transistor characteristics. This circuit utilizes those characteristics of junction transistors which are inherent in the device and do not require close control during manufacture. Desirable features of the circuit are that it can theoretically have any number of statically stable states and that these states may be achieved using only two transistors with alpha less than one or one transistor with alpha greater than one. Inherently, the circuit is able to count up or down with equal facility. The circuit achieves multistable states by controlling the feedback and hence the stability of the circuit. The amount of feedback in any circuit may be controlled by a number of parameters of the circuit. If one of these parameters is made to vary in a non-linear manner over the operating range of the circuit, and if certain other conditions are imposed, the circuit may be caused to have several regions of stable and unstable operating characteristics. Several means of varying the parameters of a circuit will be shown that will achieve the desired effect.
Radiative heating about outer planet entry probes

A study has been conducted to define the radiative, heating-rate distributions about spherically capped, 60 deg half-angle conical entry probes to the outer planets Jupiter, Saturn, and Uranus. The radiative heating rates are calculated by a direct method for the solution of the inviscid flow equations with coupled, nongray radiative transport. Results are presented for a range of entry conditions using the atmospheric models denoted as nominal, warm, and cool for each planet which show that both the magnitude and distribution of radiative heating rate are strongly dependent on the atmospheric model and the free-stream conditions.
The Sunada construction and the simple length spectrum

We show that certain families of iso-length spectral hyperbolic surfaces obtained via the Sunada construction are not generally simple iso-length spectral.
Additive number theory and the ring of quantum integers

Let m and n be positive integers. For the quantum integer [n]q = 1+q+q2+⋯+ qn−−1 there is a natural polynomial addition such that [m]q ⊕q [n]q = [m+n]q and a natural polynomial multiplication such that [m]q⊗q [n]q = [mn]q. These definitions are motivated by elementary decompositions of intervals of integers in combinatorics and additive number theory. This leads to the construction of the ring of quantum integers and the field of quantum rational numbers.
How Do Cartels Operate

This paper distills and organizes facts about cartels from about 20 European Commission decisions over 2000-2004. It describes the properties of a collusive outcome in terms of the setting of price and a market allocation, monitoring of agreements with respect to price but more importantly sales, punishment methods for enforcing an agreement and also the use of buy-backs to compensate cartel members, methods for responding to external disruptions from non-cartel suppliers and handling over-zealous sales representatives, and operational procedures in terms of the frequency of meetings and the cartel’s organizational structure.
Synthesis of α-Amino-α‘-diazomethyl Ketones via Ring Opening of Substituted Cyclopropanones with Alkyl Azides. A Facile Route to N-Substituted 3-Azetidinones

The reaction of alkyl azides with triethyl(1-methoxy-2,2-dimethyl-cyclopropoxy)silane affords a series of α-amino-α‘-diazomethyl ketones in moderate yields (38−54%). The mechanism of this novel process is discussed. The diazomethyl ketones could also be cyclized to the corresponding N-substituted 3-azetidinones in good yield upon treatment with Rh2(OAc)4.
Apparent and actual galaxy cluster temperatures

The redshift evolution of the galaxy cluster temperature function is a powerful probe of cosmology. However, its determination requires the measurement of redshifts for all clusters in a catalogue, which is likely to prove challenging for large catalogues expected from XMM-Newton, which may contain of the order of 2000 clusters with measurable temperatures, distributed around the sky. In this paper we study the apparent cluster temperature, which can be obtained without cluster redshifts. We show that the apparent temperature function itself is of limited use in constraining cosmology, and so concentrate our focus on studying how apparent temperatures can be combined with other X-ray information to constrain the cluster redshift. We also briefly study the circumstances under which the non-thermal spectral features can provide redshift information.
Carbon dioxide hydrate particles for ocean carbon sequestration

This paper presents strategies for producing negatively buoyant CO{sub 2} hydrate composite particles for ocean carbon sequestration. Our study is based on recent field observations showing that a continuous-jet hydrate reactor located at an ocean depth of 1500 m produced curved negatively buoyant cylindrical particles with diameters {approx} 2.5 cm and lengths up to {approx} 1 m. Accordingly we performed new laboratory experiments to determine the drag coefficient of such particles and, based on the measured drag coefficient and the initial settling velocity observed in the field, have concluded that the reactor efficiency (percentage of liquid CO{sub 2} converted to hydrate) in the field was {approx} 16%. Using the dissolution rates observed in the field, we conclude that such particles would ultimately sink to depth below discharge of {approx} 115 m. We have also predicted the sinking depth of particles potentially produced from various scaled-up reactors and have shown that, for example, a 10 cm diameter particle produced with a hydrate conversion of 50% could reach the ocean bottom before completely dissolving. In a real sequestration scenario, we are interested in following large groups of hydrate particles released continuously. We have previously shown that increasing particle size and hydrate conversionmore » efficiency enhances the sinking of hydrate particle plumes produced by the continuous release of CO{sub 2} in a quiescent ambient, but that a sufficiently strong current will cause the entrained particles to separate from the plume and settle discretely. In the latter case, particles of different sizes and hydrate conversions (hence different settling velocities) will follow different settling trajectories as they dissolve. This particle fractionation, if employed deliberately, spreads the discharged CO{sub 2} in the down current and vertical directions, enhancing mixing, while turbulent diffusion helps spread the CO{sub 2} in the third direction. A numerical model that incorporates these processes is used to predict the downstream concentrations and changes in pH from such particle plumes in a 'strong' current. An extension of this model simulates hydrate particles that are released continuously from a moving ship. Because of the ship speed, such particles would never form a coherent plume, but the combination of particle fractionation and advection due to the ship motion produces excellent dilution of the discharged CO{sub 2}.« less
ON THE LAST 10 BILLION YEARS OF STELLAR MASS GROWTH IN STAR-FORMING GALAXIES

The star formation rate-stellar mass relation (SFR-M *) and its evolution (i.e., the SFR main sequence) describe the growth rate of galaxies of a given stellar mass and at a given redshift. Assuming that present-day star-forming galaxies (SFGs) were always star forming in the past, these growth rate observations can be integrated to calculate average star formation histories (SFHs). Using this Main Sequence Integration (MSI) approach, we trace present-day massive SFGs back to when they were 10%-20% of their current stellar mass. The integration is robust throughout those epochs: the SFR data underpinning our calculations are consistent with the evolution of stellar mass density in this regime. Analytic approximations to these SFHs are provided. Integration-based results reaffirm previous suggestions that current SFGs formed virtually all of their stellar mass at z 2 are not the typical progenitors of SFGs today. We also check MSI-based SFHs against those inferred from analysis of the fossil record—from spectral energy distributions (SEDs) of SFGs in the Sloan Digital Sky Survey and color-magnitude diagrams (CMDs) of resolved stars in dwarf irregular galaxies. Once stellar population age uncertainties are accounted for, the main sequence is in excellent agreement with SED-based SFHs (from VESPA). Extrapolating SFR main sequence observations to dwarf galaxies, we find differences between MSI results and SFHs from CMD analysis of Advanced Camera for Surveys Nearby Galaxy Survey Treasury and Local Group galaxies. Resolved dwarfs appear to grow much slower than main sequence trends imply, and also slower than slightly higher mass SED-analyzed galaxies. This difference may signal problems with SFH determinations, but it may also signal a shift in star formation trends at the lowest stellar masses.
Gap Clearing by Planets in a Collisional Debris Disk

We apply our 3D debris disk model, SMACK, to simulate a planet on a circular orbit near a ring of planetesimals that are experiencing destructive collisions. Previous simulations of a planet opening a gap in a collisionless debris disk have found that the width of the gap scales as the planet mass to the 2/7th power (α = 2/7). We find that gap sizes in a collisional disk still obey a power law scaling with planet mass, but that the index α of the power law depends on the age of the system t relative to the collisional timescale t coll of the disk by α = 0.32(t/t coll)–0.04, with inferred planet masses up to five times smaller than those predicted by the classical gap law. The increased gap sizes likely stem from the interaction between collisions and the mean motion resonances near the chaotic zone. We investigate the effects of the initial eccentricity distribution of the disk particles and find a negligible effect on the gap size at Jovian planet masses, since collisions tend to erase memory of the initial particle eccentricity distributions. Finally, we find that the presence of Trojan analogs is a potentially powerful diagnostic of planets in the mass range ~1-10 M Jup. We apply our model to place new upper limits on planets around Fomalhaut, HR 4796 A, HD 202628, HD 181327, and β Pictoris.
Comparative diels-alder reactivities within a family of valence bond isomers : A biomimetic total synthesis of (±)-UCS1025A

A synthesis of the structurally fascinating fungal metabolite UCS1025A (1) was accomplished. It features a likely biomimetic approach to the octalin subunit via an intramolecular Diels-Alder (IMDA) reaction of a putative triene precursor (2), preceded by an efficient construction of the bisheteratriquinane subunit within that compound. Specifically, an intramolecular silyl triflate-induced cyclization of an in situ-generated silyl ketene acetal onto an imide carbonyl group (e.g., 7 to 8) was developed. The IMDA relative reactivities of a family of valence bond isomers, each differing in the precise nature of the dienophilic subunit, were determined. Under biologically relevant conditions (D2O, pH 7.2 buffer, ca. 25 degrees C), triene 2, via its lactone ring-opened congener, underwent very fast (t1/2 = 10 min) conversion to the ring-opened forms of 1 (i.e., 5a) and the tetraepimeric, alternative endo-adduct, 3 [i.e., (tetraepi)-5a].
Molar distalization with the Herbst appliance

Abstract This article reviews the dental effects of the Herbst appliance as well as itslong-term effects on the dentition. The Herbst appliance exhibits a pronounced high-pull headgear effect on the maxillary molars. Without retention, the molars tend to return to their former anteroposterior positions after the removal of the appliance. These distal movements of the maxillary molars are favorable in Class II correction. Reciprocal mesial movements of the mandibular dentition, however, may not be desirable in many instances. Even though partial recovery occurs after Herbst therapy, treatment effects can persist in the mandibular arch. The latter effect can be beneficial to those patients who have initial retroclined mandibular incisors, but unfavorable in those patients with proclined lower incisors at the beginning of treatment.
The Mid-Infrared Continua of Seyfert Galaxies

An analysis of archival mid-infrared (mid-IR) spectra of Seyfert galaxies from the Spitzer Space Telescope observations is presented. We characterize the nature of the mid-IR active nuclear continuum by subtracting a template starburst spectrum from the Seyfert spectra. The long wavelength part of the spectrum contains a strong contribution from the starburst-heated cool dust; this is used to effectively separate starburst-dominated Seyferts from those dominated by the active nuclear continuum. Within the latter category, the strength of the active nuclear continuum drops rapidly beyond ~20 μm. On average, type 2 Seyferts have weaker short-wavelength active nuclear continua as compared to type 1 Seyferts. Type 2 Seyferts can be divided into two types, those with strong polycyclic aromatic hydrocarbon (PAH) bands and those without. The latter type show polarized broad emission lines in their optical spectra. The PAH-dominated type 2 Seyferts and Seyfert 1.8/1.9s show very similar mid-IR spectra. However, after the subtraction of the starburst component, there is a striking similarity in the active nuclear continuum of all Seyfert optical types. PAH-dominated Seyfert 2s and Seyfert 1.8/1.9s tend to show weak active nuclear continua in general. A few type 2 Seyferts with weak/absent PAH bands show a bump in the spectrum between 15 and 20 μm. We suggest that this bump is the peak of a warm (~200 K) blackbody dust emission, which becomes clearly visible when the short-wavelength continuum is weaker. This warm blackbody emission is also observed in other Seyfert optical subtypes, suggesting a common origin in these active galactic nuclei.
Phi meson production cross sections in pion-baryon and baryon-baryon interactions

Abstract Phi meson production in pion-baryon and baryon-baryon interactions near the production threshold is studied in a boson-exchange model. Parameters in this model are either taken from the Bonn model for the nucleon-nucleon potential or determined from the measured phi meson decay width and the experimental data for the reactions π − p → φn and pp → ppφ . The isospin-averaged cross sections for the reactions πN → φN , πΔ → φN , NN → NNφ , which are needed in transport models to study phi meson production in heavy-ion collisions at subthreshold energies, have been evaluated. For the reactions NΔ → NNφ and ΔΔ → NNφ , which become singular when the exchanged pion is on-shell, the Peierls method is used to calculate their cross sections. We find that the cross section for the reaction πN → φN is much larger than the other cross sections.
Nanomedicine for treating spinal cord injury

Spinal cord injury results in significant mortality and morbidity, lifestyle changes, and difficult rehabilitation. Treatment of spinal cord injury is challenging because the spinal cord is both complex to treat acutely and difficult to regenerate. Nanomaterials can be used to provide effective treatments; their unique properties can facilitate drug delivery to the injury site, enact as neuroprotective agents, or provide platforms to stimulate regrowth of damaged tissues. We review recent uses of nanomaterials including nanowires, micelles, nanoparticles, liposomes, and carbon-based nanomaterials for neuroprotection in the acute phase. We also review the design and neural regenerative application of electrospun scaffolds, conduits, and self-assembling peptide scaffolds.
Separating Hydrogen From Coal Gasification Gases With Alumina Membranes

Synthesis gas produced in coal gasification processes contains hydrogen, along with carbon monoxide, carbon dioxide, hydrogen sulfide, water, nitrogen, and other gases, depending on the particular gasification process. This paper reports on development of membrane technology to separate the hydrogen from the raw gas at the high operating temperatures and pressures near exit gas conditions would improve the efficiency of the process. Tubular porous alumina membranes with mean pore radii ranging form about 9-22 {Angstrom} have been fabricated and characterized. Based on the results of hydrostatic tests, the burst strength of the membranes ranged from 800-1600 psig, with a mean value of abut 1300 psig. These membranes were evaluated for separating hydrogen and other gases. Tests of membrane permeabilities were made with helium, nitrogen, and carbon dioxide. Measurements were made at room temperature in the pressure range of 15-589 psi. In general, the relative gas permeabilities correlated qualitatively with a Knudsen flow mechanism; however, other gas transport mechanisms such as surface adsorption also may be involved.
Optical Surface Analysis of the Head-Disk-Interface of Thin Film Disks

This paper describes the design, operation, theory, and data interpretation of an Optical Surface Analyzer (OSA). The OSA can measure carbon wear, lubricant depletion/accumulation, surface roughness, and lubricant alteration on carbon coated thin film disks. This device can measure an Angstrom of carbon wear or lubricant depletion/accumulation. The OSA can also measure debris generation and lubricant degradation through a measurement of optical index change. The lateral resolution of the OSA is approximately 5 by 10 microns and the bandwidth of the device is 2 MHz. The small device size allows it to be used within a test stand environment
Design of online auctions: Proxy versus non-proxy settings

Recent years have witnessed the rapid development of online auctions. Currently, some online auctions, such as eBay, introduce a proxy bidding policy, under which bidders submit their maximum bids and delegate to a proxy agent to automatically outbid other competitors for the top bidder, whereas other online auctions do not. This paper compares these two widely used auction mechanisms (proxy setting and non-proxy setting) and characterizes the equilibrium bidding behavior and the seller's expected revenue. We find the proxy auction outperforms the non-proxy auction in terms of the seller's expected revenue. This dominance result is not prone to the specific bid announcement policy, the bidder's knowledge regarding the number of bidders, the impact of traffic congestion along the bidding process, the number of items sold through the auction, and the existence of a reserve price. We further find that the proxy setting usually fails to sustain the truthful bidding as a dominant strategy equilibrium even if no minimum bid increments are adopted, and the possibility of a low-valuation-bidder dilemma where the low-valuation bidders could be better off if all bidders collude to bid at the last minute. We also discuss the dramatically different equilibrium bidding behaviors under the two auction mechanisms.
Auger and depth profile analysis of synthetic crystals for dispersion of soft x-rays

Abstract Numerous samples have been fabricated and analyzed as part of a program to produce soft X-ray dispersion elements for various laboratory applications. The majority of this work has centered around the carbon/tungsten system, although several other low Z/tungsten pairs have been investigated. This report describes the development of certain sputter deposition techniques for fabricating these dispersion elements, based upon results obtained from X-ray reflectivity measurements and Auger depth profile analysis. The composition of the films is chiefly alternating layers of tungsten carbide and carbon, similar to other recent work [1]. Excess carbon is introduced during the deposition of the tungsten to ensure that the carbide layer is fully stoichiometric. Layer thickness ranged from ∼ 5 to 30 A for the carbide and from ∼ 15 to 80 A for the carbon. The reflectivity measurements were made using Fe and Al Kα radiation at grazing incidence. The emphasis in these studies is on the application of surface analysis results in recommending modifications to the fabrication process and in evaluating the results such modifications have on the layer stoichiometry, continuity, and periodicity of the dispersion elements so produced.
Hamilton-jacobi Formalism for Strings

Abstract It is shown that a Hamilton—Jacobi-type formalism can be set up to deal with the classical dynamics of relativistic strings and other one-dimensional extended systems. A special feature is that the formalism involves two evolution parameters which are treated on an equal footing. The corresponding Hamilton—Jacobi functions turn out to be vector potentials or Clebsch potentials, and in this sense we find a link between the string model and gauge field theory.
Stability and separation in volume comparison problems

We review recent stability and separation results in volume comparison problems and use them to prove several hyperplane inequalities for intersection and projection bodies.
An approach to the total synthesis of welwistatin.

An approach to the total synthesis of the antimicrotubule agent welwistatin is described. Key transformations include (1) a 7-endo intramolecular conjugate addition reaction of enone 6 to deliver the strained bicyclo[4.3.1]decanone 5; (2) a 6π electrocyclic ring closure of trienecarbamate 16 followed by oxidation to afford protected aniline 17; and (3) an intramolecular cyclization of acetic acid derivative 18 to give rise to indole 19.
Low‐frequency elastic‐wave scattering by an inclusion: limits of applications

SUMMARY The present investigation considers various approximations for the problem of low-frequency elastic waves scattered by a single, small inclusion of constant elastic parameters. For the Rayleigh approximation containing both near- and far-field terms, the scattered amplitudes are investigated as a function of distance from the scatterer. Near-field terms are found to be dominant for distances up to two wavelengths, after which far-field solutions correctly describe the scattered field. At a distance of two wavelengths the relative error between the total and the far-field solution is about 15 per cent and decreases with increasing distance. Deriving solutions for the linear and quadratic Rayleigh–Born approximation, the relative error between the non-linear Rayleigh approximation and the linear and quadratic Rayleigh–Born approximation as a function of the scattering angle and the parameter perturbation is investigated. The relative error reveals a strong dependence on the scattering angle, while the addition of the quadratic term significantly improves the approximation for all scattering angles and parameter perturbations. An approximation for the error caused by linearization of the problem, based entirely on the perturbations of the parameters from the background medium, and its validity range are given. We also investigate the limit of the wave parameter for Rayleigh scattering and find higher values than previously assumed. By choosing relative errors of 5 per cent, 10 per cent and 20 per cent between the exact solution and the Rayleigh approximation, we find the upper limits for the parameter kpR to be 0.55, 0.7 and 9.9, respectively.
Surface Morphology of SiGe Epitaxial Layers Grown on Uniquely Oriented Si Substrates

The 4% lattice mismatch between Si and Ge creates strain in epitaxial layers of SiGe alloys on Si, and this strain can manifest itself in the morphological structure of the surface of the epitaxial layer. This study explores the relationship of the evolution of the surface morphology of SiGe layers grown on a range of Si surface orientations. We have grown thin, strained and thick, relaxed layers of Si0.7Ge0.3 by solid source molecular beam epitaxy on substrates with surface normals rotated from [001] towards [111] by angles of θ = (0, 2, 4, 10, 22) degrees. The surface morphology was investigated by atomic force microscopy, which showed considerable ordering of surface features on relaxed samples. These features evolve from hut-like structures at 0 degrees to large mesa-like structures separated by pits and crevices at 22 degrees. The organization of these features is also shown to vary with the substrate orientation. Each surface has characteristic directions along which features are aligned, and these directions vary continuously with the angle of rotation of the substrate. Transmission electron microscopy confirmed that misfit dislocations had formed along those same directions. The state of relaxation of each layer is quantified by Raman spectroscopy in order to make a direct correlation between residual strain and surface morphology.
Universality of fixation probabilities in randomly structured populations

The stage of evolution is the population of reproducing individuals. The structure of the population is known to affect the dynamics and outcome of evolutionary processes, but analytical results for generic random structures have been lacking. The most general result so far, the isothermal theorem, assumes the propensity for change in each position is exactly the same, but realistic biological structures are always subject to variation and noise. We consider a finite population under constant selection whose structure is given by a variety of weighted, directed, random graphs; vertices represent individuals and edges interactions between individuals. By establishing a robustness result for the isothermal theorem and using large deviation estimates to understand the typical structure of random graphs, we prove that for a generalization of the Erdős-Renyi model, the fixation probability of an invading mutant is approximately the same as that of a mutant of equal fitness in a well-mixed population with high probability. Simulations of perturbed lattices, small-world networks and scale-free networks behave similarly. We conjecture that the fixation probability in a well-mixed population, (1 − r−1)/(1 − r−n), is universal: for many random graph models, the fixation probability approaches the above function uniformly as the graphs become large.
Social Mobility and Redistributive Politics

Just like economists, voters have conflicting views about redistributive taxation because they estimate its incentive costs differently. We model rational agents as trying to learn from their dynastic income mobility experience the relative importance of effort and predetermined factors in the generation of income inequality and therefore the magnitude of these incentive costs. In the long run, "left-wing dynasties" believing less in individual effort and voting for more redistribution coexist with "right-wing dynasties." This allows us to explain why individual mobility experience and not only current income matters for political attiitudes and how persistent differences in perceptions about social mobility can generate persistent differences in redistribution across countries.
The environmental justice dimensions of climate change

Abstract Nations around the world are considering strategies to mitigate the severe impacts of climate change predicted to occur in the twenty-first century. Many countries, however, lack the wealth, technology, and government institutions to effectively cope with climate change. This study investigates the varying degrees to which developing and developed nations will be exposed to changes in three key variables: temperature, precipitation, and runoff. We use Geographic Information Systems (GIS) analysis to compare current and future climate model predictions on a country level. We then compare our calculations of climate change exposure for each nation to several metrics of political and economic well-being. Our results indicate that the impacts of changes in precipitation and runoff are distributed relatively equally between developed and developing nations. In contrast, we confirm research suggesting that developing nations will be affected far more severely by changes in temperature than developed na...
A new hybrid active power filter (APF) topology

In this paper, a new hybrid active power filter topology is presented. A higher-voltage, low-switching frequency insulated gate bipolar transistor (IGBT) inverter and a lower-voltage high-switching frequency metal oxide semiconductor field effect transistor (MOSFET) inverter are used in combination to achieve harmonic current compensation. The function of the IGBT inverter is to support utility fundamental voltage and to compensate for the fundamental reactive power. The MOSFET inverter fulfills the function of harmonic current compensation. To further reduce cost and to simplify control, the IGBT and MOSFET inverters share the same DC-link via a split capacitor bank. With this approach harmonics can be cancelled over a wide frequency range. Compared to the conventional APF topology, the proposed approach employs lower dc-link voltage and generates less noise. Simulation and experimental results show that the proposed active power filter topology is capable of compensating for the load harmonics.
Comparison of tamoxifen and clomiphene citrate for ovulation induction: a meta-analysis

BACKGROUND: Both selective estrogen receptor modulators, tamoxifen and clomiphene have been used for ovulation induction for patients with anovulatory infertility. This meta-analysis sought to compare the effectiveness of tamoxifen to clomiphene for the induction of ovulation and achievement of pregnancy. METHODS: We searched MEDLINE, BIOSIS, PreMEDLINE, CINAHL, International Pharmaceutical Abstracts, DDSR, ACP Journal Club, DARE and CCTR, along with reference lists and national experts. Inclusion criteria were prospective clinical trials, which compared tamoxifen and clomiphene for ovulation induction in infertile couples with isolated anovulatory infertility. Main outcome measures were ovulation rate and clinical pregnancy rate. Pooled odds ratios were obtained using random effects meta-analysis. RESULTS: Four trials were included. After pooling all the trials, the use of tamoxifen or clomiphene citrate resulted in similar ovulation rates [odds ratio (OR) 0.755, 95% confidence interval (CI) 0.513‐1.111]. There was no benefit of tamoxifen over clomiphene citrate in achievement of pregnancy per cycle (OR 1.056, 95% CI 0.583‐1.912) or per ovulatory cycle (OR 1.162, 95% CI 0.632‐2.134). CONCLUSIONS: Clomiphene citrate and tamoxifen are equally effective in inducing ovulation. Although data regarding pregnancy rates and outcome are limited, there does not appear to be a significant benefit of one medication over the other.
EXPORTING UNDER TRADE POLICY UNCERTAINTY: THEORY AND EVIDENCE

I provide novel evidence for the impact of trade policy uncertainty on exporters. In a dynamic, heterogeneous rms model, trade policy uncertainty will delay the entry of exporters into new markets and make them less responsive to applied tari reductions. Policy instruments that reduce or eliminate uncertainty, such as binding trade policy commitments at the WTO, increase entry. The predictions are tested on disaggregated, product-level Australian imports with model-consistent measures of uncertainty. Reducing policy uncertainty generates more product entry than unilateral liberalization. The results illuminate and quantify an important new channel for trade creation.
Intrinsic linking and knotting in virtual spatial graphs

We introduce a notion of intrinsic linking and knotting for virtual spatial graphs. Our theory gives two filtrations of the set of all graphs, allowing us to measure, in a sense, how intrinsically linked or knotted a graph is; we show that these filtrations are descending and nonterminating. We also provide several examples of intrinsically virtually linked and knotted graphs. As a byproduct, we introduce the virtual unknotting number of a knot, and show that any knot with nontrivial Jones polynomial has virtual unknotting number at least 2.
Perspectives on Higgs boson and supersymmetry

We review the recent discovery of the Higgs like particle at ∼ 125 GeV and its implications for particle physics models. Specifically the implications of the relatively high Higgs mass for the discovery of supersymmetry are discussed. Several related topics such as naturalness and supersymmetry, dark matter and unification are also discussed.
Are Galactic Rotation Curves Really Flat

In this paper we identify an apparently previously unappreciated regularity in the systematics of galactic rotation curves; namely, we find that at the last detected points in galaxies of widely varying luminosity, the centripetal acceleration is found to have the completely universal form (v2/c2R)last = γ0/2 + γ*N*/2 + β*N*/R2, where γ0 and γ* are new universal constants, β* is the Schwarzschild radius of the Sun, and N* is the total amount of visible matter in each galaxy. This regularity points to a possible role for the linear potentials associated with conformal gravity, with the galaxy-independent γ0 term being found not to be generated from within individual galaxies at all but rather to be of cosmological origin, being due to the global Hubble flow of a necessarily spatially open universe of 3-space scalar curvature k = -(γ0/2)2 = -2.3 × 10-60 cm-2.
Shannon-Theoretic Limits on Noisy Compressive Sampling

In this paper, we study the number of measurements required to recover a sparse signal in CM with L nonzero coefficients from compressed samples in the presence of noise. We consider a number of different recovery criteria, including the exact recovery of the support of the signal, which was previously considered in the literature, as well as new criteria for the recovery of a large fraction of the support of the signal, and the recovery of a large fraction of the energy of the signal. For these recovery criteria, we prove that O(L) (an asymptotically linear multiple of L) measurements are necessary and sufficient for signal recovery, whenever L grows linearly as a function of M. This improves on the existing literature that is mostly focused on variants of a specific recovery algorithm based on convex programming, for which O(L log(M - L)) measurements are required. In contrast, the implementation of our proof method would have a higher complexity. We also show that O(L log(M - L)) measurements are required in the sublinear regime (L - o(M)). For our sufficiency proofs, we introduce a Shannon-theoretic decoder based on joint typicality, which allows error events to be defined in terms of a single random variable in contrast to previous information-theoretic work, where comparison of random variables are required. We also prove concentration results for our error bounds implying that a randomly selected Gaussian matrix will suffice with high probability. For our necessity proofs, we rely on results from channel coding and rate-distortion theory.
Adsorbent Materials for Carbon Dioxide Capture from Large Anthropogenic Point Sources

Since the time of the industrial revolution, the atmospheric CO(2) concentration has risen by nearly 35 % to its current level of 383 ppm. The increased carbon dioxide concentration in the atmosphere has been suggested to be a leading contributor to global climate change. To slow the increase, reductions in anthropogenic CO(2) emissions are necessary. Large emission point sources, such as fossil-fuel-based power generation facilities, are the first targets for these reductions. A benchmark, mature technology for the separation of dilute CO(2) from gas streams is via absorption with aqueous amines. However, the use of solid adsorbents is now being widely considered as an alternative, potentially less-energy-intensive separation technology. This Review describes the CO(2) adsorption behavior of several different classes of solid carbon dioxide adsorbents, including zeolites, activated carbons, calcium oxides, hydrotalcites, organic-inorganic hybrids, and metal-organic frameworks. These adsorbents are evaluated in terms of their equilibrium CO(2) capacities as well as other important parameters such as adsorption-desorption kinetics, operating windows, stability, and regenerability. The scope of currently available CO(2) adsorbents and their critical properties that will ultimately affect their incorporation into large-scale separation processes is presented.