cssi/SciSciGPT-SciSciNet huggingface dataset:
Evidence for coupling and decoupling of parts of macromolecules by temperature-modulated calorimetry†‡

Equilibrium crystals of linear macromolecules have an extended-chain macroconformation. They can melt at the equilibrium melting temperature, whereas crystallization needs considerable supercooling, even in the presence of crystal nuclei, making the overall phase transition irreversible. The same molecules with a metastable, chain-folded macroconformation may have a large amount of specific reversibility, that is, a fraction of the same polymer molecule that melts irreversibly may also show decoupled, reversible melting. The overall metastable, nanophase structure of such semicrystalline polymers may thus support local equilibria. The tool for the quantitative analysis is quasi-isothermal temperature-modulated calorimetry that can separate reversible from irreversible processes. A major review of the study of crystals of more than 20 polymers has been published. On the basis of this extensive body of information, a first discussion of decoupling of parts of macromolecules is attempted and linked to previous studies of phase equilibria. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1275–1288, 2004
The Geodesic Problem in Quasimetric Spaces

In this article, we study the geodesic problem in a generalized metric space, in which the distance function satisfies a relaxed triangle inequality d(x,y)≤σ(d(x,z)+d(z,y)) for some constant σ≥1, rather than the usual triangle inequality. Such a space is called a quasimetric space. We show that many well-known results in metric spaces (e.g. Ascoli-Arzela theorem) still hold in quasimetric spaces. Moreover, we explore conditions under which a quasimetric will induce an intrinsic metric. As an example, we introduce a family of quasimetrics on the space of atomic probability measures. The associated intrinsic metrics induced by these quasimetrics coincide with the d α metric studied early in the study of branching structures arisen in ramified optimal transportation. An optimal transport path between two atomic probability measures typically has a “tree shaped” branching structure. Here, we show that these optimal transport paths turn out to be geodesics in these intrinsic metric spaces.
Circulation and tides in the high atmosphere

Abstract At heights between 40 and 80 kilometers the prevailing wind is zonal, flowing from east to west in summer and in the opposite direction in winter. Winds above 80 kilometers show a prominent meridional component as well as a strong west to east zonal wind. The determination of the wind field at heights about 80 kilometers is hampered by superimposed periodic and irregular oscillations. The gravitational resonance theory for the large-amplitude, semi-diurnal oscillations in the wind field at heights above 80 kilometers is criticised both on observational and theoretical grounds. The gravitational origin for the semidiurnal oscillation is inconsistent with the observed 12-4-hour tide. Possible thermal sources are reviewed. Observations on irregular motion at heights above 80 kilometers are discussed and the problems associated with the transfer of energy from the lower atmosphere into the upper atmosphere are briefly considered.
Forecasting World Natural Gas Supply

World gas supply forecasting has proved difficult because its exploration, transportation, and customer bases are so heavily dependent on fluctuating economic factors. Our recent study showed that the conventional Hubbert model with one complete production cycle is not appropriate for use in forecasting gas production trends for most gas producing countries. This paper presents our forecast for the world's supply of conventional natural gas to the year 2050. We used a multicyclic Hubbert approach to develop 53 country-specific gas supply models that enable production forecasts for virtually all of the world's gas. The multicyclic modeling approach is presented in a convenient form that makes production data exhibiting two or more cycles easier to model. These models were aggregated to the regional level and to the world level. Supply models for some organizations (e.g. OPEC, non-OPEC, OECD) were also developed and analyzed. Our results indicate that the world's supply of natural gas will peak in 2014, followed by an annual depletion rate of 1%/yr. A regional analysis indicates that gas production of some regions will peak soon. North American gas production is currently (1999) at its peak. West European gas production is expected to peak in 2002. The countries of the former Soviet Union and Middle East, which comprise about 60% of world's ultimate recovery of natural gas, will be the main sources of world gas supply in the future.
Collective flow and QCD phase transition

In the first part I discuss the sensitivity of collective matter expansion in ultrarelativistic heavy-ion collisions to the transition between quark and hadronic matter (physics of the softest point of the Equation of State). A kink in the centrality dependence of elliptic flow has been suggested as a signature for the phase transition in hot QCD matter. Indeed, preliminary data of NA49 presented at this conference show first indications for the predicted kink. In the second part I have a look at the present theories of heavy-ion reactions. These remarks may also be seen as a critical comment to B. Mueller’s summary talk (nucl-th/9906029) presented at this conference.
Virtual frog dissection: interactive 3D graphics via the Web

Abstract We have developed a set of techniques for providing interactive 3D graphics via the World Wide Web (WWW) as part of the “Whole Frog” project 1 . We had three goals: 1. 1. to provide K-12 biology students with the ability to explore the anatomy of a frog with a virtual dissection tool; 2. 2. to show the feasibility of interactive visualization over the Web; and 3. 3. to show the possibility for the Web and its associated browsers to be an easily used and powerful front end for high-performance computing resources. We have developed techniques to utilize the Common Gateway Interface 2 (CGI) capability of WWW servers to provide an interactive 3D visualization front end through Web clients. These techniques have been used to make a “Virtual Frog Dissection Kit” 3 . A student using this kit has the ability to view various parts of a frog from many different angles, and with the different anatomical structures visible or invisible. For example, the student can press “form” buttons that indicate that he or she wants to view the frog from above, with the exterior and skeleton removed. An advantage to this technique, as opposed to dissecting a real frog, is that undissection is as easy as dissection. The kit has a forms 4 -based interface. Form submission results in a call to a CGI script, which in turn contacts a continuously running process on a more powerful machine to accomplish the graphics rendering of a large 3D data set representing the frog and its internal organs. The resulting image is converted to Graphics Interchange Format (GIF) encoding. When that process completes generation of the image, it passes the location of the image file and control back to the script which rewrites the image on the client. While this might sound awkward, the overall process is quite similar to how all rendering systems work, with the image being written into a local frame buffer, or sent across the network as an X-window image.
Synthesis and Characterization of the Thiogermanic Acids H4Ge4S10 and H2Ge4S9

The synthesis and structure of the thiogermanic acids H 4 Ge 4 S 1 0 and H 2 Ge 4 S 9 are reported. A novel preparation method consisting of reacting germanium oxide with liquid hydrogen sulfide containing a trace amount of water is used to form Ge 4 S 1 0 4- ions. Evaporating the hydrogen sulfide solution at room temperature leaves an unstable H 4 Ge 4 S 1 0 .xH 2 O product. The stoichiometry and structure of the thermally stable anhydrous phase are dependent on reaction time. An H 4 Ge 4 S 1 0 product with an adamantane-like cage structure is obtained at shorter reaction times. Longer reaction times produce an H 2 Ge 4 S 9 product with a more complex cage unit, a higher symmetry unit cell, and increased thermal stability. Raman, infrared, powder X-ray diffraction, and thermogravimetric data are reported for both structures.
Evidence for a NiI Active Species in the Catalytic Cross-Coupling of Alkyl Electrophiles

Addition of terpyridine to (TMEDA)Ni(CH3)2 results in the high-yield formation of (terpyridyl)NiMe (3). This NiI organometallic complex was found to be capable of transferring its methyl group to iodocyclohexane to produce methylcyclohexane in high yield. Compound 3 can also serve as an initiator for the catalytic cross-coupling of alkyl electrophiles performed under Negishi-like conditions.
An engineer looks at mathematics teaching

In this article, originally presented as an address before the National Council of Teachers of Mathematics, Past President Lee discusses the importance of mathematics courses in our educational programs — for, as he points out, mathematical concepts are essential not only to the work of the scientist and the engineer, but, in fact, to the work of the world.
Initial state propagators

It is possible to define a general initial state for a quantum field by introducinga contribution to the action defined at an initial-time boundary. The propagator for this theory is composed of two parts, one associated with the free propagation of fields and another produced by the operators of this initial action. The derivation of this propagator is shown for the case of a translationally and rotationally invariant initial state. In addition to being able to treat more general states, these techniques can also be applied to effective field theories that start from an initial time. The eigenstates of a theory with interacting heavy and light fields are different from the eigenstates of the theory in the limit where the interactions vanish. Therefore, a product of states of the noninteracting heavy and light theories will usually contain excitations of the heavier state once the interactions are included. Such excitations appear as nonlocal effects in the effective theory, which are suppressed by powers of the mass of the heavy field. By appropriately choosing the initial action, these excitations can be excised from the state leaving just effects that would be produced by a local action of the lighter fields.
ELECTROMAGNETIC PROBES OF DENSE MATTER IN HEAVY-ION COLLISIONS

Abstract Dilepton and photon production in heavy-ion collisions at SPS energies are studied in the relativistic transport model that incorporates self-consistently the change of hadron masses in dense matter. It is found that the dilepton spectra in proton-nucleus reactions can be well described by the conventional mechanism of Dalitz decay and direct vector meson decay. However, to provide a quantitative explanation of the observed dilepton spectra in central heavy-ion collisions requires contributions other than these direct decays and also various medium effects. Introducing a decrease of vector meson masses in hot dense medium, we find that these heavy-ion data can be satisfactorily explained. Furthermore, the single photon spectra in our calculations with either free or in-medium meson masses do not exceed the upper bound deduced from the experiments by the WA80 Collaboration.
Large deviations for the leaves in some random trees

Large deviation principles and related results are given for a class of Markov chains associated to the 'leaves' in random recursive trees and preferential attachment random graphs, as well as the 'cherries' in Yule trees. In particular, the method of proof, combining analytic and Dupuis-Ellis-type path arguments, allows for an explicit computation of the large deviation pressure.
A study of positrons from Soviet nuclear powered satellites as tracers for magnetospheric research

Abstract Two Soviet satellites carrying nuclear reactors operated in circular 790 km orbits (65° inclination) in 1987 and 1988. Positrons generated in the satellites' surfaces by the intense reactor gamma radiation escaped and were trapped for periods of minutes to hours in the geomagnetic field. These positrons have been observed on many occasions by gamma ray sensors on the SMM satellite (in 500 km orbit) which identify the positrons by the 511 keV gamma rays created when they annihilate in the satellite surface. The SMM detector provides a time resolution of 64 milliseconds. It has recorded positron rise-times of less than 0.5 second (corresponding to a satellite travel distance of about 1 positron gyroradius) on many occasions as it encounters the low-L edge of positrons injected by the Soviet satellites as far as half-way around the earth. We are studying the potential of these sharply defined positron shells as magnetospheric tracers and as a means for examining particle diffusion and loss processes.
2-Substituted-1,2,3,4-tetrahydroisoquinolines and chiral 3-carboxyl analogues from N-benzotriazolylmethyl-N-phenethylamines

Abstract N- Benzotriazolylmethyl- N -phenethylamines 5a – 5c and 11a – 11c cyclize in the presence of aluminum chloride to produce 1,2,3,4-tetrahydroisoquinolines 6a – 6c and 12a – 12c (70–89%) via electrophilic attack of a transient iminium cation X on the tethered phenyl ring. The Bt group in 2 - benzotriazolylmethyl-1,2,3,4-tetrahydroisoquinolines 6a – 6b was replaced (i) with hydrogen by sodium borohydride to afford N -methyl-1,2,3,4-tetrahydroisoquinolines 7a – 7b or (ii) by nucleophiles, such as Grignard reagents, a silyl enol ether or triethyl phosphite, to furnish novel N -substituted-1,2,3,4-tetrahydroisoquinolines 13a – 13c , 14 or 15 , respectively. Optically active 3-substituted-1,2,3,4-tetrahydroisoquinolines 12a – 12c were similarly prepared in high yields without racemization.
Notes on Fast Moving Strings

We review the recent work on the mechanics of fast moving strings in anti-de Sitter space times a sphere and discuss the role of conserved charges. An interesting relation between the local conserved charges of rigid solutions was found in the earlier work. We propose a generalization of this relation for arbitrary solutions, not necessarily rigid. We conjecture that an infinite combination of local conserved charges is an action variable generating periodic trajectories in the classical string phase space. It corresponds to the length of the operator on the field theory side.
The Properties of Poor Groups of Galaxies. II. X-Ray and Optical Comparisons

We use ROSAT PSPC data to study the X-ray properties of a sample of 12 poor groups that have extensive membership information. Diffuse X-ray emission is detected in nine of these groups. In all but one of the X-ray-detected groups, the X-ray emission is centered on a luminous elliptical galaxy. Fits to the surface brightness profiles of the X-ray emission suggest the presence of two X-ray components in these groups. The first component is centered on the central elliptical galaxy and is extended on scales of 20-40 h-1 kpc. The location and extent of this component, combined with its X-ray temperature (~0.7- 0.9 keV) and luminosity (~1041-42 h-2 ergs s-1), favor an origin in the interstellar medium of the central galaxy. Alternatively, the central component may be the result of a large-scale cooling flow. The second X-ray component is detected out to a radius of at least ~100-300 h-1 kpc. This component follows the same relationships found among the X-ray temperature (T), X-ray luminosity (LX), and optical velocity dispersion (σr) of rich clusters. This result suggests that the X-ray-detected groups are low-mass versions of clusters and that the extended gas component can properly be called the intragroup medium, by analogy to the intracluster medium in clusters. The failure to detect an intragroup medium in the three groups with very low velocity dispersions is consistent with their predicted X-ray luminosities and temperatures based on the relationships derived for clusters and X-ray-detected groups. The best-fit value of β derived from the σr-T relationship for groups and clusters is ~0.99 ± 0.08, implying that the galaxies and the hot gas trace the same potential with equal energy per unit mass and that the groups are dynamically relaxed. We also find a trend for the position angle of the optical light in the central elliptical galaxy to align with the position angle of the large-scale X-ray emission. This trend is consistent with that found for some rich clusters containing cD galaxies. The alignment of the central galaxy with the extended X-ray emission suggests that the formation and/or evolution of the central galaxy is linked to the shape of the global group potential. One possible scenario is that the central galaxy formed via galaxy-galaxy mergers early in the lifetime of the group and has not been subject to significant dynamical evolution recently.
Urban sensing: out of the woods

Embedded networked sensing, having successfully shifted from the lab to the environment, is primed for a more contentious move to the city to where citizens will likely be the target of data collection. This transition will warrant careful study and touch on issues that go far beyond the scientific realm.
Troubleshooting a molecular motor: a remarkably stable N-acyl pyridinium salt

Abstract With the objective of establishing why reaction of the proposed molecular motors 7 and 22 with carbonyldiimidazole and phosgene does not result in unidirectional rotation, N-ethyl-2-[4-(N,N-dimethylamino)-2-pyridinyl]benzenamine [28, 2-(2-(ethylamino)phenyl)DMAP] was examined as a model substrate. The synthesis of 28 is described. Compound 28 was found to react with phosgene to give the unexpectedly stable N-acyl pyridinium salt 30. The latter (30) is so stable that it is effectively inert to reaction with methanol. At room temperature the two methyls in the Me2N-group of 30 are nonequivalent (NMR) and the barrier to rotation around the Me2N–pyridinium bond is 18.5 kcal/mol. To the authors' knowledge, that is the first quantitative determination of the barrier to rotation around the bond between a 4-(N,N-dimethylamino) group and an N-acyl pyridinium unit. The implications of the findings regarding 30 as to troubleshooting the proposed molecular motor 7, and possible strategies to follow, are discussed.
The impact of ethanol production on US and regional gasoline markets

Abstract This study quantifies the impact of increasing ethanol production on wholesale/retail gasoline prices employing pooled regional time-series data from January 1995 to March 2008. We find that the growth in ethanol production kept wholesale gasoline prices $0.14/gallon lower than would otherwise have been the case. The negative impact of ethanol on retail gasoline prices is found to vary considerably across regions. The Midwest region has the biggest impact at $0.28/gallon, while the Rocky Mountain region had the smallest impact at $0.07/gallon. The results also indicate that the ethanol-induced reduction in gasoline prices comes at the expense of refiners’ profits. We find a net welfare loss of $0.5 billion from the ethanol support policies in multiple markets.
Debris Disks Around White Dwarfs: The DAZ Connection

We present near-infrared spectroscopic observations of 20 previously known DAZ white dwarfs obtained at the NASA Infrared Telescope Facility. Two of these white dwarfs (G29-38 and GD 362) are known to display significant K-band excesses due to circumstellar debris disks. Here we report the discovery of excess K-band radiation from another DAZ white dwarf, WD 0408-041 (GD 56). Using spectroscopic observations, we show that the excess radiation cannot be explained by a stellar or substellar companion, and is likely to be caused by a warm debris disk. Our observations strengthen the connection between the debris disk phenomena and the observed metal abundances in cool DAZ white dwarfs. However, we do not find any excess infrared emission from the most metal rich DAZs with Teff = 16,000-20,000 K. This suggests that the metal abundances in warmer DAZ white dwarfs may require another explanation.
Mach Wave Radiation from High-Speed Jets

Extensive experimental evidence is now available to support the observation that there are two components of jet mixing noise. They are the fine-scale turbulence noise and the noise from the large turbulence structures of the jet flow. The large turbulence structure’s noise radiates primarily in directions with a large inlet angle around the downstream axis of the jet. The fine-scale turbulence noise dominates in the sideline and upstream directions. This study investigates the mechanism by which large turbulence structures radiate noise. It is believed that the mechanism is Mach wave radiation. Theoretical model results and physical reasoning are presented to support the Mach wave mechanism. They are further supported by experimental measurements both in the far field and in the near acoustic field. These measurements include peak noise direction, noise-source distribution along the jet column, and near-field pressure-contour pattern. A signature pattern of the near-field pressure contours associated with Mach wave radiation is identified.
MR Imaging of Infectious Processes of the Knee

Infectious processes about the knee can result from the hematogenous spread of infection, spread from a contiguous source, direct implantation of pathogens, and prior surgery. Soft tissues, joints, and bones can be infected by bacteria, fungi, parasites, or viruses. MR imaging is useful in identifying cellulitis, abscess, septic arthritis, and osteomyelitis. The inherent tissue contrast provided by MR imaging allows for the delineation of soft-tissue infection and osteomyelitis. Therefore, MR imaging is a useful tool in evaluating the extent of infection, and in facilitating adequate debridement and drainage. MR imaging is particularly useful in the setting of chronic posttraumatic osteomyelitis and in prior surgical procedures, such as arthroscopy, anterior cruciate ligament reconstruction, and amputation.
Are Silicon Nanoparticles an Interstellar Dust Component

Silicon nanoparticles (SNPs) with oxide coatings have been proposed as the source of the observed "extended red emission" (ERE) from interstellar dust. We calculate the thermal emission expected from such particles, both in a reflection nebula such as NGC 2023 and in the diffuse interstellar medium (ISM). It is shown that Si/SiO2 SNPs (both neutral and charged) would produce a strong emission feature at 20 μm. The observational upper limit on the 20 μm feature in NGC 2023 imposes an upper limit of less than 0.2 parts per million in Si/SiO2 SNPs. The observed ERE intensity from NGC 2023 then gives a lower bound on the product ηPLf0, where ηPL 0.24 for Si/SiO2 SNPs in NGC 2023. Measurement of the R-band extinction toward the ERE-emitting region could strengthen this lower limit. The ERE emissivity of the diffuse interstellar medium appears to require 42% of solar Si abundance in Si/SiO2 SNPs even with ηPLf0 = 1. We predict IR emission spectra and show that DIRBE photometry appears to rule out such high abundances of free-flying SNPs in the diffuse ISM. We conclude that if the ERE is due to SNPs, they must be either in clusters or attached to larger grains.
Adding momentum to D1-D5 system

We construct the first example of asymptotically flat solution which carries three charges (D1, D5 and momentum) and which is completely regular everywhere. The construction utilizes the relation between gravity solutions and spectral flow in the dual CFT. We show that the solution has the right properties to describe one of the microscopic states which are responsible for the entropy of the black hole with three charges.
The importance of cooperative interactions and a solid-state paradigm to proteins: what Peptide chemists can learn from molecular crystals.

Abstract Proteins and peptides in solution or in vivo share properties with both liquids and solids. More often than not, they are studied using the liquid paradigm rather than that of a solid. Studies of molecular crystals illustrate how the use of a solid paradigm may change the way that we consider these important molecules. Cooperative interactions, particularly those involving H‐bonding, play much more important roles in the solid than in the liquid paradigms, as molecular crystals clearly illustrate. Using the solid rather than the liquid paradigm for proteins and peptides includes these cooperative interactions while application of the liquid paradigm tends to ignore or minimize them. Use of the solid paradigm has important implications for basic principles that are often implied about peptide and protein chemistry, such as the importance of entropy in protein folding and the nature of the hydrophobic effect. Understanding the folded states of peptides and proteins (especially α‐helices) often requires the solid paradigm, whereas understanding unfolded states does not. Both theoretical and experimental studies of the energetics of protein and peptide folding require comparison to a suitable standard. Our perspective on these energetics depends on the reasonable choice of reference. The use of multiple reference states, particularly that of component amino acids in the gas phase, is proposed.
Methane Partitioning and Transport in Hydrated Carbon Nanotubes

The well defined shape and size of carbon nanotubes (CNTs) makes them attractive candidates for theoretical and experimental studies of various nanoscopic phenomena such as protection and confinement of molecular species as well as transport of molecules through their interior pores. Here we investigate solute partitioning and transport using molecular dynamics simulations of CNTs in mixtures of hydrophobic solutes and water. The hydrophobic pores of CNTs provide a favorable environment for partitioning of hydrophobic solutes. We find that the transfer of a methane molecule from aqueous solution into the CNT interior is favored by about 16 kJ/mol of free energy. In 50 molecular dynamics simulations, we observe that methane molecules replace water molecules initially inside the nanotubes, and completely fill their interior channels over a nanosecond time scale. Once filled with methane molecules, the nanotubes are able to transport methane from one end to the other through successive methane uptake and rel...
The effect of caffeine ingestion on 8 km run performance in a field setting

Abstract The aim of this study was to assess the effect of caffeine ingestion on 8 km run performance using an ecologically valid test protocol. A randomized double-blind crossover study was conducted involving eight male distance runners. The participants ran an 8 km race 1 h after ingesting a placebo capsule, a caffeine capsule (3 mg · kg−1 body mass) or no supplement. Heart rate was recorded at 5 s intervals throughout the race. Blood lactate concentration and ratings of perceived exertion were recorded after exercise. A repeated-measures analysis of variance (ANOVA) identified a significant treatment effect for 8 km performance time (P < 0.05); caffeine resulted in a mean improvement of 23.8 s (95% confidence interval [CI] = 13.1 to 34.5 s) in 8 km performance time (1.2% improvement, 95% CI = 0.7 to 1.8%). In addition, a two-way (time × condition) repeated-measures ANOVA identified a significantly higher blood lactate concentration 3 min after exercise during the caffeine trial (P < 0.05). We conclude...
A Derivation of the Pole Curve Equations in the Projective Plane

Traditional four-position mechanism synthesis focuses on the poles corresponding to four displacements of a rigid body. From these poles equations for the center-point and circle-point curves are developed. However, if a pole is infinite the associated displacement is a pure translation), the established derivations for the pole curve equation break down. One can eliminate this problem by pressing the pole curve equation in the protective plane, because all points, including points at infinity, have finite homogeneous coordinates. In this paper, the pole curve equation is derived in the protective plane. This protection derivation is an analytic expression of Alt's graphical construction of the pole curve. The pole curve is the intersection of a pair of profective pencils of circles (one pencil for opposite sides of the opposite-pole quadrilateral) which are defined by the homogeneous coordinates of the poles. The resulting equations are applied to several problems in the synthesis of four-bar linkages. In addition the rotation curves, the locus of displacement poles for a four-bar linkage, are computed for linkages with sliding joints
The effect of subpixel clouds on remote sensing

Abstract The effect of subpixel clouds on remote sensing of the surface reflectivity and of the vegetation index was simulated for a thin layer of rectangular clouds. The simulation is for a 4×4 km2 field of view. It was found that a 20% cloudiness can increase the apparent surface reflectance by 0.02 for a model of Stratocumulus and by 0.08 for a fixed cloud reflectance of RC=0.5. For the measured cloudiness probability distributions it was found that the cloud effect can be eliminated if the best remote sensing case out of about 4 independent cases is chosen. This corresponds to 8–16 observation days.
Geological evidence for a migrating Tharsis plume on early Mars

Abstract The Tharsis bulge is the largest magmatic/volcanic center on Mars and in the solar system, having a volume of ~ 3 × 10 8 km 3 , with the majority of its mass emplaced more than 3.7 billion years ago. The igneous history of Tharsis has been implicated in the generation of an atmosphere and hydrosphere capable of clement conditions on early Mars. It has been proposed that an early plume migration from the southern highlands of Mars relative to a one-plate lithosphere led to the development of the Tharsis bulge in its current location along the Martian crustal dichotomy. We used geologic mapping, crustal magnetic data, crater age-dating and crater morphometry to detail a previously-unidentified path of putative plume migration. Our results indicate that extensive volcanic resurfacing occurred from a location near the present south pole to the equator around 3.8 billion years ago, obliterating older cratered terrains. The resurfacing path is manifest as smooth volcanic plains embaying ancient massifs and infilling large impact craters as well as a lack of a magnetic signature in this portion of the crust. Our results have significant ramifications for mantle dynamics and the early geologic history of Mars.
Recurrent neural networks for synthesizing linear control systems via pole placement

Recurrent neural networks are proposed to synthesize linear control systems through pole placement (assignment). The proposed neural network approach uses two coupled recurrent neural networks to compute a feedback gain matrix. Each neural network consists of two bidirectionally connected layers and each layer consists of an array of neurons. The proposed recurrent neural networks are shown to be capable of synthesizing linear control systems in real time. The operating characteristics of the recurrent neural networks and closed-loop systems are demonstrated by use of three illustrative examples.
Black hole entropy from horizon conformal field theory

Abstract String theory and “quantum geometry” have recently offered independent statistical mechanical explanations of black hole thermodynamics. But these successes raise a new problem: why should models with such different microscopic degrees of freedom yield identical results? I propose that the asymptotic behavior of the density of states at a black hole horizon may be determined by an underlying symmetry inherited from classical general relativity, independent of the details of quantum gravity. I offer evidence that a two-dimensional conformal symmetry at the horizon, with a classical central extension, may provide the needed behavior.
Development and application of a ReaxFF reactive force field for hydrogen combustion.

To investigate the reaction kinetics of hydrogen combustion at high-pressure and high-temperature conditions, we constructed a ReaxFF training set to include reaction energies and transition states relevant to hydrogen combustion and optimized the ReaxFF force field parameters against training data obtained from quantum mechanical calculations and experimental values. The optimized ReaxFF potential functions were used to run NVT MD (i.e., molecular dynamics simulation with fixed number of atoms, volume, and temperature) simulations for various H2/O2 mixtures. We observed that the hydroperoxyl (HO2) radical plays a key role in the reaction kinetics at our input conditions (T ≥ 3000 K, P > 400 atm). The reaction mechanism observed is in good agreement with predictions of existing continuum-scale kinetic models for hydrogen combustion, and a transition of reaction mechanism is observed as we move from high pressure, low temperature to low pressure, high temperature. Since ReaxFF derives its parameters from q...
MODULI SPACE FOR CONIFOLDS AS INTERSECTION OF ORTHOGONAL D6 BRANES

Abstract We show that a system of parallel D3 branes near a conifold singularity can be mapped onto an intersecting configuration of orthogonal branes in type IIA string theory. Using this brane configuration, we analyze the Higgs moduli space of the associated field theory. The dimension of the Higgs moduli space is computed from a geometrical analysis of the conifold singularity. Our results provide evidence for an extended s-rule. In addition, a discrepancy between the prediction of the brane configuration and the result obtained from a geometrical analysis is noted. This discrepancy can be traced back to worldsheet instanton effects.
Radio triggered star formation in cooling flows

The giant galaxies located at the centers of cluster cooling flows are frequently sites of vigorous star formation. In some instances, star formation appears to have been triggered by the galaxy’s radio source. The colors and spectral indices of the young populations are generally consistent with short duration bursts or continuous star formation for durations ≪1 Gyr, which is less than the presumed ages of cooling flows. The star formation properties are inconsistent with fueling by a continuously accreting cooling flow, although the prevalence of star formation is consistent with repeated bursts and periodic refueling. Star formation may be fueled, in some cases, by cold material stripped from neighboring cluster galaxies.
Relative price variability: Evidence from supply and demand events

Abstract Previous studies of relative price variability assume that all supply changes are unanticipated or that supply elasticities are equal across markets. In this paper, we extend these models by relaxing these restrictive assumptions. Our resulting theoretical expression for relative price dispersion reveals an independent role for unanticipated and anticipated supply events. Subjecting our model to empirical testing, we find that this dichotomy of supply shocks is not rejected by the data for the period 1970–1981.
Global‐scale P wave tomography optimized for prediction of teleseismic and regional travel times for Middle East events: 2. Tomographic inversion

[1] We construct a model of three-dimensional P wave velocity structure in the crust and mantle that is global in extent, but with detailed upper mantle heterogeneities throughout the greater Middle East region. Fully three-dimensional ray tracing is employed to achieve accurate travel time predictions of P and Pn arrivals, requiring the characterization of irregular and discontinuous boundaries. Therefore, we explicitly represent undulating seismic discontinuities in the crust and upper mantle within a spherical tessellation modeling framework. The tessellation-based model architecture is hierarchical in that fine node sampling is achieved by recursively subdividing a base level tessellation. Determining the required node spacing to effectively model a given set of data is problematic, given the uneven sampling of seismic data and the differing wavelengths of actual seismic heterogeneity. To address this problem, we have developed an inversion process called Progressive Multilevel Tessellation Inversion (PMTI) that exploits the hierarchical nature of the tessellation-based design and allows the data to determine the level of model complexity. PMTI serves as an alternative to existing multiresolution approaches and robustly images regional trends while allowing localized details to emerge where resolution is sufficient. To demonstrate our complete modeling concept, we construct a velocity model based on teleseismic P travel time data for global events and regional Pn travel time data for events occurring throughout the Middle East. Input data are a product of the statistical procedure called Bayesloc that simultaneously models all components of a multievent system including event locations, origin times, and arrival times (described in the Myers et al. (2011) companion paper). The initial tomographic image provides a new glimpse of the complex upper mantle velocity anomalies associated with the convergence of the Arabian and Indian plates with Eurasia. More important for event monitoring, the model accurately predicts both teleseismic and regional travel times for events occurring within the Middle East region.
Direct measurements of helium and hydrogen ion concentration and total ion density to an altitude of 940 kilometers.

Measurement of ion concentration and total ion density in exosphere using mass spectrometer and electrostatic probe
Routes to large amplitude motions of mooring systems due to slowly varying drift

The effect of second-order slowly varying wave drift (SVWD) forces on the horizontal plane motions of moored floating vessels has been studied for nearly 30 years. Large amplitude oscillations of moored vessels have been observed in the field or predicted numerically. Often, those have been incorrectly attributed to resonance or time-varying excitation from current/wind. In previous work, the authors have shown that resonance is only one of numerous interaction phenomena, and that large amplitude oscillations can be induced by SVWD forces or even time-independent excitation. Currently, there is no mathematical theory to study stability and bifurcations of mooring systems subjected to nonautonomous spectral excitation. Thus, in this paper, bifurcation boundaries are approximated by analyzing simulation data from a grid of points in the design space. These boundaries are plotted in the catastrophe sets of the corresponding autonomous system, for which a design methodology has been developed at the University of Michigan since 1985. This approach has revealed a wealth of dynamics phenomena, characterized by static (pitchfork) and dynamic (Hopf) bifurcations. Interaction of SVWD forces with the Hopf bifurcations may result in motions with amplitudes 2-3 orders of magnitude larger than those due to resonance. On the other hand, in other cases the SVWD/Hopf interaction may reduce or even eliminate limit cycles.
The asymmetric traveling salesman problem on graphs with bounded genus

We give a constant factor approximation algorithm for the asymmetric traveling salesman problem when the support graph of the solution of the Held-Karp linear programming relaxation has bounded orientable genus.
Betti strata of height two ideals

Abstract Let R = k [ x , y ] denote the polynomial ring in two variables over an infinite field k. We study the Betti strata of the family G ( H ) parametrizing graded Artinian quotients of R = k [ x , y ] having given Hilbert function H. The Betti stratum G β ( H ) parametrizes all quotients A of having the graded Betti numbers determined by H and the minimal relation degrees β, with β i = dim k Tor 1 R ( I , k ) i . We recover that the Betti strata are irreducible, and we calculate their codimension in the family G ( H ) . Theorem The codimension of G β ( H ) in G ( H ) satisfies, letting ν i = # { generators of degree i } , and β i = # { relations of degree i } , cod G β ( H ) = ∑ i > μ ( β i ) ( ν i ) . Here μ = min { i | H i i + 1 } , the initial degree of the ideals. When k is algebraically closed, we also show that the closure of a Betti stratum is the union of more special strata, and is Cohen–Macaulay (Theorem 2.18). Our method is to identify G β ( H ) as a product of determinantal varieties. Ours is a more direct argument than that of [A. Iarrobino, V. Kanev, Power Sums, Gorenstein Algebras, and Determinantal Loci, Lecture Notes in Math., vol. 1721, Springer, Heidelberg, 1999, 345+xxvii pp., Theorem 5.63], which obtains the codimension of Betti substrata of a postulation stratum for punctual subschemes of P 2 ; there we relied on a result of M. Boij determining the codimension of Betti strata of height three Gorenstein algebras [M. Boij, Betti number strata of the space of codimension three Gorenstein Artin algebras, preprint, 2001]. Key tools throughout include properties of an invariant τ ( V ) , the number of generators of the ancestor ideal V ¯ ⊂ R , and previous results concerning the projective variety G ( H ) in [A. Iarrobino, Punctual Hilbert schemes, Mem. Amer. Math. Soc. 10 (188) (1977)]. We adapt a method of M. Boij that reduces the calculation of the codimension of the Betti strata to showing that the most special stratum has the right codimension. As applications we determine which Hilbert functions are possible for Artinian quotients of R, given the socle type (Theorem 3.2), and we also determine the Hilbert function of the intersection of t general enough level ideals in R, each having a specified Hilbert function (Theorem 3.6).
Simplified Methods of Predicting Aircraft Rolling Moments Due to Vortex Encounters

It is not necessary to use time-consuming lifting surface theories for the purpose of calculating global forces and moments during wake vortex encounters. This paper presents computational methods that are currently used to quickly and accurately predict these rolling moments of an aircraft encountering a wake vortex. Appropriate modifications to strip theory are developed that account for the effects of finite wingspan. The paper shows that, in the case of an elliptic wing, the aspect ratio correction to the lift curve slope should be based on the semispan and a recipricol theorem is used to relate the rolling moment on a wing in a downwash field to that on a wing in steady rolling motion. The paper also presents calculations for a wing encountering a vortex with a Betz velocity distribution.
Pull-based broadcasting with timing constraints

The rapid growth in wireless and mobile computing has resulted in an increase in applications that would benefit from a broadcast system that considers timing constraints. Previously proposed scheduling algorithms for broadcast systems aim to minimize the mean access time, while our goal in this paper is to identify scheduling algorithms for broadcast systems that ensure requests meet their deadlines. We consider a pull-based approach in which users send explicit requests for data to a server. There are several well-known scheduling algorithms for real-time systems in non-mobile environments, and previous work in real-time mobile systems has utilized these scheduling algorithms to minimize missed deadlines. However, we demonstrate that traditional real-time algorithms do not always perform the best in a mobile environment and may perform worse than some non-real-time strategies. In this paper, we present a model of a pull-based real-time broadcast system and an analysis of the system as a Markov decision ...
Trajectory Options to Pluto via Gravity Assists from Venus, Mars, and Jupiter

Analytic and numeric techniques are used to assess trajectory options for the Pluto Express sciencecraft for a launch early in the next decade. The constraints placed on the Pluto Express trajectory for this study are severe—total  ight time to Pluto of 12 years or less using a Delta-class launch vehicle. In addition, no  ybys of Earth are permitted. Suitable trajectories are found with launch windows before, near, and after the date of the baseline launch. All of these trajectories take advantage of a gravity assist with Jupiter, and all use two or three gravity assists with Venus before arriving at Jupiter. In two cases, a Mars gravity assist is used in conjunction with three Venus gravity assists. Several asteroid  yby opportunities are presented for the baseline mission and for a backup trajectory, which launch in March 2001 and July 2002, respectively. For example, a  yby of the asteroid Seraphina (which has a radius of 32 km) can be accommodated in the baseline mission for an additional deterministic delta-velocity of 0.12 km/s, well within the capability of the system.
Mesoporous vanadium nitride as a high performance catalyst support for formic acid electrooxidation.

Mesoporous vanadium nitride (VN) with high surface area and good electrical conductivity was prepared by a solid–solid phase separation method from a Zn containing vanadium oxide, Zn3V2O8. The VN supported Pd catalyst exhibited significant catalytic activity for formic acid oxidation.
EuSnP: a novel antiferromagnet with two-dimensional, corrugated Sn sheets

Abstract Large single crystals of EuSnP were grown from a tin flux. The crystal structure of EuSnP is the NbCrN structure type. The new compound crystallizes in the tetragonal system, space group P4/nmm, with the lattice constants a=4.2783(6) A and c=8.762(2) A, at T=130 K (Z=2, R1=0.0382, wR2=0.1002). Temperature-dependent magnetic susceptibility measurements on single crystals indicate that EuSnP is an antiferromagnet with a Neel temperature of 21 K. The high temperature paramagnetic data can be fit to a Curie–Weiss law and are consistent with the assignment of a 2+ valence to the Eu ions, seven unpaired electrons. The magnetic susceptibility below the Neel temperature is anisotropic, showing a metamagnetic transition when the field is applied perpendicular to the crystallographic c axis. A spin-reorientation occurs below the Neel temperature with an applied critical field, Hc=1.5 Tesla at 2 K. Temperature dependent resistivity indicates metallic behavior with a negative magnetoresistive transition at the magnetic ordering temperature. This transition is suppressed with magnetic field.
Comprehensive definitions of breakdown points for independent and dependent observations

Summary. We provide a new definition of breakdown in finite samples, with an extension to asymptotic breakdown. Previous definitions centre on defining a critical region for either the parameter or the objective function. If for a particular outlier configuration the critical region is entered, breakdown is said to occur. In contrast with the traditional approach, we leave the definition of the critical region implicit. Our proposal encompasses previous definitions of breakdown in linear and non-linear regression settings. In some cases, it leads to a different and more intuitive notion of breakdown than other procedures that are available. An important advantage of our new definition is that it also applies to models for dependent observations where current definitions of breakdown typically fail. We illustrate our suggestion by using examples from linear and non-linear regression, and time series.
A Proposed Continuing Education Program for the IEEE Nuclear Science Group

The subject of Continuing Professional Education has received much attention recently, largely because of the current crisis in engineering unemployment. IEEE local and national management, in response to IEEE member interest, is searching for methods of implementing meaningful continuing education programs in a variety of practical situations. This paper attempts to identify some of the basic problems of engineering obsolescence, and to visualize the role of continuing engineering education as a countermeasure. It is suggested that IEEE members and local chapters themselves have an important role to fill in continuing education. A particular proposal for a program for Nuclear Science is described.