cssi/SciSciGPT-SciSciNet huggingface dataset:
Quasi-Maximum Likelihood Estimation of GARCH Models With Heavy-Tailed Likelihoods

The non-Gaussian maximum likelihood estimator is frequently used in GARCH models with the intention of capturing heavy-tailed returns. However, unless the parametric likelihood family contains the true likelihood, the estimator is inconsistent due to density misspecification. To correct this bias, we identify an unknown scale parameter ηf that is critical to the identification for consistency and propose a three-step quasi-maximum likelihood procedure with non-Gaussian likelihood functions. This novel approach is consistent and asymptotically normal under weak moment conditions. Moreover, it achieves better efficiency than the Gaussian alternative, particularly when the innovation error has heavy tails. We also summarize and compare the values of the scale parameter and the asymptotic efficiency for estimators based on different choices of likelihood functions with an increasing level of heaviness in the innovation tails. Numerical studies confirm the advantages of the proposed approach.
Predictive delay metric for OLSR using neural networks

In this paper, we propose an adaptability enhancement mechanism to be integrated with OLSR, and potentially any Mobile Ad Hoc Network (MANET) proactive routing protocol. The key of this mechanism is prediction and evaluation of the mean queuing delay as a routing metric. Neural network methods are used to predict delays. We investigated the pros and cons of using two types of neural networks, namely Multi-Layer Perceptron (MLP) and Radial Basis Function (RBF), in predicting nonstationary time series (e.g., mean queuing delay time series). We present TierUp -- our novel node-state routing table calculation algorithm, which is developed for the integration of delay prediction and OLSR. We name the extended version of OLSR as OLSR_NN. We show through ns2 simulation that compared to OLSR, OLSR_NN is able to increase data packet delivery ratio and reduce average end-to-end delay in scenarios with complex traffic patterns and various node mobility. Our simulation also shows the advantage of using neural network for delay prediction compared to moving average and exponential smoothing. The enhanced adaptability of OLSR_NN is further verified by the more balanced traffic observed in our simulation.
Transition metal photoredox catalysis of radical thiol-ene reactions.

We describe the anti-Markovnikov hydrothiolation of olefins using visible-light-absorbing transition metal photocatalysts. The key thiyl radical intermediates are generated upon quenching of photoexcited Ru*(bpz)32 with a variety of thiols. The adducts of a wide variety of olefins and thiols are formed in excellent yield (73–99%).
Taveuniamides: new chlorinated toxins from a mixed assemblage of marine cyanobacteria

Abstract Brine shrimp toxicity guided fractionation of the extracts from two mixed Fijian collections of the cyanobacteria Lyngbya majuscula and Schizothrix sp. led to the isolation of eleven novel chlorinated lipids. All of these metabolites show an intriguing constellation of unsaturation (olefinic and acetylenic bonds) and chlorination at the two termini of a 15-carbon chain. The central carbon atom of the chain (C-8) is substituted in each case with an N-acetate function. Taveuniamides A–E have an adjacent carbomethoxy group at C-9 to form a protected β-amino acid while taveuniamides F–K have a methylene group at this position. A standard assortment of 2D NMR techniques in concert with mass spectrometry and other analytical techniques were used to define the structures of these novel metabolites. Taveuniamides F, G and K were the most potent brine shrimp toxins with LD50s between 1.7–1.9 μg/mL.
Diffuse Galactic Soft Gamma-Ray Emission

The Galactic diffuse soft gamma-ray (30-800 keV) emission has been measured from the Galactic center by the High Resolution Gamma-Ray and Hard X-Ray Spectrometer balloon-borne germanium instrument to determine the spectral characteristics and origin of the emission. The resulting Galactic diffuse continuum is found to agree well with a single power law (plus positronium) over the entire energy range, consistent with RXTE and COMPTEL/Compton Gamma Ray Observatory observations at lower and higher energies, respectively. We find no evidence of spectral steepening below 200 keV, as has been reported in previous observations. The spatial distribution along the Galactic ridge is found to be nearly flat, with upper limits set on the longitudinal gradient and with no evidence of an edge in the observed region. The soft gamma-ray diffuse spectrum is well modeled by inverse Compton scattering of interstellar radiation off of cosmic-ray electrons, minimizing the need to invoke inefficient nonthermal bremsstrahlung emission. The resulting power requirement is well within that provided by Galactic supernovae. We speculate that the measured spectrum provides the first direct constraints on the cosmic-ray electron spectrum below 300 MeV.
Computing L-functions with large conductor

An algorithm is given to efficiently compute L-functions with large conductor in a restricted range of the critical strip. Examples are included for about 24000 dihedral Galois representations with conductor near 10 7 . The data shows good agreement with a symplectic random matrix model.
Determinants of Mortgage Interest Rates: Treasuries versus Swaps

The 10-year Treasury rate has long been considered the primary determinant of 30-year mortgage interest rates. The contemporaneous 10-year LIBOR swap rate is shown to better explain the contemporaneous mortgage rate than the contemporaneous 10-year Treasury rate. This result appears to hold over most of the sample period, 1987–2011, using a variety of statistical tests. Given the long-held belief that the mortgage rate is best explained by the 10-year Treasury rate, this paper makes an important contribution to the literature by demonstrating that the swap rate is superior.
Disentanglement and decoherence from classical non-Markovian noise: random telegraph noise

We calculate the two-qubit disentanglement due to classical random telegraph noise using the quasi-Hamiltonian method. This allows us to obtain analytical results even for strong coupling and mixed noise, important when the qubits have tunable working point. We determine when entanglement sudden death and revival occur as functions of qubit working point, noise coupling strength and initial state entanglement. For extended Werner states, we show that the concurrence is related to the difference of two functions: one is related to dephasing and the other longitudinal relaxation. A physical interpretation based on the generalized Bloch vector is given: revival only occurs for strongly-coupled noise and comes from the angular motion of the vector.
Further studies on beam breakup growth reduction by cavity cross-couplings in recirculating accelerators: effects of long pulse length and multiturn recirculation

Abstract Cavity cross-coupling was recently found to reduce beam breakup (BBU) growth in a recirculating accelerator known as the Spiral Line Induction Accelerator (SLIA). Here, we extend the analyses in two respects: long beam pulse lengths and a SLIA upgrade geometry which accelerates a 10 kA, 35 ns beam to 25 MeV via a 70 cavity, 7 turn recirculation. We found that when the beam pulse length τ exceeds the beam's transit time τ′ between cross-coupled cavities. BBU growth may be worsened as a result of the cross-couplings among cavities. This situation is not unlike other long pulse recirculating accelerators where beam recirculation leads to beam breakup of a regenative type. Thus, the advantage of BBU reduction by cavity cross-coupling is restricted primarily to beams with τ For the 70 gap, 7 turn SLIA upgrade, we found that cavity cross-coupling may reduce BBU growth up to factors of a thousand when the quality factor Q of the deflecting modes are relatively high (like 100). In these high Q cases, the amount of growth reduction depends on the arrangement and sequence of beam recirculation. For Q ⪅20, BBU growth reduction by factors of hundreds is observed, but this reduction is insensitive to the sequence of beam recirculation. The above conclusions were based on simple models of cavity coupling that have been used in conventional microwave literature. Not addressed is the detail design consideration that leads to the desired degree of cavity coupling.
Direct detection and drug-resistance profiling of bacteremias using inertial microfluidics

Detection of bacteria in bloodstream infections and their antibiotic susceptibility patterns is critical to guide therapeutic decision-making for optimal patient care. Current culture-based assays are too slow (>48 h), leading to excessive up-front use of broad-spectrum antibiotics and/or incorrect antibiotic choices due to resistant bacteria, each with deleterious consequences for patient care and public health. To approach this problem, we describe a method to rapidly isolate bacteria from whole blood using inertial microfluidics and directly determine pathogen identity and antibiotic susceptibility with hybridization-based RNA detection. Using the principle of Dean flow fractionation, bacteria are separated from host blood cells in a label-free separation method with efficient recovery of even low abundance bacteria. Ribosomal RNA detection can then be applied for direct identification of low abundance pathogens (~100 per mL) from blood without culturing or enzymatic amplification. Messenger RNA detection of antibiotic-responsive transcripts after brief drug exposure permits rapid susceptibility determination from bacteria with minimal culturing (~10(5) per mL). This unique coupling of microfluidic cell separation with RNA-based molecular detection techniques represents significant progress towards faster diagnostics (~8 hours) to guide antibiotic therapy.
Atomic Layer Deposition of In2O3 Using Cyclopentadienyl Indium: A New Synthetic Route to Transparent Conducting Oxide Films

Indium oxide (In2O3) forms the basis for an important class of transparent conducting oxides that see wide use in optoelectronic devices, flat-panel displays, and photovoltaics. Here we present a new method for depositing In2O3 thin films by atomic layer deposition (ALD) using alternating exposures to cyclopentadienyl indium and ozone. Using a precursor vaporization temperature of 40 °C and deposition temperatures of 200−450 °C, we measure growth rates of 1.3−2.0 A/cycle. A significant advantage of this synthesis route over previous techniques is the ability to conformally coat porous materials such as anodic aluminum oxide membranes. The deposited films are nanocrystalline, cubic phase In2O3 and are highly transparent and conducting. In situ quadrupole mass spectrometry and quartz crystal microbalance measurements elucidate the details of the In2O3 growth mechanism.
Successive refinement for the Wyner-Ziv problem and layered code design

We examine successive refinement for the Wyner-Ziv problem described in a recent paper by Steinberg and Merhav, where the authors showed that if the side information for all stages is identical, then the jointly Gaussian source with squared error distortion measure is successively refinable. We first extend this result to the case where the difference between the source and the side information is Gaussian and independent of the side information. As a byproduct, we give an alternative proof that the Wyner-Ziv problem for these sources has no rate loss-a result that was recently shown by Pradhan et al. through invoking the duality between the Gaussian Wyner-Ziv problem and the Costa problem. We then perform layered Wyner-Ziv code design for this general type of source based on nested scalar quantization, bit-plane coding, and low-density parity check (LDPC) code-based Slepian-Wolf coding (source coding with side information). We show that density evolution can be used to analyze the Slepian-Wolf code performance, provided that certain symmetry conditions, which have been dubbed dual symmetry, are satisfied by the hypothetical channel between the source and the side information. We also show that the dual symmetry condition is indeed satisfied by the hypothetical channel in our Slepian-Wolf coding setup. This justifies the use of density evolution in our LDPC code-based Slepian-Wolf code design for Wyner-Ziv coding. For the jointly Gaussian source, our layered coder performs 1.29 to 3.45 dB from the Wyner-Ziv bound for rates ranging from 0.47 to 4.68 bits per sample. When the side information is Laplacian and the source equals the side information plus an independent Gaussian noise term, our layered coder performs 1.33 to 3.90 dB from the Wyner-Ziv bound for rates ranging from 0.48 to 4.64 bits per sample.
New Rotation Periods in the Pleiades: Interpreting Activity Indicators

We present results of photometric monitoring campaigns of G, K, and M dwarfs in the Pleiades carried out in 1994-1996. We have determined rotation periods for 18 stars in this cluster. In this paper we examine the validity of using observables such as X-ray activity and the amplitude of photometric variations as indicators of angular momentum loss. We report the discovery of cool, slow rotators with high amplitudes of variation. This contradicts previous conclusions about the use of amplitudes as an alternate diagnostic of the saturation of angular momentum loss. We show that the X-ray data can be used as observational indicators of mass-dependent saturation in the angular momentum loss proposed on theoretical grounds.
Assessing psychological well-being: self-report instruments for the NIH Toolbox.

Objective Psychological well-being (PWB) has a significant relationship with physical and mental health. As a part of the NIH Toolbox for the Assessment of Neurological and Behavioral Function, we developed self-report item banks and short forms to assess PWB.
The Rise of Litigation in Human Subjects Research

Owing to widespread public concern about the adequacy of protections for human research subjects and recent instances of serious injury to subjects at several major research institutions, lawsuits against investigators, institutional review boards, and academic institutions are becoming increasingly common. Several claim-promoting conditions are ripe to promote the further growth of this litigation and raise the stakes for research institutions. While this litigation may serve a valuable compensation function for injured subjects, it will also have profound effects on institutional review boards, leading to a more legalistic, mechanistic approach to ethical review that does not further the interests of human subjects or scientific progress.
Categorical color mapping for gamut mapping: II. Using block average image

Several improvements of categorical color mapping are introduced in this paper. The categorical color mapping decides the best mapping point to keep categorical relationship between a source device and a destination device. The first improvement is that the Simplex iteration technique was implemented to the categorical color mapping in order to search the best mapping point in the destination space. The second improvement is that the categorical color mapping is designed in the CIELAB space. A block average image was used as color patches for the categorical color naming to developed a new gamut mapping strategy that challenges to carry on an image gamut mapping instead of a device gamut mapping. The above two improvements and the new trial are introduced for gamut mapping of a CRT to a printer.
Transcoding characteristics of Web images

Transcoding is a technique employed by network proxies to dynamically customize multimedia objects for prevailing network conditions and individual client characteristics. Transcoding can be performed along a number of different axes and the specific transcoding technique used depends on the type of multimedia object. Our goal in this paper is to understand the nature of typical Internet images and their transcoding characteristics. We focus our attention on transcodings intended to customize an image for file size savings. Our results allow the developers of a transcoding proxy server to choose the appropriate transcoding techniques for the important classes of Internet images. We analyze the characteristics of images available on the Web through a representative trace. We show that most GIF images accessed on the Internet are small; about 80% of the GIF images are smaller than 6 KBs. JPEG images are larger than GIF images; about 40% of the JPEG images are larger than 6 KBs. We also establish the characteristics of popular image transcoding operations. We show that for JPEG images, the JPEG compression metric and a transcoding that reduces the spatial geometry are productive transcoding operations (saves at least 50% of the file size for 50% of the images). Our systematic study of image characteristics leads to some surprising results. For example, a naive spatial geometry reduction of GIF images by a factor of 2 along each axis actually causes an increase in the file size compared to the original image for 40% of the images. Thus it is important to understand the characteristics of individual images before choosing the proper transcoding operation.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Development of low-cost silicon crystal growth techniques for terrestrial photovoltaic solar energy conversion

Abstract Single crystal silicon solar cells are potential elements of large scale solar energy conversion systems. Current costs of these cells are too high at least in part because current production methods require single crystal wafers obtained by slicing cylindrical single crystal ingots. This paper reviews a U.S. research program aimed at reducing the cost of silicon cells by developing new methods of growing silicon ribbons and sheets from which high efficiency solar cells can be fabricated. The paper also describes novel techniques for lower cost processes for ingot growth and wafer slicing which are included in this research and development program.
Scintillating Optical Fibers for Fine Grained Hodoscopes

Fast detectors with fine spatial resolution will be needed to exploit high event rates at ISABELLE. Scintillating optical fibers for fine grained hodoscopes have been developed by the authors. A commercial manufacturer of optical fibers has drawn and clad PVT scintillator. Detection efficiencies greater than 99% have been achieved for a 1 mm fiber with a PMT over lengths up to 60 cm. Small diameter PMT's and avalanche photodiodes have been tested with the fibers. Further improvements are sought for the fiber and for the APD's sensitivity and coupling efficiency with the fiber.
The acceleration sensitivity of quartz crystal oscillators: a review

A tutorial on navigation, radar, and identification systems is presented. The topics discussed are the consequences of acceleration sensitivity in crystal oscillators on the Allan variance, including the effects of sinusoidal and random vibration, phase noise and integrated phase jitter; the vector nature of quartz resonator sensitivity; the theoretical description of the cause of the acceleration sensitivity of quartz resonators; techniques for the measurement of acceleration sensitivity; and the effect of frequency multiplication on acceleration effect. Various techniques currently being used or developed for reducing the effective acceleration sensitivity are considered. The techniques fall into three general categories: reduction of the acceleration sensitivity of the resonator; passive techniques that use compensating elements in the oscillator feedback loop, e.g. a second resonator or an acceleration sensitivity capacitor; and active acceleration compensation schemes that sense the acceleration and feedback a compensating signal to a tuning network. >
Intellectual property issues and synthetic biology standards

In response to a recent article describing the Synthetic Biology Open Language (SBOL), a mechanism for enabling collaboration among synthetic biology researchers, the authors draw attention to the growing number of intellectual property issues that may affect technical standards for biomedical research. They point out that similar data exchange and interoperability frameworks in fields such as telecommunications and semiconductors have been fraught with patent disputes. They urge the biomedical research community to take heed of the lessons learned from other fields and give due consideration to policies concerning the use and exploitation of patents prior to the development of key interoperability standards.
Dynamical symmetry breaking in a 2D electron gas with a spectral node

We study a disordered 2D electron gas with a spectral node in a vicinity of the node. After identifying the fundamental dynamical symmetries of this system, the spontaneous breaking of the latter by a Grassmann field is studied within a nonlinear sigma model approach. This allows us to reduce the average two-particle Green’s function to a diffusion propagator with a random diffusion coefficient. The latter has non-degenerate saddle points and is treated by the conventional self-consistent Born approximation. This leads to a renormalized chemical potential and a renormalized diffusion coefficient, where the DC conductivity increases linearly with the density of quasiparticles. Applied to the special case of Dirac fermions, our approach provides a comprehensive description of the minimal conductivity at the Dirac node as well as for the V-shape conductivity inside the bands.
Universality Classes in Burgers Turbulence

We establish necessary and sufficient conditions for the shock statistics to approach self-similar form in Burgers turbulence with Levy process initial data. The proof relies upon an elegant closure theorem of Bertoin and Carraro and Duchon that reduces the study of shock statistics to Smoluchowski’s coagulation equation with additive kernel, and upon our previous characterization of the domains of attraction of self-similar solutions for this equation.
An analysis of algorithm-based fault tolerance techniques

Abstract We introduce a unified checksum scheme for the LU decomposition, Gaussian elimination with pairwise pivoting, and the QR decomposition. The purpose is to detect and locate a transient error during a systolic array computation. We show how to represent the error as a rank-one perturbation to the original data, so that we need not worry when the error occurred. Finally, we perform a floating point error analysis to determine the effects of rounding errors on the checksum scheme.
Possible mechanisms of atom transfer in scanning tunneling microscopy

Abstract : Various mechanisms for the sudden transfer of an atom from or to the tip of a scanning tunneling microscope are considered. It is concluded that thermal desorption could be responsible and also that quasi-contact in which the adsorbed atom is in effect touching both surfaces, which would still be separated from each other by 2-4 A can also lead to unactivated transfer via tunneling. For barrier widths as small as 0.5 A, however, tunneling becomes negligible.
Del Pezzo surfaces of degree 1 and Jacobians

We construct absolutely simple jacobians of nonhyperelliptic genus 4 curves, using Del Pezzo surfaces of degree 1.
Solutions to Point-to-Point Control Problems Using Laplace Transform Technique

The governing equations of point-to-point control problems are converted using Laplace transform from a set of linear ordinary differential equations into an equivalent set of linear algebraic equations embedded with the boundary conditions. A simple analytical procedure for evaluating open-loop control input using these algebraic equations is presented. A new concept of feedback control is also developed which involves a recursive evaluation of the open-loop control input.
Measuring small distances in N=2 sigma models

We analyze global aspects of the moduli space of Kahler forms for N=(2,2) con- formal σ-models. Using algebraic methods and mirror symmetry we study extensions of the mathematical notion of length (as specified by a Kahler structure) to conformal field theory and calculate the way in which lengths change as the moduli fields are varied along distinguished paths in the moduli space. We find strong evidence sup- porting the notion that, in the robust setting of quantum Calabi-Yau moduli space, string theory restricts the set of possible Kahler forms by enforcing "minimal length" scales, provided that topology change is properly taken into account. Some lengths, however, may shrink to zero. We also compare stringy geometry to classical general relativity in this context.
A grid-based binary model for coulomb collisions in plasmas

Both binary and grid-based Langevin equations models for Coulomb collisions are used in particle simulation of plasmas. We introduce a variant of the conventional binary collision algorithm for performing Coulomb collisions. In this algorithm particles in a configuration space cell are not paired for collisions. Instead, for every test particle in the cell, a unique field particle is defined by randomly sampling a velocity distribution defined on the grid by accumulating moments of the particle distribution function(s). The test and field particle pair then undergoes a collision using the standard methodology for binary collisions. The performance of the new algorithm is illustrated in example computations and compared to a drag-diffusion Langevin equations algorithm. The grid-based algorithms do not conserve momentum and energy, although with good particle statistics the non-conservation is relatively small. Conservation can be restored after collisions using a shift and scaling of the momenta. The comparative merits of the new algorithm are discussed.
Involutions of Double Affine Hecke Algebras

We prove the existence of an involution on double affine Hecke algebras. This involution plays a central role in the theory of Macdonald polynomials, being responsible for a Fourier type duality and allowing the construction of affine intertwiners.
Mars Free Returns via Gravity Assist from Venus

The safety of the crew is the top priority for human exploration of Mars. If an unexpected emergency occurs, a free-return trajectory can bring the spacecraft back to the Earth without a large trajectory correction maneuver. Such mission-abort scenarios are analyzed by searching for various Mars free-return trajectories, including gravity assist from Venus en route. Thorough investigations of Earth-Mars-Earth, Earth-Mars-Venus-Earth, and Earth-Venus-Mars-Earth sequences are made for the 15-year launch window beginning in 2010. Out of this study, a Mars-Venus free-return abort option, which satisfies the energy and time-of-flight constraints of NASA's Design Reference Mission in January 2014, is discovered. If aerogravity assist (consistent with the capability of the Design Reference Mission vehicle) is employed at Mars, the abort option can be improved over pure gravity assist at Mars in terms of more launch opportunities and lower time of flight. The planned mission date in January 2014 is remarkably fortuitous because the Mars-Venus abort trajectory only repeats every 32 years.
On Green-Energy-Powered Cognitive Radio Networks

A green-energy-powered cognitive radio (CR) network is capable of liberating the wireless access networks from spectral and energy constraints. The limitation of the spectrum is alleviated by exploiting cognitive networking in which wireless nodes sense and utilize the spare spectrum for data communications, whereas dependence on the traditional unsustainable energy is assuaged by adopting energy harvesting through which green energy can be harnessed to power wireless networks. Green-energy-powered CR increases the network availability and thus extends emerging network applications. Designing green CR networks is challenging. It requires not only the optimization of dynamic spectrum access but also the optimal utilization of green energy. This paper surveys the energy-efficient CR techniques and the optimization of green-energy-powered wireless networks. Existing works on energy-aware spectrum sensing, management, and sharing are investigated in detail. The state of the art of the energy-efficient CR-based wireless access network is discussed in various aspects, such as relay and cooperative radio and small cells. Envisioning green energy as an important energy resource in the future, network performance highly depends on the dynamics of the available spectrum and green energy. As compared with the traditional energy source, the arrival rate of green energy, which highly depends on the environment of the energy harvesters, is rather random and intermittent. To optimize and adapt the usage of green energy according to the opportunistic spectrum availability, we discuss research challenges in designing CR networks that are powered by energy harvesters.
Local indirect least squares and average marginal effects in nonseparable structural systems

We study the scope of local indirect least squares (LILS) methods for nonparametrically estimating average marginal effects of an endogenous cause X on a response Y in triangular structural systems that need not exhibit linearity, separability, or monotonicity in scalar unobservables. One main finding is negative: in the fully nonseparable case, LILS methods cannot recover the average marginal effect. LILS methods can nevertheless test the hypothesis of no effect in the general nonseparable case. We provide new nonparametric asymptotic theory, treating both the traditional case of observed exogenous instruments Z and the case where one observes only error-laden proxies for Z.
MR spectroscopic image reconstruction using structural information from anatomical MR images

Spectroscopic imaging (SI) techniques combine the ability of NMR spectroscopy to identify and measure biochemical constituents with the ability of MR imaging to localize NMR signals. The basic imaging technique acquires a set of spatial-frequency-domain samples on a regular grid and takes an inverse Fourier transform of the acquired data to obtain the spatial-domain image. Unfortunately, the time required to gather the data while maintaining an adequate signal-to-noise ratio (SNR) limits the number of spatial-frequency-domain samples that can be acquired. In this paper, we use a high-resolution MR scout image to obtain edge locations in the sample imaged with MRSI. MRI discontinuities represent boundaries between different tissue types, and these discontinuities are likely to appear in the spectroscopic image as well. We propose a new model that encourages edge formation in the MRSI image reconstruction wherever MR image edges occur. A major difference between our model and previous methods is that an edge found in the MR image need not be confirmed by the data; smoothing is reduced across the edge if either the MR image or the MRSI data suggests an edge. Simulations and results on in vivo MRSI data are presented that demonstrate the effectiveness of the method.
Neutron diffraction study of the contribution of grain contacts to nonlinear stress-strain behavior

[1] Repeatable, hysteretic loops in quasi-static loading measurements on rocks are well known; the fundamental processes responsible for them are not. The grain contact region is usually treated as the site of these processes, but there is little supporting experimental evidence. We have performed simultaneous neutron diffraction and quasi-static loadingexperimentsonaselectionofrockstoexperimentally isolate the response of these contact regions. Neutron diffraction measures strain in the lattice planes of the bulk of the grain material, so differences between this strain and the macroscopic response yield information about grain contact behavior. We find the lattice responds linearly to stress in all cases, oblivious to the macroscopic unrecoverable strains, curvature, and hysteresis, localizing these effects to the contacts. Neutron diffraction shows that the more granular rocks appear to distribute stresses so that the same strain appears in all the grains, independent of crystallographic orientation. INDEX TERMS: 3909 Mineral Physics: Elasticity and anelasticity; 3902 Mineral Physics: Creep anddeformation;3954MineralPhysics:Xray,neutron,andelectron spectroscopy and diffraction; 3994 Mineral Physics: Instruments and techniques; 3694 Mineralogy and Petrology: Instruments and techniques.Citation: Darling, T. W., J. A. TenCate, D. W. Brown, B. Clausen, and S. C. Vogel (2004), Neutron diffraction study of the contribution of grain contacts to nonlinear stress-strain behavior, Geophys. Res. Lett., 31, L16604, doi:10.1029/2004GL020463.
Gravity and Matter in Causal Set Theory

The goal of this paper is to propose an approach to the formulation of dynamics for causal sets and coupled matter fields. We start from the continuum version of the action for a Klein–Gordon field coupled to gravity, and rewrite it first using quantities that have a direct correspondent in the case of a causal set, namely volumes, causal relations and timelike lengths, as variables to describe the geometry. In this step, the local Lagrangian density for a set of fields f is recast into a quasilocal expression that depends on pairs of causally related points pq and is a function of the values of f in the Alexandrov set defined by those points, and whose limit as p and q approach a common point x is . We then describe how to discretize and use it to define a causal-set-based action.
Hydride-promoted demethylation of methyl phenyl ethers

Abstract Solutions of L-Selectride or SuperHydride in refluxing THF efficiently deprotect methyl phenyl ethers. L-Selectride is the more effective reagent, while electron-poor arenes work best. Unlike other hydride sources, these reagents permit ether cleavage without the reduction of aryl halides.
Zinc complexes of chiral phenols as catalysts for enantioselective addition of organozinc reagents to aldehydes

Abstract A class of zinc (II) chelates with chiral tertiary amino phenolic alcohols serve as effective catalysts for the enantioselective addition of diethylzinc to aromatic aldehydes with predictable absolute stereochemistry.
Bifurcations in a Power System Model

Bifurcations are performed for a power system model consisting of two generators feeding a load, which is represented by an induction motor in parallel with a capacitor and a combination of constant power and impedance PQ load. The constant reactive power and the coefficient of the reactive impedance load are used as the control parameters. The response of the system undergoes saddle-node, subcritical and supercritical Hopf, cyclic-fold, and period-doubling bifurcations. The latter culminate in chaos. The chaotic solutions undergo boundary crises. The basin boundaries of the chaotic solutions may consist of the stable manifold of a saddle or an unstable limit-cycle. A nonlinear controller is used to control the subcritical Hopf and the period-doubling bifurcations and hence mitigate voltage collapse.
Regularity of Harmonic Functions for Some Markov Chains with Unbounded Range

We consider a class of continuous time Markov chains on ℤd. These chains are the discrete space analogue of Markov processes with jumps. Under some conditions, as we show, harmonic functions associated with these Markov chains are Holder continuous.
The Far-Ultraviolet Spectrum of NGC 4151 as Observed with the Hopkins Ultraviolet Telescope on Astro-2

We observed NGC 4151 on six separate occasions at intervals of 1 to 3 days using the Hopkins Ultraviolet Telescope during the flight of Astro-2 aboard the space shuttle Endeavour in 1995 March. The far-UV spectra cover the spectral range from the interstellar cutoff at 912 to 1840 A with a resolution of 2-4 A. The mean spectrum, representing 4752 s of integration time, has a signal-to-noise ratio of approximately 30, and it shows profound differences compared to that obtained during the flight of Astro-1 in 1990 December. The continuum, 5.3 × 10-13 erg cm-2 s-1 A-1 at 1455 A, is 5 times brighter, the brightest UV flux ever observed for NGC 4151. All high-ionization absorption lines have strengthened considerably—S VI λλ933, 945, C III λ977, O VI λλ1032, 1038, N V λλ1239, 1243, Si IV λλ1394, 1403, and C IV λλ1548, 1551. The Lyman series absorption lines have also increased in strength, with the bulk of the absorption requiring a neutral hydrogen column density of 5 × 1017 cm-2 covering only 78% of the UV source with an effective Doppler parameter of 350 km s-1. However, up to 5 × 1020 cm-2 of neutral hydrogen that fully covers the source could be present in gas with a thermal Doppler parameter of 20 km s-1. Single-zone photoionization models of warm absorbing gas are unable to account for both the X-ray absorbing material and the UV-absorbing gas, largely because of the wide range of ionization states present in the UV and the X-ray.
1,3-Transposition of Allylic Alcohols Catalyzed by Methyltrioxorhenium

Methyltrioxorhenium (MTO) catalyzes the 1,3-transposition of allylic alcohols to generate the more stable isomer at equilibrium. The direction of the equilibrium is largely decided by the nature of the OH group, i.e., whether it is primary, secondary, or tertiary. In the case of aliphatic allylic alcohols, tertiary is preferred to secondary which is preferred to primary. For aromatic allyl alcohols, the more conjugated isomer predominates largely at equilibrium. Oxygen-18 labeling showed that the OH groups of the parent and product are the same. The reaction is first order with respect to both allyl alcohol and MTO but strongly inhibited by traces of water. Theoretical calculations suggest the same results in the case of aliphatic allyl alcohols, although aromatic allyl alcohols do not follow the predictions. Studies of deuterium-labeled substrates show a large equilibrium isotope effect (K = 1.20 ± 0.02). For isomeric allyl alcohols differing in the position of deuterium only, the isomer with the deuteri...
An Approach for Modestly Directional Communications in Mobile Ad Hoc Networks

Directional antennas are a promising technology for use in mobile ad hoc environments. By consuming smaller volumes than omni directional antennas, directional antennas enable significant increases in network capacity by allowing more simultaneous transmissions to occur within a multihop wireless network. In this paper, we present some of the challenges that face asynchronous directional channel access schemes and describe how these problems can be avoided by taking a synchronous approach. We describe a communications system architecture that enables modestly directional sectored antennas to be effectively exploited in a mobile ad hoc environment. A key part of this architecture is the Directional Synchronous Unscheduled Multiple Access (DSUMA) protocol. By making intelligent decisions regarding the enabling/disabling of sector antennas, DSUMA provides an increased density of transmissions while insuring that collisions do not occur. Our results indicate how the number of sectors per node affects performance in terms of spatial reuse, the likelihood of collisions, and overall network capacity.
DXL: a sounding rocket mission for the study of solar wind charge exchange and local hot bubble X-ray emission

The Diffuse X-rays from the Local galaxy (DXL) mission is an approved sounding rocket project with a first launch scheduled around December 2012. Its goal is to identify and separate the X-ray emission generated by solar wind charge exchange from that of the local hot bubble to improve our understanding of both. With 1,000 square centimeters proportional counters and grasp of about 10 square centimeters sr both in the 1/4 and 3/4 keV bands, DXL will achieve in a 5-minute flight what cannot be achieved by current and future X-ray satellites.
Dihalo derivatives of 3‐coordinate hypervalent phosphorus compounds

The preparation of 1,1-difluoro-3,7-di-tert-butyl-2,8-dioxa-1-phosphabicyclo[3.3.0]octa-3,6-diene (Dit-BuADPO·F2)from hexafluoropropylene oxide (HFPO) and 3,7-di-tert-butyl-2,8-dioxa-1-phosphabicyclo[3.3.0]octa-2,4,6-triene (DitBuADPO) is described. The solid state structure of DitBuADPO·F2 shows an unusual square pyramidal geometry. The structural and spectroscopic properties of DitBuADPO·F2 are compared with other oxidized derivatives of DitBuADPO that contain 5-coordinate phosphorus.
Some well characterized chemical reactivities of buckminsterfullerene (C60)

Abstract The metalation, halogenation and free radical addition chemistry of C 60 is described. Vibrational spectroscopy is a useful tool in assigning the structures of the products. Several underlying principles emerge for C 60 chemistry, some of which are supported by molecular orbital calculations.
PROPERTIES OF THE 24 DAY MODULATION IN GX 13+1 FROM NEAR-INFRARED AND X-RAY OBSERVATIONS

A 24 day period for the low-mass X-ray binary (LMXB) GX 13+1 was previously proposed on the basis of seven years of RXTE All-Sky Monitor (ASM) observations and it was suggested that this was the orbital period of the system. This would make it one of the longest known orbital periods for a Galactic LMXB powered by Roche lobe overflow. We present here the results of (1) K-band photometry obtained with the SMARTS Consortium CTIO 1.3 m telescope on 68 nights over a 10 month interval; (2) continued monitoring with the RXTE ASM, analyzed using a semi-weighted power spectrum instead of the data filtering technique previously used; and (3) Swift Burst Alert Telescope (BAT) hard X-ray observations. Modulation near 24 days is seen in both the K band and additional statistically independent ASM X-ray observations. However, the modulation in the ASM is not strictly periodic. The periodicity is also not detected in the Swift BAT observations, but modulation at the same relative level as seen with the ASM cannot be ruled out. If the 24 day period is the orbital period of system, this implies that the X-ray modulation is caused by structure that is not fixed in location. A possible mechanism for the X-ray modulation is the dipping behavior recently reported from XMM-Newton observations.
A conductivity relationship for steady-state unsaturated flow processes under optimal flow conditions

Optimality principles have been used for investigating physical processes in different areas. This work attempts to apply an optimal principle (that water flow resistance is minimized on global scale) to steady-state unsaturated flow processes. Based on the calculus of variations, we show that under optimal conditions, hydraulic conductivity for steady-state unsaturated flow is proportional to a power function of the magnitude of water flux. This relationship is consistent with an intuitive expectation that for an optimal water flow system, locations where relatively large water fluxes occur should correspond to relatively small resistance (or large conductance). Similar results were also obtained for hydraulic structures in river basins and tree leaves, as reported in other studies. Consistence of this theoretical result with observed fingering-flow behavior in unsaturated soils and an existing model is also demonstrated.
The effect of pinning on drag in coupled one-dimensional channels of particles

We consider a simple model for examining the effects of quenched disorder on drag consisting of particles interacting via a Yukawa potential that are placed in two coupled one-dimensional channels. The particles in one channel are driven and experience a drag from the undriven particles in the second channel. In the absence of pinning, for a finite driving force there is no pinned phase; instead, there are two dynamical regimes of completely coupled or locked flow and partially coupled flow. When pinning is added to one or both channels, we find that a remarkably rich variety of dynamical phases and drag effects arise that can be clearly identified by features in the velocity force curves. The presence of quenched disorder in only the undriven channel can induce a pinned phase in both channels. Above the depinning transition, the drag on the driven particles decreases with increasing pinning strength, and for high enough pinning strength, the particles in the undriven channel reach a reentrant pinned phase which produces a complete decoupling of the channels. We map out the dynamic phase diagrams as a function of pinning strength and the density of pinning in each channel. Our results may be relevant for understanding drag coupling in 1D Wigner crystal phases, and the effects we observe could also be explored using colloids in coupled channels produced with optical arrays, vortices in nanostructured superconductors, or other layered systems where drag effects arise.
Does Survey Mode Still Matter? Findings from a 2010 Multi-Mode Comparison

In this article, we present data from a three-mode survey comparison study carried out in 2010. National surveys were fielded at the same time over the Internet (using an opt-in Internet panel), by telephone with live interviews (using a national Random Digit Dialing (RDD) sample of landlines and cell phones), and by mail (using a national sample of residential addresses). Each survey utilized a nearly identical questionnaire soliciting information across a range of political and social indicators, many of which can be validated with government data. Comparing the findings from the modes using a Total Survey Error approach, we demonstrate that a carefully executed opt-in Internet panel produces estimates that are as accurate as a telephone survey and that the two modes differ little in their estimates of other political indicators and their correlates.
Interiors of the giant planets.

Various investigations concerning Jupiter, Uranus and Saturn are discussed. Revisions in the Galilean satellite ephemerides led to a new interpretation of earth-based measurements of Jovian oblateness which agrees with Pioneer measurements. In the area of scintillation theory, a semi-qualitative result was obtained for spike profiles produced by finite stellar disks viewed through Kolmogorov turbulence. It was also possible to set limits on the systematic distortion of stellar occulation profiles by turbulence which minimize the systematic distortion problem. The position of Miranda was studied for the purpose of obtaining an accurate prediction of a possible stellar occultation by Miranda in 1977, following an occultation of the same star by Uranus. In addition, using thermodynamic calculations, a model was developed for the adiabiatic cooling of Jovian-type planets and an observational test of the model was proposed. The dynamic structure of Saturn's rings was also studied.
Resonant Inclination Excitation of Migrating Giant Planets

The observed orbits of extrasolar planets suggest that many giant planets migrate a considerable distance toward their parent star as a result of interactions with the protoplanetary disk and that some of these planets become trapped in eccentricity-exciting mean motion resonances with one another during this migration. Using three-dimensional numerical simulations, we find that as long as the timescale for damping of the planets' eccentricities by the disk is close to or longer than the disk-induced migration timescale and the outer planet is more than half the mass of the inner, resonant inclination excitation will also occur. Neither the addition of a (simple, fixed) disk potential nor the introduction of a massive inner planetary system inhibit entry into the inclination resonance. Therefore, such a mechanism may not be uncommon in the early evolution of a planetary system, and a significant fraction of exoplanetary systems may turn out to be non-coplanar.