cssi/SciSciGPT-SciSciNet huggingface dataset:
Transport Taxes with Multiple Trip Purposes

A congestible urban transport system is considered in which cars and buses are used for commuting and non-commuting trips. Commuting is a strict complement to taxable labour supply. The optimal tax structure for raising a given amount of government revenue is examined for the cases where differentiation of transport tolls between trip purposes is and is not possible. An application to Belgian urban environments shows that optimal toll differentiation produces significant efficiency improvements. Without differentiation, reforming transport taxes generates substantial gains only when the labour tax can be reduced.
Catalytic coupling of C-H and C-I bonds using pyridine as a directing group.

A method for the palladium-catalyzed arylation of pyridines and pyrazoles has been developed. Both aliphatic and aromatic C−H bonds may be functionalized using this method. A bromo substituent is tolerated on the aryl iodide coupling component.
A survey of 71 earthquake bursts across southern California: Exploring the role of pore fluid pressure fluctuations and aseismic slip as drivers

[1] We investigate the cause of seismicity bursts by examining a waveform-relocated catalog for southern California between 1984 and 2002 and systematically identifying 71 isolated sequences of 40 or more earthquakes occurring within a 2-km-radius volume and a 4-week interval. Fifty-seven of the 71 bursts are difficult to interpret as primarily a main shock and its Omori-law-abiding foreshocks and aftershocks because they exhibit a more complicated evolution in space, time, and magnitude; we identify 18 of these sequences as particularly swarm-like. Evidence against a simple cascade of elastic stress triggering includes the presence of an interval of steady seismicity rate, the tendency of the largest event to strike later in the sequence, the large spatial extent of some of the swarms compared to their cumulative moment, and the weak correlation between the number of events in each burst and the magnitude of the largest event in each burst. Shallow sequences and normal faulting mechanism sequences are most likely to be swarm-like. The tendencies of the hypocenters in the swarm-like sequences to occur on vertical planes and expand over time suggest pore fluid pressure fluctuations as the most likely mechanism driving the swarm-like seismicity bursts. However, episodic aseismic slip could also be at least partly responsible and might provide a more compelling explanation for the steady rate of seismicity during swarms, whereas fluid pressure perturbations might be expected to diminish more rapidly with time. Both aftershock-like and swarm-like seismicity bursts are distributed across the entire study region, indicating that they are a general feature of tectonic faulting, rather than limited to a few geological conditions such as volcanic or geothermal areas.
20 Gy Versus 44 Gy Supplemental Beam Radiation With Pd-103 Prostate Brachytherapy: Preliminary Biochemical Outcomes From a Prospective Randomized Multi-Center Trial

Abstract Background and purpose While favorable results are achieved with combined modality irradiation, there has never been a rigorous study of the need for supplemental beam. The study reported here compares clinical outcomes with substantially different external beam radiation doses. Similar to classic randomized Wilm's tumor studies from the 1980s, the intention of the trial design was to decrementally test the need for beam radiation. Patients and methods As of June 2000, 165 of a planned 600 patients with 1997 AJC clinical stage T1c–T2a prostatic carcinoma, Gleason grade 7–10 and/or PSA 10–20ng/ml, were treated on a randomized protocol comparing 44 versus 20Gy pre-implant supplemental beam radiation, combined with Pd-103, 90 versus 115Gy, respectively (NIST-1999). Freedom from biochemical failure was defined as a serum PSA≤0.5ng/ml at last follow-up. Patients were censored at last follow-up if their serum PSA was still decreasing. Patients whose serum PSA nadired at a value >0.5ng/ml were scored as failures at the time at which their PSA nadired. The follow-up period for non-failing patients ranged from 0.5 to 4.9 years (median: 2.9 years). Accrual of 566 patients was achieved in October 2004. The study was closed at that time because of slowing accrual, due in part to the findings reported here. Results The overall actuarial freedom from biochemical progression at 3 years is 85%, with 59 patients followed beyond 3 years. A total of 21 patients have developed biochemical failure, 12 treated with 20Gy and nine treated with 44Gy. There were no clinically evident local failures. The actuarial biochemical freedom-from-failure rate at 3 years was 83% for 20Gy patients versus 88% for 44Gy patients ( P =0.64). For 112 patients with a pre-treatment PSA P =0.16). For 47 patients with a pre-treatment PSA>10ng/ml, the 3-year freedom from progression was 82% in patients receiving 20Gy beam radiation versus 72% in those who received 44Gy beam ( P =0.38). Conclusions The randomized data presented here suggests that the likelihood of biochemical cure is similar with standard (44Gy) or lower dose (20Gy) supplemental beam radiation. Since the biological effect of 20Gy external beam radiation is likely to be small, we interpret these preliminary results to suggest that supplemental beam radiation is unnecessary, in the setting of a high degree of prostate coverage by the brachytherapy prescription dose. With closure of this study, we have begun treating intermediate and high risk patients on a prospective randomized comparison of Pd-103 with 20 versus 0Gy supplemental beam radiation.
Palladium-catalyzed coupling of terminal alkynes to the free cis-diol metabolite produced from the oxidation of bromobenzene by pseudomonas putida: Synthesis of new homochiral 3-alkynyl cis-cyclohexa-3,5-diene-1,2-diols

Abstract The free cis -diol metabolite ( 1 ) produced from the oxidation of bromobenzene by Pseudomonas putida underwent Pd(0)-catalyzed coupling with trimethylsilyl acetylene, phenylacetylene and 1-hexyne providing the novel homochiral (1 S , 2 R )-3-alkynyl cis -cyclohexa-3,5-diene-1,2-diols 2–4 in good to excellent yields.
Using Hob Offset to Balance Dynamic Strength in Spur Gears

An analytical study of the effect of hob offset on dynamic tooth strength of spur gears is presented. The study was limited to equal and opposite offset values applied to the pinion and gear to maintain the standard operating center distance. The analysis presented is performed using a new version of the NASA gear dynamics code DANST. The operating speed of a transmission has a significant influence on the amount of hob offset required to equalize dynamic stresses in the pinion and gear. In the transmission studied, at low speeds, the optimum hob offset was found to fluctuate within a range. At higher speeds, the optimum value is constrained by the minimum allowed thickness at the tip of the pinion tooth. For gears that must operate over a range of speeds, an average offset value can be used. Spur gears designed with the procedure presented here can have significant improvements in load capacity.
Structural Safety Measures for Airplanes

Passenger aircraft structural design is based on a safety factor of 1.5, and this safety factor alone is equivalent to a probability of failure of between 10 S2 and 10 S3 . Yet airliners are much safer, with crashes caused by structural failure being extremely rare based on accident records. The probability of structural failure of transport aircraft is of the order of 10 S8 per flight segment. This paper looks at two additional contributions to safety—the use of conservative material properties and certification tests—using a simple model of structural failure. We find that the three safety measures together might be able to reduce the calculated probability of failure to about 10 S7 . Additional measures, such as conservative load specifications, might be responsible for the higher safety encountered in practice, explaining why passenger aircraft are so structurally safe. In addition, the paper sheds light on the effectiveness of certification tests for improving safety. It is found that certification tests reduce the calculated failure probabilities by reducing the modeling error. We find that these tests are most effective when safety factors are low and when most of the uncertainty is caused by systemic errors rather than variability.
Bu3SnH-Mediated Pinacol Coupling of 1,5- and 1,6-Dicarbonyl Compounds: Synthetic and Mechanistic Studies

A new method is described for the intramolecular pinacol coupling of 1,5- and 1,6-dicarbonyl compounds, employing Bu3SnH as the stoichiometric reductant. The key steps in this pinacol cyclization are the addition of a tin ketyl to a carbonyl group and a subsequent intramolecular SH2 reaction. The isolation of 1,3-dioxa-2-stannolanes, along with other product and labeling studies, provides strong support for the proposed homolytic substitution step, which distinguishes the pinacol cyclization from other reductive cyclizations of tin ketyls, all of which proceed through abstraction of hydrogen from Bu3SnH in the final step. An interesting consequence of the SH2 pathway is very high cis selectivity in the cyclization of 1,5-dicarbonyl compounds. Mechanistic studies furnish evidence that the steps that precede homolytic substitution, including C−C bond formation, are reversible under the reaction conditions.
Frequency-dependent Shift in the Image Centroid of the Black Hole at the Galactic Center as a Test of General Relativity

The inferred black hole in the Galactic center spans the largest angle on the sky among all known black holes. Forthcoming observational programs plan to localize or potentially resolve the image of Sgr A* to an exquisite precision, comparable to the scale of the black hole horizon. Here we show that the location of the image centroid of Sgr A* should depend on the observing frequency because of relativistic and radiative transfer effects. The same effects introduce a generic dependence of the source polarization on frequency. Future detection of the predicted centroid shift and the polarization dependence on frequency can be used to determine the unknown black hole spin and verify the validity of general relativity.
Birkhoff for Lovelock redux

We show succinctly that all metric theories with second order field equations obey Birkhoff's theorem: their spherically symmetric solutions are static.
Effect of Castration and Finasteride on Urinary Oxalate Excretion in Male Rats

We investigated the effects of castration and finasteride administration on urinary oxalate (Ox) excretion in a rat ethylene glycol (EG) model of urolithiasis. Male adult SD rats were divided into six groups. Group 1 were normal, untreated rats. The other five groups, all treated with 0.75% EG for 4 weeks; were as follows: group 2, non-castrated (intact) rats; group 3, castrated rats; group 4, castrated rats with a 4-cm testosterone implant; group 5, intact rats treated with high-dose finasteride (7.5 mg%); and group 6, intact rats treated with low-dose finasteride (0.75 mg%). Urinary Ox excretion increased 12.8-fold after 4 weeks of EG treatment (group 2 vs group 1). Both castration (group 3) and finasteride administration (groups 5 and 6) significantly decreased urinary Ox excretion compared with intact rats (group 2). We conclude that dihydrotestosterone is partially responsible for the exaggerated hyperoxaluria observed in the rat EG model of urolithiasis.
The Nature of Accreting Black Holes in Nearby Galaxy Nuclei

We have found compact X-ray sources in the center of 21 (54%) of 39 nearby face-on spiral and elliptical galaxies with available ROSAT HRI data. ROSAT X-ray luminosities (0.2-2.4 keV) of these compact X-ray sources are ~1037-1040 ergs s-1 (with a mean of 3 × 1039 ergs s-1). The mean displacement between the location of the compact X-ray source and the optical photometric center of the galaxy is ~390 pc. The fact that compact nuclear sources were found in nearly all (five of six) galaxies with previous evidence for a black hole or an active galactic nucleus (AGN) indicates that at least some of the X-ray sources are accreting supermassive black holes. ASCA spectra of six of the 21 galaxies show the presence of a hard component with relatively steep (Γ ≈ 2.5) spectral slope. A multicolor disk blackbody model fits the data from the spiral galaxies well, suggesting that the X-ray object in these galaxies may be similar to a black hole candidate in its soft (high) state. ASCA data from the elliptical galaxies indicate that hot (kT ≈ 0.7 keV) gas dominates the emission. The fact that (for both spiral and elliptical galaxies) the spectral slope is steeper than in normal type 1 AGNs and that relatively low absorbing columns (NH ≈ 1021 cm-2) were found to the power-law component indicates that these objects are somehow geometrically and/or physically different from AGNs in normal active galaxies. The X-ray sources in the spiral and elliptical galaxies may be black hole X-ray binaries, low-luminosity AGNs, or possibly young X-ray luminous supernovae. Assuming the sources in the spiral galaxies are accreting black holes in their soft state, we estimate black hole masses ~102-104 M☉.
DTA2012 Symposium: Combining Disaggregate Route Choice Estimation with Aggregate Calibration of a Dynamic Traffic Assignment Model

Dynamic Traffic Assignment (DTA) models are important decision support tools for transportation planning and real-time traffic management. One of the biggest obstacles of applying DTA in large-scale networks is the calibration of model parameters, which is essential for the realistic replication of the traffic condition. This paper proposes a methodology for the simultaneous demand-supply DTA calibration based on both aggregate measurements and disaggregate route choice observations to improve the calibration accuracy. The calibration problem is formulated as a bi-level constrained optimization problem and an iterative solution algorithm is proposed. A case study in a highly congested urban area of Beijing using DynaMIT-P is conducted and the combined calibration method improves the fits to surveillance data compared to the calibration based on aggregate measurements only.
Is there a 230Th deficit in Arctic sediments

Abstract In most of the global ocean, the radionuclide thorium-230 is removed from the water column by adsorption onto particles and deposition in seafloor sediments, at a rate approximately in balance with its local production by the decay of uranium dissolved in seawater, allowing its use in assessing rates of marine processes. However, several previous studies have suggested that the flux of 230Th to the sediments of the Central Arctic is far too small to balance its production in the overlying water column. If this is so, 230Th produced in the low particle-flux Central Arctic basins would be deposited elsewhere, either by boundary scavenging at the margins or by export from the Arctic to lower latitudes. In order to evaluate this possibility, we compare the expected 230Th production and measured inventories for five sites in the Western Arctic, combining previously published 230Th data with reported AMS radiocarbon dates, and find no evidence for a substantial deficit of 230Th in these sediments. Instead, we find evidence for near balance in the 230Th budget during both the Holocene and late glacial periods. These intervals are separated by a brief deglacial period of apparently higher sedimentation rates and 230Th deposition. During the Holocene, the average sedimentary inventory of 230Th at these sites is largely within 30% of the water column production, in good agreement with observations and model results from other ocean basins.
Analysis of Axially Symmetric External Burning Propulsion for Bluff-Base Bodies

E burning is presently visualized as a promising concept to be used for some flight missions which require or may benefit from substantial drag reduction or elimination during a portion of a supersonic trajectory. This concept was initially investigated by Strahle for the two-dimensional case, and later by Smithey for the axisymmetric case, both using the original Crocco and Lees theory as the basic model. Recently, an axisymmetric base flow theory, which is an extension of Alber and Lees' two-dimensional work, was published and was shown to agree well with experiment. Here, a parametric study for an external burning propulsion system, using this recent theory as the basic model, was carried out to investigate potential performance of such a system. The external burning zone is incorporated in the inviscid portion of the aforementioned model. It is treated as a quasi-onedimensional zone, and is considered both shear free and nonconducting. With these major assumptions, it is shown that it is possible to achieve very high base pressures using external burning. The specific impulse values obtained are lower than reported for the two-dimensional case. In many cases, the performance is less than usually achievable by conventional rocket propulsion, if current fuel-rich gas generators provide the fuel for the external burning propulsion system. Recent experiments carried out using compression surfaces to simulate external burning confirm the order of magnitude of the specific impulse obtained by this theory.
A SPATIALLY RESOLVED VERTICAL TEMPERATURE GRADIENT IN THE HD 163296 DISK

We analyze sensitive, sub-arcsecond resolution ALMA science verification observations of CO emission lines in the protoplanetary disk hosted by the young, isolated Ae star HD 163296. The observed spatial morphology of the {sup 12}CO J = 3-2 emission line is asymmetric across the major axis of the disk; the {sup 12}CO J = 2-1 line features a much less pronounced, but similar, asymmetry. The J = 2-1 emission from {sup 12}CO and its main isotopologues have no resolved spatial asymmetry. We associate this behavior with the direct signature of a vertical temperature gradient and layered molecular structure in the disk. This is demonstrated using both toy models and more sophisticated calculations assuming non-local thermodynamic equilibrium conditions. A model disk structure is developed to reproduce both the distinctive spatial morphology of the {sup 12}CO J = 3-2 line as well as the J = 2-1 emission from the CO isotopologues assuming relative abundances consistent with the interstellar medium. This model disk structure has {tau} = 1 emitting surfaces for the {sup 12}CO emission lines that make an angle of {approx}15 Degree-Sign with respect to the disk midplane. Furthermore, we show that the spatial and spectral sensitivity of these data can distinguishmore » between models that have sub-Keplerian gas velocities due to the vertical extent of the disk and its associated radial pressure gradient (a fractional difference in the bulk gas velocity field of {approx}> 5%)« less
Lanthanide catalyzed synthesis of β-hydroxyl amides

Abstract Lanthanide (III) chloride improved the reaction of carboxylic esters with β-amino alkoxides (generated in situ from β-amino alcohols) and produced β-hydroxyl amides under mild conditions, and in high yields.
Uranium content and radiogenic ages of hypersthene, bronzite, amphoterite and carbonaceous chondrites

Abstract U was measured by fission track analysis in 115 samples of hypersthene, bronzite, amphoterite and carbonaceous chondrites. On a weight basis the average values for the Cl carbonaceous and bronzite chondrites are similar to the “classic” value of 11 ppb, but the hypersthenes and amphoterites are ~50 per cent higher. Each class shows a well-determined peak in the U abundance distribution, allowing the calculation of radiogenic ages and comparison with other elements of interest.
Clinical predictors of acute response with quetiapine in psychotic mood disorders

Background In controlled studies of patients with schizophrenia, the atypical antipsychotic quetiapine, 300 mg/day, has been shown to be as effective in the treatment of positive and negative symptoms as haloperidol. However, little is known about the efficacy of quetiapine in patients with psychotic mood disorders. The purpose of this study was to assess the efficacy of quetiapine in the treatment of psychotic mood disorders in comparison with nonaffective psychotic disorders and identify clinical factors associated with quetiapine response. Method In a naturalistic setting, by reviewing medical records, we assessed response to quetiapine and factors associated with response to quetiapine in 145 consecutive patients newly treated with the drug at a nonprofit academic psychiatric hospital. These patients had received a discharge diagnosis of bipolar disorder (manic, mixed, or depressive type), major depression with psychotic features, schizophrenia, schizoaffective disorder (bipolar or depressive type), delusional disorder, or psychosis not otherwise specified (NOS) according to DSM-IV criteria. Results Patients with a diagnosis of bipolar disorder, manic, mixed, or depressed and schizoaffective disorder, bipolar type displayed higher response rates (> 74%) compared with patients with schizophrenia. However, this finding did not achieve statistical significance. A diagnosis of major depression with psychotic features (p = .02) and longer duration of illness (p = .03) were associated with less chance of responding. Conclusion Quetiapine may be a useful alternative or adjunctive treatment for patients with bipolar and schizoaffective disorders.
Rigid Supersymmetric Backgrounds of Minimal Off-Shell Supergravity

We discuss various aspects of rigid supersymmetry within minimal $ \mathcal{N}=1 $ off-shell supergravity using the old and new minimal formulations both in Lorentzian and Euclidean signatures. In particular, we construct all rigid supersymmetry backgrounds with a hypersurface orthogonal Killing vector. In the Lorentzian signature we show that AdS 4 provides a rigid supersymmetric background in both formulations albeit with different amounts of preserved supersymmetry. In the Euclidean signature we find new backgrounds of the old-minimal supergravity, including squashed four-spheres and a half-BPS version of flat space.
Generalized Borcea–Voisin Construction

C. Voisin and C. Borcea have constructed mirror pairs of families of Calabi–Yau threefolds by taking the quotient of the product of an elliptic curve with a K3 surface endowed with a non-symplectic involution. In this paper, we generalize the construction of Borcea and Voisin to any prime order and build three and four dimensional Calabi–Yau orbifolds. We classify the topological types that are obtained and show that, in dimension 4, orbifolds built with an involution admit a crepant resolution and come in topological mirror pairs. We show that for odd primes, there are generically no minimal resolutions and the mirror pairing is lost.
Wide-Angle Redshift Distortions Revisited

We explore linear redshift distortions in wide-angle surveys from the point of view of symmetries. We show that the redshift-space two-point correlation function can be expanded into tripolar spherical harmonics of zero total angular momentum S(1,2,). The coefficients of the expansion B are analogous to the Cl of the angular power spectrum and express the anisotropy of the redshift-space correlation function. Moreover, only a handful of B are nonzero: the resulting formulae reveal a hidden simplicity comparable to the distant observer limit. The B depend on spherical Bessel moments of the power spectrum and f = Ω0.6/b. In the plane-parallel limit, the results of Kaiser and Hamilton are recovered. The general formalism is used to derive useful new expressions. We present a particularly simple trigonometric polynomial expansion, which is arguably the most compact expression of wide-angle redshift distortions. These formulae are suitable for inversion because of the orthogonality of the basis functions. An alternative Legendre polynomial expansion was obtained as well. This can be shown to be equivalent to the results of Szalay and coworkers. The simplicity of the underlying theory will admit similar calculations for higher order statistics as well.
Folksonomy-Based Term Extraction for Word Cloud Generation

In this work we study the task of term extraction for word cloud generation in sparsely tagged domains, in which manual tags are scarce. We present a folksonomy-based term extraction method, called tag-boost, which boosts terms that are frequently used by the public to tag content. Our experiments with tag-boost based term extraction over different domains demonstrate tremendous improvement in word cloud quality, as reflected by the agreement between manual tags of the testing items and the cloud’s terms extracted from the items’ content. Moreover, our results demonstrate the high robustness of this approach, as compared to alternative cloud generation methods that exhibit a high sensitivity to data sparseness. Additionally, we show that tag-boost can be effectively applied even in nontagged domains, by using an external rich folksonomy borrowed from a well-tagged domain.
Knowledge and Practical Interests

Introduction 1. Contextualism 2. Knowledge Ascriptions and Gradability 3. Knowledge Ascriptions and Context-Sensitivity 4. Contextualism on the Cheap? 5. Interest-Relative Invariantism 6. Interest-Relative Invariantism vs. Contextualism 7. Interest-Relative Invariantism vs. Relativism 8. Contextualism, Interest-Relativism, and Philosophical Paradox 9. Conclusion
A constrained optimization approach to finite element mesh smoothing

Abstract The quality of a finite element solution has been shown to be affected by the quality of the underlying mesh. A poor mesh may lead to unstable and/or inaccurate finite element approximations. Mesh quality is often characterized by the “smoothness” or “shape” of the elements (triangles in 2-D or tetrahedra in 3-D). Most automatic mesh generators produce an initial mesh where the aspect ratio of the elements are unacceptably high. In this paper, a new approach to produce acceptable quality meshes from a topologically valid initial mesh is presented. Given an initial mesh (nodal coordinates and element connectivity), a “smooth” final mesh is obtained by solving a constrained optimization problem. The variables for the iterative optimization procedure are the nodal coordinates (excluding, the boundary nodes) of the finite element mesh, and appropriate bounds are imposed on these to prevent an unacceptable finite element mesh. Examples are given of the application of the above method for 2- and 3-D meshes generated using quadtree/octree automatic mesh generators. Results indicate that the new method not only yields better quality elements when compared with the traditional Laplacian smoothing, but also guarantees a valid mesh unlike the Laplacian method.
Conversion of a Re(IV) Tetrahedral Cluster to a Re(III) Octahedral Cluster: Synthesis of [(CH3)C(NH2)2]4[Re6Se8(CN)6] by a Solvothermal Route

The compound [(CH(3))C(NH(2))(2)](4)[Re(6)Se(8)(CN)(6)] has been synthesized by the reaction at 200 degrees C for 3 days of Re(4)Te(4)(TeCl(2))(4)Cl(8), KSeCN, and NH(4)Cl in superheated acetonitrile. This compound crystallizes in the space group C2/c of the monoclinic system with four formula units in a cell of dimensions a = 20.3113(14) A, b = 10.1332(7) A, c = 19.9981(14) A, beta = 106.754(1) degrees, V = 3941.3(5) A(3) (T = 153 K). The [Re(6)Se(8)(CN)(6)](4-) anion comprises an Re(6) octahedron face capped by mu(3)-Se atoms, with each Re atom liganded by a CN group. The anions and cations are connected by an extensive network of hydrogen bonds. The conversion of a Re(IV) tetrahedral cluster to a Re(III) octahedral cluster appears to be unprecedented.
Randomized hybrid linear modeling by local best-fit flats

The hybrid linear modeling problem is to identify a set of d-dimensional affine sets in RD. It arises, for example, in object tracking and structure from motion. The hybrid linear model can be considered as the second simplest (behind linear) manifold model of data. In this paper we will present a very simple geometric method for hybrid linear modeling based on selecting a set of local best fit flats that minimize a global l 1 error measure. The size of the local neighborhoods is determined automatically by the Jones' β 2 numbers; it is proven under certain geometric conditions that good local neighborhoods exist and are found by our method. We also demonstrate how to use this algorithm for fast determination of the number of affine subspaces. We give extensive experimental evidence demonstrating the state of the art accuracy and speed of the algorithm on synthetic and real hybrid linear data.
On submanifolds in locally symmetric spaces of noncompact type

Given a connected, compact, totally geodesic submanifold Y m of noncompact type inside a compact locally symmetric space of noncompact type X n , we provide a sufficient condition that ensures that ŒY  ¤ 0 2 Hm.X IR/; in low dimensions, our condition is also necessary. We provide conditions under which there exist a tangential map of pairs from a finite cover . x X ; x Y / to the nonnegatively curved duals .Xu;Yu/ .
Carbocyclic ring-enlarged oxetanocin analogues

Abstract Carbocyclic versions of 2′,3′-dideoxy-3′C-hydroxymethyl nucleosides with adenine, guanine, uracil and cytosine bases were synthesized from a common cyclopentenone precursor. The extra hydroxymethyl moiety was introduced by photochemical addition of methanol to an α-enone system.
The effects of corporate antitakeover provisions on long-term investment : empirical evidence

This paper’s empirical results indicate that the average effect of antitakeover provisions on subsequent long-term investment is negative. The interpretation of these results depends on whether one thinks that there was too much, too little, or just the right amount of longterm investment prior to the antitakeover provision adoption. We use agency theory to devise more refined empirical tests of the effects of antitakeover provision adoption by managers in firms with different incentive and monitoring structures. Governance variables (e.g. percentage of outsiders on corporate boards, and separate CEO/chairperson positions) have an insignificant impact on subsequent long-term investment behavior. However, consistent with agency theory predictions, managers in firms with better economic incentives (higher insider ownership) tend to cut subsequent long-term investment less than managers in firms with less incentive alignment. Furthermore, managers in firms with greater external monitoring (due to higher institutional ownership) also tend to cut subsequent long-term investment less than managers in firms with less external monitoring. Thus, the decrease in subsequent long-term investment is significantly less for firms where the managers have greater incentives to act in shareholders’ interests. Finally, there are interesting effects of the control variables. First, high book equity/ market equity firms cut total long-term investment more. Second, firms that were takeover targets or rumored to be takeover targets cut long-term investment more. These results suggest that inefficient firms cut long-term investment more when an antitakeover provision is adopted. # 1997 John Wiley & Sons, Ltd.
Influence of Morphology on Current–Voltage Behavior of GaN Nanowires

We demonstrate the effect that the different morphologies of molecular beam epitaxy-grown GaN nanowires (NWs) can have upon current–voltage (I–V) behavior. Two aspects of NW morphology were investigated. The first aspect was the NW diameter, $d_{{\rm NW}}$. For single-crystal Si-doped GaN NW devices with $d_{{\rm NW}} 120\, {\rm nm}$ consistently showed ohmic I–V behavior. This discrepancy is likely the result of the comparatively larger surface depletion in thin NWs, which contributes to 1) an increased contact barrier, and 2) a barrier resulting from an axial band offset between the portion of the NW directly beneath the contact and the portion extending from the contact. The second aspect of NW morphology that we investigated was NW coalescence, which occurs when neighboring NWs fuse together during growth. I–V measurements of undoped coalesced NWs showed that these structures can have a free carrier concentration that is significantly higher than the background carrier concentration that is present in single-crystal (noncoalesced), undoped NWs.
Multisensor integration and fusion model that uses a fuzzy inference system

An intelligent multisensor integration and fusion model that uses fuzzy logic is developed. Measurement data from different types of sensors with different resolutions are integrated and fused based on the confidence in them derived from information not usually used in data fusion, such as operating temperature, frequency range, fatigue cycles, etc. These are fed as additional inputs to a fuzzy inference system (FIS) that has predefined membership functions for each of these variables. The output of the FIS are weights that are assigned to the different sensor measurement data that reflect the confidence in the sensor's behavior and performance. A modular approach is adopted. It allows adding or deleting a sensor, along with its fuzzy logic controller (FLC), anytime without affecting the entire data fusion system. This paper presents a preliminary model that fuses the data from three different types of sensors that monitor the strain at a single location in a cantilever beam. This will be later extended to sensors that will be fixed at different locations on the same beam. The results from the proposed work are a stepping stone toward the development of generic autonomous sensor models that are capable of data interpretation, self-calibration, data fusion from other sources, and even learning so as to improve their performance with time. This work is aimed at the development of smart structural health monitoring systems, but has applications in diverse fields such as robotics, controls, target tracking, and biomedical imaging.
Real-time enhanced vision system

Flying in poor visibility conditions, such as rain, snow, fog or haze, is inherently dangerous. However these conditions can occur at nearly any location, so inevitably pilots must successfully navigate through them. At NASA Langley Research Center (LaRC), under support of the Aviation Safety and Security Program Office and the Systems Engineering Directorate, we are developing an Enhanced Vision System (EVS) that combines image enhancement and synthetic vision elements to assist pilots flying through adverse weather conditions. This system uses a combination of forward-looking infrared and visible sensors for data acquisition. A core function of the system is to enhance and fuse the sensor data in order to increase the information content and quality of the captured imagery. These operations must be performed in real-time for the pilot to use while flying. For image enhancement, we are using the LaRC patented Retinex algorithm since it performs exceptionally well for improving low-contrast range imagery typically seen during poor visibility poor visibility conditions. In general, real-time operation of the Retinex requires specialized hardware. To date, we have successfully implemented a single-sensor real-time version of the Retinex on several different Digital Signal Processor (DSP) platforms. In this paper we give an overview of the EVS and its performance requirements for real-time enhancement and fusion and we discuss our current real-time Retinex implementations on DSPs.
Sequential Birch reduction–allylation and Cope rearrangement of o-anisic acid derivatives

Abstract A new method for the construction of quaternary centers on cycloalkane rings is reported. The Cope rearrangement of 4-methyl-2-allyl-2-( N -pyrrolidinyl)-carboxamide-3-cyclohexenone yields 4-methyl-4-allyl-2-( N -pyrrolidinyl)-carboxamide-2-cyclohexenone in high yield. The rearrangement substrates are easily generated from Birch reduction–allylation of o -anisic acid derivatives.
Ionizing wave via high‐power HF acceleration

[1] Recent ionospheric modification experiments with the 3.6 MW transmitter at the High Frequency Active Auroral Research Program (HAARP) facility in Alaska led to discovery of artificial ionization descending from the nominal interaction altitude in the background F-region ionosphere by ∼60 km. This paper presents a physical model of an ionizing wavefront created by suprathermal electrons accelerated by the HF-excited plasma turbulence.
Catalytic asymmetric aziridination with catalysts derived from VAPOL and VANOL

This Account describes the discovery and development of the catalytic asymmetric aziridination reaction (AZ reaction) that has been the subject of efforts in our laboratory over the last 12 years. The optimized catalyst system involves catalysts generated from either the VAPOL or VANOL ligand and triphenyl borate. These catalysts are effective for formation of aziridines from the reaction of imines that bear a N-benzhydryl substituent with stabi- lized diazo compounds including the commercially available ethyl diazoacetate (EDA). The reaction is general for N-benzhydryl im- ines prepared from electron-rich and electron-poor aromatic alde- hydes, as well as from primary, secondary and tertiary aliphatic aldehydes. This reaction is highly enantioselective and diastereo- selective giving cis-3-substituted aziridine-2-carboxylates in excel- lent yields. This Account presents the scope of the AZ reaction as defined by the work that has been done in our laboratory up to the present time, as well as applications of the resulting aziridines that have been demonstrated to date.
Asynchronous computing and communication architecture toward energy efficient wireless sensor networks

An asynchronous architecture, consisting of asynchronous sampling strategies and an active MAC protocol, is proposed to achieve a better tradeoff between energy efficiency and application's performance in wireless sensor networks (WSNs). Motivated by the data correlation in dense WSNs, asynchronous sampling strategies assign time shifts to nodes' sampling moments to obtain asynchronous sensory data, which is proved to contain more information than the synchronous sensory data at the same sampling rate. Regarding event report scenario, the proposed active MAC protocol adopts the optimal random slot selection probability not only for the medium access control but also for the sampling moments of nodes. By forming an asynchronous architecture of WSNs, the approach is able to achieve energy efficiency for data gathering applications and event detection applications, respectively.
Asymptotic amplitudes and Cauchy gains: a small-gain principle and an application to inhibitory biological feedback

The notions of asymptotic amplitude for signals, and Cauchy gain for input/output systems, and an associated small-gain principle, are introduced. These concepts allow the consideration of systems with multiple, and possibly feedback-dependent, steady states. A Lyapunov-like characterization allows the computation of gains for state-space systems, and the formulation of sufficient conditions insuring the lack of oscillations and chaotic behaviors in a wide variety of cascades and feedback loops. An application in biology (MAPK signaling) is worked out in detail.
An empirical investigation of the determinants of asymmetric pricing

Abstract This article empirically investigates the cause of asymmetric pricing: retail prices responding faster to cost increases than decreases. Using daily price data for over 11,000 retail gasoline stations, I find that prices fall more slowly than they rise as a consequence of firms extracting informational rents from consumers with positive search costs. Premium gasoline prices are shown to fall more slowly than regular fuel prices, which supports theories based upon competition with consumer search. Further testing also rejects focal price collusion as an important determinant of asymmetric pricing.
Applying scheduling and tuning to on-line parallel tomography

Tomography is a popular technique to reconstruct the three-dimensional structure of an object from a series of two-dimensional projections. Tomography is resource-intensive and deployment of a parallel implementation onto Computational Grid platforms has been studied in previous work. In this work, we address on-line execution of the application where computation is performed as data is collected from an on-line instrument. The goal is to compute incremental 3-D reconstructions that provide quasi-real-time feedback to the user. We model on-line parallel tomography as a tunable application: trade-offs between resolution of the reconstruction and frequency of feedback can be used to accommodate various resource availabilities. We demonstrate that application scheduling/tuning can be framed as multiple constrained optimization problems and evaluate our methodology in simulation. Our results show that prediction of dynamic network performance is key to efficient scheduling and that tunability allows for production runs of on-line parallel tomography in Computational Grid environments.
Foundations of Markov-perfect industry dynamics: existence, purification, and multiplicity

The existence of a Markov perfect equilibrium (MPE) in the Ericson & Pakes (1995) model of dynamic competition in an oligopolistic industry with investment, entry, and exit requires admissibility of mixed entry/exit strategies, contrary to the assertion in their paper. This is problematic because the existing algorithms cannot cope with mixed strategies. To establish a solid foundation for computing dynamic industry equilibria, we introduce flrm heterogeneity in the form of randomly drawn, privately known scrap values and setup costs into the model. We show that the resulting game of incomplete information always has a MPE in cutofi entry/exit strategies that is no more demanding to compute than a (possibly nonexistent) MPE in pure entry/exit strategies of the original game of complete information. In addition, we provide a condition on the model’s primitives that ensures that the MPE is in pure investment strategies. Building on this basic existence result, we flrst show that a symmetric and anonymous MPE exists under appropriate assumptions on the model’s primitives. Second, we show that, as the distribution of the random scrap values/setup costs becomes degenerate, MPEs in cutofi entry/exit strategies converge to MPEs in mixed entry/exit strategies of the game of complete information. Finally, we provide the flrst example of multiple symmetric and anonymous MPEs in this literature.
Characterization of focal hepatic lesions with ferumoxides-enhanced T2-weighted MR imaging.

OBJECTIVE. The purpose of this study was to evaluate whether ferumoxides-enhanced MR imaging of focal hepatic lesions provides distinctive signal intensity and lesion-to-liver contrast changes for benign and malignant lesions, helping to further characterize and differentiate these lesions.MATERIALS AND METHODS. Data analysis was performed on 70 patients, with previously identified focal hepatic lesions, who underwent MR imaging of the liver before and after IV administration of ferumoxides (10 μmol Fe/kg). Lesions analyzed with pathologically proven diagnoses included metastases (n = 40), hepatocellular carcinoma (n = 11), cholangiocarcinoma (n = 6), hemangioma (n = 4), focal nodular hyperplasia (n = 6), and hepatocellular adenoma (n = 3). Response variables measured and statistically compared included the percentage of signal-intensity change and lesion-to-liver contrast.RESULTS. Focal nodular hyperplasia showed significant signal intensity loss on ferumoxides-enhanced T2-weighted images (mean, -43% ± 6...
Current Theories of Biological Aging

Several lines of evidence have led to the notion that biological aging occurs as a result of changes in information-containing molecules either at the genetic or epigenetic level. The error theory, the redundant message theory, the codon restriction theory, and the transcriptional event theory represent the major current conceptualizations of biological aging as held by most gerontologists. The finding that cultured normal human and animal cells undergo a finite number of population doublings in vitro has provided new insights into age changes at the cellular level. The number of mitotic events that cultured normal animal cells can undergo appears to be inversely related to the age of the donor. A direct proportionality exists, however, between the mean maximum life-span of a species and the number of population doublings that their cultured embryonic cells will undergo. The several biochemical decrements known to occur prior to the cessation of mitotic activity in vitro are thought to herald those manifestations of senescence seen in the whole animal. Yet to be explained is how those cell classes such as the germ plasm and continuously propagable cancer cells escape from the inevitability of biological aging.—Hayflick, L. Current theories of biological aging. Federation Proc. 34: 9–13, 1975.
Electrophilic chemistry of dodecahedrane. Direct entry to epoxydodecahedrane and the first tethered derivative

Abstract (Phenylseleno)dodecahedrane is shown to be a useful precursor of dodecahedrene (not isolated) and epoxydodecahedrane. The conjoining of two dodecahedryl units in a para relationship on a benzene ring has also been realized.
Pair-instability supernovae via collision runaway in young dense star clusters

Stars with helium cores between ∼64 and 133 M⊙ are theoretically predicted to die as pair-instability supernovae. This requires very massive progenitors, which are theoretically prohibited for Pop II/I stars within the Galactic stellar mass limit due to mass-loss via line-driven winds. However, the runaway collision of stars in a dense, young star cluster could create a merged star with sufficient mass to end its life as a pair-instability supernova, even with enhanced mass-loss at non-zero metallicity. We show that the predicted rate from this mechanism is consistent with the inferred volumetric rate of roughly ∼2 × 10−9 Mpc−3 yr−1 of the two observed pair-instability supernovae, SN 2007bi and PTF 10nmn, neither of which has metal-free host galaxies. Contrary to prior literature, only pair-instability supernovae at low redshifts z < 2 will be observable with the Large Synoptic Survey Telescope. We estimate that the telescope will observe ∼102 such events per year that originate from the collisional runaway mergers in clusters.
An effective additive basis for the integers

Abstract We give an algorithm for the enumeration of a set E of nonnegative integers with the property that each nonnegative integer x can be written as a sum of two elements of E in at least C 1 log x and at most C 2 log x ways, where C 1 , C 2 are positive constants. Such a set is called a basis and its existence has been established by Erdos. Our algorithm takes time polynomial in n to enumerate all elements of E not greater than n . We accomplish this by derandomizing a probabilistic proof which is slightly different than that given by Erdos.
The effect of state laws on capital structure

Abstract US manufacturing firms incorporated in states with stronger payout restrictions use less debt, while antitakeover statutes do not significantly reduce long-run leverage. Correcting for the endogenously determined choice of where to incorporate, we find that firms sort themselves according to state laws and capital structure needs. After accounting for self-selection, state antitakeover laws are positively associated with debt as a fraction of market value, possibly due to lower market values for these firms. Payout restrictions appear to reduce leverage for firms that have not reincorporated outside their home states. These constraints explain part of the negative relation between profitability and leverage.
A novel synthesis of 2-substituted pyrido[1,2-a]-1,3,5-triazin-4-ones by the reaction of N-fluoropyridinium salts with cyanate ion and carbonitriles: Evidence in support of a carbene intermediate

Abstract A carbene 5″ derived from N-fluoropyridinium cation is the suggested intermediate in the novel synthesis of pyridotriazines 3.