cssi/SciSciGPT-SciSciNet huggingface dataset:
Classification and application of triangular quark mass matrices

Abstract Any given pair of up and down quark mass matrices can be brought into the triangular form, at the same time eliminating their unphysical contents. Further, we show that every physically viable pair can always be reduced to one of ten triangular forms, which we list explicitly. When hermitian mass matrices are thus analyzed, it is found that any pattern of texture zeros translates into simple, analytic predictions for the quark mixings. Amongst possible hermitian matrices with five texture zeros, this method enables us to identify the unique pair which is favored by present data.
The asymmetric allylboration reaction: dependence of rate and enantioselectivity on the chiral auxiliary

Abstract The rate and enantioselectivity of the asymmetric allylboration reaction depends on the diol auxiliary.
Calibration of the NOAA AMSU-A Radiometers With Natural Test Sites

The Advanced Microwave Sounding Unit-A (AMSU-A) instruments onboard NOAA-18 and NOAA-19 are investigated by comparison of the measurements from the two satellites over Antarctica and the tropical ocean. Characteristics of the data over the two test sites are demonstrated. Thirty-day mean brightness temperatures at nadir over Antarctica from NOAA-18 and NOAA-19 measurements show that there is minimal diurnal variability ( <; 0.5 K) in the measurements during the Antarctic winter months. Therefore, these measurements provide a practical approach to determine the relative intersatellite/intersensor calibration biases. The resultant biases for the two satellites are <; 0.2 K for channels 1-5 and 8 and <; 0.6 K for the other channels. Monthly mean angular distributions of brightness temperatures at the four window channels 1-3 and 15 from the satellites over the tropical ocean are compared to those of simulations, which are obtained with an ocean model of radiative transfer. These AMSU-A data provide a unique opportunity for the investigation of the scan-position-dependent biases (or asymmetries) of the data. The biases are revealed by the difference between the observed brightness temperatures and the simulations. The results in this study provide a useful guide for the calibration and validation of microwave instruments.
Cosmological Origin of the Stellar Velocity Dispersions in Massive Early-Type Galaxies

We show that the observed upper bound on the line-of-sight velocity dispersion of the stars in an early-type galaxy, σe 400 km s-1, may have a simple dynamical origin within the ΛCDM cosmological model, under two main hypotheses. The first is that most of the stars now in the luminous parts of a giant elliptical galaxy formed at redshift z 6. Subsequently, the stars behaved dynamically just as an additional component of the dark matter. The second hypothesis is that the mass distribution characteristic of a newly formed dark matter halo forgets such details of the initial conditions as the stellar "collisionless matter" that was added to the dense parts of earlier generations of halos. We also assume that the stellar velocity dispersion does not evolve much at z 6, because a massive host halo grows mainly by the addition of material at large radii well away from the stellar core of the galaxy. These assumptions lead to a predicted number density of elliptical galaxies as a function of stellar velocity dispersion that is in promising agreement with the Sloan Digital Sky Survey data.
Changing Monetary Policy Rules, Learning, and Real Exchange Rate Dynamics

When the exchange rate is priced by uncovered interest parity and central banks set nominal interest rates according to a reaction function such as the Taylor rule, the real exchange rate will be determined by expected inflation and the output gap or the unemployment gap of the home and foreign countries. This paper examines the implications of these Taylor rule fundamentals for real exchange rate determination. Because the true parameters in central bank policy rules are unknown to the public and change over time, the model is presented in the context of a least squares learning environment. This simple learning model captures the volatility and the major swings in the real deutschemark/euro–dollar exchange rate from 1976 to 2007.
The First Supernova Explosions in the Universe

We investigate the supernova explosions that end the lives of massive Population III stars in low-mass minihalos (M ~ 106 M☉) at redshifts z ~ 20. Employing the smoothed particle hydrodynamics method, we carry out numerical simulations in a cosmological setup of pair-instability supernovae with explosion energies of ESN = 1051 and 1053 ergs. Whereas the lower explosion energy leaves part of the halo intact, we find that the more energetic explosion leads to the complete disruption of the gas in the minihalo and expels 90% of the stellar metals into a region ~1 kpc across over a timescale of 3-5 Myr. Because of this burstlike initial star formation episode, a large fraction of the universe could have been endowed with a metallicity floor, Zmin 10-4 Z☉, already at z 15.
Time-Series Analysis of Supersonic Base-Pressure Fluctuations

An investigation into the dynamic nature of supersonic base-pressure fluctuations was conducted. Two axisymmetric models, a blunt and a boattailed afterbody, were studied at a freestream Mach number of 2.46 and zero angle of attack. High-frequency pressure measurements were recorded with both radially and circumferentially positioned transducers. Blunt afterbody measurements showed rms pressure fluctuations on the order of 5% of the average base pressure. Power spectral density (PSD) estimates at the two outermost radial locations for the blunt afterbody revealed that a significant portion of the pressure fluctuation energy is contained in a peak centered near 850 Hz (Sr = 0.094). RMS pressure fluctuations on the boattailed afterbody were on the order of 4.3% of the average base pressure. The PSD estimates at the two outermost locations contained a more defined and larger peak centered near 800 Hz (Sr = 0.089) as compared to the blunt base. The two outermost radial locations on both afterbodies are subjected to similar pressure histories and, hence, display large values of coherence at low frequencies. The pressure history at the center position is not well correlated to those at the two outermost locations, resulting in low values of coherence. Possible mechanisms for the substantial pressure fluctuation energy contained at low frequencies are pulsing or flapping of the recirculation region, whereas higher-frequency energy could be attributed to large-scale turbulent structures in the shear layer.
The large cardinals between supercompact and almost-huge

I analyze the hierarchy of large cardinals between a supercompact cardinal and an almost-huge cardinal. Many of these cardinals are defined by modifying the definition of a high-jump cardinal. A high-jump cardinal is defined as the critical point of an elementary embedding $${j: V \to M}$$ j : V ? M such that M is closed under sequences of length $${\sup\{{j(f)(\kappa)\,|\,f: \kappa \to \kappa}\}}$$ sup { j ( f ) ( ? ) | f : ? ? ? } . Some of the other cardinals analyzed include the super-high-jump cardinals, almost-high-jump cardinals, Shelah-for-supercompactness cardinals, Woodin-for-supercompactness cardinals, Vopĕnka cardinals, hypercompact cardinals, and enhanced supercompact cardinals. I organize these cardinals in terms of consistency strength and implicational strength. I also analyze the superstrong cardinals, which are weaker than supercompact cardinals but are related to high-jump cardinals. Among the results, I highlight the following. Furthermore, I prove some results relating high-jump cardinals to forcing, as well as analyzing Laver functions for super-high-jump cardinals.
Enhancement of 1,2-dehydration of alcohols by alkali cations and protons: a model for dehydration of carbohydrates

We have used electronic structure calculations to investigate the 1,2-dehydration of alcohols as a model for water loss during the pyrolysis of carbohydrates found in biomass. Reaction enthalpies and energy barriers have been calculated for neat alcohols, protonated alcohols and alcohols complexed to alkali metal ions (Li+ and Na+). We have estimated pre-exponential A factors in order to obtain gas phase rate constants. For neat alcohols, the barrier to 1,2-dehydration is about 67 kcal mol−1, which is consistent with the limited experimental data. Protonation and metal complexation significantly reduce this activation barrier and thus, facilitate more rapid reaction. With the addition of alkali metals, the rate of dehydration can increase by a factor of 108 while addition of a proton can lead to an increase of a factor of 1023.
Whitehead groups of localizations and the endomorphism class group

Abstract We compute the Whitehead groups of the associative rings in a class which includes (twisted) formal power series rings and the augmentation localizations of group rings and polynomial rings. For any associative ring A, we obtain an invariant of a pair (P,α), where P is a finitely generated projective A-module and α :P→P is an endomorphism. This invariant determines (P,α) up to extensions, yielding a computation of the (reduced) endomorphism class group End 0 (A) . We also refine the analysis by Pajitnov and Ranicki of the Whitehead group of the Novikov ring, a computation which Pajitnov has used in work on circle-valued Morse theory.
Random Unitary Matrices, Permutations and Painlevé

This paper is concerned with certain connections between the ensemble of n×n unitary matrices – specifically the characteristic function of the random variable tr(U) – and combinatorics – specifically Ulam's problem concerning the distribution of the length of the longest increasing subsequence in permutation groups – and the appearance of Painleve functions in the answers to apparently unrelated questions. Among the results is a representation in terms of a Painleve V function for the characteristic function of tr(U) and (using recent results of Baik, Deift and Johansson) an expression in terms of a Painleve II function for the limiting distribution of the length of the longest increasing subsequence in the hyperoctahedral groups.
Magnetic uniaxial anisotropy of Fe films grown on vicinal Ag(001)

Step-induced magnetic anisotropy was investigated in Fe films grown on a vicinal Ag(001) substrate using the surface magneto-optic Kerr effect technique. We found that the step-induced magnetic anisotropy is independent of the Fe film thickness up to 61 ML. Step decoration with Ag or Pd atoms also shows no effect on the step-induced magnetic anisotropy. These results indicate that the step-induced magnetic anisotropy in this system does not localize at the step edges. We suggest that strain inside the Fe film due to the large lattice mismatch between fcc Ag and bcc Fe in the normal direction of the film is the dominant contribution to the step-induced magnetic anisotropy in this system.
An X-ray and Optical Investigation of the Starburst-driven Superwind in the Galaxy Merger Arp 299

We present a detailed investigation of the X-ray and optical properties of the starburst-merger system Arp299(NGC 3690, Mrk 171), with an emphasis on its spectacular gaseous nebula.
Uncertainties in Global Ocean Surface Heat Flux Climatologies Derived from Ship Observations

Abstract A methodology to define uncertainties associated with ocean surface heat flux calculations has been developed and applied to a global climatology that utilizes a summary of the Comprehensive Ocean–Atmosphere Data Set surface observations. Systematic and random uncertainties in the net oceanic heat flux and each of its four components at individual grid points and for zonal averages have been estimated for each calendar month and for the annual mean. The most important uncertainties of the 2° × 2° grid cell values of each of the heat fluxes are described. Annual mean net shortwave flux random uncertainties associated with errors in estimating cloud cover in the Tropics yield total uncertainties that are greater than 25 W m−2. In the northern latitudes, where the large number of observations substantially reduces the influence of these random errors, the systematic uncertainties in the utilized parameterization are largely responsible for total uncertainties in the shortwave fluxes, which usually r...
Enantioconvergent cross-couplings of racemic alkylmetal reagents with unactivated secondary alkyl electrophiles: catalytic asymmetric Negishi α-alkylations of N-Boc-pyrrolidine.

Although enantioconvergent alkyl–alkyl couplings of racemic electrophiles have been developed, there have been no reports of the corresponding reactions of racemic nucleophiles. Herein we describe Negishi cross-couplings of racemic α-zincated N-Boc-pyrrolidine with unactivated secondary halides, thus providing a one-pot, catalytic asymmetric method for the synthesis of a range of 2-alkylpyrrolidines (an important family of target molecules) from N-Boc-pyrrolidine, a commercially available precursor. Preliminary mechanistic studies indicated that two of the most straightforward mechanisms for enantioconvergence (dynamic kinetic resolution of the organometallic coupling partner and a simple β-hydride elimination/β-migratory insertion pathway) are unlikely to be operative.
Enantioselective Conjugate Silyl Additions to Cyclic and Acyclic Unsaturated Carbonyls Catalyzed by Cu Complexes of Chiral N-Heterocyclic Carbenes

An efficient Cu-catalyzed protocol for enantioselective addition of a dimethylphenylsilanyl group to a wide range of cyclic and acyclic unsaturated ketones, esters, acrylonitriles, and alpha,beta,gamma,delta-dienones is disclosed. Reactions are performed in the presence of 1-2 mol % of commercially available and inexpensive CuCl, a readily accessible monodentate imidazolinium salt, and commercially available (dimethylphenylsilyl)pinacolatoboron. Cu-catalyzed enantioselective conjugate additions proceed to completion within only 2 h to afford the desired silanes in 87-97% yield and 90:10-99:1 enantiomeric ratio (er). Use of a proton source (e.g., MeOH) is not required; accordingly, synthetically versatile alpha-silyl boron enolates can be obtained. The special utility of the present protocol, in comparison with the related catalytic enantioselective aldol and boronate conjugate additions, is discussed and illustrated through various functionalizations of the enantiomerically enriched beta-silylcarbonyls.
The role of coordinate systems in boundary-layer theory

The boundary layer approximation to a given flow problem is not invariant if different coordinate systems are used in the approximation process. However, a correlation theorem (Theorem 1) is given, which states that the boundary layer solution with respect to any given system can be found, by a simple substitution, from that with respect to any other system. On the basis of this theorem, the dependence of the solution on the choice of coordinates is investigated in detail. The skin friction is invariant, but the flow field is not invariant. At large distances from the wall, the flow field given by boundary layer theory depends almost entirely on the choice of coordinates, rather than on the physical problem. This dependence may be used to obtain a complete matching between the boundary layer solution and the external flow, in the following sense: Theorem 2 states how a coordinate system can be found such that the boundary layer solution with respect to this system is valid as an approximation for the entire flow field. It contains the external flow and the flow due to displacement thickness. The discussion is restricted to steady, two-dimensional, incompressible flow without separation. These restrictions, however, are not essential for many of the results.
Age of immersion as a predictor of foreign accent

This study examines the relationship between age of immersion (AOI) and the degree of perceived accent (DPA) that raters who speak native English perceive in the speech of Mandarin speakers who learned English as a second language. AOI and speech samples of variable length and linguistic context (single words, sentences, short paragraph, and self-generated picture narration) were collected from the target group (n=32, AOI=3–16) and from native speaker controls. A moderately trained native speaker panel of college students then rated the samples on how “native” they sounded using a continuous scale. Rating was broken over three separate sessions to relieve fatigue, and a reliability measure was administered at the onset and termination of each session to ensure consistency. Reliable performance was demonstrated both across judges and across sessions and indicated no single AOI demarcated a “critical period.” Instead, DPA was found to deviate from native in a highly linear manner with AOI, as did speakers' tendencies to noticeably deflect from this line. These deviations began at an AOI of about 5, although some speakers bottomed out with an AOI as early as 7, whereas nearly native ratings were given to others whose AOI was greater than 5. Females were rated as more native and variably accented than males. Ratings of native decreased with sampling length but increased with extemporization, the effect of AOI on DPA being similar for all sampling types.
Near horizon geometry of rotating black holes in five dimensions

Abstract We interpret the general rotating black holes in five dimensions as rotating black strings in six dimensions. In the near-horizon limit the geometry is locally AdS3 × S3, as in the non-rotating case. However, the global structure couples the AdS3 and the S3, giving angular velocity to the S3. The asymptotic geometry is exploited to count the microstates and recover the precise value of the Bekenstein-Hawking entropy, with rotation taken properly into account. We discuss the perturbation spectrum of the rotating black hole, and its relation to the underlying conformal field theory.
Spray-Dried Iron Fischer−Tropsch Catalysts. 2. Effect of Carburization on Catalyst Attrition Resistance

Spray drying has been recently used by this research team in the preparation of Fe Fischer−Tropsch catalysts with higher attrition resistance for use in slurry bubble column reactors. In the first paper in this series, the effects of the type, concentration, and network structure of SiO2 on the attrition resistance of two series of spray-dried Fe catalysts in their calcined state were explored and the dependence of catalyst attrition resistance on catalyst particle density was discussed. As a continuation of our previous effort, the effect of carburization on catalyst attrition resistance was studied and is presented in this paper. After carburization, the majority component of the catalysts, hematite (Fe2O3), was converted to iron carbides, mostly χ-carbide (Fe2C5). Breakage of individual catalyst particles and fines formation, which can be considered as evidence of chemical attrition, was only observed during carburization of the catalyst with low SiO2 concentration <9 wt %. With an increase in the tota...
Strategic awareness within top management teams

‘Strategic awareness’ is viewed in two ways: the extent to which an executive's perception of the organization's strategy aligns (a) with the organization's ‘realized’ strategy and (b) with the chief executive's perception. Strategic awareness is positively related to hierarchical level, but differs across the three industries studied. Awareness is greater in organizations that have recently changed their strategies than in those that have not.
Observations of limb flares with a soft X-ray telescope

The structure and evolution of 26 limb flares have been observed with a soft X-ray telescope flown on Skylab. The results are: (1) One or more well defined loops were the only structures of flare intensity observed during the rise phase and near flare maximum, except for knots which were close to the resolution of the telescope; (2) the flare core features were always sharply defined during rise phase; and (3) for the twenty events which contained loops, the geometry of the structure near maximum was that of a loop in ten cases, a loop with a spike at the top in four cases, a cusp or triangle in four cases, and a cusp combined with a spike in another two cases. Based on observation of the original film, it is suggested that flares which underwent large scale deformations had become unstable to MHD kinks. This implies that these flares occurred in magnetic flux tubes through which significant currents were flowing.
Evolution of Fragments Formed at the Rupture of a Knotted Alkane Molecule

Common experience tells us that a knot significantly weakens the polymer strand in which it is tied, which, in turn, leads to more facile chain rupture under tensile loading. Using first-principles molecular dynamics calculations we describe the dynamical evolution of the radicals that form after chain rupture of a single knotted alkane molecule in its very early stages of life. They are able to recombine, to form cyclic alkanes, and to undergo disproportionation phenomena with nearby chain segments. The breaking of a single knotted polymer chain under mechanical loading is thus predicted to reveal phenomena falling in the domain of ultrafast spectroscopy.
Materials Performance in Advanced Combustion Systems

A number of advanced technologies are being developed to convert coal into clean fuels for use as feedstock in chemical plants and for power generation. From the standpoint of component materials, the environments created by coal conversion and combustion in these technologies and their interactions with materials are of interest. The trend in the new or advanced systems is to improve thermal efficiency and reduce the environmental impact of the process effluents. This paper discusses several systems that are under development and identifies requirements for materials application in those systems. Available data on the performance of materials in several of the environments are used to examine the performance envelopes for materials for several of the systems and to identify needs for additional work in different areas.
Reversible binding of nitric oxide to an Fe(III) complex of a tetra-amido macrocycle

Nitric oxide binds reversibly to the Fe(III) complex of a well-developed tetra-amido macrocyclic ligand. Reaction with NO results in formation of a species consistent with an S = 1 {Fe–NO}6 ground state as characterized by UV-vis, IR, EPR, and Mossbauer spectroscopy. The resultant nitrosyl is labile and dissociates readily upon purging with N2, thus providing a rare example of reversible NO binding to non-heme iron.
Monopolistic competition, endogenous markups, and growth

Markup variations brought about by changing demand conditions can have a significant impact on the growth dynamics of imperfectly competitive economies: they can generate multiple steady states, as well as multiple equilibrium paths for given initial conditions. We illustrate that result in the context of two alternative models. In the first model equilibrium markups depend on the aggregate savings rate. In the second model the markup level varies with the range of intermediate goods available. We discuss some of the empirical implications of the class of models introduced in the paper.
Privatization of natural monopoly public enterprises: The regulation issue

The paper presents a simple model that calculates — as a percentage of industry revenues — the welfare gains or losses that might ensue when a public enterprise natural monopoly is replaced by a profit maximizing private monopoly. The model incorporates both the pre-privatization demand elasticity and production efficiency changes subsequent to privatization. The magnitude of the welfare changes suggests that allocative efficiency improvements do not provide a compelling rationale for post-privatization regulation. Greater consideration must be given to other regulatory objectives including distributional concerns and the need to create an institutional environment that encourages investment.
Making Clean Energy with a Kerr Black Hole: A Tokamak Model for Gamma-Ray Bursts

In this paper we present a model for making clean energy with a Kerr black hole. Consider a Kerr black hole with a dense plasma torus spinning around it. A toroidal electric current flows on the surface of the torus, which generates a poloidal magnetic field outside the torus. On the surface of the torus the magnetic field is parallel to the surface. The closed magnetic field lines winding around the torus compress and confine the plasma in the torus, as in the case of tokamaks. Although it is unclear whether such a model is stable, we look into the consequences if the model is stable. If the magnetic field is strong enough, the baryonic contamination from the plasma in the torus is greatly suppressed by the magnetic confinement, and a clean magnetosphere of electron-positron pairs is built up around the black hole. Since there are no open magnetic field lines threading the torus and no accretion, the power of the torus is zero. If some magnetic field lines threading the black hole are open and connect with loads, clean energy can be extracted from the Kerr black hole by the Blandford-Znajek mechanism. The model may be relevant to gamma-ray bursts. The energy in the Poynting flux produced by the Blandford-Znajek mechanism is converted into the kinetic energy of the electron-positron pairs in the magnetosphere around the black hole, which generates two oppositely directed jets of electron-positron pairs with superhigh bulk Lorentz factors. The jets collide and interact with the interstellar medium, which may produce gamma-ray bursts and the afterglows.
Carrier-induced group-velocity dispersion and pulse compression in semiconductor laser amplifiers

The effect of gain dispersion on pulse amplification in semiconductor laser amplifiers is investigated theoretically. A novel phenomenon, referred to as carrier-induced group-velocity dispersion, is shown to influence considerably the amplified pulse. Chirped input pulses are predicted to be compressed in the presence of carrier-induced dispersion even when the amplifier operates far below saturation. The dependence of the compression factor on device parameters such as the pulse width, the amplifier gain, and the linewidth enhancement factor are studied using a simple analytic model. The results are important for optical communication systems as they imply that semiconductor laser amplifiers can be used to compensate simultaneously for the effects of both fibre loss and fibre dispersion when used as in-line amplifiers. >
Use of the Intramolecular Heck Reaction for Forming Congested Quaternary Carbon Stereocenters. Stereocontrolled Total Synthesis of (±)-Gelsemine

Intramolecular Heck reactions of α,β-unsaturated 2-haloanilides derived from azatricyclo[4.4.0.02,8]decanone 5 efficiently install the congested spirooxindole functionality of gelsemine. Depending upon the Heck reaction conditions and the nature of the β-substituent, either products having the natural or unnatural configuration of the spirooxindole group are formed predominantly. Efforts to elaborate the hydropyran ring of gelsemine from the endo-oriented nitrile substituent of pentacyclic Heck product 18 were unsuccessful. Important steps in the ultimately successful route to (±)-gelsemine (1) are as follows: (a) intramolecular Heck reaction of tricyclic β-methoxy α,β-unsaturated 2-iodoanilide 68 in the presence of silver phosphate to form pentacyclic product 69 having the unnatural configuration of the spirooxindole fragment, (b) formation of hexacyclic aziridine 80 from the reaction of cyanide with intermediate 79 containing an N-methoxycarbonyl-β-bromoethylamine fragment, (c) introduction of C17 by r...
DNA methylation and gene silencing in cancer

Epigenetic changes such as DNA methylation act to regulate gene expression in normal mammalian development. However, promoter hypermethylation also plays a major role in cancer through transcriptional silencing of critical growth regulators such as tumor suppressor genes. Other chromatin modifications, such as histone deacetylation and chromatin-binding proteins, affect local chromatin structure and, in concert with DNA methylation, regulate gene transcription. The DNA methylation inhibitors azacitidine and decitabine can induce functional re-expression of aberrantly silenced genes in cancer, causing growth arrest and apoptosis in tumor cells. These agents, along with inhibitors of histone deacetylation, have shown clinical activity in the treatment of certain hematologic malignancies where gene hypermethylation occurs. This review examines alteration in DNA methylation in cancer, effects on gene expression, and implications for the use of hypomethylating agents in the treatment of cancer.
Basis/background for ASME code section XI proposed Appendix VIII : ultrasonic examination performance demonstration

Abstract The ASME Boiler and Pressure Vessel Code Section XI subcommittee on Inservice Inspection of Nuclear Power Plant Components has prepared and forwarded a proposed mandatory Appendix VIII, “Performance Demonstration for Ultrasonic Examination Systems.” Appendix VIII, when published, would provide a much needed solution to problems encountered when the current Code-prescribed ultrasonic examination methodology is applied to detect and size service-induced damage mechanisms. This paper provides the background and technical basis for the proposed Appendix VIII.
Estimating a distribution function in the presence of auxiliary information

For estimating the distribution functionF of a population, the empirical or sample distribution functionFn has been studied extensively. Qin and Lawless (1994) have proposed an alternative estimator\(\hat F_n \) for estimatingF in the presence of auxiliary information under a semiparametric model. They have also proved the point-wise asymptotic normality of\(\hat F_n \). In this paper, we establish the weak convergence of\(\hat F_n \) to a Gaussian process and show that the asymptotic variance function of\(\hat F_n \) is uniformly smaller than that ofFn. As an application of\(\hat F_n \), we propose to employ the meanOpen image in new window and varianceŜn2 of\(\hat F_n \) to estimate the population mean and variance in the presence of auxiliary information. A simulation study is presented to assess the finite sample performance of the proposed estimators\(\hat F_n \), andŜn2.
Picture changing operators and space-time supersymmetry

Abstract We explore the geometrical properties of fermionic vertex operators for a NSR superstring in order to establish the connection between world-sheet and target space supersymmetries. The mechanism of picture changing is obtained as a result of imposing certain constraints on a world-sheet gauge group of the NSR superstring theory. We find that picture-changing operators of different integer ghost numbers form a polynomial ring. By using properties of the picture-changing formalism, we establish a relation between the NSR and GS string theories. We show that, up to picture-changing transformations, the stress-energy tensor of the N = 1 NSR superstring theory can be obtained from the stress-energy tensor of the N = 1 GS superstring theory in a flat background by a simple field redefinition. The equations of motion of a GS superstring are shown to be fulfilled in the NSR operator formalism; they are also shown to be invariant under κ-symmetry, in terms of operator products in the NSR theory. This allows us to derive the space-time supersymmetry transformation laws for the NSR string theory. Then, we explore the properties of the κ-symmetry in the NSR formalism and find that it leads to some new relations between bosonic and fermionic correlation functions.
Synthesis of 6α-hydroxypaclitaxel, the major human metabolite of paclitaxel

Abstract 6α-Hydroxypaclitaxel, the major human metabolite of paclitaxel, was synthesized via epimerization of 6α-hydroxy-7-epipaclitaxel, which was prepared from paclitaxel in four steps in high yield. Various epimerization conditions were investigated, and the optimum conditions using DBU in xylenes afforded 80–88% isolated yield based on unrecovered starting material, along with 4-deacetyl analogs as minor products. The stereochemistry of paclitaxel 6,7-epoxide was revised in the course of this work.
Issues in Freight Transportation Regulation: Reply

The main purpose of our 1979 article, written one year prior to congressional enactment of motor carrier and railroad regulatory reform, was to identify the major transportation regulatory issues. We intended to avoid taking a proor anti-regulation position. We simply said the literature did not clearly agree on what should be done. The stated objective of the Wright comment is "to clarify the economic problems in the continuing debate on further deregulation" (p. 162). Wright pursues his objective by citing 47 articles and papers on the subject of freight transportation regulation. Pulling together and summarizing these 47 articles makes a significant contribution to the history leading to the Motor Carrier Act of 1980 (MCA). However, we observe that almost all of the references selected by Wright support deregulation. Commenting on the historical debate which preceded economic regulation of the motor carrier industry, Wright states, "There is no evidence for the allegation that economic regulation of motor carriers arose from public concern that the industry was 'overcrowded with small uneconomic units unable to satisfy the minimum standards of safety, service, or financial responsibility' " (p. 163). The following is a concise summary of the reasoning behind congressional enactment of the statutes that lead to the regulation of the motor carrier industry:
Are patents strategic barriers to entry

Abstract Patent protection restricts entry rather than preventing it. In case of a process innovation, it forces a potential entrant to sufficiently differentiate his production technology. We investigate whether a patentholder threatened by entry can strategically renew her patent. For low demand, the patent renewal is sufficient to deter entry, whereas a high demand attracts competitor, even if there is a patent. On the other hand, the renewal decision can signal information to an uninformed entrant whenever the patentholder is informed. This may act as a barrier to entry. Thus, a patent is renewed more frequently in presence of asymmetric information.
A measurement of the medium-scale anisotropy in the cosmic microwave background radiation

Observations from the first flight of the Medium Scale Anisotropy Measurement (MSAM) are analyzed to place limits on Gaussian fluctuations in the cosmic microwave background radiation (CMBR). This instrument chops a 30 min beam in a three-position pattern with a throw of +/- 40 min; the resulting data is analyzed in statistically independent single- and double-difference sets. We observe in four spectral channels at 5.6, 9.0, 16.5, and 22.5/cm, allowing the separation of interstellar dust emission from CMBR fluctuations. The dust component is correlated with the IRAS 100 micron map. The CMBR component has two regions where the signature of an unresolved source is seen. Rejecting these two source regions, we obtain a detection of fluctuations which match CMBR in our spectral bands of 0.6 x 10(exp -5) is less than Delta (T)/T is less than 2.2 x 10(exp -5) (90% CL interval) for total rms Gaussian fluctuations with correlation angle 0.5 deg, using the single-difference demodulation. Fore the double difference demodulation, the result is 1.1 x 10(exp -5) is less than Delta(T)/T is less than 3.1 x 10(exp -5) (90% CL interval) at a correlation angle of 0.3 deg.
Sharp edges of planetary rings

The ring systems of Saturn and Uranus exhibit several sharp edges across which the optical depth drops from order unity to essentially zero. At least two and perhaps all of these features are associated with the location of orbital resonances between a satellite and the ring particles. It is remarkable that the optical depth varies on a distance scale which is much finer than that over which angular momentum can be transferred between a satellite and the ring material. The important features of this phenomenon are: (1) A perturbed band of width Δa/a ≃ (M_s/M_p)^(½) adjacent to the edge within which the angular momentum transfer occurs. (2) Streamlines perturbed such that the angular momentum luminosity decreases smoothly across the band to zero at the edge even though the optical depth remains constant. (3) Dynamical equilibrium requires a relation between the random velocity, the rate of deformation and the optical depth.
The Talent system: TEXTRACT architecture and data model

We present the architecture and data model for TEXTRACT, a robust, scalable and configurable document analysis framework. TEXTRACT has been engineered as a pipeline architecture, allowing for rapid prototyping and application development by freely mixing reusable, existing, language analysis plugins and custom, new, plugins with customizable functionality. We discuss design issues which arise from requirements of industrial strength efficiency and scalability, and which are further constrained by plugin interactions, both among themselves, and with a common data model comprising an annotation store, document vocabulary and a lexical cache. We exemplify some of these by focusing on a meta-plugin: an interpreter for annotation-based finite state transduction, through which many linguistic filters can be implemented as stand-alone plugins. The framework and component plugins have been extensively deployed in both research and industrial environments, for a broad range of text analysis and mining tasks.
On the Geodesic Voronoi Diagram of Point Sites in a Simple Polygon

Given a simple polygon with n sides in the plane and a set of k point “sites” in its interior or on the boundary, compute the Voronol diagram of the set of sites using the internal “geodesic” distance inside the polygon as the metric. We describe an O((n+k) log2(n+k)) time algorithm for solving this problem and sketch a faster O((n+k) log(n+k)) algorithm for the case when the set of sites includes all reflex vertices of the polygon in question.
Eta Invariant and Conformal Cobordism

In this note we study the problem of conformally flat structures bounding conformally flat structures and show that the eta invariants give obstructions. These lead us to the definition of an Abelian group, the conformal cobordism group, which classifies the conformally flat structures according to whether they bound conformally flat structures in a conformally invariant way. The eta invariant gives rise to a homomorphism from this group to the circle group, which can be highly nontrivial. It remains an interesting question of how to compute this group.
Hydroxy-substituted triarylcarbenium bromides. Synthesis, structure, derivatization and facile conversion to highly substituted xanthenes

The tris(3,5-dialkyl-2-hydroxyphenyl)carbenium bromides (2a) (3-tert-butyl, 5-methyl) and 2b (3,5-di-tert-butyl) have been prepared by the oxidation of the corresponding tris(3,5-dialkyl-2-hydroxyphenyl)methanes with bromine. Compound 2a has been fully characterized by a single crystal X-ray study, which shows that the bromide, atypically, does not bind to the central carbon atom. The materials 2 are reactive, and the trityl alcohol (4a), methyl (7a, 7b) and phenyl (8a) derivatives can be readily prepared in good yield by reaction of 2 with the appropriate anions; X-ray structures for 4a, 7b (as its lithium salt) and 8a are reported. In solution, 2a and 4a undergo a facile, uncatalyzed, controllable intramolecular dehydration to produce the corresponding xanthene derivatives; X-ray structures for the xanthene carbocation (bromide salt) (3a) and the 9-hydroxy derivative (5a) are also reported.
Coordination chemistry of metal surfaces and metal complexes

The coordination chemistry of two isomeric molecules, acetonitrile and methyl isocyanide, has been characterized for (A) single crystal nickel surfaces as a function of crystallography and surface composition, (B) nickel catalyst surfaces and (C) molecular mononuclear and polynuclear metal complexes. Conditions have been established for the catalytic isomerization of methyl isocyanide to acetonitrile within these nickel surface and molecular complex regimes. A comparison is made of the acetonitrile and methyl isocyanide chemistry between the surface and molecular complex areas.
Cationic group 13 complexes

Abstract In order to provide a foundation for continued work on group 13 cations as a class of distinct compounds, this overview will provide a classification system based upon the reactions that are used in their formation. The literature on the formation of aluminum cations is broad so the classification system will be developed with a focus on this element. However, in most cases the reaction types are of sufficient generality such that they can be applied to gallium and indium as well. In some instances the formation of gallium and indium cations occur through unique routes. In these cases new reaction types will be defined in the gallium and indium chemistry. At this point in time the interest in group 13 cations has largely been fundamental in nature. However, there is a growing awareness that these types of complexes may be applicable to a wide range of Lewis acid mediated reactions and catalytic applications. Brief mention will be made of those that are currently known.
Norms and spectral radii of linear fractional composition operators on the ball

Abstract We give a new proof that every linear fractional map of the unit ball induces a bounded composition operator on the standard scale of Hilbert function spaces on the ball, and obtain new norm bounds analogous to the standard one-variable estimates. We also show that Cowen's one-variable spectral radius formula extends to these operators. The key observation underlying these results is that every linear fractional map of the ball belongs to the Schur–Agler class.
Stochastic Calculus for a Time-Changed Semimartingale and the Associated Stochastic Differential Equations

It is shown that under a certain condition on a semimartingale and a time-change, any stochastic integral driven by the time-changed semimartingale is a time-changed stochastic integral driven by the original semimartingale. As a direct consequence, a specialized form of the Ito formula is derived. When a standard Brownian motion is the original semimartingale, classical Ito stochastic differential equations driven by the Brownian motion with drift extend to a larger class of stochastic differential equations involving a time-change with continuous paths. A form of the general solution of linear equations in this new class is established, followed by consideration of some examples analogous to the classical equations. Through these examples, each coefficient of the stochastic differential equations in the new class is given meaning. The new feature is the coexistence of a usual drift term along with a term related to the time-change.
Chalcogenoamides: Convenient Preparations and Reactions With Metal Compounds

New Al-E (E: S, Se, Te) reagents, mixtures of (iBu2AlE)2 and (iBuAlE)n, were produced by the reaction of iBu2AlH with elemental chalcogens. They directly convert amides to chalcogenoamides. Seleno- and telluroamides serve as the ligands in their metal complexes or react with MAc2 (M: Zn, Cd, Hg) to give MSe or MTe powders.
Precise determinations of the isotopic compositions and atomic weights of molybdenum, tellurium, tin and tungsten using ICP magnetic sector multiple collector mass spectrometry

Abstract Precise determinations of the isotopic compositions of molybdenum, tellurium, tin and tungsten were obtained utilizing an inductively coupled plasma (ICP) source magnetic sector mass spectrometer equipped with multiple collectors. The results of this study are comparable to those measured by conventional and negative thermal ionization mass spectrometry (TIMS and NTIMS) and the values recommended by the International Union of Pure and Applied Chemistry (IUPAC), but with improvement in precision by up to two orders of magnitude. The relative isotopic abundances and atomic weight for each element calculated from the data obtained in this study are also in excellent agreement with previously published values. The only disagreement between this study and IUPAC recommended values is for tellurium. However, with the exception of 130Te, the Te data are in good agreement with those reported in a recent study by De Laeter [1]. The results of this study demonstrate the capability of this new instrument to produce precise and reproducible isotopic data for elements that are difficult to ionize and measure with TIMS. Furthermore, the greater precision of isotopic measurements possible with the ICP source multiple collector magnet sector mass spectrometer greatly enhances the prospects for research on the distribution and isotopic compositions of these elements in terrestrial and meteoritic materials.
Excess Returns, Inflation and the Efficiency of the Housing Market

This paper examines the influence that unexpected inflation has on the reported time pattern in housing returns. Two alternative models of expected inflation are used to study its effect: a rational expectations model and an adaptive expectations model. Findings indicate that both estimates of unexpected inflation are positively correlated with excess returns to housing. If inflation expectations are assumed to have been adaptive during the 1970s and early 1980s, serial correlation in the excess returns is shown to be greatly diminished when adjusted to control for unexpected inflation. However, substantial inertia in the pattern of the adjusted return series remains.
Recent Observations of High-Degree Solar p-Mode Oscillations at the Kitt Peak National Observatory

Abstract. A brief summary is given of a program which is currently being carried out with the McMath telescope of the Kitt Peak National Observatory in order to study high-degree (l ≳ 150) solar p-mode oscillations. This program uses a 244 × 248 pixel CID camera and the main spectrograph of the McMath telescope to obtain velocity-time maps of the oscillations which can be converted into two-dimensional (k h - ω)) power spectra of the oscillations. Several different regions of the solar spectrum have been used in order to study the oscillations at different elevations in the solar atmosphere. The program concentrates on eastward- and westward-propagating sectoral harmonic waves so that measurements can be made of the absolute rotational velocities of the solar photospheric and shallow sub-photo spheric layers. Some preliminary results from this program are now available. First, we have been unable to confirm the existence of a radial gradient in the equatorial rotational velocity as was previously suggested. Second, we have indeed been able to confirm the presence of p-mode waves in the solar chromosphere as was first suggested by Rhodes et al. (1977). Third, we have been able to demonstrate differences in photospheric and chrornospheric power spectra.
Representations of matroids and free resolutions for multigraded modules

Let k be a field, let R=k[x1,…,xm] be a polynomial ring with the standard Zm-grading (multigrading), let L be a Noetherian multigraded R-module, and let E→ΦG→L→0 be a finite free multigraded presentation of L over R. Given a choice S of a multihomogeneous basis of E, we construct an explicit canonical finite free multigraded resolution T•(Φ,S) of the R-module L. In the case of monomial ideals our construction recovers the Taylor resolution. A main ingredient of our work is a new linear algebra construction of independent interest, which produces from a representation ϕ over k of a matroid M a canonical finite complex of finite dimensional k-vector spaces T•(ϕ) that is a resolution of Kerϕ. We also show that the length of T•(ϕ) and the dimensions of its components are combinatorial invariants of the matroid M, and are independent of the representation map ϕ.