cssi/SciSciGPT-SciSciNet huggingface dataset:
Tetrathiafulvalene quinones, hydroquinones and esters

Abstract Benzocyclohexa-2,5-diene-1,4-dione-1,3-thiole-2-thione (2) was synthesized starting with 2,3-dichloronapthoquinone (1). Compounds 3 and 4 were also obtained; however, the yield of 2 can be increased through control of the temperature and reaction time. Reaction of 2 with triethylphosphite gave 5 and the tetrathiafulvalene ester 6. The tetrathiafulvalenequinone (9) was obtained by hydrolysis of 6 followed by oxidation of 8. Compound 9 was obtained more directly by hydrogenation of 2 followed by coupling with triethylphosphite and oxidation. Chloranil was used to prepare the dithiafulvene quinone 12 which was reduced, coupled with triethylphosphite to form, presumably , polymer 13. The reactions were repeated using the hexanoic acid esters of the corresponding hydroquinone thiafulvalenes. The crystal structures of 2, 3, 4, 5, 6a and 10 were determined by X-ray diffraction. Cyclic voltammetry studies show the tetrathiafulvalene quinones reduce like quinones, but do not exhibit the oxidation properties of tetrathiafulvalenes.
The Managementality Gap

While analyzing situations before making vital decisions has been practiced by realistic politicians since Machiavelli's time, business managers constantly make decisions with inadequate information and under the pressures of insufficient time. Too few managers have reached the point where they rigorously analyze alternate consequences before choosing one solution over another. A prime problem is the different mental attitude of those involved?today's top executives and the more recent management-oriented technical graduates. The potential contributions of management science to the business process are limited by the gap between the mentality of the practitioners of management science and currently successful managers. The challenge of developing certain interactions, mutual trust, and commitment is offered to both sides. Melding of the disparate talents of the charismatic intuitive leader, the management scientist, and the behavioral scientist is needed to help close the "managementality gap."
A new theory of content II : Model theory and some alternatives

This paper develops a semantical model – theoretic account of (logical) content complementing the syntactically specified account of content developed in “A New Theory of Content I”, JPL 23: 596–620, 1994. Proofs of Completeness are given for both propositional and quantificational languages (without identity). Means for handling a quantificational language with identity are also explored. Finally, this new notion of content is compared, in respect of both logical properties and philosophical applications, to alternative partitions of the standard consequence class relation proposed by Stelzner, Schurz and Wiengartner.
Base-catalyzed one-step synthesis of 5,7-disubstituted-1,2,4-triazolo[1,5-a]pyrimidines

We report a practical high-yield synthesis of 5,7-disubstituted-1,2,4-triazolo[1,5-a]pyrimidines using a base-assisted cyclocondensation of chalcone and 1,2,4-triazol-3-amine in an open reaction vessel. The same conditions can also be used for the preparation of novel imidazo[1,2-a]pyrimidine derivatives.
Two-dimensional mirror symmetry from M-theory

Abstract We construct two-dimensional gauge theories with N = (4,4) supersymmetry from branes of type IIA string theory. Quantum effects in the two-dimensional gauge theory are analyzed by embedding the IIA brane construction into M-theory. We find that the Coulomb branch of one theory and the Higgs branch of a mirror theory become equivalent at strong coupling. A relationship to the decoupling limit of the type IIA and IIB 5-branes in Matrix theory is shown. T-duality between the ALE metric and the wormhole metric of Callan, Harvey, and Strominger is discussed from a brane perspective and some puzzles regarding string duality resolved. We comment on the existence of a quantum Higgs branch in two-dimensional theories. Branes prove to be useful tools in analyzing singular conformal field theories.
Effects of quasar feedback in galaxy groups

We study the effect of quasar feedback on distributions of baryons in galaxy groups using high-resolution numerical simulations. We use the entropy-conserving GADGET code that includes gas cooling and star formation, modified to include a physically based model of quasar feedback. For a sample of 10 galaxy group-sized dark matter haloes with masses in the range of 1-5 x 10 13 M ⊙ h -1 , star formation is suppressed by more than 50 per cent in the inner regions due to the additional pressure support by quasar feedback, while gas is driven from the inner region towards the outer region of the haloes. As a result, the average gas density is 50 per cent lower in the inner region and 10 per cent higher in the outer region in the simulation, compared to a similar simulation with no quasar feedback. Gas pressure is also higher in the outer region, while temperature and entropy are enhanced in the inner region. The total group gas fraction in the two simulations generally differs by less than 10 per cent. We also find a small change of the total thermal Sunyaev-Zeldovich distortion, leading to 10 per cent changes in the microwave angular power spectrum at angular scales below 2 arcmin.
Analyzing machupo virus-receptor binding by molecular dynamics simulations.

In many biological applications, we would like to be able to computationally predict mutational effects on affinity in protein–protein interactions. However, many commonly used methods to predict these effects perform poorly in important test cases. In particular, the effects of multiple mutations, non alanine substitutions, and flexible loops are difficult to predict with available tools and protocols. We present here an existing method applied in a novel way to a new test case; we interrogate affinity differences resulting from mutations in a host–virus protein–protein interface. We use steered molecular dynamics (SMD) to computationally pull the machupo virus (MACV) spike glycoprotein (GP1) away from the human transferrin receptor (hTfR1). We then approximate affinity using the maximum applied force of separation and the area under the force-versus-distance curve. We find, even without the rigor and planning required for free energy calculations, that these quantities can provide novel biophysical insight into the GP1/hTfR1 interaction. First, with no prior knowledge of the system we can differentiate among wild type and mutant complexes. Moreover, we show that this simple SMD scheme correlates well with relative free energy differences computed via free energy perturbation. Second, although the static co-crystal structure shows two large hydrogen-bonding networks in the GP1/hTfR1 interface, our simulations indicate that one of them may not be important for tight binding. Third, one viral site known to be critical for infection may mark an important evolutionary suppressor site for infection-resistant hTfR1 mutants. Finally, our approach provides a framework to compare the effects of multiple mutations, individually and jointly, on protein–protein interactions.
The consideration of immunotherapy in the treatment of allergic asthma

Background Immunotherapy (IT) has undergone rigorous trials to evaluate its therapeutic benefit in the treatment of allergic respiratory disease. The tools of molecular biology have provided a framework with which to begin to understand the mechanistic effects of IT on the underlying inflammatory component of allergic respiratory disease. Results The clinical relevance of these observations belies our understanding of allergic inflammation as the subsoil for the development of abnormal airway physiology, heightened bronchial reactivity, and the development of chronic asthmatic symptomatology. Conclusions IT provides the potential to downregulate this inflammatory cascade, reduce IgE antibody production, and attenuate symptoms. Conceptually, early intervention of allergic disease holds the most promise as a therapeutic intervention capable of arresting the progression of the disease, altering the severity of the disease, and/or preventing the development of the respiratory disease process.
Positive diagrams for Seifert fibered spaces

Abstract Every (compact, orientable) 3-manifold can be represented by a positive Heegaard diagram (all curve crossings in the same direction), but the argument for this suggests that the minimal genus, phg( M ), for a positive diagram may be much larger than the minimal genus, hg( M ), among all diagrams. This paper investigates this situation for the class of closed orientable Seifert manifolds over an orientable base. We show that phg( M )=hg( M ) for most of these manifolds and phg( M )⩽hg( M )+2 always holds. The cases phg( M )>hg( M ) are determined and occur when the minimal genus splitting is “horizontal”. The arguments provide an alternate proof distinguishing these from “vertical” splittings.
Limits of fractality: Zeno boxes and relativistic particles

Abstract Physical fractals invariably have upper and lower limits for their fractal structure. Berry has shown that a particle sharply confined to a box has a wave function that is fractal both in time and space, with no lower limit. In this paper, two idealizations of this picture are softened and a corresponding lower bound for fractality obtained. For a box created by repeated measurements (a la the quantum Zeno effect), the lower bound is Δx ∼ Δt (ℏ/ mL ) with Δt the interval between measurements and L the size of the box. For a relativistic particle, the lower bound is the Compton wavelength, ℏ/ mc . The key step in deriving both results is to write the propagator as a sum over classical paths.
Use of edrophonium (Tensilon) in the evaluation of supraventricular tachycardias

Abstract A rapid intravenous dose (10 mg.) of edrophonium was administered to 24 patients with a variety of supraventricular tachycardias. Four with rapid sinus tachycardia showed transient sinus slowing. In 6 patients with rapid atrial flutter and in 3 with atrial fibrillation, edrophonium transiently increased atrioventricular block, and the atrial flutter or fibrillation waves became evident at the slowed ventricular response. In 11 patients with 12 episodes of paroxysmal atrial tachycardia, edrophonium converted the arrhythmia to normal sinus rhythm on six occasions. No complications were noted with the use of this drug, though minor side effects such as transient salivation, perspiration and tachypnea did occur. Edrophonium is a safe and useful pharmacologic agent in the differentiation of supraventricular tachycardias and in the conversion of paroxysmal atrial tachycardia to normal sinus rhythm.
Sequential Allylic C—H Amination/Vinylic C—H Arylation: A Strategy for Unnatural Amino Acid Synthesis from α-Olefins

Tandem reaction sequences that selectively convert multiple C–H bonds of abundant hydrocarbon feedstocks to functionalized materials enable rapid buildup of molecular complexity in an economical way. A tandem C–H amination/vinylic C–H arylation reaction sequence is described under Pd(II)/sulfoxide-catalysis that furnishes a wide range of α- and β-homophenylalanine precursors from commodity α-olefins and readily available aryl boronic acids. General routes to enantiopure amino acid esters and densely functionalized homophenylalanine derivatives are demonstrated.
Experience with the routine use of erythromycin for chlamydial infections in pregnancy

Abstract In an effort to prevent perinatal acquisition of Chlamydia trachomatis, we offered treatment with erythromycin ethylsuccinate (400 mg four times a day for seven days, given at 36 weeks' gestation) to 184 pregnant women with cervical chlamydial infections. Thirty-two women refused treatment; 24 of their infants were followed and served as the controls. Therapy was discontinued by 5 of 10 women who had gastrointestinal disturbances. Forty-seven women who completed therapy refused infant follow-up; in four (9 percent) of these women, therapy had failed to eradicate the infection. Sixty women and 59 infants completed the entire protocol; 55 (92 percent) of the women had negative cultures for chlamydia at follow-up. Chlamydial infection developed in 4 (7 percent) of the 59 infants of treated mothers, as compared with 12 (50 percent) of the 24 infants of untreated mothers; this difference was significant (P<0.001). With a success rate of 92 percent (98 of 107 patients) in treating maternal infection an...
Experimental Data for Goldfeld’s Conjecture over Function Fields

This paper presents empirical evidence supporting Goldfeld’s conjecture on the average analytic rank of a family of quadratic twists of a fixed elliptic curve in the function field setting. In particular, we consider representatives of the four classes of nonisogenous elliptic curves over with (q, 6)=1 possessing two places of multiplicative reduction and one place of additive reduction. The case of q=5 provides the largest data set as well as the most convincing evidence that the average analytic rank converges to 1/2, which we also show is a lower bound following an argument of Kowalski. The data were generated via explicit computation of the L-function of these elliptic curves, and we present the key results necessary to implement an algorithm to efficiently compute the L-function of nonisotrivial elliptic curves over by realizing such a curve as a quadratic twist of a pullback of a “versal” elliptic curve. We also provide a reference for our open-source library ELLFF, which provides all the necessary ...
Flow-driven formation of solid-like microsphere heaps

We observe the formation of heaps of repulsive microspheres, created by flowing a colloidal microsphere suspension towards a flat-topped ridge placed within a quasi two-dimensional microfluidic channel. This configuration allows for both shear and normal forces on the microspheres in contact with the ridge. The heaps, which are formed against the ridge, are characterized by two distinct phases: a solid-like bulk phase in the interior and a highly fluctuating, liquid-like state which exists along its leading edge. We observe that heaps only form above a critical flow velocity, vc, and that they are destroyed by thermal rearrangements when the flow ceases. We monitor the dynamics of heap formation using fluorescence video microscopy, measuring the heap volume and the angle of repose in response to microsphere deposition and erosion processes. We find that the steady state angle of repose, θf, increases as a function of inflow velocity, v∞, with a functional form .
OHM'S LAW IN THE FAST LANE: GENERAL RELATIVISTIC CHARGE DYNAMICS

Fully relativistic and causal equations for the flow of charge in curved spacetime are derived. It is believed that this is the first set of equations to be published that correctly describes the flow of charge, as well as the evolution of the electromagnetic field, in highly dynamical relativistic environments on timescales much shorter than the collapse time (GM/c3).
Ligand-accelerated enantioselective propargylation of aldehydes via allenylzinc reagents.

An enantioselective propargylation of aldehydes using an allenylzinc reagent generated in situ via a zinc−iodine exchange reaction is described. The enantioselectivity is controlled by addition of a catalytic amount of readily accessible and highly tunable amino alcohol ligand L13. A wide range of aldehydes can be propargylated to afford valuable and versatile homopropargyl alcohols in good to excellent yields with high levels of enantiopurity.
Biologically Based Dose‐Response Model for Neurotoxicity Risk Assessment

The regulation of neurotoxicants has usually been based upon setting reference doses by dividing a no observed adverse effect level (NOAEL) by uncertainty factors that theoretically account for interspecies and intraspecies extraploation of experimental results in animals to humans. Recently, we have proposed a four-step alternative procedure which provides quantitative estimates of risk as a function of dose. The first step is to establish a mathematical relationship between a biological effect or biomarker and the dose of chemical administered. The second step is to determine the distribution (variability) of individual measurements of biological effects or their biomarkers about the dose response curve. The third step is to define an adverse or abnormal level of a biological effect or biomarker in an untreated population. The fourth and final step is to combine the information from the first three steps to estimate the risk (proportion of individuals exceeding on adverse or abnormal level of a biological effect or biomarker) as a function of dose. The primary purpose of this report is to enhance the certainty of the first step of this procedure by improving our understanding of the relationship between a biomarker and dose of administered chemical. Several factors which need to be considered include: 1) the pharmacokinetics of the parent chemical, 2) the target tissue concentrations of the parent chemical or its bioactivated proximate toxicant, 3) the uptake kinetics of the parent chemical or metabolite into the target cell(s) and/or membrane interactions, and 4) the interaction of the chemical or metabolite with presumed receptor site(s). Because these theoretical factors each contain a saturable step due to definitive amounts of required enzyme, reuptake or receptor site(s), a nonlinear, saturable dose-response curve would be predicted. In order to exemplify this process, effects of the neurotoxicant, methlenedioxymethamphetamine (MDMA), were reviewed and analyzed. Our results and those of others indicate that: 1) peak concentrations of MDMA and metabolites are ochieved in rat brain by 30 min and are negligible by 24 hr, 2) a metabolite of MDMA is probably responsible for its neurotoxic effects, and 3) pretreatment with monoamine uptake blockers prevents MDMA neurotoxicity. When data generated from rats administerde MDMA were plotted as bilolgical effect (decreases in hippocampal serotonin concentrations) versus dose, a saturation curve best described the observed relationship. These results support the hypothesis that at least one saturable step is involved in MDMA neurotoxicity. We conclude that the mathematical relationship between biological effect and dose of MDMA, the first step of our quantitative neurotoxicity risk assessment procedure, should reflect this biological model information generated from the whole of the dose-response curve.
The Metallicity of the Monoceros Stream

We present low-resolution MMT Hectospec spectroscopy of 594 candidate Monoceros stream member stars. Based on strong color-magnitude diagram overdensities, we targeted three fields within the stream's footprint, with 178 Degree-Sign {<=} l {<=} 203 Degree-Sign and -25 Degree-Sign {<=} b {<=} 25 Degree-Sign . By comparing the measured iron abundances with those expected from smooth Galactic components alone, we measure, for the first time, the spectroscopic metallicity distribution function for Monoceros. We find the stream to be chemically distinct from both the thick disk and halo, with [Fe/H] = -1, and do not detect a trend in the stream's metallicity with Galactic longitude. Passing from b = +25 Degree-Sign to b = -25 Degree-Sign , the median Monoceros metallicity trends upward by 0.1 dex, though uncertainties in modeling sample contamination by the disk and halo make this a marginal detection. In each field, we find Monoceros to have an intrinsic [Fe/H] dispersion of 0.10-0.22 dex. From the Ca II K line, we measure [Ca/Fe] for a subsample of metal-poor program stars with -1.1 < [Fe/H] < -0.5. In two of three fields, we find calcium deficiencies qualitatively similar to previously reported [Ti/Fe] underabundances in Monoceros and the Sagittarius tidal stream.more » Further, using 90 spectra of thick disk stars in the Monoceros pointings with b Almost-Equal-To {+-}25 Degree-Sign , we detect a 0.22 dex north/south metallicity asymmetry coincident with known stellar density asymmetry at R{sub GC} Almost-Equal-To 12 kpc and |Z| Almost-Equal-To 1.7 kpc. Our median Monoceros [Fe/H] = -1.0 and its relatively low dispersion naturally fit the expectation for an appropriately luminous M{sub V} {approx} - 13 dwarf galaxy progenitor.« less
Synthesis of rhodium(III), iridium(III) and osmium(III) complexes with tris(2-aminoethanethiolato)cobalt(III)

Abstract Polynuclear sulfur bridged complexes where the neutral complex tris(2-aminoethanethiolato)cobalt(III) acts as a tridentate ligand to rhodium(III), iridium(III) and osmium(III) have been prepared. These complexes have been characterized by electronic spectroscopy, vibrational spectroscopy and nuclear magnetic resonance spectroscopy. Along with the previously prepared complexes of iron(III), ruthenium(III) and cobalt(III), these complexes form two series of complexes with the group 8 and group 9 elements from all three transition series.
An interactive software engineering tool for memory management and user program evaluation

As the use of virtual memory becomes more and more accepted, the problem of effective storage management becomes more and more important. To date most efforts to optimize the use of memory have been directed at devising memory management strategies at the operating system level that minimize the number of page faults. For example, Comeau has shown that the loading sequence of subroutines can have a considerable effect on paging activity. Hence page-fault-optimizing loaders, linkage editors and compilers have been proposed. Although the concepts of "locality" and "working set" have been known for some time (c.f. Denning), little effort has been made to provide the programmer with suitable tools for making his programs "more local". This seems to stem from the fact that, short of notions of "modular coding", little is known about what sorts of programming habits actually result in local code. Consequently, most optimization techniques used to date have assumed that user programs were an unmodifiable input to the operating system.
Orientifolds, RR torsion, and K-theory

We analyze the role of RR fluxes in orientifold backgrounds from the point of view of K-theory, and demonstrate some physical implications of describing these fluxes in K-theory rather than cohomology. In particular, we show that certain fractional shifts in RR charge quantization due to discrete RR fluxes are naturally explained in K-theory. We also show that some orientifold backgrounds, which are considered distinct in the cohomology classification, become equivalent in the K-theory description, while others become unphysical.
A Model Comparison for Characterizing Protein Motions from Structure

To understand the extent structure plays in determining protein dynamics, a comparative study is made using three computational models that characterize native state dynamics starting from known protein structures taken from four distinct SCOP classifications. A geometrical simulation [1] (FRODA) is performed based on an initial rigid cluster decomposition using FIRST [2], and the results are compared to the commonly employed elastic network model (ANM) and molecular dynamics (MD) simulations. The essential dynamics is quantified by a direct analysis of a mode subspace constructed from ANM and a principal component analysis (PCA) on both the FRODA and MD trajectories using root mean square inner (RMSIP) product and principal angles (PA). Relative subspace sizes and overlaps are visualized using the projection of displacement vectors on the model modes. Additionally, a mode subspace is constructed from PCA on an exemplar set of X-ray crystal structures in order to determine similarly with respect to the generated ensembles. Our quantitative analysis reveals there is significant overlap across the three model subspaces and the model independent subspace. The subspaces generated from all three models were found to have high overlap for all four SCOP classes of proteins investigated, although FRODA provided the most robust sampling of the native basin. These results indicate that structure is the key determinant for native state dynamics. This work is supported by NIH grant 1R21HL093531.[1] Wells S, Menor S, Hespenheide B, Thorpe MF: Constrained geometric simulation of diffusive motion in proteins. Phys Biol, 2:S127-S136 (2005).[2] Jacobs DJ, Rader A, Kuhn LA, Thorpe MF: Graph Theory Predictions of Protein Flexibility. Proteins, 44:150-65 (2001).
STIS Echelle Observations of the Intrinsic UV Absorption in the Seyfert 1 Galaxy NGC 3783

We present observations of the UV absorption lines in the Seyfert 1 galaxy NGC 3783, obtained with the medium resolution (λ/Δλ ≈ 40,000) echelle gratings of the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST). The spectra reveal the presence of three kinematic components of absorption in Lyα, C IV, and N V, at radial velocities of -1365, -548, and -724 km s-1 with respect to the systemic velocity of the host galaxy (components 1, 2 and 3, respectively); component 1 also shows absorption by Si IV. Component 3 was not detected in any of the earlier Goddard High Resolution Spectrograph (GHRS) spectra, and the C IV absorption in the other components has changed since the most recent GHRS observation obtained ~5 yr earlier. Somewhat unexpectedly, each component has a covering factor (of the continuum source+broad emission line region) of ~0.6. We have calculated photoionization models to match the UV column densities in each of the three components. The models predict a zone characterized by high-ionization parameter (U = 0.65-0.80) and column density (6.4 × 1020-1.5 × 1021 cm-2) for each component, and a second, low-ionization (U = 0.0018) and low column density (4.9 × 1018 cm-2) zone for component 1. Based on the model results, there should be strong absorption in the bandpass of the Far Ultraviolet Spectroscopic Explorer (FUSE), 912-1200 A, including saturated O VI lines at each component velocity. The models also predict large O VII and O VIII column densities, but suggest that the UV absorbers cannot account for all of the X-ray absorption detected in recent Chandra spectra. Finally, there is no evidence for a correlation between the characteristics of the UV absorbers and the UV continuum flux, and, by inference, the ionizing continuum. Hence, we suggest that the variations observed in the GHRS and STIS spectra are due in a large part to changes in the column densities of the absorbers as the result of transverse motion.
The Great Conversation and the Ethics of Inclusion

Hispanic and Latino Americans want security from terrorists as much as all other Americans. A protective membrane surrounding the country that is too porous is of little use and constitutes a danger to residents, both citizens and non-citizens alike. This much is uncontroversial. Similarly, most American citizens truly benefit from the work product of undocumented workers. Presumably, some case can be made that most undocumented workers see themselves as better off than if they had remained in their country of origin. Things become controversial when an attempt is made to balance resident safety against resident desire for inexpensive labor. The controversy inevitably escalates when consideration is given to the fairness of wages paid to undocumented workers. These moral issues cannot be ignored. However, as important as these issues are, the present argument addresses more specifically the duties educators have towards learners and potential learners regardless of their current citizenship status. The ar...
TESTER: A Computer Program to Produce Individualized Multiple Choice Tests.

This paper describes a computer program, TESTER, which produces individualized objective tests from a pool of items. Available in both PL/I and FORTRAN, TESTER may be executed either interactively or in batch.
Synthesis of triphenylphosphonium trichlorogermanate and analogs. Preparation of germylenes from triphenylphosphonium trichlorogermanate

Triphenylphosphonium trichlorogermanate was prepared in quantitative yield by reducing germanium tetrachloride-triphenylphosphine (1:1) with tributyl-tin hydride in diethyl ether. Heating the phosphonium salt at 245°C gave Ph3P-GeCl2 in 90% recrystallized yield. Treatment of the phosphonium salt with LiN(TMS)2 gave Ge[N(TMS)2]2 in 70–77% yield. Reaction of tin dichloride or zinc dichloride with triphenylphosphine and hydrogen chloride yielded tin and zinc analogs of triphenylphosphonium trichlorogermanate.
Using symmetry to optimize over the Sherali–Adams relaxation

In this paper we examine the impact of using the Sherali–Adams procedure on highly symmetric integer programming problems. Linear relaxations of the extended formulations generated by Sherali–Adams can be very large, containing $$O\left( \left( {\begin{array}{c}n\\ d\end{array}}\right) \right) $$ many variables for the level- $$d$$ closure. When large amounts of symmetry are present in the problem instance however, the symmetry can be used to generate a much smaller linear program that has an identical objective value. We demonstrate this by computing the bound associated with the level 1, 2, and 3 relaxations of several highly symmetric binary integer programming problems. We also present a class of constraints, called counting constraints, that further improves the bound, and in some cases provides a tight formulation. A major advantage of the Sherali–Adams formulation over the traditional formulation is that symmetry-breaking constraints can be more efficiently implemented. We show that using the Sherali–Adams formulation in conjunction with the symmetry breaking tool isomorphism pruning can lead to the pruning of more nodes early on in the branch-and-bound process.
Faster approximation schemes for fractional multicommodity flow problems via dynamic graph algorithms

We combine the work of Garg and Konemann, and Fleischer with ideas from dynamic graph algorithms to obtain faster (1-e)-approximation schemes for various versions of the multicommodity flow problem. In particular, if e is moderately small and the size of every number used in the input instance is polynomially bounded, the running times of our algorithms match -- up to poly-logarithmic factors and some provably optimal terms -- the Ω(mn) flow-decomposition barrier for single-commodity flow.
Network competition and branch differentiation with consumer heterogeneity

The paper provides a general framework for the analysis of noncooperative competition between multi-branch networks when consumers have heterogeneous preferences. This framework allows for ill-studied conditions, such as branch loyalty and economies of scope, to be explored in terms of their role in shaping address solutions and firm profits. Geographic and quality differentiation as well as firm profits are shown to be dependent upon the magnitude of the loyalty factor and upon the extend of economies of scope. Real world situations in the retail industry are interpreted in the light of the results of the analysis.
Chemical and Electrochemical Reduction Rates of Cyclic Nitroxides (Nitroxyls)

The reduction rates of five-membered pyrrolidine and pyrroline, and six-membered piperidine nitroxides (alternatively termed nitroxyls) containing various substituents were determined under homogeneous conditions using ascorbate, and electrochemically under heterogeneous conditions. The results were compared with data from the literature. It was shown that the increased rates of reduction of six-membered nitroxides, compared with those of the five-membered nitroxides, cannot be explained on the basis of differences in electrochemical potentials but, rather, can be ascribed to differences in the accessibility of the nitroxide group. A double bond in the five-membered nitroxyls increases the reduction rate. Within any ring system, the reduction rates of nitroxides using ascorbate can be correlated with the inductive substituent constants. The half-way potentials for electrochemical reduction within a series of nitroxides based on the same ring correlate with logarithms of the rates using ascorbate and with the inductive constants. The potentials for one-electron oxidation of the nitroxides were related to the inductive constants.
Global optimization for first order Markov Random Fields with submodular priors

This paper copes with the global optimization of Markovian energies. Energies are defined on an arbitrary graph and pairwise interactions are considered. The label set is assumed to be linearly ordered and of finite cardinality, while each interaction term (prior) shall be a submodular function. We propose an algorithm that computes a global optimizer under these assumptions. The approach consists of mapping the original problem into a combinatorial one that is shown to be globally solvable using a maximum-flow/s-t minimum-cut algorithm. This restatement relies on considering the level sets of the labels (seen as binary variables) instead of the label values themselves. The submodularity assumption of the priors is shown to be a necessary and sufficient condition for the applicability of the proposed approach. Finally, some numerical results are presented.
Navigating the Fungal Polyketide Chemical Space: From Genes to Molecules

The iterative type I polyketide synthases (IPKSs) are central to the biosynthesis of an enormously diverse array of natural products in fungi. These natural products, known as polyketides, exhibit a wide range of biological activities and include clinically important drugs as well as undesirable toxins. The PKSs synthesize these structurally diverse polyketides via a series of decarboxylative condensations of malonyl-CoA extender units and β-keto modifications in a highly programmed manner. Significant progress has been made over the past few years in understanding the biosynthetic mechanism and programming of fungal PKSs. The continuously expanding fungal genome sequence data have sparked genome-directed discoveries of new fungal PKSs and associated products. The increasing number of fungal PKSs that have been linked to their products along with in-depth biochemical and structural characterizations of these large enzymes have remarkably improved our knowledge on the molecular basis for polyketide structu...
Fuzzy inductive reasoning, expectation formation and the behavior of security prices

Abstract This paper extends the Santa Fe Artificial Stock Market Model (SFASM) studied by LeBaron, Arthur and Palmer (1999, Journal of Economic Dynamics and Control 23, 1487–1516) in two important directions. First, some might question whether it is reasonable to assume that traders are capable of handling a large number of rules, each with numerous conditions, as is assumed in the SFASM. We demonstrate that similar results can be obtained even after severely limiting the reasoning process. We show this by allowing agents the ability to compress information into a few fuzzy notions which they can in turn process and analyze with fuzzy logic. Second, LeBaron et al. have reported that the kurtosis of their simulated stock returns is too small as compared to real data. We demonstrate that with a minor modification to how traders go about deciding which of their prediction rules to rely on when making demand decisions, the model can in fact produce return kurtosis that is comparable to that of actual returns data.
Scientific Collaboratories: Evaluating their Potential

L'auteur presente une evaluation ayant pour but de repondre aux questions suivantes: la recherche scientifique repartie (laboratoire virtuel) peut-elle produire des resultats de qualite elevee? les avantages des labos virtuels compenssent-ils les inconvenients, selon les scientifiques eux-memes? en quoi le processus de recherche change-t-il dans les conditions du labo virtuel?
Catalytic Enantioselective Synthesis of Quaternary Stereocenters via Intermolecular C-Acylation of Silyl Ketene Acetals: Dual Activation of the Electrophile and the Nucleophile

A nucleophile-catalyzed asymmetric intermolecular C-acylation of silyl ketene acetals by anhydrides has been developed, furnishing quaternary stereocenters with high enantioselectivity. Mechanistic studies support the hypothesis that the reaction involves activation both of the silyl ketene acetal (generation of an enolate) and of the anhydride (formation of an acylpyridinium ion).
Massive black holes in galactic halos

The authors consider the idea that galaxy halos are composed of massive black holes as a possible resolution of two problems: the composition of dark halos, and the heating of stellar disks. It is found that in order to account for the amount of disk heating that is observed in our Galaxy and several others, the black holes must have masses MH ≡ 106M_sun;. This heating mechanism makes predictions for the dependence of the velocity dispersion on time, and for the shape of the velocity ellipsoid, that are in good agreement with observations. The authors consider the constraints on this picture set by dynamical friction causing black holes to spiral to the galactic center, by the possible presence of dark matter in dwarf spheroidal galaxies, and by the accretion of interstellar gas by the black holes producing luminous objects in the Galaxy.
Identification of binary choice models with social interactions

This paper provides a set of results on the econometric identifiability of binary choice models with social interactions. Our analysis moves beyond parametric identification results that have been obtained in the literature to consider the identifiability of model parameters when the distribution of random payoff terms is unknown. Further, we consider how identification is affected by the presence of unobservable payoff terms of various types as well as identification in the presence of certain forms of endogenous group membership. Our results suggest that at least partial identification may be achieved under assumptions that in certain contexts may be plausible.
Energy production in stars

FROM TIME IMMEMORIAL people must have been curious to know what keeps the sun shining. The first scientific attempt at an explanation was by Helmholtz about one hundred years ago, and was based on the force most familiar to physicists at the time, gravitation. When a gram of matter falls to the sun's surface it gets a potential energy Epot = −GM/R = −1.91×1015 erg/gm (1) where M = 1.99×1033 gm is the sun's mass, R = 6.96×1010 cm its radius, and G = 6.67×10−8 the gravitational constant. A similar energy was set free when the sun was assembled from intersellar gas or dust in the dim past; actually somewhat more, because most of the sun's material is located closer to its center, and therefore has a numerically larger potential energy. One‐half of the energy set free is transformed into kinetic energy according to the well‐known virial theorem of mechanics. This will permit us later to estimate the temperature in the sun. The other half of the potential energy is radiated away. We know that at present the su...
Applications of short-time homomorphic signal analysis to seismic wavelet estimation

Abstract The use of homomorphic systems to deconvolve seismic reflection and teleseismic data has been proposed and explored by a number of researchers with varying success. A careful study of the methods employed reveals a number of problems involving both the class of characteristic systems used and their numerical implementation. Furthermore, the analysis strategies used introduce deterministic constraints on the estimation of the seismic wavelet, which may lead to serious problems in determining the earth impulse response. Several novel results are presented in this paper. A class of homomorphic systems matched to the band-pass nature of seismic signals is discussed and improved and more reliable implementation algorithms are developed. The concept of short-time wavelet estimation by homomorphic filtering is introduced. This technique takes into account the specific time-varying characteristics of seismic traces. Strategies for homomorphic wavelet estimation are proposed and illustrated. The recovery of the earth impulse response may then be accomplished by combining homomorphic wavelet estimation with parametric inverse filtering.
One-Dimensional Quantum Chaos: Explicitly Solvable Cases

We present quantum graphs with remarkably regular spectral characteristics. We call them regular quantum graphs. Although regular quantum graphs are strongly chaotic in the classical limit, their quantum spectra are explicitly solvable in terms of periodic orbits. We present analytical solutions for the spectrum of regular quantum graphs in the form of explicit and exact periodic orbit expansions for each individual energy level.
On the supremum of the tails of normalized sums of independent Rademacher random variables

Abstract A well-known longstanding conjecture on the supremum of the tails of normalized sums of independent Rademacher random variables is disproved. A special case of this conjecture was recently disproved by A. Zhubr.
Random Walk in an Alcove of an Affine Weyl Group, and Non-colliding Random Walks on an Interval

We use a reflection argument, introduced by Gessel and Zeilberger, to count the number of k-step walks between two points which stay within a chamber of a Weyl group. We apply this technique to walks in the alcoves of the classical affine Weyl groups. In all cases, we get determinant formulas for the number of k-step walks. One important example is the region m>x1>x2>?>xn>0, which is a rescaled alcove of the affine Weyl group Cn. If each coordinate is considered to be an independent particle, this models n non-colliding random walks on the interval (0, m). Another case models n non-colliding random walks on a circle.
Erythropoietin-Induced Erythroid Precursor Pool Depletion Causes Erythropoietin Hyporesponsiveness

The purpose of this study is to demonstrate that the erythroid precursor depletion in bone marrow induced by recombinant human erythropoietin (rHuEPO) treatment may be another contributing factor to erythropoietin hyporesponsiveness. Healthy Wistar rats were given single dose (SD) or multiple doses (MD) of rHuEPO (100 IU/kg). In MD study, animals were challenged with thrice-weekly over two weeks. Blood, bone marrow and spleen (for SD only) were collected. The erythropoietic responses in bone marrow and spleen were quantified using a flow cytometric immunophenotyping technique. A mathematical approach involving measuring reticulocyte age distribution was developed to evaluate the reticulocyte loss due to neocytolysis. A reduced level of erythropoietic responses below the baseline was observed for both MD and SD studies. In SD study, the reticulocyte decreased below the baseline after day 6. A depletion of the bone marrow erythroid precursor cells was observed. However, neocytolysis of reticulocyte only occurs from day 3-5 after rHuEPO injection. The findings demonstrate that EPO-induced erythroid precursor depletion in bone marrow is responsible for reduced reticulocyte response and may contribute to erythropoietin hyporesponsiveness. Therefore, this study provides further justification for reducing the doses of erythropoietin-stimulating agents in anemic patients demonstrating hyporesponsiveness.
Providing emergency services in Internet telephony

Our primary focus is on emergency calling and notification. We describe the components of the existing emergency calling and notification systems and our proposed IP-based architectures, each of which uses the session initiation protocol (SIP) as the signaling framework. The architecture could increase speed, scalability, and functionality in communication services.
“Ah, you publishing scoundrel!”: A Hauntological Reading of Privacy, Moral Rights, and the Fair Use of Unpublished Works

AbstractThe doctrine of fair use, as applied to unpublished works, has long been haunted by the specters of privacy and moral rights, a haunting that reached a crisis point in the 1980s when certain court decisions appeared to be evolving a per se rule against the fair use of unpublished works. This chilly season was only partly warmed in 1992 when Congress amended the Copyright Act to clarify that the unpublished nature of a work may not itself bar a finding of fair use. In the years since, no legal case has fully tested the force of Congress’s amendment in the context of scholarly quotation. Publishers and editors in the humanities remain fearful that quotation from unpublished documents will trigger liability or threats of it. By way of analytical exorcism, this essay focuses on the fair use of unpublished works by authors who have since died, in order to make vivid the general problem of allowing privacy and moral rights to haunt the fair use doctrine. As a way of probing these poltergeists more richl...
How unitary cosmology generalizes thermodynamics and solves the inflationary entropy problem

We analyze cosmology assuming unitary quantum mechanics, using a tripartite partition into system, observer, and environment degrees of freedom. This generalizes the second law of thermodynamics to ``The system's entropy cannot decrease unless it interacts with the observer, and it cannot increase unless it interacts with the environment.'' The former follows from the quantum Bayes theorem we derive. We show that because of the long-range entanglement created by cosmological inflation, the cosmic entropy decreases exponentially rather than linearly with the number of bits of information observed, so that a given observer can reduce entropy by much more than the amount of information her brain can store. Indeed, we argue that as long as inflation has occurred in a non-negligible fraction of the volume, almost all sentient observers will find themselves in a post-inflationary low-entropy Hubble volume, and we humans have no reason to be surprised that we do so as well, which solves the so-called inflationary entropy problem. An arguably worse problem for unitary cosmology involves gamma-ray-burst constraints on the ``big snap,'' a fourth cosmic doomsday scenario alongside the ``big crunch,'' ``big chill,'' and ``big rip,'' where an increasingly granular nature of expanding space modifies our life-supporting laws of physics. Our tripartite framework also clarifies when the popular quantum gravity approximation ${G}_{\ensuremath{\mu}\ensuremath{\nu}}\ensuremath{\approx}8\ensuremath{\pi}G⟨{T}_{\ensuremath{\mu}\ensuremath{\nu}}⟩$ is valid, and how problems with recent attempts to explain dark energy as gravitational backreaction from superhorizon scale fluctuations can be understood as a failure of this approximation.
ROCKING THE LIGHTHOUSE : CIRCUMPULSAR ASTEROIDS AND RADIO INTERMITTENCY

Neutral, circumpulsar debris that enters the magnetospheres of neutron stars can disrupt current flows and electromagnetic radiation and thereby account for some of the intermittency seen in radio pulsars. This paper considers asteroids that form from supernova fallback material and how they migrate into the pulsar light cylinder before evaporating, ionizing, and perturbing particle acceleration regions. Such intrusion is expected primarily for pulsars with long spin periods and relatively cool surfaces. We show that debris disks undetectable either directly or through reflex of the neutron star can provide sufficient material over the radio-emitting lifetime of a pulsar to account for nulling and burst phenomena that occur on timescales of seconds to months. The quasi-periodic bursts in B1931+24 may be driven by a large orbiting object that perturbs a debris disk episodically.