cssi/SciSciGPT-SciSciNet huggingface dataset:
Channel access protocols for high-speed LANs using WDM: a comparative study

Extensive research and considerable progress in the dense optical wavelength division multiplexing (WDM) technology has made it the most likely candidate for implementation in next-generation high performance switches, LANs and MANs. The first key challenge is the continuous development of cost-effective optical components in order to realize practical networks. The next main challenge is to design an effective channel access protocol that will: (a) take full advantage of the existing and emerging optical technologies, (b) fairly and successfully coordinate transmissions between the networks nodes, and (c) efficiently manage the enormous fiber bandwidth. There have been many access protocols proposed for WDM networks including quite a few proposals that require many more channels than the number of nodes. The practical device characteristics impose an upper limit on the number of available WDM channels. Our focus in this paper is on systems with many nodes and small number of channels. We study the use of in-band signaling mechanism compared to the separate control channel (out-band signaling) approach. Signaling is used to achieve coordination between source and destination with respect the communication channel. The objective of this paper is to understand the key trade-offs in the protocol design for such networks through close examinations of the two approaches. Our intent is not to claim the superiority of either approach, rather to stimulate further studies on such systems.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
The Mars Exploration Rover Project: 2005 surface operations results

Abstract The twin rovers, Spirit and Opportunity, of the Mars Exploration Rover Project successfully landed on the surface of Mars in January 2004, and began an unprecedented period of surface exploration. Spirit’s landing in Gusev Crater, and its subsequent journeys to the Columbia Hills provided ample evidence for the advantages of mobile rovers over fixed landers. Opportunity's “hole in one” landing in the 20 m Eagle Crater with the essential evidence to answer the science questions for Meridiani lying meters away underscored the advantage of surface mobility. The project skillfully dealt with a host of challenges after landing, including Flash memory problems and the cold and dim light of Martian winter, to successfully extend the reach of Earth-bound scientists to two new locations on Mars. With the overwhelming success of the prime mission, NASA's decision to continue the MER journey of exploration has achieved results undreamed of before launch.
Generalized Galilei-Invariant Classical Mechanics

To describe the "slow" motions of n interacting mass points, we give the most general four-dimensional (4D) noninstantaneous, nonparticle symmetric Galilei-invariant variational principle. It involves two-body invariants constructed from particle 4-positions and 4-velocities of the proper orthochronous inhomogeneous Galilei group. The resulting 4D equations of motion and multiple-time conserved quantities involve integrals over the worldlines of the other n-1 interacting particles. For a particular time-asymmetric retarded (advanced) interaction, we show the vanishing of all integrals over worldlines in the ten standard 4D multiple-time conserved quantities, thus yielding a Newtonian-like initial value problem. This interaction gives 3D noninstantaneous, nonparticle symmetric, coupled nonlinear second-order delay-differential equations of motion that involve only algebraic combinations of nonsimultaneous particle positions, velocities, and accelerations. The ten 3D noninstantaneous, nonparticle symmetric conserved quantities involve only algebraic combinations of nonsimultaneous particle positions and velocities. A two-body example with a generalized Newtonian gravity is provided. We suggest that this formalism might be useful as an alternative slow-motion mechanics for astrophysical applications.
Boundary-layer Pitot and hot-wire surveys at a free-stream Mach number of about 20

Nozzle wall hypersonic turbulent boundary layers at free stream Mach number, using pitot, hot wire, wall pressure fluctuation and static pressure measurements
LPL: a generalized list processing language

Many programming applications, e.g., symbolic and algebraic manipulation applications and artificial intelligence applications, require the use of list structures. Several list processing languages or languages that provide for list processing have been developed, e.g. LISP 1.5, LISP 2, SLIP, PL/1, ALGOL 68, etc. With the exception of ALGOL 68 and LISP 2, none of these languages provide the user with the capability to define the cell size and/or the configuration of the list cell at runtime (PL/1 attempts to do this with BASED structures but falls short because only one component in a BASED structure can have its dimension altered at runtime). ALGOL 68 has the disadvantage that it is not yet readily available for most users, and it suffers from list tracing complexities during garbage collection. LISP 2 was an attempt to allow variable cell configurations, but the project was aborted.
Evolution of the solar nebula. VIII. Spatial and temporal heterogeneity of short-lived radioisotopes and stable oxygen isotopes

Isotopic abundances of short-lived radionuclides such as 26Al provide the most precise chronometers of events in the early solar system, provided that they were initially homogeneously distributed. On the other hand, the abundances of the three stable isotopes of oxygen in primitive meteorites show a mass-independent fractionation that survived homogenization in the solar nebula. As a result of this and other cosmochemical evidence, the degree of spatial heterogeneity of isotopes in the solar nebula has long been a puzzle. We show here that based on hydrodynamic models of the mixing and transport of isotopic anomalies formed at, or injected onto, the surface of the solar nebula, initially high levels of isotopic spatial heterogeneity are expected to fall to steady state levels (~10%) low enough to validate the use of 26Al for chronometry, but high enough to preserve the evidence for mass-independent fractionation of oxygen isotopes. The solution to this puzzle relies on the mixing being accomplished by the chaotic fluid motions in a marginally gravitationally unstable disk, as seems to be required for the formation of gas giant planets, and by the inability of alternative physical processes to drive large-scale mixing and transport in the planet-forming midplane of the solar nebula. Such a disk is also capable of large-scale outward transport of the thermally annealed dust grains found in comets, and of driving the shock fronts that appear to be responsible for much of the thermal processing of the components of primitive meteorites, creating a self-consistent picture of the basic physical processes shaping the early solar nebula.
The inter-relationships between ovarian-independent growth, tumorigenicity, invasiveness and antioestrogen resistance in the malignant progression of human breast cancer.

Among the processes contributing to the progressive acquisition of the highly malignant phenotype in breast cancer are ovarian-independent growth, antioestrogen resistance and increased metastatic potential. We have previously observed that increased invasiveness and development of ovarian-independent growth occur independently. In an attempt to define the inter-relationships between these processes further, we have compared the phenotypes of ovarian-independent, invasive and antioestrogen-resistant sublines of the ovarian-dependent human breast cancer cell line MCF-7. Cells acquiring ovarian-independent growth can retain sensitivity to anti-oestrogens. One clone of MCF-7 cells selected for stable antioestrogen resistance has become non-tumorigenic but its invasive potential remains unaltered. Thus, acquisitions of some characteristics of the progressed phenotype can occur independently. This phenomenon of independent parameters in phenotypic progression could partly explain the considerable intra- and intertumour heterogeneity characteristic of breast tumours.
Human Alveolar Macrophages Produce a Fibroblast-like Collagenase and Collagenase Inhibitor

Human macrophages have been implicated in connective tissue remodeling; however, little is known about their direct effects upon collagen degradation. We now report that human alveolar macrophages in culture produced both a collagenase and a collagenase inhibitor. The collagenase was secreted in latent form and could be activated by exposure to trypsin. Collagenase production could be increased three- to fourfold by incubating the cells with lipopolysaccharide, but synthesis was largely unaffected by exposure to phorbol myristate acetate. By several criteria, macrophage collagenase was the same as the collagenase secreted by human skin fibroblasts: (a) they were antigenically indistinguishable in double immunodiffusion; (b) both degraded type III collagen preferentially to type I, had little activity against type II collagen, and none against types IV and V, and (c) their affinity for susceptible collagens was equivalent, Michaelis constant = 1-2 microM. Collagenase inhibitory activity was also present in the macrophage-conditioned medium, and was accounted for by an antigen that showed immunologic and functional identity with the collagenase inhibitor secreted by human skin fibroblasts. The amount of inhibitor released by unstimulated cells, approximately 100 ng/10(6) cells per 24 h, was substantially augmented by both phorbol and lipopolysaccharide, although considerable variability in response to these agents was observed between macrophage populations derived from different subjects. As negligible quantities of collagenase or collagenase inhibitor were detectable intracellularly, it appeared that both proteins were secreted rapidly after synthesis. Thus, human macrophages have the capacity to modulate collagen degradation directly by production of collagenase and collagenase inhibitor.
Equilibrium Acidities and Homolytic Bond Dissociation Energies of N−H and/or O−H Bonds in N-Phenylhydroxylamine and Its Derivatives

The equilibrium acidities (pKHA values) in DMSO of the following hydroxylamines have been measured: (1) N-phenylhydroxylamine and its p-bromo and p-cyano derivatives, (2) N-benzyl-N-phenylhydroxylamine and its p-bromo and p-cyano derivatives, (3) O-benzyl-N-phenylhydroxylamine, (4) N-benzoylphenylhydroxylamine and its p-bromo and p-cyano derivatives, and (5) N-hydroxylpiperidine. The BDEs of the O−H and/or N−H bonds in these 11 weak acids have been estimated by combining their pKHA values with the oxidation potentials of their conjugate bases according to the following equation: BDEHA = 1.37pKHA + 23.1Eox(A-) + 73.3 kcal/mol.
Return to college education revisited: Is relevance relevant?

Abstract This study examines whether the size of the college earnings premium varies depending on the quality of the match between an individual's degree field and his/her occupation. The study uses the Occupational Information Network (O*NET) to obtain a new measure of the quality of occupational match for a sample of 2268 young adults with post-secondary degrees from the restricted use High School and Beyond (1980/92) data. The study finds that people whose occupations better match their degree fields earn significantly higher returns to post-secondary schooling. This result is robust to controlling for an extensive set of pre-existing differences among individuals, and to accounting for differences in earnings across post-secondary degree fields.
Boundary-layer transition effects on airplane stability and control

Surface contamination of laminar-flow airfoils can significantly modify the location of transition from laminar-to-turbulent boundary-layer flow. The contamination can be the result of insect debris, environmental effects such as ice crystals and moisture due to mist or rain, surface damage, or other contamination adhering to the surface. Location and mode of transition have a dominant effect on the lift-and-drag characteristics of a lifting surface. The influences of laminar boundary-layer flow behavior on airplane stability and control are examined through theoretical results and experimental (wind-tunnel and free-flight) data. For certain airfoils with a relatively steep pressure recovery it is shown that loss of laminar flow near the leading edge can result in premature separation of the turbulent boundary layer and, consequently, in loss of lift and control effectiveness. Aerodynamic modifications which minimize boundary-layer transition effects on airplane stability and control are also discussed.
The dynamics of resource allocation in research organizations

Abstract As a first step towards understanding the evolution of small groups in firms, this paper develops and tests a simple decision-theoretic model of research-unit evolution in which, as managers resolve their uncertainty over time, they shut down under-performing units and remove under-performing unit heads. The selection process generates several testable hypotheses about how unit and head characteristics affect the assignment of heads to units and resource allocation within the firm. Data on research units in firms is used to test the model and estimate the relative importance of the different effects on resource allocation.
Knot energies and knot invariants

This an article about some elementary geometric and combinatorial natures of various knot energies. A related "new" knot invariant -- the X-crossing number -- is introduced.
Multifragmentation: Surface instabilities or statistical decay?

Boltzmann-Nordheim-Vlasov calculations show multifragmentation that seems to originate from surface instabilities. These instabilities are traced to a sheet instability caused by the proximity interaction. Experimental data, on the other hand, suggest that multifragmentation may be dominated by phase space.
A formal model of theory choice in science

Since the work of Thomas Kuhn, the role of social factors in the scientific enterprise has been a major concern in the philosophy and history of science. In particular, conformity effects among scientists have been used to question whether science naturally progresses over time. Using neoclassical economic reasoning, this paper develops a formal model of scientific theory choice which incorporates social factors. Our results demonstrate that the influence of social factors on scientific progress is more complex than previously thought. The patterns of theory choice predicted by the model seem consistent with historical episodes of theory change.
Toda equations for Hurwitz numbers

We consider ramified coverings of P^1 with arbitrary ramification type over 0 and infinity and simple ramifications elsewhere and prove that the generating function for the numbers of such coverings is a tau-function for the Toda lattice hierarchy of Ueno and Takasaki.
Synthesis and acid- and base-promoted ring opening of polycarbocyclic oxiranes

Abstract Acid promoted ring opening of 1α,4α,4aα,9aα-tetrahydro-2β-3β-epoxy-1,4-methanoanthracene-9,10-dione and the corresponding 2-methyl derivative (i.e., 3a and 3b, respectively) afforded 4a and 4b in 26% and 49% yield, respectively. Similar results were obtained when a solution of either 3a or 3b in aqueous acetone was reacted with Na2CO3 at ambient temperature for 2 days. However, reaction of 3b with aqueous methanolic NaOH (ambient temperature, 7 days) produced a small quantity of 4b along with a novel pentacyclic diketone, 6b (44% yield). Finally, acid promoted ring opening of 1α,4α-dihydro-4aα,9aα-epoxy-1,4-methanoanthracene-9,10-dione (12) resulted in extensive skeltal rearrangement of the substrate, thereby affording 14 in low yield.
Inductive transfer and coordination of ligands in metal—metal bonded systems

Abstract Donor-acceptor complex formation between a range of neutral, dinuclear metal carboxylates and a range of Lewis bases has been monitored to obtain equilibrium constants and enthalpies for adduct formation. The acceptors studied are Rh2(but)4, Rh2(pfb)4, Mo2(pfb)4, Ru2(but)4Cl and Cr2(tfa)4(Et2O)2 (but = O2C4H7−, pfb = O2C4F7−, tfa = O2CCF3 −) and the donors include oxygen, sulphur, nitrogen and phosphorous donor atom bases. Spectrophotometric and calorimetric titrations were used to measure and apportion the experimental heats. The measured enthalpies of adduct bond formation thus correspond to stepwise complexation equilibria. Measurements with bases which varied in their covalent and electrostatic donor properties allowed definition of acid parameters to describe the dinuclear complexes by the E and C treatment. The spectral and calorimetric data point towards unusual stabilization of some of the donor-Rh dimer adduct bonds which was attributed to π-backbonding from populated Rh(II)Rh(II) π orbitals to empty donor orbitals of the proper symmetry. This provides one of the first quantitative estimates of π-backbond stabilization energies in transition metal systems. The π-backbonding effects were less pronounced for adduct formation with Ru2(but)4Cl (half-filled π orbitals) and not observed for Mo2(pfb)4 (unpopulated π orbitals). Correlation of the first and second enthalpies of adduct formation allowed determination of inductive transfer parameters to describe the inductive effects of coordination of the first base through the metal-metal bond to influence the coordination of the second base. The lowered acidity of the second metal centre upon complex formation at the first could be quantified by this treatment and the results correlated with the nature of the metal-metal bond. This correlation treatment was extended to IR data, νco of (CO)Rh2(pfb)4 (B) (B = base) adducts, and EPR data, g of (TEMPO) Rh2 (pfb)4 (B) adducts to demonstrate the relative E and C contributions to these spectral parameters. Donor complexation was observed to have profound influences upon the electronic structures of the various complexes as followed by electronic spectral shifts. The Cr2 (tfa)4(B)2 adducts provided additional means for monitoring changes in electronic structure. Magnetic susceptibilities of the Cr2(tfa)4(B)2 adducts were found to increase with B donor strength suggesting a direct exchange pathway to account for observed antiferromagnetism. Solid state measurements on three of the adducts (B = Et2O, Et3PO4, HMPA) gave -2J ranging from 611 to 688 cm−1, values which are larger than those measured for the well-studied cupric carboxylates, Cu2(O2CR)4 (B)2.
Influenza A (H1N1) and pandemic preparedness under the rule of international law.

A novel strain of Influenza A (H1N1) spread rapidly through Mexico in April 2009 and now spans the globe. By the time WHO was notified and responded, geographical containment was not feasible, leading the agency to call for mitigation. The international outbreak of SARS in 2003 and the more recent Influenza A (H5N1) among birds with limited transmission to humans helped prepare the world for the current pandemic threat. SARS galvanized the WHO to revise the antiquated International Health Regulations (IHR) in 2005, which took effect June 15, 2007. Governments instituted preparedness plans in response to avian influenza. Despite increased preparedness, the WHO and US Centers for Disease Control and Prevention (CDC) lack key powers and resources. Reminiscent of past responses, many governments are acting out of fear or economic and political self-interest rather than scientific reason. Above all, there are serious questions of global justice, as Mexicans are subject to stigma and discrimination. This article by Lawrence O. Gostin, O’Neill Professor of Global Health Law at Georgetown University, analyses WHO powers and resources including the pandemic alert system and the IHR, as well as the powers and resources of the CDC. He finds that although the response to H1N1 has been strong, the WHO and CDC need more authority and resources to deal with pandemic threats under the rule of international law.
Bose enhancement and Pauli blocking effects in transport models

Abstract The ability of semi-classical transport models to correctly simulate Pauli blocking and Bose enhancement is discussed. Inthe context of simple quantum mechanical systems, it is shown that (1 ± f) enhancements is inadequate to describesystems far from equilibrium. The relaxation of (1 + f) descriptions toward equilibrium is studied both in the context ofsimple models, including a hot pion gas confined to a box. We give simple estimates for the characteristics number of collisionsfor a system to relax toward equilibrium.
A solvable mixed charge ensemble on the line: global results

We consider an ensemble of interacting charged particles on the line consisting of two species of particles with charge ratio 2:1 in the presence of an external field. With the total charge fixed and the system held at temperature corresponding to β = 1, it is proved that the particles form a Pfaffian point process. When the external field is quadratic (the harmonic oscillator potential), we produce the explicit family of skew-orthogonal polynomials necessary to simplify the related matrix kernels. In this setting a variety of limit theorems are proved on the distribution of the number as well as the spatial density of each species of particle as the total charge increases to infinity. Connections to Ginibre’s real ensemble of random matrix theory are highlighted throughout.
Tradeoffs in metaprogramming

The design of metaprogramming languages requires appreciation of the tradeoffs that exist between important language characteristics such as safety properties, expressive power, and succinctness. Unfortunately, such tradeoffs are little understood, a situation we try to correct by embarking on a study of metaprogramming language tradeoffs using tools from computability theory. Safety properties of metaprograms are in general undecidable; for example, the property that a metaprogram always halts and produces a type-correct instance is Π02-complete. Although such safety properties are undecidable, they may sometimes be captured by a restricted language, a notion we adapt from complexity theory. We give some sufficient conditions and negative results on when languages capturing properties can exist: there can be no languages capturing total correctness for metaprograms, and no 'functional' safety properties above Σ03 can be captured. We prove that translating a metaprogram from a general-purpose to a restricted metaprogramming language capturing a property is tantamount to proving that property for the metaprogram.
Nevoid basal cell carcinoma (Gorlin) syndrome.

The nevoid basal cell carcinoma syndrome is characterized by numerous basal cell cancers and epidermal cysts of the skin, odontogenic keratocysts of the jaws, palmar and plantar pits, calcified dural folds, various neoplasms or hamartomas (ovarian fibromas, medulloblastoma, lymphomesenteric cysts, fetal rhabdomyomas, etc.) and various stigmata of maldevelopment (rib and vertebral abnormalities, cleft lip and/or palate, cortical defects of bones, etc.). Keywords: nevoid basal cell carcinoma; medulloblastoma; cardiac fibroma; epidermal cysts; odontogenic keratocysts; ovarian fibromas; patched homolog (Drosophila)
Heavy Fuels Ash Deposit Formation and Removal in Water-Cooled High-Temperature Gas Turbines

Experimental data obtained in heavy fuels operation of a gas turbine simulator with a water-cooled, transonic turbine nozzle cascade are presented. The ash fouling is characterized by the rate of decrease of the aerodynamic throat area. Particular attention is given to the cleanability of the ash deposits. A simple heat transfer analysis was performed to assist in evaluating the data. The rate of ash fouling in the water-cooled nozzle was found to be of the same order of magntude as for conventional air-cooled designs. Cleanability, both on and off-line, was found to be significantly enhanced, thus making the water-cooled gas turbine an attractive alternative for heavy fuels applications.
The strategic value of asymmetric information access for Cournot competitors

Abstract This paper develops an n-firm model of quantity competition in which a subset of k firms may obtain access to demand information observed by their rivals. The firms acquiring information access can adjust their quantity strategies in response to this extra information, which provides informational rents. We find that individual firms always have an incentive to acquire information access, but this acquisition decreases all other firms' expected profit. However, firms' information acquisition increases consumer surplus. Nevertheless, costly information and informational rents can lead to equilibria with differentially-informed competitors.
Dynamic Index Coding for Wireless Broadcast Networks

We consider a wireless broadcast station that transmits packets to multiple users. The packet requests for each user may overlap, and some users may already have certain packets. This presents a problem of broadcasting in the presence of side information, and is a generalization of the well-known (and unsolved) index coding problem of information theory. We represent the problem by a bipartite demand graph. Uncoded transmission is optimal if and only if this graph is acyclic. Next, we define a code-constrained capacity region that restricts attention to any prespecified set of coding actions. A dynamic max-weight algorithm that acts over variable length frames is developed. The algorithm allows for random packet arrivals and supports any traffic inside the code-constrained capacity region. A simple set of codes that exploit cycles in the demand graph are shown to be optimal for a class of broadcast relay problems.
Top homology of hypergraph matching complexes, p-cycle complexes and Quillen complexes of symmetric groups

Abstract We investigate the representation of a symmetric group S n on the homology of its Quillen complex at a prime p. For homology groups in small codimension, we derive an explicit formula for this representation in terms of the representations of symmetric groups on homology groups of p-uniform hypergraph matching complexes. We conjecture an explicit formula for the representation of S n on the top homology group of the corresponding hypergraph matching complex when n ≡ 1 mod p . Our conjecture follows from work of Bouc when p = 2 , and we prove the conjecture when p = 3 .
2,3:6,7-Bis(2',3'-quinolino)pentacyclo[6.5.0.04,12.05,10.09,13]tridecane

Abstract The title compound (4) was synthesized by two sequential Friedlaender condensations between pentacyclic bis(ketoester) 2 and o-aminobenzaldehyde. The dihedral angle between the two quinoline rings in 4 is 76.4°; the nonbonded NXXXN interatomic distance in 4 is 4.32 A.
Advanced MR Imaging of the Cruciate Ligaments

The anterior and posterior cruciate ligaments are crucial stabilizers of the knee. These ligaments are named by the location of their tibial attachments. Each ligament is composed of separate functional bundles that differ in size but are equally important in function. MR imaging is accurate and sensitive, making it the imaging technique of choice for evaluating these ligaments. Acute and chronic injuries involving the cruciate ligaments have typical appearances and associated findings. MR imaging interpretation must take into account atypical injuries and imaging pitfalls. Knowledge of normal ligament reconstruction techniques allows differentiation of the normal postoperative appearance from reconstruction failure and complications. Ligament reconstruction techniques, complications, and appearances are reviewed in this article.
PACE—A European programme of advanced continuing education

Abstract PACE — a European Programme of Advanced Continuing Education — originated in a proposal adopted by a Joint Europe/USA Forum held in Palo Alto, California and White Plains, N.Y. 16 to 24 September 1986. The Forum was attended by some 80 participants from the world of industry, higher education, government and several international and European organisations. It was organised by the European Society for Engineering Education (SEFI) in close cooperation with the Commission of the European Communities and sponsored by five major industrial corporations — British Telecom, IBM, Hewlett Packard, Philips and Thomson. Subsequently, the same companies, in association with representatives of European higher education institutions have decided to carry the proposal forward and created for this purpose a mechanism described below.
Distractor Filtering in Media Multitaskers

A growing amount of modern media is consumed simultaneously, a phenomenon known as 'media multitasking'. Individuals who regularly engage in this activity, heavy media multitaskers (HMMs), are more affected by irrelevant information that can intrude into a primary task than are light media multitaskers (LMMs--Ophir et al, 2009 Proceedings of the National Academy of Sciences of the USA 106 15583). However, the locus of this deficit is unknown, as previous research is consistent with both memory and attentional explanations. Here, we isolated attentional processes by employing a singleton distractor task with low working-memory demands. In this task, LMMs used top-down information to improve their performance, yet HMMs did not. This difference in performance in an established attentional capture task argues for the presence of attentional differences in HMMs and is consistent with the idea that HMMs maintain a wider attentional scope than LMMs, even when instructed otherwise.
Ionic plasma screening and long-range electron correlations in quasi-one-dimensional conductors

Abstract In quasi-one-dimensional systems with the intercalation-type doping, the dynamical response of dopant ions can substantially affect the interplay of density-wave and superconducting instabilities. A generic model system of Coulombically coupled Luttinger-liquid chains augmented by the interaction with the ion displacements is exactly solved in the forward-scattering channel providing for the resulting system excitations and electron correlations. For a jellium-like ion response, the effect of the bare electron–electron repulsion is essentially canceled by the ions. Superconducting correlations can then be developed due to a non-polarizational interaction with an additional phonon mode.
Chromium-catalyzed homoaldol equivalent reaction employing a nucleophilic propenyl acetate.

A scalable, highly regioselective chromium-catalyzed homoaldol equivalent reaction employing 3-bromopropenyl acetate as a masked homoenolate nucleophile in additions to aromatic, aliphatic, and α,β-unsaturated aldehydes under mild Cr/Mn redox conditions in good to excellent yields is reported. The resulting vinyl acetate-containing adducts are easily hydrolyzed with mild base to provide formal homoaldol adducts, or transformed to other more functionalized products by stereoselective transformations including epoxidation and cyclopropanation.
Bonding and interlayer charge transfer in the solid state compound Na1.9Cu2Se2Cu2O

Abstract The bonding and electronic structure of an electron-deficient solid Na 1.9 Cu 2 Se 2 Cu 2 O are analyzed with the extended Huckel tight-binding method. This solid consists of three kinds of layers: a Cu 2 O layer with square-coordinated oxygen atoms, an anti-PbO type Cu 2 Se 2 layer, and a cationic Na layer. The Cu 2 O layer has a closed-shell electronic structure, whereas the Cu 2 Se 2 layer needs two more electrons per Cu 2 Se 2 to complete a closed-shell configuration. Thus charge transfer takes place mainly from the Na layer to the Cu 2 Se 2 layer. The holes created by the incomplete occupancy at the Na sites reside in the Cu 2 Se 2 layer.
Information Technology and the World Economy

This paper addresses the impact of investment in information technology (IT) on the recent resurgence of world economic growth. We describe the growth of the world economy, seven regions and 14 major economies during the period 1989–2003. We allocate the growth of world output between input growth and productivity and find, surprisingly, that input growth greatly predominates! The contributions of IT investment have increased in all regions, but especially in industrialized economies and Developing Asia. Differences in per capita output are explained by differences in per capita input, rather than by variations in productivity.
The mark‐to‐market valuation and executive pay package regulations within the 2009 US (Bailout) Emergency Economic Stabilization Act

The paper shows that the effect of the Emergency Economic Stabilization Act (EESA) is ambiguous. It discusses the benefits and costs of mark‐to‐market valuation and design of executive pay package policies within the US 2009 EESA. It highlights how the mark‐to‐market valuation standard influenced financial institutions, explains why mark‐to‐market policy suspension proponents can support the EESA, and realizes how the Financial Accounting Standards Board (FASB) and Securities Exchange Commission (SEC) can count on the EESA while assessing the need and cost of the mark‐to‐market policy. Also, the paper discusses the promise of executive wage caps within the EESA. Moreover, it differentiates between executive pay packages pre‐ and post‐EESA policies.
The Cycle-Complete Graph Ramsey Numbers

In 1978 Erdos, Faudree, Rousseau and Schelp conjectured that \[ r ( C_{p},K_{r} ) = ( p-1 ) (r-1) +1 \] for every $p\,{\geq}\,r\,{\geq}\,3$, except for $p\,{=}\,q\,{=}\,3$. This has been proved for $r\,{\leq}\,6$, and for \[ p \geq r^{2}-2r\].In this note we prove the conjecture for $p\,{\geq}\,4r+2$.
Law, Ethics, and Public Health in the Vaccination Debates: Politics of the Measles Outbreak

The measles outbreak of early 2015 is symptomatic of a larger societal problem –the growing number of parents who decide against vaccinating their children. This failure is causing the resurgence of childhood diseases once eliminated from the United States.This article explores the legal and ethical landscape of vaccine exemptions. While all states require childhood vaccinations, they differ significantly in the types of religious and/or philosophical exemptions permitted, the rigor of the application process, and available review mechanisms. States with relaxed exemption policies disproportionately experience more outbreaks of vaccine-preventable disease.Vaccine exemptions are an illustration of the “tragedy of the commons,” in which parents choose not to vaccinate their children, relying on the fact that other parents will vaccinate their children, thus providing community immunity. However, the net result of many individual decisions not to vaccinate is the collapse of herd immunity and thus an upsurge in preventable disease and death.The failure to vaccinate puts others at risk, thus violating an important ethical principle. However, punishing individual parents could entrench political opposition to vaccine policy. The most ethical and effective solution is for state legislatures to tighten vaccination laws, making it more difficult to obtain non-medical exemptions.
Multipoint recognition of carboxylates by neutral hosts in non-polar solvents

Abstract A neutral molecular receptor of carboxylates has been developed using the convergent ureas as the binding site. The data indicate that chelation of the carboxylates occurs by the urea hydrogens. Asymmetric centers in the host are shown to influence the nmr spectrum of a guest bound within.
A shuffle that mixes sets of any fixed size much faster than it mixes the whole deck

Consider an n by n array of cards shufled in the following manner. An element x of the array is chosen uniformly at random. Then with probability 1/2 the rectangle of cards above and to the left of x is rotated 180deg;, and with probability 1/2 the rectangle of cards below and to the right of x is rotated 180°. It is shown by an eigenvalue method that the time required to approach- the uniform distribution is between n2/2 and cn2 in n for some constant c. On the other hand, for any k it is shown that the time needed to uniformly distribute a set of cards of size k is at most c(k)n, where c(k) is a constant times k3 In(k)2. This is established via coupling; no attempt is made to get a good constant. © 1994 John Wiley & Sons, Inc.
Forty Years of In Vitro Evolution

It has been 40 years since Spiegelman and co-workers demonstrated how RNA molecules can be evolved in the test tube. This result established Darwinian evolution as a chemical process and paved the way for the many directed evolution experiments that followed. Chemists can benefit from reflecting on Spiegelman's studies and the subsequent advances, which have taken the field to the brink of the generation of life itself in the laboratory. This Review summarizes the concepts and methods for the directed evolution of RNA molecules in vitro.
Structure, Electrochemistry, and Magnetism of the Iron(III)-Substituted Keggin Dimer, [Fe6(OH)3(A-α-GeW9O34(OH)3)2]11-

The iron(III)-substituted tungstogermanate [Fe6(OH)3(A-α-GeW9O34(OH)3)2]11- (1) has been synthesized and characterized by IR, elemental analysis, SQUID magnetometry, electron paramagnetic resonance (EPR), and electrochemistry. Single-crystal X-ray analysis was carried out on Cs4Na7[Fe6(OH)3(A-α-GeW9O34(OH)3)2]·30H2O, which crystallizes in the monoclinic system, space group C2/m, with a = 36.981(4) A, b = 16.5759(15) A, c = 16.0678(15) A, β = 95.311(3)°, and Z = 4. Polyanion 1 consists of two (A-α-GeW9O34) Keggin moieties linked via six Fe3+ ions, leading to a double-sandwich structure. The equivalent iron centers represent a trigonal prismatic Fe6 fragment, resulting in virtual D3h symmetry for 1. Electrochemistry studies revealed that 1 is stable in solution from pH 3 to at least pH 7. In pH = 3 media the reduction of the six Fe3+ centers was featured by a single voltammetric wave for most supporting electrolytes used. In that case, whatever the scan rate from 1000 mV·s-1 down to 2 mV·s-1, no splitting o...
Positive peritoneal cytology in patients with gastric cancer: natural history and outcome of 291 patients.

Background. Positive peritoneal cytology is a predictor of poor survival in patients with gastric cancer. Our aim is to more clearly define the natural history of this cohort.
Bis(imine)-copper(II) complexes as chiral lewis acid catalysts for the Diels-Alder reaction

Abstract We report the Diels-Alder reactions of imide-derived dienophiles 2a – 2d and 4b – 4d with cyclopentadiene catalysed by square-planar Cu(OTf) 2 -bis(imine) complexes. The 2,6-dichlorophenyl-substituted ligand 1a was found to be generally the most effective for a range of substrates, affording products from 83–94% enantiomeric excess. Although endo:exo diastereoselectivity for the oxo-substituted imides 2a – 2d is low, significant improvement is achieved with the thiazolidine-2-thione analogues 4b – 4d , which provide enhanced dienophile reactivity and enhanced endo:exo diastereoselection.
Reactions of naphthalene in N2O5 ? NO3 ? NO2 ? air mixtures

The reactions of naphthalene in N2O5NO3NO2N2O2 reactant mixtures have been investigated over the temperature range 272–297 K at ca. 745 torr total pressure and at 272 K and ca. 65 torr total pressure using long pathlength Fourier transform infrared absorption spectroscopy. 2,3-Dimethyl-2-butene was added to the reactant mixtures at 272 K to rapidly scavenge the NO3 radicals both initially present in the added N2O5 and formed from the thermal decomposition of N2O5 during the reactions. The data obtained in the presence and absence of added 2,3-dimethyl-2-butene showed that napthalene undergoes initial reaction with the NO3 radical to form an NO3-naphthalene adduct, which either rapidly decomposes back to the reactants (at a rate of ca. 5 × 105 s−1 at 298 K) or reacts exclusively with NO2 to form products. When NO3 radicals, N2O5 and NO2 are in equilibrium, this overall process is kinetically equivalent to reaction of naphthalene with N2O5, and previous kinetic and product studies have indeed assumed the reactions of naphthalene and alkyl-substituted naphthalenes in N2O5NO3NO2air mixtures to be with N2O5, and not with NO3 radicals.
Encoding multiple quantum coherences in non-commuting bases

Abstract Multiple quantum (MQ) coherences are characterized by their coherence number and the number of spins that make up the state, though only the coherence number is normally measured. We present a simple set of measurements that extend our knowledge of the MQ state by recording the coherences in two non-commuting bases—the x and the z bases (related by a similarity transformation). The measurement of coherences in a basis other than the usual z basis also permits the study of spin dynamics under Hamiltonians that conserve z basis coherence number.
Mechanism of Dendritic Branching

Theories of dendritic growth currently ascribe pattern details to extrinsic perturbations or other stochastic causalities, such as selective amplification of noise and marginal stability. These theories apply capillarity physics as a boundary condition on the transport fields in the melt that conduct the latent heat and/or move solute rejected during solidification. Predictions based on these theories conflict with the best quantitative experiments on model solidification systems. Moreover, neither the observed branching patterns nor other characteristics of dendrites formed in different molten materials are distinguished by these approaches, making their integration with casting and microstructure models of limited value. The case of solidification from a pure melt is reexamined, allowing instead the capillary temperature distribution along a prescribed sharp interface to act as a weak energy field. As such, the Gibbs-Thomson equilibrium temperature is shown to be much more than a boundary condition on the transport field; it acts, in fact, as an independent energy field during crystal growth and produces profound effects not recognized heretofore. Specifically, one may determine by energy conservation that weak normal fluxes are released along the interface, which either increase or decrease slightly the local rate of freezing. Those responses initiate rotation of the interface at specific locations determined by the surface energy and the shape. Interface rotations with proper chirality, or rotation sense, couple to the external transport field and amplify locally as side branches. A precision integral equation solver confirms through dynamic simulations that interface rotation occurs at the predicted locations. Rotations points repeat episodically as a pattern evolves until the dendrite assumes a dynamic shape allowing a synchronous limit cycle, from which the classic repeating dendritic pattern develops. Interface rotation is the fundamental mechanism responsible for dendritic branching.
The 5 Electron Case of Thomson's Problem

We give a rigorous computer-assisted proof that the triangular bipyramid is the unique configuration of five points on the sphere that globally minimizes the Coulomb (1/r) potential. We also prove the same result for the (1/r 2) potential. The main mathematical contribution of the paper is a fairly efficient energy estimate that works for any number of points and any power-law potential.
Existence of compatible families of proper regular conditional probabilities

Let (Ω, ℱ, μ) be a perfect probability space with ℱ countably generated, and let IB be a family of sub-σ-fields of ℱ. Under a countability condition on the family IB, I show that there exists a family {π∇}∇∈IB of regular conditional probabilities which are everywhere compatible. Under a more stringent condition on IB, I show that the π∇ can furthermore be chosen to be everywhere proper. It follows that in the Dobrushin-Lanford-Ruelle formulation of the statistical mechanics of classical lattice systems, every (perfect) probability measure is a Gibbs measure for some specification.
Transpiration in the global water cycle

Abstract A compilation of 81 studies that have partitioned evapotranspiration (ET) into its components—transpiration (T) and evaporation (E)—at the ecosystem scale indicates that T accounts for 61% (±15% s.d.) of ET and returns approximately 39 ± 10% of incident precipitation (P) to the atmosphere, creating a dominant force in the global water cycle. T as a proportion of ET is highest in tropical rainforests (70 ± 14%) and lowest in steppes, shrublands and deserts (51 ± 15%), but there is no relationship of T/ET versus P across all available data ( R 2 = 0.01). Changes to transpiration due to increasing CO 2 concentrations, land use changes, shifting ecozones and climate warming are expected to have significant impacts upon runoff and groundwater recharge.
Sufficient conditions for topological order in insulators

We prove the existence of low-energy excitations in insulating systems at general filling factor under certain conditions, and discuss in which cases these may be identified as topological excitations. In the specific case of half-filling this proof provides a significantly shortened proof of the recent higher-dimensional Lieb-Schultz-Mattis theorem.
Transfer, breakup, and fusion reactions of 6 He with 209 Bi near the Coulomb barrier

The fusion of 6He with a 209Bi target displays a large enhancement at energies near to and below the Coulomb barrier. Recently, a 4He group of remarkable intensity, which dominates the total reaction cross-section, has also been observed in the near-barrier interaction of the same system. It is argued that this transfer/breakup channel acts as a doorway state to fusion.
Jet Mixing Noise from Fine-Scale Turbulence

It is known that turhulent mixing noise from high-speed jets consists of two components. They are the noise from large turbulent structures in the form of Mach wave radiation and the less directional fine-scale turbulence noise. The Mach wave radiation dominates in the downstream direction. The fine-scale turbulence noise dominates in the sideline and upstream directions. A semiempirical theory is developed for the prediction of the spectrum, intensity, and directivity of the fine-scale turhulence noise. The prediction method is self-contained. The turbulence information is supplied by the k-e turhulence model. The theory contains three empirical constants beyond those of the k-e model. These constants are determined by best fit of the calculated noise spectra to experimental measurements. Extensive comparisons between calculated and measured noise spectra over a wide range of directions of radiation,jet velocities, and temperatures have heen carried out. Excellent agreements are found. It is believed that the present theory offers significant improvements over current empirical or semiempirical jet noise prediction methods in use. There is no first principle jet noise theory at the present time.
Identification of a Potential Receptor That Couples Ion Transport to Protein Kinase Activity

In our previous studies, we have demonstrated that the Src-coupled α1 Na/K-ATPase works as a receptor for cardiotonic steroids, such as ouabain, to regulate cellular protein kinase cascades. Here, we explore further the structural determinants of the interaction between the α1 Na/K-ATPase and Src and demonstrate that the Src-coupled α1 Na/K-ATPase allows the cell to decode the transmembrane transport activity of the Na/K-ATPase to turn on/off protein kinases. The α1 Na/K-ATPase undergoes E1/E2 conformational transition during an ion pumping cycle. The amount of E1 and E2 Na/K-ATPase is regulated by extracellular K(+) and intracellular Na(+). Using purified enzyme preparations we find that the E1 Na/K-ATPase can bind both the Src SH2 and kinase domains simultaneously and keep Src in an inactive state. Conversely, the E1 to E2 transition releases the kinase domain and activates the associated Src. Moreover, we demonstrate that changes in E1/E2 Na/K-ATPase by either Na(+) or K(+) are capable of regulating Src and Src effectors in live cells. Together, the data suggest that the Src-coupled α1 Na/K-ATPase may act as a Na(+)/K(+) receptor, allowing salt to regulate cellular function through Src and Src effectors.