cssi/SciSciGPT-SciSciNet huggingface dataset:
Cosmology of F-theory GUTs

In this paper we study the interplay between the recently proposed F-theory GUTs and cosmology. Despite the fact that the parameter range for F-theory GUT models is very narrow, we find that F-theory GUTs beautifully satisfy most cosmological constraints without any further restrictions. The viability of the scenario hinges on the interplay between various components of the axion supermultiplet, which in F-theory GUTs is also responsible for breaking supersymmetry. In these models, the gravitino is the LSP and develops a mass by eating the axino mode. The radial component of the axion supermultiplet known as the saxion typically begins to oscillate in the early Universe, eventually coming to dominate the energy density. Its decay reheats the Universe to a temperature of ∼1GeV, igniting BBN and diluting all thermal relics such as the gravitino by a factor of ∼10−4 − 10−5 such that gravitinos contribute a sizable component of the dark matter. In certain cases, non-thermally produced relics such as the axion, or gravitinos generated from the decay of the saxion can also contribute to the abundance of dark matter. Remarkably enough, this cosmological scenario turns out to be independent of the initial reheating temperature of the Universe. This is due to the fact that the initial oscillation temperature of the saxion coincides with the freeze out temperature for gravitinos in F-theory GUTs. We also find that saxion dilution is compatible with generating the desired baryon asymmetry from standard leptogenesis. Finally, the gravitino mass range in F-theory GUTs is 10 − 100MeV, which interestingly coincides with the window of values required for the decay of the NLSP to solve the problem of 7Li over-production.
Convergence of fundamental solutions of linear parabolic equations under Cheeger–Gromov convergence

In this note we show the convergence of the fundamental solutions of the parabolic equations assuming the Cheeger–Gromov convergence of the underlying manifolds and the uniform L1-bound of the solutions. We also prove a local integral estimate of fundamental solutions.
Viable prices in financial markets with solvency constraints

Abstract We study the viability of a securities market model with continuous trading in which agents are required to remain solvent at all times and cannot add funds to their portfolio of securities in excess of an exogenous endowment. A financial security is characterized by its dividends and its usefulness as a collateral for borrowing. We show that viability, a notion introduced by Harrison and Kreps (1979), is equivalent to the existence of a pair of continuous linear functionals, defined on the consumption space and “risk-adjusted reserve” space, such that their sum represents a linear pricing rule for cash flows consistent with security prices. We also show that viability is equivalent to the existence of a state price process such that the adjusted total gains from securities are local martingales. In particular, one can construct a probability measure under which the discounted total gains of securities with the same collateral quality as the riskless asset are martingales. The discounted total gains of lower quality securities are submartingales. The state price process is always equal to the process of cash flow “shadow” price times an increasing process. Finally, we characterize the riskless rate and local risk premia on securities.
Countercyclical Pricing in Customer Markets

I present a dynamic model of price determination in customer markets that are subject to exogenous business cycle fluctuations. The business cycle is described in terms of a Markov process, in which market demand alternates stochastically between fast growth (boom) and slow growth (recession) phases. In the consumers' preferred equilibrium outcome, (1) prices are below the monopoly level, and (2) prices are countercyclical when demand growth rates are positively correlated through time. A firm faces a dynamic trade-off when making its current price selection. While a higher price may raise a firm's profit in the short term, it also may diminish the firm's reputation for low prices, leading to lower profits in the future.
Possible resolution of black hole singularities from large N gauge theory

We point out that the recent conjecture relating large N gauge theories to string theory in anti-de Sitter spaces offers a resolution in principle of many problems in black hole physics. This is because the gauge theory also describes spacetimes which are not anti-de Sitter, and include black hole horizons and curvature singularities.
Universality in one-dimensional orbital wave ordering in spinel and related compounds: an experimental perspective

Recent state-of-the-art crystallographic investigations of transition metal spinel compounds have revealed that the d-orbital charge carriers undergo ordering transitions with the formation of local 'molecular bonding' units such as dimers in MgTi2O4, octomers in CuIr2S4, and heptamers in AlV2O4. Herein, we provide a unifying scheme involving one-dimensional (1D) orbital wave (OW) ordering applicable to all of these spinels. The relative phase of the orbitals in the chains is shown to be crucial to the formation of different local units, and thus both the amplitude and phase of the OW play important roles. Examination of Horibe et al's (2006 Phys. Rev. Lett. 96 086406) structure for AlV2O4 serves as the vehicle for developing the general behaviour for such orbital wave ordering. Ordered AlV2O4 will be seen to organize into three equivalent chains in 2D Kagome planes coupled so as to form units of three dimer bonds. Three additional equivalent chains manifest a more complex tetramerization with three different charge states and two different bonding schemes. The OW ordering scheme developed is extended to other spinel and related compounds with local triangular transition metal coordination and partial filling of the t2g-d orbitals.
Measuring protein interactions using Förster resonance energy transfer and fluorescence lifetime imaging microscopy

Abstract The method of fluorescence lifetime imaging microscopy (FLIM) is a quantitative approach that can be used to detect Forster resonance energy transfer (FRET). The use of FLIM to measure the FRET that results from the interactions between proteins labeled with fluorescent proteins (FPs) inside living cells provides a non-invasive method for mapping interactomes. Here, the use of the phasor plot method to analyze frequency domain (FD) FLIM measurements is described, and measurements obtained from cells producing the ‘FRET standard’ fusion proteins are used to validate the FLIM system for FRET measurements. The FLIM FRET approach is then used to measure both homologous and heterologous protein–protein interactions (PPI) involving the CCAAT/enhancer-binding protein alpha (C/EBPα). C/EBPα is a transcription factor that controls cell differentiation, and localizes to heterochromatin where it interacts with the heterochromatin protein 1 alpha (HP1α). The FLIM-FRET method is used to quantify the homologous interactions between the FP-labeled basic leucine zipper (BZip) domain of C/EBPα. Then the heterologous interactions between the C/EBPa BZip domain and HP1a are quantified using the FRET-FLIM method. The results demonstrate that the basic region and leucine zipper (BZip) domain of C/EBPα is sufficient for the interaction with HP1α in regions of heterochromatin.
Numerical error estimation for nonlinear hyperbolic PDEs via nonlinear error transport

Abstract The estimation of discretization error in numerical simulations is a key component in the development of uncertainty quantification. In particular, there exists a need for reliable, robust estimators for finite volume and finite difference discretizations of hyperbolic partial differential equations. The approach espoused here, often called the error transport approach in the literature, is to solve an auxiliary error equation concurrently with the primal governing equation to obtain a point-wise (cell-wise) estimate of the discretization error. Nonlinear, time-dependent problems are considered. In contrast to previous work, fully nonlinear error equations are advanced, and potential benefits are identified. A systematic approach to approximate the local residual for both method-of-lines and space–time discretizations is developed. Behavior of the error estimates on problems that include weak solutions demonstrates the positive properties of nonlinear error transport.
Oxidation Studies of Crystalline CVD Silicon Nitride

Oxidation studies of CVD were performed in dry oxygen, oxygen‐argon, and oxygen‐nitrogen‐argon gas mixtures of various oxygen and nitrogen partial pressures at a total pressure of 1 atm at 1100°–1400°C. Parallel oxidation studies of single‐crystal silicon were also conducted for direct comparison. It was observed that the oxidation of both and Si followed parabolic growth kinetics with activation energies of about 115 kcal/mol and about 30 kcal/mol, respectively. The formation of a single layer of and evolution of could not account for the much lower parabolic rate constants and much higher activation energy for than for Si during the oxidation. Detailed characterization of the oxidation scales using ellipsometry, step‐by‐step etching, SIMS, and XPS techniques indicated that a duplex oxidation scale consisting of and was formed when was oxidized. The intermediate scale was identified as a single‐phase material, not a physical mixture of and . The low oxidation rate and high activation energy for during the oxidation were attributed to the formation of and low oxygen diffusivity in this structurally dense phase.
Synthesis, Characterization, and Properties of Zero-Valent Iron Nanoparticles

This chapter provides an overview of synthesis, characterization and property measurements techniques important for making understanding the nature of zero valent iron nanoparticles. The chemical reactivity of nanometer-sized materials can be quite different from that of either bulk forms of a material or the individual atoms and molecules that comprise it. Advances in our ability to synthesize, visualize, characterize and model these materials have created new opportunities to control the rates and products of chemical reactions in ways not previously possible. Zero valent iron (ZVI), including non-nanoparticle forms for iron, is one of the most promising remediation technologies for the removal of mobile chlorinated hydrocarbons and reducible inorganic anions for ground water. ZVI nanoparticles may have great potential to assist environmental remediation, but there are significant scientific and technological questions that remain to be answered. Understanding of ZVI reactive metal core-shell nanoparticles requires use of particles that are as well characterized and understood as possible. In this chapter we describe the issues and provide examples that include synthesis of nanoparticles, analytical characterization of the particles and finally measurements of their chemical properties.
USING PHOSPHONATES TO PROBE STRUCTURAL DIFFERENCES BETWEEN TRANSURANIUM ELEMENTS AND THEIR PROPOSED SURROGATES

A variety of transuranium phosphonates have now been prepared and structurally characterized allowing for comparisons to be made with other metal ions that have been proposed to be surrogates for transuranics (e.g., Zr4+, Ce4+, Th4+, and U4+). The phosphonates that will be discussed in this work include Np(CH3PO3)(CH3PO3H)(NO3)(H2O)·H2O, Pu(CH3PO3)2, M[CH2(PO3)2](H2O)n (M=Ce, Th, U, Np, Pu; n = 0 − 2), and UO2An(H2O)2[CH2(PO3)(PO3H)]2 (An = Th, Np, Pu). Through the examination of these structures, rare coordination geometries for actinides have been uncovered. Simple periodic trends based solely on ionic radii are absent. However, there are examples where surrogate elements adopt the same composition and structure as transuranics, such as Pu(CH3PO3)2 versus Zr(CH3PO3)2.
A time-optimal delaunay refinement algorithm in two dimensions

We propose a new refinement algorithm to generate size-optimal quality-guaranteed Delaunay triangulations in the plane. The algorithm takes O(n log n + m) time, where n is the input size and m is the output size. This is the first time-optimal Delaunay refinement algorithm.
A convenient synthesis of L-α-vinylglycine from L-homoserine lactone

A procedure for the synthesis of L-α-vinylglycine from L-homoserine lactone is described. The route developed is convenient (only one chromatography step is required) and efficient (72% yield; ≥95% optical yield over 4 steps). Key features include the use of acid-labile protecting groups for the amino (Boc) and carboxyl (diphenylmethyl ester) groups, and the use of the phenylselenolate equivalent derived from sodium borohydride and diphenyl diselenide for L-homoserine lactone cleavage.
What after Java? From objects to actors

Abstract In this paper, we discuss some drawbacks of the Java programming language, and propose some potential improvements for concurrent object-oriented software development. In particular, we argue that Java's passive object model does not provide an effective means for building distributed applications, critical for the future of Web-based next-generation information systems. Specifically, we suggest improvements to Java's existing mechanisms for maintaining consistency across multiple threads (e.g. synchronized), sending asynchronous messages (e.g. start/run methods) and controlling resources (e.g. thread scheduling). We drive the discussion with examples and suggestions from our own work on the Actor model of computation.
Synthesis of β-difluorine-containing amino acids

Abstract A convenient strategy was developed to prepare several β-difluoroamino acids. As exemplified by the synthesis of 3,3-difluoro- l -homocysteine, 3,3-difluoro- l -homoserine and 3,3-difluoro- l -methionine, the reaction sequence all started from l -isoascorbic acid. This approach holds potential to be extended to make other β-difluorine-containing amino acids.
Analysis of Accretion and Deletion at Boundaries in Dynamic Scenes

In dynamic scenes, the presence of object boundaries is often signaled by the appearance or disappearance of occluded surfaces over time. Such regions of surface accretion or deletion can be found using matching techniques similar to those used to determine optical flow in an image sequence. Regions in one frame that are not adequately matched by any region in previous frames correspond to accretion. Regions that have no matches in subsequent frames correspond to deletion. In either case, an occlusion boundary is present. Furthermore, by associating accretion or deletion regions with a surface on one side of a boundary, it is possible to determine which side of the boundary is being occluded. This association can be based purely on visual motion-the accretion or deletion region moves with the same image velocity as the remaining visible surface to which it is attached.
D-branes and discrete torsion II

We derive D-brane gauge theories for 3/n × n orbifolds with discrete torsion and study the moduli space of a D-brane at a point. We show that, as suggested in previous work, closed string moduli do not fully resolve the singularity, but the resulting space — containing n−1 conifold singularities — is somewhat surprising. Fractional branes also have unusual properties. We also define an index which is the CFT analog of the intersection form in geometric compactification, and use this to show that the elementary D6-brane wrapped about T6/n × n must have U(n) world-volume gauge symmetry.
Exploring the Robustness of the Balance of Payments- Constrained Growth Idea in a Multiple Good Framework

This paper derives the balance of payments-constrained growth (BPCG) model as a special case of a three good framework that incorporates exportables, importables, and non-tradables. The conditions under which the canonical form of the BPCG rate can be derived are made explicit and the assumptions scrutinized. It is shown that the presence of nontradables, substitutability between exportables and importables, and incomplete specialization in expenditure generally dampen the externallyconstrained growth rate. These …ndings help explain why empirical estimates tend to overestimate the BPCG rate. Overall our …ndings underscore the observation that tests of the BPCG hypothesis are as much a test of the internal structure of the economy under consideration.
The Incentive and Selection Roles of Sales Force Compensation Contracts

Abstract Designing compensation plans with an appropriate level of incentives is a key decision faced by managers of direct sales forces. the authors use data on individual salesperson compensation contracts to show that firms design their pay plans to both discriminatingly select (i.e., attract and retain) salespeople and provide them with the right level of incentives. consistent with standard agency arguments, the authors find that firms use higher-powered incentives as the importance of agent effort increases. at the same time, the authors find strong support for the selection role of these contracts. specifically, agents with greater selling ability and lower risk aversion are associated with jobs offering higher-powered incentives. Finally, consistent with prior findings on incentive contracts, the authors find no support for the insurance implication of the typical agency model. the authors rule out alternative explanations for this anomalous result and find that the selection role of contracts bes...
The effects of a supervisor's active intervention in subordinates' judgments, directional goals, and perceived technical knowledge advantage on audit team judgments

ABSTRACT: Prior research shows that an audit supervisor’s active intervention in a subordinate’s judgment distorts that judgment. However, subordinates’ judgments are only one input into audit team judgments. How do supervisors finalize audit team judgments after actively intervening in their subordinates’ judgments? In an experiment using audit teams, supervisors with weaker or stronger goals to reach a client-preferred conclusion either were or were not asked to first actively coach a subordinate’s judgment (i.e., active intervention) before reviewing it and finalizing the audit team’s judgment. Supervisors’ intervention influenced subordinates’ inputs, which, in turn, supervisors incorporated into their final judgments. More interestingly, intervention biased supervisors’ final judgments, controlling for supervisor directional goal strength and for concurrent effects on subordinates’ inputs. However, supervisors distorted their judgments less as they perceived a larger technical knowledge advantage ove...
Kinetic resolution of unsaturated amides in a chlorocyclization reaction: concomitant enantiomer differentiation and face selective alkene chlorination by a single catalyst.

The first example of a kinetic resolution via chlorofunctionalization of olefins is reported. The enantiomers of racemic unsaturated amides were found to have different hydrogen-bonding affinities for chiral Lewis bases in numerous solvents. This interaction was exploited in developing a kinetic resolution of racemic unsaturated amides via halocyclization. The same catalyst serves to both “sense chirality” in the substrate as well as mediate a highly face-selective chlorine delivery onto the olefin functionality, resulting in stereotriad products in up to 99:1 dr and up to 98.5:1.5 er. The selectivity factors were typically greater than 50 to allow for the simultaneous synthesis of both the products and unreacted substrates in highly enantioenriched form at yields approaching 50%. The reaction employs catalytic amounts (≤0.50 mol %) of a commercially available and recyclable organocatalyst.
PI 3-kinase and disease

Phosphoinositide 3-Kinase (PI3K) is a central enzyme in a signaling pathway that mediates cellular responses to insulin and other growth factors. This enzyme phosphorylates the 3 position of phosphatidylinositol-4,5-bisphosphate to produce phosphatidyl-inositol-3,4,5-trisphosphate (PIP3) at the plasma membrane. A number of signaling proteins, including the Ser/Thr protein kinases, AKT and PDK1, contain pleckstrin homology domains that bind specifically to PIP3. Thus, the generation of PIP3 at the plasma membrane in response to activation of PI3K by growth factors results in the initiation of downstream Ser/Thr phosphorylation cascades that control a variety of cellular responses. The signaling pathway downstream of PI3K is highly conserved from worms and flies to humans and genetic analysis of the pathway has revealed a conserved role in regulating glucose metabolism and cell growth. Based on deletion of genes encoding the catalytic or regulatory subunits of PI3K in the mouse, PI3K mediates insulin dependent regulation of glucose metabolism, and defects in activation of this pathway result in insulin resistance. In contrast, mutational events that lead to hyperactivation of the PI3K pathway result in cancers. Activating mutations in PIK3CA, encoding the p110alpha catalytic subunit of PI3K or inactivating mutations in PTEN, a phosphoinositide 3-phosphatases that reverses the effects of PI3K, are among the most common events in solid tumors. PI3K driven tumors are FDG-PET positive and turning off PI 3-Kinase with PI3K inhibitors that are in human clinical trials results in an acute decline in FDG-PET signal that precedes tumor shrinkage. Importantly, there is increasing evidence that some tumors express high levels of insulin receptor and activate PI3K due to elevated serum insulin in patients with insulin resistance. These results suggest that elevations in serum insulin may partially explain the link between obesity, diabetes and cancers. The role of PI3K inhibitors for treating cancers in mouse models and in human trials will be discussed.
Further Utilization of Mucohalic Acids: Palladium-Free, Regioselective Etherification and Amination of α,β-Dihalo γ-Methoxycarbonyloxy and γ-Acetoxy Butenolides

Palladium-free etherification and amination of mucohalic acid methyl carbonates 1e (3,4-dichloro-5-methoxycarbonyloxy-5H-furan-2-one) and 1f (3,4-dibromo-5-methoxycarbonyloxy-5H-furan-2-one) and mucochloric acid acetate 1h (3,4-dichloro-5-acetoxy-5H-furan-2-one) was achieved to afford γ-functionalized α,β-unsaturated γ-butyrolactones in good to excellent yield.
Imaging Spectroscopy for Extrasolar Planet Detection

We propose that coronagraphic imaging in combination with moderate to high spectral resolution from the outset may prove more effective in both detecting extrasolar planets and characterizing them than a standard coronagraphic imaging approach. We envisage an integral-field spectrograph coupled to a coronagraph to produce a data cube of two space dimensions and one wavelength. For the idealized case where the spectrum of the star is well known and unchanging across the field, we discuss the utility of cross-correlation to seek the extrasolar planet signal and describe a mathematical approach to completely eliminate stray light from the host star (although not its Poisson noise). For the case where the point-spread function (PSF) is dominated by diffraction and scattering effects and comprises a multitude of speckles within an Airy pattern, typical of a space-based observation, we turn the wavelength dependence of the PSF to advantage and present a general way to eliminate the contribution from the star while preserving both the flux and spectrum of the extrasolar planet. We call this method spectral deconvolution. We illustrate the dramatic gains by showing an idealized simulation that results in a 20 ? detection of a Jovian planet at 2 pc with a 2 m coronagraphic space telescope, even though the planet's peak flux is only 1% that of the PSF wings of the host star. This scales to detection of a terrestrial extrasolar planet at 2 pc with an 8 m coronagraphic Terrestrial Planet Finder in ~7 hr (or less with appropriate spatial filtering). Data on the spectral characteristics of the extrasolar planet and hence on its atmospheric constituents and possible biomarkers are naturally obtained as part of this process.
Theoretical and experimental investigation of the motion of multiphase fluids containing paramagnetic nanoparticles in porous media

Abstract Paramagnetic nanoparticles are potentially useful for monitoring of immiscible fluids distribution in subsurface, as they can be induced to move by an imposed magnetic field. The nanoparticles can be designed to be preferentially adsorbed at oil–water interface, as well as to have the long-term dispersion stability with minimal retention in the porous medium to be monitored. When exposed to magnetic field, they generate sufficient interfacial movements for external detection. When paramagnetic nanoparticles are either adsorbed at oil–water or air–water interface or dispersed in one of two fluid phases co-existing in pores, and exposed to external magnetic field, the resultant particle movements displace the interface. Interfacial tension acts as a restoring force, leading to interfacial fluctuation and a pressure (sound) wave. Our previous work (Prodanovic et al., 2010) provided a theoretical explanation for the motion of the interface between a suspension of paramagnetic nanorods and a non-magnetized fluid in a cylindrical dish, as measured by phase-sensitive optical coherence tomography (PS-OCT). Here we report on additional experiments carried out with a range of in-house synthesized and surface-modified iron-oxide nanoparticles. We also improved numerical method to be volume conserving for more quantitative matching. The measurements of interfacial motion by PS-OCT reported confirm theoretical predictions of the frequency doubling and the importance of material properties, such as magnetic susceptibility, for the interface displacement. The results are encouraging: this laboratory and modeling study is thus an important step to develop a magnetic field-based method for an accurate, non-invasive determination of multiphase fluids distribution in reservoir rock. With the combined experimental and modeling work, strategies for improved nanoparticle design will be developed so that the interfacial, thereby acoustic, response can be magnified.
The Radical of a Vertex Operator Algebra Associated to a Module

Abstract The radical of a vertex operator algebra associated to a module is defined and computed.
Parity violation in top quark pair production at the Fermilab Tevatron collider

Abstract The leading weak corrections to the production of top quark pairs via q q → t t in p p collisions are evaluated. The chromoanapole form factor of the top quark and effects of parity violation are studied in the Standard Model (SM) and the Minimal Supersymmetric Model (MSSM). The parity violation effect in q q → g → t t from the SM weak corrections is found to be very small. In the MSSM, the effects of parity violation can be enhanced for tan β≜ ν2 ν1 > m t m b .
National Election Cycles and the Intermittent Political Safeguards of Federalism

Scholars have challenged the notion of “political safeguards of federalism” in a large and well-developed body of work on the use of coercive policy tools by the federal government. This study suggests, however, that there may be some utility in re-examining the political factors that help to constrain the growth of national power. Specifically, it argues that the need to win votes from subnational constituencies makes national lawmakers less supportive of mandates, preemptions, and tax sanctions during election cycles and, thus, provides an intermittent safeguard of state authority. It tests and finds evidence for hypotheses related to that general argument in analyses of the passage of coercive federalist policies over the last thirty years.
Teaching Rigid Body Mechanics Using Student-Created Virtual Environments

This paper describes a recent effort to use student-created virtual environments to teach rigid body dynamics to electrical and computer engineering senior-level undergraduates and first-year graduate students. Many of these students have no background in dynamics except for their freshman year physics course. The approach described here relies on students creating their own virtual environments, takes roughly four to five weeks of instruction, and fits within the scope of other courses that may require electrical and computer engineering students to be familiar with dynamics. The background required consists of only basic linear algebra and ordinary differential equations. By the end of the pilot class, the majority of students were able to expertly model and animate high degree-of-freedom systems, such as slip-steered vehicles, helicopters, submarines, balancing unicycles, motorcycles, and puppets. A core component of the learning philosophy is that by providing students with a venue for creating their own virtual laboratories, they are able to promote their own learning. This paper summarizes the basic material presented to students, some of the virtual environments they chose to implement with only minimal guidance, and three instruments used to assess the effectiveness of the class architecture.
Crowding Out, Deficits, and Interest Rates: Reply

Spector and Van Cott argue that ‘... statistical significance of the relationship between interest rates and the deficit is irrelevant for the question of crowding out.’ This Reply in turn argues that studies of the impact of deficits upon interest rates may be very useful in determining whether (and perhaps how) crowding out occurs and that additional empirical analysis involving the interest sensitivity of commodity demand is necessary to then quantify the actual degree of crowding out.
Mars: Near‐infrared spectral reflectance and compositional implication

Several distinct absorption features, some recognized for the first time, are evident in a newly obtained reflectance spectrum (wavelengths = 0.62-2.6 microns, reciprocal dispersion = 83) of the integral disk of Mars. The effects of Martian atmospheric CO2 have been removed from the spectrum to arrive at a reflectance spectrum that is believed to be due mostly to surface material. Absorptions, at 1.22, 1.55, and 2.05 microns are interpreted to indicate the presence of H2O ice plus high desiccated mineral hydrate, although an H2O ice phase with strongly shifted fundamental frequencies cannot be ruled out. Ferrosilicate and ferric oxide bands near and shortward of 1.0 micron are confirmed. The new observations were made on April 21-23, 1976, universal time, at the 2.24-m telescope on Mauna Kea, Hawaii, using a newly developed infrared spectrometer.
High-resolution second harmonic optical coherence tomography

A high-resolution Second Harmonic Optical Coherence Tomography (SH-OCT) system is demonstrated using a spectrum broadened femtosecond Ti:sapphire laser. An axial resolution of 4.2 μm at the second harmonic wave center wavelength of 400 nm has been achieved. Because the SH-OCT system uses the second harmonic generation signals that strongly depend on the orientation, polarization and local symmetry properties of chiral molecules, this technique provides unique contrast enhancement to conventional optical coherence tomography. The system is applied to image biological tissues like the rat-tail tendon. Images of highly organized collagen fibrils in the rat-tail tendon have been demonstrated.
Direct measurement of cyclotron coherence times of high-mobility two-dimensional electron gases

We have observed long-lived (~30 ps) coherent oscillations of charge carriers due to cyclotron resonance (CR) in high-mobility two-dimensional electrons in GaAs in perpendicular magnetic fields using time-domain terahertz spectroscopy. The observed coherent oscillations were fitted well by sinusoids with exponentially-decaying amplitudes, through which we were able to provide direct and precise measures for the decay times and oscillation frequencies simultaneously. This method thus overcomes the CR saturation effect, which is known to prevent determination of true CR linewidths in high-mobility electron systems using Fourier-transform infrared spectroscopy.
Scheduling intense applications most 'surprising' first

Certain streaming applications are required to perform sophisticated analytics within bounded time on arriving streams of data. Such applications have the interesting characteristic that the total amount of work that could be performed is unbounded. We show how recent results from algorithmic theory are useful in scheduling such applications as they allow the efficient creation of synopses of unprocessed data. These synopses can then be used to schedule the processing of the stream. In particular, we describe a preliminary implementation of a scheduler that optimizes the information rate available to applications by estimating the entropy of arriving streams. We describe the theory underlying such a scheduler and motivate how existing programming models can be extended to accommodate it by outlining a basic but functional implementation in the Java programming language. We show how results from algorithmic theory are useful in scheduling.Theory allows the efficient creation of synopses of unprocessed data.These synopses can then be used to schedule the processing of the stream.We describe the theory underlying such a scheduler.We show how existing programming models can be extended to accommodate it.
Charge transport in lithium peroxide: relevance for rechargeable metal–air batteries

The mechanisms and efficiency of charge transport in lithium peroxide (Li2O2) are key factors in understanding the performance of non-aqueous Li–air batteries. Towards revealing these mechanisms, here we use first-principles calculations to predict the concentrations and mobilities of charge carriers and intrinsic defects in Li2O2 as a function of cell voltage. Our calculations reveal that changes in the charge state of O2 dimers controls the defect chemistry and conductivity of Li2O2. Negative lithium vacancies (missing Li+) and small hole polarons are identified as the dominant charge carriers. The electronic conductivity associated with polaron hopping (5 × 10−20 S cm−1) is comparable to the ionic conductivity arising from the migration of Li-ions (4 × 10−19 S cm−1), suggesting that charge transport in Li2O2 occurs through a mixture of ionic and polaronic contributions. These data indicate that the bulk regions of crystalline Li2O2 are insulating, with appreciable charge transport occurring only at moderately high charging potentials that drive partial delithiation. The implications of limited charge transport on discharge and recharge mechanisms are discussed, and a two-stage charging process linking charge transport, discharge product morphology, and overpotentials is described. We conclude that achieving both high discharge capacities and efficient charging will depend upon access to alternative mechanisms that bypass bulk charge transport. More generally, we describe how the presence of a species that can change charge state – e.g., O2 dimers in alkaline metal-based peroxides – may impact rechargeability in metal–air batteries.
Analysis of circadian pattern reveals tissue-specific alternative transcription in leptin signaling pathway.

Background: It has been previously reported that most mammalian genes display a circadian oscillation in their baseline expression. Consequently, the phase and amplitude of each component of a signal transduction cascade has downstream consequences. Results: Here, we report our analysis of alternative transcripts in the leptin signaling pathway which is responsible for the systemic regulation of macronutrient storage and energy balance. We focused on the circadian expression pattern of a critical component of the leptin signaling system, suppressor of cytokine signaling 3 (SOCS3). On an Affymetrix GeneChip 430A2 microarray, this gene is represented by three probe sets targeting different regions within the 3' end of the last exon. We demonstrate that in murine brown adipose tissue two downstream 3' probe sets experience circadian baseline oscillation in counter-phase to the upstream probe set. Such differences in expression patterns are a telltale sign of alternative splicing within the last exon of SOCS3. In contrast, all three probe sets oscillated in a common phase in murine liver and white adipose tissue. This suggests that the regulation of SOCS3 expression in brown fat is tissue specific. Another component of the signaling pathway, Janus kinase (JAK), is directly regulated by SOCS and has alternative transcript probe sets oscillating in counter-phase in a white adipose tissue specific manner. Conclusion: We hypothesize that differential oscillation of alternative transcripts may provide a mechanism to maintain steady levels of expression in spite of circadian baseline variation.
My Bioethics Education at Georgetown

This article relates the experiences of the author in enrolling in the joint jurist doctor and philosophy program of Georgetown University. It describes and evaluates the graduate bioethics program at Georgetown. And, it explains how that program was integrated into Georgetown’s health law program.
The Online Transportation Problem

We study the online transportation problem under the assumption that the adversary has only half as many servers at each site as the online algorithm. We show that the GREEDY algorithm is $\Theta( {\rm min}(m, \lg C))$-competitive under this assumption, where m is the number of server sites and C is the total number of servers. We then present an algorithm BALANCE, which is a simple modification of the GREEDY algorithm, that is, O(1)-competitive under this assumption.
Effects of Compressibility on Boundary-Layer Turbulence

A series of turbulence measurements in a subsonic compressible turbulent boundary-layer flow in the Mach number range of 0.1 to 0.7 is described. Measurements include detailed surveys of the turbulence intensities and Reynolds shear stresses, and other quantities such as the turbulent kinetic energy. These data are examined to bring out the effects of compressibility and show that the stream-wise and transverse fluctuations and the turbulent shear stress follow a universal scaling law. A preliminary attempt is made to examine some of the assumptions made in turbulence models commonly used in numerical codes for the calculation of compressible flows.
A characterization of quasipositive Seifert surfaces (constructions of quasipositive knots and links, III)

This article was originally published in Topology 31 (1992). The present hyperTeXed redaction corrects a few typographical errors and updates the references.
DLB-SDPOP: A Multiagent Pseudo-tree Repair Algorithm for Load Balancing in WLANs

The traffic load of wireless local area networks (WLANs) is often distributed unevenly among access points. In addition, interference from collocated wireless devices operating in the same unlicensed frequency band may cause WLANs to become unstable, leading to temporary failures of access points. This paper addresses the questions of how to dynamically balance the load and how to quickly respond to instability in WLANs. We present a new decentralized multi-agent load balancing framework for WLANs that uses DLB-SDPOP, a distributed optimization algorithm, to dynamically load balance the WLAN. The algorithm implements a less expensive pseudo-tree repair mechanism instead of complete pseudo-tree reconstruction when instability problems occur. It also leverages an efficient communication mechanism to control communication overhead in heavily loaded situations. We empirically show that DLB-SDPOP improves WLAN load balancing performance significantly.
Realigning government action with public health evidence: the legal and policy environment affecting sex work and HIV in Asia

The HIV epidemic has shed light on how government regulation of sex work directly affects the health and well-being of sex workers, their families and communities. A review of the public health evidence highlights the need for supportive legal and policy environments, yet criminalisation of sex work remains standard around the world. Emerging evidence, coupled with evolving political ideologies, is increasingly shaping legal environments that promote the rights and health of sex workers but even as new legislation is created, contradictions often exist with standing problematic legislation. As a region, Asia provides a compelling example in that progressive HIV policies often sit side by side with laws that criminalise sex work. Data from the 21 Asian countries reporting under the UN General Assembly Special Session on HIV in 2010 were analysed to provide evidence of how countries' approach to sex-work regulation might affect HIV-related outcomes. Attention to the links between law and HIV-related outcomes can aid governments to meet their international obligations and ensure appropriate legal environments that cultivate the safe and healthy development and expression of sexuality, ensure access to HIV and other related services and promote and protect human rights.
Forecast improvements using a volatility index

This paper explores the possibility of improved out of sample forecasting for stock returns and foreign exchange rates using observed nonlinearities in the two series. Forecasting is done using nonparametric techniques where important information is obtained from the current level of volatility in the series. For both series forecast improvements are observed, but for stock returns the improvements are only marginal. These results indicate the usefulness and stability of some types of nonlinear modelling for financial markets.
Free biholomorphic functions and operator model theory, II☆

Let f=(f1,…,fn) be an n-tuple of formal power series in noncommutative indeterminates Z1,…,Zn such that f(0)=0 and the Jacobian detJf(0)≠0, and let g=(g1,…,gn) be its inverse with respect to composition. We assume that f and g have nonzero radius of convergence and g is a bounded free holomorphic function on the open unit ball [B(H)n]1, where B(H) is the algebra of bounded linear operators an a Hilbert space H. In this paper, several results concerning the noncommutative multivariable operator theory on the unit ball [B(H)n]1− are extended to the noncommutative domain Bf(H):={X∈B(H)n:g(f(X))=X and ‖f(X)‖⩽1} for an appropriate evaluation X↦f(X). We develop an operator model theory and dilation theory for Bf(H), where the associated universal model is an n-tuple (MZ1,…,MZn) of left multiplication operators acting on a Hilbert space H2(f) of formal power series. All the results of this paper have commutative versions.
Synthesis of 3-substituted and 3,4-disubstituted pyrazolin-5-ones

Abstract The synthesis of 3-substituted and 3,4-disubstituted pyrazolin-5-ones from acylated ethyl acetoacetates and diethyl malonates is described. The reaction of acylated ethyl acetoacetates and diethyl acetylmalonate with hydrazine (98%) gave 3-substituted pyrazolin-5-ones and malonyldihydrazide, respectively, following a deacetylation–condensation sequence. The reaction of ethyl 2-acetyl-3-hydroxy-2-butenoate and diethyl 2-(1-hydroxyethylidene)malonate with hydrazine monohydrochloride yielded ethyl 3,5-dimethyl-1 H -pyrazole-4-carboxylate and 4-ethoxycarbonyl-3-methylpyrazolin-5-one, respectively, following a dehydration–cyclocondensation sequence, in high yields.
Lighter: fast and memory-efficient sequencing error correction without counting

Lighter is a fast, memory-efficient tool for correcting sequencing errors. Lighter avoids counting k-mers. Instead, it uses a pair of Bloom filters, one holding a sample of the input k-mers and the other holding k-mers likely to be correct. As long as the sampling fraction is adjusted in inverse proportion to the depth of sequencing, Bloom filter size can be held constant while maintaining near-constant accuracy. Lighter is parallelized, uses no secondary storage, and is both faster and more memory-efficient than competing approaches while achieving comparable accuracy.
Preparation and reactions of 4-oxaspiro[2.3]hexanes

2-Methyleneoxetanes were converted in excellent yields to 4-oxaspiro[2.3]hexanes under modified Simmons–Smith conditions. Treatment of the oxaspirohexanes with BF3·Et2O provided cyclopentanones, cyclobutanones or 4-methylenetetrahydrofurans, depending on the substituents.
Effects of redox potential, steric configuration, solvent, and alkali metal cations on the binding of carbon dioxide to cobalt(I) and nickel(I) macrocycles

The binding of CO_2 to metal macrocycles has been determined electrochemically by using cyclic voltammetry or differential pulse polarography. The CO_2 binding constants, K for a series of Co(I) tetraammacrocycle complexes in (CH3)_2SO showed a strong correlation with the Co(II/I) redox potential. Although meso and d,l stereoisomers of [Co^I(Me_6[14]4,11- diene)]^+ had identical redox potentials, K_(CO_)2 differed by a factor of 10^2 for these stereoisomers, suggesting a large steric effect on CO_2 binding. Binding of CO_2 to Ni(I) tetraazamacrocycles in (CH_3)_2SO yielded a redox potential dependence similar to that of Co(I) macrocycles. A weak correlation between K_(CO_2) and the solvent dielectric constant was found for d,l-[Co(Me_6[ 14]-4,11 -diene)]^+. In tetrahydrofuran (THF), d,l-[CO(Me_6[14]4,11-diene)]^+ was found to bind CO_2 more strongly in the presence of 0.1 M Li^+ than in the presence of 0.1 M tetrabutylammonium (TBA^+). Electrochemically determined K_(CO_2)'s for Co(salen)^- and Co(Me_2salen)^- in THF indicated a strong dependence on redox potential and electrolyte cation.
Fair distribution of concerns in design and evaluation of fault-tolerant distributed computer systems

In analysing the fault tolerance capabilities of distributed computer system designs, the functionally or physically replaceable components have usually been modelled as one of the two extreme types with respect to their failure symptoms (faulty output behaviour): the fail-silent unit (FSU) model at the simplest end, and the malicious unit (MaU) model, also called the Byzantine unit model, at the other end. The basic weaknesses of these models for use in practical system design and evaluation are pointed out. The FSU model is justifiable for handling most simple parts of a system, but not so for other complex parts. The MaU model is misleading in that it tends to draw attention to events of negligible occurrence probabilities while taking attention away from events of higher occurrence probabilities. It is also pointed out that the state-of-the-art in analytic modelling and evaluation of fault-tolerant distributed computer systems has a vast weakly characterized region in the domain of conceivable component models enclosed by the two extreme models. The main constructive proposition made with respect to advancing the state-of-the-art is to establish scientific procedures for fair distribution of concerns over possible occurrences of anomalous events during system design and validation. A direction for obtaining such a fair modelling procedure relying on extensive probabilistic reasoning is proposed. The principle may have broad applicability, extending much beyond the area of fault-tolerant computing.
Dynamics of branched polymer molecules in dilute solution

Theoretical formulas for the intrinsic viscosity and viscoelastic properties of some model branched molecules in dilute solution are calculated by means of the normal coordinate method of Rouse modified to include hydrodynamic interactions. The calculations are exact except for the usual approximation of the hydrodynamic interaction by the Kirkwood-Riseman formula. The ratio of the intrinsic viscosity of a branched molecule to that of a linear molecule of the same weight is found to vary almost as the square root of the ratio of the mean square radii, instead of as the latter ratio to three-halves power, as has been postulated before. It is proposed that this square root relation is applicable in general to branched molecules of all types. Several sets of experimental data in the literature are shown to agree well with this hypothesis.