234 research outputs found
A variational approach to blending based on warping for non-overlapped images
No full textThis paper presents a new model for image blending based on warping. The model is represented by partial differential equations (PDEs) and gives a sequence of images, which has the properties of both blending of image intensities and warping of image shapes. We modified the energy functional in [W.-H. Liao, A. Khuu, M. Bergsneider, L. Vese, S.-C. Huang, S. Osher, From Landmark Matching to Shape and Open Curve Matching: A Level Set Approach, Computational and Applied Mathematics (CAM) Technical Reports 02-59, UCLA, 2002.] in order to adapt the idea of the shape warping to the image blending. The PDEs from the proposed energy functional cover not only overlapped images but also non-overlapped ones. (c) 2006 Elsevier Inc. All rights reserved.This work was partially supported by KRF-2002-070-C00004 and KOSEF R01-2000-00008. The first author was supported in part by IMA
with funds provided by NSF
Hydrogen bonding and vibrational energy relaxation of interfacial water: A full DFT molecular dynamics simulation
No full textThe air-water interface has been a subject of extensive theoretical and experimental studies due to its ubiquity in nature and its importance as a model system for aqueous hydrophobic interfaces. We report on the structure and vibrational energy transfer dynamics of this interfacial water system studied with equilibrium and non-equilibrium molecular dynamics simulations employing a density functional theory -based description of the system and the kinetic energy spectral density analysis. The interfacial water molecules are found to make fewer and weaker hydrogen (H)-bonds on average compared to those in the bulk. We also find that (i) the H-bonded OH groups conjugate to the free OH exhibit rather low vibrational frequencies (3000-3500 cm-1); (ii) the presence of a significant fraction (>10%) of free and randomly oriented water molecules at the interface (labile water), neither of whose OH groups are strong H-bond donors; (iii) the inertial rotation of free OH groups, especially from the labile water, contribute to the population decay of excited free OH groups with comparable rate and magnitude as intramolecular energy transfer between the OH groups. These results suggest that the labile water, which might not be easily detectable by the conventional vibrational sum frequency generation method, plays an important role in the surface water dynamics. © 2017 Author(s)311Nsciescopu
A fluorescent host-guest complex of cucurbituril in solution: a molecular Jack O'Lantern
No full textFluorescence enhancement of a probe molecule in solution by the container molecule cucurbituril (CB) is reported for the first time. The fluorescence of the probe 2-anilinonaphthalene-6-sulfonate (2,6-ANS) in aqueous Na2SO4 solution is found to increase by a maximum factor of 5.0 upon addition of cucurbituril. This fluorescence enhancement is the result of the formation of a host-guest inclusion complex, in which the guest 2,6-ANS is incorporated inside the cavity of the host, cucurbituril. Measurement of the enhancement as a function of cucurbituril concentration yielded a value of the equilibrium constant (K) of 52 +/- 10 M-1. It is proposed that the mode of inclusion involves the phenyl group of the 2,6-ANS, because of the relatively small size of the cucurbituril cavity. It is further proposed that the observed enhancement is a result of loss of rotational mobility of the phenyl ring relative to the naphthyl fluorophore of 2,6-ANS upon inclusion of the phenyl ring, Since the name cucurbituril is derived from the Latin word for "pumpkin," this fluorescent host-guest complex is referred to as a "molecular Jack O'Lantern," with the 2,6-ANS serving as the candle.PT: J; CR: BEHREND R, 1905, LIEBIGS ANN CHEM, V339, P1 BORTOLUS P, 1996, ADV PHOTOCHEMISTRY P, P1 BUSCHMANN HJ, 1992, J INCLUS PHENOM MOL, V14, P91 BUSCHMANN HJ, 1997, J INCLUS PHENOM MOL, V29, P167 BUSCHMANN HJ, 1998, THERMOCHIM ACTA, V317, P95 BUSCHMANN HJ, 1999, J PHOTOCH PHOTOBIO A, V121, P99 CINTAS P, 1994, J INCLUS PHENOM MOL, V17, P205 CRAM DJ, 1997, CONTAINER MOL THEIR DANTZ DA, 1998, SUPRAMOL CHEM, V9, P79 DELAPENA AM, 1993, J INCLUS PHENOM MOL, V15, P131 DIAMOND D, 1996, CHEM SOC REV, V25, P15 FREEMAN WA, 1981, J AM CHEM SOC, V103, P7367 HOFFMANN R, 1994, J CHEM SOC FARADAY T, V90, P1507 JEON YM, 1996, J AM CHEM SOC, V118, P9790 KOSOWER EM, 1975, J AM CHEM SOC, V97, P2167 KOSOWER EM, 1978, J AM CHEM SOC, V100, P4179 LI S, 1992, CHEM REV, V92, P1457 MOCK WL, 1983, J ORG CHEM, V48, P3618 MOCK WL, 1995, TOP CURR CHEM, V175, P1 MOCK WL, 1996, COMPREHENSIVE SUPRAM, V2, P477 WAGNER BD, 1998, J PHOTOCH PHOTOBIO A, V114, P151 WAGNER BD, 1999, J PHYS CHEM B, V103, P10114 WAGNER BD, 2000, J INCL PHENOM MACRO, V38, P467 WHANG DM, 1998, J AM CHEM SOC, V120, P4899; NR: 24; TC: 16; J9: CAN J CHEM; PG: 4; GA: 473RESource type: Electronic(1
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Highly r-process enhanced stars in ultra-faint dwarf galaxies
No full textHighly r-process enhanced metal-poor stars (MP r-II; [Eu/Fe] > 1 and [Fe/H]≤ -1.5) have been observed in ultra-faint dwarf (UFD) galaxy, specifically in Reticulum II (Ret II). The fact that only a few UFDs contain such stars implies that the r-process site may reflect very rare but individually prolific events, such as neutron star mergers (NSMs). Considering the relatively short star formation history of UFDs, it is puzzling how they could experience such a rare phenomenon. In this work, we show the results of cosmological hydrodynamic zoom-in simulations of isolated UFDs (Mvir ≈ 107-108 M⊙ and M∗ ≈ 10-3-104 M⊙ at z = 0) to explain the formation of MP r-II stars in UFDs. We employ a simple toy model for NSM events, adopting parameters consistent with observations, such as the NSM rate (1 per M∗ ≈ 105 M⊙) and europium (Eu) mass (MEu ≈ 105 M⊙). We identify only one simulated galaxy (Mvir} ≈ 4.6 × 107 M⊙ M∗ ≈ 3.4 × 103 M⊙ at z = 0) with abundances similar to Ret II in a simulation volume that hosts ~30 UFD analogues, indicating that such abundances are possible but rare. By exploring a range of key parameters, we demonstrate that the most important factor in determining the formation of MP r-II stars in UFDs is how quickly subsequent stars can be formed out of r-process enriched gas. We find that it takes between 10 and 100 Myr to form the first and second bursts of MP r-II stars. Over this period, Eu-polluted gas maintains the required high abundance ratios of [Eu/Fe]> 1. © 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
Fluorescence enhancement of curcumin upon inclusion into cucurbituril
No full textThe effect of the macrocyclic host compounds cucurbit[n]urils (Qn), with n = 5 - 7, on the fluorescence of the biologically active compound curcumin has been studied. Curcumin, the main constituent of the Indian spice turmeric, is of growing interest because of its wide-ranging pharmaceutical properties. This compound forms strong 2:1 host-guest inclusion complexes with Q6 (the original cucurbituril), with an overall equilibrium constant of (1.9 +/- 0.8) X 10(4) M-2. It is postulated that a Q6 host partially encapsulates each of the two phenyl groups at the ends of the curcumin molecule. The difference in magnitude of the equilibrium constants K-1 (72 +/- 2 M-1) and K-1 (260 +/- 120 M-1) for stepwise encapsulation of the two ends of the curcumin molecule indicates that encapsulation by the first Q6 significantly alters its entire electronic structure, resulting in a more favorable second encapsulation. A very large enhancement of the fluorescence of curcumin results from this complex formation, on the order of 5.0; this is a significant fraction of the polarity sensitivity factor (PSF) of 39 measured for curcumin, that is the ratio of fluorescence intensity in ethanol vs. water. Surprisingly, no such enhancement could be observed in the case of Q7, indicating that the interactions between the guest and the host cavity are not favorable in this case, contrary to expectations. Similarly, no enhancement was observed in the case of Q5, which is not unexpected, because of the extremely small size of the host cavity and portal in this case.PT: J; CR: BARIK A, 2003, PHOTOCHEM PHOTOBIOL, V77, P597 BONG PH, 2000, B KOR CHEM SOC, V21, P81 BUSCHMANN HJ, 1997, J INCLUS PHENOM MOL, V29, P167 BUSCHMANN HJ, 1998, J SOLUTION CHEM, V27, P135 BUSCHMANN HJ, 1998, THERMOCHIM ACTA, V317, P95 BUSCHMANN HJ, 2000, J INCL PHENOM MACRO, V37, P231 BUSCHMANN HJ, 2000, SUPRAMOL CHEM, V11, P225 CHIGNELL CF, 1994, PHOTOCHEM PHOTOBIOL, V59, P295 CHOI S, 2002, MACROMOLECULES, V35, P3526 CINTAS P, 1994, J INCLUS PHENOM MOL, V17, P205 DAHL TA, 1994, PHOTOCHEM PHOTOBIOL, V59, P290 DALTON L, 2003, CHEM ENG NEWS SEP, P8 DAY A, 2001, J ORG CHEM, V66, P8094 DELAPENA AM, 1993, J INCLUS PHENOM MOL, V15, P131 ELHAOUAJ M, 2001, J CHEM SOC PERK NOV, P2104 ELHAOUAJ M, 2001, J CHEM SOC PERK T 2, P804 FREEMAN WA, 1981, J AM CHEM SOC, V103, P7367 FREEMAN WA, 1984, ACTA CRYSTALLOGR B, V40, P382 HAMAI S, 1996, B CHEM SOC JPN, V69, P2469 HOFFMANN R, 1994, J CHEM SOC FARADAY T, V90, P1507 JANSEN K, 2000, VOM WASSER, V95, P229 JEON YM, 1996, J AM CHEM SOC, V118, P9790 JOVANOVIC SV, 2001, J AM CHEM SOC, V123, P3064 KHOPDE SM, 2000, PHOTOCHEM PHOTOBIOL, V72, P625 KIM J, 2000, J AM CHEM SOC, V122, P540 LAGONA J, 2003, ORG LETT, V5, P3745 LEE JW, 2003, ACCOUNTS CHEM RES, V36, P621 LIU Y, 2000, J ORG CHEM, V65, P6227 MARQUEZ C, 2001, ANGEW CHEM INT EDIT, V40, P3155 MARQUEZ C, 2001, ANGEW CHEM INT EDIT, V40, P4387 MESCHKE C, 1997, THERMOCHIM ACTA, V297, P43 MOCK WL, 1983, J ORG CHEM, V48, P3618 MOCK WL, 1986, J ORG CHEM, V51, P4440 MOCK WL, 1989, J AM CHEM SOC, V111, P2697 MOCK WL, 1990, J CHEM SOC CHEM COMM, P1509 MOCK WL, 1995, TOP CURR CHEM, V175, P1 MOCK WL, 1996, COMPREHENSIVE SUPRAM, V2, P477 NEUGEBAUER R, 1998, J CHEM SOC PERK MAR, P529 NIGAM S, 1996, J PHYS CHEM-US, V100, P7135 ROBINSON TP, 2003, BIOORG MED CHEM LETT, V13, P115 SHIM JS, 2003, CHEM BIOL, V10, P695 SUN YM, 2002, ORG LETT, V4, P2909 SZELTLI J, 1998, CHEM REV, V98, P1743 TANG B, 2002, J AGR FOOD CHEM, V50, P1355 TONNESEN HH, 2002, INT J PHARM, V244, P127 WAGNER BD, 2000, J INCL PHENOM MACRO, V38, P467 WAGNER BD, 2001, CAN J CHEM, V79, P1101 WAGNER BD, 2003, J PHYS CHEM B, V107, P10741 WHANG D, 1996, J AM CHEM SOC, V118, P11333 WHANG D, 1998, ANGEW CHEM INT EDIT, V37, P78 WRIGHT JS, 2002, J MOL STRUC-THEOCHEM, V591, P207; NR: 51; TC: 8; J9: SUPRAMOL CHEM; PG: 7; GA: 876JJSource type: Electronic(1
Synthesis and Characterization of Thionated Reduced Graphene Oxides and Their Thin Films
No full textabstract: Thiol functionalization is one potentially useful way to tailor physical and chemical properties of graphene oxides (GOs) and reduced graphene oxides (RGOs). Despite the ubiquitous presence of thiol functional groups in diverse chemical systems, efficient thiol functionalization has been challenging for GOs and RGOs, or for carbonaceous materials in general. In this work, thionation of GOs has been achieved in high yield through two new methods that also allow concomitant chemical reduction/thermal reduction of GOs; a solid-gas metathetical reaction method with boron sulfides (BxSy) gases and a solvothermal reaction method employing phosphorus decasulfide (P4S10). The thionation products, called "mercapto reduced graphene oxides (m-RGOs)", were characterized by employing X-ray photoelectron spectroscopy, powder X-ray diffraction, UV-Vis spectroscopy, FT-IR spectroscopy, Raman spectroscopy, electron probe analysis, scanning electron microscopy, (scanning) transmission electron microscopy, nano secondary ion mass spectrometry, Ellman assay and atomic force microscopy. The excellent dispersibility of m-RGOs in various solvents including alcohols has allowed fabrication of thin films of m-RGOs. Deposition of m-RGOs on gold substrates was achieved through solution deposition and the m-RGOs were homogeneously distributed on gold surface shown by atomic force microscopy. Langmuir-Blodgett (LB) films of m-RGOs were obtained by transferring their Langmuir films, formed by simple drop casting of m-RGOs dispersion on water surface, onto various substrates including gold, glass and indium tin oxide. The m-RGO LB films showed low sheet resistances down to about 500 kΩ/sq at 92% optical transparency. The successful results make m-RGOs promising for applications in transparent conductive coatings, biosensing, etc.Dissertation/ThesisPh.D. Chemistry 201
Retirement 20/20: Innovation in Pension Design
No full textToday, both the United States and Canada are experiencing a decline in Single-Employer Sponsored Defined Benefit (DB) Pension plans. In some instances, they are being replaced by Defined Contribution (DC) or Individual Account [e.g., 401(k)] plans; in other cases, by nothing. It appears that traditional sponsors of DB plans have concluded that their cost (or its variability) is larger than the rewards (e.g., a loyal work force). At the same time, two stock market meltdowns in less than a decade have indicated to all the frailties of Individual Account DC systems. What we need is a new pension system that brings most of the advantages of the DB and DC plans to the participants, while minimizing their disadvantages. We must also recognize the skill set of the participants (e.g., do not expect a blue collar worker to be an investment professional) and not anticipate or require anomalous markets (e.g., ever-stronger equity returns). Size matters. Larger plans can run at lower per unit expense ratios, and can also achieve entry into a wide variety of investment products (e.g., private placements) not available to a small plan. Larger funds also benefit from risk sharing through “Law of Large Numbers”. The model proposed is a “Jointly Governed Target Benefit Pension plan”. Such plans would have many features in common with today’s Ontario Multi-Employer Pension Plans (MEPPs), the Canada/Quebec Pension Plans (C/QPP), TIAA-CREF in the United States and the Dutch national plan. For the plan sponsor, this is a DC plan. Inherent in the concept are that smaller plans (and even individual plans) could commingle their assets to achieve “size” (e.g. a minimum investment portfolio of $10B). Investment management would be at arm’s length from the plan itself.Target Benefit, Joint Governance, Commingled Assets
Underfunding of Defined Benefit Pension Plans and Benefit Guarantee Insurance - An Overview of Theory and Empirics
No full textWe review the theoretical literature on defined benefit (DB) pension plans, particularly focusing on the issue of plan underfunding and benefit guarantee insurance schemes. The literature shows that underfunding can, under reasonable assumptions, be an equilibrium outcome even in the absence of benefit insurance. The introduction of benefit guarantee funds was a reaction to the problem of underfunding, and we summarize the ensuing standard problems of moral hazard and adverse selection. We briefly discuss the small empirical research on the subject and propose directions for future research.defined benefit pension plans, underfunding, pension benefit guarantee
Is Foreign-Owned Capital a Bad Thing to Tax?
No full textThe aging population has raised at least two concerns about tax policy. First, taxes will need to be increased to cover higher public-pension and medical-care expenses when baby boomers have retired. Second, taxes can be cut in the meantime, as the government realizes the "fiscal dividend" that accompanies its debt reduction program (that has been motivated by the aging population development). This paper uses a simple endogenous growth analysis to examine these issues. It is assumed that sales tax increases are infeasible on political grounds. Two conclusions emerge: the income tax rate levied on domestic residents should be cut during the debt-reduction period, and the tax rate on foreigners whose capital is operating in Canada should be increased later on when the bulk of the baby boomers have retired.fiscal policy, endogenous growth, open economy
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